JP2000147953A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately set the frequency of filming removing operation according to filming forming speed. SOLUTION: Electrostatic latent image of a reference image is formed on an image carrier, and its potential V (initial potential of V0) is measured (step S2). Then, the image is outputted (step S4), and a sheet number counter is incremented every time the image of one sheet is outputted (N=N+1) (step S5). When the value N of the sheet number counter reaches N1 (step S6), the electrostatic latent image of the reference image is reformed on the image carrier, and its potential V1 is measured (step S7). Amount 'V1-V0' is divided by the number N1 of image formed sheets, so as to obtain potential increase amount dV per one image formed sheet (step S8). Then, set number of sheets (n) (the number of sheets through which how many sheets of image-forming should be performed before performing filming removing processing) is changed to a value corresponding to a dV value set in a prescribed table (step S10).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art In a conventional image forming apparatus, the timing of an operation for removing filming is set in the image forming apparatus in advance in anticipation of the number of images to be formed which will affect an image due to filming. On the condition that the number of image formations has been reached, a filming removal operation is performed by manually turning on a main switch again or pressing an operation input key (JP-A-2-191980, JP-A-6-30).
No. 1316).

[0003]

The reason why filming is formed on the photoreceptor is due to the mechanical reason of the image forming apparatus (developer carrier, NOx generated by corona discharge) and the usage environment. Conditions (type of transfer paper such as paper type and additives contained in paper, temperature, operation DUTY, etc.)
The contribution of the latter use environment condition is large. The frequency of performing the filming removal operation (how many sheets of transfer paper or the like are to be formed each time image formation is performed) is empirically determined based on a standard operation environment. .

[0004] Therefore, if the frequency is uniform, there is a problem that the effect of filming appears on an image before the time for performing the filming removal operation. Conversely, if the filming removal operation is performed long before the influence of the filming appears on the image, the number of filming removal operations increases more than necessary, and there is a problem that productivity is reduced. .

It is an object of the present invention to provide an image forming apparatus capable of appropriately setting the frequency of the filming removal operation according to the filming formation speed.

[0006]

According to a first aspect of the present invention, there is provided an image carrier, an optical writing device for forming an electrostatic latent image on the image carrier, and a developing device for developing the electrostatic latent image. In an electrophotographic image forming apparatus including a developing device for converting a toner image onto a sheet and a transfer device for transferring the toner image onto a sheet, a filming substance formed on the image carrier is scraped off. A filming removing device, a sensor for measuring a surface potential of a reference image on the image carrier, a counter for counting the number of sheets on which an image is formed, and periodically operating the filming removing device. Control means for reducing the operation frequency in accordance with the amount of increase in the surface potential per sheet on which an image is formed, obtained by dividing the surface potential by the counted number of sheets. Being The image forming apparatus according to claim.

Therefore, the filming speed can be determined from the magnitude of the surface potential increase per sheet on which an image is formed, and the surface potential increase per sheet on which an image is formed can be determined. By reducing the frequency of operating the filming removing device as the size is larger, the frequency of the filming removing operation can be appropriately set according to the filming forming speed.

According to a second aspect of the present invention, in the first aspect of the present invention, the operation frequency of the filming removing device has a lower limit.

[0009] Therefore, abnormally fast filming is formed under severe operating environment conditions (such as paper type and additives contained in paper, transfer paper type, temperature, operation duty, etc.) which are out of tolerance of the image forming apparatus. Accordingly, it is possible to prevent the time required for the filming removing operation from being excessively long and the productivity from being lowered.

According to a third aspect of the present invention, in the second aspect of the present invention, the control means stops the image forming operation of the image forming apparatus when the operation frequency of the filming removing device falls below the lower limit. It is characterized by.

Accordingly, the formation of an abnormal image under severe operating environment conditions (such as the type of paper, additives contained in paper, and the like, the temperature of the transfer paper, the operation duty, etc.) which are not allowed by the image forming apparatus is prevented. be able to.

[0012]

FIG. 1 is a conceptual diagram showing a schematic configuration of an electrophotographic image forming apparatus 1 according to an embodiment of the present invention. In FIG. 1, reference numeral 2 denotes a belt-shaped image carrier (photoreceptor). The image carrier 2 is wound around a drive roller 3 and another appropriate number of support rollers 3a. The vehicle is driven to travel in the A direction. The image carrier 2 moving in this manner is uniformly charged to a predetermined polarity by the charger 4 and subsequently exposed by the imaging optical system 5 constituting the optical writing device to form an electrostatic latent image. hand,
The electrostatic latent image is developed when the image carrier 2 passes through the developing device 6, and is visualized as a toner image.

On the other hand, transfer paper, which is an example of a sheet, is fed from the paper supply unit 7 to the image carrier 2, and the toner image on the image carrier 2 is transferred onto the transfer paper by the discharging action of the transfer device 8. Is done. Next, the transfer paper is separated from the image carrier 2 while receiving the discharging action of the separation device 9, and the transfer paper after separation is transported to the fixing device 11 by the transport belt 10, and the toner image is fixed on the transfer paper. After that, it is discharged outside the machine. The toner remaining on the image carrier 2 is cleaned and removed by the cleaning device 12.

As the series of image forming operations described above is repeated, a filming substance is formed on the image carrier 2 (for details of the cause of the filming substance, see Japanese Patent Application Laid-Open No. Hei 6-301316). See). It is difficult to remove this filming substance by the cleaning device 12. Therefore, the image forming apparatus 1 is provided with a brush roller 13 constituting a filming removing device.
The brush roller 13 includes a brush 14 made of conductive metal fibers woven into a base cloth, and a roller-shaped core material 15 around which the base cloth is wound. The brush roller 13 is supported so as to be able to freely contact and separate from the image carrier 2, and is driven to rotate counterclockwise in FIG. A backup roller 16 is provided at a position facing the brush roller 13 with the image carrier 2 interposed therebetween.

A sensor for measuring the potential on the image carrier 2 is provided at a position upstream of the brush roller 13 of the movement of the image carrier 2 and downstream of the position where the electrostatic latent image is formed by the imaging optical system 5. A surface voltmeter 17 is provided.

When the filming is formed on the image carrier 2, the surface potential of the image carrier 2 is hardly attenuated by exposure by the image forming optical system 5, and the amount of attenuation is further increased as the filming lamination thickness increases. Decrease (see FIG. 2). As a result, the surface potential on the image carrier 2 after the exposure is increased (see FIG. 3), and the image after transfer is significantly deteriorated on the transfer paper (in a normal document or the like, white without characters or pictures is present). The part turns black.).

Therefore, an electrostatic latent image serving as a certain reference image is formed on the image carrier 2, and a change with time of the surface potential is sampled and compared to determine the filming state. . In the case of an analog copying machine or the like, the reference image is formed on a portion exposed in a non-image area on the transfer paper.
A member having a high light reflectance (for example, a member painted white or a blank sheet of paper) may be provided so that the surface potential can be sufficiently attenuated. In the case of a digital copying machine or the like, the output of the optical writing device may be fixed at a pattern width that is a non-image area. When an electrostatic latent image (pattern) serving as a reference image is formed on the image carrier 2, the image carrier 2 is moving.
7, the surface potential is measured by the surface voltmeter 17.

In the embodiment of the present invention, control is performed to detect the degree of filming and to change the frequency of performing the filming removal operation according to the filming speed in this manner. . Hereinafter, such control will be described.

FIG. 4 is a block diagram showing the electrical connection of the control system of the image forming apparatus 1 according to the present invention. The control system includes a CPU 21 which stores a ROM 21 storing various control programs and fixed data, a RAM 22 which stores data in a rewritable manner and serves as a work area of the CPU 20, an A / D converter 23, and an I / O interface of an input / output interface. The port 24 is connected with the bus 25. The surface potential meter 17 is connected to the A / D converter 23. Also, I
The / O port 24 has a motor 2 for driving the driving roller 3.
6 and an actuator such as a motor 27 for driving the brush roller 13. The CPU 20 is also connected to a display input device 28 including a display device such as an LED and a liquid crystal panel, and an input device such as a key switch and a matrix touch switch.

FIG. 5 is a flowchart for explaining a process for controlling the frequency of performing the filming removal operation. In an embodiment of the present invention, the control means of the present invention comprises:
This is realized in the processing shown in this flowchart.
First, an operation interval (set number) n of filming removal is set to an initial value, ie, how many sheets of transfer paper are to be subjected to the filming removal operation each time an image is formed (step S1).
After the number of image formation exceeds the set number n, the power switch of the image forming apparatus 1 is turned on and off,
Alternatively, the number of image formation is set to the set number n
Is displayed, and after the manual operation from the input device is performed, the filming removal operation is performed.

Next, an electrostatic latent image of the reference image is formed on the image carrier 2 and its potential V (initial potential: V0) is measured (step S2). The number counter is reset (N = 0) (step S3).

Then, an image is output (step S).
4) Each time one image is output, the number counter is incremented (N = N + 1) (step S5), and when the value N of the number counter reaches N1 (step S6), the electrostatic latent image of the reference image is again obtained. Is formed on the image carrier 2 and its potential V1 is measured (step S7). Then, the increase “V1−V0” of the potential V1 from the initial potential V0 is divided by the number N1 of image formations during this period to obtain a potential increase dV per image formation (step S8).

As is apparent from FIG. 3, the surface potential on the image carrier 2 and the amount of filming are substantially proportional to each other.
The same applies to the amount of filming and the number of image outputs. Therefore, under the same conditions, the surface potential on the image carrier 2 and the number of output images are also approximated in a proportional relationship. Then, the filming formation speed can be determined from the dV value.

The ROM 21 stores a table as shown in FIG. 6 in which the dV value and the set number n are associated with each other. If the dV value does not exceed the predetermined upper limit (N in step S9), The set number n is changed to a value corresponding to the dV value obtained in step S8 (step S10). Hereinafter, the processing of step S3 and subsequent steps is repeated thereafter.

For example, in the example of FIG.
~ DV4, the set number n is set to 5000
Set to sheets. Therefore, in this case, the image output is 5000
The motor 27 is driven each time a sheet is printed, and the filming removal processing is performed by the brush roller 13.

Therefore, the frequency of performing the filming removal operation can be appropriately set according to the filming formation speed.

By setting the value of the number N1 of image formation small, it is possible to perform fine control corresponding to environmental changes.

The image forming apparatus 1 has severe image forming operation conditions (a large amount of transfer paper additive, high temperature, DUTY
If the dV value becomes too large and the operation interval of the filming removing operation becomes excessively short, the time required for the filming removing operation becomes excessively long as compared with the time required for the image forming operation. Productivity decreases. Therefore, a predetermined upper limit value (lower limit value of the set number n) is set for the dV value (step S9) so that the productivity of image formation is not excessively reduced. When the dV value exceeds the upper limit value (below the lower limit value of the set number n), the image forming operation of the image forming apparatus 1 is stopped (step S11), and the abnormal image is not output. Then, the fact that the image forming operation has been stopped is displayed on the display device of the display input device 28 to notify the user (step S12).

For example, in the example of FIG.
When set to V5, the upper limit of the dV value is DV5
Is exceeded, the image forming operation of the image forming apparatus 1 is stopped.

[0030]

According to the first aspect of the present invention, since the filming speed can be determined from the amount of increase in the surface potential per sheet on which an image is formed, the sheet on which the image is formed can be obtained. By setting the frequency of operating the filming removing device to be smaller as the amount of increase in the surface potential per sheet is larger, the frequency of the filming removing operation is appropriately set according to the filming forming speed. Can be.

According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect of the present invention, wherein severe usage environment conditions outside the allowable range of the image forming apparatus (such as the type of transfer paper,
The formation of an abnormally fast filming under temperature, operation DUTY, etc.) can prevent the time required for the filming removing operation from becoming excessively long and lowering the productivity.

According to a third aspect of the present invention, there is provided the image forming apparatus according to the second aspect of the present invention, wherein severe usage environment conditions (for example, the type of transfer paper,
The formation of an abnormal image under temperature, operation DUTY, etc.) can be prevented.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the amount of attenuation of the surface potential on the image carrier and the amount of filming lamination.

FIG. 3 is a graph showing a relationship between a surface potential of an image carrier and a filming lamination amount.

FIG. 4 is a block diagram showing an electrical connection of a control system of the image forming apparatus.

FIG. 5 is a flowchart illustrating a process of controlling the frequency of performing the filming removal operation of the image forming apparatus.

FIG. 6 is a table showing a table used for the control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image carrier 6 Developing device 8 Transfer device 13 Filming removing device 17 Sensor

Continued on the front page F term (reference) 2H027 DA02 DA15 DA44 DA45 DD09 DE05 DE09 EA09 EC06 EC09 EC14 EC20 ED27 EE07 EE08 EF01 EF06 EK03 2H034 AA06 BA02 BA05 BD01 BD04 BD07 FA07 9A001 HH34 KK42

Claims (3)

[Claims] 1. An image carrier, an optical writing device that forms an electrostatic latent image on the image carrier, a developing device that develops the electrostatic latent image into a toner image, An electrophotographic image forming apparatus, comprising: a transfer device that transfers a film onto a sheet; a filming removing device that scrapes off a filming substance formed on the image carrier; and a reference on the image carrier. A sensor for measuring the surface potential of an image, a counter for counting the number of sheets on which an image has been formed, and a filming removing device that is periodically operated. An image forming apparatus comprising: a control unit configured to reduce the amount of increase in the surface potential per sheet on which an image is formed by division. 2. The apparatus according to claim 1, wherein the control means has a lower limit value for the operation frequency of the filming removing device.
An image forming apparatus according to claim 1. 3. The image forming apparatus according to claim 2, wherein the control unit stops the image forming operation of the image forming apparatus when an operation frequency of the filming removing apparatus is lower than a lower limit.