JP2001142323A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device whose cleaning time is shortened by making the cleaning time of a transfer member optimized at the jamming occurring time or the abnormal stopping time of the device. SOLUTION: This image forming device, provided with cleaning means for performing a cleaning of a transfer roller 14a by applying an electric field in the direction opposite to the electric field for development between a photoreceptor drum 10 and the transfer roller 14a, and provided with a dot number counter for counting the number of dots at the working time of performing the image exposure. When transport defect of transfer material P occurs, the cleaning of the transfer roller 14a by the above cleaning means is performed at the recovering time. The device decides the cleaning time for performing the cleaning in accordance with the number of dots counted by the above dot number counter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus such as a transfer type electrophotographic apparatus and an electrostatic recording apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus, an image carrier formed of a photoconductive substance is irradiated with image exposure light to form an electrostatic latent image.
The electrostatic latent image is developed with toner as charged particles to form a toner image, and the toner image is transferred to a transfer material such as plain paper.
It is fixed by heat and pressure to form an image.

The transfer of a toner image from an image carrier to a transfer material is performed by an electric field generated in a transfer area. The method of transferring by this electric field can be achieved with a relatively simple configuration, and is therefore generally used as a transferring means. In particular,
There are transfer by a non-contact method represented by a corona method and transfer by a contact method using a transfer member such as a roller or a brush.

[0004]

Since the non-contact type transfer by the corona discharge has a problem that ozone is generated, a contact type transfer means is often used.

However, even in the contact method, (a) the toner adheres to the outside of the image area due to the generation of the oppositely charged toner in the developing process. (B) When using a two-component developer, the ratio of the toner to the developer is reduced In order to control the toner image, a method of forming a toner image outside the image area of the image carrier and detecting and controlling the reflection density thereof is often used, so that the transfer member comes into contact with the toner image pattern. There is a problem that a transfer member such as a transfer roller and a brush is stained with toner. If the transfer member becomes dirty, the back surface of the transfer material will be stained, and the image quality will be reduced.

In order to prevent such toner contamination of the transfer member, it has been considered that the transfer member is brought into contact with the image carrier only when the transfer paper as the transfer material is in the transfer area.
However, even in this method, when a transfer trouble (jam) occurs on the transfer material or when the apparatus is abnormally stopped, the transfer member directly contacts the image bearing member on which the toner is adhered, and the toner smears on the transfer member. This causes the problem that the back surface of the subsequent transfer material is significantly contaminated. In order to solve this problem, a cleaning means for applying an electric field to the transfer member alternately to transfer dirt such as toner on the transfer member to the image carrier and clean the transfer member is disclosed in Japanese Patent Application Laid-Open No. 8-83002. It has become. However, in the conventional cleaning means, the cleaning time is fixedly determined assuming the worst case. For this reason, there is a problem that the time for recovering from the conveyance failure includes the cleaning time, and the recovery time is always long.

An object of the present invention is to provide an image forming apparatus in which the cleaning time of the transfer member is optimized by reducing the cleaning time when a jam of the transfer material occurs or when the apparatus is abnormally stopped.

[0008]

An object of the present invention is to provide a toner image on an image carrier by disposing at least an image exposing means and a developing means in the vicinity of the image carrier. 2. Description of the Related Art In an image forming apparatus, a transfer material enters between a transfer member in contact with a body, and an electric field is applied to the transfer member in a direction to transfer the toner image to the transfer material to transfer the toner image onto the transfer material. A cleaning unit for cleaning the transfer member by applying an electric field in a direction opposite to the electric field between the image carrier and the transfer member, and performing dot exposure during image exposure by the exposure unit. It has a counting means for counting the number, at the time of return after the transfer failure of the transfer material has occurred,
The image forming apparatus is characterized in that the cleaning unit cleans the transfer member, and a cleaning time for performing the cleaning is determined according to the number of dots counted by the counting unit.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is a sectional view showing an example of the configuration of the image forming apparatus of the present invention, and FIG. 2 is a block diagram showing an example of a control system of the present invention. However, the present invention is not limited to the embodiment shown in FIGS. 1 and 2, and a toner image is formed on an image carrier by an electrophotographic method, and a transfer member including a transfer roller (or a transfer brush) is used. A power source capable of transferring the toner image on the image carrier to the transfer material and applying a reverse bias voltage to the transfer member alternately, and rotating the image carrier and the transfer member alternately forward and reverse. Any image forming apparatus having a cleaning unit that cleans the transfer member by applying an electric field may be used.

1 and 2, reference numeral 10 denotes a photosensitive drum, which is a drum-shaped image carrier; 11, a scorotron charger, which is charging means; 12, a polygon mirror 12b;
An image exposing device 13 which is an image exposing means comprising a lens 12c, each mirror 12d and a laser generator (not shown); and 13 has a developing sleeve 13a enclosing a magnet roll, and a developer carried on its peripheral surface. Is applied to the image exposure portion of the photoreceptor drum 10 by applying a bias voltage to perform a reversal development on the electrostatic latent image on the photosensitive layer. Reference numeral 14a comprises a conductive elastic rubber roller, A transfer roller or a transfer roller 14a which is a transfer member for applying a transfer bias voltage or a cleaning bias voltage to a portion by a transfer roller bias power supply 34 via a sliding brush or the like.
Is in pressure contact with the photosensitive drum 10 at all times, and rotates in accordance with the rotation of the photosensitive drum 10. However, the transfer roller 14a may have a structure separated from the photosensitive drum 10 when the transfer roller bias power supply 34 is turned off. Further, the transfer roller 14a is driven to rotate in the present embodiment, but may be driven to rotate so that its peripheral speed is the same as the peripheral speed of the photosensitive drum 10.

In this embodiment, a transfer roller will be described as a transfer member. However, a conductive transfer brush for applying a transfer bias may be used. 14b is a transfer area formed by the photosensitive drum 10 and the transfer roller 14a;
Is a paper feed cassette, 16 is a transport belt, 17 is a fixing device,
Reference numerals 18a and 18b denote paper discharge rollers, 19 a cleaning device, 20 a control unit having a control CPU, and 21 a power supply O.
A power switch as N / OFF means, 22 is an image data section for storing image data obtained by reading an original image by a scanner or the like, or image data created by a computer or the like, and 23 is an image forming (printing) of the image forming means 100 An image forming program section for storing an operating program at the time; 24, a dot number counter for counting and integrating the number of image dots transmitted to the image exposing means 12 based on image data; 25, transmitting to the image exposing means during image forming operation The count number memory 25 is a non-volatile memory that stores the number of image dots that have been printed. The count number memory 25 is rewritten for each print. 26, a cleaning time determining circuit for determining a cleaning time according to the number of dots stored in the count number memory 25; 34, a transfer roller bias power supply for supplying a transfer bias voltage or a cleaning bias voltage to the transfer roller 14a; A jam determination circuit that determines the occurrence of a jam based on a paper passing signal from the sensors S1 and S2; 100, an image forming unit including an image exposing unit 12 and a transfer roller 14a for image formation; P, a transfer paper as a transfer material; S1 is a sheet passing sensor provided downstream of the timing roller 15c in the transfer of the transfer sheet P, and S2 is a sheet passing sensor provided downstream of the sheet discharging roller 18a of the fixing device 17.

When the power switch 21 is turned on, the control unit 20 controls each unit and members of the image forming unit 100 in accordance with the program of the image forming program unit 23 to perform the operation described below.

When the power switch 21 is turned on, after the elapse of the warm-up time, a display indicating that printing is possible is displayed on the display unit of the operation unit (not shown). Thereafter, when a print switch (not shown) is turned on, the photosensitive drum 10 is rotated clockwise to apply a potential to the photosensitive layer forming its peripheral surface by discharging the scorotron charger 11 first, and then to transfer image data. The image data called by the unit 22 is processed and becomes an image signal.
2 is input.

The image exposure device 12 scans and exposes the photosensitive layer of the photosensitive drum 10 in the axial direction by rotating the polygon mirror 12b with a laser beam projected from a laser generator in response to input of an image signal. Photoconductor drum 10
In combination with the rotation, an electrostatic latent image of an image is formed on the photosensitive layer. At this time, the number of image dots sent to the image exposure device 12 is counted by the dot number counter 24. This count number is stored in the count number memory 25.

The electrostatic latent image is reversal-developed by the developing device 13 and visualized to form a toner image.

In parallel with the visualization of the toner image, the transfer paper P, which is a transfer material, is fed from the paper feed cassette 15 by the operation of the carry-out roller 15a, and is fed to the timing roller 15c via the transport roller 15b. The paper is fed to the transfer area 14b in synchronization with the toner image on the body drum 10.

After the potential of the toner image on the photosensitive drum 10 is lowered by the light neutralizer 14c, the transfer paper P is further transferred to the transfer area 14b from the rear surface by the transfer roller 14a while passing through the transfer area 14b. A voltage (transfer bias voltage) having a polarity opposite to that of the toner is applied to a transfer roller bias power supply 34.
The toner image is transferred and transferred to the transfer paper P side by being applied. After the transfer paper P has passed, a voltage (cleaning bias voltage) having the same polarity as that of the developing toner is applied to the transfer roller 14 a by the transfer roller bias power supply 34, and the toner adhered to the transfer roller 14 a during the transfer is removed from the photosensitive drum 10. And the transfer roller 14a is cleaned.

The transfer paper P on which the toner image has been transferred is separated from the photosensitive drum 10 and is fixed via a transport belt 16 to a fixing device 17.
And is fused and fixed by the sandwiching heating between the heat roller 17a and the pressure roller 17b.
It is discharged to the upper surface of the apparatus main body via 18b.

The photosensitive drum 10 from which the transfer paper P has been separated is cleaned by the cleaning device 19 with the residual toner and the transfer roller 1.
The toner transferred from 4a is removed and cleaned together, and the process proceeds to the next image forming process.

The above description is the operation during normal printing. Next, the operation when a transfer trouble (jam) of the transfer paper P or an abnormal stop occurs will be described.

FIG. 1 shows an image forming apparatus according to this embodiment.
As shown in (1), a paper passing sensor S1 is provided on the downstream side of the timing roller 15c, and a paper passing sensor S2 is provided on the downstream side of the paper discharging roller 18a. In response to the paper passing signals from the paper passing sensors S1 and S2, the control unit 20 performs the following control.

If the paper passing sensor S1 on the upstream side does not pass the paper passing sensor S2 within a predetermined time after detecting the passage of the transfer paper P, the jam determination circuit 35 generates a jam (occurrence of conveyance failure), or It is determined that the device has stopped abnormally. As a result, the control unit 20 turns off the transfer roller bias power supply 34, stops the image forming operation, and displays a jam occurrence or abnormal stop on a display unit (not shown) of the apparatus.

After the cause of the jam or the cause of the abnormal stop is removed, when a return button or a print switch (not shown) is pressed, a return operation is started, and the control unit 20 turns on the transfer roller bias power supply 34. After the jam processing, the temperature of the fixing device 17 is lower than the predetermined temperature, so that the apparatus enters the warming-up mode. In the warm-up mode, the photosensitive drum 10 rotates, and a cleaning bias voltage is applied to the transfer roller 14a from the transfer roller bias power supply 34.

At the time of this return, in parallel with the heating of the fixing device 17 in the warm-up mode, the control unit 20 controls the transfer roller bias power supply 34 to
The cleaning bias voltage and the transfer bias voltage are alternately applied to a. This alternate switching of the transfer bias voltage is performed substantially every one rotation of the transfer roller 14a. As a result, not only the developing toner but also the toner of the opposite polarity (the amount is small)
Are cleaned at the same time.

The cleaning time at this time is determined by a cleaning time determination circuit 2
6, the count number memory 25 which is a nonvolatile memory
The cleaning time is determined according to the number of dots counted immediately before the abnormal stop, which is stored in the printer, so that the cleaning time is determined according to the print amount during image formation. When there is no image being formed at the time of occurrence of a conveyance failure,
Is zero, the cleaning time is set to the shortest and cleaning is performed.

During the time from when the cause of the jam processing or the abnormal stop is removed to when the return button or the print switch is pressed and the image formation is started, the temperature of the fixing device 17 is raised to a predetermined temperature and other preparatory operations are performed. Compare the warm-up time and the cleaning time determined by the present invention,
It depends on the time of those who need a long time.

[0027]

According to the present invention, the cleaning time of the transfer member when a conveyance failure such as a jam or an abnormal stop occurs is determined according to the print amount of the image being formed. When the number of images is small, the cleaning time is short, and when there is no image being formed at the time of occurrence of conveyance failure, the cleaning time of the transfer member is set to the shortest time. As a result, it is possible to provide an excellent image forming apparatus in which the recovery time in the event of conveyance failure is significantly reduced as compared with the conventional apparatus.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an image forming apparatus of the present invention.

FIG. 2 is a block diagram illustrating an example of a control system according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 photoconductor drum (image carrier) 11 scorotron charger (charging unit) 12 image exposure device (image exposure unit) 13 developing unit (developing unit) 14a transfer roller (transfer member) 14b transfer area 15 paper cassette 15c timing roller 17 Fixing Device 18a, 18b Discharge Roller 20 Controller 24 Dot Number Counter 25 Count Number Memory (Non-Volatile Memory) 26 Cleaning Time Determination Circuit 34 Transfer Roller Bias Power Supply P Transfer Paper (Transfer Material) S1 Paper Pass Sensor S2 Paper Pass Sensor

Claims (4)

[Claims] An image exposure means for developing a toner image on the image carrier; and a transfer member for contacting the image carrier with the image carrier. An image forming apparatus that transfers a toner image onto a transfer material by applying an electric field to the transfer member in a direction to transfer the toner image to the transfer material. A cleaning unit for cleaning the transfer member by applying an electric field in a direction opposite to the electric field between the member and a member; and a counting unit for counting the number of dots during image formation when performing image exposure by the exposure unit. When returning after the transfer failure of the transfer material occurs, the transfer unit is cleaned by the cleaning unit, and the cleaning time for cleaning is determined according to the number of dots counted by the counting unit. Image formation characterized by apparatus. 2. The image forming apparatus according to claim 1, wherein the cleaning of the transfer member at the time of the return is performed by alternately applying an electric field during the cleaning and an electric field in a direction opposite to the electric field during the cleaning. . 3. The image forming apparatus according to claim 1, wherein the cleaning time is set to the shortest time when there is no image being formed at the time of occurrence of the transfer material conveyance failure. 4. The number of dots counted by said counting means is stored in a non-volatile memory, and when the power is turned off after occurrence of a transfer material conveyance failure or during printing, the number of dots is stored in the non-volatile memory when the power is turned on. The image forming apparatus according to claim 1, wherein the stored number of dots is read, and a cleaning time of the transfer member at the time of warming-up is determined according to the read number of dots.