JP3261095B2 - Sheet conveying device and image forming apparatus provided with the sheet conveying device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying apparatus used for an image forming apparatus such as a printer, a copying machine, a facsimile, etc. for forming an image on a sheet such as paper or a plastic sheet, and an image provided with the sheet conveying apparatus. The present invention relates to a forming apparatus.

[0002]

2. Description of the Related Art For example, image forming apparatuses for forming a color image on a sheet of paper or the like are generally classified into four types of recording systems: a transfer drum system, an intermediate transfer system, a tandem system, and a multiple development system. Of these, in response to the recent demand for high-speed recording, a tandem method that is superior to other methods in recording speed has been often adopted. In the tandem type image forming apparatus, black, cyan, magenta, and yellow image forming units are appropriately arranged in a sheet conveying direction, and a sheet is sequentially conveyed to each of these image forming units by a sheet conveying device, and each image is formed. After sequentially transferring the toner images of each color formed by the forming unit onto the sheet, a desired color image is fixed on the sheet by a fixing device (fixing unit).

Here, the sheet conveying device used in such a tandem-type image forming apparatus has a plurality of image forming means arranged in a line in the sheet conveying direction, so that the sheet fed from the sheet feeding unit is not used. The suction conveyance is performed by an endless belt wound around a driving roller and a driven roller.

[0004]

In the tandem-type image forming apparatus as described above, a color shift occurs unless images of each color are formed on a sheet with high accuracy. However, the endless belt wound around the driving roller and the driven roller may cause a lateral displacement in a direction orthogonal to the sheet conveying direction during operation due to an error in parallelism between the driving roller and the driven roller. There is. When such a lateral shift of the belt occurs, the image forming position in the direction orthogonal to the sheet conveying direction gradually shifts from the first image forming unit to the last image forming unit, and this becomes a color shift. Will appear.

In order to improve such a problem, a protrusion is formed on the belt, and the protrusion is engaged with the grooves of the driving roller and the driven roller to prevent lateral deviation of the belt. Technology has already been devised (Japanese Unexamined Patent Publication
-277147). However, in this conventional technique, the protrusion of the belt may come off from the groove of the roller, and it has not been enough as a technique for preventing the lateral displacement of the belt. Therefore, there has been a demand for the development of a technology capable of effectively preventing the lateral displacement of the belt.

SUMMARY OF THE INVENTION The present invention has been devised in order to meet such a demand, and a sheet conveying apparatus capable of effectively preventing a lateral deviation of a belt and conveying a sheet with high accuracy, and a color shift apparatus. It is an object of the present invention to provide an image forming apparatus that hardly occurs and can meet a demand for higher image quality.

[0007]

According to the present invention, a driving roller and a driven roller are arranged at a predetermined interval in a sheet conveying direction, and an endless sheet conveying belt is wound around the driving roller and the driven roller. By driving the sheet conveying belt with the drive roller, the sheet is sequentially conveyed to a plurality of image forming units arranged in the sheet conveying direction. Projections are formed at both ends on the inner peripheral side of the sheet conveying belt. Further, small-diameter portions are formed so as to protrude from both side end surfaces of the driving roller and the driven roller. And, by supporting the projecting portion of the sheet conveying belt with the small diameter portions of the driving roller and the driven roller, the sheet supporting surface of the sheet conveying belt is kept flat, and the inner side surface of the projecting portion of the sheet conveying belt is The drive roller and the driven roller are adapted to be engaged with outer peripheral end surfaces.

[0008]

[0009]

[0010]

[0011]

[0012]

Further, an image forming apparatus according to the present invention includes the above-described sheet conveying apparatus, and image forming means for sequentially forming an image on a sheet conveyed by the sheet conveying apparatus. The image forming apparatus having such a configuration can print a sheet conveyed with high accuracy without causing a problem such as a lateral shift.
A plurality of image forming units sequentially form high-precision images.

[0014]

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a schematic configuration diagram of a color printer (image forming apparatus) using a sheet conveying apparatus according to a first embodiment of the present invention. or,
FIG. 2 is an external perspective view of the sheet conveying device according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view (a cross-sectional view taken along line AA in FIG. 2) of a main part of the sheet conveying apparatus.

First, a schematic configuration of the color printer 2 will be described with reference to FIG. The color printer 2 includes a sheet feeding unit 4 that feeds sheets 3 as transfer members one by one, a conveying unit 6 that conveys the sheet sent from the sheet feeding unit 4 to an image forming unit 5 described below, An image forming unit 5 for forming a toner image to be transferred onto the sheet conveyed by the conveying unit 6; receiving the sheet conveyed by the conveying unit 6; conveying the sheet in a predetermined direction; And a fixing unit 8 for fixing the toner image on the sheet conveyed by the transfer unit 7 to the sheet.
A paper discharge unit 10 for receiving the sheet discharged from the fixing unit 8; and an optical unit 11 for irradiating the image forming unit 5 with laser light for exposure.

The paper feed unit 4 feeds the sheets 3 stacked on the first paper feed tray 12 to a paper feed roller 13 and a reverse roller 14.
And a second paper feed unit 18 for feeding sheets (not shown) on the manual feed tray 16 by the paper feed roller 17.

The transport section 6 includes a transport path 20 for guiding the movement of the sheet 3 sent from the first paper feed section 15, a transport roller 21 disposed in the middle of the transport path 20, and a transport path 21. A pair of registration rollers 22 that receives the sheet, corrects the skew of the sheet, and feeds the sheet to the image forming unit 5, and a manual conveyance path 23 that is connected to the conveyance path 20 upstream of the registration roller pair 22 in the sheet conveyance direction. Has become.

The image forming section 5 includes a first image forming section 24 having black toner (hereinafter, abbreviated as black) and a toner containing a magenta pigment (hereinafter, abbreviated as magenta) in order from the upstream side in the sheet conveying direction. , A third image forming unit 26 having a toner containing cyan pigment (hereinafter abbreviated as cyan), and a fourth image having a toner containing a yellow pigment (hereinafter abbreviated as yellow). And part 27. Then, the first to fourth image forming units 24 to
27 is a cylindrical photosensitive drum (image forming means) 28
A developing device 30 for forming a toner image on the outer peripheral surface of the photosensitive drum 28; a cleaning device 33 including a fur brush 31 and a cleaning blade 32 for removing residual toner on the photosensitive drum 28; And a charging device 34 for charging the photoconductor drum 28 by applying a charge to the photoconductor drum 28. The image forming unit 5 can be pulled out of the image forming apparatus main body 36 integrally with the support frame 35. or,
Each photosensitive drum 28 sequentially arranged in the sheet conveying direction
The outer periphery of both ends is directly supported by bearings so that high-precision rotation is possible by suppressing rotation unevenness.
The motor is rotatably driven with high precision by a driving means (not shown) (for example, a servo motor with a planetary roller speed reducer). As a result, it is possible to prevent an image shift due to the rotation accuracy of the photosensitive drum 28.

The transfer conveyance section (sheet conveyance device) 7 includes an endless transfer belt (sheet conveyance belt) 37 made of a fluororesin material, a driving roller 38 around which the transfer belt 37 is wound, and a tension roller (driven roller) 40. And transfer rollers 41a, 41b, 41c, 41d arranged at positions facing the respective photosensitive drums 28, respectively. The transfer belt 37 is sandwiched between the transfer rollers 41 a to 41 d and the respective photosensitive drums 28. Further, belt guide rollers 42 and 43 are arranged at appropriate positions on the inner peripheral side of the transfer belt 37. In order to prevent the photosensitive drum 28, the transfer roller and the transfer belt 37 from deteriorating, the transfer / conveyance unit 7 lowers the print roller to the position indicated by the two-dot chain line when printing is stopped, and moves the tension roller 40 slightly toward the drive roller. The pressure acting on the photosensitive drum 28 and the transfer rollers 41a to 41d and the tension acting on the transfer belt 37 are released. Further, the transfer / conveyance unit 7 includes a mechanism (not shown) for separating the other magenta, cyan, and yellow transfer rollers 41b to 41d from the photosensitive drum 28 when only a monochrome image is created. Here, the driving roller 38
Is connected to a drive motor (not shown) via a torque limiter (not shown) so that when a torque equal to or more than a predetermined value acts, the drive motor slips. Accordingly, the transfer belt 37 is given a driving force by the driving roller 38, but follows the rotation of the photosensitive drum 28.

The fixing unit 8 includes a heating roller 44 having a built-in heater, a fixing roller 45, and a metal endless belt 4 wound around the heating roller 44 and the fixing roller 45.
6, and a pressure roller 47 pressed against the fixing roller 45
And Then, a donor roller 48 for supplying oil to the outer surface of the endless belt 46 and the donor roller 4
An oil roller 50 and a cleaning roller 51 that are in rolling contact with the roller 8 are arranged.

The paper discharge section 10 has a paper discharge tray 54 for guiding the sheet discharged from the fixing section 8 to the upper portion of the image forming apparatus main body 36 via a discharge path 53 and stacking the sheet with the image forming surface on the back. I have. The paper ejection cover 52 can be pulled out of the image forming apparatus main body 36 during the jam processing, and can be stored in the image forming apparatus main body 36 when the jam processing is not performed.

The optical unit 11 has a polygon scanner mirror 55, imaging lenses 56, 57 and a mirror 58 arranged corresponding to each photosensitive drum 28. Laser light is formed on an optical unit support plate 60. Slit 61
Irradiates the photosensitive drum 28 toward the photosensitive drum 28.

The color printer 2 thus configured
When a sheet is sent out from the first sheet supply unit 15 or the second sheet supply unit 18, the sheet is transferred to the photosensitive drum 28 of the first image forming unit 24 and the transfer belt 37 of the transfer transfer unit 7 by the transfer unit 6. Sent between. While the sheet is conveyed by the transfer belt 37 between the photosensitive drum 28 and the transfer rollers 41a to 41d, the toner images formed on the black, magenta, cyan, and yellow photosensitive drums 28 are sequentially formed. Transcribed. Then, the sheet on which the transfer of the color image has been completed is sent by the transfer belt 37 between the fixing roller 45 and the pressure roller 47 of the fixing unit 8, where the sheet is heated and pressed to fix the color toner image. . The sheet on which the fixing operation has been completed is discharged to the discharge tray 54.

Next, the details of the transfer / conveyance section (sheet conveyance device) 7 used in the color printer 2 will be described with reference to FIGS.

The transfer belt (sheet transfer belt) 37 of the sheet transfer device 7 has protrusions 70 and 71 made of a rubber material formed at both ends on the inner peripheral side, respectively. The inner side surfaces 70a, 71a of the drive roller 38 and the outer peripheral side end surfaces 72, 7 of the tension roller 40
3. Here, the projections 70, 7
1 is formed by bonding a ring member made of a rubber material to both ends on the inner peripheral side of the transfer belt 37. The rollers 38, 40, 41a to 41d, 42, 43 have their rotating shafts 74, 75 rotatably supported by the support frame 78 of the sheet conveying device 7 via bearings 76, 77, respectively.

The sheet conveying device 7 includes a driving roller 38
Belt guides 80 and 81 are disposed at a relatively low tension portion (loosening side) of the transfer belt 37 between the transfer roller 37 and the tension roller 40. The belt guides 80 and 81 are connected to both side surfaces 82 and 8 of the transfer belt 37.
3 to regulate the positions of both side surfaces 82 and 83 of the transfer belt 37 and to guide the smooth movement of the transfer belt 37. The belt guide means 80,
81 may be any as long as it can smoothly guide the traveling of the transfer belt 37 and prevent the lateral deviation of the transfer belt 37. For example, a guide plate and a guide block attached to the support frame 78 of the sheet conveying device 7 may be used. , Rollers, etc. Further, the belt guide means 80 and 81 are provided in FIG.
When the transfer belt 37 is slightly inclined with respect to the side surface 82 of the transfer belt 37, the traveling of the transfer belt 37 is always smoothly guided.

The sheet conveying device 7 configured as described above
Is that the projections 70, 71 are fixed to the respective rollers 38, 4 even if some force is applied to the transfer belt 37 to cause lateral displacement.
0, the outer peripheral side end surface 72 or 73 abuts, and the side surface 82 or 83 of the transfer belt 37 abuts the belt guide means 80 or 81. Specifically, in FIG. 3, when the transfer belt 37 is to be shifted leftward in the figure, the left side surface 82 of the transfer belt 37 contacts the belt guide means 80, and the inner side surface 71a of the right protrusion 71 in the figure. Is each roller 3
The transfer belt 37 is positioned by contacting the right end surfaces 73 of the transfer belts 8 and 40, and the lateral displacement of the transfer belt 37 to the left in the drawing is prevented. On the other hand, if the transfer belt 37 shifts to the right in FIG.
3 comes into contact with the belt guide means 81, and the protrusion 7 on the left side in FIG.
0 is the left end face 7 of each of the rollers 38, 40.
2, the transfer belt 37 is positioned, and the transfer belt 37 is prevented from laterally shifting rightward in the drawing.

Therefore, according to the sheet conveying device 7 having such a configuration, the sheet can be smoothly and accurately conveyed to each photosensitive drum 28. As a result, the color printer 2 using such a sheet conveying device 7
Color shift can be suppressed, and a high-precision color image can be formed. As described above, since the image shift due to the rotation accuracy of the photosensitive drum 28 is prevented, the image shift by improving the sheet transfer accuracy by the transfer belt 37 as in the present embodiment is improved. It is possible to prevent it even more reliably. In other words, in order to enable high-precision image formation without image misalignment, it is not enough to prevent image misalignment on the photosensitive drum 28 side. It is necessary to prevent it sufficiently.

Further, the sheet conveying device 7 of the present embodiment
Since the belt guides 80 and 81 are configured to guide a portion of the transfer belt 37 where the tension is small,
Even when the transfer belt 37 is in sliding contact with the belt guides 80 and 81, the contact pressure generated at the sliding contact portion between the transfer belt 37 and the belt guides 80 and 81 is relatively small, and the transfer belt 3
7 can be reduced. Therefore, according to the present embodiment, the durability of the transfer belt 37 and the durability of the sheet conveying device 7 can be improved, and a high-precision color image can be formed for a long time. Incidentally, the belt guide means 80 and 81 are arranged near the transfer roller,
When the transfer belt 37 is guided by the belt guides 80 and 81, a large tension acts on the transfer belt 37.
0, 81, the surface pressure of the sliding contact portion increases, and the transfer belt 37
Is disadvantageously worn out early. However, in the present embodiment, as described above, the portion where the tension of the transfer belt 37 is small is guided by the belt guides 80 and 81, so that such inconvenience does not occur.

[Modification of First Embodiment] The first embodiment is different from the first embodiment in that protrusions 7 are provided at both ends on the inner peripheral side of the transfer belt 37.
0, 71, and these projections 70, 71 are
8 and 40 are engaged with the outer peripheral sides of both end faces 72 and 73,
Although the portion where the tension of the transfer belt 37 is reduced is guided by the belt guides 80 and 81, the transfer belt 37 is configured to guide the portion where the tension of the transfer belt 37 is reduced by the belt guides 80 and 81. 37 can be suppressed.

However, according to the first embodiment, since the lateral deviation of the transfer belt 37 is prevented by the projections 70 and 71 and the belt guides 80 and 81, the first embodiment is performed. The lateral displacement of the transfer belt 37 can be more effectively suppressed than in the modification of the embodiment. Further, according to the first embodiment, the side surfaces 70 of the projections 70 and 71 are provided.
a, 71a and the side surfaces 82, 83 of the transfer belt 37 share and support a force in a direction orthogonal to the sheet conveying direction, and the side surfaces 70a, 71a of the protrusions 70, 71 and the transfer belt 37 Since the surface pressure acting on the side faces 82 and 83 is smaller than that of the modification of the first embodiment, the durability of the transfer belt 37 is also superior to that of the modification of the first embodiment.

In addition, in the first embodiment, the protrusions 70 and 71 are formed at both ends on the inner peripheral side of the transfer belt 37, and these protrusions 70 and 71 are formed on both end surfaces 7 of the rollers 38 and 40.
2, 73 at least at both end faces 7 of the drive roller 38 and the tension roller 40.
The transfer belt 37 can be engaged only with the outer peripheral side of the transfer belt 37.
Lateral displacement can be suppressed.

In addition, in the first embodiment, a portion where the tension of the transfer belt 37 becomes small is selected and guided by the belt guide means 80 and 81. However, the present invention is not limited to this. The belt guides 80 and 81 may be appropriately disposed at a portion where the tension of the transfer belt 37 is relatively high. This is, as mentioned above,
Since the projections 70 and 71 and the transfer belt 37 share a force in a direction orthogonal to the sheet conveying direction, the transfer belt 3
The surface pressure acting on the side surfaces 82 and 83 of the
It is because it becomes smaller than the case where there is no. However, from the viewpoint of improving the durability of the transfer belt 37, the first embodiment is more preferable.

[Second Embodiment] Hereinafter, a second embodiment of the present invention will be described.
The embodiment will be described with reference to FIG.

FIG. 4 is a cross-sectional view (corresponding to a cross-sectional view taken along the line AA in FIG. 1) of a main portion of the sheet conveying device 7 according to the present embodiment. As shown in FIG.
In this embodiment, the driving roller 38, the tension roller 4
The small-diameter portions 84 and 85 are formed so as to protrude from both side end surfaces 72 and 73 of the “0”, and the projections 70 and 71 are supported by the small-diameter portions 84 and 85. With such a configuration, both end portions 37 of the transfer belt 37 as shown in FIG.
a can be prevented from falling into the inner peripheral side (the lower side in the figure), and the sheet supporting surface of the transfer belt 37 can be held flat. In this embodiment, since the transfer belt 37 can be prevented from falling down as shown in FIG.
0 can be prevented from coming into contact with the roller end surface 72, and the durability of the transfer belt 37 can be improved.

Although the example in which the sheet conveying device 7 according to each of the above embodiments is applied to a color printer as an image forming apparatus has been described, the present invention is not limited to this, and can be widely applied to a facsimile, a copying machine, and the like. it can. In the above embodiments, an example in which the present invention is applied to an electrophotographic image forming apparatus has been described. However, the sheet conveying apparatus 7 according to the present invention can also be applied to an inkjet type image forming apparatus. .

[0039]

As described above, according to the present invention, the projecting portion of the sheet conveying belt is supported by the small diameter portions of the driving roller and the driven roller, so that the sheet supporting surface of the sheet conveying belt is kept flat and the sheet conveying belt is supported. Since the inner side surface of the projection is engaged with the outer peripheral end surfaces of the driving roller and the driven roller, not only can the lateral deviation of the sheet conveying belt be prevented, but the sheet conveying belt can be prevented from falling down, It is possible to prevent the sheet conveying belt from colliding with the end surfaces of the driving roller and the driven roller, and to improve the durability of the sheet conveying belt.

[0040]

[0041]

In the image forming apparatus of the present invention, a plurality of image forming means sequentially form high-precision images on a sheet conveyed with high accuracy without causing a problem of lateral displacement. Therefore, it is possible to meet the demand for higher image quality without causing a problem of color misregistration.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention.

FIG. 2 is an external perspective view of the sheet conveying apparatus according to the first embodiment of the present invention.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a cross-sectional view of a main part of a sheet conveying apparatus according to a second embodiment of the present invention.

FIG. 5 is an enlarged view of an end portion of the sheet conveying belt.

FIG. 6 is a cross-sectional view illustrating a relationship between a sheet conveying belt and a guide unit.

[Explanation of symbols]

2 ... Color printer (image forming apparatus), 3 ... Sheet, 7 ... Transfer transport section (sheet transport apparatus), 28 ... Photoconductor drum (image forming means), 37 ... Transfer belt (sheet transport belt) , 38... Drive roller, 40... Tension roller (driven roller), 70, 71.
2, 73 ... end face, 80, 81 ... belt guide means,
82, 83 ... side

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-100195 (JP, A) JP-A-8-268592 (JP, A) Japanese Utility Model Showa 57-70253 (JP, U) Japanese Utility Model Showa 61- 155863 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B65H 5/02 G03G 15/00

Claims (2)

(57) [Claims] 1. A driving roller and a driven roller are arranged at a predetermined interval in a sheet conveying direction, and an endless sheet conveying belt is wound around the driving roller and the driven roller. By driving
In a sheet conveying apparatus for sequentially conveying a sheet to a plurality of image forming units arranged in a sheet conveying direction, a protrusion is formed at both ends on an inner peripheral side of the sheet conveying belt, and both side surfaces of the driving roller and the driven roller are formed on both side surfaces. A small-diameter portion is formed so as to protrude, and the projecting portion of the sheet conveying belt is supported by the small-diameter portions of the driving roller and the driven roller, so that the sheet supporting surface of the sheet conveying belt is kept flat and the projecting portion of the sheet conveying belt is projected. A sheet conveying device, wherein an inner side surface of the portion is engaged with outer peripheral side end surfaces of the driving roller and the driven roller. 2. An image forming apparatus comprising: the sheet conveying device according to claim 1; and a plurality of image forming units for sequentially forming images on a sheet conveyed by the sheet conveying device.