JP2004326105A - Optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner which is used in printing equipment such as a laser printer, which is designed to obtain a stable optical output from a laser diode without being affected by temperature, and which is capable of minimizing noise through motor control by a sensorless control method. <P>SOLUTION: The optical scanner is equipped with: an optical system including a housing 150, a light source 111 that is arranged inside the housing 150, emits a laser beam, a mirror 114 for scanning the laser beam, and a plurality of optical elements for making the laser beam form an image on an image-forming surface; a motor 120 that is arranged inside the housing 150, rotates the mirror 114; and a driving chip 140 that is arranged outside the housing 150, controls the revolution speed of the motor 120 by a sensorless control method. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical scanning device used for an image forming apparatus or the like, and more particularly, to an optical scanning device in which a driving chip of a polygon mirror motor is disposed outside a housing.

  2. Description of the Related Art In a printing apparatus such as a laser printer, a latent electrostatic image corresponding to an image to be printed is generally formed by scanning light on a surface of a photosensitive medium such as a photosensitive drum or a photosensitive belt. An optical scanning device (Laser scanning Unit; LSU) to be formed is provided.

  FIG. 1 is a perspective view showing the internal configuration of a conventional optical scanning device.

  Referring to FIG. 1, a conventional optical scanning device includes a laser diode (LD) 11 for emitting laser light, and a collimator lens for converting the emitted laser light into parallel light or convergent light with respect to an optical axis. 12, a polygon mirror 14 for scanning the laser light passing through the collimator lens 12 by moving the laser light in the horizontal direction at a constant speed, and a cylinder lens 13 for forming the laser light on the surface of the polygon mirror 14 into a linear image in the horizontal direction. An Fθ lens 15 having a constant refractive index with respect to the optical axis, polarizing the uniform-velocity light reflected from the polygon mirror 14 in the main scanning direction, correcting aberrations, and focusing on the scanning surface; A reflection mirror 16 for imaging, which reflects the laser light passing through the Fθ lens 15 to form an image on the surface of the photosensitive drum 60 of the printing device, which is an image forming surface, in a dot-like manner; An optical sensor 18 for adjusting the horizontal sync, the optical system comprising optical elements such as synchronization signals the reflecting mirror 17 for reflecting the laser beam in the direction of the optical sensor 18 for synchronization signal detection are provided Te. Such an optical element is installed and sealed inside the housing 50 so as not to be contaminated by foreign substances such as dust or scattered toner.

  A motor 20 for rotating the polygon mirror 14 at a constant speed is provided inside the housing 50, and the motor 20 is installed on a circuit board 30. The circuit board 30 is provided with a driving chip 40 composed of a semiconductor integrated circuit for driving and controlling the motor 20. Further, a circuit board 10 for controlling the laser diode 11 is provided in the housing 50.

  FIG. 2 is a block diagram showing a circuit configuration of the conventional driving chip shown in FIG.

  Referring to FIG. 2, a motor 20 for rotating the polygon mirror 14 at a constant speed is provided with three position sensors 21, 22, 23 and one speed sensor 24. As the position sensors 21, 22, 23 and the speed sensor 24, a Hall sensor is usually used. The drive chip 40 includes a position signal amplifying unit 41, a speed signal amplifying and filtering unit 42, a speed control unit 43, a commutation control unit 44, and a three-phase inverter 45. . Each of the position sensors 21, 22, and 23 is connected to the position signal amplifier 41 of the drive chip 40 by two signal lines, and the speed sensor 24 is configured to amplify the speed signal of the drive chip 40 by two signal lines. And the filter unit 42. The three-phase inverter 45 is connected to the u terminal, v terminal, and w terminal of the motor 20 by three power supply lines.

  The position signal amplifier 41 amplifies the position signals Sa, Sb, Sc of the rotor of the motor 20 received from the position sensors 21, 22, 23, and transmits the amplified signal values to the commutation controller 44. The speed signal amplification and filter unit 42 amplifies and filters the speed signal Sd received from the speed sensor 24 and transmits the signal value to the speed control unit 43. The speed control unit 43 calculates a control value for controlling the rotation speed of the motor 20 based on the received speed signal value, and transmits the control value to the commutation control unit 44. The commutation control unit 44 controls the three-phase inverter 45 according to the received position signal value and speed control value, whereby the inverter 45 performs an appropriate switching sequence so that the motor 20 rotates at a constant speed. To supply current to the u terminal, v terminal and w terminal of the motor 20.

  However, in the conventional optical scanning device having the above-described configuration, since the driving chip 40 acting as a heat source is installed inside the housing 50, heat generated from the driving chip 40 causes the inside of the optical scanning device. The temperature will rise. Such an increase in the internal temperature of the optical scanning device affects the characteristics of the laser diode 11, the Fθ lens 15, and the like.

  Tables 1 and 2 below show the results of measuring the internal temperature change and the temperature change for each part in the conventional optical scanning device. Table 1 shows a change in temperature of each part of the optical scanning device according to time when the motor is continuously driven at 22,000 rpm in a low temperature / low humidity environment, and Table 2 shows a high temperature / high humidity. FIG. 6 shows a change in temperature of each part of the optical scanning device with time when a motor is continuously driven at 22,000 rpm in an environment.

  As shown in Tables 1 and 2, the rise in the internal temperature of the optical scanning device slightly varies depending on the operating environment of the optical scanning device, the operating conditions of the motor, and the like. It can be seen that the temperature increases and the longer the drive time, the greater the temperature rise in each part. In particular, the temperature rise on the surface of the drive chip is the largest, followed by the temperature rise on the bottom of the polygon mirror motor. From this, it can be seen that the largest heat source that induces a rise in the internal temperature of the optical scanning device is the driving chip.

  Thus, the temperature of the laser diode rises due to the rise in the internal temperature of the optical scanning device due to the heat generated by the driving chip. For this reason, the temperature characteristic of the laser diode changes, and there is a problem that the optical output of the laser diode cannot be accurately controlled.

  In addition, the temperature of the Fθ lens formed of a plastic material by injection molding also increases due to an increase in the internal temperature of the optical scanning device. For this reason, the refractive index and the curvature of each part of the Fθ lens are affected, and the deviation of the diameter of the light spot formed on the surface of the photosensitive medium becomes large.

  Table 3 below shows the result of measuring the diameter of a light spot due to a change in the internal temperature of the optical scanning device in the conventional optical scanning device. In Table 3, the positions of the light spots, 0 mm, -100 mm, and 100 mm indicate the center of the scanning line and the distance from the center to both ends of the scanning line, respectively, and -2 mm to +2 mm indicate the Fθ lens due to a change in temperature. Shows the change in length. Further, main and sub indicate the diameter of the light spot in the main scanning direction and the sub-scanning direction, respectively.

  As shown in Table 3, it can be seen that the diameter of the light spot formed on the surface of the photosensitive medium in the main scanning direction and the diameter in the sub-scanning direction increase by about 30 to 40 mm or more due to the temperature rise of the Fθ lens. As described above, when the diameter of the light spot formed on the surface of the photosensitive medium and the deviation thereof increase, a problem occurs in that the resolution and uniformity of the image are reduced.

  In order to prevent the above problem, it is preferable that the driving chip 40 is disposed outside the housing to be isolated from the laser diode and the Fθ lens.

  However, in this case, as shown in FIG. 2, power is supplied to the motor 20 as well as many signal lines connected to the drive chip 40 and the position sensors 21, 22, 23 and the speed sensor 24 provided on the motor 20. Power supply lines must be exposed outside the housing 50. For this reason, there is a problem that a large amount of noise is generated by an electromagnetic wave outside the housing 50. In particular, as described above, a Hall sensor is used as the position sensors 21, 22, 23 and the speed sensor 24. The output signal of this Hall sensor is a sine wave, and its output voltage is approximately ± 0.1. Since it is very weak at about 0.2 V, it is very sensitive to noise. Therefore, conventionally, it was necessary to arrange the drive chip 40 as close as possible to the position sensors 21, 22, 23 and the speed sensor 24.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to dispose a driving chip of a polygon mirror motor outside a housing so as to be affected by temperature. Another object of the present invention is to provide an optical scanning device capable of obtaining a stable optical output from a laser diode without controlling the motor and controlling a motor by a sensorless control method to minimize noise.

  In order to achieve the above object, according to one aspect of the present invention, a housing; a light source disposed inside the housing and emitting laser light; a mirror for scanning laser light; An optical system including a plurality of optical elements for imaging light; a motor disposed inside the housing and rotating a mirror; and a motor disposed outside the housing and controlling the rotation speed of the motor by a sensorless control method. An optical scanning device comprising:

  Here, the driving chip may be installed on a main printed circuit board of a printing apparatus provided with the optical scanning device.

  The drive chip and the motor are electrically connected by a cable, and the cable is preferably a flexible printed circuit board.

  The drive chip can control the motor by a sensorless control method using the back electromotive force generated from the motor. In this case, the drive chip and the motor are connected by a power supply line and a back electromotive force signal line. ing.

  In this case, the driving chip includes a motor starting unit that generates a starting signal for starting the motor, an inverter that applies a current to the motor in accordance with the starting signal, and a back electromotive force that detects a back electromotive force generated by rotation of the motor. A speed controller for generating a speed control signal by recognizing a position of a rotor of the motor and a speed of the motor based on a back electromotive force waveform detected by the back electromotive force detector; And a current controller for controlling the inverter accordingly.

  Further, the drive chip may control the motor by a sensorless control method using a current supplied to the motor.

  In this case, the driving chip includes a motor starting unit that generates a starting signal for starting the motor, an inverter that applies a current to the motor in response to the starting signal, a current detecting unit that detects a current supplied to the motor, A speed control unit for generating a speed control signal by recognizing the position of the rotor of the motor and the speed of the motor based on the waveform of the current detected by the detection unit, and a current control unit for controlling the inverter according to the speed control signal And should be included.

  Further, the drive chip may control the motor by a sensorless control method using the inductance of the motor.

  In this case, the driving chip includes a motor starting unit for generating a starting signal for starting the motor, an inverter for applying a current to the motor in response to the starting signal, and a motor inductance detecting the current and voltage supplied to the motor. And a speed control unit for generating a speed control signal by recognizing the position of the rotor of the motor and the speed of the motor based on the waveform of the inductance calculated by the inductance calculation unit. And a current controller for controlling the inverter accordingly.

  Further, the drive chip may control the motor by a sensorless control method using the third harmonic voltage of the stator of the motor.

  In this case, the driving chip includes a motor starting unit that generates a starting signal for starting the motor, an inverter that applies a current to the motor in accordance with the starting signal, and a third unit that detects a third harmonic voltage of a stator of the motor. Speed control for generating a speed control signal by recognizing the position of the rotor of the motor and the speed of the motor based on the waveform of the third harmonic voltage detected by the harmonic voltage detector and the third harmonic voltage detector And a current control unit that controls the inverter according to the speed control signal.

  Further, the driving chip may control the motor by a sensorless control method using electromagnetic flux generated between a stator and a rotor of the motor.

  In this case, the drive chip includes a motor starter for generating a start signal for starting the motor, an inverter for applying a current to the motor in response to the start signal, and a motor fixed by detecting the current and voltage supplied to the motor. An electromagnetic flux calculator that calculates the electromagnetic flux generated between the rotor and the rotor, and recognizes the rotor position and motor speed of the motor based on the electromagnetic flux waveform calculated by the electromagnetic flux calculator. It is desirable to include a speed control unit for generating a speed control signal, and a current control unit for controlling the inverter according to the speed control signal.

  According to another aspect of the present invention, a light source for emitting a laser beam, a mirror for scanning the laser beam, and a plurality of mirrors for imaging the laser beam on an image plane are provided inside the enclosure. An optical scanning device comprising: an optical system including an optical element; a motor disposed inside the enclosure and rotating a mirror; and a driving chip disposed outside the enclosure and controlling the rotation speed of the motor by a sensorless control method. Provided.

  According to still another aspect of the present invention, a light source for emitting a laser beam, a mirror for scanning the laser beam, and a plurality of optical elements for imaging the laser beam on an imaging surface are surrounded. , An optical scanning device comprising: an enclosure in which a motor for rotating a mirror is disposed; and a driving chip disposed outside the enclosure and controlling the rotation speed of the motor by a sensorless control method.

  According to the present invention, since the driving chip of the polygon mirror motor is disposed outside the housing, it is possible to prevent the temperature inside the housing from rising due to the heat generated by the driving chip. As a result, a stable light output can be obtained from the laser diode, the diameter of the light spot formed on the image forming surface and its deviation can be reduced, and the resolution and uniformity of the image can be improved.

  Further, since the motor is controlled by the sensorless control method, the number of signal lines connecting the drive chip and the motor is reduced, and noise can be minimized.

  Further, since a plurality of sensors used in the conventional optical scanning device are not used in the optical scanning device according to the present invention, the manufacturing cost can be reduced.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 3 is a perspective view showing the overall configuration of the optical scanning device according to the present embodiment.

  Referring to FIG. 3, the optical scanning device according to the present embodiment includes a housing 150 having a predetermined internal space, and an optical system including a plurality of optical elements disposed inside the housing 150.

  The housing 150 has a role of supporting the optical elements of the optical system and of preventing the optical elements from being contaminated by foreign substances such as dust or scattered toner surrounding the optical elements. Therefore, the housing 150 can be sealed.

  The optical system includes a light source that emits a laser beam, a mirror that scans the laser beam, and a plurality of optical elements such as a lens and a mirror for imaging the laser beam on an imaging plane. In the present embodiment, the polygon mirror 114 is described as an example of the mirror that scans the laser light, but other shapes are also possible. As the light source, for example, a laser diode 111 can be used. The laser diode 111 is controlled by a light source control circuit (not shown) provided on the circuit board 110. In front of the laser diode 111 (in the traveling direction of the laser light), a collimator lens 112 for converting the laser light emitted from the laser diode 111 into parallel light or convergent light with respect to the optical axis, and the laser light on the surface of the polygon mirror 114 A cylinder lens 113 that forms an image in a horizontal linear shape is arranged. The polygon mirror 114 scans the laser light that has passed through the collimator lens 112 and the cylinder lens 113 by moving the laser light horizontally at a constant speed. In front of the polygon mirror 114 (in the direction in which the laser beam travels), it has a constant refractive index with respect to the optical axis, and polarizes the uniform-speed light reflected from the polygon mirror 114 in the main scanning direction to correct aberration. Lens 115 that focuses on the scanning surface. The laser beam that has passed through the Fθ lens 115 is reflected by an imaging reflecting mirror 116 provided in front of the laser beam (in the direction in which the laser beam travels), and is a photosensitive medium of a printing apparatus, such as a photosensitive drum 160, which is an image forming surface. Image on the surface of a point. Between the Fθ lens 115 and the reflection mirror 116 for image formation, a reflection mirror 117 for detecting a synchronization signal and an optical sensor 118 for receiving laser light and performing horizontal synchronization are arranged.

  The optical scanning device according to the present embodiment includes a motor 120 for rotating the polygon mirror 114 and a driving chip 140 for controlling the motor 120 to rotate at a constant speed.

  It is desirable to use a three-phase BLDC (Brushless DC) motor as the motor 120, but other types of motors may be used. In addition, the motor 120 is disposed inside the housing 150. However, as described later, in the present embodiment, a separate circuit board for the motor 120 is not required, and thus the motor 120 can be directly installed on the housing 150.

  The driving chip 140 includes a semiconductor integrated circuit including a plurality of circuits for driving and controlling the motor 120. In particular, in the present embodiment, the motor 120 is installed inside the housing 150 as described above, while the driving chip 140 is arranged outside the housing 150. For example, the driving chip 140 may be disposed on a main printed circuit board 170 of a printing apparatus on which the optical scanning device according to the present embodiment is installed. In this case, the electrical connection between the driving chip 140 and the motor 120 may be made by a normal cable. Preferably, as shown in FIG. 3, the driving chip 140 and the motor 120 can be electrically connected by a flexible printed circuit board (FPCB) 130.

  As described above, according to the present invention, since the driving chip 140 is disposed outside the housing 150, a rise in the temperature inside the housing 150 due to heat generated from the driving chip 140 is prevented. Thereby, the temperature rise of the laser diode 111 is suppressed, and a stable light output can be obtained from the laser diode 111. Further, the temperature rise of the Fθ lens 115 is also suppressed, so that an image is formed on the surface of the photosensitive drum 160. The diameter of the light spot and its deviation are reduced, and the resolution and uniformity of the image can be improved.

  Further, in the present invention, even if the driving chip 140 is disposed outside the housing 150, the number of signal lines connecting the driving chip 140 and the motor 120 is minimized so that noise due to external electromagnetic waves can be reduced. Need to be suppressed. To this end, the driving chip 140 controls the motor 120 to rotate at a constant speed by a sensorless control method. According to such a sensorless control method, it is not necessary to provide a conventional position sensor and speed sensor in the motor 120, and therefore, a signal line for connecting these sensors to the drive chip 140 is also unnecessary.

  Therefore, according to the present invention, the number of signal lines for connecting the motor 120 disposed inside the housing 150 and the driving chip 140 disposed outside the housing 150 is reduced, and the influence of noise can be minimized. . In addition, since the optical scanning device according to the present invention does not include a position sensor and a speed sensor and does not require a separate circuit board for the motor 120, the manufacturing cost can be reduced.

  Various methods are disclosed as the sensorless control method, and various methods can be applied to the present invention.

  Hereinafter, various sensorless control methods applicable to the present invention will be described with reference to FIGS.

  FIG. 4 is a block diagram showing a circuit configuration of a drive chip adopting a sensorless control method using a back electromotive force generated from a motor as an example of the sensorless control method according to the present embodiment. FIG. 5 is a graph showing a waveform of the back electromotive force detected by the back electromotive force detection unit shown in FIG.

Referring to FIG. 4, a driving chip 140 disposed on a main printed circuit board 170 of a printing apparatus includes a motor starting unit 141, a three-phase inverter 142, a back electromotive force detection unit 143, a speed control unit 144, A commutation control unit 145 is provided. The three-phase inverter 142 is connected to the u terminal, v terminal, and w terminal of the motor 120 by _three power supply lines L ₁ , L ₂ , and L ₃ , and the back electromotive force detection unit 143 includes one back electromotive force. The motor 120 is connected by the signal line L4.

  The motor starting unit 141 generates a start signal for starting the motor 120, and the inverter 142 applies a current to the motor 120 according to the start signal to start the motor 120. The rotation of the motor 120 generates a back electromotive force, which is detected by the back electromotive force detection unit 143. At this time, as shown in FIG. 5, the waveforms of the u-phase, v-phase, and w-phase back electromotive forces Pu, Pv, and Pw detected by the back electromotive force detection unit 143 have a phase difference of 120 °. The speed control unit 144 detects the position where the waveform of the back electromotive force Pu, Pv, Pw passes through the zero (0) level, recognizes the position of the rotor of the motor 120, and determines the time interval and amplitude between the phases. And outputs a proper speed control signal. The output speed control signal is transmitted to the commutation control unit 145. The commutation control unit 145 controls the inverter 142 based on the received speed control signal, so that the inverter 142 connects the u terminal, v terminal, and w terminal of the motor 120 so that the motor 120 rotates at a constant speed. Supply current in the proper switching order.

As described above, according to the present invention, the driving chip 140 disposed on the main printed circuit board 170 of the printing device includes the motor 120 installed inside the housing 150 and the three power supply lines L ₁ and L _2. It is connected in counter electromotive force signal line _{L 4 L 3} and one. Therefore, the number of signal lines is reduced as compared with the related art, so that the influence of noise due to external electromagnetic waves can be minimized.

  FIG. 6 is a block diagram showing, as another example of the sensorless control method according to the present embodiment, a circuit configuration of a driving chip employing a sensorless control method using a current supplied to a motor.

  Referring to FIG. 6, a driving chip 240 disposed on a main PCB 170 of a printing apparatus includes a motor starting unit 241, a three-phase inverter 242, a current detecting unit 243, and a speed controlling unit 244. , A commutation control unit 245.

The motor start unit 241 generates a start signal for starting the motor 120, and the inverter 242 applies a current to the motor 120 according to the start signal to start the motor 120. The current detection unit 243 includes three power supply lines L connected between the three-phase inverter 242 and the u terminal, the v terminal, and the w terminal of the motor 120 using a current sensor or a shunt resistor. through _{1, L} 2, _{L 3,} detects a current supplied to the motor. At this time, since the waveforms of the currents supplied to the u terminal, the v terminal, and the w terminal of the motor 120 can be obtained also by the two current signals, the current detection unit 243 provides the two current signal lines I ₁ , I _{2, only two} of the three power supply lines L ₁ , L ₂ , L ₃ can be connected to, for example, L ₁ and L ₂ respectively.

  The current signal detected from the current detection unit 243 has a sine wave. Therefore, the speed control unit 244 can determine the position of the rotor of the motor 120 in the same manner as in the case of the back electromotive force in the above-described embodiment, and thereby can output an appropriate speed control signal. The current control unit 245 controls the inverter 242 according to the received speed control signal, so that the inverter 242 controls the u terminal, the v terminal, and the w terminal of the motor 120 so that the motor 120 rotates at a constant speed. Supply current in the proper switching order.

  FIG. 7 is a block diagram showing a circuit configuration of a driving chip adopting a sensorless control method using an inductance of a motor as still another example of the sensorless control method according to the present embodiment.

  Referring to FIG. 7, the driving chip 340 disposed on the main printed circuit board 170 of the printing apparatus includes a motor starting unit 341, a three-phase inverter 342, an inductance calculating unit 343, a speed control unit 344, and a commutation unit. A control unit 345 is provided.

  The functions of the motor starting unit 341, the three-phase inverter 342, and the commutation control unit 345 are the same as those in the above-described embodiment, and thus the description thereof will be omitted.

The inductance calculator 343 calculates the current supplied to the motor through _three power supply lines L ₁ , L ₂ , and L ₃ connected between the inverter 342 and the u, v, and w terminals of the motor 120, respectively. And the voltage is detected. At this time, as described above, since the waveforms of the currents supplied to the u terminal, the v terminal, and the w terminal of the motor 120 can also be obtained from the two current and voltage signals, the inductance calculation unit 343 uses the two current and voltage signals. The current and voltage signal lines P ₁ and P ₂ are connected to _two power supply lines L ₁ and L ₂ , respectively.

  Equations relating to the inductance, voltage and current of the motor 120 can be expressed as V = L (θ) × dI / dt. Here, V is voltage, L (θ) is inductance, and I is current. Therefore, the inductance L (θ), which is a function of the position θ of the magnetic flux, can be obtained from the current and voltage detected by the inductance calculator 343. The speed control unit 344 can obtain the position of the rotor of the motor 120 from the inductance waveform thus obtained, and can output an appropriate speed control signal.

  FIG. 8 is a block diagram showing a circuit configuration of a drive chip adopting a sensorless control system using a third harmonic voltage of a motor stator as still another example of the sensorless control system according to the present embodiment. .

  Referring to FIG. 8, the driving chip 440 disposed on the main PCB 170 of the printing apparatus includes a motor starting unit 441, a three-phase inverter 442, a third harmonic voltage detecting unit 443, and a speed controlling unit 444. And a commutation control unit 445.

  The functions of the motor starting unit 441, the three-phase inverter 442, and the commutation control unit 445 are the same as those in the above-described embodiment, and thus the description thereof will be omitted.

The third harmonic voltage detection unit 443 detects the voltages applied to the _three power supply lines L ₁ , L ₂ , and L ₃ connected between the inverter 442 and the u, v, and w terminals of the motor 120. Is detected. For this reason, the third harmonic voltage detector 443 is connected to the _three power supply lines L ₁ , L ₂ , L ₃ by the three voltage signal lines V ₁ , V ₂ , V ₃ respectively.

  When the motor 120 rotates, the third harmonic voltage of the stator of the motor 120 has a position component. When the third harmonic voltage detector 443 detects the stator voltage of the motor 120 of the Y connection line and sums the detected voltages, the summed voltage has a third harmonic voltage component. Therefore, the position of the rotor of the motor 120 can be obtained by using the waveform of the third harmonic voltage having the position component in the speed control unit 444, whereby an appropriate speed control signal can be output.

  FIG. 9 is a block diagram showing a circuit configuration of a driving chip adopting a sensorless control method using electromagnetic flux as another example of the sensorless control method according to the present embodiment.

  Referring to FIG. 9, the driving chip 540 disposed on the main printed circuit board 170 of the printing apparatus includes a motor starter 541, a three-phase inverter 542, an electromagnetic flux calculator 543, a speed controller 544, A flow control unit 545 is provided.

  The functions of the motor starting unit 541, the three-phase inverter 542, and the commutation control unit 545 are the same as those in the above-described embodiment, and thus the description thereof will be omitted.

The electromagnetic flux calculator 543 is supplied to the motor through _three power supply lines L ₁ , L ₂ , L ₃ connected between the inverter 542 and the u, v, and w terminals of the motor 120, respectively. Detect current and voltage. At this time, as described above, since the waveforms of the currents supplied to the u terminal, the v terminal, and the w terminal of the motor 120 can also be obtained from the two current and voltage signals, the electromagnetic flux calculation unit 543 includes two current and voltage signal line _P 1 of the _{P 2,} are connected two each to the power supply line _L 1, _{L 2} of.

  When power is applied to the u, v, and w terminals of the motor 120 to rotate the motor 120, an electromagnetic flux is generated between the stator coil and the rotor magnet. The electromagnetic flux can be obtained by an indirect method, that is, a calculation using the current and voltage detected from the electromagnetic flux calculator 543. The speed control unit 544 obtains the position of the rotor of the motor 120 from the waveform of the electromagnetic flux thus obtained, and can output an appropriate speed control signal.

  As described above, the preferred embodiments of the present invention have been described with reference to the accompanying drawings, but it is needless to say that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive various changes or modifications within the scope of the claims, and these naturally belong to the technical scope of the present invention. I understand.

  INDUSTRIAL APPLICABILITY The present invention is applicable to an optical scanning device used for an image forming apparatus or the like, and is particularly applicable to an optical scanning device in which a driving chip of a polygon mirror motor is arranged outside a housing.

FIG. 11 is a perspective view illustrating an internal configuration of a conventional optical scanning device. FIG. 2 is a block diagram showing a circuit configuration of the conventional driving chip 40 shown in FIG. FIG. 1 is a perspective view illustrating an overall configuration of an optical scanning device according to an embodiment. FIG. 3 is a block diagram showing a circuit configuration of a driving chip adopting a sensorless control system using a back electromotive force generated from a motor as an example of the sensorless control system according to the embodiment. FIG. 5 is a graph illustrating a waveform of a back electromotive force detected by the back electromotive force detection unit illustrated in FIG. 4. FIG. 4 is a block diagram showing a circuit configuration of a driving chip adopting a sensorless control method using a current supplied to a motor as another example of the sensorless control method according to the embodiment. FIG. 9 is a block diagram showing a circuit configuration of a driving chip adopting a sensorless control method using an inductance of a motor as still another example of the sensorless control method according to the embodiment. FIG. 9 is a block diagram showing a circuit configuration of a driving chip employing a sensorless control method using a third harmonic voltage of a motor stator as still another example of the sensorless control method according to the embodiment. FIG. 9 is a block diagram showing a circuit configuration of a drive chip employing a sensorless control method using electromagnetic flux as still another example of the sensorless control method according to the embodiment.

Explanation of reference numerals

110 Circuit Board 120 Motor 140 Drive Chip 150 Housing 160 Photosensitive Drum 170 Main Printed Circuit Board 111 Laser Diode 112 Collimator Lens 113 Cylinder Lens 114 Polygon Mirror 115 Fθ Lens 116 Imaging Reflection Mirror 117 Synchronization Signal Detection Reflection Mirror 118 Optical Sensor

Claims (18)

A housing;
An optical system disposed inside the housing and including a light source for emitting laser light, a mirror for scanning the laser light, and a plurality of optical elements for imaging the laser light on an imaging surface; ;
A motor disposed inside the housing to rotate the mirror;
A drive chip disposed outside the housing and controlling a rotation speed of the motor by a sensorless control method.   2. The optical scanning device according to claim 1, wherein the driving chip is installed on a main printed circuit board of a printing apparatus provided with the optical scanning device.   The optical scanning device according to claim 1, wherein the driving chip and the motor are electrically connected by a cable.   The optical scanning device according to claim 3, wherein the cable is a flexible printed circuit board.   The optical scanning device according to claim 1, wherein the motor is a three-phase BLDC motor.   The optical scanning device according to claim 1, wherein the sensorless control method uses a back electromotive force generated from the motor.   The optical scanning device according to claim 6, wherein the driving chip and the motor are connected by a power supply line and a back electromotive force signal line. The driving chip comprises:
A motor starter for generating a start signal for starting the motor;
An inverter for applying a current to the motor in response to the start signal;
A back electromotive force detection unit for detecting a back electromotive force generated by rotation of the motor;
A speed control unit that recognizes a position of a rotor of the motor and a speed of the motor based on a waveform of the back electromotive force detected by the back electromotive force detection unit and generates a speed control signal;
The optical scanning device according to claim 6, further comprising: a current controller configured to control the inverter according to the speed control signal.   The optical scanning device according to claim 1, wherein the sensorless control method uses a current supplied to the motor. The driving chip comprises:
A motor starter for generating a start signal for starting the motor;
An inverter for applying a current to the motor in response to the start signal;
A current detector for detecting a current supplied to the motor;
A speed control unit that recognizes a position of a rotor of the motor and a speed of the motor based on a waveform of the current detected by the current detection unit and generates a speed control signal;
10. The optical scanning device according to claim 9, further comprising: a current controller configured to control the inverter according to the speed control signal.   The optical scanning device according to claim 1, wherein the sensorless control method uses an inductance of the motor. The driving chip comprises:
A motor starter for generating a start signal for starting the motor;
An inverter for applying a current to the motor in response to the start signal;
An inductance calculator for detecting current and voltage supplied to the motor to calculate an inductance of the motor;
A speed control unit for generating a speed control signal by recognizing a position of a rotor of the motor and a speed of the motor based on a waveform of the inductance calculated by the inductance calculation unit;
The optical scanning device according to claim 11, further comprising: a current controller configured to control the inverter according to the speed control signal.   The optical scanning device according to claim 1, wherein the sensorless control method uses a third harmonic voltage of a stator of the motor. The driving chip comprises:
A motor starter for generating a start signal for starting the motor;
An inverter for applying a current to the motor in response to the start signal;
A third harmonic voltage detector for detecting a third harmonic voltage of the stator of the motor;
A speed control unit for generating a speed control signal by recognizing a position of a rotor of the motor and a speed of the motor based on a waveform of the third harmonic voltage detected by the third harmonic voltage detection unit;
14. The optical scanning device according to claim 13, further comprising: a current controller configured to control the inverter according to the speed control signal.   The optical scanning device according to claim 1, wherein the sensorless control method uses an electromagnetic flux generated between a stator and a rotor of the motor. The driving chip comprises:
A motor starter for generating a start signal for starting the motor;
An inverter for applying a current to the motor in response to the start signal;
An electromagnetic flux calculator for detecting an electric current and a voltage supplied to the motor and calculating an electromagnetic flux generated between a stator and a rotor of the motor;
A speed controller for generating a speed control signal by recognizing a position of a rotor of the motor and a speed of the motor based on a waveform of the electromagnetic flux calculated by the electromagnetic flux calculator;
The optical scanning device according to claim 15, further comprising: a current controller configured to control the inverter according to the speed control signal. An optical system arranged inside the enclosure and including a light source for emitting laser light, a mirror for scanning the laser light, and a plurality of optical elements for imaging the laser light on an imaging surface;
A motor disposed inside the enclosure for rotating the mirror;
A drive chip disposed outside the enclosure and controlling the rotation speed of the motor by a sensorless control method. A motor that surrounds a light source that emits laser light, a mirror that scans the laser light, and a plurality of optical elements for imaging the laser light on an image forming surface is provided, and a motor that rotates the mirror is disposed inside. The enclosure and
A drive chip disposed outside the enclosure and controlling the rotation speed of the motor by a sensorless control method.

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