JP5482467B2 - Transfer device and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a transfer apparatus used in an image forming apparatus such as a copying machine, a printer, a fax machine, and the like, and an image forming apparatus using the same.

  As a transfer device of an image forming apparatus, for example, as disclosed in Patent Document 1, the speed of the transfer belt is increased according to the angle at which the transferred sheet enters the transfer belt of the transfer unit, and the sheet is slackened. It is known to absorb water. Also, as shown in Patent Document 2, the nip width can be adjusted to an appropriate value according to the type of paper, and the toner image on the image carrier can be transferred onto the paper well regardless of the type of paper. What is possible is known.

JP-A-11-174768 Japanese Patent Laid-Open No. 11-65309

  Among transfer devices, particularly those used in a secondary transfer portion having a vertical tandem configuration, there are many cases where the paper entrance angle and the discharge angle with respect to the nip of the transfer portion are different.

  Due to the difference between the paper entrance angle and the paper discharge angle with respect to the nip, especially in the case of strong paper such as thick paper, when the rear edge of the paper reaches the nip, the rear edge of the paper jumps in the surface direction due to stress. There is a problem that the edge flipping phenomenon occurs, the nip shape is deformed, and the trailing edge transfer failure of the paper is caused.

  However, the disclosed technologies of Patent Document 1 and Patent Document 2 do not mention the trailing edge flip of the sheet at the nip of the transfer device, and cannot solve the trailing edge transfer failure of the sheet due to trailing edge flipping.

  Accordingly, the present invention provides a transfer device capable of preventing trailing edge transfer of a sheet at a nip and avoiding trailing edge transfer failure of the sheet, and an image forming apparatus using the same.

The present invention provides an image carrier that carries a toner image, and a transfer unit that presses the image carrier to form a nip and transfers the toner image carried on the image carrier to a sheet. The transfer means is configured such that the paper entrance angle and the paper discharge angle with respect to the nip are different, and the paper with respect to the nip depends on the type of paper entering the nip. The paper transport angle adjusting means changes the relationship between the entry angle and the discharge angle of the paper, and the paper transport angle adjustment means is configured so that the paper entrance angle and the discharge angle with respect to the nip become closer as the amount of paper jam of the paper increases. The main feature is to change the angle .

  According to the present invention, it is possible to approximate the paper discharge angle and the entry angle with respect to the nip by the paper transport angle adjusting means. As a result, it is possible to prevent the trailing edge of the sheet from being flipped at the nip and to avoid the trailing edge transfer failure of the sheet.

1 is an overall configuration diagram conceptually showing an image forming apparatus as an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic explanatory view showing a first embodiment of a transfer apparatus according to the present invention. Schematic explanatory drawing showing a second embodiment of the transfer device according to the present invention. Schematic explanatory drawing which shows an example of the tilting mechanism in 2nd Embodiment. Explanatory drawing which shows the permissible compatible point of the trailing edge flip of the paper and the discharge noise when the paper amount is changed in the case of the first embodiment (A) and the case of the second embodiment (B).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows the overall configuration of an image forming apparatus to which a transfer apparatus according to the present invention is applied.

  The image forming apparatus 1 forms a full-color image in which photosensitive drums 31Y, 31M, 31C, and 31K as a plurality of photosensitive members face an intermediate transfer belt 41 as an example of an intermediate transfer member and are arranged in a vertical direction. This is called a tandem type color image forming apparatus.

  The image forming apparatus 1 includes an automatic document feeder ADF at the top thereof. The documents D placed on the document placement table 15 of the automatic document feeder ADF are separated one by one, sent out to the document conveyance path, and conveyed by the conveyance drum 16.

  The document reading unit 10 reads an image of the document D being conveyed at the document image reading position RP. The first conveyance guide G1 and the document discharge roller 17 discharge the document D that has been read to the document discharge tray 18.

  The image forming apparatus 1 includes the document reading unit 10, the exposure units 20Y, 20M, 20C, and 20K, the image forming units 30Y, 30M, 30C, and 30K, the intermediate transfer unit 40, the secondary transfer unit 50, the fixing unit 60, and the paper discharge. The reversing unit 70, the paper feeding unit 90, and the like are included in one casing.

  The document reading unit 10 irradiates the image of the document D with the lamp L at the document image reading position RP, guides the reflected light by the first mirror unit 11, the second mirror unit 12, and the lens 13, and An image is formed on the light receiving surface. The imaging device CCD photoelectrically converts incident light and outputs a predetermined image signal. The image reading control unit 14 performs processing such as A / D conversion, shading correction, and compression on the image signal, and converts it into image data in a storage unit of a control unit (not shown). The image data stored in the storage unit is subjected to appropriate image processing according to conditions set by the user, and output image data is generated.

  The exposure units 20Y, 20M, 20C, and 20K are photosensitive drums charged by the main charging units 32Y, 32M, 32C, and 32K in accordance with output information output based on output image data sent from the control unit. The surfaces of 31Y, 31M, 31C, and 31K are scanned and exposed with a laser beam, and electrostatic images for Y, M, C, and BK colors are formed on the photosensitive drums 31Y, 31M, 31C, and 31K.

  The image forming unit 30Y includes a photosensitive drum 31Y, and a main charging unit 32Y, a developing unit 33Y, a first transfer roller 34Y, and a cleaning unit 35Y arranged around the photoconductive drum 31Y. The other image forming units 30M, 30C, and 30K have the same configuration as that of the image forming unit 30Y, and the main charging units 32M, 32C, and 32K are arranged around the photosensitive drums 31M, 31C, and 31K, respectively. The developing units 33M, 33C, and 33K, the first transfer rollers 34M, 34C, and 34K, and the cleaning units 35M, 35C, and 35K are disposed.

  The developing units 33Y, 33M, 33C, and 33K are developed with yellow (Y), magenta (M), cyan (C), and black (BK) toners, thereby latent images on the photosensitive drums 31Y, 31M, 31C, and 31K. Visualize the image. As a result, yellow (Y), magenta (M), cyan (C), and black (BK) toner images are formed on the photosensitive drums 31Y, 31M, 31C, and 31K.

  The first transfer rollers 34Y, 34M, 34C, and 34K of the intermediate transfer unit 40 transfer the toner images formed on the photosensitive drums 31Y, 31M, 31C, and 31K in a superimposed manner on predetermined positions on the intermediate transfer belt 41. . A color image is formed on the intermediate transfer belt 41 by superimposing the toner images of the respective colors. The intermediate transfer belt 41 formed of an endless belt moves while rotating in the direction indicated by the arrow in FIG. 1 by the driving force of the belt driving roller 42. The cleaning units 35Y, 35M, 35C, and 35K remove the toner remaining on the surfaces of the photosensitive drums 31Y, 31M, 31C, and 31K after the transfer of the toner images.

  On the other hand, the secondary transfer unit 50 transports the color image superimposed and transferred on the intermediate transfer belt 41 from the trays PG1, PG2, and PG3 of the sheet feeding unit 90, and sends out the timing by the registration rollers 91. Transferred onto the printed paper P. The belt cleaning unit 43 cleans the surface of the intermediate transfer belt 41 that has finished transferring the color image to the paper P, and the cleaned intermediate transfer belt 41 is used for the next image transfer.

  The paper P carrying the toner image is sent to the fixing unit 60, and the fixing unit 60 pressurizes and heats the paper P to fix the toner image on the paper P.

  The paper discharge reversing unit 70 conveys the paper P that has undergone the fixing process by the fixing unit 60 and discharges it to the paper discharge tray 75. When the paper P is reversed and discharged, the paper discharge guide 72 once guides the paper P downward, holds the rear end of the paper P between the paper discharge reverse rollers 73, and reversely conveys the paper P. 72 guides the paper P to the paper discharge roller 74 and discharges it.

  When image formation is performed also on the back side of the paper P, the paper discharge guide 72 conveys the paper P, which has been subjected to the fixing process of the toner image on the front surface, to the re-feed unit 80 below, and is fed by the re-feed reverse roller 81 After pinching the rear end, the paper P is reversed by reverse feeding and sent to the refeed conveyance path 82 for image formation on the back surface.

  In the image forming apparatus 1 having such a vertical tandem configuration, the secondary transfer unit 50 is obliquely downward because the transfer roller 53 and the backup roller 44 are arranged in a vertical column in a substantially vertical direction as will be described later. The entry angle of the paper P fed from the nip into the nip differs from the discharge angle from the nip.

  Therefore, the secondary transfer unit 50 is configured as a belt-type transfer device 51 shown in FIG.

  In the transfer device 51 of the first embodiment shown in FIG. 2, one of the rollers 44 around which the intermediate transfer belt 41 as an image carrier is hung is used as a backup roller, and a nip is formed at a position almost immediately below the backup roller 44. The transfer belt unit 52 is used as transfer means.

  The transfer belt unit 52 is constituted by a transfer roller 53 that substantially constitutes the nip as a main body, and an endless belt 56 is hung on the transfer roller 53 and the two rollers 54 and 55.

  The transfer roller 53 is rotationally driven in a direction opposite to that of the backup roller 44 as indicated by an arrow in FIG. 2 by a driving means such as a motor (not shown), and the endless belt 56 transfers the sheet P onto which the image has been transferred through the nip. 1 to the fixing unit 60 shown in FIG.

  The transfer belt unit 52 includes a sheet conveyance angle adjusting unit 100 for the endless belt 56, and the discharge angle of the sheet P discharged from the nip is variable.

  In the present embodiment, as the paper transport angle adjusting means 100, a pressing roller 101 that presses the endless belt 56 from the inside toward the outside in the paper transport region of the endless belt 56 is used. That is, the pressing roller 101 is disposed in contact with the inner surface of the endless belt 56 at an intermediate position between the transfer roller 53 that forms the sheet conveying surface of the endless belt 56 and one of the belt hanging rollers 54. The height position can be adjusted by a lifter (not shown).

  According to the transfer device 51 having the configuration of the first embodiment, the sheet conveying surface of the endless belt 56 is indicated by a chain line in FIG. 2 between the transfer roller 53 and the roller 54 by raising the pressing roller 101. As shown by the solid line, it is pushed up into a mountain shape.

  As a result, the discharge angle of the paper P defined by the paper conveyance surface of the endless belt 56 at the nip exit is brought close to the entry angle of the paper P fed obliquely from below to the nip.

  As a result, when used as a transfer device of the secondary transfer unit 50 in the image forming apparatus 1, it is possible to prevent the trailing edge of the sheet P from being flipped in the nip and to avoid the trailing edge transfer failure of the sheet P.

  FIG. 5A shows the sheet conveyance surface height (belt surface height) of the endless belt 56 by adjusting the height of the pressure roller 101, the trailing edge permissible area of the sheet that affects image transfer, and the nip exit side. The relationship with the discharge noise allowable area generated on the paper is shown.

  In the figure, symbol a indicates a trailing edge allowable region, b indicates a discharge noise allowable region of coated paper, and c indicates a discharge noise allowable region of uncoated paper.

  As can be seen from the figure, the trailing edge permissible area “a” of the paper can be secured as a1, a2, and a3 by increasing the belt surface height as the amount of paper jam increases. Edge transfer defects can be eliminated.

  On the other hand, when the height of the belt surface is increased and the sheet conveying surface is brought closer to the backup roller 44 in this way, an image defect of the sheet is likely to occur due to discharge noise.

  Image defects due to discharge noise are affected by the resistance of the paper surface. With coated paper having a low surface resistance, the occurrence of discharge noise is small, and the allowable discharge noise amount b varies depending on the amount of paper jam, such as b1, b2, and b3. Therefore, in the coated paper, there is a point S at which the trailing edge allowable area a and the discharge noise allowable area b are compatible over the entire amount of paper at a certain belt surface height. This eliminates the need to adjust the belt surface height in accordance with the amount of paper wrinkles on the coated paper, and maintains the belt surface height at a certain level so that the trailing edge of the paper is discharged and the discharge immediately after passing through the nip. It is possible to avoid paper image defects due to noise.

On the other hand, non-coated paper with high surface resistance tends to generate discharge noise, and the discharge noise allowable region c is smaller as c1, c2, and c3 than the coated paper even with the same amount of paper. Therefore, in the case of uncoated paper, there is no point in which the trailing edge allowable region a and the discharge noise allowable region c are compatible with each other over a full range at a certain belt surface height. For this reason, in the case of uncoated paper, the trailing edge flipping of the paper is appropriately adjusted by adjusting the belt surface height so that the trailing edge permissible area a and the discharge noise permissible area c are compatible in accordance with the amount of paper curl. It is possible to avoid sheet image defects due to discharge noise immediately after passing through the nip.
3 and 4 show a second embodiment of the transfer device 51.

  In the present embodiment, as the sheet conveyance angle adjusting means 100 of the endless belt 56 of the transfer belt unit 52, the tilt mechanism 102 that tilts the transfer belt unit 52 itself around the transfer roller 53 is used. Is the same as that of the first embodiment, and a duplicate description is omitted.

  For example, as shown in FIG. 4, the tilting mechanism 102 is provided with a lifter 103 such as a hydraulic actuator at one end of a frame 57 to which a transfer roller 53 and two rollers 54 and 55 for hanging a belt are attached. The lifter 103 can be extended so that the frame 57 can be tilted about the support shaft of the transfer roller 53.

  That is, in the second embodiment, the transfer belt unit 52 itself is tilted around the transfer roller 53 by the lifter 103, so that the sheet conveying surface of the endless belt 56 is indicated by a solid line from the state indicated by the chain line in FIG. In addition, the approach angle of the paper P can be brought close to.

  As a result, similarly to the first embodiment, it is possible to prevent the trailing edge of the paper P from being flipped in the nip, and to avoid the trailing edge transfer failure of the paper P.

  Even in the transfer device 51 of the second embodiment, the paper trailing noise allowable area a obtained by adjusting the tilt angle of the transfer belt unit 52 and the paper discharge noise allowable area due to the difference between coated paper and non-coated paper. The tendency of coexistence of b and c is almost the same as in the first embodiment as shown in FIG.

  Therefore, when coated paper is used as the paper, the trailing edge permissible area a and the discharge noise permissible area b are adjusted to a certain transfer belt unit tilt angle that provides a point S that is compatible over the entire amount of paper. maintain. Accordingly, it is possible to avoid the image defect of the sheet due to the trailing edge flip of the sheet and the discharge noise after passing through the nip without adjusting the tilt angle of the transfer belt unit 52 according to the amount of sheet curl.

  On the other hand, in the case of uncoated paper, the trailing edge flipping of the paper is appropriately adjusted according to the amount of each sheet by appropriately adjusting the transfer belt unit tilt angle in which the trailing edge allowable area a and the discharge noise allowable area c are compatible. In addition, it is possible to avoid sheet image defects due to discharge noise after passing through the nip.

  In the example shown in FIG. 4, the lifter 103 is used as the tilt mechanism 102, but the frame 57 is transferred by a gear mechanism including a gear and a drive pinion provided around the transfer roller support shaft of the frame 57. The roller 53 can be tilted around the center.

In each of the above embodiments, the configuration example in which the position of the endless belt 56 of the transfer belt unit 52 is adjusted as the paper transport angle adjusting unit 100 has been described. However, in addition to this, a member that changes the paper discharge direction is discharged. It is also possible to adopt a configuration that enters the paper path. In this case, the transfer means may have a general-purpose transfer roller structure.

  Furthermore, the paper transport angle adjusting means in the present invention includes a means for “changing the relationship between the approach angle and the discharge angle” by changing the paper entrance angle. This can be dealt with, for example, by making it possible to change the position of the registration roller 91 that feeds the paper shown in FIG.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 41 ... Intermediate transfer belt (image carrier)
51 ... Transfer device 52 ... Transfer belt unit (transfer means)
53: transfer rollers 54, 55 ... belt-suspending roller 56 ... endless belt 100 ... paper transport angle adjusting means 101 ... pressure roller 102 ... tilting mechanism 103 ... lifter (tilting mechanism)

Claims (7)

An image carrier that carries a toner image;
A transfer unit that presses against the image carrier to form a nip, and transfers a toner image carried on the image carrier to paper ;
A transfer device comprising:
The transfer means is configured such that the paper entrance angle and the discharge angle with respect to the nip are different from each other.
In accordance with the type of paper entering the nip, a paper transport angle adjusting means for changing the relationship between the paper entrance angle and the discharge angle with respect to the nip ,
The transfer apparatus according to claim 1, wherein the paper transport angle adjusting unit changes the angle so that the paper entrance angle and the paper discharge angle with respect to the nip approach each other as the paper amount of the paper increases . The transfer means includes a plurality of rollers mainly including a transfer roller that forms the nip.
An endless belt that is hung on the plurality of rollers and is in contact with the image carrier,
Configured as a transfer belt unit that conveys a sheet of paper on which an image has been transferred through the nip,
The transfer apparatus according to claim 1, wherein the sheet conveyance angle adjusting unit adjusts a position of the endless belt. When the paper type is coated paper, the paper transport angle adjusting means maintains a constant angle between the entrance angle and the discharge angle regardless of the amount of paper jam, and when the paper type is uncoated paper. The transfer device according to claim 1, wherein the angle is changed according to the amount of paper jam . An image carrier that carries a toner image;
  A plurality of rollers mainly composed of a transfer roller that press-contacts the image carrier to form the nip, and an endless belt that is suspended by the plurality of rollers and contacts the image carrier, Transfer means configured as a transfer belt unit that conveys a sheet of paper on which an image has been transferred through the nip;
A transfer device comprising:
  By adjusting the position of the endless belt, a paper transport angle adjusting means is provided for changing the relationship between the paper entrance angle and the discharge angle with respect to the nip. The paper transport angle of the endless belt is such that the paper is coated paper. The transfer device is maintained at a constant angle in the case, and when the paper is uncoated paper, the angle is changed according to the amount of paper. The paper conveying angle adjusting means of the endless belt,
  5. The transfer device according to claim 2, wherein the transfer device includes a pressing roller that presses the endless belt from the inner side toward the outer side in a sheet conveyance region of the endless belt. The paper conveying angle adjusting means of the endless belt,
5. The transfer device according to claim 2, comprising a tilting mechanism that tilts the transfer belt unit around a transfer roller that forms the nip .   An image forming apparatus comprising the transfer device according to claim 1.

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