Control device for internal combustion engine

Abstract

To provide a control device of an internal combustion engine capable of suppressing degradation of combustion characteristics of the internal combustion engine in starting a catalyst warming-up process under a situation that the internal combustion engine is operated in an Atkinson cycle.SOLUTION: A control device 100 includes a CPU 101 executing a catalyst warming-up process for warming up a catalyst 30 disposed on an exhaust passage 27 by retarding ignition timing while performing stratified combustion in an internal combustion engine 20. The CPU 101 changes air intake VT to intake target timing in the catalyst warming-up process in a case when the intake VT exists at a retarded side with respect to a reference timing, and then changes exhaust VT to exhaust target timing.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device for an internal combustion engine applied to a hybrid vehicle. [Background technology]

[0002] Patent Document 1 describes an example of an internal combustion engine equipped with an intake valve timing controller that adjusts intake valve timing and an exhaust valve timing controller that adjusts exhaust valve timing. In this internal combustion engine, each valve timing controller adjusts the valve timing by using hydraulic pressure generated by the operation of an oil pump of the internal combustion engine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-201871 A Summary of the Invention [Problem to be solved by the invention]

[0004] Some internal combustion engines are provided with a catalyst in an exhaust passage through which exhaust gas discharged from a combustion chamber flows. When starting such an internal combustion engine, if the temperature of the catalyst is low, a catalyst warm-up process is executed to warm up the catalyst. For example, the catalyst warm-up process is a process of retarding the ignition timing of the internal combustion engine while performing stratified charge combustion in the internal combustion engine. By executing such a catalyst warm-up process, the temperature of the exhaust gas discharged from the combustion chamber to the exhaust passage can be increased, so that the temperature of the catalyst can be increased early. Incidentally, when performing stratified charge combustion, a target air-fuel ratio, which is a target for the air-fuel ratio in the combustion chamber, is set to a value on the leaner side than the theoretical air-fuel ratio.

[0005] In addition, when the catalyst warm-up process is started, the intake valve timing and the exhaust valve timing are changed to their respective target timings. At this time, if the change in each valve timing is started simultaneously, the condition inside the combustion chamber changes abruptly. Therefore, one of the intake valve timing and the exhaust valve timing is changed first, and then the other is changed.

[0006] In a hybrid vehicle equipped with an internal combustion engine and an electric motor as a power source, the vehicle can be driven only by the electric motor. Therefore, the internal combustion engine may be started while the vehicle is running. In this case, if the catalyst temperature is low, a catalyst warm-up process is required even while the vehicle is running.

[0007] When the internal combustion engine is started while the vehicle is running, if the driving force required for the hybrid vehicle is large, the internal combustion engine may operate at high load immediately after starting. During high load operation, the catalyst warm-up process is not executed even if the catalyst temperature is low. In this case, the catalyst warm-up process is executed after the operating load of the internal combustion engine becomes low and it is determined that the engine is operating at low load.

[0008] In some hybrid vehicles, the internal combustion engine operates in the Atkinson cycle. When the internal combustion engine operates in the Atkinson cycle, the closing timing of the intake valve is retarded compared to when the internal combustion engine operates in the Otto cycle. Therefore, even when the piston starts to move toward the compression top dead center, the intake valve does not close for a while. As a result, part of the air introduced from the intake passage into the combustion chamber when the intake valve opens is returned to the intake passage. At this time, part of the fuel supplied to the combustion chamber by the injection valve also flows out into the intake passage together with the air.

[0009] In a hybrid vehicle, the catalyst warm-up process may be started when the internal combustion engine is operating in the Atkinson cycle. Even in this case, one of the intake valve timing and the exhaust valve timing is changed, and then the other is changed. Depending on the order of changing the valve timing, the period during which the actual air-fuel ratio in the combustion chamber is leaner than the target air-fuel ratio during stratified combustion may become longer, which may deteriorate the combustion characteristics of the internal combustion engine. [Means for solving the problem]

[0010] The control device for an internal combustion engine for solving the above problems is applied to a hybrid vehicle equipped with a spark ignition internal combustion engine and an electric motor as power sources, the internal combustion engine having an intake valve timing adjustment device for adjusting intake valve timing, an exhaust valve timing adjustment device for adjusting exhaust valve timing, an exhaust passage through which exhaust flows, and a catalyst provided in the exhaust passage. The control device includes an execution device for executing a catalyst warm-up process for warming up the catalyst by retarding ignition timing while performing stratified charge combustion in the internal combustion engine. When a target of the intake valve timing during execution of the catalyst warm-up process is set to an intake target timing, a target of the exhaust valve timing during execution of the catalyst warm-up process is set to an exhaust target timing, and the intake valve timing that is a criterion for determining whether the internal combustion engine is operating in the Atkinson cycle is set to a reference timing, the reference timing is set to be more retarded than the intake target timing. When the intake valve timing is retarded from the reference timing, the execution device changes the intake valve timing to the intake target timing in the catalyst warm-up process, and thereafter changes the exhaust valve timing to the exhaust target timing.

[0011] According to the above configuration, when the intake valve timing is retarded from the reference timing, it can be determined that the internal combustion engine is operating in the Atkinson cycle. Therefore, when the catalyst warm-up process is started under the condition that the intake valve timing is retarded from the reference timing, the intake valve timing is advanced to the intake target timing. That is, the advancement of the intake valve closing timing is started early. This makes it possible to reduce the amount of fuel flowing out together with the air into the intake passage early when the piston is moving toward the compression top dead center. As a result, the actual air-fuel ratio in the combustion chamber is less likely to deviate from the target air-fuel ratio during stratified combustion, and the combustion characteristics of the internal combustion engine are less likely to deteriorate.

[0012] Therefore, according to the above configuration, when the catalyst warm-up process is started while the internal combustion engine is operating in the Atkinson cycle, it is possible to suppress deterioration of the combustion characteristics of the internal combustion engine.

[0013] In one aspect of the control device for the above-mentioned internal combustion engine, when the intake valve timing is not retarded from the reference timing and is advanced from the target intake timing, the execution device changes the intake valve timing to the target intake timing during the catalyst warm-up processing, and then changes the exhaust valve timing to the target exhaust timing.

[0014] If the intake valve timing is not retarded from the reference timing and is advanced from the target intake timing, valve overlap may occur due to the intake valve timing being advanced. If valve overlap occurs, the internal EGR amount, which is the amount of exhaust gas flowing from the combustion chamber to the intake passage, increases. If the internal EGR amount is too large, the combustion temperature in the combustion chamber decreases, which may deteriorate the combustion characteristics.

[0015] Here, consider a case where the exhaust valve timing is changed before the intake valve timing when valve overlap occurs due to the intake valve timing being advanced. In this case, depending on the direction in which the exhaust valve timing is changed, the valve overlap may increase and the internal EGR amount may become too large. In other words, there is a risk of the combustion characteristics deteriorating.

[0016] Therefore, in the above configuration, when the intake valve timing is not retarded from the reference timing and is advanced from the target intake timing, the intake valve timing is changed before the exhaust valve timing is changed. This prevents the valve overlap from increasing. As a result, the deterioration of the combustion characteristics of the internal combustion engine when the catalyst warm-up process is started can be prevented.

[0017] In one aspect of the control device for the internal combustion engine, when the intake valve timing is not advanced from the reference timing, and the intake valve timing is retarded from the target intake timing, and further, the exhaust valve timing is retarded from the target exhaust timing, the execution device changes the exhaust valve timing to the exhaust target timing in the catalyst warm-up processing, and then changes the intake valve timing to the target intake timing.

[0018] If the intake valve timing is not advanced from the reference timing, but is retarded from the target intake timing, and the exhaust valve timing is retarded from the target exhaust timing, there is a possibility that valve overlap is occurring due to the exhaust valve timing being retarded. In this case, when the catalyst warm-up process is started, the intake valve timing is advanced toward the target intake timing, and the exhaust valve timing is advanced toward the target exhaust timing.

[0019] When valve overlap occurs due to the exhaust valve timing being set to the retarded side, if the intake valve timing is advanced before the exhaust valve timing, the valve overlap increases, and the amount of internal EGR may become too large, which may result in a deterioration of combustion characteristics.

[0020] Therefore, in the above configuration, when the intake valve timing is not advanced from the reference timing, and the intake valve timing is retarded from the target intake timing, and the exhaust valve timing is retarded from the target exhaust timing, the exhaust valve timing is changed before the intake valve timing is changed. This prevents the valve overlap from increasing. As a result, the deterioration of the combustion characteristics of the internal combustion engine when the catalyst warm-up process is started can be prevented. [Brief description of the drawings]

[0021] [Figure 1] 1 is a schematic diagram showing an outline of a hybrid vehicle to which a control device according to an embodiment is applied; [Diagram 2] 4 is a flowchart illustrating the flow of a series of processes executed by the control device. [Diagram 3] FIG. 4 is a diagram showing a table used when determining which of the intake valve timing and the exhaust valve timing is to be changed first. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, one embodiment of a control device for an internal combustion engine will be described with reference to Figs. FIG. 1 shows a hybrid vehicle 10 to which a control device 100 of the present embodiment is applied.

[0023] <Hybrid vehicle 10> The hybrid vehicle 10 has an internal combustion engine 20, which is controlled by the control device 100, a first motor generator 12, and a second motor generator 13. When at least one of the output torque of the internal combustion engine 20 and the output torque of the second motor generator 13 is input to the wheels 50 via the output shaft 14, the hybrid vehicle 10 runs. That is, in the hybrid vehicle 10, the internal combustion engine 20 and the second motor generator 13 correspond to a "power source."

[0024] The hybrid vehicle 10 has a planetary gear mechanism 15. The planetary gear mechanism 15 includes a sun gear 151, a pinion gear 152, a planetary carrier 153, and a ring gear 154. The planetary carrier 153 supports the pinion gear 152 in a state in which the pinion gear 152 can rotate and revolve. The pinion gear 152 meshes with both the sun gear 151 and the ring gear 154. The crankshaft 25 of the internal combustion engine 20 is connected to the planetary carrier 153. The first motor generator 12 is connected to the sun gear 151. The output shaft 14 is connected to the ring gear 154. That is, the planetary gear mechanism 15 can distribute the output torque of the internal combustion engine 20 to the first motor generator 12 and the wheels 50 connected to the output shaft 14.

[0025] In addition, a second motor generator 13 is also connected to the output shaft 14. <Internal Combustion Engine 20> The internal combustion engine 20 has a plurality of cylinders 21. The area above the piston 22 in each cylinder 21 is a combustion chamber 23. In the combustion chamber 23, a mixture containing fuel and air is burned. Each piston 22 is connected to a crankshaft 25 via a connecting rod 24. An intake passage 26 and an exhaust passage 27 are connected to each combustion chamber 23. Therefore, air is introduced into each combustion chamber 23 via the intake passage 26. In addition, exhaust gas generated by the combustion of the mixture in each combustion chamber 23 is discharged to the exhaust passage 27. In other words, exhaust gas flows in the exhaust passage 27. An oxygen storage type catalyst 30 is provided in the exhaust passage 27.

[0026] The intake passage 26 is opened and closed relative to the combustion chamber 23 by an intake valve 28. The exhaust passage 27 is opened and closed relative to the combustion chamber 23 by an exhaust valve 29. The internal combustion engine 20 has an intake valve timing controller 31 that adjusts the intake valve timing. The intake valve timing is the valve timing of the intake valve 28. In the following description, "intake valve timing" will be referred to as "intake VT," and the intake valve timing controller 31 will be referred to as "intake VVT ​​device 31." When the intake VT is advanced by the operation of the intake VVT ​​device 31, the opening and closing timings of the intake valve 28 are advanced. Conversely, when the intake VT is retarded, the opening and closing timings of the intake valve 28 are retarded.

[0027] The internal combustion engine 20 has an exhaust valve timing controller 32 that adjusts exhaust valve timing. The exhaust valve timing is the valve timing of the exhaust valve 29. In the following description, "exhaust valve timing" will be referred to as "exhaust VT," and the exhaust valve timing controller 32 will be referred to as the "exhaust VVT device 32." When the exhaust VT is advanced by operation of the exhaust VVT device 32, the opening and closing timings of the exhaust valve 29 are advanced. Conversely, when the exhaust VT is retarded, the opening and closing timings of the exhaust valve 29 are retarded.

[0028] The intake VVT ​​device 31 and the exhaust VVT device 32 may be devices of any operating type as long as they can change the VT. For example, the intake VVT ​​device 31 may be a hydraulically driven VVT device, or an electric VVT device equipped with an electric motor. Similarly, the exhaust VVT device 32 may be a hydraulically driven VVT device, or an electric VVT device equipped with an electric motor.

[0029] In the internal combustion engine 20, an injection valve 33 that injects fuel to be burned and an ignition plug 34 that ignites the mixture in the combustion chamber 23 are provided for each cylinder 21. In other words, the internal combustion engine 20 is a spark ignition type internal combustion engine. In this embodiment, an in-cylinder injection valve that directly injects fuel into the combustion chamber 23 is used as the injection valve 33.

[0030] The internal combustion engine 20 has various sensors. Examples of the sensors include a throttle opening sensor 111, a crank angle sensor 112, and a catalyst temperature sensor 113. The throttle opening sensor 111 detects a throttle opening SL, which is the opening of a throttle valve provided in the intake passage 26, and outputs a signal corresponding to the detection result as a detection signal to the control device 100. The crank angle sensor 112 outputs a signal corresponding to the engine speed NE, which is the rotation speed of the crankshaft 25, as a detection signal to the control device 100. The catalyst temperature sensor 113 detects a catalyst temperature TMP, which is the temperature of the catalyst 30, and outputs a signal corresponding to the detection result as a detection signal to the control device 100.

[0031] <Control device 100> The control device 100 includes a CPU 101, a ROM 102, a storage device 103, and a peripheral circuit 104. The CPU 101, the ROM 102, the storage device 103, and the peripheral circuit 104 can communicate with each other via a local network 105. The ROM 102 stores a control program executed by the CPU 101. The storage device 103 is an electrically rewritable non-volatile memory. For example, the storage device 103 stores the results of calculations performed by the CPU 101. Examples of the peripheral circuit 104 include a circuit that generates a clock signal that defines internal operations, a power supply circuit, and a reset circuit.

[0032] <Flow of processing executed by the CPU 101 to warm up the catalyst 30> In the control device 100, if the catalyst temperature TMP is low when the internal combustion engine 20 is started, the warm-up of the catalyst 30 may be requested. When the warm-up of the catalyst 30 is requested and a predetermined execution condition is satisfied, the CPU 101 executes the catalyst warm-up process. That is, the CPU 101 corresponds to the "execution device". In the catalyst warm-up process, the CPU 101 retards the ignition timing in the internal combustion engine 20. In addition, the CPU 101 increases the number of fuel injections of the injector 33 to realize stratified combustion in the combustion chamber 23. That is, the number of split injections is increased. When stratified combustion is performed in the combustion chamber 23, the CPU 101 sets a value on the leaner side than the theoretical air-fuel ratio as a target air-fuel ratio, which is a target of the air-fuel ratio of the combustion chamber 23.

[0033] In addition, in the catalyst warm-up process, the CPU 101 changes the intake VT to the intake target timing XinTr, and changes the exhaust VT to the exhaust target timing XexTr. The intake target timing XinTr is the target of the intake VT when the catalyst warm-up process is executed. The exhaust target timing XexTr is the target of the exhaust VT when the catalyst warm-up process is executed.

[0034] 2 shows a flow of a series of processes performed when the catalyst warm-up process is executed by the CPU 101. When a request to warm up the catalyst 30 is made, the CPU 101 starts executing the series of processes. In the series of processes, in the first step S11, the CPU 101 determines whether or not the execution condition for the catalyst warm-up process is satisfied. For example, the execution condition includes that the internal combustion engine 20 is operating at a low load. Therefore, even if the catalyst temperature TMP is low during operation of the internal combustion engine 20, if the internal combustion engine 20 is operating at a high load, the CPU 101 does not determine that the execution condition is satisfied. Even if the internal combustion engine 20 is operating at a high load in this way, when the load factor of the internal combustion engine 20 decreases and it is determined that the internal combustion engine 20 is operating at a low load, the CPU 101 determines that the execution condition is satisfied.

[0035] In step S11, if it is not determined that the execution condition is satisfied (NO), the CPU 101 repeats the determination in step S11 until it determines that the execution condition is satisfied. On the other hand, if it is determined that the execution condition is satisfied (S11: YES), the CPU 101 proceeds to the next step S13.

[0036] In step S13, the CPU 101 executes a process to specify which of the intake VT and exhaust VT is to be changed first. In the following description, the VT that is to be changed first of the intake VT and exhaust VT is referred to as the first VT, and the remaining VT is referred to as the second VT. For example, the CPU 101 determines the first VT and the second VT using the table shown in FIG. 3.

[0037] As shown in FIG. 3, when the intake VT is located on the retard side of the reference time XinTh, the CPU 101 determines the intake VT as the first VT and the exhaust VT as the second VT. The reference time XinTh is the intake VT that is a criterion for determining whether the internal combustion engine 20 is operating in the Atkinson cycle. For example, when the time when the piston 22 is located at the bottom dead center is defined as the bottom dead center time, the reference time XinTh is set so that the closing timing of the intake valve 28 is on the retard side of the bottom dead center time. Therefore, when the intake VT is located on the retard side of the reference time XinTh, the internal combustion engine 20 is considered to be operating in the Atkinson cycle. On the other hand, when the intake VT is not located on the retard side of the reference time XinTh, the internal combustion engine 20 is not considered to be operating in the Atkinson cycle. In other words, when the catalyst warm-up process is started under the condition that the internal combustion engine 20 is operating in the Atkinson cycle, the intake VT is selected as the first VT and the exhaust VT is selected as the second VT.

[0038] When the intake VT is not positioned on the retarded side of the reference timing XinTh and is positioned on the advanced side of the intake target timing XinTr, the CPU 101 determines the intake VT as the first VT and determines the exhaust VT as the second VT. The intake target timing XinTr is set on the advanced side of the above-mentioned reference timing XinTh.

[0039] When the intake VT is positioned on the advanced side of the intake target timing XinTr, there is a possibility that valve overlap occurs due to the intake VT being positioned on the advanced side. That is, there is a possibility that the intake valve 28 opens before the exhaust valve 29 closes. Therefore, when there is a possibility that valve overlap occurs due to the intake VT being positioned on the advanced side, the intake VT is selected as the first VT, and the exhaust VT is selected as the second VT.

[0040] When the intake VT is not positioned on the retard side of the reference timing XinTh and is positioned on the retard side of the intake target timing XinTr, the CPU 101 determines the first VT and the second VT by comparing the exhaust VT with the exhaust target timing XexTr. That is, when the exhaust VT is positioned on the retard side of the exhaust target timing XexTr, the CPU 101 determines the exhaust VT as the first VT and the intake VT as the second VT.

[0041] When the exhaust VT is positioned on the retard side of the exhaust target timing XexTr, there is a possibility that valve overlap occurs due to the exhaust VT being positioned on the retard side. That is, there is a possibility that the intake valve 28 opens before the exhaust valve 29 closes. Therefore, when there is a possibility that valve overlap occurs due to the exhaust VT being positioned on the retard side, the exhaust VT is selected as the first VT, and the intake VT is selected as the second VT.

[0042] On the other hand, when the exhaust VT is positioned on the advanced side of the exhaust target timing XexTr, the CPU 101 determines the first VT and the second VT by prioritizing the exhaust emission. In this case, the first VT and the second VT are determined from the specifications of the internal combustion engine 20.

[0043] Returning to FIG. 2, when the first VT and the second VT are determined in step S13, the CPU 101 shifts the process to step S15. In step S15, the CPU 101 starts the catalyst warm-up process. That is, the CPU 101 controls each injector 33 so as to realize stratified combustion. In addition, the CPU 101 retards the ignition timing.

[0044] Next, in step S17, the CPU 101 executes a first VT changing process to change the first VT. If the first VT is the intake VT, the CPU 101 operates the intake VVT ​​device 31 in this process so that the intake VT becomes the intake target timing XinTr. While the first VT changing process is being executed, the CPU 101 holds the second VT. When the first VT reaches the target timing, the CPU 101 shifts the process to step S19.

[0045] In step S19, the CPU 101 executes a second VT change process to change the second VT. If the second VT is the exhaust VT, the CPU 101 operates the exhaust VVT device 32 in this process so that the exhaust VT becomes the exhaust target timing XexTr. While the second VT change process is being executed, the CPU 101 holds the first VT. When the second VT reaches the target timing, the CPU 101 ends the series of processes shown in FIG. 2. That is, the CPU 101 continues to execute the catalyst warm-up process until the end condition of the catalyst warm-up process is satisfied.

[0046] For example, when it is determined that the catalyst temperature TMP has become sufficiently high, the CPU 101 determines that the end condition is satisfied and ends the catalyst warm-up process. Also, for example, even when the internal combustion engine 20 starts to operate under high load, the CPU 101 determines that the end condition is satisfied and ends the catalyst warm-up process.

[0047] <Actions and Effects of the Present Embodiment> (1) When the internal combustion engine 20 operates in the Atkinson cycle, the closing timing of the intake valve 28 is significantly retarded. Therefore, even when the piston 22 starts to move toward the compression top dead center, the intake valve 28 remains open for a while. As a result, when the piston 22 moves toward the compression top dead center, part of the mixture containing air and fuel flows out from the combustion chamber 23 into the intake passage 26. If stratified charge combustion is performed in this situation, the following problems may occur.

[0048] That is, in stratified charge combustion, a target air-fuel ratio is set to a value leaner than the theoretical air-fuel ratio. Therefore, if a portion of the fuel flows out of the combustion chamber 23 into the intake passage 26, the actual air-fuel ratio of the combustion chamber 23 becomes leaner than the target air-fuel ratio, which may deteriorate the combustion characteristics of the internal combustion engine 20. Therefore, when performing the catalyst warm-up process, it is desirable to end the engine operation in the Atkinson cycle early.

[0049] Therefore, in this embodiment, when the intake VT is retarded from the reference timing XinTh, it can be determined that the engine is operating in the Atkinson cycle, so the intake VT is changed before the exhaust VT. Since the intake target timing XinTr is set to the advanced side from the reference timing XinTh, the intake VT is advanced. That is, the advance of the closing timing of the intake valve 28 is started early. As a result, when the piston 22 moves toward the compression top dead center, the amount of fuel flowing out together with the air into the intake passage 26 can be reduced early. This makes it difficult for the actual air-fuel ratio in the combustion chamber 23 to deviate from the target air-fuel ratio during stratified combustion. Therefore, the combustion characteristics of the internal combustion engine 20 are less likely to deteriorate.

[0050] Therefore, when the catalyst warm-up process is started while the internal combustion engine 20 is operating in the Atkinson cycle, the combustion characteristics of the internal combustion engine 20 can be prevented from deteriorating. (2) If the intake VT is not retarded from the reference timing XinTh, it can be determined that the engine is not operating in the Atkinson cycle. If the intake VT is advanced from the target intake timing XinTr under this circumstance, valve overlap may occur due to the intake VT being set to the advanced side. If valve overlap occurs, the internal EGR amount, which is the amount of exhaust gas flowing from the combustion chamber 23 to the intake passage 26, increases. If the internal EGR amount is too large, the combustion temperature in the combustion chamber 23 may decrease, and the combustion characteristics may deteriorate. Therefore, when starting the catalyst warm-up process under a circumstance where valve overlap occurs, it is desirable to avoid expanding the valve overlap in order to suppress deterioration of the combustion characteristics.

[0051] In this embodiment, when the intake VT is not retarded from the reference timing XinTh and is advanced from the target intake timing XinTr, the intake VT is changed before the exhaust VT is changed. This suppresses the expansion of the valve overlap. In addition, since the intake VT is changed to a retard in this case, the valve overlap can be reduced early by retarding the intake VT. As a result, the deterioration of the combustion characteristics of the internal combustion engine 20 when the catalyst warm-up process is started can be suppressed.

[0052] (3) Also, even if the intake VT is retarded from the target intake timing XinTr, if the exhaust VT is retarded from the target exhaust timing XexTr, valve overlap may occur due to the exhaust VT being set to the retarded side.

[0053] In this embodiment, when the intake VT is not advanced from the reference timing XinTh, and the intake VT is retarded from the target intake timing XinTr, and the exhaust VT is retarded from the target exhaust timing XexTr, the exhaust VT is advanced before the intake VT is advanced. This suppresses the expansion of the valve overlap. In addition, since the exhaust VT can be advanced early, the valve overlap can be reduced early. As a result, the deterioration of the combustion characteristics of the internal combustion engine 20 when the catalyst warm-up process is started can be suppressed.

[0054] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0055] When the intake VT is not retarded from the reference timing XinTh, the intake VT and exhaust VT may be changed in an order different from that described in the above embodiment. For example, when the intake VT is advanced from the target intake timing XinTr and the exhaust VT is retarded from the target exhaust timing XexTr, the valve overlap can be reduced regardless of whether the intake VT or the exhaust VT is changed first. Therefore, in such a case, the exhaust VT may be changed first, and then the intake VT may be changed.

[0056] Also, when the intake VT is more advanced than the intake target timing XinTr and the exhaust VT is more retarded than the exhaust target timing XexTr, the first VT and the second VT may be determined based on the deviation between the intake VT and the intake target timing XinTr and the deviation between the exhaust VT and the exhaust target timing XexTr. For example, when the deviation between the intake VT and the intake target timing XinTr is greater than the deviation between the exhaust VT and the exhaust target timing XexTr, the intake VT is determined as the first VT and the exhaust VT is determined as the second VT. On the other hand, when the deviation between the exhaust VT and the exhaust target timing XexTr is greater than the deviation between the intake VT and the intake target timing XinTr, the exhaust VT is determined as the first VT and the intake VT is determined as the second VT.

[0057] The hybrid vehicle may be a vehicle having a configuration different from that of the hybrid vehicle 10 shown in FIG. 1, so long as it is equipped with an internal combustion engine 20 that may be operated in the Atkinson cycle.

[0058] The control device 100 is not limited to a device that includes a CPU 101 and a ROM 102 and executes software processing. In other words, the control device 100 may have any one of the following configurations (a) to (c). (a) The control device 100 includes one or more processors that execute various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program codes or instructions that are configured to cause the CPU to execute processes. The memory, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or special-purpose computer. (b) The control device 100 includes one or more dedicated hardware circuits that execute various processes. Examples of the dedicated hardware circuits include application specific integrated circuits, i.e., ASIC and FPGA. ASIC is an abbreviation for "Application Specific Integrated Circuit" and FPGA is an abbreviation for "Field Programmable Gate Array." (c) The control device 100 includes a processor that executes some of the various processes in accordance with a computer program, and a dedicated hardware circuit that executes the remaining processes among the various processes. [Explanation of symbols]

[0059] 10. Hybrid vehicle 12, 13...Motor generator 20…Internal combustion engine 27…Exhaust passage 28…Intake valve 29…Exhaust valve 30…Catalyst 31...Intake VVT ​​adjustment device 32…Exhaust VVT adjustment device 100...Control device 101...CPU

Claims

1. A control device for an internal combustion engine applied to a hybrid vehicle having a spark ignition internal combustion engine and an electric motor as power sources, the internal combustion engine having an intake valve timing adjustment device that adjusts intake valve timing, an exhaust valve timing adjustment device that adjusts exhaust valve timing, an exhaust passage through which exhaust flows, and a catalyst provided in the exhaust passage, a catalyst warm-up processing execution device that executes a catalyst warm-up processing by performing stratified charge combustion in the internal combustion engine and retarding an ignition timing, a target intake valve timing during execution of the catalyst warm-up process is set to an intake target timing, a target exhaust valve timing during execution of the catalyst warm-up process is set to an exhaust target timing, and the intake valve timing serving as a criterion for determining whether or not the internal combustion engine is operating in an Atkinson cycle is set to a reference timing, the reference timing is set to a more retarded side than the intake target timing, When the intake valve timing is retarded from the reference timing, the execution device changes the intake valve timing to the intake target timing in the catalyst warm-up process, and then changes the exhaust valve timing to the exhaust target timing. A control device for an internal combustion engine.

2. When the intake valve timing is not retarded from the reference timing and is advanced from the target intake timing, the execution device changes the intake valve timing to the target intake timing in the catalyst warm-up process, and then changes the exhaust valve timing to the target exhaust timing. The control device for an internal combustion engine according to claim 1.

3. When the intake valve timing is not advanced from the reference timing, the intake valve timing is retarded from the target intake timing, and the exhaust valve timing is retarded from the target exhaust timing, the execution device changes the exhaust valve timing to the target exhaust timing in the catalyst warm-up process, and then changes the intake valve timing to the target intake timing. The control device for an internal combustion engine according to claim 1 or 2.

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