JP6860424B2 - Electric vehicle control device - Google Patents

Description

The present invention relates to a control device for an electric vehicle.

There are electric vehicles such as HEVs (Hybrid Electric Vehicles) or PHEVs (Plug-in Hybrid Electric Vehicles) equipped with a traveling motor and an engine. Such an electric vehicle can switch between motor running, which runs on the power of a running motor, and engine running, which runs on the power of an engine. The traction motor is driven by the electric power stored in the main battery.

In an electric vehicle, when an abnormality is detected in the main battery during motor running, control may be performed to disconnect the main battery from the drive circuit of the running motor and switch from motor running to engine running (). For example, see Patent Document 1). Alternatively, control may be performed to start the engine and switch to batteryless running (see, for example, Patent Documents 2 and 3). Battery-less running refers to a method in which a running motor is driven by electric power generated by the power of an engine to run. By such control, it is possible to prevent the abnormality of the main battery from spreading to the entire system of the electric vehicle, and the running of the electric vehicle can be continued.

When switching from motor running to engine running or batteryless running, the control device of the electric vehicle usually drives a starter to start the engine. The starter is driven by the power of a sub-battery provided separately from the main battery. A relatively large amount of electric power is required to start the engine.

In an electric vehicle equipped with a traveling motor and an engine, the sub-battery can be sufficiently charged by generating electricity by the power of the engine while the engine is running. Further, while the motor is running, the voltage of the main battery can be lowered to charge the sub-battery.

Japanese Patent Application No. 2015-119543 Japanese Unexamined Patent Publication No. 2014-024452 JP-A-2010-247725

However, in the electric vehicle, the sub-battery may be insufficiently charged while the motor is running. For example, in an electric vehicle, power management is performed to suppress waste of power of the main battery so that the cruising range of the motor running does not decrease during the motor running. In this case, when the power consumption of other electric components such as a heater or a light is large, the amount of power supplied from the main battery to the sub battery decreases, and charging becomes insufficient. Alternatively, due to the rating of the buck converter that lowers the voltage of the main battery, when the power consumption of other electric components is large, the current supplied from the buck converter to the sub-battery is reduced, resulting in insufficient charging. Further, even if the amount of power supplied to the sub-battery is sufficient, if the sub-battery is deteriorated, the amount of charge of the sub-battery, that is, the amount of power that can be discharged from the sub-battery may be insufficient. there were.

Here, a case where the sub-battery is insufficiently charged when switching from the motor running to the engine running or the batteryless running will be examined. Even in such a case, if the main battery is normal, the power of the main battery can supplement the power of the sub battery to sufficiently drive the starter. As a result, the engine can be easily started. Alternatively, if the main battery is normal, some electric vehicles can start the engine by driving the traveling motor with the electric power of the main battery.

However, when an abnormality occurs in the main battery and the motor running is switched to engine running or batteryless running, it is necessary to disconnect the main battery from the system of the electric vehicle, so that the starter is driven by the electric power of the main battery. The power cannot be supplemented. Therefore, if the sub-battery is insufficiently charged, there is a problem that the engine cannot be started and the electric vehicle may not be able to run even if there is fuel.

On the other hand, by sufficiently charging the sub-battery with the electric power of the main battery while the motor is running, it is possible to avoid a situation in which the engine cannot be started even if an abnormality occurs in the main battery. However, due to a rare situation where an abnormality is detected in the main battery, if the power management of the main battery while the motor is running is changed so that the power of the main battery can be used without limitation, the cruising range of the motor running will be increased. The problem of lowering arises. Alternatively, if the rating of the buck converter is increased so that a sufficient charging current can be supplied to the sub-battery even when the power consumption of other electric components is high, there arises a problem that the component cost rises.

In addition, if continuous motor running for a long time is prohibited, a period of engine running is created regularly, and the sub-battery is fully charged during this period, the engine will run even if an abnormality occurs in the main battery during motor running. It is possible to avoid the situation where the engine cannot be started. However, it is not preferable to set a restriction such as prohibiting the motor running for a long time because of a rare situation where an abnormality of the main battery is detected, because the degree of freedom in the control design of the electric vehicle is reduced. Further, when the sub-battery is deteriorated, sufficient power cannot be stored in the sub-battery even if the period for charging the sub-battery is increased.

The present invention provides a control device for an electric vehicle that can reduce the possibility that the engine cannot be started and cannot run even if an abnormality is detected in the main battery when the sub-battery is insufficiently charged. The purpose.

The invention according to claim 1
A main battery that supplies electric power to a traction motor via an inverter, a sub-battery that supplies electric power to a starter that starts an engine, a step-down converter that lowers the voltage of the main battery and supplies it to the sub-battery, and the above. A control device for an electric vehicle mounted on an electric vehicle including a main battery and a main relay for opening and closing a current path between the inverter and the step-down converter.
A start control unit that starts the engine when an abnormality in the main battery is detected.
When the abnormality of the main battery is detected and the main relay is switched to open, the buck converter is temporarily stopped, and then the buck converter is restarted when the starter is driven by the start control unit. Auxiliary control unit and
It is characterized by having.

The invention according to claim 2 is the control device for an electric vehicle according to claim 1.
When the auxiliary control unit detects an abnormality in the main battery and the main relay is switched to open, the auxiliary control unit temporarily stops the buck converter, and then the starter is driven to fail to start the engine. In addition, the buck converter is restarted when the starter is driven again.

The invention according to claim 3 is the control device for the electric vehicle according to claim 1 or 2.
The auxiliary control unit is characterized in that, according to the traveling state of the electric vehicle, the regenerative power of the traveling motor is sent to the buck converter when the buck converter is restarted.

The invention according to claim 4 is the control device for an electric vehicle according to claim 3.
The auxiliary control unit is characterized in that the magnitude of the regenerative power is changed according to the voltage of the sub-battery.

The invention according to claim 5 is the control device for an electric vehicle according to any one of claims 1 to 4.
The start control unit is characterized in that it can execute an inertial start process for starting the engine by converting the kinetic energy of the electric vehicle into power without using the starter, according to the running state of the electric vehicle. And.

According to the present invention, when an abnormality in the main battery is detected by the auxiliary control unit and the main relay is switched to open, the buck converter is temporarily stopped. As a result, for example, the electric charge accumulated in the input section of the inverter (capacitor for DC link, etc.) or the input section of the buck converter (input capacitor, etc.) is maintained, and is equivalent to the high voltage of the main battery at the input terminal of the buck converter. It is possible to maintain the state where the voltage of is applied. Then, when the start control unit drives the starter, the auxiliary control unit restarts the step-down converter, so that the electric power of the charge stored in the input unit of the inverter or the step-down converter is supplied to the starter via the step-down converter. Will be done. As a result, even if the sub-battery is insufficiently charged, power can be replenished from the buck converter to sufficiently drive the starter. Therefore, the probability that the engine can be started can be increased. Therefore, even if the sub-battery is insufficiently charged while the motor is running, it is possible to reduce the situation where an abnormality is detected in the main battery and the sub-battery becomes inoperable.

It is a block diagram which shows the electric vehicle which concerns on 1st Embodiment of this invention. It is a timing chart explaining the engine start processing at the time of the battery error executed by the control device of the electric vehicle which concerns on 1st Embodiment. It is a timing chart explaining the engine start processing at the time of the battery error executed by the control device of the electric vehicle which concerns on 2nd Embodiment. It is a flowchart which shows the procedure of the engine start processing at the time of the battery error executed by the control device of the electric vehicle which concerns on 3rd Embodiment.

Hereinafter, each embodiment of the present invention will be described in detail with reference to the drawings.

(First Embodiment)
FIG. 1 is a configuration diagram showing an electric vehicle according to the first embodiment of the present invention.

The electric vehicle 1 according to the first embodiment includes an engine 21 and a traveling motor 24, and is an HEV capable of switching between engine traveling driven by the power of the engine 21 and motor traveling traveling by the power of the traveling motor 24. Alternatively, it is an electric vehicle such as a PHEV. As shown in FIG. 1, the electric vehicle 1 includes an auxiliary machine 37 including a control device 10, a main battery 31, a main relay 32, an inverter 33, a buck converter 34, a sub battery 36, and a starter 38, and an ISG (Integrated Starter Generator) 22. To be equipped. The control device 10 mounted on the electric vehicle 1 includes a battery ECU (Electric Control Unit) 11, a hybrid ECU 12, an engine ECU 13, and a TCU (Transmission Control Unit) 14. The engine ECU 13 may be referred to as an "ECU (Engine Control Unit)". Further, the electric vehicle 1 includes various sensors such as a clutch 23, a transmission 25, wheels 26, and a vehicle speed sensor 26a for detecting a running state of the electric vehicle 1. Among the above components, the hybrid ECU 12, the engine ECU 13, and the TCU 14 function as a start control unit according to the present invention.

The engine 21 generates power by burning fuel, and can transmit power to the wheels 26 via a transmission mechanism including a clutch 23 and a transmission 25. The engine 21 is started by driving the starter 38. The engine 21 is connected to the power transmission path of the wheel 26 via the clutch 23 while the engine is running, while is disconnected from the power transmission path of the wheel 26 by the clutch 23 while the motor is running.

The traveling motor 24 generates power by being electrically driven, and can transmit the power to the wheels 26 via a transmission mechanism including a transmission 25. The traveling motor 24 is connected to the power transmission path of the wheels 26 during both the motor traveling and the engine traveling. The traveling motor 24 receives a drive current from the inverter 33 to generate torque, while a regenerative current is passed through the inverter 33 to generate braking force. The traveling motor 24 gives almost no load to the power transmission path of the wheels 26 when the inverter is stopped.

The main battery 31 is a secondary battery such as a lithium ion battery or a nickel hydrogen battery, and supplies electric power for driving the traveling motor 24. The main battery 31 may be called a “high voltage battery” and outputs a voltage (for example, 100 V) higher than that of the sub battery 36 to the inverter 33 and the step-down converter 34.

The battery ECU 11 monitors the state of the main battery 31 and adjusts the inside of the main battery 31 such as adjusting the cell voltage. The battery ECU 11 transmits the abnormality detection information to the hybrid ECU 12 when an abnormality occurs in the main battery 31. The abnormality of the main battery 31 includes various abnormalities such as a temperature abnormality of the main battery 31, overcharging, a decrease in the insulation resistance of the main battery 31, and an electric leakage.

The hybrid ECU 12 controls the main relay 32, the inverter 33, the buck converter 34, and the ISG 22, and transmits a start command or a stop command for running the engine to the engine ECU 13. Further, the hybrid ECU 12 transmits a switching command for switching the intermittent state of the clutch 23 to the TCU 14. Then, through these controls, the hybrid ECU 12 controls the switching between the engine running and the motor running, and controls the motor running. Specifically, the hybrid ECU 12 switches between engine running and motor running in a normal state, for example, according to the operating range of the engine 21 and the running motor 24 and the remaining charge of the main battery 31. Further, the hybrid ECU 12 switches from the motor running to the engine running when an abnormality of the main battery 31 is detected during the motor running. Further, in controlling the motor running, the hybrid ECU 12 sends a torque command to the inverter 33 according to the driving operation of the occupant to generate torque according to the driving operation in the traveling motor 24.

The TCU 14 controls the transmission 25. Further, the TCU 14 controls to switch the intermittent state of the clutch 23 when switching between engine running and motor running.

The inverter 33 converts the electric power of the main battery 31 and outputs it to the traveling motor 24 in response to the torque command of the hybrid ECU 12. As a result, the torque corresponding to the torque command is output from the traveling motor 24. Further, when the inverter 33 receives a negative torque command from the hybrid ECU 12, the inverter 33 causes a regenerative current to flow to generate a braking force in the traveling motor 24. The inverter 33 sends a regenerative current to the main battery 31 to charge the main battery 31. The inverter 33 stops the power conversion operation when the torque command of the hybrid ECU 12 is stopped. A capacitor 33a having a relatively large capacity is provided at the input portion of the inverter 33 for a DC link.

The step-down converter 34 steps down the voltage of the main battery 31 and supplies electric power to the low-voltage circuit to which the sub-battery 36 is connected while the motor is running. A part of the electric power supplied from the buck converter 34 to the low voltage circuit is used by the auxiliary machine 37, and a part is charged to the sub-battery 36. A capacitor 34a for smoothing or removing ripples is provided at the input portion of the step-down converter 34. The step-down converter 34 can be switched between stop and operation under the control of the hybrid ECU 12. The stop of the step-down converter 34 means a state in which the output is substantially stopped regardless of whether or not the switching control is stopped.

The step-down converter 34 further has a self-diagnosis function of diagnosing whether or not a specified voltage is input to the input terminal. The step-down converter 34 is configured to spontaneously stop when the voltage of the input terminal drops and the self-diagnosis function is determined to be abnormal. Further, the self-diagnosis function is configured so that a diagnostic mask can be added based on the command of the hybrid ECU 12. By adding the diagnostic mask, the step-down converter 34 can be set to a state in which it is difficult to voluntarily stop, such as stopping the operation of the self-diagnosis function or lowering the threshold value for determining an abnormality.

The main relay 32 opens and closes the current path between the main battery 31 and the inverter 33 and the buck converter 34.

The engine ECU 13 controls an auxiliary machine 37 including a starter 38, and controls the engine 21 while the engine is running by these controls. Specifically, when the engine ECU 13 receives a start command from the hybrid ECU 12, the engine ECU 13 drives the starter 38 to start the engine 21. In addition, the engine ECU controls the auxiliary machine 37 according to the driving operation of the occupant to generate torque from the engine 21 according to the driving operation. Further, the engine ECU 13 controls the auxiliary machine 37 to stop the engine 21 based on the request of the TCU 12 that has received the stop command of the engine 21 from the hybrid ECU 12.

The sub-battery 36 is a secondary battery such as a lead battery, and supplies electric power to a plurality of ECUs including a battery ECU 11, a hybrid ECU 12, an engine ECU 13, and a TCU 14, an ISG 22, and an auxiliary machine 37. The sub-battery 36 may be referred to as an "auxiliary battery". The sub-battery 36 outputs a voltage lower than that of the main battery 31 (for example, 12V). The output voltage of the sub-battery 36 is monitored by a battery monitoring unit including a voltage sensor 36a.

The ISG 22 has a function of a motor that restarts the engine 21 after idling stop and a function of generating electricity by the power of the engine 21. While the engine is running, the ISG 22 generates electricity to charge the sub-battery 36. Further, when starting after idling stop, the ISG 22 restarts the engine 21 by using the electric power of the sub-battery 36. The function of the motor of the ISG22 can output enough torque to restart the engine 21 in a warm state such as when idling is stopped.

The starter 38 is driven by the electric power of the sub-battery 36 under the control of the engine ECU 13 to start the engine ECU 13. The starter 38 can output a large torque that can start a cold engine, and temporarily consumes a large amount of electric power as compared with other electric parts other than the traveling motor 24.

<Engine start processing when battery error occurs>
Subsequently, the engine starting process at the time of a battery error executed by the control device 10 of the electric vehicle 1 according to the first embodiment will be described. FIG. 2 is a timing chart for explaining this start-up process. Each horizontal axis in FIG. 2 represents time.

As shown in FIG. 2, when an abnormality occurs in the main battery 31 while the motor is running, the battery ECU 11 detects the abnormality and sends the abnormality detection information to the hybrid ECU 12. When the abnormality detection information is sent, the hybrid ECU 12 turns off (stops) the inverter 33 and the step-down converter 34 (timing t2, t3), and immediately after that, switches the main relay 32 to open (timing t1). By switching the main relay 32 to open, it is possible to prevent the abnormality of the main battery 31 from spreading to other systems of the electric vehicle 1. Further, since the inverter 33 and the buck converter 34 are stopped when the main relay 32 is switched to open, a large amount of electric charge is charged to the capacitors 33a and 34a of the input portions of the inverter 33 and the buck converter 34 due to the high voltage of the main battery 31. Can be retained. As a result, it is possible to maintain a state in which a voltage equivalent to the high voltage of the main battery 31 is applied to the input terminal of the step-down converter 34.

The timings t2 and t3 for stopping the buck converter 34 and the inverter 33 are preferably set before the timing t1 for switching the main relay 32 to open, as shown in FIG. As a result, after the buck converter 34 is stopped, the amount of electric charge held in the input portion between the buck converter 34 and the inverter 33 can be increased. However, the timings t2 and t3 may be at the same time as the timing t1 or slightly after the timing t1. Even in this case, after the buck converter 34 is stopped, a large amount of electric charge can be held in the input portion between the buck converter 34 and the inverter 33.

After that, the hybrid ECU 12 transmits a start command to the engine ECU 13, and the engine ECU 13 drives the starter 38 (timing t6). Further, when the starter 38 is driven, the hybrid ECU 12 turns on (operates) the buck converter 34 (timing t4), and restarts the buck converter 34 while driving the starter 38 (period T4). Since the main relay 32 is switched to open during the period T4 in which the step-down converter 34 is restarted, the power of the main battery 31 is not supplied to the step-down converter 34. However, since the electric charge is accumulated in each input portion of the buck converter 34 and the inverter 33 by the stop control of the buck converter 34 immediately before, the electric power of the electric charge can be output from the buck converter 34. As a result, even if the sub-battery 36 is not sufficiently charged and the engine 21 cannot be started by the power of the sub-battery 36 alone, the power is supplemented from the step-down converter 34 to drive the starter 38 more powerfully. Therefore, the probability that the engine 21 can be started can be increased. The timing t4 for restarting the step-down converter 34 may be slightly deviated from the drive start timing t6 of the starter 38. Even in this case, the same effect can be obtained.

On the other hand, during the period T4 in which the step-down converter 34 restarts, the voltage at the input terminal of the step-down converter 34 drops relatively rapidly, so that the hybrid ECU 12 sends a diagnostic mask to the step-down converter 34 before the voltage at the input terminal drops. Is sent (timing t5). Then, the hybrid ECU 12 continues to add the diagnostic mask until the restart of the step-down converter 34 is completed (period T5). This diagnostic mask prevents the buck converter 34 from being stopped by the self-diagnosis function during the restart of the buck converter 34.

The engine ECU 13 that executes the start control of the engine 21 shown in FIG. 2 corresponds to an example of the start control unit according to the present invention. Further, the hybrid ECU 12 that executes each control process of the main relay 32, the inverter 33, and the buck converter 34 shown in FIG. 2 corresponds to an example of the auxiliary control unit according to the present invention.

As described above, according to the electric vehicle 1 and its control device 10 of the first embodiment, when an abnormality in the main battery 31 is detected and the main relay 32 is switched to open, the buck converter 34 is temporarily stopped and the starter is started. The buck converter 34 restarts when the 38 is driven. As a result, even if the sub-battery 36 is insufficiently charged, the electric power can be supplemented to drive the starter 38 more powerfully. Therefore, according to the electric vehicle 1 of the present embodiment, even if an abnormality of the main battery 31 is detected in a situation where the remaining charge of the sub-battery 36 is low while the motor is running, the engine 21 cannot be started and the electric vehicle It is possible to reduce the possibility that 1 becomes inoperable.

(Second Embodiment)
In the second embodiment, the configurations of the electric vehicle 1 and the control device 10 are the same as those in the first embodiment shown in FIG. In the second embodiment, the engine starting process at the time of battery error is different from that in the first embodiment. Hereinafter, detailed description of similar parts will be omitted, and different parts will be described in detail. FIG. 3 is a timing chart illustrating an engine start process at the time of a battery error executed by the control device of the electric vehicle according to the second embodiment. Each horizontal axis in FIG. 3 represents time.

In the second embodiment, the same is true as in the first embodiment until the inverter 33 and the buck converter 34 are stopped based on the abnormality detection information of the main battery 31 and the main relay 32 is switched to open. In the second embodiment, as shown in FIG. 3, after the main relay 32 is switched to open, a start command is promptly transmitted from the hybrid ECU 12 to the engine ECU 13, and the engine ECU 13 drives the starter 38 (timing t6). −A). At this time, the hybrid ECU 12 does not restart the step-down converter 34. With such control, the first drive of the starter 38 can be executed more quickly, and when the sub-battery 36 is sufficiently charged, the engine 21 can be promptly started to shift to engine running. If the engine 21 can be started by the first drive process of the starter 38, the engine start process at the time of battery error ends as it is.

On the other hand, when the sub-battery 36 is insufficiently charged and the engine 21 fails to start due to the first drive of the starter 38, the hybrid ECU 12 transmits a second start command to the engine ECU 13. Then, when the engine ECU 13 drives the starter 38 again based on the start command, the hybrid ECU 12 turns on the buck converter 34 (timing t4) and restarts the buck converter 34 while driving the starter 38 (period T4). Since the main relay 32 is switched to open during the period T4 in which the step-down converter 34 is restarted, power is not supplied from the main battery 31 to the step-down converter 34. However, since the electric charge is accumulated in each input portion of the buck converter 34 and the inverter 33 by the stop control of the buck converter 34 immediately before, the electric power of the electric charge can be output from the buck converter 34. Then, by replenishing the electric power, it is possible to increase the probability that the starter 38 can be strongly driven and the engine 21 can be started even if the sub-battery 36 is insufficiently charged. The timing t4 for restarting the step-down converter 34 may be slightly shifted back and forth from the second drive start timing t7 of the starter 38. Even in this case, the same effect can be obtained.

The process of adding the diagnostic mask to the step-down converter 34 by the hybrid ECU 12 according to the period T4 in which the step-down converter 34 is restarted is the same as that of the first embodiment. The addition of the diagnostic mask prevents the buck converter 34 from stopping due to the self-diagnosis function during the restart of the buck converter 34.

The engine ECU 12 that controls the start of the engine 21 shown in FIG. 3 corresponds to an example of the start control unit according to the present invention. Further, the hybrid ECU 12 that executes each control process of the main relay 32, the inverter 33, and the buck converter 34 shown in FIG. 3 corresponds to an example of the auxiliary control unit according to the present invention.

As described above, according to the electric vehicle 1 and its control device 10 of the second embodiment, when the abnormality of the main battery 31 is detected and the main relay 32 is switched to open, the buck converter 34 is temporarily stopped. Then, when the engine 21 cannot be started by driving the starter 38 for the first time, the buck converter 34 restarts when the starter 38 is driven for the second time. Therefore, if the sub-battery 36 is sufficiently charged, the engine 21 can be quickly started and the engine running can be started. On the other hand, if the sub-battery 36 is insufficiently charged, the probability that the engine 21 can be started by supplementing the electric power from the step-down converter 34 can be increased. As a result, it is possible to reduce the possibility that the electric vehicle 1 cannot travel because the engine 21 cannot be started.

(Third Embodiment)
In the third embodiment, the configurations of the electric vehicle 1 and the control device 10 are the same as those in the first embodiment shown in FIG. In the third embodiment, the engine starting process at the time of battery error is different from that of the first embodiment and the second embodiment. Hereinafter, detailed description of similar parts will be omitted, and different parts will be described in detail. FIG. 4 is a flowchart showing a procedure of engine starting processing at the time of a battery error executed by the control device of the electric vehicle according to the third embodiment.

The control device 10 of the electric vehicle 1 of the third embodiment is one of three types of engine 21 starting processes according to the running state of the electric vehicle when an abnormality of the main battery 31 is detected during the running of the motor. Select and execute the start process. That is, when the abnormality detection information of the main battery 31 is transmitted and the start processing of FIG. 4 is started, the hybrid ECU 12 determines whether the electric vehicle 1 is running or stopped based on the output of the vehicle speed sensor 26a ( Step S1). Further, while traveling, the hybrid ECU 12 determines the magnitude of the speed (step S2). Then, if the electric vehicle 1 is stopped, the hybrid ECU 12 and the engine ECU 13 execute the first start processing of steps S3 to S9. Further, the hybrid ECU 12 and the engine ECU 13 execute the second start processing of steps S10 to S15 when the speed of the electric vehicle 1 is high, and when the speed of the electric vehicle 1 is low, the second steps S16 to S18. 3 Execute the start process.

<First start process>
The first starting process is the same as the starting process of the engine 21 at the time of the battery error shown in FIG. First, the hybrid ECU 12 stops the buck converter 34 and the inverter 33 (steps S3 and S4), and switches the main relay 32 to open (step S5). After that, the engine ECU 13 drives the starter 38 for the first time (step S6), and the hybrid ECU 12 determines whether the engine 21 has started. As a result, if the engine is started, the start process is terminated, but if the start is unsuccessful, the hybrid ECU 12 drives the engine ECU 13 to drive the starter 38 (step S8), and the buck converter 34 is driven in accordance with the drive of the starter 38. It is restarted (step S9). By such a step, the starting process shown in FIG. 3 is realized.

<Second start process>
The second starting process is a process of starting the engine 21 by supplementing the electric power for driving the starter 38 with the regenerative electric power of the traveling motor 24. When the electric vehicle 1 is in a traveling state slower than a predetermined speed and the process proceeds to step S11, the hybrid ECU 12 first stops the step-down converter 34 (step S10), and then switches the main relay 32 to open (step S10). Step S11). By stopping the step-down converter 34, even if the main relay 32 is switched to open, electric charges can be stored in the capacitors 33a and 34a of the input portions of the inverter 33 and the step-down converter 34. Here, the hybrid ECU 12 may output a zero or negative torque command to the inverter 33.

Subsequently, the hybrid ECU 12 determines the regenerative power value to be replenished by the traveling motor 24 according to the voltage value of the sub-battery 36 obtained by the voltage sensor 36a (step S12). Specifically, the hybrid ECU 12 determines the regenerative power value so that the regenerative power is small when the voltage of the sub-battery 36 is high and the regenerative power is large when the voltage of the sub-battery 36 is low. It is not possible to accurately determine whether or not the sub-battery 36 is sufficiently charged from the voltage of the sub-battery 36 alone, but the lower the voltage of the sub-battery 36, the insufficient the drive of the starter 38 and the failure to start the engine 21. Tend to do. On the other hand, when the regenerative power is generated, a braking force is generated in the traveling motor 24. Therefore, the larger the regenerative power, the more likely it is that the passenger of the electric vehicle 1 feels uncomfortable. Therefore, in step S12, the hybrid ECU 12 determines the regenerative power value as small as possible within the range in which the start of the engine 21 does not fail.

When the regenerative power value is determined, the hybrid ECU 12 causes the engine ECU 13 to drive the starter 38 (step S13), and restarts the buck converter 34 (step S14). In addition, the hybrid ECU 12 outputs a negative torque command corresponding to the regenerative power value to the inverter 33 (step S15). A braking force is generated in the traveling motor 24 by a negative torque command, and regenerative power is sent from the inverter 33 to the input unit of the buck converter 34. Each process of steps S13, S14, and S15 is time-controlled so that the step-down converter 34 is restarted and the regenerative power is supplied from the inverter 33 while the starter 38 is being driven. With such control, even if the sub-battery 36 is insufficiently charged, the regenerative power can be appropriately replenished to strongly drive the starter 38.

<Third start process>
The third starting process is a process of starting the engine 21 by using a part of the kinetic energy of the electric vehicle 1. When the electric vehicle 1 is traveling at a speed higher than the predetermined speed and the process proceeds to step S16, the hybrid ECU 12 first opens the main relay 32 so that the abnormality of the main battery 31 does not spread to other systems. Switching (step S16). Next, the hybrid ECU 12 outputs a command to the TCU 14 to control the clutch so that the clutch 23 is gradually engaged (step S17). As a result, the kinetic energy of the electric vehicle 1 is converted into power and transmitted from the wheels 26 to the engine 21 through the power transmission path. Then, when the engine 21 is rotated by this power, the hybrid ECU 12 outputs a command to the engine ECU 13 to start the engine 21 (step S18). The third start process corresponds to an example of the inertial start process according to the present invention, and the engine ECU 12 and the TCU 14 that execute the third start process correspond to an example of the start control unit according to the present invention.

As described above, according to the electric vehicle 1 and its control device 10 of the third embodiment, when the abnormality of the main battery 31 is detected, the first start process, the second start process, or the second start process is performed according to the running state of the electric vehicle 1. One of the third starting processes is selectively executed to start the engine 21. As a result, even if an abnormality occurs in the main battery 31 during the running of the motor, it is possible to shift to the engine running more reliably according to the running state of the electric vehicle 1 and without impairing the comfort of the electric vehicle 1. ..

Specifically, when the abnormality of the main battery 31 is detected, if the electric vehicle 1 is traveling at a high speed, the third starting process (steps S16 to S18) for starting the engine 21 using the kinetic energy thereof is performed. Will be executed. By this process, the engine 21 can be started more reliably. In a high-speed running state, the speed does not change significantly even if the engine 21 is rotated by using a part of the kinetic energy. Therefore, the engine 21 can be started by the third starting process without impairing the comfort of the electric vehicle 1. Further, once the kinetic energy of the electric vehicle 1 is converted into electric power and then the starter 38 is driven, energy loss corresponding to the electric power conversion efficiency occurs. However, in the third starting process, the kinetic energy of the electric vehicle 1 is directly converted into the power for rotating the engine 21, so that the energy loss can be reduced.

Further, when the abnormality of the main battery 31 is detected, if the electric vehicle 1 is in a running state at a low speed, the second starting process (steps S10 to S15) is executed. According to this process, the starter 38 is driven by the combined power of the power of the sub-battery 36, the power of the electric charge stored in the input unit of the inverter 33, and the regenerative power. Therefore, even if the sub-battery 36 is insufficiently charged, the starter 38 can be sufficiently driven and the engine 21 can be started reliably. On the other hand, if the electric vehicle 1 generates a large amount of regenerative power while traveling at a low speed, the large amount of regenerative braking gives the passenger a sense of discomfort. However, in the first starting process using the regenerative power, the regenerative power value is determined according to the voltage of the sub-battery 36, and the regenerative power as small as possible within the range in which the engine 21 can be started is generated. Therefore, it is possible to reduce the discomfort of the passenger due to the regenerative braking and maintain the comfort of the electric vehicle 1.

Further, when the abnormality of the main battery 31 is detected, if the electric vehicle 1 is in a stopped running state, the first start processing (steps S3 to S9) is executed. By this process, even if the sub-battery 36 is insufficiently charged, the electric power of the electric charge stored in the input portion of the inverter 33 is supplemented, so that the starter 38 can be sufficiently driven to start the engine 21. Can be enhanced.

Each embodiment of the present invention has been described above. However, the present invention is not limited to the above embodiment. For example, in the above embodiment, a configuration in which a sub-battery 36 for supplying electric power to an auxiliary machine is applied as the sub-battery according to the present invention has been described as an example. However, as the sub-battery according to the present invention, for example, a restart-only battery that supplies power exclusively for the ISG22 when restarting after idling stop, or both an auxiliary battery and a restart-only battery may be adopted. Further, in the above embodiment, the starter 38 of FIG. 1 is shown as the starter according to the present invention, but ISG may be adopted instead of the starter 38. Further, as a configuration for starting the engine, a configuration in which the starter is omitted and only the ISG is provided may be adopted. In this case, the ISG is used to start and restart the engine.

Further, in the above embodiment, a configuration in which an engine start process at the time of a battery error is executed in order to switch from motor running to engine running when an abnormality in the main battery 31 is detected has been described as an example. However, the engine starting process at the time of battery error may be executed to switch from motor running to batteryless running when an abnormality of the main battery is detected.

Further, in the above embodiment, an example in which a specific ECU constitutes a start control unit or an auxiliary control unit is shown, but the start control unit or the auxiliary control unit according to the present invention may be configured by another ECU. It may be composed of one ECU or a plurality of ECUs operating in cooperation with each other. Further, the ECU constituting the start control unit and the ECU constituting the auxiliary control unit may be the same, and when the start control unit and the auxiliary control unit are composed of a plurality of ECUs, the start control unit and the start control unit may be used. An ECU common to the auxiliary control unit may be included. For example, the start control unit according to the present invention may be composed of a hybrid ECU, and the auxiliary control unit may be composed of a hybrid ECU and a battery ECU. In this case, the battery ECU may detect an abnormality in the main battery and open the main relay, and the buck converter may be configured to stop driving by itself based on the abnormality detection signal of the battery ECU or the main relay open signal. Further, the hybrid ECU may be configured to start the engine and start driving the step-down converter that has been stopped.

Further, in the above embodiment, the configuration in which the hybrid ECU transmits an engine start command and an engine stop command to the engine ECU is shown. However, the engine start command and the engine stop command from the hybrid ECU may be transmitted to another ECU such as TCU, and the other ECU may be configured to start the engine in the engine ECU based on this command. In addition, the details shown in the embodiment can be appropriately changed without departing from the spirit of the invention.

1 Electric vehicle 10 Control device 11 Battery ECU
12 Hybrid ECU
13 Engine ECU
14 TCU
21 Engine 23 Clutch 24 Driving motor 26 Wheels 31 Main battery 32 Main relay 33 Inverter 34 Buck converter 36 Sub battery 37 Auxiliary machine 38 Starter

Claims (5)

A main battery that supplies electric power to a traction motor via an inverter, a sub-battery that supplies electric power to a starter that starts an engine, a step-down converter that lowers the voltage of the main battery and supplies it to the sub-battery, and the above. A control device for an electric vehicle mounted on an electric vehicle including a main battery and a main relay for opening and closing a current path between the inverter and the step-down converter.
A start control unit that starts the engine when an abnormality in the main battery is detected.
When the abnormality of the main battery is detected and the main relay is switched to open, the buck converter is temporarily stopped, and then the buck converter is restarted when the starter is driven by the start control unit. Auxiliary control unit and
A control device for an electric vehicle, which comprises. When the auxiliary control unit detects an abnormality in the main battery and the main relay is switched to open, the auxiliary control unit temporarily stops the buck converter, and then the starter is driven to fail to start the engine. The control device for an electric vehicle according to claim 1, wherein the buck converter is restarted when the starter is driven again. Claim 1 or claim, wherein the auxiliary control unit further sends the regenerative power of the traveling motor to the buck converter when the buck converter is restarted according to the running state of the electric vehicle. Item 2. The control device for an electric vehicle according to item 2. The control device for an electric vehicle according to claim 3, wherein the auxiliary control unit changes the magnitude of the regenerative power according to the voltage of the sub-battery. The start control unit is characterized in that it can execute an inertial start process for starting the engine by converting the kinetic energy of the electric vehicle into power without using the starter, according to the running state of the electric vehicle. The control device for an electric vehicle according to any one of claims 1 to 4.

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