JP2018180202A - Transfer unit and image forming apparatus provided with the same - Google Patents

Abstract

A transfer unit and an image forming apparatus equipped with the transfer unit are provided, which can prevent the inner peripheral surface of a belt from being damaged by foreign matter and prevent transfer failure from occurring. An intermediate transfer unit (transfer unit) 30 includes an intermediate transfer belt 8 and primary transfer rollers 6a to 6d for transferring toner images formed on photosensitive drums 1a to 1d onto the intermediate transfer belt 8. , and a plurality of tension rollers for tensioning the intermediate transfer belt 8 . The tension roller includes a grooved roller 50 provided with one or more spiral grooves 51 or a plurality of linear grooves 52 extending in the axial direction of the tension roller on the outer peripheral surface 50a. is a non-integer multiple of the outer peripheral length of the groove forming roller 50 . [Selection drawing] Fig. 4

Description

  The present invention relates to a transfer unit having an endless belt, a primary transfer roller for transferring a toner image onto the belt, and a plurality of stretching rollers for stretching the belt, and an image forming apparatus including the same.

  In an image forming apparatus using an electrophotographic method such as a copier, a printer, a facsimile, etc., a powder developer is mainly used, and a toner image is transferred from a photosensitive drum to an intermediate transfer belt, and the toner image is recorded as a recording medium It is common to carry out a fixing process after transfer onto the top. Foreign substances such as toner and paper dust remaining on the outer peripheral surface of the intermediate transfer belt are removed by the cleaning device, and a new toner image is formed.

  In a transfer unit having an intermediate transfer belt, a plurality of primary transfer rollers disposed on the intermediate transfer belt so as to transfer a toner image formed on the photosensitive drum opposite to the photosensitive drum with the intermediate transfer belt interposed therebetween, A plurality of tension rollers are provided to tension the belt. Some tension rollers are pressed through the intermediate transfer belt by a secondary transfer roller or a belt cleaner.

  A transfer unit provided with an intermediate transfer belt, a plurality of primary transfer rollers, and a plurality of stretching rollers is disclosed, for example, in Patent Document 1. In Patent Document 1, an axial center is provided on an outer peripheral surface of a drive roller and a driven roller (stretching roller) for the purpose of avoiding the occurrence of offset or skew or meandering of an endless belt (intermediate transfer belt). Symmetrically, a plurality of inclined grooves are provided.

JP 2005-344750 A

  By the way, the inner circumferential surface of the intermediate transfer belt rotates in contact with the stretching roller. For this reason, in the above-mentioned conventional transfer unit, for example, when foreign matter is present between the outer peripheral surface of the stretching roller and the inner peripheral surface of the intermediate transfer belt, there is a problem that the intermediate transfer belt is damaged.

  Specifically, when foreign matter adheres to the outer peripheral surface of the tension roller, the foreign material contacts the inner peripheral surface of the intermediate transfer belt each time the tension roller rotates, and the intermediate transfer belt is repeatedly damaged. Thus, the inner peripheral surface of the intermediate transfer belt is scratched along the circumferential direction. When foreign matter adheres to the inner circumferential surface of the intermediate transfer belt, the foreign matter contacts the outer circumferential surface of the stretching roller every time the intermediate transfer belt passes through the stretching roller, and the outer circumferential surface of the intermediate transfer belt Damage is repeatedly applied to the same part (the part to which the foreign matter is attached). When the damage on the inner peripheral surface of the intermediate transfer belt is aggravated and reaches the outer peripheral surface of the intermediate transfer belt, a transfer failure may be caused.

  In the transfer unit of Patent Document 1, the foreign matter attached to the outer peripheral surface of the roller or the inner peripheral surface of the endless belt passes through the contact portion between the outer peripheral surface of the roller and the inner peripheral surface of the endless belt. If the roller is fitted in the groove, it is possible to suppress damage to the endless belt. However, when the foreign matter passes through the contact portion between the outer peripheral surface of the roller and the inner peripheral surface of the endless belt, it does not fit into the groove of the roller (when it contacts the portion between the grooves). Similar to the transfer unit, the inner peripheral surface of the endless belt is scratched. Then, when the damage on the inner peripheral surface of the endless belt is aggravated and reaches the outer peripheral surface of the endless belt, it causes a transfer failure.

  The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to suppress the occurrence of scratches on the inner peripheral surface of the belt due to foreign matter, and to suppress the occurrence of transfer defects. It is an object of the present invention to provide a transfer unit capable of image forming and an image forming apparatus provided with the same.

  In order to achieve the above object, the transfer unit according to the first configuration of the present invention faces an endless belt moving along the image forming unit and an image carrier disposed in the image forming unit with the belt interposed therebetween. The image forming apparatus further comprises: a primary transfer roller arranged to transfer the toner image formed on the image carrier onto the belt; and a plurality of stretching rollers stretching the belt. The stretching roller is formed with one or more helical grooves on the outer peripheral surface, or a groove provided with a plurality of linear grooves extending in the axial direction of the stretching roller and arranged at a predetermined pitch along the circumferential direction of the outer peripheral surface The inner circumferential length of the belt is a non-integer multiple of the outer circumferential length of the grooved roller, including a roller.

  According to the transfer unit of the first configuration of the present invention, the stretching roller extends in the axial direction of one or more helical grooves on the outer circumferential surface or the stretching roller and at a predetermined pitch along the circumferential direction of the outer circumferential surface The inner circumferential length of the belt is a non-integer multiple of the outer circumferential length of the grooved roller, including a grooved roller provided with a plurality of linear grooves disposed. As a result, it is possible to suppress damage to the inner circumferential surface of the belt by foreign matter, and to suppress the occurrence of transfer failure.

  Specifically, when foreign matter adheres to the outer circumferential surface of the groove forming roller, the foreign matter is fitted into the spiral groove or the linear groove of the groove forming roller, whereby the outer circumferential surface of the groove forming roller and the inner circumferential surface of the belt It is possible to suppress the damage to the inner circumferential surface of the belt when the foreign matter passes through the contact portion. This can prevent the inner peripheral surface of the belt from being scratched. In addition, even if foreign matter does not fit into the spiral groove or linear groove of the groove forming roller (when adhering between the grooves), the inner circumferential length of the belt is a non-integer of the outer circumferential length of the groove forming roller Because it is doubled, the foreign matter adhering to the predetermined position on the outer peripheral surface of the groove forming roller comes in contact with different positions (slightly shifted positions) of the belt each time the belt makes one revolution. Therefore, repeated damage to the same portion of the inner circumferential surface of the belt can be suppressed.

  On the other hand, when foreign matter adheres to the inner circumferential surface of the belt, the foreign matter passes through the contact portion between the outer circumferential surface of the groove forming roller and the inner circumferential surface of the belt. By fitting in, it is possible to suppress that the inner peripheral surface of the belt is damaged. This can prevent the inner peripheral surface of the belt from being scratched. Further, when foreign matter passes through the contact portion between the outer peripheral surface of the groove forming roller and the inner peripheral surface of the belt, foreign matter does not fit into the spiral groove or linear groove of the groove forming roller (when contacting between grooves) However, since the inner circumferential length of the belt is a non-integer multiple of the outer circumferential length of the groove forming roller, foreign matter adhering to a predetermined position on the inner circumferential surface of the belt forms a groove each time the belt makes one revolution. Contact the roller at different positions (slightly offset). As a result, the foreign matter is inserted into and not inserted into the spiral groove or the linear groove (it is in contact between the grooves), and therefore, the same portion of the inner circumferential surface of the belt Can be suppressed from being damaged).

  As a result of the above, damage to the inner peripheral surface of the belt can be prevented from becoming worse and reaching the outer peripheral surface of the belt, so that the occurrence of a transfer failure can be suppressed.

FIG. 1 is a schematic cross-sectional view showing a configuration of an image forming apparatus on which an intermediate transfer unit according to a first embodiment of the present invention is mounted. FIG. 2 is an external perspective view of the intermediate transfer unit according to the first embodiment of the present invention as viewed from below. FIG. 2 is a cross-sectional view showing a schematic structure of an intermediate transfer unit and a secondary transfer roller according to the first embodiment of the present invention. It is a figure which shows the structure of the groove formation roller of the intermediate transfer unit of 1st Embodiment of this invention. It is an enlarged view which shows the structure of the spiral groove of the groove formation roller of the intermediate transfer unit of 1st Embodiment of this invention. It is an enlarged view which shows the structure of the spiral groove of the groove formation roller of the intermediate transfer unit of 2nd Embodiment of this invention. It is an enlarged view which shows the structure of the spiral groove of the groove formation roller of the intermediate transfer unit of 2nd Embodiment of this invention. It is a figure which shows the structure of the groove formation roller of the intermediate transfer unit of 3rd Embodiment of this invention. It is an enlarged view which shows the structure of the linear groove of the groove formation roller of the intermediate transfer unit of 3rd Embodiment of this invention. It is an enlarged view which shows the structure of the linear groove of the groove formation roller of the intermediate transfer unit of 4th Embodiment of this invention. It is an enlarged view which shows the structure of the linear groove of the groove formation roller of the intermediate transfer unit of 4th Embodiment of this invention.

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

First Embodiment
FIG. 1 is a schematic cross-sectional view showing the configuration of an image forming apparatus 100 on which an intermediate transfer unit 30 according to a first embodiment of the present invention is mounted, and shows a tandem type color image forming apparatus here. In the main body of the image forming apparatus 100, four image forming portions Pa, Pb, Pc and Pd are disposed in order from the upstream side in the transport direction (left side in FIG. 1). These image forming portions Pa to Pd are provided corresponding to images of four different colors (cyan, magenta, yellow and black), and cyan, magenta and yellow are formed by the respective steps of charging, exposure, development and transfer. And black images are sequentially formed.

  In these image forming portions Pa to Pd, photosensitive drums (image carriers) 1a, 1b, 1c and 1d for carrying visible images (toner images) of respective colors are disposed. An intermediate transfer belt (belt) 8 rotating clockwise is provided adjacent to each of the image forming portions Pa to Pd.

  A transfer sheet (recording medium) P to which a toner image is transferred is accommodated in a sheet cassette 16 at the lower portion of the apparatus, and the secondary transfer roller 9 and the intermediate transfer belt 8 are interposed through a sheet feeding roller 12a and a pair of registration rollers 12b. The sheet is conveyed to the nip portion with the driving roller 11 of FIG. A sheet made of dielectric resin is used for the intermediate transfer belt 8.

  Next, the image forming units Pa to Pd will be described. Around and below the photosensitive drums 1a to 1d rotatably disposed, charging devices 2a, 2b, 2c and 2d for charging the photosensitive drums 1a to 1d, and image information on the respective photosensitive drums 1a to 1d The developing device 3a, 3b, 3c and 3d for forming toner images on the photosensitive drums 1a to 1d, and the developer (toner) and the like remaining on the photosensitive drums 1a to 1d. The cleaning units 7a, 7b, 7c and 7d are provided.

  When image data is input from a host device such as a personal computer, first, the surfaces of the photosensitive drums 1a to 1d are uniformly charged by the chargers 2a to 2d. Next, light is irradiated according to the image data by the exposure device 5, and electrostatic latent images corresponding to the image data are formed on the respective photosensitive drums 1a to 1d. In the developing devices 3a to 3d, predetermined amounts of two-component developers (hereinafter, also referred to simply as developers) including toners of respective colors of cyan, magenta, yellow and black supplied from toner containers 4a to 4d and magnetic carriers are provided. It is filled. Toners in the developer are supplied from the developing devices 3a to 3d on the photosensitive drums 1a to 1d on which electrostatic latent images are formed, and are electrostatically attached. Thus, a toner image corresponding to the electrostatic latent image formed by the exposure from the exposure device 5 is formed.

  Then, by applying a predetermined transfer voltage to the primary transfer rollers 6a to 6d, cyan, magenta, yellow and black toner images on the photosensitive drums 1a to 1d are stretched over the driving roller 11 and the driven roller 10. The toner is primarily transferred onto the intermediate transfer belt 8. The toner and the like remaining on the surfaces of the photosensitive drums 1a to 1d after the primary transfer are removed by the cleaning units 7a to 7d.

  The intermediate transfer belt 8 is stretched around the driven roller 10 on the upstream side, the drive roller 11 on the downstream side, and backup rollers 40a and 40b described later, and the rotation of the drive roller 11 by the drive motor (not shown) Accordingly, when the intermediate transfer belt 8 starts to rotate counterclockwise, a nip portion between the transfer roller P and the secondary transfer roller 9 provided adjacent to the transfer roller P at a predetermined timing from the registration roller pair 12b ( The full-color image on the intermediate transfer belt 8 is transferred onto the transfer paper P. The transfer sheet P to which the toner image has been transferred passes through the sheet conveyance path 18 and is conveyed to the fixing unit 13.

  The transfer paper P conveyed to the fixing unit 13 is heated and pressed by the fixing roller pair 13a, and the toner image is fixed on the surface of the transfer paper P, whereby a predetermined full-color image is formed. The transfer paper P on which the full color image is formed is discharged as it is (or after it is distributed to the both-side conveyance path 20 by the branching unit 14 and the image is formed on both sides) by the discharge roller 15 to the discharge tray 17.

  2 is an external perspective view of the intermediate transfer unit 30 according to the first embodiment of the present invention as viewed from below, and FIG. 3 is a schematic view of the intermediate transfer unit 30 and the secondary transfer roller 9 according to the first embodiment of the present invention. It is sectional drawing which shows a structure.

  As shown in FIGS. 2 and 3, the intermediate transfer unit (transfer unit) 30 includes a unit body 34 composed of two side frames 31 and 32 and an upper surface frame (not shown), and the side frames 31 and 32. Between the primary transfer rollers 6a to 6d, the driven roller (cleaner facing roller) 10, the driving roller (secondary transfer facing roller) 11, the backup rollers 40a and 40b, and the endless belt stretched around these rollers The intermediate transfer belt 8 of FIG. The driven roller 10, the driving roller 11, and the backup rollers 40a and 40b are examples of the "tension roller" and the "groove forming roller" in the present invention. In FIG. 1, the backup rollers 40 a and 40 b are omitted to simplify the drawing.

  The primary transfer rollers 6 a to 6 d are disposed to face the photosensitive drums 1 a to 1 d with the intermediate transfer belt 8 interposed therebetween. The driving roller 11 is disposed to face the secondary transfer roller 9 with the intermediate transfer belt 8 interposed therebetween. The driven roller 10 is disposed opposite to a blade-like belt cleaner 19 for removing toner and the like remaining on the surface of the intermediate transfer belt 8 with the intermediate transfer belt 8 interposed therebetween.

  Here, in the present embodiment, one or more spiral grooves 51 (see FIG. 4) are provided on the outer peripheral surface of each of the driven roller 10, the driving roller 11, and the backup rollers 40a and 40b. In the following description, the driven roller 10, the driving roller 11, and the backup rollers 40a and 40b will be described as the groove forming roller 50.

  As shown in FIG. 4, the spiral groove 51 is formed by, for example, cutting the outer peripheral surface 50a of the groove forming roller 50, and is formed to a depth of 10 to 100 μm. The driving roller 11 is formed so that the depth of the spiral groove 51 is smaller than that of the driven roller 10 and the backup rollers 40a and 40b. In addition, the spiral groove 51 is formed such that the lead angle θ (inclination angle of the spiral groove 51 with respect to a plane perpendicular to the axial direction (direction of arrow A) of the groove forming roller 50) is 60 ° or less.

  As shown in FIG. 5, convex portions 55 are formed between the spiral grooves 51. A parallel surface 55 a extending in parallel with the axial direction of the groove forming roller 50 is formed on the outermost peripheral portion of the convex portion 55 in a cross sectional view along the axial direction of the groove forming roller 50. The axial length L55a of the parallel surface 55a is equal to or less than half the axial pitch P51 of the spiral groove 51.

  The inner circumferential length of the intermediate transfer belt 8 (see FIG. 3) is formed to be a non-integer multiple of the outer circumferential length of the groove forming roller 50. Further, the inner circumferential length of the intermediate transfer belt 8 is formed to be a non-integer multiple of the value obtained by dividing the outer circumferential length of the groove forming roller 50 by the number of the spiral grooves 51. That is, assuming that the inner peripheral length of the intermediate transfer belt 8 is L8, the outer peripheral length of the groove forming roller 50 is L50, and the number of spiral grooves 51 formed in the groove forming roller 50 is N51, L8 ≠ L50 × n (wherein , N is a positive integer), and L8 ≠ (L50 / N51) × n.

  In the present embodiment, as described above, the groove forming roller 50 in which one or more spiral grooves 51 are provided on the outer peripheral surface 50 a is provided, and the inner peripheral length of the intermediate transfer belt 8 is the outer peripheral length of the groove forming roller 50. It is a non-integer multiple. As a result, it is possible to suppress the occurrence of scratches on the inner peripheral surface of the intermediate transfer belt 8 due to foreign matter, and to suppress the occurrence of transfer failure.

  Specifically, when foreign matter adheres to the outer circumferential surface 50 a of the groove forming roller 50, the foreign matter is fitted into the spiral groove 51 of the groove forming roller 50, whereby the outer circumferential surface 50 a of the groove forming roller 50 and the intermediate transfer belt It is possible to suppress the damage to the inner peripheral surface of the intermediate transfer belt 8 when the foreign matter passes through the contact portion with the inner peripheral surface 8. Thereby, the inner peripheral surface of the intermediate transfer belt 8 can be prevented from being scratched. Further, even in the case where the foreign matter is not fitted into the spiral groove 51 of the groove forming roller 50 (when adhering to between the spiral grooves 51), the inner circumferential length of the intermediate transfer belt 8 is the same as that of the groove forming roller 50. Since it is a non-integer multiple of the outer peripheral length, the foreign matter attached to the predetermined position of the outer peripheral surface 50a of the groove forming roller 50 is a different position of the intermediate transfer belt 8 every time the intermediate transfer belt 8 makes one rotation Contact). Therefore, repeated damage to the same portion of the inner peripheral surface of the intermediate transfer belt 8 can be suppressed.

  On the other hand, when foreign matter adheres to the inner peripheral surface of the intermediate transfer belt 8, the foreign matter is a groove when the foreign matter passes through the contact portion between the outer peripheral surface 50a of the groove forming roller 50 and the inner peripheral surface of the intermediate transfer belt 8. By fitting into the spiral groove 51 of the forming roller 50, the inner peripheral surface of the intermediate transfer belt 8 can be prevented from being damaged. Thereby, the inner peripheral surface of the intermediate transfer belt 8 can be prevented from being scratched. When foreign matter does not fit into the spiral groove 51 of the groove forming roller 50 when the foreign matter passes through the contact portion between the outer peripheral surface 50 a of the groove forming roller 50 and the inner peripheral surface of the intermediate transfer belt 8 (helical grooves 51 Even if the inner circumferential length of the intermediate transfer belt 8 is a non-integer multiple of the outer circumferential length of the groove forming roller 50, it adheres to a predetermined position on the inner circumferential surface of the intermediate transfer belt 8). The foreign matter in contact with the groove forming roller 50 at different positions (slightly shifted positions) each time the intermediate transfer belt 8 makes one revolution. As a result, the foreign matter is inserted into and not inserted into the spiral groove 51 (it is in contact between the spiral grooves 51), so that the inner circumference of the intermediate transfer belt 8 each time the intermediate transfer belt 8 makes one revolution. Damage to the same part of the surface (the part to which the foreign matter is attached) can be suppressed.

  As a result of the above, damage to the inner peripheral surface of the intermediate transfer belt 8 can be prevented from becoming worse and reaching the outer peripheral surface of the intermediate transfer belt 8, so that transfer failure can be suppressed.

  Further, as described above, the inner peripheral length of the intermediate transfer belt 8 is a non-integer multiple of the value obtained by dividing the outer peripheral length of the groove forming roller 50 by the number of the spiral grooves 51. Thus, when foreign matter adheres to the inner peripheral surface of the intermediate transfer belt 8, the foreign matter passes through the contact portion between the outer peripheral surface 50a of the groove forming roller 50 and the inner peripheral surface of the intermediate transfer belt 8 Can be prevented from being fitted into the spiral groove 51 of the groove forming roller 50 every time (each time the spiral groove 51 is in contact with each other). For this reason, it is possible to reliably suppress that the same portion (the portion to which the foreign matter is attached) of the inner peripheral surface of the intermediate transfer belt 8 is damaged every time.

  Further, as described above, the drive roller 11 disposed opposite to the secondary transfer roller 9 with the intermediate transfer belt 8 interposed therebetween is the groove forming roller 50 (follower roller 10, backup rollers 40a and 40b) other than the drive roller 11. In comparison, the depth of the spiral groove 51 is formed to be smaller. Thus, the intermediate transfer belt 8 can be prevented from entering into the spiral groove 51 of the drive roller 11 (the intermediate transfer belt 8 is deformed in the thickness direction), so that a transfer failure occurs in the secondary transfer nip portion. Can be suppressed.

  Further, as described above, the drive roller 11 is disposed opposite to the secondary transfer roller 9 with the intermediate transfer belt 8 interposed therebetween, and the driven roller 10 disposed opposite to the belt cleaner 19 with the intermediate transfer belt 8 interposed therebetween. A groove 51 is provided. The driving roller 11 and the driven roller 10, which are disposed opposite to the secondary transfer roller 9 and the belt cleaner 19 with the intermediate transfer belt 8 interposed therebetween, are pressed by the secondary transfer roller 9 and the belt cleaner 19, the secondary transfer roller When a foreign matter passes between the belt 9 and the driving roller 11 and between the belt cleaner 19 and the driven roller 10, damage to the inner circumferential surface of the intermediate transfer belt 8 is increased. For this reason, applying the present invention to the drive roller 11 and the driven roller 10 is particularly effective.

  Further, as described above, the outermost peripheral portion of the convex portion 55 disposed between the spiral grooves 51 is parallel to the axial direction in the sectional view along the axial direction (the arrow A direction) of the groove forming roller 50 An extending parallel surface 55 a is formed, and an axial length L 55 a of the parallel surface 55 a is equal to or less than half of an axial pitch P 51 of the spiral groove 51. As a result, foreign matter adheres to the parallel surface 55 a of the outer peripheral surface 50 a of the groove forming roller 50, and foreign matter adhering to the inner peripheral surface of the intermediate transfer belt 8 does not adhere to the outer peripheral surface 50 a of the groove forming roller 50. Since it is possible to prevent contact with the parallel surface 55 a of the groove forming roller 50 when passing through the contact portion with the inner peripheral surface of the intermediate transfer belt 50, damage to the inner peripheral surface of the intermediate transfer belt 8 is more It can be suppressed.

  Further, as described above, the spiral groove 51 having a lead angle θ of 60 ° or less is formed on the outer peripheral surface 50 a of the groove forming roller 50. Accordingly, it is possible to suppress the occurrence of the sliding noise between the outer peripheral surface 50 a of the groove forming roller 50 and the inner peripheral surface of the intermediate transfer belt 8. When the lead angle θ of the spiral groove 51 is larger than 60 °, sliding noise is likely to occur between the outer peripheral surface 50 a of the groove forming roller 50 and the inner peripheral surface of the intermediate transfer belt 8.

Second Embodiment
In the intermediate transfer unit 30 according to the second embodiment of the present invention, as shown in FIG. 6, the outer periphery of the groove forming roller 50 (follower roller 10, drive roller 11, backup rollers 40a and 40b) as in the first embodiment. The surface 50 a is provided with one or more spiral grooves 51. Convex portions 55 are formed between the spiral grooves 51.

  In the present embodiment, the outermost peripheral portion of the convex portion 55 is formed by one or more non-parallel surfaces 55 b that are not parallel to the axial direction in a cross-sectional view along the axial direction (the arrow A direction) of the groove forming roller 50 . The non-parallel surface 55 b may be formed by a curved surface as shown in FIG. 6 or a flat surface as shown in FIG. 7 in a cross-sectional view along the axial direction of the groove forming roller 50.

  The remaining structure of the second embodiment is similar to that of the aforementioned first embodiment.

  In the present embodiment, as described above, the outermost peripheral portion of the convex portion 55 is formed by the non-parallel surface 55b which is not parallel to the axial direction in the sectional view along the axial direction (the arrow A direction) of the groove forming roller 50 There is. As a result, the foreign matter is easily fitted into the spiral groove 51 of the groove forming roller 50, so that the inner peripheral surface of the intermediate transfer belt 8 can be further prevented from being damaged.

  The other effects of the second embodiment are the same as those of the first embodiment.

Third Embodiment
In the intermediate transfer unit 30 according to the third embodiment of the present invention, as shown in FIG. 8, unlike the first and second embodiments, the outer peripheral surface of each of the driven roller 10, the drive roller 11, and the backup rollers 40a and 40b. A plurality of linear grooves 52 are provided in the. In the following description, the driven roller 10, the driving roller 11, and the backup rollers 40a and 40b will be described as the groove forming roller 50.

  The linear grooves 52 extend in the axial direction (arrow A direction) of the groove forming roller 50 and are provided at a predetermined pitch along the circumferential direction of the outer peripheral surface 50 a. The linear groove 52 is formed by, for example, cutting the outer peripheral surface 50a of the groove forming roller 50, and is formed to a depth of 10 to 100 μm. The driving roller 11 is formed such that the depth of the linear groove 52 is smaller than that of the driven roller 10 and the backup rollers 40a and 40b.

  As shown in FIG. 9, convex portions 56 are formed between the linear grooves 52. A parallel surface 56a extending in parallel with the circumferential direction (arrow B direction) of the groove forming roller 50 is formed on the outermost peripheral portion of the convex portion 56 in a cross-sectional view orthogonal to the axial direction of the groove forming roller 50. The circumferential length (or angle) L56a of the parallel surface 56a is equal to or less than half the circumferential pitch (or pitch angle) P52 of the linear groove 52.

  Further, as in the first and second embodiments, the inner peripheral length of the intermediate transfer belt 8 (see FIG. 3) is formed to be a non-integer multiple of the outer peripheral length of the groove forming roller 50. Further, the inner peripheral length of the intermediate transfer belt 8 is formed to be a non-integer multiple of the value obtained by dividing the outer peripheral length of the groove forming roller 50 by the number of linear grooves 52. That is, assuming that the inner peripheral length of the intermediate transfer belt 8 is L8, the outer peripheral length of the groove forming roller 50 is L50, and the number of linear grooves 52 formed in the groove forming roller 50 is N52, L8 ≠ L50 × n (wherein , N is a positive integer), and L8 ≠ (L50 / N52) × n.

  The remaining structure of the third embodiment is similar to that of the aforementioned first and second embodiments.

  In the present embodiment, as described above, the outer peripheral surface 50 a of the groove forming roller 50 is provided with the linear groove 52 and the convex portion 56 disposed between the linear grooves 52, and the convex portion 56 is provided. A parallel surface 56a extending in parallel with the circumferential direction (the arrow B direction) of the groove forming roller 50 is formed on the outermost peripheral portion of the groove forming roller 50 in a sectional view orthogonal to the axial direction of the groove forming roller 50. The direction length L56a is equal to or less than half the circumferential pitch P52 of the linear groove 52. As a result, foreign matter adheres to the parallel surface 56 a of the outer peripheral surface 50 a of the groove forming roller 50 or foreign matter adhering to the inner peripheral surface of the intermediate transfer belt 8 with the outer peripheral surface 50 a of the groove forming roller 50 Since it is possible to prevent contact with the parallel surface 56 a of the groove forming roller 50 when passing through the contact portion with the inner peripheral surface of the intermediate transfer belt 50, damage to the inner peripheral surface of the intermediate transfer belt 8 is more It can be suppressed.

  The other effects of the third embodiment are similar to those of the first and second embodiments.

Fourth Embodiment
In the intermediate transfer unit 30 according to the fourth embodiment of the present invention, as shown in FIG. 10, the outer periphery of the groove forming roller 50 (follower roller 10, driving roller 11, backup rollers 40a and 40b) as in the third embodiment. The surface 50 a is provided with a plurality of linear grooves 52. Convex portions 56 are formed between the linear grooves 52.

  In the present embodiment, the outermost peripheral portion of the convex portion 56 is at least one non-parallel surface 56 b not parallel to the circumferential direction (the arrow B direction) of the groove forming roller 50 in a cross sectional view orthogonal to the axial direction of the groove forming roller 50. It is formed by The non-parallel surface 56 b may be formed by a curved surface as shown in FIG. 10 or a flat surface as shown in FIG. 11 in a cross-sectional view orthogonal to the axial direction of the groove forming roller 50.

  The remaining structure of the fourth embodiment is similar to that of the aforementioned third embodiment.

  In the present embodiment, as described above, the outermost peripheral portion of the convex portion 56 is a nonparallel surface that is not parallel to the circumferential direction (arrow B direction) of the groove forming roller 50 in a cross sectional view orthogonal to the axial direction of the groove forming roller 50 It is formed by 56b. As a result, the foreign matter is easily fitted into the linear groove 52 of the groove forming roller 50, so that the inner peripheral surface of the intermediate transfer belt 8 can be further prevented from being damaged.

  The other effects of the fourth embodiment are the same as those of the third embodiment.

  It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is indicated not by the description of the embodiments described above but by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

  For example, although the example which applied this invention to the color printer was shown, this invention is not limited to this. Needless to say, the present invention can be applied to various image forming apparatuses such as color copying machines and digital multi-function machines having a transfer unit having a belt, a primary transfer roller, and a plurality of stretching rollers for stretching the belt.

  In the above-described embodiment, the intermediate transfer unit 30 including the four primary transfer rollers 6a to 6d disposed opposite to the four photosensitive drums 1a to 1d with the intermediate transfer belt 8 interposed therebetween has been described. The present invention is also applicable to a transfer unit provided with only one primary transfer roller disposed opposite to the photosensitive drum across the belt.

  Further, in the above embodiment, the example in which the spiral groove 51 or the linear groove 52 is provided in all the tension rollers (follower roller 10, driving roller 11, backup rollers 40a and 40b) has been described. The spiral groove 51 or the linear groove 52 may be provided only in part of the driving roller 11 and the backup rollers 40a and 40b).

  In the above embodiment, damage to the intermediate transfer belt 8 occurs when foreign matter adheres to the outer peripheral surface 50 a of the groove forming roller 50 and when foreign matter adheres to the inner peripheral surface of the intermediate transfer belt 8. In the case where foreign matter is present between the inner peripheral surface and the outer peripheral surface of the intermediate transfer belt 8 (in the case where foreign matter is mixed in the belt at the time of manufacturing the intermediate transfer belt 8), By applying the present invention, damage to the inner peripheral surface and the outer peripheral surface of the intermediate transfer belt 8 can be suppressed.

1a to 1d Photosensitive drum (image carrier)
6a to 6d Primary transfer roller 8 Intermediate transfer belt (belt)
9 secondary transfer roller 10 driven roller (stretching roller, groove forming roller, cleaner facing roller)
11 Drive roller (stretching roller, groove forming roller, secondary transfer counter roller)
19 belt cleaner 30 intermediate transfer unit (transfer unit)
40a, 40b backup roller (stretching roller, groove forming roller)
Reference Signs List 50 groove forming roller 50a outer peripheral surface 51 helical groove 52 linear groove 55, 56 convex portion 55a, 56a parallel surface 55b, 56b non-parallel surface 100 image forming apparatus L55a, L56a length P transfer paper (recording medium)
P51, P52 Pitch Pa to Pd Image forming part θ Lead angle

Claims (10)

An endless belt moving along the image forming section;
A primary transfer roller disposed opposite to the image carrier disposed in the image forming unit with the belt interposed therebetween, and transferring a toner image formed on the image carrier onto the belt;
A plurality of stretching rollers for stretching the belt;
Equipped with
The stretching roller is provided with one or more helical grooves on the outer peripheral surface, or a plurality of linear grooves extending in the axial direction of the stretching roller and arranged at a predetermined pitch along the circumferential direction of the outer peripheral surface Containing grooved rollers,
The transfer unit is characterized in that an inner circumferential length of the belt is a non-integer multiple of an outer circumferential length of the groove forming roller.   2. The transfer unit according to claim 1, wherein an inner peripheral length of the belt is a non-integer multiple of a value obtained by dividing an outer peripheral length of the groove forming roller by the number of streaks of the spiral groove or the linear groove. The groove forming roller is
Along with being provided multiple
A secondary transfer counter roller disposed opposite to the secondary transfer roller for transferring the toner image formed on the belt to a recording medium, with the belt interposed therebetween;
The secondary transfer opposing roller is formed so that the depth of the spiral groove or the linear groove is smaller than that of the groove forming roller other than the secondary transfer opposing roller. The transfer unit according to 1 or 2.   The groove forming roller according to any one of claims 1 to 3, wherein the groove forming roller includes a cleaner facing roller disposed opposite to the belt cleaner for removing the toner on the surface of the belt with the belt interposed therebetween. Transfer unit. The spiral groove and a convex portion disposed between the spiral grooves are provided on an outer peripheral surface of the groove forming roller,
A parallel surface extending in parallel to the axial direction is formed on the outermost peripheral portion of the convex portion in a sectional view along the axial direction of the groove forming roller,
The transfer unit according to any one of claims 1 to 4, wherein a length of the parallel surface in the axial direction is equal to or less than a half of a pitch of the spiral groove in the axial direction. The spiral groove and a convex portion disposed between the spiral grooves are provided on an outer peripheral surface of the groove forming roller,
The outermost periphery part of the said convex part is formed by the nonparallel surface which is not parallel to the said axial direction in the cross sectional view along the axial direction of the said groove formation roller, The any one of the Claims 1-4 characterized by the above-mentioned. The transfer unit according to item 2.   The transfer unit according to any one of claims 1 to 6, wherein the spiral groove having a lead angle of 60 ° or less is formed on an outer peripheral surface of the groove forming roller. The outer peripheral surface of the groove forming roller is provided with the linear groove and a convex portion disposed between the linear grooves,
A parallel surface extending in parallel with the circumferential direction of the groove forming roller is formed on the outermost peripheral portion of the convex portion in a cross sectional view orthogonal to the axial direction of the groove forming roller,
The transfer unit according to any one of claims 1 to 4, wherein a length of the parallel surface in the circumferential direction is equal to or less than half a pitch of the linear groove in the circumferential direction. The outer peripheral surface of the groove forming roller is provided with the linear groove and a convex portion disposed between the linear grooves,
The outermost peripheral portion of the convex portion is formed by a non-parallel surface which is not parallel to the circumferential direction of the groove forming roller in a cross sectional view orthogonal to the axial direction of the groove forming roller. The transfer unit according to any one of the above.   An image forming apparatus comprising the transfer unit according to any one of claims 1 to 9.

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