JP2015073351A - Motor control device and vehicular drive apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor control device and a vehicular drive apparatus that can easily detect a failure in a current sensor, can perform highly responsive motor control, and suppress an increase in manufacturing cost.SOLUTION: A CPU of a control circuit 6 reads in measurement values of current sensors 18u, 18v provided for two phases (U, V phases) of an electric motor 8, next if a phase angle is θ or θ+180° in the case of a zero-valued d-axis current Id or the phase angle is θ+θ' or θ+180°+θ', where θ' is a set offset value, in the case of a nonzero d-axis current Id, compares a U phase current value Iu and a V phase current value Iv, which are to be matched, and if there is a predetermined value of difference or more therebetween, determines that there is an anomaly occurring in at least either of the current sensors 18 and turns off phase opening relays 19 provided for the U phase and V phase. This isolates an inverter 3 from the electric motor 8 as a transition to a two-wheel drive mode of executing drive control on front wheels 12.

Description

  The present invention relates to a motor control device and a vehicle drive device, and more particularly to failure detection of a current sensor used for controlling an electric motor mounted on a vehicle.

  In recent years, hybrid vehicles, electric vehicles, and electric four-wheel drive vehicles that run with driving force from an electric motor have been attracting attention and put into practical use as environmentally friendly vehicles. In such a vehicle, for example, in a hybrid vehicle, a three-phase AC electric motor for driving a wheel that is controlled by an inverter device and generates a driving force is mounted. This electric motor is required to generate a desired torque that changes in response to a request from a driver with high responsiveness. For this reason, in the electric motor mounted in the hybrid vehicle, the inverter device is basically controlled using the current measurement values of at least two current sensors. And in order to perform drive control of an electric motor appropriately, the method of determining the failure of a current sensor easily by detecting the motor current of the same phase using a plurality of current sensors is disclosed (for example, Patent Document 1). According to the technique described in Patent Document 1, any pair of motor currents in a three-phase motor current is detected by each pair of current sensors to determine which current sensor is malfunctioning.

JP 2005-160136 A

  However, in the current sensor failure detection method described above, in consideration of the case where the current sensor breaks down, two current sensors are provided for each phase, for a total of four, and the output of the current sensor for each phase is compared. Then, the abnormality of the current sensor is diagnosed. As a result, the manufacturing cost increases due to an increase in the number of current sensors. For this reason, it is desirable to reduce the number of current sensors as much as possible. Further, in a configuration having one current sensor for one phase, an abnormality (for example, gain abnormality, etc.) occurs in a mode other than sticking to an upper limit value and a lower limit value (for example, power supply voltage 5V, 0V) in the current sensor. In this case, since the abnormality cannot be detected, feedback control of the electric motor is performed with an abnormal current value. As a result, an abnormal behavior of the electric motor may be caused.

  The present invention has been made to solve the above-described problems, and has as its object to easily detect a failure of a current sensor, enable highly responsive motor control, and increase the manufacturing cost. An object of the present invention is to provide a motor control device and a vehicle drive device that can be suppressed.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a motor control device, and is provided between a DC power source mounted on a vehicle and an electric motor for generating a driving force on a wheel, and a plurality of switching elements. A motor drive circuit for supplying a three-phase AC drive current to the electric motor, a control circuit for controlling the motor drive circuit, and at least two phases in a three-phase power supply line connected to the electric motor And a current sensor that detects a motor current flowing in each phase in series with the relay circuit, and the current measurement value of the two phases provided with the current sensor is The gist is to detect that one of the current sensors is abnormal when a difference between the current measurement values in at least two phases to be matched is larger than a predetermined value.

  According to the above configuration, the difference between the current values in the phases to be matched is obtained from the current values of the electric motor measured by the two current sensors provided in any two phases of the motor drive circuit output stage. If the current value is larger than the predetermined value, that is, if the current values do not match, it is determined that the current sensor is in an abnormal normal state. As a result, a failure of the current sensor can be easily detected without increasing the number of current sensors, so that the motor control device can be reduced in size by reducing the number of components, and an increase in manufacturing cost can be suppressed.

  According to a second aspect of the present invention, in the motor control device according to the first aspect, when the abnormality is detected in any of the current sensors, the relay circuit is opened, and the electric motor and the motor drive circuit are opened. The gist is to cut off between the two.

  According to the above configuration, when an abnormality occurs in any of the current sensors, the relay circuit is turned off to disconnect the motor drive circuit from the electric motor. Thereby, it is possible to prevent an abnormal behavior of the electric motor that is generated by executing feedback control with an abnormal current value.

  According to a third aspect of the present invention, in the motor control device according to the first or second aspect, the electric motor is controlled by a d-axis and q-axis current converted into a d / q coordinate system, and the d-axis current is When it is not 0, the gist is that the phase at which the current values of the two phases should coincide is offset by a predetermined angle.

  According to the above configuration, even when the d-axis current is not 0 (for example, field weakening control or the like), it is possible to determine the abnormality of the current sensor by comparing the current values at the phase offset by a predetermined angle.

  The gist of the invention according to claim 4 is to control the electric motor that drives the wheels in the vehicle drive device by using the motor control device according to any one of claims 1 to 3. .

  According to the said structure, the vehicle drive device which can control the electric motor which drives a wheel using the said motor control apparatus can be comprised.

  ADVANTAGE OF THE INVENTION According to this invention, the failure of a current sensor can be detected easily, the motor control apparatus and vehicle drive device which can control a motor with high responsiveness, and can suppress the increase in manufacturing cost can be provided.

1 is a block diagram showing a schematic configuration of an electric four-wheel drive vehicle equipped with a motor control device and a vehicle drive device according to an embodiment of the present invention. The circuit diagram which shows schematic structure of the motor control apparatus in FIG. The flowchart which shows the process sequence of the current sensor abnormality detection performed with the control circuit of a motor control apparatus. (A) is a figure which shows motor phase current when d-axis current Id = 0, (b) is a figure which shows motor phase current when d-axis current Id ≠ 0.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of an electric four-wheel drive vehicle equipped with a motor control device 1 and a vehicle drive device 10 according to an embodiment of the present invention.

  As shown in FIG. 1, the electric four-wheel drive vehicle includes an engine 15, a motor generator 11, an electric motor 8 for driving rear wheels, and a battery 2. The battery 2 is a high-voltage (for example, 245 V) DC power source, and is composed of, for example, a rechargeable battery such as chargeable / dischargeable nickel metal hydride or lithium ion. The driving force of the engine 15 and the motor generator 11 is transmitted to the front wheels 12 via a transmission (transmission) 16 to drive the front wheels 12. The output of the engine 15 is controlled by a command from an engine ECU (not shown), and may drive the motor generator 11 as well as drive the front wheels 12. The motor generator 11 is motor driven using the electric power stored in the battery 2 when driving the front wheels 12. When regenerative braking is performed by the front wheels 12, regenerative power obtained by the motor generator 11 is supplied to the battery 2 and charged. When generating power, the motor generator 11 uses the power of the engine 15 to output AC power as a generator.

  The front (front wheel) side inverter 13 is provided for arbitrarily controlling required power in the motor generator 11 based on a command from a front side control circuit (signal processing circuit) 14, and is stored in the battery 2. The generated direct current power is converted into alternating current power and supplied to the motor generator 11. At the time of regenerative braking or power generation, AC power is converted into DC power by the inverter 13 and supplied to the battery 2.

  Further, the vehicle drive device 10 mounted on the vehicle includes a rear wheel drive unit 9 and a motor control device (ECU) 1 that controls the electric motor 8 used to drive the rear wheel 7. The rear wheel drive unit 9 includes an electric motor 8, a reduction gear (differential gear) 4, and a clutch 5, and the clutch 5 is installed at the final stage of the reduction gear 4. For example, a three-phase brushless motor is used as the electric motor 8 for the drive source. The electric motor 8 is a permanent magnet type such as an IPM motor including an embedded magnet type rotor in which a permanent magnet is embedded and fixed in a rotor core, or an SPM motor including a surface magnet type rotor in which a permanent magnet is fixed to the surface of the rotor core. A synchronous motor is used.

  The driving force of the electric motor 8 is transmitted to the rear wheel 7 via the speed reducer 4 and the clutch 5, respectively, and drives the rear wheel 7. When the clutch 5 is connected, the rear wheel 7 is driven by the rotational force of the electric motor 8. When the clutch 5 is released, the electric motor 8 is mechanically disconnected from the rear wheel 7, and the rear wheel 7 does not transmit driving force to the road surface.

  The motor control device 1 includes a rear (rear wheel) side control circuit 6 and a rear side inverter 3. The control circuit 6 is connected to an auxiliary power source (not shown) having a low voltage (for example, 12V), receives a command from the vehicle control unit 17 that controls driving of the vehicle, and controls the rear wheel drive unit 9 and the like.

  Further, based on a command from the control circuit 6, an inverter 3 is provided so that required power can be braked arbitrarily in the electric motor 8, and the DC power stored in the battery 2 is converted into AC power, and the electric motor 8 is supplied. When the vehicle is braked, the electric motor 8 is regenerated by the regenerative torque from the rear wheel 7, and regenerative power can be obtained.

  The vehicle control unit 17 is connected to the engine ECU, the control circuit (front) 14, the control circuit (rear) 6 and communication means such as CAN, and commands the motor generator 11 for the front wheels and the electric motor 8 for the rear wheels. It is a controller that controls the entire drive system, such as calculating values. Based on the engine speed and torque command obtained from the vehicle control unit 17, the control circuit 14 controls the motor generator 11 and the inverter 13, and the control circuit 6 controls the electric motor 8 and the inverter 3.

Next, FIG. 2 is a circuit diagram showing a schematic configuration of the motor control device 1 in FIG.
As shown in FIG. 2, the motor control device 1 includes a control circuit 6 and an inverter 3. The high DC voltage stored in the battery 2 is connected to the inverter 3 via a power relay and a smoothing capacitor (not shown). Based on a command from the control circuit 6, it is converted into a three-phase alternating current by the inverter 3 and supplied to a three-phase electric motor 8 of U, V, and W phases, and the electric motor 8 rotates by generating a driving torque.

  The inverter 3 includes six power transistors (switching elements) U1, U2, V1, V2, W1, and W2. Two power transistors are connected in series to form the upper and lower arms of the U phase, and another two power transistors are connected in series to form the upper and lower arms of the V phase, and the remaining two Are connected in series to form an upper arm and a lower arm of the W phase. And the connection point (U, V, W) of each power transistor in each phase arm is connected to the coil end on the opposite side to the neutral point of each phase of the motor coils 8u, 8v, 8w of the electric motor 8, respectively. Yes. As the power transistor, for example, an IGBT or a MOS-FET is used.

  Further, each phase output of the motor control device 1 is provided with a current sensor 18 (18u, 18v) for detecting a motor phase current and a phase open relay (relay circuit) 19 (19u, 19v). The phase release relay 19 is a switch for switching whether or not to connect the inverter 3 to the electric motor 8. The phase release relay 19 is turned on (conductive state) when the electric motor 8 is operating, and is turned off (non-conductive state) when stopped.

  The U-phase and V-phase are provided with two U-phase and V-phase current sensors 18u and 18v for measuring three-phase currents (motor phase currents) Iu, Iv and Iw flowing through the electric motor 8. Yes. Here, the W-phase current Iw is calculated as Iw = −Iu−Iv from the U-phase current Iu and the V-phase current Iv detected by the U-phase and V-phase current sensors 18u and 18v (electric motor 8 In the motor coils 8u, 8v, and 8w of each phase, the sum of the current flowing in and the current flowing out becomes 0).

  The control circuit 6 controls the power transistors U1, U2, V1, V2, W1, and W2 included in the inverter 3. More specifically, various data used for current command value calculation are input to the control circuit 6 and three-phase drive currents (U-phase current, V-phase current, and W-phase) to be supplied to the electric motor 8 are input. A target value (target current) of the current) is determined, and a PWM signal for making the motor phase currents (each phase current value) Iu, Iv, Iw detected by the current sensor 18 coincide with the target current is output. The PWM signal of each phase output from the control circuit 6 is supplied to the gate terminals of six power transistors U1, U2, V1, V2, W1, and W2 included in the inverter 3, respectively.

  A control voltage (for example, 12V) serving as a power source for the control circuit 6 is supplied from a low-voltage battery (for example, 12V) (not shown), and an auxiliary battery is mounted as the low-voltage battery. Alternatively, the low voltage battery may be charged from the battery 2 via a DC / DC converter or the like.

  Next, an abnormality detection method for the current sensor 18 used in the motor control device 1 according to this embodiment will be described. The motor control device 1 is mounted on the vehicle drive device 10 shown in FIG. 1 and connected to the rear wheel drive unit 9.

  FIG. 3 is a flowchart showing a processing procedure for detecting an abnormality of the current sensor 18 executed by the control circuit 6 of the motor control device 1. FIG. 4A shows the motor phase current Iu, when the d-axis current Id = 0. FIG. 4B is a diagram showing motor phase currents Iu and Iv when d-axis current Id ≠ 0. 4 (a) and 4 (b) show examples of waveforms in which the horizontal axis represents the phase angle and the vertical axis represents the current value for the U-phase current Iu and the V-phase current Iv whose phases are shifted by 120 °. .

  The control circuit 6 of the motor control device 1 actually flows with respect to the d-axis current command value Id * and the q-axis current command value Iq * of the d / q coordinate system that is output based on the motor torque command. The d-axis voltage Vd and the q-axis voltage Vq are output so that the d-axis current Id and the q-axis current Iq obtained by converting each phase current value converted into the d / q coordinate system match. The three-phase voltage command values Vu, Vv, Vw converted from the d-axis voltage Vd and the q-axis voltage Vq are applied to the gate terminals of the power transistors U1, U2, V1, V2, W1, W2 in the inverter 3 as PWM signals. The input power transistors are turned on and off. As a result, the armature current flowing through the three-phase motor coils 8u, 8v, 8w of the electric motor 8 is controlled so that the drive torque of the electric motor 8 matches the motor torque command.

Here, when the control is performed only with the normal q-axis current Iq (d-axis current Id = 0), as shown in FIG. 4A, the U-phase current Iu and the V-phase current Iv have a predetermined θ. And in the phase of θ + 180 °. When Id ≠ 0 (for example, field weakening control), as shown in FIG. 4B, the phase at which the U-phase current Iu and the V-phase current Iv coincide with each other is θ ′ = tan ⁻¹ (Id / Iq), θ + θ ′ and θ + 180 ° + θ ′, which are offset (shifted) by θ ′.

  The abnormality detection of the current sensor 18 is performed by the control circuit 6 when the vehicle control is being executed. In the present embodiment, a CPU (not shown) in the control circuit 6 reads a program stored in the ROM, and executes each process of steps S301 to S307 shown in the flowchart of FIG. The processing in the flowchart shown below is executed at predetermined time intervals.

  As shown in FIG. 3, the CPU of the control circuit 6 in the rear motor control device 1 first reads the measured values of the current sensors 18 u and 18 v of the two-phase phase currents Iu and Iv flowing through the electric motor 8 ( Step S301). Subsequently, it is determined whether or not the d-axis current Id is 0 (step S302).

  Next, when the d-axis current Id is 0 (step S302: YES), the CPU determines whether or not the phase angle at which the measured value of the current sensor 18 in step S301 is read is a predetermined angle θ or θ + 180 °. (Step S303) is determined. If the phase angle is not θ or θ + 180 ° (step S303: NO), this process is terminated and the flow is exited. When the phase angle is θ or θ + 180 ° (step S303: YES), the process proceeds to step S306.

If the d-axis current Id is not 0 (step S302: NO), θ ′ (= tan ⁻¹ (Id / Iq)) is set as a predetermined offset value (step S304). Next, the CPU determines whether or not the phase angle read from the measurement value in step S301 is a predetermined angle θ + θ ′ or θ + 180 ° + θ ′ (step S305). If the phase angle is not θ + θ or θ + 180 ° + θ ′ (step S305: NO), this process is terminated and the flow is exited.

  Subsequently, it is determined whether or not the U-phase current Iu and the V-phase current Iv match in a phase that should match (step S306). When the U-phase current Iu and the V-phase current Iv match, that is, when the difference in current value between the U-phase current Iu and the V-phase current Iv is equal to or less than a predetermined value near 0 (step S306: YES), the current It is determined that the sensor 18 (18u, 18v) is normal, and this process ends and the flow is exited.

  If the U-phase current Iu and the V-phase current Iv do not match, that is, if the current value difference between the U-phase current Iu and the V-phase current Iv is larger than a predetermined value (step S306: NO), the current sensors 18u and 18v It is determined that an abnormality has occurred in at least one of them, and the phase open relays 19u and 19v provided in the U phase and the V phase are turned off (opened) (step S307). By executing the abnormality process, the inverter 3 and the electric motor 8 are disconnected, and the electric motor 8 enters a free state. Then, the CPU ends this processing and exits the flow. Thereafter, the CPU shifts to a two-wheel drive mode in which the motor generator 11 performs drive control of the front wheels 12 and is executed by the CPU of the control circuit 14 on the front side.

  Note that the abnormality detection method for the current sensor 18 used in the rear-side motor control device 1 of the above embodiment can be similarly applied to a motor control device including the front-side inverter 13 and the control circuit 14.

  Next, operations and effects of the motor control device 1 and the vehicle drive device 10 according to the embodiment of the present invention configured as described above will be described.

  According to the above embodiment, the two current sensors 18 (18u, 18) provided in any two phases (in this embodiment, the U phase and the V phase) of the output stage of the inverter 3 in the motor control unit (ECU) 1 are used. 18v), from the current values Iu and Iv of the electric motor 8 measured in 18v), the difference between the current values in the phases (θ and θ + 180 °) that should coincide with the d-axis current Id = 0 converted to the d / q coordinate system is obtained. When the difference is larger than a predetermined value in the vicinity of 0, that is, when the current values Iu and Iv do not match, it is determined that the current sensor 18 is in an abnormal state. When an abnormality occurs in either of the current sensors 18u and 18v, the phase open relay 19 (19u and 19v) is turned off (opened) to disconnect the inverter 3 from the electric motor 8. As a result, in the case of an electric four-wheel drive vehicle, a transition is made to the two-wheel drive mode with the front wheels 12.

  Further, even when the d-axis current Id for field weakening control or the like is not 0, the current sensor 18 is similarly compared by comparing the current values Iu and Iv at phases (θ + θ ′ and θ + 180 ° + θ ′) offset by a predetermined angle. Anomaly detection can be performed.

  Thereby, since it is possible to easily detect a failure of the current sensor 18 without increasing the number of current sensors 18, it is possible to downsize the motor control device 1 by reducing the number of components and to suppress an increase in manufacturing cost. Become. In addition, it is possible to prevent abnormal behavior of the electric motor 8 that occurs by executing feedback control using an abnormal current value measured by the failed current sensor 18. Furthermore, using the motor control device 1 of the present embodiment, a vehicle drive device 10 that can control the electric motor 8 that drives the rear wheel 7 can be configured and mounted on the vehicle. The front wheel 12 can be similarly configured.

  As described above, according to the embodiment of the present invention, a motor control device capable of easily detecting a failure of a current sensor, capable of highly responsive motor control, and suppressing increase in manufacturing cost, and A vehicle drive device can be provided.

  As mentioned above, although embodiment which concerns on this invention was described, this invention can also be implemented with another form.

  In the above embodiment, the current sensor 18 is provided for each of the U phase and the V phase. However, the present invention is not limited thereto, and the current sensor 18 is provided for each of the V phase and the W phase, or the W phase and the U phase. It may be.

  In the above embodiment, the vehicle is described as an electric four-wheel drive vehicle. However, the present invention is not limited to this. For example, the engine 15 and the engine 15 are related to the motor control device 1 using a three-phase alternating current as a drive source. A parallel-type hybrid vehicle including a front-wheel drive motor generator 11 directly connected to the crankshaft may be used, or may be applied to a series-type hybrid vehicle or a series-parallel type hybrid vehicle using both.

  Moreover, in the said embodiment, it can apply also to the electric vehicle which uses only the electric motor 8 as a drive source. As an electric vehicle, the electric motor 8 may be provided on the vehicle body side, or the electric motor 8 may be provided on the wheel side. Further, the vehicle may be a front wheel drive vehicle or a rear wheel drive vehicle. Alternatively, a vehicle in which the front wheels 12 are driven by the engine 15 and the rear wheels 7 are driven by the electric motor 8 may be used.

  In the said embodiment, although the abnormality detection method of the current sensor 18 provided in the inverter 3 was applied to the motor control device 1 and the vehicle drive device 10 that drive the in-vehicle three-phase AC electric motor 8, It is not limited to this, For example, you may make it use for inverters 3, such as an electric power steering apparatus and an electric brake device, or another vehicle-mounted power converter device. Moreover, you may apply to the electric equipment apparatus of the other use with which the high reliability and low cost provided with the electric motor 8 are calculated | required.

1: motor controller (ECU), 2: battery (DC power supply), 3: inverter (rear), 4: speed reducer (differential gear), 5: clutch, 6: control circuit (rear),
7: rear wheel, 8: electric motor, 8u, 8v, 8w: motor coil, 9: rear wheel drive unit, 10: vehicle drive device, 11: motor generator, 12: front wheel,
13: Inverter (front), 14: Control circuit (front), 15: Engine,
16: Transmission (transmission), 17: Vehicle control unit,
18, 18u, 18v: current sensor, 19, 19u, 19v: phase open relay,
U1, U2, V1, V2, W1, W2: power transistors (switching elements),
Iu, Iv, Iw: motor phase current, Id: d-axis current, Iq: q-axis current,
θ, θ ': Phase current phase angle

Claims (4)

A motor drive circuit that is provided between a DC power source mounted on the vehicle and an electric motor that generates driving force on the wheels, includes a plurality of switching elements, and supplies a three-phase AC drive current to the electric motor;
A control circuit for controlling the motor drive circuit;
A relay circuit provided in at least two phases in a three-phase power supply line connected to the electric motor;
A current sensor that is provided in the two phases in series with the relay circuit and detects a motor current flowing in each phase;
When the difference between the current measurement values in at least two phases where the current measurement values of the two phases provided with the current sensor should coincide with each other is larger than a predetermined value, it is detected that one of the current sensors is abnormal The motor control apparatus characterized by the above-mentioned. The motor control device according to claim 1,
When the abnormality is detected in any one of the current sensors, the relay control circuit is opened to disconnect between the electric motor and the motor drive circuit. The motor control device according to claim 1 or 2,
The electric motor is controlled by d-axis and q-axis currents, and when the d-axis current is not 0, the phase at which the current values of the two phases should be offset is offset by a predetermined angle. .   A vehicle drive device that controls the electric motor that drives a wheel by using the motor control device according to any one of claims 1 to 3.

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