KR20010059255A - Method for leakage monitoring a fuel system of vehicle - Google Patents

Abstract

PURPOSE: A method for monitoring leakage in a fuel gauge of a vehicle is provided to accurately calculate leakage volume without any error in a fuel level controlling element by compensating with calculate leakage volume. CONSTITUTION: A method for monitoring leakage in a fuel gauge of a vehicle includes the steps of stabilizing an evaporation pressure signal outputted to a fuel tank(40), sealing the fuel gauge and measuring naturally generated fuel evaporation pressure(41), forming negative pressure to the measured fuel evaporation pressure(42), diagnosing leakage with inclination of fuel vapor pressure increase in negative pressure state(43), judging whether the calculated leakage volume is lower than non-leakage limit and more than the arbitrarily set leakage limit(44), performing leakage error with No.1 monitoring according to the judged leakage volume(47), and adding monitoring if the leakage volume is lower than the arbitrarily set leakage limit and No. 1 monitoring and compensating leakage volume if not No. 1 monitoring(49).

Description

METHOOD FOR LEAKAGE MONITORING A FUEL SYSTEM OF VEHICLE}

The present invention relates to a fuel system leakage monitoring method of a vehicle, and more particularly, to a fuel system leakage monitoring method for reducing a fuel level detection error caused by the presence of a leak in a negative pressure forming section in a cylinder of a fuel system. It is about.

Fuel vapor pressure leakage monitoring device in a conventional fuel system includes a sensor (1) for detecting the evaporation gas pressure in the fuel tank as shown in FIG. Control means (2) for detecting and controlling leakage with respect to the evaporated gas pressure signal detected by the sensor (1); It consists of a shutoff valve 3 which cuts off fuel supply by the signal output from the said control means 2.

The leakage monitoring method of the fuel vapor pressure leaking from the fuel gauge is shut against the purge duty of the canister purge solenoid valve (CPS) with respect to the evaporation gas pressure signal generated from the fuel tank pressure (DTP) as shown in FIG. 2. A fuel tank evaporation pressure stabilizing step of displaying an open / closed state of the off valve SOV in a waveform form and having a delay time to stabilize the evaporation pressure as shown in FIG. 3; Measuring fuel evaporation pressure that occurs naturally in a closed state of the fuel system; Forming a negative pressure at the fuel evaporation pressure measured in the step; In this step, the monitoring is performed by diagnosing the leakage with the rising slope of the fuel vapor pressure in the negative pressure state.

In the conventional leakage monitoring method configured as described above, the shutoff valve is opened from the fuel tank so that the evaporation pressure is stabilized. The evaporation pressure rise slope is measured, the evaporation pressure rise slope is negatively pressured using the negative pressure in the cylinder, and the fuel level correction element is calculated using the change slope of the fuel system evaporation pressure signal.

Then, as in the measured evaporation pressure rise slope step, the pressure recovery slope is corrected to calculate the fuel vapor pressure rise slope in the negative pressure state.

In this case, the leakage magnitude is subtracted from the slope of the naturally occurring fuel vapor pressure rise from the slope of the fuel vapor pressure rise of the negative pressure state.

However, the conventional fuel gauge leakage monitoring method assumes that there is no leakage at all times because the monitoring is performed only once in the driving cycle when the monitoring condition is satisfied without compensating according to the presence or absence of leakage in the section for forming a match to correct the fuel evaporation pressure. Monitoring under the following conditions.

Therefore, if there is a leak in the fuel system in the section forming the match, the evaporation pressure signal will appear at different slopes even for the same tank level.

As such, the conventional monitoring method uses a leak size calculation for a fuel level adjustment element that is not accurately corrected for fuel system leakage, thereby causing an error in fuel level adjustment element.

Therefore, an object of the present invention is to repeat the fuel level correction according to the presence or absence of leakage in the interval of correcting the fuel level adjusting element by using the negative pressure in the cylinder to the evaporation pressure rising slope that occurs naturally in the state in which the fuel gauge is closed by closing the valve. By performing the compensation by level calculation, it is intended to reduce the error of the fuel level correction element.

1 is a block diagram of a conventional fuel gauge leakage monitoring device.

Figure 2 is an output waveform diagram of a conventional fuel gauge leakage monitoring device.

Figure 3 is a flow chart for a conventional fuel gauge leakage monitoring method.

Figure 4 is a flow chart for the fuel system leakage monitoring method of the present invention.

In order to achieve the above object, the present invention comprises the steps of stabilizing the evaporation pressure signal output to the fuel tank; Closing the fuel gauge in the step and measuring a naturally occurring fuel evaporation pressure; Forming a negative pressure at the fuel evaporation pressure measured in the step; Diagnosing the leak with the gradient of fuel vapor pressure rising in the negative pressure state; Determining whether the leakage size calculated in the diagnosis step is equal to or less than the leakage-free limit value and more than the arbitrarily set leakage limit value; Performing a leakage error with one monitoring according to the leakage size determined in the step; Compensating for the leakage size by the calculated leakage size is less than the predetermined set leakage limit value and not monitored once.

Therefore, according to the present invention, the fuel level correction element is compensated by compensating the leak size calculated by the fuel vapor pressure gradient to the leak size calculated by performing one or more leak monitoring according to the above or below any set limit value. The leak size can be calculated accurately without error.

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

4 is a flowchart of a fuel leakage monitoring method of the present invention, comprising: stabilizing an evaporation pressure signal output to a fuel tank (40); Sealing (41) the fuel system in step (40) and measuring a naturally occurring fuel evaporation pressure; Forming (42) a negative pressure at the fuel evaporation pressure measured in step (41); Diagnosing (43) the leakage with the rising slope of the fuel vapor pressure in the negative pressure in the step (42); Judging (44) whether the leakage magnitude calculated in the step (43) is less than or equal to the no-leakage threshold value; Determining that there is no leakage (45) if less than or equal to the no-leakage threshold in step 44; and determining (46) if it is greater than or equal to a predetermined set leakage limit if not less than or equal to the or less; ; A step (47) of performing a leakage error by monitoring once if the set leakage limit value is equal to or greater than that in the step (46); Determining 48 monitoring if the set leakage threshold is less than or equal to the predetermined value in the step 47; In step 48, if monitoring once is followed by adding monitoring and performing an initial iteration, if not monitoring once, compensating for the leakage size with the calculated leakage size.

According to the present invention, the fuel system evaporation pressure signal is detected from the sensor 1 which detects the evaporation gas pressure from the fuel tank, and the detected signal is transferred to the canister purge valve preset by the control means 2. You're in control. The shutdown control valve is opened for this duty control signal and a delay time is allowed to stabilize the evaporation pressure (step 40). The control means 2 then closes the shut-off valve to measure the slope of the evaporation pressure rise that occurs naturally in a closed state of the fuel gauge (step 41), and underpresses the evaporation pressure rise slope using the negative pressure in the cylinder (step 42) The leakage level is calculated using the change slope of the fuel system evaporation pressure signal, and the fuel vapor pressure rise in the negative pressure state is corrected by adjusting the pressure recovery slope as in the measured evaporation pressure rise slope. Calculate the slope

At this time, the leakage magnitude is subtracted from the slope of the naturally occurring fuel vapor pressure rise from the slope of the fuel vapor pressure rise of the negative pressure state (step 43).

In the state where the leak size is calculated, the control means 2 determines whether the calculated leak size is less than or equal to the no-leakage threshold value (step 44), and if the calculated leak size is less than or equal to the leak-free limit value, It is determined that there is no leakage (step 45).

However, if it is determined that the leak size is less than or equal to the predetermined set leakage limit value, the control means 2 determines whether or not the leak size is greater than or equal to the predetermined set leakage limit value (1 mm leakage) (step 47). If the magnitude is not greater than a certain set leakage limit value, it is determined whether monitoring has been performed once (step 48), and if the monitoring result of step 1 is incremented by 1, it is repeated, while calculating the leakage size. Compensation is made with the leak size obtained (step 49).

As described above, the present invention calculates the evaporation pressure signal output to the fuel tank in a state in which the fuel system is sealed, the naturally occurring fuel evaporation pressure is measured, the negative pressure is formed, and the leakage magnitude is calculated by the slope of the fuel vapor pressure rise. It is determined whether the leakage size is less than the no-leakage limit value or more than the randomly set leakage limit value. If the calculated leakage size is more than the randomly set leakage limit value, the leakage error is performed by the first monitoring and the first monitoring is performed. By compensating for the calculated leak size, the leak size can be accurately calculated without error in the fuel level correction element.

Claims (1)

Stabilizing the evaporation pressure signal output to the fuel tank; Closing the fuel gauge in the step and measuring a naturally occurring fuel evaporation pressure; Forming a negative pressure at the fuel evaporation pressure measured in the step; Diagnosing the leak with the gradient of fuel vapor pressure rising in the negative pressure state; Determining whether the leakage size calculated in the diagnosis step is equal to or less than the leakage-free limit value and more than the arbitrarily set leakage limit value; Performing a leakage error with one monitoring according to the leakage size determined in the step; The fuel gauge of the vehicle, characterized in that it comprises the step of adding the monitoring and performing the initial repetition if it is less than the predetermined set leakage limit value and performing the initial repetition, and compensating for the leakage size by the calculated leakage size if the monitoring is not the first time. Leak monitoring method.