JP4400393B2 - Laser control apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a laser control device that controls power supply to a laser light source and an image forming apparatus having such a laser control device.

  2. Description of the Related Art Conventionally, an image forming apparatus such as a printer that forms an electrostatic latent image on a photoreceptor roll by deflecting laser light from a laser diode using a polygon mirror rotated by a polygon motor is known.

  In such an image forming apparatus, a laser diode that emits laser light by a lock signal that is a state signal indicating whether the polygon motor is in a steady state that is rotating normally or is in an unstable state that is out of steady rotation There is one in which the power supply to is controlled (see, for example, Patent Document 1).

  FIG. 1 is a schematic diagram of a conventional laser control apparatus that controls the emission of laser light.

  In FIG. 1, in addition to the laser control device 100, a laser diode 13e, which is a light source that emits laser light, a laser diode substrate 13f to which the laser diode 13e is attached, and the laser light emitted from the laser diode 13e are deflected. A polygon motor 13c that rotates a polygon mirror (not shown) is shown.

  The laser control device 100 monitors the lock signal from the output unit 13g that outputs a lock signal, which is a status signal of the polygon motor 13c, at a predetermined monitoring period, and supplies power while the lock signal represents a stable state. While the lock signal is supplied to the laser diode substrate 13f and the lock signal indicates an unstable state, the power supply control circuit 102 for stopping the power supply to the laser diode substrate 13f, the Schmitt buffer 100b, and the control substrate 100a on which these are disposed. It consists of and. The power supply control circuit 102 includes an npn transistor 1021, resistors 1022 and 1023, and a p-mos transistor 1024. Further, the lock signal is transmitted to the CPU 101 and the power supply control circuit 102 through the lock signal line 100d, and the lock signal line directed to the power supply control circuit 102 passes through the Schmitt buffer 100b that makes the input signal a square wave. A motor clock line 100c for inputting a motor clock from the CPU 101 to the polygon motor 13c is also shown.

  In the laser control apparatus 100 shown in FIG. 1, when noise is included in the lock signal or when the rotation of the polygon motor 13c is slightly disturbed, the power from the power control circuit 102 to the laser diode substrate 13f is supplied. The supply becomes unstable, and the laser beam emitted from the laser diode 13e is disturbed to cause an image defect.

  FIG. 2 is a graph showing an input signal and an output signal of the laser control device shown in FIG.

  2 shows a lock signal input to the laser control apparatus 100 shown in FIG. 1, and a lower part of FIG. 2 shows a power supply signal representing a voltage output from the laser control apparatus shown in FIG. Has been. Note that dotted lines drawn at predetermined intervals represent the monitoring timing of the CPU 101 that monitors the lock signal.

The upper part shows that noise is generated on the lock signal at a timing shifted from the monitoring timing of the CPU 101, and the lower part shows noise on the lock signal as it is on the power signal. The situation is shown.
Japanese Patent Laid-Open No. 10-133136

  Therefore, in the image forming apparatus having the laser control apparatus as shown in FIG. 1, although there is a possibility that an image defect may occur due to an instantaneous fluctuation of the lock signal due to noise or the like, the fluctuation is shifted from the monitoring timing of the CPU 101. If it occurs at the timing, the CPU 101 cannot recognize that an image defect has occurred. For this reason, there is a problem that it is impossible to take measures such as stopping the image formation or warning that the image formation including the image defect has been performed although the image defect has actually occurred.

  In view of the above circumstances, an object of the present invention is to provide an image forming apparatus that is devised to improve the reliability of image quality, and a laser control apparatus that is suitable for such an image forming apparatus.

In order to achieve the above object, a laser control apparatus of the present invention comprises:
A monitor unit that monitors a state signal indicating whether the polygon mirror that deflects the laser light emitted from the laser light source is in a stable state in which the polygon mirror is rotating in a steady state or in an unstable state that is out of the steady rotation in a predetermined monitoring cycle When,
When the status signal is input and this status signal is stable, this status signal is output, and when this status signal changes to the unstable status for a time shorter than one monitoring cycle, the stable status is set. A filter unit for maintaining the output of the state signal to be represented;
And a power supply unit that supplies power to the laser light source only while the state signal output from the filter unit is input and the state signal is maintained in a stable state.

  In the laser control device of the present invention, the change to the unstable state of the state signal, which can be detected by the monitor unit, that is, when the state signal has changed to the unstable state for a time longer than the monitoring period, it is output as it is. A filter unit is provided that maintains a state signal indicating a stable state when the state signal changes to an unstable state for a period of time less than the monitoring period, in which detection by the monitor unit may be impossible. Therefore, in the laser control apparatus of the present invention, the state signal that changes to the unstable state for a time shorter than the monitoring cycle, which may not be detected by the monitor unit, is all output from the filter unit as a state signal indicating the stable state. . For this reason, in the monitor part, when the state signal showing an unstable state is output from this filter part, it can recognize reliably.

Here, the state signal is a binary signal that changes the level between a stable state and an unstable state,
The filter unit may be a low-pass filter that cuts pulses having a time width shorter than one monitoring period.

In order to achieve the above object, an image forming apparatus of the present invention comprises:
A toner having a laser light irradiation device for forming an electrostatic latent image on the surface of the photosensitive member by irradiating the surface of the photosensitive member with a laser beam modulated based on an image signal, and developing the electrostatic latent image with toner In an image forming apparatus for forming an image on a recording medium by finally transferring and fixing the image on the recording medium,
The laser beam irradiation device is
A laser light source for emitting laser light;
A polygon mirror for deflecting the laser light emitted from the laser light source;
A polygon motor for rotating the polygon mirror;
A state signal output unit that outputs a state signal indicating whether the polygon motor is in a stable state of steady rotation or in an unstable state deviating from the steady rotation;
A monitor unit for monitoring the status signal output from the status signal output unit at a predetermined monitoring cycle;
When the status signal output from the status signal output unit is input and the status signal is stable, the status signal is output, and the status signal is shorter than the one monitoring period. A filter unit that maintains the output of a state signal representing a stable state when
And a power supply unit for supplying power to the laser light source only while the state signal output from the filter unit is input and the state signal is maintained in a stable state.

  In the image forming apparatus of the present invention, when a state signal indicating an unstable state is output from the filter unit, the monitor unit can reliably recognize this, and thereby, for example, image formation can be stopped. It is possible to warn that an image defect may occur. Therefore, according to the image forming apparatus of the present invention, the reliability of the image quality can be improved.

  According to the laser control device of the present invention, in the case where the state signal indicating the unstable state is output from the filter unit, the monitor unit can reliably recognize this, and has the laser control device. According to the image forming apparatus of the present invention, the reliability of image quality can be improved.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 3 is a schematic configuration diagram of an embodiment of the image forming apparatus of the present invention, which includes an embodiment of the laser control apparatus of the present invention.

  The printer 1 shown in FIG. 3 includes a photoreceptor roll 11 that rotates in the direction of arrow A, a charger 12, a laser exposure device 13, a rotary developer 14 that rotates in the direction of arrow C, an intermediate transfer belt 15 that circulates in the direction of arrow B, A primary transfer device 19, a secondary transfer device 16, a fixing device 17, a paper tray 18, and a transport roll 20 that transports the paper 30 in the direction of arrow D are configured.

  The printer 1 creates a color toner image with four color toners of C, M, Y, and K, and finally records and transfers the color toner image onto a recording medium such as paper. An image is formed on a medium.

  The photoreceptor roll 11 shown in FIG. 3 is charged to a predetermined potential by the charger 12, and then an electrostatic latent image for K color is first formed on the surface of the photoreceptor roll by laser irradiation from the laser exposure unit 13. Is done. The electrostatic latent image created on the surface of the photoreceptor roll is developed with K-color toner, and is then primarily transferred to the intermediate transfer belt 15 by the primary transfer unit 19. Thereafter, the toner images formed respectively for the Y color, the M color, and the C color are sequentially stacked on the K color toner image to form a four color laminated color toner image, and then the color toner image is transferred to the intermediate transfer belt. 15, the paper is drawn from the paper tray 18 by the pickup roll 18 a and is secondarily transferred by the secondary transfer device 16 onto the paper 30 conveyed by the conveyance roll 20.

  The color toner image secondarily transferred onto the paper 30 is fixed on the paper by being heated and pressed by the fixing device 17.

  Next, the laser exposure device of the printer 1 will be described.

  FIG. 4 is a schematic block diagram of the laser exposure device.

  A laser exposure device 13 shown in FIG. 4 includes a laser diode 13e that is a light source of laser light, a polygon mirror 13a to which the laser light is directed, and a cylinder mirror 13b that reflects the laser light reflected by the polygon mirror 13a toward the photosensitive roll 11. A lens 13d disposed between the polygon mirror 13a and the cylinder mirror 13b, a polygon motor 13c for rotating the polygon mirror 13a in the direction of arrow E, and a lock signal output for outputting a lock signal which is a signal indicating the state of the polygon motor 13c. 13g, a laser diode substrate 13f to which the laser diode 13e is attached, and a laser control device 13h that controls power supply to the laser diode 13e through the laser diode substrate 13f based on the lock signal output from the lock signal output unit 13g. In It is.

  FIG. 5 is a schematic configuration diagram of a laser control device that is provided in the printer of this embodiment and controls the power supply to the laser diode. In addition, the same code | symbol as the code | symbol used in FIG. 1 is used for the member of the same kind as the member shown in FIG.

  Since the laser control device 13h shown in FIG. 5 is different from the conventional laser control device 100 shown in FIG. 1 only in that a filter circuit 131h is added, only the filter circuit 131h will be described below.

  The filter circuit 131h shown in FIG. 5 is a state signal representing a stable state, which is composed of a resistor 1311h and a capacitor 1312h. The state signal represents an unstable state having a time width shorter than a predetermined filter time that is equal to or longer than the monitoring period of the CPU 101. This is a low-pass filter that outputs while maintaining Note that this filter time is longer than the monitoring period of the CPU 101, and the upper limit is the time during which the state signal turns to an unstable state when it seems that a fatal abnormality has occurred in the polygon motor 13c. Set as

  FIG. 6 is a graph of an input signal and an output signal of the laser control apparatus of this embodiment.

  FIG. 6A shows the lock signal input to the filter circuit 131h in the upper stage, the signal output from the filter circuit 131h in the middle stage, the signal after passing through the Schmitt buffer 100b, and the output from the filter circuit 131h in the lower stage. A power supply signal is shown, which is shorter than a filter time (width B) that is longer than the monitoring period (width A) and is generated at a timing shifted from the monitoring timing by the CPU 101 on the lock signal shown in the upper stage. The state in which the unstable state (width C1) is maintained and outputted by the filter circuit 131h is shown.

  In FIG. 6B, the unstable state (width C1) generated on the lock signal shown in the upper stage and longer than the monitoring period (width A) and longer than the filter time (width B) is output as it is. The situation is shown.

  As described above, the unstable state detectable by the CPU 101, that is, the unstable state longer than the filter time (width B) is output as it is, and the unstable state less than the filter time is output while maintaining the stable state. By doing so, it is possible to prevent the voltage supply to the laser diode substrate 13f from being stopped, which is not recognized by the CPU 101. Accordingly, since the printer 1 of the present invention reliably recognizes the stop of the voltage supply to the laser diode substrate 13f, when the stop of the voltage supply occurs, for example, the image formation is stopped or the image defect is detected. It is possible to warn that there is a possibility that image formation including has been performed, and thus it is possible to improve the reliability of image quality. In the present embodiment, even when the CPU 101 can naturally recognize an unstable state, if it is an unstable state for a time shorter than the filter time (width B), a case where the stable state is maintained and output is given as an example. As described above, in the present invention, any filter may be used as long as it outputs an unstable state less than the monitoring period of the CPU 101 in a stable state, and the filter time may be the same length as the monitoring period of the CPU 101.

It is the schematic of the conventional laser control apparatus which controls light emission of a laser beam. It is a graph which shows the input signal and output signal of the laser control apparatus shown in FIG. 1 is a schematic configuration diagram of an embodiment of an image forming apparatus of the present invention including an embodiment of a laser control apparatus of the present invention. It is a schematic block diagram of a laser exposure device. It is a schematic block diagram of the laser control apparatus with which the printer of this embodiment is equipped and which controls the electric power supply to the laser diode. It is a graph of the input signal and output signal of the laser control apparatus of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 11 Photoconductor roll 12 Charging device 13 Laser exposure device 13a Polygon mirror 13b Cylinder mirror 13c Polygon motor 13d Lens 13e Laser diode 13f Laser diode substrate 13g Lock signal output part 13h Laser controller 131h Filter circuit 1311h Resistor 1312h Capacitor 101 CPU
102 Power supply control circuit

Claims (3)

A monitor unit for monitoring a state signal indicating whether the polygon mirror for deflecting the laser beam emitted from the laser light source is in a stable state where it is rotating normally or is in an unstable state deviating from the steady rotation at a predetermined monitoring cycle When,
When the state signal is input and the state signal is stable, the state signal is output, and when the state signal changes to the unstable state for a time shorter than one monitoring period, the stable state is set. A filter unit for maintaining the output of the state signal to be represented;
A laser control apparatus comprising: a power supply unit that supplies power to the laser light source only while a state signal output from the filter unit is input and the state signal is maintained in a stable state. The state signal is a binary signal that changes a level between a stable state and an unstable state;
2. The laser control apparatus according to claim 1, wherein the filter unit is a low-pass filter that cuts a pulse having a time width shorter than one monitoring period. A toner having a laser beam irradiation device for forming an electrostatic latent image on the surface of the photosensitive member by irradiating the surface of the photosensitive member with a laser beam modulated based on an image signal, and developing the electrostatic latent image with toner In an image forming apparatus for forming an image on a recording medium by finally transferring and fixing the image on the recording medium,
The laser beam irradiation device is
A laser light source for emitting laser light;
A polygon mirror for deflecting the laser light emitted from the laser light source;
A polygon motor for rotating the polygon mirror;
A state signal output unit that outputs a state signal indicating whether the polygon motor is in a stable state of steady rotation or an unstable state deviating from the steady rotation;
A monitor unit for monitoring the status signal output from the status signal output unit at a predetermined monitoring cycle;
When the state signal output from the state signal output unit is input and the state signal is stable, the state signal is output, and the state signal is shorter than the one monitoring period. A filter unit that maintains the output of a state signal representing a stable state when
An image is provided with a power supply unit that supplies power to the laser light source only while the state signal output from the filter unit is input and the state signal maintains a stable state. Forming equipment.

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