JP2006081283A - Brushless motor and drive circuit therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to eliminate the influence of variation in mounting position and achieve efficiency enhancement and noise reduction by making it possible to dispose a magnetic sensor so that it is not influenced by magnetic flux distortion in proximity to a rotor magnet and electrical angles are not depended on. <P>SOLUTION: A magnet 3 is placed at an end of the rotating shaft 2 of a rotor 1. It is magnetized in the direction orthogonal to the rotating shaft 2 of the rotor 1, and is rotated in synchronization with the rotor 1. A magnetic sensor that detects a change in a magnetic field due to the rotation of the magnet 3 and a circuit that computes the rotation angle of the rotor 1 from the output of the magnetic sensor are placed on the line extended from the rotating shaft 2 of the rotor 1 in positions opposite the magnet 3. A motor coil current is controlled, based on the rotation angle. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a brushless motor and its drive circuit, and more particularly to a brushless motor driven using a magnetic sensor and its drive circuit.

In general, in a brushless motor, a magnetic flux generated from a rotor magnet is detected by a magnetic sensor such as a Hall sensor or Hall IC, and the current flowing through the motor coil is switched by a switching element or the like according to an output signal from the magnetic sensor to rotate the rotor. A drive system is used. (For example, Patent Document 1)
For example, in the case of a three-phase motor, as shown in FIG. 1, the three magnetic sensors 15 are arranged at different positions near the rotor magnetic flux, and the switching circuit 13 is switched by the signal processing circuit 10 in response to an output signal from the magnetic sensor 15. Based on the power supply from the motor power supply 12, a current is passed through the motor coil 14 to rotate the rotor.

JP-A-6-276720

  In the drive system as described above, a magnetic sensor has to be arranged in the vicinity of the rotor magnet for detecting the rotating magnetic field. For this reason, the magnetic flux is distorted due to the influence of the magnetic flux generated from the current flowing in the stator core and the motor coil, and torque unevenness is generated, so that the efficiency is lowered and noise is also caused. In addition, when a plurality of magnetic sensors are arranged in accordance with the electrical angle for detecting the rotational position of the rotor as in a three-phase motor, the switching timing of the current flowing through the motor coil varies due to variations in the magnetic sensor mounting position. It was a cause of reduced efficiency and noise.

  The present invention has been made in view of such problems, and its purpose is not to be affected by magnetic flux distortion in the vicinity of the rotor magnet by detecting the rotational position of the rotor at a position away from the rotor magnet. In addition, by providing a magnetic sensor independent of the electrical angle, it is possible to eliminate the influence of variations in mounting position, thereby providing a brushless motor and its drive circuit that achieve high efficiency and low noise. is there.

  In order to solve the above problems, a brushless motor according to the present invention is a brushless motor including a rotor that is driven to rotate around a rotating shaft in accordance with a driving current flowing in a motor coil, and a direction orthogonal to the axial direction of the rotating shaft. And a magnet that generates a rotating magnetic field that is synchronized with the rotation of the rotor, and is disposed on an extension line of the rotating shaft so as to face the magnet. Magnetic detection means for generating an output signal corresponding to the magnetic field direction.

  In the brushless motor, angle calculation means for calculating a rotation angle signal of the rotor based on the output signal may be provided in the same chip.

  In order to solve the above problems, a brushless motor drive circuit according to the present invention is magnetized in a direction orthogonal to the axial direction of the rotation axis of the motor coil and the rotor, and is arranged at the end of the rotation axis. A magnet that generates a rotating magnetic field that is synchronized with the rotation of the rotor; and a magnetic detection unit that is disposed on an extension of the rotating shaft so as to face the magnet and generates an output signal corresponding to the direction of the magnetic field in the rotating magnetic field. In the brushless motor drive circuit, an angle calculation means for calculating the rotation angle signal of the rotor based on the output signal, and a control means for controlling the drive current of the motor coil based on the rotation angle signal, The control means stores a rotation angle signal calculated at the initial position of the rotor, and an offset of the rotation angle signal based on the stored rotation angle signal. And means for correcting the bets.

  In the brushless motor drive circuit, the control unit further calculates a rotation speed of the rotor from a change in the rotation angle signal from the angle calculation unit, and adjusts a motor power supply based on the rotation speed. And a means for adjusting the drive current amount of the motor coil and controlling the rotational speed of the rotor.

  In the brushless motor and the drive circuit for the brushless motor, the magnetic detection means includes a first and a second direction orthogonal to each other on a plane orthogonal to the direction of the rotation axis, each having a magnetosensitive direction. The second Hall element can be arranged on the same chip.

  In the brushless motor and the drive circuit for the brushless motor, the magnet may be a cylindrical magnet magnetized in the radial direction.

  With the above configuration, by detecting the position of the rotor at a position away from the rotor magnet, it is not affected by magnetic flux distortion in the vicinity of the rotor magnet, and the magnetic sensor can be arranged without depending on the electrical angle. It is possible to eliminate the influence of the variation in the mounting position, and to provide a brushless motor with high efficiency and low noise and its drive circuit. Further, in the motor having such a configuration, the rotor position is detected by detecting a rotating magnetic field synchronized with the rotation of the rotor by the magnet disposed at the end of the rotating shaft. The dimension of can be reduced. For this reason, the magnetic sensor (Hall element) and the magnetic detection means that integrates the circuit for calculating the rotation angle of the rotor based on the signal from the magnetic sensor into one chip can be arranged opposite to the magnet, thereby detecting the rotation angle. It is possible to provide a brushless motor with higher efficiency and lower noise, because the required variation in the electrical characteristics of the plurality of magnetic sensors is small and the mounting position deviation of the magnetic sensors is eliminated. In addition, the rotation angle signal calculated at the initial position of the rotor is stored, and the absolute position of the rotor can be grasped by correcting the offset of the rotation angle signal based on this signal. The motor current can be controlled in a form closer to a sine wave, which makes it possible to achieve high efficiency and low noise.

Hereinafter, the best mode of the present invention will be described with reference to the drawings.
<Embodiment of brushless motor>
2 and 3 are simplified views showing an embodiment of a brushless motor configuration according to the present invention, FIG. 2 shows an embodiment of an inner rotor type brushless motor, and FIG. 3 shows an embodiment of an outer rotor type brushless motor. Show.

  The rotating shaft 2 and the rotor 1 are configured to rotate synchronously, and the magnet 3 is fixedly disposed at the tip of the rotating shaft 2. Therefore, the rotation of the rotor 1 and the rotation of the magnet 3 are synchronized. The columnar magnet 3 is two-pole magnetized in a direction orthogonal to the axial direction of the rotating shaft 2, that is, in the radial direction of the column as shown in FIG. When the rotor 1 and the rotating shaft 2 rotate, the magnet 3 also rotates, and thereby a rotating magnetic field synchronized with the rotation of the rotor 1 is generated at a position near the tip of the rotating shaft 2.

  An angle detection element 5 is disposed on the extended line of the rotating shaft 2 so as to face the magnet 3 at a position where a rotating magnetic field is generated by the magnet 3. The angle detection element 5 is an element in which a Hall sensor that is two magnetic sensors and an angle calculation circuit that calculates a rotation angle based on a signal from the Hall sensor are integrated into one chip. It should be noted that making the two Hall sensors into one chip is a main requirement for relaxing the mounting accuracy, but making the angle calculation circuit into one chip is a subordinate requirement.

  The two Hall sensors have a magnetosensitive direction in first and second directions orthogonal to each other on a plane orthogonal to the axial direction of the rotating shaft 2 (virtual plane not shown in FIGS. 2 and 3). Placed in. FIG. 5 shows the arrangement of such Hall sensors. In FIG. 5, the Hall sensors 50 and 51 are arranged in directions orthogonal to each other on the XY plane, and the respective magnetosensitive directions are an X direction and a Y direction orthogonal to each other.

  The angle detection element 5 detects the rotation angle of the rotor 1 by generating an output signal corresponding to the magnetic field direction in the rotating magnetic field by the magnet 3. That is, the magnetic field direction θ can be obtained by calculating the vector sum based on the output signals of the Hall sensors 50 and 51 corresponding to the magnetic field M in the rotating magnetic field by the magnet 3.

  According to the brushless motor of the above embodiment, since the magnet and the one-chip angle detection element are arranged at positions away from the rotor and the stator, the influence of the magnetic flux generated from the motor components is small, and the rotation of the rotor A synchronized rotating magnetic field is generated. Therefore, torque unevenness can be reduced. In addition, since the rotor position is detected by the single angle detecting element, the rotor position detection is not affected by sensor variations compared to the conventional method in which the rotor position is detected by arranging a plurality of sensors according to the electrical angle. Can be realized.

<Embodiment of Brushless Motor Drive Circuit>
FIG. 6 is a block diagram showing an embodiment of a three-phase motor drive circuit according to the present invention.

  The angle detection element 5 having a configuration in which the two Hall sensors and the angle calculation circuit are integrated into one chip sends an output signal corresponding to the rotor rotational position to the signal processing circuit 60. The signal processing circuit 60 generates a three-phase drive signal from this signal, switches the switching circuit 13, and sends a current to the motor coil 14 to rotationally drive the motor. The signal processing circuit 60 further calculates the rotational speed of the rotor from the change in the output signal of the angle detection element 5 and adjusts the current amount of the motor coil 14 by adjusting the output of the motor power supply 62 based on the rotational speed. This controls the rotational speed of the rotor.

  A memory 61 is coupled to the signal processing circuit 60, and the memory 61 stores an output signal from the angle detection element 5 at an initial position that is a stop position before the rotor starts to be driven. Then, the output signal value at the initial position is set to 0, and offset correction is performed by the signal processing circuit 60 so that the output signal takes a value corresponding to the rotation angle when the rotor rotates from the initial position.

  Since the signal processing circuit 60 employs the circuit configuration shown in FIG. 6 having such a function, the absolute positions of the rotor and the stator can be known. Therefore, when PWM driving is performed, the motor current is controlled to be closer to a sine wave. This makes it possible to achieve high efficiency and low noise. The signal processing circuit 60 may include an angle calculation circuit.

<Other embodiments>
The motor drive circuit of the above embodiment can be integrated into one chip together with the angle detection element 5. At this time, all the elements of the motor drive circuit can be arranged in one chip together with the hall sensor, or any element can be arranged in one chip.

It is a block diagram of an example of the drive circuit of the conventional brushless motor. 1 is a perspective view schematically showing an embodiment of a brushless motor according to the present invention. It is a perspective view which shows another embodiment of the brushless motor based on this invention simply. 1 is a perspective view of a magnet structure in an embodiment of a brushless motor according to the present invention. It is a simplified diagram showing an example of the arrangement of the magnetic sensor in the brushless motor according to the present invention. 1 is a block diagram of an embodiment of a brushless motor drive circuit according to the present invention. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotor 2 Rotating shaft 3 Magnet 4 Stator 5 Angle detection element 13 Switching circuit 14 Motor coil 60 Signal processing circuit 61 Memory 62 Motor power supply

Claims (8)

In a brushless motor having a rotor that is driven to rotate around a rotation axis in accordance with a drive current flowing in a motor coil,
A magnet that is magnetized in a direction orthogonal to the axial direction of the rotating shaft and is arranged at an end of the rotating shaft, and generates a rotating magnetic field synchronized with the rotation of the rotor;
A brushless motor, comprising: a magnetic detection unit disposed on an extension line of the rotating shaft so as to face the magnet and generating an output signal corresponding to a magnetic field direction in the rotating magnetic field. The brushless motor according to claim 1,
In the magnetic detection means, first and second Hall elements each having a magnetosensitive direction in first and second directions orthogonal to each other on a plane orthogonal to the direction of the rotation axis are arranged on the same chip. A brushless motor characterized by The brushless motor according to claim 2,
A brushless motor comprising an angle calculating means for calculating a rotation angle signal of the rotor based on the output signal in the same chip. The brushless motor according to any one of claims 1 to 3,
The brushless motor characterized in that the magnet is a cylindrical magnet magnetized in the radial direction. A motor coil, a magnet that is magnetized in a direction perpendicular to the axial direction of the rotating shaft of the rotor and disposed at an end of the rotating shaft, and generates a rotating magnetic field synchronized with the rotation of the rotor; and an extension of the rotating shaft In a brushless motor drive circuit, comprising a magnetic detection means arranged on the line facing the magnet and generating an output signal according to the magnetic field direction in the rotating magnetic field,
Angle calculating means for calculating a rotation angle signal of the rotor based on the output signal;
Control means for controlling the drive current of the motor coil based on the rotation angle signal, the control means,
Storage means for storing a rotation angle signal calculated at an initial position of the rotor;
A drive circuit for a brushless motor, comprising: means for correcting an offset of the rotation angle signal based on the stored rotation angle signal. In the drive circuit of the brushless motor according to claim 5,
The control means further comprises:
Means for calculating a rotation speed of the rotor from a change in the rotation angle signal from the angle calculation means;
A drive circuit for a brushless motor, comprising: means for adjusting a drive current amount of the motor coil by adjusting a motor power source based on the rotation speed and controlling a rotation speed of the rotor. In the brushless motor drive circuit according to claim 5 or 6,
In the magnetic detection means, first and second Hall elements each having a magnetosensitive direction in first and second directions orthogonal to each other on a plane orthogonal to the direction of the rotation axis are arranged on the same chip. A drive circuit for a brushless motor, characterized by comprising: In the brushless motor drive circuit according to any one of claims 5 to 7,
The drive circuit of a brushless motor, wherein the magnet is a cylindrical magnet magnetized in the radial direction.

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