JP2010175731A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the rotational torque of a roller, in a wet developing device. <P>SOLUTION: A bias voltage having the same polarity as that of toner is applied to a supply roller 142 for moving the toner from the supply roller 142 to a support roller 143, when the developing device is started. Thus, developer whose toner concentration is low is supplied to the supply roller 142 and a developing roller 141. Furthermore, the rotational direction of the supply roller 142 is in the trail direction with respect to the rotational direction of the developing roller 141. As a result, the rotational torque of the respective rollers 141 to 143 is reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wet developing apparatus.

  Some developing devices for developing images use a liquid developer in which toner is dispersed in a liquid carrier. Such a developing device is called a wet developing device.

  The wet developing device includes a plurality of rollers, and the developer is conveyed between the rollers by rotating these rollers. Finally, the developer adheres to the electrostatic latent image, and the electrostatic latent image is developed. The rollers are arranged so that not only other rollers but also various members such as blades are in contact with each other.

  In the wet developing apparatus, particularly when the operation is stopped for a long period of time, the amount of developer between the rollers decreases. In such a state, the friction between the roller and a member arranged to contact the roller is increased. As a result, not only the torque when starting the rotation of the roller increases, but also the device may be damaged.

  In Patent Document 1, in order to reduce the driving torque when the developing device is started, that is, when the rotation of the roller is started, the roller that rotates the counter during the developing operation is rotated with the rotation when the developing device is started.

JP 2006-343676 A

  Just by changing the rotation direction as in the above-described prior art, the torque cannot be sufficiently reduced, and there is room for improvement.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device that can sufficiently reduce the rotational torque of a roller and prevent damage to the device.

  In order to solve the above-described problems, a developing device according to claim 1 is a developing device for developing an electrostatic latent image, and includes a support roller rotatably provided around a rotation shaft, a toner and a liquid carrier. A developer supply device for supplying the developer onto the support roller; a supply roller having a rotation axis parallel to the rotation axis of the support roller and disposed at a position for receiving the developer on the support roller; A developing roller that has a rotation axis parallel to the rotation axis of the support roller, receives the developer on the supply roller, and is disposed at a position that can face the electrostatic latent image; A potential difference generator that generates a potential difference between the support roller and the supply roller so that toner moves from the supply roller to the support roller during operation of the developer supply device, and operation of the potential difference generator Inside, on A reverse rotation device that rotates the support roller and the developing roller in the same direction and rotates the supply roller in the reverse direction, and prevents the potential difference from occurring between the support roller and the supply roller during development. And a normal rotation device that rotates the developing roller and the supply roller in the same direction and rotates the support roller in the opposite direction when performing development.

  According to this developing device, since the above-described potential difference occurs when development is not performed, a low-concentration developer is supplied to the supply roller. And since the rotation direction of the support roller at this time, a supply roller, and a developing roller is set as mentioned above, the opposing surface of each roller will move to the same direction, and rotational torque is reduced.

  According to a second aspect of the present invention, the developing device of the first aspect further includes a cleaning member disposed so as to come into contact with the support roller, and the developer supply device includes the support roller at the time of development. A first supply unit for supplying developer to the second supply unit for supplying developer to the support roller when development is not performed, along the rotation direction of the support roller by the normal rotation device, A position on the support roller for receiving the developer from the first supply unit, a position for passing the developer to the supply roller, a position for receiving the developer from the second supply unit, and a contact with the cleaning member. Preferably, the potential difference generating device and the reverse rotation device are operated during the developer supply by the second supply unit.

According to a third aspect of the present invention, in the developing device of the second aspect, the first supply unit includes a discharge unit that discharges the developer, and a first discharge that causes the discharge unit to discharge the developer when the development is performed. A control unit, wherein the second supply unit stores the developer discharged from the discharge unit, and is disposed so as to immerse the support roller in the stored developer; A second discharge control unit that discharges the developer to the discharge unit so that the support roller is immersed in the developer.
It is preferable that the potential difference generating device and the reverse rotation device operate when the support roller is immersed in the developer in the container.

  According to a fourth aspect of the present invention, it is preferable that the developing device of the third aspect further includes a rotation stopping unit that stops the rotation of the support roller, the supply roller, and the developing roller when development is not performed. The second discharge controller preferably discharges the developer from the discharge unit until the support roller is immersed in the developer in the container while the rotation is stopped.

  According to a fifth aspect of the present invention, in the developing device according to any one of the second to fourth aspects, when the development is not executed, the first difference generating device and the reverse rotation device are operated, and then the first developing device. It is preferable to further include a third discharge controller that supplies the developer to the support roller by the supply unit. In addition, it is preferable that the potential difference eliminating device and the normal rotation device are operated during the supply of the developer by the third ejection control unit.

  According to a sixth aspect of the present invention, in the developing device according to any one of the first to fifth aspects, the potential difference generating device includes a first voltage applying unit that applies a voltage to the first roller, and the first voltage applying unit. It is preferable to include a second voltage application unit that applies a voltage to the two rollers and a potential difference generation control unit that controls the first and second voltage application units so as to generate the potential difference.

  According to a seventh aspect of the present invention, in the developing device according to any one of the first to sixth aspects, the potential difference elimination device includes the first and second voltage application units and the first voltage application unit so as to eliminate the potential difference. And a potential difference elimination control unit that controls the first and second voltage application units.

  According to this developing device, when the development is not executed, the developer is supplied to the support roller and the above-described potential difference is generated, so that the low-concentration developer is supplied to the supply roller. And since the rotation direction of the support roller at this time, a supply roller, and a developing roller is set as mentioned above, the opposing surface of each roller will move to the same direction, and rotational torque is reduced.

1 is a diagram illustrating a configuration of an image forming apparatus 1. FIG. The enlarged view of the image forming unit FY. The figure which shows the structure of the liquid developer circulation device LY. FIG. 2 is a diagram illustrating a configuration of a drive system and a control system in the image forming apparatus 1. FIG. 6 is a diagram illustrating an operation of the developing unit 14 in a first step. The figure which shows operation | movement of the image development unit 14 in a 2nd step. The figure which shows operation | movement of the image development unit 14 in a 3rd step. The figure which shows operation | movement of the image development unit 14 in a 4th step.

[1] First Embodiment Hereinafter, an embodiment of an image processing apparatus of the present invention will be described with reference to the drawings.

  For convenience of explanation, in the drawings, the position and size of members may be emphasized.

<1. Image forming apparatus 1>
An image forming apparatus 1 according to an embodiment of the present invention is shown in FIG. The image forming apparatus 1 is a color printer, and includes an image forming unit 2, a paper storage unit 3, a secondary transfer unit 4, a fixing unit 5, a paper transport unit 6, and a discharge unit 7. Yes.

  The image forming unit 2 includes an intermediate transfer belt 21, a cleaning unit 22, four image forming units FY, FC, FM, and FB, and an image forming controller (not shown). The image forming unit 2 forms a toner image based on image data under the control of the image forming controller. The image forming unit 2 is a so-called tandem type in which the image forming units FY, FC, FM, and FB are arranged along the moving direction of the intermediate transfer belt 21.

  The intermediate transfer belt 21 is an electroconductive, endless, ie, loop-shaped belt member. The intermediate transfer belt 21 is stretched around a driving roller 41, a driven roller 23, and a tension roller 24. The drive roller 41 is rotated by driving of a drive motor (not shown). By this rotation, the intermediate transfer belt 21 is circulated and driven clockwise as indicated by an arrow in FIGS. When the intermediate transfer belt 21 is driven, the driven roller 23 and the tension roller 24 are driven to rotate with respect to the intermediate transfer belt 21. The tension roller 24 is disposed so as to apply an appropriate tension to the intermediate transfer belt 21 so that the intermediate transfer belt 21 does not loosen.

  The cleaning unit 22 cleans the intermediate transfer belt 21. The cleaning unit 22 includes a cleaning roller 22a and a cleaning blade 22b.

  Four image forming units FY, FM, FC, and FB are arranged near the intermediate transfer belt 21 and arranged between the cleaning unit 22 and the secondary transfer unit 4 of the intermediate transfer belt 21. The image forming units FY, FM, FC, and FB correspond to yellow (Y), magenta (M), cyan (C), and black (Bk) colors, respectively. Note that the order of arrangement of the image forming units FY, FM, FC, and FB is not limited to this, but this arrangement is preferable in consideration of the influence of the color mixture on the completed image. Details of the image forming unit will be described later with reference to FIG.

  The paper storage unit 3 is a part for storing paper for fixing a toner image, and is disposed at the lower part of the image forming apparatus 1. The paper storage unit 3 includes a paper supply cassette 31 that stores paper, a paper supply roller 32, and a paper separation roller pair 33. A sheet is an example of a recording medium.

  The secondary transfer unit 4 includes a drive roller 41 that drives the intermediate transfer belt 21, and a secondary transfer roller 42 that is disposed to face the drive roller 41. The paper is transported between the secondary transfer roller 42 and the outer peripheral surface of the intermediate transfer belt 21 by the paper transport unit 6. At this time, the toner image formed on the intermediate transfer belt 21 is transferred onto the paper.

  The fixing unit 5 is disposed on the upper side of the secondary transfer unit 4 (on the downstream side in the paper transport direction). The fixing unit 5 includes a heating roller 51 and a pressure roller 52 disposed to face the heating roller 51. The sheet after the secondary transfer is conveyed between the heating roller 51 and the pressure roller 52 by the sheet conveying unit 6. When passing between the heating roller 51 and the pressure roller 52, the toner image transferred to the sheet is fixed on the sheet by thermocompression bonding.

  The paper transport unit 6 includes a plurality of transport roller pairs 61 and registration roller pairs 62, and transports the paper from the paper storage unit 3 to the discharge unit 7 through the secondary transfer unit 4 and the fixing unit 5. In FIG. 1, only one pair of transport rollers 61 is shown, but the other transport roller pairs are arranged side by side in a direction perpendicular to the paper surface in FIG. Description of these other transport rollers is omitted.

  The discharge unit 7 includes a plurality of discharge roller pairs 71 and a discharge tray 72 provided on the upper surface of the image forming apparatus 1. The sheet after fixing is discharged to the discharge tray 72 by the discharge roller pair 71. In FIG. 1, only one pair of discharge rollers 71 is shown, but the other discharge roller pairs are arranged side by side in a direction perpendicular to the paper surface in FIG. Description of these other discharge rollers is omitted.

  Further, the image forming apparatus 1 includes liquid developer circulating devices LY, LM, LC, and LB corresponding to the image forming units FY, FM, FC, and FB, and toner tanks CY, CM, CC, and CB, respectively. . Further, the image forming apparatus 1 includes a carrier tank CCA. With these configurations, supply and recovery of the liquid developer for each color is performed. These members will be described later with reference to FIG.

<2. Image forming unit>
(2-1) Configuration of Entire Image Forming Unit Image forming units FY, FM, FC, and FB have substantially the same configuration. That is, among the four image forming units, the image forming unit FB located closest to the secondary transfer unit 4 is not provided with the carrier liquid removal roller 30, but the other configurations are the same. Therefore, in the following, the yellow image forming unit FY will be described with reference to FIG. 2, and description of the other image forming units will be omitted. FIG. 2 is a cross-sectional view showing a main configuration of the image forming unit FY.

  As shown in FIG. 2, the image forming unit FY includes a photosensitive drum 10, a charger 11, an exposure device 12, a developing unit 14, a primary transfer roller 20, a cleaning device 26, a charge removal device 13, And a carrier liquid removing roller 30. The photosensitive drum 10 is driven to rotate counterclockwise as indicated by a broken line arrow in FIG. The charger 11, the exposure device 12, the developing unit 14, the primary transfer roller 20, the cleaning device 26, and the charge eliminating device 13 are arranged around the photosensitive drum 10 in this order along the rotation direction.

  The photosensitive drum 10 is a cylindrical member, and can carry a toner image including toner charged on its surface (charged positively in this embodiment). In the photosensitive drum 10, the image forming unit FY includes a drum driving unit (not shown), and the photosensitive drum 10 is rotationally driven by the drum driving unit.

  The charger 11 is configured to uniformly charge the surface of the photosensitive drum 10 with the same polarity as the toner.

  The exposure device 12 has a light source such as an LED, and irradiates light onto the uniformly charged surface of the photosensitive drum 10 under the control of an image forming controller in accordance with image data input from an external device. . As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 10.

  The developing unit 14 holds the liquid developer including the toner and the liquid carrier so as to face the electrostatic latent image on the surface of the photosensitive drum 10, thereby attaching the toner to the electrostatic latent image. Yes. Thereby, the electrostatic latent image is developed as a toner image. Details of the developing unit 14 will be described later.

  The primary transfer roller 20 is disposed on the inner peripheral side of the intermediate transfer belt 21 so as to face the photosensitive drum 10. A voltage having a polarity opposite to that of the toner in the toner image (minus in this embodiment) is applied to the primary transfer roller 20 by a power source (not shown). That is, the primary transfer roller 20 applies a voltage having a polarity opposite to that of the toner to the intermediate transfer belt 21 at a position in contact with the intermediate transfer belt 21. Since the intermediate transfer belt 21 has conductivity, the applied voltage attracts toner to the outer peripheral surface side of the intermediate transfer belt 21 and its periphery.

  The cleaning device 26 includes a cleaning blade 262 and a residual developer conveying screw 261. The cleaning device 26 cleans the liquid developer remaining without being transferred from the photosensitive drum 10 to the intermediate transfer belt 21 by these members.

  The cleaning blade 262 is a plate-like member extending in the direction of the rotation axis of the photosensitive drum 10 and is disposed so as to scrape off the liquid developer remaining on the surface of the photosensitive drum 10. The cleaning blade 262 is disposed so that the end of the cleaning blade 262 contacts the surface of the photosensitive drum 10, thereby scraping off the liquid developer remaining on the photosensitive drum 10 as the photosensitive drum 10 rotates. .

  The residual developer conveying screw 261 is disposed in the cleaning device 26. The residual developer conveying screw 261 conveys the liquid developer scraped by the cleaning blade 262 and stored in the cleaning device 26 to the outside of the cleaning device 26.

  The static eliminator 13 has a light source for static elimination, and neutralizes the surface of the photosensitive drum 10 with light from the light source. In order to prepare for the next image formation, the static eliminator 13 is arranged so as to perform static elimination after the liquid developer is removed by the cleaning blade 262.

  The carrier liquid removal roller 30 is a substantially cylindrical member that is arranged to rotate about a rotation axis that is parallel to the rotation axis of the photosensitive drum 10. The carrier liquid removal roller 30 is configured to rotate in the same direction as the photosensitive drum 10. The carrier liquid removal roller 30 is disposed on the side where the secondary transfer unit 4 is disposed with respect to the position where the photosensitive drum 10 and the intermediate transfer belt 21 are in contact with each other. Since the surface of the carrier removal roller 30 has higher wettability than the surface of the intermediate transfer belt 21, the carrier liquid is removed from the intermediate transfer belt 21.

(2-2) Configuration of Developing Unit 14 As shown in FIG. 2, the developing unit 14 includes a developing container 140, a developing roller 141, a supply roller 142, a support roller 143, a supply roller blade 144, a development cleaning blade 145, a developer. A recovery device 146, a developing roller charger 147, a support cleaning blade 148, a first bias power source 151, a second bias power source 152, a third bias power source 153, and a developer sensor 160 are provided. The developing unit 14 further includes a roller driving device 153 described later.

  The developing container 140 is supplied with a liquid developer composed of toner particles and a liquid carrier. As will be described later, the liquid developer is supplied from the supply nozzle 278 into the developing container 140 in a state where the density adjustment between the toner and the carrier has been performed in advance. The liquid developer is supplied onto the support roller 143 toward the vicinity of the nip between the supply roller 142 and the support roller 143. The surplus falls below the support roller 143 and is stored at the bottom of the developing container 140. The stored liquid developer is collected by the liquid developer circulating devices LY, LM, LC, and LB through the flow path R2.

  The support roller 143 is disposed substantially at the center of the developing container 140 and abuts against the supply roller 142 from below to form a nip.

  The supply roller 142 is disposed in the developing container 140 such that the rotation shaft is parallel to the rotation shaft of the support roller 143 and is in contact with the support roller 143. More specifically, the supply roller 142 is disposed at an angle above the support roller 143, that is, in a direction away from the supply nozzle 278 and shifted from directly above the support roller 143. A groove for holding the liquid developer is provided on the peripheral surface of the supply roller 142.

  By driving a roller driving device 153, which will be described later, during development, the support roller 143 rotates counterclockwise and the supply roller 142 rotates clockwise as indicated by a broken line arrow in FIG.

  The liquid developer supplied from the supply nozzle 278 is temporarily retained on the upstream side of the nip in the rotation direction of the support roller 143 and the supply roller 142, and the grooves of the supply roller 142 are accompanied with the rotation of both the rollers 142 and 143. In this state, it is carried downstream in the rotational direction. The supply roller blade 144 is in pressure contact with the peripheral surface of the supply roller 142 and regulates the amount of liquid developer held by the supply roller 142 to a predetermined amount. Excess liquid developer scraped off by the supply roller blade 144 is received at the bottom of the developing container 140.

  The developing roller 141 is disposed in the upper opening of the developing container 140 so that the rotation shaft is parallel to the rotation shaft of the supply roller 142 and in contact with the supply roller 142. In the image forming apparatus 1, the rotation shaft of the developing roller 141 is disposed so as to be parallel to the rotation shaft of the photosensitive drum 10. The developing roller 141 is rotated clockwise by a roller driving device 153 described later. That is, during the development, the surface of the developing roller 141 moves in the opposite direction to the surface of the supplying roller 142 at the nip between the developing roller 141 and the supplying roller 142. As a result, the liquid developer held on the peripheral surface of the supply roller 142 is delivered to the peripheral surface of the developing roller 141. As described above, since the layer thickness of the liquid developer on the supply roller 142 is regulated to a predetermined value, the layer thickness of the liquid developer layer formed on the surface of the developing roller 141 is also maintained at a predetermined value. .

  The developing roller charger 147 applies an electric field having the same polarity as the charging polarity of the toner. By the developing roller charging unit 147, the toner in the liquid developer layer carried on the developing roller 141 is moved to the surface side of the developing roller 141, and the development efficiency is improved. The developing roller charger 147 is downstream of the contact position between the developing roller 141 and the supply roller 142 and upstream of the contact position between the developing roller 141 and the photosensitive drum 10 in the rotation direction of the developing roller 141. It is provided so as to face the peripheral surface.

  The developing roller 141 is in contact with the photosensitive drum 10, and a toner image corresponding to the image data instructed to form is formed by the potential difference between the electrostatic latent image potential on the surface of the photosensitive drum 10 and the developing bias applied to the developing roller 141. Is formed on the surface of the photosensitive drum 10 (development operation).

  The development cleaning blade 145 is developed downstream of the contact position between the development roller 141 and the photosensitive drum 10 and upstream of the contact position between the development roller 141 and the supply roller 142 in the rotation direction of the development roller 141. It arrange | positions so that the roller 141 may be contacted. The developer cleaning blade 145 removes the liquid developer on the surface of the developing roller 141 that has completed the developing operation on the photosensitive drum 10.

  The developer recovery device 146 recovers the liquid developer removed by the development cleaning blade 145 and sends the liquid developer to the flow path R1 of the corresponding liquid developer circulation device LY, LM, LC, LB. It has become. Although the liquid developer flows down along the surface of the development cleaning blade 145, since the viscosity of the liquid developer is high, the developer recovery device 146 includes delivery rollers 34 and 35 that assist the delivery of the liquid developer.

  The support cleaning blade 148 is disposed in contact with the support roller 143. The contact position between the support cleaning blade 148 and the support roller 143 is the supply nozzle in the rotation direction (the direction indicated by the dotted line in FIG. 2) when the support roller 143 is developed as viewed from the nip between the support roller 143 and the supply roller 142. It is set upstream of 278. With this arrangement, the support cleaning blade 148 scrapes off the developer remaining on the support roller 143 even after contact with the supply roller 142 during development. The developer thus scraped off is received by the developing container 140.

  Further, the support cleaning blade 148 is disposed closer to the supply nozzle 278 than just below the support roller 143 in a normal installation posture of the developing unit 14, that is, a posture in which the support roller 143 is directed downward as shown in FIG. The That is, the portion of the support roller 143 that is closest to the bottom of the developing container 140, the portion that contacts the support cleaning blade 148, the portion that receives the developer from the supply nozzle 278, and the portion that forms a nip with the supply roller 142 These are arranged in this order in the direction of rotation during development.

  The first bias power supply 151 is connected to the support roller 143 and applies a bias voltage to the support roller 143.

  The second bias power source 152 is connected to the supply roller 142 and applies a bias voltage to the supply roller 142.

  The third bias power source 153 is connected to the developing roller 141 and applies a bias voltage to the developing roller 141.

  The developer sensor 160 is a sensor that can detect the liquid level of the developer. As the developer sensor 160, for example, an optical sensor or the like is used. Provided on the side surface of the developer container 140. The height of the installation position of the developer sensor 160 viewed from the bottom of the developing container 140 is approximately the same as the height of the lower portion of the support roller 143 (the side close to the bottom of the developing container 140) viewed from the bottom of the developing container 140. That is, when the developer sensor 160 detects the developer, the support roller 143 is immersed in the developer stored in the developer container 140.

Here, “immersion” means that the developer adheres to at least a part of the support roller 143.
<3. Liquid developer circulation device>
Hereinafter, the liquid developer circulating apparatus will be described with reference to FIG. The liquid developer circulating devices LY, LM, LC, and LB have the same configuration except that the toner tanks are different. Therefore, in FIG. 3, the yellow liquid developer circulating device LY will be described as an example, and description of other liquid developer circulating devices will be omitted.

  As shown in FIG. 3, the liquid developer circulating device LY circulates and reuses the liquid developer. Examples of the liquid developer circulated by the liquid developer circulation device LY include a developer (a mixture of toner and carrier liquid) scraped from the surface of the developing roller 141 by the developing cleaning blade 145, and a developing roller from the supply roller 142. There is a developer that has not been supplied to 141, and a developer that has been scraped off from the photosensitive drum 10 by the cleaning device 26. The dotted line arrows in FIG. 3 indicate the moving direction of the developer and the carrier liquid.

  The liquid developer circulation device LY includes a residual developer tank 271, a developer storage container 272, a solid content concentration detection device 273, a carrier tank CCA, a toner tank CY, a developer reserve tank 277, and a supply nozzle 278. A residual developer collecting container 279, a liquid developer separating and extracting device 28, and a plurality of pumps P1 to P10.

  The residual developer tank 271 is connected to the development unit 14 via a flow path R1. The residual developer tank 271 is a tank that can store the developer scraped from the surface of the developing roller 141 by the developing cleaning blade 145. One pump P1 is attached between the developing unit 14 and the residual developer tank 271. The pump P <b> 1 moves the residual developer scraped from the surface of the developing roller 141 to the residual developer tank 271. The residual developer tank 271 is connected to the bottom of the developing unit 14 via a flow path R2, and a pump P5 is connected to the flow path R2. The pump P5 sends the developer from the developer container 140 to the residual developer tank 271.

  The developer container 272 is connected to the residual developer tank 271. The developer storage container 272 is a density preparation unit that prepares the developer to be supplied to the development unit 14, that is, adjusts the toner density. The developer container 272 is connected to the residual developer tank 271 via a flow path R3, and a pump P2 is connected to the flow path R3.

  The solid content concentration detection device 273 is connected to an annular flow path R4 connected to the developer container 272. The solid concentration detection device 273 detects the toner concentration in the liquid developer in the developer container 272. A pump P4 is attached on the upstream side of the solid content concentration detection device 273 in the moving direction of the developer in the annular flow path R4.

  The carrier tank CCA stores a carrier liquid. The carrier tank CCA is connected to the developer container 272 by a flow path R5 to which a pump P3 is attached. The carrier tank CCA is used in common for each color, and a common pipe (not shown) connected to the liquid developer circulating devices LY, LM, LC, and LB is connected to the carrier tank CCA. A flow path R5, which is a branch pipe for each color, extends from the common pipe to the developer storage container 272 for each color. By operating the pump P3, the carrier liquid in the carrier tank CCA is conveyed to the developer container 272, and the toner concentration in the developer container 272 is lowered.

  The toner tank CY stores a liquid developer having a high toner concentration. The toner concentration of the liquid developer in the toner tank CY is higher than the toner concentration of the liquid developer used in the developing unit 14. The toner tank CY is connected to the developer container 272 by a flow path R6 to which a pump P8 is attached. By operating the pump P8, the high-concentration liquid developer is conveyed to the developer container 272, and the toner concentration in the developer container 272 is increased.

  The developer reserve tank 277 is connected to the developer container 272 by a flow path R7 to which the pump P6 is attached. The developer reserve tank 277 is connected to the supply nozzle 278 via a flow path R8 to which a pump P7 is attached. The pump P6 conveys the developer from the developer container 272 toward the developer reserve tank 277, and the pump P7 conveys the developer from the developer reserve tank 277 toward the supply nozzle 278. In other words, the developer reserve tank 277 stores the liquid developer supplied to the developing unit 14.

  As described above, the supply nozzle 278 is arranged to supply the developer to the developing unit 14.

  The residual developer recovery container 279 temporarily stores the developer removed from the photosensitive drum 10 by the cleaning device 26.

  The liquid developer separating and extracting device 28 separates the liquid developer into toner and carrier liquid, and extracts the carrier liquid and toner separately. The liquid developer separating and extracting device 28 is disposed in the middle of the flow paths R9 and R10 connecting the residual developer collecting container 279 and the carrier tank CCA. A pump P9 is provided in the flow path R9, and the pump P9 sends the liquid developer in the residual developer recovery container 279 to the liquid developer separation and extraction device 28. The liquid developer separation and extraction device 28 separates the liquid developer stored in the residual developer collection container 279 into toner and carrier liquid. The flow path R10 is provided with a pump P10, and the pump P10 sends the separated carrier liquid to the carrier tank CCA.

<4. Image Forming Operation of Image Forming Apparatus 1>
Next, an image forming operation of the image forming apparatus 1 will be described.

  The image forming apparatus 1 that has received an image forming instruction from a personal computer (not shown) connected to the image forming apparatus 1 outputs toner images of each color corresponding to the image data that has received the generating instruction into image forming units FY, FM, It is formed using FC and FB. Specifically, an electrostatic latent image based on image data is formed on the photosensitive drum 10, and toner is supplied to the electrostatic latent image from the developing unit 14. The toner images formed in the respective image forming units 2 in this way are transferred to the intermediate transfer belt 21 and are superimposed on the intermediate transfer belt 21 to form a color toner image.

  In synchronism with the formation of the color toner image, the paper stored in the paper feed cassette 31 of the paper storage unit 3 is taken out from the paper feed cassette 31 by the paper feed roller 32, and one by one by the separation roller pair 33. It is sent to the transport unit 6. The paper is sent to the registration roller pair 62 by the transport roller pair 61 of the paper transport unit 6, the paper transport posture is corrected, and the paper is temporarily stopped. Then, the toner image is fed from the registration roller pair 62 to the secondary transfer unit 4 at the same timing as the primary transfer to the intermediate transfer belt 21, and the color toner image on the intermediate transfer belt 21 is secondarily transferred to the sheet by the secondary transfer unit 4. Is done. The sheet on which the color toner image is transferred is sent to the fixing unit 5 and the color toner image is fixed on the sheet by the action of heat and pressure.

  The sheet on which the color toner image is fixed is further sent to the discharge unit 7 and discharged by a discharge roller pair 71 to a discharge tray 72 provided outside the image forming apparatus 1.

  The residual liquid developer remaining on the intermediate transfer belt 21 after the secondary transfer is removed by the cleaning roller 22a and the cleaning blade 22b of the cleaning unit 22 of the intermediate transfer belt 21.

  The above operation is executed under the control of an image forming controller included in a control device 159 described later.

<5. Developer circulation operation>
Next, the operation of supplying the liquid developer to the developing unit 14, that is, the operation of circulating the liquid developer will be described.

  The liquid developer remaining on the developing roller 141 without being supplied to the photosensitive drum 10 during the image forming operation is scraped off by the developing cleaning blade 145 and collected in the residual developer tank 271 through the flow path R1. Further, the liquid developer received in the developing container 140 is also sent to the residual developer tank 271 through the flow path R2 by the pump P5. When the liquid developer in the developer container 272 runs out, the liquid developer is supplied from the residual developer tank 271 to the developer container 272 by the pump P2 via the flow path R3. At this time, the liquid developer remaining on the photosensitive drum 10 without being developed is scraped off by the cleaning blade 262 and stored in the residual developer collection container 279.

  The liquid developer recovered in the residual developer recovery container 279 is conveyed to the liquid developer separation / extraction device 28 via the flow path R9 by the pump P9 every predetermined amount. In the liquid developer separation / extraction device 28, the toner and the carrier liquid are separated and extracted. The carrier liquid extracted in the liquid developer separating and extracting device 28 is sent to the carrier tank CCA by the pump P10 through the flow path R10.

  On the other hand, the toner concentration of the liquid developer in the developer container 272 is detected by the solid concentration detector 273, and the concentration of the liquid developer in the developer container 272 is adjusted. Here, when the toner concentration is high, the carrier liquid is supplied from the carrier tank CCA to the developer container 272 via the flow path R5 by the pump P3. When the toner concentration is low, a liquid developer having a high toner concentration is supplied from the toner tank CY to the developer container 272 via the flow path R6 by the pump P8.

  Then, the liquid developer whose density is adjusted from the developer container 272 to the developer reserve tank 277 as needed is supplied through the flow path R7 by the pump P6, and the liquid developer stored in the developer reserve tank 277 is supplied. The agent is sent to the supply nozzle 278 via the flow path R8 by the pump P7, and is supplied from the supply nozzle 278 to the developing unit 14.

  The above operation is executed under the control of the developer circulation controller 158 described later.

<6. Control at development unit start-up>
(6-1) Control Mechanism FIG. 4 shows a control mechanism of the developing unit 14 and the liquid developer circulating device LY that operates when the developing unit 14 is activated. In the following, the start-up of the yellow developing unit 14 will be described in particular, but the same control mechanism is provided for the developing units of other colors, and the same control is performed.

  As shown in FIG. 4, the image forming apparatus 1 includes a power supply driving device 154, a control device 159, and the like in addition to the above-described members.

  The power source driving device 154 is included in the developing unit 14 and includes a first power source driving unit 154a, a second power source driving unit 154b, and a third power source driving unit 154c.

  The first power supply driving unit 154 a drives the first power supply 151 to apply a bias voltage to the support roller 143. The second power supply driving unit 154 b drives the second power supply 152 to apply a bias voltage to the supply roller 142. The third power supply driving unit 154 c drives the third power supply 153 to apply a bias voltage to the developing roller 141.

  The roller driving device 153 includes a support roller driving unit 153a, a supply roller driving unit 153b, and a developing roller driving unit 153c. Each of the support roller driving unit 153a, the supply roller driving unit 153b, and the developing roller driving unit 153c includes a motor and a gear. The support roller 143, the supply roller 142, and the developing roller 141 are rotated by driving of the support roller driving unit 153a, the supply roller driving unit 153b, and the developing roller driving unit 153c, respectively. The rotation direction during development is the direction indicated by the dotted arrow in FIG. 2, but the rotation direction of the support roller 143 and the supply roller 142 during the starting operation is opposite as described later.

  The control device 159 includes a microcomputer including a CPU, RAM, ROM, and the like. The control device 159 includes an activation controller 156, a development controller 157, a developer circulation controller 158, and the like. In addition, the activation controller 156 includes a potential difference control unit 156a, a rotation control unit 156b, and a pump control unit 156c.

The potential difference control unit 156a
The function of each part will be described later.

(6-2) Operation at Start-up The control device 159 can execute the first to fourth steps shown in Table 1 and FIGS. 5 to 8 by controlling each part of the image forming apparatus 1. In particular, the activation controller 156 performs the first to third steps. The fourth step is an operation during development, which is controlled by the development controller 157 and the developer circulation controller 158.

(First step)
As shown in Table 1 and FIG. 5, when the developing unit 14 resumes the developing operation after being stopped, that is, when the developing unit 14 is started, the rotation control unit 156 b of the start controller 156 first rotates the rollers 141 to 143. The roller driving device 153 is controlled so as to stop, i.e., not to rotate.

  Then, as shown in Table 1 and FIG. 5, the potential difference control unit 156 a controls the power supply driving device 154 in a state where the rotation of the rollers 141 to 143 is stopped, and the first power supply 151 and the second power supply 152. The third power source 153 applies a voltage of 0 (zero) V to the support roller 143, the supply roller 142, and the developing roller 143, respectively.

  At this time, as shown in Table 1 and FIG. 5, the pump control unit 156 c controls the liquid developer circulating device LY to discharge the developer from the supply nozzle 278. At this time, the pump P5 is stopped. When the developer sensor 160 detects the developer, the pump control unit 156c stops the supply of the developer by stopping the pump P7.

  With the above operation, the developer discharged from the supply nozzle 278 toward the support roller 143 is accumulated on the bottom of the developing container 140 through the support roller 143. The supply of the developer is continued until the support roller 143 is immersed in the developer accumulated in the developer container 140.

(Second step)
Next, as shown in Table 1 and FIG. 6, the potential difference control unit 156 a controls the power supply driving device 154 to supply 0 V from the first power supply 151 to the support roller 143, 400 V from the second power supply 152 to the supply roller 142, A voltage of 400 V is applied from the third power source 153 to the developing roller 141.

  Then, as shown in Table 1 and FIG. 6, the rotation control unit 156b controls the roller driving device 153 so that the developing roller 141 is in the same direction as normal (development), and the supply roller 142 and the support roller 143 are normal. Rotate in the opposite direction to the hour (dotted arrow in FIG. 6). That is, the developing roller 141 and the support roller 143 rotate clockwise, and the supply roller 142 rotates counterclockwise.

  At this time, as shown in Table 1 and FIG. 6, the supply of the developer is stopped.

  Since the arrangement position of the developer sensor 160 is set as described above, the developer in the developer container 140 adheres to the support roller 143 as shown in FIG. Since the arrangement position of the support cleaning blade 148 is set as described above, the developer D2 adhering to the support roller 143 is not scraped off by the support cleaning blade 148 and is rotated by the support roller 143. Along with this, it is carried to the nip between the support roller 143 and the supply roller 142. The developer thus conveyed reaches the developing roller 141 from the support roller 143 via the supply roller 142 as the rollers 141 to 143 rotate.

  As described above, a potential difference is generated between the supply roller 142 and the support roller 143, and in particular, a voltage having the same polarity as the toner charging polarity is applied to the supply roller 142. As a result, as indicated by a white arrow in FIG. 6, the toner in the developer D3 in the nip between the supply roller 142 and the support roller 143 is attracted to the support roller 143 side. As a result, the developer D3 having a low toner density is supplied to the supply roller 142 and the developing roller 141.

  As shown in FIG. 5, while the developing unit 14 is stopped, the developer may be dried on each of the rollers 141 to 143 to become a developer D1 having a high concentration. Such a high-concentration developer D1 causes an increase in the rotational torque of the rollers 141 to 143, but an increase in torque is avoided by supplying the low-concentration developer D3 in the second step.

  Furthermore, since the rotation directions of the rollers 141 to 143 are controlled as described above, the supply roller 142 rotates in a so-called trail direction with respect to the rotation direction of the developing roller 141. That is, the rollers 141 and 142 move in the same direction at the nip between both the rollers 141 and 142. The supply roller 142 also rotates in the trail direction with respect to the rotation direction of the support roller 143, and the rollers 142 and 143 move in the same direction at the nip between both the rollers 142 and 143. As a result, the frictional resistance between the developing roller 141 and the supply roller 142 and between the support roller 143 and the supply roller 142 is kept low. Therefore, according to this step, an effect of further reducing the torque can be obtained.

  The second step is continued at least until the developer is supplied to the nip between the developing roller 141 and the supply roller 142. The second step may further be continued until a new developer is supplied to the rollers 141 to 143 and the members (development cleaning blade 145, etc.) that contact these rollers.

  As is clear from the above description, at least the position at which the support roller 143 contacts the support cleaning blade 148, the position at which the developer is received in the second step, and the supply roller 142 (pass the developer). If the positions are aligned in this order in the rotation direction of the support roller 143 in the second step, the developer attached to the support roller 143 in the second step reaches the development roller 141 via the supply roller 142. it can.

  That is, even if the support cleaning blade 148 is disposed on the left side with respect to the support roller 143 in FIG. 6, if the liquid level of the developer is higher than the support cleaning blade 148, the developer reaches the development roller 141. can do. That is, the position of the developer surface relative to the support roller 143 is arranged between the contact position of the support cleaning blade 148 and the contact position of the supply roller 142 in the rotation direction of the support roller 143 in the second step. As described above, the positional relationship between the support cleaning blade 148 and the developer sensor 160 may be set.

(Third step)
As shown in Table 1 and FIG. 7, in this step, the potential difference control unit 156a performs the same control as in the second step.

  Then, the rotation control unit 156 rotates each of the rollers 141 to 143 in the normal direction (the direction during execution of development, that is, the direction of the dotted arrow in FIGS. 2 and 7). That is, the rotation directions of the support roller 143 and the supply roller 142 are reversed from those in the second step. That is, the developing roller 141 and the supply roller 142 rotate clockwise, and only the support roller 143 rotates counterclockwise. As a result, the supply roller 142 rotates in a so-called counter direction with respect to the rotation direction of the developing roller 141, and the rollers 141 and 142 move in the opposite directions at the nip between both rollers.

  The pump control unit 156c discharges the developer from the supply nozzle 278 by operating the pump P7.

  Similarly to the developer D3 in the second step, the toner in the developer supplied from the supply 278 to the support roller 143 is attracted to the support roller 143 by the potential difference between the supply roller 142 and the support roller 143 (FIG. 7 white arrow). As a result, the developer D3 having a low toner density is supplied to the supply roller 142 and the developing roller 141.

  By the second step, the developer D4 having a high toner density adheres on the support roller 143 from the support cleaning blade 148 to the nip with the supply roller 142 in the normal rotation direction of the support roller 143. According to the third step, the developer D4 is dispersed in the developer accumulated in the developer container 140 or scraped off by the support cleaning blade 148, thereby preventing an increase in image density due to the developer D4. be able to.

  Further, the execution period of the second step can be set to the shortest period during which the carrier liquid can be supplied to the nip between the developing roller 141 and the supply roller 142 by the rotation opposite to the normal rotation. If the period is the shortest, the developer having a high carrier concentration does not reach the developing cleaning blade 145 only by the second step. Therefore, the third step is preferably continued to such an extent that the developer can be supplied to the developing cleaning blade 145.

(4th step)
When the first to third steps are completed, development is started. That is, as shown in Table 1 and FIG. 8, under the control of the development controller 157, the power supply driving device 154 drives the first power supply 151, the second power supply 152, and the third power supply 153 to support the support roller 143, A voltage of 400 V is applied to each of the supply roller 142 and the developing roller.

  In addition, under the control of the development controller 157, the rotation directions of the rollers 141 to 143 are set to the normal direction similar to the third step, and the developer is discharged from the supply nozzle 278 under the control of the developer circulation controller 157. .

  Even if the pump control unit 156c operates the pump P5 before starting the fourth step to be described later, the amount of developer in the developing container 14 is reduced to such an extent that the support roller 143 is not immersed. Good.

  In the first to third steps, the pump control unit 156c not particularly mentioned is the above <5. The control similar to the control of the developer circulation controller 158 described in the> column may be performed.

In each step, particularly the first step, the rotation start timing of the rollers 141 to 143 is
[2] Other Embodiments a) The image forming apparatus 1 is only an example of an apparatus to which the present invention is applied. As an apparatus to which the present invention is applied, in addition to a printer, a copier, a facsimile machine, or a so-called multifunction machine (MFP, Multi Function Peripheral) having these functions can be cited.

  b) The supply roller may be disposed at a position for receiving the developer on the support roller, and the development roller may be disposed at a position for receiving the developer on the supply roller. The “receiving position” does not have to be a position where the rollers are in contact with each other like the rollers 141 to 143 of the first embodiment.

  c) The developer supply device only needs to supply the developer onto the support roller. “Supplying the developer onto the support roller” means that the developer is attached to at least the support roller. The specific method for adhering may be ejection or immersion, and can be changed as appropriate.

  d) When the developing device includes a cleaning member disposed so as to come into contact with the support roller, the developer supply device supplies the developer to the support roller at the time of development, and supplies the developer at the time of non-development It is preferable to provide the 2nd supply part.

  The support cleaning member 148 is only an example of this cleaning member, and can be replaced with another member.

  In the first embodiment, in particular, the pump P7, the supply nozzle 278, and the development controller 157 function as the first supply unit. Furthermore, the pump P7 and the supply nozzle 278 are examples of a discharge unit in the first supply unit, and the development controller 157 is an example of a first discharge control unit in the first supply unit. The first supply unit is not limited to this, and may be a mechanism that attaches the developer to the support roller by immersing a part of the support roller in the developer.

  In the first embodiment, the developing container 140 and the pump control unit 156c function as a second supply unit. Furthermore, the developing container 140 is an example of a container arranged so that the supporting roller is immersed in the developer, and the pump control unit 156c causes the discharging unit to discharge the developer so that the supporting roller is immersed in the developer. It is an example of a 2nd discharge control part. The second supply unit is not limited to this configuration, and may be a mechanism for discharging the developer, such as the pump P7 and the supply nozzle 278.

  In addition, since the pump controller 156c supplies the developer to the support roller 143 by the pump P7 and the supply nozzle 278 in the third step, it can be said that the pump controller 156c also functions as a third discharge controller.

  e) The potential difference generating device only needs to generate a potential difference between the support roller and the supply roller so that the toner moves from the supply roller to the support roller.

  The first power supply 151, the second power supply 152, the power supply driving device 154, and the potential difference control unit 156a are merely examples of a potential difference generating device. Furthermore, the first power supply 151 and the first power supply driving unit 154a are examples of the first voltage application unit, and the second power supply 152 and the second power supply driving unit 154b are examples of the second voltage application unit, and the potential difference The control unit 156a is only an example of a potential difference generation control unit.

  The potential difference to be generated may be in a range in which the developer supplied from the developer supply device or the developer received from the support roller at the time of development is supplied to the supply roller in a range in which a low concentration developer is supplied. It is not limited to. For example, instead of applying a bias voltage having the same polarity as the toner charging polarity to the supply roller 142 as in the first embodiment, the potential difference generator applies a bias voltage having a polarity opposite to the toner charging polarity to the support roller 143. In addition, a bias voltage having the same polarity as the toner charging polarity is applied to the supply roller 142, and a bias voltage having a polarity opposite to the toner charging polarity is applied to the support roller 143. May be.

  Note that “potential difference” can also be referred to as “voltage difference”.

  f) The first power supply 151, the second power supply 152, the first power supply drive unit 154a, the second power supply drive unit 154b, and the development controller 157 are merely examples of a potential difference eliminating device. More specifically, the first power supply 151 and the first power supply driving unit 154a are examples of the first voltage application unit, and the second power supply 152 and the second power supply driving unit 154a are examples of the second voltage application unit. The controller 157 is only an example of a potential difference elimination control unit.

  “Resolving the potential difference” may be rephrased as reducing the potential difference to the extent that development is possible. That is, “eliminating the potential difference” may mean that the potential values applied to the first and second rollers are the same as in the first embodiment, or “reducing the potential difference”. It may be.

  g) The reverse rotation device only needs to rotate the support roller, the developing roller, and the supply roller so that the opposing surfaces of the rollers move in the same direction. Specifically, the reverse rotation device may be configured to rotate the support roller and the developing roller in the same direction and rotate the supply roller in the reverse direction.

  The rotation control unit 156b and the roller driving device 153 according to the first embodiment are configured to rotate the support roller 143 and the supply roller 142 in the direction opposite to that during development as an example of a reverse rotation device. However, in addition to this, the rotation control unit 156b and the roller driving device 153 rotate the developing roller 141 in the opposite direction to that during development, and the rotation directions of the other two rollers 142 and 143 are the same as those during development. You may come to do.

  The rotation control unit 156b also functions as a rotation stop unit.

  h) The development controller 157 and the roller driving device 153 of the first embodiment are an example of a normal rotation device. Usually, the rotating device rotates each roller so that the surface facing the developing roller moves in the direction of the developing roller and the surface facing the developing roller and the supplying roller moves in the opposite directions. Just do it. Specifically, the normal rotating device only needs to rotate the developing roller and the supply roller in the same direction and rotate the support roller in the opposite direction.

  In the first embodiment, the first rotating device and the second rotating device share the roller driving device 153. As another form, the first and second rotating devices are separate driving devices. May be provided.

  i) The operation timing of the developer supply device, the potential difference generating device, and the reverse rotation device when development is not executed is particularly preferably before the start of development, and more specifically, when the main power (not shown) is turned on, the operation is returned from sleep. It can be set as appropriate at the time or when the stop period of the developing unit 14 exceeds a predetermined value. The predetermined value of the stop period can be counted by a timer (not shown).

  In addition, the start order and stop order of the operations of the developer supply device, the potential difference generation device, and the first rotation device at this time are not particularly limited.

  However, in order to obtain the effect of torque reduction, the start of the operation of the reverse rotation device, that is, the start of rotation of the rollers 141 to 143 in the second step of the first embodiment is at least the start of the supply of developer and the generation of a potential difference It is preferable not to precede. That is, it is preferable that the operation of the reverse rotation device starts at the same time as or after the start of the supply of the developer and the generation of the potential difference.

  The potential difference generating device only needs to be able to operate during operation of the developer supply device. That is, the potential difference generating device may generate a potential difference not only while the developer supply device is in operation but also when it is stopped. In other words, either the operation start timing of the developer supply device or the operation start timing of the potential difference generation device may precede, and either the stop timing may precede.

  j) In addition, the duration of operation of the developer supply device, the potential difference generation device, and the reverse rotation device when development is not performed can be changed as appropriate within a range where the effect of torque reduction can be exhibited. For example, the activation controller 156 may control each unit so as to continue the activation operation over a predetermined time measured by a timer (not shown). The duration of the startup operation is changed as appropriate according to the characteristics of the developer, the configuration of the developing device, and the like. The developer characteristics include carrier liquid composition, toner characteristics, toner concentration, and the like. The developing device configuration includes the surface material, radius, and rotation speed of each of the rollers 141 to 143, and the blade 145. The arrangement | positioning of other members, etc. are mentioned.

  For example, the operation from the second step to the third step in the first embodiment is performed until the low-concentration developer supplied by this operation wets the member that contacts the developing roller 141 and the member that contacts the supply roller 142. Preferably it is continued. That is, in the supply roller 142, the time required for the portion located in the nip with the support roller 143 to move to the nip with the developing roller 141, and the portion in the developing roller 141 located in the nip with the supply roller 142 is the development cleaning. It is preferable that a time obtained by adding the time to move to a position in contact with the blade 145 is set as the duration. Furthermore, it is preferable that the supply roller 142 rotates at least once. By setting the duration time in this way, the rotational torque of the rollers 141 to 143 is further reduced.

  k) The position on the support roller for receiving the developer from the first supply unit, the position for passing the developer to the supply roller, the position for receiving the developer from the second supply unit, and the position for contacting the cleaning member. It is preferable to arrange them in this order along the rotation direction of the support roller by the normal rotating device. In other words, the first supply unit, the second supply unit, and the cleaning member are arranged in this order around the support roller along the rotation direction of the support roller by the normal rotating device. As long as it is disposed between the first supply unit and the second supply unit.

  l) Embodiments obtained by combining the forms described in different columns with each other are also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming part 14 Development unit 151 1st power supply 152 2nd power supply 153 Roller drive device 154a 1st power supply drive part 154b 2nd power supply drive part 154c 3rd power supply drive part 156 Start-up controller 157 Development controller 158 Developer Circulation controller 159 Control device LY, LM, LC, LB Liquid developer circulation device

Claims (7)

A developing device for developing an electrostatic latent image,
A support roller provided rotatably around a rotation axis;
A developer supply device for supplying a developer containing toner and a liquid carrier onto the support roller;
A supply roller having a rotation axis parallel to the rotation axis of the support roller and disposed at a position for receiving the developer on the support roller;
A developing roller having a rotation axis parallel to the rotation axis of the support roller, receiving the developer on the supply roller, and disposed at a position capable of facing the electrostatic latent image;
A potential difference generating device for generating a potential difference between the support roller and the supply roller so that toner moves from the supply roller to the support roller when the developer supply device is in operation when development is not performed; ,
A reverse rotation device for rotating the support roller and the developing roller in the same direction and rotating the supply roller in the reverse direction during operation of the potential difference generating device;
A potential difference elimination device that prevents the potential difference from occurring between the support roller and the supply roller during development;
A normal rotation device that rotates the developing roller and the supply roller in the same direction and rotates the support roller in the opposite direction when performing development;
A developing device comprising: A cleaning member arranged to contact the support roller;
The developer supply apparatus is
A first supply unit for supplying a developer to the support roller when performing development;
A second supply unit that supplies developer to the support roller when development is not performed;
With
A position on the support roller for receiving the developer from the first supply unit, a position for passing the developer to the supply roller, and a second supply unit on the support roller along the rotation direction of the support roller by the normal rotation device A position for receiving the developer from, and a position for contacting the cleaning member,
The developing device according to claim 1, wherein the potential difference generation device and the reverse rotation device are operated while the developer is supplied by the second supply unit. The first supply unit includes a discharge unit that discharges the developer, and a first discharge control unit that discharges the developer to the discharge unit during development.
The second supply unit stores a developer discharged from the discharge unit, a container arranged to immerse the support roller in the stored developer, and the support roller on the developer in the container A second discharge control unit that discharges developer to the discharge unit so that
The developing device according to claim 2, wherein the potential difference generating device and the reverse rotation device are operated when the support roller is immersed in the developer in the container. A rotation stop unit that stops rotation of the support roller, the supply roller, and the development roller when development is not performed;
The development according to claim 3, wherein the second discharge control unit is configured to discharge the developer from the discharge unit until the support roller is immersed in the developer in the container while the rotation is stopped. apparatus. A third discharge control unit that supplies developer to the support roller by the first supply unit after the operation of the potential difference generation device and the reverse rotation device when the development is not performed;
5. The developing device according to claim 2, wherein the potential difference eliminating device and the normal rotating device are operated during the supply of the developer by the third ejection control unit. The potential difference generator is
A first voltage applying unit for applying a voltage to the first roller;
A second voltage application unit for applying a voltage to the second roller;
A potential difference generation control unit that controls the first and second voltage application units to generate the potential difference;
A developing device according to any one of claims 1 to 5. The potential difference eliminating device is
The first and second voltage application units;
The developing device according to claim 1, further comprising: a potential difference elimination control unit that controls the first and second voltage application units so as to eliminate the potential difference.

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