JPH11234999A - Brushless dc motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brushless DC motor in which a permanent magnet is not lengthened and a motor can be restrained from lengthening, even in a type subjected to skew magnetization. SOLUTION: Excitation of each armature winding 4 on the stator 6 side is switched by using a signal from a magnetism detector 7 installed on the stator 6 side so as to detect magnetic poles N, S of a permanent magnet 1 on the rotor 2 side. The permanent magnet 1 is magnetized in a magnetization part 1A for field system subjected to skew magnetization facing each pole part 3a of an armature core 3, differently from a magnetization part 1B for rotating position detection facing the magnetism detector 7. Each magnetic pole border line 14B of the magnetization part 1B is installed corresponding to the position of about 1/2 in the lengthwise direction of each magnetic pole border line 14A in the magnetization part 1A. The magnetism detector 7 is arranged in a gap between adjacent end portions of armature windings 4 facing the magnetization part 1B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a skew-magnetized brushless DC motor for reducing cogging torque.

[0002]

2. Description of the Related Art In a brushless DC motor, a change in polarity of a permanent magnet on a rotor side is detected by a magnetic detector comprising a Hall element to switch excitation of each armature winding, and a signal from the magnetic detector is detected. Is used to switch the excitation of each armature winding.

The configuration of such a brushless DC motor will be described with reference to FIGS. In such a brushless DC motor, a rotor 2 having a permanent magnet 1 magnetized so that magnetic poles having different polarities alternately exist in a circumferential direction, and an electric machine opposed to each magnetic pole of the permanent magnet 1 A stator 6 in which an armature 5 is formed by winding an armature winding 4 around each pole portion 3a of the child core 3;
The excitation of each armature winding 4 is switched using a signal from a magnetic detector 7 such as a Hall element provided on the stator 6 so that the magnetic pole of the permanent magnet 1 can be detected.

The rotor 2 includes a cup-shaped yoke 9 fixed to the tip of a rotating shaft 8 and an annular permanent magnet 1 fixed to the inner periphery of a cylindrical portion of the cup-shaped yoke 9. ing.

On the stator 6 side, a cylindrical stator support boss 11 is integrally supported on the flange 10. The above-mentioned rotating shaft 8 penetrates this cylindrical stator supporting boss 11 and is supported by a bearing 12 for rotation.

In the stator 6, the armature core 3 is fixed to the outer periphery of the stator support boss 11, and the armature windings 4 are respectively provided on the respective pole portions 3a projecting radially from the outer periphery of the armature core 3. The armature 5 is formed by being wound.

On the stator 6 side, there is mounted a controller which is supported by an armature support frame comprising the stator support boss 11 or the flange 10 and the armature core 3 and which switches the excitation of each armature winding 4 and the like. Printed circuit board 13
Is arranged. The excitation of each armature winding 4 is switched
The operation is performed using a signal from a magnetic detector 7 such as a Hall element which is supported by the printed circuit board 13 and faces each magnetic pole of the permanent magnet 1 on the end side of the armature 5.

In such a brushless DC motor, as is apparent from FIG. 2B, the permanent magnet 1 is driven below the field magnetized portion for generating a rotational torque for driving the magnetic detector 7. It is extended and long.

However, when the permanent magnet 1 is extended in this way, not only does the cost of the permanent magnet 1 increase, but also the length of the brushless DC motor increases.

Therefore, it is necessary to arrange the magnetic detector 7 as close to the armature 5 as possible.

FIGS. 3A and 3B show a conventional example in which the magnetic detector 7 is arranged as close to the armature 5 as possible, and FIG. 3A shows the main configuration of this brushless DC motor. FIG. 3B is an explanatory view showing a magnetized state of the permanent magnet 1 in the brushless DC motor.

In this brushless DC motor, in order to arrange the magnetic detector 7 as close to the armature 5 as possible,
As shown in FIG. 3A, the magnetic detector 7 is disposed at a gap between the ends of the adjacent armature windings 4 at the end of the armature 5.

With this configuration, the length of the permanent magnet 1 can be reduced, the cost of the permanent magnet 1 can be reduced, and the length of the brushless DC motor can be reduced.

In such a brushless DC motor, as shown in FIGS. 4A and 4B, the permanent magnet 1 is skew-magnetized at a predetermined angle with respect to its circumferential direction, in order to reduce cogging torque. Often. Note that FIG.
14A and 14B, reference numeral 14 denotes a magnetic pole boundary line which is a boundary line between the N pole and the S pole of the permanent magnet 1.

When the permanent magnet 1 is skew-magnetized in this manner, the position of the magnetic polarity change relative to the armature 5 and the position of the magnetic detector 7 for detecting the magnetic polarity change are as shown in FIG. In addition, it must be moved from the original position 7 'in the circumferential direction of the armature 5 by the dimension A so as to correspond to the tip of the magnetic pole boundary line 14 of the skew-magnetized permanent magnet 1.

In this case, if the magnetic detector 7 is arranged as close as possible to the armature 5, the magnetic detector 7 comes into contact with the end of the armature winding 4.

For this reason, in the conventional brushless DC motor, it is necessary to dispose the magnetic detector 7 away from the end of the armature winding 4 by the dimension B in the axial direction of the rotating shaft.

[0018]

For this reason, in the conventional brushless DC motor in which the skew magnetization is performed, it is necessary to lengthen the permanent magnet 1, which not only increases the cost of the permanent magnet 1, but also increases the cost. There is a problem that the length of the brushless DC motor becomes long.

An object of the present invention is to provide a brushless DC motor which does not require a long permanent magnet and can suppress an increase in the length of the motor even in a type in which skew magnetization is performed.

[0020]

According to the present invention, there is provided a rotor having a permanent magnet which is skew-magnetized at a predetermined angle with respect to the circumferential direction so that magnetic poles having different polarities alternately exist in the circumferential direction. A stator in which armature windings are respectively wound around respective pole portions of the armature core facing the respective magnetic poles of the permanent magnet to form an armature, and the stator is configured to detect the magnetic poles of the permanent magnet. The present invention is to improve a brushless DC motor that switches excitation of each armature winding using a signal from a magnetic detector provided on the side.

In the brushless DC motor according to the present invention, the permanent magnet includes a field magnetized portion that is skew-magnetized to face each pole portion of the armature core, and a rotational position detection device facing the magnetic detector. It is magnetized separately from the magnetizing part for use.
In this case, the field magnetized portion and the rotational position detecting magnetized portion
It may be constituted by an integral magnet or by a separate magnet. Each magnetic pole boundary line of the rotation position detecting magnetized portion is provided in correspondence with a position substantially half the length direction of each magnetic pole boundary line in the field magnetized portion where the skew magnetization is performed. Have been. The magnetic detector is disposed in the gap between the ends of the adjacent armature windings facing the magnetized portion for detecting the rotational position.

With this configuration, even in the skew-magnetized type, the magnetic detector is disposed in the gap between the ends of the adjacent armature windings facing the rotational position detecting magnetized portion. Can be. For this reason, even in the skew-magnetized type, the length of the permanent magnet can be shortened, and the cost of the permanent magnet can be reduced.
The length of the brushless DC motor can be reduced.

[0023]

1A and 1B show an example of an embodiment of a brushless DC motor according to the present invention. Parts corresponding to those in FIG. 4 described above are denoted by the same reference numerals.

In this brushless DC motor, the permanent magnet 1 magnetized so that magnetic poles N and S having different polarities alternately exist in the circumferential direction is formed by the pole portions 3a of the armature core 3.
The magnetic field is separated into a field magnetized portion 1A, which is skew-magnetized at a predetermined angle with respect to the circumferential direction, and a rotational position detecting magnetized portion 1B, which faces the magnetic detector 7. Have been. In this case, the field magnetized portion 1A and the rotational position detecting magnetized portion 1B may be constituted by an integral magnet or by separate magnets.

Each magnetic pole boundary line 14B of the rotational position detecting magnetized portion 1B is aligned with the skew magnetized field magnetized portion 1B.
A is provided so as to correspond to a position of about 1/2 in the longitudinal direction of each magnetic pole boundary line 14A in FIG. The magnetic detector 7 is disposed in the gap between the ends of the adjacent armature windings 4 facing the rotational position detecting magnetized portion 1B.

With such a configuration, even in the skew-magnetized type, the magnetic detector 7 is opposed to the rotational position detecting magnetized portion 1B and the gap between the ends of the adjacent armature windings 4 is formed. Can be arranged. Therefore, even in the skew-magnetized type, the length of the permanent magnet 1 can be reduced, the cost of the permanent magnet 1 can be reduced, and the brushless DC motor (in the rotation axis direction) can be reduced.
The length can be shortened.

In the above example, the outer rotor type brushless DC motor has been described. However, if the excitation is switched by a signal from a magnetic detector using a permanent magnet, an inner rotor type brushless DC motor is used. Can be similarly applied.

[0028]

According to the brushless DC motor of the present invention, even in the skew-magnetized type, the end of the armature winding adjacent to the magnetic detector is opposed to the rotational position detecting magnetized portion. It can be arranged in the gap between them. Therefore, even in the skew-magnetized type, the length of the permanent magnet can be reduced, the cost of the permanent magnet can be reduced, and the length of the brushless DC motor can be reduced. Further, according to the present invention, it is possible to provide a good brushless DC motor with little cogging torque without changing the size of the motor, the price of the permanent magnet, the arrangement of the armature and the magnetic detector.

[Brief description of the drawings]

FIGS. 1A and 1B show an example of an embodiment of a brushless DC motor according to the present invention in which skew magnetization is performed, and FIG. 1A shows an armature and a magnetic field of the brushless DC motor. Side view showing the relationship with the detector, (B)
FIG. 3 is an explanatory view showing a magnetized state of a permanent magnet of the brushless DC motor.

FIGS. 2A and 2B show a conventional brushless DC motor, FIG. 2A is a partially cutaway side view of the brushless DC motor, and FIG. 2B is a left half of the brushless DC motor. It is a longitudinal cross-sectional view.

3 (A) and 3 (B) show a conventional brushless DC motor without skew magnetization, and FIG. 3 (A) is a side view showing a relationship between an armature and a magnetic detector of the brushless DC motor. FIG. 1B is an explanatory view showing a magnetized state of a permanent magnet of the brushless DC motor.

FIGS. 4A and 4B show a conventional brushless DC motor in which skew magnetization is performed, and FIG. 4A is a side view showing a relationship between an armature and a magnetic detector of the brushless DC motor. FIG. 1B is an explanatory view showing a magnetized state of a permanent magnet of the brushless DC motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Permanent magnet 1A Field magnetized part 1B Rotational position detecting magnetized part 2 Rotor 3 Armature core 3a Pole part 4 Armature winding 5 Armature 6 Stator 7 Magnetic detector 8 Rotating shaft 9 Yoke 10 Flange 11 Stator Supporting boss 12 Bearing 13 Printed circuit board 14, 14A, 14B Magnetic pole boundary

Claims (1)

[Claims] A rotor provided with a permanent magnet skew-magnetized at a predetermined angle with respect to the circumferential direction such that magnetic poles having different polarities alternately exist in the circumferential direction; and each magnetic pole of the permanent magnet. An armature winding is wound around each pole portion of the armature core facing to the armature, and a souter is provided on the stator side so that the magnetic pole of the permanent magnet can be detected. A brushless DC motor that performs excitation switching of each of the armature windings using a signal from a magnetic detector, wherein the permanent magnet is skew-magnetized to face each pole of the armature core. The magnetized portion is separately magnetized into a field magnetized portion and a rotational position detecting magnetized portion facing the magnetic detector, and each magnetic pole boundary line of the rotational position detecting magnetized portion is skew-magnetized. Each magnet in the field magnetized part The magnetic detector is provided so as to correspond to approximately one-half of the length direction of the boundary line, and the magnetic detector is provided between the end portions of the armature windings adjacent to the rotating position detecting magnetized portion. A brushless DC motor characterized by being arranged in a gap.