JPH0527605A - Transfer device - Google Patents

Abstract

PURPOSE:To efficiently clean the soiling of toner stuck to a transfer roller by applying a bias voltage for cleaning to the transfer roller in such a manner that the polarity of the bias voltage is alternately changed over, when a transfer is not performed. CONSTITUTION:An electrostatic latent image formed on a photosensitive body 1 is developed with the positive toner, and transferred on a transfer form S by the transfer roller 5. On a transfer device 50, the negative bias is applied to the transfer roller 5 by a power source 522, when the transfer is performed, but when the transfer is not performed, the positive bias by a power source 521 and the negative bias by the power source 522 are alternately applied by alternately changing over a switch 51. Thus, the positive toner stuck to the transfer roller 5 is transferred to the photosensitive body 1 to be removed, at the time of applying the positive bias, and the stuck negative toner is transferred to the photosensitive body 1 to be removed, at the time of applying the negative bias.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for transferring a toner image from a toner image carrier (photoconductor, dielectric, etc.) in an image forming apparatus to a transfer material.

[0002]

2. Description of the Related Art As such a transfer device, conventionally, a transfer charger utilizing corona discharge is widely known, and a transfer member such as a transfer roller, a transfer belt or a transfer brush allows the transfer material to pass therethrough. A so-called contact type transfer device is also known in which transfer is performed by contacting the toner image carrier.

In such a contact type transfer device, when transferring a toner image, a transfer bias having a polarity opposite to that of the toner is usually applied to the transfer member.

[0004]

However, since such a transfer member is in contact with the toner image carrier when the transfer material is not present, the fogging in the non-image area on the toner image carrier is caused. When the toner adheres to the transfer member or when the transfer material fails to be fed to cause a so-called jam, the toner image may directly contact and adhere to the transfer member.

The toner thus adhered on the transfer member adheres to the back surface of the transfer material during the next transfer, causing a so-called back stain. In order to prevent this back stain, a cleaning method has been proposed in which a bias having the same polarity as the toner is applied to the transfer member during non-transfer (Japanese Patent Publication No. 56-39472, etc.). However, not only the toner having the original polarity but also the toner having a polarity opposite to the original polarity, which is called a reverse polarity toner, is mixed in the toner attached to the transfer member.

Therefore, the back stain cannot be completely prevented by simply switching the bias such that the transfer bias is applied during the transfer and the bias having the opposite polarity to the transfer bias is applied during the non-transfer. For example, as shown in FIG. 4, a photosensitive drum PC is used as a toner image carrier.
A positive polarity toner is used as the toner, a transfer roller R is used as the transfer member, and a negative polarity bias V _A for transfer is applied to the transfer roller during transfer by switching the switch SW (see FIG. (A)), and toner is used during non-transfer. Positive bias V of the same polarity as
And applies to the transfer roller _B considering the case (Fig. (B) refer), the toner adhering to the transfer roller during the transfer, the positive polarity in the non-image areas, etc. on the photoreceptor fogging toner t1
In addition to the above, there is a toner t2 having a negative polarity, and the negative toner adheres to the transfer roller by a van der Wausker or the like. When the switch SW is switched to apply the positive bias V _B so that the toner thus attached is returned to the photosensitive member, the positive toner remains attracted onto the transfer roller as it is (see FIG. (B)). ..

Further, as shown in Japanese Patent Laid-Open No. 63-56674, in order to remove the toner on the transfer roller, an AC voltage superposed with a DC voltage is applied to the roller so that the toner is electrically vibrated. Although there is a proposal to facilitate its removal, the cleaning effect is not sufficient for toner having a polarity opposite to the original polarity. In view of this, the present invention provides a transfer device including a transfer member that transfers a toner image onto the transfer material by allowing the transfer material to contact the toner image carrier of the image forming apparatus while allowing the transfer material to pass through the transfer material. It is an object of the present invention to provide a transfer device capable of efficiently cleaning adhered toner stains as compared with the prior art.

[0008]

As a result of the research, the present inventor has found that
In addition to the original polarity of the toner that adheres to the transfer member, there is also the opposite polarity of the toner.Therefore, when cleaning toner stains, clean the original polarity toner and reverse polarity toner. The present invention has been completed, focusing on the fact that the polarity of the cleaning bias applied to the transfer member may be switched between positive and negative so that the cleaning member can be alternately performed.

That is, according to the present invention, the transfer material is brought into contact with the toner image carrier of the image forming apparatus while allowing the transfer material to pass therethrough,
A transfer device including a transfer member for transferring a toner image onto the transfer material is characterized in that a cleaning bias voltage can be applied to the transfer member by alternately switching polarities when the transfer member is not transferred. A transfer device is provided.

As the transfer member, a transfer roller, a transfer belt, a transfer brush or the like can be considered. When the transfer member is a rotating member such as a transfer roller, in order to improve the cleaning efficiency, the time corresponding to one rotation or more of the member is set as one cycle, and the cleaning bias polarity is switched for each cycle. You can If this switching cycle is too short, it becomes similar to the application of an AC voltage, and the cleaning effect is significantly reduced, so the cycle as described above may be used.

[0011]

According to the transfer device of the present invention, the toner of the original polarity adhered to the transfer member is transferred to the toner image carrier when the cleaning bias having the same polarity as the toner is applied to the member during non-transfer. The toner having the opposite polarity is removed when the cleaning bias having the opposite polarity is applied to the member.

Thus, the polarity of the cleaning bias applied to the transfer member is alternately switched, so that toner of any polarity on the member is removed. The toner transferred to the toner image carrier is cleaned with a cleaner or the like for cleaning the residual toner on the carrier.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic structure of a copying machine using an embodiment, FIG. 2 shows the essential points of the structure of a transfer device portion, and FIG. 3 is a timing chart showing the operation of each part in the copying machine of FIG. The copying machine of FIG. 1 has a photosensitive drum 1 driven by a main motor M, and a charging roller 2 that is rotated around the photosensitive drum 1 by the main motor M, a developing device 4 using positive toner, a transfer device 50, and a residual toner. A cleaner 7 for cleaning toner and an eraser 8 are sequentially provided. An optical system 30 including a document mounting glass and the like is arranged above the photoconductor 1.

A paper feed tray 9 is arranged on the upstream side of the transfer device 50. From there, a transfer roller S and a separation plate 11 driven by a motor M via a clutch (not shown) act to transfer the transfer paper S to 1 A timing roller 1 which is sent out one by one and driven by a motor M via a clutch (not shown)
2 is fed to the transfer area in synchronization with the toner image on the photoconductor 1.

Further, on the downstream side of the transfer device 50, a static elimination needle 6 for eliminating static electricity on the paper after transfer, a guide plate 13 and a motor M are provided.
The fixing devices 14 driven by are sequentially arranged. The transfer device 50 includes a transfer roller 5 that is driven by the drum 1 to rotate, a power source 52 connected to the roller via a switch 51, and a drive unit 53 that switches and drives the switch 51. The power supply 52 includes a positive power supply 521 and a negative power supply 522, which are switched and connected by a switch 51. The power source 521 is used for cleaning the positive polarity toner attached on the transfer roller 5, and the power source 522 is used for transferring the toner image and cleaning the negative polarity (reverse polarity) toner.

The drive unit 53 switches the switch 51 based on an instruction from the control unit 500 for controlling the operation of the entire copying machine, connects the power source 522 to the transfer roller 5 at the time of transfer, and the roller 5 at the time of non-transfer. During cleaning, the power sources 521 and 522 are alternately switched and connected to the roller 5 every time the roller 5 rotates once. It should be noted that the other units are also controlled by the control unit 50.
It operates based on instructions from 0. An operation panel P is connected to the control unit 500, and a print switch SW1 for starting copying is mounted on the operation panel P.

In this example, in order to facilitate the voltage control and reduce the cost of the power transformer, the cleaning bias voltage during non-transfer has the same negative voltage as that during transfer (eg, -2K).
V) and the positive polarity is | transfer voltage | (for example, +2 KV). According to the copying machine shown in FIG. 1, when the print switch SW1 on the operation panel is pressed, the motor M starts to rotate, and the photoconductor 1 is negatively charged by the charging roller 2 and the optical system 3
The exposure unit 3 is exposed by 0 to form an electrostatic latent image.
This latent image is developed by the developing device 4 with positive polarity toner. Then, it is transferred by the transfer roller 5 onto the transfer paper S sent from the paper feed tray 9 in synchronization with the toner image. At this time, a negative bias is applied to the transfer roller by the power source 522. The transfer sheet S is separated from the photoconductor 1 by its own rigidity (hardness to bend), reaches the fixing device 14, where the toner image is fixed there, and is ejected to the outside of the machine.

On the other hand, the photoconductor 1 is cleaned of residual toner by the cleaner 7 and erased of residual charge by the eraser 8, and the same process is repeated again. In the transfer device 50,
At the time of transfer, a negative bias is applied to the transfer roller 5 by the power source 522 as in the conventional case, but at the time of non-transfer, as shown in FIG.
The positive bias due to and the negative bias due to the power supply 522 are alternately applied. As a result, the positive polarity toner attached to the transfer roller 5 can be transferred to the photoconductor 1 to be removed when the positive polarity bias is applied, and the negative polarity toner attached can be transferred to the photoconductor 1 to be removed when the negative polarity bias is applied.

In FIG. 3, a cleaning period of the roller 5 before transfer is shown, a transfer period is shown, and a cleaning period of the roller 5 after transfer is shown. As described above, the transfer roller 5 can be efficiently cleaned by alternately applying the positive bias and the negative bias for cleaning during non-transfer. As a result, it is possible to prevent the back stain of the paper S.

The present invention is particularly effective for a developing system in which reverse polarity toner is likely to be generated or a copying machine using toner. The present invention is also applicable to so-called double-sided copying. In the above-mentioned embodiment, the negatively charged photoreceptor is described as an example, but the present invention is also applicable to the positively charged photoreceptor. Further, the present invention can be applied even if the developing method is so-called reversal development, and further, if the transfer material is other than paper such as OHP paper.

[0021]

As described above, according to the present invention, there is provided a transfer member for transferring a toner image onto the transfer material by bringing the transfer material into contact with the toner image carrier of the image forming apparatus while allowing the transfer material to pass therethrough. With the transfer device provided, it is possible to provide a transfer device capable of more efficiently cleaning toner stains attached to the transfer member than before.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a copying machine that employs an embodiment of the present invention.

FIG. 2 is a diagram showing the main points of the configuration of an embodiment of the present invention.

FIG. 3 is a timing chart showing the operation of each unit of the copying machine.

FIG. 4 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 1 Photoconductor 50 Transfer Device 51 Changeover Switch 52 Power Supply 521 Positive Bias Power Supply 522 Negative Bias Power Supply 53 Switch Drive Unit 500 Control Unit P Operation Panel SW1 Print Switch S Transfer Paper

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Yamada 2-3-13 Azuchi-cho, Chuo-ku, Osaka Inside Osaka Kokusai Building Minolta Camera Co., Ltd. (72) Daisuke Nagao 2-chome, Azuchi-cho, Chuo-ku, Osaka No. 13 in Osaka Kokusai Building Minolta Camera Co., Ltd. (72) Inventor Junichi Tamaki 2-3-3 Azuchi-cho, Chuo-ku, Osaka City Osaka Kokusai Building Minolta Camera Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. A transfer device comprising a transfer member for transferring a toner image onto the transfer material by bringing the transfer material into contact with a toner image carrier of the image forming apparatus while allowing the transfer material to pass therethrough. 2. The transfer device, wherein the cleaning bias voltage is applied to the transfer member by alternately switching the polarities when the transfer is not performed.