JP2006091593A - Charging device, electrophotographic photoreceptor unit, electrophotographic imaging unit, and electrophotographic imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging device which, by comprising a body to be charged (a photoreceptor drum), a charging member (a charging roller) which faces a surface to be charged of the body to be charged, and a space retaining member of another component disposed between the body to be charged and the charging member, is capable of easily obtaining a gap between the charging member (the charging roller) and the body to be charged (the photoreceptor drum), an electrophotographic photoreceptor unit equipped with the charging device, and an electrophotographic imaging device equipped with the electrophotographic photoreceptor unit. <P>SOLUTION: The charging device that is positioned close to a surface 4a to be charged of the movable body 4 to be charged in a noncontact manner, and charges it, comprises the body 4 to be charged, the charging member 2 that faces the surface 4a to be charged of the body 4 to be charged, and the space retaining member 9 of another component disposed between the body 4 to be charged and the charging member 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a charging device having a charging member such as a charging roller for charging a photosensitive drum in an electrophotographic image forming apparatus such as a copying machine, a laser printer, and a facsimile, and an electrophotographic photosensitive member provided with the charging device. The present invention relates to a body unit, an electrophotographic image forming unit, and an electrophotographic image forming apparatus including the electrophotographic photosensitive member unit.

Conventionally, a charging roller or the like in an electrophotographic image forming apparatus is known as a charging member (see, for example, Patent Documents 1 and 2).
FIG. 5 is a schematic diagram illustrating an image forming unit of a conventional image forming apparatus. FIG. 6 is a schematic perspective view showing the vicinity of the charging roller used in the image forming apparatus of FIG. 5 and 6, the image forming apparatus 1 includes a charging roller 2, a power pack 3, a photosensitive drum 4, a surface potential meter 5, a developing roller 6, a transfer roller 7, and a cleaning device 8. Is provided.
The charging roller 2 is supplied with power from the power pack 3 and charges the photosensitive drum 4. The photosensitive drum 4 is rotated in the direction of arrow A by a driving mechanism (not shown). The surface potential meter 5 is provided immediately after the charging roller 2 along its rotation direction, and measures the potential of the surface 4 a of the photosensitive drum 4.
The developing roller 6 causes the toner to adhere to the charged photosensitive drum 4, and the transfer roller 7 transfers the toner attached to the photosensitive drum 4 to the recording paper S. The cleaning device 8 removes the toner remaining on the photosensitive drum 4 and cleans the photosensitive drum 4.
In the image forming process by the image forming apparatus 1, first, the surface 4 a of the photosensitive drum 4 is charged to a negative high potential by the charging roller 2. Subsequently, the charged surface 4a is irradiated with an exposure L made of reflected light from a document or laser light.
This exposure L has a light amount distribution corresponding to the black / white of the image to be formed, and the potential (negative potential) of each part of the surface 4a is reduced in accordance with the amount of received light, thereby corresponding to the light amount distribution on the surface 4a. Potential distribution, that is, an electrostatic latent image is formed.
When the photosensitive drum 4 rotates and the portion of the surface 4a where the electrostatic latent image is formed passes through the developing roller 6, toner corresponding to the potential distribution adheres to the surface 4a, and the electrostatic latent image becomes a toner image. Is visualized as
This toner image is transferred to the recording sheet S fed at a predetermined timing by the transfer roller 7, and the recording sheet S is conveyed in the direction of arrow B toward a fixing unit (not shown).
On the other hand, the photosensitive drum 4 after the transfer is cleaned by removing the toner remaining on the surface 4a by the cleaning device 8, and the residual charge is removed by a quenching lamp (not shown), so that the next image forming process is performed. Migrate to

In FIG. 6, the charging roller 2 is disposed between the face plates 10 via bearings 11 and spacers 9, and the photosensitive drum 4 is similarly disposed between the face plates 10 on the charging roller 2. Reference numeral 12 denotes a spring provided on the bearing 11.
Incidentally, as a general charging method in the image forming apparatus 1 described above, there is a contact charging method in which the charging roller 2 is brought into contact with the photosensitive drum 4. However, this contact charging method has the following problems.
The constituent material of the charging roller 2 oozes out from the charging roller 2 and adheres to the surface of the photosensitive drum 4, and when this adhesion proceeds, a trace of the charging roller 2 remains on the surface of the photosensitive drum 4. When an AC voltage is applied to the charging roller 2, the charging roller 2 in contact with the photosensitive drum 4 vibrates and a charging sound is generated.
Further, the toner on the surface of the photosensitive drum 4 adheres to the charging roller 2 and the charging performance is deteriorated. In particular, when the charging roller 2 seeps out, the toner becomes more easily attached. If the photosensitive drum 4 is not driven for a long time, the charging roller 2 is permanently deformed.

In order to deal with such a problem, a proximity charging method has been devised in which the charging roller 2 is brought close to the photosensitive drum 4 instead of contacting (for example, Patent Document 2). In this proximity charging method, the charging roller 2 and the photosensitive drum 4 are opposed to each other so that the closest distance is 0.005 to 0.3 mm, and a voltage is applied to the charging roller 2 to apply the voltage of the photosensitive drum 4. It performs charging.
In the proximity charging method, the charging roller 2 and the photosensitive drum 4 are not in contact with each other. Therefore, the problem occurs in the contact charging method, “adhesion of constituent materials of the charging roller to the photosensitive drum” and “non-use for a long period of time”. “Permanent deformation of the charging roller” is not a problem. Further, regarding the “decrease in charging performance of the charging roller due to toner adhesion”, the proximity charging method is superior because the amount of toner adhering to the charging roller 2 is reduced.
In such an image forming apparatus, one of the problems is to keep the closest distance between the charging roller 2 and the photosensitive drum 4 constant. Therefore, conventionally, spacers 9 and the like are provided in non-image areas (areas not involved in image formation) at both ends in the axial direction of the charging roller 2.
However, if the charging roller 2 is made of an elastic material such as rubber or elastomer, the charging roller 2 is deformed when the spacer 9 or the like receives an external force (from the photosensitive drum 4), and this deformation causes the gap to be formed. If it is not kept constant, there is a problem that the charged potential becomes unstable and image unevenness is caused thereby.
Further, when the charging roller 2 is made of rubber or elastomer in this way, the charging roller 2 may be deformed by its own weight and the gap may be changed. Further, the rubber or elastomer is subject to sag or deformation over time. Since it is likely to occur, there is a concern that the gap changes with time.
Therefore, in order to deal with such a problem and from the viewpoint of environmental protection, it is conceivable to use a non-elastic thermoplastic resin having recyclability instead of rubber or elastomer.
JP 2002-318383 A JP 05-107871 A

However, the proximity charging method using a configuration in which a spacer is provided on a charging roller made of such a thermoplastic resin (see FIG. 6) has the following problems. That is, the management of the spacer is very strict, and for example, a configuration in which the spacer is formed by winding it around a roller end portion that is a non-image portion using an adhesive tape can be made relatively easily.
However, with this configuration, there is a problem that a step corresponding to the thickness of the tape is formed at the end of the tape. That is, since the gap between the photosensitive drum and the charging roller is different between the stepped portion and the non-stepped portion, the charging characteristics on the photosensitive drum are different, and a lateral obi abnormal image is generated at the charging roller pitch.
In addition, the method of providing a ring made of a heat-shrinkable material at both ends of the charging roller has a problem that the spacer dimensions after heat-shrinkage are not stable, which also causes uneven charging characteristics on the photosensitive drum, resulting in uneven density. An abnormal image such as
Furthermore, in the method of maintaining the gap according to the hole positions of the parts that hold the charging roller and the photosensitive drum, high accuracy is required for the shape of the parts that hold the charging roller and the photosensitive drum, so that it is difficult to process the parts. There is a problem of becoming.
In view of the above-described circumstances, an object of the present invention is to provide an object to be charged (photosensitive drum), a charging member (charging roller) facing the surface to be charged of the object to be charged, and the object to be charged. A charging device capable of easily obtaining a gap between a charging member (charging roller) and a member to be charged (photoreceptor drum) by having a space holding member provided between the members as a separate component, and an electronic device including the charging device It is an object of the present invention to provide a photographic photoreceptor unit and an electrophotographic image forming apparatus including the electrophotographic photoreceptor unit.

In order to solve the above-described problems, the invention described in claim 1 is a charging device that charges a surface to be charged of a movable object to be charged in a non-contact manner, in a non-contact manner. The charging device includes: a charging member facing the surface to be charged of a member to be charged; and a space holding member by a separate part provided between the member to be charged and the charging member.
According to a second aspect of the present invention, there is provided a charging device according to the first aspect, wherein the space holding member is arranged in the body to be charged or the casing that holds the charging member.
The invention described in claim 3 is characterized in that the space holding member is a ring-shaped member.
According to a fourth aspect of the present invention, there is provided an electrophotographic photosensitive member unit having the member to be charged and the charging device according to any one of the first to third aspects.
According to a fifth aspect of the present invention, there is provided an electrophotographic image forming unit including the member to be charged, a developing unit, and the charging device according to any one of the first to third aspects.
According to a sixth aspect of the present invention, there is provided an electrophotographic image forming apparatus having the charging device according to any one of the first to third aspects.
According to a seventh aspect of the invention, there is provided an electrophotographic image forming apparatus having the electrophotographic photosensitive member unit according to the fourth aspect.
The invention described in claim 8 is characterized by an electrophotographic image forming apparatus having the electrophotographic image forming unit described in claim 5.

  According to the present invention, a space formed by a member to be charged (photosensitive drum), a charging member (charging roller) facing the surface to be charged of the member to be charged, and another component provided between the member to be charged and the charging member. By having the holding member, a gap between the charging member and the member to be charged can be easily obtained.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an embodiment of a charging device in which the present invention is applied to an image forming apparatus. FIG. 2 is a perspective view showing a spacer which is a space holding member of the charging device of the image forming apparatus (electrophotographic image forming apparatus) according to the present embodiment.
In FIG. 1, a rotatable charging roller 2 is arranged between two face plates 10 via a bearing 11, and a shaft portion of the charging roller 2 is rotatably supported by the bearing. Further, the photosensitive drum 4 is disposed between the face plates 10 in the vicinity of the charging roller 2 and is rotatably supported. Reference numeral 12 denotes a spring provided on the bearing 11.
The spacer 9 has a structure in which a sheet-like member having a predetermined width as shown in FIG. 2 is formed in a ring shape, and is arranged in a holding portion provided on the face plate 10. The photosensitive drum 4 and the charging roller 2 are arranged with a part of the spacer 9 interposed therebetween, and the charging roller 2 supported by the bearing 11 is supported by the spring 12 via the bearing 11 on the photosensitive drum 4 side. It is pressed against. The spacer 9 is disposed so as to surround the outer periphery of both ends of the charging roller 2, so that a part of the spacer 9 is disposed between the spacer 9 and the photosensitive drum 4.
In such a configuration, since the gap between the charging roller (charging member) 2 and the photosensitive drum (charged body) 4 depends only on the thickness of the spacer 9, a desired gap can be easily obtained.
Regarding the step at the end of the sheet-like member, which becomes a problem when the sheet-like member is wound around the charging roller 2 and used as the spacer 9, in the above configuration, the step is located at a place other than between the charging roller 2 and the photosensitive drum. Can be arranged.

FIG. 3 is a schematic view showing the periphery of a photosensitive drum of a monochrome laser printer using the charging device of the present invention. Next, the effect of the present invention will be described by showing an embodiment in which the charging device of the present invention is used in a monochrome laser printer.
In this monochrome laser printer, a photoconductor unit having the charging device of the present invention is used. The spacer 9 shown in FIG. 2 is disposed so that the inner periphery of the spacer is in contact with the outer periphery of a plurality of rod-shaped spacer holding portions 13 provided on the photoreceptor unit face plate 10, and the charging roller 2 has a thickness of the spacer 9. Via the photosensitive drum 4.
As the spacer 9, an endless ring made of a fluororesin and having a thickness of 60 μm was used. Further, the charging roller 2 has a body portion of 4 mm in thickness, in which an ion conductive polymer compound is blended with an ABS resin, on the outer periphery of a SUM-Ni core metal having a diameter of 9 mm. It has a surface with a mixture.
The charging roller 2 and the photosensitive drum 4 rotate in the direction of the arrow in FIG. 3 via a gear (not shown). When a voltage is applied to the charging roller 2 from a power supply unit (not shown), the photosensitive drum 4 is uniformly charged.
An electrostatic latent image is drawn on the photosensitive drum 4 by an optical writing mechanism (not shown) based on a signal from a computer or the like. Such an electrostatic latent image is visualized by becoming a toner image by toner supplied by a developing mechanism (developing roller 15 and toner conveying screw 16) provided in the developing unit.
The toner image on the photosensitive drum 4 moves to the transfer unit, and is transferred onto the transfer material S such as paper by the transfer roller 17, and the toner image is transferred into the fixing roller 19 when the transfer material S passes through the fixing unit 18. It is fixed on the transfer material S by the heat generated by the provided heater and the pressure generated between the fixing roller 19 and the pressure roller 20.

FIG. 4 is a schematic view showing an electrophotographic image forming unit using the charging device according to the present invention. In FIG. 4, the spacer 9 shown in FIG. 2 is arranged with the inner peripheral surface in contact with a plurality of spacer holding portions 13 protruding from the electrophotographic image forming unit face plate 10, and the charging roller 2 is a spacer. 9 is arranged so as to face the photosensitive drum 4 via 9.
The spacer 9 and the charging roller 2 use the same parts as in the embodiment of FIG. The charging roller 2 and the photosensitive drum 4 rotate in the direction of the arrow in FIG. 4 via a gear (not shown).
When a voltage is applied to the charging roller 2 from a power supply unit (not shown), the photosensitive drum 4 is uniformly charged. An electrostatic latent image is drawn on the photosensitive drum 4 by an optical writing mechanism (not shown) based on a signal from a computer or the like.
Such an electrostatic latent image is visualized as a toner image by a developing mechanism (developing roller 15 and toner conveying screw 16) provided in the developing unit 14.
The toner image on the photosensitive drum 4 moves to the transfer unit, and is transferred onto the transfer material S such as paper by the transfer roller 17, and the toner image is transferred into the fixing roller 19 when the transfer material S passes through the fixing unit 18. It is fixed on the transfer material S by the heat generated by the provided heater and the pressure generated between the fixing roller 19 and the pressure roller 20.
Using the monochrome laser printer having the above-described configuration, a gray solid image was output by a signal from the computer. As a result of observing this image, a good image could be obtained without the occurrence of a horizontal streak image at the charging roller pitch, which is a problem when an adhesive tape is wound around the charging roller 2 to form a spacer.
The gap between the charging roller 2 and the photosensitive drum 4 can be obtained easily and stably by arranging the space holding member in the body to be charged or the case holding the charging member.

According to the present invention, an electrophotographic photosensitive member unit capable of uniformly charging the photosensitive drum 4 can be obtained. In addition, an electrophotographic image forming unit capable of forming a good toner image on the photosensitive drum 4 can be obtained.
An electrophotographic image forming apparatus that has a charging device capable of uniformly charging the surface of a photoconductor and has an electrophotographic image forming unit including the charging device. can do.

1 is a schematic diagram illustrating an embodiment of a charging device that applies the present invention to an image forming apparatus (electrophotographic image forming apparatus). FIG. 4 is a perspective view showing a spacer that is a space holding member of the charging device of the image forming apparatus according to the present embodiment. FIG. 2 is a schematic view showing the periphery of a photosensitive drum of a monochrome laser printer using the charging device of the present invention. It is the schematic which shows the electrophotographic image formation unit using the charging device by this invention. It is the schematic explaining the conventional image forming apparatus. FIG. 2 is a schematic perspective view showing the vicinity of a charging roller used in the image forming apparatus of FIG. 1.

Explanation of symbols

2 Charging member (charging roller)
4 Charged body (photosensitive drum)
4a Surface to be charged (surface of photosensitive drum)
9 Space retaining member (spacer)
10 Housing (face plate)
14 Development unit

Claims (8)

  In a charging device that charges a charged surface of a movable body to be charged in close proximity to the surface to be charged, a charging member facing the surface to be charged of the body to be charged, and between the body to be charged and the charging member A charging device comprising a space holding member provided in a separate part.   The charging device according to claim 1, wherein the space holding member is disposed in the body to be charged or the casing that holds the charging member.   The charging device according to claim 2, wherein the space holding member is a ring-shaped member.   An electrophotographic photosensitive member unit comprising the member to be charged and the charging device according to claim 1.   An electrophotographic image forming unit comprising: the object to be charged; a developing unit; and the charging device according to claim 1.   An electrophotographic image forming apparatus comprising the charging device according to claim 1.   An electrophotographic image forming apparatus comprising the electrophotographic photosensitive member unit according to claim 4.   An electrophotographic image forming apparatus comprising the electrophotographic image forming unit according to claim 5.

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