JPH0828658A - Driving force transmission device - Google Patents

Abstract

PURPOSE:To easily engage a drive gear with a driving gear by using a gear whose tooth height is larger than that of a normal tooth, and where the part with larger tooth height is chamfered to the driving gear and the driven gear subject to the driving force through this driving gear. CONSTITUTION:When a photo-sensing drum is rotated by engaging a driving gear provided in a printer body with a drum gear (a driven gear) on a photo- sensing drum side of a laser printer, the tooth height of both the driving gear and the driven gear is larger than that of the normal gear with the same pitch circle. That means, ht=hn+DELTAh where ht is the addendum, and hn is the addendum of the normal tooth with the same pitch circle, and the tip part of the large tooth height is chamfered. When a process cartridge is mounted on the printer body, one gear is easily shifted to either the right or the left of the other gear to guarantee the smooth engagement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive transmission device composed of a drive side device and a driven side device, and more particularly to a drive transmission device in which the driven side device is detachable from the drive side device.

[0002]

2. Description of the Related Art As a device for transmitting drive by gears, there is a type in which a driven device is detachable from a drive device. For example, in an image forming apparatus typified by a printer, a facsimile, a copier, etc., it is common to mount a process cartridge in which consumables and consumable parts are integrated into the main body of the image forming apparatus for use. In such an image forming apparatus, a gear such as a photosensitive drum included in the process cartridge meshes with a drive gear inside the main body of the image forming apparatus when the process cartridge is mounted. That is, the photosensitive drum having the driven gear has a relationship of being attached / detached to / from the drive gear according to attachment / detachment of the process cartridge. Usually, helical gears having parallel teeth are used for such a driving gear and a driven gear. The parallel teeth have a tooth surface defined by an involute curve and a tip circle, and drive is transmitted in a meshed state as shown in FIG.

[0003]

However, since the addendum of the parallel teeth has the substantially flat addendum surface defined by the addendum circle, the driven side device such as the process cartridge is used as the drive side device. When installing, if the tooth tips of the drive gear and the driven gear face each other, the gears do not mesh and the driven side device cannot be mounted on the drive side device, or the gears do not mesh. There was a problem that was done. It suffices if either the drive gear or the driven gear can be adjusted so as to mesh with each other by rotating by a small angle, but if the load applied to the gear is large, the gear cannot be rotated and this is not a solution.

In order to avoid such a problem, as shown in FIG. 11, a method of moving the gears of the driving gear and the driven gear to eliminate the tooth crests, and, as shown in FIG. 12, the driving gear and the driven gear. There is a method of chamfering the tooth tip or processing it into a curved surface to eliminate the tooth tip surface. However, due to the transfer, there is a problem that the pressure angle becomes large, the gear efficiency and the meshing ratio decrease, and smooth drive transmission cannot be performed. Further, chamfering the addendum of the parallel gear reduces the tooth portion of the involute, and the meshing efficiency decreases. As described above, if the meshing ratio is reduced and smooth drive transmission cannot be performed, for example, in the case of an image forming apparatus, uneven rotation of the photosensitive drum or uneven conveyance of the paper may occur, resulting in deterioration of print quality. Become.

Therefore, it is an object of the present invention to provide a drive transmission device which can easily mesh a driven gear of a driven gear of a driven device with a driven gear of a driven gear without lowering gear efficiency and meshing ratio. To do.

[0006]

To achieve the above object, the present invention has a drive side device having a drive gear and a driven gear that meshes with the drive gear, and is driven from the drive side device via the drive gear. In the drive transmission device including the detachable driven side device that receives the transmission of, the drive gear and the driven gear are gears having chamfered portions having a higher tooth depth than the normal teeth and a higher tooth depth than the normal teeth.

Further, the driven side device of the present invention has a coupling means for coupling the driven gear to the driven device body so as to be rotatable by a minute angle. More specifically, the coupling means is
A first coupling member that rotates integrally with the driven device main body, a second coupling member that is fixed to the driven gear and is loosely fitted to the first coupling member so as to be rotatable by a small angle, and a second coupling member. And a biasing means for biasing the member in a predetermined direction. The present invention is preferably applied to an image forming apparatus provided with a detachable process cartridge. In that case, the photosensitive drum included in the process cartridge serves as a driven side apparatus.

[0008]

According to the first aspect of the present invention, in order to prevent the gear efficiency and the meshing efficiency from being lowered, the drive gear and the driven gear having the tooth depth higher than that of the gear teeth are effectively used and the gear teeth are effectively used. In order to allow the driven gear to smoothly mesh with the drive gear, a portion having a higher tooth depth than the parallel teeth is provided and this portion is chamfered.

According to the second aspect of the present invention, the driven gear is coupled to the driven device main body so that the driven gear can rotate by a small angle, so that when the driven gear does not mesh with the drive gear, the driven gear is connected to the driven gear. By rotating the gear slightly, the drive gear and the driven gear can be engaged more reliably.

According to the third aspect of the invention, the second coupling member fixed to the driven gear is urged by the urging means in a direction opposite to the rotational direction of the driven gear, for example. When the driven gear does not mesh with the drive gear, the second coupling member is loosely fitted to the first coupling member fixed to the driven device body so as to be rotatable by a small angle. By slightly rotating the second coupling member in the direction opposite to the urging direction of the urging means, the drive gear and the driven gear can be engaged with each other.

According to a fourth aspect of the present invention, in the case where the image forming apparatus main body is the driving side apparatus and the process cartridge side detachable from the image forming apparatus is the driven side apparatus,
Since any one of the features described in claim 3 is provided, it becomes easy to mount the process cartridge.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a laser printer will be described below with reference to the drawings.

First, the overall configuration of the laser printer will be described with reference to FIG. In FIG. 1, the printer 1
Has a body cover 2 that can be opened and closed. A paper guide 6 whose inner surface constitutes a part of a paper passage is provided inside the main body cover 2. The paper guide 6 can be opened and closed with the main body cover 2 open in order to perform necessary processing when a trouble such as a paper jam occurs.

A paper feeding device 3 is detachably attached to the printer 1, and the sheets stacked in the paper feeding device 3 are separated and fed one by one by a paper feeding roller 4 and a separation pad 5. A paper passage for guiding the paper sent from the paper feeding device 3 to the photosensitive drum 9 is formed between the paper chute 30 and the paper chute 30 provided on the upper surface of the process unit 24, which will be described later. Conveying rollers 7a and 7b are respectively supported by 30 and the paper guide 6.

The printer body has an exposure unit 10 that exposes the surface of the photosensitive drum 9 that has been uniformly charged by the charger 8 in advance according to image data to form an electrostatic latent image on the surface of the photosensitive drum 9. It is provided. The exposure unit 10 includes a laser diode 11, a lens 12, and a reflecting mirror 13. The toner box 14 is provided on one side of the photosensitive drum 9.
Are arranged, and the toner box 14 and the photosensitive drum 9 are arranged.
The developing unit 15 is arranged between the and.

A transfer roller 16 is provided above the photosensitive drum 9.
Are arranged in contact with the photosensitive drum 9, guide the paper between the photosensitive drum 9 and the transfer roller 16, and transfer the toner image formed on the photosensitive drum 9 to the paper. A fixing unit 19 including a heating roller 17 and a pressing roller 18 is arranged on the side of the photosensitive drum 9 opposite to the side where the developing unit 15 is arranged. In the fixing unit 19, the toner image transferred onto the sheet is melted and fixed on the sheet. A waste toner box 25 is arranged in contact with the photosensitive drum 9 between the transfer roller 16 and the fixing unit 19. The waste toner box 25 brings the cleaning blade 25a into contact with the photosensitive drum 9 to scrape and collect the toner remaining on the photosensitive drum 9 after passing the transfer roller 16 for reuse.

Further, in the printer 1, a fan (not shown), the photosensitive drum 9, the paper feed roller 4, the conveying roller 7a, and the heating roller 17 will be described later in order to radiate heat generated from the fixing section 19 to the outside. A motor (not shown) for rotating the auger spring 26a and the like is provided. Furthermore, the exposure unit 1
Below 0, the control boards 20 and 21 and the power supply unit 2 are provided.
2 are arranged. Cover body 2 constituting the housing
3 has a plurality of operation buttons and other display LEDs (not shown)
Is provided.

Among the various parts constituting the printer 1 shown in FIG. 1, the toner box 14, the developing section 15, the photosensitive drum 9, the transfer roller 16 and the like are detachable from the printer 1 as a unitized process unit 24. Has become. FIG. 2 is a sectional view of the process unit 24. As shown in FIG. 2, the toner box 14 is a substantially cylindrical container in which the toner is sealed. The toner box 14 has an agitator 14 a rotatably provided therein. An opening 14b is formed in the center. As the agitator 14a rotates, the toner inside the toner box 14 flows out through the opening 14b.

The developing section 15 includes a stirring means, that is, a first agitator 15a, a second agitator 15b and a developing roller 15.
c and a trimmer blade 15d. The first agitator 15a is arranged in the vicinity of the opening 14b of the toner box 14 in parallel with the axial direction of the toner box 14, and a wire is stretched between both end supporting members having a cross-shaped cross section, so that the first agitator 15a The toner is supplied from the opening 14b of the toner box 14 by rotation and the toner accumulated in the developing chamber 15e of the first agitator 15a by the rotation of the second agitator. The mixture is agitated and transferred to the developing chamber 15f. Second agitator 15b
Is configured to rotate a rod-shaped body, and supplies the toner accumulated in the developing chamber 15f to the developing roller 15c. The developing roller 15c is disposed near the outer peripheral surface of the photosensitive drum 9 and is rotatable about an axis parallel to the rotation axis of the photosensitive drum 9, and develops the electrostatic latent image formed on the photosensitive drum 9 with toner. It is a substantially cylindrical drum.

Below the developing roller 15c, the trimmer blade 15 is a plate-like member having a blade-shaped tip and having a length substantially equal to the axial length of the developing roller 15c.
d is disposed close to the peripheral surface of the developing roller 15c, and regulates the amount of toner electrostatically carried on the peripheral surface of the developing roller 15c.

A waste toner box 25 is further integrated with the process unit 24. Waste toner box 2
Reference numeral 5 is for scraping and collecting the toner remaining on the photosensitive drum 9 after the transfer, and the collected waste toner is recycled to the developing unit 15. The recycling means for this purpose comprises a passage member, that is, an auger pipe 26, and a rotatable spiral conveying member, that is, an auger spring 26a, which is installed inside the auger pipe 26. The auger pipe 26 extends from the bottom of the waste toner box 25 to the vicinity of the center of the upper portion of the first agitator 15 a of the developing unit 15.

As shown in FIG. 3, the auger pipe 26 comprises a chute side portion 26b and a joint portion 26c, and the chute side portion 26b is on the back side of the sheet feeding surface of the feeding chute 30 and the upper wall of the feeding chute 30. The transport chute 30 cooperates to form a tubular passage in the longitudinal direction.
It is molded integrally with. The transport chute 30 is for guiding the paper to the photosensitive drum 9, and is used for the developing unit 1.
No. 5 first agitator 15a is arranged substantially parallel to the axial direction. Shoot side portion 26b of the auger pipe 26
Extends to the center of the transfer chute 30, and the waste toner discharge port 26e is located in the center of the transfer chute 30. In the state where the transport chute 30 is assembled as described later, the waste toner discharge port 26e is aligned with the opening 28a formed in the upper frame 28 that covers the upper surface of the developing unit 15, and is located above the opening 14b of the toner box 14. It is located directly above the first agitator 15a at the adjacent position. The other end of the chute side portion 26b of the auger pipe 26 is connected to the joint portion 26c, and the joint portion 26c
The other end of is connected to the waste toner box 25.

Inside the auger pipe 26, an auger spring 26a which is a spiral conveying member is installed. The auger spring 26a is connected to the rotary drive source at one end thereof, and is connected to the auger pipe 26 from the inside of the waste toner box 25.
Of the waste toner from the bottom of the waste toner box 25 to the upper position of the first agitator 15a of the developing unit 15 by rotating the auger spring 26a in the spiral winding direction. Transport.

In this embodiment, the developing roller 15c and the trimmer blade 15d are integrated by using the lower frame 27 and the upper frame 28 to form a developing unit 31, which is used for assembling the process unit 24. The lower frame 27 has a developing chamber 1 for the first agitator 15a.
5e, a developing chamber 15f for the second agitator 15b, and an accommodating portion 29 for the developing roller 15c.
Both ends 29a and 29b of the accommodating portion 29 are connected to the developing roller 15c.
And a developing roller 15c is rotatably supported.

FIG. 3 is an exploded perspective view for explaining the assembly of the process unit 24. First, the developing unit 3
The assembling method of No. 1 will be described. First, the first agitator 15
a and the second agitator 15b respectively in the developing chamber 15e,
Attach to 15f. Next, the developing roller 15c is accommodated in the accommodating portion 29.
Attach to. First agitator 15a and second agitator 1
5b is rotatably supported by bearings (not shown) at both ends, and the developing roller 15c is rotatably supported by bearings 29a, 29b at both ends. Next, the trimmer blade 15d is attached to the lower frame 27. Further, by mounting the upper frame 28, the developing unit 31 is completed.

Next, a method of assembling the process unit 24 will be described. To assemble the process unit 24, first, the photosensitive drum 9 is mounted on the casing 32 of the process unit 24, and then the transfer roller 16 is mounted on the upper position of the photosensitive drum 9. The housing 32 is provided with a place adjacent to the photosensitive drum 9 for accommodating the developing unit 31, and the developing unit 31 is placed there. In this state, the chute 30 is connected to the first agitator 15a of the developing unit 15.
Installed on top, waste toner box 25 and chute 30
Joint portion 26 of the auger pipe 26 disposed on the back side of the
The auger spring 26a is inserted into and connected to c and the chute portion 26b. Finally, the cover 33 of the photosensitive drum 9 is attached, the side plate 34 is attached to the casing 32, and the assembly of the process unit 24 is completed. The process unit 24 thus assembled is detachably attached to the printer 1.

In the above structure, a gear is rotatably supported on the shaft of the photosensitive drum 9 in the process cartridge 21, and when the process cartridge 21 is mounted in the printer 1, the drive gear in the printer 1 is the photosensitive drum 9. It meshes with a gear (hereinafter referred to as "drum gear"). That is,
When the present invention is applied to a laser printer, the photosensitive drum 9 corresponds to the driven device and the drum gear corresponds to the driven gear. Also, the printer body corresponds to the drive side device,
A gear provided in the printer body and meshing with the drum gear corresponds to a drive gear. Since this drive gear is connected to the motor that is the drive source via a plurality of gear trains, it is virtually impossible to rotate the drive gear to the meshing position with the driven gear when the process cartridge 21 is mounted. . The driven gear can be rotated by a small angle by a coupling device to be described later to smoothly mesh with the drive gear.

An embodiment in which the present invention is applied to the printer 1 having the above structure will be described with reference to FIGS. 4 to 9. 4 and 5 show the shapes of the drive gear and the driven gear, and FIGS. 6 to 9 show a coupling device for smoothly engaging the drive gear and the driven gear.

FIGS. 4 and 5 show the shapes of the driving gear and the driven gear according to the embodiment of the present invention. The gear used in this embodiment has a higher tooth depth than the parallel teeth having the same pitch circle for both the drive gear and the driven gear. Height from the pitch circle of the gear to the actual tooth tip, i.e., the addendum and h _t, a relationship of h _t = h _n + Δh when the addendum of the parallel teeth of the same pitch circle and h _n. In the figure, (a) shows the tip circle of the drive gear,
(B) shows the addendum circle in the case of parallel teeth, and (E) shows the pitch circle. The addendum h _n of the parallel teeth is the height between the pitch circle (e) and the addendum circle (b) of the parallel tooth, and the addendum h _t of the gear of this embodiment is the pitch circle (e) and the addendum circle. The height is between (a). As described above, in the gear according to the present embodiment, the tooth clearance is higher than the parallel teeth having the same pitch circle by the height Δh between the parallel tooth tip circle (b) and the actual tooth tip circle (a). ing. By setting the tooth depth higher than that of the corresponding parallel teeth, it is possible to maintain the same pressure angle, gear efficiency, and meshing ratio as those of the corresponding parallel teeth, so that there is no uneven rotation of the photosensitive drum, and therefore print quality is improved. Is never reduced.

4 and 5, (C) shows the lower boundary line of the involute tooth surface of the drive gear, and (D) shows the root circle. Is.
The tooth surface surrounded by (b) and (c) is created by an involute curve. The part surrounded by (c) and (d) is the part where the tooth tip part of the driven gear enters, and the driven gear also has a higher tooth depth than the parallel teeth having the same pitch circle, Accordingly, the diameter of the root circle of the drive gear is made smaller than that of the corresponding parallel tooth. The tooth root portion has a shape that smoothly connects to the involute curve and does not reduce the tooth thickness of the tooth root portion.

Further, in the gear of this embodiment, the tip end portion having a high tooth depth is chamfered. In the embodiment shown in FIG. 4, the tip portion is chamfered to have an R shape, and in the embodiment shown in FIG. 5, the tip portion is chamfered and sharpened. With this configuration, when the process cartridge 21 is mounted on the printer body, even if the tooth tip portion of the driving gear and the tooth tip portion of the driven gear come into contact with each other, one gear is located on either side of the other gear. It becomes easy to escape in the direction of and smooth meshing is achieved.

Although the driving gear has been mainly described above, the driven gear meshing with the driving gear has the same shape as the driving gear.

Next, the coupling device for coupling the driven device body and the driven gear will be described with reference to FIGS.

FIG. 9 is an exploded perspective view of the coupling device 40. The coupling device 40 includes a first coupling member 41, a second coupling member 42, and a coil spring 43 that biases the second coupling member in a predetermined direction. A through hole 41a is formed at the center of the first coupling member 41 in the longitudinal direction, and a shaft having both ends supported by a casing 32 is rotatably inserted through the through hole 41a, and the photosensitive drum 9 is attached to the shaft. Is rotatably supported. Further, as shown in FIGS. 6 and 9, the outer peripheral surface of the first coupling member 41 includes a flange portion 41b and a cylindrical outer peripheral surface 41c, and the cylindrical outer peripheral surface 41c is an end of the photosensitive drum 9. It is inserted in the part and fixed. As described above, the first coupling member 41 is fixed to the photosensitive drum 9 which is the driven side main body, and
And the first coupling member 41 rotate integrally. On the flange side of the first coupling member 41, two circular arc-shaped rotation guide pieces 41d and 41e arranged concentrically with the through hole 41a face outward from a concave surface formed at the flange side end portion. Has been set up. One ends of the rotation guide pieces 41d and 41e are opposed to each other with a narrow space 41f therebetween,
The other side faces each other with an expansion space 41g in between.

A driven gear (not shown) is formed on the outer peripheral surface 42a of the second coupling member 42, and has a contact surface 42b for contacting the flange portion 41b of the first coupling member 41. At the end on the side of the contact surface 42b, a rotation restricting piece 42c is erected outward from the recessed surface. The rotation restricting piece 42c has a substantially circular cross section, and a cutout portion 42 is partially formed.
d is formed. Further, one end 42e of the rotation restricting piece 42c is bent inward. A protrusion 42f that is loosely fitted in the expansion space 41g of the first coupling member 41 is formed on the outer peripheral surface of the rotation restricting piece 42c at a portion diametrically opposed to the cutout portion 42d. Expansion space 4
When the protruding portion 42f is loosely fitted to the 1g, the rotation regulating piece 4
The outer peripheral surface of 2c is slidable on the inner peripheral surfaces of the rotation guide pieces 41d and 41e. In addition, the first coupling member 41 and the second
With the coupling member 42 of No. 1 engaged, a through hole 42g that directly communicates with the through hole 41a of the rotating first coupling member 41 is formed concentrically with the rotation restricting piece 42c, and the shaft of the photosensitive drum 9 is the first. Through the through hole 41a of the connecting member 41 to the through hole 42g of the second connecting member 42.

As shown in FIG. 9, the coil spring 43
Both end portions 43a and 43b are bent inward, one end portion 43a is locked in the narrow space 41f between the rotation guide pieces 41d and 41e, and the other end portion 43b is bent inside the rotation regulating piece 42c. The second connecting member 42 is locked to the end portion 42e on the raised side, and in this state, the second connecting member 42 is biased in a predetermined direction with respect to the first connecting member 41. Specifically, the second
The second coupling member 42 is biased in the counterclockwise direction with the inner surface of the coupling member 42 of FIG. This state is shown in FIG. The urging direction of the second coupling member 42 is opposite to the direction in which the driven gear formed on the outer peripheral surface 42a is driven by the drive gear. When the driven gear is free from the drive gear and is stopped, the driven gear is rotated counterclockwise according to the biasing force of the coil spring 43 as shown in FIG. Moreover, since the width of the expansion space 41g on the first coupling member 41 side is slightly wider than the width of the protrusion 42f on the second coupling member 42 side, the biasing force of the coil spring 43 is Against this, the second coupling member 42 can be rotated clockwise by a small angle. This state is shown in FIG. This is the state when the driven gear is driven by the drive gear.

By providing the driven side device with the coupling device 40 having the above-described structure, the second coupling member 42 is provided even if the tooth tip portion of the drive gear and the tooth tip portion of the driven gear come into contact with each other.
Since it can be rotated by a small angle in the clockwise direction, both gears can be smoothly meshed. Even if the driven gear and the driven gear operate in a state where they are not completely meshed with each other, the driving force acts on the driven gear in the clockwise direction, so that both gears are completely meshed at the same time when the operation is started. In the case of the printer shown in FIGS. 1 to 4, the printer is driven even if the paper guide 6 and the body cover 2 are sequentially closed in a state where the drive gear on the printer body side and the drum gear of the photosensitive drum 9 are not completely meshed. Immediately after that, both gears are completely meshed by the action of the coupling device 40, and the rotation of the photosensitive drum 9 and the paper feeding do not occur.

Although the coupling device for coupling the driven device body and the driven gear has been described above, a similar coupling device for coupling the driving device body and the driving gear may be further provided, and it is not provided on the driven side and only on the driving side. It may be provided. The gear formed on the outer peripheral surface of the second coupling member 42 is
It may be a pair of teeth as shown in FIG. 10 or a gear having a shape as shown in FIGS. 4 and 5. It goes without saying that the use of the gears having the shapes shown in FIGS. 4 and 5 allows smoother engagement between the drive gear and the driven gear.

[0039]

As described above, according to the first aspect of the present invention, by chamfering the portion having a higher tooth depth than the normal teeth, the drive gear and the driven gear can be smoothly meshed with each other, and It is possible to smoothly utilize power from the drive gear to the driven gear without deteriorating the pressure angle, the gear efficiency, and the meshing ratio by effectively utilizing the parallel tooth portion of the high tooth depth.

According to the second and third aspects of the invention, since the driven gear is rotatable by a small angle with respect to the driven device body, even if the tooth tips of the drive gear and the driven gear come into contact with each other. The meshing of both gears can be achieved by rotating the driven gear.

According to the invention described in claim 4, since the drum gear of the photosensitive drum and the drive gear of the image forming apparatus main body side are smoothly meshed with each other, the process cartridge cannot be mounted or the imperfect mounting is prevented. can do.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a laser printer to which the present invention is applied.

FIG. 2 is a vertical sectional view of a process unit mounted on the laser printer shown in FIG.

FIG. 3 is an exploded perspective view for explaining assembly of a process unit.

FIG. 4 is a diagram showing the shape of a gear according to an embodiment of the present invention.

FIG. 5 is a diagram showing the shape of a gear according to another embodiment of the present invention.

FIG. 6 is a vertical sectional view of a coupling device according to an embodiment of the present invention.

FIG. 7 is a side sectional view of the coupling device shown in FIG. 6 in a biased state.

8 is a side sectional view of the coupling device shown in FIG. 6 in a non-biased state.

9 is an exploded perspective view of the coupling device shown in FIG.

FIG. 10 is a diagram showing the shape of a gear wheel having parallel teeth of a conventional example.

FIG. 11 is a diagram showing a shape in which a tooth crest is removed by transferring a gear having parallel teeth of a conventional example.

FIG. 12 is a view showing a chamfered tooth tip of a gear of a conventional example.

[Explanation of symbols]

 9 Photosensitive Drum 24 Process Unit 40 Coupling Device 41 First Coupling Member 42 Second Coupling Member 43 Coil Spring

Claims (4)

[Claims] 1. A drive-side device having a drive gear, and a removable drive-side device having a driven gear that meshes with the drive gear and receiving transmission of drive from the drive-side device via the drive gear. In the drive transmission device according to the present invention, as the drive gear and the driven gear, gears having chamfered portions having a higher tooth depth than the normal teeth and having a higher tooth depth than the normal teeth are used. 2. The drive transmission device according to claim 1, wherein the driven-side device includes a coupling means that rotatably couples the driven gear to the driven device body by a minute angle. 3. The coupling means is fixed to a first coupling member which rotates integrally with the driven device body and the driven gear, and is loosely fitted to the first coupling member so as to be rotatable by a minute angle. 3. The drive transmission device according to claim 2, further comprising: a second coupling member that is formed, and a biasing unit that biases the second coupling member in a predetermined direction. 4. The drive transmission device according to claim 1, wherein the driven-side device is a photosensitive drum included in a process cartridge that is detachable from the image forming apparatus.