JPH09160460A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent staining of toner image by specifying the surface roughness of an elastic body constituting a cleaning member (cleaning roller). SOLUTION: The surface roughness of the elastic body 12b constituting the cleaning roller 12 is set so that projected and recessed parts may not be formed on the surface of the elastic body in substance or the depth of the recessed part may be equal to or under the particle size of toner in a state where the surface of the elastic body abuts on the surface of a photoreceptor 1. Since such a recessed part that much toner between the elastic body 12b and the photoreceptor 1 gets into, does not exist on the surface of the elastic body 12b when the surface of the elastic body 12b abuts on the surface of the photoreceptor 1, the toner is not captured by the surface of the roller 12. And, since the depth of the recessed part out of the fine projected and recessed parts on the surface of the elastic body 12 abutting on the photoreceptor 1 is equal to or under the particle size of the toner, when the recovered toner is stuck to the photoreceptor 1 again, it is surely brought into contact with the surface of the photoreceptor 1 and scraped even though the toner particle gets into the recessed part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image bearing member which is driven to rotate, a latent image forming means for forming an electrostatic latent image on the bearing member, and a visible image as the toner image. The present invention relates to an image forming apparatus including a developing device for converting the toner image on the image carrier to a recording medium, and a cleaning member for collecting the transfer residual toner on the image carrier after the toner image transfer. Is.

[0002]

2. Description of the Related Art In an image forming apparatus of the above type configured as a copying machine, a printer, a facsimile, or a complex machine thereof, an image carrier is repeatedly used, and therefore, the surface of the image carrier after the toner image is transferred. It is necessary to clean the surface of the image bearing member by removing and collecting the residual toner remaining on the image carrier by a cleaning member. Therefore, conventionally, various cleaning devices for cleaning the image carrier have been proposed and put into practical use, but the conventional cleaning device generally stores the toner collected from the image carrier in a waste toner tank or the like, It is configured to discard this.

By the way, in recent years, in an image forming apparatus of this type which employs an electrophotographic process, it is possible to further reduce the cost and further reduce the amount of toner to be discarded as part of measures against environmental problems. Is requested.

In view of the above point, if the transfer rate of the toner image from the image carrier to the recording medium is set to 100% to eliminate the residual toner after the transfer, the so-called cleanerless system can be adopted. it can. As a result, not only can the toner to be discarded be eliminated, but also the cleaning device can be omitted, and the image forming system can be simplified and the cost of the image forming device can be reduced. However, at present, it is difficult to make the transfer rate of the toner image 100%, and there is a problem from the viewpoint of reliability.

Therefore, as a next best measure, the transfer residual toner remaining on the surface of the image carrier after the toner image is transferred is adhered to the cleaning member to be recovered, and then the recovered toner is re-adhered to the image carrier. , A method of collecting with a developing device and reusing it has been proposed (for example, Japanese Patent Publication No.
-30274 publication). After the toner image is transferred, the transfer residual toner remaining and attached on the image carrier is temporarily collected by the cleaning member, and the collected toner is affected by the formation of the next electrostatic latent image on the image carrier. The toner re-adhered to the non-existing surface portion and further re-adhered to the surface of the image carrier is collected by the developing device. This eliminates the need for a dedicated means for transferring the collected toner to a waste toner tank or a developing device, thus reducing the cost of the image forming apparatus and reusing the toner. It can be lost.

In the conventional image forming apparatus of this type,
The cleaning member has an elastic body made of foam that comes into contact with the surface of the image carrier, and the surface of the elastic body comes into contact with the surface of the image carrier to collect the transfer residual toner and the image of the collected toner. It is configured to redeposit on the surface of the carrier.

However, when a cleaning member provided with an elastic body made of foam is used, a large number of cell holes of the foam are exposed on the surface, and the depth of each hole is larger than the particle size of the toner particles. When the surface of the elastic body of the cleaning member comes into contact with the surface of the image carrier in order to recover the transfer residual toner on the image carrier, the foamed body that constitutes the elastic body is formed. A large amount of toner enters the cell holes of. When the toner enters the cell holes in this way, when the toner collected on the cleaning member is reattached to the image carrier, the toner captured in the cell holes does not transfer to the surface of the image carrier, and the cleaning member Remains on top. In this way, the toner remaining on the cleaning member adheres to the cleaning member over time, which lowers the cleaning performance of the image carrier by the cleaning member, and the toner image formed on the image carrier is grounded. Contamination occurs and the image quality deteriorates.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to collect the transfer residual toner on a cleaning member, to reattach the recovered toner to the image carrier, and then to collect the reattached toner on the developing device. An object of the present invention is to provide an image forming apparatus capable of solving the above-mentioned problems in the image forming apparatus and preventing the occurrence of background stain on the toner image.

[0009]

In order to achieve the above object, the present invention is directed to an image carrier which is driven to rotate, a latent image forming means for forming an electrostatic latent image on the carrier, and an electrostatic latent image forming means. A developing device that visualizes the latent image as a toner image, a transfer device that transfers the toner image on the image carrier to a recording medium, and a transfer residual toner on the image carrier after the toner image transfer is temporarily collected. And a cleaning member for reattaching the collected toner to the surface portion of the image bearing member that does not affect the formation of the next electrostatic latent image, and the toner reattached to the surface of the image bearing member. And the cleaning member has an elastic body that contacts the surface of the image carrier, and the surface of the elastic body contacts the surface of the image carrier to collect the transfer residual toner. Image formation by reattaching the collected toner to the surface of the image carrier In the arrangement, the surface roughness of the elastic body constituting the cleaning member is set such that the elastic body surface is not in contact with the surface of the image carrier, and substantially no unevenness is formed on the elastic body surface, or An image forming apparatus is proposed in which the depth of the concave portion is set to be equal to or smaller than the particle diameter of the toner particles.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus according to the present invention. In the figure, a drum-shaped photoreceptor 1 which is an example of the configuration of an image carrier is rotationally driven in the clockwise direction in the figure by a driving unit (not shown), and at the time of this rotation, an action of a charging roller 2 which is an example of a charging device. As a result, the surface of the photoconductor 1 is uniformly charged with a predetermined polarity.
In this example, the charging roller 2 is connected to the voltage power source E ₁₀ , and uniformly charges the surface of the photoconductor 1 to a negative (negative) polarity while rotating in contact with the photoconductor 1. By the action of the charging roller 2, the surface of the photoconductor 1 is charged to, for example, -850V. As a charging device for uniformly charging the photoconductor 1,
It is also possible to use a charging device, such as a corona discharger, which is arranged apart from the photoconductor.

Next, in the exposure unit 3, an exposure scanning device (not shown) performs optical writing scanning with, for example, the light-modulated laser beam 11, so that a predetermined electrostatic latent image is formed on the surface of the photoconductor 1. Is formed. The surface potential of the portion A irradiated with the laser light 11 forming the electrostatic latent image is, for example, about −150V, and the surface potential of the portion B not irradiated with the laser light 11 is maintained at about −850V. As described above, in this example, the charging roller 2 and the exposure scanning device form a latent image forming unit that forms an electrostatic latent image on the image carrier made of the photoconductor 1.

The developing device 4 is provided with a developing roller 5 which is an example of a developer carrying and conveying member disposed opposite to the photoconductor 1 and a pair of stirring paddles 10A and 10B, which form the main body of the developing device. Each of the developing casings 9 is provided and rotatably supported by the casing 9. A voltage of about -600 V, for example, is applied to the developing roller 5 by the voltage power source E ₁ . A voltage having the same polarity as the charging polarity of the photoconductor 1 is applied to the developing roller 5.

In the developing device 4 illustrated here, a two-component developer D having a toner and a carrier is used, and the developer D is contained in the developing casing 9. Then, as the stirring paddles 10A and 10B rotate, the toner is charged to a predetermined polarity by friction with the carrier, that is, the same polarity as the charging polarity of the photoconductor 1 in this example, that is, a negative polarity. As described above, in the image forming apparatus of this example, the charging polarity of the toner during development is negative. A developing device using a one-component developer having no carrier may be employed.

The developing roller 5 is driven to rotate counterclockwise in the drawing, and the developer carried on the peripheral surface of the developing roller 5 is conveyed in the rotating direction of the developing roller 5, and the roller 5 is rotated.
The developer regulating member 15 oppositely arranged with a predetermined gap therebetween is scraped. The developer whose conveyance amount is regulated by the developer regulating member 15 is conveyed toward the developing section 6 where the developing roller 5 and the photoconductor 1 face each other, and the toner in the developer is conveyed to the photoconductor by the developing section 6. 1 is electrostatically attracted to the electrostatic latent image on 1 and adheres to that portion. That is, the toner charged to the negative polarity, which is the same as the charging polarity of the photoconductor, adheres to the surface portion A of the photoconductor irradiated with the laser beam, and the electrostatic latent image is visualized as a toner image. As described above, the image forming apparatus of this embodiment employs the reversal development method (negative / positive development method).

A transfer roller 7, which is an example of a transfer device, is disposed below the photoconductor 1. The transfer roller 7 rotates in the forward direction with respect to the rotation direction of the photoconductor 1, and the recording medium made of the transfer paper 16 is moved toward the transfer portion 8 between the transfer roller 7 and the photoconductor 1 in contact with the transfer roller 7. The toner image formed on the photoconductor 1 is transferred onto the transfer paper 16 by the function of the transfer roller 7 so that the toner image is fed in the direction of arrow P. That is, the power supply E ₃ applies a positive (plus) polarity voltage opposite to the charging polarity of the toner on the photoconductor 1 to the transfer roller 7, for example, a voltage of + 950V,
At this time, the toner T having a negative polarity on the photoconductor 1 (this is schematically shown in large size) is electrostatically attracted to the transfer paper 16 side and adheres to the transfer paper. Photoconductor 1
It is also possible to use a transfer device spaced apart with respect to, for example a transfer device consisting of a corona discharger.

The transfer paper 16 on which the toner image has been transferred is separated from the photoconductor 1 by a separating device (not shown), and is sent to a fixing device (not shown).
The toner image on 6 is fixed.

As described above, the image forming apparatus of this embodiment has the image carrier composed of the photosensitive member 1 which is rotationally driven, the latent image forming means for forming an electrostatic latent image on the image carrier, and the latent image forming means. It has a developing device 4 for visualizing the electrostatic latent image as a toner image, and a transfer device including a transfer roller 7 for transferring the toner image on the image carrier onto a recording medium made of transfer paper 6.

The toner image on the photoconductor 1 is transferred to the transfer paper 16 at the transfer portion 8. After the toner image is transferred, the photoconductor 1 is transferred.
The toner that did not contribute to the transfer remains adhered to the surface of the. When the transfer residual toner reaches the cleaning unit 14, it is temporarily collected by a cleaning roller 12 which is an example of a cleaning member.

The cleaning roller 12 has a core member 12a made of a rigid body, and a conductive or medium-resistance elastic body 12b fixed on the surface of the core member 12a. In the illustrated example, the core member 12a. Is made of a conductive metal having a round shaft shape, and the elastic body 12b is formed in a cylindrical shape concentric with the core member 12a. The elastic body 12b is housed in the cleaning case 17, and each end of the core member 12b is rotatably supported by the front and rear side walls of the cleaning case 17. The cleaning roller 12 is
Together with the developing roller 5, the charging roller 2, and the transfer roller 7, they are positioned substantially parallel to the photoconductor 1.

Here, in FIG. 1, most of the toner T of the toner image directed from the developing section 6 to the transfer section 8 is a toner having a charging polarity at the time of development, that is, a negative polarity toner. On the other hand, when a toner image is transferred, a positive polarity voltage opposite to the toner charging polarity at the time of development is applied to the transfer roller 7, so that the toner remaining on the photoreceptor 1 after the transfer of the toner image, That is, the transfer residual toner T ′
Is a toner in which positive and negative ones are mixed. The transfer residual toner is transferred to the cleaning unit 14 in a state in which both positive and negative polarity toners are mixed.

The cleaning roller 12 of this example drives the drive roller (not shown) in the clockwise direction in FIG. 1, that is, in the counter direction with respect to the rotation direction of the photoconductor 1 when collecting the transfer residual toner T'on the photoconductor 1. It is driven to rotate by the control means, and rotates while rubbing against the surface of the photoconductor 1. The surface of the cleaning roller 12 is pressed against the photosensitive member 1 so that the surface of the cleaning roller 12 can be elastically deformed by the photosensitive member 1. As shown in FIG. 2, a nip region N is formed at this pressed portion. This nip area N becomes a cleaning area.

In the nip area N, the transfer residual toner T'having both positive and negative polarities becomes a toner having the same polarity (negative polarity in this example) as the toner at the time of development while contacting the cleaning roller 12. It is frictionally charged. Transfer residual toner T '
However, the negative polarity, which is the charging polarity at the time of development, can be obtained.

Thus, the cleaning roller 1 of this example
2 is the transfer residual toner that is frictionally charged between the photosensitive member 1 and
It also performs the function of frictionally charging the toner so that the toner has a negative polarity, which is the original polarity. That is, the cleaning member including the cleaning roller 12 includes a toner whose transfer residual toner toward the cleaning roller 12 has a polarity opposite to the charging polarity of the toner at the time of development, and the toner has the charging polarity ( The toner is triboelectrically charged so that the toner can have the original polarity). The elastic body 12b of the cleaning roller 12 is composed of a charging series charging material capable of frictionally charging the toner to its original polarity, in this example, negative polarity.

Returning to FIG. 1, when the transfer residual toner T'on the photosensitive member 1 is collected by the cleaning roller 12, the core member 12a of the cleaning roller 12 is charged with the toner frictionally charged by the roller 12. A voltage having a polarity opposite to that of the polarity, in this example, a positive polarity voltage, for example, a voltage of +200 V is applied by the voltage power supply E ₄ . Therefore, the residual toner after the transfer of the toner image, which has passed through the transfer portion 8, that is, the residual transfer toner T ′ is electrostatically attracted to the cleaning roller 12 to which a positive voltage is applied, and adheres to the roller 12. , Are temporarily collected by this roller. As a result, the surface of the photoconductor 1 is cleaned. In this way, the cleaning roller 12 that rotates in contact with the photoconductor 1 has an electric field that allows the transfer residual toner on the photoconductor 1 to be electrostatically attracted toward the cleaning roller 12 between the cleaning roller 12 and the photoconductor 1. The voltage as described above is applied so that the voltage is formed.

The surface of the photoreceptor 1 is the cleaning roller 12
After being cleaned by, the surface is subjected to static elimination action by the static elimination lamp 13 which is an example of the static elimination device, and the above-mentioned image forming operation is continued. In this way, one toner image is formed on the photoconductor 1 and is transferred to the transfer paper 16. The region on the photoconductor 1 on which the toner image is formed is the image forming region. The area after that is the non-image forming area. When the rear end of the image forming area in the direction of rotation of the photoconductor passes through the charging roller 2, the charging roller 2 is separated from the surface of the photoconductor 1 at this time. At the same time, the switch S ₁₀ is switched to turn off the voltage application to the charging roller 2.

When the rear end of the above-mentioned image forming area passes the developing roller 5 of the developing device 4, the switch S ₁ is switched, the developing roller 5 is connected to the voltage power source E ₂ , and the developing roller 5 is connected to the developing roller 5. To prevent the toner from adhering to the photoconductor 1, a positive polarity voltage opposite to the charging polarity of the toner, for example, +
A voltage of 500V is applied. When the trailing edge of the image forming area passes through the transfer portion 8, the voltage application to the transfer roller 7 is stopped at this time.

As described above, in the illustrated image forming apparatus, after the toner image is transferred onto the recording medium made of the transfer paper 16, the transfer residual toner T ′ remaining on the photosensitive member 1 remains.
Are temporarily collected by a cleaning member including a cleaning roller 12 that rotates in contact with the photoconductor 1. When the transfer residual toner on the photoconductor 1 is collected by the cleaning roller 12, the cleaning roller 12 is electrostatically transferred to the cleaning roller 12 at the time of development so that the cleaning roller 12 is electrostatically transferred to the cleaning roller 12. A voltage having a polarity opposite to the charging polarity of the toner (positive polarity in this example) is applied.

The toner thus collected on the cleaning roller 12 is reattached to the surface portion of the photosensitive member 1 which does not affect the formation of the next latent image. That is, when the trailing edge of the image forming area after the toner image is transferred to the transfer paper 16 passes the cleaning roller 12, the switch S ₂
The cleaning roller 12 is switched to the voltage power source E.
₅ , the core member 12a of the cleaning roller 12 has the same negative polarity as the charging polarity of the toner frictionally charged by the cleaning roller, for example, -300.
A voltage of 0V is applied. An electric field is formed between the rotating cleaning roller 12 and the non-image forming area of the photoconductor 1 in the direction in which the toner on the cleaning roller 12 is discharged toward the photoconductor 1.

Due to the electric field, the toner temporarily collected on the cleaning roller 12 is reattached to the non-image forming area on the photoconductor 1 and returned. The toner redeposited on the photoconductor 1 passes under the charge removing roller 13 and the charging roller 2 separated from the photoconductor 1 by the subsequent rotation of the photoconductor 1, and reaches the developing device 4. At this time, as described above, since the positive polarity voltage opposite to the charging polarity of the toner at the time of development is applied to the developing roller 5, the negative polarity toner redeposited on the photoconductor 1 is It electrostatically moves to the developing roller 5 side and is collected in the developer in the developing device.

As described above, the toner temporarily collected by the cleaning roller 12 is reattached to the image carrier composed of the photoconductor 1, and the toner reattached to the surface of the image carrier is developed by the developing device 4. Collect electrostatically. The toner collected in the developing device 4 is reused in the developing device 4. In this way, waste toner can be eliminated,
Moreover, it is not necessary to provide a toner conveying pipe for returning the toner collected by the cleaning roller to the developing device. When the image forming operation is continuously performed, the toner collection and the re-adhesion operation are repeated a predetermined number of times.

The toner collected on the cleaning roller 12 reattaches to the non-image forming area near the rear end of the image forming area on the photosensitive member 1.
Not only the electrostatic latent image at the time of the image forming operation described above, but also the electrostatic latent image formed next is not affected. The collected toner is redeposited on the surface portion of the photoconductor 1 that does not affect the formation of the next latent image. In any of the electrostatic latent images, the toner from the cleaning roller 12 redeposits on the surface portion of the photoconductor that is formed on the photoconductor without being disturbed by the redeposition toner. It is also possible to re-adhere the toner from the cleaning roller 12 to the rear portion in the image forming area.

As described above, by applying a bias voltage having a polarity opposite to the charging polarity of the toner at the time of development to the cleaning member, the transfer residual toner on the image carrier is electrostatically transferred to the cleaning member. It is possible,
As a result, the transfer residual toner can be collected by the cleaning member, and after the collection, the polarity of the bias voltage applied to the cleaning member is switched so that the cleaning member has the same polarity as the charging polarity of the toner during development. By applying the bias voltage of, the toner collected in the cleaning member can be electrostatically transferred to the image carrier. As a result, the collected toner can be reattached to the image carrier, and the reattached toner can be collected in the developing device.

Here, as described above, the transfer unit 8
The transfer residual toner T ′ on the photoconductor 1 that has passed through is mixed with toner charged in the opposite polarity to the charging polarity of the toner at the time of development (abnormal polarity toner).
The abnormal polarity toner is triboelectrically charged with the cleaning roller 12 so as to have the same polarity as that of the toner during development.

However, the nip area N shown in FIG.
It is difficult to completely align the charging polarities of the transfer residual toners existing in the above, and there are some toners that remain the charging polarities opposite to the charging polarities of the toners at the time of development, that is, abnormal polarity toners. At the time of collecting the toner, a voltage having a polarity opposite to the charging polarity of the toner at the time of development is applied to the cleaning roller 12 as described above, and the toner having the charging polarity at the time of development is cleaned.
Is electrostatically transferred to the roller 12 and is collected by the roller 12. At this time, toner having a polarity opposite to the charging polarity at the time of development (abnormal polarity toner) is also received from the cleaning roller 12. It is attached to the cleaning roller 12 by the target scraping force. Such an abnormal polarity toner may cause the photoconductor 1 to collect during the toner recovery operation from the photoconductor 1.
If it is transferred to, the background stain on the image and the charge roller 2 are likely to occur.

Therefore, in the image forming apparatus of this embodiment, when the transfer residual toner T'is collected from the photosensitive member 1 to the cleaning roller 12 as shown in FIG.
In the contact area between the photoconductor 1 and the cleaning roller 12, that is, in the nip area N where they are in pressure contact with each other, the rotation direction of the cleaning roller 12 is controlled so that they move in opposite directions (counter direction), and The cleaning roller 12 has a drive control unit (not shown) that controls the rotation of the cleaning roller 12 so that the transfer roller residual toner on the photoconductor 1 is collected by the cleaning roller 12 with less than one rotation of the cleaning roller 12. . With the rotation of the cleaning roller 12 less than one rotation, the operation of collecting the transfer residual toner on the photoconductor 1 is completed.

With this configuration, the cleaning roller 12
Does not come into contact with the photoconductor 1 again during the toner collecting operation. Moreover, it is possible to prevent the abnormal polarity toner collected on the cleaning roller 12 from being electrostatically transferred to the surface of the photoconductor 1 after cleaning during the toner collecting operation.

If the cleaning roller 12 is rotated in the nip region N with the photoconductor 1 in the direction in which they move in the same direction as shown by the chain line arrow b in FIG. 2 when the transfer residual toner is collected. The collected toner T ″ is present on the cleaning roller 12 on the downstream side in the rotation direction of the photoconductor 1, and if the toner T ″ is an abnormal polarity toner that remains positively charged, the cleaning roller 12 is Since the same positive polarity voltage is applied during the toner recovery, the toner T ″ having the positive polarity is electrostatically attracted toward the photoconductor 1 and adheres to the photoconductor surface. Then, the cleaning failure of the photoconductor 1 occurs, and the toner adheres to the charging roller 2, so that the toner image that is subsequently formed has background stains.

In order to eliminate such a problem, as described above, the cleaning roller 12 rotates so that the cleaning roller 12 rotates in the counter direction with respect to the rotation direction of the photoconductor 1, that is, in the direction of the solid arrow a in FIG. The direction is set. At that time, the cleaning roller 12 is set to 1
When the transfer residual toner is collected from the photosensitive member 1 by rotating the photosensitive member 1 for more than a rotation, when the abnormally charged toner T ″ having a positive polarity is present in the toner collected by the cleaning roller 12, the toner is transferred to the photosensitive member 1 again. When approaching or in contact with this, the toner T ″ adheres to the photoconductor 1 and cleaning failure of the photoconductor 1 occurs. Therefore, in this example, the toner collecting operation from the photoconductor 1 to the cleaning roller 12 is completed while the cleaning roller 12 is rotationally driven for less than one rotation.

According to the above construction, the cleaning roller 1
It is possible to make it difficult to transfer the toner (abnormal polarity toner) having a polarity opposite to the charge polarity at the time of development, which is collected in No. 2, to the photoconductor 1.

The cleaning roller 12 for reattaching the collected toner on the cleaning roller 12 to the photoconductor 1
Can be rotated in any direction. In this example, the photoconductor 1
In the nip area N between the cleaning roller 12 and the photosensitive member 1, the rotation direction of the cleaning roller 12 is controlled so that the cleaning roller 12 and the photosensitive member 1 rotate in the same direction (the direction of the chain line arrow b in FIG. 2), and the rotation speed is controlled during toner collection. The rotation speed is higher than the peripheral speed of the photoconductor 1, and the toner is reattached to the photoconductor 1 efficiently in a short time.

As described above, the illustrated image forming apparatus temporarily collects the transfer residual toner on the photoconductor 1 after the toner image is transferred, and then collects the collected toner.
The cleaning member comprises a cleaning roller 12 which is reattached to the surface portion that does not affect the formation of the next electrostatic latent image, and the cleaning roller 12 is made of an elastic body 12b that contacts the surface of the photoconductor 1. The surface of the elastic body 12b comes into contact with the surface of the photoconductor 1 to collect the transfer residual toner and to reattach the collected toner to the surface of the photoconductor.

Here, as described above, in the conventionally proposed image forming apparatus of this type, the elastic body forming the cleaning roller is formed of a foamed body having a large number of cell holes exposed on the surface thereof. It had been. For this reason, when the cleaning roller rotates and the elastic body surface comes into contact with the photosensitive body surface in order to collect the transfer residual toner on the photosensitive body, the toner is not filled in the cell holes of the foam body forming the elastic body. A large amount of it will be buried. Therefore, when the collected toner on the cleaning roller is reattached to the surface of the photoconductor, the toner that has entered the cell holes may not be transferred to the photoconductor and may be deposited there.

In particular, as shown in FIG. 2, in the nip region between the cleaning roller and the photosensitive member, the toner is frictionally charged to a predetermined polarity, and the charged toner is electrostatically transferred to the cleaning roller. In this case, if the elastic body of the cleaning roller is made of foam, the toner that has entered the cell holes cannot be triboelectrically charged to a predetermined polarity. Therefore, the abnormal polarity toner that is not charged to a predetermined polarity exists in the cell hole. Therefore, to reattach the collected toner to the photoconductor,
When a voltage having the same polarity as the predetermined charging polarity of the toner is applied to the cleaning roller 12, the polarity of the applied voltage and the charging polarity of the abnormal polarity toner that has entered the cell hole are opposite to each other. For this reason, the toner becomes less likely to migrate toward the photoconductor, and remains on the cleaning roller.

In this way, when the toner trapped on the cleaning roller accumulates, the toner adheres to the surface of the cleaning roller, which gradually increases the apparent volume resistivity of the cleaning roller. ,
The effect of voltage application to the cleaning roller is reduced. As a result, the cleaning performance of the photoconductor by the cleaning roller deteriorates, and the background stain of the toner image formed on the photoconductor becomes significant. In addition, the re-adhesion performance of the toner from the cleaning roller to the photoconductor also deteriorates, so that the toner remains on the cleaning roller more and more. When a charging roller that contacts the surface of the photoconductor is used as the charging device as in the image forming apparatus shown in FIG. 1, when the cleaning performance for the photoconductor deteriorates, the cleaning is not performed by the cleaning roller and the cleaning is performed. The toner that has passed through the roller adheres to the charging roller, which reduces its function, and the toner that adheres to the roller again adheres to the photoconductor to cause background stain.

Therefore, in the image forming apparatus of this example,
The surface of the elastic body 12b forming the cleaning roller is formed so as to be smoother than that of the conventional elastic body so that a large recess such as a conventional cell hole is not formed on the surface. More specifically, the surface roughness of the elastic body 12b is determined so that the surface of the elastic body is in contact with the surface of the photoconductor, and no substantial unevenness is formed on the surface of the elastic body, or the depth of the concave portion thereof is large. Is set to be equal to or smaller than the particle size of the toner particles. The elastic body 12b is made of, for example, non-foamed solid rubber instead of foamed material, so that its surface can be finished smooth as described above.

According to the above construction, when the surface of the elastic body 12b comes into contact with the surface of the photoconductor, there is no recess on the surface of the elastic body into which a large amount of toner enters between the two, so that the toner is removed. Will not be trapped on the surface of. In addition, the elastic body 12 contacting the photoconductor 1
Even if there is minute unevenness on the surface of b, the depth of the concave portion is equal to or smaller than the toner particle size. Therefore, even if the toner particles enter the concave portion, when the collected toner is reattached to the photoconductor 1, Can surely come into contact with the surface of the photoconductor 1 and undergo a scraping action, so that the toner can be efficiently retransferred to the photoconductor 1. Further, when the transfer residual toner on the photoconductor 1 is collected, the toner does not enter a large amount into the concave portion on the surface of the elastic body, so that the toner on the cleaning roller 12 surely contacts the surface of the cleaning roller. Therefore, the toner can be efficiently triboelectrically charged to a predetermined polarity, in this example, a negative polarity, and a voltage having the same polarity as the charging polarity of the toner is applied to the cleaning roller 12 to expose the collected toner to light. When reattached to the body 1, the toner can be efficiently transferred to the surface of the photoconductor 1.

As described above, in the image forming apparatus of this embodiment, it is possible to prevent the toner from being deposited and fixed on the surface of the cleaning roller 12, and to prevent the volume specific resistance of the cleaning roller from increasing. The transfer residual toner on the photoconductor can be efficiently collected and removed over a long period of time, and the occurrence of background stain on the toner image formed on the photoconductor can be prevented.

The surface roughness of the elastic body 12b in the free state, which is not in contact with the photosensitive member 1, does not matter. Whether the toner is captured and adhered to the surface of the cleaning roller or whether the collected toner on the cleaning roller can be re-adhered to the photoconductor 1 is determined in the nip region between the cleaning roller 12 and the photoconductor 1. This is because the problem only occurs when the elastic bodies 12b are in contact with each other and the elastic body 12b receives pressure from the photosensitive body 1. Therefore, the roughness of the elastic body surface in the free state in which the elastic body 12b is not in contact with the photosensitive body 1 may be any.
It is sufficient that the elastic body surface satisfies the above-mentioned conditions when the surface of b and the surface of the photoreceptor contact each other.

In order to form the surface of the elastic body 12b so as to satisfy the above condition, the elastic body 12b is made of non-foamed solid rubber or the like as described above, and, for example, the elastic body 12b is made of foam. In addition to the configuration, a method of finishing the surface and forming a smooth skin layer on the surface can be adopted.

The present invention is an image forming apparatus that uses a roller-shaped cleaning member or an endless belt-shaped cleaning member, or an image forming apparatus that uses an endless belt-shaped cleaning member other than a drum-shaped image bearing member. It can also be applied to devices. Further, the present invention can be applied to an image forming apparatus in which an intermediate transfer member is used as a recording medium, a toner image is transferred from the image carrier to the intermediate transfer member, and then the toner image is transferred to a transfer material. Further, according to the present invention, after the image bearing member is charged by the charging device, an electrostatic latent image is formed by a portion which is not irradiated with light at the time of image exposure on the surface of the image bearing member, and the latent image potential is charged to the opposite polarity. It can also be applied to a so-called positive / positive developing type image forming apparatus in which the generated toner is adhered to the electrostatic latent image to perform development.

[0052]

According to the image forming apparatus of the present invention, the transfer residual toner is collected by the cleaning member to the cleaning member, the collected toner is reattached to the image carrier, and then the reattached toner is attached. In the image forming apparatus that collects the toner in the developing device, a large amount of toner remains on the cleaning member and is fixed to the cleaning member, which prevents the cleaning member from being deteriorated in cleaning performance of the image carrier, and is formed on the image carrier. It is possible to prevent the occurrence of background stains on the toner image.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional explanatory view of an image forming apparatus according to an exemplary embodiment of the present invention, in which the toner on a photoconductor and a cleaning roller is schematically illustrated and enlarged.

FIG. 2 is an enlarged schematic illustration of a toner and a frictional contact portion between the photosensitive member and the cleaning roller, for explaining that the charging polarities of the toner are made uniform.

[Explanation of symbols]

 4 developing device 12b elastic body T'toner

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masako Yoshii 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (1)

[Claims] 1. An image carrier that is driven to rotate, a latent image forming unit that forms an electrostatic latent image on the carrier, and a developing device that visualizes the electrostatic latent image as a toner image. A transfer device that transfers the toner image on the image carrier to the recording medium, and the transfer residual toner on the image carrier after the toner image transfer is temporarily collected, and then the collected toner is collected on the image carrier. A cleaning member for reattaching to a surface portion that does not affect the formation of the next electrostatic latent image, the toner reattached to the surface of the image carrier is collected in a developing device, and the cleaning member is used for the image bearing. An elastic body that comes into contact with the surface of the body is provided, and the surface of the elastic body comes into contact with the surface of the image carrier to collect the transfer residual toner and to reattach the collected toner to the surface of the image carrier. In the image forming apparatus, the elasticity of the cleaning member The surface roughness of,
In a state where the elastic body surface is in contact with the surface of the image bearing member, substantially no unevenness is formed on the elastic body surface, or the depth of the concave portion is set to be equal to or smaller than the particle diameter of the toner particles. An image forming apparatus characterized by the above.