JPH08110709A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Objective] When restarting after the interruption of the image forming operation, the toner existing on the photoconductor drum between the developing device and the transfer device increases the cleaning load of the cleaning device. The present invention provides an image forming apparatus in which the cleaning is prevented and the cleaning quality is improved and the image quality is improved. When the image forming operation is restarted after being interrupted, a voltage different from that during the image forming operation is applied to the contact type transfer unit,
A part of the toner on the photosensitive drum is moved to the contact type transfer means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an optical printer such as a laser printer using an electrophotographic process, a copying machine, and a facsimile machine.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus such as a laser printer, the surface of a drum-shaped or belt-shaped photosensitive member (image carrier) is charged by a charging device and then exposed by an exposure device. After an electrostatic latent image is formed and the latent image is visualized with a developer from a developing device, the latent image is visualized by a transfer device from a transfer device (transfer paper, OHP sheet).
Etc.) and is fixed by a fixing device. Then, the surface of the image carrier after the transfer is configured such that the cleaning device removes the residual developer adhering to the surface of the image carrier in preparation for the next image forming process.

In such an image forming apparatus, the operation is often interrupted during the image forming operation due to non-feeding of the transfer material to the transfer portion. In such a case, the image forming operation is restarted after the cause of the interruption of the image forming operation is removed. At this time, the developed image developed by the developing device is formed on the surface of the image carrier between the developing device and the transfer device. Exists. And
Since this developed image is not transferred to the transfer material but passed through the transfer portion, a large amount of residual developer reaches the cleaning device. Then, the amount of the developer may exceed the cleaning ability of the cleaning device to cause cleaning failure.

By the way, in recent years, a contact type transfer device has been widely used for the purpose of improving the transportability of the transfer material without ozone. In this method, a conductive transfer member to which a voltage is applied is brought into pressure contact with the image carrier, and transfer is performed while the transfer medium is held and conveyed by the image carrier and the transfer member, and there is no transfer medium in between. Sometimes, the image carrier and the transfer member come into direct contact with each other.

Japanese Unexamined Patent Publication No. 55-76368 describes an invention which solves the problem of poor cleaning of the image bearing member by utilizing the characteristics of the contact type transfer device. This is because when the image forming operation is interrupted and then restarted, the same transfer bias as that at the time of image formation is applied to the contact type transfer device to transfer the developed image on the image carrier to the transfer device. The residual developer that reaches the apparatus is suppressed to the same level as during normal image formation to reduce the load on the cleaning apparatus. The contact type transfer device cleans the transfer member for cleaning the developer on the transfer member.
Equipped with a steering device.

[0006]

However, in the image forming apparatus of the above-mentioned prior art, a large amount of the developer is transferred and adhered onto the transfer member, so that the cleaning operation of the transfer member cleaning device causes a cleaning failure. Had a problem. Then, due to the poor cleaning of the transfer member, the developer on the transfer member adheres to the back surface of the transfer material, causing backside smearing of the transfer material. The present invention has been made in view of the above points, and an object thereof is to provide an image forming apparatus with improved image quality.

[0007]

In order to achieve the above object, the present invention comprises an image bearing member, a latent image forming means for forming a latent image on the image bearing member, and a latent image forming means formed on the image bearing member. Developing means for developing the latent image with a developer, contact type transfer means to which a voltage is applied to contact the image carrier to transfer the developed image formed on the image carrier to a transfer material, and the image carrier In an image forming apparatus having a cleaning means for removing the untransferred developer on the body, a voltage applied during the image forming operation is applied to the contact type transfer means when the operation is resumed after the image forming operation is interrupted. A voltage having the same polarity as that of, but different from the voltage applied during the image forming operation is applied.

Further, according to the present invention, an image carrier, a latent image forming means for forming a latent image on the image carrier, and a plurality of developing devices for developing the latent image formed on the image carrier with a developer. A means, an intermediate transfer body that is in contact with the image carrier and onto which the developed images formed on the image carrier are sequentially transferred, and a medium that is in contact with the intermediate transfer body and is formed on the intermediate transfer body. In an image forming apparatus having a contact type transfer means to which a voltage is applied for transferring a plurality of developed images to a transfer material and a cleaning means for removing untransferred developer on the intermediate transfer body, after an image forming operation is interrupted. When the operation is restarted, a voltage having the same polarity as the voltage applied during the image forming operation but different from the voltage applied during the image forming operation is applied to the contact type transfer means. .

[0009]

According to the present invention, when the image forming operation is resumed after being interrupted, a part of the developer existing on the image carrier between the developing means and the transfer means is transferred to the contact type transfer means. Therefore, neither the image carrier nor the contact type transfer means is overloaded to the cleaning means.

Further, according to the present invention, when the image forming operation is resumed after being interrupted, a part of the developer on the intermediate transfer body is transferred to the contact type transfer means. No overload occurs on the cleaning means in any of the transfer means.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 1 is a configuration diagram of a main part showing an embodiment of an image forming apparatus of the present invention.

In FIG. 1, a photoconductive photosensitive drum 1 is shown.
Is an image carrier and rotates in the direction of arrow A. During image formation,
The photosensitive drum 1 is negatively charged by the action of the charging roller 2 to which a voltage is applied, and the potential of the non-image portion is removed by the exposure device 3 to form an electrostatic latent image. Next, the electrostatic latent image on the surface of the photoconductor drum 1 is developed by the toner having a positive charge on the image portion by the action of the developing device 4 to which a positive developing bias is applied, and the photoconductor drum whose development is completed is completed. The surface of No. 1 is neutralized by the pre-transfer exposure device 5 so that the toner image is easily transferred in the next step. On the other hand, the transfer paper 6 as a transfer material is fed from the paper feeding device (not shown) to the photosensitive drum 1.
The paper is fed in time with the image above, and the transport guide 7
The transfer roller 8 is guided by the transfer roller 8 and is conveyed to the transfer portion in pressure contact with the photosensitive drum 1.

The transfer roller 8 is a roller in which a conductive elastic member is provided in a roller shape on a conductive cored bar, and is pressed against the photosensitive drum 1 at an appropriate pressure. A negative voltage suitable for transfer at the time of image formation is applied from the power source 12 to the conductive core metal under the control of the control device 13, and the toner on the photosensitive drum 1 causes the transfer paper 6 to be transferred by the electric field formed by this voltage. And the transfer is completed. Then, the transfer paper 6 that has received the transfer
Under the action of a fixing device (not shown), a fixed image is formed on the transfer paper 6. On the other hand, the surface of the photoconductor drum 1 that has completed the transfer is not transferred by the action of the photoconductor cleaning device 9 having a blade that is pressed against the photoconductor drum 1.
Are removed, and then the light is emitted from the static elimination exposure apparatus 10 to a uniform low potential, and the series of image forming operations is completed. A transfer roller having a blade around the transfer roller 8 for contacting the surface of the transfer roller 8 and removing the toner.
A cleaning device 11 is provided.

Here, if a jam occurs before the transfer sheet 6 reaches the transfer section, the sensor (not shown) detects this and the operation of the image forming apparatus is stopped. And
After the operator removes the jammed transfer paper 6, the image forming operation is performed again, but at this time, a large amount of toner is present on the surface of the photosensitive drum 1 between the developing device 4 and the transfer portion. There is a toner. Therefore, when the toner on the photoconductor drum 1 reaches the photoconductor cleaning device 9 as it is when the image forming operation is restarted, the photoconductor cleaning device 9 is cleaned.
However, if the same transfer bias as that used during image formation is applied to the transfer roller 8 when the toner passes through the toner, a large amount of cleaning is required due to high transfer efficiency. Since the toner of (1) moves to the transfer roller 8, the cleaning load of the transfer roller cleaning device 11 may increase and a cleaning failure may occur.

Therefore, in the present invention, as shown in FIG. 2, when the image forming operation is restarted after being interrupted, an electric field weaker than the electric field formed at the time of image formation is formed in the transfer portion rather than during image formation. Also, a voltage whose absolute value is small is applied from the power supply 12 to the transfer roller 8 under the control of the controller 13. Then, a part of the toner on the photosensitive drum 1 moves to the transfer roller 8 and is removed from the transfer roller 8 by the transfer roller cleaning device 11. The toner remaining on the photosensitive drum 1 is removed by the cleaning device 9. Therefore, the toner on the photoconductor drum 1 is shared by the photoconductor cleaning device 9 and the transfer roller cleaning device 11 for cleaning, so that the cleaning failure of both is prevented. Moreover, since it is not necessary to strengthen the cleaning ability for this reason, the cost increase is prevented.

In the above embodiment, the case where a predetermined voltage suitable for image transfer is applied to the transfer roller 8 during image formation has been described, but a predetermined current is applied to the transfer roller 8. In the case of performing the transfer, a current having a smaller absolute value than that at the time of image formation may be applied to the transfer roller 8 when the image forming operation is restarted after the interruption.

Next, a second embodiment of the present invention will be described. In this embodiment, as shown in FIG.
The image forming apparatus uses a transfer belt as the contact type transfer means, which is different from that of the embodiment.
In FIG. 3, a transfer belt 20 formed of an elastic material having a medium resistance is wound around a driving roller 21 and a driven roller 22 and rotated in the arrow direction in the figure. A developed image is formed on the photoconductor drum 1 in the same manner as in the first embodiment, and the developed image is sent to the transfer portion with which the transfer belt 20 contacts. The transfer sheet is fed from a sheet feeding device (not shown) at the same timing as this, adsorbed onto the transfer belt 20 and conveyed to the transfer section. Then, a negative voltage suitable for transfer at the time of image formation is applied from the power source 24 to the transfer belt 20 through the electrode 23 under the control of the controller 25, and the toner on the photoconductor drum 1 is formed by the electric field formed by this voltage. The image is transferred to the transfer paper.

Here, also in the present embodiment, as in the first embodiment, as shown in FIG. 2, when the image forming operation is resumed after the interruption, an electric field weaker than the electric field formed during image formation in the transfer portion is generated. As a result, a voltage whose absolute value is smaller than that at the time of image formation is controlled by the control device 25 so that the power
4 is applied to the transfer belt 20 through the electrode 23.
Then, a part of the toner on the photosensitive drum 1 moves to the transfer belt 20 and is removed from the transfer belt 20 by the transfer belt cleaning device 26. The toner remaining on the photosensitive drum 1 is removed by the cleaning device 9. Therefore, the toner on the photoconductor drum 1 is shared by the photoconductor cleaning device 9 and the transfer belt cleaning device 26 to be cleaned, so that the cleaning failure of both can be prevented. Further, since it is not necessary to strengthen the cleaning ability for this reason, the cost increase is prevented.

Next, a third embodiment of the present invention will be described. In this embodiment, the present invention is applied to a multicolor image forming apparatus, and a description of the same means as in the first embodiment will be omitted. In FIG. 4, the developing device 4 is a yellow
A revolver-type developing device that develops an electrostatic latent image on the photosensitive drum 1 with toners of magenta, cyan, and black, and is rotatably provided in the arrow direction. Then, the electrostatic latent image formed on the photosensitive drum 1 is first developed by the developing device 4 with a yellow toner, and an intermediate transfer in which a voltage suitable for the intermediate transfer is applied by the power supply 33 through the electrode 32. It is transferred to the belt 31. Next, the developed image formed by the magenta toner on the photosensitive drum 1 is transferred onto the intermediate transfer belt 31 onto which the yellow developed image has already been transferred. Then, similarly, cyan and black developed images are sequentially transferred to the intermediate transfer belt 3.
1 and a full-color transfer image is formed on the intermediate transfer belt 31. At this time, the intermediate transfer belt cleaning device 34 and the transfer roller 35 are separated from the intermediate transfer belt 31 by a known method.

Then, the transfer paper 6 is fed from a paper feeding device (not shown) at a timing matched with the full-color transfer image formed on the intermediate transfer belt 31, and at this time, the control device 38 controls the conductive core metal. A transfer roller 38 similar to that of the first embodiment, to which a negative voltage suitable for transfer at the time of image formation is applied from the power source 37, contacts the intermediate transfer belt 31, and the photosensitive drum 1 is formed by the electric field formed by the voltage. The upper toner moves to the transfer paper 6 and the transfer is completed.

In such a multicolor image forming apparatus, the image forming operation may be interrupted when a full color transfer image is formed on the intermediate transfer belt 31 due to the non-feeding of the transfer paper 6. . In such a case, the full-color transfer image is transferred to the intermediate transfer belt cleaning device 3
When the toner is directly guided to 4, the toners of the four colors collectively enter and the cleaning load of the intermediate transfer belt cleaning device 34 becomes great. Therefore, in the present embodiment, as in the case of the first embodiment, as shown in FIG. 2, when the image forming operation is restarted after the interruption, an electric field weaker than the electric field formed during the image forming is formed in the transfer portion. , The voltage which is smaller in absolute value than when the image is formed
The voltage is applied from the power source 36 to the transfer roller 38 under the control of 8. Then, a part of the toner of the intermediate transfer belt 31 moves to the transfer roller 38 and the transfer roller cleaning device 3
6 is removed from the transfer roller 38. The toner remaining on the intermediate transfer belt 31 is removed by the intermediate transfer belt cleaning device 34. Therefore, since the toner on the intermediate transfer belt 31 is shared by the intermediate transfer belt cleaning device 34 and the transfer roller cleaning device 36 for cleaning, the cleaning failure of both is prevented. Moreover, since it is not necessary to strengthen the cleaning ability for this reason, the cost increase is prevented.

[0022]

As described above, according to the present invention, when the image forming operation is resumed after the interruption, a part of the developer existing on the image carrier between the developing means and the transfer means is removed. Since the image is transferred to the contact type transfer means, neither the image carrier nor the contact type transfer means is overloaded to the cleaning means. Therefore, no cleaning failure occurs and it is not necessary to strengthen the cleaning ability of the cleaning means, so that an image forming apparatus with improved image quality and reduced cost can be provided.

Further, according to the present invention, when the image forming operation is restarted after being interrupted, a part of the developer on the intermediate transfer member is transferred to the contact type transfer means. No overload occurs on the cleaning means in any of the transfer means. Therefore, no cleaning failure occurs even in the cleaning means of the intermediate transfer body, which has a large cleaning load when the image forming operation is restarted, and the cleaning ability of the cleaning means is improved. Since it is not necessary to strengthen the image forming apparatus, it is possible to provide an image forming apparatus with improved image quality and reduced cost.

[Brief description of drawings]

FIG. 1 is a main part configuration diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining the timing and level of voltage application to the transfer means in the present invention.

FIG. 3 is a main part configuration diagram showing a second embodiment of the present invention.

FIG. 4 is a main part configuration diagram showing a third embodiment of the present invention.

[Explanation of reference numerals] 1 photoconductor drum 8, 35 transfer roller 9 cleaning device 11 transfer roller cleaning device 12, 24, 37 power supply 13, 25, 38 control device 22 transfer belt 26 transfer belt cleaning Device 31 Intermediate transfer belt 34 Intermediate transfer belt cleaning device

Claims (2)

[Claims] 1. An image carrier, latent image forming means for forming a latent image on the image carrier, developing means for developing the latent image formed on the image carrier with a developer, and the image carrier. A contact-type transfer means to which a voltage is applied for contacting the body and transferring the developed image formed on the image carrier to a transfer material; and a cleaning means for removing untransferred developer on the image carrier. In the image forming apparatus having the above, when the operation is resumed after the interruption of the image forming operation, the contact type transfer means has a voltage having the same polarity as the voltage applied during the image forming operation and applied during the image forming operation. An image forming apparatus characterized in that a voltage different from that is applied. 2. An image carrier, a latent image forming means for forming a latent image on the image carrier, a plurality of developing means for developing the latent image formed on the image carrier with a developer, An intermediate transfer member, which is in contact with the image carrier and on which the developed images formed on the image carrier are successively transferred, and a plurality of developed images which are in contact with the intermediate transfer member and are formed on the intermediate transfer member. In the image forming apparatus having the contact-type transfer means to which a voltage is applied to transfer the toner to the transfer material and the cleaning means for removing the untransferred developer on the intermediate transfer body, the operation is restarted after the interruption of the image forming operation. At this time, the contact type transfer means is applied with a voltage having the same polarity as the voltage applied during the image forming operation but different from the voltage applied during the image forming operation. apparatus.