JP2006057523A - Failure diagnosis device for engine control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To execute accurate failure diagnosis of an air flow meter without using an atmospheric pressure sensor. <P>SOLUTION: The output of the air flow meter 14 is used for calculating the detected amount of air filled in a cylinder in accordance with a model expression (Step 101), and a fuel injection amount and an air/fuel ratio detected by an air/fuel ratio sensor are used for calculating the estimated amount of air filled in the cylinder (Step 102). Then, a deviation between the detected amount of air filled in the cylinder and the estimated amount of air filled in the cylinder (an air amount deviation) is calculated, and an absolute value for the air amount deviation is compared with a determined value which is set in consideration of a dispersion range in a normal condition. If the absolute value for the air amount deviation is smaller than the determined value, the air flow meter 14 is determined normal, and if the absolute value for the air amount deviation is not smaller than the determined value, the air flow meter 14 is determined abnormal (Steps 103-106). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an abnormality diagnosis device for an engine control system having a function of performing abnormality diagnosis of sensors for detecting an actual intake air amount or intake pipe pressure.

A conventional abnormality diagnosis device for an engine control system calculates an estimated intake air amount based on an engine rotation speed and an accelerator opening, as described in, for example, Japanese Patent Application Laid-Open No. 1-124352. In some cases, the estimated intake air amount is compared with a detected value (detected intake air amount) of an air flow meter to perform abnormality diagnosis.
Japanese Utility Model Publication No. 1-1124352 (first page, etc.)

  However, as in Patent Document 1, in the method of calculating the estimated intake air amount based on the engine speed and the accelerator opening, the estimated intake air amount changes under the influence of atmospheric pressure change. To put it to practical use, it is necessary to mount an atmospheric pressure sensor on the vehicle and correct the estimated intake air amount with the atmospheric pressure. For this reason, there is a problem that the number of parts and the number of conforming man-hours increase, resulting in high costs.

  Accordingly, a first object of the present invention is to enable an abnormality diagnosis of an intake air amount detection means (such as an air flow meter) to be accurately performed without using an atmospheric pressure sensor, and a second object is Thus, it is possible to distinguish between an abnormality in the intake air amount detection means and an abnormality in the intake pipe pressure detection means while accurately satisfying the demand for cost reduction.

  In order to achieve the first object, an invention according to claim 1 is an engine including intake air amount detection means for detecting an actual intake air amount and air-fuel ratio detection means for detecting an air-fuel ratio of exhaust gas. In the abnormality diagnosis device of the control system, the estimated intake air amount is calculated by the estimated intake air amount calculation means based on the air-fuel ratio detected by the air-fuel ratio detection means and the fuel injection amount, and the estimated intake air amount and the intake air amount are calculated. By comparing the detected value (detected intake air amount) of the detecting means, the abnormality diagnosing means determines whether the intake air amount detecting means is abnormal.

  According to the present invention, the air-fuel ratio and the fuel injection amount used to calculate the estimated intake air amount do not depend on the atmospheric pressure, and therefore the estimated intake air amount can be accurately calculated without being affected by changes in the atmospheric pressure. By comparing this estimated intake air amount with the detected value (detected intake air amount) of the intake air amount detection means, it is possible to diagnose abnormality of the intake air amount detection means that does not depend on the atmospheric pressure. Since the air-fuel ratio detection means used in the present invention may use an air-fuel ratio sensor installed in the exhaust system for exhaust gas purification, it is not necessary to provide new sensors for air-fuel ratio detection. Therefore, according to the present invention, it is possible to accurately perform abnormality diagnosis of the intake air amount detection means without using new sensors such as an atmospheric pressure sensor, and the requirements for cost reduction and diagnosis accuracy improvement can be satisfied at the same time. it can.

  In order to achieve the second object, an invention according to claim 2 includes an intake air amount detecting means for detecting an intake air amount, an intake pipe pressure detecting means for detecting an intake pipe pressure, an engine speed. In an abnormality diagnosis apparatus for an engine control system, comprising an engine speed detecting means for detecting the air-fuel ratio and an air-fuel ratio detecting means for detecting the air-fuel ratio of the exhaust gas, the air-fuel ratio and the fuel injection amount detected by the air-fuel ratio detecting means There is provided an estimated intake air amount calculating means for calculating an estimated intake air amount on the basis of which the relationship between the three detected values by the intake air amount detecting means, the intake pipe pressure detecting means, and the engine rotation speed detecting means is normal. A primary diagnosis is performed to determine whether either the intake air amount detection means or the intake pipe pressure detection means is abnormal depending on whether or not it is out of range. If the difference between the intake air amount detected by the intake air amount detection means and the estimated intake air amount by the estimated intake air amount calculation means is compared with a predetermined determination value, the difference is equal to or greater than the determination value. If so, the abnormality diagnosis of the intake air amount detection means is confirmed, and if the difference is less than the determination value, the abnormality diagnosis of the intake pipe pressure detection means is confirmed.

  If the engine control system is normal, the three parameters of the intake air amount, the intake pipe pressure, and the engine speed change while maintaining correlation with each other, and the remaining one parameter is uniquely determined from the two parameters. This relationship is maintained. Therefore, if the relationship between the detected values of these three parameters is within the normal variation range, it can be determined that the engine control system is normal. On the other hand, if the relationship between the detected values of the three parameters is out of the normal variation range, it can be determined that the engine control system is abnormal. However, only the relationship between the detected values of the three parameters can detect the three parameters. It cannot be specified which of the values is abnormal. In general, the engine rotation speed detection means is unlikely to fail as compared with the intake air amount detection means and the intake pipe pressure detection means. Therefore, in the present invention, it is determined that the engine control system is abnormal from the relationship between the detected values of the three parameters. If this is the case, a primary diagnosis is made that either the intake air amount detection means or the intake pipe pressure detection means is abnormal. Thereafter, in the definite diagnosis for identifying which of the intake air amount detection means and the intake pipe pressure detection means is abnormal, the estimated intake air amount and the intake air amount detection means calculated based on the air-fuel ratio and the fuel injection amount If the difference between the detected value (detected intake air amount) and the detected value is greater than or equal to the determination value, the intake air amount detection means is diagnosed as abnormal, and if the difference is less than the determination value, the intake pipe pressure detection means as abnormal To do. Accordingly, in the present invention, it is possible to distinguish between the abnormality of the intake air amount detection means and the abnormality of the intake pipe pressure detection means without using a new sensor such as an atmospheric pressure sensor, and to make a diagnosis with high accuracy. Can meet the demands of computerization and improved diagnostic accuracy at the same time.

  As described above, if the engine control system is normal, the three parameters of the intake air amount, the intake pipe pressure, and the engine speed change while maintaining correlation with each other, and the remaining one parameter is unambiguous. The primary diagnosis for determining whether or not the relationship between the detected values of the three parameters is out of the normal variation range in consideration of the fact that there is a relationship that is automatically determined is any one of claims 3 to 5. You can do this.

  For example, as in claim 3, when performing a primary diagnosis, an estimated intake pipe pressure is calculated based on a detected intake air amount detected by the intake air amount detection means and an engine speed, and the estimated intake pipe pressure and the It may be determined whether or not the relationship with the detected intake pipe pressure by the intake pipe pressure detection means is out of the normal variation range.

  Alternatively, as in claim 4, when performing the primary diagnosis, an estimated intake air amount is calculated based on the intake pipe pressure detected by the intake pipe pressure detecting means and the engine speed, and the estimated intake air amount It may be determined whether or not the relationship between the intake air amount detected by the intake air amount detection means is out of the normal variation range.

  Alternatively, as in claim 5, when the primary diagnosis is performed, the estimated engine rotation speed is calculated based on the intake air amount detected by the intake air amount detection means and the intake pipe pressure detected by the intake pipe pressure detection means. Then, it may be determined whether or not the relationship between the estimated intake air amount and the detected engine speed detected by the engine speed detecting means is out of the normal variation range.

  In any of these methods, primary diagnosis can be performed accurately without using new sensors such as an atmospheric pressure sensor.

  Hereinafter, five examples 1 to 5 embodying the best mode for carrying out the present invention will be described.

  A first embodiment of the present invention will be described with reference to FIGS. 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 which is an internal combustion engine, and an air flow meter 14 (intake air amount detection means) for detecting the intake air amount is provided downstream of the air cleaner 13. ing. On the downstream side of the air flow meter 14, a throttle valve 15 whose opening is adjusted by a DC motor or the like and a throttle opening sensor 16 for detecting the throttle opening are provided.

  Further, a surge tank 17 is provided on the downstream side of the throttle valve 15, and an intake pipe pressure sensor 18 (intake pipe pressure detecting means) for detecting the intake pipe pressure is provided in the surge tank 17. The surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 19 of each cylinder. Yes. A spark plug 21 is attached to each cylinder of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each spark plug 21.

  The intake valve 32 of the engine 11 is provided with a variable intake valve device 33 that varies the opening / closing timing and / or lift amount of the intake valve 32, and the exhaust valve 34 has an opening / closing timing of the exhaust valve 34 and / or Alternatively, a variable exhaust valve device 35 that varies the lift amount is provided.

  On the other hand, the exhaust pipe 22 of the engine 11 is provided with a catalyst 23 such as a three-way catalyst that purifies CO, HC, NOx, etc. in the exhaust gas, and detects the air-fuel ratio of the exhaust gas upstream of the catalyst 23. An air-fuel ratio sensor 24 (air-fuel ratio detection means) is provided.

  The cylinder block of the engine 11 includes a coolant temperature sensor 25 that detects the coolant temperature, and a crank angle sensor 26 that outputs a pulse signal each time the crankshaft of the engine 11 rotates a predetermined crank angle (engine speed detection means). Is attached, and the engine speed is detected based on the output pulse interval (pulse frequency) of the crank angle sensor 26.

  Outputs of these various sensors are input to an engine control circuit (hereinafter referred to as “ECU”) 27. The ECU 27 is mainly composed of a microcomputer including a CPU 28, a ROM 29, a RAM 30, a backup RAM 31, and the like. The ECU 27 executes various engine control programs stored in the ROM 30, so that the fuel injection valve 20 corresponds to the engine operating state. The fuel injection amount and the ignition timing of the spark plug 21 are controlled.

  Further, the ECU 27 executes the abnormality diagnosis routine of FIG. 2 at a predetermined period during engine operation, thereby executing the abnormality diagnosis of the air flow meter 14 as follows. First, in step 101, the amount of air in the detection cylinder (detected intake air amount) is calculated using the output of the air flow meter 14. The detected amount of air filled in the cylinder is a detected value of the amount of air filled in the cylinder, and is a model formula that takes into account the delay until the air that has passed through the air flow meter 14 flows through the intake passage and is filled in the cylinder. It is preferable to calculate the amount of air charged in the detection cylinder from the output of the air flow meter 14 using, for example.

Thereafter, the routine proceeds to step 102 where the estimated cylinder air charge amount is calculated by the following equation using the fuel injection amount and the air-fuel ratio detected by the air-fuel ratio sensor 24.
Estimated in-cylinder charged air amount = fuel injection amount x air-fuel ratio

  In the above equation, the fuel injection amount may be the required injection amount (fuel amount injected from the fuel injection valve 20) calculated by the ECU 27 based on the engine operating state or the like. Alternatively, in order to improve accuracy, the net amount of fuel sucked into the cylinder is calculated in consideration of the fuel (wet) adhering to the wall surface of the intake port or the like, and this is used as the “fuel injection amount”. You may do it. Further, it is preferable to set the air-fuel ratio detection timing in consideration of the delay until the gas burned in the cylinder flows through the exhaust pipe 22 and reaches the vicinity of the air-fuel ratio sensor 24 and the air-fuel ratio is detected. The processing in step 102 serves as an estimated intake air amount calculation means in the claims.

After calculating the estimated in-cylinder charged air amount, the process proceeds to step 103, and a deviation between the detected in-cylinder charged air amount and the estimated in-cylinder charged air amount (hereinafter referred to as “air amount deviation”) is calculated.
Air amount deviation = Detected in-cylinder charged air amount-Estimated in-cylinder charged air amount

  Thereafter, the process proceeds to step 104, where the absolute value of the air amount deviation is compared with a predetermined determination value set in consideration of the variation range at the normal time, and if the absolute value of the air amount deviation is smaller than the determination value, It is determined that the air amount deviation is within the normal variation range, the process proceeds to step 105, and it is determined that the air flow meter 14 is normal. On the other hand, if the absolute value of the air amount deviation is equal to or greater than the determination value, it is determined that the air amount deviation exceeds the normal variation range, and the routine proceeds to step 106 where it is determined that the air flow meter 14 is abnormal. . The processes in steps 103 to 106 serve as abnormality diagnosis means in the scope of claims.

  According to the first embodiment described above, the air-fuel ratio and the fuel injection amount used to calculate the estimated in-cylinder charged air amount do not depend on the atmospheric pressure. The amount of charged air can be calculated with high accuracy, and the estimated amount of charged air in the cylinder is compared with the amount of air charged in the detected cylinder determined from the output of the air flow meter 14, so that the air flow meter 14 that does not depend on atmospheric pressure can be used. Abnormal diagnosis is possible. Here, the air-fuel ratio sensor 24 that detects the air-fuel ratio used to calculate the estimated cylinder air charge amount may be an air-fuel ratio sensor installed in the exhaust system for exhaust gas purification. There is no need to provide new sensors for detecting the fuel ratio. Therefore, in the first embodiment, it is possible to accurately diagnose the abnormality of the air flow meter 14 without using new sensors such as an atmospheric pressure sensor, and simultaneously satisfy the demands for cost reduction and improvement of diagnosis accuracy. it can.

  In the first embodiment, only the abnormality diagnosis of the air flow meter 14 is performed. However, in the second embodiment of the present invention shown in FIG. 3, the abnormality of both the air flow meter 14 and the intake pipe pressure sensor 18 can be distinguished and diagnosed. I am doing so. Hereinafter, the diagnostic method of the second embodiment will be described.

  If the engine control system is normal, the three parameters of the intake air amount, the intake pipe pressure, and the engine speed change while maintaining correlation with each other, and the remaining one parameter is uniquely determined from the two parameters. This relationship is maintained. Therefore, if the relationship between the detected values of these three parameters is within the normal variation range, it can be determined that the engine control system is normal. On the other hand, if the relationship between the detected values of the three parameters is out of the normal variation range, it can be determined that the engine control system is abnormal. However, only the relationship between the detected values of the three parameters can detect the three parameters. It cannot be specified which of the values is abnormal. In general, the crank angle sensor 26 is less likely to fail than the air flow meter 14 and the intake pipe pressure sensor 18. Therefore, in the present invention, when it is determined that the engine control system is abnormal from the relationship between the detected values of the three parameters. The primary diagnosis is made when either the air flow meter 14 or the intake pipe pressure sensor 18 is abnormal. Thereafter, in the definite diagnosis for identifying which of the air flow meter 14 and the intake pipe pressure sensor 18 is abnormal, the estimated intake air amount calculated based on the air-fuel ratio and the fuel injection amount and the detected value of the air flow meter 14 ( If the difference from the detected intake air amount is equal to or greater than the determination value, the air flow meter 14 is determined to be abnormal, and if the difference is less than the determination value, the intake pipe pressure sensor 18 is determined to be abnormal.

  In this case, in the primary diagnosis for determining whether the relationship between the detected values of the three parameters of the intake air amount, the intake pipe pressure, and the engine rotational speed is out of the normal variation range, two of the three parameters are determined. In consideration of the fact that the remaining one parameter is uniquely determined from the parameters, in the second embodiment, the estimated intake pipe pressure is calculated based on the detected intake air amount by the air flow meter 14 and the engine rotational speed. It is calculated and it is determined whether or not the relationship (deviation, etc.) between the estimated intake pipe pressure and the intake pipe pressure detected by the intake pipe pressure sensor 18 is out of the normal variation range.

The abnormality diagnosis of the second embodiment described above is executed by the abnormality diagnosis routine of FIG. This routine is executed at a predetermined cycle during engine operation. When this routine is started, first, in step 201, the estimated intake pipe pressure is calculated by a map or the like based on the detected intake air amount by the air flow meter 14 and the engine speed, and then the process proceeds to step 202, where the intake pipe pressure sensor 18 calculates a deviation between the detected intake pipe pressure and the estimated intake pipe pressure (hereinafter referred to as “intake pipe pressure deviation”).
Intake pipe pressure deviation = Detected intake pipe pressure-Estimated intake pipe pressure

  Thereafter, the process proceeds to step 203, where the absolute value of the intake pipe pressure deviation is compared with a determination value K1 set in consideration of a normal variation range, and whether the absolute value of the intake pipe pressure deviation is larger than the determination value K1. The primary diagnosis which determines whether one of the air flow meter 14 and the intake pipe pressure sensor 18 is abnormal by the failure is performed. The processes in steps 202 and 203 serve as primary diagnostic means in the claims.

  If it is determined in step 203 that the absolute value of the intake pipe pressure deviation is equal to or less than the determination value K1, it is determined that the intake pipe pressure deviation is within a normal variation range, and the process proceeds to step 209. The routine is terminated when it is determined that both of the intake pipe pressure sensors 18 are normal.

  On the other hand, if it is determined in step 203 that the absolute value of the intake pipe pressure deviation is larger than the determination value K1, it is determined that either the air flow meter 14 or the intake pipe pressure sensor 18 is abnormal. The definite diagnosis for identifying which of the air flow meter 14 and the intake pipe pressure sensor 18 is abnormal by the processing of steps 204 to 208 is executed as follows.

First, in step 204, the estimated intake air amount is calculated by the following equation using the fuel injection amount and the air-fuel ratio detected by the air-fuel ratio sensor 24.
Estimated intake air amount = Fuel injection amount x Air-fuel ratio

  In the above equation, the fuel injection amount may be the required injection amount (fuel amount injected from the fuel injection valve 20) calculated by the ECU 27 based on the engine operating state or the like. Alternatively, in order to improve accuracy, the net amount of fuel sucked into the cylinder is calculated in consideration of the fuel (wet) adhering to the wall surface of the intake port or the like, and this is used as the “fuel injection amount”. You may do it. Further, it is preferable to set the air-fuel ratio detection timing in consideration of the delay until the gas burned in the cylinder flows through the exhaust pipe 22 and reaches the vicinity of the air-fuel ratio sensor 24 and the air-fuel ratio is detected.

In the next step 205, a deviation (hereinafter referred to as “air amount deviation”) between the intake air amount detected by the air flow meter 14 and the estimated intake air amount is calculated.
Air amount deviation = Detected intake air amount-Estimated intake air amount

  Thereafter, the process proceeds to step 206, where the absolute value of the air amount deviation is compared with the determination value K2 set in consideration of the variation range at the normal time, and if the absolute value of the air amount deviation is not less than the determination value K2, It is determined that the air amount deviation exceeds the normal variation range, and the process proceeds to step 208 to determine that the air flow meter 14 is abnormal.

  On the other hand, if it is determined in step 206 that the absolute value of the air amount deviation is smaller than the determination value K2, it is determined that the air amount deviation is within a normal variation range (the air flow meter 14 is normal). In step 207, it is determined that the intake pipe pressure sensor 18 is abnormal. The processing in steps 204 to 208 serves as a definite diagnosis means in the claims.

  In the second embodiment described above, the estimated intake pipe pressure is calculated based on the detected intake air amount by the air flow meter 14 and the engine speed, and the estimated intake pipe pressure and the detected intake pipe pressure by the intake pipe pressure sensor 18 are calculated. The primary diagnosis is performed to determine whether the relationship (deviation, etc.) is outside the normal variation range. When the primary diagnosis determines that there is an abnormality, the calculation is based on the air-fuel ratio and the fuel injection amount. A definite diagnosis is made by discriminating between the abnormality of the air flow meter 14 and the abnormality of the intake pipe pressure sensor 18 depending on whether or not the difference between the estimated intake air amount and the detected value (detected intake air amount) of the air flow meter 14 is equal to or larger than the determination value. Therefore, the abnormality of the air flow meter 14 and the abnormality of the intake pipe pressure sensor 18 can be distinguished and diagnosed with high accuracy without using new sensors such as an atmospheric pressure sensor. Becomes possible, it can meet the requirements of low cost and diagnostic accuracy simultaneously.

  In the second embodiment, when the primary diagnosis is performed, whether or not the relationship (deviation, etc.) between the estimated intake pipe pressure and the intake pipe pressure detected by the intake pipe pressure sensor 18 is out of the normal variation range. However, instead of this, primary diagnosis may be performed by any of the following methods.

[Other primary diagnostic methods (1)]
When performing the primary diagnosis, an estimated intake air amount is calculated by a map or the like based on the intake pipe pressure detected by the intake pipe pressure sensor 18 and the engine speed, and the estimated intake air amount and the detected intake air amount by the air flow meter 14 are calculated. It may be determined whether or not the relationship (deviation, etc.) is out of the normal variation range.

[Other primary diagnostic methods (2)]
When performing a primary diagnosis, an estimated engine rotation speed is calculated by a map or the like based on the detected intake air amount detected by the air flow meter 14 and the detected intake pipe pressure detected by the intake pipe pressure sensor 18, and the estimated intake air amount and the crank angle sensor are calculated. It may be determined whether or not the relationship (deviation, etc.) with the detected engine rotation speed by the signal 26 is out of the normal variation range.

  In the system configuration of FIG. 1, a variable intake valve device 33 that varies the opening / closing timing and / or lift amount of the intake valve 32 is mounted. In the second embodiment, the estimated intake pipe pressure is calculated based on the detected intake air amount and the engine rotational speed. However, in a vehicle equipped with the variable intake valve device 33, the variable valve amount (valve timing and / or The intake pipe pressure also changes depending on the change in the lift amount.

  In consideration of this point, in the abnormality diagnosis routine of FIG. 4 executed in the third embodiment, first, in step 201a, the estimated intake pipe pressure is estimated based on the detected intake air amount by the air flow meter 14, the engine rotational speed, and the variable valve amount. Is calculated by a map or the like. The subsequent steps 202 to 209 are the same as those in the second embodiment (FIG. 3).

  In the third embodiment described above, in the vehicle equipped with the variable intake valve device 33, the estimated intake pipe pressure can be calculated in consideration of the change in the intake pipe pressure due to the change in the variable valve amount. Can be increased.

In the fourth embodiment of the present invention shown in FIG. 5, in addition to the variable intake valve device 33, the present invention is applied to a vehicle equipped with an EGR device (not shown) that circulates part of the exhaust gas to the intake system. This is an example. In a vehicle equipped with an EGR device, the intake pipe pressure also changes depending on the EGR flow rate. Therefore, in the fourth embodiment, the EGR flow rate is estimated by the processing of steps 301 to 303 in FIG. Reflect in the estimation. Specifically, first, in step 301, an estimated EGR flow rate is calculated by a map or a model formula based on the intake pipe pressure detected by the intake pipe pressure sensor 18 and the EGR valve duty. Thereafter, the routine proceeds to step 302 where the estimated EGR flow rate is added to the detected intake air amount by the air flow meter 14 to determine the in-cylinder charged gas amount.
In-cylinder charged gas amount = detected intake air amount + estimated EGR flow rate

  Thereafter, the routine proceeds to step 303, where the estimated intake pipe pressure is calculated from a map or the like based on the cylinder charge gas amount, the engine speed, and the variable valve amount. The subsequent processing is the same as the processing of Steps 202 to 209 in FIG.

  In the fourth embodiment described above, in the vehicle equipped with the EGR device and the variable intake valve device 33, the estimated intake pipe pressure can be calculated in consideration of the change in the intake pipe pressure due to the change in the EGR flow rate and the variable valve amount. The accuracy of the estimated intake pipe pressure can be increased.

  In the fifth embodiment of the present invention shown in FIG. 6 to FIG. 8, taking into account that the intake pipe pressure changes depending on the intake air temperature, the in-cylinder charged gas amount is corrected by the intake air temperature correction coefficient corresponding to the intake air temperature. The pipe pressure is estimated. 7 is a block diagram for explaining the function of the primary diagnosis (steps 301 to 303 → steps 202 to 203), and FIG. 8 is the function of the definite diagnosis (when the primary diagnosis is judged to be abnormal) ( It is a block diagram explaining steps 204-208).

In the abnormality diagnosis routine of FIG. 6 executed in the fifth embodiment, first, in steps 301 and 302, the in-cylinder charged gas amount is calculated by the same method as in the fourth embodiment. An intake air temperature correction coefficient corresponding to the intake air temperature detected in (not shown) is calculated from a map (see FIG. 7) or the like. Thereafter, the process proceeds to step 302b, where the cylinder charge gas amount calculated in step 302 is multiplied by the intake air temperature correction coefficient to correct the cylinder charge gas amount.
In-cylinder charged gas amount = In-cylinder charged gas amount x intake air temperature correction coefficient

  Thereafter, the process proceeds to step 303, and the estimated intake pipe pressure is calculated by a map or the like based on the cylinder charge gas amount after the intake air temperature correction, the engine speed, and the variable valve amount. The subsequent processing is the same as the processing of Steps 202 to 209 in FIG.

  In the fifth embodiment described above, since the estimated intake pipe pressure is calculated by correcting the intake gas temperature in the cylinder, the accuracy of the estimated intake pipe pressure can be increased.

In the fifth embodiment, the in-cylinder charged gas amount is corrected for the intake air temperature. However, by multiplying the estimated intake pipe pressure calculated by the processing in steps 301 to 303 in FIG. 5 with the intake air temperature correction coefficient. The estimated intake pipe pressure may be corrected for the intake air temperature.
Estimated intake pipe pressure = Estimated intake pipe pressure x Intake temperature correction factor

It is a schematic block diagram of the whole engine control system in Example 1 of this invention. 3 is a flowchart illustrating a flow of processing of an abnormality diagnosis routine according to the first embodiment. 6 is a flowchart showing a flow of processing of an abnormality diagnosis routine of Example 2. 10 is a flowchart showing a flow of processing of an abnormality diagnosis routine of Example 3. 10 is a flowchart showing a flow of processing of an abnormality diagnosis routine of Example 4. 10 is a flowchart showing a flow of processing of an abnormality diagnosis routine of Example 5. It is a block diagram explaining the function (step 301-303-> step 202-203) of the primary diagnosis of Example 5. It is a block diagram explaining the function (steps 204-208) of a definite diagnosis.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 14 ... Air flow meter (intake air amount detection means), 15 ... Throttle valve, 18 ... Intake pipe pressure sensor (intake pipe pressure detection means), 20 ... Fuel injection valve, DESCRIPTION OF SYMBOLS 21 ... Spark plug, 24 ... Air-fuel ratio sensor (air-fuel ratio detection means), 26 ... Crank angle sensor (engine speed detection means), 27 ... ECU (Estimated intake air amount calculation means, abnormality diagnosis means, primary diagnosis means, confirmation Diagnostic means), 33 ... variable intake valve device, 35 ... variable exhaust valve device

Claims (5)

In an abnormality diagnosis device for an engine control system, comprising an intake air amount detection means for detecting an intake air amount and an air / fuel ratio detection means for detecting an air / fuel ratio of exhaust gas,
Estimated intake air amount calculation means for calculating an estimated intake air amount based on the air-fuel ratio detected by the air-fuel ratio detection means and the fuel injection amount;
An abnormality diagnosing unit for determining whether or not the intake air amount detecting unit is abnormal by comparing an intake air amount detected by the intake air amount detecting unit and an estimated intake air amount by the estimated intake air amount calculating unit; An abnormality diagnosis device for an engine control system, Intake air amount detection means for detecting intake air amount, intake pipe pressure detection means for detecting intake pipe pressure, engine rotation speed detection means for detecting engine rotation speed, and air-fuel ratio detection for detecting the air-fuel ratio of exhaust gas In an abnormality diagnosis device for an engine control system comprising means,
Estimated intake air amount calculation means for calculating an estimated intake air amount based on the air-fuel ratio detected by the air-fuel ratio detection means and the fuel injection amount;
The intake air amount detection means and the intake pipe are determined depending on whether or not the relationship between the three detection values by the intake air amount detection means, the intake pipe pressure detection means, and the engine rotation speed detection means is out of the normal variation range. Primary diagnosis means for executing primary diagnosis for determining whether one of the pressure detection means is abnormal;
When the primary diagnosis means determines that there is an abnormality, the difference between the intake air amount detected by the intake air amount detection means and the estimated intake air amount by the estimated intake air amount calculation means is compared with a predetermined determination value. If the difference is greater than or equal to a determination value, a definite diagnosis unit is provided for definite diagnosis as an abnormality in the intake air amount detection unit, and if the difference is less than a delimitation value, a definite diagnosis unit is provided for definite diagnosis as an abnormality in the intake pipe pressure detection unit. An abnormality diagnosis device for an engine control system,   The primary diagnosis means calculates an estimated intake pipe pressure based on the intake air amount detected by the intake air amount detection means and the detected engine rotation speed by the engine rotation speed detection means when performing the primary diagnosis, The engine control system abnormality according to claim 2, wherein it is determined whether or not a relationship between an estimated intake pipe pressure and a detected intake pipe pressure by the intake pipe pressure detecting means is out of a normal variation range. Diagnostic device.   The primary diagnosis means calculates an estimated intake air amount based on the detected intake pipe pressure by the intake pipe pressure detection means and the detected engine rotation speed by the engine rotation speed detection means when performing the primary diagnosis, 3. The engine control system abnormality according to claim 2, wherein it is determined whether or not a relationship between the estimated intake air amount and the intake air amount detected by the intake air amount detection means is out of a normal variation range. Diagnostic device.   When the primary diagnosis is performed, the primary diagnosis means calculates an estimated engine rotation speed based on the intake air amount detected by the intake air amount detection means and the intake pipe pressure detected by the intake pipe pressure detection means. The abnormality of the engine control system according to claim 2, wherein it is determined whether or not a relationship between the estimated engine rotation speed and the detected engine rotation speed by the engine rotation speed detection means is out of a normal variation range. Diagnostic device.

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