JP4207525B2 - Image forming apparatus and image forming method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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.
[0002]
[Prior art]
Conventionally, a charged photosensitive member (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. An electrophotographic image forming apparatus in which a toner image is formed 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 uses a high-viscosity and high-concentration developer, and improves the image quality by removing the liquid carrier from the developer on the photoreceptor after development.
[0003]
[Patent Document 1]
JP 2000-250319 A (paragraph [0021], FIG. 1)
[0004]
[Problems to be solved by the invention]
By the way, for example, when images having a high image occupancy ratio, which is the ratio of the image portion to the electrostatic latent image, are continuously formed, a large amount of toner adheres to the photoconductor, so that the liquid carrier that moves to the photoconductor is small. Conversely, when images with a low image occupancy rate are continuously formed, only a small amount of toner adheres to the photoconductor, so that the liquid carrier that moves to the photoconductor increases compared to when the image occupancy rate is high. Thus, the amount of movement of the liquid carrier to the photoreceptor varies greatly depending on the form of the toner image to be formed.
[0005]
However, the apparatus described in the above-described conventional patent document 1 merely includes a configuration for removing a certain amount of liquid carrier from the photosensitive member, and copes with fluctuations in the amount of liquid carrier on the photosensitive member. I can't. As a result, for example, when the amount of the liquid carrier on the photoconductor increases, the liquid carrier may be consumed wastefully. It is also conceivable that transfer conditions to the transfer medium change due to fluctuations in the amount of liquid carrier on the photoconductor, 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 photosensitive member is one of important control elements.
[0006]
The present invention has been made in view of the above problems, and provides an image forming apparatus and an image forming method capable of forming a good toner image while preventing the liquid carrier from being wasted. For the purpose.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to the present invention includes an image carrier on which an electrostatic latent image is carried on the surface as the surface moves, and a developer containing a liquid carrier and toner. A developing unit that transports the toner to a developing position opposite to the developing position, supplies the developer to the surface of the image carrier to develop the electrostatic latent image at the developing position, and a contact position that contacts the developer on the image carrier; A plurality of parts that can move between a position on the image carrier that is not in contact with the developer and that separates the liquid carrier from the image carrier while the surface rotates in the moving direction of the surface of the image carrier at the contact position. The squeegee roller, the cleaning member that removes the liquid carrier peeled from the squeegee roller from the squeegee roller, and the number of squeegee rollers positioned at the contact position to control the amount of the liquid carrier peeled from the surface of the image carrier A control means for adjusting, and a means for obtaining a ratio of the image portion in the electrostatic latent image, and the control means increases the number of squeegee rollers located at the contact position when the ratio is equal to or less than a predetermined value. It is a feature.
The image forming method according to the present invention is an image forming method for developing an electrostatic latent image formed on the surface of an image carrier with a developer containing a liquid carrier and a toner. A developer supplying process for supplying the developer to the surface of the image carrier, and a liquid carrier supplied in the developer supplying process and attached to the surface of the image carrier is peeled off from the surface of the image carrier using a plurality of squeegee rollers. The squeegee roller is configured to be movable between a contact position that contacts the developer on the image carrier and a separated position that does not contact the developer on the image carrier. The liquid carrier is peeled off from the image carrier while the surface rotates in the moving direction of the surface of the image carrier at the position, and in the peeling step, if the ratio of the image portion in the electrostatic latent image is a predetermined value or less, the contact position Squeegee located in It is characterized by increasing the number of rollers.
[0008]
According to this configuration, the developer in which the toner is dispersed in the liquid carrier is conveyed to the development position facing the image carrier by the developer carrier, and is supplied to the image carrier in contact with the image carrier at the development position. Then, the toner in the supplied developing solution adheres to the image carrier, whereby the electrostatic latent image is visualized and a toner image is formed. Here, among a plurality of peeling mechanisms capable of performing a peeling operation for peeling the liquid carrier contained in the developer supplied from the developer carrier to the image carrier from the image carrier, a peeling mechanism for performing the peeling operation. By controlling the combination, the amount of separation of the liquid carrier can be reliably adjusted. As a result, it is possible to prevent the liquid carrier from being wasted and to form a good toner image.
[0009]
Further, if the plurality of peeling mechanisms are provided side by side in the developer transport direction by the image carrier, the control of the combination of the peeling mechanisms that perform the peeling operation, for example, the peeling mechanism that performs the peeling operation The amount of the liquid carrier can be easily and reliably adjusted by increasing or decreasing the number of the liquid carriers.
[0011]
In addition, the developing unit has a container for storing the developing solution, conveys the developing solution from the container to the developing position, and is configured so that the liquid carrier removed by the cleaning member returns to the container. The liquid carrier can be used effectively by removing the liquid carrier from the squeegee roller and returning it to the container.
[0012]
The cleaning member contacts the squeegee roller (peeling mechanism) and scrapes the liquid carrier from the squeegee roller. The opening of the container extends below the position where the cleaning member contacts the squeegee roller. The liquid carrier removed by the cleaning member may return to the container under its own weight.
[0013]
According to this configuration, since the liquid carrier peeled off from the peeling mechanism by the cleaning member is configured to return to its own weight in the container for storing the developer, a separate collection tank may be provided or the collection may be performed. It is not necessary to provide a pipe for returning the liquid carrier from the tank to the container, and the apparatus configuration can be simplified and the apparatus main body can be reduced in size.
[0014]
The image forming apparatus further includes a transfer unit that transfers the toner image on the image carrier to the transfer medium, and the plurality of squeegee rollers can perform an operation of peeling the liquid carrier from the surface of the image carrier before the transfer to the transfer medium. With this configuration, since the amount of the liquid carrier contained in the developer is larger than that on the image carrier or the transfer medium after transfer to the transfer medium, many liquid carriers can be peeled off. It is possible to widen the adjustment range of the peeling amount.
[0015]
In this case, if the separation amount is adjusted so that the toner concentration of the developer remaining on the image carrier after the liquid carrier is peeled off by the peeling mechanism approaches a predetermined value, development at the time of transfer to the transfer medium is performed. Since the toner concentration of the liquid is always maintained at a value close to a predetermined value, transfer can be performed always under substantially the same transfer conditions, and a transferred toner image can be formed with high quality.
[0016]
Further, the apparatus further comprises a container for storing the developer, and is configured to return the liquid carrier peeled by the peeling mechanism to the container, and the development remaining on the image carrier after the liquid carrier is peeled by the peeling mechanism. The separation amount may be adjusted so that the toner concentration of the liquid approaches the initial value of the toner concentration of the developer stored in the container.
[0017]
According to this configuration, the separation amount is adjusted so that the toner concentration of the developer remaining on the image carrier after the liquid carrier is peeled off by the peeling mechanism approaches the initial value of the toner concentration of the developer stored in the container. , All of the peeled liquid carrier is returned to the container. For example, when the toner concentration of the developer on the image carrier 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, 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.
[0018]
Further, the apparatus further comprises a container for storing the developer and a concentration detection means for detecting a toner concentration of the developer stored in the container, and the liquid carrier separated by the peeling mechanism is returned to the container. In addition, the separation amount may be adjusted so that the toner concentration detected by the concentration detection means approaches the initial value of the toner concentration of the developer stored in the container.
[0019]
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 amount is adjusted and all of the peeled 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.
[0020]
Further, at least one of the plurality of squeegee rollers may be configured to be located at the contact position.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
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.
[0022]
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.
[0023]
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). Around the photoreceptor 11, along the rotation direction 15, the charging unit 12, the developing roller 31, squeegee rollers 51, 52, and 53 (described later), the intermediate transfer roller 41, the charge eliminating unit 13, and the cleaning unit 14. Is arranged. 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.
[0024]
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 “image carrier” of the present invention.
[0025]
The electrostatic latent image formed in this way is visualized by toner supplied from the developing roller 31 of the developing unit 30. 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 up the developing solution 32 stored in the tank 33 and applies the developing solution 31 to the developing roller 31 at the coating position 34a. A regulating blade 35 that uniformly regulates the thickness of the upper developer layer, a cleaning blade 36 that removes the developer remaining on the developing roller 31 after supplying the toner to the photosensitive member 11, and a memory 37 (FIG. 3) described later. I have. 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.
[0026]
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.
[0027]
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.
[0028]
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.
[0029]
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 developing roller 31 corresponds to the “developer carrier” of the present invention, and the tank 33 corresponds to the “container” of the present invention.
[0030]
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 medium). 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.
[0031]
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. 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. Thus, in this embodiment, the transfer bias generator 115 corresponds to the “transfer unit” of the present invention.
[0032]
Next, the configuration of the squeegee rollers 51, 52, 53 will be described. The squeegee rollers 51, 52, and 53 are rotated between the developing position 16 and the primary transfer position 44 on the photosensitive member 11, that is, in the developing carrying area where the toner image is carried, in the rotation direction (developing liquid transport direction) 15. Are arranged opposite to each other. The squeegee rollers 51, 52, 53 are supported so as to be movable in the contact / separation direction with respect to the photoreceptor 11. 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 photoconductor 11, and the separation position is a position where the squeegee rollers 51, 52, 53 are not in contact with the developer. is there.
[0033]
Further, the squeegee rollers 51, 52, and 53 are driven in the direction in which the photosensitive member 11 is driven when the roller driving motor 64 (FIG. 3) is rotationally driven by the motor driving unit 119 (FIG. 3) at the contact position. It rotates at a peripheral speed almost equal to that of the photoconductor 11 in the counterclockwise direction. The squeegee rollers 51, 52, and 53 are arranged at contact positions to peel off the liquid carrier from the photoconductor 11 by coming into contact with the liquid carrier on the surface layer of the developer 32 carried on the surface of the photoconductor 11. .
[0034]
As shown in FIG. 2, the cleaning blade 54 is in contact with the squeegee rollers 51, 52, and 53, and the liquid carrier peeled off from the photoconductor 11 by the squeegee rollers 51, 52, and 53 is respectively removed by the cleaning blade 54. It is scraped off and removed from the squeegee rollers 51, 52, 53. Here, the opening of the tank 33 extends to a position below the contact position of each cleaning blade 54 with the squeegee rollers 51, 52, 53. As a result, the liquid carrier removed from the squeegee rollers 51 to 53 by the cleaning blade 54 is returned to the tank 33 by its own weight.
[0035]
In the present embodiment, the removed liquid carrier is returned to the tank 33 by its own weight. However, the present invention is not limited to this, and the receiving tray for receiving the removed liquid carrier, and the receiving tray and the tank 33 are communicated. A recovery pipe and a pump may be provided, and the pump may be driven to forcibly return the liquid carrier to the tank 33. The liquid carrier stripping operation by the squeegee rollers 51, 52 and 53 will be described in detail later.
[0036]
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.
[0037]
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.
[0038]
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.
[0039]
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.
[0040]
FIG. 4 is a view for explaining the operation of removing the liquid carrier from the photoreceptor 11 by the squeegee roller 51. In the drawing, in the region A, that is, upstream of the squeegee roller 51 in the rotation direction 15 of the photoconductor 11, the developing solution 32 is supplied from the developing roller 31 (FIG. 1) and adheres to the photoconductor 11, and the developing bias Vb. As a result, the toner 322 moves in the liquid carrier 321 and adheres to the photoconductor 11, and a toner image (solid image in FIG. 4) is formed. Note that the thickness of the toner 322 is t1, and the thickness of the liquid carrier 321 is t2. That is, the thickness of the developer 32 on the photoconductor 11 is (t1 + t2).
[0041]
Then, the developer 32 on the photoconductor 11 is nipped between the squeegee roller 51 disposed at the contact position and the photoconductor 11, and the liquid carrier 321 on the surface layer of the developer 32 contacts and adheres to the squeegee roller 51. . Further, when the squeegee roller 51 and the photosensitive member 11 are rotated, the liquid carrier 321 is separated at substantially the center. That is, the thickness of the liquid carrier 321 remaining on the photoconductor 11 and the thickness of the liquid carrier 321 moving to the squeegee roller 51 are both about t2 / 2.
[0042]
In this way, a part of the liquid carrier 321 is peeled off from the photoreceptor 11 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 peeling amount of the liquid carrier 321 will be adjusted by controlling the combination of the squeegee rollers 51-53 arrange | positioned in a contact position. Thus, in this embodiment, the squeegee rollers 51 to 53 each correspond to the “peeling mechanism” of the present invention.
[0043]
FIGS. 5 to 8 are diagrams for explaining the relationship between the image occupancy ratio and the peeling amount of the liquid carrier. FIG. 5A shows a toner image on the photoconductor 11, and FIGS. D) shows the arrangement positions of the squeegee rollers 51, 52 and 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 photoconductor 11 has a flat plate shape.
[0044]
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.
[0045]
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 322 adhering to the photoconductor 11 by development is set to t2 = 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 photoconductor 11 is 10 μm.
[0046]
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 photoreceptor 11 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 by disposing all the squeegee rollers 51 to 53 at the separated positions. That is, the peeling amount of the liquid carrier 321 is set to zero. As a result, all the developing solution 32 on the photoconductor 11 is consumed, but the toner concentration of the consumed developing solution is equal to the initial value of the toner concentration of the developing solution 32 in the tank 33. The toner concentration is maintained at 20% by volume of the initial value.
[0047]
FIG. 6 shows a case where the image occupation ratio is 50% as shown in FIG. In this case, the toner concentration of the developing solution 32 on the photoconductor 11 is 10% by volume, and t1 = 2 μm and t2 = 8 μm, but on average, the thickness of the toner 322 is 1 μm, and the liquid carrier 321. The thickness becomes 9 μm. Therefore, more liquid carriers have moved to the photoconductor 11 than in the case of FIG.
[0048]
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 photoconductor 11, 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.
[0049]
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 photoreceptor 11 is about 18% by volume. Maintained. In addition, the toner concentration in the tank 33 has increased when many liquid carriers 321 have moved to the photoconductor 11, but decreases when the liquid carrier 321 peeled off by the squeegee roller 51 is returned to the tank 33. As a result, the initial value approaches 20% by volume.
[0050]
FIG. 7 shows a case where the image occupation rate is 20% as shown in FIG. In this case, the toner concentration of the developing solution 32 on the photoconductor 11 is 4% by volume, and t1 = 2 μm and t2 = 8 μm, but on average, the thickness of the toner 322 is 0.4 μm, and the liquid The thickness of the carrier 321 is 9.6 μm. Therefore, more liquid carriers have moved to the photoconductor 11 than in the case of FIG.
[0051]
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 photoreceptor 11 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 photoconductor 11 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 photoconductor 11 may be adversely affected.
[0052]
As a result, the toner concentration of the developer 32 remaining on the photoreceptor 11 is about 14% by volume. Further, the toner concentration in the tank 33 has increased when many liquid carriers 321 have moved to the photoreceptor 11, but the liquid carrier 321 peeled off by the squeegee rollers 51 and 52 is returned to the tank 33. , And it will approach the initial value of 20% by volume.
[0053]
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 developer 32 on the photoconductor 11 is 0% by volume, and only the liquid carrier 321 is consumed, and the toner concentration in the tank 33 increases. Then, as shown to the same figure (B)-(D), the liquid carrier 321 is peeled, respectively, by arrange | positioning all the squeegee rollers 51-53 in a contact position. Accordingly, 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.
[0054]
FIG. 9 is a flowchart showing an example of the peeling amount adjustment processing routine. The memory 116 of the engine control unit 110 stores a liquid carrier peeling amount adjustment processing program in advance. Then, the CPU 113 controls each part of the apparatus according to the program, whereby the following peeling amount adjustment processing is executed.
[0055]
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).
[0056]
If 55 <P (YES in # 12), the toner density on the photoconductor 11 is high, so that all the squeegee rollers 51 to 53 are disposed at the separated positions as described with reference to FIG. Exit the routine. If 30 <P ≦ 55 (YES in # 14), the toner density on the photoconductor 11 is medium, so that the squeegee roller 51 is moved to the contact position, for example, as described in FIG. # 20). This movement may be one, and the squeegee roller 52 or 53 may be moved instead of the squeegee roller 51.
[0057]
If 0 <P ≦ 30 (YES in # 16), the toner density on the photoconductor 11 is low, so that, for example, the squeegee rollers 51 and 52 are moved to the contact position as described with reference to FIG. 7 (# 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.
[0058]
FIG. 10 is a flowchart showing another example of the peeling 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.
[0059]
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.
[0060]
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 peeling 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.
[0061]
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.
[0062]
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.
[0063]
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.
[0064]
As described above, according to the present embodiment, the squeegee rollers 51 to 53 that are movable between the contact position that contacts the developing solution 32 on the photoconductor 11 and the separated position that does not contact are provided and arranged at the contact position. Since the combination of the squeegee rollers 51 to 53 to be controlled is controlled, the amount of separation of the liquid carrier 321 from the photoconductor 11 can be adjusted. As a result, wasteful consumption of the liquid carrier 321 can be prevented and a good toner image can be formed.
[0065]
Further, according to the present embodiment, the opening of the tank 33 is extended below the position where each cleaning blade 54 contacts the squeegee rollers 51 to 53, and the cleaning blade 54 scrapes off the squeegee rollers 51 to 53. Since the liquid carrier 321 is returned to the tank 33 by its own weight, it is necessary to provide a separate recovery tank or a pipe for returning the liquid carrier 321 from the recovery tank to the tank 33. Therefore, the apparatus configuration can be simplified and the apparatus main body can be reduced in size. 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.
[0066]
Further, according to the present embodiment, the squeegee rollers 51 to 53 are arranged to face the development carrying region so that the liquid carrier 321 is peeled off from the photoconductor 11 before the primary transfer. Since the amount of the liquid carrier contained in the developer is larger than that on the photoconductor 11 or the intermediate transfer roller 41 in FIG. 1, a large amount of the liquid carrier can be peeled off, thereby widening the adjustment range of the peeling amount. It becomes possible.
[0067]
Further, according to the present embodiment, the liquid carrier 321 is peeled from the photoconductor 11 before the primary transfer, the image occupation ratio is obtained, and the toner concentration of the developer remaining on the photoconductor 11 after the peeling is set to a predetermined value (this In the embodiment, the liquid carrier peeling amount is adjusted so as to approach the initial value of the toner density in the tank 33, so that the transfer conditions when the primary transfer is performed, that is, the toner density of the developer is always substantially equal. Accordingly, the primary transfer can always be suitably performed.
[0068]
Further, according to the operation of FIG. 9, the image occupancy ratio is obtained, and the liquid carrier 321 is obtained so that the toner concentration of the developer remaining on the photoconductor 11 after the separation approaches the initial value of the toner concentration of the developer 32 in the tank 33. In addition, the liquid carrier 321 peeled off from the photosensitive member 11 by the squeegee rollers 51 to 53 is scraped off by the cleaning blade 54 and returned to the tank 33. The change in the toner concentration of the liquid 32 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. 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. .
[0069]
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 peeled off from the photoreceptor 11 is adjusted based on the value, and the peeled liquid carrier is removed. Since it is configured to return to the tank 33, the change in 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.
[0070]
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 ( 10) can be employed.
[0071]
(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 separation of the liquid carrier 321 from the photoconductor 11 can be adjusted by controlling the combination of the squeegee rollers arranged at the contact position.
[0072]
(2) FIG. 11 is a diagram for explaining the separation amount of the liquid carrier at each contact position when three contact positions with different distances from the photoconductor 11 are provided as the contact positions of the squeegee roller 51. In FIG. 11, for convenience of explanation, the photoconductor 11 has a flat plate shape. 11 shows only the squeegee roller 51, the same applies to the squeegee rollers 52 and 53.
[0073]
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 having different distances from the photosensitive member 11 as contact positions of the squeegee rollers 51 to 53. It is a thing. Here, it is assumed that a solid image is formed on the photoconductor 11 as shown in FIG. Similarly to the above embodiment, the thickness of the toner 322 is t1, and the thickness of the liquid carrier 321 is t2. The radius of the squeegee roller 51 is R.
[0074]
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 photoconductor 11. 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 photoconductor 11 becomes t3, and a small amount of the liquid carrier 321 on the surface layer of the developer 32 on the photoconductor 11 is peeled off.
[0075]
In FIG. 8C, the contact position is set closer to the photoconductor 11 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 photoconductor 11 becomes t4 (<t3), and the liquid carrier 321 on the surface layer of the developer 32 on the photoconductor 11 is peeled off more than in the case of FIG. It is done.
[0076]
In FIG. 4D, the contact position is set closer to the photoconductor 11 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 photoconductor 11 becomes t5 (<t4), and the liquid carrier 321 on the surface layer of the developer 32 on the photoconductor 11 is peeled off more than in the case of FIG. Taken.
[0077]
As described above, according to the embodiment shown in FIG. 11, the squeegee rollers 51 to 53 can be arranged at a plurality of contact positions having different distances from the photoconductor 11 as the contact positions of the squeegee rollers 51 to 53. By changing the contact position of the rollers 51 to 53, the amount of separation of the liquid carrier 321 can be adjusted more finely, or the adjustment range can be expanded.
[0078]
(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 photosensitive member 11 is set. It may be changed. According to this embodiment, the amount of separation 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 photoconductor 11. It becomes possible to finely adjust the peeling amount or to widen the adjustment range.
[0079]
(4) In the above embodiment, as shown in FIG. 7A, for example, the thickness t1 of the toner 322 is 2 μm and the thickness t2 of the liquid carrier 321 is 8 μm. If 53 is arranged 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 322 is 1 μm, for example, the squeegee roller 53 in FIG. You may make it arrange | position in a contact position.
[0080]
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.
[0081]
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.
[0082]
(5) In the operation of FIG. 9 in the above embodiment, the liquid carrier cannot be sufficiently peeled off and returned to the tank 33 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 occupancy rate is 20%, the toner concentration of the developer 32 remaining on the photosensitive member 11 is close to about 14% by volume, but is an initial value. It does not reach 20% by volume.
[0083]
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 amount of the liquid carrier 321 peeled off can be increased and the amount returned to the tank 33 can be increased, and an increase in the toner concentration in the tank 33 can be suppressed and maintained at the initial value as much as possible.
[0084]
(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 occupation 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.
[0085]
(7) In the above embodiment, the intermediate transfer roller 41 is provided, and the toner image on the photoconductor 11 is primarily transferred to the intermediate transfer roller 41 at the primary transfer position 44, and then the secondary transfer roller 42 at the secondary transfer position 45. However, the present invention is not limited to this. For example, the intermediate transfer roller 41 is omitted, the secondary transfer roller 42 is disposed at the primary transfer position 44, and the toner image on the photoconductor 11 is transferred. It may be configured to transfer directly to the transfer paper 4 (transfer medium). In this embodiment, the transfer bias generator 115 and the secondary transfer roller 42 correspond to the “transfer unit” of the present invention.
[0086]
(8) In the above-described embodiment, the roller-shaped developing roller 31 is used as the developer carrying member. However, the present invention is not limited to this, and for example, a belt-shaped one may be used. Moreover, although the roller-like squeegee rollers 51 to 53 are used as the stripping member, the invention is not limited thereto, and for example, a belt-like member may be used.
[0087]
(9) 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 adjust the amount of peeling of the liquid carrier.
[0088]
(10) In the above embodiment, the description has been given using a printer that prints an image provided from an external device such as a host computer on transfer paper. However, the present invention is not limited to this, and a copier, 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 this case, for example, in the case of a so-called tandem apparatus that includes a photoconductor unit, an exposure unit, and a development unit for each color and is configured to sequentially transfer to the intermediate transfer belt, the liquid carrier on the photoconductor is peeled for each color. The amount can be adjusted.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an internal configuration of a printer according to an embodiment of the invention.
FIG. 2 is an enlarged view of a main part of FIG.
FIG. 3 is a block diagram showing an electrical configuration of the printer.
FIG. 4 is an explanatory diagram of a separation amount of a liquid carrier by a squeegee roller.
FIG. 5 is a diagram for explaining a relationship between an image occupancy rate and a separation amount of a liquid carrier.
FIG. 6 is a diagram for explaining the relationship between the image occupancy rate and the amount of peeling of the liquid carrier.
FIG. 7 is a diagram for explaining the relationship between the image occupancy rate and the amount of peeling of the liquid carrier.
FIG. 8 is a diagram for explaining the relationship between the image occupancy rate and the amount of peeling of the liquid carrier.
FIG. 9 is a flowchart illustrating an example of a peeling amount adjustment processing routine.
FIG. 10 is a flowchart showing another example of a peeling amount adjustment processing routine.
FIG. 11 is a diagram for explaining a peeling amount of a liquid carrier in a modified embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Photosensitive body (image carrier), 31 ... Developing roller (developer carrier), 33 ... Tank (container), 39 ... Viscometer (density detecting means), 41 ... Intermediate transfer roller (transfer means), 42 ... Secondary transfer roller (transfer means), 51 to 53 ... squeegee roller (peeling mechanism), 113 ... CPU, 115 ... transfer bias generator (transfer means)

Claims (7)

An image carrier on which an electrostatic latent image is carried on the surface as the surface moves;
Development that transports a developer containing a liquid carrier and toner to a development position facing the image carrier, and supplies the developer to the surface of the image carrier at the development position to develop the electrostatic latent image. And
The image carrier is configured to be movable between a contact position that contacts the developer on the image carrier and a separated position that does not contact the developer on the image carrier, and the surface of the image carrier is the contact position. A plurality of squeegee rollers for peeling the liquid carrier from the image carrier while rotating in the moving direction of the surface;
A cleaning member for removing the liquid carrier peeled off from the squeegee roller from the squeegee roller;
And a control means for the control the number of squeegee rollers located at the contact position to adjust the peeling amount of the liquid carrier is peeled off from the surface of the image bearing member,
Means for determining a ratio of an image portion in the electrostatic latent image,
The control unit increases the number of squeegee rollers located at the contact position when the ratio is equal to or less than a predetermined value .   The image forming apparatus according to claim 1, wherein the plurality of squeegee rollers are provided side by side in a direction in which developer is conveyed by the image carrier. The developing unit has a container for storing the developer, and conveys the developer from the container to the development position.
The image forming apparatus according to claim 1, wherein the liquid carrier removed by the cleaning member returns to the container. The cleaning member contacts the squeegee roller and scrapes the liquid carrier from the squeegee roller.
The opening of the said container is extended below the contact position to the said squeegee roller of the said cleaning member, It comprised so that the said liquid carrier removed by the said cleaning member might return to the said container with dead weight. The image forming apparatus described. A transfer means for transferring the toner image on the image carrier to a transfer medium;
The image forming apparatus according to claim 1, wherein the plurality of squeegee rollers can perform an operation of peeling the liquid carrier from the surface of the image carrier before transfer to the transfer medium. At least one image forming apparatus according to any one of claims 1 to 5 positioned in said contact position of said plurality of squeegee rollers. In an image forming method of developing an electrostatic latent image formed on the surface of an image carrier with a developer containing a liquid carrier and toner,
A developer supply step of supplying the developer to the surface of the image carrier;
A peeling step of peeling the liquid carrier supplied in the developer supplying step and attached to the surface of the image carrier from the surface of the image carrier using a plurality of squeegee rollers,
The squeegee roller is configured to be movable between a contact position that contacts the developer on the image carrier and a separated position that does not contact the developer on the image carrier. Peeling the liquid carrier from the image carrier while rotating in the moving direction of the surface of the image carrier,
In the peeling step, when the ratio of the image portion in the electrostatic latent image is a predetermined value or less, the number of the squeegee rollers located at the contact position is increased .

Images