Internal combustion engine abnormality diagnostic device

Abstract

To suppress erroneous determination regarding presence or absence of abnormality in a blow-by gas passage.SOLUTION: With an internal combustion engine 10 provided with a blow-by gas passage 31 communicating between an intake air passage 24 and a crank chamber 17, a PCV pressure sensor 35 detecting inner pressure of the blow-by gas passage 31 as PCV pressure, and an air flow meter 72 as a diagnostic object, a diagnostic device 50 executes processes to identify a unit period as a diagnostic object period when a transition of an intake air amount in the unit period satisfies first and second conditions and to determine presence or absence of abnormality in the blow-by gas passage 31 based on an index value reflecting a variation in the PCV pressure during the diagnostic object period. The first condition is that a maximum value of the intake air amount during the unit period is larger than an initiation air amount, which is the air intake amount at the beginning of the unit period, by a first threshold or more. The second condition is that cumulative time of a state in which the air intake amount is larger than the initial air amount by a second threshold or more is reference time or longer in the unit period.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to an abnormality diagnosis device for an internal combustion engine.

Background Art

[0002] Patent Document 1 discloses an internal combustion engine and its abnormality diagnosis device. The internal combustion engine includes a supercharger, a blow-by gas accumulation space, a blow-by gas passage, and a PCV pressure sensor. The compressor wheel of the supercharger is located in the middle of the intake passage. The blow-by gas accumulation space is a space partitioned by a cylinder head and a cylinder head cover. This accumulation space communicates with the crankcase. The accumulation space temporarily accumulates blow-by gas leaking from the cylinder into the crankcase. The blow-by gas passage connects the accumulation space and the upstream portion (hereinafter simply referred to as the upstream portion) of the intake passage upstream of the compressor wheel. 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 supercharger, the upstream portion of the intake passage becomes negative pressure. In this case, blow-by gas flows into the upstream portion of the intake passage through the blow-by gas passage. Assuming that the intake air amount changes under the situation where blow-by gas flows into the upstream portion of the intake passage. Along with the change in the pressure of the upstream portion of the intake passage, the amount of blow-by gas flowing into the intake passage changes and the pressure in the blow-by gas passage also changes. Thus, the change in the intake air amount and the change in the pressure in the blow-by gas passage are interlocked. And the greater the change amount of the intake air amount, the greater the change amount of the pressure in the blow-by gas passage.

[0004] Against this background, when the increase in the intake air volume at the end point relative to the intake air volume at the start point of a certain period is equal to or greater than a determination value, the abnormal diagnosis device of Patent Document 1 specifies this certain period as the target period for diagnosing abnormalities in the blow-by gas passage. Then, when the amount of change in the pressure inside the blow-by gas passage during this target period is small, the abnormal diagnosis device determines that an abnormality has occurred in the blow-by gas passage.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] When specifying the target period for abnormality diagnosis as described above, the intake air volume may not increase much until halfway through the target certain period, and the intake air volume may increase rapidly near the end of the certain period. Even in this case, if the increase in the intake air volume during the certain period becomes equal to or greater than the determination value along with the increase in the intake air volume near the end, the abnormal diagnosis device treats this certain period as the target period for abnormality diagnosis. However, in the case where the intake air volume changes as described above, since the intake air volume does not increase much from the start point until halfway through the certain period, the amount of change in the pressure inside the blow-by gas passage during the certain period tends to be small as a whole. When diagnosing abnormalities in the blow-by gas passage for such a certain period, since the amount of change in the pressure inside the blow-by gas passage is small, there is a risk of misjudging that an abnormality has occurred even though no abnormality has occurred in the blow-by gas passage.

[0007] Note that not only when determining the target period for abnormality diagnosis using the intake air volume at the end point of a certain period as a criterion, but also when determining the target period by comparing the intake air volume in the middle of a certain period with the determination value, the same problems as described above may occur depending on the change in the intake air volume.

Means for Solving the Problem

[0008] An abnormal diagnosis device for an internal combustion engine for solving the above problems includes a supercharger, a blow-by gas passage that communicates a portion upstream of the compressor wheel of the supercharger in the intake passage and the inside of the 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 the PCV pressure, and an air flow meter that detects the intake air amount. For an internal combustion engine equipped with these components, a first process is performed to obtain the transition of the intake air amount in a unit period, and when the transition of the intake air amount in the obtained unit period satisfies both a predetermined first condition and a second condition, a second process is performed to specify the unit period as a diagnosis target period of the blow-by gas passage. A third process is performed to calculate an index value reflecting the variation amount of the PCV pressure from the start to the end of the diagnosis target period, and a fourth process is performed to determine the presence or absence of an abnormality in the blow-by gas passage based on the index value of the diagnosis target period. The first condition is that in the unit period, the maximum value of the intake air amount in the unit period is larger than a predetermined first determination value compared to the starting air amount, which is the intake air amount at the start of the unit period. The second condition is that in the unit period, the integrated time in a state where the intake air amount is larger than a predetermined second determination value, which is a value smaller than the first determination value compared to the starting air amount, is equal to or longer than a reference time, which is a value smaller than the unit period.

[0009] An abnormal diagnosis device for an internal combustion engine for solving the above problems includes a supercharger, a blow-by gas passage that communicates a portion upstream of the compressor wheel of the supercharger in the intake passage and the inside of the crankcase, and a PCV pressure sensor that is installed in the blow-by gas passage and detects the pressure in the blow-by gas passage as the PCV pressure, and an air flow meter that detects the intake air amount. For an internal combustion engine equipped with the above components, a first process of obtaining the transition of the intake air amount in a unit period, and when the transition of the intake air amount in the obtained unit period satisfies both a predetermined first condition and a second condition, a second process of specifying the unit period as a diagnosis target period of the blow-by gas passage, a third process of calculating an index value reflecting the amount of change in the PCV pressure from the start period to the end period of the diagnosis target period, and a fourth process of determining the presence or absence of an abnormality in the blow-by gas passage based on the index value of the diagnosis target period are executed. The first condition is that in the unit period, the maximum value of the intake air amount in the unit period is larger than a predetermined first determination value compared to the starting air amount which is the intake air amount at the start of the unit period. The second condition is that the average variation amount, which is the value obtained by dividing the integrated value of the difference between the intake air amount and the starting air amount in the unit period by the unit period, is equal to or greater than the value obtained by multiplying a predetermined coefficient, which is a value greater than 0 and less than 1, by the value obtained by subtracting the starting air amount from the maximum value of the intake air amount in the unit period.

Effect of the Invention

[0010] In each of the above technical ideas, it is possible to suppress an incorrect determination regarding the presence or absence of an abnormality in the blow-by gas passage.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0012] <First Embodiment> Hereinafter, a first embodiment of an internal combustion engine abnormality diagnostic device will be described with reference to the drawings. As shown in FIG. 1, a vehicle 300 includes an internal combustion engine 10. The internal combustion engine 10 includes an oil pan 15 for storing lubricating oil. Above the oil pan 15, a crankcase 13 is located. Inside the crankcase 13, a crank chamber 17 for accommodating a crankshaft 14 is partitioned. Above the crankcase 13, a cylinder block 12 is located. Inside the cylinder block 12, a plurality of cylinders 22 are partitioned. In each cylinder 22, a mixture of fuel and intake air burns. Each cylinder 22 communicates with the crank chamber 17. A piston 19 is located in each cylinder 22. The piston 19 is connected to the crankshaft 14 via a connecting rod 20. Note that the combustion gas leaking from the cylinder 22 to the crank chamber 17 is called blow-by gas.

[0013] An intake passage 24 for introducing intake air from the outside is connected to each cylinder 22. A throttle valve 26 for adjusting the intake air amount G is located in the middle of the intake passage 24. An upstream side of the throttle valve 26 in the intake passage 24 is where the compressor wheel 112 of the supercharger 11 is located. An upstream side of the compressor wheel 112 in the intake passage 24 is where an air flow meter 72 for detecting the intake air amount G is located. Also, an exhaust passage 25 for discharging exhaust to the outside is connected to each cylinder 22. A turbine wheel 111 of the supercharger 11 is located in the middle of the exhaust passage 25. A bypass passage 28 that bypasses the turbine wheel 111 is connected to the exhaust passage 25. A wastegate valve 27 is located at the downstream end of the bypass passage 28. The wastegate valve 27 can adjust its opening degree. The amount of exhaust flowing through the bypass passage 28 changes according to the opening degree of the wastegate valve 27. When the opening degree of the wastegate valve 27 becomes smaller than fully open, the amount of exhaust passing through the turbine wheel 111 increases. Then, the turbine wheel 111 rotates according to the exhaust flow. At this time, the compressor wheel 112 rotates integrally with the turbine wheel 111. And the compressor wheel 112 compresses and sends out the intake air. That is, the intake air is supercharged.

[0014] A cylinder head 16 is located above the cylinder block 12. The cylinder head 16 is covered with a head cover 18 from above. The cylinder head 16 and the head cover 18 define an accumulation space 23 for temporarily accumulating blow-by gas. The accumulation space 23 communicates with the crank chamber 17 through a communication passage 21 penetrating the cylinder block 12 and the cylinder head 16. Further, the accumulation space 23 communicates with an upstream intake passage 241, which is a portion upstream of the compressor wheel 112 in the intake passage 24, through a blow-by gas pipe 33. The blow-by gas pipe 33 communicates with the accumulation space 23 through a joint 32 attached to the head cover 18. A PCV pressure sensor 35 is installed in the joint 32. The PCV pressure sensor 35 detects the absolute pressure inside the joint 32. The pressure inside the joint 32 is the same as the pressure inside the blow-by gas pipe 33. That is, the PCV pressure sensor 35 detects the PCV pressure W, which is the pressure inside the blow-by gas pipe 33. The communication passage 21, the accumulation space 23, the joint 32, and the blow-by gas pipe 33 described above constitute a blow-by gas passage 31 that communicates the crank chamber 17 and the upstream intake passage 241. Through this blow-by gas passage 31, the blow-by gas in the crank chamber 17 is returned to the intake passage 24. The detailed configuration of the internal combustion engine provided with a mechanism for returning the blow-by gas in the crank chamber 17 to the intake passage 24 is disclosed in Patent Document 1.

[0015] <Diagnostic device> The vehicle 300 is equipped with an abnormality diagnosis device (hereinafter simply referred to as the diagnosis device) 50 for the internal combustion engine 10. The diagnosis device 50 includes a CPU 51 and a memory 53. The memory 53 includes three types: RAM, ROM, and an electrically rewritable non-volatile memory. In this embodiment, these three types are collectively referred to as the memory 53. The memory 53 stores in advance various programs in which the processes to be executed by the CPU 51 are described, and various data necessary for the CPU 51 to execute the programs. For example, the diagnosis device 50 has both a function of diagnosing the internal combustion engine 10 and a function of controlling various parts of the internal combustion engine 10. The diagnosis device 50 repeatedly receives the respective detection signals from the air flow meter 72 and the PCV pressure sensor 35 at predetermined time intervals.

[0016] Due to a part of the blow-by gas pipe 33 being damaged, an opening may occur in the wall portion of the blow-by gas pipe 33. In this case, a leakage abnormality occurs in which the blow-by gas leaks from the inside to the outside of the blow-by gas pipe 33 through the opening. The leakage abnormality may also occur when the blow-by gas pipe 33 becomes detached from the upstream intake passage 241 or the joint 32. The diagnosis device 50 is capable of executing a diagnosis process for diagnosing the presence or absence of such a leakage abnormality. That is, the diagnosis process is a process that targets the blow-by gas pipe 33, which is the part on the intake passage 24 side with respect to the installation location of the PCV pressure sensor 35 in the blow-by gas passage 31. In the diagnosis process, the diagnosis device 50 uses the PCV pressure W to diagnose the presence or absence of the leakage abnormality. The relationship between the intake air amount G and the PCV pressure W, which is the premise for the diagnosis device 50 to use the PCV pressure W in the diagnosis process, will be described.

[0017] When the turbocharger 11 is performing supercharging, that is, when the intake air amount G is relatively large, the internal pressure of the upstream intake passage 241 becomes negative relative to the atmospheric pressure M. When the blow-by gas piping 33 is normal, when the upstream intake passage 241 becomes negative pressure, 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 G 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 G increases. As in the case where the blow-by gas piping 33 is normal, even when a relatively small opening exists in the blow-by gas piping 33 due to damage, when the upstream intake passage 241 becomes negative pressure, a certain amount of blow-by gas flows into the upstream intake passage 241. The amount of blow-by gas flowing into the upstream intake passage 241 increases as the intake air amount G increases. Therefore, as shown by the dotted line in FIG. 2, the PCV pressure W decreases as the intake air amount G increases. However, when the blow-by gas pipe 33 is damaged, the inside of the blow-by gas pipe 33 communicates with the atmosphere through the damaged part, so the PCV pressure W is closer to the atmospheric pressure M than when the blow-by gas pipe 33 is normal. Under the condition where negative pressure is generated in the upstream intake passage 241, the degree of change in the PCV pressure W with respect to the change in the intake air amount G is smaller than the degree when the blow-by gas pipe 33 is normal. Note that when the opening area of ​​the damage in the blow-by gas pipe 33 is considerably large or the blow-by gas pipe 33 is not included in the connection target, the degree of communication between the blow-by gas pipe 33 and the outside becomes considerably large. In this case, as shown by the dashed line in FIG. 2, the PCV pressure W does not change in conjunction with the intake air amount G and takes a value close to the atmospheric pressure M. The above-described relationship between the intake air amount G and the PCV pressure W, as well as details of the principle of diagnosing a leakage abnormality, are disclosed in Patent Document 1.

[0018] During the operation of the internal combustion engine 10, the diagnostic device 50 repeatedly executes diagnostic processing. As shown in FIG. 4, when starting the diagnostic processing, the diagnostic device 50 first executes the processing of step S10. In step S10, the diagnostic device 50 determines whether the preconditions are satisfied. The precondition is that the current intake air amount G is equal to or greater than the set air amount. The diagnostic device 50 stores the set air amount in advance. As described above, when the intake air amount G is small, it is difficult for a difference in the PCV pressure W to occur between when a leakage abnormality occurs and when it is normal. Considering this point, the set air amount is determined in advance by, for example, experiments or simulations as a value that clearly shows a difference in the PCV pressure W between when a leakage abnormality occurs and when it is normal. As a specific process in step S10, the diagnostic device 50 compares the latest intake air amount G received from the air flow meter 72 with the set air amount. Then, when the latest intake air amount G is less than the set air amount (step S10: NO), the diagnostic device 50 temporarily ends the series of diagnostic processing. In this case, the diagnostic device 50 executes the processing of step S10 again. On the other hand, when the latest intake air amount G is equal to or greater than the set air amount (step S10: YES), the diagnostic device 50 advances the processing to step S20. An example of the situation where the processing advances to step S20 is a situation where the intake air amount G increases from less than the set air amount to equal to or greater than the set air amount during the increasing process of the intake air amount G.

[0019] In step S20, the diagnostic device 50 stores the analysis data over a predetermined unit period H. Specifically, as illustrated in FIG. 3(a), the diagnostic device 50 stores, in chronological order, a plurality of intake air amounts G received from the air flow meter 72 from the time point H1 when the process advances to step S20 until the unit period H elapses. The diagnostic device 50 treats this time series as the first analysis data D1. Also, as illustrated in FIG. 3(b), the diagnostic device 50 stores, in chronological order, a plurality of PCV pressures W received from the PCV pressure sensor 35 from the time point H1 when the process advances to step S20 until the unit period H elapses. The diagnostic device 50 treats this time series as the second analysis data D2. The diagnostic device 50 measures the unit period H, for example, by counting up a counter for time measurement. Hereinafter, the start timing of the unit period H is referred to as the start period H1 of the unit period H. Also, the end timing of the unit period H is referred to as the end period H2 of the unit period H. That is, the first analysis data D1 is the time series of the intake air amount G from the start period H1 to the end period H2 of the unit period H. The second analysis data D2 is the time series of the PCV pressure W from the start period H1 to the end period H2 of the unit period H. The diagnostic device 50 stores the unit period H in advance. The unit period H is a fixed value. The unit period H is on a scale of less than 1 second, such as 0.5 seconds, for example. The unit period H is sufficiently longer than the time interval at which the air flow meter 72 and the PCV pressure sensor 35 detect the target elements, and thus the time interval at which the diagnostic device 50 receives the detection signals from these respective sensors. Therefore, each of these sensors transmits a plurality of detection signals to the diagnostic device 50 within the unit period H. The unit period H is determined in advance, for example, by an experiment or a simulation, as the length of time during which each sensor can obtain a sufficient number of data samples for diagnosing the presence or absence of a leakage abnormality using the transition information of the intake air amount G and the PCV pressure W. As shown in FIG. 4, when the unit period H elapses after the process advances to step S20, the diagnostic device 50 advances the process to step S30. Note that the process of step S20 is the first process for acquiring the transitions of the intake air amount G and the PCV pressure W in the unit period H.

[0020] In step S30, the diagnostic device 50 determines whether or not a predetermined first condition is satisfied. As shown in FIG. 3(a), the first condition is that, in the unit period H, the maximum air amount GX in the unit period H is greater than or equal to a first determination value U1 compared to the start air amount GS. The maximum air amount GX is the maximum value of the intake air amount G in the unit period H. The start air amount GS is the intake air amount G at the start H1 of the unit period H. Here, on the premise of performing the process of step S30, the diagnostic device 50 stores a first map in advance. The first map defines the correspondence between the first determination value U1 and the start air amount GS. That is, in the first map, the first determination value U1 is predetermined in correspondence with the start air amount GS. In the first map, the smaller the start air amount GS, the larger the first determination value U1. The reason for setting such a relationship will be described in the section on the operation and effects of the embodiment described later. The first determination value U1 corresponding to each start air amount GS is predetermined, for example, by experiments or simulations, as a value that makes the difference in the PCV integrated value Y described later clear between the occurrence of leakage abnormality and the normal state.

[0021] As a specific process of step S30, the diagnostic device 50 refers to the first analysis data D1 stored in step S20. Then, as shown in Fig. 3(a), the diagnostic device 50 specifies the intake air amount G at the start H1 of the unit period H as the start air amount GS among the time series of the intake air amount G in the first analysis data D1. Further, the diagnostic device 50 specifies the maximum value among the time series of the intake air amount G in the first analysis data D1 as the maximum air amount GX. In the example of Fig. 3(a), an example where the intake air amount G becomes maximum at the end H2 of the unit period H is shown. When the diagnostic device 50 specifies the start air amount GS and the maximum air amount GX, it refers to the first map. Then, the diagnostic device 50 calculates a first determination value U1 corresponding to the current start air amount GS based on the first map. After that, as shown in Fig. 3(a), the diagnostic device 50 calculates a maximum difference component ΔGX, which is a value obtained by subtracting the start air amount GS from the maximum air amount GX. Then, the diagnostic device 50 compares this maximum difference component ΔGX with the first determination value U1 corresponding to the current start air amount GS. And when the maximum difference component ΔGX is less than the first determination value U1, the diagnostic device 50 determines that the first condition is not satisfied (step S30: NO). In this case, as shown in Fig. 4, the diagnostic device 50 deletes the analysis data stored in step S20 and then ends the series of diagnostic processes. After that, the diagnostic device 50 executes the process of step S10 again.

[0022] On the other hand, as shown in Fig. 3(a), when the maximum difference component ΔGX is greater than or equal to the first determination value U1, the diagnostic device 50 determines that the first condition is satisfied (step S30: YES). In this case, as shown in Fig. 4, the diagnostic device 50 advances the process to step S40.

[0023] In step S40, the diagnostic device 50 determines whether a predetermined second condition is satisfied. As shown in FIG. 3(a), with respect to the intake air amount G at each timing in the first analysis data D1, a value obtained by subtracting the starting air amount GS from the intake air amount G at a certain timing is referred to as an air amount difference ΔG. The second condition is that, in the unit period H, the integrated time PN in a state where the air amount difference ΔG is equal to or greater than the second determination value U2 is equal to or greater than the reference time P. In other words, the second condition is that, in the unit period H, the integrated time PN in a state where the intake air amount G is greater than the starting air amount GS by an amount equal to or greater than the second determination value U2 is equal to or greater than the reference time P.

[0024] As a prerequisite for performing the process of step S40, the diagnostic device 50 stores the reference time P in advance. The reference time P is a fixed value. The reference time P is predetermined as a value smaller than the unit period H. Further, the reference time P is determined, for example, as a value greater than half of the unit period H. The reference time P is predetermined, for example, through experiments or simulations as a value that can grasp that a state where the air amount difference ΔG is relatively large exists not temporarily but over a long period. Also, the diagnostic device 50 stores a second map in advance. The second map defines the correspondence between the second determination value U2 and the starting air amount GS. That is, in the second map, the second determination value U2 is predetermined in correspondence with the starting air amount GS. In the second map, similar to the first map, the smaller the starting air amount GS, the larger the second determination value U2. When compared at the same starting air amount GS, the second determination value U2 in the second map is predetermined as a value smaller than the first determination value U1 in the first map. Note that the second determination value U2 is determined such that the following determination relationship is satisfied. The determination relationship is that the ratio of the unit period H to the first determination value U1 is equal to the ratio of the value obtained by subtracting the reference time P from the unit period H to the second determination value U2.

[0025] As a specific process of step S40, first, the diagnostic device 50 refers to the second map. Then, based on the second map, the diagnostic device 50 calculates a second determination value U2 corresponding to the starting air volume GS specified in step S30. Next, as shown in Fig. 3(a), the diagnostic device 50 refers to the first analysis data D1 stored in step S20. Then, the diagnostic device 50 subtracts the starting air volume GS from each of the plurality of intake air volumes G that make up the time series of the first analysis data D1. Thereby, the diagnostic device 50 calculates an air volume difference ΔG for the number of intake air volumes G that make up the time series of the first analysis data D1. When the diagnostic device 50 calculates a plurality of air volume differences ΔG, it compares each of these air volume differences ΔG with the second determination value U2 corresponding to the current starting air volume GS. Then, the diagnostic device 50 identifies, as target samples, the samples among the plurality of air volume differences ΔG for which the air volume difference ΔG is equal to or greater than the second determination value U2. Note that the target samples may not appear continuously in the time direction and may appear intermittently. Including such cases, the diagnostic device 50 identifies all the target samples. When the diagnostic device 50 identifies the target samples, it calculates the product of the number of target samples and the time interval for receiving the detection signal from the air flow meter 72 as the integrated time PN for determination. After this, the diagnostic device 50 compares this integrated time PN for determination with the reference time P. Then, when the integrated time PN is less than the reference time P, the diagnostic device 50 determines that the second condition is not satisfied (step S40: NO). In this case, as shown in Fig. 4, the diagnostic device 50 deletes the analysis data stored in step S20 and then ends the series of diagnostic processes. Then, the diagnostic device 50 executes the process of step S10 again.

[0026] On the other hand, as shown in Fig. 3(a), when the integrated time PN for determination is equal to or longer than the reference time P, the diagnostic device 50 determines that the second condition is satisfied (step S40: YES). In this case, the diagnostic device 50 specifies the unit period H that is the target for which the transitions of the intake air amount G and the PCV pressure W were acquired in step S20 as the diagnostic target period of the blow-by gas pipe 33. That is, when the transition of the intake air amount G in the unit period H acquired in step S20 satisfies both the first condition and the second condition, the diagnostic device 50 specifies the target unit period H as the diagnostic target period. The series of processes of step S30 and step S40 for specifying the diagnostic target period is the second process. As shown in Fig. 4, when the diagnostic device 50 specifies the diagnostic target period, the process proceeds to step S50.

[0027] In step S50, the diagnostic device 50 calculates the PCV integrated value Y. The PCV integrated value Y is an index value that reflects the amount of change in the PCV pressure W from the start period to the end period of the diagnostic target period. The start period of the diagnostic target period is the start period H1 of the unit period H. The end period of the diagnostic target period is the end period H2 of the unit period H. The diagnostic device 50 calculates the PCV integrated value Y as follows. As shown in FIG. 3(b), the diagnostic device 50 refers to the second analysis data D2 which is the time series of the PCV pressure W acquired in step S20. Then, the diagnostic device 50 specifies the PCV pressure W at the start period H1 of the unit period H as the start pressure WS among the time series of the second analysis data D2. Regarding the PCV pressure W at each timing in the second analysis data D2, the value obtained by subtracting the PCV pressure W at a certain timing from the start pressure WS is called the pressure difference ΔW. When the diagnostic device 50 specifies the start pressure WS, it calculates the pressure difference ΔW for each of the plurality of PCV pressures W constituting the time series of the second analysis data D2. Note that, due to the relationship between the intake air amount G and the PCV pressure W described above, the PCV pressure W decreases during the increase process of the intake air amount G. Therefore, each PCV pressure W of the second analysis data D2 to be analyzed in this step S50 is basically smaller than the start pressure WS. And each pressure difference ΔW basically becomes a positive value. However, due to noise or the like, the PCV pressure W may become larger than the start pressure WS and the pressure difference ΔW may become negative. In this case, the diagnostic device 50 treats the pressure difference ΔW as "0" for convenience. When the diagnostic device 50 calculates the pressure difference ΔW for each PCV pressure W constituting the time series of the second analysis data D2, it calculates the product of the integrated value of all the calculated pressure differences ΔW and the time interval for receiving the detection signal from the PCV pressure sensor 35 as the PCV integrated value Y. The PCV integrated value Y corresponds to the area shown by hatching in FIG. 3(b). As shown in FIG. 4, when the diagnostic device 50 calculates the PCV integrated value Y, it proceeds with the process to step S60. Note that the process of this step S50 is the third process for calculating an index value that reflects the amount of change in the PCV pressure W.

[0028] In step S60, the diagnostic device 50 determines the presence or absence of a leakage abnormality in the blow-by gas pipe 33 based on the PCV integrated value Y calculated in step S60. The process of this step S60 is the fourth process. Due to the relationship between the intake air amount G and the PCV pressure W described above, when a leakage abnormality occurs, the pressure difference ΔW at each timing becomes smaller compared to the normal state. At the same time, when a leakage abnormality occurs, the PCV integrated value Y becomes smaller. Therefore, when the PCV integrated value Y is equal to or greater than a predetermined determination threshold value, the diagnostic device 50 determines that the blow-by gas pipe 33 is normal. On the other hand, when the PCV integrated value Y is less than the determination threshold value, the diagnostic device 50 determines that a leakage abnormality has occurred in the blow-by gas pipe 33. The diagnostic device 50 stores the determination threshold value in advance. The determination threshold value is determined in advance, for example, by experiment or simulation as the minimum value of the PCV integrated value Y that can be obtained when the blow-by gas pipe 33 is normal. When the diagnostic device 50 determines the presence or absence of a leakage abnormality, it deletes the analysis data stored in step S20 and then ends the process of step S60. At the same time, the diagnostic device 50 temporarily ends the series of diagnostic processes. After that, the diagnostic device 50 executes the process of step S10 again. For example, when the number of times the diagnostic device 50 determines that a leakage abnormality has occurred during one trip exceeds a predetermined number of times, the warning lamp in the vehicle interior is turned on. One trip is the period from when the ignition switch of the vehicle 300 is turned on to when it is turned off.

[0029] <Actions and Effects of the First Embodiment> (1) In this embodiment, when specifying the diagnosis target period, it is conditioned that both the first condition and the second condition are satisfied. As shown in Fig. 3(a), the first condition is that the maximum difference component ΔGX, which is the difference between the starting air volume GS and the maximum air volume GX, is equal to or greater than the first determination value U1. When this first condition is satisfied, it can be grasped that the intake air volume G has increased considerably with respect to the starting air volume GS within the unit period H. Here, even in the case where the first condition is satisfied, for example, as shown by the two-dot chain line in Fig. 3(a), there may be a rapid increase case where the intake air volume G increases only during a limited period within the unit period H. Specifically, in the rapid increase case, after the start of the unit period H, a situation where the air volume difference ΔG, which is the increase amount of the intake air volume G with respect to the starting air volume GS, is small continues for a long time, and temporarily the air volume difference ΔG increases. In such a rapid increase case, even if the blow-by gas pipe 33 is normal, as shown by the two-dot chain line in Fig. 3(b), a situation where the decrease amount of the PCV pressure W with respect to the starting pressure WS is small continues for a long time. Therefore, in such a rapid increase case, even if the blow-by gas pipe 33 is normal, the PCV integrated value Y becomes small. As a result, there is a possibility of misjudging that a leakage abnormality has occurred even though the blow-by gas pipe 33 is normal.

[0030] Taking this point into consideration, in this embodiment, as the second condition, as shown by the solid line in Fig. 3(a), the second condition that the integrated time PN in a state where the air volume difference ΔG is equal to or greater than the second determination value U2 is equal to or greater than the reference time P is adopted. When this second condition is satisfied, it can be grasped that a state where the increase amount of the intake air volume G with respect to the starting air volume GS is large exists for a long time within the unit period H. By adopting such a second condition, it is highly possible to exclude the unit period H showing a transition such as the above rapid increase case from the diagnosis target period. And thereby, it is highly possible to specify only the case where the variation amount of the PCV pressure W is large not temporarily but over a long period as the diagnosis target period. If such a diagnosis target period is extracted and the presence or absence of a leakage abnormality is determined, misjudgment regarding the presence or absence of the leakage abnormality can be suppressed.

[0031] (2) In this embodiment, the first judgment value U1 and the second judgment value U2 are determined so as to satisfy the above judgment relationship. That is, in this embodiment, the ratio of the unit period H to the first judgment value U1 is equal to the ratio of the value obtained by subtracting the reference time P from the unit period H to the second judgment value U2. As shown by the dashed line in FIG. 3(a), the transition of the intake air amount G in which the intake air amount G increases linearly from the start point H1 of the unit period H and reaches the first judgment value U1 at the end point H2 is called the reference increase pattern. In this reference increase pattern, the cumulative time PN in the state in which the air amount difference ΔG is equal to or greater than the second judgment value U2 coincides with the reference time P. That is, when it is expected that the intake air amount G increases approximately linearly, the time rate of change of the intake air amount G in the reference increase pattern can be regarded as the minimum value of the time rate of change of the intake air amount G in satisfying the first condition and the second condition when each judgment value is set so as to satisfy the above judgment relationship. When both the first and second conditions are satisfied, the intake air amount G is expected to continue to increase at a high time rate of change that exceeds the reference increase pattern, as shown by the solid line in Fig. 3(a), or the intake air amount G increases rapidly in the early stage of the unit period H and the air amount difference ΔG remains large thereafter. In these cases, the actual air amount difference ΔG at each timing of the unit period H is greater than the air amount difference ΔG in the reference increase pattern. In this way, if the first judgment value U1 and the second judgment value U2 are set to satisfy the above judgment relationship, it is more likely that a case in which the intake air amount G increases at a high time rate and the air amount difference ΔG remains large can be identified as a diagnosis target period.

[0032] (3) In this embodiment, the first determination value U1 and the second determination value U2 are variably set according to the starting air amount GS. The reason for this will be explained. When the starting air amount GS is small, that is, when the intake air amount G in the unit period H is small as a whole, the degree of change in the PCV pressure W with respect to the change in the intake air amount G in the unit period H tends to be small. Under such circumstances, even if the blow-by gas pipe 33 is normal, the amount of change in the PCV pressure W will not increase unless the amount of change in the intake air amount G in the unit period H increases. That is, unless the amount of change in the intake air amount G in the unit period H increases, the difference in the amount of change in the PCV pressure W and thus the PCV integrated value Y between the abnormal and normal states of the blow-by gas pipe 33 is unlikely to occur.

[0033] Taking this point into consideration, in this embodiment, the first determination value U1 is variably set according to the starting air amount GS. Then, so as to satisfy the above determination relationship, the second determination value U2 is also variably set according to the starting air amount GS. And when the starting air amount GS is small, the first determination value U1 and the second determination value U2 are made larger than when it is large. Therefore, when the starting air amount GS is small, only the cases where the amount of change in the intake air amount G and thus the PCV integrated value Y are considerably large and it is possible to distinguish between the abnormal leakage occurrence and the normal state can be specified as the diagnosis target period. By adopting such a specific mode, false determination regarding leakage abnormality can be more effectively suppressed.

[0034] <Second Embodiment> The second embodiment of the internal combustion engine abnormality diagnosis device will be described. The second embodiment differs from the first embodiment only in the second condition and the processing content of step S40 related thereto. Therefore, hereinafter, the second condition and step S40 according to the second embodiment will be mainly described, and the description of the overlapping content with the first embodiment will be omitted or dispensed with as appropriate.

[0035] As shown by the hatched area in FIG. 5, the integrated value of the air volume difference ΔG in the unit period H is referred to as the differential integrated value GQ. Then, the value obtained by dividing this differential integrated value GQ by the unit period H is referred to as the average variation amount GV. On the other hand, the value obtained by multiplying the maximum difference component ΔGX in the unit period H by a predetermined coefficient K is referred to as the characteristic variation amount GK. The second condition of the second embodiment is that the average variation amount GV is equal to or greater than the characteristic variation amount GK. As described in the first embodiment, the maximum difference component ΔGX is the value obtained by subtracting the start air volume GS from the maximum air volume GX. The predetermined coefficient K is predetermined as "0.5".

[0036] As shown in FIG. 4, when the maximum difference component ΔGX is equal to or greater than the first determination value U1 in step S30 (step S30: YES), the diagnostic device 50 proceeds with the process to step S40. Then, in step S40, the diagnostic device 50 performs the following process. As shown in FIG. 5, first, the diagnostic device 50 calculates an air quantity difference ΔG for each of the intake air quantities G that constitute the time series of the first analysis data D1 in the same manner as in step S40 of the first embodiment. After that, the diagnostic device 50 multiplies the value obtained by integrating all the calculated air quantity differences ΔG by the time interval during which a detection signal is received from the air flow meter 72. Then, the diagnostic device 50 sets the obtained value as the differential integrated value GQ. Then, the diagnostic device 50 calculates an average variation amount GV by dividing this differential integrated value GQ by the unit period H. After that, the diagnostic device 50 calculates, as a characteristic variation amount GK, a value obtained by multiplying the maximum difference component ΔGX calculated in step S30 by a predetermined coefficient K. Then, the diagnostic device 50 compares this average variation amount GV with the characteristic variation amount GK. When the average variation amount GV is less than the characteristic variation amount GK, the diagnostic device 50 determines that the second condition is not satisfied (step S40: NO). On the other hand, when the average variation amount GV is equal to or greater than the characteristic variation amount GK, the diagnostic device 50 determines that the second condition is satisfied (step S40: YES). In this case, since the transition of the intake air quantity G in the unit period H acquired in step S20 satisfies both the first condition and the second condition, the diagnostic device 50 specifies the target unit period H as the diagnostic target period. The series of processes in steps S30 and S40 for specifying the diagnostic target period is the second process, similar to the first embodiment. When the diagnostic device 50 specifies the unit period H as the diagnostic target period, it proceeds with the process to step S50 and subsequent steps.

[0037] As the operation and effects of the second embodiment, the reason for setting the above-described second condition in the second embodiment will be explained. For this explanation, consider the values obtained by multiplying the average fluctuation amount GV and the characteristic fluctuation amount GK by the unit period H, respectively. As described above, the characteristic fluctuation amount GK is a value equal to half of the maximum difference amount ΔGX. The value obtained by multiplying this characteristic fluctuation amount GK by the unit period H corresponds to the integrated value of the air amount difference ΔG in the linear increase pattern in which the intake air amount G linearly increases from the start period H1 of the unit period H and reaches the maximum air amount GX at the end period H2, as shown by the one-dot chain line in FIG. 5. On the other hand, the value obtained by multiplying the average fluctuation amount GV by the unit period H represents the differential integrated value GQ, which is the actual integrated value of the air amount difference ΔG in the unit period H, shown by the hatched area in FIG. 5. Therefore, in the second condition, substantially, the integrated value of the air amount difference ΔG in the linear increase pattern is compared with the integrated value of the actual air amount difference ΔG. When the second condition is satisfied, it is expected that the intake air amount G will continue to increase at a high rate of change over the linear increase pattern, or the intake air amount G will increase rapidly at the initial stage of the unit period H as shown by the solid line in FIG. 5 and the air amount difference ΔG will remain large thereafter. In these cases, the actual air amount difference ΔG at each timing of the unit period H becomes larger than the air amount difference ΔG in the linear increase pattern. By adopting such a second condition, as in the first embodiment, it is highly likely that the unit period H showing a transition such as the rapid increase case shown by the two-dot chain line in FIG. 5 can be excluded from the diagnosis target period. And it becomes highly likely that only the case where the fluctuation amount of the PCV pressure W is large not temporarily but over a long period can be specified as the diagnosis target period. By extracting such a diagnosis target period and determining the presence or absence of a leakage abnormality, false determination regarding the presence or absence of the leakage abnormality can be suppressed.

[0038] <Modified Example> Each of the above embodiments can be implemented with the following modifications. Each of the above embodiments and the following modified examples can be implemented in combination with each other within a technically consistent range.

[0039] ·The method for determining the presence or absence of leakage abnormality is not limited to the example described in the above first embodiment. The method for determining the presence or absence of leakage abnormality may be based on the PCV integrated value Y. For example, as in Patent Document 1, the PCV integrated values Y for a plurality of diagnostic target periods may be integrated, and the presence or absence of leakage abnormality may be determined by comparing the integrated value with an appropriate threshold value. The content of the diagnostic process may be changed so as to realize such an aspect.

[0040] ·The index value reflecting the variation amount of the PCV pressure W is not limited to the PCV integrated value Y. This index value may be any value as long as it reflects the variation amount of the PCV pressure W from the start period to the end period of the diagnostic target period.

[0041] ·The relationship between the second determination value U2 and the starting air amount GS is not limited to the example described in the above first embodiment. The same applies to the relationship between the first determination value U1 and the starting air amount GS. The relationship between the second determination value U2 and the starting air amount GS may be set so as to satisfy the necessary condition that the difference in the PCV integrated value Y becomes clear between the occurrence and the normal state of the leakage abnormality, and the case where the air amount difference ΔG is small continues for a long time can be excluded. The same applies to the first determination value U1 in this regard. In addition, in order to satisfy the above necessary conditions, when the starting air amount GS is the first value, it is preferable that the second determination value U2 is larger than when the starting air amount GS is the second value larger than the first value. The same can be said for the first determination value U1.

[0042] ·It is not essential to define the second determination value U2 in association with the starting air amount GS. The same applies to the first determination value U1 in this regard. If the above necessary conditions are satisfied, either one or both of these two determination values may be fixed values.

[0043] ·It is not essential for the first determination value U1, the second determination value U2, the reference time P, and the unit period H to satisfy the above determination relationship. Each parameter may be set to an appropriate value so as to satisfy the above necessary conditions.

[0044] · Even when the second condition of the second embodiment is adopted, similar to the above, the method of determining the first determination value U1 can be appropriately changed. · The predetermined coefficient K is not limited to "0.5". The predetermined coefficient K may be any value greater than "0" and less than "1". When the predetermined coefficient K is changed from "0.5", the value obtained by multiplying the characteristic variation amount GK by the unit period H can be regarded as a value obtained by increasing or decreasing the integrated value of the air amount difference ΔG in the above linear increase pattern by a predetermined magnification. By increasing or decreasing the characteristic variation amount GK in this way, the ease of satisfying the second condition can be adjusted. While appropriately incorporating such adjustments, by comparing the characteristic variation amount GK, which is an index indicating the manner of increase in the intake air amount G and thus the persistence of the state where the air amount difference ΔG is large, with the average variation amount GV, there is a high possibility that only cases where the variation amount of the PCV pressure W is large not temporarily but over a long period can be specified as the diagnosis target period. If such a diagnosis target period is extracted and the presence or absence of a leakage abnormality is determined, false determination regarding the presence or absence of the leakage abnormality can be suppressed.

[0045] · The predetermined coefficient K is not limited to a fixed value. For example, the predetermined coefficient K may be increased or decreased according to the starting air amount GS. · The overall configuration of the internal combustion engine 10 is not limited to the example described in the first embodiment. For example, the PCV pressure sensor 35 may be a sensor that detects a gauge pressure, which is a relative pressure based on the atmospheric pressure M. The blow-by gas passage 31 may be a passage that directly connects the crankcase 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. As the supercharger 11, something other than an exhaust-driven type may be adopted.

Explanation of Signs

[0046] 10... Internal combustion engine 11... Supercharger 13... Crankcase 24... Intake passage 31... Blow-by gas passage 35... PCV pressure sensor 50... Diagnostic device 72... Air flow meter

Claims

1. For an internal combustion engine provided with a supercharger, a blow-by gas passage communicating a portion upstream of the compressor wheel of the supercharger in the intake passage 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 an air flow meter for detecting an intake air amount, a first process of acquiring a transition of the intake air amount in a unit period; a second process of specifying the unit period as a diagnosis target period of the blow-by gas passage when the transition of the intake air amount in the acquired unit period satisfies both a predetermined first condition and a second condition; a third process of calculating an index value reflecting a variation amount of the PCV pressure from the start period to the end period of the diagnosis target period; a fourth process of determining the presence or absence of an abnormality in the blow-by gas passage based on the index value of the diagnosis target period, and execute the first condition is that in the unit period, the maximum value of the intake air amount in the unit period is larger than a start air amount, which is the intake air amount at the start of the unit period, by a predetermined first determination value or more; the second condition is that in the unit period, an integrated time in a state where the intake air amount is larger than a predetermined second determination value, which is a value smaller than the start air amount by the first determination value, is equal to or longer than a reference time, which is a value smaller than the unit period An abnormality diagnosis device for an internal combustion engine.

2. A ratio between the unit period and the first determination value is equal to a ratio between a value obtained by subtracting the reference time from the unit period and the second determination value The abnormality diagnosis device for an internal combustion engine according to Claim 1.

3. When the start air amount is a first value, the second determination value is larger than when the start air amount is a second value larger than the first value The abnormality diagnosis device for an internal combustion engine according to Claim 2.

4. For an internal combustion engine provided with a supercharger, a blow-by gas passage communicating a portion upstream of the compressor wheel of the supercharger in the intake passage 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 an air flow meter for detecting an intake air amount, a first process of acquiring a transition of the intake air amount in a unit period; When the transition of the intake air amount in the obtained unit period satisfies both a predetermined first condition and a second condition, a second process of specifying the unit period as a diagnosis target period of the blow-by gas passage, a third process of calculating an index value reflecting the amount of change in the PCV pressure from the start period to the end period of the diagnosis target period, a fourth process of determining the presence or absence of an abnormality in the blow-by gas passage based on the index value in the diagnosis target period, are executed, The first condition is that, in the unit period, the maximum value of the intake air amount in the unit period is larger than a predetermined first determination value compared to the starting air amount which is the intake air amount at the start of the unit period, The second condition is that the average variation amount, which is the value obtained by dividing the integrated value of the difference between the intake air amount and the starting air amount in the unit period by the unit period, is equal to or greater than the value obtained by multiplying a predetermined coefficient, which is a value greater than 0 and less than 1, by the value obtained by subtracting the starting air amount from the maximum value of the intake air amount in the unit period. An abnormality diagnosis device for an internal combustion engine.

5. The predetermined coefficient is 0.5 The abnormality diagnosis device for an internal combustion engine according to claim 4.

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