JP2005091672A - Image forming apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress fluctuation of a toner concentration of a developing solution in a container.
Squeegee rollers 51 to 53 are disposed between a primary transfer position 44 and a secondary transfer position 45 on an intermediate transfer roller 41 so as to come into contact with a developer on the intermediate transfer roller 41. It is disposed so as to be able to reciprocate between a position and a separated position that does not contact the developer. The squeegee rollers 51 to 53 rotate at a circumferential speed substantially equal to that of the intermediate transfer roller 41 in the direction to follow the intermediate transfer roller 41 when the roller drive motor is rotationally driven by the motor drive unit at the contact position. The squeegee rollers 51 to 53 peel off the liquid carrier from the intermediate transfer roller 41 by being arranged at the contact position. The peeled liquid carrier is removed by the cleaning blade 54, naturally falls, collected by the receiving tray 55, and returned to the tank 33 via the pipe 56.
[Selection] Figure 1

Description

  The present invention relates to an electrophotographic image forming technique such as a printer, a copying machine, and a facsimile machine, and more particularly to an image forming technique that employs wet development as a developing method.

  Conventionally, a charged photosensitive member (latent image carrier) is exposed by an exposure unit to form an electrostatic latent image on the photosensitive member, and toner is attached to the photosensitive member by a developing unit to reveal the electrostatic latent image. 2. Description of the Related Art An electrophotographic image forming apparatus in which a toner image is formed by forming an image and the toner image is transferred onto a transfer sheet to obtain a predetermined image has been put into practical use. Here, as a developing method of the developing means, a wet developing method using a developer in which toner is dispersed in a liquid carrier is known. This wet development system has the advantages that the average particle diameter of the toner is as small as 0.1 to 2 μm, so that a high-resolution image can be obtained, and a uniform image can be obtained because of the high fluidity of the liquid. Therefore, various image forming apparatuses have been proposed (see, for example, Patent Document 1). This apparatus improves image quality by removing excess developer, particularly a liquid carrier, from the intermediate transfer medium before transferring a developed developed image (toner image) to a transfer material. .

JP 2002-296918 A (paragraph [0027], FIG. 1)

  By the way, for example, when images having a high image occupancy ratio, which is the ratio of the image portion in the electrostatic latent image, are continuously formed, a large amount of toner adheres to the photoconductor, so that the developer moves from the container storing the developer to the photoconductor. There are few liquid carriers. Conversely, when images with low image occupancy are continuously formed, only a small amount of toner adheres to the photoconductor, so that the liquid carrier that moves from the container to the photoconductor increases compared to when the image occupancy is high. . As described above, since the amount of the liquid carrier contained in the developing solution moving from the container onto the photoconductor greatly varies depending on the image occupancy rate, the toner concentration of the developing solution remaining in the container also varies accordingly. It becomes.

  However, the conventional apparatus described in Patent Document 1 merely includes a configuration for removing the liquid carrier from the intermediate transfer medium according to the type of transfer material, and the amount of liquid carrier on the intermediate transfer medium. Therefore, by adjusting the removal amount according to the above and returning the removed liquid carrier to the container, the toner concentration of the developer in the container is not suppressed from fluctuating.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus and a method thereof that can suppress fluctuations in the toner concentration of the developer in the container.

  In order to achieve the above object, the present invention has a container for storing a developer in which a toner is dispersed in a liquid carrier, and the electrostatic latent image on the latent image carrier using the developer stored in the container. In the image forming apparatus for developing the toner image to form a toner image and further transferring the toner image onto the transfer medium, the image forming apparatus further comprises a recovery means for recovering the liquid carrier from the developer adhering to the transfer medium and returning it to the container. The return amount of the liquid carrier to be returned to the container by the recovery means can be adjusted.

  In order to achieve the above object, the present invention includes a developing step of developing a latent electrostatic image on a latent image carrier using a developer in which toner is dispersed in a liquid carrier to form a toner image; A transfer step of transferring a toner image on the latent image carrier onto a transfer medium, and a recovery step of recovering the liquid carrier from the developer adhering to the transfer medium and returning it to a container for storing the developer, The return amount of the liquid carrier to be returned to the container in the recovery step is adjusted.

  According to these configurations, the liquid carrier contained in the developer that adheres to the transfer medium is collected and returned to the container that stores the developer. At this time, by adjusting the return amount of the liquid carrier returned to the container, for example, the return amount is increased when the toner concentration of the developer in the container is increased, and the return amount is decreased when the toner concentration is decreased. By doing so, it becomes possible to suppress fluctuations in the toner concentration of the developer in the container. In addition, it is not restricted to returning all the collect | recovered liquid carriers to a container, You may make it return only a part of collection | recovery amount to a container. As described above, since the return amount of the liquid carrier to be returned to the container is adjusted, fluctuations in the toner concentration of the developer in the container can be suppressed. As a result, the developer in the tank can be used without waste until the end, and the amount of liquid carrier and toner supplied from the outside can be minimized.

  By the way, the recovery means is configured so that the recovery amount of the liquid carrier can be adjusted, and adopting a configuration that returns all the liquid carriers recovered by the adjusted recovery amount to the container, only a part of the recovery amount is obtained. Compared to the configuration of returning to the container, the configuration of returning to the container can be simplified, and the return amount can be easily adjusted only by adjusting the recovery amount.

  Further, the recovery means is configured to be disposed at a contact position that contacts the developer on the transfer medium, and a stripping member that strips the liquid carrier on the surface layer of the developer by being disposed at the contact position. And the collection amount may be adjusted by controlling the amount of the liquid carrier peeled off by the stripping member. According to this configuration, when the peeling member is disposed at the contact position and contacts the developer on the transfer medium, the liquid carrier on the surface layer of the developer adheres to the peeling member, and a part of the liquid carrier peels off. However, the amount of stripping is controlled, and the recovered amount is adjusted. Thereby, the recovery amount of the liquid carrier can be easily adjusted.

  In addition, the recovery means includes, as the stripping member, a plurality of stripping members that are arranged in parallel with each other in the transport direction of the developer by the transfer medium and are opposed to the transfer medium, and among the plurality of stripping members At least one is configured to be movable between the contact position and a separation position that does not contact the developer on the transfer medium, and the transfer medium is controlled by the position control of the stripping member configured to be movable. The amount of stripping may be controlled by controlling the combination of stripping members in contact with the developer. According to this configuration, at least one of the plurality of stripping members is configured to be movable between the contact position and the separation position, and the position of the stripping member configured to be movable is controlled on the transfer medium. Since the combination of the stripping members that come into contact with the developer is controlled, it is easy and reliable to control the stripping amount of the liquid carrier by controlling the combination, for example, by increasing or decreasing the number of stripping members arranged at the contact position. Can be done.

  Further, the recovery means is a peeling member configured to be arranged as a peeling member at a plurality of contact positions that are in contact with the developer on the transfer medium and that are different in distance from the transfer medium. The stripping amount may be controlled by changing the contact position of the stripping member. According to this configuration, the amount of the liquid carrier attached to the stripping member can be controlled by changing the contact position of the stripping member to a position where the distance from the transfer medium is long or short, and thereby the liquid carrier can be controlled. Can be easily and reliably controlled.

  Further, when the amount of peeling is controlled by changing the relative speed of the contact surface of the peeling member with respect to the developer conveyed by the transfer medium, the relative speed is changed to a large value or a small value. The amount of liquid carrier adhering to the stripping member can be controlled, whereby the amount of stripping of the liquid carrier can be controlled easily and reliably.

  The recovery means further includes a cleaning member for removing the liquid carrier peeled off by the peeling member from the peeling member, and the liquid carrier removed by the cleaning member is returned to the container. Also good. According to this configuration, the liquid carrier can be effectively used by removing the liquid carrier peeled off by the peeling member from the peeling member and returning it to the container.

  The recovery means is provided below the contact position of the cleaning member to the stripping member, and recovers the liquid carrier that is removed by the cleaning member and freely falls, and the recovery unit And a communication part that communicates with the container, and the liquid carrier recovered by the recovery part via the communication part may be returned to the container. According to this configuration, since the liquid carrier removed from the stripping member by the cleaning member falls freely and is collected in the collection unit and returned to the container for storing the developer, the liquid carrier is separately removed from the stripping member. It is not necessary to provide a recovery device in the recovery unit, and the device configuration can be simplified.

  In addition, the collection unit may adjust the collection amount according to image information related to the toner image. As a result, the recovery amount of the liquid carrier is adjusted in accordance with the image information related to the toner image, and the toner concentration of the developer in the container can be suppressed from being returned to the container. When the image information is obtained as an image occupancy ratio that is a ratio of an image portion in the electrostatic latent image, and the collection amount is adjusted according to the image occupancy ratio, the image occupancy ratio is determined by the latent image carrier. Since the value corresponds to the toner concentration in the developer above, it is possible to easily adjust the collection amount according to the toner concentration without detecting the toner concentration. As a result, fluctuations in the toner concentration of the developer in the container can be reliably suppressed.

  Further, the recovery amount may be adjusted so that the toner concentration of the developer remaining on the transfer medium after the recovery of the liquid carrier by the recovery means approaches the initial value of the toner concentration of the developer stored in the container. . According to this configuration, the recovery amount is adjusted so that the toner concentration of the developer remaining on the transfer medium after the recovery of the liquid carrier by the recovery means approaches the initial value of the toner concentration of the developer stored in the container. , All of the recovered liquid carrier is returned to the container. For example, when the toner concentration of the developer on the transfer medium is high, that is, when the amount of liquid carrier carried out from the container is small, the amount of liquid carrier returned to the container is reduced or zero. On the other hand, when the toner concentration is low, that is, when there are many liquid carriers carried out of the container, the amount of liquid carrier returned to the container increases. Accordingly, the toner concentration of the developer stored in the container can be maintained at a value close to the initial value, and the replenishment of the toner or the liquid carrier to the container can be minimized.

  Further, the apparatus further comprises density detecting means for detecting the toner concentration of the developer stored in the container, and the toner concentration detected by the density detecting means approaches the initial value of the toner concentration of the developer stored in the container. The return amount may be adjusted as described above. According to this configuration, the toner concentration of the developer stored in the container is detected, and the container of the liquid carrier is set so that the detected toner concentration approaches the initial value of the toner concentration of the developer stored in the container. The return amount to is adjusted. That is, when the toner concentration of the developer in the container is higher than the initial value, the amount of liquid carrier returned to the container is increased, and when the toner concentration is low, the amount of liquid carrier returned to the container is reduced or zero. The Accordingly, the toner concentration of the developer stored in the container can be maintained at a value close to the initial value, and the replenishment of the toner or the liquid carrier to the container can be minimized.

  FIG. 1 is a diagram showing an internal configuration of a printer as an embodiment of an image forming apparatus according to the present invention, FIG. 2 is an enlarged view of a main part of FIG. 1, and FIG. 3 is a block diagram showing an electrical configuration of the printer. . This printer is a wet development type image forming apparatus that forms a single color image using a developer containing black (K) toner, and a print command signal including an image signal is sent from an external device such as a host computer to the main control unit. 100, the engine control unit 110 controls each part of the engine unit 1 in accordance with a control signal from the main control unit 100, and conveys it from the paper feed cassette 3 disposed in the lower part of the apparatus main body 2. An image corresponding to the image signal is printed out on transfer paper, copy paper, and paper (hereinafter referred to as “transfer paper”) 4.

  The engine unit 1 includes a photoreceptor unit 10, an exposure unit 20, a development unit 30, a transfer unit 40, and the like. Among these units, the photoreceptor unit 10 includes a photoreceptor 11, a charging unit 12, a charge removal unit 13, and a cleaning unit 14. The developing unit 30 includes a developing roller 31 and the like. Further, the transfer unit 40 includes an intermediate transfer roller 41 and the like.

  In the photoconductor unit 10, the photoconductor 11 is provided so as to be rotatable in an arrow direction 15 in FIG. 1 (clockwise direction in the drawing). A charging unit 12, a developing roller 31, an intermediate transfer roller 41, a charge eliminating unit 13, and a cleaning unit 14 are disposed around the photoconductor 11 along the rotation direction 15. Further, a surface area between the charging unit 12 and the developing roller 31 is an irradiation area of the light beam 21 from the exposure unit 20. In this embodiment, the charging unit 12 includes a charging roller, and a charging bias is applied from the charging bias generation unit 111 to uniformly charge the outer peripheral surface of the photoconductor 11 to a predetermined surface potential Vd (for example, Vd = DC + 600 V). It has a function as a charging means.

  A light beam 21 formed by, for example, a laser is irradiated from the exposure unit 20 toward the outer peripheral surface of the photoconductor 11 uniformly charged by the charging unit 12. The exposure unit 20 exposes the photosensitive member 11 with a light beam 21 in accordance with a control command given from the exposure control unit 112, and forms an electrostatic latent image corresponding to an image signal on the photosensitive member 11. It has a function as an exposure means. For example, when a print command signal including an image signal is given from an external device such as a host computer to the CPU 101 of the main control unit 100 via the interface 102, the CPU 113 controls the exposure control unit in response to a command from the CPU 101 of the main control unit 100. A control signal corresponding to the image signal is output to 112 at a predetermined timing. Then, in response to a control command from the exposure control unit 112, the light beam 21 is irradiated from the exposure unit 20 to the photoconductor 11, and an electrostatic latent image corresponding to the image signal is formed on the photoconductor 11. Thus, in this embodiment, the photoconductor 11 corresponds to the “latent image carrier” of the present invention.

  The electrostatic latent image formed in this way is visualized by the toner supplied from the developing roller 31 of the developing unit 30 (developing process). The developing unit 30 includes, in addition to the developing roller 31, a tank 33 that stores the developing solution 32, a coating roller 34 that pumps the developing solution 32 stored in the tank 33 and applies it to the developing roller 31, and the developing solution on the coating roller 34. A regulation blade 35 that uniformly regulates the thickness of the layer, a cleaning blade 36 that removes the developer remaining on the developing roller 31 after supplying the toner to the photoconductor 11, and a memory 37 (FIG. 3) described later are provided. The developing roller 31 rotates at a circumferential speed substantially equal to that of the photoconductor 11 in the direction of following the photoconductor 11 (counterclockwise in FIG. 1). The application roller 34 rotates in the same direction as the developing roller 31 (counterclockwise in the figure) at a peripheral speed of about twice.

  In the present embodiment, the developer 32 is a toner composed of a color pigment, an adhesive such as an epoxy resin that adheres the color pigment, a charge control agent that gives a predetermined charge to the toner, a dispersant that uniformly disperses the color pigment, and the like. Is dispersed in a liquid carrier. In this embodiment, for example, silicone oil such as polydimethylsiloxane oil is used as the liquid carrier, the toner concentration is 5 to 40% by weight, and the low-concentration developer (toner concentration is 1 to 2) often used in the wet development system. The concentration is higher than (% by weight). The type of the liquid carrier is not limited to silicone oil, and the viscosity of the developer 32 is determined by the liquid carrier to be used, each material constituting the toner, the toner concentration, etc. In this embodiment, For example, the viscosity is 50 to 6000 mPa · s.

  In this embodiment, the interval between the photosensitive member 11 and the developing roller 31 (developing gap = thickness of the developing solution layer) is set to 5 to 40 μm, for example, and the developing nip distance (the developing solution layer is the photosensitive member 11 and the developing roller 31). In this embodiment, the distance in the circumferential direction in contact with both is set to 5 mm, for example. In the case of the low-concentration developer described above, a development gap of 100 to 200 μm is required to increase the amount of toner, and in this embodiment using a high-concentration developer, the development gap can be shortened. Accordingly, the moving distance of the toner moving in the developer by electrophoresis is shortened, and a higher electric field is generated even when the same developing bias is applied, so that the developing efficiency can be improved and the developing can be performed at a high speed. It will be possible.

  In the developing unit 30 having such a configuration, the developer 32 stored in the tank 33 is pumped up by the application roller 34, and the thickness of the developer layer on the application roller 34 is uniformly regulated by the regulation blade 35. The developing solution 32 adheres to the surface of the developing roller 31 and is conveyed to the developing position 16 facing the photosensitive member 11 as the developing roller 31 rotates. For example, the toner in the developer is positively charged by the action of a charge control agent or the like.

  Then, a developing solution carried on the developing roller 31 at the developing position 16 is supplied from the developing roller 31 and adheres to the photosensitive member 11, and a developing bias Vb (for example, Vb) applied to the developing roller 31 from the developing bias generator 114. = DC + 400V), the toner moves in the developing solution from the developing roller 31 to the photoconductor 11, and the electrostatic latent image is visualized. Further, the developer remaining on the developing roller 31 without adhering to the photoconductor 11 is scraped off by the cleaning blade 36 and returns to the tank 33 by its own weight. Thus, in this embodiment, the tank 33 corresponds to the “container” of the present invention.

  The toner image formed on the photoconductor 11 as described above is conveyed to a primary transfer position 44 facing the intermediate transfer roller 41 as the photoconductor 11 rotates. The intermediate transfer roller 41 rotates at a circumferential speed substantially equal to that of the photoconductor 11 in the direction of following the photoconductor 11 (counterclockwise in FIG. 1), and the primary transfer bias (for example, DC− 400V), the toner image on the photoconductor 11 is primarily transferred to the intermediate transfer roller 41 (transfer process). Residual charges on the photoconductor 11 after the primary transfer are removed by a charge removal unit 13 made of an LED or the like, and a residual developer is removed by a cleaning unit 14. Thus, in this embodiment, the intermediate transfer roller 41 corresponds to the “transfer medium” of the present invention.

  A secondary transfer roller 42 is disposed opposite to an appropriate position of the intermediate transfer roller 41 (vertically below the intermediate transfer roller 41 in FIG. 1), and the primary transfer toner image primarily transferred to the intermediate transfer roller 41 is the intermediate transfer roller. As the roller 41 rotates, the toner is conveyed to a secondary transfer position 45 facing the secondary transfer roller 42. Further, squeegee rollers 51, 52, and 53, which will be described later, are disposed between the primary transfer position 44 and the secondary transfer position 45. On the other hand, the transfer paper 4 accommodated in the paper feed cassette 3 is conveyed to the secondary transfer position 45 by a conveyance drive unit (not shown) in synchronization with the conveyance of the primary transfer toner image. The secondary transfer roller 42 rotates at a peripheral speed equal to that of the intermediate transfer roller 41 in a direction (clockwise in FIG. 1) following the intermediate transfer roller 41, and the secondary transfer bias ( For example, when −100 μA) is applied under constant current control, the toner image on the intermediate transfer roller 41 is secondarily transferred to the transfer paper 4. The residual developer on the intermediate transfer roller 41 after the secondary transfer is removed by the cleaning unit 43. The transfer paper 4 onto which the toner image has been secondarily transferred in this manner is conveyed along a predetermined transfer paper conveyance path 5 (indicated by the one-dot chain line in FIG. 1), and the toner image is fixed by the fixing unit 6. It is discharged to the discharge tray provided in the. Further, an operation display panel 7 including a liquid crystal display and a touch panel, for example, is disposed on the upper surface of the apparatus main body 2, and accepts operation instructions from the user and displays predetermined information to notify the user.

  Next, the configuration of the squeegee rollers 51, 52, 53 will be described. The squeegee rollers 51, 52, and 53 are arranged to face each other in the rotation direction (developer transport direction) 46 between the primary transfer position 44 and the secondary transfer position 45 on the intermediate transfer roller 41. The squeegee rollers 51, 52, 53 are supported so as to be movable in the contact / separation direction with respect to the intermediate transfer roller 41. That is, for example, when actuators 61, 62, and 63 (FIG. 3) composed of solenoids or motors are driven by the contact / separation driving unit 118 (FIG. 3), the squeegee rollers 51, 52, and 53 are respectively in contact positions (FIG. 1, a reciprocating movement between a solid line) and a separated position (broken line in FIG. 1). The contact position is a position where the squeegee rollers 51, 52, 53 are in contact with the developer carried on the intermediate transfer roller 41, and the separation position is a position where the squeegee rollers 51, 52, 53 are not in contact with the developer. It is.

  Further, the squeegee rollers 51, 52, 53 are driven in a direction (in FIG. 1) when the roller drive motor 64 (FIG. 3) is rotationally driven by the motor drive unit 119 (FIG. 3) at the contact position. , Counterclockwise) at a circumferential speed substantially equal to that of the intermediate transfer roller 41. The squeegee rollers 51, 52, and 53 are arranged at contact positions and peel off the liquid carrier from the intermediate transfer roller 41 by contacting the surface liquid carrier of the developer 32 carried on the surface of the intermediate transfer roller 41. It is. The liquid carrier stripping operation by the squeegee rollers 51, 52 and 53 will be described in detail later.

  As shown in FIG. 2, the cleaning blade 54 is in contact with the squeegee rollers 51, 52, 53, and the liquid carrier peeled off from the intermediate transfer roller 41 by the squeegee rollers 51, 52, 53 is respectively the cleaning blade 54. Is scraped off and removed from the squeegee rollers 51, 52, 53. Here, a receiving tray 55 for collecting the liquid carrier is installed below the position where each cleaning blade 54 contacts the squeegee rollers 51, 52, 53, and is removed from the squeegee rollers 51-53 by the cleaning blade 54. The liquid carrier is naturally dropped and collected in the tray 55 (collection process). The tray 55 is communicated with the tank 33 via a pipe 56, and the recovered liquid carrier is transferred to the tank 33 via the pipe 56 by driving a carrier feed driving unit such as a pump (not shown). Returned. Thus, in this embodiment, the tray 55 corresponds to the “recovery part” of the present invention, and the pipe 56 corresponds to the “communication part” of the present invention.

  In the present embodiment, the removed liquid carrier is configured to be forcibly returned to the tank 33 by driving the pump. However, the present invention is not limited to this, and the tray 55 is disposed at a position higher than the tank 33. You may comprise so that the collect | recovered liquid carrier may flow down with its own weight and return to the tank 33. FIG. Furthermore, by extending the opening of the tank 33 to below the contact position of the cleaning blade 54 with the squeegee rollers 51, 52, 53, the liquid removed directly without providing the tray 55 and the pipe 56. The carrier may be configured to fall naturally and be collected in the tank 33.

  Further, in the present embodiment, the liquid carrier collected in the tray 55 is all returned to the tank 33. However, the present invention is not limited to this, and an open / close valve is provided in the pipe 56 to open and close the valve. Alternatively, only a part of the recovered liquid carrier may be returned to the tank 33.

  In FIG. 3, the main control unit 100 includes an image memory 103 for storing an image signal given from an external device via an interface 102, and the CPU 101 receives a print command signal including the image signal from the external device. When it is received via the interface 102, it is converted into job data in a format suitable for the operation instruction of the engine unit 1 and sent to the engine control unit 110.

  The memory 116 of the engine control unit 110 includes a ROM that stores a control program for the CPU 113 including preset fixed data, a RAM that temporarily stores control data for the engine unit 1, calculation results by the CPU 113, and the like. The CPU 113 stores data relating to the image signal sent from the external device via the CPU 101 in the memory 116.

  The memory 37 of the developing unit 30 stores data relating to the manufacturing lot, usage history, built-in toner characteristics, remaining amount of the developer 32, toner density, and the like. The memory 37 is electrically connected to the communication unit 38, and the communication unit 38 is attached to the tank 33, for example. When the developing unit 30 is attached to the apparatus main body 2, the communication unit 38 is arranged to face the communication unit 117 of the engine control unit 110 within a predetermined distance, for example, within 10 mm. Data can be transmitted and received in a non-contact state by wireless communication. As a result, the CPU 113 manages various information such as consumables management related to the developing unit 30.

  In this embodiment, data transmission / reception is performed in a non-contact manner using electromagnetic means such as wireless communication. For example, a connector is provided in each of the apparatus main body 2 and the developing unit 30, and the apparatus main body 2 is provided with a connector. When the developing unit 30 is mounted, data transmission and reception may be performed by mechanically fitting both connectors. The memory 37 is preferably a non-volatile memory that can store the data even when the power is off or the developing unit 30 is detached from the apparatus main body 2. Examples of the non-volatile memory include a flash memory. EEPROM, ferroelectric memory, or the like can be used.

  FIG. 4 is a view for explaining the operation of removing the liquid carrier from the intermediate transfer roller 41 by the squeegee roller 51. In the drawing, in the region A, that is, upstream of the squeegee roller 51 in the rotation direction 46 of the intermediate transfer roller 41, the developer 32 is supplied from the photosensitive member 11 (FIG. 1) and adheres to the intermediate transfer roller 41. The toner image 322 (solid image in FIG. 4) moves in the liquid carrier 321 by the next transfer bias and is primarily transferred to the intermediate transfer roller 41. Note that the thickness of the toner image 322 is t1, and the thickness of the liquid carrier 321 is t2. That is, the thickness of the developer 32 on the intermediate transfer roller 41 is (t1 + t2).

  The developer 32 on the intermediate transfer roller 41 is nipped between the squeegee roller 51 and the intermediate transfer roller 41 arranged at the contact position, and the liquid carrier 321 on the surface layer of the developer 32 comes into contact with the squeegee roller 51. Adhere to. When the squeegee roller 51 and the intermediate transfer roller 41 are further rotated, the liquid carrier 321 layer is separated at substantially the center. That is, the thickness of the liquid carrier 321 remaining on the intermediate transfer roller 41 and the thickness of the liquid carrier 321 moving to the squeegee roller 51 are both about t2 / 2.

  In this way, a part of the liquid carrier 321 is peeled off from the intermediate transfer roller 41 by the squeegee roller 51. In this embodiment, three squeegee rollers 51 to 53 are provided, and each squeegee roller 51 to 53 is configured to be movable between a contact position and a separation position, and the CPU 113 controls the position of each squeegee roller 51 to 53. Then, the amount of peeling of the liquid carrier 321 is controlled by controlling the combination of the squeegee rollers 51 to 53 arranged at the contact position, whereby the amount of recovery of the liquid carrier 321 is adjusted. Thus, in this embodiment, the squeegee rollers 51 to 53 correspond to the “stripping member” and the “collecting means” of the present invention, respectively.

  5 to 8 are diagrams for explaining the relationship between the image occupancy ratio and the amount of peeled off liquid carrier. In each figure, (A) shows the toner image on the intermediate transfer roller 41, and (B) and (C). , (D) show the arrangement positions of the squeegee rollers 51, 52, 53, respectively. 5 to 8, as in FIG. 1, the squeegee roller at the contact position is indicated by a solid line, and the squeegee roller at the separation position is indicated by a broken line. For convenience of explanation, the intermediate transfer roller 41 has a flat plate shape.

  The image occupancy rate is the ratio of the image portion to the electrostatic latent image. The main control unit 100 (FIG. 3) includes, for example, a dot counter that counts the number of on dots to which toner adheres among the pixels constituting the electrostatic latent image, and the ratio of the number of on dots to the number of dots in the entire image Has the function to calculate as the image occupancy rate. For example, the image occupancy ratio of a black solid image is 100%, and the image occupancy ratio of a white solid portion (blank portion of the image) of the image is 0%. In place of the main control unit 100, the engine control unit 110 (FIG. 3) may include the dot counter.

  In this embodiment, as described above, the developer 32 in the tank 33 uses a high-concentration developer of 5 to 40% by weight, but the toner contained in the developer 32 is a value included in the range. The density is, for example, 20% by volume (initial value of toner density). In FIG. 4, the thickness t1 of the toner image 322 transferred to the intermediate transfer roller 41 by application of the primary transfer bias is set to 2 μm, and the thickness t2 of the liquid carrier 321 is set to 8 μm. That is, the thickness (t1 + t2) of the developer 32 on the intermediate transfer roller 41 is 10 μm.

  FIG. 5 shows a case where the image occupation rate is 100% (solid image) as shown in FIG. In this case, the toner concentration of the developing solution 32 on the intermediate transfer roller 41 is 20% by volume, which is equal to the initial value of the toner concentration in the tank 33. Therefore, as shown in FIGS. 5B to 5D, the liquid carrier 321 is not collected by disposing all the squeegee rollers 51 to 53 at the separated positions. That is, the recovery amount of the liquid carrier 321 is set to zero. As a result, the developer 32 on the intermediate transfer roller 41 is completely consumed. Since the toner concentration of the consumed developer is equal to the initial value of the toner concentration of the developer 32 in the tank 33, the tank 33 The toner density is maintained at 20% by volume of the initial value.

  FIG. 6 shows a case where the image occupation ratio is 50% as shown in FIG. In this case, the toner concentration of the developer 32 on the intermediate transfer roller 41 is 10% by volume, and t1 = 2 μm and t2 = 8 μm. However, on average, the thickness of the toner image 322 is 1 μm, and the liquid The thickness of the carrier 321 is 9 μm. Therefore, more liquid carriers have moved to the intermediate transfer roller 41 than in the case of FIG.

  Therefore, as shown in FIG. 5B, when the squeegee roller 51 is arranged at the contact position, about half of the surface liquid carrier 321 is peeled off. As a result, the average thickness of the liquid carrier 321 remaining on the region B, that is, the intermediate transfer roller 41, is about 4.5 μm. Accordingly, the toner concentration of the developer 32 in the region B is about 18% by volume, which is substantially equal to the toner concentration in the tank 33.

  Then, as shown in FIGS. 4C and 4D, by arranging the squeegee rollers 52 and 53 at the separated positions, the toner concentration of the developer 32 remaining on the intermediate transfer roller 41 is about 18% by volume. Is maintained. Further, the toner concentration in the tank 33 increased when many liquid carriers 321 moved to the intermediate transfer roller 41, but when the liquid carrier 321 peeled off by the squeegee roller 51 is returned to the tank 33, It decreases and approaches the initial value of 20% by volume.

  FIG. 7 shows a case where the image occupation rate is 20% as shown in FIG. In this case, the toner concentration of the developer 32 on the intermediate transfer roller 41 is 4% by volume, and t1 = 2 μm and t2 = 8 μm, but on average, the thickness of the toner image 322 is 0.4 μm. The thickness of the liquid carrier 321 is 9.6 μm. Therefore, more liquid carriers have moved to the intermediate transfer roller 41 than in the case of FIG.

  Therefore, as shown in FIG. 5B, when the squeegee roller 51 is arranged at the contact position, about half of the surface liquid carrier 321 is peeled off. As a result, the average thickness of the liquid carrier 321 in the region B remaining on the intermediate transfer roller 41 is about 4.8 μm, and the toner concentration of the developer 32 in the region B is about 7.7% by volume. Further, as shown in FIG. 5C, when the squeegee roller 52 is disposed at the contact position, about half of the surface liquid carrier 321 is peeled off. As a result, the average thickness of the liquid carrier 321 in the region C remaining on the intermediate transfer roller 41 is about 2.4 μm. Accordingly, the toner concentration of the developing solution 32 in the region C is about 14% by volume and approaches the toner concentration in the tank 33. As shown in FIG. 4D, the squeegee roller 53 is disposed at a separated position so as not to peel off the liquid carrier 321. This is because if the liquid carrier 321 is further peeled off, the toner image on the intermediate transfer roller 41 may be adversely affected.

  As a result, the toner concentration of the developer 32 remaining on the intermediate transfer roller 41 is about 14% by volume. Further, the toner concentration in the tank 33 increased when many liquid carriers 321 moved to the intermediate transfer roller 41, but the liquid carrier 321 peeled off by the squeegee rollers 51 and 52 is returned to the tank 33. As a result, the value decreases and approaches the initial value of 20% by volume.

  FIG. 8 shows a case where the image occupation ratio is 0% (white image) as shown in FIG. In this case, the toner concentration of the developing solution 32 on the intermediate transfer roller 41 is 0% by volume, and only the liquid carrier 321 is consumed, and the toner concentration in the tank 33 increases. Therefore, as shown in FIGS. 5B to 5D, the liquid carriers 321 are respectively collected by arranging all the squeegee rollers 51 to 53 at the contact positions. As a result, the thickness in the region B after being peeled off by the squeegee roller 51 is about 5 μm, and the thickness in the region C after being peeled off by the squeegee roller 52 is about 2.5 μm. The thickness in the region D after being peeled off by the roller 53 is about 1.25 μm. Then, the liquid carrier 321 peeled off by the squeegee rollers 51 to 53 is returned to the tank 33, so that an increase in toner concentration in the tank 33 is suppressed.

  As described above, the amount of the liquid carrier 321 removed from the intermediate transfer roller 41 can be controlled by controlling the positions of the squeegee rollers 51 to 53. Therefore, it is possible to adjust the toner concentration of the developer 32 on the intermediate transfer roller 41 by controlling the positions of the squeegee rollers 51 to 53. As a result, it is possible to obtain a good image quality by suppressing fluctuations in transfer conditions during transfer onto a recording medium such as transfer paper.

  FIG. 9 is a flowchart showing an example of the recovery amount adjustment processing routine. The memory 116 of the engine control unit 110 stores a liquid carrier recovery amount adjustment processing program in advance. The CPU 113 controls each part of the apparatus according to the program, whereby the following collection amount adjustment processing is executed.

  First, the image occupancy rate P (%), which is the ratio of the image portion in the electrostatic latent image, is obtained (# 10), and the obtained image occupancy rate level is determined. That is, it is determined whether or not 55 <P (# 12). If P ≦ 55 (NO in # 12), it is determined whether 30 <P ≦ 55 (# 14) and P ≦ 30. If (NO in # 14), it is determined whether or not 0 <P ≦ 30 (# 16). If NO in # 16, P = 0, so that all the squeegee rollers 51 to 53 are moved to the contact position as described in FIG. 8 (# 18).

  If 55 <P (YES in # 12), the toner density on the intermediate transfer roller 41 is high, so that all the squeegee rollers 51 to 53 are disposed at the separated positions as described with reference to FIG. This routine ends. If 30 <P ≦ 55 (YES in # 14), the toner density on the intermediate transfer roller 41 is medium. Therefore, for example, as shown in FIG. 6, the squeegee roller 51 is moved to the contact position. (# 20). This movement may be one, and the squeegee roller 52 or 53 may be moved instead of the squeegee roller 51.

  If 0 <P ≦ 30 (YES in # 16), the toner density on the intermediate transfer roller 41 is low, so that, for example, the squeegee rollers 51 and 52 are moved to the contact position as described with reference to FIG. # 22). Two movements are sufficient, and the squeegee rollers 51 and 53 or the squeegee rollers 52 and 53 may be moved. Note that the threshold used to determine the level of image occupancy in steps # 12, # 14, and # 16 is an example, and other values may be used.

  FIG. 10 is a flowchart showing another example of the collection amount adjustment processing routine. In this operation, the developing unit 30 includes a viscometer 39 as indicated by a broken line in FIG. The viscometer 39 is disposed in the tank 33, and the toner concentration is obtained by the CPU 113 based on the viscosity of the developer 32 detected by the viscometer 39. Instead of the viscometer 39, for example, a concentration sensor composed of a transmissive optical sensor may be provided in the tank 33, and the toner concentration of the developer 32 in the tank 33 may be directly detected. Thus, in this embodiment, the viscometer 39 corresponds to the “concentration detection means” of the present invention.

  First, the toner concentration N (%) of the developing solution 32 in the tank 33 is obtained based on the detection signal from the viscometer 39 (# 30). Here, the relationship between the viscosity of the developing solution 32 detected by the viscometer 39 and the toner concentration is included in a program that is obtained in advance in an arithmetic expression or a table data format and stored in the memory 116, and based on the above relationship. Processing for determining the toner density of # 30 is executed.

  Then, it is determined whether or not the obtained toner density is N1 <N (# 32). If N ≦ N1 (NO in # 32), it is determined whether N0 <N ≦ N1 (# 34). If N.ltoreq.N0 (NO in # 32), the toner concentration has decreased, and the routine is terminated without collecting the liquid carrier. Note that N0 is an initial value of the toner concentration of the developer 32 in the tank 33, and N1 is a value satisfying N0 <N1 obtained in advance through experiments or the like.

  On the other hand, if N1 <N (YES in # 32), the toner density has increased significantly, so that, for example, the squeegee rollers 51 and 52 are moved to the contact position as described in FIG. 7 (# 36). . Two movements are sufficient, and the squeegee rollers 51 and 53 or the squeegee rollers 52 and 53 may be moved to the contact position.

  If N0 <N ≦ N1 (YES in # 34), the toner density is increased by a small amount, so that, for example, the squeegee roller 51 is moved to the contact position as described with reference to FIG. 6 (# 38). . This movement may be one, and the squeegee roller 52 or 53 may be moved to the contact position instead of the squeegee roller 51.

  In addition, based on the relationship between the viscosity of the developing solution 32 detected by the viscometer 39 and the toner concentration of the developing solution 32, the developing solution 32 corresponding to the comparison value (N0 and N1 in FIG. 10) of the toner concentration of the developing solution 32. 10 may be obtained in advance and stored in the memory 116, and the detected viscosities may be directly compared with corresponding values to determine steps # 32 and # 34 in FIG.

  As described above, according to the present embodiment, the squeegee rollers 51 to 53 that are movable between the contact position that contacts the developer 32 on the intermediate transfer roller 41 and the separation position that does not contact the intermediate transfer roller 41 are provided. Since the combination of the squeegee rollers 51 to 53 to be arranged is controlled, the amount of the liquid carrier 321 peeled off from the intermediate transfer roller 41 can be controlled. Thereby, the recovery amount of the liquid carrier 321 from the intermediate transfer roller 41 can be adjusted. Since all of the liquid carrier 321 peeled off by the squeegee rollers 51 to 53 is scraped off by the cleaning blade 54 and returned to the tank 33, the adjustment of the recovery amount adjusts the liquid carrier 321 to the tank 33. The return amount can be adjusted.

  In addition, according to the present embodiment, the liquid carrier 321 scraped off from the squeegee rollers 51 to 53 by the cleaning blade 54 is naturally dropped and collected in the receiving tray 55 and returned to the tank 33, so that the liquid carrier 321 is separately provided. There is no need to provide a device for collecting the squeegee from the squeegee rollers 51 to 53 to the tray 55, and the device configuration can be simplified. In addition, by returning the peeled liquid carrier 321 to the tank 33, the liquid carrier 321 can be used effectively, and the replenishment amount of the liquid carrier 321 can be minimized.

  Further, according to the operation of FIG. 9, the image carrier ratio is obtained, and the liquid carrier is set so that the toner concentration of the developer remaining on the intermediate transfer roller 41 after the recovery approaches the initial value of the toner concentration of the developer 32 in the tank 33. In addition to controlling the amount of 321 peeled off, all of the liquid carrier 321 peeled off from the intermediate transfer roller 41 by the squeegee rollers 51 to 53 is scraped off by the cleaning blade 54 and returned to the tank 33. It is possible to suppress the change in the toner density of the 33 developer 32 and maintain the initial value. As a result, the developer 32 in the tank 33 can be used to the end without waste, and the amount of liquid carrier, toner, etc. supplied from the outside can be minimized. In the case of the operation shown in FIG. 9, the toner concentration detecting means for the tank 33 such as the viscometer 39 is not necessary, so that the apparatus configuration can be simplified compared to the case shown in FIG. .

  Further, according to the operation of FIG. 10, the toner concentration in the tank 33 is obtained based on the detection value of the viscometer 39, the amount of liquid carrier removed from the intermediate transfer roller 41 is controlled based on the value, and the liquid removed. Since the carrier is configured to return to the tank 33, the change in the toner density in the tank 33 can be suppressed and maintained at the initial value. As a result, the developer 32 in the tank 33 can be used to the end without waste, and the amount of liquid carrier, toner, etc. supplied from the outside can be minimized.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made to the above-described one without departing from the spirit thereof. For example, the following modifications (1) to ( 11) can be adopted.

  (1) In the above embodiment, the three squeegee rollers 51 to 53 are provided. However, the present invention is not limited to this, and two or four or more squeegee rollers may be provided. That is, if a plurality of squeegee rollers are provided, the amount of the liquid carrier 321 removed from the intermediate transfer roller 41 can be controlled by controlling the combination of the squeegee rollers arranged at the contact position.

  (2) FIG. 11 is a diagram for explaining the amount of liquid carrier stripping at each contact position when three contact positions with different distances from the intermediate transfer roller 41 are provided as contact positions of the squeegee roller 51. . In FIG. 11, for convenience of explanation, the intermediate transfer roller 41 has a flat plate shape. 11 shows only the squeegee roller 51, the same applies to the squeegee rollers 52 and 53.

  In this embodiment, the actuator 54 (FIG. 3) is constituted by a motor, for example, and the squeegee rollers 51 to 53 can be arranged at a plurality of contact positions at different distances from the intermediate transfer roller 41 as contact positions of the squeegee rollers 51 to 53. It is a thing. Here, it is assumed that a solid image is transferred to the intermediate transfer roller 41 as shown in FIG. Similarly to the above embodiment, the thickness of the toner image 322 is t1, and the thickness of the liquid carrier 321 is t2. The radius of the squeegee roller 51 is R.

  In FIG. 5B, the contact position is set to a position where the surface of the squeegee roller 51 barely contacts the developer 32 on the intermediate transfer roller 41. That is, the distance L1 between the center of the squeegee roller 51 and the surface of the developer 32 is set to L1≈R and L1 ≦ R. As a result, the thickness of the liquid carrier 321 remaining on the intermediate transfer roller 41 becomes t3, and a small amount of the liquid carrier 321 on the surface layer of the developer 32 on the intermediate transfer roller 41 is peeled off.

  In FIG. 8C, the contact position is set closer to the intermediate transfer roller 41 than in FIG. That is, the distance L2 between the center of the squeegee roller 51 and the surface of the developer 32 is set to L2 <L1. As a result, the thickness of the liquid carrier 321 remaining on the intermediate transfer roller 41 becomes t4 (<t3), and the liquid carrier 321 on the surface of the developer 32 on the intermediate transfer roller 41 is larger than in the case of FIG. Stripped off.

  In FIG. 4D, the contact position is set closer to the intermediate transfer roller 41 than in FIG. That is, the distance L3 between the center of the squeegee roller 51 and the surface of the developer 32 is set to L3 <L2. As a result, the thickness of the liquid carrier 321 remaining on the intermediate transfer roller 41 becomes t5 (<t4), and the surface of the liquid carrier 321 of the developer 32 on the intermediate transfer roller 41 is further increased than in the case of FIG. Many are stripped off.

  Thus, according to the form of FIG. 11, the squeegee rollers 51 to 53 can be arranged at a plurality of contact positions whose distances from the intermediate transfer roller 41 are different from each other as the contact positions of the squeegee rollers 51 to 53. By changing the contact position of the squeegee rollers 51 to 53, the amount of the liquid carrier 321 removed from the intermediate transfer roller 41 can be controlled, and thereby the same effect as in the above embodiment can be obtained. In this embodiment, the number of squeegee rollers is not limited to a plurality, and only one squeegee roller may be provided. Even in this case, the stripping amount of the liquid carrier 321 can be controlled.

  (3) In the above embodiment, the rotational speed of the squeegee rollers 51 to 53 can be changed by the roller drive motor 64, and the relative speed of the contact surface of the squeegee rollers 51 to 53 with respect to the developer conveyed by the intermediate transfer roller 41 is set. It may be changed. According to this embodiment, the amount of peeling of the liquid carrier 321 can be increased or decreased by increasing or decreasing the peripheral speed of the squeegee rollers 51 to 53 with respect to the peripheral speed of the intermediate transfer roller 41. The same effect can be obtained. In this embodiment, the number of squeegee rollers is not limited to a plurality, and only one squeegee roller may be provided. Even in this case, the stripping amount of the liquid carrier 321 can be controlled.

  (4) In the above embodiment, for example, as shown in FIG. 7A, the thickness t1 of the toner image 322 is 2 μm and the thickness t2 of the liquid carrier 321 is 8 μm, so in FIG. If the roller 53 is disposed at the contact position, the toner image may be adversely affected. However, if there is no possibility of adversely affecting the toner image even if the squeegee roller 53 is arranged at the contact position, for example, the thickness t1 of the toner image 322 is 1 μm, the squeegee roller 53 in FIG. May be arranged at the contact position.

  If there is no possibility of adversely affecting the toner image even if the squeegee roller 53 is disposed at the contact position, the number of squeegee rollers moving to the contact position is set to a maximum of two in the operations of FIGS. On the other hand, the step of comparing may be increased by one, and a step of arranging all three squeegee rollers 51 to 53 at the contact position may be provided.

  For example, in the operation of FIG. 9, the level of the image occupation rate to be determined may be subdivided. That is, for example, if 0 <P ≦ 20, the three squeegee rollers are moved to the contact position, and if 20 <P ≦ 35, the two squeegee rollers are moved to the contact position, and 35 <P ≦ 55. For example, one squeegee roller may be moved to the contact position. Further, in the operation of FIG. 10, for example, the value N2 where N1 <N2 is also compared with the toner density N. If N2 <N, the three squeegee rollers are moved to the contact position, and N1 <N ≦ N2. If there are, two squeegee rollers are moved to the contact position, and if N0 <N ≦ N1, one squeegee roller may be moved to the contact position.

  (5) In the operation of FIG. 9 in the above embodiment, the liquid carrier cannot be sufficiently collected in a range where the image occupation ratio is low, and the toner concentration in the tank 33 tends to increase. That is, for example, as shown in FIG. 7A, since the thickness t1 of the toner 322 is 2 μm and the thickness t2 of the liquid carrier 321 is 8 μm, the squeegee roller 53 is arranged at the contact position in FIG. As a result, the toner image may be adversely affected. Therefore, as described with reference to FIG. 7, when the image occupation ratio is 20%, the toner concentration of the developer 32 remaining on the intermediate transfer roller 41 approaches up to about 14% by volume, but the initial value is set. It does not reach a certain 20% by volume.

  Therefore, for example, in step # 12, only one squeegee roller may be arranged at the contact position even when 55 <P. As a result, the recovery amount of the liquid carrier 321 can be increased and the return amount to the tank 33 can be increased, and the increase in the toner concentration in the tank 33 can be suppressed and maintained at the initial value as much as possible. .

  (6) In the above embodiment, the recovery amount of the liquid carrier 321 is adjusted, and all the recovered liquid carriers 321 are returned to the tank 33. However, the present invention is not limited to this, and the stripping amount of the liquid carrier 321 is used. The liquid carrier 321 is peeled off as much as possible within a range that does not adversely affect the toner image, for example, and the return amount of the liquid carrier 321 to the tank 33 is determined according to the image occupancy ratio (FIG. 9) or the toner concentration ( You may make it the structure adjusted according to FIG.

  (7) In the above embodiment, a dot counter that counts the number of on-dots to which toner adheres among the pixels constituting the electrostatic latent image is provided, and the ratio of the number of on-dots to the number of dots in the entire image is used as the image occupancy rate However, the method for obtaining the image occupancy rate is not limited to this. Since the image occupancy rate is a value corresponding to the amount of development, that is, the amount of toner movement from the developing roller 31 to the photoconductor 11, for example, the current flowing from the developing roller 31 to the photoconductor 11 is detected as the developing current. The amount of toner movement (development amount) may be obtained based on this and used as the image occupancy rate.

  (8) In the above embodiment, the roller-like squeegee rollers 51 to 53 are used as the stripping member, but the invention is not limited to this, and for example, a belt-like member may be used.

  (9) In the above embodiment, the squeegee rollers 51 to 53 are disposed opposite to each other between the primary transfer position 44 and the secondary transfer position 45 of the intermediate transfer roller 41, and the liquid carrier is transferred from the photoconductor 11 before the secondary transfer. I'm trying to peel it off, but it is not limited to this. For example, the squeegee rollers 51 to 53 may be arranged to face each other between the secondary transfer position 45 of the intermediate transfer roller 41 and the cleaning unit 43 so that the liquid carrier is peeled off from the intermediate transfer roller 41 after the secondary transfer.

  (10) In the above-described embodiment, all of the squeegee rollers 51 to 53 are configured to be movable between the contact position and the separated position. However, the present invention is not limited to this, and at least one squeegee roller is configured to be movable. Just keep it. For example, even in a configuration in which the squeegee roller 51 is movable and the squeegee rollers 52 and 53 are fixedly arranged at the contact position, the combination of the squeegee rollers arranged at the contact position can be controlled by the position control of the squeegee roller 51. This can control the amount of liquid carrier stripping.

  (11) In the above embodiment, a printer that prints an image provided from an external device such as a host computer on transfer paper is described. However, the present invention is not limited to this, and a copying machine, a facsimile machine, and the like are used. The present invention can be applied to a general electrophotographic image forming apparatus. In the above-described embodiment, the present invention is applied to an image forming apparatus for monochrome printing. However, the application target of the present invention is not limited to this, and the present invention can also be applied to a color image forming apparatus. .

1 is a diagram illustrating an internal configuration of a printer that is an embodiment of the present invention. FIG. The principal part enlarged view of FIG. 2 is a block diagram showing an electrical configuration of the printer. FIG. Explanatory drawing of the peeling amount of the liquid carrier by a squeegee roller. The figure explaining the relationship between an image occupation rate and the amount of peeling of a liquid carrier. The figure explaining the relationship between an image occupation rate and the amount of peeling of a liquid carrier. The figure explaining the relationship between an image occupation rate and the amount of peeling of a liquid carrier. The figure explaining the relationship between an image occupation rate and the amount of peeling of a liquid carrier. The flowchart which shows an example of collection amount adjustment processing routine. The flowchart which shows another example of collection | recovery amount adjustment process routine. The figure explaining the peeling amount of the liquid carrier in a deformation | transformation form.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Photosensitive body (latent image carrier), 33 ... Tank (container), 39 ... Viscometer (concentration detecting means), 41 ... Intermediate transfer roller (transfer medium), 51-53 ... Squeegee roller (peeling member, recovery) Means), 55 ... tray (collecting part), 56 ... piping (communication part)

Claims (13)

A container for storing a developer in which toner is dispersed in a liquid carrier; and developing the electrostatic latent image on the latent image carrier using the developer stored in the container to form a toner image; and In an image forming apparatus for transferring a toner image onto a transfer medium,
A recovery means for recovering the liquid carrier from the developer adhering to the transfer medium and returning it to the container;
An image forming apparatus characterized in that the return amount of the liquid carrier to be returned to the container by the collecting means can be adjusted.   The image forming apparatus according to claim 1, wherein the recovery unit is configured to be capable of adjusting a recovery amount of the liquid carrier, and returns all the liquid carriers recovered by the adjusted recovery amount to the container. The recovery means is configured to be disposed at a contact position that contacts the developer on the transfer medium, and includes a stripping member that strips a liquid carrier on a surface layer of the developer by being disposed at the contact position.
The image forming apparatus according to claim 2, wherein the collection amount is adjusted by controlling a removal amount of the liquid carrier by the peeling member. The recovery means includes, as the stripping member, a plurality of stripping members that are arranged opposite to the transfer medium side by side in the transport direction of the developer by the transfer medium,
At least one of the plurality of stripping members is configured to be movable between the contact position and a separation position that does not contact the developer on the transfer medium,
The image forming apparatus according to claim 3, wherein the stripping amount is controlled by controlling a combination of the stripping members in contact with the developer on the transfer medium by controlling the position of the stripping member configured to be movable. The recovery means includes, as the stripping member, a stripping member configured to be arranged at a plurality of contact positions that are in contact with the developer on the transfer medium and that have different distances from the transfer medium. ,
The image forming apparatus according to claim 3, wherein the amount of peeling is controlled by changing a contact position of the peeling member.   The image forming apparatus according to claim 3, wherein the amount of peeling is controlled by changing a relative speed of a contact surface of the peeling member with respect to the developer conveyed by the transfer medium.   The said collection | recovery means is further equipped with the cleaning member which removes the liquid carrier peeled off by the said peeling member from the said peeling member, It was comprised so that the liquid carrier removed by the said cleaning member might be returned to the said container. The image forming apparatus according to any one of?   The recovery means is provided below a contact position of the cleaning member to the stripping member, and recovers the liquid carrier that is removed by the cleaning member and freely falls, the recovery unit, and the recovery unit The image forming apparatus according to claim 7, further comprising a communication unit that communicates with the container, and returning the liquid carrier collected by the collection unit to the container via the communication unit.   The image forming apparatus according to claim 2, wherein the collection unit adjusts the collection amount in accordance with image information related to the toner image.   The image forming apparatus according to claim 9, wherein the image information is obtained as an image occupancy ratio that is a ratio of an image portion in the electrostatic latent image, and the collection amount is adjusted according to the image occupancy ratio.   11. The recovery amount is adjusted so that the toner concentration of the developer remaining on the transfer medium after the recovery of the liquid carrier by the recovery means approaches the initial value of the toner concentration of the developer stored in the container. The image forming apparatus according to any one of the above.   Concentration detection means for detecting the toner concentration of the developer stored in the container is further provided so that the toner concentration detected by the density detection means approaches the initial value of the toner concentration of the developer stored in the container. The image forming apparatus according to claim 1, wherein the return amount is adjusted. A developing step of developing the electrostatic latent image on the latent image carrier using a developer in which toner is dispersed in a liquid carrier to form a toner image;
A transfer step of transferring a toner image on the latent image carrier onto a transfer medium;
A recovery step of recovering the liquid carrier from the developer attached on the transfer medium and returning it to the container for storing the developer,
An image forming method comprising adjusting a return amount of a liquid carrier to be returned to the container in the collecting step.

Images