Abnormality diagnosis device and abnormality diagnosis method for vehicle-mounted internal combustion engine

Abstract

A device and method for diagnosing abnormalities in a vehicle-mounted internal combustion engine. The internal combustion engine is provided with a supercharger, a blowby gas passage, and a PCV pressure sensor that detects the pressure in the blowby gas passage as PCV pressure. A period during which an intake air fluctuation amount, which is the amount of change in the amount of intake air per unit time, is greater than a specified value is defined as a specific period. The diagnostic device performs the following processing: calculating a pressure fluctuation amount, which is the amount of change in the PCV pressure within the specific period; correcting the pressure fluctuation amount to a smaller value when the intake air fluctuation amount within the specific period is large compared to when the intake air fluctuation amount is small; and determining the presence or absence of an abnormality in the blowby gas passage based on the corrected pressure fluctuation.

Description

Technical Field

[0001] The present disclosure relates to an abnormality diagnosis device and an abnormality diagnosis method for a vehicle-mounted internal combustion engine. Background Art

[0002] An internal combustion engine and an abnormality diagnosis device thereof are disclosed in Japanese Patent Gazette No. 2020-186702. The internal combustion engine disclosed in Japanese Patent Gazette No. 2020-186702 has a supercharger, a blowby gas storage space, a blowby gas passage, and a PCV pressure sensor. The supercharger has a compressor impeller. The compressor impeller is located in the intake passage. The storage space is a space demarcated by the cylinder head and the cylinder head cover. The storage space is connected to the crankcase. The storage space temporarily stores the blowby gas leaking from the cylinder into the crankcase. The blowby gas passage connects the storage space to a portion of the intake passage that is upstream of the compressor impeller (hereinafter referred to as the upstream portion). The PCV pressure sensor detects the pressure in the blowby gas passage.

[0003] In the above-mentioned internal combustion engine, when the intake air is pressurized by driving the supercharger, the upstream portion of the intake passage becomes negative. In this situation, blowby gas flows into the upstream portion of the intake passage through the blowby passage. In the aforementioned situation where blowby gas flows into the upstream portion of the intake passage, the amount of intake air changes. As the pressure in the upstream portion of the intake passage changes accordingly, the amount of blowby gas flowing into the intake passage changes, and the pressure within the blowby passage also changes. In this way, the change in the intake air amount and the change in the pressure within the blowby passage occur in tandem.

[0004] Here, due to damage to a portion of the blowby gas passage or a partial disconnection between the blowby gas passage and the intake passage, the blowby gas passage may become slightly connected to the atmosphere outside. When such an abnormality occurs, the pressure change in the blowby gas passage when the intake air volume changes is smaller than under normal circumstances. Therefore, the above-mentioned internal combustion engine abnormality diagnostic device monitors the intake air volume and the pressure in the blowby gas passage to detect the presence of such an abnormality. Summary of the Invention

[0005] Problems to be solved by the invention

[0006] For example, the intake air volume can sometimes change dramatically during sudden acceleration of a vehicle. Even in this case, when an abnormality such as the one described above occurs in the blowby passage, the pressure change within the passage tends to be smaller than when the abnormality is not present. However, when the intake air volume changes dramatically due to the abnormality described above, the pressure change within the passage can become quite significant. In this case, there is a risk that the blowby passage may be mistakenly identified as normal despite the abnormality.

[0007] Technical solutions to problems

[0008] In one aspect of the present disclosure, a device for diagnosing abnormalities in a vehicle-mounted internal combustion engine is provided. The vehicle-mounted internal combustion engine includes: a supercharger having a compressor impeller; an intake passage for introducing intake air into the vehicle-mounted internal combustion engine; a blow-by gas passage connecting a portion of the intake passage upstream of the compressor impeller to the crankcase; and a PCV pressure sensor disposed in the blow-by gas passage and detecting the pressure within the blow-by gas passage as PCV pressure. A specific period is defined as a period during which an intake air fluctuation amount, which is a fluctuation in the amount of intake air per unit time, is greater than a predetermined value. The device is configured to perform: a first process of calculating a pressure fluctuation amount, which is a fluctuation amount of the PCV pressure within the specific period; a second process of correcting the pressure fluctuation amount to a smaller value when the intake air fluctuation amount within the specific period is large compared to when the intake air fluctuation amount is small; and a third process of determining, based on the corrected pressure fluctuation amount, whether an abnormality exists between a location in the blow-by gas passage where the PCV pressure sensor is located and a portion connected to the intake passage.

[0009] In another aspect of the present disclosure, a method for diagnosing abnormalities in a vehicle-mounted internal combustion engine is provided. The vehicle-mounted internal combustion engine includes: a supercharger having a compressor impeller; an intake passage for introducing intake air into the vehicle-mounted internal combustion engine; a blow-by gas passage connecting a portion of the intake passage upstream of the compressor impeller to the crankcase; and a PCV pressure sensor disposed in the blow-by gas passage and detecting the pressure within the blow-by gas passage as PCV pressure. A period during which an intake air fluctuation, which is the amount of change in the amount of intake air per unit time, is greater than a predetermined value is defined as a specific period. The abnormality diagnosis method includes calculating a pressure fluctuation amount as the amount of change in the PCV pressure within the specific period; correcting the pressure fluctuation amount to a smaller value when the intake air fluctuation amount within the specific period is large compared to when the intake air fluctuation amount is small; and determining, based on the corrected pressure fluctuation amount, whether an abnormality exists between a location in the blow-by gas passage where the PCV pressure sensor is disposed and a portion connected to the intake passage. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic diagram of the internal combustion engine.

[0011] Figure 2 It is a diagram showing the relationship between the intake air amount and the PCV pressure.

[0012] Figure 3 This is a graph showing the relationship between the intake air amount and the prescribed value.

[0013] Figure 4This is a flowchart showing the processing steps of the diagnostic process.

[0014] Figure 5 It is a time chart showing an example of transition of each parameter involved in the diagnostic process.

[0015] Figure 6 This is a schematic diagram showing an example of correction regarding the first case.

[0016] Figure 7 This is a schematic diagram showing an example of correction regarding the third situation.

[0017] Figure 8 It is a time chart showing an example of the difference in transition of each parameter according to the difference in the intake air fluctuation amount. DETAILED DESCRIPTION

[0018] Hereinafter, one embodiment of an abnormality diagnosis device for a vehicle-mounted internal combustion engine will be described with reference to the accompanying drawings.

[0019] <General Structure of Internal Combustion Engine>

[0020] like Figure 1 As shown, a vehicle 300 includes an internal combustion engine 10. The internal combustion engine 10 is a driving source of the vehicle 300. That is, the internal combustion engine 10 is a vehicle-mounted internal combustion engine.

[0021] 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 located 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 within the crankcase 13. The crank chamber 17 houses the crankshaft 14. The oil pan 15 is located below the crankcase 13. The oil pan 15 is attached to the crankcase 13. The oil pan 15 stores lubricating oil.

[0022] The internal combustion engine 10 has a plurality of cylinders 22, a plurality of pistons 19, and a plurality of connecting rods 20. Figure 1 Only one of the multiple cylinders 22 is shown. The same applies to the piston 19 and connecting rod 20. The cylinder 22 is a space defined within the cylinder block 12. A mixture of fuel and intake air is combusted in the cylinder 22. The cylinder 22 is connected to the crank chamber 17. The piston 19 is located in the cylinder 22. The piston 19 reciprocates in the cylinder 22. The piston 19 is connected to the crankshaft 14 via the connecting rod 20. The movement of the piston 19 causes the crankshaft 14 to rotate.

[0023] The internal combustion engine 10 includes a cylinder head 16 and a head cover 18. The cylinder head 16 is located above the cylinder block 12. The cylinder head 16 is attached to the cylinder block 12. The head cover 18 is located above the cylinder head 16. The head cover 18 is attached to the cylinder head 16.

[0024] 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 into the cylinders 22. The intake passage 24 is connected to each cylinder 22. The downstream portion of the intake passage 24 constitutes an intake port defined in the cylinder head 16. The exhaust passage 25 is a passage for discharging exhaust gas from the cylinders 22. The exhaust passage 25 is connected to each cylinder 22. The upstream portion of the exhaust passage 25 constitutes an exhaust port defined in the cylinder head 16.

[0025] The internal combustion engine 10 includes a throttle valve 26, an exhaust-driven supercharger 11, a bypass passage 28, and a wastegate valve (hereinafter referred to as WGV) 27. The throttle valve 26 is located in the middle of the intake passage 24. The throttle valve 26 can adjust its opening. The amount of intake air GA changes according to the opening of the throttle valve 26. The supercharger 11 includes a compressor impeller 112 and a turbine impeller 111. The compressor impeller 112 is located in the intake passage 24 at a position upstream of the throttle valve 26. The turbine impeller 111 is located in the middle of the exhaust passage 25. The bypass passage 28 is connected to a position upstream of the turbine impeller 111 and a position downstream of the turbine impeller 111 in the exhaust passage 25. The WGV 27 is located at the downstream end of the bypass passage 28. The WGV 27 can adjust its opening. The amount of exhaust gas flowing in the bypass passage 28 changes according to the opening of the WGV 27. When the WGV 27 is opened less than fully, the amount of exhaust gas passing through the turbine impeller 111 increases. Consequently, the turbine impeller 111 rotates in response to the flow of exhaust gas. At this point, the compressor impeller 112 rotates integrally with the turbine impeller 111. Furthermore, the compressor impeller 112 compresses the intake air and delivers it, effectively supercharging the intake air.

[0026] The internal combustion engine 10 has a blowby gas treatment mechanism 30 for returning blowby gas from the crank chamber 17 to the intake passage 24. Blowby gas is combustion gas that leaks from the cylinder 22 into the crank chamber 17. The blowby gas treatment mechanism 30 includes a connecting passage 21, a storage space 23, a joint 32, and a blowby gas piping 33. The storage space 23 is a space defined by the cylinder head 16 and the head cover 18. The connecting passage 21 passes through the cylinder block 12 and the cylinder head 16. Furthermore, the connecting passage 21 connects the crank chamber 17 with the storage space 23. The joint 32 is mounted on the head cover 18. One end of the blowby gas piping 33 is connected to the joint 32. The blowby gas piping 33 communicates with the storage space 23 via the joint 32. The other end of the blowby gas piping 33 is connected to the upstream intake passage 241, which is a portion of the intake passage 24 that is upstream of the compressor impeller 112. The communication passage 21, the accumulation space 23, the joint 32, and the blowby gas piping 33 constitute the blowby gas passage 31. Specifically, the blowby gas passage 31 connects the crank chamber 17 with the upstream intake passage 241. In the blowby gas passage 31, blowby gas from the crank chamber 17 passes through the communication passage 21 and reaches the accumulation space 23. The blowby gas is temporarily accumulated in the accumulation space 23. Then, the blowby gas from the accumulation space 23 passes through the blowby gas piping 33 and reaches the upstream intake passage 241.

[0027] The internal combustion engine 10 includes a PCV pressure sensor 35, a crankshaft position sensor 70, an atmospheric pressure sensor 71, an air flow meter 72, and a voltage sensor 73. The PCV pressure sensor 35 is installed at the joint 32. The PCV pressure sensor 35 detects the absolute pressure within the joint 32. The pressure within the joint 32 is the same as the pressure within the blowby gas pipe 33. Specifically, the PCV pressure sensor 35 detects the PCV pressure W, which is the pressure within the blowby gas pipe 33. The crankshaft position sensor 70 detects the rotational position SC of the crankshaft 14. The atmospheric pressure sensor 71 detects the atmospheric pressure M, which is the pressure around the internal combustion engine 10. The air flow meter 72 is located upstream of the compressor impeller 112 in the intake passage 24. The air flow meter 72 detects the intake air amount GA. The voltage sensor 73 detects the battery voltage V, which is the voltage of the vehicle 300 battery. Each of these sensors repeatedly outputs signals corresponding to the information they detect to the diagnostic device 50, described later.

[0028] Vehicle 300 includes an accelerator pedal 77, an accelerator sensor 75, a vehicle speed sensor 74, and a warning light 78. Accelerator pedal 77 is a foot pedal that is stepped on by a passenger. Accelerator sensor 75 detects the amount of accelerator pedal 77 stepped on as the accelerator operation amount ACC. Vehicle speed sensor 74 detects the speed of vehicle 300 as the vehicle speed SP. Accelerator sensor 75 and vehicle speed sensor 74 repeatedly output signals corresponding to their detected information to diagnostic device 50, described later. Warning light 78 is located inside the cabin of vehicle 300. Warning light 78 is used to indicate any abnormality in blowby gas piping 33.

[0029] <About abnormality diagnosis device>

[0030] The vehicle 300 has an abnormality diagnostic device (hereinafter referred to as the diagnostic device) 50 for the internal combustion engine 10. The diagnostic device 50 can be configured as one or more processors that perform various processes according to a computer program (software). The diagnostic device 50 can also be configured as a circuit (circuitry) including one or more dedicated hardware circuits such as integrated circuits (ASICs) for specific purposes that perform at least a part of the various processes, or a combination thereof. The processor includes a CPU 51 and a memory 52 such as RAM and ROM. The memory 52 stores program codes or instructions that enable the CPU 51 to perform processes. The memory 52, i.e., a computer-readable medium, includes all available media that can be accessed by a general-purpose or dedicated computer. In addition, the diagnostic device 50 has a storage device 53 that is an electrically rewritable non-volatile memory.

[0031] The diagnostic device 50 repeatedly receives detection signals output by the aforementioned sensors included in the vehicle 300. Based on these detection signals, the diagnostic device 50 diagnoses the condition of the internal combustion engine 10, using the internal combustion engine 10 as the diagnostic target. Furthermore, the diagnostic device 50 controls various components of the internal combustion engine 10. For example, the diagnostic device 50 calculates the engine speed based on the rotational position SC of the crankshaft 14. Furthermore, the diagnostic device 50 calculates the required engine load factor, or the requested load factor, based on the engine speed and the accelerator operation amount ACC. Furthermore, the diagnostic device 50 controls the throttle valve 26 to obtain the intake air amount GA required to achieve the requested load factor. When the requested load factor reaches a certain level, the diagnostic device 50 opens the WGV 27 to a degree less than fully open. In response, the supercharger 11 performs supercharging. When the intake air amount GA is correspondingly high, the diagnostic device 50 controls the supercharger 11 to perform supercharging. The engine load factor is a parameter that determines the amount of air filled in the cylinder 22 and is a value obtained by dividing the amount of air flowing into one cylinder 22 in each combustion cycle by a reference air amount. The reference air amount changes according to the engine speed.

[0032] <Abnormalities in the blowby gas piping>

[0033] The diagnostic device 50 can perform a diagnostic process to diagnose whether an abnormality has occurred in the blowby gas pipe 33. The abnormality diagnosed in this diagnostic process is leakage of blowby gas from the blowby gas pipe 33 to the outside (hereinafter referred to as a leakage abnormality). A leakage abnormality in the blowby gas pipe 33 occurs when one end of the blowby gas pipe 33 is disconnected from the joint 32, the other end of the blowby gas pipe 33 is disconnected from the upstream intake passage 241, or the blowby gas pipe 33 is damaged.

[0034] Based on the degree of blowby gas leakage, leakage anomalies can be categorized into the following two types. One type occurs when the blowby gas pipe 33 is completely disconnected from the joint 32 or the upstream intake passage 241 or when damage occurs in the blowby gas pipe 33 with a relatively large opening area, resulting in complete communication with the atmosphere within the blowby gas pipe 33. Hereinafter, this state of complete communication with the atmosphere within the blowby gas pipe 33 is referred to as a "full communication state." In the case of a leakage anomaly characterized by a "full communication state," the amount of blowby gas leakage is high. The other type occurs when damage occurs in the blowby gas pipe 33 with a relatively small opening area, resulting in a slight communication with the atmosphere within the blowby gas pipe 33. Hereinafter, this slight communication with the atmosphere within the blowby gas pipe 33 is referred to as a "partial communication state." This type of leakage anomaly can also occur when the connection between the blowby gas pipe 33 and the joint 32 or the connection between the blowby gas pipe 33 and the intake passage 24 is slightly loose. In the case of a partial communication state, the amount of blowby gas leakage is not significant.

[0035] The diagnostic device 50 utilizes the PCV pressure W when diagnosing the presence or absence of the above-mentioned leakage abnormality during the diagnostic process. The relationship between the intake air amount GA and the PCV pressure W, which is a premise for the diagnostic device 50 to utilize the PCV pressure W during the diagnostic process, will be described. First, the relationship between the intake air amount GA and the PCV pressure W when the blowby gas piping 33 is normal will be described. Here, when the supercharger 11 is used for boosting, that is, when the intake air amount GA is correspondingly large, a negative pressure is generated in the upstream intake passage 241. Along with this, the blowby gas in the blowby gas passage 31 flows into the upstream intake passage 241. Therefore, the PCV pressure W is lower than the atmospheric pressure M. The greater the intake air amount GA, the greater the negative pressure of the upstream intake passage 241, and therefore the greater the amount of blowby gas flowing into the upstream intake passage 241. That is, as Figure 2 As shown by the solid line, the PCV pressure W decreases as the intake air amount GA increases.

[0036] On the other hand, the relationship between the intake air amount GA and the PCV pressure W when the blowby gas pipe 33 has leakage abnormality is as follows. First, the case of the above-mentioned fully connected state will be explained. When the blowby gas pipe 33 is in the fully connected state, the inside of the blowby gas pipe 33 is completely open to the atmosphere. Therefore, in this case, Figure 2 As shown by the dot-dash line, the PCV pressure W is always close to the atmospheric pressure M regardless of whether the intake air amount GA is large or small.

[0037] Next, the case of the above-mentioned partial connection state will be explained. As mentioned above, the main reason why the blowby gas piping 33 becomes partially connected is mostly due to the damage of the blowby gas piping 33. Although it also depends on the opening area of ​​the damage, in the case of the partial connection state, unlike the case of the complete connection state, the following situation will occur. That is, when a negative pressure is generated in the upstream intake passage 241 due to the supercharging performed by the supercharger 11, a certain amount of blowby gas flows into the upstream intake passage 241. Therefore, the PCV pressure W is lower than the atmospheric pressure M. The greater the amount of intake air GA, the greater the negative pressure of the upstream intake passage 241, and therefore the greater the amount of such blowby gas flowing into the upstream intake passage 241. Therefore, as Figure 2 As shown by the middle dashed line, the larger the intake air amount GA, the lower the PCV pressure W. However, since the inside of the blowby gas pipe 33 communicates with the atmosphere via the damaged portion, the PCV pressure W is closer to the atmospheric pressure M than when the blowby gas pipe 33 is normal.

[0038] Different from the leakage abnormality described above, a blockage abnormality may occur in the blowby gas piping 33. The blockage abnormality refers to a situation where a blockage occurs in the blowby gas piping 33. When the blockage abnormality occurs, the blowby gas accumulated in the storage space 23 cannot flow into the upstream intake passage 241 through the blowby gas passage 31. On the other hand, when the internal combustion engine 10 is in operation, the blowby gas continues to be generated. The larger the intake air amount GA is, the more likely the amount of blowby gas generated is to increase. Therefore, if Figure 2 As shown by the two-dot chain line, when the intake air amount GA is large to a certain extent, the PCV pressure W is higher than the atmospheric pressure M.

[0039] <Overview of Diagnostic Processing>

[0040] The diagnostic device 50 can perform the first processing as part of the diagnostic processing. In the first processing, the diagnostic device 50 calculates the pressure variation WA as the variation of the PCV pressure W within a specific period H. "What is the specific value of the pressure variation WA" will be described later. The specific period H is a period during which the intake air variation ΔGA as the variation of the intake air amount GA per unit time becomes greater than the specified value K. "What is the specific value of the intake air variation ΔGA" will be described later. In this embodiment, the diagnostic device 50 performs the first processing on the increase process (period) of the intake air amount GA. That is, the variation of the intake air amount GA per unit time is the increase of the intake air amount GA per unit time. The diagnostic device 50 performs the first processing only when the intake air amount GA is greater than the judgment air amount GATh.

[0041] The diagnostic device 50 can perform a second process as part of the diagnostic process. In the second process, the diagnostic device 50 corrects the pressure fluctuation WA to a value that minimizes the influence of the intake air fluctuation ΔGA. Specifically, when correcting the same pressure fluctuation WA, the diagnostic device 50 corrects the pressure fluctuation WA to a smaller value when the intake air fluctuation ΔGA is large during a specific period H, compared to when the intake air fluctuation ΔGA is small. Specifically, the diagnostic device 50 divides the pressure fluctuation WA by the intake air fluctuation ΔGA. The diagnostic device 50 uses this corrected pressure fluctuation WA as the determination parameter Y.

[0042] The diagnostic device 50 can perform a third process as part of the diagnostic process. In the third process, the diagnostic device 50 determines whether a leakage anomaly exists in the blowby gas piping 33 based on the aforementioned judgment parameter Y. Here, the diagnostic device 50 repeatedly performs the aforementioned first and second processes for different specific periods H. Therefore, the diagnostic device 50 calculates the judgment parameter Y multiple times. Specifically, the diagnostic device 50 calculates the judgment parameter Y a number of times NTh. In the third process, if the cumulative parameter Z, which is the cumulative value of the judgment parameter Y calculated multiple times, is less than the judgment threshold ZTh, the diagnostic device 50 determines that the leakage anomaly has occurred.

[0043] The diagnostic device 50 pre-stores the above-mentioned determination air amount GATh as information required when performing diagnostic processing. As described above, when the intake air amount GA is small, it is difficult to generate a difference in the PCV pressure W between the leakage abnormality of the blowby gas piping 33 and the normal situation. Taking this into consideration, the determination air amount GATh is set as a value at which a significant difference in the PCV pressure W appears between the leakage abnormality and the normal situation, for example, based on an experiment or simulation. The determination air amount GATh is a value greater than the minimum value of the intake air amount GA when supercharging is performed by the supercharger 11. That is, the case where the intake air amount GA is greater than the determination air amount GATh is a case where a negative pressure condition is captured in the upstream intake passage 241. In Figure 2 An example of determining the air amount GATh is shown in FIG.

[0044] The diagnostic device 50 pre-stores the aforementioned unit time as information required for performing diagnostic processing. The unit time is a relatively short period, such as 0.1 seconds, less than one second. The unit time is set based on, for example, experiments or simulations, as a time period sufficient to extract the increase in intake air volume GA associated with the acceleration of the vehicle 300 from the transition of intake air volume GA. The unit time is sufficiently longer than the data sampling interval of the sensors used in the diagnostic processing. Therefore, the sensors output multiple detection signals to the diagnostic device 50 within the unit time.

[0045] The diagnostic device 50 pre-stores the prescribed value map as information required when performing diagnostic processing. The prescribed value map represents the relationship between the intake air amount GA and the above-mentioned prescribed value K. The prescribed value K of each intake air amount GA is the following value. That is, it is "a value in which it can be judged that the intake air variation ΔGA that may be generated by the internal combustion engine 10 is not instantaneous noise (interference), and the vehicle 300 is in the acceleration process accompanied by the supercharging of the supercharger 11, and there is a clear difference in the pressure variation WA between the leakage abnormality and the normal situation". Taking into account the relationship between the above-mentioned intake air amount GA and the PCV pressure W, the following can be said. That is, if the intake air variation ΔGA does not increase to a certain extent under the condition that the intake air amount GA is small and the negative pressure of the upstream intake passage 241 is small although it is in the supercharging process, it is difficult to generate a difference in the pressure variation WA between the leakage abnormality and the normal situation in the partially connected state. Taking this into consideration, in the prescribed value map, as Figure 3 As shown, the predetermined value K is set so that the smaller the intake air amount GA is, the larger the value is. The predetermined value map is created based on, for example, experiments or simulations. In this way, the predetermined value K is set in advance based on the corresponding relationship with the intake air amount GA.

[0046] The diagnostic device 50 stores the above-mentioned number of determinations NTh in advance as information required for executing diagnostic processing. The number of determinations NTh is set based on, for example, experiments or simulations as the minimum number of determination parameters Y required to obtain an accurate diagnostic result.

[0047] The diagnostic device 50 pre-stores the aforementioned determination threshold ZTh as information required for executing diagnostic processing. This threshold ZTh is set based on, for example, experiments or simulations, as the minimum value of the cumulative parameter Z that can be obtained when the blowby gas piping 33 is operating normally. This threshold ZTh is a value based on the number of determinations NTh.

[0048] <Specific Processing Procedures of Diagnostic Processing>

[0049] The diagnostic device 50 repeatedly executes diagnostic processing during the operation of the internal combustion engine 10. When the diagnostic device 50 performs diagnostic processing for the first time after the internal combustion engine 10 is started, it performs a reset process similar to step S34 described below before starting the diagnostic processing. After this reset, the diagnostic device 50 begins the diagnostic processing. Therefore, at the start time of the first diagnostic processing after the internal combustion engine 10 is started, the cumulative parameter Z and the cumulative number of times N are "0."

[0050] like Figure 4 As shown, when the diagnostic device 50 starts the diagnostic processing, it first performs the processing of step S21. In step S21, the diagnostic device 50 determines whether the precondition is met. The precondition is that both of the following two items are met. The first item is that in the historical record of the PCV pressure W received from the PCV pressure sensor 35, the state in which the PCV pressure W is higher than the atmospheric pressure M does not continue. The second item is that the latest battery voltage V received from the voltage sensor 73 is above the judgment voltage VTh. Regarding the first item, when the state in which the PCV pressure W is higher than the atmospheric pressure M continues, a blockage abnormality may have occurred. The first item is used to exclude such a situation. The period of confirming the historical record of the PCV pressure W is the length of time that is considered to have caused the blockage abnormality, for example, pre-set by experiments or simulations. Regarding the second item, when the battery voltage V is lower than the judgment voltage VTh, it may not be possible to apply the required voltage to the sensor used in the diagnosis. The diagnostic device 50 determines whether the precondition is satisfied by referring to the history of PCV pressure W received from the PCV pressure sensor 35, the atmospheric pressure M received from the atmospheric pressure sensor 71, and the battery voltage V received from the voltage sensor 73. If the precondition is not satisfied (step S21: NO), the diagnostic device 50 proceeds to step S50.

[0051] In step S50, the diagnostic device 50 deletes the analysis data. If the determination in step S21 is negative and the process proceeds to step S50, the diagnostic device 50 does not store the analysis data after starting the diagnostic process. Therefore, in this case, the diagnostic device 50 essentially does nothing. This also applies if the determination in step S22, described later, is negative and the process proceeds to step S50. When the diagnostic device 50 executes step S50, it temporarily terminates the series of diagnostic processes. Then, the diagnostic device 50 executes step S21 again.

[0052] On the other hand, in step S21 , when the precondition is satisfied (step S21 : YES), the diagnostic device 50 advances the process to step S22 .

[0053] In step S22, the diagnostic device 50 determines whether the intake air amount GA is greater than the determination air amount GATh. The diagnostic device 50 refers to the latest intake air amount GA received from the air flow meter 72 and the determination air amount GATh. And, when the latest intake air amount GA is lower than the determination air amount GATh (step S22: No), the diagnostic device 50 causes the processing to enter the above-mentioned step S50. On the other hand, when the latest intake air amount GA is greater than the determination air amount GATh (step S22: Yes), the diagnostic device 50 causes the processing to enter step S23. An example of a situation in which the processing enters step S23 is a situation in which the intake air amount GA increases from less than the determination air amount GATh to more than the determination air amount GATh during the increase of the intake air amount GA. That is, the rising process of the intake air amount GA is captured.

[0054] In step S23, the diagnostic device 50 stores the analysis data over the aforementioned unit time. Specifically, the diagnostic device 50 stores, in a time series format, a plurality of intake air amounts GA received from the air flow meter 72 from the time the process enters step S23 until the unit time has elapsed. The diagnostic device 50 treats this time series data as first analysis data D1. Furthermore, the diagnostic device 50 stores, in a time series format, a plurality of PCV pressures W received from the PCV pressure sensor 35 from the time the process enters step S23 until the unit time has elapsed. The diagnostic device 50 treats this time series data as second analysis data D2. The diagnostic device 50 may store the analysis data in RAM or in the storage device 53. This also applies to other parameters used in the diagnostic process. The diagnostic device 50 may measure the unit time by, for example, incrementing a time-measuring counter. When the unit time has elapsed since the process entered step S23, the diagnostic device 50 advances the process to step S24.

[0055] In step S24, the diagnostic device 50 calculates the intake air variation ΔGA. Specifically, the diagnostic device 50 refers to the first analysis data D1 stored in step S23. Furthermore, the diagnostic device 50 determines the first intake air amount GA in the time series of the first analysis data D1 as the starting air amount. In addition, the diagnostic device 50 determines the last intake air amount GA in the time series of the first analysis data D1 as the ending air amount. Then, the diagnostic device 50 calculates the value obtained by subtracting the starting air amount from the ending air amount as the intake air variation ΔGA. That is, the diagnostic device 50 of this embodiment does not divide the value obtained by subtracting the starting air amount from the ending air amount by the unit time, but instead treats the value after the above subtraction as the intake air variation ΔGA directly. Then, the diagnostic device 50 causes the processing to enter step S25.

[0056] In step S25, the diagnostic device 50 determines whether a specific condition is satisfied. The specific condition is a condition in which both the following items (A) and (B) are satisfied.

[0057] (A) The intake air fluctuation amount ΔGA calculated in step S24 is equal to or greater than a predetermined value K.

[0058] (B) The starting air amount for calculating the intake air variation ΔGA in step S24 is the minimum value in the time series of the first analysis data D1 , and the ending air amount is the maximum value in the time series of the first analysis data D1 .

[0059] To determine whether item (A) holds, the diagnostic device 50 first refers to the prescribed value map. Based on the prescribed value map, the diagnostic device 50 calculates a prescribed value K corresponding to the starting air volume. The diagnostic device 50 then compares this prescribed value K with the intake air fluctuation amount ΔGA to determine whether the magnitude relationship specified in item (A) holds. To determine whether item (B) holds, the diagnostic device 50 compares each intake air volume GA in the time series of the first analysis data D1 with the starting air volume, and also compares each intake air volume GA with the ending air volume. Thus, the diagnostic device 50 determines whether the magnitude relationship specified in item (B) holds. If the specific condition does not hold (step S25: No), the diagnostic device 50 proceeds to step S50. On the other hand, if the specific condition holds (step S25: Yes), the diagnostic device 50 identifies the series of periods during which the analysis data was stored in step S23 as the specific period H. The diagnostic device 50 then proceeds to step S26. Here, a YES determination in step S25 means that the intake air amount GA continues to increase over time in the time series of the first analysis data D1. As described above, when the intake air amount GA is relatively large (YES in step S22), the PCV pressure W decreases as the intake air amount GA increases. Given this relationship between the intake air amount GA and the PCV pressure W, if the intake air amount GA continues to increase over time in the time series of the first analysis data D1, the PCV pressure W continues to decrease over time in the time series of the second analysis data D2.

[0060] In step S26, the diagnostic device 50 calculates the pressure fluctuation amount WA. Specifically, the diagnostic device 50 refers to the aforementioned second analysis data D2, which is the time series data of the PCV pressure W. The diagnostic device 50 then determines the first PCV pressure W in the time series of the second analysis data D2 as the reference pressure. Next, the diagnostic device 50 calculates the difference between each of the multiple PCV pressures W (hereinafter referred to as a data element) constituting the time series data of the second analysis data D2 and the reference pressure. Specifically, for each data element, the diagnostic device 50 calculates the pressure difference value ΔW by subtracting the data element from the reference pressure. The diagnostic device 50 then calculates the pressure fluctuation amount WA by summing all the pressure difference values ​​ΔW. As described above, when processing proceeds to step S26, the PCV pressure W continues to decrease in the time series of the second analysis data D2. Therefore, the values ​​of each data element are generally smaller than the reference pressure value. However, due to noise, etc., the values ​​of the data elements may be larger than the reference pressure value. When the value of the data element is greater than the reference pressure value, the diagnostic device 50 calculates the pressure difference value ΔW as “0.” After calculating the pressure variation WA, the diagnostic device 50 proceeds to step S27. The process of step S26 is the first process.

[0061] In step S27, the diagnostic device 50 calculates the judgment parameter Y. Specifically, the diagnostic device 50 refers to the pressure variation WA calculated in step S26 and the intake air variation ΔGA calculated in step S24. Then, the diagnostic device 50 divides the pressure variation WA by the intake air variation ΔGA. Then, the diagnostic device 50 sets the obtained value as the judgment parameter Y. When the diagnostic device 50 calculates the judgment parameter Y, it causes the processing to enter step S28. The processing of this step S27 is the second processing. According to the definition of the intake air variation ΔGA explained in step S24, the intake air variation ΔGA is the difference between the minimum value and the maximum value of the intake air amount GA within a specific period H. That is, in the processing of step S27, the diagnostic device 50 divides the pressure variation WA by the difference between the minimum value and the maximum value of the intake air amount GA within the specific period H.

[0062] In step S28, the diagnostic device 50 updates the cumulative parameter Z. Specifically, the diagnostic device 50 adds the determination parameter Y calculated in step S27 to the currently stored cumulative parameter Z. The diagnostic device 50 then stores the resulting value as the latest cumulative parameter Z. The diagnostic device 50 then proceeds to step S29.

[0063] In step S29 , the diagnostic device 50 updates the cumulative count N. Specifically, the diagnostic device 50 adds “1” to the currently stored cumulative count N. The diagnostic device 50 then stores the obtained value as the latest cumulative count N. The diagnostic device 50 then proceeds to step S30 .

[0064] In step S30, the diagnostic device 50 determines whether the cumulative number N updated in step S30 is greater than the determination number NTh. If the cumulative number N updated in step S30 is less than the determination number NTh (step S30: No), the diagnostic device 50 advances the process to step S50.

[0065] On the other hand, in step S30 , when the cumulative number of times N is equal to or greater than the determination number of times NTh (step S30 : Yes), the diagnostic device 50 advances the process to step S31 .

[0066] In step S31, the diagnostic device 50 determines whether the cumulative parameter Z updated in step S28 is greater than or equal to the determination threshold ZTh. If the cumulative parameter Z is greater than or equal to the determination threshold ZTh (step S31: Yes), the diagnostic device 50 advances the process to step S32. In this case, the diagnostic device 50 determines in step S32 that the blowby gas piping 33 is normal. The diagnostic device 50, for example, deactivates a leakage flag indicating the presence or absence of a leakage abnormality. The diagnostic device 50 then advances the process to step S34. The diagnostic device 50 uses the activation / deactivation information of the leakage flag as information, for example, when controlling the internal combustion engine 10.

[0067] On the other hand, if the cumulative parameter Z is less than the determination threshold ZTh in step S31 (step S31: No), the diagnostic device 50 proceeds to step S33. In this case, the diagnostic device 50 determines in step S33 that a leakage abnormality has occurred in the blowby gas piping 33. For example, the diagnostic device 50 activates a leakage flag. Furthermore, the diagnostic device 50 illuminates the warning lamp 78. The diagnostic device 50 then proceeds to step S34. Thus, through the processing of steps S31, S32, and S33, the diagnostic device 50 obtains a diagnosis result indicating the presence or absence of an abnormality in the blowby gas passage 31. The processing of steps S31, S32, and S33 described above constitutes the third process.

[0068] In step S34, the diagnostic device 50 performs a reset process. Specifically, the diagnostic device 50 resets the cumulative count N and the cumulative parameter Z to "0." Furthermore, the diagnostic device 50 deletes the analysis data. The diagnostic device 50 then temporarily terminates the diagnostic processing sequence. The diagnostic device 50 then performs the process of step S21 again. If the diagnostic device 50 illuminates the warning light 78 in step S33, the warning light 78 continues to illuminate until it receives an instruction to extinguish it, for example, in response to an occupant's operation.

[0069] <Function of Implementation Method>

[0070] (A) Overall flow of diagnostic processing

[0071] Taking the case where the blowby gas pipe 33 is normal as an example, the overall flow of the diagnostic process will be described. Assume that the vehicle 300 is currently accelerating. Also, assume that the intake air amount GA is increasing along with the supercharging by the supercharger 11. Assume that Figure 5 As shown in (a), the intake air variation ΔGA becomes the judgment air amount GATh at time t1 along with the increase in the intake air amount GA (step S22: yes). Then, the diagnostic device 50 stores the analysis data per unit time (step S23). When the intake air variation ΔGA within the unit time is greater than the specified value K (step S25: yes), the diagnostic device 50 determines the period corresponding to the above-mentioned unit time as a specific period (hereinafter referred to as the first specific period) H1. As described above, when the supercharger 11 performs supercharging, the change in the intake air amount GA is linked to the change in the PCV pressure W. Therefore, in the case of Figure 5 When the intake air amount GA increases from the first air amount GA1 to the second air amount GA2 during the first specific period H1 as shown in (a), Figure 5 As shown by the solid line in (b), the PCV pressure W decreases from the first pressure W1 to the second pressure W2 during the first specific period H1. As an index representing the degree of change in the PCV pressure W, the diagnostic device 50 calculates the same as that obtained by Figure 5 The pressure variation WA is equivalent to the area indicated by the hatching in (b) (step S26). The diagnostic device 50 updates the cumulative parameter Z based on the judgment parameter Y corresponding to the pressure variation WA (step S28). Figure 5 As shown by the solid line in (c), the cumulative parameter Z increases by one step at the end time point t2 of the first specific period H1.

[0072] Assume that Figure 5As shown in (a), after the first specific period H1 ends, the increase in the intake air amount GA continues. In this case, the diagnostic device 50 determines the unit time after the first specific period H1 as the second specific period H2. Then, the diagnostic device 50 updates the cumulative parameter Z with the judgment parameter Y corresponding to the pressure change amount WA in the same manner as above. And, as Figure 5 As shown by the solid line in (c), the cumulative parameter Z increases by one step at the end time t3 of the second specific period H2. In this way, the cumulative parameter Z increases sequentially.

[0073] In contrast to the above situation, when a leakage abnormality occurs in the blowby gas piping 33, the inside of the blowby gas piping 33 is connected to the atmosphere. Therefore, the change in the PCV pressure W corresponding to the change in the intake air amount GA is small. Here, it is assumed that the blowby gas piping 33 is in a partially connected state and the first specific period H1 is reached. Furthermore, it is assumed that the intake air amount GA increases from the first air amount GA1 to the second air amount GA2. In this case, as Figure 5 As shown by the double-dashed line in (b), the PCV pressure W only decreases from the first pressure W1 to the third pressure W3 which is higher than the second pressure W2 during the first specific period H1. The pressure fluctuation amount WA at this time is smaller than the pressure fluctuation amount WA when the blowby gas piping 33 is normal. In this case, Figure 5 As shown by the two-dot chain line in (c), the integrated parameter ZA at time t2, the end of the first specific period H1, is smaller than the integrated parameter Z1 when the blowby gas pipe 33 is operating normally. Thus, when a leakage abnormality occurs in the blowby gas pipe 33, the pressure fluctuation amount WA, and therefore the integrated parameter Z, is small. Taking advantage of this, the diagnostic device 50 determines that a leakage abnormality has occurred in the blowby gas pipe 33 (step S33) when the integrated parameter Z is updated at the determination number NTh and the integrated parameter Z is small (step S31: No).

[0074] (B) Correction of pressure fluctuation WA

[0075] The diagnostic device 50 does not directly set the pressure variation WA as the judgment parameter Y, but sets the value after the pressure variation WA is corrected as the judgment parameter Y. The significance of performing this correction will be explained. For the purpose of explanation, three different situations will be considered regarding the state of the intake air variation ΔGA and the blowby gas piping 33. The first situation Q1 is a situation where the intake air amount GA increases from the first air amount GA1 to the second air amount GA2 as in the first specific period H1 mentioned above, and the blowby gas piping 33 is normal. In this first situation Q1, as Figure 5 As shown by the solid line in (b), the PCV pressure W drops from the first pressure W1 to the second pressure W2. Figure 8 The dot-dash line in (b) shows the Figure 5The solid line in (b) shows the same change in PCV pressure W. Figure 8 The dot-dash line in (a) shows the Figure 5 The solid line in (a) shows the transition of the intake air amount GA.

[0076] The second case Q2 is a case where the intake air fluctuation amount ΔGA is considerably larger than that in the first case Q1 and the blowby gas pipe 33 is normal. Figure 8 As shown by the solid line in (a), during the first specific period H1, the intake air amount GA increases from the first air amount GA1 to the third air amount GA3, which is larger than the second air amount GA2. In this case, the intake air fluctuation amount ΔGAX, which is the difference between the third air amount GA3, which is the intake air amount GA at the end time point t2 of the first specific period H1, and the first air amount GA1, which is the intake air amount at the start time point t1, is larger than the intake air fluctuation amount ΔGA1 in the first case Q1. In this second case Q2, as shown in FIG. Figure 8 As shown by the two-dot chain line in (b), from the start time point t1 to the end time point t2 of the first specific period H1, the PCV pressure W drops from the first pressure W1 to the fourth pressure W4 which is lower than the second pressure W2.

[0077] The third case Q3 is a case where the intake air fluctuation amount ΔGA is the same as that of the second case Q2 and a leakage abnormality occurs in the blowby gas pipe 33 in a partially connected state. Figure 8 As shown by the solid line in (a), similarly to the second case Q2, the intake air amount GA increases from the first air amount GA1 to the third air amount GA3 during the first specific period H1. In this third case Q3, the blowby gas piping 33 is partially connected, so the decrease in the PCV pressure W corresponding to the increase in the intake air amount GA is smaller than in the second case Q2 in which the blowby gas piping 33 is normal. In other words, Figure 8 As shown by the solid line in (b), the PCV pressure W only decreases from the first pressure W1 to the fifth pressure W5 higher than the fourth pressure W4 from the start time t1 to the end time t2 of the first specific period H1.

[0078] As described above, in the third scenario Q3, the decrease in the PCV pressure W during the first specific period H1 is smaller than in the second scenario Q2. However, since the intake air fluctuation amount ΔGAX in the third scenario Q3 is relatively large, the decrease in the PCV pressure W is correspondingly larger. Furthermore, the decrease in the PCV pressure W in the third scenario Q3 can be larger than the decrease in the PCV pressure W in the first scenario Q1, for example. In other words, Figure 8As shown in (b), the fifth pressure W5, which is the PCV pressure at the end time t2 of the first specific period H1 of the third case Q3, can be lower than the second pressure W2, which is the PCV pressure at the end time t2 of the first case Q1. In this case, Figure 8 The pressure variation WA of the third case Q3 shown by the oblique lines in (b) is Figure 5 The pressure fluctuation amount WA is large in the first case Q1 indicated by the oblique lines in (b). Even if a leakage abnormality in a partially connected state occurs, if the intake air fluctuation amount ΔGAX is considerably large, the pressure fluctuation amount WA may be larger than in the case where the intake air fluctuation amount ΔGA1 is small under normal conditions.

[0079] Assume that the pressure variation WA is not corrected as described above but is treated as the judgment parameter Y. In this case, Figure 8 As shown by the solid line in (c), the cumulative parameter ZB of the third case Q3 at the end time point t2 of the first specific period H1 is greater than Figure 8 In the first case Q1, shown by the dashed line in (c), the cumulative parameter Z1 is large. As described above, in the diagnostic process, when the cumulative parameter Z is small, it is determined that a leakage abnormality has occurred in the blowby gas pipe 33. Therefore, if the cumulative parameter Z is large despite a leakage abnormality occurring in the blowby gas pipe 33, as in the third case Q3, there is a possibility that the blowby gas pipe 33 may be mistakenly determined to be normal.

[0080] To avoid such a situation, the diagnostic device 50 corrects the pressure fluctuation amount WA. Specifically, the diagnostic device 50 divides the pressure fluctuation amount WA during the first specific period H1 by the intake air fluctuation amount ΔGA. Thus, the diagnostic device 50 corrects the pressure fluctuation amount WA to a value that has a small influence on the intake air fluctuation amount ΔGA. For example, Figure 6 As shown, in the first case Q1, since the intake air variation ΔGA1 is small, the degree of change of the judgment parameter Y from the pressure variation WA as the value before correction to the value after correction is small. Figure 7 As shown, in the third situation Q3 described above, due to the large intake air fluctuation ΔGAX, the degree of change in the judgment parameter Y from the pre-correction value of the pressure fluctuation WA to the post-correction value is significant. By performing this correction, it is possible to calculate a judgment parameter Y that reflects the actual change in PCV pressure W corresponding to the state of the blowby gas pipe 33. In other words, the judgment parameter Y reflects the change in PCV pressure W corresponding to the state of the blowby gas pipe 33, assuming that the intake air fluctuation ΔGA is substantially the same. Furthermore, even if the actual intake air fluctuation ΔGA is large, the judgment parameter Y will be small if a leakage abnormality has occurred in the blowby gas pipe 33. By using this judgment parameter Y to diagnose the blowby gas pipe 33, accurate diagnostic results can be obtained.

[0081] <Effects of Implementation>

[0082] (1) If a leakage abnormality occurs in the blowby gas pipe 33, the pressure fluctuation amount WA should be smaller than when the blowby gas pipe 33 is normal. However, if diagnostic processing is performed without correcting the pressure fluctuation amount WA, the pressure fluctuation amount WA increases as the intake air amount GA fluctuates, potentially leading to an erroneous determination that the blowby gas pipe 33 is normal. Regarding this point, in this embodiment, as described in the "Operation" section above, when the intake air fluctuation amount ΔGA during the specific period H is large, the diagnostic device 50 corrects the pressure fluctuation amount WA to a smaller value accordingly. Therefore, by performing this correction, it is possible to prevent erroneous determinations regarding the presence or absence of a leakage abnormality in the blowby gas pipe 33.

[0083] (2) The diagnostic device 50 determines whether or not there is a leakage abnormality in the blowby gas pipe 33 based on the cumulative parameter Z, which is the cumulative value of the judgment parameter Y calculated multiple times. In this case, a more reliable judgment result can be obtained compared to, for example, a case where the presence or absence of a leakage abnormality in the blowby gas pipe 33 is determined based on a single judgment parameter Y.

[0084] (3) The diagnostic device 50 divides the pressure fluctuation amount WA by the difference between the maximum and minimum values ​​of the intake air amount GA within the specific period H. By dividing the pressure fluctuation amount WA by the change in the intake air amount GA within the specific period H in this manner, the pressure fluctuation amount WA can be corrected to a value that is less affected by the intake air fluctuation amount ΔGA. Furthermore, in the configuration of this embodiment, the intake air fluctuation amount ΔGA used to determine whether the specific condition has been satisfied in step S25 is used to correct the pressure fluctuation amount WA. Therefore, there is no need to separately calculate dedicated parameters for correcting the pressure fluctuation amount WA. In this embodiment, the processing burden of the diagnostic device 50 can be minimized.

[0085] <Change Example>

[0086] The above-mentioned embodiment can be implemented by modifying as follows. The above-mentioned embodiment and the following modified examples can be implemented in combination with each other within the scope of no technical contradiction.

[0087] ·Regarding step S25, the content of item (B) of the specific condition is not limited to the example of the above-mentioned embodiment. Even if the starting air volume and the ending air volume are not the minimum and maximum values ​​of the time series of the first analysis data D1 as in the above-mentioned embodiment, as long as the intake air volume GA generally increases in the overall trend of the time series, the intake air volume GA can be regarded as being in an increasing process. Item (B) is content that can be determined as being in an increasing process in the overall trend of the time series. For example, a coordinate system is defined with time as the horizontal axis and the intake air volume GA as the vertical axis, and a regression line of the time series of the intake air volume GA is calculated in the coordinate system. Item (B) can also be used to define that the slope of the regression line is positive.

[0088] Item (B) is not essential. If the intake air fluctuation amount ΔGA is equal to or greater than the predetermined value K on the unit time scale of the above embodiment, in most cases, the intake air amount GA is likely to be increasing in the time series of the first analysis data D1.

[0089] The method for setting the specific period H is not limited to the example of the above-mentioned embodiment. For example, the specific period H may be longer than the unit time. As an example of setting a period longer than the unit time as the specific period H, the following technical solution (hereinafter referred to as the first technical solution) may also be adopted. That is, in step S23 of the diagnostic process, the analysis data is continuously stored over a period of a plurality of unit times, such as three or four times of the unit time. Furthermore, the time series of the analysis data is divided into sections for each unit time, and whether the specific conditions of the above-mentioned embodiment are met is determined for each unit time. Furthermore, when the specific conditions are met for a plurality of consecutive unit times, the plurality of consecutive unit times may be set as one specific period H. The specific period H may be a period during which the intake air variation ΔGA is greater than the specified value K.

[0090] The method for setting the unit time is not limited to the example in the above embodiment. The unit time may be equal to or greater than one second. As long as the air flow meter 72 can detect the intake air amount GA at least twice per unit time, the intake air fluctuation amount ΔGA can be calculated. Furthermore, as long as the PCV pressure sensor 35 can detect the PCV pressure W at least twice per unit time, the pressure fluctuation amount WA can be calculated.

[0091] The pressure fluctuation amount WA calculated in step S26 is not limited to the value obtained by integrating the pressure difference values ​​ΔW. For example, the absolute value of the difference between the maximum and minimum values ​​in the time series of the second analysis data D2 may be set as the pressure fluctuation amount WA. The pressure fluctuation amount WA may simply be a value reflecting the magnitude of the fluctuation in the PCV pressure W during the specific period H.

[0092] When determining the specific period H in step S25, the specific period H may be determined for the decreasing process of the intake air amount GA after the intake air amount GA transitions from increasing to decreasing. Furthermore, in step S26, the pressure fluctuation amount WA during the decreasing process of the intake air amount GA may be calculated. As described above, when negative pressure is generated in the upstream intake passage 241, changes in the intake air amount GA occur in conjunction with changes in the PCV pressure W. Therefore, when negative pressure is generated in the upstream intake passage 241, the PCV pressure W also changes in conjunction with the change in the intake air amount GA during the decreasing process of the intake air amount GA. In this case, the PCV pressure W increases as the intake air amount GA decreases. The pressure fluctuation amount WA during this increasing process of the PCV pressure W may also be calculated. In this case, the following method may be employed: Specifically, the last PCV pressure W in the time series of the second analysis data D2 is used as a reference pressure. The pressure fluctuation amount WA is then calculated as the cumulative value obtained by subtracting the values ​​of each data element from this reference pressure.

[0093] When the specific period H is determined based on the decrease in the intake air amount GA as in the above-described modification, for example, the following specific conditions may be employed in step S25. Item (A) specifies that the absolute value of the intake air fluctuation amount ΔGA is greater than or equal to a predetermined value K. The intake air fluctuation amount ΔGA herein may be defined similarly to that in the above-described embodiment. Item (B) specifies that the starting air amount is the maximum value of the first analysis data D1 and the ending air amount is the minimum value of the first analysis data D1.

[0094] The pressure variation WA may be calculated separately during both the increasing and decreasing processes of the intake air amount GA. The specific conditions of step S25 may be appropriately set to achieve this technical solution.

[0095] Regarding step S24, the method for setting the intake air fluctuation amount ΔGA is not limited to the example in the above embodiment. Instead of directly setting the value obtained by subtracting the starting air amount from the ending air amount as in the above embodiment, the value obtained by dividing the subtracted value by the unit time may be used as the intake air fluctuation amount ΔGA. In this case, the predetermined value K may be set to the same unit as the intake air fluctuation amount ΔGA. Furthermore, as described in the following modified example, the method for setting the intake air fluctuation amount ΔGA is not limited to using the ending air amount and the starting air amount in the first analysis data D1. The intake air fluctuation amount ΔGA may simply be a value that indicates the degree of change in the intake air amount GA per unit time.

[0096] Calculating the intake air fluctuation amount ΔGA does not necessarily require the use of the first analysis data D1. In other words, the intake air fluctuation amount ΔGA can also be calculated using a method other than temporarily storing the intake air amount GA in a time series format. For example, the diagnostic device 50 may calculate the intake air fluctuation amount ΔGA as the absolute value of the difference between the intake air amount GA received from the air flow meter 72 at two consecutive timings. In this case, the interval between receiving the detection signal from the air flow meter 72 is treated as the unit time. When calculating the intake air fluctuation amount ΔGA in this manner, for example, a specific period H can be determined as follows. Specifically, the intake air fluctuation amount ΔGA is repeatedly calculated, and a series of periods during which the repeatedly calculated intake air fluctuation amount ΔGA remains at or above a predetermined value K is determined as the specific period H. In this case, the predetermined value K can be calculated from a predetermined value map to determine a value corresponding to one of the two intake air amounts GA used in calculating the intake air fluctuation amount ΔGA. When this solution (hereinafter referred to as the second solution) is adopted, it is not necessary to store the unit time in advance in the diagnostic device 50. The processing content of the diagnostic process may be changed so as to realize the second solution.

[0097] When calculating the intake air fluctuation amount ΔGA in the second embodiment, the intake air amount GA sequentially received from the air flow meter 72 may be extracted at intervals to some extent for use in calculating the intake air fluctuation amount ΔGA. In other words, rather than calculating the intake air fluctuation amount ΔGA using two consecutively received data points, the intake air fluctuation amount ΔGA may be calculated using intervals of, for example, three or four intervals of the intake air amount GA sequentially received from the air flow meter 72. The number of intervals of the intake air amount GA used for calculating the intake air fluctuation amount ΔGA may be determined in advance.

[0098] Similar to the calculation of the intake air fluctuation amount ΔGA, the use of the second analysis data D2 when calculating the pressure fluctuation amount WA is not essential. For example, each time the PCV pressure W is received from the PCV pressure sensor 35, the difference between the received value and the reference pressure is calculated as the pressure difference value ΔW, and the pressure difference values ​​ΔW are sequentially accumulated to calculate the pressure fluctuation amount WA. To implement this solution, the diagnostic processing can be as follows. The PCV pressure W at the time when the intake air amount GA becomes greater than the determination air amount GATh is treated as the reference pressure. Furthermore, the pressure fluctuation amount WA is updated as described above for a certain period starting from the time when the intake air amount GA becomes greater than the determination air amount GATh. In this case, the intake air fluctuation amount ΔGA is repeatedly calculated using the second solution described above in parallel with the updating of the pressure fluctuation amount WA. Furthermore, a determination is made as to whether the certain period during which the pressure fluctuation amount WA is updated coincides with a specific period H. If the certain period during which the pressure fluctuation amount WA is updated coincides with the specific period H, the pressure fluctuation amount WA is used to calculate the determination parameter Y.

[0099] Regarding step S27, the method for correcting the pressure fluctuation amount WA is not limited to the example of the above-described embodiment. For example, when a set of a plurality of consecutive unit times is set as a specific period H, as in the first technical solution described above, the pressure fluctuation amount WA may be divided by the absolute value of the difference between the maximum and minimum values ​​of the intake air amount GA within the specific period H. The method for correcting the pressure fluctuation amount WA only needs to satisfy the following conditions. That is, when correcting the same pressure fluctuation amount WA, when the intake air fluctuation amount ΔGA within the specific period H is large, the pressure fluctuation amount WA may be corrected to a smaller value than when the intake air fluctuation amount ΔGA is small. The intake air fluctuation amount ΔGA within the specific period H mentioned here is the intake air fluctuation amount ΔGA representative of the specific period H. Regarding the intake air amount GA when a set of a plurality of consecutive unit times is set as a specific period H, for example, it may be set to the average value of the intake air fluctuation amount ΔGA for each unit time in the plurality of unit times.

[0100] When the specific period H is determined with the decrease process of the intake air amount GA as the target as in the above-mentioned modification, the pressure fluctuation amount WA may be divided by the absolute value of the intake air fluctuation amount ΔGA.

[0101] Instead of using the intake air fluctuation amount ΔGA as the parameter for correcting the pressure fluctuation amount WA, a separate parameter dedicated to the correction may be prepared. For example, the cumulative value of the intake air amount GA detected by the air flow meter 72 from the beginning to the end of the specific period H may be used as the correction parameter. Furthermore, the pressure fluctuation amount WA may be divided by the cumulative value of the intake air amount GA. Dividing the pressure fluctuation amount WA by the cumulative value of the intake air amount GA allows for correction that takes into account changes in the intake air amount GA during the specific period H, as well as changes in the intake air amount GA throughout the specific period H.

[0102] As a parameter used to correct the pressure fluctuation WA, the absolute value of the difference between the maximum and minimum values ​​of the accelerator operation amount ACC detected by the accelerator sensor 75 during a specific period H may be used. The accelerator operation amount ACC is a parameter associated with the increase or decrease in the intake air amount GA. Therefore, by using information about this difference, which reflects the change in the accelerator operation amount ACC, to correct the pressure fluctuation WA, it is possible to perform appropriate corrections to minimize the influence of the intake air fluctuation ΔGA. Furthermore, when using information about the accelerator operation amount ACC to correct the pressure fluctuation WA, even if information about the change in the intake air amount GA is occasionally unavailable, the pressure fluctuation WA can be corrected to a value that is less affected by the intake air fluctuation ΔGA.

[0103] The vehicle speed SP detected by the vehicle speed sensor 74 or the acceleration of the vehicle 300 detected therefrom may also be used as a parameter for correcting the pressure fluctuation amount WA. The increase or decrease in the intake air amount GA is related to the acceleration and deceleration (acceleration and deceleration) of the vehicle 300. Therefore, the vehicle speed SP and acceleration, which are parameters related to the acceleration and deceleration of the vehicle 300, are effective parameters for correcting the pressure fluctuation amount WA.

[0104] The method for correcting the pressure fluctuation WA is not limited to the method of dividing the pressure fluctuation WA. Any correction method is sufficient as long as it can correct the pressure fluctuation WA to a smaller value when the intake air fluctuation ΔGA within the specific period H is large compared to when the intake air fluctuation ΔGA is small.

[0105] The prescribed value K is not limited to the example in the above embodiment. The prescribed value K varies depending on the method for setting the intake air fluctuation amount ΔGA. It can be set to match the method for setting the intake air fluctuation amount ΔGA used in the diagnostic process. Furthermore, the prescribed value K only needs to satisfy the following conditions. Specifically, it must be a value greater than or equal to the minimum value of the intake air fluctuation amount ΔGA that can occur in the internal combustion engine 10 while the vehicle 300 is accelerating with supercharging by the supercharger 11, and a value that results in a significant difference in the pressure fluctuation amount WA between the occurrence of a leakage anomaly and normal conditions. The intake air fluctuation amount ΔGA is set to a positive value.

[0106] Rather than setting the predetermined value K variably according to the size of the intake air amount GA, the predetermined value K may be set to a uniform fixed value. For example, if the predetermined value K is set to a relatively large value, the aforementioned conditions for the predetermined value K are satisfied regardless of the size of the intake air amount GA. Furthermore, if the range of the intake air amount GA for calculating the pressure fluctuation amount WA is somewhat limited, the predetermined value K may be set to a value commensurate with (consistent with) the range of the intake air amount GA.

[0107] The method for setting the determination air amount GATh is not limited to the example of the above-described embodiment. Furthermore, as a prerequisite for calculating the pressure fluctuation amount WA, it is not essential to set the intake air amount GA to be greater than the determination air amount GATh (step S22). Here, as described above, the condition for determining the specific period H includes the intake air fluctuation amount ΔGA being greater than a specified value K. If the pressure fluctuation amount WA is calculated based on the specific period H that satisfies this condition, even if the intake air amount GA is not set to be greater than the determination air amount GATh, it is still possible to calculate the pressure fluctuation amount WA based on a condition where the intake air amount GA is large to some extent. Furthermore, the pressure fluctuation amount WA can be calculated based on a condition where negative pressure is generated in the upstream intake passage 241 and a period where the pressure fluctuation amount WA differs between a normal condition in the blowby gas piping 33 and a condition where a leakage anomaly occurs.

[0108] As described above, the intake air amount GA is correlated with the PCV pressure W. Therefore, as a condition for detecting the generation of a negative pressure in the upstream intake passage 241, instead of requiring the intake air amount GA to be greater than or equal to the determination air amount GATh, the PCV pressure W can be set to be less than or equal to a predetermined determination pressure. In this case, the determination pressure can be, for example, the PCV pressure W that occurs when the intake air amount GA reaches the determination air amount GATh in the above-described embodiment, when the blowby gas pipe 33 is operating normally. This determination pressure is lower than the atmospheric pressure M. In other words, if the PCV pressure W is set to be less than or equal to the determination pressure as a prerequisite for calculating the pressure fluctuation amount WA, the pressure fluctuation amount WA is generally not calculated when the blowby gas pipe 33 is fully connected. Furthermore, the presence of a leakage abnormality is primarily diagnosed only when the blowby gas pipe 33 is partially connected. However, if the analysis is limited to leakage abnormalities in the fully connected state, leakage abnormalities can be detected without using the pressure fluctuation amount WA. For example, if the PCV pressure W remains near atmospheric pressure M despite a correspondingly large intake air amount GA, it can be determined that a leakage anomaly has occurred in a fully connected state. On the other hand, detecting a leakage anomaly in a partially connected state requires a diagnosis utilizing the pressure fluctuation amount WA and, more importantly, the determination parameter Y. Based on this perspective, setting the PCV pressure W to a value below the determination pressure, as described above, is also effective when diagnosing the presence of a leakage anomaly focusing solely on the partial connection state of the blowby gas pipe 33.

[0109] When determining the specific period H, it is also possible to utilize other parameters that serve as indicators of the intake air fluctuation amount ΔGA, rather than the intake air fluctuation amount ΔGA itself. For example, the accelerator operation amount ACC can be used as such a parameter. As described above, changes in the accelerator operation amount ACC are correlated with changes in the intake air amount GA. Therefore, the correlation between changes in the accelerator operation amount ACC and changes in the intake air amount GA is investigated in advance. Furthermore, based on this relationship, a specific prescribed value for the accelerator operation amount ACC is set, corresponding to the prescribed value K of the intake air fluctuation amount ΔGA. This allows the specific period H to be determined using information on the transition of the accelerator operation amount ACC. Furthermore, the period during which the change in the accelerator operation amount ACC per unit time exceeds this specific prescribed value may be determined as the specific period H during which the intake air fluctuation amount ΔGA exceeds the prescribed value K. The change in the accelerator operation amount ACC per unit time may be calculated, for example, based on the time series of the accelerator operation amount ACC within a predetermined unit time, or may be determined as the difference between the accelerator operation amount ACC received from the accelerator sensor 75 at two consecutive timings.

[0110] PCV pressure W can also be used as a parameter for determining the specific period H. When the blowby gas pipe 33 is operating normally or during a leakage anomaly in a partially connected state, changes in the intake air amount GA are linked to changes in PCV pressure W. Therefore, the period during which the fluctuation in PCV pressure W per unit time is greater than or equal to a specific predetermined value for PCV pressure W can be defined as the specific period H during which the intake air fluctuation amount ΔGA is greater than or equal to a specific predetermined value K. This approach is also possible when only leakage anomalies in a partially connected state are targeted for abnormality detection. The specific predetermined value for PCV pressure W can be set based on the relationship between the intake air amount GA and PCV pressure W, for example, assuming the blowby gas pipe 33 is operating normally, corresponding to the specific predetermined value K for the intake air fluctuation amount ΔGA. The method for setting the fluctuation in PCV pressure W per unit time can be appropriately set in the same manner as the fluctuation in the accelerator operation amount ACC per unit time described in the above-mentioned modification. In this manner, the specific period H can also be determined using PCV pressure W itself. Furthermore, the pressure variation amount WA within the specific period H may be corrected using information on the transition of the accelerator operation amount ACC, for example.

[0111] The method for determining the presence of abnormal leakage from the blowby gas piping 33 is not limited to the example in the above embodiment. The above determination method may utilize the determination parameter Y. For example, the presence of abnormal leakage may be determined based on the value obtained by multiplying multiple determination parameters Y. The presence of abnormal leakage may also be determined based on only a single calculated determination parameter Y. The determination method is not limited as long as it can appropriately determine the presence of abnormal leakage.

[0112] The processing device for controlling the internal combustion engine 10 may be configured as a separate processing device from the diagnostic device 50. The diagnostic device 50 only needs to receive information required for performing diagnostic processing. One of the information required for performing diagnostic processing is the PCV pressure W.

[0113] The overall structure of the internal combustion engine is not limited to the example of the above embodiment. For example, a supercharger driven by the power of the crankshaft 14 may be used instead of an exhaust-driven supercharger.

[0114] The installation location of the PCV pressure sensor 35 can be modified from the example of the above embodiment. For example, the PCV pressure sensor 35 can be installed midway in the blowby gas piping 33. In this case, the presence or absence of leakage abnormalities between the location where the PCV pressure sensor 35 is installed and the portion connected to the intake passage in the blowby gas piping 33 can be diagnosed. The PCV pressure sensor 35 can accurately detect pressure fluctuations in the portion between the upstream intake passage 241, which is the source of negative pressure, and the location where the PCV pressure sensor 35 is installed.

[0115] As the PCV pressure sensor, a sensor that detects relative pressure with respect to atmospheric pressure M, that is, gauge pressure, may be used.

[0116] The configuration of the blowby gas passage is not limited to the example in the above embodiment. The blowby gas passage only needs to connect the crank chamber 17 with the upstream intake passage 241. The blowby gas passage may also be a passage that directly connects the crank chamber 17 and the upstream intake passage 241 without passing through the reservoir space 23 and the communication passage 21. The PCV pressure sensor 35 may also be provided midway in such a blowby gas passage.

Claims

1. An abnormality diagnosis device for a vehicle-mounted internal combustion engine, The vehicle-mounted internal combustion engine comprises: a supercharger having a compressor wheel; an intake passage for introducing intake air into the vehicle-mounted internal combustion engine; a blow-by gas passage connecting a portion of the intake passage upstream of the compressor impeller to the interior of the crankcase; and A PCV pressure sensor is provided in the blow-by gas passage and detects the pressure in the blow-by gas passage as the PCV pressure. A period during which the intake air variation amount, which is the variation amount per unit time of the intake air amount, is equal to or greater than a predetermined value is defined as a specific period. The abnormality diagnosis device is configured to execute a first process, a second process, and a third process. In the first process, the pressure variation amount is calculated as the variation amount of the PCV pressure in the specific period. In the second process, when the intake air fluctuation amount in the specific period is large, the pressure fluctuation amount is corrected to a smaller value than when the intake air fluctuation amount is small. In the third process, the presence or absence of an abnormality between the installation location of the PCV pressure sensor and the portion connected to the intake passage in the blowby passage is determined based on the corrected pressure fluctuation amount.

2. The abnormality diagnosis device for an in-vehicle internal combustion engine according to claim 1, The abnormality diagnosis device is configured as follows: The first process and the second process are repeatedly executed for a plurality of different specific periods, thereby calculating the corrected pressure variation a plurality of times. In the third process, when the cumulative value of the corrected pressure fluctuation amount calculated a plurality of times is smaller than a predetermined determination threshold value, it is determined that the abnormality exists.

3. The abnormality diagnosis device for an in-vehicle internal combustion engine according to claim 1, The vehicle-mounted internal combustion engine has an air flow meter for detecting the intake air amount. The abnormality diagnosis device is configured as follows: In the first process, a cumulative value of differences between each of the plurality of PCV pressures detected by the PCV pressure sensor from the start to the end of the specific period and the PCV pressure detected by the PCV pressure sensor at the start time of the specific period is calculated as the pressure variation. In the second process, as correction of the pressure fluctuation amount, the pressure fluctuation amount is divided by a difference between a maximum value and a minimum value of the intake air amount detected by the air flow meter within the specific period.

4. The abnormality diagnosis device for an in-vehicle internal combustion engine according to claim 1, The vehicle-mounted internal combustion engine has an air flow meter for detecting the intake air amount. The abnormality diagnosis device is configured as follows: In the first process, a cumulative value of differences between each of the plurality of PCV pressures detected by the PCV pressure sensor from the start to the end of the specific period and the PCV pressure detected by the PCV pressure sensor at the start time of the specific period is calculated as the pressure variation. In the second process, as correction of the pressure fluctuation amount, the pressure fluctuation amount is divided by a cumulative value of the intake air amount detected by the air flow meter from the start to the end of the specific period.

5. The abnormality diagnosis device for an in-vehicle internal combustion engine according to claim 1, The amount of depression of the accelerator pedal of the vehicle equipped with the vehicle-mounted internal combustion engine is defined as the accelerator operation amount. The vehicle includes an accelerator sensor for detecting the accelerator operation amount. The abnormality diagnosis device is configured as follows: In the first process, a cumulative value of differences between each of the plurality of PCV pressures detected by the PCV pressure sensor from the start to the end of the specific period and the PCV pressure detected by the PCV pressure sensor at the start time of the specific period is calculated as the pressure variation. In the second process, as correction of the pressure fluctuation amount, the pressure fluctuation amount is divided by a difference between a maximum value and a minimum value of the accelerator operation amount detected by the accelerator sensor within the specific period.

6. A method for diagnosing abnormalities of an on-vehicle internal combustion engine, The vehicle-mounted internal combustion engine comprises: a supercharger having a compressor wheel; an intake passage for introducing intake air into the vehicle-mounted internal combustion engine; a blow-by gas passage connecting a portion of the intake passage upstream of the compressor impeller to the crankcase; as well as A PCV pressure sensor is provided in the blow-by gas passage and detects the pressure in the blow-by gas passage as the PCV pressure. A period during which the intake air variation amount, which is the variation amount per unit time of the intake air amount, is equal to or greater than a predetermined value is defined as a specific period. The abnormality diagnosis method comprises: calculating a pressure variation amount as a variation amount of the PCV pressure within the specific period; When the intake air fluctuation amount within the specific period is large, the pressure fluctuation amount is corrected to a smaller value than when the intake air fluctuation amount is small; as well as Based on the corrected pressure fluctuation amount, it is determined whether there is an abnormality between a location where the PCV pressure sensor is installed and a portion connected to the intake passage in the blowby passage.

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