JPH09120199A - Roller electrifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrifier capable of adjusting the potential of electrification of a photoreceptor to have a target value. SOLUTION: Beside the detection of a surface potential and the correction of an applied bias, the temp. of an electrifying roller is detected and an applied voltage is corrected to attain an accurate correction. The surface potential is detected in a long cycle and a potential fluctuation during a copy or within a day is corrected in a short cycle by the detection of the temperature and the correction of the applied voltage, to prevent a defect such as reduction in the life of the photoreceptor and loss of time used for controlling caused by the execution of the detection and correction of the potential.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller charging device for an electrophotographic apparatus such as a copy machine, a printer, a facsimile machine, and more particularly to a roller charging apparatus having improved potential control.

[0002]

2. Description of the Related Art In the contact roller charging system, since a medium resistance elastic body such as rubber is used as a roller, it is possible to set the surface potential on the photoreceptor, which is the body to be charged, to a target value. More difficult than the corona charging method. There is a large variation in the resistance value due to variations in the manufacturing of the charging roller material, and there is a large variation in the resistance value due to the influence of the ambient environment, especially temperature and humidity (see Fig. 1). Change of charging potential due to change of the low speed machine (process speed 120mm /
Second) (Fig. 2: constant voltage applied to charging roller, DC-1600V: see).

SUMMARY OF THE INVENTION It is an object of the present invention to provide a roller charging device capable of controlling the charging potential of a photosensitive member to a target value in a roller charging system.

[0004]

In order to achieve the above object, a roller charging device according to a first aspect of the present invention is a roller charging device having a charging roller for contacting and charging an object to be charged. A roller charging device having a means for detecting the surface potential of a body to be charged and a means for detecting the temperature of the charging roller, wherein the detection means controls the voltage applied to the charging roller, The detection means detects the surface potential of the charged body in a long-term cycle, and the applied voltage to the charging roller is corrected and applied according to the detected value so that the surface potential becomes a desired value, and the temperature is detected. The temperature detected by the charging roller is detected by a means in a short cycle such as during repeat copying, and the applied voltage of the charging roller is corrected and applied according to the detected value and its change. And wherein the door.

The roller charging device according to the second aspect is characterized in that a polar rubber such as epichlorohydrin rubber is used as the charging roller.

That is, according to the present invention, in addition to the surface potential detection / applied bias correction, the temperature of the charging roller is detected, and the applied voltage is corrected to perform accurate correction. Surface potential detection is performed in a long-term cycle (for example, once at the start of copying, once a day (only in the morning), etc.), and correction for potential fluctuations during copying or within a day (short-term cycle) is performed by temperature detection / applied voltage correction. However, it is possible to prevent problems such as photoreceptor life and time loss used for control due to potential detection / correction.

Further, polar rubber has a large change in resistance value due to temperature, as compared with a conductive particle-dispersed medium resistance material,
In particular, since correction is required in a short cycle at low temperatures, correction by temperature prevents problems with only the potential detection / correction method.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a conceptual view of the essential parts of a copying machine using a roller charging device according to the present invention. In the figure, 1 is a photoreceptor (OPC) which is an image support, 2 is a charging roller, 3 is exposure light, 5 is image developing means, 6 is transfer means, 7 is cleaning means, 8 is static elimination light, and 9 is transfer paper. The potential detecting means 10 is placed close to the photoconductor 1 (for example, at an interval of 2 to 3 mm), the surface potential of the photoconductor 1 is detected, and the roller temperature detecting means 11 is placed close to or in contact with the charging roller 2. . In the figure, 12 is an eraser for erasing the potential of the unnecessary portion, 20
Is a signal converter, 21 is a power supply for bias application, 22 is a power supply controller, and 23 is an arithmetic and control unit such as a microcomputer. For the charging roller 2, a medium resistance / elastic body made of epirochlorohydrin rubber is used to improve the uniformity of image quality.

The operation of the portable device of this embodiment will be described. Prior to the start of copying, a constant applied bias (DC-1600
V) is applied from the power source 21 to the charging roller 2 to apply the electrometer 10
Measure and detect the electric potential. The bias voltage applied to the charging roller 2 so as to be the target potential (−900 V) from the detected potential is corrected from the relationship shown in the applied voltage correction table of FIG. 3 to determine the applied voltage during copying. The correction of the applied voltage during the copying operation is performed according to the temperature of the charging roller and its change.

FIG. 5 is a graph showing the relationship between the charging roller temperature and the charging potential. When DC-1600V is applied, environmental humidity of 60% RH (solid line) and 15% RH (broken line) for the charging roller 2 having an average resistance value is shown. The correction of the applied voltage according to the temperature is shown in FIG. Figure 5 shows the relationship between the detected temperature and the detected potential.
6% RH line (± 20 V), the applied voltage is corrected according to the temperature change as shown by the solid line in FIG. 6 showing the relationship between the charging roller temperature and the applied voltage correction table. When it does not coincide with the solid line in FIG. 5, for example, when it is located at the broken line, the applied voltage is corrected as shown by the broken line in FIG. That is, the applied bias voltage is corrected and applied so that the target charging potential is obtained by detecting the potential, and the correction voltage is used as the starting point for the correction of the charging potential due to the temperature change during copying. Rises due to movement)
The applied voltage is corrected according to. There are various other methods of surface potential detection / applied voltage correction with an electrometer, but this is an operation that does not participate in copying (image formation). Is advantageous from the point of.

[0011]

EXAMPLE As an example of the present invention, a Ricoh copier:
The above-described present invention was carried out by modifying the model name FT6500 and the process speed 430 mm / sec (65 CPM).
Potential detection / correction is performed almost once a day (during warm-up when the power is ON), and during subsequent copying, correction is only performed by the temperature of the charging roller, and deviation from the target potential is almost prevented. It was about 30V.

[0012]

As described above, the roller charging device according to the first aspect of the present invention is a repeater in a high-speed machine as compared with the potential detection / applied voltage correction for the control of the photosensitive member charging potential in the roller charging system. By correcting the applied voltage against the temperature change peculiar to roller charging, where the potential changes remarkably during copying, it is possible to improve the durability life of the photoconductor and prevent loss time used for potential detection / feedback, and high durability. There is an effect that high productivity can be obtained.
Further, it is difficult for the conventional temperature detection / applied voltage correction method to keep the target charging potential against variations / changes in resistance value due to causes other than the temperature of the charging roller. Although the ratio was large, there is an effect that the inherent weak point of the charging roller system can be overcome.

According to a second aspect of the present invention, there is provided a roller charging device in which a polar rubber such as epichlorohydrin rubber is used as the charging roller for medium resistance /
By using it as an elastic body, the deviation from the target value of the charging potential due to the resistance value change due to temperature as a weak point of polar rubber is corrected at high speed, and the uniformity is higher than that of the conductive particle dispersion type, that is, uneven charging There is an effect that a small amount of charging can be performed and the image quality can be improved.

[Brief description of the drawings]

FIG. 1 is a graph showing changes in resistance value due to the influence of ambient environment such as temperature and humidity.

FIG. 2 is a graph showing a change in charging potential due to a change in resistance value in a high speed machine and a low speed machine.

FIG. 3 is a conceptual diagram of a main part of a copying machine using a roller charging device according to the present invention.

FIG. 4 is a graph showing an applied voltage correction table.

FIG. 5 is a graph showing the relationship between charging roller temperature and charging potential.

FIG. 6 is a graph showing a relationship between a charging roller temperature and an applied voltage correction table.

[Explanation of symbols]

 1 Photoreceptor 2 Charging Roller 3 Exposure Light 5 Image Developing Means 6 Transfer Means 7 Cleaning Means 8 Electrification Light 9 Transfer Paper 10 Potential Detecting Means 11 Roller Temperature Detecting Means 12 Erasers 20 Signal Converters 21 Bias Applying Power Supplies 22 Power Supply Controllers 23 Microcomputer

Claims (2)

[Claims] 1. A roller charging device having a charging roller for contacting and charging an object to be charged, comprising: means for detecting a surface potential of the object to be charged; and means for detecting a temperature of the charging roller. A roller charging device for controlling the voltage applied to the charging roller by the both detecting means,
The potential detection means detects the surface potential of the charged body in a long-term cycle, and the applied voltage to the charging roller is corrected and applied according to the detected value so that the surface potential becomes a desired value. The temperature detection means detects the detected temperature of the charging roller in a short cycle such as during repeat copying, and controls the applied voltage of the charging roller to be corrected and applied according to the detected value and its change. Roller charging device. 2. A polar rubber such as epichlorohydrin rubber is used as the charging roller.
Roller charging device.