JP2002148954A - Belt device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt device in which the damage to the belt side tip part of an endless shaped belt caused by interference between the warped belt tip parts and units closely arranged to the outer peripheral surface of the belt is prevented while the belt is moving relative to the units and to provide an image forming device. SOLUTION: A belt pressing down member 500 having a belt pressing down surface 500a is provided to casing tip parts 300a and 300b located in the back side or in the front side of a casing 300A. Then, belt side tip parts 260a and 260b that are warped by secular change are pressed down to the position where no interference occurs with an image making unit 300 by a belt pressing down surface 400a while relative motion exists between an endless shaped belt 260 and the unit 300. Thus, the damages to the parts 260a and 260b is prevented while the belt 260 is moving relative to the unit 300.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt device having an endless belt rotatably stretched over a plurality of stretching rollers, and an image forming apparatus such as a copying machine, a facsimile or a printer having the endless belt. More specifically, the apparatus has a unit disposed close to the outer peripheral surface of the endless belt, and is configured such that the endless belt and the unit relatively move along the axial direction of the tension roller. And an image forming apparatus.

[0002]

2. Description of the Related Art Electrophotographic copying machines, facsimile machines,
As an image forming apparatus such as a laser beam printer, an endless belt such as a transfer / transport belt or an intermediate transfer belt which is rotatably stretched by a plurality of stretch rollers on a toner image developed by a developer on an image carrier. There is known a device that transfers a toner image onto a transfer material as a recording medium using a belt device provided with a recording medium.

For example, Japanese Patent Application Laid-Open No. Hei 6-202430 discloses an image forming apparatus of this type that includes a plurality of toners each having a photosensitive drum or the like as an image carrier on which a toner image composed of a charged toner is formed. A so-called tandem-type image forming apparatus in which image forming units are arranged in parallel along a moving direction of a transfer conveyance belt as a transfer conveyance member that carries and conveys transfer paper as a transfer material is shown. In this image forming apparatus, the electrostatic latent images formed on the photosensitive drums of the respective toner image forming units are developed using charged toners of different colors. And
A transfer bias is applied to the transfer belt at a transfer position where each photosensitive drum and the transfer belt are in contact with each other, and the charged toner image on each photosensitive drum is transferred onto the transfer belt by a transfer electric field generated by the transfer bias. The images are sequentially transferred to a transfer paper to form a color image.

Further, as this type of image forming apparatus, there are provided a charging roller for forming an electrostatic latent image on the photosensitive drum, a cleaning means for cleaning the photosensitive drum, and the like. Has been proposed as a photosensitive unit (for example, Japanese Patent Application No. 2000-195225). In this image forming apparatus, in addition to the photoconductor unit, a developing device that develops an electrostatic latent image formed on the photoconductor drum into a toner image is a developing unit, and the transfer conveyance belt is a belt unit. As a unit. The photoreceptor unit and the developing unit are configured to be detachable from the image forming main body by moving along the axial direction of a stretching roller that stretches the transfer conveyance belt of the belt unit. The belt unit is also configured to be detachable from the image forming main body by moving along the axial direction of the stretching roller. There is also an image forming apparatus in which the photoreceptor unit and the developing unit are integrated as an image forming unit (see, for example, JP-A-10-240026).

[0005]

However, in the belt apparatus and the image forming apparatus provided with the endless belt as described above, the end of the endless belt is warped to the outer peripheral surface due to aging. Had to be.
For this reason, for example, in the image forming apparatus, when the belt unit, the photoconductor unit, or the developing unit is attached to or detached from the image forming apparatus main body, the endless belt of the belt unit, Due to the relative movement with respect to the photoconductor unit or the developing unit, a part of the photoconductor unit or the developing unit interferes with the warped belt-side end of the endless belt, and the belt-side end of the endless belt. There was a problem that the part was damaged.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object the relative movement of an endless belt and a unit disposed close to the outer peripheral surface of the endless belt. By providing a belt device and an image forming apparatus capable of preventing breakage of the belt-side end of the endless belt due to interference between the warped belt-side end of the endless belt and the unit when performing the operation, is there.

[0007]

In order to achieve the above object, the present invention is directed to an endless belt rotatably stretched by a plurality of stretching rollers and an outer peripheral surface of the endless belt. A belt device having a unit disposed close to the endless belt and the unit configured to relatively move along the axial direction of the tension roller. And a belt pressing member that abuts on the belt side end of the endless belt due to relative movement thereof and pushes down the belt side end.

In this belt device, when the endless belt and the unit relatively move, the belt pressing member comes into contact with the belt-side end of the endless belt.
Then, the warped belt-side end of the endless belt is pressed down by the belt pressing member. Here, when the belt-side end is depressed at a position where the belt-side end deviates from the attachment / detachment path of the unit, the endless belt and the unit move relative to each other when the endless belt relatively moves. The warped belt-side end of the belt-shaped belt does not interfere with the unit. This prevents breakage of the end on the belt side due to interference between the endless belt and the unit.

According to a second aspect of the present invention, there is provided an endless belt rotatably stretched by a plurality of stretching rollers, and an image forming apparatus for forming an image disposed close to an outer peripheral surface of the endless belt. An endless belt and the image forming unit, wherein the endless belt and the image forming unit are configured to relatively move along the axial direction of the stretching roller. A belt pressing member which abuts on the belt side end of the endless belt by the relative movement of the belt to push down the belt side end.

In this image forming apparatus, when the endless belt and the image forming unit move relative to each other, the belt pressing member comes into contact with the belt-side end of the endless belt, and the belt pressing member moves. As a result, the warped belt side end of the endless belt is pushed down. Here, when the belt-side end is depressed at a position where the belt-side end deviates from the attaching / detaching path of the image forming unit, the endless belt and the image forming unit relatively move. In addition, the warped belt-side end of the endless belt does not interfere with the image forming unit. This prevents the end of the belt side from being damaged due to interference between the endless belt and the image forming unit.

According to a third aspect of the present invention, in the image forming apparatus of the second aspect, the belt pressing member abuts on a belt-side end of the endless belt by relative movement between the endless belt and the image forming unit. The belt has an inclined surface that comes into contact with the belt and gradually pushes down the end on the belt side.

In this image forming apparatus, the belt-side end of the endless belt abutting on the belt pressing member is gradually moved by the inclined surface due to the relative movement between the endless belt and the image forming unit. Be able to push down. Therefore, the impact at the time of contact between the belt pressing member and the belt-side end of the endless belt is reduced, and damage to the belt-side end of the endless belt due to the impact is prevented.

According to a fourth aspect of the present invention, in the image forming apparatus of the second or third aspect, the belt pressing member is constituted by a roller rotatably supported.

In this image forming apparatus, when the belt pressing member abuts on the belt side end of the endless belt and the endless belt and the image forming unit relatively move, the belt pressing member is moved. Comes into contact with the endless belt while rotating. This prevents the outer peripheral surface of the endless belt from being rubbed by the belt pressing member, and reduces the possibility that the outer peripheral surface of the endless belt is damaged by the rubbing.

According to a fifth aspect of the present invention, in the image forming apparatus of the second, third or fourth aspect, the image forming unit includes a plurality of image carriers having a plurality of image carriers on which a plurality of color toner images are individually formed. The image forming unit, wherein the endless belt is a transfer belt for transferring a toner image formed on each image carrier of each of the plurality of image forming units onto the recording medium. Is what you do.

In this image forming apparatus, a plurality of image forming units are arranged close to the outer peripheral surface of the endless belt. For this reason, the circumferential length and the span (the distance between the tension rollers) of the endless belt on which the image forming units are arranged are relatively long. In such an endless belt having a long circumferential length and a long span, it is difficult to eliminate the warpage of the belt side end by the tension of the tension roller, and the warpage of the belt side end tends to increase. Have. For this reason, in this image forming apparatus, the belt-side end of the endless belt due to interference between the warped belt-side end of the endless belt and the image forming unit is more likely to be damaged. In such an image forming apparatus, when the belt pressing member moves relative to the endless belt and the image forming unit, the belt pressing member moves between the warped belt-side end of the endless belt and the image forming unit. It functions particularly effectively as a means for preventing interference.

According to a sixth aspect of the present invention, in the image forming apparatus of the fifth aspect, the endless belt is displaced in a direction of pressing an inner peripheral surface of the endless belt, and the endless belt is placed on the surface of the image carrier of the image forming unit. An image forming apparatus having a nip forming member that forms a nip between the endless belt and the image carrier by contacting a surface of a belt, wherein the belt pressing member faces the nip forming member. In the vicinity of the part to be processed.

In this type of image forming apparatus, usually,
When the endless belt unit and the image forming unit are attached to and detached from the image forming apparatus main body, the endless belt and the image forming unit are separated from each other by a predetermined distance. The nip forming member is configured to be displaced in a direction of pressing the inner peripheral surface of the endless belt so that the outer peripheral surface of the endless belt comes into contact with the surface of the image carrier of the image forming unit. Have been. Therefore, when the endless belt and the image forming unit are separated from each other, the inner peripheral surface of the endless belt at a portion facing the nip forming member is pressed toward the outer peripheral surface by the nip forming member. The outer peripheral surface of the part of the endless belt is in the state closest to the image forming unit. Therefore, when the endless belt unit or the image forming unit is attached to or detached from the image forming apparatus main body, interference between the warped belt-side end of the endless belt and the image forming unit is caused by the above-described portion. Highly likely to occur in.
Therefore, in the image forming apparatus of the present invention, the belt pressing member is provided near a portion facing the nip forming member. Thereby, compared to the case where the belt pressing member is provided in another portion, the distance required for pushing down the warped belt side end of the endless belt to a position where it does not interfere with the unit is small. As a result, the size of the belt pressing member can be reduced. Further, by providing the belt pressing member near a portion facing the nip forming member, the belt pressing member can be easily arranged or formed in a part of the casing of the image forming unit. Become.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic color laser printer (hereinafter, referred to as "laser printer") as an image forming apparatus will be described below. FIG. 1 is a schematic configuration diagram of a laser printer according to the present embodiment. This laser printer includes four sets of toner image forming units 1Y for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K).
1M, 1C, 1K (hereinafter, suffixes Y, M, C, K
Indicate the members for yellow, magenta, cyan, and black, respectively) are arranged in order from the upstream side in the moving direction (direction of arrow A in the figure) of the transfer paper as the transfer target (transfer material). ing.

The toner image forming units 1Y, 1M, 1C, 1
K denotes a photosensitive drum 11 as an image carrier
Photoconductor unit 1 having Y, 11M, 11C, and 11K
0Y, 10M, 10C, and 10K, and the developing unit 20
Y, 20M, 20C, and 20K (see FIG. 2). Further, each toner image forming section 1Y, 1M, 1C, 1K
Are set such that the rotation axes of the photoconductor drums in each photoconductor unit are parallel and arranged at a predetermined pitch in the transfer paper moving direction.

The present laser printer carries the toner image forming units 1Y, 1M, 1C, and 1K, an optical writing unit 2, paper feed cassettes 3, 4, a pair of registration rollers 5, and transfer paper. The image forming apparatus includes a transfer belt unit 6 as a belt device having a transfer conveyance belt 60 as a transfer conveyance member that conveys the toner image so as to pass through the transfer position of the toner image forming unit, a fixing unit 7 of a belt fixing type, a discharge tray 8, and the like. I have. The laser printer also includes a manual feed tray (not shown), a toner supply container, a waste toner bottle, a duplex / reversing unit, a power supply unit, and the like.

The optical writing unit 2 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like. Based on image data, each of the photosensitive drums 11Y, 11M, 11C,
The surface of 11K is irradiated with laser light while scanning. The dashed line in FIG. 1 indicates the transfer path of the transfer paper. The transfer paper fed from the paper feed cassettes 3 and 4 is transported by transport rollers while being guided by a transport guide (not shown), and is transported to a temporary stop position where the registration roller pair 5 is provided. The transfer paper sent out by the registration roller pair 5 at a predetermined timing is carried on a transfer conveyance belt 60, and is conveyed so as to pass through the transfer positions of the toner image forming units 1Y, 1M, 1C, and 1K. Each toner image forming unit 1
The transfer paper on which the Y, 1M, 1C, and 1K toner images have been transferred and the color image has been formed is discharged onto a discharge tray 8 after the fixing unit 7 fixes the toner images.

FIG. 2 shows the toner image forming sections 1Y, 1M,
FIG. 3 is an enlarged view showing a schematic configuration of a yellow toner image forming unit 1Y of 1C and 1K. Other toner image forming units 1M,
1C and 1K have the same configuration, respectively, and thus description thereof is omitted. In FIG. 2, the toner image forming unit 1Y includes the photoconductor unit 10Y and the developing unit 20Y as described above. Photoconductor unit 10
Y denotes a photosensitive drum 11Y, a brush roller 12Y for applying a lubricant to the surface of the photosensitive drum, a swingable counter blade 13Y for cleaning the surface of the photosensitive drum, and a neutralization for removing the surface of the photosensitive drum. Lamp 14
And a non-contact type charging roller 15Y for uniformly charging the surface of the photosensitive drum. As the photoconductor drum of each photoconductor unit, a photoconductor drum having an organic photoconductor (OPC) layer on the surface and having a diameter of 30 mm was used.

In the photoconductor unit 10Y having the above structure, the laser beam modulated and deflected by the optical writing unit 2 is applied to the surface of the photoconductor drum 11Y uniformly charged by the charging roller 15Y to which an AC voltage is applied. When irradiated while being scanned, an electrostatic latent image is formed on the surface of the photosensitive drum 11Y. The electrostatic latent image on the photosensitive drum 11Y is
The toner image is developed by a later-described developing unit 20Y to form a yellow toner image. At the transfer position Pt where the transfer paper P on the transfer conveyance belt 60 passes, the toner image on the photosensitive drum 11Y is transferred to the transfer paper P. After a predetermined amount of lubricant is applied by a brush roller 12Y, the surface of the photosensitive drum 11Y after the transfer of the toner image is cleaned by a counter blade 13Y, and is discharged by light emitted from a discharge lamp 14Y. It is prepared for the formation of the next electrostatic latent image.

The developing unit 20Y uses a two-component developer containing a magnetic carrier and a negatively charged toner. Then, a developing roller 22Y as a developer carrying member, which is disposed so as to be partially exposed from an opening on the photosensitive drum side of the developing case 21Y, and conveying screws 23Y and 2Y.
4Y, a developing doctor 25Y, a toner density sensor (T sensor) 26Y, a powder pump 27Y, and the like. The developer contained in the developing case 21 </ b> Y is supplied to the transfer screw 23.
The toner is agitated and conveyed in Y and 24Y to be charged by friction. Then, after a part of the developer is carried on the surface of the developing roller 22Y and the layer thickness is regulated by the developing doctor 25Y,
The photosensitive drum 11Y is transported to a developing position facing the photosensitive drum 11Y.
At the developing position, the electrostatic latent image on the photosensitive drum 11Y is developed by the toner in the developer on the developing roller. The toner concentration of the developer in the developing case 21Y is detected by the toner concentration sensor 26Y, and if necessary, the powder pump 27Y
Supplies toner.

FIG. 3 is a schematic diagram of the transfer belt unit 6.
FIG. 3 is an enlarged view showing a configuration. In this transfer belt unit 6,
The transfer conveyance belt 60 used has a volume resistivity of 10⁹~
10 ¹¹Ωcm high resistance endless single layer belt
The material is PVDF (polyvinylidene fluoride)
You. The transfer / conveyance belt 60 is used to control the sensitivity of each toner image forming unit.
Opposite contact with light drum 11Y, 11M, 11C, 11K
Four grounded stretches to pass through each transfer location
It is wrapped around the frame rollers 61 to 64. These stretchers
Of the rollers, the inlet roller 61 on the upstream side in the transfer paper moving direction
Is an electrostatic suction device to which a predetermined voltage is applied from the power supply 65a.
The rollers 65 are arranged to face each other. These two
The transfer paper passing between the rollers 61 and 65 is transferred and transferred by a transfer bell.
Electrostatically adsorbed on the plate 60. In addition, downstream in the transfer paper movement direction
The side exit roller 62 frictionally drives the transfer conveyance belt 60.
Drive roller connected to a drive source (not shown).
You. Also, it is stretched between the stretching rollers 61c and 61d.
The outer peripheral surface of the transfer conveyance belt 60 is connected to a power source 66a.
Bias roller 6 to which a constant cleaning voltage is applied
6 are arranged so as to be in contact with each other. This bias row
Toner adhered onto the transfer / conveying belt 60 by the
Foreign matter is removed.

Further, as a transfer electric field forming means for forming a transfer electric field at each transfer position, a transfer bias is applied so as to come into contact with the back surface of the transfer conveying belt 60 forming a contact opposing portion which opposes the photoconductive drum. Member 67Y, 6
7M, 67C and 67K are provided. The transfer bias applying members 67Y, 67M, 67C, and 67K are fixed brushes made of Mylar, and each of the transfer bias power supplies 9Y, 9M, and 9K.
A transfer bias is applied from C and 9K. By the transfer bias applied by the transfer bias applying member, a transfer charge is applied to the transfer / conveyance belt 60, and a transfer electric field having a predetermined strength is formed between the transfer / conveyance belt 60 and the surface of the photosensitive drum at each transfer position. You.

Here, the photoreceptor unit 10
Y, 10M, 10C, 10K, and the developing unit 2
0Y, 20M, 20C, and 20K are configured to be detachable from the laser printer main body by moving along the axial direction of a stretching roller that stretches the transfer / transport belt of the belt unit.

However, in an image forming apparatus having an endless belt such as the transfer / conveying belt 60, the end of the endless belt on the belt side may be warped to the outer peripheral surface due to aging. Was. Therefore, for example, as shown in FIG. 4, when the transfer belt unit 6 is pulled out to the front side (here, the left side in the figure) of the laser printer main body 100, The warped belt side end 60a on the front side is the casing end 10a of the casing 10A on the front side of the photoreceptor units 10Y, 10M, 10C, and 10K (or the casing end 20a of the developing units 20Y, 20M, 20C, and 20K). , There is a problem that the belt-side end portion 60a on the front side of the transfer conveyance belt 60 is damaged.

Referring to FIG. 4, the photoconductor units 10Y, 10M, 10
C, 10K (or developing units 20Y, 20M, 2
0C, 20K), the end of the casing 20A of the casing 20A on the back side of the photoreceptor units 10Y, 10M, 10C, 10K is attached to the warped belt side end 60b on the back side of the transfer conveyance belt 60. 10b (or the casing end 20b on the back side of the developing units 20Y, 20M, 20C, and 20K) is hooked, and there is a problem that the belt side end 60a on the back side of the transfer conveyance belt 60 is damaged.

In the above embodiment, the case where the transfer object is the transfer paper carried and conveyed by the transfer conveyance belt 60 has been described. However, the above-described problem is caused by the fact that the transfer object is an endless belt. The same can occur in the case of a structured intermediate transfer member. FIG. 5 shows an intermediate transfer belt unit 2 in a laser printer using an intermediate transfer belt 201 composed of an endless belt as the intermediate transfer member.
00 shows one configuration example. In this laser printer,
The intermediate transfer belt 201 has a plurality of stretching rollers 202-2.
It is wound around at 05 and is rotationally driven in the direction of the arrow in the figure.
Photoconductor drums 11Y, 11M, 11 of each toner image forming unit
The toner images formed on C and 11K are transferred to primary transfer rollers 206Y, 206M, 206C, and 2C provided to face each photosensitive drum with the intermediate transfer belt 201 interposed therebetween.
The image is sequentially transferred onto the intermediate transfer belt 201 by the primary transfer electric field formed at 06K. The color image on the intermediate transfer belt 201 is applied with a grounded tension roller 203 and a predetermined secondary transfer bias in a secondary transfer portion provided near the black toner image forming portion for the fourth color. Is transferred onto the transfer paper P conveyed so as to pass between the transferred secondary transfer roller 207.

Here, the transfer belt unit 6 (or the intermediate transfer belt unit 200),
The photoreceptor units 10Y, 10M, 10C, 10K
(Alternatively, the developing units 20Y, 20M, 20C, 20
K) is drawn out to the front side of the laser printer main body 100.
The same problem occurs when the transfer belt unit (or the intermediate transfer belt unit) or the photoconductor unit (or the developing unit) is mounted.

FIG. 6 shows an example of the configuration of a laser printer which has solved the above-mentioned problem. Here, the transfer belt unit 6 and the intermediate transfer belt unit 200
Belt unit 26 having an endless belt 260
0Y, the photoconductor units 10Y, 10M, 10
C, 10K and developing units 20Y, 20M, 20C, 2
0K or the like will be described as the image forming unit 300. Further, a belt-side end 260 of the endless belt 260
a and 260b are warped to the outer peripheral surface side as shown in FIG. 6 due to the change with time.

First, the case where the image forming unit 300 is attached to and detached from the laser printer main body 100 in the direction of the arrow in FIG. In this case, the belt pressing member 40 is attached to the casing end 300b on the inner side (right side in FIG. 6) of the casing 300A of the image forming unit 300.
0 is provided. When the image forming unit 300 is attached and detached, the belt pressing member 400
Has a pressing surface 400a formed in a half-moon shape so as to abut against the belt-side ends 260a, 260b of the image forming unit 300 so as to push the belt-side ends 260a, 260b to a position where they do not interfere with the image forming unit 300. I have.

In FIG. 6, the laser printer body 10
When the image forming unit 300 is attached to and detached from the image forming unit 300 in a direction indicated by an arrow in the drawing, relative movement between the endless belt 260 and the image forming unit 300 causes the belt pressing member 40 to move.
The zero belt pressing surface 400a contacts the belt side ends 260a and 260b of the endless belt 260. That is,
When the image forming unit 300 is mounted, the belt side end 2 on the front side is used.
60a, the belt pressing surface 400a of the belt pressing member 400 abuts on the inner belt side end 260b at the time of removal.

Then, the warped belt side ends 260a and 260b of the endless belt 260 are pushed down by the belt pushing surface 400a of the belt pushing member 400. Here, the belt pressing surface 4 of the belt pressing member 400
00a, the belt side ends 260a,
260b, the belt-side end 260a,
When the endless belt 260 and the image forming unit 300 move relative to each other at a position where 260b is out of the attachment / detachment path of the image forming unit 300, the image forming unit 300
Position that does not interfere with

Thus, the laser printer body 100
When the image forming unit 300 is attached to and detached from the endless belt 260, the warped belt-side end 260 of the endless belt 260
a, 260b, the casing 3 of the image forming unit 300;
00A does not interfere with the endless belt 260, and the belt-side ends 260a and 260b of the endless belt 260 are prevented from being damaged.

Next, a case where the belt unit 260Y is attached to and detached from the laser printer main body 100 in the direction of the arrow in FIG. In this case, the belt pressing member 500 having a belt pressing surface 500a having the same shape as the belt pressing member 400 has a casing end 300a on the near side (left side in FIG. 6) of the leasing 300A of the image forming unit 300. Is provided.

The belt pressing surface 500a of the belt pressing member 500 has the same shape as the belt pressing member 400.
When the belt unit 260Y is attached and detached, the belt-side ends 260a and 260b of the endless belt 260 come into contact with each other, so that the belt-side ends 260a and 260b are pushed down to a position where they do not interfere with the image forming unit 300. It is formed as follows.

In FIG. 6, the laser printer main body 10
0, when the belt unit 260Y is attached and detached in the direction of the arrow in the figure, the endless belt 260 of the belt unit 260Y and the image forming unit 300 move relative to each other, so that the belt pressing surface of the belt pressing member 500 500
a, a belt-side end 260a of the endless belt 260,
260b contacts. That is, the belt unit 260Y
When the belt is pressed down, the belt-side end 260b on the back side is used.
Abuts on the belt pressing surface 500a of No. 0.

Then, the warped belt side ends 260a and 260b of the endless belt 260 are pushed down to a position where they do not interfere with the image forming unit 300 by the belt pushing surface 500a of the belt pushing member 500. Thereby, the endless belt 260 and the image forming unit 30
When the endless belt 260 relatively moves, the warped belt-side ends 260a and 260b of the endless belt 260 do not interfere with the casing 300A of the image forming unit 300, and the belt-side end of the endless belt 260 Parts 260a, 2
60b is prevented from being damaged.

Here, the laser printer body 100
In contrast, when only the image forming unit 300 is configured to be detachable, the belt pressing member 500 on the near side in FIG.
Need not be provided. In addition, the laser printer body 1
In the case where only the belt unit 260Y is attached and detached, the belt pressing member 400 on the rear side in FIG. 6 does not need to be provided.

The belt pressing members 400 and 500
As described above, the belt pressing surfaces 400a and 500a are inclined surfaces formed in a half-moon shape. Thereby, the endless belt 260 and the image forming unit 300
Relative to the belt pressing members 400 and 500
Belt-side end 260 of the endless belt 260 in contact with
a, 260b are gradually pushed down by the inclination of the belt pressing surfaces 400a, 500a. Therefore,
In this laser printer, the belt pressing member 4
00, 500 and the belt-side end 2 of the endless belt 260
The impact at the time of contact with the endless belt 260 due to the impact is reduced.
260b is prevented from being damaged.

Here, the belt pressing members 400, 50
It is preferable that 0 is constituted by a roller supported rotatably. That is, the belt pressing members 400, 50
The belt pressing member 40 is constituted by
0,500 is the end 2 of the endless belt 260 on the belt side.
When the endless belt 260 and the image forming unit 300 relatively move while contacting the endless belts 60a and 260b, the belt pressing members 400 and 500 come into contact with the endless belt 260 while rotating. As a result, the outer peripheral surface of the endless belt 260 is
As a result, the outer peripheral surface of the endless belt 260 is less likely to be damaged by the rubbing.

In the tandem laser printer shown in FIGS. 3 and 5, the plurality of image forming units 300 are arranged in a substantially straight line close to the outer peripheral surface of the endless belt 260. The configuration is as follows. For this reason, the circumferential length and the span (the distance between the tension rollers) of the endless belt 260 on which the image forming units 300 are arranged are relatively long. In such an endless belt 260 having a long circumferential length and a long span, it is difficult to eliminate the warpage of the belt-side ends 260a and 260b by the tension of the tension roller, and the belt-side end 2
60a and 260b have a tendency to be large.

Therefore, in the tandem laser printer, the belt-side ends 260a, 260b due to the interference between the warped belt-side ends 260a, 260b of the endless belt 260 and the image forming unit 300 are more likely to be damaged. It is easy to occur. In such a tandem laser printer, when the endless belt 260 and the image forming unit 300 relatively move, the belt pressing member 40
0,500 functions extremely effectively as a means for preventing interference between the warped belt-side ends 260a, 260b of the endless belt 260 and the casing 300A of the image forming unit 300.

On the other hand, in the laser printer having the above configuration, the belt unit 260Y and the image forming unit 3
When attaching / detaching 00, the endless belt 260 and the image forming unit 300 are separated from each other by a predetermined distance. In addition, for example, as shown in FIG. 7, this type of laser printer is displaced in a direction of pressing the inner peripheral surface of the endless belt 260 by the elastic force of the pressure spring 69, and There is a backup roller 68 as a nip forming member configured to make the outer peripheral surface of the endless belt 260 abut on the surface of the drum 11 (see FIG. 3).

Therefore, in this laser printer, the transfer / transport belt 60 and the photosensitive unit 10
When is separated, the inner peripheral surface of the endless belt 260 at the portion facing the backup roller 68 is pressed by the backup roller 68 on the outer peripheral surface.
The outer peripheral surface of the endless belt 260 at this portion is in the state closest to the image forming unit 300. Therefore, when attaching and detaching the belt unit 260Y and the image forming unit 300 to and from the laser printer main body 100, the warped belt side ends 260a and 260b of the endless belt 260 and the image forming unit 300 Is highly likely to occur in the above-mentioned portion.

Therefore, in the laser printer according to the present embodiment, the belt pressing members 400 and 500 are
It is provided near a portion facing the backup roller 68. More specifically, as shown in FIG. 7, the image forming unit 300 for restricting the backup roller 68 from being displaced more than necessary in a state where the endless belt 260 is in contact with the surface of the photosensitive drum 11. Casing 300
The belt pressing members 400 and 500 are provided in the vicinity of the backup roller receiving portion 300c formed in A. FIG. 8 shows an example of the configuration of the belt pressing members 400 and 500.

Thus, the belt pressing member 400,
The endless belt 260 has a warped belt side end 260a, 26
The distance required to push Ob down to a position where it does not interfere with the image forming unit 300 can be reduced, and the belt pressing members 400 and 500 can be reduced in size. Further, by providing the belt pressing members 400 and 500 near the backup roller receiving portion 300c, the casing 300A of the image forming unit 300 is provided.
The belt pressing members 400 and 500 can be easily arranged or formed in a part of the belt.

In the above embodiment, a laser printer having four sets of toner image forming units for forming images of four colors of yellow, magenta, cyan, and black has been described. The present invention can be applied without being limited to the number of toner image forming units, and a similar effect can be obtained. The image forming apparatus further includes a toner image forming unit, and transfers the toner image formed on the image carrier of the toner image forming unit to a transfer target such as an intermediate transfer member or transfer paper using the endless belt. As long as the image forming apparatus performs the formation, the present invention is not limited to the laser printer, but can be applied to other image forming apparatuses such as a copying machine. Further, the present invention is not limited to the above-described image forming apparatus, but may be any general belt device that uses the endless belt and includes a unit that moves in the width direction of the endless belt. Is also applicable.

[0052]

According to the first aspect of the present invention, when the endless belt and the unit move relative to each other, the end of the endless belt due to interference between the warped belt-side end of the endless belt and the unit. There is an effect that breakage of the belt side end can be prevented.

According to the second to sixth aspects of the present invention, when the endless belt and the image forming unit relatively move, the endless belt due to the interference between the warped belt-side end and the image forming unit. There is an effect that the end of the endless belt can be prevented from being damaged.

In particular, according to the third aspect of the present invention, the impact at the time of the contact between the belt pressing member and the end of the endless belt on the side of the belt is reduced, so that the impact on the belt side of the endless belt is reduced. This has the effect of preventing damage to the ends.

According to the fourth aspect of the invention, when the endless belt and the image forming unit relatively move, the belt pressing member comes into contact with the endless belt while rotating. Thus, the outer peripheral surface of the endless belt is not rubbed by the belt pressing member, and there is an effect that the outer peripheral surface of the endless belt is less likely to be damaged by the rubbing.

According to the fifth aspect of the present invention, it is difficult to eliminate the warpage of the belt side end, such as an endless belt having a long circumferential length and a long span, by the tension of the tension roller. In the image forming apparatus in which the side end is more likely to be warped and the side end of the belt is more likely to be damaged, by providing the belt pressing member, the warped belt side end of the endless belt and There is an effect that interference with the image forming unit can be extremely effectively prevented.

According to the sixth aspect of the present invention, since the belt pressing member is provided near the portion facing the nip forming member, the belt pressing member can be compared with a case where the belt pressing member is provided at another portion. As a result, the distance required to push the warped belt-side end of the endless belt to a position where it does not interfere with the unit can be reduced, and the belt pressing member can be reduced in size. Further, by providing the belt pressing member near a portion facing the nip forming member, the belt pressing member can be easily arranged or formed in a part of the casing of the image forming unit. It has the effect of becoming.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a laser printer in which the present invention is implemented.

FIG. 2 is a schematic configuration diagram of a toner image forming unit of the laser printer.

FIG. 3 is an enlarged view of a main part around a transfer belt unit of the laser printer.

FIG. 4 is a schematic diagram for explaining a problem that occurs when the transfer belt unit, the photoconductor unit, or the developing unit of the laser printer is attached and detached.

FIG. 5 is an enlarged view of a main part around an intermediate transfer belt unit of another laser printer in which the present invention is implemented.

FIG. 6 is a sectional view showing a schematic configuration of a main part of the laser printer according to the embodiment of the present invention.

FIG. 7 is a schematic sectional view showing another configuration of the belt pressing member of the embodiment.

FIG. 8 is a schematic perspective view showing an example of the configuration of the belt pressing member.

[Explanation of symbols]

Reference Signs List 1 toner image forming unit 6 transfer belt unit 9 transfer bias power supply 10Y, 10M, 10C, 10K photoconductor unit 10A photoconductor unit casing 10a, 10b photoconductor unit casing end 11Y, 11M, 11C, 11K photoconductor drum 20Y , 20M, 20C, 20K Developing unit 20A Developing unit casing 20a, 20b Developing unit casing end 60 Transfer / conveying belt 60a, 60b Transfer / conveying belt side end 61, 62, 63, 64 Tension rollers 67Y, 67K Transfer bias applying member (fixed brush) 68Y, 68M, 68C, 68K Backup roller 69Y, 69M, 69C, 69K Pressure spring 200 Intermediate transfer belt unit 201 Intermediate transfer belt 260 Endless belt 260a, 260b Belt side end of end belt 260Y Belt unit 300 Imaging unit 300A Casing of imaging unit 300a, 300b Casing end of imaging unit 300c Backup roller receiver 400, 500 Belt pressing member 400a, 500a Belt of belt pressing member Pressing surface P Transfer paper

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H030 AB02 AD05 BB42 BB44 BB46 BB71 2H032 AA05 AA15 BA09 BA18 BA23 2H072 CA07 JA03 3F049 AA03 BB06 BB07 BB08 LA02 LA05 LA07 LB03 3F101 LA01 LA02 LA05 LA07 LB03

Claims (6)

[Claims] An endless belt rotatably stretched by a plurality of stretching rollers, and a unit disposed close to the outer peripheral surface of the endless belt, wherein the endless belt and the unit And the belt device is configured to relatively move along the axial direction of the tension roller, wherein the relative movement between the endless belt and the unit abuts on the belt side end of the endless belt, A belt device comprising a belt pressing member for pressing down the belt side end. 2. An endless belt rotatably stretched by a plurality of stretching rollers, and an image forming unit for forming an image disposed close to an outer peripheral surface of the endless belt. An image forming apparatus configured such that the endless belt and the image forming unit relatively move along the axial direction of the stretching roller, wherein the endless belt and the image forming unit are moved relative to each other. An image forming apparatus comprising: a belt pressing member that abuts on a belt-side end of an endless belt and pushes down the belt-side end. 3. The image forming apparatus according to claim 2, wherein the belt pressing member abuts on a belt side end of the endless belt by a relative movement between the endless belt and the image forming unit. An image forming apparatus having an inclined surface that gradually pushes down a side end. 4. An image forming apparatus according to claim 2, wherein said belt pressing member comprises a roller rotatably supported. 5. The image forming apparatus according to claim 2, wherein said image forming unit is a plurality of image forming units having a plurality of image carriers on which toner images of a plurality of colors are individually formed. An image forming apparatus, wherein the endless belt is a transfer belt for transferring toner images formed on each image carrier of the plurality of image forming units onto the recording medium. 6. The image forming apparatus according to claim 5, wherein the endless belt is displaced in a direction of pressing an inner peripheral surface of the endless belt,
An image forming apparatus having a nip forming member for forming a nip between the endless belt and the image carrier by bringing the surface of the endless belt into contact with the surface of the image carrier of the image forming unit. An image forming apparatus, wherein the belt pressing member is provided in the vicinity of a portion facing the nip forming member.