Patent ID: 12215646

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, an abnormality diagnosis device for an internal combustion engine according to an embodiment of the present disclosure will be described with reference to the drawings. However, in the drawings, the dimensions, ratios, and the like of the respective parts may not be shown so as to completely coincide with the actual ones. Further, in some drawings, details are omitted.

FIG.1is a schematic diagram illustrating an internal combustion engine10and an abnormality diagnosis device. ECU (ElectronicControlUnit)40functions as an abnormality diagnosis device. The abnormality diagnosis device is applied to the internal combustion engine10.

The internal combustion engine10is, for example, a gasoline engine, and burns fuel to generate a driving force. The internal combustion engine has a cylinder head12and a head cover14, and also has a cylinder block and a crankcase (not shown). The cylinder head12is attached to a cylinder block. The head cover14covers the cylinder head12. An intake passage20and an exhaust passage24are connected to the cylinder head12.

A crankshaft is accommodated in the crankcase. The piston is connected to the crankshaft via a connecting rod. A combustion chamber is defined in the cylinder head12. Air flowing through the intake passage is introduced into the combustion chamber. Fuel is injected from a fuel injection valve (not shown). When the air-fuel mixture is combusted in the combustion chamber, the piston reciprocates, and the crankshaft rotates. The exhaust gas generated in the combustion is discharged to the exhaust passage24.

An air flow meter26, a compressor17, and a throttle valve28are arranged in this order from the upstream side in the intake passage20. The air flow meter26detects a flow rate (air amount) of the air flowing through the intake passage20. The throttle valve28regulates the amount of air. The larger the opening degree of the throttle valve28is, the more the amount of air increases. The smaller the opening degree, the smaller the air amount. A turbine18is provided in the exhaust passage24.

The compressor17and the turbine18are connected to form a supercharger16. The exhaust gas flowing through the exhaust passage24is blown to the turbine18, and the turbine18rotates. The compressor17rotates with the turbine18. The compressor17supercharges the air in the intake passage20. By introducing high-pressure air into the internal combustion engine10, the output of the internal combustion engine10is improved.

A bypass passage22is connected between the upstream side and the downstream side of the compressor17in the intake passage20. A bypass valve23is provided in the middle of the bypass passage22. By opening the bypass valve23, air flows to the internal combustion engine10bypassing the compressor17. When the bypass valve23is closed, more air flows to the compressor17and is supercharged.

The space15is defined by the head cover14and the cylinder head12of the internal combustion engine10. The passage13is provided in the cylinder head12and the cylinder block, and extends from the space15to the inside of the crankcase. blowby gas leaking from the combustion chamber to the crankcase passes through the passage13and is accumulated in the space15.

The coupling30is attached to the head cover14. One end of the blowby gas passage34is connected to the coupling30, and the other end is connected to a position upstream of the compressor17of the intake passage20. The blowby gas in the space15flows through the blowby gas passage34, returns to the intake passage20, and is supplied to the internal combustion engine10together with the air. The pressure sensor32detects the pressure in the blowby gas passage34.

When the throttle valve28is opened, air flows into the internal combustion engine10. The pressure in the intake passage20decreases to a negative pressure lower than the atmospheric pressure. The blowby gas flows from the space15into the low-pressure intake passage20. When the blowby gas flows, the pressure in the blowby gas passage34also becomes low, e.g., lower than atmospheric pressure. When an abnormality occurs in the blowby gas passage34, the pressure in the blowby gas passage34is less likely to decrease. For example, if the blowby gas passage34is dislodged and if the blowby gas passage34is damaged, the blowby gas passage34is opened to the atmosphere. Therefore, the pressure is equivalent to the atmospheric pressure.

ECU40is an abnormality diagnosis device, and includes an arithmetic device such as CPU (CentralProcessingUnit), RAM (RandomAccessMemory), and a storage device such as ROM (ReadOnlyMemory). ECU50performs various types of control by executing programs stored in a ROM or a storage device. ECU40acquires the pressure detected by the pressure sensor32and the air quantity detected by the air flow meter26. ECU40controls the opening degree of the bypass valve23and the opening degree of the throttle valve28.

ECU40functions as the setting unit42, the accumulating unit44, and the diagnosis unit46. The setting unit42sets a reference value with respect to the pressure in the blowby gas passage34. The accumulating unit44integrates 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 accumulating unit44does not perform the integration. The diagnosis unit46diagnoses the blowby gas passage34on the basis of the cumulative value, and determines that it is normal or abnormal.

FIG.2andFIG.3are flowcharts illustrating processing according to the embodiment. ECU40determines whether or not the pressure-monitoring condition is satisfied (S10). The monitoring condition is determined by the state of the internal combustion engine10, and may be determined, for example, by the amount of air. When the air volume shifts from decreasing to increasing, the monitoring condition is satisfied. If the determination is negative (No), the process ends. If the determination is affirmative (Yes), ECU40determines whether or not it is immediately after the monitoring condition is satisfied (S12). For example, if the elapsed time from the establishment of the monitoring condition is several milliseconds (several ms) or less, an affirmative determination is made. The setting unit42is configured to store, as a reference value, a pressure at the time when the monitoring condition is satisfied (S14).

After a negative determination or S14in S12, the setting unit42determines whether or not there is a peak in the pressure (S16). At the peak, the time derivative of the pressure is from a positive value to 0 and from 0 to a negative value. The setting unit42monitors the pressure and detects a peak from a change in the differential value. If S16is negative, a S22is performed. If the determination is affirmative, the setting unit42stores the peak-time pressure as a new reference value (S18). The accumulating unit44resets the cumulative value performed until the new reference value is stored, and also resets the counting of the integrated time (S20).

As illustrated inFIG.3, the accumulating unit44integrates the difference between the reference value of the pressure and the pressure detected by the pressure sensor32, and calculates the cumulative value S (S22). The accumulating unit44also counts up the period of integration (S24). The accumulating unit44determines whether or not the integration time t has reached a predetermined time t0or more (S26). If the determination is negative, the process ends. If the determination is affirmative, the diagnosis unit46determines whether or not the cumulative value S is equal to or greater than a predetermined value Sth (S28). When the cumulative value S is equal to or larger than Sth value (affirmative determination), the diagnosis unit46diagnoses that the blowby gas passage34is normal (S30). When the cumulative value S is less than Sth (negative determination), the diagnosis unit46diagnoses that the blowby gas passage34is abnormal (S32). Thus, the process ends.

FIGS.4A to5Bare each a diagram illustrating a time chart according to an embodiment. In each figure, the upper row represents the pressure in the blowby gas passage34. The lower row represents the amount of air flowing through the intake passage20. In each figure, a hatched portion is an integrated range.

FIG.4Ais an example in which the blowby gas passage34is normal. In the example ofFIG.4A, the air volume shifts from decreasing to increasing in the temporal t1(S10inFIG.2). The setting unit42sets the pressure P1in the time t1as a reference value (S12). The setting unit42sets the peak P1of the time t1as a reference value, and the accumulating unit44starts the integration. It also rises after the time t1and peaks in the time t2. The value of the peak P2is greater than P1. The setting unit42sets the peak P2as a reference value (S18). The pressure after the time t2is lower than the reference value P2. The cumulative value using P1as a reference value and the counting of the times are reset (S20). The accumulating unit44integrates the difference between the time period from the time t2to t3, the reference value P2, and the pressure to calculate the cumulative value S (S22inFIG.3). The duration t0from t2to t3is, for example, 400 ms.

FIG.4Bis an example in which the blowby gas passage34is abnormal. InFIG.4B, the pressure is not peaked and remains near atmospheric pressure. Air volume begins to rise t4hours. The setting unit42sets the pressure P3in the time t4as a reference value. After t4, the pressure is below the reference value P3. The accumulating unit44integrates the difference between the reference value P3and the pressure from the time t4to t5.

InFIG.4A, the blowby gas passage34is pressurized as the air volume in the intake passage20is increased. The cumulative value S becomes larger, and becomes equal to or larger than the threshold Sth. The diagnosis unit46diagnoses as normal (step30). InFIG.4B, for example, the blowby gas passage34is removed. Regardless of the amount of air, the pressure in the blowby gas passage34is maintained at the same level as the atmospheric pressure. The cumulative value S is small and less than the threshold Sth. The diagnosis unit46diagnoses an anomaly (S32).

InFIGS.5A and5B, the pressure-carrying element has two peaks. As shown inFIG.5A, the airflow begins to grow t6times. The pressure has a peak in the time t7(first peak) and a peak in the time t8(second peak). The setting unit42sets the peak P4of the time t7as a reference value, and the accumulating unit44starts the integration. The pressure P5in the time t8is higher than the pressure P4in the time t7. The setting unit42sets the higher peak P5of the two peaks as a reference value. The cumulative value using P4as a reference value and the counting of the times are reset (S20). The accumulating unit44integrates P5from the time t8to19as a reference value. The cumulative value S having the pressure P5as a reference value is larger than the cumulative value having the pressure P4as a reference value. Diagnostic accuracy increases.

In the example inFIG.5B, the airflow begins to grow t10times. Peaks in t11and t12after temporal t10. The peak P6in the time t11is greater than P7in the time t12. The accumulating unit44calculates the cumulative value S using P6as a reference value without redoing the integration. The cumulative value increases, and the accuracy of diagnosis increases.

FIGS.6A and6Bare each a diagram illustrating time charts in the comparative embodiment. In the example ofFIG.6A, the airflow begins to grow t14times. The integration is performed from t14to t15using P8of times t14as a reference value.

In the example ofFIG.6B, the pressure P9of the time t16is used as a reference value. Air volume begins to rise t16hours. However, the pressure peaks after t16because the pressure response is delayed from the change in air volume. Since the pressure near the peak is larger than the reference value P9, the integration is not performed. Since the cumulative value S becomes small, the accuracy of the diagnosis of normal/abnormal is deteriorated.

According to the present embodiment, as shown inFIG.4B, when there is no peak in the pressure, the setting unit42sets the pressure at the point in time when the air volume starts to increase as the reference value. As shown inFIG.4A, when there is a peak in the pressure, the setting unit42sets the peak pressure as a reference value. The accumulating unit44integrates the difference between the reference value and the pressure. The diagnosis unit46performs diagnosis based on the cumulative value. When the cumulative value S is large as shown inFIG.4A, the diagnosis unit46diagnoses as normal. When the cumulative value S is smaller as shown inFIG.4B, the diagnosis unit46diagnoses an error. Since the reference value is determined in accordance with the behavior of the pressure, the accuracy of the diagnosis is improved.

As shown inFIG.4A, the air-volume begins to rise t1the first point in time-before the pressure-peak occurs. The setting unit42sets the pressure P1at the time t1as a reference value, and the accumulating unit44performs integration. Peaking occurs in the subsequent t2(second point in time). The setting unit42sets the peak P2as a reference value. The accumulating unit44performs integration from t2. The diagnosis unit46performs diagnosis based on the cumulative value S obtained by the integration from t2. Since the integration is performed from the time t1, it can be diagnosed even when there is no peak after the time t1. If a peak occurs after the temporal t1, the diagnosis is performed based on the cumulative value from the peak. It is possible to secure an opportunity for diagnosis and to improve accuracy.

As shown inFIGS.5A and5B, a plurality of peaks may occur in the pressure. The accumulating unit44performs integration from the first peak. Ensure opportunities for diagnosis. The setting unit42sets a large peak among the plurality of peaks as a reference value. As shown inFIG.5A, when the peak P5after the time is larger than the previous peak P4, the accumulating unit44performs the integration again using the large peak P5as a reference value. The cumulative value S increases and the accuracy improves.

When the cumulative value S is equal to or larger than the threshold Sth, the diagnosis unit46determines that the cumulative value S is normal. When the cumulative value S is less than the threshold Sth, the diagnosis unit46determines that an error has occurred. The cumulative value S is determined according to whether the blowby gas passage34is normal or abnormal. It is possible to perform highly accurate diagnosis based on the cumulative value S.

In an abnormal condition, such as the blowby gas passage34being disengaged or the blowby gas passage34being perforated, the blowby gas passage34is opened to the atmosphere. For this reason, as shown inFIG.4B, the pressure does not have a large peak, and it is difficult to reduce with increasing air volume, and the atmospheric pressure level is maintained. The setting unit42sets the pressure at the point in time when the air amount starts to increase as a reference value. The reference value is about the same as the atmospheric pressure, and the pressure does not significantly change from the reference value. The cumulative value S decreases. Abnormalities can be accurately detected.

The condition for monitoring the pressure is that the air volume shifts from decreasing to increasing (e.g., the time t1ofFIG.4A). If there is no peak, the pressure at the point in time when the amount of air starts to increase becomes the reference value. The state of the internal combustion engine10may be set as a condition, and may be other than the air amount. For example, it may be a condition that the water temperature of the coolant of the internal combustion engine10is equal to or higher than a predetermined temperature, and that the pressure in the intake passage20is equal to or lower than a predetermined value. The duration t0during which the integration is performed may be longer than 400 ms or shorter than 400 ms.

In the above example, ECU40diagnoses the blowby gas passage34. In addition to the blowby gas passage34, embodiments may be applied to passageways that are connected to the intake passage20and through which gas passes, such as, for example, an EGR passageway.

Although the preferred embodiment of the disclosure is described above in detail, the disclosure is not limited to the specific embodiment, and various modifications and changes may be made within the scope of the disclosure described in claims.