阅读说明：本技术 同步电动机的转子 (Rotor of synchronous motor ) 是由 志津达哉 横地孝典 于 2019-07-10 设计创作，主要内容包括：一种同步电动机的转子(10),其具备转子铁芯(11)、以及永磁体(13),所述转子铁芯(11)具有磁体插入孔(17)以及形成在磁体插入孔(17)的外周侧的多个狭缝(12(12a、12b、12c)),所述永磁体(13)埋设于磁体插入孔(17)。在沿永磁体(13)的边的方向上间隔形成磁路形成狭缝(12a、12b)。在各个磁路形成狭缝(12a、12b)之间、以及在最外侧的磁路形成狭缝(12a)的外侧部分形成有磁路(14)。在规定的磁路形成狭缝(12b)与永磁体(13)之间形成调整狭缝(12c),以使通过相邻的磁路(14)的与永磁体(13)的磁极的朝向交叉的方向的单位宽度的磁感线量的差变小。(A rotor (10) of a synchronous motor is provided with a rotor core (11) and a permanent magnet (13), wherein the rotor core (11) is provided with a magnet insertion hole (17) and a plurality of slits (12a, 12b, 12c) formed on the outer peripheral side of the magnet insertion hole (17), and the permanent magnet (13) is embedded in the magnet insertion hole (17). Magnetic path forming slits (12a, 12b) are formed at intervals in a direction along the sides of the permanent magnet (13). A magnetic path (14) is formed between the magnetic path forming slits (12a, 12b) and outside the outermost magnetic path forming slit (12 a). An adjustment slit (12c) is formed between a predetermined magnetic path forming slit (12b) and the permanent magnet (13) so that the difference in the amount of magnetic induction per unit width in the direction intersecting the direction of the magnetic pole of the permanent magnet (13) passing through the adjacent magnetic path (14) is reduced.)

1. A rotor of a synchronous motor is characterized by comprising: a rotor core and a plurality of permanent magnets,

the rotor core comprises silicon steel sheet or soft magnetic material, rotor core includes: a plurality of magnet insertion holes formed at intervals in the circumferential direction, and a plurality of slits formed on the outer peripheral side of each of the magnet insertion holes,

a plurality of permanent magnets embedded in the magnet insertion holes, the magnetic poles of the permanent magnets facing in the radial direction of the rotor core,

the plurality of slits include adjustment slits and magnetic path forming slits formed at intervals in a direction intersecting with the orientation of the magnetic pole of each of the permanent magnets,

at least one of the magnetic path forming slits is a tuned slit,

magnetic paths are formed between the magnetic path forming slits and outside portions of the magnetic path forming slits that are outermost in the intersecting direction,

the adjustment slit is formed between the adjusted slit and the permanent magnet so as to reduce a difference in magnetic induction line amount per unit width in the direction of the intersection of the adjacent magnetic paths.

2. The rotor of a synchronous motor according to claim 1,

the maximum width of the adjustment slit in the direction of intersection is wider than the maximum width of the adjusted slit in the direction of intersection.

3. The rotor of a synchronous motor according to claim 1 or 2,

the adjustment slit is connected to the magnet insertion hole.

4. The rotor of a synchronous motor according to any one of claims 1 to 3,

the adjusted slit is the magnetic path forming slit located on the magnetic pole center side of the permanent magnet.

5. The rotor of a synchronous motor according to claim 4,

the crossing direction is a first direction along the sides of the permanent magnet,

a shortest distance W1 between an outer periphery of the rotor core and an edge of the magnet insertion hole at one end side in the first direction of the permanent magnet,

A distance W2 from the one end of the permanent magnet to an edge of the one end side of the magnetic path forming slit closest to the one end as the distance in the first direction,

A distance W3 from an edge of the one end side of the adjusted slit to an edge of the adjusted slit side of the magnetic path forming slit adjacent to the one end side of the adjusted slit as a distance in the first direction, and

a distance W4 from an edge of the one end side of the adjustment slit to an edge of the adjustment slit side of the magnetic path forming slit adjacent to the one end side of the adjustment slit as the distance in the first direction satisfies a relationship of the following expression (1),

(W2-W1)/W2＝W4/W3 (1)。

6. the rotor of a synchronous motor according to any one of claims 1 to 3,

the adjusted slits are the magnetic path forming slits located on both sides of the magnetic path forming slit on the magnetic pole center side of the permanent magnet.

7. A rotor of a synchronous motor is characterized by comprising: a rotor core and a plurality of permanent magnets,

the rotor core comprises silicon steel sheet or soft magnetic material, rotor core includes: a plurality of magnet insertion holes formed at intervals in the circumferential direction, and a plurality of slits formed on the outer peripheral side of each of the magnet insertion holes,

a plurality of permanent magnets embedded in the magnet insertion holes, the magnetic poles of the permanent magnets facing in the radial direction of the rotor core,

the plurality of slits are formed at intervals in a direction crossing the orientation of the magnetic poles of the respective permanent magnets,

magnetic paths are formed between the slits and outside portions of the slits outermost in the intersecting direction,

two or more types of slits having different maximum widths in the intersecting direction are formed so that a difference in the amount of magnetic induction lines per unit width in the intersecting direction passing through the adjacent magnetic paths is small.

8. The rotor of a synchronous motor according to claim 7,

at least one of the slits is a deformed slit having a shape extending from the permanent magnet side to an outer peripheral side of the rotor core, and a width in the intersecting direction changes halfway.

9. The rotor of a synchronous motor according to claim 8,

the width of the deformed slit in the direction of intersection of the permanent magnet-side end portions is larger than the width of the deformed slit in the direction of intersection of the outer peripheral-side end portions of the rotor core.

10. The rotor of a synchronous motor according to claim 8 or 9,

the deformation slit is connected to the magnet insertion hole.

11. The rotor of a synchronous motor according to any one of claims 8 to 10,

the deformation slit is the slit located on the magnetic pole center side of the permanent magnet.

12. The rotor of a synchronous motor according to claim 11,

the crossing direction is a first direction along the sides of the permanent magnet,

the end portion of the deformation slit on the permanent magnet side is an expanded portion,

a portion between an end portion of the deformation slit on the permanent magnet side and an end portion on the outer peripheral side of the rotor core is an intermediate portion,

a shortest distance W1 between an outer periphery of the rotor core and an edge of the magnet insertion hole at one end side in the first direction of the permanent magnet,

A distance W2 from the one end of the permanent magnet to an edge of the one end side of the slit closest to the one end as the distance in the first direction,

A distance W5 from an edge of the intermediate portion of the deformed slit on the one end side to an edge of the slit adjacent to the one end side of the deformed slit on the deformed slit side as the distance in the first direction, and

a distance W6 from an edge on the one end side of the expanded portion of the deformed slit to an edge on the deformed slit side of the slit adjacent to the one end side of the deformed slit as the distance in the first direction satisfies a relationship of the following expression (2),

(W2-W1)/W2＝W6/W5 (2)。

13. the rotor of a synchronous motor according to any one of claims 8 to 10,

the deformation slits are the slits located on both sides of the slit on the magnetic pole center side of the permanent magnet.

Technical Field

The present invention relates to a rotor of a synchronous motor.

Background

There are various structures of Permanent Magnet Synchronous motors (Permanent Magnet Synchronous motors), and a surface-mount Permanent Magnet Synchronous Motor (hereinafter, referred to as "spm") in which Permanent magnets are attached to an outer peripheral surface of a rotor, and a built-in Permanent Magnet Synchronous Motor (hereinafter, referred to as "ipm" (interior Permanent Magnet Synchronous Motor) "or" Synchronous Motor ") in which Permanent magnets are embedded in a rotor core are known.

Since the IPM has a structure in which the permanent magnets are embedded in the rotor, the risk of the permanent magnets scattering when the rotor rotates at high speed is small as compared with the SPM in which the permanent magnets are bonded to the surface of the rotor. In addition, since IPM does not require a curved surface for attaching the permanent magnet to the surface of the rotor to be provided in the permanent magnet like SPM, a flat permanent magnet can be used, so that cost can be reduced.

Therefore, if IPM can be adopted in, for example, a servo motor for driving a feed shaft of a machine tool, high reliability and low cost can be achieved. However, generally, IPM has a larger inductance than SPM, and causes a delay in current tracking, resulting in poor controllability. Therefore, it is not suitable for a servo motor requiring high-speed and high-precision positioning operation.

In this regard, as a rotor structure for reducing the inductance of the IPM, for example, a rotor disclosed in patent document 1 is known. The configuration of the rotor will be described below with reference to fig. 5. Fig. 5 is a diagram showing an example of a cross section of a rotor in a conventional IPM. The rotor 50 includes a rotor core 51 formed by laminating silicon steel sheets or the like, and a plurality of permanent magnets 53. The rotor core 51 includes: a plurality of magnet insertion holes 57 formed at intervals in the circumferential direction, and a plurality of slits 52 formed on the outer peripheral side of each of the magnet insertion holes 57. Each permanent magnet 53 is embedded in each magnet insertion hole 57, and the magnetic poles are oriented in the radial direction of the rotor core 51. The rotor 50 is connected at its center to a rotating shaft (not shown). The magnet insertion hole 57 and the slit 52 are holes (gaps) opened in the axial direction of the rotation shaft (direction passing through the paper surface). Magnetic paths 54 are formed between the adjacent slits 52 and between the slits 52 and the outer periphery of the rotor core 51.

Further, a stator, not shown, is disposed radially outward of the rotor 50. The stator has a substantially cylindrical shape, and a plurality of pole teeth are arranged in a circumferential direction on an inner circumferential surface of the cylindrical shape. The spaces between the teeth are called slots through which the coils are wound around the teeth to form magnetic poles.

Fig. 6 is an enlarged view of a part of the rotor 50 of fig. 5, showing the magnetic induction lines 55 generated by the permanent magnets 53 and the magnetic induction lines 56 generated by applying current to the stator coils. As is apparent from fig. 6, the slits 52 are arranged to prevent the passage of the induction magnet wire 56 caused by the energization of the stator coil. By disposing the slits 52 in this manner, the inductance of the IPM is reduced by reducing the magnetic induction lines 56 generated by supplying current to the stator coils. On the other hand, the permanent magnet 53 is magnetized in a radially outward direction, and the magnetic induction lines 55 generated by the permanent magnet 53 flow to the stator through the magnetic circuit 54.

Here, attention is paid to the amount of magnetic flux passing through each of the magnetic paths 54a and 54b distant from the magnetic pole center. The number of lines of magnetic induction 55 in fig. 6 shows the relative amount of lines of magnetic induction. For simplicity of description, the widths of the magnetic paths 54a and 54b (the width in the direction intersecting the direction of the magnetic pole of the permanent magnet 53, and the width in the left-right direction which is the direction along the side of the permanent magnet 53 in fig. 6) are set to be equal. Therefore, the same amount (three) of magnetic induction lines flow from the permanent magnet 53 to the magnetic circuit 54a and the magnetic circuit 54 b. In the magnetic circuit 54b, three of the three inflows each flow out to the stator. In the magnetic circuit 54a, one of the magnetic induction lines is missing at the connection portion between the magnetic poles, and therefore only two of the three flowing-in lines flow out to the stator.

Disclosure of Invention

As described above, in the rotor of the conventional IPM, more magnetic induction lines are generated by the permanent magnets 53 and flow into the stator through the magnetic path 54b close to the magnetic pole center than are generated by the permanent magnets 53 and flow into the stator through the magnetic path 54a far from the magnetic pole center. Since the throughput of the magnetic flux lines is almost proportional to the magnetic attraction, a large magnetic attraction is generated in a magnetic circuit with a large throughput of the magnetic flux lines, and only a small magnetic attraction is generated in a magnetic circuit with a small throughput of the magnetic flux lines. If the magnetic flux path varies depending on the magnetic circuit as described above, a difference in magnetic attraction occurs depending on the rotational position of the rotor 50. That is, the magnetic attraction force becomes large when the magnetic flux path with a large flux amount approaches the pole teeth of the stator, whereas the magnetic attraction force becomes small when the magnetic flux path with a small flux amount approaches the pole teeth of the stator. If the magnetic attraction force varies according to the rotational position of the rotor 50 as described above, a pulsation of torque called cogging torque is generated when the rotor 50 rotates.

For example, when a servo motor having a large cogging torque is used for a feed shaft of a machine tool, a defect such as a streak occurs on a cut surface. The invention aims to provide a rotor of a synchronous motor capable of reducing cogging torque.

To achieve the above object, a rotor of a synchronous motor according to the present invention has the following structure.

The rotor of a synchronous motor according to the present invention is characterized by comprising: rotor core and a plurality of permanent magnet, above-mentioned rotor core comprises silicon steel sheet or soft magnetic material, and above-mentioned rotor core includes: a plurality of magnet insertion holes formed at intervals in the circumferential direction, and a plurality of slits formed on the outer peripheral side of each of the magnet insertion holes, a plurality of the permanent magnets being buried in each of the magnet insertion holes, the magnetic poles are oriented in the radial direction of the rotor core, the plurality of slits include adjustment slits and magnetic path forming slits, the magnetic path forming slits are formed at intervals in a direction intersecting the magnetic pole direction of each of the permanent magnets, at least one of the magnetic path forming slits is a regulated slit, magnetic paths are formed between the magnetic path forming slits and outside the outermost magnetic path forming slit in the intersecting direction, the adjustment slits are formed between the adjusted slits and the permanent magnets so that a difference in magnetic induction line amount per unit width in the direction of the intersection of the adjacent magnetic paths is reduced.

In the rotor of a synchronous motor according to the present invention, a maximum width of the adjustment slits in the intersecting direction may be larger than a maximum width of the adjusted slits in the intersecting direction.

In the rotor of the synchronous motor according to the present invention, the adjustment slits may be connected to the magnet insertion holes.

In the rotor of a synchronous motor according to the present invention, the adjusted slits may be the magnetic path forming slits located on the magnetic pole center side of the permanent magnet.

In the rotor of a synchronous motor according to the present invention, the direction of intersection is a first direction along a side of the permanent magnet, a shortest distance W1 between an outer periphery of the rotor core and an edge of the magnet insertion hole at one end side of the permanent magnet in the first direction, a distance W2 from the one end of the permanent magnet to an edge of the one end side of the magnetic circuit forming slit closest to the one end as the distance in the first direction, a distance W3 from the edge of the one end side of the adjusted slit to an edge of the adjusted slit side of the magnetic circuit forming slit adjacent to the one end side of the adjusted slit as the distance in the first direction, and a distance W4 from the edge of the one end side of the adjusted slit to the edge of the magnetic circuit forming slit adjacent to the one end side of the adjusted slit as the distance in the first direction, satisfies the following formula (1).

(W2-W1)/W2＝W4/W3 (1)

In the rotor of a synchronous motor according to the present invention, the adjusted slits may be the magnetic path forming slits located on both sides of the magnetic path forming slit located on the magnetic pole center side of the permanent magnet.

The rotor of a synchronous motor according to the present invention is characterized by comprising: rotor core and a plurality of permanent magnet, above-mentioned rotor core comprises silicon steel sheet or soft magnetic material, and above-mentioned rotor core includes: a plurality of magnet insertion holes formed at intervals in a circumferential direction, and a plurality of slits formed on an outer peripheral side of each of the magnet insertion holes, wherein a plurality of permanent magnets are embedded in each of the magnet insertion holes, a magnetic pole of each permanent magnet is oriented in a radial direction of the rotor core, the plurality of slits are formed at intervals in a direction intersecting the magnetic pole orientation of each permanent magnet, magnetic paths are formed between the slits and outside portions of the slits outermost in the intersecting direction, and two or more kinds of the slits having different maximum widths in the intersecting direction are formed so that a difference in magnetic induction line amount per unit width in the intersecting direction passing through the adjacent magnetic paths is reduced.

In the rotor of a synchronous motor according to the present invention, at least one of the slits may be a deformed slit having a shape extending from the permanent magnet side to the outer peripheral side of the rotor core and having a width in the intersecting direction that changes midway.

In the rotor of a synchronous motor according to the present invention, a width of the deformed slit in the direction of the intersection of the permanent magnet-side end portions may be larger than a width of the deformed slit in the direction of the intersection of the outer peripheral-side end portions of the rotor core.

In the rotor of the synchronous motor according to the present invention, the deformation slit may be connected to the magnet insertion hole.

In the rotor of a synchronous motor according to the present invention, the deformation slit may be the slit located on the magnetic pole center side of the permanent magnet.

In the rotor of a synchronous motor according to the present invention, the intersecting direction is a first direction along sides of the permanent magnets, an end portion of the deformation slit on the permanent magnet side is an expanded portion, a portion between the end portion of the deformation slit on the permanent magnet side and an end portion on an outer peripheral side of the rotor core is an intermediate portion, a shortest distance W1 between an outer periphery of the rotor core and an edge of the magnet insertion hole at one end side of the first direction of the permanent magnet, a distance W2 from the one end of the permanent magnet to an edge on the one end side of the slit closest to the one end as the distance in the first direction, a distance W5 from the edge on the one end side of the intermediate portion of the deformation slit to an edge on the deformation slit side of the slit adjacent to the one end side of the deformation slit as the distance in the first direction, and a distance W6 from an edge of the expanded portion of the deformed slit on the one end side to an edge of the slit on the deformed slit side adjacent to the one end side of the deformed slit, as the distance in the first direction, and satisfies the following expression (2).

(W2-W1)/W2＝W6/W5 (2)

In the rotor of a synchronous motor according to the present invention, the deformed slits may be slits located on both sides of the slits located on the magnetic pole center side of the permanent magnet.

According to the rotor of the synchronous motor of the present invention, the cogging torque of the synchronous motor can be reduced.

Drawings

Fig. 1 is an enlarged view of a part of a cross section of a rotor in a first embodiment.

Fig. 2 is an enlarged view of a part of a cross section of a rotor in the second embodiment.

Fig. 3 is an enlarged view of a part of a cross section of a rotor in a modification of the second embodiment.

Fig. 4 is an enlarged view of a part of a cross section of a rotor in another modification of the second embodiment.

Fig. 5 is a diagram showing an example of a cross section of a rotor in a conventional IPM.

Fig. 6 is an enlarged view of a part of the rotor of fig. 5, showing lines of magnetic induction generated by the permanent magnets.

Detailed Description

Hereinafter, embodiments of a rotor of a synchronous motor according to the present invention will be described with reference to the drawings.

(embodiment 1)

Fig. 1 is an enlarged view of a part of a cross section of a rotor 10 of a synchronous motor according to a first embodiment. The rotor 10 of the synchronous motor according to the present embodiment has the same configuration as the rotor 50 of the synchronous motor shown in fig. 5, except for the form of the slits. In other words, referring to fig. 1 and 5 in comparison, the rotor 10 includes a rotor core 11 (corresponding to 51 in fig. 5) formed by laminating silicon steel sheets or the like, and a plurality of permanent magnets 13 (corresponding to 53 in fig. 5). The rotor core 11 includes a plurality of magnet insertion holes 17 (corresponding to 57 in fig. 5) formed at intervals in the circumferential direction. Each permanent magnet 13 is embedded in each magnet insertion hole 17, and the magnetic poles are oriented in the radial direction of rotor core 11. The rotor 10 is connected at its center to a rotating shaft (not shown). The magnet insertion hole 17 and the slit 12 described later are holes (gaps) opened in the axial direction of the rotation shaft (direction passing through the paper surface).

In the first embodiment and fig. 5, the number of the magnet insertion holes 17 (corresponding to 57 in fig. 5) and the number of the permanent magnets 13 (corresponding to 53 in fig. 5) are four, respectively, but may be other numbers depending on the number of the magnetic poles.

Note that, in the present specification, the circumferential direction of the rotor 10 or the rotor core 11 may not be a strict circumferential direction. For example, in fig. 5, the magnet insertion holes 57 (the permanent magnets 53) adjacent to each other at 90 degrees are arranged (formed) at intervals in the circumferential direction, and for example, in the case where the number of the magnet insertion holes 57 (the permanent magnets 53) is two, the magnet insertion holes 57 are arranged in the vertical direction or the horizontal direction in fig. 5.

The rotor 10 of the synchronous motor according to the first embodiment will be described in detail below with reference to fig. 1. In general, since the cross section of the rotor 10 orthogonal to the rotation axis is the same in the rotation axis direction, the shapes of the magnetic circuit, the slit, the permanent magnet, and the magnet insertion hole will be described in conjunction with the shape in the cross section orthogonal to the rotation axis.

The rotor core 11 of the rotor 10 is formed by stacking plate materials made of soft magnetic materials such as silicon steel sheets in the rotation axis direction. The rotor core 11 includes a plurality of slits 12 formed on the outer peripheral side of the magnet insertion hole 17. The plurality of slits 12 include: the adjustment slits 12c and the magnetic path forming slits 12a and 12b formed at intervals in a direction intersecting the direction (radial direction) of the magnetic pole of the permanent magnet 13. In fig. 1, the intersecting direction is a direction along the side of the permanent magnet 13 (the left-right direction in fig. 1), and the direction along the side of the permanent magnet 13 will be hereinafter referred to as "first direction" as appropriate. At least one of the magnetic path forming slits 12a and 12b is an adjusted slit, and in fig. 1, the magnetic path forming slit 12b located on the magnetic pole center side of the permanent magnet 13 is an adjusted slit. Magnetic paths 14 are formed between the magnetic path forming slits 12a, 12b and outside the outermost magnetic path forming slit 12a in the first direction.

Further, a stator, not shown, is disposed radially outward of the rotor 10. The stator has a substantially cylindrical shape, and a plurality of pole teeth are arranged in a circumferential direction on an inner circumferential surface of the cylindrical shape. The spaces between the teeth are called slots through which the coils are wound around the teeth to form magnetic poles.

As shown in fig. 1, the adjusted slits 12b and the adjusting slits 12c form a slit group 16. The maximum width of the adjustment slit 12c in the first direction is wider than the maximum width of the adjusted slit 12b in the first direction. The rotor 10 of the synchronous motor according to the first embodiment is characterized in that the adjustment slits 12c are formed between the adjusted slits 12b and the permanent magnets 13 so that the difference in the amount of magnetic induction per unit width in the first direction passing through the adjacent magnetic paths 14a and 14b is small.

In fig. 1, for simplicity of explanation, the widths (the width in the first direction) of the magnetic paths 14a and 14b are set to be equal. In fig. 1, the widths of the adjusted slits 12b and the adjusting slits 12c are determined so that the amount of magnetic flux flowing into the stator through the magnetic circuit 14a is equal to the amount of magnetic flux flowing into the stator through the magnetic circuit 14b, using the relationship shown in equation (1).

(W2-W1)/W2＝W4/W3 (1)

Fig. 1 shows W1, W2, W3, and W4 in formula (1) above. In the above equation (1), W1 is the shortest distance between the outer periphery of the rotor core 11 and the edge of the magnet insertion hole 17 at one end side (the right side in fig. 1) in the first direction of the permanent magnet 13. W2 is the distance in the first direction, and is the distance from the one end (right side in fig. 1) of the permanent magnet 13 to the edge on the one end side of the magnetic path forming slit 12a closest to the one end. W3 is a distance in the first direction from the edge of the one end side (right side in fig. 1) of the slit 12b to be adjusted to the edge of the magnetic path forming slit 12a adjacent to the one end side of the slit 12b to be adjusted on the slit 12b side. W4 is a distance in the first direction from the edge of one end side (right side in fig. 1) of the adjustment slit 12c to the edge of the magnetic path forming slit 12a adjacent to the one end side of the adjustment slit 12c on the adjustment slit 12c side.

The flow pattern of the magnetic induction lines generated by the permanent magnet 13 in the above-described configuration will be described with reference to fig. 1. In fig. 1, the permanent magnet 13 is magnetized in a radially outward direction, and the magnetic induction lines 15 show the paths of the magnetic induction lines generated by the permanent magnet 13. The number of the induction lines 15 showing the path of the induction lines indicates the relative amount of the induction lines. As described above, since the magnetic paths 14a and 14b have the same width, the same number of magnetic induction lines flow from the permanent magnet 13 into all the magnetic paths. However, the wide adjustment slits 12c in the first direction are arranged to restrict the magnetic induction lines flowing into the magnetic circuit 14b, three magnetic induction lines flow into the magnetic circuit 14a, and two magnetic induction lines flow into the magnetic circuit 14 b. When the amount of the magnetic induction lines flowing from the permanent magnet 13 into the stator through the magnetic circuit 14 is taken into consideration, two of the magnetic induction lines flowing into the magnetic circuit 14b flow out to the stator, while one of the magnetic induction lines is missing from the connection portion between the magnetic poles in the magnetic circuit 14a, and two of the three flowing in lines flow out to the stator.

In this way, by adjusting the effect of the slits 12c, unlike fig. 6 showing the flow pattern of the magnetic induction lines in the rotor of the conventional IPM, the amount of the magnetic induction lines flowing into the stator through the magnetic circuit 14 is equal between the magnetic circuit 14a and the magnetic circuit 14 b. Therefore, the magnetic attractive forces generated in all the magnetic circuits are equal, and thus the cogging torque can be reduced without variation in the magnetic attractive force when the rotor 10 rotates.

In the first embodiment, three magnetic path forming slits 12a and 12b are provided for each pole, but the number of magnetic path forming slits 12a and 12b for each pole is not limited to three. The magnetic path forming slits 12a and 12b may be present at a plurality of intervals in the direction of the magnetic pole (vertical direction in fig. 1). The adjustment slits 12c may be present at a plurality of intervals along the direction of the magnetic pole (vertical direction in fig. 1).

In the first embodiment, the case where the widths of the magnetic circuits 14a and 14b are equal to each other is exemplified, but the present invention is not limited thereto.

In the first embodiment, the magnetic path forming slits 12a and 12b are determined and the width of the slit 12c is adjusted so that the amount of magnetic flux flowing into the stator through the magnetic path 14a is equal to the amount of magnetic flux flowing into the stator through the magnetic path 14b, according to the equation (1). However, the present invention is not limited to this example. Even if the relation of the equation (1) is not satisfied, if the adjustment slit 12c having the width in the first direction is present, the difference between the amount of magnetic induction lines flowing into the stator through the magnetic circuit 14a and the amount of magnetic induction lines flowing into the stator through the magnetic circuit 14b can be reduced, and the cogging torque can be reduced.

The adjustment slit 12c may be connected to the magnet insertion hole 17. In this case, the same effects as described above can be obtained.

In the first embodiment, the slit group 16 (the adjusted slits 12b and the adjusting slits 12c) is present on the magnetic pole center side of the permanent magnet 13. However, the position of the slit group 16 is not limited as long as the change in the magnetic induction lines of the adjacent magnetic circuits 14a and 14b can be reduced. For example, two magnetic path forming slits 12a located on both sides of the magnetic path forming slit 12b on the magnetic pole center side of the permanent magnet 13 may be used as adjusted slits, and the adjusting slit 12c may be disposed between each of the magnetic path forming slits 12a (adjusted slits) and the permanent magnet 13. This is a configuration in which two deformed slits 18 in fig. 4 (a modified example of the second embodiment) to be described later are separated vertically to form an adjusted slit and an adjusting slit.

(embodiment 2)

The rotor 10 of the synchronous motor according to the second embodiment will be described below. Fig. 2 is an enlarged view of a part of a cross section of the rotor 10 of the synchronous motor according to the second embodiment. In the second embodiment, the adjusted slits 12b and the adjusting slits 12c in the first embodiment are provided integrally to form the deformed slits 18. Since other configurations are the same as those of the first embodiment, descriptions of the same configurations are omitted as appropriate.

As shown in fig. 2, the plurality of slits 12 and 18 are formed at intervals in a direction intersecting with the direction (radial direction) of the magnetic pole of the permanent magnet 13, and in the second embodiment, the intersecting direction is a direction along the side of the permanent magnet 13 (left-right direction, i.e., first direction) as in the first embodiment. Magnetic paths 14 are formed between the slits 12, 18 and outside portions of the slits 12 outermost in the first direction. The rotor 10 of the synchronous motor according to the second embodiment is characterized in that two or more kinds of slits 12 and 18 having different maximum widths in the first direction are formed so that a difference in the amount of magnetic induction per unit width in the first direction passing through the adjacent magnetic paths 14 is small.

At least one of the slits 12 and 18 is a deformed slit 18, and the deformed slit 18 has a shape extending from the permanent magnet 13 side to the outer peripheral side of the rotor core 11 and having a width in the first direction changing halfway. In fig. 2, the width of the end portion of the deformed slit 18 on the permanent magnet 13 side in the first direction is wider than the width of the end portion of the deformed slit 18 on the outer peripheral side of the rotor core in the first direction.

In fig. 2, the widths (the width in the first direction) of the magnetic path 14a and the magnetic path 14b are set to be equal. In fig. 2, the widths of the slits 12 and 18 are determined so that the amount of magnetic flux flowing into the stator through the magnetic circuit 14a is equal to the amount of magnetic flux flowing into the stator through the magnetic circuit 14b, using the relationship expressed by the equation (2).

(W2-W1)/W2＝W6/W5 (2)

Fig. 2 shows W1, W2, W5, and W6 in the above formula (2). Here, the end portion of the deformation slit 18 on the permanent magnet 13 side is referred to as an "expanded portion", and a portion between the end portion of the deformation slit 18 on the permanent magnet 13 side and the end portion on the outer peripheral side of the rotor core 11 is referred to as an "intermediate portion". In the above equation (2), W1 is the shortest distance between the outer periphery of the rotor core 11 and the edge of the magnet insertion hole 17 at one end side (the right side in fig. 2) in the first direction of the permanent magnet 13. W2 is the distance in the first direction, and is the distance from the one end (right side in fig. 2) of the permanent magnet 13 to the edge of the one end side of the slit 12 closest to the one end. W5 is a distance in the first direction, and is a distance from the edge of the one end side (the right side in fig. 1) of the middle portion of the deformed slit 18 to the edge of the slit 12 adjacent to the one end side of the deformed slit 18 on the deformed slit 18 side. W6 is a distance in the first direction, and is a distance from the edge on one end side (the right side in fig. 1) of the expanded portion of the deformed slit 18 to the edge on the deformed slit 18 side of the slit 12 adjacent to the one end side of the deformed slit 18.

The flow pattern of the magnetic induction lines generated by the permanent magnet 13 in the above-described configuration will be described with reference to fig. 2. In fig. 2, the permanent magnet 13 is magnetized in a radially outward direction, and the magnetic induction lines 15 show the paths of the magnetic induction lines generated by the permanent magnet 13. The number of the induction lines 15 showing the path of the induction lines indicates the relative amount of the induction lines. As described above, since the magnetic paths 14a and 14b have the same width, the same number of magnetic induction lines flow from the permanent magnet 13 into all the magnetic paths. However, the maximum width of the deformed slit 18 disposed on the magnetic pole center side in the first direction (the left-right direction in fig. 2) is wider than the maximum width of the other slits 12 in the first direction, so that the number of magnetic induction lines flowing into the magnetic circuit 14b is limited, three magnetic induction lines flow into the magnetic circuit 14a, and two magnetic induction lines flow into the magnetic circuit 14 b. Here, if attention is paid to the amount of magnetic induction lines flowing from the permanent magnet 13 into the stator through the magnetic circuit 14, two of the magnetic induction lines flowing into the magnetic circuit 14b flow into the stator, while one of the magnetic induction lines is missing from the connection portion between the magnetic poles in the magnetic circuit 14a, and two of the three flowing into the stator flow out.

As described above, the effect of deforming the slits 18 is that the amount of magnetic induction lines passing through each magnetic circuit 14 is equal, unlike fig. 6 which shows the flow pattern of magnetic induction lines in the rotor of the conventional IPM. Therefore, as in the first embodiment, since the magnetic attractive forces generated in all the magnetic circuits 14 are equal to each other, the magnetic attractive force does not change when the rotor 10 rotates, and thus the cogging torque can be reduced.

In the second embodiment, three slits 12 and 18 are arranged for each pole, as in the first embodiment, but the number of slits 12 and 18 for each pole is not limited to three. The slits 12 and 18 may be present at a plurality of positions apart from each other in the direction of the magnetic pole (vertical direction in fig. 2).

In the second embodiment, the case where the widths of the magnetic circuits 14a and 14b are equal to each other is described as an example, but the present invention is not limited to this.

In the second embodiment, the widths of the slits 12 and 18 are determined so that the amount of magnetic flux flowing into the stator through the magnetic circuit 14a is equal to the amount of magnetic flux flowing into the stator through the magnetic circuit 14b, according to equation (2). However, the present invention is not limited to this example. Even if two or more kinds of slits 12 and 18 having different maximum widths are formed instead of the relationship of expression (2), the difference between the amount of magnetic flux flowing into the stator through the magnetic circuit 14a and the amount of magnetic flux flowing into the stator through the magnetic circuit 14b can be reduced, and the cogging torque can be reduced.

The deformation slit 18 may be connected to the magnet insertion hole 17. In this case, the same effects as described above can be obtained.

In the second embodiment, the position where the width of the deformation slit 18 in the first direction is the widest (the position where the width is the largest) is the end on the permanent magnet 13 side. However, the location of maximum width may be other portions of the deformation slit 18. Fig. 3 is an enlarged view of a part of a cross section of a rotor in a modification of the second embodiment. As shown in fig. 3, the position of the maximum width in the deformed slit 18 may be located in the vicinity of the approximate middle in the direction of the orientation of the magnetic poles (the up-down direction in fig. 2). In this case, the same effects as described above can be obtained.

In addition, in the second embodiment described above, the deformation slits 18 are present on the magnetic pole center side of the permanent magnet 13. However, the position of the deformation slit 18 is not limited as long as the difference in the amount of magnetic induction lines per unit width in the first direction passing through the adjacent magnetic paths 14a and 14b can be made small. Fig. 4 is an enlarged view of a part of a cross section of a rotor in another modification of the second embodiment. As shown in fig. 4, two slits on both sides of the slit 12 on the magnetic pole center side of the permanent magnet 13 may be used as the deformation slits 18. In this case, the same effects as described above can be obtained.