JP5712567B2 - Photosensitive drum unit, process cartridge including the photosensitive unit, and image forming apparatus - Google Patents

Description

  The present invention relates to a photosensitive drum unit provided in an image forming apparatus such as a laser printer or a copying machine, a process cartridge including the photosensitive unit, and an image forming apparatus.

2. Description of the Related Art Image forming apparatuses such as laser printers and copiers are provided with a process cartridge in the main body of the image forming apparatus.
The process cartridge is a member for transferring contents to be represented such as characters and figures to a recording medium such as paper, and is provided with a photosensitive drum unit on which the contents to be transferred are formed. Accordingly, the process cartridge is also provided with various means for forming the content to be transferred on the photosensitive drum unit. Examples thereof include means for performing development, charging, and cleaning.

  The photosensitive drum provided in the photosensitive drum unit is a cylindrical member. When the photosensitive drum is actuated, the photosensitive drum rotates about the axis of the cylinder, and noise may be generated along with the rotation. The following can be cited as causes of noise. That is, if a charging roller is used as a device for charging the photosensitive drum, and an AC voltage is superimposed in addition to a DC voltage to uniformly charge the photosensitive drum, the static between the charging roller and the photosensitive drum is obtained. Noise is generated by the same principle as that of a capacitive speaker due to the capacitance. Further, when cleaning is performed by bringing the cleaning blade into contact with the photosensitive drum, the cleaning blade may chatter, and noise may be generated at this time.

  As means for reducing these noises, Patent Documents 1 to 3 disclose a technique of inserting a damping member inside the photosensitive drum.

Japanese Patent No. 3257267 JP 2005-62463 A Japanese Patent Laid-Open No. 2005-4005

  However, when these damping members are inserted, the manufacturing cost of the photosensitive drum increases, and therefore, a method for manufacturing the damping member has been devised in order to reduce the cost as much as possible. Specifically, after forming into a cylindrical shape by extrusion and then forming a slit by machining, a method of forming a slit from the beginning by extruding by devising a mold, recycled resin, etc. In order to use low-cost raw materials and to shorten the cycle time, methods such as enhancing cooling and increasing the extrusion speed have been used. However, these cost reduction measures may deteriorate the dimensional accuracy of the damping member and the shape accuracy such as roundness, straightness, and cylindricity, and may cause deterioration of the accuracy of the photosensitive drum. .

  That is, the method of forming slits by extrusion molding is difficult to maintain accuracy due to its nature, the roundness deteriorates, and depending on the cooling conditions, the outer diameter differs in the longitudinal direction after extrusion due to residual stress. Easy to do. Therefore, if the die (mold) is poorly designed, uneven thickness may occur, or the roundness and the outer diameter difference before and after extrusion after cutting may be further emphasized.

  Also in the case of injection molding, measures such as shortening the molding cycle have been made by using inexpensive raw materials, enhancing cooling, and improving mold release properties. As a method for improving the releasability, an axial taper may be provided on the outer surface of the damping member. However, these cost reduction measures may deteriorate the dimensional accuracy of the damping member and the shape accuracy such as roundness, straightness, and cylindricity, and may contribute to deterioration of the accuracy of the photosensitive drum. It was.

On the other hand, image forming apparatuses such as laser printers and copiers are required to have higher precision in the photosensitive drums with the progress of higher definition and colorization. Deterioration in accuracy has become a problem. In particular, when the shake accuracy of the photosensitive drum is deteriorated, image blur, distortion, and color shift appear.
Here, “runout” is the maximum radial displacement measured at an arbitrary axial position when the photosensitive drum is rotated with respect to the central axis of the photosensitive drum, and is defined by JIS B0621. Means runout.

  The conventional photosensitive drum units as described in Patent Documents 1 to 3 have a certain effect from the viewpoint of vibration suppression. However, when a large number of photosensitive drum units are manufactured at low cost, especially when a plurality of damping members are used for one photosensitive drum unit, the photosensitive drum unit that produces a large number of photosensitive drums while keeping the deflection of the photosensitive drum below a certain level. In view of this, no consideration has been given to suppressing variations in the fluctuation of the photosensitive drum between the two. Therefore, in the prior art, there has been a problem that there is a large variation in the shake of the photosensitive drum between the photosensitive drum units.

  SUMMARY OF THE INVENTION Accordingly, the present invention provides a photosensitive drum unit capable of suppressing the fluctuation of the photosensitive drum from one individual to another even when the photosensitive drum is controlled to a certain level or less and produced at a low cost. Is an issue. In addition, a process cartridge and an image forming apparatus including the photosensitive drum unit are provided.

  The present invention will be described below. Here, for ease of understanding, reference numerals of the drawings are given in parentheses, but the present invention is not limited to this.

  The invention according to claim 1 includes a cylindrical photosensitive drum (11), and a cylindrical damping member (20, 30) fixed without sliding inside the cylindrical shape of the photosensitive drum. The damping member has a cylindrical outer peripheral surface that is in contact with the inner surface of the photosensitive drum over the entire length in the axial direction, and has outer diameters at both ends in the cylindrical axial direction of the damping member. Are formed in such a manner that a plurality of damping members are arranged in the axial direction of the photosensitive drum, and adjacent damping members are arranged so that the sides having large outer diameters do not face each other. A photosensitive drum unit (10).

According to a second aspect of the present invention, in the photosensitive drum unit (10) of the first aspect, adjacent damping members are arranged such that the sides having the smaller outer diameters face each other and the damping members are spaced apart . It is characterized by.

  According to a third aspect of the present invention, in the photosensitive drum unit (10) according to the first or second aspect, the damping member (20, 30) is provided with a slit (22, 32) along the axial direction. It is characterized by being.

  According to a fourth aspect of the present invention, there is provided a housing (2), the photosensitive drum unit (10) according to any one of claims 1 to 3 disposed in the housing, and a photosensitive member disposed in the housing. And a means for charging the body drum.

  A fifth aspect of the present invention is an image forming apparatus that includes the process cartridge (1) according to the fourth aspect and forms an image by applying a rotational driving force to the process cartridge.

  According to the present invention, with respect to the shake of the photosensitive drum unit, it is possible to suppress the fluctuation of the shake among the individual units and to keep the magnitude of the shake to a certain level or less.

It is a schematic diagram of a process cartridge. FIG. 2A is an external perspective view of the photosensitive drum unit, and FIG. 2B is a perspective view illustrating a part thereof. It is an external appearance perspective view of a damping member. 4A is a front view of the damping member, FIG. 4B is a rear view of the damping member, and FIG. 4C is a left side view of the damping member. It is a figure for demonstrating arrangement | positioning of a damping member. It is a figure for demonstrating the positional relationship of a slit among arrangement | positioning of a damping member. It is a figure for demonstrating a shake measuring device, Fig.7 (a) is a front view, FIG.7 (b) is a side view.

  The above-described operation and gain of the present invention will be clarified from embodiments for carrying out the invention described below. Hereinafter, the present invention will be described based on embodiments shown in the drawings. However, the present invention is not limited to these embodiments.

  FIG. 1 is a diagram schematically showing a configuration of a process cartridge 1 including a photosensitive drum unit 10 (see FIG. 2) according to one embodiment. By inserting and arranging such a process cartridge 1 in an image forming apparatus main body (not shown), an image forming apparatus such as a laser printer, a copying machine, or a facsimile functions. This will be described in detail below.

  The process cartridge 1 has a housing 2 that forms the outline of the process cartridge 1, and various components are contained inside the housing. Specifically, the present embodiment includes a photosensitive drum unit 10 (see FIG. 2), a charging roller 3, a developing roller 4, a regulating member 5, a transfer unit 6, and a cleaning blade 7. When a medium such as paper moves along the line indicated by P in FIG. 1 inside the process cartridge 1, an image is formed on the medium.

  The photosensitive drum unit 10 is formed with characters, figures and the like to be transferred to a recording medium such as paper. FIG. 2A is an external perspective view of the photosensitive drum unit 10. FIG. 2B shows a perspective view of a part of the photosensitive drum unit 10. As can be seen from FIGS. 2A and 2B, the photosensitive drum unit 10 includes a photosensitive drum 11, a flange 12, a drive flange 13, and damping members 20 and 30. Hereinafter, the photosensitive drum unit 10 will be described with reference to FIG.

The photosensitive drum 11 is a member in which a photosensitive layer is coated on the outer peripheral surface of a cylindrical drum cylinder. The drum cylinder is configured by applying a photosensitive layer to a conductive cylindrical cylinder such as aluminum. The photosensitive layer to be formed is not particularly limited, and known ones can be applied depending on the purpose.
A drive flange 13 is attached to one end of the photosensitive drum 11 as will be described later, and a flange 12 is disposed at the other end. Further, as can be seen from FIG. 2B, damping members 20 and 30 are inserted into the cylindrical cylinder.

  The flange 12 is a member formed of resin, and a fitting portion that is fitted inside the cylinder of the photosensitive drum 11 and a bearing portion that is arranged so as to cover one end surface of the photosensitive drum 11 are formed coaxially. Has been. The bearing portion has a disk shape that covers the end surface of the photosensitive drum 11, and is provided with a portion that receives a shaft provided in the image forming apparatus main body. Further, a ground plate made of a conductive material is disposed on the flange 12, thereby electrically connecting the photosensitive drum 11 and the image forming apparatus main body.

  The drive flange 13 is a member that is attached to the end of the photosensitive drum 11 opposite to the flange 12. The drive flange 13 receives the driving force from the image forming apparatus main body and rotates the photosensitive drum unit 10 itself, and also transmits the rotational force to other rollers (such as a charging roller) adjacent to the photosensitive drum unit 10. Have Specifically, the drive flange 13 has a bearing (not shown) that receives a rotation shaft included in the main body of the image forming apparatus, and receives a rotational driving force from the main body of the image forming apparatus. Further, as can be seen from FIGS. 2A and 2B, a gear shape is formed on the outer peripheral surface 13a of the drive flange 13, and the gear shape provided on the adjacent roller (charging roller or the like). Rotation driving force is transmitted by meshing with.

  The damping members 20 and 30 are substantially cylindrical members that are inserted inside the photosensitive drum 11. FIG. 3 is a perspective view of the vibration damping member 20. FIG. 4 shows a two-dimensional diagram. 4A is a front view, FIG. 4B is a rear view, and FIG. 4C is a left side view. Since the shape of the damping member 30 is the same as that of the damping member 20, only the damping member 20 will be described here, and the description of the damping member 30 will be omitted.

  As can be seen from FIGS. 3 and 4, the damping member 20 is a cylindrical member. However, the damping member 20 is provided with a slit 22 having a predetermined width along a cylindrical axis in a cylindrical main body 21. Therefore, as can be seen from FIG. 4C, the damping member 20 is C-shaped in a cross section orthogonal to the cylindrical axis. In addition, a groove 23 is formed in parallel with the slit 22 on the outer peripheral surface of the main body 21 on the opposite side in the diameter direction of the portion where the slit 22 is provided.

As described above, by providing the slit 22 in the main body 21, when the vibration damping member 20 is inserted into the photosensitive drum 11, the vibration damping member is bent to reduce the outer diameter to facilitate insertion into the photosensitive drum. can do. Further, when the main body 21 is disposed in the photosensitive drum 11, the vibration damping member can be fixed in the photosensitive drum 11 by pressing the photosensitive drum 11 from the inside.
Further, by providing the groove 23 on the side opposite to the slit 22, the vibration damping member 20 is further easily bent, and the pressing force can be controlled by the width and depth of the groove.

Here, the specific magnitude | size of each structure with which the damping member 20 is equipped is not specifically limited, It can change suitably.
However, the outer diameter of the main body 21 is preferably slightly larger than the inner diameter of the photosensitive drum 11. Thereby, the damping member 20 can be brought into close contact with the inner surface of the photosensitive drum 11 by the elastic force of the main body 21.
The main body 21 preferably has a thickness of 2 mm or more and a length of 50 mm or more. This is because the greater the weight of the main body, the greater the effect of vibration suppression.
Further, in order to reduce the outer diameter to such an extent that it can be easily inserted into the photosensitive drum, and from the viewpoint of the effect of absorbing elastic deformation, the width of the slit 22 is preferably 1 mm or more. The depth of the groove 23 is 0.5 mm or more from the viewpoint of ease of bending when inserted into the photosensitive drum, strength of adhesion to the inner surface of the photosensitive drum after insertion, and vibration suppression effect. Preferably there is.

  Further, as can be seen from FIGS. 4A and 4B, the outer diameter of the damping member 20 is tapered so as to be different between the one end side and the other end side in the axial direction. However, in FIG. 4, the degree of taper is exaggerated for easy understanding. The taper angle α is preferably as small as possible, and is set to 0.3 ° or less, more preferably 0.1 ° or less. When the damping member is manufactured by injection molding, the cycle time can be shortened in order to reduce the manufacturing cost. As one method, it is preferable to provide a taper to improve the releasability.

  Such damping members 20, 30 are molded from resin. Examples of the resin include ABS, polyethylene, polystyrene, polypropylene, acrylic, polyvinyl chloride, polycarbonate, various rubbers, and the like, and may be a mixture of a plurality of materials. Recycled resins such as PET bottles can also be used. A mixture of these resins with an inorganic filler may be used. By kneading the inorganic filler, shrinkage of the base resin during production can be suppressed, and a highly accurate vibration damping member can be manufactured. It becomes possible. It is also possible to improve the vibration damping effect by kneading the inorganic filler. Examples of the inorganic filler include talc, calcium carbonate, mica scale, glass, and carbon fiber.

  Further, in addition to the above-described shape, the damping members 20 and 30 may be formed with a C surface or a taper in the vicinity of the end thereof. This facilitates insertion into the photosensitive drum 11.

Such a damping member can be manufactured by extrusion molding, slitting, injection molding, or the like.
In the case of extrusion molding, a die (die) corresponding to the cross-sectional shape of the vibration damping member is prepared, and a molten or semi-molten material is introduced into the die and pressed. Thereafter, individual damping members can be manufactured through cooling and cutting processes.
Slit processing is a method of forming slits and grooves in a cylindrical member formed of a material of a damping member by cutting. Here, the slit processing can be formed at the time of extrusion by devising an extrusion die.
In injection molding, a damping member is manufactured by injecting and cooling a molten material into a mold corresponding not only to the cross-sectional direction but also to the axial direction thereof.

  The photosensitive drum unit 10 having each member as described above is formed by combining as follows. That is, in the present embodiment, as can be seen from FIG. 2B, the two damping members 20 and 30 are arranged in the axial direction inside the cylindrical shape of the photosensitive drum 11. FIG. 5 shows a diagram for explanation. FIG. 5A is a diagram illustrating one mode of arrangement of the damping members 20 and 30 in the photosensitive drum 11, and FIG. 5B is a diagram illustrating another mode.

In the embodiment of FIG. 5A, the two damping members 20 and 30 are arranged such that the sides with the smaller outer diameters face each other. Moreover, in the aspect of FIG.5 (b), it arrange | positions so that the side with a small outer diameter and the side with a large outer diameter may face in the two damping members 20 and 30. FIG. That is, in this invention, it arrange | positions so that the sides with a large outer diameter may not face each other.
As a result, in the plurality of photoconductor units, the magnitude of the shake between the photoconductor units can be suppressed to a predetermined size or less, and variations can be suppressed. Accordingly, it is possible to provide a photosensitive drum unit having a stable quality.
In the conventional photosensitive drum unit, even if the damping member is inserted, the fluctuation of the shaking between the photosensitive drum units is large. Among them, many products with large fluctuations were included, and such products could not be provided as products and were wasted.
On the other hand, according to the present invention, it is possible to suppress the variation between the photosensitive drum units, and it is possible to suppress the absolute value of the shake within a predetermined range. Therefore, it is possible to efficiently provide a photosensitive drum unit having a stable quality.

  In FIG. 5, only the side where the outer diameter of the damping members 20 and 30 is large is shown as being in contact with the inner surface of the photosensitive drum 11, but this is for ease of viewing, and the damping is actually performed. The inner surface of the photosensitive drum 11 is in contact with the entire length in the axial direction due to the effect of bending due to the shape and material of the member such as the slit of the vibrating members 20 and 30. Accordingly, the force for pressing the photosensitive drum 11 varies depending on the vibration damping members 20 and 30. That is, the larger the outer diameter of the damping member, the larger the force for pressing the photosensitive drum from the inside, and the greater the force of elastically deforming the photosensitive drum when the circularity of the damping member is poor. Therefore, if the vibration control members are arranged so that the large outer diameter sides face each other, the pressing force for elastically deforming the photosensitive drum becomes larger, and the deflection accuracy of the photosensitive drum is deteriorated.

  In this embodiment, the example which has arrange | positioned the two damping members 20 and 30 was shown, However, It is not limited to this, You may arrange | position three or more damping members. At this time, the sides having large outer diameters are prevented from facing each other at any position.

In the present embodiment, the damping members 20 and 30 include the slits 22 and 32 and the grooves 23 and 33, but these are not necessarily required. However, when the slits 33 and 32 are provided, it is preferable to arrange the damping members 20 and 30 as follows. FIG. 6 shows an explanatory diagram. 6A is a perspective view, and FIG. 6B is a view seen from the direction indicated by the arrow VIb in FIG. 6A. In FIG. 6A, the two damping members 20 and 30 are shown apart from each other for easy understanding, but in actuality, they are arranged close to each other as shown in FIG. In FIG. 6B, the positions of the slits 32 and the grooves 33 of the damping member 30 are indicated by broken lines.
In the vibration damping member 30, the main body 31 corresponds to the main body 21, the slit 32 corresponds to the slit 22, and the groove 33 corresponds to the groove 23. The broken line A is the axis of the photosensitive drum 11, the broken line B is the direction in which the slit 22 of the damping member 20 extends (parallel to the axis), and the broken line C is the direction in which the slit 32 of the damping member 30 extends (parallel to the axis). Each represents.

As can be seen from FIG. 6, the vibration damping member 20 and the vibration damping member 30 are preferably arranged as follows. That is, consider the angle formed by the radial direction connecting the axis A and the slit 22 of the damping member 20 and the radial direction connecting the axis A and the slit 32 of the damping member 30. This angle may be on the side of 0 to 180 degrees and on the side of 0 to -180 degrees. When the absolute value is θ, θ is 60 degrees or more and 120 degrees or less. Preferably it is 90 degrees.
Therefore, the position of the slit 22 of the damping member 20 has an angle of 60 degrees or more and 120 degrees or less around the axis centering on the axis of the photosensitive drum 11 with respect to the position of the slit 32 of the damping member 30. Has been placed.
Thereby, in the plurality of photoconductor units, it is possible to further suppress fluctuations between the photoconductor units to be equal to or less than a predetermined size, thereby suppressing variations. Accordingly, it is possible to provide a photosensitive drum unit having a stable quality.

  Here, the damping members 20 and 30 are fixed so as not to slide inside the photosensitive drum 11 even when the photosensitive drum 11 rotates. The damping members 20 and 30 are fixed to the inner side of the photosensitive drum 11 by holding the main body 21 by the internal pressure of the elastic deformation or using an adhesive.

  After the damping members 20 and 30 are inserted as described above, the flange 12 and the drive flange 13 are attached to both ends of the photosensitive drum 11 to form the photosensitive drum unit 10.

  Returning to FIG. 1, the description of the process cartridge 1 will be continued. The charging roller 3, the developing roller 4, the regulating member 5, the transfer unit 6, and the cleaning blade 7, which are other configurations provided inside the housing 2 of the process cartridge 1, are as follows.

The charging roller 3 charges the photosensitive drum 11 by applying a voltage from the image forming apparatus main body. This is performed by the charging roller 3 rotating following the photosensitive drum 11 and contacting the outer peripheral surface of the photosensitive drum 11.
The developing roller 4 is a roller that supplies a developer to the photosensitive drum 11. Then, the electrostatic latent image formed on the photosensitive drum 11 is developed by the developing roller 4. The developing roller 4 includes a fixed magnet.
The regulating member 5 is a blade that adjusts the amount of developer adhering to the outer peripheral surface of the developing roller 4 and imparts triboelectric charge to the developer itself.
The transfer unit 6 is a roller for transferring an image formed on the photosensitive drum 11 to a recording medium such as paper.
The cleaning blade 7 is a blade that contacts the outer peripheral surface of the photosensitive drum 11 and removes the developer remaining after the transfer by the tip.

  Each of the above-mentioned rollers is housed rotatably inside the housing 2. That is, each roller rotates inside the housing 2 as necessary to exert its function.

  Here, each roller and blade provided in the process cartridge 1 has been described, but the members provided here are not limited thereto, and other members, parts, developer, etc. that are normally provided in the process cartridge Is preferably provided.

  Such a process cartridge 1 is mounted on the image forming apparatus main body and operates. Details are as follows. When an image is formed, the photosensitive drum 11 is rotated by a driving force from the image forming apparatus main body and charged by the charging roller 3. In this state, the photosensitive drum 11 is irradiated with laser light corresponding to image information using various optical members provided therein, and an electrostatic latent image based on the image information is obtained. This latent image is developed by the developing roller 4.

  On the other hand, a recording medium such as paper is set in the main body of the image forming apparatus, and is transported to a transfer position by a feed roller, a transport roller or the like provided in the main body of the image forming apparatus. A transfer unit 6 is disposed at the transfer position. A voltage is applied to the transfer unit 6 as the recording medium passes, and an image is transferred from the photosensitive drum 11 to the recording medium. Thereafter, the image is fixed to the recording medium by applying heat and pressure to the recording medium. Then, the recording medium on which the image is formed is discharged from the image forming apparatus main body by a discharge roll or the like.

  The following examples further illustrate the invention. However, the present invention is not limited to the examples. In this embodiment, 10 units (No. 1 to No. 10) of the photosensitive drum units arranged as shown in FIG. 5A and 10 units (No. 1) of the photosensitive drum units arranged as shown in FIG. No. 11 to No. 20) and 10 units (No. 21 to No. 30) of photosensitive drum units arranged so as to be reversed in the left and right directions in FIG. In addition, as a comparative example, 10 units of photosensitive drum units (No. 31 to No. 40) in which two damping members having large outer diameters face each other were prepared and the shake was measured. Further, θ shown in FIG. 6 was 90 degrees.

  In this embodiment, the photosensitive drum is made of an aluminum alloy (alloy number 3003 defined by JIS standard), and has an outer diameter of 30 mm, a thickness of 0.75 mm, and a length of 340 mm. The damping member is made of a resin in which talc is mixed with ABS, and has an outer diameter of 28.8 mm, a length of 100 mm, a wall thickness of 4.4 mm, a groove width of 2 mm, a groove depth of 0.8 mm, and a slit width of 3.0 mm.

The runout was measured as follows. FIG. 7 shows a schematic diagram of a shake measuring machine. FIG. 7 shows a state at the time of measurement. FIG. 7A is a front view and FIG. 7B is a side view. The shake measuring machine includes a motor, a joint, a high-precision spindle unit, and a measuring roller which are arranged on the left and right sides of the photosensitive drum, respectively. This unit can be retracted outward in the axial direction of the photosensitive drum by an air cylinder and an LM guide (not shown). Further, an anti-swaying roller is provided on the upper portion of the photosensitive drum, and can be raised and lowered by an air cylinder (not shown) when the unit moves forward and backward. A drum cradle is provided below the photosensitive drum, and can be raised and lowered in two stages by an air cylinder (not shown).
Before the measurement, the left and right units are moved backward, the rocking roller is raised, and the drum cradle is raised to a position where the photosensitive drum can be easily placed. When the photosensitive drum is placed on the drum cradle, the drum cradle is lowered by one step, the left and right units move forward, and the measuring roller is inserted into the photosensitive drum. Next, the drum cradle is lowered one more stage to place the photosensitive drum on the measuring roller, and at the same time, the anti-sway roller descends to stop the drum from shaking.
In this state, the left and right motors are rotated, the amount of displacement on the upper side of the photosensitive drum is measured with a laser measuring machine, and this is used as a measured value of shake. As the laser measuring machine, an Anritsu laser outer diameter measuring machine (detection unit: KL1003BN, display unit: KL3000A) was used.
After the measurement is completed, the anti-sway roller is raised and the drum cradle is raised by one step, the photosensitive drum is moved away from the measurement roller, the left and right units are retracted, and the drum cradle is raised by one more step. Then, take out the photoconductor drum after measurement.
Here, the rotation of the measuring roller is manufactured to be 1 μm or less, and the vibration of the photosensitive drum can be measured with high accuracy. Usually, since the shake of the photosensitive drum is maximum near the center, the laser measuring machine is arranged in the center of the drum, and the measured value is used as the shake value. In addition, the total runout defined by the JIS standard must be measured by rotating it around the center axis of the photoconductor drum. However, with this measuring machine, the inner surface of the end of the photoconductor drum is used as a reference. It also includes the effects of roundness and thickness deviation at the end.
Table 1 shows the results.

As can be seen from Table 1, no. 1-No. No. 30 was able to keep the runout smaller than 30 μm. On the other hand, no. 31-No. In 40, there was a case where the deflection was larger than 30 μm or more.
Also, from the viewpoint of variation, as can be seen from the standard deviation, No. 1-No. The example of 30 is No. 31-No. Better than 40.

DESCRIPTION OF SYMBOLS 1 Process cartridge 10 Photosensitive drum unit 11 Photosensitive drum 12 Flange 13 Drive flange 20 Damping member 21 Main body 22 Slit 23 Groove 30 Damping member 31 Main body 32 Slit 33 Groove

Claims (5)

A cylindrical photosensitive drum;
A cylindrical damping member fixed without sliding inside the cylindrical shape of the photosensitive drum,
The damping member has a cylindrical outer peripheral surface that is in contact with the inner surface of the photosensitive drum over the entire axial length, and has an outer diameter at both ends of the cylindrical axial direction of the damping member. Are formed differently,
A plurality of the damping members are arranged in the axial direction of the photosensitive drum, and the adjacent damping members are arranged so that the sides having the larger outer diameters do not face each other. 2. The photosensitive drum unit according to claim 1, wherein the vibration damping members adjacent to each other are arranged such that the sides having the smaller outer diameters face each other and the vibration damping members are spaced apart from each other .   The photosensitive drum unit according to claim 1, wherein the damping member is provided with a slit along an axial direction.   A process cartridge comprising: a housing; and the photosensitive drum unit according to claim 1 disposed in the housing; and means for charging the photosensitive drum disposed in the housing.   An image forming apparatus comprising the process cartridge according to claim 4 and forming an image by applying a rotational driving force to the process cartridge.

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