JP2010122335A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus wherein a liquid developer can be supplied to an image forming part stably without deteriorating the liquid developer in a developer circulation part even when the image forming part is stopped caused by the abnormality of the apparatus. <P>SOLUTION: The image forming apparatus 1 includes: the image forming part 2 that supplies the liquid developer containing toner and carrier liquid in a mixed state to a photoreceptor 10 and develops an electrostatic latent image; and the developer circulation part LY that collects the residual liquid developer from the image forming part 2 after a developing process, and supplies the liquid developer whose toner concentration has been adjusted, to the image forming part 2. When the abnormality is detected and the image forming part 2 is stopped, the collection and supply of the liquid developer between the image forming part 2 and the developer circulation part LY are stopped, and the liquid developer is circulated in the developer circulation part LY. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus provided with a liquid developing device used for a copying machine, a printer, a facsimile, a composite machine using the electrophotographic method, and the like.

  Conventionally, as a method for forming an image on a sheet, a liquid developing method using a liquid developer in which toner is mixed in a carrier liquid is known. An image forming apparatus applied to this liquid development system supplies a developer from an developing roller to an image carrier, forms a toner image from an electrostatic latent image on the image carrier, and transfers the toner image to a sheet. The image forming unit includes a fixing unit that fixes a toner image formed by the image forming unit on a sheet, and a discharge unit that discharges the fixed sheet.

  Some liquid developing devices used in such image forming apparatuses are designed to perform development after once drawing up the liquid developer from a developer storage tank that stores the liquid developer adjusted to a predetermined concentration. . For example, a developing roller for performing development is provided so as to face the image carrier, and a part of the developing roller is immersed in a liquid developer stored in a developer storage tank, and rotated to rotate the liquid developer. Is attached to the surface, and the attached liquid developer is brought into contact with the image carrier to perform development. Usually, the liquid developer adhering to the developing roller is not completely consumed by the development, and a part thereof remains on the developing roller. The liquid developer remaining on the surface of the developing roller is scraped off by a cleaning blade after development and falls as it is to the developer storage tank.

  However, when a low-density image is formed using the above-described liquid developer, a large amount of toner remains on the developing roller, and conversely, when a high-density image is formed, a large amount of medium liquid is transferred to the developing roller. Therefore, when it falls into the developer storage tank, density unevenness occurs in the liquid developer stored in the developer storage tank. Such density unevenness of the liquid developer stored in the developer storage tank causes density unevenness of the liquid developer carried on the developing roller, and thus causes unevenness in the density of the finally obtained image. There was a problem.

  In view of such problems, in Patent Document 1, a recovery unit that recovers the liquid developer remaining on the surface of the developing roller after being subjected to development, and a recovered developer storage tank that stores the recovered liquid developer The recovery developer storage tank is provided with a liquid level sensor for detecting the liquid level of the stored liquid developer, and a predetermined amount of liquid developer is stored. When detected, the circulation of the liquid developer entering and exiting the collected developer storage tank is stopped. In a state where a predetermined amount of liquid developer is stored in the recovered developer storage tank, stirring and concentration detection are performed, and then a concentration adjusting agent is supplied to the recovered developer storage tank to adjust to a predetermined concentration. The liquid developer adjusted to a predetermined concentration is conveyed from the collected developer storage tank to the developer storage tank. Then, the liquid developer stored in the developer storage tank is attached to the developing roller, and the attached liquid developer is brought into contact with the image carrier to perform development. Thus, the supply and recovery of the liquid developer is repeated between the developer storage tank and the recovered developer storage tank.

However, in the above-described prior art, when an image formation cannot be performed due to, for example, an abnormality in the bias applied to the developing device during image formation, the driving of the image forming unit such as the developing device is stopped. It is necessary to inspect and repair the defective part. At this time, when the supply and recovery of the liquid developer is stopped between the developer storage tank and the recovered developer storage tank, the liquid developer being recovered and the liquid developer being supplied remain in the pipe, and the storage tank The liquid developer remains on the liquid developer, and the liquid developer may be deteriorated. If the developer circulation section with the collected developer storage tank or pipe is stopped for a long time, developer aggregates may adhere to the storage tank, and the pipes may become clogged. It is necessary to collect in the tank and clean the pipe and storage tank. In this way, it is necessary to dispose of the liquid developer, clean the developer circulation section, and newly carry toner and carrier liquid into the recovered developer storage tank, and adjust the concentration of the liquid developer again. When an abnormality occurs in this manner and the image forming unit stops, there is a problem in that it is necessary to adjust the density of the liquid developer from the beginning again and transport it to the developing device after performing the above-described operation.
JP 2007-216908 (paragraphs [0027] and [0030], FIG. 1)

  The present invention has been made to solve the above-described problems. Even when the image forming unit stops due to an abnormality in the apparatus, the liquid developer is not deteriorated in the developer circulating unit, and is stable. An object of the present invention is to provide an image forming apparatus that supplies a liquid developer to an image forming unit.

  In order to achieve the above object, the present invention provides an image forming unit that develops an electrostatic latent image by supplying a liquid developer in which toner and a carrier liquid are mixed to an image carrier, and remains after development from the image forming unit. A developer circulation unit that collects the liquid developer and supplies the liquid developer with adjusted toner density to the image forming unit, and detects the abnormality and stops the image forming unit; The recovery and supply of the liquid developer in the developer circulation section is stopped, and the liquid developer is circulated in the developer circulation section.

  According to this configuration, the liquid developer is supplied to the image carrier in the image forming unit to develop the electrostatic latent image, and when the liquid developer in the image forming unit is consumed, the liquid developer is supplied from the developer circulating unit. Is supplied, but the liquid developer circulates in the developer circulation section during a period in which an abnormality cannot be detected and image formation can be performed.

  According to a second aspect of the present invention, the image forming section includes a developing unit that develops an electrostatic latent image by supplying a liquid developer to the image carrier, and the developer circulating unit includes the developing unit. A developer concentration adjusting unit that stores a residual developer remaining after development by a developer and adjusts a toner concentration by adding a carrier liquid or a high-concentration liquid developer to the residual developer, and an adjusted development that stores the concentration-adjusted developer A developer storage unit, a recovery transport unit that transports the residual developer from the developer to the developer concentration adjustment unit, and transports the density adjusted developer from the developer concentration adjustment unit to the adjusted developer storage unit. Connecting the first supply transport unit, the second supply transport unit transporting the density-adjusted developer from the adjusted developer storage unit to the developer, the recovery transport unit, and the second supply transport unit. Bypass transport section and the bypass transport And the second supply conveyance unit, and between the bypass conveyance unit and the recovery conveyance unit, respectively, and the density adjustment is performed from the adjusted developer storage unit to the developer concentration adjustment unit via the bypass conveyance unit. And a switching unit that switches to transport the used developer.

  According to this configuration, when the liquid developer is supplied from the developing device to the image carrier to develop the electrostatic latent image, and the liquid developer in the developing device is consumed, the liquid developer is removed from the adjusted developer storage unit. While being transported to the developing device via the second supply transport unit, the switching unit switches the transport direction of the liquid developer during a period in which image formation cannot be performed due to an abnormality, and the adjusted developer storage unit and the second supply transport Part of the liquid developer passes from the second supply transport unit through the bypass transport unit, and further from the bypass transport unit through the recovery transport unit to the developer concentration adjusting unit.

  According to the first aspect of the present invention, when the liquid developer is supplied to the image carrier in the image forming unit to develop the electrostatic latent image, and the liquid developer in the image forming unit is consumed, the developer circulation is performed. The liquid developer is supplied from the part, but the liquid developer is circulated in the developer circulation part during a period in which image formation cannot be performed by detecting an abnormality of the apparatus, so that the liquid developer is not deteriorated. Accordingly, it is possible to save the trouble of discarding the liquid developer and cleaning the pipe and the storage container. When the abnormality is resolved, the liquid developer can be supplied quickly and stably from the developer circulation unit to the image forming unit.

  According to the second aspect of the present invention, when the liquid developer is supplied from the developing unit to the image carrier to develop the electrostatic latent image, and the liquid developer in the developing unit is consumed, the liquid developer Is transported from the adjusted developer reservoir to the developing device via the second supply transport unit, but the switching unit switches the transport direction of the liquid developer during a period when image formation cannot be performed due to an abnormality being detected. The liquid developer in the storage unit and the second supply conveyance unit is conveyed from the second supply conveyance unit through the bypass conveyance unit, and further from the bypass conveyance unit through the collection conveyance unit to the developer concentration adjusting unit. Accordingly, during a period in which image formation cannot be performed due to an abnormality in the apparatus, the liquid developer passes between the developer concentration adjusting unit and the adjusted developer storing unit between the first and second supply conveyance units, the bypass conveyance unit, and the collection conveyance unit. The liquid developer is not deteriorated. When the abnormality is resolved, the switching unit returns the transport direction of the liquid developer, and the liquid developer can be supplied quickly and stably from the adjusted developer storage unit to the developing device.

  Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. The embodiment of the present invention shows the most preferable form of the invention, and the use of the invention and the terms shown here are not limited thereto.

  The image forming apparatus according to the present embodiment will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of a tandem type color printer showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a schematic cross-sectional view of the image forming apparatus excluding the developer circulation portion, and FIG. 3 is an enlarged cross-sectional view of one of the image forming portions.

  As shown in FIG. 1, an image forming apparatus 1 is arranged in an upper main body 1A in which various units and parts for image formation are housed, and a lower part of the upper main body 1A, and a developer circulation for each color. It is comprised from the lower side main-body part 1B in which the part LY, LM, LC, LB is accommodated. Here, the piping connecting the upper main body 1A and the lower main body 1B is not shown.

  The upper main body 1A includes a paper storage unit 3 for storing paper, a tandem image forming unit 2 for forming a toner image based on image data, and a toner image transferred by the image forming unit 2 on the paper. A fixing unit 5 for fixing, a paper discharge unit 6 for discharging the fixed paper, and a paper transport unit 7 for transporting the paper from the paper storage unit 3 to the paper discharge unit 6 are provided.

  As shown in FIG. 2, the image forming unit 2 includes image forming units FY, FM, FC, and FB respectively corresponding to yellow (Y), magenta (M), cyan (C), and black (Bk) colors. The intermediate transfer belt 21 includes a secondary transfer unit 4 that transfers a toner image onto a sheet, and a belt cleaning unit 22 for the intermediate transfer belt 21.

  The intermediate transfer belt 21 is a belt-like member having an endless shape, that is, a loop shape, which is wider than a sheet having the maximum length in the direction perpendicular to the usable sheet conveying direction and having conductivity. 2 is driven to circulate clockwise. In the circulation driving of the intermediate transfer belt 21, the surface facing outward is hereinafter referred to as a front surface, and the other surface is referred to as a back surface.

  Four image forming units FY, FM, FC, and FB are arranged in the vicinity of the intermediate transfer belt 21 between the belt cleaning unit 22 and the secondary transfer unit 4 of the intermediate transfer belt 21. 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.

  The image forming units FY, FM, FC, and FB include a photoconductor 10 that is an image carrier, a charger 11, an exposure device 12, a developing device 14, a primary transfer roller 20, a cleaning unit 26, a static elimination unit. Device 13. Further, among the image forming units, the image forming unit FB disposed at the position closest to the secondary transfer unit 4 is not provided with the carrier liquid removing roller 30, but the other configurations are the same.

  Corresponding to each of the image forming units FY, FM, FC, and FB, developer circulation portions LY, LM, LC, and LB (see FIG. 1) are provided, respectively, for supplying and collecting the liquid developer of each color. It has come to be.

  The photosensitive member 10 is a cylindrical member, and amorphous silicon is used as a photosensitive material for forming a photosensitive layer. The photoconductor 10 may be an organic photoconductor (OPC photoconductor). A toner image containing toner charged on the surface (charged positively in this embodiment) can be carried. The photoreceptor 10 is a member that can rotate counterclockwise in FIG.

  As shown in FIG. 3, a charger 11, an exposure device 12, a developing device 14, a primary transfer roller 20, a cleaning unit 26, and a static eliminator 13 are provided around the photoconductor 10 in the order of rotation of the photoconductor 10. It is done.

  The charger 11 can uniformly charge the surface of the photoconductor 10. The exposure device 12 has a light source such as an LED, and irradiates light onto the uniformly charged surface of the photoconductor 10 in accordance with image data input from an external device. As a result, an electrostatic latent image is formed on the surface of the photoreceptor 10.

  The developing device 14 holds the liquid developer containing the toner and the liquid carrier so as to face the electrostatic latent image on the surface of the photoreceptor 10, thereby attaching the toner to the electrostatic latent image. Thereby, the electrostatic latent image is developed as a toner image.

  The developing device 14 includes a developing container 140, a developing roller 141, a supply roller 142, a support roller 143, a supply roller blade 144, a developing cleaning blade 145, a developer recovery unit 146, and a developing roller charger 147.

  The developing container 140 is a container that receives a liquid developer including 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 is performed in advance. The liquid developer is supplied toward the nip portion between the supply roller 142 and the support roller 143, and the surplus portion falls below the support roller 143 and is stored at the bottom of the developing container 140. The stored liquid developer is collected through a pipe 883 at a developer circulation section described later.

  The support roller 143 is disposed substantially at the center of the developing container 140 and abuts against the supply roller 142 to form a nip portion. The supply roller 142 is arranged not diagonally above the support roller 143 but obliquely upward in the direction away from the supply nozzle 278, and a groove for holding the liquid developer is provided on the peripheral surface thereof. As indicated by dotted arrows in the figure, the support roller 143 rotates counterclockwise and the supply roller 142 rotates clockwise.

  The liquid developer supplied from the supply nozzle 278 is temporarily retained on the upstream side in the rotation direction of the nip portion, and is moved upward while being held in the groove of the supply roller 142 as both rollers 142 and 143 rotate. Carried to. 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 be 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 as to be in contact with the supply roller 142. The developing roller 141 is rotated in the same direction as the supply roller 142, whereby the liquid developer held on the peripheral surface of the supply roller 142 is transferred to the peripheral surface of the developing roller 141. 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 moves the toner in the developer layer carried on the developing roller 141 to the surface side of the developing roller 141 by applying a charging potential having the same polarity as the charging polarity of the toner, thereby improving the developing efficiency. It fulfills the action of The developing roller charger 147 faces the peripheral surface of the developing roller 141 on the downstream side in the rotation direction of the contact portion with the supply roller 142 of the developing roller 141 and on the upstream side with the contact portion with the photoreceptor 10. Is provided.

  The developing roller 141 is in contact with the photoconductor 10, and a toner image corresponding to the image data is formed on the surface of the photoconductor 10 by the potential difference between the electrostatic latent image potential on the surface of the photoconductor 10 and the developing bias applied to the developing roller 141. Is done.

  The developing cleaning blade 145 is arranged so as to contact the downstream side in the rotation direction of the contact portion of the developing roller 141 with the photosensitive member 10, and removes the liquid developer on the surface of the developing roller 141 that has completed the developing operation on the photosensitive member 10. Remove.

  The developer recovery unit 146 recovers the liquid developer removed by the development cleaning blade 145 and sends the liquid developer to the first recovery pipe 81 of the body developer circulation unit by a screw roller. The liquid developer flows down along the surface of the development cleaning blade 145. Since the viscosity of the liquid developer is high, a delivery roller for assisting delivery of the liquid developer is provided below the developer recovery unit 146. .

  The primary transfer roller 20 is disposed on the back surface of the intermediate transfer belt 21 so as to face the photoreceptor 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 from 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 surface side of the intermediate transfer belt 21 and its periphery.

  The carrier liquid removal roller 30 is a substantially cylindrical member that can rotate in the same direction as the photoconductor 10 around a rotation axis parallel to the rotation axis of the photoconductor 10. The carrier liquid removing roller 30 is disposed on the secondary transfer unit 4 (see FIG. 2) side from the position where the photoreceptor 10 and the intermediate transfer belt 21 are in contact with each other, and removes the carrier liquid from the surface of the intermediate transfer belt 21. It is a member to do. The removed carrier liquid is collected in the developer circulation section through a pipe (not shown).

  The cleaning unit 26 is for cleaning the liquid developer remaining on the photoreceptor 10 and includes a cleaning blade 262 and a developer conveying screw 261. The cleaning blade 262 is a plate-like member that slidably contacts the surface of the photoconductor 10, scrapes off the liquid developer remaining on the surface of the photoconductor 10 as the photoconductor 10 rotates, and the developer transport screw 261 performs cleaning. The liquid developer scraped by the blade 262 and stored in the cleaning unit 26 is conveyed to the outside of the cleaning unit 26.

  The static eliminator 13 has a light source for static elimination, and removes the liquid developer by the cleaning blade 262 and removes the surface of the photoconductor 10 with light from the light source in preparation for the next round of image formation.

  Returning to FIG. 2, the secondary transfer unit 4 is a part that transfers the toner image formed on the intermediate transfer belt 21 to a sheet, and includes a support roller 41 that supports the intermediate transfer belt 21, and a support roller 41. And a secondary transfer roller 42 arranged to face each other.

  The cleaning unit 22 is for cleaning the carrier liquid remaining on the intermediate transfer belt 21 after the toner image is transferred to the sheet. The developer is scraped off by a cleaning blade, and the developer outside the cleaning unit 22 is removed. Transport to the circulation section.

  The paper storage unit 3 is a part for storing a paper for fixing a toner image, and is disposed below the upper main body 1A. The paper storage unit 3 has a paper feed cassette that stores paper. The paper transport unit 7 includes a plurality of transport roller pairs, and transports the paper from the paper storage unit 3 to the secondary transfer unit 4, the fixing unit 5, and the paper discharge unit 6. The fixing unit 5 is a part for fixing the toner image on the sheet, and is disposed on the upper side of the secondary transfer unit 4. The fixing unit 5 includes a heating roller and a pressure roller disposed so as to face the heating roller. The paper discharge unit 6 is a portion from which the paper on which the toner image has been fixed by the fixing unit 5 is discharged, and is disposed at the top of the image forming apparatus 1.

  Next, the configuration of the developer circulation unit will be described with reference to FIGS. FIG. 4 is a diagram schematically showing the overall configuration of the developer circulation unit LY, and FIG. 5 is a block diagram showing the functional configuration of the control unit of the developer circulation unit. Since the developer circulation portions LM, LC, and LB have the same configuration as the developer circulation portion LY, the developer circulation portion LY in FIG. 4 will be described as a representative.

  As shown in FIG. 4, the developer circulating unit LY supplies the liquid developer to the photoreceptor 10 and then the residual developer (toner and carrier liquid) scraped off from the surface of the developing roller 141 by the developing cleaning blade 145. ), The residual developer scraped from the supply roller 142 by the supply roller blade 144 (see FIG. 3), and the intermediate transfer belt by the carrier liquid removing roller 30 (see FIG. 3) after transferring the toner image onto the paper. 21 is a device for recovering, circulating, and reusing the residual developer (mainly carrier liquid) scraped from the surface of 21.

  The developer circulation unit LY includes a residual developer tank 271, a developer generation container 272 that is a developer concentration adjusting unit, a concentration detector 273, a carrier tank 274, a toner tank 275, and an adjusted developer storage unit. A developer reserve tank 277, a carrier separator 279, a plurality of pipes 81 to 88, 881 to 883 connecting these tanks, pumps P1 to P10, three-way valves V1 and V2, which are switching units, and A control unit 90 is provided.

  The residual developer tank 271 is connected to the developing device 14 via the first recovery pipe 81 and is connected to the developing device 14 via the pipe 883 and is recovered from the developing device 14 side via the respective pipes 81 and 883. A tank for temporarily storing the liquid developer. A first pump P 1 is attached in the middle of the first recovery pipe 81, and a pump P 8 is attached in the middle of the pipe 883.

  In the developing unit 14, after the liquid developer is supplied to the photoreceptor 10, the liquid developer scraped off from the surface of the developing roller 141 by the developing cleaning blade 145 passes through the first recovery pipe 81 by driving the first pump P1. The residual developer tank 271 is conveyed. Further, in the developing unit 14, the liquid developer that is not supplied from the supply roller 142 to the developing roller 141 and is collected at the bottom of the developing container 140 is conveyed to the residual developer tank 271 through the pipe 883 by driving the pump P8. . These residual developers collected in the residual developer tank 271 are conveyed to the developer generation container 272. At this time, the three-way valve V2 is set to convey the residual developer of the developing device 14 to the residual developer tank 271. The three-way valve V2 will be described in detail later.

  In order to transport the residual developer from the residual developer tank 271 to the developer generation container 272, the developer generation container 272 is connected to the residual developer tank 271 via the second recovery pipe 82, and this second recovery is performed. A second pump P2 is attached to the pipe 82. The residual developer in the residual developer tank 271 is conveyed to the developer generation container 272 through the second recovery pipe 82 by driving the second pump P2. The first recovery pipe 81, the second recovery pipe 82, the first pump P1, and the second pump P2 described above constitute a recovery transport unit.

  In the developer generating container 272, as will be described later, a liquid developer having a toner concentration higher than that of the liquid developer used in the developing device 14 or a carrier liquid is added to the residual developer, whereby the residual developer toner. The density is adjusted to an appropriate range. Further, the amount of liquid developer stored in the developer generation container 272 is constantly detected by a liquid amount detection unit (not shown), and the liquid amount of the liquid developer is adjusted to an appropriate range. The liquid developer (concentration-adjusted developer) adjusted to a predetermined toner concentration is agitated by the agitating member 276 and supplied to the developer reserve tank 277, which is an adjusted developer reservoir.

  The density detector 273 is for detecting the toner density of the liquid developer stored in the developer generation container 272. A concentration detector 273 is connected to an annular circulation pipe 85 connected to the developer generation container 272. A pump P5 is attached to the circulation pipe 85. The liquid developer in the developer generation container 272 is guided to the concentration detector 273 from the inlet end of the circulation pipe 85 by driving the pump P5, and then returned to the developer generation container 272 from the outlet end of the circulation pipe 85.

  The toner tank 275 is a tank that stores a liquid developer having a toner concentration higher than that of the liquid developer used in the developing device 14. When the concentration detector 273 determines that the toner concentration in the developer generation container 272 is lower than the appropriate range, the high concentration liquid developer is supplied from the toner tank 275 to the developer generation container 272, and the developer The liquid developer in the generation container 272 has a predetermined toner concentration. The toner tank 275 and the developer generation container 272 are connected by a toner pipe 86, and the supply of the high-concentration liquid developer to the developer generation container 272 is driven by a pump P6 provided in the middle of the toner pipe 86. Executed.

  The carrier separator 279 separates and extracts the carrier liquid from the residual developer collected by the cleaning unit 26. The cleaning unit 26 and the carrier separator 279 are connected by a pipe 881 to which a pump P9 is attached. The residual developer in the cleaning unit 26 is sent to the carrier separator 279 by driving the pump P9. Further, a pipe 882 to which a pump P10 is attached is provided between the carrier separator 279 and the carrier tank 274. The carrier liquid extracted by the carrier separator 279 is sent to the carrier tank 274 by driving the pump P10.

  The carrier tank 274 is a tank that stores a carrier liquid. When the concentration detector 273 determines that the toner concentration in the developer generation container 272 is higher than the appropriate range, the carrier liquid is supplied from the carrier tank 274 into the developer generation container 272, and the developer generation container The liquid developer in 272 has a predetermined toner concentration. The carrier tank 274 and the developer generation container 272 are connected by a carrier pipe 87, and the supply of the carrier liquid to the developer generation container 272 is performed by driving a pump P7 provided in the middle of the carrier pipe 87. The

  The developer reserve tank 277 is a tank that stores the liquid developer supplied to the developing device 14. The developer reserve tank 277 is connected to the developer generation container 272 by the first supply pipe 83, and is driven from the developer generation container 272 by driving a third pump P3 provided in the middle of the first supply pipe 83. The developer whose density has been adjusted to the toner density is supplied.

  The supply nozzle 278 is a member for supplying the liquid developer stored in the developer reserve tank 277 to the developing device 14 (developing container 140). The supply nozzle 278 and the developer reserve tank 277 are connected by a second supply pipe 84, and the supply of the liquid developer from the developer reserve tank 277 to the developing device 14 is performed by a second supply pipe 84 attached to the second supply pipe 84. It is executed by driving the four pump P4. The first supply pipe 83 and the third pump P3 described above constitute a first supply conveyance unit, and the second supply pipe 84 and the fourth pump P4 constitute a second supply conveyance unit. At this time, the three-way valve V1 is set so as to convey the liquid developer in the developer reserve tank 277 to the developing device 14. The three-way valve V1 and the bypass pipe 88 will be described in detail next.

  The 1st recovery pipe 81 and the 2nd supply pipe 84 are connected by the bypass pipe 88 which is a bypass conveyance part via the three-way valves V1 and V2 as a switching part.

  The three-way valve V1 is provided in the middle of the second supply pipe 84 that connects the developer reserve tank 277 and the supply nozzle 278 closer to the developing device 14 than the fourth pump P4. The three-way valve V <b> 1 transfers the liquid developer in the developer reserve tank 277 to the developing device 14 during normal time, the liquid developer in the developer reserve tank 277, and the liquid developer in the second supply pipe 84. It is possible to switch to the conveyance at the time of abnormality that conveys to the bypass pipe 88.

  The three-way valve V2 is provided in the middle of the first recovery pipe 81 that connects the developing device 14 and the residual developer tank 271 toward the developing device 14 from the first pump P1. The three-way valve V2 conveys the residual developer of the developing device 14 to the residual developer tank 271 and the liquid developer of the bypass pipe 88 from the first recovery pipe 81 to the residual developer tank 271. It can be switched to conveyance at the time of abnormality.

  Switching of the three-way valves V1 and V2 and driving of the pumps P1 to P10 are controlled by the control unit 90. The control unit 90 includes a CPU (Central Processing Unit) that performs arithmetic processing, a ROM (Read Only Memory) that stores each control program, and a RAM (Random Access) that temporarily stores data such as arithmetic processing and control processing. Etc.).

  FIG. 5 is a block diagram illustrating a functional configuration of the control unit 90. The control unit 90 includes a valve control unit 92, a liquid level determination unit 93, and a pump control unit 94. The three-way valves V 1 and V 2, the pumps P 1 to P 10, the concentration detector 273, and the abnormality detection unit 101 are connected to the control unit 90.

  The abnormality detection unit 101 outputs an abnormality signal indicating that image formation is impossible when an abnormality occurs in the image forming unit 2 or the fixing unit 5 such as the developing device 14 and image formation cannot be performed. Send to 90.

  The valve control unit 92 conveys the three-way valves V1 and V2 during normal operation (conveys the residual developer of the developing device 14 to the residual developer tank 271 and the liquid in the developer reserve tank 277 when the image formation is possible). When the developer is conveyed to the developing device 14 and an abnormality signal is input from the abnormality detection unit 101, the three-way valves V1 and V2 are conveyed when abnormal (the liquid developer and the second supply in the developer reserve tank 277 are supplied). The liquid developer in the pipe 84 is switched to a state where the liquid developer is conveyed to the residual developer tank 271 via the bypass pipe 88.

  The pump control unit 94 gives a drive or stop control signal to the pumps P1 to P10 to control its operation. Based on the switching control of the three-way valves V1 and V2 by the valve control unit 92, the determination result by the liquid level determination unit 93, and the determination result of the toner concentration by the concentration detector 273, the pump control unit 94 performs pumps related thereto. To control the operation.

  Next, an image forming operation of the image forming measure 1 according to the present embodiment will be described with reference to FIGS. When an image forming instruction is received from a personal computer (not shown) connected to the image forming apparatus 1, the image forming apparatus 1 displays toner images of respective colors corresponding to the image data for which the image forming instruction has been received, in the image forming unit FY. , FM, FC, and FB. Specifically, an electrostatic latent image based on image data is formed on the photoconductor 10, and a liquid developer is supplied from the developing device 14 to the electrostatic latent image to form a toner image. The toner image formed by each image forming unit is transferred to the intermediate transfer belt 21 and is superimposed on the intermediate transfer belt 21 to form a color toner image.

  In the paper storage unit 3, the stored paper is taken out one by one by a paper feed roller (not shown) and conveyed along the paper conveyance unit 7. Then, the paper is sent to the secondary transfer unit 4 in synchronization with the primary transfer on the intermediate transfer belt 21, and the color toner image on the intermediate transfer belt 21 is secondarily transferred to the paper by the secondary transfer unit 4. .

  The sheet on which the color toner image is transferred is further conveyed to the fixing unit 5 where heat and pressure are applied, and the color toner image is melted and fixed on the sheet. Further, the sheet is discharged outside the image forming apparatus 1 by the discharge unit 6. The toner remaining on the intermediate transfer belt 21 after the secondary transfer is removed from the intermediate transfer belt 21 by the cleaning unit 22 of the intermediate transfer belt 21.

  Next, FIG. 3 to FIG. 5 show the operation of supplying the liquid developer to the developing device and circulating the liquid developer collected from the image forming unit 2 in the developer circulating unit and the operation of the developer circulating unit in the event of an abnormality. This will be explained based on.

  The liquid developer remaining on the developing roller 141 without being supplied to the photoconductor 10 at the time of image formation is scraped off by the developing cleaning blade 145. The three-way valve V <b> 2 is in a normal transport state, and the scraped liquid developer is recovered in the residual developer tank 271 through the first recovery pipe 81. Further, the residual developer that is not supplied from the supply roller 142 to the developing roller 141 and is stored in the developing container 140 is collected in the residual developer tank 271 through the pipe 883. Further, the carrier liquid extracted by the carrier separator 279 from the residual developer recovered by the cleaning unit 26 is recovered to the carrier tank 274. The pump controller 94 drives the first pump P1 and the pumps P8, P9, and P10 in order to execute such liquid circulation.

  The residual developer recovered in the residual developer tank 271 is supplied to the developer storage container 272 through the second recovery pipe 82 when the pump control unit 94 drives the second pump P2. The stirring member 276 provided in the developer generation container 272 rotates, and the residual developer is stirred by the stirring member 276 in the developer generation container 272.

  When the liquid level determination unit 93 determines that the liquid level of the liquid developer is a predetermined value, the control unit 90 causes the pump control unit 94 to stop driving the second pump P2, and the developer generation container 272. The supply of residual developer to is stopped.

  When the developer generation container 272 is filled with the residual developer, the density detector 273 then detects the toner concentration in the developer generation container 272. When the density detector 273 detects that the toner density is high, when the pump control unit 94 drives the pump P 7, the carrier liquid is supplied from the carrier tank 274 through the carrier pipe 87 to the developer generation container 272. On the other hand, when it is detected that the toner concentration is low, when the pump controller 94 drives the pump P6, the liquid developer having a high toner concentration is supplied from the toner tank 275 to the developer generation container 272 through the toner pipe 86. .

  Thereafter, the density detector 273 detects the toner density in the developer generation container 272 again. If the toner density is within an appropriate range, the pump control unit 94 drives the third pump P3 as necessary. By driving the third pump P3, the liquid developer is supplied from the developer generation container 272 to the developer reserve tank 277 through the first supply pipe 83. Further, the pump control unit 94 appropriately drives the fourth pump P4. The three-way valve V1 is in a normal conveyance state, and the liquid developer stored in the developer reserve tank 277 is conveyed to the supply nozzle 278 through the second supply pipe 84 by driving of the fourth pump P4, and is supplied to the developing device 14. Supplied.

  Here, for example, when an abnormality occurs in the bias applied to the developing device 14 and image formation cannot be performed, the abnormality detection unit 101 sends an abnormality signal to the control unit 90. Based on this abnormality signal, the valve control unit 92 simultaneously switches the three-way valves V1 and V2 to conveyance at the time of abnormality. That is, the supply of the liquid developer from the developer reserve tank 277 to the developing device 14 is stopped by switching the three-way valve V1 to the conveyance at the time of abnormality, and the liquid developer in the developer reserve tank 277 and the second supply pipe 84 are stopped. This liquid developer can be conveyed to the bypass pipe 88. Further, when the three-way valve V2 is switched to the conveyance at the time of abnormality, the recovery of the residual developer from the developing device 14 to the residual developer tank 271 is stopped, and the liquid developer in the bypass pipe 88 is transferred from the first recovery pipe 81 to the residual developer. It can be transferred to the tank 271.

  In addition, when an abnormal signal is input to the control unit 90, the pumps P1 to P7 are driven based on the abnormal signal, and the developer circulation unit LY such as the density detector 273 and the stirring member 276 is further driven. Only the member is driven.

  Accordingly, the liquid developer in the developer reserve tank 277 and the liquid developer in the second supply pipe 84 pass through the bypass pipe 88 and the first recovery pipe 81 by driving the pumps P4 and P1, and enter the residual developer tank 271. Be transported. The residual developer in the residual developer tank 271 is conveyed to the developer generation container 272 through the second recovery pipe 82 by driving the second pump P2. The toner concentration of the liquid developer in the developer generation container 272 is detected by the concentration detector 273. A high-concentration liquid developer is supplied from the toner tank 275 or a carrier liquid is supplied from the carrier tank 274 into the developer generation container 272 so as to obtain a predetermined toner concentration. The density-adjusted developer adjusted to a predetermined toner density is supplied to the developer reserve tank 277 by driving the third pump P3. As described above, when an abnormality occurs and image formation cannot be performed, the liquid developer passes between the developer reserve tank 277, the residual developer tank 271, and the developer generation container 272 by a bypass pipe 88. And circulate through the first and second recovery pipes 81 and 82 and the first and second supply pipes 83 and 84.

  When inspection and repair of the developing device 14 is completed and the switch of the abnormality detection unit 101 is returned to the original state, image formation becomes possible and output of the abnormality signal is stopped. The three-way valves V1 and V2 are switched to normal transport, and the residual developer in the developing device 14 can be transported to the residual developer tank 271 and the liquid developer in the developer reserve tank 277 can be transported to the developing device 14. It becomes.

  Further, a bypass pipe may be connected via a three-way valve between the second supply pipe 84 and the pipe 883 for collecting the residual developer from the developer container 140 to the residual developer tank 271. In this configuration, when an abnormality occurs and image formation cannot be performed, the three-way valve is switched to an abnormal conveyance by an abnormality signal of the abnormality detection unit 101, and the residual developer in the pipe 883 is changed to the residual developer tank 271. It is conveyed to. Accordingly, the residual developer in the pipe 883 can be circulated through the tanks and pipes in the developer circulation section LY.

  According to the first embodiment, the image forming apparatus 1 includes an image forming unit 2 that develops an electrostatic latent image by supplying a liquid developer, which is a mixture of toner and carrier liquid, to the photoconductor 10, and the image forming unit. And a developer circulation unit LY that collects the liquid developer remaining after development from the image forming unit 2 and supplies the liquid developer with the adjusted toner density to the image forming unit 2. When the image forming unit 2 stops when an abnormality is detected Then, recovery and supply of the liquid developer in the image forming unit 2 and the developer circulation unit LY are stopped, and the liquid developer is circulated in the developer circulation unit LY.

  According to this configuration, when the image forming unit 2 supplies the liquid developer to the photoconductor 10 to develop the electrostatic latent image, and the liquid developer in the image forming unit 2 is consumed, the liquid is supplied from the developer circulating unit LY. Although the developer is supplied, the liquid developer circulates in the developer circulation portion LY during a period in which image formation cannot be performed by detecting an abnormality of the apparatus, so that the liquid developer is not deteriorated. Accordingly, it is possible to save the trouble of discarding the liquid developer and cleaning the pipe and the storage container. When the abnormality is eliminated, the liquid developer can be quickly and stably supplied from the developer circulation unit LY to the image forming unit 2.

  The present invention can be used for an image forming apparatus provided with a liquid developing unit used in a copying machine, a printer, a facsimile, a composite machine using the electrophotographic method, and the like.

1 is an overall schematic cross-sectional view of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of an image forming apparatus excluding a developer circulation portion according to an embodiment of the present invention. These are sectional drawings which expand and show one of the image forming parts concerning the embodiment of the present invention. FIG. 3 is a configuration diagram of a developer circulation portion of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a block diagram of a control unit of the image forming apparatus according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming part 10 Photoconductor (image carrier)
14 Developing Unit 81 First Recovery Pipe (Recovery Transport Unit)
82 Second recovery pipe (collection transport section)
83 1st supply pipe (1st supply conveyance part)
84 2nd supply pipe (2nd supply conveyance part)
85 Circulation pipe 86 Toner pipe 87 Carrier pipe 88 Bypass pipe (bypass transport section)
DESCRIPTION OF SYMBOLS 90 Control part 92 Valve control part 93 Liquid level determination part 94 Pump control part 101 Abnormality detection part 140 Developer container 141 Developing roller 142 Supply roller 143 Support roller 145 Developer cleaning blade 146 Developer collection part 271 Residual developer tank 272 Developer generation Container (developer concentration adjustment unit)
273 Concentration detector 274 Carrier tank 275 Toner tank 277 Developer reserve tank (adjusted developer reservoir)
278 Supply nozzle LB, LC, LM, LY Developer circulation part P1-P10 Pump V1, V2 Three-way valve (switching part)

Claims (2)

An image forming unit that develops an electrostatic latent image by supplying a liquid developer in which toner and carrier liquid are mixed to the image carrier, and collecting the liquid developer remaining after development from the image forming unit and adjusting the toner density A developer circulating section for supplying the liquid developer to the image forming section,
When the abnormality is detected and the image forming unit stops, recovery and supply of the liquid developer in the image forming unit and the developer circulating unit are stopped, and the liquid developer is circulated in the developer circulating unit. An image forming apparatus. The image forming unit includes a developing device that supplies a liquid developer to an image carrier to develop an electrostatic latent image,
The developer circulation unit stores a residual developer remaining after development by the developer, and adds a carrier liquid or a high-concentration liquid developer to the residual developer to adjust a toner concentration, and An adjusted developer storage section for storing the density-adjusted developer, a recovery transport section for transporting the residual developer from the developing device to the developer density adjustment section, and the developer density adjustment for the density-adjusted developer A first supply transport unit that transports the density-adjusted developer from the adjusted developer storage unit to the developer, and a recovery transport unit. Provided in the bypass conveyance unit connecting the second supply conveyance unit, between the bypass conveyance unit and the second supply conveyance unit, and between the bypass conveyance unit and the collection conveyance unit, respectively, and the adjusted developer storage Part An image forming apparatus, comprising a switching section for switching so as to convey the density-adjusted developer to the developer concentration adjusting section via the path conveying section.

Images