JP4349051B2 - Image forming apparatus - Google Patents

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.

  Conventional electrophotographic image forming apparatuses include the following. 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 visualize the electrostatic latent image. Then, a toner image is formed, and the toner image is primarily transferred onto an intermediate transfer medium such as an intermediate transfer belt or an intermediate transfer drum (primary transfer step). The toner image on the intermediate transfer medium is conveyed to a secondary transfer position and secondarily transferred to a recording medium such as transfer paper (secondary transfer process). 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 the developed developed image (toner image) to a recording medium such as a transfer material. It is a thing.

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. It is not possible to cope with fluctuations in As a result, it is conceivable that secondary transfer conditions vary due to variations in the amount of liquid carrier on the intermediate transfer medium, making it difficult to perform suitable transfer. Therefore, in order to obtain good image quality, adjusting the amount of liquid carrier contained in the developer on the intermediate transfer medium is one of important control elements.

    The present invention has been made in view of the above problems, and provides an image forming apparatus capable of obtaining favorable image quality by suppressing fluctuations in transfer conditions (secondary transfer conditions) from an intermediate transfer medium to a recording medium. For the purpose.

  In order to achieve the above object, the present invention develops an electrostatic latent image on a latent image carrier using a developer in which toner is dispersed in a liquid carrier to form a toner image. Primary transfer position and secondary transfer in an image forming apparatus that performs primary transfer onto an intermediate transfer medium at a transfer position, and transports a toner image on the intermediate transfer medium to a secondary transfer position for secondary transfer onto a recording medium. An adjusting means for adjusting the amount of the liquid carrier contained in the developer adhering to the intermediate transfer medium between the positions, and the adjusting means includes an applying member configured to apply the liquid carrier to the intermediate transfer medium. An image forming apparatus capable of controlling a ratio of a toner and a liquid carrier on an intermediate transfer medium by adjusting an amount of the liquid carrier on the intermediate transfer medium by controlling an amount of liquid carrier applied by a member. .

  According to these configurations, by adjusting the amount of liquid carrier contained in the developer that adheres to the intermediate transfer medium, the toner concentration of the developer that adheres to the intermediate transfer medium is always maintained at a value close to a predetermined value. Can do. Thereby, fluctuations in the transfer conditions (secondary transfer conditions) from the intermediate transfer medium to the recording medium are suppressed, transfer can be performed under substantially the same transfer conditions, and good image quality can be obtained. According to the present invention, since the toner density is adjusted immediately before the toner image is transferred to a recording medium such as transfer paper, the transfer conditions can be controlled reliably.

  One aspect of the adjusting means includes an applying member configured to be able to apply a liquid carrier to the intermediate transfer medium, and controlling the amount of the liquid carrier applied by the applying member, thereby controlling the liquid carrier on the intermediate transfer medium The amount is adjusted. According to this configuration, for example, when the toner concentration of the developer adhering to the intermediate transfer medium is increased with respect to a predetermined value, the toner concentration is decreased to a predetermined value by applying the liquid carrier. Thereby, the fluctuation | variation of transfer conditions is suppressed and favorable image quality can be obtained.

  Another aspect of the adjusting means is configured to be disposed at a contact position in contact with the developer on the intermediate transfer medium, and stripping off the liquid carrier on the surface layer of the developer by being disposed at the contact position. A removal member is provided, and the amount of liquid carrier on the intermediate transfer medium is adjusted by controlling the amount of removal of the liquid carrier by the removal member. According to this configuration, for example, when the toner concentration of the developer adhering to the intermediate transfer medium is decreased from a predetermined value, the toner concentration is increased to a predetermined value by peeling off the liquid carrier. Thereby, the fluctuation | variation of transfer conditions is suppressed and favorable image quality can be obtained.

  In addition, the adjusting unit includes, as the stripping member, a plurality of stripping members that are arranged to face each other in the developer transfer direction of the intermediate transfer medium so as to face the intermediate transfer medium, and the plurality of stripping members At least one of them is configured to be movable between the contact position and a separation position that does not contact the developer on the intermediate transfer medium, and the position control of the stripping member configured to be movable is performed as described above. The amount of stripping may be controlled by controlling the combination of stripping members in contact with the developer on the intermediate transfer medium. 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 intermediate transfer medium is controlled by position control of the stripping member configured to be movable. Since the combination of the stripping members that come into contact with the developer is controlled, it is easy 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, and It can be done reliably.

  In addition, the adjusting means may be a stripping member configured to be disposed at a plurality of contact positions that are in contact with the developer on the intermediate transfer medium and have different distances from the intermediate transfer medium as the stripping member. A stripping member may be provided, and the stripping amount may be controlled by changing a contact position of the stripping member. According to this configuration, the amount of 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 intermediate transfer medium is long or a short position. It is possible to easily and reliably control the amount of carrier peeling.

  Further, when the stripping amount is controlled by changing the relative speed of the contact surface of the stripping member with respect to the developer conveyed by the intermediate transfer medium, the relative speed is changed to a large value or a small value. Thus, 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.

  A container for storing the developer; a cleaning member for removing the liquid carrier peeled off by the peeling member; and a recovery means for returning the liquid carrier removed by the cleaning member to the container. May be further provided. 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.

  Further, the liquid carrier amount on the intermediate transfer medium may be adjusted so that the toner concentration of the developer remaining on the intermediate transfer medium after the adjustment of the liquid carrier amount by the adjusting unit approaches a predetermined value. According to this configuration, the toner concentration of the developer at the time of transfer to the recording medium is always maintained at a value close to a predetermined value, so that fluctuations in transfer conditions can be suppressed and good image quality can be obtained.

  The intermediate transfer medium further includes a container for storing the developer, and is configured to return the liquid carrier peeled off by the peeling member to the container, and after the liquid carrier is peeled off by the peeling member. The stripping amount may be adjusted so that the toner concentration of the developer remaining on the container approaches the initial value of the toner concentration of the developer stored in the container. According to this configuration, the amount of stripping is performed so that the toner concentration of the developer remaining on the intermediate transfer medium after the liquid carrier is stripped by the stripping member approaches the initial value of the toner concentration of the developer stored in the container. Is adjusted and all of the stripped liquid carrier is returned to the container. For example, when the toner concentration of the developer on the intermediate 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. As a result, fluctuations in the transfer conditions can be suppressed, the toner concentration of the developer stored in the container can be maintained at a value close to the initial value, the developer in the container can be used effectively, and toner or The replenishment of the liquid carrier can be minimized.

  Further, the apparatus further comprises a container for storing the developer and a concentration detecting means for detecting a toner concentration of the developer stored in the container, and the liquid carrier peeled off by the stripping member is returned to the container. In addition, the stripping amount may be adjusted so that the toner density detected by the density detection unit approaches the initial value of the toner density of the developer stored in the container. According to this configuration, the toner concentration of the developer stored in the container is detected, and the liquid carrier is peeled off so that the detected toner concentration approaches the initial value of the toner concentration of the developer stored in the container. The take-up is adjusted and all of the stripped liquid carrier is returned to the container. 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 As a result, the toner concentration of the developer stored in the container can be maintained at a value close to the initial value, the developer in the container can be used effectively, and replenishment of toner or liquid carrier to the container can be minimized. can do.

  The adjusting unit may adjust the amount of liquid carrier on the intermediate transfer medium in accordance with image information related to the toner image. As a result, the amount of liquid carrier on the intermediate transfer medium is adjusted in accordance with the image information related to the toner image, so that fluctuations in transfer conditions are suppressed, and good image quality can be obtained. If the image information is obtained as an image occupancy ratio that is a ratio of the image portion to the electrostatic latent image, and the liquid carrier amount on the intermediate transfer medium is adjusted according to the image occupancy ratio, the image occupancy Since the rate is a value corresponding to the toner concentration in the developer on the latent image carrier, the liquid carrier amount on the intermediate transfer medium can be easily adjusted according to the toner concentration without detecting the toner concentration. It can be carried out. As a result, fluctuations in the transfer conditions are reliably suppressed, and good image quality can be obtained.

  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. Thus, in this embodiment, the transfer paper 4 corresponds to the “recording medium” of the present invention.

  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 position 16 (described later) 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 (primary 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 “intermediate 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, between the primary transfer position 44 and the secondary transfer position 45, squeegee rollers 51, 52, 53, and a carrier applier 57, which will be described later, are disposed. 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 by constant current control, the toner image on the intermediate transfer roller 41 is secondarily transferred to the transfer paper 4 (secondary transfer step). 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.

  Next, the configuration of the carrier applicator 57 will be described. The carrier applier 57 is disposed between the primary transfer position 44 and the secondary transfer position 45 on the intermediate transfer roller 41 so as to face each other. The carrier applicator 57 applies an arbitrary amount of liquid carrier onto the intermediate transfer roller 41. For example, a liquid carrier supply source such as a tank for storing the liquid carrier, and a liquid carrier stored in the tank. Is constituted by a liquid carrier supply means such as a supply roller that pumps up and supplies the toner onto the intermediate transfer roller 41. Similar to the squeegee rollers 51 to 53, this supply roller is supported so as to be movable toward and away from the intermediate transfer roller 41. When applying a liquid carrier, the supply roller contacts the intermediate transfer roller 41. On the other hand, when the liquid carrier is not applied, the supply roller can be retracted from the intermediate transfer roller 41 to the separated position. When applying the liquid carrier, for example, the application amount of the liquid carrier is adjusted by controlling the rotation speed of the supply roller. Thus, in this embodiment, the carrier applicator 57 corresponds to the “applying member” and “adjusting means” of the present invention.

  Note that the configuration of the carrier applicator 57 is not limited thereto, and for example, a supply nozzle or the like is disposed on the intermediate transfer roller 41 as a liquid carrier supply unit, and the liquid carrier is discharged onto the intermediate transfer roller 41. May be. In this case, the application amount of the liquid carrier is adjusted by controlling the discharge amount.

  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. 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.

  Further, in this embodiment, the recovered liquid carrier is returned to the tank 33. However, the recovered liquid carrier is supplied to the carrier applicator 57, and the liquid carrier is supplied to the carrier applicator 57. It may be used as In this case, the tray 55 may be used as it is as a supply source for the carrier applier 57. Thereby, the replenishment amount of the liquid carrier to the carrier applicator 57 can be minimized.

  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. And the amount of stripping off of the liquid carrier 321 is adjusted by controlling the combination of the squeegee rollers 51 to 53 arranged at the contact position. Thus, in this embodiment, the squeegee rollers 51 to 53 correspond to the “stripping member” and the “adjusting 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 peeled off by disposing all the squeegee rollers 51 to 53 at the separated positions. That is, the stripping 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 stripping amount adjustment processing routine. The memory 116 of the engine control unit 110 stores a stripping amount adjustment processing program for the liquid carrier in advance. Then, the CPU 113 controls each part of the apparatus according to the program, whereby the following stripping 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 stripping 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, so the routine is terminated without stripping off 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. As a result, the amount of liquid carrier contained in the developer on the intermediate transfer roller 41 can be adjusted. That is, by controlling the liquid carrier 321 in the decreasing direction, the toner concentration of the developing solution adhering to the intermediate transfer roller 41 (that is, the ratio between the toner and the liquid carrier) can be adjusted.

  Further, according to the present embodiment, since the carrier applicator 57 is provided, the direction in which the liquid carrier 321 is increased can be controlled by controlling the application amount of the liquid carrier 321 applied on the intermediate transfer roller 41. Can do. In this way, since the increase / decrease control of the liquid carrier 321 is possible, the amount of liquid carrier on the intermediate transfer roller 41 can be arbitrarily controlled, and the toner concentration of the developer 32 adhering to the intermediate transfer roller 41 can be controlled. It becomes possible to adjust. Thereby, even when the toner concentration of the developing solution 32 on the intermediate transfer roller 41 is increased or decreased with respect to the predetermined value, it can always be maintained at a value close to the predetermined value. As a result, fluctuations in transfer conditions from the intermediate transfer roller 41 to the recording medium such as the transfer paper 4 are suppressed, transfer can be performed under substantially the same transfer conditions, and good image quality can be obtained. Furthermore, since the toner density is adjusted immediately before the toner image is transferred to a recording medium such as the transfer paper 4, it is possible to reliably control the transfer conditions.

  Here, the toner density on the intermediate transfer roller 41 is adjusted by executing the stripping process and the applying process of the liquid carrier 321, but the toner density is adjusted only by one of the processes. You may comprise.

  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 occupancy ratio is obtained, and the liquid concentration is adjusted so that the toner concentration of the developing solution remaining on the intermediate transfer roller 41 after peeling off approaches the initial value of the toner concentration of the developing solution 32 in the tank 33. Since the removal amount of the carrier 321 is controlled, 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 concentration of the developer 32 in the tank 33 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 ( 9) 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, 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.

  (7) 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.

  (8) 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 when the squeegee roller 51 is configured to be 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.

  (9) In the above embodiment, a printer that prints an image provided from an external device such as a host computer on transfer paper has been described. However, the present invention is not limited to this, and a copying machine, a facsimile machine, or the like is 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. . In short, a toner image developed using a developer in which toner is dispersed in a liquid carrier is temporarily carried on an intermediate transfer medium such as an intermediate transfer roller, an intermediate transfer belt, or an intermediate transfer drum, and then the toner image is recorded on the recording medium. The present invention can be applied to all image forming apparatuses that perform secondary transfer.

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. FIG. 2 is a block diagram showing an electrical configuration of the printer. 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 a peeling amount adjustment process routine. The flowchart which shows another example of a stripping 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 4 ... Transfer paper (recording medium), 11 ... Photoconductor (latent image carrier), 33 ... Tank (container), 39 ... Viscometer (density detection means), 41 ... Intermediate transfer roller (intermediate transfer medium), 51- 53 ... Squeegee roller (peeling member, adjusting means), 55 ... receiving tray (collecting part), 56 ... piping (communication part), 57 ... carrier applicator (applying member, adjusting means)

Claims (1)

The electrostatic latent image on the latent image carrier is developed using a developer in which toner is dispersed in a liquid carrier to form a toner image, and the toner image is primarily transferred onto an intermediate transfer medium at a primary transfer position. And an image forming apparatus for transporting the toner image on the intermediate transfer medium to a secondary transfer position and performing secondary transfer onto a recording medium.
Adjusting means for adjusting the amount of liquid carrier contained in the developer that adheres to the intermediate transfer medium between the primary transfer position and the secondary transfer position;
The adjusting means includes an applying member configured to be able to apply a liquid carrier to the intermediate transfer medium,
The ratio of the toner on the intermediate transfer medium to the liquid carrier can be controlled by adjusting the amount of liquid carrier on the intermediate transfer medium by controlling the amount of liquid carrier applied by the applying member. Image forming apparatus.

Images