JP2022114558A - Image forming apparatus and manufacturing method thereof - Google Patents

Abstract

[PROBLEMS] To provide an image forming apparatus in which an intermediate transfer belt is stretched by a tension roller having a spiral groove formed along the circumferential direction of the roller so as to circulate in the axial direction of the roller. By polishing along the circumferential direction of the tension roller, generation of tension lines due to irregularities in the circumferential direction of the roller at the ridge line is suppressed.
SOLUTION: In a longitudinal cross section of a tension roller 113, a ridge line portion of a groove structure 31 is subjected to polishing along a circumferential direction of the tension roller 113. - 特許庁
[Selection diagram] Fig. 3

Description

The present invention relates to an image forming apparatus having an intermediate transfer belt that carries a toner image and transfers the toner image onto a recording material, and an image forming apparatus having spiral grooves on the surface of a tension roller that stretches the intermediate transfer belt. The present invention relates to a device and its manufacturing method.

Conventionally, a toner image formed on an image carrier is transferred onto an intermediate transfer belt passing through a primary transfer portion, conveyed to a secondary transfer portion, and collectively secondary-transferred onto a recording material fed to the secondary transfer portion. Image forming apparatuses are widely used. The intermediate transfer belt is generally formed in an endless shape, and is stretched over one or more stretching rollers (a drive roller, a tension roller, a steering roller, a support roller, etc.) and supported in a tensioned state.

Foreign matter such as dust and developer may enter the inner side of the intermediate transfer belt. If foreign matter enters between the tension roller and the belt, the pressure applied to the belt locally increases due to the height of the foreign matter. As a result, streak-like deformation (tension line) may occur in a part of the width direction of the belt along the circumferential direction.

Therefore, in Japanese Unexamined Patent Application Publication No. 2002-100000, spiral grooves are formed on the circumferential surface of the tension roller to suppress local increases in pressure even if foreign matter adheres to the inner surface of the belt, thereby preventing the occurrence of tension lines. suppressed.

JP 2018-169578 A

However, in the conventional image forming apparatus, if the unevenness (surface roughness) in the roller circumferential direction is large at the ridge between the grooves of the tension roller, the roller becomes locally sharp in the circumferential direction. As a result, the contact pressure on the intermediate transfer belt locally increases. As a result, there is a possibility that streak-like permanent deformation (hereinafter referred to as a tension line) will occur in the circumferential direction of the intermediate transfer belt.

Accordingly, the present invention has been made in view of the problems that exist in such conventional techniques. That is, by forming a spiral groove on the peripheral surface of the tension roller, the occurrence of tension lines due to adhesion of foreign matter is suppressed, and the occurrence of tension lines due to unevenness in the roller circumferential direction at the ridges of the grooves is suppressed. It is an object of the present invention to provide an image forming apparatus capable of

In order to solve the above problems, the present invention provides an image carrier, an image forming unit that forms a toner image on the image carrier, an endless belt member to which the toner image is transferred from the image carrier, a tension roller for stretching the belt member, the tension roller having a spiral groove formed on the peripheral surface of the tension roller so as to rotate around the axial direction of the tension roller. In the axial direction of the tension roller, the width of the groove is 100 μm or more and 500 μm or less, the depth of the groove is 10 μm or more and 40 μm or less, and the ridge portion formed between the grooves has a flat portion polished along the circumferential direction of the tension roller, and the width of the flat portion is 30 μm or more and 150 μm or less in the axial direction of the tension roller.

Further, the present invention comprises an image carrier, an image forming section for forming a toner image on the image carrier, an endless belt member to which the toner image is transferred from the image carrier, and a belt member stretched. a tension roller, the tension roller having a spiral groove formed on the peripheral surface of the tension roller so as to revolve around the axial direction of the tension roller; The width of the groove is 100 μm or more and 500 μm or less, and the depth of the groove is 10 μm or more and 40 μm or less in the axial direction of the suspension roller, and the ridge formed between the grooves is the tension roller. and the width of the curved surface portion is 30 μm or more and 150 μm or less in the axial direction of the tension roller.

The present invention also provides a method of manufacturing an image forming apparatus having a tension roller for stretching an endless belt member onto which a toner image is transferred, wherein the belt member is rotated around the axial direction of the tension roller. a cutting step of forming a spiral groove on the peripheral surface of the tension roller; and a polishing step of polishing along the circumferential direction of the tension roller.

According to the present invention, by forming a helical groove on the circumferential surface of the tension roller, it is possible to suppress the occurrence of tension lines due to adhesion of foreign matter, etc., and to prevent tension lines due to unevenness in the roller circumferential direction at the ridges of the grooves. It is possible to provide an image forming apparatus capable of suppressing the occurrence of

Cross-sectional view of an image forming apparatus FIG. 2 is a perspective view of a support roller of Example 1; FIG. 2 is a longitudinal partial cross-sectional view of the support roller of Example 1. FIG. FIG. 4 is a longitudinal partial cross-sectional view of the support roller of Example 2; Diagram showing belt deflection due to groove structure Diagram showing belt waviness due to groove structure

Preferred embodiments of the present invention will be exemplarily described in detail below with reference to the accompanying drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment are not intended to limit the scope of the present invention only to them. .

(Image forming device)
FIG. 1 is an explanatory diagram of the configuration of the image forming apparatus in this embodiment. As shown in FIG. 1, the image forming apparatus 100 has yellow, magenta, cyan, and black image forming units 109Y, 109M, 109C, and 109Bk arranged along an intermediate transfer belt 101 as a belt member. That is, the image forming apparatus of this embodiment is a so-called tandem type intermediate transfer type full-color printer.

In the image forming unit 109Y, a yellow toner image is formed on the photosensitive drum 103Y and transferred to the intermediate transfer belt 101. FIG. In the image forming section 109M, a magenta toner image is formed and transferred onto the yellow toner image on the intermediate transfer belt 101 in a manner similar to that of the image forming section 109Y. In the image forming units 109C and 109Bk, a cyan toner image and a black toner image are formed in the same procedure as in the image forming unit 109M, and transferred onto the intermediate transfer belt 101 in order.

The four-color toner images carried on the intermediate transfer belt 101 are conveyed to the secondary transfer portion T2 and secondary transferred onto the recording material P all at once. The recording material P taken out from the recording material cassette 120 is separated sheet by sheet by a separation roller 121 and conveyed to registration rollers 122 . The registration roller 122 feeds the recording material P to the secondary transfer portion T2 in timing with the toner image on the intermediate transfer belt 101 .

A secondary transfer roller 111 contacts the intermediate transfer belt 101 on the drive roller 110 to form a secondary transfer portion T2. The recording material P on which the four-color toner images are secondarily transferred by passing through the secondary transfer portion T<b>2 is separated from the intermediate transfer belt 101 by curvature and sent to the fixing device 112 . The fixing device 112 heats and presses the recording material P at the nip portion between the fixing roller 112a and the pressure roller 112b to fix the image on the recording material P. FIG. The recording material P on which the image is fixed by the fixing device 112 is discharged outside the machine.

(Image forming section)
The image forming units 109Y, 109M, 109C, and 109Bk are configured substantially the same except that the toner colors used in the respective developing devices are yellow, magenta, cyan, and black. In the following, the process of forming a toner image for the image forming unit 109Y for yellow will be described, and redundant description of the other image forming units 109M, 109C, and 109Bk will be omitted.

The image forming unit 109Y has a charging roller 104, an exposure device 105, a developing device 106, a primary transfer roller 107Y, and a drum cleaning device 108 arranged around a photosensitive drum 103Y as an image carrier. The photosensitive drum 103Y has a photosensitive layer formed on its surface and rotates in the direction of the arrow at a predetermined process speed. The charging roller 104 charges the surface of the photosensitive drum 103Y to a uniform potential. The exposure device 105 scans a laser beam with a rotating mirror to write an electrostatic image of the image on the surface of the photosensitive drum 103Y. The developing device 106 transfers toner to the photosensitive drum 103Y to develop the electrostatic image into a toner image. A voltage is applied to the primary transfer roller 107Y to transfer the toner image carried on the photosensitive drum 103Y to the intermediate transfer belt 101. FIG. The drum cleaning device 108 rubs the photosensitive drum 103Y with a cleaning blade to collect transfer residual toner remaining on the photosensitive drum 103Y.

(intermediate transfer unit)
As shown in FIG. 1, the driving roller 110 stretches and drives an intermediate transfer belt 101, which is an example of an endless intermediate transfer belt. A frame 8 (not shown) is a frame member that rotatably supports the drive roller 110 . The intermediate transfer unit 124 integrally assembles a frame 8, an intermediate transfer belt 101, a drive roller 110, a steering roller 1, support rollers 113 and 114 as tension rollers, and primary transfer rollers 107Y, 107M, 107C, and 107Bk. . Intermediate transfer unit 124 as a replacement unit is integrally removable from the housing structure of image forming apparatus 100 .

The intermediate transfer belt 101 is stretched around a drive roller 110, a steering roller 1, support rollers 113 and 114, and primary transfer rollers 107Y, 107M, 107C and 107Bk. A secondary transfer roller 111 as a secondary transfer outer roller contacts the outer surface of the intermediate transfer belt 101 and forms a secondary transfer portion T2 (transfer nip) between itself and the driving roller 110 to transfer the toner image onto the recording material. Form. That is, the drive roller 110 and the secondary transfer roller 111 sandwich the intermediate transfer belt 101 to form the secondary transfer portion T2. Here, the driving roller 110 also functions as an inner secondary transfer roller as a facing roller facing the secondary transfer roller 111 with the intermediate transfer belt 101 interposed therebetween. The support roller 114 has a crown shape in which the outer diameter is maximum at the substantially central portion in the axial direction, and the outer diameter gradually decreases toward both ends. This is to prevent the central portion of the support roller 114 from bending due to the tension of the intermediate transfer belt 101 and wrinkling of the central portion of the intermediate transfer belt 101 . The primary transfer rollers 107Y, 107M, 107C, and 107Bk are composed of metal rollers (metal rollers), and are pressed against the inner surface of the intermediate transfer belt 101 by a pressure structure (not shown). Here, in this embodiment, the primary transfer rollers 107Y, 107M, 107C, and 107Bk are made of metal. In this case, if the intermediate transfer belt 101 is nipped between the rigid photosensitive drum and the rigid primary transfer roller, the photosensitive drum may be damaged. Therefore, the primary transfer rollers are arranged so as to be offset with respect to the rotation direction of the intermediate transfer belt so as not to face the photosensitive drums 103Y, 103M, 103C, and 103Bk. As a result, the pressure applied to the intermediate transfer belt 101 is set smaller than when the primary transfer roller is a general sponge roller. The steering roller 1 is connected to a tension spring 21 that applies a predetermined tension to the intermediate transfer belt 101, and also functions as a tension roller. The steering roller 1 is tiltable about a tilting axis that intersects the rotation axis of the steering roller. The position of the intermediate transfer belt 101 in the width direction is positioned within a predetermined range by tilting the steering roller 1 about the tilting axis.

The intermediate transfer belt 101 is composed of a resin belt having a polyimide (PI) base layer, and has a tensile elastic modulus E of 18000 N/cm 2 and a thickness of 0.08 mm. The intermediate transfer belt 101 is preferably made of highly rigid resin such as polyvinylidene fluoride (PVDF), polyamide, polyimide resin (PI), polyethylene terephthalate (PET), and polycarbonate (PC). The thickness of the intermediate transfer belt 101 is desirably in the range of 0.02 mm to 0.50 mm. If the intermediate transfer belt 101 is too thin, sufficient durability against wear cannot be obtained.

The belt cleaning device 102 rubs the intermediate transfer belt 101 with the cleaning blade 102b to collect the transfer residual toner. The cleaning blade 102 b is in contact with the winding area where the intermediate transfer belt 101 is wound around the steering roller 1 . The direction of the tip of the cleaning blade 102 b is arranged in the counter direction with respect to the moving direction V of the intermediate transfer belt 101 . The belt cleaning device 102 causes the tip of the cleaning blade 102 b to contact the outer surface of the intermediate transfer belt 101 to collect transfer residual toner or the like that has not been transferred to the recording material P and remains on the intermediate transfer belt 101 . The cleaning blade 102b is made of urethane rubber. The hardness of the urethane rubber is 75 degrees in JIS-A hardness, and the thickness of the urethane rubber is 2 mm. The contact angle of the cleaning blade 102b is 25°, and the contact pressure is 3 N/m (30 gf/cm). However, the present invention is not limited to these.

(tension line)
When the intermediate transfer belt 101 stretched and supported by a plurality of tension rollers is rotationally driven, streak-shaped uneven portions (tension lines) may occur on the intermediate transfer belt 101 along the conveying direction of the intermediate transfer belt 101 . . The tension line is formed when the tension applied to the intermediate transfer belt 101 becomes uneven and local stress is generated, or when the surface of the intermediate transfer belt is scratched by a sharp object such as a foreign object. Sometimes.

The reason why the tension becomes uneven is that when dust, carriers, etc. enter the back surface of the intermediate transfer belt, the dust, carriers, etc. adhere to the tension roller, and the pressure at the contact portion between the intermediate transfer belt 101 and the tension roller increases. This is because it becomes large locally.

If a soft material such as rubber is used for the tension roller, even if dust or carrier enters the contact portion between the tension roller and the intermediate transfer belt 101, the tension roller will be crushed, resulting in a large localized pressure. It doesn't take much. However, it is difficult to make all of the tension rollers from rubber because of the high cost.

The tension line gradually deteriorates as the rotation is repeated, and the size of the unevenness increases or the number of the unevenness increases.

When a tension line occurs, unevenness of the tension line and microscopic deterioration of the intermediate transfer belt cause non-uniform transferability, resulting in an image with vertical streaks.

Next, the groove structure 31 of the support rollers 113 and 114, which characterizes this embodiment, will be described.

2 is a perspective view of the support rollers 113 and 114, and FIG. 3 is a longitudinal partial sectional view of the support rollers 113 and 114. As shown in FIG.

As shown in FIG. 2, support rollers 113 and 114 as tension rollers in this embodiment have a groove structure as a spiral groove formed on the peripheral surface so as to revolve around the axial direction of each support roller. 31. By providing such a groove structure 31, even if a foreign substance, a carrier, or the like adheres to the back surface of the intermediate transfer belt 101 or the surfaces of the holding rollers 113 and 114, the foreign substance can enter the groove portion of the groove structure 31. be able to. As a result, it is possible to suppress the local increase in the contact pressure on the back surface of the intermediate transfer belt due to the dust and carrier adhered to the surfaces of the support rollers 113 and 114, thereby suppressing the occurrence of tension lines.

A spiral groove structure 31 is provided as a surface structure of the support rollers 113 and 114 . The spiral groove structure 31 is substantially parallel to the circumferential direction, but is slightly inclined with respect to the tangential direction of the cylindrical surfaces of the support rollers 113 and 114. The contact position moves. By making the support rollers 113 and 114 into the helical groove structure 31, the ease of processing is improved, and the outer diameter deflection and straightness of the roller surfaces can be improved. The angle between the helical groove portion of the groove structure 31 and the circumferential direction (tangential direction) of the support rollers 113 and 114 in this embodiment is greater than 0 degrees and less than 10 degrees. More preferably, it is greater than 0 degrees and 5 degrees or less.

As shown in FIG. 3, the longitudinal cross section of the groove structure 31 (the cross section of the support rollers 113, 114 parallel to the axial direction of the support rollers 113, 114) consists of a large number of grooves. The groove of the groove structure 31 is formed with a V-shaped inner groove slope 32 . That is, the groove structure 31 has a first inclined plane portion arranged on one side and a second inclined plane portion arranged on the other side and facing the first inclined plane. A flat portion W<b>1 is formed adjacent to the in-groove slope 32 between adjacent groove structures 31 . That is, in this embodiment, the ridges formed between the groove structures 31 are flat in the longitudinal cross section of the support rollers 113 and 114 . By doing so, the ridgeline portion of the groove structure 31 can be made gentler than the inclination angle of the in-groove inclined surface 32 (the inclination angle may be zero). As a result, stress concentration on the intermediate transfer belt at the ridges of the groove structure 31 can be reduced.

A method of manufacturing the groove structure 31 in this embodiment will be described.

In this embodiment, the groove structure 31 is formed by cutting using a lathe. (Cutting Step) It is preferable that the groove width L is 100 μm or more and 500 μm or less, and the groove depth D is 10 μm or more and 40 μm or less. In this embodiment, the pitch of the grooves is set so that there is no gap between adjacent grooves during cutting.

If the groove width L is less than 100 μm, dust and carriers will not enter the groove. As a result, the contact pressure on the back surface of the intermediate transfer belt locally increases due to the dust and carrier adhering to the surfaces of the support rollers 113 and 114, and tension lines may occur. The longitudinal width of the region in which the groove structure 31 is formed is at least greater than the maximum imaging region width. Both ends of the region where the groove structure 31 is formed are formed so as to be outside both ends of the maximum image forming region. In this embodiment, it is formed over substantially the entire lengthwise region of the support rollers 113 and 114 (the entire region of the large-diameter portion).

As described above, the intermediate transfer belt 101 preferably has a thickness of 0.02 mm or more and 0.50 mm or less. If the groove width L is larger than 500 μm, the bent intermediate transfer belt 101 extremely enters the groove structure 31 as shown in FIG. As a result, as shown in FIG. 6, there is a possibility that waviness will occur in the stretched portions of the support rollers 113 and 114 .

In this embodiment, the flat portion W1 is formed by polishing (mirror-finishing) the outer diameters of the support rollers 113 and 114 so as to remove the sharp tip of the groove after the groove inner slope 32 is formed. . (Polishing Step) Specifically, a polishing cloth having a predetermined roughness is brought into contact with the peripheral surfaces of the supporting rollers 113 and 114 along the longitudinal direction of the supporting rollers. By rotating the support rollers 113 and 114 in this state, the ridgeline portion of the groove structure 31 is polished (mirror-finished) along the circumferential direction of the support rollers 113 and 114 . As a result, the ridge line portion (groove tip) of the groove structure 31 is polished along the roller circumferential direction, and the height (unevenness) of the ridge line portion of the groove structure 31 can be substantially the same in the roller circumferential direction. . As a result, the unevenness (surface roughness) of the ridge line portion of the groove structure 31 in the roller circumferential direction is configured to be smaller than the surface roughness of the valley portion side of the side surface of the groove structure 31 . Alternatively, the peripheral surface of the support roller may be previously ground in the circumferential direction so as to form the flat portion W1, and the groove pitch X may be widened so that the flat portion W1 remains when the in-groove slope 32 is formed.

The width of the flat portion W1 is preferably 30 μm or more and 150 μm or less.

If the flat portion W1 is less than 30 μm, there is a possibility that the unevenness of the ridge portion in the roller circumferential direction cannot be sufficiently reduced. In addition, the contact pressure on the back surface of the intermediate transfer belt 101 locally increases at the contact portions between the support rollers 113 and 114 and the intermediate transfer belt 101, and tension lines may occur.

If the flat portion W1 is larger than 150 μm, there is a possibility that dust or carrier having a size that may cause a tension line to adhere to the flat portion W1. As a result, the contact pressure at the contact portion between the dust or carrier and the back surface of the intermediate transfer belt is locally increased, and a tension line may occur.

Moreover, the ratio of the flat portion W1 to the groove pitch X is preferably 5% or more and 30% or less. If this ratio is less than 5%, it becomes difficult to reduce the surface roughness of the ridge line. Moreover, if this ratio is more than 30%, the ratio of the flat portion will increase, and there is a possibility that the effect of suppressing the tension line will decrease.

As described above, by providing the flat portion W1 of 30 μm or more and 150 μm or less in the groove structure 31, it is possible to reduce local stress concentration on the intermediate transfer belt 101 and suppress the occurrence of tension lines. can. This makes it possible to provide an image forming apparatus capable of outputting stable image quality.

FIG. 4 is a longitudinal partial sectional view of the support rollers 113 and 114 of the second embodiment. Example 2 differs from Example 1 in the tip shape of the groove structure 31 . In Example 1, in the cross section of the groove structure 31 in the longitudinal direction, the ridgeline portion of the groove structure 31 is a flat portion, but in this example, it is formed in a curved shape (arc shape). By doing so, the inclination angle of the ridgeline portion of the groove structure 31 can be made gentler than the inclination angle of the in-groove inclined surface 32 . As a result, local stress concentration on the intermediate transfer belt 101 due to the ridges of the groove structure 31 can be reduced.

The cross section of the groove structure 31 in the longitudinal direction is composed of a large number of grooves, and the groove structures 31 that are adjacent to each other in the axial direction of the cylindrical surface are formed such that the groove inner slope 32 and the circular arc portion W2 as the curved surface portion are adjacent to each other. ing.

It is preferable that the groove width L of the groove structure 31 is 100 μm or more and 500 μm or less, and the groove depth D is 10 μm or more and 40 μm or less.

If the groove width L is less than 100 μm, dust and carriers will not enter the groove. As a result, the contact pressure on the back surface of the intermediate transfer belt locally increases due to the dust and carrier adhering to the surfaces of the support rollers 113 and 114, and tension lines may occur.

As described above, the intermediate transfer belt 101 preferably has a thickness of 0.02 mm or more and 0.50 mm or less. is extremely intrusive. As a result, as shown in FIG. 6, there is a possibility that waviness will occur in the stretched portions of the support rollers 113 and 114 .

The width of arc portion W2 is preferably 30 μm or more and 150 μm or less. If the arc portion W2 is less than 30 μm, the contact pressure on the back surface of the intermediate transfer belt 101 is locally increased at the contact portions between the support rollers 113 and 114 and the intermediate transfer belt 101, and tension lines may occur.

If the arc portion W2 is larger than 150 μm, there is a possibility that dust or carrier having a size that can generate a tension line will adhere to the arc portion W2. As a result, the contact pressure at the contact portion between the dust or carrier and the back surface of the intermediate transfer belt is locally increased, and a tension line may occur. As described above, by providing the arc portion W2 of 30 μm or more and 150 μm or less between the groove structures 31, the local stress concentration on the intermediate transfer belt 101 can be reduced, and the tension line can be reduced. The occurrence can be suppressed. Further, as in Example 1, the ratio of the arc portion W2 to the groove pitch X is preferably 5% or more and 30% or less. This makes it possible to provide an image forming apparatus capable of outputting stable image quality.

Further, the circular arc portion W2 is polished in the roller circumferential direction as in the first embodiment. That is, after the roller is machined to form the in-groove slope 32, the sharp tip of the groove crest is ground along the circumferential direction of the roller. By doing so, the surface roughness of the ridge line portion of the groove structure 31 can be made smaller than the surface roughness of the valley portion side of the groove structure 31 . In this embodiment, while the support rollers 113 and 114 are being rotated, the peripheral surfaces of the rollers are polished with a polishing cloth facing each other for a predetermined period of time.

In this embodiment, in the longitudinal cross section of the support rollers 113 and 114, the shape between the groove structures 31 is the circular arc portion 2, but the shape is not limited to this. For example, the shape between adjacent groove structures 31 may be arcs. For example, the shape between groove structures 31 may be part of an ellipse.

When the side surface of the groove structure 31 is a curved surface, a ridge portion (upwardly convex area) sandwiched between positions where the in-groove inclination angle 32 of the groove structure 31 is maximum is defined as a curved surface portion W2.

[others]
In this embodiment, in the cross section of the support roller in the longitudinal direction, the shape between the groove structures 31 is the circular arc portion W2 (curved surface portion W2) or the flat portion W1. However, the shape between the groove structures 31 is not limited to the above shape. For example, the shape between the groove structures 31 may be a shape in which both the flat portion W1 and the arc portion W2 are combined. For example, the boundary (corner) between the flat portion W1 and the in-groove slope 32 of Example 1 is polished so that the in-groove slope 32 and the flat portion W1 are connected by a smooth curve, and the flat portion W1 and the curved surface portion W2 are connected. A gentle slope may be formed on both sides. In this case, the width in the longitudinal direction, which is the sum of the flat portion W1 and the curved portion W2, should be 30 μm or more and 150 μm or less.

Also, in the longitudinal cross section of the support roller, the groove structure 31 is formed in a V shape, but the groove shape may be a U shape, a trapezoidal shape, a sine wave shape, a rectangular shape, or the like.

Reference Signs List 1 steering roller 8 frame 21 tension spring 31 groove structure 32 slope in groove 100 image forming apparatus 101 intermediate transfer belt,
102 belt cleaning device 102b cleaning blade 103Y, 103M, 103C, 103Bk photosensitive drum 104 charging roller 105 exposure device 106 developing device 107Y, 107M, 107C, 107Bk primary transfer roller 108 drum cleaning device 109Y, 109M, 109C, 109Bk image forming section 110 Drive roller 111 Secondary transfer roller 112 Fixing device 113, 114 Support roller 120 Recording material cassette 121 Separation roller 122 Registration roller 124 Intermediate transfer unit 300 Sensor unit D Groove depth L Groove width W1 Flat portion W2 Circular arc portion X Groove pitch

Claims (6)

an image carrier;
an image forming unit that forms a toner image on the image carrier;
an endless belt member to which the toner image is transferred from the image carrier;
and a tension roller that stretches the belt member,
The tension roller has a spiral groove formed on the peripheral surface of the tension roller so as to rotate around the axial direction of the tension roller,
In the axial direction of the tension roller, the width of the groove is 100 μm or more and 500 μm or less, and the depth of the groove is 10 μm or more and 40 μm or less,
The ridges formed between the grooves have flat portions polished along the circumferential direction of the tension roller, and the width of the flat portion in the axial direction of the tension roller is 30 μm or more, An image forming apparatus having a thickness of 150 μm or less. an image carrier;
an image forming unit that forms a toner image on the image carrier;
an endless belt member to which the toner image is transferred from the image carrier;
and a tension roller that stretches the belt member,
The tension roller has a spiral groove formed on the peripheral surface of the tension roller so as to rotate around the axial direction of the tension roller,
In the axial direction of the tension roller, the width of the groove is 100 μm or more and 500 μm or less, and the depth of the groove is 10 μm or more and 40 μm or less,
The ridge formed between the grooves has a curved surface portion that is ground along the circumferential direction of the tension roller, and the width of the curved surface portion is 30 μm or more in the axial direction of the tension roller. An image forming apparatus having a thickness of 150 μm or less.
In the cross section of the tension roller parallel to the axial direction of the tension roller, the ridge line has a flat portion polished along the circumferential direction of the tension roller, 2. The image forming apparatus according to claim 1, wherein the flat portion has a width of 30 [mu]m or more and 150 [mu]m or less. 3. The image forming apparatus according to claim 1, wherein the groove portion is formed by a first flat portion arranged on one side surface and a second flat portion arranged on the other side surface. 4. The image forming method according to any one of claims 1 to 3, wherein the width of the area in which the groove is formed is larger than the width of the maximum image forming area in the axial direction of the tension roller. Device. 5. The image forming apparatus according to claim 1, wherein the belt member has a thickness of 0.02 mm or more and 0.50 mm or less. A method for manufacturing an image forming apparatus having a tension roller for tensioning an endless belt member to which a toner image is transferred, the method comprising:
a cutting step of forming a spiral groove in the peripheral surface of the tension roller so as to revolve around the tension roller in the axial direction;
and a polishing step of polishing ridges formed between the grooves along the circumferential direction of the tension roller in a cross section of the tension roller parallel to the axial direction of the tension roller. A method for manufacturing an image forming apparatus characterized by:

Images