JP2007062167A - Image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image formation device of high quality which enables a polygons motor rotational frequency to be stably controlled, a horizontal synchronizing signal to be prevented from being unexpectedly defeated, the polygons motor rotational frequency to be quickly changed, the time for a laser to irradiate a photosensitive drum surface to be shortened, a discharge time of laser to be shortened and the life of the image formation device to be prolonged by changing a rotational speed with performing a compulsive luminescence of laser at changing the polygons motor rotational frequency or by repeating the operation of a laser compulsive ON/OFF in the image formation device with a print mode in which the polygons motor rotational frequency is composed of two changes or more. <P>SOLUTION: When changing the print mode accompanied by the alteration of the polygons motor rotational frequency, the polygons motor rotational frequency is controlled by compulsorily discharging the laser beam. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus used for a laser printer or the like that scans a photosensitive drum with laser light modulated based on image information from an external device such as a personal computer to record an image.

  In a conventional laser printer, image information that is code data is converted into an image signal that is bit data by an image signal generator, and the image signal is transmitted to a laser driving device that emits laser light. The laser driving device is based on the image signal. The laser emission is ON / OFF modulated, and the modulated laser beam is scanned on the photosensitive drum by a laser scanning device equipped with a rotating polygon mirror to form an electrostatic latent image.

  FIG. 9 is a diagram showing a configuration of a conventional image forming apparatus. Reference numeral 101 denotes a laser unit including a laser diode, which generates modulated laser light. Reference numeral 102 denotes a rotating polygon mirror (polygon mirror) that reflects laser light, and is driven to rotate by a polygon motor 103. A photoelectric conversion device 104 is disposed in the laser scanning path, and is used for detecting the position of the laser beam by outputting a detection signal when the laser beam is irradiated.

  Here, when the polygon motor 103 rotates, the laser light passes through the imaging lens 105, is reflected by the folding mirror 106, and scans on the photosensitive drum 107.

  An electrostatic latent image corresponding to an image signal can be formed at a predetermined position on the photosensitive drum 107 by modulating the laser light in synchronization with the timing of laser incidence on the photoelectric conversion device 104.

  Next, rotation control of the polygon motor 103 will be described. In the laser printer, there is a method of performing rotation control of the polygon motor 103 using a signal of the photoelectric conversion device 104 that detects the position of the laser beam.

  FIG. 10 shows a block diagram of a circuit related to polygon motor rotation control.

  As the polygon motor 103, a three-phase drive type brushless DC motor is often used, and the three-phase motor 103 includes a three-phase motor coil 108, a hall element 109 for detecting the position of the motor rotor, and a motor drive circuit 110. The motor drive circuit 110 sequentially supplies current to each phase of the three-phase motor coil 108 based on the signal from the motor rotor position detection Hall element 109 to rotate the motor. The current flowing through the motor coil is controlled according to speed control signals (acceleration signal and deceleration signal) input from the printer control device 111.

  The printer control device 111 outputs an acceleration signal if the laser detection signal from the photoelectric conversion device 104 is equal to or greater than a predetermined period, and outputs a deceleration signal if the laser detection signal is equal to or less than the predetermined period. The rotational speed is controlled to the rotational speed corresponding to the predetermined period.

  FIG. 11 shows the timing of turning on the laser beam and the timing of the acceleration signal / deceleration signal. A reference pulse signal is generated in the printer control device 111, and the / reference pulse signal and the laser detection signal (/ horizontal synchronization signal) from the photoelectric conversion device 104 are compared to generate an acceleration signal / deceleration signal.

The conventional polygon motor is started up by performing laser lighting control as shown in FIG. 12 (repetition of LaserON → LaserOFF → LaserON → LaserOFF →...). At that time, when the laser is turned on, the reference pulse signal and the laser detection signal (/ horizontal synchronization signal) from the photoelectric conversion device 104 are compared to generate an acceleration signal / deceleration signal.
Japanese Patent Laid-Open No. 11-125788

  However, when the polygon motor is continuously rotated while the polygon motor is rotating at a constant speed, the laser at that time can be controlled by repeating ON / OFF of the laser lighting performed when the polygon motor is started up. When OFF, the rotation speed of the polygon motor does not decrease and the rotation speed increases again, and the rotation speed of the polygon motor cannot be reduced.

  Further, when the polygon motor is continuously increased while the polygon motor is rotating, if the control is performed only by turning on the laser, it is not possible to change the rotation speed quickly.

  The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to rotate a polygon motor in an image forming apparatus having a print mode in which the rotation speed of the polygon motor is 2 or more. It is an object of the present invention to provide a high-quality image forming apparatus capable of performing stable polygon motor rotation speed control, preventing horizontal sync signal loss, and quick polygon motor rotation speed change when the number is changed.

  An image forming apparatus according to the present invention includes a laser that emits laser light modulated by an image signal, a rotating polygon mirror that reflects the laser light while rotating to form a scanning line, and a polygon motor that drives the rotating polygon mirror. A photosensitive drum that forms an image at a position irradiated with the scanning line; and a photodetector that is disposed at the extreme end of the scanning line and generates and outputs a detection signal when irradiated with the laser beam. A rotation speed control means for controlling the rotation speed of the polygon motor based on the period of the detection signal and the period of the reference pulse; and the detection signal is input to force the laser to emit light or to extinguish the polygon motor. In an image forming apparatus comprising: a control unit that controls the operation / stop of the polygon motor; and a unit that has two or more types of print modes in which the rotation speed of the polygon motor is different. When the print mode change involving a change of the rolling speed, forcibly emit laser light, and controlling the rotational speed of the polygon motor.

  The image forming apparatus according to the present invention has a plurality of laser beam emission controls to control the rotation speed of the polygon motor when the print mode is changed with a change to reduce the rotation speed of the polygon motor.

  The image forming apparatus according to the present invention has a plurality of laser beam emission controls to control the rotation speed of the polygon motor when the print mode is changed with a change that increases the rotation speed of the polygon motor.

  The image forming apparatus according to the present invention is characterized in that the control of the laser light repeats forcibly emitting and not emitting laser light alternately.

  The image forming apparatus according to the present invention is characterized in that the rotation speed of the polygon motor is controlled when laser light is forcibly emitted.

  The image forming apparatus according to the present invention is characterized in that the compulsory emission end timing of the laser beam is set when the rotation speed of the polygon motor falls within an arbitrary range of a predetermined rotation speed.

  According to the present invention, in an image forming apparatus having a print mode in which the rotation speed of the polygon motor is 2 or more, the rotation speed is changed by forcibly emitting the laser when the rotation speed of the polygon motor is changed, or By repeating ON / OFF, stable polygon motor rotation speed control, prevention of horizontal sync signal loss, quick change of polygon motor rotation speed, and reduction of the time that the laser irradiates the photosensitive drum surface. Therefore, it is possible to provide a high-quality image forming apparatus that can shorten the laser emission time and extend the life of the image forming apparatus.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  Embodiment 1 of the present invention will be described below with reference to the drawings.

  FIG. 2 is a block diagram of a circuit related to the polygon motor drive of the image forming apparatus showing an embodiment of the present invention.

  In FIG. 2, reference numeral 103 denotes a polygon motor as drive means for driving the rotary polygon mirror to rotate, and the rotary polygon mirror 102 is rotated in accordance with acceleration and deceleration signals from a rotation control circuit 4 described later.

  Reference numeral 104 denotes a photoelectric conversion device serving as a light detection unit including a light receiving element, and outputs a horizontal synchronization signal when a laser beam scanned by a rotating polygon mirror is incident. The horizontal synchronization signal is output to a rotation control circuit 4, a microcomputer 5, and an image signal generator 8 which will be described later.

  Reference numeral 101 denotes a laser drive device including a semiconductor laser, which emits the semiconductor laser in response to a laser drive signal.

  Reference numeral 4 denotes a rotation control circuit, which compares the horizontal synchronization signal from the photoelectric conversion device 104 with the cycle of a reference pulse signal from the microcomputer 5 to be described later, and sends an acceleration / deceleration signal to the polygon motor 103 so that the cycles match. Is output to control the rotation speed of the polygon motor 103. Further, the motor is rotated / stopped by a motor drive request signal from the microcomputer 5 described later.

  Reference numeral 5 denotes a microcomputer (hereinafter referred to as MPU) having a RAM, a ROM, a timer, and the like. As described above, the MPU 5 outputs to the rotation control circuit 4 the motor drive request signal for instructing rotation / stop of the polygon motor 103 and the reference pulse signal for instructing the control rotation speed. Further, the MPU 5 has a function of controlling laser light emission, and outputs a light emission permission signal which is a signal for allowing laser light emission and a light emission request signal for forcibly emitting the laser light.

  Further, control for predicting the next horizontal synchronization signal generation timing based on the period of the horizontal synchronization signal and periodically making the light emission request signal active (HIGH) (hereinafter referred to as laser horizontal synchronization ON / OFF control). Contains the function to perform. The light emission permission signal, the light emission request signal, and the image signal transmitted from the image signal generator 8 are subjected to a logic given by a logical expression defined by an OR gate 7 and an AND gate 6, and then a laser drive signal. Is generated. That is, if the light emission permission signal is OFF (LOW), the laser is always turned off. When the light emission permission signal is ON (HIGH), either the light emission request signal is ON (HIGH) or the image signal is ON (HIGH). In such a case, the laser emits light.

  FIG. 1 is a flowchart showing the control performed in the MPU 5 when the rotational speed of the polygon motor 103 of the present embodiment is lowered, and FIG. 3 is a timing chart explaining the temporal transition of this control. Hereinafter, the control will be described with reference to FIGS. 1 and 3.

  First, the polygon motor 103 is rotating at a steady rotation speed (S101). At this time, laser horizontal synchronization ON / OFF control is performed, and the polygon motor 103 maintains a steady rotational speed. FIG. 8 is a timing chart of laser light emission and horizontal synchronization signal during steady rotation. Next, when the rotational speed of the polygon motor is decreased (S102), the laser is forcibly kept on (S103). Then, the horizontal synchronization signal is detected, it is determined whether the polygon motor is within an arbitrary rotational speed (S104), the laser is turned on until the rotational speed is within the arbitrary rotational speed, and when the rotational speed is within the arbitrary rotational speed, The laser horizontal synchronization ON / OFF control is performed again (S105).

  The dodd part of FIG. 3 is a laser forced lighting part.

  The above is the “control for reducing the rotational speed of the polygon motor” in the present embodiment.

  In this embodiment, the image forming apparatus having the print mode in which the rotation speed of the polygon motor is the second speed has been described. Further, the same control may be performed for an image forming apparatus having a print mode in which the rotation speed of the polygon motor is 2nd or higher.

  As described above, in an image forming apparatus having a print mode in which the rotation speed of the polygon motor is 2 speeds or more, when the rotation speed of the polygon motor is lowered, the rotation speed is changed by forcibly emitting laser light. Therefore, it is possible to provide a high-quality image forming apparatus capable of performing the polygon motor rotation speed control, preventing the horizontal synchronization signal from being lost, and quickly changing the polygon motor rotation speed.

  The “control for increasing the rotation speed of the polygon motor”, which is the second embodiment, will be described.

  Circuits related to driving the polygon motor are the same as those in the first embodiment, and are omitted.

  FIG. 4 is a flowchart showing the control performed in the MPU 5 when the rotational speed of the polygon motor 103 of this embodiment is increased, and FIG. 5 is a timing chart explaining the temporal transition of this control. Hereinafter, the control will be described with reference to FIGS. 4 and 5.

  First, the polygon motor 103 is rotating at a steady rotation speed (S401). At this time, laser horizontal synchronization ON / OFF control is performed, and the polygon motor 103 maintains a steady rotational speed. FIG. 8 is a timing chart of laser light emission and horizontal synchronization signal during steady rotation. Next, when the rotation speed of the polygon motor is increased (S402), the laser is forcibly kept on (S403). Then, a horizontal synchronization signal is detected, it is determined whether the polygon motor is within an arbitrary rotational speed (S404), the laser is turned on until it is within the arbitrary rotational speed, and when the rotational speed is within the arbitrary rotational speed, Again, laser horizontal synchronization ON / OFF control is performed (S405).

  The dodd part of FIG. 5 is a laser forced lighting part.

  The above is the control for increasing the rotation speed of the polygon motor of this embodiment.

  In this embodiment, the image forming apparatus having the print mode in which the rotation speed of the polygon motor is the second speed has been described. Further, the same control may be performed for an image forming apparatus having a print mode in which the rotation speed of the polygon motor is 2nd or higher.

  As described above, in an image forming apparatus having a print mode in which the rotation speed of the polygon motor is 2 speeds or more, when the polygon motor rotation speed is increased, the rotation speed is changed by forcibly emitting the laser. Thus, it is possible to provide a high-quality image forming apparatus capable of performing the polygon motor rotation speed control and preventing the horizontal synchronization signal from being lost.

  The “control for increasing the rotational speed of the polygon motor”, which is Embodiment 3, will be described.

  Circuits related to driving the polygon motor are the same as those in the first embodiment, and are omitted.

  FIG. 6 is a flowchart showing the control performed in the MPU 5 when the rotational speed of the polygon motor 103 of this embodiment is increased, and FIG. 7 is a timing chart explaining the temporal transition of this control. Hereinafter, the control will be described with reference to FIGS. 6 and 7.

  First, the polygon motor 103 is rotating at a steady rotation speed (S601). At this time, laser horizontal synchronization ON / OFF control is performed, and the polygon motor 103 maintains a steady rotational speed. FIG. 8 is a timing chart of laser light emission and horizontal synchronization signal during steady rotation. Next, when the rotation speed of the polygon motor is increased (S602), the laser is forcibly turned on. Then, it is determined whether or not the polygon motor is within an arbitrary rotational speed. If the rotational speed is not an arbitrary rotational speed, the laser is forcibly turned off for an arbitrary time (S606). The laser is forcibly turned on again (S603). If the rotation speed is not at an arbitrary value, the laser is forcibly turned off (S606). If the rotation speed is at an arbitrary value, the laser horizontal synchronization is turned on again. / OFF control is performed (S605).

  The dodd part of FIG. 7 is a laser forced lighting part.

  The above is the control for increasing the rotation speed of the polygon motor of this embodiment.

  In this embodiment, the image forming apparatus having the print mode in which the rotation speed of the polygon motor is the second speed has been described. Further, the same control may be performed for an image forming apparatus having a print mode in which the rotation speed of the polygon motor is 2nd or higher.

  As described above, in an image forming apparatus having a printing mode in which the rotation speed of the polygon motor is 2 speeds or more, when the rotation speed of the polygon motor is increased, laser forcible ON / OFF is repeatedly performed to change the rotation speed. High-quality image formation that can quickly change the polygon motor speed, reduce the time that the laser irradiates the photosensitive drum surface, shorten the laser emission time, and extend the life of the image forming device Equipment can be provided.

Control flowchart used in the first embodiment Block diagram used in Examples 1-3 Control timing chart used in Example 1 Control flowchart used in the second embodiment Control timing chart used in Example 2 Control flowchart used in Embodiment 3 Control timing chart used in Example 3 Timing chart used in Examples 1 to 3 The figure which showed the structure of the conventional image forming apparatus Block diagram of circuits related to polygon motor rotation control / Timing chart of horizontal sync signal and acceleration / deceleration signal Conventional control timing chart

Explanation of symbols

4 Rotation control device 5 Microcomputer (MPU)
8 Image signal generator 101 Laser drive device 102 Rotating polygon mirror 103 Polygon motor 104 Photoelectric conversion device 105 Imaging lens 106 Folding mirror 107 Photosensitive drum 108 Motor coil 109 Hall element 110 Motor drive circuit 111 Printer control device

Claims (6)

A laser that emits laser light modulated by an image signal;
A rotating polygon mirror that reflects the laser beam while rotating to form a scanning line;
A polygon motor for driving the rotary polygon mirror;
A photosensitive drum for forming an image at a position irradiated with the scanning line;
A photodetector that is disposed at the extreme end of the scanning line and generates and outputs a detection signal when irradiated with the laser beam;
A rotational speed control means for controlling the rotational speed of the polygon motor based on the period of the detection signal and the period of the reference pulse;
A control means for inputting the detection signal, forcibly turning on or off the laser, and controlling operation / stop of the polygon motor;
Means having two or more types of print modes in which the rotation speed of the polygon motor is different;
In an image forming apparatus comprising:
An image forming apparatus, wherein a laser beam is forcibly emitted to control a rotational speed of a polygon motor when a print mode is changed with a change in the rotational speed of the polygon motor.   The image forming apparatus according to claim 1, wherein when changing a print mode accompanied by a change that reduces the rotation speed of the polygon motor, a plurality of laser light emission controls are provided to control the rotation speed of the polygon motor.   3. The image forming apparatus according to claim 1, wherein when changing a print mode accompanied by a change that increases the rotation speed of the polygon motor, the image forming apparatus has a plurality of laser light emission controls to control the rotation speed of the polygon motor.   4. The image forming apparatus according to claim 2, wherein the control of the laser beam repeats forcibly emitting and not emitting laser beam alternately.   5. The image forming apparatus according to claim 1, wherein the rotation speed of the polygon motor is controlled when laser light is forcibly emitted.   6. The image forming apparatus according to claim 1, wherein the laser beam compulsory emission end timing is when the rotation speed of the polygon motor falls within an arbitrary range of the predetermined rotation speed.

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