JP2010078793A - Aligner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To render double protection with a simple constitution, as compared with a prior art. <P>SOLUTION: An aligner includes: a motor 38 including a Hall element H1 for detecting the rotating speed of a rotor 50 in the state where power is supplied from a power source 52, and outputting a signal showing the rotating speed, a Hall element H4 for detecting the rotating speed of the rotor 50 in the state where power is supplied from a power source 56 different from the first power source (power source 52), and outputting a signal showing the rotating speed, and a PLL circuit 60 for detecting whether or not the rotating speed of a polygon mirror 36 reaches a target rotating speed required for image formation based on the signal showing the rotating speed, output from the Hall element H1; a signal output circuit 44 for detecting whether or not the rotating speed of the motor 38 is equal to or more than a predetermined threshold; and a laser diode driver 40 that controls a laser diode 34 so that light corresponding to image information may be emitted from the laser diode 34 only when detecting that the rotating speed is equal to or more than the predetermined threshold. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exposure apparatus and an image forming apparatus.

  Conventionally, a plurality of reflecting surfaces are provided, and a polygon mirror that reflects light from a laser diode as an irradiating means on each of the plurality of reflecting surfaces, and light reflected by the polygon mirror is predetermined on the photosensitive member. There has been known an exposure apparatus (optical scanning apparatus) provided with a motor as a rotation driving means for rotating a polygon mirror so as to be scanned in a different direction (main scanning direction) (for example, see Patent Document 1).

  In the exposure apparatus described in Patent Document 1, an encoder (for example, a rotation detection unit) that detects rotation of the motor and outputs a rotation detection signal indicating the rotation speed (rotation speed) (rpm) of the motor in the motor. Frequency generator), a clock generation circuit that generates a reference clock signal indicating a target rotation speed (target rotation speed) per unit time of the motor, and a motor rotation speed and clock generation circuit indicated by a rotation detection signal from the encoder. If the difference from the target rotational speed indicated by the reference clock signal is within a predetermined value, an on (ON) level signal is output, and if the difference is greater than a predetermined value, it is off (OFF). A PLL (Phase Locked Loop) circuit that outputs a level signal is provided.

  Conventionally, the laser drive unit receives the power supply instruction only when the signal from the PLL circuit is in the normal rotation state (that is, when it is on level) and the signal from the monitoring unit is in the normal operation enabled state. A power supply control unit that gives a power supply instruction to the power supply unit that supplies power to the power supply unit, and a light emission instruction only when the signal from the PLL circuit is in a normal rotation state and the signal from the monitoring unit is in a normal operable state Accordingly, an image forming apparatus including an exposure apparatus including a light emission permission control unit that gives a light emission permission to a light emission permission grant unit that gives light emission permission to a laser driving unit is known (for example, see Patent Document 2).

In the exposure apparatus described in Patent Document 2, the laser driving unit receives power supply, a light emission permission signal, and an image signal, and causes a laser diode to emit laser light modulated based on the image signal. That is, the laser drive unit is provided with a signal state from a PLL circuit provided in the exposure apparatus for detecting whether or not it is in a normal rotation state, and a housing of the image forming apparatus provided outside the exposure apparatus. The light emission is controlled based on the state of a signal from a switch for detecting whether or not the body door is closed or a switch for detecting whether or not the photoconductor is mounted. Thus, in the exposure apparatus described in Patent Document 2, double protection is performed by using two detection means, that is, a detection means provided in the exposure apparatus and a detection means provided outside the exposure apparatus. .
JP 2002-169121 A JP 2006-88443 A

  The present invention provides an exposure apparatus and an image forming apparatus that can perform double protection with a simple configuration by providing two independent detection means in the exposure apparatus as compared with the conventional technique. With the goal.

  In order to achieve the above object, an exposure apparatus according to a first aspect of the present invention comprises an irradiation means for irradiating light and a plurality of reflecting surfaces, and the light irradiated from the irradiating means at each of the plurality of reflecting surfaces. A light reflecting means for reflecting the light, a rotating means for rotating the light reflecting means so that the light reflected by the light reflecting means is scanned in a predetermined direction, and a state in which power is supplied from the first power source A first detector for detecting the rotational speed of the rotating means and outputting a signal indicating the rotational speed, wherein the rotational speed of the rotating means is supplied from a second power source different from the first power source. A second detection unit that detects a rotation number and outputs a signal indicating the rotation number, and a rotation number of the light reflecting means for forming an image based on the signal indicating the rotation number output by the first detection unit. The first detecting whether or not the target rotational speed A second driving unit configured to detect whether or not the rotation number is equal to or greater than a predetermined threshold value based on a rotation drive unit including an output unit and a signal indicating the rotation number output by the second detection unit; When the detection means and the first detection means detect that the target rotational speed is detected, and the second detection means detects that the rotation speed is equal to or higher than a predetermined threshold, the image information The irradiation unit is controlled so that based light is emitted from the irradiation unit, and when it is detected by the first detection unit that the target rotation speed is not detected, and by the second detection unit In at least one of the cases in which it is detected that the value is less than the threshold value, an irradiation control unit that controls the irradiation unit so as not to be irradiated with light is configured.

  In order to achieve the above object, an exposure apparatus according to a second aspect of the present invention includes an irradiation unit that irradiates light and a plurality of reflection surfaces, and each of the plurality of reflection surfaces is irradiated from the irradiation unit. Power is supplied from a first power supply, a light reflecting means for reflecting the reflected light, a rotating means for rotating the light reflecting means so that the light reflected by the light reflecting means is scanned in a predetermined direction. A first detection unit that detects the number of rotations of the rotation unit in a state and outputs a signal indicating the number of rotations, and the light reflection unit based on the signal indicating the number of rotations output by the first detection unit Power is supplied from a rotation drive unit having first detection means for detecting whether or not the rotation number is a target rotation number for image formation, and a second power source different from the first power source. Detecting the rotation speed of the light reflecting means Based on the second detection unit that outputs a signal indicating the rotation number and the signal indicating the rotation number output by the second detection unit, whether or not the rotation number is equal to or greater than a predetermined threshold value When it is detected that the target rotational speed is detected by the second detection means for detecting the first detection means and the first detection means, and is detected by the second detection means to be equal to or greater than a predetermined threshold value In addition, the irradiation unit is controlled so that light based on image information is emitted from the irradiation unit, and the first detection unit detects that the target rotation speed is not detected, and the second In at least one of the cases where it is detected by the detection means that it is less than a predetermined threshold value, it is configured to include an irradiation control means for controlling the irradiation means so that light is not irradiated.

  In order to achieve the above object, an exposure apparatus according to a third aspect of the present invention includes an irradiation unit that irradiates light and a plurality of reflection surfaces, and each of the plurality of reflection surfaces is irradiated from the irradiation unit. Power is supplied from a first power supply, a light reflecting means for reflecting the reflected light, a rotating means for rotating the light reflecting means so that the light reflected by the light reflecting means is scanned in a predetermined direction. A first detector for detecting the rotational speed of the rotating means and outputting a signal indicating the rotational speed in a state where the rotational speed of the rotating means is detected and detecting the rotational speed of the rotating means in a state where electric power is supplied from the first power source; Based on the second detection unit that outputs a signal indicating the rotation number and the signal that indicates the rotation number output by the first detection unit, the rotation number of the light reflecting unit is a target rotation number for forming an image. First detection means for detecting whether or not A second driving unit that detects whether the rotation number of the light reflecting unit is equal to or greater than a predetermined threshold based on a signal indicating the rotation number output by the rotation driving unit and the second detection unit; Based on the image information when the detection means and the first detection means detect that the target rotational speed is detected and the second detection means detects that the target rotational speed is greater than or equal to a predetermined threshold value. The irradiation means is controlled so that the irradiated light is emitted from the irradiation means, and when the first detection means detects that the target rotational speed is not detected, and is determined in advance by the second detection means. In at least one of the cases where it is detected that the value is less than the threshold value, it is configured to include irradiation control means for controlling the irradiation means so that light is not irradiated.

  An exposure apparatus according to a fourth aspect of the present invention is the exposure apparatus according to the first or third aspect, wherein the first detection unit and the second detection unit detect the number of rotations of the rotating means. This is a magnetic sensor.

  An exposure apparatus according to a fifth aspect of the present invention is the exposure apparatus according to the second aspect of the present invention, wherein the first detection unit is a magnetic sensor that detects the number of rotations of the rotating means, and the second detection unit is the The optical sensor detects the rotational speed of the light reflecting means.

  In order to achieve the above object, an image forming apparatus according to a sixth aspect of the present invention is based on the exposure apparatus according to any one of the first to fifth aspects and the light irradiated by the exposure apparatus. And image forming means for forming the image on an image forming medium.

  According to each of the first and second aspects of the invention, compared with the prior art, by providing two detection means having independent power supply systems in the exposure apparatus, a simple structure and a double structure are provided. It has the effect that it can protect.

  According to the third aspect of the invention, compared to the conventional technique, double detection is performed with a simple configuration by providing two independent detection means, that is, two different detection means in the exposure apparatus. Has the effect of being able to.

  According to the fourth aspect of the present invention, there is an effect that double protection can be performed using two different magnetic sensors.

  According to the fifth aspect of the present invention, there is an effect that double protection can be performed using a magnetic sensor and an optical sensor.

  According to the invention described in claim 6, it is possible to form an image on an image forming medium using an exposure apparatus that can perform double protection with a simple configuration as compared with the conventional technique. It has the effect.

Hereinafter, embodiments of the present invention will be described.
[First Embodiment]
First, the first embodiment will be described. FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present embodiment.

  As shown in FIG. 1, the image forming apparatus 10 includes a photosensitive drum 12, a charger 14, an exposure device (laser scanning unit) 16, a developing unit 18, a transfer unit 20, a fixing unit 22, a paper storage unit 24, and a cleaner 26. , A static eliminator 28, a control unit 30, and an image processing unit 32.

  The photosensitive drum 12 is an image carrier that rotates in the direction of arrow A. The charger 14 charges the surface of the photosensitive drum 12. The exposure device 16 scans the photosensitive drum 12 by reflecting the laser beam emitted from the laser diode with a polygon mirror. The developing unit 18 develops the electrostatic latent image formed on the photosensitive drum 12 with toner to form a toner image on the photosensitive drum 12. The transfer device 20 transfers the toner image on the photosensitive drum 12 onto the image forming medium P. The fixing device 22 fixes the toner image transferred onto the image forming medium P. The paper storage unit 24 stores paper P that is an image forming medium. The cleaner 26 cleans the surface of the photosensitive drum 12. The static eliminator 28 removes residual charges on the surface of the photosensitive drum 12.

  The control unit 30 controls each device of the image forming apparatus 10 (controls the entire image forming apparatus 10).

  The image processing unit 32 receives image information (image data) of a document read by a scanner (not shown) as an image reading unit and image information (image data) input from an external computer (not shown). Image processing is performed to obtain image information necessary for forming an image based on the image information on the image forming medium.

  Next, the operation of the image forming apparatus 10 of the present embodiment will be described. Note that the operation of each of these devices is controlled by the control unit 30.

  First, image information read from a document by a scanner or image information generated by an external computer or the like is input to the image processing unit 32 and image processing is performed. The control unit 30 acquires the image information subjected to image processing by the image processing unit 32 and inputs a signal based on the acquired image information to the exposure device 16. In the present embodiment, laser light based on image information is irradiated onto the photosensitive drum 12 by the exposure device 16 so that an electrostatic latent image corresponding to the image information is formed on the photosensitive drum 12. Based on the image information, the control unit 30 outputs a Low level signal to the exposure device 16 at a timing when the laser beam is desired to be irradiated, and outputs a High level signal at a timing when the laser beam is not irradiated. Output to the exposure device 16. The exposure device 16 modulates the laser light. That is, the exposure device 16 modulates the laser beam based on the signal based on the image information, and the modulated laser beam (that is, the light based on the image information) is uniformly charged by the charger 14. The surface of the photosensitive drum 12 is irradiated. When the surface of the photosensitive drum 12 is irradiated with laser light, an electrostatic latent image corresponding to image information is formed on the photosensitive drum 12.

  The electrostatic latent image formed on the photosensitive drum 12 is developed with toner by the developing unit 18, and a toner image is formed on the photosensitive drum 12. The toner image formed on the photoconductive drum 12 is conveyed toward the transfer unit 20 disposed facing the photoconductive drum 12 as the photoconductive drum 12 rotates in the direction of arrow A.

  On the other hand, the paper P stored in the paper storage unit 24 is supplied toward the nipping portion (nip portion) between the photosensitive drum 12 and the transfer device 20, and the toner image on the photosensitive drum 12 is transferred by the transfer device 20. Is transferred onto the paper P. The toner image transferred onto the paper P is fixed by the fixing device 22. Thereby, a desired image is obtained. That is, an image based on the light (laser light) irradiated by the exposure device 16 is formed on the paper P as an image forming medium. After the transfer of the toner image onto the paper P, the adhering matter such as residual toner adhering to the surface of the photosensitive drum 12 is cleaned by the cleaner 26, and the residual charge on the surface of the photosensitive drum 12 is removed by the static eliminator 28. Thus, one image forming operation is completed.

  FIG. 2 is a schematic block diagram of the exposure device 16 of the image forming apparatus 10 of the present embodiment.

  As shown in the figure, the exposure apparatus 16 includes a laser diode (LD) 34 as an irradiating means for irradiating laser light, a polygon mirror 36 as a light reflecting means, a motor 38 as a rotation driving means, and a laser as an irradiation control means. A diode driver (LD driver) 40, a power supply control circuit 42, and a signal output circuit 44 as second detection means are provided.

  The laser diode 34 is supplied with electric power necessary for laser beam irradiation and is controlled by the laser diode driver 40 to irradiate the laser beam.

  The polygon mirror 36 includes a plurality of reflection surfaces (for example, six surfaces) 36a, and each of the plurality of reflection surfaces 36a reflects the laser light emitted from the laser diode 34.

  The motor 38 guides the light reflected by the polygon mirror 36 to the photosensitive drum 12 as the surface to be scanned through the fθ lens, and moves on the photosensitive drum 12 in a predetermined direction, for example, the photosensitive drum 12. The polygon mirror 36 is rotated so as to be scanned in the main scanning direction which is the direction of the rotation axis (not shown). Further, the motor 38 detects whether or not the rotational speed (rotational speed) (rpm) of the polygon mirror 36 is a target rotational speed for image formation, and outputs a detection signal indicating the detection result. In the present embodiment, when the rotation speed of the motor 38 is the target rotation speed by a PLL circuit provided in the motor 38, the details of which will be described below, the rotation speed of the polygon mirror 36 is set to the target rotation speed. A low level signal (ON signal) indicating that is output. When the rotation speed of the motor 38 is not the target rotation speed, the PLL circuit outputs a high level signal (off signal) indicating that the rotation speed of the polygon mirror 36 is not the target rotation speed. In addition, the motor 38 outputs a rotation detection signal indicating the detection result by detecting the rotation speed of the motor 38 (more specifically, the rotation speed of the rotor).

  The laser diode driver 40 becomes operable by receiving supply of electric power necessary for operation. Further, when the laser diode driver 40 becomes operable and receives an irradiation permission signal indicating irradiation (light emission) permission, the laser light based on the image information (more specifically, a laser based on a signal based on the image information). The laser diode 34 is controlled so that light is emitted from the laser diode 34. In addition, the laser diode driver 40 is configured to output a laser beam in at least one of the cases where the power necessary for the operation is not supplied or the forced turn-off signal which is a signal indicating that the laser beam irradiation is not permitted. Control is performed so that laser light is not irradiated from the diode 34. More specifically, when the laser diode driver 40 is not operable (that is, when the power necessary for the operation is not supplied), the operation is stopped and the irradiation control of the laser diode 34 is not performed. Thus, the laser diode 34 is controlled not to be irradiated with laser light. Further, when the laser diode driver 40 is operable and receives a forced turn-off signal, the laser diode driver 40 controls the laser diode 34 not to emit laser light.

  When the state of the detection signal from the motor 38 is a state (on-level state) indicating that the rotational speed of the polygon mirror 36 is the target rotational speed, the power supply control circuit 42 Control is performed so that power that can be operated is supplied to the laser diode driver 40, and power that enables the laser diode 34 to irradiate laser light is supplied to the laser diode 34. In addition, the power supply control circuit 42 outputs power that enables the laser diode driver 40 to operate when the state of the detection signal from the motor 38 is a state (off-level state) indicating that it is not the target rotational speed. Control is performed so that the laser is not supplied to the diode driver 40, and control is performed so that power that enables the laser diode 34 to irradiate the laser light is not supplied to the laser diode 34. In the present embodiment, when the detection signal from the motor 38 is a high level signal, the signal is on level, and when the detection signal from the motor 38 is a low level signal, the signal is off level. It is a state.

  When the number of rotations indicated by the rotation detection signal from the motor 38 is equal to or greater than a predetermined threshold value and the signal input from the control unit 30 indicates a low level state, the signal output circuit 44 outputs an irradiation permission signal ( In this embodiment, a low level signal) is output to the laser diode driver 40. Here, the predetermined threshold value means that, for example, if the rotation speed of the motor 38 is less than that value, the irradiation intensity of the laser light applied to the polygon mirror 36 becomes very high, causing damage to the device. It refers to a value obtained experimentally in advance so as to increase the possibility. The signal output circuit 44 is at least one of the case where the rotation number indicated by the rotation detection signal from the motor 38 is less than a predetermined threshold value or the case where the signal input from the control unit 30 indicates a high level state. In this case, a forced turn-off signal (a high level signal in the present embodiment), which is a signal indicating that laser beam irradiation by the laser diode 34 is not permitted, is output to the laser diode driver 40.

  As shown in FIG. 3, the motor 38 includes a rotor 50 as rotating means, an encoder 39 that detects the number of rotations of the motor 38, a three-phase Y-connected coil 1, a coil 2, a coil 3 (not shown), A power source (first power source) 52 and a motor driver 54 are provided.

  The encoder 39 includes Hall elements (magnetic sensors) H1, H2, and H3 that are provided at positions rotated by 60 ° with respect to each other and detect the position of the rotor 50. By detecting the position of the rotor 50 by these Hall elements H1, H2, and H3, the rotational speed of the motor 38 can be detected. In the present embodiment, the Hall element H1 connected to the PLL circuit 60, which will be described in detail below, corresponds to the first detection unit.

  The rotator 50 performs main scanning in which the laser beam reflected by the polygon mirror 36 is in a predetermined direction (in this embodiment, the rotation axis (not shown) of the photosensitive drum 12) on the photosensitive drum 12. The polygon mirror 36 is rotated so as to be scanned in the direction), and has a magnetic pole property.

  Electric power for operating each of the Hall elements H1 to H3 is supplied to the Hall elements H1 to H3 by the power source 52, and a current is passed through the coils 1 to 3. That is, each of the Hall elements H <b> 1 to H <b> 3 detects the rotation speed of the rotor 50 with power supplied from the power supply 52 and outputs a signal indicating the rotation speed (rotation detection signal).

  The motor driver 54 controls the switching of the current flowing through each of the coils 1 to 3 in accordance with the position of the rotor 50 detected by the Hall elements H1 to H3, thereby changing the magnetic field to change the rotor 50. Control to rotate. By this control, the polygon mirror 36 is rotated.

  Further, in the motor 38 of the present embodiment, a Hall element (magnetic sensor) H4 is provided so as to be able to detect the rotational speed of the motor, similarly to the Hall elements H1 to H3. The hall element H4 is supplied with electric power from a power source (second power source) 56 different from the first power source. With this power supply, the hall element H4 can detect the rotational speed of the motor. It becomes. The hall element H4 detects the number of rotations of the motor and outputs a rotation detection signal indicating the detected number of rotations to the signal output circuit 44. For example, when a three-phase brushless motor is used for the motor 38, the Hall element H4 outputs 6 pulses each time the motor 38 makes one revolution (that is, every time the rotor 50 makes one revolution). Note that the Hall element H4 of the present embodiment corresponds to the second detection unit. As shown in FIG. 4, the Hall elements H1 to H3 and the Hall element H4 include an amplifier circuit that amplifies a signal from the Hall element body, a Schmitt trigger circuit, and an output transistor in addition to the Hall element body. And

  In addition, the motor 38 of the present embodiment is provided with a clock generation circuit 58 that generates a reference clock signal indicating a target rotation number (target rotation speed) per unit time of the motor. Further, a PLL (Phase Locked Loop) circuit 60 is provided in the motor driver 54. The PLL circuit 60 is configured so that any one of the Hall elements H1 to H3, for example, in this embodiment, the rotation number of the motor 38 indicated by the rotation detection signal from the Hall element H1 and the reference clock signal generated by the clock generation circuit 58 are obtained. This is a circuit for controlling the rotation of the rotor 50 so that the difference from the target rotational speed shown is within a predetermined value. If the difference between the rotation speed of the motor 38 indicated by the rotation detection signal from the Hall element H1 and the target rotation speed indicated by the reference clock signal generated by the clock generation circuit 58 is within a predetermined value, the PLL circuit 60 An ON level signal is output to the power supply control circuit 42. In addition, the PLL circuit 60 outputs an OFF level signal to the power supply control circuit 42 when the difference is larger than a predetermined value. In the present embodiment, an on-level signal output from the PLL circuit 60 is a low-level signal, while an off-level signal is a high-level signal.

  As shown in FIG. 3, the power supply control circuit 42 provided in the exposure apparatus 16 of the present embodiment includes an inverter 42a, a PNP transistor 42b, and a power source 42c. The input terminal of the inverter 42 a is connected to the output terminal of the PLL circuit 60. The output terminal of the inverter 42a is connected to the base terminal of the PNP transistor 42b. The emitter terminal of the PNP transistor 42b is connected to the power source 42c. The collector terminal of the PNP transistor 42b is connected to the LD driver 40 and the laser diode 34, and is grounded via a capacitor 42d. The emitter terminal and the base terminal of the PNP transistor 42b are connected via a resistor 42e. With the above configuration, when an on-level (low-level) signal is output from the PLL circuit 60, the power that enables the LD driver 40 to operate is supplied from the power source 42c to the LD driver 40, and the laser diode 34 can be irradiated. Is supplied to the laser diode 34. On the other hand, when an off level (high level) signal is output from the PLL circuit 60, the supply of power from the power source 42c to the LD driver 40 and the laser diode 34 is stopped.

  As shown in FIG. 5, in the signal output circuit 44, one input terminal is an L active (low active) terminal, an AND circuit 44a, a flip-flop circuit 44b, an AND circuit 44c, and one input terminal is L active. An AND circuit 44d as a terminal, a flip-flop circuit 44e, a NOR circuit 46 whose output terminal is an L active output terminal, and an inverter 48 are provided.

  As shown in the figure, the L active (low active) input terminal of the AND circuit 44a is connected to the output terminal of the Hall element H4 and to the power supply Vreg via the resistor 44f. The H active (high active) input terminal (that is, the input terminal that is not the L active terminal), which is the other input terminal of the AND circuit 44a, is connected to the power supply Vreg. The L active input terminal of the AND circuit 44a is connected to the input terminal of the AND circuit 44c. The H active input terminal of the circuit 44a is connected to the L active clear terminal (CLR terminal) of the flip-flop circuit 44b and to the L active clear terminal (CLR terminal) of the flip-flop circuit 44e. The AND circuit 44a outputs a high level signal from the output terminal when a high level signal is input to the H active input terminal and a low level signal is input to the L active input terminal, and the low level is output to the H active input terminal. Or a low level signal is output from the output terminal in at least one of cases where a high level signal is input to the L active input terminal. The data input terminal (D terminal) of the flip-flop circuit 44b is connected to the output terminal of the circuit 44a. The flip-flop circuit 44b is supplied with electric power from the power supply Vreg via the resistor 44g, and can operate when supplied with this electric power. The data output terminal (Q terminal) of the flip-flop circuit 44b is connected to the input terminal of the AND circuit 44c. The AND circuit 44c outputs a high level signal from the output terminal when a high level signal is input to two input terminals, and when a low level signal is input to at least one of the two input terminals, A low level signal is output from the output terminal. The output terminal of the AND circuit 44c is connected to the input terminal of the AND circuit 44d. The L active input terminal which is the other input terminal of the circuit 44d is grounded. The AND circuit 44d outputs a high-level signal from the output terminal when a low-level signal is input to the L active input terminal and a high-level signal is input to the other input terminal, and is output to the L active input terminal. When a high level signal is input or when at least one of a low level signal is input to the other input terminal, a low level signal is output from the output terminal. The output terminal of the AND circuit 44d is connected to the data input terminal (D terminal) of the flip-flop circuit 44e. The flip-flop circuit 44e is supplied with electric power from the power source Vreg via the resistor 44h, and can operate when supplied with this electric power. As shown in FIG. 5, the data inversion output terminal (Q bar terminal) of the flip-flop circuit 44e is connected to the input terminal of the NOR circuit 46 whose output terminal is L active. The other input terminal of the NOR circuit 46 is connected to the control unit 30 described above, and a signal based on the image information is input from the control unit 30 to the other input terminal of the NOR circuit 46. As described above, this signal is at a low level at the timing when the laser beam is desired to be irradiated, and at a high level at a timing when the laser beam is not irradiated. The output terminal of the NOR circuit 46 outputs a high level signal when both signals input to the two input terminals are at low level, and the signal input to at least one of the two input terminals is high. In the case of level, a low level signal is output. The output terminal of the NOR circuit 46 is connected to the input terminal of the inverter 48. The output terminal of the inverter 48 outputs a low level signal when the signal input to the input terminal is high level, and outputs a high level signal when the signal input to the input terminal is low level. An output terminal of the inverter 48 is connected to the LD driver 40.

  In the present embodiment, each device (44a to 44h and other devices) of the signal output circuit 44 is set (adjusted) as follows. That is, for example, when a three-phase brushless motor is used for the motor 38, the number of pulses per unit time of the rotation detection signal input from the Hall element H4 to the L active input terminal of the AND circuit 44a is as described above. The flip-flop circuit outputs a low-level signal from the data inversion output terminal of the flip-flop circuit 44e when it is 6 times or more of the predetermined threshold value and is less than 6 times the predetermined threshold value. The resistance value of the signal output circuit 44 and the capacitance of the capacitor are appropriately set (adjusted) so that a high-level signal is output from the data inversion output terminal 44e. Thereby, the signal output circuit 44 uses the low level signal as the irradiation permission signal when the rotation speed is equal to or higher than a predetermined threshold based on the rotation detection signal indicating the rotation speed output by the Hall element H4. When the rotation speed is less than a predetermined threshold value, a high level signal is output to the laser diode driver 40 as a forced extinction signal. That is, the signal output circuit 44 detects whether or not the rotational speed is equal to or higher than a predetermined threshold based on the rotational detection signal indicating the rotational speed output by the Hall element H4, and the rotational speed is determined in advance. If it is equal to or higher than the threshold value, a low level signal is output to the laser diode driver 40 as an irradiation permission signal, and if the rotation speed is less than a predetermined threshold value, a high level signal is used as a forced extinction signal. Output to the laser diode driver 40.

  As described above, the exposure apparatus 10 according to the present embodiment includes the laser diode 34 as an irradiation unit for irradiating light and the plurality of reflecting surfaces 36a, and each of the plurality of reflecting surfaces 36a is separated from the laser diode 34. A polygon mirror 36 as light reflecting means for reflecting the irradiated light, and a rotor 50 as rotating means for rotating the polygon mirror 36 so that the light reflected by the polygon mirror 36 is scanned in a predetermined direction. The Hall element H1 as a first detection unit that detects the rotation speed of the rotor 50 and outputs a signal indicating the rotation speed in a state where power is supplied from the power supply 52 as the first power supply, a first power supply ( A second detector for detecting the rotational speed of the rotor 50 and outputting a signal indicating the rotational speed in a state where power is supplied from a power source 56 as a second power source different from the power source 52) First detecting means for detecting whether or not the rotational speed of the polygon mirror 36 is a target rotational speed for image formation based on the Hall element H4 and the signal indicating the rotational speed output by the Hall element H1. Based on a motor 38 serving as a rotational drive means having a PLL circuit 60 as a signal and a signal indicating the rotational speed output by the Hall element H4, it is detected whether or not the rotational speed is equal to or greater than a predetermined threshold value. When it is detected by the signal output circuit 44 as the second detection means and the PLL circuit 60 that the rotation speed is the target rotational speed, and the signal output circuit 44 detects that it is greater than or equal to a predetermined threshold value, the image The laser diode 34 is controlled so that the light based on the information is emitted from the laser diode 34, and the target rotation speed is not achieved by the PLL circuit 60. Is detected, and at least one of the cases where the signal output circuit 44 detects that the value is less than a predetermined threshold value, the irradiation control means for controlling the laser diode 34 so that the light is not irradiated. The laser diode driver 40 is provided.

[Second Embodiment]
Next, a second embodiment will be described. The same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the first embodiment, the Hall element H4 is used as the second detection unit. However, in the present embodiment, as shown in FIG. 6, an optical sensor 70 is used as the second detection unit.

  The optical sensor 70 includes a light emitting unit that emits light and a light receiving unit that receives light. In the present embodiment, the optical sensor 70 is provided so that each reflecting surface 36a of the polygon mirror 36 can be detected. For example, the optical sensor 70 is provided at a position where the light receiving unit can receive the reflected light reflected by the reflecting surface 36a when each of the reflecting surfaces 36a reaches a predetermined position. ing. For example, when the number of reflecting surfaces 36a of the polygon mirror 36 is 6, when the polygon mirror 36 rotates once, the optical sensor 70 outputs a rotation detection signal having six pulses. That is, when the number of reflection surfaces 36a of the polygon mirror 36 is N, when the polygon mirror 36 makes one rotation, the optical sensor 70 outputs a rotation detection signal having N pulses.

  Power for operating the optical sensor 70 is supplied to the optical sensor 70 by the power source 57. That is, the optical sensor 70 detects the number of rotations of the polygon mirror 36 with power supplied from the power source 57 and outputs a signal indicating the number of rotations (rotation detection signal).

  In the present embodiment, each device (44a to 44h and other devices) of the signal output circuit 44 is set (adjusted) as follows. That is, for example, when the number of reflection surfaces 36a of the polygon mirror 36 is N, the number of pulses per unit time of the rotation detection signal input from the optical sensor 70 to the L active input terminal of the AND circuit 44a is A flip-flop is output when a low level signal is output from the data inversion output terminal of the flip-flop circuit 44e when it is N times or more of the predetermined threshold value and less than N times the predetermined threshold value. The resistance value of the signal output circuit 44, the capacitance of the capacitor, and the like are appropriately set (adjusted) so that a high-level signal is output from the data inversion output terminal of the circuit 44e. Thereby, the signal output circuit 44 uses the low level signal as the irradiation permission signal when the rotation speed is equal to or higher than a predetermined threshold based on the rotation detection signal indicating the rotation speed output by the optical sensor 70. When the rotational speed is less than a predetermined threshold value, a high level signal is output to the laser diode driver 40 as a forced extinction signal. That is, the signal output circuit 44 detects whether or not the rotational speed is equal to or higher than a predetermined threshold based on the rotational detection signal indicating the rotational speed output by the optical sensor 70, and the rotational speed is determined in advance. If it is equal to or higher than the threshold value, a low level signal is output to the laser diode driver 40 as an irradiation permission signal, and if the rotation speed is less than a predetermined threshold value, a high level signal is used as a forced extinction signal. Output to the laser diode driver 40.

  As described above, the exposure apparatus according to the present embodiment includes the laser diode 34 as the irradiation unit for irradiating light and the plurality of reflection surfaces 36a, and each of the plurality of reflection surfaces 36a is irradiated from the laser diode 34. A polygon mirror 36 as light reflecting means for reflecting the reflected light, and a rotor 50 as rotating means for rotating the polygon mirror 36 so that the light reflected by the polygon mirror 36 is scanned in a predetermined direction, In the state where power is supplied from the power source 52 as the first power source, the number of rotations of the rotor 50 is detected, and a signal indicating the number of rotations is output. First detecting means for detecting whether or not the rotational speed of the polygon mirror 36 is a target rotational speed for image formation based on the signal indicating the rotational speed that has been generated. The polygon mirror 36 rotates in a state where power is supplied from a motor 38 as a rotation driving means having the PLL circuit 60 and a power source 57 as a second power source different from the first power source (power source 52). The number of rotations is determined in advance based on an optical sensor 70 as a second detection unit that detects the number and outputs a signal indicating the number of rotations (rotation detection signal), and a signal indicating the number of rotations output by the optical sensor 70. A signal output circuit 44 serving as a second detection means for detecting whether or not the threshold value is greater than or equal to the threshold value, and a threshold value that is detected by the PLL circuit 60 and that is the target rotational speed and that is predetermined by the signal output circuit 44 When the above is detected, the laser diode 34 is controlled so that the light based on the image information is emitted from the laser diode 34, and the PLL circuit 60 controls the laser diode 34. When at least one of the case where it is detected that the rotational speed is not the target rotational speed and the case where the signal output circuit 44 detects that the rotational speed is less than a predetermined threshold value, the laser diode 34 is controlled so that light is not irradiated. And a laser diode driver 40 as irradiation control means.

[Third Embodiment]
Next, a third embodiment will be described. The same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the first embodiment, the Hall element H4 is used as the second detection unit. However, in the present embodiment, the second detection unit is connected to the PLL circuit 60 as shown in FIG. Any one of the Hall elements H2 and H3 other than the Hall element H1 is used. In the example of FIG. 7, a case where the Hall element H <b> 3 is used as the second detection unit is illustrated.

  In the present embodiment, each device (44a to 44h and other devices) of the signal output circuit 44 is set (adjusted) as follows. That is, for example, when a three-phase brushless motor is used for the motor 38, the number of pulses per unit time of the rotation detection signal input from the Hall element H3 to the L active input terminal of the AND circuit 44a is as described above. The flip-flop circuit outputs a low-level signal from the data inversion output terminal of the flip-flop circuit 44e when it is 6 times or more of the predetermined threshold value and is less than 6 times the predetermined threshold value. The resistance value of the signal output circuit 44 and the capacitance of the capacitor are appropriately set (adjusted) so that a high-level signal is output from the data inversion output terminal 44e. Thereby, the signal output circuit 44 uses the low level signal as the irradiation permission signal when the rotation speed is equal to or greater than a predetermined threshold based on the rotation detection signal indicating the rotation speed output by the Hall element H3. When the rotation speed is less than a predetermined threshold value, a high level signal is output to the laser diode driver 40 as a forced extinction signal. That is, the signal output circuit 44 detects whether or not the rotation speed is equal to or higher than a predetermined threshold based on the rotation detection signal indicating the rotation speed output by the Hall element H3, and the rotation speed is determined in advance. If it is equal to or higher than the threshold value, a low level signal is output to the laser diode driver 40 as an irradiation permission signal, and if the rotation speed is less than a predetermined threshold value, a high level signal is used as a forced extinction signal. Output to the laser diode driver 40.

  As described above, the exposure apparatus according to the present embodiment includes the laser diode 34 as the irradiation unit for irradiating light and the plurality of reflection surfaces 36a, and each of the plurality of reflection surfaces 36a is irradiated from the laser diode 34. A polygon mirror 36 as light reflecting means for reflecting the reflected light, and a rotor 50 as rotating means for rotating the polygon mirror 36 so that the light reflected by the polygon mirror 36 is scanned in a predetermined direction, In the state where power is supplied from the power source 52 as the first power source, the rotation speed of the rotor 50 is detected and a signal indicating the rotation speed is output. In this state, the Hall element H3 (or H2) as a second detection unit that detects the rotation speed of the rotor 50 and outputs a signal indicating the rotation speed, and the Hall element H1 Therefore, the rotation provided with the PLL circuit 60 as the first detection means for detecting whether or not the rotation speed of the polygon mirror 36 is the target rotation speed for image formation based on the output signal indicating the rotation speed. Based on a signal indicating the rotational speed output by the motor 38 as the driving means and the Hall element H3 (or H2), it is detected whether the rotational speed of the polygon mirror 36 is equal to or greater than a predetermined threshold value. When the signal output circuit 44 as the detection means 2 and the PLL circuit 60 detect that the rotation speed is the target rotation speed and the signal output circuit 44 detects that it is equal to or greater than a predetermined threshold value, the image information The laser diode 34 is controlled so that the light based on the laser beam is emitted from the laser diode 34, and it is not the target rotation speed by the PLL circuit 60 As an irradiation control means for controlling the laser diode 34 so that light is not irradiated in at least one of the cases where it is detected and the signal output circuit 44 detects that it is less than a predetermined threshold value. And a laser diode driver 40.

  In the first embodiment, the second embodiment, and the third embodiment, between the laser diode 34 and the polygon mirror 36 on the optical path of the laser light emitted from the laser diode 34. In addition, shutter means for moving the shielding member on the optical path by the control may be provided, and shutter control means for controlling the shutter means may be provided. In this case, the shutter control means operates as follows. For example, when the shutter control unit detects that the target rotation speed is detected by the PLL circuit 60 and the signal output circuit 44 detects that the shutter speed is equal to or higher than a predetermined threshold value, there is a shielding member on the optical path. The shutter unit is controlled so that the shutter speed does not occur, and at least one of the case where it is detected by the PLL circuit 60 that the rotation speed is not the target rotation speed, and the case where the signal output circuit 44 detects that the rotation speed is less than a predetermined threshold value. In this case, the shutter unit is controlled so that the shielding member moves on the optical path.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment. It is a schematic block diagram of the exposure apparatus of the image forming apparatus of 1st Embodiment. It is a figure for demonstrating the exposure apparatus of 1st Embodiment. It is a figure for demonstrating a Hall element. It is a figure for demonstrating a signal output circuit. It is a figure for demonstrating the exposure apparatus of 2nd Embodiment. It is a figure for demonstrating the exposure apparatus of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 16 Exposure apparatus 30 Control part 34 Laser diode 36 Polygon mirror 38 Motor 39 Encoder 40 Laser diode driver H1-H4 Hall element 42 Power supply control circuit 44 Signal output circuit 52 Power supply 54 Motor driver 56 Power supply 60 PLL circuit

Claims (6)

Irradiating means for irradiating light;
A light reflecting means comprising a plurality of reflecting surfaces, and reflecting the light emitted from the irradiating means at each of the plurality of reflecting surfaces;
Rotating means for rotating the light reflecting means so that the light reflected by the light reflecting means is scanned in a predetermined direction, and the number of rotations of the rotating means in a state where power is supplied from the first power source. A first detector for detecting and outputting a signal indicating the rotational speed; a signal indicating the rotational speed by detecting the rotational speed of the rotating means while power is supplied from a second power source different from the first power source; Whether the rotation speed of the light reflecting means is a target rotation speed for image formation based on the second detection section that outputs the signal and the signal indicating the rotation speed output by the first detection section Rotational drive means comprising first detection means for detecting
Second detection means for detecting whether or not the rotational speed is equal to or greater than a predetermined threshold based on a signal indicating the rotational speed output by the second detection unit;
When the first detection means detects that the rotation speed is the target rotation speed and the second detection means detects that the rotation speed is equal to or greater than a predetermined threshold, light based on image information is The irradiation unit is controlled to be irradiated from the irradiation unit, and when it is detected by the first detection unit that the rotation speed is not the target rotation speed, and less than a predetermined threshold value by the second detection unit. In at least one of the cases where it is detected, irradiation control means for controlling the irradiation means so that light is not irradiated;
Exposure apparatus. Irradiating means for irradiating light;
A light reflecting means comprising a plurality of reflecting surfaces, and reflecting the light emitted from the irradiating means at each of the plurality of reflecting surfaces;
Rotating means for rotating the light reflecting means so that the light reflected by the light reflecting means is scanned in a predetermined direction, and the number of rotations of the rotating means in a state where power is supplied from the first power source. A first detection unit that detects and outputs a signal indicating the number of rotations, and a target for forming an image of the number of rotations of the light reflecting means based on the signal indicating the number of rotations output by the first detection unit; A rotation drive means comprising a first detection means for detecting whether or not the rotation speed;
A second detection unit that detects the number of rotations of the light reflecting means and outputs a signal indicating the number of rotations when power is supplied from a second power source different from the first power source;
Second detection means for detecting whether or not the rotational speed is equal to or greater than a predetermined threshold based on a signal indicating the rotational speed output by the second detection unit;
When the first detection means detects that the rotation speed is the target rotation speed, and the second detection means detects that the rotation speed is equal to or greater than a predetermined threshold, light based on image information is The irradiation unit is controlled to be irradiated from the irradiation unit, and when it is detected by the first detection unit that it is not the target rotation speed, and when the second detection unit is less than a predetermined threshold value In at least one of the cases where it is detected, irradiation control means for controlling the irradiation means so that light is not irradiated; and
Exposure apparatus. Irradiating means for irradiating light;
A light reflecting means comprising a plurality of reflecting surfaces, and reflecting the light emitted from the irradiating means at each of the plurality of reflecting surfaces;
Rotating means for rotating the light reflecting means so that the light reflected by the light reflecting means is scanned in a predetermined direction, and the number of rotations of the rotating means in a state where power is supplied from the first power source. A first detector for detecting and outputting a signal indicating the rotational speed; a second detection for detecting the rotational speed of the rotating means and outputting a signal indicating the rotational speed in a state where power is supplied from the first power source; And a first detection for detecting whether or not the rotational speed of the light reflecting means is a target rotational speed for image formation based on a signal indicating the rotational speed output by the first detector and the first detector Rotational drive means comprising means;
Second detection means for detecting whether or not the rotation speed of the light reflecting means is equal to or greater than a predetermined threshold based on a signal indicating the rotation speed output by the second detection unit;
When the first detection means detects that the rotation speed is the target rotation speed and the second detection means detects that the rotation speed is equal to or greater than a predetermined threshold, light based on image information is The irradiation unit is controlled to be irradiated from the irradiation unit, and when it is detected by the first detection unit that the rotation speed is not the target rotation speed, and less than a predetermined threshold value by the second detection unit. In at least one of the cases where it is detected, irradiation control means for controlling the irradiation means so that light is not irradiated;
Exposure apparatus.   4. The exposure apparatus according to claim 1, wherein the first detection unit and the second detection unit are magnetic sensors that detect the number of rotations of the rotation unit.   The exposure apparatus according to claim 2, wherein the first detection unit is a magnetic sensor that detects the rotation speed of the rotation unit, and the second detection unit is an optical sensor that detects the rotation number of the light reflection unit. An exposure apparatus according to any one of claims 1 to 5,
Image forming means for forming an image based on the light irradiated by the exposure device on an image forming medium;
An image forming apparatus including:

Images