JP6428458B2 - Embedded magnet type motor - Google Patents

Description

  The present invention relates to an embedded magnet type motor in which a permanent magnet is embedded in a rotor.

2. Description of the Related Art Conventionally, an embedded magnet type motor in which a permanent magnet is embedded in an arc-shaped slit that is convex toward the rotation center side of a rotor is known. This embedded magnet type motor can output a combined torque that is the sum of magnet torque and reluctance torque, so it is possible to obtain strong torque performance even if ferrite magnets are used without using rare earth magnets such as neodymium magnets. It is.
However, in order to increase the torque, it is necessary to embed as many magnets as possible in the slit, so that both end portions of the magnets are arranged near the surface of the rotor. In this case, since the magnet end portion is likely to receive a reverse magnetic field from the stator and there is a background that the ferrite magnet has a lower holding force and is easier to demagnetize compared to the neodymium magnet, ensure the magnet's demagnetization resistance. Is required. On the other hand, Patent Document 1 increases the permeance of the magnet end arranged near the surface of the rotor and improves demagnetization resistance by magnetizing the magnet so that it is parallel to the d-axis direction. Techniques for making them disclosed are disclosed.

JP 2008-187802 A

By the way, in the case of general radial magnetization, the thickness of the magnet with respect to the orientation direction is uniform, whereas when magnetized in parallel with the d-axis direction, the thickness of the magnet with respect to the orientation direction is the center of the magnet. Becomes the thinnest and the permeance becomes small. For this reason, in the case of radial magnetization, demagnetization starts from the corners of the magnet, but when magnetized in parallel with the d-axis direction, the magnet center portion is more easily demagnetized than the magnet end portion. As shown in FIG. 8, when a rotating magnetic field is generated in the stator 2, a magnetic flux (shown by a broken line) generated by the rotating magnetic field is generated between the magnet 7 on the innermost side of the rotor and the magnet 7 on the outermost side. Since it flows into the path 6a and acts as a reverse magnetic field on the magnet 7 on the innermost diameter side of the rotor, there is a problem that the magnet center portion with the smallest permeance is most likely to be demagnetized.
The present invention has been made to solve the above problems, and an object of the present invention is to provide an embedded magnet type motor that can improve the demagnetization resistance of a permanent magnet disposed on the innermost diameter side of the rotor. is there.

The present invention according to claim 1 includes a stator that generates a rotating magnetic field and a rotor that is rotatably disposed on the inner peripheral side of the stator, and three or more slits per pole in the radial direction of the rotor. An embedded magnet type motor, in which a permanent magnet is embedded in the slit, wherein the slit formed on the innermost diameter side of the rotor among the three or more layers of slits is referred to as a first slit. The slit formed at one outer diameter side from one slit is called a second slit, the slit formed at one outer diameter side from the second slit is called a third slit, and the first slit and the a magnetic path is provided between the second slit is referred to as a first magnetic path, said magnetic path is provided between the second slit and the third slit second magnetic path call, also the slit Split in the longitudinal direction Among the bridges connecting the inner diameter side and the outer diameter side of the slit, the bridge that divides the first slit is called a first bridge, and the bridge that divides the second slit is called a second bridge. the width der width ≦ 0.5 × the second magnetic path of the first magnetic path is, the slit and the permanent magnet has a circular arc shape which is convex toward the rotation center side of the rotor.
Further, in the present invention according to claim 2, the width of the first magnetic path <the width of the second magnetic path, and the width of the first magnetic path = the width of the first bridge, and the slit And the said permanent magnet has the circular arc shape which becomes convex at the rotation center side of the said rotor.

According to the first aspect, by setting the width ≦ 0.5 × width of the second magnetic path of the first magnetic path, it is possible to suppress the magnetic flux flowing from the stator to the first magnetic path, the rotor innermost diameter side The reverse magnetic field applied to the permanent magnet is reduced. As a result, it is possible to improve the demagnetization resistance of the permanent magnet on the innermost side of the rotor.
According to the second aspect of the present invention, the first magnetic path flows into the first magnetic path by setting the width of the first magnetic path <the width of the second magnetic path and the width of the first magnetic path = the width of the first bridge. Since the magnetic flux can flow through the first bridge, the reverse magnetic field applied to the permanent magnet on the innermost side of the rotor is reduced. As a result, it is possible to improve the demagnetization resistance of the permanent magnet on the innermost side of the rotor.

FIG. 4 is a quarter cross-sectional view of the rotor according to the first embodiment. 1 is a cross-sectional view of an embedded magnet type motor according to Embodiment 1. FIG. 3 is a graph showing the effect of the invention according to Example 1. 4 is a quarter cross-sectional view of a rotor according to Embodiment 2. FIG. 6 is a quarter cross-sectional view of a rotor according to Embodiment 3. FIG. FIG. 6 is a quarter sectional view of a rotor according to a fourth embodiment. 10 is a graph showing the effect of the invention according to Example 4; It is a partial cross section figure of the rotor explaining the subject of a prior art.

  The mode for carrying out the present invention will be described in detail with reference to the following examples.

[Example 1]
As shown in FIG. 2, the embedded magnet type motor 1 according to the first embodiment includes a stator 2 that constitutes an armature and a rotor 3 that constitutes a field element. FIG. 2 is a cross-sectional view of the motor 1, but hatching for displaying the cross section is omitted.
The stator 2 includes a stator core 4 having a predetermined number of teeth 4a and an armature coil 5 wound around the teeth 4a, and three-phase alternating current is applied to the armature coil 5 through an inverter (not shown). This generates a rotating magnetic field.
The rotor 3 includes a rotor core 6 that is rotatably disposed on the inner peripheral side of the stator 2 and a permanent magnet 7 embedded in the rotor core 6, and rotates in synchronization with a rotating magnetic field generated in the starter 2. .

As shown in FIG. 1, the rotor core 6 has three layers of slits 8 per pole in the rotor radial direction, and permanent magnets 7 are inserted into the slits 8.
The slit 8 is formed in an arc shape in which the rotation center side of the rotor 3 is convex, and both ends of the slit 8 are extended to the vicinity of the outer peripheral surface of the rotor 3. The slit width is constant.
The permanent magnet 7 is, for example, a ferrite magnet, has an arc shape that matches the shape of the slit 8, and is embedded in the entire slit 8. The permanent magnet 7 is magnetized in parallel with the d-axis direction. In the present invention, the direction of the magnetic flux generated by the magnetic poles of the rotor 3 (the central axis of the permanent magnet 7) is defined as the d-axis, and the direction electrically orthogonal to the d-axis is defined as the q-axis (see FIG. 1).

Hereinafter, the slit 8 formed on the innermost diameter side of the rotor 3 is referred to as a first slit 8a, and the slit 8 formed on the outer diameter side from the first slit 8a is referred to as a second slit 8b. One slit 8 formed on the outer diameter side of the slit 8b, that is, on the outermost diameter side of the rotor 3, is referred to as a third slit 8c. The magnetic path provided between the first slit 8a and the second slit 8b is referred to as the first magnetic path 6a, and the magnetic path provided between the second slit 8b and the third slit 8c is the second magnetic path. Called 6b.
In the rotor 3 of the first embodiment, as shown in FIG. 1, the width of the first magnetic path 6a (hereinafter referred to as magnetic path width A) is the width of the second magnetic path 6b (hereinafter referred to as magnetic path width B). ) Is formed smaller. Further, the outer peripheral surface of the rotor core 6 is formed in a circular arc shape so that the magnetic path width on the outer diameter side from the first slit 8a is substantially constant.

[Operation and Effect of Example 1]
In the rotor 3 according to the first embodiment, the arc-shaped permanent magnet 7 is magnetized in parallel with the d-axis direction. Therefore, even if both ends of the permanent magnet 7 are arranged close to the outer peripheral surface of the rotor 3, demagnetization is difficult. Become. Further, since the magnetic path width A is smaller than the magnetic path width B, the magnetic flux flowing from the stator 2 to the first magnetic path 6a can be suppressed as compared with the configuration of the magnetic path width A = magnetic path width B. As a result, the reverse magnetic field applied to the permanent magnet 7 on the innermost side of the rotor, that is, the central portion of the permanent magnet 7 inserted into the first slit 8a is reduced, so that it is possible to improve demagnetization resistance at the central portion of the magnet. is there. In addition, the center part (magnet center part) of the permanent magnet 7 means the center part of the longitudinal direction which cross | intersects d axis | shaft.
The graph shown in FIG. 3 is a result of obtaining a correlation between the magnetic path width A / the magnetic path width B and the demagnetization factor of the magnet center portion by simulation. As shown in the graph, the demagnetization factor decreases as the magnetic path width A / magnetic path width B decreases. However, if the magnetic path width A is too small, the q-axis magnetic flux flowing through the first magnetic path 6a is reduced, and the torque may be reduced due to magnetic saturation of the q-axis magnetic path. Therefore, it is desirable to appropriately set the magnetic path width A within a range where necessary torque can be secured.

Hereinafter, other embodiments according to the present invention will be described.
Note that components and configurations that are common to those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof is omitted.
[Example 2]
The second embodiment is an example in which a bridge 9 for reinforcing the rotor 3 by dividing the slit 8 in the longitudinal direction is provided.
As shown in FIG. 4, the bridge 9 is provided in each of the first slit 8 a and the second slit 8 b having a long slit length, and the first slit 8 a and the second slit 8 b are divided into three in the longitudinal direction. .
Hereinafter, the bridge 9 that divides the first slit 8a is referred to as a first bridge 9a, and the bridge 9 that divides the second slit 8b is referred to as a second bridge 9b. Both the first bridge 9a and the second bridge 9b are provided in parallel with the d-axis direction and are located at the same distance from the magnetic pole center.

In the rotor 3 of the second embodiment, in addition to the configuration of the first embodiment (magnetic path width A <magnetic path width B), the width of the first bridge 9a (hereinafter referred to as bridge width C) is the width of the second bridge 9b. (Hereinafter referred to as bridge width D) is formed larger (bridge width C> bridge width D).
By making the bridge width C larger than the bridge width D, the magnetic flux flowing from the stator 2 into the first magnetic path 6a and the magnetic flux flowing from the second magnetic path 6b through the second bridge 9b into the first magnetic path 6a are It is possible to flow through one bridge 9a. As a result, the reverse magnetic field applied to the magnet central portion on the innermost side of the rotor inserted into the first slit 8a is reduced, so that it is possible to improve the demagnetization resistance of the magnet central portion.

Example 3
The third embodiment is another example in which a first bridge 9a that divides the first slit 8a and a second bridge 9b that divides the second slit 8b are provided.
As shown in FIG. 5, in the rotor 3 of the third embodiment, the bridge width C adds the magnetic path width A and the bridge width D in addition to the configuration of the first embodiment (magnetic path width A <magnetic path width B). It is formed in a combined size (bridge width C = magnetic path width A + bridge width D).
According to said structure, all the magnetic flux which flows into the 1st magnetic path 6a from the stator 2 and the magnetic flux which flows into the 1st magnetic path 6a from the 2nd magnetic path 6b through the 2nd bridge | bridging 9b are all 1st bridge | bridging 9a. It is possible to flow. As a result, the reverse magnetic field applied to the magnet central portion on the innermost side of the rotor inserted into the first slit 8a is reduced, so that it is possible to improve the demagnetization resistance of the magnet central portion.
Moreover, in the structure of Example 3, since the bridge width C is not increased more than necessary, the leakage magnetic flux of the permanent magnet 7 passing through the first bridge 9a can be reduced.

Example 4
The fourth embodiment is an example in which a first bridge 9a that divides at least the first slit 8a is provided.
As shown in FIG. 6, the rotor 3 of the fourth embodiment is formed such that the magnetic path width A is equal to the bridge width C in addition to the configuration of the first embodiment (magnetic path width A <magnetic path width B). (Magnetic path width A = bridge width C).
By making the magnetic path width A equal to the bridge width C, the magnetic flux flowing from the stator 2 to the first magnetic path 6a can flow to the first bridge 9a. As a result, the amount of magnetic flux applied to the permanent magnet 7 on the innermost diameter side of the rotor is reduced, so that it is possible to improve demagnetization resistance at the magnet center.

  The graph shown in FIG. 7 is the result of obtaining the correlation between the magnetic path width A / bridge width C and the demagnetization factor of the magnet center by simulation. As shown in the graph, when the magnetic path width A = bridge width C (magnetic path width A / bridge width C = 1), the demagnetization factor is minimized. Further, if the magnetic path width A is made smaller than the bridge width C (magnetic path width A / bridge width C> 1), more demagnetization occurs in the portion other than the magnet center portion. The effect is reduced compared to the case of width C. Therefore, by forming the magnetic path width A and the bridge width C to be equal in size, the resistance to demagnetization at the magnet center can be improved.

[Modification]
In the first embodiment, an example in which three layers of slits 8 per pole are formed in the rotor core 6 is described, but four or more layers of slits 8 may be formed.
In the relationship between the magnetic path width A and the bridge width C, the magnetic path width A> the bridge width C or the magnetic path width A ≦ 2 × the bridge width C may be satisfied.
The bridges 9 described in the second to fourth embodiments are not necessarily provided in parallel with the d-axis direction, and may be provided in the radial direction with respect to the arc shape of the slit 8, for example. Further, the first bridge 9a and the second bridge 9b may not be located at the same distance from the magnet center.
In the first to fourth embodiments, the slit 8 and the permanent magnet 7 are described as arc shapes, but a curved shape having a larger curvature than the arc may be used.
In the first embodiment, an example of an 8-pole motor is described, but the present invention can be applied to a motor structure other than an 8-pole motor.

DESCRIPTION OF SYMBOLS 1 Embedded magnet type motor 2 Stator 3 Rotor 6a 1st magnetic path 6b 2nd magnetic path 7 Permanent magnet 8 Slit 8a 1st slit 8b 2nd slit 8c 3rd slit 9 Bridge 9a 1st bridge 9b 2nd bridge

Claims (8)

A stator (2) that generates a rotating magnetic field, and a rotor (3) that is rotatably arranged on the inner peripheral side of the stator (2), and three or more layers per pole in the radial direction of the rotor (3) An embedded magnet type motor (1) in which a slit (8) is formed and a permanent magnet (7) is embedded in the slit (8),
Of the three or more layers of slits (8), the slit (8) formed on the innermost diameter side of the rotor (3) is referred to as a first slit (8a), one outside of the first slit (8a). The slit (8) formed on the radial side is referred to as a second slit (8b), and the slit (8) formed on the outer diameter side from the second slit (8b) is the third slit (8c). The magnetic path provided between the first slit (8a) and the second slit (8b) is called the first magnetic path (6a), and the second slit (8b) and the third slit ( 8c) and a second magnetic path (6b) a magnetic path is provided between the call,
Of the bridge (9) that divides the slit (8) in the longitudinal direction to connect the inner diameter side and the outer diameter side of the slit (8), the bridge (1) that divides the first slit (8a) 9) is called the first bridge (9a), and the bridge (9) dividing the second slit (8b) is called the second bridge (9b).
Ri width der width ≦ 0.5 × the second magnetic path of the first magnetic path (6a) (6b),
The embedded magnet type motor, wherein the slit (8) and the permanent magnet (7) have a circular arc shape protruding toward the rotation center side of the rotor (3) . A stator (2) that generates a rotating magnetic field, and a rotor (3) that is rotatably arranged on the inner peripheral side of the stator (2), and three or more layers per pole in the radial direction of the rotor (3) An embedded magnet type motor (1) in which a slit (8) is formed and a permanent magnet (7) is embedded in the slit (8),
Of the three or more layers of slits (8), the slit (8) formed on the innermost diameter side of the rotor (3) is referred to as a first slit (8a), one outside of the first slit (8a). The slit (8) formed on the radial side is referred to as a second slit (8b), and the slit (8) formed on the outer diameter side from the second slit (8b) is the third slit (8c). The magnetic path provided between the first slit (8a) and the second slit (8b) is called the first magnetic path (6a), and the second slit (8b) and the third slit ( 8c) is called the second magnetic path (6b),
Of the bridge (9) that divides the slit (8) in the longitudinal direction to connect the inner diameter side and the outer diameter side of the slit (8), the bridge (1) that divides the first slit (8a) 9) is called the first bridge (9a), and the bridge (9) dividing the second slit (8b) is called the second bridge (9b).
The width of the first magnetic path (6a) <the width of the second magnetic path (6b), and the width of the first magnetic path (6a) = the width of the first bridge (9a),
The embedded magnet type motor, wherein the slit (8) and the permanent magnet (7) have a circular arc shape protruding toward the rotation center side of the rotor (3) . In the interior magnet type motor (1) according to claim 1 or 2 ,
An embedded magnet type motor characterized in that the width of the first bridge (9a)> the width of the second bridge (9b) . In the interior magnet type motor (1) according to claim 1 or 2 ,
An embedded magnet type motor characterized by: width of the first bridge (9a) = width of the first magnetic path (6a) + width of the second bridge (9b) . In the interior magnet type motor (1) according to claim 1,
A width of the first magnetic path (6a) ≧ a width of the first bridge (9a) . In the interior magnet type motor (1) according to claim 1 ,
An embedded magnet type motor characterized by: width of the first magnetic path (6a) ≦ 2 × width of the first bridge (9a) . In the interior magnet type motor (1) according to any one of claims 1 to 6 ,
When the direction connecting the rotation center of the rotor (3) and the magnetic pole center is defined as the d-axis direction,
The permanent magnet (7) is magnetized in parallel with the d-axis direction, and is an embedded magnet type motor. In the interior magnet type motor (1) according to any one of claims 1 to 7,
An embedded magnet type motor having three layers of slits (8) per pole in the radial direction of the rotor (3).

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