JP6507546B2 - Charging device, process cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to a charging device, a process cartridge, and an image forming apparatus.

  In recent years, as a charging apparatus used in an electrophotographic image forming apparatus, a contact charging system in which an image carrier is charged by bringing a conductive charging roll into direct contact from the viewpoint of space saving and cost reduction It is the subject.

  For example, in Patent Document 1, “a charging roll that charges a body to be charged by pressing against a rotating body to be charged and being driven to rotate, and a cleaning member that cleans the charging roll by pressing on a surface of the charging roll A first receiving portion for supporting the charging roll to press the charging roll against the member to be charged, and a second receiving portion for supporting the cleaning member and pressing the cleaning member against the charging roll. A holding member having a single structure, and urging means for urging the holding member to the side of the member to be charged to press the charging roll against the member to be charged; At least one of the second receiving portions is shaped to give freedom to the charging roller in the pressure contact direction with the charging roll on the first receiving portion side, and the cleaning on the second receiving portion side The image forming apparatus characterized in that it is shaped to provide a degree of freedom in the direction of press-contacting to the charging roll. "Is proposed for wood.

JP, 2010-049290, A

  An object of the present invention is to provide a charging device that suppresses periodic streak-like charging defects even when stored for a long time under a high temperature and high humidity environment.

The above-mentioned subject is solved by the following means. That is,
The invention pertaining to < 1 > is
A charging roll that charges a member to be charged by rotating in contact with the member to be charged;
A cleaning roll comprising an axial core and an elastic layer provided on the outer peripheral surface of the axial core, wherein the compressive residual strain ratio of the elastic layer is 5% or less, wherein the charging roll rotates in contact with the charging roll A cleaning roll for cleaning the charging roll;
A holding member having a first bearing portion for holding an axial core of the charging roll, and a second bearing portion for holding an axial core of the cleaning roll;
A pressure member which brings the charging roll into contact with the member to be charged and the cleaning roll into contact with the charging roll by pressing the holding member;
Equipped with
The charging device may be such that a difference between an inner diameter of the second bearing portion and an outer diameter of an axial center of the cleaning roll is 0.01 mm or more and 0.12 mm or less.

The invention pertaining to < 2 > is
The elastic layer of the cleaning roll is the charging device according to < 1 > , which is a polyurethane foam layer.

The invention relating to < 3 > is
The cleaning roll is a charging device according to < 1 > or < 2 > , which is a roll that is driven to rotate by the charging roll.

The invention pertaining to < 4 > is
A charging roll that charges a member to be charged by rotating in contact with the member to be charged;
A cleaning roll comprising an axial core and an elastic layer provided on the outer peripheral surface of the axial core, wherein the compressive residual strain ratio of the elastic layer is 5% or less, wherein the charging roll rotates in contact with the charging roll A cleaning roll for cleaning the charging roll;
A holding member having a first bearing portion for holding an axial core of the charging roll, and a second bearing portion for holding an axial core of the cleaning roll;
A pressure member which brings the charging roll into contact with the member to be charged and the cleaning roll into contact with the charging roll by pressing the holding member;
Equipped with
The difference between the inner diameter of the second bearing portion and the outer diameter of the axial center of the cleaning roll is 0.04 mm or more and 0.08 mm or less.
In the charging device, the amount of biting in of the cleaning roll with respect to the charging roll is 0.5 mm or more and 0.8 mm or less.

The invention pertaining to < 5 > is
The charging device according to any one of < 1 > to < 4 > , and
It is a process cartridge that is attached to and detached from the image forming apparatus.

The invention pertaining to < 6 > is
An object to be charged,
A charging unit configured to charge the surface of the member to be charged, the charging unit including the charging device according to any one of < 1 > to < 4 > ;
Electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged member to be charged;
Developing means for developing an electrostatic charge image formed on the surface of the member to be charged as a toner image;
A transfer unit configured to transfer a toner image formed on the surface of the member to be charged to the surface of a recording medium;
Fixing means for fixing the toner image transferred to the surface of the recording medium;
An image forming apparatus comprising:

According to the invention relating to < 1 > , < 2 > , or < 3 >, when the compression residual strain rate of the elastic layer of the cleaning roll exceeds 5%, or the second bearing portion that holds the axial center of the cleaning roll Compared to the case where the difference between the inner diameter and the outer diameter of the cleaning roller shaft core exceeds 0.12 mm, the charging device provides periodic charging defects even when stored for a long time in a high temperature and high humidity environment. Be done.

According to the invention relating to < 4 > , compared to the case where the biting amount of the cleaning roll with respect to the charging roll exceeds 1.2 mm, streaks are formed on the surface of the member to be charged even when stored for a long time under high temperature and high humidity environment. A charging device is provided that suppresses the formation of a deposit.

According to the invention as described in < 5 > and < 6 >, when the compression residual strain rate of the elastic layer of the cleaning roll exceeds 5% or the inner diameter of the second bearing portion which holds the axial center of the cleaning roll and the cleaning roll A process cartridge that suppresses periodic streak-like charging defects even when stored for a long time in a high-temperature, high-humidity environment, as compared to the case where a charging device whose difference with the outer diameter of the shaft core exceeds 0.12 mm is applied An image forming apparatus is provided.

FIG. 1 is a schematic configuration view showing an example of an image forming apparatus according to the present embodiment. It is a cross-sectional side view which shows an example of the process cartridge which concerns on this embodiment. FIG. 6 is a perspective view showing the charging device in a state in which the shaft core of the charging roll and the shaft core of the cleaning roll according to the present embodiment are held by a holding member. It is an enlarged side view of FIG.

  Hereinafter, an image forming apparatus according to the present embodiment will be described.

<Image forming apparatus>
The image forming apparatus according to the present embodiment includes an image carrier (an example of a member to be charged), a charging unit that charges the surface of the image carrier, and an electrostatic charge that forms an electrostatic charge image on the surface of the charged image carrier. Image forming means, developing means for developing an electrostatic charge image formed on the surface of the image carrier as a toner image, transfer means for transferring the toner image formed on the surface of the image carrier onto the surface of the recording medium, And fixing means for fixing the toner image transferred to the surface of the recording medium. The charging device according to the present embodiment is applied as the charging unit.

The image forming apparatus according to the present embodiment directly transfers the toner image formed on the surface of the image carrier to the recording medium; the toner image formed on the surface of the image carrier is an intermediate transfer member An intermediate transfer type device that performs primary transfer to the surface and secondarily transfers the toner image transferred to the surface of the intermediate transfer member to the surface of the recording medium; cleans the surface of the image carrier before charging after transferring the toner image A known image forming apparatus such as an apparatus provided with a cleaning means; an apparatus provided with a diselectrification means for diselectrifying the surface of the image holding member before electrification after transferring a toner image is applied.
In the case of an intermediate transfer type apparatus, for example, an intermediate transfer member to which a toner image is transferred on the surface, and a primary transfer on which the toner image formed on the surface of the image carrier is primarily transferred to the surface of the intermediate transfer member. A configuration is applied that includes: means; and secondary transfer means for secondary transfer of the toner image transferred to the surface of the intermediate transfer member to the surface of the recording medium.

  In the image forming apparatus according to the present embodiment, for example, the part including the charging unit may have a cartridge structure (process cartridge) which is detached from the image forming apparatus. As the process cartridge, for example, a process cartridge (see FIG. 2) including the charging device according to the present embodiment is used as the charging unit.

  Hereinafter, although an example of the image forming apparatus according to the present embodiment is shown, the present invention is not limited to this. The main parts shown in the figure will be described, and the description of the other parts will be omitted.

FIG. 1 is a schematic configuration view showing an image forming apparatus according to the present embodiment.
The image forming apparatus shown in FIG. 1 is an electrophotographic first to output an image of each color of yellow (Y), magenta (M), cyan (C) and black (K) based on color separated image data. The fourth image forming units 10Y, 10M, 10C, and 10K (image forming means) are provided. These image forming units (hereinafter sometimes referred to simply as “units”) 10Y, 10M, 10C, and 10K are arranged side by side at a predetermined distance from each other in the horizontal direction. The units 10Y, 10M, 10C, and 10K may be process cartridges that can be detached from the image forming apparatus.

Above the units 10Y, 10M, 10C, and 10K in the drawing, an intermediate transfer belt 20 as an intermediate transfer member is provided. The intermediate transfer belt 20 is wound around a drive roll 22 and a support roll 24 in contact with the inner surface of the intermediate transfer belt 20, which are spaced apart from each other in the left to right direction in FIG. The vehicle travels in the direction toward the unit 10K. A force is applied to the support roll 24 in a direction away from the drive roll 22 by a spring or the like (not shown), and a tension is applied to the intermediate transfer belt 20 wound around both. Further, an intermediate transfer member cleaning device 30 is provided on the side of the image carrier of the intermediate transfer belt 20 so as to face the drive roll 22.
Also, yellow, magenta, cyan and black contained in the toner cartridges 8Y, 8M, 8C and 8K in the developing devices (developing means) 4Y, 4M, 4C and 4K of the units 10Y, 10M, 10C and 10K, respectively. The toner including four color toners is supplied.

  Since the first to fourth units 10Y, 10M, 10C, and 10K have the same configuration, here, the first unit that forms the yellow image disposed on the upstream side in the traveling direction of the intermediate transfer belt The 10Y will be described as a representative. The second to fourth reference numerals are attached to parts equivalent to the first unit 10Y by substituting magenta (M), cyan (C) and black (K) instead of yellow (Y). The description of the units 10M, 10C, and 10K is omitted.

The first unit 10Y has a photoreceptor 1Y acting as an image carrier. Around the photosensitive member 1Y, the electrostatic charge image is exposed by charging the charging device 2Y for charging the surface of the photosensitive member 1Y to a predetermined potential and the laser beam 3Y based on the color-separated image signal. Exposure device (an example of electrostatic charge image forming means) 3 to be formed, a development device (an example of development means) 4Y for developing an electrostatic charge image by supplying toner charged to the electrostatic charge image, an intermediate transfer belt A primary transfer roll 5Y (one example of a primary transfer means) to be transferred onto the image forming apparatus 20 and a photoreceptor cleaning device (one example of a cleaning means) 6Y for removing toner remaining on the surface of the photoreceptor 1Y after primary transfer are sequentially disposed. .
The primary transfer roll 5Y is disposed inside the intermediate transfer belt 20, and is provided at a position facing the photoreceptor 1Y. Further, a bias power supply (not shown) for applying a primary transfer bias is connected to each of the primary transfer rolls 5Y, 5M, 5C, and 5K. Each bias power supply varies the transfer bias applied to each primary transfer roll under control of a control unit (not shown).

Hereinafter, an operation of forming a yellow image in the first unit 10Y will be described.
First, prior to the operation, the surface of the photoreceptor 1Y is charged to a potential of -600 V to -800 V by the charging device 2Y.
Here, although not shown in FIG. 1, the charging device 2Y for charging the surface of the photosensitive member 1Y has a charging roll and a cleaning roll for cleaning the charging roll. The charging device 2Y further includes a holding member for holding the shaft core of the charging roll and the shaft core of the cleaning roll, and a pressure member for pressing the holding member. Details will be described later.

The photoreceptor 1 </ ^b > Y is formed by laminating a photosensitive layer on a conductive (for example, volume resistivity at 20 ° C .: 1 × 10 ⁻⁶ Ωcm or less) substrate. This photosensitive layer usually has a high resistance (resistance of general resin), but has the property that the resistance of the portion irradiated with the laser beam changes when the laser beam 3Y is irradiated. Therefore, the laser beam 3Y is output to the charged surface of the photosensitive member 1Y through the exposure device 3 in accordance with the yellow image data sent from the control unit (not shown). The laser beam 3Y is applied to the photosensitive layer on the surface of the photoreceptor 1Y, whereby an electrostatic charge image of a yellow image pattern is formed on the surface of the photoreceptor 1Y.

The electrostatic image is an image formed on the surface of the photosensitive member 1Y by charging, and the laser beam 3Y lowers the resistance of the irradiated portion of the photosensitive layer, and the charge on the surface of the photosensitive member 1Y flows. On the other hand, it is a so-called negative latent image which is formed by the residual charge of the portion not irradiated with the laser beam 3Y.
The electrostatic charge image formed on the photosensitive member 1Y is rotated to a predetermined development position as the photosensitive member 1Y travels. Then, at this developing position, the electrostatic charge image on the photosensitive member 1Y is made visible (developed image) as a toner image by the developing device 4Y.

  In the developing device 4Y, for example, an electrostatic charge image developer containing at least a yellow toner and a carrier is accommodated. The yellow toner is frictionally charged by being stirred inside the developing device 4Y, and has a charge of the same polarity (negative polarity) as the charged charge on the photosensitive member 1Y, and the developer roll (the developer holding member One example is held on top. Then, as the surface of the photosensitive member 1Y passes through the developing device 4Y, the yellow toner is electrostatically attached to the electrostatic latent image portion on the surface of the photosensitive member 1Y, and the latent image is developed by the yellow toner . The photoreceptor 1Y on which the yellow toner image is formed is subsequently traveled at a predetermined speed, and the toner image developed on the photoreceptor 1Y is conveyed to a predetermined primary transfer position.

When the yellow toner image on the photosensitive member 1Y is conveyed to the primary transfer, a primary transfer bias is applied to the primary transfer roll 5Y, and an electrostatic force from the photosensitive member 1Y toward the primary transfer roll 5Y is applied to the toner image. The toner image on 1 Y is transferred onto the intermediate transfer belt 20. The transfer bias applied at this time is the (+) polarity opposite to the polarity (−) of the toner, and is controlled to +10 μA by the control unit (not shown) in the first unit 10Y, for example.
On the other hand, the toner remaining on the photosensitive member 1Y is removed and collected by the photosensitive member cleaning device 6Y.

Further, the primary transfer bias applied to the primary transfer rolls 5M, 5C and 5K after the second unit 10M is also controlled according to the first unit.
Thus, the intermediate transfer belt 20 to which the yellow toner image is transferred in the first unit 10Y is sequentially conveyed through the second to fourth units 10M, 10C, and 10K, and the toner images of the respective colors are superimposed and transferred in multiples. Ru.

  The intermediate transfer belt 20 on which toner images of four colors are multiply transferred through the first to fourth units is disposed on the intermediate transfer belt 20 and the image holding surface side of the intermediate transfer belt 20 and the support roll 24 in contact with the inner surface of the intermediate transfer belt. It leads to the secondary transfer part comprised from the secondary transfer roll (an example of a secondary transfer means) 26 which was carried out. On the other hand, recording paper (an example of a recording medium) P is fed at a predetermined timing to a gap where the secondary transfer roll 26 and the intermediate transfer belt 20 contact via a supply mechanism, and the secondary transfer bias is a support roll. 24 is applied. The transfer bias applied at this time is the same as the polarity (−) of the toner (−), and the electrostatic force from the intermediate transfer belt 20 to the recording paper P is applied to the toner image. Is transferred onto the recording paper P. The secondary transfer bias at this time is determined according to the resistance detected by a resistance detection unit (not shown) that detects the resistance of the secondary transfer portion, and is voltage controlled.

  Thereafter, the recording paper P is sent to the pressure contact portion (nip portion) of the pair of fixing rolls in the fixing device (an example of the fixing means) 28, the toner image is fixed on the recording paper P, and a fixed image is formed.

Examples of the recording paper P to which the toner image is transferred include plain paper used for electrophotographic copying machines, printers and the like. As the recording medium, in addition to the recording paper P, an OHP sheet or the like can also be mentioned.
In order to further improve the smoothness of the image surface after fixing, the surface of the recording paper P is also preferably smooth. For example, coated paper obtained by coating the surface of plain paper with a resin or the like, art paper for printing, etc. are suitably used. Be done.

  The recording paper P for which the fixing of the color image is completed is carried out toward the discharge unit, and a series of color image forming operations are completed.

  Hereinafter, the process cartridge and the charging device according to the present embodiment will be described with reference to FIGS. 2 to 4.

<Process cartridge, charging device>
As shown in FIG. 2, the process cartridge 300 includes, as charging means, the charging device 200 according to the present embodiment, the photosensitive member 12 (an example of a member to be charged), and a single housing 120. In the process cartridge 300, the charging device 200 and the photosensitive member 12 are assembled in a single case 120 and accommodated in the case 120.
The process cartridge 300 according to the present embodiment is, for example, detachably mounted to the image forming apparatus of FIG. 1 by mounting means (not shown).

The charging device 200 charges the photosensitive member 12 by rotating in contact with the photosensitive member 12, and the cleaning roller 100 cleans the charging roller 14 by rotating in contact with the charging roller 14. By pressing the holding member 110 holding the shaft core 14A of the charging roll and the shaft core 100A of the cleaning roll, the charging roll 14 is brought into contact with the photosensitive member 12 and the cleaning roll 100 is charged. And a pressure member 128 to be brought into contact with the
As shown in FIGS. 3 and 4, the holding member 110 holds a first bearing hole 112 (an example of a first bearing portion) for holding the shaft core 14A of the charging roll, and a second for holding the shaft core 100A of the cleaning roll. And a bearing hole 114 (an example of a second bearing portion).
The cleaning roll 100 has an axial core 100A and an elastic layer 100B provided on the outer peripheral surface of the axial core 100A, and the compressive residual strain rate of the elastic layer 100B is 5% or less. Further, the difference between the inner diameter of the second bearing hole 114 for holding the shaft core 100A of the cleaning roll and the outer diameter of the shaft core 100A of the cleaning roll is 0.01 mm or more and 0.12 mm or less.

  In the charging device 200 having the above configuration, when the holding member 110 is pressed toward the photosensitive member 12 by the pressing member 128 and the photosensitive member 12 is rotationally driven, the charging roll 14 rotates while being in contact with the photosensitive member 12. The cleaning roll 100 rotates while in contact with the charging roll 14.

Here, in the conventional charging device, for the purpose of not inhibiting the rotation of the cleaning roll 100, in the holding member 110, the second bearing hole 114 for holding the axis 100A of the cleaning roll and the axis 100A of the cleaning roll The fit was designed loose. Specifically, the inner diameter of the second bearing hole 114 is designed to be excessively larger than the outer diameter of the shaft core 100A of the cleaning roller so that the shaft core 100A of the cleaning roller has a degree of freedom. However, in this design, when the cleaning roll 100 rotates, the axial center 100A moves in the contact direction of the charging roll 14, and the relative position between the cleaning roll 100 and the charging roll 14 fluctuates. As a result, the pressure applied to the charging roller 14 of the cleaning roller 100 fluctuates with respect to the rotation of the cleaning roller 100, and the pressure applied to the photosensitive member 12 of the charging roller 14 also fluctuates. As a result, the formation of the nip between the charging roll 14 and the photosensitive member 12 is not stable, the charging of the photosensitive member 12 by the charging roll 14 becomes uneven, and periodic streak-like charging defects occur.
Therefore, the charging device 200 according to the present embodiment is designed to tightly fit the second bearing hole 114 holding the axial core 100A of the cleaning roll and the axial core 100A of the cleaning roll. Specifically, the difference between the inner diameter of the second bearing hole 114 and the outer diameter of the shaft core 100A of the cleaning roll is 0.01 mm or more and 0.12 mm or less. Thereby, the movement of the shaft core 100A of the cleaning roll in the contact direction of the charging roll 14 is suppressed, and the fluctuation of the relative position between the cleaning roll 100 and the charging roll 14 is suppressed.

On the other hand, when the second bearing hole 114 and the core 100A of the cleaning roll are designed to be tightly fitted, the cleaning roll 100 continues to be in contact with the charging roll 14 under high temperature and high humidity environment (for example, 45 ° C./95) In the case of long-term storage (for example, one month) at% RH), the cleaning roll 100 is likely to be distorted. When distortion occurs in the cleaning roll 100, as in the case where the relative position between the cleaning roll 100 and the charging roll 14 changes, the pressure on the charging roll 14 of the cleaning roll 100 fluctuates.
Therefore, in the charging device 200 according to the present embodiment, the difference between the inner diameter of the second bearing hole 114 and the outer diameter of the axial core 100A of the cleaning roll is in the above range, and the compression of the elastic layer of the cleaning roll 100 is further performed. Reduce the residual strain rate to 5% or less. As a result, even when stored for a long time under a high temperature and high humidity environment, the generation of distortion of the cleaning roll 100 is suppressed, and the fluctuation of the pressure applied to the charging roll 14 of the cleaning roll 100 is suppressed. As a result, the variation of the pressure applied to the photosensitive member 12 by the charging roller 14 is also suppressed, and the nip formation between the charging roller 14 and the photosensitive member 12 is stably performed, and the charging of the photosensitive member 12 by the charging roller 14 is uniform. Sex is easier to maintain.

From the above, according to the charging device 200 according to the present embodiment, even when stored for a long time in a high temperature and high humidity environment, the uniformity of charging of the photosensitive member 12 by the charging roll 14 is easily maintained, and periodic The streak-like charging failure is suppressed.
Further, even in the case of long-term storage in a high temperature and high humidity environment, periodic streak-like charging failure is suppressed, so that the life of the charging device 200 can be extended.

Hereinafter, the process cartridge 300 including the charging device 200 will be described with reference to FIG.
In the housing 120 in which the charging device 200 is housed, a pair of holding members 110 are attached to both axial end portions (right and left side end portions in FIG. 2) of the charging roll 14 and the cleaning roll 100 in the main body portion 122. A pair of attachment parts 124 are integrally provided.

  In the mounting portion 124, a guide groove 126 is formed along the extending direction of the mounting portion 124 (the direction intersecting with the axial direction of the charging roll and the cleaning roll). The holding member 110 is fitted in the guide groove 126 and disposed on the tip end side, and is guided by the guide groove 126 and extends in a direction in which the mounting portion 124 extends (a direction intersecting the axial direction of the charging roll and the cleaning roll Can be slid along).

  The outer side surfaces of the pair of attachment portions 124 are thick and the tip end extends, and a pair of bearing portions 132 for holding the photosensitive member 12 is provided at the tip portion. A bearing hole 134 is coaxially formed in the pair of bearing portions 132, and the end of the shaft core 12A of the photosensitive member 12 is rotatably inserted into the bearing hole 134, and the charging roll 14 and the cleaning roll are formed. The single housing 120 is assembled together with the housing 100. In addition, the housing | casing 120 does not need to be formed in one (integrally), and should just be a member which can support the holding member 110 at least.

  A pressure member 128 (for example, a compression coil spring) is provided on the proximal end side in the guide groove 126. When the holding member 110 is pressed toward the photosensitive member 12 by the pressure (for example, the spring force) of the pressing member 128 (in the direction of the arrow 15), the charging roller 14 is pressed against the photosensitive member 12. , And the cleaning roll 100 is in contact with the charging roll 14 in a pressed state.

  The process cartridge 300 is not limited to the above configuration, and may have the charging device 200 according to the present embodiment. Specifically, at least one selected from other means such as an image carrier (for example, a photosensitive body), a developing means, an electrostatic charge image forming means, and a transfer means, if necessary. It may be a configuration.

  Next, the state in which the shaft core 14A of the charging roll and the shaft core 100A of the cleaning roll are held by the holding member 110 will be described in more detail.

  As shown in FIGS. 3 and 4, the charging roll 14 and the cleaning roll 100 are disposed in contact with each other at a predetermined bite amount. The charging roll 14 has a charging layer 14B on the outer peripheral surface of its shaft core 14A, and the end of the shaft core 14A is held by the holding member 110. The cleaning roll 100 has an elastic layer 100B on the outer peripheral surface of its shaft core 100A, and the end of the shaft core 100A is held by the holding member 110. Further, on the opposite side of the holding member 110 to the photosensitive member 12, a pressing member 128 for pressing the holding member 110 to the photosensitive member 12 side is disposed.

  A first bearing hole 112 and a second bearing hole 114 are formed in the holding member 110 at predetermined intervals along the longitudinal direction (vertical direction in FIG. 3). The end of the shaft core 14A of the charging roll is rotatably inserted into the first bearing hole 112, and the end of the shaft core 100A of the cleaning roll is rotatably inserted into the second bearing hole 114. That is, holding the shaft core means holding the shaft core rotatably by inserting the shaft core into the bearing portion (for example, a bearing hole).

  In this embodiment, the fitting between the second bearing hole 114 for holding the cleaning roller shaft core 100A and the cleaning roller shaft core 100A is designed to be tight. Specifically, the inner diameter D2 of the second bearing hole 114 holding the shaft core 100A of the cleaning roll (hereinafter sometimes simply referred to as "the inner diameter D2 of the second bearing hole 114") and the outside of the cleaning roller shaft core 100A. The difference with the diameter D1 (hereinafter sometimes referred to simply as "the outer diameter D1 of the shaft core 100A") is 0.01 mm or more and 0.12 mm or less, preferably 0.01 mm or more and 0.08 mm or less, more preferably 0. It is set as 04 mm or more and 0.08 mm or less. By setting the difference between the inner diameter D2 of the second bearing hole 114 and the outer diameter D1 of the shaft core 100A to 0.01 mm or more and 0.12 mm or less, the rotation of the cleaning roll 100 is different between the cleaning roll 100 and the charging roll 14 The variation of the relative position between them is suppressed, and the variation of the pressure on the charging roller 14 of the cleaning roller 100 is suppressed. Further, by setting the difference between the inner diameter D2 of the second bearing hole 114 and the outer diameter D1 of the shaft core 100A to 0.01 mm or more, generation of a streak-like fixed substance on the surface of the photosensitive member is suppressed. .

  Here, when the second bearing hole 114 has a shape such as an elliptical shape, the difference (minimum difference) between the minimum diameter of the inner diameter D2 of the second bearing hole 114 and the outer diameter D1 of the shaft core 100A is 0.01 mm or more If the difference (maximum difference) between the maximum diameter of the inner diameter D2 of the second bearing hole 114 and the outer diameter D1 of the shaft core 100A is 0.12 mm or less, it is included in the range of the difference.

  Although the charging roll 14 and the photosensitive member 12 are adjusted to a fixed relative position by a spring, the inner diameter of the first bearing hole 112 for holding the axial core 14A of the charging roll and the outer diameter of the axial core 14A of the charging roll From the viewpoint of suppressing the fluctuation of the relative position between the charging roll 14 and the photosensitive member 12, the difference of the distance is, for example, 0.01 mm or more and 0.15 mm or less, preferably 0.02 mm or more and 0.1 mm or less.

In the charging device 200 according to the present embodiment, when the holding member 110 is pressed toward the photosensitive member 12 by the pressing member 128 (in the direction of the arrow 15), the cleaning roll 100 contacts the charging roll 14 and is determined in advance. The elastic layer 100 B is elastically deformed along the outer peripheral surface of the charging roller 14 to form the nip portion 101. The charging roller 14 contacts the photosensitive member 12 and is pressurized with a predetermined load, and the charging layer 14 B elastically deforms along the outer peripheral surface of the photosensitive member 12 to form a nip portion 102. Then, when the photosensitive member 12 is rotationally driven in the direction of the arrow 16 by a motor (not shown), the charging roller 14 is driven to rotate in the direction of the arrow 17 by the rotation of the photosensitive member 12 to charge the photosensitive member 12. The rotation of the roll 14 causes the cleaning roll 100 to rotate in the direction of the arrow 18 to clean the charging roll 14.
The charging roller 14 and the cleaning roller 100 are preferably driven to rotate in accordance with the coating (filming) of the external toner additive, but the invention is not limited thereto, and may be independently rotated.

Next, each component of the charging device 200 will be described. In addition, the code | symbol is abbreviate | omitted and demonstrated.
(Charging roll)
The charging roll has, for example, a shaft core and a charging layer. The charging layer is a layer for applying charge to a photosensitive member (an example of a member to be charged), and is provided, for example, on a conductive elastic layer provided on the outer peripheral surface of the shaft core and on the outer peripheral surface of the conductive elastic layer. And a conductive surface layer (hereinafter sometimes referred to as "surface layer"). For example, an adhesive layer (not shown) is provided between the shaft core and the conductive elastic layer.
However, the charging roll according to the present embodiment is not limited to the above layer configuration, and for example, a configuration in which an intermediate layer is provided between the shaft core and the conductive elastic layer, or between the conductive elastic layer and the surface layer The structure which provided the resistance adjustment layer or the transition prevention layer may be sufficient. Also, the surface layer may not be provided.

In the present specification, conductivity means that the volume resistivity at 20 ° C. is less than 1 × 10 ¹³ Ωcm.

-Axis core-
The shaft functions as an electrode and a support member of the charging roll, and for example, a conductive shaft is applied. Examples of the material of the shaft core include metals such as iron (free-cutting steel etc.), copper, brass, stainless steel, aluminum, nickel, etc .; and iron plated with chromium, nickel, etc .; As a conductive axial core, the member (for example, resin, ceramic member) which performed the plating process to the outer peripheral surface, the member (for example, resin, ceramic member) etc. with which the electrically conductive agent was disperse | distributed are mentioned. The shaft core may be a hollow member (cylindrical member) or a non-hollow member.

-Adhesive layer-
Examples of the material of the adhesive layer include a known adhesive which is a composition having an electrical conductivity by adhering the shaft core and the conductive elastic layer. Examples of the adhesive include a resin composition containing an electron conductive agent, and a resin composition containing a conductive resin.

-Conductive elastic layer-
The conductive elastic layer contains an elastic material and a conductive agent. The conductive elastic layer may optionally contain other additives. The conductive elastic layer may also serve as the resistance adjustment layer.

As an elastic material, for example, isoprene rubber, chloroprene rubber, epichlorohydrin rubber, butyl rubber, urethane rubber, silicone rubber, fluororubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide Copolymer rubbers, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubbers, ethylene-propylene-diene copolymer rubbers, acrylonitrile-butadiene copolymer rubbers, natural rubber, rubbers obtained by mixing these, etc. may be mentioned.
Among these elastic materials, silicone rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, and a mixture of these are preferable.
The rubber material may be foamed or non-foamed.

The conductive agent includes an electron conductive substance and an ion conductive substance.
Examples of the electron conductive substance include carbon blacks such as ketjen black and acetylene black, pyrolytic carbon, graphite, zinc, aluminum, copper, iron, metals such as iron, nickel, chromium and titanium, ZnO-Al ₂ O ₃ , SnO ₂ -Sb ₂ O ₃ , In ₂ O ₃ -SnO ₂ , ZnO-TiO ₂ , MgO-Al ₂ O ₃ , FeO-TiO ₂ , TiO ₂ , SnO ₂ , Sb ₂ O ₃ , In ₂ O ₃ , ZnO And known metal oxides such as MgO.
Examples of the ion conductive material include known salts such as quaternary ammonium salts, perchlorates of alkali metals, and perchlorates of alkaline earth metals.
These conductive agents may be used alone or in combination of two or more.

The content of the conductive agent is not particularly limited as long as the target characteristics of the conductive elastic layer can be obtained.
Specifically, in the case of the electron conductive material, the content of the conductive agent is preferably 1 part by mass or more and 90 parts by mass or less with respect to 100 parts by mass of the elastic material.
On the other hand, in the case of the ion conductive material, the content of the conductive agent is preferably 0.01 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the elastic material.

  Other additives in the conductive elastic layer include well-known additives such as a softener, a plasticizer, a vulcanizing agent, a vulcanization accelerator, an antioxidant, a surfactant, and a coupling agent.

The volume resistivity of the conductive elastic layer is, for example, preferably 10 ³ Ωcm or more and 10 ¹⁴ Ωcm or less, preferably 10 ⁵ Ωcm or more and 10 ¹² Ωcm or less, more preferably, when the conductive elastic layer doubles as a resistance adjustment layer. Is 10 ⁷ Ωcm or more and 10 ¹² Ωcm or less.

The volume resistivity of the conductive elastic layer is a value measured by the following method. A sheet-like measurement sample is collected from the conductive elastic layer, and the measurement jig (R12702A / B resistivity chamber: made by ADVANTEST CORPORATION) and high resistance measurement are measured according to JIS-K-6911 (1995). Voltage is applied to adjust the electric field (applied voltage / composition sheet thickness) to 1000 V / cm for 30 seconds using a sensor (R8340A digital high-resistance / micro-ammeter: manufactured by ADVANTEST CORPORATION), and the flowing current value It calculates using a following formula.
Volume resistivity (Ω cm) = (19.63 × applied voltage (V)) / (current value (A) × measurement sample thickness (cm))

  Although the thickness of the conductive elastic layer varies depending on the device to which the charging roll is applied, for example, 1 mm or more and 10 mm or less is preferable, and 2 mm or more and 5 mm or less is more preferable.

  The thickness of the conductive elastic layer is a value measured by the following method. Using a single-edged knife, cut at 20 mm positions at both axial ends of the conductive elastic layer (charging roll) and three parts at the center, and observe the cross section of the cut sample at an appropriate magnification according to the thickness of 5 to 50 times. The film thickness was measured and taken as the average value. As a measurement apparatus, Keyence Corporation digital microscope VHX-200 is used.

-Surface layer-
The surface layer contains, for example, a resin and, if necessary, other additives.

  As the resin, for example, acrylic resin, fluorine modified acrylic resin, silicone modified acrylic resin, cellulose resin, polyamide resin, copolymer nylon, polyurethane resin, polycarbonate resin, polyester resin, polyimide resin, polyimide resin, epoxy resin, silicone resin, polyvinyl alcohol resin Polyvinyl butyral resin, cellulose resin, polyvinyl acetal resin, ethylene tetrafluoroethylene resin, melamine resin, polyethylene resin, polyvinyl resin, polyarylate resin, polythiophene resin, polyethylene terephthalate resin (PET), fluorine resin (polyvinylidene fluoride resin, 4 Fluorinated ethylene resin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexene Hexafluoropropylene copolymer (FEP) and the like). The resin is preferably one obtained by curing or crosslinking a curable resin with a curing agent or a catalyst.

  As other additives in the surface layer, for example, a conductive agent, a filler (for example, porous resin particles), a curing agent, a vulcanizing agent, a vulcanization accelerator, an antioxidant, a surfactant, a coupling agent, etc. Well-known additives which can be added to the surface layer of the Other additives also include silicone oils.

The volume resistivity of the surface layer is, for example, 10 ³ Ωcm or more and 10 ¹⁴ Ωcm or less, preferably 10 ⁵ Ωcm or more and 10 ¹² Ωcm or less, more preferably 10 ⁷ Ωcm or more and 10 ¹² Ωcm or less.

The volume resistivity of the surface layer is a value measured by the following method. The surface layer is applied to a flat plate of metal such as aluminum or stainless steel or a sheet-like rubber material having a volume resistance of 10 Ωcm or less to obtain a measurement sample. For the measurement sample, according to JIS-K-6911 (1995), a measurement jig (R12702A / B resistivity chamber: made by Advantest) and a high resistance measuring instrument (R8340A digital high resistance / microammeter: made by Advantest) After applying a voltage adjusted so that the electric field (applied voltage / composition sheet thickness) to be 1000 V / cm for 30 seconds, the following equation is calculated from the flowing current value.
Volume resistivity (Ω cm) = (19.63 × applied voltage (V)) / (current value (A) × measurement sample film thickness (cm))

  The surface roughness Rz of the surface layer is from 2 μm to 10 μm from the viewpoint of ensuring the uniformity of charging to the photosensitive member by the charging roll, and from the viewpoint of suppressing the coating (filming) of the toner on the photosensitive member Or less, preferably 3 μm to 8 μm, more preferably 3 μm to 6 μm.

  The surface roughness Rz of the surface layer is a value measured by the following method. According to JIS B 0601 (1994), the axial direction both ends 20 mm of a surface layer (charging roll) and three places of a center part were measured, and it was considered as the average value. As a measuring device, Surfcom 1400 manufactured by Tokyo Seimitsu Co., Ltd. is used. Measurement conditions are cut-off: 0.8 mm, measurement length: 2.4 mm, traverse speed: 0.3 mm / sec.

  The surface layer is formed by dispersing each component in a solvent to prepare a coating solution, applying the coating solution on the conductive elastic layer formed in advance, and then heating.

(Cleaning roll)
The cleaning roll has a shaft core and an elastic layer provided on the outer peripheral surface of the shaft core.

-Axis core-
As the shaft core, the same shaft core as that of the charging roller described above can be used.

-Elastic layer-
The elastic layer is preferably a foam layer having a porous three-dimensional structure, and hollows and irregularities (hereinafter sometimes referred to as "cells") may be present inside or on the surface.

  The elastic layer is polyurethane, polyethylene, polyamide, olefin, melamine, polypropylene, NBR (acrylonitrile-butadiene copolymer rubber), EPDM (ethylene-propylene-diene copolymer rubber), natural rubber, styrene butadiene rubber, chloroprene, silicone, nitrile And foamable resin materials or rubber materials.

  Among these foamable resin materials or rubber materials, from the viewpoint of suppressing the occurrence of distortion due to long-term storage in a high temperature and high humidity environment, cleaning foreign substances such as toner and toner external additive by rubbing with a charging roll From the viewpoint, a foamable resin material is preferable, and polyurethane is suitably applied. That is, the elastic layer is preferably a polyurethane foam layer.

  The polyurethane is not particularly limited, and, for example, polyols (for example, polyester polyols, polyether polyols, acrylic polyols etc.) and isocyanates (2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4 Reaction products of diphenylmethane diisocyanate, tolidine diisocyanate, 1,6-hexamethylene diisocyanate, etc., and reaction products by these chain extenders (eg, 1,4-butanediol, trimethylolpropane etc.) .

The elastic layer is formed using, as necessary, a foaming agent, a foam stabilizer, etc. in addition to the above-described foamable resin material or rubber material. In particular, in the case of polyurethane, foaming is generally performed using a foaming agent, a foam stabilizer and the like.
As the foaming agent, known foaming agents such as water and azo compounds (for example, azodicarbonamide, azobisisobutyronitrile etc.) are used.
Also, as a foam stabilizer, silicone foam stabilizer (eg, dimethyl silicone oil, methyl hydrogen silicone oil, diphenyl silicone oil, methylphenyl silicone oil, straight silicone such as chlorophenyl silicone oil; alkyl modified silicone oil, aralkyl modified silicone Oil, polyether-modified silicone oil, polyester-modified silicone oil, fluoroalkyl-modified silicone oil, amino-modified silicone oil, alkoxy-modified silicone oil, epoxy-modified silicone oil, modified silicone oil such as carboxyl group-modified silicone oil, etc. A foam stabilizer is used.

The compressive residual strain rate of the elastic layer is 5% or less, preferably 3% or less. By setting the compression residual strain rate to 5% or less, the occurrence of distortion of the cleaning roll is suppressed even when stored for a long time in a high temperature and high humidity environment, and fluctuation of pressure applied to the charging roll of the cleaning roll is suppressed. As a result, the fluctuation of the pressure applied to the photosensitive member (an example of the member to be charged) of the charging roller is suppressed, and the nip formation between the charging roller and the photosensitive member is stably performed. Uniformity is likely to be maintained.
Here, the compressive residual strain rate is preferably as close to zero as possible from the viewpoint of suppressing the occurrence of strain, but the ease of obtaining a cleaning roll product or the compressive residual strain rate when producing an elastic layer is preferable. From the viewpoint of easiness of control of the lower limit value of the compression residual strain rate is 0.5%.
In addition, the measurement of a compression residual distortion rate is performed by the method based on JIS-K6401.

  In addition, as a method of controlling the compression residual strain rate of an elastic layer to 5% or less, when an elastic layer is a foaming layer, compounding quantities, such as a raw material, a foaming agent, a foam stabilizer, foaming conditions (temperature, time, stirring Method of controlling the cell diameter of the foam layer by changing the rotation speed of the machine, the shape of the stirring blade, etc .; when the elastic layer is a resin having a crosslinked structure, the blending amounts of raw materials, crosslinking agents, catalysts, etc. There are known methods such as a method of controlling the degree of crosslinking of the resin by changing the crosslinking conditions (temperature, time, etc.) and the like.

The biting amount of the cleaning roll with respect to the charging roll is 0.2 mm or more and 1.2 mm or less, preferably 0.3 mm or more and 1.0 mm or less, and more preferably 0.5 mm or more and 0.8 mm or less. Here, the biting amount of the cleaning roll with respect to the charging roll refers to the recessed thickness of the recessed portion of the cleaning roll in contact with the charging roll relative to the cleaning roll not in contact with the charging roll. That is, the concave thickness refers to the concave thickness of the elastic layer of the cleaning roll.
By setting the biting amount to 0.2 mm or more and 1.2 mm or less, generation of a streak-like fixed substance on the surface of the photosensitive member is suppressed. In addition, generation of streak-like density unevenness that periodically appears on the outer periphery of the cleaning roll (hereinafter, referred to as “axial direction of outer peripheral pitch”) is further suppressed. Furthermore, sufficient cleaning performance is exhibited, and contamination and fogging due to the adhesion of the toner of the charging roll and the toner external additive are suppressed.

  Although the thickness of an elastic layer changes with apparatuses which apply a cleaning roll, 1.0 mm-10 mm are mentioned, for example, 1.5 mm-8 mm are mentioned further. The measurement of the thickness of the elastic layer is performed by the same method as the measurement of the thickness of the conductive elastic layer described above.

The elastic layer may have a tubular shape formed on the entire outer peripheral surface of the shaft core, or may be formed by spirally winding a strip-shaped elastic member around the outer peripheral surface of the shaft core. .
In addition, the elastic layer may be formed, for example, by applying a mixture of a component constituting the elastic layer and a foaming agent or a foam stabilizer that contributes to foaming on the outer peripheral surface of the shaft core, and molding and foaming. Alternatively, a foam provided with through holes in advance may be adhered to the outer peripheral surface of the shaft core using an adhesive, and then the outer diameter may be polished.

(Holding member)
Examples of the holding member include synthetic resin materials such as polyacetal and polycarbonate from the viewpoint of high rigidity, high slidability, or abrasion resistance. Further, from the viewpoint of further enhancing the abrasion resistance, the above-mentioned synthetic resin material may contain glass fiber, carbon fiber and the like. The shape of the holding member is not particularly limited, but may be a single configuration.

(Pressure member)
The pressing member may be any member that can press the holding member toward the photosensitive member, and examples thereof include a compression coil spring, a disc spring, a plate spring, a rubber member, and the like.

The charging device according to the present embodiment described above charges the photosensitive member as a member to be charged provided in an electrophotographic image forming apparatus, but the present invention is not limited thereto. It can apply also to the use which charges a processing subject. As a processing object, for example, a processing object (for example, an electronic device) for the purpose of removing electricity for giving a reverse polarity charge to the charge which has been charged so as not to cause electrostatic destruction by charging and neutralizing it; Processing object (eg, solid material) for quality treatment (eg, hydrophilization treatment, hydrophobization treatment); treatment object for food processing, sterilization in medical field, sterilization treatment (eg, food, various medical treatments) Equipment);
Even in the case where the charging device according to the present embodiment is applied to use for charging these objects to be charged, periodic streak-like charging defects, that is, processing defects can be suppressed for the same reasons as described above. .

  Hereinafter, the present invention will be described in more detail by way of examples. However, these examples do not limit the present invention. In the following description, “parts” means “parts by mass” unless otherwise noted.

Example 1
The charging roll A, the cleaning roll A, and the holding member A were manufactured by the following procedure.

[Preparation of Charged Roll A]
(Formation of conductive elastic layer)
A mixture of the composition shown in Table 1 below is kneaded with an open roll, and an outer diameter of 12.3 mm outer diameter of a conductive shaft core made of SUS303 using an adhesive layer and a press molding machine. A 5 mm roll was formed. Thereafter, the outer diameter of the roll was adjusted to 12.0 mm by polishing to obtain an elastic roll having a conductive elastic layer.

(Formation of surface layer)
Among the compositions shown in Table 2 below, N-methoxymethylated polyamide (F30K / Nagase Chemtex), polyvinyl butyral resin (trade name: S-Lec BL-1 / Sekisui Chemical Industry), carbon black (MONARCH 1000 / Cabot) A mixture obtained by diluting 15 parts by mass of the mixture with 85 parts by mass of methanol and dispersing it in a bead mill was used to obtain a dispersion, of which the porous polyamide filler (2001 UDNAT1 / Alkema) of the compositions shown in Table 2 and an acid catalyst (NACURE 4167 / King industry ) And ether-modified polydimethylsiloxane (BYK 307 / BYK) were mixed and stirred to obtain a surface layer coating solution. After dip coating on the surface of the elastic roll, it was crosslinked by heating at 140 ° C. for 30 minutes and dried. As a result, a charging roll A having a surface layer with a thickness of 10 μm was obtained.

[Preparation of Cleaning Roll A]
First, a free-cutting steel cut to an outer diameter of 5.990 mm is used as the material, an adhesive is applied to the nickel-plated shaft core, and a urethane foam with a compression residual strain rate of 3% (product name EP70: manufactured by Inoac Corporation) Is cut into a size of 15 mm × 15 mm × 350 mm, a through hole is made at the center, and inserted and bonded to the shaft core, and then the urethane foam is polished to an outer diameter to make the outer diameter of the roll 10.0 mm. did. Thus, a cleaning roll A having a urethane foam (a polyurethane foam layer) was obtained. In addition, the compression residual distortion rate was measured by the above-mentioned method. The same applies to the measurement of the following compressive residual strain rate.

[Preparation of Cleaning Roll B]
A cleaning roll B was obtained in the same manner as the cleaning roll A except that the outer diameter of the axial core of the cleaning roll was set to 5.960 mm.

[Preparation of Cleaning Roll C]
A cleaning roll C was obtained in the same manner as the cleaning roll A except that the outer diameter of the axial core of the cleaning roll was changed to 5.920 mm.

[Preparation of Cleaning Roll D]
A cleaning roll D was obtained in the same manner as the cleaning roll A except that the outer diameter of the axial core of the cleaning roll was set to 5.880 mm.

[Preparation of Cleaning Roll E]
A cleaning roll E was obtained in the same manner as the cleaning roll B, except that a urethane foam (product name RR26: manufactured by Inoac Corporation) having a compression residual strain rate of 5% was used.

[Preparation of Cleaning Roll F]
A cleaning roll F was obtained in the same manner as the cleaning roll E except that a urethane foam (product name RR80: manufactured by Inoac Corporation) having a compression residual strain rate of 6% was used.

[Preparation of Cleaning Roll G]
A cleaning roll G was obtained in the same manner as the cleaning roll E, except that the outer diameter of the axial core of the cleaning roll was set to 5.995 mm.

[Preparation of Cleaning Roll H]
A cleaning roll H was obtained in the same manner as the cleaning roll E except that the outer diameter of the axial core of the cleaning roll was 5.870 mm.

[Preparation of Holding Member A]
By cutting a single polyacetal holding member, as a first bearing portion for holding the shaft core of the charging roll, a first bearing hole with an inner diameter of 8.000 mm and a second bearing for holding the shaft core of the cleaning roll A holding member A provided with a second bearing hole with an inner diameter of 6.000 mm as a part was obtained. The distance between the center of the first bearing hole and the center of the second bearing hole is 10.4 mm.

[Preparation of Holding Member B]
A holding member B was obtained in the same manner as the holding member A except that the distance from the center of the first bearing hole to the center of the second bearing hole was 10.8 mm.

[Preparation of Holding Member C]
A holding member C was obtained in the same manner as the holding member A except that the distance from the center of the first bearing hole to the center of the second bearing hole was 9.8 mm.

[Preparation of Holding Member D]
A holding member D was obtained in the same manner as the holding member A except that the distance from the center of the first bearing hole to the center of the second bearing hole was 9.7 mm.

[Preparation of Holding Member E]
A holding member E was obtained in the same manner as the holding member A except that the distance from the center of the first bearing hole to the center of the second bearing hole was 10.9 mm.

[Examples 1-8, comparative examples 1-4]
In the combination shown in Tables 3 and 4, together with the charging roll, the cleaning roll and the holding member, a compression coil spring separately prepared as a pressing member is charged on the process cartridge of the image forming apparatus (DocuCenter-4 C5570 manufactured by Fuji Xerox Co., Ltd.) It was installed as a device. This image forming apparatus was used as the image forming apparatus of Examples 1 to 8 and Comparative Examples 1 to 3. The cleaning roll was mounted so as to be driven to rotate by the charging roll.

[Image quality evaluation]
The following image quality evaluation was performed using the image forming apparatus of each example. After the image forming apparatus is left in a high temperature and high humidity environment of 45 ° C./95% RH for one month, a halftone image (A2 paper (C2 paper) manufactured by Fuji Xerox Co., Ltd.) in a 22 ° C./55% RH environment Continuously output 3 sheets of image density 30%), and continuously output 50,000 sheets of halftone images of 5% image density by feeding A4 paper (C2 paper made by Fuji Xerox) horizontally, and then environment at 28 ° C / 85% RH Below, similarly, 50,000 sheets of halftone images are continuously output, and then, similarly, 50,000 sheets of halftone images are continuously output under an environment of 10 ° C./15% RH. After completion of the output of the 50,000th sheet under an environment of 10 ° C./15%RH, three halftone images having an image density of 30% were continuously output on A3 paper.
And about the halftone image outputted to the 1st sheet under 22 ° C / 55% RH environment, generation | occurrence | production of generation | occurrence | production of the density | concentration nonuniformity of the linear direction of the axial direction of the outer peripheral pitch of the cleaning roll by storage was evaluated.
In addition, in the 10 ° C./15% RH environment, a stripe shape in the process direction (A3 sheet conveyance direction) is applied to the halftone image output to the third sheet (total 1506 sheets) of the A3 sheet output last. The occurrence of uneven density was evaluated. The results are shown in Tables 3 and 4.

Evaluation criteria are as follows.
G1: No occurrence of streaks G2: Occurrence of slight streaks partially G3: Occurrence of slight streaks G4: Occurrence of slight streaks G5: Occurrence of streaks

From the results of the image quality evaluation, Examples 1 to 8 are in the axial direction and the process direction of the outer peripheral pitch of the cleaning roll even when stored for a long time (one month) under high temperature and high humidity environment (45 ° C., 95% RH). It was found that the occurrence of streak-like density unevenness was suppressed.
In particular, in Examples 6 and 7 in which the compressive residual strain rate is 5% or less, the occurrence of uneven density in the axial direction of the outer peripheral pitch of the cleaning roll as compared with Comparative Example 1 in which the compressive residual strain rate exceeds 5%. Was found to be suppressed.
Similarly, in Example 7 in which the difference between the inner diameter of the second bearing hole and the outer diameter of the axial center of the cleaning roll is 0.01 mm or more and 0.12 mm or less, the difference is more than Comparative Example 3 in which the difference exceeds 0.12 mm, It was found that the occurrence of streak-like density unevenness in the axial direction of the outer peripheral pitch of the cleaning roll was suppressed.
Further, Example 6 in which the amount of biting in of the cleaning roll with respect to the charging roll is 1.2 mm has streaky density unevenness in the axial direction of the outer peripheral pitch of the cleaning roll as compared with Example 8 in which the amount of biting in exceeds 1.2 mm. Was found to be more suppressed.
From the above results, it was found that, when the charging device of this example is applied, periodic streak-like charging failure is suppressed even when stored for a long time under a high temperature and high humidity environment. In addition, when the charging device of this example was applied, it was found that the formation of streak-like fixed matter was suppressed even when stored for a long time under a high temperature and high humidity environment.

1Y, 1M, 1C, 1K photoconductors (an example of an object to be charged)
2Y, 2M, 2C, 2K charging device (an example of charging means)
3 Exposure device (an example of electrostatic charge image forming means)
3Y, 3M, 3C, 3K laser beams 4Y, 4M, 4C, 4K developing devices (an example of developing means)
5Y, 5M, 5C, 5K primary transfer roll (an example of primary transfer means)
6Y, 6M, 6C, 6K photoconductor cleaning device (an example of the cleaning means)
8Y, 8M, 8C, 8K Toner cartridge 10Y, 10M, 10C, 10K Image forming unit 12 Photosensitive member (an example of a member to be charged)
14 charging roll 14A shaft of charging roll 14B charging layer 20 intermediate transfer belt (an example of an intermediate transfer member)
22 Drive roll 24 Support roll 26 Secondary transfer roll (an example of secondary transfer means)
30 Intermediate Transfer Member Cleaning Device 100 Cleaning Roll 100A Shaft Core 100B of Cleaning Roll Elastic Layer 110 Holding Member 112 First Bearing Hole (Example of First Bearing Portion)
114 Second bearing hole (an example of second bearing)
120 case 128 pressing member 200 charging device (an example of charging means)
300 Process Cartridge P Recording Paper (Example of Recording Medium)

Claims (3)

A charging roll that charges a member to be charged by rotating in contact with the member to be charged;
A cleaning roll comprising an axial core and an elastic layer provided on the outer peripheral surface of the axial core, wherein the compressive residual strain ratio of the elastic layer is 5% or less, wherein the charging roll rotates in contact with the charging roll A cleaning roll for cleaning the charging roll;
A holding member having a first bearing portion for holding an axial core of the charging roll, and a second bearing portion for holding an axial core of the cleaning roll;
A pressure member which brings the charging roll into contact with the member to be charged and the cleaning roll into contact with the charging roll by pressing the holding member;
Equipped with
The difference between the inner diameter of the second bearing portion and the outer diameter of the axial center of the cleaning roll is 0.04 mm or more and 0.08 mm or less.
The charging device, wherein a biting amount of the cleaning roll with respect to the charging roll is 0.5 mm or more and 0.8 mm or less. A charging device according to claim 1 ,
Process cartridge that is attached to and detached from the image forming apparatus. An object to be charged,
A charging unit for charging the surface of the member to be charged, comprising: the charging unit according to claim 1 ;
Electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged member to be charged;
Developing means for developing an electrostatic charge image formed on the surface of the member to be charged as a toner image;
A transfer unit configured to transfer a toner image formed on the surface of the member to be charged to the surface of a recording medium;
Fixing means for fixing the toner image transferred to the surface of the recording medium;
An image forming apparatus comprising: