JPS6160432B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic copying apparatus, and specifically to a copying method in an electrophotographic copying apparatus using a wet development visible image transfer method.

The copying apparatus transfers a visible image formed on a photoreceptor to a sheet through charging, exposure, and development steps.

First, referring to FIG. 1, an example of a copying apparatus to which the present invention is applied will be explained. The photoreceptor 1 has a photoconductor layer formed on its circumferential surface, and is rotated in the direction of the arrow to undergo continuous electrophotographic processing. When the photoreceptor 1 rotates, first at the charging position, the photoconductor layer, which is the photoreceptor surface on which an electrostatic latent image is formed, is transferred to the main corona discharger 2, which is the charging means.
The entire surface is uniformly charged. This main corona discharger 2 is connected to a high voltage power source (not shown).

The charged photosensitive surface moves to the next exposure position. At this position, an optical system 3 serving as a light image irradiation means for projecting an image of a document (not shown) onto the photosensitive surface is arranged. This causes the image of the document to be projected onto the photosensitive surface, dissipating the charge in the exposed areas and forming an electrostatic latent image of the image.

The photoreceptor 1 on which the electrostatic latent image has been formed is developed by a developing device 4 serving as a developing means at the next developing position, and becomes a visible image using toner. This developing device 4 has a developing tank 4a containing a developer containing toner and a developing tray 4b disposed close to the circumferential surface of the photoreceptor 1, and the main switch of the device is turned on. In this state, a pump (not shown) is pumping up the developer onto the developing tray 4b. Therefore, a portion of the circumferential surface of the photoreceptor 1 is immersed in the developer during operation of the apparatus.

The photoreceptor 1, on which the electrostatic latent image has been developed into a visible image, moves to the next transfer position. At this location, a visible toner image is transferred from the photoreceptor surface to the sheet. This sheet is transported to a sheet path P by a paper feeding device (not shown) at the same speed as the circumferential speed of the photoreceptor 1.
is sent into close contact with the circumferential surface of the photoreceptor. A transfer corona discharger 5 that generates corona discharge is arranged at a position corresponding to the back surface of the sheet that is in close contact with the sheet. The corona discharger 5 has the same structure as the main corona discharger 2, emits charges of the same polarity, and electrostatically attracts the toner image from the photoreceptor surface to the sheet surface.

The sheet onto which the toner image has been transferred passes through a fixing device (not shown) and then is discharged from the apparatus.

By the way, toner still remains on the surface of the photoreceptor after the above transfer step. If the toner remaining on the surface of the photoreceptor after the toner image has been transferred to the sheet, so-called residual toner, is left unremoved, it may stain the sheet or damage the surface of the photoreceptor in the next copying process. It may stick to the photoreceptor and impair its function as a photoreceptor. Therefore, cleaning means for removing the residual toner is provided.

The cleaning means is composed of a roller 6 impregnated with a cleaning liquid that releases the toner from the surface of the photoreceptor and makes it easy to peel off, and a blade 7 that peels off the toner. It is brought into contact with the surrounding surface. Note that as the cleaning liquid, a developer or its mother liquid is used.

After the transfer process, the photoreceptor 1 is moved to the roller 6.
The remaining toner is then removed by the blade 7 and the surface is cleaned, but since the charge from the corona discharger remains on the surface, the charge is removed at the next charge removal position.

As a means for eliminating static electricity, an AC corona discharger 8 for static elimination connected to an AC power source is disposed at the static elimination position, and the electric charge remaining on the surface of the photoreceptor is eliminated by the discharge of the AC corona discharger 8. As a result, the potential state on the photoreceptor is made substantially uniform, in preparation for the next copying process.

As described above, the photoreceptor that has gone through the steps of charging, exposure, development, transfer, cleaning, and neutralization either stops or continues to repeat the above steps.

By the way, when copying a single object, the surface of the photoreceptor is charged by the main corona discharger 2,
Comparing the respective areas exposed by the optical system 3 that irradiates the object with a light image that covers the entire surface of the subject, the charged area is wider and the exposed area is narrower. This means that the photoreceptor 1 has an unexposed area in addition to the image irradiation surface that is the exposed area, and since this area naturally has an electric charge, toner will adhere to this area during the development process. do. Toner adhering to areas other than the irradiation surface, which are in front of the irradiation surface in the rotational direction of the photoreceptor 1, are always removed by the cleaning means 6 and 7. However, when the photoreceptor 1 stops at the end of the transfer process during the final copying, the toner in the unexposed area behind the irradiation surface is not cleaned, and the surface of the photoreceptor 1 is It will remain in the.

Therefore, it is necessary to remove the toner before starting a new copying operation, and in this apparatus, only a cleaning operation is performed before the above-described charging process of the surface of the photoreceptor. In this cleaning operation, when the main switch of the apparatus is turned on, only the photoreceptor 1 is first rotated before the start of the charging exposure copying operation. When the cleaning operation for a certain period of time is completed, the print switch for starting the copying operation becomes operable for the first time. The circuit for transitioning from cleaning to copying is such that when the main switch is turned on, a timer is activated and only the cleaning operation is performed, and when the timer is turned off, the circuit including the print switch is closed. ing.

However, the toner remaining on the photoreceptor 1 will stick to the photoreceptor 1 after the device is left unused for a long time, making cleaning difficult.

Further, the charge on the surface of the photoreceptor 1 caused by the main corona discharger 2 is first exposed to light by irradiation with a light image, and most of it is dissipated, and toner having a charge of the opposite polarity adheres to the remaining charge portion. It becomes a toner image.
As described above, this toner image is adsorbed to the sheet during the transfer process, so that the charge of the image portion remains on the light image irradiated surface of the photoreceptor. Furthermore, as described above, charges remain in the unexposed areas.

Therefore, on the surface of the photoreceptor 1, which is brought to the charge removal position after the transfer process and through the cleaning process, charges remain on the surface of the photoreceptor 1, which is not uniform over the entire surface but is scattered in small and dense areas.

The remaining electric charges are uniformly removed by the AC corona discharger 8 which uniformly discharges the electric charge onto the surface of the photoreceptor during repeated copying in short periods. However, if it is stopped for a long time (several minutes to several tens of minutes), it is thought that the residual charge forms a relatively stable electric field on the photoreceptor. Photoreceptor with charges trapped in the tissue The charges remaining in a small density on the photoreceptor, which has become fatigued due to so-called continuous copying, change the trapped state over time, and even if an AC corona for charge removal is applied, , it is not possible to remove static electricity uniformly over the entire surface.

The present invention provides an electrophotographic copying method that uniformly removes charges remaining on a photoreceptor that has been idle for a long time, uniformizes the image forming characteristics of the photoreceptor, and obtains a copy that is faithful to the original and free of stains. The purpose is to provide

The copying method of the present invention improves copy quality by simply controlling the operation process at the start and end of the copying operation, without using any special equipment, in order to uniformize the image forming characteristics of the photoreceptor. This can be improved. In order to remove non-uniform charges remaining on a photoreceptor that has been stopped for a long time, the present invention charges the entire surface of the photoreceptor to the same polarity as the residual charge using a transfer corona discharger. By eliminating static electricity with an AC corona discharger, residual electric charges are uniformly removed over the entire surface. In other words, when the entire surface of the photoreceptor is charged and neutralized, the influence of the charges trapped inside the photoreceptor is alleviated, and uneven residual charges are easily removed.

The present invention will be explained below with reference to FIG.

First, an electrophotographic copying apparatus to which the present invention is applied is
A timer _T1 is provided to control the cleaning operation circuit A for a certain period of time when the main switch _SW1 is closed, and only after this cleaning operation is completed is the print switch ^SW2 ready for operation. Note that when the main switch SW ₁ is closed, the developing device 4 (see FIG. 1) starts operating, and continues to operate until the main switch SW 1 is opened. print switch
When SW ₂ is activated, a timer T ₂ is activated to close the image forming characteristic equalization operation circuit B for a certain period of time and perform the above operation. When the image forming characteristic uniformization operation is completed, the copying operation circuit C is activated. When the above copying operation is completed, the switch _SW3 is switched and the timer _T3 operates the sticking prevention operation circuit D for a certain period of time.

That is, the power supply E of the copying machine includes a resistor R ₁ and a constant voltage diode in series with the main switch SW ₁ .
A CR timer T ₁ whose main components include Z ₁ , a capacitor C ₁ and a transistor relay circuit Tr ₁ as a switching element is connected. When the main switch SW ₁ is now closed, the cleaning operation circuit A connected in parallel with the timer T ₁ is closed via the relay RA ₁ , and the timer is also activated.
_T1 works. This cleaning operation is performed by the roller 6, blade 7, and developing device 4 that are in contact with the circumferential surface of the photoreceptor 1 as it rotates.
This removes the toner remaining on the surface. The cleaning operation time t ₁ is controlled by the timer T ₁ and is controlled by the main switch SW _1.
It is related to the OFF time; for example, if the main switch is off for a long time, the time _t1 is set to be longer. At this time, each corona discharger is in an off state.

When time t ₁ has elapsed, timer T ₁ is activated to operate relay RA ₁ . The operation of relay RA ₁ closes normally open contact RA _1-1 . This results in
The device is placed in a state where it is ready to start a copying operation.

Then, when print switch SW ₂ is closed,
Relay K ₁ operates to close normally open contact K _1-1 , and timer T ₂ and imaging characteristic equalization operation begin to operate. In FIG. 1, the image-forming characteristic uniformization operation is performed using a transfer corona discharger 5 and a static elimination AC corona discharger 8.
The transfer corona discharger 5 discharges a discharge onto the surface of the rotating photoreceptor 1.
After uniformly charging the entire surface of the photoreceptor 1, a discharge charge from an AC corona discharger 8 for static elimination connected to an AC power source is applied to the photoreceptor 1, thereby uniformly removing the charge on the entire surface. The time _t2 during which this image forming characteristic uniformization operation is performed is controlled by a timer _T2 . The configuration of timer _T2 is as follows:
Since it is the same as T ₁ , only the reference numeral is given and its explanation will be omitted.

When time t ₂ elapses, timer T ₂ switches relay RA ₂
is operated to open the image forming characteristic equalization operation circuit B. Due to the operation of relay RA ₂ , normally open contacts
RA _2-1 is closed. By opening the contact RA _2-1 , the copying operation circuit C is closed, the copying operation is started, and the required number of copies can be obtained. This copying operation includes charging the entire surface of the photoreceptor 1 with the main corona discharger 2, forming an electrostatic latent image by irradiating a light image with the optical system 3, making the electrostatic latent image visible with the developing device 5, and making the electrostatic latent image visible with the transfer means. Transfer of a visible image onto a sheet, etc.

Then, when the above copying operation is completed, the switch is turned on.
SW ₃ switches to the position shown by the broken line, and the toner sticking prevention operation circuit D and timer T ₃ operate. The anti-sticking operation is an operation that removes toner remaining on the surface of the photoreceptor 1 and prevents it from sticking to the surface of the photoreceptor 1. This operation is performed without immediately stopping the photoreceptor 1 after transfer. It rotates for more than half a turn and then stops. As a result, all parts of the photoreceptor 1 to which toner is attached are passed through the cleaning section, so that no toner remains on the surface.

The time _t3 of the above-mentioned sticking prevention operation is controlled by the timer _T3 , and when the timer _T3 elapses, the contact _RA3-1 of the timer _T3 is opened and all steps are completed. B, C, D operation circuits, timer T ₂
returns to its original state, and at the same time, timer T ₃ also self-opens, and contact RA _3-1 also ends in its original closed state.

Note that the timer _T1 is used to first perform only a cleaning operation on the photoreceptor when the device is started, and the cleaning operation itself continues to operate even after the time _t1 has elapsed. There is.

As described above, in an electrophotographic copying apparatus in which the photoconductor is cleaned by turning on the main switch, and the print switch becomes ready for operation, when the print switch is operated, the copying operation starts immediately. First, the timer _T1 operates the static eliminating means and the transfer means for a certain period of time to completely remove residual potential stored unevenly on the surface of the photoreceptor, thereby making the image forming characteristics uniform. According to the copying method of the present invention, the charge on the photoreceptor becomes uniform over the entire surface due to the discharge of the main corona discharger 2, and an electrostatic latent image is formed by light image irradiation and visualized by the developing means. The copied image reproduced on the sheet is faithful to the original.

Furthermore, after the copying operation is completed, if all the corona dischargers are turned off and the photoreceptor 1 is rotated more than half a turn, the toner-stained surface of the photoreceptor will be passed through the cleaning section, making it easier to This removes toner and reduces the chance of it sticking to the surface, prevents sheet background stains and damage to the photoreceptor surface due to residual toner, and shortens the cleaning operation time at start-up, reducing copying time. I have it.

Furthermore, when the corona discharger is operated during the cleaning operation, the surface of the photoreceptor becomes charged in the dark area, and a large amount of toner is sent to the cleaning section.
However, according to the copying method of the present invention, each corona discharger cannot operate until the cleaning operation is completed, so the dark area charging is reduced. No problems will occur due to this.

[Brief explanation of the drawing]

FIG. 1 is a side view schematically showing an electrophotographic copying apparatus that implements the electrophotographic copying method of the present invention;
The figure is an electrical circuit diagram for implementing the invention. 1... Photoconductive photoreceptor, 2... Main corona discharger, 3
...Optical system, 4...Developing device, 5...Transfer means, 6,7
...Cleaning means, 8...AC corona discharger for static elimination, T1...Timer for controlling cleaning operation, _{T2 ...} Timer for controlling image forming characteristic equalization operation, _T3 ...Timer for controlling toner sticking prevention operation.

Claims (1)

[Scope of Claims] 1. Charging a photoconductive photoreceptor by a charging means,
An electrostatic latent image with an exposed area smaller than the charged area is formed on the charged photoconductive photoreceptor by a light image irradiation means, and this electrostatic latent image is made visible by a developing means, and this visible image is is transferred to a sheet using a transfer corona discharger, and the residual potential on the photoconductive photoreceptor after the visible image transfer is removed using an AC discharger for static elimination. In an electrophotographic copying method in which residual developer is removed by a cleaning means, by turning on a print switch that starts a copying operation, the transfer corona discharger and the static elimination AC corona discharger are each operated for a predetermined time. The photoconductive photoreceptor is fully charged by the transfer corona discharger, and after the photoconductive photoreceptor is neutralized by the charge removal AC corona discharger, a copying operation is performed. An electrophotographic copying method.