JPH09281849A - Photoreceptor supporting structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve image forming accuracy by eliminating the unevenness of the rotation of an image carrier caused by eccentricity. SOLUTION: A pair of flanges 4 constituted so that the moment of inertia of at least one of them is greater than that of the image carrier 3 are attached to both ends of the cylindrical image carrier 3 whose surface has a photoreceptive layer 3b and a bar-like drum shaft 5 is fixed in the flanges 4 by shrink fitting. Therefore, the angular velocity of the image carrier 3 is stabilized by the flywheel effects of the flanges 4 and the unevenness of the rotation of the image carrier 3 is made extremely little. At this time, the flanges 4 and the drum shaft 5 are fixed by the shrink fitting, so that the image carrier 3 is not made eccentric with respect to the drum shaft 5 because a backlash does not exist between the flanges 4 and the drum 5. Thus, the rotational accuracy of the image carrier 3 is enhanced and the image forming accuracy can be improved as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive member supporting structure used in an electrophotographic apparatus such as a copying machine or a laser printer.

[0002]

2. Description of the Related Art In an electrophotographic apparatus in which a photosensitive drum is used as an image bearing member, a photosensitive member supporting structure for rotatably supporting the photosensitive drum is essential. This photosensitive member support structure requires high precision in supporting the photosensitive drum, because if the photosensitive drum is not supported eccentrically, uneven rotation of the photosensitive drum occurs and image quality is deteriorated. Especially,
In a color electrophotographic apparatus having a structure in which a plurality of photosensitive drums are rotationally driven in synchronization with each other, higher accuracy is required to eliminate color misregistration of each color.

In Japanese Patent Laid-Open No. 1-193888, flanges having a rotational moment higher than the rotational moment (inertia moment) of the photosensitive drum are attached to both ends of a cylindrical photosensitive drum, and the photosensitive drum is produced by the flywheel effect of the flange. Discloses an invention in which the angular velocity of is stabilized and the uneven rotation thereof is reduced.

[0004]

SUMMARY OF THE INVENTION However, Japanese Patent Laid-Open No.
In the invention disclosed in Japanese Patent No. 193888, mounting of the drum shaft on the photosensitive drum having the flange mounted is
Since the drum shaft is formed by inserting the drum shaft into the shaft hole formed in the central portion of the flange, there is a problem that the photosensitive drum is eccentrically rotated due to the gap between the shaft hole and the drum shaft. Moreover, since the flange has a large rotational moment, if the photosensitive drum is eccentric with respect to the drum shaft, uneven rotation of the photosensitive drum is rather increased. Therefore, in the invention disclosed in Japanese Patent Application Laid-Open No. 1-193888, a balancer mounting portion is provided at several places on the flange, and the balancer is mounted on the balancer mounting portion according to how uneven rotation occurs. However, this has a problem that the assembling work is complicated and it takes time to assemble.

In Japanese Laid-Open Patent Publication No. 2-150883, both ends of a cylindrical photosensitive drum and a flange are brought into contact with each other with a tapered surface, the drum shaft is passed through the two flanges, and the drum shaft and the flange are fixed in the axial direction. The invention of a photoreceptor supporting structure having such a structure is disclosed. The axial fixing of the drum shaft and the flange is performed by a pin attached to one side of the drum shaft and a screw engagement of a nut with a screw provided on the other side of the drum shaft. With such a structure, it is possible to reduce the eccentricity of the photosensitive drum with respect to the drum shaft on the nut side. Therefore, it is conceivable to reduce such rotation unevenness of the photosensitive drum by applying such a photosensitive member support structure to a structure in which the rotational moment of the flange is larger than that of the photosensitive drum. However, the structure disclosed in Japanese Patent Laid-Open No. 2-150883 requires a complicated assembling work such as fixing a nut to a screw on the drum shaft, and thus has a problem of poor assembling property.

[0006]

According to the first aspect of the present invention,
A cylindrical image bearing member, a pair of flanges attached to both ends of the image bearing member, at least one of which has a larger moment of inertia than the image bearing member, and fixed on the flanges by shrink fitting to be coaxial with the image bearing member. And a rod-shaped drum shaft arranged in the. Therefore, since the flange has a large moment of inertia, the angular velocity of the image carrier is stabilized by the flywheel effect, and the uneven rotation thereof is reduced. At this time, since the flange and the drum shaft are fixed by shrink fit, there is no play between the flange and the drum shaft, and therefore the image carrier does not decenter with respect to the drum shaft. As a result, the rotation accuracy of the image carrier is increased, and the image forming accuracy is improved.

According to a second aspect of the invention, in the photoreceptor supporting structure according to the first aspect, at least one of the flanges is
A weight part extending in the inner axial direction of the image carrier is provided. This increases the moment of inertia of the flange without increasing the diameter of the flange or the protruding portion.

According to a third aspect of the present invention, in the photosensitive member support structure according to the second aspect, the weight part has a larger diameter at the tip than the outer diameter of the weight part and a smaller diameter than the inner diameter of the image carrier. , A guide member that is more flexible than the image carrier. This prevents the tip of the weight portion from damaging the image carrier when the flange is mounted on the image carrier.

The invention according to claim 4 is the invention according to claims 1 to 3.
In the photosensitive member support structure according to any one of the above, one or both of an end portion of the image carrier and a flange portion abutting the end portion is formed in a tapered shape, and the drum is provided only for one flange. The shaft was fixed by shrink fitting, the drum shaft was passed through the other flange, and the flange was pressed and fixed to the image carrier by an elastic member. As a result, the end of the image carrier is brought into contact with the flange that is shrink-fitted and fixed to the drum shaft, and in this state, the flange is attached to the drum shaft and this flange is attached to the other end of the image carrier by the elastic member. Press on to complete the whole assembly. Therefore, the assembling work is facilitated and the assembling time is shortened.

[0010]

An embodiment of the present invention will be described with reference to the drawings. First, a front frame 1 and a rear frame 2 of an electrophotographic apparatus (not shown) are provided, and a photosensitive drum 3 as an image carrier is rotatably supported between these frames 1 and 2. This photosensitive drum 3 has a thin hollow cylindrical base portion 3a made of aluminum, nickel or the like with C
It has a structure in which a photosensitive layer 3b made of a photoconductive photosensitive material such as e, CdS or Si is formed.

A pair of flanges 4 are attached to both ends of the photosensitive drum 3 which are open. These flanges 4 are made of a material having a relatively high specific gravity such as brass and stainless steel, and the moment of inertia of the flange 4 is the photosensitive drum 3.
Is bigger than. Further, the flange 4 is joined to the end portion of the photosensitive drum 3 by a tapered surface.

The flange 4a on the rear frame 2 side is shrink-fitted and fixed to the drum shaft 5 of the photosensitive drum 3 formed in a rod shape, and has a weight portion 6 extending in the inner axial direction of the photosensitive drum 3. The weight portion 6 is arranged with a slight gap between the inner peripheral surface of the photosensitive drum 3 and the outer peripheral surface of the drum shaft 5, and is made of a material softer than the photosensitive drum at the tip, for example, a resin such as polyacetal. The guide member 7 is provided. The guide member 7 has a larger diameter than the outer diameter of the weight portion 6 and a smaller diameter than the inner diameter of the photosensitive drum 3, and has a tapered tip end.

The flange 4b on the front frame 1 side has an insertion hole 8 through which the drum shaft 5 is inserted. The front plate 9 fixed to the front frame 1 is rotatably mounted via a bearing BB. Further, the flange 4b is slidably attached to the bearing BB in a direction of coming in contact with and separating from the bearing BB, and is biased in a direction of being separated from the bearing BB by a coil spring 10 as an elastic member. In the direction away from the bearing BB, the flange 4b moves toward the photosensitive drum 3
Is the direction of contacting the end of the. Furthermore, the flange 4b
Includes a stopper 11 that prevents the front plate 9 from coming off.

In the vicinity of the flange 4a on the rear frame 2 side, a cylindrical supporter 12 is provided on the drum shaft 5 with two bearings B.
It is rotatably attached via B. Supporter 1
2 is sandwiched between a nut 14 that is screwed into a screw portion 13 formed on a part of the drum shaft 5 and a step portion 15 formed on the drum shaft 5, and the nut 14 is tightened to tighten the nut 14 The flange 12a is pressed against the rear frame 2, whereby the drum shaft 5 is rotatably attached to the rear frame 2 via the supporter 12. That is, on the front frame 1 side, the flange 4b through which the drum shaft 5 is inserted is rotatably attached to the front frame 1 via the front plate 9, and on the rear frame 2 side, the drum shaft 5 is connected to the rear frame via the supporter 12. The photosensitive drum 3 is rotatably supported between the front frame 1 and the rear frame 2 by being rotatably attached to the front frame 1.

A motor bracket 18 for fixing a drive motor 17 is fixed to the rear frame 2 via a stud 16. As a result, the drive motor 17 has its rotation shaft 17 a arranged coaxially with the drum shaft 5. The rotary shaft 17a of the drive motor 17 arranged coaxially
The drum shaft 5 and the drum shaft 5 are connected by a coupling 19.

In such a structure, when the rotating shaft 17a of the drive motor 17 which is energized rotates, the rotating shaft 1
The drum shaft 5 connected to 7a via the coupling 19 rotates, and the photosensitive drum 3 is rotationally driven. This enables an electrophotographic process such as formation and development of a desired electrostatic latent image on the photosensitive layer 3b of the photosensitive drum 3.

At this time, since the flange 4 has a larger moment of inertia than the photosensitive drum 3, the flywheel effect stabilizes the angular velocity of the photosensitive drum 3 and the uneven rotation thereof is reduced. Moreover, one flange 4a and the drum shaft 5
And are fixed by shrink fit, so flange 4
The play between the drum shaft 5 and the drum shaft 5 is extremely small, and the drum shaft 5
However, the photosensitive drum 3 is not eccentric. Therefore, the rotation accuracy of the photosensitive drum 3 is increased, and the image formation accuracy by the electrophotographic prorus is improved.

Here, the one flange 4a is provided with a weight portion 6 extending in the inner axial direction of the photosensitive drum 3. Therefore, the moment of inertia of the flange 4 increases without increasing the diameter of the flange 4a or the protruding portion to the outside. This makes it possible to reduce the uneven rotation of the photosensitive drum 3 due to the increase in the moment of inertia and to reduce the size of the structure.

Next, the assembly work will be described.
First, one flange 4a is shrink-fitted and fixed to the drum shaft 5 in advance, and the drum shaft 5 in this state is fixed to the rear frame 2
Attach to In this case, the supporter 12 is fitted to the rear frame 2, and the drum shaft 5 is fitted to the supporter 12. When the step portion 15 of the drum shaft 5 comes into contact with the supporter 12, the nut 14 is screwed into the screw portion 13 of the drum shaft 5 and tightened. As a result, the supporter 12 and the drum shaft 5 are attached to the rear frame 2. At this time, if the drive motor 17 is fixed to the stud 16 via the motor bracket 18, the rotary shaft 17 a of the drive motor 17 and the drum shaft 5 are connected via the coupling 19.

Next, the photosensitive drum 3 is attached to one of the flanges 4a.
Plug in. At this time, since the guide member 7 that is more flexible than the photosensitive drum 3 is provided at the tip of the weight portion 6 of the flange 4a, it is possible to prevent the photosensitive drum 3 from being damaged.

Next, the other flange 4b is inserted into the end of the drum shaft 5. That is, the insertion hole 8 of the flange 4b
The drum shaft 5 is passed through. If the front plate 9 is attached to the front frame 1 in this state, the flange 4
b is rotatably attached to the front frame 1, and the assembly is completed. At this time, the flange 4b is pressed against the end portion of the photosensitive drum 3 by the coil spring 10, and the photosensitive drum 3 is sandwiched between the two flanges 4a and 4b. In this state, the end portion of the photosensitive drum 3 and the flanges 4a and 4b are in contact with each other by the tapered surface, so that the drum shaft 5
The photosensitive drum 3 is reliably positioned with respect to the surface, and the eccentric rotation of the photosensitive drum 3 is prevented also from this surface.

As described above, according to the structure of this embodiment, the assembling work is extremely easy, and the assembling and maintenance work is facilitated and the assembling and maintenance time is shortened.

In this embodiment, the photoconductor 3 is exemplified as the image carrier, but in practice, the image carrier may be an intermediate transfer roller or the like to which the toner image is transferred from the photoconductor 3. good.

[0024]

According to the first aspect of the present invention, a pair of flanges are provided at both ends of the image carrier, at least one of which has a larger moment of inertia than the image carrier, and the drum shaft is shrink-fitted to the flanges. Since it is fixed by means of the flywheel effect of the flange, the angular velocity of the image carrier can be stabilized and uneven rotation of the image carrier can be reduced, and in this case, the rattling between the flange and the drum shaft can be reduced. It is possible to prevent the eccentricity of the image carrier with respect to the drum shaft by eliminating the fixing by fitting. Therefore, the rotation accuracy of the image carrier can be increased, and the image forming accuracy can be improved.

According to the second aspect of the present invention, since the weight portion is provided on at least one of the flanges, it is possible to increase the moment of inertia of the flange without increasing the diameter of the flange or the protruding portion. It is possible to reduce the unevenness in rotation due to the stabilization of the angular velocity and to downsize the device.

According to the third aspect of the present invention, since the guide member that is softer than the image bearing member is provided in the weight portion, the tip of the weight portion damages the image bearing member when the flange is attached to the image bearing member. Such a thing can be prevented.

According to a fourth aspect of the present invention, one or both of the end portion of the image bearing member and the flange portion contacting the end portion is formed in a tapered shape, and only one of the flanges has a drum shaft. Was fixed by shrink fitting, and the drum shaft was penetrated to the other flange and the flange was pressed and fixed to the image bearing member by the elastic member, which facilitates assembly and maintenance work, and The maintenance time can be shortened.

[Brief description of drawings]

FIG. 1 is an overall vertical cross-sectional side view showing an embodiment of the present invention.

FIG. 2 is an overall vertical cross-sectional side view showing one process of assembly.

[Explanation of symbols]

 3 image carrier 3b photosensitive layer 4 flange 5 drum shaft 6 parts by weight 7 guide member 10 elastic member

Claims (4)

[Claims] 1. A cylindrical image bearing member, a pair of flanges attached to both ends of the image bearing member, at least one of which has a larger moment of inertia than the image bearing member, and fixed to the flanges by shrink fitting. And a rod-shaped drum shaft arranged coaxially with the image carrier, and a photosensitive member support structure. 2. The photoconductor support structure according to claim 1, wherein at least one of the flanges is provided with a weight portion extending in the inner axial direction of the image carrier. 3. The weight part has a guide member at its tip, which has a diameter larger than the outer diameter of the weight part and smaller than the inner diameter of the image carrier, and which is formed more flexibly than the image carrier. The photosensitive member support structure according to claim 2, wherein 4. One or both of an end portion of an image carrier and a flange portion abutting the end portion is formed in a taper shape, and the drum shaft is shrink-fitted only to one of the flange portions. 4. The image bearing member according to claim 1, wherein the drum shaft is passed through the other flange, and the flange is pressed and fixed to the image carrier by an elastic member. Photoconductor support structure.