Rotor of rotary electric machine

Abstract

To provide a rotor of a rotary electric machine in which occurrence of sudden demagnetization associated with an increase of a magnet temperature can be suppressed in a rotor that is provided with a magnet having a distribution of a coercive force.SOLUTION: A rotor 10 of a rotary electric machine includes a rotor core 20 having a substantially annular shape about a rotation center RC, and a plurality of magnetic pole parts 30 disposed along the circumferential direction of the rotor core 20. Each of the magnetic pole parts 30 has a magnet accommodation hole 31 formed in the rotor core 20 and extending in the axial direction, and at least one permanent magnet 41 accommodated in the magnet accommodation hole 31. In the permanent magnet 41, a distribution of a coercive force is formed in a prescribed direction. The permanent magnet 41 is accommodated in the magnet accommodation hole 31 in such a way that the direction of the distribution of a coercive force matches the axial direction and the coercive force of an outer end 45 in the axial direction is larger than the coercive force of an inner portion.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] In recent years, efforts to realize a low-carbon or carbon-free society have become more active, and research and development into electrification technologies has been conducted to reduce CO2 emissions and improve energy efficiency in vehicles. Electrification technologies include rotating electric machines such as electric motors and generators, and rotating electric machines are installed 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 magnet is a magnet with a distribution of coercive force throughout the magnet, and the coercive force of the high-temperature side permanent magnet portion located in the high-temperature portion inside the motor is set higher than the coercive force of the low-temperature side permanent magnet portion located in the low-temperature portion inside the motor that is cooler than the high-temperature side permanent magnet portion. This achieves a motor with high motor characteristics and low cost. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6841130 Summary of the Invention [Problem to be solved by the invention]

[0005] In motors including permanent magnets with a coercive force distribution in a single magnet, such as that described in Patent Document 1, rapid demagnetization can occur in parts of the permanent magnet with low coercive force as the magnet temperature rises, leaving room for improvement.

[0006] The present invention provides a rotor for a rotating electrical machine that is provided with magnets having a distribution of coercive force and that can suppress the occurrence of sudden demagnetization that accompanies a rise in magnet temperature. [Means for solving the problem]

[0007] The present invention provides a rotor core having a substantially annular shape centered on a rotation axis; a plurality of magnetic pole portions provided along a circumferential direction of the rotor core, Each magnetic pole portion has a magnet accommodating hole formed in the rotor core and extending in the axial direction, and at least one magnet accommodated in the magnet accommodating hole, The magnet has a coercive force distribution formed in a predetermined direction, The magnet is accommodated in the magnet accommodating hole so that the direction of the distribution of the coercive force is the axial direction and so that the coercive force at the outer end in the axial direction is greater than the coercive force at the inner portion. [Effects of the Invention]

[0008] According to the present invention, it is possible to suppress the occurrence of sudden demagnetization that accompanies a rise in magnet temperature. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of a rotor 10 of a rotating electrical machine according to an embodiment of the present invention. [Figure 2] 1 is a view of the permanent magnet 41 housed in the magnet housing hole 31 as seen from the axial direction of the rotor 10. FIG. [Figure 3] 1 is a perspective view of a permanent magnet 41 accommodated in a magnet accommodating hole 31 so that the direction of the distribution of coercive force is the axial direction. [Figure 4] 10 is a perspective view of a permanent magnet 41A accommodated in a magnet accommodating hole 31 so that the direction of the distribution of coercive force is the radial direction. FIG. [Figure 5] 1 shows an example of a graph comparing the heat resistance of several types of permanent magnets. [Figure 6]10 shows a side view of a magnet group 40 of a first modified example in which large permanent magnets 41L are arranged on both outer sides in the axial direction and small permanent magnets 41S are arranged on the inner side. [Figure 7] 10 shows a magnetic pole portion 30 of a second modified example in which the coercive force of the permanent magnet 41 is differentiated for each magnet accommodating hole 31. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of a rotor for a rotating electric machine according to the present invention will be described below with reference to the accompanying drawings. In this specification, the terms axial, radial, and circumferential refer to directions based on the rotational axis of the rotor. Furthermore, the axially inner side refers to the center side of the rotor in the axial direction, and the axially outer side refers to the side away from the center of the rotor in the axial direction. Furthermore, the circumferentially inner side refers to the circumferential center side of the magnetic pole portion, and the circumferentially outer side refers to the side away from the circumferential center of the magnetic pole portion.

[0011] 1 and 2, a rotor 10 of a 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 provided along the circumferential direction of the rotor core 20. Although not shown, the rotating electric machine also includes the rotor 10 and a stator to which a coil is attached, and the rotor 10 is rotationally driven by interaction between a magnetic field of the stator generated by passing a current through the coil and a magnetic field of the rotor 10 generated by permanent magnets 41 (described later) attached to the rotor 10.

[0012] The rotor core 20 is formed by stacking a plurality of magnetic steel plates, each having a substantially annular shape, in the axial direction. A through-hole 21 is formed in the center of the rotor core 20, penetrating the rotor core 20 in the axial direction, and a rotor shaft (not shown) is press-fitted into the through-hole 21.

[0013] A plurality of (here, 12) magnetic pole portions 30 are provided at equal intervals along the circumferential direction at radially outer positions of the rotor core 20. Each magnetic pole portion 30 has a magnet accommodating hole 31 that is formed in the rotor core 20 and extends in the axial direction, and a permanent magnet 41 accommodated in the magnet accommodating hole 31. Note that reference numeral 45 in FIG. 2 denotes the outer end portion of the permanent magnet 41 in the axial direction.

[0014] Each magnetic pole portion 30 is provided with three magnet accommodating holes 31. The three magnet accommodating holes 31 are arranged in a substantially U-shape that opens toward the outside of the rotor core 20. Each magnet accommodating hole 31 accommodates at least one permanent magnet 41.

[0015] Fig. 3 shows an example of a permanent magnet 41 housed in one magnet housing hole 31. Note that the shades of color given to the permanent magnet 41 in Fig. 3 are conceptually given to explain the distribution of coercive force, which will be described later.

[0016] A plurality of permanent magnets 41 (four in this example) are stacked in the axial direction and housed in the magnet accommodating holes 31. Each permanent magnet 41 has a rectangular parallelepiped shape. In this specification, a plurality of permanent magnets 41 stacked and housed in one magnet accommodating hole 31 may be collectively referred to as a magnet group 40. The magnet group 40 may also be composed of one long permanent magnet 41 inserted into each magnet accommodating hole 31.

[0017] Permanent magnet 41 has a high coercivity portion (high coercivity portion 411) and a low coercivity portion (low coercivity portion 412) within a single magnet, i.e., it is a magnet with a distribution of coercivity. Here, "high coercivity" means that high coercivity portion 411 has a relatively higher coercivity than low coercivity portion 412, and "low coercivity" means that low coercivity portion 412 has a relatively lower coercivity than high coercivity portion 411. Note that there is no clear division between high coercivity portion 411 and low coercivity portion 412.

[0018] Coercivity is a resistance force that maintains the initial magnetic force by withstanding environmental loads such as thermal history that tend to cause loss of magnetic force and opposing magnetic fields. The high coercivity portion 411 is a portion that is less susceptible to demagnetization (i.e., weakening of magnetic force) when placed in a high-temperature environment, for example, and can also be described as a portion with high heat resistance. The low coercivity portion 412 is a portion that is more susceptible to demagnetization when placed in a high-temperature environment, for example, and can also be described as a portion with low heat resistance.

[0019] 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 permanent magnet 41 is formed to have a uniform coercive force 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.

[0020] The permanent magnets 41 are accommodated in the magnet accommodating holes 31 so that the direction of coercive force distribution is the axial direction of the rotor 10 and so that the coercive force of the axial outer end 45 is greater than the coercive force of the inner portion. More specifically, each permanent magnet 41 is accommodated in the magnet accommodating hole 31 so that a high coercive force portion 411 is provided on the axial outer side and a low coercive force portion 412 is provided on the axial inner side. In addition, the high coercive force portions 411 are arranged at the axial outer end 45 of each of the multiple permanent magnets 41.

[0021] The outer end 45 in the axial direction of the permanent magnet 41 is a portion through which magnetic flux flows easily and where the magnet temperature is likely to rise. As will be described in detail later, while the rotating electric machine is running, demagnetization progresses from the corners 45c of the outer end 45 of the permanent magnet 41 to the center (see the black arrows) as shown in Figure 2, but because the outer end 45 is a uniformly high coercive force portion 411, the occurrence of rapid demagnetization due to a rise in magnet temperature is suppressed.

[0022] Next, the heat resistance of the permanent magnet 41 will be explained by comparing it with the permanent magnet 41A that is accommodated in the magnet accommodating hole 31 so that the direction of the distribution of the coercive force is the radial direction of the rotor 10, and a permanent magnet whose coercive force is uniform within a single magnet (hereinafter also referred to as a uniform magnet).

[0023] 4 (magnet group 40A) is a magnet having a distribution of coercive force within a single magnet, similar to the permanent magnet 41 of this embodiment, but is housed in the magnet housing hole 31 so that the direction of the distribution of coercive force is perpendicular to the axial direction of the rotor 10, for example, the radial direction. A distribution of coercive force appears at the outer axial end 45A of the permanent magnet 41A, that is, a high coercive force portion 411A having a high coercive force and a low coercive force portion 412A having a low coercive force are formed.

[0024] Figure 5 is an example of a graph comparing the heat resistance of several types of permanent magnets, with the horizontal axis representing magnet temperature and the vertical axis representing the heat resistance of the magnet. The higher the heat resistance on the vertical axis, the higher the heat resistance. The thin dashed line is a graph for a homogeneous magnet without heavy rare earth or other additives. The thick dashed line is a graph for a homogeneous magnet in which heavy rare earth or other additives have been added to the entire magnet. The thin solid line is a graph for permanent magnet 41A in which the coercive force distribution direction is radial. The thick solid line is a graph for permanent magnet 41 of this embodiment in which the coercive force distribution direction is axial.

[0025] When a rotating electric machine is in operation, the heat generated by the machine affects the permanent magnets, causing the magnet temperature to rise. This basically leads to demagnetization of the permanent magnets and a decrease in their heat resistance. In other words, as the magnet temperature rises, a voltage drop occurs in the rotating electric machine, causing a decrease in the output of the rotating electric machine.

[0026] As shown in Figure 5, homogeneous magnets without additives undergo demagnetization relatively easily as the magnet temperature rises, and their heat resistance gradually decreases. In particular, heat resistance decreases significantly in the high temperature range.

[0027] Uniform magnets with additives are less likely to demagnetize as the magnet temperature rises, and maintain their heat resistance up to high temperatures. However, because the additives are added to the entire magnet, rotors 10 equipped with uniform magnets with additives increase manufacturing costs.

[0028] The permanent magnet 41A, which has a radial distribution of coercive force, is less likely to demagnetize even as the magnet temperature rises, and maintains its heat resistance up to relatively high temperatures. The permanent magnet 41A also has higher heat resistance than a homogeneous magnet without additives. Furthermore, the permanent magnet 41A can reduce the manufacturing costs of the rotor 10 compared to a homogeneous magnet with additives (i.e., a magnet in which the additive is uniformly applied throughout the magnet).

[0029] However, when the temperature of permanent magnet 41A exceeds a predetermined temperature in the high-temperature range, it undergoes a sudden demagnetization, resulting in a rapid decline in its heat resistance. To explain in more detail, as described above, the axial outer end 45A of permanent magnet 41A has a distribution of coercive force, and outer end 45A is a portion through which magnetic flux flows easily, making it prone to a rise in magnet temperature. While the rotating electric machine is running, demagnetization progresses from corner 45c (see FIG. 2) of permanent magnet 41A toward the center, and when it progresses to low-coercive force portion 412A, where coercive force is low, the heat resistance of permanent magnet 41A rapidly declines.

[0030] Returning to FIG. 5, the permanent magnet 41 of this embodiment has lower heat resistance than the permanent magnet 41A, but higher heat resistance than a homogeneous magnet without additives, and maintains its heat resistance up to relatively high temperatures. The permanent magnet 41 can reduce the manufacturing costs of the rotor 10 compared to when a homogeneous magnet with additives (i.e., a magnet in which the additive is uniformly added throughout the magnet) is used. Furthermore, the permanent magnet 41 does not experience the sudden demagnetization that occurs with the permanent magnet 41A in high temperature regions. This is because the axial outer end 45 of the permanent magnet 41 is a uniformly high coercive force portion 411.

[0031] In this way, the permanent magnet 41 of this embodiment is accommodated in the magnet accommodating hole 31 so that the direction of the distribution of the coercive force is axial and so that the coercive force of the axial outer end 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 sudden demagnetization due to an increase in magnet temperature.

[0032] (First Modification) The magnitude of the coercive force may be different for each permanent magnet 41 housed in a stacked state in the magnet housing hole 31. Specifically, the rotor 10 may be configured so that the permanent magnets 41 arranged on the outer side in the axial direction have a greater coercive force than the permanent magnets 41 arranged on the inner side. The magnitude of the coercive force may be different depending on the size of the permanent magnets 41, for example.

[0033] FIG. 6 shows a side view of the magnet assembly 40 in which large permanent magnets 41L are arranged on both outer sides in the axial direction and small permanent magnets 41S are arranged on the inner side. Here, "large" means that the permanent magnets 41L are relatively larger than the permanent magnets 41S, and "small" means that the permanent magnets 41S are relatively smaller than the permanent magnets 41L. In the example shown in FIG. 6, the permanent magnets 41L and 41S are alternately stacked, but the arrangement of the permanent magnets 41 is not limited to this. For example, three permanent magnets 41 of different sizes (large, medium, and small) may be prepared and arranged in the order large, medium, small, medium, and large from one end to the other in the axial direction.

[0034] Each permanent magnet 41L, 41S is housed in the magnet housing hole 31 so that the distribution of coercive force is in the axial direction, and larger permanent magnets 41L are arranged on both outer axial sides. The permanent magnets 41L, 41S differ in size due to their different axial lengths (thicknesses). The larger the size of the permanent magnet 41, the greater its heat resistance. Therefore, by arranging the permanent magnets 41L on both outer axial sides, the coercive force of the outer axial end 45 can be increased.

[0035] The permanent magnets 41L and 41S may have different sizes due to their different circumferential lengths.

[0036] (Second Modification) In each magnetic pole portion 30, the permanent magnets 41 may have different coercive forces for each magnet accommodating hole 31. Specifically, the permanent magnets 41 accommodated in the outer magnet accommodating holes 31 in the circumferential direction of each magnetic pole portion 30 may have a greater coercive force than the permanent magnets 41 accommodated in the inner magnet accommodating holes 31.

[0037] 7 shows a magnetic pole section 30 in which permanent magnets 41L with large coercive force are placed in the two outermost magnet accommodating holes 31 in the circumferential direction of the three magnet accommodating holes 31, and permanent magnets 41S with small coercive force are placed in the innermost magnet accommodating hole 31. Here, the permanent magnets 41L are large in size to increase their coercive force, and the permanent magnets 41S are small in size to decrease their coercive force. In each magnet accommodating hole 31, each permanent magnet 41L, 41S is accommodated in the magnet accommodating hole 31 so that the distribution of coercive force is in the axial direction.

[0038] In each magnetic pole portion 30, magnetic flux tends to flow easily through the permanent magnets on the circumferential outside, but in this modified example 2, the permanent magnet 41L is positioned on the circumferential outside where magnetic flux tends to flow easily, and the coercive force is increased, thereby improving the heat resistance of the magnetic pole portion 30 in the circumferential direction.

[0039] The configurations of the above-described modified example 1 and modified example 2 can be combined as appropriate.

[0040] Although one embodiment of the present invention and various modifications thereof have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such an embodiment. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above embodiment may be combined in any manner without departing from the spirit of the invention.

[0041] This specification describes at least the following: In parentheses, components corresponding to those in the above-described embodiments are shown as examples, but the present invention is not limited to these.

[0042] (1) a rotor core (rotor core 20) having a substantially annular shape centered on a rotation axis (rotation axis RC); A rotor (rotor 10) for a rotating electric machine including a plurality of magnetic pole portions (magnetic pole portions 30) provided along the circumferential direction of the rotor core, Each magnetic pole portion has a magnet accommodating hole (magnet accommodating hole 31) formed in the rotor core and extending in the axial direction, and at least one magnet (permanent magnet 41) accommodated in the magnet accommodating hole, The magnet has a coercive force distribution formed in a predetermined direction, The magnet is accommodated in the magnet accommodating hole so that the direction of the distribution of the coercive force is the axial direction and so that the coercive force of the outer end (outer end 45) in the axial direction is greater than the coercive force of the inner portion. Rotor of a rotating electric machine.

[0043] According to (1), magnets with a coercive force distribution are provided in the magnetic pole portions of the rotor core, allowing for heat resistance up to high temperatures. Furthermore, the rotor manufacturing costs can be reduced compared to magnets with uniform coercive force and added heavy rare earth elements. Furthermore, the magnets are housed in the magnet housing holes so that the coercive force distribution is axial and the coercive force at the outer axial end is greater than that at the inner portion. Therefore, the coercive force is greater and the coercive force distribution is uniform at the outer axial end, where magnetic flux flows more easily. This prevents rapid demagnetization due to rising magnet temperature.

[0044] (2) A rotor for a rotating electric machine according to (1), A plurality of magnets (permanent magnets 41L, 41S) are accommodated in one of the magnet accommodating holes, The magnet (permanent magnet 41L) arranged on the outside in the axial direction has a larger coercive force than the magnet (permanent magnet 41S) arranged on the inside. Rotor of a rotating electric machine.

[0045] According to (2), the coercive force is large at the outer end in the axial direction where magnetic flux flows easily, so that the occurrence of sudden demagnetization can be more reliably suppressed.

[0046] (3) A rotor for a rotating electric machine according to (2), The magnets arranged on the outer side in the axial direction are larger in size than the magnets arranged on the inner side. Rotor of a rotating electric machine.

[0047] According to (3), by increasing the size of the magnets arranged on the outside in the axial direction, the coercive force at the outer end in the axial direction can be increased.

[0048] (4) A rotor for a rotating electric machine according to (3), The magnets arranged on the outer side in the axial direction are longer in the axial direction than the magnets arranged on the inner side. Rotor of a rotating electric machine.

[0049] According to (4), by making the magnets arranged on the outer side in the axial direction longer in the axial direction, the coercive force at the outer end in the axial direction can be increased.

[0050] (5) A rotor for a rotating electric machine according to any one of (1) to (4), Each magnetic pole portion has a plurality of the magnet accommodating holes along the circumferential direction, The magnet (permanent magnet 41L) accommodated in the magnet accommodating hole on the outer side in the circumferential direction of each magnetic pole portion has a larger coercive force than the magnet (permanent magnet 41S) accommodated in the magnet accommodating hole on the inner side. Rotor of a rotating electric machine.

[0051] According to (5), the coercive force of the magnets on the outer circumferential side, where magnetic flux flows easily, is large in each magnetic pole portion, so that the occurrence of sudden demagnetization can be more reliably suppressed. [Explanation of symbols]

[0052] 10 rotors 20 rotor core 30 Magnetic pole part 31 Magnet receiving hole 41 Permanent magnets (magnets) 45 Outer edge RC rotation axis

Claims

1. a rotor core having a substantially annular shape centered on a rotation axis; a plurality of magnetic pole portions provided along a circumferential direction of the rotor core, Each magnetic pole portion has a magnet accommodating hole formed in the rotor core and extending in the axial direction, and at least one magnet accommodated in the magnet accommodating hole, The magnet has a coercive force distribution formed in a predetermined direction, The magnet is accommodated in the magnet accommodating hole so that the direction of the distribution of the coercive force is the axial direction and so that the coercive force of the outer end portion in the axial direction is greater than the coercive force of the inner portion. Rotor of a rotating electric machine.

2. 2. The rotor of a rotating electric machine according to claim 1, A plurality of magnets are accommodated in each of the magnet accommodating holes, The magnets arranged on the outside in the axial direction have a larger coercive force than the magnets arranged on the inside. Rotor of a rotating electric machine.

3. 3. The rotor of a rotating electric machine according to claim 2, The magnets arranged on the outer side in the axial direction are larger in size than the magnets arranged on the inner side. Rotor of a rotating electric machine.

4. 4. The rotor of a rotating electric machine according to claim 3, The magnets arranged on the outer side in the axial direction are longer in the axial direction than the magnets arranged on the inner side. Rotor of a rotating electric machine.

5. A rotor for a rotating electric machine according to any one of claims 1 to 4, Each magnetic pole portion has a plurality of the magnet accommodating holes along the circumferential direction, the magnets accommodated in the magnet accommodating holes on the outer side in the circumferential direction of each magnetic pole portion have a larger coercive force than the magnets accommodated in the magnet accommodating holes on the inner side; Rotor of a rotating electric machine.

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