This application claims priority to Japanese Patent Application No. 2022-135931 filed on Aug. 29, 2022, incorporated herein by reference in its entirety.
The present disclosure relates to an internal combustion engine abnormality diagnosis device.
Japanese Unexamined Patent Application Publication No. 2020-186702 (JP 2020-186702 A) discloses an internal combustion engine and an abnormality diagnosis device for an internal combustion engine. The internal combustion engine includes a supercharger, a blow-by gas storage space, a blow-by gas passage, and a positive crankcase ventilation (PCV) pressure sensor. A compressor wheel of the supercharger is positioned in an intake passage. The storage space is a space defined by a cylinder head and a cylinder head cover. The storage space communicates with the inside of a crankcase. Thus, the storage space can temporarily store a blow-by gas that has leaked out of cylinders into the crankcase. The blow-by gas passage connects between the storage space and a portion (hereinafter referred to simply as an “upstream portion”) of the intake passage upstream of the compressor wheel. The PCV pressure sensor detects a pressure in the blow-by gas passage.
When intake air is pressurized by driving the supercharger in the internal combustion engine, the upstream portion of the intake passage is subjected to a negative pressure with respect to the atmospheric pressure. In this case, the blow-by gas flows into the upstream portion of the intake passage through the blow-by gas passage. It is assumed that the intake air amount is varied in the above situation in which the blow-by gas flows into the upstream portion of the intake passage. When the pressure in the upstream portion of the intake passage is varied accordingly, the amount of the blow-by gas that flows into the intake passage is varied, and the pressure in the blow-by gas passage is also varied. Such variations in the intake air amount and variations in the pressure in the blow-by gas passage that occur in conjunction with each other become particularly conspicuous when the intake air amount is considerably large and the negative pressure in the upstream portion is high to a certain degree.
In such a background, the abnormality diagnosis device disclosed in JP 2020-186702 A monitors fluctuations in the pressure in the blow-by gas passage for a diagnosis of an abnormality in the blow-by gas passage on condition that the intake air amount is equal to or more than a determination value determined in advance. The abnormality diagnosis device determines that an abnormality is caused in the blow-by gas passage when fluctuations in the pressure in the blow-by gas passage are small.
The abnormality diagnosis according to JP 2020-186702 A is made on the assumption that the negative pressure in the upstream portion of the intake passage is high to a certain degree. The magnitude of the negative pressure caused in the upstream portion for an equal intake air amount is not always uniform, but may be different in accordance with the operating state of the internal combustion engine. In consideration of this respect, it is conceivable to set the determination value for the intake air amount for prescribing a condition for executing an abnormality diagnosis to be considerably large, in order to always extract a situation in which the negative pressure in the upstream portion is high as a target period for an abnormality diagnosis, irrespective of the operating state of the internal combustion engine. In this case, however, the condition for executing an abnormality diagnosis is not easily met. When the determination value for the intake air amount is set to be small, on the other hand, the execution condition is met in a situation in which the intake air amount and the pressure in the blow-by gas passage are not varied in conjunction with each other. Thus, it is necessary to set, as a condition for executing an abnormality diagnosis, a condition that allows detecting that the intake air amount and the pressure in the blow-by gas passage are varied in conjunction with each other and that does not excessively reduce the opportunity to execute an abnormality diagnosis.
In order to address the foregoing issue, an internal combustion engine abnormality diagnosis device is intended for an internal combustion engine that includes a supercharger, a blow-by gas passage that communicates between a portion of an intake passage upstream of a compressor wheel of the supercharger and an inside of a crankcase, a positive crankcase ventilation (PCV) pressure sensor that is installed in the blow-by gas passage and that detects a pressure in the blow-by gas passage as a PCV pressure, and a crankshaft; the internal combustion engine abnormality diagnosis device executes a first process of specifying, as a specific period, a period for which an amount of fluctuations in an intake air amount per unit time is equal to or more than a prescribed value on condition that the intake air amount is equal to or more than a determination air amount, a second process of calculating an amount of fluctuations in the PCV pressure during the specific period, and a third process of determining, based on the amount of fluctuations in the PCV pressure, presence or absence of an abnormality in a portion of the blow-by gas passage on the intake passage side with respect to a location at which the PCV pressure sensor is installed; and the internal combustion engine abnormality diagnosis device sets the determination air amount to a smaller value when a rotational speed of the crankshaft is high than when the rotational speed of the crankshaft is low.
Basically, the following holds true in a situation in which the blow-by gas passage is normal. That is, when the rotational speed of the crankshaft is low, the amount of fluctuations in the PCV pressure during the specific period may become large only when the intake air amount is large to a certain degree. When the rotational speed of the crankshaft is high, on the other hand, the amount of fluctuations in the PCV pressure during the specific period may become large, whether the intake air amount is small or large. In the above configuration, in consideration of this respect, the determination air amount is rendered smaller when the rotational speed of the crankshaft is high than when the rotational speed of the crankshaft is low. Thus, a situation in which the amount of fluctuations in the PCV pressure during the specific period can be detected with high precision, whether the rotational speed of the crankshaft is low or high. In the above configuration, moreover, the execution condition is met not only in a certain specific range of the intake air amount, but also in a wide range of the intake air amount that is varied in accordance with the rotational speed of the crankshaft. Specifically, the range of the intake air amount in which the third process can be executed is expanded when the rotational speed of the crankshaft is high. From the above, the opportunity to execute the third process can be secured as much as possible.
Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein:
An internal combustion engine abnormality diagnosis device according to an embodiment will be described below with reference to the drawings.
Schematic Configuration of Internal Combustion Engine
As illustrated in
The internal combustion engine 10 includes a cylinder block 12, a crankcase 13, an oil pan 15, and a crankshaft 14. The crankcase 13 is positioned below the cylinder block 12. The crankcase 13 is attached to the cylinder block 12. The crankcase 13 includes a crank chamber 17. The crank chamber 17 is a space defined inside the crankcase 13. The crank chamber 17 houses the crankshaft 14. The oil pan 15 is positioned below the crankcase 13. The oil pan 15 is attached to the crankcase 13. The oil pan 15 stores oil for lubrication.
The internal combustion engine 10 includes a plurality of cylinders 22, a plurality of pistons 19, and a plurality of connecting rods 20. In
The internal combustion engine 10 includes a cylinder head 16 and a head cover 18. The cylinder head 16 is positioned above the cylinder block 12. The cylinder head 16 is attached to the cylinder block 12. The head cover 18 is positioned above the cylinder head 16. The head cover 18 is attached to the cylinder head 16.
The internal combustion engine 10 includes an intake passage 24 and an exhaust passage 25. The intake passage 24 is a passage for introducing intake air to the cylinders 22. The intake passage 24 is connected to the cylinders 22. A downstream portion of the intake passage 24 is constituted as an intake port defined in the cylinder head 16. The exhaust passage 25 is a passage for discharging exhaust from the cylinders 22. The exhaust passage 25 is connected to the cylinders 22. An upstream portion of the exhaust passage 25 is constituted as an exhaust port defined in the cylinder head 16.
The internal combustion engine 10 includes a throttle valve 26, a supercharger 11 driven by exhaust, a bypass passage 28, and a waste gate valve (hereinafter referred to as a “WGV”) 27. The throttle valve 26 is positioned in the middle of the intake passage 24. The degree of opening of the throttle valve 26 is adjustable. An amount (hereinafter referred to simply as an “intake air amount”) GA of intake air is varied in accordance with the degree of opening of the throttle valve 26. The supercharger 11 includes a compressor wheel 112 and a turbine wheel 111. The compressor wheel 112 is positioned in the intake passage 24 upstream of the throttle valve 26. The turbine wheel 111 is positioned in the middle of the exhaust passage 25. The bypass passage 28 is connected to the exhaust passage 25 upstream and downstream of the turbine wheel 111. The WGV 27 is positioned at the downstream end of the bypass passage 28. The degree of opening of the WGV 27 is adjustable. The amount of exhaust that flows through the bypass passage 28 is varied in accordance with the degree of opening of the WGV 27. When the WGV 27 is opened to a degree of opening less than fully open, the amount of exhaust that passes through the turbine wheel 111 is increased. Then, the turbine wheel 111 is rotated in accordance with the flow of the exhaust. At this time, the compressor wheel 112 is rotated together with the turbine wheel 111. Then, the compressor wheel 112 compresses and feeds intake air. That is, the intake air is supercharged.
The internal combustion engine 10 includes a blow-by gas processing mechanism 30 that returns a blow-by gas in the crank chamber 17 to the intake passage 24. The blow-by gas is a combustion gas that leaks out of the cylinders 22 to the crank chamber 17. The blow-by gas processing mechanism 30 includes a communication path 21, a storage space 23, a joint 32, and blow-by gas piping 33. The storage space 23 is a space defined by the cylinder head 16 and the head cover 18. The communication path 21 penetrates the cylinder block 12 and the cylinder head 16. The communication path 21 communicates between the crank chamber 17 and the storage space 23. The joint 32 is attached to the head cover 18. One end of the blow-by gas piping 33 is connected to the joint 32. The blow-by gas piping 33 communicates with the storage space 23 via the joint 32. The other end of the blow-by gas piping 33 is connected to an upstream intake passage 241 that is a portion of the intake passage 24 upstream of the compressor wheel 112. The communication path 21, the storage space 23, the joint 32, and the blow-by gas piping 33 constitute the blow-by gas passage 31. That is, the blow-by gas passage 31 communicates between the crank chamber 17 and the upstream intake passage 241. In the blow-by gas passage 31, a blow-by gas in the crank chamber 17 is led to the storage space 23 through the communication path 21. The storage space 23 temporarily stores the blow-by gas. Then, the blow-by gas in the storage space 23 is led to the upstream intake passage 241 through the blow-by gas piping 33.
The internal combustion engine 10 includes a positive crankcase ventilation (PCV) pressure sensor 35, a crank position sensor 70, an atmospheric pressure sensor 71, and an airflow meter 72. The PCV pressure sensor 35 is installed at the joint 32. The PCV pressure sensor 35 detects the absolute pressure in the joint 32. The pressure in the joint 32 is equal to the pressure in the blow-by gas piping 33. That is, the PCV pressure sensor 35 detects a PCV pressure W that is the pressure in the blow-by gas piping 33. The crank position sensor 70 is positioned in the vicinity of the crankshaft 14. The crank position sensor 70 detects a rotational position SC of the crankshaft 14. The atmospheric pressure sensor 71 detects an atmospheric pressure M that is the pressure around the internal combustion engine 10. The airflow meter 72 is positioned in the intake passage 24 upstream of the compressor wheel 112. The airflow meter 72 detects an intake air amount GA. These sensors repeatedly output a signal that matches information detected by the sensors themselves to a diagnosis device 50 to be discussed later.
The vehicle 300 includes a voltage sensor 73, an accelerator sensor 74, and an indication lamp 78. The voltage sensor 73 detects a battery voltage V that is the voltage of a battery of the vehicle 300. The accelerator sensor 74 detects an accelerator operation amount ACC that is the amount of depression of an accelerator pedal of the vehicle 300. The voltage sensor 73 and the accelerator sensor 74 repeatedly output a signal that matches information detected by the sensors themselves to the diagnosis device 50 to be discussed later. The indication lamp 78 is positioned in a vehicle cabin of the vehicle 300. The indication lamp 78 is provided to indicate an abnormality in the blow-by gas piping 33.
Abnormality Diagnosis Device
The vehicle 300 includes an abnormality diagnosis device (hereinafter referred to simply as a “diagnosis device”) 50 for the internal combustion engine 10. The diagnosis device 50 may be constituted as one or more processors that execute various processes in accordance with a computer program (software). The diagnosis device 50 may be constituted as one or more dedicated hardware circuits, such as application specific integrated circuits (ASICs), that execute at least a part of the various processes, or circuitry that includes a combination of such circuits. The processor includes a central processing unit (CPU) 51 and a memory 53 such as a random access memory (RAM) and a read only memory (ROM). The memory 53 stores a program code or an instruction configured to cause the CPU 51 to execute a process. The memory 53, that is, a computer readable medium, includes any medium that is available and accessible to a general-purpose or dedicated computer. The memory 53 includes a non-volatile memory that is electrically rewritable.
The diagnosis device 50 repeatedly receives detection signals output from the sensors of the vehicle 300. The diagnosis device 50 diagnoses the state of the internal combustion engine 10 as a diagnosis target based on such detection signals. In addition, the diagnosis device 50 controls various portions of the internal combustion engine 10. For example, the diagnosis device 50 calculates an engine rotational speed NE that is the rotational speed of the crankshaft 14 based on the rotational position SC of the crankshaft 14. The diagnosis device 50 repeatedly calculates the engine rotational speed NE. The diagnosis device 50 calculates a required load factor that is a required value of an engine load factor based on the calculated engine rotational speed NE, accelerator operation amount ACC, etc. Then, the diagnosis device 50 controls the throttle valve 26 so as to be able to obtain the intake air amount GA that achieves the required load factor. When the required load factor is high to a certain degree, the diagnosis device 50 controls the WGV 27 to a degree of opening less than fully open. Accordingly, the supercharger 11 performs supercharging. The diagnosis device 50 causes the supercharger 11 to perform supercharging in a situation in which the intake air amount GA is considerably large. The engine load factor is a parameter that determines the amount of air to be charged into the cylinders 22, and is a value obtained by dividing the amount of air that flows into each of the cylinders 22 per combustion cycle by a reference air amount. The reference air amount is varied in accordance with the engine rotational speed NE.
Abnormality in Blow-by Gas Piping
The diagnosis device 50 can execute a diagnosis process of diagnosing whether an abnormality has occurred in the blow-by gas piping 33. This diagnosis process diagnoses an abnormality (hereinafter referred to as a “leakage abnormality”) in which a blow-by gas leaks out of the blow-by gas piping 33. A leakage abnormality in the blow-by gas piping 33 is caused when one end of the blow-by gas piping 33 is detached from the joint 32, when the other end of the blow-by gas piping 33 is detached from the upstream intake passage 241, or when the blow-by gas piping 33 is damaged. The blow-by gas piping 33 constitutes a portion of the blow-by gas passage 31 on the intake passage 24 side with respect to the installation location of the PCV pressure sensor 35. That is, the diagnosis device 50 diagnoses an abnormality in the portion of the blow-by gas passage 31 on the intake passage 24 side with respect to the installation location of the PCV pressure sensor 35 in the diagnosis process.
Leakage abnormalities are classified into the following two patterns from the viewpoint of the degree of the amount of the blow-by gas that leaks out. In a first pattern, the inside of the blow-by gas piping 33 completely communicates with the atmosphere as the blow-by gas piping 33 is completely detached from the joint 32 or the upstream intake passage 241 or as the blow-by gas piping 33 is damaged to have a considerably large opening area. Hereinafter, the state in which the inside of the blow-by gas piping 33 completely communicates with the atmosphere is referred to as a “complete communication state”. A large amount of blow-by gas leaks out when a leakage abnormality in the pattern of the complete communication state is caused. In a second pattern, the inside of the blow-by gas piping 33 slightly communicates with the atmosphere as the blow-by gas piping 33 is damaged to have a small opening area. Hereinafter, the state in which the inside of the blow-by gas piping 33 slightly communicates with the atmosphere is referred to as a “partial communication state”. A leakage abnormality in this pattern may also be caused as the connection between the blow-by gas piping 33 and the joint 32 is slightly loosened or when the connection between the blow-by gas piping 33 and the upstream intake passage 241 is slightly loosened. Not a large amount of blow-by gas leaks out when a leakage abnormality in the pattern of the partial communication state is caused.
The diagnosis device 50 uses the PCV pressure W to diagnose the presence or absence of the leakage abnormality in the diagnosis process. The relationship between the intake air amount GA and the PCV pressure W as a precondition for the diagnosis device 50 to use the PCV pressure W in the diagnosis process will be described. The relationship between the intake air amount GA and the PCV pressure W may be varied in accordance with the engine rotational speed NE as discussed later. The relationship between the intake air amount GA and the PCV pressure W is described for a certain specific range of the engine rotational speed NE.
First, the relationship between the intake air amount GA and the PCV pressure W at the time when the blow-by gas piping 33 is normal is described. When supercharging is performed by the supercharger 11, that is, when the intake air amount GA is considerably large, the internal pressure of the upstream intake passage 241 becomes negative with respect to the atmospheric pressure M. Accordingly, the blow-by gas in the blow-by gas passage 31 flows into the upstream intake passage 241. As a result, the PCV pressure W becomes lower than the atmospheric pressure M. The amount of blow-by gas that flows into the upstream intake passage 241 becomes larger since the negative pressure in the upstream intake passage 241 becomes higher as the intake air amount GA is larger. That is, the PCV pressure W becomes lower as the intake air amount GA is larger, as indicated by the continuous line in
On the contrary, the relationship between the intake air amount GA and the PCV pressure W at the time when a leakage abnormality is caused in the blow-by gas piping 33 is as follows. First, the complete communication state is described. When the blow-by gas piping 33 is in the complete communication state, the inside of the blow-by gas piping 33 is completely open to the atmosphere. Therefore, in this case, the PCV pressure W has a value in the vicinity of the atmospheric pressure M, irrespective of whether the intake air amount GA is large or small, as indicated by the long dashed short dashed line in
Next, the partial communication state is described. When the blow-by gas piping 33 is in the partial communication state, the main cause of such a state is often damage to the blow-by gas piping 33, as described above. In the partial communication state, unlike the complete communication state, the following occurs, depending on the opening area due to the damage. That is, when a negative pressure is caused in the upstream intake passage 241 as supercharging is performed by the supercharger 11, a certain amount of blow-by gas flows into the upstream intake passage 241. Then, the PCV pressure W becomes lower than the atmospheric pressure M. The amount of blow-by gas that flows into the upstream intake passage 241 becomes larger since the negative pressure in the upstream intake passage 241 becomes higher as the intake air amount GA is larger. Therefore, the PCV pressure W becomes lower as the intake air amount GA is larger, as indicated by the dashed line in
A clogging abnormality may be caused in the blow-by gas piping 33, besides the leakage abnormality described above. The clogging abnormality is caused when the blow-by gas piping 33 is clogged. When a clogging abnormality is caused, the blow-by gas stored in the storage space 23 cannot flow into the upstream intake passage 241 via the blow-by gas passage 31. On the other hand, the blow-by gas is continuously generated when the internal combustion engine 10 is operating. The amount of generated blow-by gas tends to become larger as the intake air amount GA is larger. Therefore, the PCV pressure W becomes higher than the atmospheric pressure M when the intake air amount GA is large to a certain degree, as indicated by the long dashed double-short dashed line in
Overview of Diagnosis Process
The diagnosis device 50 can execute a first process as a part of the diagnosis process. In the first process, the diagnosis device 50 specifies a specific period H, for which an intake air fluctuation amount ΔGA is equal to or more than a prescribed value K, the intake air fluctuation amount ΔGA being the amount of fluctuations in the intake air amount GA per unit time. The prescribed value K will be discussed later. In the present embodiment, the diagnosis device 50 performs the first process while the intake air amount GA is increasing. That is, the amount of fluctuations in the intake air amount GA per unit time is the amount of increase in the intake air amount GA per unit time. The diagnosis device 50 stores the unit time in advance. The unit time is considerably short, and less than 1 second, e.g. 0.1 seconds. The unit time has been determined based on experiments or simulations as a length of time that allows extracting a rise in the intake air amount GA that accompanies acceleration etc. of the vehicle 300, for example. The unit time is sufficiently longer than the data sampling interval of sensors that are used in the diagnosis process. Thus, the sensors output a plurality of detection signals to the diagnosis device 50 within the unit time.
The diagnosis device 50 can execute a second process as a part of the diagnosis process. In the second process, the diagnosis device 50 calculates a pressure fluctuation amount WA that is the amount of fluctuations in the PCV pressure W during the specific period H specified in the first process. The specific definition of the pressure fluctuation amount WA will be discussed later.
The diagnosis device 50 repeatedly performs the first process and the second process a number of times of determination NTh during a plurality of specific periods H. Consequently, the diagnosis device 50 calculates a number of pressure fluctuation amounts WA, the number corresponding to the number of times of determination NTh. The diagnosis device 50 stores the number of times of determination NTh in advance. The number of times of determination NTh has been determined based on experiments or simulations, for example, as a minimum number of pressure fluctuation amounts WA required to obtain an accurate diagnosis result.
The diagnosis device 50 can execute a third process as a part of the diagnosis process. In the third process, the diagnosis device 50 determines the presence or absence of a leakage abnormality in the blow-by gas piping 33 based on a determination parameter Y obtained by correcting the pressure fluctuation amount WA. The pressure fluctuation amount WA may be increased and reduced in accordance with the magnitude of the intake air fluctuation amount ΔGA during the specific period H. The determination parameter Y is a value obtained by correcting the pressure fluctuation amount WA to a value that is not significantly affected by the intake air fluctuation amount ΔGA. In the third process, the diagnosis device 50 calculates an integrated parameter Z as an integrated value of a plurality of determination parameters Y obtained by repeatedly performing the first process and the second process. The diagnosis device 50 determines that a leakage abnormality is caused when the integrated parameter Z is less than a determination threshold ZTh. The diagnosis device 50 stores the determination threshold ZTh in advance. The determination threshold ZTh has been determined based on experiments or simulations, for example, as a minimum value of the integrated parameter Z that may be taken when the blow-by gas piping 33 is normal. The determination threshold ZTh has a value determined on the assumption of the number of times of determination NTh.
Determination Air Amount
The diagnosis device 50 performs the first process, and then the second process, only when a specific execution condition is met. When the blow-by gas piping 33 is normal, the intake air amount GA and the PCV pressure W are varied in conjunction with each other only when the intake air amount GA is considerably large and a negative pressure is caused in the upstream intake passage 241. When a negative pressure is not caused in the upstream intake passage 241, the intake air amount GA and the PCV pressure W are not varied in conjunction with each other even when the blow-by gas piping 33 is normal, and thus it is not likely that there is a difference in the pressure fluctuation amount WA between when a leakage abnormality is caused in the blow-by gas piping 33 and during normal times. In the light of this respect, the diagnosis device 50 performs the first process when an execution condition that the intake air amount GA is equal to or more than a determination air amount GATh that ensures the occurrence of a negative pressure in the upstream intake passage 241 is met. That is, in the present embodiment, the diagnosis device 50 starts to execute the first process when the intake air amount GA has become equal to or more than the determination air amount GATh while the intake air amount GA is increasing. Thus, the diagnosis device 50 specifies the specific period H for a period for which the intake air amount GA continues to be equal to or more than the determination air amount GATh. The determination air amount GATh prescribed by a first map to be discussed later is substantially constant in the scale of the unit time.
The diagnosis device 50 variably sets the determination air amount GATh in accordance with the engine rotational speed NE. The diagnosis device 50 stores the first map in advance as information that is necessary to that end. As illustrated in
In the first map, as illustrated in
Prescribed Value
The determination air amount GATh is considered to be an indicator that allows grasping a situation in which a negative pressure is caused in the upstream intake passage 241 as an average environmental field during the specific period H. A situation in which a negative pressure is caused in the upstream intake passage 241 can be roughly covered using the determination air amount GATh as a threshold for executing the first process. When a negative pressure is caused in the upstream intake passage 241, however, the degree of variations in the PCV pressure W with respect to instantaneous variations in the intake air amount GA may be different in accordance with the magnitude of the negative pressure. For example, the degree of variations in the PCV pressure W with respect to variations in the intake air amount GA during the specific period H may be small when the negative pressure as an average value during the specific period H is relatively low. In such a situation, the PCV pressure W are not fluctuated significantly unless the intake air fluctuation amount ΔGA during the specific period H becomes large, even if the blow-by gas piping 33 is normal. That is, it is not likely that there is a difference in the pressure fluctuation amount WA between when a leakage abnormality is caused and during normal times, unless the intake air fluctuation amount ΔGA during the specific period H becomes large. In the light of this respect, the diagnosis device 50 variably sets the prescribed value K for specifying the specific period H in the first process in accordance with the intake air amount GA at the time when the first process is executed. The diagnosis device 50 stores a second map in advance as information to be provided to that end. As illustrated in
As illustrated in
Specific Process Procedure of Diagnosis Process
The diagnosis device 50 repeatedly executes the diagnosis process during operation of the internal combustion engine 10. When the diagnosis process is performed for the first time after the internal combustion engine 10 is started, the diagnosis device 50 performs a reset process, as in step S32 to be discussed later, before the diagnosis process is started. After that, the diagnosis device 50 starts the diagnosis process. Therefore, the integrated parameter Z and a number of times of integration N have been set to “0” when the first diagnosis process is started after the internal combustion engine 10 is started.
As illustrated in
In step S50, the diagnosis device 50 erases analysis data. When the determination in step S20 is NO and the process proceeds to step S50, the diagnosis device 50 has not stored analysis data after the start of the diagnosis process. Therefore, the diagnosis device 50 performs substantially nothing in this case. In this respect, the same applies when the determination in step S22 to be discussed later is NO and the process proceeds to step S50. When the process in step S50 is executed, the diagnosis device 50 temporarily ends the series of processes of the diagnosis process. After that, the diagnosis device 50 executes the process in step S20 again.
When the precondition is met in step S20 (step S20: YES), on the other hand, the diagnosis device 50 proceeds to step S21. In step S21, the diagnosis device 50 calculates a determination air amount GATh to be used in step S22 to be discussed later. Specifically, the diagnosis device 50 references the first map and the latest engine rotational speed NE. Then, the diagnosis device 50 calculates a determination air amount GATh corresponding to the latest engine rotational speed NE based on the first map. After that, the diagnosis device 50 proceeds to step S22.
In step S22, the diagnosis device 50 determines whether the intake air amount GA is equal to or more than the determination air amount GATh. Specifically, the diagnosis device 50 references the latest intake air amount GA received from the airflow meter 72 and the determination air amount GATh calculated in step S21. When the latest intake air amount GA is not equal to or more than the determination air amount GATh (step S22: NO), the diagnosis device 50 proceeds to step S50. When the latest intake air amount GA is equal to or more than the determination air amount GATh (step S22: YES), on the other hand, the diagnosis device 50 proceeds to step S23. Examples of the situation in which the process proceeds to step S23 include a situation in which the intake air amount GA is increased from being less than the determination air amount GATh to the determination air amount GATh or more while the intake air amount GA is increasing. That is, a rise in the intake air amount GA is covered.
In step S23, the diagnosis device 50 stores analysis data over the unit time. Specifically, the diagnosis device 50 chronologically stores a plurality of intake air amounts GA received from the airflow meter 72 since the process proceeds to step S23 until the unit time elapses. The diagnosis device 50 treats these chronological data as first analysis data D1. The diagnosis device 50 also chronologically stores a plurality of PCV pressures W received from the PCV pressure sensor 35 since the process proceeds to step S23 until the unit time elapses. The diagnosis device 50 treats these chronological data as second analysis data D2. The diagnosis device 50 may measure the unit time by counting up a timer for time measurement, for example. The diagnosis device 50 proceeds to step S24 when the unit time elapses since the process proceeds to step S23.
In step S24, the diagnosis device 50 calculates an intake air fluctuation amount ΔGA. Specifically, the diagnosis device 50 references the first analysis data D1 stored in step S23. Then, the diagnosis device 50 specifies an initial intake air amount GA, in the time series of the first analysis data D1, as a start air amount. The diagnosis device 50 also specifies a final intake air amount GA, in the time series of the first analysis data D1, as an end air amount. Then, the diagnosis device 50 calculates a value obtained by subtracting the start air amount from the end air amount as the intake air fluctuation amount ΔGA. After that, the diagnosis device 50 proceeds to step S25.
In step S25, a prescribed value K to be used in step S26 to be discussed later is calculated. Specifically, the diagnosis device 50 references the second map, the start air amount specified in step S24, and the engine rotational speed NE at the timing when the start air amount is received. Then, the diagnosis device 50 calculates a prescribed value K corresponding to the start air amount and the engine rotational speed NE based on the second map. After that, the diagnosis device 50 proceeds to step S26.
In step S26, the diagnosis device 50 determines whether a specific condition is met. The specific condition is that both the following items (A) and (B) are met.
For the item (A), the diagnosis device 50 determines whether the item (A) is met by comparing the intake air fluctuation amount ΔGA calculated in step S24 and the prescribed value K calculated in step S25. For the item (B), the diagnosis device 50 determines whether the item (B) is met by comparing each intake air amount GA in the times series of the first analysis data D1 with the start air amount and the end air amount. When the specific condition is not met (step S26: NO), the diagnosis device 50 proceeds to step S50. When the specific condition is met (step S26: YES), on the other hand, the diagnosis device 50 specifies the period for which analysis data are stored in step S23 as a specific period H. After that, the diagnosis device 50 proceeds to step S27. The diagnosis device 50 specifies a specific period H through the processes in step S24, step S25, and step S26 in the manner described above. The processes in step S24, step S25, and step S26 constitute the first process.
When the determination in step S26 turns YES, it is meant that the intake air amount GA continues increasing as the time transitions in the time series of the first analysis data D1. As described above, the PCV pressure W becomes lower in accordance with an increase in the intake air amount GA in a situation in which the intake air amount GA is equal to or more than the determination air amount GATh (step S22: YES). Due to the relationship between the intake air amount GA and the PCV pressure W, when the intake air amount GA continues increasing in the time series of the first analysis data D1, the PCV pressure W continues decreasing as the time transitions in the time series of the second analysis data D2.
In step S27, the diagnosis device 50 calculates a pressure fluctuation amount WA. Specifically, the diagnosis device 50 references the second analysis data D2 that contain chronological data on the PCV pressure W. Then, the diagnosis device 50 specifies an initial PCV pressure W, in the time series of the second analysis data D2, as a reference pressure. Next, the diagnosis device 50 calculates a difference between each (hereinafter referred to as a “data element”) of the plurality of PCV pressures W that constitute the time series of the second analysis data D2 and the reference pressure. That is, the diagnosis device 50 calculates, for each data element, a value obtained by subtracting the data element from the reference pressure as a pressure difference value ΔW. Then, the diagnosis device 50 calculates a value obtained by integrating all the pressure difference values ΔW as the pressure fluctuation amount WA. As described above, the PCV pressure W continues decreasing in the time series of the second analysis data D2 in a situation in which the process proceeds to step S27. Therefore, the value of each data element is basically smaller than the value of the reference pressure. However, the value of the data element may be larger than the value of the reference pressure because of noise etc. The diagnosis device 50 calculates the pressure difference value ΔW as “0” when the value of the data element is larger than the value of the reference pressure. When the pressure fluctuation amount WA is calculated, the diagnosis device 50 proceeds to step S28. The process in step S27 constitutes the second process.
In step S28, the diagnosis device 50 updates the integrated parameter Z. Specifically, the diagnosis device 50 first divides the pressure fluctuation amount WA calculated in step S27 by the intake air fluctuation amount ΔGA calculated in step S24. Then, the diagnosis device 50 determines the obtained value as the determination parameter Y. Next, the diagnosis device 50 adds the determination parameter Y to the integrated parameter Z that is presently stored. Then, the diagnosis device 50 stores the obtained value as the latest integrated parameter Z. At this time, the diagnosis device 50 overwrites the integrated parameter Z that has been stored so far with the latest integrated parameter Z. After that, the diagnosis device 50 proceeds to step S29.
In step S29, the diagnosis device 50 updates the number of times of integration N. That is, the diagnosis device 50 adds “1” to the number of times of integration N that is presently stored. Then, the diagnosis device 50 stores the obtained value as the latest number of times of integration N. At this time, the diagnosis device 50 overwrites the number of times of integration N that has been stored so fart with the latest number of times of integration N. After that, the diagnosis device 50 proceeds to step S30.
In step S30, the diagnosis device 50 determines whether the number of times of integration N updated in step S29 is equal to or more than the number of times of determination NTh. When the number of times of integration N updated in step S29 is not equal to or more than the number of times of determination NTh (step S30: NO), the diagnosis device 50 proceeds to step S50.
When the number of times of integration N is equal to or more than the number of times of determination NTh in step S30 (step S30: YES), on the other hand, the diagnosis device 50 proceeds to step S31. In step S31, the diagnosis device 50 determines the presence or absence of a leakage abnormality in the blow-by gas piping 33 based on the latest integrated parameter Z that is presently stored. When the integrated parameter Z is equal to or more than the determination threshold ZTh, the diagnosis device 50 determines that the blow-by gas piping 33 is normal. In this case, the diagnosis device 50 turns off a leakage flag that indicates occurrence of a leakage abnormality, for example. When the integrated parameter Z is not equal to or more than the determination threshold ZTh, on the other hand, the diagnosis device 50 determines that a leakage abnormality has been caused in the blow-by gas piping 33. In this case, the diagnosis device 50 turns on the leakage flag, and turns on the indication lamp 78, for example. After that, the diagnosis device 50 proceeds to step S32. The diagnosis device 50 obtains the result of a diagnosis as to the presence or absence of an abnormality in the blow-by gas passage 31 through the processes in step S28, step S29, step S30, and, step S31 in the manner described above. The processes in step S28, step S29, step S30, and, step S31 constitute the third process. The diagnosis device 50 uses information as to whether the leakage flag is on or off as information for controlling the internal combustion engine 10, for example.
In step S32, the diagnosis device 50 performs a reset process. That is, the diagnosis device 50 resets the number of times of integration N and the integrated parameter Z to “0”. The diagnosis device 50 also erases the analysis data. After that, the diagnosis device 50 temporarily ends the series of processes of the diagnosis process. After that, the diagnosis device 50 executes the process in step S20 again. When the indication lamp 78 is turned on in step S31, the diagnosis device 50 keeps on the indication lamp 78 until an instruction to turn off the indication lamp 78 is received in response to an operation by an occupant, for example.
Functions of Embodiment
(A) Overall Flow of Diagnosis Process
The overall flow of the diagnosis process will be described using a case where the blow-by gas piping 33 is normal as an example. It is assumed that the internal combustion engine 10 is now being supercharged. It is assumed that the intake air amount GA is increasing. It is assumed that the intake air amount GA has reached the determination air amount GATh at time t1 as the intake air amount GA is increased as illustrated in
It is assumed that the intake air amount GA continues increasing also after the first specific period H1 is ended as illustrated in
When a leakage abnormality is caused in the blow-by gas piping 33, the inside of the blow-by gas piping 33 communicates with the atmosphere. Therefore, variations in the PCV pressure W that match variations in the intake air amount GA become smaller. It is assumed that the first specific period H1 has come when the blow-by gas piping 33 is in the partial communication state. It is assumed that the intake air amount GA is increased from the first air amount GA1 to the second air amount GA2. In this case, the PCV pressure W is only lowered from the first pressure W1 to a third pressure W3 that is higher than the second pressure W2 in the first specific period H1, as indicated by the long dashed double-short dashed line in
(B) Relationship Between Determination Air Amount and Engine Rotational Speed
In relation to the content of the first map, the diagnosis device 50 sets the determination air amount GATh to a smaller value as the engine rotational speed NE is higher. The reason for variably setting the determination air amount GATh in accordance with the engine rotational speed NE in this manner will be described.
The relationship between the intake air amount GA and the PCV pressure W for a case where the blow-by gas piping 33 is normal is compared between when the engine rotational speed NE is in a first range R1 and when the engine rotational speed NE is in a second range R2 as illustrated in
An amount of reduction in the PCV pressure W caused when the intake air amount GA is increased by a certain constant value is referred to as a “PCV variation amount”. That is, the PCV variation amount is an index that indicates the degree of variations in the PCV pressure W with respect to variations in the intake air amount GA. When the engine rotational speed NE is in the first range R1, the PCV variation amount is large only in a situation in which the intake air amount GA is considerably large, e.g. when the intake air amount GA is equal to or more than a predetermined air amount L, as indicated by the continuous line in
Thus, in the above configuration, the determination air amount GATh is variably set in accordance with the engine rotational speed NE. Consequently, only a situation in which the PCV pressure W is varied in conjunction with the intake air amount GA can be detected with high precision, whether the engine rotational speed NE is low or high. In other words, a suitable diagnosis situation that is a situation in which the pressure fluctuation amount WA tends to be different between when a leakage abnormality is caused and during normal times can be detected with high precision, whether the engine rotational speed NE is low or high. When the determination air amount GATh is variably set in accordance with the engine rotational speed NE, a suitable diagnosis situation can be detected not only in a certain specific range of the intake air amount GA, but also in a wide range of the intake air amount GA that is varied in accordance with the engine rotational speed NE. Specifically, the range of the intake air amount GA in which a suitable diagnosis situation is detected is expanded as the engine rotational speed NE is higher. Thus, a large number of suitable diagnosis situations can be detected.
(C) Relationship Between Prescribed Value and Engine Rotational Speed
In relation to the content of the second map, the diagnosis device 50 sets the prescribed value K to a larger value as the engine rotational speed NE is lower on condition that the intake air amount GA is constant. The reason for variably setting the prescribed value K in accordance with the engine rotational speed NE in this manner will be described.
The PCV variation amount is compared between when the engine rotational speed NE is in the first range R1 and when the engine rotational speed NE is in the second range R2 for a case where the intake air amount GA is equal to or more than the predetermined air amount L in
Thus, in the present embodiment, the prescribed value K is set to a larger value when the engine rotational speed NE is low than when the engine rotational speed NE is high. In this case, only a case where the intake air fluctuation amount ΔGA is large can be extracted as a specific period H, as a target period for an abnormality diagnosis, when the engine rotational speed NE is low. In a situation in which the intake air fluctuation amount ΔGA is large, the pressure fluctuation amount WA is large if the blow-by gas piping 33 is normal. The difference in the pressure fluctuation amount WA between when a leakage abnormality is caused and during normal times becomes distinct when a situation in which the pressure fluctuation amount WA is large is determined as a target period for an abnormality diagnosis. As a result, it is easy to determine the presence or absence of a leakage abnormality.
(1) In the present embodiment, the determination air amount GATh is set to a smaller value as the engine rotational speed NE is higher. Thus, as described in (B) of the functions section of the embodiment, the pressure fluctuation amount WA can be calculated in a situation in which the pressure fluctuation amount WA tends to be different between when a leakage abnormality is caused and during normal times, whether the engine rotational speed NE is low or high. An accurate determination result can be obtained by determining the presence or absence of a leakage abnormality in the blow-by gas piping 33 based on the pressure fluctuation amount WA calculated in such a situation. Moreover, as described in (B) of the functions section of the embodiment, a large number of situations in which the pressure fluctuation amount WA tends to be different between when a leakage abnormality is caused and during normal times can be detected, which allows securing as many opportunities to update the integrated parameter Z as possible, and hence as many opportunities to determine the presence or absence of a leakage abnormality as possible.
(2) In the present embodiment, the determination air amount GATh is variably set in accordance with the engine rotational speed NE, and further the prescribed value K is set to a larger value as the engine rotational speed NE is lower. Thus, as described in (C) of the functions section of the embodiment, an erroneous determination as to the presence or absence of a leakage abnormality in the blow-by gas piping 33 can be reliably prevented.
Modifications
The above embodiment can be modified as follows. The above embodiment and the following modifications can be combined with each other as long as no technical contradiction occurs.
Also when the specific period H is specified while the intake air amount GA is decreasing, the specific period H may be specified for a period for which a situation in which the intake air amount GA is equal to or more than the determination air amount GATh continues. It is assumed that a condition that the intake air amount GA is equal to or more than the determination air amount GATh is met at a certain specific timing. In this case, it is expected that the intake air amount GA continues to be equal to or more than the determination air amount GATh for the period in the scale of the unit time according to the above embodiment. Thus, also when the specific period H is specified while the intake air amount GA is decreasing, specification of the specific period H may be started when the intake air amount GA has become equal to or more than the determination air amount GATh. That is, the execution condition for specifying the specific period H is that the intake air amount GA is equal to or more than the determination air amount GATh, as in the above embodiment. While the intake air amount GA is decreasing, however, the intake air amount GA may become less than the determination air amount GATh while the above unit time elapses. In the light of this respect, the specific condition may include the following content when the specific period H is specified while the intake air amount GA is decreasing. That is, the specific condition includes the end air amount in the first analysis data D1 being equal to or more than the determination air amount GATh. The determination air amount GATh may be the determination air amount GATh to be used to determine whether the above execution condition is met, or may be a value separately calculated based on the engine rotational speed NE at a timing corresponding to the end air amount.
Number | Date | Country | Kind |
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2022-135931 | Aug 2022 | JP | national |