JP2013025121A - Optical scanner and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of a photoreceptor on which an electrostatic latent image is formed, by avoiding the photoreceptor being exposed when a light beam for detecting a synchronization signal is emitted.SOLUTION: An optical scanner comprises: light beam generation means; a polygon mirror 105 that scans and deflects the light beam generated by the light beam generation means; a magnetic force detection sensor that detects a reference position of the polygon mirror 105; a synchronization sensor 112 that detects the light beam at a position outside of a photoreceptor exposure range on a scanning path; and an optical scanner controller 134 that, on the basis of the reference position of the polygon mirror 105 detected by the magnetic force detection sensor 126, controls a generation timing of a synchronization detection light beam detected by the synchronization sensor 112. The optical scanner controller 134 controls the generation timing so as to prevent the photoreceptor from being exposed to the synchronization detection light beam.

Description

  The present invention relates to an optical scanning device and an image forming apparatus.

In an electrophotographic image forming apparatus used in a laser printer, a fax machine, a digital multi-function peripheral, etc., an optical scanning apparatus using a polygon mirror which is a rotating polygon mirror, for example, is widely used as an exposure apparatus.
This optical scanning device is known to include a light beam detecting means for detecting the light beam scanned and deflected by the rotary polygon mirror at a predetermined position on the scanning path in order to detect the exposure reference position in the main scanning direction. ing.

  In this optical scanning device, a sensing device such as a light receiving sensor is arranged on the scanning path of the light beam, while the light beam is turned on immediately before scanning the light receiving sensor to indicate the exposure reference position in the main scanning direction. A signal is detected. Therefore, it is necessary to detect the rotation angle of the optical deflector and synchronize the scanning timing of the light beam with the rotational phase of the optical deflector such as a polygon motor.

However, in the first sequence in which the light beam is switched from the off state to the on state, the rotation angle of the optical deflector is not known, and therefore it is necessary to light the light beam for a period of time equal to or longer than one scan of the optical deflector. When the light beam is turned on for one scanning or more of the optical deflector, there is a problem that the photosensitive member that forms the electrostatic latent image is exposed.
In recent years, in order to detect the characteristics of a light source that emits a light beam, there is a light source driver that has a process of lighting for a predetermined time when the light source is shifted to a lighting state. When this light source driver is used, there is also a problem that the photosensitive member that forms the electrostatic latent image is exposed even by lighting for light source characteristic detection.

  In order to solve this problem, Patent Document 1 discloses an optical scanning device using a polygon mirror for generating a horizontal synchronization signal for the purpose of detecting at low cost that a light beam has passed a predetermined scanning position. Instead of using a sensor for detecting the light beam, the polygon mirror is provided with detection signal generating means for generating an output signal when the polygon mirror reaches a predetermined rotational position, and the light source control circuit outputs an output signal from the detection signal generating means. Generating a horizontal synchronization signal based on the above is disclosed.

  Further, in Patent Document 2, for the purpose of accurately controlling the rotation angle of the polygon mirror and controlling the image writing start position with high accuracy, the angle of the light receiving sensor for detecting the horizontal synchronization signal is set for each polygon mirror. Corresponding storage is disclosed. In this configuration, the drive signal to the polygon motor is supplied by converting the sine wave by PWM conversion, and the sine wave angle corresponding to the drive signal when the light beam emitted from the semiconductor laser is detected by the light receiving sensor, Stored in correspondence with each surface of the polygon mirror. Also, in the adjustment process, a light receiving sensor is provided and the angle for each polygon mirror surface is stored, but in the printing process, the light receiving sensor is removed and a horizontal synchronization signal is generated based on the stored angle for each polygon mirror surface. Has been.

The optical scanning device described in Patent Document 1 is similar to the present invention described below in that control for generating a horizontal synchronizing signal is performed using a signal when a predetermined rotational position is reached from a polygon motor. doing. However, in this optical scanning device, a detection signal generating means for detecting a predetermined rotational position of the polygon mirror is provided in the polygon mirror itself, and a sensor for detecting a light beam for generating a horizontal synchronization signal is not used. When there is an environmental change in the machine, it cannot be reflected. Therefore, the image writing start position may vary with the environmental change.
In addition, the image forming apparatus described in Patent Document 2 adds a storage unit that stores changes in the position of the light receiving sensor due to temperature and thermal expansion in consideration of the influence on environmental changes in the machine. Since the number of influential environmental parameters increases, the storage section increases, and it is necessary to add measuring means such as temperature measuring means and humidity measuring means for detecting the environmental parameters, which increases the cost of the optical scanning device system. Inviting problems occur.

  Furthermore, in the conventional method of turning on the light beam and detecting the horizontal synchronization signal by the light beam incident on the light receiving sensor, the light beam lighting timing and The problem that the light beam is exposed to the photosensitive member due to unnecessary light emission due to the rotation angle of the polygon mirror being out of synchronization cannot be solved.

  The present invention has been made in view of the above circumstances, and when the light beam for detecting the synchronization signal is turned on, exposure to the photosensitive member forming an electrostatic latent image is avoided, and deterioration of the photosensitive member is prevented. The purpose is to do.

  The present invention includes a light beam generating means, a light deflecting means for scanning and deflecting the light beam generated by the light beam generating means, a position detecting means for detecting a reference position of the light deflecting means, and a scanning path for the light beam. Based on the reference position of the light beam detecting means for detecting at a position outside the upper exposure range of the photosensitive member and the light deflecting means detected by the position detecting means, the light beam for synchronous detection detected by the light beam detecting means A control unit that controls the generation timing, and the control unit controls the generation timing so as not to expose the photoconductor with the synchronization detection light beam.

  According to the present invention, since the timing for turning on the synchronization detection light beam is controlled based on the detection of the reference position of the optical deflector, the photosensitive member that forms the electrostatic latent image by turning on the synchronization detection light beam. Exposure can be avoided and deterioration of the photoreceptor can be prevented.

It is a figure explaining the structure of the optical scanning device of the 1st Embodiment of this invention. It is a figure explaining the structure of the polygon mirror which is an optical deflector of 1st Embodiment. It is a figure explaining the structure of the magnet for magnetism detection of the polygon mirror of 1st Embodiment. It is a figure explaining the control block structure of the conventional optical scanning device. It is a figure explaining the control block structure of the optical scanning device of 1st Embodiment. It is a figure explaining the timing chart at the time of steady operation of the optical scanning device of a 1st embodiment. It is a figure explaining the timing chart at the time of the light source lighting start of the conventional optical scanning device. It is a figure explaining the timing chart at the time of the light source lighting start of the optical scanning device of 1st Embodiment. It is a flowchart explaining the control procedure at the time of the light source lighting start of the optical scanning device of 1st Embodiment. It is a figure explaining the structure of the magnet for magnetism detection of the polygon mirror of the 2nd Embodiment of this invention. It is a figure explaining the timing chart at the time of steady operation of the optical scanning device of a 2nd embodiment. It is a figure explaining the timing chart at the time of the light source lighting start of the optical scanning device of 2nd Embodiment. It is a flowchart explaining the control procedure at the time of the light source lighting start of the optical scanning device of 2nd Embodiment. It is a figure explaining the structure of the magnet for magnetism detection of the polygon mirror of the 3rd Embodiment of this invention. It is a figure explaining the timing chart at the time of the steady operation of the optical scanning device of 3rd Embodiment. It is a timing chart at the time of the light source lighting start of the optical scanning device carrying the polygon mirror of 3rd Embodiment. It is a figure explaining the control block of the optical scanning device of 3rd Embodiment. It is a figure explaining the structure of the image forming apparatus carrying the optical scanning device of the 1st-3rd embodiment of this invention.

Embodiments of an optical scanning device of the present invention will be described below with reference to the drawings.
In an optical scanning device that deflects light using an optical deflector such as a polygon mirror, it is necessary to turn on a light beam when scanning a light receiving sensor in order to detect a horizontal synchronization signal. Therefore, in the optical scanning device according to the present embodiment, a horizontal synchronization signal is detected based on a deflection scanning position signal (such as an FG signal described later) generated when the polygon mirror as an optical deflector reaches a predetermined rotational position. The light beam lighting timing for controlling is controlled. Hereinafter, this embodiment will be described.

FIG. 1 is a diagram illustrating the configuration of the optical scanning device according to the first embodiment of the present invention.
1 includes a light source 101, a coupling lens 102, an aperture 103, a cylindrical lens 104, a polygon mirror 105, lenses 106 and 107, a mirror 108, a photosensitive member 109 as a photosensitive medium, a synchronous mirror 110, and a synchronous lens 111. , Having a synchronization sensor 112. The light source 101 is a semiconductor laser element that emits a light beam for optical scanning, and is driven according to image data by a driving unit (not shown). The coupling lens 102 is a lens for adapting the light beam emitted from the light source 101 to the optical system. The aperture 103 is a diaphragm member for making the light beam from the coupling lens 102 into a predetermined shape.
The cylindrical lens 104 is a lens that condenses the light beam incident from the aperture 103 in the sub-scanning direction.

  The polygon mirror 105 reflects the light incident from the cylindrical lens 104 on the deflection reflection surface. The lenses 106 and 107 form an image of the light beam from the polygon mirror 105 on the photoconductor 109. The mirror 108 bends the optical path of the light beam from the lenses 106 and 107 and guides the light beam to the photoconductor 109. The photoconductor 109 is uniformly charged by a charging device (not shown) and then scanned by a light beam from the mirror 108 to form an electrostatic latent image.

  The synchronous mirror 110 and the synchronous lens 111 collect the light beam from the lens 106 on the synchronous sensor 112. The synchronization sensor 112 is a light detection element such as a photodiode, and detects a light beam from the synchronization lens 111 to generate a horizontal synchronization signal, that is, a synchronization detection signal.

The light beam emitted from the light source 101 which is a semiconductor laser element is a divergent light beam and is coupled to the subsequent optical system by the coupling lens 102. The form of the coupled light beam is in accordance with the optical characteristics of the subsequent optical system, and may be a weak divergent light beam, a weak condensing light beam, or a parallel light beam. .
When the light beam that has passed through the coupling lens 102 passes through the opening of the aperture 103, a portion having a low light intensity at the periphery of the light beam is blocked, that is, the beam is shaped, and the cylindrical lens 104 that is a linear imaging optical system. Is incident on.

  The cylindrical lens 104 has a substantially semi-cylindrical shape, and a direction without power that does not refract light is directed to the main scanning direction, and has a power to collect light in the sub-scanning direction. The light is condensed in the scanning direction and is condensed in the vicinity of the deflection reflection surface of the polygon mirror 105 which is an optical deflector.

The light beam reflected by the deflecting and reflecting surface of the polygon mirror 105 passes through the two lenses 106 and 107 constituting the scanning optical system while being deflected at a constant angular velocity as the polygon mirror 105 rotates at a constant speed. The optical path is bent by 108, and the light is condensed and scanned as a light spot on the surface which is the photosensitive surface of the photoconductive photosensitive member 109 forming the surface to be scanned. As a result, an electrostatic latent image is formed on the photoconductor 109.
Prior to scanning, the light beam is incident on the synchronization mirror 110 and reflected, and is collected by the synchronization lens 111 onto the synchronization sensor 112 which is a light receiving element. The timing of optical writing with the light beam to the photoconductor 109 is determined by an optical scanning device controller which is a control unit described later based on the output signal of the synchronization sensor 112.

FIG. 2 is a diagram illustrating the configuration of the polygon mirror 105 that is the optical deflector of the first embodiment.
FIG. 2 is a side view of the polygon mirror. The polygon mirror 105 has a polygon mirror main body 105b as a rotating body attached to a rotation shaft 105a. A driving magnet and a magnetic force detection magnet 105c (FIG. 3) are attached to the rotation shaft 105a of the polygon mirror 105. On the other hand, a drive control circuit board 122 a having a coil unit 124 and a motor control unit 122 is provided on the upper surface of the motor base 120.

  The motor control unit 122 is configured by a control circuit centered on the motor driver 132 (FIG. 4), and the coil unit 124 is provided with a three-phase driving coil 124a so as to face the driving magnet. . In the vicinity of the coil unit 124, a magnetic force detection sensor 126 such as a Hall element is disposed at a position facing the magnetic force detection magnet 105c in order to detect the magnetic force of the magnetic force detection magnet 105c (FIG. 3) on the polygon mirror 105 side. Has been.

FIG. 3 is a diagram illustrating the configuration of the magnetic force detection magnet 105c of the polygon mirror 105 according to the first embodiment.
As shown in FIG. 3, the magnetic force detection magnet 105 c is magnetized so that six north poles and six south poles are alternately arranged, and the magnetic force detection magnet 105 c is magnetic force detection sensor (hall element) 126. The polygon mirror 105 is positioned with respect to the drive control circuit board 122a so as to be positioned above.
When the polygon mirror 105 is rotated, a repulsive force and an attractive force are generated between the driving magnet and the driving coil 124a by supplying alternating currents that are out of phase to the three-phase driving coil 124a. The polygon mirror 105 is rotated at a rotation speed of. Due to the rotation of the polygon mirror 105, the magnetic force detection magnet 105c also rotates.

  As the magnetic force detection magnet 105c rotates, the magnetic force detection sensor (hall element) 126 generates an output voltage due to a change in the magnetic force lines of the magnetic force detection magnet 105c. Here, the output voltage from the magnetic force detection sensor 126 is an AC signal having a frequency proportional to the rotational speed of the polygon mirror 105, that is, the rotational speed of the magnetic force detection magnet 105c. The motor driver 132 (FIG. 4) detects the rotational speed of the polygon mirror 105 based on this AC signal, and controls it to achieve the target rotational speed.

In the polygon mirror 105 of FIG. 3, since the magnetic force detection magnet 105c is composed of 12 poles, an AC signal of 6 cycles is generated from the magnetic force detection sensor 126 per one rotation of the polygon mirror. Further, since the number of polygon mirrors 105 is 6, the synchronization detection signal from the synchronization sensor 112 is detected 6 times per rotation of the polygon mirror.
In the present embodiment, the number of poles of the magnetic force detection magnet 105c for detecting the rotation speed of the polygon mirror 105 is 12, the number of faces of the polygon mirror 105 is 6, and the number of poles is twice the number of mirror faces.

FIG. 4 is a diagram for explaining the configuration of a control block of a conventional optical scanning device.
4 includes control blocks for a laser driver 130, a motor driver 132, and an optical scanning device controller 134. The optical scanning device also includes a light source 101, a polygon motor (not shown), a magnetic force detection sensor 126, a synchronization mirror 110, and a synchronization sensor 112.

The optical scanning device controller 134 is a control unit that performs overall control of electronic components constituting the optical scanning device such as the light source 101 and the polygon motor. The optical scanning device controller 134 is connected to the laser driver 130, the motor driver 132, and the synchronization sensor 112. A lighting data signal to the light source 101 is output to the laser driver 130 based on image data from a controller or an image processing unit (not shown) and the timing of the optical scanning device, and the light source 101 fails based on the signal from the laser driver 130. Detect error conditions.
The optical scanning device controller 134 issues polygon motor start and stop commands to the motor driver 132 based on an image forming command from an engine control unit configured by a CPU or the like that performs overall control of the image forming apparatus (not shown). On the other hand, based on the signal output from the motor driver 132 of the polygon motor, the rotation state, failure, and error information of the polygon motor are detected.

  The laser driver 130 is connected to the light source 101 and outputs a lighting signal to the light source 101 based on a lighting signal from the optical scanning device controller 134. The light source 101 emits a light beam based on a lighting signal from the laser driver 130. The light beam emitted from the light source 101 enters the polygon mirror 105 that is a rotating body of the polygon motor, and is reflected by the polygon mirror 105. The reflected light beam scans in accordance with the rotation of the polygon mirror 105, and is transmitted and reflected by the lenses 102, 104, 106, 107, the mirror 108, etc. of FIG.

  A part of the scanning light beam is reflected in a direction different from that of the photoconductor 109 by the synchronous mirror 110 provided outside the image forming area on the photoconductor 109. The light beam reflected by the synchronization mirror 110 passes through the synchronization lens 111 and is collected on the synchronization sensor 112. A light detection element such as a photodiode mounted on the synchronization sensor 112 detects a light beam from the synchronization lens 111 and generates a synchronization detection signal. That is, only the light beam scanned at a predetermined timing by the polygon mirror 105 is detected, and a synchronization detection signal is generated.

  The synchronization detection signal generated by the synchronization sensor 112 is output to the optical scanning device controller 134. The optical scanning device controller 134 detects the synchronization detection signal from the synchronization sensor 112 as a scanning reference timing signal and uses it as a reference signal for the polygon mirror 105 to scan in the main scanning direction. That is, based on the synchronization detection signal, the timing for outputting the lighting data of the light source 101 to the laser driver 130 is controlled, and the rotation of the polygon mirror 105 and the timing of the lighting data of the light source 101 are synchronized.

FIG. 5 is a diagram illustrating a configuration of a control block of the optical scanning device according to the first embodiment.
The control block of the optical scanning device shown in FIG. 5 compares the magnetic force detection signal from the magnetic force detection sensor 126 of the polygon motor not only with the motor driver 132 but also with the optical scanning device controller 134, as compared with FIG. 4 showing the conventional control block. Is different in that it also outputs.
As described above, the magnetic force detection sensor 126 is composed of a Hall element or the like, and detects the magnetic force of the magnetic force detection magnet 105c disposed on the polygon mirror 105 side. The motor driver 132 detects the rotation speed of the polygon mirror 105 based on the magnetic force detection signal detected by the magnetic force detection sensor 126, and controls the rotation speed to be a target rotation speed.

  In addition to this, in this embodiment, the optical scanning device controller 134 detects the reference position of the polygon mirror 105, for example, its rotational position, based on the magnetic force detection signal detected from the magnetic force detection sensor 126. That is, the rotation angle position (rotation phase) serving as a reference for the polygon mirror 105 is detected. By detecting the rotational phase of the polygon mirror 105, the optical scanning device controller 134 controls the timing of lighting data of the light source 101 output to the laser driver 130. The control method will be described later.

FIG. 6 is a diagram for explaining a timing chart during steady operation of the optical scanning device according to the first embodiment.
The timing chart of FIG. 6 shows a signal (referred to as an FG signal) obtained by comparing the output signal from the magnetic force detection sensor 126 (referred to as a HALL signal), an output signal from the synchronous sensor 112 (referred to as a synchronous detection signal; referred to as a BD signal), and synchronization. It comprises a light source lighting signal (referred to as a BD_DATA signal) for entering the sensor 112, an image data signal (referred to as a VIDEO_DATA signal) to the light source 101, and a lighting data signal (referred to as an LD_DATA signal) to the light source 101.
The output signal from the magnetic force detection sensor 126 constituted by a Hall element or the like, that is, the HALL signal, changes as the magnetic force from the magnetic force detection magnet 105c attached to the polygon mirror 105 changes in accordance with the rotation of the polygon mirror 105. To do. That is, since the magnetic force detection magnet 105c is disposed so that the S pole and the N pole are adjacent to each other, the HALL signal is output as an AC signal.

The HALL signal is generated as an FG signal (compared signal) through a comparator circuit (not shown) of the optical scanning device controller 134.
The comparison process from the HALL signal to the FG signal may be performed by the motor driver 132 instead of the optical scanning device controller 134. In order to control the rotational speed of the polygon mirror 105, the motor driver 132 may require an FG signal obtained by comparing the HALL signal. In this case, since the comparison processing circuit is shared, a configuration in which the FG signal processed by the motor driver 132 is output from the motor driver 132 to the optical scanning device controller 134 is also conceivable. In the case of this configuration, since there is no connection from the magnetic force detection sensor 126 to the optical scanning device controller 134, the control block in FIG. 5 is the same as the control block in FIG.

  In the configuration shown in FIG. 3, that is, a configuration using a polygon motor in which the magnetic force detection magnet 105c has 12 poles and the polygon mirror 105 has 6 mirror surfaces, the BD signal ( The synchronization detection signal) and the FG signal are out of phase but the period is the same. That is, the BD signal and the FG signal are out of phase by the amount of deviation of the magnetization position of the magnetism detecting magnet 105c with respect to the polygon mirror surface. The period is 6 rotations of the polygon mirror 105, the mirror surface is 6 surfaces, 6 BD signals are detected, and the FG signal is detected 12 poles, but 12 S poles and N poles are detected. And the periods coincide.

In order to detect the BD signal, it is necessary to turn on the light source 101 at a timing when the synchronization sensor 112 scans the light beam. Therefore, in order to turn on the light source 101, the optical scanning device controller 134 counts back a predetermined timing from the BD signal, and a BD_DATA (light source lighting data) signal at a timing before (immediately before) the light beam scans the synchronization sensor 112. To activate. By making the BD_DATA signal active, the laser driver 130 turns on the light source 101, and the light beam from the light source 101 is incident on the synchronization sensor 112 to detect the BD signal.
When the BD signal is input to the optical scanning device controller 134, the optical scanning device controller 134 makes the BD_DATA signal inactive to prevent unnecessary light beam emission.

When there is no image data to be exposed to the photoconductor 109, it is not necessary to expose the photoconductor 109, so the light source lighting signal (data) to the light source 101 is only the BD_DATA signal for detecting the BD signal.
On the other hand, when image data to be exposed to the photoconductor 109 is supplied from a controller or an image processing unit (not shown), the image data to be exposed to the photoconductor 109 is processed in units of lines. That is, as shown as “VIDEO_DATA” in the figure, the image data of the first line (line 1), the second line (line 2),... Are processed within one period of the BD signal.

  As for the processing timing of this VIDEO_DATA signal, after detecting the BD signal, the data for one line is processed at the timing when the main scanning writing timing has elapsed. This main scan writing timing is processed in a common time for line1, line2, line3... If the processing is not performed in a common time, the main scanning timing of the image data exposed to the photoconductor 109 differs from line to line, resulting in an abnormal image in which the image data array of the output image is shifted in the main scanning direction.

  The final lighting data (LD_DATA) signal to the light source 101 is a signal obtained by combining the VIDEO_DATA signal whose main scanning writing timing is adjusted and the light source lighting signal (BD_DATA signal) for detecting the BD signal. That is, it becomes an LD_DATA signal composed of a VIDEO_DATA signal corresponding to an image area exposed to the photoconductor 109 and a BD_DATA signal corresponding to a non-image area incident on the synchronization sensor 112.

FIG. 7 is a diagram for explaining a timing chart at the start of lighting of the light source of the conventional optical scanning device.
The timing chart of FIG. 7 shows a signal (FG signal) obtained by comparing output signals from the magnetic force detection sensor 126, an output signal (BD signal) from the synchronization sensor 112, and a forced turn-off signal (LDOFF signal) of the light source 101. And a light source lighting signal (BD_DATA signal) for entering the synchronization sensor 112.

In an optical scanning device using a laser diode or the like as the light source 101, in order to prevent the light beam from the laser diode from irradiating a fixed point for safety standards, the polygon mirror is always activated before the light source 101 is turned on. It is necessary to ensure that it can be deflected.
Therefore, in an optical scanning device using a rotator such as a polygon motor for the polygon mirror, the light source 101 is turned on after detecting that the polygon motor is rotating at regular intervals. That is, a lock signal notifying that the polygon motor is locked is output from the motor driver 132 to the optical scanning device controller 134, and the light source 101 is turned on based on the lock signal.

  In the conventional optical scanning device, the light source 101 is turned on by detecting the lock signal of the polygon motor. In other words, in order to turn on the light source 101, the forced light extinction signal (LDOFF signal) is canceled (High → Low), and the light source lighting for detecting the synchronization detection signal is started (BD_DATA signal is activated). . Therefore, when the LDOFF signal release timing is not synchronized with the mirror rotation phase of the polygon motor, and the LDOFF signal is released at the polygon mirror position where the light beam is incident on the synchronization sensor 112, the maximum of one surface of the polygon mirror 105 is obtained. It is necessary to turn on the light source 101 only for a period (time).

  In other words, this is the time when the section of period a in FIG. 7 reaches one surface of the polygon mirror 105. When the light source 101 is turned on and the first BD signal (synchronization detection signal) is detected, the BD_DATA signal is negated and the light source 101 is turned off. After a predetermined timing has elapsed from the first BD signal, in FIG. 7, after the period b has elapsed, the BD_DATA signal is asserted and the light source 101 is turned on immediately before the synchronization sensor 112 is scanned. The second BD signal is detected at the timing of entering the synchronous sensor 112 by lighting with the BD_DATA signal.

  During steady rotation of the polygon motor, the BD signal can be detected by activating the BD_DATA signal after the period b has elapsed from the immediately preceding BD signal. This period b is before the timing when the light beam is incident on the synchronization sensor 112, and the timing is behind the rear end portion of the effective image area where the light beam is exposed to the photosensitive member 109. That is, in the invalid image area at the rear end of the main scanning, the light source 101 is turned on at a timing before the timing at which the light beam can enter the synchronization sensor 112. The timing before the timing at which the light beam is incident on the synchronization sensor 112 is always in front of the light source 101 even if the mounting position of the synchronization sensor 112 varies. It is necessary to light up.

  On the other hand, the light source lighting start timing has a period a. At the time of starting the light source, there is no BD signal immediately before serving as a reference as in the second period b, so the first lighting timing is not synchronized with the polygon rotation phase. Therefore, as described above, during the period a, one surface of the maximum polygon mirror 105 is turned on, and the light is turned on during the effective image area which is the exposure period of the photosensitive member 109. The side streak is lit unnecessarily. This unnecessary lighting on the photoconductor 109 damages the photoconductor 109 and accelerates deterioration.

FIG. 8 is a diagram illustrating a timing chart at the start of lighting of the light source of the optical scanning device according to the first embodiment.
The timing chart of FIG. 8 is configured similarly to FIG. 8 differs from FIG. 7 in the assertion timing of the BD_DATA signal that is a lighting start signal at the time of starting the light source lighting. That is, in FIG. 7, the BD_DATA signal is asserted at the timing when the forced extinction signal (LDOFF signal) is released, but in the timing chart of FIG. 8, BD_DATA is passed after a period c has elapsed from the assertion edge of the FG signal after the LDOFF signal is released. The signal is asserted. This indicates that the lighting timing of the first BD signal detection is managed (controlled) from the FG signal edge.

Thus, unnecessary light emission to the photoconductor 109 can be prevented by the first lighting for detecting the BD signal. That is, as in the period d and the period b in FIG. For the second BD signal detection lighting, the BD_DATA signal is asserted after a period d has elapsed from the first BD signal as in FIG.
As described above, according to this embodiment, the timing of asserting the BD_DATA signal, and hence the timing of detecting the BD signal, is changed between the first and second and subsequent times, and here, the optical scanning device controller 134 switches the switching. Do.

FIG. 9 is a flowchart illustrating a control procedure at the time of starting lighting of the light source of the optical scanning device according to the first embodiment.
When there is an instruction to turn on the light source 101 in the optical scanning device controller 134, first, a polygon motor that is an optical deflector is activated (S101). After starting the polygon motor, the motor lock signal from the motor driver 132 is monitored to determine whether the polygon motor has rotated normally (S102). If the polygon motor is rotating normally (S102, YES), the forced extinction state is canceled (S103). That is, the LDOFF signal is switched from High to Low. When the LDOFF signal switches to Low, it shifts to the ready state for sync detection lighting.

  In the ready state for synchronous detection lighting, a signal obtained by comparing the signals from the Hall elements of the polygon motor or the FG signal from the motor driver 132 is monitored to determine whether the FG signal is asserted (S104). If it is not asserted (S104, NO), it waits (waits) until the FG signal assert edge occurs. When it is detected that the FG signal is asserted (S104, YES), the time is counted from the assert edge, and when the predetermined period c has elapsed (S105, YES), the light source lighting signal BD_DATA signal is switched to High, that is, The light source is turned on for synchronization detection (S106). When the BD_DATA signal is switched to High and the light source 101 is turned on for synchronization detection, the light beam is incident on the synchronization sensor 112 in synchronization with the scanning of the polygon mirror 105, and the BD signal can be detected. If a BD signal is detected (S107, YES), the BD_DATA signal is negated, that is, the light source is turned off (S108), and the first BD signal detection operation is terminated.

Thereafter, the counter control is performed based on the first BD signal, and the BD_DATA signal for detecting the second BD signal is asserted after the elapse of period b or d.
By the above control flow, the lighting timing of the light source 101 and the rotation angle of the polygon mirror 105 are synchronized by synchronizing the assertion timing of the BD_DATA signal at the start of lighting of the light source and the timing of the rising edge of the FG signal of the polygon mirror 105. Further, exposure to the photoconductor 109 can be prevented. As a result, unnecessary exposure to the photoconductor 109 can be prevented, and the photoconductor 109 can be prevented from being deteriorated by exposure of the light source 101.
Other embodiments of the present invention will be described below. In addition, except for a different part from 1st Embodiment demonstrated below of other embodiment, it is common in 1st Embodiment.

FIG. 10 is a diagram illustrating the configuration of the magnetic force detection magnet 105c of the polygon mirror 105 according to the second embodiment of this invention.
FIG. 10 shows the configuration of the magnetic force detection magnet 105c of the polygon mirror 105 according to the second embodiment of the present invention. The number of poles of the magnetic force detection magnet 105c and the number of surfaces of the polygon mirror 105 are different from those in FIG. That is, in the first embodiment shown in FIG. 3, the magnetism detecting magnet 105c has 12 poles and the polygon mirror 105 has 6 faces. In the second embodiment of FIG. The detection magnet 105c has two poles, and the polygon mirror 105 has four faces.

FIG. 11 is a diagram illustrating a timing chart during a steady operation of the optical scanning device according to the second embodiment of the present invention. In other words, FIG. 11 is a timing chart at the time of steady operation of the optical scanning device equipped with the polygon mirror 105 of the second embodiment of the present invention shown in FIG.
The period of the HALL signal, the FG signal, and the BD signal is different from FIG. 6 of the timing chart of the first embodiment.

  In the configuration using the polygon motor in which the number of poles of the magnetic force detection magnet 105c shown in FIG. 10 is two and the number of mirror faces of the polygon mirror 105 is four, four BD signals are detected during one rotation of the polygon mirror 105. Since the FG signal detects the S pole and the N pole twice, it has one cycle.

FIG. 12 is a diagram illustrating a timing chart at the start of lighting of the light source of the optical scanning device according to the second embodiment.
FIG. 12 is a timing chart at the start of lighting of the light source of the optical scanning device equipped with the polygon mirror 105 of the second embodiment shown in FIG. The period of the FG signal and the BD signal is different from FIG. 8 showing the timing chart of the first embodiment.
In the configuration of the polygon mirror 105 shown in FIG. 10, four BD signals are detected during one rotation of the polygon mirror 105, and the FG signal detects two S poles and N poles. The light source 101 for detecting the first BD signal is turned on by asserting the BD_DATA signal after elapse of a predetermined period c from the assertion edge of the FG signal after releasing the LDOFF signal. Therefore, unnecessary light emission to the photoconductor 109 can be prevented.

  FIG. 13 is a flowchart for explaining a control procedure at the time of starting lighting of the light source of the optical scanning device according to the second embodiment. That is, FIG. 13 is a control flowchart at the time of starting lighting of the light scanning apparatus equipped with the polygon mirror 105 of the second embodiment shown in FIG.

  In the configuration of the polygon mirror 105 shown in FIG. 10, four BD signals are detected during one rotation of the polygon mirror 105, and the FG signal detects two S poles and N poles, so this is one cycle. From the relationship between the BD signal and the FG signal, the edge of the FG signal serving as a reference for the BD signal may be not only the assert edge but also the negate edge. By activating the BD_DATA signal after elapse of a predetermined time corresponding to the assert edge or negate edge from the selected edge, it is possible to prevent deterioration of the photoconductor 109 due to unnecessary light emission to the photoconductor 109.

  That is, when the light scanning device controller 134 is instructed to turn on the light source 101, the polygon motor, which is an optical deflector, is first activated (S201). After starting the polygon motor, the motor lock signal from the motor driver 132 is monitored to determine whether the polygon motor has rotated normally (S202). When the polygon motor is rotating normally (S202, YES), the forced light source off state is canceled (S203). That is, the LDOFF signal is switched from High to Low. When the LDOFF signal switches to Low, it shifts to the ready state for sync detection lighting.

  In the ready state for sync detection lighting, the signal (FG signal) that compares the signal from the hall element of the polygon motor (HALL signal) or the FG signal from the motor driver 132 is monitored, and the FG signal is asserted or negated. If it is not asserted or negated (S204, NO), it waits (waits) until the FG signal assert edge or negate edge occurs. When it is detected that the FG signal is asserted or negated (S204, YES), the time is counted from the asserted edge or negated edge, and when the predetermined period c has elapsed (S205, YES), the light source lighting signal BD_DATA signal is Switching to High, that is, the light source is turned on for synchronization detection (S206). When the BD_DATA signal is switched to High and the light source 101 is turned on for synchronization detection, the light beam is incident on the synchronization sensor 112 in synchronization with the scanning of the polygon mirror 105, and the BD signal can be detected. If a BD signal is detected (S207, YES), the BD_DATA signal is negated, that is, the light source is turned off (S208), and the first BD signal detection operation is terminated.

FIG. 14 is a diagram illustrating the configuration of the magnetic force detection magnet 105c of the polygon mirror 105 according to the third embodiment of the present invention.
FIG. 14 shows a configuration of the polygon mirror 105 of the third embodiment, and the number of poles of the magnetic force detection magnet 105c is different from that of the polygon mirror 105 of FIG. In the polygon mirror 105 shown in FIG. 3, the magnetic force detection magnet 105 c has 12 poles and the polygon mirror 105 has 6 faces. In the polygon mirror 105 shown in FIG. 14, the number of poles of the magnetism detecting magnet 105c is 6, and the number of faces of the polygon mirror 105 is 6.

FIG. 15 is a diagram illustrating a timing chart during steady operation of the optical scanning device according to the third embodiment of the present invention.
FIG. 16 is a timing chart at the start of lighting of the light source of the optical scanning device equipped with the polygon mirror 105 of the third embodiment shown in FIG. The period of the FG signal and the BD signal is different from the timing chart shown in FIG. 8 of the first embodiment.
In the configuration of the magnetism detection magnet 105c of the polygon mirror 105 shown in FIG. 14, six BD signals are detected during one rotation of the polygon mirror 105, and the FG signal detects six S poles and N poles. It becomes a cycle. The light source lighting timing for detecting the first BD signal is determined by asserting the BD_DATA signal after elapse of a predetermined period c from the assertion edge or negation edge of the FG signal after the LDOFF signal is released. Unnecessary light emission to the photoconductor 109 can be prevented by turning on the light source. That is, the control flow can be controlled by the same flow as shown in FIG.

FIG. 17 is a diagram illustrating a control block of the optical scanning device according to the present embodiment.
The control block of the optical scanning device in FIG. 17 is different from the control block in FIG. 5 in that a memory 136 is connected to the optical scanning device controller 134. The memory 136 connected to the optical scanning device controller 134 stores the time from the edge detection of the FG signal to the activation of the BD_DATA signal in order to detect the first BD signal when the light source 101 is turned on. .

  The time from the edge detection of the FG signal to the activation of the BD_DATA signal varies depending on the magnetization position of the magnetic force detection magnet 105c with respect to the polygon mirror surface. Since the magnetizing position of the magnetism detecting magnet 105c varies due to individual differences of the polygon mirror 105, it is necessary to store time for each polygon motor. When the light source 101 of the optical scanning device is turned on by measuring the phase of the FG signal from the polygon mirror 105 with respect to the BD signal detected by the synchronization sensor 112 and storing it in the memory in the assembly process of the optical scanning device. Based on the phase information from the memory 136, the elapsed time for activating the BD_DATA signal from the asserted edge or negated edge of the FG signal is controlled. Thus, unnecessary light emission from the optical scanning device to the photosensitive member 109 can be prevented regardless of individual differences of the polygon motor.

FIG. 18 is a diagram illustrating the configuration of an image forming apparatus equipped with the optical scanning device according to the first to third embodiments of the present invention described above.
The image forming apparatus includes a photosensitive drum 10, a charging unit 12, a toner cartridge 14 as a developing unit, a transfer roller 16, a cleaner (not shown) that removes toner on the photosensitive drum 10, an intermediate transfer belt 20, The intermediate transfer roller 22, an intermediate transfer belt cleaning device 24, a transfer device 26, a paper feed registration sensor 28, a fixing device 30, a paper discharge roller 32, and an optical scanning device 40 are included.

When the start button of the color image forming apparatus is pressed or the print job start signal from the printer host is validated, the optical scanning device 40 exposes the timing-controlled light beam onto the photosensitive drum 10. In this optical scanning device, a polygon mirror 105, which is a multi-surface reflecting mirror, is rotated by a polygon motor to scan a light beam from a light source, and a light beam is written on each surface to be scanned of the photosensitive drum 10 to form an electrostatic latent image. To do.
The formed electrostatic latent image is developed with the toner supplied from the toner cartridge 14, and a single color image is formed on the photosensitive drum 10, and is transferred onto the intermediate transfer belt 20 by the transfer roller 16. The intermediate transfer belt 20 conveys the toner image transferred by rotating the intermediate transfer roller 22 as a driving roller in a predetermined direction.

  On the other hand, when the job start signal is validated, the image forming apparatus separates the transfer sheets S one by one from the sheet feeding device, feeds and feeds them, and the sheet feeding registration sensor 28 detects the transfer sheet S. Then, the paper feeding is temporarily stopped. The registration roller 28 a is rotated in synchronization with the conveyance of the toner image on the intermediate transfer belt 20, and the transfer sheet S is sent between the intermediate transfer belt 20 and the transfer device 26. The transfer device 26 transfers the toner image to the transfer paper S, and the fixing device 30 applies heat and pressure to the transfer paper S on which the toner image to be conveyed is transferred and fixes it. After fixing, the transfer paper S is discharged by a paper discharge roller 32 attached to a paper discharge device and stacked on a paper discharge tray (not shown).

As described above, this embodiment is an optical scanning device that exposes a photosensitive member that forms an electrostatic latent image by deflecting a light beam with a polygon mirror that is an optical deflector, and the polygon mirror is a predetermined mirror. Based on the deflection scanning position signal generated when the rotation position is reached, the light beam forced lighting timing for detecting the horizontal synchronization signal is controlled. In other words, since the lighting timing for detecting the horizontal synchronization signal of the light beam and the rotation phase of the polygon mirror are synchronized, in the optical scanning device using the polygon mirror, the rotation control of the polygon motor is not complicated. The horizontal synchronization signal can be detected at a timing in accordance with the change in characteristics of the optical components of the optical scanning device accompanying the environmental change. In addition, the timing for turning on the light beam for detecting the horizontal synchronization signal is controlled based on the deflection scanning position signal output when the polygon mirror reaches the predetermined rotation position, so that the horizontal synchronization signal is detected. Therefore, the light beam is turned on to prevent exposure of the photosensitive member forming an electrostatic latent image and to prevent deterioration of the photosensitive member.
In the above description of the embodiment, the optical deflector has been described as a polygon mirror. However, the polygon mirror here is a generic term for those having a function of deflecting and scanning light.

  DESCRIPTION OF SYMBOLS 101 ... Light source, 102 ... Coupling lens, 103 ... Aperture, 104 ... Cylindrical lens, 105 ... Polygon mirror, 105a ... Rotating shaft, 105b ... Polygon mirror main body, 105c ... Magnet for detecting magnetic force, 106, 107 ... Lens, 108 ... Mirror, 109 ... Photoconductor, 110 ... Synchronous mirror, 111 ... Synchronous lens, 112 ... Synchronous sensor, DESCRIPTION OF SYMBOLS 120 ... Motor base, 122 ... Motor control unit part, 122a ... Drive control circuit board, 124 ... Coil unit, 124a ... Driving coil, 126 ... Magnetic force detection sensor (Hall element , 130 ... Laser driver, 132 ... Motor driver, 134 ... Optical scanning device controller, 136 ... Memory

Japanese Patent Laid-Open No. 10-2137760 JP 2010-52313 A

Claims (11)

A light beam generating means; a light deflecting means for scanning and deflecting the light beam generated by the light beam generating means; a position detecting means for detecting a reference position of the light deflecting means; and a photoconductor on the scanning path. Controls the generation timing of the synchronization detection light beam detected by the light beam detection means based on the reference position of the light beam detection means for detecting at a position outside the exposure range and the light deflection means detected by the position detection means. A control unit,
The control unit is an optical scanning device that controls the generation timing so as not to expose the photoconductor with the synchronization detection light beam. The optical scanning device according to claim 1,
The control unit is an optical scanning device that performs control to generate a synchronization detection light beam when the position detection unit detects the reference position of the light deflection unit. In the optical scanning device according to claim 1 or 2,
An optical scanning device that stops the generation of the synchronization detection light beam when the synchronization detection light beam is detected by a light beam detection means. In the optical scanning device according to any one of claims 1 to 3,
The optical scanning device, wherein the light deflection means is a rotary polygon mirror, and the position detection means detects a rotational position of the rotary polygon mirror. The optical scanning device according to claim 4,
The position detection means is an optical scanning device which is a magnet for detecting magnetic force provided in the rotary polygon mirror and a Hall element. The optical scanning device according to claim 5,
An optical scanning device in which the number of mirror surfaces of the rotary polygon mirror is ½ times the number of poles of a magnetic force detection magnet provided in the position detection means. The optical scanning device according to claim 5,
An optical scanning device in which the number of mirror surfaces of the rotary polygon mirror is twice the number of poles of a magnetic force detection magnet provided in the position detection means. The optical scanning device according to claim 5,
An optical scanning device in which the number of mirror surfaces of the rotary polygon mirror is the same as the number of magnetic detection magnets provided in the position detection means. The optical scanning device according to any one of claims 1 to 8,
An optical scanning device comprising storage means for storing a time from detection of the reference position to generation of the synchronization detection light beam at the start of lighting of the light beam generation means. In the optical scanning device according to any one of claims 1 to 9,
Timing control for emitting the first synchronization detection light beam at the start of lighting of a light source that generates a light beam by the light beam detection means in the control unit, and second and subsequent synchronization detection light beams An optical scanning device having switching means for switching timing control for emission.   An image forming apparatus comprising the optical scanning device according to claim 1.

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