JPS5848904B2 - Cleaning time control method for electrophotographic copying machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a toner cleaning time for a wet-type development transfer type electrophotographic copying machine that performs copying after cleaning the toner stuck on the surface of a photoreceptor after a pause and before starting copying operation. Regarding control method.

In a wet development transfer type electrophotographic copying machine, when the photoreceptor stops rotating, the developer adhering to the photoreceptor surface dries, the solvent evaporates, and the toner adheres to the photoreceptor surface.

Therefore, when the main switch and copy switch of the copying machine are turned on again, the photoconductor is rotated for a certain period of time or a period proportional to the rotation stop time to clean the toner adhering to the photoconductor surface, and then The copy operation was started.

However, the cleaning time set in this way does not necessarily match the time required to clean the stuck toner, and sometimes the cleaning is insufficient and the copy image has stuck toner attached, and other times The cleaning time was excessive and there was a lot of waiting time for copying.

In FIG. 1, a solid line A indicates the relationship between the rotation stop time of the photosensitive drum and the required cleaning time.

Therefore, for example, if the required cleaning time is set to a certain length as shown in B, the cleaning time becomes excessive and the waiting time for starting copying becomes longer than necessary.

On the other hand, if the cleaning time is kept constant to a certain extent as shown in C, the cleaning time becomes insufficient and uncleaned toner is transferred to the copy image, resulting in defective copies.

Furthermore, the relationship A between the rotation stop time of the photoreceptor drum and the required cleaning time is also related to the evaporation rate of the developer attached to the photoreceptor drum surface, and this depends on environmental conditions such as temperature and humidity. Therefore, it is difficult to set a constant and appropriate cleaning time.

On the other hand, as one of the conventional techniques, there is a method that utilizes the discharge of the capacitor from the time when the rotation of the photoreceptor stops, and uses the time inversely proportional to the residual potential of the capacitor as the cleaning time. Although this method is better than the method of keeping the cleaning time constant, the characteristics shown by curves D and E still result in excessive or insufficient cleaning time.

Another known method is to move the developing electrode, cleaning member, squeeze member, etc. away from the photoreceptor surface to prevent the developer from adhering to the photoreceptor surface when the photoreceptor is stopped, but this requires a very complicated mechanism. It is expensive and its effects are not perfect.

Therefore, an object of the present invention is to provide a wet development transfer type electrophotographic copying machine that performs copying after cleaning the toner adhering to the surface of the photoconductor after a pause and before starting a copying operation, by cleaning the toner too much or too little. To provide a toner cleaning time control method for an electrophotographic copying machine, which can obtain high-quality copy images and shorten copy waiting time.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

FIG. 2 is a schematic diagram of a wet development transfer type electrophotographic copying machine to which the present invention is applied.

Around the photosensitive drum 1 having a photoconductive insulating layer on its surface, a charging corona discharger 2, an exposure optical system 3, a developing plate 4 of a developing device, a squeeze roller 5, a squeeze blade 6,
A transfer paper guide γ, a transfer corona discharger 8, a transfer paper peeling roller 9, a cleaning roller 10, a cleaning blade 11, a static elimination corona discharger 12, and the like are arranged at predetermined positions.

When the print switch is turned on, the photosensitive drum 1 rotates at a constant speed in the direction of the arrow, and its surface is first uniformly charged to a predetermined polarity by the charging corona discharger 2.

For example, a selenium photoreceptor has positive polarity.

Next, when an original image is projected onto this surface by the exposure optical system 3, the charged charges are selectively dissipated in accordance with the original image, and an electrostatic latent image is formed thereon.

Next, the developer from the developing device is sent between the surface of the photoreceptor drum 1 and the developer tray 4 through the supply port 4a of the developer tray 4, so that the latent image comes into contact with the developer. It absorbs toner and becomes a visible image.

Excess developer solution adhering to the surface of the photoreceptor drum is removed by a squeeze roller 5, and developer solution adhering to the squeeze roller 5 is scraped off by a squeeze blade 6.

The toner image on the surface of the photoreceptor drum obtained by development has
The transfer paper S sent from the transfer paper guide γ is stacked,
A transfer corona discharger 8 applies a charge stronger than the toner held by the latent image on the surface of the photoreceptor, thereby transferring this toner to the transfer paper side and performing transfer.

After the transfer, the transfer paper S is peeled off from the surface of the photoreceptor by a peeling roller 9 and discharged to a predetermined location.

After the transfer paper S is separated, there is a residual transfer “” on the surface of the photoreceptor.
Toner is attached and the potential of the latent image remains.

Therefore, it is necessary to remove these from the photoreceptor surface before starting the next copying cycle.

First, remove the residual toner using the IJ cleaning roller 1.
0 is brought into contact with the surface of the photoreceptor and rotated, and at the same time, a cleaning liquid is caused to flow down between the cleaning recess roller 10 and the cleaning blade 11.

Next, the residual potential is removed by neutralization using an electric field having a polarity opposite to that of the latent image charge of the charge eliminating corona discharger 12 connected to the alternating current power supply AC.

Therefore, this charge eliminating corona discharger may be of a type that is connected to a DC power source having a polarity opposite to that of the latent image charge.

One copying cycle of this device is completed by removing the charge from the surface of the photoreceptor, but once one copy or continuous copying is completed, the photoreceptor drum and other devices are stopped.

After a while, the solvent portion of the developer that has passed through the developing tray 4 and adhered to the surface of the photoreceptor drum evaporates, and a portion of the toner dries and is fixed to the surface of the photoreceptor drum.

Further, as time passes, the solvent evaporates in the cleaning section, a portion of the squeeze roller, and the contact section between the developing section and the photoconductor surface, and the toner adheres to the photoconductor surface.

Therefore, when performing the next copy, it is necessary to remove this fixed toner with a cleaning device including a cleaning roller 10 and a cleaning blade 11 before entering the charging step, which is the first step of the copying cycle.

Now, the fixed toner cleaning time control method according to the present invention is carried out as follows.

First, explain the equipment used.

A photoconductor surface potential detection electrode 21 is provided on the surface of the developing tray 4 facing the photoconductor surface on the photoconductor entrance side, and is insulated from the photoconductor surface potential detecting electrode 21 over the entire width of the developing tray 4 .

This detection electrode 21 is connected to a potential measurement circuit 22, which is connected to a cleaning operation circuit 24 via a determination circuit 23.
It is also connected to the copying operation circuit 25.

Further, the charging characteristics of the photoreceptor used and the toner must have a relationship as shown in FIG. 3, for example.

In other words, the surface potential of the toner is directly proportional to the applied corona voltage on both electrode sides, whereas the surface potential of the photoreceptor is directly proportional to the applied corona voltage on one pole (the negative electrode in the case of a selenium photoreceptor). This is a relationship in which the surface potential is balanced.

After the device has stopped, when the main switch and copy/print switch of the device are turned on to start copying again, the cleaning device 1
0, 11, static elimination corona discharger 12 and cleaning time control circuit 22. 23 works, and the photosensitive drum 1 rotates once.

In the case of a selenium photoreceptor, no matter how strong a corona discharge is applied to it, the exposed areas to which toner is not adhered exhibit only a charge of about -100 cm, but the toner adhered areas exhibit a charging potential of -IOOV or more.

Therefore, when the surface potential of the photoreceptor after static elimination corona discharge is measured by the detection electrode 21 and the potential measurement circuit 22, it is possible to determine whether or not toner is attached to the surface of the photoreceptor (θ).
The degree of adhesion is detected.

Therefore, for example, if the photoreceptor surface potential is -100V or less, the determination circuit 23 immediately sends the copy operation circuit 25 to the photoconductor surface potential.
is activated to start copying, and if the photoreceptor surface potential exceeds -ioov, the cleaning operation circuit 24 is
Continue to operate until the voltage drops below 100V.

This is determined each time the photoreceptor drum rotates, or the required cleaning time is calculated during the first revolution, and the cleaning operation circuit is operated for a corresponding period of time.

By the way, in such a wet development type copying machine, a development electrode is provided on the development tray, and the surface potential of the photoconductor detected by a similar detection electrode is calculated to determine the necessary bias voltage to prevent scumming. may be applied.

In such a case, the cleaning time control circuit according to the present invention and the bias voltage application circuit described above may be used in combination.

The cleaning time control method according to the present invention can also be carried out as follows.

That is, as schematically shown in FIG.
The surface of the photosensitive drum 1 is irradiated with light through a lens 32, and the reflected light is received by a light receiving element 33.

By rotating the photosensitive drum 1 once, the light receiving element 3
Detect changes in the current flowing through 3.

Since the current flowing through the light-receiving element 33 differs when toner is attached to the surface of the photoreceptor and when it is not, the presence or absence of toner attachment and its degree can be determined based on this change.

Since the photoreceptor and the toner have different optical properties in various respects such as reflectance, chromaticity, brightness, etc., various optical measurements can be performed using these optical properties.

As described above, according to the present invention, the toner cleaning time prior to the start of copying is controlled by measuring the amount of toner adhering to the surface of the photoreceptor, so toner cleaning is carried out in just the right amount and the cleaning It is possible to eliminate the occurrence of defective copies due to insufficient copying and unnecessary copy waiting time due to excessive cleaning.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the photosensitive drum rotation stop time and the required cleaning time, FIG. 2 is a schematic diagram of a wet development transfer type copying machine to which an embodiment of the present invention is applied, and FIG. The figure shows the charging characteristics of the photoreceptor and toner used in the above embodiment, and FIG. 4 is a schematic diagram showing another embodiment of the present invention. 12... Corona discharger for static elimination, 21...
- Photoreceptor surface potential detection electrode, 31... Light emitting element, 32... Lens, 33... Light receiving element.

Claims (1)

[Claims] 1. In a wet development transfer type electrophotographic copying machine that performs copying after cleaning the toner adhering to the surface of the photoconductor after a pause and before starting copying operation, the time required for the cleaning is A cleaning time control method for an electrophotographic copying machine, characterized in that the cleaning time is controlled by measuring the amount of toner adhering to the body surface. 2. The toner amount is measured by taking advantage of the difference in Teiden characteristics between the photoreceptor and the adhered toner, charging the surface of the photoreceptor to which the toner is attached, and measuring the surface potential of the photoreceptor. A cleaning time control method according to claim 1. 3. According to claim 1, the amount of toner is measured by optically measuring the surface of the photoreceptor to which the toner is attached by utilizing the difference in optical properties between the photoreceptor and the adhering liquid toner. Cleaning time control method.