JP2008069693A - Failure diagnosis system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of early and correctly detecting abnormality of a fuel supply system in a failure diagnosis system of an internal combustion engine for diagnose failures of the fuel supply system of each cylinder. <P>SOLUTION: To solve the problem, this invention comprises a first detection means for detecting a fluctuation amount of engine speed of each cylinder when the internal combustion engine is in an idling state, a second detection means for detecting a torque fluctuation amount of each cylinder of the internal combustion engine, and a diagnosis means for diagnosing failures of the fuel supply system of each cylinder based on the detection results of the first/second detection means. The invention is designed to diagnose abnormalities of the fuel supply system of each cylinder in view of the torque fluctuation amount of each cylinder as well as the engine speed fluctuation amount of each cylinder. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a failure diagnosis technique for an internal combustion engine, and more particularly to a technique for diagnosing a failure in a fuel supply system.

Conventionally, as a technique for diagnosing a failure or abnormality in a fuel supply system of an internal combustion engine, a correction amount exceeds a reference range in a system that corrects the fuel injection amount of each cylinder in order to eliminate fluctuations in engine speed during idle operation. There is known a technique for forcibly increasing or decreasing a correction amount when a cylinder is present, and determining whether or not a fluctuation in the engine speed caused thereby matches the increase or decrease of the correction amount (for example, , See Patent Document 1).
JP 2002-188501 A JP 2006-138293 A JP 2000-186603 A JP 10-122031 A Japanese Patent No. 2595663 JP 11-44246 A

  By the way, during the idling operation of the internal combustion engine, the fuel injection amount of each cylinder is extremely small, and therefore the amount of fluctuation of the engine speed due to the failure of the fuel supply system tends to be extremely small. Therefore, in order to increase the accuracy of fault diagnosis in the above-described conventional technology, the correction amount of the fuel injection amount needs to be greatly increased or decreased.

  However, if the correction amount of the fuel injection amount is significantly increased or decreased, the engine speed fluctuates significantly, which may give the driver a sense of discomfort.

  On the other hand, a method of gradually increasing or decreasing the correction amount of the fuel injection amount is conceivable, but the time required for the failure diagnosis process becomes longer. If the time required for the failure diagnosis process becomes long, it is assumed that the internal combustion engine deviates from the idle operation state before the completion of the failure diagnosis process. In such a case, there is a possibility that failure of the fuel supply system cannot be detected at an early stage.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to quickly detect an abnormality in the fuel supply system in an internal combustion engine failure diagnosis system for diagnosing a fuel supply system failure in each cylinder. Providing technology that can be detected accurately.

  In order to solve the above-described problems, the present invention provides an internal combustion engine failure diagnosis system capable of detecting an engine rotation fluctuation amount for each cylinder when the internal combustion engine is in a steady operation state, in addition to the engine rotation fluctuation amount for each cylinder. The abnormality of the fuel supply system of each cylinder is diagnosed in consideration of the torque fluctuation amount for each cylinder.

  Specifically, the failure diagnosis system for an internal combustion engine according to the present invention includes first detection means for detecting an engine rotation fluctuation amount for each cylinder when the internal combustion engine is in a steady operation state, and torque fluctuation for each cylinder of the internal combustion engine. Second detection means for detecting the amount, and diagnosis means for diagnosing a failure in the fuel supply system of each cylinder based on the detection results of the first and second detection means.

  The torque fluctuation amount between the cylinders can be detected even when the internal combustion engine deviates from the steady operation state. On the contrary, when the internal combustion engine deviates from the steady operation state, the target fuel injection amount of each cylinder increases, so that the difference between the torque fluctuation amount at the time of failure and the torque fluctuation amount at the time of normality is easily clarified. For this reason, it is possible to perform a failure diagnosis even if the internal combustion engine does not continue the steady operation state for a long time.

  On the other hand, the amount of torque fluctuation when the internal combustion engine is in a transient operation state may be relatively large even in a cylinder in which the fuel supply system is normal. For this reason, there is a possibility of erroneous diagnosis that the fuel supply system of the cylinder is out of order.

  However, in the internal combustion engine failure diagnosis system according to the present invention, normal cylinders are selected based on the amount of engine rotation fluctuation during steady operation, so that there is no erroneous diagnosis that the normal cylinders have failed. . Furthermore, since the engine rotation fluctuation amount at the time of steady operation can be detected in a very short time, the internal combustion engine does not have to continue the steady operation state for a long time.

  Therefore, according to the failure diagnosis system for an internal combustion engine according to the present invention, it is possible to detect a failure in the fuel supply system early and accurately.

  In the internal combustion engine failure diagnosis system according to the present invention, the diagnosis means includes a torque fluctuation amount detected by the second detection means for the fuel supply system of the cylinder having the maximum engine rotation fluctuation amount detected by the first detection means. Failure diagnosis based on the above may be performed.

  According to such a configuration, failure diagnosis based on the torque fluctuation amount is performed only for the cylinder having a relatively large engine rotation fluctuation amount, so that the failure diagnosis accuracy can be improved.

  In the failure diagnosis system for an internal combustion engine according to the present invention, the diagnosis means includes a torque detected by the second detection means for a fuel supply system of a cylinder whose engine rotation fluctuation amount detected by the first detection means exceeds a predetermined amount. A failure diagnosis based on the fluctuation amount may be performed.

  According to such a configuration, failure diagnosis based on the torque fluctuation amount is performed only for the cylinder having a large absolute value of the engine rotation fluctuation amount, so that the failure diagnosis accuracy can be improved.

  The diagnosis means performs failure diagnosis based on the torque fluctuation amount detected by the second detection means for the fuel supply system of the cylinder in which the engine rotation fluctuation amount detected by the first detection means exceeds the predetermined amount. By doing so, the fault diagnosis accuracy may be further improved.

  Further, as a specific execution method of the failure diagnosis in the present invention, the multiplication value of the engine rotation fluctuation amount detected by the first detection means and the torque fluctuation amount detected by the second detection means exceeds the reference value. It is possible to exemplify a method of diagnosing that the fuel supply system has failed on the condition that

  When the multiplication value of the engine rotation fluctuation amount and the torque fluctuation amount is used as a parameter, the difference between the normal time and the failure time is larger than when only one of the engine rotation fluctuation amount or the torque fluctuation amount is used as a parameter. Is promoted and amplified. Therefore, it is possible to further improve the failure diagnosis accuracy and detect a minor failure.

  In addition, as another execution method of the failure diagnosis in the present invention, in a method for determining whether or not the torque fluctuation amount is larger than a predetermined diagnosis reference value for a cylinder whose engine rotation fluctuation amount is maximum and / or exceeds a predetermined amount, The diagnostic reference value may be variable according to the magnitude of the engine rotation fluctuation amount.

  For example, the diagnosis reference value may be increased as the engine rotation fluctuation amount is reduced, thereby suppressing the occurrence of misdiagnosis and improving the diagnosis accuracy.

  According to the present invention, an abnormality in a fuel supply system can be detected early and accurately in a failure diagnosis system for an internal combustion engine that diagnoses a failure in a fuel supply system of each cylinder.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. An internal combustion engine 1 shown in FIG. 1 includes a plurality of four cylinders (first cylinder (# 1), second cylinder (# 2), third cylinder (# 3), and fourth cylinder (# 4)) 2. A compression ignition type internal combustion engine (diesel engine).

  Each cylinder 2 is provided with a fuel injection valve 3 that injects fuel directly into the cylinder 2. The fuel injection valve 3 is connected to a common rail 4, and the common rail 4 communicates with a fuel pump 6 through a fuel supply pipe 5.

  The fuel discharged from the fuel pump 6 is supplied to the common rail 4 through the fuel supply pipe 5 and is distributed from the common rail 4 to the fuel injection valve 3 of each cylinder 2. The fuel injected from the fuel injection valve 3 is burned together with the air introduced from the intake passage 7. Gas (burned gas) burned in the cylinder 2 is discharged to the exhaust passage 8.

  The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU) 9 for controlling the operating state of the internal combustion engine 1. The ECU 9 is electrically connected to the fuel injection valve 3 and the fuel pump 6 and controls the fuel injection valve 3 and the fuel pump 6 based on measured values of various sensors such as the crank position sensor 10.

  For example, the ECU 9 executes failure diagnosis processing that is the gist of the present invention in addition to known control such as fuel injection amount control based on the operating conditions of the internal combustion engine 1. The failure diagnosis process is a process for diagnosing a failure in the fuel supply system (including the path from the common rail 4 to the fuel injection valve 3 and the fuel injection valve 3) of each cylinder 2.

  Hereinafter, the failure diagnosis process in this embodiment will be described. In the failure diagnosis process in the present embodiment, the ECU 9 uses two parameters, namely, an engine rotation fluctuation amount when the internal combustion engine 1 is in an idle operation state and a torque fluctuation amount when the internal combustion engine 1 is in a non-idle operation state. Based on this, failure diagnosis of the fuel supply system of each cylinder 2 is performed.

  The ECU 9 corrects the fuel injection amount of each cylinder 2 in order to suppress the engine rotation fluctuation between the cylinders when the internal combustion engine 1 is in the idling operation state (hereinafter, such control is referred to as “idle fuel injection control”). Called).

  Specifically, the ECU 9 determines the engine rotation speed of the cylinder 2 burned immediately before the engine rotation speed of each cylinder 2 during the expansion stroke (for example, the time required to rotate 90 ° CA from the top dead center of the expansion stroke). Compare with

For the cylinder 2 whose engine speed is higher than that of the cylinder 2 burned immediately before, the ECU 9 corrects the fuel injection amount in the next cycle of the cylinder 2 by reducing the amount. On the other hand, for the cylinder 2 whose engine rotational speed is lower than that of the cylinder 2 burned immediately before, the ECU 9 increases and corrects the fuel injection amount of the next cycle of the cylinder 2.

  At this time, the fuel injection amount of the cylinder 2 in which a failure has occurred in the fuel supply system is excessive or small as compared with the target fuel injection amount, so that the engine rotation fluctuation amount of the cylinder 2 increases and the fuel injection amount The amount of correction increases. As shown in FIG. 2, the correction amount at that time increases as the degree of failure increases (in other words, the difference between the target fuel injection amount and the actual fuel injection amount increases).

  Therefore, the ECU 9 can diagnose that the fuel supply system of the cylinder 2 is abnormal when detecting the cylinder 2 in which the correction amount in the idle fuel injection control exceeds the threshold value.

  By the way, since the target fuel injection amount is small when the internal combustion engine 1 is in the idling operation state, the difference between the normal engine rotation fluctuation amount and the engine rotation fluctuation amount at the time of failure tends to be small. As a result, when the fuel supply system failure diagnosis is performed using only the correction amount of the fuel injection control during idling as a parameter, the diagnosis accuracy tends to be low and it is difficult to detect a minor failure.

  On the other hand, a method of diagnosing a failure in the fuel supply system of each cylinder 2 using a torque fluctuation amount between cylinders during non-idle operation where the target fuel injection amount is relatively large as a parameter is conceivable.

  FIG. 3 is a diagram showing the relationship between the angular acceleration fluctuation amount of the crankshaft correlated with the torque fluctuation amount and the degree of failure of the fuel supply system. As shown in FIG. 3, as the degree of failure of the fuel supply system increases, the angular acceleration fluctuation amount increases. Therefore, it can be diagnosed that the fuel supply system of the cylinder 2 whose angular acceleration fluctuation amount exceeds the threshold value is abnormal.

  However, when the internal combustion engine 1 is in a non-idle operation state, it is necessary to take into account variations in the amount of change in angular acceleration accompanying acceleration / deceleration (Δα in FIG. 3). When failure diagnosis is performed in consideration of such variation Δα, it is erroneously diagnosed that the fuel supply system is malfunctioning in Example C in FIG. 3 or the example in FIG. There is a possibility that the fuel supply system in D is erroneously diagnosed as being normal despite the failure.

  Therefore, in the failure diagnosis process of the present embodiment, the ECU 9 performs the correction only for the cylinder 2 in which the correction amount in the idle fuel injection control is the largest among the four cylinders and / or the correction amount in the idle fuel injection control exceeds the predetermined amount. In addition, failure diagnosis based on the angular acceleration fluctuation amount was performed.

  According to such a failure diagnosis method, failure diagnosis based on the angular acceleration fluctuation amount is not performed for the normal cylinder 2 as in Example C in FIG. 3, so that the fuel supply system of the cylinder 2 is normal. Nevertheless, it is no longer misdiagnosed as malfunctioning.

  Further, for minor failures such as Example D in FIG. 3, the occurrence of misdiagnosis is suppressed by performing failure diagnosis using the product of the correction amount of the fuel injection control during idling and the angular acceleration fluctuation amount as a parameter. can do.

  Specifically, the failure diagnosis may be performed on the condition that the multiplication value of the correction amount of the fuel injection control during idling and the angular acceleration fluctuation amount is larger than a predetermined reference value. According to such a failure diagnosis method, compared with the case where the failure diagnosis is performed with only one of the correction amount of the fuel injection control during idling and the angular acceleration fluctuation amount during non-idle operation as a parameter, The difference with time is encouraged and amplified. Therefore, the failure diagnosis accuracy is improved, and a minor failure as shown in Example D in FIG. 3 can be detected.

  Hereinafter, failure diagnosis processing in the present embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing a failure diagnosis routine. This failure diagnosis routine is a routine that is interrupted at predetermined intervals, and is stored in advance in the ROM of the ECU 9.

  In the failure diagnosis processing routine, the ECU 9 first determines whether or not a failure diagnosis condition is satisfied in S101. Examples of the failure diagnosis condition include a condition that the target fuel injection amount is a certain amount or more. At this time, the above-described constant amount is a sufficiently large amount as compared with the target fuel injection amount during the idling operation.

  If a negative determination is made in S101, the ECU 9 once ends the execution of this routine. On the other hand, if an affirmative determination is made in S101, the ECU 9 proceeds to S102.

  In S102, the ECU 9 determines which cylinder 2 of the first cylinder (# 1) to the fourth cylinder (# 4) is the cylinder 2 in the expansion stroke.

  In S103, the ECU 9 determines whether or not the correction amount of the idle fuel injection control of the cylinder (hereinafter referred to as "diagnostic cylinder") 2 determined in S102 is the maximum amount among the four cylinders 2. .

  The correction amount of the idle fuel injection control for each cylinder 2 is obtained by an idle fuel injection control routine as shown in FIG. In the idle fuel injection control routine of FIG. 5, the ECU 9 determines whether or not a predetermined condition is satisfied in S201. As predetermined conditions, the speed of the vehicle equipped with the internal combustion engine 1 is zero, the operation amount of the accelerator pedal is zero, and the difference between the actual engine speed and the target speed is within an allowable value. Conditions can be exemplified.

  If a negative determination is made in S201, the ECU 9 ends the execution of this routine. On the other hand, if an affirmative determination is made in S201, the ECU 9 calculates the engine rotation fluctuation amount of each cylinder 2 in S202.

  In S203, the ECU 9 calculates a correction amount of the fuel injection amount of each cylinder 2 in accordance with the engine rotation fluctuation amount calculated in S202, and stores those calculation results in a predetermined area of the ECU 9 RAM or backup RAM. .

  In S204, the ECU 9 corrects the target fuel injection amount of each cylinder 2 based on the correction amount calculated in S203.

  Returning to FIG. 4, the ECU 9 reads the correction amount of each cylinder 2 obtained by the idle fuel injection control routine of FIG. 3 in S103 from the RAM or the backup RAM, and the correction amount of the diagnostic cylinder 2 is four cylinders. It is determined whether or not 2 is the maximum.

  If a negative determination is made in S103, the ECU 9 ends the execution of this routine. On the other hand, if an affirmative determination is made in S103, the ECU 9 proceeds to S104.

  In S104, the ECU 9 determines whether or not the correction amount of the diagnostic cylinder 2 is larger than a predetermined amount. If a negative determination is made in S104, the ECU 9 ends the execution of this routine. On the other hand, if an affirmative determination is made in S104, the ECU 9 proceeds to S105.

In S105, the ECU 9 calculates the angular acceleration fluctuation amount of the diagnostic cylinder 2. Specifically, E
The CU 9 first calculates the engine rotational speed when rotating 90 ° CA from the top dead center of the expansion stroke of the diagnostic cylinder. Next, the ECU calculates angular acceleration by differentiating the engine rotational speed. Further, the ECU 9 calculates the absolute value of the difference between the angular acceleration of the cylinder 2 burned immediately before the diagnostic cylinder 2 and the angular acceleration of the diagnostic cylinder 2.

  In S106, the ECU 9 calculates a multiplication value of the correction amount of the diagnostic cylinder 2 and the angular acceleration fluctuation amount.

  In S107, the ECU 9 determines whether or not the multiplication value calculated in S106 is larger than a reference value.

  If an affirmative determination is made in S107, the ECU 9 proceeds to S108 and diagnoses that the fuel supply system of the diagnostic cylinder 2 has failed. On the other hand, if a negative determination is made in S107, the ECU 9 proceeds to S109 and diagnoses that the fuel supply system of the diagnostic cylinder 2 is normal.

  As described above, the ECU 9 executes the failure diagnosis processing routine, thereby realizing the first detection means, the second detection means, and the diagnosis means according to the present invention. As a result, it becomes possible to detect the failure of the fuel supply system early and accurately.

  In this embodiment, an in-line four-cylinder compression ignition type internal combustion engine has been described as an example. However, the present invention is not limited to this, and a multi-cylinder internal combustion engine may be used. It may be an institution.

1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. It is a figure which shows the relationship between the grade of the failure of a fuel supply system, and the correction amount of idle time fuel injection control. It is a figure which shows the relationship between the grade of the failure of a fuel supply system, and angular acceleration fluctuation amount. It is a flowchart which shows a failure diagnosis processing routine. It is a flowchart which shows a fuel injection control routine at the time of idling.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Fuel injection valve 4 ... Common rail 5 ... Fuel supply pipe 6 ... Fuel pump 9. .... ECU
10 .... Crank position sensor

Claims (5)

First detection means for detecting an engine rotation fluctuation amount for each cylinder when the internal combustion engine is in a steady operation state;
Second detecting means for detecting a torque fluctuation amount for each cylinder of the internal combustion engine;
Diagnostic means for diagnosing a failure in the fuel supply system of each cylinder based on the detection results of the first and second detection means;
A failure diagnosis system for an internal combustion engine, comprising:   2. The failure diagnosis according to claim 1, wherein the diagnosis unit is based on a torque fluctuation amount detected by the second detection unit with respect to a fuel supply system of a cylinder having the maximum engine rotation fluctuation amount detected by the first detection unit. A fault diagnosis system for an internal combustion engine, characterized in that:   2. The diagnosis unit according to claim 1, wherein the diagnosis unit is based on a torque fluctuation amount detected by the second detection unit for a fuel supply system of a cylinder in which the engine rotation fluctuation amount detected by the first detection unit exceeds a predetermined amount. A failure diagnosis system for an internal combustion engine characterized by performing failure diagnosis.   2. The torque variation detected by the second detection unit according to claim 1, wherein the diagnosis unit detects a fuel supply system of a cylinder in which the engine rotation variation amount detected by the first detection unit is maximum and exceeds a predetermined amount. A failure diagnosis system for an internal combustion engine characterized by performing failure diagnosis based on a quantity.   5. The diagnosis unit according to claim 1, wherein a multiplication value of the engine rotation fluctuation amount detected by the first detection unit and the torque fluctuation amount detected by the second detection unit exceeds a reference value. A failure diagnosis system for an internal combustion engine that diagnoses that the fuel supply system of the cylinder has failed on the condition that

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