JPS6253830B2 - - 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 remaining developer 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 a 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 preprocessing step before starting the process.

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, a means for transferring a visible image by the developing means onto a transfer material, means for cleaning the rotary body in order to reuse the rotary body; rotating the rotary body a predetermined amount before forming an electrostatic latent image by the electrostatic latent image forming means and operating the developing means;
Deactivate and contact/contact the cleaning means mentioned above.
control means for non-contact operation, the control means having timer means for operating the developing means at the same time as or after a predetermined time after the start of the predetermined rotation, and performing a counting operation after the start of the predetermined rotation;
During the predetermined rotation, the timer means counts a predetermined period of time to bring the cleaning means into contact operation, and the timer time of the timer means is set so that the cleaning means contacts the operating location of the developing means on the rotating body. The present invention provides an image forming apparatus.

Thereby, the friction caused by the cleaning means at the start of rotation of the rotary body or the friction when the cleaning means is brought into contact with the rotary body can be further reduced.

In the present invention, the cleaning means, which has been separated during rest, 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 means is brought into contact with the surface of the rotating body to which the liquid has been applied, after a predetermined period of time after the developing means for applying the liquid is activated. It works.

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. or,
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 rotating body is neutralized to a substantially uniform potential so that the rotating 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 roller 9 are not brought into 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 action 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, the cleaning blade 10 is kept out of contact with the photoreceptor 1, but the developing roller 5 is brought into contact with the photoreceptor 1 and the photoreceptor is rotated. This makes it possible to wet the entire surface of the photoreceptor 1, thereby reducing the frictional resistance between the photoreceptor 1 and the cleaning blade 6, and making 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, drum 1
Clean the toner remaining on the peripheral surface of the printer 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. Similar to step A, this prevents the toner from drying and accumulating while adhering to the cleaning blade or developing roller to the photoreceptor due to capillary action during the copy pause.

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 (or a step signal in the opposite direction) from the Q terminal in response to an impulse signal to the S terminal, and are released by an impulse to the res terminal; 44 to 49 are inputs, respectively. A well-known timer that outputs a 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 well-known differential circuits for inverting input signals. , 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 with 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 photoreceptor, and CLIN is a signal for bringing the blade 10 into contact with the photoreceptor. signal, CHAG1, CHAG
2, CHAG3 is the activation signal for the primary charger 2, secondary charger 4, and transfer charger 7, LAMP1 is the lighting signal for the lamp 12 for light image exposure, and LAMP2 is the lighting signal for the lamp 4 for full-surface exposure. , OPT are signals for reciprocating the optical scanning system 14, and T1 to T6 are output signals from the 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 CHAG
2, Lamp 5 from LAMP 2, AC corona discharger 4
is activated, the exposure lamp 12 is turned on by the signal LAMP1, and after _T3 , exposure scanning of the original starts to form an electrostatic latent image. When the scanning is completed, the lamp 12 and the primary charger 2 are turned off, and the lamp 5 is turned off for a period of T4 from the END signal obtained when the optical system returns to its original position.
Then, the AC corona discharger 4 and the blade 10 are turned on to remove static electricity, make the surface uniform in potential, and remove residual 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 rotation 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 rotation of the drum and the operation of the developing unit may be turned on and off at the same time, or the rotation of the drum may be stopped if the copy button is not pressed within a predetermined time after switching. 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 1 as shown in Figure 2.
In states 4 to 4, the developing roller is brought into contact and not brought into contact with each other, but the pump 61 is not operated. 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 10 and the surface of the photoreceptor 1. The operation timing follows FIG. 6. 7
Reference numeral 1 denotes a corona discharger (-) 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 can be brought into contact with it a little later than when 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.

In addition, a developer moisture absorbing and retaining member (sponge, etc.) 7 comes into contact with the blade operation (contact, non-contact).
3 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 be brought into contact with the surface at the same time as 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 elastic 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 in a direction parallel to its surface, the contact surface does not deform at the pressure contact position, but is elastically deformed 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 brought out of 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. This reduces the frictional resistance between the photoreceptor 1 and the cleaning blade 6 when copying is started.

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 in the direction of the arrow in the figure at the same speed as the photoreceptor. 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 in 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. 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 during step D, the developer 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, like step A, is step E in the sequence of FIG.

This control can be performed using FIGS. 4 and 5. The pump 88 is turned on at T ₁ and turned off at T _4.
It is done according to the position of.

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 contacts, but after that time has passed, the second
If the light 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 the drawing]

Figure 1 is a schematic diagram of the electrophotographic process; Figure 2;
FIG. 6 is a schematic diagram of an electrophotographic process to which the present invention can be applied, FIG. 3 is a time chart of the electrophotographic method in this embodiment, FIG. 4 is an example of a sequence control circuit in this embodiment, and FIG. 6, 7, and 8 are schematic diagrams of other electrophotographic processes to which the present invention can be applied, and FIG. 9 is a time chart in FIG. 8. Figure 8, 9
85 is a developing roller, 85 is an auxiliary roller, 88 is a liquid pump, 87 is a developing container, 11 is a bias power source, and 10 is a cleaning blade.

Claims (1)

[Claims] 1. a rotating body, means for forming an electrostatic latent image on the rotating body, means for developing the electrostatic latent image, and means for transferring a visible image by the developing means onto a transfer material;
a means for cleaning the rotary body in order to reuse the rotary body; and a means for rotating the rotary body a predetermined amount and activating or inactivating the developing means before forming an electrostatic latent image by the electrostatic latent image forming means. and control means for operating the cleaning means in a contact or non-contact manner, the control means operating the developing means at the same time as or after a predetermined time after the start of the predetermined rotation, and performs a counting operation after the start of the predetermined rotation. The cleaning means is provided with a timer means, and the timer means counts a predetermined time during the predetermined rotation to cause the cleaning means to contact operation, and the timer time of the timer means is applied to the operating portion of the developing means on the rotary body for the cleaning. An image forming apparatus characterized in that the means are set to make contact.