JPH0631367U - motor - Google Patents

Abstract

(57) [Summary] [Object] To provide a motor capable of performing highly accurate speed control of a rotor plate even when a magnet plate is inclined with respect to a circuit board. [Structure] A circuit board 12 is attached to one side of a stator plate, a drive shaft 13 of the rotor plate is rotatably held by the stator plate, and a magnet plate is attached to the rotor plate so as to face the circuit board 12. The wiring pattern 18 for attaching a current to the rotation driving coil is attached to a part of the circuit board 12, and the magnet plate is provided with a torque magnetizing portion for obtaining a torque and a periphery of the torque magnetizing portion. In a motor provided with a speed detecting magnetized portion for generating a frequency signal on a circuit board 12 facing the speed detecting magnetized portion and being point-symmetrical with respect to the drive shaft 13. The FG patterns 19 and 20 for generating the frequency signal by the velocity detecting magnetized portion were provided only at two portions.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a motor for driving, for example, a polygon mirror of a laser beam printer, which requires highly accurate speed control.

[0002]

[Prior art]

 Conventionally, the motor shown in FIG. 5 is known as such a motor. In FIG. 5, reference numeral 1 denotes a stator plate, and the circuit board 2 is attached to the stator plate 1. Reference numeral 3 denotes a rotor plate. A drive shaft 4 of the rotor plate 3 penetrates the circuit board 2 and is rotatably held by the stator plate 1. A magnet plate 5 is attached to the rotor plate 3. ing.

As shown in FIG. 6, the magnet plate 5 has a torque magnetizing portion 5a for rotating the rotor plate 3 and a frequency signal generated around the torque magnetizing portion 5a. And a magnetizing portion 5b for speed detection are provided. The shaded area A indicates the north pole and the part B indicates the south pole. Further, the speed detecting magnetized portion 5b is provided on the outer peripheral side of the torque magnetizing portion 5a. Therefore, it is necessary to provide a large number of speed detecting magnetized portions 5b finely and alternately with N poles and S poles for speed detection. This is because it is difficult to magnetize a large number of N poles and S poles when provided inside.

A rotation drive coil 7 for rotating the rotor plate 3 is attached to the back surface of the circuit board 2, and a portion of the front surface of the circuit board 2 is used for rotation drive as shown in FIG. A wiring pattern 8 for passing a current through the coil 7 is provided. Further, on the surface of the circuit board 2, an FG (frequency generator) pattern 9 for generating a frequency signal corresponding to the rotation speed of the rotor plate 3 is provided at a position facing the detection magnetizing portion 5b. It is given in an arc shape except for.

Now, when an electric current is applied to the rotary drive coil 7, a torque is generated in the torque magnetizing portion 5 a of the magnet plate 5, and the rotor plate 3 is rotated by this torque. As the rotor plate 3 rotates, a frequency signal corresponding to the rotation speed of the rotor plate 3 is generated in the FG pattern 9 by the detection magnetizing portion 5b of the magnet plate 5. Then, this frequency signal is sliced at a predetermined level, and the detection pulse is output only during the period when the frequency reaches the predetermined level, and the rising time of this detection pulse and the rising time of the reference pulse output from the circuit not shown. The rotation speed of the rotor plate 3 is controlled with high accuracy by controlling the current flowing through the rotation drive coil 7 so that the time difference between the rising times is not generated.

[0006]

[Problems to be solved by the device]

 However, when the magnet plate 5 is inclined with respect to the circuit board 2, the magnetic flux cut by the FG pattern 9 changes in intensity. That is, a strong magnetic field and a weak magnetic field are generated on the magnet plate 5, and these strong and weak parts are located at positions approximately 180 degrees symmetrical to each other with respect to the drive shaft 4. When this strong magnetic field is rotating at a position facing the FG pattern 9 and the weak magnetic field is rotating at the wiring pattern 8, as shown in FIG. 8, the amplitude of the output of the frequency signal Fg is When it becomes larger (period T1), conversely, the weak magnetic field is rotating at a position facing the FG pattern 9, and the strong magnetic field is rotating the wiring pattern 8, the amplitude of the frequency signal Fg is small. (Period T2).

As a result, when the frequency signal Fg is sliced at a predetermined level H1 and the detection pulse P1 is output, the rising edge of the detection pulse P1 causes the rotor plate 1 to rotate at a constant speed and the frequency signal Fg. Although the frequency is constant, it deviates from the rising time of the reference pulse P0. For this reason, there is a problem in that the rotation speed control of the rotor plate 1 may be misaligned and high-precision speed control cannot be performed.

The present invention has been made in view of the above problems, and an object thereof is to provide a motor capable of performing highly accurate speed control of a rotor plate even if a magnet plate is inclined with respect to a circuit board. To provide.

[0009]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, this invention mounts a circuit board on one side of a stator plate and rotatably holds the drive shaft of a rotor on the stator plate by penetrating the circuit board. A rotation driving coil is provided on the circuit board, a magnet plate is attached to the rotor so as to face the circuit board, and a wiring pattern for applying a current to the rotation driving coil is applied to a part of the circuit board, On the magnet plate, a torque magnetizing section for obtaining torque by magnetic lines of force generated by the rotary drive coil, and a frequency signal according to the rotational speed of the rotor is generated around the torque magnetizing section. In a motor provided with a magnetizing portion for speed detection for causing the magnetizing portion for speed detection, the circuit is opposed to the magnetizing portion for speed detection and is point-symmetrical with respect to the drive shaft only at two locations on the circuit board The serial speed detecting magnetized portion, characterized in that a FG pattern Generating an said frequency signal.

[0010]

[Action]

 This invention is an FG pattern for generating the frequency signal by the magnetizing portion for speed detection only on a portion of the circuit board facing the magnetizing portion for speed detection and being point-symmetrical with respect to the drive shaft. Even if a strong magnetic field is generated due to the tilt of the magnet plate, the weak magnetic field rotates when the strong magnetic field rotates at a position facing one FG pattern. Since the position opposite to the pattern is rotated, the magnitude of the frequency signal output from the FG pattern is constant.

[0011]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 10 denotes a motor for driving a polygon mirror or the like of a laser beam printer. The motor 10 includes a stator plate 11 and a circuit board 12 attached to the stator plate 11. The drive shaft 13 penetrates the circuit board 12 and is rotatably held by the stator board 11. The rotor board 14 is provided with the magnet board 15 which faces the circuit board 12 and is attached to the rotor board 14. There is.

As shown in FIG. 2, the magnet plate 15 has a torque magnetizing portion 15a for rotating the rotor plate 14, and a frequency signal generated around the torque magnetizing portion 15a. And a magnetizing portion 15b for speed detection are provided. The shaded area A shows the north pole and the part B shows the south pole.

A rotation driving coil 17 for rotating the rotor plate 14 is attached to the back surface of the circuit board 12, and a part of the front surface of the circuit board 12 is used for rotation driving as shown in FIG. A wiring pattern 18 for applying a current to the coil 17 is provided. Further, the surface of the circuit board 12 is provided with two arc-shaped FG patterns 19 and 20 for outputting a frequency signal according to the rotation speed of the rotor plate 14. The FG patterns 19 and 20 are arranged at positions symmetrical with respect to the drive shaft 13, and are electrically connected in series. No FG pattern is provided at a position 12a which is symmetrical to the wiring pattern 18 with respect to the drive shaft 13.

Further, on the circuit board 12, a crystal oscillator circuit (not shown) that generates a reference pulse, and a coil 17 for rotation drive based on the reference pulse and the frequency signal output from the FG patterns 19 and 20. A control circuit and the like (not shown) for controlling the electric current of are provided.

Now, when the rotor circuit 14 and the magnet plate 15 are rotated at a predetermined speed by controlling the current of the rotation driving coil 17 by the control circuit, the FG patterns 19, 20 detect the speed of the magnet plate 15. The magnetic flux of the magnetizing portion 15b is cut off. At this time, an AC voltage is generated in the FG patterns 19 and 20, and the AC voltage is proportional to the strength of the magnetic field of the velocity detecting magnetized portion 15b. The frequency of the AC voltage depends on the rotation speed of the rotor plate 14, and is output from the FG patterns 19 and 20 as a frequency signal Sf as shown in FIG. Then, the frequency signal Sf is sliced at a predetermined level H1 and the detection pulse P1 is output only during a period of a predetermined level H1 or higher. The rising time of the detection pulse P1 and the reference pulse P0 output from the crystal oscillator circuit are detected. Compare with the rise time.

If the rotation speed of the rotor plate 14 is rotating at a predetermined speed, the frequency of the frequency signal Sf is a predetermined frequency, and as shown in FIG. 4, the rising time of the detection pulse P1 and the reference pulse P0 are set. When the rising time coincides with the rotation speed of the rotor plate 14 deviating from the predetermined speed, the frequency of the frequency signal Sf becomes higher or lower, so that the rising time of the detection pulse P1 deviates from the rising time of the reference pulse P0. Come on. The rotation speed of the rotor plate 14 is controlled to a predetermined speed by controlling the current of the rotation driving coil 17 so that this deviation becomes zero.

By the way, when the magnet plate 15 is inclined with respect to the circuit board 12, a portion having a strong magnetic field and a portion having a weak magnetic field are generated with respect to the circuit board 12. These strong and weak portions are symmetrical with respect to the drive shaft 13 by approximately 180 degrees.

Therefore, when the portion having a strong magnetic field rotates at the position facing the FG pattern 19, the portion having a weak magnetic field rotates at the position facing the FG pattern 20. Further, when the strong magnetic field is rotating the wiring pattern 18, the weak magnetic field is rotating at the position 12a where the FG pattern is not applied, so that the FG patterns 19 and 20 output. The magnitude of the output of the frequency signal Sf is constant. That is, the magnitude of the output of the frequency signal Sf is constant regardless of the inclination of the magnet plate 15, and as long as the rotor plate 11 is rotating at a constant speed, the rising time of the reference pulse P0 and the rising of the detection pulse P1. There will be no difference from the time point. Therefore, the speed of the rotor plate 11 can be controlled with high accuracy.

[0020]

[Effect of device]

 As described above, the present invention provides the speed detecting magnetized portion only on the portion of the circuit board that faces the speed detecting magnetized portion and is point-symmetric with respect to the drive axis. Since the FG pattern for generating the frequency signal is provided, even if a strong and weak magnetic field occurs due to the tilt of the magnet plate, a weak magnetic field is generated when the strong magnetic field is rotating at a position facing the FG pattern. Also rotates at a position opposed to the FG pattern, so that the magnitude of the frequency signal output from the FG pattern is constant, and highly accurate speed control of the rotor plate can be performed.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration of a motor according to the present invention,

FIG. 2 is a plan view showing a magnetized state of a magnet plate,

FIG. 3 is a plan view showing a circuit board,

FIG. 4 is a graph showing the relationship between a frequency signal output from an FG pattern, a detection pulse, and a reference pulse;

FIG. 5 is a side view showing the configuration of a conventional motor,

FIG. 6 is a plan view showing a magnetized state of a magnet plate,

FIG. 7 is a plan view showing a circuit board used in a conventional motor.

FIG. 8 is a graph showing a relationship between a frequency signal output from a conventional FG pattern, a detection pulse, and a reference pulse.

[Explanation of symbols]

 Reference Signs List 11 stator plate 12 circuit board 13 drive shaft 14 rotor plate 15 magnet plate 18 wiring pattern 19 FG pattern 20 FG pattern

Claims (1)

[Scope of utility model registration request] 1. A circuit board is attached to one side of a stator plate, a drive shaft of the rotor plate is rotatably held by the stator plate by penetrating the circuit board, and a rotation drive coil is provided on the circuit board. And a magnet plate is attached to the rotor plate so as to face the circuit board, and a wiring pattern for flowing an electric current to the rotation drive coil is applied to a part of the circuit board, and the magnet plate is provided with the rotation drive. Magnetizing portion for obtaining torque by magnetic force lines generated in the coil for magnetizing, and magnetizing portion for speed detection for generating a frequency signal according to the rotational speed of the rotor around the magnetizing portion for torque. In the motor provided with the part, the speed detecting magnetizing part is provided only at two portions on the circuit board that face the speed detecting magnetizing part and are point-symmetrical with respect to the drive shaft. Yo Motor, characterized in that a FG pattern for generating the frequency signal.