Motor drive device

Abstract

To properly rotate a rotary rotor core.SOLUTION: A motor drive device has a rotor, a stator, and a controller that controls current flowing through the stator. The rotor has: a shaft; a fixed rotor core that is fixed to the shaft; and a rotary rotor core that is mounted on the shaft and rotates relative to the shaft between a same polarity position at which a magnetic pole direction is the same as that of the fixed rotor core and a reverse polarity position which is located on the front side in the rotation direction relative to the same polarity position and at which the magnetic pole direction is reverse polarity to the fixed rotor core. When the rotary rotor core is rotated from the reverse polarity position to the same polarity position in a state where torque to a front side in the rotation direction is being applied onto the fixed rotor core, the controller changes a current phase angle so as to apply, onto both the fixed rotor core and the rotary rotor core, torque to the front side in the rotation direction, and increases the current flowing through the stator.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a motor drive device.

[0002] The motor disclosed in Patent Document 1 has a fixed rotor core and a rotating rotor core. The fixed rotor core is fixed to a shaft, and the rotating rotor core is rotatable relative to the shaft. As the rotating rotor core rotates relative to the shaft, it moves between a homopolar position where its magnetic poles are aligned with those of the fixed rotor core, and an antipolar position where its magnetic poles are aligned with those of the fixed rotor core. In this motor, when the rotating rotor core is rotated relative to the shaft, the current flowing through the motor is increased. This applies torque to the rotating rotor core, causing it to rotate relative to the shaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-141777 Summary of the Invention [Problem to be solved by the invention]

[0004] When torque is applied to the fixed rotor core in the forward direction of rotation and the rotating rotor core is in the reverse polarity position, increasing the motor current may cause torque to be applied in the reverse direction to the rotating rotor core. In this case, it becomes difficult to move the rotating rotor core to the same polarity position. This specification proposes a technology for more appropriately rotating the rotating rotor core. [Means for solving the problem]

[0005] The motor drive device disclosed in this specification includes a rotor, a stator, and a control device that controls a current flowing through the stator. The rotor includes a shaft, a fixed rotor core fixed to the shaft, and a rotating rotor core attached to the shaft and rotating relative to the shaft between a homopolar position where its magnetic poles are aligned with the fixed rotor core and an opposite polarity position where its magnetic poles are aligned with the fixed rotor core and are positioned forward of the homopolar position in the direction of rotation and where its magnetic poles are aligned with the fixed rotor core. When the rotating rotor core is rotated from the opposite polarity position to the homopolar position while torque is being applied to the fixed rotor core forward in the direction of rotation, the control device changes the current phase angle and increases the current flowing through the stator so that torque is applied to both the fixed rotor core and the rotating rotor core forward in the direction of rotation.

[0006] In this motor drive device, when the rotating rotor core is rotated from the opposite pole position to the same pole position while torque is being applied to the fixed rotor core in the forward direction of rotation, the control device changes the current phase angle so that torque is applied in the forward direction to both the fixed rotor core and the rotating rotor core. Therefore, the rotating rotor core rotates in the forward direction and moves toward the same pole position. The control device also increases the current flowing through the stator to suppress a decrease in torque applied to the fixed rotor core when changing the current phase angle. Therefore, the rotating rotor core can be rotated from the opposite pole position to the same pole position while properly rotating the rotor. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. [Figure 2] FIG. [Figure 3] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] The motor drive device 10 of the embodiment shown in FIG. 1 has a motor 12 and a control device 90. The motor drive device 10 is mounted on an electric vehicle and drives the wheels of the electric vehicle. The motor 12 has a rotor 20 and a stator 80. The stator 80 has a cylindrical shape. The rotor 20 is arranged radially inside the stator 80 and concentrically with the stator 80. The rotor 20 is arranged rotatably about a rotation axis AX.

[0009] The rotor 20 has a shaft 22, a fixed rotor core 30, and two rotating rotor cores 40. The central axis of the shaft 22 is the rotation axis AX. The fixed rotor core 30 and the rotating rotor core 40 are each made of a material with high magnetic permeability. The fixed rotor core 30 and the rotating rotor core 40 each have a cylindrical shape with a through hole in the center. The shaft 22 is inserted through the central hole of each of the fixed rotor core 30 and the rotating rotor core 40. The fixed rotor core 30 is fixed to the shaft 22. Each rotating rotor core 40 is rotatable relative to the shaft 22 around the rotation axis AX. That is, each rotating rotor core 40 is rotatable relative to the fixed rotor core 30. The rotating rotor cores 40 are arranged on both sides of the fixed rotor core 30 in the direction along the rotation axis AX. In other words, the fixed rotor core 30 is arranged between the two rotating rotor cores 40 in the direction along the rotation axis AX.

[0010] As shown in Fig. 2, a plurality of magnetic poles 32 are arranged inside the fixed rotor core 30. The magnetic poles 32 are, for example, permanent magnets. The plurality of magnetic poles 32 are arranged rotationally symmetrically with respect to the rotation axis AX. The magnetic poles 32 include magnetic poles 32a with north poles arranged on the outside and magnetic poles 32b with south poles arranged on the outside. The magnetic poles 32a and 32b are arranged alternately in the circumferential direction.

[0011] As shown in Fig. 2, a plurality of magnetic poles 42 are arranged inside the rotating rotor core 40. The magnetic poles 42 are, for example, permanent magnets. The plurality of magnetic poles 42 are arranged rotationally symmetrically with respect to the rotation axis AX. The magnetic poles 42 include magnetic poles 42a with north poles arranged on the outside and magnetic poles 42b with south poles arranged on the outside. The magnetic poles 42a and 42b are arranged alternately in the circumferential direction.

[0012] Grooves 34 extending in the circumferential direction are provided on the side surface of the fixed rotor core 30. Pins 44 protruding from the side surface are provided on the side surface of the rotating rotor core 40. The pins 44 are disposed within the grooves 34. When the rotating rotor core 40 rotates, the pins 44 move within the grooves 34.

[0013] The rotor 20 can rotate forward in the rotational direction shown in Figures 2 and 3. The rotating rotor core 40 rotates relative to the fixed rotor core 30 between the opposite-pole position shown in Figure 2 and the same-pole position shown in Figure 3. As shown in Figure 2, in the opposite-pole position, the magnetic poles 32a and 42b are arranged at the same position in the circumferential direction, and the magnetic poles 32b and 42a are arranged at the same position in the circumferential direction. Therefore, the magnetic poles 32 and 42 that are at the same position in the circumferential direction have opposite magnetic pole orientations. In the opposite-pole position, a large amount of magnetic flux is short-circuited inside the rotor 20, so less magnetic flux reaches the stator 80 from the rotor 20. As shown in Figure 3, in the same-pole position, the magnetic poles 32a and 42a are arranged at the same position in the circumferential direction, and the magnetic poles 32b and 42b are arranged at the same position in the circumferential direction. Therefore, the magnetic poles 32 and 42 that are at the same position in the circumferential direction have the same magnetic pole orientation. In the same-pole position, less magnetic flux is short-circuited inside the rotor 20, and therefore more magnetic flux reaches the stator 80 from the rotor 20. In the same-pole position shown in Figure 3, the rotating rotor core 40 is located further forward in the direction of rotation than in the opposite-pole position shown in Figure 2.

[0014] Although not shown, the stator 80 has a stator core and a coil wound around the stator core. The control device 90 is configured with an inverter or the like. The control device 90 supplies a three-phase AC current to the coil of the stator 80. The control device 90 rotates the rotor 20 by controlling the current supplied to the stator 80 (hereinafter referred to as the stator current). The control device 90 also controls the stator current to rotate the rotating rotor core 40 relative to the fixed rotor core 30, thereby controlling the position of the rotating rotor core 40. That is, while the rotor 20 is rotating, the rotating rotor core 40 rotates relative to the fixed rotor core 30. When driving the motor 12 with high torque, the control device 90 controls the position of the rotating rotor core 40 to a homopolar position. In the homopolar position, a large amount of magnetic flux reaches the stator 80 from the rotor 20, allowing the motor 12 to be driven with high torque. Furthermore, when driving the motor 12 at a high rotational speed, the control device 90 controls the position of the rotating rotor core 40 to the reverse pole position. In the reverse pole position, the magnetic flux reaching the stator 80 from the rotor 20 is small, so the back electromotive force generated in the coil of the stator 80 is reduced. Therefore, the motor 12 can be driven at a high rotational speed.

[0015] Next, a control method for moving the rotating rotor core 40 from the reverse pole position shown in Fig. 2 to the same pole position shown in Fig. 3 will be described. When the rotating rotor core 40 is in the reverse pole position as shown in Fig. 2, the control device 90 supplies current to the stator at a predetermined current phase angle (i.e., advance angle) to apply torque to the fixed rotor core 30 in the forward direction (i.e., the same direction as the rotation direction) while maintaining the reverse pole position of the rotating rotor core 40, thereby rotating the rotor 20. At this time, the control device 90 controls the current phase angle of the stator current to an angle at which torque is efficiently applied to the fixed rotor core 30. The control device 90 rotates the rotating rotor core 40 from the reverse pole position shown in Fig. 2 to the same pole position shown in Fig. 3 by sequentially performing first and second controls described below.

[0016] In the first control, the control device 90 changes the current phase angle to an angle at which forward torque is applied to both the fixed rotor core 30 and the rotating rotor core 40, and also increases the stator current. First, we will explain the problem that occurs when the current phase angle is not changed. In the state of FIG. 2, if the stator current is increased without changing the current phase angle, the forward torque applied to the fixed rotor core 30 increases, but torque may be applied to the rotating rotor core 40 in the reverse direction (i.e., the direction opposite to the rotation direction). This is because, in the reverse pole position, the magnetic pole orientation of the rotating rotor core 40 is opposite to the magnetic pole orientation of the fixed rotor core 30. When torque is applied in the reverse direction to the rotating rotor core 40, the rotating rotor core 40 rotates in the opposite direction relative to the fixed rotor core 30. In other words, the rotating rotor core 40 rotates in a direction away from the reverse pole position shown in FIG. 3. When the rotating rotor core 40 rotates in the opposite direction in this way, it becomes difficult to control the position of the rotating rotor core 40, and it becomes difficult to move the rotating rotor core 40 to the opposite pole position in FIG.

[0017] In contrast, in the first control, the control device 90 increases the stator current while changing the current phase angle to an angle at which forward torque is applied to both the fixed rotor core 30 and the rotating rotor core 40 in the reverse pole position state shown in FIG. 2. Changing the current phase angle in this way applies forward torque to the rotating rotor core 40, causing the rotating rotor core 40 to rotate in the forward direction relative to the fixed rotor core 30. In other words, the rotating rotor core 40 moves toward the homopolar position shown in FIG. 3. Furthermore, changing the current phase angle makes it difficult to apply torque to the fixed rotor core 30, but the control device 90 prevents a decrease in the torque applied to the fixed rotor core 30 by increasing the stator current. Therefore, the rotating rotor core 40 can be rotated toward the homopolar position shown in FIG. 3 while maintaining smooth rotation of the rotor 20.

[0018] When the rotating rotor core 40 approaches the homopolar position due to the first control, the control device 90 executes the second control. In the second control, the control device 90 changes the current phase angle to an angle at which torque is efficiently applied to the fixed rotor core 30 (i.e., a normal angle). When the rotating rotor core 40 approaches the homopolar position, torque can be applied in the forward direction to both the fixed rotor core 30 and the rotating rotor core 40 even if the current phase angle is a normal angle. This allows the rotating rotor core 40 to move to the homopolar position while efficiently rotating the rotor 20.

[0019] As described above, according to the embodiment, it is possible to appropriately control the position of the rotating rotor core 40. Therefore, it is not necessary to provide the rotor 20 with a mechanism (for example, a spring) for controlling the position of the rotating rotor core 40, and the rotor 20 can have a simple structure.

[0020] In other embodiments, the rotating rotor core 40 may be rotated from the opposite pole position to the same pole position by only the first control.

[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 variations of 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. Furthermore, the technology exemplified in this specification or drawings simultaneously achieves multiple objectives, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0022] 10: motor drive device, 12: motor, 20: rotor, 22: shaft, 30: fixed rotor core, 32: magnetic pole, 40: rotating rotor core, 42: magnetic pole, 80: stator, 90: control device

Claims

[Claim 1] A motor drive device, A rotor, a stator; a control device for controlling the current flowing through the stator; and The rotor is A shaft and a fixed rotor core fixed to the shaft; a rotating rotor core attached to the shaft and rotating relative to the shaft between a homopolar position where the magnetic poles are oriented in the same polarity as the fixed rotor core and an opposite polarity position where the magnetic poles are oriented in the opposite polarity as the fixed rotor core and are positioned forward of the homopolar position in the direction of rotation; and a motor drive device in which, when the rotating rotor core is rotated from the opposite pole position to the same pole position while torque is being applied to the fixed rotor core on the front side in the rotation direction, the control device changes the current phase angle and increases the current flowing through the stator so that torque is applied to both the fixed rotor core and the rotating rotor core on the front side in the rotation direction.

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