JPH0691726B2 - Brushless motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a brushless motor, and more specifically, a plurality of spirally wound coils are arranged on a stator yoke, and a permanent magnet is provided at a position facing these on a rotor side. The present invention relates to a flat brushless motor that is arranged and detects a rotational phase of a rotor by a detection element, and sequentially supplies a current to the coil at a predetermined timing to obtain a rotational driving force.

[Conventional technology]

FIG. 8 shows an example of a capstan motor used in a magnetic recording / reproducing apparatus or the like 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 spirally wound coils 3 are arranged in the stator yoke 1 at equal positions in the circumferential direction. The rotor yoke 4 has a rotating shaft 5 and a bush 6 attached thereto.
And a multi-pole magnet 7 corresponding to the spiral coil 3 is attached to the rotor yoke 4 at a position facing the spiral coil 3. Furthermore, an FG magnet 8 magnetized at a fine pitch is provided around the outer peripheral portion of the rotor yoke 4, and a magnetic detection element 9 attached to the stator yoke 1, generally a magnetic resistance of a semiconductor for detecting a change in magnetic resistance. Although an element is used, the rotation state of the rotating shaft 5 is detected by the magnetic detection element 9 through the change of the magnetic field by the magnet 8.

10 is a Hall element fixed to the stator yoke 1,
The Hall element 10 can detect the phase of the multi-pole magnet 7 when the rotor yoke 4 rotates around the axis 5.

Reference numeral 11 is a ball bearing, and 12 is a metal bearing, and the rotary shaft 5 is supported by the housing 2 by these bearings.

Therefore, in the brushless motor configured as described above, when a magnetic field is formed by the status yoke 1 and the multi-pole magnet 7 and a current flows through the spiral coil 3,
Since a force is generated, a current is switched and supplied to the coil 3 at a predetermined timing by the output from the Hall element 10 to generate a rotational torque, and the rotor yoke 4 is rotationally driven. To describe the case of three phases, in this case, the combined torque is generated in the form as shown in FIG.

That is, assuming that the number of magnetic poles of the multi-pole magnet 7 is n, the coil 3 of each phase has a phase angle with respect to these poles. Since the coils are arranged on the stator yoke 1 with the electrical angle shifted by 120 °, the magnetic flux density distribution in the coils 3 of each phase is as shown in (a) of FIG.
The phase, the second phase of the (b), and the third phase of the (c) change in the state of a sine wave respectively deviated. In addition, according to the output from the Hall element 10, the coil 3 of each phase is shown in FIG. 9 (B).
Since currents are sequentially supplied in the positive and negative directions at the timings shown in (a) to (c), torque is generated as shown in (d) of (C) of FIG. 9 due to each phase. The combined torque has a waveform as shown in (e), and torque ripple occurs.

Therefore, such torque ripple causes uneven rotation. When 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 uneven rotation is ΔN, Since the relationship of the equation (1) is established, particularly in the case of a capstan having a low rotational speed N, the rotational unevenness ΔN due to the torque ripple T is caused.
However, the magnetic recording / reproducing apparatus has a problem that low-frequency wow and flutter in an audio signal and jitter in a video signal occur, which has conventionally been dealt with by increasing inertial force. Doing so is against the weight saving of the device.

[Problems to be solved by the invention]

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 ripples, contribute to the improvement of rotational performance and contribute to weight reduction, and that is suitable for a magnetic recording / reproducing apparatus and the like. To provide.

[Means for solving problems]

In order to achieve such an object, the present invention arranges n spiral coils on a stator yoke at equal positions in the circumferential direction, and multipoles magnetized to n poles at positions facing the spiral coils. A rotor yoke having a magnet is provided, and a phase of the multi-pole magnet is detected by a Hall element fixed to the stator yoke to control energization of the n spiral coils to rotationally drive the rotor yoke. In the brushless motor, a magnetic resistance pattern in which at least three magnetic resistance elements are arranged in the circumferential direction at a pitch of an electrical phase angle of 60 degrees is provided on the status yoke on the side facing the multi-pole magnet, By superimposing the magnetoresistive change output of the magnetoresistive pattern associated with driving on the drive voltage, the torque ripple generated in the motor is reduced. It is characterized in that as erase Chi.

(Operation) According to the brushless motor of the present invention, by disposing the resistor pattern composed of a plurality of magnetic resistance elements on the stator yoke, when the magnetized magnetic pole on the rotor yoke side passes through the position of this magnetic resistance element. At the same time, the resistance change occurs in each magnetoresistive element according to the change of the N and S poles. Therefore, it becomes possible to drive the motor so as to cancel the torque ripple generated in the motor by superimposing the composite wave of such resistance change on the drive voltage of the motor.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail and specifically with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. Here, G _{1 to} G ₃ are magnetoresistive elements made of semiconductors arranged on the stator yoke 1 by pattern formation while maintaining a pitch angle θ _X of a predetermined phase, which will be described later. In this example, the multipole magnet 7 is used. The number of poles n is 8, that is, the pitch angle of the poles is Pitch angle Is set to.

Thus, as shown in FIG. 2, the multi-pole magnet 7 is fixed on the rotor yoke 4 side, and the magnetoresistive element pattern 20 having the magnetoresistive elements G ₁ , G ₂ and G ₃ is formed on the rotor yoke 4 and the hole. The element 10 is provided on the stator yoke 1 side.

In the motor configured as described above, the rotor yoke 4
As the multipole magnets N and S pass through the positions of the magnetoresistive elements G _{1 to} G ₃ , the resistance value R of the magnetoresistive elements changes, but the change value ΔR / R is As shown in FIG. 3, it changes according to the strength H of the magnetic field. Moreover, the resistance change value is not applied in the direction of the magnetic field H, and the stronger the magnetic field is, the smaller the resistance change value is, and the largest when the magnetic field H is zero. Thus, in each of the magnetoresistive elements G ₁ , G ₂ and G ₃ , where the NS pole of the multipole magnet 7 changes, as shown in (A), (B) and (C) of FIG. 3, respectively. A resistance change output is generated, and as a result, an output having a waveform as shown in FIG. 3D is obtained from the magnetic resistor pattern 20. Therefore, when the magnetoresistive pattern 20 is configured as shown in FIG. 5A and the resistance R _O between the magnetoresistive pattern 20 and the reference voltage Vcc is made sufficiently large, the magnetoresistive pattern 20 is energized.
A rippled waveform voltage V _B as shown in FIG. 5B 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.
A rotation control signal is obtained by amplifying the output from the FG by the FG amplifier 21, and further passing through the waveform shaping circuit 22, the triangular wave generating circuit 23 and the sample hold circuit 24.

Therefore, a drive voltage is obtained by supplying this rotation control signal to the drive amplifier 26. When the motor 25 is driven, the output V _B obtained from the magnetic resistor pattern 20 provided on the stator yoke 1 is obtained. Is amplified by an amplifier 27, the amplified output is combined with a rotation control signal or a drive voltage, and the motor 25 is controlled via a logic circuit 28.

By doing so, the peak of the output obtained from the magnetoresistive pattern 20 is three times the number of poles n of the magnet 7 as described in the section of FIG. ), The frequency of the waveform of the torque ripple generated in the motor is also 3n, so (A) in FIG.
The torque ripple can be eliminated as shown in (B) and (C). That is, FIG. 8 and FIG.
As described with reference to the figure, the output from the magnetoresistive pattern 20 has a valley at the switching point between the S pole and the N pole of the Hall element output, while the phases of the magnetoresistive elements G _{1 to} G ₃ are different. And the phase of the Hall element match, it is possible to drive and control the motor 25 so that the torque ripple disappears by matching the valley of the torque ripple with the peak of the magnetoresistive element output.

In the above description, the pitch angle θ _X of the magnetoresistive element is 15
In the above description, the pitch angle θ _X is
It is clear that the same combined resistance waveform can be generated from the magnetoresistive pattern if the pitch is 30 °, 60 °, 120 °, that is, 60 ° in electrical angle. If the number of poles is n, and the magnetic resistance pattern is formed so that at least three magnetoresistive elements are arranged in the circumferential direction while maintaining the pitch angle θ _X as shown by the electrical phase angle of 60 °, the same is true. It means that a similar effect can be obtained by generating a waveform of various combined resistances.

〔The invention's effect〕

As described above, according to the present invention, n spiral coils (3) are arranged on the stator yoke (1) at equal positions in the circumferential direction, and n poles are arranged at the opposing positions of the spiral coils. A rotor yoke (4) having a magnetized multi-pole magnet (7), and the hall element (10) fixed to the stator yoke detects the phase of the multi-pole magnet to obtain the n spiral coils. In a three-phase brushless motor that controls the energization of the rotor yoke to rotationally drive the rotor yoke, the status yoke (1) on the surface side facing the multi-pole magnet (7) has an electrical phase angle pitch of 60 degrees. A magnetoresistive pattern (20) in which at least three magnetoresistive elements (G1, G2, G3) are arranged in the circumferential direction is provided, and a magnetoresistive change output of the magnetoresistive pattern accompanying the driving of the rotor yoke is driven. By superimposing, since cancel the torque ripple generated in the motor, smooth torque is maintained, it becomes possible to provide a suitable brushless motor capstan motor inertia is small weight and size.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of the configuration of a stator yoke of the brushless motor of the present invention, FIG. 2 is an exploded perspective view of the brushless motor of the present invention, and FIG. 3 is a magnetic resistance element on the stator yoke. FIG. 4 is a curve diagram showing a change in resistance value, FIG. 4 is an explanatory diagram of resistance generated from the magnetoresistive element pattern by the magnetoresistive element, FIG. 5A is a circuit configuration diagram of the magnetoresistive element pattern, and FIG. FIG. 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 a torque ripple disappearance process in the brushless motor of the present invention, and FIG. FIG. 9 is a cross-sectional view showing an example of the configuration of a conventional brushless motor, and FIG. 9 is a diagram showing changes in the magnetic flux generated in each coil and the current supplied to the coil in the conventional brushless motor. It is explanatory drawing which shows the relationship between supply timing and the shape of the torque ripple generated in a motor. 1 ...... stator yoke, 3 ...... spiral coil, 4 ...... yoke, 5 ...... rotating shaft, 7 ...... multipolar magnet, 10 ...... Hall element, G _1, G _2, G ₃ ...... magnetoresistive Element, 20 ... Magnetoresistive pattern, 21, 26, 27 ... Amplifier, 22 ... Waveform shaping circuit, 23 ... Triangular wave generation circuit, 24 ... Sample hold circuit, 25 ... Motor, 28 ... Logic circuit .

Claims (1)

[Claims] 1. A multi-pole magnet in which n spiral coils (3) are arranged on a stator yoke (1) at equal positions in the circumferential direction, and n poles are magnetized at opposite positions of the spiral coils. The rotor yoke (4) having (7) is provided, and the phase of the multi-pole magnet is detected by the Hall element (10) fixed to the stator yoke to control the energization to the n spiral coils, In a three-phase type brushless motor that drives to rotate, the status yoke (1) on the side facing the multi-pole magnet (7) has at least three magnetoresistive elements (pitch at an electrical phase angle of 60 degrees). G1, G2, G3) are arranged in the circumferential direction, and a magnetoresistive change output of the magnetoresistive pattern accompanying the drive of the rotor yoke is superposed on the drive voltage. Brushless motor is characterized in that so as to cancel the torque ripple generated in the motor.