JP2023152796A - Image forming apparatus and photoreceptor drum assembly set - Google Patents

Abstract

To provide an image forming apparatus that has a plurality of photoreceptor drum assemblies arranged in one housing, and that can prevent the generation of an unpleasant beat sound.SOLUTION: An image forming apparatus is such that: in at least half of a plurality of photoreceptor drum assemblies, the absolute value of the difference between the mass of each photoreceptor drum assembly and the average value of the masses of all the photoreceptor drum assemblies satisfies being less than 0.01% or 0.80% or more relative to the average value.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image forming apparatus such as a copying machine or a printer, and a photosensitive drum assembly set.

In printers, copiers, etc., when a charged electrophotographic photoconductor (OPC) is irradiated with light, the charge is removed from that area and an electrostatic latent image is created.Toner adheres to the electrostatic latent image to obtain an image. I can do it.

Image forming apparatuses using such electrophotographic technology are generally equipped with a charging member, an exposure device, a developing device, a transfer device, etc. in addition to an electrophotographic photoreceptor.
In the image forming apparatus, first, the surface of the photoreceptor is charged by a charging member, and then an electrostatic latent image is formed on the surface of the photoreceptor by irradiating the photoreceptor with light carrying image information using an exposure device. Next, a developing device brings the toner into contact with the surface of the photoreceptor to form a toner image corresponding to the electrostatic latent image, and a transfer device transfers the toner image onto the transfer target and heats and melts it to fix it. The print is completed.
At this time, methods for charging the photoreceptor with a charging member include a non-contact charging method represented by corona charging and the like, and a contact charging method represented by brush charging.

In addition, the image forming apparatus is equipped with a developing device for multiple colors around one photoreceptor, and forms a color image on the photoreceptor, and then transfers this toner image to form a color image. There are also so-called tandem-type devices, which are equipped with individual developing devices on photoreceptors to form monochromatic images, are placed side by side, and are sequentially overlaid and transferred to form a color image. Widely used.

Incidentally, in image forming apparatuses employing the above-mentioned contact charging method, since uneven charging tends to occur if only a DC voltage is used, the applied voltage is generally a DC voltage with an AC voltage superimposed thereon.
However, when a DC voltage superimposed with an AC voltage is applied to the charging device, there is a problem in that a harsh high-frequency sound is generated. This was thought to be caused by charging noise when the photoreceptor was charged with an alternating current voltage and vibrations when the photoreceptor came into contact with a member such as a cleaning blade.
As a solution to this problem, methods have been proposed such as inserting a damping member into the photoreceptor or increasing the thickness of the conductive support of the photoreceptor.

For example, Patent Document 1 (Japanese Unexamined Patent Publication No. 2008-203850) describes a hollow cylindrical base as an electrostatic imaging drum that can substantially eliminate harsh acoustic noise by preventing or suppressing acoustic resonance in the imaging member. an electrostatographic imaging drum comprising: at least one imaging layer disposed on a hollow cylindrical gas; and an acoustic attenuating material at least partially applied to and in close contact with the inner surface of the hollow cylindrical substrate. is disclosed.

Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2009-42440) discloses a method that prevents the occurrence of noise, chatter, and resonance sound of the photoreceptor due to vibration, and provides stable and good image quality without image unevenness or poor cleaning. As an electrophotographic photoreceptor that enables this, the inner surface of the hollow cylindrical photoreceptor has a vibration damping member whose cross section perpendicular to the axis of the photoreceptor is C-shaped, and the C-shaped end of the vibration damping member has An electrophotographic photoreceptor comprising a cylindrical holding member having a convex portion extending toward the center of a C-shaped cross section, and a concave portion for holding the convex portion on the inner surface of the vibration damping member. is disclosed.

Patent Document 3 (Japanese Unexamined Patent Publication No. 2014-102374) describes a cylindrical member as a vibration damping member that can more reliably suppress the vibration of the photoreceptor drum below a certain level and ease the conditions for its installation. A holding member, a swinging member having at least a portion disposed inside the holding member in a cylindrical shape, and a member connecting the swinging member to the holding member so that the swinging member can swing. A vibration damping member including an elastic member is disclosed.

Patent Document 4 (Japanese Unexamined Patent Publication No. 2015-59990) describes an image holding body that can suppress vibrations occurring in the image holding body, including a cylinder having a cylindrical shape and holding an image on its surface, and a cylinder that holds an image on its surface. A transmission member fixed to one axial end of the cylindrical body and transmitting rotational force from a drive source; and a transmission member fixed to the other axial end of the cylindrical body and rotatably supported by a cylindrical shaft. The supporting member is fitted into the cylindrical body and supported by the cylindrical body between the transmission member and the supporting member, and the center of gravity in the axial direction is at the center of the cylindrical body in the axial direction. An image holder is disclosed, comprising: a contact member located closer to the other end than the other end. Since the other end of the image holder is a sliding bearing, when the image holder vibrates, the other end becomes a free end and vibrates. Furthermore, since the mass on the other end side is increased, shaking on the other end side of the image carrier is suppressed. By suppressing the shaking on the other end side of the image holding body, vibrations occurring in the image holding body are suppressed.

Japanese Patent Application Publication No. 2008-203850 JP2009-42440A Japanese Patent Application Publication No. 2014-102374 JP2015-59990A

As mentioned above, the "harsh high-frequency sound" that occurs when a DC voltage superimposed on an AC voltage is applied to a charging device can be solved by inserting a damping member inside the photoreceptor or by removing the conductive material of the photoreceptor. This problem can be solved to some extent by increasing the thickness of the support.
However, in the case of an image forming apparatus that has a configuration in which multiple photoreceptors are arranged in one housing, such as a tandem-type image forming apparatus, even if such measures are implemented, it may cause a ``disgusting sound''. The problem was that it produced an "unpleasant humming sound" that was different from "high-frequency sound."

Therefore, an object of the present invention is to provide a structure in which a plurality of photoconductors, more specifically, a "photoconductor drum assembly" including a photoconductor drum and flange members at both ends thereof are arranged in one housing. An object of the present invention is to provide an image forming apparatus that can suppress generation of unpleasant humming noise.

In order to solve this problem, the present invention suppresses the generation of "unpleasant humming noise" by adjusting the mass of each photoreceptor.

The gist of the present invention exists in [1] to [8] below.

[1] An image forming apparatus having a configuration in which a plurality of photoreceptor drum assemblies are arranged in one housing, in which at least half of the plurality of photoreceptor drum assemblies have a mass of each photoreceptor drum assembly. and an average value of the mass of all photoreceptor drum assemblies, the absolute value of which is less than 0.01% or 0.80% or more of the average value.

[2] The plurality of photoreceptor drum assemblies each include a photoreceptor drum, and a coating material is attached to the inner peripheral surface of the photoreceptor drum of at least one of the photoreceptor drum assemblies, [1] The image forming apparatus described in .

[3] The image forming apparatus according to [1] or [2], wherein a mass adjustment member is disposed on at least one photoreceptor drum assembly among the plurality of photoreceptor drum assemblies.
[4] The image forming apparatus according to [3], wherein the mass adjustment member is a resin member or a metal member.

[5] Each of the plurality of photoreceptor drum assemblies includes a photoreceptor drum, and the photoreceptor drum of at least one of the photoreceptor drum assemblies has a configuration in which a cutting portion is provided. The image forming apparatus according to any one of [4].

[6] Each of the plurality of photoreceptor drum assemblies includes a photoreceptor drum and a flange member at both ends of the photoreceptor drum, and the flange of at least one photoreceptor drum assembly among the plurality of photoreceptor drum assemblies The image forming apparatus according to any one of [1] to [5] above, wherein the mass of the member is different from the mass of the flange members of other photoreceptor drum assemblies.
[7] The image according to [6], wherein the shape of the flange member of at least one photoreceptor drum assembly among the plurality of photoreceptor drum assemblies is different from the shape of the flange member of the other photoreceptor drum assemblies. Forming device.

[8] A photoreceptor drum assembly set consisting of a plurality of photoreceptor drum assemblies, in which at least half of the plurality of photoreceptor drum assemblies have a mass that is greater than the mass of each photoreceptor drum assembly and the mass of all the photoreceptor drum assemblies. A photosensitive drum assembly set, wherein the absolute value of the difference from the average value is less than 0.01% or 0.80% or more with respect to the average value.

The image forming apparatus proposed by the present invention can suppress the generation of "unpleasant humming noise" by adjusting the mass of each photoreceptor drum assembly as described above.

FIG. 2 is a diagram illustrating a configuration example of an image composition device. FIG. 2 is a diagram illustrating a configuration example of an electrophotographic cartridge. FIG. 2 is a perspective view showing an example of a photoreceptor drum assembly. FIG. 2 is a cross-sectional view showing an example of a photoreceptor drum assembly. FIG. 3 is a partially cross-sectional perspective view showing a state in which a coating material is applied to the inner circumferential surface of a photoreceptor drum. (A) is a sectional view showing a state in which a mass adjustment member is disposed within the photoreceptor drum, and (B) is a perspective view of the mass adjustment member. (A) is a perspective view showing an example of a state in which a cutting portion is provided on the inner circumferential surface near the opening of the photoreceptor drum, and (B) is a cross-sectional view showing an enlarged view of the vicinity of the opening of the photoreceptor drum. It is a diagram. FIG. 7 is a perspective view showing another example in which a cutting portion is provided on the inner circumferential surface of the photoreceptor drum near the opening. FIG. 3 is a perspective view showing an example of a flange member attached to an end of a photoreceptor drum, in which (A) is a basic form, (B) is an example of a form with a hollowed out part, and (C) is a mating part. It is a figure which showed an example of the form which lengthened. FIG. 7 is a diagram showing a waveform image of the sound intensity when a humming sound is generated. A range of 3.6 seconds was extracted from the audio analysis graph (vertical axis: sound intensity, horizontal axis: time [seconds]) for the frequency of 2.0 to 2.5 kHz in Example 1, and the background part of the graph (black) was extracted. This is a color-coded diagram showing the waveform part of the sound (light color). A range of 3.6 seconds was extracted from the audio analysis graph for frequencies 2.0 to 2.5 kHz (vertical axis: sound intensity, horizontal axis: time [seconds]) in Example 2, and the background part of the graph (black) was extracted. This is a color-coded diagram showing the waveform part of the sound (light color). A range of 4.6 seconds was extracted from the audio analysis graph for frequencies 2.0 to 2.5 kHz (vertical axis: sound intensity, horizontal axis: time [seconds]) in Example 3, and the background part of the graph (black) was extracted. This is a color-coded diagram showing the waveform part of the sound (light color). A range of 3.6 seconds was extracted from the audio analysis graph (vertical axis: sound intensity, horizontal axis: time [seconds]) for the frequency of 2.0 to 2.5 kHz in Comparative Example 1, and the background part of the graph (black) was extracted. This is a color-coded diagram showing the waveform part of the sound (light color). A range of 3.6 seconds was extracted from the audio analysis graph (vertical axis: sound intensity, horizontal axis: time [seconds]) for the frequency of 2.0 to 2.5 kHz in Comparative Example 2, and the background part of the graph (black) was extracted. This is a color-coded diagram showing the waveform part of the sound (light color). A range of 1.8 seconds was extracted from the audio analysis graph (vertical axis: sound intensity, horizontal axis: time [seconds]) for the frequency of 2.0 to 2.5 kHz in Comparative Example 3, and the background part of the graph (black) was extracted. This is a color-coded diagram showing the waveform part of the sound (light color). A range of 4.6 seconds was extracted from the audio analysis graph (vertical axis: sound intensity, horizontal axis: time [seconds]) for the frequency of 2.0 to 2.5 kHz in Example 4, and the background part of the graph (black) was extracted. This is a color-coded diagram showing the waveform part of the sound (light color). A range of 4.6 seconds was extracted from the audio analysis graph (vertical axis: sound intensity, horizontal axis: time [seconds]) for the frequency of 2.0 to 2.5 kHz in Example 5, and the background part of the graph (black) was extracted. This is a color-coded diagram showing the waveform part of the sound (light color).

<<Image forming apparatus of the present invention>>
An image forming apparatus according to the present invention has a configuration in which a plurality of photosensitive drum assemblies are arranged in one housing.

Here, the term "photoreceptor drum assembly" includes a cylindrical photoreceptor drum and accessories that rotate together with the cylindrical photoreceptor drum. For example, the photoreceptor drum, materials or members attached to the inner peripheral surface of the photoreceptor drum or placed inside the photoreceptor drum, flange members attached to both ends of the photoreceptor drum, etc. rotate together with the photoreceptor drum. Therefore, it is included in the photoreceptor drum assembly. The term "mass of the photoreceptor drum assembly" means the total mass of these.

The present inventor investigated the cause of "unpleasant humming" in an image forming apparatus having a configuration in which a plurality of photoconductor drum assemblies are arranged in one housing, and found that each photoconductor drum assembly It was confirmed that this is because the peak frequency of the charging sound generated when charging with an AC voltage is slightly different between the photoreceptor drum assemblies. Furthermore, since the peak frequency of the charging sound (high-frequency sound) generated by each photoreceptor drum assembly is affected by the mass of each photoreceptor drum assembly, we focused on the relationship between the masses of each photoreceptor drum assembly. As a result, the "difference between the average value of the mass of each photoconductor drum assembly and the mass of all photoconductor drum assemblies" is adjusted to a specific ratio with respect to the average value, that is, greater than or equal to a specific value or less than a specific value. As a result, it was found that the generation of unpleasant humming noises could be suppressed.
Based on this knowledge, the image forming apparatus of the present invention sets the absolute value of the difference between the mass of each photoreceptor drum assembly and the average value of the masses of all photoreceptor drum assemblies to be a predetermined ratio with respect to the average value. It has been adjusted as follows.

Considering such problems and solution of the present invention, the present image forming apparatus of the present invention has a configuration in which a plurality of photosensitive drum assemblies are arranged in one housing, and other configurations. can be said to be arbitrary.

<<Image forming apparatus according to an example of an embodiment of the present invention>>
The present invention will be described below based on the configuration of an image forming apparatus (hereinafter referred to as "this image forming apparatus") according to an example of an embodiment of the present invention. However, the image forming apparatus of the present invention is not limited to this image forming apparatus. The present invention is not limited to the following embodiments, and can be implemented with various modifications within the scope of the gist.

This image forming apparatus functions as an image forming apparatus by having a configuration as shown in FIG. 1, for example.
Examples of the image forming apparatus include a laser printer, a copying machine, a facsimile machine, and the like.
The charging method in this image forming apparatus may be either a negative charging method in which the surface of the photoreceptor is charged with a negative charge or a positive charging method in which the surface of the photoreceptor is charged with a positive charge.

As shown in FIG. 1, this image forming apparatus includes a plurality of electrophotographic cartridges 1A, a secondary transfer belt 1B, a fixing roller 1C, and a secondary transfer roller 1D in a housing 2. However, it is optional to include members other than these as necessary.

Although FIG. 1 shows the case of four electrophotographic cartridges 1A disposed in the housing 2, the number is arbitrary as long as it is two or more. Among these, 2 or more are preferable, 4 or more are more preferable, while 16 or less are preferable, and 8 or less are more preferable.
As described later, the electrophotographic cartridge 1A includes a photoreceptor drum assembly 10, but when installing the photoreceptor drum assembly in an image forming apparatus, the electrophotographic cartridge may be configured as shown in FIG. 1 and then installed. However, it may be directly installed in the form of a photoreceptor drum assembly. Even when directly installed in the form of photoreceptor drum assemblies, the number of photoreceptor drum assemblies disposed in the housing 2 is arbitrary as long as it is two or more, and among these, two or more is preferable, and four or more are preferable. is more preferable, on the other hand, 16 or less is preferable, and 8 or less is more preferable.

<Electrophotographic cartridge 1A>
As shown in FIGS. 1 and 2, the plurality of electrophotographic cartridges 1A each have the same configuration, and the electrophotographic cartridge 1A includes a photosensitive drum assembly 10, a charging roller 3, a developing roller 4, a transfer roller 5, It includes a cleaning blade 8 and a toner container 9. However, the electrophotographic cartridge 1A is not limited to this configuration, and other configurations may be used as long as the photosensitive drum assembly 10 is included. That is, the above-mentioned member may not be provided, or another member may be provided.

The electrophotographic cartridge 1A can be configured to be detachable from the main body of an electrophotographic apparatus such as a copying machine or a laser beam printer. If the electrophotographic cartridge 1A is removable in this way, for example, when the photoreceptor or other members deteriorate, the electrophotographic cartridge 1A can be removed from the image forming apparatus main body and a new electrophotographic cartridge 1A can be installed in the image forming apparatus main body. This makes maintenance and management of the image forming apparatus easier.

In the electrophotographic cartridge 1A, images are recorded in the following manner.
When forming an image, the photoreceptor drum assembly 10 is rotated by the driving force from the image forming apparatus main body, and the surface of the photoreceptor drum assembly 10 (the photosensitive surface of the photoreceptor drum 11, which will be described later) is heated to a predetermined level by the charging roller 3. charged to a potential. Subsequently, the charged photosensitive surface of the photosensitive drum assembly 10 is exposed by an exposure device (not shown) according to the image to be recorded, and an electrostatic latent image is formed on the photosensitive surface. Next, the toner T in the toner container 9 is charged to a predetermined polarity, and in this state is carried while being carried by the developing roller 4, and comes into contact with the surface of the photoreceptor drum assembly 10, thereby forming the electrostatic latent image. A corresponding toner image is formed on the photosensitive surface of photoreceptor drum assembly 10. This toner image is then transferred to the secondary transfer belt 1B by the transfer roller 5, transferred to the recording paper P by the secondary transfer roller 1D, and fixed to the recording paper P by the fixing roller 1C. However, there are cases where the image is directly transferred onto the recording paper P without passing through the secondary transfer belt 1B. On the other hand, the toner T remaining on the photosensitive surface of the photosensitive drum assembly 10 without being transferred is scraped off by the cleaning blade 8 and collected.

<Photoreceptor drum assembly 10>
The photosensitive drum assembly 10 includes at least a photosensitive drum 11 and flange members at both ends thereof. The flange member includes a flange 12 at one end and a drive flange 13 at the other end.
The photoreceptor drum assembly of the present invention may have any other configuration as long as it includes a photoreceptor drum.

In the plurality of electrophotographic cartridges 1A, the shape and size of the photosensitive drum assemblies 10 are the same.

The photosensitive drum 11 may be any one having a configuration in which the outer peripheral surface of a cylindrical conductive support is coated with a photosensitive layer. The photosensitive layer may be of a single layer type or a laminated type having a charge generation layer and a charge transport layer, and other layers such as a protective layer may be laminated on the photosensitive layer. Furthermore, other layers such as an undercoat layer may be interposed between the conductive support and the photosensitive layer to improve adhesiveness or blocking properties.

The conductive support is a cylindrical body made of a conductive material such as aluminum.
Examples of the conductive material include metal materials such as aluminum, aluminum alloy, stainless steel, copper, and nickel, and resin materials imparted with conductivity by coexisting conductive powder such as metal, carbon, and tin oxide; Examples include aluminum, nickel, ITO (indium oxide tin oxide alloy), and the like. Resin, glass, paper, etc. may be vapor-deposited or coated on the surface of the conductive material. Furthermore, the surface of the cylinder made of a conductive material may be coated with a conductive material having an appropriate resistance value in order to control conductivity, surface properties, etc., or to cover defects. Furthermore, when using a metal material such as an aluminum alloy as the conductive support, the metal material may be used after being anodized.

A driving flange 13 is detachably attached to one end of the photosensitive drum 11 in the cylindrical axial direction, and a flange 12 is detachably attached to the other end.

The flange 12 is a member formed of resin, and includes a disc-shaped bearing portion 12a disposed to cover one end surface of the photoreceptor drum 11, and one surface side of the bearing portion 12a protrudes to cover the photoreceptor drum 11. A fitting portion 12b that is fitted inside the cylinder is formed coaxially with the fitting portion 12b.
The bearing portion 12a has a disk shape that covers the end surface of the photoreceptor drum 11, and is provided with a portion 12c for receiving a shaft provided in the main body of the image forming apparatus.
Further, a grounding plate (not shown) made of a conductive material is disposed on the flange 12, thereby electrically connecting the photosensitive drum 11 and the main body of the image forming apparatus.

The drive flange 13 is a member attached to an end of the photoreceptor drum 11 on the opposite side to the flange 12 .
The drive flange 13 rotates the photoreceptor drum assembly 10 itself in response to driving force from the image forming apparatus main body, and also transmits this rotational force to other rollers (such as a charging roller) adjacent to the photoreceptor drum assembly 10. It has the function of Specifically, the drive flange 13 includes a shaft 13a that connects to a rotation shaft of the image forming apparatus main body, and receives rotational driving force from the image forming apparatus main body.
Further, a gear 13b is formed on the outer peripheral surface of the drive flange 13, and rotational driving force is transmitted by meshing with a gear shape provided on an adjacent roller (such as a charging roller).
Furthermore, the drive flange 13 is formed with a fitting portion 13c that is fitted inside the cylinder of the photoreceptor drum 11 and is coaxial with the shaft 13a and the gear 13b.

<Adjustment of mass of photoreceptor drum assembly 10>
In this image forming apparatus, in at least half of the respective photoreceptor drum assemblies 10 in the plurality of electrophotographic cartridges 1A, the mass of each photoreceptor drum assembly 10 and the average value of all the masses of all the photoreceptor drum assemblies 10 are determined. It is preferable to adjust the absolute value of the difference to be less than 0.01% or 0.80% or more with respect to the average value.
By adjusting the mass of the plurality of photoreceptor drum assemblies 10 in this way, it is possible to prevent the generation of unpleasant humming noise in an image forming apparatus having a configuration in which a plurality of photoreceptor drum assemblies are disposed in one housing. Can be suppressed.
From this point of view, it is more preferable that the absolute value of the difference between the mass of each photoreceptor drum assembly 10 and the average value of the masses of the plurality of photoreceptor drum assemblies is 0.00% with respect to the average value.
On the other hand, it is preferable that the absolute value of the difference between the mass of each photoreceptor drum assembly 10 and the average value of the masses of the plurality of photoreceptor drum assemblies is 0.80% or more with respect to the average value, particularly 1. 00% or more, preferably 1.20% or more, and even more preferably 1.50% or more.

When the photoreceptor drum assembly 10 includes the photoreceptor drum 11 , the flange 12 , and the drive flange 13 , the mass of the photoreceptor drum assembly 10 is the total mass of the photoreceptor drum 11 , the flange 12 , and the drive flange 13 .
Furthermore, when the photoreceptor drum assembly 10 further includes members such as a vibration damping member within the photoreceptor drum 11, as will be described later, these also rotate together with the photoreceptor drum 11, so the mass of these members also increases. included in the mass of the body drum assembly 10.

Normally, even if you try to manufacture photoreceptor drums with high precision, there will be a difference of about ±0.5% in the target photoreceptor drum mass. It is considered that it is impossible for the amount to be less than 0.01%. On the other hand, a difference of ±0.8% or more from the target photoreceptor drum assembly mass, for example, the average mass of multiple photoreceptor drum assemblies, is a problem when manufacturing photoreceptor drums industrially. Considering accuracy, this is normally not possible. Therefore, in order to adjust the mass of each photoreceptor drum assembly so that at least half of the photoreceptor drum assemblies have a difference from the average value of less than 0.01% or 0.80% or more, as described above, Special mass adjustment means must be implemented for the required photoreceptor drum assembly.

As mentioned above, the means for adjusting the mass of the photoreceptor drum assembly 10, that is, the special mass adjustment means implemented for the photoreceptor drum assembly 10 that requires mass adjustment, include the following 1) to 4. ) can be cited as a representative example. Among the following methods 1) to 4), one method may be selected, or two or more methods may be selected and combined.

1) A method of adjusting the mass of the photoreceptor drum assembly 10 by attaching a coating material to the inner peripheral surface of the photoreceptor drum 11. 2) A method of adjusting the mass of the photoreceptor drum assembly 10 by arranging a mass adjustment member on the photoreceptor drum assembly 10. 3) A method of adjusting the mass of the photoreceptor drum assembly 10 by providing a cutting part in a part of the photoreceptor drum 11. 4) A method of adjusting the mass of the flange 12 or the driving flange 13, or both of them. Method of adjusting the mass of the photoreceptor drum assembly 10 by

However, the means for adjusting the mass of the photosensitive drum assembly 10 is not limited to the methods 1) to 4) above. Any method may be used as long as the mass can be adjusted without impairing the function of the photoreceptor drum assembly 10.

1) A method of adjusting the mass by applying a coating material to the inner circumferential surface of the photoreceptor drum 11 includes, for example, as shown in FIG. Examples include methods of coating. However, it is not limited to this.
In the case of 1) above, the coating material is attached to the photoconductor drum 11 of at least one photoconductor drum assembly 10 among the plurality of photoconductor drum assemblies 10 . For example, the coating material 20 is attached to the inner circumferential surface of the conductive support of the photoreceptor drum 11 of at least one photoreceptor drum assembly 10 .

The mass of the photoreceptor drum assembly 10 can be adjusted by adjusting the specific gravity and amount of coating material 20, such as coating thickness and coating width.
At this time, the coating material 20 may include adhesive resins such as cyanoacrylate resin, epoxy resin, acrylic resin emulsion, and modified silicone resin from the viewpoint of adhesiveness. Among these, cyanoacrylate resins are more preferred from the viewpoint of quick drying properties.
From the viewpoint of ease of coating work, it is preferable to apply the coating material on the inner circumferential surface at a position 10 to 100 mm from both ends of the conductive support, and at a position 10 to 50 mm from both ends of the conductive support. It is more preferable to apply it to the inner circumferential surface of. At this time, it is preferable to apply the coating to a uniform thickness all around the circumference.
The coating material can be applied by any method, including brush coating, spray coating, and quantitative coating using a dispenser. Among these, quantitative application using a dispenser is preferred from the viewpoint of precision in adjusting the amount of application.

As for the above 2) method of adjusting the mass by arranging a mass adjustment member in the photoreceptor drum assembly 10, for example, as shown in FIG. A method of inserting and arranging two or more can be mentioned. However, it is not limited to this.
Note that "arranging" the mass adjustment member means installing it at that position by any means.
In the case of 2) above, the mass adjustment member is disposed in at least one photoconductor drum assembly 10 among the plurality of photoconductor drum assemblies 10. For example, the mass adjustment member 21 will be disposed within the conductive support of the photoreceptor drum 11 of at least one photoreceptor drum assembly 10 .

The shape of the mass adjustment member 21 is arbitrary. For example, as shown in FIG. 6, it may be cylindrical, solid cylindrical, or any other shape, but from the viewpoint of preventing eccentricity when the photoreceptor drum assembly rotates, A columnar or cylindrical shape is preferred.
The mass of the photosensitive drum assembly 10 can be adjusted by the size (length, thickness, etc.), specific gravity, and number of the mass adjustment members 21.

From the viewpoint of rigidity, the material of the mass adjustment member 21 may be resin, metal, or the like.
Examples of the resin include various rubbers such as ABS, polyethylene, polystyrene, polypropylene, acrylic, polyvinyl chloride, polycarbonate, polyethylene terephthalate, and synthetic rubber, and even if it is a mixture of multiple materials. good. Recycled resins such as PET bottles can also be used. Furthermore, these resins may be kneaded with an inorganic filler. Among these, polycarbonate, polyethylene terephthalate, and synthetic rubber are preferred, and polyethylene terephthalate is more preferred, from the viewpoint of matching the coefficient of linear expansion with the aluminum alloy of the conductive support of the photoreceptor drum.
Examples of the metal include aluminum, aluminum alloy, copper, and copper alloy. Among these, aluminum and aluminum alloy are more preferable from the viewpoint of matching the coefficient of linear expansion with the aluminum alloy of the conductive support of the photoreceptor drum.

The mass adjustment member 21 may be a member that functions only as a weight, a damping member with a damping function, or a member with other functions.
Regarding the configuration example of the vibration damping member, the description in paragraphs 0025 to 0038 of JP-A No. 2014-102374 is adapted here.

3) A method of adjusting the mass by providing a cutting part in a part of the photoreceptor drum 11 is, for example, as shown in FIG. A thin cut portion 22A is provided by cutting the circumferential surface, or a plurality of grooves are cut into the inner circumferential surface of the conductive support of the photoreceptor drum 11 to provide a cut portion 22B, as shown in FIG. Here are some methods. However, the present invention is not limited to these, and the shape of the cutting part and the position where the cutting part is provided can be changed as appropriate.
In the case of 3) above, the photosensitive drum 11 of at least one photosensitive drum assembly 10 among the plurality of photosensitive drum assemblies 10 has a configuration in which a cutting portion is provided. For example, the conductive support of the photoreceptor drum 11 of at least one photoreceptor drum assembly 10 is provided with the cutting portion 22A or the cutting portion 22B.

As a method of making the mass of the flange 12 or the drive flange 13 or both of them different (4) above, for example, a method of making the shape of the flange 12 or the drive flange 13 different can be mentioned. For example, for the basic shape shown in FIG. 9(A), as shown in FIG. 9(B), a lightened part 23 may be provided in the fitting part 12b (13c) that is press-fitted into the conductive support, or As shown in (C), the length of the fitting portion 12b (13c) may be changed. However, the present invention is not limited to these, and the mass can be adjusted by arbitrarily changing the shape of the flange 12 or the drive flange 13. Furthermore, the mass can be adjusted by changing the wall thickness of part or all of the flange 12 or drive flange 13.
In the case of 4) above, at least one photoconductor drum assembly 10 among the plurality of photoconductor drum assemblies 10 has a flange 12 or a drive flange 13 whose mass is greater than the mass of the flange member of the other photoconductor drum assemblies 10. It will be different. For example, the shape of the flange 12 or drive flange 13 of at least one photoreceptor drum assembly 10 is different from the shape of the flange members of the other photoreceptor drum assemblies 10, resulting in a different mass.

<Case 2>
The casing 2 is for storing each member constituting the image forming apparatus, and the shape and material of the casing 2 are arbitrary as long as it can hold the photosensitive drum assembly or the electrophotographic cartridge.

<Members other than the photosensitive drum assembly 10 constituting the electrophotographic cartridge 1A>
Next, components other than the photosensitive drum assembly 10 that constitute the electrophotographic cartridge 1A, such as the developing roller 4, the transfer roller 5, the cleaning blade 8, and the toner container 9, will be sequentially described.
Note that the electrophotographic cartridge 1A may optionally include any members, parts, developer, etc. that can be included in the electrophotographic cartridge.

The charging roller 3 charges the photoreceptor drum 11 by applying voltage from the main body of the image forming apparatus. This is because the charging roller 3 rotates following the photoreceptor drum 11 and the photoreceptor drum 11 rotates.
This is done by contacting the outer peripheral surface of the
In performing charging, charging may be performed using a DC voltage, or may be performed by superimposing an AC voltage on a DC voltage. When charging is performed by superimposing an alternating current voltage on a direct current voltage, the effects of the present invention can be further enjoyed.

The developing roller 4 is a roller that supplies developer to the photosensitive drum 11. Then, the electrostatic latent image formed on the photosensitive drum 11 is developed by the developing roller 4 . Note that the developing roller 4 has a built-in fixed magnet.

The transfer roller 5 is placed in a position to sandwich the conveyed recording medium such as paper between the photoconductor drum assembly 10 and when the recording medium passes between the photoconductor drum assembly 10 and the transfer roller 5. , a voltage is applied to the transfer roller 5 so that the image is transferred from the photosensitive drum assembly 10 to the recording medium.

The cleaning blade 8 comes into contact with the outer circumferential surface of the photoreceptor drum 11 and uses its tip to scrape off the developer remaining after the transfer and collect the remaining toner.
However, if there is little or almost no toner remaining on the surface of the photosensitive drum 11, the cleaning blade may not be provided.

The toner container 9 contains toner T and can supply the toner to the surface of the developing roller 4 .
The type of toner T is arbitrary, and in addition to powdered toner, polymerized toner using suspension polymerization method, emulsion polymerization method, etc. can be used.

<<Photoconductor drum assembly set>>
In a plurality of photoconductor drum assemblies 10 whose mass is adjusted as described above, that is, at least half of the plurality of photoconductor drum assemblies 10, the average of the mass of each photoconductor drum assembly and the mass of all photoconductor drum assemblies. A set (" The photoreceptor drum assembly set may be provided as a "photoreceptor drum assembly set".
For example, if the four photoreceptor drum assemblies 10 whose masses have been adjusted as described above are provided as one photoreceptor drum assembly set, the provider can use the photoreceptor drum assemblies 10 without adjusting their mass. By incorporating it into an electrophotographic cartridge or an image forming apparatus, it is possible to suppress the generation of unpleasant humming noise.
The number of photoreceptor drum assemblies included in the photoreceptor drum assembly set is arbitrary as long as it is 2 or more, and among these, 2 or more is preferable, 4 or more is more preferable, while 16 or less is preferable, and 8 or more are preferable. or less is more preferable.

＜＜Explanation of words＞＞
In the present invention, when expressed as "X to Y" (X, Y are arbitrary numbers), unless otherwise specified, it means "more than or equal to X and less than or equal to Y", and also means "preferably greater than It also includes the meaning of "small".
In addition, when expressed as "more than or equal to X" (X is any number) or "less than or equal to Y" (Y is any number), the expression "preferably greater than X" or "preferably less than Y" should be used. It also includes intent.

The invention will be further illustrated by the following examples. However, the examples are not intended to limit the invention in any way.

In Examples 1 to 5 and Comparative Example 3, when manufacturing the photoreceptor drum assembly, parts and materials constituting the photoreceptor drum assembly (conductive support, undercoat layer after drying, charge after drying) were prepared in advance. After measuring or calculating the mass of the generation layer, charge transport layer after drying, flange, and drive flange, and calculating the mass that needs to be adjusted for each of the four photoreceptor drum assemblies, adjust each mass using the method described below. The mass of the photoreceptor drum assembly was adjusted.

<Coating material 1>
Instant adhesive cyanone ET (manufactured by Koukatsu Gas Kogyo Co., Ltd., main component: ethoxyethyl cyanoacrylate, specific gravity: 1.07, viscosity: >800 mPa・s)

[Example 1]
(First photoconductor drum assembly: Fabrication of photoconductor drum assembly 1-1)
A conductive support (made of aluminum) with a diameter of 30 mm, an axial length of 360 mm, a wall thickness of 0.8 mm, and a mass of 69.00 g is coated uniformly around the entire circumference on the inner peripheral surface at a position of 10 to 50 mm from both ends. 0.10 g of Coating Material 1 was applied so that the thickness was as follows.
Next, a subbing layer (thickness after drying: 1.25 μm), a charge generation layer (adhesion amount: 0.40 g/m ² ), a charge transport layer (thickness after drying) are coated on the outer peripheral surface of this conductive support. : 32 μm) to prepare a photoreceptor drum.
Thereafter, a cylindrical mass adjusting member (made of polyethylene terephthalate resin, diameter: 28.3 mm, axial length: 200 mm, wall thickness: 5.6 mm, mass: 53.00 g) is placed in the center of the interior of the photoreceptor drum. was inserted, and a flange was press-fitted to one end of the photoreceptor drum, and a drive flange was press-fitted to the other end, thereby producing a photoreceptor drum assembly 1-1. The mass of the photosensitive drum assembly 1-1 was 162.24 g.

(Second photoconductor drum assembly: Fabrication of photoconductor drum assembly 1-2)
Photoreceptor drum assembly 1-2 was produced in the same manner as photoreceptor drum assembly 1-1, using each member having the mass listed in Table 1, except that the coating amount of coating material 1 was changed to 0.12 g. . The mass of the photosensitive drum assembly 1-2 was 162.24 g.

(Third photoconductor drum assembly: Fabrication of photoconductor drum assembly 1-3)
Photoreceptor drum assembly 1-3 was produced in the same manner as photoreceptor drum assembly 1-1, using each member having the mass listed in Table 1, except that the coating amount of coating material 1 was changed to 0.09 g. . The mass of photoreceptor drum assembly 1-3 was 162.24 g.

(Fourth photoreceptor drum assembly: Fabrication of photoreceptor drum assembly 1-4)
A photoreceptor drum assembly 1-4 was produced in the same manner as photoreceptor drum assembly 1-1, using each member having the mass listed in Table 1, except that the amount of coating material 1 applied was changed to 0.20 g. . The mass of photoreceptor drum assembly 1-4 was 162.25 g.

[Example 2]
(First photoconductor drum assembly: Fabrication of photoconductor drum assembly 2-1)
A conductive support (made of aluminum) with a diameter of 30 mm, an axial length of 360 mm, a wall thickness of 0.8 mm, and a mass of 69.00 g is coated uniformly around the entire circumference on the inner peripheral surface at a position of 10 to 50 mm from both ends. 0.10 g of the coating material 1 was applied so that the thickness was as follows.
Next, a subbing layer (thickness after drying: 1.25 μm), a charge generation layer (adhesion amount: 0.40 g/m ² ), a charge transport layer (thickness after drying) are coated on the outer peripheral surface of this conductive support. : 32 μm) to prepare a photoreceptor drum.
Thereafter, a cylindrical mass adjusting member (made of polyethylene terephthalate resin, diameter: 28.3 mm, axial length: 200 mm, wall thickness: 5.6 mm, mass: 53.00 g) is placed in the center of the interior of the photoreceptor drum. A flange was press-fitted into one end of the photoreceptor drum, and a drive flange was press-fitted into the other end of the photoreceptor drum, thereby producing a photoreceptor drum assembly 2-1. Note that the flange and the drive flange have the same shape and mass as those used in the first embodiment. The mass of the photosensitive drum assembly 2-1 was 162.24 g.

(Second photoconductor drum assembly: Fabrication of photoconductor drum assembly 2-2)
A photoreceptor drum assembly 2-2 was prepared in the same manner as the photoreceptor drum assembly 2-1 using each member having the mass listed in Table 1, except that the coating amount of the coating material 1 was changed to 0.09 g. did. The mass of the photosensitive drum assembly 2-2 was 162.24 g.

(Third photoconductor drum assembly: Fabrication of photoconductor drum assembly 2-3)
A photoreceptor drum assembly 2-3 was produced in the same manner as the photoreceptor drum assembly 2-1 using each member having the mass listed in Table 1. The mass of the photosensitive drum assembly 2-3 was 162.17 g.

(Fourth photoconductor drum assembly: Fabrication of photoconductor drum assembly 2-4)
A photoreceptor drum assembly 2-4 was prepared in the same manner as the photoreceptor drum assembly 2-1 using each member having the mass listed in Table 1, except that the coating amount of the coating material 1 was changed to 0.32 g. did. The mass of the photosensitive drum assembly 2-4 was 162.33 g.

[Example 3]
(First photoconductor drum assembly: Fabrication of photoconductor drum assembly 3-1)
A conductive support (made of aluminum) with a diameter of 30 mm, an axial length of 360 mm, a wall thickness of 0.8 mm, and a mass of 69.00 g is coated with an undercoat layer (thickness after drying: 1.0 mm) on the outer peripheral surface of the conductive support. A photoreceptor drum was prepared by sequentially providing a charge generation layer (adhering amount: 0.40 g/m ² ), a charge transport layer (film thickness after drying: 32 μm).
Thereafter, a cylindrical mass adjustment member (made of polyethylene terephthalate resin, diameter 28.3 mm, axial length 200 mm, wall thickness 5.6 mm, mass 53.00 g) is inserted into the center inside the photoreceptor drum, A flange was press-fitted into one end of the photoreceptor drum, and a drive flange was press-fitted into the other end to produce a photoreceptor drum assembly 3-1. Note that the flange and the drive flange have the same shape and mass as those used in the first embodiment. The mass of the photoreceptor 3-1 drum assembly was 162.24 g.

(Second photoconductor drum assembly: Fabrication of photoconductor drum assembly 3-2)
The photosensitive drum assembly 3-1 was made in the same manner as the photosensitive drum assembly 3-1, except that the axial length of the mass adjusting member 1 was changed to 212 mm, the mass was changed to 56.52 g, and each member having the mass listed in Table 1 was used. A body drum assembly 3-2 was manufactured. The mass of the photosensitive drum assembly 3-2 was 165.74 g.

(Third photoconductor drum assembly: Fabrication of photoconductor drum assembly 3-3)
Photosensitive drum assembly 3-1 was prepared in the same manner as photosensitive drum assembly 3-1, except that the axial length of mass adjusting member 1 was changed to 217 mm, the mass was changed to 58.05 g, and each member having the mass listed in Table 1 was used. A body drum assembly 3-3 was produced. The mass of the photosensitive drum assembly 3-3 was 167.24 g.

(Fourth photoreceptor drum assembly: Fabrication of photoreceptor drum assembly 3-4)
A photoreceptor drum assembly 3-4 was produced in the same manner as the photoreceptor drum assembly 3-1 using each member having the mass listed in Table 1. The mass of the photosensitive drum assembly 3-4 was 162.25 g.

[Example 4]
(First photoconductor drum assembly: Fabrication of photoconductor drum assembly 7-1)
A conductive support (made of aluminum) with a diameter of 30 mm, an axial length of 360 mm, a wall thickness of 0.8 mm, and a mass of 69.03 g is coated uniformly around the entire circumference on the inner circumferential surface at positions 10 to 50 mm from both ends. 0.10 g of the coating material 1 was applied so that the thickness was as follows.
Next, a subbing layer (thickness after drying: 1.25 μm), a charge generation layer (adhesion amount: 0.40 g/m ² ), a charge transport layer (thickness after drying) are coated on the outer peripheral surface of this conductive support. : 32 μm) to prepare a photoreceptor drum.
Thereafter, a mass adjustment member (synthetic rubber adhesive, thickness 1.5 mm, mass 21.98 g) is attached to the center of the interior of the photoreceptor drum, and a flange is attached to one end of the photoreceptor drum and a flange is attached to the other end. A drive flange was press-fitted to produce a photoreceptor drum assembly 7-1. Note that the flange and the drive flange have different shapes and masses from those used in the first embodiment. The mass of the photosensitive drum assembly 7-1 was 104.54 g.

(Second photoconductor drum assembly: Fabrication of photoconductor drum assembly 7-2)
A photoreceptor drum assembly 7-2 was produced in the same manner as the photoreceptor drum assembly 7-1 using each member having the mass listed in Table 1, except that the mass of the mass adjustment member was changed to 22.21 g. . The mass of the photosensitive drum assembly 7-2 was 104.81 g.

(Third photoconductor drum assembly: Fabrication of photoconductor drum assembly 7-3)
A photoreceptor drum assembly 7-3 was prepared in the same manner as the photoreceptor drum assembly 7-1 using each member having the mass listed in Table 1, except that the mass of the mass adjusting member was changed to 20.04 g. did. The mass of the photosensitive drum assembly 7-3 was 102.65 g.

(Fourth photoconductor drum assembly: Fabrication of photoconductor drum assembly 7-4)
A photoreceptor drum assembly 7-4 was prepared in the same manner as the photoreceptor drum assembly 7-1 using each member having the mass listed in Table 1, except that the mass of the mass adjusting member was changed to 21.10 g. did. The mass of the photosensitive drum assembly 7-4 was 103.75 g.

[Example 5]
(First photoconductor drum assembly: Fabrication of photoconductor drum assembly 8-1)
A conductive support (made of aluminum) with a diameter of 30 mm, an axial length of 360 mm, a wall thickness of 0.8 mm, and a mass of 69.05 g is coated uniformly around the entire circumference on the inner circumferential surface at a position 10 to 50 mm from both ends. 0.10 g of the coating material 1 was applied so that the thickness was as follows.
Next, a subbing layer (thickness after drying: 1.25 μm), a charge generation layer (adhesion amount: 0.40 g/m ² ), a charge transport layer (thickness after drying) are coated on the outer peripheral surface of this conductive support. : 32 μm) to prepare a photoreceptor drum.
Thereafter, a mass adjustment member (synthetic rubber adhesive, wall thickness 2.2 mm, mass 27.20 g) is attached to the center of the interior of the photoreceptor drum, and a flange is attached to one end of the photoreceptor drum and a flange is attached to the other end. A drive flange was press-fitted to produce a photoreceptor drum assembly 8-1. Note that the flange and the drive flange have different shapes and masses from those used in the first embodiment. The mass of the photosensitive drum assembly 8-1 was 109.81 g.

(Second photoconductor drum assembly: Fabrication of photoconductor drum assembly 8-2)
A photoreceptor drum assembly 8-2 was produced in the same manner as photoreceptor drum assembly 8-1 using each member having the mass listed in Table 1, except that the mass of the mass adjustment member was changed to 27.95 g. . The mass of the photosensitive drum assembly 8-2 was 110.63 g.

(Third photoconductor drum assembly: Fabrication of photoconductor drum assembly 8-3)
A photoreceptor drum assembly 8-3 was prepared in the same manner as the photoreceptor drum assembly 8-1 using each member having the mass listed in Table 1, except that the mass of the mass adjustment member was changed to 28.25 g. did. The mass of the photosensitive drum assembly 8-3 was 110.82 g.

(Fourth photoconductor drum assembly: Fabrication of photoconductor drum assembly 8-4)
A photoreceptor drum assembly 8-4 was prepared in the same manner as the photoreceptor drum assembly 8-1 using each member having the mass listed in Table 1, except that the mass of the mass adjustment member was changed to 29.04 g. did. The mass of photoreceptor drum assembly 8-4 was 111.62 g.

[Comparative example 1]
(First photoconductor drum assembly: Fabrication of photoconductor drum assembly 4-1)
A conductive support (made of aluminum) with a diameter of 30 mm, an axial length of 360 mm, a wall thickness of 0.8 mm, and a mass of 68.99 g is coated with an undercoat layer (thickness after drying: 1.0 mm) on the outer peripheral surface of the conductive support. A photoreceptor drum was prepared by sequentially providing a charge generation layer (adhering amount: 0.40 g/m ² ), a charge transport layer (film thickness after drying: 32 μm).
Thereafter, a cylindrical mass adjustment member (made of polyethylene terephthalate resin, diameter 28.3 mm, axial length 200 mm, wall thickness 5.6 mm, mass 53.00 g) is inserted into the center inside the photoreceptor drum, A flange was press-fitted into one end of the photoreceptor drum, and a drive flange was press-fitted into the other end to produce a photoreceptor drum assembly 4-1. Note that the flange and the drive flange have the same shape and mass as those used in the first embodiment. The mass of the photoreceptor 4-1 drum assembly was 162.23 g.

(Second photoconductor drum assembly: Fabrication of photoconductor drum assembly 4-2)
A photoreceptor drum assembly 4-2 was produced in the same manner as the photoreceptor drum assembly 4-1 using each member having the mass listed in Table 1. The mass of the photosensitive drum assembly 4-2 was 162.03 g.

(Third photoconductor drum assembly: Fabrication of photoconductor drum assembly 4-3)
A photoreceptor drum assembly 4-3 was produced in the same manner as the photoreceptor drum assembly 4-1 using each member having the mass listed in Table 1. The mass of the photosensitive drum assembly 4-3 was 162.01 g.

(Fourth photoreceptor drum assembly: Fabrication of photoreceptor drum assembly 4-4)
A photoreceptor drum assembly 4-4 was produced in the same manner as the photoreceptor drum assembly 4-1 using each member having the mass listed in Table 1. The mass of the photosensitive drum assembly 4-4 was 161.88 g.

[Comparative example 2]
(First photoconductor drum assembly: Fabrication of photoconductor drum assembly 5-1)
A conductive support (made of aluminum) with a diameter of 30 mm, an axial length of 360 mm, a wall thickness of 0.8 mm, and a mass of 69.89 g is coated with an undercoat layer (film thickness after drying: 1. A photoreceptor drum was prepared by sequentially providing a charge generation layer (adhering amount: 0.40 g/m ² ), a charge transport layer (film thickness after drying: 32 μm).
Thereafter, a cylindrical mass adjustment member (made of polyethylene terephthalate resin, diameter 28.3 mm, axial length 200 mm, wall thickness 5.6 mm, mass 53.00 g) is inserted into the center inside the photoreceptor drum, A flange was press-fitted into one end of the photoreceptor drum, and a drive flange was press-fitted into the other end to produce a photoreceptor drum assembly 5-1. Note that the flange and the drive flange have the same shape and mass as those used in the first embodiment. The mass of the photosensitive drum assembly 5-1 was 162.13 g.

(Second photoconductor drum assembly: Fabrication of photoconductor drum assembly 5-2)
A photoreceptor drum assembly 5-2 was produced in the same manner as the photoreceptor drum assembly 5-1 using each member having the mass listed in Table 1. The mass of the photosensitive drum assembly 5-2 was 162.03 g.

(Third photoconductor drum assembly: Fabrication of photoconductor drum assembly 5-3)
A photoreceptor drum assembly 5-3 was produced in the same manner as the photoreceptor drum assembly 5-1 using each member having the mass listed in Table 1. The mass of the photosensitive drum assembly 5-3 was 162.01 g.

(Fourth photoreceptor drum assembly: Fabrication of photoreceptor drum assembly 5-4)
A photoreceptor drum assembly 5-4 was produced in the same manner as the photoreceptor drum assembly 5-1 using each member having the mass listed in Table 1. The mass of the photosensitive drum assembly 5-4 was 161.88 g.

[Comparative example 3]
(First photoconductor drum assembly: Fabrication of photoconductor drum assembly 6-1)
A conductive support (made of aluminum) with a diameter of 30 mm, an axial length of 360 mm, a wall thickness of 0.8 mm, and a mass of 68.79 g is coated uniformly around the entire circumference on the inner circumferential surface at a distance of 10 to 50 mm from both ends. 0.7 g of the above-mentioned coating material 1 was applied so that the thickness was as follows.
Next, a subbing layer (thickness after drying: 1.25 μm), a charge generation layer (adhesion amount: 0.40 g/m ² ), a charge transport layer (thickness after drying) are coated on the outer peripheral surface of this conductive support. : 32 μm) to prepare a photoreceptor drum.
Then, a cylindrical mass adjustment member (made of polyethylene terephthalate resin, diameter 28.3 mm, axial length 200 mm, wall thickness 5.6 mm, mass 52.70 g) is inserted into the center of the interior of the photoreceptor drum, A flange was press-fitted into one end of the photoreceptor drum, and a drive flange was press-fitted into the other end to produce a photoreceptor drum assembly 6-1. Note that the flange and the drive flange have the same shape and mass as those used in the first embodiment. The mass of the photosensitive drum assembly 6-1 was 162.33 g.

(Second photoconductor drum assembly: Fabrication of photoconductor drum assembly 6-2)
A photoreceptor drum assembly 6-2 was prepared in the same manner as the photoreceptor drum assembly 6-1, using each member having the mass listed in Table 1, except that the coating amount of the coating material 1 was changed to 0.1 g. did. The mass of the photosensitive drum assembly 6-2 was 162.03 g.

(Third photoconductor drum assembly: Fabrication of photoconductor drum assembly 6-3)
A photoreceptor drum assembly 6-3 was produced in the same manner as the photoreceptor drum assembly 6-2 using each member having the mass listed in Table 1. The mass of the photosensitive drum assembly 6-3 was 162.02 g.

(Fourth photoreceptor drum assembly: Fabrication of photoreceptor drum assembly 6-4)
A photoreceptor drum assembly 6-4 was prepared in the same manner as the photoreceptor drum assembly 6-1, using each member having the mass listed in Table 1, except that the coating amount of the coating material 1 was changed to 1.00 g. did. The mass of the photosensitive drum assembly 6-4 was 163.70 g.

<Calculation of the ratio (%) of the absolute value of the difference between the mass of each of the first to fourth photoconductor drum assemblies and the average value of the masses of all photoconductor drum assemblies to the average value>
The ratio (%) of the absolute value of the difference between the mass of each photoconductor drum assembly and the average value of the masses of all photoconductor drum assemblies to the average value was calculated from the following formula. Table 2 shows the results calculated for Examples 1 to 5 and Comparative Examples 1 to 3.

Ratio (%) of (absolute value of the difference between the mass of each of the first to fourth photoconductor drum assemblies and the average value of the mass of all photoconductor drum assemblies) to the above average value
= {[(Average value of mass of all photoreceptor drum assemblies) - (Mass of each photoreceptor drum assembly)]/Average value of mass of all photoreceptor drum assemblies}×100

<Evaluation of humming noise>
In an image forming apparatus using four photoreceptor drum assemblies, the photoreceptor drum assemblies of Examples 1 to 5 and Comparative Examples 1 to 3 whose masses were adjusted as shown in Table 2 were used, and the occurrence occurred during operation of the image forming apparatus. We conducted measurements of the whining noise.
The four photosensitive drum assemblies obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were attached to a contact charging type, tandem type image forming apparatus.

While printing was being performed, an IC recorder was applied from the outside to a portion of the image forming apparatus housing near the photoreceptor drive unit, and the sound during operation was measured. Using audio analysis software, only the high frequency band around 2 kHz was extracted from the measured audio data, and temporal changes in the strength of the sound were confirmed. Note that any software can be used for audio analysis for evaluating beat noise.
If the strength of the sound is such that the peaks and nodes of the waveform are repeated periodically, as shown in Figure 10, it is determined that there is a beat in the sound. If the period) was in the range of 0.1 seconds to 2 seconds, it was judged as an unpleasant humming sound.
1.8 to 4.6 of the sound analysis graphs (vertical axis: sound intensity, horizontal axis: time [seconds]) at frequencies 2.0 to 2.5 kHz for Examples 1 to 5 and Comparative Examples 1 to 3. Figures 11 to 18 show extracted seconds and color-coded graph background parts (black) and sound waveform parts (light colors). Note that the beating period in Example 2 could not be measured because the periodic interval between nodes was too narrow.

Table 2 shows the results of measuring the presence or absence of unpleasant humming sounds and, if any, the beating period. The unpleasant buzzing sound was evaluated based on the following criteria.
1: No humming noise 2: Slight humming noise, but not unpleasant 3: Unpleasant humming noise

From Table 2, in all of Examples 1 to 5, no unpleasant whining noise was observed, or even if the humming noise was generated, it was at a level that did not cause discomfort. On the other hand, in the comparative example, an unpleasant humming sound was confirmed.
As a result, in an image forming apparatus having a configuration in which a plurality of photoreceptor drum assemblies are arranged in one housing, at least half of the plurality of photoreceptor drum assemblies have a mass of each photoreceptor drum assembly. If the image forming apparatus satisfies the condition that the absolute value of the difference between the average value of the mass of all the photoreceptor drum assemblies and the average value of the mass of all the photoreceptor drum assemblies is less than 0.01% or 0.80% or more with respect to the average value, it is considered uncomfortable. It was found that the generation of whining noise can be suppressed.

1 Image forming apparatus 1A Electrophotographic cartridge 1B Secondary transfer belt 1C Fixing roller 1D Secondary transfer roller 2 Housing 3 Charging roller 4 Developing roller 5 Transfer roller 8 Cleaning blade 9 Toner container 10 Photoconductor drum assembly 11 Photoconductor drum 12 Flange 12a Bearing part 12b Fitting part 12c Shaft receiving part 13 Drive flange 13a Shaft 13b Gear 13c Fitting part 20 Coating material 21 Mass adjustment members 22A, 22B Cutting part 23 Lightening part

Claims (8)

An image forming apparatus having a configuration in which a plurality of photoreceptor drum assemblies are disposed in one housing, wherein the mass of each photoreceptor drum assembly and the total photoreceptor in at least half of the plurality of photoreceptor drum assemblies are An image forming apparatus, wherein the absolute value of the difference between the mass of the body drum assembly and the average value is less than 0.01% or 0.80% or more with respect to the average value. The image according to claim 1, wherein each of the plurality of photoreceptor drum assemblies includes a photoreceptor drum, and a coating material is attached to an inner peripheral surface of the photoreceptor drum of at least one of the plurality of photoreceptor drum assemblies. Forming device. The image forming apparatus according to claim 1, wherein a mass adjustment member is disposed on at least one photosensitive drum assembly among the plurality of photosensitive drum assemblies. The image forming apparatus according to claim 3, wherein the mass adjustment member is a resin member or a metal member. The image forming apparatus according to claim 1, wherein each of the plurality of photoreceptor drum assemblies includes a photoreceptor drum, and the photoreceptor drum of at least one of the plurality of photoreceptor drum assemblies is provided with a cutting section. Device. Each of the plurality of photoreceptor drum assemblies includes a photoreceptor drum and a flange member at both ends of the photoreceptor drum, and the mass of the flange member of at least one photoreceptor drum assembly among the plurality of photoreceptor drum assemblies is The image forming apparatus according to claim 1, wherein the mass of the flange member of the other photoreceptor drum assemblies is different from that of the flange members of the other photoreceptor drum assemblies. The image forming apparatus according to claim 6, wherein the shape of the flange member of at least one photoreceptor drum assembly among the plurality of photoreceptor drum assemblies is different from the shape of the flange member of the other photoreceptor drum assemblies. A photoreceptor drum assembly set comprising a plurality of photoreceptor drum assemblies, in which at least half of the plurality of photoreceptor drum assemblies have a mass of each photoreceptor drum assembly and an average value of the mass of all photoreceptor drum assemblies. A photosensitive drum assembly set, wherein the absolute value of the difference is less than 0.01% or 0.80% or more with respect to the average value.

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