Internal combustion engine abnormality diagnosis device

Abstract

To provide an abnormality diagnosis device of an internal combustion engine capable of appropriately diagnosing the presence / absence of an abnormality when a detection value of a sensor has pulsation.SOLUTION: A CPU 52 executes a smoothing process M10 with a pressure detection value P by a pressure sensor 62 as input. The CPU 52 diagnoses the presence / absence of an abnormality in a blow-by gas passage 42 or the like based on a diagnostic pressure Psm output by the smoothing process M10. The smoothing process M10 is a process of calculating the diagnostic pressure Psm based on the maximum and minimum values of the detection value P.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] A blow-by gas passage that returns blow-by gas in a crankcase of an internal combustion engine to an intake passage is well known. However, if the blow-by gas passage is separated from the intake passage or is damaged, the blow-by gas may leak to the outside. Therefore, an abnormality diagnosis device that diagnoses the presence or absence of an abnormality in the blow-by gas passage has been proposed in the past, for example, as shown in Patent Document 1 below. This abnormality diagnosis device diagnoses the presence or absence of an abnormality based on a detection value of the pressure in the blow-by gas passage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-186702 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the detected pressure value fluctuates, and therefore there is a risk that the accuracy of diagnosing the presence or absence of an abnormality may decrease due to pressure pulsation. [Means for solving the problem]

[0005] Means for solving the above problems and their effects will be described below. The abnormality diagnosis device for an internal combustion engine is applied to an internal combustion engine equipped with a blow-by gas passage for returning blow-by gas that has flowed from a combustion chamber into a crankcase to an intake passage, and executes a detection value acquisition process for acquiring a detection value of the pressure in the blow-by gas passage, a smoothing process for suppressing fluctuations in the detection value, and a diagnosis process for diagnosing the presence or absence of an abnormality in the blow-by gas passage based on an output value of the smoothing process, wherein the smoothing process includes an extreme value acquisition process for acquiring maximum and minimum values ​​of the detection value, and an output value calculation process for calculating the output value using the maximum and minimum values ​​as inputs, and the output value calculation process includes at least one of a process for reducing the responsiveness of the output value to fluctuations in the detection value when the difference between the maximum and minimum values ​​is large compared to when the difference is small, and a process for calculating the output value according to a simple average of the maximum and minimum values.

[0006] By reducing the responsiveness of the output value to the detection value, the fluctuation of the output value can be suppressed. Here, the appropriate value for the degree of reduction in the responsiveness of the output value to the detection value differs between when the fluctuation of the detection value is large and when it is small. In other words, if an appropriate degree of reduction in the responsiveness is applied when the fluctuation is large to when the fluctuation is small, the responsiveness of the detection value may be excessively reduced. In contrast, by reducing the responsiveness of the output value to the fluctuation of the detection value when the difference between the maximum value and the minimum value is large compared to when the difference is small, the degree of reduction in the responsiveness can be set to an appropriate value. This allows the presence or absence of an abnormality to be diagnosed appropriately based on the output value.

[0007] In addition, the simple average of the maximum and minimum values ​​suppresses fluctuations in the detected value and accurately represents the actual pressure, so that the presence or absence of an abnormality based on the output value can be appropriately diagnosed by calculating the output value according to the simple average value. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing the configuration of an internal combustion engine and a control device according to a first embodiment. [Diagram 2]4 is a flowchart showing a procedure of a process executed by a control device according to the embodiment. [Diagram 3] 4 is a time chart illustrating the pressure fluctuation according to the embodiment. [Figure 4] 13(a) to 13(c) are time charts illustrating the transition of the diagnostic pressure in the embodiment and a comparative example. [Diagram 5] 10 is a flowchart showing a procedure of a process executed by a control device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] <First embodiment> Hereinafter, the first embodiment will be described with reference to the drawings. A compressor 14a of a turbocharger 14 is provided in an intake passage 12 of an internal combustion engine 10 shown in Fig. 1. A throttle valve 16 is provided downstream of the compressor 14a in the intake passage 12. Air in the intake passage 12 flows into a combustion chamber 24 defined by a cylinder head 18, a cylinder block 20, and a piston 22. The reciprocating motion of the piston 22 is converted into the rotational motion of a crankshaft 28. In response to the reciprocating motion of the piston 22, the air-fuel mixture combusted in the combustion chamber 24 is discharged as exhaust gas to an exhaust passage 30. A turbine 14b of the turbocharger 14 is provided in the exhaust passage 30.

[0010] A crankcase 32 is provided at the end of the cylinder block 20 opposite the cylinder head 18. An oil pan 34 is attached to the crankcase 32. The blow-by gas in the crankcase 32 flows through the communication passage 26 into a pressure accumulator 40 defined by the cylinder head 18 and the head cover 29. The blow-by gas in the pressure accumulator 40 is returned to the intake passage 12 through a blow-by gas passage 42. More specifically, the blow-by gas passage 42 is connected to the intake passage 12 upstream of the compressor 14a.

[0011] The control device 50 operates the operating parts of the internal combustion engine 10, such as the throttle valve 16, to control the torque and exhaust component ratio, which are the control variables of the internal combustion engine 10 as the controlled object. The control device includes a CPU 52, a ROM 54, and a peripheral circuit 56. The peripheral circuit 56 includes a circuit that generates a clock signal that regulates the internal operation, a power supply circuit, a reset circuit, and the like. The CPU 52 executes the programs stored in the ROM 54 to control the control variables and to perform various processes, such as abnormality diagnosis processing for the blow-by gas passage.

[0012] FIG. 1 shows a block diagram of the abnormality diagnosis process. That is, the smoothing process M10 is a process for calculating the diagnostic pressure Psm by taking in the detection value P of the pressure in the blow-by gas passage 42 detected by the pressure sensor 62. The diagnostic process M12 takes the intake air amount Ga detected by the air flow meter 64 as an input in addition to the diagnostic pressure Psm. The diagnostic process M12 determines that an abnormality has occurred when the degree of decrease in the diagnostic pressure Psm is equal to or less than a predetermined value when the intake air amount Ga is increasing. That is, when the intake air amount Ga increases, the pressure in the blow-by gas passage 42 decreases due to the intake of air. In contrast, when an abnormality occurs in which the blow-by gas flows out to the outside, the decrease in pressure is slow.

[0013] The smoothing process M10 is a process for suppressing fluctuations in the detection value P. That is, the detection value P has pressure pulsations having a period equal to the interval at which the compression top dead center occurs. Therefore, the smoothing process M10 smoothes the detection value P to generate the diagnostic pressure Psm. This will be described in detail below.

[0014] Fig. 2 shows a detailed procedure of the smoothing process M10. The process shown in Fig. 2 is realized by the CPU 52 repeatedly executing a program stored in the ROM 54, for example, at a predetermined interval. In the following, the step number of each process is represented by a number preceded by "S".

[0015] In the series of processes shown in FIG. 2, the CPU 52 first samples the detection value P(n) (S10). Here, the "n" in parentheses after "P" indicates the timing of sampling. Next, the CPU 52 substitutes a value obtained by subtracting the previous detection value P(n-1) from the detection value P(n) into the differential pressure ΔP (S12). Then, if the differential pressure ΔP is equal to or greater than zero (S14: YES), the CPU 52 substitutes "1" into the state Pstate(n) (S16). On the other hand, if the CPU 52 determines that the differential pressure ΔP is negative (S14: NO), it substitutes "-1" into the state Pstate(n) (S18).

[0016] When completing the processes of S16 and S18, the CPU 52 judges whether or not the sum of the state Pstate(n) and the state Pstate(n-1) is "0" (S20). This process is a process for judging whether or not it is a point in time when the detection value P changes from an increase to a decrease, or from a decrease to an increase. When the CPU 52 judges that it is "0" (S20: YES), it judges whether or not the state Pstate(n) is positive (S22). This process is a process for judging whether or not it is a point in time when the detection value P changes from a decrease to an increase.

[0017] When the CPU 52 determines that the state Pstate is positive (S22: YES), it assigns the detection value P(n) to the minimum value Peakb (S24). That is, the CPU 52 simply regards the current detection value P(n) as the minimum value. On the other hand, when the CPU 52 determines that the state Pstate is equal to or lower (S22: NO), it assigns the detection value P(n) to the maximum value Peak (S26). That is, the CPU 52 simply regards the current detection value P(n) as the maximum value.

[0018] When completing the process of S24, the CPU 52 assigns the value of the counter C to the period T of the pressure pulsation, and then initializes the counter C (S28). When the CPU 52 completes the processes of S26 and S28, it executes the process of substituting the detection value P(n) for the detection value P(n-1), the process of substituting the state Pstate(n) for the state Pstate(n-1), and the process of incrementing the counter C (S30).

[0019] When the CPU 52 completes the process of S30 or when a negative determination is made in the process of S20, the CPU 52 determines whether the period T is equal to or greater than a lower limit TL and equal to or less than an upper limit TH (S32). The lower limit TL and the upper limit TH are variably set according to the rotation speed NE of the crankshaft 28. The median value of a predetermined range determined by the lower limit TL and the upper limit TH is the interval at which the compression top dead center occurs. The lower limit TL and the upper limit TH are values ​​obtained by shifting the interval at which the compression top dead center occurs by a predetermined margin. This process is for determining whether pressure pulsation due to the period T occurs during the interval at which the compression top dead center occurs.

[0020] If the CPU 52 judges positive in the process of S32, it assigns the value obtained by subtracting the minimum value Peakb from the maximum value Peak to the amplitude PP (S34). Next, the CPU 52 calculates the smoothing coefficient K using the amplitude PP as an input (S36). More specifically, the CPU 52 calculates a smaller smoothing coefficient K when the amplitude PP is large than when it is small. Specifically, in a state where map data is stored in advance in the ROM 54, the CPU 52 performs a map calculation to determine the value of the smoothing coefficient K. Here, the map data is data in which the amplitude PP is an input variable and the smoothing coefficient K is an output variable. The smoothing coefficient K is a value greater than "0" and less than "1".

[0021] Next, the CPU 52 subtracts the diagnostic pressure Psm from the detected value P(n) and multiplies the result by the smoothing coefficient K, and assigns the sum of the result and the diagnostic pressure Psm to the diagnostic pressure Psm (S38). This process corresponds to calculating an exponential moving average process value of the detected value P(n). Here, the weighting coefficient by which the detected value P(n) is multiplied is the smoothing coefficient K, and the weighting coefficient by which the diagnostic pressure Psm is multiplied is "1-K".

[0022] When the CPU 52 completes the process of S38 or when a negative determination is made in the process of S32, the CPU 52 temporarily ends the series of processes shown in FIG. Here, the operation and effects of this embodiment will be described.

[0023] The CPU 52 calculates the diagnostic pressure Psm based on the detection value P when predetermined diagnostic conditions, including a condition that the intake air amount Ga increases, are met. 3 shows the fluctuation of the detection value P. The CPU 52 determines the amplitude PP by subtracting the minimum value Peakb from the maximum value Peakt of the detection value P. The CPU 52 then changes the value of the smoothing coefficient K in accordance with the amplitude PP. This allows the diagnosis using the diagnostic pressure Psm to be performed quickly and with high accuracy.

[0024] Fig. 4(a) illustrates the transition of the detection value P and the amount of change InΔP when the intake air amount Ga increases. Fig. 4(a) shows a case where the detection value P is a minimum value at time t1, when the initial value of the detection value for calculating the amount of change InΔP is calculated. In this case, the amount of pressure decrease from time t1 tends to be calculated as a small value. Therefore, even if the pressure is actually normal, it is likely to be determined to be abnormal.

[0025] FIG. 4(b) shows a case where the detection value P becomes a maximum value at time t1 when the initial value of the detection value for calculating the change amount InΔP is calculated. In this case, the amount of pressure decrease from time t1 tends to be calculated as a large value. Therefore, even if there is an abnormality, it is likely to be determined as normal.

[0026] In Fig. 4(c), the solid line indicates the transition of the detection value P and its change amount InΔP. The dashed line indicates the diagnostic pressure Psm according to this embodiment and its change amount InΔP. The two-dot chain line indicates the transition of the value after smoothing processing and its change amount InΔP when the value of the smoothing coefficient K is set smaller than in this embodiment. Note that the change amount InΔP of the detection value P has a range, so the transition between the minimum value and the maximum value is shown.

[0027] As shown in Fig. 4(c), when the detection value P is used, it is difficult to set the change amount InΔP to an appropriate value as a variable indicating the presence or absence of a blow-by gas leakage abnormality. On the other hand, when the smoothing coefficient K is excessively small, the pressure pulsation can be sufficiently suppressed, but the pressure reduction rate becomes slow, so that the time required for diagnosis becomes long. Therefore, there are fewer opportunities to perform diagnosis, and there is a risk that an abnormality cannot be detected promptly.

[0028] According to the present embodiment described above, the following actions and effects can be obtained. (1) As shown in Fig. 3, the CPU 52 determines the time interval between a pair of chronologically adjacent maximum values ​​Peak of the detection value P as the period T of the pressure pulsation. Then, the diagnostic pressure Psm is calculated on the condition that the period T is within a predetermined range. This makes it possible to prevent diagnosis from being performed when the detection value P contains unexpected noise that is different from the pressure pulsation synchronized with the interval at which the compression top dead center occurs.

[0029] <Second embodiment> The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0030] Fig. 5 shows the procedure of the smoothing process M10 according to this embodiment. The process shown in Fig. 5 is realized by the CPU 52 repeatedly executing a program stored in the ROM 54, for example, at a predetermined interval. For convenience, the same step numbers are given to the processes in Fig. 5 that correspond to the processes shown in Fig. 2.

[0031] In the series of processes shown in Fig. 5, when the CPU 52 makes a positive determination in the process of S32, it assigns the simple average value of the maximum value Peakt and the minimum value Peakb to the diagnostic pressure Psm (S40). The simple average value Peakabe is indicated by an asterisk in Fig. 3. When the CPU 52 completes the process of S40, it temporarily ends the series of processes shown in Fig. 5.

[0032] <Correspondence> The correspondence between the matters in the above embodiment and the matters described in the "Means for solving the problem" section above is as follows: The abnormality diagnosis device corresponds to the control device 50. The detection value acquisition process corresponds to the process of S10. The smoothing process corresponds to the smoothing process M10. The diagnosis process corresponds to the diagnosis process M12. The extreme value acquisition process corresponds to the processes of S12 to S26. The output value calculation process corresponds to the processes of S34 to S38 and S40.

[0033] <Other embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0034] In the process of S24, the previous detection value P(n-1) may be substituted for the minimum value Peakb. In the process of S26, the previous detection value P(n-1) may be substituted for the maximum value Peak.

[0035] The process for reducing the responsiveness of the diagnostic pressure Psm to the fluctuation of the detection value P is not limited to the smoothing process. For example, a first-order lag filter process or a second-order lag filter process may be used.

[0036] In the process of S40 in Fig. 5, the simple average value is substituted for the diagnostic pressure Psm, but this is not limited thereto. For example, a value obtained by smoothing the simple average value may be substituted for the diagnostic pressure Psm. Here, the smoothing coefficient K of the smoothing process may be a fixed value. However, the smoothing coefficient K may be variable depending on the amplitude PP.

[0037] The process of S32 may be omitted. In other words, it is not necessary to execute the process of determining whether or not the cycle T corresponds to the interval between occurrences of the compression top dead center. [Explanation of symbols]

[0038] 10. Internal combustion engine 12…Intake passage 14…Turbocharger 18…Cylinder head 20…Cylinder block 26…Communication path 29…Head cover 32…Crankcase 42…Blow-by gas passage 50...Control device

Claims

[Claim 1] The present invention is applied to an internal combustion engine having a blow-by gas passage for returning blow-by gas that has flowed from the combustion chamber into the crankcase to the intake passage, a detection value acquisition process for acquiring a detection value of a pressure in the blow-by gas passage; A smoothing process for suppressing fluctuations in the detection value; a diagnosis process for diagnosing whether or not there is an abnormality in the blow-by gas passage based on the output value of the smoothing process; The smoothing process is an extreme value acquisition process for acquiring maximum and minimum values ​​of the detection value; an output value calculation process of calculating the output value using the maximum value and the minimum value as inputs, An abnormality diagnosis device for an internal combustion engine, wherein the output value calculation process includes a process for reducing the responsiveness of the output value to fluctuations in the detection value when the difference between the maximum value and the minimum value is large compared to when the difference is small.

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