JPH06202440A - Contact electrostatic charging device, body to be electrostatically charged and process cartridge - Google Patents

Abstract

PURPOSE:To prevent defective electrostatic charging of a photosensitive drum by smoothly rotating an electrostatic charging roller which is rotated following the photosensitive drum. CONSTITUTION:The electrostatic charging roller 2 is pressed to the photosensitive drum 1 by a supporting member 3 and a spring member 5, and a contact nip part N is formed between both of them. By driving and rotating the drum 1, the roller 2 is rotated following it. Voltage is impressed on the roller 2 by an external power source 6, so that the surface of the drum 1 is electrostatically charged. A high friction part 2a is formed at a part corresponding to a non- image formed area on the outside of the image formed area 1b of the drum 1 on the surface of the roller 2. The high friction part 2a is annularly formed and is crossed with the contact nip part N. When the drum 1 is rotated, one part of the high friction part 2b is always brought into contact with the surface of the drum 1, and strong contact frictional force acts between the drum 1 and the roller 2, thereby, the roller 2 is smoothly rotated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact charging device and an object to be charged which are suitable for use in an electrophotographic image forming apparatus such as a copying machine or a laser beam printer.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional charging device having a charging roller.

This charging device is a member to be charged (photosensitive drum).
1 and contacts the photosensitive drum 1 with the contact nip portion N.
, A conductive charging roller 2 for forming the charging roller 2, a conductive supporting member 3 for rotatably supporting the charging roller 2 at both ends, and a biasing of the supporting member 3 toward the photosensitive drum 1. A spring member 5 that presses against the photosensitive drum 1 with an appropriate pressing force, and a power source 6 that applies a voltage to the charging roller 2 via the spring member 5 and the support member 3 are mainly configured members.

First, when the photosensitive drum 1 is rotationally driven in the direction of arrow R1 by a driving means (not shown), the charging roller 2
Rotates following the arrow R2. A voltage obtained by superimposing a DC voltage and an AC voltage is applied to the charging roller 2 by the power source 6 to charge the photosensitive drum 1 via the contact nip portion N. At this time, as the superimposed voltage, a voltage (Vac + Vdc) obtained by superimposing an AC voltage Vac having a peak-to-peak voltage Vpp that is twice or more the charging start voltage and a DC voltage Vdc is applied to the charging roller 2 to apply the photosensitive drum. 1 Uniformly charge the surface.

The charged photosensitive drum 1 is subsequently exposed to laser light 7 corresponding to print information,
An electrostatic latent image is formed. This electrostatic latent image is generated by the blade 10
Is developed by the developing sleeve 9 whose toner layer thickness is regulated to form a toner image. The toner image is transferred onto the transfer material P that is inserted between the photosensitive drum 1 and the transfer roller 11.
And then fixed on the transfer material P by a fixing device (not shown). The transfer material P on which the toner image is fixed is
The final copy is obtained by discharging the image forming apparatus outside the main body.

The charging roller 2 is constructed so as to be driven and rotated by the rotation of the photosensitive drum 1 in the direction of arrow R1. This driven rotation is carried out by the photosensitive drum 1 and the charging roller 2. With the frictional force of both acting on the contact nip portion N with the contact nip portion N, the operation is effectively performed without slipping.

[0007]

However, according to the above-mentioned conventional technique, the driven roller 2 is rotated by the contact friction between the surface of the photosensitive drum and the surface of the charging roller, and the photosensitive drum 1 is formed by the spring member 5 or the like. In the case where the pressing force of the charging roller 2 against is constant, the contact frictional force between the two depends solely on the surface state of the two, and the following problems occur.

That is, when toner or paper powder adheres to the surface of the photosensitive drum or the surface of the charging roller due to the use of the image forming apparatus, the apparent friction coefficient between the two becomes low and slippery. Then, in the case where a cleaner 13 for removing frictional resistance between the support member 3 that rotatably supports the charging roller 2 and the charging roller 2 and dirt on the charging roller 2 shown in FIG. 6 is attached. Depending on frictional resistance,
There is slippage between the photosensitive drum 1 and the charging roller 2,
In extreme cases, the charging roller 2 may stop. If the charging roller 2 slips or stops in this way, the rotation of the charging roller 2 may be uneven, and foreign matter may easily accumulate in the contact nip portion N.
As a result, the photosensitive drum 1 cannot be uniformly charged,
There arises a problem that streak-shaped image defects appear on the image.

In view of this, the present invention provides a charging roller by providing at least one of the member to be charged (for example, the above-mentioned photosensitive drum) and the charging roller with a high friction portion for increasing the contact frictional force between them. An object of the present invention is to provide a charging device, a body to be charged, and a process cartridge which are smoothly driven and rotated to prevent charging failure.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a contact charging device contacts a charged body to form a contact nip portion with the charged body. In addition, in the contact charging device that has a charging roller that is driven to rotate by the rotation of the charged body and charges the charged body by applying a voltage to the charging roller, It is characterized in that the outer peripheral surface is provided with a high friction portion which is formed in an annular shape along the circumferential direction and intersects with the contact nip portion.

In this case, it is preferable that the high friction portion is formed in a portion of the charging roller that is in contact with the non-image forming area of the body to be charged.

Further, the member to be charged rotates the charging roller through the contact nip portion, and the member to be charged is charged through the contact nip portion by the voltage applied to the charging roller. It is characterized in that it has a high friction portion which is formed in an annular shape along the circumferential direction on the outer peripheral surface on the end portion side of the charged body and which intersects the contact nip portion.

In this case, it is preferable that the high friction portion is provided in a non-image forming area outside the image forming area.

Further, the process cartridge is characterized by having the above-mentioned contact charging device or the member to be charged.

[0015]

According to the above structure, the high friction portion is formed in an annular shape along the circumferential direction of the body to be charged or the charging roller and intersects the contact nip portion. Therefore, the high friction portions contact each other through the contact nip portion. The charging body and the charging roller are always in contact with each other via the high friction portion. Therefore, the contact frictional force acting between them can be increased.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> First, Embodiment 1 of the present invention will be described with reference to FIGS. Note that (a) is the charging roller 2
FIG. 3 is a view of the part viewed from the axial direction, and FIG. 3B is a view showing the vicinity of one end part when viewed from the direction perpendicular to the axis.

The photosensitive drum 1 as a member to be charged is formed in a cylindrical shape and is rotatably supported by a driving member (not shown). On the outer peripheral surface of the photosensitive drum 1, a high friction portion 1a and an image forming area 1b are formed. The image forming area 1b is an area where an electrostatic latent image and a toner image are formed on the outer peripheral surface of the photosensitive drum 1.
Is formed over the entire circumference on the central side in the axial direction. The high friction portion 1a is formed outside the image forming area on the outer peripheral surface of the photosensitive drum 1, that is, in the non-image forming area. Since the non-image forming area is normally formed on the end side of the photosensitive drum 1 in the axial direction, the high friction portion 1a is also formed on the end side of the photosensitive drum 1. The high-friction portion 1a is formed in an annular shape over the entire outer peripheral surface of the photosensitive drum 1 by spraying, applying liquid rubber, adhering an adhesive rubber sheet, or the like. The high-friction portion 1a is formed so as to intersect a contact nip portion N between the photosensitive drum 1 and the charging roller 2 described below.

The charging roller 2 is composed of a conductive core metal 2b arranged along the axial direction of the photosensitive drum 1, a conductive elastic layer surrounding the core metal 2b, and a high resistance layer on the surface of the elastic layer. Has been done. The charging roller 2 has its outer peripheral surface in contact with the outer peripheral surface of the photosensitive drum 1 to form a contact nip portion N having an appropriate width with the photosensitive drum 1. The high-friction portion 1a of the photosensitive drum 1 described above is formed in an annular shape so as to intersect with the contact nip portion N, so that a part of the high-friction portion 1a always contacts the outer peripheral surface of the charging roller 2. It has become.

The core 2b of the charging roller 2 is rotatably supported by support members 3 near both ends. The support member 3 is formed of a conductive member and is urged toward the photosensitive drum 1 by the spring member 5 with an appropriate force. As a result, the charging roller 2
The outer peripheral surface of the photosensitive drum 1 is pressed with a predetermined force to form the above-mentioned contact nip portion N with the photosensitive drum 1.

An external power source 6 is connected to the spring member 5, and an AC bias is applied to the charging roller 2 by the external power source 6 via the spring member 5, the supporting member 3 and the core metal 2b.

Next, the operation of the photosensitive drum 1, the charging roller 2 and the like will be described.

The photosensitive drum 1 is driven by a driving means (not shown).
When is driven to rotate, the charging roller 2 is driven to rotate via the contact nip portion N. At this time, since an AC bias is applied to the charging roller 2 via the external power source 6, the surface of the photosensitive drum 1 is uniformly charged.

By the way, when image formation is repeated over a long period of time, dirt such as paper powder and residual toner adheres to the surface of the photosensitive drum 1 and the surface of the charging roller 2. When these dirts are attached, the apparent friction coefficient between the photosensitive drum 1 and the charging roller 2 is lowered, and slippage occurs between them. When the slippage occurs, unlike the photosensitive drum 1, the charging roller 2 that does not have a driving unit rotates irregularly or, in an extreme case, stops rotating. Irregular rotation or stoppage of the rotation causes defective charging of the photosensitive drum 1, resulting in defective images.

Therefore, in the present invention, the above-mentioned high friction portion 1a is formed on the photosensitive drum 1. The high-friction portion 1a that is annular and intersects the contact nip portion N between the photosensitive drum 1 and the charging roller 2 is formed so that a part of the high friction portion 1a always contacts the surface of the charging roller 2 when the photosensitive drum 1 rotates. Therefore, the rotational force of the photosensitive drum 1 is
Since it is effectively transmitted to the charging roller 2 via the charging roller 2, the charging roller 2 does not slip even if some dirt adheres to the surface of the photosensitive drum 1 or the charging roller 2.
The photosensitive drum 1 is reliably driven and rotated.

Therefore, the charging of the photosensitive drum 1 by the charging roller 2 is performed uniformly, and it is possible to prevent charging failure due to uneven charging.

In the above embodiment, since the pressing force of the spring member 5 for pressing the charging roller 2 against the photosensitive drum 1 is constant, the frictional force acting between the photosensitive drum 1 and the charging roller 2 is , The charging roller 2 which is driven by the photosensitive drum 1 and is rotated by the photosensitive drum 1 by increasing the contact frictional force between them by contacting them via the high friction portion 1a. It makes sure that the driven rotation of the will not slip. <Embodiment 2> In Embodiment 2, as shown in FIG. 2, a high friction portion is formed on the charging roller 2. In the first embodiment, the high-friction portion 1a formed in the non-image forming area of the photosensitive drum 1 is instead formed in the non-image forming area of the charging roller 2, that is, near the end portion of the charging roller 2. The high friction portion 2 a on the charging roller 2 is formed in an annular shape along the outer peripheral surface of the charging roller 2 and intersects the contact nip portion N. Therefore, when the photosensitive drum 1 rotates, a part of the high-friction portion 1a of the charging roller 2 which rotates following the photosensitive drum 1 is always in contact with the surface of the photosensitive drum 1, and the rotational force of the photosensitive drum 1 is high. Charging roller 2 via friction portion 2a
Effectively transmitted to.

According to the present embodiment, when it is relatively difficult to form the high friction portion on the photosensitive drum 1 by using the adhesive rubber or the like, or the processing such as coating is performed on the charging roller 2 made of a conductive resin or the like. It is especially effective when it is easy. <Embodiment 3> Embodiment 3 shown in FIG. 3 is an embodiment in which high-friction portions are formed on both the photosensitive drum 1 and the charging roller 2. A high-friction portion 1a is formed on the photosensitive drum 1, a high-friction portion 2a is formed on the charging roller 2, and at the contact nip portion N between the photosensitive drum 1 and the charging roller 2, the high-friction portion 1a and the photosensitive drum 2a are formed. To make contact.

For example, when a cleaner 13 made of urethane or the like is brought into contact with the charging roller 2 in order to remove toner stains or the like received by the charging roller 2 due to poor cleaning of the photosensitive drum 1, the charging roller 2 is contacted with the cleaner 13. Since frictional force is applied in the direction to suppress the driven rotation of 2,
Further, it is necessary to increase the frictional force between the photosensitive drum 1 and the charging roller 2. Photosensitive drum 1 and charging roller 2 described above
Forming the high-friction portions 1a and 2a on both sides is effective when it is desired to further increase the frictional force between the photosensitive drum 1 and the charging roller 2 as described above. <Embodiment 4> FIG. 4 shows a process cartridge P according to the present invention.
An example applied to C is shown. Reference numeral 1 is a photosensitive drum, 2 is a charging roller in contact with the photosensitive drum 1, 7 is a laser beam for exposing the photosensitive drum 1, and 9 is a toner that adheres to an electrostatic latent image formed on the photosensitive drum 1 for development. 2 shows a developing sleeve.
The photosensitive drum 1 and the developing sleeve 9 rotate in the directions of arrow R1 and arrow R9, respectively. Reference numeral 12 denotes a cleaning blade for cleaning the transfer residual toner on the photosensitive drum 1.
Reference numeral 15 is a drum shutter for protecting the photosensitive drum 1. A toner 16 is a developer.
Reference numeral 10 is a developing blade for coating the toner on the developing sleeve 9 to a uniform thickness, and 17 is a cleaning toner reservoir for accumulating the toner collected by the cleaning blade.

The photosensitive drum 1 provided with a high-friction portion having a large friction coefficient in the non-image forming area at the end of the photosensitive drum 1 reliably rotates the charging roller 2 in a driven manner, whereby the charging roller 2 receives stable charging. . An electrostatic latent image is written on the charged photosensitive drum 1 by the modulated laser light 7 and is developed by the developing sleeve 9 to form a toner image (visible image). The toner image on the photosensitive drum 2 is
The image is transferred by a transfer member (not shown), and the process proceeds to the fixing step.

As described above, by applying the present embodiment to the process cartridge PC, it is possible to construct a very compact process cartridge PC which can stably charge the photosensitive drum 1.

[0031]

As described above, according to the present invention, an annular shape is formed along the circumferential direction on the outer peripheral surface of at least one of the member to be charged and the charging roller that abut against each other to form the contact nip portion. By providing a high friction portion that is formed and intersects the contact nip portion, the contact friction force between the charged body and the charging roller can be increased, so that the rotational force of the charged body can be effectively applied to the charging roller. Therefore, the rotation of the charging roller can be reliably transmitted without slipping. As a result, the charging failure of the charging target due to the sliding or stopping of the charging roller, which has been apt to occur in the past, is eliminated, the charging target is stably charged, and the image failure due to the charging failure of the photosensitive drum is effectively prevented. be able to.

[Brief description of drawings]

FIG. 1A is a diagram of a photosensitive drum according to a first exemplary embodiment as viewed from a direction along an axis. FIG. 3B is a diagram of the photosensitive drum of Example 1 viewed from a direction perpendicular to the axis.

FIG. 2A is a diagram of the charging roller according to the second exemplary embodiment as viewed from a direction along an axis. (B) is the figure which looked at the charging roller of Example 2 from the direction orthogonal to an axis | shaft.

FIG. 3A is a diagram of a photosensitive drum and a charging roller according to a third exemplary embodiment as viewed from a direction along an axis. FIG. 6B is a view of the photosensitive drum and the charging roller of the third embodiment as seen from a direction perpendicular to the axis.

FIG. 4 is a vertical sectional view of a process cartridge according to a fourth embodiment of the present invention.

FIG. 5 is a view of a conventional photosensitive drum and a charging roller as viewed from the axial direction.

FIG. 6 is an operation explanatory view showing cleaning of a conventional charging roller.

[Description of Reference Signs] 1 charged body (photosensitive drum) 1a, 2a high friction part 2 charging roller N contact nip part PC process cartridge

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michihito Yamazaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kazushige Sakurai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroki Kisu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (5)

[Claims] 1. A charging roller which contacts a charged body to form a contact nip portion with the charged body and which is rotated by rotation of the charged body, and applies a voltage to the charging roller. In the contact charging device that charges the body to be charged by doing so, a high friction that is formed in an annular shape along the circumferential direction on the outer peripheral surface of the end portion of the charging roller and intersects the contact nip portion. A contact charging device characterized in that a part is provided. 2. The contact charging device according to claim 1, wherein the high-friction portion is formed in a portion of the charging roller that is in contact with a non-image forming area of the body to be charged. 3. A charged body to be charged through the contact nip portion by a driven roller rotating the charging roller via the contact nip portion, and an end portion of the charged body. A high-friction portion that is formed in an annular shape along the circumferential direction on the side outer peripheral surface and that intersects with the contact nip portion. 4. The charged body according to claim 3, wherein the high friction portion is provided in a non-image forming area outside the image forming area. 5. A process cartridge comprising the contact charging device or the member to be charged according to claim 1. Description: