JPH09327940A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a detection signal at arbitrary timing as required. SOLUTION: A photosensitive drum 4 is electrified when the preparation of an optical system is completed so as to form an image on the photosensitive drum 4 by sending a video signal from an image controller in synchronous with a horizontal synchronizing signal sent from a printer control circuit for turning ON/OFF a laser driving signal in order to transfer the image on a paper for fixing a toner image. During the formation of the image, a synchronizing light sensor 32 detects the horizontal synchronizing signal sent from a polygon mirror 31. When no horizontal synchronizing signal is detected at the timing due to the stable rotation of a scanner motor, a compensatory signal forming circuit 33 outputs a compensatory signal so as to continuous the controlling of the scanner motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, such as an electrophotographic printer, which forms an image on a photosensitive member by exposure.

[0002]

2. Description of the Related Art In a conventional image forming apparatus, a laser beam modulated by image information is scanned by a rotating polyhedron and is exposed on a photosensitive drum to form an image. The scanning polyhedron is detected to control the rotating polyhedron. Then, when the scanning light is not detected by the light detecting means due to a failure or a malfunction, the operation of the rotating polyhedron is stopped as an error.

[0003]

However, in the above-mentioned conventional example, while the control means turns on the laser light source and rotates the rotating polyhedron, the light detecting means detects the scanning light signal for checking or the like. Therefore, there is a problem that a detection signal cannot be obtained at an arbitrary timing and the life of a motor for driving the rotating polyhedron, a laser light source, etc. is shortened.

When the detection signal cannot be detected,
The rotating polyhedron controlled by the detection signal becomes uncontrollable and must stop rotating. Therefore, in order to reduce the number of rotations and restore the device, it is necessary to restart the rotating polyhedron, and it takes time to restore, and the cause of the error is unknown.

The object of the present invention is to solve the above problems,
An object of the present invention is to provide an image forming apparatus that obtains a detection signal at an arbitrary timing as needed.

[0006]

An image forming apparatus according to the present invention for achieving the above object comprises an image processing means for generating pixel information, an image forming means for forming an image on a recording medium, and the pixel information. In an image forming apparatus including an exposure unit that exposes a photosensitive drum based on the above, a laser light output circuit that outputs a laser light modulated by the pixel information, and a laser light output from the laser light output circuit is reflected. Rotating polyhedron for scanning on photosensitive drum, photodetecting means for detecting the position of scanning light scanned by the rotating polyhedron, and signal generation for enabling pseudo output of detection signal of the photodetecting means at arbitrary timing And means.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the illustrated embodiment. FIG. 1 is a sectional view of the laser beam printer of the first embodiment, FIG. 2 is a block diagram of a control system block circuit, and FIG. 3 is a block diagram of an optical system. Inside the laser beam printer 1 of FIG. 1, a folding mirror 3 is arranged in front of the optical unit 2, and a photosensitive drum 4 is arranged in the reflection direction of the folding mirror 3. Around the photosensitive drum 4, a charging device 5, a developing device 6, a transfer device 7, and a cleaner 8 are provided.
Are arranged in sequence, a cassette 9 is provided on the right side surface of the laser beam printer 1, and a paper feed roller 10, a conveyance roller 11, and a paper feed sensor 1 are arranged in the left direction from the cassette 9.
2, the transfer device 7, the fixing device 13, the paper discharge sensor 14, and the paper discharge tray 15 are sequentially arranged.

In the control system of FIG. 2, the input / output of the image controller 20 is connected to the printer control circuit 21, and the output of the printer control circuit 21 is connected to the main motor 22, the high voltage system control circuit 23, and the optical system control circuit 24. Has been done.

In the optical system of FIG. 3, a polygon mirror 31 rotated by a scanner motor (not shown) is arranged in front of the laser diode 30, and the photosensitive drum 4 and the synchronizing optical sensor are arranged in the reflection direction of the polygon mirror 31. 32 are arranged. And the optical sensor 3 for synchronization
The output of 2 is directly connected to the printer control circuit 21 via the complementary signal generation circuit 33.

In the optical unit 2, the laser light is modulated by the data of the video signal sent from the image controller 20, and the polygon mirror 31 scans the photosensitive drum 4 via the folding mirror 3. The charger 5 uniformly charges the photosensitive drum 4, and the developing device 6 develops the electrostatic latent image on the photosensitive drum 4 into a toner image. Then, the transfer unit 7 transfers the toner image on the photosensitive drum 4 onto the sheet, and then the cleaner 8 collects the toner remaining on the photosensitive drum 4.

The paper housed in the cassette 9 is supplied by the paper feed roller 10, and the paper supplied by the carry roller 11 is carried. The paper feed sensor 12 detects that the paper has been conveyed, determines the timing of starting image formation, and detects a malfunction of the machine. Further, the toner image transferred to the paper by the transfer unit 7 is heated and fixed by the fixing device 13, and the distance from the laser light irradiation position on the photosensitive drum 4 to the transfer position and the transfer position to the paper feed sensor 12 are determined. The paper discharge sensor 14 arranged so that the distances are equal to each other detects the presence or absence of paper discharged from the fixing device 13 and discharges the paper from the paper discharge tray 15.

The image controller 20 receives print data and commands from a computer (not shown), creates image data for one page, sends a PRFD signal to the printer control circuit 21, and thereby supplies paper from the cassette 9 to the photosensitive drum. 4 and the like are conveyed to a position before reaching the image forming unit and stopped. Then, the image controller 20
An RNT signal is output and this sheet is supplied to the image forming unit to instruct image formation. On the other hand, the printer control circuit 21
Outputs a horizontal sync signal to the image controller 20,
A video signal for one line is sent from the image controller 20 to the printer control circuit 21 in synchronization with the horizontal synchronizing signal, and a desired image is printed.

Further, the printer control circuit 21 outputs a motor drive signal for driving the main motor 22, and the high voltage control signal output from the printer control circuit 21 to the high voltage control circuit 23 causes charging AC and charging D, respectively.
The output of each bias of C, development, transfer (+), and transfer (-) is controlled. From the printer control circuit 21 to the optical system control circuit 24, a scanner acceleration signal for accelerating the rotation of the scanner motor of the polygon mirror 31, a scanner deceleration signal for decelerating the rotation of the scanner motor of the polygon mirror 31, a laser diode 30. Laser drive signal for controlling the lighting of the laser light of the laser diode 30
A laser light amount control signal for changing the amount of light emitted by the printer is output, and the optical system control circuit 24 causes the printer control circuit 2
A horizontal synchronization signal and a complementation request signal, which are obtained when the synchronization optical sensor 32 detects that the laser light is reflected by the polygon mirror 31, are output to 1.

FIG. 4 is a flow chart showing that when the PRNT signal is input while the main motor 22 is stopped, the main motor 22 is driven to start feeding and carrying the paper. At the same time, the scanner acceleration signal is input, and the rotation of the scanner motor that drives the polygon mirror 31 is accelerated. The printer control circuit 21 determines the rotation speed of the scanner motor from the cycle of the horizontal synchronizing signal, and inputs the scanner deceleration signal when the rotation speed is faster than the specified rotation speed.
By inputting the scanner acceleration signal when it is late,
The number of rotations of the scanner motor is kept constant to bring the optical system into a state capable of forming an image.

When the preparation of the optical system is completed, charging AC and charging DC are input to charge the photosensitive drum 4. Then, the printer control circuit 21 outputs a horizontal synchronizing signal to the image controller 20, and the image controller 20 sends out a video signal in synchronization with the horizontal synchronizing signal. In accordance with this video signal, the laser drive signal is turned on / off to form an image on the photosensitive drum 4, this image is developed and transferred to a sheet, and then the toner image is fixed by the fixing device 13 and the sheet discharge tray 15 is formed.
Discharged from

During image formation, since the scanner motor is constantly rotating at a specified rotation speed, the detection timing of the horizontal synchronizing signal can be almost specified. Therefore, when the horizontal synchronizing signal is not detected at that timing, the complementary signal is output from the complementary signal generation circuit 33 to continue the control of the scanner motor. If the horizontal sync signal is not continuously detected for the specified number of times or more, it is determined that there is a failure and the scanner motor is stopped.

FIG. 5 shows the configuration of the optical system of the second embodiment, and the same symbols as those in FIG. 3 represent the same members. A light emitting means 35 is provided for generating and detecting the complementary signal,
The output of the printer control circuit 21 is connected to the complementary signal generation circuit 33, and the output of the complementary signal generation circuit 33 is the light emitting means 35.
It is connected to the.

Similar to the first embodiment, when the scanning light sensor 32 cannot detect the scanning light, the printer control circuit 2
1 outputs a complementation request signal to the complementation signal generation circuit 33 to cause the light emitting means 35 to emit light. This signal is sent to the optical sensor 3 for synchronization.
If 2 can be detected, the control is continued as in the first embodiment. If the synchronizing optical sensor 32 cannot detect a signal, the synchronizing optical sensor 32 or the signal line is broken and the scanner motor is stopped. .

Further, the optical sensor for synchronization 32 is used while the control is continued.
When it is determined that the scanning light cannot be detected continuously for a predetermined number of times or more and it is determined that there is a failure, it is determined that the laser diode 30 or the scanner motor has a failure. By performing such control, when the horizontal synchronization signal cannot be detected and it is determined that there is a failure, the failure point can be determined in more detail.

[0020]

As described above, the image forming apparatus according to the present invention detects the scanning light by pseudo-obtaining the scanning light detection signal at an arbitrary timing in accordance with the request of the image processing means and the control means. Even if a signal cannot be detected, control can be returned quickly without lowering the rotational speed of the rotating polyhedron, and the cause of the failure can be detected in more detail, resulting in damage to optical system components. Can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a laser beam printer according to a first embodiment.

FIG. 2 is a configuration diagram of a block circuit of a control system.

FIG. 3 is a configuration diagram of an optical system.

FIG. 4 is a flow chart diagram.

FIG. 5 is a configuration diagram of an optical system according to a second embodiment.

[Explanation of symbols]

 1 Laser Beam Printer 2 Optical Unit 4 Photosensitive Drum 7 Transfer Device 13 Fixing Device 20 Image Controller 21 Printer Control Circuit 24 Optical System Control Circuit 30 Laser Diode 31 Polygon Mirror 32 Synchronous Optical Sensor 33 Complementary Signal Generation Circuit 35 Light Emitting Means

Claims (4)

[Claims] 1. An image forming apparatus comprising: an image processing unit for generating pixel information; an image forming unit for forming an image on a recording medium; and an exposing unit for exposing a photosensitive drum based on the pixel information. A laser light output circuit that outputs laser light modulated by the pixel information, a rotating polyhedron that reflects the laser light from the laser light output circuit and scans the photosensitive drum, and a scanning light that is scanned by the rotating polyhedron. An image forming apparatus comprising: a light detecting unit that detects a position; and a signal generating unit that can output a detection signal of the light detecting unit in a pseudo manner at an arbitrary timing. 2. The image according to claim 1, further comprising a light emitting means capable of emitting light at an arbitrary timing, and causing the light emitting means to emit light when an error occurs in detection of scanning light by the light detecting means that can be detected at any time. Forming equipment. 3. The rotating polyhedron is controlled at the cycle of the detection signal of the photodetecting means, and if there is an error in the detection of the photodetecting means, the control is continued by supplementing with the output signal of the signal generating means. The image forming apparatus according to claim 1, configured to do so. 4. The image forming apparatus according to claim 3, wherein the rotating polyhedron is stopped when the output of the signal generating unit continues for a predetermined number of times or more.