Rotor of a rotating electric machine
The rotor design with axially aligned, higher-coercivity outer magnets and varying sizes addresses rapid demagnetization and heat resistance issues, enhancing motor performance and cost-effectiveness.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- HONDA MOTOR CO LTD
- Filing Date
- 2024-04-12
- Publication Date
- 2026-07-02
AI Technical Summary
Rapid demagnetization occurs in permanent magnets of rotating electrical machines due to temperature rise, particularly in low-coercivity regions, leading to reduced motor performance and increased manufacturing costs when using magnets with uniform additives.
A rotor design with a coercivity distribution where outer magnets have higher coercivity than inner magnets, aligned axially, and varying magnet sizes to enhance heat resistance and suppress demagnetization.
Suppresses rapid demagnetization at high temperatures, maintains heat resistance, and reduces manufacturing costs by using strategically positioned magnets with varying coercivity and sizes.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a rotor of a rotating electrical machine provided with a magnet having a distribution of coercive force.
Background Art
[0002] In recent years, efforts to achieve a low-carbon society or a decarbonized society have been actively pursued, and in vehicles as well, research and development on electrification technologies have been conducted to reduce CO2 emissions and improve energy efficiency. As an electrification technology, there is, for example, a rotating electrical machine such as an electric motor or a generator, and the rotating electrical machine is mounted on electric vehicles such as battery electric vehicles, hybrid vehicles, fuel cell vehicles, etc.
[0003] For example, Patent Document 1 discloses a motor including a rotor and a permanent magnet. In the motor of Patent Document 1, the permanent magnet is a magnet having a coercive force distribution in one body, and the coercive force of the high-temperature side permanent magnet portion located at a high-temperature portion inside the motor is set higher than the coercive force of the low-temperature side permanent magnet portion located at a low-temperature portion inside the motor where the temperature is lower than that of the high-temperature side permanent magnet portion. Thereby, a motor with high motor characteristics and low cost is realized.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] In a motor including a permanent magnet having a coercive force distribution in one body as described in Patent Document 1, rapid demagnetization may occur in a portion of the permanent magnet where the coercive force is low as the magnet temperature rises, and there is room for improvement.
[0006] The present invention provides a rotor for a rotating electric machine that can suppress the occurrence of rapid demagnetization due to a rise in magnet temperature, in a rotor equipped with magnets having a distribution of coercivity. [Means for solving the problem]
[0007] The present invention A rotor core having a roughly ring-shaped centered on the axis of rotation, A rotor of a rotating electric machine comprising a plurality of magnetic pole portions provided along the circumferential direction of the rotor core, Each magnetic pole portion has a magnet housing hole that extends axially formed in the rotor core, and is housed in the magnet housing hole. magnet It has stone, The aforementioned magnet has a coercive force distribution formed in a predetermined direction within a single unit. The magnet is housed in the magnet housing hole such that the direction of the distribution of coercivity is in the axial direction, and the coercivity at the outer end in the axial direction is greater than the coercivity at the inner portion. 、 Multiple magnets are housed in one of the magnet housing holes. The magnets positioned on the outside in the axial direction have a greater coercivity than the magnets positioned on the inside. The magnets positioned on the outside in the axial direction are larger in size than the magnets positioned on the inside. . [Effects of the Invention]
[0008] According to the present invention, it is possible to suppress the occurrence of rapid demagnetization that occurs when the magnet temperature rises. [Brief explanation of the drawing]
[0009] [Figure 1] A perspective view of rotor 10 of a rotating electric machine according to one embodiment of the present invention. [Figure 2] This 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. [Figure 3] This is a perspective view of a permanent magnet 41 housed in a magnet housing hole 31 such that the direction of the coercivity distribution is axial. [Figure 4] This is a perspective view of a permanent magnet 41A housed in a magnet housing hole 31 such that the direction of the coercivity distribution is radial. [Figure 5] An example of a graph comparing the heat resistance of several types of permanent magnets is shown. [Figure 6] This is a side view of the magnet group 40 of the first modified example, 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 inside. [Figure 7] The second modified example shows a magnetic pole section 30 in which the coercivity of the permanent magnet 41 is varied for each magnet housing hole 31. [Modes for carrying out the invention]
[0010] Hereinafter, an embodiment of the rotor of the rotating electric machine of the present invention will be described based on the attached drawings. In this specification, the terms axial, radial, and circumferential directions refer to directions relative to the rotation axis of the rotor. Furthermore, the axial inner side refers to the central side of the rotor in the axial direction, and the axial outer side refers to the side away from the center of the rotor in the axial direction. Furthermore, the circumferential inner side refers to the circumferential center side of the magnetic pole portion, and the circumferential outer side refers to the side away from the circumferential center of the magnetic pole portion.
[0011] As shown in Figures 1 and 2, the rotor 10 of the rotating electric machine comprises a rotor core 20 having a substantially annular shape centered on the rotation axis RC, and a plurality of magnetic pole portions 30 provided along the circumferential direction of the rotor core 20. Although not shown in the figures, the rotating electric machine comprises a rotor 10 and a stator to which coils are attached. The magnetic field of the stator generated by passing current through the coils interacts with the magnetic field of the rotor 10 generated by permanent magnets 41 attached to the rotor 10 (described later), thereby driving the rotor 10 to rotate.
[0012] The rotor core 20 is formed by stacking multiple electromagnetic steel sheets, each having a roughly annular shape, in the axial direction. A through hole 21 is formed in the center of the rotor core 20, penetrating in the axial direction, and a rotor shaft (not shown) is press-fitted and fixed into the through hole 21.
[0013] A plurality (here, 12) of magnetic pole portions 30 are provided at equal intervals along the circumferential direction at a position radially outside the rotor core 20. Each magnetic pole portion 30 has a magnet accommodation hole 31 extending in the axial direction formed in the rotor core 20 and a permanent magnet 41 accommodated in the magnet accommodation hole 31. Note that the reference numeral 45 in FIG. 2 represents the outer end portion of the permanent magnet 41 in the axial direction.
[0014] Each magnetic pole portion 30 is provided with three magnet accommodation holes 31. The three magnet accommodation holes 31 are arranged in a substantially U-shape opening toward the outside of the rotor core 20. At least one permanent magnet 41 is accommodated in each magnet accommodation hole 31.
[0015] FIG. 3 shows an example of the permanent magnet 41 accommodated in one magnet accommodation hole 31. Note that the shading of the color attached to the permanent magnet 41 in FIG. 3 is conceptually attached to explain the distribution of the coercive force described later.
[0016] A plurality (here, 4) of permanent magnets 41 are laminated in the axial direction and accommodated in the magnet accommodation hole 31. Each permanent magnet 41 has a rectangular parallelepiped shape. In this specification, the permanent magnets 41 laminated and accommodated in one magnet accommodation hole 31 may be collectively referred to as a magnet group 40. Further, the magnet group 40 may be constituted by one long permanent magnet 41 inserted through each magnet accommodation hole 31.
[0017] The permanent magnet 41 has a portion with a high coercive force (high coercive force portion 411) and a portion with a low coercive force (low coercive force portion 412) in one body, that is, it is a magnet having a distribution of coercive force. Here, "high coercive force" means that the high coercive force portion 411 has a relatively higher coercive force than the low coercive force portion 412, and "low coercive force" means that the low coercive force portion 412 has a relatively lower coercive force than the high coercive force portion 411. Note that it should be noted that there is no clear boundary between the high coercive force portion 411 and the low coercive force portion 412.
[0018] Coercivity is the resistance force that maintains the initial magnetic force against environmental stresses such as thermal history and reverse magnetic fields that would otherwise cause the magnetic force to be lost. The high-coercivity section 411 is the part that experiences less demagnetization (i.e., weakening of magnetic force) when placed in a high-temperature environment, and can also be described as having high heat resistance. The low-coercivity section 412 is the part that experiences a greater degree of demagnetization when placed in a high-temperature environment, and can also be described as having low heat resistance.
[0019] The coercivity of the permanent magnet 41 is formed to have a gradient in one direction. Specifically, the permanent magnet 41 has high coercivity sections 411 formed on both outer sides in a predetermined direction, and a low coercivity section 412 formed between the high coercivity sections 411, i.e., on the inside in the predetermined direction. Furthermore, the coercivity of the permanent magnet 41 is uniform in a direction perpendicular to the predetermined direction. In this specification, "uniform coercivity" means that the coercivity is within a predetermined tolerance range.
[0020] The permanent magnets 41 are housed in the magnet housing holes 31 such that the direction of the coercivity distribution is in the axial direction of the rotor 10, and that the coercivity of the outer axial end 45 is greater than that of the inner portion. More specifically, each permanent magnet 41 is housed in the magnet housing holes 31 such that a high coercivity portion 411 is provided on the axially outer side and a low coercivity portion 412 is provided on the axially inner side. In addition, high coercivity portions 411 are arranged at the axially outer end 45 of multiple permanent magnets 41.
[0021] The outer axial end 45 of the permanent magnet 41 is a part where magnetic flux flows easily and the magnet temperature tends to rise. As will be described in detail later, during the operation of the rotating electric machine, demagnetization progresses from the corner 45c of the outer end 45 of the permanent magnet 41 to the center (see black arrows), but since the outer end 45 is a uniformly high coercivity area 411, the occurrence of rapid demagnetization due to the rise in magnet temperature is suppressed.
[0022] Next, regarding the heat resistance of the permanent magnet 41, we will explain it by comparing it with a permanent magnet 41A housed in a magnet housing hole 31 such that the direction of the coercivity distribution is in the radial direction of the rotor 10, and a permanent magnet in which the coercivity is uniform within a single unit (hereinafter also referred to as a uniform magnet).
[0023] The permanent magnet 41A (magnet group 40A) shown in Figure 4 is a magnet that has a distribution of coercivity within a single object, similar to the permanent magnet 41 in this embodiment. However, it is housed in the magnet housing hole 31 such that the direction of the coercivity distribution is perpendicular to the axial direction of the rotor 10, for example, in the radial direction. At the outer end 45A in the axial direction of the permanent magnet 41A, a distribution of coercivity appears, forming a high-coercivity portion 411A, which is a portion with high coercivity, and a low-coercivity portion 412A, which is a portion with low coercivity.
[0024] Figure 5 is an example of a graph comparing the heat resistance of several types of permanent magnets, where the horizontal axis represents the magnet temperature and the vertical axis represents the heat resistance of the magnet. The higher the position on the vertical axis, the higher the heat resistance. The thin dashed line is the graph of a uniform magnet without additives such as heavy rare earth elements. The thick dashed line is the graph of a uniform magnet with additives such as heavy rare earth elements added to the entire magnet. The thin solid line is the graph of permanent magnet 41A, where the direction of the coercivity distribution is radial. The thick solid line is the graph of permanent magnet 41 of this embodiment, where the direction of the coercivity distribution is axial.
[0025] When a rotating electric machine is in operation, the heat generated by the machine affects the permanent magnets, causing their temperature to rise. This essentially leads to demagnetization of the permanent magnets and a decrease in their heat resistance. In other words, a high magnet temperature causes a voltage drop in the rotating electric machine, reducing its output.
[0026] As shown in Figure 5, a homogeneous magnet without additives demagnetizes relatively easily as the magnet temperature rises, and its heat resistance gradually decreases. In particular, the heat resistance decreases significantly at high temperatures.
[0027] Uniform magnets with additives are less prone to demagnetization even when the magnet temperature rises, and their heat resistance is maintained up to high temperatures. However, because the additives are added to the entire magnet, the rotor 10 equipped with uniform magnets containing additives has increased manufacturing costs.
[0028] The permanent magnet 41A, which has a radial distribution of coercivity, is less prone to demagnetization even when the magnet temperature rises, and maintains its heat resistance up to relatively high temperatures. The permanent magnet 41A also has higher heat resistance compared to the case where a uniform magnet without additives is used. Furthermore, the permanent magnet 41A can reduce the manufacturing cost of the rotor 10 compared to the case where a uniform magnet with additives (i.e., a magnet in which the additive is uniformly added throughout the magnet) is used.
[0029] However, when the permanent magnet 41A exceeds a predetermined temperature in the high-temperature range, rapid demagnetization occurs, causing a sharp decrease in heat resistance. To explain in more detail, as mentioned above, a coercive force distribution is formed at the outer axial end 45A of the permanent magnet 41A, and the outer end 45A is a part where magnetic flux flows easily and the magnet temperature tends to rise. During the operation of the rotating electric machine, demagnetization progresses from the corner 45c (see Figure 2) of the permanent magnet 41A to the center, and when it progresses to the low-coercive force section 412A, the heat resistance of the permanent magnet 41A decreases sharply.
[0030] Returning to Figure 5, the permanent magnet 41 of this embodiment has lower heat resistance than the permanent magnet 41A, but higher heat resistance than a uniform magnet without additives, and maintains heat resistance up to relatively high temperatures. The permanent magnet 41 can reduce the manufacturing cost of the rotor 10 compared to using a uniform magnet with additives (i.e., a magnet in which the additive is uniformly added throughout the entire magnet). Furthermore, the permanent magnet 41 does not experience the rapid demagnetization seen in the permanent magnet 41A at high temperatures. This is because the outer axial end 45 of the permanent magnet 41 is uniformly a high-coercivity section 411.
[0031] Thus, in this embodiment, the permanent magnet 41 is housed in the magnet housing hole 31 such that the direction of the coercivity distribution is axial, and the coercivity of the outer end 45 in the axial direction is greater than that of the inner portion. This reduces the manufacturing cost of the rotor 10 and suppresses the occurrence of rapid demagnetization due to the rise in magnet temperature.
[0032] (First variation) The coercivity of each permanent magnet 41 stacked and housed in the magnet housing hole 31 may be varied. Specifically, the rotor 10 may be configured such that the permanent magnets 41 positioned on the outer side in the axial direction have greater coercivity than the permanent magnets 41 positioned on the inner side. The coercivity can be varied, for example, by the size of the permanent magnets 41.
[0033] Figure 6 shows a side view of a magnet group 40 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 inside. Here, "larger size" means that the permanent magnets 41L are relatively larger than the permanent magnets 41S, and "smaller size" means that the permanent magnets 41S are relatively smaller than the permanent magnets 41L. In the example shown in Figure 6, the permanent magnets 41L and permanent magnets 41S are stacked alternately, 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 of 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 such that the distribution of coercivity is axial, and larger permanent magnets 41L are positioned on both outer sides in the axial direction. Each permanent magnet 41L, 41S differs in size from the others due to their different lengths (thickness) in the axial direction. The heat resistance of a permanent magnet 41 increases as its size increases. Therefore, by positioning the permanent magnets 41L on both outer sides in the axial direction, the coercivity of the outer end 45 in the axial direction can be increased.
[0035] Furthermore, the permanent magnets 41L and 41S may be configured to have different sizes from each other by having different lengths in the circumferential direction.
[0036] (Second variation) In each magnetic pole section 30, the coercivity of the permanent magnets 41 may be varied for each magnet housing hole 31. Specifically, the permanent magnets 41 housed in the outer magnet housing holes 31 in the circumferential direction of each magnetic pole section 30 may have a greater coercivity than the permanent magnets 41 housed in the inner magnet housing holes 31.
[0037] Figure 7 shows the magnetic pole section 30 in which permanent magnets 41L with high coercivity are placed in the outermost magnet housing holes 31 in the circumferential direction, and permanent magnets 41S with low coercivity are placed in the inner magnet housing hole 31. Here, the size of the permanent magnet 41L is increased to increase its coercivity, and the size of the permanent magnet 41S is decreased to decrease its coercivity. In each magnet housing hole 31, the permanent magnets 41L and 41S are housed in the magnet housing hole 31 such that the distribution of coercivity is axial.
[0038] In each magnetic pole section 30, magnetic flux tends to flow to the permanent magnet on the outer circumferential side. However, in this modified example 2, the permanent magnet 41L is positioned on the outer circumferential side where magnetic flux flows more easily, and the coercivity is increased, thereby improving the heat resistance of the magnetic pole section 30 in the circumferential direction.
[0039] The configurations of the aforementioned modified examples 1 and 2 can be combined as appropriate.
[0040] Although one embodiment of the present invention and various modifications have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to these embodiments. It is clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these are also understood to naturally fall within the technical scope of the present invention. Furthermore, the components of the above embodiments may be combined in any way without departing from the spirit of the invention.
[0041] This specification includes at least the following: The components and other elements corresponding to those in the embodiments described above are shown in parentheses as examples, but are not limited thereto.
[0042] (1) A rotor core (rotor core 20) having a roughly annular shape centered on the rotation axis (rotation axis RC), A rotor (rotor 10) of a rotating electric machine comprising a plurality of magnetic pole portions (magnetic pole portion 30) provided along the circumferential direction of the rotor core, Each magnetic pole portion has an axially extending magnet housing hole (magnet housing hole 31) formed in the rotor core, and at least one magnet (permanent magnet 41) housed in the magnet housing hole. The magnet has a coercive force distribution formed in a predetermined direction. The magnet is housed in the magnet housing hole such that the direction of the distribution of coercivity is in the axial direction, and the coercivity of the outer end (outer end 45) in the axial direction is greater than the coercivity of the inner portion. Rotor of a rotating electric machine.
[0043] According to (1), since magnets with a distribution of coercivity are provided in the magnetic pole portion of the rotor core, heat resistance can be maintained up to high temperatures, and the manufacturing cost of the rotor can be reduced compared to magnets with uniform coercivity and the addition of heavy rare earth elements. Furthermore, since the magnets are housed in the magnet housing holes such that the direction of the distribution of coercivity is axial, and the coercivity at the outer end in the axial direction is greater than that at the inner part, the coercivity is large and the distribution of coercivity is uniform at the outer end in the axial direction where magnetic flux flows easily. Therefore, the occurrence of rapid demagnetization due to the rise in magnet temperature can be suppressed.
[0044] (2) The rotor of the rotating electric machine described in (1), Multiple magnets (permanent magnets 41L, 41S) are housed in one of the magnet housing holes. The magnet (permanent magnet 41L) positioned on the outside in the axial direction has a greater coercivity than the magnet (permanent magnet 41S) positioned on the inside. Rotor of a rotating electric machine.
[0045] According to (2), the coercivity is greater at the outer end in the axial direction where magnetic flux flows easily, so the occurrence of rapid demagnetization can be suppressed more reliably.
[0046] (3) The rotor of the rotating electric machine described in (2), The magnets positioned on the outside in the axial direction are larger in size than the magnets positioned on the inside. Rotor of a rotating electric machine.
[0047] According to (3), the coercivity of the outer end in the axial direction can be increased by increasing the size of the magnets positioned on the outer side in the axial direction.
[0048] (4) The rotor of the rotating electric machine described in (3), The magnets positioned on the outside in the axial direction are longer in the axial direction than the magnets positioned on the inside. Rotor of a rotating electric machine.
[0049] According to (4), by making the magnets positioned on the outer side in the axial direction longer in the axial direction, the coercivity of the outer end in the axial direction can be increased.
[0050] (5) A rotor of a rotating electric machine as described in any of (1) to (4), Each magnetic pole portion has a plurality of magnet housing holes along the circumferential direction, The magnets (permanent magnets 41L) housed in the outer magnet housing holes in the circumferential direction of each magnetic pole portion have greater coercivity than the magnets (permanent magnets 41S) housed in the inner magnet housing holes. Rotor of a rotating electric machine.
[0051] According to (5), since the coercivity of the outer magnets in the circumferential direction, where magnetic flux flows easily, is greater in each magnetic pole, the occurrence of rapid demagnetization can be suppressed more reliably. [Explanation of symbols]
[0052] 10 rotors 20 rotor cores 30 Magnetic pole part 31 Magnet housing holes 41 Permanent magnets (magnets) 45 Outer edge RC rotation axis
Claims
1. A rotor core having a roughly ring-shaped centered on the axis of rotation, A rotor of a rotating electric machine comprising a plurality of magnetic pole portions provided along the circumferential direction of the rotor core, Each magnetic pole portion has a magnet housing hole that extends axially and is formed in the rotor core, and a magnet housed in the magnet housing hole. The aforementioned magnet has a coercive force distribution formed in a predetermined direction within a single unit. The magnet is housed in the magnet housing hole such that the direction of the distribution of coercivity is in the axial direction, and the coercivity at the outer end in the axial direction is greater than the coercivity at the inner portion. Multiple magnets are housed in one of the magnet housing holes. The magnets positioned on the outside in the axial direction have a greater coercivity than the magnets positioned on the inside. The magnets positioned on the outside in the axial direction are larger in size than the magnets positioned on the inside. Rotor of a rotating electric machine.
2. A rotor for a rotating electric machine according to claim 1, The magnets positioned on the outside in the axial direction are longer in the axial direction than the magnets positioned on the inside. Rotor of a rotating electric machine.
3. A rotor for a rotating electric machine according to claim 1 or 2, Each magnetic pole portion has a plurality of magnet housing holes along the circumferential direction, The magnet housed in the outer magnet housing hole in the circumferential direction of each magnetic pole portion has a greater coercivity than the magnet housed in the inner magnet housing hole. Rotor of a rotating electric machine.