Rotor

Abstract

To vary a magnetic flux amount of a rotor depending on rotating speed and torque.SOLUTION: A rotor includes a shaft, a rotor core fixed to the shaft, a first movable member that is attached to the shaft and relatively rotates with respect to the rotor core around the shaft depending on rotating speed of the rotor, a second movable member that is attached to the shaft and relatively rotates with respect to the rotor core around the shaft depending on torque applied to the rotor. A short circuit flux of the rotor core varies depending on a position of the first movable member, and the short circuit flux of the rotor core varies depending on a position of the second movable member.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a rotor.

[0002] The rotor disclosed in Patent Document 1 has a fixed core and a movable core. The movable core is rotatable relative to the fixed core. The movable core is provided with a guide groove extending obliquely to the radial direction. A weight is disposed in the guide groove. When the rotation speed of the rotor increases, the weight moves radially outward due to centrifugal force. Then, the inner surface of the guide groove is pushed by the weight, and the movable core rotates relative to the fixed core. As the movable core rotates relative to the fixed core in this manner, the amount of magnetic flux extending from the rotor to the stator (hereinafter, referred to as the magnetic flux amount of the rotor) decreases. As the magnetic flux amount of the rotor decreases when the rotation speed of the rotor is high, the back electromotive voltage generated in the stator is reduced. Therefore, an electric motor having this rotor can operate at a high rotation speed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-242461 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the rotor of Patent Document 1, the amount of magnetic flux of the rotor changes according to the rotation speed. On the other hand, in an electric motor, the appropriate amount of magnetic flux may differ depending on the rotation speed and torque. This specification proposes a rotor that can change the amount of magnetic flux of the rotor according to the rotation speed and torque. [Means for solving the problem]

[0005] The rotor disclosed in this specification includes a shaft, a rotor core fixed to the shaft, a first movable member attached to the shaft and rotating around the shaft relative to the rotor core in response to the rotation speed of the rotor, and a second movable member attached to the shaft and rotating around the shaft relative to the rotor core in response to the torque applied to the rotor. The short-circuit magnetic flux of the rotor core changes depending on the position of the first movable member. The short-circuit magnetic flux of the rotor core changes depending on the position of the second movable member.

[0006] The short-circuit magnetic flux refers to magnetic flux generated from the rotor core that returns to the rotor core via the first movable member or the second movable member without passing through the stator.

[0007] In this rotor, the first and second movable members rotate in response to the rotation speed of the rotor and the torque applied to the rotor, changing the short-circuit magnetic flux of the rotor core, thereby allowing the amount of magnetic flux in the rotor to be changed in response to the rotation speed and torque. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of an electric motor taken along a rotation axis. [Diagram 2] FIG. 4 is an explanatory diagram of the position of the movable member 10 when viewed along a direction parallel to the rotation axis. [Diagram 3] FIG. 4 is an explanatory diagram of the position of the movable member 20 when viewed along a direction parallel to the rotation axis. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The electric motor shown in Fig. 1 is mounted on an electric vehicle. The electric motor drives the wheels of the electric vehicle. The electric motor includes a rotor 30 and a stator 32. The stator 32 has a cylindrical shape. The rotor 30 is disposed radially inside the stator 32. The rotor 30 is disposed rotatably about a rotation axis AX.

[0010] The rotor 30 has a shaft 22, a rotor core 24, a movable member 10, and a movable member 20. The shaft 22 is arranged so that its central axis coincides with the rotation axis AX. The rotor core 24 has a cylindrical shape. The rotor core 24 is made of a material having high magnetic permeability. The shaft 22 is inserted into a central hole of the rotor core 24. The rotor core 24 is fixed to the shaft 22. A plurality of magnetic poles are arranged inside the rotor core 24. The magnetic poles of the rotor core 24 are, for example, permanent magnets. The magnetic poles of the rotor core 24 are arranged rotationally symmetrical with respect to the rotation axis AX.

[0011] The movable members 10, 20 are disposed on either side of the rotor core 24 in the direction along the rotation axis AX. In other words, the rotor core 24 is disposed between the movable members 10 and 20 in the direction along the rotation axis AX.

[0012] (Structure of Movable Member 10) The movable member 10 has a cylindrical shape. The movable member 10 is made of a material having high magnetic permeability. A shaft 22 is inserted into a central hole of the movable member 10. The movable member 10 can rotate relatively to the shaft 22 about a rotation axis AX. Magnetic poles are arranged inside the movable member 10. The magnetic poles of the movable member 10 are, for example, permanent magnets. The magnetic poles of the movable member 10 are arranged rotationally symmetrical with respect to the rotation axis AX.

[0013] The housing 12 and frame 14 are disposed on the opposite side of the movable member 10 from the rotor core 24. The frame 14 is disposed between the movable member 10 and the housing 12. The frame 14 is fixed to a side surface of the movable member 10. Therefore, the frame 14 rotates integrally with the movable member 10 about the shaft 22. The housing 12 is fixed to the shaft 22. In other words, the housing 12 is fixed to the rotor core 24 via the shaft 22. Therefore, the frame 14 rotates relative to the housing 12.

[0014] A plurality of guide grooves 12a are provided on the side surface of the housing 12 facing the frame 14. As shown in FIG. 2(a), each guide groove 12a extends along the radial direction. In addition, a plurality of guide holes 14a are provided in the frame 14. As shown in FIG. 1, each guide hole 14a penetrates the frame 14 in a direction parallel to the rotation axis AX. As shown in FIG. 2(a), each guide hole 14a extends along a direction inclined with respect to the radial direction. That is, each guide hole 14a extends so as to be displaced in the circumferential direction as it moves radially outward. As shown in FIG. 1, a rod-shaped weight 16 is provided inside the rotor 30, extending from the guide groove 12a to the guide hole 14a. The weight 16 can slide radially inside the guide groove 12a. A spring 18 is disposed inside each guide groove 12a. The spring 18 biases the weight 16 radially inward (i.e., toward the rotation axis AX). Therefore, when the rotor 30 is at rest, as shown in FIG. 2(a), each weight 16 is located at the end of the guide groove 12a on the inner circumferential side.

[0015] FIG. 2(a) shows a state where each weight 16 is located at the end of the inner circumference side of the guide groove 12a. FIG. 2(b) shows a state where each weight 16 is located at the end of the outer circumference side of the guide groove 12a. When each weight 16 moves radially outward in the guide groove 12a from the state shown in FIG. 2(a), each weight 16 presses the inner surface of the guide hole 14a, causing the frame 14 to rotate relative to the housing 12. Therefore, as shown in FIG. 2(b), when each weight 16 moves to the end of the outer circumference side of the guide groove 12a, the angle of the frame 14 with respect to the housing 12 changes. In this way, the frame 14 rotates relative to the housing 12 as a result of the weight 16 moving in the guide groove 12a. As described above, the frame 14 is fixed to the movable member 10, and the housing 12 is fixed to the rotor core 24. Therefore, when the frame 14 rotates relative to the housing 12, the movable member 10 rotates relative to the rotor core 24.

[0016] When the movable member 10 is in the position shown in FIG. 2(a), the magnetic poles of the movable member 10 are in a position of the same polarity as the magnetic poles of the rotor core 24 in the axial direction. Therefore, in the state shown in FIG. 2(a), all of the magnetic flux reaches the stator 32 from the rotor core 24. When the movable member 10 is in the position shown in FIG. 2(b), the magnetic poles of the movable member 10 are in a position of the opposite polarity to the magnetic poles of the rotor core 24 in the axial direction. Therefore, a short circuit occurs between the magnetic poles. Therefore, in the state shown in FIG. 2(b), little magnetic flux reaches the stator 32 from the rotor core 24.

[0017] (Operation of the movable member 10) When the electric motor is driven, the entire rotor 30 rotates around the rotation axis AX. When the rotation speed of the rotor 30 is low, the centrifugal force acting on each weight 16 is small, so each weight 16 is supported in the position shown in Figure 2(a) by the spring 18. As described above, in the state shown in Figure 2(a), all of the magnetic flux reaches the stator 32 from the rotor 30.

[0018] When the rotation speed of the rotor 30 increases, the centrifugal force acting on each weight 16 increases. When the rotation speed of the rotor 30 exceeds a certain value, each weight 16 moves toward the outer periphery in the guide groove 12a against the spring 18, as shown in FIG. 2(b). Therefore, the frame 14 and the movable member 10 rotate relative to the housing 12 and the rotor core 24. As described above, in the state of FIG. 2(b), the short-circuit magnetic flux of the rotor 30 increases, and the magnetic flux reaching the stator 32 from the rotor 30 decreases. Thereafter, when the rotation speed of the rotor 30 decreases, each weight 16 is returned to the position of FIG. 2(a) by the spring 18, and the movable member 10 is returned to the position of FIG. 2(a).

[0019] As described above, in the rotor 30 of the embodiment, the short-circuit magnetic flux increases during high-speed rotation and disappears during low-speed rotation. During high-speed rotation, the short-circuit magnetic flux increases and the magnetic flux reaching the stator 32 decreases, so that the back electromotive force generated in the stator 32 can be reduced. Therefore, the maximum rotation speed of the rotor 30 can be improved.

[0020] (Structure of Movable Member 20) The movable member 20 has a cylindrical shape. The movable member 20 is made of a material having high magnetic permeability. As shown in FIG. 1, a shaft 22 is inserted into a central hole of the movable member 20. The movable member 20 can rotate relatively to the shaft 22 around the rotation axis AX. A plurality of magnetic poles are arranged inside the movable member 20. The magnetic poles are, for example, permanent magnets. The plurality of magnetic poles are arranged rotationally symmetrically with respect to the rotation axis AX. A guide bar 25 is fixed to a side surface of the movable member 20. FIGS. 3(a) to (c) show the relative position of the movable member 20 with respect to the shaft 22 (i.e., the relative position of the movable member 20 with respect to the rotor core 24). In FIG. 3, an arrow W indicates the front side of the rotor 30 in the rotation direction. FIG. 3(b) shows the intermediate position of the movable member 20. FIG. 3(a) shows a first position where the movable member 20 is located forward of the intermediate position in the rotation direction. FIG. 3(c) shows a second position where the movable member 20 is located rearward in the rotational direction from the intermediate position.

[0021] Two torsion springs 41, 42 are connected to the movable member 20. The torsion springs 41, 42 are provided on the side surfaces of the movable member 20. As shown in FIG. 3(b), one end 41a of the torsion spring 41 is fixed to the shaft 22. The other end 41b of the torsion spring 41 contacts the guide bar 25 from the rear side. One end 42a of the torsion spring 42 is fixed to the shaft 22. The other end 42b of the torsion spring 42 contacts the guide bar 25 from the front side.

[0022] In the intermediate position shown in FIG. 3(b), no force is applied to the guide bar 25 from the torsion springs 41 and 42. When the movable member 20 rotates from the intermediate position to the first position shown in FIG. 3(a), the torsion spring 42 expands. Therefore, in the first position, the torsion spring 42 applies a force to the movable member 20 toward the intermediate position (i.e., toward the rear side in the circumferential direction). Note that, in the first position, the torsion spring 41 is not in contact with the guide bar 25. When the movable member 20 rotates from the intermediate position to the second position shown in FIG. 3(c), the torsion spring 41 expands. Therefore, in the second position, the torsion spring 41 applies a force to the movable member 20 toward the intermediate position (i.e., toward the front side in the circumferential direction). Note that, in the second position, the torsion spring 42 is not in contact with the guide bar 25.

[0023] In the intermediate position shown in FIG. 3(b), the magnetic poles of the movable member 20 are opposite in polarity to the magnetic poles of the rotor core 24 in the axial direction. Therefore, a short circuit occurs between the magnetic poles. Therefore, in the intermediate position, the magnetic flux reaching the stator 32 from the rotor core 24 is small. In the first and second positions shown in FIG. 3(a) and FIG. 3(c), the magnetic poles of the movable member 20 are opposite in polarity to the magnetic poles of the rotor core 24 in the axial direction. Therefore, in the first and second positions, all of the magnetic flux reaches the stator 32 from the rotor core 24.

[0024] (Operation of the movable member 20) When the electric motor is driven, the entire rotor 30 rotates around the rotation axis AX. When the torque is small, the guide bar 25 is supported by the torsion springs 41 and 42, so that the movable member 20 is located in the intermediate position shown in Fig. 3(b). In the intermediate position, the short-circuit magnetic flux of the rotor 30 is large, and the magnetic flux reaching the stator 32 from the rotor 30 is small.

[0025] When a high torque is applied to the front side in the rotational direction of the electric motor, the torsion spring 42 expands and the movable member 20 moves to the first position, as shown in Fig. 3(a). When the movable member 20 moves to the first position, the short-circuit magnetic flux of the rotor 30 disappears and the magnetic flux reaching the stator 32 from the rotor 30 increases. Thereafter, when the torque applied to the rotor 30 decreases, the torsion spring 42 returns the movable member 20 to the intermediate position.

[0026] When a high torque is applied to the rear side in the rotational direction of the electric motor, the torsion spring 41 expands, and the movable member 20 moves to the second position, as shown in Fig. 3(c). When the movable member 20 moves to the second position, the short-circuit magnetic flux of the rotor 30 disappears, and the magnetic flux reaching the stator 32 from the rotor 30 increases. Thereafter, when the torque applied to the rotor 30 decreases, the torsion spring 41 returns the movable member 20 to the intermediate position.

[0027] As described above, in the rotor 30 of the embodiment, the short-circuit magnetic flux disappears at high torque and increases at low torque. Since the short-circuit magnetic flux disappears at high torque, the electric motor can be operated at high torque. Since the short-circuit magnetic flux increases at low torque, the loss generated in the electric motor can be reduced. In this way, the rotor 30 can achieve operation at high torque and reduced loss at low torque.

[0028] As described above, in the rotor 30 of the embodiment, the short-circuit magnetic flux of the rotor 30 can be changed according to the torque and the rotation speed. More specifically, in a state where the torque is low and the rotation speed is high, both the movable member 10 and the movable member 20 are disposed at positions where the short-circuit magnetic flux is high. In addition, in a state where the torque is high and the rotation speed is high, the movable member 10 is disposed at a position where the short-circuit magnetic flux is eliminated, while the movable member 20 is disposed at a position where the short-circuit magnetic flux is high. In addition, in a state where the torque is low and the rotation speed is low, the movable member 10 is disposed at a position where the short-circuit magnetic flux is high, while the movable member 20 is disposed at a position where the short-circuit magnetic flux is eliminated. In addition, in a state where the torque is high and the rotation speed is low, both the movable member 10 and the movable member 20 are disposed at a position where the short-circuit magnetic flux is eliminated. In this way, the magnetic flux amount of the rotor 30 can be changed in multiple stages according to the rotation speed and the torque. [Explanation of symbols]

[0029] 10: Movable parts 20: Movable parts 22: Shaft 24: Rotor core 30:Rotor

Claims

[Claim 1] A rotor, A shaft, A rotor core fixed to the shaft; a first movable member attached to the shaft and configured to rotate about the shaft relative to the rotor core in response to a rotational speed of the rotor; a second movable member attached to the shaft and configured to rotate about the shaft relative to the rotor core in response to torque applied to the rotor; having a short-circuit magnetic flux of the rotor core changes depending on a position of the first movable member, The short-circuit magnetic flux of the rotor core changes depending on the position of the second movable member. Rotor.

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