JP2006220927A - Transfer device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the occurrence of transfer failure by enhancing the adhesion between a recording medium and a photoreceptor belt along a side parting from the photoreceptor belt. <P>SOLUTION: In the transfer device 10, a blade 58 presses the recording medium P to the photoreceptor drum 16 on the upstream side in the conveyance direction of a transfer corotron 42. Also, a blade 64 abuts on the rear surface of the photoreceptor drum 16 on the downstream side in the conveyance direction of the blade 58 and bends the photoreceptor drum 16 from the rear surface side to the front surface side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides a transfer for transferring a toner image onto a recording medium by superimposing a recording medium on the toner image carried on the surface of the image carrier belt, and applying a non-contact charge opposite to the toner charge to the back surface of the recording medium. The present invention relates to an apparatus and an image forming apparatus including the transfer device.

  As a transfer method in an electrophotographic image forming apparatus, a recording medium is superposed on a toner image carried on an image carrier such as a photosensitive belt, a photosensitive drum, or an intermediate transfer belt, and a transfer corotron is applied to the back surface of the recording medium. A corona transfer method in which a toner image is transferred to a recording medium by applying a charge having a polarity opposite to that of the toner is known. In this transfer apparatus using the corona transfer method, the transfer corotron and the recording medium are not in contact with each other, and the recording medium is not pressed against the image carrier as in the roller transfer method. Tends to get worse. If the adhesion between the recording medium and the image carrier is deteriorated, the image cannot be transferred and white spots occur. In particular, when performing double-sided printing, the recording medium is curved along the heat roll of the fixing device in the front surface fixing process, and warps away from the image carrier in the back surface transfer process. The adhesion between the medium and the image carrier tends to deteriorate.

For this reason, in the transfer apparatus using the corona transfer method, various configurations for improving the adhesion between the recording medium and the image carrier have been devised (see, for example, Patent Documents 1 and 2). In Patent Document 1, the position of a guide piece that guides the recording medium to the intermediate transfer belt is strictly positioned to improve the adhesion between the recording medium and the intermediate transfer belt. However, since the warping of the recording medium is not taken into consideration at all, it is not a configuration that can reliably ensure the adhesion between the recording medium and the intermediate transfer belt. In Patent Document 2, as shown in FIG. 5, the recording medium P, the photosensitive belt 16, and the recording medium P are pressed against the photosensitive belt 16 by bringing the blade 58 into contact with the back surface of the recording medium P. I am trying to improve the adhesion. However, in this configuration, the slack of the photosensitive belt 16 is corrected by the urging force of the blade 58, and the photosensitive belt 16 moves to the back side together with the recording medium P. Therefore, along the side away from the photosensitive belt 16. The recording medium P cannot be brought into close contact with the photosensitive belt 16.
JP-A-9-15996 Japanese Patent Laid-Open No. 2000-242092

  The present invention has been made in consideration of the above facts, and aims to improve the adhesion between the recording medium and the image carrier belt along the side away from the image carrier belt, and to suppress the occurrence of transfer defects. And

  The transfer device according to claim 1 is a transfer device for transferring the toner image carried on the surface of the image carrier belt to a recording medium, and is provided on the back surface of the recording medium superimposed on the surface of the image carrier belt. Non-contact transfer means for applying a charge opposite to the toner charge, a recording medium guide member that contacts the back surface of the recording medium and presses the recording medium against the surface of the image carrier belt, and conveyance of the recording medium guide member And an image carrier belt guide member that bends the image carrier belt from the back surface side to the front surface side on the downstream side in the direction.

  In the transfer device according to claim 1, the recording medium is superimposed on the toner image carried on the surface of the image carrier belt, and a charge having a polarity opposite to the toner charge is given to the back surface of the recording medium by the transfer means in a non-contact manner. Thus, the toner image is transferred to the recording medium.

  Here, the recording medium is pressed against the surface of the image carrier belt by the recording medium guide member that is in contact with the back surface of the recording medium. The pressing force of the recording medium guide member causes the image carrier belt to loosen. The image carrier belt is displaced together with the recording medium toward the back side of the image carrier belt. For this reason, since there is no change in the positional relationship between the recording medium and the image carrier belt on the downstream side in the transport direction of the recording medium guide member, if the recording medium is warped away from the image carrier belt, the recording medium And the image carrier belt are not in close contact with each other.

  Therefore, in the present invention, the image carrier belt is bent from the back surface side to the front surface side by the image carrier belt guide member on the downstream side in the transport direction of the recording medium guide member. As a result, even when the recording medium is warped on the side escaping from the surface of the image carrier belt, such as a back surface transfer step in double-sided printing, the adhesion between the recording medium and the image carrier belt can be improved, Transfer defects can be suppressed.

  A transfer apparatus according to a second aspect is the transfer apparatus according to the first aspect, wherein the image carrier belt guide member is a plate that contacts a back surface of the image carrier belt.

  In the transfer device according to claim 2, the image carrier belt is urged from the front surface side to the back surface side by the recording medium guide member that is in contact with the back surface of the recording medium, and on the downstream side in the transport direction of the recording medium guide member, It is received by the plate in contact with the back side. As a result, the image carrier belt is bent from the back surface side to the front surface side on the downstream side in the conveyance direction of the recording medium guide member, thereby reducing the gap between the recording medium and the adhesion between the recording medium and the image carrier belt. And transfer defects such as white spots can be suppressed.

  A transfer apparatus according to a third aspect is the transfer apparatus according to the first aspect, wherein the image carrier belt guide member is a roll that contacts a back surface of the image carrier belt.

  In the transfer device according to claim 3, the image carrier belt is urged from the front surface side to the back surface side by the recording medium guide member in contact with the back surface of the recording medium, and on the downstream side in the transport direction of the recording medium guide member, It is received by the roll in contact with the back side. As a result, the image carrier belt is bent from the back surface side to the front surface side on the downstream side in the conveyance direction of the recording medium guide member, thereby reducing the gap between the recording medium and the adhesion between the recording medium and the image carrier belt. And transfer defects such as white spots can be suppressed.

  Further, since the roll is brought into contact with the back surface of the image carrier belt, wear on the back surface of the image carrier belt can be suppressed.

  An image forming apparatus according to a fourth aspect includes the transfer device according to any one of the first to third aspects.

  According to a fourth aspect of the present invention, the transfer device according to any one of the first to third aspects described above is provided, and in the toner image transfer process, the recording that warps away from the image carrier belt. The adhesion between the medium and the image carrier belt is improved. For this reason, even during double-sided printing, transfer defects such as white spots can be suppressed and a good image can be formed.

  Since the present invention is configured as described above, it is possible to improve the adhesion between the recording medium and the image carrier belt along the side away from the image carrier belt, and to suppress the occurrence of transfer defects.

  A first embodiment of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, an image forming apparatus 1 including a transfer device 10 of the present invention is a color laser printer using an electrophotographic system, and a toner image is formed on a photosensitive belt 16 by an image forming unit 14. The toner image is transferred to the recording medium P transported from the paper feed cassette 20 to the transfer unit 22 by the transport roll 18. Then, the recording medium P onto which the toner image has been transferred is pressurized and heated by the fixing device 12 on the downstream side in the transport direction of the transfer unit 22 to fix the toner image on the recording medium P, and is discharged to the stacker 26 by the paper discharge roll 24. The paper is ejected. When images are formed on both the front and back sides of the recording medium P, the conveyance path on the downstream side in the conveyance direction of the fixing device 12 is switched, and the recording medium P with the toner image fixed on the surface reverses the front and back sides. Is transported to the rear surface transport path 28. Then, the recording medium P with the front and back reversed is conveyed by the conveying belt 29 to the upstream side of the transfer unit 22 in the conveying direction, and again conveyed by the conveying roller 18 to the transfer unit 22, and a toner image is transferred from the photosensitive belt 16 to the back surface. Transcribed. Then, the recording medium P passes through the fixing device 12, the toner image is fixed on the back surface, and is discharged to the stacker 26 by the discharge roll 24.

  The image forming unit 14 is provided with a photosensitive belt 16. The photosensitive belt 16 is rotated by two rolls 34 arranged in a horizontal direction of two rolls 31 and 32 and rolls 31 and 32 arranged along a conveyance path 30 extending in the vertical direction. The flat surfaces 16A, 16B, 16C, and 16D are formed vertically and horizontally. The upper and lower flat surfaces 16A and 16B are longer than the left and right flat surfaces 16C and 16D.

  A plurality of print engines 36 that form toner images of different colors such as red and black on the surface of the photoreceptor belt 16 are arranged along the lower flat surface 16B. Each print engine 36 includes a charger 37, an exposure head 38, and a developer 39 that are sequentially arranged in the rotation direction of the photosensitive belt 16 (the direction of arrow A in the figure). The charger 37 uniformly charges the photosensitive belt 16 with a charging corotron, a charging roll, or the like. Further, the exposure head 38 exposes the charged surface of the photosensitive belt 16 with an LED array, an optical scanning device (Raster Optical Scanner), or the like to form an electrostatic latent image on the photosensitive belt 16 based on image data. . The developing device 39 contains a one-component developer made of toner or a two-component developer made of toner or carrier, and transports the developer to the developing roll 39A while stirring the developer in the developing device 39. The developing device 39 applies a developing bias to the developing roll 39A, and moves the toner from the developing roll 39A onto the electrostatic latent image on the photosensitive belt 16. As a result, the electrostatic latent image on the photoreceptor belt 16 is visualized with toner.

  The transfer device 10 is disposed so as to face a flat surface 16D facing the transfer portion 22 of the photosensitive belt 16. The transfer device 10 includes a transfer corotron 42 facing the flat surface 16D across the conveyance path. The transfer corotron 42 discharges toward the back surface of the recording medium P, gives the toner charge on the photosensitive belt 16 to the recording medium P in a non-contact manner and gives a charge having a polarity opposite to that of the toner. Transcript.

  Further, a cleaning mechanism 44 (cleaner blade is shown) such as a cleaner blade and a cleaner roll is disposed facing the flat surface 16C of the photosensitive belt 16. The cleaning mechanism 44 removes untransferred residual toner remaining on the photosensitive belt 16 without being transferred to the recording medium P by the transfer unit 22 from the photosensitive belt 16.

  The fixing device 12 disposed on the downstream side in the conveyance direction of the transfer unit 22 is in contact with the transfer surface of the recording medium P and rotates, and the recording medium P is pressed against the heat roll 46 between the recording medium P and recording. A pressure roll 48 that rotates in contact with the back surface of the medium P is provided, and a fixing nip N is formed by the heat roll 46 and the pressure roll 48. A heater lamp 50 such as a halogen lamp is disposed inside the heat roll 46, and the surface of the heat roll 46 is heated. Therefore, when the recording medium P to which the toner image is transferred passes through the fixing nip N, the recording medium P is heated and pressurized, and the toner on the recording medium is melted and fixed to the recording medium P.

  Here, the fixing device 12 is provided with a release agent supply device 13. The release agent supply device 13 includes a donor roll 52 in contact with the surface of the heat roll 46, a tank 54 storing a release agent such as silicon oil, a donor roll 52, and a release agent in the tank 54 that absorbs sponge and the like. A metering roll 56 that is in contact with the body is provided.

  A metering blade (not shown) is in contact with the surface of the metering roll 56. The metalling blade contacts the surface of the metalling roll 56 with a predetermined pressure, and regulates (measures) the release agent on the surface of the metalling roll 56 to a predetermined thickness with micron order accuracy.

  A release agent having a predetermined thickness on the surface of the metalling roll 56 is conveyed to the surface of the heat roll 46 by the donor roll 52, and a layer of the release agent having a predetermined thickness is formed on the surface of the heat roll 46. Is formed. This improves the releasability of the toner on the recording medium P from the surface of the heat roll 46 in the fixing nip N, so that fixing failure and toner fixing offset can be prevented.

  Here, the transfer device 10 will be described.

  As shown in FIGS. 2 and 3, in the transfer device 10, a transfer corotron 42 is disposed facing the flat surface 16 </ b> D of the photosensitive belt 16. A blade 58 is supported on the upstream side wall of the transfer corotron 42 in the conveying direction. The blade 58 is an elastic film and extends in the width direction of the photosensitive belt 16. A blade pressing arm 60 is disposed upstream of the transfer corotron 42 in the conveyance direction. Further, a solenoid 62 is disposed facing the flat surface 16D with the transfer corotron 42 therebetween. The blade pressing arm 60 is rotatably supported at the central portion on the upstream side in the transport direction of the transfer corotron 42, and one end thereof is connected to the movable iron core 62 </ b> A of the solenoid 62. Further, the other end portion of the blade pressing arm 60 is bent toward the downstream side in the transport direction in the vicinity of the blade 58 and the surface of the photosensitive belt 16, and elastically deforms the blade 58 toward the downstream side in the transport direction.

  As shown in FIG. 2, when the solenoid 62 is de-energized and the movable iron core 62A returns to the coil side, the other end of the blade pressing arm 60 swings to the downstream side in the transport direction, and the blade 58 is moved to the photosensitive belt 16. Separate from the surface of the. Further, as shown in FIG. 3, when the solenoid 62 is excited and the movable iron core 62A is pushed out from the coil side, the other end of the blade pressing arm 60 swings upstream in the transport direction, and the blade 58 is exposed. The surface of the body belt 16 is brought into surface contact. As a result, the recording medium P is pressed against the surface of the photosensitive belt 16. When the recording medium P is conveyed to the transfer unit 22, the solenoid 62 is excited and the blade 58 contacts the recording medium P.

  Further, on the back side of the flat surface 16D of the photosensitive belt 16, a metal plate 64 extending in the width direction of the photosensitive belt 16 is supported by a support member (not shown). The plate 64 extends from between the roll 31 and the roll 32 toward the back surface of the flat surface 16D of the photoreceptor belt 16, and bends upstream in the transport direction at two locations, so that the front end portion 64A is formed on the flat surface 16D. The back surface is brought into surface contact with the transfer corotron 42.

  That is, the recording medium P is pressed against the surface of the photosensitive belt 16 by the blade 58 that is in contact with the back surface of the recording medium P. However, the slackness of the photosensitive belt 16 is corrected by the pressing force of the blade 58, and the photosensitive belt 16 is exposed. The body belt 16 is displaced together with the recording medium P to the back side of the photoreceptor belt 16. Therefore, when the recording medium P is warped away from the photosensitive belt 16, there is no change in the positional relationship between the recording medium P and the photosensitive belt 16, so that the recording medium P is separated from the photosensitive belt 16. When warped to the side, the recording medium P and the photosensitive belt 16 are not in close contact with each other.

  However, the photosensitive belt 16 displaced to the back surface side is received by the front end portion 64A of the plate 64 within the effective electric field range of the transfer corotron 42 on the downstream side in the conveyance direction of the blade 58, and is bent from the back surface side to the front surface side. . As a result, the gap between the photosensitive belt 16 and the recording medium P is reduced, so that the recording medium P warps on the side where the recording medium P escapes from the surface of the photosensitive member 16 belt, such as a transfer process on the back surface of the recording medium P in double-sided printing. Even in this case, the adhesion between the recording medium P and the photosensitive belt 16 can be improved, and transfer defects such as white spots can be suppressed.

  Next, a second embodiment will be described. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment, and description is abbreviate | omitted.

  As shown in FIG. 4, in the transfer device 100, a roll 66 is brought into contact with the back surface of the photosensitive belt 16 instead of the plate 64. Similarly to the plate 64, the roll 66 also receives the photosensitive belt 16 displaced to the back side by the blade 58 and curves it from the back side to the front side. As a result, the adhesiveness between the recording medium P warped away from the surface of the photosensitive belt 16 and the photosensitive belt 16 is increased, and transfer defects such as white spots are suppressed.

  Here, the roll 66 rotates following the rotation of the photosensitive belt 16. For this reason, abrasion of the back surface of the photoreceptor belt 16 can be suppressed.

  In the first and second embodiments, the present invention has been described with reference to an example of a transfer device that transfers a toner image carried on a photosensitive belt to a recording medium P by a transfer corotron. The present invention can also be applied to other transfer apparatuses that transfer a toner image carried on a belt-like image carrier to a recording medium by a corona transfer method.

  In the first and second embodiments, the plate and the roll are brought into contact with the back surface of the photosensitive belt, but various members such as an elastic member and a bar can be used as the members to contact the back surface of the image carrier belt. Things are applicable.

1 is a diagram illustrating a schematic configuration of an image forming apparatus including transfer apparatuses according to first and second embodiments. It is sectional drawing which shows the transfer apparatus of 1st Embodiment. It is sectional drawing which shows the transfer apparatus of 1st Embodiment. It is sectional drawing which shows the transfer apparatus of 2nd Embodiment. It is sectional drawing which shows the conventional transfer apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Transfer apparatus 16 Photosensitive belt (image carrier belt)
42 Transfer corotron (transfer means)
58 blade (recording medium guide member)
64 plate (image carrier belt guide member)
66 roll (image carrier belt guide member)
P Recording medium

Claims (4)

A transfer device for transferring a toner image carried on the surface of an image carrier belt to a recording medium,
Transfer means for applying a charge opposite in polarity to the toner charge in a non-contact manner on the back surface of the recording medium superimposed on the surface of the image carrier belt;
A recording medium guide member that abuts the back surface of the recording medium and presses the recording medium against the surface of the image carrier belt;
An image carrier belt guide member that bends the image carrier belt from the back surface side to the front surface side on the downstream side in the transport direction of the recording medium guide member;
A transfer device comprising:   The transfer device according to claim 1, wherein the image carrier belt guide member is a plate that contacts a back surface of the image carrier belt.   The transfer device according to claim 1, wherein the image carrier belt guide member is a roll that contacts a back surface of the image carrier belt.   An image forming apparatus comprising the transfer device according to claim 1.

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