Control device for a hybrid vehicle

Abstract

The present application aims at avoiding misjudgment in combustion deterioration determination during catalyst warm-up. A control device executes first catalyst warm-up control, which delays first ignition timing of an engine and keeps engine torque and engine speed constant to perform a constant-point operation for obtaining a required engine output, when warm-up of the catalyst is not completed and the required engine output is below a predetermined threshold. The control device executes second catalyst warm-up control, which delays second ignition timing of the engine by an amount smaller than that of the first ignition timing delay and sets engine torque and engine speed to obtain the required engine output, when warm-up of the catalyst is not completed and the required engine output is above the predetermined threshold. The control device allows combustion deterioration determination when the first catalyst warm-up control is being executed and prohibits combustion deterioration determination when the second catalyst warm-up control is being executed.

Description

Technical Field

[0001] This invention relates to a control device for a hybrid vehicle. Background Technology

[0002] A control device for a hybrid vehicle is known to warm up the catalyst for purifying engine exhaust in a hybrid vehicle equipped with an engine and a rotary electric motor (see, for example, Patent Document 1). Various technologies other than Patent Document 1 have been proposed for warming up the catalyst in hybrid vehicles.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2014-159255 Summary of the Invention

[0004] Conventional hybrid vehicles sometimes maintain engine operation at a fixed point by applying load to the engine through a rotary motor and warming up the catalytic converter by delaying ignition timing. Here, engine operation at a fixed point means running the engine while maintaining constant engine torque and engine speed. Thus, when maintaining engine operation at a fixed point while warming up the catalytic converter, combustion degradation can be easily detected because constant engine torque and engine speed are assumed. That is, even if the engine is controlled to maintain constant engine torque and engine speed, changes in engine torque or engine speed can be observed, indicating combustion degradation. If combustion degradation is detected, countermeasures such as increasing the fuel injection quantity or changing the fuel injection method can be taken.

[0005] However, when using a catalytic converter warm-up method that accompanies the engine's scheduled operation, the following adverse situations may occur. For example, suppose the required engine output increases before the catalytic converter has fully warmed up. Previously, in such cases, catalytic converter warm-up accompanied by ignition timing retardation was preferentially disabled to obtain the required engine output. In this situation, if the catalytic converter has not fully warmed up, it cannot function effectively.

[0006] Therefore, to prevent the catalytic converter from failing to function fully, it is necessary to run the engine while the catalytic converter is warming up to obtain the desired engine output as much as possible. One way to achieve this is to run the engine while simultaneously increasing the engine speed to obtain the desired engine output, using ignition timing delay for catalytic converter warm-up. Here, increasing the engine speed is to account for the decrease in engine torque caused by the ignition timing delay. That is, the engine speed is used to compensate for the decrease in engine torque caused by the ignition timing delay, thereby obtaining the desired engine output. By implementing this control, the desired engine output can be obtained while the catalytic converter is warming up. Furthermore, even if the desired engine output cannot be obtained, an engine output close to the desired output can be obtained.

[0007] However, when using this method, misjudgments may occur if combustion degradation determination is performed. Specifically, if combustion degradation determination is performed under operating conditions where engine torque decreases or engine speed changes without engine idling, misjudgments may occur. In cases of misjudgment, for example, even if combustion degradation is not observed, if it is determined to have occurred, implementing combustion degradation countermeasures such as increasing fuel injection may actually lead to further combustion degradation or exhaust degradation.

[0008] Patent document 1 does not solve this problem.

[0009] Therefore, the challenge of the control device for hybrid vehicles disclosed in this specification is to avoid misjudgment in the determination of combustion degradation during catalyst warm-up.

[0010] The aforementioned problem is achieved through a control device for a hybrid vehicle comprising: an engine connected to an exhaust pipe containing a catalyst; and a rotary motor. The control device performs the following control: when the catalyst warm-up is incomplete and the required engine output is below a preset threshold, a first catalyst warm-up control is executed. This first catalyst warm-up control delays the engine's ignition timing by a first time and applies a load to the engine via the rotary motor, maintaining constant engine torque and engine speed to achieve the desired engine output. Furthermore, when the catalyst warm-up is incomplete and the desired engine output is above the preset threshold, a second catalyst warm-up control is executed. This second catalyst warm-up control delays the ignition timing by a second time, with a delay amount less than that in the first ignition timing delay, and sets the engine torque and engine speed to obtain the desired engine output. The control device also allows combustion degradation determination to be performed while the first catalyst warm-up control is being executed, and prohibits combustion degradation determination while the second catalyst warm-up control is being executed.

[0011] In the control device of the hybrid vehicle with the above structure, the engine is equipped with an injector for in-cylinder injection, and when the control device performs the second catalyst warm-up control, it selects a fuel injection mode for stratified combustion in the engine.

[0012] Furthermore, in the control device of the hybrid vehicle with the above-described structure, the combustion injection method for performing the stratified combustion can be partial lift injection.

[0013] Invention Effects

[0014] The control device for hybrid vehicles disclosed in this specification can avoid misjudgments in the determination of combustion degradation during catalyst warm-up. Attached Figure Description

[0015] Figure 1 This is a schematic diagram showing the general structure of a hybrid vehicle with a control device for a hybrid vehicle having an implementation method.

[0016] Figure 2 This is a schematic diagram showing the general structure of the engine in the hybrid vehicle described in the embodiment.

[0017] Figure 3 This is a graph showing the relationship between the required engine output Pe during catalyst warm-up performed by the control device of the hybrid vehicle in the embodiment, and the engine torque Te, engine speed Ne, and emitted hydrocarbons HC.

[0018] Figure 4 This is a flowchart illustrating an example of the control performed by the control device of a hybrid vehicle according to an embodiment. Detailed Implementation

[0019] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, in the drawings, the dimensions, proportions, etc., of each part are not sometimes illustrated in a manner completely consistent with the actual situation. Furthermore, sometimes detailed descriptions are omitted from the drawings.

[0020] (Implementation Method)

[0021] [Structure of Hybrid Vehicles] First, refer to Figure 1 The hybrid electric vehicle (hereinafter referred to as "vehicle") 100 of the embodiment will be described. Figure 1 This is a schematic diagram illustrating a vehicle 100. The vehicle 100 includes an engine 1, a first electric generator (hereinafter referred to as 1MG) 61, a second electric generator (hereinafter referred to as 2MG) 62, a planetary gear mechanism 63, a transmission mechanism 64, and drive wheels 70. Furthermore, the vehicle 100 includes a Hybrid Vehicle Electronic Control Unit (HVECU) 30, a Power Control Unit (PCU) 40, an Engine Electronic Control Unit (ECU) 50, a battery 80, and a battery ECU 81. Additionally, the vehicle 100 includes a vehicle speed sensor 92 and a throttle opening sensor 93. The vehicle 100 in this embodiment is a so-called two-motor hybrid vehicle, but the form of the hybrid vehicle is not particularly limited. For example, it could be a so-called one-motor hybrid vehicle that includes one electric generator and a clutch in the power transmission path between the electric generator and the engine.

[0022] HVECU 30 switches between EV driving mode and HV driving mode. Therefore, HVECU 30 sends an engine start command to engine ECU 50. Furthermore, HVECU 30 includes a required engine output calculation unit 31. The required engine output calculation unit 31 calculates the required engine output Pe to be borne by engine 1 in the required output of vehicle 100. Engine ECU 50 controls the intake air volume or ignition timing accompanying the operation of engine 1. Engine ECU 50 includes a first catalytic converter warm-up control unit 51, a second catalytic converter warm-up control unit 52, a combustion degradation determination unit 53, a combustion improvement control unit 54, and a catalytic converter temperature estimation unit 55. HVECU 30 and engine ECU 50 cooperate to control vehicle 100. In this embodiment, HVECU 30 and engine ECU 50 are equivalent to the control devices of vehicle 100. HVECU 30 and engine ECU 50 can be configured as a single integrated control device. HVECU 30 and engine ECU 50 will be described in more detail later.

[0023] refer to Figure 2 Engine 1 is the primary drive source for vehicle operation. Engine 1 has multiple cylinders 2 within its cylinder block. Figure 2 Only one cylinder 2 is shown in the diagram. A piston 3 is slidably housed within each cylinder 2. A combustion chamber 2a is formed between the piston 3 and the cylinder head, which is located on the upper side of the cylinder block. The piston 3 is connected to the crankshaft 5 via a connecting rod 4. An injector 6 and a spark plug 7 are provided in the combustion chamber 2a for injecting fuel into the cylinder. The fuel injected from the injector 6 forms a mixture in the combustion chamber 2a and is ignited by the spark plug 7. If the ignited mixture burns and explodes, the piston 3 is pressed down. The pressed piston 3 transmits the explosive force to the crankshaft 5 via the connecting rod 4, causing the crankshaft 5 to rotate. A crankshaft angle sensor 15 for detecting the crankshaft angle is provided in the engine 1. The engine 1 is a gasoline engine, but is not limited to this; it can also be a diesel engine.

[0024] The engine 1 has an air intake 8 and an exhaust port 9 arranged facing the combustion chamber 2a. An intake pipe 10 is connected to the air intake 8. An exhaust pipe 11 is connected to the exhaust port 9.

[0025] On the intake manifold 10, an air filter 12, an air flow meter 13, a throttle valve 17, and an intake manifold 18 are sequentially arranged from the upstream side of the intake air flow. The air flow meter 13 detects the amount of air flowing in the intake manifold 10. The throttle valve 17 adjusts the amount of air supplied to the combustion chamber 2a. The intake manifold 10 is branched by the intake manifold 18 and connected to the intake ports 8 of each cylinder.

[0026] On the exhaust pipe 11, an exhaust manifold 20 and a catalyst 21 are sequentially arranged from the upstream side of the exhaust flow. The catalyst 21 purifies the exhaust.

[0027] Engine 1 has an intake valve 23 for opening and closing the intake port 8 and an exhaust valve 24 for opening and closing the exhaust port 9. The intake valve 23 is opened and closed by a valve mechanism 25. The exhaust valve 24 is opened and closed by a valve mechanism 26.

[0028] The engine 1 in this embodiment uses in-cylinder injection, but it can also use port injection. Furthermore, it can have both in-cylinder injection injectors and port injection injectors, and the injection method can be switched as needed.

[0029] The engine ECU 50 includes a central processing unit (CPU), random access memory (RAM), read-only memory (ROM), and storage devices. The engine ECU 50 controls the engine 1 by executing programs stored in the ROM or storage devices. The storage devices contain programs or maps used for control.

[0030] The engine ECU 50 executes a program to function as the first catalyst warm-up control unit 51 and the second catalyst warm-up control unit 52 for warming up the catalyst 21.

[0031] The first catalytic converter warm-up control unit 51 includes a first ignition timing control unit 51a electrically connected to the spark plug 7. The throttle valve 17 is electrically connected to the first catalytic converter warm-up control unit 51. The first catalytic converter warm-up control unit 51 performs first catalytic converter warm-up control when the catalytic converter 21 has not fully warmed up and the required engine output Pe is lower than a preset threshold Peth. Here, the threshold Peth is appropriately set within a range that allows the engine 1 to be loaded via the first MG 61. Furthermore, the required engine output Pe is calculated by the HVECU 30, which will be described later. The first catalytic converter warm-up control performs first ignition timing delay via the first ignition timing control unit 51a and sets the engine torque and engine speed to obtain the required engine output. That is, in the first catalytic converter warm-up control, since the engine 1 can be loaded via the first MG 61, catalytic converter warm-up can be performed while the engine 1 is running in the target state. In this embodiment, the catalytic converter is warmed up while maintaining a constant engine torque Te and engine speed Ne of engine 1 to obtain the required engine output Pe. Specifically, the first catalytic converter warm-up control adjusts the intake air volume by applying a load to engine 1 through the first MG61 and adjusting the opening of the throttle valve 17, thereby maintaining a constant engine torque Te while warming up the catalytic converter.

[0032] The second catalytic converter warm-up control unit 52 includes a second ignition timing control unit 52a electrically connected to the spark plug 7. The second catalytic converter warm-up control unit 52 performs second catalytic converter warm-up control when the catalytic converter 21 has not fully warmed up and the required engine output Pe is above a preset threshold Peth. The second catalytic converter warm-up control involves delaying the second ignition timing via the second ignition timing control unit 52a and setting the engine torque Te and engine speed Ne of the engine 1 to obtain the required engine output Pe. Here, the delay amount in the second ignition timing delay is less than the delay amount in the first ignition timing delay.

[0033] The second catalytic converter warm-up control unit 52 includes an injection mode selection unit 52b electrically connected to the injector 6. When performing the second catalytic converter warm-up control, the injection mode selection unit 52b selects an injection mode with high flame retardancy. Specifically, partial-lift injection is performed by the injector 6. By performing partial-lift injection, stratified combustion can be achieved. By performing partial-lift injection, the necessary injection quantity is injected multiple times, thereby effectively achieving stratified combustion. Thus, by selecting an injection mode with high flame retardancy, the occurrence of combustion degradation can be suppressed.

[0034] The engine ECU 50 functions as a combustion degradation determination unit 53, a combustion improvement control unit 54, and a catalyst temperature estimation unit 55 by executing programs.

[0035] The combustion degradation determination unit 53 determines whether combustion degradation has occurred based on changes in engine speed Ne. For example, if the change in engine speed Ne is too large relative to the detection value of the throttle opening sensor 93 (described later), combustion degradation can be determined to have occurred. The method for determining combustion degradation is not limited to this, and conventionally known methods can be used. For example, it can be determined whether combustion degradation has occurred based on any one or a suitable combination of changes in air-fuel ratio, cylinder pressure, and torque. These methods are known, so their detailed descriptions are omitted here.

[0036] When the combustion improvement control unit 54 determines that combustion degradation has occurred, it takes measures to improve the combustion degradation state by increasing the combustion injection quantity or changing the fuel injection method. Here, changing the fuel injection method is, for example, switching from port injection to in-cylinder injection when port injection is used. In this embodiment, since only an in-cylinder injection injector 6 is provided, the combustion improvement control unit 54 is electrically connected to the injector 6 and increases the fuel injection quantity.

[0037] The catalyst temperature estimation unit 55 estimates the temperature of the catalyst 21 based on information such as the amount of air intake. Alternatively, a catalyst temperature sensor may be provided instead of the catalyst temperature estimation unit 55, and the temperature of the catalyst 21 may be detected by the catalyst temperature sensor.

[0038] A water temperature sensor 56 is electrically connected to the engine ECU 50 to detect the temperature of the coolant circulating in the engine 1.

[0039] The engine ECU 50 is electrically connected to the air flow meter 13 and the crankshaft angle sensor 15. The engine ECU 50 calculates the engine speed Ne based on the detection value of the crankshaft angle sensor 15. The engine ECU 50 calculates the output of engine 1 based on the detection values ​​of the air flow meter 13 and the crankshaft angle sensor 15.

[0040] MG61 and MG62 are rotary motors, connected to battery 80 via PCU40, HVECU30, and battery ECU81. MG61 and MG62 function as motors that generate driving force for the vehicle based on power supplied from battery 80. Furthermore, MG61 and MG62 also function as generators that produce regenerative power to charge battery 80 based on power transmitted from engine 1 or drive wheels 70. The power supplied between MG61 and MG62 and battery 80 is regulated by PCU40. MG62 serves as a second drive source for vehicle operation. MG61 also functions as a starter motor when starting engine 1.

[0041] PCU40 is a power control device configured to control the input and output of power between the 1st MG61 and the 2nd MG62 and the battery 80. Although not shown, PCU40 includes an inverter, a boost converter, a system main relay (SMR), a motor ECU, etc.

[0042] Planetary gear mechanism 63 mechanically connects the crankshaft 5 of engine 1, the rotating shaft of the first MG61, the rotating shaft of the second MG62, and the output shaft of planetary gear mechanism 63. Planetary gear mechanism 63 includes a rotating sun gear, a ring gear rotating coaxially with the sun gear, a pinion revolving around the sun gear as a center, and a planet carrier rotating coaxially with the sun gear according to the revolution of the pinion. The planet carrier is connected to the crankshaft 5 of engine 1. The sun gear is connected to the rotating shaft of the first MG61. The ring gear is linked to the rotating shaft of the second MG62. Through transmission mechanism 64, the driving force of engine 1 or the first MG61 and second MG62 is transmitted to the drive wheel 70.

[0043] Like the engine ECU 50, the HVECU 30 has a CPU, RAM, ROM, and storage devices. The HVECU 30 controls the entire system of the vehicle 100 by executing programs stored in the ROM or storage devices. The HVECU 30 is electrically connected to the vehicle speed sensor 92 and the throttle opening sensor 93.

[0044] HVECU30 switches the driving mode of vehicle 100 to either EV driving mode or HV driving mode. In EV driving mode, the vehicle travels using the second MG62 as the power source while engine 1 is stopped. In HV driving mode, engine 1 is driven, and the vehicle travels using engine 1 as the power source. Even when at least one of the first MG61 and the second MG62 is used in conjunction with engine 1, this is still considered HV driving mode.

[0045] The driving mode is switched based on the required torque for the vehicle 100 calculated from the detection value of the vehicle speed sensor 92 or the detection value of the throttle opening sensor 93. For example, if the required torque is less than the starting threshold for starting the engine 1, the EV driving mode is selected to stop the engine 1 in order to improve fuel consumption. If the required torque is greater than or equal to the starting threshold for starting the engine 1, the HV driving mode is selected to start the engine 1.

[0046] HVECU30 functions as the required engine output calculation unit 31. HVECU30 obtains the required output of vehicle 100 based on the detection value of vehicle speed sensor 92 or throttle opening sensor 93. Then, HVECU30 calculates the required engine output Pe to be borne by engine 1 in the required output. The calculated required engine output Pe is then transferred to engine ECU50.

[0047] [Catalyst Warm-up Control] Next, an example of control in this embodiment will be described. First, refer to... Figure 3 The control policy for catalyst warm-up is explained. Then, refer to... Figure 4 The flowchart shown illustrates an example of the control performed by HVECU30 and engine ECU50.

[0048] exist Figure 3 The figure shows the changes in engine torque Te, engine speed Ne, and hydrocarbon HC content relative to the desired engine output Pe. Figure 3 The solid lines shown are graphs representing the numerical changes in this embodiment, while the dashed lines are graphs representing the numerical changes in the comparative examples.

[0049] In this embodiment, the catalytic converter warm-up process differs depending on whether the desired engine output Pe is below a preset threshold Peth or above the threshold Peth. When the desired engine output Pe is below the threshold Peth, first catalytic converter warm-up control is performed. Then, when the desired engine output Pe is above the threshold Peth, second catalytic converter warm-up control is performed. For example, the scenario where the desired engine output Pe is above the threshold Peth can be assumed to be when the vehicle 100 is in motion.

[0050] In the first catalytic converter warm-up control, the first ignition timing is delayed. Furthermore, a load is applied to engine 1 via the first MG61, resulting in constant engine torque Te and engine speed Ne. By applying a load to engine 1 via the first MG61, engine 1 can be operated with the target engine torque Te and engine speed Ne. In the comparative example, the first catalytic converter warm-up control is performed similarly.

[0051] In the second catalytic converter warm-up control, a second ignition timing delay is performed. This delay is less than the delay in the first ignition timing delay. In contrast, in the comparative example, when the required engine output Pe exceeds the threshold Peth, catalytic converter warm-up itself, accompanied by ignition timing delay, is prohibited.

[0052] Here, in the region where the desired engine output Pe is above the threshold Peth, this embodiment and the comparative example are compared when the desired engine output Pe is the same. The engine torque Te in this embodiment is lower than the torque Te in the comparative example. This is because ignition timing delay was not performed in the comparative example, but it was performed 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. Thus, the higher engine speed Ne is to compensate for the decrease in engine torque Te caused by the ignition timing delay.

[0053] In the second catalyst warm-up control, unlike the first catalyst warm-up control, the engine torque Te or engine speed Ne changes in order to obtain the desired engine output Pe.

[0054] Comparing the hydrocarbon (HC) emissions of this embodiment with those of the comparative example, the emissions of HC in this embodiment are lower. This is because, in the comparative example, the ignition timing delay is eliminated and catalytic converter warm-up is stopped, while in this embodiment, a second catalytic converter warm-up control is performed accompanied by a second ignition timing delay. Thus, in this embodiment, the hydrocarbon (HC) emissions can be suppressed compared to the comparative example when the desired engine output Pe is the same.

[0055] The above is the control policy for catalyst warm-up in this embodiment.

[0056] Next, refer to Figure 4 An example of the control performed by HVECU30 and engine ECU50 will be explained.

[0057] In step S1, the HVECU 30 determines whether ignition is on. If the determination is affirmative ("yes") in step S1, the process proceeds to step S2. Conversely, if the determination is negative ("no") in step S1, the process of step S1 is repeated. The determination result in step S1 is notified to the engine ECU 50. Furthermore, when ignition is on, the HVECU 30 begins to calculate the required engine output Pe using the required engine output calculation unit 31 and notifies the engine ECU 50 of the calculated required engine output Pe.

[0058] In step S2, the engine ECU 50 determines whether the catalyst 21 is in a state of not being warmed up. This determination is based on an estimated value calculated by the catalyst temperature estimation unit 55. If the estimated value calculated by the catalyst temperature estimation unit 55 is lower than a preset threshold, the catalyst 21 is in a state of not being warmed up. If the determination in step S2 is "yes," the process proceeds to step S3. Conversely, if the determination in step S2 is "no," the engine ECU 50 terminates the process.

[0059] In step S3, the engine ECU 50 determines whether the first catalytic converter warm-up control can be performed. The conditions for determining whether the first catalytic converter warm-up control can be performed include the coolant temperature detected by the coolant temperature sensor 56 exceeding a preset lower limit value for performing the catalytic converter warm-up control. This condition is considered to prevent emissions from worsening when performing catalytic converter warm-up control at excessively low coolant temperatures. Furthermore, as another condition, the engine 1 can be considered to be not in engine check mode and that all components are functioning normally. The determination of whether the functions of each component are normal can be made, for example, by determining that no abnormalities are detected in on-board diagnostics (OBD). It is assumed that if these conditions are insufficient, proper catalytic converter warm-up cannot be performed. 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 of step S3 is repeated.

[0060] In step S4, the first catalytic converter warm-up control unit performs first catalytic converter warm-up control. That is, the first ignition timing is delayed by the first ignition timing control unit 51a. Furthermore, the engine 1 is subjected to a load by the first MG61, ensuring that the engine torque Te and engine speed Ne are kept constant. This promotes the warm-up of the catalytic converter 21. After the processing in step S4, the engine ECU 50 proceeds to step S5.

[0061] Furthermore, the first catalyst warm-up control is performed when the required engine output Pe is lower than the threshold Peth. If both steps S2 and S3 are determined to be Yes, the first catalyst warm-up control is executed without determining whether the required engine output Pe is lower than the threshold Peth.

[0062] In step S5, the engine ECU 50 determines whether the required engine output Pe, as notified by the HVECU 30, is above the threshold Peth. If the determination in step S5 is "No," the process proceeds to step S6. Conversely, if the determination in step S5 is "Yes," the process proceeds to step S9.

[0063] 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.

[0064] In step S7, the combustion degradation determination unit 53 determines whether combustion degradation has occurred in the engine 1. If the fluctuation of the engine speed Ne is too large relative to the detection value of the throttle opening sensor 93, the combustion degradation determination unit 53 determines that combustion degradation has occurred. The combustion degradation determination in step S7 is performed under the state of first catalyst warm-up control. In the first catalyst warm-up control, the engine 1 operates at the target engine torque Te and engine speed Ne. Therefore, the accuracy of combustion degradation determination is high. Data on the fluctuation of engine speed Ne when combustion degradation has not occurred can be obtained in advance through experiments or simulations. By comparing this fluctuation data with the actual detection value, it is possible to determine with high accuracy whether combustion degradation has occurred. 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 of step S2 is repeated.

[0065] In step S8, the combustion improvement control unit 54 increases the fuel injection quantity. This improves the combustion conditions. After the process in step S8, the process in step S2 is repeated.

[0066] In step S9, second catalytic converter warm-up control is performed by the second catalytic converter warm-up control unit 52. The second catalytic converter warm-up control unit 52 performs a second ignition timing delay via the second ignition timing control unit 52a, and sets the engine torque Te and engine speed Ne of engine 1 to obtain the desired engine output Pe. The delay amount in the second ignition timing delay is less than the delay amount in the first ignition timing delay. Therefore, compared to when performing first catalytic converter warm-up control, it is easier to obtain a high engine torque Te. Therefore, it is easier to obtain an engine output Pe above the threshold Peth.

[0067] In the second catalyst warm-up control, partial-lift injection is selected as the injection method for engine 1 by the injection method selection unit 52b. Partial-lift injection enables stratified combustion. Stratified combustion exhibits high flame retardancy, thus reducing the likelihood of combustion degradation.

[0068] After the processing in step S9, the processing in step S2 is repeated. Unlike the case where step S6 was performed, when step S9 was performed, the combustion degradation determination as in step S7 is not performed. Combustion degradation determination is prohibited during the execution of the second catalyst warm-up control.

[0069] This is because, in the second catalytic converter warm-up control, changes in engine torque Te or engine speed Ne are considered in order to obtain the desired engine output Pe. If the engine torque Te or engine speed Ne changes, a misjudgment may occur in the combustion degradation determination. Suppose that combustion degradation determination is performed while the second catalytic converter warm-up control is in effect, and the result is a determination that combustion degradation has occurred. In this case, combustion improvement control is performed in the same manner as in step S8. However, if the determination that combustion degradation has occurred is a misjudgment, combustion improvement control will still be performed and fuel injection will be increased even if combustion degradation has not occurred. This could potentially lead to combustion degradation or exhaust degradation. Therefore, in this embodiment, combustion degradation determination during the second catalytic converter warm-up control is prohibited. This avoids the possibility of misjudgment itself.

[0070] Furthermore, stratified combustion based on partial lift injection is performed during the second catalytic converter warm-up control. This reduces the likelihood of combustion degradation by injecting fuel with high flammability. Therefore, it is believed that the drawback of prohibiting combustion degradation assessment during the second catalytic converter warm-up control is less likely to occur.

[0071] (Effect)

[0072] According to this embodiment, when the required engine output Pe is above a preset threshold Peth, second catalytic converter warm-up control is performed. Then, combustion degradation determination during second catalytic converter warm-up control is disabled. This avoids erroneous determinations of combustion degradation.

[0073] In the first catalyst warm-up control, by maintaining the engine torque and engine speed at a constant point to obtain the desired engine output, the accuracy of combustion degradation determination during the first catalyst warm-up control can be improved.

[0074] When the second catalyst warm-up control is performed, in engine 1, by selecting a stratified combustion fuel injection method using injectors 6 that perform in-cylinder injection, combustion deterioration is less likely to occur.

[0075] The above embodiments are merely examples for implementing the present invention, and the present invention is not limited to these. Various modifications to these embodiments are within the scope of the present invention, and other various embodiments are possible within the scope of the present invention, as is evident from the above description.

[0076] Symbol Explanation

[0077] 1-Engine, 2-Cylinder, 3-Piston, 4-Connecting rod, 5-Crankshaft, 6-Injector, 7-Spark plug, 10-Intake manifold, 11-Exhaust manifold, 12-Air filter, 13-Air flow meter, 15-Crankshaft angle sensor, 17-Throttle valve, 21-Catalyst, 30-HVECU, 31-Required engine output calculation unit, 40-PCU, 50-Engine ECU, 51-First catalyst warm-up control unit, 51a-First ignition timing control unit, 52- 52a - Second catalytic converter warm-up control unit, 52b - Injection mode selection unit, 53 - Combustion degradation judgment unit, 54 - Combustion improvement control unit, 55 - Catalyst temperature estimation unit, 56 - Water temperature sensor, 61 - 1st MG, 62 - 2nd MG, 63 - Planetary gear mechanism, 64 - Transmission mechanism, 70 - Drive wheel, 80 - Battery, 81 - Battery ECU, 92 - Vehicle speed sensor, 93 - Throttle opening sensor, 100 - Hybrid vehicle.

Claims

1. A control device for a hybrid vehicle, the hybrid vehicle comprising: an engine connected to an exhaust pipe containing a catalyst; and a rotary electric motor, the control device for the hybrid vehicle being characterized in that... The control device performs the following control: If the catalyst warm-up is incomplete and the required engine output is lower than a preset threshold, a first catalyst warm-up control is executed. This first catalyst warm-up control delays the engine's ignition timing by a first time and applies a load to the engine via the rotary motor, maintaining constant engine torque and engine speed to achieve the desired engine output during fixed-point operation. If the catalyst warm-up is not complete and the desired engine output is above a preset threshold, a second catalyst warm-up control is executed. This second catalyst warm-up control involves a second ignition timing delay with a delay amount less than that in the first ignition timing delay, and the engine torque and engine speed are set to obtain the desired engine output. The control device also allows combustion degradation determination to be performed when the first catalyst warm-up control is being executed, and prohibits combustion degradation determination when the second catalyst warm-up control is being executed.

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

3. The control device for a hybrid vehicle according to claim 2, characterized in that, The combustion injection method for stratified combustion is partial lift injection.

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