JP2007171439A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize image formation through maintaining a preferable state of a developer by collecting the developer in a simple configuration and reusing the developer while avoiding a color mixing of developers. <P>SOLUTION: An image forming apparatus comprises: a plurality of image carriers 10; a plurality of developing devices 30 for developing electrostatic latent images formed on the plurality of the image carriers by using different color developers respectively regarding a nonvolatile solvent as the carrier; an intermediate transfer body 40 for conveying to successively transfer, superpose and carry developer images developed with a primary transfer part corresponding to each of the plurality of the image carriers; and an output device for outputting to transfer the developer image superposed from the intermediate transfer body on a conveying path with a secondary transfer body 40. The image forming apparatus collects the developer from an intermediate transfer body squeezing device 52Y arranged in the downstream side of a moving direction of the primary transfer part of an intermediate transfer body and image carrier squeezing devices (13M, 14M) of a second color with the same developer collection part 15M. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention includes a plurality of image carriers, a plurality of developing devices that develop electrostatic latent images formed on the plurality of image carriers using a liquid developer having a non-volatile solvent as a carrier, An intermediate transfer body that sequentially transfers, develops, and transports the developed toner images at a primary transfer portion corresponding to each of a plurality of image carriers, and a secondary transfer of the toner images superimposed from the intermediate transfer bodies The present invention relates to an image forming apparatus including an output device that outputs an image by transferring the image to a sheet material on a conveyance path.

  Various wet image forming apparatuses that develop a latent image using a high-viscosity liquid developer in which a toner composed of a solid component is dispersed in a liquid solvent and visualize the electrostatic latent image have been proposed. The developer used in this wet image forming apparatus is obtained by suspending solids (toner particles) in an electrically insulating organic solvent (carrier) made of silicon oil, mineral oil, edible oil, or the like. The toner particles have a very fine particle diameter of about 1 μm. By using such fine toner particles, the wet image forming apparatus can achieve higher image quality than a dry image forming apparatus using powder toner particles having a particle diameter of about 7 μm.

The carrier constituting the developer has a function of making the toner particles charged and further uniformly dispersed in addition to preventing the scattering of the toner particles having a particle diameter of about 1 μm. It also plays a role in making it easy to move by electric field action. As described above, the carrier is a necessary component in the toner storage, toner conveyance, development, and transfer processes, but also adheres to the non-image area, and excessive carrier after the development causes a transfer disorder and the like. Therefore, the carrier is usually removed (squeezed) from the developer on the photosensitive member and the intermediate transfer member (see, for example, Patent Document 1). In the wet image forming apparatus, when an intermediate transfer belt or a secondary transfer belt is used, the liquid developer (carrier and solid content) adhering to the belt surface is removed by a cleaning blade (for example, In the recycling of the developer, a plurality of developing devices are selectively arranged to face the photosensitive drum, and a squeeze device corresponding to each developing device is provided on the downstream side of the developing device. Similar to the developing device, it is selectively placed opposite to the photosensitive drum, the excess developer developed on the photosensitive drum by this squeeze device is squeezed, and the excess developer collected in the squeeze device is circulated. There is a system for circulating and transporting to a corresponding developing device for reuse (for example, see Patent Document 3).
JP 2002-296918 A JP 2002-189354 A JP 2003-107913 A

  However, in the above-described conventional developer recycling system, a plurality of developing devices and a squeeze device corresponding to the developing device are selectively disposed opposite to a single photosensitive drum to develop the developer in the latent image. A first color latent image is formed on the photosensitive drum, the first color developer is developed on the latent image, the first color excess developer is squeezed, and the first color developer is developed. The visible image developed into the latent image proceeds to the process of creating the second color latent image, forms the second color latent image, develops the second color developer on the latent image, and squeezes the second color excess developer. To do. The so-called color superimposing method on the photosensitive drum, in which the same color development and squeezing are repeated for the fourth color to form a toner image on the photosensitive drum, and the toner images superimposed on the color are transferred onto the transfer paper in a batch. The color image forming apparatus. Here, a squeeze device corresponding to each developing device is provided, and consideration is given to the color mixing of the surplus developer squeezed by the squeeze device while being selectively opposed to the photosensitive drum.

  However, unnecessary fog toner is included in the visible image overlaid on the photosensitive drum. When this is squeezed, not only the fog toner but also the latent image and a part of the visible image developed. The toner is collected by the squeeze device, and color mixing cannot be prevented. Therefore, if the excess developer collected by this squeeze device is transported to a corresponding developing device and reused, color mixing proceeds gradually in the developing device, so it is impossible to maintain a preferable developer state. is there.

  Therefore, the present invention collects the developer with a simple configuration, transports the developer from which the color mixture of the developer has been removed, and reuses it to maintain a preferable developer state and form a stable image. It is something that can be done.

  To this end, the present invention provides a plurality of image carriers and a plurality of electrostatic latent images formed on the plurality of image carriers using a different color liquid developer using a non-volatile solvent as a carrier. A developing device, an intermediate transfer member that sequentially transfers the developed developer images in a primary transfer portion corresponding to each of the plurality of image carriers, and superimposes and conveys the developed developer images. An output device that transfers and outputs the developer image to a sheet material on the conveyance path by a secondary transfer unit, and arranges developer recovery means at a plurality of positions so as to recover excess developer and perform image formation. In the image forming apparatus, each of the image carrier squeeze device disposed upstream of the primary transfer portion of each of the image carriers as the developer collecting unit and the primary transfer portion of the intermediate transfer member. Move more An intermediate transfer body squeeze device that includes an intermediate transfer body squeeze device disposed on the downstream side, and excludes the intermediate transfer body squeeze device disposed on the most downstream side in the moving direction of the intermediate transfer body, and the intermediate transfer body squeeze The developer is collected in the same developer collecting section from the image carrier squeeze device disposed downstream of the apparatus in the moving direction of the intermediate transfer member.

  The developer collecting means includes an image carrier cleaning device disposed downstream in the movement direction from the primary transfer portion of the image carrier, and further upstream in the movement direction of the intermediate transfer member than the intermediate transfer member squeeze device. The developer collected in the developer collecting section of the arranged image carrier cleaning device and the developer collected in the same developer collecting section are merged into the same flow path, and the second intermediate transfer body is moved. The intermediate transfer body cleaning device is disposed downstream of the next transfer portion in the movement direction and upstream of the first color primary transfer portion in the movement direction, and developed by the developer recovery portion of the intermediate transfer body cleaning device. The developer is combined in the same flow path as the developer recovered in the developer recovery portion of the first color image carrier squeeze device.

  The output device includes a transfer roller that transfers the developer image to a sheet material and a cleaning blade that contacts the roller. The developer collected by the cleaning blade is joined to the same flow path, and the same The developer merged in the flow path is conveyed to a carrier buffer tank through filter means, separated and stored by the filter means, and the stored carrier is distributed and conveyed from the carrier buffer tank to the plurality of developing devices. A developer conveying means is provided.

  According to the present invention, the developer is recovered from each part of the image carrier, the intermediate transfer member, and the transfer unit with a simple configuration. Further, the recovered developer is transported together and the carrier is separated by the filter and stored. Then, by distributing and conveying this to the developing device, the carrier reuse rate can be averaged and stable reuse can be achieved. For example, even if the developer is in a mixed color state or contains paper dust, the developer is collected together by a pump and removed by a filter, so that the developer can be recovered with a simple configuration and the color of the developer can be reduced. The removed developer can be transported to the developing device and reused, and a stable developer can be formed while maintaining a preferable developer state.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing main components constituting an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing main components of an image forming unit, a developing unit, and an intermediate transfer member squeeze device. In FIG. 1, the image forming unit, the developing unit, and the intermediate transfer member squeeze device are different from each other in the colors of yellow (Y), magenta (M), cyan (C), and black (K). The same numbers are used with Y, M, C, and K representing each. Among them, FIG. 2 shows the configuration of a yellow (Y) image forming unit, a developing unit, and an intermediate transfer member squeeze device. Details of each image forming unit, developing unit, and intermediate transfer member squeeze device will be described below with reference to FIG.

  The image forming unit includes a cleaning device including a latent image eraser 16Y, an image carrier cleaning blade 17Y, and a developer recovery unit 18Y, a charging roller 11Y, and an exposure unit along the rotation direction (movement direction) of the outer periphery of the image carrier 10Y. A cleaning device including a unit 12Y, a developing roller 20Y of the developing unit 30Y, an image carrier squeeze roller 13Y, and a cleaning blade 14Y and a developer recovery unit 15Y, which are auxiliary components, is disposed. The developing unit 30Y includes a cleaning blade 21Y, a developer supply roller 32Y using an anilox roller, a regulating blade 33Y for regulating the developer supply amount, a developer compression roller 22Y, and a developer on the surface of the developing roller 20Y. A cleaning blade 23Y that removes the toner is disposed, and a developer stirring roller 34Y that stirs the developer in a uniformly dispersed state is disposed in a developer container (reservoir) 31Y in which the liquid developer is accommodated. Further, a primary transfer roller 51Y of the primary transfer unit 50Y is disposed at a position facing the image carrier 10Y with the intermediate transfer body 40 interposed therebetween, and an intermediate transfer body squeeze device 52Y is disposed downstream of the intermediate transfer body 40 in the moving direction. Further, a primary transfer portion 50 (M, C, K) for each color and an intermediate transfer body squeeze device 52 (M, C, K) are arranged. The intermediate transfer member squeeze device 52Y includes an intermediate transfer member squeeze roller 53Y, a backup roller 54Y, an intermediate transfer member squeeze roller cleaning blade 55Y, and a developer recovery unit 15M.

  The liquid developer accommodated in the developer container 31Y is a low-concentration (about 1 to 2 wt%) and low-viscosity volatile at room temperature using Isopar (trademark: exon) as a carrier, which is generally used conventionally. It is not a volatile liquid developer having a high concentration and a high viscosity, but a liquid developer having a non-volatile solvent at room temperature as a carrier. That is, the liquid developer in the present embodiment is a solid developer having an average particle diameter of 1 μm in which a colorant such as a pigment is dispersed in a thermoplastic resin in a liquid solvent such as an organic solvent, silicon oil, mineral oil, or edible oil. It is a liquid developer having a high viscosity (about 30 to 10,000 mPa · s) which is added together with a dispersant and has a toner solid content concentration of about 25%. The liquid developer accommodated in the developer container 31Y is developed in such a manner that it is dispersed from the developer cartridge 72Y at a high density of about 35 to 55% by weight according to the developer concentration that changes with the development on the image carrier. The carrier is supplied from the carrier cartridge 71Y to the developer container 31Y and stirred by the liquid developer agitating roller 34Y to obtain a uniform dispersion state, and 25% of the toner is dispersed in 75% of the carrier by a general weight ratio. It has been made.

  In the image forming unit and developing unit 30Y, the image carrier 10Y is uniformly charged by the charging roller 11Y, and the input image is input by the exposure unit 12Y having an optical system such as a semiconductor laser, a polygon mirror, and an F-θ lens. Based on the signal, a modulated laser beam is irradiated to form an electrostatic latent image on the charged image carrier 10Y. Then, the amount of developer supplied is regulated by the regulating blade 33Y from the developer container 31Y storing the liquid developer of each color (here yellow), and the developer is supplied from the developer supply roller 32Y to the developing roller 20Y to carry the image. The electrostatic latent image formed on the body 10Y is developed.

  The intermediate transfer member 40 is an endless elastic belt member and is wound around and stretched between a driving roller 41 and a tension roller 42. The image transfer members 10Y, 10M, and 50K are primary transfer units 50Y, 50M, 50C, and 50K. It is rotationally driven by the drive roller 41 while abutting 10C and 10K. The primary transfer units 50Y, 50M, 50C, and 50K are arranged such that the primary transfer rollers 51Y, 51M, 51C, and 51K are opposed to the image carriers 10Y, 10M, 10C, and 10K with the intermediate transfer member 40 interposed therebetween. Using the contact position with 10M, 10C, and 10K as the transfer position, the developed toner images of the respective colors on the image carriers 10Y, 10M, 10C, and 10K are sequentially superimposed and transferred onto the intermediate transfer body 40 to obtain a full color toner. An image is formed. The toner images formed on the plurality of image carriers (photosensitive members) 10Y, 10M, 10C, and 10K are sequentially transferred onto the intermediate transfer member 40 in such a manner that the toner images are superimposed and supported on the sheet material. Next transfer. Therefore, when transferring the toner image to the sheet material in the secondary transfer process, even if the sheet material surface is not smooth due to the fiber, etc., the secondary transfer characteristics are improved following this non-smooth sheet material surface. An elastic belt member is employed as the means for making it.

  In the secondary transfer unit 60, a secondary transfer roller 61 is disposed opposite to the belt driving roller 41 with the intermediate transfer body 40 interposed therebetween, and a cleaning device including a cleaning blade 62 and a developer recovery unit 63 of the secondary transfer roller is disposed. Is done. In the secondary transfer unit 60, the sheet material conveyance path L is synchronized with the timing at which a full-color toner image or a single-color toner image formed on the intermediate transfer body 40 reaches the transfer position of the secondary transfer unit 60. Then, a sheet material such as paper, film or cloth is conveyed and supplied, and a single-color toner image or a full-color toner image is secondarily transferred to the sheet material. A fixing unit (not shown) is disposed in front of the sheet material conveyance path L, and a single color toner image or a full color toner image transferred onto the sheet material is fused and fixed to a recording medium (sheet material) such as paper. Image formation on the final sheet material is completed. Even if the secondary transfer roller 61 is a sheet material whose surface is not smooth due to fibers or the like, as a means for improving the secondary transfer characteristics following the surface of the non-smooth sheet material, the surface is coated with an elastic body. It is composed of rollers. This is an elastic belt employed in the intermediate transfer body 40 that sequentially transfers the toner images formed on the plurality of image carriers 10Y, sequentially superimposes them on the intermediate transfer body 40, and transfers them to the sheet material collectively. The purpose is the same as that of the member.

  On the side of the tension roller 42 that stretches the intermediate transfer body 40 together with the belt drive roller 41, a developer compression roller 43 is disposed to face the intermediate transfer body 40 along the outer periphery thereof. A cleaning device including a cleaning blade 46 and a developer recovery unit 47 is disposed downstream of the intermediate transfer member 40 in the moving direction of the intermediate transfer member 43. A cleaning device including a cleaning blade 44 and a developer recovery unit 45 is also disposed on the outer periphery of the developer compression roller 43 so that the residual toner on the intermediate transfer body 40 is transferred to the intermediate transfer body with respect to the developer compression roller 43. A bias is applied in the direction of pressing to 40. After passing through the secondary transfer unit 60, the intermediate transfer body 40 proceeds to the winding portion of the tension roller 42, and after the developer is compressed by the developer compression roller 43, the cleaning blade 46 moves the intermediate transfer body 40 onto the intermediate transfer body 40. Cleaning is performed, and the process proceeds to the primary transfer unit 50 again.

  In the developer container 31Y, the toner particles in the liquid developer have a positive charge. The developer is agitated by the agitation roller 34Y to be in a uniformly dispersed state, and the developer supply roller 32Y rotates. The developer is pumped up from the developer container 31Y, the developer amount is regulated by the regulating blade 33Y, and supplied to the developing roller 20Y. Initially, the developer stored in the developer container 31Y is uniformly dispersed in the carrier at approximately a toner weight ratio of about 25%. However, in the development on the image carrier 10Y, the image duty is high. However, in the case of development with a low image duty, the toner consumption ratio decreases. In other words, the toner weight ratio of the developer stored in the developer container 31Y changes with development on the image carrier 10Y, and this change is constantly monitored and dispersed approximately to a toner weight ratio of about 25%. It is necessary to maintain and control the state.

  In order to control the density of the developer in the developer container 31Y, as a means for detecting the density, a transmission type photosensor for detecting the dispersion weight ratio of the toner (not shown) or torque detection for detecting the stirring torque of the developer stirring roller 34Y. Each developing unit 30Y is provided with a reflection type photosensor for detecting the means and the developer liquid level in the developer container 31Y. When the toner dispersion weight ratio decreases at a predetermined developer amount, a predetermined amount of developer dispersed at a high concentration of about 35 to 55% is added from the developer cartridge 72Y to the developer container 31Y. To do. Conversely, when the toner dispersion weight ratio increases, a predetermined amount of carrier is replenished from the carrier cartridge 71Y to the developer container 31Y. By these replenishment, the toner weight ratio is controlled to about 25%. The developer density control is performed by a controller (CPU) that manages the image signal, predicting the developer density in the developing unit 30Y according to the output image density, and replenishing from the developer cartridge 72Y and the carrier cartridge 71Y. It is also possible to predictively control the quantity. Such predictive control can improve control responsiveness and reliability.

  As described above, in the image forming apparatus according to the present embodiment, the developer dispersed from the developer cartridge 72Y to the developer container 31Y in a high concentration according to the developer concentration that changes as the image carrier is developed. Each carrier is replenished from the carrier cartridge 71Y, and 25% of the toner is uniformly dispersed in 75% of the carrier in an approximate weight ratio. In order to exhibit a preferable secondary transfer function and fixing function in a stage where an image is formed through various process steps, is secondarily transferred to a final stage sheet material, and proceeds to a fixing step (not shown) using this developer. It is desirable that the liquid developer is in a dispersion state of approximately 40% to 60% in approximate toner weight ratio. Therefore, the image carrier squeeze device (13-15) and the image carrier cleaning device having the cleaning blade as described above as so-called developer collecting means for removing and collecting excess developer and excess carrier at a plurality of positions as appropriate. (17, 18), an intermediate transfer member squeeze device (52-55), an intermediate transfer member cleaning device (42-47), and a secondary transfer roller cleaning device (62, 63). These cleaning blades are, for example, the cleaning blade 14Y of the image carrier squeeze roller 13Y, the cleaning blade 17Y of the image carrier 10Y, the cleaning blade 55Y of the intermediate transfer body squeeze device 52Y, the cleaning blade 62 of the secondary transfer roller 61, and the intermediate transfer. These are a cleaning blade 44 for the body developer compression roller 43 and a cleaning blade 46 for the intermediate transfer body 40.

  In this embodiment, for example, the developer scraped and collected by the cleaning blade 14Y in the developer collecting section 15Y for the first color and the developer scraped and collected by the cleaning blade 44 in the developer collecting section 45 and cleaned by the developer collecting section 47 are cleaned. The developer scraped and collected by the blade 46 is joined in the same flow path. Then, the developer scraped and collected by the cleaning blade 17Y in the developer collecting portion 18Y and the developer scraped and collected by the cleaning blade 55Y and the cleaning blade 14M of the next color are joined to the developer collecting portion 15M through the same flow path. In the second and subsequent colors, the collected developer is similarly merged into the same flow path. Then, the developer scraped and collected by the cleaning blade 17K in the developer collecting unit 18K for the fourth color and the developer scraped and collected by the cleaning blade 55K in the developer collecting unit 56K are merged into the same flow path. Further, the combined flow path and the developer flow path scraped and collected by the cleaning blade 62 into the developer recovery section 63 are merged with the developer recovery flow path 70 and conveyed from the pump 76 to the filter means 77.

  The developer thus scraped and collected by each cleaning blade is stored in the carrier buffer tank 74 through the filter 77 from the collection channel 70 combined with the channel to be transported, and can be reused. When the developer developed from a plurality of developing units is collected, the toner is mixed and cannot be reused as it is collected. Therefore, filter means 77 is provided in the transport path to filter the toner particles and only the carrier. Is reusable. The reuse of the carrier stored in the carrier buffer tank 74 is performed by supplying the developer from the developer cartridge 72Y to the developer container (reservoir) 31Y by distributing and transporting the carrier to the carrier cartridge 71Y through the developer transport path 78. This is performed by supplying a carrier from the cartridge 71Y.

  The filter unit 77 merges the developer channels collected through the developer collecting units with the collection channel and then filters the toner solid component and paper powder from the carrier component. An electric filter or other filter is used. The carrier that has been separated from the toner and becomes reusable is stored in the carrier buffer tank 74, and the carrier once stored in the buffer is distributed and transported to the carrier cartridges 71Y of the plurality of developing units to be reused. Carrier reuse rate is averaged to enable stable reuse. Therefore, the pump 76 for transporting the developer functions in common with the filter unit 77, and a simple and inexpensive configuration can be realized together with the transport path. Further, since the developer recovered from the cleaning device for the secondary transfer roller 61 and the intermediate transfer member 40 may contain foreign matter, paper dust, and the like, there is a method of discarding without reuse. However, the collected developer from each part can be reused by setting a filtering process as in the present embodiment and filtering foreign matter and paper dust together. Note that the color mixing toner, foreign matter, paper dust, and the like removed by the filter unit 77 are exchanged based on the detection result of the filter state detection unit (not shown) to stably maintain the filtering function. Can do.

  The carrier component may be relatively short when the toner weight ratio supplied from the developer cartridge 72Y is high, and conversely, the carrier component may be relatively excessive when the toner weight ratio supplied from the developer cartridge is low. . In the present embodiment, when the carrier component becomes insufficient, the replenishment operation can be easily performed by configuring the carrier cartridge 71Y in the carrier transport path along with the developer cartridge 72Y so as to be detachable. Further, not only when the toner weight ratio is low, but also when developing with a high image duty, the secondary transfer is performed while supplying the developer from the developer cartridge 72Y with a toner weight ratio of about 35 to 55% as the developer is consumed. During fixing, the toner weight ratio is increased to about 40% to 60%, so that the amount of recovered carrier increases, and the carrier component becomes relatively surplus. As described above, since the developer cartridge 72Y contains the developer dispersed at a high density of about 35 to 55% by weight of the toner, the more the developer is consumed by the development with a high image duty, the more the carrier component. Recovering is relatively surplus. In the present embodiment, when the carrier component becomes excessive, in this embodiment, another carrier storage tank 73 is detachably provided separately from the carrier buffer tank 74 so that the full carrier storage tank 73 can be removed together with the carrier. ing. This makes it possible to replace the full carrier storage tank with an empty carrier storage tank and store it, thereby enabling efficient and efficient reuse of the carrier and the capacity of the carrier buffer tank 74. This is useful for downsizing the apparatus.

  Alternatively, the carrier cartridge 71Y may be omitted, and the carrier may be appropriately supplied directly from the carrier buffer tank 74 to the developer container 31Y. When the carrier cartridge 71Y is configured to be detachable in the carrier transport path along with the developer cartridge 72Y, and the carrier cartridge 71Y is configured to be detachable and compatible with the carrier storage tank 73, the carrier cartridge 71Y that has become empty can be obtained. Can be used as the carrier storage tank 73 as it is, and convenience can be improved. The carrier may be able to flow in and out of the carrier cartridge 71Y and the carrier storage tank 73 in both directions. However, if the carrier has a check valve function so as to prevent the outflow, the detachment operation is possible. Also convenient.

  On the other hand, it may be supplied to the developer container 31Y after being blended in a blending bottle or the like provided separately from the developing unit as a developer blending means, but with respect to the developer concentration in the developer container 31Y that changes every moment. Therefore, in order to prevent the time lag of control, appropriate consideration is necessary. As in the present embodiment, the developer and the carrier dispersed in a high concentration based on the detection contents of the detection means for detecting the dispersion weight ratio of the toner and the detection means for detecting the developer amount in the developing unit are stored in the developer container 31Y. By adopting a configuration in which the water is replenished and stirred to uniformly disperse, stable concentration control can be achieved without a time lag of concentration control.

  As described above, in the present embodiment, the developer is scraped off and collected by the cleaning device included in the developer collecting means, and is distributed and conveyed to the developing unit 30Y for reuse. Further, each developer collecting means will be described. . The development unit 30Y includes a cleaning blade 23Y that cleans the developer compression roller 22Y that compresses the liquid developer toner carried on the development roller 20Y, and a cleaning blade 21Y that cleans the development roller 20Y. The cleaning blade 21Y is disposed on the downstream side in the rotation direction of the developing roller 20Y from the developing nip portion where the developing roller 20Y contacts the image carrier 10Y, and scrapes off the developer remaining on the developing roller 20Y. The developer in the developer compression roller 22Y is scraped off and removed by rotating in the direction of the arrow in the figure, and the developer in the reservoir 31Y is joined (joined) to be reused. Note that the merged carrier and toner are not in a mixed color state.

  The image carrier squeeze device is disposed on the downstream side in the rotational direction from the developing roller 20Y so as to face the image carrier 10Y, and presses and slides against the image carrier squeeze roller 13Y to clean the surface. The cleaning blade 14Y and the developer recovery unit 15Y have a function of recovering excess carrier and originally unnecessary fog toner from the developer developed on the image carrier 10Y and increasing the toner particle ratio in the visible image. . In this embodiment, the image carrier squeeze roller 13Y rotates with the image carrier 10Y at substantially the same peripheral speed, and an excess carrier of about 5 to 10% by weight from the developer developed on the image carrier 10Y. Both the rotational driving loads are collected to reduce the disturbance effect on the visible toner image of the image carrier 10Y. Excess carrier and unnecessary fog toner collected by the image carrier squeeze roller 13Y are collected from the image carrier squeeze roller 13Y by the action of the cleaning blade 14Y and pooled. Note that the collected surplus carrier and fog toner are collected from the dedicated isolated image carrier 10Y, so that no color mixing phenomenon occurs in the image forming portions of the respective colors.

  In the primary transfer unit 50Y, the image carrier 10Y and the intermediate transfer member 40 move at the same speed, and the developer image developed on the image carrier 10Y is transferred to the intermediate transfer member 40 by the primary transfer roller 51Y. In addition, the driving load of movement is reduced, and the disturbance effect on the visible toner image of the image carrier 10Y is suppressed. The primary transfer portion 50Y for the first color does not cause a color mixing phenomenon since it is the first primary transfer, but since the second and subsequent colors transfer different toner images onto the already transferred primary toner image portions and superimpose colors, the intermediate transfer body 40 is used. The reverse transfer development causes the toner to transfer from the toner to the image carrier 10 (M, C, K), and the reverse transfer toner and the untransferred toner are mixed and carried on the image carrier 10 (M, C, K) together with the surplus carrier. Moved from the image carrier by the action of the cleaning blade 17 (M, C, K) and pooled.

  Desirable dispersion state of the developer (toner dispersed in the carrier) in order to perform a preferable secondary transfer function and fixing function at the stage of secondary transfer to the final stage sheet material and proceeding to the fixing process not shown in the figure. Is approximately 40% to 60% in terms of the toner weight ratio as described above. The intermediate transfer member squeeze device 52Y is provided as means for further removing excess carrier from the intermediate transfer member 40 when the developer has not reached the desired dispersion state at this final stage. The intermediate transfer member squeeze device 52Y is disposed downstream of the primary transfer unit 50Y in the moving direction of the intermediate transfer member 40, and is disposed opposite to the intermediate transfer member squeeze roller 53Y and the intermediate transfer member squeeze roller 53Y across the intermediate transfer member 40. The backup roller 54Y, the intermediate transfer member squeeze roller 53Y, and a cleaning blade 55Y that cleans the surface by sliding contact with the intermediate transfer member squeeze roller 53Y and a developer recovery unit 15M, and recovers excess carrier from the developer primarily transferred to the intermediate transfer member 40. In addition, the function of increasing the toner particle ratio in the visible image and collecting originally unnecessary fog toner is provided. The developer recovery unit 15M uses a recovery mechanism for a carrier recovered by the cleaning blade 14M of the magenta image carrier squeeze roller disposed downstream in the moving direction of the intermediate transfer member 40, as a cleaning blade 55Y of the intermediate transfer member squeeze roller 53Y. It is also used for both. In this way, in the developer recovery unit 15 (M, C, K) of the image carrier squeeze device for the second and subsequent colors, the intermediate transfer member 40 is moved from the primary transfer unit 50 (Y, M, C) of the preceding color. By using it as the developer recovery part of the intermediate transfer member squeeze device 52 (Y, M, C) arranged on the downstream side in the direction, the interval between them can be regulated uniformly, and the structure is simplified and reduced in size. Can be achieved.

  The first color intermediate squeeze squeeze part is the first intermediate squeeze squeeze, so no color mixing phenomenon occurs. However, after the second color, a different toner image is transferred to the already transferred primary toner image part and overlaid. Therefore, when the toner is transferred from the intermediate transfer body 40 to the intermediate transfer body squeeze roller 53Y, the toner is mixed in color and carried and moved by the intermediate transfer body squeeze roller 53Y together with the surplus carrier. Collected from 53Y and pooled. Further, when the squeeze ability by the image carrier 10Y at the primary transfer site upstream of the intermediate transfer member squeeze process and the squeeze ability of the image carrier squeeze roller 53Y are performed with sufficient ability, not all primary transfer processes are performed. It is not necessary to provide the intermediate transfer body squeeze device 52 further downstream in the moving direction of the intermediate transfer body 40.

  The sheet material is supplied in accordance with the timing at which the toner image superimposed on the intermediate transfer body 40 reaches the secondary transfer portion, and the toner image is secondarily transferred to the sheet material and proceeds to the fixing process, and the final sheet material When the above image formation is completed, but a sheet material supply trouble such as a jam occurs, not all the toner images are transferred to the secondary transfer roll and collected. In addition, in the normal secondary transfer process, the toner image on the intermediate transfer body 40 is not 100% secondary-transferred and transferred to the sheet material, and a secondary transfer residue of several percent occurs. In particular, when a sheet material supply trouble such as a jam occurs, the toner image is transferred in contact with the secondary transfer roller 61 without the sheet material interposed, and the back surface of the sheet material is stained. A bias in a direction in which the toner particles of the liquid developer are pressed against the intermediate transfer body 40, that is, a bias having the same polarity as the charging polarity of the toner particles is applied to the developer compression roller 43 with respect to these unnecessary toner images. This bias applied when a trouble such as a jam occurs may be applied to the secondary transfer roller 61 or the intermediate transfer member squeeze roller 53Y (any one). As a result, the toner particles of the liquid developer remaining on the intermediate transfer member 40 are pressed against the intermediate transfer member 40 to be in a developer compressed state, and the carrier liquid is collected (squeezed) on the secondary transfer roller 61 side to improve efficiency. The intermediate transfer member 40 is often cleaned by the intermediate transfer member cleaning blade 46 and the secondary transfer roller 61 is cleaned by the secondary transfer roller cleaning blade 62. Thus, the cleaning blade 62 of the secondary transfer roller is provided as a means for removing the developer (toner dispersed in the carrier) transferred to the secondary transfer roller 61, and collects the developer from the secondary transfer roller 61. Pooled. The pooled developer is in a mixed color state and may contain foreign matters such as paper dust, but these are separated by the filter 77 as described above.

  FIG. 3 is a diagram for explaining another embodiment of the image forming apparatus according to the present invention. An image carrier squeeze device (on the upstream side in the rotation direction from the primary transfer portion 50Y of the first color image carrier 10Y) 13Y, 14Y, 15Y) and the developer recovered from the intermediate transfer body cleaning device (46, 47) are merged into the same flow path, and the recovery flow path 70 ', which is different from the other recovery flow paths 70, and the pump 76 'and the filter 77' are configured to be conveyed to the carrier buffer tank 74. In the intermediate transfer member cleaning device, unnecessary substances such as paper dust of the sheet material are collected together with the developer, and the fluidity is poor. Therefore, by collecting the developer collected from the image carrier squeeze device for the first color in the same flow path, the developer is made rich in the collecting conveyance path to improve the fluidity and facilitate the collection. is doing. The intermediate transfer body cleaning device is disposed at a position downstream of the secondary transfer unit 60 of the intermediate transfer body 40 in the movement direction and downstream of the first color primary transfer portion 50Y in the movement direction. Further, as the charging roller 11Y and the developer compression roller 22Y shown in FIG. 2, a corona discharger is used instead of the roller, and the image carrier 10Y is uniformly charged by corona discharge by the corona discharger, thereby developing toner. The particles are pressed against the developing roller 20Y to be in a developer compressed state. Further, in the intermediate transfer body cleaning device, the developer compression roller 43, the cleaning blade 44, and the developer recovery unit 45 shown in FIG. 1 can be omitted, and the configuration thereof is shown.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, in the above-described embodiment, an endless elastic belt member is used as an intermediate transfer member, and a tandem color image forming apparatus in which a plurality of image forming units corresponding to each development color are arranged in parallel on the intermediate transfer member has been described. Supports a plurality of image forming portions corresponding to each development color on a cylindrical rotating support, and sequentially rotates each image forming portion to the transfer position of the intermediate transfer member by rotating the rotating support. The present invention may be applied to a rotary type color image forming apparatus that transfers images in a superimposed manner, and an intermediate transfer drum may be used. In this case, the intermediate transfer member cleaning blade provided on the intermediate transfer member is a full-color toner image that is further transferred from the intermediate transfer member to the recording medium during the primary transfer process of transferring the toner image from the image forming unit to the intermediate transfer member. The single-color toner image is separated from the intermediate transfer member until it passes, and then after the so-called printing operation is finished, the intermediate transfer member is brought into edge contact and pressure-sliding contact.

1 is a diagram illustrating main components constituting an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating main components of an image forming unit, a developing unit, and an intermediate transfer body squeeze device. It is a figure explaining other embodiment of the image forming apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image carrier, 11 ... Charge roller, 12 ... Exposure unit, 13 ... Image carrier squeeze roller, 14, 17, 21, 23, 44, 46, 55, 62 ... Cleaning blade, 15, 18, 45, 47 , 63 ... developer recovery unit, 16 ... latent image eraser, 20 ... developing roller, 22 ... developer compression roller, 30 ... developing unit, 31 ... developer container, 32 ... developer supply roller, 33 ... regulating blade, 21 34 ... Stirring roller, 40 ... Intermediate transfer member, 41, 42 ... Belt drive roller, 43 ... Developer compression roller, 50 ... Primary transfer part, 51 ... Primary transfer backup roller, 52 ... Intermediate transfer member squeeze device, 53 ... Intermediate transfer body squeeze roller, 54 ... backup roller, 60 ... secondary transfer unit, 61 ... secondary transfer roller, 70 ... developer recovery flow path, 71 ... carrier Cartridges, 72 ... developer cartridge, 73 ... carrier storage tank, 74 ... carrier buffer tank, 75 and 76 ... pumps, 77 ... Filter, 78 ... developer conveying path

Claims (5)

A plurality of image carriers, a plurality of developing devices for developing the electrostatic latent images formed on the plurality of image carriers using liquid developers of different colors using a non-volatile solvent as a carrier; An intermediate transfer member that sequentially transfers the developed developer images in a primary transfer portion corresponding to each of the image carriers, and carries and superimposes and conveys the developer image. In an image forming apparatus provided with an output device that transfers and outputs to a sheet material on a conveyance path in a transfer unit, and arranges developer collecting means at a plurality of positions to collect surplus developer and perform image formation. As the developer recovery means, an image carrier squeeze device disposed upstream of the primary transfer portion of each of the image carriers and a downstream of the primary transfer portion of the intermediate transfer member in the moving direction. Placed An intermediate transfer body squeeze device, the intermediate transfer body squeeze device excluding the intermediate transfer body squeeze device disposed on the most downstream side in the moving direction of the intermediate transfer body, and the intermediate transfer body squeeze device from the intermediate transfer body squeeze device; An image forming apparatus, wherein the developer is collected in the same developer collecting unit from the image carrier squeeze device disposed downstream in the moving direction. The developer collecting means includes an image carrier cleaning device disposed downstream in the movement direction from the primary transfer portion of the image carrier, and further upstream in the movement direction of the intermediate transfer member than the intermediate transfer member squeeze device. 2. The developer collected in the developer collecting section of the arranged image carrier cleaning device and the developer collected in the same developer collecting section are merged in the same flow path. The image forming apparatus described. A developer for the intermediate transfer body cleaning device, comprising the intermediate transfer body cleaning device disposed downstream of the secondary transfer portion of the intermediate transfer body in the movement direction and upstream of the primary transfer portion of the first color; 2. The image forming apparatus according to claim 1, wherein the developer collected in the collecting unit is joined to the same flow path as the developer collected in the developer collecting unit of the first color image carrier squeeze device. . The output device includes a transfer roller that transfers the developer image onto a sheet material and a cleaning blade that contacts the roller, and the developer collected by the cleaning blade is joined to the same flow path. The image forming apparatus according to claim 2 or 3. The developer merged in the same flow path is conveyed to a carrier buffer tank through filter means, separated and stored by the filter means, and the stored carrier is transferred from the carrier buffer tank to the plurality of developing devices. The image forming apparatus according to claim 4, further comprising a developer conveying unit that distributes and conveys the developer.

Images