JPH05134486A - Belt driving device for image forming device - Google Patents

Abstract

PURPOSE:To easily prevent the meandering and the slip of an endless belt at low cost by forming a driving roller so that it may have a surface driven and rotated while giving such a moving habit that the endless belt is always shifted to a center side. CONSTITUTION:Motors 23 and 24 for driving the belt are respectively connected to the ends of both roller shafts 18C and 21C of the driving rollers 18 and 21, and the roller part 18A in the center part of the roller 18 and the roller parts 18B on both sides thereof are constituted of high friction coefficient material such as rubber and low friction coefficient material such as metal, respectively, and both roller parts 18A and 18B are integrally fixed on the roller shaft 18C. By driving and rotating the driving roller 18 by the motor 23, the carrying force of the belt is relatively strengthened more on the center side than on both sides and such a moving habit that the belt is always shifted to the center side is given, because the outer peripheral surfaces of the roller part 18A has high friction coefficient and the outer peripheral surface of the roller parts 18B on both sides have low friction coefficient as for the roller part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device for various endless belts used in an image forming apparatus.

[0002]

2. Description of the Related Art In image forming apparatuses such as electronic copying machines, printers, and facsimiles, various endless belts that are driven to rotate in a predetermined direction are used.

FIG. 6 shows an example of a color type electronic copying machine provided with a photoconductor belt and an endless belt such as a transfer belt. While clarifying the whole construction, the conventional problems will be described below. Will be described in.

In FIG. 1, the endless photoconductor belt 1 has two
It is stretched around the rollers 18 and 19 of the book and arranged vertically. The photosensitive belt 1 is rotationally driven at a constant speed Vp in the direction of the arrow, and its surface is first uniformly charged by the charging charger 3.
The optical writing device 10 at the recording unit 4 with respect to this charged surface
When the optical writing is performed by, an electrostatic latent image is formed on the surface of the photosensitive belt 1. In the image forming apparatus of the type that performs image exposure, an electrostatic latent image is formed by forming and projecting a document image on the recording unit 4.

On the right side of the photosensitive belt 1, developing devices 5, 6, 7 and 8 are arranged in order from the top, and in each of these, developers of different colors, for example, yellow toner, magenta toner and cyan are provided. The toners of the respective colors of the toner and the black toner are stored respectively.
The electrostatic latent image is sequentially visualized for each color. For example, first, an electrostatic latent image for yellow is formed on the photosensitive belt 1, and this is visualized as a yellow toner image by the developing device 5 containing the toner.

On the other hand, the transfer paper is sent from the paper feeding section 9 in the direction of the arrow, and the transfer paper sent in this direction is conveyed to the transfer belt 2 made of a dielectric material at the registration roller 11 at a timing. It is supposed to be done.

The transfer paper is a paper adsorption charger 12
By this, it is adsorbed on the transfer belt 2 rotating in the direction of the arrow, and in this adsorbed state, it is carried leftward on the belt at a speed of Vf. At this time, the visible image of the first color (for example, a yellow toner image) formed on the photosensitive belt 1 is transferred onto the transfer paper by the action of the transfer charger 14. During this transfer, the contact / separation switching roller 13 is raised so that the transfer belt portion facing the transfer charger 14 comes into contact with the photosensitive belt 1.

After the transfer, the transfer paper is fed to the position shown by the broken line, and thereafter, the transfer belt 2 reverses in the direction opposite to the arrow direction with the contact / separation switching roller 13 descending, and the transfer paper becomes V.
It is designed to be returned to the virtual line position at a speed of r. During this period, the residual toner on the photoconductor belt 1 is cleaned by the cleaning device 30, and the surface of the photoconductor belt 1 is subjected to the charge removal action by the charge remover 31. Next, as described above, the photosensitive belt 1 is charged and optically written,
A second-color electrostatic latent image is formed, and this is visualized as a magenta toner image by the developing device 6 containing, for example, magenta toner.

On the other hand, the transfer belt 2 again rotates in the direction of the arrow again, and at this time, the second color image (for example, magenta toner image) on the photoconductor 1 is transferred onto the transfer paper fed together with the belt. At that time, the contact / separation switching roller 13 is raised. After that, the above-described operation is performed in the same manner, the toner images of the respective colors are sequentially transferred onto the same transfer paper, and when the number is the largest, the transfer is performed four times in total. That is, the four color toner images are transferred and transferred onto the transfer paper. After all such transfer is completed, the transfer paper is transferred to the imaginary line position by the path switching member 15 to fix the fixing device 1.
6, the toner image on the transfer paper is fixed by this device section, and then the transfer paper is ejected to the tray 17.

The photosensitive belt 1 is composed of both rollers 1
8 and 19, and the lower roller 18 of these rollers is a driving roller, and the upper roller 19 is
Is a driven roller that rotates as the photosensitive belt 1 rotates. The transfer belt 2 is stretched between the rollers 21 and 22, and among these rollers, the roller 2 on the left side of the drawing is used.
1 is a driving roller, and the right roller 22 is a driven roller.

When driving such a series of endless belts, slip easily occurs between the drive roller and the belt. Further, the belt is displaced in the axial direction of the drive roller, and the belt is apt to meander. If such belt slipping or meandering occurs, color misregistration easily occurs when a color image is formed.

Therefore, in order to prevent the belt from meandering, flanges for restricting the movement of the belt are provided at both ends of the driving roller. However, if the belt itself meanders, the belt side edge The part may hit the flange part with a strong force, and the belt may be deformed or damaged.

Therefore, for example, Japanese Patent Laid-Open No. 63-30108.
According to the publication No. 4, etc., a crown roller is used as a driving roller in order to prevent the belt from meandering. With this method, it is difficult to bring the belt into uniform contact with the photoconductor at the transfer position, and a backup member is used to improve the contact property. Then, the structure is apt to be complicated, the rotational load of the belt is increased, and the belt life is shortened.

In addition, according to Japanese Patent Application Laid-Open No. 64-2070, etc., the belt tension roller is made non-parallel so that the belt is moved to one side, and the belt and the roller engage with each other in an uneven manner. An engaging portion is provided. With this method, a predetermined tension difference is generated on both side edges of the belt, which makes it difficult to uniformly contact the photosensitive member with the belt, which may cause uneven transfer.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to provide a belt driving device for an image forming apparatus which has a simple structure and is low in cost, and which can prevent the belt from meandering and slipping.

[0016]

In order to achieve the above-mentioned object, the present invention has a drive roller which spans an endless belt between at least one driven roller and rotationally drives the endless belt. , Of the roller portion of this drive roller, the outer peripheral surface of the roller portion on the center side in the widthwise direction of the endless belt and the outer peripheral surfaces of the roller portions on both sides of the end portion are always moved toward the center side. The present invention proposes a structure formed on a surface that can be rotationally driven when given.

It is effective to make the outer peripheral surface of the central roller portion a high friction coefficient surface and the outer peripheral surfaces of both roller portions a low friction coefficient surface.

It is also effective to make the outer peripheral surface of the central roller portion rough and the outer peripheral surfaces of both roller portions smooth.

Further, it is effective to form a lubricating coating on the outer peripheral surfaces of the roller portions on both sides.

Further, it is effective that the roller portion on the center side and the roller portions on both sides have outer peripheral surfaces having substantially the same diameter.

[0021]

The present invention will be described in detail below with reference to the illustrated embodiments.

FIG. 1 shows a belt driving device according to an embodiment of the present invention. A photosensitive belt 1 which is an example of the constitution of an endless belt,
The drive roller 18 is a parallel roller body, and the drive roller 18 is also a parallel roller body, and the flange portions 19A are provided at both ends.
It is suspended between the driven roller 19 and the driven roller 19.
The transfer belt 2, which is an example of a configuration of an endless belt, includes a driving roller 21 that is a parallel roller body and a driven roller 22 that is also a parallel roller body and has flange portions 22A at both ends. It is suspended in the middle. Although both belts have one driven roller instead of a plurality of driven rollers in the present example, the present invention can be applied when a plurality of driven rollers are used.

Here, the feature of the present invention lies in the outer peripheral surface of the roller portion of the drive roller for driving the belt to rotate and the outer peripheral surface of the roller portion on the center side in the width direction of the endless belt and the outer periphery of the roller portions on both sides thereof. The surface is formed so as to be rotationally driven by being given a movement habit in the direction in which the endless belt is moved toward the center side.

The drive rollers 18 and 21 shown in FIG. 1 are the drive rollers having such a structure.

Further, this structure will be described in detail. Both roller shafts 1 of the driving roller 18 and the driving roller 21.
A motor 2 for driving a belt is provided at one end of 8C and 21C.
3, 24 are connected to each other. Of these, the roller portion 18A on the center side of the drive roller 18 is made of a material having a high friction coefficient such as rubber as shown in FIG.
B is made of a material having a low friction coefficient such as metal, and both roller portions 18A and 18B are integrally fixed to a roller shaft 18C.

When the driving roller 18 is rotationally driven by the motor 23 shown in FIG. 1, the outer peripheral surface of the central roller portion 18A of the roller portions has a high friction coefficient surface, and the outer peripheral surfaces of the roller portions 18B on both sides are high. Since the surface has a low friction coefficient, the conveyance force of the belt is relatively stronger on the center side than on both sides, and the movement habit is given in the direction in which the belt is always moved to the center side. Like That is, the photosensitive belt 1 is rotationally driven while being given a movement habit in the direction of being moved to the center side.

Due to such a function, meandering of the photosensitive belt 1 is prevented, and uneven speed of the left and right belt portions can be reduced. Further, since the frictional force between the central roller portion 18A and the belt becomes large, the photoconductor belt 1 is prevented from slipping. On the other hand, if all of the drive rollers are made of a material having a low friction coefficient (for example, a metal material), slippage is likely to occur between the drive roller and the belt. Further, in the case where the driving roller is provided with the flange portions at both ends, when the belt is deviated, the flange portion may deform or damage the belt. , Such fear disappears. That is, in order to more reliably prevent the photosensitive belt 1 from meandering, even if the belt movement restricting flange portions are provided at both ends of the driving roller 18, the belt side edge portion does not hit the flange portion with a strong force. Therefore, the belt 1 can be prevented from being deformed or damaged. This also applies to each of the embodiments described later.

When the belt is offset, transfer defects may occur on the offset side and on the opposite side. However, the use of the drive roller of this example eliminates such a risk.

Further, since the driving roller 18 is not a crown roller but a parallel roller, the photosensitive belt 1
Will come into uniform contact with the developing devices 5 to 8 (FIG. 6) on the flat surface in the belt width direction. Moreover, since the belt peripheral speed does not differ between the center side and both side edges, uneven development occurs. And the like are less likely to occur, and an image with uniform density can be obtained. As described above, the driven roller 19 is provided with the flange portions 19A at both ends, so that the movement of the photoconductor belt 1 in the width direction is restricted.

The transfer belt 2 shown in FIG. 1 supports and conveys the transfer paper, and should be called a transfer paper support belt. This belt is provided between the driving roller 21 and the driven roller 22. It is stretched over. The belt 2 may also be stretched over a plurality of driven rollers.

The motor 24 is connected to the roller shaft 21C of the drive roller 21 as described above.
The transfer belt 2
Are rotationally driven in the Vf direction and the Vr direction, respectively. In the drive roller 21, the central roller portion 21A is made of a high friction coefficient material, the outer peripheral surface is formed as a high friction coefficient surface, and the roller portions 21B, 21B on both sides are made of a low friction coefficient material. The outer peripheral surface is formed as a low friction coefficient surface. By using such a driving roller 21, the transfer belt 2 is prevented from meandering and slipping, just like the photosensitive belt 1.

As shown in FIG. 2, each of the driving rollers 18 and 21 has a roller portion 18
A and 18B may be constituted by separate members, and a roller constitution may be adopted in which only the central surface layer is a high friction coefficient material layer and only the surface layers on both sides are low friction coefficient material layers. Also, each outer peripheral surface of each roller portion may be a high friction coefficient surface or a low friction coefficient surface. With any of the driving rollers, the roller can be easily manufactured, and if rubber or the like is used as the high friction coefficient material, the roller can be manufactured at a relatively low cost.

The drive roller 118 shown in FIG. 3 corresponds to the drive roller 18 shown in FIG.
The photosensitive belt 1 is stretched between the driven roller of the book.

In this drive roller 118, the outer peripheral surface of the central roller portion 118A is rough, whereas
The outer peripheral surfaces of the roller portions 118B on both sides are smooth surfaces. For example, the roller portion 118A on the center side is a rough surface having a saw-toothed concavo-convex shape, and the large frictional force of this portion substantially drives the photosensitive belt. In addition, in FIG.
It is the figure which made the roller part 118A of the center the cross section.

As described above, the central roller portion 118A can be called a belt driving portion, but in contrast to this,
The roller portions 118B having smooth surfaces on both sides are to be guide portions of the belt. In any case, by using such a driving roller, the photoconductor belt is rotationally driven while being given a movement habit in a direction in which it is always moved to the center side.

Of course, such a structure can be adopted as a driving roller for driving the transfer belt, and it is possible to prevent the transfer belt from meandering and slipping together with the photosensitive belt.

The drive roller in the case of the present example can be manufactured by the same material as it is, and the manufacturing cost can be reduced, and the precision can be improved. Furthermore, when rotating at high speed, the coefficient of thermal expansion of the roller becomes constant in any part,
Bending of the roller is less likely to occur, and the change in outer diameter of the roller is prevented from becoming uneven. Therefore, a difference in peripheral speed of the belt (a difference in the belt width direction) is less likely to occur, and a copy paper that is less likely to cause color misregistration and uneven density can be obtained.

The drive roller 118 'shown in FIG. 5 is different from the drive roller shown in FIGS. 3 and 4 in that a lubricating coating 119 is formed on the outer peripheral surfaces of the roller portions (belt guide portions) 118B on both sides which are not used for driving the belt. It was done like this.

If the drive roller is constructed in this way, the belt can be made more slippery with respect to the roller portions on both sides. That is, the belt becomes easy to move in the axial direction of the drive roller only with respect to the roller portions on both sides, and the meandering correction of the belt is effectively performed. Further, the belt is less likely to be wrinkled or damaged. A specific material example of the lubricating coating 119 may be a fluorine resin coating or a molybdenum solid coating. The drive roller 118 'shown in FIG. 5 can be adopted not only as the roller for driving the photosensitive belt but also as the roller for driving the transfer belt.

In the drive rollers shown in FIGS. 2, 3 and 5, the central roller portion and the roller portions on both sides are almost
Preferably, when the outer peripheral surfaces have completely the same diameter, the belt can be flattened in the width direction thereof, and uneven transfer and uneven development can be suppressed. For example, if the diameter of the central roller portion (high friction coefficient surface, rough surface portion) is made larger than that of both roller portions (low friction coefficient surface, smooth surface),
The transferability of the roller portions on both sides is poor, and transfer unevenness is likely to occur. Similarly, uneven development easily occurs. If both roller portions have the same outer peripheral surface, there is no such possibility, and a high-quality image without unevenness can be obtained.

The present invention can also be applied to a belt driving device that drives an endless belt other than the photosensitive belt and the transfer belt.

[0042]

According to the belt driving device of the first aspect, the meandering of the endless belt and the slipping of the driving roller can be suppressed, and the driving roller is
It is not necessary to use a deformed structure to prevent meandering.
Then, such a function can be achieved with a simple configuration and at low cost.

According to the belt drive device of the second aspect, since the outer peripheral surface of each roller portion only needs to have a high friction coefficient surface or a low friction coefficient surface, the drive roller can be easily manufactured. It is possible and advantageous in cost.

According to the belt driving device of the third aspect, since the driving roller can be integrally manufactured from the same material, the manufacturing cost can be reduced, and the precision can be improved. ..

According to the belt driving device of the fourth aspect, the belt can be made slippery with respect to the roller portions on both sides, and the meandering of the belt can be effectively corrected.

According to the belt driving device of the fifth aspect, it is possible to effectively suppress the occurrence of uneven transfer and uneven development.

[Brief description of drawings]

FIG. 1 is a perspective view of a belt driving device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of an example of a driving roller included in the belt driving device.

FIG. 3 is a partial cross-sectional view of another example of the driving roller included in the belt driving device.

FIG. 4 is a cross-sectional view of a central roller portion of a driving roller included in the belt driving device.

FIG. 5 is a partial cross-sectional view of still another example of the driving roller included in the belt driving device.

FIG. 6 is a schematic configuration diagram of an example of a color type electronic copying machine used for explaining a conventional technique.

[Explanation of symbols]

 1 Photoreceptor Belt as an Endless Belt 2 Transfer Belt as an Endless Belt 18 Drive Roller 18A Central Roller Part 18B Both Sides Roller Part 19 Driven Roller 21 Drive Roller 21A Central Side Roller Part 21B Both Sides Roller Part 22 Driven Roller 118 Drive roller 118A Central roller portion 118B Both side roller portions 118 'Drive roller 119 Lubricating film

Claims (5)

[Claims] 1. Between at least one driven roller,
An endless belt is stretched over, and a drive roller that rotationally drives the endless belt is provided, and among the roller portions of the drive roller,
The endless belt is rotatably driven while being given a habit of moving the outer peripheral surface of the roller portion on the center side in the width direction and the outer peripheral surfaces of the roller portions on both sides thereof in a direction in which the endless belt is always moved to the center side. A belt driving device for an image forming apparatus, which is formed on a flat surface. 2. The belt driving device for an image forming apparatus according to claim 1, wherein the outer peripheral surface of the central roller portion is a high friction coefficient surface, and the outer peripheral surfaces of both roller portions are low friction coefficient surfaces. 3. The outer peripheral surface of the central roller portion is roughened,
The belt driving device of the image forming apparatus according to claim 1, wherein the outer peripheral surfaces of the roller portions on both sides are smooth. 4. A belt driving device for an image forming apparatus according to claim 3, wherein a lubricating coating is formed on the outer peripheral surfaces of the roller portions on both sides. 5. The belt driving device for an image forming apparatus according to claim 1, wherein the roller portion on the center side and the roller portions on both sides are outer peripheral surfaces having substantially the same diameter.