JP2007171344A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for flexibly supplying a carrier to a developer container in order to perform stable image formation by maintaining a specific state of a developer in the developer container. <P>SOLUTION: An excessive developer and an excessive carrier are collected from a developer collection means such as image carrier squeezing devices (13-15), image carrier cleaning devices (17, 18), intermediate transfer body squeezing devices (52-55), intermediate transfer body cleaning devices (42-47), and further secondary transfer roller cleaning devices (62, 63) to a carrier buffer tank 74. The carrier is distributed and conveyed to each color developer container 31 from the carrier buffer tank 74 in order to control the toner weight ratio of the developer in a developer container constant. <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, supports, and transports the developed toner images at a primary transfer portion corresponding to each of a plurality of image carriers, and a secondary toner image that is superimposed from the intermediate transfer body. The present invention relates to an image forming apparatus including an output device that transfers an image to a sheet material on a conveyance path by a transfer unit and outputs an image.

  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 unit, the developer is selectively disposed opposite to the photosensitive drum, the excess developer developed on the photosensitive drum by the squeeze device is squeezed, and the excess developer collected in the squeeze device is circulated. There is a system for recirculating and transporting to a corresponding developing device (see, for example, Patent Document 3).
JP 2002-296918 A JP 2002-189354 A JP 2003-107913 A

  In the above conventional developer recycling system, the excess developer developed on the photosensitive drum by the squeeze device is squeezed, and the excess developer collected in the squeeze device is circulated and conveyed to the corresponding developing device by the circulation device. It is only a system.

  By the way, in such a system, when the toner density of the developed image formed by the image forming apparatus is high, the toner density in the developing device decreases, and conversely, when the toner density of the developed image formed is low. According to the type of image formed by the image forming apparatus, the toner concentration changes every time a plurality of developing devices. Therefore, originally, for example, a detection unit that detects the toner dispersion weight ratio is provided for each developing device, and the developer is developed from the developer cartridge and the carrier cartridge based on the detection result by such a detection unit. In addition, it is necessary to replenish a predetermined amount of the carrier and control the toner weight ratio in the developing device to be substantially constant. When the toner weight ratio is controlled to be constant, there are cases where the amount of carrier is insufficient and excessive cases occur. Therefore, a developer that can flexibly cope with excess and shortage of carriers in both cases. Recycling system is required.

  However, the above-described conventional developer recycling system is a system in which excess developer is squeezed and the collected developer is circulated and conveyed to the developing device, and the above is not considered at all. .

  Accordingly, the present invention provides a configuration in which a carrier is flexibly supplied to a developer container in order to maintain the state of the developer in the developer container and perform stable image formation.

  To this end, the present invention according to claim 1 includes a plurality of image carriers and liquid developers of different colors using a non-volatile solvent as a carrier for the electrostatic latent images formed on the plurality of image carriers. A plurality of developing devices that use and develop, an intermediate transfer member that sequentially transfers, superimposes, carries, and transports the developed developer image in a primary transfer unit corresponding to each of the plurality of image carriers; And an output device that transfers the developer image superimposed from the intermediate transfer member onto a sheet material on the conveyance path at the secondary transfer unit and outputs it, and collects the excess developer by arranging developer recovery means at a plurality of positions. In the image forming apparatus configured to perform image formation, the developer collecting means includes an image carrier squeeze device, an image carrier cleaning device, an intermediate transfer member squeeze device, an intermediate transfer member cleaning device, and a secondary transfer roller cleaner. Each of the developing devices, the collected developer collected from the developer collecting means is joined to the same flow path and collected in a buffer tank, and carriers from the buffer tank to a plurality of developer containers are collected. And is distributed and conveyed.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the collected developer joined to the same flow path passes through the filter means and is collected in the buffer tank. And

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, a single pump is provided for sucking the collected developer from each developer collecting means. Features.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the buffer tank is provided with a toner density sensor.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, when the buffer tank detects a density higher than a predetermined density by the toner density sensor, the use of the carrier from the buffer tank is stopped. It is characterized by having a mode to perform.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fourth aspect, when the buffer tank detects a density higher than a predetermined density by the toner density sensor, the user can replace the buffer tank. An exchange mode for prompting is provided.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the fourth aspect, when the toner density sensor detects a density higher than a predetermined density by the toner density sensor, the filter means of the filter means is notified to the user. It is characterized by having a filter replacement mode for prompting replacement.

  According to the present invention, after collecting the developer from the image carrier squeeze device, the image carrier cleaning device, the intermediate transfer member squeeze device, the intermediate transfer member cleaning device, and the secondary transfer roller cleaning device to the buffer tank, Since the carrier is distributed and conveyed from the buffer tank to a plurality of developer containers, the carrier can be flexibly supplied to the developer containers, so that the toner weight ratio of the developer containers is controlled to be constant. Therefore, stable image formation can be performed.

  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 to the developer container 31Y from the carrier storage tank 73 and the carrier buffer tank 74 and stirred by the liquid developer stirring roller 34Y to make it uniformly dispersed. In the toner, 25% of the toner is dispersed.

  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 portions 50Y, 50M, 50C, and 50K are arranged so 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 storage tank 73 and the carrier buffer tank 74 to the developer container 31Y. By these replenishment, the toner weight ratio is controlled to about 25%.

  Adjustment for replenishing a predetermined amount of carrier from the carrier storage tank 73 and the carrier buffer tank 74 to the developer container 31Y is performed by controlling the operation of the pump 75Y, and from the developer cartridge 72Y to a high density of about 35 to 55% by weight. Adjustment for replenishing a predetermined amount of developer dispersed in the developer container 31Y is performed by controlling the operation of the pump 79Y.

  In addition, the developer density control is performed by a controller (CPU) that manages image signals, predicting the consumption amount of the developer by counting the number of dots of the output image, and developing in the developing unit 30Y accordingly. It is also possible to predict and control the replenishment amount from the developer cartridge 72Y, the carrier storage tank 73, and the carrier buffer tank 74 by predicting the agent concentration. 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. Carriers are replenished from the carrier storage tank 73 and the carrier buffer tank 74, respectively, and 25% of the toner is uniformly dispersed in 75% of the carrier by the 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 member 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 and the developer collecting section 47 are collected. The developer scraped and collected by the cleaning 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 carrier filtered by the filter unit 77 is temporarily stored in the carrier buffer tank 74, distributed and transported to the plurality of developer containers 31Y, and the carrier reuse rate in the plurality of developer containers 31Y is averaged to stably reuse the carrier. Is possible. Further, as described above, the developer is sucked and joined by the single pump 76 from each developer collection section to the carrier buffer tank 74 through the filter means, so that a feeding means such as a pump is provided for each developing unit. There is no need.

  The developer 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 conveyed, 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 carrier stored in the carrier buffer tank 74 is reused by being distributed and conveyed to the developer container 31Y through the developer conveying path 78. As described above, the toner weight ratio in the developer container 31Y is about 25%. Therefore, the amount of carrier supplied to the developer container (reservoir) 31Y is adjusted by controlling the operation of the pump 75Y.

  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. A carrier in which toner or the like is separated and reusable is stored in the carrier buffer tank 74, and the carrier once stored in the buffer is distributed and transported to the developer containers (reservoirs) 31Y of a plurality of developing units for reuse. By doing so, the carrier reuse rate is averaged and stable reuse is possible. 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 buffer tank 74 is provided with a toner density sensor (not shown). When the toner density sensor detects a density equal to or higher than a predetermined density, the carrier buffer tank 74 has a mode for canceling carrier reuse from the carrier buffer tank 74. It can also be left. Such modes include a prohibit mode that prohibits the reuse of carriers from the carrier buffer tank 74, an exchange mode that prompts the user to replace the carrier buffer tank 74, or a density that exceeds a predetermined density is detected by a toner density sensor. Since it is considered that the reason is that the state of the filter is deteriorated, various modes such as a filter replacement mode that prompts the user to replace the filter can be set.

  In the present 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, or the necessary amount of carrier is recovered. When larger than the amount, a new carrier can be replenished with the carrier storage tank 73. In this way, when the carrier is depleted in the image forming apparatus, it can be quickly supplied from the carrier storage tank 73, or the full carrier storage tank 73 can be replaced with an empty carrier storage tank and stored. Therefore, it is possible to efficiently reuse the carrier without waste, and it is not necessary to set the capacity of the carrier buffer tank 74 to be extremely large, which is useful for downsizing the apparatus. The carrier storage tank 73 is configured such that a carrier can be supplied to the developer transport path 78 and a carrier can be collected from the developer transport path 78 by a mechanism (not shown).

  The carrier stored in the carrier storage tank 73 is also distributed and conveyed to the developer container (reservoir) 31Y through the developer conveyance path 78. Similar to the carrier stored in the carrier buffer tank 74, the carrier stored in the carrier storage tank 73 is also used to control the toner weight ratio in the developer container (reservoir) 31Y to about 25%.

  In addition, by preferentially using the carrier stored in one of the carrier storage tank 73 and the carrier buffer tank 74, the management of the carrier can be facilitated. For example, the carrier stored in the carrier buffer tank 74 is preferentially used, so that the recovered carrier can be preferentially used and the carrier stored in the new carrier storage tank 73 can be preserved. .

  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, in the present embodiment, a new carrier storage tank 73 is detachably configured in the carrier transport path along with the developer cartridge 72Y so that the replenishment operation can be easily performed. Further, not only when the toner weight ratio is low but also when developing with a high image duty, along with the consumption of the developer, secondary transfer is performed while replenishing the developer with a toner weight ratio of about 35 to 55% from the developer cartridge 72Y. 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, the carrier storage tank 73 different from the carrier buffer tank 74 is detachably provided so that the full carrier storage tank 73 can be removed together with the carrier. . 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.

  Next, an embodiment in which the carrier cartridge 71 is provided in front of the developing container 31 will be described with reference to FIG. FIG. 3 is a diagram showing the main components constituting the image forming apparatus according to the embodiment of the present invention having a carrier cartridge. In this embodiment, as shown in FIG. 3, a carrier cartridge 71Y is provided in front of the developer container 31Y via a pump 75Y, and a carrier storage tank is provided in the carrier cartridge 71Y via a developer conveyance path 78. 73 and the carrier buffer tank 74 are configured to receive the carrier. In this embodiment, the usage forms of the various developer recovery devices, the pump 76, the filter 77, the carrier storage tank 73, the carrier buffer tank 74, and the like are the same as those described above.

  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 stirring roller 34Y to obtain a uniform dispersion state, and 25% of the toner is dispersed in 75% of the carrier by the approximate weight ratio. Let 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.

  Adjustment for replenishing a predetermined amount of carrier from the carrier cartridge 71Y to the developer container 31Y is performed by controlling the operation of the pump 75Y, and the developer dispersed from the developer cartridge 72Y at a high concentration of about 35 to 55% by weight of the toner. Adjustment for replenishing the developer container 31Y by a predetermined amount is performed by controlling the operation of the pump 79Y.

  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%. In addition, the developer density control is performed by a controller (CPU) that manages image signals, predicting the consumption amount of the developer by counting the number of dots of the output image, and developing in the developing unit 30Y accordingly. It is also possible to predict and control the replenishment amount from the developer cartridge 72Y and the carrier cartridge 71Y by predicting the agent concentration. Such predictive control can improve control responsiveness and reliability.

  The carriers stored in the carrier storage tank 73 and the carrier buffer tank 74 are distributed and conveyed to the carrier cartridge 71Y through the developer conveyance path 78, whereby the developer from the developer cartridge 72Y is transferred to the developer container (reservoir) 31Y. Is performed by replenishing the carrier from the carrier cartridge 71Y.

  When the carrier cartridge 71Y is used, 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 empty carrier cartridge 71Y can be used as it is as the carrier storage tank 73, and convenience can be enhanced. 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.

  As a developer blending means, it may be blended in a blending bottle provided separately from the developing unit and then supplied to the developer container 31Y, but the developer concentration in the developer container 31Y that changes every moment is controlled. In order to prevent the time lag from occurring, 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 member 40 side, 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 body 40 are pressed against the intermediate transfer body 40 to be in a developer compressed state, and the carrier liquid is collected (squeezed) on the secondary transfer roller 61 side, thereby improving 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. As described above, the cleaning blade 62 of the secondary transfer roller is provided as 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 is separated by the filter 77 as described above.

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. FIG. 2 is a diagram illustrating main components constituting an image forming apparatus according to an embodiment of the present invention including a carrier cartridge.

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, 75,76,79 ... pumps, 77 ... Filter, 78 ... developer conveying path

Claims (7)

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 body that sequentially transfers, develops, carries, and transports the developed developer images at primary transfer portions corresponding to the image transfer bodies, and two developer images superimposed from the intermediate transfer body. In an image forming apparatus comprising: an output device that transfers to a sheet material on a conveyance path at the next transfer unit and outputs the image; and a developer collecting means is disposed at a plurality of positions to collect surplus developer and perform image formation The developer recovery means includes an image carrier squeeze device, an image carrier cleaning device, an intermediate transfer member squeeze device, an intermediate transfer member cleaning device, and a secondary transfer roller cleaning device. An image forming apparatus characterized in that the collected developer collected from the developer collecting means is merged into the same flow path and collected in a buffer tank, and the carrier is distributed and conveyed from the buffer tank to a plurality of developer containers. . The image forming apparatus according to claim 1, wherein the collected developer combined in the same flow path is collected in the buffer tank through the filter unit. 3. The image forming apparatus according to claim 1, wherein a single pump is provided for sucking the collected developer from each developer collecting means. 4. The image forming apparatus according to claim 1, wherein the buffer tank is provided with a toner concentration sensor. 5. The image forming apparatus according to claim 4, further comprising: a mode in which carrier use is stopped from the buffer tank when the toner density sensor detects a density higher than a predetermined density in the buffer tank. 5. The image forming apparatus according to claim 4, further comprising an exchange mode that prompts a user to replace the buffer tank when the toner density sensor detects the density of the buffer tank at a predetermined density or higher. 5. The image forming apparatus according to claim 4, further comprising a filter replacement mode that prompts a user to replace a filter of the filter means when the toner density sensor detects a density higher than a predetermined density in the buffer tank. apparatus.

Images