Rotating electric machines

Abstract

To provide a rotary electric machine in which field weakening is suppressed and field weakening current, that is, motor current is suppressed.SOLUTION: A rotary electric machine system 100 includes a stator 12 in which a three-phase coil with a pole pair number p is arranged and that has slots with a slot number Z1, and a first rotor 16 and a second rotor 18 that are rotatable relative to the stator 12 and are arranged separately from each other, and the first rotor 16 and the second rotor 18 each have magnetic poles with a number of pole pairs Z2 and a number of pole pairs Z3, and the number of pole pairs p, the number of slots Z1, the number of pole pairs Z2, and the number of pole pairs Z3 satisfy conditions of Z2=Z1±Z3, and Z3=p, and can change the relative phase angle between the first rotor 16 and the second rotor 18, and by controlling the relative phase angle and a stator current flowing through the stator 12, field weakening control of the back electromotive force is performed by combining the back electromotive force due to the magnetic poles with the number of pole pairs Z2 and the back electromotive force due to the magnetic poles with the number of pole pairs Z3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rotating electric machine. [Background technology]

[0002] In a typical rotating electric machine, the maximum torque of the motor can be increased by increasing the rotor magnetic force. However, this also increases the induced voltage, exceeding the upper voltage limit for motor control, making it impossible to rotate at high speeds.

[0003] To address this issue, a configuration has been disclosed in which the rotor's field magnet is composed of a first field magnet and a second field magnet that can rotate relative to the first field magnet, and a mechanism is provided that changes the phase of the combined magnetic poles of the field magnet relative to the first field magnet as the rotor rotates (Patent Document 1).In this mechanism, by aligning the magnetic poles of different polarities of the first and second field magnets at low rotation speeds, the governor moves due to centrifugal force as the rotation speed increases, and a relative rotational force can be applied to the second field magnet.

[0004] Also disclosed is a configuration in which a rotor, on which field magnets of different polarities are arranged alternately in the rotational direction, is divided into two halves in the axial direction, and the relative axial position of one of the halves of the rotor is changed relative to the other halves of the rotor depending on the torque direction of the rotor, or the phase of the composite magnetic poles of the field magnets is changed relative to the magnetic poles of the other halves of the rotor depending on the torque direction of the rotor (Patent Document 2).

[0005] Also disclosed is a configuration that includes a rotating means capable of changing the relative phase between an inner rotor having an inner permanent magnet and an outer rotor having an outer permanent magnet, a first member that is rotatable integrally with the outer rotor, and a second member that is rotatable integrally with the inner rotor and that, together with the first member, defines a pressure chamber inside the inner rotor, and that changes the relative phase between the inner rotor and the outer rotor by supplying a working fluid to the pressure chamber (Patent Document 3).

[0006] Furthermore, a rotating electric machine control system has been disclosed that includes a stator with stator coils arranged at multiple locations along the circumferential direction, and first and second rotors that are rotatable relative to the stator and arranged separately in the direction of the rotation axis, and that performs vector control of the current in the stator coils so as to transition the phase between the rotors, which is the relative phase difference between the second rotor and the first rotor (Patent Document 4).In this configuration, by switching the magnetic properties of the first and second rotors between an in-phase (same polarity) state and an opposite-phase (opposite polarity) state, it becomes possible to increase maximum torque by using the in-phase state at low speeds and to reduce induced voltage by using the opposite-phase state at high speeds. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 11-69743 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-262534 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-244040 [Patent Document 4] Japanese Patent Application Laid-Open No. 2014-204517 Summary of the Invention [Problem to be solved by the invention]

[0008] According to conventional technology, the fundamental wave of the magnet magnetic flux is changed by changing the relative phase angle of the two rotors, but the harmonics of the magnet magnetic flux are not taken into consideration. Changing the relative phase angle can cause harmonics to become larger than the fundamental wave, and if harmonics are not taken into consideration, there is a risk that the inverter's withstand voltage will be exceeded.

[0009] In view of the above-mentioned problems, one object of the present invention is to provide a rotating electric machine with improved efficiency by adjusting the skew angle in accordance with the operating point of the motor while taking into consideration both the fundamental wave and harmonics of the magnetic flux of the magnet. [Means for solving the problem]

[0010] One aspect of the present invention is a rotating electric machine comprising: a stator having slots of Z1 and in which three-phase coils of p pole pairs are arranged; and first and second rotors that are rotatable relative to the stator and arranged separately from each other, wherein the first rotor and the second rotor have magnetic poles of Z2 pole pair number and magnetic poles of Z3 pole pair number, respectively, and the number of pole pairs p, the number of slots Z1, the number of pole pairs Z2, and the number of pole pairs Z3 satisfy the conditions Z2=Z1±Z3 and Z3=p, and the relative phase angle between the first rotor and the second rotor can be changed, and by controlling the relative phase angle and the stator current flowing through the stator, the back electromotive force due to the magnetic poles of Z2 pole pair number and the back electromotive force due to the magnetic poles of Z3 pole pair number are combined to perform field-weakening control of the back electromotive force.

[0011] Here, in the field-weakening control of the back electromotive force, it is preferable to set the relative phase angle at which the component of the back electromotive force due to the magnetic poles of the pole pair number Z2 is minimized.

[0012] Alternatively, it is preferable to determine in advance appropriate combinations of the relative phase angle and the stator current to be passed through the stator according to the operating point and store them in a database, and to set the relative phase angle and the stator current to be passed through the stator according to the operating point by referring to the database. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a rotating electric machine in which field weakening is suppressed and the field weakening current, i.e., the motor current, is suppressed. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram showing a configuration of a rotating electrical machine system according to an embodiment of the present invention; [Figure 2] FIG. 3 is a diagram illustrating a configuration of magnetic poles of a first rotor in the first embodiment. [Figure 3] 3A and 3B are diagrams illustrating a configuration of magnetic poles of a second rotor in the first embodiment. [Figure 4] FIG. 4 is a diagram showing the relationship between the relative phase angle (skew angle) and the no-load back electromotive force in the first embodiment. [Figure 5] FIG. 4 is a diagram showing the relationship between the relative phase angle (skew angle) and the no-load back electromotive force amplitude in the first embodiment. [Figure 6] FIG. 10 is a diagram illustrating a configuration of magnetic poles of a second rotor in a second embodiment. [Figure 7] FIG. 10 is a diagram showing the relationship between the relative phase angle (skew angle) and the no-load back electromotive force amplitude in the second embodiment. [Figure 8] FIG. 10 is a diagram illustrating a configuration of magnetic poles of a first rotor in a third embodiment. [Figure 9] 10 is a diagram showing the configuration of magnetic poles of a second rotor in a third embodiment. FIG. [Figure 10] FIG. 11 is a diagram showing the relationship between the relative phase angle (skew angle) and the no-load back electromotive force amplitude in the third embodiment. [Figure 11] 5A and 5B are diagrams showing the relationship between rotation speed and torque in each control method of the rotating electrical machine system according to the embodiment of the present invention. [Figure 12] FIG. 4 is a diagram showing a motor current at an operating point A in the embodiment of the present invention. [Figure 13] FIG. 4 is a diagram showing a motor current at an operating point B in the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] [First embodiment] As shown in Fig. 1, a rotating electric machine system 100 according to a first embodiment of the present invention includes a rotating electric machine 102, a drive circuit 104, a power supply 106, and a control device 108. The rotating electric machine system 100 is mounted on, for example, a hybrid vehicle, an electric vehicle, or a fuel cell vehicle. The rotating electric machine system 100 can be used as a motor that generates driving force, and can also be used as a generator or a motor generator that has both the functions of a motor and a generator.

[0016] The rotating electric machine 102 includes a housing 10, a stator 12, a rotating shaft 14, a first rotor 16, a second rotor 18, a locking mechanism 20, a bearing 22, and a rotation angle sensor 24. Note that the second rotor 18 may be configured to slide relative to the rotating shaft 14 without providing the bearing 22. In this embodiment, only one rotation angle sensor 24 is provided for sensorless control, but a rotation angle sensor 24 may also be provided for each of the first rotor 16 and the second rotor 18.

[0017] The rotating electric machine 102 generates a driving force for the rotating shaft 14 using electric power supplied from a power source 106 by a drive circuit 104 controlled by a control device 108. The drive circuit 104 also converts the rotational energy given to the rotating shaft 14 into electric power and regenerates it into the power source 106. The drive circuit 104 can be configured to include an inverter that converts the electric power from the power source 106 into AC. The power source 106 can be configured to include a power storage system including, for example, a secondary battery.

[0018] The housing 10 is configured to mechanically support the rotating electric machine 102. The housing 10 houses a stator 12, a rotating shaft 14, a first rotor 16, a second rotor 18, a locking mechanism 20, a bearing 22, and a rotation angle sensor 24.

[0019] The stator 12 includes a stator core and a stator coil. The stator core is a hollow cylindrical member made of a laminate of electromagnetic steel sheets stacked in the axial direction of the rotating shaft 14. However, the material constituting the stator core is not limited to electromagnetic steel sheets, and may be a magnetic material such as amorphous metal, nanocrystalline soft magnetic material, or dust core. The stator coil is a coil arranged in multiple slots on the inner peripheral surface of the stator core. A magnetic field can be generated in the stator coil by passing a current from a power source 106 to the stator coil via a drive circuit 104.

[0020] A first rotor 16 and a second rotor 18 are arranged axially at a distance from each other on the rotating shaft 14. In the rotating electrical machine system 100 of this embodiment, the second rotor 18 is arranged between the two divided first rotors 16a and 16b.

[0021] The first rotors 16a and 16b are fixed to the rotary shaft 14. The second rotor 18 is installed so as to be movable in the rotational direction relative to the rotary shaft 14. That is, the second rotor 18 is rotatable relative to the rotary shaft 14. For example, the second rotor 18 is attached to the rotary shaft 14 via a bearing 22, and is rotatable relative to the rotary shaft 14 by the bearing 22.

[0022] Furthermore, the second rotor 18 is provided with a locking mechanism 20 so that it can be fixed to the rotating shaft 14. For example, a gear is provided between the first rotor 16 (16a, 16b) and the second rotor 18, and the locking mechanism 20 using a lock pin can be used to lock the second rotor 18 so that it does not rotate relative to the rotating shaft 14. However, the locking mechanism provided on the second rotor 18 is not limited to this, and any mechanism can be used as long as it can fix the second rotor 18 to the rotating shaft 14.

[0023] During normal operation of the rotating electrical machine system 100, the locking mechanism 20 prevents the second rotor 18 from rotating relative to the rotating shaft 14, allowing both the first rotor 16 (16a, 16b) and the second rotor 18 to contribute to the rotation of the rotating shaft 14. On the other hand, during field adjustment, the locking mechanism 20 is released to allow the second rotor 18 to rotate relative to the rotating shaft 14, allowing the second rotor 18 to rotate relative to the first rotor 16 (16a, 16b) and adjusting its circumferential position, thereby adjusting the field of the rotor as a whole.

[0024] In this configuration, with the locking mechanism 20 in the engaged state and the first rotor 16 (16a, 16b) and the second rotor 18 not rotating relative to the rotating shaft 14 (normal operating state), a rotating magnetic field is formed by passing a current through the stator coil of the stator 12, thereby generating an output torque that rotates the rotating shaft 14 relative to the stator 12. Conversely, the rotational energy of the rotating shaft 14 can be converted into a current flowing through the stator coil of the stator 12 and regenerated.

[0025] Furthermore, by opening the locking mechanism 20 and allowing the second rotor 18 to rotate relative to the rotating shaft 14 (adjustment state), and passing current through the stator coil of the stator 12 to form a rotating magnetic field, it is possible to generate output torque from the first rotor 16 (16a, 16b) to the rotating shaft 14 while adjusting the relative phase angle (skew angle) of the magnetic poles of the first rotor 16 (16a, 16b) and the second rotor 18.

[0026] At this time, rotation angle sensors 24 are provided on the first rotor 16 (16a, 16b) and the second rotor 18, and the control device 108 receives the rotation angles of the first rotor 16 (16a, 16b) and the second rotor 18 output from the rotation angle sensors 24 and adjusts the relative phase angle (skew angle) of the magnetic poles. That is, when adjusting the relative phase angle (skew angle) of the magnetic poles of the first rotor 16 (16a, 16b) and the second rotor 18, the lock mechanism 20 is first released to set the second rotor 18 in a state (adjustment state) that allows it to rotate with respect to the rotating shaft 14. In the adjustment state, the relative phase angle (skew angle) of the magnetic poles of the first rotor 16 (16a, 16b) and the second rotor 18 is changed by passing a current through the stator coil of the stator 12. Then, when the relative phase angle (skew angle) between the first rotor 16 (16a, 16b) and the second rotor 18 reaches a desired value, the locking mechanism 20 is brought into the coupled state, and the first rotor 16 (16a, 16b) and the second rotor 18 can be returned to a state in which they are fixed to the rotating shaft 14. It is preferable to use so-called vector control for the current flowing through the stator coil of the stator 12.

[0027] The method for adjusting the relative phase (skew angle) between the first rotor 16 and the second rotor 18 is not particularly limited, and may include a configuration in which a mechanical mechanism such as an actuator is provided to rotate the first rotor 16 and the second rotor 18 relative to each other.

[0028] The first rotor 16 (16a, 16b) has a base fixed to the rotating shaft 14 and a laminated body made of electromagnetic steel sheets stacked in the axial direction on the outer periphery of the base. However, the material constituting the laminated body is not limited to electromagnetic steel sheets, and can be a magnetic material such as amorphous metal, nanocrystalline soft magnetic material, or dust core. A plurality of first magnets and second magnets are respectively arranged in the laminated body along the circumferential direction.

[0029] In this embodiment, when 24 slots are provided at equal intervals (equal angles) on the inner peripheral wall of stator 12 and three-phase stator coils are arranged as distributed windings, an eight-pole fundamental rotating magnetic field is generated when a sinusoidal current is passed through the three-phase stator coils. In addition, a 40-pole harmonic rotating magnetic field (fifth-order harmonic rotating magnetic field) that rotates in the opposite direction to the fundamental rotating magnetic field is also generated.

[0030] As shown in the partial cross-sectional view of Figure 2, the first rotor 16 (16a, 16b) includes first magnets 30 and second magnets 32 that are arranged at equal intervals along the circumferential direction. In Figure 2, the magnetic pole directions of the first magnets 30 and second magnets 32 are indicated by arrows pointing from the south pole to the north pole.

[0031] The first magnets 30 have 40 magnetic poles arranged at equal intervals (equal angles) along the outer periphery (rotor circumferential direction) of the first rotor 16. The second magnets 32 have 8 magnetic poles arranged at equal intervals (equal angles) along the outer periphery of the first rotor 16. In the rotating electric machine system 100 of this embodiment, the first magnets 30 are arranged on the outer diameter portion of the rotor, which is the outermost periphery of the first rotor 16, and the second magnets 32 are arranged on the inner diameter portion of the rotor inside the first magnets 30. However, this is not limited to this, and the arrangement of the first magnets 30 and the second magnets 32 may be interchanged.

[0032] The second rotor 18 comprises a laminated body made of electromagnetic steel sheets stacked in the axial direction. However, the material constituting the laminated body is not limited to electromagnetic steel sheets, and may be a magnetic material such as amorphous metal, nanocrystalline soft magnetic material, or dust core. As shown in the partial cross-sectional view of FIG. 3, the second rotor 18 comprises a first magnet 34 and a second magnet 36 arranged at equal intervals along the circumferential direction of the laminated body. In FIG. 3, the magnetic pole directions of the first magnet 34 and the second magnet 36 are indicated by arrows pointing from the south pole to the north pole, respectively.

[0033] In the present embodiment, the second rotor 18 has first magnets 34 and second magnets 36 arranged in the same manner as the first rotor 16. That is, the first magnets 34 have 40 magnetic poles arranged at equal intervals (equal angles) along the outer periphery of the second rotor 18. The second magnets 36 have 8 magnetic poles arranged at equal intervals (equal angles) along the outer periphery of the second rotor 18. In the present embodiment, the first magnets 34 are arranged at the outermost periphery of the second rotor 18, and the second magnets 36 are arranged inside the first magnets 34. However, this is not limiting, and the arrangement of the first magnets 34 and the second magnets 36 may be interchanged.

[0034] Hereinafter, the spatial magnetic field formed by the 8-pole second magnets 32 and 36 in the first rotor 16 and the second rotor 18 will be described as the fundamental wave, and the spatial magnetic field formed by the 40-pole first magnets 30 and 34 will be described as the harmonic (5th harmonic).

[0035] Furthermore, when the second rotor 18 is rotated relative to the first rotor 16, the state in which the magnetic pole directions of the first magnet 30 and the first magnet 34 and the second magnet 32 ​​and the second magnet 36 are aligned is defined as the relative phase angle (skew angle) between the first rotor 16 and the second rotor 18 being 0.

[0036] 4(a) to 4(c) show the change in no-load back electromotive force versus the electrical angle when the relative phase angle (skew angle) is 0, 45°, and 9°, respectively. As shown in FIG. 4(a), when the relative phase angle (skew angle) is 0, the magnetization directions of the first magnet 30 and the first magnet 34, and the second magnet 32 ​​and the second magnet 36, are the same in the first rotor 16 and the second rotor 18. Therefore, both the fundamental wave and the fifth harmonic fluctuate with maximum amplitude. As shown in FIG. 4(b), when the relative phase angle (skew angle) is 45°, the magnetization directions of the first magnet 30 and the first magnet 34, and the second magnet 32 ​​and the second magnet 36, are opposite in the first rotor 16 and the second rotor 18. Therefore, both the fundamental wave and the fifth harmonic are approximately zero.

[0037] In contrast, as shown in Figure 4(c), when the relative phase angle (skew angle) is 9°, the magnetization directions of the first magnet 30 and the first magnet 34 in the first rotor 16 and the second rotor 18 are opposite, but the magnetization directions of the second magnet 32 ​​and the second magnet 36 are not opposite. As a result, the fifth harmonic is nearly zero, but the fundamental wave fluctuates with a certain amount of amplitude.

[0038] FIG. 5 shows the relationship between the no-load back electromotive force amplitude and the relative phase angle (skew angle) between the first rotor 16 and the second rotor 18. When the relative phase angle (skew angle) is 0, the no-load back electromotive force amplitudes of the fundamental wave and the fifth harmonic each reach their maximum values, allowing the rotating electric machine system 100 as a whole to output high torque. When the relative phase angle (skew angle) is 9°, the fundamental wave exhibits a certain degree of no-load back electromotive force amplitude, but the no-load back electromotive force amplitude of the fifth harmonic is almost zero. Therefore, the output torque of the rotating electric machine system 100 as a whole can be limited. Furthermore, when the relative phase angle (skew angle) is 45°, the no-load back electromotive force amplitudes of both the fundamental wave and the fifth harmonic are almost zero. Therefore, the output torque of the rotating electric machine system 100 as a whole can be made almost zero.

[0039] [Second embodiment] As shown in the partial cross-sectional view of Fig. 6, the rotating electric machine system 100 of the second embodiment is configured such that the magnetization direction of the magnetic poles of the first magnets 34 of the second rotor 18 is opposite to that of the first magnets 34 of the second rotor 18 of the first embodiment. In Fig. 6, the magnetic pole directions of the first magnets 34 and the second magnets 36 are indicated by arrows pointing from the south pole to the north pole. The other configurations are the same as those of the rotating electric machine system 100 of the first embodiment.

[0040] 7 shows the relationship between the no-load back electromotive force amplitude and the relative phase angle (skew angle) between the first rotor 16 and the second rotor 18 in this embodiment. When the relative phase angle (skew angle) is 0, the no-load back electromotive force amplitude of the fundamental wave is at a maximum value, but the no-load back electromotive force amplitude of the fifth harmonic is at a minimum value and is approximately 0. When the relative phase angle (skew angle) is 45°, the no-load back electromotive force amplitude of the fundamental wave is at a minimum value and is approximately 0, but the no-load back electromotive force amplitude of the fifth harmonic is at a maximum value. Furthermore, when the relative phase angle (skew angle) is 36°, the sum of the no-load back electromotive force amplitudes of the fundamental wave and the fifth harmonic is at a minimum value.

[0041] According to this embodiment, the no-load back electromotive force amplitudes of the fundamental wave and the fifth harmonic can be maximized independently by adjusting the relative phase angle (skew angle) between the first rotor 16 and the second rotor 18. This improves the controllability of the output torque of the rotating electrical machine system 100.

[0042] Note that, because changing the magnetization direction of the first magnets 34 of the second rotor 18 as in this embodiment changes the distribution of the magnetic fields in the first rotor 16 and the second rotor 18, it is preferable to optimize the shape and configuration of each of the first rotor 16 and the second rotor 18. By optimizing the first rotor 16 and the second rotor 18 to have different shapes and configurations, the performance of the rotating electrical machine system 100 can be further improved.

[0043] [Third embodiment] In the rotating electric machine system 100 of the third embodiment, the first magnets 30 and 34 of the first rotor 16 and the second rotor 18 are arranged in the shape of spokes with their magnetization directions oriented in the circumferential direction, as shown in the partial cross-sectional views of Figures 8 and 9. In Figures 8 and 9, the magnetic pole directions of the first magnets 30, second magnets 32, first magnets 34, and second magnets 36 are indicated by arrows pointing from the south pole to the north pole.

[0044] In this embodiment, the first magnet 30 of the first rotor 16 and the first magnet 34 of the second rotor 18 are configured so that they are magnetized in opposite directions.

[0045] 10 shows the relationship between the no-load back electromotive force amplitude and the relative phase angle (skew angle) between the first rotor 16 and the second rotor 18 in this embodiment. As in the second embodiment, when the relative phase angle (skew angle) is 0, the no-load back electromotive force amplitude of the fundamental wave is at a maximum value, but the no-load back electromotive force amplitude for the fifth harmonic is at a minimum value and is approximately 0. When the relative phase angle (skew angle) is 45°, the no-load back electromotive force amplitude of the fundamental wave is at a minimum value and is approximately 0, but the no-load back electromotive force amplitude for the fifth harmonic is at a maximum value. Furthermore, when the relative phase angle (skew angle) is 36°, the sum of the no-load back electromotive force amplitudes of the fundamental wave and the fifth harmonic is at a minimum value.

[0046] In the rotating electrical machine systems 100 according to the first to third embodiments, 24 slots are provided in the stator 12 to form an 8-pole three-phase magnetic field, and the first rotor 16 and the second rotor 18 are configured to switch between an 8-pole fundamental wave and a 40-pole harmonic (5th order harmonic), but the present invention is not limited to this. That is, it is sufficient that the number of slots Z1 in the stator, the number of pole pairs p of the three-phase coil, the number of pole pairs Z2 of the first magnets 30 and 34, and the number of pole pairs Z3 of the second magnets 32 and 36 satisfy the following conditions: [Number 1] Z2=Z1±Z3 Z3=P

[0047] In the first to third embodiments, the number of slots in the stator Z1 is 24, the number of pole pairs in the three-phase coil p is 4, the number of pole pairs in the first magnets 30 and 34 is Z2 is 20, and the number of pole pairs in the second magnets 32 and 36 is Z3 is 4.

[0048] Furthermore, if the skew angle at which the magnetization directions of the divided rotor magnets 2 coincide is defined as 0°, the component of the no-load back electromotive force, which corresponds to the number of pole pairs Z3, is maximum at a skew angle of 0° and minimum at (180 / Z3)°. Similarly, the component of the no-load back electromotive force, which corresponds to the number of pole pairs Z2, is maximum at a skew angle of (0+α)° and minimum at (180 / Z2+α)°, repeating every (360 / Z2)°. Here, α represents the phase shift between the divided first magnets 30 and 34 at the skew angle at which the magnetization directions of the second magnets 32 and 36 coincide (a skew angle of 0° in this embodiment). α is 0° in the first embodiment and (180 / Z2)° in the second and third embodiments.

[0049] [Control method for rotating electrical machine system] In this embodiment, when weakening the magnetic field of the back electromotive force, the relative phase angle and the stator current flowing through the stator 12 are controlled to combine the back electromotive force due to the magnetic poles of pole pair number Z2 and the back electromotive force due to the magnetic poles of pole pair number Z3, thereby performing field weakening control of the back electromotive force.

[0050] 11 shows the relationship between rotation speed and torque when the fundamental wave and the harmonic (fifth harmonic) are switched by adjusting the relative phase angle (skew angle) between the first rotor 16 and the second rotor 18. Note that this embodiment shows control in the rotating electrical machine system 100 in the second and third embodiments described above.

[0051] Here, harmonic driving is a drive control in which the relative phase angle (skew angle) between the first rotor 16 and the second rotor 18 is set so that the fundamental wave component is minimized and the harmonic driving is maximized, and then a three-phase current with a drive frequency that is the same multiple as the harmonic order is passed through the three-phase coil of the stator 12 for the rotation of the first rotor 16 and the second rotor 18. Harmonic drive control makes it possible to output high torque. However, since the harmonics of the no-load back electromotive force are maximized, the no-load back electromotive force is large and the drive frequency is also high, making it impossible to drive up to high rotational speeds.

[0052] When the rotating electric machine system 100 in the second and third embodiments is driven at fifth harmonic frequencies, the relative phase angle (skew angle) between the first rotor 16 and the second rotor 18 is set to 45°, and a three-phase current having a drive frequency five times higher than the rotation of the first rotor 16 and the second rotor 18 is passed through the three-phase coil of the stator 12.

[0053] Fundamental wave drive is a drive control in which the relative phase angle (skew angle) between the first rotor 16 and the second rotor 18 is set so that harmonics are minimized, and then a three-phase current having the same drive frequency as the rotation of the first rotor 16 and the second rotor 18 is passed through the three-phase coils of the stator 12. With fundamental wave drive control, the harmonics of the no-load back electromotive force are minimized, and therefore the no-load back electromotive voltage is relatively small, making it possible to achieve high output even in the high-speed rotation range.

[0054] However, in the high-speed rotation range, even if there is only the fundamental wave of the no-load back electromotive force, a field-weakening current must be passed to suppress the no-load back electromotive force, which tends to reduce efficiency. Therefore, in the fundamental wave drive control of this embodiment, it is preferable to set the relative phase angle (skew angle) between the first rotor 16 and the second rotor 18 so that the harmonics are minimized and the fundamental wave is made as small as possible.

[0055] When the rotating electric machine system 100 according to the second and third embodiments is fundamental wave driven, the relative phase angle (skew angle) between the first rotor 16 and the second rotor 18 is set to one of 0°, 18°, and 36°, and a three-phase current having the same drive frequency as the rotation of the first rotor 16 and the second rotor 18 is passed through the three-phase coils of the stator 12. In particular, to improve efficiency, it is preferable to set the relative phase angle (skew angle) between the first rotor 16 and the second rotor 18 to one of 18° and 36° so that harmonics are minimized and the fundamental wave is minimized as much as possible. The back electromotive force generated when the skew angle is set to one of 18° and 36° is smaller than the back electromotive force generated when the skew angle is set to 0°. This suppresses the field weakening current and reduces the motor current, thereby improving the efficiency of the rotating electric machine system 100.

[0056] Fig. 12 shows the results of comparing the motor current of the rotating electrical machine system 100 when the skew angle is adjusted at the operating point A in Fig. 11. Also, Fig. 13 shows the results of comparing the motor current of the rotating electrical machine system 100 when the skew angle is adjusted at the operating point B in Fig. 11.

[0057] At operating point A, the larger the skew angle, the smaller the field-weakening current and the smaller the motor current. At operating point B, the motor current is minimized when the skew angle is 18°. This is because the no-load back electromotive force becomes too small at a skew angle of 36°, increasing the current required to generate torque. Therefore, it is preferable to adjust the skew angle in accordance with the required torque, not just the rotation speed. For example, it is preferable to create a command value map for the skew angle, d-axis current, and q-axis current in advance to achieve optimal control according to the operating point specified by the rotation speed and torque, and then control the rotating electrical machine system 100 based on that command value map.

[0058] As described above, in the rotating electric machine system 100 according to the above embodiment, the relative phase angle (skew angle) between the first rotor 16 and the second rotor 18 is adjusted and the d-axis current and q-axis current are controlled in accordance with the operating point determined by the rotation speed and torque. This makes it possible to provide a rotating electric machine system 100 that suppresses field weakening and suppresses the field weakening current, i.e., the motor current. [Explanation of symbols]

[0059] 10 housing, 12 stator, 14 rotating shaft, 16 first rotor, 18 second rotor, 20 locking mechanism, 22 bearing, 24 rotation angle sensor, 30, 34 first magnet, 32, 36 second magnet, 100 rotating electric machine system, 102 rotating electric machine, 104 drive circuit, 106 power supply, 108 control device.

Claims

1. a stator having a number Z1 of slots and in which three-phase coils with a number p of pole pairs are arranged; a first rotor and a second rotor that are rotatable relative to the stator and are arranged separately from each other; the first rotor and the second rotor have magnetic poles with a pole pair number Z2 and magnetic poles with a pole pair number Z3, respectively; The number p of pole pairs, the number Z1 of slots, the number Z2 of pole pairs, and the number Z3 of pole pairs are Z2 = Z1 ± Z3 Z3 = p Meet the conditions of The relative phase angle between the first rotor and the second rotor can be changed, a rotating electric machine characterized in that by controlling the relative phase angle and the stator current flowing through the stator, a back electromotive force due to the magnetic poles of the pole pair number Z2 and a back electromotive force due to the magnetic poles of the pole pair number Z3 are combined to perform field-weakening control of the back electromotive force.

2. 2. The rotating electric machine according to claim 1, In the field-weakening control of the back electromotive force, the relative phase angle is set so that the component of the back electromotive force due to the magnetic poles of the pole pair number Z2 is minimized.

3. 3. The rotating electric machine according to claim 1, a database of appropriate combinations of the relative phase angle and the stator current to be passed through the stator according to an operating point, the appropriate combinations being determined in advance, and the database being referenced to set the relative phase angle and the stator current to be passed through the stator according to the operating point.

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