JP2015184477A - Image forming apparatus and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that suppresses a discharge noise generated when contact charging is performed, in which a voltage obtained by superposing an AC voltage on a DC voltage is applied to charge the surface of an electrophotographic photoreceptor.SOLUTION: An image forming apparatus includes: for example, a cylindrical electrophotographic photoreceptor 7; a cylindrical silencer 15 (cylindrical member) that is provided inside the electrophotographic photoreceptor 7 to have the outer peripheral surface in contact with the inner peripheral surface of the electrophotographic photoreceptor 7, and has a running torque of 15 N m or more, which is required to be rotated relative to the circumferential direction of the electrophotographic photoreceptor 7; and a charging device 8 of a contact charging system that applies a voltage obtained by superposing an AC voltage to a DC voltage to charge the surface of the electrophotographic photoreceptor.

Description

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

In a conventional electrophotographic image forming apparatus, a toner image formed on the surface of an electrophotographic photosensitive member is transferred to a recording medium through processes of charging, exposure, development, and transfer.
As an electrophotographic photosensitive member for use in such an electrophotographic image forming apparatus, an electrophotographic photosensitive member in which a cylindrical member is inserted inside a conductive substrate has been proposed for the purpose of suppressing discharge noise during charging. (Patent Document 1).

Japanese Patent No. 3257267

  An object of the present invention is to provide a charging means of a contact charging system (hereinafter referred to as “DC + AC voltage application system”) that charges a surface of an electrophotographic photosensitive member by applying a voltage in which an AC voltage is superimposed on a DC voltage. Another object of the present invention is to provide an image forming apparatus that suppresses discharge noise even when the AC voltage of the charging means is increased in frequency.

  The above problem is solved by the following means.

The invention according to claim 1 is a cylindrical electrophotographic photosensitive member;
An outer peripheral surface is provided inside the electrophotographic photosensitive member in contact with the inner peripheral surface of the electrophotographic photosensitive member, and a rotational torque required for relative rotation in the circumferential direction of the electrophotographic photosensitive member is 15 N · m. A cylindrical member as described above;
A contact charging method charging means for charging the surface of the electrophotographic photosensitive member by applying a voltage obtained by superimposing an AC voltage on a DC voltage;
An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive member;
Developing means for developing the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image;
Transfer means for transferring the toner image to the surface of the recording medium;
An image forming apparatus comprising:

The invention according to claim 2 is the image formation according to claim 1, wherein the cylindrical member includes a slit extending in an axial direction of the electrophotographic photosensitive member and a constriction portion extending in the axial direction of the electrophotographic photosensitive member. apparatus.

The invention according to claim 3 is the image forming apparatus according to claim 1 or 2, wherein the cylindrical member is a molded body of acrylonitrile-butadiene-styrene resin.

The invention according to claim 4 is the image forming apparatus according to any one of claims 1 to 3, wherein a rotation speed of the electrophotographic photosensitive member is 150 mm / s or more.

The invention according to claim 5 is the image forming apparatus according to any one of claims 1 to 4, wherein the frequency of the AC voltage of the charging unit is 1300 Hz or more.

The invention according to claim 6 is a cylindrical electrophotographic photosensitive member,
An outer peripheral surface is provided inside the electrophotographic photosensitive member in contact with the inner peripheral surface of the electrophotographic photosensitive member, and a rotational torque required for relative rotation in the circumferential direction of the electrophotographic photosensitive member is 15 N · m. A cylindrical member as described above;
A contact charging method charging means for charging the surface of the electrophotographic photosensitive member by applying a voltage obtained by superimposing an AC voltage on a DC voltage;
And a process cartridge which is detachable from the image forming apparatus.

  According to the first or second aspect of the invention, in the image forming apparatus provided with the charging means of the DC + AC voltage application method, compared with the case where the rotational torque of the cylindrical member is outside the above range, the AC of the charging means An image forming apparatus that suppresses discharge noise even when the voltage is increased in frequency is provided.

  According to the third aspect of the present invention, in the image forming apparatus provided with the DC + AC voltage application type charging unit, the AC voltage of the charging unit is increased compared to the case where the cylindrical member is an acrylic resin molded body. An image forming apparatus that suppresses discharge noise even when the frequency is increased is provided.

  According to the fourth aspect of the invention, the discharge noise is suppressed even when the rotational speed of the electrophotographic photosensitive member is increased to 150 mm / s or more, compared to the case where the rotational torque of the cylindrical member is outside the above range. An image forming apparatus is provided.

  According to the fifth aspect of the present invention, even when the rotational torque of the cylindrical member is out of the above range, the discharge noise is suppressed even when the frequency of the AC voltage of the charging means is increased to 1300 Hz or higher. A forming apparatus is provided.

  According to the sixth aspect of the present invention, in the image forming apparatus provided with the DC + AC voltage application type charging unit, the AC voltage of the charging unit is increased compared to the case where the rotational torque of the cylindrical member is outside the above range. A process cartridge that suppresses discharge noise even when the frequency is increased is provided.

Schematic configuration diagram showing an example of an image forming apparatus according to the present embodiment Schematic configuration diagram showing another example of the image forming apparatus according to the present embodiment It is a schematic sectional drawing which shows an example of the electrophotographic photoreceptor which concerns on this embodiment. It is a schematic side view of the cylindrical member which concerns on this embodiment. It is XX sectional drawing of FIG.

  Embodiments that are examples of the present invention will be described below.

<Image forming apparatus>
The image forming apparatus according to the present embodiment includes a cylindrical electrophotographic photosensitive member and a DC + AC voltage application method (contact that charges a surface of the electrophotographic photosensitive member by applying a voltage obtained by superimposing an AC voltage on a DC voltage) (Charging system) charging means, electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, and a developer formed on the surface of the electrophotographic photoreceptor by a developer containing toner. A developing unit that develops the electrostatic latent image to form a toner image; and a transfer unit that transfers the toner image to the surface of the recording medium.
A cylindrical member (hereinafter also referred to as “cylindrical silencer”) is provided inside the electrophotographic photosensitive member. The cylindrical silencer is provided inside the electrophotographic photosensitive member with its outer peripheral surface in contact with the inner peripheral surface of the electrophotographic photosensitive member.
The cylindrical silencer has a rotational torque (hereinafter referred to as “rotational torque of the cylindrical silencer”) required to rotate relatively in the circumferential direction of the electrophotographic photosensitive member is 15 N · m or more.

  Here, an image forming apparatus employing a contact charging type charging unit is known from the viewpoint of low power consumption, space saving, and cost reduction. As a charging means of the contact charging method, a charging means of a DC + AC voltage application method (a contact charging method in which a voltage obtained by superimposing an AC voltage on a DC voltage is applied to charge the surface of the electrophotographic photosensitive member) is known. It has been. In charging by a DC + AC voltage application type charging means, an AC voltage is applied, and therefore the charging means (charging member such as a charging roll) contacting the electrophotographic photosensitive member vibrates by the frequency of the AC voltage, This vibration becomes a factor causing the electrophotographic photosensitive member to vibrate. When the electrophotographic photosensitive member vibrates, the vibration becomes a high-frequency vibration sound and generates noise called discharge sound.

  On the other hand, in order to suppress this discharge noise, by inserting a cylindrical member into the electrophotographic photosensitive member (its conductive substrate), the vibration of the electrophotographic photosensitive member due to the application of an alternating voltage is suppressed, A technique for suppressing discharge noise (for example, Japanese Patent No. 3257267) is also known.

  However, in recent years, the discharge volume tends to be higher and louder due to the increase in the speed of the electrophotographic apparatus (specifically, the rotation speed of the electrophotographic photosensitive member) and the accompanying increase in the frequency of the alternating voltage. In the current situation, when the alternating voltage to be applied is increased in frequency, the technology for suppressing the discharge noise cannot completely suppress the discharge noise.

Therefore, in the image forming apparatus according to the present embodiment, a cylindrical silencer is provided in the electrophotographic photosensitive member so that the rotational torque required for relative rotation in the circumferential direction of the electrophotographic photosensitive member is 15 N · m or more. Is provided. Thereby, in the image forming apparatus provided with the DC + AC voltage application type charging means, even if the AC voltage of the charging means is increased, the discharge noise is suppressed.
The reason for this is not clear, but it is difficult for the cylindrical silencer to rotate relatively in the circumferential direction of the electrophotographic photosensitive member, so that the inner peripheral surface of the electrophotographic photosensitive member and the outer peripheral surface of the cylindrical silencer face each other. This is because the contact state with respect to the circumferential direction of the electrophotographic photosensitive member is easily maintained, and it is considered that the vibration suppressing effect of the electrophotographic photosensitive member by the cylindrical silencer is enhanced.

In particular, as described above, for example, when the rotational speed of the electrophotographic photosensitive member is increased to 150 mm / s or more (for example, 150 mm / s to 300 mm / s), the discharge sound tends to increase. However, in the image forming apparatus according to the present embodiment, even if the rotation speed of the electrophotographic photosensitive member is increased within the range, the discharge noise is suppressed. Here, the rotation speed is the amount of movement per unit time that the surface of the electrophotographic photosensitive member moves in the circumferential direction.
Furthermore, for example, when the frequency of the AC voltage of the charging means applied when charging the surface of the electrophotographic photosensitive member is increased to 1300 Hz or higher (for example, 1300 Hz to 2500 Hz), the discharge sound tends to increase. However, in the image forming apparatus according to the present embodiment, the discharge noise is suppressed even if the AC voltage of the charging unit is increased in the range.

The DC voltage (absolute value) of the charging means is, for example, preferably 500 V to 900 V, and preferably 600 V to 800 V.
On the other hand, the peak-to-peak voltage of the AC voltage of the charging means is, for example, 1000 V or more and 3000 V or less, and preferably 1500 V or more and 2500 V or less.
The alternating current of the charging means is, for example, preferably 1 mA or more and 4 mA or less, and preferably 2 mA or more and 3 mA or less.

In the image forming apparatus according to the present embodiment, the rotational torque of the cylindrical silencer is 15 N · m or more, and is preferably 20 N · m or more, more preferably 25 N · m or more from the viewpoint of suppressing discharge noise. Here, the upper limit value of the rotational torque of the cylindrical silencer is that the electrophotographic photosensitive member and the cylindrical silencer are composed of separate members from the viewpoint of suppressing discharge noise, and the inner peripheral surface of the electrophotographic photosensitive member and the cylindrical shape Assuming that the non-adhered state is secured with the outer peripheral surface of the silencer, the higher the better. However, in terms of manufacturing, the upper limit value of the rotational torque of the cylindrical silencer is specifically 100 N · m or less, for example.
The rotational torque of the cylindrical silencer is, for example, the surface roughness Ra of the inner peripheral surface of the electrophotographic photosensitive member and the outer peripheral surface of the cylindrical silencer, and the size of the outer diameter of the cylindrical silencer relative to the inner diameter of the electrophotographic photosensitive member ( The outer diameter of the cylindrical silencer in a non-arranged state inside the electrophotographic photosensitive member) and the material of the electrophotographic photosensitive member and the cylindrical silencer are adjusted. The rotational torque of the cylindrical silencer is also adjusted by, for example, the thickness of the cylindrical silencer (the difference between the outer diameter and the inner diameter).

The rotational torque of the cylindrical silencer required to rotate the electrophotographic photosensitive member relative to the circumferential direction is the rotational torque required to rotate the cylindrical silencer circumferentially with the electrophotographic photosensitive member fixed. is there.
The rotational torque of the cylindrical silencer is measured as follows. Using a manual torque gauge (BTG90CN-S: Tohnichi Manufacturing Co., Ltd.), with a cylindrical silencer placed inside the electrophotographic photosensitive member, attach a torque gauge jig to the cylindrical silencer, Turn the gauge from the stationary state to the rotating state, and measure the maximum torque (value when changing from static frictional force to dynamic frictional force).
The value of the rotational torque of the cylindrical silencer is the average value obtained by performing the above measurement three times in an environment of normal temperature and humidity (22 ° C., 50% RH).

  In the image forming apparatus according to the present embodiment, from the viewpoint of increasing the rotational torque of the cylindrical silencer and suppressing the discharge noise, an inner peripheral surface (hereinafter simply referred to as “electrophotography”) in contact with the outer peripheral surface of the cylindrical silencer in the electrophotographic photosensitive member. The surface roughness Ra of the inner peripheral surface of the photosensitive member is preferably 1.3 μm or less, and the surface roughness Ra of the outer peripheral surface of the cylindrical silencer is preferably 0.7 μm or less.

The surface roughness Ra of the inner peripheral surface of the electrophotographic photosensitive member (the inner peripheral surface in contact with the outer peripheral surface of the cylindrical silencer) is preferably 1.0 μm or less, more preferably 0.7 μm or less from the viewpoint of suppressing discharge noise. It is. The surface roughness Ra of the inner peripheral surface of the electrophotographic photosensitive member is preferably smaller, but is preferably 0.3 μm or more from the viewpoint of manufacturing.
Here, the surface roughness Ra of the inner peripheral surface in contact with the outer peripheral surface of the cylindrical silencer in the electrophotographic photosensitive member is within the above range means that the surface roughness of at least the inner peripheral surface of the portion in contact with the outer peripheral surface of the cylindrical silencer. This indicates that Ra is within the above range. Of course, the surface roughness Ra of the entire inner peripheral surface of the electrophotographic photosensitive member may be in the above range.
The surface roughness Ra of the inner peripheral surface of the electrophotographic photosensitive member is adjusted, for example, by cutting the inner peripheral surface.

The surface roughness Ra of the outer peripheral surface of the cylindrical silencer is preferably 0.5 μm or less, more preferably 0.3 μm or less, from the viewpoint of suppressing discharge noise. The surface roughness Ra of the outer peripheral surface of the cylindrical silencer is preferably smaller, but is preferably 0.1 μm or more from the viewpoint of manufacturing.
The surface roughness Ra of the outer peripheral surface of the cylindrical silencer is adjusted, for example, by cutting the outer peripheral surface.

The surface roughness Ra of the inner peripheral surface of the electrophotographic photosensitive member and the outer peripheral surface of the cylindrical silencer is a value measured by the following measuring method.
First, the part which has the surface used as a measuring object is cut out with a cutter etc., and a measurement sample is acquired. The measurement sample is measured using a stylus type surface roughness measuring machine (Surfcom 1400A: manufactured by Tokyo Seimitsu Co., Ltd.). As the measurement conditions, based on JIS B0601-1994, the evaluation length Ln = 4 mm, the reference length L = 0.8 mm, and the cut-off value = 0.8 mm.

  The image forming apparatus according to the present embodiment includes an apparatus having fixing means for fixing a toner image transferred to the surface of a recording medium; direct transfer for directly transferring the toner image formed on the surface of the electrophotographic photosensitive member to the recording medium Type apparatus; intermediate transfer in which the toner image formed on the surface of the electrophotographic photosensitive member is primarily transferred onto the surface of the intermediate transfer member, and the toner image transferred onto the surface of the intermediate transfer member is secondarily transferred onto the surface of the recording medium. Type apparatus; apparatus provided with cleaning means for cleaning the surface of the electrophotographic photosensitive member after the toner image is transferred and before charging; after the toner image is transferred, the surface of the image carrier is irradiated with a charge-removing light before charging. A known image forming apparatus, such as an apparatus provided with a static elimination means for removing electricity; an apparatus provided with an electrophotographic photosensitive member heating member for increasing the temperature of the electrophotographic photosensitive member and reducing the relative temperature is applied.

  In the case of an intermediate transfer type apparatus, the transfer means includes, for example, an intermediate transfer body on which a toner image is transferred onto the surface, and a primary transfer that primarily transfers the toner image formed on the surface of the image holding body onto the surface of the intermediate transfer body. And a secondary transfer unit that secondarily transfers the toner image transferred onto the surface of the intermediate transfer member onto the surface of the recording medium.

  The image forming apparatus according to the present embodiment may be either a dry developing type image forming apparatus or a wet developing type (developing type using a liquid developer).

  Note that in the image forming apparatus according to the present embodiment, for example, the portion including the electrophotographic photosensitive member may have a cartridge structure (process cartridge) that is detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge including the electrophotographic photosensitive member according to this embodiment is preferably used. In addition to the electrophotographic photosensitive member, the process cartridge may include at least one selected from the group consisting of a charging unit, an electrostatic latent image forming unit, a developing unit, and a transfer unit.

  Hereinafter, an example of the image forming apparatus according to the present embodiment will be described, but the present invention is not limited thereto. In addition, the main part shown to a figure is demonstrated and the description is abbreviate | omitted about others.

FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present embodiment.
As shown in FIG. 1, an image forming apparatus 100 according to this embodiment includes a process cartridge 300 including an electrophotographic photosensitive member 7, an exposure device 9 (an example of an electrostatic latent image forming unit), and a transfer device 40 (primary. Transfer device) and an intermediate transfer member 50. In the image forming apparatus 100, the exposure device 9 is disposed at a position where the electrophotographic photosensitive member 7 can be exposed from the opening of the process cartridge 300, and the transfer device 40 is interposed between the electrophotographic photosensitive member via the intermediate transfer member 50. 7, and a part of the intermediate transfer member 50 is disposed in contact with the electrophotographic photosensitive member 7. Although not shown, it also has a secondary transfer device that transfers the toner image transferred to the intermediate transfer member 50 to a recording medium (for example, paper). The intermediate transfer member 50, the transfer device 40 (primary transfer device), and the secondary transfer device (not shown) correspond to an example of a transfer unit.

  A process cartridge 300 in FIG. 1 includes an electrophotographic photosensitive member 7, a charging device 8 (an example of a charging unit), a developing device 11 (an example of a developing unit), and a cleaning device 13 (an example of a cleaning unit) in a housing. I support it. The cleaning device 13 includes a cleaning blade (an example of a cleaning member) 131, and the cleaning blade 131 is disposed so as to contact the surface of the electrophotographic photosensitive member 7. The cleaning member may be a conductive or insulating fibrous member instead of the cleaning blade 131, and may be used alone or in combination with the cleaning blade 131.

  In FIG. 1, as an image forming apparatus, a fibrous member 132 (roll shape) for supplying the lubricant 14 to the surface of the electrophotographic photosensitive member 7 and a fibrous member 133 (flat brush shape) for assisting in cleaning are shown. Examples are provided, but these are arranged as necessary.

  Here, in the image forming apparatus 100 shown in FIG. 1, although not shown in FIG. 1, a cylindrical silencer 15 is inserted inside the electrophotographic photosensitive member 7 (its conductive substrate) (see FIG. 3). .

  Hereinafter, each configuration of the image forming apparatus according to the present embodiment will be described.

-Electrophotographic photoreceptor and cylindrical silencer-
As shown in FIG. 3, the electrophotographic photosensitive member 7 has a cylindrical silencer 15 inserted therein. Further, flanges 7 </ b> A are provided at both ends of the electrophotographic photoreceptor 7. FIG. 3 is a cross-sectional view taken along the axial direction of the electrophotographic photosensitive member 7.

Examples of the electrophotographic photoreceptor 7 include an inorganic photoreceptor in which a photosensitive layer provided on a cylindrical conductive substrate is made of an inorganic material, and an organic photoreceptor in which a photosensitive layer is made of an organic material.
As the organic photoreceptor, for example, a functionally separated photoreceptor in which a charge generation layer that generates charges upon exposure and a charge transport layer that transports the generated charges are stacked on a cylindrical conductive substrate, Examples thereof include a photoreceptor in which a single-layer type photosensitive layer in which the same layer performs the function of generating charge and the function of transporting charge is provided on a conductive substrate.
Examples of the inorganic photoreceptor include a photoreceptor in which a photosensitive layer made of amorphous silicon is provided on a cylindrical conductive substrate.

In the electrophotographic photosensitive member 7, examples of the conductive substrate include a metal drum containing metal (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or an alloy (stainless steel, etc.). Is mentioned. Here, “conductive” means that the volume resistivity is less than 10 ¹³ Ωcm.

  For example, the cylindrical silencer 15 has an axial length shorter than the axial length of the electrophotographic photosensitive member 7, and is located in the central portion of the electrophotographic photosensitive member 7 in the axial direction. Is provided. However, the present invention is not limited to this, and the cylindrical silencer 15 only needs to be provided at least in the axial central portion of the electrophotographic photosensitive member 7, and is provided to extend to the axial end of the electrophotographic photosensitive member 7. It may be.

For example, the cylindrical silencer 15 has an outer diameter larger than the inner diameter of the electrophotographic photosensitive member 7, and is provided in a state where the inner peripheral surface is pressed and slidable inside the electrophotographic photosensitive member 7. Specifically, for example, the outer diameter of the cylindrical silencer 15 is preferably larger than the inner diameter of the electrophotographic photosensitive member 7 (its conductive substrate) in a range of 0.2 mm to 9 mm. However, from the viewpoint of increasing the rotational torque of the cylindrical silencer 15 and suppressing discharge noise, the outer diameter of the cylindrical silencer 15 is 28 when the inner diameter of the electrophotographic photosensitive member 7 (its conductive substrate) is 28.0 mm. .2 mm or more and 37 mm or less is preferable. The outer diameter of the cylindrical silencer 15 is the outer diameter of the cylindrical silencer 15 in a state where it is not disposed inside the electrophotographic photosensitive member.
Here, the thickness of the cylindrical silencer 15 is preferably in the range of, for example, 3 mm or more and 5 mm or less from the viewpoint of suppressing discharge noise.

  As shown in FIGS. 4 and 5, the cylindrical silencer 15 includes, for example, a slit 15 </ b> A extending in the axial direction of the electrophotographic photoreceptor 7 and a constricted portion 15 </ b> B extending in the axial direction of the electrophotographic photoreceptor 7. Yes. Specifically, for example, the cylindrical silencer 15 is an arcuate curved body with both end faces in the circumferential direction spaced apart from each other, and has a groove along the axial direction on the side opposite to the separated part in the radial direction. Consists of the body. In the cylindrical silencer 15 composed of this curved body, the separated portion is the slit 15A, and the portion where the groove portion is provided and the wall thickness is thin is the constricted portion 15B. Note that the constricted portion 15B may be provided by bending a part of the arcuate curved body into an arcuate shape so as to protrude toward the inner side.

The cylindrical silencer 15 decreases the outer diameter by pushing the outer peripheral surface facing in the radial direction and reducing the width of the slit 15A. When the cylindrical silencer 15 is inserted into the electrophotographic photosensitive member 7 in this state, the cylindrical silencer 15 acts to expand the width of the slit 15A while being inserted by elastic deformation. For this reason, the cylindrical silencer 15 is arranged in a state of pressing the inner peripheral surface inside the electrophotographic photosensitive member 7.
The constricted portion 15B of the cylindrical silencer 15 is provided as necessary. However, when the constricted portion 15B is provided in the cylindrical silencer 15, the width of the slit 15A is easily reduced, and the operation of inserting the cylindrical silencer 15 into the electrophotographic photosensitive member with the outer diameter being reduced becomes easy.

The cylindrical silencer 15 is formed of a molded body such as resin (for example, acrylic resin, acrylonitrile-butadiene-styrene resin (ABS resin), polycarbonate resin, etc.), rubber (for example, urethane rubber), metal (for example, stainless steel, etc.), for example. Is done. Among these, the cylindrical silencer 15 is preferably composed of a molded body of acrylonitrile-butadiene-styrene resin (ABS resin) from the viewpoint of suppressing discharge noise.
In addition, when the cylindrical silencer 15 is formed of resin or rubber, it includes additives such as a well-known filler (for example, glass fiber) added to a resin molded body, a rubber molded body, or the like. It may be.

-Charging device-
The charging device 8 is a DC + AC voltage application type charging device (a contact charging type charging device that charges the surface of the electrophotographic photosensitive member 7 by applying a voltage in which an AC voltage is superimposed on the DC voltage).
As the charging device 8, for example, a contact charger including a charging member such as a conductive or semiconductive charging roller, a charging brush, a charging film, a charging rubber blade, a charging tube, or the like is used.

-Exposure device-
Examples of the exposure device 9 include optical system devices that expose the surface of the electrophotographic photoreceptor 7 with light such as semiconductor laser light, LED light, and liquid crystal shutter light in a predetermined image-like manner. The wavelength of the light source is set within the spectral sensitivity region of the electrophotographic photosensitive member. As the wavelength of the semiconductor laser, near infrared having an oscillation wavelength near 780 nm is the mainstream. However, the present invention is not limited to this wavelength, and an oscillation wavelength laser in the 600 nm range or a laser having an oscillation wavelength of 400 nm to 450 nm as a blue laser may be used. In addition, a surface-emitting type laser light source that can output a multi-beam is also effective for color image formation.

-Developer-
Examples of the developing device 11 include a general developing device that performs development by bringing a developer into contact or non-contact with the developer. The developing device 11 is not particularly limited as long as it has the functions described above, and is selected according to the purpose. For example, a known developing device having a function of attaching a one-component developer or a two-component developer to the electrophotographic photosensitive member 7 using a brush, a roller, or the like can be used. Among these, those using a developing roller holding the developer on the surface are preferable.

  The developer used in the developing device 11 may be a one-component developer including a toner alone or a two-component developer including a toner and a carrier. Further, the developer may be magnetic or non-magnetic. A well-known thing is applied for these developers.

-Cleaning device-
As the cleaning device 13, a cleaning blade type device including a cleaning blade 131 is used.
In addition to the cleaning blade method, a fur brush cleaning method and a simultaneous development cleaning method may be employed.

-Transfer device-
As the transfer device 40, for example, a contact transfer charger using a belt, a roller, a film, a rubber blade, etc., or a known transfer charger such as a scorotron transfer charger using a corona discharge or a corotron transfer charger. Can be mentioned.

-Intermediate transfer member-
As the intermediate transfer member 50, a belt-like member (intermediate transfer belt) containing polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber or the like having semiconductivity is used. Further, as the form of the intermediate transfer member, a drum-like member may be used in addition to the belt-like member.

FIG. 2 is a schematic configuration diagram illustrating another example of the image forming apparatus according to the present embodiment.
The image forming apparatus 120 shown in FIG. 2 is a tandem multicolor image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, four process cartridges 300 are arranged in parallel on the intermediate transfer member 50, and one electrophotographic photosensitive member is used for one color. The image forming apparatus 120 has the same configuration as that of the image forming apparatus 100 except that it is a tandem system.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

(Examples 1-9, Comparative Examples 1-2)
An electrophotographic photosensitive member (hereinafter referred to as “photoreceptor drum”) having an inner peripheral surface roughness Ra shown in Table 1 and a cylindrical shape having an outer peripheral surface roughness Ra, outer diameter and inner diameter shown in Table 1. The silencer was incorporated into the image forming apparatus “Fuji Xerox, DocuCentre IV C5570”, and the discharge sound was evaluated under the following conditions. In addition, various measurements were performed.
Photoconductor drum: Outer diameter 30 mmφ, inner diameter 28 mmφ, axial length 365 mm, aluminum alloy base is used. Photosensitive drum rotation speed: 175 mm / s
・ Charging roll: elastic body with outer diameter of 12mmφ and axial length of 354.5mm (with 8mmφ stainless steel core)
・ Applied voltage during charging: DC voltage of 700V, AC voltage with peak voltage of 2000V, frequency of 1300Hz, current of 1.0mA is applied ・ Cylindrical silencer: axial length 100mm, cylindrical molded body made of ABS resin (Structure with slit and constriction: see FIGS. 4 and 5))

-Measurement of rotational torque of cylindrical silencer-
The rotational torque of the cylindrical silencer arranged inside the photosensitive drum was measured according to the method described above.

-Evaluation of discharge sound-
The discharge volume generated at a high frequency was measured with a measuring device “Ono Sokki Integral Average Sound Level Meter LA5560”.
Moreover, the harshness of the discharge sound volume was evaluated based on the following audible level: A: Almost inaudible (40 dB or less)
B: You can hear it if you listen well (exceeding 40 dB and less than 43 dB)
C: Normal operating sound (exceeding 43 dB and less than 46 dB)
D: Slightly irritating (over 46 dB and below 49 dB)
E: Quite annoying (greater than 49 dB)

  From the above results, it can be seen that the discharge noise is suppressed in this example as compared with the comparative example.

(Examples 101 to 102)
An electrophotographic photosensitive member (hereinafter referred to as “photoreceptor drum”) having an inner peripheral surface roughness Ra shown in Table 2 and a cylindrical shape having an outer peripheral surface roughness Ra, outer diameter and inner diameter shown in Table 2. The silencer was incorporated into the image forming apparatus of Example 1. Then, according to Table 2, the discharge sound was evaluated under the same conditions as in Example 1 except that the rotational speed of the photosensitive drum and the frequency of the AC voltage applied during charging were changed. In addition, various measurements were performed.

  From the above results, it can be seen that in this embodiment, the discharge noise is suppressed even when the rotational speed of the photosensitive drum is increased or the frequency of the AC voltage applied during charging is increased.

  7 Electrophotographic photosensitive member, 8 charging device, 9 exposure device, 11 developing device, 13 cleaning device, 14 lubricant, 15 cylindrical silencer (cylindrical member), 15A slit, 15B constricted portion, 100 image forming device, 120 Image forming apparatus, 300 process cartridge

Claims (6)

A cylindrical electrophotographic photoreceptor;
An outer peripheral surface is provided inside the electrophotographic photosensitive member in contact with the inner peripheral surface of the electrophotographic photosensitive member, and a rotational torque required for relative rotation in the circumferential direction of the electrophotographic photosensitive member is 15 N · m. A cylindrical member as described above;
A contact charging method charging means for charging the surface of the electrophotographic photosensitive member by applying a voltage obtained by superimposing an AC voltage on a DC voltage;
An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive member;
Developing means for developing the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image;
Transfer means for transferring the toner image to the surface of the recording medium;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the cylindrical member includes a slit extending in an axial direction of the electrophotographic photosensitive member and a constricted portion extending in the axial direction of the electrophotographic photosensitive member.   The image forming apparatus according to claim 1, wherein the cylindrical member is a molded body of acrylonitrile-butadiene-styrene resin.   The image forming apparatus according to claim 1, wherein a rotation speed of the electrophotographic photosensitive member is 150 mm / s or more.   The image forming apparatus according to claim 1, wherein a frequency of the alternating voltage of the charging unit is 1300 Hz or more. A cylindrical electrophotographic photoreceptor;
An outer peripheral surface is provided inside the electrophotographic photosensitive member in contact with the inner peripheral surface of the electrophotographic photosensitive member, and a rotational torque required for relative rotation in the circumferential direction of the electrophotographic photosensitive member is 15 N · m. A cylindrical member as described above;
A contact charging method charging means for charging the surface of the electrophotographic photosensitive member by applying a voltage obtained by superimposing an AC voltage on a DC voltage;
And a process cartridge which is detachable from the image forming apparatus.