JPS6290671A - Exposure level control for copying machine - Google Patents

Abstract

PURPOSE:To set an exposure voltage to an optimum value automatically with an inexpensive constitution by controlling the electrostatic charging voltage of a charger and the exposure voltage of an exposing device so that a dark potential and a light potential are as high as their reference potentials. CONSTITUTION:The electrostatic charger 3 which is applied with a high charging voltage VCC from a charging power source 2, the exposing device 5 which is supplied with the exposure voltage VF from an exposure power source 4 and exposes a photosensitive drum 1, a developing device 6 which develops an electrostatic latent image formed on the photosensitive drum 1, and a cleaner 7 which cleans up the photosensitive drum 1 are arranged at the periphery of the photosensitive drum 1. Then, a potential detector 8 which detects the surface potential of the photosensitive drum 1 is arranged between an exposure position and the developing device 6. The output signal of the detector 8 is converted by an AD converter 9 into a digital value, which is inputted to a control circuit 10 to perform feedback control over the output voltages of the charging power source 2 and exposure power source 4 so that the dark potential and light potential coincide with their reference voltages.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exposure level control IT device for copying and having a charger and an exposure device.

[Prior Art] As is well known, an electrostatic latent image is formed on a photoconductor, developed with toner, and transferred to recording paper.
In a copyist who copies manuscripts, the photoreceptor is charged to give it photosensitivity.

■Exposing the photoreceptor to a light image creates an electrostatic latent image.

■Develop the electrostatic latent image with toner.

■Transfer the developed image to recording paper.

■Fix the transferred image.

■Clean the photoreceptor.

By performing a series of steps, the image read from the original is recorded on recording paper.

In addition, in multicolor copying, the original image is separated into colors, and each color separation image is charged, exposed, and developed as described above.

Repeating a series of transfer, fixing, and cleaning processes,
By superimposing images of each separated color on the same recording paper, a multicolor print identical to the original image is obtained.

In such a monochrome or multicolor copying machine, in order to obtain a copied image of optimum image quality, it is necessary to adjust the exposure voltage of the exposure device to an optimum value at the time of shipment or repair.

Conventionally, the exposure voltage of such an exposure device has been adjusted by (1) setting the charging voltage of the charger near the reference value, (2) measuring the surface potential of the photoreceptor in this state, and setting the measured value as the reference value. Adjust the charging voltage of the charger to match the value, (3) Set the exposure voltage of the exposure device to near the reference value, (4)
) This process involves adjusting the exposure voltage until the optimum image quality is achieved while copying a blank document.

Therefore, there are problems in that it is time consuming and troublesome.

Therefore, in addition to the exposure device, a reference light source with a standard exposure amount is provided, and the light amount of this reference light source and the light amount of the exposure device are automatically compared before the start of the copying cycle, and the light amount of the exposure device is compared to that of the reference light source. A device that automatically adjusts to the amount of light was published in Japanese Patent Application Laid-Open No. 58-
It is proposed in No. 44464.

[Problems to be Solved by the Invention] However, the method proposed in Japanese Patent Application Laid-Open No. 58-44464 has the problem of increased costs because a reference light source must be provided in addition to the exposure device.

The present invention has been made to solve these problems, and its purpose is to provide an exposure level control device for copying machines that is inexpensive and can automatically set the exposure voltage of an exposure device to an optimal value. Our goal is to provide the following.

[Means for Solving the Problems] The present invention includes a detector that detects the surface potential of a photoreceptor, and a detector that detects the dark potential in a state where the photoreceptor is not exposed to light, and the detected value is equal to the dark potential. a first control means for feedback controlling the charging voltage of the charger so as to match the reference potential; and a first control means for causing the detector to detect the bright potential in a state where the photoconductor is exposed to light by the exposure device, and the detected value is the bright potential. a second control means for feedback controlling the exposure voltage of the exposure device so as to match the reference potential; and storing information regarding the exposure voltage when the bright potential detected by the detector matches the reference potential of the bright potential. By providing a non-volatile memory, the above object is achieved.

[Operation 1] The first control means sets the charging voltage of the charger so that the dark potential matches its reference potential. The second control means sets the exposure voltage of the exposure device so that the bright potential matches the reference potential after setting the charging voltage.

[Example 1 Hereinafter, the present invention will be explained based on Examples.

FIG. 1 is a block diagram showing one embodiment of the present invention,
A charger 3 to which a high charging voltage VCC from a charging power source 2 is applied around the photosensitive drum 1; an exposure device 5 to which an exposure voltage Vf is applied from an exposure power source 4 to expose the photosensitive drum 1;
A developing device 6 that develops the electrostatic latent image formed on the photosensitive drum 1
A cleaner 7 for cleaning the photosensitive drum 1 is disposed, and a potential detector 8 for detecting the surface potential of the photosensitive drum 1 is disposed between the exposed area and the developing device 6. The output signal of the potential detector 8 is converted into a digital value by the AD converter 9 and inputted to the control circuit 10, and the output voltages of the charging power source 2 and the exposure power source 4 are feedback-controlled based on the output signal of the detector 8. is configured to be

Figure 2 shows the control circuit 1 to control the exposure voltage to the optimum value.
0 is a flowchart showing the operations to be executed. When the automatic exposure level setting mode is set on a console (not shown), the control circuit 10 first puts the photosensitive drum 1 into a driving state (step 20), and then controls the charging power source 2. Then, the charging voltage VCC applied to the charger 3 is set to the initial value VccO (step 21). As a result, the photosensitive drum 1 is at Vcc.

charged at a charging voltage of

Next, the control circuit 10 causes the potential detector 8 to detect the dark potential in the charged state of V CCO, and takes in the digital value of the detected potential from the AD converter 9 (step 22). At this time, it is checked whether the detected dark potential matches the reference dark potential, and if it is lower than the reference dark potential, the charged voltage V
CC is increased by one step from the initial value V CCO, and if it is higher, CC is decreased by one step from the initial value 1iFf V cco (step 24.25 >. Then, the new charged voltage Vcc that has been increased or decreased is The dark potential is detected again in the applied state, and it is checked whether it matches the reference dark potential.

If the dark potential matches the reference dark potential due to such a rise or fall in the charging voltage VCC, then the exposure voltage V
After setting f to the initial value VfO (step 26), the exposure device 5 is turned on and the photosensitive drum 1 is exposed (step 27). Then, the bright potential at the exposure voltage VfO is detected by the potential detector 8, and the digital value of the detected potential is taken in from the AD converter 9 (step 28). Next, check whether the bright potential detected at this time matches the reference bright potential, and if it is lower than the reference bright potential, increase the exposure voltage Vf by one step from the initial value VfO, and conversely, if it is higher, f is lowered by one step from the initial value VfO (step 29
~31). Then, the bright potential is detected again in the application state of the new exposure voltage Vf that has been increased or decreased, and it is checked whether it matches the reference bright potential.

When the bright potential matches the reference bright potential due to such an increase or decrease in the exposure voltage Vf, the value of the exposure voltage at this time is stored in the nonvolatile memory 11, and in the subsequent copying process, the value of the exposure voltage is stored in the nonvolatile memory 11. Exposure is performed using the exposure voltage value stored in step 11 (step 32). When all of the above processes are completed, the photosensitive drum 1 is stopped, and the charger 3 and the exposure device 5 are returned to the OFF state.

Note that the information stored in the nonvolatile memory 11 may not be the value of the exposure voltage itself, but may be a coefficient or a ratio with respect to the reference exposure voltage.

[Effect of the Invention 1] As explained above, the present invention includes a detector that detects the surface potential of a photoreceptor, and a detector that detects the dark potential in a state where the photoreceptor is not exposed to light. a first control means for feedback controlling the charging voltage of the charger so as to match the reference potential; and a first control means for causing the detector to detect the bright potential in a state where the photoconductor is exposed to light by the exposure device, and the detected value is the bright potential. a second control means for feedback controlling the exposure voltage of the exposure device so as to match the reference potential;
Since a non-volatile memory is provided that stores information regarding the exposure voltage at the moment when the bright potential detected by the detector matches the reference potential of the bright potential, the exposure voltage can be set to the optimum value extremely easily and with an inexpensive configuration. Can be set automatically.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a flowchart showing processing for automatically setting the exposure voltage of the exposure device. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 2... Charging power source, 3... Charger, 4, Exposure power source, 5... Exposure device, 8... Potential detector, 10... Control circuit, 11 ...Non-volatile memory.

Claims (1)

[Claims] In a copying machine equipped with a charger that charges a photoreceptor to give it photosensitivity, and an exposure device that exposes the photoreceptor to light to form an electrostatic latent image, the surface potential of the photoreceptor is adjusted. a first detector that detects a dark potential in a state in which the photoreceptor is not exposed to light; and a first controller that causes the detector to detect a dark potential in a state in which the photoreceptor is not exposed, and feedback-controls the charging voltage of the charger so that the detected value matches a reference potential of the dark potential; control means for causing the detector to detect a bright potential in a state where the photoreceptor is exposed by the exposure device, and controlling the exposure voltage of the exposure device so that the detected value matches a reference potential of the bright potential; Exposure level control of a copying machine, comprising: second control means for feedback control; and a nonvolatile memory that stores information regarding the exposure voltage when the bright potential detected by the detector matches the reference potential of the bright potential. Device.