JP2013176233A - Induction motor, electric drive system, and electric vehicle including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction motor having high torque, an electric drive system, and an electric vehicle including the same.SOLUTION: An induction motor includes a rotor 130 having a cage conductor comprising many slots provided in a rotor iron core 137, conductive bars embedded in the slots, and a conductive end ring 134 short-circuiting those bars on both axial end faces. The cage conductor short-circuits a first bar interlinked mainly with a fundamental wave magnetic flux and a second bar interlinked mainly with a third harmonic wave component, at the end ring 134.

Description

  The present invention relates to an induction motor, an electric drive system, and an electric vehicle including them.

  A rotating electrical machine for a vehicle, such as a drive motor for a hybrid electric vehicle, requires acceleration performance such as starting, overtaking, etc., so an instantaneous acceleration torque is required for the motor. In the case of induction motors used in automobiles, it is necessary to energize a large current to generate this instantaneous torque, so the circuit loss that occurs in the inverter switching elements and bus bars is large, and the inverter is used from the viewpoint of heat generation countermeasures. There is a problem that the volume becomes large. Therefore, it is desired to reduce the inverter current when instantaneous torque is generated, that is, to improve the torque characteristics of the motor.

  As an example of the countermeasure, Patent Document 1 discloses a technique for increasing the apparent fundamental wave magnetic flux density and improving the torque by distributing the gap magnetic flux density of the motor in a substantially trapezoidal shape.

US Pat. No. 7,741,750

  In Patent Document 1, in order to make the gap magnetic flux density distribution substantially trapezoidal, the magnetic circuit is forcibly saturated by narrowing the widths of the stator teeth and the rotor teeth. As a result, although the peak value of the waveform itself is limited by magnetic saturation, it can be increased as a fundamental wave component, and torque can be improved. As a result, the current value required for torque generation can be reduced, and inverter loss can also be reduced.

  In this case, however, the magnetic circuit of the motor is always saturated (higher harmonics are superposed) under both driving conditions of acceleration of the vehicle that generates instantaneous torque and normal cruise. As a result, there is a concern that motor loss such as iron loss and copper loss due to harmonics increases and fuel consumption of the vehicle increases. Furthermore, an increase in noise caused by harmonics becomes a problem even under driving conditions where it is desired to ensure quietness in the vehicle during cruising.

  Therefore, the present invention provides an induction motor for an electric vehicle that instantaneously increases the torque only under the driving conditions that require acceleration torque.

  In order to solve the above problems, for example, the configuration described in the claims is adopted.

  The present application includes a plurality of means for solving the above-described problems. For example, a number of slots provided in the rotor core, conductive bars embedded in the slots, and shafts of these bars are provided. A rotor having a squirrel-cage winding composed of a conductive end ring that is short-circuited at both end faces in the direction, and the squirrel-cage conductor mainly includes a first bar interlinked with the fundamental wave magnetic flux, and a third The induction motor is configured to short-circuit the second bar that interlinks the second harmonic component with the end ring.

  According to the present invention, it is possible to provide an induction motor that can increase the instantaneous torque during acceleration and suppress the heat generation of the inverter without impairing the characteristics during vehicle cruising, and has excellent drive system characteristics.

  Problems, configurations, and effects other than those described above will become apparent from the description of the following examples.

The block diagram which shows the structure of the hybrid electric vehicle to which the rotary electric machine which is an Example of this invention is applied. The circuit diagram which shows the circuit structure of the inverter apparatus which is one Example of this invention. BRIEF DESCRIPTION OF THE DRAWINGS The cross-section figure of the induction motor which is one Example of this invention. 1 is a structural diagram that is one embodiment of the present invention. The elements on larger scale which show the cross-section of the induction motor which is one Example of this invention. The elements on larger scale which show the stator slot structure of the induction motor which is one Example of this invention. The elements on larger scale which show the rotor structure of the induction motor which is one Example of this invention. The measurement result which compared the torque at the time of this invention application with a prior art example. The elements on larger scale which show the rotor structure of the induction motor which is another Example of this invention. The elements on larger scale which show the rotor structure of the induction motor which is another Example of this invention.

  Hereinafter, embodiments of the present invention will be described by taking a drive motor used in a hybrid electric vehicle as an example.

[Example 1]
First, the configuration of a vehicle to which the rotating electrical machine of this embodiment is applied will be described with reference to FIG. In this embodiment, a hybrid electric vehicle having two different power sources will be described as an example.

  The hybrid electric vehicle of this embodiment is an engine ENG that is an internal combustion engine, a four-wheel drive type that is configured to drive the front wheels FLW and FRW by the rotating electric machine MG1 and the rear wheels RLW and RRW by the rotating electric machine MG2. Is.

  In the present embodiment, a description will be given of a case where the front wheels WFLW and FRW are driven by the engine ENG and the rotating electrical machine MG1, and the rear wheels RLW and RRW are driven by the rotating electrical machine MG2, respectively. The rear wheels RLW and RRW may be driven by the rotating electrical machine MG2.

  A transmission T / M is mechanically connected to the front wheel axle FDS of the front wheels FLW and FRW via a differential FDF. A rotating electrical machine MG1 and an engine ENG are mechanically connected to the transmission T / M via a power distribution mechanism PSM. The power distribution mechanism PSM is a mechanism that controls composition and distribution of rotational driving force. The AC side of the inverter device INV is electrically connected to the stator winding of the rotating electrical machine MG1. The inverter device INV is a power conversion device that converts DC power into three-phase AC power, and controls the driving of the rotating electrical machine MG1. A battery BAT is electrically connected to the DC side of the inverter device INV.

  A rotating electrical machine MG2 is mechanically connected to the rear wheel axle RDS of the rear wheels RLW and RRW via a differential device RDF and a reduction gear RG. The AC side of the inverter device INV is electrically connected to the stator winding of the rotating electrical machine MG2. Here, the inverter device INV is shared by the rotating electrical machines MG1 and MG2, and includes the power module PMU1 and the drive circuit device DCU1 for the rotating electrical machine MG1, and the power module PMU2 and the drive circuit device DCU2 for the rotating electrical machine MG2. And a motor control unit MCU.

  A starter STR is attached to the engine ENG. The starter STR is a starting device for starting the engine ENG.

  The engine control unit ECU calculates a control value for operating each component device (throttle valve, fuel injection valve, etc.) of the engine ENG based on input signals from sensors and other control units. This control value is output as a control signal to the drive device of each component device of the engine ENG. Thereby, the operation of each component device of the engine ENG is controlled.

  The operation of the transmission T / M is controlled by a transmission control unit TCU. The transmission control unit TCU calculates a control value for operating the transmission mechanism based on an input signal from a sensor or another control unit. This control value is output as a control signal to the drive mechanism of the transmission mechanism. Thereby, the operation of the transmission mechanism of the transmission T / M is controlled.

  The battery BAT is a high-voltage lithium ion battery having a battery voltage of 200 V or higher, and charge / discharge, life, and the like are managed by the battery control unit BCU. The battery control unit BCU receives a voltage value, a current value, and the like of the battery BAT in order to manage charging / discharging and life of the battery. Although not shown, a low-voltage battery having a battery voltage of 12v is also mounted as a battery, and is used as a power source for a control system, a radio and a light.

  The engine control unit ECU, the transmission control unit TCU, the motor control unit MCU, and the battery control unit BCU are electrically connected to each other via the in-vehicle local area network LAN, and are also electrically connected to the general control unit GCU. Has been. Thus, bidirectional signal transmission is possible between the control devices, and mutual information transmission, detection value sharing, and the like are possible. The general control unit GCU outputs a command signal to each control unit according to the driving state of the vehicle. For example, the general control unit GCU calculates the required torque value of the vehicle according to the accelerator depression amount based on the driver's acceleration request, and uses this required torque value to improve the engine ENG driving efficiency. Side output torque value and rotary electric machine MG1 side output torque value, the distributed engine ENG side output torque value is output as an engine torque command signal to the engine control unit ECU, and the distributed rotary electric machine MG1 side Is output to the motor control unit MCU as a motor torque command signal.

  Next, the operation of the hybrid electric vehicle of this embodiment will be described.

  When the hybrid electric vehicle starts, when traveling at a low speed (traveling region where the driving efficiency (fuel consumption) of the engine ENG decreases), the front wheels FLW and FRW are driven by the rotating electrical machine MG1. In this embodiment, the case where the front wheels FLW and FRW are driven by the rotating electrical machine MG1 at the start of the hybrid electric vehicle and at low speed traveling will be described. However, the front wheels FLW and FRW are driven by the rotating electrical machine MG1 and the rotating electrical machine MG2 is driven. May drive the rear wheels RLW and RRW (four-wheel drive traveling may be performed). Direct current power is supplied from the battery BAT to the inverter device INV. The supplied DC power is converted into three-phase AC power by the inverter device INV. The three-phase AC power obtained in this way is supplied to the stator winding of the rotating electrical machine MG1. As a result, the rotating electrical machine MG1 is driven to generate a rotational output. This rotational output is input to the transmission T / M via the power distribution mechanism PSM. The input rotation output is shifted by the transmission T / M and input to the differential FDF. The input rotational output is distributed to the left and right by the differential FDF and transmitted to the left and right front wheel axles FDS. Thereby, the front wheel axle FDS is rotationally driven. Then, the front wheels FLW and FRW are rotationally driven by the rotational driving of the front wheel axle FDS.

  During normal driving of the hybrid electric vehicle (when traveling on a dry road surface, where the driving efficiency (fuel efficiency) of the engine ENG is good), the front wheels FLW and FRW are driven by the engine ENG. For this reason, the rotational output of the engine ENG is input to the transmission T / M via the power distribution mechanism PSM. The input rotation output is shifted by the transmission T / M. The changed rotational output is transmitted to the front wheel axle FDS via the differential FDF. As a result, the front wheels FLW and FRW are driven to rotate by the WH-F. Further, when it is necessary to charge the battery BAT by detecting the state of charge of the battery BAT, the rotational output of the engine ENG is distributed to the rotating electrical machine MG1 via the power distribution mechanism PSM, and the rotating electrical machine MG1 is rotationally driven. . Thereby, rotating electrical machine MG1 operates as a generator. By this operation, three-phase AC power is generated in the stator winding of the rotating electrical machine MG1. The generated three-phase AC power is converted into predetermined DC power by the inverter device INV. The DC power obtained by this conversion is supplied to the battery BAT. Thereby, the battery BAT is charged.

  During the four-wheel drive driving of the hybrid electric vehicle (when driving on a low μ road such as a snowy road and the driving efficiency (fuel consumption) of the engine ENG is good), the rear wheels RLW and RRW are driven by the rotating electrical machine MG2. To drive. Further, as in the normal running, the front wheels FLW and FRW are driven by the engine ENG. Further, since the amount of power stored in the battery BAT is reduced by driving the rotating electrical machine MG1, the rotating electrical machine MG1 is rotationally driven by the rotational output of the engine ENG to charge the battery BAT, as in the normal running. In order to drive the rear wheels RLW and RRW by the rotating electrical machine MG2, DC power is supplied from the battery BAT to the inverter INV. The supplied DC power is converted into three-phase AC power by the inverter device INV, and the AC power obtained by this conversion is supplied to the stator winding of the rotating electrical machine MG2. As a result, the rotating electrical machine MG2 is driven to generate a rotational output. The generated rotation output is decelerated by the reduction gear RG and input to the differential device RDF. The input rotational output is distributed to the left and right by the differential RDF and transmitted to the left and right rear wheel axles RDS. As a result, the rear wheel axle RDS is rotationally driven. Then, the rear wheels RLW and RRW are rotationally driven by the rotational driving of the rear wheel axle RDS.

  During acceleration of the hybrid electric vehicle, the front wheels FLW and FRW are driven by the engine ENG and the rotating electrical machine MG1. In this embodiment, the case where the front wheels FLW and FRW are driven by the engine ENG and the rotating electric machine MG1 during acceleration of the hybrid electric vehicle will be described. However, the front wheels FLW and FRW are driven by the engine ENG and the rotating electric machine MG1 to rotate. The rear wheels RLW and RRW may be driven by the electric machine MG2 (four-wheel drive traveling may be performed). The rotational outputs of engine ENG and rotating electrical machine MG1 are input to transmission T / M via power distribution mechanism PSM. The input rotation output is shifted by the transmission T / M. The changed rotational output is transmitted to the front wheel axle FDS via the differential FDF. Thereby, the front wheels FLW and FRW are rotationally driven.

  During regeneration of a hybrid electric vehicle (when depressing the brake, depressing the accelerator, or decelerating when the accelerator is depressed), the rotational force of the front wheels FLW and FRW is changed to the front wheel axle FDS and differential FDF. Then, it is transmitted to the rotary electric machine MG1 through the transmission T / M and the power distribution mechanism PSM, and the rotary electric machine MG1 is rotationally driven. Thereby, rotating electrical machine MG1 operates as a generator. By this operation, three-phase AC power is generated in the stator winding of the rotating electrical machine MG1. The generated three-phase AC power is converted into predetermined DC power by the inverter device INV. The DC power obtained by this conversion is supplied to the battery BAT. Thereby, the battery BAT is charged. On the other hand, the rotational force of the rear wheels RLW, RRW is transmitted to the rotating electrical machine MG2 via the rear wheel axle RDS, the differential device RDF, and the speed reducer RG, thereby rotating the rotating electrical machine MG2. Thereby, rotating electrical machine MG2 operates as a generator. By this operation, three-phase AC power is generated in the stator winding of the rotating electrical machine MG2. The generated three-phase AC power is converted into predetermined DC power by the inverter device INV. The DC power obtained by this conversion is supplied to the battery BAT. Thereby, the battery BAT is charged.

  FIG. 2 shows the configuration of the inverter device INV of this embodiment.

  As described above, the inverter unit INV includes the power modules PMU1, PMU2, the drive circuit units DCU1, DCU2, and the motor control unit MCU. The power modules PMU1 and PMU2 have the same configuration. The drive circuit units DCU1 and DCU2 have the same configuration.

  The power modules PMU1 and PMU2 constitute a conversion circuit (also referred to as a main circuit) that converts DC power supplied from the battery BAT into AC power and supplies the AC power to the corresponding rotating electrical machines MG1 and MG2. The conversion circuit can also convert AC power supplied from the corresponding rotating electrical machines MG1 and MG2 into DC power and supply the DC power to the battery BAT.

  The conversion circuit is a bridge circuit, and is configured such that a series circuit for three phases is electrically connected in parallel between the positive electrode side and the negative electrode side of the battery BAT. The series circuit is also called an arm and is constituted by two semiconductor elements.

  The arm is configured such that, for each phase, the power semiconductor element on the upper arm side and the power semiconductor element on the lower arm side are electrically connected in series. In this embodiment, an IGBT (insulated gate bipolar transistor) which is a switching semiconductor element is used as the power semiconductor element. A semiconductor chip constituting the IGBT includes three electrodes, a collector electrode, an emitter electrode, and a gate electrode. A diode of a different chip from the IGBT is electrically connected between the collector electrode and the emitter electrode of the IGBT. The diode is electrically connected between the emitter electrode and the collector electrode of the IGBT so that the direction from the emitter electrode of the IGBT toward the collector electrode is a forward direction. As the power semiconductor element, a MOSFET (metal oxide semiconductor field effect transistor) may be used instead of the IGBT. In this case, the diode is omitted.

  The u-phase arm of the power module PMU1 is configured by electrically connecting the emitter electrode of the power semiconductor element Tpu1 and the collector electrode of the power semiconductor element Tnu1 in series. The v-phase arm and the w-phase arm are configured in the same manner as the u-phase arm, and the emitter electrode of the power semiconductor element Tpv1 and the collector electrode of the power semiconductor element Tnv1 are electrically connected in series, so that the power module PMU1 In the v-phase arm, the emitter electrode of the power semiconductor element Tpw1 and the collector electrode of the power semiconductor element Tnw1 are electrically connected in series, whereby the w-phase arm of the power module PMU1 is configured. Also for the power module PMU2, the arms of the respective phases are configured in the same connection relationship as that of the power module PMU1 described above.

  The collector electrodes of the power semiconductor elements Tpu1, Tpv1, Tpw1, Tpu2, Tpv2, and Tpw2 are electrically connected to the high potential side (positive electrode side) of the battery BAT. The emitter electrodes of the power semiconductor elements Tnu1, Tnv1, Tnw1, Tnu2, Tnv2, and Tnw2 are electrically connected to the low potential side (negative electrode side) of the battery BAT.

  The midpoint of the u-phase arm (v-phase arm, w-phase arm) of the power module PMU1 (the connection portion between the emitter electrode of the upper arm side power semiconductor element and the collector electrode of the lower arm side power semiconductor element) of each arm is rotated. It is electrically connected to the u-phase (v-phase, w-phase) stator winding of the electric machine MG1.

  The midpoint of the u-phase arm (v-phase arm, w-phase arm) of the power module PMU2 (the connection portion between the emitter electrode of the upper arm side power semiconductor element and the collector electrode of the lower arm side power semiconductor element) of each arm rotates. It is electrically connected to the u-phase (v-phase, w-phase) stator winding of the electric machine MG2.

  A smoothing electrolytic capacitor SEC is electrically connected between the positive electrode side and the negative electrode side of the battery BAT in order to suppress fluctuations in DC voltage caused by the operation of the power semiconductor element.

  The drive circuit units DCU1 and DCU2 output drive signals for operating the power semiconductor elements of the power modules PMU1 and PMU2 based on the control signal output from the motor control unit MCU, and drive units for operating the power semiconductor elements. It is composed of circuit components such as an insulated power supply, an interface circuit, a drive circuit, a sensor circuit, and a snubber circuit (all not shown).

  The motor control unit MCU is an arithmetic unit composed of a microcomputer. The motor control unit MCU receives a plurality of input signals and sends control signals for operating the power semiconductor elements of the power modules PMU1 and PMU2 to the drive circuit units DSU1 and DSU2. Output. Torque command values τ * 1, τ * 2, current detection signals iu1 to iw1, iu2 to iw2, and magnetic pole position detection signals θ1 and θ2 are input as input signals.

  The torque command values τ * 1 and τ * 2 are output from the host control device in accordance with the driving mode of the vehicle. The torque command value τ * 1 corresponds to the rotating electrical machine MG1, and the torque command value τ * 2 corresponds to the rotating electrical machine MG2. The current detection signals iu1 to Iw1 are detection signals for the u-phase to w-phase input current supplied from the conversion circuit of the inverter device INV to the stator winding of the rotating electrical machine MG1, and are currents of a current transformer (CT) and the like. It is detected by a sensor. The current detection signals iu2 to Iw2 are detection signals for the u-phase to w-phase input current supplied from the inverter device INV to the stator winding of the rotating electrical machine MG2, and are detected by a current sensor such as a current transformer (CT). It has been done. The magnetic pole position detection signal θ1 is a detection signal of the rotation magnetic pole position of the rotating electrical machine MG1, and is detected by a magnetic pole position sensor such as a resolver, an encoder, a Hall element, or a Hall IC. The magnetic pole position detection signal θ2 is a detection signal of the rotation magnetic pole position of the rotating electrical machine MG1, and is detected by a magnetic pole position sensor such as a resolver, an encoder, a Hall element, or a Hall IC.

  The motor control unit MCU calculates a voltage control value based on the input signal, and uses the voltage control value as a control signal (PWM signal) for operating the power semiconductor elements Tpu1 to Tnw1, Tpu2 to Tnw2 of the power modules PMU1 and PMU2. (Pulse width modulation signal)) is output to the drive circuit units DCU1 and DCU2.

  Generally, the PWM signal output from the motor control unit MCU is such that the time-averaged voltage becomes a sine wave. In this case, since the instantaneous maximum output voltage is the voltage of the DC line that is the input of the inverter, when a sine wave voltage is output, its effective value is 1 / √2. Therefore, in the hybrid electric motor vehicle of the present invention, the effective value of the input voltage of the motor is increased in order to increase the output of the motor with a limited inverter device. That is, the PWM signal of the MCU is made to be only ON and OFF in a rectangular wave shape. By doing so, the peak value of the rectangular wave becomes the voltage Vdc of the DC line of the inverter, and the effective value thereof becomes Vdc. This is the method for increasing the effective voltage value.

  However, the rectangular wave voltage has a problem that the current waveform is disturbed because the inductance is small in the low rotation speed region, and this causes an unnecessary excitation force in the motor and noise. Therefore, rectangular wave voltage control is used only during high-speed rotation, and normal PWM control is performed at low frequencies.

Next, a specific configuration of the rotating electrical machine MG2 according to the present invention will be described with reference to FIGS.
3 to 7 are a plan view and a partially enlarged view showing the rotary electric machine MG2 according to one embodiment of the present invention, and the same portions are denoted by the same reference numerals. In the present embodiment, a case where a three-phase induction motor is used as the rotating electrical machine MG2 will be described as an example. Here, the configuration of the rotary electric machine MG2 will be described, but the rotary electric machine MG1 may have the same configuration, or only the MG1 may be configured as a permanent magnet type three-phase synchronous motor.

  As shown in FIGS. 3 and 5, the rotating electrical machine MG <b> 2 is rotated by a magnetic action between the stator 110 that generates a rotating magnetic field and the stator 110, and via an inner peripheral side of the stator 110 and a gap 160. And a rotor 130 arranged to be rotatable.

  As shown in FIGS. 3, 5, and 6, the stator 110 includes a stator core 111 including a core back 112 and teeth 113, and a stator slot 121 into which a stator winding 120 that generates a magnetic flux when energized is inserted. And.

  The stator core 111 is formed by laminating a plurality of plate-shaped molded members formed by punching plate-shaped magnetic members in the axial direction. Here, the axial direction means a direction along the rotation axis of the rotor.

  As shown in FIGS. 5 and 6, the stator winding 120 is embedded in the stator slot 121, but the winding pitch of the winding is a short-pitch winding smaller than the magnetic pole pitch (not shown). The stator slot 121 has a stator slot opening 123. The circumferential width Ws of the opening is sufficiently smaller than the circumferential width (wire diameter in the figure) Wc of the stator winding 120. Dimension.

  As shown in FIG. 3 to FIG. 5 and FIG. 7, the rotor 130 includes a rotor core 137 that constitutes the magnetic path on the rotation side, and a first magnetic non-conductive metal such as aluminum or copper. A bar 131, a second bar 132, and a shaft 135 serving as a rotation axis are provided.

  Here, the second bar 132 has a smaller cross-sectional area than the first bar 131, and is disposed between the first bars 131. That is, when viewed in the radial direction, the first bar 131 and the second bar 132 are arranged at positions where they do not intersect, in other words, the circumferential end of the first bar 131 and the second bar 132. It is the structure arrange | positioned so that it may have the rotor core 137 between the circumferential direction edge parts.

  Further, the radial height h2 of the second bar 132 is configured to be 1/3 or less of the radial height h1 of the first bar 131. Further, the second bar 132 is disposed closer to the outside in the radial direction than the first bar 131. That is, the arrangement is such that the radial center of the second bar 132 is located radially outside the radial center of the first bar 131.

  The first bar 131 and the second bar 132 extend in the axial direction, and an end ring 134 for short-circuiting these bars 131 and 132 at the axial end portion is provided to constitute a squirrel-cage winding. .

  The effect of the above configuration will be described below.

  In an electric vehicle equipped with an induction motor drive system, in the case of operating conditions having an instantaneous torque, it is common to increase the motor torque by controlling the slip to increase the torque current component. On the other hand, if the drive system is capable of overexcitation control, the excitation current can be increased instantaneously, and the control range of the torque current can be expanded to further improve the torque.

  When overexcitation control is applied, the in-machine magnetic flux of the motor increases in proportion to the excitation current to increase the excitation current, and magnetic saturation of the magnetic circuit is promoted. When the magnetic saturation of the motor is promoted, the third harmonic is superimposed on the gap magnetic flux density distribution waveform. The third harmonic is a component having a wavelength three times that of the fundamental wave and rotating at a frequency that is three times the time. If the number of magnetic poles of the motor is 4 and the power supply frequency (fundamental wave frequency) rotates at 50 Hz, the synchronization speed is 1500 r / min. On the other hand, the rotating magnetic field due to the third harmonic has a wavelength three times that of the fundamental wave, and therefore becomes 12 poles for 4 fundamental wave poles. In addition, since the frequency is three times that in time, the frequency is 150 Hz with respect to the fundamental wave frequency of 50 Hz, and the synchronization speed is 1500 r / min, which matches the rotating magnetic field of the fundamental wave component. That is, the third harmonic component is a component that contributes as an effective torque in the same manner as the rotating magnetic field of the fundamental component.

  As described above, since the wavelength of the third harmonic component is shorter than the fundamental wave magnetic flux, if the number of bars is determined based on a general induction motor design method, the third harmonic component is determined. The components cannot sufficiently interlink with the bar, and as a result, it cannot be used as an effective torque.

  In view of this problem, the present invention is provided with a first bar 131 having a large cross-sectional area and a second bar 132 having a small cross-sectional area, as shown in FIGS. 3, 5, and 7. That is, the number of the first bars 131 is determined based on a conventional induction motor design method, and mainly plays a role of capturing the fundamental wave magnetic flux. On the other hand, the second bar 132 is provided between the first bars 131 to play a role of capturing the third harmonic magnetic flux having a short wavelength. Here, as shown in FIG. 7, the radial height h2 of the second bar 132 is configured to be 1/3 or less than the radial height h1 of the first bar 131. This is because the penetration depth of the third harmonic magnetic flux component in the conductive material is 1/3 of the fundamental wave. In addition, the reason why the cross-sectional areas of the respective bars are different is that the first bar 131 mainly interlinks with the fundamental wave, that is, the fundamental wave current always flows under all operating conditions. This is to reduce the bar loss. On the other hand, the second bar 132 only needs to function when instantaneous torque is generated. If a large cross-sectional area is unnecessarily secured, the flow of the fundamental wave magnetic flux interlinking with the first bar 131 is obstructed. This is because it is effective.

  Further, with respect to the amplitude of the third-order harmonic component, other influential harmonic components, particularly slot harmonic components generated due to the stator slot opening 123, and magnetomotive force generated by winding of the stator winding 120 When the amplitude of the harmonic component is large, only the loss due to the slot harmonic and magnetomotive force harmonic component occurs in the second bar 132, and the third harmonic component cannot be used. Therefore, in this embodiment, as shown in FIGS. 5 and 6, the stator winding 120 is wound with a short-pitch winding, thereby minimizing the influence of the magnetomotive force harmonic component and the stator slot. The influence of the slot harmonic component is minimized by narrowing the circumferential width Ws of the opening to be equal to or smaller than the wire diameter of the stator winding 120.

  FIG. 8 shows the result of measuring the torque in the case of the above-described configuration and comparing it with the conventional example. In the figure, the current on the horizontal axis is standardized as the rated current of 1.0, the energization current during overexcitation control 1.5 times and 2.0 times, and the vertical axis is the rated current conduction condition of the conventional example. The torque at is standardized as 1.0.

  As shown in FIG. 8, compared with the conventional example, the torque in the present invention is improved in any energized state, and it has been confirmed that the torque improvement is promoted particularly as the overexcitation state becomes remarkable. .

  In summary, the induction motor configuration described in the present embodiment enables the magnetic saturation in the motor machine to be turned on by turning on the overexcitation control when the electric vehicle is in an operating state that requires instantaneous torque. The fundamental wave torque can be improved by the action of the third harmonic component that is promoted and the gap magnetic flux density component is superimposed. Also, in the case of driving conditions that do not require instantaneous torque, such as when cruising, turning off overexcitation control will not cause harmonic loss or noise due to the third harmonic, so there will be no increase in fuel consumption. Can also ensure the quietness.

[Example 2]
FIG. 9 is a partially enlarged view of a rotor cross section showing another embodiment of the present invention. The same parts as those in FIG. 7 are denoted by the same reference numerals.

  The configuration of FIG. 9 is different from the configuration of FIG. 7 in that two second bars 132 are arranged between the first bars 131. When configured in this manner, the same effect as that of the configuration of FIG. 7 can be obtained, and the number of bars linked to the third harmonic component increases, so that a higher torque improvement effect can be obtained.

Example 3
FIG. 10 is a partially enlarged view of a rotor cross section showing another embodiment of the present invention. The same parts as those in FIG. 7 are denoted by the same reference numerals.

  The configuration of FIG. 10 is different from the configuration of FIGS. 7 and 9 in that the second bar 132 is disposed between the first bars 131 and the third bar 133 is placed on the head of the first bar 131 ( This is a point provided on the outer side in the radial direction. The cross-sectional area of the third bar 133 is the same as the cross-sectional area of the second bar 132. When configured in this way, the same effects as in FIGS. 7 and 9 can be obtained. Further, the third bar can be regarded as the second bar, substantially equalizing the circumferential pitch of the second bar 132, and apparently increasing the number of bars interlinking with the third harmonic component. Therefore, a higher torque improvement effect can be obtained.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  In addition, each component shows what is considered necessary for the explanation, and does not necessarily show all the components when compared with actual products.

110 Stator 111 Stator Iron Core 112 Core Back 113 Teeth 120 Stator Winding 121 Stator Slot 122 Stator Slot Opening 130 Rotor 131 First Bar 132 Second Bar 133 Third Bar 134 End Ring 135 Shaft 136 Rotor slot opening 137 Rotor core 160 Gap

Claims (9)

A number of slots provided in the rotor core, and conductive bars embedded in the slots;
In an induction motor including a rotor having a squirrel-cage conductor composed of conductive end rings that short-circuit these bars at both axial end faces,
The cage conductor is an induction motor that is configured by short-circuiting a first bar mainly linked with a fundamental wave magnetic flux and a second bar mainly linked with a third harmonic component by the end ring. A squirrel-cage conductor comprising a number of slots provided in a rotor core, a conductive bar embedded in the slot, and a conductive end ring that short-circuits the conductive bar at both axial end surfaces. In an induction motor equipped with a rotor having
The conductive bar comprises a first bar and a second bar;
The first bar has a larger cross-sectional area than the second bar,
Having the rotor core between a circumferential end of the first bar and a circumferential end of the second bar;
An induction motor in which the radial center of the second bar is located radially outside the radial center of the first bar. In the induction motor according to claim 2,
An induction motor in which the radial length of the second bar is 1/3 or less of the radial length of the first bar. In the induction motor according to claim 2,
An induction motor provided with a slit on the head side of the first bar. In the induction motor according to claim 2,
An induction motor in which a third bar having a smaller cross-sectional area than the first bar is provided on the head side of the first bar. In the induction motor according to claim 2,
A stator core, a stator slot provided at equal intervals in the circumferential direction of the stator core, and a stator having a stator winding housed in the stator slot,
The rotor is rotatably supported via the stator and a gap,
An induction motor in which a circumferential width of an opening of the stator slot is smaller than a circumferential width of the stator winding. The induction motor according to claim 6,
An induction motor in which a winding pitch of the stator winding is smaller than a magnetic pole pitch. A battery for supplying power;
A rotating electric machine that outputs a driving torque by the supplied electric power;
In an electric drive system comprising a control device for controlling the drive torque,
The rotating electric machine is the induction motor according to claim 1 to 7,
The control device is an electric drive system that controls the induction motor by overexcitation. A battery for supplying power;
A rotating electric machine that outputs a driving torque for driving the vehicle with the supplied electric power;
In an electric vehicle including a drive system including a control device that controls the drive torque,
The said drive system is an electric vehicle which is a drive system of Claim 8.