Control device for hybrid vehicle

Abstract

To provide a control device for a hybrid vehicle which is resistant to a decrease in fuel efficiency.SOLUTION: The present invention provides a control device for a hybrid vehicle including an engine and a motor as driving power sources, the control device comprising: a switching unit that switches to hybrid traveling in which the vehicle travels by power of the engine when a required driving force for the hybrid vehicle is equal to or greater than a switching value, and switches to motor traveling in which the vehicle travels by power of the motor when the required driving force is less than the switching value; an acquisition unit that acquires a temperature of the engine; and a setting unit that sets the switching value to a larger value as the temperature of the engine becomes lower.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] There is a technique for controlling the fuel injection amount and the like based on the temperature of the engine (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A hybrid vehicle equipped with such an engine and a motor as a driving power source is known. When hybrid driving is performed by the power of the engine when the temperature of the engine is low, the efficiency of the engine may decrease and the fuel consumption may decrease.

[0005] Therefore, an object of the present invention is to provide a control device for a hybrid vehicle that suppresses a decrease in fuel consumption.

Means for Solving the Problems

[0006] The above object can be achieved by a control device for a hybrid vehicle including an engine and a motor as a driving power source, the control device including: a switching unit configured to switch to hybrid driving in which the vehicle travels by the power of the engine when a required driving force applied to the hybrid vehicle is equal to or greater than a switching value, and to switch to motor driving in which the vehicle travels by the power of the motor when the required driving force is less than the switching value; an acquisition unit configured to acquire the temperature of the engine; and a setting unit configured to set the switching value to a larger value as the temperature of the engine is lower.

[0007] The acquisition unit acquires the charge amount of the battery that is the power source of the motor, and the higher the charge amount of the battery, the setting unit may set the switching value to a larger value.

[0008] The acquisition unit acquires the vehicle speed of the hybrid vehicle, and the lower the vehicle speed, the setting unit may set the switching value to a larger value.

Effect of the Invention

[0009] According to the present invention, it is possible to provide a control device for a hybrid vehicle that suppresses a decrease in fuel consumption.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0011] [Schematic Configuration of Hybrid Vehicle] Figure 1 is a schematic configuration diagram of the hybrid vehicle 1 of this embodiment. The hybrid vehicle 1 includes an ECU (Electronic Control Unit) 100, an engine 10, a first motor generator (hereinafter referred to as "first MG (Motor Generator)") 14, a second motor generator (hereinafter referred to as "second MG") 15, a PCU (Power Control Unit) 17, a battery 18, a power split mechanism 50, a transmission mechanism 51, a transmission 52, a drive shaft 53, a differential gear 54, and drive wheels 55. The engine 10 has four cylinders in this embodiment. If the engine 10 has a plurality of cylinders, the number of cylinders is not limited to four. The engine 10 is a gasoline engine, but is not limited thereto and may be a diesel engine. The engine 10, the first MG 14, and the second MG 15 are the driving power sources for the running of the hybrid vehicle 1.

[0012] Each of the first MG 14 and the second MG 15 has a function as a motor that outputs torque by power supply and a function as a generator that generates regenerative power when torque is applied. The first MG 14 and the second MG 15 are electrically connected to the battery 18 via the PCU 17. The PCU 17 supplies power from the battery 18 to the first MG 14 or the second MG 15. That is, the battery 18 is the power source for the first MG 14 and the second MG 15. The PCU 17 causes the battery 18 to receive the regenerative power generated in the first MG 14 or the second MG 15.

[0013] The power split mechanism 50 mechanically connects the crankshaft of the engine 10, the rotation shaft of the first MG 14, and the output shaft of the power split mechanism 50. The output shaft of the power split mechanism 50 is connected to the transmission mechanism 51. The rotation shaft of the second MG 15 is connected to the transmission mechanism 51. The transmission mechanism 51 is connected to the transmission 52. The transmission 52 is connected to the drive shaft 53. The driving forces of the engine 10, the first MG 14, and the second MG 15 are transmitted to the drive wheels 55 via the transmission mechanism 51, the transmission 52, the drive shaft 53, and the differential gear 54.

[0014] The transmission 52 is a stepped automatic transmission provided between the second MG15 and the drive shaft 53. The transmission 52 changes the gear ratio under the control of the ECU 100.

[0015] The ECU 100 is an electronic control unit including an arithmetic processing circuit that performs various arithmetic processes related to the running control of the vehicle, and a memory that stores control programs and data. The ECU 100 is an example of a control device for a hybrid vehicle. The ECU 100 functionally realizes a switching unit, an acquisition unit, and a setting unit, which will be described later.

[0016] An ignition switch 71, an accelerator opening sensor 72, a vehicle speed sensor 73, a water temperature sensor 74, and a SOC (State Of Charge) sensor 75 are electrically connected to the ECU 100. The ignition switch 71 detects the on / off state of the ignition. The accelerator opening sensor 72 detects the operation position of the accelerator pedal. The vehicle speed sensor 73 detects the vehicle speed V of the hybrid vehicle 1. The water temperature sensor 74 detects the water temperature T, which is the temperature of the cooling water of the engine 10. Note that the water temperature T is an example of the temperature of the engine 10. Instead of the water temperature sensor 74, an oil temperature sensor that detects the temperature of the lubricating oil of the engine 10 may be provided. The SOC sensor 75 detects the SOC, which is the charge amount of the battery 18. Note that when the SOC sensor 75 is not provided, the ECU 100 may calculate the SOC based on the current value and voltage value of the battery 18.

[0017] [Running Switching Control] Figure 2 is a flowchart illustrating the running switching control. This control is repeatedly executed at a predetermined cycle when the ignition is on. The ECU 100 acquires the required driving force Pv, the vehicle speed V, the water temperature T, and the SOC (step S1). The required driving force Pv is calculated by the ECU 100 based on the accelerator opening, the driving state, and the like. The vehicle speed V, the water temperature T, and the SOC are acquired by the ECU 100 using the vehicle speed sensor 73, the water temperature sensor 74, and the SOC sensor 75, respectively. Step S1 is an example of the process executed by the acquisition unit.

[0018] Next, the ECU 100 sets a switching value Ps based on the vehicle speed V, the water temperature T, and the SOC, which will be described in detail later (step S2). Step S2 is an example of the process executed by the setting unit. Next, the ECU 100 determines whether the required driving force Pv is equal to or greater than the switching value Ps (step S3).

[0019] If the answer in step S3 is No, the ECU 100 performs motor driving (step S4). In motor driving, driving is performed with at least one of the first MG 14 and the second MG 15 as a power source while the engine 10 is stopped. In motor driving, the engine 10 stops. Thereby, the fuel consumption is improved.

[0020] If the answer in step S3 is Yes, the ECU 100 performs hybrid driving (step S5). In hybrid driving, the engine 10 drives and driving is performed with the engine 10 as a power source. Even when at least one of the first MG 14 and the second MG 15 and the engine 10 are used in combination, it is included in hybrid driving. In hybrid driving, the engine 10 drives. Therefore, the acceleration responsiveness is improved and drivability is ensured.

[0021] [Method for Setting the Switching Value Ps] The method for setting the switching value Ps will be described. FIGS. 3A and 3B are exemplary diagrams of a map defining the switching value Ps. In the maps of FIGS. 3A and 3B, the vertical axis represents the required driving force Pv and the horizontal axis represents the vehicle speed V. FIG. 3A shows the case where the SOC is constant and the water temperature T is low and the case where it is high. As shown in FIG. 3A, the lower the water temperature T, the larger the switching value Ps is set. In other words, the lower the water temperature T, the smaller the hybrid driving region becomes. Since the efficiency of the engine 10 decreases as the water temperature T decreases, the reduction in fuel consumption is suppressed by reducing the hybrid driving region.

[0022] FIG. 3B shows the case where the water temperature T is constant and the SOC is low and the case where it is high. As shown in FIG. 3B, the higher the SOC, the larger the switching value Ps is set. In other words, the higher the SOC, the larger the motor driving region becomes. Thereby, the driving frequency of the engine 10 is suppressed and the fuel consumption is improved.

[0023] When the vehicle speed is less than the speed v1, the switching value Ps is constant. When the vehicle speed is equal to or greater than the speed v1 and less than the speed v2, the switching value Ps increases as the vehicle speed decreases. When the vehicle speed is equal to or greater than the speed v2, the switching value Ps is constant. Thus, the lower the vehicle speed V, the larger the switching value Ps is set. Thereby, when the vehicle speed V is low, the driving frequency of the engine 10 is suppressed and the fuel efficiency is improved.

[0024] As described above in detail with respect to the embodiments of the present invention, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. [Explanation of Signs]

[0025] 1 Hybrid vehicle 10 Engine 14 First motor generator 15 Second motor generator 18 Battery 73 Vehicle speed sensor 74 Water temperature sensor 75 SOC sensor 100 ECU (control device, switching unit, acquisition unit, setting unit)

Claims

1. A control device for a hybrid vehicle equipped with an engine and a motor as a driving power source, a switching unit that switches to hybrid driving in which the vehicle travels by the power of the engine when the required driving force for the hybrid vehicle is equal to or greater than a switching value, and switches to motor driving in which the vehicle travels by the power of the motor when the required driving force is less than the switching value, an acquisition unit that acquires the temperature of the engine, and a setting unit that sets the switching value to a larger value as the temperature of the engine is lower. A control device for a hybrid vehicle comprising the same.

2. The acquisition unit acquires the charge amount of a battery that is a power source of the motor, and the setting unit sets the switching value to a larger value as the charge amount of the battery is higher. The control device for a hybrid vehicle according to Claim 1.

3. The acquisition unit acquires the vehicle speed of the hybrid vehicle, and the setting unit sets the switching value to a larger value as the vehicle speed is lower. The control device for a hybrid vehicle according to Claim 2.

Images