JP2001194924A - Image forming device - Google Patents

Abstract

(57) [PROBLEMS] To prevent occurrence of tooth contact between a photosensitive drum gear and a transfer drum gear when a transfer drum is brought into pressure contact with a photosensitive drum. SOLUTION: Photosensitive drum gear 40 and transfer drum gear 4
The tooth tips 40a, 41a of the photosensitive drum gear 40 and the transfer drum gear 41 are formed by applying pressure when the transfer drum is pressed against the photosensitive drum by forming the first tooth tips 40a, 41a in an arc shape. Move relatively to a normal meshing state, and the occurrence of tooth contact between the photosensitive drum gear 40 and the transfer drum gear 41 can be prevented.

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 or a printer for forming an image by using an electrophotographic system, and more particularly, to a transfer material which can contact and separate from an image carrier. The present invention relates to an image forming apparatus provided with a transfer material carrier that carries and conveys.

[0002]

2. Description of the Related Art As an image forming apparatus for forming a full-color image, for example, as shown in FIG. 5, a drum-type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) as an image carrier is used.
A toner image of each color is sequentially formed thereon, and the toner image of each color is superimposedly transferred onto a transfer material (paper) adsorbed on a transfer drum as a rotating transfer material carrier to form a full car image. An image forming apparatus has been proposed.

In this image forming apparatus (in the figure, an electrophotographic color copying machine), when a copy button (not shown) is pressed, an original G placed on an original platen glass 1 is exposed and scanned by an exposure lamp 2. The reflected light image from the original G is converted into a full color sensor (CCD) by the imaging lens 3.
4 to obtain a color separation image signal. The full-color sensor 4 separates the document G into a number of pixels, and generates an image signal that has been photoelectrically converted according to the density of each pixel. The exposure device 5 converts the input image signal into an optical signal at a laser output unit (not shown), and reflects the converted optical signal, a laser beam L, at a polygon mirror 5a rotating at high speed. Through the f / θ lens 5b and the mirror 5c, the light is projected onto the photosensitive drum 6 which is rotationally driven in the direction of arrow a by the driving means (not shown) for each of the separated colors. At this time, the photosensitive drum 6 is uniformly charged to a predetermined potential of negative polarity by the corona charger 7, and sequentially forms an electrostatic latent image of each color on the photosensitive drum 6 by projecting the laser beam L. .

[0004] Each developing unit 8 stores toner of each color of yellow, cyan, magenta and black.
The developing device for the first color (for example, yellow developing device 8y) among y, 8c, 8m, and 8bk is brought close to the photosensitive drum 6, and the electrostatic latent image on the photosensitive drum 6 is negatively charged. The image is reversely developed with toner, and is visualized as a toner image (for example, a yellow toner image). Each developing unit 8y, 8
c, 8m, and 8bk are selectively approached to the photosensitive drum 6 in accordance with the respective separation colors.

Then, in synchronism with the formation of the toner image on the photosensitive drum 6, each of the cassettes 9a, 9b, 9c, 9d
The transfer material P of a predetermined size selected from the above is transported to the transfer drum 11 through the transport path 10. The transfer material P can also be supplied to the transfer drum 11 from the manual feed tray 12. The transfer drum 11 is brought into contact with the photosensitive drum 6 at the transfer section, and is rotated by the rotation of the photosensitive drum 6.

Around the transfer drum 11, a suction roller 13 and a suction brush 14 for electrostatically attracting the transfer material P to the peripheral surface of the transfer drum 11, and a transfer brush 1 as a transfer unit
5. Separation charger 16 for separating transfer material P from transfer drum 11 surface, separation claw 17, separation push-up roller 18, outer eliminator 19 and inner eliminator 20 for eliminating charge on transfer drum 11 surface, transfer drum 11 surface Cleaning (cleaning)
And a transfer drum cleaning roller 22 for performing the cleaning. A transfer sheet (not shown) on which the transfer material P is electrostatically attracted is provided on the peripheral surface of the transfer drum 11. As the transfer sheet, a polycarbonate resin film is used.

Then, at a predetermined timing, the suction brush 1
4, the transfer material P is urged by the suction roller 13 so as to be in contact with the surface of the transfer drum 11 (transfer sheet), and the transfer material P is electrostatically suctioned on the transfer drum 11 (transfer sheet) surface. Let it. The transfer material P electrostatically attracted to the surface of the transfer drum 11 is moved in the direction of the arrow of the transfer drum 11 (counterclockwise).
Position (transfer section) facing the photosensitive drum 6 by the rotation of
And the first color toner image (yellow toner image) on the photosensitive drum 6 is transferred to the transfer material P by the transfer brush 15 to which the transfer bias is applied. After this transfer, the transfer residual toner remaining on the photosensitive drum 6 is removed by the photosensitive drum cleaning device 23, and is used for forming a toner image of the next color.

In the same manner, each of the developing units 8c containing cyan, magenta and black toners,
The cyan toner image, the magenta toner image, and the black toner image formed and carried on the photosensitive drum 6 by 8 m and 8 bk, respectively, are sequentially formed on the toner image (yellow toner image) of the transfer material P absorbed and carried on the surface of the transfer drum 11. Multiple transfer is performed to form a full-color image. Then, the transfer material P is separated from the surface of the transfer drum 11 by the action of the separation charger 16, the action of the separation claw 17, and the action of the separation pushing roller 18. The transfer material P separated from the surface of the transfer drum 11 is transferred to the fixing roller 24a of the fixing device 24 and the pressure roller 2a.
After a full-color image is heat-fixed on the surface by heating and pressing between 4b, the sheet is discharged onto the tray 25, and a series of image forming operations is completed. After the image forming operation is completed, scattered toner and the like adhering to the surface of the transfer drum 11 (transfer sheet) are discharged by the outer static eliminator 19 and the inner static eliminator 20, and then transferred to the transfer drum pressing brush 21. Transfer drum 11
The transfer drum is brought into contact with the inside of the (transfer sheet) and is cleaned and removed by the transfer drum cleaner 22.

The transfer drum 11 is separated from the photosensitive drum 6 by a predetermined distance except during the image forming operation, as shown in FIG.

As shown in FIG. 6, the transfer drum 11 is rotatably supported by a transfer drum supporting side plate 30, and the transfer drum supporting side plate 30 is supported so as to be swingable about a swing shaft 31. . Therefore, the transfer drum 11 is
1 and keeps the separated state by its own weight. When the image forming operation is started, the photosensitive drum 6 is driven to rotate, and then the pressing cam 32 as a contacting / separating means is driven by a drive (not shown). By means (stepping motor or the like), the rotation is made in the direction of the arrow (clockwise) around the rotation shaft 33 as the rotation center.

As the pressure cam 32 rotates, a cam follower support 36 urged by a pressure spring 35 disposed on a shaft 34 of the transfer drum support side plate 30 and a cam follower rotatably supported by the cam follower support 36. The pressing force is transmitted via the transfer roller 37 to oscillate and press the transfer drum 11 in the pressing direction. Then, as shown in FIGS. 7 and 8, after the transfer drum 11 comes into contact with the photosensitive drum 6, the pressing cam 33 is stopped at a predetermined angle of rotation. By displacing the pressurizing spring 35 further than at the time of contact, a stable pressing force is ensured. FIG. 8 is a schematic sectional view in the longitudinal direction of FIG.

As shown in FIG. 8, the photosensitive drum 6 has a front flange 6a, a rear flange 6b, and a cylindrical drum cylinder 6c supported therebetween. Is fixed to the photosensitive drum gear 6d for transmitting the light. The transfer drum 11 has a front flange 11a, a rear flange 11b, and a cylindrical transfer sheet 11c supported between the front flange 11a and the rear flange 11b. Rotational drive from the photosensitive drum 6 is transmitted to the front flange 11a. The transfer drum gear 11d is fixed.

Further, the front flange 11a and the rear flange 11
b, spacer rubber 11 which is a cylindrical rubber ring
When the transfer drum 11 is pressed against the photosensitive drum 6, the spacer rubber 11 e is brought into contact with the front flange 6 a and the rear flange 6 b of the photosensitive drum 6 to perform positioning. Thereby, the surface of the drum cylinder 6c of the photosensitive drum 6 and the transfer sheet 1 of the transfer drum 11 are transferred.
The gap between the surfaces 1c is maintained at a predetermined value, and the surfaces are pressed against each other. At the same time, the backlash between the photosensitive drum gear 6d and the transfer drum gear 11d is simultaneously absorbed.

The photosensitive drum 6 is driven to rotate by driving a photosensitive drum shaft 6e, which is a rotating shaft thereof, by driving means (not shown). This driving means (not shown) is connected to the right side of the photosensitive drum shaft 6e in FIG. 8, and drives the photosensitive drum shaft 6e and the photosensitive drum 6 to rotate at a constant speed of, for example, 15 rpm. Then, the photosensitive drum 6 is rotated at 15 rpm, and the transfer drum 11 is pressed against the photosensitive drum 6 during image formation, and the photosensitive drum gear 6d and the transfer drum gear 11d mesh with each other.
It is driven and rotated at rpm.

[0015]

In the prior art described above, when the transfer drum 11 comes into pressure contact with the photosensitive drum 6 during image formation, as shown in FIG. 9, the photosensitive drum gear 6d and the transfer drum gear 11d are moved. In some cases, a state different from the normal state (see FIG. 10) in which the tooth tips come into contact with each other occurs, and the rotation may continue with an abnormality in which the normal engagement between the photosensitive drum gear 6d and the transfer drum gear 11d cannot be obtained.

The photosensitive drum gear 6d and the transfer drum gear 11
d is generally 0.5 to 1.2 module, pressure angle 20 °
Alternatively, a 14.5 ° spur gear is used, and the gear tip portion has a flat portion. For this reason, the transfer drum 11
Drum gear 11 when is pressed against the photosensitive drum 6
d and various conditions when the tooth tips of the photosensitive drum gear 6d contact each other (for example, the pressing force of the transfer drum 11, the pressing speed,
The rotational speed of the photosensitive drum 6, the rotational load of the transfer drum 11,
Due to minute differences in the surface properties of the tooth tip), there is a certain probability of contact with the tooth tip.

When such a state in which the transfer drum gear 11d and the photosensitive drum gear 6d come into contact with each other is generated, FIG.
As shown in (1), the photosensitive drum 6 and the transfer drum 11 cannot keep a constant gap in the longitudinal direction, and the contact side of the photosensitive drum gear 6d and the transfer drum gear 11d with the tooth tip is widened. When this state occurs, an abnormality occurs in the transfer step of the image forming process.

That is, since the gap (gap) between the photosensitive drum 6 and the transfer drum 11 on the side of the photosensitive drum gear 6d and the transfer drum gear 11d is wide, the transfer becomes abnormal. In particular, poor transfer or transfer on the side of the photosensitive drum gear 6d and the transfer drum gear 11d. An image defect occurs due to omission or the like. Further, the rotation of the photosensitive drum gear 6d and the transfer drum gear 11d in the state of contact with the tooth tip (abnormal state) continues from the time when the transfer drum 11 is pressed against the photosensitive drum 6 until the start of laser exposure on the photosensitive drum 6, If the gears are engaged normally before the transfer starts, the first color image (yellow toner image)
An image defect shifted from the image of the fourth color occurs.

Similarly, depending on the timing at which the gears of the photosensitive drum gear 6d and the transfer drum gear 11d are brought into a normal gear mesh from an abnormal state of contact with the tooth tip, the images of the first and second colors and the third and fourth colors are shifted or the images of the first to third colors are changed. Is shifted from the image of the fourth color, and an image defect occurs.

Therefore, according to the present invention, when the transfer drum is pressed against the photosensitive drum, the contact between the transfer drum gear and the photosensitive drum gear does not occur, thereby preventing the occurrence of transfer failure and the like. It is an object to provide an image forming apparatus capable of forming an image.

[0021]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a rotatable image carrier on which a developer image is formed, and a rotatable transfer material which carries and conveys a transfer material on its surface. A carrier, a contact / separation unit for pressing and contacting the transfer material carrier with the image carrier, and separating the transfer material carrier from the image carrier at the transfer unit by the contact / separation unit In a contact state, the image forming apparatus further includes a gear transmission unit that transmits a rotational drive of the image carrier to the transfer material carrier to rotate the transfer material carrier in a driven manner. At least disposed on one side in the longitudinal direction of the transfer material carrier, at least, an image carrier gear portion that is rotated together with the rotation drive of the image carrier, and disposed so as to mesh with the image carrier gear portion, The image carrier gear meshes with the image carrier gear to rotate the image carrier. And a transfer material carrier gear portion that transmits driving gears to the transfer material carrier, such that the transfer material carrier gear portion is relatively movable when pressed against the image carrier gear portion. Further, each tooth tip of the image carrier gear portion and the transfer material carrier gear portion is formed in a non-planar shape.

Further, the entirety of each tooth tip of the image carrier gear portion and the transfer material carrier gear portion is formed in an arc shape.

[0023] Further, an acute angle slope is formed on both sides of each tooth tip of the image carrier gear portion and the transfer material carrier gear portion,
The tip of the slope is formed in an arc shape.

Further, the opposite side of the tooth tip of the image carrier gear portion and the transfer material carrier gear portion from the side where the rotational force is transmitted is formed as an acute-angled inclined surface, and the leading end side of the inclined surface is formed. It is characterized by being formed in an arc shape.

Each tooth tip of the image carrier gear portion and the transfer material carrier gear portion is formed at the tip of a tooth tip surface of a standard tooth profile.

[0026] Further, on the transfer material carried on the surface of the transfer material carrier, developer images of different colors sequentially formed on the image carrier in the transfer section are superimposed and transferred to form a color image. It is characterized by being formed.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. <Embodiment 1> The image forming apparatus according to the present embodiment shown in FIG. 1 is the same as the above-described conventional image forming apparatus except for the shapes of the teeth of the photosensitive drum gear and the transfer drum gear. In the following, only the tooth shapes of the photosensitive drum gear and the transfer drum gear will be described. Note that members other than the photosensitive drum gear and the transfer drum gear of the present embodiment will be described with the same reference numerals as in the above-described conventional image forming apparatus.

The above-mentioned conventional photosensitive drum gear 6d and transfer drum gear 11d generally have a module of 0.5 to
1.2, a spur gear having a pressure angle of 20 ° or 14.5 ° was used, and the gear tip had a flat portion (FIG. 9).
reference). For this reason, various conditions (for example, the pressing force of the transfer drum 11, pressurization, and the like) when the transfer drum gear 11 d and the respective tooth tips of the photosensitive drum gear 6 d abut when the transfer drum 11 abuts on the photosensitive drum 6 abut. Due to minute differences in the speed, the rotation speed of the photosensitive drum 6, the rotational load of the transfer drum 11, and the surface properties of the tooth tip, the contact between the transfer drum gear 11d and the photosensitive drum gear 6d may occur.

Therefore, in the image forming apparatus of the present embodiment, the photosensitive drum gear 40 of the photosensitive drum 6 and the transfer drum gear 41 of the transfer drum 11 shown in FIG. With a spur gear having an angle of 14.5 °, arc-shaped tooth tips 40a and 41a were formed at the tips. The radius R of the tooth tips 40a and 41a is 0.3 mm, and is formed in an arc shape outside the outer diameter D of the standard gear obtained by adding the module m to the pitch circle diameter Dp.

As described above, in the present embodiment, the tip portions 40a, 41a of the photosensitive drum gear 40 and the transfer drum gear 41 are provided.
Are formed in an arc shape, and as described in the above-described conventional technique, when the transfer drum 11 is pressed against the photosensitive drum 6, the photosensitive drum gear 40 and the transfer drum gear 41 are pressed.
Even when the tooth tips 40a, 41a of the transfer drum 11 abut against each other, there is no flat portion at the tip of the tooth tip, so that the pressing force when the transfer drum 11 is pressed against the photosensitive drum 6, the photosensitive drum gear 40 and the transfer drum gear 41 The tooth tips 40a and 41a move relatively to each other, and a normal meshing state is established.

Further, since the tip portions 40a and 41b of the photosensitive drum gear 40 and the transfer drum gear 41 are formed outside the outer diameter D of the standard gear, the photosensitive drum 6 and the transfer drum 1
The meshing ratio of 1 does not change from the above-described conventional example, and the rotation of the photosensitive drum 6 is smoothly transmitted to the transfer drum 11 by a gear.

Accordingly, it is possible to prevent the occurrence of transfer failure, and in the case of the above-described color image forming apparatus, it is possible to prevent color shift of the transferred image and obtain a good image.

<Embodiment 2> The image forming apparatus according to the present embodiment is also the same as the above-described conventional image forming apparatus except for the shape of the teeth of the photosensitive drum gear and the transfer drum gear. In the following, only the tooth shapes of the photosensitive drum gear and the transfer drum gear will be described.

As shown in FIG. 3, the photosensitive drum gear 40 and the transfer drum gear 41 according to the present embodiment are a spur gear having a module m = 0.6 and a pressure angle of 14.5 °, and having both ends at 45 ° at both ends. A slope was formed, and the tip portions formed arc-shaped tooth tips 40b and 41b. Tooth tips 40b, 41b
The radius R of the arc at the tip is 0.2 mm and is formed outside the outer diameter D of the standard gear obtained by adding the module m to the pitch circle diameter Dp.

As described above, in the present embodiment, the tip portions 40b, 41b of the photosensitive drum gear 40 and the transfer drum gear 41 are provided.
By forming a 45 ° slope on both sides of the tip and forming the tip thereof in an arc shape, as described in the above-described related art,
When the transfer drum 11 is pressed against the photosensitive drum 6, the tip 40 b of the photosensitive drum gear 40 and the tooth tip 40 b of the transfer drum gear 41.
Even when the transfer drums 1b abut against each other, there is no flat portion at the tip of the tooth tip, and therefore the tooth tips 40b of the photosensitive drum gear 40 and the transfer drum gear 41 are pressed by the pressing force when the transfer drum 11 is pressed against the photosensitive drum 6. 41b move relatively to each other to enter a normal meshing state.

Further, since the tip portions 40b and 41b of the photosensitive drum gear 40 and the transfer drum gear 41 are formed outside the outer diameter D of the standard gear, the photosensitive drum 6 and the transfer drum 1
The meshing ratio of 1 does not change from the above-described conventional example, and the rotation of the photosensitive drum 6 is smoothly transmitted to the transfer drum 11 by a gear.

Therefore, the occurrence of transfer failure can be prevented, and in the case of the above-described color image forming apparatus, the color shift of the transferred image can be prevented, and a good image can be obtained.

<Embodiment 3> An image forming apparatus according to the present embodiment is also the same as the above-described conventional image forming apparatus except for the shapes of the teeth of the photosensitive drum gear and the transfer drum gear. In the following, only the tooth shapes of the photosensitive drum gear and the transfer drum gear will be described.

The photosensitive drum gear 40 in the present embodiment
4, the transfer drum gear 41 is a spur gear having a module m = 0.6 and a pressure angle of 14.5 ° as shown in FIG. The tip portions formed arc-shaped tooth tips 40c and 41c. The radius R of the arc shape at the tips of the tooth tips 40c and 41c is 0.1 mm, and is formed outside the outer diameter of the standard gear obtained by adding the module m to the pitch circle diameter Dp.

As described above, in the present embodiment, the tip portions 40c, 41c of the photosensitive drum gear 40 and the transfer drum gear 41 are provided.
The surface opposite to the rotation transmission direction (the direction of the arrow) is formed as a 45 ° inclined surface and the tip is formed in an arc shape, so that the transfer drum 11 is added to the photosensitive drum 6 as described in the above-mentioned conventional technique. Even when the photosensitive drum gear 40 and the tooth tips 40c, 41c of the transfer drum gear 41 abut against each other, there is no flat portion at the tip of the tooth tip. Due to the pressure, the tooth tips 40c and 41c of the photosensitive drum gear 40 and the transfer drum gear 41 move relatively to each other, and a normal meshing state is established.

Further, only the surfaces of the photosensitive drum gear 40 and the transfer drum gear 41 which are opposite to the rotation transmitting direction (the direction of the arrow) of the tooth tips 40c, 41c are formed with a 45 ° slope, so that the photosensitive drum 6 and the transfer drum The meshing ratio of the photosensitive drum 6 does not change from the above-described conventional example, and the rotation of the photosensitive drum 6 is smoothly transmitted to the transfer drum 11 by a gear.

Accordingly, it is possible to prevent the occurrence of transfer failure, and in the case of the above-described color image forming apparatus, it is possible to prevent color shift of the transferred image and obtain a good image.

In each of the above embodiments,
Although an arc portion or a slope portion is further formed on the tooth tip of the standard gear, a similar effect can be obtained by forming the tip portion of the tooth tip of the standard gear in an arc shape or a slope. Further, in each of the above-described embodiments, the radius R of the arc shape at the tip of the tooth tip is set to 0.
Although it was 1 to 0.3 mm, this is not limited depending on the size of the module.

[0044]

As described above, according to the present invention, the image carrier gear portion can be relatively moved when the image carrier gear portion and the transfer material carrier gear portion are pressed against each other. By forming each tooth tip portion of the transfer material carrier gear portion in a non-planar shape, it is possible to prevent the transfer material carrier gear portion and the image carrier gear portion from hitting the tooth tip beforehand, A good image can be obtained by preventing the occurrence of transfer failure.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a contact state between a transfer drum and a photosensitive drum of an image forming apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a diagram illustrating a photosensitive drum gear of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a photosensitive drum gear of the image forming apparatus according to Embodiment 2 of the present invention.

FIG. 4 is a diagram illustrating a photosensitive drum gear of an image forming apparatus according to Embodiment 3 of the present invention.

FIG. 5 is a schematic configuration diagram showing an image forming apparatus in a conventional example.

FIG. 6 is a diagram showing a state in which a transfer drum and a photosensitive drum are separated in a conventional example.

FIG. 7 is a diagram showing a contact state between a transfer drum and a photosensitive drum in a conventional example.

FIG. 8 is a cross-sectional view showing a contact state between a transfer drum and a photosensitive drum in a conventional example.

FIG. 9 is a diagram showing a defective state in which the tooth tips of the transfer drum gear and the photosensitive drum gear are in contact with each other.

FIG. 10 is a diagram illustrating a state in which a transfer drum gear and a photosensitive drum gear are normally meshed.

FIG. 11 is a cross-sectional view showing a contact state between a transfer drum and a photosensitive drum in a defective state in which a tooth tip of a transfer drum gear and a photosensitive drum gear contact in a conventional example.

[Explanation of symbols]

6 Photosensitive Drum (Image Carrier) 11 Transfer Drum (Transfer Material Carrier) 40 Photosensitive Drum Gear (Image Carrier Gear) 40a, 40b, 40c, 41a, 41b, 41c
Tooth tip 41 Transfer drum gear (transfer material carrier gear)

Continuation of the front page (72) Inventor Hisawa Okubo 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H030 AA01 BB02 BB23 BB43 BB53 2H032 AA05 AA15 BA01 BA16 BA23 BA30 DA03 DA12 2H071 CA05 DA09 DA15 EA18 3J103 AA02 CA25 CA63 CA66 FA05 FA18 FA30 GA02 GA57 GA58 GA74

Claims (6)

[Claims] 1. A rotatable image carrier on which a developer image is formed, a rotatable transfer material carrier for carrying and transporting a transfer material on a surface, and attaching the transfer material carrier to the image carrier. A contact / separation unit that presses and abuts against the image carrier, and a rotation unit that rotates the image carrier when the transfer material carrier abuts on the image carrier at the transfer unit by the contact / separation unit. A gear transmission unit for transmitting the rotation to the transfer material carrier by transmitting the rotation to the transfer material carrier, wherein the gear transmission unit is disposed at least on one side in the longitudinal direction of the transfer material carrier. At least an image carrier gear portion that is rotated together with the rotation of the image carrier, and is disposed so as to be meshable with the image carrier gear portion, and rotates the image carrier by meshing with the image carrier gear portion. Transfer material carrier for transmitting drive to the transfer material carrier A gear portion, and the image carrier gear portion and the transfer material carrier gear are configured to be relatively movable when the transfer material carrier gear portion is pressed against the image carrier gear portion. An image forming apparatus, wherein each tooth tip of a part is formed in a non-planar shape. 2. The image forming apparatus according to claim 1, wherein the entire tooth tips of the image carrier gear portion and the transfer material carrier gear portion are formed in an arc shape. 3. A sharp angled slope is formed on both sides of each tooth tip of the image carrier gear portion and the transfer material carrier gear portion, and a tip side of the slope is formed in an arc shape. The image forming apparatus according to claim 1. 4. An acute-angled slope of each of the tooth tips of the image carrier gear section and the transfer material carrier gear section opposite to the transmission side of the rotational force is formed, and the tip end side of the slope is formed. The image forming apparatus according to claim 1, wherein the image forming apparatus is formed in an arc shape. 5. The tooth tip of the image carrier gear portion and the transfer material carrier gear portion is formed at the tip of a tooth tip surface of a standard tooth profile. 5. The image forming apparatus according to claim 3 or 4. 6. A color image formed by superimposing and transferring developer images of different colors sequentially formed on the image carrier in the transfer section on the transfer material carried on the surface of the transfer material carrier. The image forming apparatus according to claim 1, wherein the image forming apparatus is formed.