JP6270010B2 - Vehicle power control device - Google Patents

Description

  The present invention relates to a power generation control technique for a power generation unit mounted on a vehicle that is driven to travel by an electric motor.

In an electric vehicle that travels by driving an electric motor with electric power supplied from an in-vehicle battery, a vehicle equipped with a range extender that is a power generation unit has been developed. A range extender is composed of a small power generation engine and a generator, for example, and increases the cruising range of an electric vehicle by supplying the generated power to an electric motor or using it for charging an in-vehicle battery. be able to.
By the way, in recent years, development of fuel cells has progressed, and vehicles equipped with fuel cells have been proposed. Furthermore, vehicles that use fuel cells instead of engines have been proposed as range extenders for electric vehicles.
For example, in Patent Document 1, in a vehicle equipped with a fuel cell, the fuel cell and the battery are supplied to an electric motor as a power supply source to drive a drive wheel so that the vehicle can run. Further, Patent Document 1 discloses a technique for controlling the output of the fuel cell so that the battery charge rate (SOC) is maintained at a target charge rate set close to the lower limit after the battery power is used. Has been.

Japanese Patent No. 5101583

  In the vehicle disclosed in Patent Document 1, electric power is supplied from the battery to the electric motor until the battery charging rate reaches the target charging rate, and when the battery charging rate falls below the target charging rate, The output from the fuel cell is controlled based on the difference between the current charging rate of the battery and the target charging rate so as to cover the power consumption of the vehicle used by the motor or the like and maintain the target charging rate.

  However, the efficiency of a fuel cell generally decreases when the output increases or the output fluctuates. Even if an engine-driven generator is used instead of the fuel cell, the engine speed range is limited. Therefore, when the power generation output of the power generation unit is set based on the charge rate and the target charge rate after reaching the target charge rate as in Patent Document 1, it must be output from the power generation unit so that the vehicle power consumption is sufficient. In particular, when the vehicle power consumption is high, such as when driving at high speed, or when the vehicle power consumption fluctuates, the efficiency of the power generation unit may be reduced. Therefore, there is a problem that a large amount of fuel is consumed during traveling after the battery power is consumed.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a vehicle power control device that can suppress fuel consumption of a power generation unit such as a fuel cell. .

  In order to achieve the above object, a power control device for a vehicle according to the present invention is a power control device for a vehicle that supplies power from a power generation unit that consumes fuel and a power generation to an electric motor for driving. , Selection of switching from the first mode in which the power generation unit is stopped and the electric motor is driven by the electric power supplied from the battery to the second mode in which the power generation unit is forcibly started to travel A mode selection unit that controls the power generation output of the power generation unit, and the power generation control unit selects the first mode when the vehicle starts to travel, and the mode selection unit The power generation output of the power generation unit is controlled to a constant predetermined value until the charge rate of the battery becomes less than a predetermined target charge rate after the second mode is selected by It is characterized in.

Preferably, when the first mode is selected, the power generation control unit switches the power generation unit from the start of travel of the vehicle until the charge rate of the power generation unit becomes less than the target target charge rate. The electric motor may be driven by electric power supplied from the battery after being stopped.
In addition, it is preferable that a reaching target charging rate setting unit for setting the reaching target charging rate is provided.
In addition, preferably, a charge rate detection unit that detects a current charge rate of the battery, the power generation control unit, when the charge rate of the power generation unit becomes less than the target target charge rate, The power generation output may be controlled based on the difference between the target charging rate and the current charging rate.

Preferably, the power generation unit includes: a fuel remaining amount detection unit that detects a remaining amount of fuel in the power generation unit; and a power generation start determination unit that determines power generation start of the power generation unit based on power consumption of the vehicle. When the power generation start determination is made, the control unit sets a target charging rate of the battery so as to decrease as the remaining fuel amount decreases, and controls the power generation output based on the target charging rate. Good.
Preferably, the power generation start determination unit calculates a vehicle speed equivalent value based on power consumption of the vehicle, and determines the power generation start when the vehicle speed equivalent value exceeds a predetermined threshold.
Preferably, a charge rate detection unit that detects a current charge rate of the battery is provided, and the power generation control unit determines whether the target charge rate and the current charge rate are the same when the power generation start determination is made. The power generation output may be controlled based on the difference.
Preferably, the power generation unit is a fuel cell.

  According to the vehicle power control apparatus of the present invention, the first mode in which the electric motor is driven by the electric power supplied from the battery when the vehicle starts to travel is selected, and the second mode is selected. Since the power generation output of the power generation unit is controlled to a certain predetermined value until the battery charging rate becomes less than the predetermined target charging rate, before the battery charging rate becomes less than the predetermined target charging rate By starting the power generation by the power generation unit, it is possible to delay the decrease in the charging rate of the battery. Until the charging rate becomes less than the predetermined target charging rate, fuel is consumed by power generation, but power can be generated with a constant power output with high efficiency, so that fuel consumption can be suppressed. Then, by delaying the battery charge rate decrease, the operation that deteriorates the fuel consumption efficiency after the charge rate becomes less than the target charge rate is delayed, and the overall fuel consumption from the start to the end of vehicle travel is reduced. Can be suppressed.

It is a schematic block diagram of the drive system of the electric vehicle which concerns on one Embodiment of this invention. It is a graph which shows an example of transition of the charging rate at the time of vehicles running in EV priority mode and TOTAL fuel consumption priority mode of this embodiment, fuel remaining, and power generation output. It is a graph which shows an example of transition of the charging rate, fuel remaining amount, and electric power generation output at the time of vehicle driving | running | working by the EV priority mode in the low output and low speed driving state of this embodiment, and a high output and high speed driving state.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a drive system of a vehicle 1 according to an embodiment of the present invention.
A vehicle 1 that employs a power control device 2 according to an embodiment of the present invention is an electric vehicle that drives left and right traveling drive wheels 5 via a differential 4 by an electric motor 3.
The vehicle 1 is equipped with a battery 6 and a fuel cell 8 as a power supply device that supplies electric power to the electric motor 3 for driving.

The fuel cell 8 generates electricity using hydrogen stored in a fuel tank 9 mounted on the vehicle as fuel. The electric power generated by the fuel cell 8 is supplied to the primary side of the DC-DC converter 10 to be boosted, and can be supplied from the secondary side of the DC-DC converter 10 to the electric motor 3 via the inverter 11. Yes. The battery 6 can supply power to the electric motor 3 via the inverter 11.
The fuel cell 8 and the battery 6 via the DC-DC converter 10 are connected in parallel, and surplus power output from the fuel cell 8 is supplied to the battery 6 to charge the battery 6. Further, when the power output from the power generation unit 7 is insufficient with respect to the power required for driving the electric motor 3, the power is supplied from the battery 6.

The vehicle 1 is equipped with a charger 12. The charger 12 is an AC-DC converter, which converts an AC voltage supplied from an external power supply through an outlet 13 into a direct current, and supplies the direct current to the battery 6 to charge the battery 6.
The fuel tank 9 is provided with a fuel remaining amount detector 20 (fuel remaining amount detecting unit) for detecting the remaining amount of fuel (remaining amount of hydrogen). Further, the battery 6 is provided with a battery monitoring unit 21 (charge rate detection unit) that monitors the charge rate of the battery 6.

  The vehicle 1 also includes a mode switching device 23 (mode selection unit) that can be operated by the driver, a target charging rate setting device 24 (target reaching charge rate setting unit), and a travelable distance display device 25. . The mode switching device 23 can be switched between an EV priority mode (first mode) and a TOTAL fuel consumption priority mode (second mode). Forcibly at the start of driving or at the time of READYON (when the vehicle power is on) The EV priority mode is selected, and the TOTAL fuel consumption priority mode can be selected by the driver's operation. The EV priority mode is a mode in which the power of the battery 6 is used with priority, and the TOTAL fuel consumption priority mode is a mode in which the power consumption of both the battery 6 and the fuel cell 8 is used to suppress fuel consumption. The target target charge rate setting device 24 is a device that sets the target target charge rate SOCb, which is the charge rate of the battery 6 that should be ensured at a minimum when the vehicle 1 finishes traveling, and can be set by the driver. The travelable distance display device 25 is disposed at a position visible to the driver, and has a function of displaying a travelable distance using only the power of the battery 6 described later.

  The control unit 22 (power generation start determination unit, power generation control unit) includes a CPU (Central Processing Unit), a storage device (ROM, RAM), an input / output interface, and the like. The remaining amount of fuel, the charging rate of the battery 6 from the battery monitoring unit 21, the mode selected from the mode switching device 23, the reaching target charging rate SOCb from the reaching target charging rate setting device 24, the accelerator operation amount of the vehicle 1, the air conditioner, etc. The vehicle operation information such as the operation information of the in-vehicle device is inputted, the operation control of the electric motor 3 through the inverter 11, the output control of the fuel cell 8 through the DC-DC converter 10, and the switching of the mode switching device 23. As a reference for the operation, the travelable distance display device 25 displays the travelable distance.

The control unit 22 inputs the charging rate of the battery 6 from the battery monitoring unit 21 when the vehicle 1 is READYON, that is, when the vehicle starts to travel. Calculate and display. If the driver intends to drive for a distance less than or equal to the travelable distance, the driver switches to the EV priority mode without operating the mode switching device 23, and if the driver plans to drive for a distance longer than the travelable distance, The mode switching device 23 may be switched to the TOTAL fuel consumption priority mode.
FIG. 2 is a graph showing an example of the transition of the charging rate of the battery 6, the remaining fuel amount, and the power generation output when the vehicle is traveling in the EV priority mode and the TOTAL fuel efficiency priority mode of the present embodiment.

In FIG. 2, from the state where the charging rate SOC of the battery 6 is 100% and the remaining amount of fuel is a value Qfa close to 100%, the vehicle 1 starts traveling and the maximum possible traveling is completed A) The graph shows the transition of the charging rate SOC of the battery 6, (B) the remaining fuel amount Qf, and (C) the power generation output Pf of the fuel cell 8. In FIG. 2, the solid line indicates the TOTAL fuel consumption priority mode, and the broken line indicates the EV priority mode.
The control unit 22 performs output control of the fuel cell 8 in the EV priority mode from when the vehicle travels until the operation to the TOTAL fuel consumption priority mode is input in the mode switching device 23.

  The control unit 22 sequentially inputs the charging rate SOC of the battery 6 from the battery monitoring unit 21 in the EV priority mode when the TOTAL fuel consumption priority mode is not selected. As shown by the broken line in FIG. The power generation by the fuel cell 8 is not performed until the target target charging rate SOCb input by the target target charging rate setting device 24 is less than the SOCb. Therefore, not all of the vehicle power consumption is covered by the output from the battery 6, and accordingly, the charging rate SOC of the battery 6 decreases. Then, after the charge rate SOC of the battery 6 reaches the target target charge rate SOCb, the deviation between the current charge rate SOC and the target target charge rate SOCb is set so that the charge rate SOC maintains the target target charge rate SOCb. Based on this, electric power is supplied from the fuel cell 8.

When the mode switching device 23 is switched to the TOTAL fuel consumption priority mode before the current charging rate SOC reaches the target target charging rate SOCb after the vehicle starts running, the power generation of the fuel cell 8 is started from that point, The power generation output is set to a predetermined value Pf1. The predetermined value Pf1 may be set to the highest value of the output efficiency (= power generation amount / fuel consumption amount) of the fuel cell 8. The fuel cell 8 generally has a low output and a high output efficiency. Then, after the charging rate SOC of the battery 6 has reached the attainment target charging rate SOCb, as in the EV priority mode, the current charging rate SOC and the reaching target are set so that the charging rate SOC maintains the reaching target charging rate SOCb. Electric power is supplied from the fuel cell 8 based on the deviation from the charging rate SOCb.
Thus, in the present embodiment, if the EV priority mode is set after the start of traveling, only the power of the battery 6 is used until the ultimate target charging rate SOCb is reached. Therefore, when the travel distance is short and the travel is completed only with the electric power of the battery 6, no fuel is consumed.

  On the other hand, when the mode is switched to the TOTAL fuel consumption priority mode, the fuel cell 8 generates power at a low output, so that a reduction in the charging rate SOC is suppressed. Thereby, the time when the charging rate SOC decreases until it reaches the attainment target charging rate SOCb can be extended after the EV priority mode. In the TOTAL fuel consumption priority mode, the fuel cell 8 generates power with a low output (predetermined value Pf1) with good output efficiency until the charge rate SOC reaches the target charge rate SOCb after the start of power generation. It is done. In the EV priority mode, the fuel is not consumed until the charging rate reaches the target charging rate SOCb, but after it becomes less than the target charging rate SOCb, the output is determined according to the vehicle power consumption and the fuel consumption is greatly increased. Immediately, the remaining fuel level will drop. However, in the TOTAL fuel economy priority mode, a long power generation time with reduced fuel consumption is ensured and the vehicle travels longer than the distance that can be traveled only by the power of the battery 6, for example, up to the point (a) in FIG. 2. In this case, the remaining amount of fuel can be suppressed as compared with the EV priority mode. Thereby, in the TOTAL fuel consumption priority mode, it is possible to extend the travelable time and increase the cruising distance.

Furthermore, in this embodiment, a function of extending the cruising distance is provided in a high output / high speed traveling state regardless of the switching of the mode switching device 23.
The control unit 22 performs power generation start determination for determining the high output / high speed travel state of the vehicle 1 during vehicle travel (power generation start determination unit). The control unit 22 sequentially calculates the vehicle power consumption that is the sum of the power consumption of the electric motor 3 and the power consumption of other in-vehicle devices, and smoothes the vehicle power consumption using a filter or the like to obtain a vehicle speed change equivalent value. . Then, when this vehicle speed change equivalent value continues for a predetermined time Ta or more and exceeds a predetermined threshold value Va set in advance, it is determined that the vehicle 1 is in a high output / high speed running state (power generation start determination). )do. The predetermined threshold value Va and the predetermined time Ta may be appropriately set to values that can determine that the output state from the fuel cell 8 is in a high output / high speed running state. Even if the vehicle power consumption continues for the predetermined time Ta or more and does not exceed the threshold value Va, when the charging rate of the battery 6 reaches the target reaching charging rate SOCb, the power generation start determination is also made at that time.

The control unit 22 further calculates and controls the power generation output Pf of the fuel cell 8 every predetermined calculation cycle (for example, several milliseconds) after the power generation start determination is made. The power generation output Pf is calculated by the following equation (1).
Pf = α × (SOCt−SOC) (1)
In Equation (1), SOC is the current charging rate of the battery 6 input from the battery monitoring unit 21. SOCt is a target charging rate, and is calculated for each predetermined calculation period together with equation (1) by the following equation (2). α is an output gain, for example, 0 when the charging rate SOC is higher than the target charging rate SOCt, and the difference between the target charging rate SOCt and the charging rate SOC increases when the charging rate SOC is lower than the target charging rate SOCt. Accordingly, the output gain α may be set to increase.
SOCt = SOCb + (SOCa−SOCb) × {(Qf−Qfb) / (Qfa−Qfb)} (2)

  In Equation (2), SOCa is a charging rate at the start, and is used by storing the charging rate of the battery 6 when the power generation start determination is made. Qf is the current remaining fuel amount input from the remaining fuel amount detector 20, and Qfa is the starting fuel amount. The starting fuel remaining amount Qfa is used by storing the fuel remaining amount when the power generation start determination is made. Qfb is an attainment target fuel remaining amount, which is at least the remaining amount of fuel that is required when the vehicle finishes traveling. The target fuel remaining amount Qfb may be set by the driver, or may be set in advance to a positive value close to 0, for example.

FIG. 3 shows an example of changes in the charging rate of the battery 6, the remaining amount of fuel, and the power generation output when the vehicle is traveling in the EV priority mode in the low output / low speed traveling state and in the high output / high speed traveling state of the present embodiment. It is a graph which shows.
In FIG. 3, as in FIG. 2, from the state where the charging rate SOC of the battery 6 is 100% and the remaining amount of fuel is a value Qfa close to 100%, the vehicle 1 starts traveling and travels as much as possible. , (A) the charging rate SOC of the battery 6, (B) the remaining fuel amount Qf, and (C) the power generation output Pf of the fuel cell 8. In FIG. 3, the solid line is the transition in the high output / high speed running state where the power generation output Pf is set using the above formulas (1) and (2), and the broken line is the EV priority mode in the low output / low speed running state. It shows the transition. In addition, a two-dot chain line in FIG. 2A indicates a transition of the target charging rate SOCt set in the high output / high speed traveling state.

As described above, when the vehicle 1 is in a high output / high speed running state and the vehicle power consumption continues for a predetermined time Ta or more and exceeds the threshold value Va, the charge rate SOC of the battery 6 reaches the EV priority mode, for example. Even if the target charging rate SOCb does not decrease, it is determined that power generation is started and power generation of the fuel cell 8 is started. Therefore, as shown in FIG. 3, in the high output / high speed running state, power generation is started earlier than the EV priority mode in the low output / low speed running state. By starting power generation early in this way, the output of the fuel cell 8 can be suppressed, and the shortage relative to the vehicle power consumption is compensated by the output from the battery 6.
After the power generation is started, the target charge rate SOCt is set to decrease as the fuel remaining amount Qf decreases, and the fuel remaining amount Qf reaches the target fuel remaining amount Qfb and the target charge rate SOCt is The target charging rate SOCt is set so that the reaching target charging rate SOCb is reached at the same time. Since the power generation output Pf is calculated based on the difference between the target charge rate SOCt and the current charge rate SOC, feedback control is accurately performed so that the charge rate SOC matches the target charge rate SOCt.

  Since the target charging rate SOCt is gradually lowered as the remaining fuel amount Qf decreases and is controlled so as to reach the reaching target charging rate SOCb at the same time as the remaining fuel amount Qf reaches the reaching target fuel remaining amount Qfb. The actual charging rate SOC of the battery 6 also reaches the target charging rate SOCb at substantially the same time as the target charging rate SOCt. Accordingly, the cruising range in which the vehicle can travel the maximum distance from the state where the charging rate of the battery 6 is 100% and the remaining fuel amount is the starting fuel remaining amount Qfa to the ultimate target charging rate SOCb and the remaining fuel amount Qfb is possible. Distance. In the high power / high speed running state, the fuel cell 8 outputs until the fuel remaining amount Qf reaches the target fuel remaining amount Qfb, and the target charging rate SOCt is gradually decreased as the fuel remaining amount Qf decreases. Thus, it is possible to secure a power generation time from the start of power generation to the end of travel, and to suppress the output of the fuel cell 8.

  In the EV priority mode in the low output / low speed running state, since the charging rate SOC of the battery 6 has already reached the ultimate target charging rate SOCb after the start of power generation, it is difficult to increase the output from the battery 6. When the power consumption is greatly increased, the output from the fuel cell 8 must be greatly increased in accordance with the fluctuation. On the other hand, in the high output / high speed running state, since the charging rate SOC exceeds the ultimate target charging rate SOCb in the period from the start of power generation to the end of running, even if the vehicle power consumption temporarily increases, the battery As a result, the output from the fuel cell 8 can be increased and fluctuations in the output of the fuel cell 8 can be suppressed.

  As described above, even in the EV priority mode, in the high power / high speed running state, the charging start timing is advanced and the remaining fuel amount Qf decreases until the remaining fuel amount Qf reaches the target fuel remaining amount Qfb. By reducing the target charging rate SOCt, it is possible to secure the power generation time and to keep the output of the fuel cell 8 constant. Since the efficiency of the fuel cell 8 generally decreases as the output increases, the efficiency of the fuel cell 8 is improved by suppressing the output of the fuel cell 8. Further, since the fluctuation of the output of the fuel cell 8 can be suppressed even with respect to the fluctuation of the vehicle power consumption, the efficiency of the fuel cell 8 can be improved also in this respect.

As described above, by having the function of extending the cruising distance in a high output / high speed traveling state, even if the mode switching device 23 is set to the EV priority mode without scheduling the traveling distance, for example, a highway In the situation where the high power / high speed driving state continues like when driving, the fuel cell 8 can generate power efficiently, the fuel consumption can be suppressed, and the cruising distance can be increased.
In the low power / low speed driving state in the EV priority mode, the power generation start determination is not made at an early stage, but the power consumption of the electric motor 3 is small, so that the fuel cell 8 does not need to have a high output, and thus the efficiency of the fuel cell 8 is improved. The decline is suppressed.

  Further, in this embodiment, the power generation start determination is performed based on the vehicle speed equivalent value calculated by smoothing the vehicle power consumption, and when the vehicle speed equivalent value exceeds the threshold value Va for a predetermined time Ta or more, the vehicle outputs high power and high speed. Assuming that the vehicle is in a running state, it is determined to start power generation. Therefore, since the power generation start determination is determined based on the vehicle speed equivalent value obtained by smoothing the vehicle power consumption, it is difficult to be affected by uphill or downhill slopes, and the influence of output fluctuation due to acceleration / deceleration is also suppressed. The high output / high speed driving state can be determined stably and accurately.

This is the end of the description of the embodiment of the invention, but the invention is not limited to this embodiment.
For example, the present embodiment has a function of setting the target charging rate SOCt and extending the cruising distance in a high output / high speed traveling state, but this function may be deleted. In the present invention, by enabling at least the TOTAL fuel consumption priority mode, fuel consumption can be suppressed when traveling longer than the distance that can be traveled only by the electric power from the battery 6.

  In the present embodiment, the fuel cell 8 is used as the power generation unit, but a unit in which an engine and a generator are combined may be used instead of the fuel cell 8. In this case, the vehicle is a hybrid vehicle capable of the series mode, but even in such a vehicle, the generator and the engine are driven and controlled, and the output from the generator is controlled in the same manner as the output control of the fuel cell. By doing so, the engine can be operated efficiently and the cruising distance can be increased.

1 Vehicle 3 Electric Motor 6 Battery 8 Fuel Cell (Power Generation Unit)
20 Fuel level detector (fuel level detector)
21 Battery monitoring unit (charge rate detector)
22 Control unit (power generation start determination unit, power generation control unit)
23 Mode switching device (mode selection part)
24 Target charging rate setting device (target charging rate setting unit)

Claims (7)

A power control device for a vehicle that supplies power from a power generation unit that consumes fuel and generates electricity to an electric motor for driving from a battery,
The power generation unit is stopped and the electric motor is driven by the electric power supplied from the battery to switch to the second mode in which the power generation unit is forced to start and travel. A mode selector,
A power generation control unit for controlling the power generation output of the power generation unit;
A charge rate detector for detecting a current charge rate of the battery,
The power generation control unit selects the first mode at the start of travel of the vehicle, and the battery charging rate is a predetermined target charging rate after the second mode is selected by the mode selection unit. The power generation output of the power generation unit is controlled to a constant predetermined value until the power is less than the value, and when the first mode is selected, the battery charge rate is less than the target target charge rate from the start of travel of the vehicle. The electric power control apparatus for a vehicle is characterized in that the electric power generation unit is stopped until the electric motor is driven, and the electric motor is driven by electric power supplied from the battery.   The vehicle power control apparatus according to claim 1, further comprising an attainment target charge rate setting unit that sets the attainment target charge rate.   The power generation control unit controls the power generation output based on a difference between the target charging rate and the current charging rate when the charging rate of the battery becomes less than the target charging rate. The power control apparatus for a vehicle according to claim 1 or 3. A fuel remaining amount detecting unit for detecting the remaining amount of fuel in the power generation unit;
A power generation start determination unit that determines the power generation start of the power generation unit based on the power consumption of the vehicle,
The power generation control unit sets a target charging rate of the battery so as to decrease as the remaining fuel amount decreases when the power generation start determination is made, and the power generation output based on the target charging rate The vehicle power control device according to claim 1, wherein the vehicle power control device controls the power of the vehicle.   The power generation start determination unit calculates a vehicle speed equivalent value based on power consumption of the vehicle, and determines the power generation start when the vehicle speed equivalent value exceeds a predetermined threshold. Vehicle power control device.   The power generation control unit controls the power generation output based on a difference between the target charging rate and the current charging rate when the power generation start determination is made. Vehicle power control device.   The vehicle power control apparatus according to claim 1, wherein the power generation unit is a fuel cell.

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