JPS6394292A - Copying machine - Google Patents

Abstract

PURPOSE:To hold the surface of a photosensitive body at a proper state for a long period and to obtain a toner image of always high quality by executing cleaning work under the state that the quantity of light reaching the surface of the photosensitive body is changed from that of copying. CONSTITUTION:If a start button 39 is depressed when the time length suspending copying work exceeds a prescribed time, a CPU 31 excites a solenoid 36, and when the surface of an original platen 2 is white, the quantity of light reaching the photosensitive drum 11 is reduced by a required value within a range >=20% and <=70%. After exciting the solenoid 36, the CPU 31 controls a lamp driver 38 or the like, sets these parts to the same state as copying work and then drives a cleaning device 22 or the like to clean the drum 11. Consequently, substances generated by discharge based upon paper powder, tale and corotron can be efficiently removed and a toner image with high quality can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an electrostatic copying machine, and more particularly to a copying machine equipped with a cleaning device for keeping the surface of a photoreceptor in good condition.

``Prior Art'' ゛An electrostatic copying machine projects an image after applying an electric charge to the surface of a cylindrical or belt-shaped photoreceptor to form an electrostatic latent image, which is used to create an image. ing.

FIG. 4 shows the general configuration of such a conventionally used copying machine. In this copying machine, a document table 2 is provided at the top of a main body 1. A scanner unit 3 is arranged below the document table 2 . The scanner unit 3 includes a fluorescent lamp 4, first to third mirrors 5 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 of arrows A and B in the figure. The second and third mirrors 6.7 are also integrated and are movable in both directions of arrows A and 8.

In this copying machine, a charger (charge corotron) 12 is arranged around a cylindrical photoreceptor drum 11 for applying electric charge. When a high voltage is applied to the charger 12 while the photosensitive drum 11 is rotating in the direction of the arrow (clockwise), the drum surface is uniformly charged. In this state, the light beam emitted from the fluorescent lamp 4 is reflected on the surface of the document (not shown), passes through the fourth mirror 9, etc., and reaches the exposed area 13 on the drum surface, whereupon the electric charge on that area disappears and the electrostatic A 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 formed with toner. The toner image is developed and a toner image is created.When this toner image passes near a transfer device (transfer corotron) 15, it is transferred to a copy sheet 17 fed from a supply tray 16.
transcribed into. The copy paper after the toner image has been transferred is transported by a transport device 18 and reaches a fixing device (heat roll) 19, where it is fixed. After the fixing, the copy paper is discharged to the discharge tray 21 outside the machine.

On the other hand, toner that has not been transferred to the copy paper 17 remains on the surface of the drum that has passed near the transfer device 15. Therefore, the photosensitive drum 11 is removed by the cleaning device 22.
cleaned by. After cleaning, the drum surface is charged again by the charger 12, and preparations are made for forming an electrostatic latent image.

"Problems to be Solved by the Invention" As described above, the photoreceptor on which an electrostatic latent image is formed can be used repeatedly by cleaning. However, when a photoreceptor is repeatedly used for a long period of time, various substances adhere to and accumulate on its surface. Examples of such things include paper powder and talc caused by copy paper, discharge products from corotron, such as nitrogen oxides NOx, and water H20 impregnated in these.
etc. can be mentioned.

When such substances adhere or accumulate on the photoreceptor, its charging characteristics deteriorate, causing "bleeding" in the toner image or, in some cases, "missing" of the image.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a copying machine that can maintain the surface of a photoreceptor in good condition for a long period of time and can always obtain high-quality toner images.

"Means for Solving the Problems" The present invention includes (i) an irradiation source for irradiating light onto a document, and (ii) formation of an electrostatic latent image by the light irradiated by the irradiation source. (iii) a light amount variable means that changes the amount of light reaching the photoreceptor from the irradiation source; (IV) a developing device that develops the electrostatic latent image;
(v) a cleaning device that cleans toner remaining on the photoconductor; and (vi) a photosensitive device that operates the cleaning device for a predetermined period of time with the light amount of the irradiation source set to a pair other than during copying operation by the light amount variable means described above. The copying machine is provided with body cleaning control means. That is, cleaning is performed while the amount of light from the irradiation source is limited by the photoreceptor cleaning control means to remove deposits on the photoreceptor.

Here, when the photoconductor cleaning control means is instructed to start a copying operation when an electrostatic latent image has not been formed on the photoconductor for a certain period of time or more, the photoconductor cleaning control means first cleans the surface of the photoconductor and then starts the copying operation. It may be something like starting. Alternatively, cleaning of the photoreceptor surface may be started at a designated time or date.

Note that during cleaning, it is also effective to raise the temperature of the surface of the photoreceptor and lower the humidity.

According to the present invention, cleaning work is performed with the copying machine in a specific state during a time period that is not directly related to copying work, thereby achieving efficient removal of deposits.

"Example" The present invention will be described in detail below with reference to Examples.

FIG. 1 shows the main part of the electric circuit of a copying machine in one embodiment of the present invention. The copying machine of this embodiment has a fourth
It has basically the same mechanism as the copying machine shown in the figure.
It is also equipped with a CPU (central processing unit) 31. C
The PU 31 is connected to various parts within the main body of the copying machine via a bus 32 such as a data bus, and is configured to perform desired control. Of these, the ROM 33 is a read-only memory that stores control procedures as described later. Further, the RAM 34 is a random access memory for temporarily storing various data. The timer 35 is a circuit for measuring the time during which the copying machine is not performing a copying operation and for 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 aperture 37. The light amount diaphragm 37 is, for example, a fourth
It is arranged near the lens 8 shown in the figure, and is used to limit the amount of light reaching the photosensitive drum 11 to a predetermined value.

The lamp driver 38 is for lighting the fluorescent lamp 4 shown in FIG. Start Pokun 39 is
This is a switch located on a console panel (not shown), and in a normal copying machine, when pressed, the copying operation starts immediately. Although other parts are also connected to the bus 32, they are not important for the explanation of this embodiment, so illustration of these parts is omitted.

FIG. 2 is for explaining the cleaning operation of this copying machine. The CPU 31 monitors the length of time T during which no copying work is being performed using the timer 35, and waits until this reaches an arbitrarily set time t between 1 hour and 1 minute to 8 hours. N), when the start button 39 for starting the copying operation is pressed (step ■; Y), the normal copying operation is started (
Step ■).

On the other hand, if the start button 39 is pressed when the length of time T during which no copying work is performed exceeds the time, the CPU 31 excites the solenoid 36, If the surface of the original platen 2 is white, the amount of light reaching the photosensitive drum 11 is reduced by a desired shift from 20% to 70% (step (2)).

At this time, the amount of light reaching the photoreceptor drum 11 is 1.0
~1.5NAcm.

In addition to operating the light aperture by excitation of the solenoid 36, it is also possible to insert an optical filter into the optical path, for example. Furthermore, if the part of the document table 2 that is illuminated by the fluorescent lamp 4 in this cleaning mode is a special part with a predetermined density, the light reaches the photoreceptor 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 aperture 37 or an optical filter. Similarly, by controlling the voltage applied to the fluorescent lamp 4, it is possible to reduce the amount of advance that reaches the photoreceptor drum 11 to a desired value.

After the solenoid 36 is energized, the CP[j 31 then controls the lamp driver 38 and the like to set these parts in the same state as in the copying operation (step 2). However, in this case, the feeding of the copy paper 17 from the supply tray 16 and the operation of the fixing device 19 are not performed. In this state, the cleaning device 22 and the like are operating, and the photosensitive drum 11 is being cleaned. At this time, it is desirable that the developing potential of the developing device 14 is set to about 250 to 700 ■, and the cleaning time (step ■) is required to be about 60 seconds to 10 minutes.

When the cleaning time ends (Y), CP[j31 demagnetizes the solenoid 36 and returns the light intensity to the original level. Also, the length of time T measured by the timer 35 is cleared to zero. Then, in the same way as when the copying operation is stopped, controls such as turning off the fluorescent lamp 4 and stopping the driving of the motor are performed (step (2)). After this, the CPU 31 starts normal copying work (step 2).

That is, in the case of this embodiment, at the start of copying work after no copying has been performed for a long time, the photosensitive drum 1 is
1 and then start the copying operation. Therefore, even if no copying is performed for a long time, good images can always be obtained.

"Modified Example" FIG. 3 shows a cleaning operation for a copying machine as a modified example of the present invention. In this modified example, as a result of time measurement by the timer, if the time T exceeds the time (step ■), the above-mentioned Cleaning work is performed (step ■). That is, if a normal copying operation is being performed, it is given priority, and then the cleaning operation of the present invention is performed. When this cleaning work is completed, the timer that measures the time T is cleared, and all the work is completed.

This modification has the advantage that when the start button is pressed to perform a copy operation, the copy can be performed quickly at any time.

In the embodiments and modifications, the photoreceptor is described as a photoreceptor drum, but the present invention can be similarly applied to a photoreceptor belt. Furthermore, although the temperature inside the copying machine was not mentioned in the explanation of the embodiment, if cleaning is performed by increasing the temperature near the surface of the photoreceptor using a heater, etc., the humidity in this area will decrease, increasing the effectiveness of cleaning. Can be done. Therefore, when cleaning is being performed, a heater or the like may be energized as necessary.

Further, in the embodiment and the modified example, a timer is used to determine the timing of cleaning, but cleaning may be performed using a clock mechanism, for example, at 12 o'clock in the middle of the night, or cleaning may be performed once every Sunday. By doing so, it is also possible to avoid conflict between cleaning and copying operations.

"Effects of the Invention" As explained above, according to the present invention, cleaning work is performed with the light 1 reaching the photoconductor being changed from that during copying, so that deposits such as paper dust can be efficiently removed. This makes it possible to effectively reproduce halftones and the like.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main parts of the electric circuit of a copying machine according to an embodiment of the present invention, FIG. 2 is a flowchart showing the main parts of the operation of the copying machine according to this embodiment, and FIG. FIG. 4 is a flowchart showing a main part of the operation of a copying machine as a modification of the above, 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 maximum aperture, 38...Lamp driver. Applicant: Fuji Xerox Co., Ltd. Agent

Claims (1)

[Scope of Claims] 1. An irradiation source for irradiating a document with light, a photoreceptor that forms an electrostatic latent image with the light irradiated by the irradiation source, and a photoreceptor that reaches the photoreceptor from the irradiation source. A light amount variable means for changing the light amount, a developing device for developing the electrostatic latent image, a cleaning device for cleaning toner remaining on the photoreceptor, and a light amount variable means for controlling the light amount of the irradiation source except during copying operation. a photoconductor cleaning control means for operating the cleaning device for a predetermined period of time with the value set to . 2. When the photoconductor cleaning control means is instructed to start a copying operation when an electrostatic latent image has not been formed on the photoconductor for a certain period of time or more, the photoconductor cleaning control means first cleans the surface of the photoconductor and then starts the copying operation. The copying machine according to claim 1, characterized in that the copying machine starts the copying machine. 3. The copying machine according to claim 1, wherein the photoconductor cleaning control means starts cleaning the photoconductor surface at a specified time or date. 4. The copying machine according to claim 1, wherein the photoconductor cleaning control means heats the surface of the photoconductor to reduce the humidity of that area when cleaning the photoconductor.