JP5880062B2 - Transfer device - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to a transfer apparatus capable of mechanically correcting in advance a reduction in image quality of a formed image due to central distortion that is likely to occur on a transfer belt in a secondary transfer portion.

  Conventionally, a toner image is formed on a photoreceptor by electrophotography using toner, the toner image is primarily transferred to a belt, the primary transfer image is secondarily transferred to a sheet, and the transferred toner image is transferred by a fixing device. An image forming apparatus that forms a monochrome or full-color image by fixing on a sheet is known. (For example, see Patent Documents 1 and 2.)

  In Patent Document 1, in order to form a high-quality image without color misregistration or color unevenness on an image transferred from the image carrier to the intermediate transfer belt, the position where the drive is transmitted from the image carrier to the intermediate transfer belt is the image carrier. There has been proposed a configuration that is located downstream of the primary transfer position at which an image is transferred from the body to the intermediate transfer belt with respect to the conveyance direction of the intermediate transfer belt.

  In Patent Document 2, in order to prevent non-uniformity such as transfer, charging, and charge removal due to corona discharge when a toner image on a belt-shaped intermediate transfer member is retransferred to a transfer material, the curved surface shape of the surface to be charged is used. It has been proposed to use a corona discharger in which a sawtooth electrode having a tip portion extending along the line is used as a discharge electrode.

JP-A-10-091010 JP 2001-356564 A

  By the way, in either of the above Patent Documents 1 and 2, in order to form a high-quality image, in Patent Document 1, the drive transmission position to the intermediate transfer belt is devised, and in Patent Document 2, the corona used for the transfer unit. The electrode shape of the discharger has been devised.

  However, in order to form a high-quality image, the state of the transfer portion of the intermediate transfer belt is also an important requirement. For example, in a secondary transfer roller type image forming apparatus using a transfer belt as described above, distortion tends to occur on the center side of the transfer belt before and after the roller.

  When distortion occurs on the center side of the transfer belt, the sheet tends to gather on the center side when the transfer material (paper) enters the transfer belt of the secondary transfer portion. When distortion is collected on the center side of the sheet, non-uniformity occurs in the transferred image, and the image quality of the image is degraded.

  However, neither of Patent Documents 1 and 2 mentions that distortion easily occurs at the center side of the transfer belt, and therefore, naturally, there is no suggestion of an apparatus or method for correcting the distortion. Not done.

The present invention solves the above-described conventional problems , and corrects the central distortion of the transfer belt that easily occurs in the secondary transfer portion , and also transfers the image to the printing medium that easily occurs in the center of the secondary transfer portion. to prevent distortion, and to provide a transfer device which image quality degradation of the formed image mechanistically can be 矯 positive.

In order to solve the above-described problems, a transfer device according to the present invention includes a transfer belt and a first of the plurality of rollers that are press-contacted by the transfer roller via the transfer belt that is circulated around the plurality of rollers. One belt support roller, a second belt support roller of the plurality of rollers provided adjacent to the first belt support roller upstream in the movement direction of the transfer belt, and the first belt support A third belt support roller of the plurality of rollers disposed between the roller and the second belt support roller and press-contacting the transfer belt so as to stretch the transfer belt from the inside to the outside; comprising an auxiliary guide section consisting of a plate-shaped horizontal portion and the standing portion is hook, the said third belt support rollers, in order to correct the prone central distortion to the transfer belt, the central portion from both end portions go to Thus are gradually formed thicker in diameter, the auxiliary guide faces apart the transfer belt to approximately 1/4 the peripheral surface of the transfer belt of the second belt support roller is passed over, the standing The installation portion is warped in a direction of gradually separating from the transfer belt from the center portion to both end portions on the opposite side surface facing the second belt support roller .
In order to solve the above-described problem, a transfer device according to the present invention includes a first roller that circulates and moves a transfer belt that is stretched around a plurality of rollers, and a first roller that is pressed by the transfer roller via the transfer belt. In the transfer device having two rollers, a third roller is disposed between the first roller and the second roller and presses against the transfer belt so as to stretch the transfer belt from the inside to the outside. A roller and an auxiliary guide arranged to face the first roller across the transfer belt and guide the conveyance of the printing medium, and the third roller is located at the center from both ends. The diameter of the auxiliary guide is gradually increased as it goes, and the auxiliary guide is formed on the opposite side surface facing the first roller, the surface that guides the conveyance of the printing medium, gradually from the center to both ends. Belt It is formed in a shape warped in a direction away.

According to the transfer device of the present invention, to correct the central distortion-prone transfer belt at the secondary transfer section, and to prevent distortion of the transferred image on the recording medium with prone in the secondary transfer portion center, formed There is an effect that the image quality deterioration of the image can be mechanically corrected .

1 is a cross-sectional view illustrating an internal configuration of a full-color image forming apparatus (printer) according to Embodiment 1 of the invention. (a) is an enlarged view showing the configuration in the vicinity of the secondary transfer portion in the configuration of the printer according to the first embodiment, and (b) is a driven roller, correction auxiliary roller, drive roller, transfer belt, primary belt in (a). FIG. 4C is a perspective view showing only the transfer roller taken out, and FIG. 5C is a view showing the correction auxiliary roller in a state where the transfer belt in FIG. (a) is an enlarged view showing the configuration in the vicinity of the secondary transfer portion in the configuration of the printer according to the second embodiment, and (b) is a driven roller, a correction auxiliary roller, a drive roller, a transfer belt, and an auxiliary in (a). FIG. 4C is a perspective view showing only the guide and the primary transfer roller, and FIG. 5C is a view showing the transfer belt shown in FIG.

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

  FIG. 1 is a cross-sectional view illustrating an internal configuration of a full-color image forming apparatus (hereinafter simply referred to as a printer) according to Embodiment 1 of the present invention.

  A printer 1 shown in FIG. 1 is an electrophotographic secondary transfer tandem color image forming apparatus, and includes an image forming unit 2, a transfer belt unit 3, a toner supply unit 4, a paper feeding unit 5, and a belt type fixing device. It comprises a unit 6 and a transport unit 7 for duplex printing.

  The image forming unit 2 is in contact with the lower running unit surface 8a of the transfer belt 8 of the transfer belt unit 3 and multi-stages four developing devices 9 (9m, 9c, 9y, 9k) from right to left in FIG. It consists of a side-by-side configuration. The image forming unit 2 is held by a frame of the printer 1 main body so as to be movable up and down from a printing execution position shown in FIG. 1 to a maintenance position below it.

  Of the four developing devices 9, three developing devices 9m, 9c, and 9y on the downstream side (right side in the figure) are magenta (M), cyan (C), and yellow (Y), which are subtractive three primary colors, respectively. A mono-color image is formed with the color toner, and the developing device 9k forms a monochrome image mainly with black (K) toner used for characters and dark portions of the image.

  Each of the developing devices 9 has the same configuration except for the color of the toner that develops the image. Therefore, the configuration of the developing device 9k for black (K) toner will be described below as an example.

  The developing device 9 includes a photosensitive drum 11 at the top. The photosensitive drum 11 has a peripheral surface made of, for example, an organic photoconductive material. A cleaner 12, a charging roller 13, an optical writing head 14, and a developing roller 16 of a developing device 15 are arranged around the periphery of the photosensitive drum 11.

  The developing device 15 includes a housing 17 that covers the outside, a partition wall 18 provided inside, a developing roller 16, a first stirring and conveying screw 19, and a second stirring and conveying screw 21. The first and second agitating / conveying screws 19 and 21 are each composed of a screw shaft and a fin that is integrally formed with the screw shaft and rotates, although not particularly illustrated.

  The developing unit 15 includes a reserve tank 22 of the toner supply unit 4 and yellow (Y), magenta (M), cyan (C), and black (K) as indicated by Y, M, C, and K in FIG. ) Is supplied.

  The transfer belt unit 3 has an endless transfer belt 8 that extends in the shape of a flat loop in the left-right direction in the figure at approximately the center of the main unit, and the transfer belt 8 is stretched over the transfer belt 8. A driving roller 23 and driven rollers 24 and 25 are provided that circulate in a counterclockwise direction indicated by an arrow a in the figure.

  The driven roller 25 is disposed adjacent to the downstream side (the upper side in FIG. 1) of the driving roller 23, and the correction auxiliary roller 26 is disposed between the driving roller 23 and the driven roller 25. The correction auxiliary roller 26 is also a driven roller that rotates in accordance with the circulating movement of the transfer belt 8.

  In the transfer belt 8, the toner image on the photosensitive drum 11 is directly transferred (primary transfer) by the primary transfer roller 27 to the lower belt surface 8a that circulates downward. The primary transfer roller 27 is in pressure contact with the photosensitive drum 11 from the back surface of the transfer belt 8 through the transfer belt 8.

  The transfer belt 8 conveys the primary-transferred toner image to the secondary transfer unit in order to transfer (secondary transfer) to the paper. The secondary transfer portion is formed by a driven roller 25, the transfer belt 8, and a secondary transfer roller 28 that is in pressure contact with the driven roller 25 via the transfer belt 8.

  The transfer belt 8, the driving roller 23, the driven rollers 24 and 25, the correction auxiliary roller 26, and the primary transfer roller 27 are integrally incorporated in the transfer belt unit 3.

  The transfer belt unit 3 is provided with a belt cleaner 31 having a cleaning blade 29 that comes into contact with the surface of the drive roller 23. A waste toner collection container 32 is detachably disposed below the belt cleaner 31.

  In the belt cleaner 31, the cleaning blade 29 comes into contact with the surface of the transfer belt 8 to scrape and remove the waste toner, and the waste toner is sent to a waste toner collection container 32 below by a conveying screw.

  The toner supply unit 4 includes four reserve tanks 22 indicated by Y, M, C, and K, which are disposed from the left to the right above the upper running unit of the transfer belt 8, and the reserve tanks 22. A toner cartridge 33 for replenishing toner indicated by Y, M, C, and K is detachably disposed.

  The four toner cartridges 33 store yellow (Y), magenta (M), cyan (C), and black (K) toner, respectively, and the four reserve tanks 22 are respectively mounted on the toner. The toner is replenished from the cartridge 33.

  These four reserve tanks 22 are hidden behind the opposite side of the transfer belt unit 3 in FIG. 1, but are connected to the corresponding developing devices 15 of the developing device 9 by toner supply paths.

  Although not particularly shown, the toner supply unit 4 is held on the frame of the printer 1 main body so as to be able to be raised and lowered from the printing execution position shown in FIG. 1 to a maintenance position above it.

  On the left side of the toner supply unit 4, two electrical parts 34 are disposed from the left side of the belt cleaner 31 to above the drive roller 23. The electrical unit 34 includes a circuit board on which a control device including a plurality of electronic components is mounted.

  The paper feed unit 5 includes two paper feed cassettes 35 (35a, 35b) arranged in two upper and lower stages. A paper take-out roller 36, a feed roller 37, a separating roller 38, and a standby conveyance roller pair 39 are disposed in the vicinity of the paper feed opening (right side in the drawing) of the two paper feed cassettes 35, respectively.

  In the paper conveyance direction (vertical upward direction in the figure) of the standby conveyance roller pair 39, the above-described secondary transfer roller 28 that is in pressure contact with the driven roller 25 via the transfer belt 8 is disposed, and the above-described secondary transfer roller 28 is applied to the paper. The next transfer portion is formed.

  A belt-type heat fixing unit 6 is disposed downstream (upward in the drawing) of the secondary transfer portion. On the further downstream side of the belt-type heat fixing unit 6, a pair of carry-out rollers 41 for carrying out the fixed paper from the belt-type heat fixing unit 6, and a paper discharge tray on which the carried paper is formed on the upper surface of the apparatus. A paper discharge roller pair 43 for discharging the paper to 42 is provided.

  The conveyance unit 7 for double-sided printing also serves as an opening / closing member whose outer surface (right outer surface in the drawing) opens or shields the inside of the printer 1 from the side surface to the outside.

  The duplex printing transport unit 7 has a start return path 44a that branches rightward in the figure from immediately before the paper discharge roller pair 43, an intermediate return path 44b that bends downward, and a left lateral direction opposite to the above. Thus, a return path consisting of a terminal return path 44c for finally inverting the return sheet is provided.

  Further, five pairs of return rollers 45 (45a, 45b, 45c, 45d, 45e) are arranged in the middle of the return path. The exit of the end return path 45e joins the conveyance path to the pair of standby conveyance rollers 39 corresponding to the sheet feeding cassette 35a below the sheet feeding section 5.

  FIG. 2A is an enlarged view showing the configuration in the vicinity of the secondary transfer portion in the configuration of the printer 1 of the first embodiment, and FIG. 2B is a diagram illustrating the driven roller 25 and the correction in FIG. FIG. 2C is a perspective view showing only the auxiliary roller 26, the driving roller 23, the transfer belt 8, and the primary transfer roller 27. FIG. 2C shows the transfer belt 8 of FIG. FIG.

  2A, 2B, and 2C, the same components as those shown in FIG. 1 are denoted by the same reference numerals as those in FIG. 2A also shows a cam base 46 of the transfer belt unit 3 that is not shown in FIG.

  As shown in FIGS. 2A, 2B, and 2C, on the transfer belt unit 3 side in the secondary transfer portion of this example, a plurality of rollers that are rotated by being laid around a transfer belt 8 that circulates and moves. Of these, a driven roller 25 as a first belt support roller is disposed.

  As shown in FIG. 2A, a transfer roller 28 is pressed against the driven roller 25 via the transfer belt 8. The transfer belt 8 circulates in the counterclockwise direction as indicated by an arrow a in FIGS. 1 and 2B.

  Adjacent to the driven roller 25 in the moving direction upstream of the transfer belt 8 (downward in FIGS. 2A, 2B, and 2C), a second belt support of the plurality of rollers is provided. A driving roller 23 as a roller is provided.

  A correction auxiliary roller 26 as a third belt support roller of the plurality of rollers is provided between the driven roller 25 as the first belt support roller and the drive roller 23 as the second belt support roller. It is arranged.

  As shown in FIG. 2 (c), the correction auxiliary roller 26 is a drum-shaped elongated roller whose diameter gradually increases from the both ends toward the center. The correction auxiliary roller 26 is in pressure contact with the transfer belt 8 so as to stretch the transfer belt 8 from the inside to the outside.

  The correction auxiliary roller 26 corrects the central distortion that tends to occur in the transfer belt 8 in the secondary transfer portion due to its drum-shaped shape, and brings the recording medium into contact with both sides sequentially from the center portion of the transfer belt 8. To function.

  In this way, not only the central distortion of the transfer belt 8 is corrected, but also the recording medium is brought into contact with both sides sequentially from the central portion of the transfer belt 8, so that there is a problem that air enters between the recording medium and the transfer belt. Thus, it is possible to always form a high-quality image.

  FIG. 3A is an enlarged view showing the configuration in the vicinity of the secondary transfer portion in the configuration of the printer according to the second embodiment, and FIG. 3B is a driven roller and an auxiliary for correction in FIG. FIG. 3C is a perspective view showing only a roller, a driving roller, a transfer belt, an auxiliary guide, and a primary transfer roller, and FIG. 3C is a view with the transfer belt of FIG. 3B removed.

  In this example, since the configuration other than the newly installed auxiliary guide 47 is the same as that in the first embodiment, FIGS. 3A, 3B, and 3C are necessary for explanation. Only the portions are given the same numbers as in FIGS. 2 (a), (b), and (c).

  The auxiliary guide 47 shown in FIGS. 3 (a), 3 (b), and 3 (c) is a hook-shaped member having a plate-like horizontal portion 47a and a standing portion 47b. The auxiliary guide 47 is held by fixing the horizontal portion 47 a to the guide portion frame 48.

  The auxiliary guide 47 is disposed so as to face the substantially ¼ circumferential surface around which the transfer belt 8 of the driving roller 23 is stretched, with the transfer belt 8 interposed therebetween. Further, although the standing portion 47b of the auxiliary guide 47 does not appear clearly in the drawing, the opposite side surface facing the drive roller 23 is cut so as to become thinner from the both end portions to the central portion.

  In other words, the auxiliary guide 47 is warped on the opposite side surface facing the drive roller 23 in a direction gradually separating from the transfer belt 8 from the center to both ends.

  In this configuration, the recording medium is recorded on the secondary transfer portion formed by the driven roller 25, the transfer belt 8, and the secondary transfer roller 28 that is in pressure contact with the driven roller 25 via the transfer belt 8 shown in FIG. The auxiliary guide 47 assists that the recording medium sequentially contacts both sides from the central portion of the transfer belt 8 due to the warp of the opposite side surface of the standing portion 47b.

  As described above, since the recording medium is assisted to sequentially contact both sides from the center of the transfer belt 8, a problem that air enters between the recording medium and the transfer belt is better prevented. An image having an image quality can be formed.

Although several embodiments of the present invention have been described, the present invention is included in the invention described in the claims and the equivalents thereof. Hereinafter, the invention described in the scope of claims of the present application will be appended.
[Appendix 1]

A transfer belt;
A first belt support roller of the plurality of rollers that is pressed by a transfer roller via the transfer belt that is circulated and laid around a plurality of rollers;
A second belt support roller of the plurality of rollers provided adjacent to the first belt support roller upstream in the movement direction of the transfer belt; and
A third of the plurality of rollers disposed between the first belt support roller and the second belt support roller and press-contacting the transfer belt so as to stretch the transfer belt from the inside to the outside. A belt support roller of
With
The third belt support roller is formed so that its diameter gradually increases from both ends toward the center in order to correct the center distortion that tends to occur in the transfer belt.
A transfer device characterized by that.
[Appendix 2]

A cross-section composed of a plate-like horizontal portion and a standing portion further includes a saddle-shaped auxiliary guide,
The auxiliary guide is opposed to the substantially 1/4 circumferential surface on which the transfer belt of the second belt support roller is stretched across the transfer belt,
The standing portion is warped in a direction gradually separating from the transfer belt from a center portion to both end portions on the opposite side surface facing the second belt support roller.
The transfer apparatus according to appendix 1, wherein:
[Appendix 3]

The second belt support roller is configured as a drive roller that rotates by receiving a driving force from a drive source to circulate and move the transfer belt, and the first belt support roller and the third belt support roller are , Configured as a driven roller that rotates according to the circulating movement of the transfer belt,
The transfer apparatus according to appendix 1 or 2, wherein:

  INDUSTRIAL APPLICABILITY The present invention can be used for an image forming apparatus that can mechanically correct a deterioration in image quality of a formed image due to central distortion that is likely to occur on a transfer belt in a secondary transfer portion.

1 Full-color image forming device (printer)
DESCRIPTION OF SYMBOLS 2 Image formation part 3 Transfer belt unit 4 Toner supply part 5 Paper feed part 6 Belt type fixing unit 7 Conveyor unit for double-sided printing 8 Transfer belt 8a Lower running part surface 9 (9y, 9m, 9c, 9k) Developing device 11 Photoconductor Drum 12 Cleaner 13 Charging roller 14 Optical writing head 15 Developer 16 Developing roller 17 Housing 18 Bulkhead 19 First stirring and conveying screw 21 Second agitating and conveying screw 22 Reserve tank 23 Drive rollers 24 and 25 Drive roller 26 For correction Auxiliary roller 27 Primary transfer roller 28 Secondary transfer roller 29 Cleaning blade 31 Belt cleaner 32 Waste toner collection container 33 Toner cartridge 34 Electrical section 35 (35a, 35b) Paper feed cassette 36 Paper take-out roller 37 Feed roller 38 Rolling roller 39 Standby Transport roller 41 Unloading roller pair 42 Discharging tray 43 Discharging roller pair 44a Start return path 44b Intermediate return path 44c End return path 45 (45a, 45b, 45c, 45d, 45e) Return roller pair 46 Transfer belt unit cam base 47 Auxiliary guide 47a Horizontal part 47b Standing part 48 Guide part frame

Claims (3)

A transfer belt;
A first belt support roller of the plurality of rollers that is pressed by a transfer roller via the transfer belt that is circulated and laid around a plurality of rollers;
A second belt support roller of the plurality of rollers provided adjacent to the first belt support roller upstream in the movement direction of the transfer belt; and
A third of the plurality of rollers disposed between the first belt support roller and the second belt support roller and press-contacting the transfer belt so as to stretch the transfer belt from the inside to the outside. A belt support roller of
An auxiliary guide having a bowl-shaped cross section composed of a plate-like horizontal portion and a standing portion,
With
It said third belt support rollers, in order to correct the prone central distortion in the transfer belt are gradually formed thicker in diameter toward the central portion from both end portions,
The auxiliary guide is opposed to the substantially 1/4 circumferential surface on which the transfer belt of the second belt support roller is stretched across the transfer belt,
The standing portion is warped in a direction gradually separating from the transfer belt from a center portion to both end portions on the opposite side surface facing the second belt support roller.
A transfer device characterized by that. The second belt support roller is configured as a drive roller that rotates by receiving a driving force from a drive source to circulate and move the transfer belt, and the first belt support roller and the third belt support roller are , Configured as a driven roller that rotates according to the circulating movement of the transfer belt,
The transfer device of claim 1 Symbol mounting, characterized in that. In a transfer apparatus having a first roller that circulates and moves a transfer belt stretched around a plurality of rollers, and a second roller that is pressed by the transfer roller via the transfer belt,
A third roller disposed between the first roller and the second roller and in pressure contact with the transfer belt so as to stretch the transfer belt from the inside to the outside;
An auxiliary guide that is disposed to face the first roller across the transfer belt and guides the conveyance of the printing medium;
With
The third roller is formed so that the diameter gradually increases from the both ends to the center.
The auxiliary guide is formed in a shape that gradually faces away from the transfer belt from a center portion to both end portions of a surface that is opposite to the first roller and that guides the conveyance of the printing medium. Yes,
A transfer device characterized by that.