JPS6129504B2 - - 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, and this appears 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. , 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 charge or charging time of the photoconductor. Even if you try to compensate for the fatigue of
The fatigue characteristics gradually deviated from predictions, and complete fatigue correction could not be performed.

Therefore, in the present invention, the amount of charge or charging time of the photoreceptor during copying is detected, 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 projected onto the photosensitive drum 1 as a light image by the imaging lens 5 . This photoreceptor ram 1 is first charged by a charging charger 6, and is moved in the direction of arrow B in synchronization with the document moving in the direction of 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, numeral 11 detects the charging current from the electrode installed in the charging charger 6 to detect the amount of charging on the photoreceptor during copying, and outputs it as a digital value. Detection device, 12 is charge detection device 11
This is a first counting storage device that counts and adds and stores the detected values detected by the . 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. Arithmetic device 1
6 performs arithmetic processing on the stored contents of the first and second count storage devices 12 and 15, and adjusts the photoreceptor at that time according to a control program set in advance in the program circuit 17 to correct fatigue of the photoreceptor. generates a control signal corresponding to the fatigue of the charge amount 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 first and second counting storage devices 1
The control program is advanced in accordance with changes in the stored contents of 2 and 15, and at least one of the charge amount, exposure amount, and development bias voltage is sequentially changed to correct fatigue of the photoreceptor. 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 this invention.

Figure 2 shows the relationship between the copy size and the number of copies.The coefficient P is based on A3, and 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 value obtained by adding the counted value of the amount of electrostatic charge (referred to as β) to this converted total number of copies n ₁ + an ₂ + bn ₃ +
cn ₄ +β 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 ₇ are the total value, V ₁ V7 to _V7 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.

Figures 4 to 6 show different detection means of a charge detection device that detects the amount of charge or charging time of a photoreceptor during copying, and the same parts as in Figure 1 are given the same reference numerals. . E is a power source that applies a high voltage to the charger electrode 6a of the charger 6. In FIG. 4, an electrode 10 made of a metal piece is installed inside the casing 6b of the charging charger 6, a part of the current flowing through the casing 6b is taken out, and the charging current is detected by a Schmitt integration circuit 11a. to detect the amount of charge.

In FIG.
1b, the amount of charge is detected. In addition, the charging current to be detected is the value obtained by detecting from all charging devices such as the transfer charger and the static electricity removal charger in addition to the charging charger (main charger), processing each detected value with a coefficient corresponding to the contribution rate of each, and adding it. The amount of charge may be detected by. FIG. 6 shows the case of detecting the charging time. When the power supply circuit to the charging charger 6 is turned on by the relay switch S, the start of charging is detected by the terminal voltage of the resistor R, and the timer 11c is activated. The charging time can be detected if the output signal is output every predetermined time period until the switch S is turned off.

Next, as a control means, when controlling the amount of charge instead of controlling the developing bias voltage, it is sufficient to control the voltage applied to the charger 6 by the amount of charge control circuit 18, and control the amount of exposure. In this case, the brightness may be changed by controlling the voltage or current of the lamp 4 using the exposure amount control circuit 19. 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 amount of charge or charge time during copying, accumulates and counts these, and calculates the total value based on the total number. Since program control is performed to determine the degree of fatigue of the photoconductor and correct the fatigue, the fatigue correction corresponding to actual photoconductor fatigue is far more accurate than program control based only on the number of copies. This allows you to always obtain high-quality copied images.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between the copy size and the number of copies, and FIG. 3 is a control program for controlling the developing bias voltage based on the total value. 4 and 5 are explanatory diagrams showing different examples of the charging amount detection means, and FIG. 6 is an explanatory diagram showing an example of the charging time detection means. 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
coefficient storage device, 13...copy size detection device,
14... Copy number detection device, 15... Second coefficient 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, a charge detection device that detects the amount of charge or charging 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: