JPH04240667A - Electrophotographic system image forming device - Google Patents

Abstract

PURPOSE:To prevent the deviation of notch and the staining of an image ground from occurring by detecting the change of the film thickness of a resin layer and accurately grasping the deterioration degree of an overcoat drum. CONSTITUTION:Image system processing equipments such as an electrostatic charger 2, a developing device 3 and a cleaning unit 4 are arranged around the overcoat drum 1, and a film thickness detector 5 is provided on the downstream side of the cleaning unit 4. The detector 5 detects the film thickness by applying an AC current to the induction coil of a probe, making the probe abut on the surface of the photosensitive body 1 and grasping the change of the number of magnetic fluxes penetrating the induction coil as the change of the current. The film thickness of the coating layer of the drum 1 is measured when the drum is not used and when a specified time elapses, and the deterioration degree is decided by comparing the measured value with the past measured result.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile machine using the Carlson process.

0002

[Prior Art] Image forming apparatuses such as electrophotographic copying machines and laser printers generally use drum-shaped or belt-shaped photoreceptors. The drum has a resin layer (protective layer) on top of the conductive substrate, which is a normal photoreceptor, and the photoconductive layer.
has been established.

0003

[Problems to be Solved by the Invention] However, this overcoat drum causes changes in the film pressure of the resin layer due to sliding contact with the following items (■ to ■), which causes notch shift in the image and background stains. It had become. ■ Toner or carrier, inlet/outlet seals for development ■ Blades, brushes, toner scatter prevention seals for cleaning ■ Other sealing members around the photoreceptor

0
[004] This invention was made in view of the above points, and it is possible to accurately grasp the degree of deterioration of the overcoat drum,
The purpose is to prevent image notch displacement and background stains from occurring.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a film thickness measuring means for measuring the film thickness of the coating layer of an overcoat drum when it is not in use and after a predetermined period of time has elapsed; The apparatus further includes a comparing means for comparing the measurement results obtained by the measuring means and determining the degree of deterioration of the overcoat drum.

The present invention also includes a film thickness measuring means for measuring the film thickness of the coating layer of the overcoat drum when not in use, when power is turned on by a main switch, or when the number of images formed reaches a predetermined number; The apparatus may also include a comparison means for comparing each measurement result to determine the degree of deterioration of the overcoat drum.

Furthermore, it is desirable to provide a developing bias setting means for setting a developing bias during image formation in accordance with the comparison result by the comparing means.

[0008]

[Function] According to the image forming apparatus according to the present invention, the film thickness of the coating layer of the overcoat drum is measured by the film thickness measuring means when the overcoat drum is not in use and after a predetermined period of time has elapsed (or when the power is turned on by the main switch or when the number of sheets to be formed is Since the degree of deterioration of the overcoat drum is determined by comparing the results of each measurement with the comparison means to determine the degree of deterioration of the overcoat drum, the degree of deterioration can be accurately grasped.

Further, if the developing bias setting means sets the developing bias at the time of image formation in accordance with the comparison result by the comparing means, it is possible to prevent notch shift and background staining of the image.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 2 is a schematic configuration diagram showing the image forming section of a copying machine embodying the present invention and a control system related to film thickness detection of a photoreceptor.

In this copying machine, 1 is an overcoat drum, which is a photoreceptor having a protective layer, around which image forming process equipment such as a charger 2, a developer 3, and a cleaning unit 4 are arranged. The film thickness detector 5 according to the present invention is disposed downstream of the cleaning unit 4 so that the appropriate film thickness of the protective layer can be detected in a state where the surface of the photoreceptor 1 is not covered with toner. It has become.

As shown in FIG. 3, this film thickness detector 5 consists of a probe 11, an induction coil 12, and a current detector 13, and one end of the induction coil 12 and one end of the current detector 13 are connected to an AC power source 14. are doing.

Here, as the thickness of the protective layer 1b covering the photosensitive layer 1a becomes thinner depending on the frequency of use of the photoreceptor 1, the distance between the protective layer 1b and the probe 11 gradually increases. The number of magnetic fluxes passing through the induction coil 12 also decreases, and the current flowing through the induction coil 12, that is, the current detector 1
The current I detected by 3 also becomes smaller. FIG. 4 shows the relationship between the thickness D of the protective layer 1b and the current I.

The current detector 13 outputs an analog value (voltage) corresponding to the magnitude of the current I to the control circuit 6. This analog value similarly decreases as the current I decreases, so it decreases as the protective layer 1b of the photoreceptor 1 becomes thinner.

The control circuit 6 shown in FIG. 2 controls the entire copying machine in an integrated manner, and as shown in FIG.
and a microcomputer (hereinafter abbreviated as "CPU") 23. The A/D converter 21 receives the output of the film thickness detector 5, that is, the output of the current detector 13 (analog value).
is converted into a digital value and inputted to the CPU 23 via the I/O port 22.

[0016] The CPU 23 is a microprocessor, RO
A microcomputer consisting of M, RAM, non-volatile memory, etc., converts the output of the film thickness detector 5 with the A/D converter 21 when the photoreceptor 1 is not in use (for example, immediately after replacing the photoreceptor). is input to measure the film thickness of the protective layer 1b of the photoreceptor 1, and the measured value is stored in the internal non-volatile memory as a set value, and the developing device is activated by the high voltage power supply 7 during copying according to the set value. The developing bias to be applied to the developing roller 3a in the developing roller 3 is set.

Further, after a predetermined period of time has elapsed since the time of measuring the film thickness of the photoreceptor 1 when it is not in use, or when the power is turned on by turning on the main switch of the copying machine, or when the number of copies reaches a predetermined number, as shown in FIG. Execute processing like this.

That is, the thickness of the protective layer 1b of the photoreceptor 1 is measured in the same manner as when the photoreceptor 1 is not in use, and the measured value is compared with the setting value stored in the nonvolatile memory.
Determine the degree of deterioration. If the respective values are the same, the developing bias to be applied to the developing roller 3a is fixed,
Otherwise, the developing bias is varied according to the data shown in FIG. 6 (previously stored in the ROM).

In other words, as described above, as the thickness of the protective layer 1b of the photoreceptor 1 becomes thinner, the output of the film thickness detector 5 decreases in proportion to the thickness, and as shown in FIG. The developing bias may be increased to prevent this from happening.

Although an embodiment in which the present invention is applied to a copying machine has been described above, the present invention is not limited to this, and can be applied to an optical printer such as a laser printer or an electrophotographic image forming apparatus such as a facsimile machine. .

[0021]

As explained above, according to the present invention, it is possible to accurately grasp the degree of deterioration in the film thickness of the coating layer (protective layer) of the overcoat drum (photoreceptor having a protective layer).
By changing the developing bias according to the degree of deterioration, it is possible to prevent notch displacement and background staining of the image.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram showing processing according to the present invention performed by a CPU 23 in FIG. 5;

FIG. 2 is a schematic configuration diagram showing an image forming section of a copying machine embodying the present invention and a control system related to film thickness detection of a photoreceptor.

3 is a circuit diagram showing a configuration example of the film thickness detector 5 of FIG. 2. FIG.

4 is a diagram showing the relationship between the thickness D of the protective layer of the photoreceptor 1 and the current I in FIGS. 2 and 3. FIG.

FIG. 5 is a block configuration diagram showing details of a control system related to film thickness detection in this embodiment.

FIG. 6 is a diagram for explaining the operation of this embodiment.

[Explanation of symbols]

1 Photoreceptor 3 Developing device
3a Developing roller 5 Film thickness detector 6 Control circuit
7 High voltage power supply 11 Probe 12 Induction coil 13 Current detector 14 AC power supply 21 A/D converter 22 I/O port

Claims (3)

[Claims] 1. A film thickness measuring means for measuring the film thickness of the coating layer of the overcoat drum when not in use and after a predetermined period of time has elapsed, and comparing each measurement result by the film thickness measuring means to determine the thickness of the overcoat drum. 1. An electrophotographic image forming apparatus comprising: comparison means for determining a degree of deterioration. 2. A film thickness measuring means for measuring the film thickness of the coating layer of the overcoat drum when not in use, when power is turned on by a main switch, or when the number of images formed reaches a predetermined number; 1. An electrophotographic image forming apparatus comprising: comparing means for comparing each measurement result to determine the degree of deterioration of the overcoat drum. 3. The electrophotographic image forming apparatus according to claim 1 or 2, further comprising a developing bias setting means for setting a developing bias during image formation according to the comparison result by the comparing means. An electrophotographic image forming device.