JPH10207133A - Electrophotographic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of toner image on the front surface (the first side) at the timed of transferring a toner image on the rear surface (the second side) by setting the static charge polarity of the toner used in image forming devices to the same polarity, and providing a corona discharges for inverting the toner polarity of each toner image recorded on the first side between the image forming devices. SOLUTION: After the black toner 15, magenta toner 16, cyan toner 17, and yellow toner 18 electrified to the positive polarities by the image forming devices 1-4 are transferred on the front surface of paper sheet 14, a toner polarity inverting corotron 25 applied with negative voltage changes the static charge polarity of the toner on the front surface of the paper sheet to negative from positive. Thereafter, the black toner 19, magenta toner 20, cyan toner 21, and yellow toner 22 electrified to the positive polarity by the image forming device 5-8 are transferred on the rear surface of the paper 14. In this structure, since the polarity of the toner on the front surface of the paper sheet is the same as the voltage applied to a toner-transfer corona discharge 25, the toner on the front surface of the paper sheet is not attracted to the toner-transfer corona discharges 25, and the toner image on the front surface of the paper sheet is not disturbed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic apparatus capable of performing double-sided printing.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional printing apparatus. Photoconductor 9, charging device 10, LED array 11, developing device 12,
In the image forming apparatus 1 including the toner transfer corotron 13, the photoconductor 9 is charged by the charger 10, and a latent image is formed on the photoconductor 9 by the LED array 11. Developing machine 12
The black toner 15 adheres to the latent image formed on the photoreceptor 9 to develop. The black toner 15 on the photoconductor 9 is transferred to the surface of the paper 14 by the toner transfer corotron 13. Subsequently, the magenta toner 16, the cyan toner 17, and the yellow toner 18 are transferred to the surface of the paper 14 by the image forming apparatuses 2, 3, and 4. Thereafter, the sheet conveying direction is changed by bending the sheet by 180 °, and the image forming apparatuses 5, 6,
The printing surface of the paper 7 is set to the back side, and the black toner 19, the magenta toner 20, the cyan toner 21, and the yellow toner 22 are transferred to the
Transfer to the back of The toner transferred to the front surface and the back surface of the sheet 14 is fixed on the sheet 14 by the heat rolls 23 and 24.

[0003]

Means for transferring a toner to a sheet having a plurality of image forming apparatuses for double-sided printing and having the same polarity of toner used in all the image forming apparatuses. Is a corona discharger. In a printing apparatus having only one fixing device for simultaneously fixing toner on both sides of a sheet to a sheet, the toner is transferred to one side of the sheet and then to the opposite side of the sheet. At this time, the paper surface on which the unfixed toner image is formed faces the corona discharger for transferring the toner to the opposite surface. At this time, since a high voltage having a polarity opposite to that of the toner is applied to the wire of the corona discharger for toner transfer, the toner on the paper surface is attracted to the wire, and the toner on the paper surface scatters, And the toner image on the paper surface is disturbed.

Further, if the voltage applied to the wire of the corona discharger for toner transfer is reduced in order to suppress the disturbance of the toner image, there has been a problem that the transfer efficiency is reduced and the print density is reduced.

An object of the present invention is to provide an electrophotographic apparatus which does not deteriorate the toner image on the front surface (first surface) when transferring the toner image to the back surface (second surface).

[0006]

The object of the present invention is to provide a photoconductor,
A charger for uniformly charging the photoconductor, an exposure device for irradiating the charged photoconductor with laser light to form a latent image on the photoconductor, and supplying a toner to the latent image to form a toner image on the photoconductor; And at least two image forming apparatuses each including a transfer device for transferring the toner image onto a recording material, wherein the first image forming apparatus forms the first surface of the recording material. In an electrophotographic apparatus which forms a toner image for recording and forms a toner image for recording on a second surface of a recording material by a second image forming apparatus, the toner used in the first image forming apparatus is The charging polarity and the charging polarity of the toner used in the second image forming device are set to be the same, and the first and second image forming devices are recorded on the first surface between the first and second image forming devices. This is achieved by providing a corona discharger for reversing the toner polarity of the toner image.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. In the printing apparatus configured as shown in FIG. 1, black toner 15, magenta toner 16, cyan toner 17 positively charged by image forming apparatuses 1, 2, 3, 4
After the yellow toner 18 is transferred to the surface of the paper 14, the absolute value is sufficient to cause corona discharge but low enough not to disturb the toner image on the paper surface (at least the toner used in the image forming device 5). The toner reversal corotron 25 to which a negative voltage is applied (lower than the absolute value of the voltage applied to the transfer corotron) changes the charge polarity of the toner on the paper surface from positive to negative. Corotron 25 for toner polarity reversal
The opposing corotron 26 arranged at a position facing the
A positive voltage is applied to attract electric charges generated from the toner polarity reversal corotron 25 and guide the electric charges to the paper.

Thereafter, the black toner 19, magenta toner 20, cyan toner 21 and yellow toner 22 positively charged by the image forming devices 5, 6, 7 and 8 are transferred to the back surface of the paper 14. The toner transferred to the front surface and the back surface of the sheet 14 is fixed on the sheet 14 by the heat rolls 23 and 24.

The printing apparatus constructed as shown in FIG. 2 differs from FIG. 1 in that the paper transport path change roll 27 is disposed at a position facing the toner polarity reversal corotron 25 and the paper transport path change roll 27 is provided. Is grounded or has a positive voltage value, and the other printing processes are the same.

The printing apparatus constructed as shown in FIG. 3 differs from FIG. 1 in that the toner polarity reversal corotron 25 is opposed to the photoreceptor used in the image forming apparatus 5. Other printing processes are the same.

According to the present invention, the polarity of the toner is reversed during the change from the one-side (front) image forming device to the opposite one-side (back) image forming device along the sheet conveying path. A corona discharger is provided, and the wire of the corona discharger is set at a voltage high enough to reverse the toner polarity and at a voltage that does not disturb the toner image on the paper. The paper surface on which the toner image has been formed faces the corona discharger for toner transfer, but the toner polarity on the paper surface is the same as the voltage applied to the corona discharger for toner transfer. It is not attracted to the transfer corona discharger and the toner image on the paper surface is not disturbed. Further, since a voltage for obtaining good transfer efficiency can be applied to the corona discharger for toner transfer, high print quality can be obtained. If the polarity of the toner for the front surface and the toner for the back surface is reversed when the developer is stirred inside the developing device, the corona discharger for inverting the polarity of the toner is unnecessary, but in this case, the developer for the front surface and the back surface is used. Need to change the toner. By using the same developer and toner for the front and rear surfaces, the development period of the developer and toner can be shortened, and the cost can be reduced due to mass production effects. In the embodiment of the present invention, the toner is positively charged, and a negative voltage is applied to the corona discharger for inverting the polarity of the toner.
Even if a positive voltage is applied to the corona discharger for inverting the polarity of the toner, the same effect is obtained because the polarity of the voltage applied to the corona discharger for inverting the polarity of the toner is opposite to that of the toner. .

[0012]

As described above, according to the present invention, the back surface
It is possible to provide an electrophotographic apparatus that does not deteriorate the toner image on the front surface (first surface) when transferring the toner image to the (second surface).

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of an electrophotographic apparatus of the present invention.

FIG. 2 is a schematic configuration diagram showing another embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing another embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing a conventional technique.

[Explanation of symbols]

1,2,3,4,5,6,7,8 ... image forming device, 9 ... photoconductor, 1
0: charger, 11: LED array, 12: developing device, 1
3: Corotron (transfer device) for toner transfer, 14: paper, 2
3, 24: heat roll, 25: corotron (corona discharger) for reversing toner polarity, 26: opposing corotron, 27 ...
Paper transport path change roll (paper transport path change member).

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yoji Hirose 1060 Takeda, Hitachinaka City, Ibaraki Prefecture Inside Hitachi Koki Co., Ltd. (72) Inventor Akio Tsujida 1060 Takeda, Hitachinaka City, Ibaraki Prefecture Inside Hitachi Koki Co., Ltd.

Claims (5)

[Claims] A photoreceptor, a charger for uniformly charging the photoreceptor, an exposure device for irradiating the charged photoreceptor with laser light to form a latent image on the photoreceptor, and applying a toner to the latent image. A first image forming apparatus including at least two or more image forming apparatuses each including a developing device that supplies and forms a toner image on a photoconductor, and a transfer device that transfers the toner image onto a recording material; An electrophotographic apparatus that forms a toner image to be recorded on a first surface of a recording material by a second image forming device and forms a toner image to be recorded on a second surface of the recording material by a second image forming device; The charging polarity of the toner used in the image forming device is set to the same polarity as the charging polarity of the toner used in the second image forming device, and the polarity between the first image forming device and the second image forming device is changed. A corona discharger for reversing the toner polarity of the toner image recorded on the first surface. Electrophotographic equipment. 2. A conductive sheet transport path changing member is provided in contact with a surface of the first image forming apparatus opposite to a surface of a sheet on which a toner image is formed, and opposed to the corona discharger. The electrophotographic apparatus according to claim 1, wherein: 3. An electrophotographic apparatus according to claim 1, wherein said sheet transport path changing member has a potential or a ground potential having a polarity opposite to a voltage applied to said corona discharger. 4. A corona discharger in which a voltage having a polarity opposite to a voltage applied to a wire of the corona discharger is applied to the wire at a position facing the corona discharger for inverting the polarity of the toner. 2. An electrophotographic apparatus according to claim 1, wherein a sheet passes between said two opposed corona dischargers. 5. The electrophotographic apparatus according to claim 1, wherein a voltage value applied to a wire of the corona discharger for inverting toner polarity is lower than a voltage value applied to a wire of a transfer device.