JPH0146872B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic method and apparatus for performing an electrophotographic process in a transfer electrophotographic apparatus. Generally, in the electrophotographic process, a two-layer photoreceptor consisting of a photoconductive layer and a conductive substrate is charged with positive or negative polarity, and then imagewise exposed to form an electrostatic latent image, which is then subjected to a development process to become visible. The method of obtaining an image and the method of forming a three-layer photoreceptor consisting of a transparent insulating layer, a photoconductive layer and a conductive substrate with positive polarity (when the photoconductive layer is an N-type semiconductor) or negative polarity (when the photoconductive layer is a P-type semiconductor) (time) primary charging is performed, followed by image exposure and AC charging or secondary charging with the opposite polarity to the primary charging to eliminate the primary charge and form an electrostatic latent image, and then further expose the entire surface to increase the contrast of the latent image. Then, there is a method of obtaining a visible image through a developing process. Figure 1 illustrates the latter process, where 1 is a photoreceptor that rotates in the direction of the arrow, 2 is a DC corona discharger that performs primary charging, 3 is an optical image, and 4 is a photoreceptor that rotates in the direction of the arrow.
5 performs secondary charging with a corona discharger, 5 is a full-surface exposure source, 6 is a developer that develops a latent image with toner dispersed in the carrier, and 7 is a transfer charger that uses corona discharge with the same polarity as the primary charging. Transfer visible image onto paper 8
A cleaning member 10 removes toner remaining on the photoreceptor in order to use the photoreceptor again after transfer.
It is removed by

However, there is a drawback that the toner removed by the cleaning member 10 accumulates and adheres to the vicinity of the cleaning member, which adversely affects the next image forming process.

In particular, when the developing device used in the electrophotographic process is a liquid type developing device in which toner is dispersed in a carrier liquid, the following drawbacks occur.

That is, when the electrophotographic apparatus is at rest, that is, when the photoreceptor is stopped, developer remains on the cleaning member 10 (cleaning blade) and the surface of the photoreceptor that comes into contact with it, and while the electrophotographic apparatus is at rest, the developer remaining in the electrophotographic apparatus dries and the toner in the liquid dries. . Dry toner is difficult to peel off from the photoreceptor. Therefore, when the photoreceptor is rotated to start the electrophotographic process next time, the image is missing or smeared due to poor cleaning of that area, and good image formation cannot be expected.

As stated in Patent Publication No. 31453 of 1975,
Before starting the process, the above-mentioned defects can be eliminated by supplying developer to the cleaning blade with a pump or by providing a sponge moistened with developer to the cleaning blade to moisten the contact area between the cleaning blade and the photoreceptor. was.

However, the use of pumps, sponges, etc. makes the structure complicated, and the contact area between the blade and the photoreceptor cannot be completely cleaned during rest.

An object of the present invention is to eliminate the above-mentioned drawbacks and to provide an image forming apparatus with less image staining.Another object of the present invention is to provide an image forming apparatus having a process sequence for obtaining high quality images from the beginning. Another object of the present invention is to provide an image formatting apparatus having an improved post-processing step after the process is completed.

That is, the present invention includes a rotating body, a means for forming an electrostatic latent image on the rotating body, a means for developing the electrostatic latent image, and a visible image developed by the developing means is transferred to a transfer material. means for cleaning the rotating body in order to reuse the rotating body; and cleaning means for rotating the rotating body after completion of transfer by the transferring means and activating or inactivating the developing means; and a control means for contacting and non-contact operation, the control means having first and second timer means for performing a counting operation after the start of the post-rotation, and during the post-rotation, the first timer means The cleaning means is operated in a non-contact manner by counting a first predetermined time, and the second timer means then deactivates the developing means by counting a second predetermined time. The present invention provides an image forming apparatus in which the time is set such that the developing means becomes inactive after the surface of the rotary body with which the cleaning means does not come into contact passes through the developing means.

Thereby, it is possible to prevent the surface of the rotating body from becoming dirty after the transfer is completed, and in particular, it is also possible to remove dirt that occurs when the cleaning means is brought into non-contact with the rotating body.

In this embodiment, the cleaning means, which had been separated during the pause, is brought into contact with the surface of the rotating body to which the liquid has been applied before forming a latent image, and the cleaning is carried out after a predetermined period of time after the developing means for applying the liquid is activated. It is what activates the means.

As a result, the surface of the rotating body can be wetted, the friction between the cleaning means and the rotating body can be reduced, and the rotating body can rotate smoothly. Further, the latent image can be formed after the cleaning means has rotated for a predetermined period of time after the cleaning means is activated, thereby making it possible to form the latent image while avoiding partial stains that occur when the cleaning means comes into contact with the cleaning means and before the contact.

Furthermore, after the completion of the transfer (end of process), the cleaning means is operated to remove the residual toner, and then the cleaning means is separated from the rotating body.
Further, after the cleaning means is separated from the rotary body, the rotary body is rotated while the developing means is operated, and the rotary body is cleaned by the developing means.

The effect will be enhanced if the surface of the rotary body is neutralized to a substantially uniform potential so that the rotary body is not developed during this rotation.
As a result, the surface of the rotating body and the cleaning means can be left uncontaminated, and image formation after the apparatus is stopped becomes extremely good.

An embodiment will be described using an electrophotographic copying apparatus that follows the process of FIG.

In Figure 2, liquid developer is applied to the photoreceptor 1 by a roller 9.
This uses a roller developing device that attaches the film to the surface and develops it. 1 to 8 are the same as those in FIG.

1 is a drum-shaped version of the endless three-layer photoreceptor described above. Reference numeral 10 denotes a well-known cleaning blade, which is provided so that its edge comes into contact with the surface of the rotating downward portion of the drum during cleaning.

12 is a lamp for exposing the original; 1
Reference numeral 4 denotes an optical system that forms an original optical image on the surface of the photoreceptor 1.

In the exposure process, the lamp 12 and the optical system 14 are moved forward in the direction of the arrow in synchronization with the rotation of the drum 1, and the original is slit exposed and scanned to form an original image on the surface of the drum 1. Afterward ramp 12,
The optical system 14 moves back and returns to its original position.

Reference numeral 11 denotes a power source for applying a bias voltage to the developing roller to increase the amount of toner adhesion and to remove fog.

In this example, the developing roller 9 is
is brought into contact with the rotating body, and after the contact tip surface passes through the blade area, the cleaning blade 10 is brought into contact with the rotating body 1, and the rotating body 1 is allowed to rotate idly for a predetermined period of time. 1 to form an electrostatic latent image.

After the transfer process is completed, the rotating body 1 is allowed to rotate idly for a predetermined period of time while the cleaning blade 10 and the developing roller 9 are in contact with each other, and then the cleaning blade is brought out of contact with the developing roller after its contacting tip surface has passed through the roller area. Make contactless.

By the way, the states of the developing roller 9 and the cleaning blade 10 are (1) a developing operation state where the roller 9 is in contact with the photoconductor, (2) a state where the roller 9 is not in contact, and (3) a state where the blade 1 is in contact with the photoreceptor.
0 is a cleaning operation state in which the blade 10 is in contact with the photoconductor (4) and a cleaning non-operation state in which the blade 10 is not in contact with the photoreceptor. From these combinations, five combinations are used in this example.

That is, when the power of the copying machine is turned on in step A before copying in FIG.
Also, do not let it come into contact with the photoreceptor 1. Since the blade 10 and the roller 9 are not in contact with each other before the power switch is turned on, it is possible to prevent the toner from locally adhering to the photoreceptor due to liquid turning around due to capillary development of the developing roller 9 and cleaning blade 10.

Note that it is also possible to bring the roller 9 into contact at the same time as the power is turned on.

In step B, cleaning blade 1
0 is not in contact with the photoreceptor 1, but the developing roller 5 is brought into contact with the photoreceptor 1 and the photoreceptor is rotated. This wets the entire surface of the photoreceptor 1
It is possible to reduce the frictional resistance between the cleaning blade 6 and the cleaning blade 6, and to make cleaning easier. At this time, the potential on the photoreceptor is preferably a non-developing potential, but it is practically arbitrary.

In step C, cleaning blade 1
0 is the operating state in which the photoreceptor 1 is in contact. During this step, when the copy button is turned on after the entire circumferential surface has been completely cleaned, copying is performed. After the transfer process is completed, the toner remaining on the peripheral surface of the drum 1 is cleaned before it dries.

Here, cleaning the entire circumferential surface means rotating the rotating body while keeping the blade in contact with the blade for at least the distance from the cleaning area to the latent image forming area (exposure area).

In step D, the cleaning blade 10 is brought out of contact with the photoreceptor 1 while keeping the roller 9 in contact, and the photoreceptor 1 is rotated so that its entire surface is completely cleaned by the developing roller 9 without using the cleaning blade. . At this time, the photoreceptor 1 is kept at a non-developing potential, and if necessary, a bias voltage is applied to the developing roller by the bias power supply 11 to prevent toner from adhering to the photoreceptor, thereby increasing the cleaning effect. The non-developing potential of a photoreceptor is obtained by removing static electricity from its surface using light, AC corona discharge, or the like. It is also possible to selectively apply biases of different polarities or potentials to the developing roller in step C and step D, respectively. In the final step E, both the cleaning blade 10 and the developing roller 9 are removed from the photoreceptor 1.
The rotation of the photoreceptor is stopped. This prevents the toner from drying and accumulating while adhering to the blade developing roller or photoreceptor due to capillary action on the photoreceptor of the cleaning blade or developing roller during the copying pause, as in step A.

An example of a sequence control circuit of a copying machine for obtaining the above steps will be explained with reference to FIG. 4 and its time chart in FIG.

41 to 43 are well-known flip-flops that output a step signal from the Q terminal (in Q, a step signal in the opposite direction) in response to an impulse signal to the S terminal, and are released by an impulse to the res terminal; 44 to 49, respectively. A well-known timer that outputs an input step signal after a delay time _t1 to _t6 and stops outputting when there is no input; 51 is a well-known differentiating circuit for forming impulses; 52 to 55 are for inverting input signals; A well-known inverter circuit, 56 is a well-known OR circuit, 57 to 61 are well-known AND circuits, Sw is a main switch signal for powering on the copying machine, CP is an input signal for starting copying by the copy button, END is a signal indicating that the copying process has ended, RoT is an output signal for rotating the photosensitive drum 1, DEV is a signal for bringing the developing roller 9 into contact with the photosensitive drum, and CLIN is a signal for the blade 10.
signal for contacting the photoconductor, CHAG1,
CHAG2 and CHAG3 are operation signals for the primary charger 2, secondary charger 4, and transfer charger 7, respectively, and LAMP1
is the lighting signal of the lamp 12 for light image exposure,
LAMP2 is a lighting signal for lamp 4 for full exposure;
OPT is a signal for reciprocating the optical scanning system 14, T
1 to T6 are output signals from timers 44 to 49.

Signals DEV and CLIN are input to the solenoid that contacts the roller and blade, and RoT, LAMP,
CHAG is input to a relay that turns on the energized line to the drum motor, lamp, and high voltage transformer.
OPT is input to a clutch that moves the optical system in synchronization with the drum motor.

Each of the above signals is generated at the timing shown in FIG. To explain the operation, the drum starts rotating as soon as the power switch is turned on, and after T1, the developing device starts operating.
After T2, the blade becomes operational.

Then press the copy button and at the same time the signal
Lamp 5 and AC corona discharger 4 are activated by CHAG2 and LAMP2, exposure lamp 12 is turned on by signal LAMP1, and after _T3 , exposure scanning of the original starts.
Forms an electrostatic latent image. When the scanning is finished, the lamp 12,
During T4 from the END signal obtained when the primary charger 2 is turned off and the optical system returns to its original position, the lamp 5, AC corona discharger 4 and blade 10
Rotate the toner while it is turned on to remove static electricity and bring the surface to a uniform potential, and remove any remaining toner before drying. Thereafter, during T5, the operation of the blade is turned off to prevent toner from adhering to the blade, and the drum rotates idly, and after T6, the rotation of the drum is stopped.

Note that primary charging operates earlier than exposure depending on the position of the primary charger on the photoreceptor and the exposure area. Also END
The signal corresponds to the end of transcription.

Further, it is preferable that the time period T4 to T6 is at least one revolution of the drum or more, but it is necessary to determine the time period T1 to T3 in consideration of the copying speed. Here, the drum rotation on/off and the developer operation on/off may be turned on and off at the same time.
It is also possible to stop the drum rotation if the copy button is not pressed within a predetermined time after SW. The delay times T1 to T6 are determined by a well-known timer circuit that uses the charging time of a capacitor, but if the photoreceptor on the drum is endless, a time signal is obtained by counting a series of clock pulses generated as the drum rotates. or, if it has an end, it can be formed by a circuit that obtains a time signal at a cam position provided on the drum.

FIG. 6 shows a pump 61 from a solvent 62 to a developing tray 60.
An example is shown in which the solution is pumped up and developed here. The condition of the blade and developer is as shown in Figure 2 (1).
In the states of (4) to (4), the contacting and non-contacting of the developing roller is changed to the operation and non-operation of the pump 61. In this case as well, the same sequence control as in FIGS. 4 and 5 is performed.

Figure 7 is similar to the developing method shown in Figure 6.
0 is a pipe that supplies the developer pumped up by the pump 61 to the contact portion between the blade and the surface of the photoreceptor 1. The operation timing follows FIG. 6.

Reference numeral 71 denotes a corona charger for squeezing out the developer adhering to the surface of the photoreceptor after development. This charger is synchronized with the operation of the developer, but when the surface of the photoreceptor that is about to start development passes the charger position, the charger is turned on, and the tip of the photoreceptor surface that has completed development is positioned at the charger position. It is more preferable to turn off the charger when passing through.

In this example, since the surface of the photoreceptor is wetted with the liquid from the pipe 70, the blade 10 may be brought into contact with it slightly after the pump 61 is turned on.

Therefore, by turning on the power switch, the pump 61 is turned on.
is turned on, the blade 10 is then brought into contact, and the photoreceptor is rotated for a predetermined period of time. The photoreceptor may start rotating in synchronization with turning on the power switch.
Also, a developer moisture absorbing and retaining member (sponge, etc.) 73 contacts in synchronization with the blade operation (contact, non-contact).
When placed near the blade, the blade can come into contact with the surface of the photoreceptor almost at the same time as the power switch is turned on.

In addition, if the blade has a property of having little contact stiffness, or if a roller cleaner or brush cleaner is used instead of the blade, the cleaner can come into contact with the surface when the power switch is turned on.

In short, the blade is brought into contact with the wet photoreceptor surface and the blade is brought into contact with the photoreceptor before electrostatic latent image formation.

The term "blade contact" means that the blade is brought into pressure contact with the photoreceptor to the point where it can perform a cleaning action. Therefore, the blade can also be brought into the above state by being gradually pressed against it.

FIG. 8 shows another embodiment of the present invention. 1~ in the diagram
4 is the same as that in FIG.

The developing roller has a structure in which a central rigid body is covered with tensile open cells, and the elastic open cells are further covered with a layer having a large number of through holes. When the developing roller 9 comes into pressure contact with the photoreceptor 1, the contact surface does not deform in a direction parallel to the contact surface at the pressure contact position, but deforms elastically in a direction perpendicular to the contact surface. A refresh roller 85 presses the developing roller in the developer 89 held in the inner container 86 and is used to replace the developer contained in the elastic open cell body of the developing roller 9.

The process sequence for this example is shown in FIG.

In step B, the cleaning blade 10
is not in contact with the photoreceptor 1. The developing roller 9 is brought into contact with the photoreceptor 1 and the refresh roller 85, and the pump 88 is operated to supply developer 89 from the developer tub 87 to the inner container 86, thereby rotating the photoreceptor. As a result, when the developing roller 9 comes into contact with the photoreceptor 1, the developer 89 contained in the elastic open cell in the developing roller 9 is squeezed out through the layer having a large number of through holes, moistening the entire surface of the photoreceptor. Photoconductor 1 and cleaning blade 6 when copying starts
Reduces frictional resistance.

During this time, it is preferable to turn on the AC charge 4, but the potential on the photoreceptor is arbitrary. In step C, the cleaning blade 10 and the developing roller 9 are brought into contact with the photoreceptor 1 to perform preliminary cleaning.

During this step, the copy is made after thoroughly cleaning the surface. The process of converting the electrostatic latent image on the photoreceptor 1 into a visible image using the developing roller 9 will be described below.

The developing roller 9 rotates at the same speed as the photoreceptor, which rotates in the direction of the arrow in the figure. When the developing roller 9 is in pressure contact with the photoreceptor 1, it is contained in the developer drawn up by the rotational force of the developing roller and the elastic open-cell foam squeezed out by the pressure contact between the developing roller and the photoreceptor. The electrostatic latent image on the photoreceptor is visualized by the developer. The developing roller 9 absorbs and removes the excess developer on the photoreceptor using the restoring force of the elastic open cell material when the pressure contact with the photoreceptor is released. The developing roller 9 further rotates, comes into pressure contact with the refresh roller 15 in the developing solution in the inner container 86, exchanges the developing solution, and then comes into contact with the photoreceptor again, repeating the developing process.

In step D, the cleaning blade 10 is brought out of contact with the photoreceptor 1 while the developing roller 9 remains in contact with the photoreceptor 1, and the entire surface of the photoreceptor 1 is rotated to be cleaned by the developing roller 9 without using the cleaning blade. . At this time, it is possible to increase the effect by setting the photoreceptor 1 to a non-developing potential or by applying a bias voltage to the developing roller 9 from the bias power supply 11 as necessary.

It is also possible to selectively apply biases of different polarities or potentials to the developing roller 9 in steps C and D. During step D, when the developing roller 9 is separated from the photoreceptor 1 in step E, which will be described later, while the inner container 86 is filled with developer, the developer is pumped up by the developing roller 9 and the developed image squeezed out from the elastic open cell material. The liquid may adhere to the photoreceptor and dry and solidify during copying pauses, resulting in poor cleaning. Therefore, in this embodiment, the above-mentioned drawbacks can be easily eliminated by stopping the developer supply pump to the inner container. That is, by stopping the pump 18 during step E, the developer in the inner container 86 is removed. The developing roller 9 rotates in the air while being in pressure contact with the photoreceptor and the refresh roller. The developer contained in the continuous elastic bubbles in the developing roller 9 is removed by pressure contact with the refresh roller, and the developing roller, which does not contain developer, cleans the surface of the photoreceptor when it comes into contact with the photoreceptor. To prevent unnecessary developer from remaining on the surface of the photoreceptor even when the photoreceptor is separated. In step E, both the cleaning blade 10 and the developing roller 9 are kept out of contact with the photoreceptor 1.

This is step E in the sequence of FIG. 3, similar to step A.

This control can be performed using FIGS. 4 and 5, and the pump 88 is turned on at the position _T1 and turned off at the position _T4 .

In the above example, exposure does not start even if the copy button is turned on for a predetermined period of time (while the photoreceptor is rotating) after the blade makes contact, but after that time, the second
If the photoreceptor does not turn on after a certain period of time, the rotation of the photoreceptor can be stopped to protect the surface of the photoreceptor.

At the same time, the blade or the blade and the developing roller may be made non-contact. If the copy button is turned on after the rotating body is stopped, the optical system starts to move for exposure after the photoconductor is rotated by at least the distance from the cleaning area to the exposure area (predetermined rotation).

However, when the blade and the developing roller are made non-contact, exposure starts through steps similar to those from turning on the power switch after turning on the copy button. Also, if the copy button is turned on again during step C during the copy pause, exposure is started at the same time as the copy button is turned on or after a predetermined rotation speed. When the copy button is turned on at step D, the blade is brought into contact with the copy button, and after a predetermined rotation, exposure is started. Step E
When the copy button is turned on at this time, the developing roller and the blade are sequentially brought into contact with each other as in the steps described above, and after a predetermined rotation, exposure is started. When the copy button is turned on after the photoreceptor rotation has stopped, exposure starts through the same steps as when the power switch is turned on. It is also possible to turn off the power switch when the rotating body stops.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the electrophotographic process; Figure 2;
Fig. 3 is a time chart using the electrophotographic method in this embodiment, Fig. 4 is an example of a sequence control circuit in this embodiment, Fig. 5 is a time chart of Fig. 4, and Figs. 6, 7, and 8 are other electronic A schematic diagram of the photographic process, FIG. 9 is a time chart in FIG. 8. In FIG. 8, 9 is a developing roller, 85 is an auxiliary roller, 88 is a liquid pump, 87 is a developing container, 1
1 is a bias power supply, and 10 is a cleaning blade.

Claims (1)

[Scope of Claims] 1. A rotating body, means for forming an electrostatic latent image on the rotating body, means for developing the electrostatic latent image, and a visible image developed by the developing means on a transfer material. a means for transferring, a means for cleaning the rotary body in order to reuse the rotary body, a means for rotating the rotary body after completion of transfer by the transfer means, and activating or inactivating the developing means; control means for operating the cleaning means in a contact or non-contact manner, the control means having first and second timer means for performing a counting operation after the start of the post-rotation, and during the post-rotation, the first timer means The means causes the cleaning means to operate in a non-contact manner by counting a first predetermined time, and subsequently the second timer means causes the cleaning means to operate in a non-contact manner by counting a first predetermined time.
The developing means is deactivated by counting for a predetermined period of time, and the timer time of the second timer means is set such that the developing means is activated after the surface of the rotary body that has made the cleaning means non-contact passes through the developing means. An image forming apparatus characterized in that the image forming apparatus is set to be inoperative.