JP2000019802A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the quality of an image by easily and stably forming a transfer nip. SOLUTION: This image forming device is provided with a photoreceptor drum, a process cartridge 24 having a drum gear 17 and a holding member 13, an engagement holding groove 12a for inserting/removing a projecting part 13a, a supporting member freely attachably/detachably supporting the process cartridge 24, a transfer means, a drive source, a driving gear 21 which is engaged with the drum gear 17, to transmit rotation from the drive source to the drum gear 17, a positioning means abutted on the holding member 13 to position the photoreceptor drum and an energizing means 25 for energizing the process cartridge 24. An angle β formed by a straight line L1 and the surface S1 of the engagement holding groove 12a is made larger than the engagement pressure angle of the drum gear 17 with the driving gear 21.

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.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus, the surface of a photosensitive drum is uniformly and uniformly charged by a charging roller, and is exposed by an exposure device to form an electrostatic latent image. ing. The electrostatic latent image is developed by a developing roller into a toner image, and the toner image is transferred to a printing medium by a transfer roller and fixed by a fixing device. The print medium is a transport belt,
The sheet is conveyed by a medium conveying unit including a transfer roller and the like.

[0003] By the way, parts having a relatively short life, such as a photosensitive drum and a developing roller, can be replaced.
2. Description of the Related Art An image forming apparatus has been provided in which a photosensitive drum, a developing roller, and the like are housed in a process cartridge, and the process cartridge is detachable from an apparatus main body. In this case, a projecting member is formed on the process cartridge,
An engagement holding groove is formed in a frame of the image forming apparatus, and the process cartridge is set on the frame by bringing the protrusion member into contact with the bottom of the engagement holding groove and engaging the engagement member.

The process cartridge is pressed from above toward a transfer roller, so that a transfer nip is formed between the photosensitive drum and the transfer roller. In addition, the projecting member is engaged with the engagement holding groove, and a downward force is applied to the process cartridge when rotation is transmitted from the apparatus main body side to a drum gear formed integrally with the photosensitive drum. An image forming apparatus is also provided.

In this case, a contact member for preventing the process cartridge from rotating is formed near the engagement holding groove.

[0006]

However, in the conventional image forming apparatus, when the medium transport unit is detachably mounted on the apparatus main body, the photosensitive drum is accurately positioned with respect to the transfer roller. Can not do it. Therefore, it is difficult to stably form the transfer nip.

Particularly, in the case of an image forming apparatus capable of forming a color image, a plurality of process cartridges are removably mounted on the apparatus main body.
It becomes more difficult to stably form the transfer nip between the photosensitive drum of each process cartridge and each transfer roller. As a result, the image quality deteriorates. The present invention solves the problems of the conventional image forming apparatus, and provides an image forming apparatus capable of easily and stably forming a transfer nip and improving image quality. With the goal.

[0008]

For this purpose, in the image forming apparatus of the present invention, a photosensitive drum for forming a toner image, a drum gear formed integrally with the photosensitive drum, and the photosensitive drum A process cartridge including a holding member having a projection formed on the same axis as the photosensitive drum, and an engagement holding groove for inserting and removing the projection, and A support member that detachably supports the process cartridge, a transfer unit that is disposed to face the photoconductor drum, and transfers a toner image on the photoconductor drum to a print medium;
A drive gear meshed (engaged) with the drum gear and transmitting rotation from the drive source to the drum gear; a positioning means abutted on the holding member and positioning the photosensitive drum with respect to the transfer means; Urging means for urging the process cartridge toward the positioning means.

The angle formed by the straight line connecting the center of the drum gear and the center of the drive gear and the surface of the engagement holding groove is made larger than the pressure angle of engagement between the drum gear and the drive gear. You.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a schematic diagram of the image forming apparatus according to the first embodiment of the present invention. In the figure, reference numeral 100 denotes an image forming apparatus such as a tandem-type color electrophotographic printer.
At 0, a printing medium (not shown) is fed out of a medium cassette 102 by a hopping roller 101,
The paper is fed by the paper feed roller 103 and is transported
After being conveyed, the toner is conveyed by being attracted to the semiconductive conveyance belt 22 as a medium conveyance means by static electricity.

[0011] The yellow, magenta, cyan and black image forming units 1 face the conveyor belt 22.
05 to 108, and the image forming units 105 to
8, a photosensitive drum 16 as an image carrier is provided, and the photosensitive drum 16 is provided around the photosensitive drum 16.
A charging roller 113 for uniformly and uniformly charging the surface of the photosensitive drum 16 in accordance with print information to form an electrostatic latent image by exposing the surface of the photosensitive drum 16; A developing roller 115 as a developing unit for developing a toner image of each color by developing the toner image, and a cleaning device 116 as a cleaning unit are provided. The photosensitive drum 16, charging roller 113, exposure device 114, developing roller 115, cleaning device 116
The process cartridge 24 is configured by integrally assembling the components.

The toner images of each color on the photosensitive drum 16 are sequentially transferred to a printing medium by a transfer roller 26 as a transfer means, and a color toner image is formed. Thereafter, the print medium on which the toner image has been formed is transferred to the conveyance belt 2.
The toner image is separated from the sheet 2 and sent to the fixing device 112, where the color toner image is fixed by the fixing device 112 to form a color image.

The conveyor belt 22 is provided with the idle roller 1
22, 123, a tension roller 124 that applies tension to the transport belt 22, and a drive roller 125. When the drive roller 125 is rotated by driving a drive source (not shown), the idle roller 1
22 and 123 and the tension roller 124 are rotated, and the transport belt 22 is run.

Further, an attraction roller 126 is provided to face the idle roller 122 via the transport belt 22, and the attraction roller 126 is pressed toward the idle roller 122 to apply an attraction voltage. Thereby, the print medium is adsorbed on the conveyor belt 22. Next, a support structure of each process cartridge 24 will be described.

FIG. 1 is a sectional view showing a set state of a process cartridge according to a first embodiment of the present invention, and FIG.
FIG. 4 is a perspective view showing a set state of the process cartridge according to the first embodiment of the present invention, and FIG. 4 is a sectional view of a main part of the process cartridge according to the first embodiment of the present invention. In the figure, 11 is a frame of the image forming apparatus 100 (FIG. 2), 12 is a support member fixed to the frame 11, 24 is a process cartridge, and the process cartridge 24 is for supporting the photosensitive drum 16. A holding member 13 and a cover 14 that covers an upper surface of the holding member 13 are provided. The holding member 13 is integrally formed by projecting outward from the process cartridge 24, and is formed by projecting inward of the process cartridge 24 on the same axis as the projecting portion 13a. Drum 13 and a drum gear 17 provided by the support shaft 13b.
Are rotatably supported. The photosensitive drum 16
And the drum gear 17 are integrally formed.

By the way, the process cartridge 24
Is set on the process cartridge set stage set on the frame 11, a support member 12 is fixed to the frame 11, and the support member 12 is provided with a “U” -shaped notch having an open upper end. Thus, an engagement holding groove 12a for inserting and removing the protrusion 13a is formed. Therefore, the projecting portion 13a is
a into the process cartridge 2
4 is positioned in the transport direction of the print medium.

A support frame 23 as positioning means for supporting the transport belt 22 is provided below the process cartridge 24, and the process cartridge 24 is supported by an urging means 25.
, The contact portion 23a formed at the upper end of the support frame 23 and the contact portion 13c formed at the lower end of the holding member 13 are brought into contact with each other. At this time,
A drive gear 21 rotatably disposed with respect to the frame 11 and rotated in the direction of arrow A by a drive source (not shown) is meshed with the drum gear 17, and the photosensitive drum 16 is moved together with the drum gear 17 in the direction of arrow B. Rotated. Then, with the rotation of the driving gear 21, the driving force F0 is generated in the direction of the meshing pressure angle α at the meshing point between the drum gear 17 and the driving gear 21, and is applied to the drum gear 17. As a result, the protruding portion 13a is located on the downstream surface S of the engagement holding groove 12a in the transport direction of the print medium.
1 by a force F generated in parallel with the driving force F0.

When a straight line connecting the center of the drum gear 17 and the center of the drive gear 21 is L1, the angle β formed by the straight line L1 and the surface S1 is
7 and the drive gear 21 are set to be larger than the engagement pressure angle α. The meshing pressure angle α is determined by the tangent between the pitch circle of the drum gear 17 and the pitch circle of the drive gear 21 when the drum gear 17 and the drive gear 21 mesh with each other.
And the line perpendicular to the tangent to the tooth surface of the drive gear 21. Further, the meshing pressure angle α
Is the angle formed by the straight line L1 and the tangent between the tooth surface of the drum gear 17 and the tooth surface of the drive gear 21.

The support frame 23 is formed with a projecting engagement portion 23b projecting upward, and the cover 14 is formed with a projecting piece 14a engaged with the projection engagement portion 23b. The rotation of the process cartridge 24 is prevented by the deviation of the balance of the center of gravity or by the rotational force transmitted from the drive gear 21 to the drum gear 17.

Further, the surface S is formed so that the process cartridge 24 can be removed from the frame 11.
1 at the contact point P1 where the protruding portion 13a abuts, at a position closer to the transport path of the print medium than the straight line L2 extending in a direction perpendicular to the surface S1 and toward the downstream side in the transport direction of the print medium. The drive gear 21 is provided at a position where the drive force F0 is generated.

Next, the operation of the image forming apparatus 100 having the above-described configuration will be described.
a, and set the process cartridge 24 on the process cartridge setting stage. Next, the process cartridge 24 is urged downward by the urging means 25 so that the drum gear 17 and the drive gear 21 are meshed. At this time, the contact portion 13c and the contact portion 23a are brought into contact by the urging means 25. Further, the protrusion 13a is brought into contact with the surface S1.

Subsequently, when the printing operation is started, the printing medium is fed out of the medium cassette 102 one by one by the hopping roller 101, and the driving gear 21 is rotated in the direction of the arrow A by the driving source, and the drum gear 17 is rotated. , And the photosensitive drum 16 is rotated together with the drum gear 17 in the direction of arrow B. At this time, the driving force F0 is generated in the direction of the meshing pressure angle α at the meshing point between the drum gear 17 and the driving gear 21 with the rotation of the driving gear 21, and is applied to the drum gear 17. As a result, the protrusion 13a is pressed against the surface S1 by the force F.

At this time, as described above, the angle β
Is larger than the meshing pressure angle α, the force F is applied at an angle γ to the straight line L2. Therefore,
The component F1 of the force F acts downward along the surface S1, and the holding member 13 is pushed toward the transfer roller 26 by a force obtained by adding the component F1 to the urging force of the urging means 25. become.

Therefore, the contact portion 13c is moved to the contact portion 23a.
Therefore, the photosensitive drum 16 can be accurately positioned with respect to the transfer roller 26. As a result, the transfer nip can be easily and stably formed between the photosensitive drum 16 and the transfer roller 26, so that the toner image can be stably transferred to the print medium, and the image quality can be improved. Can be improved.

Further, it is not necessary to provide any special support means for supporting the process cartridge 24, and the rotation of the drive gear 21 can be transmitted to the drum gear 17. When the projecting portion 13a is pressed against the surface S1 with the force F, the process cartridge 24 is displaced by the imbalance of the center of gravity of the process cartridge 24 or by the rotational force transmitted from the drive gear 21 to the drum gear 17. The process cartridge 24 does not rotate because the convex piece 14a and the protruding engagement portion 23b are engaged with each other.

Next, a second embodiment of the present invention will be described. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol. FIG. 5 is a sectional view showing a set state of a process cartridge according to a second embodiment of the present invention;
FIG. 6 is a sectional view of a main part of a process cartridge according to a second embodiment of the present invention.

In this case, the transfer roller 2 as a transfer means
6 is connected to the support frame 2 via a bearing 50.
The shaft 51 is provided rotatably with respect to the shaft 3, and a contact member 52 as positioning means is provided at one end of the shaft 51.
Then, the contact portion 13c of the holding member 13 is pressed against the contact portion 52a of the contact member 52 by the urging means 25.

Therefore, the contact portion 13c is connected to the contact portion 52a.
Therefore, the photosensitive drum 16 can be accurately positioned with respect to the transfer roller 26. As a result, the transfer nip can be easily and stably formed, so that the toner image can be stably transferred onto the print medium, and the image quality can be improved.

Further, the photosensitive drum 16 is transferred to the transfer roller 2.
6, the transfer nip can be formed more stably without being affected by dimensional changes due to deformation of the support frame 23 such as bending and warping. it can. Next, a third embodiment of the present invention will be described. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol.

FIG. 7 is a sectional view showing a set state of a process cartridge according to a third embodiment of the present invention, and FIG.
FIG. 9 is a sectional view of a main part of a process cartridge according to a third embodiment of the present invention. In this case, the shaft 54 of the transfer roller 26 as a transfer unit is connected to the support frame 2 via a contact member 55 as a positioning unit forming a bearing.
3 is rotatably supported. And the holding member 1
3 is brought into contact with the contact member 55 by the urging means 25.
Is pressed against the contact portion 55a.

Therefore, the photosensitive drum 16 can be accurately positioned with respect to the transfer roller 26.
The transfer nip can be formed more stably without being affected by a change in dimensions due to deformation of the support frame 23 such as bending and warping. Next, a fourth embodiment of the present invention will be described. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol.

FIG. 9 is a sectional view showing a set state of a process cartridge according to a fourth embodiment of the present invention.
0 is a sectional view of a main part of a process cartridge according to a fourth embodiment of the present invention. In this case, a shaft 51 of the transfer roller 26 as a transfer unit is rotatably supported by the support frame 23 via a bearing 50, and a cylindrical contact member 62 serving as a positioning unit is provided at one end of the shaft 51. Is arranged. And the holding member 13
Is pressed against the contact member 62 by the urging means 25.

Therefore, the contact portion 13c is connected to the contact member 62.
Therefore, the photosensitive drum 16 can be accurately positioned with respect to the transfer roller 26. As a result, the transfer nip can be easily and stably formed, so that the toner can be stably transferred to the print medium, and the image quality can be improved.

The photosensitive drum 16 is transferred to the transfer roller 26.
Therefore, the transfer nip can be formed more stably without being affected by a change in dimensions due to deformation of the support frame 23 such as bending and warping. Next, a fifth embodiment of the present invention will be described. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol.

FIG. 11 is a sectional view showing a set state of a process cartridge according to a fifth embodiment of the present invention. In this case, the arc-shaped contact portion 13 f of the holding member 13 is formed concentrically with the photosensitive drum 16 (FIG. 10), and the contact portion 13 f is contacted by the urging means 25.
a.

Therefore, the process cartridge 24 is slightly rotated by the imbalance of the center of gravity of the process cartridge 24 or by the rotational force transmitted from the drive gear 21 to the drum gear 17, and the contact portion 23a
When the contact portion 13f is inclined, the contact portion 13f has an arc shape, so that the photosensitive drum 16 does not rise, and the distance between the photosensitive drum 16 and the transfer roller 26 as a transfer unit is constant. Then, the contact portion 13f is changed to the contact portion 23.
a, the photosensitive drum 16 can be accurately positioned with respect to the transfer roller 26. As a result, the transfer nip can be easily and stably formed, so that the toner image can be stably transferred onto the print medium, and the image quality can be improved.

Next, a sixth embodiment of the present invention will be described. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol. FIG. 12 is a sectional view showing a set state of the process cartridge according to the sixth embodiment of the present invention, and FIG. 13 is a sectional view showing a main part of the process cartridge according to the sixth embodiment of the present invention.

In this case, the transfer roller 2 as a transfer means
The sixth shaft 54 is rotatably supported by the support frame 23 via the contact member 55. Then, the contact portion 13c of the holding member 13 is pressed against the contact portion 23a of the support frame 23 by the urging means 25. The contact portion 55a is formed concentrically with the transfer roller 26 and has an arc shape. The contact member 55 is provided with the urging means 6.
1 urges the contact portion 13c. Therefore, the contact member 55 can be slightly rotated in both directions about the shaft 54. The contact member 55 and the support frame 23 constitute a positioning unit.

As a result, since the photosensitive drum 16 can be accurately positioned with respect to the transfer roller 26, the transfer nip is not affected by a change in dimensions due to deformation of the support frame 23 such as bending and warping. Can be easily and stably formed. Further, even if the center of gravity of the process cartridge 24 is out of balance or the rotational force transmitted from the drive gear 21 to the drum gear 17, the process cartridge 24 is slightly rotated and the contact portion 13c is tilted. Since 55a has an arc shape, the photosensitive drum 16 does not rise.

Further, since the contact portion 55a has an arc shape, the distance between the center of the transfer roller 26 and the contact portion 13c becomes constant at any position in the rotation direction of the transfer roller 26, so that the photosensitive drum 16 and transfer roller 2
6 is constant. Therefore, the transfer nip can be formed more stably. Next, a seventh embodiment of the present invention will be described. In addition, about what has the same structure as 4th Embodiment, the description is abbreviate | omitted by attaching the same code | symbol.

FIG. 14 is a sectional view showing a set state of a process cartridge according to a seventh embodiment of the present invention. In this case, a protruding engagement portion 23d protruding upward is formed on the support frame 23, and the protruding engagement portion 23d and the lower surface 13g of the holding member 13 are engaged. Therefore, it is possible to prevent the process cartridge 24 from being rotated by the imbalance in the center of gravity of the process cartridge 24 or by the rotational force transmitted from the drive gear 21 to the drum gear 17.

The drive gear 21 is rotated in the direction of arrow A by a drive source (not shown), the rotation is transmitted to the drum gear 17, and the photosensitive drum 16 (FIG. 13) is rotated in the direction of arrow B together with the drum gear 17. . Then, with the rotation of the driving gear 21, the driving force F0 is generated in the direction of the meshing pressure angle α at the meshing point between the drum gear 17 and the driving gear 21, and is applied to the drum gear 17. As a result, the protrusion 13a is pressed against the surface S1 by the force F.

Here, the engaging portion P11 between the projecting engaging portion 23d and the holding member 13 is formed by an extension line L3 of the driving force F0.
It is set so that it is located on the print medium transport path side from above. Therefore, the driving force F0 does not act in a direction to separate the driving gear 21 and the drum gear 17, and does not generate a reaction force against the component force F1. In the present embodiment, the engaging portion P11 is formed in a flat shape. However, when at least one of the protruding engaging portion 23d and the lower surface 13g of the holding member 13 is formed by an arc-shaped or cylindrical boss,
The engagement position can be stabilized.

Since the contact portion 13c is stably brought into contact with the contact member 62 as the positioning means, the photosensitive drum 16 can be accurately positioned with respect to the transfer roller 26 as the transfer means. . As a result, the transfer nip can be easily and stably formed, so that the toner image can be stably transferred onto the print medium, and the image quality can be improved.

In general, when a gear is meshed with another gear, one set of teeth meshes (engages) in a region near the pitch point, and two teeth in regions before and after the region.
A pair of teeth mesh. Therefore, when the drum gear 17 is meshed with the drive gear 21, when the rotation is transmitted, the number of meshing teeth and the backlash between the teeth fluctuate, and the effective tooth strength fluctuates. As a result, the force F transmitted from the drive gear 21 to the drum gear 17 becomes uneven.

Therefore, the drive gear 21 and the drum gear 17
An eighth embodiment of the present invention in which the force F transmitted to the motor is prevented from becoming uneven will be described. In addition, about what has the structure same as 5th Embodiment, the description is abbreviate | omitted by attaching | subjecting the same code | symbol. FIG. 15 is a first view showing the meshing state between the driving gear and the drum gear according to the eighth embodiment of the present invention, and FIG. 16 is a diagram showing the meshing state between the driving gear and the drum gear according to the eighth embodiment of the present invention. It is the 2nd figure shown.

In this case, the contact portion 13f of the holding member 13 (FIG. 11) having an arc shape is connected to the photosensitive drum 16 (FIG. 1).
3) is formed concentrically with the contact portion 13 f
With this, it is brought into contact with the contact portion 23a. Further, the drum gear 17 and the drive gear 21 (only the drum gear 17 is shown in FIG. 15) are each formed by a spiral gear such as a helical gear, and the meshing ratio, that is, the number of meshing teeth, is increased. The tooth width d1 is set so as to be 2 or more. In this case, at one edge of the drum gear 17 and the drive gear 21, regions AR1 where two sets of teeth mesh with each other,
An area AR2 where one set of teeth meshes and an area AR3 where two sets of teeth mesh are sequentially formed, and at the other edge of the drum gear 17 and the drive gear 21, an area AR4 where the two sets of teeth mesh with each other. The area AR5 where the teeth mesh with each other and the area AR6 where the two sets of teeth mesh with each other are sequentially formed, but the drum gear 17 and the drive gear 21 are formed by a spiral gear, and the number of meshing teeth becomes two or more. To tooth width d1
Are set, the areas AR2, A in which one set of teeth mesh
R5 does not coincide in the circumferential direction. Note that d2 is the engagement length.

Therefore, when rotation is transmitted from the driving gear 21 to the drum gear 17, the number of meshing teeth and backlash between the teeth can be prevented from fluctuating, and the effective tooth strength can be stabilized. Can be. as a result,
It is possible to prevent the force F transmitted from the drive gear 21 to the drum gear 17 from becoming uneven. And since the contact part 13f is stably contacted with the contact part 23a,
The photosensitive drum 16 can be accurately positioned with respect to the transfer roller 26 as a transfer unit. As a result, the transfer nip can be easily and stably formed, so that the toner image can be stably transferred onto the print medium, and the image quality can be improved.

The present invention is not limited to the above embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0050]

According to the present invention, as described above, in an image forming apparatus, a photosensitive drum for forming a toner image, a drum gear formed integrally with the photosensitive drum, and the photosensitive member Rotatably supports the drum, and
A process cartridge including a holding member having a protrusion formed on the same axis as the photosensitive drum, a support including an engagement holding groove for inserting and removing the protrusion, and detachably supporting the process cartridge; A member, a transfer unit disposed opposite to the photoconductor drum, for transferring a toner image on the photoconductor drum to a print medium, a driving source, and a driving unit; A drive gear that transmits the photosensitive drum to the transfer member, and a biasing unit that biases the process cartridge toward the positioning unit. Have.

The angle formed by the straight line connecting the center of the drum gear and the center of the drive gear and the surface of the engagement holding groove is made larger than the engagement pressure angle between the drum gear and the drive gear. In this case, rotation is transmitted from the drive gear to the drum gear, and the photosensitive drum is rotated together with the drum gear. At this time, with the rotation of the driving gear, a driving force is generated and applied to the drum gear, and the protruding portion is pressed against the surface of the engagement holding groove. Then, a component force of the force by which the protrusion is pressed against the surface of the engagement holding groove acts downward along the surface of the engagement holding groove, and the holding member is a force obtained by adding a component force to the urging force of the urging means. It is pushed toward the transfer means.

Therefore, since the holding member is stably brought into contact with the positioning means, the photosensitive drum can be accurately positioned with respect to the transfer means. As a result, the transfer nip can be easily and stably formed, so that the toner image can be stably transferred onto the print medium, and the image quality can be improved. Also,
Since there is no need to provide any special support means for supporting the process cartridge, the rotation of the drive gear can be transmitted to the drum gear.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a set state of a process cartridge according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of an image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a perspective view illustrating a set state of a process cartridge according to the first embodiment of the present invention.

FIG. 4 is a sectional view of a main part of the process cartridge according to the first embodiment of the present invention.

FIG. 5 is a sectional view showing a set state of a process cartridge according to a second embodiment of the present invention.

FIG. 6 is a sectional view of a main part of a process cartridge according to a second embodiment of the present invention.

FIG. 7 is a sectional view showing a set state of a process cartridge according to a third embodiment of the present invention.

FIG. 8 is a sectional view of a main part of a process cartridge according to a third embodiment of the present invention.

FIG. 9 is a sectional view showing a set state of a process cartridge according to a fourth embodiment of the present invention.

FIG. 10 is a sectional view of a main part of a process cartridge according to a fourth embodiment of the present invention.

FIG. 11 is a sectional view showing a set state of a process cartridge according to a fifth embodiment of the present invention.

FIG. 12 is a sectional view illustrating a set state of a process cartridge according to a sixth embodiment of the present invention.

FIG. 13 is a sectional view of a main part of a process cartridge according to a sixth embodiment of the present invention.

FIG. 14 is a sectional view showing a set state of a process cartridge according to a seventh embodiment of the present invention.

FIG. 15 is a first diagram illustrating a meshing state between a drive gear and a drum gear according to an eighth embodiment of the present invention.

FIG. 16 is a second diagram illustrating a meshing state between a drive gear and a drum gear according to an eighth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Support member 12a Engagement holding groove 13 Holding member 13a Projection part 16 Photoconductor drum 17 Drum gear 21 Drive gear 23 Support frame 23b Projection engagement part 24 Process cartridge 25, 61 Energizing means 26 Transfer roller 51, 54 Shaft 52, 55 , 62 contact member 55a contact portion 100 image forming apparatus F0 driving force L1 straight line β angle

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Ken Kikuchi 4-11-12 Shibaura, Minato-ku, Tokyo F-term (reference) 2H032 AA05 BA05 BA18 DA08 2H035 CA07 CB03 CB04 CD09 CD14 CG03 2H071 BA04 BA13 BA16 BA22 CA02 CA05 DA09 DA15 DA26

Claims (14)

[Claims] 1. A photosensitive drum for forming a toner image, a drum gear formed integrally with the photosensitive drum, and the photosensitive drum rotatably supported, and
A process cartridge including a holding member having a projection formed on the same axis as the photosensitive drum; and (b) an engagement holding groove for inserting and removing the projection, wherein the process cartridge is detachably attached. A supporting member for supporting; (c)
A transfer unit that is disposed to face the photosensitive drum and transfers a toner image on the photosensitive drum to a print medium;
(D) a drive source, (e) a drive gear meshed with the drum gear and transmitting rotation from the drive source to the drum gear, and (f) abutting on the holding member to transfer the photosensitive drum to the transfer unit. Positioning means for positioning with respect to
(G) urging means for urging the process cartridge toward positioning means, and (h) a straight line connecting the center of the drum gear and the center of the drive gear, and the surface of the engagement holding groove. An image forming apparatus is characterized in that the angle formed by the angle is larger than the angle of engagement pressure between the drum gear and the drive gear. 2. The image forming apparatus according to claim 1, wherein the positioning unit is a support frame that rotatably supports the transfer unit. 3. The image forming apparatus according to claim 1, wherein the positioning unit is a contact member provided on a shaft of the transfer unit. 4. The image forming apparatus according to claim 3, wherein the contact member has a cylindrical shape. 5. The image forming apparatus according to claim 1, wherein the holding member has an arc shape. 6. The image forming apparatus according to claim 5, wherein the arc shape is formed concentrically with the photosensitive drum. 7. The image forming apparatus according to claim 3, wherein the contact member has a contact portion having an arc shape. 8. The image forming apparatus according to claim 7, wherein the arc shape of the contact member is formed concentrically with the transfer unit. 9. The image forming apparatus according to claim 3, wherein the contact member is urged toward the holding member. 10. The image forming apparatus according to claim 1, wherein the holding member includes a projecting engagement portion for preventing the process cartridge from rotating. 11. The image forming apparatus according to claim 10, wherein the protruding engagement portion and the holding member are engaged with each other on a printing medium conveyance path side from an extension of a driving force applied to the drum gear with rotation of the driving gear. apparatus. 12. The image forming apparatus according to claim 10, wherein at least one of the projecting engagement portion and the holding member has one of a cylindrical shape and an arc shape. 13. The image forming apparatus according to claim 1, wherein the drum gear and the drive gear are meshed with two or more meshing teeth. 14. The image forming apparatus according to claim 13, wherein the drum gear and the drive gear are spiral gears.