Control system for hybrid vehicles

Abstract

To avoid misjudgments in determining combustion deterioration during catalyst warm-up. [Solution] The control device performs a first catalyst warm-up control when the catalyst has not warmed up and the requested engine output is lower than a preset threshold, by performing a first ignition timing retardation on the engine and maintaining constant engine torque and engine speed to obtain the requested engine output. The control device performs a second catalyst warm-up control when the catalyst has not warmed up and the requested engine output is above a preset threshold, by performing a second ignition timing retardation with a retardation amount smaller than the retardation amount in the first ignition timing retardation, and by setting the engine torque and engine speed to obtain the requested engine output. The control device permits the execution of a combustion deterioration judgment when the first catalyst warm-up control is being performed, and prohibits the execution of a combustion deterioration judgment when the second catalyst warm-up control is being performed.

Description

Technical Field

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

Background Art

[0002] In a hybrid vehicle including an engine and a rotating electric machine, a control device for a hybrid vehicle that warms up a catalyst for purifying the exhaust gas of the engine is known (for example, see Patent Document 1). Regarding warm-up of the catalyst in a hybrid vehicle, various proposals have been made other than Patent Document 1.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventional hybrid vehicles sometimes perform catalyst warm-up by applying a load to the engine with a rotating electric machine while maintaining the engine at a fixed-point operation and retarding the ignition timing. Here, the fixed-point operation of the engine means operating the engine while keeping the engine torque and the engine speed constant. Thus, when performing catalyst warm-up while maintaining the fixed-point operation state of the engine, it is premised that the engine torque and the engine rotation are constant, so that it is possible to easily determine combustion deterioration. That is, even though the engine is controlled so that the engine torque and the engine speed are constant, if changes in the engine torque or the engine speed are observed, it can be determined that combustion deterioration has occurred. When it is determined that combustion deterioration has occurred, countermeasures against combustion deterioration such as increasing the fuel injection amount or changing the fuel injection method can be taken.

[0005] However, when adopting a catalytic converter warm-up method that involves constant engine operation, the following inconveniences may arise. For example, consider a scenario where the required engine output increases before the catalytic converter has fully warmed up. Traditionally, in such cases, catalytic converter warm-up with ignition timing retardation was prohibited, and obtaining the required engine output was prioritized. In this case, it is conceivable that the catalytic converter will not be fully warmed up and may not be able to function adequately.

[0006] To avoid a situation where the catalyst cannot function properly, it is necessary to operate the engine in a way that allows the catalyst to warm up while obtaining the desired engine output as much as possible. One way to operate the engine that can satisfy this requirement is to retard the ignition timing to warm up the catalyst while increasing the engine speed to obtain the desired engine output. The reason for increasing the engine speed here is to compensate for the decrease in engine torque caused by retarding the ignition timing. In other words, the engine speed is used to compensate for the decrease in engine torque caused by retarding the ignition timing, thereby obtaining the desired engine output. By implementing this control, the desired engine output can be obtained while warming up the catalyst. Even if the desired engine output cannot be obtained, an engine output close to the desired engine output can be obtained.

[0007] However, if combustion deterioration is determined when such a configuration is adopted, there is a possibility of misjudgment of combustion deterioration. In other words, if combustion deterioration is determined when the engine is not operated at a fixed point, and the engine torque decreases or the engine speed changes as a result, misjudgment of combustion deterioration may occur. If misjudgment of combustion deterioration occurs, for example, if combustion deterioration is determined to be occurring when it is not, measures to counter combustion deterioration, such as increasing the fuel injection amount, may be implemented, which could actually lead to combustion deterioration or exhaust deterioration.

[0008] Patent Document 1 does not solve these problems.

[0009] Therefore, the control device for the hybrid vehicle disclosed herein aims to avoid erroneous judgments in determining combustion deterioration during catalyst warm-up. [Means for solving the problem]

[0010] The above problem is solved by a control device for a hybrid vehicle equipped with an engine connected to an exhaust pipe with a catalyst and a rotating electric machine, wherein the control device performs a first catalyst warm-up control, which, when the catalyst has not warmed up and the requested engine output is lower than a preset threshold, performs a first ignition timing retardation in the engine, applies a load to the engine using the rotating electric machine, and performs fixed-point operation to obtain the requested engine output while keeping the engine torque and engine speed constant; and when the catalyst has not warmed up and the requested engine output is above a preset threshold, performs a second ignition timing retardation, which is smaller than the retardation amount in the first ignition timing retardation, and sets the engine torque and engine speed of the engine to obtain the requested engine output; and the control device further permits the execution of a combustion deterioration judgment when the first catalyst warm-up control is being executed and prohibits the execution of the combustion deterioration judgment when the second catalyst warm-up control is being executed.

[0011] In the control device for the hybrid vehicle with the above configuration, the engine is equipped with an injector that performs in-cylinder injection, and the control device can be configured to select a fuel injection mode that performs stratified combustion in the engine when the second catalyst warm-up control is being performed.

[0012] Furthermore, in the control device for the hybrid vehicle with the above configuration, the combustion injection mode for stratified combustion can be a partial lift injection mode. [Effects of the Invention]

[0013] The control device for hybrid vehicles disclosed herein can avoid erroneous judgments in determining combustion deterioration during catalyst warm-up. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a schematic diagram showing the general configuration of a hybrid vehicle equipped with a control device for a hybrid vehicle according to an embodiment. [Figure 2] Figure 2 is a schematic diagram showing the general configuration of the engine in a hybrid vehicle according to an embodiment. [Figure 3] Figure 3 is a chart showing the relationship between the required engine power Pe during catalyst warm-up performed by the control device of the hybrid vehicle in the embodiment, engine torque Te, engine speed Ne, and emitted hydrocarbons HC. [Figure 4] Figure 4 is a flowchart showing an example of the control performed by the control device of the hybrid vehicle in this embodiment. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the dimensions and proportions of each part in the drawings may not be shown to be exactly the same as those of the actual parts. Also, some details may be omitted in the drawings.

[0016] (Embodiment) [Configuration of the Hybrid Vehicle] First, with reference to Figure 1, the hybrid electric vehicle (hereinafter simply referred to as "vehicle") 100 of the embodiment will be described. Figure 1 is a schematic diagram illustrating vehicle 100. Vehicle 100 includes an engine 1, a first motor generator (hereinafter referred to as the first MG) 61, a second motor generator (hereinafter referred to as the second MG) 62, a planetary gear mechanism 63, a transmission mechanism 64, and drive wheels 70. Vehicle 100 also includes an HVECU (Hybrid Vehicle Electronic Control Unit) 30, a PCU (Power Control Unit) 40, an engine ECU (Electronic Control Unit) 50, a battery 80, and a battery ECU 81. Furthermore, vehicle 100 includes a vehicle speed sensor 92 and an accelerator opening sensor 93. Vehicle 100 in this embodiment is a so-called two-motor hybrid vehicle, but the type of hybrid vehicle is not particularly limited. For example, it may be a so-called one-motor hybrid vehicle equipped with a single motor-generator and a clutch in the power transmission path between this single motor-generator and the engine.

[0017] The HVECU30 switches between EV driving mode and HV driving mode. To do this, the HVECU30 issues an engine start command to the engine ECU50. The HVECU30 also includes a requested engine output calculation unit 31. The requested engine output calculation unit 31 calculates the requested engine output Pe that will be handled by the engine 1 from the requested output of the vehicle 100. The engine ECU50 controls the intake air volume and ignition timing in conjunction with the operation of the engine 1. The engine ECU50 includes a first catalyst warm-up control unit 51, a second catalyst warm-up control unit 52, a combustion deterioration determination unit 53, a combustion improvement control unit 54, and a catalyst temperature estimation unit 55. The HVECU30 and the engine ECU50 cooperate to control the vehicle 100. In this embodiment, the HVECU30 and the engine ECU50 correspond to the control devices of the vehicle 100. The HVECU30 and the engine ECU50 may be integrated into a single control device. The HVECU30 and Engine ECU50 will be explained in more detail later.

[0018] Referring to FIG. 2, the engine 1 is a first driving source for vehicle running. The engine 1 includes a plurality of cylinders 2 in a cylinder block (only one cylinder 2 is shown in FIG. 2). In each cylinder 2, a piston 3 is slidably accommodated. The piston 3 forms a combustion chamber 2a between itself and a cylinder head disposed above the cylinder block. The piston 3 is connected to a crankshaft 5 via a connecting rod 4. The combustion chamber 2a is provided with an injector 6 for injecting fuel into the cylinder and a spark plug 7. The fuel injected from the injector 6 is mixed in the combustion chamber 2a and ignited by the spark plug 7. When the ignited air-fuel mixture burns and explodes, the piston 3 is pushed down. The pushed-down piston 3 transmits the explosion force to the crankshaft 5 via the connecting rod 4, rotating the crankshaft 5. The engine 1 is provided with a crank angle sensor 15 for detecting the crank angle. The engine 1 is a gasoline engine, but is not limited thereto and may be a diesel engine.

[0019] The engine 1 includes an intake port 8 and an exhaust port 9 provided so as to face the combustion chamber 2a. An intake pipe 10 is connected to the intake port 8. An exhaust pipe 11 is connected to the exhaust port 9.

[0020] The intake pipe 10 is provided with an air cleaner 12, an air flow meter 13, a throttle valve 17 and an intake manifold 18 in order from the upstream side of the intake air flow. The air flow meter 13 detects the amount of air flowing in the intake pipe 10. The throttle valve 17 adjusts the amount of air sent into the combustion chamber 2a. The intake pipe 10 branches at the intake manifold 18 and is connected to the intake port 8 of each cylinder.

[0021] The exhaust pipe 11 is provided with an exhaust manifold 20 and a catalyst 21 in order from the upstream side of the exhaust flow. The catalyst 21 performs exhaust purification.

[0022] The engine 1 includes an intake valve 23 that opens and closes an intake port 8 and an exhaust valve 24 that opens and closes an exhaust port 9. The intake valve 23 is opened and closed by a valve operating mechanism 25. The exhaust valve 24 is opened and closed by a valve operating mechanism 26.

[0023] The engine 1 of this embodiment is of an in-cylinder injection type, but may also be of a port injection type. Further, both an injector for in-cylinder injection and an injector for port injection may be provided, and the injection method may be switched as needed.

[0024] The engine ECU 50 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a storage device, and the like. The engine ECU 50 controls the engine 1 by executing programs stored in the ROM and the storage device. Programs and maps used for control are stored in the storage device.

[0025] By executing a program, the engine ECU 50 functions as a first catalyst warming control unit 51 and a second catalyst warming control unit 52 for warming up the catalyst 21.

[0026] The first catalyst warm-up control unit 51 includes a first ignition timing control unit 51a that is electrically connected to the spark plug 7. The throttle valve 17 is electrically connected to the first catalyst warm-up control unit 51. The first catalyst warm-up control unit 51 performs first catalyst warm-up control when the catalyst 21 has not warmed up and the requested engine output Pe is lower than a preset threshold Peth. Here, the threshold Peth is set appropriately within the range in which the first MG 61 can load the engine 1. The requested engine output Pe is calculated by the HVECU 30, which will be described later. If the calculated requested engine output Pe is lower than the threshold Peth, the first catalyst warm-up control is performed. The first catalyst warm-up control performs first ignition timing retardation by the first ignition timing control unit 51a and sets the engine torque and engine speed of the engine so that the requested engine output can be obtained. In other words, in the first catalyst warm-up control, the first MG61 can apply a load to the engine 1, so that the catalyst can be warmed up while the engine 1 is running in the desired state. In this embodiment, the catalyst is warmed up while performing fixed-point operation to obtain the required engine output Pe by keeping the engine torque Te and engine speed Ne of the engine 1 constant. Specifically, the first catalyst warm-up control applies a load to the engine 1 with the first MG61 and adjusts the intake amount by adjusting the opening of the throttle valve 17, thereby warming up the catalyst while keeping the engine torque Te constant.

[0027] The second catalyst warm-up control unit 52 includes a second ignition timing control unit 52a that is electrically connected to the spark plug 7. The second catalyst warm-up control unit 52 executes a second catalyst warm-up control when the catalyst 21 has not warmed up and the requested engine output Pe is greater than or equal to a preset threshold Peth. The second catalyst warm-up control is a warm-up control that performs a second ignition timing retardation by the second ignition timing control unit 52a and sets the engine torque Te and engine speed Ne of the engine 1 so that the requested engine output Pe is obtained. Here, the amount of retardation in the second ignition timing retardation is smaller than the amount of retardation in the first ignition timing retardation.

[0028] The second catalyst warm-up control unit 52 includes an injection mode selection unit 52b that is electrically connected to the injector 6. When the second catalyst warm-up control is being performed, the injection mode selection unit 52b selects an injection mode with high combustion resistance. Specifically, it performs partial lift injection by the injector 6. By performing partial lift injection, stratified combustion can be achieved. By injecting the required amount in multiple passes using partial lift injection, stratified combustion can be effectively achieved. By selecting an injection mode with high combustion resistance in this way, the occurrence of combustion deterioration can be suppressed.

[0029] The engine ECU 50 functions as a combustion deterioration determination unit 53, a combustion improvement control unit 54, and a catalyst temperature estimation unit 55 by executing a program.

[0030] The combustion deterioration determination unit 53 determines whether or not combustion deterioration is occurring based on the behavior of the engine speed Ne. For example, if the fluctuation range of the engine speed Ne is too large compared to the value detected by the accelerator opening sensor 93, which will be described later, it can be determined that combustion deterioration is occurring. The method for determining combustion deterioration is not limited to this, and conventionally known methods can be used. For example, it is possible to determine whether or not combustion deterioration is occurring by using any of the following: fluctuations in the air-fuel ratio, in-cylinder pressure, torque fluctuations, or an appropriate combination of these. Since these methods are well known, a detailed explanation will be omitted here.

[0031] When the combustion improvement control unit 54 determines that combustion deterioration is occurring, it takes measures to improve the combustion deterioration state, such as increasing the amount of fuel injected or changing the fuel injection method. Here, changing the fuel injection method means, for example, switching from port injection to in-cylinder injection when port injection is used. In this embodiment, since only an injector 6 for in-cylinder injection is equipped, the combustion improvement control unit 54 is electrically connected to the injector 6 and increases the amount of fuel injected.

[0032] The catalyst temperature estimation unit 55 estimates the temperature of the catalyst 21 based on information such as the intake air volume. Alternatively, instead of the catalyst temperature estimation unit 55, a catalyst temperature sensor may be installed to detect the temperature of the catalyst 21.

[0033] The engine ECU 50 is electrically connected to a water temperature sensor 56 that detects the temperature of the coolant circulating inside the engine 1.

[0034] The engine ECU 50 is electrically connected to the air flow meter 13 and the crank angle sensor 15. The engine ECU 50 calculates the engine speed Ne based on the value detected by the crank angle sensor 15. The engine ECU 50 calculates the engine output of engine 1 based on the value detected by the air flow meter 13 and the value detected by the crank angle sensor 15.

[0035] The first MG61 and the second MG62 are rotating electric machines, each connected to the battery 80 via the PCU40, HVECU30, and battery ECU81. The first MG61 and the second MG62 function as motors that generate vehicle driving force in response to power supplied from the battery 80. Furthermore, the first MG61 and the second MG62 also function as generators that generate regenerative power to charge the battery 80 in response to power transmission from the engine 1 and the drive wheels 70. The power exchanged between the first MG61 and the second MG62 and the battery 80 is regulated by the PCU40. The second MG62 is a second power source for vehicle propulsion. The first MG61 also functions as a starter when starting the engine 1.

[0036] PCU40 is a power control device configured to control the input and output of power between the first MG61 and the second MG62 and the battery 80. Although not shown in the diagram, PCU40 includes an inverter, a boost converter, an SMR (System Main Relay), a motor ECU, and the like.

[0037] The planetary gear mechanism 63 mechanically connects the crankshaft 5 of engine 1, the rotating shaft of the first MG 61, the rotating shaft of the second MG 62, and the output shaft of the planetary gear mechanism 63. The planetary gear mechanism 63 includes a sun gear that rotates on its own axis, a ring gear that rotates coaxially with the sun gear, a pinion gear interposed between the sun gear and the ring gear and revolving around the sun gear, and a carrier that rotates coaxially with the sun gear in accordance with the revolution of the pinion gear. The carrier is connected to the crankshaft 5 of engine 1. The sun gear is connected to the rotating shaft of the first MG 61. The ring gear is linked to the rotating shaft of the second MG 62. The driving forces of engine 1, the first MG 61, and the second MG 62 are transmitted to the drive wheels 70 via the transmission mechanism 64.

[0038] The HVECU30, like the engine ECU50, is equipped with a CPU, RAM, ROM, and storage device. The HVECU30 controls the entire system of the vehicle 100 by executing programs stored in the ROM and storage device. The HVECU30 is electrically connected to the vehicle speed sensor 92 and the accelerator pedal position sensor 93.

[0039] The HVECU30 switches the driving mode of the vehicle 100 between EV driving mode and HV driving mode. In EV driving mode, the vehicle is driven using the second MG62 as the power source with the engine 1 stopped. In HV driving mode, the vehicle is driven using the engine 1 as the power source. The case in which at least one of the first MG61 and the second MG62 is used in combination with the engine 1 is also included in HV driving mode.

[0040] The driving mode is switched based on the required torque for the vehicle 100, which is determined from the values ​​detected by the vehicle speed sensor 92 and the accelerator pedal position sensor 93. For example, if the required torque is less than the starting threshold for starting engine 1, the EV driving mode is selected, in which engine 1 is stopped in order to improve fuel efficiency. If the required torque is equal to or greater than the starting threshold for starting engine 1, the HV driving mode is selected, in which engine 1 is started.

[0041] HVECU30 functions as a requested engine output calculation unit 31. HVECU30 acquires the requested output of the vehicle 100, which is obtained based on the detection values ​​of the vehicle speed sensor 92 and the accelerator opening sensor 93. HVECU30 then calculates the requested engine output Pe that will be handled by engine 1 from the requested output. The calculated requested engine output Pe is passed to the engine ECU 50.

[0042] [Catalytic Converter Warm-Up Control] Next, an example of control in this embodiment will be described. First, the control policy for catalytic converter warm-up will be explained with reference to Figure 3. Then, an example of control performed by the HVECU30 and engine ECU50 will be explained with reference to the flowchart shown in Figure 4.

[0043] Figure 3 shows the changes in engine torque Te, engine speed Ne, and hydrocarbon HC content with respect to the required engine power Pe. The solid line in Figure 3 is a graph showing the changes in the values ​​for this embodiment, while the dashed line is a graph showing the changes in the values ​​for the comparative example.

[0044] In this embodiment, the catalyst warm-up process differs depending on whether the requested engine output Pe is lower than or equal to a preset threshold Peth. If the requested engine output Pe is lower than the threshold Peth, a first catalyst warm-up control is performed. If the requested engine output Pe is equal to or equal to the threshold Peth, a second catalyst warm-up control is performed. An example of a case where the requested engine output Pe is equal to or equal to the threshold Peth is when the vehicle 100 is in motion.

[0045] In the first catalyst warm-up control, the first ignition timing retardation is performed. Furthermore, the first MG61 applies a load to engine 1, and fixed-point operation is performed to keep engine torque Te and engine speed Ne constant. By applying a load to engine 1 with the first MG61, engine 1 can be operated at the target engine torque Te and engine speed Ne. The first catalyst warm-up control is performed similarly in the comparative example.

[0046] In the second catalytic converter warm-up control, a second ignition timing retardation is performed. The amount of retardation in this case is smaller than the amount of retardation in the first ignition timing retardation. In contrast, in the comparative example, when the required engine output Pe exceeds the threshold Peth, catalytic converter warm-up with ignition timing retardation is prohibited.

[0047] Here, we compare this embodiment with the comparative example when the requested engine output Pe is the same in the region where the requested engine output Pe is above the threshold Peth. The engine torque Te in this embodiment is lower than the engine torque Te in the comparative example. This is because the ignition timing is not retarded in the comparative example, whereas it is retarded in this embodiment. On the other hand, the engine speed Ne in this embodiment is higher than the engine speed Ne in the comparative example. The reason for this higher engine speed Ne is to compensate for the decrease in engine torque Te caused by the retardation of the ignition timing.

[0048] In the second catalytic converter warm-up control, unlike the first catalytic converter warm-up control, the engine torque Te and engine speed Ne are changed in order to obtain the desired engine output Pe.

[0049] Comparing the emissions of hydrocarbons (HC) in this embodiment with those in the comparative example, the emissions in this embodiment are lower. This is because, in the comparative example, ignition timing retardation is discontinued and catalyst warm-up is stopped, whereas in this embodiment, a second catalyst warm-up control is performed accompanied by a second ignition timing retardation. Thus, in this embodiment, hydrocarbon emissions (HC) can be suppressed compared to the comparative example when the required engine output Pe is the same.

[0050] The above outlines the control strategy for catalyst warm-up in this embodiment.

[0051] Next, with reference to Figure 4, an example of the control performed by the HVECU30 and the engine ECU50 will be described.

[0052] In step S1, the HVECU 30 determines whether the ignition is on or off. If the determination in step S1 is positive (Yes), the process proceeds to step S2. On the other hand, if the determination in step S1 is negative (No), the process in step S1 is repeated. The result of the determination in step S1 is notified to the engine ECU 50. When the ignition is turned on, the HVECU 30 starts calculating the requested engine output Pe using the requested engine output calculation unit 31 and notifies the engine ECU 50 of the calculated requested engine output Pe.

[0053] In step S2, the engine ECU 50 determines whether the catalyst 21 is in an unwarmed state. Whether the catalyst 21 is in an unwarmed state is determined based on the estimated value estimated by the catalyst temperature estimation unit 55. If the estimated value by the catalyst temperature estimation unit 55 is lower than a preset threshold, the catalyst 21 is considered to be in an unwarmed state. If the determination in step S2 is Yes, the process proceeds to step S3. On the other hand, if the determination in step S2 is No, the engine ECU 50 terminates the process.

[0054] In step S3, the engine ECU 50 determines whether the first catalytic converter warm-up control is executable. The conditions for determining whether the first catalytic converter warm-up control is executable include that the coolant temperature detected by the water temperature sensor 56 is above the lower limit of the water temperature preset for executing the catalytic converter warm-up control. This condition is in place to avoid the possibility that executing the catalytic converter warm-up control when the coolant temperature is too low may actually worsen emissions. Other conditions that can be included are that the engine is not in check mode and that all parts of the engine 1 are functioning normally. Whether all parts are functioning normally can be determined, for example, by determining that no abnormalities are detected in the OBD (On-Board Diagnostics) diagnosis. If these conditions are not met, it is assumed that the catalytic converter cannot be properly warmed up. Therefore, it is determined whether these conditions are met. If the determination in step S3 is Yes, the process proceeds to step S4. On the other hand, if the determination in step S3 is No, the process in step S3 is repeated.

[0055] In step S4, the first catalyst warm-up control unit performs the first catalyst warm-up control. Specifically, the first ignition timing control unit 51a performs the first ignition timing retardation. In addition, the first MG61 applies a load to the engine 1, and fixed-point operation is performed in which the engine torque Te and engine speed Ne remain constant. This promotes the warm-up of the catalyst 21. After the processing in step S4, the engine ECU 50 proceeds to step S5.

[0056] The first catalyst warm-up control is performed when the requested engine output Pe is lower than the threshold Peth. If both step S2 and step S3 result in a Yes determination, the first catalyst warm-up control is performed uniformly without determining whether the requested engine output Pe is lower than the threshold Peth.

[0057] In step S5, the engine ECU 50 determines whether the requested engine output Pe notified by the HVECU 30 is greater than or equal to the threshold Peth. If the determination in step S5 is No, the process proceeds to step S6. On the other hand, if the determination in step S5 is Yes, the process proceeds to step S9.

[0058] In step S6, the first catalyst warm-up control unit 51 continues the first catalyst warm-up control. Then, the process proceeds to step S7.

[0059] In step S7, the combustion deterioration determination unit 53 determines whether or not combustion deterioration is occurring in the engine 1. The combustion deterioration determination unit 53 determines that combustion deterioration is occurring if the fluctuation range of the engine speed Ne is too large relative to the value detected by the accelerator opening sensor 93. The combustion deterioration determination in step S7 is performed while the first catalyst warm-up control is in operation. During the first catalyst warm-up control, the engine 1 operates at the target engine torque Te and engine speed Ne. Therefore, the accuracy of the combustion deterioration determination is high. Data on the fluctuation range of the engine speed Ne when combustion deterioration is not occurring can be obtained in advance through experiments or simulations. By comparing this fluctuation range data with the actual detected value, it is possible to accurately determine whether or not combustion deterioration is occurring. If the determination in step S7 is Yes, the process proceeds to step S8. On the other hand, if the determination in step S7 is No, the process from step S2 is repeated.

[0060] In step S8, the combustion improvement control unit 54 increases the fuel injection amount. This improves the combustion state. After the process in step S8, the process from step S2 is repeated.

[0061] In step S9, the second catalyst warm-up control unit 52 performs a second catalyst warm-up control. The second catalyst warm-up control unit 52 performs a second ignition timing retardation using the second ignition timing control unit 52a, and sets the engine torque Te and engine speed Ne of engine 1 so that the required engine output Pe is obtained. The amount of retardation in the second ignition timing retardation is smaller than the amount of retardation in the first ignition timing retardation. Therefore, it is easier to obtain a higher engine torque Te compared to when the first catalyst warm-up control is performed. Therefore, it is easier to obtain a required engine output Pe that is equal to or greater than the threshold Peth.

[0062] In the second catalytic converter warm-up control, the injection mode selection unit 52b selects partial lift injection as the injection mode for engine 1. Partial lift injection enables stratified combustion. Stratified combustion has high combustion resistance and is less prone to combustion deterioration.

[0063] After the processing in step S9, the processing from step S2 is repeated. When step S9 is performed, unlike when the processing in step S6 is performed, a combustion deterioration judgment like in step S7 is not performed. When the second catalyst warm-up control is being executed, the combustion deterioration judgment is prohibited.

[0064] This is because the second catalytic converter warm-up control takes into account changes in engine torque Te and engine speed Ne in order to obtain the desired engine output Pe. Changes in engine torque Te and engine speed Ne can lead to misjudgments in the combustion deterioration determination. Suppose a combustion deterioration determination is performed while the second catalytic converter warm-up control is running, and it is determined that combustion deterioration has occurred. In this case, combustion improvement control is performed as in step S8. However, if the determination that combustion deterioration has occurred is incorrect, combustion improvement control will be performed and fuel injection will be increased even though combustion deterioration has not occurred. As a result, this may actually lead to combustion deterioration and exhaust deterioration. For this reason, in this embodiment, combustion deterioration determination is prohibited while the second catalytic converter warm-up control is running. This makes it possible to avoid misjudgments altogether.

[0065] Furthermore, in the second catalytic converter warm-up control, stratified combustion is performed using partial lift injection. Because a fuel injection with high combustion resistance is used in this way, combustion degradation is less likely to occur. In this respect as well, it is unlikely that prohibiting combustion degradation detection while the second catalytic converter warm-up control is in operation will cause any adverse effects.

[0066] [effect] According to this embodiment, the second catalyst warm-up control is performed when the requested engine output Pe is equal to or greater than a preset threshold Peth. Furthermore, the combustion deterioration judgment is prohibited while the second catalyst warm-up control is being performed. This prevents erroneous judgments regarding combustion deterioration.

[0067] In the first catalyst warm-up control, by performing fixed-point operation to obtain the required engine output while keeping the engine torque and engine speed constant, the accuracy of combustion deterioration detection during the first catalyst warm-up control can be improved.

[0068] When the second catalytic converter warm-up control is being performed, the engine 1 selects a fuel injection mode that performs stratified combustion using an injector 6 that performs in-cylinder injection, thereby making it less likely for combustion deterioration to occur.

[0069] The embodiments described above are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention, and it is obvious from the above description that various other embodiments are possible within the scope of the present invention. [Explanation of symbols]

[0070] 1...Engine, 2...Cylinder, 3...Piston, 4...Connecting rod, 5...Crankshaft, 6...Injector, 7...Spark plug, 10...Intake pipe, 11...Exhaust pipe, 12...Air cleaner, 13...Air flow meter, 15...Crank angle sensor, 17...Throttle valve, 21...Catalytic converter, 30...HVECU, 31...Required engine power calculation unit, 40...PCU, 50...Engine ECU, 51...First catalytic converter warm-up control unit, 51a...First ignition Timing control unit, 52... Second catalyst warm-up control unit, 52a... Second ignition timing control unit, 52b... Injection mode selection unit, 53... Combustion deterioration determination unit, 54... Combustion improvement control unit, 55... Catalyst temperature estimation unit, 56... Water temperature sensor, 61... First MG, 62... Second MG, 63... Planetary gear mechanism, 64... Transmission mechanism, 70... Drive wheel, 80... Battery, 81... Battery ECU, 92... Vehicle speed sensor, 93... Accelerator opening sensor, 100... Hybrid vehicle

Claims

1. A control device for a hybrid vehicle comprising an engine connected to an exhaust pipe equipped with a catalyst, and a rotating electric motor, The control device is If the catalyst has not warmed up and the required engine output is lower than a preset threshold, a first catalyst warm-up control is performed, which involves retarding the ignition timing of the engine, applying a load to the engine using the rotating electric motor, and performing fixed-point operation to obtain the required engine output while keeping the engine torque and engine speed constant. If the catalyst has not warmed up and the requested engine output is above a preset threshold, a second catalyst warm-up control is performed, which involves a second ignition timing retardation with a retardation amount smaller than that in the first ignition timing retardation, and setting the engine torque and engine speed of the engine so that the requested engine output can be obtained. The control device further permits the execution of the combustion deterioration determination when the first catalyst warm-up control is being performed, and prohibits the execution of the combustion deterioration determination when the second catalyst warm-up control is being performed. Control system for hybrid vehicles.

2. The engine is equipped with an injector that performs in-cylinder injection, The control device is When the second catalyst warm-up control is being performed, the engine selects a fuel injection mode that performs stratified combustion using the injector that performs in-cylinder injection. A control device for a hybrid vehicle according to claim 1.

3. The combustion injection mode used for stratified combustion is partial lift injection. A control device for a hybrid vehicle according to claim 2.

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