JPH04174881A - Cleaning method of copying roller - Google Patents

Abstract

PURPOSE:To make it unnecessary to provide a power source of reversed polarity and to clean the toner on the surface of a copying roller easily and securely by rotating the copying roller in the condition to charge an image holding body while stopping the application of voltage to the copying roller. CONSTITUTION:After a toner image is copied to a copying paper P, the application of voltage to a charged roller 2 in maintained by a control means 8 while a copying roller 4 is rotated one round, the charging to an image holding body 1 is maintained, and the application of voltage to the roller 4 is stopped. As a result, the toner attached to the surface of the roller 4 is returned to the surface of the holding body 1 which has a higher voltage, and it is removed together with the toner remaining on the surface of the holding body 1 in the copying by a cleaning device 5. Consequently, a power source of reversed polarity is not necessary to provide, and the surface of the copying roller can be cleaned easily and securely.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is used in image forming apparatuses such as electrostatic copying machines and laser beam printers to transfer toner images formed on the surface of an image carrier. The present invention relates to a method for cleaning a transfer d-ra used for transferring onto a material.

<Prior Art> Recently, a drum-shaped image carrier and a transfer roller to which a bias voltage is applied are equipped, and with the bias voltage applied to the transfer roller, the transfer roller transfers a copy paper, etc. 2. Description of the Related Art Image forming apparatuses have come into use that transfer a toner image formed on the surface of an image carrier to a transfer material by bringing a material into pressure contact with the surface of the image carrier.

The above configuration includes a transfer charger that electrostatically attaches the transfer material to the surface of the image carrier and transfers the toner image onto the surface of the image carrier, and a separation charger that separates the transfer material after transfer from the surface of the image carrier. Since it is unnecessary, there is no risk of generating harmful ozone, and since it is a close-contact transfer, there is an advantage that no blurring occurs in the image.

In the above image forming apparatus, jams etc. may occur,
If fog occurs on the image when the transfer material is small in size, toner adheres to the surface of the transfer roller, causing stains on the back of the transfer material. Therefore, each time an image is formed, the surface of the transfer roller must be cleaned to remove adhering toner.

In addition to mechanical toner removal methods, methods for cleaning the surface of the transfer roller include, for example, eliminating static electricity from the surface of the image carrier after image transfer, and applying a voltage of opposite polarity to the transfer roller to the transfer roller. There is an electrical releaning method in which the toner is returned from the surface of the transfer roller to the surface of the image carrier (for example, see Japanese Patent Laid-Open No. 1-292385).

<Problems to be Solved by the Invention> The image forming apparatus described in the above publication employs reversal development in which the image bearing member and the transfer roller are charged with opposite polarities. To apply voltage,
A power source (such as a transformer) for charging the image carrier may be connected to the transfer roller.

However, in the case of an image forming apparatus that uses a normal development method instead of reversal development, the image bearing member and the transfer roller are charged to the same polarity, so a power supply with opposite polarity is not installed, and the cleaning method described above is not used. If it were to be adopted, it would be necessary to separately prepare a power source with a reverse polarity, which would increase the economic burden and require a space to house it, which would hinder miniaturization of the image forming apparatus.

The present invention has been made in view of the above circumstances, and
It is an object of the present invention to provide a method for cleaning a transfer roller that can easily and reliably clean the surface of the transfer roller without requiring a power source of opposite polarity.

Means for Solving the Problems> In order to solve the above problems, the transfer roller cleaning method of the present invention includes stopping the application of voltage to the transfer roller and cleaning the transfer roller while the image carrier is charged. is rotated to return the toner on the surface of the transfer roller to the image carrier.

According to the transfer roller cleaning method of the present invention having the above configuration, by stopping the application of bias voltage to the transfer roller while maintaining the charge on the image carrier, the toner on the surface of the transfer roller can be removed from the image. Since it can be returned to the surface of the carrier,
The transfer roller can be cleaned without the need for a reverse polarity power source.

<Example> The transfer roller cleaning method of the present invention will be described below with reference to drawings showing an example in which the transfer roller cleaning method of the present invention is applied to an electrostatic copying machine as an image forming apparatus.

As shown in FIG. 2, the electrostatic copying machine of this embodiment includes a charging roller 2 around a drum-shaped image carrier 1 for charging the image carrier 1, and a charging roller 2 indicated by a white arrow in the figure. As shown, an optical system (not shown) that exposes the surface of the image carrier 1, a developing device 3 that develops the electrostatic latent image formed on the surface of the image carrier 1 by exposure, and an image carrier 1 that develops the image by developing it. The image carrier 1 includes a transfer roller 4 that transfers the toner image formed on the image carrier 1 onto a transfer material P such as copy paper, and a cleaning device 5 that removes toner remaining on the image carrier 1.

Then, the charging roller 2 charges the surface of the image carrier 1 rotating at a constant speed.
is uniformly charged, exposed to light by an optical system to form an electrostatic latent image, and developed as a toner image by the developing device 3. This toner image is transferred to a conveying path 6.
is transferred onto the conveyed transfer material P by the transfer roller 4, and the cleaning device 5 removes and cleans the toner remaining on the surface of the image carrier 1 after the transfer, thereby completing one cycle of image formation. finish. Further, the transfer material P peeled off from the image carrier 1 is guided to a fixing device (not shown) via a conveyance path 7, and after the toner image is fixed thereon, it is discharged from the device.

The developing device 3 includes a casing 31 containing a developer therein.
and a developing roller 32 rotatably disposed in an opening formed in a portion of the casing 31 facing the image carrier 1.

The charging roller 2, transfer roller 4 and developing roller 32
are all connected to a single power source (such as a transformer) 9 via a control means 8.

The operation of the image forming apparatus including the above-mentioned parts will be explained with reference to the waveform diagram shown in FIG.

When copying is started, first, the drive of the image carrier 1 is turned on and the image carrier 1 starts rotating, and at the same time, a voltage of +250V is applied from the power supply 9 to the developing roller 32 by the control means 8. Ru.

Next, the control means 8 applies a voltage of +700V from the power source 9 to the charging roller 2, so that the surface of the image carrier 1 is +
It is charged to 700V.

Next, according to the image forming cycle described above, exposure is first performed using an optical system, and the surface of the image carrier 1 is exposed to light.
An electrostatic latent image corresponding to the original image is formed. In this electrostatic latent image, the potential of the portion to which toner is to be attached remains unchanged, while the potential of other portions is decreased. When charged toner is supplied to this electrostatic latent image by the developing roller 32 of the developing device 3, the toner is transferred only to the high-potential portion of the electrostatic latent image. is visualized as a toner image.

Next, when the transfer material P is supplied from the conveyance path 6 between the image carrier 1 and the transfer roller 4 , a voltage of +700 V is applied to the transfer roller 4 from the power source 9 by the control means 8 . After the toner image on the surface of the image carrier 1 is transferred onto the surface of the transfer material P by the transfer roller 4, the transfer material P is conveyed along the conveyance path 7, and as described above, is transferred to the fixing device (not shown). After the image is fixed, it is ejected from the device.

After the transfer of the toner image onto the transfer material P is completed, the charging roller 2 is controlled by the control means 8 while the transfer roller 4 rotates once.
A voltage of +700μ is maintained on the image carrier 1.
While the charging of the transfer roller 4 is maintained, the application of voltage to the transfer roller 4 is stopped. Then, the toner adhering to the surface of the transfer roller 4 returns to the surface of the image carrier 1, which has a higher voltage, and the cleaning device 5 removes the toner from the image carrier 1 along with the toner remaining on the surface of the image carrier 1 during transfer. It is removed from the surface and the transfer roller 4 and image carrier 1 are cleaned. Further, during the cleaning, in order to prevent the toner from moving from the developing roller 32 to the charged image carrier 1, the control means 8 causes the power supply 9 to supply the developing roller 32 with a voltage higher than that of the image carrier 1. ,+950
A voltage of V is applied.

After cleaning of the transfer roller 4 and image carrier 1 is completed, in the case of continuous copying, the above steps are repeated as many times as necessary, as shown in FIG. 1, and in the case of single copying, When the above cleaning is completed,
The driving of the image carrier 1 is stopped, and the developing roller 32 is stopped.
Application of voltage to is stopped.

The transfer roller 4 is cleaned during the first cleaning in order to prevent stains on the back of the transfer material when restarting image formation after the image forming apparatus has stopped due to a jam or the like. You can do this before copying.

In order to clean the transfer roller 4 before the first copy, after voltage is applied to the charging roller 2 and the surface of the image carrier 1 is charged, until the voltage is applied to the transfer roller 4. period can be used. In that case, in order to prevent the toner from moving from the developing roller 32 to the charged image carrier 1, as shown by the dashed line in FIG. Voltage higher than the voltage of image carrier 1 (+900V in the figure)
All you have to do is apply .

As described above, in this embodiment, while the transfer roller 4 rotates once, voltage is maintained to be applied to the charging roller 2 to maintain charging of the image carrier 1, and at the same time, the developing roller 32
To prevent the toner from moving from the developing roller 32 to the charged image bearing member 1 by applying a voltage higher than that of the image bearing member 1, the application of voltage to the transfer roller 4 is stopped. Accordingly, the toner adhering to the surface of the transfer roller 4 can be returned to the surface of the image carrier 1, which has a higher voltage, and can be removed from the surface of the image carrier 1 by the cleaning device 5. Therefore, according to this embodiment, there is no need for a power source of opposite polarity, which increases the economic burden and requires a storage space, which hinders miniaturization of the image forming apparatus. can be cleaned easily and reliably.

Note that the transfer roller cleaning method of the present invention is not limited to the above embodiments.

For example, in the above embodiment, cleaning is performed after each copy and, if necessary, before the first copy, or even if cleaning is performed before and after each copy. However, cleaning may be performed at other times.

Furthermore, the configuration of the apparatus to which the cleaning method of the present invention is applied is not limited to that shown in the drawings. For example, as a means for charging the image carrier 1, a charger may be used instead of the charging roller 2.

As the image carrier 1, various shapes such as a drum shape or a belt shape can be used.

The present invention can be applied not only to the electrostatic copying machine shown in the figure but also to other image forming apparatuses such as laser beam printers.

In addition, various changes can be made without changing the gist of the present invention.

<Effects of the Invention> The transfer roller cleaning method of the present invention is configured as described above, and the transfer roller is cleaned by stopping the voltage application to the transfer roller while maintaining the charge on the image bearing member. The toner adhering to the surface can be returned to the surface of the image carrier, which has a higher voltage. Therefore, according to the present invention, it is possible to easily and reliably clean the surface of the transfer roller without requiring a power source of opposite polarity.

[Brief explanation of the drawing]

FIG. 1 is a waveform diagram showing the operation of each part in an embodiment of the transfer roller cleaning method of the present invention, and FIG. 2 is a waveform diagram showing the main parts of an electrostatic copying machine as an image forming apparatus to which the above embodiment is applied. FIG. 2 is a schematic diagram showing the configuration. DESCRIPTION OF SYMBOLS 1... Image carrier, 4... Transfer roller, 8... Control means, 9... Power supply.

Claims (1)

[Claims] 1. An image comprising an image carrier and a transfer roller that presses a transfer material against the surface of the image carrier with a bias voltage applied and transfers the toner image formed on the surface to the transfer material. A cleaning method for removing toner adhering to the surface of the transfer roller of a forming device, the method comprising: stopping the application of voltage to the transfer roller and rotating the transfer roller with the image carrier charged; A method for cleaning a transfer roller, comprising returning toner on the surface of the transfer roller to an image carrier.