Internal combustion engine anomaly diagnostic device

Abstract

To provide an abnormality diagnostic device for an internal combustion engine capable of improving diagnostic accuracy.SOLUTION: An abnormality diagnostic device for an internal combustion engine includes: a reference value setting section that sets a reference value relative to pressure in a passage connected to an intake passage of the internal combustion engine; an integrating section that integrates a difference between the reference value and the pressure from the time when the pressure has fallen below the reference value and acquires an integrated value; and a diagnostic section that diagnoses an abnormality of the passage on the basis of the integrated value. The reference value setting section sets pressure after a predetermined period from the time when the internal combustion engine decelerates as the reference value.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] Blow-by gas may leak from the combustion chamber of an internal combustion engine into the crankcase. The blow-by gas flows through a blow-by gas passage and is refluxed to the intake passage. Techniques for detecting an abnormality in the blow-by gas passage based on the pressure in the blow-by gas passage have been developed (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, due to the behavior of the pressure, the accuracy of the diagnosis may decrease. Therefore, an object is to provide an abnormality diagnosis device for an internal combustion engine that can improve the diagnosis accuracy.

Means for Solving the Problems

[0005] The above object can be achieved by an abnormality diagnosis device for an internal combustion engine, comprising a reference value setting unit that determines a reference value for the pressure in a passage connected to the intake passage of the internal combustion engine, an integration unit that obtains an integrated value by integrating the difference between the reference value and the pressure from the time when the pressure falls below the reference value, and a diagnosis unit that diagnoses an abnormality in the passage based on the integrated value. The reference value setting unit sets the pressure after a predetermined period from the time when the internal combustion engine is decelerating as the reference value.

[0006] The reference value setting unit may set the pressure after the predetermined period from the time when the decrease amount of the air in the intake passage becomes equal to or more than a predetermined amount as the reference value.

[0007] The system includes a period setting unit that sets a predetermined period based on the amount of air reduction, and if the amount of air reduction at a first time is equal to or greater than the predetermined amount, and the amount of air reduction at a second time after the first time is equal to or greater than the predetermined amount, the period setting unit sets a first period which is the predetermined period for the first time, and sets a second period which is the predetermined period for the second time, and the reference value setting unit may set the pressure at the time when the later of the first and second periods has elapsed as the reference value.

[0008] If the amount of air decreasing in the intake passage is less than the predetermined amount, the reference value setting unit may use the pressure at the time when the air is increasing as the reference value.

[0009] The diagnostic unit may diagnose the passage as normal if the cumulative value is equal to or greater than a predetermined value, or it may diagnose the passage as abnormal if the cumulative value is less than the predetermined value. [Effects of the Invention]

[0010] We can provide an internal combustion engine anomaly diagnostic device that can improve the accuracy of the diagnosis. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic diagram illustrating an internal combustion engine and a diagnostic device. [Figure 2] Figure 2 is a flowchart illustrating the process according to the embodiment. [Figure 3] Figure 3 is a flowchart illustrating the process according to the embodiment. [Figure 4] Figures 4(a) to 4(c) illustrate time charts in the embodiment. [Figure 5] Figures 5(a) to 5(d) illustrate time charts in the embodiment. [Figure 6]Figures 6(a) and 6(b) illustrate time charts in comparative examples. [Modes for carrying out the invention]

[0012] The abnormality diagnosis device for the internal combustion engine of this embodiment will be described below with reference to the drawings. However, the dimensions and proportions of each part in the drawings may not perfectly match those of the actual parts. Also, some details may be omitted in the drawings.

[0013] Figure 1 is a schematic diagram illustrating an internal combustion engine 10 and a diagnostic device. The ECU (Electronic Control Unit) 40 functions as a diagnostic device. The diagnostic device is applied to the internal combustion engine 10.

[0014] The internal combustion engine 10 is, for example, a gasoline engine that burns fuel to generate driving force. The internal combustion engine has a cylinder head 12 and a head cover 14, and also a cylinder block and crankcase (not shown). The cylinder head 12 is mounted on the cylinder block. The head cover 14 covers the cylinder head 12. The cylinder head 12 is connected to an intake passage 20 and an exhaust passage 24.

[0015] The crankshaft is housed in the crankcase. The piston is connected to the crankshaft via a connecting rod. The cylinder head 12 is partitioned into a combustion chamber. Air flowing through the intake passage is introduced into the combustion chamber. Fuel is injected from a fuel injector (not shown). The mixture of fuel and air burns in the combustion chamber, causing the piston to reciprocate and the crankshaft to rotate. The exhaust generated by combustion is discharged into the exhaust passage 24.

[0016] In the intake passage 20, an air flow meter 26, a compressor 17, and a throttle valve 28 are arranged in order from the upstream side. The air flow meter 26 detects the flow rate (amount of air) of the air flowing through the intake passage 20. The throttle valve 28 adjusts the amount of air. The larger the opening degree of the throttle valve 28, the greater the amount of air. The smaller the opening degree, the smaller the amount of air. A turbine 18 is provided in the exhaust passage 24.

[0017] The compressor 17 and the turbine 18 are connected to form a supercharger 16. The exhaust flowing through the exhaust passage 24 is blown against the turbine 18, causing the turbine 18 to rotate. The compressor 17 rotates together with the turbine 18. The compressor 17 supercharges the air in the intake passage 20. By introducing high-pressure air into the internal combustion engine 10, the output of the internal combustion engine 10 is improved.

[0018] A bypass passage 22 is connected between the upstream side and the downstream side of the compressor 17 in the intake passage 20. A bypass valve 23 is provided in the middle of the bypass passage 22. By opening the bypass valve 23, the air bypasses the compressor 17 and flows into the internal combustion engine 10. When the bypass valve 23 is closed, more air flows into the compressor 17 and is supercharged.

[0019] A space 15 is partitioned by the head cover 14 and the cylinder head 12 of the internal combustion engine 10. The passage 13 is provided in the cylinder head 12 and the cylinder block and extends from the space 15 to the inside of the crankcase. The blow-by gas leaking from the combustion chamber to the crankcase passes through the passage 13 and accumulates in the space 15.

[0020] The joint 30 is attached to the head cover 14. One end of the blow-by gas passage 34 is connected to the joint 30, and the other end is connected to a position upstream of the compressor 17 in the intake passage 20. The blow-by gas in the space 15 flows through the blow-by gas passage 34, refluxes into the intake passage 20, and is supplied to the internal combustion engine 10 together with the air. The pressure sensor 32 detects the pressure in the blow-by gas passage 34.

[0021] When the throttle valve 28 opens, air flows into the internal combustion engine 10. The pressure in the intake passage 20 decreases and becomes a negative pressure lower than the atmospheric pressure. The blow-by gas flows from the space 15 into the low-pressure intake passage 20. When the blow-by gas flows, the pressure in the blow-by gas passage 34 also becomes low, for example, lower than the atmospheric pressure. When the amount of air in the intake passage 20 decreases, the pressure in the blow-by gas passage 34 increases. When an abnormality occurs in the blow-by gas passage 34, it becomes difficult for the pressure in the blow-by gas passage 34 to change. For example, when the blow-by gas passage 34 is detached and when the blow-by gas passage 34 is damaged, the blow-by gas passage 34 is opened to the atmosphere. Therefore, the pressure becomes approximately the same as the atmospheric pressure.

[0022] The ECU 40 is an abnormality diagnostic device and includes an arithmetic device such as a CPU (Central Processing Unit), and storage devices such as a RAM (Random Access Memory) and a ROM (Read Only Memory). The ECU 40 performs various controls by executing programs stored in the ROM and the storage device. The ECU 40 acquires the pressure detected by the pressure sensor 32 and the amount of air detected by the air flow meter 26. The ECU 40 controls the opening degree of the bypass valve 23 and the opening degree of the throttle valve 28.

[0023] The ECU 40 functions as a reference value setting unit 42, an integration unit 44, a diagnosis unit 46, and a period setting unit 48. The reference value setting unit 42 sets a reference value for the pressure in the blow-by gas passage 34. The integration unit 44 integrates the difference between the pressure and the reference value when the pressure is lower than the reference value. The integration unit 44 does not perform integration when the pressure is higher than the reference value. The diagnosis unit 46 diagnoses the blow-by gas passage 34 based on the integrated value and determines whether it is normal or abnormal. The period setting unit 48 sets the period until the reference value setting unit 42 determines the reference value of the pressure.

[0024] Figures 2 and 3 are flowcharts illustrating the process according to the embodiment. The ECU 40 obtains the amount of air from the airflow meter 26 and calculates the decrease in the amount of air dG at regular intervals (for example, every 160 m seconds). The period setting unit 48 determines whether the decrease in the amount of air dG from 160 m seconds (ms) ago is greater than or equal to a predetermined amount dGth (step S10). dGth is, for example, -8 g / s. If the determination is positive (Yes), the period setting unit 48 sets a delay d (a predetermined period) (step S12). If the determination in step S10 is negative (No), the period setting unit 48 considers the delay d to be zero. After step S12 or if the determination is negative in step S10, the ECU 40 counts up the time (step S14).

[0025] The ECU 40 determines whether the count c has become greater than or equal to the delay d (step S16). If the determination is negative, the count continues (step S14). If the determination is positive, the ECU 40 determines whether the pressure monitoring condition has been met (step S18). The monitoring condition is determined by the state of the internal combustion engine 10, and may be determined by, for example, the amount of air. For example, the monitoring condition may be met when the amount of air changes from decreasing to increasing. If the determination in step S18 is negative (No), the process ends. If the determination is positive (Yes), the ECU 40 determines whether it is immediately after the monitoring condition has been met (step S20). For example, if the elapsed time since the monitoring condition was met is within a few ms, the determination is positive.

[0026] As shown in Figure 3, the reference value setting unit 42 stores the reference value of the pressure (step S22). If the delay d is set to a value other than 0, the pressure at the time the delay d has elapsed becomes the reference value. If d=0, the pressure when the monitoring condition is met becomes the reference value.

[0027] If a negative determination is made in step S20 or after step S22, the integrating unit 44 calculates the integrated value S by integrating the difference between the reference pressure value and the pressure detected by the pressure sensor 32 (step S24). The integrating unit 44 also counts up the time to be integrated (step S26). The integrating unit 44 determines whether the integrated time t has reached a predetermined time t0 or more (step S28). If the determination is negative, the process ends. If the determination is positive, the diagnostic unit 46 determines whether the integrated value S is greater than or equal to a predetermined value Sth (step S30). If the integrated value S is greater than or equal to Sth (positive determination), the diagnostic unit 46 diagnoses that the blow-by gas passage 34 is normal (step S32). If the integrated value S is less than Sth (negative determination), the diagnostic unit 46 diagnoses that the blow-by gas passage 34 is abnormal (step S34). The process ends here.

[0028] Figures 4(a) to 5(d) illustrate time charts in the embodiment. In each of Figures 4(a) to 4(c), the upper section represents the pressure in the blow-by gas passage 34. The lower section represents the amount of air Ga flowing through the intake passage 20. In each figure, the shaded area represents the integrated range.

[0029] Figure 4(a) shows an example where the blow-by gas passage 34 is functioning normally and the internal combustion engine 10 is significantly decelerating. When a vehicle equipped with the internal combustion engine 10 decelerates, the engine reduces the amount of air it takes in to decelerate. The ECU 40 calculates the difference dG between the amount of air 160ms ago and the amount of air at the present time. Corresponding to the deceleration of the internal combustion engine 10, at time t1, dG becomes dGth (e.g., -8g / s) or greater. The period setting unit 48 sets a delay d (step S12). The delay d is longer the larger the absolute value of the change in air amount dG, and shorter the smaller the absolute value. For example, the count of delay d starts from time t1 (step S14). Around time t2, the amount of air transitions from decreasing to increasing (step S18 in Figure 2). The pressure at time t2 is P1. At time t3, after time t2, the count c reaches the delay d. The reference value setting unit 42 sets the pressure P2 at time t3 as the reference value (step S22).

[0030] The pressure responds with a delay to the change in air volume Ga, and at time t3, P2 is higher than P1. After time t3, the pressure falls below P2. The integration unit 44 integrates the difference between the reference pressure P2 and the pressure during the period from time t3 to time t4 and calculates the integrated value S (step S24). The period during which integration is performed (the period from t3 to t4) t0 is, for example, 400 ms.

[0031] Figure 4(b) shows an example where the blow-by gas passage 34 is abnormal and the internal combustion engine 10 decelerates significantly. A delay d is set at time t5. At time t7, the delay d has elapsed and a reference pressure value P3 is set. Although the amount of air has increased at time t6, the pressure remains near atmospheric pressure due to the blow-by gas passage 34 being disconnected, etc. The reference value P3 is also about the same as atmospheric pressure. The integrating unit 44 integrates the difference between the reference value P3 and the pressure for the period from time t7 to t8.

[0032] In Figure 4(a), as the amount of air in the intake passage 20 increases, the pressure in the blow-by gas passage 34 decreases. The cumulative value S becomes large and exceeds the threshold Sth. The diagnostic unit 46 diagnoses it as normal (step S32). In Figure 4(b), for example, the blow-by gas passage 34 is disconnected. Regardless of the amount of air, the pressure in the blow-by gas passage 34 remains at approximately the same level as atmospheric pressure. The cumulative value S is small and below the threshold Sth. The diagnostic unit 46 diagnoses it as abnormal (step S34).

[0033] Figure 4(c) shows an example where the blow-by gas passage 34 is normal and the internal combustion engine 10 does not decelerate significantly. The change in air pressure dG is less than dGth. Assume that the monitoring conditions were set at time t9. The reference value setting unit 42 uses the pressure P4 immediately after establishment as the reference value (step S22). The integration unit 44 performs integration from t9 to t10. The integrated value S is greater than or equal to the threshold Sth. The diagnostic unit 46 diagnoses it as normal (step S32). If the change in air pressure dG is less than dGth and the blow-by gas passage 34 is abnormal, the pressure is near atmospheric pressure, similar to the example in Figure 4(b), so the integrated value S is less than the threshold Sth. The diagnostic unit 46 diagnoses it as abnormal (step S34).

[0034] In the examples shown in Figures 5(a) to 5(d), the internal combustion engine 10 repeatedly decelerates and accelerates. Figure 5(a) represents the amount of air Ga. Figure 5(b) represents the change in air amount dG. Figures 5(c) and 5(d) represent the delay.

[0035] As shown in Figure 5(a), the amount of air Ga increases and decreases repeatedly in accordance with the acceleration and deceleration of the internal combustion engine 10. At time t11 (first time point), the change in air amount dG is greater than or equal to dGth. At time t12, dG becomes a positive value. At time t13 (second time point), the change in air amount dG is again greater than or equal to dGth. At time t14, dG becomes a positive value. The period setting unit 48 sets a delay d1 (first period) in accordance with the decrease in the amount of air at time t11, and sets a delay d2 (second period) in accordance with the decrease in the amount of air at time t13. Delay d1 is subtracted from time t12. Delay d2 is subtracted from time t13.

[0036] In the example in Figure 5(c), at time t14, when the count of delay d2 begins, the remaining time of delay d1 is greater than that of delay d2. That is, the time t15 when delay d1 ends is later than the time t16 when delay d2 ends. The period setting unit 48 adopts delay d1. The reference value setting unit 42 uses the pressure at the time delay d1 ends as the reference value.

[0037] In the example in Figure 5(d), at time t14, when the count of delay d2 begins, delay d2 is longer than the remaining time of delay d1. That is, the time t17 when delay d2 ends is later than the time t15 when delay d1 ends. The period setting unit 48 adopts delay d2. The reference value setting unit 42 uses the pressure at the time delay d2 ends as the reference value.

[0038] Figures 6(a) and 6(b) illustrate time charts in comparative examples. In the example in Figure 6(a), the air volume begins to increase at time t18. Using the pressure P7 at time t18 as the reference value, the pressure is accumulated from t18 to t19.

[0039] In the example in Figure 6(b), the air volume begins to increase at time t20. The pressure P8 at time t20 is used as the reference value. However, because the pressure response lags behind the change in air volume, the pressure peaks at time t21, after time t20. Since the pressure near the peak is greater than the reference value P8, integration is not performed. As the integrated value S becomes smaller, the accuracy of diagnosing normality or abnormality decreases.

[0040] According to this embodiment, as shown at time t1 in Figure 4(a), the amount of air Ga decreases as the internal combustion engine 10 decelerates. When the change in air amount dG is greater than or equal to the threshold dGth, the period setting unit 48 sets a delay d. The reference value setting unit 42 sets the pressure at time t3, after the delay d has elapsed from time t1, as the reference value. The integration unit 44 integrates the difference between the reference value and the pressure. The diagnostic unit 46 performs a diagnosis based on the integrated value. The pressure responds with a delay to the deceleration of the internal combustion engine 10. When the delay d has elapsed, the pressure has increased in accordance with the deceleration. Since this pressure is set as the reference value, the integrated value S becomes larger. The accuracy of the diagnosis is improved.

[0041] As the amount of air decreases in accordance with the deceleration of the internal combustion engine 10, deceleration can be detected from the amount of air. For example, when the amount of air decrease dG in the intake passage 20 exceeds a predetermined amount dGth, a delay d is set. The reference value setting unit 42 uses the pressure after the delay d has elapsed as the reference value. The pressure response to the decrease in the amount of air is delayed. Since a reference value is set according to the delay in the response, the cumulative value S becomes larger. The accuracy of the diagnosis is improved. Alternatively, the deceleration of the internal combustion engine 10 may be detected from indicators other than the amount of air, such as vehicle speed, and the pressure at the point where a delay d has elapsed from the point of significant deceleration may be used as the reference value.

[0042] As shown in Figure 5(b), if the amount of air loss dG at times t11 and t13 is greater than or equal to dGth, the period setting unit 48 sets delays d1 and d2 based on the amount of air loss dG. The larger the absolute value of the amount of loss dG, the longer the corresponding delay. In the example in Figure 5(c), delay d1 finishes later than delay d1 and d2. The reference value setting unit 42 uses the pressure at time t15, when delay d1 has elapsed, as the reference value. In the example in Figure 5(d), delay d2 finishes later than delay d1 and d2. The reference value setting unit 42 uses the pressure at time t17, when delay d2 has elapsed, as the reference value. The pressure rises because a longer waiting time is required after deceleration. By using a higher pressure as the reference value, the accuracy of the diagnosis is improved.

[0043] In the example in Figure 4(c), the decrease in air volume dG is less than dGth. The period setting unit 48 does not set a delay d. The reference value setting unit 42 uses the pressure at the point in time when the air volume is increasing (e.g., t9) as the reference value. Diagnosis is possible even when the air volume has not decreased significantly.

[0044] If the cumulative value S is greater than or equal to the threshold Sth, the diagnostic unit 46 determines that it is normal. If the cumulative value S is less than the threshold Sth, the diagnostic unit 46 determines that it is abnormal. The cumulative value S is determined depending on whether the blow-by gas passage 34 is normal or abnormal. Highly accurate diagnosis is possible based on the cumulative value S.

[0045] In abnormal conditions such as the blow-by gas passage 34 being disconnected or having a hole in it, the blow-by gas passage 34 is opened to the atmosphere. As shown in Figure 4(b), the pressure does not decrease significantly with increasing air volume and remains at approximately atmospheric pressure. The reference value setting unit 42 uses the pressure at the point when the air volume begins to increase as the reference value. The reference value is approximately the same as atmospheric pressure, and the pressure does not change significantly from the reference value. The cumulative value S becomes smaller. Abnormalities can be detected with high accuracy.

[0046] The conditions for monitoring pressure may be an increase in air volume, or a transition from a decrease to an increase in air volume. The condition can be anything related to the state of the internal combustion engine 10, and may not be limited to air volume. For example, the conditions may be that the coolant temperature of the internal combustion engine 10 is above a predetermined temperature, or that the pressure in the intake passage 20 is below a predetermined value. The timing for starting the subtraction of the delay may be at the time the delay is set, as shown in Figure 4(a), or when the change in air volume dG becomes positive, as shown in Figures 5(c) and 5(d). The period t0 during which integration is performed may be longer than 400ms or shorter than 400ms.

[0047] In the example above, the ECU 40 diagnoses the blow-by gas passage 34. Besides the blow-by gas passage 34, the embodiment can also be applied to other passages connected to the intake passage 20 through which gas passes, such as the EGR passage.

[0048] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0049] 10 Internal combustion engine, 12 Cylinder head, 13 Passage, 14 Head cover, 15 Space, 16 Supercharger, 17 Compressor, 18 Turbine, 20 Intake passage, 22 Bypass passage, 23 Bypass valve, 24 Exhaust passage, 26 Airflow meter, 28 Throttle valve, 30 Fitting, 32 Pressure sensor, 34 Blow-by gas passage, 40 ECU, 42 Reference value setting unit, 44 Accumulation unit, 46 Diagnostic unit, 48 Period setting unit

Claims

1. A reference value setting unit that determines a reference value for the pressure in a passage connected to the intake passage of an internal combustion engine, From the point in time when the pressure falls below the reference value, an integration unit calculates the difference between the reference value and the pressure and obtains the integrated value. A diagnostic unit that diagnoses abnormalities in the passage based on the cumulative value, The system comprises a period setting unit that sets a predetermined period based on the amount of air reduction in the intake passage, The reference value setting unit sets the pressure after a predetermined period from the time when the internal combustion engine is decelerating as the reference value. The reference value setting unit sets the pressure after the predetermined period from the point in time when the amount of air lost in the intake passage exceeds a predetermined amount as the reference value. If the amount of air reduction at the first time point is equal to or greater than the predetermined amount, and the amount of air reduction at the second time point after the first time point is equal to or greater than the predetermined amount, the period setting unit sets a first period which is the predetermined period for the first time point, and sets a second period which is the predetermined period for the second time point. The reference value setting unit is an internal combustion engine abnormality diagnosis device in which the pressure at the time when the later of the first and second periods has elapsed is used as the reference value.

2. The diagnostic unit diagnoses the passage as normal if the cumulative value is equal to or greater than a predetermined value. The diagnostic unit diagnoses that the passage is abnormal if the cumulative value is less than the predetermined value, as described in claim 1 for the internal combustion engine abnormality diagnostic device.

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