KR20130062872A - Brushless motor - Google Patents

Abstract

PURPOSE: A brushless motor with a buried magnet type is provided to effectively reduce a torque ripple only by a simple structure. CONSTITUTION: A brushless motor comprises a rotor which rotates around a rotary shaft and a plurality of magnets(12); and a stator which is arranged near a rotor. The plurality of magnets are dipped in the outer circumference of the rotor core to make the standard line extended from a rotary shaft and a center point between both edges on a magnet side, to cross each other at a right angle. The rotor core comprises a pair of slits(40) which are symmetrically arranged between both edges on the magnet, based on the standard line. The slit is inclined to make an outer end(40a) to be located at a more distant position from the standard line than the location of an inner end(40b). The inner end is located in the outer side than 8th division line when dividing the gap between the edges of the magnet into 11 pieces.

Description

Brushless Motor {BRUSHLESS MOTOR}

TECHNICAL FIELD The present invention relates to a brushless motor of a buried magnet type, and more particularly, to a structure of a slit formed in a rotor.

In a brushless motor, there are a surface magnet type (SPM) and an embedded magnet type (IPM) according to the difference in the mounting method of the magnet to the rotor. In the case of an SPM motor, a magnet is attached to the outer peripheral surface of the rotor, and in the case of an IPM motor, a magnet is embedded in the rotor.

Compared to the SPM motor, the IPM motor has the advantage that the magnet does not fall from the rotor and can actively use reluctance torque. An IPM motor is used as a drive source of the compressor used for an air conditioner, a refrigerator, etc., for example.

In the case of an IPM motor, in order to improve a magnetic characteristic, several slits may be formed in the outer peripheral side of the permanent magnet embedded in the rotor. Various shapes or arrangements have been proposed for the plurality of slits.

For example, Japanese Unexamined Patent Application Publication No. 2011-78283 discloses an IPM motor in which a plurality of slits are inclined in a rotational direction or a rotation opposite direction of the motor, or an IPM motor in which a plurality of slits are inclined toward the center line of the magnetic pole. Is disclosed.

In particular, Japanese Patent Application Laid-Open No. 2011-78283 proposes to shift the phases of torques of neighboring magnetic poles such as alternately changing the inclination direction of the magnetic pole slit in the rotational direction and the rotational opposite direction. It has been disclosed that the harmonic component of? Can be offset to reduce the torque ripple.

Japanese Patent Laid-Open No. 2011-78283

In the method of Unexamined-Japanese-Patent No. 2011-78283, there existed a problem that a slit structure was complicated and difficult to handle, such as making a shape and arrangement | positioning of a slit asymmetrical between adjacent magnetic poles.

Accordingly, an object of the present invention is to provide a brushless motor capable of effectively reducing torque ripple even with a slit having a simple structure.

The brushless motor according to the present invention includes a rotor including a rotor core and a plurality of magnets and a stator disposed with a gap around the rotor, wherein the plurality of magnets have a rectangular parallelepiped shape. The rotor core is embedded at equal intervals in the outer circumferential portion of the rotor core so that the center point between the reference line extending radially from the rotation axis and both edges of the side of the magnet is orthogonal, and the rotor core is connected to the reference line between both edges of the magnet. A pair of slits disposed symmetrically with respect to the slits, the slits being inclined so that an outer end radially outwardly from the rotation axis is located farther from the reference line than an inner end radially inwardly, and divided in parallel with the reference line The center point and the edge of the magnet by a line The inner end of the slit is located outward from the eighth dividing line from the reference line toward the edge when the paper is divided into eleven.

In this way, when the slit is positioned in the predetermined range near the end of the magnet, the torque ripple can be effectively suppressed even with the slit having a simple structure.

The inclination angle of the slit is preferably set to 80 degrees or less with respect to the line perpendicular to the reference line.

For example, although only the pair of slits may be formed in the rotor core, a center slit disposed on the reference line and penetrating in the direction of the rotation axis may be further formed in the rotor core. In addition, a group of auxiliary slits arranged in a line symmetry with respect to the reference line may be further formed in a portion between the center slit of the rotor core and the pair of slits.

According to the brushless motor of the present invention, torque ripple can be effectively suppressed and productivity can be improved.

1 is a schematic perspective view showing a motor of an embodiment.
2 is a schematic cross-sectional view of a motor.
FIG. 3 is a schematic sectional view seen from line II of FIG. 2.
4 is an enlarged schematic view of an essential part of FIG. 3.
5 is a graph showing the relationship between the inclination angle of the slit and the torque ripple.
6 is a view for explaining the inclination of the slit.
7 is a graph showing the relationship between the position where the slit is formed and the torque ripple.
8 is a schematic view showing a motor of a modification.
9 is a schematic view showing a motor of a modification.
10 is a schematic view showing a motor of a modification.
(A) and (b) is a schematic diagram which shows the modification of a slit.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the following description is merely an illustration in nature and does not limit the present invention, its application or its use.

(Whole configuration of motor)

1-3 shows the motor 1 of this embodiment. This motor 1 is an inner rotor type brushless motor, for example, used as a drive source of a compressor such as a refrigerator. The motor 1 is composed of a shaft 2, a motor case 3, a rotor 4, a stator 5, a power distribution member 7 and the like.

As shown in FIG. 2, the shaft 2 is supported by the bearing 6 on the motor case 3 and rotates about the rotation axis A. As shown in FIG. In the middle part of the shaft 2, the rotor 4 of which the external appearance was cylindrical was fixed in the state which centered the shaft 2 and rotation.

The rotor 4 is comprised from the rotor core 11, the plural (6 in this embodiment) magnets 12, etc. As shown in FIG. The rotor core 11 is formed in a cylindrical shape by laminating a plurality of disk-shaped metal plates in the direction of the rotation axis A (the direction in which the rotation axis A extends). This motor 1 is what is called an embedded magnet type motor (IPM motor), and each magnet 12 is embedded in the outer peripheral part of the rotor core 11.

As shown in FIG. 3, the magnets 12 have the same shape and dimensions and have a rectangular parallelepiped shape. Specifically, as shown in FIG. 4, each magnet 12 has an elongated flat plate shape, and has a pair of rectangular side surfaces 12a and a pair of longitudinal cross-sections connected to these side surfaces 12a. 12b) and a pair of cross sections 12c. These magnets 12 are arranged so that the S pole and the N pole are alternately aligned at equal intervals in the circumferential direction with the cross section 12c facing the direction of the rotation axis A. As shown in FIG. The detailed structure of the rotor 4 is mentioned later.

Inside the motor case 3, a stator 5 having a cylindrical appearance is mounted. The inner circumferential surface of the stator 5 faces the outer circumferential surface of the rotor 4 with a slight gap.

The stator 5 is comprised from the stator core 21, the coil 22, etc. The stator core 21 has a donut-shaped base portion 21a and a plurality of teeth portions 21b protruding radially from the inner circumferential surface of the base portion 21a in the center direction (nine in the present embodiment). Each of these tooth portions 21b is provided with a plurality of coils 22 (nine in this embodiment) by winding a wire with an insulating insulator (not shown) interposed therebetween.

Inside the motor case 3, a power distribution member 7 composed of a connecting terminal or the like is provided. Current supplied from a power source outside the drawing with respect to the motor 1 is supplied to the respective coils 22 through this distribution member 7 at a predetermined timing. Thereby, the magnetic field between each magnet 12 of the rotor 4 and each coil 22 of the stator 5 fluctuates, a torque generate | occur | produces, and the shaft 2 rotates. This motor 1 is capable of both forward and reverse rotation, and rotates according to the method of controlling the supply current.

When the shaft 2 rotates, the magnetic force fluctuates between the rotor 4 and the stator 5, causing torque ripple (pulsation). In order to effectively suppress this torque ripple, the slit 40 is formed in the rotor core 11 of this motor 1. In particular, the position and angle of the slit 40 are devised so that torque ripple can be efficiently suppressed with a simple configuration in consideration of the improvement of productivity.

(Detailed Configuration of Rotor)

4, the outer peripheral part of the rotor core 11 in which the magnet 12 was embedded seen from the direction of the rotating shaft A is shown. In all six outer peripheral parts, the structure is the same. Conditions, such as the position and angle of the magnet 12 and the slit 40, are demonstrated using this drawing.

The magnet 12 is embedded in the rotor core 11 near the outer circumferential edge of the rotor core 11 with its side surface 12a facing in the radial direction. In detail, when the virtual reference line S extending radially from the center (rotation axis A) passes through the center point C between both edges of the side surface 12a of the magnet 12, The reference line S is set to be orthogonal to the side surface 12a.

In the part of the rotor core 11 in which both edges of the magnet 12 are located, a pair of flux barriers 30 are formed in order to prevent the short circuit of magnetic flux. Specifically, at each end of the side 12a of the magnet 12, specifically, at the end where the side 12a facing the radially outer side is connected to the longitudinal section 12b, the flux barrier ( 30, an elongated hole penetrating the rotor core 11 in the direction of the rotation axis A is formed.

The flux barrier 30 has a cross section spreading radially outward from each end. Specifically, the cross section includes the periphery of the edge of the side surface 12a facing the radially outer side of the magnet 12 (the corner portion between the side surface 12a and the longitudinal section 12b) and the rotor core 11. It forms an approximately fan shape or an approximately square shape to the vicinity of the outer circumferential surface of).

The outer peripheral portion of the rotor core 11 radially outward of the magnet 12 penetrates a portion between the flux barriers 30 in the direction of the rotation axis A, similarly to the flux barrier 30. Two slits 40 are formed. The position and shape of these slits 40 are line symmetrical with respect to the reference line S. FIG.

Each slit 40 has an elongated substantially rectangular cross section extending substantially radially. An end portion (also referred to as outer end 40a) located radially outward of the slit 40 is located farther from the reference line S than an end portion (also referred to as inner end 40b) located radially inward of the slit 40. Inclined to

In this motor 1, the outer end 40a of each slit 40 is substantially parallel with the outer peripheral edge part of the rotor core 11 which each opposes, and the inner end 40b of each slit 40 is It is substantially parallel to the side 12a of the magnet 12.

Inclination angle (theta) from the side surface 12a of the magnet 12 of each slit 40 is set to 80 degrees or less.

Specifically, as shown in FIG. 4, the major axis m of each slit 40 (a line passing through the width center of the slit 40) is the side surface 12a of the magnet 12 (in FIG. 4). The angle which intersects the reference line n parallel to the side surface 12a) is set to be 80 degrees or less. In this way, torque ripple can be suppressed by setting the inclination angle θ of each slit 40.

5 shows a test result (graph) performed to determine the relationship between the inclination angle θ of the slit 40 and the torque ripple. The vertical axis represents the magnitude of the torque ripple. The horizontal axis represents the inclination angle θ of the slit 40. The broken line has shown the test result when the slit 40 is not formed as a comparison object.

In addition, in a test, as shown by the arrow in FIG. 6, the slit 40 inclines the slit 40 from the state orthogonal to the side surface 12a of the magnet 12 (inclined angle (theta) = 90 degrees). Torque ripple was measured at a predetermined angle. All conditions except for the inclination angle θ are the same.

As shown in Fig. 5, it was confirmed that the torque ripple becomes small as the inclination angle θ becomes smaller. In particular, when compared with the case where the slit 40 is not formed, it was confirmed that torque ripple becomes small at about 80 degrees or less. However, if the inclination angle θ is made too small, the outer end 40a of the slit 40 contacts the flux barrier 30, so the inclination angle θ is preferably 20 ° or more.

Therefore, torque ripple can be suppressed by setting the inclination angle (theta) of each slit 40 to 80 degrees or less.

Each slit 40 is arranged in the vicinity of the flux barrier 30.

Specifically, as shown in FIG. 4, the center point C and the edge C are formed on the side surface 12a of the magnet 12 by imaginary dividing lines D ₁ to D ₁₀ parallel to the reference line S. As shown in FIG. Let's say we divided 11 into E). In this case, the inner end 40b of the slit 40 is disposed so as to be located outside the _eighth dividing line D ₈ from the reference line S toward the edge E.

In other words, when the length of the half of the magnet 12 is assumed to be L, the dividing line passing through the point close to the center point C side by the length of 3/11 × L from the end portion 12b of the magnet 12. are arranged such that the inner end (40b) of the slit 40 is located at (D ₈₎ than the end portion (12b) side. Thus, by setting the formation position of each slit 40, torque ripple can be suppressed.

FIG. 7 shows test results (graphs) performed to determine the relationship between the position at which the slit 40 is formed and the torque ripple. The vertical axis represents the magnitude of the torque ripple. The horizontal axis is the position of the inner end 40b of the slit 40, and is a distance from the edge E (the end portion 12b) of the magnet 12 of the dividing lines D ₁ to D ₁₀ shown in FIG. It is shown. The broken line has shown the test result when the slit 40 is not formed as a comparison object. In addition, the test conditions are the same except for the formation position of the slit 40.

As shown in FIG. 7, it has been confirmed that the torque ripple decreases as the slit 40 approaches the edge E side of the magnet 12. In particular, when compared with the case where the slit 40 is not formed, the position of approximately 3/11 × L from the edge E (the position of the eighth dividing line D ₈ toward the edge from the reference line S) is compared. It was confirmed that torque ripple becomes small on the edge E side.

However, if the slit 40 is formed on the edge E side too much, it is in contact with the flux barrier 30, and thus the position of 1/11 × L from the edge E (10 from the reference line S toward the edge E). to form a second split line slit 40 than the center point (C) side of the position (D ₁₀₎₎ is preferred.

In consideration of both the inclination angle θ and the formation position, in particular, the inclination angle θ is 40 ° to 80 °, and the formation position is 1/11 × L to 3/11 × from the edge of the magnet 12. It is preferable to set it as the range of L.

(Modified example)

8-10, the modified example of embodiment was shown. As shown in the above embodiment, when the two slits 40 and 40 are arranged at predetermined positions and formed at predetermined angles, the effect of suppressing torque ripple can be obtained.

However, it may be desired to further form the slit 40 by improvement of motor characteristics. In this case, as shown in FIG. 8 and the like, each slit 40 may be formed by penetrating in the direction of the rotation axis A at a position that is line symmetric with respect to the reference line S. FIG.

Specifically, in the case where three slits 40 are formed, the additional slits 40 (center slits 51) are arranged on the reference line S, as shown in FIG. In the case where the slit 40 is further increased, as shown in Figs. 9 and 10, the additional slits 40 (secondary slits 52) are increased by two. In this case, the auxiliary slit 52 is arrange | positioned so that the position and inclination-angle (theta) may become equal in the part between the center slit 51 and the slit 40 of both ends.

In this way, the number of slits can be increased without disturbing the suppression effect of the torque ripple obtained by the pair of slits 40 of the predetermined form. Furthermore, since the slit 40 is symmetrical, there is an advantage in that the productivity is excellent, and stable motor characteristics can be exhibited in all rotational directions.

In addition, the brushless motor which concerns on this invention is not limited to embodiment mentioned above, It also includes other various structures.

For example, the cross-sectional shape of the slit 40 shown in embodiment is only an example. The cross-sectional shape of the slit 40 may be rectangular as shown in FIG. 11A, or may be elliptical as shown in FIG. 11B.

1 motor
2 shaft
4 rotor
5 stator
11 rotor core
12 magnet
12a side
12b longitudinal section
30 flux barrier
40 slits
40a outer
40b inner
A axis of rotation
S baseline
C center point
D dividing line

Claims (5)

A rotor rotating about an axis of rotation and including a rotor core and a plurality of magnets,
Including a stator disposed with a gap around the rotor,
The plurality of magnets have a rectangular parallelepiped shape and are embedded at equal intervals in an outer circumferential portion of the rotor core such that a center point between a reference line extending radially from the rotation axis and both edges of the side surface of the magnet is orthogonal to each other.
The rotor core includes a pair of slits disposed symmetrically with respect to the baseline between both edges of the magnet,
The slit is inclined such that an outer end radially outward from the rotation axis is located farther from the reference line than an inner end radially inward, and is divided between the center point and the edge of the magnet by a dividing line parallel to the reference line. The brushless motor, wherein the inner end of the slit is located outward from the eighth dividing line toward the edge from the reference line when it is divided into eleven. The method according to claim 1,
And the inclination angle of the slit is 80 ° or less with respect to the line perpendicular to the reference line. 3. The method according to claim 1 or 2,
And the rotor core includes only the pair of slits. 3. The method according to claim 1 or 2,
And a center slit disposed on the reference line and passing through the rotor core in the direction of the rotation axis. 5. The method of claim 4,
And the rotor core further comprises a group of auxiliary slits disposed in a line symmetry with respect to the reference line at a portion between the center slit and the pair of slits.

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