KR19980040288A - Hybrid electric vehicle driving device and method thereof - Google Patents

Abstract

The present invention relates to a hybrid electric vehicle drive device, comprising: a start switch; A drive mode selection switch; Battery capacity detecting means; Battery current / voltage sensing means; Battery temperature sensing means; Fuel amount sensing means; Engine speed detection means; Power supply means for sequentially supplying power according to the operation of the start switch; When the power is supplied, set the drive mode, output the engine drive signal according to the detected battery capacity and fuel level, output the throttle valve drive signal according to the detected engine speed, and the engine speed is within the set range. A hybrid control means for outputting a power connection signal, determining whether a system failure occurs according to the detected temperature, voltage, charge current, charge capacity, and fuel amount, and outputting a wave blocking signal in case of a failure; Connection means for driving in accordance with the power connection signal to connect the power supply lines between the devices of the vehicle, or to cut off the power supply line according to the power disconnection signal; Throttle valve driving means for varying the opening amount of the throttle valve in accordance with the throttle valve driving signal; It includes an engine control means for driving the engine according to the engine drive signal, and based on the LLS that supplies a constant output power regardless of load fluctuation, by varying the power flow according to the vehicle driving conditions, to maximize fuel efficiency It can increase the efficiency of the system.

Description

Hybrid electric vehicle driving device and method thereof

The present invention relates to a hybrid electric vehicle driving device and a method thereof, and more particularly, to a hybrid electric vehicle driving device and a method for driving according to the selective driving of the gasoline engine and the electric motor.

BACKGROUND ART Conventional automobiles are mainly driven according to gasoline engine driving, and electric vehicles, in which engines are driven by motor operation by electricity, have been developed due to an increase in environmental pollution caused by gasoline engine automobiles.

Gasoline cars have the disadvantage of increasing the environmental pollution by exhausting a lot of exhaust gas, electric vehicles have the advantage of preventing environmental pollution, but there is a disadvantage that can not run for a long time because it is driven by a battery.

In order to solve the disadvantages of the gasoline vehicle and the electric vehicle as described above, the hybrid vehicle is a vehicle that combines the functions of the gasoline vehicle and the electric vehicle.

A hybrid electric vehicle is a vehicle in which a general gasoline engine driving function and an electric motor driving function are inherent, that is, a vehicle capable of driving a general gasoline vehicle or an electric vehicle as needed.

Hybrid electric vehicles are composed of components that are different from those of conventional gasoline and electric vehicles such as engines, alternators, batteries, and motors, and therefore, various driving methods are required such as engine alternator on / off control according to battery power conditions when driving a vehicle. do.

In the drive system of the hybrid electric vehicle, the power supply flow, that is, the power flow, is shown in FIG. 5, such as the output power output when the engine generator is driven, the charge power charged by the battery, the motor drive power, and the regenerative power. It can be represented by the flow of power.

In such a power flow, a hybrid electric vehicle can be driven under optimum conditions according to the motor driving power, regenerative power, battery remaining capacity (State Over Charge (SOC)), DC link voltage and current, and vehicle speed. Proper on / off control of the auxiliary power unit must be made.

Such a driving method can be classified into two types as follows.

1. Power Tracking Strategy (PTS): A method of varying the output power of the APU according to changes in driving power such as axels and brakes.

2. Load Leveling Rtrategy (LLS): A method of constantly supplying power to the APU regardless of driving power conversion.

The PTS has the advantage of reducing the peak power demand of the battery and increasing the battery life by varying the output power of the APU according to a change in the amount of power required according to the driving state, and the LLS has a driving power amount. By constantly outputting power without any problem, the APU efficiency is affected by the conversion of the load power (battery power, motor drive power).

In other words, as shown in FIG. 6, when the APU is the power source, the battery load is Z1, and the motor load is Z2, the PTS exhibits a great variation in the motor load Z1 seen from the APU side, and the DC link voltage. And the rate of change of the current is very large in real time (at the time of driving state), and the battery remaining capacity with respect to the battery overload (SOC) conversion and filtering time of the battery voltage signal according to the power variation of the motor load (Z2). There is a drawback that the compensation must be made.

In addition, since the response of the generator corresponding to power tracking is slow, it is difficult to substantially implement PTS.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks, and in driving a hybrid electric vehicle, by varying the power flow according to the vehicle driving state based on the LLS supplying a constant output power regardless of load variation. Another object of the present invention is to provide a hybrid electric vehicle driving device and a method thereof for maximizing fuel efficiency and increasing system efficiency.

The structure of this invention for achieving the said objective is a start switch; A drive mode selection switch; Battery capacity sensing means for sensing battery capacity; Battery current / voltage sensing means for sensing current and voltage of the battery; Battery temperature sensing means for sensing a temperature of the battery; Fuel amount detecting means for detecting a fuel amount; Engine speed detection means for detecting an engine speed; Power supply means for sequentially supplying power according to the operation of the start switch; When the power is supplied, the driving mode is selected according to the operation of the driving mode selection switch, or the driving mode is set according to the power consumption of the motor, the engine driving signal is output according to the detected battery capacity and fuel amount, and the engine is driven. And outputs a throttle valve drive signal according to the detected engine speed, outputs a power connection signal when the engine speed is within the setting range, and outputs a power connection signal when the engine speed is within the setting range. Hybrid control means for determining whether a system failure occurs according to the detected temperature, voltage, charge current, charge capacity, and fuel amount of the battery, and outputting a wave blocking signal when the failure occurs; Connection means driven according to a power connection signal output from the hybrid control means to connect a power supply line between devices of the vehicle, or to cut off the power supply line according to a power cutoff signal; Throttle valve driving means for varying the opening amount of the throttle valve according to the throttle valve driving signal output from the hybrid control means; And engine control means for driving the engine in accordance with the engine drive signal output from the hybrid control means.

Another configuration of the present invention for achieving the above object comprises the steps of sequentially supplying power in accordance with the operating state of the start switch; Selecting a driving mode by the user or setting the driving mode according to the power consumption of the motor; After the driving mode is set, driving the engine according to the remaining capacity of the battery and the fuel amount; Controlling the opening amount of the throttle valve according to the engine speed detected according to the engine driving; Connecting a power supply line between the devices when the detected engine speed is within a set range; Determining whether a failure of the system occurs according to the sensed battery temperature, charge current, voltage, charge capacity, and fuel amount; In the case of a failure of the system comprises the step of shutting off the power supply line supplied to each device.

1 is a block diagram of a hybrid electric vehicle driving device according to an embodiment of the present invention;

2 is a flowchart of an initial driving operation of a hybrid electric vehicle according to an embodiment of the present invention;

3 is a flowchart illustrating a driving mode selection operation of a hybrid electric vehicle according to an embodiment of the present invention;

4A to 4B are flowcharts of driving operations of the hybrid electric vehicle according to the embodiment of the present invention.

5 is a state diagram showing a power supply flow of a typical hybrid electric vehicle,

6 is a state diagram showing a load state of a general hybrid electric vehicle.

With the above configuration, the most preferred embodiment which can be easily carried out by those skilled in the art with reference to the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a hybrid electric vehicle driving apparatus according to an embodiment of the present invention, Figure 2 is a flow chart of the initial driving operation of a hybrid electric vehicle according to an embodiment of the present invention, Figure 3 is an embodiment of the present invention 4 is a flowchart illustrating a driving mode selection operation of the hybrid electric vehicle according to an embodiment of the present invention.

As shown in FIG. 1, a hybrid electric vehicle according to an exemplary embodiment of the present invention includes a battery capacity detecting unit 10 that detects a capacity of a battery, and a battery voltage / current detection unit that detects a voltage and a current of a battery. 15, the battery temperature sensor 20 for detecting the temperature of the battery, the fuel amount sensor 25 for detecting the fuel amount, the engine speed sensor 30 for detecting the engine speed, and the start switch (IG), a power supply unit 70 for sequentially supplying power according to the operation state of the start switch IG, a mode selection switch S1, and the sensing units 10, 15, 20, 25, 30 ) And a hybrid control unit 35 for outputting a plurality of control signals for performing a control operation for driving the vehicle according to the signal applied to the output terminal of the switch (S1), and to the output terminal of the hybrid control unit 35 Connected to the applied control signal A throttle valve driver 40 for varying an opening amount of the throttle valve, a DC link unit 45 connected to an output terminal of the hybrid controller 35 to form or cut off a power supply line according to a control signal applied thereto; A display unit 50 which displays a driving mode and a vehicle state selected according to a control signal applied to an output terminal of the hybrid controller 35, and a battery according to a control signal applied to an output terminal of the hybrid controller 35. Warning unit 55 for warning the state of insufficient capacity and fuel amount, motor drive unit 60 for driving the electric motor according to the control signal applied to the output terminal of the hybrid control unit 35, and the hybrid control unit 35 To the engine control unit 65 for outputting an engine control signal for driving the engine according to the control signal applied to the output terminal of The lure is.

The plurality of sensing units 10, 15, 20, 25, and 30 according to the exemplary embodiment of the present invention use known techniques, but not limited to those known in the art, and any technique capable of performing a corresponding function may be used.

The driving operation of the hybrid electric vehicle according to the embodiment of the present invention by the above configuration is as follows.

When the driver puts the ignition key in operation, the initial operation shown in FIG. 2 is performed.

First, in the state in which the initial operation is locked because no power is supplied to the system, the power supply unit 75 determines whether the first state ACC of the start switch IG is turned on (S110 to S120), and When the first state is turned on, power is supplied to the DC-DC converter, and power is supplied to the accessory unit (S130).

When the first state of the start switch IG is not turned on in the above, the state in which all power supply is cut off is maintained (S140).

In the state where the first state of the start switch IG is turned on, the power supply unit 75 determines whether the second state of the start switch IG is turned on (S150). When the second state of the start switch IG is turned on, the engine is supplied to the engine control unit 65 so that the engine can be driven, and the power is supplied to the counter (S160 to S120).

In the state where the second state of the start switch IG is turned on, the power supply unit 75 determines whether the third state Stsrt of the start switch IG is turned on (S180), and the start switch IG. When the third state is turned on, power is supplied to the motor and power is supplied to the hybrid controller 35 (S190 to S200).

As power is supplied to the hybrid controller 35, the hybrid controller 35 performs a driving mode selection operation illustrated in FIG. 3 and drives the vehicle accordingly.

After the third state is turned on, the start switch IG is automatically turned on to maintain the state (S210).

After the power is supplied to the system according to the driving of the start switch IG as described above, the hybrid controller 35 determines whether the driving mode is selected by the driver, and when the driver does not select the driving mode, Set the drive mode according to the power consumption.

The driver operates the HEV (Hybrid Emission Vehicle) mode for driving the gasoline engine by operating the drive mode selector switch S1, that is, a mode for driving the vehicle as a gasoline vehicle, or a Zero Emission Vehicle (ZEV) mode for not driving the gasoline engine. In operation S310, a mode for driving the vehicle with the electric vehicle is selected.

Therefore, the hybrid controller 35 sets the ZEV mode or the HEV mode to the driving mode according to the operation of the driving mode selection switch S1 (S320).

However, when the driving mode selection switch S2 is not operated, the driver determines that the driving mode selection operation is not performed, and arbitrarily sets the driving mode to the hybrid controller 35 according to the power consumption of the vehicle speed motor.

The hybrid controller 35 measures the power consumption of a vehicle speed motor, that is, a motor for driving the engine to drive the electric vehicle (S330). The ZEV mode for not driving the engine is set to the drive mode, and when the measured power consumption of the motor is greater than the set power, the HEV mode for driving the gasoline engine is set to the drive mode (S340 to S360).

The set power of the motor according to the embodiment of the present invention is the power measured when the motor reaches the highest speed, and the power consumption measured when the speed is about 100 kph at a grade of about 0%. .

As described above, the hybrid controller 35 sets the driving mode according to the mode selection of the driver or the power consumption of the motor, and then performs an operation for driving the vehicle according to the routine shown in FIG. 4.

First, the hybrid controller 35 initializes all the usage variables, and then receives a plurality of data measured by the sensing units 10, 1, 20, 25, and 30 according to the vehicle driving state (S410 ˜ S420).

The battery capacity detector 10 detects the current capacity of the battery of the vehicle and outputs a signal corresponding thereto, and the battery voltage / current detector 15 detects the current and voltage supplied from the battery to the vehicle. Outputs a signal, and the battery temperature detector 20 detects a current temperature of the battery and outputs a corresponding signal, and the fuel amount detector 25 detects an amount of fuel stored in a fuel tank of the vehicle. The engine speed sensor 30 detects the speed of the engine being driven and outputs a corresponding signal.

As described above, signals output from the plurality of sensing units 10, 15, 20, 25, and 30 are input to the hybrid controller 35, and the hybrid controller 35 drives the engine with the remaining capacity of the battery detected first. In operation S430, it is determined whether the vehicle can be driven even if the vehicle engine is not currently driven, compared with the first set capacity, which is the minimum capacity.

When the remaining capacity of the current battery is greater than or equal to the first predetermined capacity, the vehicle may be driven by the power supplied from the battery even without driving the engine, and the display unit 50 is driven to drive the currently set driving mode. Indicate the ZEV mode (S440).

Even when the ZEV mode is set according to the driving mode selection operation, the hybrid controller 35 drives the display unit 50 to indicate that the ZEV mode is set.

The display unit 50 is driven according to the signal output from the hybrid controller 35 to display the operation state of the vehicle to be displayed by the hybrid controller 35.

However, when the remaining capacity of the battery is less than the first predetermined capacity, the hybrid controller 35 determines that the vehicle cannot be driven by driving the motor by the battery and drives the warning unit 55 to recharge the battery. Warn the driver that the state (S450).

After performing the battery recharge warning operation, the hybrid controller 35 compares the amount of fuel stored in the vehicle with the set amount and determines whether the vehicle can be driven according to engine driving (S460).

When the HEV mode is set in the driving mode selection operation, it is determined whether the engine can be driven by directly comparing the fuel amount and the set amount of the vehicle.

When the fuel amount of the current vehicle is less than the set amount (about 1L), it is determined that the engine cannot be driven by the current fuel amount, and the warning unit 55 is driven to warn the driver that the fuel needs to be recharged. (S470).

However, the hybrid controller 35 outputs an engine driving signal for driving the engine to the engine controller 65 when the fuel amount of the current vehicle is larger than the set amount, and thus the engine controller 65 drives the engine. (S480).

As the engine starts to operate, a power generation operation of a generator (not shown) is performed, and the hybrid control unit 35 detects the engine speed in order to control the output of the generator according to the engine speed detected by the current engine driving. And the maximum rotational speed (about 3000 rpm) are compared (S490). When the engine speed is greater than the maximum rotational speed, the throttle valve close signal is output to reduce the engine speed.

According to the throttle valve close signal output from the hybrid control unit 35, the throttle valve driving unit 40 is driven to close the throttle valve (not shown), thereby reducing the engine speed (S500).

However, when the engine speed is smaller than the maximum rotation speed, the detected engine speed is compared with the minimum speed again (S510), and when the detected engine speed is smaller than the minimum speed, the engine speed is increased to increase the engine speed. Outputs the valve open signal.

According to the throttle valve open signal output from the hybrid controller 35, the throttle valve driver 40 is driven to open a throttle valve (not shown), thereby increasing the engine speed (S520).

When the engine speed detected according to the engine driving is located between the maximum and minimum rotation speed, the hybrid controller 35 drives the display unit 35 to indicate that the current driving mode is the HEV mode ( In operation S530, the DC link unit 45 is driven to connect the power supply lines of the battery, the engine, and the motor (S540).

The DC-link unit 45 according to the embodiment of the present invention is made of a magnetic switch, and as the DC-link unit 45 is driven, as shown in FIG. Power connections such as power, battery-charged power, motor drive power, and regenerative power are made.

After connecting the DC link as described above, the hybrid control unit 35 determines the state of charge according to the current, voltage, etc. of the battery that is variable according to the driving of the generator as shown in FIG. To control the flow.

First, the temperature of the battery is compared with the maximum temperature (about 50 ° C.) (S550). When the current battery temperature is smaller than the maximum temperature, the battery voltage and the maximum voltage are again compared (S560).

When the voltage of the battery is less than the maximum voltage again compared to the minimum voltage (S570), and if the voltage of the battery is greater than the minimum voltage again compares the charging current and the maximum current of the battery (S580).

When the charging current of the battery is smaller than the maximum current, the charging capacity of the battery is again compared with the second predetermined capacity (about 80%), which is the maximum capacity (S590), and the battery charging capacity is smaller than the second predetermined capacity. In comparison with the fuel amount and the set amount again (S600).

When the amount of fuel is greater than the set amount, the hybrid controller 35 repeatedly performs the above-described comparison operation. When the amount of fuel is less than the set amount, the hybrid controller 35 displays the state in which the fuel is recharged by driving the display unit 50. (S610).

In the above comparison operation, the battery temperature is higher than the maximum temperature, the voltage of the battery is higher than the maximum voltage, or lower than the minimum voltage, the charging current of the battery is higher than the maximum current, or the charging capacity of the battery is second. If more than the set capacity or the fuel amount is smaller than the set amount, it is determined that the current engine is impossible to drive, and the warning unit 55 is driven to warn the driver that an abnormality has occurred in the system, and then the DC link unit The driving of the 45 is stopped to cut off the power supply line (S620 ˜ 630).

As the driving of the DC link unit 45 is stopped, each power supply line is cut off, and the hybrid controller 35 outputs a corresponding signal to the engine controller 65 to stop driving of the engine.

The engine stops running accordingly to prevent the risk of fire and explosion due to system failure.

However, when the state of charge and fuel of the battery according to the engine drive is good, the engine is continuously driven.

As described above, according to the embodiment of the present invention, the fuel flow is maximized by varying the power flow according to the vehicle driving state based on the LLS that supplies a constant output power regardless of load fluctuation. It is possible to provide a hybrid electric vehicle driving apparatus and method having an effect of increasing the efficiency of the system and increasing the efficiency of the system.

Claims (22)

A start switch; A drive mode selection switch; Battery capacity sensing means for sensing battery capacity; Battery current / voltage sensing means for sensing current and voltage of the battery; Battery temperature sensing means for sensing a temperature of the battery; Fuel amount detecting means for detecting a fuel amount; Engine speed detection means for detecting an engine speed; Power supply means for sequentially supplying power according to the operation of the start switch; When the power is supplied, the driving mode is selected according to the operation of the driving mode selection switch, or the driving mode is set according to the power consumption of the motor, the engine driving signal is output according to the detected battery capacity and fuel amount, and the engine is driven. Outputs a throttle valve drive signal according to the detected engine speed, outputs a power connection signal when the engine speed is within the set range, and detects the temperature, voltage, charge current, charge capacity, and fuel level of the detected battery. A hybrid control means for determining whether a failure of the system has occurred and outputting a wave blocking signal if a failure occurs; Connection means driven according to a power connection signal output from the hybrid control means to connect a power supply line between devices of the vehicle, or to cut off the power supply line according to a power cutoff signal; Throttle valve driving means for varying the opening amount of the throttle valve according to the throttle valve driving signal output from the hybrid control means; And an engine control means for driving the engine according to the engine drive signal output from the hybrid control means. The hybrid electric vehicle drive device according to claim 1, further comprising display means for displaying a set driving mode of the vehicle. The hybrid electric vehicle drive device according to claim 1, further comprising a warning means for warning a vehicle of insufficient battery charge capacity and a low fuel amount. The power supply unit of claim 1, wherein the power supply means supplies power to the DC-DC converter and the accessory unit of the vehicle when the first state of the start switch is turned on in a locked state of an initial operation in which power is not supplied to the system, The hybrid electric vehicle driving device which supplies power to the engine control means when the second state is turned on, and supplies power to the motor and the hybrid control means when the third state is turned on. The method of claim 1, wherein the hybrid control means sets the drive mode according to the operation of the drive mode selection switch, or measures the power consumption of the motor when the drive mode selection switch is not operated, When the power consumption is smaller than the set power, the ZEV mode which does not drive the gasoline engine is set as the drive mode. When the measured power consumption of the motor is larger than the set power, the HEV mode which drives the gasoline engine is set as the drive mode. Hybrid electric vehicle drive unit. The hybrid electric vehicle driving apparatus according to claim 1, wherein the hybrid control means drives the display means to indicate that the driving mode is the ZEV mode when the remaining capacity of the current battery is equal to or greater than the first predetermined capacity. 7. The method of claim 6, wherein the hybrid control means, when the remaining capacity of the battery is smaller than the first set capacity, determines that the vehicle is incapable of driving by driving the motor by the battery and drives the warning means to recharge the battery. A hybrid electric vehicle drive unit that warns the driver that it should be. The method according to claim 7, wherein the hybrid control means performs the battery recharge warning operation, and then compares the fuel amount and the set amount of the vehicle, and if the fuel amount of the current vehicle is less than the set amount, the current fuel amount is the set amount. And if less, determine that the engine cannot be driven by the current fuel amount, and drive the warning means to warn the driver that the fuel needs to be refilled. The method of claim 8, wherein the hybrid control means outputs an engine driving signal for driving the engine to the engine control means when the amount of fuel in the current vehicle is larger than the set amount, and the engine speed detected by the engine driving is maximized. And a signal for closing the throttle valve when the engine speed is greater than the rotational speed, and outputting a signal for opening the throttle valve when the detected engine speed is smaller than the minimum speed. 10. The method of claim 9, wherein the hybrid control means, when the engine speed detected according to the engine driving falls within a setting range between the maximum and minimum rotation speed, the display means is driven to drive the display means And displaying the HEV mode, and then driving the connection means to connect the power supply lines of the battery, the engine and the motor. The method of claim 1, wherein the hybrid control means, wherein the detected battery temperature is higher than the maximum temperature, the voltage of the battery is higher than the maximum voltage or lower than the minimum voltage, or the charging current of the battery is higher than the maximum current. Or, if the battery charge capacity is greater than the second set capacity or the fuel amount is smaller than the set amount, it is determined that the engine cannot be driven at present, and the warning means is driven to warn the driver that an abnormality has occurred in the system. Next, the driving device of the hybrid electric vehicle to stop the power supply line by stopping the driving of the connecting means. 12. The hybrid electric vehicle drive device according to claim 11, wherein the hybrid control means cuts off the power supply line and then outputs a signal for stopping the engine to the engine control means. Sequentially supplying power according to the operating state of the start switch; Selecting a driving mode by the user or setting the driving mode according to the power consumption of the motor; After the driving mode is set, driving the engine according to the remaining capacity of the battery and the fuel amount; Connecting a power supply line between the devices when the detected engine speed is within a set range; Determining whether a system failure occurs according to the sensed battery temperature, charge current, voltage, charge capacity, and fuel amount; And interrupting a power supply line supplied to each device in the event of a failure of the system. 15. The method of claim 13, wherein the power supply step comprises: supplying power to the DC-DC converter and the accessory unit of the vehicle when the first state of the start switch is turned on while the initial operation in which power is not supplied to the system is locked. Wow; Supplying power to the engine control means when the second state of the start switch is turned on; And supplying power to the motor and the hybrid control means when the third state of the start switch is turned on. The method of claim 13, wherein the setting of the driving mode comprises: setting a driving mode according to the operation of the driving mode selection switch; When the driving mode selection switch is not operated, measuring the power consumption of the motor and comparing it with the set power; Setting a ZEV mode not to drive a gasoline engine as a drive mode when the measured power consumption of the motor is smaller than the set power; And setting the HEV mode for driving the gasoline engine to the drive mode when the measured power consumption of the motor is greater than the set power. The hybrid electric vehicle driving device of claim 13, further comprising, in the engine driving step, indicating that the driving mode is the ZEV mode when the remaining capacity of the current battery is greater than or equal to the first predetermined capacity. The method of claim 16, further comprising: alerting the driver that the battery needs to be recharged by determining that the vehicle cannot be driven by driving the motor by the battery when the remaining capacity of the battery is smaller than the first predetermined capacity. Hybrid electric vehicle driving device. 18. The method of claim 17, wherein after performing the battery recharge warning operation, the fuel amount of the vehicle is compared with the set amount, and when the fuel amount of the current vehicle is smaller than the set amount, the engine is not driven by the current fuel amount. And alerting the driver that the fuel is to be refilled. The method of claim 13, wherein the controlling of the throttle valve opening amount comprises: closing the throttle valve when the engine speed detected by the engine driving is greater than the maximum rotation speed; And if the detected engine speed is less than the minimum speed, opening the throttle valve. 20. The method of claim 19, wherein when the engine speed detected according to the engine driving is within a setting range between the maximum speed and the minimum speed, indicating that the current driving mode is the HEV mode, and then the battery, the engine, and the motor. And connecting a power supply line of the hybrid electric vehicle. The method of claim 13, wherein in determining whether the system has failed, the detected battery temperature is higher than the maximum temperature, the voltage of the battery is higher than the maximum voltage or lower than the minimum voltage, or the charging current of the battery is lowered. If it is higher than the maximum current, the charge capacity of the battery is larger than the second set capacity, or the fuel amount is smaller than the set amount, it is determined that the engine can not be driven at present, and the warning means is driven to indicate that an abnormality has occurred in the system. Warning the driver, and then stopping driving of the connecting means to cut off the power supply line. 22. The method of claim 21, further comprising shutting off the power supply line and then stopping the engine.