JP2009003236A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device, capable of preventing degradation of image quality. <P>SOLUTION: A color printer 1 capable of forming developing agent image based on image information comprises a main body part 2 including a plurality of first image forming units FY, FM, FC and FB, a first transfer belt 231, and an elastic roller 237. The first image forming units FY, FM, FC and FB can form images of respective colors based on the image information. The images formed by the first image forming units FY, FM, FC and FB are transferred respectively to the first transfer belt 231. An intermediate transfer roller 237, which has at least a surface formed of an elastic member, receives transfer of the images from the first transfer belt 231, and transfers the transferred images to a paper. The main body part 2 can internally store the first image forming units FY, FM, FC and FB, the first transfer belt 231, and the intermediate transfer roller 237, and further includes an openable and closable shutter part 272 disposed in the vicinity of the intermediate transfer roller 237. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus capable of forming a developer image based on image information.

  An image forming apparatus capable of forming a color image is formed on a plurality of image carriers that can carry an electrostatic latent image, a plurality of developing devices that can supply a developer to each image carrier, and each image carrier. The image forming apparatus includes a transfer member for transferring the developed developer image onto a sheet, a sheet conveying unit that conveys a sheet on which an image can be formed, and a discharge unit that discharges the sheet on which the image is formed. In this image forming apparatus, a developer is supplied from the developing device to the electrostatic latent image carried on the image carrier. The developer image formed on the image carrier is transferred to a transfer member, and transferred from the transfer member to a sheet conveyed by a sheet conveying unit.

Here, in general, an image forming apparatus capable of forming a color image forms an image using three or four general color developers. However, in addition to this, there is an image forming apparatus in which the reproducibility of an image is improved using a special color such as gold or silver. In such an image forming apparatus, the developing devices are arranged in a line (see Patent Document 1).
JP 2002-229293 A

  In the image forming apparatus described in Patent Document 1, since a plurality of developing devices are arranged in a line, the entire apparatus is increased in size and the installation area is increased. For this purpose, it is conceivable to arrange several developing devices on the upper side or the lower side of other developing devices and to arrange transfer members according to the rows of the developing devices. However, in this case, it is difficult to synchronize when transferring the image from each transfer member to the paper, and there is a risk that the image quality will be lowered.

  As another problem, the surface of the transfer member on the side of the image carrier is made of an elastic member, so that the image on the image carrier can be accurately transferred from the transfer member to the sheet. Therefore, for example, in a conventional intermediate transfer belt, an elastic layer that is easily elastically deformed is formed on the surface of a highly rigid substrate. However, the fact that the transfer member is easily elastically deformed means that when a toner image is transferred from each developing device to the transfer member to form a full-color image, the images are not superposed and the image quality may be deteriorated. It means that there is.

  An object of the present invention is to prevent deterioration in image quality.

  An image forming apparatus according to claim 1 is an image forming apparatus capable of forming a developer image based on image information, and includes a plurality of first image forming units, a first transfer member, and a transfer roller. It has a body. The first image forming unit is a unit capable of forming an image of each color based on image information. The first transfer member transfers the image formed by the first image forming unit. The intermediate transfer roller transfers the image from the first transfer member and transfers the transferred image to a sheet. The main body can house the first image forming unit, the first transfer member, and the intermediate transfer roller, and has a shutter unit that is disposed in the vicinity of the intermediate transfer roller and can be opened and closed.

  In this image forming apparatus, an image is formed by the first image forming unit based on the image information. The developer images formed by the plurality of first image forming units are each transferred while being synchronized with the first transfer member, and the image on the first transfer member is transferred to the intermediate transfer roller as the first transfer member circulates. The Then, the image is transferred from the intermediate transfer roller to the sheet, and the sheet is discharged to the outside.

  Here, since the shutter portion is formed, a special color unit capable of transferring an image to the intermediate transfer roller through the shutter portion can be mounted on the upper side of the main body. In addition, when the spot color unit is mounted on the upper side of the main body in this way, the image paper is used to transfer the image formed by the spot color unit to the intermediate transfer roller in synchronization with the image formed by the first image forming unit. Transfer to is performed in a single transfer. For this reason, it is possible to prevent a decrease in overlay accuracy associated with a case where a sheet is transferred a plurality of times, and it is possible to prevent a deterioration in image quality.

  An image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect, wherein the second transfer member that can pass through the shutter portion and come into contact with the intermediate transfer roller and the second transfer member can be transferred. The image forming apparatus further includes at least one second image forming unit that forms an image, and further includes a detachable spot color unit on an upper side of the main body.

  Here, since the spot color unit can be mounted on the upper side of the main body, a plurality of first image forming units and second image forming units can be arranged one above the other in the vertical direction, compared to a case where each image forming unit is arranged side by side. The installation area can be reduced. In addition, since the images of the first transfer member and the second transfer member are transferred to the sheet via the intermediate transfer roller, the image can be transferred to the sheet at once, and the overlay accuracy of the image is reduced. Can be prevented.

  An image forming apparatus according to a third aspect is the image forming apparatus according to the second aspect, wherein the intermediate transfer roller is a member whose surface is at least elastically deformable.

  Here, since at least the surface of the intermediate transfer roller is formed of an elastic member, the first transfer member can be formed of a member that is not easily elastically deformed, such as a resin. For this reason, it is possible to prevent the first transfer member from being elastically deformed when coming into contact with the image carrier, and it is possible to prevent the image quality from deteriorating.

  An image forming apparatus according to a fourth aspect is the image forming apparatus according to the second or third aspect, wherein the second transfer member contacts the intermediate transfer roller when the special color unit is mounted on the upper side of the main body.

  Here, transfer from the second transfer member to the intermediate transfer roller is facilitated.

  An image forming apparatus according to a fifth aspect is the image forming apparatus according to any one of the second to fourth aspects, wherein the first transfer member and the second transfer member are resin-made annular belt members.

  An image forming apparatus according to a sixth aspect is the image forming apparatus according to any one of the second to fifth aspects, wherein the first and second image forming units are arranged in a line, and the image information is displayed on the surface. A plurality of image carriers that can carry the electrostatic latent image formed on the basis thereof, and a plurality of developing devices that are arranged in a line and can supply a developer to each image carrier. .

  In this image forming apparatus, an electrostatic latent image is formed on the image carrier based on the image information, and a developer image is formed on the image carrier by supplying the developer to the electrostatic latent image from the developing device. Is done.

  An image forming apparatus according to a seventh aspect is the image forming apparatus according to the sixth aspect, wherein two second image forming units are arranged side by side. The transfer member passes above the two second image forming unit developing devices and then circulates toward the lower intermediate transfer roller.

  Here, the developer is less likely to spill from the second image forming unit onto the second transfer member. For this reason, it is possible to prevent a deterioration in image quality due to the developer spilling on the second transfer member.

  In the present invention, it is possible to prevent deterioration in image quality.

  Hereinafter, an embodiment of an image processing apparatus of the present invention will be described based on the drawings. For convenience of explanation, the position and size of the members are drawn with emphasis as appropriate in the drawings. In the following embodiments, a printer will be described as an example of the image processing apparatus of the present invention, but the present invention is not limited to this. That is, the image processing apparatus of the present invention only needs to include an image forming unit, and may be a so-called multi-function peripheral (MFP) having a function as a copying machine or a facsimile machine or only a copying function. Specific configurations of these members described below, other members, and the like can be appropriately changed.

1. Overall Configuration A schematic configuration of a color printer 1 as an image forming apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a front view showing a main configuration of the color printer 1.

  The color printer 1 is an apparatus capable of forming a color image based on image information, and includes a main body 2 and a spot color unit 3.

  The main body unit 2 transfers a toner image formed by the first image forming unit 21, a tandem-type first image forming unit 21 that forms a toner image, a paper storage unit 22 that stores paper, and the first image forming unit 21 onto the paper. 1 transfer unit 23, fixing unit 24 for fixing the transferred toner image on the paper, discharge unit 25 for discharging the fixed paper, and paper for conveying the paper from the paper storage unit 22 to the discharge unit 25 A transport unit 26 and a frame 27 are mainly provided.

  The first image forming unit 21 includes first image forming units FY, FM, FC, and FB corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (Bk).

  The first image forming units FY, FM, FC, and FB are between a first driving roller 233 and a first driven roller 234 of the first transfer unit 231 described below and below the first intermediate transfer belt 231. Four are arranged side by side. 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. FIG. 2 is an overall enlarged view of the image forming unit. As shown in FIGS. 1 and 2, the first image forming units FY, FM, FC, and FB include a photosensitive drum 211 as an electrostatic latent image carrier, a charger 212 as a charging device, and an exposure device. As an LED exposure device 213, a liquid developing device 214, a drum cleaning device 215, a charge eliminating device 216, a developer tank 217 and a carrier liquid tank 218, and a liquid developer circulating device 28. The configuration of each image forming unit is the same.

  The photosensitive drum 211 is a member on which an electrostatic latent image is formed based on image information, and can carry a toner image including toner charged on the surface (charged to a positive polarity in this embodiment). The photosensitive drum 211 is a member that can rotate counterclockwise in FIG.

  The charger 212 is a device that can uniformly charge the surface of the photosensitive drum 211.

  The LED exposure device 213 has an LED light source, and can irradiate the charged surface of the photosensitive drum 211 with light corresponding to image data to form an electrostatic latent image on the surface of the photosensitive drum 211.

  As shown in FIG. 2, the liquid developing device 214 is for supplying a liquid developer to the first photosensitive drum 211, and includes a developing roller 214a, a supply roller 214b, a support roller 214c, and a developer. A supply member 214d, a doctor blade 214e, a developer removing blade 214g, and a developer charging device 214f are provided.

  The developing roller 214 a is disposed so as to contact the photosensitive drum 211. The supply roller 214b is for supplying a liquid developer to the developing roller 214a, and is in contact with the lower part of the developing roller 214a. The support roller 214c is a member for supporting the liquid developer together with the supply roller 214b, and is arranged so that the outer peripheral surface is in contact with the supply roller 214b. The tip of a doctor blade 214e is in contact with the supply roller 214b. The doctor blade 214e regulates the layer thickness of the liquid developer carried on the supply roller 214b to be supplied to the development roller 214a to a predetermined value. The developer supply member 214d is a member for supplying the liquid developer near the contact portion between the supply roller 214d and the support roller 214c. The developer removing blade 214e is a member for removing the liquid developer remaining on the developing roller 214a without being supplied to the photosensitive drum 211, and scrapes off the liquid developer on the developing roller 214a. The developer charging device 214f is a device for charging the toner in the liquid developer carried on the developing roller 214a, and is disposed in the vicinity of the developing roller 214a.

  The drum cleaning device 215 is a device for cleaning the developer remaining on the photosensitive drum 211 without being transferred from the photosensitive drum 211 to the intermediate transfer belt 231, and includes a residual developer conveying screw 215 a and a drum cleaning blade. 215b. The residual developer conveying screw 215 a is a member for conveying the residual developer scraped by the drum cleaning blade 215 b and stored in the drum cleaning device 215 to the outside of the drum cleaning device 215. Is arranged. The drum cleaning blade 215b is in sliding contact with the surface of the photosensitive drum 211, and after transferring a developer image formed on the surface of the photosensitive drum 211 to a first intermediate transfer belt 231 described later, the drum cleaning blade 215b is applied to the surface of the photosensitive drum 211. It is a member for scraping off the remaining developer. The drum cleaning blade 215b is a plate-like member extending in the direction in which the photosensitive drum 211 extends.

  The static eliminator 216 includes a light source. After the developer is removed by the drum cleaning blade 215b, the surface of the photosensitive drum 211 is neutralized with light from the light source to prepare for the next image formation.

  The developer tank 217 and the carrier liquid tank 218 are arranged side by side above the first intermediate transfer belt 231 and are portions for storing the liquid toner and the carrier liquid supplied to each liquid developing device 214.

  The configuration of the liquid developer circulating device 28 will be described with reference to FIG. 3 showing the overall configuration of the liquid developer circulating device 28 arranged below each image forming unit in FIG. The liquid developer circulating device 28 is a device for processing a liquid developer that is not used for image formation so that it can be used again. As shown in FIG. 3, a first recovery container 281 and a separation / extraction device 282 are used. A second recovery container 283, an adjustment container 284, a toner tank 217, a carrier tank 218, and a reserve tank 287. The toner tank 217 and the carrier tank 218 are disposed on the upper part of the printer main body 2 as shown in FIG.

  The first recovery container 281 is a container for storing the liquid developer removed from the photosensitive drum 211 by the drum cleaning blade 215b of the drum cleaning device 215 and transported by the residual developer transport screw 215a.

  The separation and extraction device 282 is a device for separating the liquid developer in the first recovery container 281 into toner and carrier liquid, and is connected to the first recovery container 281 through a pump P9 through a pipe. The separation and extraction device 282 includes a storage container 282a capable of storing a liquid developer, an electrode roller 282b disposed in the storage container 282a, and a blocking roller 282c disposed to face the electrode roller 282b and blocking the carrier liquid. A scraping blade 282d that scrapes off the toner adhering to the electrode roller 282b, and a voltage applying device 282e that applies a voltage to the container 282a, the electrode roller 282b, and the blocking roller 282c. Here, in the separation and extraction device 282, the liquid developer in the first recovery container 281 is transported to the storage container 282a by the pump P9 and stored in the storage container 282a. A voltage having the same polarity as the toner is applied to the container 282a and the blocking roller 282c by the voltage applying device 282e, and a voltage having a polarity opposite to that of the toner is applied to the electrode roller 282c. In this state, the electrode roller 282c rotates, and the toner attached to the electrode roller 282c is scraped off by the toner scraping blade 282d. By this operation, the carrier liquid remains in the container 282a and the toner is scraped off by the scraping blade 282d. In this way, the liquid developer is separated into the carrier liquid and the toner. When it is detected by a carrier liquid concentration measuring device (not shown) that the toner concentration in the carrier liquid is equal to or lower than a specified value, the pump P10 is operated, and the carrier liquid passes through the pipe provided with the pump P10 to the carrier tank 218.

  The second recovery container 283 is a container for recovering the liquid developer remaining without being used for image formation of the developing roller 214a and the liquid developing device 214, and is supplied to the liquid developing device 214 by a pipe to which a pump P5 is attached. The developer removal blade 214g is connected to a developer removal device which is one of the constituent elements by a pipe to which the pump P1 is attached.

  The adjustment container 284 is a container for adjusting the toner concentration of the liquid developer, and is connected to the second collection container 283 by a pipe to which the pump P2 is attached. A solid content concentration detection device 288 is attached to the adjustment container 284 via a pipe to which the pump P4 is attached. The solid concentration detector 288 detects the concentration of the liquid developer stored in the adjustment container 284.

  The toner tank 285 stores a liquid developer having a higher toner concentration than the liquid developer used in the liquid developing device 214, and is connected to the adjustment container 284 by a pipe to which a pump P8 is attached.

  The carrier tank 286 stores a carrier liquid, and is connected to the adjustment container 284 by a pipe to which the pump P3 is attached and to the separation and extraction device 282 by a pipe to which the pump P10 is attached.

  The reserve tank 287 stores the liquid developer supplied to the liquid developing device 214, and is connected to the adjustment container 284 by a pipe to which the pump P6 is attached, and to the developer supply member 214d by a pipe to which the pump P7 is attached. Has been. Each pump has a function of delivering the liquid developer in one direction.

  As shown in FIG. 1, the paper storage unit 22 is a part for storing a paper on which a toner image is fixed, and is disposed at the lower part of the color printer 1. The paper storage unit 22 includes a paper feed cassette 221 that stores paper. The paper feed cassette 221 is provided with a paper feed unit 222 to the paper transport unit 26 at the upper end.

  The first transfer unit 23 is a part that transfers a toner image formed on the photosensitive drum 211 to a sheet, and includes a first intermediate transfer belt 231, a plurality of primary transfer rollers 232, and a first drive roller 233. A first driven roller 234, a first tension roller 235, a first carrier liquid removing device 236, an intermediate transfer roller 237, a secondary transfer roller 238, and a first intermediate transfer belt cleaning device 239. Yes.

  The first intermediate transfer belt 231 is a member to which a toner image formed on the photosensitive drum 211 is transferred, and is an endless belt-like member. The first intermediate transfer belt 231 is disposed above each first image forming unit FY, FM, FC, and FB having the photosensitive drum 211 and the liquid developing device 214, and as shown by an arrow in FIG. Circulated around. In addition, the surface of the first intermediate transfer belt 231 is conventionally a conductive resin belt (PI, PAA, PVDF, polycarbonate, etc.) or an elastic member (NBR, hydrin, urethane, silicone, etc.) on the resin belt. Is a member coated with a fluorine-based or urethane-based coating layer. However, in the present embodiment, as will be described later, since the image is transferred onto the sheet by the intermediate transfer roller 237, it is not necessary to form the elastically deformable material. Can be formed. In addition, the surface facing outward in the circulation drive is hereinafter referred to as a front surface, and the other surface is referred to as a back surface.

The primary transfer roller 232 is a member for performing primary transfer, that is, a member for transferring an image from the photosensitive drum 211 to the first intermediate transfer belt 231, and the photosensitive drum of the first intermediate transfer belt 231. It arrange | positions so that 211 may contact the back surface of the part which is contacting. The primary transfer roller 232 is applied with a voltage (negative in this embodiment) opposite to the charging polarity of the toner in the toner image formed on the surface of the photosensitive drum 211 from a power source (not shown). ing. That is, the primary transfer roller 232 applies a voltage having a polarity opposite to the charging polarity of the toner to the first intermediate transfer belt 231 at a position where it is in contact with the first intermediate transfer belt 231. Since the first intermediate transfer belt 231 has conductivity, the applied voltage attracts toner to the surface side of the first intermediate transfer belt 231 and the periphery thereof. Here, the primary transfer roller 232 is an elastic material, for example, foam or rubber, and has a resistance value of 1.0 × 10 ^{3 to} 1.0 × 10 ⁹ Ω, preferably 1.0 × 10 ⁴ to 1. 0 × 10 ⁷ Ω.

  The first drive roller 233 is disposed in the vicinity of the FY toner image forming unit and is in contact with the back surface of the intermediate transfer belt 231. The first drive roller 233 is connected to a motor (not shown) and is a roller for circulating the first intermediate transfer belt 231.

  The first driven roller 234 is disposed to face the first drive roller 233 and is a member that contacts the back surface of the first intermediate transfer belt 231.

  The first tension roller 235 is a member that applies tension to the first intermediate transfer belt 231 and is in contact with the back surface of the first intermediate transfer belt 231 between the first drive roller 233 and the first driven roller 234. Has been placed.

  The first carrier liquid removing device 236 is a device for removing excess carrier liquid from the developer image transferred to the first intermediate transfer belt 231, and is in the vicinity of the first image forming unit FY and the first intermediate transfer device. The belt 231 is arranged on the downstream side in the moving direction. The first carrier liquid removing device 236 includes a roller 236a for holding the first intermediate transfer belt 231 to remove the carrier liquid, and a collecting device 236b for collecting excess carrier liquid adhering to the roller 236a. And an opposing roller 236c sandwiching the first intermediate transfer belt 231 together with the roller 236a. A layer having higher wettability to the carrier liquid than the first intermediate transfer belt 231 is disposed on the surface of the roller 236a.

  The intermediate transfer roller 237 is disposed so as to face the first driven roller 234 with the first intermediate transfer belt 231 interposed therebetween, and is a roller for transferring the developer image on the first intermediate transfer belt 231 to a sheet. is there. Further, the intermediate transfer roller 237 is formed by a member whose surface can be elastically deformed so that the surface of the roller can follow the irregularities present on the surface of the paper that is the recording medium, and is attached to the first intermediate transfer belt 231. It arrange | positions so that it may contact from an upper side. If the intermediate transfer roller 237 is not composed of a member that can be elastically deformed, the transfer efficiency may be reduced at the concave portion on the surface of the sheet, and a high-quality image may not be obtained. In other words, the surface of the intermediate transfer roller 237 only needs to be formed of an elastic member that can follow the unevenness of the surface of the paper to be used. When the sheet to be used is limited to a special specification sheet with high surface smoothness, the surface of the intermediate transfer roller 237 does not have to have elasticity. Further, the intermediate transfer roller 237 can transfer the developer image onto the sheet conveyed by the first sheet conveying unit 26, and a predetermined nip is provided between the intermediate transfer roller 237 and the first intermediate transfer belt 231. The first intermediate transfer belt 231 is elastically deformed.

  The secondary transfer roller 238 is a roller for transferring the toner image transferred to the intermediate transfer roller 237 to the sheet conveyed by the sheet conveying unit 26, and is disposed to face the intermediate transfer roller 237. ing.

  The first intermediate transfer belt cleaning device 239 is a device for cleaning the first intermediate transfer belt 231 and is disposed in the vicinity of the first driven roller 234. The first intermediate transfer belt cleaning device 239 includes a blade 239a disposed so as to contact the first intermediate transfer belt 231 and a storage case 239b for storing the developer scraped by the blade 239a. Yes.

  The fixing unit 24 is a portion that fixes the toner image on the paper, and is disposed on the downstream side of the position where the image is transferred from the intermediate transfer roller 237 to the paper in the paper transport direction. The fixing unit 24 includes a heating roller 241 that is in contact with the toner image transferred to the paper, and a pressure roller 242 that is disposed to face the heating roller 241.

  The discharge unit 25 is a part from which the sheet on which the toner image is fixed by the fixing unit 24 is discharged, and is disposed on the side of the color printer 1.

  The paper transport unit 26 is a part for transporting paper from the paper storage unit 22 to the discharge unit 25 and includes a plurality of roller pairs.

  The frame 27 is a member that can accommodate the first image forming unit 21, the fixing unit 24, and the like therein, and includes a discharge tray 271 and a shutter unit 272. The discharge tray 271 is a member on which the paper discharged by the discharge unit 25 can be placed, and is a plate-like portion disposed in the vicinity of the discharge unit 25. The shutter portion 272 is disposed in the vicinity of the intermediate transfer roller 237 and is opened when the spot color unit 3 is mounted on the upper side of the main body portion 2.

  The spot color unit 3 is detachable on the upper side of the main body 2 and includes a second image forming unit 31 and a second transfer unit 32.

  The second image forming unit 31 includes two second image forming units FS and FG corresponding to the respective colors of silver (S) and gold (G).

  The second image forming units FS and FG are arranged below the second intermediate transfer belt 321 described later, and are arranged above the first image forming units FY, FM, FC, and FB. For this purpose, the liquid developing devices of the second image forming units FS and FG are arranged above the liquid developing device 214. Since the second image forming units FS and FG have the same configuration as the first image forming units FY, FM, FC, and FB, description thereof is omitted.

  The second transfer unit 32 is a part for transferring the image formed by each of the second image forming units FS and FG to the intermediate transfer roller 237, and includes a second intermediate transfer belt 321, a second drive roller 322, and the like. , A second driven roller 323, a counter roller 324, a second carrier liquid removing device 325, a second intermediate transfer belt posture maintaining roller 326, and a second intermediate transfer belt cleaning device 327.

  The second intermediate transfer belt 321 is an annular belt, and is formed of a high-rigidity resin that is not easily elastically deformed, like the first intermediate transfer belt 231. The second intermediate transfer belt 321 is a member to which images formed by the second image forming units FS and FG are transferred, and is a member for transferring the images to the intermediate transfer roller 237. Further, the second intermediate transfer belt 321 is formed with a nip having a predetermined width with the intermediate transfer roller 237 in a state where the special color unit 3 is mounted on the upper side of the main body 2, that is, the intermediate transfer roller 237 is elastically deformed. I am letting.

  The second drive roller 322 is a roller for circulating the second intermediate transfer belt 321 and is disposed in the vicinity of the second image forming unit FG.

  The second driven roller 323 is disposed so as to face the second drive roller 322.

  The counter roller 324 is positioned so as to face the intermediate transfer roller 237 with the second intermediate transfer belt 321 sandwiched in a state where the spot color unit 3 is mounted on the upper side of the main body 2, and the second intermediate transfer belt 321 is intermediate-transferred. This is a roller for contacting the roller 237.

  The second carrier liquid removing device 325 is a device for removing excess carrier liquid from the developer image transferred to the second intermediate transfer belt 321 from the second image forming units FS and FG, and is a second image forming unit. A roller 325a disposed near the FG and downstream of the second intermediate transfer belt 321 in the moving direction, a recovery device 325b for recovering excess carrier liquid adhering to the surface of the roller 325a, and a roller 325a disposed opposite the roller 325a. And an opposing roller 325c that sandwiches the first intermediate transfer belt 321.

  The two second intermediate transfer belt posture maintaining rollers 326 are rollers for supporting the posture of the second intermediate transfer belt 321 uniformly, and are disposed in the vicinity of the second image forming unit FS.

  The second intermediate transfer belt cleaning device 327 is provided so as to face one of the second intermediate transfer belt posture maintaining rollers 326, and a blade 327a that is in contact with the surface of the second intermediate transfer belt 321 and scraped by the blade 327a. And a storage case 327b for storing the taken developer.

2. Operation Next, an image forming operation of the wet color printer 1 will be described with reference to FIG.

  First, a description will be given of a case where an image is formed with respect to image data using a special color (silver and gold) developer. In this case, the spot color unit 3 is mounted on the upper side of the main body 2 before the image forming operation is performed. Then, upon receiving an image formation instruction from a personal computer (PC) connected to the wet color printer 1, toner images of each color corresponding to the image data for which the creation instruction has been received are first image forming units FY, FM, FC, It is formed by the FB and the second image forming units FS and FG. Specifically, an electrostatic latent image based on image data is formed on the photosensitive drum 211, and a liquid developer is supplied from the liquid developing device 214 to the electrostatic latent image. The developer images formed by the second image forming units FS and FG in this manner are transferred onto the second intermediate transfer belt 321 while being superimposed on each other. Then, the second intermediate transfer belt 321 is transferred to the intermediate transfer roller 237 as the second intermediate transfer belt 321 is circulated. At this time, the developer images formed by the first image forming units FY, FM, FC, and FB are transferred while being superimposed on the first intermediate transfer belt 231, and a color image is formed on the first intermediate transfer belt 231. Is done. Then, as the first intermediate transfer belt 231 circulates, the first carrier liquid removing device 236 removes the excess carrier liquid of the color image. The color image is transferred to the intermediate transfer roller 237 so as to overlap the image transferred from the second intermediate transfer belt 321 as the first intermediate transfer belt 231 circulates.

  In synchronization with the formation of the color toner image, the paper stored in the paper storage unit 22 is taken out from the paper storage unit 22 one by one by a paper feeding device (not shown) and conveyed along the paper conveyance unit 26. Then, the sheet is sent to a position where it can come into contact with the intermediate transfer roller 237, and a color image is transferred from the intermediate transfer roller 237 to the sheet. The sheet on which the color image is transferred is conveyed to the fixing unit 24 by the sheet conveying unit 26, and the color image is fixed on the sheet. The sheet on which the color image is fixed is discharged from the discharge unit 25 and placed on the discharge tray 271.

  Here, when the image on the intermediate transfer roller 237 is completed on the first intermediate transfer belt 231, the residual developer is cleaned as the first intermediate transfer belt 231 circulates. That is, the residual developer on the surface of the first intermediate transfer belt 231 is scraped off by the blade 239a of the first intermediate transfer belt cleaning device 239 and stored in the storage case 239b. Similarly, the second intermediate transfer belt 321 is also cleaned by the second intermediate transfer belt cleaning device 327.

  In the case of image data that does not use a special color developer, a developer image is formed by the first image forming units FY, FM, FC, and FB, and the respective images are superimposed on the first intermediate transfer belt 231. It is transcribed. Then, the image transferred to the first intermediate transfer belt 231 is transferred from the first intermediate transfer belt 231 to the intermediate transfer roller 237 and transferred to a sheet. The sheet onto which the image has been transferred is conveyed to the fixing unit 24 where the image is fixed. Thereafter, the sheet is discharged from the discharge unit 25 to the discharge tray 271. At this time, the spot color unit 3 may not be used for the image forming operation and may be removed from the main body 2.

  When the image forming operation is completed, the liquid developer remaining on the photosensitive drum 211 without being used in the image forming operation is scraped off by the drum cleaning device 215. The liquid developer scraped off and the liquid developer remaining inside the liquid developing device 214 are reused by the liquid developer circulating device 28. Specifically, during the image forming operation, the liquid developer remaining on the photosensitive drum 211 without being transferred from the photosensitive drum 211 to the first and second intermediate transfer belts 231 and 321 is removed by the drum cleaning blade 215b. It is collected in the drum cleaning device 215 and conveyed to the first recovery container 281 by the residual developer conveying screw 215a. The liquid developer recovered in the first recovery container 281 is conveyed to the separation and extraction device 282 and separated into toner and carrier liquid, and then the carrier liquid is conveyed to the carrier tank 286. In addition, the liquid developer contained in the liquid developing device 214 and not used for image formation and the liquid developer removed by the developer removing blade 214g from the developing roller 214a of the liquid developing device 214 are recovered in the second recovery container 283. The The liquid developer stored in the second recovery container 283 is conveyed to the adjustment container 284, and in the adjustment container 284, the toner from the toner tank 285 and the carrier liquid from the carrier tank 286 are supplied as necessary, and the liquid developer is supplied. The developer concentration is adjusted. The liquid developer whose density is adjusted is conveyed to the reserve tank 287. The liquid developer in the reserve tank 287 is supplied to the developer supply member 214d.

  Here, in the state where the spot color unit 3 is mounted on the upper side of the main body unit 2, the second image forming unit 31 is disposed on the upper side of the first image forming unit 21. This is smaller than the case where the two image forming units 31 are arranged so as not to overlap in the vertical direction. In addition, after the images are transferred from the first intermediate transfer belt 231 and the second intermediate transfer belt 321 to the intermediate transfer roller 237, the images are transferred to a sheet, so that the images are not superposed at the time of transfer. The accompanying deterioration in image quality can be prevented. Further, in order to transfer an image from the intermediate transfer roller 237 to the sheet, the first intermediate transfer belt 231 and the second intermediate transfer belt 321 do not need to be formed of an elastically deformable member, and are more elastic than rubber. It can be formed of a resin material that is not easily deformed. For this reason, it is possible to prevent the image quality from being deteriorated due to the elastic deformation of the intermediate transfer belt mainly in the circulation direction.

3. Other Embodiments (a) Although the color printer 1 has been described in the above embodiment, the present invention is not limited to this, and may be a copying machine, a multifunction machine, or the like.

  (B) In the above embodiment, a wet developer is used. However, the present invention is not limited to this, and an apparatus for forming an image using a dry developer may be used.

  (C) Further, in the above-described embodiment, the case where there are two special color image forming units has been described. However, the present invention is not limited to this, and may be three, four, or one depending on conditions. .

1 is an overall schematic diagram of a color printer 1. FIG. 1 is an overall view of an image forming unit. 1 is an overall schematic diagram of a developer circulation device.

Explanation of symbols

1 Color printer (image forming device)
2 Main body (main body)
3 Special Color Unit 22 Paper Storage Unit 25 Discharge Unit 26 Paper Conveying Unit 211 Photosensitive Drum (Image Carrier)
214 Liquid developing device 231 First intermediate transfer belt (first transfer member)
237 Intermediate transfer roller 321 Second intermediate transfer belt (second transfer member)
FY, FM, FC, FB First image forming unit FS, FG Second image forming unit

Claims (7)

An image forming apparatus capable of forming a developer image based on image information,
A plurality of first image forming units capable of forming images of respective colors based on image information;
A first transfer member to which images formed by the first image forming unit are respectively transferred;
An intermediate transfer roller for transferring an image from the first transfer member and transferring the transferred image to paper;
A shutter unit capable of accommodating the first image forming unit, the first transfer member, and the intermediate transfer roller therein;
An image forming apparatus provided with a main body having. A second transfer member that can pass through the shutter portion and come into contact with the intermediate transfer roller;
And at least one second image forming unit that forms an image that can be transferred to the second transfer member, and further includes a detachable spot color unit on the upper side of the main body.
The image forming apparatus according to claim 1.   The image forming apparatus according to claim 2, wherein at least a surface of the intermediate transfer roller is an elastically deformable member. The second transfer member contacts the intermediate transfer roller in a state where the spot color unit is mounted on the upper side of the main body.
The image forming apparatus according to claim 2.   The image forming apparatus according to claim 2, wherein the first transfer member and the second transfer member are resin-made annular belt members. The first and second image forming units are:
A plurality of image carriers arranged in a row and capable of carrying an electrostatic latent image formed on the surface based on image information;
A plurality of developing devices arranged in a row and capable of supplying a developer to each of the image carriers;
have,
The image forming apparatus according to claim 2. The spot color unit has the two second image forming units arranged side by side,
The second transfer member passes above the two second image forming units and then circulates toward the lower intermediate transfer roller.
The image forming apparatus according to claim 6.

Images