Abnormality diagnostic device for internal combustion engine

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 into the intake passage. Technologies for detecting abnormalities in the blow-by gas passage based on the pressure in the blow-by gas passage have been developed (for example, Patent Document 1, etc.).

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 capable of improving 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, which includes 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 integrates the difference between the reference value and the pressure from the time when the pressure falls below the reference value to obtain an integrated 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 pressure sensor may further include a period setting unit that sets the predetermined period based on the amount of air reduction, and when the amount of air reduction at a first time point is equal to or greater than the predetermined amount and when the amount of air reduction at a 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 that is the predetermined period for the first time point and sets a second period that is the predetermined period for the second time point, and the reference value setting unit may set the pressure at the time when the later of the first period and the second period has elapsed as the reference value.

[0008] When the amount of the air in the intake passage that has decreased is less than the predetermined amount, the reference value setting unit may set the pressure at a point in time when the air is increasing as the reference value.

[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) to 4(c) are diagrams illustrating time charts in the embodiment. [Diagram 5] 5(a) to 5(d) 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. 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, the pressure in the blow-by gas passage 34 becomes difficult to change. For example, when the blow-by gas passage 34 is disconnected or 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 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 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 integrating 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 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 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 for the pressure.

[0024] 2 and 3 are flow charts illustrating the process according to the embodiment. The ECU 40 acquires the air volume from the air flow meter 26, and calculates the reduction amount dG of the air volume at regular time intervals (e.g., every 160 ms). The period setting unit 48 determines whether the reduction amount dG from the air volume 160 ms ago is equal to or greater than 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 (predetermined period) (step S12). If the determination is negative (No) in step S10, the period setting unit 48 regards the delay d as 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 is equal to or greater than 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 monitor condition is satisfied (step S18). The monitor condition is determined by the state of the internal combustion engine 10, and may be determined by the air amount, for example. As an example, the monitor condition may be satisfied when the air amount transitions from a decrease to an increase. If the determination is negative (No) in step S18, the processing ends. If the determination is positive (Yes), the ECU 40 determines whether the monitor condition has just been satisfied (step S20). For example, if the time that has elapsed since the monitor condition was satisfied is within a few ms, the determination is positive.

[0026] 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 when the delay d has elapsed becomes the reference value. If d=0, the pressure when the monitoring condition is satisfied becomes the reference value.

[0027] After the negative determination in step S20 or step S22, 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 S24). The integrating unit 44 also counts up the integrated time (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 diagnosing unit 46 determines whether the integrated value S is a predetermined value Sth or more (step S30). If the integrated value S is Sth or more (positive determination), the diagnosing 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 diagnosing 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) are diagrams illustrating time charts in the embodiment. In each of Figures 4(a) to 4(c), the upper part represents the pressure in the blow-by gas passage 34. The lower part represents the amount of air Ga flowing through the intake passage 20. In each diagram, the shaded part represents the integrated range.

[0029] FIG. 4(a) shows an example in which the blow-by gas passage 34 is normal and the internal combustion engine 10 decelerates significantly. When a vehicle equipped with the internal combustion engine 10 decelerates, the internal combustion engine 10 reduces the amount of air to be sucked in and decelerates. The ECU 40 calculates the difference dG between the amount of air 160 ms before and the current amount of air. Corresponding to the deceleration of the internal combustion engine 10, dG becomes equal to or greater than dGth (e.g., −8 g / s) at time t1. The period setting unit 48 sets the delay d (step S12). The delay d is longer as the absolute value of the amount of change in air dG is larger, and shorter as the absolute value is smaller. For example, counting of the delay d is started from time t1 (step S14). Around time t2, the amount of air changes from a decrease to an increase (step S18 in FIG. 2). The pressure at time t2 is P1. At 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 a reference value (step S22).

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

[0031] FIG. 4(b) shows an example in which 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. The amount of air has increased at time t6, but the pressure remains close to atmospheric pressure due to the blow-by gas passage 34 being disconnected, etc. The reference pressure P3 is also approximately the same as atmospheric pressure. The integrating unit 44 integrates the difference between the reference pressure P3 and the pressure during the period from time t7 to t8.

[0032] 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 S32). 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 S34).

[0033] FIG. 4(c) is an example in which the blow-by gas passage 34 is normal and the internal combustion engine 10 does not decelerate significantly. The change in the amount of air dG is less than dGth. Assume that the monitor conditions are arranged at time t9. The reference value setting unit 42 sets the pressure P4 immediately after the establishment as the reference value (step S22). The integrating unit 44 performs integration from t9 to t10. The integrated value S is equal to or greater than the threshold value Sth. The diagnosis unit 46 diagnoses the condition as normal (step S32). If the change in the amount of air dG is less than dGth and the blow-by gas passage 34 is abnormal, the pressure is near atmospheric pressure as in the example of FIG. 4(b), so the integrated value S is less than the threshold value Sth. The diagnosis unit 46 diagnoses the condition as abnormal (step S34).

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

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

[0036] In the example of Fig. 5(c), at time t14 when the counting of delay d2 begins, the remaining time of delay d1 is greater than delay d2. That is, time t15 when delay d1 ends is later than time t16 when delay d2 ends. Period setting unit 48 uses delay d1. Reference value setting unit 42 sets the pressure at the end of delay d1 as the reference value.

[0037] In the example of Fig. 5(d), at time t14 when the count of delay d2 begins, delay d2 is greater than the remaining time of delay d1. That is, time t17 when delay d2 ends is later than time t15 when delay d1 ends. Period setting unit 48 adopts delay d2. Reference value setting unit 42 sets the pressure at the end of delay d2 as the reference value.

[0038] 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 t18. The pressure P7 at time t18 is set as a reference value, and integration is performed from t18 to t19.

[0039] In the example of Figure 6(b), the air volume begins to increase at time t20. The pressure P8 at time t20 is set 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. Because the pressure near the peak is greater than the reference value P8, no integration is performed. Because the integrated value S becomes smaller, the accuracy of the normal / abnormal diagnosis decreases.

[0040] According to this embodiment, as shown at time t1 in FIG. 4(a), the air amount Ga decreases as the internal combustion engine 10 decelerates. When the change in the air amount dG is equal to or greater than the threshold value dGth, the period setting unit 48 sets a delay d. The reference value setting unit 42 sets the pressure at time t3, when the delay d has elapsed since time t1, 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. 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 response to the deceleration. Since the pressure is set as the reference value, the accumulated value S becomes large. The accuracy of the diagnosis is improved.

[0041] Since the air volume decreases in response to the deceleration of the internal combustion engine 10, deceleration can be detected from the air volume. For example, when the reduction amount dG of air in the intake passage 20 becomes equal to or greater than a predetermined amount dGth, a delay d is determined. The reference value setting unit 42 sets the pressure after the delay d has elapsed as the reference value. The pressure response to the reduction in the air volume is delayed. Since the reference value is set according to the response delay, the integrated value S becomes large. The accuracy of diagnosis is improved. The deceleration of the internal combustion engine 10 may be detected from an index other than the air volume, such as the vehicle speed, and the pressure at the time when the delay d has elapsed from the time of large deceleration may be set as the reference value.

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

[0043] In the example of Fig. 4(c), the decrease in the air volume dG is less than dGth. The period setting unit 48 does not set the delay d. The reference value setting unit 42 sets the pressure at the time when the air volume is increasing (for example, t9) as the reference value. Diagnosis is possible even if the air volume is not greatly decreased.

[0044] 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.

[0045] 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 opened to the atmosphere. As shown in FIG. 4(b), the pressure is not likely to decrease with an increase in the amount of air, and remains at approximately atmospheric pressure. The reference value 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.

[0046] The condition for monitoring the pressure may be that the amount of air is increasing, or that the amount of air is shifting from a decrease to an increase. Any condition other than the amount of air may be used as long as it is the state of the internal combustion engine 10. For example, the condition may be that the temperature of the cooling water of the internal combustion engine 10 is equal to or higher than a predetermined temperature, or that the pressure in the intake passage 20 is equal to or lower than a predetermined value. The timing for starting subtraction of the delay may be when the delay is set as shown in FIG. 4(a), or when the amount of change dG of the air becomes positive as shown in FIG. 5(c) and FIG. 5(d). The period t0 during which the integration is performed may be longer or shorter than 400 ms.

[0047] 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.

[0048] 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]

[0049] 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 reference value setting unit, 44 integrating unit, 46 diagnosis unit, 48 period setting unit

Claims

1. a reference value setting unit that determines a reference value for a pressure in a passage connected to an intake passage of the internal combustion engine; 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, The reference value setting unit sets the reference value to a pressure a predetermined period after the internal combustion engine starts to decelerate.

2. 2. The abnormality diagnosis device for an internal combustion engine according to claim 1, wherein the reference value setting unit sets the reference value to the pressure after the predetermined period of time from the point in time when the amount of air in the intake passage has decreased by a predetermined amount or more.

3. a period setting unit that sets the predetermined period based on the amount of air reduced, When the amount of reduction in the air is equal to or greater than the predetermined amount at a first time point and the amount of reduction in the air is equal to or greater than the predetermined amount at a second time point after the first time point, the period setting unit sets a first period that is the predetermined period for the first time point and sets a second period that is the predetermined period for the second time point; 3. The abnormality diagnosis device for an internal combustion engine according to claim 2, wherein the reference value setting unit sets the pressure at a point in time when one of the first period and the second period, whichever ends later, has elapsed as the reference value.

4. 4. The abnormality diagnosis device for an internal combustion engine according to claim 2, wherein, when the amount of decrease in the air in the intake passage is less than the predetermined amount, the reference value setting unit sets the pressure at a point in time when the air is increasing as the reference value.

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 the predetermined value.

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