JPS6129505B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a program control device for correcting fatigue of a photoreceptor in an electrophotographic copying machine that repeatedly uses the same photoreceptor.

Generally, the photoreceptor in a transfer-type electrophotographic copying machine gradually becomes fatigued as the number of times it is used increases, which manifests as an increase in the dark decay rate or an increase in residual potential, resulting in a decrease in the image density of the copy, and A decrease in contrast occurs. In this case, the above-mentioned adverse effects on the copied material can be prevented by changing the exposure amount, charging amount, developing bias voltage, etc. in the copying process depending on the progress of fatigue of the photoreceptor. Measuring photoreceptor fatigue is extremely difficult.

Therefore, a control program is set by predicting the fatigue of the photoreceptor depending on the number of copies, and the number of copies is counted and the control program is advanced accordingly to sequentially change the exposure amount, charge amount, developing bias voltage, etc. Program control methods have been proposed to compensate for photoreceptor fatigue. However, even if you count the number of copies, the degree of fatigue of the photoconductor differs depending on the copy size, and also varies depending on the amount of exposure or exposure time of the photoconductor. Even when attempting to correct fatigue, the fatigue characteristics gradually deviated from predictions, making complete fatigue correction impossible.

Therefore, in the present invention, the exposure amount or exposure time of the photoconductor during copying is detected and the value is counted and stored, and the number of copies is counted and stored for each copy size, and depending on the stored contents,
The amount of charge during the copying process according to a preset control program to correct fatigue of the photoreceptor,
At least one of exposure amount or development bias voltage
By stepping the control program so as to sequentially change the photoreceptor, fatigue correction of the photoreceptor can be performed accurately, and good quality of copied images can always be obtained.

The present invention will be explained below with reference to the accompanying drawings. FIG. 1 shows an embodiment of the present invention, in which numeral 1 is a photosensitive drum having a photosensitive layer on its surface, and an original 3 placed on a contact glass 2 is irradiated with light by a lamp 4. The reflected light is irradiated onto the photosensitive drum 1 by the imaging lens 5. The photosensitive drum 1 is first charged by a charging charger 6, and is moved in the direction of the arrow B in synchronization with the document moving in the direction of the arrow A.
direction, is exposed to light to form a latent image, the latent image passes through a developing device 7 and is developed with toner, and then the image is transferred onto paper that is run in the direction of arrow C by a transfer charger 8. After the transfer, the cleaning device 9 cleans the surface of the photoreceptor.

Next, to explain the block diagram in FIG. 1, 11 detects the exposure amount or exposure time of the photoreceptor during copying based on the signal from the photoelectric conversion element 10 placed near the lamp 4, and outputs it as a digital value. The exposure detection device 12 is a first counting storage device that counts and adds and stores the detected values detected by the exposure detection device 11. On the other hand, the copy size detection device 13 linked to the copy size switching device detects the copy size, the copy number detection device 14 linked to the copy counter detects the number of copies, and the second count storage circuit 15 detects the copy size. The number of copies is counted and stored for each copy size. The arithmetic device 16 includes first and second counting storage devices 12,
15, and generates a control signal corresponding to the fatigue of the photoreceptor at that time according to a control program for correcting the fatigue of the photoreceptor set in advance in the program circuit 17, and calculates the amount of charge. The control circuit 18, the exposure amount control circuit 19, and the developing bias voltage control circuit 20 control at least one of the charging amount, the exposure amount, and the developing bias voltage in the copying process. Then, the control program is advanced in accordance with changes in the stored contents of the first and second count storage devices 12 and 15, and at least one of the charge amount, the exposure amount, and the developing bias voltage corrects the fatigue of the photoreceptor. It changes sequentially as follows. In this embodiment, the arithmetic unit 16, the charging control circuit 18, the exposure amount control circuit 19, and the developing bias voltage control circuit 20 constitute the control means in the present invention.

Figure 2 shows the relationship between the copy size and the number of copies.The coefficient P is based on A3, and the coefficients are a, b, c.
is the length or area ratio of B4, A4, and B5 copy sheets to A3, for example, a
Set as = 3/4, b = 1/2, c = 3/8.
If the number of copies for each copy size of A3, B4, A4, and B5 is respectively n ₁ , n ₂ , n ₃ , and n ₄ , the total number of copies converted to A3 is n ₁ +an ₂ +bn ₃ +cn ₄ . Such calculations may be performed by the calculation device 16, but
The number of copies converted by the arithmetic unit 16 may be stored in the second counting storage device 15 each time the number of copies increases. The total number of copies added to the calculated value of exposure amount (referred to as α) n ₁ + an ₂ + bn ₃ +
cn ₄ +α is a value (assumed to be x) indicating the degree of fatigue of the photoreceptor.

FIG. 3 shows an example of a control program for correcting fatigue of the photoreceptor by changing the developing bias voltage according to the total value x, where x ₁ to x ₄ are the total value, V ₁ V4 to _V4 represent the developing bias voltage, and the developing bias voltage is increased stepwise as the total value x increases.

Such a program control device can be easily implemented using, for example, a microcomputer, in which case the first and second counting storage devices are non-volatile constant access memories (RAMs).
Using different addresses, the arithmetic unit 16
A fixed storage device (ROM) may be used as the CPU and the program circuit 17.

Note that the exposure amount may be detected by subtracting the developing current and the transfer current from the current flowing through the photoreceptor, that is, the charging current. Further, when controlling the amount of charge, the voltage applied to the charger 6 may be controlled by the charge amount control circuit 18, and when controlling the amount of exposure, the voltage applied to the lamp 4 may be controlled by the amount of exposure control circuit 19. The brightness may be changed by controlling the voltage or current. Furthermore, if a control program is set to appropriately combine the control of the developing bias voltage, the amount of charge, and the amount of exposure, more effective fatigue correction of the photoreceptor can be performed.

As described above, the program control device of the present invention detects not only the number of copies but also the copy size and the exposure amount or exposure time during copying, cumulatively counts them, and determines the exposure based on the total value. Since program control is performed to determine the degree of body fatigue and compensate for the fatigue, it is possible to perform fatigue correction corresponding to actual photoreceptor fatigue with much higher accuracy than program control based only on the number of copies. I can do it,
A high quality copy image is always obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between copy size and number of copies,
FIG. 3 is a diagram showing an example of a control program for controlling the developing bias voltage based on the total numerical value. 1... Photosensitive drum, 3... Document, 4... Lamp, 5... Imaging lens, 6... Charging charger,
7...Developing device, 8...Transfer charger, 9...
Cleaning device, 10...Photoelectric conversion element, 11
...exposure amount or exposure time detection device, 12...first
counting storage device, 13...copy size detection device,
14... Copy number detection device, 15... Second counting storage device, 16... Arithmetic device, 17... Program circuit, 18... Charge amount control circuit, 19... Exposure amount control circuit, 20... Development Bias voltage control circuit.

Claims (1)

[Claims] 1. In an electrophotographic copying machine that uses the same photoreceptor repeatedly, an exposure detection device that detects the exposure amount or exposure time of the photoreceptor during copying, and a first counter that counts and stores the values detected by the device a storage device, a size detection device that detects the copy size, a number detection device that detects the number of copies, and a second device that counts and stores the number of copies for each copy size based on the detected values of the size detection device and the number of copies. a counting storage device; a program circuit storing a control program for sequentially changing at least one of the amount of charge, the amount of exposure, or the developing bias voltage in the copying process in order to correct fatigue of the photoreceptor; control means for controlling at least one of the amount of charge, the amount of exposure, or the developing bias voltage in the copying process according to the control program stored in the program circuit according to the stored content of the counting storage device. A program control device for an electrophotographic copying machine, characterized in that: