JP2000262029A - Brushless dc motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brushless DC motor which does not need to change the mounting position of a magnet position sensor, regardless of the magnetization pattern of a magnet. SOLUTION: This brushless DC motor is provided with a rotor 3, which are provided with the N poles and S poles of magnets 2 alternately in the direction of inside periphery, and a stator 7 which is arranged inside this rotor 3, and this detects the rotational position of the rotor 3 with a magnet position sensor 8 provided on the side of the stator 7 and switches the excitation winding 6 of the stator 7 and performs excitation. The magnet position sensor 8 is supported by the stator 7, so that it faces opposite the center in the width direction of a stator iron core 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless DC motor having a magnet position sensor.

[0002]

2. Description of the Related Art FIG. 2 is a longitudinal sectional view of a conventional brushless DC motor of this type.

[0003] This brushless DC motor has a magnet N 2 supported on the inner periphery of a cylindrical portion 1 a of a rotor yoke 1.
A rotor 3 having poles and S poles alternately arranged in the inner circumferential direction, a rotating shaft 4 supporting the center of the bottom 1b of the rotor yoke 1, and the rotating shaft 4 rotatably penetrates the center via a bearing. A stator core 5 fixed to the outer periphery of the stator boss 9 is provided, and radial salient poles 5 on the outer periphery of the stator core 5 are provided.
a, and a stator 7 disposed in the rotor 3 with the exciting windings 6 wound therearound, and detecting the rotational position of the rotor 3 by three magnet position sensors 8 provided on the stator 7 side. Printed circuit board 1 supported on the side
In the control unit 0, the excitation winding 6 of the stator 7 is switched to excite. In this case, each magnet position sensor 8 is arranged so as to face an end of the magnet in the width direction.

FIGS. 3A to 3C show magnetization patterns of a magnet 2 used in a conventional brushless DC motor. FIG. 3A shows a general straight magnetization, and FIG.
(B) and (C) all show skew magnetization. FIG.
In (B) and (C), the skew directions are different, and the skew angle θ is arbitrary.

In this case, in order to use the magnet 2 which has been magnetized as shown in FIGS. 3A to 3C, each magnet position sensor 8 needs to be arranged as shown in FIG. As shown, it was necessary to match any of the positions A, Y, and Z. That is, the position of the magnet 2 may be the position A when the magnetization is the straight magnetization as shown in FIG. 3A, but the position of the skew magnetization in FIGS. 3B and 3C may be either the Y position or the Z position. It is necessary to make it.

[0006]

As described above, the conventional brushless DC motor has a problem that the position of the magnet position sensor 8 must be changed according to the magnetization pattern of the magnet 2.

SUMMARY OF THE INVENTION An object of the present invention is to provide a brushless DC motor which does not need to change a mounting position of a magnet position sensor irrespective of a magnetization pattern of a magnet.

[0008]

SUMMARY OF THE INVENTION The present invention comprises a rotor in which N and S poles of a magnet are alternately provided in an inner circumferential direction, and a stator disposed in the rotor, and the rotational position of the rotor is determined by the stator. A brushless DC motor that performs excitation by switching an exciting winding of a stator by detecting a magnet position sensor provided on a side of the brushless DC motor is improved.

The brushless DC motor according to the present invention is characterized in that the magnet position sensor is supported by the stator so as to face the center of the stator core in the width direction.

As described above, when the magnet position sensor is supported by the stator so as to face the center portion in the width direction of the stator core, even if the magnet is skew-magnetized, the position where the boundary of the magnetic pole of the magnet crosses the skew. Be constant. Therefore, no matter what type of magnet,
They can correspond at the same position.

[0011]

FIG. 1 shows an example of an embodiment of a brushless DC motor according to the present invention.

In the brushless DC motor of this embodiment, each magnet position sensor 8 is supported by the stator 7 so as to face substantially the center of the stator core 5 in the width direction. That is, each magnet position sensor 8 is press-fitted between the salient poles 5a adjacent to the stator core 5 via rubber or plastic so as to face the center of the stator core 5 in the width direction (Z direction). It is arranged and provided. Each magnet position sensor 8 is attached, for example, to the tip of a cylindrical fixed insulating leg (not shown) that stands upright in a direction perpendicular to the printed circuit board 10, and leads inside each fixed insulating leg are connected to each magnet position sensor 8. The line passes and the printed circuit board 10
It is electrically connected to the circuit above. Other configurations are the same as those in FIG. 2 described above, and corresponding portions are denoted by the same reference numerals.

When the magnet position sensor 8 is supported by the stator 7 so as to face the center of the stator core 5 in the width direction, the magnet 2 is skewed as shown in FIGS. 3B and 3C. Even when the magnet 2 is magnetized, the position where the boundary of the magnetic pole of the magnet 2 crosses becomes constant. Therefore, any type of magnet 2 can be made to correspond at the same position.

[0014]

In the brushless DC motor according to the present invention, the magnet position sensor is supported by the stator so as to face the center of the stator core in the width direction. The position where the boundary line between the magnetic poles of the magnet crosses becomes constant, so that any type of magnet can be made to correspond at the same position.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of an embodiment of a brushless DC motor according to the present invention.

FIG. 2 is a longitudinal sectional view showing a conventional brushless DC motor.

FIGS. 3A to 3C are front views showing three types of magnetized patterns of the magnet.

FIG. 4 is a cross-sectional view of a main part showing an installation position of each magnet position sensor according to three types of magnetization patterns of magnets in a conventional brushless DC motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotor yoke 1a Tubular part 2 Magnet 3 Rotor 4 Rotating shaft 5 Stator iron core 5a Salient pole 6 Excitation winding 7 Stator 8 Magnet position sensor

Claims (1)

[Claims] 1. A magnet position, comprising: a rotor in which N-poles and S-poles of magnets are alternately provided in an inner circumferential direction; and a stator disposed in the rotor, wherein a rotational position of the rotor is provided on the stator side. In a brushless DC motor for performing excitation by switching an exciting winding of the stator by detecting with a sensor, the magnet position sensor is supported by the stator so as to face a center portion of the stator core in a width direction of the stator core. A brushless DC motor characterized in that: