JPH0812532B2 - Copier - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic copying machine, and more particularly to a copying machine provided with a cleaning device for keeping a surface of a photoconductor good.

“Prior Art” Electrostatic copying machines project an image by applying an electric charge to the surface of a cylindrical or belt-shaped photoreceptor, form an electrostatic latent image, and use this to create an image. There is.

FIG. 4 shows a general structure of such a copying machine which has been conventionally used. In this copying machine, a document table 2 is provided above the main body 1. A scanner unit 3 is arranged below the document table 2. The scanner unit 3 includes a fluorescent lamp 4 and first to third mirrors 5.
7 to 7, a lens 8 and a fourth mirror 9. The fluorescent lamp 4 and the first mirror 5 are integrated, and are movable in both directions A and B in the figure. The second and third mirrors 6 and 7 are also integrated and are movable in both directions of arrows A and B.

In this copying machine, a charging device (charge corotron) 12 for applying an electric charge is arranged around a cylindrical photosensitive drum 11. When a high voltage is applied to the charger 12 while the photoconductor drum 11 is rotating in the arrow direction (clockwise direction), electric charges are uniformly charged on the drum surface. In this state, the light beam emitted from the fluorescent lamp 4 is reflected on the original surface (not shown), passes through the fourth mirror 9 and the like, and is exposed at the exposed portion 13 on the drum surface.
When the charge reaches, the charge in that portion disappears and an electrostatic latent image is formed. Since the photosensitive drum 11 is rotating in the direction of the arrow, the drum surface on which the electrostatic latent image is formed passes through the developing device 14. At this time, the electrostatic latent image is developed with toner to form a toner image. When this toner image passes near the transfer device (transfer corotron) 15,
It is transferred to copy paper 17 sent from 16. The copy sheet after the transfer of the toner image is conveyed by the conveying device 18 and reaches a fixing device (heat roll) 19 where it is fixed. The copy paper after fixing is discharged to the discharge tray 21 outside the machine.

On the other hand, the toner that has not been transferred to the copy paper 17 remains on the surface of the drum that has passed the vicinity of the transfer device 15.
Therefore, the photoconductor drum 11 is cleaned by the cleaning device 22. The surface of the drum after cleaning is charged again by the charger 12 to prepare for forming an electrostatic latent image.

“Problems to be Solved by the Invention” As described above, the photoconductor on which the electrostatic latent image is formed can be repeatedly used by cleaning. However, when the photoconductor is repeatedly used for a long period of time, various substances adhere to and deposit on the surface of the photoconductor. Examples of such materials include paper powder and talc caused by copy paper, discharge products by corotron, for example, nitrogen oxide NO _X , and water H ₂ O impregnated therein.

When such a substance adheres to and accumulates on the photoconductor, the charging characteristics of the photoconductor deteriorate, causing "bleeding" in the toner image and, in some cases, "missing" of the image.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a copying machine which can keep a photoreceptor surface in a good condition for a long period of time and always obtain a good quality toner image.

"Means for Solving Problems" In the present invention, (i) an irradiation source for irradiating a document with light, and (ii) a photosensitive for forming an electrostatic latent image by the light emitted by the irradiation source. Body, (iii) light amount varying means for changing the amount of light reaching the photoconductor from the irradiation source, (iv) a developing device for developing an electrostatic latent image, and (v) toner remaining on the photoconductor A cleaning device for cleaning the photoconductor, and (vi) controlling the light quantity varying means to irradiate the photoconductor with the light quantity of a predetermined bell that forms a constant toner layer after development. The copying machine is provided with a photosensitive member cleaning control unit that operates in parallel for a long predetermined time.

That is, in the copying machine of the present invention, formation of an electrostatic latent image by irradiation with a predetermined amount of light and development of the electrostatic latent image,
By the cleaning control means for cleaning the toner layer formed on the photoconductor by the development for a sufficiently long time, the deposits that deteriorate the charging characteristics of the photoconductor are removed together with the toner.

Here, the photoconductor cleaning control means operates the development device and the cleaning device when a copying work start instruction is issued in a state where the control of the development device and the cleaning device by the photoconductor cleaning control means is not performed for a certain period of time or more. The photosensitive member cleaning may be performed by operating for a sufficiently long predetermined time. Further, the cleaning of the surface of the photoconductor may be started at a designated time or date. At the time of cleaning, it is also effective to raise the temperature of the surface of the photoconductor and lower the humidity.

According to the present invention, cleaning work is performed in a specific state of a copying machine during a time period that is not directly related to copying work, and efficient removal of adhering substances is realized.

[Examples] The present invention will be described in detail below with reference to Examples.

FIG. 1 shows an essential part of an electric circuit of a copying machine according to an embodiment of the present invention. The copying machine of this embodiment has basically the same mechanism as the copying machine shown in FIG. 4, and is equipped with a CPU (central processing unit) 31. CPU31
Is connected to various parts in the main body of the copying machine by a bus 32 such as a data bus to perform desired control. Of these, the ROM 33 is a read-only memory that stores a control procedure to be described later. RAM34 is a random access memory for temporarily storing various data.
It is a memory. The timer 35 is a circuit for measuring the time during which the copying machine is not performing a copying operation and determining the length of time during which a cleaning operation, which will be described later, is performed. The solenoid 36 is a component for operating the light amount diaphragm 37.
The light amount diaphragm 37 is arranged, for example, in the vicinity of the lens 8 shown in FIG. 4, and is for limiting the light amount reaching the photosensitive drum 11 to a predetermined value.

The lamp driver 38 is for turning on the fluorescent lamp 4 shown in FIG. The start button 39 is a switch arranged on the console panel (not shown),
In a normal copying machine, when this is pressed, copying work is started immediately. Other components are also connected to the bus 32, but they are not shown because they are not important for the description of this embodiment.

FIG. 2 is for explaining the cleaning operation of this copying machine. The CPU 31 monitors the length of time T during which the copying operation is not performed by the timer 35, and until it reaches the arbitrarily set time t from 1 hour 1 minute to 8 hours (step; N ), When the start button 39 for starting copy work is pressed (step; Y), normal copy work is started (step).

On the other hand, when the start button 39 is pressed when the length T of the time when the copying operation is not performed becomes the time t or more (step; Y), the CPU 31 causes the solenoid 36 to operate.
When the surface of the platen 2 is white, the amount of light reaching the photosensitive drum 11 is reduced by a desired value from 20% to 70% (step). At this time, the amount of light reaching the photosensitive drum 11 is 1.0 to 1.5 NAcm.

In addition to operating the light quantity diaphragm by exciting the solenoid 36, for example, an optical filter can be inserted in the optical path. Further, if the portion of the document table 2 illuminated by the fluorescent lamp 4 in this cleaning mode is a special portion having a predetermined density, it reaches the photoconductor drum 11 without particularly reducing the passage of light. The amount of light decreases. Therefore, in such a case, it is not necessary to use the light quantity diaphragm 37 or the optical filter. Similarly, by controlling the voltage applied to the fluorescent lamp 4, it is possible to reduce the amount of light reaching the photoconductor drum 11 to a desired value.

When the solenoid 36 is excited, the CPU 31 thereafter controls the lamp driver 38 and the like to set these parts in the same state as the copying operation (step). However, in this case, when the copy paper 17 is sent out from the supply tray 16,
The fixing device 19 is not operated. In this state, the cleaning device 22 and the like are operating, and the photoconductor drum 11 is being cleaned. At this time, the developing potential of the developing device 14 is
It is desirable that it is set to about 250V-700V. Also, the cleaning time (step) requires about 60 seconds to 10 minutes.

When the cleaning time is over (Y), the CPU 31 demagnetizes the solenoid 36 and restores the light amount. Also, timer 35
Clear the length of time T to be measured to zero. Then, the control such as turning off the fluorescent lamp 4 and stopping the driving of the motor is performed in the same manner as when the copying operation is stopped (step). After this, CPU31
Will start the normal copying operation (step).

That is, in the case of this embodiment, when the copying operation is started after the copying is not performed for a long time, the photosensitive drum is first
11 will be cleaned and then the copying operation will be started. Therefore, it is possible to always obtain a good image even when copying is not performed for a long time.

"Modification" FIG. 3 shows a cleaning operation of a copying machine as a modification of the present invention. In this modified example, as a result of the timer measuring the time, when the time T is equal to or longer than the time t (step), the above-mentioned cleaning work is performed on condition that the copy work is not being carried out at that time (step; N). Is performed (step). That is, when the normal copying work is performed, the copying work is preferentially performed, and then the cleaning work of the present invention is performed. When this cleaning work is completed, the timer that measured the time T is cleared and all the work is completed.

This modified example has an advantage that when the start button is pressed to perform the copying operation, the copying can be performed quickly at any time.

It should be noted that although the photoconductor is described as the photoconductor drum in the embodiments and the modified examples, the present invention can be similarly applied to a photoconductor belt. Further, although the temperature inside the copying machine was not mentioned in the description of the embodiment, if the temperature near the surface of the photoconductor is raised by a heater or the like for cleaning, the humidity of this portion is reduced and the cleaning effect is enhanced. You can Therefore, the heater or the like may be energized as needed during cleaning.

Further, in the embodiments and the modified examples, the timing of cleaning is determined by using the timer, but the cleaning may be performed by using the clock mechanism, for example, at 12:00 midnight or on Sunday. This also makes it possible to avoid the conflict between cleaning and copying.

[Advantages of the Invention] As described above, according to the present invention, by forming a uniform toner layer on a photoconductor and performing the operation of removing the toner layer in parallel for a sufficiently long time, the photoconductor is Since the cleaning is performed, it is possible to efficiently and sufficiently remove the adhered substances such as paper dust, and it is possible to favorably reproduce the halftone.

[Brief description of drawings]

FIG. 1 is a block diagram showing an essential part of an electric circuit of a copying machine according to an embodiment of the present invention, FIG. 2 is a flow chart showing an essential part of the operation of the copying machine according to this embodiment, and FIG. FIG. 4 is a flow chart showing an essential part of the operation of a copying machine as a modification, and FIG. 4 is a schematic configuration diagram showing an example of a conventional copying machine. 4 ... Fluorescent lamp, 11 ... Photosensitive drum, 14 ... Developing device, 22 ... Cleaning device, 31 ... CPU, 33 ... ROM, 35 ... Timer, 36 ... Solenoid, 37 ... Light intensity Aperture, 38 ... Lamp driver.

Claims (4)

[Claims] 1. An irradiation source for irradiating a document with light, a photoconductor that forms an electrostatic latent image by the light emitted by the irradiation source, and a light amount that reaches the photoconductor from the irradiation source is changed. Light amount changing means, a developing device for developing the electrostatic latent image, a cleaning device for cleaning the toner remaining on the photoconductor, and a constant toner layer is formed after development by controlling the light amount changing means. And a photoconductor cleaning control means for operating the developing device and the cleaning device in parallel for a sufficiently long predetermined time so as to irradiate the photoconductor with a predetermined amount of light. Machine. 2. The photoconductor cleaning control means, when the start of copy work is instructed in a state where the control of the photoconductor cleaning control means by the photoconductor cleaning control means is not performed for a certain period of time or more, the developing device is controlled. 2. The copying machine according to claim 1, wherein the cleaning device is operated for a sufficiently long predetermined time. 3. A copying machine according to claim 1, wherein the photoconductor cleaning control means starts cleaning of the photoconductor surface at a designated time or date and time. 4. The photosensitive member cleaning control means heats the surface of the photosensitive member when cleaning the photosensitive member to lower the humidity of the portion.
Copier described in item.