JP2000276027A - Electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the useless rotation of a photoreceptor drum in case of emergency stop by detecting the phase of the rotation of the photoreceptor drum and performing the stop sequence of a high-voltage unit. SOLUTION: In the case of forming an image by an image forming part 24, time control is ordinarily performed by using the clock of a timer part 13 by a control part 36. For example, when a copying start switch is inputted, previously fixed operation such as reading an image, feeding transfer paper, forming a latent image on the photoreceptor drum, developing it and transferring a toner image to the transfer paper is successively executed by setting the time as reference. When the transfer paper is wound round a roller or jammed in the middle of a carrying path, the control part 36 outputs an emergency stop signal and switches the control from the time control to phase control. When the control is switched to the phase control, the control part 36 fetches the phase of a driving motor 10 transmitted from an encoder 12, detects the rotational angle of the photoreceptor drum and performs the control. Namely, the photoreceptor drum is stopped by performing specified sequence by using the phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus, and more particularly to an electrophotographic apparatus capable of stopping a photosensitive member promptly and without any trouble in an emergency stop.

[0002]

2. Description of the Related Art An electrophotographic apparatus includes a charging device for charging a photoconductor with a predetermined potential around a photoconductor, an exposure device for exposing an image on the photoconductor surface, a developing device for developing a latent image with toner, and a transfer paper. And a fixing device for fixing the toner.

In digital electrophotography, a reversal developing method in which toner is applied to a portion shown in FIG. In a reversal developing electrophotographic apparatus, the charging potential is -50.
0 to -900 volts, and the charging potential of the developing sleeve (hereinafter referred to as "developing bias") is -50 to -30.
-300 to -800 compared to the normal development method of 0 volt
It is set high with bolts.

The charging device is installed at a predetermined angle away from the developing device on the upstream side in the rotation direction of the photosensitive drum, and normally applies a predetermined potential to both of them, so that the carrier is not attracted to the photosensitive drum. Absent. However, when the portion charged by the charger and the potential of the photosensitive drum is not lowered passes through the front surface of the developing device in which the application of the developing bias is stopped,
At the portion shown in FIG. 5B, the carrier is attracted to the photosensitive drum.

Therefore, in an image forming apparatus using the reversal developing method, when a jam occurs inside and an emergency stop of the apparatus is performed, a charger and other high-voltage units are stopped in a predetermined sequence to cause a carrier outflow or a black solid. Had to be prevented.

For example, in a developing device, an emergency stop has been conventionally performed in the event that a transfer paper jam or the like occurs, as follows. That is, after the application of the charging device is stopped, the photosensitive drum is rotated for a predetermined time, and thereafter, the rotation of the photosensitive drum is stopped, and the voltage application to the developing device is stopped. This prevents the charged portion of the photosensitive drum from reaching the developing device where no bias is applied, thereby preventing the carrier from being sucked from the developing device and adhering to the surface of the photosensitive drum.

[0007]

However, conventionally, since the driving of the photosensitive drum was stopped simultaneously with the stop of the developing bias of the developing device, the rotation amount of the photosensitive drum was increased.

The rotation amount of the photosensitive drum increases for the following reasons. That is, in a digital image forming apparatus, since control can be performed by continuous numerical values, time is used for controlling the apparatus. Therefore, when stopping the photosensitive drum, to confirm that the charged portion has passed the developing unit,
Even after the application of the charging device was stopped, the photosensitive drum was rotated at a normal speed, and was rotated at a predetermined speed during a period until the driving of the motor was stopped. Then, the rotation angle of the photosensitive drum is obtained from the rotation speed and the elapsed time, and after a predetermined time, the driving of the rotation drum is stopped.

In other words, if the drive of the photosensitive drum is stopped and rotated by inertia in accordance with the timing of stopping the application of the charger, the rotation speed of the photosensitive drum cannot be sensed thereafter, and the position of the charged portion cannot be specified. There is a possibility that the part reaches the developing device and the carrier is sucked. Since the rotation position of the photosensitive drum cannot be determined in this way, the photosensitive drum was driven at a normal high-speed rotation until the application of the developing device was stopped. Further, even after the drive of the photosensitive drum is stopped, the photosensitive drum rotates by its own inertia,
The number of rotations before the photosensitive drum actually stops has increased.

As described above, when the high-pressure unit is emergency-stopped in a predetermined sequence due to the occurrence of a jam or the like, it is possible to prevent the carrier from adhering and unnecessary black solids, but the stopping time is increased and the rotation of the photosensitive drum is required. And the wound paper may enter the cleaning unit to damage the cleaning unit and the photoconductor.

Further, in the reversal developing method, in addition to the developing device, the application of other high-voltage units and the like cannot be stopped immediately at the time of emergency stop, but must be sequentially stopped in a predetermined sequence.

Further, since copying and other operations cannot be performed until the photosensitive drum reaches a predetermined rotation speed and stabilizes, the time elapsed from the start of rotation is measured at the time of driving, and the rotation is stabilized because the predetermined time has elapsed. It was assumed that the photosensitive drum had been started, so that the photosensitive drum was idled extra until the work was started.

[0013]

According to the present invention, in order to solve the above-mentioned problems, an electrophotographic apparatus is constituted as follows.

That is, at the time of an emergency stop of the electrophotographic apparatus,
The rotation phase of the photosensitive drum is detected to determine the rotation state, and a stop sequence of the high-pressure unit such as the developing device is performed based on the rotation phase.

This makes it possible to actually detect the rotational position of the photosensitive drum during an emergency stop, stop application of the developing device after the charged portion has passed, and prevent problems such as carrier outflow. Before the application of the photosensitive drum is stopped, the rotation of the photosensitive drum is stopped and the photosensitive drum is rotated by inertia so that the photosensitive drum can pass through the charging unit, thereby preventing unnecessary rotation of the photosensitive drum during an emergency stop.

For the detection of the phase, for example, a pulse used for drive control of the drive motor of the photosensitive drum is used,
Alternatively, an encoder is installed on the photosensitive drum, and detection is performed by the encoder. Further, an encoder used for drive control of the drive motor of the photosensitive drum may be used.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the electrophotographic apparatus of the present invention will be described.

FIG. 1 schematically shows a digital copying machine.

As shown in FIG. 1, the digital copying machine 2 includes a scanner section 20 for reading an original, an image processing section 22 for editing and processing an image, an image forming section 24 for printing an image on paper, and an image forming section. Paper feeder 26 that supplies paper to 24
And a finishing unit 28 that finally finishes the printed document
, A sorter unit 30 for discharging a document, a switch unit 32 having various input switches, an image display unit 34, a control unit 36, a timer unit 13, and the like.

The scanner section 20 has a glass plate on the upper surface. When an operation switch is turned on with a document placed on the glass plate, a reading lamp or the like moves to read the document. The original is read as a digital signal, and the read image signal is sent to the control unit 36. In the case of copying, an image signal is sent from the control unit 36 to the image forming unit 24, and printing is immediately performed.

As shown in FIG. 3, the image forming section 24 includes a charging section 41, a photosensitive drum 42, an exposure section 46 by a laser 44, a developing device 48, a transfer charging device 49, a separation charging device 51, The image forming apparatus includes a cleaning unit 50, a fixing device 53, and the like, forms an image from the transmitted image signal, and prints the image on a sheet from the sheet feeding unit 26. The paper supply unit 26 stores paper of various sizes and supplies a predetermined size to the image forming unit 24 according to an instruction from the control unit 36.

The charger 41 is, for example, a scoroton charger, and uniformly charges the photosensitive drum 42 to a predetermined voltage, for example, -600 V, before the latent image forming process.

Further, in the image forming section 24, the photosensitive drum 42 is formed by coating a photosensitive layer on the surface of a cylindrical substrate made of, for example, aluminum having a diameter of 80 mm, and includes a drive motor 10 for driving the photosensitive drum 42; An encoder 12 (refer to FIG. 1) for detecting the rotational phase of the photosensitive drum 42 is provided. The photosensitive layer has a thickness of 15 to 30 μm.
m, the dielectric constant is 2.0 to 5.0, and the substrate is grounded. The photosensitive drum 42 rotates at a speed of, for example, 280 mm / sec, and the rotation phase of the photosensitive drum 42 is measured by the encoder 12. After being uniformly charged by the corona charger 41 while rotating, it is exposed by a laser 44 to form an electrostatic latent image on the surface.

The laser beam emitted from the laser 44 is reflected by the polygon mirror 43 and is irradiated on the surface of the photosensitive drum 42 via an optical system 45 such as an f-θ lens. The polygon mirror 43 is rotating, and the main scanning of the laser beam is performed by the rotation, and the sub-scanning is performed by the rotation of the photosensitive drum 42. The formed electrostatic latent image is visualized by the toner of the developing device 48.

The developing device 48 includes a magnet roller 14,
It comprises a developing sleeve 16 and the like, has a developer inside, and forms a magnetic brush. The developer comprises a toner of a polyester material having an average particle size of 8.5 μm and a ferrite coating carrier having an average particle size of 60 μm, and the toner concentration is controlled to 4 to 6%. The developing sleeve 16
Is applied with a predetermined bias voltage (about -600 V), the toner is transferred from the photosensitive drum 42 onto the transfer paper by the transfer charger 49, and the transfer paper on which the toner is transferred is
The photosensitive drum is separated from the photosensitive drum by the separation charger 51, and is fixed by the fixing unit 53.

The transfer charger 49 is installed to face the photosensitive drum 42, and discharges electric charges from the back side of the transfer paper superposed on the photosensitive drum 42 electrostatically carrying the toner image, thereby transferring the toner image. Transfer toner to paper. Transfer charger 4
9 is preferably a scotron discharger, but may be a corotron charger, a charging roller, or the like.

The separation charger 51 includes a scotron discharger, a corotron charger, a charging roller, and the like, and removes electricity from the transfer paper adsorbed on the photosensitive drum 42 to separate the transfer paper from the photosensitive drum 42.

The toner remaining on the surface of the photosensitive drum 42 without being transferred is collected by the cleaning unit 50. The cleaning unit 50 includes a blade that comes into contact with the photosensitive drum 42, and scrapes off toner, dust, and the like attached to the surface of the photosensitive drum 42, and stores the scraped toner and toner in the toner box.

Further, the electric history of the photosensitive drum is erased by the pre-exposure lamp, and the next print cycle is started. The fixing device 53 applies pressure and heat to the transfer paper on which the toner image has adhered, and fixes the toner on the transfer paper.

The finishing unit 28 performs operations such as a stapling mechanism, a center folding mechanism, sorting, and grouping. The sorter unit 30 is a discharge mechanism that discharges the printed transfer paper in a predetermined state. The switch unit 32 is installed on the upper surface of the digital copying machine 2 and allows input of enlargement / reduction of a print image, designation of print paper, designation of the number of prints, and the like.

Normally, the image forming section 24 forms an image by
The time is controlled by the control unit 36 using the clock of the clock unit 13. For example, when a switch for starting copying is input, an image is read, a transfer sheet is sent, a latent image is formed on the photosensitive drum 42, development is performed. Predetermined operations such as transfer of a toner image to a transfer sheet are sequentially executed based on time.

Then, the transfer paper is wound around the roller,
When jamming occurs in the middle of the transport path, the control unit 36 issues an emergency stop signal and switches control from time control to phase control. When the control is switched to the phase control, the control unit 36 takes in the phase of the drive motor 10 sent from the encoder 12, detects the rotation angle of the photosensitive drum 42, and performs control. That is, a predetermined sequence is performed using the phase, and the photosensitive drum 42 is stopped.

Next, the stop state at the time of an emergency stop will be specifically described with reference to FIG.

As shown in FIG. 4, when the switch of the electrophotographic apparatus 2 is turned on, normal operation is started and normal operation is performed (F-1). When the transfer paper is jammed, an emergency stop signal is issued (F-2), and the control by the control unit 36 is changed from time control to control based on the phase of the photosensitive drum 42 (F-3). Then, the application of the charger 41 is stopped (F-4), and at the same time, the photosensitive drum 4
The power of the second drive motor 10 is cut off (F-6).

Further, the phase at the time when the application of the charger 41 is stopped is detected (F-5), and the value is sent to the control unit 36. Even when the power supply to the drive motor 10 of the photosensitive drum 42 is stopped, the photosensitive drum 42 continues to rotate due to inertia,
The phase in the meantime is detected by the encoder 12.

The control unit 36 detects the rotation of the photosensitive drum 42 from the phase detected by the encoder 12 provided on the photosensitive drum 42, and confirms that the charging stop point has passed the developing unit 48 (F-7). Then, the application of the voltage of the developing device 48 is stopped (F-9).

As a result, the drive motor 10 for the photosensitive drum 42 can be stopped at the same time as the application of the charging device 41 is stopped without causing carrier outflow or the like, thereby preventing unnecessary rotation of the photosensitive drum 42 due to inertia. be able to. When the rotation speed of the photosensitive drum 42 due to inertia is small, the power cutoff timing of the drive motor 10 of the photosensitive drum 42 may be appropriately delayed.

The present invention is not limited to stopping the application of the developing device.
It may be used for stopping the application of the voltage of another high voltage portion.

[0039]

Embodiments will be described below with reference to the drawings.

FIGS. 2 and 6 show the amount of rotation of the photosensitive drum 42 according to the present invention and the conventional example. FIG. 2 shows a control method according to the present invention. In FIG.
The energized state of the developing device is shown. The horizontal axis is the time axis.

First, when the switch is turned on, the photosensitive drum rotates, and electricity is supplied to each of the charging device and the developing device to start normal use. When a jam occurs at tp, the control unit issues an emergency stop signal to stop charging of the charger, and at the same time, shuts off the power supply of the drive motor of the photosensitive drum. At the same time, the control unit uses the phase signal from the phase detector of the photosensitive drum for control.

At this time, the power supply to the developing unit is not interrupted yet, and the electric charge is applied. Then, when the control section detects from the phase of the photosensitive drum that the charging stop portion of the charging device has reached the developing device, the application of the developing device is stopped. As a result, the photosensitive drum stops at time t1 from the transmission of the emergency stop signal.

On the other hand, in the conventional example shown in FIG. 6, since the power supply of the drive motor for the photosensitive drum is cut off at a time ts after a predetermined margin after the bias of the developing device is stopped, the emergency stop is performed. It takes t2 from the transmission of the signal to the stop of the photosensitive drum, and it can be seen that the rotation amount until the stop is increased.

Thus, the stop time of the photosensitive drum can be advanced, and unnecessary rotation of the photosensitive drum at the time of emergency stop can be limited.

[0045]

According to the image forming apparatus of the present invention, the control of the high-voltage devices is performed not by time control at the time of stoppage, but by using the rotation phase of the drive motor of the photosensitive drum. Accordingly, fine and accurate control becomes possible, and when an emergency stop such as the occurrence of a jam is performed, the rotation of the photosensitive drum can be directly detected and controlled, and unnecessary rotation of the photosensitive drum can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an outline of a digital copying machine according to the present invention.

FIG. 2 is a graph showing a rotation state of a photosensitive drum according to the present invention.

FIG. 3 is a diagram illustrating an image forming unit.

FIG. 4 is a flowchart relating to a stop of a drive motor according to the present invention.

FIG. 5 is a diagram illustrating a charged state.

FIG. 6 is a graph showing a rotation state of a photosensitive drum according to a conventional example.

[Explanation of symbols]

 2 Digital Copier 10 Drive Motor 12 Encoder 13 Timing Unit 14 Magnet Roller 16 Developing Sleeve 20 Scanner Unit 22 Image Processing Unit 24 Image Forming Unit 26 Feeding Unit 28 Finishing Unit 30 Sorter Unit 32 Switch Unit 34 Image Display Unit 36 Control Unit 41 Charger 42 Photosensitive drum 43 Polygon mirror 44 Laser 45 Optical system 46 Exposure unit 48 Developing unit 49 Transfer charger 50 Cleaning unit 51 Separation charger 53 Fixer

Claims (3)

[Claims] 1. A latent image formed on the surface of a photoreceptor is visualized by a toner in a developing unit, the visualized toner image is transferred from the photoreceptor to a transfer paper, and the toner on the transfer paper is removed. An electrophotographic apparatus of a reversal development type in which a recording image is formed by fixing in a fixing unit, wherein the rotation phase of the photoconductor is used for controlling image formation. 2. The image forming apparatus according to claim 1, wherein image forming control is performed using time during normal image forming, and image forming control is performed using a rotational phase of said photosensitive member during emergency stop. An electrophotographic apparatus according to the above. 3. In an emergency stop, a charging operation of a charger for charging the surface of the photoconductor is stopped, a charging stop position on the photoconductor is detected from a rotation phase, and a rotation amount of the photoconductor is detected by a phase detection unit. 2. The electrophotographic apparatus according to claim 1, wherein when the charging stop position passes through the developing device, the application of the bias of the developing device is stopped.