JP2011211839A - Drive unit of electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable more accurate detection of an open failure of a switching element for an inverter connected to a motor.SOLUTION: A drive unit of a hybrid vehicle is equipped with: a motor; an inverter; and a controller. The controller includes: an operating point changing unit (S10 to S16) which, when the motor is driven at an operating point for rectangular wave control, changes a motor operation point to an operating point in an area where overmodulation control is applied; and an open failure judging unit (S18) which, when the operating point has been changed by the operating point changing unit and the motor is under overmodulation control, counts the number of times of a q-axis current Iq having exceeded an operating point changing threshold Iqth, the q-axis current Iq being derived based on a current flowing through the motor, and, when the counted number of times is equal to or more than a given number of times in a given time, determines that an open failure of the switching element has occurred.

Description

  The present invention relates to a drive device for an electric vehicle, and more particularly to a drive device for an electric vehicle equipped with a motor connected to an inverter.

  Conventionally, a hybrid vehicle equipped with an engine and a motor, which are internal combustion engines, is known as a driving power source. An inverter may be connected to this motor for driving. An inverter is a circuit that combines a plurality of switching elements and diodes. An upper arm switching element and an upper arm diode connected in parallel are used as an upper arm element, and a lower arm switching element and a lower arm diode are connected in parallel. As an arm element, these are connected in series and connected in parallel in a plurality of phases as a unit of one phase. For example, in a three-phase AC motor, each phase arm in which an upper arm element and a lower arm element are connected in series is connected in parallel corresponding to each phase of U phase, V phase, and W phase. An inverter is used.

  Thus, since two switching elements are used for each phase, the inverter connected to the three-phase rotating electrical machine includes six switching elements. If a malfunction occurs in the operation of one of these switching elements, the positive side or the negative side of the alternating current waveform of the phase including the switching element is missing, which is a so-called open failure. If the switching element has an open failure, the motor operation is not normal, and it is necessary to accurately detect the open failure.

  For example, in Japanese Patent Laid-Open No. 2008-92690 (Patent Document 1), as a motor control system capable of detecting an open failure of a switching element of an inverter, when d-axis current Id and q-axis current Iq are viewed, Id = At 0, Iq becomes a constant value of the command value, but at the time of an open failure, the absolute value of Id becomes a waveform distorted around 0, the absolute value of Iq becomes a waveform distorted around the Iq command value, and the ratio is It is described that it takes a certain value instead of zero. It is described that an open failure can be detected when the Id absolute value exceeds a certain threshold and the ratio between the Id absolute value and the Iq absolute value is within a predetermined range.

JP 2008-92690 A

  As described above, in the conventional technology, in a motor to which an inverter is connected, an open failure is determined based on an evaluation relating to a current flowing in each phase of the motor. That is, as an evaluation regarding the current flowing through each phase, in addition to the method using the offset current in which the sum of the currents of each phase deviates from zero as well known, the absolute value of the Id current and Iq described in Patent Document 1 are used. There is a method using the absolute value of the current.

  As described in Patent Document 1, an evaluation value obtained by setting a threshold value that serves as an evaluation standard for the Id current and a threshold value range that serves as an evaluation standard for the ratio between the Id absolute value and the Iq absolute value, respectively. It is possible to determine whether or not there is an open failure by comparing with. Thus, in the method using the threshold value, if the original current value is small, the difference from the threshold value is also small, and it may be difficult to accurately determine the open failure.

  The objective of this invention is providing the drive device of the electric vehicle which can perform the open fault determination of the switching element which comprises an inverter more correctly.

  An electric vehicle driving apparatus according to the present invention operates an inverter that converts a DC voltage supplied from a power storage device into an AC voltage and outputs the AC voltage, a motor driven by the output voltage of the inverter, and a switching element included in the inverter. And a control device for driving and controlling the motor by switching a plurality of control modes including overmodulation control, wherein the control device is configured such that the motor performs rectangular wave control or PWM control. An operating point change processing unit that changes the operating point of the motor to a region to which the overmodulation control is applied when the operating point is being driven, and the operating point is changed by the operating point change processing unit. When the motor is overmodulated, the number of times that the q-axis current derived based on the current flowing through the motor exceeds the operating point change threshold is counted. Count value; and a and determines the open failure determination section open failure has occurred in the switching element when the predetermined number of times or more within a predetermined time.

  In the electric vehicle driving apparatus according to the present invention, the electric vehicle is a hybrid vehicle equipped with an internal combustion engine as a driving power source, and the motor is connected to an output shaft of the internal combustion engine via a power distribution mechanism. The control device is capable of controlling the operation of the internal combustion engine, and the operating point change processing unit is configured to operate the motor when the motor is driven at an operating point to which rectangular wave control or PWM control is applied. By changing the rotational speed of the internal combustion engine, the rotational speed of the motor may be changed to the operating point in the region where the overmodulation control is applied via the power distribution mechanism.

  In the electric vehicle driving apparatus according to the present invention, the electric vehicle is configured such that the output of the motor is output to an axle via a transmission capable of shifting to a plurality of stages, and the control device includes the transmission. The operating point change processing unit changes the gear stage of the transmission when the motor is driven at an operating point to which rectangular wave control or PWM control is applied. Thus, the rotational speed of the motor may be changed to an operating point in a region where the overmodulation control is applied without substantially changing the vehicle speed.

  In the electric vehicle drive device according to the present invention, the electric vehicle includes a power conversion device capable of boosting a DC voltage from the power storage device and outputting the boosted voltage to the inverter, and the control device includes the voltage. The boosted voltage can be set by controlling the operation of the conversion device, and the operating point change processing unit is operated when the motor is driven at an operating point to which rectangular wave control or PWM control is applied. The operating point of the motor may be changed to an operating point in a region to which the overmodulation control is applied by changing the boosted voltage by the voltage converter.

  In the electric vehicle drive device according to the present invention, the control device overmodulates the control mode of the motor when the open failure determination unit determines that the q-axis current exceeds an operating point change threshold. It is also possible to execute control for temporarily switching from PWM control to PWM control.

  In the driving device for an electric vehicle according to the present invention, the operating point change processing unit is configured such that the motor is rectangular-wave controlled in a higher rotation speed range than a motor rotation speed range in which an open failure of the switching element can be detected. The motor operating point may be changed to the operating point of the overmodulation control region when PWM control is performed in a lower rotational region than the motor rotational speed range.

  Furthermore, in the drive device for an electric vehicle according to the present invention, the operating point change processing unit determines that the count value of the number of times that the q-axis current exceeds the operating point change threshold is a predetermined number of times within a predetermined time by the open failure determination unit. When it is determined that an open failure has not occurred in the switching element, a process of returning the operating point of the motor to the operating point before the change after the predetermined time may be executed.

  According to the drive device for an electric vehicle according to the present invention, after changing the motor operating point to the overmodulation control region, the open-circuit failure of the switching element of the inverter is determined by comparing the q-axis current with the operating point change threshold. In such overmodulation control, the disturbance of each phase current of the motor due to an open failure appears more greatly than in other control modes such as PWM control and rectangular wave control. Therefore, the open failure of the switching element of the inverter can be more accurately performed by evaluating the q-axis current after changing the motor operating point to overmodulation control in which current disturbance becomes large. As a result, it is possible to prevent a secondary failure in which the permanent magnet is demagnetized and torque cannot be output when the motor drive is continued with an open failure.

1 is a schematic configuration diagram of a hybrid vehicle equipped with a drive device for an electric vehicle according to an embodiment of the present invention. It is a figure which shows the circuit structure of the converter and inverter which are contained in the drive device shown in FIG. It is a figure which shows the map which prescribes | regulates the control mode of a motor. It is a flowchart which shows the process sequence of the operating point change and open failure determination which are performed by the control apparatus. It is a figure which shows a mode that the operating point of a motor is changed from a rectangular wave control area | region to an overmodulation control area | region on the map similar to FIG. It is a timing chart which shows the operating point change process performed by a control apparatus. It is a timing chart which shows the open failure determination process performed by a control apparatus. It is a flowchart which shows another example of the operating point change process performed by a control apparatus. FIG. 9 is a timing chart showing processing for changing an operating point in FIG. 8. FIG. It is a flowchart which shows another example of the operating point change process performed by a control apparatus. It is a figure which shows the operating point change process of FIG. 10 with a map.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments according to the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the accompanying drawings. In this description, specific shapes, materials, numerical values, directions, and the like are examples for facilitating the understanding of the present invention, and can be appropriately changed according to the application, purpose, specification, and the like.

  FIG. 1 shows a schematic configuration of a hybrid vehicle 1 equipped with an electric vehicle drive device according to an embodiment of the present invention. In FIG. 1, the power transmission system is illustrated as a round bar-shaped shaft element, the power system is illustrated by a solid line, and the signal system is illustrated by a broken line. FIG. 2 shows a circuit configuration and the like of the converter 35 and the inverters 36 and 38 constituting the driving device of the present embodiment. In the following description, a two-motor hybrid vehicle will be described as an example. However, the present invention may be applied to a one-motor hybrid vehicle, or depending on an aspect of the present invention, only a motor may be used as a driving power source. The present invention may be applied to an electric vehicle having the following.

  As shown in FIG. 1, the hybrid vehicle 1 includes a power distribution mechanism in which an engine 12 as a driving power source, a motor (MG2) 14 as another driving power source, and an output shaft 18 of the engine 12 are connected. The motor (MG1) 24 to which the rotating shaft 22 is connected via the motor 20, the battery (power storage device) 16 capable of supplying driving power to the motors 14, 24, and the operations of the engine 12 and the motors 14, 24 are integrated. And a control device (ECU (Electronic Control Unit)) 10 that controls charging / discharging of the battery 16.

  The engine 12 is an internal combustion engine that uses gasoline, light oil, or the like as fuel, and based on commands from the control device 10, cracking, throttle opening, fuel injection amount, ignition timing, and the like are controlled to start and operate the engine 12. , Stop, etc. are controlled.

  An engine speed sensor 28 for detecting the engine speed Ne is provided in the vicinity of the output shaft 18 extending from the engine 12 to the power distribution mechanism 20. Further, the engine 12 is provided with a temperature sensor 13 that detects a temperature Tw of cooling water that is an engine cooling medium. Each detection value by the rotation speed sensor 28 and the temperature sensor 13 is transmitted to the control device 10.

  The power distribution mechanism 20 can be suitably configured by, for example, a planetary gear mechanism. The power input from the engine 12 to the power distribution mechanism 20 via the output shaft 18 is transmitted to the drive wheels 34 via the transmission 30 and the axle 32 so that the vehicle 1 can travel with the engine power.

  The transmission 30 can decelerate and output the rotation input from at least one of the engine 12 and the motor 14 to the axle 32, and can be switched between a plurality of shift stages according to a command from the control device 10. is there. As the speed change mechanism used in the transmission 30, any known structure may be used, and a continuously variable speed change mechanism that smoothly and continuously shifts may be used instead of a step-like speed change.

  The power distribution mechanism 20 can input a part or all of the power of the engine 12 input via the output shaft 18 to the motor (MG1) 24 via the rotary shaft 22. At this time, for example, the motor 24 suitably configured by a three-phase synchronous AC motor functions as a generator, and is the battery 16 charged after the generated three-phase AC voltage is converted into a DC voltage by the inverter 36? Alternatively, it is used as a drive voltage for the motor (MG2) 14.

  The motor (MG1) 24 can also function as an electric motor that is rotationally driven by the electric power supplied from the battery 16 via the converter (voltage converter) 35 and the inverter 36, and the motor (MG1) 24 rotates. The power that is driven and output to the rotary shaft 22 is input to the engine 12 via the power distribution mechanism 20 and the output shaft 18 to perform cranking. Further, the motor 24 can be used as driving power by rotating the motor 24 with the electric power supplied from the battery 16 and outputting the power to the axle 32 via the power distribution mechanism 20 and the transmission 30.

  The motor (MG2) 14 that mainly functions as an electric motor can be suitably configured by, for example, a three-phase synchronous AC motor, and the DC voltage supplied from the battery 16 is boosted by the converter 35 as necessary, and thereafter The inverter 38 is rotationally driven by being converted into a three-phase AC voltage and applied as a drive voltage. The motive power output to the rotary shaft 15 by driving the motor (MG2) 14 is transmitted to the drive wheels 34 via the transmission 30 and the axle 32, and so-called EV traveling is performed with the engine 12 stopped. . The motor (MG2) 14 also has a function of assisting the engine output by outputting the driving power when there is a sudden acceleration request due to the driver's accelerator operation.

  Further, the motor (MG2) 14 can function as a generator during regenerative braking of the vehicle, and generates AC power by power input from the drive wheels 34 via the transmission 30 and the rotating shaft 15. The three-phase AC voltage generated and output by the motor 14 is converted into a DC voltage by the inverter 38, and then the battery 16 can be charged.

  As the battery 16, for example, a chargeable / dischargeable secondary battery such as a lithium ion battery or a nickel metal hydride battery, or a power storage device such as an electric double layer capacitor can be suitably used. The battery 16 is provided with a voltage sensor 40 that detects a battery voltage Vb, a current sensor 42 that detects a battery current Ib that enters and leaves the battery 16, and a temperature sensor 44 that detects a battery temperature Tb. The detection values by the sensors 40, 42, and 44 are input to the control device 10 and used to control the state of charge (SOC) of the battery 16.

  As shown in FIG. 2, a positive electrode bus 50 and a negative electrode bus 52 are connected to the positive and negative terminals of the battery 16, respectively. System main relays SMR 1 and SMR 2 are provided on positive electrode bus 50 and negative electrode bus 52. The system main relays SMR1 and SMR2 are relays that can be switched off and switched so that the high-voltage power supply system can be disconnected from the motors 14 and 24 when the motors 14 and 24 are stopped. . The system main relays SMR1 and SMR2 are controlled to be disconnected and connected in accordance with control signals S1 and S2 transmitted from the control device 10.

  Power is supplied from the battery 16 to the converter 35 via a smoothing capacitor 54 that suppresses and smoothes fluctuations in voltage and current. The converter 35 includes a reactor and two switching elements (for example, IGBTs) each having a diode connected in antiparallel. The converter 35 is a circuit having a function of boosting the DC voltage on the battery 16 side using the energy storage action of the reactor. The converter 35 has a bidirectional function, and when the power from the inverters 36 and 38 is supplied to the battery 16 as charging power, the high voltage on the inverters 36 and 38 is stepped down to a voltage suitable for charging the battery 16. It also has a function to

  Converter 35 can boost battery voltage Vb to a desired voltage value by turning on / off each switching element in accordance with control signals S3, S4 transmitted from control device 10. Thereby, an optimum voltage can be supplied to the inverters 38 and 36 in accordance with the operating conditions of the motors 14 and 24. The voltage between the positive bus 50 and the negative bus 52 of the inverters 36 and 38 is sometimes referred to as a system voltage VH. In this sense, the converter 35 sets the system voltage VH according to the operation status of the motors 14 and 24. It will have the function to change. For example, when the motors 14 and 24 are operated at high torque and high rotation, the system voltage VH is increased so as to be increased, and when the energy saving operation is performed, the system voltage VH is decreased. Here, the system voltage VH becomes a minimum value when the battery voltage Vb is supplied to the inverters 36 and 38 as it is due to the inactivation of the converter 35, while the system voltage VH is a boost upper limit value due to restrictions on the performance of the converter 35 and the like. There is a maximum voltage value VHmax.

  The output voltage of the converter 35 is supplied to inverters 36 and 38 via a smoothing capacitor 56 that suppresses and smoothes fluctuations in voltage and current. The voltage across the smoothing capacitor 56, that is, the system voltage VH is detected by the voltage sensor 57 and input to the control device 10. Control device 10 performs feedback control of converter 35 based on a comparison between detected system voltage VH and system voltage command value VH *. Thereby, the boosted voltage by converter 35 can be matched with system voltage command value VH * quickly and accurately.

  An MG1 inverter 36 and an MG2 inverter 38 are connected in parallel to the positive bus 50 and the negative bus 52 to which the smoothing capacitor 56 is connected between the lines. Each inverter 36 and 38 is a circuit that performs power conversion between AC power and DC power.

  When the motor (MG1) 24 is caused to function as a generator, the inverter 36 converts the AC three-phase regenerative power generated by the motor (MG1) 24 into DC power and supplies it to the battery 16 as a charging current. Has a conversion function. The inverter 38 connected to the motor (MG2) 14 converts DC power from the battery 16 side into AC three-phase driving power and supplies the motor (MG2) 14 as driving power when the vehicle 1 is in power running. It has an orthogonal conversion function and an AC / DC conversion function that converts AC three-phase regenerative power from the motor (MG2) 14 to DC power and supplies it as a charging current to the battery 16 when the vehicle 1 is braked.

  Such inverters 36 and 38 are circuits in which a plurality of switching elements (for example, IGBT) and a plurality of diodes are combined, and an upper arm switching element connected in reverse parallel to an upper arm switching element is used as an upper arm element, and a lower arm is formed. A switching element in which a lower arm diode is connected in antiparallel is a lower arm element, and these are connected in series, and a unit of one phase is connected in parallel in a plurality of phases. For example, in a three-phase AC motor, corresponding to each phase of U phase, V phase, and W phase, an inverter in which each phase arm in which upper arm elements and lower arm elements are connected in series is connected in parallel for three phases. Is used. The six switching elements included in each of the inverters 36 and 38 are on / off controlled in accordance with control signals S5 to S10 and S11 to S16 transmitted from the control device 10, whereby the orthogonal transform function and the AC / DC transform function described above are performed. Can be played.

  For example, wiring drawn from the connection point between the upper switching element and the lower switching element of the U-phase arm is connected to the U-phase coils of the motors 14 and 24. Similarly, the wiring drawn from the connection point between the upper switching element and the lower switching element of the V-phase arm is connected to the V-phase coil of the motors 14 and 24, and the connection between the upper switching element and the lower switching element of the W-phase arm. The wires drawn from the points are connected to the W-phase coils of the motors 14 and 24. In the example of FIG. 2, in the motors 14 and 24, each phase coil is commonly connected at the neutral point, so the wiring drawn from each phase arm of the inverters 38 and 36 is not the neutral point of each phase coil. Will be connected to the other terminal.

  In this way, wiring is performed from the respective phase arms of the inverters 36 and 38 to the respective phase coils of the motors 24 and 14. Through this wiring, the drive current is supplied from the inverters 36 and 38 to the motors 24 and 14 when the motor is driven, and the generated current is supplied from the motors 14 and 24 to the inverters 38 and 36 during the regeneration. In this way, the current flowing through the phase coils of the motors 14 and 24 passes through the wirings that connect the inverters 38 and 36 to the motors 14 and 24.

  Of the three wires connecting the inverter 36 and the motor 24, the currents Iv and Iw flowing through the wires corresponding to the V-phase and the W-phase are appropriately detected as the currents flowing through the U-phase and W-phase coils of the motor 24. Each is detected using the sensor 58 and transmitted to the control device 10. The remaining U-phase current Iu is calculated by the control device 10 from the detected values of Iv and Iw from the relationship of Iu + Iv + Iw = 0. Similarly, the currents Iv and Iw flowing through the wires corresponding to the V phase and the W phase among the three wires connecting the inverter 38 and the motor 14 are appropriate as the currents flowing through the U phase and W phase coils of the motor 14. Is detected using a current detection sensor 58 and transmitted to the control device 10. In this case as well, the remaining U-phase current Iu is calculated in the control device 10.

  The motors 14 and 24 are provided with rotation angle sensors 60 made of, for example, a resolver. The rotor rotation angles θ1 and θ2 of the motors 14 and 24 detected by the respective rotation angle sensors 60 are transmitted to the control device 10 and used for calculation of the motor rotation speed, generation of a motor current command value, and the like.

  The control device 10 includes a CPU that executes various control programs, a ROM that stores a control program and a control map in advance, and a RAM that temporarily stores a control program read from the ROM, detection values by each sensor, and the like. It is suitably configured by a microcomputer composed of, for example. As shown in FIGS. 1 and 2, the control device 10 includes an engine speed Ne, a battery current Ib, a battery voltage Vb, a battery temperature Tb, an accelerator opening signal Acc, a vehicle speed Sv, an engine coolant temperature Tw, and a system voltage VH. , Motor currents Iu, Iw, rotor rotation angles θ1, θ2, etc. are input ports, and control signals for controlling the operation or operation of engine 12, system main relays SMR1, SMR2, converter 35, inverters 36, 38, etc. An input / output interface including an output port for outputting a signal.

  The control device 10 includes an operating point change processing unit 62 and an open failure determination unit 64. Specifically, the operating point change processing unit 62 and the open failure determination unit 64 function according to a control program executed in the CPU, and details thereof will be described later.

  In the present embodiment, a description will be given assuming that the operation control and state monitoring of the engine 12, the motors 14 and 24, the converter 35, the inverters 36 and 38, the battery 16, and the like are performed by one control device 10, but for example, the engine 12 The engine ECU for controlling the operation state of the motor, the motor ECU for controlling the drive of the motors 14, 24 by controlling the operation of the converter 35 and the inverters 36, 38, the battery ECU for managing the SOC of the battery 16, and the like are individually provided. The control device may be configured to control the individual ECUs as a hybrid ECU.

  FIG. 3 shows a map used for controlling the motors 14 and 24. This map defines the relationship between the rotational speed of the motor and the torque, and is stored in advance in the ROM in the control device 10. By referring to this map, the control device 10 can drive the motors 14 and 24 at the operating points of the following plurality of control modes within the substantially trapezoidal outline indicated by a thick line.

  Generally, three control methods are known as control modes for an AC motor: PWM control, overmodulation control, and rectangular wave control. In the map shown in FIG. 3, the region from the low speed rotation region to the medium speed rotation region is the PWM control region A1, the region from the medium speed rotation region to the high speed rotation region is the overmodulation control region A2, and the region at the highest speed rotation side is rectangular. It is a wave control area A3, and the boundaries of the control areas A1, A2, A3 are indicated by dotted lines.

  The PWM control method is used as a general sine wave PWM control, and controls on / off of switching elements in each phase arm according to a voltage comparison between a sine wave voltage command value and a carrier wave (generally a triangular wave). To do. As a result, for a set of a high level period corresponding to the on period of the upper arm switching element and a low level period corresponding to the on period of the lower arm element, the duty is set so that the motor input voltage becomes a sine wave within a certain period. The ratio is controlled. With the PWM control method, smooth rotation can be obtained even in a relatively low rotation range, but the modulation rate (or voltage utilization rate) that is the ratio of the amplitude of the motor input voltage to the system voltage VH that is the inverter input voltage is maximized. Can only be increased to 0.61.

  On the other hand, in the rectangular wave control method, one pulse of a rectangular wave whose ratio between the high level period and the low level period is 1: 1 is applied to the AC motor within the predetermined period. Thereby, the modulation factor can be increased to 0.78, and the output in a relatively high rotation range can be improved. Further, since the field weakening current can be reduced, the occurrence of copper loss in the AC motor can be suppressed and the energy efficiency can be improved. Furthermore, since the number of times of switching in the inverters 36 and 38 can be reduced, there is also an advantage that switching loss can be suppressed.

  The overmodulation control method is an intermediate control method between PWM control and rectangular wave control, and the PWM control is performed in a state where the amplitude of the sinusoidal voltage command value is amplified to be larger than the amplitude of the carrier wave. By performing PWM control similar to the method, it is possible to generate a motor input voltage distorted in a substantially sinusoidal shape shifted in the direction of increasing voltage, thereby increasing the modulation factor to a range of 0.61 to 0.78. be able to. However, the overmodulation control method has a characteristic that control responsiveness is poor compared with PWM control, and the deviation or disturbance of the actual current with respect to the current command value tends to appear greatly.

  In an AC motor, the induced voltage increases as the rotational speed and output torque increase, and the required voltage increases accordingly. The boosted voltage by the converter, that is, the system voltage VH needs to be set higher than the required motor voltage. On the other hand, as described above, there is an upper limit (system voltage maximum value VHmax) in the voltage value that can be boosted by the converter 35.

  Therefore, in the region where the required motor voltage is lower than the maximum value of the system voltage VH, for example, 650 V, the maximum torque control by the PWM control method or the overmodulation control method is applied, and the output torque is torqued by the motor current control according to the vector control. Control is performed to meet the command T *. On the other hand, when the necessary motor voltage exceeds the system voltage maximum value VHmax, the rectangular wave control method is applied according to the weakening magnetic field control while maintaining the system voltage VH at the maximum value VHmax. In this case, since the amplitude of the motor input voltage is fixed, torque control is performed by voltage phase control of a rectangular wave pulse based on the deviation between the estimated torque value and the torque command value.

  In the example of FIG. 2, since the inverters 38 and 36 connected to the motors 14 and 24 which are three-phase AC motors use two switching elements for each phase, each of the inverters 38 and 36 includes six switching elements. It is. If a malfunction occurs in the operation of one of these switching elements, the positive side or the negative side of the alternating current waveform of the phase including the switching element is missing, which is a so-called open failure. When such an open failure occurs, an excessive current is discharged from the battery due to disturbance of the motor input current, leading to a decrease in battery performance. Therefore, it is necessary to detect an open failure of the switching element in the inverter in a timely manner.

  On the other hand, depending on the operation state of the motor, there is an operating point where an open failure of the switching element of the inverter cannot be detected or is difficult to detect. This is because the disturbance amount of the motor current is relatively small and it is difficult to detect it by comparison with the determination threshold. One method is considered to set the determination threshold value smaller, but even if the switching element operates normally, it is determined that there is an open failure when the motor current fluctuates due to noise or the like. The possibility increases and the accuracy of open failure determination decreases.

  Therefore, in the control device 10 of the present embodiment, when the motor is driven by the rectangular wave control in a higher rotation speed range than the motor rotation speed range in which an open failure of the switching element of the inverter can be detected, compared to other control modes. After changing the motor operating point to the overmodulation control area where the amount of current disturbance at the time of open failure increases, the open failure of the inverter switching element is compared with the operating point change threshold for the q-axis current of the motor current. I decided to judge. Below, the open failure determination of the switching element performed in the control apparatus 10 is demonstrated in detail.

  First, the open failure determination of the switching element of the MG1 inverter 36 will be described with reference to FIGS. FIG. 4 is a flowchart showing a processing procedure for operating point change and open failure determination. FIG. 5 is a diagram showing on the same map as FIG. 3 how the operating point of the motor (MG1) 24 is changed from the rectangular wave control region to the overmodulation control region. FIG. 6 is a nomographic chart showing the timing of changing the motor rotational speed in the operating point changing process executed by the control device 10. FIG. 7 is a timing chart showing an open failure determination process executed by the control device 10. FIG. 7 shows an example in which it is assumed that the U-phase upper arm switching element of the inverter 36 has an open failure.

  The processing shown in FIG. 4 is read from the ROM or RAM at predetermined time intervals and executed by the CPU under the condition that the motor 24 is driven while the engine 12 is operating. However, the present invention is not limited to this, and may be executed when a predetermined amount or more of disturbance is detected in the current flowing through the motor 24.

  First, in step S10, it is determined whether or not the rotation speed Nm1 of the motor 24 is in a high rotation region where an open failure cannot be detected or is difficult to detect. Here, as shown in FIG. 5, since the motor rotation speed range R in which the one-phase open failure can be detected is stored in advance, the motor rotation speed Nm1 calculated from the detection value of the rotation angle sensor 60 is the motor rotation speed. Judgment is made based on whether the rotational speed is higher than the range R or not. In step S10, it is also confirmed whether the current motor control method is rectangular wave control. This is because it is not necessary to change the operating point when the current control mode is overmodulation control. If an affirmative determination is made in step S10, the process proceeds to the next step S12. On the other hand, if a negative determination is made, the process ends.

  Subsequently, in step S12, it is determined whether or not the q-axis current Iq is larger than the operating point change threshold value Iqth. Here, the q-axis current is used as the determination target value because the q-axis current Iq is 3 considering the motor rotation angle θ1 based on each phase current Iu, Iv, Iw detected and calculated by the current detection sensor 58. This is because it is easy to accurately detect an open failure by using a q-axis current Iq, also called a torque current, as a determination target among the d-axis current Id and the q-axis current Iq that are phase-to-phase converted. In addition, the operating point change threshold Iqth is obtained by experiment or the like and stored in advance, and is a value that is large and can accurately detect a one-phase open failure so that current disturbance due to another factor such as noise is not determined as an open failure. Set to Since the q-axis current Iq and the operating point change threshold value Iqth may be either positive or negative, it is preferable to compare them with absolute values. If an affirmative determination is made in step S12, the process proceeds to the next step S14. On the other hand, if a negative determination is made, the process ends.

  Next, in step S14, a motor rotation speed change amount necessary for the control mode of the motor 24 to be switched to overmodulation control is calculated. Here, an operating point 68 of the same torque that is included in the rotational speed range R and to which overmodulation control is applied is selected, the rotational speed of this operating point 68 is set to the target rotational speed Nm1 *, and this target rotational speed is set. The motor rotational speed change amount is calculated by subtracting the current rotational speed Nm1 of the operating point 66 from Nm1 *. Note that the control mode and the rotational speed Nm1 of the current operating point 66 are temporarily stored in the RAM.

  Then, in the subsequent step 16, the rotational speed Ne of the engine 12 is decreased so that the rotational speed of the motor 24 becomes the target rotational speed Nm1 *. This is shown in the alignment chart of FIG. As shown in the figure, at the timing t0 when the q-axis current Iq falls below the operating point change threshold value Iqth, the rotational speed of the engine 12 is decreased to set the rotational speed of the motor 24 to the target rotational speed Nm * 1. At this time, the rotational speed of the engine 12 is reduced by adjusting the throttle valve opening, ignition timing, and the like.

  In the subsequent step S18, open failure determination is executed. The state of this open failure determination is shown in FIG. As shown in the figure, if the q-axis current Iq falls below the operating point change threshold Iqth after the timing t0 when the rectangular wave control is switched to the overmodulation control, it is counted as an abnormality. In the present embodiment, every time the q-axis current Iq falls below the operating point change threshold value Iqth, control for temporarily switching the control mode of the motor 24 from overmodulation control to PWM control is executed. In this way, by temporarily switching to PWM control with excellent control response and relatively small motor current, overmodulation control in which excessive current may be drawn from the battery due to current disturbance is continued. The battery 16 is protected by avoiding it.

  When the count value is greater than or equal to a predetermined number of times within a failure detection confirmation time (for example, 2 seconds), it is determined that there is an open failure in the switching element of the inverter 36, whereas when the count value is less than the predetermined number, an open failure is detected. Judged as none. If it is determined that there is an open failure, the control device 10 may take necessary measures such as notifying the driver of the occurrence of the open failure through visual and / or auditory senses.

  Referring to FIG. 4 again, after the open failure determination process as described above is completed and when a predetermined time t1 (eg, 3 to 4 seconds) has elapsed from the timing t0 (YES in step S20), step S22 is performed. Thus, the process of returning the rotational speed of the engine 12 is executed. As a result, the rotational speed of the motor 24 is returned to the original rotational speed Nm1, as shown in the nomographic chart on the right side in FIG. However, if it is determined in step S18 that there is an open failure, for example, the driving of the motor 24 may be stopped, or the control mode may be limited to PWM control.

  As described above, in the control device 10 of the present embodiment, the disturbance of each phase current of the motor due to the open failure of the switching element appears more in the overmodulation control than in the rectangular wave control. By evaluating the q-axis current Iq after changing the motor operating point to overmodulation control, the open failure determination of the switching element of the inverter 36 can be performed more accurately. As a result, it is possible to prevent a secondary failure that the motor 24 is demagnetized and cannot output torque when the drive of the motor 24 is continued with an open failure.

  Next, with reference to FIGS. 8 and 9, an operation point change for determining an open failure of the MG2 inverter 38 will be described. FIG. 8 is a flowchart showing an operating point change process and an open failure determination process executed by the control device 10. FIG. 9 is a timing chart showing the operating point change process of FIG. Here, the points different from the operating point change process and the open failure determination process of the MG1 inverter 36 described above will be mainly described, and the same steps will be assigned the same processes, and the description thereof will be omitted with the aid of them.

  The processing shown in FIG. 8 is read from the ROM or RAM at predetermined time intervals and executed by the CPU under the condition where the motor 14 is driven. However, the present invention is not limited to this, and may be executed when a predetermined amount or more of disturbance is detected in the current flowing through the motor 14. Further, the processes in steps S10, S12, S14, S18 and S20 in FIG. 8 are the same as those shown in FIG.

  As shown in FIG. 8, following step S14, the gear position of the transmission 30 is selected in step S24. The transmission 30 has been described above as having a plurality of shift stages, but here, for example, has two shift stages, HI and LO, and either HI or LO according to a command from the control device 10. An example is shown in which switching to a gear position is possible.

  Referring to FIG. 9, at the timing t0 when the q-axis current Iq falls below the operating point change threshold value Iqth, the gear position of the transmission 30 is switched from LO to HI. Accordingly, the operating point of the motor 14 is changed from the rectangular wave control region to the overmodulation control region A2 while the rotational speed of the axle 32 and the wheel 34, that is, the vehicle speed Sv is substantially maintained, and the motor rotational speed is reduced. Can do. After changing the operating point of the motor 14 to the operating point to which the overmodulation control is applied in this way, the open failure determination in step S18 described above is executed.

  Then, after completion of the open failure determination in step S18 and when a predetermined time t1 (eg, 3 to 4 seconds) has elapsed from the timing t0 (YES in step S20), the transmission 30 is changed in step S26. A process of changing the gear position from HI to LO and returning the operating point of the motor 14 to the original operating point is executed. However, if it is determined in step S18 that there is an open failure in the switching element of the inverter 38, for example, processing such as stopping driving of the motor 14 or limiting the control mode to PWM control may be performed. .

  As described above, in the control device 10 of the present embodiment, in the overmodulation control, since the disturbance of each phase current of the motor due to the open failure of the switching element appears more than in the rectangular wave control, the shift stage of the transmission 30 is switched. Thus, by evaluating the q-axis current Iq after changing the motor operating point from the rectangular wave control to the overmodulation control, the open failure determination of the switching element of the inverter 38 can be performed more accurately. As a result, it is possible to prevent a secondary failure that the motor 14 is demagnetized and cannot output torque when the drive of the motor 14 is continued with an open failure.

  Next, still another example of the motor operating point changing process will be described with reference to FIGS. FIG. 10 is a flowchart of still another operating point changing process executed by the control device 10. FIG. 11 is a diagram showing the operating point changing process of FIG. 10 as a map.

  The process shown in FIG. 10 is applicable to both the motors 14 and 24, and is read from the ROM or RAM at predetermined time intervals and executed by the CPU. However, the present invention is not limited to this, and may be executed when a predetermined amount or more of disturbance is detected in the current flowing through the motors 14 and 24. Moreover, since the process of step S10, S12, S18, and S20 in FIG. 10 is the same as that of what is shown in FIG. 4, description here is abbreviate | omitted by assistance.

  Referring to FIG. 10, if it is determined in step S12 that q-axis current Iq is larger than operating point change threshold Iqth (YES in step S12), the boosted voltage (that is, system voltage VH) by converter 35 is increased in step S28. Execute the process to be changed. Specifically, as shown in FIG. 11, when the motors 14 and 24 are controlled by the rectangular wave at the system voltage VH1 where the system voltage VH is lower than the maximum boosted voltage VHmax, the system voltage VH is raised to the maximum boosted voltage VHmax. As a result, the referenced map is changed. Accordingly, in the map shown at the upper side in FIG. 11, the operating point 70 to which the rectangular wave control is applied at the system voltage VH1 does not change the motor rotation speed Nm, and the overmodulation control at the lower map in FIG. The operating point 72 can be changed.

  Following the boost voltage changing process, it is determined in step S30 whether or not the motors 14 and 24 are driven by overmodulation control. In this determination, the control device 10 is driven by overmodulation control if the modulation factor (or voltage utilization factor), which is the ratio of the amplitude of the motor input voltage to the system voltage VH, is greater than 0.61 and less than 0.78. Can be determined. After changing the operating point of the motors 14 and 24 to the operating point to which overmodulation control is applied in this way, the open failure determination in step S18 described above is executed.

  Then, after the open failure determination in step S18 is over and when a predetermined time t1 (eg, 3 to 4 seconds) has elapsed from the timing t0 (YES in step S20), the boost voltage is changed in step S30. Then, processing for returning the operating point of the motors 14 and 24 to the original operating point is executed. In the example shown in FIG. 11, the system voltage VH is lowered from VHmax to VH1. However, if it is determined in step S18 that there is an open failure in the switching elements of the inverters 36 and 38, for example, processing such as stopping the driving of the motors 14 and 24 and limiting the control mode to PWM control is performed. You may go.

  As described above, in the control device 10 of the present embodiment, the disturbance of each phase current of the motor due to the open failure of the switching element appears more in the overmodulation control than in the rectangular wave control. By evaluating the q-axis current Iq after changing the operating point from rectangular wave control to overmodulation control, it is possible to more accurately determine the open failure of the switching elements of the inverters 36 and 38. As a result, it is possible to prevent a secondary failure in which the motors 14 and 24 continue to be driven with an open failure and demagnetize so that torque cannot be output.

  In addition, the drive device of the electric vehicle which concerns on this invention is not limited to the thing of the structure of embodiment described above, A various improvement and deformation | transformation are included.

  In the above description, the motor operating point is changed from rectangular wave control to overmodulation control, and the open failure determination of the switching element of the inverter is performed. However, PWM control is performed in a lower rotation range than the motor rotation speed range R. Also when the open failure determination of the inverter connected to the motor driven by the above is performed, the motor operating point may be changed from PWM control to overmodulation control. If the example mentioned above is followed, it is realizable by raising the engine speed Ne, switching the gear stage of the transmission 30 from HI to LO, and lowering the boost voltage.

  Further, in the above, when the motor is controlled in a rectangular wave in a higher rotation range than the motor rotation speed range R in which an open failure of the switching element can be detected, or in a lower rotation area than the motor rotation speed range R. Although it has been described that the process of changing the motor operating point to the operating point of the overmodulation control region is executed when PWM control is being performed, when the open failure determination of the switching element is performed, the motor is controlled by rectangular wave control or PWM When being controlled, a process of changing the motor operating point to the operating point of the overmodulation control region may be executed regardless of the motor rotation speed.

  Furthermore, in the above description, the motor operating point is returned to the operating point before the change after completion of the open failure determination. However, the q-axis current Iq exceeds the operating point change threshold Iqth by the open failure determination in step S18. The process of returning the motor operating point may be executed only when it is determined that the count value of the number of times is less than the predetermined number of times within the failure detection confirmation time and no open failure of the switching element has occurred.

DESCRIPTION OF SYMBOLS 1 Hybrid vehicle, 10 Control apparatus, 12 Engine, 13 Temperature sensor, 14, 24 Motor, 15 Rotating shaft, 16 Battery, 18 Output shaft, 20 Power distribution mechanism, 22 Rotating shaft, 28 Engine rotational speed sensor, 30 Transmission, 32 axles, 34 drive wheels, 35 converters, 36, 38 inverters, 40, 57 voltage sensors, 42 current sensors, 44 temperature sensors, 50 positive buses, 52 negative buses, 54, 56 smoothing capacitors, 58 current detection sensors, 60 revolutions Angle sensor, 62 operating point change processing unit, 64 open failure determination unit, 66, 68, 70, 72 operating point, A1 PWM control region, A2 overmodulation control region, A3 rectangular wave control region, Acc accelerator opening signal, Ib Battery current, Id d-axis current, Iq q-axis current, Iqth operating point change threshold, Iu U-phase current, Iv V phase current, Iw W phase current, Ne engine speed, Nm, Nm1, Nm2 motor speed, R speed range, S1 to S16 control signal, SMR1, SMR2 system main relay, Sv vehicle speed, T * torque command, t0 Timing or predetermined time, Tb battery temperature, Tw cooling water temperature, Vb battery voltage, VH, VH1 system voltage, VH * system voltage command value, VHmax system voltage maximum value or maximum boost voltage, θ1, θ2 rotor rotation angle.

Claims (7)

A plurality of controls including overmodulation control by controlling operation of an inverter that converts a DC voltage supplied from a power storage device into an AC voltage and outputs it, a motor driven by the output voltage of the inverter, and a switching element included in the inverter A drive device for an electric vehicle comprising a control device for driving and controlling the motor by switching modes,
The controller is
An operating point change processing unit that changes the operating point of the motor to a region to which the overmodulation control is applied when the motor is driven at an operating point to which rectangular wave control or PWM control is applied;
Counts the number of times that the q-axis current derived based on the current flowing through the motor exceeds the operating point change threshold when the operating point is changed by the operating point change processing unit and the motor is overmodulated. And an open failure determination unit that determines that an open failure has occurred in the switching element when the count value is equal to or greater than a predetermined number of times within a predetermined time. In the drive device of the electric vehicle according to claim 1,
The electric vehicle is a hybrid vehicle equipped with an internal combustion engine as a driving power source, the motor is connected to the output shaft of the internal combustion engine via a power distribution mechanism, and the control device controls the operation of the internal combustion engine. The operating point change processing unit is configured to change the rotational speed of the internal combustion engine when the motor is driven at an operating point to which rectangular wave control or PWM control is applied. A drive device for an electric vehicle, wherein the rotational speed of the motor is changed to that of an operating point in a region to which the overmodulation control is applied via a power distribution mechanism. In the control apparatus of the electric vehicle according to claim 1 or 2,
The electric vehicle is configured such that the output of the motor is output to an axle via a transmission capable of shifting to a plurality of speeds, and the control device is capable of selectively controlling the speed of the transmission, and the operating point The change processing unit is configured to change the speed of the motor without substantially changing a vehicle speed by changing a gear position of the transmission when the motor is driven at an operating point to which rectangular wave control or PWM control is applied. An apparatus for controlling an electric vehicle, wherein the rotational speed is changed to that of an operating point in a region to which the overmodulation control is applied. In the control apparatus of the electric vehicle according to claim 1,
The electric vehicle includes a power conversion device capable of boosting a DC voltage from the power storage device and outputting the boosted voltage to the inverter, and the control device sets the boost voltage by controlling the operation of the voltage conversion device. The operating point change processing unit changes the boosted voltage by the voltage converter when the motor is driven at an operating point to which rectangular wave control or PWM control is applied. A control apparatus for an electric vehicle, wherein an operating point of a motor is changed to an operating point in a region to which the overmodulation control is applied. In the drive device of the electric vehicle as described in any one of Claims 1-4,
The control device executes control for temporarily switching the motor control mode from overmodulation control to PWM control when the open failure determination unit determines that the q-axis current has exceeded the operating point change threshold. Electric vehicle drive device characterized by In the drive device of the electric vehicle as described in any one of Claims 1-5,
The operating point change processing unit is configured such that the motor is controlled by a rectangular wave in a high rotation speed range that is higher than a motor rotation speed range in which an open failure of the switching element can be detected, or lower than the motor rotation speed range. An apparatus for driving an electric vehicle, which performs a process of changing a motor operating point to an operating point in an overmodulation control region when PWM control is performed in a rotation region. In the drive device of the electric vehicle as described in any one of Claims 1-6,
In the operating point change processing unit, the open failure determination unit causes the count value of the number of times that the q-axis current exceeds the operating point change threshold to be less than a predetermined number within a predetermined time, and an open failure occurs in the switching element. When it is determined that the motor does not exist, a process for returning the operating point of the motor to the operating point before the change is performed after the predetermined time has elapsed.

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