JPH0984306A - Dc brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC brushless motor which makes it possible to improve the output voltage of a pole position detector by improving the magnet, to stabilize the rotation of the motor and to realize a low-cost by extending the selection of the detectors. SOLUTION: A magnet 7 is mainly magnetized in the direction for forming an air gap to a stator S and magnetized in an end face direction different from the magnetizing direction thereby to form a detecting magnetic field at the surface opposed to a pole position detector 9. Thus, the detector 9 sends the stable output voltage to a motor drive IC side without depending upon the leakage magnetic flux of the main magnetization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC brushless motor used in various audio / visual equipment or information equipment. More specifically, it improves the output voltage of a magnetic pole position detecting element by improving a magnet. The present invention relates to a DC brushless motor that can be driven.

[0002]

2. Description of the Related Art FIG. 8 is a cross-sectional view of a main part of a conventionally used DC brushless motor, and FIG. 9 is a view showing a positional relationship between a stator and a magnetic pole position detecting element in FIG. . In FIG. 8 or 9, 41 is a shaft, and the shaft 41 is rotatably supported by a bearing holder 43 via a bearing 42. A core 44 made by laminating a plurality of thin plates such as silicon steel plates is fixed to the bearing holder 43, and a drive coil 45 is formed on a plurality of salient poles arranged in the circumferential direction on the core 44, and a stator is formed. Constitutes S.

A cup-shaped yoke 46 is fixed to the shaft 41 via a boss, and an inner surface of the yoke 46 is multi-pole magnetized in the radial direction on the circumference with a gap in the stator S. The formed annular magnet 47 is held and constitutes the rotor R. In the figure, reference numeral 48 denotes a base substrate, on which magnetic pole position detecting elements 49 for detecting the leakage magnetic flux of the magnet 47 are evenly arranged every 120 ° on the circumference. The rotational position of the rotor R is detected by.

In this way, the three magnetic pole position detecting elements 49 detect the rotational position of the rotor R by the leakage magnetic flux, and the output voltage of the magnetic pole position detecting element 49 receives the leakage magnetic flux and the output voltage of the magnetic pole position detecting element 49 is a dedicated motor drive IC. Then, the IC side receives the output voltage and controls the energization directions of the drive coils of a plurality of phases, and the motor is rotationally driven so as to be sequentially switched as the rotor R rotates.

[0005]

However, in the above configuration, the magnetic pole position detecting element 49 is the magnet 4
Since it is necessary to detect the leakage magnetic flux of No. 7, the magnetic pole position detecting element 49 must be a rank product with high sensitivity, or the magnet 47 itself must be replaced with a strong magnetic force, which is very expensive. It was disadvantageous in terms of cost. In particular, when it comes to highly sensitive rank products, it is very difficult to obtain because of the limited quantity.

When the magnet 47 is skew-magnetized, the magnetic pole position detecting element 49 moves from the core slot center in the arrow direction as shown in FIG. 9, and the magnet 47 is located at this position. Even if an attempt is made to detect the leakage flux of the above, most of the leakage flux will be absorbed by the core 44, so that the output voltage will be reduced even if a highly sensitive rank product is used. Therefore, the motor driving IC receiving this output voltage malfunctions, which causes uneven rotation, resulting in extremely unstable rotation of the motor.

Therefore, the present invention solves the above problem and improves the output voltage of the magnetic pole position detecting element by improving the magnet to stabilize the rotation of the motor and select the magnetic pole position detecting element. An object of the present invention is to provide a DC brushless motor whose cost can be reduced by expanding the width.

[0008]

SUMMARY OF THE INVENTION A DC brushless motor according to the present invention is a magnet which is rotatably held by a stator composed of drive coils of a plurality of phases with a gap and a magnetic pole for detecting the magnetic pole position of the magnet. Equipped with a position detection element,
In a DC brushless motor in which the drive coil is energized and controlled based on a detection signal of the magnetic pole position detection element, the magnet is mainly magnetized in a direction forming a gap with respect to the stator and The magnetic field for detection is formed on the surface facing the magnetic pole position detection element by magnetizing in an end face direction different from the magnetic direction.
The main magnetization may be skew-magnetized.

[0009]

The magnet is magnetized in the direction in which a gap is formed with respect to the stator, and is magnetized in the end face direction different from the magnetizing direction, so that the magnetic field for detecting the magnetic field on the surface facing the magnetic pole position detecting element. By forming the above, the magnetic pole position detection element sends a stable output voltage to the IC side without depending on the leakage magnetic flux of the main magnetization.

[0010]

[First Embodiment] FIG. 1 is a cross-sectional view of an essential part of a DC brushless motor according to a first embodiment of the present invention, and FIG.
It is the figure which showed the magnetized state of the magnet in FIG.
FIG. 3 is a TN characteristic diagram comparing the motor according to the present invention with the conventional motor. FIG. 1 shows the structure of a radial gap type DC brushless motor.
In the figure, 1 is a shaft, and this shaft 1 is rotatably supported by a bearing holder 3 via a bearing 2. A core 4 made by laminating a plurality of thin plates such as silicon steel plates is fixed to the bearing holder 3, and a drive coil 5 is formed on a plurality of salient poles arranged in the circumferential direction on the core 4, and a stator is provided. Constitutes S.

A cup-shaped yoke 6 is fixed to the shaft 1 via a boss, and an annular magnet 7 is held on the inner surface of the yoke 6 in the stator S with a gap.
It constitutes the rotor R. Reference numeral 8 in the drawing denotes a base substrate, and a magnetic pole position detecting element 9 for detecting the magnetic pole position of the magnet 7 is arranged on the base substrate 8, and the magnetic pole position detecting element 9 detects the rotational position of the rotor R. are doing. For the magnetic pole position detecting element 9, for example, 1 on the circumference
Three pieces are provided every 20 °.

The structure of the magnet 7 will be described with reference to FIG. 2 (a) is a perspective view of the annular magnet, FIG. 2 (b) is an expanded view of the magnet, the upper diagram shows the state of main magnetization, and the lower diagram shows the state of end face magnetization. is there. As can be seen from this figure, the magnet 7 is magnetized in the direction of forming an air gap with respect to the stator S in order to obtain a predetermined rotational driving force in cooperation with the magnetic field formed by the stator S. By applying, multi-poles are magnetized in the radial direction on the circumference. Further, the magnetic field is magnetized in an end face direction different from the magnetizing direction, and a magnetic field for detection is formed on the surface facing the magnetic pole position detecting element.

In this way, the magnetic pole position detecting element 9
Can detect the magnetic pole position without depending on the leakage flux of the main magnetization of the magnet 7, and can improve the output voltage of the magnetic pole position detection element according to the strength of the magnetic field of the end face magnetization. . Further, in the motor provided with the magnet, as shown in FIG. 3, compared to the conventional motor characteristic graph shown by the broken line, the drop at the time of high load can be improved and the applicable range thereof is expanded. .

[0014]

[Second Embodiment] FIG. 4 is a view showing a magnetized state of a magnet according to a second embodiment of the present invention. In the figure, the main magnetization of the magnet 17 is skewed, and the end face thereof is also magnetized as in the above-described embodiment. In this case, the magnetic pole position detection element can be brought to the core slot center even when skew magnetization is performed by offsetting the circumferential angle from the main magnetization and magnetizing the end faces.

With this configuration, not only the output voltage of the magnetic pole position detecting element is improved, but also when the magnetic pole position detecting element cannot be arranged on a predetermined substrate, the angle between the main magnetization and the end surface magnetization is changed. By shifting the position, it is possible to move it by an electric angle.

[0016]

[Third Embodiment] FIG. 5 is a view showing a magnetized state of a magnet in a third embodiment of the present invention. In the figure,
The end surface magnetization is subdivided from the main magnetization. The magnet 27 is a magnet whose end face is divided and magnetized into 3n pieces, where n is the number of main magnetized divisions, and an end face magnetized magnetic pole is formed in accordance with the main magnetized magnetic pole. By doing so, the magnetization curve of the end face magnetization becomes close to a sine wave, so that smooth rotation of the motor can be obtained, which is more effective.

[0017]

[Fourth Embodiment] FIG. 6 is a sectional view of the essential parts of a DC brushless motor according to a fourth embodiment of the present invention.
It is the figure which showed the magnetized state of the magnet in FIG.
The present embodiment describes an axial gap type DC brushless motor. In FIG. 6, the shaft 31 is provided with a stator base 3 via a ball bearing 32.
3 is rotatably supported. The stator base 33 is provided with drive coils 35 of a plurality of phases, and constitutes a stator S.

On the other hand, a yoke 36 is fixedly attached to the shaft 31, and a disk-shaped magnet 37 is held by the stator S via an axial gap in the yoke 36 to form a rotor R. There is. Incidentally, reference numeral 39 in the drawing denotes a magnetic pole position detecting element arranged on the outer periphery of the drive coil. Here, as shown in FIG. 7, even in the case of the disk-shaped magnet 37, in order to drive the magnet 37 to rotate, main magnetization is applied to the stator S in the direction in which a gap is formed, and the magnetization direction is different from that. The end faces are magnetized.

With this structure, the magnetic pole position detecting element 39 can be brought from the inside of the coil to the outer peripheral portion thereof, so that the magnetic pole position of the magnet can be detected without being affected by the magnetic field of the coil, and at the same time, easily. The thickness can be reduced.

[0020]

As described above, according to the present invention, the magnet is mainly magnetized in the direction in which the air gap is formed with respect to the stator, and is magnetized in the end face direction different from the magnetizing direction. By forming the detection magnetic field on the surface facing the magnetic pole position detection element, the magnetic pole position detection element can send a stable output voltage to the IC side without depending on the leakage magnetic flux of the main magnetization. No malfunction occurs on the IC side, and the motor rotation can be smoothly stabilized.

Further, with the above construction, the magnetic pole position detecting element itself does not need to use a rank item having high sensitivity, the degree of freedom in selecting the element can be increased, and the cost can be easily reduced. it can.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a DC brushless motor according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a magnetized state of the magnet in FIG.

FIG. 3 is a TN characteristic diagram comparing a motor according to the present invention with a conventional motor.

FIG. 4 is a diagram showing a magnetized state of a magnet according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a magnetized state of a magnet according to a third embodiment of the present invention.

FIG. 6 is a cross-sectional view of main parts of a DC brushless motor according to a fourth embodiment of the present invention.

7 is a diagram showing a magnetized state of the magnet in FIG.

FIG. 8 is a cross-sectional view of a main part of a conventionally used DC brushless motor.

9 is a diagram showing a positional relationship between a stator and a magnetic pole position detection element in FIG.

[Explanation of symbols]

 5, 35, 45 ... drive coil 7, 17, 27, 37, 47 ... magnet 9, 39, 49 ... magnetic pole position detection element S ... stator

Claims (2)

[Claims] 1. A stator comprising drive coils of a plurality of phases,
DC including a magnet rotatably held via a gap and a magnetic pole position detecting element for detecting a magnetic pole position of the magnet, and energizing the drive coil based on a detection signal of the magnetic pole position detecting element. In the brushless motor, the magnet is mainly magnetized in a direction forming an air gap with respect to the stator, and is magnetized in an end face direction different from the magnetizing direction so that the magnetic pole position detecting element is provided. A DC brushless motor characterized in that a magnetic field for detection is formed on the surface facing the DC brushless motor. 2. The DC brushless motor according to claim 1, wherein the main magnetization is skewed.