JP3047589B2 - Engine intake system failure judgment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake system failure determining apparatus for determining a failure of an intake system of an engine.

[0002]

2. Description of the Related Art In a so-called L-Jetro type fuel injection control device for an engine, a basic injection amount is obtained based on an intake air amount and an engine speed, and the basic injection amount is corrected according to an engine operating state. Then, the fuel injection amount is determined. By the way, there is a case where the vacuum hose comes off on the downstream side of the throttle valve and the air abnormally flows into the intake manifold without passing through the air flow meter. At this time, in the fuel injection control device,
Since the fuel injection amount is determined based on the intake air amount detected by the air flow meter, the air-fuel ratio is shifted to the lean side by the increased air flow rate due to the abnormal inflow of the air, and the drivability may be deteriorated. .

Similarly, when an abnormality such as characteristic deterioration of the air flow meter itself occurs, the output of the air flow meter deviates from the actual intake air amount by an amount corresponding to the characteristic deterioration. The fuel ratio may shift to the lean side or the rich side, and the drivability may be deteriorated. For this reason, as disclosed in, for example, Japanese Patent Application Laid-Open No. 1-208549, at least the throttle opening, the engine speed,
A system has been proposed which determines a failure of the intake system based on three parameters of the intake pressure. This is a so-called D-Jetro system in which an intake pressure is detected to calculate a fuel injection amount, and an intake air amount is calculated based on an intake pressure detected by an intake pressure sensor.

[0004]

However, in such a conventional intake system failure determination apparatus, the failure of the intake system is determined based on at least parameters of the throttle opening, the engine speed, and the intake pressure. Therefore, when a failure occurs, it cannot be determined whether the failure is caused by intake leak due to a vacuum hose coming out or the like, or deterioration of characteristics of the intake pressure sensor itself (deterioration of characteristics of an air flow meter in an L-JETRO type). There is a defect.

The present invention has been made in view of such circumstances, and provides an intake system failure diagnosis apparatus which can determine an intake system failure while determining the cause of the intake system failure.

[0006]

For this reason, the present invention is based on FIG.
As shown in the figure, a rotation speed detecting means A for detecting the engine speed.
And intake air amount detecting means B for detecting an intake air amount of the engine.
In an engine for controlling a control target of the engine based on the detection signals of the detection means A and B, an intake negative pressure detection means C for detecting an intake negative pressure of the engine, and an intake negative pressure detection means C intake air amount and the at least the intake air amount is small region based on the detection signal of said rotational speed detecting means a and the
Multiple diagnostics with different intake air volume divided into large areas
Diagnostic area setting means D for setting an operating area; comparing means E for comparing the output value of the intake air amount detecting means B with a reference value of the intake air amount for each of the plurality of set diagnostic operating areas; Abnormality determination means F for determining an abnormality of the intake system from the comparison result in the diagnostic operation region.

[0007]

[Operation] In other words, the normal intake leakage amount is the engine speed, intake air
Since the pressure is almost constant regardless of the negative pressure, the magnitude of the intake air volume is determined based on the detected engine speed and intake negative pressure.
In addition to setting a plurality of diagnostic operation regions different from each other, the detection value of the intake air amount detection means is compared with a reference value in each diagnostic operation region, and further, an abnormality in the intake system is determined based on the comparison result. did.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, a throttle valve 3 is interposed in an intake passage 2 of an engine body 1, and a fuel injection valve 4 as a control target is provided in the intake passage 2 downstream of the throttle valve 3 . Further, an air flow meter 5 as an intake air amount detecting means for detecting an intake air amount, a throttle sensor 6 for detecting an opening degree of a throttle valve 3, and an intake air as an intake pressure detecting means for detecting an intake pressure of the intake passage 2. The pressure sensor 7 and the pressure sensor 7 are provided in the intake system, and their detection signals are input to a control device 8 composed of a digital computer or the like. The exhaust passage 9 is provided with an air-fuel ratio sensor 10 for detecting the air-fuel ratio from, for example, the oxygen concentration in the exhaust gas. The detection signal of the air-fuel ratio sensor 10 is input to the control device 8. Further, a detection signal from a rotation speed sensor 11 as rotation speed detecting means for detecting the engine rotation speed is input to the control device 8.

The control device includes a ROM (Read Only Memory) 81, a RAM (Random Access Memory) 82,
A PU (microprocessor) 83, an input port 84 and an output port 85 are provided, and these are connected to each other by a bidirectional bus 86. The control device 8 controls the air flow meter 5
After calculating the basic injection amount based on the intake air amount detected by the engine speed and the engine speed detected by the speed sensor 11, the basic injection amount is calculated based on the air-fuel ratio and the like detected by the air-fuel ratio sensor 10. After the correction, the fuel injection amount is calculated. Then, the control device 8 outputs a pulse signal corresponding to the calculated fuel injection amount to the fuel injection valve 4 to perform the fuel injection.

Here, the control device 8 constitutes a diagnosis area setting means, a comparison means, and an abnormality determination means. Next, the operation will be described with reference to the flowchart of FIG. The routine shown in this flowchart is executed at predetermined time intervals in a time synchronous manner. At S1, various signals such as the engine speed, intake pressure, intake air amount and the like are read.

In S2, the first and second judgment values T1 and T2 for judging the abnormality of the intake system are reset to initial values (= 0). In S3, the detected engine speed N is set to a predetermined value N1.
(For example, 1500 rpm) or less and whether or not the detected intake pressure P is greater than or equal to a predetermined value P1 (for example, 400 mmHg). If YES, proceed to S4, and if NO, proceed to S6. This determination is provided to determine an operation region in which the amount of intake air supplied to the engine is small (hereinafter, referred to as a first operation region).

In step S4, a reference value Q1 of the intake air amount is retrieved from a map based on the detected engine speed and intake pressure, and is then obtained by interpolation calculation. This reference value is set in a map corresponding to the engine speed and the intake pressure as shown in FIG. 4, and the reference value is set so as to decrease as the engine speed increases, and as the intake pressure decreases. It is set to be large. This reference value corresponds to a normal intake air amount of the intake system.

In S5, a deviation (= 100 × (Q1-Q) / Q1) between the detected intake air amount Q and the reference value Q1 is calculated, and the calculated value is set to a first determination value T1. On the other hand, if it is determined in S3 that it is not in the first operation range, then in S6
It is determined whether the detected engine speed N is equal to or higher than a predetermined value N2 (eg, 3000 rpm) and the detected intake pressure P is equal to or lower than a predetermined value P2 (eg, 300 mmHg).
If S, the process proceeds to S7, and if NO, the routine ends. This determination is provided to determine an operation region where the amount of intake air is large (hereinafter, referred to as a second operation region). Here, the first and second operation regions constitute a diagnostic operation region.

In step S7, a reference value Q2 of the intake air amount is retrieved from the map based on the detected engine speed and intake pressure, and is then obtained by interpolation calculation. In S8, the difference between the detected intake air amount Q and the reference value Q2 (= 100 ×
(Q2−Q) / Q2) and calculate the calculated value as a second determination value T.
Set to 2. In S9, the first determination value T1 is 10
% And the second determination value T2 is 10% or more. If YES, it is determined that there is an abnormality in the intake system, and S10
If the determination is NO, the process proceeds to S11. In this determination, it is determined whether or not the output of the air flow meter 5 is shifted by 10% or more with respect to the amount of intake air supplied to the engine (corresponding to Q1 and Q2) in the first and second operation regions.

If the output is shifted by 10% or more, it is determined in S10 whether the first judgment value T1 is larger than the second judgment value T2 by a predetermined value TA (for example, 10%). The process advances to S12, and if NO, the process advances to S13. In this determination, it is determined whether the abnormality of the intake system is due to intake air leakage or deterioration of the characteristics of the air flow meter 5 by comparing the deviation between the first operation region and the second operation region. Here, the predetermined value TA is determined from individual engine characteristics.

Next, the reason why it is possible to determine whether an abnormality is caused by leakage of intake air or an abnormality caused by deterioration of the air flow meter 5 will be described with reference to FIG. First, an equal intake air amount curve when the intake system is normal changes as shown by a solid line in FIG. 5 with respect to the engine speed and the intake negative pressure. When the intake air leaking into the engine due to the intake of air not passing through the air flow meter 5 due to the removal of the vacuum hose or the like, the intake air amount actually introduced into the engine becomes the intake air amount based on the output value of the air flow meter 5. On the other hand, it increases by the amount of intake leakage. Further, when the intake air leak occurs, the intake negative pressure detected by the intake pressure sensor 7 decreases, so that the equal intake air amount curve is on the high intake air amount side (upper right side in FIG. 5) as shown by the chain line in FIG. Shift by a predetermined amount. Here, in the case of intake air leakage, since the amount of intake air leakage is generally substantially constant irrespective of changes in the engine speed and the intake negative pressure (engine load), the equal intake air approximate curve shows the absolute value of the total intake air amount. There is a correlation that the smaller the value, the larger the shift.

On the other hand, when the characteristic of the air flow meter 5 is deteriorated, the intake air amount based on the output value of the air flow meter 5 is shifted to the plus side or the minus side by the amount of the characteristic deterioration with respect to the actual intake air amount. The equal intake air amount curve shifts to the upper right or lower left in FIG. There is no correlation that the shift amount at this time increases as the absolute value of the total intake air amount decreases, as in the case of the intake leak. In addition, when the intake air leaks, the intake air amount does not change to the negative side.

Therefore, in an operation region where the intake air amount is small (first operation region in this embodiment) and in an operation region where the intake air amount is large (second operation region in this embodiment),
By comparing the output value of the air flow meter 5 with the reference value and comparing the comparison results, it is possible to determine whether an abnormality in the intake system is an intake leak or a characteristic deterioration of the air flow meter 5.

Therefore, in S10, the first judgment value T1 in the first operation region where the intake air amount is small is a predetermined value T larger than the second judgment value T2 in the second operation region where the intake air amount is large.
If it is determined that the value is larger than A, it is determined in S12 that the intake system is abnormal due to intake leakage, otherwise, S
In 13, it is determined that the intake system is abnormal due to the characteristic deterioration of the air flow meter 5.

In S11, it is determined whether the first determination value T1 is -10% or less and the second determination value T2 is -10% or less.
If YES, the process proceeds to S13, and if NO, the process proceeds to S14. Here, when T1 ≦ −10% and T2 ≦ −10%, the deviation of the output of the air flow meter 5 with respect to the actual intake air amount is less than 10% in consideration of the determination in S9, so that the intake system is It can be determined that it is normal.

Therefore, it is determined in S14 that the intake system is normal. On the other hand, although it is determined in S9 that T1 ≧ 10% and T2 ≧ 10%, in S11, T1 ≦ −10%.
When it is determined that 10% and T2 ≦ −10%, the deviation of the output of the air flow meter 5 from the actual intake air amount is large, and the output characteristic of the air flow meter 5 is largely deviated from the regular product. 5 is judged to be deteriorated.

Therefore, in S13, the air flow meter 5
Is determined to have deteriorated. As described above, both when setting the first and second diagnostic operating region based on the engine speed and the intake pressure, after comparing the output value and the reference value of the airflow meter 5 at each diagnostic operation region, Since the abnormality of the intake system is determined based on the comparison result, the abnormality of the intake system can be accurately determined while accurately determining whether the intake air leaks or the characteristic deterioration of the air flow meter 5. This allows
Since it is possible to shorten the time required for the failure diagnosis of the service technician, it is possible to obtain an effect that the repair cost burden on the vehicle user can be reduced.

In this embodiment, the diagnostic operation region is set to two regions. However, the diagnostic operation region may be further increased. In this case, the accuracy of the failure diagnosis can be improved. Further, in the present embodiment, since the intake pressure sensor is installed in the engine, the failure can be determined by the control device mounted on the vehicle.
When the intake pressure sensor is not installed, a failure can be determined by using an off-board diagnostic device having an intake pressure sensor and a function of reading necessary data from a control device mounted on the vehicle through communication.

[0024]

As described above, the present invention increases the amount of intake air based on the detected engine speed and intake negative pressure.
While setting multiple diagnostic operation areas with different small relationships ,
After comparing the detected value of the intake air amount detecting means with the reference value in each diagnostic operation region, the abnormality of the intake system is determined based on the comparison result, so that the intake air leakage and the deterioration of the intake air amount detecting means are determined. Thus, it is possible to accurately determine the abnormality of the intake system while accurately determining whether the malfunction has occurred, thereby shortening the time required for the failure diagnosis by the service person.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of the present invention.

FIG. 2 is a configuration diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart of the above.

FIG. 4 is a diagram for explaining the operation of the above.

FIG. 5 is another view for explaining the operation of the above.

[Explanation of symbols]

4 Fuel injection valve 5 Air flow meter 7 Intake pressure sensor 8 Control device 11 Rotation speed sensor

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02D 45/00 F02D 41/18 F02D 41/22

Claims (1)

(57) [Claims] An engine speed detecting means for detecting an engine speed;
An intake air amount detecting means for detecting an intake air amount of the engine, wherein an intake negative pressure of the engine is detected based on a detection signal of the detecting means. Pressure detection means, at least a region where the amount of intake air is small and an amount of intake air based on detection signals from the intake negative pressure detection means and the rotation speed detection means.
Multiple diagnostics with different intake air volume divided into large areas
Diagnostic area setting means for setting an operating area; comparing means for comparing an output value of the intake air amount detecting means with a reference value of the intake air amount for each of the plurality of set diagnostic operating areas; Abnormality determination means for determining an abnormality in the intake system from the comparison result in (1).