JPH0636119B2 - Electrophotographic device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrophotographic apparatus such as an electrophotographic copying machine. More specifically, the photoconductor is rotated by the control of the control device, the surface of the photoconductor is charged by the charging device, and the charged surface is subjected to image exposure by the image exposure device to form an electrostatic image. Is developed into a toner image by a developing device, the recording paper is fed by the paper feeding means so as to come into contact with the surface of the photoconductor holding the toner image, the toner image is transferred onto the recording paper by the discharge transfer device, and the surface of the photoconductor after the transfer is transferred. The present invention relates to an improvement in an electrophotographic apparatus in which a step of cleaning with a magnetic brush cleaning apparatus is repeated a predetermined number of times.

2. Description of the Related Art In the electrophotographic apparatus as described above, the residual toner adhering to the drum-shaped or belt-shaped photoconductor after being transferred onto the recording paper is removed by the magnetic brush, but is not transferred during transfer. If a portion (hereinafter referred to as an untransferred portion) is generated, the residual toner in the untransferred portion is not removed,
On the contrary, since the image is developed, there is a problem that a good quality copy image cannot be obtained in the next copying operation.

Conventionally, in order to solve the above-mentioned problems, what has been developed is one in which the photoconductor is destaticized before cleaning by photo-elimination or AC corona discharge. It is a situation in which the effect cannot be achieved. Further, a magnetic brush having an improved cleaning effect by applying an AC bias voltage has been developed, but it is a situation in which a sufficient effect cannot be achieved in the untransferred portion as described above. .

OBJECT OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art by preventing the generation of residual toner that cannot be greened by a magnetic brush, and cleaning it well to prevent scumming. An object of the present invention is to provide an electrophotographic apparatus capable of obtaining a recording paper on which a clear image is recorded with high productivity.

As a result of research to achieve the above-mentioned object, the present inventor has obtained the following findings. The residual toner in the untransferred portion is the toner in the portion where the toner image formed on the photoconductor is not covered by the recording paper at the time of transfer, and is directly discharged by the discharge transfer device at the time of transfer, for example, corona discharge, It is charged and charged. This is because the discharge transfer device discharges not only in the width direction of the photoconductor but also in the direction of rotation, and a uniform discharge is given to the back surface from the leading edge to the trailing edge of the recording paper to perform uniform transfer. What must be done must start the discharge before the leading edge of the recording paper enters the discharge surface and stop the discharge after the trailing edge of the recording paper goes out of the discharge surface. This is because even if the discharge transfer device discharges only while the paper is passing, it discharges not only on the back surface of the recording paper but also on the surface of the photoconductor substantially equal to the area of the discharge surface before and after it. Therefore, the residual toner on the untransferred portion is not removed by the magnetic brush of the magnetic brush cleaning device, but is developed on the contrary. Further, in the non-transfer portion, the recording paper of an appropriate size is not fed to the discharge transfer position of the discharge transfer device in an appropriate state, and the toner image formed on the photoconductor is covered with the recording paper at the discharge transfer position. It became clear that it would occur if there was not. From the above, when recording paper of an appropriate size is not fed in an appropriate state at the time of transfer, by setting the discharge transfer device to the inoperative state, the recording paper is covered by the discharge transfer position. The present inventors have found that it is possible to prevent charging of residual toner in a portion of a toner image that is not present, that is, an untransferred portion, and it is possible to sufficiently clean the photoconductor with a magnetic brush cleaning device.

The present invention has been completed on the basis of the above-mentioned findings, and its constitution is to rotate a photoconductor under the control of a control device, charge the photoconductor surface with a charging device, and image the charged surface with an image exposure device. An electrostatic image is formed by applying exposure light, the electrostatic image is developed into a toner image by a developing device, and the recording paper is fed by a paper feeding unit so as to come into contact with the surface of the photoconductor holding the toner image. The electrophotographic process in which the process of transferring the toner image to the recording paper by the discharge transfer device that gives a uniform discharge from the front end to the rear end of the sheet and cleaning the photoconductor surface after the transfer with the magnetic brush cleaning device is repeated a predetermined number of times. In the apparatus, a sensor for detecting the recording paper fed by the paper feeding means is provided, and whether or not the recording paper fed by the control device to the toner image holding position on the photoconductor surface completely overlaps based on the output information of the sensor. It is determined, when it is determined that whether an electrophotographic apparatus, characterized by controlling the discharge transfer device in the step in a non-actuated.

The present invention is configured as described above, and when a recording paper of an appropriate size is fed in an appropriate state at the time of transfer, it is appropriately transferred to the recording paper without generating an untransferred portion. The residual toner adhering to the photoconductor after the transfer is only in the transfer portion and is not charged, and is appropriately removed by the magnetic brush cleaning device. On the other hand, when a recording paper of an appropriate size is not fed in an appropriate state at the time of transfer, the discharge transfer device is set to the inoperative state, so that the transfer paper is not wastefully transferred and is formed on the photoconductor. Since the formed toner image is not charged, the residual toner adhering to the photoconductor after passing through the discharge transfer device is appropriately removed by the magnetic brush cleaning device.

The case where it is determined that the size or the feeding state of the recording sheet fed to the discharge transfer device is inappropriate will be exemplified as follows. When the size of the recording paper is smaller in length and / or width than the toner image formed on the photoconductor, even when the size of the recording paper is the same as or larger than the size of the toner image, the discharge transfer position of the discharge transfer device is If the leading edge or trailing edge of the recording paper is not fed so that it matches the toner image, or if the recording paper is not stored in the paper feed cassette or if a jam occurs in the paper feed path and the paper is not fed to the discharge transfer position. Etc. In order to determine whether the size or the feeding state of the recording paper fed to the discharge transfer device is appropriate, for example, a sensor incorporated as a part of the process control device that operates the electrophotographic device is provided in the feeding path to transfer the sheet. Sometimes the recording paper fed from the paper feed cassette reaches the sensor, the time it takes to pass the sensor,
Alternatively, when multiple sensors are provided, the time to reach each sensor or the time to pass each sensor is detected, and the length or width of the recording paper fed, the size of discharge transfer, etc. Paper feed time to reach the position,
This is performed by determining the speed or the paper feeding attitude, and comparing the result of the determination of the recording paper with the size of the toner image formed on the photoconductor, the arrival time or speed of the toner image at the discharge transfer position, and the like. .

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

First Embodiment A first embodiment will be described with reference to FIG. FIG. 1 is an explanatory view for schematically explaining the electrophotographic copying machine of the first embodiment. The electrophotographic copying machine shown in the figure includes a charger 1, an exposure device 2, a magnetic brush developing device 3 (hereinafter referred to as a developing device),
Transfer device with corona discharge electrode 4, separator 5, fixing device 6,
Drum-shaped photoreceptor 7, magnetic brush cleaning device 8
(Hereinafter referred to as a cleaning device), a paper feed cassette 9 for accommodating recording paper, a resist roller 10, and a sensor 11 for detecting the recording paper are provided, and are configured to be operated by a process control device (not shown). . When the sensor 11 detects a recording paper of an appropriate size within a predetermined time after the registration roller 10 is operated, the transfer device 4 reaches the transfer device 4 with the leading end of the recording paper. The discriminating means is composed of, for example, a microcomputer operated in association with the process control device so as to be set in the non-operating state when the sensor 11 is not detected within the predetermined time, although the operating unit is sometimes set in the operating state. Controlled by.

The electrophotographic copying machine shown in the figure is constructed as described above, and the copying operation is performed as follows. When a copy start switch (not shown) is turned on, the photoconductor 7 starts rotating. During one rotation of the photoconductor 7, the photoconductor 7 is sequentially subjected to the processes of charging, exposure, development, transfer, separation, and cleaning, and the recording paper separated after the transfer is subjected to a fixing process. , One copy is formed. That is, the photoconductor 7 is charged by the charger 1 and the original image is exposed by the exposure device 2 to form a latent image. The latent image formed on the photoconductor 7 is developed by the developing device 3 to form a toner image. The toner image is registered by the registration roller 10 such that the leading edge of the toner image reaches the transfer device 4 at the same time and speed.
It is transferred by the transfer device 4 to the recording paper fed by the transfer device 4. At that time, the toner forming the toner image is 60 to 90.
% Is transferred to the recording paper, but 10 to 40% remains as the residual toner while being attached to the photoconductor 7. The residual toner is
After the recording paper is separated from the photoconductor 7, it is adsorbed by the magnetic brush of the cleaning device 8 and removed from the photoconductor 7.
On the other hand, the recording paper separated from the photoconductor 7 by the separator 5 after the transfer is fed to the fixing device 6, and the transferred original image is fixed.

In the above operation, the transfer device 4 is operated as follows.
The recording paper stored in the paper feed cassette 9 is immediately fed from the paper feed cassette 9 to the registration roller 10 under process control. Then, in the transfer device 4, the operation of the registration roller 10 is started by the process control so that the front end of the recording paper coincides with the front end of the toner image. When the sensor 11 detects the leading edge of the recording paper within a predetermined time after the registration roller 10 is activated, it is determined that the recording paper is fed properly, and the transfer device 4 is set to the operating state. Then, the transfer is properly performed as usual. However, the recording paper may be sent to the sensor 11 earlier or later than the predetermined time.
Is detected, the transfer state of the recording paper is determined to be inappropriate, the transfer device 4 is set to the non-operating state, and the transfer is not performed on the transfer paper. Of course, when the recording paper is not stored in the paper feed cassette 9, or when the recording paper is not fed such as when the recording paper is jammed, the sensor 11 cannot detect it within the predetermined time. , The transfer device 4 is set in the non-operating state.

As described above, in the present embodiment, when the recording paper of an appropriate size is fed, if the leading edge of the recording paper does not reach the transfer device 4 at an appropriate time, it is formed on the photoconductor 7 at the transfer position. Although the leading edge or the trailing edge of the toner image is not covered with the recording paper, the leading edge or the trailing edge of the toner image is not discharged because the transfer device 4 is set in the inoperative state. The toner to be formed is adsorbed by the magnetic brush of the cleaning device 8 and easily removed.

In the present embodiment, it is preferable that the sensor 11 be configured so as to be able to detect the trailing edge of the recording paper as well, and whether the length of the recording paper is a predetermined length or more. Can also be determined. That is, even if the front end of the recording paper is detected by the sensor 11 within a predetermined time, if the elapsed time until the rear end is detected is short, the length of the recording paper is shorter than the predetermined length. When the elapsed time is long, it can be determined that it is longer than the predetermined length. Therefore, when it is determined that the length of the recording paper is shorter than the predetermined length, the trailing edge of the recording paper passes through the transfer device 4 even if the recording paper is properly fed. By configuring the transfer device 4 so that the transfer device 4 can be set to the non-operation state, it is possible to prevent the transfer image from being discharged to the toner image not covered with the recording paper. Further, a plurality of the sensors are arranged in a direction orthogonal to the paper feeding direction of the recording paper, and the sensor corresponding to the width of the toner image is set to the operating state,
The transfer device may be configured not to operate when the sensors set to the operating state do not operate at the same time. In this case, whether or not the width of the recording paper is equal to or larger than the set width, whether the recording paper is properly fed through the paper feed path without being inclined, or the recording paper is bent. Since it is possible to determine whether or not the paper is being properly fed, it is possible to determine whether or not a recording paper that is narrower than a predetermined width is fed or is fed in an improper feeding state. The transfer device 4 can be set to the inactive state. further,
Multiple sensors are arranged in the paper feed path direction of the recording paper, the time when the leading edge of the recording paper arrives at each sensor is detected, and it is possible to determine whether the feeding speed of the recording paper is appropriate from the difference between the times. May be.

When an AC discharge electrode such as an AC corona discharge electrode is used, the separator 5 has an effect of discharging the photoconductor and the residual toner, so that the separator 5 can be controlled by the process control regardless of the operating state of the transfer device 4. It is preferably set to be activated.

Second Embodiment A second embodiment will be described with reference to FIG. Figure 1 shows the second
FIG. 1 is an explanatory diagram schematically illustrating an electrophotographic copying machine according to an embodiment. In the figure, the same reference numerals as those in FIG. 1 indicate the same functional members. In the electrophotographic copying machine shown in FIG. 2, the magnetic brush unit A serves as a developing device and a cleaning device as compared with the electrophotographic copying machine shown in FIG.
The difference is that a copy can be formed. That is, in the second rotation of the photoconductor 7, the charging, exposing, developing, transferring, and separating processes, and the fixing process of the recording paper separated after the transfer are performed in the same manner as shown in FIG. In the second rotation, the charging device 1, the transfer device 4, the separator 5 and the like are set in the non-operating state, and the magnetic brush unit A is operated as a cleaning device to remove the residual toner adhering to the photoconductor 7. It At that time, at the time of transfer, the transfer device 4 is set to the activated or inactivated state in association with the recording paper to be fed as in the case shown in FIG. The residual toner adhering to the body is adsorbed by the magnetic brush and removed without being charged by the transfer device 4.

As described in the embodiments, the electrophotographic apparatus of the present invention discriminates whether or not the size of the recording paper or the paper feeding state is appropriate at the time of transfer, and when it is determined that the recording paper is not suitable, the electrophotographic apparatus is not operated. Since the toner image that is not covered by the recording paper is not charged at the discharge transfer position of the transfer device as in the conventional device, the photosensitive member is set after the transfer device is set. The residual toner adhering to the toner can be removed by a magnetic brush cleaning device.

As described above, the present invention can achieve the above object by the above-mentioned configuration.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of the first embodiment of the present invention, and FIG. 2 is a schematic explanatory view of the same second embodiment. 3 ... Magnetic brush developing device, 4 ... Transfer device, 7 ... Drum-shaped photoconductor, 8 ... Magnetic brush cleaning device, 9 ... Paper feed cassette, 10 ... Registration roller, 11 ... Sensor, A ...... Magnetic brush unit.

Claims (2)

[Claims] 1. A photoconductor is rotated by the control of a control device, the surface of the photoconductor is charged by a charging device, and an imagewise exposure is made to enter the charged surface by an image exposure device to form an electrostatic image. The image is developed into a toner image by the developing device, and the recording paper is fed by the paper feeding means so as to come into contact with the surface of the photoconductor holding the toner image,
Repeat the process of transferring the toner image to the recording paper by the discharge transfer device that gives uniform discharge to the back surface from the front end to the rear end of the recording paper, and cleaning the photoconductor surface after the transfer with the magnetic brush cleaning device a predetermined number of times. In the electrophotographic apparatus, a sensor for detecting the recording paper fed by the paper feeding means is provided, and whether or not the recording paper fed by the control device to the toner image holding position on the photoconductor surface is completely overlapped based on the output information of the sensor. The electrophotographic apparatus is characterized in that the discharge transfer apparatus in the above step is controlled to be inoperative when it is judged to be negative. 2. The electrophotographic apparatus according to claim 1, wherein the developing device and the magnetic brush cleaning device are commonly used.