Vehicle

To provide a vehicle in which an increase or fluctuations in engine vibration or noise during external electric power supply can be suppressed. A vehicle includes an electric power generation device, a battery connected to the electric power generation device via a power line, an external electric power supply device that interconnects the power line and external equipment, and an ECU that controls charging and discharging of the electric power generation device and the battery. The ECU starts an engine and supplies electric power generated by a generator to the battery and the external equipment in a case where a SOC is equal to or less than a use lower limit SOC and supplies the external equipment with electric power from the battery in a case where the SOC exceeds a use upper limit SOC. In addition, the ECU executes fixed point control for controlling the engine and the generator.

This application is based on and claims the benefit of priority from Japanese Patent Application No. 2018-051212, filed on 19 Mar. 2018, the content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a vehicle. More specifically, the present invention relates to a vehicle provided with an electric power generation device generating electric power by using the power of an engine, an electric power storage device, and an external electric power supply device supplying external equipment outside the car with electric power in an electric power line interconnecting the electric power generation device and the electric power storage device.

Related Art

Japanese Unexamined Patent Application, Publication No. 2013-184642 discloses a hybrid vehicle provided with a generator generating electric power by using the power of an engine, a battery storing the electric power generated by the generator, and an external electric power supply device connecting the generator and the battery to external equipment and supplying the external equipment with the electric power generated by the generator or electric power discharged from the battery. Vehicles provided with such external electric power supply devices are highly convenient in that the vehicles allow electrical equipment such as large heating and household appliances to be used under environments where no electric power supply is available during disasters or outdoor leisure activities.

The required electric power in the external equipment appropriately varies with user operation. In this regard, in the vehicle disclosed in Japanese Unexamined Patent Application, Publication No. 2013-184642, electric power corresponding to the required electric power is supplied to the external equipment by battery charging-discharging amount adjustment. In the vehicle disclosed in Japanese Unexamined Patent Application, Publication No. 2013-184642, the engine is started and the battery is charged with the electric power generated by the generator in a case where the remaining capacity of the battery is insufficient.

SUMMARY OF THE INVENTION

Engine operation and electric power generation during external electric power supply result in engine vibration or engine noise, yet engine vibration or engine noise during external electric power supply is inadequately studied in Japanese Unexamined Patent Application, Publication No. 2013-184642. When the required electric power of the external equipment increases, for example, the engine vibration or the engine noise increases correspondingly, and then a user may feel some discomfort.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a vehicle in which an increase or fluctuations in engine vibration or engine noise during external electric power supply can be suppressed.

(1) A vehicle (such as a vehicle V to be described later) includes an electric power generation device (such as an engine E, a generator G, and a second inverter22to be described later) including an engine (such as the engine E to be described later) and a generator (such as the generator G to be described later) that generates electric power by using power of the engine, an electric power storage device (such as a battery3to be described later) that is connected to the electric power generation device via an electric power line (such as a main electric power line2to be described later) and stores electric power generated by the electric power generation device, an external electric power supply device (such as an external electric power supply device5to be described later) that interconnects the electric power line and external equipment (such as external equipment9to be described later) and supplies the external equipment with electric power in the electric power line, and a controller (such as an electronic control unit7and an FI-ECU71and an MOT-ECU72of the electronic control unit7to be described later) that controls charging and discharging of the electric power generation device and the electric power storage device during external electric power supply by the external electric power supply device. The controller starts the engine and supplies electric power generated by the generator to the electric power storage device and the external equipment in a case where a remaining capacity (such as a battery SOC to be described later) of the electric power storage device is equal to or less than a predetermined first remaining capacity (such as a use lower limit SOC to be described later). The controller supplies the external equipment with electric power discharged from the electric power storage device in a case where the remaining capacity of the electric power storage device exceeds a second remaining capacity (such as a use upper limit SOC to be described later) exceeding the first remaining capacity. The controller executes fixed point control for controlling the engine such that an engine rotation speed is maintained constant while the generator generates electric power.

(2) In this case, it is preferable that the controller controls the engine and the generator so as to be maintained at engine torque set on the basis of an operation point at which a fuel consumption rate is minimized when the fixed point control is executed.

(3) In this case, it is preferable that the controller sets the first remaining capacity on the basis of an electric power storage device temperature (such as a battery temperature to be described later) as a temperature of the electric power storage device and increases the first remaining capacity as the electric power storage device temperature decreases in a case where the electric power storage device temperature is equal to or lower than a predetermined first temperature (such as a switching temperature to be described later).

(4) In this case, it is preferable that the controller sets a charging electric power limit as a limit with respect to charging electric power at a time of charging of the electric power storage device on the basis of an electric power storage device temperature (such as a battery temperature to be described later) as a temperature of the electric power storage device and executes variable control for controlling the engine and the generator such that the engine rotation speed changes in accordance with charging electric power for the electric power storage device set on the basis of the charging electric power limit in a case where the electric power storage device temperature is equal to or lower than a predetermined second temperature (such as a fixed point operation lower limit temperature to be described later).

(1) In the present invention, the controller starts the engine and supplies the electric power generated by the generator to the electric power storage device and the external equipment in a case where the remaining capacity of the electric power storage device is equal to or less than the first remaining capacity during external electric power supply. In a case where the remaining capacity of the electric power storage device exceeds the second remaining capacity, which exceeds the first remaining capacity, during external electric power supply, the controller supplies the electric power discharged from the electric power storage device to the external equipment. Here, the controller executes the fixed point control for controlling the engine such that the engine rotation speed is maintained constant while the generator generates electric power. Therefore, according to the present invention, the engine rotation speed is maintained constant irrespective of fluctuations in the electric power required by the external equipment while the generator generates electric power, and thus fluctuations in vibration or noise generated by the engine are also suppressed. In the present invention, the fixed point control is executed while the generator generates electric power, and thus the output electric power of the generator also becomes constant. Accordingly, in a case where the external equipment requires small electric power, the charging electric power for the electric power storage device increases correspondingly and the electric power storage device can be charged in a short time, and thus the burden on the engine during external electric power supply also can be reduced. In addition, the burden on an exhaust gas purification device can be reduced, engine oil consumption can be suppressed, and engine service life extension can be achieved by means of a constant engine rotation speed.

(2) In the present invention, when the fixed point control is executed, the controller controls the engine and the generator so as to be maintained at the engine torque set on the basis of the operation point at which the fuel consumption rate is minimized. Therefore, according to the present invention, the generator is capable of continuously generating electric power while the engine continuously operates at the operation point at which the fuel consumption rate is minimized, and thus fuel consumption during external electric power supply can be suppressed.

(3) The discharging performance of the electric power storage device declines as the temperature of the electric power storage device decreases. More specifically, the use lower limit remaining capacity of the electric power storage device increases as the temperature of the electric power storage device decreases. Here, the use lower limit remaining capacity is the minimum remaining capacity that needs to be reserved so that predetermined required discharging electric power (such as several kilowatts) is continuously discharged from the electric power storage device. In other words, the electric power storage device is incapable of continuously discharging the required discharging electric power once the remaining capacity falls below the use lower limit remaining capacity. In contrast, in the present invention, the controller increases the first remaining capacity as the electric power storage device temperature decreases when the electric power storage device temperature is a low temperature that is equal to or lower than the first temperature. Therefore, according to the present invention, the electric power storage device can be charged before the remaining capacity of the electric power storage device falls below the use lower limit remaining capacity at a low temperature at which the use lower limit remaining capacity increases as described above, and thus a remaining capacity required for continuous discharging of the required discharging electric power can be reserved for the electric power storage device.

(4) The charging performance of the electric power storage device declines as the temperature of the electric power storage device decreases. More specifically, the charging electric power limit of the electric power storage device approaches 0 as the temperature of the electric power storage device decreases. Here, the charging electric power limit is a limit with respect to the charging electric power at a time of charging of the electric power storage device. In other words, the electric power storage device may deteriorate when the electric power storage device is continuously supplied with charging electric power exceeding the charging electric power limit. In contrast, in the present invention, the controller causes the charging electric power limit to approach 0 as the electric power storage device temperature decreases when the electric power storage device temperature is a low temperature that is equal to or lower than the second temperature. In addition, the controller executes the variable control for controlling the engine and the generator such that the engine rotation speed changes in accordance with the charging electric power for the electric power storage device set on the basis of the charging electric power limit in a case where the electric power storage device temperature is equal to or lower than the second temperature at which the charging electric power limit approaches 0. As a result, at a low temperature at which the charging performance of the electric power storage device declines, it is possible to charge the electric power storage device while preventing overcharging that promotes malfunction or deterioration of the electric power storage device.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

Hereinafter, a first embodiment of the present invention will be described with reference to accompanying drawings.FIG. 1is a diagram illustrating the configuration of a vehicle V according to the present embodiment. The vehicle V is a so-called hybrid vehicle provided with a motor generator M, an internal combustion engine E (hereinafter, referred to as “engine E”), and a generator G.FIG. 1illustrates the configurations of the vehicle V and external equipment9connected to the vehicle V and driven by electric power supplied from the vehicle V.

The vehicle V is provided with a drive wheel W, the motor generator M, the engine E, the generator G, an electric power supply system1, and an electronic control unit7comprehensively controlling the motor generator M, the engine E, the generator G, in-vehicle equipment8, and the electric power supply system1.

The electronic control unit7is provided with an FI-ECU71and an MOT-ECU72, which are microcomputers capable of communicating with each other. The FI-ECU71mainly controls the engine E. The MOT-ECU72mainly controls the motor generator M, the generator G, the in-vehicle equipment8, and the electric power supply system1.

The motor generator M mainly generates power for traveling of the vehicle V. The motor generator M has an output shaft connected to the drive wheel W. The torque that is generated by electric power being supplied from the electric power supply system1to the motor generator M and the motor generator M being caused to perform power running is transmitted to the drive wheel W via a power transmission mechanism (not illustrated), and then the drive wheel W is rotated and the vehicle V travels. In addition, the motor generator M acts as a generator by being caused to perform regenerative operation during deceleration of the vehicle V. The electric power that the motor generator M generates during the regenerative operation is supplied to the electric power supply system1.

A crankshaft as an output shaft of the engine E is connected to the generator G via a power transmission mechanism (not illustrated). The generator G generates electric power by being driven by the power that is generated by the engine E. The electric power that is generated by the generator G is supplied to the electric power supply system1.

The electric power supply system1is provided with a first inverter21connected to the motor generator M, a second inverter22connected to the generator G, a battery3connected to the inverters21and22via a main electric power line2and storing the electric power that is generated by the motor generator M and the generator G, a voltage converter23provided on the main electric power line2, an external electric power supply device5interconnecting the main electric power line2and the external equipment9and supplying the external equipment9with the electric power in the main electric power line2, and a battery ECU6as an electronic control unit monitoring the state of the battery3.

The battery3is a secondary battery capable of performing both discharging for converting chemical energy into electric energy and charging for converting electric energy into chemical energy. Although a case where a so-called lithium ion storage battery performing charging and discharging by lithium ions moving between electrodes is used as the battery3will be described below, the present invention is not limited thereto.

Both positive and negative poles of the battery3are connected to the first inverter21and the second inverter22via the main electric power line2. A battery contactor24interconnecting or disconnecting the battery3and the voltage converter23is provided between the voltage converter23and the battery3on the main electric power line2.

The battery contactor24is opened or closed in accordance with a command signal transmitted from the battery ECU6. Once the battery contactor24is opened, the battery3is disconnected from the voltage converter23and the external electric power supply device5and the battery3becomes incapable of performing charging and discharging. Once the battery contactor24is closed, the battery3is connected to the voltage converter23and the external electric power supply device5and the battery3becomes capable of performing charging and discharging.

The battery3is provided with a battery sensor unit31for estimating the internal state of the battery3. A plurality of sensors constitutes the battery sensor unit31, and the sensors detect physical quantities necessary for acquiring the remaining capacity of the battery3, the temperature of the battery3, and so on in the battery ECU6and transmit signals corresponding to detected values to the battery ECU6. More specifically, the battery sensor unit31is constituted by, for example, a voltage sensor detecting the terminal voltage of the battery3, a current sensor detecting a current flowing through the battery3, and a temperature sensor detecting the temperature of the battery3. The battery ECU6calculates a battery SOC [%] expressing the remaining capacity of the battery3as a percentage on the basis of a known algorithm using the detected value that is transmitted from the battery sensor unit31. In addition, the battery ECU6acquires a battery temperature [° C.], which is the temperature of the battery3, on the basis of the detected value that is transmitted from the battery sensor unit31. Information relating to the battery SOC and the battery temperature acquired in the battery ECU6as described above is transmitted to the FI-ECU71and the MOT-ECU72by CAN communication (not illustrated).

The first inverter21is a pulse width modulation-based PWM inverter and is provided with a bridge circuit configured by bridge connection of a plurality of switching elements (such as IGBTs) driven in accordance with a gate drive signal generated by a gate drive circuit (not illustrated) of the MOT-ECU72. The first inverter21has a direct current input-output side connected to the voltage converter23via the main electric power line2. The first inverter21has an alternating current input-output side connected to respective coils of the U, V, and W phases of the motor generator M. During the power running of the motor generator M, the first inverter21generates a driving force by operating under the gate drive signal from the gate drive circuit, converting the direct current that is applied from the main electric power line2to the direct current input-output side into a three-phase alternating current, and supplying the three-phase alternating current to the motor generator M. During the regenerative operation of the motor generator M, the first inverter21operates under the gate drive signal from the gate drive circuit, converts the three-phase alternating current that is applied from the motor generator M to the alternating current input-output side into a direct current, and supplies the direct current to the main electric power line2.

The second inverter22is a pulse width modulation-based PWM inverter and is provided with a bridge circuit configured by bridge connection of a plurality of switching elements (such as IGBTs) driven in accordance with the gate drive signal generated by the gate drive circuit (not illustrated) of the MOT-ECU72. The second inverter22has a direct current output side connected to the voltage converter23via the main electric power line2. The second inverter22has an alternating current input side connected to respective coils of the U, V, and W phases of the generator G. During electric power generation by the generator G using the power generated by the engine E, the second inverter22operates under the gate drive signal from the gate drive circuit, converts the three-phase alternating current that is applied from the generator G to the alternating current input side into a direct current, and supplies the direct current to the main electric power line2. The engine E, the generator G, the second inverter22, and so on constitute an electric power generation device according to the present invention.

The voltage converter23is, for example, a bidirectional DC-DC converter provided with a plurality of switching elements (such as IGBTs) driven by the gate drive signal generated by the gate drive circuit (not illustrated) of the MOT-ECU72. The voltage converter23operates under the gate drive signal from the gate drive circuit. In a case where the motor generator M is driven with the electric power that is discharged from the battery3, the voltage converter23boosts the voltage of the direct current supplied from the battery3, supplies the direct current to the first inverter21, and allows a current flow from the battery3side to the first inverter21side. In a case where the battery3is charged with the electric power that is generated by the generator G and the motor generator M and in a case where the electric power that is generated by the generator G during external electric power supply is supplied to the battery3, the in-vehicle equipment8, and the external equipment9, the voltage converter23steps down the voltage of the direct current supplied from the inverters21and22, supplies the direct current to the battery3, and allows a current flow from the inverter21side and the inverter22side to the battery3side.

The in-vehicle equipment8is connected between the voltage converter23and the battery contactor24on the main electric power line2. The in-vehicle equipment8is electrical equipment driven by the electric power in the main electric power line2. Examples of the in-vehicle equipment8include air-conditioning equipment and acoustic equipment. The in-vehicle equipment8can become an internal load consuming the electric power discharged from the battery3or the electric power generated by the generator G during external electric power supply.

The external electric power supply device5is provided with an inlet51to which an external electric power supply connector93of the external equipment9can be connected, an external electric power supply electric power line52interconnecting the inlet51and the main electric power line2, and an external electric power supply contactor53provided on the external electric power supply electric power line52. The external electric power supply device5supplies the external equipment9with the electric power of the direct current in the main electric power line2when the vehicle V is stopped.

The external electric power supply electric power line52is connected between the voltage converter23and the battery contactor24on the main electric power line2. Accordingly, the direct current electric power discharged from the battery3and the direct current electric power generated by the generator G when the vehicle V is stopped and stepped down by the voltage converter23are supplied to the external equipment9via the external electric power supply electric power line52and the inlet51.

The external electric power supply contactor53is opened or closed in accordance with a command signal transmitted from the MOT-ECU72. Once the external electric power supply contactor53is opened, the inlet51and the main electric power line2are disconnected and external electric power supply becomes incapable of being performed. Once the external electric power supply contactor53is closed, the inlet51and the main electric power line2are interconnected and external electric power supply becomes capable of being performed.

The external equipment9is provided with an external inverter91converting a direct current into a single-phase alternating current, an external electric power supply cable92interconnecting the vehicle V and the external inverter91, and a plurality of electrical equipment94and95connected to the external inverter91(examples of the electrical equipment94and95including a heating device and a rice cooker outside a car and a portable terminal used in a car). One end side of the external electric power supply cable92is connected to the external inverter91, and the other end side of the external electric power supply cable92is connected to the inlet51via the external electric power supply connector93. The external inverter91converts the direct current electric power that is supplied from the external electric power supply device5of the vehicle V via the external electric power supply cable92into a single-phase alternating current and supplies the single-phase alternating current to the electrical equipment94and95. The external equipment9can become an external load consuming the electric power discharged from the battery3or the electric power generated by the generator G during external electric power supply.

The FI-ECU71and the MOT-ECU72control the engine E, the generator G, the second inverter22, the voltage converter23, the battery contactor24, and the external electric power supply contactor53such that the electric power required in the in-vehicle equipment8and the external equipment9is supplied during external electric power supply by the external electric power supply device5.

In a case where sufficient electric power is stored in the battery3, the ECUs71and72supply the electric power that is discharged from the battery3to the in-vehicle equipment8and the external equipment9. In this case, the ECUs71and72stop electric power generation by the engine E and the generator G.

In a case where the electric power that is stored in the battery3is insufficient, the ECUs71and72operate the engine E and supply the electric power generated by the generator G to the in-vehicle equipment8, the external equipment9, and the battery3. More specifically, the ECUs71and72convert the three-phase alternating current electric power generated by the engine E and the generator G into direct current electric power by driving the second inverter22, step down the direct current electric power output from the second inverter22by further driving the voltage converter23, and supply the direct current electric power to the in-vehicle equipment8, the external equipment9, and the battery3.

Here, the electric power generated by means of the engine E and the generator G can be varied by adjustment of the output of the engine E and the excitation intensity of the generator G. Accordingly, during external electric power supply by the external electric power supply device5, the ECUs71and72are capable of controlling the engine E and the generator G under two operation modes, one being a variable electric power generation operation mode and the other being a fixed point electric power generation operation mode. The variable electric power generation operation mode is an operation mode in which the electric power generated by the engine E and the generator G is actively varied in accordance with the electric power required by the in-vehicle equipment8and the external equipment9. The fixed point electric power generation operation mode is an operation mode in which the electric power generated by the engine E and the generator G is maintained constant irrespective of the electric power required by the in-vehicle equipment8and the external equipment9.

FIG. 2is a diagram illustrating a breakdown of generated electric power and consumed electric power in the variable electric power generation operation mode. InFIG. 2, the left side illustrates generated electric power at a time of zero load when the consumed electric power in the in-vehicle equipment8and the external equipment9is 0 and the right side illustrates generated electric power at a time of maximum load when the consumed electric power in the in-vehicle equipment8and the external equipment9is at its maximum.

As illustrated on the right side ofFIG. 2, the electric power generated by the generator G during external electric power supply is consumed mainly in the external equipment9, the in-vehicle equipment8, the battery3, and the voltage converter23. In addition, part of the generated electric power is consumed by various losses. As illustrated on the left side ofFIG. 2, at the time of zero load, the consumed electric power in the in-vehicle equipment8and the external equipment9becomes 0. Accordingly, in the variable electric power generation operation mode, the ECUs71and72decrease the electric power generated by the engine E and the generator G by the decrease in the passing electric power of the voltage converter23and the consumed electric power in the in-vehicle equipment8and the external equipment9such that the charging electric power for the battery3at the maximum load and the charging electric power for the battery3at the zero load are substantially equal to each other.

FIG. 3is a diagram illustrating a breakdown of generated electric power and consumed electric power in the fixed point electric power generation operation mode. InFIG. 3, the left side illustrates generated electric power at a time of zero load and the right side illustrates generated electric power at a time of maximum load as inFIG. 2.

As illustrated inFIG. 3, in the fixed point electric power generation operation mode, the ECUs71and72control the engine E and the generator G such that the generated electric power becomes constant irrespective of whether the current load is the maximum load or the zero load, that is, irrespective of the consumed electric power in the in-vehicle equipment8and the external equipment9. Accordingly, at the zero load as compared with the maximum load, the consumed electric power in the in-vehicle equipment8and the external equipment9decreases and the charging electric power of the battery3increases by the amount by which the passing electric power of the voltage converter23decreases.

Accordingly, the charging time of the battery3in the variable electric power generation operation mode is constant irrespective of the consumed electric power in the in-vehicle equipment8and the external equipment9. The charging time of the battery3in the fixed point electric power generation operation mode changes in accordance with the consumed electric power of the in-vehicle equipment8and the external equipment9. More specifically, the charging time of the battery3shortens as the consumed electric power of the in-vehicle equipment8and the external equipment9decreases. Accordingly, the charging time of the battery3in the fixed point electric power generation operation mode is always shorter than the charging time of the battery3in the variable electric power generation operation mode. Accordingly, the electric power generation period (that is, the operation time of the engine E) in the fixed point electric power generation operation mode is shorter than the electric power generation period in the variable electric power generation operation mode.

FIG. 4is a flowchart illustrating a specific procedure of external electric power supply processing in the ECUs71and72. The external electric power supply processing ofFIG. 4is repeatedly executed at a predetermined control cycle in the ECUs71and72as a power switch (not illustrated) in the vehicle V is turned ON and a power switch (not illustrated) in the external inverter91is turned ON after the external electric power supply connector93is connected to the inlet51while vehicle V remains stopped.

First, in S1, the ECUs71and72acquire the battery temperature from the battery ECU6. Next, in S2, the ECUs71and72determine whether or not the acquired battery temperature is equal to or lower than a predetermined fixed point operation lower limit temperature.

In a case where the determination result in S2is NO, the ECUs71and72proceed to S3, perform external electric power supply under the fixed point electric power generation operation mode (seeFIG. 6to be described later), and terminate the processing ofFIG. 4. In a case where the determination result in S2is YES, the ECUs71and72determine that no external electric power supply can be executed under the fixed point electric power generation operation mode, proceed to S4, and perform external electric power supply under the variable electric power generation operation mode.

The operation mode is switched in accordance with the battery temperature, as in the processing ofFIG. 4, for the reason to be described below with reference toFIG. 5.

FIG. 5is a diagram illustrating the temperature characteristics of the charging performance of the battery3. InFIG. 5, the horizontal axis represents the battery temperature [° C.] and the vertical axis represents the charging electric power limit [kW] of the battery3. The charging performance of the battery3declines as the battery temperature decreases. More specifically, the charging electric power limit, which is a limit with respect to the charging electric power at a time of charging of the battery3, approaches 0 as the battery temperature decreases. In other words, the battery3may deteriorate when the battery3is continuously supplied with charging electric power exceeding the charging electric power limit.

As described with reference toFIGS. 2 and 3, the charging electric power of the battery3is constant, irrespective of a load, while external electric power supply is performed under the variable electric power generation operation mode. In contrast, the charging electric power of the battery3varies with a load while external electric power supply is performed under the fixed point electric power generation operation mode. In addition, the charging electric power of the battery3during the external electric power supply under the fixed point electric power generation operation mode is maximized at a zero load. Hereinafter, the maximum value of the charging electric power of the battery3during the external electric power supply under the fixed point electric power generation operation mode will be referred to as maximum charging electric power. In other words, during the external electric power supply under the fixed point electric power generation operation mode, the battery3may be continuously supplied with the maximum charging electric power.

As illustrated inFIG. 5, the charging electric power limit becomes smaller than the maximum charging electric power in a case where the battery temperature is equal to or lower than the fixed point operation lower limit temperature defined as 0° C. or less. In other words, in a case where the battery temperature is equal to or lower than the fixed point operation lower limit temperature, the battery3may deteriorate once the maximum charging electric power is continuously supplied to the battery3. Accordingly, the ECUs71and72execute external electric power supply under the fixed point electric power generation operation mode in a case where the battery temperature is higher than the fixed point operation lower limit temperature (see S3ofFIG. 4) and prohibit the fixed point electric power generation operation mode and execute external electric power supply under the variable electric power generation operation mode in a case where the battery temperature is equal to or lower than the fixed point operation lower limit temperature (see S4ofFIG. 4).

FIG. 6is a flowchart illustrating a specific procedure of external electric power supply processing in the fixed point electric power generation operation mode.

First, in S11, the ECUs71and72acquire the battery SOC from the battery ECU6. Next, in S12, the ECUs71and72set a use lower limit SOC, which is a threshold with respect to the battery SOC, on the basis of the battery temperature acquired in S1ofFIG. 4. More specifically, the ECUs71and72set the use lower limit SOC by searching a map as exemplified inFIG. 7Aon the basis of the battery temperature. According to the map ofFIG. 7A, the use lower limit SOC is set to a constant value irrespective of the battery temperature, more specifically, to a high temperature lower limit SOC indicated by a thick broken line7ainFIG. 7Ain a case where the battery temperature is higher than a switching temperature set higher than the fixed point operation lower limit temperature (seeFIG. 5). In a case where the battery temperature is equal to or lower than the switching temperature, the use lower limit SOC is set so as to increase in value as the battery temperature decreases. Details of the map ofFIG. 7Awill be described in detail later.

Next, in S13, the ECUs71and72determine whether or not the battery SOC acquired in S11is equal to or less than the use lower limit SOC set in S12. In a case where the determination result of S13is YES, the ECUs71and72set an electric power generation flag Fgen, which specifies that electric power generation by the engine E and the generator G is in progress, to “1” (see S14), and then the ECUs71and72execute fixed point control of the engine E and the generator G, supply the electric power generated by the engine E and the generator G to the in-vehicle equipment8, the external equipment9, and the battery3(see S15), and terminate this processing. The electric power generation flag Fgen is “0” immediately after the external electric power supply processing ofFIG. 4is initiated.

A specific procedure of the fixed point control of the engine E and the generator G will be described below. First, the ECUs71and72estimate the altitude of the point where the vehicle V is stopped on the basis of the detected value of an atmospheric pressure sensor (not illustrated). Next, the ECUs71and72select one corresponding to the estimated altitude from a plurality of operation point decision maps determined in advance. As exemplified inFIG. 8, the operation point decision map is a map associating engine output [kWh] (see the solid lines ofFIG. 8) with operation points of the engine E characterized by an engine rotation speed [rpm] (horizontal axis ofFIG. 8) and engine torque [Nm] (vertical axis ofFIG. 8). The plurality of operation point decision maps is stored for each altitude in the ECUs71and72. Also stored in the plurality of operation point decision maps is information relating to a BSFC bottom line indicating a set of operation points at which the net fuel consumption rate [g/kWh] is minimized as indicated by a thick broken line8a.

Further, the ECUs71and72calculate the engine output that minimizes the net fuel consumption rate by searching the operation point decision map selected in accordance with the altitude on the basis of a fixed point control rotation speed [rpm] determined in advance. In the example ofFIG. 8, this corresponds to calculating the engine output that passes through an intersection point P between a line8bindicating the fixed point control rotation speed and the BSFC bottom line8aindicated by the thick broken line. The fixed point control rotation speed is an engine rotation speed determined by a procedure to be described later with reference toFIG. 9and is constant in value irrespective of the altitude.

Further, the ECUs71and72calculate target engine torque [Nm] corresponding to a target load with respect to the engine E and target generator torque [Nm] realizing the target engine torque on the basis of the fixed point control rotation speed and the engine output calculated in advance. Further, the ECUs71and72adjust the intake air amount and the fuel injection amount of the engine E such that the calculated target engine torque is realized and adjust the excitation intensity of the generator G such that the target generator torque is realized. As a result, during the execution of the fixed point control, the engine rotation speed is maintained constant at the fixed point control rotation speed determined in advance and the engine torque is maintained constant at the target engine torque determined such that the net fuel consumption rate is minimized.

Although a case where the engine E and the generator G are controlled such that the engine torque is directly above the BSFC bottom line8ahas been described in the above fixed point control, the present invention is not limited thereto. Alternatively, in the fixed point control, the engine E and the generator G may be controlled such that the engine torque becomes close to the BSFC bottom line8awithout having to be limited to being directly above the BSFC bottom line8a.

Returning back toFIG. 6, in a case where the determination result in S13is NO, the ECUs71and72determine whether or not the battery SOC acquired in S11exceeds a use upper limit SOC defined as a value exceeding the use lower limit SOC (see S16). In a case where the determination result of S16is NO, the battery ECU6determines whether or not the electric power generation flag Fgen is “1” (see S17). In a case where the determination result of S17is YES, that is, in a case where the fixed point control is in progress and the battery SOC is yet to reach the use upper limit SOC, the ECUs71and72proceed to S15in order to continue charging the battery3and execute the fixed point control of the engine E and the generator G.

In a case where the determination result in S16is YES, the ECUs71and72set the electric power generation flag Fgen to “0” (see S18), and then the ECUs71and72stop the operation of the engine E and the electric power generation by the generator G, supply the in-vehicle equipment8and the external equipment9with the electric power discharged from the battery3(see S19), and terminate this processing. In a case where the determination result of S17is NO, that is, in a case where discharging of the battery3is in progress and the battery SOC is yet to reach the use upper limit SOC, the ECUs71and72proceed to S19in order to continue discharging the battery3and stop the operation of the engine E and the electric power generation by the generator G.

The map ofFIG. 7Awill be described in detail below.FIG. 7Ais a diagram illustrating an example of a use lower limit SOC decision map for decision of the use lower limit SOC in accordance with the battery temperature. InFIG. 7A, the horizontal axis represents the battery temperature and the vertical axis represents the use lower limit SOC.

According to the flowchart illustrated inFIG. 6, the fixed point control of the engine E and the generator G is executed and the battery3is charged with the electric power generated by the generator G as a result once the battery SOC of the battery3falls below the use lower limit SOC during external electric power supply. In other words, the electric power required by the in-vehicle equipment8and the external equipment9needs to be covered by the electric power discharged from the battery3while the battery SOC exceeds the use lower limit SOC. In other words, the battery3needs to be in a state where the battery3is capable of continuously supplying electric power equal to or greater than required discharging electric power determined in view of, for example, various losses or the electric power required by the in-vehicle equipment8and the external equipment9while the battery SOC exceeds the use lower limit SOC.

FIG. 7Bis a diagram illustrating the temperature characteristics of the discharging performance of the battery3. More specifically,FIG. 7Bis a diagram illustrating the temperature characteristics of the discharging performance of the battery3in a state where the battery SOC is the high temperature lower limit SOC (seeFIG. 7A). InFIG. 7B, the horizontal axis represents the battery temperature [° C.] and the vertical axis represents the discharging electric power limit [kW] of the battery3. The discharging performance of the battery3declines as the battery temperature decreases as in the case of the charging performance. More specifically, the discharging electric power limit, which is a limit with respect to the discharging electric power at a time of discharging of the battery3, approaches 0 as the battery temperature decreases. In other words, the battery3is incapable of continuously discharging electric power exceeding the discharging electric power limit. Accordingly, the discharging electric power limit becomes equal to or less than the required discharging electric power in a case where the battery temperature is equal to or lower than the switching temperature as illustrated inFIG. 7B, and thus the battery3is incapable of continuously discharging the required discharging electric power. Accordingly, the use lower limit SOC is set so as to increase as the battery temperature decreases in a case where the battery temperature is equal to or lower than the switching temperature as illustrated inFIG. 7A.

FIG. 7Cis a diagram illustrating the temperature characteristics of the discharging performance of the battery3. More specifically,FIG. 7Cis a diagram illustrating the temperature characteristics of the discharging performance of the battery3adjusted such that the battery SOC at each battery temperature becomes the use lower limit SOC defined by the map ofFIG. 7A. InFIG. 7C, the horizontal axis represents the battery temperature [° C.] and the vertical axis represents the discharging electric power limit [kW] of the battery3. As illustrated inFIG. 7C, the battery3becomes capable of continuously discharging the required discharging electric power by the battery SOC being reserved so as to reach at least the use lower limit SOC.

Next, a procedure for setting the fixed point control rotation speed will be described with reference toFIG. 9.FIG. 9is a diagram illustrating the relationship between the engine rotation speed and the engine output during the fixed point control. InFIG. 9, the horizontal axis represents the engine rotation speed [rpm] and the vertical axis represents the engine output [kW] at a time when the operation point of the engine E during the fixed point control is changed on the BSFC bottom line. InFIG. 9, the thick solid line indicates the engine rotation speed-engine output relationship on low ground (with an altitude of, for example, 0 [m]) and the thick broken line indicates the engine rotation speed-engine output relationship on high ground (with an altitude of, for example, 1,000 [m]).

As illustrated inFIG. 9, the engine output, that is, the generated electric power during the fixed point control increases as the engine rotation speed increases. In addition, as illustrated inFIG. 9, the engine output and the generated electric power are lower on the high ground than on the low ground. Accordingly, the fixed point control rotation speed is set to an engine rotation speed at which the electric power required at a time of the maximum load can be covered by the in-vehicle equipment8and the external equipment9even on the high ground with the high ground where the engine output decreases assumed. Once the fixed point control rotation speed is set as described above, the generated electric power becomes larger on the low ground than on the high ground. Accordingly, the increment in generated electric power on the low ground is absorbed by the increment in charging electric power for the battery3as illustrated inFIG. 9.

The vehicle V according to the present embodiment described above has the following effects.

(1) The ECUs71and72start the engine E and supply the electric power generated by the generator G to the battery3and the external equipment9in a case where the battery SOC is equal to or less than the use lower limit SOC during external electric power supply. In a case where the battery SOC exceeds the use upper limit SOC, which exceeds the use lower limit SOC, during external electric power supply, the ECUs71and72supply the electric power discharged from the battery3to the external equipment9. Here, the ECUs71and72execute the fixed point control for controlling the engine such that the engine rotation speed is maintained constant while the generator G generates electric power. Therefore, according to the vehicle V, the engine rotation speed is maintained constant at the fixed point control rotation speed irrespective of fluctuations in the electric power required by the external equipment9while the generator G generates electric power, and thus fluctuations in vibration or noise generated by the engine E are also suppressed. In the vehicle V, the fixed point control is executed while the generator G generates electric power, and thus the output electric power of the generator G also becomes constant. Accordingly, in a case where the external equipment9requires small electric power, the charging electric power for the battery3increases correspondingly and the battery3can be charged in a short time, and thus the burden on the engine E during external electric power supply also can be reduced. In addition, the burden on an exhaust gas purification device can be reduced, engine oil consumption can be suppressed, and engine service life extension can be achieved by means of a constant engine rotation speed.

(2) When the fixed point control is executed, the ECUs71and72control the engine E and the generator G so as to be maintained at the engine torque set on the basis of the operation point at which the net fuel consumption rate is minimized (operation point directly above the BSFC bottom line). Therefore, according to the vehicle V, the generator G is capable of continuously generating electric power while the engine E continuously operates at the operation point at which the net fuel consumption rate is minimized, and thus fuel consumption during external electric power supply can be suppressed.

(3) When the battery is at a low temperature that is equal to or lower than the switching temperature, the ECUs71and72increase the use lower limit SOC as the battery temperature decreases. Therefore, according to the vehicle V, the battery3can be charged before the battery SOC falls below the use lower limit SOC at a low temperature at which the use lower limit SOC increases as described above, and thus a remaining capacity required for continuous discharging of the required discharging electric power can be reserved for the battery3.

(4) When the battery is at a low temperature that is equal to or lower than a second temperature, the ECUs71and72cause the charging electric power limit to approach 0 as the battery temperature decreases. In addition, in a case where the battery temperature is equal to or lower than the fixed point operation lower limit temperature at which the charging electric power limit approaches 0, the ECUs71and72select the variable electric power generation operation mode in which the engine E and the generator G are controlled such that the engine rotation speed changes in accordance with the charging electric power for the battery3, which is set on the basis of the charging electric power limit. As a result, at a low temperature at which the charging performance of the battery3declines, it is possible to charge the battery3while preventing overcharging that promotes malfunction or deterioration of the battery3.

Second Embodiment

Hereinafter, a second embodiment of the present invention will be described with reference to the accompanying drawings. In the following description, the same reference numerals are given to configurations identical to those of the first embodiment and detailed descriptions of the configurations are omitted.

FIG. 10is a diagram illustrating the configuration of a vehicle VA according to the present embodiment. The vehicle VA according to the present embodiment is different from the first embodiment in terms of the configurations of an electric power supply system1A and external equipment9A. More specifically, the electric power supply system1A according to the present embodiment further includes a downverter25A. The downverter25A interconnects the in-vehicle equipment8and the section between the voltage converter23and the battery contactor24on the main electric power line2. The downverter25A steps down the direct current electric power in the main electric power line2in accordance with a command from the battery ECU6and supplies the direct current electric power to the in-vehicle equipment8.

The external equipment9A according to the present embodiment is different from the first embodiment in terms of the configuration of an external inverter91A. More specifically, the functions of the external inverter91A include stepping down the direct current electric power that is supplied from the external electric power supply device5via the external electric power supply cable92to a voltage corresponding to the electrical equipment94and95and converting the direct current electric power into a single-phase alternating current.

EXPLANATION OF REFERENCE NUMERALS

V, VA VEHICLEE ENGINE (ELECTRIC POWER GENERATION DEVICE)G GENERATOR (ELECTRIC POWER GENERATION DEVICE)1,1A ELECTRIC POWER SUPPLY SYSTEM2MAIN ELECTRIC POWER LINE (ELECTRIC POWER LINE)22SECOND INVERTER (ELECTRIC POWER GENERATION DEVICE)3BATTERY (ELECTRIC POWER STORAGE DEVICE)5EXTERNAL ELECTRIC POWER SUPPLY DEVICE7ELECTRONIC CONTROL UNIT (CONTROLLER)71FI-ECU (CONTROLLER)72MOT-ECU (CONTROLLER)9,9A EXTERNAL EQUIPMENT