JP6282326B2 - Permanent magnet type motor and electric power steering device - Google Patents

Description

  The present invention relates to a rotation in which a magnetic projection is provided between a stator in which multiple multiphase windings are wound around a stator core, and a permanent magnet having a different polarity arranged adjacent to the rotor core. The present invention relates to a permanent magnet type motor composed of a child and an electric power steering apparatus equipped with the same.

  Patent Document 1 discloses a multi-phase winding motor having a multi-phase winding group composed of a multi-phase winding and an inverter for driving the multi-phase winding in a single AC motor. ing. In such a motor, the torque of the entire motor is obtained by energizing the inverters so that the torque ripple generated by one multiphase winding and the torque ripple generated by another multiphase winding are in opposite phases. Ripple can be offset.

Japanese Patent Application Laid-Open No. 7-298685

However, in a multi-phase winding AC motor, when a plurality of multi-phase windings are arranged close to each other, the magnetic flux generated by one multi-phase winding is linked to other multi-phase windings. A voltage is generated in the other multiphase winding. Since this is superimposed as a disturbance on the applied voltage to be energized by the inverter of the other multi-phase winding, it is more difficult to control the motor by canceling the torque ripple generated by the multi-phase windings in opposite phases. There was a problem of becoming.
In view of the above problems, the present invention provides a permanent magnet type motor capable of ensuring the controllability of the motor and an electric power steering apparatus equipped with the permanent magnet type motor.

The permanent magnet type motor of the present invention includes a stator having a stator core in which an armature winding is housed in a slot, and a rotor core facing the stator via an air gap on the inner peripheral side of the stator. And the armature winding is a plurality of sets of multiphase windings, and each of the plurality of sets of armature windings is supplied with current from an individual inverter. The permanent magnets are arranged circumferentially on the surface of the rotor core, the polarities of the adjacent permanent magnets are opposite to each other, and the rotor core is between the adjacent permanent magnets. A protrusion made of a magnetic material projecting from the non-magnetic gap between the protrusion and the permanent magnet, and a non-magnetic gap between the protrusion and the permanent magnet. The protrusion protruding from the rotor core during The angle occupied in the circumferential direction of the rotor core formed by laminating combine to steel sheet having a different said projections are arranged and the portion of the protrusion is in contact with the permanent magnets adjacent to each other.

The permanent magnet type motor according to the present invention has a magnetic protrusion between adjacent permanent magnets for a multiplex multiphase winding AC motor, so that the reluctance torque can be increased in each multiphase winding, The motor output can be increased. On the other hand, by arranging a permanent magnet on the surface of the rotor core, the magnetic gap between the rotor and the stator can be increased, and a non-magnetic gap is provided between the permanent magnet and the protrusion. Therefore, magnetic coupling between multiphase windings, that is, increase in mutual inductance can be suppressed, so even when the control response frequency of the current is high, disturbance voltages are not easily superimposed between the multiphase windings, and the torque ripple is offset. Such motor control becomes possible. Further, the protrusion protruding from the rotor core between the adjacent permanent magnets is configured by combining and laminating steel plates having the protrusions having different angles in the circumferential direction of the rotor core. In addition, since a part of the protrusion is disposed in contact with the adjacent permanent magnet, torque ripple and cogging torque can be reduced.
The same effect can be achieved also in the electric power steering apparatus equipped with the permanent magnet type motor according to the present invention.
Other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention with reference to the drawings.

It is explanatory drawing which shows the connection method of the armature winding of the multiplex multiphase winding alternating current motor in Embodiment 1 of this invention. FIG. 3 is an explanatory diagram showing an equivalent circuit of armature windings between a set of multiple multiphase winding AC motors in the first embodiment. FIG. 3 is an explanatory diagram showing a q-axis equivalent circuit configuration of the multiplex multiphase winding AC motor according to the first embodiment. FIG. 3 is an explanatory diagram illustrating a configuration of the electric drive device according to the first embodiment. 1 is a cross-sectional view showing a configuration of a multi-phase winding permanent magnet type motor in Embodiment 1. FIG. 3 is a circuit diagram illustrating a method for driving the multiplex multiphase winding AC motor according to Embodiment 1. FIG. 3 is an explanatory diagram showing torque characteristics of the multiplex multiphase winding AC motor according to Embodiment 1. FIG. It is explanatory drawing which simplifies and shows the rotor which concerns on Embodiment 2. FIG. FIG. 9 is a diagram showing the no-load rotation speed and the iron core length when the electrical angle θt occupied by the surface of the protruding portion facing the stator iron core is changed. FIG. 10 is an explanatory diagram illustrating a rotor according to a third embodiment in a simplified manner. FIG. 11 is a diagram illustrating the no-load rotation speed and the iron core length when the thickness h of the permanent magnet is constant and the height h of the protrusion is changed. FIG. 10 is an explanatory diagram illustrating a rotor according to a fourth embodiment in a simplified manner. It is a figure which shows the change of the rated torque at the time of changing the space | interval of a permanent magnet and a projection part regarding FIG. 12, making the width | variety of a projection part constant. FIG. 10 is an explanatory diagram showing a configuration of a rotor in a fifth embodiment. FIG. 3 is a perspective view showing a rotor in the first embodiment. FIG. 10 is a perspective view showing a rotor in a sixth embodiment. FIG. 4 is an explanatory diagram illustrating a voltage waveform of a motor terminal in the first embodiment. It is explanatory drawing which shows the structure of a general electric power steering apparatus.

Embodiment 1 FIG.
FIG. 18 is an explanatory diagram showing a configuration of a general electric power steering device of an automobile. The driver steers a steering wheel (not shown), and the torque is transmitted to the shaft 3 via a steering shaft (not shown). At this time, the torque detected by the torque sensor 4 is converted into an electric signal and transmitted to an ECU (Electronic Control Unit) through the connector 1 through a cable (not shown). The ECU includes an inverter circuit that drives the control board and the motor. On the other hand, vehicle information such as vehicle speed is converted into an electrical signal and transmitted to the ECU via the connector 2. The ECU calculates necessary assist torque from the vehicle information such as the torque and the vehicle speed, and supplies current to the permanent magnet type motor 5 through the inverter.

  The permanent magnet type motor 5 is arranged in a direction parallel to the movement direction Dr (indicated by an arrow) of the rack shaft. The power supply to the ECU is sent from the battery or alternator via the power connector 6. Torque generated by the motor 5 is decelerated by a gear box 7 containing a belt (not shown) and a ball screw (not shown), and a rack shaft (not shown) inside the housing 8 is moved in the direction Dr. Thrust is generated to assist the driver's steering force. Thereby, the tie rod 9 moves, the tire can steer and the vehicle can be turned. Assisted by the torque of the permanent magnet type motor 5, the driver can turn the vehicle with a small steering force. The rack boot 10 is provided so that foreign matter does not enter the apparatus. The motor 5 and the ECU are integrated to constitute an electric drive device.

  FIG. 4 is an explanatory diagram showing the configuration of the electric drive device according to the first embodiment. In addition, in each figure, the same code | symbol shows the same or equivalent part. The electric drive device has a structure in which a multiple multiphase winding AC motor, which is a permanent magnet type motor of the present invention, and an ECU are integrated. First, a permanent magnet type motor having multiple multiphase windings will be described. The permanent magnet motor 5 includes a stator core 11 configured by laminating electromagnetic steel plates, an armature winding 12 housed in the stator core 11, and a frame 13 that fixes the stator core 11. Further, the frame 13 is fixed by a housing 14 and a bolt 15 provided on the front surface of the motor 5. The housing 14 is provided with a bearing 15a. The bearing 15a, together with the bearing 15b, rotatably supports a rotating shaft (shaft) 16. The bearing 15b is supported by a wall portion 17 provided integrally with the frame 13 or separately. A rotor core 18 is press-fitted into the shaft 16, and a permanent magnet 19 is fixed to the rotor core 18. A pulley 20 that drives the rack shaft is coupled to the front end of the shaft 16. A sensor permanent magnet 21 is coupled to the rear end of the shaft 16.

  The frame 13 is fixed by a housing that also serves as a heat sink 24 provided on the rear surface portion of the motor 5. A case 25 is hermetically fixed to the rear surface of the heat sink 24. Inside the case 25, a control board 26 of the ECU and a switching element 27 constituting an inverter circuit for driving the motor 5 are housed with an intermediate member 34 interposed. The switching element 27 dissipates heat generated by being placed on the heat sink 24. A sensor unit 28 that detects the rotational position of the motor 5 is provided with a substrate 30 with a magnetic sensor 29 facing the sensor permanent magnet 21 coupled to the shaft 16, and the rotational position of the motor 5 detected by the magnetic sensor 29. Is output to the control board 26 via the connection member 31. Reference numeral 32 denotes a support part for fixing the connection member 31 to the substrate 30, and 33 denotes a recess 33 provided in the heat sink 24 with respect to the substrate 30.

  FIG. 5 is a cross-sectional view showing the configuration of a multi-phase winding permanent magnet motor. A stator 42 is provided on the outer peripheral side of the rotor 41, and the stator 42 has an armature winding 12 and a stator core 11. The stator core 11 includes an annular core back 43 made of a magnetic material such as an electromagnetic steel plate, and teeth 44 extending from the core back 43 to the inner peripheral side. The armature winding 12 is accommodated in a slot 45 provided between adjacent teeth 44. Although not shown, insulating paper or the like is inserted between the armature winding 12 and the stator core 11 to ensure electrical insulation. For example, a total of 48 teeth 44 are provided, and therefore the number of slots 45 is also 48. Slot numbers 1 to 48 are assigned to the slots 45. In the slot 45, the coil of the armature winding 12 is accommodated.

  The first armature winding set is composed of three phases U1, V1 and W1 (see FIG. 1), and the second armature winding set is composed of U2, V2 and W2 phases. It is configured. As shown in FIG. 5, the windings are arranged in the order of U1, U2, W1, W2, V1, V2 from the first slot, and in the order of U1, U2, W1, W2, V1, V2 after the seventh slot. Arranged in the same order up to the 48th. That is, the first armature winding and the second armature winding are disposed in adjacent slots. However, the armature windings are arranged so that the current directions of U1 of the first slot and U1 of the seventh slot are opposite to each other. In other words, the distributed winding is wound from the first slot to the seventh slot. The armature winding straddles a total of six teeth 44. This corresponds to an electrical angle of 180 degrees, and the short winding coefficient is 1, so that the magnetic flux generated by the permanent magnet can be used effectively, a small and high torque motor can be obtained, and the amount of permanent magnet can be reduced. There is an effect that the cost can be reduced as compared with a motor having a small winding coefficient.

  On the inner peripheral side of the stator 42, a rotor 41 including a permanent magnet 19 that faces the stator core is provided on the surface of the rotor core 18. Eight permanent magnets 19 are arranged in the circumferential direction. The polarities of adjacent permanent magnets 19 are opposite to each other. Further, protrusions 46 are provided between the permanent magnets 19 on the surface of the rotor core 18. A non-magnetic gap 47 for reducing leakage magnetic flux is provided between the projection 46 and the permanent magnet 19 on both sides of the projection 46. The protrusion 46 has the effect of reducing the gap of the motor 5 and increases the inductance. As a result, the flux-weakening control can easily exert an effect, and there is an effect that the torque can be improved during high-speed rotation. The rotor core 18 is configured by laminating electromagnetic steel plates and the like, and the electromagnetic steel plates are connected to each other by a crimping portion (not shown). A shaft 16 passes through the center of the rotor core 18. In FIG. 5, a metal protective tube may be provided so as to cover the outer periphery of the permanent magnet 19 in order to prevent the permanent magnet 19 from scattering. The protective tube is made of a nonmagnetic metal such as aluminum or SUS (stainless steel).

  FIG. 6 is a circuit diagram illustrating a method for driving the multi-phase winding AC motor according to the first embodiment. As shown in the figure, the 6-phase (U1, V1, W1, U2, V2, W2) armature windings of the multi-phase winding AC motor 5 are connected to the three-phase terminals (U1 ′, V1) of the first inverter. ', W1'), U1 and U1 ', U2 and U2', V1 and V1 ', V2 and V2', W1 and W1 ', W2 on the three-phase terminals (U2', V2 ', W2') of the second inverter And W2 ′ are connected to each other.

  In such a multi-phase winding motor 5 driven by a plurality of inverters, the magnetic flux generated by the multi-phase winding group is linked to the other multi-phase winding group, so that the other multi-phase windings are combined. A voltage is generated in the wire set. This is superimposed as a disturbance on the voltage applied to the other multi-phase winding set by the inverter, so that the motor control that cancels the torque ripple generated by each multi-phase winding set in the opposite phase is more effective. There was a problem of becoming difficult.

  FIG. 1 is an explanatory diagram showing a connection method of armature windings of a motor having double three-phase windings. FIG. 1A is an explanatory diagram of Δ connection, and FIG. 1B is an explanatory diagram of Y connection. The present invention can be applied to both Δ connection and Y connection. An equivalent circuit of the U1 phase of the first winding group (first armature winding group) and the U2 phase armature winding of the second winding group (second armature winding group) is expressed as shown in FIG. be able to. In FIG. 2, Vu represents each terminal voltage of the winding, Iu represents current, R represents resistance, Ve represents induced voltage, lm represents leakage inductance, M represents mutual inductance, and subscripts 1 and 2 represent primary sides, respectively. , Secondary side. N is a turn ratio referred to as a transformer. Of these values, especially lm and M are different from values used in normal motor control, and indicate the inductances between multiple two phases arranged in parallel.

  In general, in the multi-phase winding AC motor, the number of windings in parallel is the same, and therefore n = 1. Equivalent circuit of V1 phase and V2 phase, W1 phase and W2 phase, U1 phase and V2 phase, U1 phase and W2 phase, V1 phase and U2 phase, V1 phase and W2 phase, W1 phase and U2 phase, W1 phase and V2 phase 2 is also the same as FIG. 2, so in the case of three-phase equilibrium, even if coordinate conversion is performed from the UVW three-phase to the dq axis of the rotor, the equivalent circuit on this dq axis is the same as the equivalent circuit shown in FIG. Become.

  Further, an equivalent circuit of the q-axis when coordinate-converted to the rotor dq-axis is shown in block diagram form in FIG. In the figure, vq1 and vq2 are q-axis voltages of the first winding group and the second winding group, iq1 and iq2 are q-axis currents of the first winding group and the second winding group, respectively, and Lq1 and Lq2 are respectively Q-axis components of the self-inductance of the windings of the first winding set and the second winding set, Ra1 and Ra2 are resistance components of the windings of the first winding set and the second winding set, and Mq12 and Mq21 are the first It is the q-axis component of the mutual inductance of the winding between the winding set and the second winding set. s represents a differential operator of Laplace transform. vq12 and vq21 are disturbance voltages superimposed on the first winding group and the second winding group due to the mutual inductance between the first winding group and the second winding group, respectively. FIG. 3 shows an equivalent circuit on the rotor q-axis, but the equivalent circuit on the rotor d-axis has the same configuration. Since the disturbance voltage is proportional to the differential value s, which is the control response frequency of the current, it increases as the current is controlled at high speed by motor control, making motor control that cancels torque ripple at a high response frequency difficult. .

  Next, the reason why torque ripple can be reduced by the permanent magnet type motor of the first embodiment will be described. As shown in FIG. 5, the slot pitch of the stator core of the permanent magnet type motor is 360 degrees / 48 × 4 = 30 degrees in electrical angle since the number of slots is 48 and the number of poles is 8. Further, since the first armature winding and the second armature winding are accommodated in the adjacent slots 45, U1 and U2 are out of phase with each other by an electrical angle of 30 degrees. V1 and V2, and W1 and W2 are also 30 degrees out of phase with each other. Therefore, when a three-phase alternating current having a phase difference of 30 degrees is applied to the first armature winding and the second armature winding, the electricity generated by the magnetomotive force of the first armature winding The phase of the sixth-order torque ripple generated by the sixth-order torque ripple and the magnetomotive force of the second armature winding is reversed, and the sixth-order torque ripple is canceled. A circuit in which two inverters, such as a first inverter and a second inverter as shown in FIG. 3, are provided, and currents having different phases are passed between the first armature winding and the second armature winding, respectively, are controlled individually. Can be realized. A similar effect can be obtained if the difference in current phase between the first armature winding and the second armature winding is around 20 to 40 degrees.

  FIG. 7 is an explanatory diagram showing torque characteristics of the multiplex multiphase winding AC motor according to the first embodiment. In the figure, the torque characteristic is represented by a torque value when the horizontal axis is the rotational speed. Since the output of the multi-phase winding AC motor is represented by the product of the rotational speed and the torque, in order to increase the output of the multi-phase winding AC motor, the torque characteristics in FIG. It is necessary to make it. Here, as shown in FIG. 7, the torque characteristics can be classified into the operation region A and the operation region B based on the difference in the drive conditions. In the operation region A, the amount of current supplied to the motor is limited, and thus the dependency on the rotational speed of the torque is small. In the operation region B, the amount of voltage supplied to the motor is limited, so the dependency on the rotational speed of the torque is large. That is, in order to increase the output of the motor, it is necessary to improve both the torques in the operation region A and the operation region B having different drive conditions.

  In the multi-phase winding AC motor according to the first embodiment, in operation region A, a substantially constant d-axis current is supplied regardless of the rotational speed in order to maximize torque, and in operation region B, voltage saturation is alleviated. A different d-axis current is supplied for each rotation speed. Here, the torque T of the multiplex multiphase winding AC motor of the first embodiment is expressed as follows.

  Where φm in equation (1) is the amount of magnetic flux generated by the permanent magnet, id and iq are the d-axis and q-axis currents supplied to the multiplex multiphase winding, respectively, and P is the number of magnetic poles of the multiplex multiphase winding AC motor. Represent. Also, one item on the right side is magnet torque, and two items are reluctance torque. In the first embodiment, as shown in FIG. 8, a stator core (armature) made of a magnetic material protruding from a rotor core (field magnetic core) 18 is disposed between adjacent permanent magnets 19. Since it has the projection part 46 of the angle (theta) t which a surface occupies, Lq showing especially the ease of a magnetic flux of q-axis direction improves compared with Ld. Therefore, in Embodiment 1, since the d-axis current is supplied in the operation region A and the operation region B, the reluctance torque of the equation (1) can be used, and the torque in the operation region A and the operation region B (high speed region). Therefore, it is possible to increase the output of the multi-phase winding AC motor. Here, the inductance Lq of the motor depends on the angle θt occupied by the surface of the motor projection 46 shown in FIG. 8 that faces the stator core, and the torque in the operation region A and the operation region B adjusts θt. Can be determined. In FIG. 8, θm is an angle occupied by a surface of the permanent magnet 19 provided on the surface of the rotor core 18 that faces the stator core, and O is the rotation center of the rotor.

  Next, consider the influence of the disturbance voltage in the first embodiment. Here, as can be seen from FIG. 3, in the multi-phase winding AC motor having multiplexed windings, disturbance voltages interact with each other to obtain disturbance values iq1 ′ and iq2 ′ for the current control system. Works. The disturbance values iq1 ′ and iq2 ′ are expressed as follows from the q-axis equivalent circuit block diagram of FIG.

  Here, iq1 and iq2 are q-axis currents of the respective windings of the first winding group and the second winding group, and Ra1 and Ra2 are resistances of the windings of the first winding group and the second winding group, respectively. Lq1 and Lq2 are q-axis components of the self-inductance of each of the first winding group and the second winding group, and Mq12 is the winding of the first winding group and the second winding group. It is a q-axis component of mutual inductance representing interference.

  From the above, when the current control frequency is increased, the Laplace transform differential operator s is increased, and the disturbance value is substantially dependent on the magnetic coupling Mq12 / Lq1 or the magnetic coupling Mq12 / Lq2 from the above equation. It is clear. When the magnetic coupling increases, the disturbance value increases. When the disturbance of the current control system increases, the response of the current control system cannot be increased, and the controllability of the motor deteriorates. The armature according to the first embodiment may be considered as Mq12 / Lq1≈Mq12 / Lq2 because the first winding group and the second winding group are symmetrical structures. Therefore, the magnetic coupling will be described for Mq12 / Lq1. Here, the armature coils U1 and U2 are arranged in adjacent slots, and θ is represented by the following expression when the angle between the adjacent slots is θ (electrical angle).

  Here, P is the number of magnetic poles of the multi-phase winding AC motor, N is the number of slots, and in the first embodiment, P = 8 and N = 48, so θ = 30 degrees (electrical angle). Here, for example, when current is supplied to the armature coil U1 of the first winding group to generate the magnetic flux φU1, the magnetic flux φU2 interlinked with the armature coil U2 of the second winding group is simply expressed as follows. As shown.

  This is because the armature coils U1 and U2 have a phase difference of θ = 30 degrees (electrical angle) in electrical angle. Moreover, the relationship of Formula (5) is materialized also in the combination of the armature coil which adjoins between another 1st winding set and 2nd winding set. Equation (5) is a relational expression regarding magnetic flux, but the same relational expression holds for the voltage Vu2 generated in the armature coil U2 when the voltage Vu1 is applied to the armature coil U1. It shows that the same relational expression holds for the voltage generated at U2-V2 of the second winding set when U1-V1 of the first winding set of the motor is excited.

  Therefore, when dq-axis conversion is performed on the magnetic flux generated in the multi-phase winding set of the armature when current is supplied to the first winding set, the q-axis flux φq1 of the first winding set, the second winding The following formula is established for a set of q-axis magnetic flux φq2.

  As shown in equation (7), at 0.866, the magnetic coupling between the first winding group and the second winding group is large, and the response of the current control system cannot be sufficiently increased, and the controllability of the motor is good. There was no problem. On the other hand, in the first embodiment, the magnetic coupling is reduced by devising the structure on the rotor 41 side. As shown in FIG. 5, the rotor 41 has a permanent magnet 19 disposed on the surface of the rotor core 18. Eight permanent magnets 19 are arranged in the circumferential direction, and the magnetization directions of the permanent magnets 19 are magnetized so that the magnetization directions of the permanent magnets 19 adjacent in the circumferential direction are opposite to each other. Since the magnetic gap between the rotor 41 and the stator 42 can be increased by disposing the permanent magnet 19 on the surface of the rotor core 18, the magnetic coupling between the first winding group and the second winding group is reduced. The effect that it can be obtained.

  In addition, a protrusion 46 is provided between the adjacent permanent magnets 19. The protrusion 46 is made of a magnetic material. The rotor core 18 is configured by laminating steel plates such as electromagnetic steel plates and SPCC (cold rolled steel plates), and the protrusions 46 are configured to be integrated by punching the electromagnetic steel plates and SPCC with a die. The Since the protrusions 46 are provided, the inductance can be improved, the effect of weakening magnetic flux control can be easily exhibited, and the torque at high speed rotation can be improved. In addition, reluctance torque can be generated, the motor torque can be improved, and the amount of permanent magnet 19 used can be reduced. Between the permanent magnet 19 and the protrusion 46, nonmagnetic gap portions 47 are provided on both sides of the protrusion 46. The gap 47 may be an air gap (air), or may be made of a nonmagnetic metal such as aluminum or SUS (stainless steel) or a resin. When the gap 47 is a gap, the weight can be reduced.

  The presence of the nonmagnetic gap portion 47 can reduce the leakage magnetic flux generated between the permanent magnet 19 and the protruding portion 46. Therefore, there is an effect that the torque can be improved and the usage amount of the permanent magnet 19 can be reduced. At the same time, the non-magnetic gap 47 also acts as a magnetic gap between the stator 42 and the rotor 41, thereby reducing the magnetic coupling between the windings of the first winding group and the second winding group. There is an effect that can be done.

  FIG. 15 is a perspective view showing the rotor in the first embodiment. In FIG. 15, the nonmagnetic gap 47 provided between the permanent magnet 19 and the protrusion 46 is provided over the entire axial direction. By adopting such a configuration, it is possible to effectively reduce the leakage magnetic flux generated between the permanent magnet 19 and the protrusion 46 and to effectively reduce the above-described magnetic coupling. However, the nonmagnetic gap portion 47 is not necessarily provided over the entire axial direction. If the width of the protruding portion 46 is increased in a part of the axial direction so as to contact the side surface of the permanent magnet 19, the permanent magnet 19 can be positioned in the circumferential direction. Position accuracy can be improved. As a result, there is an effect that torque ripple caused by unbalance on the rotor side can be reduced.

With the above configuration,

The controllability can be improved. As a result, the voltage Vu2-v2 generated at the U2-V2 terminal of the second winding set when the U1-V1 terminal of the first winding set of the motor is excited with the voltage Vu1-v1.

It is shown that holds. FIG. 17 shows a voltage waveform when an AC voltage is applied to the motor terminal of the first winding group and the voltage of the motor terminal of the second winding group is measured. The voltage on the vertical axis is normalized so that Vu1-v1 is 1. Further, the frequency of the voltage was set to 1 kHz as a high frequency so that the resistance with respect to the reactance of the armature winding can be ignored. The voltage waveform was a sine wave. From FIG. 17, Vu2-v2 is sufficiently smaller than the value obtained by multiplying Vu1-v1 by 0.866. Therefore, the condition of equation (9) is satisfied, and the relationship between the first winding set and the second winding set is satisfied. It can be seen that a motor with small magnetic coupling and good controllability was obtained.

  Furthermore, by providing the nonmagnetic gap portion 47, the effects of reducing the leakage magnetic flux between the permanent magnet 19 and the projection 46 and improving the torque during high-speed rotation can be obtained as described above. In the above description, the multi-phase winding AC motor having 8 poles and 48 slots in which the winding sets have an electrical phase difference of 30 ° has been described. The multi-phase winding is not limited to the phase difference, the number of poles, and the number of slots, but the winding is electrically separated into two and each winding set is driven by a different motor driving device For the line AC motor, the same effect as described above can be obtained.

  In the above description, the case where the armature winding is wound across a plurality of teeth 44 has been described, but the same applies to the case where the armature winding is wound around one tooth 44 in a concentrated manner. This holds true. Further, in the above description, the case where the winding pitch of the armature winding is a full-pitch winding with an electrical angle of 180 ° has been described, but the same effect as described above can be obtained even when the electrical angle is other than 180 °. In the above description, the multi-phase winding AC motor is described in which the windings are electrically separated into two winding sets and are driven by two different motor driving devices. The same effect as described above can be obtained when the number of winding sets separated and the number of motor driving devices are increased.

  If the multiple multiphase winding AC motor of the first embodiment is applied to the electric power steering apparatus, torque ripple can be reduced and the steering feeling of the driver can be improved. Further, it is possible to improve the quietness of a vehicle equipped with the electric power steering device. Since the output of the multi-phase winding AC motor is improved, the electric power steering device can be reduced in size and weight, and the vehicle equipped with the electric power steering device can be reduced in size and weight.

Embodiment 2.
FIG. 8 shows the structure of the rotor, and only two poles are shown for simplicity. The angle occupied by the surface of the projection 46 facing the stator core is θt. FIG. 9 is a diagram showing the no-load rotation speed and the iron core length (the length of the iron core in the rotation axis direction) when θt is changed in FIG. The value is a ratio to the value when the protrusion 46 is not provided, that is, when θt = 0. θt is expressed in electrical angle. The permanent magnet 19 imposes a condition that the cross-sectional area in the motor cross section (the cross section perpendicular to the rotation axis) is constant, and the iron core length is adjusted so that the rated torque is equal to that when θt = 0. As the width θt of the protrusion 46 is increased from 0, the width of the protrusion 46 increases, so that the reluctance torque can be used instead of the magnet torque. And the no-load rotation speed increases. When 0 <θt ≦ 50 (degrees), the motor core length can be reduced, and at the same time, the no-load rotational speed is increased. The reluctance torque can be used in the operation region B (high speed region), the magnet torque can be used in the operation region A (low rotation region), and the torque in the operation region B can be increased without increasing the rotation shaft length as compared with the case where no protrusion is provided. It can be improved.

  Moreover, since the magnetic gap between the rotor 41 and the stator 42 can be increased by arranging the permanent magnet 19 on the surface of the rotor core as described above, the first winding group and the second winding group The effect that magnetic coupling can be reduced is obtained. Further, since the non-magnetic gap 47 is provided between the permanent magnet 19 and the protrusion 46, the leakage magnetic flux generated between the permanent magnet 19 and the protrusion 46 can be reduced, and at the same time, the non-magnetic gap 47 Since this also acts as a magnetic gap between the stator 42 and the rotor 41, the magnetic coupling between the armature coils of the first winding group and the second winding group can be reduced.

  In particular, an electric power steering motor requires a high rotational speed because it must be turned at a high speed in order to avoid obstacles during emergency avoidance, and requires a high torque during garage entry and parking. Furthermore, if an increase in weight that deteriorates fuel consumption must be avoided, the length cannot be increased because the attachment performance is not deteriorated, and the iron core length equivalent to θt = 0 without the protrusion 46 is added to the constraint, It can be said that 0 <θt ≦ 50 (degrees) is the optimum range.

Embodiment 3 FIG.
FIG. 10 shows the structure of the rotor, and only one pole is shown for simplicity. The thickness of the permanent magnet 19 is Tm, and the height of the protrusion 46 (the height of the protrusion 46 from the lower end surface of the permanent magnet) is h. FIG. 11 is a diagram showing the no-load rotation speed and the iron core length when the thickness h of the permanent magnet 19 is constant and the height h of the protrusion 46 is changed. The value is a ratio to h = 0 when there is no protrusion 46. The permanent magnet 19 imposes a condition that the cross-sectional area in the motor cross-section is constant, and the iron core length is adjusted so that the rated torque is equal to that when h = 0.

  Since the height of the protrusion 46 increases as h / Tm increases, the reluctance torque can be used instead of the magnet torque, the iron core length decreases, the winding resistance also decreases, and the no-load rotation speed Becomes larger. When h / Tm = 1, that is, when the height of the protrusion 46 is equal to the thickness of the permanent magnet 19, the iron core length is minimum. In general, a motor having a large saliency such as a reluctance motor has a large torque ripple, so the range of h / Tm> 1 is not desirable because the steering feeling is deteriorated, and the range of 0 <h / Tm ≦ 1 is a motor control. It is the optimal range that satisfies the characteristics and high rotation performance. Even in this region, the length of the iron core can be shortened compared to the case where there is no protrusion 46, and therefore the motor can be reduced in size, which is advantageous in terms of fuel efficiency improvement and attachment.

  Further, since the permanent magnet 19 is arranged on the surface of the rotor core 18 as described above, the magnetic gap between the rotor 41 and the stator 42 can be increased, so that the first winding group and the second winding group The magnetic coupling can be reduced. Further, since the non-magnetic gap 47 is provided between the permanent magnet 19 and the protrusion 46, the leakage magnetic flux generated between the permanent magnet 19 and the protrusion 46 can be reduced, and at the same time, the non-magnetic gap 47 Since this also acts as a magnetic gap between the stator 42 and the rotor 41, the magnetic coupling between the armature coils of the first winding group and the second winding group can be reduced.

Embodiment 4 FIG.
FIG. 12 shows the structure of the rotor, and only one pole is shown for simplicity. The angles in the circumferential direction of the nonmagnetic gap portion 47 between the permanent magnet 19 and the protrusion 46 are denoted by θa1 and θa2. Here, θa1 = θa2. By setting θa1 = θa2, there is an effect that the torque ripple can be reduced because the magnetic balance is achieved. FIG. 13 is a diagram showing a change in the rated torque when the distance between the permanent magnet 19 and the protrusion 46, that is, the circumferential angle of the nonmagnetic gap 47 is changed while the width of the protrusion 46 is constant. . The value is a ratio when the interval is zero and 100%. Θa on the horizontal axis is defined as θa = θa1 + θa2.

  As the interval θa increases from 0, the amount of magnetic flux leaking from the permanent magnet 19 in the rotor 41 decreases, so the amount of magnetic flux contributing to the torque increases and the rated torque increases. If the interval θa exceeds 10 degrees, the permanent magnet 19 magnetic flux that contributes to torque decreases, so the effect of decreasing the permanent magnet 19 magnetic flux itself increases. When the interval θa exceeds 20 degrees, the rated torque is reduced as compared with the case of the interval 0.

  From the above, the range of 0 <θa <20 ° is the optimum range for increasing the rated torque. Further, as described above, by arranging the permanent magnet 19 on the surface of the rotor core 18, the magnetic gap between the rotor 41 and the stator 42 can be increased, so that the first winding group and the second winding group The effect that magnetic coupling can be reduced is obtained. Further, since the non-magnetic gap 47 is provided between the permanent magnet 19 and the protrusion 46, the leakage magnetic flux generated between the permanent magnet 19 and the protrusion 46 can be reduced, and at the same time, this non-magnetic gap Since 47 also acts as a magnetic gap between the stator 42 and the rotor 41, the magnetic coupling between the armature coils of the first winding group and the second winding group can be reduced.

Embodiment 5. FIG.
In the first to fourth embodiments so far, the example in which the nonmagnetic gap portion 47 is provided uniformly in the direction of the rotation axis of the motor has been described, but the present invention is not limited thereto. FIG. 14 shows a structure in which the iron core with the protrusions 46 and the iron core without the protrusions 46 or with a small protrusion 46 or the iron cores having the protrusions 46 serving as permanent magnet pressers are combined and laminated in the fifth embodiment. It is explanatory drawing. For simplification, only one pole is shown.

  In FIG. 14, the portions indicated by A <b> 1 and A <b> 2 are regions where the protrusion 46 is in contact with the permanent magnet 19 and there is no nonmagnetic gap 47. The portions indicated by B1 and B2 are regions where nonmagnetic gap portions 47 are provided. The portions indicated by C1 and C2 are regions provided with nonmagnetic gap portions 47 wider than B1 and B2. D is an area without the protrusion 46. The protrusions 46 in the areas indicated by A 1 and A 2 can be used for positioning the permanent magnet 19. Also, torque ripple and cogging torque can be changed if the shape, such as the width and height of the protrusion 46, is different. Therefore, the torque ripple and cogging torque can be reduced by combining them in the direction of the rotation axis as shown in FIG. The effect that it can be obtained. Further, the rotor core 18 as shown in FIG. 14 can be laminated by devising the configuration of the mold, and the above-described effects can be obtained without significantly increasing the cost.

Embodiment 6 FIG.
In the first to fifth embodiments so far, the example in which the non-magnetic gap between the permanent magnet 19 and the protrusion 46 of the rotor core 18 is air has been described. However, the present invention is not limited to this. FIG. 16 is a perspective view showing a rotor in which a nonmagnetic gap portion is constituted by a resin member 48. The nonmagnetic gap portion is disposed so that the resin member abuts against the side surface of the permanent magnet 19. As a result, the permanent magnet 19 can be positioned in the circumferential direction, and manufacturing variations on the rotor side can be reduced, so that a motor having a small cogging torque and torque ripple can be obtained. Further, by fixing the radial direction of the permanent magnet 19 by the resin member 48, the effect of preventing the permanent magnet 19 from scattering can be obtained. Further, if the adhesive is omitted, an effect that production cost and material cost can be reduced can be obtained. The same effect can be obtained with the gap portion 47 of the nonmagnetic portion, not limited to resin, but also with a metal such as nonmagnetic aluminum or SUS. However, since resin is lighter than metal, it has the effect of reducing motor weight and reducing inertia.
It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

Claims (3)

A stator having a stator core in which an armature winding is housed in a slot, and a rotor core facing the stator via an air gap on the inner peripheral side of the stator, and can be rotated around a rotating shaft. And a rotor supported by
The armature winding is a plurality of sets of multiphase windings,
The plurality of sets of armature windings are each supplied with current from an individual inverter,
On the surface portion of the rotor core, permanent magnets are arranged in the circumferential direction, and the polarities of the adjacent permanent magnets are opposite to each other,
Between the adjacent permanent magnets, there is provided a protrusion made of a magnetic material protruding from the rotor core,
A non-magnetic gap is interposed between the protrusion and the permanent magnet in the whole or a part in the rotation axis direction, and the protrusion protrudes from the rotor core between the adjacent permanent magnets. Is formed by combining and stacking steel plates having the protrusions having different angles in the circumferential direction of the rotor core, and a part of the protrusions are disposed in contact with the adjacent permanent magnets. A permanent magnet type motor characterized by having The armature windings are two sets of three-phase windings,
The first set of armature windings is supplied with current from a first inverter,
The second set of armature windings is supplied with current from a second inverter,
For the two sets of three-phase windings, the first set of armature windings are U1, V1, and W1, and the second set of armature windings are U2, V2, and W2 phases. When
The U1 phase and U2 phase windings are placed in adjacent slots,
The V1 phase and V2 phase windings are placed in adjacent slots,
The W1 phase and W2 phase windings are placed in adjacent slots,
The first inverter and the second inverter are driven by shifting the phases of the currents flowing through the first set of three-phase windings and the second set of three-phase windings from an electrical angle of 20 degrees to 40 degrees. The permanent magnet motor according to claim 1, wherein An electric power steering apparatus comprising the permanent magnet type motor according to claim 1 or 2 .

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