JPH0815959A - Charging roller contact / separation mechanism - Google Patents

Abstract

(57) [Abstract] [Purpose] A simple structure ensures a sufficient contact area, contact pressure, and gap during separation, and realizes economical and highly reliable contact / separation operation of the charging roller. . [Structure] Photosensitive belt driving means for rotating the photosensitive belt 100 around a driving roller 101 to rotate the photosensitive belt and the photosensitive belt 10.
In a charging roller contacting / separating mechanism having a charging roller 106 that is charged to 0, a driving roller gear 111 that drives the driving roller 101 is held, and is driven by an arm-shaped bearing member 114 that rotates about the axis of the driving roller gear 111. The idle gear 112 is meshed with the roller gear 111, and the other end of the arm-shaped bearing member 114 opposite to the idle gear 112 is connected to the charging roller 10 from the inside of the photoreceptor belt 100.
A backup roller 113 that moves toward and away from No. 6 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contacting / separating mechanism of a charging roller used in an image forming apparatus such as a copying machine, a facsimile, a laser printer, etc., which uses an electrophotographic process. The present invention relates to a contact / separation mechanism of a charging roller provided with a backup roller that moves up and down with respect to the charging roller via the photosensitive belt by using a driving force for driving the photosensitive belt for the separating operation.

[0002]

2. Description of the Related Art Conventionally, in order to reduce the ozone gas and applied voltage generated by a corona discharge type charging charger, a DC voltage is applied while directly contacting and rotating a photosensitive member to perform a charging process. A charging roller that does this has been put into practical use. However, if the charging roller is left in contact with the photosensitive member for a long time and the apparatus itself is left for a long time, the elastic plasticizer forming the charging roller exudes to contaminate the photosensitive member or deform the charging roller. However, there is a problem that the image quality is adversely affected as a result. Therefore, there is a mechanism in which the solenoid is turned on / off to move the charging roller toward and away from the photoconductor in accordance with the operation timing of the apparatus.

Further, as a reference technical document relating to a conventional contact / separation mechanism, for example, a "contact charging device" disclosed in Japanese Patent Laid-Open No. 2-39169 is known. This is provided with a pressure contact releasing means for holding the charging member in the second state of non-pressure contact with respect to the first state in which the charging member is pressed against the surface of the member to be charged with a predetermined pressing force.

[0004]

However, in the conventional contacting / separating mechanism of the charging roller as described above, since the number of constituent parts is large, the cost of parts is increased and the installation space is required. There was a problem. Further, there is a problem in that charging efficiency cannot be improved because a sufficient contact area between the charging roller and the photosensitive member cannot be obtained simply by urging the charging roller to contact the photosensitive member using the pressing member. It was Further, when the contact pressure or the contact position (securing the gap) of the charging roller is required, there is a problem that the conventional mechanism cannot handle it.

The present invention has been made in view of the above, and is economical and highly reliable with a simple structure, ensuring a sufficient contact area, contact pressure, and a gap at the time of separation. The purpose is to realize the contacting / separating operation of the charging roller.

[0006]

In order to achieve the above object, in a contacting / separating mechanism of a charging roller according to a first aspect of the present invention, a photoconductor drive is provided in which a photoconductor belt is wound around a drive roller and driven to rotate. And a charging roller contacting / separating mechanism having a charging roller for charging the photosensitive belt, an arm-shaped bearing member holding a driving gear for driving the driving roller and rotating about the driving gear shaft as a fulcrum. An idle gear is meshed with the drive gear, and a backup roller is provided at the other end of the arm-shaped bearing member opposite to the idle gear, the backup roller being in contact with and separated from the charging roller from the inside of the photosensitive belt. It is a thing.

Further, in the charging / contacting mechanism of the charging roller according to the second aspect, the axial distance l ₁ between the driving roller and the charging roller and the axial distance l between the driving roller and the backup roller are set. ₂ and ₂ are arranged so as to satisfy the relationship of l ₂ > l ₁ .

Further, in the contacting / separating mechanism of the charging roller according to the third aspect, the photosensitive member driving means rotates the driving roller in a direction opposite to the rotation of the image forming operation after the image forming process is completed. It is a thing.

In the charging roller contacting / separating mechanism according to a fourth aspect of the present invention, the bearing member of the charging roller is provided with a cylindrical shape, and the bearing member of the backup roller is provided with a cylindrical shape so as to be in contact with the cylindrical shape. It is provided.

[0010]

In the contact / separation mechanism for the charging roller according to the present invention (claim 1), when the driving roller is stopped, the backup roller lowers and separates from the charging roller by the weight of the backup roller and the bearing member, and the charging roller is driven. When the roller rotates, the idle gear meshing with the drive gear rotates, and a force acts substantially in the pressure angle direction of the gear, and the backup roller mounted on the other side of the bearing member becomes the charging roller with the drive roller shaft as the fulcrum. When the drive roller stops, the charging roller is separated from the photoconductor belt again by rotating and moving in the contact direction.

Further, in the contact / separation mechanism of the charging roller according to the present invention (claim 2), the axial distance between the driving roller and the charging roller is l ₁ , and the axial distance between the driving roller and the backup roller is l _2. In this case, the relationship is set to l ₂ <l ₁ to increase the contact width (nip width) between the charging roller and the photoconductor belt and effectively secure the contact area.

Further, in the contacting / separating mechanism of the charging roller according to the present invention (claim 3), the photoconductor driving means rotates the driving roller in a direction opposite to the rotation of the image forming operation after the image forming process is completed. By doing so, the contacting / separating operation of the charging roller is performed more positively.

Further, according to the contacting / separating mechanism of the charging roller of the present invention (claim 4), the bearing member of the charging roller is provided with a cylindrical shape, and the bearing member of the backup roller is provided with a cylindrical shape so as to be in contact with the cylindrical shape. By providing it, the positional accuracy between the charging roller and the backup roller is secured, and the contact pressure between the photosensitive belt and the charging roller is made constant.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an explanatory diagram showing a main part configuration of an image forming portion in an image forming apparatus to which a contacting / separating mechanism of a charging roller according to the present invention is applied. In the figure, 100 is a photoconductor belt using an OPC (organic photoconductor) on which an electrostatic latent image is formed. The photosensitive belt 100 is configured to run in the A direction by a driving roller 101, driven rollers 102 and 103, and a pressure roller 104 provided inside. Further, each functional unit based on the electrophotographic process is provided around the photoconductor belt 100. That is, the exposure unit 105 for irradiating the photoconductor belt 100 with image light, the charging roller 106 for uniformly charging the photoconductor belt 100 to a high voltage, and the toner on the electrostatic latent image formed on the photoconductor belt 100. A developing unit 107 that adheres, a transfer belt 108 that transfers the toner image on the photoconductor belt 100 onto a recording sheet, a cleaning unit 109 that removes and collects the residual toner on the photoconductor belt 100 after the transfer, and a cleaning unit 109 after the cleaning process. A charge eliminating unit 110 that erases the residual charges of the photosensitive belt 100 and restores the potential of the initial level is provided.

Next, a basic image forming operation in the image forming apparatus configured as described above will be described. The surface of the photoconductor belt 100 is uniformly charged to a high potential by supplying a DC voltage from a power pack (not shown) to the charging roller 106 in contact with the photoconductor belt 100. Immediately after that, the exposure unit 10 is formed on the surface of the photosensitive belt 100.
When the image light is irradiated by 5, the potential of the irradiated portion decreases. Since the image light has a distribution of the amount of light according to the black / white of the image, the photoconductor belt 1 is irradiated by the image light.
A potential distribution corresponding to the recorded image, that is, an electrostatic latent image is formed on the surface 00.

After that, when the portion on which the electrostatic latent image is formed passes through the developing portion 107, toner adheres according to the level of the potential, and a toner image is formed by visualizing the electrostatic latent image. . The recording paper is conveyed by a registration roller (not shown) to the portion where the toner image is formed at a predetermined timing, and overlaps with the toner image. This toner image is transferred to the transfer roller 108.
After being transferred to the recording paper by the recording paper, the recording paper is separated from the photosensitive belt 100. The separated recording paper is conveyed through a conveyance path, thermally fixed by a fixing unit (not shown), and then ejected to the outside of the machine. After the transfer process is completed, the surface of the photoconductor belt 100 is cleaned by the cleaning unit 109, and the charge removing unit 1 is further removed.
The residual charges are erased by 10 and the image forming process is prepared for the next time.

Next, the structure of the contact / separation mechanism of the charging roller 106 will be described with reference to FIGS. In the figure, 1
Reference numeral 11 is a drive roller gear for driving the drive roller 101, 112 is an idle gear that meshes with the drive roller gear 111, and 113 is a backup roller provided to face the charging roller 106 inside the photosensitive belt 100. Further, the backup roller 113 is supported on the tip end side of an arm-shaped bearing member 114, and the drive gear 111 shaft is arranged so that the idle gear 112 meshes with the drive roller gear 111 by passing the shaft of the drive roller 101 through the bearing member 114. It is swingably supported at the center. That is, the backup roller 113 is provided so that it can move toward and away from the charging roller 106.

Both ends of the charging roller 106 are axially passed through the bearing member 201, and a pressure spring 202 for urging the charging roller 106 is erected on the bearing member 201. A pressure support member 203 is attached on the upper side via a side plate 204. Therefore, as shown in FIG. 2, the charging roller 106 is supported with the same configuration on the front side and the back side (not shown). A drive joint 205 is attached to the shaft on the rear side of the drive roller 101, and a drive joint 206 that fits into the recess of the drive joint 205 and gives a rotational force is provided.

Next, the operation of the contacting / separating mechanism of the charging roller 106 configured as described above will be described. 3 shows a state where the charging roller 106 is separated from the photoconductor belt 100, and FIG. 4 shows a state where the charging roller 106 has the photoconductor belt 100.
Is in contact with. That is, FIG. 3 is a non-operating state, and FIG. 4 is an operating state. More specifically, as shown in FIG. 3, when the driving roller 101 is stopped (the photosensitive belt 100 is stopped), the backup roller 113 and the bearing member 114 are moved by their own weights to lower the backup roller 113 and separate the charging roller 106 from the charging roller 106. are doing. Next, the driving roller 101 rotates (photosensitive belt 10
0), the idle gear 112 meshed with the drive roller gear 111 is rotated as shown in FIG. At this time, generally in the direction of the pressure angle of the gear (for example,
Since the force acts on the bearing roller 114, the backup roller 113 mounted on the other side of the bearing member 114 rotationally moves in the direction contacting the charging roller 106 with the shaft of the driving roller 101 as a fulcrum. Then, when the driving roller 101 stops, the charging roller 106 is separated from the photosensitive belt 100 again as shown in FIG.

Further, regarding the contact / separation structure of the charging roller 106 with respect to the photosensitive belt 100, the recording width (length in the main scanning direction) in the image forming apparatus is relatively short, for example, recording paper size A4 vertical or B4 vertical. As shown in FIG. 5, the feeding device keeps the charging roller 106 and the photoconductor belt 100 apart from each other by providing the contacting / separating mechanism on one side. On the other hand, when the state where the charging roller 106 and the photoconductor belt 100 are not separated from each other in a wide width such as when the recording paper size is A4 width or more is handled, by providing a contacting / separating mechanism on both sides as shown in FIG. You can also do it.

Next, the charging roller 106 and the photosensitive belt 1
The securing of the contact area with 00 will be described. As shown in FIG. 7, when the center distance between the driving roller 101 axis and the charging roller 106 axis and l _1, the center distance between the driving roller 101 axis and the backup roller 113 and l _2, l ₂ ≒ l ₁
When (l ₂ and l ₁ are substantially equal), the contact width (nip width) between the charging roller 106 and the photosensitive belt 100 is small. On the other hand, as shown in FIG. 8, when the axial relationship between the driving roller 101 axis and the charging roller 106 axis and the backup roller 113 axis is l ₂ <l ₁ , the charging roller 106 and the photoconductor belt 100 come into contact with each other. The width (nip width) increases. Generally, the charging roller 106 and the photoconductor belt 100
It is known that the larger the contact width with the charging efficiency is, the more the charging efficiency is improved. From this point, the configuration of FIG. 8 becomes more effective.

Further, in FIG. 2, the rotation directions of the drive joints 205 and 206 which are the drive means are such that A'is a forward rotation. Depending on the method of the driving means, in a mechanism such as one that does not use a clutch or one in which backlash cannot be obtained in the reverse rotation direction, by providing a means for forcibly rotating in the reverse direction (direction of arrow C), the contact / separation operation is performed. I do.

Further, as shown in FIGS. 2, 5 and 6,
A cylindrical shape 201a is provided coaxially with a bearing member 201 that supports the charging roller 100. And this cylindrical shape 20
The bearing member 114 supporting the backup roller 113 is provided with a cylindrical shape 114a corresponding to 1a. As a result, the charging roller 106 and the backup roller 113
Position accuracy is secured, and the contact pressure of the charging roller 106 to the photosensitive belt 100 becomes constant.

[0024]

As described above, according to the contacting / separating mechanism of the charging roller according to the present invention (claim 1), the backup roller and the bearing member are self-weighted when the drive roller is stopped. When the drive roller rotates, the idler gear meshing with the drive gear rotates, and a force acts substantially in the pressure angle direction of the gear to attach the backup roller to the other bearing member. Is in contact with the charging roller by rotating in the direction of contacting the charging roller with the driving roller shaft as a fulcrum. When the driving roller stops, the charging roller is separated from the photoconductor belt again. It is possible to secure a contact pressure, a gap at the time of separation, and an economical and highly reliable contact / separation operation of the charging roller.

According to the contact / separation mechanism for the charging roller of the present invention (claim 2), the axial distance between the driving roller and the charging roller is l ₁ , and the axial distance between the driving roller and the backup roller is in case of a l _2, the contact width between the charging roller and the photosensitive belt that relationship as l ₂ <l ₁ (nip width)
To secure the contact area effectively,
The charging efficiency can be improved.

Further, according to the contacting / separating mechanism of the charging roller according to the present invention (claim 3), the photosensitive member driving means rotates the driving roller in a direction opposite to the rotation of the image forming operation after the image forming processing is completed. Since it is performed, the contacting / separating operation of the charging roller can be more positively performed.

Further, according to the contact / separation mechanism of the charging roller of the present invention (claim 4), the bearing member of the charging roller is provided with a cylindrical shape, and the bearing member of the backup roller is cylindrical so as to be in contact with the cylindrical shape. By providing the shape, the positional accuracy between the charging roller and the backup roller can be secured, and the contact pressure between the photosensitive belt and the charging roller can be made constant, so that the charging can be made uniform and the photosensitive belt can be prevented from slipping. It is also possible to stabilize the driving by.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a main part configuration of an image forming portion in an image forming apparatus to which a contacting / separating mechanism of a charging roller according to the present invention is applied.

FIG. 2 is an explanatory view showing a contacting / separating mechanism of a charging roller according to the present invention.

FIG. 3 is an explanatory diagram showing a separated state in the contact / separation mechanism of the charging roller according to the present invention.

FIG. 4 is an explanatory diagram showing a contact state in the contact / separation mechanism of the charging roller according to the present invention.

FIG. 5 is an explanatory diagram showing a contacting / separating mechanism of the charging roller according to the present invention at an A4 vertical width or less.

FIG. 6 is an explanatory view showing a contacting / separating mechanism when the charging roller according to the present invention is wide.

FIG. 7 is an explanatory diagram showing an example of the relationship between the charging roller and the backup roller with respect to the drive roller shaft according to the present invention.

FIG. 8 is an explanatory diagram showing an example of the relationship between the charging roller and the backup roller with respect to the drive roller shaft according to the present invention.

[Explanation of symbols]

 100 Photoreceptor Belt 101 Drive Roller 106 Charging Roller 111 Drive Roller Gear 112 Idle Gear 113 Backup Roller 114 Bearing Member 114a Cylindrical Shape 201 Bearing Member 201a Cylindrical Shape 205, 206 Drive Joint (Drive Means)

Claims (4)

[Claims] 1. A drive for driving a drive roller in a contact / separation mechanism of a charge roller, which has a drive means for rotating a photosensitive belt around a drive roller for rotation and a charging roller for charging the photosensitive belt. An arm-shaped bearing member that holds a gear and rotates about the drive gear shaft as a fulcrum,
An idle gear is meshed with the drive gear, and a backup roller is provided at the other end of the arm-shaped bearing member opposite to the idle gear, the backup roller being in contact with and separated from the charging roller from the inside of the photosensitive belt. A charging / contacting mechanism for the charging roller. Wherein said drive roller and the center distance l ₁ between the charging roller and the center distance l ₂ between said backup roller and the drive roller, so as to satisfy the relation l _2> l ₁ The contacting / separating mechanism of the charging roller according to claim 1, wherein the mechanism is arranged. 3. The contact of the charging roller according to claim 1, wherein the photoconductor driving means rotates the driving roller in a direction opposite to the rotation of the image forming operation after the image forming process is completed. Separation mechanism. 4. The charging roller according to claim 1, wherein the bearing member of the charging roller has a cylindrical shape, and the bearing member of the backup roller has a cylindrical shape so as to be in contact with the cylindrical shape. Contact and separation mechanism.