JP2013019314A - Failure determining apparatus for multi-cylinder internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a failure determining apparatus for a multi-cylinder internal combustion engine, capable of precisely detecting imbalance between multiple cylinders due to small shift and large shift of an operation angle of an intake valve.SOLUTION: An engine control computer 15 measures rotation variation of a multi-cylinder internal combustion engine during idling in each of a state in which an operation angle of an intake valve 7 is small and a state in which the operation angle is large, and determines imbalance between multiple cylinders on the basis of the results. The engine control computer 15 determines small shift of the operation angle of the intake valve 7 when the rotation variation is large only while the operation angle of the intake valve 7 is small, determines large shift of the operation angle of the intake valve 7 when the rotation variation is large only while the operation angle is large, and determines lean shift of an injector 5 when the rotation variation is large in both of the states.

Description

  The present invention relates to an abnormality determination device for a multi-cylinder internal combustion engine that includes a variable working angle mechanism that varies a working angle of an intake valve.

  As an abnormality of the multi-cylinder internal combustion engine, there is an air-fuel ratio imbalance. The air-fuel ratio imbalance occurs when the fuel injection amount of the injector of a specific cylinder becomes smaller or larger than that of other cylinders, and if this occurs, the rotational fluctuation of the internal combustion engine during idling will occur. growing. Therefore, conventionally, in many multi-cylinder internal combustion engines such as in-vehicle, for example, as seen in Patent Document 1, as an abnormality determination device for a multi-cylinder internal combustion engine, the rotational fluctuation of the multi-cylinder internal combustion engine during idling is measured, and the result The air-fuel ratio imbalance between the cylinders is determined based on the above.

JP 2010-024977 A JP 2007-016693 A

  By the way, in recent years, as seen in, for example, Patent Document 2, a multi-cylinder internal combustion engine having a working angle variable mechanism that makes a working angle of an intake valve variable has been put into practical use. In this type of multi-cylinder internal combustion engine, a small deviation or a large deviation in the operating angle of the intake valve may occur as an abnormality that increases the rotational fluctuation. A small deviation in the operating angle of the intake valve is an abnormality in which the operating angle of the intake valve of the specific cylinder becomes smaller than that of the other cylinders. It is an anomaly that becomes larger than.

  In this regard, the abnormality determination device of Patent Document 1 can determine the abnormality of the air-fuel ratio imbalance, but it must always accurately determine even the imbalance between cylinders due to a small or large deviation in the operating angle of the intake valve. Can not be.

  The present invention has been made in view of such circumstances, and the problem to be solved is a multi-cylinder internal combustion engine that can accurately determine an imbalance between cylinders due to a small shift or large shift in the operating angle of the intake valve. An object of the present invention is to provide an engine abnormality determination device.

  In order to solve the above problems, in the invention according to claim 1 as an abnormality determination device for a multi-cylinder internal combustion engine having a variable working angle mechanism that varies a working angle of an intake valve, a state in which the working angle is reduced and a working angle The rotational fluctuation of the multi-cylinder internal combustion engine that is idling is measured in each of the states where the engine is increased, and the determination of the imbalance between cylinders is performed based on the results.

  Rotational fluctuations due to a decrease in the intake air amount due to a small shift in the intake valve operating angle are conspicuous when the operating angle is reduced, but are not so prominent when the operating angle is increased. On the other hand, the rotational fluctuation due to the large deviation of the operating angle of the intake valve does not appear so remarkably when the operating angle is reduced, but it appears significantly when the operating angle is increased. Therefore, it is difficult to determine whether or not there is a large deviation in the operating angle even if the operating angle of the multi-cylinder internal combustion engine during idling with the operating angle of the intake valve being small is determined, and the operating angle of the intake valve is large. Even if it is based on the rotational fluctuation of the multi-cylinder internal combustion engine during idling in the performed state, it is difficult to determine whether or not there is a small deviation in the operating angle.

  In that respect, in the above configuration, the rotational fluctuation of the multi-cylinder internal combustion engine during idling is measured in each of a state where the operating angle of the intake valve is reduced and a state where the operating angle is increased. Therefore, it is possible to accurately determine the presence or absence of both a small shift and a large shift in the operating angle of the intake valve. Therefore, according to the above configuration, it is possible to accurately determine an imbalance between cylinders due to a small shift or large shift in the operating angle of the intake valve.

  As described above, when a small deviation in the operating angle of the intake valve occurs, rotational fluctuation during idling becomes large only when the operating angle is reduced, and a large deviation in the operating angle of the intake valve occurs. When this occurs, the rotational fluctuation during idling becomes large only when the operating angle is increased. On the other hand, when an injector lean shift occurs in which the fuel injection amount of a specific cylinder is smaller than that of other cylinders, rotational fluctuations during idling occur both when the operating angle of the intake valve is reduced and when it is increased. growing.

  Therefore, as described in claim 2, when the rotational fluctuation becomes large only when the operating angle of the intake valve is reduced, the operating angle of the intake valve of the specific cylinder becomes smaller than that of the other cylinders. If the rotational fluctuation increases only when the intake valve operating angle is increased, it is determined that the operating angle of the intake valve of a specific cylinder is larger than the other cylinders. When the rotational fluctuation becomes large in both states, the cause of the inter-cylinder imbalance can be specified if it is determined that the lean deviation of the injector in which the fuel injection amount of the specific cylinder is smaller than that of the other cylinders. It becomes possible.

  Further, as described in claim 3, when the magnitude of the rotational fluctuation when the operating angle is small is A and the magnitude of the rotational fluctuation when the operating angle is large is B, the difference in rotational fluctuation is If A−B is equal to or greater than the predetermined determination value β, it is determined that the operating angle of the specific cylinder is smaller than that of the other cylinders, and the difference in rotational fluctuation B−A is equal to or greater than the predetermined determination value α. If so, it is possible to discriminate between a small shift and a large shift in the operating angle by determining that the operating angle of the specific cylinder is larger than that of the other cylinders. Furthermore, as described in claim 4, the rotational fluctuation difference AB is less than the determination value β, the rotational fluctuation difference BA is less than the determination value β, and at least one of the rotational fluctuations A and B is predetermined. If it is determined that the fuel injection amount of the specific cylinder is smaller than that of the other cylinders, it is determined that the injector lean shift is smaller than the other cylinders. It is possible to determine the deviation.

1 is a schematic diagram schematically showing a configuration of a multi-cylinder internal combustion engine to which an abnormality determination device according to an embodiment of the present invention is applied. (A) When a small deviation of the working angle occurs, (b) When a large deviation of the working angle occurs, and (c) When a lean deviation of the injector occurs, A graph showing the relationship. 6 is a graph showing the relationship between the working angle and the air-fuel ratio when a small working angle shift occurs, when a large working angle shift occurs, when an injector lean shift occurs, and when a rich shift of the injector occurs. The flowchart which shows the process sequence of the imbalance determination routine applied to the said embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying an abnormality determination device for a multi-cylinder internal combustion engine according to the present invention will be described below in detail with reference to FIGS.
First, a configuration of a multi-cylinder internal combustion engine to which the abnormality determination device of the present embodiment is applied will be described with reference to FIG.

  As shown in the figure, an intake pipe 1 of a multi-cylinder internal combustion engine includes an air cleaner 2 for purifying intake air, an air flow meter 3 for detecting the intake air amount, and a throttle valve 4 for adjusting the intake air amount in order from the upstream. Is arranged. The intake pipe 1 is branched for each cylinder by the intake manifold 21 and then connected to the intake port 6 of each cylinder formed in the cylinder head 20 of the multi-cylinder internal combustion engine. An injector 5 for injecting fuel is installed in each intake port 6 of each cylinder. The intake port 6 of each cylinder is connected to the combustion chamber 8 of each cylinder via an intake valve 7.

  On the other hand, the combustion chamber 8 of each cylinder is connected to an exhaust port 10 of each cylinder formed in the cylinder head 20 via an exhaust valve 9. The exhaust port 10 is connected to the exhaust pipe 11 via an exhaust manifold 22 that joins the exhausts of the cylinders. The exhaust pipe 11 is provided with an air-fuel ratio sensor 12 that detects the air-fuel ratio of the air-fuel mixture burned in the combustion chamber 8, and a first catalyst 13 and a second catalyst 14 that purify the exhaust gas.

  Such a multi-cylinder internal combustion engine is controlled by an engine control computer 15. In addition to the air flow meter 3 and the air-fuel ratio sensor 12 described above, the engine control computer 15 is connected to a number of sensors such as a crank angle sensor 17 that detects the rotational phase of the crankshaft 16 that is the engine output shaft. In addition to the injector 5 described above, the engine control computer 15 is connected to actuator drive circuits such as a throttle motor 18 that drives the throttle valve 4 and a working angle variable mechanism 19 that varies the working angle of the intake valve 7. Yes.

  In the multi-cylinder internal combustion engine configured as described above, a so-called imbalance among cylinders, in which the generated torque of each cylinder varies, may occur. The inter-cylinder imbalance occurs due to, for example, a lean shift of the injector 5 in which the fuel injection amount of the specific cylinder is smaller than that of the other cylinder, and a rich shift of the injector 5 in which the fuel injection amount of the specific cylinder is larger than that of the other cylinder. Further, in this multi-cylinder internal combustion engine provided with the working angle variable mechanism 19, the working angle of the intake valve 7 of the specific cylinder is smaller than that of the other cylinders, and the working angle of the intake valve 7 of the specific cylinder is the other. An imbalance between cylinders also occurs due to a large shift in the operating angle that is larger than that of the cylinder.

  In this embodiment, the rotational fluctuation of the idling multi-cylinder internal combustion engine is measured in each of the state where the operating angle of the intake valve 7 is reduced and the state where the operating angle is increased, and the cylinder is determined based on the results. Interim imbalance is determined. And the lean deviation of the injector 5 and the small deviation and the large deviation of the operating angle of the intake valve 7 are discriminated from the result. Note that the rich shift of the injector 5 is separately determined by calculating the slope of the output of the air-fuel ratio sensor 12.

Next, the detail of the discrimination | determination aspect of the factor of the imbalance between cylinders based on the measurement result of rotation fluctuation is demonstrated.
First, FIG. 2A shows the relationship between the engine load and the rotation fluctuation when the operating angle of the intake valve 7 is small. If the operating angle of the intake valve 7 is small and a small shift of the same operating angle occurs, the effect of the shift is relatively large because the operating angle is small in the first place, and the amount of intake air in the cylinder where the small shift has occurred The rate of decline increases. On the other hand, even if a small deviation of the same operating angle occurs when the operating angle of the intake valve 7 is large, since the operating angle is large in the first place, the influence of the deviation becomes relatively small, and the cylinder where the small deviation occurs The rate of decrease of the intake air amount is slight. Therefore, as shown in the figure, when a small shift in the operating angle of the intake valve 7 occurs, significant rotational fluctuation occurs in a state where the operating angle is reduced.

  FIG. 2B shows the relationship between the engine load and the rotational fluctuation when the operating angle of the intake valve 7 is largely deviated. If a large deviation in the operating angle occurs when the operating angle of the intake valve 7 is large, the valve overlap of the intake / exhaust valve increases and the intake air amount decreases greatly. For this reason, if a large shift in the operating angle occurs when the operating angle of the intake valve 7 is large, the generated torque is greatly reduced in the cylinder in which the large shift has occurred. On the other hand, when the operating angle of the intake valve 7 is small, since the valve overlap of the intake and exhaust valves does not occur when the operating angle increases somewhat, even if the operating angle deviates greatly, a significant torque reduction occurs. Absent. Therefore, as shown in the figure, when a large deviation in the operating angle of the intake valve 7 occurs, significant rotational fluctuations occur when the operating angle is increased.

  On the other hand, FIG. 2C shows the relationship between the engine load and the rotational fluctuation when the lean deviation of the injector 5 occurs. The rotational fluctuation due to the lean deviation of the injector 5 is due to a shortage of the fuel injection amount and is not related to the intake air amount, and therefore occurs regardless of the operating angle of the intake valve 7. For this reason, the rotational fluctuation due to the lean deviation of the injector 5 becomes large both when the operating angle of the intake valve 7 is large and small.

  Thus, when a small deviation in the operating angle of the intake valve 7 occurs, a significant rotational fluctuation occurs only when the operating angle is small, and when a large deviation in the operating angle of the intake valve 7 occurs, the same operating angle is Significant rotational fluctuations occur only in large states. In addition, when the lean deviation of the injector 5 occurs, significant rotational fluctuation occurs in both the small and large operating angles of the intake valve 7. Accordingly, the lean deviation of the injector 5 and the small deviation of the working angle are detected from the rotational fluctuations of the multi-cylinder internal combustion engine during idling measured in the state where the working angle of the intake valve 7 is reduced and the state where the working angle is increased. Thus, it is possible to determine a large deviation in the working angle. Incidentally, FIG. 3 shows the relationship between the air-fuel ratio and the working angle at the time of occurrence of small deviation, large deviation, lean deviation of the injector (INJ) 5, and rich deviation, respectively.

  Next, details of processing relating to determination of the imbalance between cylinders in the present embodiment will be described. This determination is performed through the process of the imbalance determination routine shown in FIG. Note that the processing of this routine is repeatedly executed by the engine control computer 15 at predetermined control cycles.

  When the processing of this routine is started, first, in step S100, the engine start has been completed, the warm-up of the multi-cylinder internal combustion engine has been completed, the imbalance determination has not been completed, and idling. Whether or not a determination condition such as driving is established is confirmed. If the determination condition is not satisfied here (S100: NO), the processing of this routine is terminated as it is.

  If the determination condition is satisfied (S100: YES), it is confirmed in step S101 whether or not the operating angle of the intake valve 7 is increased. If the operating angle of the intake valve 7 is increased (S101: YES), the rotational fluctuation A of the multi-cylinder internal combustion engine during idling with the increased operating angle of the intake valve 7 is measured in step S102. Is done. On the other hand, if the operating angle of the intake valve 7 is reduced (S101: NO), the rotational fluctuation B of the multi-cylinder internal combustion engine during idling with the reduced operating angle of the intake valve 7 is measured in step S103. Is done. Then, when the rotational fluctuations A and B during idling in both the state in which the operating angle of the intake valve 7 is increased and the state in which the intake valve 7 is decreased are measured, the determination of the imbalance between cylinders is made in step S104 and subsequent steps.

  In the multi-cylinder internal combustion engine to which the present embodiment is applied, basically, during idling, the operating angle of the intake valve 7 is reduced and the operating angle of the intake valve 7 is increased. Opportunities for measuring the rotational fluctuation A of the multi-cylinder internal combustion engine are limited. For such a reason, when it is difficult to complete the determination of the imbalance between cylinders because the opportunity for measuring the rotational fluctuation A is not obtained, the operating angle of the intake valve 7 is increased to measure the rotational fluctuation A. It is recommended to perform idling operation.

  When the measurement of the rotational fluctuations A and B is finished and the process proceeds to step S104, the value obtained by subtracting the rotational fluctuation B from the rotational fluctuation A (AB) is equal to or greater than the predetermined determination value β in step S104. It is determined whether or not. That is, here, although the rotational fluctuation A of the multi-cylinder internal combustion engine during idling with the operating angle of the intake valve 7 increased is large, the rotational fluctuation B of the multi-cylinder internal combustion engine during idling with the operating angle reduced is large. Whether or not is in a small state is determined. Here, if the rotational fluctuation difference AB is equal to or greater than the predetermined determination value β (S104: YES), it is determined in step S105 that a small deviation in the operating angle of the intake valve 7 has occurred. Thus, the processing of this routine is finished.

  On the other hand, if the difference A−B in the rotational fluctuation is less than the determination value β (S104: NO), the value (B−A) obtained by subtracting the rotational fluctuation A from the rotational fluctuation B is greater than or equal to the predetermined determination value α in step S106. It is determined whether or not. That is, here, although the rotational fluctuation B of the multi-cylinder internal combustion engine during idling with the operating angle of the intake valve 7 reduced is large, the rotational fluctuation A of the multi-cylinder internal combustion engine during idling with the operating angle increased. Whether or not is in a small state is determined. If the rotational fluctuation difference B−A is equal to or larger than the predetermined determination value α (S106: YES), it is determined in step S107 that a large deviation in the operating angle of the intake valve 7 has occurred. This routine is finished.

  If the difference B-A in rotational fluctuation is less than the determination value α (S106: NO), it is determined in step S108 that there is no deviation in the operating angle of the intake valve 7. Then, in the subsequent step S109, it is determined whether or not any of the rotation fluctuation A and the rotation fluctuation B is equal to or greater than a predetermined determination value γ. If either of the rotational fluctuations A and B is greater than or equal to the determination value γ (S109: YES), it is determined in step S110 that a lean deviation of the injector 5 has occurred, and the processing of this routine this time is performed. Is terminated. On the other hand, if both the rotational fluctuations A and B are less than the determination value γ (S109: NO), it is determined in step S111 that there is no lean deviation of the injector 5, and the processing of this routine is terminated. The

Next, the operation of this embodiment will be described.
In the present embodiment, the rotational fluctuation of the multi-cylinder internal combustion engine during idling is measured in each of a state where the operating angle of the intake valve 7 is reduced and a state where the operating angle is increased. When it is confirmed that the rotational fluctuation is large only when the operating angle of the intake valve 7 is small (when the rotational fluctuation difference AB is equal to or larger than the determination value β), the operating angle is small. It is determined that a deviation has occurred. On the other hand, when it is confirmed that the rotational fluctuation increases only when the operating angle of the intake valve 7 is increased (when the rotational fluctuation difference B-A is equal to or larger than the determination value α), the operating angle is increased. It is determined that a deviation has occurred. Furthermore, when it is confirmed that the rotational fluctuation is large both in the state where the operating angle of the intake valve 7 is increased and decreased, it is determined that the lean deviation of the injector 5 has occurred.

According to the abnormality determination device for a multi-cylinder internal combustion engine of the present embodiment described above, the following effects can be obtained.
(1) In the present embodiment, rotational fluctuations of the idling multi-cylinder internal combustion engine are measured in a state where the operating angle of the intake valve 7 is reduced and a state where the operating angle is increased, and based on the results. Thus, the determination of the imbalance between cylinders is performed. For this reason, it is possible to accurately determine whether or not both the small deviation and the large deviation of the operating angle of the intake valve 7 have occurred. Therefore, according to the present embodiment, it is possible to accurately determine an imbalance between cylinders due to a small shift or large shift in the operating angle of the intake valve.

  (2) In the present embodiment, when the rotational fluctuation increases only when the operating angle of the intake valve 7 is reduced (when the rotational fluctuation difference AB is equal to or larger than the determination value β), the same operating angle is obtained. It is determined that there is a small deviation. Further, when the rotational fluctuation becomes large only when the operating angle of the intake valve 7 is increased (when the rotational fluctuation difference B−A is equal to or larger than the determination value α), a large deviation of the operating angle occurs. It is determined. Further, when the rotational fluctuation becomes large both when the operating angle of the intake valve 7 is reduced and when it is increased (the rotational fluctuation difference AB is less than the determination value β and the rotational fluctuation difference BA is the determination value). When it is less than α and at least one of the rotational fluctuations A and B is equal to or greater than a predetermined determination value γ, it is determined that the lean deviation of the injector 5 has occurred. Therefore, it is possible to suitably specify the factor of the imbalance between cylinders.

In addition, the said embodiment can also be changed and implemented as follows.
In the above embodiment, the lean displacement of the injector 5 is determined together with the large and small displacements of the operating angle of the intake valve 7, but if the lean displacement determination of the injector 5 is not particularly necessary. Alternatively, only the determination of the large or small deviation of the operating angle of the intake valve 7 may be performed.

  In the above embodiment, the operating angle is largely deviated from the rotational fluctuation of the multi-cylinder internal combustion engine during idling measured in the state where the operating angle of the intake valve 7 is reduced and the state where the operating angle is increased. Although the small deviation is determined, if the determination is not particularly necessary, it may be confirmed that there is a deviation in the operating angle of the intake valve 7 of the specific cylinder. That is, if it is confirmed that the rotational fluctuation of the multi-cylinder internal combustion engine during idling is large in either a state where the operating angle of the intake valve 7 is reduced or a state where the operating angle is increased, a small deviation or a large deviation However, it may be determined only that the operating angle of the intake valve 7 of the specific cylinder is deviated.

  In the above-described embodiment, it is determined whether the operating angle of the intake valve 7 is large or small. However, when only one of these determinations is required, only one of the determinations is performed. You may do it.

  DESCRIPTION OF SYMBOLS 1 ... Intake pipe, 2 ... Air cleaner, 3 ... Air flow meter, 4 ... Throttle valve, 5 ... Injector, 6 ... Intake port, 7 ... Intake valve, 8 ... Combustion chamber, 9 ... Exhaust valve, 10 ... Exhaust port, 11 DESCRIPTION OF SYMBOLS ... Exhaust pipe, 12 ... Air-fuel ratio sensor, 13 ... 1st catalyst, 14 ... 2nd catalyst, 15 ... Engine control computer, 16 ... Crankshaft, 17 ... Crank angle sensor, 18 ... Throttle motor, 19 ... Working angle variable mechanism 20 ... cylinder head, 21 ... intake manifold, 22 ... exhaust manifold.

Claims (4)

In the abnormality determination device for a multi-cylinder internal combustion engine having a working angle variable mechanism that varies a working angle of the intake valve,
Rotational fluctuation of a multi-cylinder internal combustion engine that is idling is measured in each of a state in which the operating angle is reduced and a state in which the operating angle is increased, and imbalance among cylinders is determined based on the results. An abnormality determination device for a multi-cylinder internal combustion engine. When the rotational fluctuation increases only in a state where the operating angle is reduced, it is determined that the operating angle of the specific cylinder is smaller than that of the other cylinders, and the operating angle is increased. Only when the rotational fluctuation is large, it is determined that the working angle of the specific cylinder is larger than that of the other cylinders, and when the rotational fluctuation is large in both states, The abnormality determination device for a multi-cylinder internal combustion engine according to claim 1, wherein it is determined that the fuel injection amount is smaller than that of the other cylinders. When the magnitude of the rotational fluctuation when the working angle is small is A and the magnitude of the rotational fluctuation when the working angle is large is B, the rotational fluctuation difference AB is a predetermined value. If it is greater than or equal to the determination value β, it is determined that the operating angle of the specific cylinder is smaller than that of the other cylinders, and if the rotational fluctuation difference B−A is equal to or greater than the predetermined determination value α, The abnormality determination device for a multi-cylinder internal combustion engine according to claim 1, wherein it is determined that the operating angle of the specific cylinder is larger than that of the other cylinders. Specified if the rotational fluctuation difference AB is less than the determination value β, the rotational fluctuation difference BA is less than the determination value α, and at least one of the rotational fluctuations A and B is greater than or equal to the predetermined determination value γ The abnormality determination device for a multi-cylinder internal combustion engine according to claim 3, wherein it is determined that the injector has a lean deviation in which the fuel injection amount of the cylinder is smaller than that of the other cylinders.

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