JP2004212479A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of feeding unevenness in the case of feeding while scattering developer by an alternative electric field. <P>SOLUTION: The developer T is fed to the vicinity of a photoreceptive drum 2 where an electrostatic latent image on the photoreceptive drum 2 is developed by moving an endless belt 101 carrying the developer T on the surface of an alternative electric field generating member 41. Then, the start position of the generation of an alternative electric field is constituted within the range of each position separated by about five times of a distance between the alternative electric field generating member 41 and the photoreceptive drum 2 to an upstream side and a downstream side from the most adjacent position of the alternative electric field generating member 41 to the photoreceptive drum 2 or within each position respectively separated by about 10mm to the upstream side and the downstream side in the feeding direction of the developer T. Also, the distance between the alternative electric field generating member 41 and the photoreceptive drum 2 is about 0.5-5mm. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a developing device that develops an electrostatic latent image formed on an image carrier by causing a developer to fly by an alternating electric field, and an image forming apparatus including the same.
[0002]
[Prior art]
At present, non-contact developing devices that perform development without bringing a developer carrier into contact with an image carrier are attracting attention as a developing device applied to an image forming apparatus using an electrophotographic process such as a copying machine or a printer. A developing device using a powder cloud method, a jumping method, or an electric field curtain (traveling wave electric field) that is an alternating electric field formed over a predetermined range has been proposed.
As a developing device using an electric field curtain, for example, Patent Literature 1 and Patent Literature 2 disclose a power supply that generates a plurality of types of alternating voltages having phases different from each other, and a plurality of power supplies arranged at predetermined intervals in a predetermined base material. A member for transporting the developer while flying the developer by a traveling wave electric field (an example of an alternating electric field) formed by applying an alternating voltage from the power supply to the electrode (hereinafter, referred to as an alternating electric field generating member) Has been proposed. As a result, the developer is transported while flying along the traveling wave electric field, and moves onto the image carrier near the image carrier.
Japanese Patent Application Laid-Open No. H11-163,086 discloses a pre-charging means for pre-charging the developer conveyed by a developer carrying carrier, and an electric field curtain generating means for applying an electric field curtain on the developer carrying carrier (for an alternating electric field generating member). An example) is proposed. As a pre-charging means in this apparatus, a pre-charging roller made of, for example, urethane foam is used, and the pre-charging roller is provided so as to be in contact with the developer carrying member, and the tip of the pre-charging roller is attached to the pre-charging roller. A blade is provided so as to be in contact with the blade. The pre-charging roller is configured to perform pre-charging of the developer by rubbing the developer with the developer carrying member, and to regulate the layer thickness of the developer. With such a configuration, the developer can be supplied with a uniform layer thickness, and the developer can be uniformly charged to an appropriate charge amount. As a result, it is described that the developer can be prevented from being scattered at the time of conveyance and fogging of an image to be formed.
Further, Japanese Patent Application Laid-Open No. H11-163,086 discloses a developing device that conveys a developer by moving a belt-shaped member (moving on a surface facing an image carrier) on a peripheral surface of a member that generates the traveling wave electric field. It is shown. Thereby, charging of the member that generates the traveling wave electric field and sticking of the developer can be prevented, and the traveling wave electric field is stabilized, and the developer can fly smoothly and be supplied to the image carrier. Patent Literature 4 describes that the development can be performed and stable development and image formation can be performed.
[0003]
[Patent Document 1]
Japanese Patent Publication No. 5-31146 [Patent Document 2]
Japanese Patent Publication No. 5-31147 [Patent Document 3]
JP-A-3-21967 [Patent Document 4]
Japanese Patent Application Laid-Open No. 2002-91160 [Non-Patent Document 1]
IS & Ts NIP 15: 1999 International Conference on Digital Printing Technologies p.262-265
[0004]
[Problems to be solved by the invention]
However, when the developer is transported while flying by the traveling wave electric field (alternating electric field), the transport unevenness occurs during the transport, resulting in a problem that vertical stripe-like development unevenness occurs on the image carrier. . On the other hand, Patent Documents 1 to 4 do not disclose any measures for preventing transport unevenness during transport of the developer by the traveling wave electric field.
It has been found from various experiments that when the developer is transported while flying using the traveling wave electric field (an example of the alternating electric field), toner transport unevenness occurs in the form of vertical stripes in the developer transport direction. It is considered that this is because the developer concentrates on a predetermined portion due to an imbalance in the charged state of the developer. The uneven transport of the developer becomes remarkable as the transport length of the developer by the traveling electric field becomes longer, and it is difficult to repair (improve) the transport unevenness once generated on the upstream side of the transport during the transport.
As a solution to this problem, the transport length of the developer due to the traveling wave electric field is shortened, or the developer is caused to fly at a certain place by the alternating electric field without forming the traveling wave electric field as the most extreme configuration (the traveling direction). However, there are various restrictions on the configuration of the apparatus, such as the difficulty in arranging the developer supply means at the electric field generating position due to interference with the adjacent image carrier. Therefore, there is a limit to simply shortening the transport length (including preventing the transport length), and a sufficient effect of suppressing transport unevenness cannot be obtained.
Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a developing apparatus for preventing transport unevenness when transporting developer while flying by an alternating electric field, and an image forming apparatus including the same. It is to provide a device.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a developing device which develops an electrostatic latent image formed on an image carrier which is opposed to an image carrier by causing the developer to fly. A developer transporting means for transporting the developer toward the vicinity; and a plurality of electrodes arranged at a predetermined interval in a predetermined base material and to which a plurality of phases of AC voltages are applied, wherein the developer is generated by an alternating electric field generated between the electrodes. An alternating electric field generating member for causing the developer conveyed by the conveying means to fly, wherein the developer conveying means transfers the developer by a method different from a method of conveying the developer by the alternating electric field. The image forming apparatus is configured as a developing device characterized by being transported.
According to such a configuration, the developer reaches the vicinity of the image carrier where development of the electrostatic latent image on the image carrier (transfer of the developer from the developing device to the image carrier) is performed. Is transported by the developer transporting means by a method different from the method of transporting by the alternating electric field (such as the traveling wave electric field), so that restrictions on the arrangement of the developer supply means are eliminated, and the Since the transport length of the developer due to the traveling wave electric field can be shortened, it is possible to prevent uneven transport of the developer (that is, uneven development).
[0006]
Also, the developer conveying means moves the belt-like member carrying the developer on the surface of the alternating electric field generating member on the side facing the image carrier, so that the developer is moved to the position where the alternating electric field is generated. That are configured to carry
As a result, it is possible to shorten the toner transport distance due to the alternating electric field without greatly changing the configuration of the developing device disclosed in Patent Document 4.
[0007]
According to the experimental results described later, the starting position of the generation of the alternating electric field is located upstream and downstream of the position closest to the image carrier in the alternating electric field generating member in the transport direction of the developer. Each of which is located within a range of about 5 times the distance between the alternating electric field generating member and the image carrier, or about 10 mm away from the upstream side and the downstream side, respectively. The one configured to fall within the range is suitable for preventing development unevenness due to uneven transport of the developer and development omission due to deterioration in development efficiency.
[0008]
Further, according to the experimental results described later, if the distance between the alternating electric field generating member and the image carrier is not less than about 0.5 mm and not more than about 5 mm, so-called developer fogging or development omission is observed. This is suitable for preventing
Further, the present invention may be regarded as an image forming apparatus including the developing device.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments and examples of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. The following embodiments and examples are mere examples embodying the present invention, and do not limit the technical scope of the present invention.
Here, FIG. 1 is a schematic sectional view of a copying machine as an example of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic sectional view of a developing device provided in the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of an alternating electric field generating member in a developing device provided in the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a developing device provided in the image forming apparatus according to the embodiment of the present invention. FIG. 5 is a diagram showing an example of a waveform of an alternating voltage applied to the electrode of the alternating electric field generating member in FIG. 5. FIG. 5 shows the start of generation of a traveling wave electric field (alternating electric field) by the developing device provided in the image forming apparatus according to the embodiment of the present invention. FIG. 6 is a table showing an experimental result on a relationship between a position and development unevenness, and FIG. 6 shows an experimental result on a relationship between a distance to a photosensitive drum and a developing performance of a developing device provided in the image forming apparatus according to the embodiment of the present invention. It is a table.
[0010]
First, a schematic configuration of a copying machine 1 which is an example of an image forming apparatus according to an embodiment of the present invention will be described with reference to FIG.
The upper part of the copying machine 1 is a document reading unit 110. The automatic document feeder 112 provided in the document reading unit 110 automatically forms a plurality of documents set on a document set tray on the upper surface of the automatic document feeder 112 one by one on a glass plate. This is a device that feeds the original onto a document table 111.
The reading optical system of the document reading unit 110 scans an image of a document placed on the document table 111 or fed by the automatic document feeder 112 onto the document table 11 to read the image. , A first scanning unit 113, a second scanning unit 114, an optical lens 115 for forming reflected light from a document on a CCD line sensor 116, a CCD line sensor 116 as a photoelectric conversion element, and the like. It is configured. The first scanning unit 113 includes an exposure lamp unit 113a for exposing the surface of the original, a first mirror 113b for reflecting a reflected light image from the original in a predetermined direction, and the like. Further, the second scanning unit 114 includes second and third mirrors 114a and 114b for guiding the reflected light from the document reflected from the first mirror to the CCD line sensor 116.
The document image read by the document reading unit 110 is sent as image data to an image data input unit (not shown), and after the image data is subjected to predetermined image processing, the image processing The image forming unit 210 is temporarily stored in a memory of the image forming unit, and the image data in the memory is read out after the image processing is completed or in response to a predetermined output instruction from the outside to constitute an image forming unit 210 disposed below the document reading unit. Is transferred to the writing unit 227.
[0011]
The writing unit 227 includes a semiconductor laser light source (not shown) that emits a laser beam in accordance with the content of image data transferred from the image processing unit or an external device, and a polygon mirror that deflects the laser beam at an equal angular velocity. (Not shown), and comprises an f-θ lens (not shown) that corrects the laser beam deflected at a constant angular velocity on the photosensitive drum 2 so as to be deflected at a constant velocity. In the present embodiment, a laser writing unit is used as the writing unit 227, but a solid-scanning optical writing head unit using a light emitting element array such as an LED or an EL may be used. As the photosensitive drum 2, for example, a photoconductive layer such as amorphous silicon (a-Si), selenium (Se), or an organic optical semiconductor (OPC) is formed on an outer peripheral surface of a conductive substrate (metal drum) made of aluminum or the like. Is formed in the form of a thin film, but is not particularly limited.
Further, the image forming unit 210 includes a charger 223 around the photosensitive drum 2 for charging the photosensitive drum 2 to a predetermined potential, and a toner on the electrostatic latent image formed on the photosensitive drum 2. A developing device 100 for supplying a toner image to the developing device 100, a transfer device 225 for transferring a toner image formed on the surface of the photosensitive drum 2 to a recording sheet (paper), and a static eliminator 229 for neutralizing the photosensitive drum 2; A cleaning device 226 for collecting excess toner on the photosensitive drum is also provided. The recording sheet on which the image has been transferred by the image forming unit 210 is then sent to the fixing unit 217, where the image is fixed on the recording sheet.
On the discharge side of the image forming unit 210, in addition to the fixing unit 217, a switchback path 221 for reversing the direction (front and rear) of the recording sheet in order to form an image again on the back surface of the recording sheet is provided. A post-processing device 260 that performs a stapling process and the like on the formed recording sheet and has a lifting tray 261 is provided. The recording sheet on which the toner image is fixed by the fixing unit 217 is guided to the post-processing device 260 by the discharge roller 219 through the switchback path 221 as necessary, where a predetermined post-processing is performed. After that, it is discharged onto the elevating tray 261.
Further, the copying machine 1 serves as a paper supply unit for supplying a recording sheet to the image forming unit 210, and communicates with a sheet tray 251 provided below the image forming unit 210 and the switchback path 221 to supply the recording sheet. In addition to a double-sided unit 255 for temporarily retracting recording sheets when image formation is performed on both sides of the copier 1 and a multi-stage paper supply unit 270 having a plurality of paper feed trays 252 and 253, a hand protruding from the side of the copier 1 is provided. A manual sheet feeding device 300 having a difference tray 254 is provided. The image forming apparatus further includes a conveying unit 250 that conveys the recording sheets set on the trays 251, 252, 253, and 254 to a transfer position of the image forming unit 210 by the transfer unit 225. The duplex unit 255 can be replaced with a normal paper cassette, and the duplex unit 255 can be replaced with a normal paper cassette.
[0012]
Next, the developing device 100 having the features of the copying machine 1 will be described with reference to a schematic sectional view of the developing device 100 shown in FIG.
As shown in FIG. 2, the developing device 100 includes a casing 40, an alternating electric field generating member 41, a mixing paddle 42, a supporting member 43, a developer supplying member 44, a developer collecting member 45, a developer layer thickness regulating member 46, and the like. The multi-phase AC power supply 47 is connected to the alternating electric field generating member 41.
The casing 40 accommodates the developer T therein, and supports members constituting the developing device 100 as needed.
The mixing paddle 42 is for mixing the developer T contained in the casing 40.
The alternating electric field generating member 41 has a belt shape so as to form a substantially flat surface facing the developing area of the photosensitive drum 2. In the present embodiment, the alternating electric field generating member 41 has a substantially planar shape. However, the present invention is not limited to this. For example, the alternating electric field generating member 41 may have a shape that forms a gentle curved surface. Absent.
The alternating electric field generating member 41 is arranged to be slightly inclined with respect to the vertical direction in the developing device 100 and to be substantially parallel to a tangent to a developing area on the surface of the photosensitive drum 2.
Also, the belt-shaped alternating electric field generating member 41 is opposite to the surface for transporting the developer T (the surface facing the photosensitive drum 2) so that the belt-like alternating electric field generating member 41 can be maintained in a state facing the developing area of the photosensitive drum 2. The supporting member 43 for holding the alternating electric field generating member 41 is provided on the surface on the side. Examples of the material of the support member 43 include ABS (Acrylonitrile-Butadiene-Styrene: acrylonitrile butadiene styrene) resin.
[0013]
At the lower end of the alternating electric field generating member 41, the developer supply member 44 for supplying the developer T accommodated in the casing 40 is provided.
The developer supply member 44 is provided in contact with the alternating electric field generating member 41 at a predetermined pressure in a width direction (a depth direction in FIG. 2) via an endless belt 101 described later. The pressing force of the developer supply member 44 is given by a spring or the like.
The developer supply member 44 is provided with a developer layer thickness regulating member 46 for regulating the thickness of the developer layer formed on the surface thereof so as to abut.
The material of the developer supply member 44 is not particularly limited, and examples thereof include silicone, urethane, solid rubber such as EPDM (ethylene-propylene-methylene copolymer), and foamed rubber. In addition, conductivity may be imparted by adding carbon black or an ionic conductive agent. In the example shown in FIG. 2, a bias voltage is applied by the DC power supply 48.
The positional relationship between the developer supply member 44 and the alternating electric field generating member 41 may be adjusted by adjusting the elastic modulus. Further, the voltage applied to the developer supply member 44 may be set to an appropriate value, and a function of charging the developer T to the developer supply member 44 may be added. Alternatively, a thin blade (for example, the same material as that of the developer supply member 44 can be used) may be provided in front of the developer supply member 44 to charge the developer T. .
An endless belt 101 (an example of the belt-shaped member) is provided on the surface of the alternating electric field generating member 41 (the surface facing the photosensitive drum 2) so as to cover the surface in the circumferential direction. The endless belt 101 is moved (rotated) at a predetermined peripheral speed in the transport direction of the developer T by a belt driving member 102 provided in the casing 40.
As the endless belt 101 moves at a predetermined peripheral speed, the developer T supplied by the developer supply member 44 is carried on the endless belt 101, and the developer T And the surface of the alternating electric field generating member 41 is constantly renewed, so that charging on the surface and sticking of the developer T are prevented.
[0014]
Here, the alternating electric field generating member 41 will be described with reference to FIGS.
FIG. 3 is a schematic sectional view of the alternating electric field generating member 41.
The alternating electric field generating member 41 transports the developer T while flying it by an electric field curtain action. As shown in FIG. 3, in the vicinity of the photosensitive drum 2, an insulating layer 41a, a surface protective layer 41c, A plurality of sets of long traveling wave generating electrodes 41b for generating an electric field curtain action are sequentially and continuously arranged (arranged) in a base made of.
When a multi-phase alternating voltage is applied from the multi-phase AC power supply 47 to these traveling wave generating electrodes 41b,... 41b, an electric field which is an alternating electric field in a direction parallel to the surface of the alternating electric field generating member 41 is obtained. A curtain is generated, and the developer T is conveyed to the developing area by the action of the electric field curtain.
As a specific configuration of the alternating electric field generating member 41, for example, the base material 41a: polyimide (thickness: 25 μm), the traveling wave generating electrode 41b: copper (thickness: 18 μm), the surface protection layer 41c: polyimide (thickness) 25 μm).
The traveling wave generating electrodes 41b are arranged in parallel with each other with an interval of about 50 dpi (dot per inch) to 300 dpi, that is, about 500 μm to 85 μm (interelectrode pitch λ), and have a width of about 40 μm to 250 μm. It is a micro electrode. In the example shown in FIG. 3, the four traveling wave generating electrodes 41b constitute one set, and for example, a four-phase alternating voltage having a voltage waveform as shown in FIG. 4 is applied to each set of these traveling wave generating electrodes 41b. I do. Thereby, the traveling wave electric field is formed on the traveling wave generating electrodes 41b... 41b. Of course, the present invention is not limited to this, and any other device that applies an alternating voltage of a plurality of phases (two or more phases), such as applying a three-phase alternating voltage with one set of three traveling wave generating electrodes 41b, may be used. May be used. The voltage waveform may be a sine wave or a trapezoidal wave, and the range of the voltage value is preferably about 100 V to 3 kV. Further, the frequency range is preferably 100 Hz to 5 kHz. However, these voltage values and frequencies may be set to appropriate values depending on the shape of the traveling wave generating electrode 41b, the transport speed of the developer T, the material used for the developer T, and the like, and are not particularly limited. .
In this way, the developer T conveyed by the endless belt 101 is applied to the photosensitive drum 2 in the vicinity of the photosensitive drum 2 by the traveling wave electric field which is an alternating electric field generated between the traveling wave generating electrodes 41b. It is transported while flying. As a result, the flying developer T moves to the photosensitive drum 2 side, and the electrostatic latent image on the photosensitive drum 2 is developed.
[0015]
Returning to FIG. 2, the description of the developing device 100 will be continued.
The driving speed of the endless belt 101 is preferably controlled to a level considered to be substantially stationary with respect to the transport speed of the developer T by the traveling wave electric field. It is set to be about 1/10 to 1/100 of the transport speed by the electric field. The speed of the endless belt 101 may be provided by, for example, a method of providing two infrared sensors, each of which detects a time when the developer T arrives, or a method of measuring using a high-speed video camera. Non-Patent Document 1).
Further, the endless belt 101 is provided with a constant tension so as to come into contact with the alternating electric field generating member 41 with substantially uniform pressure over the entire contact surface, and is formed on the surface thereof by the traveling wave generating electrode 41b. The traveling-wave electric field (electric-field curtain) thus applied acts uniformly.
Examples of the material of the endless belt 101 include organic insulating materials such as polyimide, PET (polyethylene terephthalate), polytetrafluoroethylene, polyfluoroethylene propylene, and PTFE (polytetrafluoroethylene), and silicon, isoprene, and butadiene. Rubber materials can be mentioned. The endless belt 101 has a thickness of 5 μm to 200 μm, preferably about 10 μm to 100 μm, though it depends on the pitch λ between the electrodes in the alternating electric field generating member 41.
As the belt driving member 102, a metal roller member such as SUS (stainless steel) or iron, or a member having a cored bar and covered with a member such as rubber, a film, a sponge, or the like is used.
[0016]
Further, in this embodiment, in order to make the rotation of the endless belt 101 smooth, a driving auxiliary member 103 is provided so as to abut against the belt driving member 102 via the endless belt 101. . As a result, the endless belt 101 is sandwiched between the belt driving member 102 and the driving auxiliary member 103, and the contact with the belt driving member 102 is increased to obtain a high driving force. . Further, a uniform tension is applied to the endless belt 101 by the driving auxiliary member 103 in the width direction (direction substantially perpendicular to the moving direction). Thereby, the endless belt 101 and the alternating electric field generating member 1 are configured to contact with substantially uniform pressure over the entire contact surface.
Similar to the belt driving member 102, the driving auxiliary member 103 may be a metal roller member such as SUS or iron, or a member made of a metal core and covered with a member such as rubber, film or sponge. Can be Further, the shape of the driving auxiliary member 103 is not limited to a roller shape but may be a plate shape or a square shape. Further, the driving auxiliary member 103 may be provided with a pressing means (not shown) for pressing and contacting the belt driving member 102. As the pressing means, for example, a means capable of applying a pressing force, such as a leaf spring or a coil spring, can be used.
Examples of the rotation mechanism of the driving auxiliary member 103 include a driven rotation mechanism by contact with the endless belt 101, and a connection driving mechanism that connects a driving source of the belt driving member 102 by a gear or a pulley and a belt. . Although not shown, another driving source may be provided for the driving auxiliary member 103. Further, by electrically grounding the driving auxiliary member 103, the potential charged on the surface of the endless belt 101 can be eliminated.
[0017]
At the upper end of the alternating electric field generating member 41, the developer T remaining on the endless belt 101 without contributing to the development of the electrostatic latent image on the photosensitive drum 2 is collected in the casing 40. The developer collecting member 45 is provided. The material of the developer collecting member 45 is not particularly limited. For example, the same material as the developer supplying member 44 may be used.
In the present embodiment, the developer collecting member 45 is configured to rotatably contact the endless belt 101 on the surface of the alternating electric field generating member 41. However, the present invention is not limited to this. Or a non-rotating configuration.
Further, in this embodiment, the endless belt 101 is used as a cleaning member for removing the developer T adhering (remaining) on the endless belt 101 and collecting the developer T in the developer accumulation section 40a of the casing 40. A cleaning blade 104 is provided which comes into contact with the belt driving member 102 through the cleaning blade 104. The cleaning blade 104 is fixed to a part of the casing 40. Examples of the material of the cleaning blade 104 include SUS, nickel-coated iron, urethane, and silicone rubber.
In the example shown in FIG. 2, the endless belt 101 and the developer accumulating portion are arranged so that the developer T does not re-adhere to the portion between the cleaning blade 104 and the developer supply member 44 of the endless belt 101. A partition member 105 is provided to separate the endless belt 101 from the portion 40a, so that the endless belt 101 can be more effectively cleaned.
[0018]
According to the configuration of FIG. 2 described above, the developer T performs development of the electrostatic latent image on the photosensitive drum 2 (transfer of the developer T from the developing device 100 to the image carrier 2). The endless belt 101 and the belt drive member 102 (an example of the developer conveying means) for moving the endless belt 101 are transported to the vicinity of the image carrier 2, that is, the alternating electric field (the traveling wave electric field). And the developer supply member 44 and the developer recovery member 45 can be arranged at positions where they do not interfere with the photosensitive drum 2, and the traveling wave electric field (an example of an alternating electric field) ), The transport length of the developer T can be shortened, so that uneven transport of the developer (that is, uneven development) can be prevented.
[0019]
Next, referring to FIG. 5, the start position of the generation of the traveling wave electric field (the alternating electric field) (that is, the arrangement start position P1 of the traveling wave generating electrode 41b to which the alternating voltage is applied (see FIG. 3)) and the development. An experimental result regarding the relationship with unevenness will be described.
FIG. 5A shows a case where the distance between the alternating electric field generating member 41 and the photosensitive drum 2 (hereinafter referred to as a developing gap D (see FIG. 3) is 3 mm). An experiment in which the presence or absence of development unevenness when the start position of the traveling wave electric field in the transport direction (the same as the transport direction of the developer T by the alternating electric field generating member 41; hereinafter, referred to as the developer transport direction) was visually confirmed was checked. It is a table showing the results.
FIG. 5B is a table similar to FIG. 5A when the developing gap D is 2 mm.
Other conditions in this experiment are as follows: the width of the traveling wave generating electrode 41b in the developer transport direction is 128 μm, the pitch λ between the electrodes is 508 μm, the alternating voltage applied to the traveling wave generating electrode 41b is ± 1 kV, The frequency of the alternating voltage is 750 Hz, and the bias voltage of the photosensitive drum 2 is 1.5 kV.
[0020]
5A and 5B, the starting position Xd of the traveling-wave electric field is located on the upstream side of the position P0 of the alternating electric field generating member 41 closest to the photosensitive drum 2 (see FIG. 3). The ratio to the developing gap D when the positive side (+) and the downstream side is negative (-) (hereinafter referred to as a developing gap ratio). The values in parentheses are numerical values representing the start position Xd of the traveling wave electric field in mm.
From the experimental results shown in FIG. 5A, when the developing gap D is 3 mm, the start position Xd of the traveling wave electric field is increased by 7 times (Xd = 7) It can be seen that when the development gap ratio is -6 times (Xd = -6) or less on the downstream side in the developer transport direction, development unevenness occurs.
Similarly, from the experimental results shown in FIG. 5B, when the developing gap D is 2 mm, the start position Xd of the traveling-wave electric field is increased by 7 times in the developing gap ratio on the upstream side in the developer conveying direction. When Xd = 7 or more, or when the developing gap ratio becomes −7 times (Xd = −7) or less on the downstream side in the developer conveying direction, development unevenness occurs.
Here, the development unevenness that occurs when the start position Xd of the traveling wave electric field is on the upstream side (+ side) in the developer transport direction is due to the longer developer transport length as described above. This is caused by the unevenness of developer conveyance that occurs. On the other hand, when the start position Xd of the traveling wave electric field is set to the downstream side (− side) in the developer transport direction, the development unevenness is caused by the lack of the developer flying toward the photosensitive drum 2. This is caused by development failure (development omission) due to the above.
On the other hand, from the experimental results shown in FIGS. 5A and 5B, the start position Xd of the traveling-wave electric field is shifted with respect to the photosensitive drum 2 regardless of whether the developing gap D is 3 mm or 2 mm. If the developing gap ratio is in the range of about 5 times (−5 ≦ Xd ≦ 5) in the upstream and downstream directions of the developer transport direction from the closest position P0, almost no development unevenness occurs. I understand that there is no.
When the starting position Xd of the traveling-wave electric field is expressed in mm, the starting position Xd of the traveling-wave electric field is located upstream of the position P0 closest to the photosensitive drum 2 in the developer conveying direction. It can be seen that development unevenness does not occur within a range of about 10 mm away from each other in each direction toward the downstream side.
[0021]
Next, experimental results regarding the relationship between the development gap D and the development performance will be described with reference to FIG.
FIG. 6 is a table showing the results of experiments in which the quality of development performance was visually checked when the development gap D (unit: mm) was changed. In FIG. 6, “◎” indicates that the developing performance is good, and “○” indicates that a so-called fog in which the developer adheres to a relatively small amount of the area where development is unnecessary is generated. A case where development omission occurs due to a shortage of the developer flying toward the surface is indicated by “，”, and a case where development omission with remarkable development omission occurs is indicated by “×”.
The other conditions in this experiment are, as in FIG. 5, the width of the traveling wave generating electrode 41b in the developer transport direction is 128 μm, the pitch λ between the electrodes is 508 μm, and the alternating voltage applied to the traveling wave generating electrode 41b. The applied voltage is ± 1 kV, the frequency of the alternating voltage is 750 Hz, and the bias voltage of the photosensitive drum 2 is 1.5 kV. Further, the start position Xd of the traveling wave electric field is made to coincide with the position P0 closest to the photosensitive drum 2.
From the experimental results shown in FIG. 6, it can be seen that the fogging occurs when the developing gap D is too small (D = 0.5 mm), and the development omission occurs when the developing gap D is too large (D ≧ 4 mm). . From this, it is understood that the developing gap D is desirably set in a range of about 1.0 mm or more and about 3.5 mm or less.
However, since some development omissions can be covered by correcting the bias voltage, taking this into consideration, and assuming that some fog is acceptable, the development gap D is about 0.5 mm or more and about 0.5 mm or more. In the range of 5 mm or less, practical image quality can be maintained.
[0022]
In the embodiment described above, an electrostatic latent image is formed by writing optical information on the photosensitive drum 2 (image carrier) charged with a predetermined charge, but is not limited to this. Instead of an ion-flow type, an electrostatic charge latent image is formed directly on a dielectric (an example of the image carrier), or an electrode having a plurality of openings, such as a toner jet type. By applying a voltage, an electrostatic latent image is formed in the space (in this case, the space where the electrostatic latent image is formed is regarded as the image carrier), and the developer is recorded in the space of the electrostatic latent image. The present invention is also applicable to a developing apparatus of a type in which an image is formed by flying on a medium.
[0023]
【The invention's effect】
As described above, according to the present invention, the alternating electric field is applied to the vicinity of the image carrier where development of the electrostatic latent image on the image carrier (transfer of the developer from the developing device to the image carrier) is performed. Since a means for transporting the developer by a method different from the transport method is provided, restrictions on the arrangement of the developer supply means are eliminated, and the transport length of the developer by the alternating electric field (traveling wave electric field) can be shortened. In addition, it is possible to prevent uneven transport of the developer (that is, uneven development). Further, if the belt carrying the developer moves on the surface of the alternating electric field generating member to convey the developer to the position where the alternating electric field is generated, the configuration of the conventional developing device disclosed in Patent Document 4 is disclosed. Can be shortened without significantly changing the toner transport distance due to the alternating electric field.
Here, the starting position of the generation of the alternating electric field is located upstream and downstream of the position closest to the image carrier in the alternating electric field generating member in the transport direction of the developer. If it is configured so as to be within the range of each position about 5 times the distance of, or within the range of each position about 10 mm away from the upstream side and the downstream side, it is possible to obtain a good development without uneven development. Development can be performed.
If the distance between the alternating electric field generating member and the image carrier is about 0.5 mm or more and about 5 mm or less, it is possible to perform good development without so-called fog or development omission.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a copying machine as an example of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic sectional view of a developing device provided in the image forming apparatus according to the embodiment of the present invention.
FIG. 3 is a schematic sectional view of an alternating electric field generating member in a developing device provided in the image forming apparatus according to the embodiment of the present invention.
FIG. 4 is a diagram illustrating an example of a waveform of an alternating voltage applied to an electrode of an alternating electric field generating member in a developing device provided in the image forming apparatus according to the embodiment of the present invention.
FIG. 5 is a table showing experimental results regarding a relationship between a start position of generation of a traveling-wave electric field (alternating electric field) by a developing device provided in the image forming apparatus according to the embodiment of the present invention and development unevenness.
FIG. 6 is a table showing experimental results relating to a relationship between a distance of a developing device included in an image forming apparatus according to an embodiment of the present invention to a photosensitive drum and developing performance.
[Explanation of symbols]
1. Image forming apparatus 2. Photoconductor drum (image carrier)
40 casing 41 alternating electric field generating member 41a insulating layer (base material)
41b: traveling wave generating electrode 41c: surface protective layer (base material)
42 mixing paddle 43 support member 44 developer supply member 45 developer recovery member 46 developer layer thickness regulating member 47 polyphase AC power supply 48 DC power supply 100 developing device 101 endless belt (band-like member, Developer transfer means)
102 driving member 103 driving auxiliary member 104 cleaning blade 105 partition member 110 image reading unit 210 image forming unit 254 manual tray 300 manual sheet feeding device

Claims (6)

In a developing device that develops an electrostatic latent image formed on an image carrier opposingly arranged by flying a developer,
Developer conveying means for conveying a developer toward the vicinity of the image carrier;
A plurality of electrodes arranged at predetermined intervals in a predetermined base material and having a plurality of AC voltages applied thereto, wherein the developer conveyed by the developer conveying means is caused to fly by an alternating electric field generated between the electrodes; An alternating electric field generating member for causing
The developing device, wherein the developer conveying means conveys the developer by a method different from a method of conveying the developer by the alternating electric field. The developer conveying means conveys the developer to a position where the alternating electric field is generated by moving a belt-like member carrying the developer on a surface of the alternating electric field generating member on a side facing the image carrier. The developing device according to claim 1, wherein the developing device is configured to perform the following. The starting position of the generation of the alternating electric field is located upstream and downstream of a position of the alternating electric field generating member closest to the image carrier in the transport direction of the developer. The developing device according to claim 1, wherein the developing device is configured to be within a range of each position which is about five times as long as a distance from the carrier. The starting position of the generation of the alternating electric field is approximately 10 mm apart from the position closest to the image carrier in the alternating electric field generating member by about 10 mm in the conveying direction of the developer. The developing device according to claim 1, wherein the developing device is configured to be inside. The developing device according to any one of claims 1 to 4, wherein a distance between the alternating electric field generating member and the image carrier is about 0.5 mm or more and about 5 mm or less. An image forming apparatus comprising the developing device according to claim 1.

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