Control device of hybrid vehicle

Abstract

To provide a control device of a hybrid vehicle which secures high output of an engine while restraining emission from being deteriorated at cold time.SOLUTION: A control device of a hybrid vehicle includes an engine and a motor as a traveling power source. It comprises: a first control unit which sets the number of split jet of fuel in one combustion cycle to a first number and controls rotational frequency of the engine to a first rotational frequency when request output of the engine is an output threshold value or more and temperature of the engine is below a temperature threshold value indicating cold, and executes a first process to further advance ignition time than when the request output is less than the output threshold value and the temperature is less than the temperature threshold value; and a second control unit which sets the split jet number to a second number less than the first number while maintaining the ignition time if the temperature in the engine becomes the temperature threshold value or more while executing the first process and controls the rotational frequency of the engine to a second rotational frequency higher than the first rotational frequency by controlling the motor.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] 2. Description of the Related Art A control device for a hybrid vehicle that performs a predetermined control when the vehicle is cold is known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-071664 A Summary of the Invention [Problem to be solved by the invention]

[0004] When high power output is required when the engine is cold, for example, increasing the engine speed to ensure high power output may result in a deterioration of emissions, whereas maintaining the engine speed at a low speed with priority given to preventing the deterioration of emissions may result in a failure to ensure high power output.

[0005] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a control device for a hybrid vehicle that ensures high engine output while suppressing deterioration of emissions when the vehicle is cold. [Means for solving the problem]

[0006] The above object can be achieved by a control device for a hybrid vehicle having an engine and a motor as driving power sources, the control device comprising: a first control unit that, when a required output of the engine is equal to or greater than an output threshold and a temperature of the engine is less than a temperature threshold indicating a cold state, executes a first process to set the number of split injections of fuel in one combustion cycle to a first number, control the engine speed to a first speed, and advance the ignition timing more than when the required output is less than the output threshold and the temperature is less than the temperature threshold; and a second control unit that, when the temperature of the engine becomes equal to or greater than the temperature threshold while executing the first process, sets the number of split injections to a second number which is less than the first number while maintaining the ignition timing, and controls the motor to control the engine speed to a second speed which is higher than the first speed. Effect of the Invention

[0007] According to the present invention, a control device for a hybrid vehicle can be provided. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a hybrid vehicle. [Diagram 2] FIG. 1 is a schematic configuration diagram of an engine. [Diagram 3] 3 is a flowchart illustrating an example of engine control. [Figure 4] 4 is a timing chart illustrating engine control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [General configuration of hybrid vehicle] FIG. 1 is a schematic diagram of a hybrid vehicle 1 according to the present embodiment. The hybrid vehicle 1 includes an ECU (Electronic Control Unit) 100, an engine 10, a first motor (hereinafter referred to as a "first MG (Motor Generator)") 14, a second motor (hereinafter referred to as a "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 54, and drive wheels 55. In the present embodiment, the engine 10 has four cylinders 11 to #4. The number of cylinders of the engine 10 is not limited to four as long as the engine 10 has a plurality of cylinders. The engine 10 is a gasoline engine, but may be a diesel engine. The engine 10, the first MG 14, and the second MG 15 are power sources for driving the hybrid vehicle 1.

[0010] Each of the first MG 14 and the second MG 15 has a function as a motor that outputs torque when supplied with electric power, and a function as a generator that generates regenerative electric power when torque is applied to the first MG 14 and the second MG 15. The first MG 14 and the second MG 15 are electrically connected to a battery 18 via a PCU 17. The PCU 17 supplies electric power from the battery 18 to the first MG 14 or the second MG 15. The PCU 17 causes the battery 18 to receive regenerative electric power generated in the first MG 14 or the second MG 15. As described above, the battery 18 can be charged by an external power source via a plug 80. That is, the hybrid vehicle 1 is a plug-in hybrid vehicle, but is not limited thereto.

[0011] The power split mechanism 50 mechanically connects the crankshaft of the engine 10, the rotating 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 a transmission mechanism 51. The rotating shaft of the second MG 15 is connected to the transmission mechanism 51. The transmission mechanism 51 is connected to a transmission 52. The transmission 52 is connected to a drive shaft 53. The driving forces of the engine 10, the first MG 14, and the second MG 15 are transmitted to drive wheels 55 via the transmission mechanism 51, the transmission 52, the drive shaft 53, and the differential 54.

[0012] The transmission 52 is a stepped automatic transmission provided between the second MG 15 and the drive shaft 53. The transmission 52 changes its gear ratio under the control of the ECU 100.

[0013] The ECU 100 is an electronic control unit including a calculation processing circuit that performs various calculation processes related to the driving control of the hybrid vehicle 1, and a memory that stores control programs and data. The ECU 100 is an example of a control device for the hybrid vehicle 1. The ECU 100 functionally realizes a first control unit and a second control unit, which will be described later.

[0014] Signals are input to the ECU 100 from an ignition switch 71, a water temperature sensor 72, a crank angle sensor 73, an air flow meter 74, and an accelerator opening sensor 75. The ignition switch 71 detects the on / off state of the ignition. The water temperature sensor 72 detects the temperature of the coolant for the engine 10. The crank angle sensor 73 detects the engine rotation speed, which is the rotation speed of the crankshaft of the engine 10. The air flow meter 74 detects the amount of intake air introduced into the engine 10. The accelerator opening sensor 75 detects the operating position of the accelerator pedal. The coolant temperature is one example of the temperature of the engine 10, and for example, the temperature of the lubricating oil may be detected instead of the coolant temperature.

[0015] The ECU 100 switches the driving mode of the hybrid vehicle 1 to a motor driving mode or a hybrid driving mode. The motor driving mode is a mode in which the hybrid vehicle 1 drives using only the second MG 15 as a driving power source by utilizing the electric power stored in the battery 18. The hybrid driving mode is a mode in which the hybrid vehicle 1 drives using at least the driving force of the engine 10. For example, when the driving force required for the hybrid vehicle 1 is less than the driving mode switching threshold, the motor driving mode is selected. When the driving force required for the hybrid vehicle 1 is equal to or greater than the driving mode switching threshold, the hybrid driving mode is selected.

[0016] [Engine outline] FIG. 2 is a schematic diagram of the engine 10. The engine 10 has a cylinder 11, a piston 31, a connecting rod 32, a crankshaft 33, an intake passage 35, an intake valve 36, an exhaust passage 37, and an exhaust valve 38. FIG. 2 illustrates one cylinder 11 out of four cylinders of the engine 10. An air-fuel mixture is burned in the cylinder 11. The piston 31 is accommodated in the cylinder 11 so as to be capable of reciprocating, 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 and the crankshaft 33 convert the reciprocating motion of the piston 31 into the rotational motion of the crankshaft 33.

[0017] An in-cylinder injection valve 41 is provided in the cylinder 11. The in-cylinder injection valve 41 injects fuel directly into the cylinder 11. An ignition device 42 is provided in the cylinder 11, which ignites, by spark discharge, an air-fuel mixture of the intake air introduced through the intake passage 35 and the fuel injected by the in-cylinder injection valve 41. In addition to the in-cylinder injection valve 41, a port injection valve that injects fuel toward the intake port 35p may be provided.

[0018] The in-cylinder injection valve 41 is capable of split injection. Split injection means that the total fuel injection amount within one combustion cycle is split and injected into multiple injections. For example, fuel can be injected during both the intake stroke and the compression stroke. The number of split injections is controlled by 100. The total fuel injection amount is controlled according to the operating state of the engine 10.

[0019] The intake passage 35 is connected to an intake port 35p of the cylinder 11 via an intake valve 36. The exhaust passage 37 is connected to an exhaust port 37p of the cylinder 11 via an exhaust valve 38. The intake passage 35 is provided with the above-mentioned air flow meter 74 and a throttle valve 40 that controls the amount of intake air.

[0020] In the exhaust passage 37, from the upstream side, a catalyst 43 and a GPF (Gasoline Particulate Filter) 44 are provided. The catalyst 43 contains catalytic metals such as platinum (Pt), palladium (Pd), rhodium (Rh), etc., has oxygen storage capacity, and purifies NOx, HC, and CO. The GPF 44 is a porous ceramic structure, and collects exhaust particulates in the exhaust gas.

[0021] The throttle valve 40 can increase or decrease the amount of intake air introduced into the cylinder 11 by increasing or decreasing the opening degree thereof. The opening degree of the throttle valve 40 is controlled in accordance with the required opening degree from the ECU 100.

[0022] In the hybrid vehicle 1 equipped with the engine 10 as described above, the mode may be switched from the motor driving mode to the hybrid driving mode after the ignition is turned on. When the driving mode switching threshold value for switching from the motor driving mode to the hybrid driving mode is set to a relatively high value, high output may be required from the engine 10 immediately after switching to the hybrid driving mode. For example, when high output is required from the engine 10 immediately after a cold start, the ECU 100 executes the following engine control to ensure high output from the engine 10 while suppressing deterioration of emissions.

[0023] [Engine Control] FIG. 3 is a flowchart illustrating engine control. This control is repeatedly executed while the ignition is on. The ECU 100 determines whether the catalyst 43 is warming up (step S1). The ignition timing of the engine 10 while the catalyst 43 is warming up is retarded from the optimal ignition timing at which the output of the engine 10 is maximized. If the answer is No in step S1, this control ends. If the answer is Yes in step S1, it is determined whether the required output for the engine 10 is equal to or greater than the output threshold P (step S2). If the answer is No in step S2, this control ends.

[0024] If the answer is Yes in step S2, the ECU 100 determines whether the temperature of the coolant of the engine 10 is less than the temperature threshold value T (step S3). If the answer is Yes in step S3, the ECU 100 executes a first process (step S4). Step S4 is an example of a process executed by the first control unit. If the answer is No in step S3, the ECU 100 executes a second process (step S5). Step S5 is an example of a process executed by the second control unit. The first and second processes are processes for controlling the number of split injections by the in-cylinder injection valve 41, the engine speed, and the ignition timing.

[0025] In this embodiment, the number of split injections in the first process is 3. The ignition timing in the first process is more advanced than the ignition timing set when the required output is less than the output threshold P and the coolant temperature is less than the temperature threshold T. The engine speed in the first process is maintained at the upper limit value R1.

[0026] In this embodiment, the number of split injections in the second process is two. The ignition timing in the second process is maintained at the ignition timing set in the first process. The engine speed in the second process is controlled by the first MG 14 to be higher than the upper limit value R1 and equal to or lower than the upper limit value R2. The upper limit value is set taking into consideration the number of split injections of fuel. The upper limit value of the engine speed is set to a higher value as the number of split injections of fuel decreases. This is because if the number of split injections is large, the time required to energize the in-cylinder injection valve 41 becomes longer, and there is a risk that the number of split injections cannot be achieved when the engine speed is high.

[0027] As described above, when the temperature of the cooling water is less than the temperature threshold T, the first process sets the number of split fuel injections to three. Since atomization of the injected fuel deteriorates when the engine is cold, it is necessary to increase the total amount of fuel injection accordingly. Furthermore, if the amount of fuel injected per injection is large when the engine is cold, the amount of unburned fuel adhering to the inner surface of the cylinder 11 increases, which may result in deterioration of emissions. By setting the number of split injections to three in the first process as in this embodiment, fuel atomization is promoted and the amount of unburned fuel is reduced. This makes it possible to suppress deterioration of emissions.

[0028] Furthermore, the ignition timing in the first process is more advanced than the ignition timing set when the required output is less than the output threshold P and the coolant temperature is less than the temperature threshold T. By advancing the ignition timing, it is possible to increase the portion of the energy generated by the combustion of the fuel that contributes to increasing the output of the engine 10. This ensures high output of the engine 10.

[0029] In the second process, the ignition timing in the first process is maintained, so that high output of the engine 10 is ensured. In addition, the number of split fuel injections is reduced, and the engine speed is increased by the first MG 14 more than in the first process. In this way, the output of the engine 10 is ensured by increasing the engine speed while maintaining the ignition timing. As described above, high output of the engine 10 is ensured while preventing deterioration of emissions when the engine is cold.

[0030] Fig. 4 is a timing chart showing an example of engine control, which shows the transition of the coolant temperature, the required engine output, the actual engine output, the engine torque, the engine speed, the excess air ratio, the ignition timing, the number of split injections, and the total fuel injection amount.

[0031] At time t0, the catalyst 43 is warming up, the required output is less than the output threshold P, and the coolant temperature is less than the temperature threshold T. In this state, the excess air ratio is maintained at 100%, the number of split injections is set to three, and the engine speed is maintained at the upper limit value R1. Since the excess air ratio is constant, the total fuel injection amount decreases as the coolant temperature gradually increases.

[0032] When the required output becomes equal to or higher than the output threshold P (time t1), the ignition timing is gradually advanced, and the engine torque increases while the engine speed is maintained at the upper limit value R1. As a result, the actual engine output increases. Furthermore, when the coolant temperature becomes equal to or higher than the temperature threshold value T (time t2), the number of split injections is set to two while maintaining the ignition timing constant, and the engine speed increases toward the upper limit value R2 by the first MG 14. As a result, the actual engine output increases. Note that since the engine speed and the coolant temperature are increasing, the total fuel injection amount gradually increases. In this way, a high output of the engine 10 is ensured while suppressing deterioration of emissions.

[0033] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0034] 1 Hybrid vehicles 10 Engine 14 First motor 100 ECU (control device for hybrid vehicle, first control unit, second control unit)

Claims

[Claim 1] A control device for a hybrid vehicle having an engine and a motor as a driving power source, a first control unit that executes a first process to set a number of split injections of fuel in one combustion cycle to a first number, control a rotation speed of the engine to a first rotation speed, and advance an ignition timing more than when the required output of the engine is less than the output threshold and the temperature of the engine is less than a temperature threshold indicating a cold state; and a second control unit that, when the temperature of the engine becomes equal to or higher than the temperature threshold value while the first process is being executed, sets the number of split injections to a second number which is lower than the first number while maintaining the ignition timing, and controls the motor to control the engine speed to a second number which is higher than the first number.

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