JPH0990784A - Electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the back contamination of a sheet without complicating the mechanism by interrupting the application of a voltage of reverse polarity to the charged polarity of toner to a transfer roller every prescribed time when no recording medium is present between a photoreceptor and the transfer roller. SOLUTION: A voltage of reverse polarity to the charged polarity of toner is applied from a power source 6 to a transfer roller for transferring the toner image formed on a photoreceptor 1 to a sheet. When no sheet is present between the photoreceptor 1 and the transfer roller 5, a switching device 7 interposed between the power source 6 and the transfer roller 5 generates a pulse-like voltage to interrupt the application of the voltage to the transfer roller 5 every fixed time. It is preferred to set the period of the pulse-like voltage applied to the transfer roller 5 to 0.1-0.5 second, and the ON-duty to 10-50% or less. Thus, the toner adhered to the transfer roller can be returned to the photoreceptor 1, and the back contamination of the sheet can be solved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus equipped with a transfer device for transferring toner carried on a photosensitive member or the like onto a recording medium.

[0002]

2. Description of the Related Art Conventionally, a transfer device of an electrophotographic apparatus has used a corotron transfer device utilizing corona discharge.
However, this transfer device requires a high voltage of about 3 kV to 5 kV in order to transfer the toner developed on the photoconductor to the paper, and this high voltage causes problems such as an increase in the cost of the power supply and electric shock during maintenance work. was there. Therefore, in recent years, a contact transfer device capable of transferring at a lower voltage than a corotron transfer device has been attracting attention. In this apparatus, a transfer roller made of a conductive foam material or the like is brought into pressure contact with a photoconductor, a low voltage of about 1 kV is applied to the transfer roller, and the toner developed on the photoconductor is transferred to a sheet.

However, since the contact-type transfer device is in contact with the photoconductor, the photoconductor is not contacted with the photoconductor due to a slight residual toner on the photoconductor that has passed through the cleaning device or a trouble such as paper jam. The developed toner or the like adheres to the transfer roller, and when the toner adheres to the transfer roller, the toner adheres to the back surface of the paper, and the back surface is contaminated.

Therefore, measures have been taken such as a method of collecting the toner adhering to the transfer roller by a fur brush and a method of preventing the toner from adhering by separating the transfer roller from the photosensitive member when the paper is not passed.

[0005]

However, the method using a fur brush requires a fur brush driving unit and a blower, and the method of separating the fur brush from the photosensitive member has a problem in that it is mechanically complicated. Was.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide an electrophotographic apparatus in which the back surface of a sheet does not stain without being mechanically complicated.

[0007]

In order to achieve this object, the present invention provides a voltage of a polarity opposite to the charging polarity of toner to the transfer roller when there is no recording medium between the toner image carrier and the transfer roller. It is provided with control means for stopping the application of the voltage by the applying means for applying at a constant time interval.

Further, the period of the pulsed voltage applied to the transfer roller by the control means is set to 0.1 second or more and 0.5 second or less, preferably 0.2 second or more and 0.4 second or less, and the on-duty is set. 10% or more and 50% or less, preferably 2
It is set to 0% or more and 40% or less.

[0009]

According to the present invention, the toner adhering to the transfer roller can be returned to the toner image carrier by the above-mentioned structure.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an electrophotographic apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a photoconductor, 2 is a contact type charging device, 3 is an exposure device, 4 is a developing device, 5 is a contact type transfer device, 6 is a power source connected to the contact type transfer device 5, and 7 is a pulse. A switching device for generating a uniform voltage, and a cleaning device 8.

The operation of the electrophotographic apparatus having the above-described structure according to the embodiment of the present invention will be described below. The photoconductor 1 charged by the contact type charging device 2 is exposed by the exposure device 3 to form an electrostatic latent image. Further, the developing device 4
In, a visible image is formed by a developer such as toner. Further, the sheet transferred between the photoconductor 1 and the contact type transfer device 5 is transferred to the paper by the contact type transfer device 5 to which a voltage having a polarity opposite to the charging polarity of the toner from the power source 6 is applied via the switching device 7. Toner is transferred. The toner on the paper is fixed by a fixing device (not shown). On the other hand, the residual toner remaining on the photoconductor 1 without being transferred to the paper is removed by the cleaning device 8. Further, after the toner is transferred to the paper, the contact type transfer device 5 has a switching device 7
As a result, a pulsed voltage in which the voltage from the power source 6 is turned on and off is applied, and the toner attached to the contact type transfer device 5 is moved to the photoconductor 1.

The target image can be obtained as described above. Next, an experiment conducted to evaluate the effect of the pulsed voltage applied when the paper is not passed on the backside of the paper will be described.

A continuous black pattern is printed continuously on 100 sheets, which is most likely to cause back stains on the paper. At this time, the conditions of the pulse voltage applied when the paper is not passed and other conditions are set as shown below.

As a condition of the pulse voltage, the period is 0.0
It is 5 seconds to 1.00 seconds and the on-duty is 5% to 60%. As another condition, the peripheral speed of the photoconductor 1 is set to 2
5 mm / sec, the applied voltage to the contact type charging device 2 is -1.2
kV, the applied voltage to the developing roller is -300 V, and the applied voltage to the contact type transfer device 5 is 1 kV.

The state of the backside stain of the 100th sheet obtained as described above was evaluated, and the result is shown in (Table 1). An example of the pattern of the voltage applied to the contact type transfer device 5 is shown in FIG.
Shown in

[0016]

[Table 1]

[0017]

As described above, according to the present invention, when the recording medium is not present between the toner image carrier and the transfer roller, the voltage applied by the applying means applies a voltage having a polarity opposite to the charging polarity of the toner to the transfer roller. Control means for stopping the application of the electric field at regular intervals, and the period of the pulsed voltage applied to the transfer roller by the control means is 0.1 seconds or more and 0.5 seconds or less, preferably 0.2 seconds or more. By setting the on-duty to 10% or more and 50% or less, preferably 20% or more and 40% or less, the toner adhered to the transfer roller can be returned to the toner image carrier, and the on-duty of the paper can be reduced. It has become possible to eliminate dirt on the back.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electrophotographic apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a pattern of a voltage applied to a contact type transfer device of an electrophotographic apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 1 Photoreceptor 2 Contact Charging Device 3 Exposure Device 4 Developing Device 5 Contact Transfer Device 6 Power Supply 7 Switching Device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuhiro Tsuru, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Yoshihiro Goto, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A transfer roller provided in contact with the toner image carrier for transferring a toner image formed on the toner image carrier onto a recording medium, and a transfer roller having a polarity opposite to the charging polarity of the toner on the transfer roller. An application unit for applying a voltage and a control unit for stopping the application of the voltage to the transfer roller by the application unit at regular intervals when there is no recording medium between the toner image carrier and the transfer roller. An electrophotographic device characterized by being provided. 2. A cycle of a pulsed voltage applied to the transfer roller by the control means is 0.1 second or more and 0.5 second or less, and an on-duty is 10% or more and 50% or less. The electrophotographic apparatus according to claim 1, which is characterized in that. 3. A cycle of a pulsed voltage applied to the transfer roller by the control means is 0.2 seconds or more and 0.4 seconds or less, and an on-duty is 20% or more and 40% or less. The electrophotographic apparatus according to claim 1, which is characterized in that.