Internal combustion engine anomaly diagnostic device

Abstract

To provide an abnormality diagnostic device for an internal combustion engine that enables improvement of diagnostic accuracy.SOLUTION: An abnormality diagnostic device for an internal combustion engine includes: a setting section connected to an intake passage to determine a reference value relative to pressure in the passage where gas flows; an integration section that integrates a difference between the reference value and the pressure and acquires an integrated value from the time point when the pressure falls below the reference value; and a diagnostic section that makes a diagnosis of an abnormality of the passage on the basis of the integrated value. When there is no peak in the pressure, the setting section sets the reference value on the basis of a state of the internal combustion engine, and when there is a peak in the pressure, the setting section sets the peak 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 into the intake passage. A technique for detecting an abnormality in the blow-by gas passage based on the pressure in the blow-by gas passage has 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 internal combustion engine abnormality diagnosis device including a setting unit that is connected to an intake passage and determines a reference value for the pressure in a passage through which gas flows, 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. When there is no peak in the pressure, the setting unit sets the reference value based on the state of the internal combustion engine, and when there is a peak in the pressure, the setting unit sets the peak as the reference value.

[0006] If there is no peak in the pressure at the first time point, and the pressure shows a peak at a second time point after the first time point, the setting unit may set the reference value based on the state of the internal combustion engine at the first time point, the accumulating unit may start accumulating from the first time point, the setting unit may set the peak to the reference value at the second time point, the accumulating unit may start accumulating from the second time point, and the diagnostic unit may diagnose an abnormality based on the accumulated value from the second time point.

[0007] If the pressure has a first peak and a second peak, the setting unit may set the larger of the first peak and the second peak to the reference value.

[0008] If there is no peak in the pressure, the setting unit may set the reference value based on the amount of air in the internal combustion engine.

[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 a 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) and 4(b) illustrate time charts in the embodiment. [Figure 5] Figures 5(a) and 5(b) 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 onto 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 an abnormality occurs in the blow-by gas passage 34, it becomes difficult for the pressure in the blow-by gas passage 34 to decrease. For example, when the blow-by gas passage 34 is detached or 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 50 performs various controls by executing programs stored in the ROM and storage devices. The ECU 40 acquires the pressure detected by the pressure sensor 32 and the air amount 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 setting unit 42, an integration unit 44, and a diagnosis unit 46. The 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. When the pressure is higher than the reference value, the integration unit 44 does not perform integration. The diagnosis unit 46 diagnoses the blow-by gas passage 34 based on the integrated value and determines whether it is normal or abnormal.

[0024] Figures 2 and 3 are flowcharts illustrating the process according to the embodiment. The ECU 40 determines whether the pressure monitoring condition has been met (step S10). 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. The monitoring condition is met when the amount of air changes from decreasing to increasing. If the determination 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 S12). For example, if the elapsed time since the monitoring condition was met is within a few milliseconds (a few milliseconds), the determination is positive. The setting unit 42 stores the pressure at the time the monitoring condition was met as a reference value (step S14).

[0025] If a negative determination is made in step S12, or after step S14, the setting unit 42 determines whether or not there is a pressure peak (step S16). At a peak, the time derivative of the pressure changes from a positive value to 0, and then from 0 to a negative value. The setting unit 42 monitors the pressure and detects the peak from the change in the derivative value. If a negative determination is made in step S16, step S22 is performed. If a positive determination is made, the setting unit 42 stores the pressure at the peak as a new reference value (step S18). The integrating unit 44 resets the accumulated value up to the time the new reference value was stored, and also resets the integrating time count (step S20).

[0026] As shown in Figure 3, the integration 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 S22). The integration unit 44 also counts up the time to be integrated (step S24). The integration unit 44 determines whether the integrated time t has reached a predetermined time t0 or more (step S26). 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 S28). 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 S30). 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 S32). The process ends here.

[0027] Figures 4(a) to 5(b) illustrate time charts in the embodiment. In each figure, the upper section represents the pressure in the blow-by gas passage 34. The lower section represents the amount of air flowing through the intake passage 20. In each figure, the shaded area represents the cumulative range.

[0028] Figure 4(a) shows a normal example of the blow-by gas passage 34. In the example of Figure 4(a), the amount of air changes from decreasing to increasing at time t1 (step S10 in Figure 2). The setting unit 42 uses the pressure P1 at time t1 as the reference value (step S12). The setting unit 42 uses the peak P1 at time t1 as the reference value, and the integrating unit 44 starts integrating. The pressure continues to rise after time t1 and has a peak at time t2. The peak value P2 is greater than P1. The setting unit 42 uses the peak P2 as the reference value (step S18). The pressure after time t2 is below the reference value P2. The integrated value with P1 as the reference value and the time count are reset (step S20). The integrating unit 44 calculates the integrated value S by integrating the difference between the reference value P2 and the pressure for the period from time t2 to t3 (step S22 in Figure 3). The period t0 from t2 to t3 is, for example, 400 ms.

[0029] Figure 4(b) shows an example of an abnormal blow-by gas passage 34. In the example in Figure 4(b), the pressure does not have a peak and remains near atmospheric pressure. At time t4, the amount of air begins to increase. The setting unit 42 uses the pressure P3 at time t4 as the reference value. After time t4, the pressure is below the reference value P3. The integration unit 44 integrates the difference between the reference value P3 and the pressure from time t4 to t5.

[0030] 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 30). 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 S32).

[0031] In the examples of Figures 5(a) and 5(b), the pressure has two peaks. As shown in Figure 5(a), the amount of air begins to increase at time t6. The pressure has a peak at time t7 (first peak) and a peak at time t8 (second peak). The setting unit 42 uses the peak P4 at time t7 as the reference value, and the integrating unit 44 starts integrating. The pressure P5 at time t8 is higher than the pressure P4 at time t7. The setting unit 42 uses the higher of the two peaks, P5, as the reference value. The integrated value with P4 as the reference value and the time count are reset (step S20). The integrating unit 44 performs integrating from time t8 to t9 with P5 as the reference value. The integrated value S with pressure P5 as the reference value is greater than the integrated value with pressure P4 as the reference value. The accuracy of the diagnosis is improved.

[0032] In the example shown in Figure 5(b), the amount of air begins to increase at time t10. Peaks are observed at t11 ​​and t12, after time t10. The peak P6 at time t11 is greater than P7 at time t12. The integration unit 44 calculates the integrated value S using P6 as the reference value without redoing the integration. The integrated value becomes larger, and the accuracy of the diagnosis improves.

[0033] 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 t14. Using the pressure P8 at time t14 as the reference value, the pressure is accumulated from t14 to t15.

[0034] In the example in Figure 6(b), the pressure P9 at time t16 is used as the reference value. The air volume begins to increase at time t16. However, because the pressure response lags behind the change in air volume, the pressure peaks after time t16. Since the pressure near the peak is greater than the reference value P9, integration is not performed. As the integrated value S becomes smaller, the accuracy of diagnosing normality or abnormality decreases.

[0035] According to this embodiment, as shown in Figure 4(b), if there is no pressure peak, the setting unit 42 uses the pressure at the point when the air volume begins to increase as the reference value. As shown in Figure 4(a), if there is a pressure peak, the setting unit 42 uses the peak pressure as the reference value. The integrating unit 44 integrates the difference between the reference value and the pressure. The diagnostic unit 46 performs a diagnosis based on the integrated value. If the integrated value S is large, as shown in Figure 4(a), the diagnostic unit 46 diagnoses it as normal. If the integrated value S is small, as shown in Figure 4(b), the diagnostic unit 46 diagnoses it as abnormal. Since the reference value is determined according to the behavior of the pressure, the accuracy of the diagnosis is improved.

[0036] As shown in Figure 4(a), the amount of air begins to increase at time t1 (first time point) before a pressure peak occurs. The setting unit 42 uses the pressure P1 at time t1 as the reference value, and the integration unit 44 performs integration. A peak occurs at the following time t2 (second time point). The setting unit 42 uses the peak P2 as the reference value. The integration unit 44 performs integration from t2. The diagnostic unit 46 performs a diagnosis based on the integrated value S obtained from the integration from t2. Since integration is performed from time t1, a diagnosis is possible even if there is no peak after time t1. If a peak occurs after time t1, the diagnosis is performed based on the integrated value from the peak. This ensures opportunities for diagnosis and improves accuracy.

[0037] As shown in Figures 5(a) and 5(b), multiple peaks may occur in the pressure. The integration unit 44 starts the integration from the first peak to ensure an opportunity for diagnosis. The setting unit 42 uses the largest peak among the multiple peaks as the reference value. As shown in Figure 5(a), if the later peak P5 is larger than the earlier peak P4, the integration unit 44 uses the larger peak P5 as the reference value and recalculates the integration. The integrated value S becomes larger, and the accuracy improves.

[0038] 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.

[0039] In abnormal conditions such as when the blow-by gas passage 34 is disconnected or has a hole in it, the blow-by gas passage 34 is opened to the atmosphere. Therefore, as shown in Figure 4(b), the pressure does not have a large peak and does not decrease easily with increasing air volume, maintaining approximately atmospheric pressure. The 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.

[0040] The condition for monitoring the pressure is that the air volume transitions from decreasing to increasing (for example, time t1 in Figure 4(a)). If there is no peak, the pressure at the point when the air volume begins to increase becomes the reference value. The condition can be anything other than the state of the internal combustion engine 10. For example, the condition could be that the water temperature of the cooling water in 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 period t0 over which the accumulation is performed may be longer or shorter than 400 ms.

[0041] In the example above, the ECU 40 diagnoses the blow-by gas passage 34. In addition to the blow-by gas passage 34, the embodiment can be applied to other passages connected to the intake passage 20 through which gas passes, such as the EGR passage.

[0042] 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 invention as described in the claims. [Explanation of Symbols]

[0043] 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 Setting unit, 44 Accumulation unit, 46 Diagnostic unit

Claims

1. A setting unit connected to the intake passage, which determines a reference value for the pressure in the passage through which the gas flows, 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. The system comprises a diagnostic unit that diagnoses abnormalities in the passage based on the cumulative value, If there is no peak in the pressure, the setting unit sets the reference value based on the state of the internal combustion engine. If the pressure has a peak, the setting unit sets the peak to the reference value, which is an abnormality diagnosis device for an internal combustion engine.

2. If there is no peak in the pressure at the first time point, and the pressure shows a peak at a second time point after the first time point, the setting unit sets the reference value based on the state of the internal combustion engine at the first time point, and the accumulating unit starts accumulating from the first time point. At the second time point, the setting unit sets the peak to the reference value, and the integrating unit starts integrating from the second time point. The diagnostic unit diagnoses an abnormality based on the cumulative value from the second time point, as described in claim 1.

3. An abnormality diagnosis device for an internal combustion engine according to claim 1 or 2, wherein, if the pressure has a first peak and a second peak, the setting unit sets the larger of the first peak and the second peak to the reference value.

4. If there is no peak in the pressure, the setting unit sets the reference value based on the amount of air in the internal combustion engine. An abnormality diagnosis device for an internal combustion engine according to claim 1 or 2.

5. 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 when the cumulative value is less than a predetermined value, as described in claim 1 or 2 for the internal combustion engine abnormality diagnostic device.

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