Hybrid vehicle control device

Abstract

To suppress occurrence of torque level difference associated with switch of a combustion system by warm-up control in a range of avoiding overcharge of a battery.SOLUTION: An electronic control unit 30 calculates a torque fluctuation amount of an engine 11 caused when a combustion system of the engine 11 is switched to homogeneous combustion from stratified combustion at present time during execution of warm-up control, and also calculates generated power of a generator motor 12 necessary for absorption of the torque fluctuation amount. The electric control unit 30 determines whether or not the generated power can be charged in the battery 13, and also executes a torque fluctuation suppression control absorbing the torque fluctuation of the engine 11 associated with the switching by power generation of the generator motor 12 when switching the combustion system to the homogeneous combustion from the stratified combustion by the warm-up control under the condition of determining that charging can be performed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 describes a control device for a hybrid vehicle that performs warm-up control to promote warm-up of the exhaust catalyst while suppressing deterioration of fuel economy by increasing the torque required by the engine and using the resulting increase in engine torque to generate electricity from a generator motor. This control device determines the regenerative torque of the generator motor based on the increase in the torque required by the engine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-110604 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when warming up the engine or exhaust catalyst, it is possible to switch between homogeneous combustion and stratified combustion. However, when warming up the engine or exhaust catalyst, a torque step occurs in the engine depending on the combustion method, which may lead to a deterioration in drivability. [Means for solving the problem]

[0005] A hybrid vehicle control device that solves the above problem is applied to a hybrid vehicle that has an engine that generates torque used for driving, a generator motor that receives torque from the engine and generates electricity, and a battery that can be charged with the electricity generated by the generator motor, and is a control device that performs warm-up control accompanying a switchover of the engine's combustion method from stratified combustion to homogeneous combustion, and is configured to perform the following during the warm-up control: calculate the amount of torque fluctuation of the engine that occurs when the combustion method is switched, calculate the generated power of the generator motor necessary to absorb the torque fluctuation of the engine based on the calculation result of the torque fluctuation amount, determine whether the battery can be charged with power based on the calculation result of the generated power, and, on the condition that it is determined that the battery can be charged, perform torque fluctuation suppression control that absorbs the torque fluctuation of the engine that occurs when the combustion method is switched by using the power generated by the generator motor. [Effects of the Invention]

[0006] The control device for a hybrid vehicle has the advantage of being able to suppress the occurrence of a torque step that occurs when the combustion method is switched from stratified combustion to homogeneous combustion due to warm-up control, to a degree that allows overcharging of the battery to be avoided. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating a schematic configuration of an embodiment of a control device for a hybrid vehicle; [Figure 2] 3 is a flowchart showing a procedure for torque fluctuation suppression control executed by the control device. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of a control device for a hybrid vehicle will be described in detail below with reference to FIGS. <Configuration of a control device for a hybrid vehicle> As shown in Fig. 1, a hybrid vehicle 10 to which the control device of this embodiment is applied includes an engine 11, a generator motor 12, and a battery 13. The engine 11 generates torque used for running the hybrid vehicle 10 by burning fuel. The generator motor 12 is drivingly connected to the engine 11 and is electrically connected to the battery 13 via an inverter 14. The generator motor 12 functions as both an electric motor that receives power from the battery 13 to generate torque and a generator that receives torque from the engine 11 to generate electricity. The inverter 14 adjusts the power supplied from the battery 13 to the generator motor 12 and the power generated by the generator motor 12 to charge the battery 13.

[0009] The engine 11 includes a combustion chamber 20 that burns fuel, an intake passage 21 that is a passage through which intake air is introduced into the combustion chamber 20, and an exhaust passage 22 that is a passage through which exhaust gas is discharged from the combustion chamber 20. A throttle valve 23 that adjusts the flow rate of intake air flowing into the combustion chamber 20 is installed in the intake passage 21. An in-cylinder injector 24 that injects fuel into the intake air that has flowed into the combustion chamber 20 through the intake passage 21 is installed in the combustion chamber 20. An ignition device 25 that ignites the mixture of intake air and fuel by spark discharge is also installed in the combustion chamber 20. Furthermore, an exhaust purification catalyst 26 is installed in the exhaust passage 22 to purify the exhaust.

[0010] The hybrid vehicle 10 is further equipped with an electronic control unit 30 as a control device. The electronic control unit 30 includes a processor 31 and a memory 32. The memory 32 stores programs and data for controlling the hybrid vehicle 10 in advance. Detection signals from sensors installed in various parts of the hybrid vehicle 10 are input to the electronic control unit 30. These sensors include a water temperature sensor 33, a crank angle sensor 34, and an air flow meter 35. The water temperature sensor 33 is a sensor that detects the temperature of the cooling water of the engine 11. The crank angle sensor 34 is a sensor that detects the rotation angle of the crankshaft, which is the output shaft of the engine 11. The air flow meter 35 is a sensor that detects the flow rate of intake air flowing through the intake passage 21 of the engine 11. The electronic control unit 30 then performs various controls of the hybrid vehicle 10 based on the detection results of these sensors. For example, the electronic control unit 30 controls the engine 11 by adjusting the opening ratio of the throttle valve 23, the timing and amount of fuel injection by the injector 24, the timing of ignition of the air-fuel mixture by the ignition device 25, etc. The electronic control unit 30 also controls the power of the generator motor 12 by controlling the inverter 14. The control of the hybrid vehicle 10 by the electronic control unit 30 is performed by the processor 31 executing a program read from the memory 32.

[0011] The engine 11 mounted on the hybrid vehicle 10 of this embodiment is configured to be able to switch between stratified charge combustion and homogeneous charge combustion. Specifically, the engine 11 performs homogeneous combustion by injecting fuel from the injector 24 during the intake stroke, thereby forming an air-fuel mixture in the combustion chamber 20 in which the fuel is homogeneously dispersed in the intake air. The engine 11 also performs lean combustion by injecting fuel from the injector 24 during the compression stroke, thereby forming a rich air-fuel mixture layer and a lean air-fuel mixture layer in the combustion chamber 20. In normal engine control, the electronic control unit 30 basically causes the engine 11 to perform homogeneous charge combustion.

[0012] <About warm-up control> The electronic control unit 30 executes warm-up control to promote warm-up of the exhaust purification catalyst 26, for example, during a cold start of the engine 11. The electronic control unit 30 determines whether the exhaust purification catalyst 26 is in an unwarmed state based on the coolant temperature of the engine 11, etc. Then, the electronic control unit 30 executes warm-up control when it is determined that the exhaust purification catalyst 26 is in an unwarmed state.

[0013] When the electronic control unit 30 starts warm-up control, it switches the combustion method of the engine 11 from homogeneous combustion to stratified combustion. Also, when the electronic control unit 30 starts warm-up control, it performs ignition retard, which sets the ignition timing of the engine 11 to a later timing than normal. Then, when the warm-up of the engine 11 and the exhaust purification catalyst 26 is completed, the electronic control unit 30 switches the combustion method from stratified combustion to homogeneous combustion and stops the ignition retard, thereby ending the catalyst warm-up control.

[0014] If the electronic control unit 30 detects a deterioration in the combustion state of the engine 11 after starting catalyst warm-up control, it switches the combustion method to homogeneous combustion while maintaining the ignition retard. The electronic control unit 30 detects a deterioration in the combustion state of the engine 11 based on, for example, the amount of rotational fluctuation of the engine 11 obtained from the detection results of the crank angle sensor 34. In this case, if the electronic control unit 30 subsequently detects an improvement in the combustion state, it switches the combustion method of the engine 11 back to stratified combustion. Therefore, switching between stratified combustion and homogeneous combustion may be repeated while catalyst warm-up control is being executed.

[0015] <Torque fluctuation suppression control> As described above, the electronic control unit 30 executes catalyst warm-up control that involves switching the combustion method of the engine 11 between homogeneous combustion and stratified combustion. If the combustion method of the engine 11 is switched from stratified combustion to homogeneous combustion during or at the end of such catalyst warm-up control, the torque of the engine 11 may increase, resulting in torque fluctuations. During catalyst warm-up control, the electronic control unit 30 executes torque fluctuation suppression control to suppress torque fluctuations that accompany the combustion method switch.

[0016] 2 shows a processing procedure of the electronic control unit 30 relating to torque fluctuation suppression control. The electronic control unit 30 repeatedly executes the processing of FIG. 2 at every predetermined control cycle while warm-up control is being executed.

[0017] 2 , the electronic control unit 30 first acquires the current values ​​of the engine speed NE, engine load factor KL, ignition retard amount, and state of charge (SOC) of the battery 13 in step S100. The ignition retard amount represents the amount of retardation of the ignition timing due to warm-up control. The electronic control unit 30 calculates the engine speed NE based on the detection result of the crank angle sensor 34. The electronic control unit 30 also calculates the engine load factor KL based on the detection result of the air flow meter 35, the engine speed NE, the opening rate of the throttle valve 23, etc. The engine load factor KL represents the intake air filling rate of the combustion chamber 20. Furthermore, the electronic control unit 30 sequentially calculates the amount of discharge of the battery 13 relative to the generator motor 12 and the amount of charge of the battery 13 by the generator motor 12 based on the control status of the inverter 14. The electronic control unit 30 then calculates the state of charge (SOC) of the battery 13 based on the calculated amount of charge and discharge of the battery 13.

[0018] In the next step S110, the electronic control unit 30 calculates an expected torque fluctuation amount based on the current values ​​of the engine rotation speed NE, the engine load factor KL, and the ignition retard amount. The expected torque fluctuation amount represents a predicted value of the torque fluctuation amount of the engine 11 that would occur if the combustion method of the engine 11 were to be switched from stratified combustion to homogeneous combustion at the current time.

[0019] Next, in step S120, the electronic control unit 30 calculates the required generated power based on the calculation result of the predicted torque fluctuation amount. The required generated power represents the power generated by the generator motor 12 that is required to absorb the torque fluctuation of the engine 11 according to the predicted torque fluctuation amount. In this embodiment, the electronic control unit 30 converts the generated power required to absorb the torque fluctuation into the state of charge (SOC) of the battery 13, and calculates this value as the value of the required generated power.

[0020] Next, in step S130, the electronic control unit 30 determines whether the battery 13 can be charged with power corresponding to the calculated required power generation. Specifically, in making the determination in step S130, the electronic control unit 30 determines whether the sum of the current charging rate SOC of the battery 13 and the required power generation is less than the upper limit charging rate of the battery 13. The upper limit charging rate represents the upper limit value of the charging rate SOC of the battery 13. If the electronic control unit 30 determines in step S130 that the battery 13 is chargeable (YES), the electronic control unit 30 proceeds to step S140. On the other hand, if the electronic control unit 30 determines in step S130 that the battery 13 is not chargeable (NO), the electronic control unit 30 simply ends the processing of FIG. 2 for the current control cycle.

[0021] When the process proceeds to step S140, the electronic control unit 30 determines whether or not the combustion method will be switched from stratified combustion to homogeneous combustion due to warm-up control. The switching of the combustion method from stratified combustion to homogeneous combustion due to warm-up control here includes a switch in response to a deterioration in the combustion state during warm-up control and a switch in response to the end of warm-up control. If the electronic control unit 30 determines that the switch to homogeneous combustion will not be performed (NO), it ends the process shown in FIG. 2 for the current control cycle. On the other hand, if the electronic control unit 30 determines that the switch to homogeneous combustion will be performed (YES), it performs torque fluctuation suppression control in step S150. In the torque fluctuation suppression control, the electronic control unit 30 generates torque by the generator motor 12 to absorb torque fluctuations in the engine 11 that occur when the combustion method is switched from stratified combustion to homogeneous combustion. After the torque fluctuation suppression control is completed, the electronic control unit 30 ends the process shown in FIG. 2 for the current control cycle.

[0022] <Actions and Effects of the Embodiment> The operation and effects of this embodiment will be described. When the combustion method of the engine 11 is switched from homogeneous combustion to stratified combustion, the exhaust temperature rises. In addition, when the ignition timing of the engine 11 is retarded, the exhaust temperature also rises. When the exhaust purification catalyst 26 is not yet warmed up, the electronic control unit 30 performs warm-up control to switch the combustion method from homogeneous combustion to stratified combustion and retard the ignition timing, thereby promoting the warm-up of the exhaust purification catalyst 26. Then, when the warm-up of the exhaust purification catalyst 26 is completed, the electronic control unit 30 switches the combustion method of the engine 11 from stratified combustion to homogeneous combustion and stops the ignition retard, thereby ending the warm-up control.

[0023] Note that during stratified charge combustion, the combustion of the engine 11 is likely to become unstable even during homogeneous charge combustion. Therefore, if the combustion state of the engine 11 deteriorates during warm-up control, the electronic control unit 30 restores the combustion state by switching the combustion method from stratified charge combustion to homogeneous charge combustion while continuing the ignition retard.

[0024] Even if the torque generated by the engine 11 is the same, stratified charge combustion results in a higher intake air filling rate in the combustion chamber 20 than homogeneous charge combustion. While the fuel injection timing can be changed immediately to switch the combustion method, changing the intake air filling rate takes some time. Therefore, immediately after switching from stratified charge combustion, homogeneous charge combustion is performed with a higher intake air filling rate than normal. As a result, the torque of the engine 11 may temporarily increase when the stratified charge combustion is switched to homogeneous charge combustion. Furthermore, if stratified charge combustion is performed under unstable combustion conditions, the combustion conditions may improve when the engine 11 switches to homogeneous charge combustion. Therefore, torque fluctuations in the engine 11 may occur when the combustion method is switched from stratified charge combustion to homogeneous combustion due to a deterioration in the combustion conditions during warm-up control or the end of warm-up control. To address this issue, the electronic control unit 30 performs torque fluctuation suppression control, which absorbs torque fluctuations in the engine 11 caused by switching the combustion method by using the power generation of the generator-motor 12.

[0025] There is an upper limit to the amount of power that can be charged to the battery 13. Therefore, if torque fluctuation suppression control is performed when the SOC of the battery 13 is close to the upper limit SOC, the battery 13 may be overcharged.

[0026] On the other hand, the torque fluctuation of the engine 11 caused by switching from stratified charge combustion to homogeneous charge combustion varies depending on the operating state of the engine 11 at the time of the switch. For example, when the engine speed NE is high, the torque fluctuation upon switching to homogeneous charge combustion is greater than when it is low. Furthermore, when the engine load factor KL is high, the torque fluctuation upon switching to homogeneous charge combustion is greater than when it is low. Furthermore, when the ignition retard amount is large, the torque fluctuation upon switching to homogeneous charge combustion is greater than when it is small. The electronic control unit 30 accurately predicts the torque fluctuation of the engine 11 that would occur if switching from stratified charge combustion to homogeneous charge combustion were currently performed based on the engine speed NE, engine load factor KL, and ignition retard amount. Based on the predicted torque fluctuation, the electronic control unit 30 calculates the power generated by the generator motor 12 required to suppress torque fluctuations through torque fluctuation suppression control. Furthermore, based on the required power generation, the electronic control unit 30 determines whether the state of charge (SOC) of the battery 13 would exceed the upper limit state of charge when torque fluctuation suppression control is performed. The electronic control unit 30 then performs torque fluctuation suppression control on the condition that it determines that the state of charge of the battery 13 does not exceed the upper limit state of charge. Therefore, the control device for the hybrid vehicle 10 of this embodiment has the advantage of being able to suppress the occurrence of torque steps that accompany switching of the combustion method due to warm-up control to a range that allows overcharging of the battery 13 to be avoided. [Explanation of symbols]

[0027] 10 Hybrid vehicles 11 Engine 12 Generator motor 13 Battery 14 Inverter 20 Combustion chamber 21 Intake passage 22 Exhaust passage 23 Throttle valve 24 injectors 25 Ignition system 26 Exhaust purification catalyst 30 Electronic Control Unit 31 processors 32 memory 33 Water temperature sensor 34 Crank angle sensor 35 Air flow meter

Claims

[Claim 1] 1. A control device that is applied to a hybrid vehicle that includes an engine that generates torque used for driving, a generator motor that receives torque from the engine and generates electricity, and a battery that can be charged with the electricity generated by the generator motor, and that performs warm-up control involving switching of a combustion method of the engine from stratified charge combustion to homogeneous charge combustion, calculating a torque fluctuation amount of the engine that occurs when the combustion method is switched; calculating a generated power of the generator motor required to absorb the torque fluctuation of the engine according to the calculation result of the torque fluctuation amount; determining whether the battery can be charged with power corresponding to the calculation result of the generated power; executing torque fluctuation suppression control to absorb torque fluctuations of the engine caused by switching of the combustion method by power generation of the generator motor on condition that it is determined that the battery is chargeable; is carried out during the execution of the warm-up control. A control device for a hybrid vehicle.

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