JP2008215113A - Abnormality diagnostic device of internal combustion engine control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To specify an abnormal region causing an abnormality when an abnormality (abnormality in air-fuel ratio) occurs in a control system of an internal combustion engine. <P>SOLUTION: An "abnormality diagnosis of an air fuel ratio control system" for determining whether there is an abnormality in an air-fuel ratio control system as an abnormality in a first level, is executed. When an abnormality in the air-fuel ratio control system (abnormality in air-fuel ratio) is detected, so as to specify the abnormal region, an "abnormality diagnosis of an EGR system 36" for determining whether there is an abnormality in the EGR system 36, and an "abnormality diagnosis of a purge system 41" for determining whether there is an abnormality in the purge system 41, are executed as an abnormality in a second level. As a result, when it is determined that there is an abnormality in the EGR system 36, the EGR system 36 is specified to be the cause of the abnormality of the air-fuel ratio, and when it is determined that there is an abnormality in the purge system 41, the purge system 41 is specified to be the cause of the abnormality in the air-fuel ratio. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an abnormality diagnosis device for an internal combustion engine control system that determines the presence or absence of an abnormality in the internal combustion engine control system.

  In an electronically controlled internal combustion engine in recent years, an exhaust gas sensor (an air-fuel ratio sensor, an oxygen sensor, etc.) that detects an air-fuel ratio, rich / lean, etc. of exhaust gas is provided in an exhaust pipe, and an actual operation is performed based on the output of the exhaust gas sensor. Air-fuel ratio feedback control is performed to feedback-control the fuel injection amount, intake air amount, etc. so that the air-fuel ratio matches the target air-fuel ratio.

As an abnormality diagnosis device for such an air-fuel ratio control system, for example, as described in Patent Document 1 (Japanese Patent Laid-Open No. 1-2237336), the output value of the oxygen sensor is set for each cylinder or each cylinder group. In some cases, the air-fuel ratio is determined to be abnormal when a cylinder or a group of cylinders is accumulated a predetermined number of times and a large deviation in the accumulated value is detected in the distribution of all accumulated values.
JP-A-1-237336 (first page, etc.)

  As shown in FIG. 2, the causes of the air-fuel ratio abnormality include intake system abnormality (for example, purge system abnormality), fuel system abnormality (for example, fuel injection valve abnormality), ignition system abnormality (for example, ignition). Abnormalities in various parts such as abnormalities in the plug and abnormalities in the exhaust system (for example, abnormalities in the exhaust gas recirculation system) can be considered.

  However, in the abnormality diagnosis of Patent Document 1, when a cylinder or a group of cylinders having a large deviation in the cumulative value of the output of the oxygen sensor is detected, it is simply determined that the air-fuel ratio is abnormal. It is not possible to identify the abnormal part (failure part) that causes the problem. For this reason, when an abnormality in the air-fuel ratio occurs, inspect the air flow meter, fuel injection valve, air-fuel ratio sensor, purge system, exhaust gas recirculation system, etc. individually at a vehicle maintenance factory of an automobile dealer, There is a problem that it is necessary to specify an abnormal part that causes an abnormality in the air-fuel ratio, and a lot of man-hours are spent on the work of specifying the abnormal part. In addition, if the abnormal part cannot be identified, all parts suspected of abnormal may be replaced with new parts. In such a case, there is a possibility that even normal parts that do not actually need to be replaced will be replaced. There is.

  The present invention has been made in consideration of these circumstances. Accordingly, the object of the present invention is to identify an abnormal part on-board when an abnormality occurs in the internal combustion engine control system, and maintainability. An object of the present invention is to provide an abnormality diagnosis device for an internal combustion engine control system capable of improving the engine.

  In order to achieve the above object, the invention according to claim 1 is the case where the presence or absence of the first level abnormality of the internal combustion engine control system is determined by the first level abnormality diagnosis means and it is determined that the first level abnormality is present. In addition, the second level abnormality diagnosis means determines the presence or absence of the second level abnormality in order to identify the abnormal part causing the abnormality of the first level.

  In this configuration, when a first level abnormality occurs in the internal combustion engine control system, it is determined whether there is a second level abnormality that can cause the first level abnormality, and it is determined that there is a second level abnormality. For example, it is possible to determine that the cause of the first level abnormality is the second level abnormality and specify the abnormal part. As a result, when a first level abnormality of the internal combustion engine control system occurs, an abnormal part can be identified on-board (a self-diagnosis function of a control device mounted on the vehicle). It is possible to quickly repair or replace abnormal parts at maintenance shops, etc., and to reduce the work of identifying abnormal parts, and to replace normal parts that do not actually need to be replaced. The situation can also be prevented, and maintenance can be improved.

  Specifically, as in claim 2, it is preferable to determine whether the air-fuel ratio control system is abnormal as the first level abnormality. In this way, when an abnormality occurs in the air-fuel ratio control system, which is an important control system that has a large effect on emissions and drivability among various control systems of the internal combustion engine (that is, when an abnormality in the air-fuel ratio occurs) ), It is possible to identify the abnormal part that is the cause of the abnormality.

  In this case, as in claim 3, it may be determined whether there is an abnormality in the exhaust gas recirculation system that recirculates a part of the exhaust gas of the internal combustion engine to the intake system as a second level abnormality. Since an abnormality in the exhaust gas recirculation system can cause an abnormality in the air-fuel ratio, when an abnormality occurs in the air-fuel ratio control system (that is, when an abnormality in the air-fuel ratio occurs), the exhaust gas recirculation is detected as a second level abnormality. By determining whether or not the system is abnormal, it is possible to determine whether or not the exhaust gas recirculation system is an abnormal part causing the abnormality of the air-fuel ratio.

  Further, as in claim 4, it may be determined whether or not there is an abnormality in the purge system in which the fuel evaporative gas generated by the evaporation of the fuel in the fuel tank as the second level abnormality is sucked into the intake system. Since an abnormality in the purge system can cause an abnormality in the air-fuel ratio, when an abnormality occurs in the air-fuel ratio control system (that is, when an abnormality in the air-fuel ratio occurs), an abnormality in the purge system is detected as a second level abnormality. By determining the presence or absence, it is possible to determine whether or not the purge system is an abnormal part causing the abnormality of the air-fuel ratio.

Hereinafter, an embodiment embodying the best mode for carrying out the present invention will be described.
First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. A throttle valve 16 whose opening is adjusted by a motor 15 and a throttle opening sensor 17 for detecting the opening (throttle opening) of the throttle valve 16 are provided on the downstream side of the air flow meter 14.

  Further, a surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 for detecting the intake pipe pressure is provided in the surge tank 18. The surge tank 18 is provided with an intake manifold 20 for introducing air into each cylinder of the engine 11, and a fuel injection valve 21 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 20 of each cylinder. Yes. An ignition plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each ignition plug 22.

  Further, the engine 11 is provided with an intake side variable valve timing device 32 that varies the valve timing (opening / closing timing) of the intake valve 30 and an exhaust side variable valve timing device 33 that varies the valve timing of the exhaust valve 31. Yes.

  On the other hand, the exhaust pipe 23 of the engine 11 is provided with an exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting the air-fuel ratio or rich / lean of the exhaust gas. A catalyst 25 such as a three-way catalyst for purifying gas is provided.

  A cooling water temperature sensor 26 that detects the cooling water temperature and a crank angle sensor 28 that outputs a pulse signal each time the crankshaft 27 of the engine 11 rotates a predetermined crank angle are attached to the cylinder block of the engine 11. Based on the output signal of the crank angle sensor 28, the crank angle and the engine speed are detected.

  A part of the exhaust gas is recirculated to the intake side between the upstream or downstream side of the catalyst 25 in the exhaust pipe 23 and the surge tank 18 on the downstream side of the throttle valve 16 in the intake pipe 12. An EGR pipe 34 is connected, and an EGR control valve 35 for adjusting the EGR amount (exhaust gas recirculation amount) is provided in the middle of the EGR pipe 34. An EGR system 36 (exhaust gas recirculation system) is constituted by the EGR pipe 34, the EGR control valve 35, and the like.

  Further, fuel evaporative gas (evaporative gas) generated by evaporating the fuel in the fuel tank (not shown) is adsorbed by an adsorbent (not shown) such as activated carbon in the canister 38 through the communication pipe 37. A purge pipe 39 is connected between the canister 38 and the downstream side of the throttle valve 16 in the intake pipe 12 for sucking the evaporated fuel adsorbed in the canister 38 into the intake pipe 12. A purge control valve 40 for adjusting the fuel evaporative gas purge amount is provided in the middle of the purge pipe 39. The purge pipe 39 may be connected to the surge tank 18. The canister 38, the purge pipe 39, the purge control valve 40 and the like constitute a purge system 41.

  Outputs of the various sensors described above are input to a control circuit (hereinafter referred to as “ECU”) 29. The ECU 29 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount of the fuel injection valve 21 according to the engine operating state. The ignition timing of the spark plug 22 is controlled.

  Further, the ECU 29 executes an air-fuel ratio control program (not shown) to change the fuel injection amount, the intake air amount, etc. so that the air-fuel ratio detected based on the output of the exhaust gas sensor 24 matches the target air-fuel ratio. (Feedback) The air-fuel ratio F / B control to be controlled is executed.

  Further, the ECU 29 first executes an abnormality diagnosis program shown in FIGS. 3 and 4 to be described later, and first determines whether there is an abnormality in the air-fuel ratio control system as an abnormality of the first level. Execute. In this abnormality diagnosis of the air-fuel ratio control system, it is determined whether the air-fuel ratio abnormality is present by determining whether the air-fuel ratio F / B correction amount of the air-fuel ratio F / B control is within a predetermined normal range. .

By the way, as shown in FIG. 2, the cause of the abnormality of the air-fuel ratio may be abnormalities in various parts such as an intake system abnormality, a fuel system abnormality, an ignition system abnormality, and an exhaust system abnormality.
More specifically, the abnormality in the intake system includes an abnormality in the air flow meter 14, an abnormality in the purge system 41, an abnormality in the intake valve control system (abnormality in the intake side variable valve timing device 32, the intake side variable valve lift device, etc.). And abnormalities in the airflow control system (abnormalities in swirl flow control devices, tumble flow control devices, etc.)

  Examples of the abnormality in the fuel system include an abnormality in the fuel injection valve 21 and an abnormality in a fuel pressure control system such as a fuel pump. Examples of the abnormality in the ignition system include an abnormality in the ignition plug 22 and an abnormality in the ignition coil. Examples of abnormalities in the exhaust system include abnormalities in the EGR system 36, abnormalities in the exhaust valve control system (abnormalities in the exhaust side variable valve timing device 33, the exhaust side variable valve lift device, etc.), abnormalities in the exhaust gas sensor 24, and the like.

  Therefore, when the ECU 29 determines that there is an abnormality in the air-fuel ratio by the abnormality diagnosis of the air-fuel ratio control system, the ECU 29 determines that the abnormality is the second level abnormality in order to identify the abnormal part that causes the abnormality in the air-fuel ratio. “EGR diagnosis of EGR system 36” for determining the presence / absence of abnormality of the EGR system 36 and “abnormality diagnosis of the purge system 41” for determining the presence / absence of abnormality of the purge system 41 as the second level abnormality are executed.

  An abnormality in the EGR system 36 or an abnormality in the purge system 41 can cause an abnormality in the air-fuel ratio. Therefore, when an abnormality in the air-fuel ratio control system occurs (that is, when an abnormality in the air-fuel ratio occurs), If it is determined whether or not there is an abnormality, and it is determined that there is an abnormality in the EGR system 36, the EGR system 36 can be identified as an abnormal part causing an abnormality in the air-fuel ratio, and an abnormality in the purge system 41 If it is determined that there is an abnormality in the purge system 41, it can be determined that the purge system 41 is an abnormal part causing an abnormality in the air-fuel ratio.

The processing contents of the abnormality diagnosis program shown in FIGS. 3 and 4 executed by the ECU 29 will be described below.
The abnormality diagnosis program shown in FIGS. 3 and 4 is executed at a predetermined cycle while the ECU 29 is turned on. When this program is started, first, in step 101, it is determined whether or not an abnormality diagnosis execution condition for the air-fuel ratio control system is satisfied. Here, the abnormality diagnosis execution condition of the air-fuel ratio control system is, for example, that it is in a predetermined operation state (for example, a steady operation state), that the air-fuel ratio F / B control is being performed, and that the exhaust gas sensor 24 is normal. is there.
If it is determined in step 101 that the abnormality diagnosis execution condition for the air-fuel ratio control system is not satisfied, the program is terminated without performing the processing from step 102 onward.

On the other hand, if it is determined in step 101 that the abnormality diagnosis execution condition for the air-fuel ratio control system is satisfied, the air-fuel ratio control system determines whether the air-fuel ratio control system is abnormal as a first level abnormality. The abnormality diagnosis is executed as follows. First, in step 102, after reading the air-fuel ratio F / B correction amount FAF of the air-fuel ratio F / B control, the process proceeds to step 103, where the air-fuel ratio F / B correction amount FAF is within the normal range (lower limit side determination value α < By determining whether or not the air-fuel ratio F / B correction amount FAF <the upper limit side determination value β), it is determined whether there is an abnormality in the air-fuel ratio.
The processing of these steps 101 to 103 serves as first level abnormality diagnosis means in the claims.

  In step 103, the air-fuel ratio F / B correction amount FAF is within the normal range (lower limit side determination value α <air-fuel ratio F / B correction amount FAF <upper limit side determination value β), and there is no abnormality in the air-fuel ratio (normal). If it is determined, the program is terminated without performing the processing from step 104 onward.

  In contrast, in step 103, the air-fuel ratio F / B correction amount FAF is outside the normal range (air-fuel ratio F / B correction amount FAF ≦ lower limit side determination value α or upper limit side determination value β ≦ air-fuel ratio F / B correction). In the case where it is determined that the air-fuel ratio is abnormal, the process proceeds to step 104 and whether or not the abnormality diagnosis execution condition of the EGR system 36 is satisfied (for example, whether or not it is in a predetermined operation state). Etc.).

  In this step 104, when it is determined that the abnormality diagnosis execution condition of the EGR system 36 is established, the EGR abnormality is determined as the second level abnormality in order to identify the abnormal part causing the abnormality of the air-fuel ratio. An abnormality diagnosis of the EGR system 36 for determining the presence or absence of an abnormality in the system 36 is executed as follows.

  First, in step 105, the EGR control valve 35 is controlled so as to stop the function of the EGR system 36 (set the EGR amount to 0), and then the process proceeds to step 106, where the air-fuel ratio F / B correction amount FAF is read. At that time, after the time necessary for the air-fuel ratio of the exhaust gas to actually change after the EGR control valve 35 is controlled to stop the function of the EGR system 36, the air-fuel ratio F / B correction amount FAF is reached. Should be read.

Thereafter, the routine proceeds to step 107, where it is determined whether the air-fuel ratio is abnormal by determining whether the air-fuel ratio F / B correction amount FAF is within the normal range.
If it is determined in step 107 that there is no abnormality (normal) in the air-fuel ratio, that is, if the air-fuel ratio has become normal from abnormality by stopping the function of the EGR system 36, the process proceeds to step 108. It is determined that there is an abnormality in the EGR system 36, and the EGR system 36 is specified as an abnormal part causing the abnormality in the air-fuel ratio.

  In this case, the abnormality flag is set to ON and a warning lamp (not shown) provided on the instrument panel of the driver's seat is turned on, or a warning display section (not shown) of the driver's seat instrument panel is provided. ) And a warning to the driver, and the abnormality information (abnormality code or the like) is stored in a rewritable nonvolatile memory such as a backup RAM (not shown) of the ECU 29.

On the other hand, if it is determined in step 107 that the air-fuel ratio is abnormal, that is, if the air-fuel ratio remains abnormal even when the function of the EGR system 36 is stopped, step 109 is performed. Then, it is determined that there is no abnormality (normal) in the EGR system 36.
Thereafter, the process proceeds to step 110 in FIG. 4 to determine whether or not an abnormality diagnosis execution condition for the purge system 41 is satisfied (for example, whether or not it is in a predetermined operation state).

  In this step 110, when it is determined that the abnormality diagnosis execution condition of the purge system 41 is satisfied, the purge is performed as the second level abnormality in order to identify the abnormal part causing the abnormality of the air-fuel ratio. An abnormality diagnosis of the purge system 41 for determining whether there is an abnormality in the system 41 is executed as follows.

First, in step 111, the purge control valve 40 is controlled to stop the function of the purge system 41 (the fuel evaporative gas purge amount is set to 0), and then the process proceeds to step 112 to read the air-fuel ratio F / B correction amount FAF. . At that time, after the purge control valve 40 is controlled so as to stop the function of the purge system 41, the time required for the actual change of the air-fuel ratio of the exhaust gas has elapsed, and then the air-fuel ratio F / B correction amount FAF is reached. Should be read.
Thereafter, the process proceeds to step 113, where it is determined whether the air-fuel ratio is abnormal by determining whether the air-fuel ratio F / B correction amount FAF is within the normal range.

  If it is determined in step 113 that there is no abnormality (normal) in the air-fuel ratio, that is, if the air-fuel ratio becomes normal from abnormality due to the stop of the function of the purge system 41, the routine proceeds to step 114, It is determined that there is an abnormality in the purge system 41, and the purge system 41 is identified as an abnormal part causing the abnormality in the air-fuel ratio.

  In this case, the abnormality flag is set to ON and a warning lamp (not shown) provided on the instrument panel of the driver's seat is turned on, or a warning display section (not shown) of the driver's seat instrument panel is provided. ) And a warning to the driver, and the abnormality information (abnormality code or the like) is stored in a rewritable nonvolatile memory such as a backup RAM (not shown) of the ECU 29.

On the other hand, if it is determined in step 113 that the air-fuel ratio is abnormal, that is, if the air-fuel ratio remains abnormal even when the function of the purge system 41 is stopped, the process proceeds to step 115. Then, it is determined that there is no abnormality (normal) in the purge system 41.
The processing of these steps 104 to 115 serves as second level abnormality diagnosis means in the claims.

  In the present embodiment described above, the “diagnosis of the air-fuel ratio control system” that determines whether there is an abnormality in the air-fuel ratio control system is executed as the first level abnormality, and an abnormality in the air-fuel ratio control system occurs (that is, When the air-fuel ratio abnormality occurs), the EGR system 36 determines whether or not the EGR system 36 is abnormal as a second-level abnormality in order to identify the abnormal part causing the air-fuel ratio abnormality. "Abnormality diagnosis of the purge system 41" for determining whether or not the purge system 41 is abnormal as a second level abnormality. As a result, if it is determined that there is an abnormality in the EGR system 36, the EGR system 36 is identified as an abnormal part causing the abnormality in the air-fuel ratio, and if it is determined that there is an abnormality in the purge system 41, the purge The system 41 is identified as an abnormal part causing the abnormality of the air-fuel ratio.

  As a result, when an abnormality occurs in the air-fuel ratio control system, the abnormal part can be identified on-board (the ECU 29 mounted on the vehicle). Can be repaired and replaced, reducing the work of identifying the abnormal part, and can prevent the occurrence of replacement of normal parts that do not actually need to be replaced. Can be improved.

  The abnormality diagnosis method for the air-fuel ratio control system, the abnormality diagnosis method for the EGR system 36, and the abnormality diagnosis method for the purge system 41 are not limited to the methods described in the above embodiments, and may be changed as appropriate. For example, it is determined whether there is an abnormality in the EGR system 36 based on the air-fuel ratio F / B correction amount when the EGR control valve 35 is controlled so as to change the EGR amount by a predetermined amount, or the fuel evaporative gas purge amount is set. The presence or absence of abnormality of the purge system 41 may be determined based on the air-fuel ratio F / B correction amount when the purge control valve 40 is controlled to change by a predetermined amount.

  In the above embodiment, the abnormality diagnosis of the EGR system 36 and the abnormality diagnosis of the purge system 41 are executed in order to identify the abnormal part that causes the abnormality of the air-fuel ratio control system (abnormality of the air-fuel ratio). However, the present invention is not limited to this. An abnormality diagnosis of the air flow meter 14, an abnormality diagnosis of the intake valve control system (an abnormality diagnosis of the intake side variable valve timing device 32, the intake side variable valve lift device, etc.), an abnormality of the airflow control system Diagnosis (abnormal diagnosis of swirl flow control device, tumble flow control device, etc.), abnormality diagnosis of fuel injection valve 21, abnormality diagnosis of fuel pressure control system, abnormality diagnosis of ignition plug 22, abnormality diagnosis of ignition coil, exhaust valve control system Abnormal diagnosis (abnormal diagnosis of exhaust side variable valve timing device 33, exhaust side variable valve lift device, etc.), exhaust gas sensor 24 It is also possible to perform a normal diagnosis.

  Further, in the above embodiment, the present invention is applied to the technique for identifying the abnormal part causing the abnormality of the air-fuel ratio control system, but this causes the abnormality of other systems other than the air-fuel ratio control system. You may make it apply this invention to the technique which pinpoints an abnormal site | part.

It is a schematic block diagram of the whole engine control system in one Example of this invention. It is a figure for demonstrating the cause of abnormality of an air fuel ratio. It is a flowchart (the 1) explaining the flow of a process of an abnormality diagnosis program. It is a flowchart (the 2) explaining the flow of a process of an abnormality diagnosis program.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 16 ... Throttle valve, 21 ... Fuel injection valve, 22 ... Spark plug, 23 ... Exhaust pipe, 24 ... Exhaust gas sensor, 29 ... ECU (1st level abnormality diagnostic means, Second level abnormality diagnosis means), 34 ... EGR piping, 35 ... EGR control valve, 36 ... EGR system (exhaust gas recirculation system), 38 ... canister, 39 ... purge piping, 40 ... purge control valve, 41 ... purge system

Claims (4)

First level abnormality diagnosis means for determining the presence or absence of a first level abnormality in the internal combustion engine control system;
When the first level abnormality diagnosis means determines that there is an abnormality of the first level, the presence or absence of an abnormality of the second level is determined in order to identify an abnormal part causing the abnormality of the first level. An abnormality diagnosis device for an internal combustion engine control system, comprising: a second level abnormality diagnosis means.   2. The abnormality diagnosis device for an internal combustion engine control system according to claim 1, wherein the first level abnormality diagnosis unit determines whether the air-fuel ratio control system is abnormal as the first level abnormality. 3.   The second level abnormality diagnosing means determines whether or not there is an abnormality in an exhaust gas recirculation system that recirculates a part of exhaust gas of an internal combustion engine to an intake system as the second level abnormality. The abnormality diagnosis device for the internal combustion engine control system according to claim.   The second level abnormality diagnosing means determines whether or not there is an abnormality in the purge system that sucks into the intake system fuel evaporative gas generated by evaporation of fuel in the fuel tank as the second level abnormality. The abnormality diagnosis device for an internal combustion engine control system according to claim 2 or 3.

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