KR100427269B1 - Method of deciding trouble for system controlling air and fuel ratio feedback - Google Patents

Abstract

A failure determination method of an air-fuel ratio feedback control system is disclosed. A failure determination method of the disclosed air-fuel ratio feedback control system includes: (a) checking a cooling water temperature, an intake air temperature, an engine speed, and a filling efficiency; (b) determining whether a predetermined time has elapsed after the start mode is terminated; (c) determining whether the intake air temperature is within a predetermined range when the condition in step (b) is satisfied; (d) determining whether an engine stall (start-up), start-up, fuel cut, air volume sensor failure (AFS Fail) is satisfied if the conditions in step (c) are satisfied; (e) determining whether the engine speed is within a specific range when the condition in step (d) is satisfied; (f) if the condition in step (e) is satisfied, determining whether the filling efficiency (EV%) is within a specific range; (g) determining whether or not the air-fuel ratio feedback control determination start water temperature is higher than the condition in step (f); (h) determining whether the TPS output voltage is greater than or equal to a predetermined value (XTHPS) when the condition in step (g) is satisfied; (i) determining whether to start an air-fuel ratio (A / F) feedback when the condition in step (h) is satisfied; (j) determining whether to start fuel amount control and fuel amount learning by air-fuel ratio feedback when the condition in step (i) is satisfied; (k) determining an engine off; and the engine off. According to the present invention, there is an advantage that the misjudgment of the fuel system failure can be prevented and the increase of the exhaust gas (E / M) can be prevented.

Description

Fault determination method of air-fuel ratio feedback control system {METHOD OF DECIDING TROUBLE FOR SYSTEM CONTROLLING AIR AND FUEL RATIO FEEDBACK}

The present invention relates to a failure determination method of an air and fuel ratio feedback control system, and more particularly, an air-fuel ratio feedback control system for preventing a false determination of a failure of a fuel system and preventing an increase in exhaust gas. It relates to a failure determination method of.

In terms of performance of gasoline engine vehicles (exhaust gas, fuel economy, and power performance), the automatic control of fuel amount (fuel ratio) by oxygen sensor is the most important. Therefore, when an abnormality occurs in the fuel quantity (fuel ratio) feedback system, the ECU determines a failure and regulates a check engine lamp (MIL On) such as an engine check.

In view of the determination conditions, first, the coolant temperature sensor (WTS), the intake air temperature sensor (ATS), the air mass sensor (AFS), and the throttle position sensor (hereinafter referred to as TPS) according to the real time determination The sensor of the back should be normal.

In addition, the check engine lamp (MIL) is not turned on according to the fault determination by misfire monitoring, and the number of fault determination should be 0. (Typically, MIL is lit when two fault determinations are made.)

The failure determination method checks the cooling water temperature, the intake air temperature, the engine speed, and the filling efficiency, as shown in FIG. 1 (step 10).

Subsequently, after the start mode is terminated, it is determined whether a predetermined time (XTO2H_FBM; 30 seconds) has elapsed, the cooling water temperature is equal to or higher than the specific temperature (XWTO2_FBM), and the intake air temperature is within a predetermined predetermined range (XATO2C_FBM; -40C <intake temperature <XATO2H_FBM; 215C Determine if you are (Typically all operating areas are included) (steps 20, 30)

Subsequently, when the conditions in the above step are satisfied, it is determined whether the engine stall (start-up off), start-up, fuel cut, air flow sensor failure (AFS Fail) is performed, and the engine speed is determined in a specific range ( XNO2L_FBM; 1750 < engine speed <XNO2H_FBM;

When the condition in the above step is satisfied, it is determined whether the filling efficiency (EV%) is within a specific range (XO2EVL_FBM; 20% <EV% <XO2EVH_FBM; 60%), and the air-fuel ratio feedback control determination start water temperature (XWTFB; 7 ° C). (Step 60, 70) This means that if the temperature of the cooling water temperature oxygen sensor (O2 sensor) feedback control start is higher than the water temperature, the fault can be determined from the air-fuel ratio feedback control point.

In addition, if the condition in the above step is satisfied, it is determined whether the air-fuel ratio (A / F) feedback is started, and the fuel amount control and the fuel amount learning are started by the air-fuel ratio feedback (steps 80 and 90). In step 100, the flow is terminated (step 100).

On the other hand, when the condition in step 80 is not satisfied, the MIL is turned on by determining the air-fuel ratio feedback system failure. (Step 110) This means that the vehicle inspection is required.

The above steps 30, 50 and 60 are usually the actual driving area of the vehicle, that is, the vehicle condition while driving the exhaust gas test mode (LA-4, EC), and the failure determination is always performed in the real driving mode (most common). to be.

On the other hand, the normal decision is when the air-fuel ratio feedback control is started.

On the other hand, similar to the air-fuel ratio feedback fault determination, North America and Europe regulated the fault determination of the fuel system, requiring that the MIL be turned on when the exhaust gas exceeds the risk level of environmental pollution (national regulation) due to the abnormal fuel system. have.

Data calibration is performed as follows to properly determine the fuel system abnormality without exceeding the exhaust gas regulation value.

When a failure occurs to a certain extent, a failure determination will be made, and how much allowance of the exhaust gas to be regulated is most important. It will be slightly different for each EMS, but the current MELCO logic maps as follows.

First, by using the data of the ECU (Rich shift), forced lean (Lean Shift), the exhaust gas test is performed in parallel. The final decision of the data is determined by monitoring the air / fuel ratio (A / F) learning values and the air / fuel ratio integral values of the forced rich and the forced lean states with a margin for the exhaust gas regulation value. In other words, the A / F learning value and the A / F integral value exceed the failure determination threshold.

When an abnormality occurs in such a fuel system, in the conventional art as described above, a misjudgment occurs due to an air-fuel ratio (A / F) feedback system failure.

In general, the fuel system has a lot of instantaneous failures, and thus, a sudden excessive fuel quantity rich or excessive leanness may occur at a normal fuel quantity (performance ratio) learning value. If the fuel amount is 30% thinner than the normal fuel system, air-fuel ratio control may be as follows. (Problem condition: Acceleration pedal LTI (Light Tip In) condition after fuel system abnormality)

When the fuel amount is excessively lean, the oxygen sensor is fixed near 0V at a low output voltage, and the air-fuel ratio integral controls the fuel amount increase control to the feedback control upper limit. Nevertheless, when the fuel increase control is no longer possible due to the fuel shortage, the oxygen sensor continues to make a lean determination. When the driver does not step on the momentary pedal or drives very weakly, the output voltage of the oxygen sensor is continuously It is judged as lean and cannot be controlled beyond the upper limit of integral gain, so there is no opportunity for the proportional gain to fluctuate and the air-fuel ratio cannot be controlled.

If this condition is maintained for a certain time (approximately 30 seconds from the current basis), the fuel system abnormality judgment is made and the air-fuel ratio feedback system is malfunctioned.

In particular, the most important one in North America is a system failure determination method that has a decisive effect on exhaust gas and performance. Therefore, in case of misjudgment, serious situation may occur due to loss of reliability of the manufacturer's technology and fines.

On the other hand, if there is no problem as described above is as follows. When the accelerator pedal is operated suddenly, the acceleration fuel increase and the catalyst protection enrichment correction are applied due to the momentary change of the operating range, so that the output voltage of the oxygen sensor can easily transverse 0.45V, and there is no problem in starting the feedback. .)

And the fuel feedback feedback control equation is shown in Equation 1 below.

here,

T _B = amount of basic fuel injected by EV (filling efficiency),

K _LRN = feedback area air and fuel ratio (fuel quantity) learning value by oxygen sensor rich / lean determination,

K _MTCH = performance ratio matching correction factor,

K _AFND = air-fuel ratio correction coefficient for NRD change at low temperature

K _PRGLEAN = air-fuel ratio lean correction factor at initial inflow of purge air,

K _AS = weight correction factor after start-up,

= Acceleration and deceleration fuel quantity correction factor.

The _KMTCH is mapped so that lambda = 1 for all regions outside the feedback mode condition, and the learning values converge within 1 ± 0.07 in all regions. In addition, K _FB is a correction coefficient, and is defined as follows.

K _FB = 1 ± K _{P +} K _I (fuel amount feedback correction factor),

In the above, K _P = proportional coefficient, K _I = integral coefficient.

As shown in FIG. 2, the oxygen sensor located in the exhaust manifold checks the amount of oxygen in the exhaust gas, and determines that the oxygen sensor output is rich when the output of the oxygen sensor is 0.5V or more, and lean when it is less. Oxygen sensor (O2S) output range: 0 ~ 1V)

In addition, in the above Equation 1, the learning value K _LRN quantitatively learns the rich / lean degree by using the oxygen sensor output when the predetermined A / F learning condition in the feedback (F / B) mode is satisfied. The learning value K _LRN is updated by sampling the air-fuel ratio learning value for a certain period of time. Based on the learning value, A / F = 1 (but only in the F / B area) is followed by subtraction or addition control to the fuel amount of proportional coefficient (KP) and integral coefficient (KI).

In the prior art, when the fuel amount is excessively lean or rich, the air / fuel ratio feedback system failure determination may occur prior to the fuel system failure determination because the A / F feedback system is not normally controlled as described above. Since a very lean fuel is held, the HC, CO, and NOX emissions due to the lean fuel richness, rich control, and incomplete combustion are more than several times the steady state. As a result of the fuel system richness and lean similarity, the increase of exhaust gas was confirmed by test data.

The present invention has been made to solve the above problems, and the failure of the air-fuel ratio feedback control system to prevent the misjudgment of the fuel system failure (excessive rich or excessive lean), and to prevent the increase of the exhaust gas (E / M) Its purpose is to provide a determination method.

1 is a schematic flowchart sequentially illustrating a failure determination method of an air-fuel ratio feedback control system according to the related art.

2 is a determination waveform diagram according to an oxygen sensor output.

3 is a schematic flowchart sequentially showing a failure determination method of the air-fuel ratio feedback control system according to the present invention.

The failure determination method of the air-fuel ratio feedback control system of the present invention for achieving the above object comprises the steps of: (a) checking the cooling water temperature, intake air temperature, engine speed, and filling efficiency; (b) determining whether a predetermined time has elapsed after the start mode is terminated; (c) determining whether the intake air temperature is within a predetermined range when the condition in step (b) is satisfied; (d) determining whether an engine stall (start-up), start-up, fuel cut, air flow sensor failure (AFS Fail) is satisfied if the conditions in step (c) are satisfied; (e) determining whether the engine speed is within a specific range when the condition in step (d) is satisfied; (f) if the condition in step (e) is satisfied, determining whether the filling efficiency (EV%) is within a specific range; (g) determining whether or not the air-fuel ratio feedback control determination start water temperature is higher than the condition in step (f); (h) determining whether the TPS output voltage is greater than or equal to a predetermined value (XTHPS) when the condition in step (g) is satisfied; (i) determining whether to start an air-fuel ratio (A / F) feedback when the condition in step (h) is satisfied; (j) determining whether to start fuel amount control and fuel amount learning by air-fuel ratio feedback when the condition in step (i) is satisfied; (k) determining an engine off; and the engine off.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a schematic flowchart sequentially illustrating a failure determination method of the air-fuel ratio feedback control system according to the present invention.

Referring to the drawings, in the failure determination method of the air-fuel ratio feedback control system according to the present invention, first, the cooling water temperature, the intake air temperature, the engine speed, and the filling efficiency are checked.

Subsequently, it is determined whether or not a predetermined time (XTO2H_FBM; 30 seconds) has elapsed after the startup mode is terminated.

If a predetermined time (XTO2H_FBM; 30 seconds) has elapsed in step 220, the cooling water temperature is above a specific temperature (XWTO2_FBM), and the intake air temperature is within a predetermined range (XATO2C_FBM; -40C <intake temperature <XATO2H_FBM; 215C). To judge. (Typically all operating areas are included) (step 230)

If the condition in step 230 is satisfied, it is determined whether the engine stall (start-up off), start-up, fuel cut, air flow sensor failure (AFS Fail) is performed (step 240).

When the condition in step 240 is satisfied, it is determined whether the engine speed rpm is within a specific range (XNO2L_FBM; 1750 <engine speed <XNO2H_FBM; 3500) (step 250).

If the condition in step 250 is satisfied, it is determined whether the filling efficiency (EV%) is within a specific range (XO2EVL_FBM; 20% <EV% <XO2EVH_FBM; 60%) (step 260).

This means that when the cooling water temperature is greater than or equal to the O2 sensor feedback control determination start water temperature, fault determination is possible from the air-fuel ratio feedback control point.

Subsequently, when the condition in step 260 is satisfied, it is determined whether the air-fuel ratio feedback control determination start water temperature (XWTFB; 7 ° C.) or more is reached (step 270).

In addition, if the condition in step 270 is satisfied, it is determined whether the TPS output voltage is greater than or equal to a predetermined value (XTHPS).

In particular, the above-described steps 230, 250 and 260 are normal vehicle driving conditions, that is, vehicle conditions during driving of the exhaust gas test modes LA-4 and EC, and failure determination is always performed in the real driving (most common) mode.

Subsequently, it is judged whether to start the air-fuel ratio (A / F) feedback, and the fuel amount control and fuel amount learning by the air-fuel ratio feedback are started (steps 290 and 300). The engine off is determined and the flow is terminated. (Step 310)

If the condition in step 290 is not satisfied, the MIL is turned on by determining the air-fuel ratio feedback system failure (step 320). This means that the vehicle needs to be checked.

In FIG. 3, if the condition in each determination step except for step 320 is not satisfied, the flow (logic) is performed again.

On the other hand, as described in the prior art, the automatic feedback control of fuel amount (fuel ratio) by the oxygen sensor is most important in terms of actual gasoline engine vehicle performance (exhaust gas, fuel economy, and power performance). Therefore, when there is an abnormality in the fuel quantity (fuel ratio) feedback system, it is determined by the ECU and regulated Check Engine Lamp (MIL On).

The air-fuel ratio feedback system failure determination method is currently regulated only in the United States, but is gradually being applied worldwide as the importance of OBD-ll (self-diagnosis) is increasing.

In the prior art, there have been cases where a fuel system failure is incorrectly determined as an air-fuel ratio feedback system failure. Therefore, the present invention suppresses the case where the fuel system abnormality is misjudged as a failure of the air-fuel ratio feedback system. To this end, add important items to the fault determination condition as follows.

First, sensors such as a cooling water temperature sensor (WTS), an intake air temperature sensor (ATS), an air volume sensor (AFS), and a TPS in accordance with real time determination should be normal. And according to the fault determination by misfire monitoring, the MIL (check engine lamp) is not turned on and the number of fault determination should be 0. (Typically, MIL is turned on when the fault determination is made twice.)

In particular, in the present invention, step 280, which constitutes a feature of the present invention, that is, conditions for preventing an air-fuel ratio feedback system misjudgement in an excessively rich and lean state, has the following physical meanings.

The fuel is excessive and lean, and the output voltage of the oxygen sensor is fixed at around 1 V (excess rich) or 0 V (excess lean), so that the air-fuel ratio feedback system is normal but reaches the upper or lower clip value of the feedback integral. In the case where the fuel amount is lean or rich, the monitoring of the fuel system failure determination is continued, rather than the failure of the air-fuel ratio feedback system, for the air-fuel ratio feedback control.

In other words, the driver's accelerator pedal operation is applied to change the driving range and the acceleration fuel amount and the catalyst protection region rich correction value, the output voltage of the oxygen sensor can be changed, the air-fuel ratio feedback control and air-fuel ratio (fuel amount) learning can be normally performed, In this case, the TPS output voltage is added to the air-fuel ratio feedback failure determination condition because the fuel system failure determination can be performed normally without an error of the air-fuel ratio feedback system failure.

Therefore, when it is difficult to start the air-fuel ratio feedback control due to the fuel system failure in the application of the present invention is to more accurately monitor using the oxygen sensor and the throttle output voltage in order to prevent the misjudgment of the air-fuel ratio (A / F) feedback control system system failure. . That is, when the throttle opening degree is sufficiently changed but the air-fuel ratio feedback is not started, the air-fuel ratio feedback system is diagnosed as a failure.

On the other hand, the normal decision is a case where the air-fuel ratio feedback control is started. When the air-fuel ratio feedback control is started under the judging conditions, it is determined as normal.

As described above, the failure determination method of the air-fuel ratio feedback control system according to the present invention has the following effects.

When the fuel amount (A / F) is lean or excessive fuel system abnormality, there is a case in which the conventional technology is incorrectly judged as the air-fuel ratio feedback system failure before completing the fuel amount (A / F) learning and determining the fuel system failure. On the other hand, in the present invention, it is possible to suppress the case of incorrect judgment by adding the number of times of output voltage switching of the oxygen sensor to the failure determination condition of the air-fuel ratio (A / F) feedback control system to accurately determine whether the fuel amount feedback control is not performed due to the abnormal fuel system. .

In other words, when the oxygen sensor output voltage is fixed to the lower or upper limit because the fuel is rich or lean, the fuel amount (fuel ratio) learning is performed before the change of the operating area and the acceleration / catalyst protection increase by the operation of the accelerator pedal. It is possible to start the air-fuel ratio feedback control by allowing the output of the oxygen sensor to be changed by the correction, so that the fuel amount learning value can be calculated later to determine the fuel system failure, and the air-fuel ratio feedback control system can be prevented from being judged.

In the case of a fuel system abnormality, if the air fuel ratio control system is incorrectly judged by the prior art, the fuel consumption (fuel ratio) can no longer be learned because the air fuel ratio control system is already broken inside the ECU. Inflow could be a significant problem in terms of exhaust gas.

However, in the present invention, by suppressing the above misjudgment, it is possible to control the air / fuel ratio (A / F) feedback normally since it gives a delay to monitor the fuel system failure judgment, and also the theoretical air / fuel ratio after a predetermined time by the air-fuel ratio learning. Since the control becomes possible, the abrupt increase period of exhaust gas can be shortened and the increase of exhaust gas can be prevented.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent embodiments are possible. Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

Claims (2)

(a) checking the cooling water temperature, the intake air temperature, the engine speed, and the filling efficiency; (b) determining whether a predetermined time has elapsed after the start mode is terminated; (c) determining whether the intake air temperature is within a predetermined range when the condition in step (b) is satisfied; (d) determining whether an engine stall (start-up), start-up, fuel cut, air flow sensor failure (AFS Fail) is satisfied if the conditions in step (c) are satisfied; (e) determining whether the engine speed is within a specific range when the condition in step (d) is satisfied; (f) if the condition in step (e) is satisfied, determining whether the filling efficiency (EV%) is within a specific range; (g) determining whether or not the air-fuel ratio feedback control determination start water temperature is higher than the condition in step (f); (h) determining whether the TPS output voltage is greater than or equal to a predetermined value (XTHPS) when the condition in step (g) is satisfied; (i) determining whether to start an air-fuel ratio (A / F) feedback when the condition in step (h) is satisfied; (j) determining whether to start fuel amount control and fuel amount learning by air-fuel ratio feedback when the condition in step (i) is satisfied; (k) determining an engine off; engine failure determination method comprising a. The method of claim 1, And if the condition in step (i) is not satisfied, turning on the MIL according to the air-fuel ratio feedback system failure determination.