JP2017050991A - Rotor structure for rotary electric machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of forming a larger cavity in a rotor by dispersing a stress applied to the cavity.SOLUTION: A rotor structure comprises: a rotor core configured by laminating an electromagnetic steel sheet with which a plurality of magnet insertion holes are formed along an outer circumference; and permanent magnets embedded in the magnet insertion holes. In a region closer to the outer circumference than the permanent magnets in a radial direction of the rotor core, the rotor structure includes two or more cavities that are provided side by side in the radial direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rotor structure of a rotating electrical machine.

  Conventionally, in a rotor of an embedded magnet synchronous motor, by providing a gap in a region on the outer peripheral side of a permanent magnet embedded in the rotor, a magnetic flux generated in a gap formed between the rotor and the stator is reduced. A technique for reducing harmonic components and suppressing iron loss is known (see Patent Document 1).

JP 2012-34473 A

  By the way, since the said space | gap provided in a rotor has a high iron loss suppression effect, so that opening area is large, it is preferable to provide a space | gap as large as possible from a viewpoint of iron loss suppression. However, in the high-speed rotation range of the rotating electrical machine, excessive stress is applied to the end of the gap provided in the rotor in the rotor radial direction. Therefore, there is a limit to the size of the void that can be formed, which is a problem.

  An object of this invention is to provide the technique which can form a big space | gap with a rotor by dispersing the stress concerning a space | gap.

  A rotor structure of a rotating electrical machine according to the present invention includes a rotor core configured by laminating electromagnetic steel plates in which a plurality of magnet insertion holes are formed along an outer periphery, and a permanent magnet embedded in the magnet insertion hole. In the radial direction of the rotor core, two or more gaps are provided side by side along the radial direction in a region on the outer peripheral side of the permanent magnet.

  According to the present invention, two or more voids provided in the rotor are formed side by side along the radial direction of the rotor. Thereby, since the stress concerning a space | gap can be disperse | distributed, a big space | gap can be formed with a rotor.

FIG. 1 is a view for explaining a rotor structure of a rotating electrical machine according to the first embodiment. FIG. 2 is a diagram showing an analysis result obtained by analyzing the relationship between the size of the air gap formed in the rotor and the stator iron loss. FIG. 3 is a diagram for explaining an analysis target according to the analysis result shown in FIG. FIG. 4 is a diagram for explaining the difference in stress concentration between the rotor structure of the rotating electrical machine according to the first embodiment and the conventional example. FIG. 5 is a diagram showing a magnetic flux density waveform of the stator according to the conventional example and the rotor structure of the first embodiment. FIG. 6 is a diagram showing a high-order component of the magnetic flux density in the analysis result shown in FIG. FIG. 7 is a diagram showing an analysis result obtained by analyzing torque and iron loss due to the rotor structure of the conventional example and the first embodiment. FIG. 8 is a view for explaining the rotor structure of the rotating electrical machine of the second embodiment. FIG. 9 is a diagram for explaining a difference in stress concentration location between the rotor structure of the rotating electrical machine of the second embodiment and the conventional example. FIG. 10 is a diagram showing analysis results obtained by analyzing torque and iron loss depending on the rotor structure of the conventional example and the second embodiment. FIG. 11 is a diagram for explaining the rotor structure of the first embodiment. FIG. 12 is a diagram for explaining the rotor structure of the second embodiment. FIG. 13 is a diagram for explaining the rotor structure of the third embodiment. FIG. 14 is a diagram for explaining a rotor structure of a general IPM motor. FIG. 15 is a diagram for explaining a conventional rotor structure.

-First embodiment-
FIG. 1 is a view for explaining the rotor structure of the present embodiment. What is shown in the figure is a configuration diagram of a rotor (rotor) 6 provided in a rotating electrical machine that constitutes an electric motor or a generator as viewed from a cross section perpendicular to the axial direction. ). The rotating electrical machine of the present embodiment is a so-called IPM (Interior Permanent Magnet) type rotating electrical machine in which a permanent magnet is embedded in the rotor 6, and has a rotor structure in which one permanent magnet 3 is arranged per pole. Have. Here, an 8-pole rotor is taken as an example, but the number of poles is not limited to this.

  The rotor core (rotor core) 1 is formed in a cylindrical shape by a so-called laminated electrical steel sheet structure formed by laminating an electromagnetic steel sheet having a thickness of several hundreds of μm in a ring shape in an axial direction. In addition, a magnet insertion hole 2 for embedding the permanent magnet 3 (hereinafter, also simply referred to as a magnet hole 2) is formed in the electromagnetic steel sheet single plate, and a flux barrier 4 is provided at both ends in the circumferential direction of the magnet hole 2. Is formed.

  As described above, the magnet hole 2 is an I-type hole formed in a single electromagnetic steel sheet for embedding the permanent magnet 3, and is provided at a constant mechanical angle so that the longitudinal direction is along the circumferential direction of the rotor core 1. Formed. Since the rotor 6 of this embodiment has an octupole structure, the magnet hole 2 is formed every 45 degrees of mechanical angle. FIG. 1 shows only one pole.

  By laminating the electromagnetic steel sheets in which the magnet holes 2 are formed in the axial direction, holes for embedding the permanent magnets 3 are formed in the rotor core 1. And the permanent magnet 3 is fixed in the state inserted in the hole of the rotor core 1. The permanent magnets 3 are arranged along the circumferential direction of the rotor core 1 such that the magnetic poles formed by the permanent magnets 3 are equally spaced from each other and the polarities of the adjacent magnetic poles are different from each other. The direction of the magnetic flux produced by the permanent magnet 3 is the d-axis, and the direction perpendicular to the d-axis electrically and magnetically is the q-axis.

  The permanent magnet 3 has a circumferential width smaller than that of the magnet hole 2 and is embedded in the magnet hole 2 so that the center of the magnet hole 2 in the circumferential direction coincides with the d axis. By being arranged in this way, flux barriers 4 as space portions are formed at both ends in the circumferential direction of the magnet hole 2. This space portion has a lower magnetic permeability than the electromagnetic steel sheet, that is, has a large magnetic resistance. Therefore, the flux barrier 4 acts as a magnetic barrier in which the magnetic flux (flux) is difficult to pass in the magnetic circuit formed by the permanent magnet 3 in the rotor 6.

  Then, by forming the gaps 5 so as to form two rows arranged in the substantially radial direction of the rotor 6, a rotor structure characteristic of the present invention is configured.

  Like the flux barrier 4, the air gap 5 is a space portion provided in the electromagnetic steel sheet constituting the rotor core 1. In the present embodiment, as shown in FIG. 1, two gaps 5 are provided in the rotor core 1 in a region on the outer peripheral side of the magnet hole 2 side by side in the substantially radial direction of the rotor core 1. The row formed by the two gaps 5 (gap row 7) is a region on the outer peripheral side of the magnet hole 2, and is approximately d-axis on the d-axis side from both circumferential ends of the permanent magnet 3. It is provided so that it may become parallel.

  Here, before describing the details of the air gap 5 which is a feature of the present embodiment, a conventional rotor structure for comparison with the present invention, and characteristics and problems due to the structure will be described with reference to analysis data and the like. To do.

  An embedded magnet type motor (IPM motor), which has a structure in which a permanent magnet is embedded in a rotor core with a plurality of magnet insertion holes, can effectively utilize not only magnet torque but also reluctance torque, and the motor outputs Torque density can be improved. Therefore, the IPM motor is widely used as a drive source for an electric vehicle and a motor for generating electricity (rotary electric machine). FIG. 14 shows a general rotor shape of an IPM motor in which one permanent magnet is arranged per pole. Note that the rotor shape shown in FIG. 14 is the same as the rotor shape of this embodiment, except that the gap 5 of the rotor shape of this embodiment is not provided.

  The rotor shape of the IPM motor is such that the flux barriers 4 provided at both ends in the circumferential direction of the magnet insertion hole 2 are magnetic barriers when the magnetic flux emitted from the permanent magnet 3 leaks to the opposite pole side of the permanent magnet 3. Therefore, the magnetic flux from the permanent magnet 3 can be linked to the stator side without leakage, and the torque performance can be improved.

  On the other hand, from the viewpoint of the cruising distance of an electric vehicle, there is a demand for higher efficiency of the IPM motor and improvement of continuous output performance. To that end, it is necessary to reduce the loss of the IPM motor. And in order to reduce a loss, it is especially important to reduce the iron loss which becomes dominant in a high-speed rotation area in the loss of a motor.

  On the other hand, in Japanese Unexamined Patent Application Publication No. 2012-34473 (see Patent Document 1), in the rotor in which one permanent magnet is arranged per pole as in FIG. A rotor structure characterized by forming a (flux barrier) has been proposed (see FIG. 15). According to this rotor structure, the magnetic flux generated from the permanent magnet can be collected at the center of the magnetic pole, and the magnetomotive force can be made close to a sine wave, so that the magnetic flux generated in the gap between the rotor and the stator can be reduced. Harmonic components can be reduced to reduce iron loss.

  However, in the high-speed rotation region of the motor, excessive stress is applied to the radial end of the gap due to the centrifugal force accompanying rotation, so the size of the gap provided in the radial direction depends on the relationship between the strength of the rotor core and the stress. Limits arise. An analysis result obtained by analyzing this point will be described with reference to FIGS.

  FIG. 3 is an analysis target of the analysis result shown in FIG. 2 and is a diagram showing a part of the rotor provided in the IPM motor. The curve on the right side of the drawing shows the outer periphery of the rotor core 1, and a gap 40 is provided in a region on the outer peripheral side of the permanent magnet 3 of the rotor core 1. The radial length of the gap 40 indicated by W in the figure corresponds to the radial length [W] of the gap 40 indicated by the horizontal axis of FIG.

  FIG. 2 shows the radial length [W] of the air gap 40 formed in the outer peripheral region of the embedded permanent magnet in the rotor core provided in the IPM motor rotating at a certain rotational speed, and the air gap. FIG. 6 is a diagram showing the relationship between the reduction effect [%] of the stator iron loss according to the length of 40 and the maximum stress applied to the radial end of the air gap 40. The broken line in the figure indicates the stator iron loss, and the solid line indicates the maximum stress applied to the radial end portion of the air gap 40. And the double line in a figure has shown the limit value (stress limit) which a stator core breaks with the stress accompanying rotation of a motor. The maximum stress indicated by the solid line corresponds to the scale shown on the right side of the figure, and is expressed as a ratio to the stress limit when the stress limit is 1.

  From the analysis results shown in FIG. 2, it can be seen that the effect of reducing the stator iron loss increases as the gap 40 increases. However, on the other hand, it can be seen that the larger the gap 40, the greater the maximum stress applied to the end of the gap 40 in the rotor radial direction. That is, in the analysis result shown in FIG. 2, the effect of reducing the iron loss can be obtained as the gap 40 is made larger, but it is made larger than a certain size due to the limitation by the stress limit. Indicates that you can't. Further, since the solid line indicating the maximum stress in FIG. 2 shifts to the left side as the motor rotation speed increases, only the smaller gap 40 can be formed as the upper limit value of the motor rotation speed increases.

  The present invention makes it possible to form a larger gap in a region on the outer peripheral side than the permanent magnet 3 of the rotor core 1 on the premise that the strength itself of the rotor core 1 is not different from the conventional one, and obtain a higher iron loss reduction effect. The purpose is to provide technology that can be used. Hereinafter, details of the rotor structure of the first embodiment according to the present invention will be described.

  Returning to FIG. 1, the description will be continued. As described above, in the present embodiment, in the rotor core 1, two gaps 5 are provided side by side so as to form the gap row 7 along the radial direction of the rotor core 1 in the region on the outer peripheral side of the magnet hole 2. More specifically, the direction of the gap row 7 is such that the two gaps 5 constituting the gap row 7 intersect at least a part of each gap 5 on an arbitrary straight line drawn from the rotation center of the rotor 6 to the outer periphery. It is provided as follows. Furthermore, the gap row 7 is formed substantially parallel to the d-axis.

  FIG. 4 compares the stress concentration locations of the conventional example (FIG. 4A) in which one gap is provided in the outer peripheral region from the magnet hole 2 and this embodiment (FIG. 4B). FIG.

  A portion indicated by an ellipse in the figure is a stress concentration portion accompanying the rotation of the rotor 6. As can be seen from the figure, in the conventional example, the stress applied to the gap is concentrated at the radial end of the gap. On the other hand, in this embodiment, by arranging two gaps 5 side by side in the rotor radial direction, locations where stress concentrates are dispersed at the respective radial ends of the two gaps 5. Further, the total size of the two gaps 5 of the present embodiment is larger than the size of one gap according to the conventional example. That is, by forming two gaps 5 side by side in a substantially radial direction, stress applied to the gap 5 can be dispersed, so that a larger gap in the radial direction of the rotor 6 is formed in a region on the outer peripheral side than the magnet hole 2. It becomes possible to form.

  Further, as shown in FIG. 1, the gap row 7 formed by the gaps 5 in the present embodiment is located on the d-axis side in the region on the outer peripheral side of the magnet hole 2 and on the d-axis side with respect to both circumferential ends of the permanent magnet 3 constituting one magnetic pole. In addition, two rows are formed, one row at a position symmetrical with respect to the d-axis. By providing the gap 5 in such an arrangement, the magnetic flux interlinked with the stator becomes closer to a sine wave, so that the harmonic component of the magnet magnetic flux interlinked with the stator can be reduced (see FIGS. 5 and 6). .

  FIG. 5 is a diagram showing the relationship between the electrical angle [°] (horizontal axis) of the rotor 6 and the magnetic flux density [T] (vertical axis) of the magnetic flux linked to the stator. A solid line shows the measurement result of this embodiment, and a dotted line shows the measurement result of the conventional example. As can be seen from the figure, the magnetic flux density particularly in the vicinity of the electrical angles of 60 [°] and 240 [°] changes to a smoother curve as compared with the conventional example, and the chain is connected to the stator as the rotor 6 rotates. It can be seen that the magnetic flux density of the intersecting magnetic flux has a waveform closer to a sine wave.

  FIG. 6 is a diagram showing the magnetic flux density of higher order components (third order, fifth order, seventh order, and ninth order) in the magnetic flux interlinking with the stator. In each order, the left side shows the measurement result of the conventional example, and the right side shows the measurement result of the present embodiment. As can be seen from the figure, it can be seen that the third-order and fifth-order harmonic components are reduced as compared with the conventional example.

  Here, the iron loss is the total of hysteresis loss and eddy current loss. The hysteresis loss is proportional to the frequency of the stator interlinkage magnetic flux, and the eddy current loss is proportional to the square of the frequency of the stator interlinkage magnetic flux. Accordingly, the rotor structure of the present embodiment suppresses the harmonic component of the magnet magnetic flux emitted from the permanent magnet 3, thereby reducing the iron loss particularly in the high rotation range of the motor.

  FIGS. 7A and 7B are diagrams comparing the torque and iron loss of the conventional example and this embodiment. The torque and iron loss values (%) of the present embodiment represent relative ratios when the torque and iron loss of the conventional example shown on the left side of each figure are 100%. As can be seen from the figure, the torque is almost the same while the iron loss is reduced by about 2%. That is, according to the rotor structure of the present embodiment, it is possible to reduce the iron loss while maintaining the torque. This is because, in the rotor structure of the present embodiment, the gaps 5 are arranged side by side in a substantially radial direction (substantially parallel to the d-axis), and the harmonics do not cancel out the main magnetic flux of the permanent magnet 3. It shows that only the components can be reduced.

  As described above, the rotor structure of the first embodiment includes the rotor core 1 configured by laminating the electromagnetic steel plates in which the plurality of magnet insertion holes 2 are formed along the outer periphery, and the permanent magnet 3 embedded in the magnet insertion hole 2. In the radial direction of the rotor core 1, there are two or more gaps 5 arranged side by side along the radial direction in a region on the outer peripheral side of the permanent magnet 3. Thereby, since the location where the stress concerning a space | gap concentrates by rotation of the rotor 6 can be disperse | distributed, a bigger space | gap can be provided along the radial direction of a rotor.

  In addition, since the rotor structure of the first embodiment can be provided with a larger gap 5 in the radial direction of the rotor 6 as described above, the rotor core 1 is located on the outer peripheral side of the magnet hole 2 and the permanent magnet 3. When a total of two rows are provided in a position symmetric with respect to the d axis in the region on the d axis side from both ends in the circumferential direction, the effect of suppressing the harmonic component of the magnet magnetic flux emitted from the permanent magnet 3 is further enhanced. The iron loss in the high rotation range can be further reduced.

-Second Embodiment-
FIG. 8 is a view for explaining the rotor structure of the second embodiment. The rotor structure of the present embodiment is the same as the rotor structure of the first embodiment, in particular, the one closer to the rotation center of the rotor 6 (the one closer to the permanent magnet 3) of the two gaps 5 constituting the gap row 7. Are different in that the gap 5 is connected to the magnet hole 2.

  Similarly to the first embodiment, the gap row 7 of the present embodiment is a region on the outer peripheral side of the magnet hole 2 in the rotor core 1 and also from both ends in the circumferential direction of the permanent magnet 3 constituting one magnetic pole. It is provided on the d-axis side so as to be substantially parallel to the d-axis. In addition, the gap row 7 is formed in two rows, one row at a position symmetrical with respect to the d-axis.

  FIG. 9 shows a conventional example (FIG. 9A) in which one gap is connected to the magnet hole 2 in a region on the outer peripheral side of the magnet hole 2, and the present embodiment (FIG. 9B). It is a figure which compares the stress concentration location with.

  A portion indicated by an ellipse in the figure is a stress concentration portion accompanying the rotation of the rotor. In the conventional example, the stress applied to the air gap is concentrated on the radial end portion of one air gap provided in the rotor core 1. In contrast, in the present embodiment, two gaps 5 are arranged side by side in the rotor radial direction, so even if one of the gaps 5 is connected to the magnet hole 2, the same as in the first embodiment. In addition, the locations where the stress is concentrated are dispersed at the respective radial ends of the two gaps 5.

  Further, by connecting one of the two gaps 5 constituting the gap row 7 to the magnet hole 2, the opening area as a total of the two gaps 5 is made larger than that of the conventional example in a manner different from the first embodiment. Can be formed. Thereby, the bigger iron loss reduction effect can be acquired (FIG. 10).

  10A and 10B are diagrams comparing torque and iron loss in the conventional example and the second embodiment. The torque and iron loss values (%) of the present embodiment represent relative ratios when the torque and iron loss of the conventional example shown on the left side of each figure are 100%. As can be seen from the figure, while the torque is almost the same, the iron loss is reduced by about 5% or more.

  As described above, in the rotor structure of the second embodiment, the gap that is located closest to the rotation center of the rotor 6 among the gaps 5 provided side by side is connected to the magnet insertion hole 2. Thereby, since the location where the stress applied to the air gap is concentrated by the rotation of the motor can be dispersed, a larger air gap can be provided along the radial direction of the rotor.

  In addition, since the rotor structure of the second embodiment can be provided with a larger gap 5 in the radial direction of the rotor 6, the rotor core 1 is on the outer peripheral side of the magnet hole 2 and at both ends in the circumferential direction of the permanent magnet 3. When a total of two rows are provided in the region closer to the d-axis than the d-axis, the effect of suppressing the harmonic component of the magnet magnetic flux emitted from the permanent magnet 3 is further enhanced, and the rotor 6 is rotated at a high speed. It is possible to further reduce the iron loss in the region.

  In the following, another example having the characteristics according to the first or second embodiment described so far, that is, a plurality of gaps 5 in the rotor radial direction in a region on the outer peripheral side of the magnet hole 2 in the rotor core 1. Another embodiment including a rotor structure having gap rows 7 arranged in a row will be described. Even with the rotor structure as described below, the same technical effects as those described in the first or second embodiment can be obtained as long as the gap row 7 having the above characteristics is provided. In the following description, points that do not particularly mention the rotor structure according to each example are the same as those of the rotor structure according to the first or second embodiment.

Example 1
FIG. 11 is a diagram for explaining the rotor structure of the first embodiment. The rotor 6 according to the first embodiment has two permanent magnets 3 per pole. The two permanent magnets 3 are arranged in a substantially V shape that opens to the outer peripheral side of the rotor 6. Even in such a rotor shape, both end portions in the circumferential direction of the permanent magnet 3 constituting one magnetic pole on the outer periphery side of the magnet hole 2 in the rotor core 1 as in the first and second embodiments. Further, in the region closer to the d-axis, a total of two gap rows 7 are formed so as to be substantially parallel to the d-axis at positions symmetrical to the d-axis.

-Example 2-
FIG. 12 is a diagram for explaining the rotor structure of the second embodiment. The rotor 6 according to the second embodiment has three permanent magnets 3 per pole. One of the three sheets is arranged so that the longitudinal direction is along the outer periphery of the rotor 6 (radially outermost position), as in the first and second embodiments, and the other two permanent magnets. 3 is arranged in a substantially V shape so as to open to the outer peripheral side of the rotor 6 on the rotation center side of the rotor 6 relative to the permanent magnet 3 arranged at the radially outermost peripheral position. The gap row 7 is provided in a region on the outer peripheral side of the rotor core 1 with respect to the permanent magnet 3 arranged at the radially outermost peripheral position.

-Example 3-
FIG. 13 is a diagram for explaining the rotor structure of the third embodiment. The rotor 6 according to Example 3 has one permanent magnet 3 per pole as in the first and second embodiments. However, the gap row 7 is composed of three gaps 5. Of the three gaps 5 constituting the gap row 7, the gap 5 closest to the outer circumference of the rotor 6 is formed so as to be connected to the outer circumference of the rotor 6.

  As described above, in the rotor structure according to the present invention as in the rotor structures of Examples 1 to 3, the number of permanent magnets 3 and the arrangement (arrangement angle) of the permanent magnets 3 are not particularly limited. Further, as shown in the third embodiment, the position in the rotor radial direction of the gap row 7 is not particularly limited as long as the rotor core 1 satisfies the characteristics arranged in the region on the outer peripheral side of the permanent magnet 3. Furthermore, the number of the gaps 5 constituting the gap row 7 is not limited to two, and may be three or more. Further, the number of the gap rows 7 is not particularly limited as long as it is provided symmetrically with respect to the d axis.

  The present invention is not limited to the above-described embodiments and examples, and various modifications and applications are possible. For example, in the above description, the gap 5 has been described as a space portion. However, the gap 5 is not necessarily a space and may be filled with a nonmagnetic material such as a resin material.

DESCRIPTION OF SYMBOLS 1 ... Rotor core 2 ... Magnet insertion hole 3 ... Permanent magnet 4 ... Flux barrier 5 ... Air gap

Claims (4)

In a rotor structure of a rotating electrical machine comprising: a rotor core configured by laminating electromagnetic steel plates formed with a plurality of magnet insertion holes along the outer periphery; and a permanent magnet embedded in the magnet insertion hole.
The rotor core has a gap that is provided side by side along the radial direction in the radial direction of the rotor core in the outer peripheral side of the permanent magnet.
A rotor structure of a rotating electrical machine characterized by the above. Among the gaps provided side by side, the gap located on the most central side of the rotor core is connected to the magnet insertion hole.
The rotor structure for a rotating electrical machine according to claim 1. Among the gaps provided side by side, the gap located on the outermost peripheral side of the rotor core is connected to the outer circumference.
The rotor structure for a rotating electrical machine according to claim 1. The two or more gaps provided side by side are provided symmetrically with respect to the d-axis formed by the permanent magnet.
The rotor structure of the rotating electrical machine according to any one of claims 1 to 3, wherein the rotor structure is a rotating electrical machine.