Control system for hybrid vehicles

Abstract

To provide a control device for hybrid vehicles that can further reduce the fuel consumption rate of the engine. [Solution] A control device for a hybrid vehicle equipped with an idle stop prohibition switch that allows the driver to select whether or not to prohibit the execution of idle stop control, wherein when the idle stop prohibition switch is ON, the range in which motor operation is permitted is wider than when the idle stop prohibition switch is OFF.

Description

Technical Field

[0001] The present invention relates to a control device for a hybrid vehicle.

Background Art

[0002] Conventionally, as driving modes, an engine mode in which the driving force of an engine is transmitted to wheels and an assist mode in which the driving forces of an engine and a motor generator are transmitted to wheels are provided. When the state of charge of a lithium-ion battery is low, a vehicle control device that secures power for engine restart and avoids restrictions on idling stop control due to power shortage by reducing the execution frequency of the assist mode has been proposed in Patent Document 1.

[0003] In Patent Document 1, it has been proposed that fuel can be reduced and the fuel consumption performance of a vehicle can be improved by actively executing the assist mode even in a driving situation where the fuel reduction effect is small. Further, conventionally, a vehicle provided with a switch (hereinafter referred to as an "IS prohibition switch") that prohibits the execution of idling stop control is known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, with the conventional technology described above, even if the IS disable switch is used to disable idle stop control, power for restarting the engine is still secured in the lithium-ion battery. Therefore, even though there is no need to reduce the frequency of assist mode execution, the frequency of assist mode execution, which contributes to improved fuel efficiency, is reduced. For this reason, conventional technology had the problem that there was room to further reduce the engine's fuel consumption rate.

[0006] This invention was made to solve the above-mentioned problems and aims to provide a control device for a hybrid vehicle that can further reduce the fuel consumption rate of the engine. [Means for solving the problem]

[0007] The control device for a hybrid vehicle according to the present invention controls a hybrid vehicle equipped with an engine, a motor linked to the engine, a battery that exchanges power with the motor, a control unit that performs idle stop control which automatically stops the engine when predetermined automatic stop conditions are met and restarts the engine when predetermined restart conditions are met while the engine is automatically stopped, and an idle stop prohibition switch which allows the user to select whether or not to prohibit the execution of the idle stop control, wherein when the idle stop prohibition switch is ON, the range in which the motor is permitted to be driven is wider than when the idle stop prohibition switch is OFF. [Effects of the Invention]

[0008] The present invention can provide a control device for a hybrid vehicle that can further reduce the fuel consumption rate of the engine. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram of a vehicle equipped with a control device for a hybrid vehicle according to one embodiment of the present invention. [Figure 2] Figure 2 is a conceptual diagram showing a first correction map and a second correction map referenced by a control device of a hybrid vehicle according to one embodiment of the present invention. [Figure 3] Figure 3 is a conceptual diagram showing a first auxiliary map and a second auxiliary map referenced by a control device of a hybrid vehicle according to one embodiment of the present invention. [Figure 4] Figure 4 is a flowchart showing the map selection operation of a control device for a hybrid vehicle according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] A control device for a hybrid vehicle according to one embodiment of the present invention controls a hybrid vehicle equipped with an engine, a motor linked to the engine, a battery that exchanges power between the motor and the engine, a control unit that performs idle stop control which automatically stops the engine when predetermined automatic stop conditions are met and restarts the engine when predetermined restart conditions are met while the engine is automatically stopped, and an idle stop prohibition switch which allows the user to select whether or not to prohibit the execution of idle stop control. The control device for a hybrid vehicle according to one embodiment of the present invention is characterized in that when the idle stop prohibition switch is ON, the range in which the motor is permitted to be driven is wider than when the idle stop prohibition switch is OFF. As a result, the control device for a hybrid vehicle according to one embodiment of the present invention can further reduce the fuel consumption rate of the engine. [Examples]

[0011] Hereinafter, a hybrid vehicle equipped with a control device for a hybrid vehicle according to one embodiment of the present invention will be described with reference to the drawings.

[0012] As shown in Figure 1, the hybrid vehicle 1 consists of an engine 2, a transmission 3, a clutch 4, drive wheels 5, an ISG (Integrated Starter Generator) 6, a battery 7, and an ECU (Electronic Control Unit) 8.

[0013] Engine 2 has multiple cylinders. In this embodiment, engine 2 generates power by performing a series of four strokes for each cylinder, consisting of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.

[0014] In this embodiment, the transmission 3 is configured as a normally meshing AMT (Automated Manual Transmission) consisting of a parallel shaft gear mechanism. Alternatively, the transmission 3 may be configured as another type of transmission, such as a DCT (Dual-Clutch Transmission).

[0015] The clutch 4 is located in the power transmission path between the engine 2 and the transmission 3. The clutch 4 connects or disconnects the engine 2 and the drive wheels 5 by connecting or disconnecting the power transmission path from the engine 2 to the transmission 3.

[0016] The ISG6 is configured to work in conjunction with the crankshaft of engine 2. The ISG6 has the function of an electric motor that rotates when power is supplied and outputs driving force to the crankshaft of engine 2, and the function of a generator that converts the rotational force input from the crankshaft into electricity. In this embodiment, the ISG6 constitutes a motor.

[0017] Battery 7 is composed of a rechargeable secondary battery, such as a lithium-ion battery. Battery 7 exchanges power with ISG 6. That is, Battery 7 stores the power generated by ISG 6 and supplies power to drive ISG 6.

[0018] The ECU8 is composed of 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.

[0019] In the ROM of this computer unit, a program for making the computer unit function as the ECU8 is stored together with various constants and various maps. That is, when the CPU executes the program stored in the ROM using the RAM as a working area, this computer unit functions as the ECU8 in the present embodiment.

[0020] Connected to the input port of the ECU8 are various sensors including a vehicle speed sensor 11 for detecting the vehicle speed, an accelerator opening sensor 12 for detecting the operation amount of the accelerator pedal (hereinafter also simply referred to as "accelerator opening"), a brake stroke sensor 13 for detecting the operation amount of the brake pedal (hereinafter also simply referred to as "brake stroke"), a battery sensor 14 for detecting the state of the battery 7 such as the charge and discharge current of the battery 7 and the voltage between the terminals of the battery 7, and an idling stop prohibition switch 15.

[0021] Connected to the output port of the ECU8 are various controlled objects including the ISG6, an injector 21 for supplying fuel to the engine 2, and a spark plug 22 for igniting in the combustion chamber of the engine 2. When the engine 2 is constituted by an engine that does not require a spark plug such as a diesel engine, the spark plug 22 is removed from the configuration of the hybrid vehicle 1.

[0022] The ECU8 controls various control targets connected to the output port based on information obtained from various sensors connected to the input port. In this embodiment, the ECU8 functions as a control unit 30 that performs idle stop control, which 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.

[0023] The idle stop disable switch 15 is a switch that allows the driver and other occupants to select whether or not to disable the idle stop control performed by the control unit 30. In this embodiment, the idle stop disable switch 15 is provided on the instrument panel of the hybrid vehicle 1.

[0024] If the idle stop disable switch 15 is OFF, the ECU 8 determines that the automatic stop condition is met when the vehicle speed detected by the vehicle speed sensor 11 is below a predetermined vehicle speed and the brake stroke detected by the brake stroke sensor 13 is above a predetermined amount, while the engine 2 is running.

[0025] When the ECU 8 determines that the automatic stop condition has been met, it automatically stops the engine 2 by stopping fuel injection by the injector 21 and ignition by the spark plug 22. With the engine 2 automatically stopped, the ECU 8 determines that the restart condition has been met when the brake stroke detected by the brake stroke sensor 13 falls below a predetermined amount.

[0026] When the ECU 8 determines that the restart conditions have been met, it restarts the engine 2 by rotating the crankshaft of the engine 2 with the ISG 6, then starting the fuel supply by the injector 21 and igniting the spark plug 22. The automatic stop and restart conditions described above are examples only and are not limited to these.

[0027] (Operating point correction control) The ECU8 can perform operating point correction control, which uses the ISG6 to correct the operating point of engine 2 so that the fuel consumption rate of engine 2 is reduced. The operating point of engine 2 is represented by the torque output by engine 2 and the rotational speed of engine 2.

[0028] The ECU8 prohibits the execution of operating point correction control if the accelerator opening detected by the accelerator opening sensor 12 is greater than or equal to a predetermined value, and allows the execution of operating point correction control if the accelerator opening detected by the accelerator opening sensor 12 is not greater than or equal to a predetermined value.

[0029] If the torque output by the engine 2, which is operating at an operating point with a low fuel consumption rate, is insufficient to meet the required torque corresponding to the accelerator opening detected by the accelerator opening sensor 12, the ECU 8 performs operating point correction control by having the ISG 6 output the insufficient torque.

[0030] If the torque output by engine 2, which is operating at an operating point with a low fuel consumption rate, is excessive for the required torque, ECU8 performs operating point correction control by converting the excess torque into electricity using ISG6.

[0031] As shown in Figure 2, the ROM of the ECU8 stores a first correction map and a second correction map that represent the range of torque that can be corrected by the ISG6 with respect to the charge level of the battery 7 (hereinafter also simply referred to as "SOC").

[0032] In Figure 2, the first correction map is referenced by the ECU 8 when the idle stop disable switch 15 is OFF, and the range in which correction is permitted by the ISG 6 is indicated by reference numeral 41.

[0033] In this embodiment, the second correction map is shown superimposed on the first correction map for easier understanding of the invention, but it is stored separately in ROM. The second correction map is referenced by the ECU 8 when the idle stop disable switch 15 is ON, and the torque range for which correction by the ISG 6 is permitted is set to be wider, including the range indicated by reference numeral 42 in addition to the range indicated by reference numeral 41.

[0034] Thus, when the idle stop disable switch 15 is ON, the ECU 8 widens the range in which correction by operating point correction control is permitted, that is, the range in which the ISG 6 is permitted to be driven in the operating point correction control, compared to when the idle stop disable switch 15 is OFF.

[0035] (Drive assist control) The ECU8 can perform drive assist control to assist the engine 2 by driving the ISG6 in order to output driving force in response to acceleration requests. The ECU8 permits the execution of drive assist control if the accelerator opening detected by the accelerator opening sensor 12 is equal to or greater than a predetermined value, and prohibits the execution of drive assist control if the accelerator opening detected by the accelerator opening sensor 12 is not equal to or greater than a predetermined value.

[0036] If the torque output by the engine 2 is insufficient to meet the required torque according to the accelerator opening detected by the accelerator opening sensor 12, the ECU 8 performs drive assistance control by having the ISG 6 output the insufficient torque.

[0037] As shown in Figure 3, the ROM of the ECU8 stores a first auxiliary map and a second auxiliary map that represent the torque range for which assistance by the ISG6 is permitted for the SOC of the battery 7.

[0038] In Figure 3, the first auxiliary map is referenced by the ECU 8 when the idle stop disable switch 15 is OFF, and the range in which the ISG 6 allows assistance is indicated by reference numeral 43.

[0039] In this embodiment, the second auxiliary map is shown superimposed on the first auxiliary map for easier understanding of the invention, but it is stored separately in ROM. The second auxiliary map is referenced by the ECU 8 when the idle stop disable switch 15 is ON, and the torque range for which assistance is permitted by the ISG 6 is set to be wider than the range indicated by reference numeral 43, extending to the range indicated by reference numeral 44.

[0040] Thus, when the idle stop disable switch 15 is ON, the ECU 8 widens the range in which assistance by drive assist control is permitted, that is, the range in which the ISG 6 is permitted to be driven in the drive assist control, compared to when the idle stop disable switch 15 is OFF.

[0041] The map selection operation of the ECU8 configured as described above will be explained with reference to Figure 4. Note that the map selection operation described below will be repeatedly executed throughout the period that the ECU8 is operating.

[0042] First, in S1, the ECU8 determines whether the idle stop disable switch 15 (indicated as "IS disable SW" in the diagram) is ON or OFF. If the ECU8 determines in S1 that the idle stop disable switch 15 is ON, it executes the process in S2. If the ECU8 determines in S1 that the idle stop disable switch 15 is NOT ON, it executes the process in S4.

[0043] In S2, ECU8 selects a second correction map as the map to refer to when performing operating point correction control. After executing the process in S2, ECU8 executes the process in S3.

[0044] In S3, ECU8 selects the second auxiliary map as the map to refer to when performing drive assist control. After executing the process in S3, ECU8 terminates the map selection operation.

[0045] In S4, ECU8 selects the first correction map as the map to refer to when performing operating point correction control. After executing the process in S4, ECU8 executes the process in S5.

[0046] In S5, ECU8 selects the first auxiliary map as the map to refer to when performing drive assist control. After executing the process in S5, ECU8 terminates the map selection operation.

[0047] As described above, the control device for the hybrid vehicle according to this embodiment can further reduce the fuel consumption rate of the engine 2 when the idle stop prohibition switch 15 is ON, by widening the range in which correction by operating point correction control is permitted compared to when the idle stop prohibition switch 15 is OFF.

[0048] Furthermore, the control device for the hybrid vehicle according to this embodiment widens the range in which assistance by drive assist control is permitted when the idle stop prohibition switch 15 is ON compared to when the idle stop prohibition switch 15 is OFF. This increases the frequency with which the ISG 6 is driven when the hybrid vehicle 1 is accelerated with the idle stop prohibition switch 15 ON, thereby improving drivability.

[0049] In this embodiment, when the restart conditions are determined to be met, the ECU 8 restarts the engine 2 by rotating the crankshaft of the engine 2 with the ISG 6, and then starting the fuel supply by the injector 21 and the ignition of the spark plug 22.

[0050] Similarly, when starting the engine 2, the ECU 8 may start the engine 2 by first rotating the crankshaft of the engine 2 with the ISG 6, and then initiating the fuel supply by the injector 21 and the ignition of the spark plug 22.

[0051] Alternatively, the hybrid vehicle 1 may be further equipped with a starter motor, and the ECU 8 may start the engine 2 by first rotating the crankshaft of the engine 2 with the starter motor, and then initiating the fuel supply by the injector 21 and the ignition of the spark plug 22.

[0052] Alternatively, the ECU8 may be configured to reset the idle stop disable switch 15 to OFF during the initialization process when the ECU8 starts up, or it may be configured to store the state of the idle stop disable switch 15 in flash memory and reproduce the state of the idle stop disable switch 15 during the initialization process of the ECU8.

[0053] Although embodiments of the present invention have been disclosed above, it is clear that modifications can be made to these embodiments without departing from the scope of the present invention. The embodiments of the present invention are disclosed on the premise that equivalents with such modifications are included in the invention described in the claims. [Explanation of Symbols]

[0054] 1. Hybrid vehicle 2 engines 6 ISG (Motor) 7 Batteries 15. Idling stop disable switch 30 Control Unit

Claims

1. The engine and A motor that works in conjunction with the aforementioned engine, A battery that exchanges power with the motor, A control unit that performs idle stop control, which automatically stops the engine when predetermined automatic stop conditions are met, and restarts the engine when predetermined restart conditions are met while the engine is automatically stopped, A control device for a hybrid vehicle that controls a hybrid vehicle equipped with an idle stop prohibition switch that allows the user to select whether or not to prohibit the execution of the idle stop control, A control device for a hybrid vehicle that, when the idle stop prohibition switch is ON, widens the range in which the motor is permitted to operate compared to when the idle stop prohibition switch is OFF.

2. The control unit, The motor can perform operating point correction control to correct the operating point of the engine so that the fuel consumption rate of the engine is reduced. The control device for a hybrid vehicle according to claim 1, wherein when the idle stop prohibition switch is ON, the range in which correction by the operating point correction control is permitted is wider than when the idle stop prohibition switch is OFF.

3. The control unit, In order to output a driving force in response to an acceleration request, it is possible to perform drive assist control that assists the engine's drive by driving the motor, A control device for a hybrid vehicle according to claim 1 or 2, wherein when the idle stop prohibition switch is ON, the range in which assistance by the drive assist control is permitted is wider than when the idle stop prohibition switch is OFF.

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