JPH10293477A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the speed fluctuation of an intermediate transfer belt by disposing one of secondary transfer means in the position always abutting on the intermediate transfer belt and providing a flywheel rotated together with one secondary transfer means. SOLUTION: A paper sheet is supplied to between a secondary transfer roll 9 and the intermediate transfer belt 2, in the contact state of the secondary transfer roll 9 with a backup roll 7c. Then, the steel flywheel 12 is concentrically disposed on the rotary shaft of the backup roll 7c. Therefore, even if the transfer roll 9 is brought into contact with/separated from the belt 2 or the paper P is supplied/ejected to a secondary transferring position, to perform a secondary transfer, the belt 2 is hardly elongated/contracted and further, the rotational speed of the belt 2 is never drastically fluctuated for an instant. Even in an image on the paper P, the occurrence of an image blur, density unevenness and a color smear caused by the elongation and contraction and speed fluctuation of the belt 2 can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine and a printer, and more particularly, to a primary transfer of a toner image formed on an image carrier such as a photosensitive drum to an intermediate transfer belt. Further, the present invention relates to an improvement in an image forming apparatus for forming an image on a transfer material by secondary-transferring the toner image from the intermediate transfer belt onto a transfer material such as paper.

[0002]

2. Description of the Related Art A conventional image forming apparatus includes, for example, a cylindrical photosensitive drum on which single-color toner images of yellow, magenta, cyan, and black are sequentially formed, and a cylindrical peripheral surface of the photosensitive drum. A primary transfer roll disposed in contact with the photosensitive drum, an endless intermediate transfer belt sandwiched between the photosensitive drum and the primary transfer roll, and a plurality of intermediate transfer belts around which the intermediate transfer belt is rotatably stretched. And a secondary transfer roll movably disposed so as to sandwich the intermediate transfer belt between one of the rolls (hereinafter, also referred to as a backup roll).

In such an image forming apparatus, a transfer voltage is applied between a primary transfer roll and a photosensitive drum to transfer a monochromatic toner image from the photosensitive drum to an intermediate transfer belt, and then to a backup roll. The toner image is formed on the transfer material by sandwiching the intermediate transfer belt with the secondary transfer roll and supplying the transfer material between the secondary transfer roll and the intermediate transfer belt. Finally, an image is formed by heating and pressing the transfer material with a fixing device. In the case of forming a color image, a multicolor toner image may be formed by transferring each single-color toner image onto an intermediate transfer belt in a superimposed manner, and then the multicolor toner image may be collectively transferred to a transfer material. . Hereinafter, a portion between the photosensitive drum and the primary transfer roll is referred to as a primary transfer position, and a portion between the backup roll and the secondary transfer roll is referred to as a secondary transfer position.

[0004] By the way, in such an apparatus that performs transfer while the photosensitive drum or the like is rotated, in general, if rotation speed unevenness occurs in a rotation driving unit that rotates the photosensitive drum or the like, the transfer is performed. In this case, the transfer position of the toner image is shifted, and image blur, uneven density, and color shift occur. Therefore, conventionally, as disclosed in JP-A-6-95563, a flywheel is disposed on the drive rotation shaft of the photosensitive drum, or as disclosed in JP-A-2-199464 and JP-A-4-2588967. As disclosed, a technique has been proposed in which a flywheel is provided on a drive roll of a photosensitive belt to suppress unevenness in the drive speed of a photosensitive drum or a photosensitive belt. Further, Japanese Patent Application Laid-Open No. 6-19270 proposes a technique in which a flywheel is disposed on a driving roll of a transfer belt that suctions and conveys a transfer material, thereby suppressing unevenness in the transfer of the transfer material. According to these techniques, when a photosensitive drum or the like is driven, the drive speed unevenness generated due to the gears of the drive means is absorbed by the inertia of the flywheel, thereby driving the photosensitive drum or the like. Speed unevenness can be suppressed, and image unevenness and color shift caused by a drive system such as a photosensitive drum can be suppressed.

[0005]

However, even if the technique for suppressing the drive speed unevenness is used, the density unevenness and the color shift in the image forming apparatus having the above-mentioned intermediate transfer belt cannot be completely suppressed. Was.

[0006] The case where density unevenness or color misregistration occurs will be specifically described. For example, in a color image forming apparatus having the above-mentioned intermediate transfer belt, a single color toner image on a photosensitive drum is superimposed on the intermediate transfer belt. At the time of alignment, it is necessary to move the secondary transfer roll to a position separated from the belt so that the toner image does not adhere. On the other hand, after a predetermined multicolor toner image is formed on the intermediate transfer belt, it is necessary to press the secondary transfer roll against the belt peripheral surface. Therefore, in the above-described image forming apparatus, after a predetermined multicolor toner image is formed on the transfer belt, the secondary transfer roll is pressed against the intermediate transfer belt to secondarily transfer the multicolor toner image to the transfer material. Further, it is necessary to separate them for the formation of the next multicolor toner image, and the driving load of the intermediate transfer belt fluctuates due to these separation and contact operations. As a result, even if the drive system tries to rotate the intermediate transfer belt at a constant drive speed, a slip occurs between the drive roll and the intermediate transfer belt when the drive load of the belt fluctuates,
Temporary rotational speed fluctuations occur in the intermediate transfer belt, and if transfer is performed on the primary transfer side during the temporary rotational speed fluctuations, the transfer position of the toner image shifts, image blurring and density unevenness occur. , A color shift occurs.

In addition, when the transfer material is inserted between the intermediate transfer belt and the outer secondary transfer roll, or when the transfer material is discharged from between the intermediate transfer belt and the outer secondary transfer roll, the outer and inner secondary transfer rolls are removed. The pressure contact state between the transfer rolls fluctuates, and the driving load of the intermediate transfer belt fluctuates temporarily. As a result, a slip occurs between the drive roll and the belt, and image blur, density unevenness, and color shift occur.

Further, in the above-described image forming apparatus, since the toner image is transferred from the intermediate transfer belt to the transfer material, the outer secondary transfer roll is generally formed by taking the transfer efficiency into consideration.
The intermediate transfer belt is pressed against the inner secondary transfer roll at a position where the intermediate transfer belt is slightly pushed inward. Therefore, the intermediate transfer belt expands / contracts according to the pressure contact / separation of the outer secondary transfer roll. As a result, in the above-described image forming apparatus,
The belt at the primary transfer position also expands / shrinks in accordance with the pressure contact / separation of the outer secondary transfer roll, and the transfer position of the toner image in the primary transfer fluctuates, causing image blurring, density unevenness, and color misregistration.

As described above, the conventional technique cannot solve the image blur, the density unevenness, and the color shift caused by the load fluctuation of the intermediate transfer belt and the elongation / shrinkage of the belt.

Accordingly, an object of the present invention is to provide an image forming apparatus capable of minimizing image blur, density unevenness, and color misregistration caused by load fluctuation of the intermediate transfer belt and elongation / shrinkage of the belt. It is in.

[0011]

That is, a first aspect of the present invention is directed to an image bearing member for carrying a toner image and a primary transfer position between the image bearing member disposed opposite to the image bearing member. , An intermediate transfer belt rotatably disposed so as to pass through the primary transfer position, and an intermediate transfer belt disposed so as to be able to approach and separate from each other via the intermediate transfer belt to form a secondary transfer position. A pair of secondary transfer means, and one or a plurality of rotators on which the intermediate transfer belt is erected and rotatably drives the belt, and transfers the toner image from the image carrier to the intermediate transfer belt at the primary transfer position. Thereafter, at a secondary transfer position, a pair of secondary transfer means sandwiches the intermediate transfer belt and the transfer material, so that an image forming apparatus that transfers a toner image onto the transfer material is premised. Always contact the transfer belt While disposed location, an image forming apparatus provided with a flywheel which rotates together with the one of the secondary transfer unit.

In such an image forming apparatus, the pair of secondary transfer means may be any as long as they can be sandwiched so as not to hinder the movement of the intermediate transfer belt and the transfer material.
It can be constituted by a secondary transfer roll made of a conductive rubber material and rotatably disposed, and a backup roll made of a conductive rubber material and rotatably disposed.
Further, in the present invention, one of the secondary transfer units may be disposed at a position where it is always in contact with the intermediate transfer belt. At this time, the intermediate transfer belt is stretched over only a plurality of rotating bodies. It may be disposed rotatably by itself, or may be rotatably disposed by being stretched around the one secondary transfer unit together with one or more rotating bodies.

The flywheel rotates together with the one secondary transfer means, and exerts a certain inertia force when stopping the rotation.

In the first aspect of the present invention, one of the secondary transfer units is disposed at a position where the secondary transfer unit is always in contact with the intermediate transfer belt, and a flywheel that rotates together with the one of the secondary transfer units is provided. Therefore, the speed fluctuation of the intermediate transfer belt that occurs when the intermediate transfer belt is held between the pair of secondary transfer units can be suppressed.

According to a second aspect of the present invention, there is provided an image carrier for carrying a toner image, a primary transfer means disposed opposite to the image carrier and forming a primary transfer position between the image carrier and An intermediate transfer belt rotatably disposed so as to pass through the primary transfer position, and a pair of secondary transfer means that are disposed so as to be able to approach and separate from each other via the intermediate transfer belt and form a secondary transfer position, The intermediate transfer belt is erected and has one or a plurality of rotating members for rotating the belt. After the toner image is transferred from the image carrier to the intermediate transfer belt at the primary transfer position, a pair of rotators is provided at the secondary transfer position. The secondary transfer means presupposes an image forming apparatus that transfers the toner image onto the transfer material by sandwiching the intermediate transfer belt and the transfer material, from the primary transfer position to the secondary transfer position in the rotation direction of the intermediate transfer belt. In between Push-up means is provided which is pressed against the intermediate transfer belt and pushes up and deforms the intermediate transfer belt, and furthermore, the push-up means, when the intermediate transfer belt is sandwiched by a pair of secondary transfer means, This is an image forming apparatus that is movably disposed so as to increase and decrease the push-up amount.

The push-up means is pressed against the intermediate transfer belt from the primary transfer position to the secondary transfer position in the rotation direction of the intermediate transfer belt to push up and deform the intermediate transfer belt. When the intermediate transfer belt is sandwiched by the secondary transfer means, it is sufficient that the intermediate transfer belt is movably disposed so as to increase or decrease the push-up amount of the intermediate transfer belt.
The push-up roll is disposed in pressure contact with the intermediate transfer belt and rotates according to the movement of the intermediate transfer belt, and an elastic member such as a spring for pushing up the push-up roll to press against the intermediate transfer belt. .

According to the second invention of the present application, a push-up means which is pressed against the intermediate transfer belt between the primary transfer position and the secondary transfer position in the rotation direction of the intermediate transfer belt and pushes up and deforms the intermediate transfer belt. The lifting means is disposed so as to be movable so as to increase or decrease the lifting amount of the intermediate transfer belt when the intermediate transfer belt is held between the pair of secondary transfer members. The extension / shrinkage of the intermediate transfer belt when the intermediate transfer belt is held by the secondary transfer means is suppressed.

Further, in the second invention of the present application, the push-up means is provided with a push-up force from a direction within ± 10 ° from a bisector of an angle formed by a belt moving direction upstream and downstream of the push-up means. It is preferable that the transfer belt be pressed against the transfer belt. This makes it possible to reduce a moving load due to friction or the like when the lifting unit is moved, as compared to a case where the lifting unit is pressed obliquely to the moving direction of the intermediate transfer belt.

Further, in the second invention of the present application, it is desirable that the contact amount between the push-up means and the intermediate transfer belt is set to a necessary minimum. For example, the contact portion with the intermediate transfer belt is located at the center angle of the push-up roll. It is desirable to arrange so that it is not more than 20 degrees. Thereby, the pushing-up force of the elastic member is 45% or less of the belt tension.
It can be set to 8 kgf or less, and it is possible to easily attach and assemble using a spring or the like generally used as an elastic member.

Finally, in the second aspect of the present invention, it is preferable that the distance between the rotator driving the intermediate transfer belt and the primary transfer position is short. In particular, it is desirable that the distance from the rotator to the primary transfer position in the rotational movement direction of the intermediate transfer belt is set to be less than half the distance from the rotator to the secondary transfer position. As a result, the amount of elongation / shrinkage of the belt at the primary transfer position can be suppressed to at most half or less of the amount of elongation / shrinkage of the belt at the secondary transfer position.
The effect on image quality due to shrinkage can be effectively suppressed.

[0021]

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

Embodiment 1 FIG. 1 shows an image forming apparatus according to this embodiment. The image forming apparatus sequentially forms toner images of each color on the photosensitive drum 1 and then transfers the single-color toner images onto the intermediate transfer belt 2 in a superimposed manner to form a multicolor toner image. By transferring and fixing the color toner image on the paper P, the paper P
A full-color image is formed on the image.

In FIG. 1, reference numeral 1 denotes a photosensitive drum formed in a cylindrical shape and rotatably disposed, 3 denotes a charging corotron to which a charging voltage is applied between the photosensitive drum 1, and 4 denotes a charging corotron. Laser exposure means 5 for exposing the subsequent photosensitive drum 1 in accordance with image information includes four developing units 5k, 5y, 5m, 5c for supplying yellow, magenta, cyan, and black toners to the photosensitive drum 1. Is a rotary developing means provided. In such an image forming apparatus, the photosensitive drum 1 is charged by the charging corotron 3 in a state where the rotary type developing unit 5 is rotated so that a developing unit (for example, 5 k) of a predetermined color faces the photosensitive drum 1. The laser exposure means 4 is charged to a uniform potential.
Exposing the photosensitive drum 1 to form an electrostatic latent image on the photosensitive drum 1, and then developing the electrostatic latent image with toner of the developing unit (for example, 5 k) to obtain a predetermined color A monochromatic toner image (black in the above example) is formed.

In FIG. 1, reference numeral 6 denotes a photosensitive drum 1
The primary transfer roll 2, which is disposed to face the photosensitive drum 1 and to which a transfer voltage is applied between the photosensitive drum 1 and the photosensitive drum 1,
And an intermediate transfer belt 7 rotatably disposed so as to pass between the transfer belt 6 and the transfer corotron 6.
Is stretched to rotatably support the intermediate transfer belt 2 3
One support roll, 8 is a drive motor for rotationally driving one support roll 7a, 9 is movably disposed to face the other one support roll 7c, and a transfer voltage is applied to the other support roll 7c. Secondary transfer roll applied. Reference numeral 10 denotes a registration roll pair for supplying the paper P between the rolls 7c and 9;
A fixing roll pair 11 heats and presses the paper P. In the following, the support roll 7a directly rotated and driven by the drive motor 8 is also referred to as a drive roll, the support roll 7c in which the secondary transfer roll 9 is arranged to face is also referred to as a backup roll, and further, another support roll is provided. Roll 7b
Is also called an idler roll. Further, the backup roll 7c and the secondary transfer roll 9 are formed of a conductive elastic material, and when pressed against each other, a nip having a predetermined width is formed. In such an image forming apparatus, first, while the intermediate transfer belt 2 is rotationally driven by the drive motor 8, the single-color image formed on the photosensitive drum 1 between the photosensitive drum 1 and the primary transfer roll 6 is formed. The toner is transferred to the intermediate transfer belt 2, and this transfer is repeated as necessary to superimpose a plurality of single-color toner images on the intermediate transfer belt 2 to form a multicolor toner image. Next, in a state where the secondary transfer roll 9 is in contact with the backup roll 7c, the paper P is supplied from the registration roll pair 10 between the secondary transfer roll 9 and the intermediate transfer belt 2, so that the paper P is multiplied. A color (single color) toner image is formed. Finally, the sheet P is transferred to the fixing roll pair 1
By heating and pressing in step 1, a (color) image is formed on the paper P. Hereinafter, a portion between the photosensitive drum 1 and the primary transfer roll 6 is called a primary transfer position, and a portion between the secondary transfer roll 9 and the backup roll 7c is called a secondary transfer position.

In such an image forming apparatus, when the secondary transfer roll 9 is brought into contact with / separated from the backup roll 7c, or when the paper P is supplied / supplied between the secondary transfer roll 9 and the intermediate transfer belt 2. At the time of discharging, the rotational driving load of the intermediate transfer belt 2 fluctuates temporarily, and the rotational speed fluctuates, or the belt 2 expands / shrinks due to the pressure contact of the secondary transfer roll 9. As a result, the moving speed of the belt 2 at the primary transfer position temporarily fluctuates, and the belt 2 expands / contracts, so that the transfer position of the toner image is shifted before and after these, and image blurring and density Unevenness, color shift, etc. will occur.

Therefore, in this embodiment, as shown in FIG. 2, a steel flywheel 12 is disposed concentrically on the rotation axis of the backup roll 7c.

In this embodiment, as shown in FIG. 3, a push-up roll 13a is rotatably brought into contact with the inside of the intermediate transfer belt 2 between the idler roll 7b and the backup roll 7c. Is
A slide rail extending in a direction in which the intermediate transfer belt 2 is pressed against the intermediate transfer belt 2 by a push-up force from a direction within ± 10 ° from a bisector of an angle formed by the belt moving directions upstream and downstream of the push-up roll 13a. The lifting roll 13a was supported by 13b. Further, the lifting roll 13a was pressed against the intermediate transfer belt 2 with a force of 0.6 N / mm by a spring 13c arranged in parallel with the slide rail 13b. Further, as shown in FIG. 4, the contact portion between the push-up roll 13a and the intermediate transfer belt 2 was set so that the central angle θ of the push-up roll 13a was 17.5 °. As a result, a moving load due to friction or the like when the lifting roll 13a moves along the slide rail 13b can be minimized, and the lifting roll 13a is moved to the intermediate transfer belt 2
A common spring 13c was used as the spring 13c, and it could be easily mounted and assembled. Incidentally, in such a setting, the friction load when moving the push-up roll 13a is 5% or less of the push-up force.

Furthermore, in this embodiment, in the rotating direction of the intermediate transfer belt 2, the length of the intermediate transfer belt 2 between the driving roll 7a to the primary transfer position and l _1, from the separated position of the drive roll 7a the intermediate transfer length of the belt 2 until the secondary transfer position in the case of the l _2, sets the primary transfer position as l ₁ / l ₂ is 0.14.

An experiment was conducted in which an image was continuously formed on a plurality of sheets P using such an image forming apparatus. As a result, even if the secondary transfer roll 9 is moved toward or away from the intermediate transfer belt 2 to perform the secondary transfer, or if the paper P is supplied / discharged to the secondary transfer position, the intermediate transfer belt 2 is almost stretched. /
There was no shrinkage, and the rotational speed of the intermediate transfer belt 2 also did not fluctuate largely once. Also, in the images of the second and subsequent sheets of paper P, image blur, density unevenness, and color misregistration caused by expansion and contraction and speed fluctuation of the intermediate transfer belt 2 did not occur. Incidentally, the elongation of the intermediate transfer belt 2 was suppressed to 5 μm or less.

By the way, in such an image forming apparatus, shown in the case of changing the distance l ₁ from the drive roll 7a to the primary transfer position 40 to 80 mm, the image shift amount in the first transfer in Table 1. As shown in the table, l ₁ / l ₂
Is less than 1/2, it can be seen that the amount of image shift due to the expansion and contraction of the belt can be suppressed to the allowable specification of 2.5 μm or less. Incidentally, the intermediate transfer belt 2 in the present embodiment has a width of 364 mm and a thickness of 0.3 mm.
08 mm, cross-sectional area 29.12 mm ² , perimeter 527.5 m
m, Young's modulus is 660 kgf / mm ² .

[0031]

[Table 1]

In such an image forming apparatus,
When the winding angle θ of the intermediate transfer belt 2 with respect to the push-up roll 13a is set to be equal to or less than 20 degrees, the push-up force by the spring 13c is reduced to 45% of the belt 2 tension.
It can be set to 1.8 kgf or less, which is the following. In such a case, similarly to the present embodiment, the push-up roll 13
It is possible to use a general spring 13c for pressing a to the intermediate transfer belt 2 and easily attach and assemble it. Below, the lifting force is 1.3kg
f, Table 2 shows an example of the relationship between the moving load of the push-up roll 13a due to the sliding friction of the slide rail 13b and the amount of elongation of the belt 2 under the condition that the spring constant of the spring 13c is 0.6 N / mm.

[0033]

[Table 2]

[0034]

As described in detail above, according to the first aspect of the present invention, one of the secondary transfer means is disposed at a position where it is always in contact with the intermediate transfer belt, and the other is provided together with the one of the secondary transfer means. By providing a rotating flywheel, it is possible to suppress the speed fluctuation of the intermediate transfer belt that occurs when the intermediate transfer belt is sandwiched between the pair of secondary transfer units,
Image blur, density unevenness, and color misregistration due to load fluctuation of the intermediate transfer belt can be suppressed as much as possible.

Further, in the second invention of the present application, a push-up means which is pressed against the intermediate transfer belt in a rotational direction of the intermediate transfer belt from the primary transfer position to the secondary transfer position, and pushes up and deforms the intermediate transfer belt. The lifting means is movably disposed such that when the intermediate transfer belt is sandwiched between the pair of secondary transfer members, the lifting means is movable so as to increase or decrease the lifting amount of the intermediate transfer belt. Since the elongation / shrinkage of the intermediate transfer belt when the intermediate transfer belt is nipped by the next transfer means is suppressed, image blur, density unevenness, and color misregistration due to the elongation / shrinkage of the intermediate transfer belt are suppressed as much as possible. can do.

[Brief description of the drawings]

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

FIG. 2 is a side view of a main part of the image forming apparatus of FIG.

FIG. 3 is a configuration diagram of a lifting means in the apparatus of FIG. 1;

FIG. 4 is a diagram showing a contact state between a push-up roll and an intermediate transfer belt.

FIG. 5 is an explanatory diagram of an arrangement of a peripheral portion of an intermediate transfer belt in the apparatus of FIG. 1;

[Explanation of symbols]

1: photosensitive drum (image carrier), 6: primary transfer roll,
2: intermediate transfer belt, 9: secondary transfer roll, 7c: backup roll (secondary transfer means), P: paper (transfer material), 12: flywheel, 13a: push-up roll,
θ: central angle, 13c: spring (elastic member)

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Norio Hokari 2274 Hongo, Ebina City, Kanagawa Prefecture, within Fuji Xerox Co., Ltd. (72) Inventor Junichiro Samejima 2274 Hongo, Ebina City, Kanagawa Prefecture, within Fuji Xerox Co., Ltd.

Claims (5)

[Claims] An image carrier that carries a toner image; a primary transfer unit that is arranged to face the image carrier to form a primary transfer position between the image carrier and the image carrier; and passes through the primary transfer position. An intermediate transfer belt rotatably disposed as described above, a pair of secondary transfer means disposed so as to be able to approach and separate from each other via the intermediate transfer belt and forming a secondary transfer position, and the intermediate transfer belt And one or more rotators for rotating the belt, and after transferring the toner image from the image carrier to the intermediate transfer belt at the primary transfer position, a pair of secondary transfer means is provided at the secondary transfer position. In an image forming apparatus that transfers a toner image onto a transfer material by sandwiching an intermediate transfer belt and a transfer material, one of the secondary transfer units is disposed at a position that always contacts the intermediate transfer belt. Secondary transfer means An image forming apparatus characterized in that a flywheel that rotates. 2. An image carrier that carries a toner image, a primary transfer unit that is disposed to face the image carrier and forms a primary transfer position between the image carrier, and passes through the primary transfer position. An intermediate transfer belt rotatably disposed as described above, a pair of secondary transfer means disposed so as to be able to approach and separate from each other via the intermediate transfer belt and forming a secondary transfer position, and the intermediate transfer belt And one or more rotators for rotating the belt, and after transferring the toner image from the image carrier to the intermediate transfer belt at the primary transfer position, a pair of secondary transfer means is provided at the secondary transfer position. An image forming apparatus that transfers a toner image onto a transfer material by sandwiching the intermediate transfer belt and a transfer material, wherein the intermediate transfer belt is moved from a primary transfer position to a secondary transfer position in a rotation direction of the intermediate transfer belt. A push-up means that is pressed and deforms by pushing up the intermediate transfer belt is provided, and the push-up means increases or decreases the push-up amount of the intermediate transfer belt when the intermediate transfer belt is sandwiched by a pair of secondary transfer means. The image forming apparatus is provided so as to be movable as described above. 3. The push-up means is pressed against the intermediate transfer belt by a push-up force from a direction within ± 10 ° from a bisector of an angle formed by a belt moving direction upstream and downstream of the push-up means. The image forming apparatus according to claim 2, wherein: 4. The push-up means has a push-up roll formed in a cylindrical shape and rotatably disposed in pressure contact with the intermediate transfer belt, and the push-up roll has a contact portion with the intermediate transfer belt. Is 2 at the center angle of the push-up roll.
The image forming apparatus according to claim 2, wherein the image forming apparatus is disposed so as to be at 0 ° or less. 5. The distance from the rotating body that rotationally drives the intermediate transfer belt to the primary transfer position in the rotational movement direction of the intermediate transfer belt is less than half the distance from the rotating body to the secondary transfer position. 3. The method according to claim 2, wherein
The image forming apparatus as described in the above.