Internal combustion engine abnormality diagnosis device

Abstract

To detect only a situation which provides an accurate diagnostic result while minimizing reduction in a diagnostic opportunity when diagnosing abnormality in a blow-by gas passage.SOLUTION: A diagnostic device 50 is for an internal combustion engine 10 which comprises a supercharger 11, a blow-by gas passage 31 which communicates a section of the supercharger 11 on an upstream side of a compressor wheel in an intake passage 24 with an interior of a crank case 13, a PCV pressure sensor 35 which detects a pressure in the blow-by gas passage 31 as a PCV pressure and a crank shaft 14. The diagnostic device executes the processes to: identify duration when a variation of an intake air amount per unit time is equal to or larger than a predetermined value as specific duration under an execution condition that the intake air amount is equal to or larger than a determination air amount; calculate the variation of the PCV pressure in the specific duration; and determine existence of abnormality in the blow-by gas passage 31 on the basis of the variation of the PCV pressure. The diagnostic device makes the determination air amount smaller when a rotation speed of the crank shaft 14 is high than the same when the rotation speed of the crank shaft 14 is low.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an abnormality diagnosis device for an internal combustion engine. [Background technology]

[0002] Patent Document 1 discloses an internal combustion engine and an abnormality diagnosis device thereof. The internal combustion engine has a supercharger, a blow-by gas accumulation space, a blow-by gas passage, and a PCV pressure sensor. A compressor wheel of the supercharger is located in the intake passage. The accumulation space is a space partitioned by a cylinder head and a cylinder head cover. This accumulation space communicates with the inside of the crankcase. Therefore, the accumulation space can temporarily accumulate blow-by gas that leaks from the cylinder into the crankcase. The blow-by gas passage connects the accumulation space with a portion of the intake passage that is upstream of the compressor wheel (hereinafter simply referred to as the upstream portion). The PCV pressure sensor detects the pressure in the blow-by gas passage.

[0003] In the above internal combustion engine, when the intake air is pressurized by driving the turbocharger, the upstream portion of the intake passage becomes negative pressure relative to atmospheric pressure. In this case, blow-by gas flows into the upstream portion of the intake passage through the blow-by gas passage. Suppose that the amount of intake air changes under the above-mentioned situation in which blow-by gas flows into the upstream portion of the intake passage. If the pressure in the upstream portion of the intake passage changes accordingly, the amount of blow-by gas flowing into the intake passage changes and the pressure in the blow-by gas passage changes. Such a linked change between the amount of intake air and the pressure in the blow-by gas passage becomes particularly noticeable when the amount of intake air is relatively large and the negative pressure in the upstream portion becomes relatively large.

[0004] In view of this background, the abnormality diagnosis device disclosed in Patent Document 1 monitors pressure fluctuations in the blow-by gas passage as an abnormality diagnosis for the blow-by gas passage, provided that the intake air amount is equal to or greater than a predetermined judgment value. When the pressure fluctuations in the blow-by gas passage are small, the abnormality diagnosis device determines that an abnormality has occurred in the blow-by gas passage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-186702 A Summary of the Invention [Problem to be solved by the invention]

[0006] The abnormality diagnosis in Patent Document 1 is premised on a certain degree of negative pressure in the upstream portion of the intake passage. Here, the magnitude of the negative pressure generated in the upstream portion for the same intake air amount is not always uniform, but may vary depending on the operating state of the internal combustion engine. In consideration of this point, in order to always extract a situation in which the negative pressure in the upstream portion is large regardless of the operating state of the internal combustion engine as a target period for abnormality diagnosis, it is conceivable to set the judgment value of the intake air amount that specifies the execution condition of the abnormality diagnosis to a considerably large value. However, in this case, it becomes difficult to establish the execution condition of the abnormality diagnosis. On the other hand, if the judgment value of the intake air amount is set to a small value, the execution condition is established in a situation in which the intake air amount and the pressure in the blow-by gas passage do not change in conjunction with each other. Therefore, it is necessary to set a condition as the execution condition of the abnormality diagnosis that can detect the change in conjunction between the intake air amount and the pressure in the blow-by gas passage, but does not excessively reduce the opportunity to execute the abnormality diagnosis. [Means for solving the problem]

[0007] The abnormality diagnosis device for an internal combustion engine to solve the above problem targets an internal combustion engine having a turbocharger, a blow-by gas passage that communicates between the upstream portion of the intake passage relative to the compressor wheel of the turbocharger and the inside of the crankcase, a PCV pressure sensor installed in the blow-by gas passage and detecting the pressure in the blow-by gas passage as a PCV pressure, and a crankshaft, and executes a first process of specifying, with an execution condition that the intake air volume is equal to or greater than a determined air volume, a period during which the fluctuation amount per unit time of the intake air volume is equal to or greater than a prescribed value as a specific period, a second process of calculating the fluctuation amount of the PCV pressure in the specific period, and a third process of determining the presence or absence of an abnormality in the portion of the blow-by gas passage on the intake passage side with respect to the installation location of the PCV pressure sensor based on the fluctuation amount of the PCV pressure, and sets the determined air volume to a smaller value when the rotational speed of the crankshaft is high than when it is low.

[0008] Basically, under the condition that the blow-by gas passage is normal, the following can be said. That is, when the rotation speed of the crankshaft is low, the fluctuation amount of the PCV pressure in the specific period can be large only when the intake air amount is relatively large. On the other hand, when the rotation speed of the crankshaft is high, the fluctuation amount of the PCV pressure in the specific period can be large regardless of whether the intake air amount is small or large. In consideration of this point, in the above configuration, the judged air amount is made smaller when the rotation speed of the crankshaft is high than when it is low. This makes it possible to detect with high accuracy a situation in which the fluctuation amount of the PCV pressure in the specific period is large, regardless of whether the rotation speed of the crankshaft is low or high. Moreover, in the above configuration, the execution condition is established not only in a certain range of the intake air amount, but also in a wide range of the intake air amount that increases or decreases depending on the rotation speed of the crankshaft. Specifically, when the rotation speed of the crankshaft is high, the range of the intake air amount in which the third process can be executed is expanded. This makes it possible to maximize the opportunity to execute the third process. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of an internal combustion engine. [Diagram 2] FIG. 2 is a graph showing the relationship between the intake air amount and the PCV pressure for a specific range of engine rotation speeds. [Diagram 3] FIG. 3 is a diagram showing the relationship between the engine rotation speed and the determined air amount. [Figure 4] FIG. 4 is a diagram showing the relationship between the intake air amount, the specified value, and the engine rotation speed. [Diagram 5] FIG. 5 is a flowchart showing the procedure of the diagnosis process. [Figure 6] FIG. 6 is a time chart showing an example of the transition of each parameter related to the diagnosis process. [Figure 7] FIG. 7 is a diagram showing the relationship between the intake air amount and the PCV pressure in two different ranges of engine rotation speed when the blow-by gas piping is normal. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of an abnormality diagnosis device for an internal combustion engine will be described with reference to the drawings. <General configuration of internal combustion engine> As shown in Fig. 1, a vehicle 300 has an internal combustion engine 10. The internal combustion engine 10 is a drive source for the vehicle 300. In other words, the internal combustion engine 10 is an on-board internal combustion engine.

[0011] The internal combustion engine 10 has 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 has a crank chamber 17. The crank chamber 17 is a space partitioned inside 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 oil for lubrication.

[0012] The internal combustion engine 10 has a plurality of cylinders 22, a plurality of pistons 19, and a plurality of connecting rods 20. Note that FIG. 1 shows only one of the plurality of cylinders 22. The same applies to the pistons 19 and the connecting rods 20. The cylinders 22 are spaces partitioned inside the cylinder block 12. In the cylinders 22, a mixture of fuel and intake air is burned. The cylinders 22 communicate with the crank chamber 17. The pistons 19 are located in the cylinders 22. The pistons 19 reciprocate in the cylinders 22. The pistons 19 are connected to the crankshaft 14 via the connecting rods 20. The crankshaft 14 rotates in response to the movement of the pistons 19.

[0013] The internal combustion engine 10 has 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.

[0014] The internal combustion engine 10 has 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 is configured as 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 is configured as an exhaust port defined in the cylinder head 16.

[0015] The internal combustion engine 10 has 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 intake passage 24. The throttle valve 26 is capable of adjusting its opening. The amount of intake air (hereinafter, simply referred to as intake air amount) GA changes according to the opening of the throttle valve 26. The supercharger 11 has a compressor wheel 112 and a turbine wheel 111. The compressor wheel 112 is located upstream of the throttle valve 26 in the intake passage 24. The turbine wheel 111 is located in the exhaust passage 25. The bypass passage 28 is connected to the upstream side and downstream side of the turbine wheel 111 in the exhaust passage 25. The WGV 27 is located at the downstream end of the bypass passage 28. The WGV 27 is capable of adjusting its opening. The amount of exhaust gas flowing through the bypass passage 28 changes depending on the opening of the WGV 27. When the WGV 27 is opened less than fully open, the amount of exhaust gas passing through the turbine wheel 111 increases. Then, the turbine wheel 111 rotates in response to the flow of the exhaust gas. At this time, the compressor wheel 112 rotates integrally with the turbine wheel 111. The compressor wheel 112 then compresses the intake air and sends it out. That is, the intake air is supercharged.

[0016] The internal combustion engine 10 has a blow-by gas treatment mechanism 30 for returning the blow-by gas in the crank chamber 17 to the intake passage 24. The blow-by gas is a combustion gas leaking from the cylinder 22 to the crank chamber 17. The blow-by gas treatment mechanism 30 has a communication passage 21, an accumulation space 23, a joint 32, and a blow-by gas piping 33. The accumulation space 23 is a space partitioned by the cylinder head 16 and the head cover 18. The communication passage 21 penetrates the cylinder block 12 and the cylinder head 16. The communication passage 21 communicates with the crank chamber 17 and the accumulation 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 accumulation space 23 via the joint 32. The other end of the blow-by gas pipe 33 is connected to an upstream intake passage 241, which is an upstream portion of the intake passage 24 with respect to the compressor wheel 112. The communication passage 21, the accumulation space 23, the joint 32, and the blow-by gas pipe 33 constitute a blow-by gas passage 31. That is, the blow-by gas passage 31 communicates the crank chamber 17 with the upstream intake passage 241. In the blow-by gas passage 31, the blow-by gas in the crank chamber 17 reaches the accumulation space 23 through the communication passage 21. The accumulation space 23 temporarily accumulates the blow-by gas. Then, the blow-by gas in the accumulation space 23 reaches the upstream intake passage 241 through the blow-by gas pipe 33.

[0017] The internal combustion engine 10 has a PCV pressure sensor 35, a crank position sensor 70, an atmospheric pressure sensor 71, and an air flow meter 72. The PCV pressure sensor 35 is installed in the joint 32. The PCV pressure sensor 35 detects the absolute pressure in the joint 32. The pressure in the joint 32 is the same as the pressure in the blow-by gas pipe 33. That is, the PCV pressure sensor 35 detects the PCV pressure W, which is the pressure in the blow-by gas pipe 33. The crank position sensor 70 is located near the crankshaft 14. The crank 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 wheel 112 in the intake passage 24. The air flow meter 72 detects the intake air amount GA. Each of these sensors repeatedly outputs a signal corresponding to the information detected by itself to a diagnosis device 50 described later.

[0018] The vehicle 300 has a voltage sensor 73, an accelerator sensor 74, and an alert lamp 78. The voltage sensor 73 detects a battery voltage V, which is the voltage of the battery of the vehicle 300. The accelerator sensor 74 detects an accelerator operation amount ACC, which is the amount of depression of an accelerator pedal in the vehicle 300. The voltage sensor 73 and the accelerator sensor 74 repeatedly output signals according to the information detected by themselves to a diagnostic device 50, which will be described later. The alert lamp 78 is located in the passenger compartment of the vehicle 300. The alert lamp 78 is for notifying of an abnormality in the blow-by gas piping 33.

[0019] <About the abnormality diagnosis device> The vehicle 300 has an abnormality diagnosis device (hereinafter, simply referred to as a diagnosis device) 50 for the internal combustion engine 10. The diagnosis device 50 may be configured as one or more processors that execute various processes according to a computer program (software). The diagnosis device 50 may be configured as one or more dedicated hardware circuits, such as an application specific integrated circuit (ASIC), that execute at least a part of the various processes, or a circuit including a combination thereof. The processor includes a CPU 51 and a memory 53, such as a RAM and a ROM. The memory 53 stores program codes or instructions that are configured to cause the CPU 51 to execute the processes. The memory 53, i.e., a computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. The memory 53 includes an electrically rewritable non-volatile memory.

[0020] The diagnostic device 50 repeatedly receives detection signals output from the above-mentioned sensors of the vehicle 300. The diagnostic device 50 diagnoses the state of the internal combustion engine 10 as a diagnosis target based on the detection signals. In addition, the diagnostic device 50 controls various parts of the internal combustion engine 10. For example, the diagnostic device 50 calculates an engine rotation speed NE, which is the rotation speed of the crankshaft 14, based on the rotation position SC of the crankshaft 14. The diagnostic device 50 repeatedly calculates the engine rotation speed NE. The diagnostic device 50 calculates a required load factor, which is a required value of the engine load factor, based on the calculated engine rotation speed NE, the accelerator operation amount ACC, and the like. Then, the diagnostic device 50 controls the throttle valve 26 so as to obtain an intake air amount GA that achieves this required load factor. When the required load factor is relatively high, the diagnostic device 50 opens the WGV 27 to an opening smaller than full opening. Accordingly, the supercharger 11 starts supercharging. The diagnosis device 50 causes the turbocharger 11 to perform turbocharging under a condition in which the intake air amount GA is appropriately large. The engine load factor is a parameter that determines the amount of air charged into the cylinders 22, and is a value obtained by dividing the amount of air that flows into one cylinder 22 per combustion cycle by a reference air amount. The reference air amount changes depending on the engine speed NE.

[0021] <About blow-by gas piping abnormalities> The diagnostic device 50 can execute a diagnostic process to diagnose whether or not an abnormality has occurred in the blow-by gas piping 33. The abnormality to be diagnosed in this diagnostic process is an abnormality in which blow-by gas leaks from the blow-by gas piping 33 to the outside (hereinafter, referred to as a leakage abnormality). The leakage abnormality in the blow-by gas piping 33 occurs when one end of the blow-by gas piping 33 comes off from the joint 32, the other end of the blow-by gas piping 33 comes off from the upstream intake passage 241, or 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 position of the PCV pressure sensor 35. That is, in the diagnostic process, the diagnostic device 50 targets the portion of the blow-by gas passage 31 on the intake passage 24 side with respect to the installation position of the PCV pressure sensor 35 for abnormality diagnosis.

[0022] The leakage abnormality can be classified into the following two patterns from the viewpoint of the degree of leakage of the blow-by gas. One is a pattern in which the inside of the blow-by gas pipe 33 is completely connected to the atmosphere as a result of the blow-by gas pipe 33 being completely detached from the joint 32 or the upstream intake passage 241, or as a result of the occurrence of damage in the blow-by gas pipe 33 with a considerably large opening area. Hereinafter, the state in which the inside of the blow-by gas pipe 33 is completely connected to the atmosphere is referred to as a completely connected state. When a leakage abnormality of the completely connected state occurs, the amount of leakage of the blow-by gas increases. The other pattern is a pattern in which the inside of the blow-by gas pipe 33 is slightly connected to the atmosphere as a result of the occurrence of damage in the blow-by gas pipe 33 with a small opening area. Hereinafter, the state in which the inside of the blow-by gas pipe 33 is slightly connected to the atmosphere is referred to as a partially connected state. This type of leakage abnormality pattern can also occur when 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. When a leakage abnormality in the partial communication state pattern occurs, the amount of leakage of blow-by gas is not very large.

[0023] In the diagnostic process, the diagnostic device 50 uses the PCV pressure W when diagnosing the presence or absence of the leakage abnormality. The relationship between the intake air amount GA and the PCV pressure W, which is a prerequisite for the diagnostic device 50 to use the PCV pressure W in the diagnostic process, will be described. As will be described later, the relationship between the intake air amount GA and the PCV pressure W can change depending on the engine speed NE. Here, the relationship between the intake air amount GA and the PCV pressure W will be described for the case where the engine speed NE is within a certain range of values.

[0024] First, the relationship between the intake air amount GA and the PCV pressure W when the blow-by gas piping 33 is normal will be described. Here, when supercharging is performed by the turbocharger 11, that is, when the intake air amount GA is relatively large, the internal pressure of the upstream intake passage 241 (hereinafter, the description of the internal pressure will be omitted) 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 flowing into the upstream intake passage 241 increases as the intake air amount GA increases because the negative pressure of the upstream intake passage 241 increases. That is, as shown by the solid line in FIG. 2, the PCV pressure W decreases as the intake air amount GA increases. In other words, when the blow-by gas piping 33 is normal, under a situation in which the upstream intake passage 241 is in a negative pressure due to the drive of the turbocharger 11, the PCV pressure W changes in conjunction with the change in the intake air amount GA.

[0025] In contrast, the relationship between the intake air amount GA and the PCV pressure W when a leakage abnormality occurs in the blow-by gas piping 33 is as follows. First, the case of the above-mentioned complete communication state will be 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, as shown by the dashed dotted line in Figure 2, regardless of the amount of intake air GA, the PCV pressure W becomes a value close to the atmospheric pressure M. And even if the amount of intake air GA changes, there is almost no corresponding change in the PCV pressure W.

[0026] Next, the case of the above-mentioned partial communication state will be described. As described above, when the blow-by gas pipe 33 is in the partial communication state, the main cause is often damage to the blow-by gas pipe 33. Although it depends on the opening area of ​​the damage, in the case of the partial communication state, the following occurs, unlike the case of the complete communication state. That is, when negative pressure is generated in the upstream intake passage 241 due to supercharging 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 flowing into the upstream intake passage 241 increases as the intake air amount GA increases because the negative pressure in the upstream intake passage 241 increases. Therefore, as shown by the dashed line in FIG. 2, the PCV pressure W decreases as the intake air amount GA increases. However, since the inside of the blow-by gas pipe 33 is in communication with the atmosphere through the damaged portion, the PCV pressure W becomes closer to the atmospheric pressure M than when the blow-by gas pipe 33 is normal. In addition, under the condition that negative pressure is generated in the upstream intake passage 241, the degree of change in the PCV pressure W relative to the change in the intake air amount GA is smaller than when the blow-by gas piping 33 is normal.

[0027] In addition to the leakage abnormality described above, a clogging abnormality may occur in the blow-by gas pipe 33. A clogging abnormality is when a clogging occurs in the blow-by gas pipe 33. When a clogging abnormality occurs, the blow-by gas accumulated in the accumulation space 23 cannot be caused to flow into the upstream intake passage 241 via the blow-by gas passage 31. On the other hand, when the internal combustion engine 10 is operating, the blow-by gas continues to be generated. The amount of blow-by gas generated tends to increase as the intake air amount GA increases. Therefore, as shown by the two-dot chain line in FIG. 2, when the intake air amount GA is relatively large, the PCV pressure W becomes higher than the atmospheric pressure M.

[0028] <Diagnosis process overview> The diagnostic device 50 can execute a first process as part of the diagnostic process. In the first process, the diagnostic device 50 specifies a specific period H during which the intake air fluctuation amount ΔGA, which is the amount of fluctuation per unit time of the intake air amount GA, is equal to or greater than a specified value K. The specified value K will be described later. In this embodiment, the diagnostic device 50 performs the first process while the intake air amount GA is increasing. That is, the amount of fluctuation per unit time of the intake air amount GA is the amount of increase per unit time of the intake air amount GA. The diagnostic device 50 stores the above unit time in advance. The unit time is a length that is considerably short, such as 0.1 seconds, less than 1 second. The unit time is determined based on experiments or simulations as a length of time that can extract the rising process of the intake air amount GA associated with, for example, acceleration of the vehicle 300. The unit time is sufficiently longer than the data sampling interval of the sensor used in the diagnostic process. Therefore, the sensor outputs multiple detection signals to the diagnostic device 50 within the unit time.

[0029] The diagnostic device 50 can execute a second process as part of the diagnostic process. In the second process, the diagnostic device 50 calculates a pressure fluctuation amount WA, which is a fluctuation amount of the PCV pressure W during the specific period H specified in the first process. A specific definition of the pressure fluctuation amount WA will be described later.

[0030] The diagnostic device 50 repeats the above-mentioned first process and second process for a number of determination times NTh for a plurality of specific periods H. In this way, the diagnostic device 50 calculates the pressure fluctuation amount WA for the number of determination times NTh. The diagnostic device 50 stores this number of determination times NTh in advance. The number of determination times NTh is determined based on, for example, an experiment or a simulation as the minimum number of pressure fluctuation amounts WA required to obtain an accurate diagnosis result.

[0031] The diagnostic device 50 can execute a third process as part of the diagnostic process. In the third process, the diagnostic device 50 judges the presence or absence of a leakage abnormality in the blow-by gas piping 33 based on a judgment parameter Y obtained by correcting the pressure fluctuation amount WA. Here, the pressure fluctuation amount WA can be large or small depending on the magnitude of the intake fluctuation amount ΔGA in the specific period H. The above judgment parameter Y is a value obtained by correcting the pressure fluctuation amount WA to a value that is less affected by the intake fluctuation amount ΔGA. In the third process, the diagnostic device 50 calculates an integrated parameter Z as an integrated value of a plurality of judgment parameters Y obtained by repeating the first process and the second process. Then, the diagnostic device 50 judges that a leakage abnormality has occurred when the integrated parameter Z is less than a judgment threshold value ZTh. The diagnostic device 50 stores the judgment threshold value ZTh in advance. The judgment threshold value ZTh is determined based on, for example, an experiment or a simulation as the minimum value of the integrated parameter Z that can be taken when the blow-by gas piping 33 is normal. Note that the judgment threshold value ZTh is a value based on the number of judgments NTh.

[0032] <About the judged air volume> The diagnostic device 50 performs the first process and the second process only when a specific execution condition is satisfied. Here, when the blow-by gas piping 33 is normal, the intake air amount GA and the PCV pressure W change in conjunction with each other only when the intake air amount GA is sufficiently large and the upstream intake passage 241 is under negative pressure. When the upstream intake passage 241 is not under negative pressure, the above-mentioned linked change does not occur even if the blow-by gas piping 33 is normal, so that the pressure fluctuation amount WA is unlikely to differ between when a leakage abnormality occurs in the blow-by gas piping 33 and when the pressure fluctuation amount WA is normal. In consideration of this point, the diagnostic device 50 performs the first process with the execution condition that the intake air amount GA is equal to or greater than the judged air amount GATh that can guarantee the generation of negative pressure in the upstream intake passage 241. That is, in this embodiment, the diagnostic device 50 performs the first process when the intake air amount GA is equal to or greater than the judged air amount GATh, targeting the increase process of the intake air amount GA. In this way, the diagnosis device 50 identifies the specific period H as a period during which the intake air amount GA continues to be equal to or greater than the reference air amount GA. Note that, on the above-mentioned scale of unit time, the reference air amount GATh defined in the first map described later is substantially the same.

[0033] The diagnosis device 50 variably sets the above-mentioned judged air amount GATh depending on the engine rotation speed NE. As information required for this purpose, the diagnosis device 50 stores a first map in advance. As shown in Fig. 3, the first map shows the correspondence relationship between the engine rotation speed NE and the judged air amount GATh. The first map is created based on, for example, an experiment or a simulation. The reason for variably setting the judged air amount GATh depending on the engine rotation speed NE will be explained in the section on operation below.

[0034] As shown in FIG. 3, in the first map, the judged air amount GATh is smaller when the engine speed NE is high than when it is low. In detail, in the first map, the higher the engine speed NE, the smaller the judged air amount GATh is. The judged air amount GATh at each engine speed NE is equal to or greater than the minimum value of the intake air amount GA under the condition that the upstream intake passage 241 becomes negative pressure at each engine speed NE. Furthermore, the judged air amount GATh at each engine speed NE is set as a value at which the PCV pressure W changes considerably greatly in conjunction with the intake air amount GA at each engine speed NE. In relation to the upstream intake passage 241 becoming negative pressure, the intake air amount GA basically exceeds the judged air amount GATh when the turbocharger 11 is performing supercharging. However, depending on the operating state of the internal combustion engine 10, the intake air amount GA may exceed the judged air amount GATh under the condition that the supercharger 11 is not performing supercharging.

[0035] <Regarding the specified values> The above-mentioned judged air amount GATh can be said to be an index for grasping the situation in which the upstream intake passage 241 is under negative pressure as an average environmental field in the specific period H. By using this judged air amount GATh as a threshold value for whether or not to execute the first process, the situation in which the upstream intake passage 241 is under negative pressure can be roughly grasped. However, even in the same category that the upstream intake passage 241 is under negative pressure, the degree of change in the PCV pressure W relative to the instantaneous change in the intake air amount GA may differ depending on the magnitude of the negative pressure. For example, when the negative pressure as the average value in the specific period H is relatively small, the degree of change in the PCV pressure W relative to the change in the intake air amount GA in the specific period H may be small. Under such circumstances, even if the blow-by gas piping 33 is normal, the fluctuation of the PCV pressure W will not be large unless the intake fluctuation amount ΔGA in the specific period H becomes large. In other words, unless the intake fluctuation amount ΔGA in the specific period H becomes large, a difference in the pressure fluctuation amount WA is unlikely to occur between when the leakage abnormality occurs and when normal. In consideration of this, the diagnostic device 50 variably sets the specified value K for identifying the specific period H in the first process according to the intake air amount GA when the first process is executed. As information for this purpose, the diagnostic device 50 stores a second map in advance. As shown in FIG. 4, the second map shows the correspondence relationship between the intake air amount GA and the specified value K. In detail, the second map shows the correspondence relationship between the intake air amount GA and the specified value K for a plurality of different engine speeds NE. The plurality of engine speeds NE include various values ​​from the minimum value to the maximum value of the engine speed NE that the internal combustion engine 10 can take in an operating state. When using the second map, the value between adjacent engine speeds NE may be, for example, interpolated. Note that, for convenience, in the example of FIG. 4, the correspondence relationship between the intake air amount GA and the specified value K is shown for only two engine speeds NE, that is, when the engine speed NE is a first value NE1 and when the engine speed NE is a second value NE2. The second value NE2 is higher than the first value NE1. The reason why the specified value K is set to a different value for each engine speed NE will be explained in the section on operation below. The second map is created based on, for example, an experiment or a simulation.

[0036] As shown in FIG. 4, the second map basically has the following characteristics. When the intake air amount GA is small, the specified value K is larger than when the intake air amount GA is large at a certain engine speed NE. More specifically, at a certain engine speed NE, the smaller the intake air amount GA, the larger the specified value K. This characteristic is because, as described above, when the intake air amount GA is small and the negative pressure is small, the difference in the pressure fluctuation amount WA between when a leakage abnormality occurs and when normal is difficult to become clear unless the intake fluctuation amount ΔGA is large. Also, in the second map, when the intake air amount GA is small, the specified value K is larger than when the engine speed NE is high. More specifically, at a certain intake air amount GA, the specified value K is larger than when the engine speed NE is low. The reason for providing this characteristic will be explained in the section on operation described later. In the second map, the specified value K is set as a value at which a clear difference in the pressure fluctuation amount WA occurs between when a leakage abnormality occurs and when normal is possible at each engine speed NE.

[0037] <Specific steps of diagnostic processing> The diagnostic device 50 repeatedly executes diagnostic processing while the internal combustion engine 10 is operating. When the diagnostic device 50 executes diagnostic processing for the first time after the internal combustion engine 10 is started, the diagnostic device 50 executes a reset process that is the same as step S32 described below prior to the start of the diagnostic processing. The diagnostic device 50 then starts the diagnostic processing. Therefore, at the start of the first diagnostic processing after the internal combustion engine 10 is started, the integration parameter Z and the integration count N are "0".

[0038] As shown in FIG. 5, when the diagnostic device 50 starts the diagnostic process, it first executes the process of step S20. In step S20, the diagnostic device 50 judges whether or not the preconditions are satisfied. The preconditions are, for example, that both of the following two items are satisfied. The first item is that in the history of the PCV pressure W from a certain period before received from the PCV pressure sensor 35, the PCV pressure W does not continue to be higher than the atmospheric pressure M. The second item is that the latest battery voltage V received from the voltage sensor 73 is equal to or higher than the determination voltage VTh. Regarding the first item, if the PCV pressure W continues to be higher than the atmospheric pressure M, there is a possibility that a clogging abnormality has occurred. The first item is for eliminating such a situation. The above-mentioned certain period is determined in advance, for example, by an experiment or a simulation, as the length of time during which a clogging abnormality can be considered to have occurred. Regarding the second item, when the battery voltage V is lower than the determination voltage VTh, there is a possibility that a necessary voltage cannot be applied to the sensor used for diagnosis. The diagnostic device 50 determines whether the precondition is met by referring to the history of the 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 met (step S20: NO), the diagnostic device 50 advances the process to step S50.

[0039] In step S50, the diagnostic device 50 erases the analysis data. If the determination in step S20 above is NO and the process proceeds to step S50, the diagnostic device 50 has not stored any analysis data since the start of the diagnostic process. Therefore, in this case, the diagnostic device 50 does nothing substantially. This is also the case when the determination in step S22 described below is NO and the process proceeds to step S50. After executing the process of step S50, the diagnostic device 50 temporarily ends the series of steps in the diagnostic process. After this, the diagnostic device 50 executes the process of step S20 again.

[0040] On the other hand, in step S20, if the precondition is met (step S20: YES), diagnostic device 50 advances the process to step S21. In step S21, the diagnostic device 50 calculates a judged air amount GATh to be used in step S22 described later. Specifically, the diagnostic device 50 refers to a first map and the latest engine speed NE. Then, the diagnostic device 50 calculates a judged air amount GATh corresponding to the latest engine speed NE based on the first map. After that, the diagnostic device 50 advances the process to step S22.

[0041] In step S22, the diagnostic device 50 judges whether the intake air amount GA is equal to or greater than the judged air amount GATh. Specifically, the diagnostic device 50 refers to the latest intake air amount GA received from the air flow meter 72 and the judged air amount GATh calculated in step S21. If the latest intake air amount GA is less than the judged air amount GATh (step S22: NO), the diagnostic device 50 advances the process to the above-mentioned step S50. On the other hand, if the latest intake air amount GA is equal to or greater than the judged air amount GATh (step S22: YES), the diagnostic device 50 advances the process to step S23. An example of a situation in which the process advances to step S23 is a situation in which the intake air amount GA increases from less than the judged air amount GATh to equal to or greater than the judged air amount GATh while the intake air amount GA is increasing. In other words, the process of the increase in the intake air amount GA is captured.

[0042] In step S23, the diagnostic device 50 stores the analysis data over the unit time. Specifically, the diagnostic device 50 stores a plurality of intake air amounts GA received from the air flow meter 72 in a time series until the unit time has elapsed since the process proceeded to step S23. The diagnostic device 50 handles this time series as first analysis data D1. The diagnostic device 50 also stores a plurality of PCV pressures W received from the PCV pressure sensor 35 in a time series until the unit time has elapsed since the process proceeded to step S23. The diagnostic device 50 handles this time series as second analysis data D2. The diagnostic device 50 may measure the unit time by, for example, counting up a counter for measuring time. When the unit time has elapsed since the process proceeded to step S23, the diagnostic device 50 advances the process to step S24.

[0043] In step S24, the diagnostic device 50 calculates the intake fluctuation amount ΔGA. Specifically, the diagnostic device 50 refers to the first analysis data D1 stored in step S23. Then, the diagnostic device 50 specifies the first intake air amount GA in the time series of the first analysis data D1 as the starting air amount. The diagnostic device 50 also specifies 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 a value obtained by subtracting the starting air amount from the ending air amount as the intake fluctuation amount ΔGA. After this, the diagnostic device 50 advances the process to step S25.

[0044] In step S25, the diagnostic device 50 calculates a specified value K to be used in step S26 described later. Specifically, the diagnostic device 50 refers to the second map, the starting air amount identified in step S24, and the engine speed NE at the timing when the starting air amount is received. Then, the diagnostic device 50 calculates the specified value K corresponding to the starting air amount and the engine speed NE based on the second map. After that, the diagnostic device 50 advances the process to step S26.

[0045] In step S26, the diagnostic device 50 determines whether or not a specific condition is met. The specific condition is that both of the following items (A) and (B) are met. (A) The intake fluctuation amount ΔGA calculated in step S24 is equal to or greater than the specified value K calculated in step S25. (B) The starting air volume identified in step S24 is the minimum value in the time series of the first analysis data D1, and the ending air volume identified in step S24 is the maximum value in the time series of the first analysis data D1.

[0046] The diagnostic device 50 judges whether the item (A) is satisfied by comparing the intake fluctuation amount ΔGA calculated in step S24 with the specified value K calculated in step S25. The diagnostic device 50 judges whether the item (B) is satisfied by comparing each intake air amount GA in the time series of the first analysis data D1 with the start air amount and the end air amount. If the specific condition is not satisfied (step S26: NO), the diagnostic device 50 proceeds to step S50. On the other hand, if the specific condition is satisfied (step S26: YES), the diagnostic device 50 specifies the series of periods in which the analysis data is stored in step S23 as a specific period H. After this, the diagnostic device 50 proceeds to step S27. As described above, the diagnostic device 50 specifies the specific period H through the processes of steps S24, S25, and S26. The processes in steps S24, S25, and S26 are the first process.

[0047] Here, the determination in step S26 being YES 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, in a situation where the intake air amount GA is equal to or greater than the judgment air amount GATh (step S22: YES), the PCV pressure W decreases as the intake air amount GA increases. Due to this relationship between the intake air amount GA and the PCV pressure W, if the intake air amount GA continues to increase in the time series of the first analysis data D1, then in the time series of the second analysis data D2, the PCV pressure W continues to decrease over time.

[0048] In step S27, the diagnostic device 50 calculates the pressure fluctuation amount WA. Specifically, the diagnostic device 50 refers to the above-mentioned second analysis data D2, which is a time series of the PCV pressure W. Then, the diagnostic device 50 specifies 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 data elements) constituting the time series of the second analysis data D2 and the reference pressure. That is, the diagnostic 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 diagnostic device 50 calculates a value obtained by accumulating all the pressure difference values ​​ΔW as the pressure fluctuation amount WA. As described above, in a situation in which the process proceeds to step S27, the PCV pressure W continues to decrease in the time series of the second analysis data D2. Therefore, the value of each data element is basically smaller than the value of the reference pressure. However, due to noise or the like, the value of the data element may be greater 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 fluctuation amount WA, the diagnostic device 50 advances the process to step S28. The process of step S27 is the second process.

[0049] In step S28, the diagnostic device 50 updates the integrated parameter Z. Specifically, the diagnostic device 50 first divides the pressure fluctuation amount WA calculated in step S27 by the intake fluctuation amount ΔGA calculated in step S24. Then, the diagnostic device 50 sets the obtained value as the judgment parameter Y. Next, the diagnostic device 50 adds this judgment parameter Y to the currently stored integrated parameter Z. Then, the diagnostic device 50 stores the obtained value as the latest integrated parameter Z. At this time, the diagnostic device 50 overwrites the integrated parameter Z stored up to that point with the latest integrated parameter Z. After this, the diagnostic device 50 advances the process to step S29.

[0050] In step S29, the diagnostic device 50 updates the accumulated number N. That is, the diagnostic device 50 adds "1" to the accumulated number N currently stored. Then, the diagnostic device 50 stores the obtained value as the latest accumulated number N. At this time, the diagnostic device 50 overwrites the accumulated number N stored up to that point with the latest accumulated number N. After this, the diagnostic device 50 advances the process to step S30.

[0051] In step S30, the diagnostic device 50 determines whether the cumulative number N updated in step S30 is equal to or greater than the determination number NTh. If the cumulative number N updated in step S29 is less than the determination number NTh (step S30: NO), the diagnostic device 50 advances the process to step S50.

[0052] On the other hand, in step S30, if the integrated number N is equal to or greater than the determination number NTh (step S30: YES), diagnostic device 50 advances the process to step S31. In step S31, the diagnostic device 50 judges whether or not there is a leakage abnormality in the blow-by gas piping 33 based on the latest integrated parameter Z currently stored. When the integrated parameter Z is equal to or greater than the judgment threshold ZTh, the diagnostic device 50 judges that the blow-by gas piping 33 is normal. In this case, the diagnostic device 50, for example, turns off a leakage flag indicating the occurrence of a leakage abnormality. On the other hand, when the integrated parameter Z is less than the judgment threshold ZTh, the diagnostic device 50 judges that a leakage abnormality has occurred in the blow-by gas piping 33. In this case, the diagnostic device 50, for example, turns on the leakage flag and turns on the notification lamp 78. After this, the diagnostic device 50 proceeds to the process of step S32. As described above, the diagnostic device 50 obtains a diagnosis result of whether or not there is an abnormality in the blow-by gas passage 31 through the processes of steps S28, S29, S30, and S31. The processes of steps S28, S29, S30, and S31 are the third process. The diagnostic device 50 utilizes the information on whether the leakage flag is on or off as one piece of information for controlling the internal combustion engine 10, for example.

[0053] In step S32, the diagnostic device 50 performs a reset process. That is, the diagnostic device 50 resets the number of integration times N and the integration parameter Z to "0". The diagnostic device 50 also erases the analysis data. After this, the diagnostic device 50 temporarily ends a series of diagnostic processes. After this, the diagnostic device 50 executes the process of step S20 again. Note that, when the diagnostic device 50 turns on the notification lamp 78 in step S31, the diagnostic device 50 continues to turn on the notification lamp 78 until it receives a command to turn off the notification lamp 78 in response to, for example, an operation by the occupant.

[0054] <Operation of the embodiment> (A) Overall flow of diagnostic processing The overall flow of the diagnosis process will be described by taking the case where the blow-by gas piping 33 is normal as an example. Now, it is assumed that the internal combustion engine 10 is being supercharged. Also, it is assumed that the intake air amount GA is increasing. As shown in FIG. 6(a), it is assumed that the intake air amount GA becomes the judged air amount GATh at time t1 with the increase in the intake air amount GA (step S22: YES). Then, the diagnosis device 50 stores the analysis data over the unit time (step S23). If the intake fluctuation amount ΔGA in this unit time is equal to or greater than the specified value K (step S26: YES), the diagnosis device 50 specifies the period corresponding to the above unit time as a specific period (hereinafter referred to as a first specific period) H1. As described above, when the supercharger 11 is performing supercharging and the upstream intake passage 241 is under negative pressure, the change in the intake air amount GA and the change in the PCV pressure W are linked to each other. Therefore, as shown in (a) of FIG. 6, 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 by the solid line in (b) of FIG. 6, the PCV pressure W decreases from the first pressure W1 to the second pressure W2 during the first specific period H1. As an index showing the degree of change in the PCV pressure W, the diagnostic device 50 calculates a pressure fluctuation amount WA corresponding to the hatched area in (b) of FIG. 6 (step S27). The diagnostic device 50 updates the integrated parameter Z by the judgment parameter Y according to the pressure fluctuation amount WA (step S28). That is, as shown by the solid line in (c) of FIG. 6, the integrated parameter Z increases by one step at the end time t2 of the first specific period H1.

[0055] As shown in (a) of FIG. 6, it is assumed that the intake air amount GA continues to increase even after the end of the first specific period H1. In this case, the diagnostic device 50 specifies the unit time after the first specific period H1 as the second specific period H2. Then, the diagnostic device 50 updates the integrated parameter Z with the judgment parameter Y according to the pressure fluctuation amount WA in the same manner as described above. Then, as shown by the solid line in (c) of FIG. 6, the integrated parameter Z increases by one step at the end time t3 of the second specific period H2. In this manner, the integrated parameter Z increases sequentially.

[0056] Now, when a leakage abnormality occurs in the blow-by gas pipe 33, the inside of the blow-by gas pipe 33 is in communication with the atmosphere. Therefore, the change in the PCV pressure W according to the change in the intake air amount GA becomes small. Here, it is assumed that the first specific period H1 is reached when the blow-by gas pipe 33 is in a partially communicated state. And, 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 shown by the two-dot chain line in FIG. 6(b), the PCV pressure W only decreases from the first pressure W1 to the third pressure W3 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 blow-by gas pipe 33 is normal. In this case, as shown by the two-dot chain line in FIG. 6(c), the integrated parameter ZA at the end time t2 of the first specific period H1 is smaller than the integrated parameter Z1 when the blow-by gas pipe 33 is normal. In this way, when a leakage abnormality occurs in the blow-by gas piping 33, the pressure fluctuation amount WA and therefore the integrated parameter Z become small. By utilizing this point, the diagnostic device 50 determines that a leakage abnormality occurs in the blow-by gas piping 33 if the integrated parameter Z is small when the update count of the integrated parameter Z reaches the determination count NTh (step S31).

[0057] (B) Relationship between the determined air volume and engine speed In relation to the contents of the first map, the diagnosis device 50 sets the judged air amount GATh to a smaller value as the engine rotation speed NE increases. The reason why the judged air amount GATh is set to be variable depending on the engine rotation speed NE in this manner will be explained.

[0058] As shown in Fig. 7, the relationship between the intake air amount GA and the PCV pressure W when the blow-by gas piping 33 is normal is compared between the case where the engine speed NE is in the first range R1 and the case where the engine speed NE is in the second range R2. The upper limit value of the first range R1 is smaller than the lower limit value of the second range R2. Note that Fig. 7 shows the relationship between the intake air amount GA and the PCV pressure W in an easy-to-understand schematic manner, and the relationship between the intake air amount GA and the PCV pressure W may, strictly speaking, include small fluctuations as shown in Fig. 2. Also, Fig. 7 exaggerates the difference between the case where the engine speed NE is in the first range R1 and the case where the engine speed NE is in the second range R2 in order to make the difference between these two cases easier to understand.

[0059] Here, the amount of decrease in the PCV pressure W when the intake air amount GA increases by a certain value is referred to as the PCV change amount. That is, the PCV change amount is an index showing the degree of change in the PCV pressure W relative to the change in the intake air amount GA. As shown by the solid line in FIG. 7, when the engine speed NE is in the first range R1, the PCV change amount becomes large only under a situation where the intake air amount GA is considerably large, for example, when the intake air amount GA is equal to or larger than the predetermined air amount L. When the PCV change amount becomes large, the amount of decrease in the PCV pressure W relative to the atmospheric pressure M also becomes large to some extent. An example of a situation where the intake air amount GA becomes large when the engine speed NE is relatively low is when the vehicle is traveling on an uphill road. Unlike the case where the engine speed NE is in the first range R1, as shown by the two-dot chain line in FIG. 7, when the engine speed NE is in the second range R2, the PCV change amount is large even if the intake air amount GA is equal to or smaller than the predetermined air amount L. For example, during constant speed traveling on a highway, the engine speed NE may be relatively high and the intake air amount GA may be small. Reflecting the existence of such a situation, as shown by the two-dot chain line in Figure 7, when the engine speed NE is in the second range R2, the amount of change in PCV is large whether the intake air amount GA is small or large. Thus, the range of the intake air amount GA where the amount of change in PCV is large varies depending on the engine speed NE. In other words, the range of the intake air amount GA where the upstream intake passage 241 is under negative pressure and the PCV pressure W varies in conjunction with the intake air amount GA varies depending on the engine speed NE.

[0060] Therefore, in the above configuration, the judged air amount GATh is set to be variable according to the engine speed NE. This makes it possible to detect with high accuracy only the situation in which the PCV pressure W changes in conjunction with the intake air amount GA, whether the engine speed NE is low or high. In other words, it becomes possible to detect with high accuracy a diagnosis favorable situation in which the pressure fluctuation amount WA is likely to differ between when a leakage abnormality occurs and when normal, whether the engine speed NE is low or high. In addition, when the judged air amount GATh is set to be variable according to the engine speed NE in detecting such a diagnosis favorable situation, it is possible to target not only a specific range of the intake air amount GA, but also a wide range of the intake air amount GA that increases or decreases according to the engine speed NE. Specifically, the higher the engine speed NE, the wider the range of the intake air amount GA in which the diagnosis favorable situation is detected. Therefore, it is possible to detect many diagnosis favorable situations.

[0061] (C) Relationship between the specified value and engine speed In relation to the contents of the second map, under the condition that the intake air amount GA is the same, the diagnostic device 50 sets the specified value K to a larger value as the engine rotation speed NE decreases. The reason why the specified value K is set to be variable depending on the engine rotation speed NE in this manner will be explained.

[0062] For example, in Fig. 7, the PCV change amount is compared between when the intake air amount GA is equal to or greater than the predetermined air amount L and when the engine speed NE is in the first range R1 and the second range R2. In this case, the PCV change amount tends to be smaller in the former case than in the latter case. Although the above-mentioned diagnosis favorable situation can be detected as a candidate for the specific period H by using the judged air amount GATh, if the PCV change amount is small when the blow-by gas piping 33 is normal, the difference in the pressure fluctuation amount WA between when a leakage abnormality occurs and when normal is unlikely to become large.

[0063] Therefore, in this embodiment, when the engine rotation speed NE is low, the specified value K is set to a larger value than when the engine rotation speed NE is high. In this case, when the engine rotation speed NE is low, only the case when the intake fluctuation amount ΔGA is large can be extracted as the specific period H, which is the target period for abnormality diagnosis. When the intake fluctuation amount ΔGA is large, if the blow-by gas piping 33 is normal, the pressure fluctuation amount WA will be large. If the case when the pressure fluctuation amount WA is large is set as the target period for abnormality diagnosis, the difference in the pressure fluctuation amount WA between when a leakage abnormality occurs and when normal becomes clear. As a result, it becomes easier to distinguish whether or not there is a leakage abnormality.

[0064] <Effects of the embodiment> (1) In this embodiment, the higher the engine speed NE, the smaller the judged air amount GATh is set to. As a result, as described in (B) of the operation of the embodiment, the pressure fluctuation amount WA can be calculated for a situation in which the pressure fluctuation amount WA is likely to differ between when a leakage abnormality occurs and when the engine speed NE is normal, regardless of whether the engine speed NE is low or high. By judging 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, an accurate judgment result can be obtained. Furthermore, as described in (B) of the operation of the embodiment, by being able to detect many situations in which the pressure fluctuation amount WA is likely to differ between when a leakage abnormality occurs and when the engine speed NE is normal, it is possible to maximize the opportunities to update the integrated parameter Z, and thus the opportunities to judge the presence or absence of a leakage abnormality.

[0065] (2) In this embodiment, the judged air amount GATh is set to be variable depending on the engine speed NE, and further, the lower the engine speed NE, the larger the specified value K is set to. This makes it possible to reliably prevent erroneous judgment as to whether or not there is a leakage abnormality in the blow-by gas piping 33, as described in (C) of the operation of the embodiment.

[0066] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modified examples can be combined with each other to the extent that no technical contradiction occurs.

[0067] The specific condition for identifying the specific period H is not limited to the above embodiment. The specific period H may be a period that captures the process of the intake air amount GA changing, such as the intake air amount GA increasing. The specific period H may be a period that satisfies the condition that the intake air fluctuation amount ΔGA is equal to or greater than the specified value K during the change process of the intake air amount GA. The specific condition may be a condition that can identify the specific period H. As an example of changing the specific condition, item (B) may be changed. From the viewpoint of capturing the change process of the intake air amount GA, item (B) may be a condition that can determine that the intake air amount GA is increasing as a trend of the entire time series of the first analysis data D1. In determining such a condition, the following requirement may be adopted as item (B). That is, the requirement is that the slope of the regression line of the time series of the intake air amount GA is positive in an orthogonal coordinate system with the horizontal axis being time and the vertical axis being the intake air amount GA.

[0068] Item (B) may be omitted under specific conditions. If the intake air fluctuation amount ΔGA is equal to or greater than the specified value K on the scale of unit time in the above embodiment, in most cases, it is highly likely that the intake air amount GA is increasing in the time series of the first analysis data D1. In other words, even if item (B) is omitted, the process in which the intake air amount GA is changing can be captured as the specific period H.

[0069] The method for setting the unit time is not limited to the example in the above embodiment. The unit time may be one second or more. If the air flow meter 72 can detect the intake air amount GA at least twice within the unit time, the intake fluctuation amount ΔGA can be calculated. Also, if the PCV pressure sensor 35 can detect the PCV pressure W at least twice within the unit time, the pressure fluctuation amount WA can be calculated. The specific condition may be set to an appropriate content according to the unit time.

[0070] The pressure fluctuation amount WA is not limited to the sum of 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 defined as the pressure fluctuation amount WA. The pressure fluctuation amount WA may be any value that reflects the magnitude of the degree of fluctuation of the PCV pressure W during the specific period H.

[0071] The specific period H may be specified for the period during which the intake air amount GA is decreasing after the intake air amount GA has changed from an increase to a decrease. Then, the pressure fluctuation amount WA may be calculated during the period during which the intake air amount GA is decreasing. As described above, when negative pressure is generated in the upstream intake passage 241, the change in the intake air amount GA and the change in the PCV pressure W are linked. Therefore, when negative pressure is generated in the upstream intake passage 241, the PCV pressure W changes with the change in the intake air amount GA even during the period during which the intake air amount GA is decreasing. Specifically, the PCV pressure W increases with the decrease in the intake air amount GA. The pressure fluctuation amount WA during such an increase in the PCV pressure W may be calculated. When the pressure fluctuation amount WA is calculated for the period during which the intake air amount GA is decreasing as the specific period H, various contents of the diagnosis process, such as the method of calculating the intake fluctuation amount ΔGA, the method of determining the specific condition, and the method of calculating the pressure fluctuation amount WA, may be changed appropriately. For example, in regard to the intake fluctuation amount ΔGA, the absolute value of the difference between the start air amount and the end air amount in the first analysis data D1 may be defined as the intake fluctuation amount ΔGA.

[0072] Now, even when the specific period H is specified for the period during which the intake air amount GA is decreasing, the specific period H may be specified for the period during which the intake air amount GA is equal to or greater than the judged air amount GA. Here, it is assumed that the condition that the intake air amount GA is equal to or greater than the judged air amount GATh is satisfied at a certain timing. In this case, if the scale of unit time in the above embodiment is used, it is expected that the state in which the intake air amount GATh is equal to or greater than the judged air amount GATh will continue during that period. Therefore, even when the specific period H is specified for the period during which the intake air amount GA is decreasing, the specific period H may be specified when the intake air amount GA is equal to or greater than the judged 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 greater than the judged air amount GATh, as in the above embodiment. However, during the decrease in the intake air amount GA, the intake air amount GA may become less than the judged air amount GATh during the passage of the above unit time. In consideration of this point, when the specific period H is specified for the period during which the intake air amount GA is decreasing, the specific condition may include the following content. That is, the content that the final air amount in the first analysis data D1 is equal to or greater than the judged air amount GATh may be included. The judged air amount GATh here may be the judged air amount GATh used to judge whether the above-mentioned execution condition is satisfied or may be a value calculated separately based on the engine speed NE at the timing corresponding to the final air amount.

[0073] In calculating the specified value K, it is not essential to use the intake air amount GA and the engine speed NE at the start of the specific period H as in the above embodiment. For example, the average value of the intake air amount GA during the specific period H and the average value of the engine speed NE during the specific period H may be used to calculate the corresponding specified value K. The specified value K may be calculated using the intake air amount GA and the engine speed NE that represent the specific period H.

[0074] The method of determining the intake fluctuation amount ΔGA is not limited to the example of the above embodiment. The intake fluctuation amount ΔGA may represent the degree of change in the intake air amount GA per unit time. A method other than using the first analysis data D1 may be adopted to calculate the intake fluctuation amount ΔGA. For example, the diagnosis device 50 may calculate the absolute value of the difference between the intake air amount GA received from the air flow meter 72 at two consecutive timings as the intake fluctuation amount ΔGA. In this case, the reception interval of the detection signal from the air flow meter 72 may be treated as the unit time. Then, if the intake fluctuation amount ΔGA is equal to or greater than the specified value K, the period from when one of the two intake air amounts GA is received to when the other is received may be specified as the specific period H. The specified value K at this time may be calculated, for example, based on the intake air amount GA received first and the engine speed NE at the timing of receiving it. In addition, when calculating the intake fluctuation amount ΔGA in the aspect of this modified example, the specific period H may be specified, for example, as follows. That is, the intake fluctuation amount ΔGA may be repeatedly calculated, and a series of periods during which the repeatedly calculated intake fluctuation amount ΔGA is equal to or greater than the specified value K may be specified as the specific period H. When calculating the intake fluctuation amount ΔGA in this modified embodiment, the period during which the intake air amount GA is equal to or greater than the determined air amount GATh may also be specified.

[0075] When calculating the intake fluctuation amount ΔGA in the above modified embodiment, the intake air amount GA received sequentially from the air flow meter 72 may be thinned out to a certain extent and used to calculate the intake fluctuation amount ΔGA. In other words, instead of calculating the intake fluctuation amount ΔGA using two pieces of data received in succession, the intake air amount GA may be calculated using data spaced apart, for example, every third or fourth piece of data among the intake air amounts GA received sequentially from the air flow meter 72. It is only necessary to determine in advance how many intervals of the intake air amount GA are to be used to calculate the intake fluctuation amount ΔGA.

[0076] As with the calculation of the intake fluctuation amount ΔGA, it is not essential to use the second analysis data D2 in calculating the pressure fluctuation amount WA. In accordance with the above-described method of calculating the intake fluctuation amount ΔGA, the absolute value of the difference between the PCV pressure W received from the PCV pressure sensor 35 at two different timings may be calculated as the pressure fluctuation amount WA.

[0077] It is not essential to correct the pressure fluctuation amount WA to a value that is less affected by the intake fluctuation amount ΔGA. The pressure fluctuation amount WA may be used as is to update the integrated parameter Z. The first map may be a formula or a table instead of the example described in the above embodiment. The same applies to the second map.

[0078] The method of setting the specified value K in the second map is not limited to the example of the above embodiment. The specified value K does not necessarily have to be larger as the engine speed NE becomes lower. For a certain intake air amount GA, if the specified value K is larger in the case of a low engine speed NE than in the case of a high engine speed NE, it is preferable in terms of preventing erroneous determination of the presence or absence of a leakage abnormality. Here, the specified value K, together with the judged air amount GATh, constitutes a threshold for specifying the specific period H, which is the period for which the pressure fluctuation amount WA is calculated. At each engine speed NE, the specified value K and the judged air amount GATh may be set to complement each other so that a clear difference is produced in the pressure fluctuation amount WA between when a leakage abnormality occurs and when normal. If this point can be guaranteed, the method of determining the specified value K can be changed as appropriate. For example, the second map may be one that defines only two correspondence relationships between the specified value K and the engine speed NE, instead of the one in the above embodiment in which three relationships between the specified value K, the intake air amount GA, and the engine speed NE are associated with each other. Also, the second map may define only two correspondence relationships between the specified value K and the intake air amount GA. The specified value K may be a uniform fixed value.

[0079] The method of setting the judged air amount GATh in the first map is not limited to the example of the embodiment. The judged air amount GATh does not necessarily have to become smaller as the engine speed NE becomes higher. The judged air amount GATh may be smaller in the case where the engine speed NE is high than in the case where the engine speed NE is low. As described in the above modification, the judged air amount GATh may be determined in consideration of the specified value K so that a clear difference in the pressure fluctuation amount WA occurs at each engine speed NE between when a leakage abnormality occurs and when normal. As a base condition for this, the judged air amount GATh may be a smaller value when the engine speed NE is high than when the engine speed NE is low. The judged air amount GATh for each engine speed NE may be a value equal to or larger than the minimum value of the intake air amount GA under the condition that the upstream intake passage 241 becomes negative pressure at each engine speed NE.

[0080] As described above, the intake air amount GA and the PCV pressure W are related to each other. Therefore, instead of the condition that the intake air amount GA is equal to or greater than the judged air amount GATh, a condition that the PCV pressure W is equal to or less than a predetermined judged pressure may be set as a condition for detecting a state in which a negative pressure is generated in the upstream intake passage 241. The judged pressure in this case may be, for example, the PCV pressure W when the intake air amount GA becomes the judged air amount GATh in the above embodiment in a state in which the blow-by gas piping 33 is normal. Note that such a judged pressure is smaller than the atmospheric pressure M. In other words, when the condition that the PCV pressure W is equal to or less than the judged pressure is set as a premise for calculating the pressure fluctuation amount WA, the pressure fluctuation amount WA is basically not calculated in the complete communication state of the blow-by gas piping 33. Then, the presence or absence of a leakage abnormality is diagnosed mainly for only the partial communication state of the blow-by gas piping 33. Here, as far as the leakage abnormality in the complete communication state is concerned, it is possible to grasp the leakage abnormality without using the pressure fluctuation amount WA. For example, if the PCV pressure W is maintained at a value close to the atmospheric pressure M even though the intake air amount GA is relatively large, it can be determined that a leakage abnormality occurs in the complete communication state. On the other hand, in order to detect a leakage abnormality in the partial communication state, a diagnosis using the pressure fluctuation amount WA is necessary. From this perspective, in diagnosing the presence or absence of a leakage abnormality only in the partial communication state of the blow-by gas piping 33, it is also effective to set the condition that the PCV pressure W is equal to or lower than the judgment pressure as described above.

[0081] When using the judged pressure instead of the judged air amount GATh as in the above modified example, the judged pressure may be set variably according to the engine speed NE from the same viewpoint as in the above embodiment.

[0082] In determining the specific period H, other parameters that are indicative of the intake fluctuation amount ΔGA may be used instead of the intake fluctuation amount ΔGA itself. For example, the accelerator operation amount ACC may be used as such a parameter. There is a relationship between the increase / decrease in the accelerator operation amount ACC and the increase / decrease in the intake air amount GA. Therefore, the relationship between the increase / decrease in the accelerator operation amount ACC and the increase / decrease in the intake air amount GA is examined in advance. Then, based on the relationship, if a specified value dedicated to the accelerator operation amount ACC corresponding to the specified value K of the intake fluctuation amount ΔGA is set, it is possible to determine the specific period H using information on the transition of the accelerator operation amount ACC. Then, a period in which the fluctuation amount of the accelerator operation amount ACC per unit time is equal to or greater than the specified value may be determined as the specific period H in which the intake fluctuation amount ΔGA is equal to or greater than the specified value K. The fluctuation amount of the accelerator operation amount ACC per unit time may be calculated, for example, from the time series of the accelerator operation amount ACC in a predetermined unit time, or may be the difference between the accelerator operation amount ACC received from the accelerator sensor 74 at two consecutive timings.

[0083] When a specified value dedicated to the accelerator depression amount ACC is used as in the above modification, the specified value may be set variably according to the engine rotation speed NE from the same viewpoint as in the above embodiment.

[0084] The method of determining whether or not there is a leakage abnormality in the blow-by gas piping 33 is not limited to the example of the above embodiment. The above determination method may be one that utilizes the pressure fluctuation amount WA. For example, the presence or absence of a leakage abnormality may be determined by a value obtained by multiplying a plurality of pressure fluctuation amounts WA. The presence or absence of a leakage abnormality may be determined based only on the pressure fluctuation amount WA calculated once. As long as the presence or absence of a leakage abnormality can be appropriately determined, the determination method is not important.

[0085] The processing device that controls the internal combustion engine 10 and the diagnostic device 50 may be configured as separate processing devices. The diagnostic device 50 only needs to be able to receive information necessary for performing diagnostic processing. The overall configuration of the internal combustion engine is not limited to the example of the above embodiment. For example, a variable displacement type turbocharger having a nozzle vane may be used. A turbocharger that is not an exhaust-driven type but is driven by the power of the crankshaft 14 may be used.

[0086] The installation location of the PCV pressure sensor 35 may be changed from the example of the above embodiment. For example, the PCV pressure sensor 35 may be provided midway through the blow-by gas piping 33. In this case, the presence or absence of a leakage abnormality can be diagnosed for the portion of the blow-by gas piping 33 that is closer to the intake passage side than the installation location of the PCV pressure sensor 35. 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 installation location of the PCV pressure sensor 35.

[0087] The PCV pressure sensor may be a sensor that detects a gauge pressure, which is a relative pressure based on the atmospheric pressure M. The configuration of the blow-by gas passage is not limited to the example of the above embodiment. The blow-by gas passage only needs to communicate between the crank chamber 17 and the upstream intake passage 241. The blow-by gas passage may be a passage that directly connects the crank chamber 17 and the upstream intake passage 241 without passing through the accumulation space 23 and the communication passage 21. The PCV pressure sensor 35 may be installed in the middle of such a blow-by gas passage. [Explanation of symbols]

[0088] 10. Internal combustion engine 11...Turbocharger 13…Crankcase 14…Crankshaft 17…Crankcase 24…Intake passage 31…Blow-by gas passage 33…Blow-by gas piping 35…PCV pressure sensor 50...Diagnostic equipment 112…Compressor wheel 241…Upstream intake passage

Claims

1. The present invention is directed to an internal combustion engine having a turbocharger, a blow-by gas passage that communicates a portion of an intake passage upstream of a compressor wheel of the turbocharger with the inside of a crankcase, a PCV pressure sensor that is installed in the blow-by gas passage and detects the pressure in the blow-by gas passage as a PCV pressure, and a crankshaft, a first process for specifying, as a specific period, a period during which a fluctuation amount of the intake air amount per unit time is equal to or greater than a specified value, with an intake air amount being equal to or greater than a reference air amount as an execution condition; A second process of calculating a fluctuation amount of the PCV pressure during the specific period; a third process for determining whether or not there is an abnormality in a portion of the blow-by gas passage on the side of the intake passage with respect to a location of the PCV pressure sensor based on an amount of fluctuation in the PCV pressure; Run When the rotation speed of the crankshaft is high, the determined air amount is set to a smaller value than when the rotation speed is low. An abnormality diagnosis device for internal combustion engines.

2. When the rotation speed of the crankshaft is low, the specified value is set to a value larger than when the rotation speed of the crankshaft is high.

2. The internal combustion engine abnormality diagnosis device according to claim 1.

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