JPS6210671A - Corotron overcurrent controller - Google Patents

Abstract

PURPOSE:To continue the subsequent copying work in a certain degree by fixing the output voltage when the discharging current value reaches a certain current value independently of protection from an overcurrent due to accidents. CONSTITUTION:When a potential Vp at a point P rises to reach a voltage value V1 of a constant voltage source 14, the detection signal is superposed on a monitor signal of the output of a comparator 11. When this detection signal is inputted, a CPU 10 instructs a high voltage power source 7 to fix the output voltage by a remote signal. Since the copy work is possible hereafter though the picture quality is degraded and the voltage applied to a corona wire 5 does not rise though copying is continued, arcing, break of the corona wire 5, etc. are not caused.

Description

DETAILED DESCRIPTION OF THE INVENTION Ltj=1. TECHNICAL FIELD The present invention relates to output ii control to a corona discharger that uniformly charges the surface of a photoreceptor.

In the case of an electrophotographic copying machine, the surface of the photoreceptor is uniformly charged and an electrostatic latent image is formed thereon by exposure. The first place must always be charged at a constant rate.

Generally, a corotron that uses corona discharge is used to charge the surface of a photoreceptor, and a high voltage is applied to a corona wire stretched parallel to and close to the photoreceptor to cause corona discharge and charge the photoreceptor. By keeping this applied voltage constant, the surface potential of the photoreceptor can be kept constant.

However, as the photoreceptor deteriorates over time, a constant surface potential cannot be obtained with the same applied voltage, and it is necessary to gradually increase the applied voltage.

Therefore, some devices are equipped with a surface potential S1 for detecting the surface potential of the photoreceptor to control the voltage applied to the corona wire.

FIG. 2 is a schematic explanatory diagram of the discharge.

Reference numeral 1 denotes a drum-shaped photoreceptor, and a corotron 2, a surface electrometer 3, and a developing device 4 are arranged in this order around its circumference.

The corona wire F-5 is composed of a corona wire 5 stretched close to the width direction of the photoconductor 1 and a shield 6 arranged to surround the corona wire 5. A high voltage is applied to the high voltage voltage rA7.

In the figure, the photoreceptor 1 rotates in the J1 direction, and while being charged by the corotron 2, the surface receives the static Xfi? 1
After that, the developer 4 forms a toner image, and the toner image is transferred to the paper. Although not shown, the fused and copied paper is discharged outside the machine. Ru. "Here, the charged surface potential of the photoreceptor 1 is detected by the surface potentiometer 3, and based on the detected value, the microcomputer 8
By turning on the high voltage power supply 7 and increasing the voltage applied to the corona wire 5, a constant surface potential can be maintained even when the photoreceptor deteriorates.

In addition, in the past, in order to protect the power supply, corotron, or photoreceptor from overcurrent caused by abnormalities such as short circuits and arcs in the corotron, the current flowing through the corona wire was detected, and when the current reached a certain level, the current was forcibly reduced or output I was trying to stop it.

1 -1 However, as mentioned above, deterioration of the photoreceptor due to aging causes the voltage applied to the corotron wire to gradually increase, so eventually an overcurrent due to an accident and an increase in the applied voltage over time This had the disadvantage that it could not be distinguished from the increase in current accompanying the increase in current.

Therefore, as the applied voltage increases over time, when the current approaches a predetermined current value for accident prevention, there is a considerable overcurrent, which is not a favorable condition for the corotron and photoreceptor.

Furthermore, when a predetermined current value was reached under such conditions, a protective device was used to reduce the current and stop the output, making it impossible to perform any further copying operations. Workers were sometimes forced into inconvenience.

The present invention has been developed in view of the above, and its purpose is, in addition to protecting against overcurrent due to accidents, to fix the output voltage when the discharge current reaches a certain constant current value. The object of the present invention is to provide a corotron overcurrent control device that allows subsequent copying work to be continued to a certain extent and prevents IO scratches on the roller 1-con, photoreceptor, etc. due to an increase in discharge current over time.

The configuration of the present invention is shown in FIG. 1 and will be explained.

In an electrophotographic copying machine that controls the output of the corona discharger A to keep the surface potential of the photoreceptor constant, B is a discharge current detection means for detecting the discharge current value of the corona discharger A.

C is a comparison means for comparing and detecting whether the current value detected by the surface discharge current detection means B has reached a predetermined current value.

Reference numeral D denotes a comparison means (2) for comparing a constant current value higher than a predetermined current value in the comparison means with the current value detected by the discharge current detection means B.

E is an output control means which inputs the signals from the two comparison means IC and IID and controls the output to the corop discharge 5A.

The present invention is constructed as described above, and when the current value detected by the discharge current detection means B reaches the current value set in the comparison means IC and the detection signal thereof is inputted, the output control means E performs a large Fix the output voltage to discharger A.

Furthermore, the current value detected by the discharge current detection means B is the same as that of the comparison means 1.
When the current value set in rD is reached and the output control means E inputs the detection signal, the output to the corona discharger A is stopped.

When the comparison means IC detects that the detected current value has reached the predetermined current value, it means that the discharge current has increased over time to the same predetermined current value, and then the voltage is applied to the thick discharger A. Since the voltage is fixed, the copying operation can be continued, although the quality of the copied image gradually deteriorates.

At the same time, a positive signal for suppressing the increase in the discharge current over time is output to the high voltage power source 7 to control the output voltage of the high voltage power source 7.

The output voltage is applied to a corona wire 5, and one end P of the corona wire 5 is grounded via a current detection resistor 13 and connected to the input terminals of the two comparators 11 and 12.

A constant voltage source 14 is connected to the other input terminal of the comparator 11, and a constant voltage source 15 is connected to the other input terminal of the comparator 12, and each is compared with the potential at point P.

The constant voltage source 14 is set to a voltage value v1 at which the increase in the discharge current over time does not cause problems such as cutting and arcing of the corona wire 5, and the constant voltage source 15 is set to a voltage value v1 that prevents problems such as cutting and arcing of the corona wire 5, and the constant voltage source 15 is set to a voltage value v1 that prevents problems such as breaking of the corona wire 5 and arcing. The voltage value V2 is set to detect the current, and the constant voltage iT! The voltage value V2 of the constant voltage source 15 is higher than the voltage value ■1 of the constant voltage source 14.

Further, the CPU 10 outputs a display signal to the display 16 for controlling the display on the display 16 installed on the surface of the copying machine.

In the control system as described above, damage to the corona charger, photoreceptor, etc. can usually be prevented by the method described above.

Furthermore, when the comparison means IID detects that the detected current value has reached the predetermined current value, it means that an overcurrent has flowed due to a short circuit to the corona discharger or an abnormality in the arc snow, and in this case, the output Since this is stopped, the corona discharger A, the photoreceptor, etc. can be protected.

LJ Hereinafter, one embodiment of the present invention illustrated in FIG. 3 and subsequent figures will be described.

Note that the side of the copy shown in Figure 1 and Figure 2 is also used in this embodiment.

FIG. 3 is a block diagram of the control system in this embodiment.

The control center is the CPU 10, and the surface electrometer 3
In addition to the detection signal from the comparator 11, the monitor signal from the comparator 11 and the FALT signal from the comparator 12 are input.

In addition, the surface potential of the remote signal and the output stop signal is detected from the CPU IO using the surface potential control 3, and based on the detected value, the CPU 10 controls the high-voltage voltage vA7 using the remote signal and gradually connects it to the corona wire 5. The applied voltage will be increased.

As the voltage applied to the corona wire 5 increases, the current flowing through the current detection resistor 13 also increases, and the potential Vp at point P increases.

The operation of this control system will be explained below based on a flowchart (FIG. 4).

The potential Vr at point P is the voltage 1+lI V of the constant voltage source 14,
At a lower stage, steps ■ and ■ are repeated, and when the potential VP at point P further exceeds the limit and reaches the voltage value V1 of the constant voltage source 14 (step ■), the monitor signal of the output of the comparator 11 is Remove the detection signal.

When the CPU 10 receives this detection signal, it instructs the output voltage of the high-voltage power supply 7 to be fixed using a remote signal (step 2).

Thereafter, although the image quality deteriorates, copying work is possible, and even if copying continues, the voltage applied to the corona wire A7-5 does not increase, so arcing and cutting of the corona wire 5 do not occur.

In addition, it is possible to prevent adverse effects on the photoreceptor due to an increase in discharge current.

Then, an instruction is further displayed on the display 16 (step ■), so it is known that the deterioration of the photoconductor, etc. has reached a point where it is affecting the image quality, and that it is time to replace the photoconductor shade. be able to.

In addition, due to short circuit accidents or arcing, etc., Corona Wire A7
-5, and when the potential VP at point P reaches the voltage value ■2 of the constant voltage source 15 (step ■), CPIJl
An output stop signal is outputted from o to the high voltage power supply 7 (step ■), and the voltage application to the corona wire I'/-5 is avoided.

Therefore, damage to the power supply, corotron, etc. due to overcurrent can be prevented.

In this example, a comparator is used to detect that the predetermined current value of the discharge current has been reached, but the potential at point P is converted to digital 1 direct by an A/D converter and converted to c p u io. You may also input it.

In this case, the setting of the predetermined voltage value and all subsequent operations are performed by software.

The present invention fixes the voltage value applied to the corona discharger when the increase in discharge current due to deterioration of the photoreceptor during loading exceeds a predetermined current value, so the corona wire is not disconnected. This is convenient because it prevents problems such as streaks and arcing, and adverse effects on the photoreceptor, and also allows subsequent copying work to be carried out, allowing copying to continue until the photoreceptor, etc. is maintained.

Furthermore, if a short circuit or arcing occurs and an excessive shoulder current flows through the corona wire, voltage application is stopped, thereby preventing damage to the power supply, corona discharger, etc.

[Brief explanation of the drawing]

Fig. 1 is a diagram corresponding to the claims of the present invention, Fig. 2 is a schematic diagram partially showing the copying mechanism around the photoreceptor, Fig. 3 is a control system block diagram of an embodiment according to the present invention, and Fig. 4 is It is a flowchart showing the operation of the same control system. 1... drum-shaped photoreceptor, 2... corotron, 3...
・Surface electrometer, 4... Current aI device, 5... Corona wire, 6... Shield, 7... High voltage power supply, 8...
Microcomputer, 10...CPU, 11...
Comparator, 12... Comparator, 13... Current detection resistor,
14.15... constant voltage source, 16... indicator.

Claims (1)

[Claims] In an electrophotographic copying machine that controls the output of corona discharge current in order to keep the surface potential of the photoreceptor constant, there is provided a discharge current detection means for detecting the discharge current of a corona discharger, and a current value detected by the detection means. Comparing means I for comparing and detecting whether a predetermined current value has been reached; and comparing means II for comparing the detected current value with a constant current value higher than the predetermined current value in the comparing means I. The output control means inputs the signals from the comparison means I and II and controls the output to the corona discharger, and the output control means detects from the comparison means I that the detected current value has reached the predetermined current value. When detecting and inputting a detection signal, fix the output voltage to the corona discharger,
Further, when the comparison means II detects that the detected current value has reached the predetermined current value and inputs a detection signal, the output to the corona discharger is stopped. Control device.