Rotor

Abstract

To vary a magnetic flux amount of a rotor depending on torque.SOLUTION: A rotor includes: a shaft; a rotor core fixed to the shaft; a movable member that is attached to the shaft and can relatively rotate with respect to the rotor core around the shaft among an intermediate position, a first position positioned on the front side in a rotation direction of the rotor core with respect to the intermediate position, and a second position positioned on the rear side in the rotation direction of the rotor core with respect to the intermediate position; a first spring for energizing the movable member from the first position toward the intermediate position; and a second spring for energizing the movable member from the second position toward the intermediate position. A short circuit flux of the rotor core is greater when the movable member exists at the intermediate position than that when the movable member exists at the first position and when the movable member exists at the second position.SELECTED DRAWING: Figure 2

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 rotor rotation speed 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. When 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. When the rotor rotation speed is high, the magnetic flux amount of the rotor decreases, thereby reducing the back electromotive voltage generated in the stator. 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 torque. This specification proposes a rotor that can change the amount of magnetic flux of the rotor according to the torque. [Means for solving the problem]

[0005] The rotor disclosed in this specification includes a shaft, a rotor core fixed to the shaft, a movable member attached to the shaft and rotatable around the shaft relative to the rotor core between an intermediate position, a first position located forward of the rotor core in a rotational direction relative to the intermediate position, and a second position located rearward of the rotor core in a rotational direction relative to the intermediate position, a first spring that urges the movable member from the first position toward the intermediate position, and a second spring that urges the movable member from the second position toward the intermediate position. When the movable member is at the intermediate position, there is more short-circuit magnetic flux in the rotor core than when the movable member is at the first position and when the movable member is at the second position.

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

[0007] When a high torque is applied to this rotor in the acceleration or deceleration direction, acceleration is applied to the movable member on the front or rear side of the rotation direction. Therefore, when a high torque is applied to the rotor, the movable member is located at the first or second position. In this state, the short-circuit magnetic flux in the rotor core is small. Furthermore, when the torque applied to the rotor becomes small, the movable member moves to the intermediate position due to the force applied from the first or second spring. In this state, the short-circuit magnetic flux in the rotor core is large. As described above, this rotor can change the amount of short-circuit magnetic flux according to the magnitude of the torque, and can change the amount of magnetic flux in the rotor. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of an electric motor 10 taken along an axial direction. [Diagram 2] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (Structure of electric motor 10) An electric motor 10 shown in Fig. 1 is mounted on an electric vehicle. The electric motor 10 drives the wheels of the electric vehicle. The electric motor 10 includes a rotor 20 and a stator 30. The stator 30 has a cylindrical shape. The rotor 20 is disposed radially inside the stator 30. The rotor 20 is disposed rotatably about a rotation axis AX.

[0010] The rotor 20 has a shaft 22, a rotor core 24, and two movable members 26. 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] 1, the movable members 26 are disposed on both sides of the rotor core 24 in the direction along the rotation axis AX. In other words, the rotor core 24 is disposed between the two movable members 26 in the direction along the rotation axis AX. Since each movable member 26 has the same structure, only one of the movable members 26 will be described below.

[0012] The movable member 26 has a cylindrical shape. The movable member 26 is made of a material having high magnetic permeability. The shaft 22 is inserted into a central hole of the movable member 26. The movable member 26 can rotate relatively to the shaft 22 about the rotation axis AX. A plurality of magnetic poles are arranged inside the movable member 26. The magnetic poles of the movable member 26 are, for example, permanent magnets. The magnetic poles of the movable member 26 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 26. FIGS. 2(a) to (c) show the relative position of the movable member 26 with respect to the shaft 22 (i.e., the relative position of the movable member 26 with respect to the rotor core 24). In FIG. 2, the arrow W indicates the front side of the rotor 20 in the rotation direction. FIG. 2(b) shows the intermediate position of the movable member 26. FIG. 2(a) shows the first position where the movable member 26 is located forward of the intermediate position in the rotation direction. FIG. 2(c) shows a second position where the movable member 26 is located rearward in the rotational direction from the intermediate position.

[0013] Two torsion springs 41, 42 are connected to the movable member 26. The torsion springs 41, 42 are provided on the side surfaces of the movable member 26. As shown in FIG. 2(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.

[0014] In the intermediate position shown in FIG. 2(b), no force is applied to the guide bar 25 from the torsion springs 41 and 42. When the movable member 26 rotates from the intermediate position to the first position shown in FIG. 2(a), the torsion spring 42 expands. Therefore, in the first position, the torsion spring 42 applies a force to the movable member 26 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 26 rotates from the intermediate position to the second position shown in FIG. 2(c), the torsion spring 41 expands. Therefore, in the second position, the torsion spring 41 applies a force to the movable member 26 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.

[0015] In the intermediate position shown in FIG. 2(b), the magnetic poles of the movable member 26 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 30 from the rotor core 24 is small. In the first and second positions shown in FIG. 2(a) and FIG. 2(c), the magnetic poles of the movable member 26 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 30 from the rotor core 24.

[0016] (Operation of electric motor 10) When the electric motor 10 is driven, the entire rotor 20 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 26 is located in the intermediate position shown in Fig. 2(b). In the intermediate position, the short-circuit magnetic flux of the rotor 20 is large, and the magnetic flux reaching the stator 30 from the rotor 20 is small.

[0017] 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 26 moves to the first position, as shown in Fig. 2(a). When the movable member 26 moves to the first position, the short-circuit magnetic flux of the rotor 20 disappears and the magnetic flux reaching the stator 30 from the rotor 20 increases. Thereafter, when the torque applied to the rotor 20 decreases, the torsion spring 42 returns the movable member 26 to the intermediate position.

[0018] 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 26 moves to the second position, as shown in Fig. 2(c). When the movable member 26 moves to the second position, the short-circuit magnetic flux of the rotor 20 disappears, and the magnetic flux reaching the stator 30 from the rotor 20 increases. Thereafter, when the torque applied to the rotor 20 decreases, the torsion spring 41 returns the movable member 26 to the intermediate position.

[0019] As described above, in the rotor 20 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 10 can be operated at high torque. Since the short-circuit magnetic flux increases at low torque, the loss generated in the electric motor 10 can be reduced. In this way, the rotor 20 can achieve operation at high torque and reduced loss at low torque.

[0020] The torsion springs 41, 42 may have the same characteristics or different characteristics. In the above embodiment, when a force is applied to the movable member 26 from one of the springs 41, 42, no force is applied to the movable member 26 from the other spring. With this configuration, the movable member 26 can be moved appropriately according to the torque. However, in other embodiments, there may be a position where a force is applied to the movable member 26 from both the springs 41, 42. Also, in the above embodiment, the springs 41, 42 are torsion springs, but the springs 41, 42 may be other types of springs.

[0021] Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings achieves multiple objectives simultaneously, and achieving one of the objectives itself has technical utility. [Explanation of symbols]

[0022] 20: Rotor 22: Shaft 24: Rotor core 26: Movable parts 41: Torsion spring 42: Torsion spring

Claims

[Claim 1] A shaft, A rotor core fixed to the shaft; a movable member attached to the shaft and rotatable about the shaft relative to the rotor core between an intermediate position, a first position located forward of the intermediate position in a rotational direction of the rotor core, and a second position located rearward of the intermediate position in a rotational direction of the rotor core; a first spring that biases the movable member from the first position toward the intermediate position; a second spring that biases the movable member from the second position toward the intermediate position; having when the movable member is in the intermediate position, the short-circuit magnetic flux of the rotor core is greater than when the movable member is in the first position and when the movable member is in the second position; Rotor.

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