EP1129855A9

EP1129855A9 - Image forming method and device

Info

Publication number: EP1129855A9
Application number: EP99954363A
Authority: EP
Inventors: Masahiro Aizawa; Masaichiro Tatekawa; Masahiko Hashimoto; Masayoshi Miura; Yoshitaka Kitaoka; Takahiro Tsujimoto; Akira Ryoji; Taichi Itoh; Hidenori Tomachi; Katsutoshi Ogawa; Akira Kumon
Original assignee: Matsushita Electric Industrial Co Ltd; Array AB
Current assignee: Panasonic Holdings Corp; Array AB
Priority date: 1998-11-04
Filing date: 1999-11-04
Publication date: 2002-05-15
Also published as: EP1129855A1; WO2000026035A1; AU1076400A

Abstract

Disposed on one side of a controlling plate (30) that is positioned opposite the other side across a row of orifices (12A) is an oscillation transmitting plate (155). The other side of the controlling plate (30) is brought into contact with a toner conveying roller (1). One end of the oscillation transmitting plate (155) is connected to an oscillation generating body (60) and the other end has an oscillation absorbing body (64). A progressive wave is propagated parallel to the orifice row (12A) and a standing wave is formed in a direction orthogonal to the orifice row (12A).

Description

TECHNICAL FIELD

The present invention generally relates to copying machines, facsimile machines, and printers. This invention particularly relates to image forming devices capable of recording by jets of a developer such as toner onto a recording medium.

BACKGROUND ART

In recent years, with the improvement in the performance of personal computers, large amounts of documents are now being handled in many offices. Moreover, with the advance in network technology, printers and copying machines of extended processing capabilities have been applied widely. Color documentation also tends to increase.
There is an image forming device employing a direct marking technique capable of direct image formation on paper. For example, Japanese Patent Gazette No. S44-26333 shows an image forming device of the toner jet type as a direct marking technique. An accelerating electric field is created between the developer sleeve for charging and supplying toner and the opposing electrode, wherein the toner is carried through the air by the accelerating electric field. An image signal is input to an electrode of the print head having developer pass orifices, to control the charged toner's controlling lattice pass amount. The charged toner adheres onto the recording paper in front of the opposing electrode, thereby forming an image thereon. For example, in order to form dots of about 100 µm, the diameter of each developer pass orifice should also be miniaturized to around 100 µm.
However, in such a case, the size of resulting dots may become too small or dots themselves may not be shot at all because the developer pass orifice becomes clogged with dust scattered within the device or with toner particles.
That is, the entire toner on the developer sleeve cannot be charged uniformly. There is always a charge distribution. In addition to forward polarity-charged toner (i.e., toner which is forced into flight toward the opposing electrode from the developer sleeve by an electric field applied between the developer sleeve and the opposing electrode at image formation time), reverse polarity-charged toner and non-charged toner are present as a mixture. Toner useful for image formation is a forward polarity toner; however, a part of the reverse polarity toner is forced into flight along with the forward polarity toner by toner-to-toner cohesion and adhesion. An electric field, which is created between the opposing electrode and the print head at recording time, acts as a force that repels the reverse polarity toner back to the print head from the recording paper (the opposing electrode). As a result, the reverse polarity toner thus repelled comes to adhere to the surface of the print head and to the internal surface of the developer pass orifice. Moreover, the non-charged toner easily separates from the developer sleeve, so that the non-charged toner falls in the developer pass orifice and adheres thereto.
Such a phenomenon occurs repeatedly every time a voltage is applied to the print head. As a result, toner is deposited more and more on the print head as image formation is repeatedly carried out and the amount of deposit of the toner gradually increases. Moreover, contaminants such as dust also adhere to the print head, thereby promoting a buildup of toner deposits. As a result, the developer pass orifice may be clogged up strongly. These toner deposits and contaminants exert effects on an electric field that is formed by an electrode for toner pass control or physically prevent the passing of toner through the developer pass orifice, causing the thinning of dots and dot errors.
Accordingly, it is necessary to provide suitable cleaning means for providing protection against clogging of the developer pass orifice. In respect to such cleaning, various methods have been proposed. For example, the following methods have been known in the art.
(1) Method making utilization of an electric field (Japanese Unexamined Patent Gazette Nos. S58-104771 and S59-188450)
(2) Method making utilization of a stream of air (Japanese Unexamined Patent Gazette Nos. S58-122569 and H02-509789)
(3) Method in which an oscillation is applied to the printer head (Japanese Unexamined Patent Gazette Nos. H03-57658, H04-161353, and H04-257461)
However, the method (1) making utilization of an electric field finds it difficult to remove non-charged toner particles contained in the toner and contaminants such as dust scattered in the air. On the other hand, the method (2) which makes utilization of a stream of air is able to remove non-charged toner particles et cetera but finds it difficult to remove toner whose charge amount is large and which therefore strongly adheres to the print head. In other words, it is relatively easy to remove toner adhering to the surface of the print head. On the other hand, in order to remove strongly-adhered toner particles such as toner particles heavily charged and adhering to the inside of the developer pass orifice, it is required to subject the toner particles to an extremely fast air stream. This necessitates the provision of a large-sized pump.
In the method (3) making utilization of an oscillation, for the case of a standing wave, its node portion amplitude becomes smaller. Therefore it is difficult to remove toner and a spot may be formed. Furthermore, since the print head and the developer sleeve are located in very close proximity to each other or brought into contact with each other, toner may be emitted from the developer sleeve when an oscillation is applied. The print head will not be cleaned, rather contaminated, unless the emitted toner is collected positively.

DISCLOSURE OF THE INVENTION

Accordingly, an object of the present invention is to achieve sufficiently high cleaning power with a relatively small-sized device for the realization of an image forming device with an increased reliability in an oscillation cleaning method in which an oscillation is applied to the print head.
First and second inventions of the present application are image forming methods. More specifically, the first invention provides an image forming method comprising the steps of supporting a charged developer on a developer supporting body, applying a specified voltage to an opposing electrode positioned face to face with the developer supporting body, making use of an insulating substrate which is placed between the developer supporting body and the opposing electrode and through which a plurality of developer pass orifices are formed in a row and an image signal electrode which is arranged around each developer pass orifice in the insulating substrate and to which a voltage according to an image signal is applied, and forcing the developer on the developer supporting body into flight so as to pass through a specified developer pass orifice for making a record on an image receiving body supported between the insulating substrate and the opposing electrode, and removing particles of the developer or contaminants adhering to around the developer pass orifice, wherein the developer particles/contaminants removing step is performed by applying to the insulating substrate an oscillation resulting from a combination of a progressive wave and a standing wave. In this case, it is preferable that the progressive wave propagates in a direction parallel to the developer pass orifice row and that the standing wave is formed in a direction orthogonal to the developer pass orifice row.
Since the progressive wave is made to propagate in a direction parallel to the developer pass orifice row, this avoids the generation of nodes and antinodes of an oscillation, thereby providing uniform oscillations. On the other hand, since the standing wave is formed in a direction orthogonal to the developer pass orifice row, this suppresses the damping of oscillation, thereby making it possible to cause the periphery of the developer pass orifice to be oscillated greatly.
On the other hand, the second invention comprises the steps of supporting a charged developer on a developer supporting body, applying a specified voltage to an opposing electrode positioned face to face with the developer supporting body, making use of an insulating substrate which is placed between the developer supporting body and the opposing electrode and through which a plurality of developer pass orifices are formed in a row and an image signal electrode which is arranged around each developer pass orifice in the insulating substrate and to which a voltage according to an image signal is applied, and forcing the developer on the developer supporting body into flight so as to pass through a specified developer pass orifice for making a record on an image receiving body supported between the insulating substrate and the opposing electrode, and removing particles of the developer or contaminants adhering to around the developer pass orifice, wherein the developer particles/contaminants removing step includes the steps of causing an oscillation from an oscillation generating source positioned on one of sides facing each other across the developer pass orifice row to propagate to the insulating substrate, absorbing an oscillation propagating in a direction parallel to the developer pass orifice row, and reflecting, at the other side, an oscillation propagating in a direction orthogonal to the developer pass orifice row toward the developer pass orifice row.
As a result of such arrangement, a progressive wave is formed by absorption of an oscillation transmitted from the oscillation generating source on one side and an oscillation transmitted to the insulating substrate is reflected, giving rise to a standing wave by interference between a reflected wave and an incident wave. At this time, it is preferable that the position of the oscillation reflecting end is adjusted in such a way that a standing wave is formed having its antinodes in the vicinity of the developer pass orifices.
If the aforesaid method further comprises, prior to the step of propagating an oscillation from the oscillation generating source to the insulating substrate, the step of amplifying the oscillation from the oscillation generating source, this allows the periphery of the developer pass orifice to be oscillated sufficiently without having to increase the amplitude of the oscillation generating source.
It is preferable that prior to the step of absorbing an oscillation, the step of reducing the amplitude of the oscillation is carried out. This facilitates oscillation absorption.
It is preferable that the step of suppressing, while an oscillation from the oscillation generating source is absorbed, the damping of the oscillation is carried out. This ensures that oscillations from the oscillation generating source are positively propagated all over the developer pass orifice row.
A third invention of the present application relates to an image forming device. More specifically, the third invention provides an image forming device comprising a developer supporting body for supporting and, at the same time, conveying a developer, an opposing electrode positioned face to face with the developer supporting body, a developer pass controlling member, placed between the developer supporting body and an image receiving body and having at least one developer pass orifice row formed by arrangement of a plurality of developer pass orifices, for performing control so that in response to an image signal the developer conveyed by the developer supporting body is forced into flight so as to pass through a specified developer pass orifice for adhesion onto the image receiving body, and an oscillation applying member for applying an oscillation to the developer pass controlling member so that particles of the developer adhering to the developer pass controlling member are removed. The image forming device of the third invention is characterized in that the oscillation applying member is so configured as to achieve application of an oscillation to the developer pass controlling member by a combination of a progressive wave and a standing wave. Here, it is preferable that the oscillation applying member is configured so that the oscillation of the progressive wave propagates in a direction parallel to the developer pass orifice row and the oscillation of the standing wave is formed in a direction orthogonal to the developer pass orifice row.
The progressive wave is made to propagate in a direction parallel to the developer pass orifice row as described above, as a result of which arrangement the occurrence of formation of oscillation nodes and antinodes is prevented from taking place, thereby making it possible to obtain uniform oscillations. On the other hand, the standing wave is formed in a direction orthogonal to the developer pass orifice row, as a result of which oscillation damping is suppressed. This makes it possible to cause the periphery of the developer pass orifice to be oscillated greatly.
Fourth and fifth inventions of the present application are inventions suitable for forming a standing wave in the developer pass controlling member. More specifically, the fourth invention is directed to an image forming device comprising a developer supporting body which is formed rotatably about a rotation axis extending in a specified direction and which rotates about the rotation axis with a developer supported on its peripheral surface for conveying the developer, a developer pass controlling member, positioned face to face with the peripheral surface of the developer supporting body and having at least one developer pass orifice row in which a plurality of developer pass orifices capable of being passed through by the developer is arranged in the direction of the rotation axis of the developer supporting body, for performing control in response to an external image signal so that the developer is forced into flight from the developer supporting body so as to pass through a developer pass orifice, an image receiving body positioned opposite the developer supporting body across the developer pass controlling member, and an opposing electrode for guiding the developer, which has passed through the developer pass orifice of the developer pass controlling member, toward the image receiving body so that the developer is adhered to the image receiving body. The image forming device of the fourth invention further comprises an oscillation applying member for applying an oscillation to one of portions on both sides located opposite to each other across the developer pass orifice row in the developer pass controlling member, wherein the other of the side portions in the developer pass controlling member is in contact with the developer supporting body so that an oscillation, generated in the developer pass controlling member by application of an oscillation by the oscillation applying member and traveling from the oscillation-applied portion toward the developer pass orifice row, is reflected in the opposite direction.
As a result of such arrangement, an oscillation from the oscillation applying member is reflected at a contact portion at which the developer pass controlling member and the developer supporting body come into contact with each other, thereby giving rise to a standing wave between the developer pass controlling member and the oscillation applying member. If developer pass orifice portions or their neighboring areas are arranged not to correspond to nodes of the standing wave, this enables such portions to be oscillated at all times by the standing wave. Accordingly, the developer is effectively prevented from being built up within the developer pass orifices and around there. This positively prevents the developer pass orifices from being clogged up by a buildup of developer deposits.
In the fourth invention, preferably the other of the side portions in the developer pass controlling member is wound around the peripheral surface of the developer supporting body, so that it comes into surface to surface contact with the developer supporting body. In such a case, preferably it is set that L3 > λ/4 where λ is the wavelength of an oscillatory wave and L3 is the length of contact of the developer pass controlling member and the developer supporting body in the circumferential direction of the developer supporting body.
In this case, by the application of oscillation, the occurrence of swelling or the like in the developer pass controlling member is prevented, whereby the developer pass controlling member and the developer supporting body can be brought into contact with each other with increased stability. As a result, a reflected wave of the oscillation is stably formed, ensuring that a standing wave is positively formed in the developer pass controlling member. Further, if it is set that L3 > λ/4, this prevents an oscillation traveling from the oscillation applying member toward the developer pass orifice row from jumping over a contact portion of the developer pass controlling member and the developer supporting body, thereby ensuring that such an oscillation is reflected positively. As a result, the amplitude of the standing wave is increased to a further extent.
On the other hand, the fifth invention is directed to an image forming device comprising a developer supporting body which is formed rotatably about a rotation axis extending in a specified direction and which rotates about the rotation axis with a developer supported on its peripheral surface for conveying the developer, a developer pass controlling member, positioned face to face with the peripheral surface of the developer supporting body and having at least one developer pass orifice row in which a plurality of developer pass orifices capable of being passed through by the developer is arranged in the direction of the rotation axis of the developer supporting body, for performing control in response to an external image signal so that the developer is forced into flight from the developer supporting body so as to pass through a developer pass orifice, an image receiving body positioned opposite the developer supporting body across the developer pass controlling member, and an opposing electrode for guiding the developer, which has passed through the developer pass orifice of the developer pass controlling member, toward the image receiving body so that the developer is adhered to the image receiving body. The image forming device of the fifth invention further comprises an oscillation applying member for applying an oscillation to one of portions on both sides located opposite to each other across the developer pass orifice row in the developer pass controlling member, wherein the other of the side portions in the developer pass controlling member is in contact with the developer supporting body through a spacer member so that an oscillation, generated in the developer pass controlling member by application of an oscillation by the oscillation applying member and traveling from the oscillation-applied portion toward the developer pass orifice row, is reflected in the opposite direction. As a result of such arrangement, the same operation and effects as the fourth invention can be obtained. Further, the spacer member may be extendedly positioned along the rotation axis direction of the developer supporting body. In this case, the space defined between the developer pass controlling member and the developer supporting body is kept constant.
In the forth or fifth invention, the oscillation applying member may be made up of an oscillation transmitting body extendedly positioned along the rotation axis direction of the developer supporting body and an oscillation generating source disposed at at least one of lengthwise ends of the oscillation transmitting body. As a result of such arrangement, all the developer pass orifices of the developer pass orifice row are prevented from being clogged up by a buildup of developer deposits.
Further, the oscillation applying member may be configured so that a standing wave, whose node and antinode correspond to a reflecting end and to the developer pass orifice, respectively, in the developer pass controlling member, is obtained. As a result of such arrangement, the developer pass orifice portions of the developer pass controlling member undergo a greatest displacement and the effect of clogging prevention for the developer pass orifices is achieved to the full.
The position of the aforesaid reflecting end is preferably determined as follows.
That is, it is preferable that L1 is set such that L1 < λ/2 where λ is the wavelength of an oscillation and L1 is the distance between the developer pass orifice row and the reflecting end. In this case, in the developer pass orifice row the developer pass orifice portion or its neighboring area is oscillated at all times by a standing wave. Particularly, if L1 is set such that L1 ≈ λ/4, this forms a standing wave whose antinodes correspond to the position of the developer pass orifice row.
Further, it is preferable that the position of the reflecting end is set to L2 > λ/4 where λ is the wavelength of an oscillation and L2 is the distance between the oscillation transmitting body and the reflecting end. That is, if the distance L2 is set below λ/4, this makes it difficult to produce a standing wave. In addition, the reflecting end portion is oscillated. As a result, there occurs a liberation of heat at that portion and the spacer member et cetera may wear away. On the other hand, if the distance L2 is set above λ/4, this efficiently generates a standing wave, therefore preventing the developer pass orifices from being clogged up by. a buildup of developer deposits.
Further, it is preferable that an oscillation reflecting means for reflecting an oscillation traveling from the oscillation applying member toward the developer pass orifice row in the opposite direction is positioned opposite the developer pass orifice row across the reflecting end in the developer pass controlling member and L4 is set such that L4 ≈ (2n + 1) x λ/4 where λ is the wavelength of an oscillation, L4 is the distance between the developer pass orifice row and the oscillation reflecting means, and n is an integer. That is, in addition to the reflecting end, a second reflecting end may be provided. Here, the oscillation reflecting means may be implemented by an oscillation reflecting plate fixed to the developer pass controlling means or by a holding member for holding the developer pass controlling member.
In such a case, an oscillation propagating downstream of the reflecting end in the oscillation propagation direction is reflected by the oscillation reflecting means. As a result, the developer pass orifice portions of the developer pass controlling member undergo a much greater displacement. Preferably, the position of the oscillation reflecting means is so determined that a standing wave is formed such that its antinode corresponds to a developer pass orifice.
Sixth and seventh inventions of the present application are inventions suitable for generating uniform oscillations in the row direction of the developer pass orifice row. More specifically, the sixth invention of the present application is directed to an image forming device comprising a developer supporting body for supporting and, at the same time, conveying a developer, an opposing electrode positioned face to face with the developer supporting body, a developer pass controlling member, placed between the developer supporting body and an image receiving body and having at least one developer pass orifice row formed by arrangement of a plurality of developer pass orifices, for performing control in response to an image signal so that the developer conveyed by the developer supporting body is forced into flight so as to pass through a specified developer pass orifice for adhesion onto the image receiving body, and an oscillation applying member for applying an oscillation to the developer pass controlling member so that particles of the developer adhering to the developer pass controlling member are removed. In the image forming device of the sixth invention, the oscillation applying member is equipped with an oscillating plate extending parallel to the row direction of the developer pass orifice row and fixed to a surface of the developer pass controlling member, a piezoelectric element extending parallel to the row direction so as to be superimposed on the oscillating plate and fixed to a surface of the oscillating plate opposite to a contact surface in contact with the developer pass controlling member, and a regulating body for regulating expansion and contraction of the piezoelectric element in the row direction, whereby oscillations of the same phase in the row direction can be applied to portions of the developer pass orifices of the developer pass controlling member.
With such arrangement, when a voltage is applied to the piezoelectric element, the piezoelectric element undergoes flexure and deformation together with the oscillating plate. At this time, since the expansion and contraction of the piezoelectric element in the row direction is regulated, this makes the oscillating plate flex exclusively in a direction orthogonal to the row direction. As a result, oscillatory waves transmitted to the developer pass controlling member from the oscillating plate become oscillatory waves of equal phase in the row direction, wherein oscillations of the same phase are applied to the respective developer pass orifice portions of the developer pass controlling member, and cleaning capability spots along the row direction are prevented. Accordingly, the developer is removed uniformly, thereby ensuring that the clogging of the developer pass orifices by a buildup of developer deposits is prevented positively. Stable image formation is realized accordingly.
Further, the seventh invention of the present application is directed to an image forming device comprising a developer supporting body for supporting and, at the same time, conveying a developer, an opposing electrode positioned face to face with the developer supporting body, a developer pass controlling member, placed between the developer supporting body and an image receiving body and having at least one developer pass orifice row formed by arrangement of a plurality of developer pass orifices, for performing control in response to an image signal so that the developer conveyed by the developer supporting body is forced into flight so as to pass through a specified developer pass orifice for adhesion onto the image receiving body, and an oscillation applying member for applying an oscillation to the developer pass controlling member so that particles of the developer adhering to the developer pass controlling member are removed. The oscillation applying member is equipped with an oscillating plate extending parallel with the row direction of the developer pass orifice row and fixed to a surface of the developer pass controlling member, an oscillation generating source for applying an oscillation to one end of the oscillation transmitting body so that an oscillatory wave is generated which travels parallel to the row direction from the one end of the oscillation transmitting body toward the other end thereof, and an oscillation controlling part for controlling the oscillation so that the oscillatory wave in the oscillation transmitting body becomes a non-standing wave.
As a result of such arrangement, a non-standing, oscillatory wave propagates to the oscillating plate extending parallel to the developer pass orifice row. As a result, oscillatory waves transmitted to the developer pass controlling member from the oscillation transmitting body become oscillatory waves of equal phase in the row direction, wherein oscillations of the same phase are applied to the respective developer pass orifice portions of the developer pass controlling member. Accordingly, the developer is removed uniformly, thereby ensuring that the clogging of the developer pass orifices by a buildup of developer deposits is prevented positively. Stable image formation is realized accordingly.
Furthermore, the oscillation controlling part may be equipped with a clamp means for catching therein the other end of the oscillation transmitting body while shifting its clamp position so that the position, at which an oscillation at the other end of the oscillation transmission body is reflected, is varied with time. In this case, an oscillatory wave traveling from one end to the other of the oscillation transmitting body is reflected at the clamp position at the other end. Then, a progressive wave and a reflected wave are superimposed with each other, giving rise to a standing wave on the oscillation transmitting body. Since the clamp means causes the clamp position to vary with time, the oscillatory wave formed on the oscillation transmitting body is momentarily a standing wave. However, it becomes non-standing with time and substantially becomes a non-standing wave.
Further, unlike the above, the oscillation controlling part may be equipped with an auxiliary agitating means for slightly disturbing an oscillation from the oscillation generating source in the oscillation transmitting body. In this case, an oscillation from the oscillation generating part in the oscillation transmitting body is disturbed slightly by the auxiliary agitating means. As a result, the oscillatory wave in the oscillation transmitting body becomes a non-standing wave.
Eighth and ninth inventions of the present application are image forming devices suitable for suppressing the damping of an oscillation from the oscillation generating source. More specifically, the image forming device of the eighth invention comprises a developer supporting body for conveying and, at the same time, supporting a charged developer, an opposing electrode positioned face to face with the developer supporting body, a developer pass controlling member having an insulating substrate which is placed between the developer supporting body and the opposing electrode and through which a plurality of developer pass orifices are formed in a row and an image signal electrode which is arranged around each developer pass orifice in the insulating substrate and to which a voltage according to an image signal is applied, for forcing the developer on the developer supporting body into flight so as to pass through a specified developer pass orifice for adhesion onto an image receiving body supported between the developer pass controlling member and the opposing electrode, and an oscillation applying member having an oscillation generating source and an oscillation transmitting body which is connected, at at least one of ends thereof, to the oscillation generating source and disposed on the developer pass controlling member so as to extend parallel to the developer pass orifice row for transmitting an oscillation from the oscillation generating source to each developer pass orifice portion of the developer pass controlling member. The oscillation characteristic of the oscillation transmitting body varies along the propagation direction of an oscillation from the oscillation generating source for suppressing the damping of oscillation in the oscillation transmitting body. The oscillation gradually undergoes damping in the propagation direction. However, since the oscillation characteristic of the oscillation transmitting body varies along the propagation direction, this results in suppressing oscillation damping, thereby improving cleaning power.
Further, the image forming device of the ninth invention comprises a developer supporting body for conveying and, at the same time, supporting a charged developer, an opposing electrode positioned face to face with the developer supporting body, a developer pass controlling member having an insulating substrate which is placed between the developer supporting body and the opposing electrode and through which a plurality of developer pass orifices are formed in a row and an image signal electrode which is arranged around each developer pass orifice in the insulating substrate and to which a voltage according to an image signal is applied, for forcing the developer on the developer supporting body into flight so as to pass through a specified developer pass orifice for adhesion onto an image receiving body supported between the developer pass controlling member and the opposing electrode, and an oscillation applying member having an oscillation generating source and an oscillation transmitting body which is connected, at one of ends thereof, to the oscillation generating source and disposed on the developer pass controlling member so as to extend parallel to the developer pass orifice row for transmitting an oscillation from the oscillation generating source to each developer pass orifice portion of the developer pass controlling member. The oscillation transmitting body decreases in rigidity from the one end toward the other end. As a result of such arrangement, the oscillation transmitting body has the characteristic that the oscillation transmitting body becomes readily oscillated as it extends from its one end toward the other end and the damping of oscillation from the oscillation generating source is suppressed.
The oscillation transmitting body may be implemented by an oscillation transmitting plate the plate width of which varies with the distance from the oscillation generating source. Alternatively, the plate thickness of the oscillation transmitting plate may vary with the distance from the oscillation generating source.
Further, a lateral face of the oscillation transmitting body on the side of the developer pass orifices may be formed into a wavy shape. This makes it possible to make the node and antinode of an amplitude dull at oscillation application time and uniform cleaning performance is obtained throughout the lengthwise direction of the developer pass controlling member.
The wave pitch of the wavy shape of the oscillation transmitting body may be substantially a half of the wavelength of an oscillation in the oscillation transmitting body. As a result of such arrangement, the amplitude node/antinode of the oscillation transmitting body becomes smaller. Further, the difference of level between a concave portion and a convex portion of the wavy shape may be substantially a quarter of the wavelength of an oscillation in the developer pass controlling member. As a result of such arrangement, an oscillatory wave traveling from the oscillation transmitting body toward the developer pass controlling member undergoes a phase difference of 90 degrees between a wave traveling from a convex portion (crest) of the wavy shape of the oscillation transmitting body and a wave traveling from a concave portion (trough) thereof, as a result of which the oscillatory wave becomes an oscillatory wave of relatively the same phase. Accordingly, uniform cleaning power is obtained.
The oscillation transmitting body, formed by an oscillation transmitting plate whose plate width or plate thickness becomes gradually smaller and having a wavy shape on the developer pass orifice side, is especially preferable.
A tenth invention of the present application is an invention suitable for amplifying an oscillation from the oscillation generating source and propagating it to the developer pass controlling member. More specifically, an image forming device of the tenth invention comprises a developer supporting body for conveying and, at the same time, supporting a charged developer, an opposing electrode positioned face to face with the developer supporting body, a developer pass controlling member having an insulating substrate which is placed between the developer supporting body and the opposing electrode and through which a plurality of developer pass orifices are formed in a row and an image signal electrode which is arranged around each developer pass orifice in the insulating substrate and to which a voltage according to an image signal is applied, for forcing the developer on the developer supporting body into flight so as to pass through a specified developer pass orifice for adhesion onto an image receiving body supported between the developer pass controlling member and the opposing electrode, and an oscillation applying member having an oscillation generating source and an oscillation transmitting body which is connected, at one of ends thereof, to the oscillation generating source and disposed on the developer pass controlling member so as to extend parallel to the developer pass orifice row for transmitting an oscillation from the oscillation generating source to each developer pass orifice portion of the developer pass controlling member. The oscillation transmitting body is characterized in that a portion of the oscillation transmitting body connected to the oscillation generating source is greater in rigidity than a portion of the oscillation transmitting body disposed on the developer pass controlling member.
As a result of such arrangement, the oscillation of the oscillation generating source is amplified in the portion of the oscillation transmitting body disposed on the developer pass controlling member for propagation to the developer pass controlling member. As a result, high cleaning power can be obtained without increasing the oscillation of the oscillation generating source.
Further, an eleventh invention of the present application is an invention suitable for propagating a progressive wave to the oscillation transmitting body. More specifically, an image forming device of the eleventh invention comprises a developer supporting body for conveying and, at the same time, supporting a charged developer, an opposing electrode positioned face to face with the developer supporting body, a developer pass controlling member having an insulating substrate which is placed between the developer supporting body and the opposing electrode and through which a plurality of developer pass orifices are formed in a row and an image signal electrode which is arranged around each developer pass orifice in the insulating substrate and to which a voltage according to an image signal is applied, for forcing the developer on the developer supporting body into flight so as to pass through a specified developer pass orifice for adhesion onto an image receiving body supported between the developer pass controlling member and the opposing electrode, and an oscillation applying member having an oscillation generating source and an oscillation transmitting body which is connected, at one of ends thereof, to the oscillation generating source, which is provided, at the other end, with an oscillation absorbing means for absorbing an oscillation from the oscillation generating source, and which is disposed on the developer pass controlling member so as to extend parallel to the developer pass orifice row for transmitting an oscillation from the oscillation generating source to each developer pass orifice portion of the developer pass controlling member. The oscillation transmitting body is characterized in that a portion of the oscillation transmitting body at which the oscillation absorbing means is disposed is greater in rigidity than a portion of the oscillation transmitting body disposed on the developer pass controlling member.
As a result of such arrangement, oscillatory energy propagated from the oscillation generating source is absorbed by the oscillation absorbing means positioned at the end of the oscillation transmitting body. This causes an oscillation input from the oscillation generating source to propagate in one direction, so that there exists no reflected wave from the side of the oscillation absorbing means. Because of this, no standing wave is formed on the oscillation transmitting body and the oscillation becomes a progressive wave.
Apart from the above, when the amplitude of an oscillation is great, it is difficult for the oscillation absorbing means to satisfactorily absorb the oscillation. If the portion at which the oscillation absorbing means is disposed is set greater in rigidity than the portion overlying the developer pass controlling member, this diminishes the amplitude of the oscillations of the portion having the oscillation absorbing means, ensuring that oscillatory energy is absorbed positively by the oscillation absorbing means. Particularly, if the plate width is increased for making a variation in the rigidity of the oscillation transmitting body, this increases the contact area of the oscillation absorbing means and the oscillation transmitting body. As a result, oscillatory energy per unit area is reduced. This especially facilitates the oscillation absorbing means to absorb an oscillation. As a result, uniform amplitudes are given to the developer pass controlling member, making it possible to achieve uniform cleaning.
In the tenth invention or in the eleventh invention, the plate width of the portion of the oscillation transmitting body disposed on the developer pass controlling member may be varied according to the distance from the oscillation generating source. In this case, the damping of an oscillation from the oscillation generating source is suppressed.
Further, in any of the inventions 7, 8, and 10, the other end of the oscillation transmitting body may be equipped with an oscillation absorbing means for absorbing an oscillation from the one end of the oscillation transmitting body. In this case, as described above, an oscillation input from the oscillation generating source propagates in one direction, so that there exists no reflected wave from the side of the oscillation absorbing means. Because of this, a progressive wave propagates on the oscillation transmitting body and no oscillation nodes and antinodes are created, thereby making it possible to achieve uniform cleaning of the developer pass controlling member.
Further, the oscillation absorbing means may be composed of two or more kinds of viscoelastic bodies having different characteristics.
That is, an oscillation in the oscillation transmitting body is transmitted, through the developer pass controlling member, to components having various natural frequencies and their reflected waves are returned to the oscillation transmitting body. Accordingly, it is required that the oscillation absorbing means absorbs not only oscillations of unitary frequency from the oscillation generating source but also oscillations of other frequencies. Dampers of rubber, PZT, or the like vary in the value of damping coefficient with respect to frequency if their configuration differs. To cope with this, if the oscillation absorbing means is composed of two or more kinds of viscoelastic bodies having different characteristics, this makes it possible to damp various frequencies input to the oscillation absorbing means.
Further, for example, if the oscillation absorbing means is composed of rubber hardened by addition of a metallic filler, this increases its weight, thereby increasing the coefficient of damping. It becomes possible to achieve effective oscillation damping. On the other hand, since the hardened rubber has a high spring constant, this produces the inconvenience that an input oscillatory wave becomes susceptible to being reflected. To cope with this, if the oscillation absorbing means is composed of two types of rubber materials such as soft rubber and hard rubber, the occurrence of oscillatory wave reflection is prevented by the soft rubber and oscillation damping is carried out by the hard rubber. This ensures that oscillatory energy input to the oscillation absorbing means is satisfactorily and positively absorbed and oscillations of uniform amplitude are applied to the developer pass controlling member.
Further, the oscillation transmitting body may be in tension in its longitudinal direction. In this case, the warping of the oscillation transmitting body is prevented, ensuring that oscillations are positively applied to the oscillation transmitting body. This is particularly effective when the oscillation transmitting body is formed of an oscillation transmitting plate.
Further, it is preferable that the image forming device further comprises a holding member for holding, on a side opposite to the developer pass orifice row across the oscillation transmitting body, the developer pass controlling member, and that the oscillation transmitting body is disposed so that L5 > λ/2 where λ is the wavelength of an oscillation and L5 is the distance between the oscillation transmitting body and the holding member. This prevents the holding member from being oscillated by the oscillation of the oscillation transmitting body, thereby making it possible to propagate an oscillation from the oscillation generating source to the developer pass controlling member without a damping of the oscillation of the oscillation generating source.
Further, when forming a non-standing wave oscillation in parallel with the developer pass orifice row as in the foregoing seventh to eleventh inventions, it is preferable that a standing wave is formed in a direction orthogonal to the developer pass orifice row so that the periphery of the developer pass orifice can be oscillated at greater amplitudes.
As a means for forming a standing wave in a direction orthogonal to the developer pass orifice row, the developer pass controlling member may be, on a side opposite the oscillation transmitting body across the developer pass orifice row, in line contact with the developer supporting body in parallel with the row direction of the developer pass orifice row so that a reflecting end for reflecting an oscillation from the oscillation transmitting body is formed. In this case, an oscillation transmitted from the oscillation transmitting body to the developer pass controlling member travels toward the developer pass orifice row and is reflected at the reflecting end. This progressive wave is superimposed with a reflected wave, forming a standing wave in a direction orthogonal to the row direction of the developer pass orifice row.
An arrangement may be made in which the developer pass controlling member passes around a peripheral face of the developer supporting body so that the developer pass controlling member is brought into surface-to-surface contact with the developer supporting body. Unlike this arrangement, another arrangement may be made in which a spacer means, disposed extendedly along the developer pass orifice row, is positioned at a reflecting end of the developer pass controlling member and the developer pass controlling member is brought into contact with the developer supporting body through the spacer means.
This ensures that a progressive wave is reflected accurately and positively in the developer pass controlling member, thereby facilitating the formation of excellent standing waves.
On the other hand, when providing the aforesaid reflecting end, it is preferable that the oscillation applying member is so configured as to apply an oscillation so that an oscillatory wave in a direction orthogonal to the row direction of the developer pass orifice row in the developer pass controlling member becomes a standing wave whose node and antinode correspond to the reflecting end and to the developer pass orifice row, respectively. In this case, the developer pass orifices undergo a greatest displacement, whereby removal of the developer can be carried out efficiently.
A twelfth invention of the present application is an invention suitable for providing protection against contamination by a removed developer. More specifically, an image forming device of the twelfth invention comprises developer supplying means for charging a developer and supplying the charged developer supported on a developer supporting body, an opposing electrode which is positioned face to face with the developer supplying means and to which a specified voltage is applied, an insulating substrate having a plurality of developer pass orifices and interposed between the developer supplying means and the opposing electrode, an image signal electrode which is disposed around the developer pass orifice of the insulating substrate and to which a voltage for controlling, in response to an image signal, the pass amount of the developer passing through the developer pass orifice, and an oscillation applying member, having an oscillation generating source and an oscillation transmitting body connected to the oscillation generating source and positioned in the vicinity of the developer pass orifice of the insulating substrate, for applying an oscillation to the insulating substrate, wherein the developer is adhered to an image receiving body placed between the opposing electrode and the insulating substrate or to the opposing electrode for forming an image. The image forming device of the twelfth invention further comprises a controlling means for bringing the operation of the developer supplying means to a halt and, at the same time, causing the oscillation applying means to operate, when no image formation is being performed.
As a result of such arrangement, application of an oscillation to the insulating substrate is carried out when no image is being formed (e.g., when the recording paper is being moved after the image formation), so that the already-formed image will not be disturbed even though the developer jumps out from the developer supporting body by the applied oscillation. Moreover, at such oscillation application time the operation of the developer supporting body is brought into a stop and no new developer is supplied, so that the amount of the developer jumping out from the developer supporting body becomes smaller.
Apart from the above, of the developer built up around the developer pass orifice of the insulating substrate, there exist not only developer particles of forward polarity but also developer particles of reverse polarity. If an oscillation is applied with the electric potential of the opposing electrode held at the same level as the image formation time, a force of flight from the opposing electrode toward the insulating substrate will act on such reverse-polarity developer particles. Therefore, even when the reverse-polarity developer particles are flown once from the insulating substrate toward the opposing electrode, these particles are forced into adverse flight toward the insulating substrate by the action force of an electric field, as a result of which the insulating substrate becomes contaminated. Moreover, if the opposing electrode remains at the same electric potential level as the image formation time, a developer that has jumped out from the developer supporting body by the oscillation application also returns to the insulating substrate and is likely to adhere thereto even when developer particles of reverse polarity of the developer are once moved toward the opposing electrode.
To cope with the above, an arrangement may be made in which, when no image formation is being carried out, the controlling means brings the operation of the developer supplying means to a halt while causing the oscillation applying means to operate and causes the opposing electrode and the developer supporting body to have the same electric potential at least at the early stage of an oscillation application operation by the oscillation applying member. As a result of such arrangement, at the time when an oscillation is applied, the opposing electrode and the developer supporting body are at the same electric potential level, thereby avoiding the returning of the reverse-polarity developer particles. As a result, the clogging of the insulating substrate is prevented. Further, another arrangement may be made in which the opposing electrode and the developer supporting body are at the same electric potential level during the entire period of oscillation application. Alternatively, the opposing electrode and the developer supporting body may be at the same potential level only at the early stage of oscillation application and thereafter their electric potential may be switched to an appropriate level. Even when such switching in electric potential is made, since an oscillation is applied with the operation of the developer supplying means stopped (i.e., without a new supply of developer), the jumping-out of a developer from the develop supporting body by the applied oscillation is almost completed at the early stage of the oscillation application. Therefore, a further jumping-out of the developer from the developer supporting body due to such electric potential switching, will be prevented.
Further, an arrangement may be made in which the opposing electrode is positioned movably so as to be able to change its face opposite to the developer supporting body, and when no image formation is being carried out, the controlling means brings the operation of the developer supplying means to a halt while causing the oscillation applying means to operate and causes the opposing electrode and the developer supporting body to have the same electric potential at least at the early stage of an oscillation application operation by the oscillation applying member while shifting the opposing electrode. As a result of such arrangement, a developer, flown from the insulating substrate toward the opposing electrode by application of an oscillation to the insulating substrate, moves to a position not facing the developer supporting body by movement of the opposing electrode. This therefore prevents the developer from adversely being brought back to around the developer pass orifice of the insulating substrate and facilitates collection of such a developer.
Further, an arrangement may be made in which, when no image formation is being carried out, the controlling means brings the operation of the developer supplying means to a halt while causing the oscillation applying means to operate, causes the opposing electrode and the developer supporting body to have the same electric potential at least at the early stage of an oscillation application operation by the oscillation applying member while shifting the opposing electrode, and thereafter changes the electric potential of the opposing electrode or the image signal electrode so as to form between the insulating substrate and the opposing electrode an electric field capable of aiding the flight of a charged developer from the insulating substrate toward the opposing electrode.
With this invention, since there is made a change in the electric potential of the opposing electrode or the image signal electrode while moving the opposing electrode, the face of the opposing electrode facing, at the early stage of the oscillation application, the developer supporting body, i.e., the developer pass orifice of the insulating substrate, will be placed in a different direction at the moment of such an electric potential change. This therefore prevents the developer, jumped out from the insulating substrate et cetera at the early stage of the oscillation application and then adhering to the opposing electrode, from being forced into adverse flight to around the developer pass orifice of the insulating substrate by a change in electric potential.
Further, since an electric field for aiding the flight of a charged developer from the insulating substrate toward the opposing electrode is formed between the insulating substrate and the opposing electrode by switching the electric potential of the opposing electrode or the image signal electrode, removal force by the electric field will act on the developer adhering to the insulating substrate in addition to mechanical removal force by the oscillation application. This facilitates removal of a developer strongly adhering to the insulating substrate. Moreover, it becomes possible to reduce oscillatory energy to be applied to the insulating substrate by enhancing the action force of the electric field, which is advantageous for avoiding troubles such as a liberation of heat by oscillation and debonding of the oscillation transmitting body.
An arrangement may be made in which an ac voltage is applied to the opposing electrode so that an electric field capable of aiding the flight of a charged developer from the insulating substrate toward the opposing electrode is formed between the insulating substrate and the opposing electrode. That is, there exist a developer of forward polarity and another of reverse polarity, so that the removal of developer particles overlying the insulating substrate is facilitated by application of an oscillation by the oscillation applying member and an alternating electric field by the aforesaid ac voltage.
Furthermore, an arrangement may be made in which, when no image formation is being carried out, the controlling means brings the operation of the developer supplying means to a halt while activating the oscillation applying means and reverse the relationship in electric potential size between the developer supporting body and the image signal electrode with respect to the relationship in electric potential size between the developer supporting body and the image signal electrode during the image formation. In this case, a change means for changing a voltage that is applied to the developer supporting body may be provided. This arrangement prevents, at the time of applying an oscillation, a developer from jumping out from the developer supporting body caused by such oscillation application. Moreover, by the action of the electric field, developer particles present between the developer supporting body and the insulating substrate are forced into flight toward the developer supporting body, thereby achieving effective developer removal.
A thirteenth invention of the present application is directed to an image forming device comprising a developer supplying means for charging a developer and supplying the charged developer supported on a developer supporting body, an opposing electrode which is positioned face to face with the developer supplying means and to which a specified voltage is applied, an insulating substrate having a plurality of developer pass orifices and interposed between the developer supplying means and the opposing electrode, an image signal electrode which is disposed around the developer pass orifice of the insulating substrate and to which a voltage for controlling, in response to an image signal, the pass amount of the developer passing through the developer pass orifice, and an oscillation applying member, having an oscillation generating source and an oscillation transmitting body connected to the oscillation generating source and positioned in the vicinity of the developer pass orifice of the insulating substrate, for applying an oscillation to the insulating substrate, wherein the developer is adhered to an image receiving body placed between the opposing electrode and the insulating substrate or to the opposing electrode for forming an image and, at the time when no image formation is being performed, the oscillation applying member is activated. Further, in the image forming device of the thirteenth invention, a plurality of image forming units, each units comprising a combination of the developer supplying means, the insulating substrate having the developer pass orifices and the image signal electrode, the oscillation applying member, and the opposing electrode, are provide, each of the oscillation applying members of the plurality of image forming units is driven independently of the other, and each of voltages of the opposing electrodes of the plurality of image forming units is controlled independently of the other.
As a result of such arrangement, it becomes possible to realize a multicolor image forming device by a plurality of image forming units of the present invention. Also in such a multicolor image forming device, each image forming unit operates independently of the other and there is no need for simultaneous oscillation application. Therefore, there is no need to provide individual driving circuits for the oscillation generating sources and individual power supplies for the opposing electrodes, which makes it possible to provide an inexpensive image forming device.
Further, the plural oscillation applying members are connected, through a drive switching means for sequential driving of the oscillation generating sources, to a single common driving circuit for driving the oscillation generating sources. This arrangement advantageously contributes to reducing the costs of the image forming device.
Furthermore, the driving circuit of the oscillation generating sources may be implemented by a frequency auto-following type circuit. That is, although a self-excited oscillator circuit can be employed as a driving circuit for the oscillation generating source, the natural frequency of an oscillatory system including the oscillation applying member and the insulating substrate varies greatly in some case because of, for example, the tension of the oscillation transmitting body and the insulating substrate. However, the use of a frequency auto-following type circuit makes it possible to apply stable oscillations to the insulating substrate without being affected greatly by the natural frequency.
Additionally, the plural opposing electrodes are connected, through a voltage switching means, to a single common power supply. In this case, there is no need to provide individual power supplies to the respective opposing electrodes, thereby advantageously contributing to lowering costs.
Further, preferably the oscillation applying member in the foregoing twelfth or thirteenth invention is formed as follows. That is, the plural developer pass orifices of the insulating substrate are arranged in a single row or in several rows, the oscillation transmitting body is disposed in parallel with the developer pass orifice row, the oscillation applying member is so configured as to apply an oscillation which becomes a progressive wave in a direction parallel to the developer pass orifice row and a standing wave in a direction orthogonal to the row direction of the developer pass orifice row.
Fourteenth and fifteenth inventions of the present application are particularly suitable for image forming devices with a transferring means. More specifically, an image forming device of the fourteenth invention comprises a developer supporting body for conveying and, at the same time, supporting a charged developer, an opposing electrode positioned face to face with the developer supporting body, an intermediate image holding member interposed between the developer supporting body and the opposing electrode, a developer pass controlling member, having an insulating substrate which is placed between the developer supporting body and the intermediate image holding member and through which a plurality of developer pass orifices are formed in a row and an image signal electrode which is arranged around each developer pass orifice in the insulating substrate and to which a voltage according to an image signal is applied, for forcing the developer on the developer supporting body into flight so as to pass through a specified developer pass orifice for adhesion onto the intermediate image holding member, a conveying means for conveying the intermediate image holding member, a transferring means for transferring an intermediate image on the intermediate image holding member onto an image receiving body, and a developer removing means for removing particles of the developer adhering to the developer pass controlling member. In the image forming device of the fourteenth invention, the transferring means is characterized in that it is so configured as to enter the non-operation state when the developer particles, removed from the developer pass controlling member and then adhering to the intermediate image holding member, have been conveyed.
As a result of such arrangement, developer particles adhering to the developer pass controlling member are removed by the operation of the developer removing means. In this way, the developer pass controlling member is cleaned. At this time, even when such a removed developer adheres to the intermediate image holding member, the transferring means is placed in its non-operation state when the developer has been conveyed. Therefore, the developer adhering to the intermediate image holding member will not be transferred onto the transferring means, thereby providing protection against contamination of the transferring means.
Further, preferably the transferring means is so configured as to be pushed toward the intermediate image holding member with the image receiving body caught between itself and the intermediate image holding member when placed in the operation state whereas, when placed in the non-operation state, the transferring means moves away from the intermediate image holding member. As a result of such arrangement, in the non-operation state the transferring means and the intermediate image holding member are physically separated from each other, thereby ensuring that contamination of the transferring means is prevented positively.
On the other hand, the image forming device of the fifteenth invention comprises a developer supporting body for conveying and, at the same time, supporting a charged developer, an opposing electrode positioned face to face with the developer supporting body, an intermediate image holding member interposed between the developer supporting body and the opposing electrode, a developer pass controlling member, having an insulating substrate which is placed between the developer supporting body and the intermediate image holding member and through which a plurality of developer pass orifices are formed in a row and an image signal electrode which is arranged around each developer pass orifice in the insulating substrate and to which a voltage according to an image signal is applied, for forcing the developer on the developer supporting body into flight so as to pass through a specified developer pass orifice for adhesion onto the intermediate image holding member, a conveying means for conveying the intermediate image holding member, a transferring means for transferring an intermediate image on the intermediate image holding member onto an image receiving body, and a developer removing means for removing particles of the developer adhering to the developer pass controlling member. The transferring means is characterized in that it includes a cleaning means for removing developer particles adhering to the transferring means. In this case, since the transferring means is kept clean at all times by the cleaning means, this provides protection against contamination of the inside of the device and contamination of the recording paper.
Each of the foregoing inventions can be applied to a device with a plurality of recording units. In such a case, the following configuration is preferable. That is, it is preferable that a plurality of recording units are provided, each recording unit including the developer supporting body, the opposing electrode, the developer pass controlling member, and the developer removing means, that the conveying means is so configured as to successively convey the intermediate image holding member between the developer pass controlling member and the opposing electrode of each recording unit, that the developer pass controlling members of the plural recording units are so configured as to operate one after another at intervals of a first time difference for forming on the intermediate image holding member an intermediate image resulting from superimposition of developers from the plural recording units, and that the developer removing means of the plural recording units are so configured as to operate one after another at intervals of a second time difference different from the first time difference for preventing respective developers removed from the plural recording units by the developer removing means from being superimposed on the intermediate image holding member.
As a result of such arrangement, the operation timing of the developer removing means differs for each recording unit, therefore causing the adhesion position of developers removed from the developer pass controlling members on the intermediate image holding member to be scattered. This therefore provides protection against accumulation of developer particles from the respective recording units at the same area in the intermediate image holding member. This provides positive protection against contamination caused by direct contact of the accumulated developer particles and the developer pass controlling member and against adverse flight of the developer toward the developer pass controlling member.
Further, it is preferable that the developer removing means comprises an oscillation applying member including an oscillation generating source for applying an oscillation to developer pass orifice portions of the developer pass controlling member.when the developer pass controlling member is in the non-operation state and an oscillation transmitting body connected, at at least one of ends thereof, to the oscillation generating source and disposed on the developer pass controlling member so as to extend parallel to the developer pass orifice row for transmitting an oscillation from the oscillation generating source to each developer pass orifice portion of the developer pass controlling member. Further, it is preferable that the oscillation applying member is so configured as to apply an oscillation which becomes a progressive wave in a direction parallel to the developer pass orifice row and a standing wave in a direction orthogonal to the developer pass orifice row.
A sixteenth invention of the present application is an invention suitable for multicolor image forming devices. More specifically, the sixteenth invention is directed to an image forming device comprising a developer supporting body which rotates with a developer electro-magnetically supported on its peripheral surface, an opposing electrode, placed face to face with the developer supporting body, for electro-magnetically attracting the developer supported on the developer supporting body and a developer pass controlling member, interposed between the developer supporting body and the opposing electrode and having at least one developer pass orifice row arranged in the rotational axis direction of the developer supporting body, for controlling the passing of the developer through the developer pass orifices in response to an external image signal, wherein an image receiving body is interposed between the opposing electrode and the developer pass controlling member for adhesion of the developer thereonto. In the image forming device of the sixteenth invention, the image forming device further comprises a plurality of print heads each comprising a combination of the developer supporting body and the developer pass controlling member, the image receiving body is so positioned as to successively pass through between the developer pass controlling member and the opposing electrode of each print head, and the image forming device further comprises an oscillation applying member, positioned in the developer pass controlling member of each print head and extending along the developer pass orifice row, for applying an oscillation to the developer pass controlling members and an oscillation reflecting body, positioned in the developer pass controlling member of each print head and placed opposite the oscillation applying member across the developer pass orifice row, for reflecting an oscillatory wave transmitted from the oscillation applying member.
With this invention, it is possible to realize a multicolor image forming device with a plurality of print heads. Owing to the reflection of an oscillatory wave by the oscillation reflecting body, the transmission efficiency of oscillation is improved and it is also possible to form a standing wave between the oscillation applying member and the oscillation reflecting body. If the developer pass orifice portions or their neighboring areas are arranged not to correspond to nodes of the standing wave, this makes it possible to cause these portions to be oscillated greatly by the standing wave. This provides effective protection against a buildup of developer deposits in the inside of the developer pass orifices and therearound.
The plurality of print heads may be provided with individual oscillation generating sources each of which is driven independently of the other for driving its oscillation applying member. In this case, even when a multicolor image forming device is formed, each of oscillators of the print heads operates independently of the other and there is no need for simultaneous application of oscillations, therefore eliminating the need for the provision of individual driving circuits for driving these oscillation generating sources. This advantageously contributes to reducing the costs of the image forming device.
Further, an arrangement may be made in which each print head has the oscillation applying member and the oscillation reflecting body, the oscillation applying member and the oscillation reflecting body being positioned opposite to each other across the developer pass orifice so as to be disposed on the front side and on the far side, respectively, with respect to the traveling direction of the image receiving body.
That is to say, as stated above, of the toner deposited around the developer pass orifice of the developer pass controlling means there exist not only toner particles of forward polarity (toner particles which exhibit a polarity capable of electro-magnetically being attracted by the opposing electrode) but also toner particles of reverse polarity. Therefore, together with the toner particles of forward polarity, the toner particles of reverse polarity are forced into flight toward the image receiving body by toner-to-toner cohesion and adhesion. In such an arrangement that the image receiving body successively passes through the plural print heads, when a toner of reverse polarity, supplied from a print head which has previously been passed through by the image receiving body and adhering to the image receiving body, reaches the next print head, the toner is forced into adverse flight toward the developer pass controlling means of the next print head from the image receiving body by electro-magnetic force. This may result in contamination of the periphery of the developer pass orifice.
On the other hand, even when a toner of reverse polarity, supplied to the image receiving body from the previously passed-through print head and adhering thereto, is forced into adverse flight at an area of the next print head, if the oscillation applying member and the oscillation reflecting member are disposed on the front side and on the far side, respectively, with respect to the traveling direction of the image receiving body, this prevents the toner from readily adhering to around the developer pass orifice by an oscillation applied by the oscillation applying member to the developer pass controlling means of that print head and, even when adhered to around the developer pass orifice the adhered toner will be removed with ease. Accordingly, this provides protection against contamination of the developer pass controlling means of the next print head by toner particles of the previous print head.
Further, the oscillation applying members of the plural print heads may be connected to a single common oscillation generating source by which the oscillation applying members are oscillated. In this case, the single oscillation generating source is shared between the plural print heads, thereby advantageously contributing to reducing the costs of the image forming device.
Furthermore, it is preferable that an oscillation cutting-off means for cutting off the transfer of an oscillation from the common oscillation generating source to each oscillation applying member is interposed therebetween. In this case, even when the single oscillation generating source is shared between each print head, each of the oscillation applying members of the print heads can be operated independently of the other by the operation of the oscillation cutting-off means. This is useful when cleaning the developer pass controlling means by selectively causing the oscillation applying member of each print head to operate at the time when no image is being formed in any print head, i.e., at the time when no image is being formed by control of the developer pass controlling means, instead of causing the oscillation applying member of each print head to operate at all times.
Seventeenth to nineteenth inventions of the present application are inventions suitable for applying oscillations from both sides positioned opposite each other across the developer pass orifice row. More specifically, an image forming device of the seventeenth invention comprises a developer supporting body for supporting and conveying a charged developer, a developer pass controlling member, having a developer pass orifice row of a plurality of developer pass orifices through which the developer passes, for controlling, in response to an external image signal, the passing of the developer supplied from the developer supporting body through the developer pass orifices, and an image receiving body onto which the developer, which has passed through a developer pass orifice, adheres. The developer pass controlling member has an insulating substrate in which the developer pass orifices are formed, a pair of bar-like oscillation transmitting bodies are positioned opposite each other across the developer pass orifice row and extend along the developer pass orifice row, and oscillation generating sources are disposed at both ends of each of the pair of oscillation transmitting bodies.
Further, an image forming device of the eighteenth invention comprises a developer supporting body for supporting and conveying a charged developer, a developer pass controlling member, having a developer pass orifice row of a plurality of developer pass orifices through which the developer passes, for controlling, in response to an external image signal, the passing of the developer supplied from the developer supporting body through the developer pass orifices, and an image receiving body onto which the developer, which has passed through a developer pass orifice, adheres. The developer pass controlling member has an insulating substrate in which the developer pass orifices are formed, one ends of bar-like oscillation transmitting bodies, positioned opposite each other across the developer pass orifice row and extending along the developer pass orifice row, are connected together to form a U-shaped oscillation transmitting body, and an oscillation generating source is disposed in the oscillation transmitting body.
In such a case, oscillations from positions on both sides of the developer pass orifice row are transmitted to the developer pass orifice row, thereby causing the periphery of the developer pass orifice row to be oscillated greatly. This ensures that a buildup of developer deposits is prevented more positively.
Further, in the eighteenth invention, an arrangement may be made in which an oscillation generating source is disposed at each end of the oscillation transmitting body. In this case, oscillations by the oscillation generating sources positioned at the both ends of the oscillation transmitting body propagate through the oscillation transmitting body, as a result of which the oscillation transmitting body is oscillated greatly. This causes the insulating substrate to undergo much greater oscillation. This ensures that the buildup of developer deposits is prevented more effectively.
Further, in the eighteenth invention, another arrangement may be made in which the both ends of the U-shaped oscillation transmitting body are connected together to form an annular oscillation transmitting body. In this case, if a plurality of oscillation generating sources are provided at parts of the oscillation transmitting body, this causes the insulating substrate to be oscillated more greatly.
For the case of the provision of a plurality of oscillation generating sources as described above, it is preferable that the oscillation generating sources are so configured as to differ in oscillation phase from each other. In this case, there is generated a progressive wave in the oscillation transmitting body, thereby preventing formation of a portion that becomes a node in the insulating substrate. Because of this, the entire insulating substrate is uniformly oscillated, thereby eliminating the inconvenience that developer deposits build up in portions corresponding to nodes of oscillation mode.
The oscillation generating source may be so configured as to operate at all times when the developer pass controlling member is in operation and a detecting means for detecting whether the developer pass orifice becomes clogged may be provided in which the oscillation generating source is so configured as to operate according to the detection result. Here, the detecting means is so designed to directly detect clogging of the developer pass orifice or to detect whether the image is formed normally by test printing. More specifically, an arrangement may be made in which the detecting means is made up of a light emitting means capable of light emission toward the image receiving body and a light receiving means capable of receiving reflected light resulting from reflection of light emitted from the light emitting means by the image receiving body, and the detecting means thus configured detects whether the image is formed normally from the absence or presence of reflected light.
Further, an image forming device of the nineteenth invention comprises a developer supporting body for supporting and conveying a charged developer, a developer pass controlling member, having a developer pass orifice row of a plurality of developer pass orifices through which the developer passes, for controlling, in response to an external image signal, the passing of the developer supplied from the developer supporting body through the developer pass orifices, and an image receiving body onto which the developer, which has passed through a developer pass orifice, adheres. In the image forming device of the nineteenth invention, the developer pass controlling member has an insulating substrate in which the developer pass orifices are formed, an oscillation transmitting body, one end of which is fixed to the insulating substrate whereas the other end is oscillatably configured so as to cause the insulating substrate to be oscillated, is disposed on each side of the developer pass orifice row of the insulating substrate, extending along the developer pass orifice row, and an oscillation generating source is disposed on the oscillation transmitting body.
An arrangement may be made in which the oscillation transmitting body is formed into a flat plate-like shape extending along the developer pass orifice row and an end of the flat plate-like oscillation transmitting body on the far side with respect to the developer pass orifice row is fixed to the insulating substrate and a plurality of the oscillation generating sources are disposed along the developer pass orifice row.
Furthermore, an arrangement may be made in which the oscillation transmitting body is formed into a comb-like shape extending along the developer pass orifice row and an end of each of comb teeth of the comb-like oscillation transmitting body on the far side thereof with respect to the developer pass orifice row is fixed to the insulating substrate and the oscillation generating source is disposed on each of the comb teeth.
In this case, when the oscillation generating source oscillates, the other end of the oscillation transmitting body bends and strikes the insulating substrate. This causes the insulating substrate to be oscillated, thereby preventing a buildup of developer deposits. As a result, the clogging of the developer pass orifice is prevented and stable image formation is achieved.
An arrangement may be made in which the oscillation generating sources disposed on the oscillation transmitting bodies on both sides of the developer pass orifice row are arranged at the same pitch and oscillation generating sources on one side of the developer pass orifice row are so arranged as to be half-pitch deviated with respect to oscillation generating sources on the other side. If the oscillation generating sources on the oscillation transmitting bodies on both sides of the developer pass orifice row are arranged at the same pitch so that oscillation generating sources on the one side are positioned face to face with their corresponding oscillation generating sources on the other side, this creates regions not sandwiched between oscillators in the developer pass orifice row. In these regions, the magnitude of oscillation becomes relatively small. To cope with this, the oscillation generating sources on the oscillation transmitting bodies on the one side are arranged so as to be half-pitch deviated with respect to the oscillation generating sources on the oscillation transmitting bodies on the other side, which makes it possible to cause the entire developer pass orifice row to be oscillated uniformly. This prevents a buildup of developer deposits all over the developer pass orifice row.
An arrangement may be made in which each of the oscillation generating sources is oscillated by application of a voltage and the phases of voltages that are applied to the oscillation generating sources on the oscillation transmitting bodies on each side are the same. In this case, oscillations from each side are synthesized, thereby making it possible to cause the periphery of the developer pass orifice row to be oscillated more greatly. On the other hand, the phases of voltages that are applied to the oscillation generating sources on the oscillation transmitting bodies on each side may be deviated from each other. In this case, it is possible to cause every region in the vicinity of the developer pass orifice row to be oscillated uniformly and in each case it is possible to effectively prevent a buildup of developer deposits.
It is preferable that an oscillatory system, made up of the oscillation transmitting body on each side, the oscillation generating source on each side, and the insulating substrate, is so configured as not to causes a node of the oscillation at the position of each developer pass orifice. For example, it is preferable that the oscillatory system is so configured as to become either a primary oscillatory mode or a tertiary oscillatory mode. That is, if the position of a developer pass orifice corresponds to a node of the oscillation, this reduces the oscillation of the periphery of the developer pass orifice, resulting in being unsatisfactory for protection against a buildup of developer deposits. Accordingly, it is preferable that the position of each developer pass orifice is so arranged as not to correspond to a node of the oscillation. Particularly, if the oscillatory system is either a primary oscillatory mode or a tertiary oscillatory mode, this causes the position of each developer pass orifice to correspond to an antinode of the oscillation, thereby causing the periphery of the developer pass orifice to be oscillated greatly.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a diagram schematically showing an arrangement of an image forming device.
Figure 2(a) is a cross-sectional view taken along line A-A of Figure 2(b) and Figure 2(b) is a top plan view of a print head.
Figure 3 is a perspective view of a print head in relation to a preferred embodiment (a first embodiment) for print head oscillation.
Figure 4 is a corresponding diagram to Figure 3, showing a print head in relation to a variation.
Figure 5 is a corresponding diagram to Figure 3, showing a print head in relation to another variation.
Figure 6 is a corresponding diagram to Figure 3, showing a print head in relation to still another variation.
Figure 7 is a diagram showing an arrangement of an oscillation generating body in relation to a variation.
Figure 8 is a perspective view of a print head in relation to a preferred embodiment (a second embodiment) for print head oscillation.
Figure 9 is a top plan view of the print head.
Figure 10 is a cross-sectional view taken along line B-B of Figure 9.
Figure 11 is a corresponding diagram to Figure 8, showing a print head in relation to a variation.
Figure 12 is a cross-sectional view of the print head in relation to the variation.
Figure 13 is a perspective view of a print head in relation to a preferred embodiment for causing the periphery of a developer pass orifice to be oscillated at large amplitudes.
Figure 14 is a cross-sectional view of the print head.
Figure 15 is a corresponding diagram to Figure 14, showing a print head in relation to a variation.
Figure 16 is a corresponding diagram to Figure 14, showing a print head in relation to another variation.
Figure 17 is a corresponding diagram to Figure 14, showing a print head in relation to still another variation.
Figure 18 is a corresponding diagram to Figure 14, showing a print head in relation to a further variation.
Figure 19 is a corresponding diagram to Figure 14, showing a print head in relation to a still further variation.
Figure 20 is a corresponding diagram to Figure 14, showing a print head in relation to a variation.
Figure 21 is a diagram showing a relationship between the damping of an oscillation in a controlling plate and the space between an oscillation transmitting plate and a holding member.
Figure 22 is a perspective view of a print head in relation to a preferred embodiment (a first embodiment) for uniform oscillation in the direction of a row of developer pass orifices.
Figure 23 is a side view of an oscillation generating body.
Figure 24 is a perspective view of a print head in relation to a preferred embodiment (a second embodiment) for uniform oscillation in the direction of a row of developer pass orifices.
Figure 25(a) is a top plan view of an oscillation absorbing body, Figure 25(b) is a front view of the oscillation absorbing body, and Figure 25(c) is a side view of the oscillation absorbing body.
Figure 26 is a perspective view of a print head in relation to a preferred embodiment (a third embodiment) for uniform oscillation in the direction of a row of developer pass orifices.
Figure 27 is a perspective view of a print head in relation to a preferred embodiment (a fourth embodiment) for uniform oscillation in the direction of a row of developer pass orifices.
Figure 28 is a cross-sectional view showing in detail an arrangement of an auxiliary oscillation agitator.
Figure 29 is a top plan view of an oscillation transmitting plate in relation to a preferred embodiment (a first embodiment) for oscillation-damping suppression.
Figure 30 is a perspective view of a controlling plate in relation to a preferred embodiment (a second embodiment) for oscillation-damping suppression.
Figure 31(a) is a top plan view of a controlling plate in relation to a preferred embodiment (a third embodiment) for oscillation-damping suppression and Figure 31(b) is a cross-sectional view taken along line C-C of Figure 31(a).
Figure 32 is a top plan view of an oscillation transmitting plate in relation to a preferred embodiment (a fourth embodiment) for oscillation-damping suppression.
Figure 33 is a diagram schematically showing an arrangement of an image forming device in relation to a preferred embodiment (a second embodiment) for protection against contamination by removed toner particles.
Figure 34 is a diagram schematically showing an arrangement of an image forming device in relation to a preferred embodiment (a third embodiment) for protection against contamination by removed toner particles.
Figure 35 is a diagram schematically showing an arrangement of an image forming device in relation to a preferred embodiment (a fourth embodiment) for protection against contamination by removed toner particles.
Figure 36 is a diagram schematically showing an arrangement of an image forming device in relation to a preferred embodiment (a first embodiment) for protection against contamination of a transfer mechanism by removed toner particles.
Figure 37 is a diagram schematically showing an arrangement of an image forming device in relation to a preferred embodiment (a second embodiment) for protection against contamination of a transfer mechanism by removed toner particles.
Figure 38 is a diagram schematically showing an arrangement of an image forming device in relation to a preferred embodiment (a third embodiment) for protection against contamination of a transfer mechanism by removed toner particles.
Figure 39 is a timing chart of the operation of a print head.
Figure 40 is a timing chart of the operation of a print head in relation to a variation.
Figure 41 is a perspective view of a print head unit.
Figure 42 is a schematic diagram of an image forming device in relation to a preferred embodiment (a first embodiment) for multicolor image forming device cleaning.
Figure 43 is a circuit diagram for driving of an oscillator in relation to a preferred embodiment (a second embodiment) for multicolor image forming device cleaning.
Figure 44 is an explanatory diagram of an oscillation applying member in relation to a preferred embodiment (a third embodiment) for multicolor image forming device cleaning.

BEST MODES FOR CARRYING OUT THE INVENTION

By making reference to the accompanying drawings, embodiments of the present invention will be described below.
Referring to Figure 1, there is shown an arrangement of an image forming device according to the present embodiment. In Figure 1, the toner conveying roller 1 supports and, at the same time, conveys a toner 4 as a developer. Further, the toner conveying roller 1 serves also as a charging electrode capable of charging the toner 4. The toner conveying roller 1 can be composed of metal such as aluminum and iron and of alloy. Preferably, the outer diameter of the toner conveying roller 1 is from about 16 mm to about 20 mm. In the present embodiment, as the toner conveying roller 1, a cylinder of aluminum, having an outer diameter of 20 mm and a thickness of 1 mm, is used. Further, the toner conveying roller 1 is connected to ground, which is however not to be deemed restrictive. For example, a dc voltage or an ac voltage may be applied to the toner conveying roller 1.
The regulating blade 2 is for formation of from one to three layers of toner on the toner conveying roller 1. The regulating blade 2 is composed of an elastic member such as urethane and its hardness, free end length (the length of a portion projecting from the installation part), and linear load to the toner conveying roller 1 are preferably from 40 degrees to 80 degrees ( JIS K6301 A-Scale), from 5 mm to 15 mm, and from 5 g/cm to 40 g/cm, respectively. The regulating blade 2 may be placed electrically in the float state or connected to ground. Alternatively, a dc voltage or an ac voltage may be applied to the regulating blade 2. In the present embodiment, the regulating blade 2 is used in the float state.
The toner 4 is caught between the toner conveying roller 1 and the regulating blade 2 and subjected to slight agitation there. Then, the toner 4 receives an electric charge from the toner conveying roller 1 and becomes charged. In the present embodiment, as the toner 4, particles of a nonmagnetic substance, having a negative charge of - 10 µC/g and an average particle diameter of 8 µm, are used.
The supplying roller 3 is formed by applying, for about 2 mm to about 6 mm, synthetic rubber such as expanded urethane around a metallic shaft of iron or the like (a metallic shaft having a diameter of 8 mm is used in the present embodiment) and its hardness is 30 degrees (one processed in the form of a roller was measured using a method according to JIS K6301 A-Scale). The amount of penetration of the supplying roller 3 into the toner conveying roller 1 is preferably from about 0.1 mm to about 2 mm. Also, the supplying roller 3 may be configured to be connected to ground. Alternatively, a dc voltage or an ac voltage may be applied to the supplying roller 3. The supplying roller 3 helps the charging of the toner 4. In addition, the supplying roller 3 controls the supply amount of the toner 4.
The opposing electrode 5 is for forming an electric field between itself and the toner conveying roller 1. As a material to form the opposing electrode 5, a metallic plate, a metallic roller, a film formed by dispersing conductive fillers in a resin, or the like is preferably used. Further, when such a film is employed as the opposing electrode 5, its resistance is preferably from about 10² to about 10¹¹ Ω/cm. Applied from a dc power supply 9 to the opposing electrode 5 is a dc voltage of from about 500 to about 2000 V. In the present embodiment, a dc voltage of 1000 V is applied to the opposing electrode 5.
As the recording method, a method may be employed wherein the toner 4 is adhered onto a conveyor belt (not shown in the figure) for formation of an image thereon and the image thus formed is transferred to a sheet of recording paper for fixation thereon. However, in the present embodiment, a sheet of recording paper 6 is placed overlying the opposing electrode 6 and the toner 4 is adhered thereonto for direct image formation on the recording paper 6, as shown in Figure 1. Alternatively, an arrangement may be made in which the opposing electrode 5 is processed in the form of an endless film and an image is formed directly on the film and thereafter the formed image is transferred onto the recording paper. When forming an image, the recording paper 6 is fed at a specified rate by a paper feeding roller 7. In the present embodiment, the rate at which the recording paper 6 is fed is 65 mm/s.
Referring to Figure 2, there is schematically shown an arrangement of the print head 10 disposed between the toner conveying roller 1 and the opposing electrode 5. Figure 2(a) is a cross-sectional view of the print head 10. Figure 2(b) is a top plan view of the print head 10 when viewed from the side of the toner conveying roller 1. Further, in Figure 2(b), the lateral direction of the drawing is the direction in which the recording paper travels (the Y direction) and the vertical direction is the crosswise direction of the recording paper (the X direction).
As shown in Figure 2, a plurality of orifices 12 as developer pass orifices are formed through an insulating substrate 14 of the controlling plate 30. These orifices 12 form an orifice row 12A arranged along the recording paper crosswise direction. The number of the orifice rows 12A is not limited to two. The number of the orifice rows 12A may be one or three or more. Positioned at a surface of the toner conveying roller 1 of the insulating substrate 14 are a plurality of image signal electrodes 11 that are formed into a ring shape so as to enclose each orifice 12. This is not deemed restrictive. For example, the image signal electrode 11 may be positioned on the internal wall of the orifice 12. In the present embodiment, a ring-like electrode having an internal diameter of 150 µm and an outer diameter of 250 µm is used as the image signal electrode 11. A thin insulating resin layer (not shown in the figure) having a thickness of 5 µm to 20 µm is formed on the surface of each electrode.
It is preferable that the insulating substrate 14 of the controlling plate 30 be formed of an insulating film having a thickness of 10 to 100 µm. Materials such as polyimide and polyethylene terephtalate are preferably used to form the insulating substrate 14. In the present embodiment, an insulating film of polyimide having a thickness of 25 µm is used. The orifices 12 are arranged in staggered fashion for mutual interpolation in order that a full black image is formed when toner is emitted from all the orifices 12. The diameter of the orifice 12 is preferably 50 to 200 µm. In the present embodiment, the diameter of the orifice 12 is 145 µm. The image signal electrode 11 is composed of metal such as copper and preferably has a thickness of 5 to 30 µm. Each image signal electrode 11 is individually connected, through a lead line 31A, to an image signal power supply 13 which is an image signal voltage switching means. Further, a voltage of about 400 V is usually applied to the image signal electrode 11. In the present invention, a voltage of 300 V is applied for the formation of dots. On the other hand, a voltage of -100 V is applied for the non-formation of dots. The distance between the opposing electrode 5 and the controlling plate 30 preferably ranges between 50 µm and 1000 µm. In the present embodiment, the distance is 250 µm. Further, the distance between the toner conveying roller 1 and the controlling plate 30 is preferably from 0 µm to 200 µm. In the present embodiment, the distance is 30 µm.
Further, an arrangement may be made, in which one end of the controlling plate 30 is fixed to the print head unit whereas the other end thereof is stretched by, for example, a spring so that tension is applied to the controlling plate 30.
Next, the operation of the image forming device of the present embodiment will be described below.
When a voltage whose level is above a specified value is applied to the image signal electrode 11 in response to an external image signal, an acceleration electric field is created between the toner conveying roller 1 and the image signal electrode 11. The toner 4 on the toner conveying roller 1 overcomes the toner conveying roller 1 in image force and starts flying toward the image signal electrode 11. Then the toner 4, forced into flight, passes through the orifice 12 enclosed by the image signal electrode 11. Having passed through the orifice 12, the toner 4 is pulled by a voltage applied to the opposing electrode 5 in the direction of the opposing electrode 5 and lands on the recording paper 6. On the other hand, when a voltage of less than the specified value (including zero) is applied to the image signal electrode 11, the toner 4 on the toner conveying roller 1 is not forced into flight. Therefore, the toner 4 remains supported on the toner conveying roller 1 because the intensity of an electric field formed between the toner conveying roller 1 and the image signal electrode 11 is insufficient. Further, in order to obtain the same effects as above, an arrangement may be made, in which a voltage of reverse polarity is applied to the image signal electrode 11 so that the direction of an electric field between the toner conveying roller 1 and the image signal electrode 11 is reversed.
Thereafter, the toner 4 adhering to the recording paper 6 is fixed by a fixing roller 8, thereby making a record of the desired image on the recording paper 6.
As image formation is repeatedly carried out, the toner 4 and contaminants will be built up in the vicinity of the orifice 12 of the controlling plate 30. To cope with such a buildup of toner/contaminant deposits, the following step is taken. That is, during image formation, or in the period during which image formation is brought into a halt (for example, immediately after the power is applied to the device, and during the period from the time that a sheet of recording paper 6 passes through between the controlling plate 30 and the opposing electrode 5 to the time that a next sheet of recording paper 6 is fed when forming in succession an image on plural sheets of recording paper 6), the controlling plate 30 is oscillated for removal of the toner 4 accumulated in the vicinity of the orifice 12.

PREFERRED EMBODIMENTS FOR OSCILLATING CONTROLLING PLATE

Next, preferred embodiments for causing the controlling plate 30 to be oscillated will be described.

(EMBODIMENT 1)

Figure 3 shows the controlling plate 30 developed in plane. An oscillation transmitting plate 151 is disposed in parallel with the orifice row 12A of the controlling plate 30. In other words, the oscillation transmitting plate 151 is so disposed as to extend along the rotation axis direction of the toner conveying roller 1. The oscillation transmitting plate 151 is formed into a bar-like shape and adhered to the controlling plate 30. Such adhesion can be implemented by thermocompression bonding or by the use of epoxy adhesive or isocyanate adhesive. Provided at both ends of the oscillation transmitting plate 151 are oscillation generating bodies 60 and 60.
The oscillation generating body 60 includes an oscillator 16 and an oscillation amplifier ( horn) 17. For example, as the oscillator 16, a bolted oscillator of the Langevin type can be used. The oscillator 16 is attached to the horn 17. The horn 17 is formed such that as it extends downward its cross-sectional area continuously and smoothly decreases and the oscillatory energy of the oscillator 16 is concentrated for transmission to the oscillation transmitting plate 151.
The oscillation transmitting plate 151 should have such a rigidity that an oscillation is not absorbed but transmitted. For example, the oscillation transmitting plate 151 may be formed of metal. More specifically, stainless steel may be used to form the oscillation transmitting plate 151 and its plate width and thickness may be 5 mm and about 0.2 mm, respectively. The horn 17 also should have such a rigidity that an oscillation is not absorbed but transmitted. It is preferable that the horn 17 has the same natural frequency as the oscillator 16. The horn 17 may be formed of metal. More specifically, it is preferable for the horn 17 to be formed of stainless steel or aluminum because of easy formation.
A sine wave of not more than 1 MHz (e.g., 20 kHz) is preferable for the oscillation frequency of the oscillator 16. This is because that if the oscillating frequency becomes high it is impossible to ignore a liberation of heat in a surface where the controlling plate 30 and the oscillation transmitting plate 151 are adhered together and because that the degree of oscillation damping increases.
Next, the operation of applying an oscillation to the controlling plate 30 will be explained.
When a voltage is applied to the oscillators 16 and 16, the oscillation of each oscillator 16 is transmitted, through the oscillation transmitting plate 151, to the controlling plate 30.
Since the insulating substrate 14 of the controlling plate 30 is formed of polyimide or the like, the insulating substrate 14 exhibits viscoelasticity. Because of this, if the oscillator 16 is disposed directly on the controlling plate 30, the oscillation of the oscillator 16 will be absorbed by the time that the oscillations have reached the orifice row 12A. However, if the oscillation transmitting plate 151 is disposed overlying the controlling plate 30 and the oscillation of the oscillator 16 is made to propagate to the oscillation transmitting plate 151, this arrangement makes it possible to cause the oscillation of the oscillator 16 to be transmitted to the orifice row 12A. Further, the oscillator 16 is attached to the horn 17, thereby making it possible to amplify the oscillation of the oscillator 16 for propagation to the oscillation transmitting plate 151. Moreover, if the phases of voltages that are applied to the pair of the oscillators 16 and 16 are so set as to differ from each other, this creates a progressive wave in the oscillation transmitting plate 151. This therefore prevents a portion which becomes a node of the oscillation from being formed in the controlling plate 30. As a result, the entire controlling plate 30 is oscillated, thereby eliminating the inconvenience that the toner 4 is deposited on the node portion.
Here, oscillation suitable for cleaning in the vicinity of the orifice 12 depends upon the oscillatory system. If the amplitude is 20 µm and the frequency is 20 kHz, this setting was found to achieve efficient cleaning. This value, when converted into oscillation accelerations (the single amplitude a = 10 µm; the frequency = 20 kHz), becomes a velocity maximum value νmax = 1.3m/s and an acceleration maximum value αmax = 1.6 x 10⁵m/s², for the oscillation displacement x = a sinω t, the velocity ν = a ωcosωt, the acceleration αv = - a ω²sinω t (t: time; ω: angular speed = 2 πf; π: pi; f: frequency). This acceleration is compared with an acceleration by an electric field. An acceleration by an electric field acting on a toner at the time of printing is F = qE = m × (Q/M) x E = mαe, where F is the electric field force, q is the charge amount, E is the electric field, Q/M is the charge amount per toner weight, m is the mass of a single toner particle, and αe is the acceleration. Accordingly, αe = (Q/M) × E = (Q/M) × Vc/Lk (Vc: the voltage applied to the signal electrode at the time of printing; Lk: the distance between the toner conveying roller and the signal electrode). Here, the charge amount per toner weight (Q/M) = 10 µC/g, Vc = 300 V, and Lk = 30 µm, so that αe = 10 × 10⁵m/s². That is, an oscillation acceleration greater than an electric field force acting on toner at the time of printing acts on the toner particles adhering to around the orifice, and efficient cleaning can be obtained.

(VARIATION)

Further, the oscillation transmitting plate 15 and the oscillation generating body 60 may be positioned opposite each other across the orifice row 12A. Further, as shown in Figure 4, a pair of bar-like oscillating plates are disposed opposite each other across the orifice row 12A and one ends of the oscillating plates are connected together to form a U-shaped oscillation transmitting plate 152. In this case, as shown in Figure 4, the oscillation generating bodies 60 and 60 may be disposed at both ends of the U-shaped oscillation transmitting plate 152. Furthermore, as shown in Figure 5, a pair of bar-like oscillating plates are disposed opposite each other across the orifice row 12A and one ends and other ends of the oscillating plates are connected together to form an annular oscillation transmitting plate 153. In this case, as shown in Figure 5, the oscillation generating bodies 60 and 60 may be disposed at curbed portions at both ends of the annular oscillation transmitting plate 153.
Further, an alternative arrangement may be made in which the oscillation generating body 60 is disposed at only one end of a bar-like oscillation transmitting plate 154, as shown in Figure 6. In this case, the other end of the oscillation transmitting plate 154 may be fixed.
Additionally, the oscillation generating body is not limited to a combination of the oscillator 16 and the horn 17. As shown in Figure 7, the oscillation generating body may be implemented by a bimorph which is a combination of piezoelectric elements 18 and 19. Employment of such an arrangement makes it possible to provide a down-sized oscillation generating body.

(EMBODIMENT 2)

Referring to Figure 8, there is shown the controlling plate 30 according to the second embodiment. A pair of oscillation generating bodies 160 and 160, positioned opposite each other across the orifice row 12A, each extend along the orifice row 12A. Note that one of the oscillation generating bodies 160 and 160 positioned opposite each other across the orifice row 12A is not shown in the figure.
Each oscillation generating body 160 is comb-shaped extending along the orifice row 12A. A far-side end of each comb tooth 161 with respect to the orifice row 12A is jointed to a fixing portion adhered to the controlling plate 30. Each comb tooth 161 has a cantilever structure (see Figure 8 or Figure 10).
Furthermore, as shown in Figure 9, the comb teeth 161 of the oscillation generating bodies 160 and 160 on both sides of the orifice row 12A are arranged at the same pitch and the comb teeth 161 of the oscillation generating body 160 on one side are arranged to be half-pitch deviated from their corresponding comb teeth 161 of the oscillation generating body 160 on the other side. Mounted on each comb tooth 161 is an oscillator 162. It is designed such that the phase of voltages that are applied to the oscillators 162 of the oscillation generating body 160 disposed on one side of the orifice row 12A is deviated from the phase of voltages that are applied to the oscillators 162 of the oscillation generating body 160 disposed on the other side.
Next, the operation of applying an oscillation to the controlling plate 30 will be described.
A voltage is applied to each oscillator 162. When the oscillator 162 is oscillated, the comb tooth 161 having a cantilever structure undergoes flexure and its free end starts striking the controlling plate 30. This causes the controlling plate 30 to be oscillated for protection against a buildup of toner deposits. As a result, the clogging of the orifice 12 is prevented, thereby making it possible to realize stable image-formation.
Further, since the comb teeth 161, 161, ... are arranged along the orifice row 12A, this makes it possible to cause the entire orifice row 12A to be oscillated. This effectively oscillates the periphery of the orifice 12.
Furthermore, since the pair of the oscillation generating bodies 160 and 160 are arranged opposite each other across the orifice row 12A, oscillations are transmitted to the orifice row 12A from both lateral directions thereof. This makes it possible to relatively increase the oscillation of the periphery of the orifice 12. As a result, it becomes possible to provide effective protection against a buildup of toner deposits in the vicinity of the orifices 12.
Further, if the oscillators 162, 162, ... on the oscillation generating bodies 160 and 160 on both sides of the orifice row 12A are disposed at the same pitch so as to be positioned face to face with each other, this results in producing a region in the orifice row 12A that is not sandwiched between a pair of oscillators 162 and 162. In such a region, the degree of oscillation becomes relatively small. However, if the oscillators 162, 162, ... on the oscillation generating bodies 160 and 160 positioned on both sides of the orifice row 12A are disposed at the same pitch and the oscillators 162 on the oscillation generating body 160 on one side of the orifice row 12A are deviated half pitch from the oscillators 162 on the oscillation generating body 160 on the other side, this arrangement makes it possible to cause the entire orifice row 12A to be oscillated uniformly, thereby making it possible to provide protection against a buildup of toner deposits all over the orifice row 12A.
Further, if the phase of voltages that are applied to the oscillators 162, 162, ... on the oscillation generating body 160 on one side of the orifice row 12A is deviated from the phase of voltages that are applied to 162, 162, ... on the oscillation generating body 160 on the other side, this makes it possible to cause the entire region in the vicinity of the orifice row 12A to be oscillated uniformly. Accordingly, it becomes possible to provide effective protection against a buildup of toner deposits. An arrangement may be made in which voltages of the same phase are applied to the oscillators 162, 162, ... on the pair of the oscillation generating bodies 160 and 160. In this case, oscillations from each side are synthesized, thereby making it possible to cause the periphery of the orifice row 12A to be oscillated greatly.
Furthermore, if, in an oscillatory system organized between the pair of the oscillation generating bodies 160 and 160, the position of each orifice 12 corresponds to an oscillation node, this decreases the oscillation of the periphery of the orifice 12. Therefore, it is impossible to provide effective protection against a buildup of toner deposits. To cope with such a problem, if the oscillation system is organized such that its oscillation mode is either a primary mode or a tertiary mode as indicated by chain single-dashed lines of Figure 10, the position of the orifice row 12A corresponds to oscillation antinodes, thereby increasing the amplitude in the vicinity of the orifice row 12A. This therefore effectively prevents toner from adhering to around the orifice row 12A. Setting the oscillation mode of the oscillatory system to a primary mode or to a tertiary mode can be made by, for example, changing the oscillating frequency of the oscillator 162, changing the length, width, thickness or material of the oscillation generating body 160, changing the thickness and width or material of the controlling plate 30, or changing the placement position of the oscillation generating body 160.

(VARIATION)

As shown in Figure 11, an arrangement may be made in which a flat plate-like oscillation generating body 163 extending along the orifice row 12A is employed and a plurality of oscillators 162, 162, ... are provided on the oscillation generating body 163. The oscillation generating body 163 may be disposed on only one side of the orifice row 12A. Alternatively, the oscillation generating body 163 may be disposed on both sides of the orifice row 12A.
Furthermore, as shown in Figure 12, the oscillation generating body 164 may be formed in such a manner that a fixing member 165 as a separate member from a comb tooth 166 is placed on the comb tooth 166 and a base of the comb tooth 166 is fixed.

PREFERRED EMBODIMENTS FOR CAUSING ORIFICE PERIPHERY TO BE OSCILLATED AT LARGE AMPLITUDE

Next, preferred embodiments for causing the periphery of the orifice 12 to be oscillated at larger amplitudes will be described.
As shown in Figure 13, the oscillation transmitting plate 151 is disposed along the orifice row 12A in the controlling plate 30. An oscillation reflecting plate 71, by which an oscillatory wave (generated in the controlling plate 30 by application of an oscillation by the oscillation generator 60 and the oscillation transmitting plate 151 and traveling from the oscillation transmitting plate 151 toward the orifice row 12A) is reflected, is adhered by thermocompression bonding on one side of the orifice row 12A opposite to the side where the oscillation transmitting plate 151 is positioned. Like the oscillation transmitting plate 151, the oscillation reflecting plate 71 is also extendedly disposed along the rotation axis direction of the toner conveying roller 1. In other words, the orifice row 12A, the oscillation transmitting plate 151, and the oscillation reflecting plate 71 are disposed in parallel with one another.
As a material to form the oscillation reflecting plate 71, a material, which has a rigidity capable of transmitting an oscillation without absorbing it and whose oscillation characteristic greatly differs from the impedance of oscillation transmission of the controlling plate 30, is especially preferable when improving the efficiency of reflection. When using a resin (e.g., polyimide) to form the insulating substrate 14 of the controlling plate 30, it is preferable to use a metal greatly differing in the value of ρc (i.e., a product of the density ρ and the sound velocity c). Specifically, stainless steel and spring steel are preferable. Further, the plate width and thickness may be set to 5 mm and to about 0.2 mm, respectively. Adhesion to the controlling plate 30 may be carried out by thermocompression bonding or by the use of epoxy adhesive or isocyanate adhesive.
Next, the operation of applying an oscillation to the controlling plate 30 will be described below.
When a voltage is applied to the oscillator 16 of each oscillation generating body 60, the oscillation of the oscillator 16 is transmitted and applied to the controlling plate 30 through the horn 17 and the oscillation transmitting plate 151. This generates in the controlling plate 30 oscillatory waves traveling from a portion to which the oscillation transmitting plate 151 (an oscillation applying portion) is adhered toward the orifice row 12A (toward the oscillation reflecting plate 71) and toward the side opposite the orifice row 12A. Of these oscillatory waves, one that travels from the oscillation transmitting plate 151 toward the orifice row 12A goes beyond the orifice row 12A to arrive at an end (i.e., a reflection end 32) of the oscillation reflecting plate 71 on the side of the oscillation transmitting plate 151 and is reflected by the reflection end 32. Then, as shown in Figure 14, a progressive wave and a reflected wave are superimposed with each other, thereby forming between the reflection end and the oscillation transmitting plate 15 a standing wave s (indicated by a chain double-dashed line in Figure 14) whose node corresponds to the reflection end 32.
In view of the above, if each orifice's 12 portion of the controlling plate 30 or its neighboring area is so arranged as not to correspond to a node of the standing wave s, this causes the portion to be oscillated at all times. This effectively prevents particles of the toner 4 which have not passed through the orifice 12 from adhering to the inside of the orifice 12 or to its peripheral edge portion. Even when particles of the toner 4 adheres to such a portion, it is possible to effectively remove them by the following arrangement. That is, a distance L1 along an oscillation progress route between the reflection end 32 and the orifice row 12A is so set as to satisfy L1 < λ/2 where λ is the wavelength of the standing wave s. Particularly, if the distance L1 is set such that L1 = λ/4, this causes the orifice row 12A to correspond to antinodes of the standing wave s, thereby subjecting each orifice's 12 portion to a greatest displacement. For example, the wave length λ when an oscillation is applied to the controlling plate 30 is about 4 mm for the oscillating frequency = 40 kHz. Accordingly, if the distance between the reflection end 32 which is a contact portion of the toner conveying roller 1 and the controlling plate 30 and the orifice 12 is so set as to fall below 2 mm, this ensures that the peripheral portion of the orifice 12 is oscillated positively. In the present embodiment, the distance is 1 mm.
Further, it is preferable that a distance L2 along an oscillatory wave progress route between the reflection end 32 and the oscillation transmitting plate 151 be so set as to satisfy L2 > λ/4. The reason is as follows. That is, if the distance L2 is λ/4 or less, this makes it difficult to form the standing wave s and further causes the reflection end 32 to be oscillated, which is accompanied by a liberation of heat, wear of the oscillation reflecting plate 71 or the like. It is more preferable that the distance L2 be so set as to satisfy L2 > 3λ/4.
As described above, the arrangement that in the controlling plate 30 the oscillation generating body 60 and the oscillation transmitting plate 151 for oscillation application are disposed on one side of the orifice row 12A and the oscillation reflecting plate 71 for oscillatory wave reflection is disposed on the other side of the orifice row 12A, makes it possible to form the standing wave s between the reflection end 32 and the oscillation transmitting plate 151. The standing wave s provides protection against the clogging of each orifice 12 by a buildup of the toner 4. Therefore, it is possible to form a stable image with a simplified arrangement over a long period of time.

(VARIATION)

The placement position of the oscillation transmitting plate 151 and that of the oscillation reflecting plate 71 with respect to the orifice row 12A may be switched.
Further, as shown in Figure 15, the oscillation reflecting plate 72 may be adhered to a surface of the controlling plate 30 on the side of the opposing electrode 5.
Furthermore, as shown in Figure 16, an arrangement may be made in which the toner conveying roller 1 and the controlling plate 30 come into contact with each other. As a result of such arrangement, an oscillation node is formed at a contact portion of the toner conveying roller 1 and the controlling plate 30 (i.e., at the reflection end 32). As a result, the standing wave s is formed in the controlling plate 30, thereby ensuring that the periphery of the orifice 12 is oscillated positively.
Further, as another arrangement of bringing the toner conveying roller 1 into contact with the controlling plate 30, a spacer 73 may be disposed on the controlling plate 30 for protection against wear of the controlling plate 30 or reduction in friction force of the controlling plate 30, as shown in Figure 17. In addition to achieving the aforesaid purposes, the spacer 73 has a function of keeping a gap defined between the controlling plate 30 and the toner conveying roller 1 uniform in the row direction of the orifice row 12A. Since the spacer 73 and the toner 4 rub against each other, this may cause the spacer 73 to become charged according to the material used to form the spacer 73, thereby affecting the electric field of printing and the charge amount of the toner 4. Preferably, the spacer 73 is coupled to a mechanism capable of electric charge elimination and its material is superior in conductivity and wear resistance. More specifically, resins such as polyamide, polyimide, and polyca filled with a conductive filler and metals such as stainless steel and aluminum are especially preferable. Moreover, the spacer 73 may be composed of metal or the like. In this case, any kind of metal can be used as long as it has a rigidity capable of reflecting an oscillatory wave without absorbing an oscillation. For example, the spacer 73 is formed of a metallic plate of stainless steel (preferably coated with diamond like carbon (DLC)) and its plate width and plate thickness are set to about 5 mm and about 0.2 mm, respectively. By the provision of such a spacer 73, it becomes possible to make the position of the reflection end 32 with respect to each orifice 12 stable and the distance L1 between the reflection end 32 and the orifice 12 can be maintained constant. Further, also the distance between the toner conveying roller 1 and the controlling plate 30 can be maintained constant.
In addition to the above, as shown in Figure 18, in order to provide protection against undulation of the controlling plate 30, the controlling plate 30 may be wound around the toner conveying roller 1. That is, when the contacting of the toner conveying roller 1 and the controlling plate 30 becomes unsteady because the controlling plate 30 undergoes an undulation, oscillatory wave reflection likewise becomes unsteady. As a result, the amplitude of oscillations around the orifice row 12A diminishes. Moreover, if the controlling plate 30 undergoes an undulation, this contributes to variations in the landing position of the toner 4 on the recording paper 6. In order to avoid these drawbacks, the foregoing arrangement of Figure 18, in which the controlling plate 30 is passed around the toner conveying roller 1, is preferable. With such arrangement, the contacting portion of the controlling plate 30 and the toner conveying roller 1 is made longer, thereby providing protection against the occurrence of undulation in the controlling plate 30, and it becomes possible to reflect an oscillatory wave in a steady manner. Further, it is preferable that the contacting length L3, along which the controlling plate 30 and the toner conveying roller 1 are in contact with each other, is not less than about 1/4 of the oscillatory wavelength λ of the controlling plate 30.
Further, in order to make the reflection of an oscillatory wave steadier, it is preferable that an oscillation reflecting member 81 be disposed in parallel with the orifice row 12A and downstream of the reflection end 32 in the direction of oscillation propagation, as shown in Figure 19. In other words, the oscillation reflecting member 81 and the orifice row 12A are positioned opposite to each other across the reflection end 32. Further, the oscillation reflecting member 81 may be disposed on a surface of the controlling plate 30 on the side of the opposing electrode 5. Like the oscillation reflecting plate 71, as a material to form the oscillation reflecting member 81, a material, which has a rigidity capable of transmitting an oscillation without absorbing it and whose oscillation characteristic greatly differs from the impedance of oscillation transmission of the controlling plate 30, is especially preferable in improving the efficiency of reflection. When resin (e.g., polyimide) is used to form the insulating substrate 14 of the controlling plate 30, it is preferable to use a metal greatly differing in the value of ρc (i.e., a product of the density ρ and the sound velocity c). Specifically, stainless steel or spring steel is preferable. Further, it is preferable that the plate width and plate thickness be set to 5 mm and to about 0.2 mm, respectively. If the oscillation reflecting member 81 is free from warping and bending, this makes it possible to obtain the effect of providing protection against the occurrence of undulation in the controlling plate 30, and the effect of reducing landing errors of the toner 4. Adhesion of the oscillation reflecting member 81 to the controlling plate 30 may be done by thermocompression bonding or by the use of epoxy adhesive or isocyanate adhesive. When the oscillation reflecting member 81 is disposed in the way described above, its reflection end corresponds to a node of the oscillatory wave. As a result, nodes and antinodes of the oscillatory wave are formed in the controlling plate 30 at pitches of 1/4 of the oscillatory wavelength λ. It is therefore preferable that the distance L4 between the oscillation reflecting member 81 and the orifice row 12A is set to L4 ≈ (2n + 1) × λ/4 (the number n is an integer) for causing the periphery of the orifice 12 to correspond to an oscillatory wave antinode. In the present embodiment, the wavelength λ is 4 mm, so that the distance L4 is selected from among values of 3 mm, 5 mm, 7 mm, 9 mm, and so on.
As shown in Figure 20, an arrangement may be made in which, instead of providing the oscillation reflecting member 81, holding members 82A and 82B for holding the controlling plate 30 are employed and the controlling plate 30 is sandwiched between the holding members 82A and 82B to form a reflection end.
Further, the orifice row 12A and holding members 82C and 82D of the controlling plate 30, positioned opposite each other across the oscillation transmitting plate 151, are preferably separated by a distance of not less than λ/2 with respect to the oscillation transmitting plate 151. The reason is as follows.
The ordinate of Figure 21 indicates the amplitude ratio of oscillation in the controlling plate 30 resulting from dividing an amplitude at a position 200 mm away from the oscillation transmitting plate 151 by an amplitude at a position 20 mm away from the oscillation transmitting plate 151. In other words, the ordinate indicates the oscillation damping. On the other hand, the abscissa of Figure 21 results from division of a distance between the oscillation transmitting plate 151 and the holding members 82C and 82D (see L5 of Figure 20) by the wavelength λ of an oscillatory wave in the controlling plate 30. In this case, since the frequency of the oscillation source is 40 kHz, the wavelength λ is 4 mm. The amplitude was measured using a laser Doppler system.
As can be seen from Figure 21, when the distance between the oscillation transmitting plate 151 and the holding members 82C and 82D is small, there is a significant oscillation damping. If the space between the oscillation transmitting plate 151 and the holding members 82C and 82D is increased above about λ/2, then the damping of oscillation is reduced because, when the space between the oscillation transmitting plate 151 and the holding members 82C and 82D is not greater than the distance at which oscillatory wave nodes and antinodes are formed, the holding members 82C and 82D are oscillated by the oscillation of the oscillation transmitting plate 151. As a result, the oscillatory energy of the oscillation transmitting plate 151 is consumed by the oscillation of the holding members 82C and 82D. To cope with this, it is preferable that the space between the oscillation transmitting plate 151 and the holding members 82C and 82D is set to a value at which oscillatory wave nodes and antinodes are formed and that the oscillation transmitting plate 151 and the holding members 82C and 82D are so arranged as to be separated from each other by a distance of not less than λ/2.

PREFERRED EMBODIMENTS FOR UNIFORM OSCILLATION IN ORIFICE ROW DIRECTION

Next, preferred embodiments for causing each orifice 12 to be oscillated uniformly in the direction of the orifice row 12A will be described below.

(EMBODIMENT 1)

As shown in Figure 22, disposed on the controlling plate 30 is an oscillation generating body 167 which extends parallel with the row direction of the orifice rows 12A (i.e., the X direction of Figure 22) which is hereinafter referred to also as the row direction. Only one of the orifice rows 12A is shown in Figure 22. The oscillation generating body 167 is formed into a bar-like shape or into a plate-like shape and is fixedly adhered to the controlling plate 30. Such adhesion may be implemented by thermocompression bonding. The oscillation generating body 167 is operable to generate a wave capable of causing the controlling plate 30 to undergo flexure and deformation, such as a transversal wave. In the present embodiment, the oscillation generating body 167 is implemented by a unimorph or bimorph formed by lamination of an oscillating plate 167b and an oscillator 167a. The oscillating plate 167b extends parallel with the row direction of the orifice row 12A and is adhered to the surface of the controlling plate 30. The oscillator 167a extends parallel with the row direction of the orifice row 12A so that it is superimposed with the oscillating plate 167b and is adhered to the surface of the oscillating plate 167b. The length of the oscillator 167a and that of the oscillating plate 167b in the direction orthogonal to the orifice row 12A are identical with each other. As the oscillating plate 167b, for example, a plate of stainless steel having a plate width of about 5 mm and a plate thickness of about 0.3 mm can preferably be used. On the other hand, as the oscillator 167a, for example, a piezoelectric element (PZT) can preferably be used.
Further, a rigid bar 167c extending in the row direction is adhered to the surface of the oscillator 167a as a regulating body by which the expansion and contraction of the oscillator 167a in the row direction is regulated. As the rigid bar 167c, a material with a high Young's modulus, such as stainless steel, can preferably be used. This suppresses the flexure of the controlling plate 30 in the row direction, as a result of which plane waves of the same phase (i.e., whose phases are aligned in the row direction) are applied to the respective orifices 12 of the orifice row 12A.
That is, as shown in Figure 23, owing to expansion and contraction of the oscillator 167a in the Y direction, i.e., expansion and contraction in the direction indicated by an arrow A, the oscillation generating body 167 deflects in the direction indicated by an arrow B (i.e., in the Z direction orthogonal to the X and Y directions) because of the difference in rigidity between the oscillator 167a and the oscillating plate 167b. However, since flexure in the row direction is regulated by the rigid bar 167c, the amounts of flexure in the B direction become equal in any cross section in the row direction. Therefore, by causing the oscillator 167a to be expanded and contracted periodically, the controlling plate 30 is repeatedly subjected to periodical flexure/deformation, as a result of which it becomes possible to generate oscillations of the same phase at any point in the row direction.
Also in such a case, if the oscillating frequency is excessively high, it becomes impossible to ignore a liberation of heat in a surface where the controlling plate 30 and the oscillation generating body 167 are adhered together and the degree of oscillation dumping increases. A sine wave of not more than a frequency of 1 MHz (e.g., 20 kHz) is preferable for the oscillation of the oscillation generating body 167.
Further, it is possible that plane waves of the same phase in the row direction (the X direction) propagate from the oscillation generating body 167 in the Y direction orthogonal to the row direction to the controlling plate 30, thereby making it possible to cause each orifice 12, 12, ... to be oscillated uniformly. This therefore prevents or cancels the clogging of each orifice 12, 12, ... in a uniform manner.

(EMBODIMENT 2)

Referring to Figure 24, there is shown the controlling plate 30 according to the second embodiment in which an oscillation transmitting plate 155, which is formed into a bar-like shape or into a plate-like shape, is fixedly adhered to the controlling plate 30, extending parallel with the orifice row 12A.
Mounted at one end of the oscillation transmitting plate 155 is the oscillation generating body 60 having the oscillator 16 and the horn 17. On the other hand, an oscillation absorbing body 64 is disposed at the other end of the oscillation transmitting plate 155 so that wave motion departed from the oscillator 16 is absorbed for providing protection against reflection of an oscillatory wave.
As the oscillation absorbing body 64, for example, silicon rubber can preferably be used. However, the oscillation absorbing body 64 may be in the form of a fluid or may be formed using a piezoelectric element.
Since it is long and narrow in the row direction, the oscillation transmitting plate 155 is flexible in the row direction. Accordingly, the oscillation of the oscillation generating body 60 becomes a transverse wave, propagating through the oscillation transmitting plate 155. However, since the transverse wave is absorbed by the oscillation absorbing body 64 at the other end of the oscillation transmitting plate 155, there is generated no reflected wave from the other end. As a result, only a progressive wave in one direction is formed on the oscillation transmitting plate 155, so that there is generated no standing wave along the row direction on the orifice row 12A. This therefore makes it possible to cause each orifice 12, 12, ... to oscillated uniformly, thereby preventing or canceling the clogging of each orifice 12, 12, ... in a uniform manner.
The oscillation absorbing body 64 may be formed of a combination of oscillation absorbing plates 64a and 64b and rigid body plates 64c and 64d, as shown in Figure 25. It is possible to obtain sufficient oscillation damping by interposing the oscillation absorbing plates 64a and 64b between the rigid body plates 64c and 64d so that the oscillation absorbing plates 64a and 64b are closely adhered to the oscillation transmitting plate 155. Moreover, if the rigid body plates 64c and 64d are formed of a material having a sufficient heat transfer rate such as aluminum, this makes it possible to readily release heat, generated from the oscillation absorbing plates 64a and 64b in the course of absorbing an oscillation, to the outside. Further, as shown in Figure 25(c), in order to enhance the releasing of heat, a heat releasing fin 64e may be disposed in the rigid body plate 64c. Further, in order to promote the transmission of an oscillation from the oscillation transmitting plate 155 to the oscillation absorbing plates 64a and 64b, for example, silicon grease may be applied between the oscillation absorbing plates 64a and 64b and the oscillation transmitting plate 155. Furthermore, the rigid body plates 64c and 64d may be tightened with screws for application of an appropriate pressure to the oscillation absorbing plates 64a and 64b. In order to promote the transfer of heat from the oscillation absorbing plates 64a and 64b to the rigid body plates 64c and 64d, for example, silicon grease may be applied between the oscillation absorbing plates 64a and 64b and the rigid body plates 64c and 64d. It is preferable that the length of the section of damping of the oscillation transmitting plate 155 by the oscillation absorbing body 64 be at least the half-wavelength of a flexual wave on the oscillation transmitting plate 155, more preferably, not less than the quadri-wavelength of a flexual wave.
Further, as the oscillation absorbing plates 64a and 64b, any material may be used as long as it exhibits a viscoelasticity sufficient enough to damp oscillations. For example, butyl rubber and silicon rubber can preferably be used to form the oscillation absorbing plates 64a and 64b. Moreover, the paired oscillation absorbing plates 64a and 64b may be formed of the same material, but they may be formed of different materials. More specifically, ferrite rubber with a rubber hardness of 80 degrees according to JIS-K6301 A-scale (formed by adding powders of ferrite to butyl rubber), and silicon rubber with a rubber hardness of 10 degrees according to JIS-K6301 A-scale may be used for forming the oscillation absorbing plates 64a and 64b, respectively. The following effects will be obtained if the oscillation absorbing plates 64a and 64b are composed of different materials as described above.
That is, a transverse wave in the oscillation transmitting plate 155 is transmitted through the controlling plate 30 to components having various natural frequencies and their reflected waves are brought back to the oscillation transmitting plate 155. Accordingly, the oscillation absorbing body 64 is required to absorb not only a single-frequency oscillation from the oscillation generating body 60 but also oscillations of other frequencies. For example, the damping coefficient of rubber varies with the frequency according to its molecular structure and composition. Therefore, if the oscillation absorbing plates 64a and 64b are formed of plural types of viscoelastic bodies, this makes it possible to damp oscillations of various frequencies which are input to the oscillation absorbing body 64. Further, if the paired oscillation absorbing plates 64a and 64b are both formed of rubber hardened by addition of a metallic filler or the like thereto, their weight increases. As a result, the damping coefficient increases, thereby making it possible to effectively damp oscillations. However, since hard rubber is high also in spring constant, an input oscillatory wave is readily reflected. To cope with this, if the paired oscillation absorbing plates 64a and 64b are formed of soft rubber and hard rubber, respectively, this makes it possible to prevent reflection of an oscillatory wave by the soft rubber whereas oscillations are damped by the hard rubber.
The arrangement that the oscillation absorbing body 64 is formed of a plurality of dampers is applicable to an oscillation absorbing body using a fluid as well as to an oscillation absorbing body using a piezoelectric element, in addition to an oscillation absorbing body using rubber.

(EMBODIMENT 3)

Referring to Figure 26, there is shown the controlling plate 30 according to the third embodiment in which the oscillation transmitting plate 155 is disposed in parallel with the orifice row 12A and the oscillation generating body 60 having the oscillator 16 and the horn 17 is positioned at one end of the oscillation transmitting plate 155.
Further, provided at the other end of the oscillation transmitting plate 155 is a clamp mechanism 65 as an oscillation condition changing means for changing the dynamic and geometric conditions of an oscillation. During excitation by the oscillator 16, the oscillation transmitting plate 155 is caught in the clamp mechanism 65, and the point, at which a flexual wave is reflected, is shifted by appropriately changing the clamp position along the longitudinal direction of the oscillation transmitting plate 155. The clamp mechanism 65 is so arranged as to be movable in a free manner along the longitudinal direction of the oscillation transmitting plate 155, i.e., along the row direction of the orifice row 12A. As the material to form clamp portions 65a and 65b of the clamp mechanism 65, a material having a rigidity capable of positively reflecting a flexual wave and a viscoelasticity capable of suppressing generation of abnormal sounds at clamp time. For instance, aluminum coated with vinyl can preferably be used. The clamp portions 65a and 65b, shown in Figure 26, each have a pointed end. However, the clamp mechanism 65 may be formed into any shape as long as the oscillation transmitting plate 155 is supported positively. Shapes containing flat and curved surfaces are, of course, applicable.
Next, the operation of applying an oscillation to the controlling plate 30 will be described below.
When a voltage is applied to the oscillator 16, the oscillation of the oscillator 16 is transmitted, through the horn 17 and the oscillation transmitting plate 155, to the controlling plate 30.
A flexual wave on the oscillation transmitting plate 155 departs from its one end at which the oscillation generating body 60 is disposed and is reflected at the other end at which the clamp mechanism 65 is positioned. At this time, superimposition of an incident wave and a reflected wave gives rise to a standing wave. The position of nodes of the standing wave differs depending upon the reflection condition of an extreme point, upon the length and thickness of the oscillation transmitting plate 155, or upon the oscillating frequency. Therefore, during excitation, the clamp position of the oscillation transmitting plate 155 is changed by the clamp mechanism 65 so that at least one of the extreme point reflection condition and the oscillating length of the oscillation transmitting plate 155 is changed. Because of such arrangement, the positions of antinodes and nodes of the standing wave are made to vary appropriately, and it is possible to cause an oscillating wave in the oscillation transmitting plate 155 to become a non-standing wave. This therefore causes each orifice 12, 12, ... to be oscillated uniformly, thereby preventing or canceling the clogging of each orifice 12, 12, ... in a uniform manner. When excitation is carried out by a resonance system, there are changes in natural frequency with changes in oscillation condition. To cope with this, for example, an arrangement may be made in which a matching circuit (not shown ) is inserted in a driving circuit (not shown) of the oscillator 16 for the following of a natural frequency to perform control according to the natural frequency .

(EMBODIMENT 4)

Referring to Figure 27, there is shown the controlling plate 30 according to the fourth embodiment in which an auxiliary exciting unit 66 is provided at the other end of the oscillation transmitting plate 155. The auxiliary exciting unit 66 is required just to disturb an oscillation from the oscillator 16. For example, the auxiliary exciting unit 66 may be implemented by a bimorph of PZT plates 66a and 66b as shown in Figure 28. In order to provide protection against destruction of the PZT plates 66a and 66b by self distortion at oscillation time, these PZT plates 66a and 66b may be sandwiched between the rigid body plates 66c and 66d. The reference numeral 66e denotes a power supply for applying a voltage to the PZT plates 66a and 66b. As the material to form the rigid body plates 66c and 66d, any material serving as a sufficient load with respect to the PZT plates 66a and 66b may be used. For example, aluminum can preferably be used. An arrangement may be made in which the rigid body plates 66c and 66d are further tightened with a clamping means such as screws so as to apply an appropriate load to the PZT plates 66a and 66b.
Next, the operation of applying an oscillation to the controlling plate 30 will be described below.
When a voltage is applied to the oscillator 16, a flexual wave on the oscillation transmitting plate 155 departs from one end thereof at which the oscillation generating body 60 is disposed and is reflected at the other end at which the auxiliary excitation unit 66 is positioned and, at this time, superimposition of an incident wave and a reflected wave gives rise to a standing wave. However, since an extremely small oscillation is applied by the auxiliary exciting unit 66, this disturbs an oscillation from the oscillator 16, thereby causing antinodes and nodes of the standing wave to appropriately shift without remaining at the same point. This therefore causes each orifice 12, 12, ... to be oscillated uniformly, thereby preventing or canceling the clogging of each orifice 12, 12, ... in a uniform manner.
In order to achieve the effect of disturbing an oscillation with the auxiliary exciting unit 66 with efficiency, it is preferable that the frequency of the oscillator 16 does not closely resemble that of the auxiliary exciting unit 66. For example, by a setting that the frequency of the oscillator 16 is about 40 kHz and that of the auxiliary exciting unit 66 is about 55 kHz, it becomes possible to provide effective protection against generation of a standing wave.
As described above, if a non-standing wave is propagated parallel with the orifice row 12A and, on the other hand, a standing wave is formed in a direction orthogonal to the orifice row 12A as described in the part labeled "PREFERRED EMBODIMENTS FOR CAUSING ORIFICE PERIPHERY TO BE OSCILLATED AT LARGE AMPLITUDE", this makes it possible to cause the periphery of the orifice to be oscillated uniformly in the direction of the orifice row 12A and at larger amplitudes.

PREFERRED EMBODIMENTS FOR SUPPRESSING OSCILLATION DAMPING

Next, preferred embodiments for suppressing the damping of oscillation will be described below.

(EMBODIMENT 1)

Referring to Figure 29, there is shown an oscillation transmitting plate 156 according to the first embodiment. Formed at one end 41 of the oscillation transmitting plate 156 (shown on the left-hand side of the figure) is a U-shaped portion to which the horn 17 of the oscillation generating body 60 is fixed with screws, and the oscillation absorbing body 64 is fixed to the other end 42 (shown on the right-hand side of the figure). Further, instead of the provision of the oscillation absorbing body 64 at the other end 42, an arrangement may be made in which a U-shaped portion similar to the one formed in the one end 41 is formed at the other end 42 and the U-shaped portion is fixed to a frame (not shown) which does not oscillate. The oscillation transmitting plate 156 is adhered, substantially at its mid section, to the controlling plate 30, wherein the width of the adhesion portion is tapered, becoming thinner toward the right-hand side. In other words, the width of the oscillation transmitting plate 156 becomes narrower from the one end 41 toward the other end 42. Such tapering suppresses the damping of oscillation in the oscillation propagation direction in the oscillation transmitting plate 156. That is, when the one end 41 of the oscillation transmitting plate 156 is oscillated, an oscillation propagates on the oscillation transmitting plate 156 while at the same time oscillatory energy is absorbed. This results in a decrease in oscillation amplitude at the other end 42. However, if the rigidity of the oscillation transmitting plate 156 is made to become smaller in the direction away from the oscillation generating body 60, this results in an increase in amplitude of an oscillation energy even when it is small. Because of this, the damping of oscillation in the oscillation propagation direction in the oscillation transmitting plate 156 is suppressed, which makes it possible to cause even the periphery of the orifice 12, the position of which is remotest from the oscillation generating body 60, to be oscillated sufficiently.
In order to obtain the same effects as the above, the plate thickness of the oscillation transmitting plate 156 may be made to become thinner from the one end 41 toward the other end 42. However, reducing the plate width is much preferable because it achieves considerable cost reduction in view of control of the etching time when employing techniques such as etching. That is, since the effect of the oscillation transmitting plate 156 can be obtained just by making its width smaller, this provides an easy manufacture and cost reduction. Further, it is preferable that the plate thickness of the oscillating plate ranges between about 0.2 mm and about 1 mm. The use of such a plate thickness range facilitates mounting of the oscillating plate in a narrow space.

(EMBODIMENT 2)

Referring to Figure 30, there is shown the controlling plate 30 according to the second embodiment. In the second embodiment, a lateral face of an oscillation transmitting plate 157 on the side of the orifice 12 in an adhesion portion of the oscillation transmitting plate 157 and the controlling plate 30, has a wavy shape 61. The wave pitch of the wavy shape 61 is set to a value of about half the oscillation wavelength when an oscillation propagates on the oscillation transmitting plate 157. Further, the wave level difference of the wavy shape 61, i.e., the distance between a convex portion (a top portion) and a concave portion (a bottom portion) of a wave of the wavy shape 16, is set to a value about a quarter of the wavelength of an oscillation propagating on the controlling plate 30. By employing such a wave shape, the distance between the wave concave portion and the orifice 12 is made longer than that between the wave convex portion and the orifice 12 by a length of about a quarter of the wavelength of an oscillation propagating on the controlling plate 30. Because of this, if the wave concave and convex portions corresponds to an antinode and to a node of the oscillation on the oscillation transmitting plate 157, respectively, this causes an oscillation-propagation deviation of 90 degrees between the wave concave portion and the wave convex portion in the orifice's 12 portion. Accordingly, the node and antinode of the oscillation become sluggish in the vicinity of the orifice 12, thereby making it possible to perform uniform cleaning in the row direction of the orifice row 12A.
It is preferable that the oscillation transmitting plate 157 is prepared using stainless steel and its thickness is 0.2 mm.
Further, an arrangement, in which the plate width of the oscillation transmitting plate 157 becomes gradually narrower from one end thereof toward the other end, is further preferable because the damping of amplitude can be suppressed.

(EMBODIMENT 3)

Further, as shown in Figures 31(a) and (b), an arrangement may be made in which an electrode pattern 11B is formed using the same material that the image signal electrode 11 is formed (e.g., copper) so that its width becomes gradually narrower along the orifice row 12A for variations in the oscillation characteristic. In other words, the electrode pattern 11B whose width becomes gradually narrower from one end (the left-hand side end in Figure 31) toward the other end (the right-hand side end in Figure 31) may be so formed as to extend substantially parallel with the orifice row 12A and an oscillation transmitting plate 158 of stainless steel or the like is fixed on the side of the one end . As a result of such arrangement, the damping of an oscillation propagating from the one end side to the other end side is suppressed based on the characteristics of the controlling plate 30 itself. There is no need for the oscillation transmitting plate to extend from the one end toward the other end.

(EMBODIMENT 4)

Referring to Figure 32, there is shown an oscillation transmitting plate 159 according to the fourth embodiment.
Of the ends of the oscillation transmitting plate 159, one end 43 (shown on the left-hand side of the figure) serves as an oscillation generating part to which the horn 17 of the oscillation generating body 60 is fixed and the other end 44 (shown on the right-hand side of the figure) serves as an oscillation absorbing part to which the oscillation absorbing body 64 is fixed. The oscillation transmitting plate 159 is adhered, at its mid section, to the controlling plate 30. The plate width at the mid section is made smaller than the plate width at the one end 43 serving as an oscillation generating part. Such a reduction in plate width results in the drop in rigidity. Therefore, an oscillation by the oscillation generating body 60 is amplified at the mid section. As a result, it is possible to apply to the controlling plate 30 an oscillation at larger amplitudes.
Further, the mid section of the oscillation transmitting plate 159 becomes smaller in plate thickness from the one end 43 towards the other end 44. Because of such tapering, the damping of oscillation in the oscillation transmitting plate 159 is suppressed. In order to obtain the same effects, the plate thickness of the oscillation transmitting plate 159 may be made to become thinner from the one end 43 toward the other end 44.
On the other hand, the plate width of the other end 44 serving as an oscillation absorbing part of the oscillation transmitting plate 159 expands beyond that of the mid section thereof. By such improvement in the rigidity, the oscillation amplitude of the other end 44 becomes smaller than that of the mid section, thereby facilitating absorption of oscillatory energy in the oscillation absorbing body 64. The same effects as above can be obtained by making the plate thickness of the other end 44 thicker than that of the mid section. However, increasing the plate width provides a greater area of contact between the oscillation absorbing body 64 and the oscillation transmitting plate 159, resulting in a reduction in oscillatory energy per unit area. This further facilitates energy absorption in the oscillation absorbing body 64. With the oscillation transmitting plate 159 having such a form, it becomes possible to apply oscillations of the same amplitude along the orifice row 12A, thereby achieving uniform cleaning.
It may be arranged such that tension is made to act on the oscillation transmitting plates 151 to 159 in their longitudinal direction. Such tension application provides protection against warp of the oscillation transmitting plate 159, thereby positively causing an oscillation to be propagated to the controlling plate 30. In order to cause tension to act on the oscillation transmitting plates 151 to 159, the following may be taken. That is, for example, with one end of the oscillation transmitting plate caught between the clamp members, the clamp members are pulled outwardly in the longitudinal direction of the oscillation transmitting plate.

PREFERRED EMBODIMENTS SUITABLE FOR PROTECTION AGAINST CONTAMINATION BY REMOVED TONER

Next, preferred embodiments for providing protection against contamination of an already-formed image by toner particles removed by oscillation application will be described below.

(EMBODIMENT 1)

An image forming device according to the first embodiment has the same basic configuration as the one shown in Figure 1 and its description is therefore omitted. The image forming device of the first embodiment has a controlling means (not shown) for cleaning of the print head 10. If a voltage of - 100 V is applied to the image signal electrode 11, in other words if no image formation is being carried out, the controlling means receives a cleaning signal and sends to a roller driving means (not shown) a rotation stop signal to stop the rotation of the toner conveying roller 1 and, at the same time, sends to an oscillation driving circuit (not shown) a driving signal, and further sends to a voltage switching means (not shown) a switch signal so that the opposing electrode 5 is placed in the grounded state.
Next, the cleaning operation of the image forming device will be described below.
In the period that the operation of forming an image is brought into a halt, i.e., in the period that no image formation is being carried out (for example, immediately after the power is applied to the device or in the period from the time that a recording paper sheet is fed to the time that another recording paper is conveyed when a plurality of the recording paper 6 are conveyed at continuous image forming time), the oscillator 16 is operated to perform the following cleaning operations.
That is, the rotation of the toner conveying roller 1 is brought into a stop and an oscillation voltage is applied to the oscillator 16 to cause it to start oscillating. This applies an oscillation to around the orifice 12 of the print head 10 through the oscillation transmitting plate 151.
Of the toner that is built up around the orifice 12, there is not only the presence of toner particles of forward polarity but also the presence of toner particles of reverse polarity. If an oscillation is given to the opposing electrode 5 with its polarity remaining the same as the time of image formation, this causes a force of attraction to act on the reverse-polarity toner adhering to around the orifice 12. As a result, the toner particles are drawn from the opposing electrode 5 toward the print head 10. Therefore, even when the reverse polarity toner is once forced into flight toward the opposing electrode 5 by oscillation, it is again forced into adverse flight toward the print head 10 by the action of an electric field and spreads beyond around the orifice 12, resulting in rather contaminating the print head 10 in some case. Moreover, when operated with the print head 10 and the toner conveying roller 1 brought into contact with each other or into extremely close proximity to each other, toner is forced out from the toner conveying roller 1 by a stream of air caused by oscillation application. Also in this case, of the forced out toner, there is the presence of toner particles of forward polarity in addition to the presence of toner particles of reverse polarity, so that if a voltage of either forward polarity or reverse polarity is applied to the opposing electrode 5, this forces either one of the toner particles of forward polarity or the toner particles of reverse polarity into adverse flight toward the print head 10. This may contaminate the print head 10.
However, at the time when an oscillation is applied, the opposing electrode 5 is so switched as to enter the grounded state. Therefore, the toner conveying roller 1 and the opposing electrode 5 are identical in electric potential with each other, so that no electric field works on the toner 4 and contaminants. This positively forces the toner 4 to be flown toward the opposing electrode 5. Further, at the time when an oscillation is applied, the rotation of the toner conveying roller 1 is brought into a halt, so that after an elapse of a certain period of time from the application of the oscillation, the toner 4 will not be forced out from the toner conveying roller 1.
For example, an arrangement (not shown) may be made in which a power supply for applying a voltage to the toner conveying roller 1 and a switch for switching the toner conveying roller 1 between the voltage applied state and the grounded state are provided. When no image formation is being performed, a voltage is applied to the toner conveying roller 1 so that the relationship in electric potential size between the toner conveying roller 1 and the image signal electrode 11 is reversed with respect to the potential size relationship at the time when forming an image. In this case, at the time of applying an oscillation, it is possible to actively force the toner 4 present between the toner conveying roller 1 and the controlling plate 30 into flight toward the toner conveying roller 1, thereby making it possible to achieve effective cleaning of the print head 10. In addition to the above, it becomes possible to provide protection against discharge of the toner from the toner conveying roller 1 by a stream of air caused by oscillation application.

(EMBODIMENT 2)

Referring to Figure 33, there is shown an image forming device according to the second embodiment. Its basic configuration and others are the same as the image forming device shown in Figure 1 and only differences therebetween will be described below.
That is, the opposing electrode 5 is a roller type and is so configured as to be rotatably driven by a driving means such as a motor (not shown). A cleaning blade 23A is brought into contact with the opposing electrode 5 at a side thereof opposite to the print head 10. Disposed beneath the opposing electrode 5 is a toner collecting container 23B. A controlling means for cleaning (not shown) receives a cleaning signal and sends to a roller driving means (not shown) a rotation stop signal for stopping the rotation of the toner conveying roller 1 while at the same time sending a driving signal to an oscillation driving circuit (not shown), a switch signal to a voltage switching means 29 so that the opposing electrode 5 is placed in the grounded state, and a rotation driving signal to an opposing electrode driving means (not shown).
During image formation, the opposing electrode 5 stops rotating, being at rest. The opposing electrode 5 starts rotating when the print head 10 is cleaned. In the present embodiment, the opposing electrode 5 rotates counterclockwise. By virtue of the working of the oscillator 16, the toner 4 adhering to around the orifice 12 is forced out toward the opposing electrode 5. The voltage of the opposing electrode 5 at that time is switched from the image forming time voltage (+ 1000 V) and is connected to ground like the toner conveying roller 1. The toner 4 and contaminants, which have been emitted toward the opposing electrode 5, are collected in the toner collecting container 23B by the cleaning blade 23A when the opposing electrode 5 rotates.
The toner 4 emitted toward the opposing electrode 5 is collected in the way as described above, thereby providing protection against adverse flight of the toner 4 from the opposing electrode 5 toward the print head 10. The print head 10 is prevented from being contaminated by the adversely-flown toner.

(EMBODIMENT 3)

Referring to Figure 34, there is shown an image forming device according to the third embodiment. Its basic configuration and others are the same as the image forming device shown in Figure 33 and only differences therebetween will be described below.
Connected to the rotatable opposing electrode 5 is a voltage switching means 291 which allows the opposing electrode 5 to be switched between the state of being connected to a dc power supply 9, the state of being connected to ground, and the state of being connected to an ac power supply 31B. The frequency and the voltage of the ac power supply 31B are 4 kHz and 1.5 kV (Vpp), respectively. A controlling means for cleaning (not shown) receives a cleaning signal and sends to a roller driving means (not shown) a rotation stop signal for stopping the rotation of the toner conveying roller 1 while at the same time sending a driving signal to an oscillation driving circuit (not shown), a switching signal to the voltage switching means 291 so that the opposing electrode 5 is placed in the grounded state in the first half (first stage) of an oscillation application operation and then in the state in which an ac voltage is applied to the opposing electrode 5 in the second half of the oscillation application operation, and a rotation driving signal to an opposing electrode driving means (not shown).
Accordingly, at the time of cleaning the print head 10, the opposing electrode 5 is switched from the image forming voltage state (i.e., + 1000 V) to the grounded state (i.e., 0 V); however, after an elapse of a specified period of time from the start of the cleaning, the opposing electrode 5 is switched to the ac power supply 31B.
Since application of an oscillation is carried out when the operation of the toner conveying roller 1 is at rest, this provides protection against emission of toner from the toner conveying roller 1 in the second half of the oscillation application operation. At this time, the opposing electrode 5 is switched to the ac power supply 31B so that an alternating voltage is applied to the opposing electrode 5. The resulting alternating electric field will work only on removal of toner remaining around the orifice. The alternating electric field and oscillation together force toner of forward polarity as well as toner of reverse polarity into flight from the print head 10 toward the opposing electrode 5 for achieving cleaning. As has been describe above, cleaning is carried out with the aid of electric field force, which makes it possible to remove toner particles and contaminants even with small oscillation acceleration. Since the opposing electrode 5 is shifted, the toner flown onto the opposing electrode 5 is collected in the collection container 23B by the cleaning blade 23A. This accordingly provides protection against adverse flight of the toner from the opposing electrode 5 toward the print head 10.
That is, an ac voltage is applied to the opposing electrode 5 in the second half of the oscillation application operation, which allows a cleaning electric field force to work between the opposing electrode 5 and the print head 10. As a result, it is possible to remove strongly adhered toner. Further, if such a cleaning electric field force is enhanced, this makes it possible to reduce oscillatory energy to be applied, providing the advantage of avoiding the occurrence of troubles such as the destruction of the print head 10.

(EMBODIMENT 4)

Referring to Figure 35, there is shown an image forming device according to the fourth embodiment. This is an example when the present invention is applied to a multicolor image forming device. The present image forming device comprises four image forming units for colors of yellow, magenta, cyan, and black, each image forming units including a head unit 25 having components such as the toner conveying roller 1 and the supplying roller 3, the print head 10 having the oscillation transmitting plate 151 and the oscillation generating body 60, and the opposing electrode 5. These four image forming units are arranged in a single row and a conveyor belt 20 is positioned between the print head 10 and the opposing electrode 5 of each image forming unit so that the carrier side of the endless belt travels in the row direction. The conveyor belt 20 travels in the direction indicated by an arrow in the figure by the rotation of a driving roller 21A. The conveyor belt 20 is a conductive seamless belt formed by filling a resin such as polyimide, polycarbonate, and polyethylene with a conductive filler. In the present embodiment, the conveyor belt 20 is formed of polyimide.
In the present embodiment, the recording paper 6 is fed to the conveyor belt 20 by a paper feeding roller 7. In a paper adsorbing brush 20A connected to ground, static charge is applied to the conveyor belt 20 and the recording paper 6 is statically adsorbed onto a surface of the conveyor belt 20 facing the print head 10. The recording paper 6 is conveyed as the conveyor belt 20 travels and the four colors are image-formed one after another. A toner image, which has been image-formed on the recording paper 6, is heated, pressurized, and fixed on the recording paper 6 in the fixing roller 8.
Driving of the oscillation generating bodies 60 is carried out as follows. That is, only the oscillation generating body 60 of the image forming unit for the color in the image forming operation stop timing, is driven. Accordingly, only one driving circuit 31 is provided for the four oscillation generating bodies 60 and they are selectively driven in color order by a changeover switch 33. The voltage of the opposing electrodes 5 is also switched in synchronization with the operation timing of the oscillation generating bodies 60. Such switching is made also by the changeover switch 291. Accordingly, the one dc power supply 9 and the one ac power supply 31B are shared between each image forming unit.
In the way described above, the oscillation driving circuit 31, the high voltage power supply 9, and the ac power supply 31B are shared between each image forming unit, which contributes to preventing device costs from increasing beyond allowable limits even for the case of multicolor image forming devices.
If the oscillation generating bodies 60 of the image forming units are in disagreement in their natural frequency with each other, this causes the oscillation generating body 60 to vary in their amplitude. Accordingly, it is preferable to control the natural frequency of the oscillation generating bodies 60 and to perform design so that the natural frequency band Q of the oscillator 16 becomes narrow. In other words, it is preferable that the natural frequency band Q of the oscillator 16 be made narrow for accelerating the start of the oscillator 16. In the present embodiment, the natural frequency band Q is about 1000 and the oscillation frequency is 40 kHz. In this case, the start rate of the oscillator 16 is 1000/40000 = 25 ms. In this case, the experiment result proves that if the amplitude around the orifice row 12A is 10 µm, then the time necessary for cleaning is 50 ms. On the other hand, the oscillation generating body 60 is driven when no image formation is being carried out, so that a period of drivable time is found by dividing the distance between each image forming unit by the traveling velocity of the recording paper 6. For example, if the distance between each image forming unit is 50 mm and the traveling velocity of the recording paper 6 is 100 mm/s, then the drivable time is 500 ms which is much longer than the time necessary for completing a cleaning operation (50 ms). Accordingly, if the natural frequency band Q is set narrow, this makes it possible to employ the common driving circuit 31.
Further, it is preferable that the driving circuit 31 for the oscillation generating bodies 60 be implemented by a frequency auto-following circuit so that variations in natural frequency can be absorbed on the circuit side.
If the voltage switching means 291, such as a switch and a relay, is used for controlling the voltage of the opposing electrodes 5, the two power supplies 9 and 31B for image formation and cleaning suffice. When using a relay, due to the switching of a high voltage, there occurs noise at the time of such switching. This may cause the malfunction of peripheral circuits. In this case, it is preferable that a filter such as ferrite is placed at the high voltage output side for cutting off the noise.

PREFERRED EMBODIMENTS FOR PROTECTION AGAINST CONTAMINATION OF TRANSFER MECHANISM BY REMOVED TONER

Next, preferred embodiments for providing protection against contamination of a transfer mechanism or the like by toner particles removed from the print head will be described below.

(EMBODIMENT 1)

Referring to Figure 36, there is shown an arrangement of an image forming device according to the first embodiment. In the image forming device of the first embodiment, the toner 4 is adhered onto the conveyor belt 20 for formation of an intermediate image. Thereafter, the intermediate image is transferred onto the recording paper 6. The basic configuration and others of the image forming device of the first embodiment are the same as the image forming device shown in Figure 1 and only differences therebetween will be explained below.
The conveyor belt 20 is formed by an endless type belt and wound around the roller-like opposing electrode 5 and around a backup roller 21. For the convey belt 20 to be conveyed continuously, at least one of the opposing electrode 5 and the backup roller 21 is formed as a driving roller. The opposing electrode 5 and the backup roller 21 together form a conveying means for conveying the conveyor belt 20. The conveyor belt 20 may be formed of conductive carbon-scattered polycarbonate, having a thickness of about 150 µm. Further, its peripheral length may be set to about 340 mm for recording paper according to the JIS A4 standard.
A transfer mechanism 40 includes the backup roller 21 and a transfer roller 22 capable of approaching to and moving away from the backup roller 21. In other words, the transfer mechanism 40 applies, at operation time (at transfer time), a voltage of a specified level to the transfer roller 22 and, at the same time, causes the transfer roller 22 to approach the backup roller 21 so that the conveyor belt 20 and the recording paper 6 are caught between the transfer roller 22 and the backup roller 21, and the intermediate image on the conveyor belt 20 is transferred onto the recording paper 6. The applied voltage to the transfer roller 22 depends upon various characteristics such as the amount of charge of a toner that is used, the humidity of environment, and the like. Preferably, the applied voltage to the transfer roller 22 is the 600-1500 V range. In the present embodiment, the applied voltage is 1000 V. On the other hand, at non-operation time (at non-transfer time), the transfer roller 22 is connected to ground and forced to move away from the backup roller 21.
The transfer roller 22 is formed preferably of a metallic roller which is coated, for about 2-6 mm, with conductive filler-scattered foamed urethane. Preferably, the rubber hardness of the foamed urethane on the surface of the transfer roller 22 ranges between 30 degrees and 60 degrees. Pressing force of the transfer roller 22 against the backup roller 21 is preferably from about 50 N to about 200 N and such pressing starts before the recording paper 6 is inserted and conveyed between the transfer roller 22 and the backup roller 21.
The recording paper 6, onto which the intermediate image has been transferred, is conveyed by the rotation of the backup roller 21 to the fixing roller 8 serving as a fixing means. Thereafter, the image on the recording paper 6 is fixed by the fixing roller 8.
After the recording paper 6 has passed through the transfer mechanism 40, the transfer roller 22 is moved away from the backup roller 21 by a mechanism 22A capable of causing the transfer roller 22 to approach and move away from the backup roller 21. In the present embodiment, the paper feed rate is 65 mm/s. Residual toner left on the conveyor belt 20 after transfer by the operation of the transfer roller 22 is removed by the cleaning blade 23A of the conveyor belt cleaning unit 23 and collected in the toner collecting container 23B. Here, the cleaning blade 23A is formed of urethane rubber, having a thickness of 3 mm. Other than urethane rubber, the cleaning blade 23A may be formed of rubber such as silicon rubber and butyl rubber, resin such as polyester resin and acrylic resin, and metal such as stainless steel. When the collection container 23B is completely filled with collected toner particles, the toner collecting container 23B is replaced with a new one.
Particles of the toner 4, emitted when the orifice 12 of the controlling plate 30 was cleaned by application of an oscillation by the oscillation generating body 60 and the oscillation transmitting plate 151, adhere once to the conveyor belt 20. However, if the transfer roller 22 remains pushed against the backup roller 21, this causes the toner particles to be transferred onto the transfer roller 22 itself. As a result, the transfer roller 22 becomes contaminated. Particularly, such contamination becomes significant when the transfer roller 22 remains in the voltage-applied state. To cope with this, switching control is performed so that the transfer power supply to the transfer roller 22 is turned off in the timing that the toner adhering to the conveyor belt 20 comes into contact with the transfer controller 22.
That is to say, the toner adhering to the conveyor belt 20 is conveyed to the transfer mechanism 40 at a time difference according to the travel velocity of the conveyor belt 20. Therefore, taking into consideration such a time difference, after an elapse of a specified length of time from the time that the cleaning operation of the controlling plate 30 is carried out, the applied voltage to the transfer roller 22 is turned off.
Further, as described above, there exist toner particles of forward polarity and toner particles of reverse particles in the toner emitted at the time when the orifice 12 is subjected to cleaning. Accordingly, it is preferable that the voltage polarity of the transfer roller 22 is reversed with respect to the voltage polarity when the toner image is transferred to a sheet of recording paper and, in addition, that the transfer roller 22 is moved away from the backup roller 21. Therefore, in the present embodiment, in order to ensure that the transfer roller 22 is prevented from being contaminated, the transfer power supply is subjected to switching control and, in addition, the transfer roller 22 is forced to move away from and approach the backup roller 21 so that the transfer roller 22 is prevented from coming into physical contact with the toner image.
That is, the transfer mechanism 40 is placed in the non-operating state when a specified length of time has been elapsed since the oscillation generating body 60 was operated and thereafter the non-operating state of the transfer mechanism 40 is maintained as long as the operating continuous time of the oscillation generating body 60.
Thereafter, the toner on the conveyor belt 20 which has passed through the transfer mechanism 40 is scraped away by the cleaning blade 23A and collected in the toner collecting container 23B.
As described above, the application of a voltage to the transfer roller 22 is brought into a halt and the transfer roller 22 is moved away from the backup roller 21 during the period that the toner blown away toward the conveyor belt 20 when the print head is oscillated is facing the transfer roller 22, thereby making it possible to provide positive protection against contamination of the transfer roller 22.

(EMBODIMENT 2)

Referring to Figure 37, there is shown an image forming device according to the second embodiment. In the second embodiment, the transfer roller 22 is so configured as to come into contact with the conveyor belt 20 (more precisely, in contact with the recording paper 6 at transfer time) at all times and the transfer roller 22 is equipped with a transfer roller cleaning device 24. The basic arrangement and others of the second embodiment are the same as the image forming device shown in Figure 36 and only differences therebetween will be described below.
The transfer roller cleaning device 24 is made up of a blade 24A of urethane rubber having a thickness of 3 mm and a toner collecting container 24B. The edge of the cleaning blade 24A comes into contact with the transfer roller 22, and as the transfer roller 22 rotates toner particles and contaminants are scraped away from the surface of the transfer roller 22. Other than urethane rubber, rubber such as silicon rubber, butyl rubber and resin such as polyester resin and acrylic rubber, and metal such as stainless steel may be used to form the cleaning blade 24A. It is preferable that the surface uneveness of the transfer roller 22 be small. In the present embodiment, as the transfer roller 22, urethane rubber covered with a fluorine tube is used.
The toner collecting container 24B is formed integrally with the toner collecting container 23B of the conveyor belt cleaning device 23, and if the collected toner is discarded and replaced at the same time, this preferably reduces the frequency of maintenance. In such a case, it is preferable that the capacity of the toner collecting container 23B of the conveyor belt cleaning device 23 be set larger than that of the toner collecting container 24B of the transfer roller cleaning device 24. Further, it may be designed such that the toner that is collected from the transfer roller cleaning device 24 is delivered to the toner collecting container 23B of the conveyor belt cleaning device 23 and only the toner collecting container 23B of the conveyor belt cleaning device 23 is discarded for replacement with a new one. Further, conversely, an arrangement may be made in which the toner that is collected by the conveyor belt cleaning device 23 is delivered to the toner collecting container 24B of the transfer roller cleaning device 24 and only the toner collecting container 24B of the transfer roller cleaning device 24 is discarded for replacement with a new one. That is, it is possible to omit either one of the toner collecting container 24B of the transfer roller cleaning device 24 and the toner collecting container 23B of the conveyor belt cleaning device 23 by toner collecting container sharing.
The toner, emitted at the time of cleaning the orifice 12 of the controlling plate 30 and adhering onto the conveyor belt 20, once adheres to the transfer roller 22; however, the toner on the transfer roller 22 is removed by the transfer roller cleaning device 24. This accordingly makes it possible to provide protection against contamination of the recording paper 6 and the drop in performance of the transfer roller 22. Particularly, the transfer roller 22 is not required to perform approaching/moving-away operations, thereby providing a configuration suitable for high-speed printers.
With the present embodiment, toner particles and contaminants adhering to around the orifice 12 of the print head are removed by applying an oscillation to the print head. Then, the toner particles and contaminants thus removed are once adhered to the conveyor belt 20 and then to the transfer belt 22 and thereafter removed by the cleaning means 23. This ensures that the transfer roller 22 is positively maintained clean. Because of this, it is possible to provide protection against the drop in transfer efficiency, recording paper contamination, and in-device contamination. Furthermore, if the toner collecting container 24B is so configured as to serve also as the toner collecting container 23A of the conveyor belt cleaning device 23, this makes it possible to provide the transfer roller cleaning device 24 without increasing the number of times that the toner collecting container 24B is replaced.

(EMBODIMENT 3)

Referring to Figure 38, there is shown an image forming device according to the third embodiment. The third embodiment is an example in which the present invention is applied to a multicolor printer. Four sets of head units 25 shown in Figure 36 are provided. First to fourth image forming units 51, 52, 53, and 54 for four colors of yellow, magenta, cyan, and black, respectively, are arranged in succession. Each image forming unit 51, 52, 53, and 54 is made up of a set of the toner conveying roller 1, the controlling plate 30, the oscillation generating body 60, the opposing electrode 5, et cetera.
The conveyor belt 20, wound around the roller 21A and around the backup roller 21, travels successively between the controlling plate 30 and the opposing electrode 5 of each of the first to fourth image forming units 51-54. More specifically, the conveyor belt 20 travels in the direction indicated by an arrow of the figure (e.g., in the clockwise direction in Figure 38) by the rotation of the backup roller 21. The conveyor belt 20 is a conductive, seamless belt and is preferably formed of resin, such as polyimide, polyca, and polyethylene, filled with a conductive filler. In the present embodiment, polyimide is used to form the conveyor belt 20.
In synchronization with the movement of the conveyor belt 20, the first to fourth image forming units 51-54 operate so that images of four colors are printed in successive on the conveyor belt 20. The intermediate image formed on the conveyor belt 20 is sandwiched, together with the recording paper 6, between the transfer roller 22 and the backup roller 21 and is transferred onto the recording paper 6. The toner image transferred on the recording paper 6 is heated and pressurized in the fixer 8, whereby it is fixed on the recording paper 6.
Next, by making reference to Figure 39, the formation of an image and the operation timing of the oscillator 16 will be described. In Figure 39, the first to fourth image forming units 51-54 are referred to as a first, a second, a third, and a fourth color image forming unit, respectively.
As shown in Figure 39, in each of the image forming units of the first to fourth colors, the applied voltage of the image signal electrode 11 is switched in synchronization with that of the opposing electrode 5. On the other hand, the oscillator 16 is given a voltage in the period during which the applied voltage of the image signal electrode 11 and that of the opposing electrode 5 are turned off.
The image signal electrodes 11 of the image forming units operate one after another at intervals of a specified, first time difference T1 so that toner particles from the plural image forming units are superimposed on the conveyor belt 20 to form thereon an intermediate image. In other words, the second image forming unit 52 starts its image forming operation after an elapse of the first time T1 since the first image forming unit 51 started its image forming operation. The third image forming unit 53 starts its image forming operation after an elapse of the first time T1 since the second image forming unit 52 started its image forming operation. The fourth image forming unit 54 starts its image forming operation after an elapse of the first time T1 since the third image forming unit 53 started its image forming operation.
On the other hand, the oscillators 16 of the image forming units operate one after another at intervals of a second time difference T2 greater than the first time difference T1 so that toner particles removed from the respective image forming units are not superimposed on the same position on the conveyor belt 20. That is, there is a specified time difference between the time interval T2 according to which each oscillator 16 starts its operation and the time interval T1 according to which each image forming unit starts its image forming operation.
More specifically, the oscillator 16 of the first color is driven upon completion of the first color image formation (at the time when the applied voltage of the image signal electrode 11 and that of the opposing electrode 5 are switched from ON to OFF). On the other hand, the oscillators 16 of the second to fourth colors are each driven after an elapse of a specified delay time ΔT since the image formation of each color was completed. In other words, the delay time ΔT (note that the delay time of the first color is zero) is provided between the time that the image formation of each color is completed and the time that the oscillator 16 starts operating. The delay time ΔT differs among the four colors. If the same delay time ΔT is set for all the four colors, then the position on the conveyor belt 20 at which toner is emitted by the operation of each oscillator 16 becomes the same for all the four colors. In this case, when a larger amount of toner is emitted from the print head 10, each emitted toner sequentially lies upon another. Accordingly, particularly in the fourth color image forming unit, the toner 4 accumulated on the conveyor belt 20 comes into mechanical contact with the print head 10 and the toner 4 is forced into adverse flight toward the print head 10 by an electric field generated by the accumulated toner 4, resulting in contamination of the print head 10 in some case. To cope with such problems, in the present embodiment, there is provided a difference between the time interval according to which each oscillator 16 starts operating and the time interval of the image formation of each image forming unit, thereby dispersing the position of toner emission by oscillation for forestalling contamination of the print head 10 and improving device reliability.
Further, also in the present embodiment, it is preferable that the toner collecting container 23B of the conveyor belt cleaning device 23 is so configured as to serve also as the toner collecting container 24B of the transfer roller cleaning device 24.

(VARIATION)

The operation of each oscillator 16 may be performed before the operation of forming an image begins (e.g., immediately after the power of the image forming device is turned on and immediately after a series of image signals is received). For example, as shown in Figure 40, after the power is turned on, a voltage may sequentially be applied to the oscillators 16 of the first to fourth colors for pre-cleaning. In this case, in the initial cleaning, there is no need to cause each oscillator 16 to operate at intervals of the second time difference T2 (in the example of Figure 40 the oscillators of the respective colors are operated sequentially and continuously), thereby making it possible to complete cleaning of all of the image forming units 51-54 in a short time.

PREFERRED EMBODIMENTS FOR CLEANING MULTICOLOR IMAGE FORMING DEVICE

Next, preferred embodiments for efficiently causing the periphery of developer pass orifices of a developer pass controlling means of each head unit at the time of performing multicolor image formation by successive passing between each head unit and each opposing electrode, will be described below.

(EMBODIMENT 1)

The basic arrangement and others of the present embodiment are the same as the image forming device shown in Figure 38 and only differences therebetween will be explained. That is, the image forming device of the present embodiment comprises first to fourth head units 25, 25, ... in which four colors of the toner 4 (i.e., yellow (Y), magenta (M), cyan (C), and black (B)) are stored for forming a color image.
Figure 41 illustrates one of the head units 25. Provided face to face across the orifice row 12A on the controlling plate 30 are the oscillation transmitting plate 151 and the oscillation reflecting plate 71, which is the same as described above. The oscillation transmitting plate 151 is positioned on the front side in the traveling direction of the conveyor belt 20 with respect to the orifice row 12A, and provided on the far side in the traveling direction is the oscillation reflecting plate 71. Referring to Figure 42, there is shown the position relationship between the oscillation transmitting plate 151, the oscillation reflecting plate 71, and the oscillation generating body 60 in each of the head units 25(Y), 25(M), 25(C), and 25(B) of the colors of yellow, magenta, cyan, and black. Note that some members are omitted in Figure 42.
If a voltage is applied to the oscillator 16 when an image is being formed or when the formation of an image is being stopped, the oscillation of the oscillator 16 is transmitted and applied, through the horn 17 and the oscillation transmitting plate 151, to the controlling plate 30.
Here, the toner 4 causes clogging and contamination in the controlling plate 30. More specifically, the toner 4 is accumulated in the inside of the orifice 12, causing clogging of the orifice 12. Further, the toner 4 is accumulated on a surface of the controlling plate 30 on the side of the conveyor belt 20, causing contamination. In the latter cause, the toner 4 adhering to the controlling plate surface is charged, so that the electric field created between the controlling plate 30 and the conveyor belt 20 is disturbed. The toner 4 may not be flight-controlled successfully. Accordingly, it is required that the toner 4 adhering to the surface of the controlling plate 30 on the side of the conveyor belt 20 be cleaned thoroughly.
Adhesion of the toner 4 to a belt-side surface of the controlling plate 30 is attributed to the fact that there is coexistence of toner particles that are charged negatively and toner particles that are charged positively in the toner 4. Of the toner 4 which has been once forced into flight toward the intermediate image holding belt 2, particles of the toner 4 charged positively are pulled back to the controlling plate 30. That is, during image formation, an electric field created between the controlling plate 30 and the opposing electrode 5 forces particles of the toner 4 of negative polarity into flight from the controlling plate 30 toward the conveyor belt 20 and, at the same time, forces particles of the toner 4 of positive polarity into flight from the conveyor belt 20 toward the controlling plate 30.
Accordingly, with the arrangement of the present embodiment for color image formation in which images of yellow, magenta, cyan, and black are formed in that order, when the conveyor belt 20 is delivered from the yellow head unit 25(Y) to the magenta head unit 25(M), in the magenta head unit 25(M) a magenta image is formed overlying a yellow image already formed on the conveyor belt 20. At this time, if the toner 4 of yellow adhering to the conveyor belt 20 contains therein positively-charged particles, these toner particles are attracted to the controlling plate 30 of the magenta head unit 25(M). As a result, the controlling plate 30 of the magenta head unit 25(M) is contaminated. Such contamination is likely to take place in areas of the controlling plate 30 of the magenta head unit 25(M) in the vicinity of the yellow head unit 25(Y).
On the other hand, for the case of the present embodiment, the oscillation transmitting plate 151 of each head unit 25 is positioned on the front side of the orifice 12 with respect to the traveling direction of the conveyor belt 20 so that an oscillation is extensively applied to the front side of the orifice 12 in the controlling plate 30 by the oscillation transmitting plate 151. Because of this, even when the positive polarity toner 4 supplied from one head unit 25 and adhering to the conveyor belt 20 is forced into flight toward the controlling plate 30 of the next head unit 25, the toner 4 will not readily adhere to the controlling plate 30. Even when the toner 4 adheres to the controlling plate 30, the toner 4 can be removed readily.

(EMBODIMENT 2)

Only major parts of the second embodiment are shown in Figure 43. The oscillators 16(Y), 16(M), 16(C), and 16(B) of the head units 25(Y), 25(M), 25(C), and 25(B) are coupled, through a switching circuit (for example, a relay et cetera), to a single common driving circuit 80. The switching circuit 81 is for selective driving of the oscillators 16(Y), 16(M), 16(C), and 16(B) of the head units 25.
When forming a color image, the conveyor belt 20 is delivered from the left-hand side to the right-hand side in Figure 42 and the image is formed by gradually shifting in timing the colors of yellow, magenta, cyan, and black in that order. As a technique of providing protection against clogging or of cleaning a clogging, there is a method in which an oscillation is applied after the formation of an image is completed or before the formation of an image begins to eliminate a clogging created during image formation, and there is another method in which an oscillation is applied when an image is being formed so as to provide in advance a state free from the occurrence of clogging.
Generally, clogging is seldom occurs during formation of an image on one sheet of recording paper. It is therefore possible to eliminate clogging by applying an oscillation between the time that an image is formed on a sheet of recording paper and the time that the formation of an image on the next recording paper starts (hereinafter called the paper-to-paper cleaning). When applying an oscillation also during image formation, such an oscillation should not be the one with a large amplitude which itself has adverse effects on the flight control of the toner 4.
When thinking of a case of performing paper-to-paper cleaning, in the operation of formation of a color image the head units 25(Y), 25(M), 25(C), and 25(B) deviate from each other in image forming timing. That is, the image forming position of the intermediate image holding belt 2 is delivered in front of each head unit 25(Y), 25(M), 25(C), and 25(B) at time intervals so that recording is effected by signals delayed for such an interval. Accordingly, the timing at which paper-to-paper cleaning is performed differ among the head units 25(Y), 25(M), 25(C), and 25(B) and the oscillators 16(Y), 16(M), 16(C), and 16(B) can be driven at different timings for performing cleaning.
For the case of the present embodiment, as described above, the provision of the switching circuit 81 makes it possible for each of the oscillators 16(Y), 16(M), 16(C), and 16(B) of the respective head units 25 to be driven at an appropriate timing independently of another. Additionally, the driving circuit 80 is shared between each head unit 25, thereby being advantageous for the aspect of costs.

(EMBODIMENT 3)

With respect to the third embodiment, its only major parts are shown in Figure 44. That is, the horn 17 of a single oscillation source 60 is coupled, through a branching member 82, to the oscillation transmitting plates 151(Y), 151(M), 151(C), and 151(B) of the head unit 25(Y), 25(M), 25(C), and 25(B). The oscillation source 60 (comprised of the oscillator 16 and the horn 17) is shared between each head unit 25. Positioned at branching portions of the branching member 82 are oscillation cutting-off means 83(Y), 83(M), 83(C), and 83(B). Each oscillation cutting-off means 83, formed of oscillation absorbing material such as silicon rubber, is disposed so that each branching portion of the branching member is caught therein for preventing an oscillation from being transmitted therebeyond.
As a result of such arrangement, with respect to the controlling plate 30 of the head unit 25 not subjected to cleaning, the oscillation of the horn 17 is prevented from being transmitted to the oscillation transmitting plate 151 by the oscillation cutting-off means 83, thereby making it possible to perform paper-to-paper cleaning. Additionally, the oscillation source 60 is shared between each head unit 25, being advantageous in the aspect of costs.

Claims

An image forming method comprising the steps of:

supporting a charged developer on a developer supporting body;

applying a specified voltage to an opposing electrode positioned face to face with said developer supporting body;

making use of an insulating substrate which is placed between said developer supporting body and said opposing electrode and through which a plurality of developer pass orifices are formed in a row and an image signal electrode which is arranged around each said developer pass orifice in said insulating substrate and to which a voltage according to an image signal is applied, and forcing said developer on said developer supporting body into flight so as to pass through a specified developer pass orifice for making a record on an image receiving body supported between said insulating substrate and said opposing electrode; and

removing particles of said developer or contaminants adhering to around said developer pass orifice;

wherein said developer particles/contaminants removing step is performed by applying to said insulating substrate an oscillation resulting from a combination of a progressive wave and a standing wave.
The image forming method of claim 1, wherein said progressive wave propagates in a direction parallel to said developer pass orifice row and wherein said standing wave is formed in a direction orthogonal to said developer pass orifice row.
An image forming method comprising the steps of:

supporting a charged developer on a developer supporting body;

applying a specified voltage to an opposing electrode positioned face to face with said developer supporting body;

making use of an insulating substrate which is placed between said developer supporting body and said opposing electrode and through which a plurality of developer pass orifices are formed in a row and an image signal electrode which is arranged around each said developer pass orifice in said insulating substrate and to which a voltage according to an image signal is applied, and forcing said developer on said developer supporting body into flight so as to pass through a specified developer pass orifice for making a record on an image receiving body supported between said insulating substrate and said opposing electrode; and

removing particles of said developer or contaminants adhering to around said developer pass orifice;

wherein said developer particles/contaminants removing step includes the steps of causing an oscillation from an oscillation generating source positioned on one of sides facing each other across said developer pass orifice row to propagate to said insulating substrate, absorbing an oscillation propagating in a direction parallel to said developer pass orifice row, and reflecting, at the other of said sides, an oscillation propagating in a direction orthogonal to said developer pass orifice row toward said developer pass orifice row.
The image forming method of claim 3 further comprising, prior to said step of propagating an oscillation from said oscillation generating source to said insulating substrate, the step of amplifying said oscillation from said oscillation generating source.
The image forming method of claim 3 or claim 4 further comprising, prior to said step of absorbing an oscillation, the step of reducing the amplitude of said oscillation.
The image forming method of claim 3 or claim 4 further comprising the step of suppressing, while an oscillation from said oscillation generating source is absorbed, the damping of said oscillation.
The image forming method of claim 6 further comprising, prior to said step of absorbing an oscillation, the step of reducing the amplitude of said oscillation.
An image forming device comprising:

a developer supporting body for supporting and, at the same time, conveying a developer;

an opposing electrode positioned face to face with said developer supporting body;

a developer pass controlling member, placed between said developer supporting body and an image receiving body and having at least one developer pass orifice row formed by arrangement of a plurality of developer pass orifices, for performing control in response to an image signal so that said developer conveyed by said developer supporting body is forced into flight so as to pass through a specified developer pass orifice for adhesion onto said image receiving body; and

an oscillation applying member for applying an oscillation to said developer pass controlling member so that particles of said developer adhering to said developer pass controlling member is removed;

wherein said oscillation applying member is so configured as to achieve application of an oscillation to said developer pass controlling member by a combination of a progressive wave and a standing wave.
The image forming device of claim 8, wherein said oscillation applying member is configured so that the oscillation of said progressive wave propagates in a direction parallel to said developer pass orifice row and the oscillation of said standing wave are formed in a direction orthogonal to said developer pass orifice row.
An image forming device comprising:

a developer supporting body which is formed rotatably about a rotation axis extending in a specified direction and which rotates about said rotation axis with a developer supported on its peripheral surface for conveying said developer;

a developer pass controlling member, positioned face to face with said peripheral surface of said developer supporting body and having at least one developer pass orifice row in which a plurality of developer pass orifices capable of being passed through by said developer is arranged in the direction of said rotation axis of said developer supporting body, for performing control in response to an external image signal so that said developer is forced into flight from said developer supporting body so as to pass through a developer pass orifice;

an image receiving body positioned opposite said developer supporting body across said developer pass controlling member; and

an opposing electrode for guiding said developer, which has passed through said developer pass orifice of said developer pass controlling member, toward said image receiving body so that said developer is adhered to said image receiving body;

said image forming device further comprising:

an oscillation applying member for applying an oscillation to one of portions on both sides located opposite each other across said developer pass orifice row in said developer pass controlling member;

wherein the other of said side portions in said developer pass controlling member is in contact with said developer supporting body so that an oscillation, generated in said developer pass controlling member by application of an oscillation by said oscillation applying member and traveling from said oscillation-applied portion toward said developer pass orifice row, is reflected in the opposite direction.
The image forming device of claim 10, wherein the other of said side portions in said developer pass controlling member is wound around said peripheral surface of said developer supporting body, establishing surface to surface contact with said developer supporting body.
The image forming device of claim 11, wherein it is set that L3 > λ/4 where λ is the wavelength of an oscillatory wave and L3 is the length of contact of said developer pass controlling member and said developer supporting body in the circumferential direction of said developer supporting body.
An image forming device comprising:

a developer supporting body which is formed rotatably about a rotation axis extending in a specified direction and which rotates about said rotation axis with a developer supported on its peripheral surface for conveying said developer;

a developer pass controlling member, positioned face to face with said peripheral surface of said developer supporting body and having at least one developer pass orifice row in which a plurality of developer pass orifices capable of being passed through by said developer is arranged in the direction of said rotation axis of said developer supporting body, for performing control in response to an external image signal so that said developer is forced into flight from said developer supporting body so as to pass through a developer pass orifice;

an image receiving body positioned opposite said developer supporting body across said developer pass controlling member; and

an opposing electrode for guiding said developer, which has passed through said developer pass orifice of said developer pass controlling member, toward said image receiving body so that said developer is adhered to said image receiving body;

said image forming device further comprising:

an oscillation applying member for applying an oscillation to one of portions on both sides located opposite each other across said developer pass orifice row in said developer pass controlling member;

wherein the other of said side portions in said developer pass controlling member is in contact with said developer supporting body through a spacer member so that an oscillation, generated in said developer pass controlling member by application of an oscillation by said oscillation applying member and traveling from said oscillation-applied portion toward said developer pass orifice row, is reflected in the opposite direction.
The image forming device of claim 13, wherein said spacer member is extendedly positioned along the rotation axis direction of said developer supporting body.
The image forming device of any of claims 10-14, wherein said oscillation applying member is made up of an oscillation transmitting body extendedly positioned along the rotation axis direction of said developer supporting body and an oscillation generating source disposed at at least one of lengthwise ends of said oscillation transmitting body.
The image forming device of claim 15, wherein said oscillation applying member is configured so that a standing wave, whose node and antinode correspond to a reflecting end and to said developer pass orifice, respectively, in said developer pass controlling member, is obtained.
The image forming device of claim 15, wherein L1 is set such that L1 < λ/2 where λ is the wavelength of an oscillation and L1 is the distance between said developer pass orifice row and said reflecting end.
The image forming device of claim 17, wherein said distance L1 is set such that L1 ≈ λ/4.
The image forming device of claim 15, wherein L2 is set such that L2 > λ/4 where λ is the wavelength of an oscillation and L2 is the distance between said oscillation transmitting body and said reflecting end.
The image forming device of claim 15,

wherein oscillation reflecting means for reflecting an oscillation traveling from said oscillation applying member toward said developer pass orifice row in the opposite direction is positioned opposite said developer pass orifice row across said reflecting end in said developer pass controlling member; and

wherein L4 is set such that L4 ≈ (2n + 1) × λ/4 where λ is the wavelength of an oscillation, L4 is the distance between said developer pass orifice row and said oscillation reflecting means, and n is an integer.
The image forming device of claim 20, wherein said oscillation reflecting means is implemented by an oscillation reflecting plate fixed to said developer pass controlling means or by a holding member for holding said developer pass controlling member.
An image forming device comprising:

a developer supporting body for supporting and, at the same time, conveying a developer;

an opposing electrode positioned face to face with said developer supporting body;

a developer pass controlling member, placed between said developer supporting body and an image receiving body and having at least one developer pass orifice row formed by arrangement of a plurality of developer pass orifices, for performing control in response to an image signal so that said developer conveyed by said developer supporting body is forced into flight so as to pass through a specified developer pass orifice for adhesion onto said image receiving body; and

an oscillation applying member for applying an oscillation to said developer pass controlling member so that particles of said developer adhering to said developer pass controlling member are removed;

wherein said oscillation applying member, equipped with an oscillating plate extending parallel with the row direction of said developer pass orifice row and fixed to a surface of said developer pass controlling member, a piezoelectric element extending parallel with said row direction so as to be superimposed on said oscillating plate and fixed to a surface of said oscillating plate opposite a contact surface thereof in contact with said developer pass controlling member, and a regulating body for regulating expansion and contraction of said piezoelectric element in said row direction, whereby oscillations of the same phase in said row direction can be applied to portions of said developer pass orifices of said developer pass controlling member.
An image forming device comprising:

a developer supporting body for supporting and, at the same time, conveying a developer;

an opposing electrode positioned face to face with said developer supporting body;

a developer pass controlling member, placed between said developer supporting body and an image receiving body and having at least one developer pass orifice row formed by arrangement of a plurality of developer pass orifices, for performing control in response to an image signal so that said developer conveyed by said developer supporting body is forced into flight so as to pass through a specified developer pass orifice for adhesion onto said image receiving body; and

an oscillation applying member for applying an oscillation to said developer pass controlling member so that particles of said developer adhering to said developer pass controlling member are removed;

wherein said oscillation applying member is equipped with an oscillating plate extending parallel with the row direction of said developer pass orifice row and fixed to a surface of said developer pass controlling member, an oscillation generating source for applying an oscillation to one end of said oscillation transmitting body so that an oscillatory wave is generated which travels parallel to said row direction from said one end of said oscillation transmitting body toward the other end thereof, and an oscillation controlling part for controlling said oscillation so that said oscillatory wave in said oscillation transmitting body becomes a non-standing wave.
The image forming device of claim 23, wherein said oscillation controlling part is equipped with clamp means for catching therein said other end of said oscillation transmitting body while shifting its clamp position so that the position, at which an oscillation at said other end of said oscillation transmission body is reflected, is varied with time.
The image forming device of claim 23, wherein said oscillation controlling part is equipped with auxiliary agitating means for slightly disturbing an oscillation from said oscillation generating source in said oscillation transmitting body.
An image forming device comprising:

a developer supporting body for conveying and, at the same time, supporting a charged developer;

an opposing electrode positioned face to face with said developer supporting body;

a developer pass controlling member having an insulating substrate which is placed between said developer supporting body and said opposing electrode and through which a plurality of developer pass orifices are formed in a row and an image signal electrode which is arranged around each said developer pass orifice in said insulating substrate and to which a voltage according to an image signal is applied, for forcing said developer on said developer supporting body into flight so as to pass through a specified developer pass orifice for adhesion onto an image receiving body supported between said developer pass controlling member and said opposing electrode; and

an oscillation applying member having an oscillation generating source and an oscillation transmitting body which is connected, at at least one of ends thereof, to said oscillation generating source and disposed on said developer pass controlling member so as to extend parallel to said developer pass orifice row for transmitting an oscillation from said oscillation generating source to each developer pass orifice portion of said developer pass controlling member;

wherein the oscillation characteristic of said oscillation transmitting body varies along the propagation direction of said oscillation from said oscillation generating source for suppressing the damping of oscillation in said oscillation transmitting body.
An image forming device comprising:

a developer supporting body for conveying and, at the same time, supporting a charged developer;

an opposing electrode positioned face to face with said developer supporting body;

a developer pass controlling member having an insulating substrate which is placed between said developer supporting body and said opposing electrode and through which a plurality of developer pass orifices are formed in a row and an image signal electrode which is arranged around each said developer pass orifice in said insulating substrate and to which a voltage according to an image signal is applied, for forcing said developer on said developer supporting body into flight so as to pass through a specified developer pass orifice for adhesion onto an image receiving body supported between said developer pass controlling member and said opposing electrode; and

an oscillation applying member having an oscillation generating source and an oscillation transmitting body which is connected, at one of ends thereof, to said oscillation generating source and disposed on said developer pass controlling member so as to extend parallel to said developer pass orifice row for transmitting an oscillation from said oscillation generating source to each developer pass orifice portion of said developer pass controlling member;

wherein said oscillation transmitting body decreases in rigidity from said one end toward the other end.
The image forming device of claim 26 or claim 27, wherein said oscillation transmitting body is implemented by an oscillation transmitting plate the plate width of which varies with the distance from said oscillation generating source.
The image forming device of claim 26 or claim 27, wherein said oscillation transmitting body is implemented by an oscillation transmitting plate the plate thickness of which varies with the distance from said oscillation generating source.
The image forming device of claim 26 or claim 27, wherein a lateral face of said oscillation transmitting body on the side of said developer pass orifices is formed into a wavy shape.
The image forming device of claim 30,

wherein the wave pitch of said wavy shape of said oscillation transmitting body is substantially a half of the wavelength of an oscillation in said oscillation transmitting body; and

wherein the difference in level between a concave portion and a convex portion of said wavy shape is substantially a quarter of the wavelength of an oscillation in said developer pass controlling member.
An image forming device comprising:

a developer supporting body for conveying and, at the same time, supporting a charged developer;

an opposing electrode positioned face to face with said developer supporting body;

a developer pass controlling member having an insulating substrate which is placed between said developer supporting body and said opposing electrode and through which a plurality of developer pass orifices are formed in a row and an image signal electrode which is arranged around each said developer pass orifice in said insulating substrate and to which a voltage according to an image signal is applied, for forcing said developer on said developer supporting body into flight so as to pass through a specified developer pass orifice for adhesion onto an image receiving body supported between said developer pass controlling member and said opposing electrode; and

an oscillation applying member having an oscillation generating source and an oscillation transmitting body which is connected, at one of ends thereof, to said oscillation generating source and disposed on said developer pass controlling member so as to extend parallel to said developer pass orifice row for transmitting an oscillation from said oscillation generating source to each developer pass orifice portion of said developer pass controlling member;

wherein a portion of said oscillation transmitting body connected to said oscillation generating source is greater in rigidity than a portion of said oscillation transmitting body disposed on said developer pass controlling member.
An image forming device comprising:

a developer supporting body for conveying and, at the same time, supporting a charged developer;

an opposing electrode positioned face to face with said developer supporting body;

a developer pass controlling member having an insulating substrate which is placed between said developer supporting body and said opposing electrode and through which a plurality of developer pass orifices are formed in a row and an image signal electrode which is arranged around each said developer pass orifice in said insulating substrate and to which a voltage according to an image signal is applied, for forcing said developer on said developer supporting body into flight so as to pass through a specified developer pass orifice for adhesion onto an image receiving body supported between said developer pass controlling member and said opposing electrode; and

an oscillation applying member having an oscillation generating source and an oscillation transmitting body which is connected, at one of ends thereof, to said oscillation generating source, which is provided, at the other end, with oscillation absorbing means for absorbing an oscillation from said oscillation generating source, and which is disposed on said developer pass controlling member so as to extend parallel to said developer pass orifice row for transmitting an oscillation from said oscillation generating source to each developer pass orifice portion of said developer pass controlling member;

wherein a portion of said oscillation transmitting body at which said oscillation absorbing means is disposed is greater in rigidity than a portion of said oscillation transmitting body disposed on said developer pass controlling member.
The image forming device of claim 32 or claim 33, wherein the plate width of said portion of said oscillation transmitting body disposed on said developer pass controlling member varies according to the distance from said oscillation generating source.
The image forming device of any of claims 23, 27, and 32, wherein the other end of said oscillation transmitting body is equipped with oscillation absorbing means for absorbing an oscillation from said one end of said oscillation transmitting body.
The image forming device of claim 33 or claim 35, wherein said oscillation absorbing means is composed of two or more types of viscoelastic bodies having different characteristics.
The image forming device of any of claims 23, 26, 27, 32, and 33, wherein said oscillation transmitting body is in tension in its longitudinal direction.
The image forming device of any of claims 23, 26, 27, 32, and 33,

wherein said image forming device further comprises a holding member for holding, on a side positioned opposite said developer pass orifice row across said oscillation transmitting body, said developer pass controlling member; and

wherein L5 is set such that L5 > λ/2 where λ is the wavelength of an oscillation and L5 is the distance between said oscillation transmitting body and said holding member.
The image forming device of any of claims 23, 26, 27, 32, and 33, wherein said oscillation applying member is so configured as to apply an oscillation which causes a standing wave in a direction orthogonal to the row direction of said developer pass orifice row.
The image forming device of claims 23, 26, 27, 32, and 33, wherein said developer pass controlling member is, on a side located opposite said oscillation transmitting body across said developer pass orifice row, in line contact with said developer supporting body in parallel with the row direction of said developer pass orifice row so that a reflecting end for reflecting an oscillation from said oscillation transmitting body is formed.
The image forming device of claim 40, wherein said developer pass controlling member is wound around a peripheral face of said developer supporting body so that said developer pass controlling member is brought into surface-to-surface contact with said developer supporting body.
The image forming device of claim 40, wherein spacer means, disposed extendedly along said developer pass orifice row, is positioned at a reflecting end of said developer pass controlling member and said developer pass controlling member is brought into contact with said developer supporting body through said spacer means.
The image forming device of claim 40, wherein said oscillation applying member is so configured as to apply an oscillation so that an oscillatory wave in a direction orthogonal to the row direction of said developer pass orifice row in said developer pass controlling member becomes a standing wave whose node and antinode correspond to said reflecting end and to said developer pass orifice row, respectively.
An image forming device comprising:

developer supplying means for charging a developer and supplying said charged developer supported on a developer supporting body;

an opposing electrode which is positioned face to face with said developer supplying means and to which a specified voltage is applied;

an insulating substrate having a plurality of developer pass orifices and interposed between said developer supplying means and said opposing electrode;

an image signal electrode which is disposed around said developer pass orifice of said insulating substrate and to which a voltage for controlling, in response to an image signal, the pass amount of said developer passing through said developer pass orifice; and

an oscillation applying member, having an oscillation generating source and an oscillation transmitting body connected to said oscillation generating source and positioned in the vicinity of said developer pass orifice of said insulating substrate, for applying an oscillation to said insulating substrate;

wherein said developer is adhered to an image receiving body placed between said opposing electrode and said insulating substrate or to said opposing electrode for forming an image; and

wherein said image forming device further comprises controlling means for bringing the operation of said developer supplying means to a halt while activating said oscillation applying means, when no image formation is being performed.
The image forming device of claim 44, wherein, when no image formation is being carried out, said controlling means brings the operation of said developer supplying means to a halt while activating said oscillation applying means and causes said opposing electrode and said developer supporting body to have the same electric potential at least at the early stage of an oscillation application operation by said oscillation applying member.
The image forming device of claim 45,

wherein said opposing electrode is positioned movably so as to be able to change its face opposite to said developer supporting body; and

wherein, when no image formation is being carried out, said controlling means brings the operation of said developer supplying means to a halt while activating said oscillation applying means and causes said opposing electrode and said developer supporting body to have the same electric potential at least at the early stage of an oscillation application operation by said oscillation applying member while shifting said opposing electrode.
The image forming device of claim 46,
wherein, when no image formation is being carried out, said controlling means brings the operation of said developer supplying means to a halt while activating said oscillation applying means, causes said opposing electrode and said developer supporting body to have the same electric potential at least at the early stage of an oscillation application operation by said oscillation applying member while shifting said opposing electrode, and thereafter changes the electric potential of said opposing electrode or said image signal electrode so as to form between said insulating substrate and said opposing electrode an electric field capable of aiding the flight of a charged developer particle from said insulating substrate toward said opposing electrode.
The image forming device of claim 47, wherein an ac voltage is applied to said opposing electrode so that an electric field capable of aiding the flight of a charged developer particle from said insulating substrate toward said opposing electrode is formed between said insulating substrate and said opposing electrode.
The image forming device of claim 44, wherein, when no image formation is being carried out, said controlling means brings the operation of said developer supplying means to a halt while activating said oscillation applying means and reverse the relationship in electric potential size between said developer supporting body and said image signal electrode with respect to the relationship in electric potential size between said developer supporting body and said image signal electrode during image formation.
The image forming device of claim 49 further comprising change means for changing a voltage that is applied to said developer supporting body.
An image forming device comprising:

developer supplying means for charging a developer and supplying said charged developer supported on a developer supporting body;

an opposing electrode which is positioned face to face with said developer supplying means and to which a specified voltage is applied;

an insulating substrate having a plurality of developer pass orifices and interposed between said developer supplying means and said opposing electrode;

an image signal electrode which is disposed around said developer pass orifice of said insulating substrate and to which a voltage for controlling, in response to an image signal, the pass amount of said developer passing through said developer pass orifice; and

an oscillation applying member, having an oscillation generating source and an oscillation transmitting body connected to said oscillation generating source and positioned in the vicinity of said developer pass orifice of said insulating substrate, for applying an oscillation to said insulating substrate;

wherein said developer is adhered to an image receiving body placed between said opposing electrode and said insulating substrate or to said opposing electrode for forming an image and, at the time when no image formation is being performed, said oscillation applying member is activated;

wherein a plurality of image forming units each comprising a combination of said developer supplying means, said insulating substrate having said developer pass orifices and said image signal electrode, said oscillation applying member, and said opposing electrode are provided; and

wherein each of said oscillation applying members of said plurality of image forming units is driven independently of the other and each of voltages of said opposing electrodes of said plurality of image forming units is controlled independently of the other.
The image forming device of claim 51, wherein said plural oscillation applying members are connected, through drive switching means for sequential driving of said oscillation generating sources, to a single common driving circuit for driving said oscillation generating sources.
The image forming device of claim 44 or claim 52, wherein said driving circuit of said oscillation generating sources is a frequency auto-following type circuit.
The image forming device of claim 51, wherein said plurality of opposing electrodes are connected, through voltage switching means, to a single common power supply.
The image forming device of claim 44 or claim 51,

wherein said plurality of developer pass orifices of said insulating substrate are arranged in a single row or in several rows;

wherein said oscillation transmitting body is disposed in parallel with said developer pass orifice row; and

wherein said oscillation applying member is so configured as to apply an oscillation which becomes a progressive wave in a direction parallel to said developer pass orifice row and a standing wave in a direction orthogonal to the row direction of said developer pass orifice row.
An image forming device comprising:

a developer supporting body for conveying and, at the same time, supporting a charged developer;

an opposing electrode positioned face to face with said developer supporting body;

an intermediate image holding member interposed between said developer supporting body and said opposing electrode;

a developer pass controlling member, having an insulating substrate which is placed between said developer supporting body and said intermediate image holding member and through which a plurality of developer pass orifices are formed in a row and an image signal electrode which is arranged around each said developer pass orifice in said insulating substrate and to which a voltage according to an image signal is applied, for forcing said developer on said developer supporting body into flight so as to pass through a specified developer pass orifice for adhesion onto said intermediate image holding member;

conveying means for conveying said intermediate image holding member;

transferring means for transferring an intermediate image on said intermediate image holding member onto an image receiving body; and

developer removing means for removing particles of said developer adhering to said developer pass controlling member;

wherein said transferring means is so configured as to enter the non-operation state when said developer particles, removed from said developer pass controlling member and then adhering to said intermediate image holding member, have been conveyed.
The image forming device of claim 56, wherein said transferring means is so configured as to be pushed toward said intermediate image holding member with said image receiving body caught between itself and said intermediate image holding member when placed in the operation state whereas, when placed in the non-operation state, said transferring means moves away from said intermediate image holding member.
An image forming device comprising:

a developer supporting body for conveying and, at the same time, supporting a charged developer;

an opposing electrode positioned face to face with said developer supporting body;

an intermediate image holding member interposed between said developer supporting body and said opposing electrode;

a developer pass controlling member, having an insulating substrate which is placed between said developer supporting body and said intermediate image holding member and through which a plurality of developer pass orifices are formed in a row and an image signal electrode which is arranged around each said developer pass orifice in said insulating substrate and to which a voltage according to an image signal is applied, for forcing said developer on said developer supporting body into flight so as to pass through a specified developer pass orifice for adhesion onto said intermediate image holding member;

conveying means for conveying said intermediate image holding member;

transferring means for transferring an intermediate image on said intermediate image holding member onto an image receiving body; and

developer removing means for removing particles of said developer adhering to said developer pass controlling member;

wherein said transferring means includes cleaning means for removing particles of said developer adhering to said transferring means.
The image forming device of any of claims 56-58,

wherein said developer removing means comprises an oscillation applying member including an oscillation generating source for applying an oscillation to developer pass orifice portions of said developer pass controlling member when said developer pass controlling member is in the non-operation state and an oscillation transmitting body connected, at at least one of ends thereof, to said oscillation generating source and disposed on said developer pass controlling member so as to extend parallel to said developer pass orifice row for transmitting an oscillation from said oscillation generating source to each said developer pass orifice portion of said developer pass controlling member; and

wherein said oscillation applying member is so configured as to apply an oscillation which becomes a progressive wave in a direction parallel to said developer pass orifice row and a standing wave in a direction orthogonal to said developer pass orifice row.
The image forming device of any of claims 56-58,

wherein a plurality of recording units are provided, each said recording unit including said developer supporting body, said opposing electrode, said developer pass controlling member, and said developer removing means;

wherein said conveying means is so configured as to successively convey said intermediate image holding member between said developer pass controlling member and said opposing electrode of each said recording unit;

wherein said developer pass controlling members of said plural recording units are so configured as to operate one after another at intervals of a first time difference for forming on said intermediate image holding member an intermediate image resulting from superimposition of developer particles from said plural recording units; and

wherein said developer removing means of said plural recording units are so configured as to operate one after another at intervals of a second time difference different from said first time difference for preventing respective developer particles removed from said plural recording units by said developer removing means from being superimposed on said intermediate image holding member.
The image forming device of claim 60,

wherein said developer removing means comprises an oscillation applying member including an oscillation generating source for applying an oscillation to developer pass orifice portions of said developer pass controlling member when said developer pass controlling member is in the non-operation state and an oscillation transmitting body connected, at at least one of ends thereof, to said oscillation generating source and disposed on said developer pass controlling member so as to extend parallel to said developer pass orifice row for transmitting an oscillation from said oscillation generating source to each said developer pass orifice portion of said developer pass controlling member; and

wherein said oscillation applying member is so configured as to apply an oscillation which becomes a progressive wave in a direction parallel to said developer pass orifice row and a standing wave in a direction orthogonal to said developer pass orifice row.
An image forming device comprising:

a developer supporting body which rotates with a developer electro-magnetically supported on its peripheral surface;

an opposing electrode, placed face to face with said developer supporting body, for electro-magnetically attracting said developer supported on said developer supporting body; and

a developer pass controlling member, interposed between said developer supporting body and said opposing electrode and having at least one developer pass orifice row arranged in the rotational axis direction of said developer supporting body, for controlling the passing of said developer through said developer orifices in response to an external image signal;

wherein an image receiving body is interposed between said opposing electrode and said developer pass controlling member for adhesion of said developer thereonto;

wherein said image forming device further comprises a plurality of print heads each comprising a combination of said developer supporting body and said developer pass controlling member;

wherein said image receiving body is so positioned as to successively pass through between said developer pass controlling member and said opposing electrode of each said print head;

wherein said image forming device further comprises:

an oscillation applying member, positioned in said developer pass controlling member of each said print head and extending along said developer pass orifice row, for applying an oscillation to said developer pass controlling members; and

an oscillation reflecting body, positioned in said developer pass controlling member of each said print head and placed opposite said oscillation applying member across said developer pass orifice row, for reflecting an oscillatory wave transmitted from said oscillation applying member.
The image forming device of claim 62, wherein said plurality of print heads are provided with individual oscillation generating sources each of which is driven independently of the other for driving its oscillation applying member.
The image forming device of claim 62, wherein each of said plurality of print heads has said oscillation applying member and said oscillation reflecting body, said oscillation applying member and said oscillation reflecting body being positioned opposite each other across said developer pass orifice so as to be disposed on the front side and on the far side, respectively, with respect to the traveling direction of said image receiving body.
The image forming device of claim 62, wherein said oscillation applying members of said plural print heads are connected to a single common oscillation generating source by which said oscillation applying members are oscillated.
The image forming device of claim 65, wherein oscillation cutting-off means, operable to cut off the transfer of an oscillation from said common oscillation generating source to each of said oscillation applying members, is interposed therebetween.
An image forming device comprising:

a developer supporting body for supporting and conveying a charged developer;

a developer pass controlling member, having a developer pass orifice row formed of a plurality of developer pass orifices through which said developer passes, for controlling, in response to an external image signal, the passing of said developer supplied from said developer supporting body through said developer pass orifices; and

an image receiving body onto which said developer, which has passed through a developer pass orifice, adheres;

wherein said developer pass controlling member has an insulating substrate in which said developer pass orifices are formed;

wherein a pair of bar-like oscillation transmitting bodies for oscillating said insulating substrate are disposed on said insulating substrate, said oscillation transmitting bodies being positioned opposite each other across said developer pass orifice row and extending along said developer pass orifice row; and

wherein oscillation generating sources are disposed at both ends of each of said pair of oscillation transmitting bodies.
An image forming device comprising:

a developer supporting body for supporting and conveying a charged developer;

a developer pass controlling member, having a developer pass orifice row formed of a plurality of developer pass orifices through which said developer passes, for controlling, in response to an external image signal, the passing of said developer supplied from said developer supporting body through a developer pass orifice; and

an image receiving body onto which said developer, which has passed through said developer pass orifice, adheres;

wherein said developer pass controlling member has an insulating substrate in which said developer pass orifices are formed;

wherein bar-like oscillation transmitting bodies for oscillating said insulating substrate are disposed on said insulating substrate, said oscillation transmitting bodies extending along said developer pass orifice row and being positioned opposite each other across said developer pass orifice row; and

wherein one ends of said bar-like oscillation transmitting bodies on said both sides are connected together to form a U-shaped oscillation transmitting body.
The image forming device of claim 68, wherein an oscillation generating source is disposed at each end of said oscillation transmitting body.
The image forming device of claim 68, wherein the both ends of said U-shaped oscillation transmitting body are connected together to form an annular oscillation transmitting body.
The image forming device of claim 70, wherein a plurality of oscillation generating sources are disposed at respective parts of said oscillation transmitting body.
The image forming device of any of claims 67, 69, and 71, wherein said oscillation generating sources are so configured as to differ in oscillation phase from each other.
The image forming device of any of claims 67-71, wherein said oscillation generating source is so configured as to operate at all times when said developer pass controlling member is in operation.
The image forming device of any of claims 67-71 further comprising:

detecting means for detecting whether said developer pass orifice becomes clogged;

wherein said oscillation generating source is so configured as to operate according to the result of said detection.
An image forming device comprising:

a developer supporting body for supporting and conveying a charged developer;

a developer pass controlling member, having a developer pass orifice row formed of a plurality of developer pass orifices through which said developer passes, for controlling, in response to an external image signal, the passing of said developer supplied from said developer supporting body through a developer pass orifice; and

an image receiving body onto which said developer, which has passed through said developer pass orifice, adheres;

wherein said developer pass controlling member has an insulating substrate in which said developer pass orifices are formed;

wherein an oscillation transmitting body, one end of which is fixed to said insulating substrate whereas the other end is oscillatably configured so as to cause said insulating substrate to be oscillated, is disposed on each side of said developer pass orifice row of said insulating substrate, extending along said developer pass orifice row; and

wherein an oscillation generating source is disposed on said oscillation transmitting body.
The image forming device of claim 75,

wherein said oscillation transmitting body is formed into a flat plate-like shape extending along said developer pass orifice row and an end of said flat plate-like oscillation transmitting body on the far side thereof with respect to said developer pass orifice row is fixed to said insulating substrate; and

a plurality of said oscillation generating sources are disposed along said developer pass orifice row.
The image forming device of claim 75,

wherein said oscillation transmitting body is formed into a comb-like shape extending along said developer pass orifice row and an end of each of comb teeth of said comb-like oscillation transmitting body on the far side thereof with respect to said developer pass orifice row is fixed to said insulating substrate; and

wherein said oscillation generating source is disposed on each of said comb teeth.
The image forming device of claim 76 or claim 77, wherein said oscillation generating sources disposed on said oscillation transmitting bodies on said both sides of said developer pass orifice row are arranged at the same pitch and oscillation generating sources on one side of said developer pass orifice row are so arranged as to be half-pitch deviated with respect to oscillation generating sources on the other side.
The image forming device of claim 76 or claim 77,

wherein each of said oscillation generating sources is oscillated by application of a voltage; and

wherein the phases of voltages that are applied to said oscillation generating sources on said oscillation transmitting bodies on each side are the same.
The image forming device of claim 76 or claim 77,

wherein each of said oscillation generating sources is oscillated by application of a voltage; and

wherein the phases of voltages that are applied to said oscillation generating sources on said oscillation transmitting bodies on each side are deviated from each other.
The image forming device of claim 76 or claim 77, wherein an oscillatory system, made up of said oscillation transmitting body on each side, said oscillation generating source on each side, and said insulating substrate, is so configured as not to cause a node at the position of each said developer pass orifice.
The image forming device of claim 81, wherein said oscillatory system is so configured as to be either a primary oscillatory mode or a tertiary oscillatory mode.