JPH04350882A - Transfer device for image forming device - Google Patents

Abstract

PURPOSE:To provide the transfer device for the image forming device where a transformer is reduced and the constitution is simplified. CONSTITUTION:In the transfer device 1 of the image forming device, a toner image is transferred to a transfer paper by an electrified transfer roll 2 and the transfer roll 2 is cleaned by impressing voltage to a fur brush 3. The power source, such as a transformer 6, is provided with a first tap 6a to generate high voltage for transferring and a second tap 6b to generate low voltage for cleaning. A changeover means, such as a changeover part 5, is provided to changeover between the high voltage and the before mentioned low voltage and impressing to the fur brush 6, formed with an electrically conductive member. A detection means consisting of a transfer paper detection switch 7 detecting a transfer period and a control part 8 is provided. A changeover control means, such as a control part 8, is provided to impress the above mentioned high voltage to the fur brush 3, for at least during the transferring period.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device for an image forming apparatus that transfers a toner image onto a transfer paper using a charged transfer roller and cleans the transfer roller by applying a voltage to a fur brush.

0002

[Prior Art] Conventionally, a photoreceptor drum and a transfer roller are brought into pressure contact, and when transfer starts, a voltage is applied to the transfer roller to transfer the toner image on the photoreceptor drum to transfer paper. Image forming apparatuses are known.

Further, a fur brush is in contact with the transfer roller, and by applying a voltage to the fur brush after the transfer is completed, residual toner on the transfer roller is drawn to the fur brush and cleaned.

0004

However, the conventional image forming apparatus requires a transformer for applying voltage to the transfer roller and a transformer for applying voltage to the fur brush, resulting in high cost. At the same time, space for arranging transformers and the like is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a transfer device for an image forming apparatus that can simplify the configuration by reducing the number of transformers.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention transfers a toner image onto a transfer paper using a charged transfer roller, and also cleans the transfer roller by applying a voltage to a fur brush. In a transfer device of an image forming apparatus, a power supply having a first tap that generates a high voltage for the transfer and a second tap that generates a low voltage for the cleaning, the high voltage and the low voltage. a switching means for switching and applying the high voltage to the fur brush formed of a conductive member; a detection means for detecting a transfer period; and a switching control means for applying the high voltage to the fur brush at least during the transfer period. It is something that

[0007]

[Operation] According to the transfer device of the image forming apparatus configured as described above,
At least during the transfer period, a high voltage from the first tap is applied to the fur brush, the transfer roller is charged via the fur brush, and the toner image is transferred to the transfer paper. Also,
Due to the potential difference between the voltage applied to the fur brush and the voltage of the transfer roller, residual toner on the transfer roller is attracted to the fur brush and cleaned.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a schematic diagram showing an example of an image forming apparatus equipped with a transfer device according to the present invention. The image forming apparatus has a document mounting table 21 and a document presser 22 on its upper surface, and is equipped with an optical system L and an image forming means P inside.

The optical system L includes a light source consisting of a halogen lamp 23 and a reflecting plate 24, reflecting mirrors 25, 26, 27,
It is composed of a lens section 28 and a fixed mirror 29. When the copying operation is started, the light from the light source is reflected by the original placed on the original placing table 21, and the reflected light is guided to the lens section 28 via the reflecting mirrors 25 to 27. Thereafter, the following photosensitive drum 30 is exposed through the fixed mirror 29.

The image forming means P includes a photosensitive drum 30, a main charging device 31, a blank lamp 32, a developing device 33, a transfer device 1, a cleaning section 34, a charge eliminating lamp 341, and the like. After the surface of the photosensitive drum 30 is charged by the main charging device 31, it is exposed to the reflected light to form an electrostatic latent image.

The electrostatic latent image is developed with toner by the developing device 33, transferred to a transfer paper by the transfer device 1, and then separated from the photosensitive drum 30. On the other hand, in order from upstream in the feeding direction, the paper feed port 35, paper feed cassettes 36, 37, paper feed rollers 38, 39, conveyance roller pair 40, conveyance roller pair 4
1 and a pair of registration rollers 42 are provided, whereby the transfer paper is fed to the photosensitive drum 30. Further, after the electric charge remaining on the photoreceptor drum 30 is discharged by the discharge lamp 341, the cleaning section 34 cleans the toner remaining on the surface of the photoreceptor drum 30 after transfer.

A conveyor belt 43, a fixing device 44, a discharge roller 45, etc. are arranged downstream in the conveyance direction of the transfer paper after transfer. After the transfer paper is transferred, it is fixed by a fixing device 44, and then transferred to a discharge tray 4 by a discharge roller 45.
It is discharged at 6.

Next, the detailed structure of the transfer device 1 will be explained. That is, the transfer device 1 includes a transfer roller 2, a fur brush 3, a cleaning blade 4, and the like. The transfer roller 2 has a circumferential surface made of sponge, urethane rubber, or the like, and is arranged so as to be in pressure contact with the photosensitive drum 30. By charging the transfer roller 2, the toner image on the photosensitive drum 30 is transferred to the transfer paper. The fur brush 3 is made of a material such as conductive rayon having a predetermined resistance value, and is used to charge the transfer roller 2 with a voltage from a switching section 5, which will be described later, and to clean residual toner on the transfer roller 2. Note that the cleaning blade 4 is for cleaning the fur brush 3.

Next, a block configuration showing an example of the electrical system of the transfer device 1 will be explained using FIG. 1. The switching unit 5 switches to either the high voltage from the first tap 6a of the power transformer 6 or the low voltage from the second tap 6b in response to a switching signal from the control unit 8, and converts it into a DC voltage. The voltage is applied to the shaft portion of the fur brush 3. That is, the tap 6a outputs, for example, 2.5KV AC, and the tap 6b outputs, for example, 300V AC. When a high voltage is applied to the fur brush 3, the transfer roller 2 is charged via the fur brush 3. On the other hand, when a low voltage is applied to the fur brush 3, the electric charge on the transfer roller 2 increases to the fur brush 3.
At the same time, the residual toner on the transfer roller 2 is attracted by the electric potential difference between the fur brush 3 and the transfer roller 2.

The transfer paper detection switch 7 is arranged near the paper feed side of the transfer device 1 (see FIG. 2), and is turned off when the leading edge of the transfer paper passes and returns to on when the rear edge of the transfer paper passes. be. The control section 8 detects the transfer period based on the signal from the transfer paper detection switch 7, and outputs a switching signal to the switching section 5 to apply a high voltage to the fur brush 3 during the transfer period. Furthermore, the control section 8 outputs a switching signal to the switching section 5 to apply a low voltage to the fur brush 3 during periods other than the transfer period. That is, the control section 8
For example, it has a built-in timer and the transfer paper detection switch 7
When a predetermined period of time has elapsed since the off signal from the transfer roller 2 was input, it is determined that the transfer paper has reached the pressure contact portion between the transfer roller 2 and the photoreceptor drum 30 and transfer has started. It is determined that the transfer is completed when a predetermined period of time has elapsed since the off signal was inverted to the on signal.

Next, the operation of the transfer device 1 having the above structure will be explained. When copying is started and the leading edge of the transfer paper reaches the transfer paper detection switch 7, the transfer paper detection switch 7 is turned off, the switching unit 5 is switched by the control unit 8, and the high voltage for transfer is applied to the fur brush 3. The transfer roller 2 is charged via the fur brush 3, and the toner image on the photoreceptor drum 30 is transferred to the transfer paper due to the potential difference between the transfer roller 2 and the photoreceptor drum 30.

After that, when the trailing edge of the transfer paper passes, the transfer paper detection switch 7 is turned on, the switching unit 5 is switched by the control unit 8, and a low voltage for cleaning is applied to the fur brush 3, and the transfer roller is switched on. 2 is discharged through the fur brush 3, and due to the potential difference between the fur brush 3 and the transfer roller 2, residual toner adhering to the transfer roller 2 is attracted to the fur brush 3 and cleaned.

In this way, during the transfer period, the fur brush 3
Since a high voltage for transfer is applied to the transfer roller 2 and the transfer roller 2 is charged via the fur brush 3, a transformer for directly charging the transfer roller 2 is not required. Also,
After the transfer, a low voltage for cleaning is applied to the fur brush 3, and the residual toner on the transfer roller 2 is cleaned. Note that since the voltage of the transfer roller 2 is always lower than the voltage of the fur brush 3, the residual toner adhering to the transfer roller 2 is attracted to the fur brush 3 and cleaned even during transfer.

Note that the voltage for cleaning the transfer roller 2 is preferably lower than the high voltage for transfer due to the lifespan of the photosensitive drum 30, but even if the voltage is higher than the above-mentioned high voltage, the transfer roller 2 may remain. It can attract and clean toner. That is, by continuing to apply high voltage to the fur brush 3 even after the transfer is completed, the transfer roller 2 can be cleaned.

[0020]

[Effects of the Invention] Since the present invention charges the transfer roller by applying a high voltage to the fur brush, it is only necessary to have a power source for applying voltage to the fur brush. transformer can be omitted. Therefore, the configuration of the image forming apparatus can be simplified and space can be saved. Furthermore, by applying voltage to the fur brush during the transfer period, the transfer roller can be cleaned even during the transfer period.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of an electrical system of a transfer device according to the present invention.

FIG. 2 is a schematic configuration diagram showing an example of an image forming apparatus including a transfer device according to the present invention.

[Explanation of symbols]

1 Transfer device 2 Transfer roller 3 Fur brush 4 Cleaning blade 5 Switching section 6 Power transformer 6a First tap 6b Second tap 7 Transfer paper detection switch 8 Control section 30 Photosensitive drum

Claims (1)

[Claims] 1. In a transfer device of an image forming apparatus that transfers a toner image onto a transfer paper using a charged transfer roller and cleans the transfer roller by applying a voltage to a fur brush, a high voltage for the transfer is applied. a power source having a first tap that generates the low voltage and a second tap that generates the low voltage for cleaning; and a power source that switches between the high voltage and the low voltage and applies the high voltage and the low voltage to the fur brush formed of a conductive member. A transfer device for an image forming apparatus, comprising a switching device, a detection device for detecting a transfer period, and a switching control device for applying the high voltage to the fur brush at least during the transfer period.