JP2020156192A - Rotor of ipm motor - Google Patents

Abstract

To provide a rotor of an IPM motor, capable of reducing a rotor iron loss, while using a high intensity steel plate of a yield strength of 780 MPa or more as a base steel of a rotor iron core.SOLUTION: A rotor of an IPM motor, comprises: a rotor main body 1 in which a plurality of steel plates is laminated; a plurality of pair insertion holes 2 provided to the rotor main body 1 so as to be separated in a peripheral direction 1b of the rotor main body 1; and a plurality of permanent magnets 3 inserted into each insertion hole 20. When a region divided with an outer edge of the rotor main body 1, an outer diameter long side 30 of the pair of permanent magnets 3 inserted into the pair of insertion holes 20 contained in the pair insertion holes 2 and an extension line of the outer diameter long side 30, and a line obtained by extending a short side 31 on an outer side of the pair of permanent magnets 3 to the outer edge of the rotor main body 1 is a region M, each steel plate includes a base steel plate, and a low iron loss steel plate which is provided in at least one part of the region in the region M and is integrated with the base steel plate, and has an iron loss smaller than that of the base steel plate.SELECTED DRAWING: Figure 4

Description

The present invention relates to a rotor of an IPM motor having excellent iron loss characteristics and suitable for high-speed rotation.

The IPM motor is a high-efficiency PM motor that uses a permanent magnet and is capable of high-speed rotation because the permanent magnet is embedded in the rotor core. The iron core of the IPM motor is divided into a stator core and a rotor core. Since an alternating magnetic field is applied to the stator core from the winding coil, it is necessary to use a steel plate with a small iron loss for the stator core in order to improve efficiency. On the other hand, since a permanent magnet is embedded in the rotor core, the influence of the alternating magnetic field is smaller than that of the stator core. However, since a certain amount of iron loss also occurs in the rotor core, it is necessary to use a steel plate having a small iron loss as in the stator core. Generally, as the stator core and the rotor core, electromagnetic steel sheets having improved soft magnetic properties by adding Si to ultra-low carbon steel are used.

In recent years, there has been a demand for improved output while maintaining the motor size. Since there is a limit to the increase in torque, further high-speed rotation of the rotor is required. Therefore, for example, as in Patent Document 1, a rotor using a high-strength steel plate instead of an electromagnetic steel plate has been invented as a material for the iron core of the rotor so that the permanent magnet does not pop out due to centrifugal force at high speed rotation.

FIG. 1 is an example of a rotor (8 poles) of an IPM motor shown in Patent Document 1. In this 8-pole rotor, 16 permanent magnets are used because one pole is composed of two permanent magnets 3. Further, as shown in FIG. 2, in the IPM motor, the central axis of the permanent magnet forming one pole is called the d-axis 5, the axis between the poles is called the q-axis 6, and the permanent magnet and its outer side are called. The portion that supports the centrifugal force applied to the bridge portion 7 is called a bridge portion 7. If high-speed rotation is performed with the conventional design using an electromagnetic steel plate as the material of the rotor core, the centrifugal force applied to the bridge portion 7 may increase, leading to the destruction of the rotor. Increasing the strength of the bridge portion 7 is effective as one means for preventing the rotor from being destroyed.

However, since high-strength steel sheets are not materials having low iron loss characteristics like electromagnetic steel sheets, it is known that when high-strength steel sheets are used for rotor cores, the increase in iron loss causes a decrease in motor efficiency.

Japanese Unexamined Patent Publication No. 2012-217318 Japanese Unexamined Patent Publication No. 6-330255 Japanese Unexamined Patent Publication No. 2016-29876

Therefore, in Patent Document 2, an attempt is made to increase the strength while suppressing an increase in iron loss of a steel sheet used for a rotor. However, its yield strength remains below 780 MPa. Higher strength and lower iron loss of the rotor core are in a contradictory relationship, and it is difficult to achieve both with the same material.

Further, Patent Document 3 optimizes the spatial magnetic flux distribution between the rotor and the stator by replacing the region around the q-axis of the rotor iron core with a non-magnetic resin, while suppressing wind damage, and high efficiency of the motor. I am trying to make it. However, since an electromagnetic steel plate is used for the rotor core, the strength of the bridge portion is low and it cannot withstand the centrifugal force due to high-speed rotation.

The present invention has been made to solve the above problems, and an object of the present invention is to use an IPM motor capable of reducing rotor iron loss while using a high-strength steel plate having a yield strength of 780 MPa or more as a base steel plate of a rotor core. To provide a rotor.

In order to solve the above problems, the present inventors have carried out an electromagnetic field simulation of a motor using a high-strength steel plate for a rotor core. As a result, as shown in FIG. 3, it was found that the main portion where iron loss occurs in the rotor is the outer peripheral portion of the rotor, particularly between the d-axis and the bridge portion. Based on this knowledge, it was newly found that the occurrence of rotor iron loss can be reduced by replacing the iron loss occurrence site with a low iron loss material while using a high-strength steel plate as the base steel of the rotor core.

The electromagnetic field simulation of FIG. 3 was performed using an electromagnetic steel sheet 50A290 as a material for the rotor core and the stator core, and the rotation speed of the IPM motor was 7,000 rpm and the torque was 5 Nm.

Therefore, even if the base steel sheet used for the rotor of the IPM motor is a steel sheet with a yield strength of 780 MPa or more, a part of the base steel sheet at the iron loss occurrence site is replaced with a low iron loss steel sheet, and the base steel sheet and the low iron loss steel sheet are replaced. By making the rotor of the IPM motor integrated with the above, it is possible to achieve both high strength and low iron loss.

The rotor of the IPM motor of the present invention includes a rotor body in which a plurality of steel plates are laminated, a pair of insertion holes, and a plurality of insertion hole pairs provided in the rotor body separated in the circumferential direction of the rotor body. With a plurality of permanent magnets inserted into the insertion holes, when each permanent magnet inserted into the insertion hole is viewed along the axial direction of the rotor body, each permanent magnet has a rectangular outer shape and the rotor body. It has an outer diameter side long side located on the outer diameter side of the rotor body, and the outer diameter side long side of a pair of permanent magnets inserted into a pair of insertion holes included in a pair of insertion holes and the outer edge of the rotor body. When the region M is defined by the extension line of the long side on the outer diameter side and the line extending the outer short sides of the pair of permanent magnets toward the outer edge of the rotor body, the steel plate includes the base steel plate and the region. It includes a low iron loss steel plate which is provided in at least a part of M and is integrated with the base steel plate and has a lower iron loss than the base steel plate.

At this time, it is preferable that the base steel sheet has a yield strength of 780 MPa or more. Further, the low iron loss steel sheet is preferably a steel sheet having a magnetic characteristic W _15/50 of 15 W / kg or less. Note that W _15/50 indicates an iron loss obtained under the conditions of a magnetic flux density of 1.5 T and a frequency of 50 Hz.

At least a part of the region M provided with the low iron loss steel plate includes the outer edge of the rotor body and is preferably a region of 1/4 of the total area of the region M, which is 1/2. Is even more preferable.

Further, on the outer edge of the rotor body, a recess may be provided at the center of two pairs of insertion holes adjacent to each other in the circumferential direction of the rotor body.

According to the rotor of the IPM motor of the present invention, the steel plate constituting the rotor body is provided with the base steel plate in at least a part of the region M and is integrated with the base steel plate, and the iron loss is lower than that of the base steel plate. Since a low iron loss steel sheet is included, the rotor iron loss can be reduced while using a high strength steel sheet having a yield strength of 780 MPa or more as the base steel sheet of the rotor core.

FIG. 5 is a plan view of a rotor using a high-strength steel plate having a yield strength of 780 MPa or more according to an embodiment of Patent Document 1. It is a top view which showed the d-axis and the q-axis of the rotor of FIG. It is the iron loss distribution obtained by the electromagnetic field simulation about the rotor of FIG. It is a front view which shows the rotor of the IPM motor according to Embodiment 1 of this invention. It is a front view which shows the pair of permanent magnets 3 of FIG. 4 and the periphery thereof enlarged. It is a perspective view which shows the rotor of the IPM motor of FIG. It is explanatory drawing which shows the result of the electromagnetic field simulation of the motor using the rotor of FIG. It is a front view which shows the rotor of the IPM motor according to Embodiment 2 of this invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The present invention is not limited to each embodiment, and the components can be modified and embodied without departing from the gist thereof. In addition, various inventions can be formed by appropriately combining the plurality of components disclosed in each embodiment. For example, some components may be removed from all the components shown in the embodiments. Furthermore, the components of different embodiments may be combined as appropriate.

Embodiment 1.
FIG. 4 is a front view showing the rotor of the IPM motor according to the first embodiment of the present invention, FIG. 5 is an enlarged front view showing the pair of permanent magnets 3 of FIG. 4 and their periphery thereof, and FIG. 6 is a view. It is a perspective view which shows the rotor of the IPM motor of 4.

As shown in FIG. 4, the rotor of the IPM motor of the present embodiment has a rotor main body 1, a plurality of insertion hole pairs 2, and a plurality of permanent magnets 3.

The rotor body 1 is an annular member having a through hole 10 in the center. As particularly shown in FIG. 6, the rotor body 1 is formed by laminating a plurality of steel plates 11. The steel plates 11 are overlapped with each other in the axial direction 1a of the rotor body 1 and integrated.

As particularly shown in FIG. 4, the rotor main body 1 is provided with a plurality of insertion hole pairs 2 spaced apart from each other in the circumferential direction 1b of the rotor main body 1. Each insertion hole pair 2 includes a pair of insertion holes 20 respectively. The insertion hole 20 penetrates the rotor body 1 from one end to the other end of the rotor body 1 in the axial direction 1a. The pair of insertion holes 20 included in each insertion hole pair 2 are arranged so as to form a V shape that extends outward in the radial direction 1c of the rotor main body 1. The pair of insertion holes 20 are separated from each other in the radial direction 1c of the rotor body 1.

A permanent magnet 3 is inserted into each insertion hole 20. The permanent magnet 3 has a rectangular parallelepiped outer shape, and extends from one end to the other end of the rotor body 1 in the axial direction 1a. As shown in FIGS. 4 and 5, when each permanent magnet 3 inserted into the insertion hole 20 is viewed along the axial direction 1a of the rotor body 1, each permanent magnet 3 has a rectangular outer shape. The rotor body 1 has an outer diameter side long side 30 located on the outer diameter side. Short sides 31 are provided on both sides of the outer diameter side long side 30. A gap 21 is provided between the short side 31 and the inner wall of each insertion hole 20. The void 21 contributes to the reduction of the leakage flux.

Here, as shown in FIG. 5, the outer diameter side long side 30 of the pair of permanent magnets 3 inserted into the outer edge 12 of the rotor body 1 and the pair of insertion holes 20 included in the insertion hole pair 2 and the outer diameter thereof. The region separated by the extension line 30a of the side long side 30 and the line 31a extending the outer short side 31 of the pair of permanent magnets 3 toward the outer edge 12 of the rotor body 1 is referred to as a region M. The region M can be defined for each insertion hole pair 2. That is, a plurality of regions M exist apart from each other in the circumferential direction of the rotor main body 1.

The rotor main body 1 includes a rotor core 100 and a yoke 101 integrated with the rotor core 100. The rotor core 100 occupies a portion of the entire rotor body 1 excluding a part of the region M (the region occupied by the yoke 101). The yoke 101 occupies at least a part of the region M for each insertion hole pair 2. The yoke 101 of the present embodiment includes the outer edge of the rotor body 1 and occupies a region of 1/4 of the total area of the region M. The outer edge of the yoke 101 constitutes the outer edge of the rotor body 1 in the region M. Further, it is more preferable that the yoke 101 includes the outer edge of the rotor body 1 and occupies a region halved of the total area of the region M. The yoke 101 may occupy all of the region M.

The rotor core 100 is manufactured by laminating the base steel plates 110. The base steel sheet 110 preferably has a yield strength of 780 MPa or more. More specifically, the rotor iron core 100 is manufactured by laminating the base steel plate 110 in which the through hole 10 and the insertion hole 20 are punched by press working. The outer edge of each base steel plate 110 is provided with a missing portion with respect to a circle. When the base steel plates 110 are laminated, the missing portion forms a yoke insertion hole into which the yoke 101 is inserted. The missing portion has a pair of side wall portions extending away from each other as they move away from the outer edge of the rotor core 100.

The yoke 101 is manufactured by laminating a low iron loss steel plate 111 having a lower iron loss than the base steel plate 110. As the low iron loss steel sheet 111, it is preferable to use a steel sheet having a magnetic characteristic W _15/50 of 15 W / kg or less. W _15/50 indicates the iron loss obtained under the conditions of a magnetic flux density of 1.5 T and a frequency of 50 Hz. The yoke 101 is manufactured by laminating a plurality of low iron loss steel plates 111 punched into a predetermined shape by press working to the same product thickness as the rotor core 100, and then integrating the low iron loss steel plates 111 by caulking or the like. Will be done. The yoke 101 is inserted into the yoke insertion hole formed by the missing portion when the base steel plates 110 are laminated. The yoke 101 can be integrated with the rotor core 100 by spot welding 102 (see FIG. 6) from the upper surface and the lower surface of the rotor core 100.

That is, in the rotor of the IPM motor of the present embodiment, the base steel plate 110 and the base steel plate 110 are provided in a part of the region M and are integrated with the base steel plate 110 on the steel plate 11 constituting the rotor main body 1. A low iron loss steel sheet 111 having a lower iron loss than that of the steel sheet 111 is included. The base steel sheet 110 preferably has a yield strength of 780 MPa or more.

Next, FIG. 7 is an explanatory diagram showing the result of electromagnetic field simulation of the motor using the rotor of FIG. An electromagnetic field simulation of the motor using the rotor of FIG. 4 was carried out. The conditions are the same as the electromagnetic field simulation of FIG. That is, an electromagnetic steel plate 50A290 was used as the material for the rotor core and the stator core, and the rotation speed of the IPM motor was 7,000 rpm and the torque was 5 Nm. As shown in FIG. 7, a quarter of the region M shown in FIG. 4 has a low iron loss as compared with the electromagnetic field simulation of FIG. 3 (a rotor using a high-strength steel plate having a yield strength of 780 MPa or more shown in FIG. 1). In the rotor replaced with the material, the iron loss generated on the outer peripheral portion of the rotor, particularly between the d-axis and the bridge portion, was suppressed. More specifically, at a rotation speed of 7500 rpm and a torque of 5.7 Nm, the rotor iron loss generated at 21 W in the rotor using the high-strength steel plate having a yield strength of 780 MPa or more shown in FIG. 1 is in the region M shown in FIG. In the rotor in which 1/4 was replaced with a low iron loss material, the torque was reduced to 17 W, which was about 20%.

In such a rotor of an IPM motor, the steel plate 11 constituting the rotor body 1 is provided with the base steel plate 110 in at least a part of the region M and is integrated with the base steel plate 110, and is more iron than the base steel plate 110. Since the low iron loss steel plate 111 having a low loss is included, the rotor iron loss can be reduced while using a high strength steel plate having a yield strength of 780 MPa or more as the base steel plate 110 of the rotor core. Since a high-strength steel plate with a yield strength of 780 MPa or more is used near the bridge of the rotor where stress is concentrated due to centrifugal force during high-speed rotation, it has the strength to withstand high-speed rotation, and the merit of improving output by high-speed rotation is It is secured.

Embodiment 2.
FIG. 8 is a front view showing the rotor of the IPM motor according to the second embodiment of the present invention. As shown in FIG. 8, in the rotor of the IPM motor of the second embodiment, a plurality of recesses 4 are formed on the outer edge of the rotor main body 1. The recess 4 is arranged at the center of two insertion holes pair 2 adjacent to each other in the circumferential direction 1b of the rotor body 1. The center here means the center position of two insertion holes pair 2 in the circumferential direction 1b. Other configurations are the same as those in the first embodiment.

Further, since the recess 4 is provided at the center of the pair of two insertion holes adjacent to each other in the circumferential direction of the rotor body on the outer edge of the rotor body, the iron loss suppressing effect is enhanced.

1 Rotor body 11 Steel plate 110 Base steel plate 111 Low iron loss steel plate 2 Insertion hole vs. 20 Insertion hole 3 Permanent magnet 30 Outer diameter side long side 31 Short side 4 Recession

Claims (6)

The rotor body with multiple steel plates laminated and
A plurality of insertion hole pairs provided in the rotor body, each including a pair of insertion holes and separated from each other in the circumferential direction of the rotor body,
With a plurality of permanent magnets inserted into the insertion hole,
When each permanent magnet inserted into the insertion hole is viewed along the axial direction of the rotor body, each permanent magnet has a rectangular outer shape and a long side on the outer diameter side located on the outer diameter side of the rotor body. Have and
The outer edge of the rotor body, the outer diameter side long side and the extension line of the outer diameter side long side of the pair of permanent magnets inserted into the pair of insertion holes included in the insertion hole pair, and the pair. When the region M is defined as a region in which the outer short side of the permanent magnet is separated by a line extending toward the outer edge of the rotor body.
The steel plate
Base steel plate and
A low iron loss steel sheet which is provided in at least a part of the region M and is integrated with the base steel sheet and has a lower iron loss than the base steel sheet is included.
IPM motor rotor. The base steel sheet has a yield strength of 780 MPa or more.
The rotor of the IPM motor according to claim 1. The low iron loss steel sheet is a steel sheet having a magnetic characteristic W _15/50 of 15 W / kg or less.
The rotor of the IPM motor according to claim 1 or 2. At least a part of the region M provided with the low iron loss steel plate includes the outer edge of the rotor body and is a region of 1/4 of the total area of the region M.
The rotor of the IPM motor according to any one of claims 1 to 3. At least a part of the region M provided with the low iron loss steel plate includes the outer edge of the rotor body and is a region halved of the total area of the region M.
The rotor of the IPM motor according to any one of claims 1 to 3. At the outer edge of the rotor body, a recess is provided at the center of two pairs of insertion holes adjacent to each other in the circumferential direction of the rotor body.
The rotor of the IPM motor according to any one of claims 1 to 5.