Internal combustion engine control device and control method

Abstract

The present application provides an internal combustion engine control device and control method. The control device is applied to an internal combustion engine provided with an EGR device that causes a portion of exhaust gas flowing through an exhaust passage to flow back to an intake passage as EGR gas. The EGR device has an EGR passage and an EGR valve. The control device is provided with a CPU that controls opening and closing of the EGR valve. The CPU performs: a determination process that determines whether a temperature of the internal combustion engine is the same degree as an outside air temperature; and a shaft offset elimination process that causes the EGR valve to perform opening and closing operation in a case where it is determined in the determination process that the temperature of the internal combustion engine is the same degree as the outside air temperature during a stop of operation of the internal combustion engine.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an internal combustion engine control device and a control method. BACKGROUND

[0002] A control device that controls an EGR device of an internal combustion engine is disclosed in Japanese Patent Application Publication No. 2014-240631. The EGR device is provided with an EGR passage and an electronically controlled EGR valve that is provided to the EGR passage. A first end of the EGR passage is connected to a portion of an exhaust passage that is upstream of a turbocharger turbine, and on the other hand, a second end of the EGR passage is connected to a portion of an intake passage that is downstream of a throttle valve.

[0003] In a case where an amount of EGR gas that flows into the intake passage when the EGR valve is closed, that is, an EGR gas leakage amount is equal to or more than a prescribed amount, the control device repeatedly performs opening and closing operations of the EGR valve at the time of operation stop of the internal combustion engine.

[0004] Generally, the EGR valve is provided with a valve housing made of metal, an EGR passage is formed inside the valve housing, a valve seat is provided to the valve housing, and a valve core. The valve core is supported to the valve housing in a state where the valve core is movable in a separation direction that separates from the valve seat and a direction that approaches the valve seat that is the opposite direction of the separation direction. Such an EGR valve allows the passage of EGR gas by separating the valve core from the valve seat at the time of opening. On the other hand, the EGR valve restricts the passage of EGR gas by pressing the valve core against the valve seat at the time of closing.

[0005] Such an EGR valve is assembled so that the center axis of the valve seat and the center axis of the valve core substantially coincide. However, at the time of operation of the internal combustion engine, high-temperature EGR gas flows through the EGR passage. That is, the EGR valve is exposed to high-temperature EGR gas. As a result, there is a case where the valve housing that supports the valve core is thermally deformed, and the center axis of the valve core relatively deviates from the center axis of the valve seat. In a case where the EGR valve is opened while the center axis of the valve core relatively deviates from the center axis of the valve seat as described above, the valve core is pressed against the valve seat in a state where the center axis of the valve core relatively deviates from the center axis of the valve seat. In this case, even if the EGR valve is closed, a relatively large gap is formed between the valve seat and the valve core. Even in this state, the valve housing is cooled and the thermal deformation of the valve housing is eliminated, but since a frictional force is generated between the valve seat and the valve core, the state where the center axis of the valve core relatively deviates from the center axis of the valve seat is maintained. That is, the state where a relatively large gap is formed between the valve seat and the valve core is maintained. As a result, the amount of EGR gas that leaks to the intake passage via the EGR valve becomes relatively large despite the fact that the EGR valve is closed. SUMMARY

[0006] To solve the above problems, according to a first aspect of the present application, there is provided an internal combustion engine control device of an internal combustion engine. The internal combustion engine includes: an intake passage; an exhaust passage; and an EGR device that causes a portion of exhaust gas flowing through the exhaust passage to flow back to the intake passage as EGR gas. The EGR device includes: an EGR passage having a first end connected to the exhaust passage and a second end connected to the intake passage; and an EGR valve provided in the EGR passage. The EGR valve includes: a valve housing made of metal and forming the EGR passage; a valve seat provided in the valve housing; a valve core supported in the valve housing so as to be movable in a direction away from the valve seat and a direction approaching the valve seat; and an actuator that operates to move the valve core in the direction away from the valve seat and the direction approaching the valve seat. The EGR valve is configured to restrict the flow of the EGR gas in the EGR passage by pressing the valve core against the valve seat when closed, and to allow the flow of the EGR gas in the EGR passage by moving the valve core away from the valve seat when open. The internal combustion engine control device includes an execution device configured to control the EGR valve by operating the actuator. The execution device is configured to execute: a determination process that determines whether the temperature of the internal combustion engine is the same as the outside air temperature; and a shaft offset elimination process that causes the EGR valve to perform opening and closing operations during a stop of operation of the internal combustion engine when it is determined in the determination process that the temperature of the internal combustion engine is the same as the outside air temperature.

[0007] To solve the above problem, according to a second aspect of the present application, there is provided an internal combustion engine control method. The internal combustion engine includes: an intake passage; an exhaust passage; and an EGR device that causes a portion of exhaust gas flowing through the exhaust passage to flow back to the intake passage as EGR gas. The EGR device includes: an EGR passage having a first end connected to the exhaust passage and a second end connected to the intake passage; and an EGR valve provided in the EGR passage. The EGR valve includes: a valve housing made of metal and forming the EGR passage; a valve seat provided in the valve housing; a valve element supported in the valve housing so as to be movable in a direction away from the valve seat and a direction approaching the valve seat; and an actuator that operates to move the valve element in the direction away from the valve seat and the direction approaching the valve seat. The EGR valve is configured to restrict the flow of the EGR gas in the EGR passage by pressing the valve element against the valve seat at the time of closing, and to allow the flow of the EGR gas in the EGR passage by moving the valve element away from the valve seat at the time of opening. The internal combustion engine control method includes: a step of determining whether the temperature of the internal combustion engine is the same as the outside air temperature; and a step of causing the EGR valve to perform opening and closing operation during the operation stop of the internal combustion engine, in a case where it is determined in the step of determining that the temperature of the internal combustion engine is the same as the outside air temperature. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a schematic configuration view showing a vehicle provided with an internal combustion engine control device.

[0009] Figure 2 is a cross-sectional view showing an EGR valve in an EGR device provided in the internal combustion engine.

[0010] Figure 3 is a cross-sectional view schematically showing a state in which the center axis of the valve element is relatively offset from the center axis of the valve seat in the EGR valve.

[0011] Figure 4 is a flowchart showing a processing routine executed by a CPU of the internal combustion engine control device.

[0012] Figure 5 is a graph showing an example of experimental results of the relationship between the leakage amount of EGR gas leaked to the intake passage via the EGR valve and the number of operations of the EGR valve.

[0013] Figure 6 is a graph showing an example of experimental results of the progress of the leakage amount of EGR gas leaked to the intake passage via the EGR valve. DETAILED DESCRIPTION

[0014] Hereinafter, according to Figures 1-6 An embodiment of an internal combustion engine control device will be described.

[0015] Figure 1 The vehicle 10 shown is provided with an internal combustion engine 20, a detection system 70, and a control device 80 that controls the operation of the internal combustion engine 20. The control device 80 corresponds to an "internal combustion engine control device".

[0016] <Internal combustion engine>

[0017] The internal combustion engine 20 is provided with a plurality of cylinders 21 and a crankshaft 22. In Figure 1 , only one of the plurality of cylinders 21 is illustrated. The internal combustion engine 20 is provided with a water jacket 23 through which cooling water flows for cooling the plurality of cylinders 21. A piston 24 that reciprocates within the cylinder 21 is provided within the cylinder 21. The piston 24 is linked to the crankshaft 22 via a connecting rod 25. The crankshaft 22 rotates by the reciprocation of the piston 24 within the plurality of cylinders 21.

[0018] The internal combustion engine 20 is provided with an intake passage 26, an intake valve 27, and an electronically controlled throttle valve 28. The intake passage 26 is a passage through which air introduced into the plurality of cylinders 21 flows. In the case where the intake valve 27 is open, the air that flows through the intake passage 26 is introduced into the cylinder 21. The throttle valve 28 adjusts the amount of air, i.e., the intake air amount, that flows through the intake passage 26.

[0019] The internal combustion engine 20 is provided with a fuel injection valve 29, an ignition device 30, an exhaust passage 31, and an exhaust valve 32. The fuel injection valve 29 injects fuel supplied to the cylinder 21. In the cylinder 21, a mixture gas containing the air introduced from the intake passage 26 and the fuel injected from the fuel injection valve 29 is combusted by ignition of the ignition device 30. The piston 24 reciprocates within the cylinder 21 using the power obtained by the combustion of the mixture gas. In addition, exhaust gas is generated in the cylinder 21 due to the combustion of the mixture gas. Such exhaust gas is discharged from the cylinder 21 to the exhaust passage 31 in the case where the exhaust valve 32 is open.

[0020] The internal combustion engine 20 is provided with a turbocharger 35 of an exhaust-driven type. The turbocharger 35 has a turbine 36 and a compressor 37. The turbine 36 is provided to the exhaust passage 31. The compressor 37 is provided to a portion of the intake passage 26 located upstream of the throttle valve 28. The turbine 36 is driven by the flow force of the exhaust gas that flows through the exhaust passage 31. The compressor 37 is driven in synchronization with the driving of the turbine 36. By the driving of the turbine 36, the air that flows through the intake passage 26 is pressurized and introduced into the cylinder 21.

[0021] The internal combustion engine 20 is provided with an EGR device 40. The EGR device 40 is a device that causes a portion of the exhaust gas flowing through the exhaust passage 31 to flow back to the intake passage 26 as EGR gas. The EGR device 40 has an EGR passage 41 and an electronically controlled EGR valve 42 provided to the EGR passage 41. The first end of the EGR passage 41 is connected to the exhaust passage 31, and the second end of the EGR passage 41 is provided to the intake passage 26. Specifically, the first end of the EGR passage 41 is connected to a portion of the exhaust passage 31 located upstream of the turbo 36. The second end of the EGR passage 41 is connected to a portion of the intake passage 26 located downstream of the throttle valve 28.

[0022] Referring to Figure 2 and Figure 3 The EGR valve 42 will be described in detail.

[0023] The EGR valve 42 has a valve housing 51 made of metal, a valve seat 52, a valve core 53, and an actuator 56.

[0024] The valve housing 51 is made of, for example, aluminum or an aluminum alloy. The EGR passage 41 penetrates the valve housing 51. That is, the EGR passage 41 is formed in the valve housing 51. The portion of the EGR passage 41 formed inside the valve housing 51 is referred to as an "in-housing passage 41a". In the case where the EGR valve 42 is open, EGR gas flows through the in-housing passage 41a in the direction indicated by the arrow in the figure. Figure 2

[0025] The in-housing passage 41a has an upstream end portion 411, an intermediate portion 412, and a downstream end portion 413. The intermediate portion 412 is located between the upstream end portion 411 and the downstream end portion 413 in the flow direction of the EGR gas in the in-housing passage 41a. That is, the intermediate portion 412 is connected to both the upstream end portion 411 and the downstream end portion 413. The diameter of the upstream end portion 411 is larger than the diameter of the intermediate portion 412, and thus a step 414 is formed at the boundary between the upstream end portion 411 and the intermediate portion 412.

[0026] The valve seat 52 is disposed to the step 414. The valve seat 52 is annular. For example, the valve seat 52 is provided to the valve housing 51 by laser welding processing. In the case where the EGR valve 42 is open, EGR gas passes inside the valve seat 52.

[0027] The valve core 53 has a shaft 54 and a valve body 55 fixed to the shaft 54. The shaft 54 is supported so as to be able to move in and out with respect to the valve housing 51. The valve body 55 is configured so as to be able to contact the entire circumference of the valve seat 52. In the present embodiment, the EGR valve 42 is designed so that the center axis 52z of the valve seat 52 and the center axis 53z of the shaft 54 of the valve core 53 substantially coincide. By the two center axes 52z, 53z substantially coinciding, not only is it meant that the two center axes 52z, 53z are in the same straight line, but it also includes cases where the two center axes 52z, 53z are in the same plane. Figure 2 ​The case where the two center axes 52z, 52z are completely coincident as shown is also included in the case where the two center axes 52z, 52z are slightly offset within the range of manufacturing errors. Also, hereinafter, the center axis 53z of the shaft 54 of the valve element 53 will be simply referred to as "the center axis 53z of the valve element 53".

[0028] The valve element 53 is movable in a direction away from the valve seat 52 (away direction X1) and a direction approaching the valve seat 52 (approaching direction X2) which is the opposite direction of the away direction X1. When the valve element 53 moves in the away direction X1, the valve body 55 is away from the valve seat 52, and thus the EGR valve 42 is open. In the case where the EGR valve 42 is open as described above, the EGR valve 42 allows the EGR gas to flow through the EGR passage 41 toward the intake passage 26. On the other hand, when the valve element 53 moves in the approaching direction X2, the valve body 55 is pressed against the valve seat 52, and thus the EGR valve 42 is closed. In the case where the EGR valve 42 is closed as described above, the EGR valve 42 restricts the EGR gas from flowing through the EGR passage 41 toward the intake passage 26.

[0029] The actuator 56 operates in accordance with an instruction from the control device 80. When the actuator 56 operates, the output of the actuator 56 is transmitted to the valve element 53, and thus the valve element 53 moves in the away direction X1. Therefore, the EGR valve 42 is open. On the other hand, when the operation of the actuator 56 is stopped, the output of the actuator 56 is no longer transmitted to the valve element 53. Therefore, the valve element 53 moves in the approaching direction X2, and thus the valve element 53 is pressed against the valve seat 52. As a result, the EGR valve 42 is closed.

[0030] In the case where the EGR valve 42 is open in the state where the internal combustion engine 20 is operating, the EGR gas at a high temperature flows through the EGR passage 41. That is, the valve housing 51 is exposed to the EGR gas at a high temperature. Therefore, the valve housing 51 is thermally deformed due to the heat. Since the shaft 54 of the valve element 53 is supported to the valve housing 51, when the valve housing 51 is thermally deformed, as shown in FIG. 6, the center axis 53z of the valve element 53 can be relatively offset from the center axis 52z of the valve seat 52. Figure 3 In the case where the EGR valve 42 is closed in the state where the center axis 53z of the valve element 53 is relatively offset from the center axis 52z of the valve seat 52, a relatively large gap can be formed between the valve seat 52 and the valve body 55.

[0031] <Detection system>

[0032] As Figure 1As shown, the detection system 70 is provided with a plurality of sensors. The plurality of sensors output signals corresponding to detection results to the control device 80. The detection system 70 is provided with a water temperature sensor 71, an outside air temperature sensor 72, and an odometer 73 as sensors. The water temperature sensor 71 detects a water temperature that is a temperature of cooling water circulating in the internal combustion engine 20, that is, cooling water flowing in the water jacket 23. The outside air temperature sensor 72 detects an outside air temperature of the vehicle 10. The odometer 73 detects a cumulative value of a travel distance of the vehicle 10, that is, a cumulative travel distance. In the following description, the water temperature detected by the water temperature sensor 71 is referred to as "water temperature TPw", the outside air temperature detected by the outside air temperature sensor 72 is referred to as "outside air temperature TPo", and the cumulative travel distance detected by the odometer 73 is referred to as "cumulative travel distance La".

[0033] <Control Device>

[0034] The control device 80 adjusts the opening degree of the throttle valve 28, the fuel injection amount of the fuel injection valve 29, and the ignition timing of the ignition device 30 on the basis of the detection values of the plurality of sensors 71 to 73. In addition, the control device 80 controls the opening and closing of the EGR valve 42 by operating the actuator 56 of the EGR valve 42.

[0035] The control device 80 is provided with a CPU 81 and a memory 82. Various control programs executed by the CPU 81 are stored in the memory 82. In the present embodiment, the CPU 81 corresponds to an "execution device".

[0036] The CPU 81 executes a determination process and a shaft offset elimination process.

[0037] The determination process is a process of determining whether the temperature of the internal combustion engine 20 is the same degree as the outside air temperature. For example, in the determination process, the CPU 81 determines whether the temperature of the internal combustion engine 20 is the same degree as the outside air temperature on the basis of the water temperature TPw. At this time, in a case where the water temperature TPw is equal to or lower than a determination temperature TPwth, the CPU 81 determines that the temperature of the internal combustion engine 20 is the same degree as the outside air temperature. On the other hand, in a case where the water temperature TPw is higher than the determination temperature TPwth, the CPU 81 determines that the temperature of the internal combustion engine 20 is not the same degree as the outside air temperature. The determination temperature TPwth is set as a determination criterion of whether the water temperature TPw is equal to the outside air temperature.

[0038] The shaft misalignment elimination process is a process executed during the operation stop of the internal combustion engine 20 in a case where it is determined in the determination process that the temperature of the internal combustion engine 20 and the outside air temperature are of the same degree. In the shaft misalignment elimination process, the CPU 81 causes the EGR valve 42 to perform opening and closing operation. In the present embodiment, the CPU 81 causes the EGR valve 42 to perform opening and closing operation only once in the shaft misalignment elimination process. In addition, the number of times of opening and closing operation of the EGR valve 42 in conjunction with the execution of the shaft misalignment elimination process can be two or more.

[0039] Referring to Figure 4 The process routine executed by the CPU 81 for the purpose of eliminating the relative misalignment between the center axis 52z of the valve seat 52 and the center axis 53z of the valve core 53 in the EGR valve 42 will be described. This process routine is executed at every prescribed control cycle by the CPU 81 repeating the control program stored in the memory 82.

[0040] In the present process routine, in step S11, the CPU 81 determines whether or not the execution completion flag FLG is set to off. With respect to the execution completion flag FLG, it is set to on in a case where the shaft misalignment elimination process has been executed to completion, and on the other hand, it is set to on in a case where the shaft misalignment elimination process has not been executed. The execution completion flag FLG is set to off when the operation of the internal combustion engine 20 is started. In a case where the execution completion flag FLG is set to off (S11: Yes), the CPU 81 shifts the process to step S13. On the other hand, in a case where the execution completion flag FLG is set to on (S11: No), the CPU 81 temporarily ends the present process routine.

[0041] In step S13, the CPU 81 determines whether or not the prohibition condition of the shaft misalignment elimination process is satisfied. For example, the CPU 81 determines that the prohibition condition is satisfied in a case where the cumulative travel distance La is the determination distance Lath or more, and on the other hand, determines that the prohibition condition is not satisfied in a case where the cumulative travel distance La is less than the determination distance Lath.

[0042] Here, referring to Figure 5 The reason for setting the prohibition condition will be described. Figure 5is a graph showing experimental results of the relationship between the number of operations of the EGR valve 42 and the EGR leakage amount. The number of operations here means the number of opening and closing operations of the EGR valve 42. The EGR leakage amount here means the amount of EGR gas that leaks to the intake passage 26 via the EGR valve 42 during the operation stop period of the internal combustion engine 20. In the case of a small number of operations, the EGR leakage amount increases as the number of operations increases. As the EGR valve 42 repeatedly performs the opening and closing operations, the wear of the valve seat 52 and the valve body 55 of the valve core 53 gradually increases, and thus it is presumed that the EGR leakage amount increases. However, after the number of operations exceeds the determination number Cnth, the EGR leakage amount decreases as the number of operations increases. It is presumed that this is because, due to the increased wear of the valve seat 52 and the valve body 55, the valve seat 52 becomes a shape that corresponds to the shape of the valve body 55, and as a result, even if the state in which the center axis 53z of the valve core 53 is relatively offset from the center axis 52z of the valve seat 52 is maintained, it is not easy to form a gap between the valve seat 52 and the valve body 55 when the EGR valve 42 is closed.

[0043] Therefore, in the present embodiment, the cumulative value of the travel distance of the vehicle 10 that corresponds to the determination number Cnth is set as the determination distance Lath. Therefore, in the case where the cumulative travel distance La is equal to or more than the determination distance Lath, it is considered that the reduction effect of the EGR leakage amount that is generated by performing the axis offset elimination process is likely to be low. That is, in the case where the cumulative travel distance La is equal to or more than the determination distance Lath, the advantage of performing the axis offset elimination process is small, and thus it is determined that the prohibition condition of the axis offset elimination process is established.

[0044] Returning to Figure 4 In the case where it is determined that the prohibition condition is established (S13: YES), the CPU 81 temporarily ends the present processing routine. On the other hand, in the case where it is determined that the prohibition condition is not established (S13: NO), the CPU 81 shifts the processing to step S15.

[0045] In step S15, the CPU 81 determines whether the operation of the internal combustion engine 20 is in the stop period. In the case where the operation of the internal combustion engine 20 is in the stop period (S15: YES), the CPU 81 shifts the processing to step S17. On the other hand, in the case where the internal combustion engine 20 is in the operation period (S15: NO), the CPU 81 temporarily ends the present processing routine.

[0046] In step S17, the CPU 81 determines whether the temperature of the internal combustion engine 20 is the same degree as the outside air temperature. That is, step S17 corresponds to "determination processing". In the case where it is determined that the temperature of the internal combustion engine 20 is the same degree as the outside air temperature (S17: YES), the CPU 81 shifts the processing to step S19. On the other hand, in the case where it is determined that the temperature of the internal combustion engine 20 is not the same degree as the outside air temperature (S17: NO), the CPU 81 temporarily ends the present processing routine.

[0047] In step S19, the CPU 81 executes the shaft offset elimination processing. That is, the CPU 81 executes the shaft offset elimination processing in the case where it is determined that the temperature of the internal combustion engine 20 is the same degree as the outside air temperature during the operation stop of the internal combustion engine 20. When the opening / closing operation of the EGR valve 42 accompanying the execution of the shaft offset elimination processing is completed, the CPU 81 shifts the processing to step S21.

[0048] In step S21, the CPU 81 sets the execution completion flag FLG to ON. Thereafter, the CPU 81 temporarily ends the present processing routine.

[0049] <Effects of the Present Embodiment>

[0050] Figure 6 is a graph showing the experimental results of the progress of the EGR leakage amount. The EGR leakage amount referred to herein is the amount of EGR gas that leaks to the intake passage 26 via the EGR valve 42 during the operation stop of the internal combustion engine 20. Figure 6 The solid line in indicates the progress of the EGR leakage amount when the EGR valve 42 is closed while the temperature of the internal combustion engine 20 is the same degree as the normal temperature. Figure 6 The dashed line in indicates the progress of the EGR leakage amount when the EGR valve 42 is closed while the temperature of the internal combustion engine 20 is higher than the normal temperature.

[0051] As shown in Figure 6 , in the case where the EGR valve 42 is closed while the temperature of the internal combustion engine 20 is the high temperature, the center axis 53z of the valve core 53 is relatively offset from the center axis 52z of the valve seat 52, and thus the gap between the valve seat 52 and the valve body 55 is relatively wide. On the other hand, in the case where the EGR valve 42 is closed while the temperature of the internal combustion engine 20 is the same degree as the normal temperature, the center axis 53z of the valve core 53 is not so much offset from the center axis 52z of the valve seat 52, and thus the gap between the valve seat 52 and the valve body 55 is relatively narrow. Therefore, in the case where the EGR valve 42 is closed while the temperature of the internal combustion engine 20 is the high temperature, the EGR leakage amount is more than in the case where the EGR valve 42 is closed while the temperature of the internal combustion engine 20 is the same degree as the normal temperature.

[0052] Here, immediately after the operation of the internal combustion engine 20 is stopped, the temperature of the valve housing 51 of the EGR valve 42 is also high, and the degree of thermal deformation of the valve housing 51 is relatively large. Therefore, even if the EGR valve 42 is caused to perform the opening and closing operation immediately after the operation of the internal combustion engine 20 is stopped, the relative displacement of the center axis 52z of the valve seat 52 and the center axis 53z of the valve core 53 cannot be eliminated. However, as time elapses from the time point at which the operation of the internal combustion engine 20 is stopped, the temperature of the internal combustion engine 20 gradually decreases, and therefore the temperature of the valve housing 51 gradually decreases. When the temperature of the valve housing 51 decreases, the degree of thermal deformation of the valve housing 51 also decreases. That is, the shape of the valve housing 51 gradually returns to the original shape.

[0053] Therefore, in the present embodiment, when it is determined that the temperature of the internal combustion engine 20 decreases to the same degree as the outside air temperature after the operation of the internal combustion engine 20 is stopped, the shaft displacement elimination process is executed. That is, the shaft displacement elimination process is executed after the temperature of the valve housing 51 sufficiently decreases and the degree of thermal deformation of the valve housing 51 sufficiently decreases. When the EGR valve 42 is caused to perform the opening and closing operation after the shape of the valve housing 51 returns, the displacement of the center axis 52z of the valve seat 52 and the center axis 53z of the valve core 53 is eliminated during the period in which the valve body 55 is separated from the valve seat 52. Since the valve body 55 is pressed against the valve seat 52 in this state, the gap between the valve seat 52 and the valve body 55 can be reduced. Thus, the amount of EGR gas that leaks to the intake passage 26 via the EGR valve 42 can be reduced. That is, after the shaft displacement elimination process is executed, the EGR valve 42 can be caused to close while the gap between the valve seat 52 and the valve body 55 is small. Therefore, the amount of EGR gas that leaks to the intake passage 26 via the EGR valve 42 can be reduced. Figure 6 The EGR leakage amount illustrated in the graph is the same degree as the EGR leakage amount in the case where the EGR valve 42 is caused to close in a state in which the temperature of the internal combustion engine 20 is the same degree as the normal temperature.

[0054] In the present embodiment, the following effects can be obtained.

[0055] (1) When the EGR valve 42 is caused to close in a state in which the degree of thermal deformation of the valve housing 51 is large, the center axis 53z of the valve core 53 is relatively displaced from the center axis 52z of the valve seat 52, as described above. In a case where the center axis 53z of the valve core 53 is displaced from the center axis 52z of the valve seat 52 even after the temperature of the valve housing 51 sufficiently decreases and the thermal deformation of the valve housing 51 is eliminated, an external force acts on the shaft 54 that is supported to the valve housing 51. Therefore, if the state in which the center axis 53z of the valve core 53 is displaced from the center axis 52z of the valve seat 52 continues for a long period of time, the shaft 54 can be deformed. In this regard, in the present embodiment, when the temperature of the valve housing 51 becomes sufficiently low and the degree of thermal deformation of the valve housing 51 sufficiently decreases, the relative displacement of the center axis 52z of the valve seat 52 and the center axis 53z of the valve core 53 is eliminated by execution of the shaft displacement elimination process. Thus, the above-described external force that acts on the shaft 54 can be reduced, and therefore the deformation of the shaft 54 during the period in which the EGR valve 42 is closed can be suppressed.

[0056] (2) In this embodiment, the temperature of the cooling water circulating in the internal combustion engine 20, i.e., the water temperature TPw, is used to determine whether the temperature of the internal combustion engine 20 is the same as the outside air temperature. That is, it is not necessary to install a new detection system in the internal combustion engine 20 to detect the temperature of the valve housing 51 or the degree of deformation of the valve housing 51.

[0057] (3) In this embodiment, when the accumulated driving distance La becomes a determination distance Lath or more, the advantage of being able to determine whether to perform axle offset elimination processing becomes smaller, and therefore the execution of axle offset elimination processing is prohibited. As a result, the electrical power consumed by the internal combustion engine 20 during the period when the internal combustion engine 20 is not running can be reduced.

[0058] (Example of Change)

[0059] The above-described embodiments can be implemented by modification as follows. The above-described embodiments and the following modifications can be combined with each other to implement them within the scope of technical inconsistency.

[0060] ·exist Figure 4 In step S13 of the processing routine shown, the cumulative number of times the EGR valve 42 is operated can also be used to determine whether the prohibition condition is met. In this case, if the cumulative number of times the EGR valve 42 is operated is greater than or equal to the number of determinations Cntth, the prohibition condition is determined to be met; on the other hand, if the cumulative number of operations is less than the number of determinations Cntth, the prohibition condition is determined to be not met. Thus, if the cumulative number of times the EGR valve 42 is operated is greater than or equal to the number of determinations Cntth, the execution of the shaft offset elimination process can be prohibited. Even in this case, the same effect as the effect (3) of the above-described embodiment can be obtained.

[0061] ·exist Figure 4 In the processing routine shown, step S13 can also be omitted.

[0062] • The judgment temperature TPwth can be fixed at a specified temperature, or it can be varied according to the current outside air temperature. In the latter case, the judgment temperature TPwth can be set to be higher as the outside air temperature TPo.

[0063] • In the above-described embodiment, the temperature of the cooling water circulating in the internal combustion engine 20, that is, the water temperature TPw, is used to determine whether the temperature of the internal combustion engine 20 becomes the same degree as the outside air temperature, but it is not limited thereto. For example, the duration of the state in which the operation of the internal combustion engine 20 is stopped can be used to determine whether the temperature of the internal combustion engine 20 becomes the same degree as the outside air temperature. In this case, it can be determined that the temperature of the internal combustion engine 20 becomes the same degree as the outside air temperature when the duration is equal to or longer than a predetermined determination duration.

[0064] • The control device 80 is not limited to the configuration having the processing circuit configured to have the CPU and the ROM and to execute the software processing. That is, the control device 80 can be any of the following (a) to (c).

[0065] (a) The control device 80 has one or more processors that execute various processes according to computer programs. The processor includes the CPU and a memory such as the RAM and the ROM. The memory stores program codes or instructions configured to cause the CPU to execute the processes. The memory, that is, the computer readable medium includes any available medium that can be accessed by a general-purpose or special-purpose computer.

[0066] (b) The control device 80 has one or more dedicated hardware circuits that execute various processes. As the dedicated hardware circuit, for example, an application specific integrated circuit, that is, an ASIC or an FPGA can be cited. In addition, the ASIC is an abbreviation for "Application Specific Integrated Circuit", and the FPGA is an abbreviation for "Field Programmable Gate Array".

[0067] (c) The control device 80 has: a processor that executes a part of various processes according to computer programs; and a dedicated hardware circuit that executes the remaining processes among the various processes.

[0068] • The vehicle can be a hybrid vehicle that also has a motor generator as a power source, as long as it has the internal combustion engine 20 and the control device 80.

Claims

1. An internal combustion engine control device, wherein, The internal combustion engine has the following features: Intake passage; Exhaust passage; and The EGR device causes a portion of the exhaust gas flowing through the exhaust passage to flow back into the intake passage as EGR gas. The EGR device has: The EGR passage has a first end connected to the exhaust passage and a second end connected to the intake passage; and An EGR valve is installed in the EGR passage. The EGR valve has: The valve body is made of metal and has the EGR passage formed therein; Valve seat, disposed on the valve body; The valve core is supported on the valve body in a state in which it can move in a departure direction away from the valve seat and in an approach direction that is opposite to the departure direction and approaches the valve seat. and The actuator operates to move the valve core in the departure direction and the approach direction. The EGR valve is configured such that, when closed, it restricts the flow of EGR gas in the EGR passage by pressing the valve core against the valve seat; conversely, when open, it allows the flow of EGR gas in the EGR passage by removing the valve core from the valve seat. The internal combustion engine control device includes an actuator that controls the EGR valve by activating the actuator. To eliminate the relative misalignment between the central axis of the valve seat and the central axis of the valve core in the EGR valve, the actuator is configured to perform the following process: The determination process involves determining whether the temperature of the internal combustion engine is the same as the outside air temperature. and Shaft offset elimination process: During the period when the internal combustion engine is stopped, if the determination process determines that the temperature of the internal combustion engine is at the same level as the outside air temperature, the EGR valve is opened and closed.

2. The internal combustion engine control device according to claim 1, wherein, The actuator is configured such that, during the determination process, if the temperature of the cooling water circulating in the internal combustion engine is below the determination temperature, it is determined that the temperature of the internal combustion engine is the same as the outside air temperature.

3. The internal combustion engine control device according to claim 1 or 2, wherein, The internal combustion engine is mounted on the vehicle. The actuator is configured to prevent the execution of the axle offset elimination process when the cumulative value of the vehicle's travel distance exceeds a predetermined distance.

4. The internal combustion engine control device according to claim 1 or 2, wherein, The actuator is configured to prevent the execution of the shaft offset elimination process when the cumulative number of times the EGR valve is operated exceeds the number of determinations.

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