JP2004101599A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of surely preventing image deterioration by preventing damage or crack from occurring even when an endless belt is tensioned from its outer peripheral surface by a pressing member. <P>SOLUTION: In a color copying machine as the image forming apparatus provided with an intermediate transfer belt 10 as the endless belt used for forming an image, and a belt driving means rotating and carrying the belt 10 by laying the belt 10 on a driving roller rotated by receiving rotational driving force and at least one or more driven roller, the belt driving means is equipped with a tension roller 7 as the pressing member for pressing the belt 10 from the outer peripheral surface, and inclined surfaces 7a where pressing force is made weaker toward the outside are formed on both ends of the roller 7 in a longitudinal direction orthogonal to the rotating and carrying direction of the belt 10. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer, and more particularly, to an image forming apparatus including an endless belt for forming an image, such as an intermediate transfer belt and a photosensitive belt.
[0002]
[Prior art]
2. Description of the Related Art In recent years, image forming apparatuses that output color images, such as color copiers and color printers, have been increasing in accordance with market requirements.
The color image forming apparatus includes a so-called tandem type in which a plurality of photosensitive members provided side by side are provided with developing devices individually. In this tandem-type image forming apparatus, the images on the respective photoconductors are temporarily superimposed on the intermediate transfer body by the primary transfer device and are sequentially transferred. Then, the composite color image on the intermediate transfer body is collectively transferred to a transfer material such as transfer paper by a secondary transfer device.
[0003]
[Problems to be solved by the invention]
In the tandem-type image forming apparatus, when an intermediate transfer belt of an endless belt is used as the intermediate transfer body, the intermediate transfer belt is moved from the outer peripheral surface side by a tension roller due to a belt tension and a layout with other members. It may be pressed (for example, see Patent Document 1). FIG. 7 is an explanatory diagram in a case where the intermediate transfer belt 10 is pressed by the tension roller 20 from the outer peripheral surface side. When the width of the tension roller 20 is shorter than the width of the intermediate transfer belt 10, when the tension roller 20 presses the intermediate transfer belt 10, the intermediate transfer belt 10 bends at a portion in contact with the roller end. Normally, since the roller end of the tension roller 20 is formed at a right angle, stress concentrates on a portion of the intermediate transfer belt 10 that comes into contact with the roller end, and the outer peripheral surface of the portion is scratched or cracked. May be. Since the outer peripheral surface of the intermediate transfer belt 10 is an image forming surface, there is a problem that if the surface is scratched or cracked, image deterioration occurs.
[0004]
Image deterioration due to scratches or cracks on the outer peripheral surface of the intermediate transfer belt is a problem that can occur not only in the case of the intermediate transfer belt but also in the case of a photosensitive belt.
[0005]
The present invention has been made in view of the above problems, and its purpose is to prevent the occurrence of scratches and cracks even when tension is applied to the endless belt from the outer peripheral surface with a pressing member, An object of the present invention is to provide an image forming apparatus capable of reliably preventing image deterioration.
[0006]
[Patent Document 1]
JP-A-11-202645 (page 4, FIG. 1)
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 includes an endless belt used for image formation, a driving roller rotating by receiving a rotational driving force, and at least one or more driven rollers. A belt driving unit that stretches a belt and rotates and conveys the endless belt, wherein the belt driving unit includes a pressing member that presses the endless belt from an outer peripheral surface; At both ends in the longitudinal direction orthogonal to the direction of the endless belt rotation and conveyance, inclined surfaces are formed such that the pressing force becomes weaker toward the outside.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a reinforcing member having a predetermined width is formed at both ends on the back surface of the endless belt, and the belt width of the reinforcing member is adjusted. The end position on the center side in the direction is set outside the end position on the center side in the longitudinal direction of the inclined surface of the pressing member.
According to a third aspect of the present invention, in the image forming apparatus of the first or second aspect, the pressing member is configured using a roller-shaped member.
According to a fourth aspect of the present invention, in the image forming apparatus of the first or second aspect, the pressing member is formed using a semicircular member.
According to a fifth aspect of the present invention, in the image forming apparatus of the first, second, third or fourth aspect, the endless belt is an intermediate transfer belt.
According to a sixth aspect of the present invention, in the image forming apparatus of the first, second, third or fourth aspect, the endless belt is a photosensitive belt.
According to the first to sixth aspects of the present invention, in the portion of the endless belt that comes into contact with the inclined surface of the pressing member, the pressing force of the pressing member is gradually reduced, and the pressing member of the endless belt is gradually reduced. Stress does not concentrate on the portion that comes into contact with the end. Therefore, it is possible to prevent the stress caused by the pressing member from concentrating on a part of the endless belt, thereby preventing the outer peripheral surface from being damaged or cracked.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment in which the present invention is applied to a color electrophotographic copying machine (hereinafter, referred to as “color copying machine”) which is an electrophotographic copying machine which is an image forming apparatus will be described. FIG. 1 is a schematic configuration diagram of a color copying machine according to the present embodiment.
[0009]
An intermediate transfer belt 10 is provided at the center of the main body of the color copying machine. The intermediate transfer belt 10 is wound around three support rollers 3, 4, and 5 in the illustrated example, and is rotated and conveyed clockwise in the figure. Then, an intermediate transfer belt cleaning device that removes residual toner remaining on the intermediate transfer belt 10 after image transfer on the downstream side of the third support roller 5 among the three support rollers with respect to the moving direction of the intermediate transfer belt 10. 6 is provided. Further, a tension roller 7 for pressing the intermediate transfer belt 10 from the outer peripheral surface is provided downstream of the intermediate transfer belt cleaning position and upstream of the primary transfer position with respect to the moving direction of the intermediate transfer belt 10.
Further, on the intermediate transfer belt 10 stretched between the first support roller 3 and the second support roller 4 among the three support rollers, black, cyan, magenta, yellow The four photoconductors 1B, C, M, and Y are arranged side by side.
[0010]
On the other hand, a secondary transfer device 8 is provided on the opposite side of the intermediate transfer belt 10 from the third support roller 5. In the illustrated example, the secondary transfer device 8 is configured by a transfer roller, is disposed by being pressed against the third support roller 5 via the intermediate transfer belt 10, and transfers the image on the intermediate transfer belt 10 to the sheet S. .
A fixing device (not shown) for fixing a transfer image on a sheet is provided downstream of the secondary transfer device 8 in the sheet conveyance direction. This fixing device is configured by pressing a pressure roller against a fixing belt, for example, an endless belt.
[0011]
Now, when making a copy using this color copier, an original is set on a contact glass of a scanner (not shown), and a document holding cover (not shown) is closed and pressed.
When a start switch (not shown) is pressed, the scanner is driven to emit light from a light source, and the reflected light from the original surface is input to a reading sensor through an imaging lens to read the original contents.
[0012]
When the start switch is pressed, the first support roller 3 is rotationally driven by a drive motor (not shown), and the other two support rollers 4 and 5 are driven to rotate, and the intermediate transfer belt 10 is rotationally conveyed. At the same time, the photoreceptors 1B, 1C, 1M, and 1Y are rotated by individual image forming means to form black, cyan, magenta, and yellow single-color images on the respective photoreceptors. Then, as the intermediate transfer belt 10 rotates, the single-color images are sequentially transferred by the four primary transfer devices 2B, C, M, and Y to form a composite color image on the intermediate transfer belt 10.
[0013]
On the other hand, when the start switch is pressed, the sheet S is fed out from a paper cassette (not shown), and is stopped by abutting against a registration roller (not shown).
[0014]
Then, the registration roller is rotated in time with the composite color image on the intermediate transfer belt 10, the sheet S is sent between the intermediate transfer belt 10 and the secondary transfer device 8, and is transferred by the secondary transfer device 8. A color image is recorded on the sheet S.
The sheet S after the image transfer is conveyed by the secondary transfer device 8 and sent to a fixing device (not shown). After fixing the transferred image by applying heat and pressure by the fixing device, the sheet S is discharged by a discharge roller and discharged. Stack on paper tray.
[0015]
On the other hand, with respect to the intermediate transfer belt 10 after the image transfer, the intermediate transfer belt cleaning device 6 removes residual toner remaining on the intermediate transfer belt 10 after the image transfer, and prepares for image formation again.
[0016]
Here, as described above, since the roller end of the conventional tension roller is substantially at a right angle, as shown in FIG. 7, stress concentrates on a portion in contact with the roller end of the intermediate transfer belt, and the surface of the belt is damaged. There were cases where cracks or cracks occurred. Since the outer peripheral surface of the intermediate transfer belt 10 is an image forming surface, there is a problem that if the outer peripheral surface is damaged by a scratch or a crack, image deterioration occurs.
[0017]
[Example 1]
Therefore, in the color copying machine according to the present embodiment, inclined surfaces are formed at both ends of the tension roller 7 in the longitudinal direction orthogonal to the direction of rotation and conveyance of the intermediate transfer belt so that the pressing force becomes weaker toward the outside. More specifically, inclined surfaces are formed at both ends of the tension roller 7 so that the roller diameter becomes smaller from the center in the longitudinal direction of the roller toward the end. FIG. 2 is a front view of the tension roller 7. At both ends of the tension roller 7, the length L ₁ of the portion from the respective end portions, the angle theta ₁ of the inclined surface 7a which makes with the extension line of the roller surface is formed. For example, the length _{L 1} from the end 9 mm, the angle theta ₁ is 5 degrees. Note that the angle θ ₁ is about 7 degrees at the maximum.
[0018]
FIG. 3 is an explanatory diagram when the intermediate transfer belt 10 is pressed by the tension roller 7 according to the present embodiment. By using the tension roller 7 having this configuration, when the intermediate transfer belt 10 is pressed, the pressing force of the belt portion facing the inclined surface 7a gradually becomes weaker toward the belt end. Therefore, the stress that has conventionally concentrated on the portion of the intermediate transfer belt 10 that is in contact with the roller end is dispersed to the portion of the tension roller 7 that is in contact with the inclined surface 7a, thereby preventing damage to the outer peripheral surface of the intermediate transfer belt 10. Can be. As a result, image deterioration due to breakage of the intermediate transfer belt 10 can be reliably prevented.
[0019]
The intermediate transfer belt 10 may be provided with reinforcing members for preventing the end portions from being scraped at both ends of the back surface. This reinforcing member is integrated with the intermediate transfer belt 10, and the strength (bending rigidity) of that portion is improved. However, as shown in FIG. 4, when the end position 11a of the reinforcing member 11 on the center side in the belt width direction coincides with the end position 21b on the center side in the roller longitudinal direction of the inclined surface 21a of the tension roller 21, the intermediate transfer belt Stress concentrates at the end position 11a of the reinforcing member 11 at the center side of the belt width direction 10 in FIG. Then, cracks are easily formed in that portion. Therefore, in the color copying machine according to the present embodiment, as shown in FIG. 5, the end position 11a of the reinforcing member 11 on the center side in the belt width direction is the end position on the center in the roller longitudinal direction of the tension roller inclined surface 7a. 7b so that they do not coincide with each other. It should be noted that the dimensions in the drawing are examples.
The end position 11a of the reinforcing member 11 on the center side in the belt width direction is located outside the end position 7b of the inclined surface 7a of the tension roller 7 on the central side in the roller longitudinal direction, and faces the tension roller inclined surface 7a. . Thus, it is possible to prevent the stress from being concentrated on the end position 11a of the reinforcing member 11 on the center side of the intermediate transfer belt 10 in the belt width direction, and to prevent cracks from being generated in that portion.
[0020]
[Example 2]
In the first embodiment, the pressing member is formed of a roller-shaped member, but may be formed of a semicircular member. FIG. 6A is a front view of the semicircular pressing member 9, and FIG.
At both ends of the semicircular type pressing member 9, the length L ₂ of the portions from each end, the angle theta ₂ of the inclined surface 9a is formed which forms with respect to the extension line of the pressing member surface. For example, the length _{L 2} from the end portion is 9 mm, the angle theta ₂ is 5 degrees. The angle theta ₂ is about up to 7 degrees. The material of the semicircular pressing member 9 is, for example, an aluminum material having a thickness of 1.5 mm. Further, the outer peripheral radius R of the semicircular pressing member 9 can be set arbitrarily, but is, for example, about 10 mm.
By providing the semicircular pressing member 9 and pressing the intermediate transfer belt 10 from the outer peripheral surface, the same effect as in the first embodiment can be obtained.
[0021]
In the first and second embodiments, the pressing members for pressing the intermediate transfer belt from the outer peripheral surface have been described. However, the same effect can be obtained when the photosensitive belt is pressed from the outer peripheral surface using these pressing members. Of course.
[0022]
As described above, according to the present embodiment, the endless belt is stretched around the endless belt used for image formation, the driving roller rotating by receiving the rotational driving force, and at least one or more driven rollers. And a belt driving unit for rotating and conveying the endless belt, wherein the belt driving unit includes a pressing member for pressing the endless belt from an outer peripheral surface, and the endless belt of the pressing member is provided. At both ends in the longitudinal direction orthogonal to the direction of rotation of the belt-like belt, inclined surfaces were formed such that the pressing force became weaker toward the outside.
In the color copying machine as the image forming apparatus, a reinforcing member having a predetermined width is formed at both ends on the back surface of the endless belt. The position of each part was set so as to be outside the position of the end of the inclined surface of the pressing member on the center side in the longitudinal direction. Therefore, since the end position of the reinforcing member on the center side in the belt width direction does not match the end position on the center side in the longitudinal direction of the inclined surface of the pressing member, the end position of the reinforcing member on the center side in the belt width direction of the endless belt. Stress is not concentrated on Thereby, cracks do not occur at the end positions of the reinforcing member on the center side in the belt width direction of the endless belt, and the durability can be improved.
In the color copying machine as the image forming apparatus, the pressing member is configured using a tension roller that is a roller-shaped member. Since the tension roller is in rolling contact with the outer peripheral surface of the endless belt, resistance is small, and smooth rotation and conveyance of the endless belt can be obtained.
In the color copying machine as the image forming apparatus, the pressing member is formed using a semicircular pressing member that is a semicircular member. Therefore, component costs and assembly costs can be reduced as compared with the case where the pressing member is configured using a roller-shaped member.
In the color copying machine as the image forming apparatus, the endless belt is an intermediate transfer belt. Therefore, it is possible to prevent scratches and cracks on the outer peripheral surface of the intermediate transfer belt, thereby preventing image deterioration.
In the color copying machine as the image forming apparatus, the endless belt is a photosensitive belt. Therefore, it is possible to prevent scratches and cracks on the outer peripheral surface of the photoreceptor belt, thereby preventing image deterioration.
[0023]
【The invention's effect】
According to the first to sixth aspects of the present invention, even when tension is applied to the endless belt from the outer peripheral surface by the pressing member, scratches and cracks can be prevented, and image deterioration can be reliably prevented. Has an effect. Also, there is an excellent effect that the durability of the endless belt can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a color copying machine according to an embodiment of the present invention.
FIG. 2 is a front view of a tension roller.
FIG. 3 is an explanatory diagram in which an intermediate transfer belt is pressed from an outer peripheral surface by a tension roller.
FIG. 4 is an explanatory diagram illustrating a state in which an end position of a reinforcing member on a belt center portion side coincides with an end position of a tension roller inclined surface on a roller center portion side;
FIG. 5 is an explanatory diagram illustrating a state in which an end position of a reinforcing member at a belt center portion side faces a tension roller inclined surface.
FIG. 6A is a front view of a semicircular pressing member.
(B) is AA sectional drawing of a semicircle type press member.
FIG. 7 is an explanatory diagram in which a conventional tension roller presses an intermediate transfer belt from an outer peripheral surface.
[Explanation of symbols]
1B, C, M, Y Photoconductors 2B, C, M, Y Primary transfer devices 3, 4, 5 Support roller 6 Intermediate transfer belt cleaning device 7 Tension roller 7a Inclined surface 7b End of inclined surface on roller center side Position 8 Secondary transfer device 9 Semicircular pressing member 9a Inclined surface 10 Intermediate transfer belt 11 Reinforcement member 11a End position of reinforcement member on belt center side 20 Conventional tension roller

Claims (6)

An endless belt used for image formation;
A driving roller that rotates by receiving a rotational driving force, and an image forming apparatus that has a belt driving unit that stretches the endless belt around at least one or more driven rollers and rotationally conveys the endless belt.
The belt driving means includes a pressing member that presses the endless belt from an outer peripheral surface,
An image forming apparatus, wherein an inclined surface is formed at both ends of the pressing member in a longitudinal direction orthogonal to the direction of rotation of the endless belt such that the pressing force becomes weaker toward the outside. The image forming apparatus according to claim 1,
On the back surface of the endless belt, a reinforcing member having a predetermined width is formed at both ends,
An image forming apparatus, wherein an end position of the reinforcing member on the center side in the belt width direction is set to be outside of an end position on a center side in the longitudinal direction of the inclined surface of the pressing member. The image forming apparatus according to claim 1, wherein
An image forming apparatus, wherein the pressing member is configured using a roller-shaped member. The image forming apparatus according to claim 1, wherein
An image forming apparatus, wherein the pressing member is formed using a semicircular member. The image forming apparatus according to claim 1, 2, 3, or 4,
An image forming apparatus, wherein the endless belt is an intermediate transfer belt. The image forming apparatus according to claim 1, 2, 3, or 4,
An image forming apparatus, wherein the endless belt is a photosensitive belt.

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