JP2005107053A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of an image forming apparatus of a tandem type in which the color of a formed image is not uniform owing to speed changes in a transfer belt or a transfer conveyance belt, which are caused by fluctuations in friction between the transfer belt or the transfer conveyance belt and a photoreceptor. <P>SOLUTION: The image forming apparatus has a damping member 31. The damping member 31 comes into contact with the back of the intermediate transfer belt 10 between an image forming unit 20 and a tension roller 21 which is one of a plurality of rollers, the image forming unit 20 being disposed upstream, in the moving direction of the intermediate transfer belt 10, of a drive roller 6 which is one of the plurality of rollers and rotates the intermediate transfer belt 10 and being disposed the furthest upstream among the units 20 in the moving direction of the intermediate transfer belt 10, and the tension roller 21 being disposed immediately upstream of the most upstream image forming unit 20. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  _{The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile machine, and more particularly to a tandem color image forming apparatus.}

  _{Generally, as a tandem type full-color image forming apparatus using an electrophotographic process, a toner image is sequentially superimposed and transferred onto an intermediate transfer belt using an intermediate transfer belt (intermediate transfer member) (primary transfer), and a color toner. After forming an image, a color toner image on an intermediate transfer belt is transferred to a recording medium (recording paper, hereinafter simply referred to as paper) at a secondary transfer position to form a color image (such as this). Such a color image forming apparatus is called an intermediate transfer tandem color image forming apparatus). On the other hand, there is also a type in which toner images are sequentially superimposed and transferred onto a sheet conveyed on a sheet transfer conveyance belt to form a color image (such a color image forming apparatus has a direct tandem color image forming apparatus). Called an image forming device).}

  _{In the tandem type image forming apparatus as described above, for example, in an apparatus using an intermediate transfer belt, the frictional resistance between the photosensitive drum and the intermediate transfer belt fluctuates due to variations in the respective surface states. The change in the frictional resistance between the photosensitive drum and the intermediate transfer belt affects the moving speed of the intermediate transfer belt, the moving speed fluctuates, and the transfer position of each color shifts, resulting in uneven color in the formed image. Such a phenomenon occurs. Also, speed fluctuations may occur in the intermediate transfer belt due to impacts caused by turning on / off the transfer bias and contact / separation of the intermediate transfer belt with paper, which may cause uneven color in the formed image.}

  _{In order to prevent the above phenomenon from occurring due to fluctuations in the speed of the intermediate transfer belt, images of yellow, magenta, cyan, and black toner are created on the photosensitive belt and then superimposed on the intermediate transfer belt and transferred onto the paper. In the image forming apparatus configured as described above, in order to prevent the impact when the belt cleaner comes in contact with and separates from the surface of the intermediate transfer belt from being transmitted to the downstream side of the intermediate transfer belt, the rear surface of the intermediate transfer belt is There is one in which a fluctuation suppressing member made of a member having high resistance is brought into contact (see Patent Document 1).}

JP-A-9-160437 (Claim 11, paragraph 0027, FIG. 5)

  _{However, in Patent Document 1, development devices corresponding to four colors are arranged along the photosensitive belt, and the toner images formed on the photosensitive belt are superimposed on the intermediate transfer belt and then transferred onto the paper. In the apparatus having the configuration, the intermediate transfer body cleaner is brought into contact with and separated from the intermediate transfer belt in order to remove the toner remaining on the intermediate transfer belt after the transfer. Has been disclosed, which is relaxed by bringing it into contact with the back surface of the intermediate transfer belt, but is suitable when the fluctuation suppressing member is applied to a tandem type full color image forming apparatus using an intermediate transfer belt or a transfer conveyance belt. There is no consideration regarding the proper arrangement position, and there is a possibility that the effect of the variation suppressing member may not be sufficiently obtained depending on the arrangement place.}

  _{Therefore, in order to solve such a problem, the present invention provides a movable intermediate transfer member supported by a plurality of rollers onto which each color toner image is sequentially superimposed and transferred, and a moving direction of the intermediate transfer member. A plurality of image forming units each having an image carrier that carries a toner image for each color, and a toner image on the image carrier facing the image carrier across the intermediate transfer member. An image forming apparatus having a primary transfer means for transferring to the intermediate transfer body and a secondary transfer means for transferring a toner image on the intermediate transfer body to a recording medium. An image forming unit arranged on the upstream side in the movement direction of the intermediate transfer body and on the upstream side in the movement direction of the intermediate transfer body with respect to a drive roller that rotationally drives a certain intermediate transfer body, and arranged on the most upstream side In front of the upstream image forming unit The image forming apparatus is obtained - color characterized by having a braking member which contacts the rear surface of the intermediate transfer member between one La - multiple filtration.}

  _{In the present invention, it is desirable to provide a facing member that contacts the surface of the intermediate transfer member at a position facing the braking member and sandwiching the intermediate transfer member.}

  _{In the present invention, it is desirable that the surface of the facing member is conductive and grounded.}

  _{Further, in the present invention, it is desirable to change the contact pressure of the braking member against the intermediate transfer member in accordance with the number of images formed.}

  _{Furthermore, according to the present invention, a transfer transfer body that is supported by a plurality of rollers that transport a recording medium, and a toner image for each color that is arranged along the moving direction of the transfer transport body is carried. An image forming apparatus comprising: a plurality of image forming units having an image carrier; and transfer means for transferring a toner image on the image carrier to the recording medium so as to face the image carrier with the conveyance belt member interposed therebetween. The drive roller that rotationally drives the transfer conveyance body, which is one of the plurality of rollers, is disposed upstream of the transfer conveyance body in the movement direction and on the most upstream side in the movement direction of the transfer conveyance body. And a braking member that abuts against the back surface of the transfer conveyance body between the image forming unit formed and the one of the plurality of rollers immediately upstream of the image forming unit disposed on the most upstream side. Color image forming apparatus It is.}

_{Again, in the present invention, an opposing member that contacts the surface of the intermediate transfer member is provided at a position that faces the braking member and sandwiches the intermediate transfer member, and the contact pressure of the braking member to the intermediate transfer member is set as the number of images formed. It is desirable to change according to.}

  _{As described above, according to the first aspect of the present invention, the image forming unit disposed upstream of the intermediate transfer member in the moving direction and on the most upstream side with respect to the moving direction of the intermediate transfer member, and disposed on the most upstream side. Since the braking member that contacts the back surface of the intermediate transfer body between the plurality of rollers immediately upstream of the formed image forming unit is disposed, the intermediate transfer body between the drive roller and the braking member is disposed. In addition, since the speed fluctuation can be prevented, a color image without color unevenness can be obtained.}

  _{According to the second aspect of the present invention, it is possible to prevent a change in color of the color image due to a decrease in transfer efficiency due to a transition of the intermediate transfer belt from a normal position by the contact of the braking member.}

  _{According to the third aspect of the present invention, since the intermediate transfer belt can be neutralized without arranging any other neutralization member for the intermediate transfer belt, an increase in cost can be suppressed.}

  _{According to the invention of claim 4, a good color image can be obtained even when the surface roughness of the intermediate transfer member is deteriorated by repeating the image formation.}

  _{According to the fifth to seventh aspects of the present invention, a good color image can be obtained even in a color image forming apparatus using a transfer conveyance body.}

  _{Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.}

  _{FIG. 1 is a diagram schematically showing an example of an intermediate transfer tandem type color printer 1 used as a color image forming apparatus. In the illustrated printer 1, document image data sent from an external computer (not shown) is shown. Either full-color image output or monochrome image output is selected according to the color information. In FIG. 1, reference numeral 2 denotes an amorphous silicon (a-Si) photosensitive member, an organic photosensitive member (OPC), and the like, which is an image carrier, 3 is a charging unit, 4 is an exposure unit, 5 is a developing device, In the intermediate transfer tandem type color image forming apparatus, the image forming unit 20 composed of the photoconductor 2, the charging unit 3, the exposure unit 4, the developing device 5 and the like is provided for the number of colors such as yellow, magenta, cyan, and black. It is arranged. 10 is an intermediate transfer belt which is an intermediate transfer body for transferring the toner images formed by these image forming units in an overlapping manner, 6 is a drive roll for this intermediate transfer belt, 7 is a fixing device, and 8 is an intermediate transfer belt 10. A cleaning blade 9 for cleaning the remaining residual toner, 9 is a final transfer member, such as transfer paper, recording paper, printing paper, card, envelope, postcard, label paper, OHP sheet, and 11 is a paper feed cassette. .}

  _{FIG. 2 is a schematic configuration diagram showing the relationship between the intermediate transfer belt 10 in FIG. 1 and the driving roller and image forming unit. 21 is a tension roll, 22 is a secondary transfer from the intermediate transfer belt 5 to the final transfer member 9. A backup roll provided at a position 23 is a primary transfer roll for transferring a toner image formed on the photosensitive member 3 to the intermediate transfer belt 5, and 24 is a final toner image transferred onto the intermediate transfer belt 5. This is a secondary transfer roll for transferring to the transfer member 9.}

  _{The operation of the intermediate transfer tandem image forming apparatus will be briefly described with reference to FIG. 2 according to FIG. 1. When print data is sent from a computer (not shown), the control unit of the image forming apparatus performs printing. The data is divided into image data corresponding to, for example, yellow, magenta, cyan, and black. The image data corresponding to each color is appropriately processed and then sent to the exposure unit 4 corresponding to each color, and the surface of the photoreceptor 2 charged by the charging unit 3 is exposed to create an electrostatic latent image. The electrostatic latent image is developed by the developing device 2 to form a toner image on the surface of the photoreceptor 2. The toner images formed on the photoconductors 2 corresponding to the respective colors in this way are transferred in a superimposed manner onto the intermediate transfer belt 10 driven by the driving roll 6 in accordance with the timing by the primary transfer roll. As a result, a color toner image is formed. The color toner image thus formed on the intermediate transfer belt 10 is secondarily transferred to the final transfer member 9 fed from the paper feed cassette 11 by the secondary transfer roll 24 and fixed by the fixing device 7. Eject the paper. The residual toner remaining on the intermediate transfer belt 10 is scraped off and cleaned by the cleaning blade 8 to prepare for the next image formation.}

  _{In FIG. 2, the braking member 31 urged by the urging member 32 abuts on the back surface of the intermediate transfer belt 10 between the image forming unit 20 and the tension roller 21 on the most upstream side as viewed from the drive roller 6. ing. Here, the surface of the braking member 31 is preferably made of a material having a large frictional resistance such as a rubber material, and is preferably made of urethane, EPDM, or the like. Further, the urging member 32 is not particularly limited as long as it is made of a springy member, but is preferably made of a wire spring, a leaf spring, or the like. The braking member 31 is preferably in contact with the intermediate transfer belt 10 over the entire length perpendicular to the conveyance direction of the intermediate transfer belt 10. The braking member 31 is preferably in contact with the back surface of the intermediate transfer belt 10 with a width of 0.1 to 3 mm. In this configuration, the braking member 31 is made of urethane rubber and has a width of 2.2 mm and the intermediate transfer belt 10. It is in contact with the back of the.}

  _{A uniform tension is generated in the intermediate transfer belt 10 between the drive roller 6 and the braking member 31 by the driving force of the driving roller 6 and the braking force of the braking member 31, so that a speed fluctuation occurs in the intermediate transfer belt 10. It is possible to suppress this. This makes it possible to obtain a good color image without color misregistration. The braking force generated by the contact of the braking member 31 is set to a minimum value that does not cause the speed fluctuation of the intermediate transfer belt 10, thereby increasing the driving force for driving the driving roller 6 more than necessary. There is nothing.}

  _{FIG. 3 shows another embodiment of the present invention, and the same reference numerals are assigned to the same components as those in FIG. In FIG. 3, a shaft 34 which is a facing member is brought into contact with the intermediate transfer belt 10 at a position corresponding to the braking member 31 with the intermediate transfer belt 10 interposed therebetween. Note that both ends of the shaft 34 are fixed to a frame of the apparatus main body (not shown). The shaft 34 is preferably configured such that its surface is rotatable so that the intermediate transfer belt can be driven smoothly. As the position of the intermediate transfer belt 10 changes upward in the drawing of the intermediate transfer belt 10 due to the contact of the braking member 31, the angle of entry of the intermediate transfer belt into the nip formed by the photoreceptor 3 and the primary transfer roll 23 is horizontal. The primary transfer efficiency is lowered due to the deviation from the toner image, so that the transfer efficiency of the toner image corresponding to the color of the image forming unit on the most upstream side as viewed from the drive roller 6 to the transfer belt 10 is lowered. Occurrence of a phenomenon that the color of the color toner image formed on the transfer member 9 is different from the desired one is prevented by sandwiching the intermediate transfer belt 10 between the shaft 34 and the braking member 31 that are fixed in position. be able to.}

  _{Note that the surface of the shaft 34 is made of a conductive member such as stainless steel, and the surface of the shaft 34 is further grounded via an axis of the shaft 34 attached to a frame of a metal device main body (not shown). Has been. As a result, the charge remaining on the surface of the intermediate transfer belt 10 can be eliminated, so that excellent primary transfer characteristics can be obtained.}

  _{Here, the surface of the intermediate transfer belt 10 is initially in a smooth state, but as the image formation is repeated, it comes into contact with the photoconductor or the final transfer member 9 at the secondary transfer position. Further, the surface of the intermediate transfer belt 10 is gradually adhered to the surface of the intermediate transfer belt 10 due to adhesion of titanium oxide, silica, a release agent, or the like, which is a toner component, or paper powder or talc derived from the final transfer member 9. To change. For this reason, the friction coefficient between the intermediate transfer belt 10 and the photosensitive member 3 and the like varies as image formation is repeated. Accordingly, if the braking force by the braking member 31 is set to the minimum necessary value in the initial stage as described above, the braking force will be excessive or insufficient. It is desirable to reset the braking force to be smaller or larger. For this purpose, the support member 33 that supports one end of the spring 32 that is an urging member is displaced in the intermediate transfer belt 10 side or in the reverse direction. As a result, the spring 32 can be further compressed or expanded to increase or decrease the braking force of the braking member 31.}

  _{As shown in FIG. 5, a specific method for increasing or decreasing the braking force of the braking member 31 is such that a worm gear 35 is attached to the attachment portion 34 of the support member 33, and the worm gear 35 is attached to the attachment portion 34. The required amount of the stepping motor 36 is taken in and out of the gear gear 35 so that the supporting member can be moved in the vertical direction by the required amount, whereby the braking force of the braking member 31 can be increased or decreased.}

  _{FIG. 4 is a schematic configuration diagram showing the relationship between the intermediate transfer belt 10 of a direct transfer tandem type color printer 1b used as a color image forming apparatus, a driving roller, an image forming unit, and the like, and the illustrated color printer 1b. The same reference numerals are assigned to the same components as those of the color printer 1 shown in FIGS. When printing data is sent from a computer (not shown), the final transfer member 9 is transported from a paper feeding device (not shown) along with the start of image formation, and the tension roll 21 and the paper suction. When the final transfer member 9 passes through the nip of the roll 41, the final transfer member 9 is charged and attracted to the transfer conveyance belt 10b, which is a transfer conveyance body. For example, a toner image corresponding to each color is directly transferred onto the final transfer member 9 when passing through the nip between the image forming unit 20 corresponding to each color of yellow, magenta, cyan, and black and the transfer roller 23b. In this way, the toner images are formed on the final transfer member 9 adsorbed to the transfer conveyance belt 10b, and the final transfer member 9 is formed so that the final transfer member 9 corresponds to the drive roll 6 of the transfer conveyance belt 10b. When the position reaches the position, the final transfer member 9 is separated from the transfer conveyance belt 10b by the curvature separation, and the final transfer member 9 having the color toner image formed on the surface thereof is conveyed to the fixing device 7 and the color toner image. Is fixed and discharged. The toner adhering to the transfer / conveying belt 10b faces the auxiliary roll 22b and is scraped off and cleaned by the cleaning blade 8 provided in contact with the transfer / conveying belt 10b to prepare for the next image formation.}

  _{In FIG. 4, the braking member 31 urged by the urging member 32 abuts on the back surface of the transfer conveyance belt 10 b between the image forming unit 20 on the most upstream side when viewed from the drive roll 6 and the tension roll 21. ing. The braking member 31 is preferably in contact with the transfer / conveying belt 10b over the entire length perpendicular to the conveying direction of the transfer / conveying belt 10b.}

  _{A uniform tension is generated in the transfer conveyance belt 10b between the drive roller 6 and the braking member 31 by the driving force of the driving roller 6 and the braking force of the braking member 31, so that a speed fluctuation occurs in the intermediate transfer belt 10. It is possible to suppress this. This makes it possible to obtain a good color image without color misregistration. Note that the braking force generated by the contact of the braking member 31 is set to a minimum value that does not cause a speed fluctuation in the transfer conveyance belt 10b, thereby increasing the driving force for driving the driving roller 6 more than necessary. There is nothing.}

  _{Further, a shaft 34 as an opposing member is brought into contact with the transfer conveyance belt 10b at a position corresponding to the braking member 31 with the transfer conveyance belt 10b interposed therebetween. Note that both ends of the shaft 34 are fixed to a frame of the apparatus main body (not shown). The shaft 34 is preferably configured such that its surface is rotatable so that the intermediate transfer belt can be driven smoothly. As the position of the transfer conveyance belt 10b is changed upward in the drawing of the transfer conveyance belt 10b by the contact of the braking member 31, the angle of entry of the transfer conveyance belt 10b into the nip formed by the photoreceptor 3 and the transfer roll 23b is changed from the horizontal. The transfer efficiency is lowered due to the shift, whereby the transfer efficiency of the toner image corresponding to the color of the image forming unit on the most upstream side as viewed from the drive roller 6 to the final transfer member 9 is lowered, and the final transfer member The phenomenon that the color of the color toner image formed on the sheet 9 is different from the desired one can be prevented by sandwiching the transfer conveyance belt 10b between the shaft 34 and the braking member 31 that are fixed in position. it can.}

  _{Since the surface of the shaft 34 is configured such that an insulating material such as a fluororesin is applied to a metal such as aluminum, the charge applied to the final transfer member 9 is removed by the sheet adsorbing roll 41. Therefore, the final transfer member 9 can be stably conveyed by the transfer conveyance belt 10b.}

  _{Here, the surface of the transfer / conveyance belt 10b is initially smooth, but as the image formation is repeated, the contact with the photoconductor and the contact with the final transfer member 9 at the paper suction position The surface of the transfer / conveyance belt 10b gradually changes as the toner components such as titanium oxide, silica, mold release agent, paper dust and talc derived from the final transfer member 9 adhere to the surface of the transfer / conveyance belt 10b. To do. For this reason, the friction coefficient between the transfer conveyance belt 10b and the photosensitive member 3 and the like changes as image formation is repeated. Therefore, if the braking force by the braking member 31 is set to the minimum necessary value as described above, the braking force will be excessive or insufficient. It is desirable to reset the power to a smaller or larger value. For this purpose, the support member 33 that supports one end of the spring 32 that is an urging member is shifted in the transfer conveyance belt 10b side or in the reverse direction. As a result, the spring 32 can be further compressed or expanded to increase or decrease the braking force of the braking member 31.}

  _{As shown in FIG. 5, a specific method for increasing or decreasing the braking force of the braking member 31 is such that a worm gear 35 is attached to the attachment portion 34 of the support member 33, and the worm gear 35 is attached to the attachment portion 34. The required amount of the stepping motor 36 is taken in and out of the gear gear 35 so that the supporting member can be moved in the vertical direction by the required amount, whereby the braking force of the braking member 31 can be increased or decreased.}

_{1 is a cross-sectional view of an intermediate transfer tandem color image forming apparatus using an intermediate transfer belt to which the present invention is applied. FIG. 2 is a schematic configuration diagram illustrating a configuration around an intermediate transfer belt of an intermediate transfer tandem type color image forming apparatus using an intermediate transfer belt to which Embodiment 1 of the present invention is applied. FIG. 5 is a schematic configuration diagram illustrating a configuration around an intermediate transfer belt of an intermediate transfer tandem color image forming apparatus to which a second embodiment of the present invention is applied. FIG. 6 is a schematic configuration diagram showing a configuration around an intermediate transfer belt of a direct transfer tandem color image forming apparatus having a transfer conveyance belt to which a third embodiment of the present invention is applied. It is the figure which showed the method of changing the braking force of a braking member.}

Explanation of symbols

_{1, 1b Tandem color printer
10 Intermediate transfer belt
10b Transfer conveyor belt
23 Primary transfer roll
23b Transcription roll
24 Secondary transfer roll
31 Braking member
32 Biasing member
34 Shaft}

Claims (7)

  _{A movable intermediate transfer member supported by a plurality of rollers on which each color toner image is sequentially transferred in a superimposed manner, and a toner image for each color arranged on the moving direction of the intermediate transfer member. A plurality of image forming units having an image carrier, and primary transfer means for transferring a toner image on the image carrier to the intermediate transfer member so as to face the image carrier across the intermediate transfer member; In an image forming apparatus having secondary transfer means for transferring a toner image on the intermediate transfer member to a recording medium,
  The drive roller that rotationally drives the intermediate transfer member, which is one of the plurality of rollers, is disposed on the upstream side in the movement direction of the intermediate transfer member and on the most upstream side in the movement direction of the intermediate transfer member. A color member comprising a braking member that abuts against the back surface of the intermediate transfer member between the image forming unit and one of the plurality of rollers immediately upstream of the image forming unit disposed on the most upstream side. An image forming apparatus;   2. The color image forming apparatus according to claim 1, further comprising a facing member that contacts the surface of the intermediate transfer member at a position facing the braking member and sandwiching the intermediate transfer member.   3. The color image forming apparatus according to claim 2, wherein the surface of the facing member is conductive and grounded.   4. A color image forming apparatus according to claim 2, wherein the contact pressure of the braking member to the intermediate transfer member is changed in accordance with the number of image forming sheets.   A plurality of images having a movable transfer carrier supported by a plurality of rollers for conveying a recording medium, and an image carrier that is arranged along the moving direction of the transfer carrier and carries a toner image for each color. In an image forming apparatus comprising: a forming unit; and a transfer unit that transfers the toner image on the image carrier to the recording medium so as to face the image carrier with the conveyance belt member interposed therebetween.
  The drive roller that rotationally drives the transfer conveyance body, which is one of the plurality of rollers, is disposed on the upstream side in the movement direction of the transfer conveyance body and on the most upstream side in the movement direction of the transfer conveyance body. A color member comprising a braking member that abuts on the back surface of the transfer conveyance body between the image forming unit and one of the plurality of rollers located immediately upstream of the image forming unit disposed on the most upstream side. An image forming apparatus;   6. The color image forming apparatus according to claim 5, further comprising a facing member that contacts the surface of the transfer carrier at a position facing the braking member and sandwiching the transfer carrier.   6. The color image forming apparatus according to claim 1, wherein a contact pressure of the braking member to the transfer conveyance body is changed in accordance with the number of image forming sheets.}

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