JP2000274299A - Failure diagnostic device for intake air quantity detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately diagnose failure by diagnosing a characteristic change failure of the intake air quantity detecting device, when a detection value of the intake air quantity and a learning value thereof are compared with each other and the predetermined number or more operation area, in which the detection value is changed at a predetermined ratio or more in relation to the learning value. SOLUTION: Each detecting signal of an air flow meter 6, a crank angle sensor 9 and a throttle sensor 11 is taken into a control unit 12, and a learning value L-AFM of the intake air quantity is searched from a map, on the basis of the detected engine speed and the extent of throttle opening. Continuously, a discrimination whether US is changed at the prescribed ratio or more in relation to the L-AFM or not is done. When it is 'YES', operation area of this stage is stored. A number N of the operation area, in which change more than the prescribed ratio is discriminated, is counted up, and when the counted value exceeds the prescribed value, the air flowmeter 6 is diagnosed to have characteristic change failure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for diagnosing a malfunction of a device for detecting an intake air amount of an internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine equipped with an electronically controlled fuel injection device, it is common to control a fuel injection amount in proportion to a cylinder intake air amount to control an air-fuel ratio to a target value.

In such control, if an air flow meter (intake air amount detecting device) for detecting an intake air amount such as an intake air flow rate or an intake pressure fails, the control of the fuel injection amount and thus the air-fuel ratio cannot be performed normally. I'm trying to diagnose.

[0004]

However, in the conventional air flow meter failure diagnosis, when the detected value (output voltage) of the intake air amount sticks to the upper limit value or the lower limit value, or is fixed to the intermediate potential. In such a case, a failure is diagnosed, and the output gradient (the gradient of the output voltage with respect to the actual intake air amount) and the offset amount (the intake air amount 0
A characteristic change failure (e.g., initial output voltage in the state) cannot be diagnosed, and fail-safe control cannot be performed when the characteristic failure diagnosis occurs.

The present invention has been made in view of such a conventional problem, and based on a successive change of an intake air amount detection value under the same condition, a characteristic change failure such as an output inclination or an offset amount has been performed. It is an object of the present invention to provide a failure diagnosis device for an intake air amount detection device capable of diagnosing a failure.

[0006]

SUMMARY OF THE INVENTION Therefore, the invention of claim 1 is, as shown in FIG. 1, a failure diagnosing device for an intake air amount detecting device for detecting an intake air amount of an internal combustion engine. Intake air amount learning means for learning the detected value of the intake air amount by the intake air amount detection device for each operation region using the rotation speed as a parameter; and the detection value of the intake air amount and the intake air amount learning by the intake air amount detection device. Diagnostic means for comparing the learned value of the intake air amount obtained by the means with the intake air amount detection device based on a difference level between the two.

According to the first aspect of the present invention, the intake air amount learning means learns a detected value of the intake air amount at least for each operating region in which the engine speed is a parameter, and the diagnosis means includes a step of detecting the intake air amount. The detected value of the intake air amount by the device and the learned value of the intake air amount by the intake air amount learning means are compared, and the presence or absence of a failure of the intake air amount detection device is diagnosed based on the difference level between the two.

With this arrangement, if the output inclination or the offset amount of the intake air amount detector changes, the detection value changes with respect to the same intake air amount. Is different from the learning value at. Therefore, based on the difference level between the two, it is possible to diagnose whether or not there is a characteristic change failure in which output characteristics such as the output inclination and the offset amount of the intake air amount detection device greatly change.

In addition, since the detection value of the intake air amount is not compared with a fixed reference value, but is compared with a learning value that is sequentially learned, diagnosis is performed. With respect to a change in temperature or the like, an erroneous diagnosis can be prevented by comparing these with learned values obtained by learning these.

[0010] In the invention according to claim 2, the diagnostic means is such that when the detected value of the intake air amount changes by a predetermined ratio or more with respect to the learned value, the intake air amount detection device fails. Is diagnosed.

According to the second aspect of the present invention, the difference between the detected value and the learned value increases in proportion to the output level for the same degree of characteristic change, but is based on the rate of change of the detected value with respect to the learned value. In this configuration, the failure diagnosis can be accurately performed irrespective of the output level, that is, the magnitude of the intake air amount.

According to a third aspect of the present invention, the diagnostic means includes the step of, when there is a predetermined number or more of operating regions in which the difference level between the detected value of the intake air amount and the learned value is determined to be large.
Diagnosing that the intake air amount detecting device is out of order.

According to the third aspect of the invention, for example, when the detected value of the intake air amount changes by a predetermined ratio or more with respect to the learned value as described above, the difference level between the detected value and the learned value is changed. When it is determined to be large, and when the number of operating regions determined in this way is equal to or more than a predetermined number, it is diagnosed that the intake air amount detection device has failed.

Thus, erroneous diagnosis of sudden changes in output characteristics can be prevented, and diagnostic accuracy can be improved. Also,
The invention according to claim 4 is characterized in that the initial value of the learned value of the intake air amount detection is a value at the time of normal operation of the intake air amount detection device.

According to the fourth aspect of the present invention, when the learning is not progressing, a value close to the normal value of the intake air amount detecting device is used as the learning value. Accuracy can be ensured.

The invention according to claim 5 is characterized in that the intake air amount learning means learns a detected value of the intake air amount which is determined to have a small difference level with respect to the learned value of the intake air amount. .

According to the fifth aspect of the present invention, it is determined that the level of difference from the learned value is small, for example, when the amount of change in the detected value of the intake air amount with respect to the learned value is less than a predetermined ratio. Since only the detected value is learned, the reliability of the learned value learned as a normal value is improved, and the diagnostic accuracy is improved.

According to a sixth aspect of the present invention, the intake air amount learning means calculates a weighted average of the detected value of the intake air amount over time, or adds the latest detected value to the previous learned value and the previous learned value. The learning is performed by performing an arithmetic operation of adding a deviation from the learning value of a predetermined ratio.

According to the present invention, the past detection value and the latest detection value are averaged to absorb the instantaneous change in the detection value and to absorb the variation in the characteristic and the environmental change. Can be learned, the reliability of the learning value is improved, and the diagnostic accuracy is improved.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. In FIG. 2 showing an internal combustion engine provided with an intake air amount detecting device according to one embodiment and a control system thereof, air is supplied to an internal combustion engine 1 through an air cleaner 2, an intake duct 3, a throttle chamber 4, and an intake manifold 5. Inhaled.

The intake duct 3 is provided with an air flow meter 6 as an intake air amount detection device, and detects an intake air flow rate Q as a mass flow rate. The throttle chamber 4 is provided with a throttle valve 7 which is linked to an accelerator pedal (not shown) or driven by an actuator, and controls the intake air flow rate Q.

The intake manifold 5 comprises a collector portion 5a downstream of the throttle valve 7 and a branch portion 5b branched for each cylinder further downstream, and each branch portion 5b has an electromagnetic fuel injection valve as fuel injection means. Numeral 8 is provided to inject and supply fuel which is pressure-fed from a fuel pump (not shown) and controlled to a predetermined pressure by a pressure regulator.

A crank angle sensor 9 for outputting a reference signal for each predetermined crank angle position corresponding to a specific stroke of each cylinder and outputting a unit crank angle signal for each unit crank angle (for example, 1 ° or 2 °). A water temperature sensor 10 for detecting the temperature of the cooling water of the engine, a throttle sensor 11 for detecting the opening of the throttle valve 7 and the like are provided, and detection signals from these are input to a control unit 12 with a built-in microcomputer.

The control unit 12 detects the engine rotational speed Ne by measuring the cycle of each reference signal output from the crank angle sensor 9 or the number of unit crank angle signal inputs within a predetermined time. The fuel injection control and the ignition control are performed in accordance with the engine operating state obtained based on the above, while the failure diagnosis of the air flow meter 6 which is the intake air amount detection device is performed as follows.

FIG. 3 shows a flowchart of a failure diagnosis routine of the air flow meter according to the first embodiment. In step 1, the intake air amount US detected by the air flow meter 6 is read.

In step 2, the engine speed Ne detected based on the signal from the crank angle sensor 9 and the throttle opening TVO detected by the throttle sensor 11 as a representative value of the engine load are read.

In step 3, based on the read engine rotational speed and throttle opening, a learned value L-AFM of the intake air amount is retrieved from a map of the learned intake air amount using these as parameters.

In step 4, the detection value US of the intake air amount is compared with a learning value L-AFM to determine whether the detection value US has changed by a predetermined ratio or more with respect to the learning value L-AFM.

If the change is less than the predetermined ratio, the routine proceeds to step 5, where the learned value of the intake air amount is updated and learned according to the following equation. The functions of Steps 3 and 4 constitute the intake air amount learning means.

L-AFM _new ← m · (L-AFM _old ) +
(1-m) · US In step 4, the learning value L-AFM of the detection value US is obtained.
If it is determined that the change with respect to is equal to or greater than the predetermined ratio, the process proceeds to step 6.

In step 6, the operation range (N
e, TVO). In step 7, the number N of the operation regions (Ne, TVO) in which the change is determined to be equal to or more than the predetermined ratio is counted up.

In step 8, it is determined whether or not the number N of the operation regions is equal to or greater than a predetermined value No. Then, the predetermined value N
If it is less than o, this routine is terminated. If it is more than the predetermined value, the process proceeds to step 9 where it is diagnosed that the air flow meter 6 has a characteristic change failure such as an output gradient or an offset amount. The functions from step 7 to step 9 constitute diagnostic means.

In this manner, based on the difference level between the real-time detection value of the air flow meter 6 and the learning value, the presence or absence of a characteristic change failure in which the output characteristics such as the inclination and offset of the output of the air flow meter 6 greatly changes. Can be diagnosed, and erroneous diagnosis can be prevented with respect to variations in characteristics and environmental changes.

The initial value of the learning value L-AFM is:
By setting the value at the time of normal operation of the intake air amount detection device, it is possible to secure diagnostic accuracy of a predetermined level or more from the beginning. Further, since only the detection value determined to have a small difference level from the learning value is learned, the reliability of the learning value learned as a normal value is improved, and the diagnostic accuracy is improved.

The learning of the intake air amount is not limited to the above-mentioned weighted average calculation. For example, a calculation for adding a predetermined ratio of the deviation between the latest detection value and the previous learning value to the previous learning value is performed as follows. Such a configuration may be adopted.

L-AFM _new ← L-AFM _old + k · [U
S- (L-AFM _old )] Then, the value of the coefficient k in the weighted average calculation or the calculation of adding the deviation by a predetermined ratio in the weighted average calculation is determined by absorbing the instantaneous change in the detection value and the characteristic variation and the environment. Is set to a value that allows learning of the change in.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a system configuration diagram according to an embodiment of the present invention.

FIG. 3 is a flowchart showing a diagnosis routine of the air flow meter according to the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 6 Air flow meter 7 Throttle valve 9 Crank angle sensor 11 Throttle sensor 12 Control unit

Claims (6)

[Claims] 1. A failure diagnosis device for an intake air amount detection device for detecting an intake air amount of an internal combustion engine, wherein the detection of the intake air amount by the intake air amount detection device at least for each operation region in which the engine speed is a parameter. Intake air amount learning means for learning the value; comparing the detected value of the intake air amount by the intake air amount detection device with the learned value of the intake air amount by the intake air amount learning means; A diagnostic means for diagnosing the presence / absence of a failure in the air amount detection device. A failure diagnosis device for the intake air amount detection device, comprising: 2. The method according to claim 1, wherein the diagnosing means diagnoses that the intake air amount detecting device has failed when the detected value of the intake air amount has changed by a predetermined ratio or more with respect to the learning value. The failure diagnosis device for an intake air amount according to claim 1. 3. The intake air amount detecting device has failed when the diagnostic means determines that the difference between the detected value of the intake air amount and the learning value is large in a predetermined number of operating regions. The failure diagnosis device for an intake air amount according to claim 1, wherein the failure is diagnosed. 4. An initial value of a learning value for detecting the amount of intake air is:
3. The failure diagnosis device for an intake air amount detecting device according to claim 1, wherein the value is a normal value of the intake air amount detecting device. 5. The intake air amount learning means according to claim 1, wherein the intake air amount learning means learns a detected value of the intake air amount whose change amount with respect to the learned value of the intake air amount is less than a predetermined ratio. A failure diagnosis device for the intake air amount detection device according to any one of the above. 6. The intake air amount learning means calculates a weighted average of a detected value of the intake air amount over time, or determines a deviation between a latest learned value and a previous learned value in a previous learned value. The method according to claim 1, wherein learning is performed by performing an operation of adding a ratio.
6. A failure diagnosis device for an intake air amount detection device according to any one of claims 1 to 5.