JP2005266278A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that prevents an image defect such as image flow. <P>SOLUTION: The image forming apparatus having a photoreceptor and an exposure means that exposes the surface of the photoreceptor with a light emitting diode is provided with a heat transfer means that guides heat from the exposure means to the vicinity of the photoreceptor and dissipates the heat. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus in which a discharge product generated on the surface of a photoreceptor absorbs moisture and no elephant flow occurs.

  A photosensitive member whose surface is charged and exposed to form an electrostatic latent image; a developing unit that develops the latent image on the surface by attaching toner to the surface of the photosensitive member; and a toner formed by the developing unit An electrophotographic apparatus having transfer fixing means for transferring and fixing an image onto an appropriate recording medium such as plain paper is widely used as a copying machine or a printer.

  In the image forming apparatus, since the photosensitive member is charged by a discharge device such as a corotron, it is considered that if the operation is continued for a long time, the surface of the photosensitive member is deteriorated or discharge products are accumulated.

  Therefore, every time a certain number of prints are performed, it is widely performed to clean the surface of the photoconductor to remove the deteriorated layer and discharge products on the surface.

  Conventionally, it has been common to clean a photoreceptor by bringing a member such as a blade into contact therewith, but the surface of the photoreceptor may be damaged by the blade. In addition, there is a problem that the cleaning ability decreases when the blade is worn.

As a means for solving the problems of the conventional discharge product removal method, an image forming apparatus provided with a renewal means for bringing a single-foam sponge roller into contact with a photosensitive member at a predetermined cycle via a web has been proposed (Patent Document 1). ).
JP-A-8-123195

  In the image forming apparatus, the web is brought into contact with the surface of the photoconductor to mechanically remove the deteriorated layer and discharge products on the surface of the photoconductor, so that the web is brought into contact with the photoconductor. In addition to the need for such a member, when the web comes into contact with the surface of the photoreceptor, the surface of the photoreceptor is marked, and image defects such as brush marks may occur due to the trace.

  Further, since the photosensitive member is usually cleaned every time a predetermined number of sheets, for example, 100 sheets are printed, the discharge products accumulated on the surface of the photosensitive member while adsorbing the photosensitive member adsorb moisture in the air. As a result, defects such as image drift may occur.

  The present invention has been made to solve the above problems, and an object thereof is to provide an image forming apparatus in which image defects such as image flow do not occur.

  The invention according to claim 1 is an image forming apparatus including a photoconductor and an exposure unit that exposes a surface of the photoconductor with a light emitting diode, and conducts heat from the exposure unit to the vicinity of the photoconductor. The present invention relates to an image forming apparatus comprising a heat transfer means for radiating heat.

  In the image forming apparatus, the heat generated by the exposure unit is guided to the vicinity of the photoconductor by the heat transfer unit and dissipated, whereby the surface of the photoconductor is heated and the discharge generated on the surface of the photoconductor is generated. The moisture adsorbed on the product evaporates. Therefore, it is possible to prevent the discharge product from adsorbing moisture in the air and generating an image flow, so that it is not necessary to separately provide a heating means for heating the surface of the photoreceptor. Further, since heat does not accumulate in the exposure means, a light-emitting diode array or a driver circuit mounted with high density can be used as the exposure means, and a high-density image can be obtained.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the heat transfer unit includes the exposure unit, and a development unit that develops the latent image formed on the photoconductor by the exposure unit. The present invention relates to an image forming apparatus provided between the two.

  In the image forming apparatus, since the exposure unit and the development unit are separated by the heat transfer unit, the flow of air in the direction from the development unit to the exposure unit is blocked. In addition, the ambient temperature in the vicinity of the exposure unit is higher than other places in the image forming apparatus, for example, in the vicinity of the development unit, and the exposure unit is usually at a lower position than the development unit, and is therefore heated by the exposure unit. As the air rises, an air flow in the direction toward the developing means is generated. Therefore, the toner cloud generated in the vicinity of the developing unit does not float toward the exposing unit and the exposing unit is not contaminated.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the heat transfer means is a heat sink provided in a driver circuit that drives a light emitting diode provided in the exposure means. About.

  In the image forming apparatus, the surface of the photoconductor is heated by using a heat sink provided in the driver circuit, which is the most heat-generating portion in the exposure unit, so that the discharge product on the surface of the photoconductor absorbs moisture in the air. In addition to preventing the occurrence of image flow due to absorption, overheating of the driver circuit can also be prevented.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the heat transfer unit is configured to dissipate heat from the heat radiating unit disposed in the vicinity of the photoconductor and the driver circuit. The present invention relates to an image forming apparatus including a heat pipe that transmits to a heat radiating unit.

  In the image forming apparatus, heat from the driver circuit is immediately transferred to the heat radiating member by a heat pipe. Therefore, the heat generated in the driver circuit is efficiently removed, and the photosensitive member can be efficiently heated.

  As described above, according to the image forming apparatus of the present invention, the occurrence of image defects such as image flow can be effectively prevented.

1. Embodiment 1
(1) Configuration A color printer as an example of an image forming apparatus that can suitably carry out the image forming method and the discharge product removing method of the present invention will be described below.

  As shown in FIG. 1, the color printer 10 includes a print unit 30 that forms a color image with toners of four colors of cyan, magenta, yellow, and black, a paper feed tray 16 that is positioned below the print unit 30, and a print And a stacking tray 17 located above the unit 30.

  As shown in FIGS. 1 and 2, the print unit 30 is developed by developing units 12C, 12M, 12Y, and 12K for cyan, magenta, yellow, and black, and developing units 12C, 12M, 12Y, and 12K, respectively. Photoconductors 13C, 13M, 13Y, and 13K and an intermediate transfer belt 14. The developing units 12C, 12M, 12Y, and 12K and the photosensitive members 13C, 13M, 13Y, and 13K are arranged in parallel so as to face the intermediate transfer belt. The developing units 12C, 12M, 12Y, and 12K correspond to developing means in the present invention.

  The color printer 10 is a so-called tandem full-color printer, and the four color toner images developed by the developing units 12C, 12M, 12Y, and 12K are transferred onto the intermediate belt 14 while the intermediate transfer belt 14 makes one round. Superimposed.

  Above the paper feed tray 16, a paper feed roller 18 is arranged so as to abut on the leading end of the paper P set in the paper feed tray 16 in the transport direction. Further, the transport path 19 for transporting the paper P is S-shaped upward from the side of the paper feed tray 16 where the paper feed roller 18 is provided to the stacking tray 17 via a transfer unit 22 and a fixing unit 28 described later. It extends to. Two sets of transport rollers 20 are arranged on the transport path 19. The paper P is fed one by one from the paper feed tray 16 along the transport path 19 along the transport path indicated by the two-dot chain line arrow in FIG. 1 by a paper feed roller 18 and a paper handling means (not shown). It is conveyed upward by the conveyance roller 20 and is conveyed to the stacking tray 17 via the transfer unit 22 and the fixing unit 28.

  The transfer unit 22 is provided with a belt conveyance roller 24A around which the intermediate transfer belt 14 is wound, and a transfer roller 26 pressed against the belt conveyance roller 24A. The intermediate transfer belt 14 is sandwiched between the nip portion of the belt conveyance roller 24A and the transfer roller 26, and the toner image is transferred from the intermediate transfer belt 14 when the paper P passes through the nip portion.

  A fixing unit 28 is disposed above the transfer unit 22. The fixing unit 28 includes a heat roller 28A and a backup roller 28B pressed against the heat roller 28A. When the paper P passes through the nip portion between the heat roller 28A and the backup roller 28B, the toner melts and solidifies. The image is fixed. The paper P on which the toner image has been fixed by the fixing unit 28 is discharged onto the stacking tray 17 by a paper discharge roller 29 disposed on the downstream side of the fixing unit 28 in the transport direction.

  Hereinafter, the print unit 30 will be described in more detail.

  As shown in FIGS. 1 and 2, the intermediate transfer belt 14 includes a belt conveyance roller 24A, a belt conveyance roller 24B disposed below the belt conveyance roller 24A, and an obliquely upper side of the belt conveyance roller 24B. It is wound around and supported by a belt conveyance roller 24C disposed on the opposite side of the conveyance path.

  The outer surface of the intermediate transfer belt 14 is a transfer surface 14A to which a toner image is transferred. The development units 12C, 12M, 12Y, and 12K, and the photoreceptors 13C, 13M, 13Y, and 13K face the transfer surface 14A. Are arranged in parallel, and the photosensitive members 13C, 13M, 13Y, and 13K are in contact with the transfer surface 14A. On the other hand, transfer rollers 32C, 32M, 32Y, and 32K are disposed on the opposite side of the photoreceptors 13C, 13M, 13Y, and 13K across the intermediate transfer belt 14, and the intermediate transfer belt 14 includes the transfer rollers 32C, 32M, and 32Y. , 32K are pressed against the photoreceptors 13C, 13M, 13Y, 13K.

  The photoreceptors 13C, 13M, 13Y, and 13K rotate in the counterclockwise direction as indicated by an arrow b in FIG.

  In FIG. 2, a toner concentration detection sensor 15 is disposed adjacent to the downstream side of the photoreceptor 13K with respect to the rotation direction of the intermediate transfer belt 14 indicated by an arrow a and facing the transfer surface 14A. The toner concentration detection sensor 15 has a function of detecting the concentration of toner transferred to the transfer surface 14A.

  Hereinafter, the developing units 12C, 12M, 12Y, and 12K and the photoreceptors 13C, 13M, 13Y, and 13K will be described. Hereinafter, the developing units 12C, 12M, 12Y, and 12K may be collectively referred to as “developing unit 12”, and the photosensitive members 13C, 13M, 13Y, and 13K may be collectively referred to as “photosensitive member 13”.

  As shown in FIGS. 2 and 3, an intermediate transfer belt 14, a brush roller 34, a charging roller 36, and a developing unit 12 are provided around the photoconductor 13 in order along the rotation direction b. The intermediate transfer belt 14, the brush roller 34, and the charging roller 36 are all in contact with the photosensitive surface 13 </ b> A of the photoreceptor 13. Further, between the charging roller 36 and the developing unit 12, an LED array head 40 that performs line exposure of the photosensitive surface 13A is disposed. The LED array head 40 corresponds to the exposure means in the present invention. A heat sink 42 as an example of the heat transfer means of the present invention is fixed to the driver circuit 40A of the LED array head 40. The heat sink 42 extends toward the vicinity of the photoreceptor 13. The distance between the tip of the heat sink 42 and the photosensitive member 13 is 5 mm.

  In addition, as a heat sink that can be mounted on the LED array head 40, a surface opposite to the photosensitive member 13, that is, a heat radiating surface 43A, is formed in a cylindrical shape along the photosensitive surface 13A, as in the heat sink 43 of FIG. Can also be mentioned. The heat sink 43 is disposed such that the distance between the heat radiation surface 43A and the photosensitive surface 13A is 5 mm or less.

  In the example shown in FIGS. 3 and 4, the heat generated in the driver circuit 40 </ b> A is transferred to the heat sink 42 or 43. The heat transmitted to the heat sink 42 or 43 moves toward the heat radiating surface 42A or 43A and is radiated from the heat radiating surface 42A or 43A toward the photosensitive surface 13A. As a result, the photosensitive surface 13A is heated.

  The LED array head 40 can also be equipped with a heat transfer means including a heat radiating member and a heat pipe that transfers heat from the driver circuit to the heat radiating member. An example of the heat transfer means is shown in FIG. 5 includes a mounting portion 44C fixed to the driver circuit 40A of the LED array head 40, a heat radiating portion 44B disposed facing the photoconductor 13, and heat from the mounting portion 44C to the heat radiating portion 44B. It is comprised from the heat pipe 44A which transmits. The heat radiating portion 44B has a heat radiating surface 44D formed in a cylindrical surface shape along the photosensitive surface 13A.

  In the example shown in FIG. 5, the heat generated in the driver circuit 40A moves from the mounting portion 44C to the heat radiating portion 44B via the heat pipe 44A. Then, the heat radiating portion 44B is heated, heat is radiated from the heat radiating surface 44D toward the photosensitive surface 13A, and the photosensitive surface 13A is heated.

  As shown in FIGS. 3 and 4, the developing unit 12 is positioned below the developing roller 38 and the developing roller 38 disposed so as to face the photosensitive member 13, and the two-component developer is placed on the developing roller 38. Screw feeders 39A and 39B, and a housing 37 for housing the developing roller 38 and the screw feeders 39A and 39B. The two-component developer contains toner and magnetic carrier particles as main components. An opening 37 </ b> A is provided in a portion of the housing 37 that faces the photoreceptor 13.

  As shown in FIG. 3, the developing roller 38 is disposed such that a gap, that is, a developing gap is formed between the developing roller 38 and the photosensitive surface 13A. The developing roller 38 includes a cylindrical magnet roll 38B and a sleeve 38A that covers the magnet roll 38B. The magnet roll 38B has a cylindrical shape and is fixed to the color printer 10, and the sleeve 38A moves around the axis of the magnet roll 38B in the rotation direction b of the photosensitive member 13 as shown by an arrow c in FIG. It rotates in the same counterclockwise direction, in other words, in a direction facing the photoconductor 13 at the portion facing the photoconductor 13, and in other words, it rotates against. Thereby, the transfer efficiency of the toner from the developing roller 38 to the photosensitive member 13 is enhanced.

  A trimming blade 41 that aligns the height of the magnetic brush in cooperation with the trimming pole S <b> 2 extends toward the developing roller 38 at the opposing portion of the trimming pole S <b> 2. A negative developing bias voltage is applied to the developing roller 38.

  The operation of the color printer 10 will be described. The color printer 10 is normally operated in a development mode in which an image is formed on the paper P. However, the color printer 10 is operated in a discharge product scraping mode for a predetermined time, for example, 3 to 5 minutes every 100 sheets. The

  The development mode and the discharge product scraping mode will be described below.

(2-1) Development Mode In the development mode, the photoconductor 13 rotates counterclockwise at a constant speed.

  Accordingly, the photosensitive surface 13A is negatively charged by the charging roller 36. Next, the charged surface of the photosensitive surface 13A is exposed by the LED array head 40, whereby the potential of the exposed portion of the charged surface is lowered to form an electrostatic latent image. Then, in the developing unit 12, the toner charged to a negative voltage is electrically attached to the latent image formed on the photosensitive surface 13 </ b> A, that is, the potential lowering portion of the charged surface by the developing roller 38. The electrostatic latent image is developed to form a toner image. The toner adhering to the photosensitive surface 13A is electrically drawn toward the intermediate transfer belt 14 by the transfer roller 32 to which a positive transfer voltage having a polarity opposite to that of the toner is applied. As a result, the toner image on the photosensitive surface 13A is transferred from the photosensitive member 13 to the intermediate transfer belt.

  Hereinafter, the developing process in the developing roller 38 will be described in detail.

  When the sleeve 38A rotates along the rotation direction c, first, the developer supplied into the housing 37 by the screw feeders 39A and 39B is adsorbed on the surface of the sleeve 38A by the pickup pole N2. Here, on the surface of the sleeve 38A, there are a magnetic field from the transport pole N3 toward the development pole S1, a magnetic field from the pick-off pole N1 toward the development pole S1, a magnetic field in the direction from the pickup pole N2 toward the trimming pole S2, and from the transport pole N3. A magnetic field directed to the trimming pole S2 is formed, and the developer has a structure in which toner adheres to the surface of the magnetic carrier particles. Therefore, the developer adsorbed on the surface of the sleeve 38A is arranged in the direction of the lines of magnetic force on the surface of the sleeve 38A. In other words, it rises and forms a magnetic brush.

  The magnetic brush formed on the surface of the sleeve 38A in the vicinity of the pickup pole N2 moves from the trimming pole S2, the transport pole N3, the developing pole S1, and the pickoff pole N1 as the sleeve 38A rotates along the rotation direction c. It is conveyed from right to left. The height of the magnetic brush is made uniform when passing through the trimming pole S2, the toner on the magnetic brush is transferred to the photoconductor 13 in the vicinity of the developing pole S1, and the surface of the sleeve 38A is almost only a magnetic carrier. The brush remains. The magnetic brush, which is almost only a magnetic carrier, falls off the surface of the sleeve 38A at the pick-off pole N1 and returns into the housing 37 as the sleeve 38A rotates.

  In the developing mode, the sleeve 38A rotates in the rotational direction c as described above, so that fresh developer is always replenished at the pickup pole N2 and conveyed to the developing pole S1, and toner is transferred to the photosensitive member at the developing pole S1. 13 and the latent image on the photosensitive surface 13A is developed.

  In the development mode, heat generated by the LED array head 40 is transmitted to the photoconductor 13 by the heat sinks 42 and 43 or the heat transfer member 44. Thereby, the photosensitive surface 13A is heated, and the occurrence of image flow due to moisture absorption by the discharge products formed on the photosensitive surface 13A is prevented. At the same time, the heat generated in the LED array head 40 is removed by the heat sinks 42 and 43 or the heat transfer member 44, so that the LED array head is prevented from overheating.

(2-2) Discharge Product Scraping Mode In the discharge product scraping mode, charging by the charging roller 36 and exposure by the LED array head 40 are stopped, and the developing roller 38 is also stopped. Therefore, since the magnetic brush on the sleeve 38A is also stopped, a new magnetic brush containing a large amount of toner is not replenished from the housing 37. Here, since a developing bias voltage is applied to the developing roller 38, all of the toner remaining on the magnetic brush when the sleeve 38A is stopped is transferred to the photosensitive member 13 and almost or not on the sleeve 38A. A magnetic brush that consists entirely of magnetic carrier particles remains.

  On the other hand, since the photosensitive member 13 rotates in the direction of the arrow b at a constant speed as in the developing mode, the photosensitive surface 13A is rubbed with a magnetic brush on the sleeve 38A. Thereby, the discharge product generated on the photosensitive surface 13A is removed.

  Instead of stopping the sleeve 38A, the sleeve 38A may be rotated intermittently at regular intervals, or it may be rotated at a constant peripheral speed. 5% or less of the peripheral speed of the photoreceptor 13 is preferable.

(3) Features of the color printer of Embodiment 1 As described above, in the color printer 10, the photosensitive surface 13A of the photosensitive member 13 is heated by heat from the heat sinks 42, 43 or the heat transfer member 44. Generation of image defects such as image flow can be effectively prevented without providing a separate heating means for heating the photosensitive member 13. Further, since the heat generated in the driver circuit 40A of the LED array head 40 is also effectively removed, the LED array head 40 is not overheated.

  Further, in the example in which the heat sink 42 or the heat sink 43 is used as the heat transfer means, the LED array head 40 and the developing unit 12 are separated by the heat sink 42 or the heat sink 43, so that the air from the LED array head 40 toward the developing unit 12 The flow of is interrupted. In addition, the ambient temperature of the LED array head 40 is higher than that in other places of the color printer 10, for example, the vicinity of the developing unit 12, and the LED array head 40 is lower than the developing unit 12. As a result, the heated air rises and an air flow in the direction toward the developing unit 12 is generated. Therefore, the toner cloud generated in the vicinity of the developing unit 12 floats toward the LED array head 40 and the LED array head 40 is not contaminated by the toner cloud.

  On the other hand, in the example in which the heat transfer member 44 is used as the heat transfer means, the heat pipe 44A provided in the heat transfer member 44 has very good heat transfer efficiency, so that the heat generated by the LED array head 40 is more efficiently transferred to the photosensitive surface 13A. It has the feature that it can be used for heating.

FIG. 1 is a schematic cross-sectional view illustrating an outline of the configuration of the color printer according to the first embodiment. FIG. 2 is an enlarged view showing a configuration of a printing unit of the laser printer shown in FIG. FIG. 3 is an enlarged cross-sectional view showing the configuration of the developing unit and the vicinity thereof in the print unit shown in FIG. 4 is an enlarged cross-sectional view showing another example in which a heat sink is attached to the LED array head in the developing unit shown in FIG. FIG. 5 is an enlarged cross-sectional view showing an example in which the LED array head is provided with heat transfer means including a heat pipe and a heat radiating member in the developing unit shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Color printer 13 Photoconductor 14 Intermediate transfer belt 34 Brush roller 36 Charging roller 38 Developing roller 40 LED array head 40A Driver circuit 42 Heat sink 43 Heat sink 44 Heat transfer means 44A Heat pipe 44B Heat radiation part

Claims (4)

An image forming apparatus comprising a photoconductor and an exposure unit that exposes a surface of the photoconductor with a light emitting diode,
An image forming apparatus, comprising: a heat transfer means for guiding the heat from the exposure means to the vicinity of the photoconductor to dissipate the heat.   The image forming apparatus according to claim 1, wherein the heat transfer unit is provided between the exposure unit and a developing unit that develops a latent image formed on the photoconductor by the exposure unit.   The image forming apparatus according to claim 1, wherein the heat transfer unit is a heat sink provided in a driver circuit that drives a light emitting diode included in the exposure unit.   The image forming apparatus according to claim 1, wherein the heat transfer unit includes a heat radiating unit disposed in the vicinity of the photoconductor and a heat pipe that transfers heat from the driver circuit to the heat radiating unit.

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