Motor

Abstract

To provide a motor capable of significantly reducing a cogging torque while maintaining a maximum torque value.SOLUTION: A motor 1 includes a rotor 2 that rotates around a central axis C and a stator 3 arranged to face the rotor 2 radially outward. The rotor 2 has a plurality of hole portions 212 penetrating in an axial direction and arranged side by side in a circumferential direction and a plurality of magnets 22 arranged on the plurality of hole portions 212. A cross section perpendicular to the axial direction of the magnet 22 has a longitudinal shape. When the inner diameter of the stator 3 is D1, a distance in the radial direction between the rotor 2 and the stator 3 is T1, and a length in a direction perpendicular to the longitudinal direction of the cross section of the magnetic 22 is T2, a condition where 0.007≤T1 / D1≤0.009 and 0.045≤T2 / D1≤0.046 is fulfilled.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a motor.

Background Art

[0002] Conventionally, a motor having an IPM (Interior Permanent Magnet) structure including an annular stator having coils, and a rotor rotatably disposed inside the stator in the radial direction and having a plurality of magnets fixed in a rotor core has been widely known. The rotor core has a plurality of magnet mounting holes that accommodate a plurality of magnets arranged at equal intervals along the circumferential direction (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the prior art, the arrangement and structural relationship between the stator and the rotor are not properly defined, and there is a problem that cogging torque cannot be sufficiently suppressed. In addition, when suppressing the cogging torque, there is a concern that the maximum torque value, which is the output of the motor, may decrease.

[0005] In view of the above points, an object of the present disclosure is to provide a motor capable of significantly reducing cogging torque while maintaining the maximum torque value.

Means for Solving the Problems

[0006] Exemplary motors of the present disclosure include a rotor that rotates around a central axis, and a stator that is disposed opposite to the rotor in the radial direction. The rotor has a plurality of holes that penetrate in the axial direction and are arranged side by side in the circumferential direction, and a plurality of magnets disposed in the plurality of holes. A cross-section of the magnet orthogonal to the axial direction is elongate. When the inner diameter of the stator is D1, the radial interval between the rotor and the stator is T1, and the length of the cross-section of the magnet in a direction orthogonal to the longitudinal direction is T2, the following formulas (1) and (2) are satisfied. 0.007 ≤ T1 / D1 ≤ 0.009 ···(1) 0.045 ≤ T2 / D1 ≤ 0.046 ···(2)

Advantages of the Invention

[0007] According to the configuration of the present disclosure, it is possible to provide a motor capable of significantly reducing cogging torque while maintaining the maximum torque value.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0009] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. Note that the scope of the present disclosure is not limited to the following embodiments, and can be arbitrarily changed within the scope of the technical idea of the present disclosure.

[0010] In this book, the direction in which the central axis of the motor extends is simply referred to as the "axial direction", the direction orthogonal to the central axis centered on the central axis of the motor is simply referred to as the "radial direction", and the direction along the arc centered on the central axis is simply referred to as the "circumferential direction". The "axial direction" of the motor is the depth direction of the paper surface in FIG. 1. The central axes of the rotor and the stator coincide with the central axis of the motor. Also, in this book, a cross-section parallel to the radial direction is referred to as a "cross-sectional plane". The "parallel" and "orthogonal" used in this book do not represent parallel and orthogonal in a strict sense, but include approximately parallel and approximately orthogonal.

[0011] <1. Overall Configuration of Motor> FIG. 1 is a cross-sectional view of a motor 1 according to an embodiment of the present disclosure. The motor 1 shown in FIG. 1 has a rotor 2 and a stator 3.

[0012] The rotor 2 is arranged to face the stator 3 on the inner side in the radial direction. The rotor 2 has, for example, a cylindrical shape extending in the axial direction. The rotor 2 rotates around the central axis C. The rotor 2 has a rotor core 21 and magnets 22.

[0013] The rotor core 21 has a cylindrical shape extending in the axial direction. The rotor core 21 has a shaft hole 211 located at the radial center portion. The shaft hole 211 extends in the axial direction, and a shaft (not shown) is inserted therein. The central axis C of the motor 1 and the rotor core 21 coincides with the central axis (rotation axis) of the shaft. The rotor core 21 is formed by laminating, for example, a plurality of magnetic steel plates in the axial direction. The detailed configuration of the rotor core 21 will be described later.

[0014] The magnets 22 are arranged on the inner side in the radial direction of the outer edge portion of the rotor core 21. A plurality of magnets 22 are arranged side by side in the circumferential direction. The axial length of the magnets 22 generally coincides with the axial length of the rotor core 21. The magnets 22 are attached to the rotor core 21. The detailed configuration of the magnets 22 will be described later.

[0015] The stator 3 is arranged to face the rotor 2 radially outward. The stator 3 has, for example, a cylindrical shape extending in the axial direction. For example, the stator 3 is arranged with a predetermined radial interval T1 on the radially outer side of the rotor 2. The stator 3 has a stator core 31 and a coil 32.

[0016] The stator core 31 has a cylindrical shape extending in the axial direction. The stator core 31 is formed, for example, by laminating a plurality of magnetic steel plates in the axial direction. The stator core 31 has a core back 311 and teeth 312. The cross section of the core back 311 is an annular shape. The teeth 312 extend radially inward from the inner peripheral surface of the core back 311. The plurality of teeth 312 are arranged at predetermined intervals in the circumferential direction. In this embodiment, the stator core 31 has 48 teeth 312.

[0017] The coil 32 is provided surrounding the outer periphery of the teeth 312. An insulator (not shown) is interposed between the coil 32 and the teeth 312. The insulator is composed of an insulating member such as synthetic resin, for example. The coil 32 is formed by winding a conducting wire around the outer periphery of the teeth 312.

[0018] <2. Detailed Configuration of Rotor> The rotor core 21 has holes 212. The holes 212 are arranged radially inward of the outer edge of the rotor core 21. The holes 212 penetrate the rotor core 21 in the axial direction. The plurality of holes 212 are arranged side by side in the circumferential direction. In this embodiment, the rotor core 21 has 8 holes 212.

[0019] The plurality of magnets 22 are arranged in the plurality of holes 212. In this embodiment, two magnets 22 are arranged for each one hole 212. The cross section of the magnet 22 perpendicular to the axial direction is longitudinal. In other words, in this embodiment, the cross section of the magnet 22 parallel to the radial direction of the rotor 2 is rectangular. For example, the magnet 22 has a length T2 in a direction perpendicular to the longitudinal direction of the cross section perpendicular to the axial direction.

[0020] When the inner diameter of the stator 3 is D1, the radial distance between the rotor 2 and the stator 3 is T1, and the length in the direction orthogonal to the longitudinal direction of the cross section of the magnet 22 is T2, the motor 1 satisfies the following formulas (1) and (2).

[0021] 0.007 ≦ T1 / D1 ≦ 0.009 ···(1) 0.045 ≦ T2 / D1 ≦ 0.046 ···(2)

[0022] Furthermore, it is more preferable that the motor 1 satisfies the following formulas (3) and (4).

[0023] T1 / D1 = 0.008 ···(3) T2 / D1 = 0.046 ···(4)

[0024] Next, the influence of the relationships of the inner diameter D1, the distance T1, and the length T2 of the motor 1 on the cogging torque and the maximum torque value was evaluated. The results are shown in Table 1, FIGS. 2, 3, and 4. FIG. 2 is a graph showing the relationship between the radial distance T1 between the rotor 2 and the stator 3 and the cogging torque of the motors of the examples and comparative examples. FIG. 3 is a graph showing the relationship between the length T2 of the magnet 22 and the cogging torque of the motors of the examples and comparative examples. FIG. 4 is a graph showing the maximum torque values of the motors of the examples and comparative examples.

[0025]

Table 1

[0026] In this evaluation, the distance T1 with respect to the inner diameter D1 of the motors 1 of Examples E1, E2, E3, and E4 is 0.007 to 0.009 (0.007 ≦ T1 / D1 ≦ 0.009). The length T2 with respect to the inner diameter D1 of the motors 1 of Examples E1, E2, E3, and E4 is 0.045 to 0.046 (0.045 ≦ T2 / D1 ≦ 0.046). That is, the motors 1 of Examples E1, E2, E3, and E4 all satisfy the above formulas (1) and (2). In particular, the motor 1 of Example E4 satisfies the above formulas (3) and (4).

[0027] On the other hand, none of the motors of Comparative Examples C1, C2, and C3 satisfy at least one of the above formulas (1) and (2).

[0028] Regarding the influence of the radial distance T1 between the rotor 2 and the stator 3 on the cogging torque, according to Table 1 and FIG. 2, it can be seen that for the motors 1 of Examples E1, E2, E3, and E4, the cogging torque is 0.02 to 0.04 Nm for each, and can be suppressed low. On the other hand, it can be seen that for the motors of Comparative Examples C1, C2, and C3, the cogging torque is 0.37 to 0.48 Nm for each, and has become very high.

[0029] Regarding the influence of the length T2 of the magnet 22 on the cogging torque, according to Table 1 and FIG. 3, it can be seen that for the motors 1 of Examples E1, E2, E3, and E4, the cogging torque is 0.02 to 0.04 Nm for each, and can be suppressed low. On the other hand, it can be seen that for the motors of Comparative Examples C1, C2, and C3, the cogging torque is 0.37 to 0.48 Nm for each, and has become very high.

[0030] Note that for the motor of Comparative Example C3, the length T2 of the magnet 22 with respect to the inner diameter D1 of the stator is 0.046 (T2 / D1 = 0.046), which satisfies the above formula (2), but the radial distance T1 between the rotor 2 and the stator 3 with respect to the inner diameter D1 of the stator is 0.006 (T1 / D1 = 0.006), which does not satisfy the above formula (1). Since the motor of Comparative Example C3 does not satisfy one of the above formulas (1) and (2), the cogging torque is very high.

[0031] Regarding the maximum torque values of the motors of the examples and comparative examples, according to Table 1 and FIG. 4, for the motors 1 of Examples E1, E2, E3, and E4 and the motors of Comparative Examples C1, C2, and C3, the maximum torque values are both 80 to 95 Nm, and it can be said that they can maintain substantially the same output. In particular, the motor 1 of Example E4 that satisfies the above formulas (3) and (4) has a higher maximum torque value compared to the motors 1 of other examples, which is preferable.

[0032] By appropriately configuring the inner diameter D1, the interval T1, and the length T2 of the motor 1 so as to satisfy the above formulas (1) and (2), it is possible to significantly reduce the cogging torque while maintaining the maximum torque value. Furthermore, by limiting the configuration of the motor 1 to specific design values so as to satisfy the above formulas (3) and (4), it is possible to further increase the maximum torque value and significantly reduce the cogging torque.

[0033] In addition, the hole portion 212 extends radially outward as it goes from the central portion in the circumferential direction toward both end portions in the circumferential direction. That is, as shown in FIG. 1, when viewed from the axial direction, the hole portion 212 has a V-shaped cross section in which the central portion in the circumferential direction is bent and both end portions in the circumferential direction extend radially outward. Both end portions in the circumferential direction of the hole portion 212 extend to the vicinity of the outer peripheral edge of the rotor 2.

[0034] Magnets 22 are inserted on both sides of the central portion in the circumferential direction of the hole portion 212. That is, the magnets 22 are respectively arranged on both sides of the central portion in the circumferential direction of the hole portion 212. On both sides of the central portion in the circumferential direction of the hole portion 212, the width of the hole portion 212 in the direction orthogonal to the direction in which the hole portion 212 extends is the same as the length T2 of the magnet 22. Note that the width of the hole portion 212 and the length T2 of the magnet 22 are not limited to exactly the same length, and include cases where the width of the hole portion 212 is slightly larger than the length T2 of the magnet 22.

[0035] The rotor 2 further has a gap portion 23. The gap portion 23 extends in the axial direction. In this embodiment, the gap portion 23 penetrates the rotor core 21 in the axial direction, but it may be formed as a recess in the rotor core 21. The gap portion 23 is adjacent to the magnet 22. Specifically, the gap portion 23 is located between the two magnets 22 of the hole portion 212 and between both end portions in the circumferential direction of the hole portion 212 and the magnet 22. The gap portion 23 serves as a flux barrier related to the magnetic flux of the motor 1.

[0036] By configuring the hole portion 212, which is the housing portion for the magnet 22 that is close to the outer peripheral portion of the rotor 2, the magnet 22, and the gap portion 23 as described above, the magnetic flux generated near the outer peripheral portion of the rotor 2 is adjusted. As a result, it becomes possible to maintain the maximum torque value and enhance the effect of significantly reducing the cogging torque.

[0037] <3. Others> As described above, the embodiments of the present disclosure have been explained. However, the scope of the present disclosure is not limited to this, and various modifications such as addition, omission, substitution, and other changes can be made without departing from the gist of the present disclosure.

[0038] For example, the dimensions of the motors of the examples and comparative examples used in the explanations related to Table 1, FIGS. 2, 3, and 4 are merely examples, and the present disclosure is not limited to these configurations, and other dimensions may be used. Also, the shape, size, quantity, and arrangement of the coils and magnets of the motor are not limited to the configurations described above, and other shapes, sizes, quantities, and arrangements may be used.

Industrial Applicability

[0039] The present disclosure can be used for motors.

Explanation of Reference Numerals

[0040] 1 ··· motor, 2 ··· rotor, 3 ··· stator, 21 ··· rotor core, 22 ··· magnet, 23 ··· gap portion, 31 ··· stator core, 32 ··· coil, 211 ··· shaft hole, 212 ··· hole portion, 311 ··· core back, 312 ··· teeth, C ··· central axis, D1 ··· inner diameter, T1 ··· interval, T2 ··· length

Claims

1. A rotor that rotates about a central axis, A stator disposed radially outside the rotor, And having, The rotor, A plurality of holes penetrating in the axial direction and arranged side by side in the circumferential direction, A plurality of magnets arranged in the plurality of holes, And having, The cross-section of the magnet perpendicular to the axial direction is longitudinal, The radial distance between the rotor and the stator is constant in the circumferential direction, When the inner diameter of the stator is D1, the distance is T1, and the length of the magnet in the direction perpendicular to the longitudinal direction of the cross-section is T2, a motor that satisfies the following formulas (1) and (2). 0.007 ≤ T1 / D1 ≤ 0.009... (1) 0.045 ≤ T2 / D1 ≤ 0.046... (2)

2. The motor according to claim 1, which satisfies the following formulas (3) and (4). T1 / D1 = 0.008... (3) T2 / D1 = 0.046... (4)

3. The motor according to claim 1 or claim 2, wherein the holes extend radially outward as they go toward both ends in the circumferential direction with respect to the central portion in the circumferential direction.

4. The motor according to claim 3, wherein the width of the holes in the direction perpendicular to the direction in which the holes extend is the same as the length T2 of the magnet on both sides of the central portion in the circumferential direction of the holes.

5. The magnets are respectively arranged on both sides of the central portion in the circumferential direction of the holes, The rotor has a gap portion extending in the axial direction, The motor according to claim 3 or claim 4, wherein the gap portion is located between the two magnets in the holes and between both ends in the circumferential direction in the holes and the magnets.

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