JPS63157655A - Brushless motor - Google Patents

Abstract

PURPOSE:To eliminate torque ripple, generated upon driving the title motor, and obtain a brushless motor having smooth torque, by a method wherein a signal output from a magnetic resistance element, provided on a stator yoke, is superposed on the driving voltage of the motor. CONSTITUTION:A multi-pole magnet 7 is fixed to a rotor yoke 4 and a magnetic resistance body pattern 20, on which magnetic resistance elements G1-G3 are formed, and Hall elements 10 are provided on the stator yoke 1 side of the rotor yoke 4. When respective poles of the multi-pole magnet 7 pass through the positions of the magnetic resistance elements G1-G3 in conduction with the rotation of the yoke 4, the values of resistance of the magnetic resistance elements are changed. The change of the value of resistance is converted into the change of voltage and the voltage is amplified and synthesized with motor driving voltage to control a motor. The number off crests of an output, obtained from the magnetic resistance body pattern 20, is three times the number of poles of the magnet 7 while the frequency of torque ripple generated in the motor is three times the number of poles of the magnet 7, therefore, the torque ripple may be eliminated.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a brushless motor, and more specifically, a stator yoke is provided with a plurality of spiral coils, and a permanent magnet is located on the rotor side facing the coils. The present invention relates to a flat type brushless motor in which rotational driving force is obtained by detecting the rotational phase of the rotor with a detection element and sequentially switching and supplying current to the coils at predetermined timing.

[Conventional technology]

FIG. 8 shows an example of a capstan motor used in a magnetic recording/reproducing device, etc., as an example of a conventional flat type brushless motor of this type. Here, 1 is a stator yoke attached to a housing 2, and a plurality of spiral coils 3 are arranged in the circumferential direction of the stator yoke 1. Also,
The rotor yoke 4 is held on the rotating shaft 5 via a bush 6, and a spiral coil 3 is mounted on the rotor yoke 4.
A corresponding multipolar magnet 7 is attached at a position opposite to . Furthermore, FG magnets 8 magnetized at a fine pitch are provided around the outer periphery of the rotor yoke 4.
The magnetic sensing element 9 attached to the stator yoke 1 is generally a semiconductor magnetic resistance element that detects changes in magnetic resistance.
The rotational state of the rotating shaft 5 is detected through the fluctuation of the magnetic field caused by the magnetic field.

1O is a Hall element fixed to the stator yoke 1, and the phase of the multipolar magnet 7 when the rotor yoke 4 rotates around the axis 5 can be detected by this Hall element 1O.

11 is a ball bearing, 1 is a metal bearing, and the rotating shaft 5 is supported by the housing 2 by these bearings.

Therefore, in the brushless motor configured as described above, a current is switched and supplied to the coil 3 at a predetermined timing based on the output from the Hall element 10, thereby generating a rotational torque and rotationally driving the rotor yoke 4. Now, let us discuss the case where such a motor has three phases. In this case, a composite torque is generated in the form shown in FIG. 9.

That is, assuming that the number of magnetic poles of the multi-pole magnet 7 is n, the coils 3 of each phase are arranged on the stator yoke 1 in a state facing these poles.
As shown in Figure 9 (A), the magnetic flux density distribution is the first phase of (a), the second phase of (b), and the second phase of (c).
It changes in the state of a sine wave that is shifted from the third phase of . Note that current is sequentially supplied to the coil 3 of each phase in the positive and negative directions at the timings shown by (A) to (C) in FIG. 9(B), respectively, according to the output from the Hall element IO. Due to the phase, torque is generated as shown in (d) of FIG. 9(C), and the combined torque of these has a waveform form as shown in (e), and a torque ripple occurs.

Therefore, rotational unevenness occurs due to such torque ripple, but if the magnitude of the torque ripple is T, the rotation speed of the rotating shaft 5 is N, the inertial force is J, and the rotational unevenness is ΔN, then ΔNCC□ ... ( 1) N2 ・J Since the relationship of formula (1) holds, especially for capstans with low rotational speed N, rotational unevenness ΔN due to torque ripple T
As a result, magnetic recording and reproducing devices suffer from problems such as low-frequency wow and flutter in audio signals and sheet stutter in video signals. Conventionally, this problem has been solved by increasing the inertial force. Doing so would go against the goal of reducing the weight of the device.

[Problem that the invention seeks to solve]

In view of the above-mentioned conventional problems, an object of the present invention is to provide a brushless motor that can suppress the occurrence of torque ripple, improve rotational performance, contribute to weight reduction, and is suitable for magnetic recording and reproducing devices. The aim is to provide data.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a rotor yoke having a multipolar magnet magnetized to n poles, and a stator yoke for rotating the rotor yoke. In a phase-type brushless motor, a magnetoresistive pattern in which at least three magnetoresistive elements are arranged circumferentially at a pitch of 60" electrical phase angle is provided on the surface of the stator yoke that faces the multipolar magnet. Features.

[Effect]

According to the brushless motor of the present invention, the stator yoke is provided with a resistor pattern consisting of a plurality of magnetoresistive elements, so that when the magnetized magnetic pole on the rotor yoke side passes through the position of the magnetoresistive element, the N , a change in resistance occurs in each magnetoresistive element in response to a change in the south pole. Therefore, by superimposing a composite wave of such resistance changes on the drive voltage of the motor, it becomes possible to drive the motor so as to cancel out the torque ripple occurring in the motor.

〔Example〕

Embodiments of the present invention will be described in detail and specifically below based on the drawings.

FIG. 1 shows an embodiment of the invention. Here, G, -G,
are semiconductor magnetoresistive elements arranged on the stator yoke 1 by patterning while maintaining a predetermined phase pitch angle θ× as described later. In this example, the number of poles n of the multipolar magnet 7 is 8, and has been done.

Thus, as shown in FIG. 2, a multipolar magnet 7 is fixed on the rotor yoke 4 side, and a magnetoresistive pattern 20 in which magnetoresistive elements G, , G2, and G are formed and a Hall element are attached to the rotor yoke 4. lO is provided on the stator yoke 1 side.

In the motor configured in this way, the rotor yoke 4
As the multipole magnets N and S pass through the positions of the magnetoresistive elements 61 to G3, the resistance value R of the magnetoresistive element changes, and the change value ΔR/R is shown in Fig. 3. As shown in , it changes depending on the magnetic field strength H. Furthermore, the resistance change value is not applied in the direction of the magnetic field H; the stronger the magnetic field is, the smaller it is, and the value is greatest where the magnetic field H is ;. Thus, in the individual magnetoresistive elements G, , G2, and G, the resistance changes as shown in (8), CB), and (C) of FIG. 3, respectively, where the NS pole of the multipolar magnet 7 changes. An output is generated, and as a result, an output having a waveform as shown by CD in FIG. 3 is obtained from the magnetoresistive pattern 20. Therefore, if the magnetoresistive pattern 20 is configured as shown in FIG. 5A, and the resistance RO between it and the reference voltage Vcc is made sufficiently large and the magnetoresistive pattern 20 is energized, the structure shown in FIG. 5B will be obtained. A waveform voltage VB with ripples is obtained.

FIG. 6 shows the configuration of the control circuit of the brushless motor of the present invention. Here, 21 is an FG amplifier, 22 is a waveform shaping circuit that shapes the waveform into a rectangular wave, 23 is a triangular wave generation circuit, and 24
is a sample and hold circuit, and when the motor 25 rotates, the output from the FG of the motor is amplified by the FG amplifier 21, and the waveform shaping circuit 22. A rotation control signal is obtained by passing through a triangular wave generation circuit 23 and a sample hold circuit 24.

Therefore, by supplying this rotation control signal to the drive amplifier 26, a drive voltage can be obtained.
When driving the stator yoke 1, the output v8 obtained from the magnetoresistive pattern 20 provided on the stator yoke 1 is amplified by the amplifier 2f, and the amplified output is combined with the rotation control signal or drive voltage, and the logic circuit 28 is The motor 25 is controlled through the motor 25.

In this way, the peak of the output obtained from the magnetoresistive pattern 20 is three times the number of poles n of the magnet 7, as explained in connection with FIG. ), the frequency of the torque ripple waveform generated in the motor is also 3n, so (A) in Figure 7
, (B) and (C), it is possible to eliminate the torque ripple. That is, as explained based on FIGS. 8 and 9, S of the Hall element output
While the output from the magnetoresistive pattern 20 becomes a valley at the switching point between the pole and the north pole, the phase of the magnetoresistive elements 61 to G3 and the phase of the Hall element match, so torque ripple is reduced. By matching the valleys with the peaks of the output of the magnetoresistive element, it becomes possible to drive and control the motor 25 so that the torque ripple disappears.

In addition, in the above explanation, the pitch angle θX of the magnetoresistive element is set to 1.
Although we have described the case where the pitch angle is 5°, for example, the pitch angle θX
30°, 60°, 120° i.e. 60° in electrical angle
It is clear that a similar composite resistance waveform can be generated from the magnetoresistive pattern if the pitch is set to If a magnetoresistive pattern is formed in such a way that at least three magnetoresistive elements are arranged in the circumferential direction while maintaining the pitch angle θX as shown in , it is possible to generate a similar combined resistance waveform and obtain the same effect. It means that you can.

〔Effect of the invention〕

As explained above, according to the present invention, by superimposing the signal output from the magnetoresistive element provided on the stator yoke on the drive voltage of the motor, it is possible to eliminate the torque ripple that occurs when the motor is driven. It has become possible to provide a brushless motor that maintains smooth torque, has small inertia, and is suitable for lightweight and small capstan motors.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an example of the configuration of the stator yoke of the brushless motor of the present invention, Fig. 2 is an exploded perspective view of the brushless motor of the invention, and Fig. 3 is a magnetoresistive element on the stator yoke. 4 is an explanatory diagram of the resistance generated from the magnetoresistive pattern by the magnetoresistive element, FIG. 5A is a circuit configuration diagram of the magnetoresistive pattern, and FIG. 5B is the 6 is a configuration diagram of a control circuit according to the present invention; FIG. 7 is a series of waveform curve diagrams for explaining the torque ripple disappearance process in the plusless motor of the present invention; Figure 8 is a cross-sectional view showing an example of the configuration of a conventional brushless motor, and Figure 9 shows changes in the magnetic flux generated in each coil in the conventional brushless motor, the supply timing of the current supplied to the coils, and the changes generated in the motor. FIG. 3 is an explanatory diagram showing the relationship between the torque ripple and the shape of the torque ripple. DESCRIPTION OF SYMBOLS 1... Stator yoke, 3... Spiral coil, 4... Stator yoke, 5... Rotating shaft, 7... Multipolar magnet, 10... Hall element, Gl, G2. G3... Magnetoresistive element, 20... Magnetoresistive pattern, 21.28.27... Amplifier, 22... Waveform shaping circuit, 23... Triangular wave generation circuit, 24... Sample hold circuit , 25...Motor, 28...Logic circuit. Figure 1 Figure 3 Figure 4 Figure 8

Claims (1)

[Scope of Claims] A three-phase brushless motor comprising a rotor yoke having a multipolar magnet magnetized to n poles, and a stator yoke that rotates the rotor yoke, wherein the multipolar magnet of the stator yoke A brushless motor characterized in that a magnetoresistive pattern in which at least three magnetoresistive elements are arranged in the circumferential direction at a pitch of an electrical phase angle θx=60° is provided on a surface facing the motor.