JP2024172879A - Vehicle control device - Google Patents

Abstract

To provide a control device for a vehicle that enables both of suppression of excessive lowering of SOC and suppression of deterioration of fuel economy.SOLUTION: When at least either one of a condition where a use electric power amount of a power storage device in a traveling period of a prescribed distance is a predetermined prescribed use electric power amount or smaller (Yes in Step S2) or a condition where a charge electric power amount of the power storage device in the traveling period of the prescribed distance is a predetermined prescribed charge electric power amount or larger (Yes in Step S4) is satisfied, a charge residual amount (charge start SOC) of the power storage device for determining starting of an internal combustion engine is switched to a second charge start SOC that is a value smaller than a reference threshold value (first charge start SOC) (Step S3).SELECTED DRAWING: Figure 2

Description

The present invention relates to a control device for a vehicle equipped with a generator that converts the power of an internal combustion engine into electricity, and an electric motor that generates drive torque by receiving power from at least one of the electricity generated by the generator and the electricity stored in an electricity storage device.

Patent Document 1 describes a control device for a hybrid vehicle that includes a generator that converts engine power into electricity and charges an electricity storage device with the converted electricity, and an electric motor that outputs drive torque when power is supplied from the electricity storage device, and is configured to operate the engine and generator to charge the electricity storage device when the remaining charge (SOC) of the electricity storage device falls below a predetermined value. This hybrid vehicle is further configured to be able to charge the electricity storage device at the driver's request even when the SOC is equal to or greater than a predetermined value and charging of the electricity storage device is stopped. Specifically, an SOC recovery switch is provided that can select between two charging modes, a strong charging mode and a weak charging mode, and an off mode that turns off charging in the charging modes.

When the strong charging mode is selected by the SOC recovery switch, the control device operates the engine and generator to start charging the power storage device even if the SOC is equal to or higher than a predetermined value. Furthermore, when the weak charging mode is selected by the SOC recovery switch, the control device switches between performing charging and not performing charging depending on the driving load. Specifically, charging is kept stopped when the driving load is low, and charging is started when the driving load is high, even if the SOC is equal to or higher than a predetermined value. Furthermore, in the off mode, charging is started when the SOC falls below a predetermined value, just like in normal operation.

The system is configured to start charging regardless of the driving load if a predetermined period of time has elapsed since the weak charging mode was selected, if charging has not been performed for a predetermined period of time, if the amount of decrease in SOC since the weak charging mode was selected is equal to or exceeds a predetermined amount, or if the driving distance since the weak charging mode was selected is equal to or exceeds a predetermined distance.

JP 2014-201250 A

The control device for the hybrid vehicle described in Patent Document 1 determines to start the engine and begin charging when the SOC of the power storage device falls below a predetermined value or when the running load becomes a predetermined load. Therefore, for example, even if the power storage device can be charged by running downhill after the SOC of the power storage device falls below a predetermined value, the engine is started when the SOC falls below the predetermined value. Or, even if the running load temporarily increases to overtake a preceding vehicle and then decreases by running at a constant speed, the engine is started when the running load increases. In other words, the engine is started in response to temporary changes in the SOC of the power storage device or changes in the running load. As a result, there are more opportunities to start the engine, which may result in worsening fuel efficiency.

The present invention was made with a focus on the above technical problems, and aims to provide a vehicle control device that can simultaneously suppress excessive drops in SOC and suppress deterioration of fuel economy.

To achieve the above object, the present invention provides a vehicle control device that includes an internal combustion engine, a generator capable of converting at least a portion of the power output from the internal combustion engine into electric power, an electric motor that outputs a drive torque when supplied with electric power, and an electric storage device that receives the electric power generated by the generator and outputs electric power to the electric motor, and that starts the internal combustion engine and starts generating power by the generator to convert the power of the internal combustion engine into electric power when the remaining charge of the electric storage device falls below a predetermined reference threshold, and includes a controller that controls the internal combustion engine and the generator, and the controller switches the remaining charge of the electric storage device, which determines whether to start the internal combustion engine, to a value lower than the reference threshold when at least one of the following conditions is met: the amount of power used by the electric storage device during a predetermined driving period is equal to or less than a predetermined amount of power used, and the amount of power charged to the electric storage device during the predetermined driving period is equal to or more than a predetermined amount of power charged.

According to the present invention, when the remaining charge of the power storage device falls below a reference threshold, the internal combustion engine is started and power generation by the generator is initiated. Also, when the amount of power used during a specified driving period is below a specified amount of power used, or when the amount of power charged during a specified driving period is a specified amount of power charged, the remaining charge for determining whether to start the internal combustion engine is switched to a value lower than the reference threshold. In other words, when the driving conditions are such that the amount of power used is low or the amount of power charged is high, resulting in a small decrease in the remaining charge of the power storage device, the threshold for determining whether to start the internal combustion engine is made small. Therefore, under conditions in which an excessive decrease in the remaining charge of the power storage device is unlikely to occur, the internal combustion engine is unlikely to start, so that it is possible to both suppress an excessive decrease in the remaining charge of the power storage device and suppress a deterioration in fuel efficiency.

FIG. 2 is a block diagram illustrating an example of a control device according to an embodiment of the present invention. 4 is a flowchart illustrating an example of control executed by a control device according to an embodiment of the present invention.

The vehicle in the embodiment of the present invention is a vehicle equipped with an internal combustion engine, a generator capable of converting at least a portion of the power output from the internal combustion engine into electric power, and an electric motor that outputs drive torque when supplied with electric power. For example, the vehicle may be a series-type hybrid vehicle that runs by generating engine power using a generator and supplying electric power from at least one of the generator and an electric storage device to the electric motor, or a series-parallel type hybrid vehicle that runs by generating part of the engine power using a generator, transmitting the surplus power to the drive wheels, and supplying electric power from at least one of the generator and an electric storage device to the electric motor.

The engine mounted on the vehicle can be configured in the same way as engines installed in conventional hybrid vehicles. That is, it may be a gasoline engine equipped with a throttle valve for controlling the amount of air supplied to the combustion chamber, a fuel injection device for injecting fuel into the combustion chamber, and a spark plug for igniting the air-fuel mixture, and configured so that the output power can be controlled by controlling the opening of the throttle valve, the amount of fuel injected from the fuel injection device, and the ignition timing of the spark plug. The engine may be a variety of engines, such as a diesel engine or a hydrogen engine.

The generator and motor can be configured in the same way as a motor used as a driving force source in a conventional hybrid vehicle or electric vehicle. In other words, they can be configured as a motor generator that functions as a generator that converts part of the power of the output shaft (rotor shaft) into electric power when the output shaft (rotor shaft) is rotated, and as a motor that applies torque to the output shaft when electricity is applied. Specifically, they can be configured as a permanent magnet synchronous motor or an induction motor.

The generator and motor are each connected to a power control unit consisting of an inverter or converter, and these power control units are connected to a power storage device consisting of a secondary battery or capacitor. Furthermore, each power control unit is connected so that the generator and motor can exchange power without going through the power storage device.

The vehicle is equipped with various sensors, such as a sensor that detects the remaining charge of the power storage device (hereinafter referred to as SOC), a sensor that detects the distance traveled by the vehicle, map information from a navigation system, and a GPS receiver that identifies the current location of the vehicle.

An electronic control unit (hereinafter, referred to as ECU) 1 is provided for controlling the engine, generator, and electric motor. FIG. 1 shows a block diagram for explaining the configuration of the ECU 1. The ECU 1 is mainly composed of a microcomputer, and receives signals from various sensors provided in the vehicle, and outputs command signals for controlling the output torque and rotation speed of the engine 2, generator 3, and electric motor 4 based on the input signals and pre-stored maps and arithmetic expressions. In the example shown in FIG. 1, only a signal from a sensor (SOC sensor) 5 that detects the SOC of the power storage device is shown as a signal input to the ECU 1. This ECU 1 corresponds to the "controller" in the embodiment of the present invention.

The ECU 1 shown in FIG. 1 includes a driving state determination unit 6, an electric power usage determination unit 7, and a regenerative electric power determination unit 8. The driving state determination unit 6 determines whether or not an EV driving mode in which the vehicle runs only on the power of the electric motor 4 has been selected from among the driving modes selectable by the vehicle. Specifically, it determines whether the engine 1 is stopped and whether the electric motor 4 is outputting a driving torque for driving the drive wheels using the electric power supplied from the power storage device, or is applying a regenerative torque for reducing the rotation speed of the drive wheels.

The power usage determination unit 7 determines the amount of power used by the power storage device during a predetermined period during which the EV driving mode is selected. Specifically, the power usage of the power storage device after the EV driving mode is selected is stored, and the power usage from the time of determination to the predetermined period prior is integrated. The power usage can be calculated by sequentially calculating the values detected by a voltmeter, ammeter, etc. provided in the power control unit connected to the electric motor 4, or can be calculated by accumulating the amount of decrease in SOC during driving.

The regenerative power amount determination unit 8 determines the amount of power (charged power amount) regenerated and charged to the power storage device within a predetermined period during which the EV driving mode is selected. Specifically, the regenerative power of the power storage device after the EV driving mode is selected is stored, and the regenerative power from the time of determination to the predetermined period before is integrated. The regenerative power can be found by sequentially calculating the detected values of a voltmeter, ammeter, etc. provided in the power control unit connected to the electric motor 4, or by accumulating the increase in SOC during braking (regenerative) driving.

The vehicle configured as described above is configured to start the engine 2 and convert at least a portion of the power of the engine 2 into electricity by the generator 3 to charge the electricity storage device when the actual SOC falls to a charge start SOC that is set to a value higher than the lower limit SOC in order to prevent the actual SOC from falling to a lower limit SOC that is predetermined based on the characteristics of the electricity storage device. In other words, the vehicle is configured to output power from the engine 2 that is equal to or greater than the combined energy of the power required for the vehicle and the power required to restore the SOC of the electricity storage device. This charge start SOC corresponds to the "reference threshold" in an embodiment of the present invention.

On the other hand, the amount and rate of decline in the SOC of the power storage device differs between cases where a relatively large driving force is required, such as when the vehicle is traveling uphill, and cases where a large driving force is not required, such as when the vehicle is traveling at a constant speed on a flat road or traveling downhill. Therefore, if the charging start SOC is set to a constant value even when such driving conditions are different, there is a possibility that the number of opportunities to start the engine 2 will increase, such as when charging of the power storage device is started even when it is not actually necessary to charge the power storage device, and fuel efficiency will deteriorate.

Therefore, the control device in the embodiment of the present invention is configured to vary the charge start SOC depending on the driving conditions. A flowchart for explaining an example of this control is shown in FIG. 2. In the example shown in FIG. 2, first, the driving state determination unit 6 determines whether the EV driving mode is selected and the vehicle is running, that is, whether the vehicle is running only with the electric motor 4 (step S1). In other words, it determines whether the engine 2 and the generator 3 are stopped and the vehicle is running by supplying power only from the storage device to the electric motor 4. This step S1 can be determined based on whether a command signal to the engine 2 or a command signal to the power control unit for operating the generator 3 has not been output, or whether the required driving force is lower than a predetermined driving force.

If the result of step S1 is negative because the vehicle is not running on the power of the electric motor 4 alone, for example because torque is being transmitted from the engine 2 to the drive wheels or the power of the engine 2 is being converted to electricity by the generator 3, step S1 is executed repeatedly.

On the other hand, if the vehicle is traveling using only the power of the electric motor 4 and step S1 is judged to be positive, it is judged whether the driving conditions are such that the amount or rate of decrease in the SOC of the power storage device is small. In the example shown in FIG. 2, the driving conditions are configured to judge whether the amount or rate of decrease in the SOC is small based on the amount of power used and the amount of regenerated power for a specified distance traveled up to the point where step S1 is judged to be positive.

Specifically, if the answer in step S1 is affirmative, the power usage determination unit 7 first determines whether the amount of power usage during the period in which the predetermined distance was traveled is equal to or less than the predetermined amount of power usage (step S2). This step S2 is for determining, for example, whether the vehicle is traveling on a flat road where constant speed travel is possible, or on a downhill road that does not require a large driving torque, and therefore the predetermined distance and the predetermined amount of power usage are set to distances and amounts of power that allow the above determination. The period in which the predetermined distance was traveled corresponds to the "predetermined driving period" in the embodiment of the present invention.

If the power usage is equal to or less than the predetermined power usage amount and thus the answer is affirmative in step S2, the urgency of charging the power storage device is lower than the first charge start SOC that is predefined assuming various driving conditions. In other words, even if the actual SOC falls below the first charge start SOC, it is unlikely to fall to the lower limit SOC, or it is considered that it will take a long time to fall to the lower limit SOC.

Therefore, if the answer to step S2 is affirmative, the charging start SOC is switched to a second charging start SOC that is lower than the first charging start SOC (step S3), and this routine is temporarily terminated.

On the other hand, when the SOC of the power storage device repeatedly increases and decreases, such as when the vehicle is traveling on a road that alternates between uphill and downhill, both the amount of power used and the amount of regenerated power become large, and the overall SOC decrease amount and decrease rate (time change rate) may be small. Therefore, if the amount of power used is greater than the predetermined amount of power used and the result is a negative judgment in step S2, the regenerative power amount judgment unit 8 judges whether the amount of regenerative power during the period when the predetermined distance was traveled is equal to or greater than the predetermined amount of regenerative power (step S4). The predetermined amount of regenerative power in step S4 may be a predetermined fixed value, or may be a variable value according to the amount of power used determined by the power usage judgment unit 7. The period when the predetermined distance was traveled in step S4 may be the same period as in step S2.

If the regenerative power amount is equal to or greater than the predetermined regenerative power amount and thus the answer is affirmative in step S4, the process proceeds to step S3. In other words, the charging start SOC is switched to the second charging start SOC. Conversely, if the regenerative power amount is less than the predetermined regenerative power amount and thus the answer is negative in step S4, the process returns to step S1.

As described above, when driving in EV driving mode, if the amount of power used during a period of driving a specified distance is small or the amount of regenerated power is large, the charge start SOC for determining the start of charging of the power storage device is switched to a second charge start SOC that is lower than the first charge start SOC. This makes it difficult for the engine 2 to start under conditions where excessive drop in the SOC of the power storage device is unlikely to occur, thereby making it possible to both suppress excessive drop in the SOC of the power storage device and suppress deterioration of fuel efficiency.

In the above-described control example, the system is configured to determine whether the driving conditions are such that the amount or rate of decrease in the SOC of the storage device is small based on the driving history up to the present time, but the system may also be configured to determine whether the driving conditions are such that the amount or rate of decrease in the SOC of the storage device is small based on the driving route from the present time onwards, and switch the charging start SOC.

Specifically, the current position of the vehicle is identified using a navigation system and a GPS receiver, and the amount of power used and regenerated when traveling along the searched driving route toward the vehicle's destination is calculated, and if the calculated amount of power used is equal to or less than a predetermined amount of power used, or if the amount of regenerated power is equal to or greater than the predetermined amount of regenerated power, the charging start SOC may be switched to the second charging start SOC.

Alternatively, the amount and rate of SOC decline for each traveled route may be stored in ECU 1, and the charging start SOC may be switched to the second charging start SOC when it is predicted from the vehicle's current position that the vehicle will travel along a route where the amount and rate of SOC decline stored in ECU 1 is small.

1. Electronic Control Unit (ECU)
Reference Signs List 2 engine 3 generator 4 electric motor 5 SOC sensor 6 running state determination unit 7 power usage determination unit 8 regenerative power amount determination unit

Claims (1)

a generator capable of converting at least a portion of the power output from the internal combustion engine into electric power; an electric motor that outputs a drive torque when supplied with electric power; and an electric storage device that is supplied with electric power generated by the generator and outputs electric power to the electric motor,
A vehicle control device that starts the internal combustion engine and starts power generation by converting motive power of the internal combustion engine into electric power by the generator when a remaining charge amount of the power storage device becomes equal to or less than a predetermined reference threshold value,
a controller for controlling the internal combustion engine and the generator;
The controller:
A vehicle control device characterized in that, when at least one of the following conditions is met: the amount of power used by the power storage device during a specified driving period is equal to or less than a predetermined amount of power used, and the amount of power charged to the power storage device during the specified driving period is equal to or greater than a predetermined amount of power charged, the vehicle control device switches a remaining charge amount of the power storage device, which is used to determine whether to start the internal combustion engine, to a value lower than the reference threshold value.

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