Vehicle control device

Abstract

To provide a vehicle control device that can extend the engine stop time and improve fuel economy.SOLUTION: A vehicle includes: an Integrated Starter Generator (ISG) 4 that generates electricity using driving force of an engine 2; a first battery 5 and a second battery 6 that store electricity generated by the ISG 4; a first electrical load 8 that operates using electric power received from the first battery 5; and a control unit that automatically stops the engine 2 when predetermined automatic stop conditions are satisfied, and restarts the engine 2 when predetermined restart conditions are satisfied while the engine 2 is automatically stopped. When a charge level of the first battery 5 falls to a first predetermined value or less while the engine 2 is automatically stopped, if a charge level of the second battery 6 exceeds a second predetermined value, the control unit performs control to supply electric power from the second battery 6 to the first electrical load 8 while the engine 2 remains stopped.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device. [Background technology]

[0002] Patent Document 1 proposes a technology that includes a first battery and a second battery with different characteristics, a connection switch that forms one of two connection states: a first connection state in which the first battery and the second battery are connected in parallel to two types of electrical loads, or a second connection state in which the parallel connection is disconnected so that the battery is connected to one of the electrical loads and the second battery is connected to the other electrical load, and a connection switch control unit that controls the connection state of the connection switch, where the connection switch control unit sets the connection switch to the second connection state while the vehicle is in an EV driving mode in which it can run using power output by the motor generator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-128163 Summary of the Invention [Problem to be solved by the invention]

[0004] However, while the conventional technology described above can extend the engine stop time and improve fuel economy by extending the time spent in EV driving mode, there has been a demand for further extending the engine stop time to improve fuel economy.

[0005] The present invention has been made to solve the above-mentioned problems, and has an object to provide a vehicle control device that can extend the engine stop time and improve fuel efficiency. [Means for solving the problem]

[0006] The vehicle control device of the present invention is a vehicle control device provided with an engine that generates driving force to run the vehicle, a generator that generates electricity using the driving force of the engine, a first battery that stores the electricity generated by the generator, a second battery that stores the electricity generated by the generator, an electrical load that operates using electricity supplied from the first battery, and a control unit that automatically stops the engine when a predetermined automatic stop condition is met, and restarts the engine when a predetermined restart condition is met while the engine is automatically stopped, and is configured to control the engine to supply electricity from the second battery to the electrical load while keeping the engine stopped if the charge level of the first battery drops below a first predetermined value during the automatic stop of the engine, while the charge level of the second battery exceeds a second predetermined value. [Effects of the Invention]

[0007] The present invention can provide a vehicle control device that can extend the engine stop time and improve fuel economy. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a vehicle equipped with a vehicle control device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram of a control circuit of a vehicle equipped with a vehicle control device according to an embodiment of the present invention. [Figure 3] FIG. 3 is a flowchart showing the power control operation of the vehicle control device according to one embodiment of the present invention. [Figure 4] FIG. 4 is a timing diagram showing an example of the state of each part when the power control operation of the vehicle control device according to the embodiment of the present invention is executed. DETAILED DESCRIPTION OF THE INVENTION

[0009] A vehicle control device according to one embodiment of the present invention includes an engine that generates driving force for propelling the vehicle, a generator that generates electricity using the driving force of the engine, a first battery that stores the electricity generated by the generator, a second battery that stores the electricity generated by the generator, an electric load that operates using power supplied from the first battery, and a control unit that automatically stops the engine when a predetermined automatic stop condition is met and restarts the engine when a predetermined restart condition is met while the engine is automatically stopped, wherein when the charge level of the first battery falls below a first predetermined value while the charge level of the second battery exceeds a second predetermined value, the control unit controls the engine to supply power to the electric load from the second battery while keeping the engine stopped. This allows the vehicle control device according to the embodiment of the present invention to extend the engine stop time and improve fuel efficiency. [Example]

[0010] A vehicle equipped with a vehicle control device according to an embodiment of the present invention will be described below with reference to the drawings.

[0011] As shown in FIG. 1, the vehicle 1 is configured to include an engine 2, a transmission 3, an ISG (Integrated Starter Generator) 4, a first battery 5, a second battery 6, an electric load switching device (hereinafter simply referred to as "SW") 7, a first electric load 8, a second electric load 9, a high-voltage battery 10, a motor generator (hereinafter simply referred to as "MG") 11, an inverter (hereinafter simply referred to as "INV") 12, and drive wheels 13.

[0012] The engine 2 is formed with a plurality of cylinders. In this embodiment, the engine 2 generates power by performing a series of four strokes for each cylinder, which are an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.

[0013] The transmission 3 changes the speed of the power generated by the engine 2. In this embodiment, the transmission 3 is configured as an AMT (Automated Manual Transmission). However, the transmission 3 may be configured as another transmission such as a CVT (Continuously Variable Transmission), an AT (Automatic Transmission), a DCT (Dual-Clutch Transmissions), or an AGS (Auto Gear Shift). The power that has been changed in speed by the transmission 3 is transmitted to drive wheels 13.

[0014] The ISG4 is connected to the crankshaft of the engine 2. The ISG4 functions as an electric motor that rotates when power is supplied from the first battery 5 to rotate the engine 2, and also functions as a generator that converts the rotational force input from the crankshaft by the drive of the engine 2 into electric power. The ISG4 starts the engine 2 by functioning as an electric motor. The ISG4 charges the first battery 5 and the second battery 6 by functioning as a generator.

[0015] The first battery 5 stores the power generated by the ISG 4. The first battery 5 is configured as a rechargeable secondary battery. In this embodiment, the first battery 5 is configured as a lead battery. The second battery 6 stores the power generated by the ISG 4. The second battery 6 is configured as a rechargeable secondary battery. In this embodiment, the second battery 6 is configured as an alkaline storage battery such as a lithium ion battery or a nickel-metal hydride storage battery.

[0016] SW7 connects either the first battery 5 or the second battery 6 to the first electrical load 8. In normal operation, SW7 connects the first battery 5 to the first electrical load 8. That is, in normal operation, the first battery 5 supplies power to the first electrical load 8, and the second battery 6 supplies power to the second electrical load 9. When SW7 connects the second battery 6 to the first electrical load 8, the second battery 6 supplies power to the first electrical load 8 and the second electrical load 9.

[0017] The first electrical loads 8 are general loads that are used temporarily and do not require a stable power supply compared to the second electrical loads 9. The first electrical loads 8 include an electric compressor for an air conditioner and an electric pump that circulates the coolant for the engine 2.

[0018] The second electric load 9 is a protected load that requires a constant stable power supply. For example, the second electric load 9 includes a headlight, lamps and meters provided on an instrument panel, a car navigation system, and the like.

[0019] The high-voltage battery 10 stores the power generated by the MG 11. The high-voltage battery 10 is configured as a rechargeable secondary battery. In this embodiment, the high-voltage battery 10 is configured as an alkaline storage battery such as a lithium-ion battery or a nickel-metal hydride storage battery.

[0020] The MG11 is connected to the high-voltage battery 10 via the INV12. The MG11 functions as an electric motor that rotates when power is supplied from the high-voltage battery 10 to generate power that is transmitted to the drive wheels 13, and also functions as a generator that converts the rotational force transmitted from the drive wheels 13 into electric power. The MG11 drives the vehicle 1 by functioning as an electric motor. The MG11 charges the high-voltage battery 10 by functioning as a generator.

[0021] 2, the vehicle 1 further includes an ECU (Electronic Control Unit) 14. The ECU 14 is a computer unit including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory for storing backup data, and the like, an input port, and an output port.

[0022] The ROM of this computer unit stores various constants, various maps, etc., as well as a program for causing the computer unit to function as the ECU 14. That is, the CPU executes the program stored in the ROM using the RAM as a work area, causing the computer unit to function as the ECU 14 in this embodiment.

[0023] Various sensors are connected to the input port of the ECU 14, including a first battery sensor 21 that detects the charge / discharge current and terminal voltage of the first battery 5, a second battery sensor 22 that detects the charge / discharge current and terminal voltage of the second battery 6, a vehicle speed sensor 23 that detects the vehicle speed, and a brake stroke sensor 24 that detects the amount of brake pedal operation (hereinafter simply referred to as the "brake stroke").

[0024] The output port of the ECU 14 is connected to various control objects including the ISG 4, the SW 7, the INV 12, an injector 26 that injects fuel into the engine 2, and an ignition plug 27 that ignites fuel in the combustion chamber of the engine 2. The ECU 14 controls the various control objects connected to the output port based on information obtained from various sensors connected to the input port.

[0025] The ECU 14 functions as a control unit 30 that automatically stops the engine 2 when predetermined automatic stop conditions are met, and restarts the engine 2 when predetermined restart conditions are met while the engine 2 is automatically stopped.

[0026] In this embodiment, when the engine 2 is in operation, the ECU 14 determines that the automatic stop condition is met when the vehicle speed detected by the vehicle speed sensor 23 is 0 and the brake stroke detected by the brake stroke sensor 24 is equal to or greater than a predetermined amount.

[0027] When it is determined that the automatic stop condition is met, the ECU 14 automatically stops the engine 2 by stopping the injection of fuel by the injector 26 and the ignition of the spark plug 27. When the brake stroke detected by the brake stroke sensor 24 becomes less than a predetermined amount while the engine 2 is automatically stopped, the ECU 14 determines that the restart condition is met.

[0028] When it is determined that the restart conditions are met, the ECU 14 causes the ISG 4 to rotate the crankshaft of the engine 2, and then restarts the engine 2 by starting the supply of fuel by the injector 26 and the ignition of the spark plug 27.

[0029] The ECU 14 switches the driving state of the vehicle 1 between HEV driving, in which the vehicle 1 is driven using at least the driving force generated by the engine 2, and EV driving, in which the vehicle 1 is driven using only the driving force generated by the MG 11.

[0030] When HEV driving is selected by ECU 14, vehicle 1 may be driven only by the driving force generated by engine 2, or vehicle 1 may be driven by both the driving force generated by engine 2 and the driving force generated by MG11.

[0031] In this embodiment, the ECU 14 determines that the automatic stop condition for the engine 2 is satisfied when the driving state of the vehicle 1 is switched from HEV driving to EV driving. Also, the ECU 14 determines that the restart condition for the engine 2 is satisfied when the driving state of the vehicle 1 is switched from EV driving to HEV driving.

[0032] When the charge amount of the first battery 5 falls below a first predetermined value TH1 during automatic stop of the engine 2, if the charge amount of the second battery 6 exceeds a second predetermined value TH2, the ECU 14 controls the SW7 to supply power from the second battery 6 to the first electric load 8 while keeping the engine 2 stopped, and to disconnect the first battery 5 from the first electric load 8.

[0033] The ECU 14 calculates the charge amount of the first battery 5 from the detection result of the first battery sensor 21. The first predetermined value TH1 is set to a value at which it is determined that the charge amount of the first battery 5 is insufficient. The ECU 14 calculates the charge amount of the second battery 6 from the detection result of the second battery sensor 22. The second predetermined value TH2 is set to a value at which it is determined that the charge amount of the second battery 6 is insufficient.

[0034] When the charge level of the second battery 6 falls below a second predetermined value TH2 while the engine 2 is stopped and power is being supplied from the second battery 6 to the first electrical load 8, the ECU 14 controls the ISG 4, the injector 26, and the spark plug 27 to restart the engine 2 and charge the first battery 5 and the second battery 6.

[0035] The power control operation by the ECU 14 configured as above will be described with reference to Fig. 3. The power control operation described below is repeatedly executed during the period in which the engine 2 is automatically stopped.

[0036] First, in S1, the ECU 14 determines whether the charge amount of the first battery 5 is equal to or less than a first predetermined value TH1. If it is determined in S1 that the charge amount of the first battery 5 is equal to or less than the first predetermined value TH1, the ECU 14 executes the process of S2. If it is determined in S1 that the charge amount of the first battery 5 is not equal to or less than the first predetermined value TH1, the ECU 14 ends the power control operation.

[0037] In S2, the ECU 14 determines whether the charge amount of the second battery 6 exceeds a second predetermined value TH2. If it is determined in S2 that the charge amount of the second battery 6 exceeds the second predetermined value TH2, the ECU 14 executes the process of S3. If it is determined in S2 that the charge amount of the second battery 6 does not exceed the second predetermined value TH2, the ECU 14 executes the process of S4.

[0038] In S3, if the second battery 6 is not connected to the first electric load 8, the ECU 14 controls the SW7 to connect the second battery 6 to the first electric load 8 while keeping the engine 2 stopped. After executing the process of S3, the ECU 14 executes the process of S2.

[0039] In S4, the ECU 14 controls the ISG 4, the injector 26, and the spark plug 27 to restart the engine 2 and charge the first battery 5 and the second battery 6. After executing the process of S4, the ECU 14 ends the power control operation.

[0040] The effect of the power control operation executed by the ECU 14 described above will be described with reference to Fig. 4. Fig. 4 shows, from top to bottom, an example of the operating state of the engine 2, the charge amount of the first battery 5, and the charge amount of the second battery 6 in chronological order.

[0041] During the period when the engine 2 is automatically stopped, the electricity stored in the first battery 5 and the second battery 6 is consumed by the first electrical load 8 and the second electrical load 9, respectively, and the charge amount of the first battery 5 and the charge amount of the second battery 6 decrease over time.

[0042] At time t1, the charge amount of the second battery 6 exceeds the second predetermined value TH2, so when the charge amount of the first battery 5 falls below the first predetermined value TH1, the engine 2 remains automatically stopped while power is supplied from the second battery 6 to the first electrical load 8, and the connection between the first battery 5 and the first electrical load 8 is cut off.

[0043] As a result, the charge level of the first battery 5 is maintained, and the power stored in the second battery 6 is consumed by the first electrical load 8 and the second electrical load 9, so the charge level of the second battery 6 continues to decrease over time.

[0044] At time t2, when the charge amount of the second battery 6 becomes equal to or less than the second predetermined value TH2, the engine 2 is restarted to charge the first battery 5 and the second battery 6, and the charge amount of the first battery 5 and the charge amount of the second battery 6 increase over time.

[0045] Thus, compared to the conventional technology in which charging of the first battery 5 must be started at time t1, in this embodiment, the stop time of the engine 2 is extended until time t2, and fuel efficiency is improved by the amount of the extended stop time of the engine 2, i.e., time t2 - time t1.

[0046] As described above, when the charge amount of the first battery 5 falls below the first predetermined value TH during automatic stop of the engine 2, if the charge amount of the second battery 6 exceeds the second predetermined value TH2, the vehicle control device of this embodiment supplies power from the second battery 6 to the first electrical load 8 while keeping the engine 2 stopped, thereby extending the stop time of the engine 2 and improving fuel efficiency.

[0047] Furthermore, in the vehicle control device of this embodiment, when the charge level of the second battery 6 drops below the second predetermined value TH2 while the engine 2 is stopped and power is being supplied from the second battery 6 to the first electrical load 8, the vehicle control device restarts the engine 2 to charge the first battery 5 and the second battery 6, thereby maintaining the first battery 5 and the second battery 6 within a normal charge level range.

[0048] Furthermore, when supplying power from the second battery 6 to the first electrical load 8 while the engine 2 is stopped, the vehicle control device according to this embodiment disconnects the first battery 5 from the first electrical load 8, thereby preventing the second battery 6 from discharging to the first battery 5. Therefore, the vehicle control device according to this embodiment suppresses discharging of the second battery 6, thereby extending the stop time of the engine 2 and improving fuel efficiency.

[0049] In this embodiment, an example has been described in which the first battery 5 is composed of a lead battery and the second battery 6 is composed of an alkaline storage battery, but the first battery 5 and the second battery 6 may each be composed of a secondary battery of another type.

[0050] In addition, in this embodiment, an example has been described in which, while the engine 2 is stopped and power is being supplied from the second battery 6 to the first electrical load 8, if the charge amount of the second battery 6 falls below the second predetermined value TH2, the ECU 14 restarts the engine 2 to charge the first battery 5 and the second battery 6.

[0051] In contrast, when the charge amount of the second battery 6 falls below a second predetermined value TH2 while the engine 2 is stopped and power is being supplied from the second battery 6 to the first electrical load 8, the ECU 14 may restart the engine 2 and charge either the first battery 5 or the second battery 6.

[0052] In addition, in this embodiment, an example has been described in which the ECU 14 determines the timing to switch the connection of SW7 and the timing to restart the engine 2 based on the results of comparing the charge amount of the first battery 5 with a first predetermined value TH1 and the results of comparing the charge amount of the second battery 6 with a second predetermined value TH2.

[0053] In response to this, the ECU 14 may determine the timing for switching the connection of SW7 and the timing for restarting the engine 2 based on the results of comparing the terminal voltage of the first battery 5 with the first predetermined voltage V1 and the results of comparing the terminal voltage of the second battery 6 with the second predetermined voltage V2.

[0054] Specifically, when the terminal voltage of the first battery 5 drops below a first predetermined voltage V1 during automatic stop of the engine 2, if the terminal voltage of the second battery 6 exceeds a second predetermined voltage V2, the ECU 14 may control SW7 to supply power from the second battery 6 to the first electrical load 8 while keeping the engine 2 stopped, and to disconnect the first battery 5 from the first electrical load 8.

[0055] In addition, when the voltage between the terminals of the second battery 6 drops below a second predetermined voltage V2 while the engine 2 is stopped and power is being supplied from the second battery 6 to the first electrical load 8, the ECU 14 may control the ISG 4, the injector 26, and the spark plug 27 to restart the engine 2 and charge the first battery 5 and the second battery 6.

[0056] While the present invention has been described with reference to an embodiment thereof, it will be apparent that modifications may be made thereto without departing from the scope of the present invention, and the present invention is disclosed with the understanding that equivalents of such modifications are intended to be encompassed within the scope of the appended claims. [Explanation of symbols]

[0057] 1 vehicle 2 engines 4 ISG (generator) 5. First Battery 6 Second Battery 8. First Electrical Load (Electrical Load) 30 Control Unit

Claims

1. an engine that generates driving force to run the vehicle; a generator that generates electricity using the driving force of the engine; a first battery that stores the electric power generated by the generator; a second battery that stores the electric power generated by the generator; an electric load that operates by receiving power from the first battery; a control unit that automatically stops the engine when a predetermined automatic stop condition is met, and restarts the engine when a predetermined restart condition is met while the engine is automatically stopped; A vehicle control device provided with a control unit for controlling a vehicle, the control unit controlling the engine to supply power from the second battery to the electrical load while the engine is stopped, when the charge amount of the first battery falls below a first predetermined value while the charge amount of the second battery exceeds a second predetermined value.

2. The control unit 2. The vehicle control device according to claim 1, wherein, when the charge amount of the second battery falls below the second predetermined value while the engine is stopped and power is being supplied from the second battery to the electrical load, the vehicle control device controls the engine to restart and charge at least one of the first battery and the second battery.

3. The control unit 3. The vehicle control device according to claim 2, wherein when power is supplied from the second battery to the electrical load while the engine is stopped, the control device controls so as to disconnect the first battery from the electrical load.

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