Control system for hybrid vehicles

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 Art

[0002] A control device for a hybrid vehicle that performs predetermined control during cold operation is known (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 high power is required during cold operation, for example, if the engine speed is increased to ensure high power, emissions may deteriorate. On the other hand, if the prevention of emission deterioration is prioritized and the engine speed is maintained at a low level, there is a risk that high power cannot be ensured.

[0005] Therefore, an object of the present invention is to provide a control device for a hybrid vehicle that ensures high engine power while suppressing deterioration of emissions during cold operation.

Means for Solving the Problems

[0007] According to the present invention, a control device for hybrid vehicles can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of a hybrid vehicle. [Figure 2] This is a schematic diagram of the engine's configuration. [Figure 3] This is a flowchart illustrating engine control. [Figure 4] This is a timing chart illustrating engine control. [Modes for carrying out the invention]

[0009] [Overall configuration of a hybrid vehicle] Figure 1 is a schematic 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 (hereinafter referred to as "first MG (Motor Generator)") 14, a second motor (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 54, and drive wheels 55. In this embodiment, the engine 10 has four cylinders 11 to #4. The number of cylinders in the engine 10 is not limited to four, as long as it has multiple cylinders. The engine 10 is a gasoline engine, but is not limited to this and may be a diesel engine. The engine 10, the first MG 14, and the second MG 15 are the power sources for driving the hybrid vehicle 1.

[0010] The first MG14 and the second MG15 each have the function of a motor that outputs torque when power is supplied, and the function of a generator that generates regenerative power when torque is applied. The first MG14 and the second MG15 are electrically connected to the battery 18 via the PCU 17. The PCU 17 supplies power from the battery 18 to the first MG14 or the second MG15. The PCU 17 also causes the battery 18 to receive regenerative power generated by the first MG14 or the second MG15. As described above, the battery 18 can be charged by an external power source via the plug 80. In other words, the hybrid vehicle 1 is a plug-in hybrid vehicle, but is not limited to this.

[0011] The power split mechanism 50 mechanically connects the crankshaft of the engine 10, the rotating shaft of the first MG14, 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 rotating shaft of the second MG15 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 MG14, and the second MG15 are transmitted to the 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 located between the second MG15 and the drive shaft 53. The transmission 52 changes the gear ratio under the control of the ECU 100.

[0013] The ECU100 is an electronic control unit comprising an arithmetic processing circuit that performs various calculations related to the driving control of the hybrid vehicle 1, and a memory that stores control programs and data. The ECU100 is an example of a control device for the hybrid vehicle 1. The ECU100 functionally implements the first control unit and the second control unit, which will be described later.

[0014] The ECU 100 receives signals from the ignition switch 71, water temperature sensor 72, crank angle sensor 73, airflow meter 74, and accelerator pedal position 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 in the engine 10. The crank angle sensor 73 detects the engine speed, which is the rotational speed of the crankshaft of the engine 10. The airflow meter 74 detects the amount of intake air introduced into the engine 10. The accelerator pedal position sensor 75 detects the operating position of the accelerator pedal. Note that the coolant temperature is just one example of the temperature of the engine 10; for example, the temperature of the lubricating oil could be detected instead of the coolant temperature.

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

[0016] [Engine Overview] Figure 2 is a schematic configuration diagram of the engine 10. The engine 10 has cylinders 11, pistons 31, connecting rods 32, a crankshaft 33, an intake passage 35, intake valves 36, an exhaust passage 37, and exhaust valves 38. In Figure 2, one of the four cylinders 11 of the engine 10 is illustrated. Combustion of the air-fuel mixture takes place in the cylinder 11. The piston 31 is reciprocally accommodated in the cylinder 11 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 directly injects fuel into the cylinder 11. In the cylinder 11, an ignition device 42 is provided 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 means of spark discharge. In addition to the in-cylinder injection valve 41, a port injection valve for injecting fuel toward the intake port 35p may be provided.

[0018] The in-cylinder injection valve 41 is capable of split injection. Split injection is to divide the total fuel injection amount within one combustion cycle into multiple injections. For example, fuel injection is possible during the intake stroke and the compression stroke, respectively. 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 the intake port 35p of the cylinder 11 via the intake valve 36. The exhaust passage 37 is connected to the exhaust port 37p of the cylinder 11 via the exhaust valve 38. In the intake passage 35, the above-described air flow meter 74 and a throttle valve 40 for controlling the intake air amount are provided.

[0020] In the exhaust passage 37, a catalyst 43 and a GPF (Gasoline Particulate Filter) 44 are provided from the upstream side. The catalyst 43 contains, for example, catalytic metals such as platinum (Pt), palladium (Pd), and rhodium (Rh), has an oxygen storage capacity, and purifies NOx, HC, and CO. The GPF 44 is a porous ceramic structure and collects exhaust particles 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 its opening degree. The opening degree of the throttle valve 40 is controlled according to the required opening degree from the ECU 100.

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

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

[0024] If the answer in step S2 is Yes, the ECU 100 determines whether the temperature of the engine 10's coolant is below the temperature threshold T (step S3). If the answer in step S3 is Yes, the ECU 100 executes the first process (step S4). Step S4 is an example of a process executed by the first control unit. If the answer in step S3 is No, the ECU 100 executes the second process (step S5). Step S5 is an example of a process executed by the second control unit. The first and second processes control 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 treatment is three. The ignition timing in the first treatment is advanced compared to 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 treatment is maintained at the upper limit 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 from the ignition timing set in the first process. The engine speed in the second process is controlled by the first MG14 to be higher than the upper limit R1 and below the upper limit R2. The upper limit is set considering the number of split fuel injections. The upper limit of the engine speed is set to a higher value as the number of split fuel injections decreases. This is because if the number of split injections is large, the time required to energize the in-cylinder injection valve 41 will be prolonged, and there is a risk that the number of split injections cannot be achieved at high engine speeds.

[0027] As described above, when the coolant temperature is below the temperature threshold T, the first treatment sets the number of fuel injections to three. During cold starts, atomization of the injected fuel deteriorates, so the total fuel injection amount needs to be increased accordingly. Also, if the amount of fuel injected in one go is large during cold starts, the amount of unburned fuel adhering to the inner surface of the cylinder 11 increases, which may worsen emissions. By setting the number of injections to three in the first treatment as in this embodiment, fuel atomization is promoted and the amount of unburned fuel is reduced. This makes it possible to suppress the deterioration of emissions.

[0028] Furthermore, the ignition timing in the first process is advanced compared to 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, the portion of the energy generated by the combustion of fuel that contributes to increasing the output of the engine 10 can be increased. This ensures high output from the engine 10.

[0029] In the second process, the ignition timing from the first process is maintained, thus ensuring high output from engine 10. Furthermore, the number of fuel injection segments is reduced, and the engine speed increases compared to the first process due to the first MG14. By increasing the engine speed while maintaining the ignition timing in this way, the output of engine 10 is ensured. As described above, high output from engine 10 is ensured while preventing deterioration of emissions during cold starts.

[0030] Figure 4 is a timing chart illustrating engine control. Figure 4 shows the changes in coolant temperature, engine demand power, actual engine power, engine torque, engine speed, excess air ratio, ignition timing, number of injection segments, and total fuel injection amount.

[0031] At time t0, the catalyst 43 is warming up, the required power is below the power threshold P, and the coolant temperature is below the temperature threshold T. In this state, the air-fuel ratio is maintained at 100%, the number of injection segments is set to 3, and the engine speed is maintained at the upper limit R1. Because the air-fuel ratio is constant, the total fuel injection amount decreases as the coolant temperature gradually rises.

[0032] When the requested output exceeds 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 R1. As a result, the actual engine output increases. Furthermore, when the coolant temperature exceeds the temperature threshold T (time t2), the number of split injections is set to 2 while maintaining a constant ignition timing, and the engine speed increases towards the upper limit R2 by the first MG14. As a result, the actual engine output increases. In addition, since the engine speed and coolant temperature are rising, the total fuel injection amount gradually increases. In this way, high output from engine 10 is ensured while suppressing the deterioration of emissions.

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

[0034] 1. Hybrid vehicle 10 Engines 14. First Motor 100 ECUs (Hybrid vehicle control units, first control unit, second control unit)

Claims

[Claim 1] A control device for a hybrid vehicle having an engine and a motor as a power source for driving, A first control unit performs a first process in which, when the requested output of the engine is equal to or greater than an output threshold and the engine temperature is below a temperature threshold indicating a cold state, the number of fuel injections per combustion cycle is set to a first number, the engine speed is controlled to a first speed, and the ignition timing is advanced compared to when the requested output is below the output threshold and the temperature is below the temperature threshold, A control device for a hybrid vehicle, comprising: a second control unit that, if the engine temperature exceeds the temperature threshold during the execution of the first process, maintains the ignition timing, sets the number of divided injections to a second number which is less than the first number, and controls the motor to control the engine speed to a second speed which is higher than the first speed.

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