JPH0683166A - Electrostatic charging device - Google Patents

Abstract

PURPOSE:To easily and inexpensively clearly clean an electrostatic charging roller by rubbing a cleaning member against the electrostatic charging roller at 1st and 2nd positions in accordance with the rotating direction of the electrostatic charging roller while press-contacting with the normally and reversely rotating electrostatic charging roller. CONSTITUTION:This device is provided with the normally and reversely rotating electrostatic charging roller 3 electrostatically charging an image carrier 1 while abutting on the surface of the image carrier 1 in an image forming device, the cleaning member 4 cleaning the roller 3 while press-contacting with the roller 3 and rubbing against the roller 3 at the 1st and the 2nd positions in accordance with the rotating direction of the roller 3, and an auxiliary pressuring member 18 which abuts on the member 4 in the case the member 4 is at the 1st position so as to increase the press-contact force of the member 4 to the roller 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device used in an image forming apparatus.

[0002]

2. Description of the Related Art An image forming apparatus such as a copying machine or a printer has a charging device for charging an image carrier, and this charging device generally uses a corona discharger. JP-A-58-19
In Japanese Patent No. 4061, a charging roller is brought into contact with the surface of an image carrier, the image carrier is charged by the charging roller, a conductive cleaning element is arranged in the vicinity of the charging roller, and the conductive cleaning element is used. What cleans the charging roller is described.

In Japanese Patent Laid-Open No. 3-101768, a charging roller is brought into contact with the surface of the image carrier to charge the image carrier, and the sponge material is placed in contact with the charging roller. It is described that the charging roller is cleaned with a lever sponge material.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the charging device described in Japanese Patent No. 4061, a conductive cleaning element is arranged in the vicinity of the charging roller in a non-contact manner and the charging roller is cleaned by the conductive cleaning element. Therefore, the toner mechanically pressed against the charging roller Dust that is difficult to be charged, such as paper dust, is difficult to remove from the charging roller. Moreover, a device for collecting dust and the like attached to the conductive cleaning element is required, which is complicated and expensive.

In the charging device disclosed in Japanese Patent Laid-Open No. 3-101768, a sponge material is placed in contact with the charging roller, and the charging roller is cleaned by the sponge material so that the surface of the sponge material becomes uneven. Since there are streaky cleaning marks on the charging roller, the charging roller cannot be cleaned cleanly. further,
The sponge material is apt to be clogged with toner or dust in air bubbles, has a poor cleaning effect, and has a short life.

In particular, in the above charging device, when the charging roller is pressed against the surface of the image carrier, dust such as toner and paper powder firmly adheres to the charging roller and cannot be removed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a charging device which can remedy the above-mentioned drawbacks and clean the charging roller easily and at low cost.

[0008]

In order to achieve the above object, the invention according to claim 1 is a charging roller for contacting the surface of an image carrier in an image forming apparatus to charge the image carrier and to reverse it in a forward and reverse direction. , The first position and the second position being pressed against the charging roller and depending on the rotation direction of the charging roller.
And a cleaning member for rubbing the charging roller to clean the charging roller, and an auxiliary member for abutting the cleaning member when the cleaning member is in the first position to increase the pressure contact force of the cleaning member with respect to the charging roller. And a pressure member.

According to a second aspect of the present invention, in the charging device according to the first aspect, the cleaning member is normally rotated during an image forming operation of the image forming apparatus and rubs against the charging roller at the first position. During the non-image forming operation of the image forming apparatus, the reverse rotation is performed and the charging roller is rubbed at the second position.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the charging device described above, the time for rubbing the charging roller at the second position of the cleaning member is longer than the time for rubbing the charging roller at the first position of the cleaning member.

The invention according to claim 4 is the invention according to claim 1 or 2.
Alternatively, in the charging device described in the paragraph 3, after the charging roller is switched from the second position to the first position, at least one rotation is performed before the image forming operation of the image forming apparatus, and then the charging bias is changed. The application starts the charging of the image carrier.

According to a fifth aspect of the present invention, in the charging device according to the first aspect, the second aspect, the third aspect, or the fourth aspect, the portion of the cleaning member that slides on the charging roller at the second position has an abrasive material. Is.

According to a sixth aspect of the present invention, in the charging device according to the fifth aspect, the particle size of the abrasive is smaller than the particle size of the toner.

[0014]

According to the present invention, the charging roller contacts the surface of the image carrier to charge the image carrier, and the charging roller rotates in the forward and reverse directions. The cleaning member is pressed against the charging roller and rubs against the charging roller at the first position and the second position according to the rotation direction of the charging roller to clean the charging roller. The cleaning member is the first auxiliary pressure member.
When it is in the position, the cleaning member is brought into contact with the cleaning member to increase the pressure contact force of the cleaning member with respect to the charging roller.

According to a second aspect of the invention, in the charging device according to the first aspect, the cleaning member is normally rotated during the image forming operation of the image forming apparatus and rubs against the charging roller at the first position to form an image. During the non-image forming operation of the apparatus, it is reversed and rubs against the charging roller at the second position.

According to a third aspect of the present invention, in the charging device according to the first or second aspect, the cleaning member is the second one.
The rubbing is performed on the charging roller at the position, and the rubbing is performed on the charging roller at the first position for a time longer than the rubbing time.

According to a fourth aspect of the invention, in the charging device according to the first, second or third aspect, the charging roller is the second.
After the position is switched to the first position, the image carrier is rotated at least one revolution before the image forming operation of the image forming apparatus, and then the charging of the image carrier is started by applying the charging bias.

According to a fifth aspect of the present invention, in the charging device according to the first aspect, the second aspect, the third aspect, or the fourth aspect, the portion of the cleaning member having the abrasive material rubs against the charging roller at the second position.

According to a sixth aspect of the present invention, in the charging device according to the fifth aspect, the portion of the cleaning member having the abrasive having a particle diameter smaller than the toner particle diameter rubs against the charging roller at the second position. .

[0020]

FIG. 2 shows an example of an image forming apparatus to which the present invention is applied. The image carrier 1 including a photoconductor drum having a photoconductive layer such as an organic photoconductor, A-Si, and A-Se is driven by a drive unit and is rotated in the arrow direction while being held by a rotation shaft (not shown). The charging device 2 has a charging roller 3 and a cleaner 4, and the cleaner 4 is composed of a cleaning member including a cleaning blade. The charging roller 3 is constantly rotatably pressed against the image carrier 1 and is rotated by being driven by the image carrier 1. This charging roller 3
Is applied with a charging bias from the power source 5 through the control means 6 so that the surface of the image carrier 1 is uniformly charged and uniformly charged.

A light source 7 including a semiconductor laser and a light emitting diode emits an optical image according to a predetermined electric signal and irradiates the surface uniformly charged by the charging device 2 of the image carrier 1 to perform image exposure. Form an electrostatic latent image. The developing device 8 contains a developer inside, and the developing sleeve 9 rotates to supply the developer to the image carrier 1 to visualize the electrostatic latent image on the image carrier 1 as a toner image.

On the other hand, the transfer paper 10 is fed from a paper feeding device and sent by a registration roller in synchronism with the toner image on the image carrier 1 so that the toner image on the image carrier 1 is transferred.
1 is transferred. The transfer device 11 includes a transfer roller 1
2, a cleaning blade 13 and a toner collection box 14, and a transfer bias is applied to the transfer roller 12 from the power supply 15 through the control means 16 to apply an electric charge to the transfer paper 10 so that the toner on the image carrier 1 is transferred. The image is transferred onto the transfer paper 10. The cleaning blade 13 is the transfer roller 1.
The transfer roller 12 is cleaned by scraping the toner from 2 to the toner collecting box 14. The transfer paper 10 on which the toner image has been transferred has the toner image fixed by a fixing device (not shown), and becomes a recorded matter. Further, the residual toner on the image carrier 1 is removed by the cleaning device 17 after the transfer of the toner image.

FIG. 1 shows the charging device 2 and the image carrier 1 in an enlarged manner. The charging device 2 has an auxiliary pressing member 18 including a charging roller 3, a cleaning member 4 and a stopper. The above-mentioned image forming operation (charging, exposure, development of the image carrier 1,
During the transfer and cleaning operations), the drive unit rotates the image carrier 1 in the forward direction and the charging roller 3 in the forward direction as indicated by the solid line in the figure, and the cleaning member 4 is at the position indicated by the solid line in the figure (hereinafter referred to as the first position). Then, the charging roller 3 is pressed and rubbed.
In this case, the cleaning member 4 is brought into pressure contact with the charging roller 3 and rubs only with its own elastic pressure.

During a predetermined preliminary rotation that is sufficiently shorter than the image forming operation time, the drive unit reverses the image carrier 1 and the charging roller 3 reversely as shown by the broken line in the figure, and the cleaning member 4 moves to the position shown by the broken line in the figure ( In the following, referred to as a second position), the charging roller 3 is pressed and rubbed. In this case, the cleaning member 4 contacts the auxiliary pressure member 18, and the auxiliary pressure member 18 increases the pressure contact force with respect to the charging roller 3.

Here, the cleaning member 4 is provided so that the tip portion thereof is always in pressure contact with the charging roller 3, and the frictional force with the charging roller 3 causes the cleaning member 4 to automatically move to the first position when the charging roller 3 rotates in the forward direction. When the charging roller 3 is rotated in the reverse direction, the charging roller 3 is automatically switched to the second position.

FIG. 5 shows a timing chart of this example. During the standby time when the image forming operation is not performed, the image carrier 1 and the charging roller 3 are stopped, the control units 6 and 16 are turned off, and the bias is not applied to the charging roller 3 and the transfer roller 12. When the image forming operation is performed, the image carrier 1 is reversely rotated by the drive unit for a predetermined preliminary rotation time prior to the image forming operation, and the charging roller 3 is driven and reversely rotated by the image carrier 1. The preliminary rotation time may be provided after the image forming operation, and the image carrier 1 and the charging roller 3 may be reversed after the image forming operation.

The cleaning member 4 contacts the auxiliary pressure member 18 and slides against the charging roller 3 at the second position to clean the charging roller 3, and the auxiliary pressure member 18 is charged by the charging roller 3 of the cleaning member 4. Increase the pressure contact force against. Therefore, the cleaning member 4 is pressed against the charging roller 3 and rubs against the charging roller 3 more strongly at the second position than at the first position.
The cleaning action on the charging roller 3 is strong, and the toner and dust firmly adhered to the charging roller 3 are removed.

After the pre-rotation time has elapsed, the image carrier 1 is rotated in the normal direction by the drive unit, and the charging roller 3 is driven by the image carrier 1 to rotate in the normal direction. The cleaning member 4 is switched to the first position by the frictional force with the charging roller 3, and slides on the charging roller 3 by its own elastic force to clean the charging roller 3. The image forming operation is started after the charging roller 3 has rotated one rotation or more from the start of normal rotation, and the charging roller 3 is applied with a charging bias from the power source 5 by the control means 6 to apply the electric charge to the image carrier 1. The image carrier 1 is thereby uniformly charged.

As shown in FIG. 3, during normal rotation of the image carrier 1 and the charging roller 3, the residual toner 19 on the image carrier 1 adheres to the peripheral surface of the charging roller 3 and is scraped off by the cleaning member 4. It drops on the surface of the image carrier 1 and is collected by the developing device 8 for reuse. As shown in FIG. 4A, during the pre-rotation time, when the image carrier 1 and the charging roller 3 are reversed, the residual toner 19 on the charging roller 3 is scraped off by the cleaning member 4 and the surface of the image carrier 1 is removed. To fall. As shown in FIG. 4B, the charging roller 3 rotates in the normal direction after the pre-rotation time has elapsed, and the residual toner 1 on the charging roller 3
9 is scraped off by the cleaning member 4 and the image carrier 1
After the charging roller 3 is normally rotated by one rotation or more and all the residual toner 19 on the charging roller 3 is scraped off by the cleaning member 4, the charging roller 3 is biased from the power source 5 by the control means 6 to the charging bias. Is applied to the image carrier 1
To be uniformly charged.

As shown in FIG. 6, the cleaning member 4 is composed of a cleaning blade held by a cleaner holder 20. This cleaning blade 4 is made of rubber 21
And a rubber containing an abrasive in the upper part 22 thereof, or a rubber containing an abrasive in the upper part 22.
The one in which 2 is integrally attached to the rubber portion 21 is used. The cleaning blade 4 may have an upper portion 22 having an abrasive material such as sandpaper and may be integrally attached to the rubber portion 21.
Further, as shown in FIG. 7, the cleaning blade 4 may be configured such that the portion 22 having the abrasive is only the portion in contact with the charging roller 3.

As shown in FIG. 8, the cleaning blade 4
During the image forming operation in which the charging roller 3 is rotated in the normal direction, the rubber portion 21 is pressed against the charging roller 3 and rubs against it to clean the surface of the charging roller 3. Further, the cleaning blade 4 cleans the surface of the charging roller 3 during the pre-rotation time in which the charging roller 3 is reversely rotated during the non-image forming operation, because the portion 22 having the abrasive material is pressed against the charging roller 3 and rubs against it. Then, the toner and dust firmly adhered to the charging roller 3 are removed.
Since this pre-rotation time is much shorter than the image forming operation time, the surface of the charging roller 3 is not excessively shaved by the abrasive-containing portion 22 of the cleaning blade 4.

When the abrasive-containing portion 22 of the cleaning blade 4 has a particle diameter larger than that of the toner, as shown in FIG. 9B, the toner 19 is formed in the groove 23 cut with the abrasive. It becomes impossible to clean the toner due to the inclusion of. Therefore, in this example, as the abrasive-containing portion 22 of the cleaning blade 4, an abrasive having a particle diameter smaller than that of the toner is used. As shown in FIG. 9A, the toner 19 is provided in the groove 23 cut by the abrasive. The toner can be cleaned without entering.

In this example, one cleaner 4 switches between two types of pressure-rubbing forces on the charging roller 3 according to the rotation direction of the charging roller 3, so that a simple and reliable cleaning action can be obtained, and the charging roller 3 can be obtained. The strong dirt can be removed without scraping off the surface of the charging roller 3 more than necessary. Further, the toner scraped off from the charging roller 3 by the cleaner 4 falls on the surface of the image carrier 1 and adheres to it, and is collected and reused by the developing device 8. Therefore, a toner conveying device and a toner collecting box holder are unnecessary. Yes, it is a simple and inexpensive device.

The cleaner 4 is placed in the second position rather than the first position.
Since the pressure contact rubbing force against the charging roller 3 is strong at the position of and has a scraping effect on the charging roller 3, the abrasion of the charging roller 3 is caused by rubbing against the charging roller 3 at the second position during the image forming operation. It can be prevented that the life of the charging roller 3 is shortened due to the increase of the number, and that the image vibrates and vibrates when vibrated by being strongly pressed and rubbed against the charging roller 3 at the second position during the image forming operation. Can be prevented.

Further, the cleaner 4 is located at the first position rather than the second position.
The charging roller 3 is normally rotated for one rotation or more and all the residual toner 19 on the charging roller 3 is scraped off by the cleaning member 4, and then the charging roller 3 is applied with a charging bias to cause the image carrier 1 to move. Is uniformly charged, it is possible to uniformly charge the image carrier 1 without unevenness. Further, the cleaner 4 has the portion 22 having the abrasive in the second position.
Are pressed against the charging roller 3 and rub against each other, so that the charging roller 3
The cleaning action is further improved, and the particle size of the abrasive is smaller than the particle size of the toner, so that the toner 19 does not enter the groove 23 scraped by the abrasive of the charging roller 3 and cleaning cannot be disabled. .

[0036]

As described above, according to the first aspect of the present invention, the charging roller for contacting the surface of the image carrier in the image forming apparatus to charge the image carrier for normal and reverse rotation, and the charging roller A cleaning member that is pressed against the charging roller and rubs the charging roller at a first position and a second position according to the rotation direction of the charging roller to clean the charging roller, and the cleaning member is at the first position. In this case, since the auxiliary pressure member for contacting the cleaning member and increasing the pressure contact force of the cleaning member with the charging roller is provided, a simple and reliable cleaning action can be obtained.
Strong dirt on the charging roller can be removed without scraping off the surface of the charging roller more than necessary.

According to the second aspect of the invention, in the charging device of the first aspect, the cleaning member is normally rotated during the image forming operation of the image forming apparatus and is moved to the charging roller at the first position. The rubbing rubbing causes the cleaning member to reversely rotate during the non-image forming operation of the image forming apparatus and rub against the charging roller at the second position. Therefore, the cleaning member press-contacts the charging roller at the second position during the image forming operation. It is possible to prevent the abrasion of the charging roller from being increased and the life of the charging roller to be shortened by rubbing, and the cleaning member rubs strongly against the charging roller at the second position during the image forming operation. It is possible to prevent the image from being shaken and being blurred.

According to a third aspect of the present invention, in the charging device according to the first or second aspect, the time for which the charging roller is rubbed at the second position of the cleaning member is the first of the cleaning member. It is possible to prevent the abrasion of the charging roller from being increased and the life of the charging roller to be shortened because it is longer than the time of sliding on the charging roller at the position.

According to the invention of claim 4, in the charging device of claim 1, 2 or 3, the image forming apparatus is operated after the charging roller is switched from the second position to the first position. Since the charging of the image carrier is started by applying the charging bias after rotating at least one rotation prior to the image forming operation, it is possible to uniformly charge the image carrier.

According to a fifth aspect of the present invention, in the charging device according to the first aspect, the second aspect, the third aspect, or the fourth aspect, the portion of the cleaning member that slides on the charging roller at the second position is made of an abrasive material. Since it has, the cleaning action of the charging roller is further improved.

According to a sixth aspect of the invention, in the charging device according to the fifth aspect, since the particle size of the abrasive is smaller than the particle size of the toner, the toner is left in the groove scraped by the abrasive of the charging roller. Cleaning does not become impossible without entering.

[Brief description of drawings]

FIG. 1 is a front view showing a charging device as an example of an image forming apparatus to which the present invention is applied.

FIG. 2 is a schematic view showing the image forming apparatus.

FIG. 3 is a diagram for explaining the charging device.

FIG. 4 is a diagram for explaining the charging device.

FIG. 5 is a timing chart of the image forming apparatus.

FIG. 6 is a front view showing a cleaner of the charging device.

FIG. 7 is a front view showing a cleaner of another charging device.

FIG. 8 is a diagram for explaining the charging device.

FIG. 9 is a diagram for explaining the charging device.

[Explanation of symbols]

 1 Image Carrier 2 Charging Device 3 Charging Roller 4 Cleaning Member 18 Auxiliary Pressing Member

Claims (6)

[Claims] 1. A charging roller for contacting the surface of an image carrier in an image forming apparatus to charge the image carrier for normal and reverse rotation, and a charging roller pressed against the charging roller according to the rotation direction of the charging roller. And a cleaning member for cleaning the charging roller by rubbing between the first position and the second position, and the cleaning member contacting the cleaning member when the cleaning member is in the first position and charging the cleaning member. A charging device, comprising: an auxiliary pressure member that increases a pressure contact force with respect to the roller. 2. The charging device according to claim 1, wherein the cleaning member is normally rotated during an image forming operation of the image forming apparatus and rubs against the charging roller at the first position. A charging device which reverses and rubs against the charging roller at the second position during a non-image forming operation. 3. The charging device according to claim 1, wherein a time for rubbing the charging roller at the second position of the cleaning member is slid on the charging roller at the first position of the cleaning member. A charging device characterized by being longer than the rubbing time. 4. The charging device according to claim 1, 2 or 3, wherein at least the charging roller is switched from the second position to the first position before the image forming operation of the image forming apparatus. A charging device, characterized in that charging of the image carrier is started by applying a charging bias after rotating one or more times. 5. The charging device according to claim 1, 2 or 3 or 4, wherein a portion of the cleaning member that slides on the charging roller at the second position has an abrasive. . 6. The charging device according to claim 5, wherein the abrasive has a particle diameter smaller than that of the toner.