JPH0854765A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To realize a high printing quality by resolving the lowering of effective printing speed and the deterioration of controlling accuracy in an electrophotographic device using continuous paper. CONSTITUTION:This device is provided with a surface potential detecting means 3 provided between the position of an exposure stage by an exposure means 10 and the position of a developing stage by developing means 4 and 5 and measuring a high potential part, an intermediate potential part and a low potential part, a perforation position detecting means 21 detecting the position of the perforation of the continuous paper, and used paper length information 22 previously inputted, and also, the potential of the intermediate potential part is measured in the midst of printing operation in a non-printing area on a photoreceptor corresponding to the vicinity of the perforation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus, and in particular, it forms a three-step potential consisting of a high potential part, an intermediate potential part and a low potential part on a uniformly charged photoreceptor. The present invention relates to an electrophotographic apparatus that forms toner images of two colors while a photoreceptor rotates once.

[0002]

2. Description of the Related Art A high potential portion on a uniformly charged photoreceptor,
An electrophotographic process in which a three-step potential composed of an intermediate potential part and a low potential part is formed, and a two-color toner image is formed during one rotation of the photoconductor is also called a tri-level method. It is known from US Pat. No. 4,078,929 and the like. This method uses a high-potential portion (V
H), the intermediate potential part (VM) formed by irradiating the photosensitive member with a laser light amount of about a half exposure amount, and the photosensitive member is irradiated with a laser light amount of about 3 to 4 times the half exposure amount. To form a three-stage potential consisting of a low potential portion (VL), and then the first developing means causes the high potential portion (VH) to normally develop the toner charged to the opposite polarity to the photoconductor. The second developing means reversely develops the toner charged to the same potential as the photoconductor on the low potential portion (VL), and the intermediate potential portion (VM) is not developed and becomes the background portion (blank sheet portion). At this time, the bias voltage (VBH) between the high potential portion (VH) and the intermediate potential portion (VM) is applied to the first developing means for performing regular development, and the second phenomenon means for performing reversal development. Has a low potential part (VL) and an intermediate potential part (VM)
Bias voltage (VBL) between and is applied. After the development, the toners having different polarities on the photoconductor are made to have the same polarity by the pre-transfer charger and transferred to the paper at once, and then the toner is fixed on the paper by the fixing device.

[0003]

The advantage of the tri-level method is that since two color toner images can be formed by one optical system, it is inexpensive and high speed can be secured, and the printing position is accurate. . However, the disadvantage of the tri-level system is that since a three-step potential is formed, the difference between the developing section potential and the background section potential is higher than that of an apparatus using a two-step potential.
The so-called potential contrast is reduced. Generally, in an apparatus using a two-step potential, the potential contrast is increased to some extent in consideration of potential variations due to photoconductor manufacturing lot differences, light fatigue, environment, etc., to prevent deterioration of print quality due to potential variations of the photoconductor. ing. If the potential contrast is low, the potential of the photosensitive member fluctuates, so that a print quality problem such as a decrease in print density or occurrence of fog is likely to occur. Therefore, in order to secure and maintain high print quality by the tri-level method, it is important to reduce the potential fluctuation of the photoconductor.

SUMMARY OF THE INVENTION An object of the present invention is to solve the deterioration of effective printing speed and the deterioration of control accuracy in an electrophotographic apparatus using continuous paper, and to realize high printing quality.

[0005]

SUMMARY OF THE INVENTION The above-mentioned object is an electrophotographic apparatus using a folding continuous paper having perforations, and a charging means for uniformly charging a photoconductor and a high charging method on the photoconductor uniformly charged. An exposure unit that forms a three-step potential composed of a potential section, an intermediate potential section, and a low potential section, and a toner having a polarity opposite to that of the photoconductor in the high potential section of the three-step potential using the contact magnetic brush developing method. Of the three potentials using a contact magnetic brush developing method and a developing means for supplying
In an electrophotographic apparatus including a developing unit that supplies toner having the same polarity as that of a photoconductor to a low potential portion, the high potential is provided between an exposure process position by the exposure unit and a development process position by the developing unit. Potential detection means for measuring the sheet, intermediate potential portion and low potential portion, perforation position detection means for detecting the perforation position of the continuous paper, and pre-input used paper length information and in the vicinity of the perforation It is achieved by measuring the potential of the intermediate potential portion during the printing operation in the non-printing area on the photoconductor corresponding to.

[0006]

In the electrophotographic apparatus constructed as described above, the potential of the intermediate potential section is measured during the printing operation by the surface potential detecting means, the perforation position detecting means and the used paper length information. It is possible to realize high print quality without lowering the effective print speed of.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram showing the outline of an embodiment of the present invention. The photoconductor 1 is arranged so as to be rotatable at a constant speed in the direction of arrow A, and the charger 2, the surface potential sensor 3, the first developing device 4, the second developing device 5, the pre-transfer charger 6, are arranged around the photoconductor 1. Transfer device 7, erase lamp 8,
A cleaning device 9 is arranged. In addition, the surface potential sensor 3 installed between the exposure position of the optical system 10 and the first developing device 4.
Is driven by the surface potential detecting device 12 to measure the potential on the photoconductor 1. Based on this measured value, a charge amount control device 14 that controls the applied voltage or current of the high-voltage power supply 13, a light amount control device 11 that controls the laser light amount, and the first developing device 4
Bias voltage control device 16 for controlling the bias high voltage power supply 15 for applying a bias voltage to the developing roll and bias voltage control device 18 for controlling the bias high voltage power supply 17 for applying the bias voltage to the developing roll of the second developing device 5. Composed of. On the other hand, the continuous paper 19 is conveyed by the paper conveying device 20 at a speed synchronized with the photoconductor 1, and
The continuous paper perforation detection device 21 detects the perforation position of the continuous paper. The surface potential detecting device 12 is configured to measure the potential of the intermediate potential portion in the non-printing area on the photoconductor corresponding to the vicinity of the perforations of the continuous paper based on the perforation position information and the previously used paper length information 22. Drive timing is determined.

Next, the printing process of this apparatus will be described. The photoconductor 1 is uniformly charged by the charger 2, and a laser beam emitted from the optical system 10 forms a three-step potential. The high potential portion (VH) is normally developed by the first developing device 4 with toner having a polarity opposite to that of the photoconductor 1. At this time, the first
A bias voltage (VBH) is applied to the developing roll of the developing device 4, and toner is not developed in the intermediate potential portion (VM) and the low potential portion (VL). Next, in the low potential portion (VL), the toner having the same polarity as that of the photoconductor 1 is reversely developed by the second developing device 5.
At this time, the bias voltage (VBL) is applied to the developing roll of the second developing device 5, and the intermediate potential part (VM) and the high potential part are applied.
No toner is developed on (VH). Needless to say, the same effect can be obtained even when the reversal development is performed by the first developing device 4 and the regular development is performed by the second developing device 5. After development,
The toners having different polarities on the photoconductor 1 are made to have the same polarity by the pre-transfer charger 6 and transferred to the paper 19 by the transfer device 7. The untransferred toner remaining on the photoconductor 1 is cleaned by the cleaning device 9 and the above process is repeated. Further, the toner transferred onto the sheet 19 is heated and pressed by a fixing device (not shown) to be fixed on the sheet.

Next, the potential control operation according to the present invention will be specifically described when the photoconductor 1 is negatively charged. During the printing operation, the non-printing area (the position corresponding to the vicinity of the sheet perforation) on the photoconductor 1 is determined by the sheet perforation position detection signal by the continuous sheet perforation position detection 21 and the previously used sheet length information 22. Each time the non-printed area passes under the surface potential sensor 3 by the rotation of the identified photoconductor, the surface potential sensor 3 causes the surface potential sensor (intermediate potential portion) of the non-printed area to move.
(VM)) is detected. The intermediate potential unit (VM) adjusts the laser light amount (PM) by the exposure amount control device 11 so as to be constant at a predetermined value. Further, the intermediate potential unit (VM) controls the charge amount by the charge amount control device so as to be constant at a predetermined value. Next, a constant potential difference (ΔVB = −1) with respect to the intermediate potential part (VM).
The bias voltage is adjusted so as to secure (00V). That is, when the intermediate potential portion (VM) = − 490V, the bias voltage (VBH) applied to the first developing device 4 for normal development is VB.
H = −490−100 = −590V, and the bias voltage (VBL) applied to the second developing device 5 for reversal development is
VBL = −490 + 100 = −390V. Here, when VM = −450V, VBH = −550V,
VBL = -350V.

[0010]

As described above, according to the present invention,
By controlling the electric potential of the photoconductor during the printing operation, it is possible to stabilize the print density and reduce the unevenness of the print density in the high-potential portion and the low-potential portion without lowering the printing speed of the electrophotographic apparatus using continuous paper. It can be lost.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing a light decay curve of a photoconductor and a potential distribution on the photoconductor.

[Explanation of symbols]

3 ... Surface potential sensor, 10 ... Light quantity control device, 11 ...
Surface potential detection device, 13 ... Charge amount control device, 15 ... Bias voltage control device, 17 ... Bias voltage control device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Takahashi 1060 Takeda, Katsuta City, Ibaraki Prefecture Hitachi Koki Co., Ltd.

Claims (1)

[Claims] 1. An electrophotographic apparatus using folding continuous paper having perforations, comprising: charging means for uniformly charging a photosensitive member; and a high potential part, an intermediate potential part and a low potential part on the uniformly charged photosensitive member. The exposing means for forming a three-step potential composed of a potential part and the contact magnetic brush developing method are used to perform the above-mentioned three steps.
Among the potentials of the three steps, a developing means for supplying toner having a polarity opposite to that of the photoconductor to the high potential part, and a low potential part having the same polarity as the photoconductor to the low potential part of the three potentials by using the contact magnetic brush developing method. In an electrophotographic apparatus provided with a developing means for supplying toner, the high potential portion, the intermediate potential portion and the low potential portion are provided between the exposure step position by the exposure means and the development step position by the developing means. A surface potential detection unit for measuring, a perforation position detection unit for detecting a perforation position of the continuous paper, and a pre-input use paper length information, and a non-printing area on the photoconductor corresponding to the vicinity of the perforation. In the electrophotographic apparatus, the electric potential of the intermediate electric potential portion is measured during a printing operation.