JP3347622B2 - Photoconductor drum and electrophotographic image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive drum used in an electrophotographic recording system and an electrophotographic image forming apparatus using the drum.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus such as a copying machine or a printer, a cylindrical drum base having a photosensitive layer on an outer peripheral surface is provided at both ends in a longitudinal direction.
A photosensitive drum to which a flange member for rotatably supporting the drum base is attached is widely used.

In the above-mentioned photosensitive drum, various methods have been proposed for attaching a flange member to the drum base. Among them, particularly representative methods are the press-fitting method and the clearance fit method.

In the press-fitting method, a flange member having a guide portion having an outer diameter slightly larger than the inner diameter of the drum base is used at a fitting portion between the cylindrical drum base and the flange member. The flange member is fixed by press-fitting into the openings at both ends in the longitudinal direction. This press-fitting method does not require the drum base and the flange member to be bonded to each other, and is excellent in simplicity of assembly.

On the other hand, the clearance fit method uses a flange member having a guide portion having an outer diameter slightly smaller than the inner diameter of the drum base at a fitting portion between the cylindrical drum base and the flange member. The parts are fitted into the openings at both ends in the longitudinal direction of the drum base. However, this alone causes the flange member to fall off from the drum base, so as a fixing method, the fitting portion between the drum base and the flange member is bonded with an adhesive or a flange member is attached to a stay-like member that passes through the inside of the drum base. Means such as screwing are taken.
As a result, it is possible to insert the drum member and the flange member without applying excessive force when attaching the drum member, and it is possible to remove only the drum substrate by screwing or the like. It can be downed.

[0006]

However, when the above press-fitting method is used, an excessive force may be required when the flange member is inserted into the drum base, and the same applies when the flange member is removed. Must be replaced together with the flange member. Further, there is a type in which a heater is built in the drum substrate to prevent moisture absorption on the surface of the drum substrate. In this case, it is necessary to replace the heater when the photosensitive drum is replaced, which increases the cost. .

On the other hand, when the clearance fit method is used, a slight gap is formed between the inner diameter of the drum base and the outer diameter of the flange member. The center of rotation of the drum may be biased and attached, and the distance from the center of rotation to the surface of the drum base may be non-uniform.

In the case of monochrome recording, it is possible to eliminate the influence of the eccentricity by directly contacting a positioning member provided in the developing device with the surface of the photosensitive drum. Yellow for drums,
In an apparatus that performs development by sequentially bringing the magenta, cyan, and black developing devices close to each other, when the positioning member of the developing device is brought into contact with or separated from the photosensitive drum, the rotation load of the photosensitive drum is fluctuated. Causes color shift between colors. Therefore, the distance between the surface of the photosensitive drum and the surface of the developing roller is guaranteed by bringing the positioning member of the developing device into contact with a portion other than the photosensitive drum. Variations occur in the distance between the surfaces, and due to the variations, an appropriate amount of toner is not supplied to the surface of the photosensitive drum, and color unevenness may occur.

In addition, in the case of bonding, when an adhesive having a high curing speed is used in addition to the above two problems, the adhesive is cured before the flange member is fitted into a proper position with respect to the drum base. Conversely, when an adhesive having a slow curing speed is used, the time required for curing is long, and the assembly time is required, so that the productivity may be reduced.

[0010] The present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a photosensitive drum which can be easily replaced and can accurately and uniformly make the distance from the rotation center of the photosensitive drum to the drum surface and an electrophotographic image forming apparatus using the same. To provide.

[0011]

In order to achieve the above object, a typical configuration according to the present invention is a cylindrical drum base having a photosensitive layer on the outer surface and flange fitting portions at both longitudinal ends. A flange member having an outer diameter slightly smaller than the inner diameter of the flange fitting portion and having a guide portion capable of fitting into the flange fitting portion, and rotation of the photosensitive drum provided at a plurality of locations of the guide portion. And a projection having a distance from the center substantially equal to the inner diameter of the flange fitting portion,
In the photosensitive drum in which the protrusion is fitted into the flange fitting portion and the flange member is mounted on the drum base, the protrusion is formed integrally with the flange member.

In the above configuration, when the flange member is press-fitted into the drum base and attached, the protrusion and the flange fitting portion may be pressed into contact with each other. Removal becomes possible.
Further, since there is no gap between the flange members of the drum base, the distance from the rotation center of the photosensitive drum to the drum surface becomes uniform.

If the drum base is thin, the press-fitting may deform the drum base. In such a case, an intermediate fit is formed within the range of the processing accuracy of the flange fitting portion and the projection. The difference between the maximum distance and the minimum distance from the rotation center of the photosensitive drum to the surface of the drum base during press-fitting is different from the rotation center of the photosensitive drum when the drum base is biased in the loose fit. By making the distance equal to the difference between the maximum distance and the minimum distance to the surface of the substrate, it is possible to minimize the non-uniformity of the distance from the rotation center of the photosensitive drum to the surface of the drum.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a photosensitive drum according to the present invention and an electrophotographic image forming apparatus using the same will be described with reference to the drawings.

First Embodiment FIGS. 1 to 4 show a first embodiment. FIG. 1 is an exploded perspective view of a photosensitive drum, FIG. 2 is a sectional explanatory view of the photosensitive drum, FIG.
FIG. 4 is an explanatory view of the dimensions of a drum base and a flange member, and FIG. 4 is an explanatory view of the overall configuration of an electrophotographic image forming apparatus using the photosensitive drum.

Here, as the order of the description, first, the overall configuration of the electrophotographic image forming apparatus will be described, and then the configuration of the photosensitive drum will be described.

{Overall Configuration of Electrophotographic Image Forming Apparatus} This electrophotographic image forming apparatus (copier) is a color image forming apparatus having four developing units as shown in FIG. The image of the original G placed on the top of the apparatus is scanned by the exposure apparatus 1 having a well-known optical system, a laser scanner, and the like.
The light is projected onto the rotating cylindrical photosensitive drum 2. At this time,
The photosensitive drum 2 is uniformly charged by a primary charger 3, and an electrostatic latent image is formed by the exposure.

When the latent image reaches a developing site where the developing device 4 is disposed to face, toner is applied to the latent image to form a toner image. Since the image forming apparatus uses four color toners of yellow, magenta, cyan, and black, the developing device 4 includes a yellow developing device 4Y, a magenta developing device 4M, and a cyan developing device 4 containing toners of the respective colors.
C and a black developing unit 4Bk are provided, which can selectively take an operating position close to the photosensitive drum 2 and a retracted position separated therefrom.

The formation of a color image will be briefly described. A latent image corresponding to the yellow component color of a document is formed on the photosensitive drum 1, and when the latent image reaches a developing site where the developing device 4 is disposed, a yellow developing image is formed. The device 4Y takes an operating position close to the photosensitive drum 2 and applies yellow toner to the latent image to form a yellow toner image.

When the toner image reaches a transfer portion where the photosensitive drum 2 and the transfer drum 5 rotating in synchronization with the photosensitive drum 2 are opposed to each other, the transfer material (not shown) until this time is transferred to the suction roller 6 and the suction charger. The toner is supplied to and attracted to the transfer drum 5 through 7, and then reaches the transfer site. Here, the yellow toner image on the photosensitive drum 2 is transferred to the transfer material by the operation of the transfer charger 8.

Thereafter, the transfer material rotates while riding on the transfer drum 5. On the other hand, the residual toner remaining on the photosensitive drum 2 even after the transfer is removed by the cleaner 9, and then a latent image of the original magenta component color is formed on the photosensitive drum 2 in the same manner as described above. Is reached, the magenta developing device 4M reaches the operating position by this time, and magenta toner is applied to the latent image to form a magenta toner image.

Further, when the magenta toner image reaches the transfer portion, the yellow toner image on the transfer drum reaches the transfer portion at the same time, and the magenta toner image is superimposed and transferred. Similarly, a cyan toner image and a black toner image are sequentially transferred to the transfer material, and the transfer process ends.

Thereafter, the transfer material is separated from the transfer drum 5 by the action of the separation claw 10, reaches the fixing device 12 via the transport path 11, and the toner image is fixed and fixed on the transfer material, and is discharged out of the apparatus.

The transfer drum 5 is neutralized by the static eliminators 13, 14 and 15, and the attached toner is removed by the cleaner 18 to prepare for the next transfer step.

{Structure of Photosensitive Drum} Next, the structure of the photosensitive drum 2 will be described with reference to FIGS. The photosensitive drum 2 includes a cylindrical drum base 16 and flange members attached to both ends of the drum base 16 in the longitudinal direction.
Consists of 17

The drum substrate 16 is formed by forming a photosensitive layer on the surface of a cylindrical aluminum substrate. Also,
The flange members 17 are made of metal, and fit into the openings at both ends of the drum base 16. At this time, in order to prevent the flange member 17 from falling off from the drum base 16 and to prevent the drum base 16 from rotating idly with respect to the flange member 17, the flange member 17 is mounted on a stay (not shown) passing through the inside of the drum base 16. Screw. The photosensitive drum 2 is integrally rotatable by passing a shaft provided in the apparatus main body through a hole 17a provided in the flange member 17.

At the longitudinal opening of the drum base 16,
After drawing the aluminum substrate, as shown in FIG. 2, the inner periphery of the opening is cut to form the flange fitting portion 16a.

On the other hand, the flange member 17 is formed with a guide portion 17b having an outer diameter slightly smaller than the inner diameter of the fitting portion 16a so that the flange member 17 can be fitted into the fitting portion 16a. Projections 17c are provided at a plurality of positions in the circumferential direction. The guide portion serves as a rough guide when the flange member 17 is fitted into the fitting portion 16a.
Reference character c fixes the flange member 17 by press-fitting the fitting portion 16a.

FIG. 3 shows a front view and a side view of the flange member. In FIG. 3, three projections 17c are integrally formed at equal intervals in the circumferential direction on a guide portion 17b fitted into the flange fitting portion 16a. Then, the protrusion 17
The center of the circular edge connecting the outer circumference of c is equal to the center of the hole 17a which is the rotation center of the photosensitive drum 2, and the outer diameter dF is substantially equal to the inner diameter of the flange fitting portion 16a of the drum base 16 (in the present embodiment, Equal or slightly larger).

Thus, the flange member 17 is connected to the drum base.
When the projection 17c is inserted into the flange 16, the projection 17c is press-fitted into the flange insertion portion 16a, so that the flange member 17 can be attached and fixed to the drum base 16. In FIG. 2, d is a drum base.
It is a press-fitting white of 16 and flange 17.

With the above configuration, the protrusions
Since only 17c is press-fitted, an excessive force is not required at the time of attachment and detachment as in the case where the entire periphery of the flange member 17 is press-fitted into the flange fitting portion 16a. Further, since the projection 17c is in pressure contact with the inner periphery of the fitting portion 16a, there is no danger that the drum base will be attached to the flange member in a biased manner as in a loose fit. The distance to the surface becomes uniform.

[Second Embodiment] Next, as a second embodiment, a case where the drum base 16 is thin will be described. When the drum base 16 is thin, when the flange member 17 is press-fitted, as shown in FIG. 5, the drum base 16 may be deformed by the influence of the projection 17c. That is, the drum base 16 swells at the projection 17c, and the drum base 16 is dented at the portion without the projection 17c. As a result, the distance from the rotation center of the photosensitive drum 2 to the drum surface becomes non-uniform.

Therefore, in that case, the flange fitting portion 16a
The inner diameter and the outer diameter of the projection 17c are fitted by an intermediate fit within the range of processing accuracy. That is, in the range of the processing accuracy of the inner diameter of the flange fitting portion 16a and the outer diameter of the projection 17c, when the inner diameter of the flange fitting portion 16a is small or the outer diameter of the projection 17c is large, both are fitted by press fitting, Conversely, when the inside diameter of the flange fitting portion 16a is large or the outside diameter of the projection 17c is small, the two are fitted by loose fit.

At the time of press-fitting, as shown in FIG.
the distance r1 from the center of rotation of the portion swollen by c;
The difference (r1 -r2) from the distance r2 from the center of rotation of the concave portion in the portion without the protrusion 17c occurs as the distance non-uniformity.

On the other hand, at the time of loose fit, as shown in FIG. 6, since the drum base 16 is mounted deviated from the rotation center, the distance r3 from the rotation center of the photosensitive drum 2 to the part farthest from the rotation center and the rotation center The difference (r3-r4) from the distance r4 to the adjacent part occurs as the nonuniformity of the distance.

Therefore, when fitting by an intermediate fit, within the range of processing accuracy, the above (r1-r2) when the inner diameter of the flange fitting portion 16a is the smallest and the outer diameter of the projection 17c is the largest. And (r3 -r4)
) Is configured to be equal. This allows
The non-uniformity of the distance can be minimized without increasing the processing accuracy of the drum base 16 and the flange member 17.

That is, as shown in FIG. 7 (a), in the press-fitting, as shown in FIG. 7 (a), the non-uniformity Δr becomes maximum when the press-fitting white d is maximum in the range of the machining accuracy, and in the loose fit, the press-fitting white d becomes negative. When it becomes maximum (when the gap is the largest), the non-uniformity Δr becomes maximum.

On the other hand, in the intermediate fit, if the range of the processing accuracy is the same, as shown in FIG.
2) dF, d such that = (r3 -r4) =. DELTA.rmax
By configuring i, the non-uniformity can be minimized.

For example, in FIGS. 2 and 3, the outer diameter φdc of the drum base 16 is 180 mm, the inner diameter φdi of the flange insertion portion 16a is φ176H8 (tolerance 0 to +0.063) mm, and the width l i of the flange insertion portion 16a is 20 mm. , Thickness other than the fitting part tc = 3 mm
When the number of the projections 17c is 3, the width b = 10 mm, the outer diameter φdF = φ176 (tolerance +0.029 to +0.069) mm, and (r1−r2) = (r3−) r4) is satisfied, and the non-uniformity of the distance can be suppressed.

[Other Embodiments] In the above-described embodiment,
Although the example in which the rectangular projection 17c is formed is shown, a hemispherical projection 17c as shown in FIG. 8 or a rib-shaped projection 17c as shown in FIG. Alternatively, the same effects as those of the above-described embodiment can be obtained even with the device attached.

In the above-described embodiment, an example in which the number of the projections 17c is three has been described. However, the number and the width b of the projections 17c impair the ease of attachment and detachment of the flange member 17 and the effects described above. Of course, it is possible to change the value within the range that does not exist, and the value is not limited to the value described above.

Further, in the above-described embodiment, a copying machine has been exemplified as an electrophotographic image forming apparatus. However, the present invention is not limited to the copying machine, but can be applied to a printer, a facsimile machine, and the like.

[0043]

The present invention is constructed as described above.
When the flange member is press-fitted and attached to the drum base, the protrusion and the flange fitting portion may be pressed into contact with each other, and the partial press-fitting allows the attachment and detachment with an appropriate force. Further, since there is no gap between the flange members of the drum base, the distance from the rotation center of the photosensitive drum to the drum surface becomes uniform, and a high-quality image can be obtained.

When the drum base is thin,
Although the drum base may be deformed by the press fitting,
In such a case, the intermediate fitting should be used within the range of the processing accuracy of the flange fitting portion and the protrusion, and the difference between the maximum distance and the minimum distance from the rotation center of the photosensitive drum to the surface of the drum base during press-fitting. The distance between the center of rotation of the photoconductor drum and the surface of the drum base during clearance fit is equal to the difference between the maximum distance and the minimum distance from the center of rotation of the photoconductor drum to the surface of the drum base. This makes it possible to minimize uniformity.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a photosensitive drum.

FIG. 2 is an explanatory sectional view of a photosensitive drum.

FIG. 3 is a front view and a side view of a flange member.

FIG. 4 is an explanatory diagram of an overall configuration of an electrophotographic image forming apparatus using the photosensitive drum.

FIG. 5 is an explanatory diagram showing a state in which a drum base is deformed by press-fitting.

FIG. 6 is an explanatory view showing a state in which the distance from the rotation center to the drum surface due to loose fit is deviated.

FIG. 7 is a graph for explaining non-uniformity from the rotation center of the photosensitive drum to the drum surface.

FIG. 8 is an explanatory view of an embodiment in which a protrusion is made hemispherical.

FIG. 9 is an explanatory view of an embodiment in which a protrusion is formed in a rib shape.

[Explanation of symbols]

 A: Image forming apparatus 1: Exposure apparatus 2: Photoconductor drum 3: Primary charging device 4: Developing device 4Bk: Black developing device 4C: Cyan developing device 4M: Magenta developing device 4Y: Yellow developing device 5: Transfer drum 6: Adsorption Roller 7: Adsorption charger 8: Transfer charger 9: Cleaner 10: Separation claw 11: Transport path 12: Fixing device 13: Static eliminator 14: Static eliminator 15: Static eliminator 16: Drum base 16a: Flange fitting part 17 Flange member 17a Hole 17b Guide part 17c Projection part 18 Cleaner

Claims (4)

(57) [Claims] 1. A cylindrical drum base having a photosensitive layer on an outer surface and having flange fitting portions at both ends in a longitudinal direction, and an outer diameter slightly smaller than an inner diameter of the flange fitting portion, wherein the flange fitting is performed. A flange member having a guide portion that can be fitted into the portion; and projection portions provided at a plurality of locations of the guide portion and having a distance from the rotation center of the photosensitive drum substantially equal to the inner diameter of the flange fitted portion. A photosensitive drum in which the protrusion is fitted into the flange fitting portion to attach a flange member to a drum base, wherein the protrusion is integrally formed with the flange member. 2. The projection has a distance from the rotation center of the photosensitive drum equal to or slightly larger than the inner diameter of the flange fitting portion, and the projection is pressed into the flange fitting portion. 2. The photosensitive drum according to claim 1, wherein the flange member is attached to the drum base. 3. When the flange member is inserted into and attached to the drum base, if the distance from the rotation center of the photosensitive drum to the surface of the drum base is deviated, the protrusion is located between the flange insertion part. And the difference between the maximum distance and the minimum distance from the rotation center of the photosensitive drum to the surface of the drum base during press-fitting is different from the distance from the rotation center of the photosensitive drum to the surface of the drum base during clearance fit. 2. The photosensitive drum according to claim 1, wherein an outer diameter of the projection and an inner diameter of the flange fitting portion are configured to be equal to a difference between a maximum distance and a minimum distance. 4. An electrophotographic image forming apparatus for developing a latent image formed on a photosensitive drum with a developer and transferring and recording the latent image on a recording medium, wherein the photosensitive drum according to any one of claims 1 to 3. An electrophotographic image forming apparatus, comprising: developing means for developing a latent image formed on the photosensitive drum; and transferring means for transferring an image developed by the developing means to a recording medium. apparatus.