JP2009116032A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that performs development with a liquid developer, the apparatus being capable of suppressing unevenness of image quality by restraining excessive supply of the a liquid developer to a developing roller. <P>SOLUTION: The image forming apparatus include: an electrostatic latent image carrier; a developer carrier that supplies the liquid developer to the electrostatic latent image carrier; and a developer conveying means that conveys the liquid developer to the developer carrier. The image forming apparatus develops a latent image on the electrostatic latent image carrier by using the liquid developer. In the image forming apparatus, the developer conveying means includes a developing roller 91, a supply roller 92, and a supply roller 93 disposed opposite to one another. At least two or more suction nozzles 53 are disposed in the vicinity of the nip area of the supply rollers 92 and 93. Using the suction nozzle 53, excessive liquid developer is sucked. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that performs development using a liquid developer.

  An electrophotographic image forming apparatus that performs development using a liquid developer includes a photosensitive drum on which an electrostatic latent image is formed, and a developing roller for supplying the liquid developer to the photosensitive drum. . In this image forming apparatus, the liquid developer is supplied in a stable amount to the photosensitive drum, so that the image quality is kept constant.

  Conventionally, as an image forming apparatus as described above, for example, as disclosed in Patent Document 1, in order to keep an appropriate amount of liquid developer in a developing device, the liquid level of the liquid developer is adjusted by a liquid level detection sensor. What is detected is known. The liquid level detection sensor includes a float switch, and detects the liquid amount according to the width of the vertical movement of the float. However, such a float switch cannot detect a liquid developer having a high viscosity or a small specific gravity with high sensitivity.

  In Patent Document 2, as a method of stably supplying a liquid developer to a photosensitive drum without using the liquid level detection sensor as described above, a photosensitive drum and a photosensitive drum are supplied from a developer tank in which the liquid developer is stored. It is described that a developer is supplied between the developer roller and the excess developer that has passed between the photosensitive drum and the developer roller is collected in a developer tank and reused. However, in this method, it is not desirable to return the developer that has passed between the photosensitive drum and the developing roller to the developer tank because the developer concentration has changed.

  Patent Document 3 describes a method of supplying a developer to a developing roller by an anilox roller. Here, the liquid developer is temporarily supplied from the developer tank to another storage section, and the anilox roller is arranged in a state where a part of the developer is immersed in the storage section. A uniform thin layer is formed. However, in this method, since the anilox roller is always immersed in the liquid developer, the developer is excessively attached, and the attached developer may be excessively supplied to the downstream development roller.

Further, Patent Document 4 is provided with a pressure sensor for detecting the pressure of the liquid developer as a wet electrophotographic apparatus that allows a uniform developer to be applied to the developing roller over the entire printing width. It is described that the oversupply of the liquid developer is prevented by detecting that it has been reached. However, it is very complex and difficult to detect and control the pressure of the liquid developer.
JP 59-126570 A JP 2001-92258 A JP 200412710 A JP 2000-250318 A

On the other hand, in the conventional image forming apparatus using the pumping roller and the supply roller, as shown in FIG. 7A, the liquid developer 56 is likely to adhere to both end surfaces of the pumping roller 40c. In order to solve this problem, the present inventors considered that the excessive liquid developer 56 adhered is sucked by the suction device on the end face side of the pumping roller 40c.
However, in the case of a roller having a large diameter, unless the suction area is increased, it is excessively supplied to both ends of the downstream supply roller 40b (FIG. 7B), and as a result, the developer is excessively supplied to the developing roller. There is. In addition, in the case of a toner having a very high viscosity and a high yield value, there is a case where only the vicinity of the suction port can be sucked because of low fluidity.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that performs development using a liquid developer and that can suppress excessive supply of the liquid developer to the developing roller and suppress unevenness in image quality. .

（６）前記液体現像剤の搬送の停止は、前記液体現像剤の供給停止、前記ローラの駆動停止、そして吸引停止、の順で制御されることを特徴とする（４）に記載の画像形成装置。 In order to solve the above problems, an image forming apparatus of the present invention has the following configuration.
(1) An electrostatic latent image carrier, a developer carrier for supplying a liquid developer to the electrostatic latent image carrier, and a developer conveying means for conveying the liquid developer to the developer carrier. An image forming apparatus that develops a latent image on the electrostatic latent image carrier using the liquid developer, wherein the developer conveying means includes at least two rollers facing each other, and the roller An image forming apparatus comprising: at least two suction units in the vicinity of a nip region of the first and second portions, and using the suction units, the excess liquid developer is sucked.
(2) The image forming apparatus according to (1), wherein the suction unit is disposed outside an image forming region width.
(3) The image forming apparatus according to (1) or (2), wherein an end surface of the roller is pressed by an elastic member to prevent the liquid developer from entering the end surface of the roller.
(4) The image forming apparatus according to any one of (1) to (3), further comprising supply means for supplying the liquid developer to the vicinity of a nip region of the roller.
(5) The pumping capacity of the liquid developer by the roller is a flow rate A, the supply capacity from the supply means is a flow rate B, the nip passage capacity is a flow rate C, and the total suction capacity by at least two suction means is 5. The image forming apparatus according to claim 4, wherein each of the flow rates A, B, C, and D satisfies the following formula (1) when expressed as a total flow rate D:

(6) The image forming according to (4), wherein the stop of transport of the liquid developer is controlled in the order of stop of supply of the liquid developer, stop of driving of the roller, and stop of suction. apparatus.

  According to the present invention, in an image forming apparatus that performs development using a liquid developer, at least two or more suction units are disposed in the vicinity of the nip region between the upstream roller and the downstream roller, and excess liquid developer is provided. Therefore, excessive supply to the downstream roller can be prevented. As a result, excessive supply of the liquid developer to the developing roller can be suppressed, and unevenness in image quality can be suppressed.

The image forming apparatus according to the present invention will be described in detail below.
FIG. 1 is a schematic longitudinal cross-sectional view showing a main configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 1 includes a tandem image forming unit 50 that forms a toner image based on image data, a paper storage unit 22 that stores paper, and a secondary that transfers a toner image formed by the image forming unit 50 to the paper. A transfer unit 23; a fixing unit 24 including a pair of rollers 51 and 52 for fixing the transferred toner image on the paper; a paper discharge device 25 that discharges the fixed paper; and a paper discharge unit that receives the discharged paper. A paper tray 27 and the like are provided in the casing 2. The image forming apparatus 1 further includes a paper transport unit 26 that transports paper from the paper storage unit 22 to the paper discharge device 25.

  The image forming unit 50 includes an intermediate transfer belt 29, a cleaning unit 28 for the intermediate transfer belt 29, and image forming units 21Y, 21M, 21C, and 21B that correspond to yellow, magenta, cyan, and black, respectively. A primary transfer roll 20 is provided opposite to each image forming unit via the intermediate transfer belt 29. The intermediate transfer belt 29 is an endless belt-like member having conductivity, and is circulated and driven clockwise in FIG. In the following description, a surface facing outward in the circulation drive may be referred to as a front surface, and the other surface may be referred to as a back surface.

  The image forming units 21Y, 21M, 21C, and 21B are disposed downstream of the cleaning unit 28 and upstream of the secondary transfer unit 23 in the moving direction of the intermediate transfer belt 29 along the intermediate transfer belt 29. Arranged in this order. Note that the order of arrangement of the image forming units 21Y, 21M, 21C, and 21B is not limited to this, but this arrangement is desirable in consideration of the influence of the color mixture on the completed image. The secondary transfer unit 23 includes a roller 211 having an intermediate transfer belt 29 stretched thereon and a secondary transfer roller 41 disposed to face the roller 211.

The image forming units 21Y, 21M, 21C, and 21B have substantially the same configuration. As an example, FIG. 2 shows a cross-sectional view illustrating a schematic configuration of the image forming unit 21Y.
The image forming unit 21Y includes a photosensitive drum 10, a charger 11, an LED exposure device 12, a yellow developing device 40Y, a primary transfer roller 20, a cleaning blade 31a for the photosensitive drum 11, a static eliminating device 13, and a carrier removing roller 30. I have. The other image forming units 21M, 21C, and 21B are provided with developing devices corresponding to the respective colors. Further, among the image forming units, the image forming unit 21B located on the most downstream side in the moving direction of the intermediate transfer unit 29 is not provided with the carrier removing roller 30 because the image forming unit is not located downstream thereof. Other configurations are the same.

  The photosensitive drum 10 is a substantially cylindrical member that is arranged to be rotatable about a rotation axis that is perpendicular to the moving direction of the intermediate transfer belt 29 and parallel to the surface direction of the intermediate transfer belt 29. In FIG. It can rotate clockwise. The photosensitive drum 10 can carry a charged toner, that is, a toner image containing a charged toner, on the surface thereof.

  The cleaning blade 31 a, the charge eliminating device 13, the charger 11, the exposure device 12, and the yellow developing device 40 </ b> Y are arranged around the photoconductive drum 10 along with the photoconductive drum 10 along the rotation direction of the photoconductive drum 10. They are arranged in this order as seen from the primary transfer position with which the transfer roller 20 contacts.

  The charger 11 can uniformly charge the surface of the photosensitive drum 10. The LED exposure device 12 has an LED light source, irradiates the charged surface of the photosensitive drum 10 with light corresponding to the image information in accordance with image information from an external device (not shown), and electrostatically irradiates the surface of the photosensitive drum 10. A latent image is formed.

  The yellow developing device 40Y holds a liquid developer (hereinafter, also simply referred to as a developer) containing yellow toner and a carrier which is an insulating liquid so as to face the electrostatic latent image, thereby electrostatically Toner can be applied to the latent image and the electrostatic latent image can be developed as a toner image. This toner image is primarily transferred to the intermediate transfer belt 29 by the primary transfer roller 20. Details of the primary transfer roller 20 will be described later.

  The cleaning blade 31 a is a blade-like member disposed so as to be in contact with the photosensitive drum 10. The cleaning blade 31a removes the developer remaining on the surface of the photosensitive drum 10 after the primary transfer.

  The neutralization device 13 includes a light source. After the residual developer is removed by the cleaning blade 31a, the surface of the photosensitive drum 10 is neutralized by light from the light source to prepare for the next image formation.

The primary transfer roller 20 is disposed in contact with the back surface of the intermediate transfer belt 29. A voltage having a polarity opposite to the charging polarity of the toner in the toner image is applied to the primary transfer roller 20 from a power source (not shown). Since the intermediate transfer belt 29 has conductivity, the applied voltage attracts toner to the surface side of the intermediate transfer belt 29 and its periphery.
During the primary transfer, a small amount of carrier may be transferred from the photosensitive drum 10 to the intermediate transfer belt 29 together with the toner. This carrier transfer may interfere with primary transfer in the downstream image forming unit and cause image defects such as image blurring and blurring. Providing the carrier removal roller 30 can prevent such an image defect.

  In this embodiment, the carrier removal roller 30 is incorporated in the cleaning unit 31 together with the cleaning blade 31a. The cleaning unit 31 is provided in the image forming unit 21Y. In addition to the cleaning blade 31a and the carrier removing roller 30, the cleaning unit 31 contacts the surface of the carrier removing roller 30 to remove the carrier liquid attached to the surface of the carrier removing roller 30. The carrier removing blade 31b, the carrier removed from the carrier removing roller 31a, and the developer (including toner and carrier) removed from the surface of the photosensitive drum 10 by the cleaning blade 31a are conveyed to the outside of the cleaning unit 31. The conveying member 31c is provided. The image forming unit 21Y may further include a separation unit that separates the carrier and the toner in order to reuse the carrier and the toner conveyed by the conveyance member 31c.

  The image forming apparatus 1 that has received an image forming instruction from an external device such as a personal computer forms toner images of each color corresponding to the image information that has received the creating instruction using the image forming units 21Y, 21M, 21C, and 21B. To do. The image formed by each image forming unit is transferred to the intermediate transfer belt 29 and superimposed on the intermediate transfer belt 29 to form a color toner image.

  In synchronism with the formation of the color toner image, the paper stored in the paper storage unit 22 is taken out from the paper storage unit 22 one by one by a paper feeding device (not shown) and transported on the paper transport unit 26. Then, the sheet is sent to the secondary transfer unit 23 in synchronization with the primary transfer to the intermediate transfer belt 29, and the color toner image on the intermediate transfer belt 29 is secondarily transferred to the sheet by the secondary transfer unit 23. The sheet on which the color toner image has been transferred is further conveyed to the fixing unit 24 where the color toner image is fixed on the sheet by heat and pressure. Further, the paper is discharged by a paper discharge device 25 to a paper discharge tray 27 provided on the outer periphery of the image forming apparatus 1. The toner remaining on the intermediate transfer belt 29 after the secondary transfer is removed from the intermediate transfer belt 29 by the cleaning unit 28 of the intermediate transfer belt 29.

(Developer)
FIG. 2 shows the developing device 40Y in the yellow image forming unit 21Y. Hereinafter, the configuration of the developing device will be described by taking the developing device 40Y as a representative. The developing devices in the other image forming units 21M, 21C, and 21B are configured similarly to the developing device 40Y.
The developing device 40Y includes a developing container 9, a developing roller 91, supply rollers 92 and 93, a developing cleaning blade 961, and a supply roller doctor blade 921. The developer container 9 is provided with a developer supply nozzle 94 that supplies the developer onto the supply roller 93.

  As shown by arrows in FIG. 2, the developing roller 91 and the supply roller 92 rotate in opposite directions at the contact positions, and the supply rollers 92 and 93 rotate in the same direction at the contact positions. . Thus, when the developer is supplied from the developer supply nozzle 94 onto the lowermost supply roller 93, the developer is sent from the supply roller 93 to the supply roller 92 and the development roller 91.

  That is, the developer supplied to the surface of the supply roller 93 is conveyed to the surface of the supply roller 92 that is in contact with the supply roller 93. On the surface of the supply roller 92, a supply roller doctor blade 921 for regulating the developer layer thickness is provided. The doctor blade 921 regulates the developer layer thickness on the surface of the supply roller 92 to a predetermined amount. A developing roller 91 is disposed so as to be in contact with the supply roller 92, and a developer is applied to the surface thereof from the supply roller 92. Since the developer layer thickness is regulated to a predetermined value on the surface of the supply roller 92, the developer layer thickness formed on the surface of the developing roller 91 is also kept at the predetermined value. The developing roller 91 is in contact with the photosensitive drum 10, and the toner according to the image instructed to form from an external device by the potential difference between the electrostatic latent image on the surface of the photosensitive drum 10 and the developing bias applied to the developing roller 91. An image is formed on the surface of the photosensitive drum 10.

  Excess developer that has fallen from the supply rollers 92 and 93 accumulates at the bottom of the developing container 9 and is discharged through a first discharge pipe 98 provided at the bottom. The developer remaining on the surface of the developing roller 91 without being developed is removed by the developing cleaning blade 961 and discharged from the second discharge pipe 99. In FIG. 2, reference numeral 97 is provided to improve development efficiency by pushing toner dispersed randomly in the developer layer carried on the surface of the developing roller 91 toward the developing roller in the developer layer. Development charging device. In this embodiment, a corotron charging device is used.

  FIG. 3 shows a developer circulation mechanism 8 for supplying and discharging the developer. As shown in the figure, the developer is fed from the developer storage tank 87 to the supply nozzle 94 by the pump P7. Excess developer accumulated at the bottom of the developing container 9 is sent to the recovery tank 83 via the first discharge pipe 98. Excess developer removed from the surface of the developing roller 91 by the developing cleaning blade 961 is also sent to the recovery tank 83 via the second discharge pipe 99 by the pump P1. The developer in the collection tank 83 is further sent to the stirring tank 84 by the pump P2.

  The agitation tank 84 includes an agitation device, and a high concentration developer having a toner concentration higher than that of the developer used in the developing device 9 sent from the tank 85 by the pump P8 (the toner concentration of the developer used in the developing device 9 is 25%, The toner concentration of the high-concentration developer in the tank 85 is set to 30%), or the carrier liquid sent from the tank 86 by the pump P3 is stirred and mixed with the collected developer sent from the collection tank 83. Then, the developer after stirring is sent to the developer storage tank 87 by the pump P6. Further, the agitation tank 84 is provided with a circulation path 840 provided with a toner concentration detection device 841, and the developer in the agitation tank 84 is circulated by the pump P4.

  The toner concentration detection device 841 is connected to the control unit 100 and adjusts the toner concentration of the developer in the stirring tank 84. That is, a specified amount of the collected developer is sent from the collection tank 83 into the stirring tank 84, and the toner concentration in the collected developer is measured by the toner concentration detection device 841. If the toner concentration is lower than the specified value, a high concentration developer having a toner concentration higher than that of the developer used in the developing device 9 from the tank 85 (for example, the toner concentration of the developer used in the developing device 9 is 25% by weight, and the high concentration development in the tank 85 is performed. The toner concentration of the agent is set to 30% by weight), and a necessary amount is sent to the agitation tank 84 by the pump P8 and agitated for a specified time. If the toner concentration is higher than the specified value, a necessary amount of carrier liquid is sent from the tank 86 to the stirring tank 84 by the pump P3 and stirred for a specified time. After the agitation, the toner concentration detecting device 841 confirms the toner concentration, and the developer whose concentration is adjusted in the agitation tank 84 by the pump P6 is sent to the developer storage tank 87.

  On the other hand, the developer removed from the surface of the photosensitive drum 10 by the cleaning blade 31a is sent from the recovery tank 81 to the separation and extraction device 40 for separating and extracting the carrier liquid from the developer by the pump P9. The carrier liquid separated and extracted by the separation and extraction device 40 is sent to the tank 86 by the pump P10.

  As shown in FIGS. 4 and 5, the image forming unit 21 </ b> Y further includes a developer suction nozzle 53 (suction unit) in addition to the developer supply nozzle 94. 4 shows a partially broken plan view in the vicinity of the supply roller 93, and FIG. 5 shows a side surface in the vicinity of the supply rollers 92 and 93.

Developer supply nozzles 94 are provided at both ends of the vicinity of the nip region 101 of the rollers 92 and 93, respectively. The suction nozzle 53 is connected to a pipe (not shown) at the rear end, and is configured to feed the liquid developer sucked by the pump to the recovery tank 83 (see FIG. 3).

  The tip of each suction nozzle 53 is positioned at a height in the vicinity of the nip region 101 (hereinafter, simply referred to as the nip portion 101) of the rollers 92 and 93, and in the vicinity of both ends of the roller 93 and outside the width of the image formation region Is arranged. By arranging the tip of each suction nozzle 53 in this way, the liquid developer excessively attached to both ends of the roller 93 can be removed by suction.

Here, the conveyance (pumping) capacity of the liquid developer by the rollers 92 and 93 is the flow rate A, the supply capacity from the supply nozzle 94 is the flow rate B, the nip passage capacity is the flow rate C, and the suction nozzles 53 and 53. When the total suction capacity is expressed by their total flow rate D, each flow rate A, B, C, D is preferably configured to satisfy the relationship of the following formula (1).

By satisfying the relationship of the above formula (1), the developer spread in the axial direction of the roller 93 can be reliably collected at the flow rate D before reaching the end of the roller 93. This makes it easy to collect even a highly viscous developer. Further, stable suction performance independent of the roller diameter can be obtained. Further, it is preferable that B> C in order to form a developer pool at the nip entrance above the roller 93 and prevent the developer from running out.
Furthermore, by setting A> B, it is possible to keep only a minimum amount of developer on the roller 93, which is effective in maintaining the stability of the developer.

  Further, as shown in FIG. 5, the tip of the supply nozzle 94 is located near the nip portion in the same manner as the suction ports of the respective suction nozzles 53, so that the amount of developer accumulated on the roller 93 is practically zero. It becomes possible. In this case, the transport of the liquid developer can be stopped more reliably by stopping the supply of the developer from the supply nozzle 94, stopping the driving of the rollers 92 and 93, and stopping the suction by the suction nozzles 53 in this order. .

An elastic sealing material 55 (elastic member) is filled between the container 9 and the end surfaces of the rollers 92 and 93, particularly between both end surfaces of the rollers 92 and 93 near the nip portion, and are in pressure contact with the end surfaces of the rollers 92 and 93. . As a result, the developer spread to the end surface of the roller 93 without being completely sucked is prevented from entering the end surfaces of the rollers 92 and 93 by the elastic seal 55, so that liquid developer is reliably prevented from accumulating on the roller end surface. be able to.
The elastic seal 55 is not particularly limited as long as it does not absorb the liquid developer and has elasticity, and examples thereof include chloroprene rubber (CR), nitrile rubber (NBR), polyurethane, and silicone rubber.

  By being configured in this way, the adhesion of the developer to both ends of the rollers 92 and 93 is suppressed. As a result, the developer is prevented from being excessively supplied to the supply roller 40b and the development roller 40a on the downstream side, The developer layer thickness on the surface of the developing roller 40a can be kept constant, and a constant image quality can be maintained.

  Next, another embodiment of the present invention is shown in FIG. In this embodiment, a pumping type developing device 109 is used instead of the developing device 1 shown in FIG. Others are the same as those in the above-described embodiment, and thus the same components are denoted by the same reference numerals and description thereof is omitted.

  In the developing device 109 according to this embodiment, a developing roller 91, a supply roller 192, and a pumping roller 193 are disposed in a developing container 194 in this order. Each roller 91, 192, 193 is configured to rotate in opposite directions (the direction of rotation is indicated by an arrow). A toner concentration measuring device 198 and a liquid level monitoring sensor 199 are provided on the wall surface near the bottom of the container 194.

  The developing container 194 stores the developer (the stored developer is indicated by a symbol L). When the toner concentration in the developing container 194 measured by the toner concentration measuring device 198 is lower than a specified value, a high-concentration liquid developer having a toner concentration higher than that of the developer stored in the developing container 194 is supplied. A required amount of high-concentration liquid developer is supplied to the developing container 40 from the supply nozzle 201. On the other hand, when the toner concentration measured by the toner concentration measuring device 198 is higher than the specified value, a required amount of carrier liquid is supplied from the supply nozzle 202 for supplying the carrier liquid to the developing container 194.

  The supply roller 192 and the pumping roller 193 constitute the developer conveying means of the present invention. At the bottom of the developing container 194, stirring spirals 196 and 197 for stirring the stored developer are installed.

  Further, a supply roller doctor blade 195 is in pressure contact with the supply roller 192 and a development cleaning blade 961 is in pressure contact with the development roller 91 to remove excess developer.

  In the developing device 109 configured as described above, the pumping roller 193 has its lower half nearly immersed in the stored developer in the developing container 40, and rotates in this state to pump up the developer. The developer thus pumped up is sent to the developing roller 91 through the supply roller 192, and a part thereof is used for development. The remaining excess developer is removed by the doctor blade 195 and the cleaning blade 961 and falls in the developing container 194.

  A liquid level monitoring sensor 199 disposed in the developing container 194 detects whether or not the liquid level of the developer in the developing container 194 is a predetermined value. When it is detected that the liquid level of the developer is lower than the predetermined value, the high-concentration developer is supplied from the nozzle 201 and the carrier liquid is supplied from the nozzle 202 to the predetermined liquid level in the container 40 at a specified rate. The

  Also in this embodiment, a suction nozzle 200 similar to the suction nozzle 53 in the above-described embodiment is provided in the vicinity of the nip region between the supply roller 192 and the pumping roller 193 and outside the image forming region width of the rollers 192 and 193. It arrange | positions similarly to embodiment. Further, it is desirable that an elastic seal similar to the elastic seal 55 in the above-described embodiment is filled between the developing container 40 and the rollers 192 and 193.

  In this way, the adhesion of the developer to both ends of the pumping roller 193 is suppressed, so that the developer is not excessively supplied to the supply roller 192 and the development roller 91 on the downstream side, and the development of the surface of the development roller 91 is prevented. The layer thickness of the agent can be kept constant, and a constant image quality can be maintained.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above embodiment. For example, one suction nozzle 53 is provided at each end of the roll, but it is needless to say that two or more suction nozzles may be provided at both ends.

1 is a schematic explanatory diagram illustrating an embodiment of an image forming apparatus of the present invention. It is explanatory drawing which shows the outline | summary of the image forming unit 21Y shown in FIG. FIG. 3 is an explanatory diagram illustrating a liquid developer circulation processing mechanism in the image forming unit 21 </ b> Y illustrated in FIG. 2. FIG. 3 is a partially broken plan view showing the vicinity of a supply roller 93 in FIG. 2. FIG. 3 is a schematic side view showing the vicinity of supply rollers 92 and 93 in FIG. 2. It is explanatory drawing which shows the outline | summary of the image forming unit in the image forming apparatus concerning other embodiment of this invention. (A) shows a state in which the developer has adhered to both ends of the pumping roller in the conventional image forming apparatus, and (b) shows a state in which the developer in (a) has been excessively supplied to both ends of the supply roller. It is explanatory drawing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Photosensitive drum (electrostatic latent image carrier)
DESCRIPTION OF SYMBOLS 11 Charging device 12 Exposure device 13 Neutralizing device 20 Primary transfer roller 21Y Image forming unit corresponding to yellow color 29 Primary transfer belt 53 Suction nozzle 91 Developing roller 92 Supply roller 93 Supply roller 94 Developer supply nozzle

Claims (6)

An electrostatic latent image carrier, a developer carrier for supplying a liquid developer to the electrostatic latent image carrier, and a developer conveying means for conveying the liquid developer to the developer carrier, An image forming apparatus for developing a latent image on the electrostatic latent image carrier using a liquid developer,
The developer conveying means is composed of at least two or more rollers facing each other, and is provided with at least two suction means in the vicinity of the nip region of the rollers, and suctions excess liquid developer using the suction means. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the suction unit is disposed outside an image forming region width.   3. The image forming apparatus according to claim 1, wherein an end face of the roller is pressed by an elastic member to prevent the liquid developer from entering the end face of the roller.   The image forming apparatus according to claim 1, further comprising a supply unit that supplies the liquid developer to a vicinity of a nip region of the roller. The conveyance capacity of the liquid developer by the roller is a flow rate A, the supply capability from the supply unit is a flow rate B, the nip passage capability is a flow rate C, and the total suction capability by at least two suction units is the total flow rate thereof. 5. The image forming apparatus according to claim 4, wherein each of the flow rates A, B, C, and D satisfies the relationship of the following formula (1) when represented by D. 6.

  The image forming apparatus according to claim 4, wherein the stop of the transport of the liquid developer is controlled in the order of stop of the supply of the liquid developer, stop of driving of the roller, and stop of suction.

Images