Rotor of rotating electrical machine

Abstract

The invention provides a rotor of a rotary electric machine, which is provided with a magnet having a coercive force distribution and can restrain sudden demagnetization caused by temperature rise of the magnet. A rotor (10) of a rotating electrical machine is provided with: a rotor core (20) having a substantially circular ring shape centered on a rotation axis RC; and a plurality of magnetic pole parts (30) provided along the circumferential direction of the rotor core (20). Each of the magnetic pole parts (30) has a magnet housing hole (31) formed in the rotor core (20) and extending in the axial direction, and at least one permanent magnet (41) housed in the magnet housing hole (31). A distribution of coercive force is formed in a predetermined direction in the permanent magnet (41), and the permanent magnet (41) is housed in the magnet housing hole (31) such that the coercive force at an outer end portion (45) in the axial direction is greater than the coercive force at an inner portion in the axial direction with the distribution direction of the coercive force as the axial direction.

Description

Technical Field

[0001] The present invention relates to a rotor of a rotating electrical machine provided with magnets having a distribution of coercive forces. Background Art

[0002] In recent years, efforts to achieve a low-carbon or decarbonized society have been actively underway. Research and development related to electrification technologies is being conducted to reduce CO2 emissions and improve energy efficiency in vehicles. Examples of electrification technologies include rotating electrical machines such as motors and generators. These rotating electrical machines are used in electric vehicles such as battery-powered electric vehicles, hybrid vehicles, and fuel cell vehicles.

[0003] For example, Patent Document 1 discloses a motor equipped with a rotor and including permanent magnets. In the motor of Patent Document 1, the permanent magnets have a coercive force distribution within a single unit. The coercive force of the hot-side permanent magnet portion (located in the high-temperature portion of the motor and exposed to high temperatures) is set higher than the coercive force of the cold-side permanent magnet portion (located in the low-temperature portion of the motor and exposed to lower temperatures). This achieves a low-cost motor with excellent motor characteristics.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 6841130 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] In a motor including permanent magnets with coercive force distribution in a single body as described in Patent Document 1, the low coercive force portion of the permanent magnet may rapidly demagnetize as the magnet temperature rises, and there is still room for improvement in this regard.

[0009] The present invention provides a rotor of a rotating electric machine capable of suppressing the occurrence of rapid demagnetization caused by a temperature increase of the magnets in a rotor provided with magnets having a coercive force distribution.

[0010] Solutions to Problems

[0011] The present invention provides a rotor of a rotating electrical machine, comprising:

[0012] a rotor core having a substantially annular shape centered on a rotation axis; and

[0013] A plurality of magnetic pole portions are arranged along the circumference of the rotor core, wherein:

[0014] Each magnetic pole portion has a magnet receiving hole formed in the rotor core and extending in the axial direction, and at least one magnet received in the magnet receiving hole.

[0015] A distribution of coercive force is formed in the magnet along a predetermined direction.

[0016] The magnet is accommodated in the magnet accommodation hole such that the coercive force distribution direction is in the axial direction and the coercive force of the outer end portion in the axial direction is greater than the coercive force of the inner portion in the axial direction.

[0017] Effects of the Invention

[0018] According to the present invention, it is possible to suppress the occurrence of rapid demagnetization caused by a temperature increase of the magnet. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a perspective view of a rotor 10 of a rotating electrical machine according to one embodiment of the present invention.

[0020] Figure 2 This is a diagram of the permanent magnet 41 housed in the magnet housing hole 31 as viewed from the axial direction of the rotor 10 .

[0021] Figure 3 This is a perspective view of the permanent magnet 41 housed in the magnet housing hole 31 with the coercive force distribution direction oriented in the axial direction.

[0022] Figure 4 This is a perspective view of the permanent magnet 41A housed in the magnet housing hole 31 with the coercive force distribution direction oriented in the radial direction.

[0023] Figure 5 An example of a graph showing a comparison of heat resistance of various permanent magnets.

[0024] Figure 6 A side view of a magnet group 40 according to a first modified example is shown, in which larger permanent magnets 41L are arranged on both outer sides in the axial direction and smaller permanent magnets 41S are arranged on the inner side.

[0025] Figure 7 The magnetic pole portion 30 of the second modified example is shown, in which the coercive force of the permanent magnet 41 in each magnet receiving hole 31 is different.

[0026] Description of reference numerals:

[0027] 10 rotors

[0028] 20 rotor core

[0029] 30 Magnetic pole

[0030] 31 Magnet receiving hole

[0031] 41 Permanent magnet (magnet)

[0032] 45 outer end

[0033] RC rotation axis. DETAILED DESCRIPTION

[0034] An embodiment of a rotor for a rotating electrical machine according to the present invention is described below with reference to the accompanying drawings. In this specification and other documents, the terms "axial," "radial," and "circumferential" refer to directions relative to the rotor's axis of rotation. Furthermore, "axially inward" refers to the side axially toward the rotor center, while "axially outward" refers to the side axially away from the rotor center. Furthermore, "circumferentially inward" refers to the side circumferentially toward the center of the magnetic pole portion, while "circumferentially outward" refers to the side circumferentially away from the center of the magnetic pole portion.

[0035] like Figure 1 and Figure 2 As shown, the rotor 10 of the rotating electric machine includes a rotor core 20 having a substantially annular shape centered on a rotation axis RC, and a plurality of magnetic pole portions 30 arranged along the circumference of the rotor core 20. Although not shown, the rotating electric machine includes the rotor 10 and a stator having coils mounted thereon. The rotor 10 is driven to rotate by the interaction of the magnetic field of the stator generated by the flow of current through the coils and the magnetic field of the rotor 10 generated by permanent magnets 41 (described later) mounted on the rotor 10.

[0036] The rotor core 20 is formed by laminating a plurality of substantially annular electromagnetic steel sheets in the axial direction. A through hole 21 is formed in the center of the rotor core 20 so as to pass through the rotor core 20 in the axial direction. A rotor shaft (not shown) is press-fitted into the through hole 21 and fixed thereto.

[0037] A plurality of (here, 12) magnetic pole portions 30 are arranged at equal intervals along the circumferential direction at radially outer positions of the rotor core 20. Each magnetic pole portion 30 has a magnet receiving hole 31 extending in the axial direction formed in the rotor core 20 and a permanent magnet 41 received in the magnet receiving hole 31. Figure 2 Reference numeral 45 in FIG. 4 denotes an outer end portion of the permanent magnet 41 in the axial direction.

[0038] Each magnetic pole portion 30 is provided with three magnet receiving holes 31. The three magnet receiving holes 31 are arranged in a substantially U-shape that opens toward the outside of the rotor core 20. At least one permanent magnet 41 is received in each magnet receiving hole 31.

[0039] Figure 3 : shows an example of a permanent magnet 41 accommodated in one magnet accommodation hole 31. Figure 3 The light and dark colors on the permanent magnet 41 are conceptually added to explain the coercive force distribution described later.

[0040] Multiple permanent magnets 41 (here, four) are stacked axially and housed in magnet-receiving holes 31. Each permanent magnet 41 has a rectangular parallelepiped shape. In this specification, multiple permanent magnets 41 stacked and housed in a single magnet-receiving hole 31 are sometimes collectively referred to as a magnet group 40. Alternatively, a magnet group 40 may consist of a single, elongated permanent magnet 41 inserted into each magnet-receiving hole 31.

[0041] The permanent magnet 41 has a coercive force distribution within a single body, consisting of a high-coercive force portion (high-coercive force portion 411) and a low-coercive force portion (low-coercive force portion 412). "High coercive force" here means that the high-coercive force portion 411 has a relatively higher coercive force than the low-coercive force portion 412, while "low coercive force" means that the low-coercive force portion 412 has a relatively lower coercive force than the high-coercive force portion 411. It should be noted that there is no clear distinction between the high-coercive force portion 411 and the low-coercive force portion 412.

[0042] Coercive force is the resistance to maintaining the initial magnetic force by resisting environmental loads such as thermal history that cause loss of magnetic force, as well as opposing magnetic fields. The high-coercive force portion 411, for example, is the portion that experiences the least degree of demagnetization (i.e., weakening of the magnetic force) when exposed to high temperatures, and can be said to have high heat resistance. The low-coercive force portion 412, for example, is the portion that experiences the greatest degree of demagnetization when exposed to high temperatures, and can be said to have low heat resistance.

[0043] The coercive force of the permanent magnet 41 is formed to have a gradient in one direction. Specifically, the permanent magnet 41 has high-coercive force portions 411 formed on both outer sides in a predetermined direction, and low-coercive force portions 412 formed between the high-coercive force portions 411, i.e., on the inner side in the predetermined direction. Furthermore, the coercive force of the permanent magnet 41 is formed to be uniform in a direction perpendicular to the predetermined direction. In this specification, "uniform coercive force" means that the coercive force is within a predetermined tolerance range.

[0044] The permanent magnets 41 are housed in the magnet housing holes 31 such that their coercive force distribution is axially directed in the rotor 10 direction, and the coercive force of their axially outer ends 45 is greater than that of their inner portions. Specifically, each permanent magnet 41 is housed in the magnet housing holes 31 such that a high-coercive force portion 411 is provided axially outwardly and a low-coercive force portion 412 is provided axially inwardly. Furthermore, the high-coercive force portion 411 is disposed at the axially outer ends 45 of each of the permanent magnets 41.

[0045] The outer end portion 45 of the permanent magnet 41 in the axial direction is a portion where magnetic flux easily flows and magnet temperature easily rises. Figure 2The corner portion 45 c of the outer end portion 45 of the permanent magnet 41 shown in the figure demagnetizes progressively toward the center (see black arrow). However, the outer end portion 45 is uniformly formed into the high coercive force portion 411 , thereby suppressing the occurrence of rapid demagnetization due to a rise in magnet temperature.

[0046] Next, the heat resistance of the permanent magnet 41 will be described by comparing the permanent magnet 41A housed in the magnet housing hole 31 with its coercive force distributed in the radial direction of the rotor 10 with a single permanent magnet having uniform coercive force (hereinafter also referred to as a homogeneous magnet).

[0047] Figure 4 The illustrated permanent magnet 41A (magnet group 40A) is a magnet having a coercive force distribution within a single body, similar to the permanent magnet 41 of the present embodiment. However, it is housed in the magnet housing hole 31 such that the coercive force distribution is oriented in a direction perpendicular to the axial direction of the rotor 10, for example, in the radial direction. A coercive force distribution is present at the axially outer end 45A of the permanent magnet 41A, forming a high-coercive force portion 411A, which has a high coercive force, and a low-coercive force portion 412A, which has a low coercive force.

[0048] Figure 5 This is an example of a graph comparing the heat resistance of various permanent magnets, with the horizontal axis representing the magnet temperature and the vertical axis representing the heat resistance of the magnet. The heat resistance on the vertical axis means that the higher the position, the higher the heat resistance. The thin dashed line is a graph of a homogeneous magnet without heavy rare earth additives. The thick dashed line is a graph of a homogeneous magnet with heavy rare earth additives added to the entire magnet. The thin solid line is a graph of a permanent magnet 41A with a radial coercive force distribution direction. The thick solid line is a graph of a permanent magnet 41 of this embodiment with an axial coercive force distribution direction.

[0049] When a rotating electrical machine is driven, the heat generated by the rotating electrical machine affects the permanent magnets, causing the magnet temperature to rise. This typically leads to progressive demagnetization of the permanent magnets, reducing their heat resistance. Specifically, when the magnet temperature rises, the rotating electrical machine's voltage drops, reducing the output of the rotating electrical machine.

[0050] like Figure 5 As shown in the figure, homogeneous magnets without additives are more susceptible to demagnetization as the magnet temperature rises, and their heat resistance gradually decreases. In particular, heat resistance decreases significantly in high temperature ranges.

[0051] Homogeneous magnets containing additives are less likely to experience demagnetization even when the magnet temperature rises, and can maintain heat resistance in high temperature ranges. However, since additives must be added to the entire magnet, the manufacturing cost of the rotor 10 having homogeneous magnets containing additives increases.

[0052] Permanent magnets 41A, with their radially distributed coercive force, are less likely to demagnetize even when the magnet temperature rises, maintaining heat resistance up to a relatively high temperature range. Compared to homogeneous magnets without additives, permanent magnets 41A also have higher heat resistance. Furthermore, compared to homogeneous magnets containing additives (i.e., magnets with additives uniformly applied throughout the magnet), permanent magnets 41A can reduce the manufacturing cost of rotor 10.

[0053] However, when the temperature of the permanent magnet 41A exceeds the specified temperature in the high temperature range, it demagnetizes rapidly, resulting in a sharp drop in heat resistance. Specifically, as described above, a coercive force distribution is formed at the axial outer end 45A of the permanent magnet 41A. In addition, the outer end 45A is a portion where magnetic flux easily flows and the magnet temperature easily rises. When the rotating electric machine is driven, when the corner 45c (see Figure 2 ) Demagnetization progresses toward the central portion, and when it develops to the low coercive force portion 412A with low coercive force, the heat resistance of the permanent magnet 41A decreases sharply.

[0054] return Figure 5 While the heat resistance of the permanent magnet 41 of this embodiment is lower than that of the permanent magnet 41A, it is higher than that of a homogeneous magnet without additives, and its heat resistance is maintained even in relatively high temperature ranges. Compared to using a homogeneous magnet containing additives (i.e., a magnet with additives uniformly added throughout the magnet), the permanent magnet 41 can reduce the manufacturing cost of the rotor 10. Furthermore, the permanent magnet 41 does not experience the rapid demagnetization that occurs with the permanent magnet 41A in high temperature ranges. This is because the axially outer end 45 of the permanent magnet 41 is uniformly formed into a high coercive force portion 411.

[0055] In this way, the permanent magnet 41 of this embodiment is accommodated in the magnet accommodating hole 31 in such a manner that the coercive force distribution direction is axial and the coercive force of the axial outer end portion 45 is greater than the coercive force of the inner portion, thereby reducing the manufacturing cost of the rotor 10 and suppressing the occurrence of rapid demagnetization caused by the increase in magnet temperature.

[0056] (First Modification)

[0057] The permanent magnets 41 stacked and accommodated in the magnet accommodation holes 31 may each have a different coercive force. Specifically, the rotor 10 may be configured so that the coercive force of the permanent magnets 41 arranged axially outward is greater than that of the permanent magnets 41 arranged inward. For example, the difference in coercive force can be achieved based on the size of the permanent magnets 41.

[0058] Figure 6The side view of the magnet group 40 is shown, in which larger permanent magnets 41L are arranged on both outer sides in the axial direction and smaller permanent magnets 41S are arranged on the inner side. Here, "larger" means that the permanent magnets 41L are relatively larger than the permanent magnets 41S, and "smaller" means that the permanent magnets 41S are relatively smaller than the permanent magnets 41L. Figure 6 In the example shown, permanent magnets 41L and permanent magnets 41S are alternately stacked. However, the arrangement of permanent magnets 41 is not limited to this. For example, a configuration may be employed in which three permanent magnets 41 of different sizes (large, medium, and small) are prepared and arranged in the order of large, medium, small, medium, and large from one axial end toward the other.

[0059] Each permanent magnet 41L, 41S is housed in the magnet housing hole 31 so that its coercive force is distributed axially. Furthermore, larger permanent magnets 41L are positioned on both axially outer sides. The sizes of the permanent magnets 41L, 41S differ due to their different axial lengths (thicknesses). The larger the permanent magnet 41, the greater its heat resistance. Therefore, by positioning the permanent magnets 41L on both axially outer sides, the coercive force of the axially outer ends 45 can be increased.

[0060] Furthermore, the permanent magnets 41L and 41S may be configured to have different sizes due to differences in their circumferential lengths.

[0061] (Second Modification)

[0062] The coercive force of the permanent magnets 41 in each magnet receiving hole 31 of each magnetic pole portion 30 may be different. Specifically, the coercive force of the permanent magnets 41 received in the magnet receiving holes 31 on the circumferential outer side of each magnetic pole portion 30 may be greater than that of the permanent magnets 41 received in the magnet receiving holes 31 on the inner side.

[0063] Figure 7 The magnetic pole portion 30 is shown in which permanent magnets 41L with a larger coercive force are arranged in the two outer magnet receiving holes 31 in the circumferential direction of the three magnet receiving holes 31, while permanent magnets 41S with a smaller coercive force are arranged in the inner magnet receiving hole 31. Here, the coercive force of permanent magnets 41L is increased by increasing their size, while the coercive force of permanent magnets 41S is reduced by reducing their size. In each magnet receiving hole 31, permanent magnets 41L and 41S are accommodated in such a way that the coercive force distribution is axially oriented.

[0064] In each magnetic pole portion 30 , magnetic flux easily flows toward the permanent magnet on the circumferential outer side. However, in this second modification, the permanent magnet 41L is arranged on the circumferential outer side where magnetic flux easily flows to increase the coercive force, thereby improving the heat resistance of the circumferential magnetic pole portion 30 .

[0065] Furthermore, the structures of the above-described Modification 1 and Modification 2 can be combined as appropriate.

[0066] While one embodiment of the present invention and various modifications have been described above with reference to the accompanying drawings, the present invention is not limited to this embodiment. Obviously, those skilled in the art will be able to conceive of various modifications or amendments within the scope of the technical solution, and it should be understood that these modifications and amendments also fall within the technical scope of the present invention. Furthermore, the various components of the above-described embodiment may be arbitrarily combined without departing from the gist of the invention.

[0067] This specification includes at least the following matters: In parentheses, corresponding components in the above-described embodiment are shown as examples, but the present invention is not limited thereto.

[0068] (1) A rotor (rotor 10) of a rotating electrical machine, comprising:

[0069] a rotor core (rotor core 20 ) having a substantially annular shape centered on a rotation axis (rotation axis RC); and

[0070] A plurality of magnetic pole portions (magnetic pole portions 30 ) are arranged along the circumference of the rotor core, wherein:

[0071] Each magnetic pole portion includes a magnet receiving hole (magnet receiving hole 31 ) formed in the rotor core and extending in the axial direction, and at least one magnet (permanent magnet 41 ) received in the magnet receiving hole.

[0072] A coercive force distribution is formed in the magnet along a predetermined direction.

[0073] The magnet is accommodated in the magnet accommodation hole such that the coercive force distribution direction is in the axial direction and the coercive force of the outer end portion (outer end portion 45 ) in the axial direction is greater than the coercive force of the inner portion in the axial direction.

[0074] According to (1), magnets with a coercive force distribution are provided at the magnetic pole portion of the rotor core, thereby maintaining heat resistance in the high-temperature region. In addition, the manufacturing cost of the rotor can be reduced compared to magnets with uniform coercive force and added heavy rare earth elements. Furthermore, the magnets are accommodated in the magnet accommodation hole in such a manner that the coercive force distribution direction is axial and the coercive force of the axial outer end portion is greater than the coercive force of the inner portion. Therefore, the coercive force is large and the coercive force distribution is uniform at the axial outer end portion where the magnetic flux easily flows. Therefore, the occurrence of rapid demagnetization caused by the increase in magnet temperature can be suppressed.

[0075] (2) The rotor of the rotating electrical machine according to (1), wherein:

[0076] A plurality of magnets (permanent magnets 41L, 41S) are housed in one of the magnet housing holes.

[0077] The coercive force of the magnet (permanent magnet 41L) arranged on the outer side in the axial direction is larger than the coercive force of the magnet (permanent magnet 41S) arranged on the inner side in the axial direction.

[0078] According to (2), the coercive force of the axially outer end portion where the magnetic flux easily flows is large, and thus the occurrence of rapid demagnetization can be suppressed more reliably.

[0079] (3) The rotor of the rotating electrical machine according to (2), wherein:

[0080] The size of the magnet disposed on the outer side in the axial direction is larger than the size of the magnet disposed on the inner side in the axial direction.

[0081] According to (3), by increasing the size of the magnet disposed on the outer side in the axial direction, the coercive force of the outer end portion in the axial direction can be increased.

[0082] (4) The rotor of the rotating electrical machine according to (3), wherein:

[0083] The magnet arranged on the outer side in the axial direction is longer in the axial direction than the magnet arranged on the inner side in the axial direction.

[0084] According to (4), by lengthening the magnet disposed on the axially outer side in the axial direction, the coercive force of the axially outer end portion can be increased.

[0085] (5) The rotor of the rotating electrical machine according to any one of (1) to (4), wherein:

[0086] Each magnetic pole portion has a plurality of magnet receiving holes along the circumferential direction.

[0087] The coercive force of the magnets (permanent magnets 41L) accommodated in the magnet accommodation holes on the circumferential outer side of each magnetic pole portion is greater than the coercive force of the magnets (permanent magnets 41S) accommodated in the magnet accommodation holes on the circumferential inner side.

[0088] According to (5), in each magnetic pole portion, the coercive force of the magnet on the outer side in the circumferential direction, where the magnetic flux easily flows, is large, and thus the occurrence of rapid demagnetization can be suppressed more reliably.

Claims

1. A rotor of a rotating electrical machine, comprising: a rotor core having a substantially annular shape centered on a rotation axis; and A plurality of magnetic pole portions are arranged along the circumference of the rotor core, wherein: Each magnetic pole portion has a magnet receiving hole formed in the rotor core and extending in the axial direction, and at least one magnet received in the magnet receiving hole. A coercive force distribution is formed in the magnet along a predetermined direction. The magnet is accommodated in the magnet accommodation hole such that the coercive force distribution direction is the axial direction and the coercive force of the outer end portion in the axial direction is greater than the coercive force of the inner portion in the axial direction.

2. The rotor of the rotating electrical machine according to claim 1, wherein A plurality of magnets are accommodated in one of the magnet accommodating holes. The coercive force of the magnet disposed on the outer side in the axial direction is greater than the coercive force of the magnet disposed on the inner side in the axial direction.

3. The rotor of the rotating electrical machine according to claim 2, wherein: The size of the magnet disposed on the outer side in the axial direction is larger than the size of the magnet disposed on the inner side in the axial direction.

4. The rotor of the rotating electrical machine according to claim 3, wherein: The magnet arranged on the outer side in the axial direction is longer in the axial direction than the magnet arranged on the inner side in the axial direction.

5. The rotor of the rotating electrical machine according to any one of claims 1 to 4, wherein: Each magnetic pole portion has a plurality of magnet receiving holes along the circumferential direction. The coercive force of the magnets accommodated in the magnet accommodation holes on the outer side in the circumferential direction of each magnetic pole portion is greater than the coercive force of the magnets accommodated in the magnet accommodation holes on the inner side in the circumferential direction.

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