JP2005168116A - Permanent magnet embedded brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a permanent magnet embedded brushless motor of high efficiency and low noise by reducing a variation in rotor position detection. <P>SOLUTION: A magnetic detecting element 14 detects the position of a rotor 6 in which plate-shaped permanent magnets 8 are embedded in truncated chevron shape in a rotor core 7 so that the near centers of the opposite faces of adjacent permanent magnets 8 are positioned on the same circumference. The magnetic detecting element is installed substantially at the center of the opposite faces of adjacent permanent magnets 8 in the direction of the axis of the rotor 6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a permanent magnet embedded brushless motor mounted on an electric device such as various home appliances such as a washing machine.

  In recent years, with the miniaturization of home appliances and the like, there is an increasing tendency for motors mounted on electrical devices such as various home appliances to be highly efficient brushless motors. There is a brushless motor of a permanent magnet embedded type (hereinafter referred to as “IPM”) having a permanent magnet inside the rotor core, which is small and can generate a large torque.

Here, the drive control of the IPM motor includes a sensorless type and a type in which the rotor position is detected by a magnetic detection element such as a Hall IC. In the latter case, the attachment position of the magnetic detection element depends on the rotor axial direction and the circumferential direction. In the axial direction, the attachment position is considered to be any position (for example, Patent Documents) 1).
JP 2000-197291 A (right column on page 2, line 7 to line 14)

  However, a magnetic detection element such as a Hall IC that detects magnetic flux for detecting the rotor position of an IPM brushless motor with a built-in plate magnet as described above is determined based on the value of magnetic flux density when determining polarity. In some cases, variations occurred.

  For this reason, the rotor position detection varies due to the variation in the magnetic flux position and the variation in the magnetic flux density for determining the polarity of the magnetic detection element. The position of the innermost diameter of the opposing surfaces of the adjacent plate magnets in the direction was the largest.

  Here, when driving the IPM brushless motor, an energization waveform to the winding is created and driven based on the same position information. When the variation in the same position information becomes large, the energization switching variation and the energization waveform disturbance This has been a cause of motor efficiency and noise deterioration.

  An object of the present invention is to provide a high-efficiency, low-noise IPM brushless motor that reduces variations in rotor position detection.

  The IPM brushless motor of the present invention has been made in view of the above-described conventional problems, and a plate-like permanent magnet is disposed in the rotor core, and the approximate center of the facing surfaces of the adjacent permanent magnets is on the same circumference. In this way, the attachment position of the magnetic detection element for detecting the position of the rotor embedded in the letter C is the approximate center of the opposing surfaces of the adjacent permanent magnets in the axial direction of the rotor.

  According to the first aspect of the present invention, an IPM brushless motor with high efficiency and low noise can be obtained.

  In the invention according to claim 1 of the present application, a rotor in which a plate-like permanent magnet is embedded in a rotor core in a substantially square shape so that the approximate center of the opposed surfaces of the adjacent permanent magnets is on the same circumference. And an embedded permanent magnet brushless motor that detects the position of the rotor from the magnetic flux generated by the permanent magnet via a magnetic detection element, and the mounting position of the magnetic detection element is adjacent in the axial direction of the rotor It is a permanent magnet embedded brushless motor, characterized in that it is approximately at the center of the opposing surfaces of the permanent magnet.

  With the above configuration, the polarity of the permanent magnet is sharply reversed, so that a position error due to variations in detection sensitivity of the rotor position detecting element is reduced, and the permanent magnet position can be detected correctly.

  FIG. 1 shows a specific configuration of an IPM brushless motor according to the present invention, which includes a stator 1, a rotor 6, a bearing 11 that rotatably holds the rotor 6, and a sensor circuit.

  The rotor 6 includes a rotor core 7 in which electromagnetic steel plates are laminated, a rotor core 7 and a shaft 10 in which a plate-like permanent magnet 8 is embedded in a rectangular hole provided in the rotor core 7 and the permanent magnet 8 is inserted through a rotor cup 9. It is integrated and configured. Here, since the rectangular hole is formed in a square shape so that the approximate center of the opposing surfaces of adjacent holes is on the same circumference, the permanent magnet 8 is also embedded accordingly. Yes. Further, the stator 1 is integrally solidified with a thermosetting resin 4 with a winding 3 applied to a stator core 2.

  The sensor circuit is configured by mounting a magnetic detection element 14 such as a Hall IC for detecting the rotor position on a printed circuit board 13. The magnetic detection element 14 is disposed in the axial direction of the rotor 6 so as to face the permanent magnet 8, and specifically, on the vicinity of the central portion of the surface facing the adjacent permanent magnet 8 with a predetermined distance. is there. FIG. 2 is a conceptual diagram showing the relative positional relationship between the printed circuit board 13 and the permanent magnet 8. In addition, although the magnetic detection element 14 is not drawn in the figure, it is arranged at a predetermined position on the opposite surface side of the printed printed board 13.

  Next, regarding the magnetic detection element 14 facing the permanent magnet 8, an appropriate position in the radial direction of the rotor 6 will be described with reference to FIGS. 3 and 4.

  Here, since the position detection of the rotor 6 is performed in a limited range where the magnetic flux density is close to 0, the position of the rotor 6 can be detected more accurately as the change in the magnetic flux density in the range becomes steeper. .

  In this regard, when the examination is performed at the position shown in FIG. 3 on the basis of the surfaces of the adjacent permanent magnets 8 facing each other, as shown in FIG. Compared with the change in magnetic flux density on the inner diameter side (see FIG. 3), the change in the radius R1 (approximately the center of the opposing surface of the adjacent permanent magnet 8; see FIG. 3) is steep, that is, the magnetic flux density is around zero. It can be seen that the slope at has increased.

  Therefore, the configuration in which the position of the magnetic flux detector 14 is substantially the center of the opposing surfaces of the adjacent permanent magnets 8 maximizes the change in magnetic flux density with respect to the change in the position of the permanent magnets 8. Variation in position error due to variation in sensitivity can be minimized.

  The brushless motor according to the present invention can be applied to various home appliances such as washing machines that require high efficiency and low noise.

Sectional drawing which shows the IPM brushless motor of this invention The figure which shows the relative positional relationship of the permanent magnet embedded in the rotor and the printed circuit board (magnetic detection element) in the IPM brushless motor of this invention. The figure which shows the attachment position of the rotor position detection element in the IPM brassless motor of this invention (A) And (b) is a figure which shows the change of the magnetic flux by the permanent magnet of the IPM brushless motor of this invention.

Explanation of symbols

6 Rotor 7 Rotor Core 8 Permanent Magnet 13 Printed Circuit Board 14 Magnetic Sensor

Claims (1)

  A rotor in which a plate-shaped permanent magnet is embedded in a rotor core in a square shape so that the approximate center of the opposed surfaces of the adjacent permanent magnets is on the same circumference, and the position detection of the rotor is performed magnetically. In an embedded permanent magnet brushless motor that uses a magnetic flux generated by the permanent magnet via a detection element, the mounting position of the magnetic detection element is approximately the center of the facing surface of the adjacent permanent magnet in the axial direction of the rotor. A permanent magnet embedded type brushless motor.