JP2001105650A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute cleaning of an opening of a print head 10 by applying vibration to the print head 10. SOLUTION: A toner conveying roller 1 for carrying and conveying toner, a print head 10 having a plurality of openings, an image signal electrode, and a vibration transferring member 15 provided thereon and an opposing electrode, are disposed in the above order. When image forming is not performed, rotation of the toner conveying roller 1 is stopped and vibration is applied to the print head 10 by means of the vibration transferring member 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a facsimile, and a printer, and more particularly to an image forming apparatus for performing recording by ejecting a developer such as toner onto a recording medium.

[0002]

2. Description of the Related Art In recent years, offices have dealt with a large amount of documents in accordance with the improvement of personal computer capabilities. In addition, printers and copiers having high processing capabilities have become widespread due to advances in network technology, and color documents have been increasing. It is in.

One of the image forming apparatuses is a direct marking method for forming an image directly on paper. For example, Japanese Patent Publication No. 44-26333 discloses a toner ejection type image forming apparatus which is one of the direct marking methods. This is achieved by generating an accelerating electric field that causes the toner to fly between a developing sleeve and a counter electrode that charges and supplies the toner, and by inputting an image signal to an electrode of a print head having a developer passage hole, the charged toner is charged. Is controlled to control the amount of light passing through the control grid, and the charged toner is attached to the recording paper in front of the counter electrode to form an image. For example, 100μ
In order to form dots of about m, the diameter of the developer passage hole needs to be as small as about 100 μm.

[0004] However, there are cases where the dots become smaller or the dots cannot be printed. This is due to clogging of the developer passage hole due to dust and dust scattered in the apparatus, and clogging due to toner.

That is, not all of the toner on the developing sleeve is uniformly charged, and there is always a distribution in the charging, and the toner charged to the forward polarity (the toner between the developing sleeve and the opposing electrode during image formation). In addition to the toner that flies from the developing sleeve toward the counter electrode due to the electric field applied therebetween, toner charged to the opposite polarity and uncharged toner are also present. Toners useful for image formation are of normal polarity, but due to the cohesion and adhesion between toners, part of the toner of the opposite polarity flies along with the toner of the normal polarity. The electric field formed between the counter electrode and the print head during recording acts on the toner of the opposite polarity as a force to return the toner from the recording paper (counter electrode) to the print head. The toner adheres to the print head surface and the inner surface of the developer passage hole. In addition, since the uncharged toner is easily separated from the developing sleeve, it falls into the developer passage hole and adheres.

Since such a phenomenon occurs repeatedly each time a voltage is applied to the print head, toner is deposited on the print head every time image formation is repeated, and the amount of deposition gradually increases. In addition, foreign substances such as dust and dust also adhere to the head, which triggers the accumulation of toner,
It can cause strong clogging. Accumulated toner or foreign matter affects the electric field formed by the toner passage control electrode, or physically prevents toner from passing through the developer passage hole, causing dot thinning or dot error. It is.

Therefore, an appropriate cleaning means for preventing the developer passage hole from being clogged is required. Various methods have been proposed for this cleaning. For example, the following methods are known.

1) A method using an electric field (Japanese Patent Laid-Open No. 58-10477)
1, JP-A-59-188450), 2) Method using air flow (JP-A-58-122569,
-509789), 3) A method of applying vibration to a print head (JP-A-3-5765)
8, JP-A-4-161353, JP-A-4-216072, JP-A-4-25746
1).

[0009]

However, in the method using the electric field of 1), it is difficult to remove the uncharged toner contained in the toner and foreign matters such as dust and dust scattered in the air. . In the method 2) using the air flow, it is possible to remove non-charged toner and the like, but it is difficult to remove the toner having a large charge amount because it is strongly attached to the print head. That is, although it is relatively easy to remove the toner adhered to the print head surface, it is very difficult to remove firmly adhered toner such as toner with a large amount of charge adhered inside the developer passage hole. And a large pump is required.

In the method using the vibration of 3), in the case of a standing wave, the amplitude of the portion of the node becomes small, so that the toner hardly falls off and spots may occur. In addition, since the print head and the developing sleeve are very close to or in contact with each other, toner may be blown out of the developing sleeve due to the application of vibration, and the print head may be contaminated unless the toner is reliably collected. become.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly reliable image forming apparatus which obtains a sufficiently high cleaning ability with a relatively small apparatus in a vibration cleaning system for applying vibration to a print head. .

[0012]

The invention according to claim 1 is
A developer supply unit configured to charge the developer and supply the developer by being carried on a developer carrier; a counter electrode that is disposed to face the developer supply unit and is applied with a predetermined voltage; An insulating substrate disposed between the developer supply means and the counter electrode, and provided around the developer passage hole of the insulating substrate, and the developer passage according to an image signal. An image signal electrode to which a voltage for controlling the amount of the developer passing through the hole is applied, a vibration source, and a vibrating source connected to the vibrating source and provided near the developer passing hole of the insulating base. Having a vibration transmitting member, comprising a vibration imparting means for imparting vibration to the insulating base, a recording member disposed between the counter electrode and the insulating base, the recording member, or An image forming apparatus for forming an image by adhering the developer to the counter electrode; A is, when not performed in the formation of the image, while activating the vibrating means, and is characterized in that it comprises a control means for stopping the operation of said developer supply means.

Therefore, when the image is not formed, for example, when the recording paper is moved after the image is formed, the vibration is applied to the insulating base material. Even if it jumps out,
It does not disturb already formed images. In addition, when the vibration is applied, the operation of the developer carrier is stopped, and no new developer is supplied, so that the amount of the developer jumping out of the developer carrier is reduced.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, when the control unit does not form the image, the control unit activates the vibration imparting unit while the developing unit operates. Stop the operation of the agent supply means,
The counter electrode and the developer carrier are set to the same potential at least at the initial stage of the application of the vibration by the vibration applying unit.

The toner deposited around the developer passage hole of the insulating base material includes not only the toner of the normal polarity but also the toner of the opposite polarity. If vibration is applied while the opposite electrode is kept at the same potential as during image formation, the toner of the opposite polarity will
Since a force that flies from the counter electrode to the insulating base acts, even if the insulating substrate is once flanked by vibrations toward the counter electrode, it flies back to the insulating base by the action of the electric field again and the insulating base is re-formed. The material is soiled. In addition, the toner that is ejected from the developer carrier due to the vibration is insulated even if the opposite-polarity toner once moves to the counter electrode side, as long as the counter electrode is kept at the same potential as that during image formation. It becomes easy to adhere back to the substrate.

On the other hand, in the case of the invention according to claim 2, since the counter electrode and the developer carrying member have the same potential at the time of applying the vibration, the return of the opposite polarity toner is avoided,
Clogging of the insulating base material is prevented. The counter electrode and the developer carrier may be set to the same potential during the entire period of the vibration application, or may be set to the same potential only at the initial stage and then switched to an appropriate potential. Even if such switching is performed, vibration is applied in a state in which the operation of the developer supply unit is stopped, that is, in a state in which new developer is not supplied,
The ejection of the developer from the developer carrier due to the vibration is substantially completed in the initial stage of the application of the vibration, and the switching of the potential does not cause the developer to newly eject from the developer carrier.

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the counter electrode is provided so as to be movable so that a surface facing the developer carrier can be changed. The control means, when not performing the image formation, activates the vibration applying means, stops the operation of the developer supply means, and moves the counter electrode while moving the vibration applying means. At least at the beginning of the application, the counter electrode and the developer carrier are set to the same potential.

Accordingly, the toner which has been blown from the insulating base material to the counter electrode by applying vibration to the insulating base material moves to a position which does not face the developer carrier due to the movement of the counter electrode. It is possible to avoid returning to the periphery of the passage hole, and it is also easy to collect the toner.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, when the control unit does not form the image, the control unit activates the vibration applying unit while the developing unit operates. Stop the operation of the agent supply means,
In addition, the counter electrode and the developer carrier are set at the same potential at least at the initial stage of the application of the vibration by the vibration applying unit while moving the counter electrode, and then the charging is performed between the insulating base material and the counter electrode. The potential of the counter electrode or the image signal electrode is changed so as to form an electric field that assists the developed developer to fly from the insulating base material to the counter electrode.

In the present invention, the potential of the counter electrode or the image signal electrode is changed while moving the counter electrode.
The surface of the counter electrode facing the developer carrier, that is, the developer passing hole of the insulating base material at the beginning of the vibration application is facing the other at the time of the potential change. Therefore, it is possible to prevent the toner that has jumped out of the insulating base material or the like and attached to the counter electrode in the initial stage of the vibration application from back-floating around the developer passage hole of the insulating base material due to the change in the potential.

The switching of the potential of the counter electrode or the image signal electrode causes the charged developer to fly from the insulating base to the counter electrode between the insulating base and the counter electrode. Since an assisting electric field is formed, the toner adhering to the insulating base material is subjected to the removing force by the electric field in addition to the mechanical removing force by applying vibration, and the toner adhered firmly. However, it is easily removed. In addition, by increasing the acting force of the electric field, it is possible to reduce the vibration energy to be applied to the insulating base material, which is advantageous in avoiding troubles such as heat generation due to the vibration and peeling of the vibration transmission member. Become.

According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the charged developer is transferred from the insulating base material to the counter electrode between the insulating base material and the counter electrode. An alternating voltage is applied to the counter electrode in order to form an electric field that assists the flight to the ground.

That is, since there are toner having forward polarity and toner having opposite polarity, the toner on the insulating base material is insulated by the vibration applied by the vibration applying means and the alternating electric field by the alternating voltage. It is easier to remove from the material.

According to a sixth aspect of the present invention, in the image forming apparatus according to the first aspect, the control means activates the vibration applying means when the image is not formed, while the developing means Stop the operation of the agent supply means,
Further, the magnitude relationship between the potentials of the developer carrier and the image signal electrodes is reversed from the magnitude relationship between the potentials during image formation.

According to this, when the vibration is applied, an electric field is generated such that the developer flies from the insulating base material toward the developer carrier, so that the developer from the developer carrier accompanying the vibration is applied. Jumping out is prevented. In addition, the developer existing between the developer carrier and the insulating base material flies toward the developer carrier by the action of the electric field, and the developer is effectively removed.

According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the image forming apparatus further includes a changing unit for changing a voltage applied to the developer carrier. That is, the voltage applied to the image signal electrode may be changed, but even if the voltage applied to the developer carrier is changed in this manner, the potential between the developer carrier and the image signal electrode at the time of applying vibration is changed. The magnitude relationship can be reversed from the magnitude relationship of the potential during image formation.

The invention according to claim 8 is a developer supply means for supplying a developer by charging the developer and supporting the developer on a developer carrier;
A counter electrode to which a predetermined voltage is applied, which is disposed to face the developer supply unit, and having a plurality of developer passage holes, disposed between the developer supply unit and the counter electrode; An insulating substrate, and an image signal provided around the developer passage hole of the insulation substrate, to which a voltage for controlling a passing amount of the developer passing through the developer passage hole according to the image signal is applied. An electrode, a vibration generating source, and a vibration transmitting member connected to the vibration generating source and provided near the developer passage hole of the insulating base, for applying vibration to the insulating base. Means, a recording member is disposed between the counter electrode and the insulating base material, and the developer is attached to the recording member or the counter electrode to form an image, and the image is formed. An image forming apparatus that operates the vibration applying unit when not performing the operation. A plurality of image forming units provided by combining the developer supply unit, the insulating base having the developer passage hole and the image signal electrode, the vibration applying unit, and the counter electrode; The vibration applying means of each of the plurality of image forming units is driven independently of each other, and the voltage of each of the counter electrodes is controlled independently of each other.

According to the present invention, a multicolor image forming apparatus can be realized by a plurality of image forming units. Even in a multi-color image forming apparatus, these units operate independently of each other and do not need to apply vibration at the same time. A low-cost image forming machine can be provided.

According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the plurality of vibration applying means are provided for one common driving circuit for driving each of the vibration generating sources. It is characterized by being connected via a drive switching means for sequentially driving the respective vibration sources.

According to this configuration, since one drive circuit is provided and the drive switching means is provided, the drive switching means is shared by a plurality of vibration applying means, which is advantageous in reducing the cost of the image forming apparatus.

According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the driving circuit of the vibration source is an automatic frequency tracking type circuit.

In the ninth aspect of the present invention, a self-excited oscillation circuit can be used as a drive circuit of the vibration source. The stable vibration can be given to the insulating base material without being largely affected by the natural frequency of the vibration system including the means and the insulating base material.

According to an eleventh aspect of the present invention, in the image forming apparatus according to the eighth aspect, the plurality of opposed electrodes are connected to one common power supply via a voltage switching unit. I do.

According to this, it is not necessary to provide a power supply for each opposing electrode, which is advantageous for cost reduction.

According to a twelfth aspect of the present invention, in the image forming apparatus according to any one of the first to eleventh aspects, the developer carrying member and the insulating base material are arranged such that the developer passage The vibration transmitting member is in contact with a side opposite to the vibration transmitting member across the hole so as to form a reflection end for reflecting a vibration wave transmitted from the vibration transmitting member.

Therefore, it is possible to form a standing wave between the vibration transmitting member and the reflection end, thereby increasing the transmission efficiency of the vibration, and increasing the standing wave portion at or near the developer passage hole. If no nodes are formed, the portion can be relatively vibrated by the standing wave, and the developer can be effectively prevented from accumulating in or around the developer passage hole.

According to a thirteenth aspect of the present invention, in the image forming apparatus according to the twelfth aspect, the developer carrier and the insulating base are in contact with each other via a spacer forming the reflection end. It is characterized by the following.

That is, even if the developer carrier is moved to supply the developer, the developer carrier only slides on the spacer and does not slide with the insulating base material. Wear and deterioration of the insulating base material are prevented.

According to a fourteenth aspect of the present invention, in the image forming apparatus according to the thirteenth aspect, the plurality of developer passage holes of the insulating base are arranged in one or several rows, and the vibration transmitting member and the spacer The feature is that the spacer extends along the row of the developer passage holes, and the thickness of the spacer is constant over its entire length.

According to this, in the case where the plurality of developer passage holes are arranged in one or several rows, the same operation and effect as the invention according to claim 13 can be obtained, and the developer carrying member and the insulating base material can be separated. The distance (gap) from the developer passage hole portion becomes constant at all the developer passage hole portions, and the image quality can be stabilized.

According to a fifteenth aspect of the present invention, in the image forming apparatus according to any one of the twelfth to fourteenth aspects, the distance between the reflection end and the developer passage hole is:
It is characterized in that it is smaller than half the wavelength of the vibration applied to the insulating base material.

Accordingly, the portion of the developer passage hole of the insulating base material is prevented from becoming a node of the vibration wave, and the portion can be vibrated greatly.

According to a sixteenth aspect of the present invention, in the image forming apparatus according to any one of the twelfth to fifteenth aspects, the vibration imparted to the insulating base by the vibration imparting means is provided in the image forming apparatus. A standing wave having an end as a node and an antinode at or near the center of the developer passage hole.

Thus, the developer passage hole portion of the insulating base can be vibrated greatly.

According to a seventeenth aspect of the present invention, in the image forming apparatus according to the twelfth or thirteenth aspect, the wavelength of the vibration is λ, and the developer passing therethrough is located closest to the vibration transmitting member. When the distance between the center of the hole and the reflection end is L1, L1 <λ / 2.

Thus, the portion of the developer passage hole in the insulating base material can be largely vibrated.

According to an eighteenth aspect of the present invention, in the image forming apparatus according to the twelfth or thirteenth aspect, the wavelength of the vibration is λ, and the distance between the vibration transmitting member and the reflection end is L2. In this case, L2> λ / 4.

Thus, the portion of the developer passage hole of the insulating base material is prevented from becoming a node of the vibration wave, and the portion can be vibrated greatly.

[0049]

As described above, according to the present invention, when an image is not formed, the operation of the developer supply means is stopped, the vibration applying means is operated, and the developer passage hole of the insulating base material is formed. Since the portion is vibrated, it is advantageous in preventing the developer passage hole from being clogged by the developer, and a highly reliable image forming apparatus can be obtained.

[0050]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described with reference to the drawings.

<First Embodiment> FIG. 1 shows the configuration of an image forming apparatus according to the present embodiment. In FIG.
Reference numeral denotes a toner transport roller provided in the toner container, which is a developer carrying member that carries and transports the toner 4 as a developer, and also serves as a charging electrode that charges the toner 4. The toner container accommodates the regulating blade 2, the supply roller 3, and the toner 4 in addition to the toner transport roller 1, and these constitute a toner charging supply unit (developer supply unit) 25.

The toner conveying roller 1 can be made of a metal such as aluminum or iron, or an alloy. In this embodiment, the outer diameter of the toner conveying roller 1 is 20 mm.
An aluminum cylinder having a thickness of 1 mm and a thickness of 1 mm was used. In the present embodiment, the toner transport roller 1 is grounded. However, the present invention is not limited to this, and a constant voltage or an alternating voltage may be applied to the toner transport roller 1.

The regulating blade 2 forms one to three toner layers on the toner conveying roller 1. This regulating blade 2 is made of an elastic member such as urethane,
The hardness is preferably 40 to 80 degrees (JIS K6301 A scale), the free end length (the length of the portion protruding from the mounting portion) is 5 to 15 mm, and the linear pressure on the toner conveying roller 1 is preferably 5 to 40 g / cm. It is. The regulating blade 2 may be in an electrically floating state, may be grounded, or may be configured to apply a DC or AC voltage. In the present embodiment, it is used in a float state.

The toner 4 is sandwiched between the toner conveying roller 1 and the regulating blade 2, and receives a small charge from the toner conveying roller 1 to receive and charge the toner. In the present embodiment, a non-magnetic material having an average particle diameter of 8 μm is used as the toner 4 and a negative charge (forward polarity) of −10 μC / g is given.

The supply roller 3 is provided with a synthetic rubber such as urethane of about 2 to 6 mm provided around a metal shaft (in this embodiment, a shaft having a diameter of 8 mm) such as iron.
0 degrees (roller-shaped JIS K6301 A
Scale). The amount of biting of the supply roller 3 into the toner conveying roller 1 is preferably about 0.1 to 2 mm. The supply roller 3 may also be grounded,
A constant voltage or an alternating voltage may be applied. The supply roller 3 not only assists the charging of the toner 4 but also controls the supply amount of the toner 4.

The toner conveying roller 1 and the supply roller 3 are driven to rotate by roller driving means (motor) 27.

The counter electrode 5 forms an electric field between the counter electrode 5 and the toner conveying roller 1, and a metal plate, a metal roller, a film in which a conductive filler is dispersed in a resin, or the like can be suitably used. When a film is used, the resistance of the film is preferably about 10 ² to 10 ¹¹ Ω / cm. The opposite electrode 5 is connected to voltage switching means 30 for switching between a state connected to the DC power supply 9 and a state grounded. The DC power supply 9 applies a DC voltage of about 500 to 2000 V to the counter electrode 5, and in the present embodiment, a voltage of 1000 V is applied.

For image formation, the toner 4 may be directly adhered on the counter electrode 5 or, as shown in FIG. 1, a recording sheet 6 may be placed on the counter electrode 5 and the toner 4 may be adhered thereon. In this case, the paper is fed by the paper feed roller 7, and after the toner is attached, the fixing is performed by the fixing roller 8. Further, the counter electrode 5 may be processed into an endless film shape, recorded directly on the film, and then transferred to recording paper. In the present embodiment, the paper feeding speed is 65 mm / s.

FIG. 2 is a view showing a schematic configuration of a print head 10 disposed between the toner conveying roller 1 and the counter electrode 5, and FIG. 2A is a sectional view of the print head 10.
FIG. 2B shows a state in which the print head 10 is connected to the toner conveying roller 1.
It is the top view seen from the side. In FIG. 2B,
The horizontal direction in the drawing is the moving direction (Y direction) of the recording paper 6, and the vertical direction is the width direction (X direction) of the recording paper 6.

As shown in FIG. 2, a plurality of openings 1 are formed in an insulating base material 14 constituting the print head 10 as developer passage holes.
2 are formed on rows arranged in the width direction of the recording paper. The number of the opening rows is not limited to two, but may be one or three or more. A plurality of image signal electrodes 11 formed in a ring shape so as to surround the openings 12 are provided on the surface of the insulating base material 14 on the toner conveying roller 1 side. In addition,
The image signal electrode 11 is not limited to this, and may be provided on the inner wall of the opening 12. In the present embodiment, a ring-shaped electrode having an inner diameter of 150 μm and an outer diameter of 250 μm is used as the image signal electrode 11. 5-20μ on the surface of each electrode
m, a thin insulating resin layer (not shown) was provided.

The insulating substrate 14 has a thickness of 10 to 100 μm.
It is preferable to use a material such as polyimide or polyethylene terephthalate. In this embodiment, a polyimide having a thickness of 25 μm is used. In order to form an all black image when recording by flying toner from all the openings 12,
The openings 12 are arranged in a staggered manner so as to complement each other. The diameter of the opening 12 is preferably 50 to 200 μm, and in the present embodiment, the diameter of the opening 12 is 145 μm. The image signal electrode 11 is made of a metal such as copper, and has a thickness of 5 to 5.
30 μm is preferred. The image signal electrode 11 is a lead wire 11
A, an image signal power supply 1 serving as an image signal voltage switching means
3 are independently connected to each other. Although a voltage of about 400 V is normally applied to the image signal electrode 11, in the present embodiment, a voltage of 300 V is applied for dot formation, and a voltage of -100 V is applied for non-dot formation. And The distance between the counter electrode 5 and the insulating base 14 is 50 to
1000 μm is preferred. In this embodiment, the thickness is 250 μm. Further, the distance between the toner conveying roller 1 and the insulating base material is preferably 0 to 200 μm. In this embodiment, 30 μm
m.

As shown in FIG. 3, a plate-shaped vibration transmitting member 15 extending parallel to the rows of the openings 12 is fixed to the surface of the insulating base material 14 (the surface on the side of the toner conveying roller 1). The vibration transmitting member 15 can be fixed by bonding or the like, and may be fixed by, for example, thermocompression bonding or an epoxy-based adhesive. The vibration generating sources 60 are provided at both ends of the vibration transmitting member 15, respectively.

The vibration source 60 includes a vibrator 16 and a vibration amplifier (horn) 17. As the vibrator 16,
For example, a bolted Langevin type vibrator can be used. The vibrator 16 includes a vibration amplifier (horn) 17
Attached to. The horn 17 is formed such that its cross-sectional area is continuously and smoothly reduced as it goes downward, and is configured to concentrate the vibration energy of the vibrator 16 and transmit it to the vibration transmission member 15. . Therefore, the vibration of the vibrator 16 propagates in the longitudinal direction (X direction) of the vibration transmitting member 15, and then is transmitted from the vibration transmitting member 15 to the insulating base material 14, and the Y direction moves toward the row of the openings 12.
Will propagate in that direction. Thus, the inner surface of the opening 12 and the periphery thereof are cleaned by the vibration propagated to the periphery of the opening 12.

The vibration transmitting member 15 may have any rigidity capable of transmitting the vibration without absorbing the vibration. For example, the vibration transmitting member 15 may be formed of metal. Specifically, for example, stainless steel may be used. Further, the plate width may be set to 5 mm and the plate thickness may be set to about 0.2 mm. The horn 17 has a rigidity capable of transmitting the vibration without absorbing the vibration, and preferably has the same resonance frequency as the resonance frequency of the vibrator 16, and may be formed of, for example, metal. Specifically, it is particularly preferable to use, for example, stainless steel or aluminum because the molding is easy.

The vibrator 16 is driven by a drive circuit 31, and the vibration is preferably a sine wave of 1 MHz or less, for example, 40 kHz. This is because heat generation of the vibration transmitting member 15 and the vibrator 16 cannot be ignored when the vibration frequency increases, and that the degree of vibration attenuation increases.

As shown in FIG. 4, when the insulating base material 14 and the toner conveying roller 1 are set to be in contact with each other, the contact portion between the toner conveying roller 1 and the insulating base material 14 causes the reflection end 32 which reflects the vibration wave. And a node of vibration is formed at the reflection end. Therefore, the wavelength of the vibration is set to λ,
(Particularly, the distance between the edge of the row of apertures 12 on the vibration transmission member 15 side and the reflection end 32) of the row 12 located on the side of the vibration transmission member 15 and L1 is set to be smaller than λ / 2.
2 is located at the antinode of the vibration, and the periphery of each opening 12 can be vibrated reliably. For example, the wavelength when vibration is applied to the insulating base material 14 is about 4 mm when the vibration frequency is 40 kHz. Therefore, the vibration reflection end 3 which is a contact portion between the toner conveying roller 1 and the insulating base material 14
If the distance between the opening 2 and the opening 12 is 2 mm or less, the opening 12
Can be vibrated reliably. In this embodiment, the distance is 1 mm.

The vibration transmitting member 15 and the reflection end 32
Is larger than λ / 4, the periphery of each opening 12 can be an antinode of vibration, and can be effectively vibrated.

In FIG. 1, reference numeral 26 denotes control means for cleaning the print head 10. The control means 26 receives a cleaning signal when the voltage applied to the image signal electrode 11 is -100 V, and controls the roller drive means 27. While a rotation stop signal of the toner conveying roller 1 is given, a drive signal is given to the vibration drive circuit 31, and a switching signal is given to the voltage switching means 30 so that the counter electrode 5 is in the ground state.

Next, the operation of the image forming apparatus will be described.

When a voltage higher than a predetermined value is applied to the image signal electrode 11 in response to an external image signal, an accelerating electric field is formed between the toner conveying roller 1 and the image signal electrode 11,
The toner 4 on the toner transport roller 1 is
And fly toward the image signal electrode 11 side. The flying toner 4 passes through an opening 12 surrounded by the image signal electrode 11, and the toner 4 passing through the opening 12 is applied to the opposite electrode 5 by a voltage applied to the opposite electrode 5.
And adheres to the recording paper 6. On the other hand, when a voltage equal to or less than a predetermined value (including zero) is applied to the image signal electrode 11, the intensity of the electric field formed between the toner transport roller 1 and the image signal electrode 11 is not sufficient. Toner 4 does not fly, and the toner transport roller 1
It is still carried on. Next, the image is fixed on the recording paper 6 using the fixing roller 8.

In order to obtain the same effect, a reverse voltage may be applied to the image signal electrode 11 to reverse the direction of the electric field between the toner transport roller 1 and the image signal electrode 11. .

When the image forming operation is repeated, toner 4 and foreign matter are deposited around the opening 12 of the print head 10, so that the image forming operation is stopped (a period during which no image is formed), for example, Immediately after the power is turned on to the apparatus, or when a plurality of recording papers 6 are conveyed during continuous image formation, the recording paper is sent out, and then during a period in which the next recording paper is conveyed, the vibrator 16 is operated. Perform the following cleaning operation.

That is, the rotation of the toner transport roller 1 is stopped, and a vibration voltage is applied to the vibrator 16 to vibrate the vibrator 16. As a result, vibration is applied to the periphery of the opening 12 of the print head 10 through the vibration transmitting member 15. Vibration suitable for cleaning around the opening 12 depends on the amplitude and frequency. In this embodiment, by setting the amplitude to 20 μm and the frequency to 20 kHz, good cleaning performance was obtained. When this value is converted to vibration acceleration,
Assuming that one-sided amplitude a = 10 μm and frequency f = 20 kHz, vibration displacement x = asinωt, speed υ = aωcosωt, acceleration αv =
−aω ² sinωt (t: time, ω: angular velocity = 2πf, π:
(Pi: f: frequency), so the maximum value of the speed υmax = 1.3
m / s and the maximum value of acceleration αmax = 1.6 × 10 ⁵ m / s ² . When this acceleration is compared with the acceleration due to the electric field, the acceleration due to the electric field acting on the toner at the time of image formation is as follows: electric field force F, electric charge q, electric field E, electric charge per weight of toner Q / M, mass of one toner particle Is m, F =
qE = m × (Q / M) × E = mαe. Therefore, αe = (Q
/ M) × E = (Q / M) × Vc / Lk (Vc: applied voltage of the signal electrode during image formation, Lk: distance between the toner transport roller and the signal electrode). Here, the charge amount per weight of toner Q /
Since M = 10μC / g, Vc = 300V, Lk = 30μm, αe = 1.0 × 1
0 ⁵ m / s ² That is, since a vibration acceleration larger than the electric field force acting on the toner during image formation acts on the toner attached around the opening, good cleaning performance can be obtained.

In the toner accumulated around the opening 12, not only the toner of the forward polarity but also the toner of the opposite polarity exist. If the vibration is applied while the polarity of the counter electrode 5 is kept the same as the polarity at the time of image formation, a force for attracting the toner of the opposite polarity attached to the periphery of the opening 12 from the counter electrode 5 toward the print head 10 acts. Therefore, even if the toner of the opposite polarity is once ejected to the counter electrode 5 side by vibration, it will again fly to the print head 10 side by the action of the electric field and diffuse to a wider area than the periphery of the opening 12, Instead, the print head 10 may be soiled. Further, the print head 10 and the toner transport roller 1
When they are used in contact with or very close to each other, toner may be blown out of the toner conveying roller 1 by an air current generated by applying vibration. In this case as well, since the toner to be blown out has a forward polarity and a reverse polarity, when a voltage of either polarity is applied to the counter electrode 5, the toner of either polarity becomes the print head 1.
The print head 10 may fly back to zero and become soiled.

On the other hand, in the case of the above-described image forming apparatus, the electric field does not act on the toner 4 or the foreign matter because the toner transport roller 1 and the counter electrode 5 have the same potential when the vibration is applied. Therefore, the toner 4 can be surely blown to the counter electrode 5 side. When the vibration is applied, the toner transport roller 1
Since the rotation of the toner transport roller 1 is stopped, if a certain period of time has elapsed since the application of the vibration,
Will not jump out.

-Modification- In the above embodiment, the toner transport roller 1 and the print head 10 are directly contacted. However, as shown in FIG. 5, the print head 10 and the toner transport roller 1 are brought into contact with each other. Instead, a plate-shaped vibration reflection member 18 extending parallel to the vibration transmission member 15 may be provided on the opposite side of the vibration transmission member 15 across the opening 12. The vibration reflection member 18 may be fixed to the back surface of the print head 10 by bonding or the like, or may be fixed to the front surface. When the vibration reflecting member 18 is adhered to the front surface or the back surface of the print head 10 as described above, the vibration propagated from the vibration transmitting member 15 passes through the opening 12 and is reflected by the vibration reflecting member 18. The vibration reflecting member 18 has a rigidity capable of transmitting vibration without absorbing the vibration, and a vibration characteristic that is significantly different from the impedance of the vibration transmission of the print head 10 is particularly desirable for increasing the reflection efficiency. When a resin such as polyimide is used for the insulating base material 14 of the print head 10, the density ρ,
It is desirable to use a metal or the like that greatly differs in the value of ρc obtained by the product of the sound speed c. Specifically, stainless steel or spring steel is suitable. Also, the plate width is 5 mm and the plate thickness is 0.2
It may be set to about mm. For bonding to the print head 10, for example, thermocompression bonding or an epoxy-based or isocyanate-based adhesive can be used.

As another configuration for bringing the print head 10 into contact with the toner conveying roller 1, as shown in FIG. 6, a spacer 19 is attached to the print head 10 in order to prevent the wear of the print head 10 or reduce the frictional force. Is preferably provided. The spacer 19 has an effect of maintaining the gap between the print head 10 and the toner conveying roller 1 uniformly in the column direction of the openings 12 in addition to achieving the above object. Since the spacer 19 rubs against the toner 4, depending on the material thereof, the spacer 19 is charged to cause an electric field for image formation or the toner 4.
May affect the charge amount. Therefore, it is preferable to connect the spacer 19 to a mechanism for removing charges, and to use a material excellent in conductivity and abrasion resistance for the material.
Specifically, polyamide filled with a conductive filler,
Resins such as polyimide and polycarbonate, and metals such as stainless steel and aluminum are particularly desirable. Spacer 1
When the metal 9 is made of metal or the like, the spacer 19 can also serve as the vibration reflection member 18.

Although not shown, for example, a power supply for applying a voltage to the toner transport roller 1 and a switch for switching the toner transport roller 1 between a voltage applied state and a grounded state may be provided. Good. When image formation is not performed, a voltage is applied to the toner transport roller 1, and the magnitude relationship between the potential of the toner transport roller 1 and the image signal electrode 11 is reversed from the magnitude relationship of the potential during image formation. You may make it. That is,
When the vibration is applied, an electric field may be formed so that the toner 4 flies from the image signal electrode 11 toward the toner conveying roller 1. In this case, the toner transport roller 1
The toner 4 existing between the print head 10 and the print head 10 can be positively caused to fly toward the toner transport roller 1, and the print head 10 can be effectively cleaned. At the same time, it is possible to prevent the toner from being blown out of the toner transport roller 1 by the air current generated by the application of the vibration.

<Embodiment 2> FIG. 7 shows Embodiment 2 of the present invention.
1 shows an image forming apparatus according to the first embodiment. Since the basic configuration and operation of the present embodiment are the same as those of the first embodiment, only different parts will be described.

That is, the counter electrode 5 is of a roller type and can be driven to rotate by a driving means (motor) 28. A cleaning blade 21 is in contact with the opposite side of the counter electrode 5 from the print head 10, and a toner collecting container 20 is provided below the counter electrode 5. The cleaning control unit 26 receives the cleaning signal and sends the toner conveying roller 1 to the roller driving unit 27.
, A driving signal is supplied to the vibration driving circuit 31, a switching signal is supplied to the voltage switching means 30 so that the counter electrode 5 is grounded, and a rotation driving signal is supplied to the counter electrode driving means 28. .

During the image forming operation, the counter electrode 5 is stationary without rotating. When cleaning the print head 10, the counter electrode 5 rotates. In this embodiment, it rotates counterclockwise. Opening 1 by the operation of vibrator 16
The toner 4 attached to the periphery 2 is blown to the counter electrode 5 side. At this time, the voltage of the counter electrode 5 is switched from +1000 V at the time of image formation by the voltage switching means 30 and is grounded similarly to the toner supply roller 1. The toner 4 and foreign matter which have protruded to the counter electrode 5 side are rotated by the rotation of the counter electrode 5.
The toner is collected in the toner collecting container 20 by the cleaning blade 21.

Since the toner 4 that has been blown off to the counter electrode 5 is collected, it is possible to prevent the toner 4 from flowing from the counter electrode 5 toward the print head 10 in the reverse direction.
It is possible to prevent the print head 10 from being contaminated by the reverse flying toner.

<Embodiment 3> FIG. 8 shows Embodiment 3 of the present invention.
1 shows an image forming apparatus according to the first embodiment. Since the basic configuration and operation of the present embodiment are the same as those of the second embodiment, only different portions will be described.

The rotatable counter electrode 5 is connected to voltage switching means 30 for switching between a state connected to the DC power supply 9, a grounded state, and a state connected to the AC power supply 32. AC power supply 32 has a frequency of 4 kHz and a voltage of 1.5 k
V (Vpp). The control means 26 for cleaning receives the cleaning signal and
7, a rotation stop signal of the toner conveying roller 1 is given.
A drive signal is supplied to the vibration drive circuit 31 and the voltage switching means 30
Then, a switching signal is applied so that the counter electrode 5 is grounded in the first half (initial stage) of the application of the vibration, and an alternating voltage is applied to the counter electrode 5 in the second half, and a rotation driving signal is further applied to the counter electrode driving means 28.

Therefore, at the time of cleaning the print head 10, the counter electrode 5 is switched from +1000 V at the time of image formation to the ground state (0 V), as in the first embodiment. Is switched to the AC power supply 32 after elapse.

Since the application of the vibration is performed while the operation of the toner conveying roller 1 is stopped, the toner does not jump out of the toner conveying roller 1 in the latter half of the application of the vibration. At this time, the switching to the AC power supply 32 is performed so that the alternating voltage is applied to the counter electrode 5, and the alternating electric field generated thereby acts only on the removal of toner and foreign matter remaining around the opening. Then, both of the alternating electric field and the vibration combine to cause not only the forward polarity toner but also the opposite polarity toner from the print head 10 to the counter electrode 5.
To clean it. Since the cleaning is performed with the assistance of the electric field force, the toner and the foreign matter can be removed even with a small vibration acceleration. Since the opposing electrode 5 is moving, the toner blown off onto the opposing electrode 5 is collected by the cleaning blade 21 into the collecting container 20. Therefore, it is possible to prevent the toner from flying backward from the counter electrode 5 to the print head 10.

That is, according to the present embodiment, the first embodiment
In addition to the effect of the device 2, the alternating voltage is applied to the counter electrode 5 in the latter half of the vibration application, so that an electric field force for cleaning can be applied between the counter electrode 5 and the print head. The adhered toner can be removed. Further, if the cleaning electric field force is increased, the vibration energy to be applied can be reduced, which is advantageous in avoiding troubles such as breakage of the print head 10.

<Fourth Embodiment> FIG. 9 shows a fourth embodiment of the present invention.
1 shows an image forming apparatus according to the first embodiment. This is an example in which the present invention is applied to a multicolor printer. The toner charging / supplying unit 25, the print head 10 having the vibration applying unit, and the counter electrode 5 are all provided four each, and each constitutes an image forming unit for yellow, magenta, cyan, and black. These image forming units are arranged in a row, and a recording paper transport belt 22 is provided so that the carrier side of the endless belt runs between the print head 10 and the counter electrode 5 of the unit in the row direction. The transport belt 22 runs in the direction of the arrow in FIG. The transport belt 22 may be a conductive seamless belt in which a resin such as polyimide, polycarbonate, or polyethylene is filled with a conductive filler. In this embodiment, polyimide is used.

In this embodiment, the recording paper 6 is supplied to the transport belt 22 by the paper feed roller 7, and the transport belt 22 is applied with static electricity by the grounded paper suction brush 23, so that the recording paper 6 It is electrostatically attracted to the surface facing the print head 10. The recording paper 6 is transport belt 2
The paper is conveyed by the travel of No. 2 and images of four colors are sequentially formed. The toner image on the recording paper 6 on which the image is formed is heated and pressed by the fixing device 8 and is fixed on the recording paper 6.

The driving of the vibrator 16 drives only the color unit at the timing when the image forming operation is stopped. Accordingly, only one drive circuit 31 of the vibrator 16 is prepared, and the vibrator 16 is driven by being switched by the drive switching means (switch) 33 in the order of each color. The voltage of the counter electrode 5 is also
The voltage switching means (switching switch) 30 is also used for this switching, so that one DC power supply 9 and one AC power supply 32 are shared by each unit.

As described above, the vibration drive circuit 31, the high-voltage power supply 9
In addition, since the AC power supply 32 is shared by each unit, the cost of the apparatus is not significantly increased even in the case of a multicolor image forming apparatus.

If the resonance frequencies of the oscillators 16 of each unit are not uniform, the amplitude of each oscillator 16 varies. Therefore, it is desirable to manage the resonance frequency of the vibrator 16 and design the resonance frequency band Q of the vibrator 16 to be narrow. Further, it is desirable that the drive circuit 31 of the vibrator 16 be an automatic frequency tracking type circuit so that the variation in the resonance frequency can be absorbed by the circuit side.

When the voltage control means 30 such as a switch or a relay is used to control the voltage of the opposing electrode 5, only two power supplies 9 and 32 for image formation and cleaning can be used. When a relay is used, since high voltage is switched, noise is generated at the time of switching, which may cause malfunction of peripheral circuits. In such a case, it is preferable to insert a filter such as ferrite on the high voltage output side to cut noise.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a partial detailed view of a print head ((a) is (b)
(A) is a sectional view taken along the line A-A, and (b) is a plan view.

FIG. 3 is a perspective view of a print head.

FIG. 4 is a partial cross-sectional view of a print head.

FIG. 5 is a partial cross-sectional view of a print head according to a modification.

FIG. 6 is a partial sectional view of a print head according to another modification.

FIG. 7 is a schematic configuration diagram of an image forming apparatus according to a second embodiment of the present invention.

FIG. 8 is a schematic configuration diagram of an image forming apparatus according to a third embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of an image forming apparatus according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Toner conveyance roller (developer carrier) 2 Regulator blade 3 Supply roller 4 Toner (developer) 5 Counter electrode 6 Recording paper (recording member) 8 Fixing roller 9 Power supply for printing of counter electrode 10 Print head 11 Image signal electrode 12 Opening (developer passage hole) 14 Insulating base 15 Vibration transmitting member 16 Vibrator 17 Vibration amplifier (horn) 18 Vibration reflection member 19 Spacer 30 Voltage switching means of counter electrode 31 Vibration drive circuit 32 Vibration reflection end 60 Vibration source

 ──────────────────────────────────────────────────続 き Continued on the front page (71) Applicant 597063831 Announced Brygga 13 421 57 Vestro Fround a Sweden (72) Inventor Masayoshi Miura 1006 Odakadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Tsujimoto Takahiro Kadoma 1006, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Masaichiro Tachikawa 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Masahiro Aizawa 1006 Kadoma, Kadoma, Osaka Prefecture Address: Matsushita Electric Industrial Co., Ltd. (72) Akira Ryuji, Inventor Akira 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Masahiko Hashimoto 3-1-1, Higashi-Mita, Tama-ku, Kawasaki City, Kanagawa Prefecture Matsushita Giken Co., Ltd. F term (reference) 2C162 AE25 AE31 AE74 AE84 AE93 AJ07 CA02 CA12 CA24

Claims (18)

[Claims] A developer supply unit configured to charge the developer and supply the developer by being carried on a developer carrier; a counter electrode disposed to face the developer supply unit and to which a predetermined voltage is applied; An insulating base material having a plurality of developer passage holes, disposed between the developer supply means and the counter electrode, provided around the developer passage hole of the insulating base material, and in accordance with an image signal. An image signal electrode to which a voltage for controlling the amount of developer passing through the developer passage hole is applied, a vibration source, and the developer of the insulating base material connected to the vibration source. A vibration transmitting member provided in the vicinity of the passage hole, and a vibration applying means for applying vibration to the insulating base material, wherein a recording member is disposed between the counter electrode and the insulating base material. The developer is attached to a recording member or the counter electrode to form an image. An image forming apparatus, comprising: a control unit configured to operate the vibration applying unit and stop the operation of the developer supply unit when the image formation is not performed. apparatus. 2. The image forming apparatus according to claim 1, wherein the control unit is configured to:
While activating the vibration applying unit, the operation of the developer supplying unit is stopped, and the counter electrode and the developer carrier are set to the same potential at least at the initial stage of the application of the vibration by the vibration applying unit. Image forming apparatus. 3. The image forming apparatus according to claim 2, wherein the counter electrode is movably provided so that a surface facing the developer carrier can be changed. When not forming the image,
While operating the vibration applying unit, the operation of the developer supply unit is stopped, and the counter electrode and the developer carrier are moved at least at the initial stage of the vibration application by the vibration applying unit while moving the counter electrode. An image forming apparatus having the same potential. 4. The image forming apparatus according to claim 3, wherein the control unit is configured not to perform the image formation.
While operating the vibration applying unit, the operation of the developer supply unit is stopped, and the counter electrode and the developer carrier are moved at least at the initial stage of the vibration application by the vibration applying unit while moving the counter electrode. The same potential, and then the counter electrode or the counter electrode so that an electric field is formed between the insulating base and the counter electrode, which assists the charged developer to fly from the insulating base to the counter electrode. An image forming apparatus, wherein the potential of an image signal electrode is changed. 5. The image forming apparatus according to claim 4, wherein the charged developer between the insulating base and the counter electrode assists the flying of the charged developer from the insulating base to the counter electrode. An image forming apparatus, wherein an alternating voltage is applied to the counter electrode to form an electric field. 6. The image forming apparatus according to claim 1, wherein the control unit is configured to:
While activating the vibration applying means, stopping the operation of the developer supply means, and reversing the magnitude relationship of the potential between the developer carrier and the image signal electrode with the magnitude relationship of the potential during image formation. An image forming apparatus comprising: 7. The image forming apparatus according to claim 6, further comprising a change unit that changes a voltage applied to the developer carrier. 8. A developer supply means for charging the developer and supplying it by being carried on a developer carrying member; a counter electrode arranged to face the developer supply means and to which a predetermined voltage is applied; An insulating base material having a plurality of developer passage holes, disposed between the developer supply means and the counter electrode, provided around the developer passage hole of the insulating base material, and in accordance with an image signal. An image signal electrode to which a voltage for controlling the amount of developer passing through the developer passage hole is applied, a vibration source, and the developer of the insulating base material connected to the vibration source. A vibration transmitting member provided in the vicinity of the passage hole, and a vibration applying means for applying vibration to the insulating base material, wherein a recording member is disposed between the counter electrode and the insulating base material. The developer is attached to a recording member or the counter electrode to form an image. An image forming apparatus that operates the vibration applying unit when the image is not formed, wherein the developer supply unit, the insulating base having the developer passage hole and the image signal electrode, A plurality of image forming units each including a combination of the vibration applying unit and the counter electrode are provided, and the vibration applying units of each of the plurality of image forming units are driven independently of each other, and each of the counter electrodes is Wherein the voltages are controlled independently of each other. 9. The image forming apparatus according to claim 8, wherein the plurality of vibration applying units control the respective vibration generating sources with respect to one shared driving circuit that drives the respective vibration generating sources. An image forming apparatus, wherein the image forming apparatus is connected via drive switching means for sequentially driving. 10. The image forming apparatus according to claim 9, wherein the driving circuit of the vibration source is an automatic frequency tracking type circuit. 11. The image forming apparatus according to claim 8, wherein the plurality of counter electrodes are connected to one common power supply via a voltage switching unit. 12. The image forming apparatus according to claim 1, wherein the developer carrier and the insulating base material are connected to each other with the developer passage hole interposed therebetween. An image forming apparatus, wherein the image forming apparatus is in contact with an opposite side of the transmission member so as to form a reflection end for reflecting a vibration wave transmitted from the vibration transmission member. 13. The image forming apparatus according to claim 12, wherein the developer carrier and the insulating base are in contact with each other via a spacer forming the reflection end. Forming equipment. 14. The image forming apparatus according to claim 13, wherein the plurality of developer passage holes of the insulating base are arranged in one row or several rows, and the vibration transmitting member and the spacer are formed of the developer. An image forming apparatus extending along a row of through holes, wherein the thickness of the spacer is constant over its entire length. 15. The image forming apparatus according to claim 12, wherein a distance between the reflection end and the developer passage hole is a wavelength of vibration applied to the insulating base. An image forming apparatus characterized by being smaller than half of the image forming apparatus. 16. The image forming apparatus according to claim 12, wherein the vibration imparted to the insulating base by the vibration imparting means causes the reflection end to be a node and causes the development. An image forming apparatus comprising: a standing wave having an antinode at the center of the agent passage hole or in the vicinity thereof. 17. The image forming apparatus according to claim 12, wherein a wavelength of the vibration is λ, a center of a developer passage hole located closest to the vibration transmitting member, and the reflection. An image forming apparatus, wherein L1 <λ / 2, where L1 is the distance from the end. 18. The image forming apparatus according to claim 12, wherein when the wavelength of the vibration is λ and the distance between the vibration transmitting member and the reflection end is L2, L2> λ / 4. An image forming apparatus, comprising: