JP2017153316A - Electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology utilizing a step-down converter as much as possible in an electric vehicle comprising the step-down converter that supplies power with the voltage of a main power source lowered even after a self-diagnosis function outputs an abnormality detection signal.SOLUTION: A step-down converter 20 includes a self-diagnosis circuit that notifies an ECU 8 of an abnormality detection signal when abnormality is detected. The ECU, when receiving the abnormality detection signal, checks whether or not the environmental state of the step-down converter is in a prescribed normal range, and when in the normal range, the ECU transmits to the step-down converter a forced action command signal that forcedly operates the step-down converter by ignoring the detected abnormality. Further, the ECU checks whether or not the output voltage of the step-down converter is in a range of an allowable voltage including a target voltage, and when the output voltage is outside of the allowable range, the ECU transmits to the step-down converter a control switching signal for switching to open loop control by cutting off a feedback control loop.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electric vehicle. The electric vehicle in this specification means an automobile provided with a traveling motor, and includes an electric automobile, a hybrid vehicle, a fuel cell vehicle, and the like.

  A specific type of electric vehicle includes two types of power sources: a main power source that supplies power to the motor for traveling, and an auxiliary battery that outputs power to a vehicle-mounted electrical device whose output voltage is lower than the voltage of the main power source. . Furthermore, the specific type of electric vehicle includes a step-down converter that steps down the power of the main power source in order to charge the auxiliary battery. The step-down converter includes a self-diagnosis circuit that detects an internal abnormality. When the self-diagnosis function detects an internal abnormality, it transmits an abnormality detection signal to the host controller that controls the step-down converter.

  Even if the step-down converter fails, the vehicle can continue to travel if the auxiliary battery has a remaining amount. In the electric vehicle disclosed in Patent Document 1, when the abnormality detection signal is received from the step-down converter, the host controller drives the vehicle out of devices that operate with the power of the auxiliary battery according to the remaining amount of the auxiliary battery. This limits the operation of devices that are not essential to the vehicle, and reduces the load on the auxiliary battery to maintain a state where it can run.

JP 2005-229706 A

  In the technique of Patent Document 1, the host controller limits the operation of the device according to the remaining amount of the auxiliary battery based on the determination of the self-diagnosis function of the step-down converter. On the other hand, even if the step-down converter transmits an abnormal signal, the step-down converter may still be usable. For example, when the self-diagnosis function itself in the step-down converter malfunctions. Alternatively, although the step-down converter has an abnormality, there is a possibility that it can be used continuously if performance is degraded. This specification makes the host controller that has received the abnormality detection signal from the step-down converter diagnose the state of the step-down converter, and uses the step-down converter as much as possible even after the self-diagnostic function of the step-down converter outputs the abnormality detection signal. Provide technology.

  The electric vehicle disclosed in this specification includes a main power source, an auxiliary battery, a step-down converter, and a controller (higher-order controller). The main power supply supplies power to the traveling motor. The main power source may be a battery that stores electric power or a power generation device such as a fuel cell. The auxiliary battery has an output voltage lower than the voltage of the main power supply, and supplies power to the on-vehicle electric device (auxiliary machine). The step-down converter has an input terminal connected to the main power supply and an output terminal connected to the auxiliary battery, and supplies the auxiliary battery with the electric power of the main power supply reduced to a target voltage. The step-down converter includes a feedback control loop that operates based on a command value determined based on the difference between the output voltage and the target voltage. Further, the step-down converter includes a self-diagnosis circuit that notifies the controller of an abnormality detection signal when an abnormality is detected. When receiving the abnormality detection signal, the controller checks whether or not the environmental state of the step-down converter is within a predetermined normal range. The environmental state is information regarding the step-down converter that can be acquired by the controller. Specific examples of the environmental state include the input voltage, output voltage, and temperature of the step-down converter. The controller stops the step-down converter when the environmental state is outside the normal range. On the other hand, when the environmental state is within the normal range, the controller transmits a forced operation command signal for ignoring the detected abnormality to the step-down converter. The controller checks whether the output voltage of the step-down converter is within a predetermined allowable range including the target voltage while the step-down converter is operating based on the forced operation command signal. Then, when the output voltage of the step-down converter is within an allowable range, the controller operates the step-down converter as it is. When the controller is out of the allowable range, the controller transmits a control switching signal for causing the step-down converter to interrupt the feedback control loop and to perform open loop control based on a command value determined based on the input terminal voltage and the target voltage.

  When the step-down converter receives the abnormality detection signal, the controller of the electric vehicle first checks the environmental state. If the environmental conditions are within the normal range, the buck converter still has the potential to be used. Therefore, when the environmental state is within the normal range, the controller forcibly operates the step-down converter and verifies whether the abnormality detection signal is correctly output. Even after the abnormality detection signal is output, the controller continues the operation as long as the output voltage is within an allowable range. If the output voltage is outside the allowable range, the controller determines that there is an abnormality in the feedback loop and switches to open loop control. As described above, in the electric vehicle disclosed in this specification, the host controller again diagnoses the step-down converter that outputs the abnormality detection signal by the self-diagnosis function, and uses the step-down converter as much as possible. Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a block diagram of the electric vehicle (hybrid vehicle) of an Example. It is a block diagram of an internal configuration of a step-down converter. It is a flowchart of the step-down converter diagnostic process which ECU performs.

  An electric vehicle according to an embodiment will be described with reference to the drawings. The electric vehicle according to the embodiment is a hybrid vehicle. FIG. 1 shows a block diagram of the hybrid vehicle 2. The hybrid vehicle 2 includes an engine 10 and a motor 7 for traveling. The output torques of the engine 10 and the motor 7 are synthesized by the gear set 11 and transmitted to an axle (not shown). Further, the gear set 11 may transmit a part of the output torque of the engine 10 to the axle and transmit the rest to the output shaft of the motor 7. In this case, the motor 7 functions as a generator. That is, the hybrid vehicle 2 can generate electric power with the motor 7 while traveling at the output of the engine 10. Moreover, the hybrid vehicle 2 may generate electric power with the motor 7 using the kinetic energy of the vehicle when the brake pedal is depressed. The electric power obtained by the power generation of the motor 7 is used for charging the main battery 3.

  The main battery 3 is connected to the low voltage end of the boost converter 5 via the system main relay 4. The high voltage end of the boost converter 5 is connected to the DC end of the inverter 6. A motor 7 is connected to the AC terminal of the inverter 6. Boost converter 5 boosts the power of main battery 3 and supplies it to inverter 6. The output voltage of the main battery 3 is 300 volts, for example, and the boost converter 5 boosts the voltage to 600 volts, for example.

  The main battery 3 is also connected to the input terminal 20 a of the step-down converter 20 via the system main relay 4. The output terminal 20 b of the step-down converter 20 is connected to the auxiliary battery 9. Note that the negative electrode of the output terminal 20b of the step-down converter 20 is connected to the negative electrode of the auxiliary battery 9 via the ground G. The output voltage of the auxiliary battery 9 is 12 volts, for example. The auxiliary battery 9 supplies electric power to the on-vehicle electric device 17 that operates at 12 volts. The electric device 17 is, for example, a car navigation system or a room lamp. In the present specification, an electric system that transmits power of a voltage (specifically, for example, less than 100 volts) much lower than the output voltage of the main battery 3 is referred to as an auxiliary system, and the electric system connected to the auxiliary system Equipment is collectively referred to as auxiliary equipment. A device indicated by reference numeral 17 in the drawing represents a plurality of auxiliary machines.

  Step-down converter 20 steps down the power of main battery 3 and supplies it to auxiliary battery 9. In other words, the auxiliary battery 9 is charged with the power of the main battery 3 via the step-down converter 20. Step-down converter 20 steps down the output voltage (300 volts) of main battery 3 to a voltage (for example, 12.5 volts) slightly higher than the output voltage of auxiliary battery 9.

  The step-up converter 5, the inverter 6, and the step-down converter 20 are controlled by an ECU 8 (Electronic Control Unit) which is a higher-order controller thereof. The ECU 8 controls the step-up converter 5, the inverter 6, and the step-down converter 20 based on various vehicle information. Specifically, the ECU 8 determines a torque (requested torque) that the vehicle should output based on the vehicle speed and the accelerator opening. Further, the ECU 8 supplies the required torque with the motor 7 and the motor 7 based on the remaining amount of the main battery 3 (SOC: State Of Charge), the temperature of the main battery 3, the temperature of the inverter 6, and the like. Divide into power torque. Then, the ECU 8 gives a target value to each of the step-up converter 5, the inverter 6, and the step-down converter 20 based on the torque to be provided by the motor 7, and drives them.

  On the other hand, the boost converter 5, the inverter 6, and the step-down converter 20 have a self-diagnosis function that detects their own abnormality, and the ECU 8 detects abnormality detected from the self-diagnosis circuit of the boost converter 5, the inverter 6, and the step-down converter 20. The signal is monitored. When the ECU 8 receives the abnormality detection signal, the ECU 8 executes a predetermined process and checks whether the device that has transmitted the abnormality detection signal is still usable. When the ECU 8 determines that the device that has transmitted the abnormality detection signal cannot be used, the ECU 8 immediately stops the vehicle. When the ECU 8 determines that the device that has transmitted the abnormality detection signal can be used, the ECU 8 continuously operates the device within a possible range according to the state of the abnormality. A console 15 and a nonvolatile memory 16 are connected to the ECU 8, and a predetermined warning lamp of the console 15 is turned on according to the abnormal state, and data indicating the abnormal state is stored in a diagnosis area of the nonvolatile memory 16. Store. The data in the diagnosis area is used by the service staff to check the vehicle state during vehicle maintenance.

  From here, the relationship between ECU8 and the step-down converter 20 is demonstrated. The first voltage sensor 12 is connected to the input terminal 20 a of the step-down converter 20, and the second voltage sensor 13 is connected to the output terminal 20 b of the step-down converter 20. The step-down converter 20 is attached with a temperature sensor 14 for measuring the temperature. The measured values of the first and second voltage sensors 12 and 13 and the measured value of the temperature sensor 14 are transmitted to the ECU 8. When the ECU 8 receives the abnormality detection signal from the step-down converter 20, the ECU 8 checks the state of the step-down converter 20 based on the measurement values of the voltage sensors 12, 13 and the temperature sensor 14, and continues using the step-down converter 20 if possible. To do.

  FIG. 2 shows a block diagram of the internal configuration of the step-down converter 20. First, the configuration between the input end 20a and the output end 20b will be described. A filter circuit 23 composed of a coil and a capacitor is connected to the input terminal 20a. A power circuit 24 that converts direct current to alternating current is connected to the filter circuit 23. The power circuit 24 is a DC-AC conversion circuit using four transistors 24a to 24d. The power circuit 24 is connected to the primary coil of the transformer 25. A rectifier circuit 26 is connected to the secondary coil of the transformer 25. A smoothing circuit 27 composed of a coil and a capacitor is connected between the rectifier circuit 26 and the output terminal 20b.

  The DC power input to the input terminal 20 a is smoothed by the filter circuit 23 and then input to the power circuit 24. The power circuit 24 converts the DC power input by the switching operation of the four transistors 24 a to 24 d into AC and transmits the AC power to the primary coil of the transformer 25. The transformer 25 reduces the voltage of the input AC power at a predetermined ratio and outputs it to the secondary coil. The AC power output to the secondary coil is returned to DC by the rectifier circuit 26, smoothed by the smoothing circuit 27, and output from the output terminal 20b. Since the filter circuit 23, the power circuit 24 (DC-AC conversion circuit), the rectifier circuit 26, and the smoothing circuit 27 shown in FIG. 2 are well known, detailed description thereof is omitted. The power circuit 24 determines the magnitude of the output voltage. The transistors 24a to 24d of the power circuit 24 are driven by a PWM (Pulse Width Modulation) signal from the microprocessor unit 21 (MPU 21). The output voltage of step-down converter 20 is determined by the duty ratio of the PWM signal applied to transistors 24a-24d of power circuit 24.

  A memory 30 is connected to the MPU 21, and a program executed by the MPU 21 is stored in the memory 30. The programs stored in the memory 30 include a control program 30a that controls the transistors 24a to 24d of the power circuit 24, a self-diagnosis program 30b that detects whether or not an abnormality has occurred inside the step-down converter 20, and the like.

  A target value (target voltage Vtgt) of the output voltage Vout of the step-down converter 20 is sent from the ECU 8 which is a host controller. The ECU 8 determines the target voltage Vtgt based on the torque that the motor 7 should output. Further, the ECU 8 acquires the input terminal voltage Vin from the measurement value of the first voltage sensor 12. The ECU 8 also transmits the acquired input terminal voltage Vin to the step-down converter 20.

  The MPU 21 periodically executes the control program 30a, and determines the duty ratio of the PWM signal supplied to the transistors 24a to 24d of the power circuit 24 based on the input terminal voltage Vin, the output voltage Vout, and the target voltage Vtgt. . More specifically, the MPU 21 determines a duty ratio corresponding to the step-down ratio based on the input terminal voltage Vin and the target voltage Vtgt, and based on the difference between the output voltage Vout and the target voltage Vtgt, Correct the ratio. In other words, the MPU 21 determines a PWM signal (including a duty ratio) to be supplied to the transistors 24a to 24d of the power circuit 24 based on the difference between the output voltage Vout and the target voltage Vtgt. As shown in FIG. 2, the step-down converter 20 includes a feedback loop 29 including a difference unit 22 that obtains a difference between the output voltage Vout and the target voltage Vtgt.

  The step-down converter 20 includes a sensor group 28 that detects an internal state. The sensor group 28 includes, for example, sensors that detect overvoltage, sensors that detect overcurrent, and disconnection detection sensors. The MPU 21 periodically executes the self-diagnosis program 30b and checks the measurement values obtained from the sensor group 28. In the self-diagnosis program 30b, it is checked whether or not the measurement values obtained from each of the sensor groups 28 belong to a predetermined normal range. The MPU 21 transmits an abnormality detection signal to the ECU 8 when the measurement value obtained from each of the sensor groups 28 is outside the normal range. Further, when step-down converter 20 detects an abnormality, step-down operation is stopped. That is, the MPU 21 turns off all the transistors 24a to 24d of the power circuit 24.

  In step-down converter 20, a case where an abnormality detection signal is erroneously output is assumed. For example, this is a case where the sensor has failed due to foreign matter mixed into the casing of the step-down converter 20. In such a case, no abnormality has actually occurred, and although the step-down converter 20 can be used as before, an abnormality detection signal is output. Alternatively, when an abnormality detection signal is output due to a temporary overcurrent, the step-down converter 20 can be used if the overcurrent is eliminated. Therefore, the ECU 8 that has received the abnormality detection signal diagnoses the state of the step-down converter 20 again and uses the step-down converter 20 as much as possible.

  As described above, the first voltage sensor 12 is connected to the input terminal 20a of the step-down converter 20, and the second voltage sensor 13 is connected to the output terminal 20b. The first voltage sensor 12 measures the input terminal voltage Vin, and the second voltage sensor 13 measures the output terminal voltage Vout (output voltage Vout). Further, the step-down converter 20 is provided with a temperature sensor 14 for measuring the temperature thereof. The measured values of the first and second voltage sensors 12 and 13 and the measured value of the temperature sensor 14 are sent to the ECU 8.

  FIG. 3 shows a flowchart of the step-down converter diagnostic process executed by the ECU 8. When the ECU 8 receives the abnormality detection signal from the step-down converter 20, the ECU 8 executes the process of FIG. When the abnormality detection signal is received, the ECU 8 checks the environmental state of the step-down converter 20 (S2). The environmental state is information regarding the step-down converter 20 that can be acquired by the ECU 8, and specifically, the input terminal voltage Vin measured by the first voltage sensor 12 and the output terminal voltage Vout measured by the second voltage sensor 13. (Output voltage Vout), the temperature of the step-down converter measured by the temperature sensor 14, and the like. The ECU 8 checks whether or not each of these environmental states is within a predetermined normal range. If at least one of the environmental conditions is out of the predetermined normal range, the ECU 8 determines that there is an abnormality (S3: YES), and executes an abnormality process (S12). In the abnormal process, the ECU 8 turns on the warning lamp of the console 15 and stores data indicating that an abnormality has occurred in the nonvolatile memory 16. When the environmental condition outside the normal range is a specific state, the ECU 8 may stop the vehicle immediately.

  When all the environmental conditions are within the normal range, that is, when no abnormality is detected in the environmental condition check in step S2 (S3: NO), the ECU 8 turns on another warning lamp of the console 15 (S4). Alternatively, the ECU 8 lights the same warning lamp that is turned on in step S12 in a color different from that in step S12. The warning light that is turned on in step S4 has a meaning of prompting the driver to perform maintenance.

  Next, the ECU 8 transmits a forced operation command signal to the step-down converter 20 (S5). As described above, the self-diagnosis program 30b of the step-down converter 20 stops the step-down operation when an abnormality is detected. The forced operation command signal is a command signal that causes the MPU 21 of the step-down converter 20 to ignore the measurement data of the sensor group 28 and resume the step-down operation. The step-down converter 20 that has received the forcible operation command signal activates the control program 30a and outputs the PWM signal supplied to the transistors 24a to 24d of the power circuit 24 so that the difference between the output voltage Vout and the target voltage Vtgt becomes zero. The duty ratio is determined, and the transistor is driven by the PWM signal. That is, the step-down converter 20 resumes the step-down operation. At this time, the MPU 21 operates using the feedback loop 29 described above so that the output voltage Vout matches the target voltage Vtgt by feedback control.

  Next, the ECU 8 checks whether or not the output voltage Vout of the step-down converter 20 is within a predetermined allowable range (S6). The allowable range here is set to a predetermined range including the target voltage Vtgt. For example, the target voltage Vtgt is set to 13 volts that is slightly higher than 12 volts that is the output voltage of the auxiliary battery 9, and the allowable range is set to 12 to 14 volts.

  When the output voltage Vout is within the allowable range (S6: YES), the ECU 8 determines that the step-down converter 20 can be used as before, and continues to use the step-down converter 20 as it is (S7). However, since the step-down converter 20 has already output the abnormality detection signal, there is a risk that abnormality will occur again. Therefore, the ECU 8 periodically checks the environmental condition thereafter (S8). Specifically, the ECU 8 starts a timer that serves as a trigger for executing an environmental condition check routine. After step S8, the ECU 8 starts a timer each time the environmental state check is executed, so that the environmental state check is periodically performed.

  On the other hand, if the determination in step S6 is NO, that is, if the output voltage Vout is outside the allowable range when the step-down converter 20 is forcibly operated, the ECU 8 causes the feedback loop 29 of the step-down converter 20 to function normally. Judge that it is not. In this case, the ECU 8 transmits a control switching command signal to the step-down converter 20 (S13). The control switching command signal is a command for causing the step-down converter 20 to interrupt the feedback control loop and to perform open loop control based on a command value determined based on the input terminal voltage Vin and the target voltage Vtgt. The MPU 21 of the step-down converter 20 that has received the control switching command signal cuts off the feedback loop 29 and performs open loop control based on the command value determined based on the input terminal voltage Vin and the target voltage Vtgt. Specifically, the MPU 21 determines a duty ratio by an equation [coefficient × target voltage Vtgt / (input terminal voltage Vin × transformer winding ratio)], and outputs a PWM signal whose phase is shifted by the duty ratio to each transistor. 24a to 24d.

  For the step-down converter 20 that has started the open loop control, the ECU 8 checks again whether or not the output voltage Vout is within the allowable range (S14). The allowable range here is the same as the allowable range used in step S6. When the output voltage Vout is within the allowable range by the open loop control, the ECU 8 determines that the step-down converter can be used, and continues to use the step-down converter 20 as it is (S14: YES, S7). Also in this case, the ECU 8 periodically checks the environmental condition thereafter (S8).

  On the other hand, if the output voltage Vout is out of the allowable range even by the open loop control, the ECU 8 determines that the step-down converter 20 cannot be used, and executes the abnormality process similar to step S12 ( S14: NO, S15).

  In this way, the ECU 8 performs a diagnosis again on the step-down converter 20 that has output the abnormality detection signal by the internal diagnosis circuit, and verifies whether or not the step-down converter 20 can be continuously used. The ECU 8 determines that the step-down converter 20 can be used and continues to use it. In this way, the ECU 8 utilizes the step-down converter 20 that outputs the abnormality detection signal by the self-diagnosis circuit as much as possible. However, the ECU 8 periodically checks the environmental state of the step-down converter 20 for the step-down converter 20 that has once transmitted the abnormality detection signal. The ECU 8 strengthens monitoring of the step-down converter 20 and monitors whether the state of the step-down converter 20 is deteriorated.

  Points to be noted regarding the technology described in the embodiments will be described. The ECU 8 corresponds to an example of a “controller that controls the step-down converter” in the claims. The MPU 21 that executes the self-diagnosis program 30b and the sensor group 28 that measures the internal state of the step-down converter 20 correspond to an example of the “self-diagnosis circuit” in the claims.

  The electric vehicle of the example was a hybrid vehicle 2. The technology disclosed in this specification is also preferably applied to an electric vehicle and a fuel cell vehicle. When the technique disclosed in this specification is applied to a fuel cell vehicle, the main battery 3 in FIG. 1 is replaced with a fuel cell.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Hybrid vehicle 3: Main battery 4: System main relay 5: Boost converter 6: Inverter 7: Motor 8: ECU (controller)
9: Auxiliary battery 10: Engine 11: Gear set 12, 13: Voltage sensor 14: Temperature sensor 15: Console 16: Non-volatile memory 17: Electrical equipment 20: Step-down converter 20a: Input end 20b: Output end 21: Microprocessor Unit (MPU)
22: subtractor 23: filter circuit 24: power circuit 24a-24d: transistor 25: transformer 26: rectifier circuit 27: smoothing circuit 28: sensor group 29: feedback loop 30: memory 30a: control program 30b: self-diagnosis program

Claims (1)

A main power supply that supplies power to the motor for traveling;
An auxiliary battery for supplying electric power to an on-vehicle electric device whose output voltage is lower than the voltage of the main power source;
A step-down converter having an input terminal connected to the main power supply and an output terminal connected to the auxiliary battery, and stepping down the electric power of the main power supply to a target voltage and supplying the auxiliary battery to the auxiliary battery;
A controller for controlling the step-down converter;
With
The step-down converter includes a feedback control loop that operates based on a command value determined based on a difference between an output voltage and a target voltage, and a self-diagnosis circuit that notifies the controller of an abnormality detection signal when an abnormality is detected With
The controller is
Upon receiving the abnormality detection signal, it is checked whether the environmental condition of the step-down converter is within a predetermined normal range,
If the environmental condition is outside the normal range, stop the step-down converter,
When the environmental state is within the normal range, a forced operation command signal for ignoring the detected abnormality is transmitted to the step-down converter,
Check whether the output voltage of the step-down converter is within a predetermined allowable range including the target voltage while the step-down converter is operating based on the forced operation command signal,
When the output voltage of the step-down converter is within the allowable range, the step-down converter is operated as it is,
When the output voltage of the step-down converter is out of the allowable range, the step-down converter causes the feedback control loop to be interrupted and an open loop based on a command value determined based on the input terminal voltage and the target voltage Send a control switching signal to control,
The electric vehicle characterized by the above-mentioned.

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