Abnormality diagnostic device for internal combustion engine

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 technology]

[0002] Blow-by gas may leak from the combustion chamber of an internal combustion engine to the crankcase. The blow-by gas flows through a blow-by gas passage and is returned to 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, etc.). [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, there is a risk that the accuracy of the diagnosis may decrease due to the behavior of the pressure. Therefore, an object of the present invention is to provide an abnormality diagnosis device for an internal combustion engine that is capable of improving the accuracy of the diagnosis. [Means for solving the problem]

[0005] The above object can be achieved by an abnormality diagnosis device for an internal combustion engine comprising 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 integrating unit that accumulates the difference between the reference value and the pressure from the point in time when the pressure falls below the reference value to obtain an integrated value, and a diagnosing unit that diagnoses an abnormality in the passage based on the integrated value, wherein if there is no peak in the pressure, the setting unit sets the reference value based on a state of the internal combustion engine, and if there is a peak in the pressure, the setting unit sets the peak as the reference value.

[0006] If the pressure does not have a peak at a 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 a state of the internal combustion engine at the first time point, the integrating unit may start integrating from the first time point, and at the second time point the setting unit may set the peak to the reference value and the integrating unit may start integrating from the second time point, and the diagnosing unit may diagnose an abnormality based on the integrated value from the second time point.

[0007] When 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 as the reference value.

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

[0009] The diagnosing unit may diagnose the passage as normal when the integrated value is equal to or greater than a predetermined value, and may diagnose the passage as abnormal when the integrated value is less than the predetermined value. Effect of the Invention

[0010] It is possible to provide an abnormality diagnosis device for an internal combustion engine that can improve diagnostic accuracy. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram illustrating an internal combustion engine and an abnormality diagnosis device. [Diagram 2] FIG. 2 is a flowchart illustrating a process according to the embodiment. [Diagram 3] FIG. 3 is a flowchart illustrating a process according to the embodiment. [Figure 4] 4(a) and 4(b) are diagrams illustrating time charts in the embodiment. [Diagram 5] 5(a) and 5(b) are diagrams illustrating time charts in the embodiment. [Figure 6]6(a) and 6(b) are diagrams illustrating time charts in a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The abnormality diagnosis device for an internal combustion engine according to the present embodiment will be described below with reference to the drawings. However, the dimensions, ratios, etc. of each part in the drawings may not be illustrated to be completely consistent with the actual ones. Also, some details may be omitted in the drawings.

[0013] 1 is a schematic diagram illustrating an internal combustion engine 10 and an abnormality diagnosis device. An ECU (Electronic Control Unit) 40 functions as the abnormality diagnosis device. The abnormality diagnosis 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 has a cylinder block and a crankcase (not shown). The cylinder head 12 is attached to the cylinder block. The head cover 14 covers the cylinder head 12. An intake passage 20 and an exhaust passage 24 are connected to the cylinder head 12.

[0015] The crankcase houses a crankshaft. The pistons are connected to the crankshaft via connecting rods. A combustion chamber is defined in the cylinder head 12. Air that flows through an intake passage is introduced into the combustion chamber. Fuel is injected from a fuel injection valve (not shown). The mixture of fuel and air is burned in the combustion chamber, causing the piston to reciprocate and the crankshaft to rotate. Exhaust gas generated by the combustion is discharged into an 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 this order from the upstream side. The air flow meter 26 detects the flow rate (air volume) of air flowing through the intake passage 20. The throttle valve 28 adjusts the volume of air. The larger the opening of the throttle valve 28, the larger the air volume. The smaller the opening, the smaller the air volume. The turbine 18 is provided in the exhaust passage 24.

[0017] The compressor 17 and the turbine 18 are connected to form the turbocharger 16. Exhaust gas 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 the 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 downstream side of the compressor 17 of the intake passage 20. A bypass valve 23 is provided in the middle of the bypass passage 22. By opening the bypass valve 23, air bypasses the compressor 17 and flows to the internal combustion engine 10. By closing the bypass valve 23, more air flows to the compressor 17 and is supercharged.

[0019] A space 15 is defined by the head cover 14 and the cylinder head 12 of the internal combustion engine 10. A 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. Blow-by gas that leaks from the combustion chamber into 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 a 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 of the intake passage 20. The blow-by gas in the space 15 flows through the blow-by gas passage 34, returns to the intake passage 20, and is supplied to the internal combustion engine 10 together with 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 drops and becomes a negative pressure lower than atmospheric pressure. 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 drops, for example, to a pressure lower than atmospheric pressure. If an abnormality occurs in the blow-by gas passage 34, the pressure in the blow-by gas passage 34 becomes difficult to drop. For example, if the blow-by gas passage 34 is disconnected or damaged, the blow-by gas passage 34 is opened to the atmosphere. As a result, the pressure becomes approximately the same as atmospheric pressure.

[0022] The ECU 40 is an abnormality diagnosis device and includes a calculation 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 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 setting unit 42, an integrating unit 44, and a diagnosing unit 46. The setting unit 42 sets a reference value for the pressure in the blow-by gas passage 34. The integrating 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 integrating unit 44 does not perform integration. The diagnosing unit 46 diagnoses the blow-by gas passage 34 based on the integrated value and determines whether it is normal or abnormal.

[0024] 2 and 3 are flow charts illustrating the process according to the embodiment. The ECU 40 judges whether or not the pressure monitor condition is satisfied (step S10). The monitor condition is determined by the state of the internal combustion engine 10, and may be determined by the amount of air, for example. When the amount of air changes from a decrease to an increase, the monitor condition is deemed satisfied. If the judgment is negative (No), the process ends. If the judgment is positive (Yes), the ECU 40 judges whether or not the monitor condition has just been satisfied (step S12). For example, if the time elapsed since the satisfaction of the monitor condition is within a few milliseconds (ms), the judgment is deemed positive. The setting unit 42 stores the pressure when the monitor condition is satisfied as a reference value (step S14).

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

[0026] As shown in FIG. 3, the integrating unit 44 integrates the difference between the reference pressure value and the pressure detected by the pressure sensor 32 to calculate the integrated value S (step S22). The integrating unit 44 also counts up the integrated time (step S24). The integrating unit 44 judges whether the integrated time t has reached a predetermined time t0 or more (step S26). If the judgment is negative, the process ends. If the judgment is positive, the diagnosing unit 46 judges whether the integrated value S is a predetermined value Sth or more (step S28). If the integrated value S is Sth or more (positive judgment), the diagnosing unit 46 diagnoses that the blow-by gas passage 34 is normal (step S30). If the integrated value S is less than Sth (negative judgment), the diagnosing unit 46 diagnoses that the blow-by gas passage 34 is abnormal (step S32). The process ends here.

[0027] 4(a) to 5(b) are diagrams illustrating time charts in the embodiment. In each diagram, the upper part represents the pressure in the blow-by gas passage 34. The lower part represents the amount of air flowing through the intake passage 20. In each diagram, the shaded part represents the integrated range.

[0028] FIG. 4(a) shows an example in which the blow-by gas passage 34 is normal. In the example of FIG. 4(a), the amount of air changes from a decrease to an increase at time t1 (step S10 in FIG. 2). The setting unit 42 sets the pressure P1 at time t1 as a reference value (step S12). The setting unit 42 sets the peak P1 at time t1 as a 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 sets the peak P2 as a 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 integrates the difference between the reference value P2 and the pressure during the period from time t2 to t3 to calculate the integrated value S (step S22 in FIG. 3). The period t0 from t2 to t3 is, for example, 400 ms.

[0029] FIG. 4(b) shows an example in which the blow-by gas passage 34 is abnormal. In the example of FIG. 4(b), the pressure does not peak and remains close to atmospheric pressure. The amount of air starts to increase at time t4. The setting unit 42 sets the pressure P3 at time t4 as a reference value. After time t4, the pressure falls below the reference value P3. The integrating unit 44 integrates the difference between the reference value P3 and the pressure from time t4 to t5.

[0030] In FIG. 4(a), as the amount of air in the intake passage 20 increases, the pressure in the blow-by gas passage 34 decreases. The integrated value S increases and becomes equal to or greater than the threshold value Sth. The diagnostic unit 46 diagnoses the condition as normal (step S30). In FIG. 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 approximately equal to atmospheric pressure. The integrated value S is small and less than the threshold value Sth. The diagnostic unit 46 diagnoses the condition as abnormal (step S32).

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

[0032] In the example of FIG. 5(b), the amount of air starts to increase at time t10. There are peaks at t11 ​​and t12 after time t10. Peak P6 at time t11 is greater than peak P7 at time t12. The integrating unit 44 calculates the integrated value S using P6 as the reference value without redoing the integration. The larger the integrated value, the higher the accuracy of the diagnosis.

[0033] 6(a) and 6(b) are diagrams illustrating time charts in a comparative example. In the example of Fig. 6(a), the amount of air starts to increase at time t14. Pressure P8 at time t14 is used as a reference value, and integration is performed from t14 to t15.

[0034] In the example of Figure 6(b), pressure P9 at time t16 is set as the reference value. The air volume starts to increase at time t16. However, because the pressure response lags behind the change in air volume, the pressure peaks after time t16. Because the pressure near the peak is greater than the reference value P9, no integration is performed. Because the integrated value S becomes smaller, the accuracy of normal / abnormal diagnosis decreases.

[0035] According to this embodiment, as shown in FIG. 4(b), when there is no pressure peak, the setting unit 42 sets the pressure at the point when the air amount starts to increase as the reference value. As shown in FIG. 4(a), when there is a pressure peak, the setting unit 42 sets the peak pressure as the reference value. The accumulating unit 44 accumulates the difference between the reference value and the pressure. The diagnosing unit 46 performs diagnosis based on the accumulated value. When the accumulated value S is large as shown in FIG. 4(a), the diagnosing unit 46 diagnoses normality. When the accumulated value S is small as shown in FIG. 4(b), the diagnosing unit 46 diagnoses abnormality. Since the reference value is determined according to the behavior of the pressure, the accuracy of diagnosis is improved.

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

[0037] As shown in Figures 5(a) and 5(b), multiple pressure peaks may occur. The integrating unit 44 performs integration from the first peak. This ensures an opportunity for diagnosis. The setting unit 42 sets the larger of the multiple peaks as the reference value. As shown in Figure 5(a), if a later peak P5 is larger than an earlier peak P4, the integrating unit 44 uses the larger peak P5 as the reference value and restarts the integration. The integrated value S becomes larger, improving accuracy.

[0038] When the integrated value S is equal to or greater than the threshold value Sth, the diagnosis unit 46 determines that the operation is normal. When the integrated value S is less than the threshold value Sth, the diagnosis unit 46 determines that the operation is abnormal. The integrated 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 integrated value S.

[0039] In an abnormal state, such as when the blow-by gas passage 34 is disconnected or has a hole, the blow-by gas passage 34 is open to the atmosphere. Therefore, as shown in FIG. 4(b), the pressure does not have a large peak, and is unlikely to decrease with an increase in the amount of air, and remains at approximately atmospheric pressure. The setting unit 42 sets the pressure at the time when the amount of air 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 integrated 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 a decrease to an increase (for example, time t1 in Figure 4(a)). If there is no peak, the pressure at the point in time when the air volume starts to increase becomes the reference value. The condition can be the state of the internal combustion engine 10, and can be something other than the air volume. For example, the condition can be that the temperature of the cooling water of the internal combustion engine 10 is equal to or higher than a predetermined temperature, and that the pressure in the intake passage 20 is equal to or lower than a predetermined value. The period t0 during which the accumulation is performed can be longer or shorter than 400 ms.

[0041] In the above example, 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 a passage connected to the intake passage 20 and through which gas passes, such as an EGR passage.

[0042] Although a preferred embodiment of the present invention has been described in detail above, the present invention is not limited to such a specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0043] 10 internal combustion engine, 12 cylinder head, 13 passage, 14 head cover, 15 space, 16 turbocharger, 17 compressor, 18 turbine, 20 intake passage, 22 bypass passage, 23 bypass valve, 24 exhaust passage, 26 air flow meter, 28 throttle valve, 30 joint, 32 pressure sensor, 34 blow-by gas passage, 40 ECU, 42 setting section, 44 integrating section, 46 diagnosis section

Claims

1. a setting unit connected to the intake passage and configured to determine a reference value for a pressure in the passage through which gas flows; an integrating unit that integrates a difference between the reference value and the pressure from a point in time when the pressure falls below the reference value to obtain an integrated value; a diagnosis unit for diagnosing 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 a state of the internal combustion engine, When the pressure has a peak, the setting unit sets the peak as the reference value.

2. When the pressure does not have a peak at a first time point and the pressure peaks at a second time point after the first time point, the setting unit sets the reference value based on a state of the internal combustion engine at the first time point, and the integrating unit starts integration 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 integration from the second time point, 2. The abnormality diagnosis device for an internal combustion engine according to claim 1, wherein the diagnosis unit diagnoses an abnormality based on an integrated value from the second point in time.

3. 3. The internal combustion engine abnormality diagnosis device according to claim 1, wherein, when the pressure has a first peak and a second peak, the setting unit sets the larger of the first peak and the second peak as the reference value.

4. 3. The abnormality diagnosis device for an internal combustion engine according to claim 1, wherein, when there is no peak in the pressure, the setting unit sets the reference value based on an air amount in the internal combustion engine.

5. The diagnostic unit diagnoses that the passage is normal when the integrated value is equal to or greater than a predetermined value, 3. The abnormality diagnosis device for an internal combustion engine according to claim 1, wherein the diagnosing unit diagnoses that the passage is abnormal when the integrated value is less than a predetermined value.

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