JP4821919B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent developing accuracy from being deteriorated and to prevent a developer carrier and a latent image carrier from being damaged. <P>SOLUTION: By satisfying first and second conditions simultaneously, developer 32 is made to lie on an entire abutting part between a photoreceptor and a developing roller 31, so that a surface of the photoreceptor or the developing roller 31 is prevented from being damaged. By satisfying a third condition, the unnecessary developer 32 on the photoreceptor is all removed finely before developing an electrostatic latent image formed in an image area on the photoreceptor by the developing roller 31, so that the unnecessary developer 32 is prevented from remaining and being accumulated on the photoreceptor. The developing accuracy is therefore prevented from being deteriorated, for example, ghost is caused by accumulation of the useless developer 32 on the photoreceptor. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

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

  Conventionally, a charged photosensitive member (latent image carrier) is exposed by an exposure unit to form an electrostatic latent image on the photosensitive member, and toner is attached to the photosensitive member by a developing unit to reveal the electrostatic latent image. 2. Description of the Related Art An electrophotographic image forming apparatus in which a toner image is formed by forming an image and the toner image is transferred onto a transfer sheet to obtain a predetermined image has been put into practical use. Here, as a developing method of the developing means, a wet developing method using a developer (liquid developer) in which toner is dispersed in a liquid carrier is known. As an image forming apparatus employing such a wet development system, a developer storage section for storing a liquid developer and a liquid developer supported on the surface by being immersed in the liquid developer, the liquid developer is used. An application roller to be pumped out, a developing roller (developer carrying member) on which a liquid developer is applied to the surface by contacting the application roller, and an electrostatic latent image carried on the surface by contacting the developing roller Is known to include a photoconductor that is developed with a liquid developer. In the image forming apparatus having such a configuration, the liquid developer once carried on the surface of the applying roller is applied to the developing roller, so that the liquid developer is uniformly applied to the surface of the developing roller. The electrostatic latent image carried on the surface of the latent image carrier is developed with the liquid developer uniformly applied to the developing roller as described above, thereby forming an image having no density unevenness.

  However, in the image forming apparatus having such a configuration, the liquid developer accumulated on the end surface of the application roller immersed in the liquid developer runs up to the development roller and the photosensitive member as the application roller rotates. was there. In this way, the amount of liquid developer intervening in the nip portion between the developing roller and the photosensitive member is non-uniform throughout the nip portion due to the liquid developer running from the end surface of the coating roller to the developing roller and the photosensitive member. End up. As a result, density unevenness occurs in the formed image, and development accuracy deteriorates.

  In order to solve such a problem, a technique described below has been conventionally proposed. For example, in the apparatus described in Patent Document 1, the length in the width direction of the developing roller is configured to be longer than the length of the application region of the application roller and shorter than the length of the application roller including the non-application region. This prevents the liquid developer collected on both end faces of the application roller from running up to the developing roller. In other words, by configuring the coating roller so that the entire length of the coating roller is longer than that of the developing roller, both ends of the coating roller do not come into contact with the developing roller. As a result, the liquid developer accumulated on both end surfaces of the coating roller is developed. It is possible to prevent the roller from running up. Further, since the entire length of the developing roller is configured to be longer than the application area of the application roller, both ends of the development roller do not come into contact with the application area of the application roller. It is possible to prevent the agent from accumulating. In this way, it is possible to prevent image quality deterioration such as density unevenness occurring in the obtained image due to the useless liquid developer running from the coating roller to the developing roller.

JP 2000-235306 A (paragraph [0019], FIG. 4)

  By the way, a coating region is provided at a substantially central portion of the developer carrier (developing roller) corresponding to the surface region of the latent image carrier that forms an image. Then, development processing is executed using the developer carried on the application area of the developer carrying body. However, the apparatus configured as described above may have the following problems. That is, at the contact portion between the developer carrier and the latent image carrier, the central portion (application region) of the developer carrier to which the liquid developer is applied and the developer carrier to which the liquid developer is not applied Since the coefficient of friction between the both ends of the body and the latent image carrier is different, the developer carrier and the latent image carrier are prevented from rotating smoothly while being in contact with each other. As a result, the developer carrier or the surface of the latent image carrier may be scratched at both ends of the developer carrier to which the liquid developer is not applied and the contact portion between the latent image carrier and the developer carrier. there were.

  The present invention has been made in view of the above problems, and an object of the present invention is to prevent the development accuracy from being deteriorated and to prevent the developer carrier and the latent image carrier from being damaged.

In order to achieve the above object, the present invention develops an electrostatic latent image with a latent image carrier that rotates and moves in a first direction and a liquid developer applied from a coating area while contacting the latent image carrier. And a coating member that has the coating region over the entire width in the second direction orthogonal or substantially orthogonal to the first direction, and applies the liquid developer to the developer carrier in the coating region. A regulating member that regulates the amount of liquid developer carried by the coating member in the coating region, a transfer unit that transfers a toner image on the latent image carrier developed by the developer carrier, comprising a first cleaning member for removing the liquid developer on the latent image bearing member passes through the transfer portion, and a second cleaning member for removing the liquid developer on the developer carrier, before Symbol second direction The width of the coating area The width of the developer carrying member, the latent image bearing member of an image area of width, the width of the first cleaning member, restricting the width of the regulating member regulates the amount of liquid developer carried on the coating region, When the widths of the second cleaning members are W1, W2, W3, W4, W5, and W6, respectively, the first condition (condition A), the second condition (condition B), the third condition (condition C), It has 5 conditions (condition D) .

  Here, the first condition is a configuration in which W1> W2 and both end portions of the developer carrying member in the second direction are disposed inside both end portions of the application region. The second condition is a configuration in which W2> W3 and both end portions of the image area in the second direction are disposed inside both end portions of the developer carrier. The third condition is a configuration in which W4> W2 and both end portions of the developer carrying member in the second direction are arranged inside the both end portions of the first cleaning member.

  With such a configuration, by satisfying the first condition, both end portions of the developer carrying member in the second direction are arranged inside both end portions of the application region, so that the liquid accumulated at the end of the application region. The developer can be prevented from running up to the developer carrying member. Therefore, it is possible to prevent the liquid developer from being applied nonuniformly on the surface of the developer carrying member by the rushed liquid developer. Therefore, by developing the electrostatic latent image formed in the image area of the latent image carrier with the liquid developer applied nonuniformly on the developer carrier, density unevenness occurs in the formed toner image. Can be prevented.

  Moreover, the following effects can be obtained by satisfying the first and second conditions at the same time. First, since the first condition is satisfied, both ends of the developer carrier in the second direction are arranged inside the both ends of the application region, so that the liquid developer is spread over the entire surface of the developer carrier. Can be applied. In addition, since the second condition is satisfied, both end portions of the image area in the second direction are arranged inside the both end portions of the developer carrying member, so that the developing process with the developer on the developer carrying member is executed. During this time, both ends of the developer carrier abut against the latent image carrier outside the image area on the latent image carrier. Therefore, by satisfying the first and second conditions at the same time, the entire contact portion between the latent image carrier and the developer carrier, including the part other than the image area to be developed on the latent image carrier, is formed. A liquid developer can be interposed. Therefore, the friction coefficient of the entire corresponding contact portion can be made the same, and the rotation of the latent image carrier and the developer carrier can be stabilized while abutting. Therefore, it is possible to prevent the surface of the developer carrier or the latent image carrier from being damaged.

  Furthermore, by satisfying the third condition, the both ends of the developer carrying member in the second direction are disposed inside the both ends of the first cleaning member, so that the liquid development remaining on the latent image carrying member can be obtained. All of the agent can be removed including the liquid developer adhering to areas other than the image area on the latent image carrier. Therefore, before the electrostatic latent image formed on the image area on the latent image carrier is developed by the developer carrier, all unnecessary liquid developer on the latent image carrier can be removed cleanly. Further, it is possible to prevent unnecessary liquid developer from remaining and accumulating on the latent image carrier. Therefore, it is possible to prevent the development accuracy from deteriorating due to, for example, ghosting due to accumulation of useless liquid developer on the latent image carrier.

  A regulating member that regulates the amount of the liquid developer on the developer carrying member; and wherein the regulating member is capable of regulating the amount of the liquid developer carried in the application region. When the regulation width is W5, the fourth condition may be satisfied. Here, the fourth condition is a configuration in which W5> W2 and both end portions of the developer carrying member in the second direction are disposed inside both end portions of the regulation width. With such a configuration, by satisfying the fourth condition, both ends of the developer carrying member in the second direction are arranged inside both ends of the regulation width, and therefore the entire surface of the developer carrying member The liquid developer whose liquid amount is regulated can be applied as a uniform film. As described above, since the liquid developer can be uniformly applied to the entire surface of the developer carrier, the liquid developer uniformly applied to the developer carrier is formed in the image region on the latent image carrier. The electrostatic latent image can be developed. Therefore, density unevenness when developing the electrostatic latent image can be suppressed. In addition, since the liquid amount of the liquid developer is regulated and applied to the developer carrier, it is possible to prevent wasteful liquid developer from remaining and collecting at the end of the developer carrier and the like. Can do.

Also, the fifth condition, with W6> W2, both end portions of the developer carrying member in the second direction is configured to be disposed inside the both end portions of the second cleaning member. With such a configuration, by satisfying the fifth condition, both ends of the developer carrying member in the second direction are disposed inside both ends of the second cleaning member. After the electrostatic latent image is developed, any unnecessary liquid developer remaining on the developer carrying member can be removed before the liquid developer is applied to the surface from the application region. Therefore, when a liquid developer is applied to the surface of the developer carrier, unnecessary liquid developer remains on the surface, preventing the liquid developer from being applied unevenly on the surface. can do. Therefore, by developing the electrostatic latent image formed in the image area on the latent image carrier with the liquid developer applied nonuniformly on the developer carrier, density unevenness is caused in the formed toner image. Can be prevented. Further, every time the electrostatic latent image formed in the image area on the latent image carrier is developed, all unnecessary liquid developer is removed from the developer carrier, so that the developer carrier It is possible to prevent unnecessary liquid developer from accumulating at the end of the sheet. Therefore, it is possible to prevent the accumulated unnecessary liquid developer from entering the contact portion between the developer carrying member and the image area on the latent image carrying member. Therefore, developing the electrostatic latent image on the latent image carrier with wasteful liquid developer around the contact portion may cause uneven density in the formed toner image. Deterioration can be prevented.

  In addition, the coating area, the developer carrier, and the image area may be configured such that the central portions of W1, W2, and W3, which are the widths in the second direction, are linear or substantially linear.

1 is a diagram illustrating an internal configuration of a printer that is a first embodiment of the present invention. FIG. The principal part enlarged view of FIG. FIG. 2 is a block diagram showing an electrical configuration of the printer. FIG. 3 is a schematic diagram illustrating a positional relationship between a developing unit and a photoreceptor cleaning unit. Sectional drawing which looked at FIG. 2 from the AA sectional view of FIG. The perspective conceptual diagram which shows an anilox roller. The schematic diagram of a wire bar.

  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 image forming apparatus is a so-called tandem type color printer, and the four-color photoconductors of yellow (Y), magenta (M), cyan (C), and black (K) are used as the “latent image carrier” of the present invention. 11Y, 11M, 11C, and 11K are arranged in the apparatus main body 2 side by side. This printer employs a wet development system to form a full-color image by superimposing the toner images on the photoconductors 11Y, 11M, 11C, and 11K, or a monochrome image using only a black (K) toner image. Is formed. In this printer, when a print command signal including an image signal is given to the main control unit 100 from an external device such as a host computer, the engine control unit 110 causes each part of the engine unit 1 to respond to the control signal from the main control unit 100. The image corresponding to the image signal is printed out on the recording medium 4 such as transfer paper, copy paper, and OHP paper conveyed from the paper feed cassette 3 disposed in the lower part of the apparatus main body 2.

  In the engine unit 1, four photoconductors 11 </ b> Y, 11 </ b> M, and 11 </ b> C arranged in parallel along the circumferential direction 47 of the intermediate transfer belt 41 (corresponding to the “transfer medium” of the present invention) that is one component of the transfer unit 40. , 11K, a charging unit 12, an exposure unit 20, a developing unit 30 (30Y, 30M, 30C, 30K) and a photoconductor cleaning unit 14 are provided. Further, the developing units 30Y, 30M, 30C, and 30K each have a tank 33 (33Y, 33M, 33C, and 33K) (corresponding to the “developer storage unit” of the present invention) that stores a developing solution 32 in which each color toner is dispersed. Each has. Note that the configurations of the charging unit 12, the exposure unit 20, the developing unit 30, and the photosensitive member cleaning unit 14 are the same for all toner colors. Therefore, here, the configuration relating to yellow will be described, and the other toner colors will be denoted by the same or corresponding symbols, and description thereof will be omitted.

  As shown in FIG. 2, the photoconductor 11Y is rotatably provided in the direction of the arrow D1 (in the drawing, the clockwise direction, corresponding to the “first direction” of the present invention), and its diameter is about 40 mm. . A charging unit 12, a developing roller 31, a charge eliminating unit (not shown), and a photoconductor cleaning unit 14 are disposed around the photoconductor 11Y along the rotation direction. Further, a surface area between the charging unit 12 and the developing position 16 is an irradiation area of the light beam 21 from the exposure unit 20. The charging unit 12 is applied with a charging bias from the charging bias generator 111 to uniformly charge the outer peripheral surface of the photoconductor 11Y to a predetermined surface potential Vd (for example, Vd = DC + 600 V), and functions as a charging unit. Have.

  A light beam 21 formed by a laser, for example, is irradiated from the exposure unit 20 toward the outer peripheral surface of the photoreceptor 11Y uniformly charged by the charging unit 12. The exposure unit 20 exposes the photoconductor 11Y by the light beam 21 in accordance with a control command given from the exposure control unit 112, and forms a yellow electrostatic latent image corresponding to the image signal on the photoconductor 11Y. Thus, 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 11Y, and an electrostatic latent image for yellow corresponding to the image signal is formed on the photoconductor 11Y. . When a patch image is formed as necessary, a control signal corresponding to a patch image signal of a predetermined pattern (for example, a solid image, a fine line image, a white line image, etc.) set in advance is controlled from the CPU 113. A yellow electrostatic latent image corresponding to the pattern is given to the portion 112 and formed on the photoconductor 11Y.

  The yellow electrostatic latent image formed in this way is visualized by yellow toner supplied from the developing roller 31 of the developing unit 30Y (developing step). The yellow toner image formed on the photoconductor 11Y is conveyed to a primary transfer position 42Y (corresponding to the “transfer position” in the present invention) facing the primary transfer roller 53Y as the photoconductor 11Y rotates. The The primary transfer roller 53Y is disposed so as to sandwich the intermediate transfer belt 41 with the photoreceptor 11Y. The intermediate transfer belt 41 is stretched around a plurality of rollers 43a to 45. The intermediate transfer belt 41 and the photosensitive member 11Y are moved in a direction 47 (counterclockwise in FIG. 1) that is driven by the driving motor (not shown). Drive around at the same peripheral speed. When a primary transfer bias (for example, DC-400 V) is applied from the transfer bias generator 115, the yellow toner image on the photoreceptor 11Y is primarily transferred to the intermediate transfer belt 41 at the primary transfer position 42Y ( Transfer process). The residual charge on the photoconductor 11Y after the primary transfer is removed by a neutralization unit such as an LED, and the residual developer is removed by the photoconductor cleaning unit 14. The configuration and operation of the developing unit 30Y and the configuration and operation of the photoconductor cleaning unit 14 will be described in detail later.

  The other toner colors are configured in the same manner as yellow (Y), and a toner image corresponding to the image signal is formed. The yellow (Y), magenta (M), cyan (C), and black (K) toner images formed on the photoconductors 11Y, 11M, 11C, and 11K are primary transfer rollers 53Y, 53M, and 53C. , 53K and primary transfer positions 42Y, 42M, 42C, and 42K, respectively, are superimposed on the surface of the intermediate transfer belt 41 to form a full-color toner image.

  The toner image formed on the intermediate transfer belt 41 is conveyed to a secondary transfer position 49 sandwiched between rollers 45 and 48 as the intermediate transfer belt 41 rotates. On the other hand, the recording medium 4 accommodated in the paper feed cassette 3 (FIG. 1) is conveyed to the secondary transfer position 49 by a conveyance unit 70 described later in synchronization with the conveyance of the primary transfer toner image. The roller 48 rotates in the direction of following the intermediate transfer belt 41 (clockwise in FIG. 1) at the same peripheral speed as the intermediate transfer belt 41, and a secondary transfer bias is applied from the transfer bias generator 115. Then, the toner image on the intermediate transfer belt 41 is secondarily transferred to the recording medium 4. As the roller 48, for example, a rubber having a rubber hardness of about 50 degrees in JIS-A and having a diameter of about 25 mm can be used. In this embodiment, since roller transfer is adopted, the transfer condition can be set by constant voltage control, or the transfer condition can be set by constant current control. Further, instead of roller transfer, transfer may be performed by corona discharge. In this case, transfer conditions can be set by controlling the output of corona discharge. The residual developer on the intermediate transfer belt 41 after the secondary transfer is removed by the cleaning blade 51.

  The recording medium 4 onto which the toner image has been secondarily transferred as described above is conveyed along a predetermined conveying path 5 (the chain line in FIG. 1), and the toner image is fixed to the recording medium 4 by the fixing unit 60. Then, it is discharged to a discharge tray provided at the upper part of the apparatus main body 2. The fixing unit 60 includes a heating roller 61 incorporating a heater 61 h and a pressure roller 62 that contacts the heating roller 61. The heater controller 116 controls the operation of the heater 61h, so that the fixing temperature in the fixing unit 60 can be adjusted to an arbitrary temperature.

  In the image forming apparatus according to this embodiment, a transport unit 70 for transporting the recording medium 4 along a predetermined transport path 5 is provided. As shown in FIG. 1, the transport unit 70 is provided with a paper feed roller 71 corresponding to the paper feed cassette 3, and the recording medium 4 accommodated in the paper feed cassette 3 is received by the paper feed roller 71. Each sheet is taken out and conveyed to the feed roller 72. The feed roller 72 transports the recording medium 4 to the gate roller 73 and temporarily stands by at the gate roller position. Then, as described above, the gate roller 73 is driven at the timing corresponding to the secondary transfer operation, and the recording medium 4 is sent to the secondary transfer position 49. Further, on the discharge tray side, a pre-discharge roller 74, a discharge roller 75, and a reverse roller 76 are provided, and the secondary transferred recording medium 4 passes through the fixing unit 60, the pre-discharge roller 74, and the discharge roller 75. It is conveyed to the discharge tray side.

  Here, in order to perform double-sided printing, it is necessary to reverse the recording medium 4 and transport it to the gate roller 73 again, so that the discharge roller 75 can rotate forward and backward. That is, when the recording medium 4 is directly discharged to the discharge tray, the recording medium 4 continues to rotate forward and is completely conveyed to the discharge tray. On the other hand, when reversing and refeeding, when the rear end of the recording medium 4 reaches a predetermined position between the pre-discharge roller 74 and the discharge roller 75, the discharge roller 75 rotates reversely to reverse the recording medium 4. Feed into roller 76. As a result, the recording medium 4 is conveyed to the refeed intermediate roller 77 along the reverse path 5a. Then, the re-feed intermediate roller 77 and the pre-re-feed gate roller 78 transport the recording medium 4 to the gate roller 73 and temporarily stand by at the gate roller position. In this way, reverse refeeding of the recording medium 4 is performed. At this time, the surface of the recording medium 4 that is in contact with the intermediate transfer belt 71 at the secondary transfer position 49 and onto which an image is transferred is the surface opposite to the surface on which the image has been previously transferred. In this way, images can be formed on both sides of the recording medium 4. Further, when the secondary transfer is performed on the opposite surface, the surface on which the image has been transferred first comes into contact with the roller 48. At this time, the toner not completely fixed on the recording medium 4 is applied to the roller 48. May adhere. Thus, the toner adhering to the roller 48 is removed by the cleaning blade 52.

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

  The memory 117 of the engine control unit 110 includes a ROM that stores a control program of the CPU 113 including preset fixed data, a RAM that temporarily stores control data of the engine unit 1 and a calculation result by the CPU 113, and the like. Become. The CPU 113 stores data relating to the image signal sent from the external device via the CPU 101 in the memory 117.

  Next, the configuration and operation of the developing unit 30Y and the configuration and operation of the photoconductor cleaning unit 14 will be described in detail with reference to FIGS. 2 and 4 to 6. 4 is a schematic diagram showing the arrangement relationship between the developing unit and the photosensitive member cleaning unit, and is a diagram seen from the left side in FIG. 2, and FIG. 5 is a cross-sectional view of FIG. FIG. 6 is a conceptual perspective view of an anilox roller having grooves formed on the surface. The configurations of the developing units 30M, 30C, and 30K are the same as the configuration of the developing unit 30Y, and the same components are denoted by the same or corresponding reference numerals, and the description thereof is omitted.

  The developing unit 30Y includes, in addition to the developing roller 31 (corresponding to the “developer carrier” of the present invention), a tank 33Y that stores a developer 32 in which yellow toner is dispersed, and a developer that is stored in the tank 33Y. A stirring roller 37 that stirs 32, a coating roller 34 that pumps the developer 32 and applies it to the developing roller 31, and a regulation blade 35 that uniformly regulates the thickness of the developer layer on the coating roller 34 (present invention). And a developing roller cleaning unit 36 that removes the developer remaining on the developing roller 31 after the toner is supplied to the photoconductor 11Y. The developing roller 31 rotates at a peripheral speed substantially equal to that of the photoconductor 11Y in the direction of following the photoconductor 11Y (counterclockwise in FIG. 2). Further, the application roller 34 rotates at a circumferential speed substantially equal to that of the developing roller 31 in a direction (clockwise in the figure) that follows the developing roller 31.

  In this embodiment, the developer 32 (corresponding to the “liquid developer” of the present invention) is applied to a color pigment having an average particle size of about 0.1 to 5 μm, an adhesive such as an epoxy resin to which the color pigment is adhered, and a toner. A toner composed of a charge control agent that gives a predetermined charge, a dispersant that uniformly disperses the color pigment, and the like is dispersed in a liquid carrier. In this embodiment, for example, a silicone oil such as polydimethylsiloxane oil is used as the liquid carrier, and the toner concentration is 5 to 40% by weight. 2% 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 100 to 10,000 mPa · s.

  In this embodiment, the distance between the photoconductor 11Y and the developing roller 31 (development gap = thickness of the developer layer) is set to, for example, 5 to 40 μm, and the development nip distance (the developer layer is the photoconductor 11Y 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.

  The agitating roller 37 draws up the developer 32 stored in the tank 33Y and conveys it to the application roller 34. The lower portion of the stirring roller 37 is immersed in the developer 32 stored in the tank 33Y, and is spaced apart from the coating roller 34 with a width of about 1 mm. Further, the stirring roller 37 is rotatable around its central axis, and the central axis is below the rotation central axis of the application roller 34. Further, the stirring roller 37 rotates in the same direction as the rotation direction of the application roller 34 (clockwise in FIG. 5). The stirring roller 37 has a function of pumping up the developer 32 stored in the tank 33Y and transporting it to the application roller 34, and also has a function of stirring the developer 32 in order to maintain it in an appropriate state. ing. As such a stirring roller, for example, a roller made of metal such as iron and having a diameter of about 20 mm can be used.

  The application roller 34 supplies the liquid developer 32 conveyed from the tank 33Y by the stirring roller 37 to the developing roller 31. This application roller 34 is called a so-called anilox roller in which grooves 34a are formed in a uniform and spiral shape on the surface of a metallic roller such as iron and nickel plated, as shown in FIG. Its diameter is about 25 mm. In the present embodiment, as shown in FIG. 6, a groove 34a is formed with the entire surface of the application roller 34 as the application region. Further, the width of the coating roller 34 in the X direction (see FIGS. 4 and 6, corresponding to the “second direction” of the present invention) substantially perpendicular to the rotation direction D1 of the latent image carrier is W1. The application roller 34 contacts the developing solution 32 while rotating clockwise, thereby supporting the developing solution 32 in the groove 34 a and conveying the supported developing solution 32 to the developing roller 31. Accordingly, the application roller 34 can apply the developer 32 to the developing roller 31 with the width W1 in the X direction in which the groove 34a is formed (the width in the X direction of the application region).

  Further, the surface of the application roller 34 is in pressure contact with a later-described elastic layer of the development roller 31 in order to appropriately apply the developer 32 on the application roller 34 to the development roller 31. Further, the application roller 34 can rotate around its central axis, and the central axis is below the rotation central axis of the developing roller 31. The application roller 34 rotates in a direction (clockwise in FIG. 5) opposite to the rotation direction of the developing roller 31 (counterclockwise in FIG. 5).

  The regulation blade 35 abuts on the surface of the application roller 34 and regulates the amount of the developer 32 on the application roller 34. That is, the regulation blade 35 plays a role of scraping off the excess developer 32 on the application roller 34 and measuring the amount of the developer 32 on the application roller 34 supplied to the development roller 31. The width of regulation in the X direction that can be regulated is W5. The restriction blade 35 is made of urethane rubber as an elastic body, and is supported by a restriction blade support member 351 made of metal such as iron. The rubber hardness of the regulation blade 35 is about 62 degrees according to JIS-A, and the hardness (about 62 degrees) of the contact portion of the regulation blade 35 with the coating roller 34 surface is the elasticity of the developing roller 31 described later. It is lower than the hardness (about 85 degrees) of the press contact portion of the body layer to the surface of the application roller 34. In the present embodiment, the regulation blade 35 is disposed so that the tip thereof faces the downstream side in the rotation direction of the application roller 34, and performs so-called trail regulation.

The developing roller 31 carries the developer 32 and conveys it to the developing position 16 facing the photoreceptor 11Y in order to develop the electrostatic latent image carried on the photoreceptor 11Y by the developer 32. The developing roller 31 is provided with an elastic body layer as an example of an elastic portion having conductivity on the outer peripheral portion of an inner core made of metal such as iron, and has a diameter of about 20 mm. The elastic body layer has a two-layer structure. As the inner layer, urethane rubber having a rubber hardness of about 30 degrees JIS-A and a thickness of about 5 mm is used, and as the surface layer (outer layer), the rubber hardness is JIS. A urethane rubber having a thickness of about 30 μm at about 85 ° A is provided. The developing roller 31 is in pressure contact with the coating roller 34 and the photoreceptor 11Y in a state of being elastically deformed with the surface layer serving as a pressure contact portion. The width of the developing roller 31 in the X direction is W2.

  Further, the developing roller 31 can rotate around its central axis, and the central axis is below the rotational central axis of the photoconductor 11Y. Further, the developing roller 31 rotates in a direction opposite to the rotation direction D1 of the photoconductor 11Y (counterclockwise in FIG. 3). When developing the electrostatic latent image formed on the photoconductor 11Y, an electric field is formed between the developing roller 31 and the photoconductor 11Y.

  The developing roller cleaning unit 36 includes a rubber developing roller cleaning blade 361 (corresponding to the “second cleaning member” of the present invention) that is in contact with the surface of the developing roller 31, and performs development at the developing position 16. This is an apparatus for removing the developer 32 remaining on the developing roller 31 by scraping it off with the developing roller cleaning blade 361 after it is broken. The width in the X direction (corresponding to the “width of the second cleaning member” in the present invention) in which the developer 32 can be removed by the developing roller cleaning blade 361 is W6. The surface of the developing roller 31 is the width of W6. The developer 32 can be removed.

  In the developing unit 30 </ b> Y configured as described above, the stirring roller 37 rotates around its central axis, thereby pumping up the developer 32 stored in the tank 33 </ b> Y and transporting it to the application roller 34. The developer 32 conveyed to the application roller 34 reaches the contact position of the regulation blade 35 by the rotation of the application roller 34. Then, when passing through the corresponding contact position, the surplus portion of the developing solution 32 is scraped off by the regulating blade 35 and the amount of the developing solution 32 supplied to the developing roller 31 is measured. That is, as described above, the application roller 34 is provided with the groove 34a. Therefore, the regulating blade 35 that contacts the application roller 34 develops from the application roller 34 while leaving the developer 32 carried in the groove 34a. The liquid 32 is scraped off. In addition, since the dimension of the groove 34 a is determined so that the amount of the developer 32 supplied to the developing roller 31 is an appropriate amount, when the regulating blade 35 scrapes off the developer 32 on the application roller 34. In this case, the developer 32 measured in an appropriate amount by the groove 34a remains in the groove 34a.

  In this manner, the developer 32 stored in the tank 33Y is pumped out by the application roller 34, the amount of the developer 32 on the application roller 34 is uniformly regulated by the regulation blade 35, and the uniform developer 32 is It is applied to the surface of the developing roller 31 and conveyed to the developing position 16 facing the photoconductor 11Y as the developing roller 31 rotates. For example, the toner in the developer 32 is positively charged by the action of a charge control agent or the like. Then, the developing solution 32 carried on the developing roller 31 at the developing position 16 is supplied from the developing roller 31 and adheres to the photosensitive member 11Y, and the developing bias Vb (applied to the developing roller 31 from the developing bias generator 114). For example, Vb = DC + 400V), the yellow toner moves from the developing roller 31 to the photoreceptor 11Y, and the yellow electrostatic latent image is visualized. Further, the developer remaining on the developing roller 31 without adhering to the photoconductor 11Y is scraped off by the developing roller cleaning blade 361.

  As described above, the yellow toner image formed on the photoreceptor 11Y in this way is primarily transferred to the intermediate transfer belt 41 at the primary transfer position 42Y, and remains on the photoreceptor 11Y after the primary transfer is completed. The developing solution 32 is removed by the photoconductor cleaning unit 14. The photoconductor cleaning unit 14 includes a rubber photoconductor cleaning blade 141 (corresponding to the “first cleaning member” of the present invention) in contact with the surface of the photoconductor 11Y, and a toner image on the intermediate transfer belt 41. After the primary transfer, the developer 32 remaining on the photoreceptor 11Y can be scraped off and removed by the photoreceptor cleaning blade 141. The width in the X direction (corresponding to the “width of the first cleaning member” in the present invention) by which the photosensitive member cleaning blade 141 can remove the developing solution 32 is W4, and the developing solution 32 is transferred to the photosensitive member 11Y with the width of W4. Can be removed from the surface.

  Subsequently, FIG. 4 shows an arrangement relationship among the photosensitive member 11Y, the developing roller 31, the coating roller 34, the recording medium 4, the photosensitive member cleaning blade 141, the developing roller cleaning blade 361, and the regulating blade 35 in the X direction (second direction). The details will be described with reference to FIG. In the present embodiment, the width W3 in the X direction of the recording medium 4 is the maximum width of the image area in the present invention, that is, the area where the electrostatic latent image is formed on the photoreceptor 11Y.

  In this embodiment, as shown in FIG. 4, the photoconductor 11Y, the developing roller 31, the coating roller 34, and the recording are arranged so that the substantially central portions of the respective widths W1 to W6 in the X direction are positioned on a straight line CL. The medium 4, the photoreceptor cleaning blade 141, the developing roller cleaning blade 361, and the regulation blade 35 are disposed.

Furthermore, in this embodiment,
First condition:
W1> W2 and both ends of the developing roller 31 are arranged inside both ends of the application roller 34 (application region) in the X direction. Second condition:
W2> W3 and both ends of the recording medium 4 (image area) are arranged inside both ends of the developing roller 31 in the X direction. Third condition:
W4> W2 and both end portions of the developing roller 31 are disposed inside the both end portions of the photoconductor cleaning blade 141 in the X direction. Fourth condition:
W5> W2 and in the X direction, both ends of the developing roller 31 are arranged inside both ends of the regulating blade 35 (regulating width). Fifth condition:
The widths W1 to W6 are set so as to satisfy the following five conditions: W6> W2 and both ends of the developing roller 31 are arranged inside the both ends of the developing roller cleaning blade 361 in the X direction. ing.

  Next, operations of the developing unit 30Y and the photoconductor cleaning unit 14 will be described in detail with reference to FIG. First, the developer 32 conveyed to the application roller 34 by the rotation of the stirring roller 37 is carried by the groove 34 a formed on the surface of the application roller 34, and is conveyed to the development roller 31. At this time, the developer accumulated on the end surface 34 b of the application roller 34 moves toward the development roller 31 by the centrifugal force generated by the rotation of the application roller 34. However, since the first condition is satisfied, both ends of the application roller 34 are located outside both ends of the developing roller 31. Accordingly, the developer 32 that runs up the end surface of the application roller 34 by centrifugal force does not adhere to the developing roller 31.

  Further, the amount of the developer 32 applied from the application roller 34 to the developing roller 31 is regulated by the regulating blade 35. However, since the fourth condition is satisfied, the entire surface of the developing roller 31 is satisfied. It is possible to uniformly apply the developer 32 whose amount is regulated. When the second condition is satisfied, a portion other than the image area on the photosensitive member 11Y (for example, the end of the developing roller 31) at the contact portion (developing position 16) between the photosensitive member 11Y and the developing roller 31. (See FIG. 5), the developer 32 can be interposed.

  Further, after the developing process at the developing position 16 is completed, the developer 32 remaining on the surface of the developing roller 31 satisfies the fifth condition, so that the developing remaining at the end of the developing roller 31 is performed. The liquid 32 can be removed cleanly by the developing roller cleaning blade 361. Further, the developer 32 adhering to the photoconductor 11Y during the developing process from the end of the developing roller 31 is cleanly removed by the photoconductor cleaning blade 141 when the third condition is satisfied after the transfer process is completed. .

  As a specific configuration of the image forming apparatus that satisfies the first to fifth conditions, for example, the following can be employed.

Width of coating roller 34 (width of coating area) W1 = 313 mm
Width of developing roller 31 (width of developer carrying member) W2 = 307 mm
Width of recording paper 4 (width of image area) W3 = 297 mm
Width of photosensitive member cleaning blade 141 (width of first cleaning member) W4 = 329 mm
Width of regulation blade 35 (regulation width) W5 = 316mm
The width of the developing roller cleaning blade 361 (the width of the second cleaning member) W6 = 316 mm
The width of the stirring roller 37 is 337 mm.
Photoconductor width 392mm
The width of the intermediate transfer belt 41 is about 320 mm.
Cleaning blade 51, 52 width 316mm
Roller 48 width 300mm
When an image was formed using the image forming apparatus designed as described above, it was possible to prevent the development accuracy from being deteriorated and to prevent the developing roller 31 and the photosensitive member from being damaged. .

  As described above, in this embodiment, by satisfying the first condition, the both end portions of the developing roller 31 are disposed inside the both end portions of the applying roller 34 in the X direction. It is possible to prevent the developer 32 accumulated in 34 b from running up to the developing roller 31 due to the centrifugal force accompanying the rotation of the application roller 34. Therefore, it is possible to prevent the developer 32 from being applied non-uniformly on the surface of the developing roller 31 by the run-up developer 32. Therefore, by developing the electrostatic latent image formed in the image areas of the photoconductors 11Y, 11M, 11C, and 11K with the developer 32 applied nonuniformly on the developing roller 31, the density of the formed toner image is increased. Unevenness can be prevented from occurring.

  Moreover, the following effects can be obtained by satisfying the first and second conditions at the same time. First, since the first condition is satisfied, both ends of the developing roller 31 are arranged inside the both ends of the applying roller 34 (application region) in the X direction. 32 can be applied to the entire surface of the developing roller 31. Since the second condition is satisfied, both end portions of the image area are arranged inside the both end portions of the developing roller 31 in the X direction, so that the developing process using the developer 32 on the developing roller 31 is executed. During this time, both end portions of the developing roller 31 are in contact with the photoconductor outside the image area on the photoconductor. Therefore, by satisfying the first and second conditions at the same time, the developer 32 is interposed in the entire contact portion between the photoconductor and the developing roller 31 including the portion other than the image area to be developed on the photoconductor. Can be made. Therefore, the friction coefficient of the entire corresponding contact portion can be made the same, and the rotation of the photoconductor and the developing roller while abutting can be stabilized. Therefore, it is possible to prevent the surface of the photoreceptor or the developing roller 31 from being damaged.

  Further, since the developing solution 32 is applied to the entire surface of the developing roller 31 by the application roller 34, there is a possibility that the developing solution 32 pools on both end faces of the developing roller 31. Since both end portions of the developing roller 31 are in contact with the photoconductor outside the image area, both end portions of the developing roller 31 are not in contact with the electrostatic latent image formed in the image area on the photoconductor. Therefore, when developing the electrostatic latent image, the electrostatic latent image is developed with the developer 32 accumulated on both end surfaces of the developing roller 31, thereby causing density unevenness in the toner image formed on the photoconductor. It can be prevented from occurring.

  Furthermore, by satisfying the third condition, the both ends of the developing roller 31 are disposed inside the both ends of the photosensitive member cleaning blade 141 in the X direction, and therefore the developer 32 remaining on the photosensitive member. Can be completely removed including the developer 32 adhering to areas other than the image area on the photoreceptor. Therefore, before developing the electrostatic latent image formed on the image area on the photoconductor by the developing roller 31, all the unnecessary developer 32 on the photoconductor can be removed cleanly. It is possible to prevent unnecessary developer 32 from remaining and accumulating. Therefore, it is possible to prevent the development accuracy from deteriorating due to, for example, ghosting due to the accumulation of useless developer 32 on the photosensitive member.

  Further, by satisfying the fourth condition, both end portions of the developing roller 31 are arranged inside the both end portions of the regulation width in the X direction, so that the entire surface of the developing roller 31 is placed on the application roller 34 on the application roller 34. The developer 32 whose amount is regulated can be applied as a uniform film. As described above, since the developing solution 32 can be uniformly applied to the entire surface of the developing roller 31, the electrostatic latent image formed on the image area on the photosensitive member by the developing solution 32 uniformly applied to the developing roller 31. The image can be developed. Therefore, density unevenness when developing the electrostatic latent image can be suppressed. Further, since the amount of the developer 32 is regulated and applied to the developing roller 31, it is possible to prevent the waste liquid developer from remaining on the end surface of the developing roller 31 and collecting.

  Further, by satisfying the fifth condition, both ends of the developing roller 31 are disposed inside both ends of the developing roller cleaning blade 361 in the X direction, so that the electrostatic latent image on the photosensitive member is developed. Thereafter, before the developing solution 32 is applied to the surface by the applying roller 34, all unnecessary developing solution 32 remaining on the developing roller 31 can be removed. Therefore, when the developing solution 32 is applied to the surface of the developing roller 31, unnecessary developing solution 32 remains on the surface, thereby preventing the developing solution 32 from being applied unevenly on the surface. Can do. Therefore, by developing the electrostatic latent image formed in the image area on the photoreceptor with the developing solution 32 applied nonuniformly on the developing roller 31, it is possible to prevent density unevenness from occurring in the formed toner image. Can do. Further, every time the electrostatic latent image formed on the image area on the photosensitive member is developed, all unnecessary developer 32 is removed from the developing roller 31. It is possible to prevent the unnecessary developing solution 32 from being accumulated. Therefore, it is possible to prevent the accumulated unnecessary developer 32 from entering the contact portion between the developing roller 31 and the image area on the photosensitive member. Therefore, developing the electrostatic latent image on the photoconductor with the useless developer 32 wrapping around the contact portion deteriorates the developing accuracy such as density unevenness in the formed toner image. Can be prevented.

  In this embodiment, the developer 32 measured in a certain amount can be applied to the developing roller 31 by carrying the developer 32 in the groove of the application roller 34 (anilox roller). Therefore, the developing solution 32 can be uniformly applied to the developing roller 31 with high accuracy. As described above, the developing roller 31 to which the developing solution 32 is uniformly applied comes into contact with the photosensitive member to develop the electrostatic latent image on the photosensitive member, thereby improving the developing accuracy of the electrostatic latent image. be able to.

  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 of the present invention. For example, in the above embodiment, an anilox roller is used as the application roller 34, but instead, a wire bar 39 as schematically shown in FIG. 7 may be used. The wire bar 39 can be configured by, for example, winding a wire 391 having a wire diameter of 100 μm around a core bar at a pitch interval of 100 μm. A recess 39a between the wires formed by winding the wire 391 around the metal core has the same effect as the groove 34a in the anilox roller (application roller 34).

  In addition, the coating roller 34 and the wire bar 39 described above have a recess in the coating region with the entire width in the X direction as the coating region, but satisfy the above first to fifth conditions. If so, it is of course possible to adopt a configuration in which the end portion does not have a concave portion and the liquid developer (developer 32) cannot be carried by the end portion having no concave portion.

  Moreover, you may use a roller with the flat surface, without using an anilox roller or a wire bar. In this case, a necessary gap may be provided between the regulating blade 35 and the roller, and the distance between the gaps may be set as a film thickness so that the developer 32 is supported on the surface of the roller with the film thickness. Even if comprised in this way, it has the same effect as embodiment mentioned above.

  Moreover, in the said embodiment, although it was set as the structure where the approximate center of each width W1-W6 is located on the straight line CL, it is good also as a structure where the one edge part of each width is located on a straight line.

  In the above embodiment, the exposure unit 20 is provided in a one-to-one correspondence with each of the photoconductors 11Y, 11M, 11C, and 11K, and each of the photoconductors 11Y, 11M, 11C, and 11K has a corresponding electrostatic latent. Although configured to form an image, for example, one exposure unit is provided, and the irradiation direction of the laser beam is switched using a mirror or the like, thereby corresponding to each of the photoreceptors 11Y, 11M, 11C, and 11K. The electrostatic latent image may be formed. In addition, an exposure unit using an LED array may be used, or a latent image writing unit that performs so-called writing charging may be used. In short, any configuration may be used as long as it can form a one-to-one electrostatic latent image on each of the photoconductors 11Y, 11M, 11C, and 11K.

  In the above embodiment, the developing roller is used as the developer carrying member and the drum-like photosensitive member is used as the latent image carrying member. However, even if these are constituted by belt-like members, they do not deviate from the above-described purpose. Have the same effect.

  In the above-described embodiment, the regulation blade 35 performs the trail regulation. However, the regulation blade 35 may be arranged so that the tip of the regulation blade 35 faces the upstream side in the rotation direction of the application roller 34 to perform so-called counter regulation. I do not care.

In the above embodiment, the relationship between the width W1 of the application region and the regulation width W5 of the regulation blade in the X direction (second direction) is W5> W1.
However, if the fourth condition is satisfied,
W1> W5
It doesn't matter. Even if comprised in this way, it has the same effect as the above.

  In the above embodiment, the present invention is embodied in a tandem color printer. However, the configuration according to the present invention may be applied to a so-called monochrome printer.

  In the above embodiment, a printer that prints an image supplied from an external device such as a host computer on transfer paper is described. However, the present invention is not limited to this, and includes a copying machine, a facsimile machine, and the like. The present invention can be applied to a general electrophotographic image forming apparatus. In short, a liquid developer in which toner is dispersed in a liquid carrier is once carried by an application roller, and then the carried liquid developer is applied to the developer carrier and the liquid developer applied to the developer carrier. Thus, the present invention can be applied to all image forming apparatuses that develop an electrostatic latent image on a latent image carrier.

  DESCRIPTION OF SYMBOLS 11 ... Photoconductor (latent image carrier), 141 ... Photoconductor cleaning blade (first cleaning member), 31 ... Developing roller (developer carrier), 32 ... Developer (liquid developer), 33Y, 33M, 33C , 33K ... tank (developer container), 34 ... coating roller (anilox roller), 35 ... regulating blade (regulating member), 361 ... developing roller cleaning blade (second cleaning member), 39 ... wire bar, 41 ... Intermediate transfer belt (transfer medium), D1 ... first direction, X ... second direction, W1 ... width of application area, W2 ... width of developer carrier, W3 ... maximum width of image area, W4 ... first cleaning member Width, W5: regulation width, W6: width of the second cleaning member, CL: straight line

Claims (5)

A latent image carrier that rotates in a first direction;
A developer carrier that abuts the latent image carrier and develops the electrostatic latent image with a liquid developer applied from a coating region;
An application member that has the application region over the entire width in the second direction orthogonal or substantially orthogonal to the first direction, and applies the liquid developer to the developer carrier in the application region;
A regulating member that regulates the amount of liquid developer carried by the coating member in the coating region;
A transfer unit for transferring a toner image on the latent image carrier developed by the developer carrier;
A first cleaning member that removes the liquid developer on the latent image carrier that has passed through the transfer portion;
A second cleaning member for removing the liquid developer on the developer carrier,
Prior Symbol second direction, the coating region of a width, said developer carrying member having a width, the latent image bearing member of an image area of width, the width of the first cleaning member, the regulating member is supported on the coating region and any regulatory width for regulating the amount of the liquid developer, respectively the width of the second cleaning member, when the W1, W2, W3, W4, W5, W6, and having all of the following conditions Image forming apparatus.
Condition A : W1> W2, and both end portions of the developer carrying member in the second direction are disposed inside both end portions of the application region.
Condition B : When W2> W3, both end portions of the image area in the second direction are arranged inside both end portions of the developer carrier.
Condition C : W4> W2, and both end portions of the developer carrying member in the second direction are disposed inside the both end portions of the first cleaning member.
Condition D : W6> W2, and both end portions of the developer carrying member in the second direction are disposed inside both end portions of the second cleaning member.
Condition E: The width W1 of the coating member and the regulation width W5 of the regulation member satisfy W1 <W5. W5> In W2, the end portions of said developer carrying member in the second direction, the image forming apparatus 請 Motomeko 1, wherein that will be located inside the both end portions of the restriction width.   The coating area, the developer carrier, and the image area are provided such that the central portions of W1, W2, and W3, which are widths in the second direction, are positioned on a straight line or a substantially straight line. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the application member is an anilox roller that carries a liquid developer in the application region.   The image forming apparatus according to claim 1, wherein the application member is a wire bar that carries a liquid developer in the application region.

Images