Control device for a hybrid vehicle

Abstract

To provide a control device of a hybrid vehicle which restrains an emission from deteriorating while restraining discomfort for a driver.SOLUTION: A control device is used for a hybrid vehicle that includes: an engine and a motor which are a power source for traveling; a gas sensor used for detecting prescribed component within exhaust gas of the engine and executing feedback control of combustion state of the engine; and a heater which activates the gas sensor. The control device of the hybrid vehicle comprises: a first start control part which starts the engine when an electric travel mode is selected as a travel mode, in which the vehicle stops the engine and travels by the motor and temperature of cooling water of the engine is below a first threshold value after; and a second start control part which starts the engine after activating the gas sensor by the heater when the electric travel mode is selected and the temperature of the cooling water is the first threshold value or more and is below the second threshold value higher than the first threshold value.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] In a hybrid vehicle equipped with an engine and a motor, it is possible to travel in an electric driving mode by the motor (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] When the engine is started due to an increase in the required output to the vehicle in the electric driving mode, the output of the engine is controlled to be a high output before the warm-up of the engine is completed, and there is a risk that emissions will deteriorate. Therefore, it is desirable to complete the warm-up of the engine in advance before the required output to the vehicle increases. However, if the engine is started to complete the warm-up of the engine uniformly while the electric driving mode is selected, the engine starts even though the electric driving mode is selected, which gives the driver a sense of discomfort.

[0005] Therefore, an object of the present invention is to provide a control device for a hybrid vehicle that suppresses deterioration of emissions while suppressing a sense of discomfort to the driver.

Means for Solving the Problems

[0006] The above object is achieved by a control device for a hybrid vehicle having an engine and a motor as driving power sources, a gas sensor used to detect a predetermined component in the exhaust gas of the engine and perform feedback control on the combustion state of the engine, and a heater for activating the gas sensor. When an electric driving mode in which the engine is stopped and the vehicle is driven by the motor is selected as the driving mode and the temperature of the cooling water of the engine is less than a first threshold value, there is a first start control unit for starting the engine. When the electric driving mode is selected and the temperature of the cooling water is greater than or equal to the first threshold value and less than a second threshold value that is higher than the first threshold value, there is a second start control unit for activating the gas sensor by the heater and then starting the engine. This can be achieved by a control device for a hybrid vehicle provided with the above components.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a control device for a hybrid vehicle that suppresses deterioration of emissions while suppressing discomfort to the driver.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0009] [Schematic Configuration of Hybrid Vehicle] Figure 1 is a schematic configuration diagram of the hybrid vehicle 1. In the hybrid vehicle 1, a K0 clutch 14, a motor 15, a wet clutch 18, and a transmission 19 are sequentially provided in the power transmission path from the engine 10 to the drive wheels 13. The engine 10 and the motor 15 are mounted as the driving power sources of the hybrid vehicle 1. The engine 10 is, for example, a V-type 6-cylinder gasoline engine, but the number of cylinders is not limited to this, and it may be an in-line gasoline engine or a diesel engine. The K0 clutch 14, the motor 15, the wet clutch 18, and the transmission 19 are provided in the transmission unit 11. The transmission unit 11 and the left and right drive wheels 13 are drivingly connected via a differential 12.

[0010] The K0 clutch 14 is provided between the engine 10 and the motor 15 on the same power transmission path. The K0 clutch 14 receives hydraulic pressure supply from the released state and becomes engaged, connecting the power transmission between the engine 10 and the motor 15. The K0 clutch 14 becomes released in response to the stop of the hydraulic pressure supply, cutting off the power transmission between the engine 10 and the motor 15. The engaged state means a state in which both engaging elements of the K0 clutch 14 are connected and the engine 10 and the motor 15 have the same rotational speed. The released state means a state in which both engaging elements of the K0 clutch 14 are separated.

[0011] The motor 15 is connected to the battery 16 via the inverter 17. The motor 15 functions as a motor that generates the driving force of the vehicle in response to the power supply from the battery 16, and also functions as a generator that generates electric power for charging the battery 16 in response to the power transmission from the engine 10 or the drive wheels 13. The electric power exchanged between the motor 15 and the battery 16 is adjusted by the inverter 17.

[0012] The inverter 17 is controlled by an ECU (Electronic Control Unit) 100, which will be described later, and converts the DC voltage from the battery 16 into an AC voltage, or converts the AC voltage from the motor 15 into a DC voltage. In the case of a power running operation where the motor 15 outputs torque, the inverter 17 converts the DC voltage of the battery 16 into an AC voltage and adjusts the power supplied to the motor 15. In the case of a regenerative operation where the motor 15 generates electricity, the inverter 17 converts the AC voltage from the motor 15 into a DC voltage and adjusts the power supplied to the battery 16.

[0013] The transmission 19 is a stepped automatic transmission that switches the gear ratio in multiple steps by switching the gear stage, but is not limited thereto and may be a continuously variable transmission. The transmission 19 is provided between the motor 15 and the drive wheels 13 on the power transmission path. A wet clutch 18 is provided that is engaged upon receiving hydraulic pressure supply to directly connect the motor 15 and the transmission 19.

[0014] The transmission unit 11 is further provided with an oil pump 21 and a hydraulic control mechanism 22. The hydraulic pressure generated by the oil pump 21 is supplied to the K0 clutch 14, the wet clutch 18, and the transmission 19 respectively via the hydraulic control mechanism 22. The hydraulic control mechanism 22 is provided with respective hydraulic circuits for the K0 clutch 14, the wet clutch 18, and the transmission 19, and various hydraulic control valves for controlling their operating hydraulic pressures. Note that instead of the wet clutch 18, a torque converter equipped with a lock-up clutch may be provided.

[0015] The hybrid vehicle 1 is provided with an ECU 100 as a control device for the vehicle. 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 functionally realizes a first starting control unit and a second starting control unit, which will be described in detail later.

[0016] ECU 100 controls the driving of engine 10 and motor 15. Specifically, ECU 100 controls the throttle opening degree, ignition timing, and fuel injection amount of engine 10 to control the torque and rotational speed of engine 10. ECU 100 controls inverter 17 to adjust the amount of power transfer between motor 15 and battery 16, thereby controlling the rotational speed and torque of motor 15. Also, ECU 100 performs drive control of K0 clutch 14, wet clutch 18, and transmission 19 through the control of hydraulic control mechanism 22.

[0017] Signals from ignition switch 71, crank angle sensor 72a, motor rotational speed sensor 72b, water temperature sensor 73, air flow meter 74, and air-fuel ratio sensor 75 are input to ECU 100. Crank angle sensor 72a detects the rotational speed of the crankshaft of engine 10, that is, the engine rotational speed. Motor rotational speed sensor 72b detects the rotational speed of the output shaft of motor 15. Water temperature sensor 73 detects the temperature of the cooling water of engine 10. Air flow meter 74 detects the intake air amount of engine 10. Air-fuel ratio sensor 75 detects the air-fuel ratio of the exhaust gas passing through catalyst 43.

[0018] Also, heater 76 is electrically connected to ECU 100. Heater 76 heats the element of air-fuel ratio sensor 75 to the activation temperature. When air-fuel ratio sensor 75 is heated to the activation temperature, ECU 100 can perform feedback control of the air-fuel ratio of engine 10 based on the detection result of air-fuel ratio sensor 75. For example, when the target air-fuel ratio is the stoichiometric air-fuel ratio and the detection result of air-fuel ratio sensor 75 indicates a rich air-fuel ratio, ECU 100 reduces the fuel injection amount, for example, to adjust the air-fuel ratio to the stoichiometric air-fuel ratio. Also, when the detection result of air-fuel ratio sensor 75 indicates a lean air-fuel ratio, ECU 100 increases the fuel injection amount to adjust the air-fuel ratio to the stoichiometric air-fuel ratio. Thus, the combustion state of engine 10 can be feedback-controlled based on the detection result of air-fuel ratio sensor 75.

[0019] The ECU 100 drives the hybrid vehicle in either an electric driving mode (hereinafter referred to as the BEV (Battery Electric Vehicle) mode) or a hybrid driving mode (hereinafter referred to as the HEV (Hybrid Electric Vehicle) mode). In the BEV mode, the ECU 100 releases the K0 clutch 14 and drives by the power of the motor 15. In the HEV mode, the ECU 100 switches the K0 clutch 14 to the engaged state and drives at least by the power of the engine 10. Note that the HEV mode includes a mode of driving only by the power of the engine 10 and a mode of driving with both the engine 10 and the motor 15 as power sources by powering the motor 15.

[0020] The switching of the driving mode is performed based on the required driving force of the vehicle obtained from the vehicle speed and the accelerator opening, the SOC (State Of Charge) indicating the power storage amount of the battery 16, etc. For example, when the required driving force is relatively small and the SOC is relatively high, the BEV mode is selected. When the required driving force is relatively large or the SOC of the battery 16 is relatively low, the HEV mode is selected.

[0021] A BEV switch 77 is connected to the ECU 100. The BEV switch 77 is provided in the vehicle interior and is a switch that can switch the driving mode to the BEV mode by the driver's manual operation. When the BEV switch 77 is on, the ECU 100 makes it less likely to switch the driving mode from the BEV mode to the HEV mode compared to when it is off.

[0022] [Schematic Configuration of Engine] Figure 2 is a schematic configuration diagram of the engine 10. The engine 10 has cylinders 30, pistons 31, connecting rods 32, a crankshaft 33, an intake passage 35, an intake valve 36, an exhaust passage 37, and an exhaust valve 38. Only one of the plurality of cylinders 30 of the engine 10 is shown in Figure 2. Combustion of the air-fuel mixture takes place in the cylinder 30. The piston 31 is reciprocally accommodated in each cylinder 30 and is connected to the crankshaft 33, which is the output shaft of the engine 10, via the connecting rod 32. The connecting rod 32 converts the reciprocating motion of the piston 31 into the rotational motion of the crankshaft 33.

[0023] The intake passage 35 is connected to the intake port of each cylinder 30 via the intake valve 36. The exhaust passage 37 is connected to the exhaust port of each cylinder 30 via the exhaust valve 38. The intake passage 35 is provided with an air flow meter 74 and a throttle valve 40 for adjusting the amount of intake air. The exhaust passage 37 is provided with a catalyst 43 for exhaust purification. An air-fuel ratio sensor 75 is provided downstream of the catalyst 43.

[0024] The cylinder 30 is provided with an in-cylinder injection valve 41. The in-cylinder injection valve 41 injects fuel directly into the cylinder 30. Incidentally, instead of the in-cylinder injection valve 41 or in addition to the in-cylinder injection valve 41, a port injection valve for injecting fuel toward the intake port may be provided. Each cylinder 30 is provided with an ignition device 42 for igniting the air-fuel mixture of the intake air introduced through the intake passage 35 and the fuel injected by the in-cylinder injection valve 41 by spark discharge.

[0025] [Control Executed by the ECU] Figure 3 is a flowchart showing an example of the control executed by the ECU 100. This control is repeatedly executed at a predetermined cycle with the ignition on. The ECU 100 determines whether it is before the first start of the engine 10 after the ignition is turned on (step S1). If the answer in step S1 is No, this control ends. If the answer in step S1 is Yes, the ECU 100 determines whether the BEV switch 77 is on (step S2). If the answer in step S2 is No, this control ends.

[0026] When the answer is Yes in step S2, the ECU 100 determines whether the temperature of the cooling water of the engine 10 is less than the threshold value α (step S3). The threshold value α is set to the maximum value of the temperature of the cooling water at which there is a risk of emission deterioration when the engine 10 is started and high power is immediately output from the engine 10. The threshold value α is an example of a first threshold value.

[0027] When the answer is Yes in step S3, the ECU 100 starts the engine 10 (step S4). Specifically, the engine 10 is cranked by the motor 15 by engaging the K0 clutch 14 to start the engine 10. As a result, the driving mode is switched from the BEV mode to the HEV mode, the warm-up operation of the engine 10 is performed, and the temperature rise of the engine 10 and the temperature rise of the catalyst 43 are achieved. Thereby, an increase in the required output to the hybrid vehicle 1 during traveling in the BEV mode can suppress the deterioration of emissions when the engine 10 is started at high power. Steps S2 to S4 are an example of the processes executed by the first start control unit.

[0028] The required output to the engine 10 in step S4 is limited to the output necessary for the warm-up operation, and it is preferably as low as possible from the viewpoint of suppressing the deterioration of emissions. Further, when step S4 is executed, the ECU 100 also turns off the BEV switch 77.

[0029] If the answer is No in step S3, it is determined whether the temperature of the cooling water is less than the threshold value β (step S5). The threshold value β is a temperature higher than the threshold value α. The threshold value β is an example of a second threshold value. The threshold value β is set to the minimum value of the temperature of the cooling water at which the deterioration of emissions is suppressed when the engine 10 is started. That is, when the temperature of the cooling water is equal to or higher than the threshold value β, even if the required output to the hybrid vehicle 1 during traveling in the BEV mode increases and the engine 10 is started at high power, the deterioration of emissions is suppressed. Therefore, when the answer is No in step S5, the ECU 100 permits BEV travel (step S6).

[0030] If the answer in step S5 is Yes, the ECU 100 determines whether or not the activation of the air-fuel ratio sensor 75 has been completed (step S7). The ECU 100 regards the air-fuel ratio sensor 75 as activated when the impedance of the element of the air-fuel ratio sensor 75 becomes equal to or less than a predetermined value. There is an inverse proportional relationship between the temperature and the impedance of the element of the air-fuel ratio sensor 75. Note that the heating of the air-fuel ratio sensor 75 by the heater 76 starts when the ignition is turned on.

[0031] If the answer in step S7 is No, the ECU 100 permits BEV travel (step S6). If the answer in step S7 is Yes, the ECU 100 starts the engine 10 (step S4). Steps S2, S3, S5, S7, and S4 are examples of processes executed by the second start control unit. In this way, travel in the BEV mode is continued until at least the air-fuel ratio sensor 75 is activated. By maintaining travel in the BEV mode as much as possible in this way, it is possible to suppress the discomfort of the driver, and by starting the engine 10 after the activation of the air-fuel ratio sensor 75 is completed, it is possible to suppress the deterioration of emissions.

[0032] In the above embodiment, the air-fuel ratio sensor 75 is used as an example of the gas sensor, but the present invention is not limited to this. For example, as the gas sensor, an oxygen sensor that detects the oxygen concentration in the exhaust gas may be used.

[0033] In the above embodiment, as an example of the hybrid vehicle, a vehicle equipped with the engine 10 and the motor 15 as the travel power sources is illustrated, but the present invention is not limited to this. For example, as the travel power sources, a vehicle equipped with an engine and first and second motors, and further including a planetary gear mechanism including a sun gear connected to the first motor, a drive wheel, a ring gear connected to the second motor, and a carrier connected to the engine may be used as the hybrid vehicle.

[0034] As described above, the embodiments of the present invention have been described in detail, but 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.

Description of Symbols

[0035] 1 Hybrid vehicle 10 Engine 15 Motor 75 Air-fuel ratio sensor (gas sensor) 76 Heater 100 ECU (First start control unit, Second start control unit)

Claims

【Claim 1】 A control device for a hybrid vehicle having an engine and a motor as driving power sources, a gas sensor used to detect a predetermined component in the exhaust gas of the engine and feedback control the combustion state of the engine, and a heater for activating the gas sensor, wherein: a first start control unit for starting the engine when an electric driving mode in which the engine is stopped and the vehicle is driven by the motor is selected as the driving mode and the temperature of the cooling water of the engine is less than a first threshold value; a second start control unit for activating the gas sensor by the heater and then starting the engine when the electric driving mode is selected and the temperature of the cooling water is equal to or higher than the first threshold value and less than a second threshold value higher than the first threshold value; A control device for a hybrid vehicle comprising the above.

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