KR101602069B1 - Method for diagnosing leakage of fuel tank of vehicle - Google Patents

Abstract

The present invention relates to a method to diagnose a fuel leak of a vehicle, capable of easily diagnosing a fuel leak without an existing additional diagnosis device by diagnosing whether fuel in a fuel tank of a vehicle is leaked or not at an End-Of-Line (EOL) step by using a natural vacuum leakage detection (NVLD) module, a tank pressure sensor, and an engine control unit (ECU). The method includes: a step of determining a preset fuel leak diagnosis condition is satisfied or not after receiving switch information from the NVLD module.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a fuel leakage diagnosis method,

The present invention relates to a method of diagnosing a fuel leak in a vehicle, and more particularly, to a method of diagnosing a fuel leak in a vehicle, including an end of line (EOL) process using a NVLD (Natural Vacuum Leakage Detection) module, a tank pressure sensor, The present invention relates to a method for diagnosing a fuel leak of a vehicle, which is capable of easily diagnosing a fuel leak without existing additional diagnostic equipment by diagnosing whether a fuel leak exists in the fuel tank of the vehicle.

Recently, due to the accelerated pollution of the environment, regulation of exhaust gas, which has a great influence on air pollution in the automobile industry, is increasingly being regulated. In each country, automobile manufacturers are forced to reduce exhaust gas through various regulations. In particular, monitoring and fault diagnosis of exhaust gas related parts such as OBD (On Board Diagnosis) regulation is required.

The exhaust gas of the automobile mainly includes the unburned gas discharged from the crankcase and the evaporated gas generated by the evaporation of the fuel in the fuel tank as the external temperature increases, in addition to the combustion gas discharged through the muffler.

Since the evaporative gas in the dual fuel tank is composed of hydrocarbons and acts as an air pollutant causing the destruction of the ozone layer when discharged into the atmosphere, the evaporation gas generated by the evaporation of the fuel can be called a canister It is collected and stored in strong activated carbon, and it can be combusted by flowing into the intake air when the engine is driven.

If there is a leak in the fuel system from the fuel tank to the engine of the vehicle, the evaporation gas will flow out into the atmosphere. Therefore, the engine controller (ECU) correctly detects the leakage corresponding to the leak size of 0.5 mm and 1.0 mm To be detected.

As a result, each automobile manufacturer uses its own end-of-line (EOL) test to determine whether there is a leak in the fuel system of the vehicle. .

On the other hand, the system using NVLD (Natural Vacuum Leakage Detection) module among the various leak diagnosis systems detects the pressure change in the tank due to changes in outside temperature while the vehicle is stopped for several hours, and relatively easily diagnoses 0.5 mm leakage .

In addition, the existing system requires a separate idle section for leak diagnosis due to the fluctuation of the tank pressure sensor value when driving the vehicle. In the NVLD system, the diagnosis can be made while the engine is stopped, Go) vehicle leak diagnosis system.

However, in order to diagnose leaks based on only the NVLD component's own information, it is essential to satisfy the environmental conditions such as the engine stopping time (for example, about 4 hours) and the outside temperature change condition (for example, about 6 ° C) It can not be distinguished by diagnostic size because it is diagnosed as same as 0.5mm leak.

Accordingly, in the case of a vehicle equipped with an NVLD system, there is a problem that a separate tester is used to perform the EOL diagnosis or a separate part (for example, a pressure sensor, a canister shut-off valve) for the EOL diagnosis is mounted.

SUMMARY OF THE INVENTION The present invention has been conceived to solve the above problems, and it is an object of the present invention to provide a fuel supply system for a vehicle, which can prevent fuel leakage in a fuel tank of a vehicle in a vehicle assembly completion stage (EOL) by using an NVLD module, a tank pressure sensor and an engine controller The present invention provides a method of diagnosing a fuel leak of a vehicle that can diagnose fuel leakage easily without existing existing diagnostic equipment.

According to an aspect of the present invention, there is provided an engine control system for a vehicle, comprising: (a) receiving switch information from an NVLD (Natural Vacuum Leakage Detection) module through an engine controller of a vehicle; ; (b) controlling the opening of the purge valve and the opening time of the purge valve after raising the RPM of the engine until the predetermined target RPM value is reached, when the fuel leak diagnosis condition is satisfied; (c) when the tank pressure of the tank pressure sensor reaches a predetermined target pressure value within a predetermined threshold time, the purge valve is closed and the first tank pressure recovery slope value is calculated within the predetermined first tank pressure range, Calculating a second tank pressure recovery slope value within a predetermined second tank pressure range if the calculated first tank pressure recovery slope value is greater than or equal to a predetermined threshold value; And (d) if the calculated second tank pressure recovery slope value is less than a preset threshold value, calculating a difference value between the first and second tank pressure recovery slope values, Fuel ratio of the vehicle.

Preferably, in step (c), if the tank pressure does not reach a preset target pressure value within a predetermined threshold time, the switch information is received from the NVLD module and the switch is closed, and if the tank pressure is less than a predetermined threshold value Fuel leakage can be diagnosed.

Preferably, when the switch information is received from the NVLD module and the switch is opened and the tank pressure is equal to or higher than a predetermined threshold value, it is checked whether the purge valve is abnormal.

Preferably, if there is no abnormality of the purge valve, the NVLD module can be diagnosed by the switch-open fixation.

Preferably, when the switch information is received from the NVLD module and the switch is open and the tank pressure is less than a predetermined threshold value, the NVLD module can be diagnosed as switch open adherence.

Preferably, the first tank pressure range may be set to be lower than the second tank pressure range.

According to the fuel leakage diagnosis method of the present invention as described above, when there is a fuel leak in the fuel tank of the vehicle in the vehicle assembly completion stage (EOL) using the NVLD module, the tank pressure sensor and the engine controller The fuel leakage can be easily diagnosed without the existing additional diagnostic equipment.

Further, according to the present invention, the EOL diagnosis can be performed through the diagnostic logic inside the engine controller (ECU) of the vehicle, so that the additional cost reduction for the equipment for EOL diagnosis (for example, for external tester or vehicle parts mounting) There is a possible advantage.

In addition, according to the present invention, in the case of a conventional NVLD system, in the absence of an additional part (for example, a canister shut-off valve) There is an immediate testable benefit.

Further, according to the present invention, in the case of a system without a tank pressure sensor, since the conditions of forming the vapor pressure indirectly need to be grasped, the possibility of false diagnosis and cancellation of the diagnosis is increased, but if the direct vapor pressure is detected by the tank pressure sensor, Therefore, there is an advantage that accurate diagnosis result can be obtained.

Further, according to the present invention, in a system without a tank pressure sensor, a threshold value such as a purge flow rate for forming a constant negative pressure in the tank and a switch opening time of the NVLD module must be set through a plurality of vehicle tests, , And when the tank pressure sensor is present, it is directly controlled according to the tank pressure value, so that the development for this part can be omitted, and the vehicle development cost is advantageously reduced.

1 is a block diagram schematically illustrating an apparatus for implementing a method of diagnosing fuel leakage of a vehicle according to an embodiment of the present invention.
2 is a conceptual diagram for explaining a control process for diagnosing fuel leakage of a vehicle according to an embodiment of the present invention.
3 to 5 are overall flowcharts for explaining a method of diagnosing fuel leakage of a vehicle according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it should be understood that the following embodiments are provided so that those skilled in the art will be able to fully understand the present invention, and that various modifications may be made without departing from the scope of the present invention. It is not.

1 is a block diagram schematically illustrating an apparatus for implementing a method of diagnosing fuel leakage of a vehicle according to an embodiment of the present invention.

Referring to FIG. 1, an apparatus for implementing a method for diagnosing fuel leakage of a vehicle according to an embodiment of the present invention includes an oxygen sensor 100, a tank pressure sensor 200, a purge valve (CPV) 300, A canister 400, an NVLD module 500, an engine controller (ECU) 600, and the like.

Here, the oxygen sensor 100 is installed in an engine of a vehicle and performs a function of outputting an electrical signal corresponding to the change of the air-fuel ratio of the exhaust gas discharged from the engine. The tank pressure sensor 200 performs a function of detecting the difference between the atmospheric pressure and the pressure in the tank. The purge valve 300 functions to supply the evaporator gas of the canister 400 to the engine intake air. The canister 400 functions to collect the evaporative gas generated in the fuel tank. The NVLD module 500 performs the function of monitoring the pressure in the fuel system and the external temperature. The engine controller (ECU) 600 performs a function of controlling the entire system of the vehicle.

In the case of the NVLD module 500, a pressure relief valve positioned between the canister 400 and the atmosphere for reducing excessive pressure difference between both ends, and a pressure switch closed when the pressure in the tank is lower than a predetermined level , And a self-controller for monitoring the change in the outside air temperature and the switch closing information and transmitting the information to the engine controller (ECU) 600 may be mounted.

When the engine is driven, the engine controller (ECU) 600 confirms whether the switch of the NVLD module 500 is closed or not by communicating. When the engine is closed, the pressure of the tank is indirectly confirmed This is possible.

Hereinafter, a method for diagnosing fuel leakage of a vehicle according to an embodiment of the present invention will be described in detail.

2 is a conceptual diagram for explaining a control process for diagnosing fuel leakage of a vehicle according to an embodiment of the present invention.

Referring to FIGS. 1 and 2, when there is a diagnosis request by an external diagnostic device and the engine controller (ECU) 600 satisfies the internal diagnosis activation condition, the engine controller (ECU) .

This is to prevent starting-off due to additional evaporative gas (HC) being supplied when the purge valve 300 is opened at a certain rate at the normal idle RPM of the vehicle (e.g., about 650 rpm). When the idle RPM of the vehicle reaches the target value, a certain level of negative pressure in the tank (for example, -7 hPa) is formed through the opening of the purge valve 300.

At this time, the engine controller (ECU) 600 closes the purge valve 300 when the pressure in the tank reaches the target value (for example, -7 hPa) through the value of the tank pressure sensor 200. The difference in the time taken for the negative pressure in the tank to recover to the atmospheric pressure level differs depending on the presence or absence of leakage during the closing control of the purge valve 300. [

That is, in the case of the leak system, the negative pressure formed in the tank due to the leak is recovered to the atmospheric pressure level faster than the normal system. By monitoring the tank pressure recovery slope immediately after closing of the purge valve 300 using this characteristic, the presence or absence of leakage can be grasped.

In general, there is a distinguishable difference between the tank pressure recovery slope between the 0.5 mm leak and the normal system. However, when there is steam generation due to the rise in the fuel temperature, the pressure recovery rate of the normal system increases, There is a phenomenon that becomes impossible. To overcome this, the tank pressure is divided into two sections and monitored.

First, the first tank pressure recovery slope S1 is monitored (e.g., in the range of about -5 hPa to -2 hPa). In other words. When the negative pressure formed during the opening of the purge valve 300 is equal to or lower than the NVLD relief pressure, the purge valve 300 is quickly returned to the relief pressure level after closing. Since the pressure relief function of the NVLD module 500 is not operated thereafter, the atmospheric pressure level is restored according to the natural recovery rate according to the leakage level. When steam is generated in the tank, the recovery speed to the atmospheric pressure is accelerated due to the vapor pressure, and as a result, the normal system can be diagnosed as a leak system.

Second, the second tank pressure recovery slope S2 is monitored (e.g., in the range of about 0 hPa to 1 hPa). That is, there is a pressure increase due to the vapor pressure regardless of the leakage level of the system after the pressure in the tank is restored to the atmospheric pressure level. The slope of this section is proportional to the vapor pressure in the tank.

When the difference (S1-S2) between the first and second tank pressure recovery slopes is calculated, the pressure recovery speed difference due to the vapor pressure can be corrected, and the pressure fluctuation speed due to leakage can be derived. That is, since the vapor pressure intensity can be directly grasped and corrected to the diagnostic value, there is a benefit that the prevention of misdiagnosis and the case of canceling diagnosis are reduced.

3 to 5 are general flowcharts for explaining a method of diagnosing a fuel leak of a vehicle according to an embodiment of the present invention. Unless otherwise described, it is revealed that the engine controller (ECU) 600 performs as a main body.

3, information (for example, outside temperature, switch information, etc.) is received from the NVLD module 500 through the engine controller (ECU) 600 of the vehicle (S100) (S101).

That is, when there is an EOL leak diagnosis request through the external diagnostic device, the engine controller (ECU) 600 receives outside temperature, switch information, etc. from the NVLD module 400 through communication with the NVLD module 500. Upon completion of the communication for the information, whether or not the test is possible is determined including the internal variable of the engine controller (ECU) 600, and the condition (that is, the fuel leak diagnosis condition) is as follows.

The fuel leak diagnosis conditions include a switch current opening of the NVLD module 500, a tank pressure condition (e.g., <2hPa), an elapsed time condition after the engine start (e.g., <= 1200s), an engine coolant temperature condition (e.g. > = 70degC), the coolant temperature condition (eg. <= 70degC), the NVLD module 500 ambient temperature and coolant temperature difference conditions (eg. <= 15 degC) The engine idle condition, the ambient temperature condition of the NVLD module 500 (e.g., 0degC to 30degC), the ambient temperature elevation value condition of the NVLD module 500 after startup (e. <5 degC), low loading value of the canister 400, fuel level conditions (eg, 5L to 40L), no associated component error, and air-fuel ratio control normal operation.

As a result of the determination in step S101, if the fuel leak diagnosis condition is not satisfied, it is determined that there is no result (S102), and the process proceeds to step S110 to transmit the diagnosis result to the external tester.

Otherwise, if the fuel leakage diagnosis condition is satisfied, the RPM of the engine is increased until the predetermined target RPM value is reached (S103 and S104), then the opening of the purge valve 300 is controlled, 300 are calculated (S105).

Next, it is determined whether the tank pressure of the tank pressure sensor 200 reaches a predetermined target pressure value (for example, -7 hPa) within a predetermined threshold time (for example, 30 s) If the tank pressure does not reach the predetermined target pressure value within the predetermined threshold time, the "B" process described below is performed.

If it is determined in step S106 that the tank pressure of the tank pressure sensor 200 reaches the preset target pressure value within a predetermined threshold time, the purge valve 300 is closed and the first tank pressure range , A range of about -5 hPa to -2 hPa) (S107). On the other hand, it is preferable that the first tank pressure range is set to be lower than the second tank pressure range.

Thereafter, it is determined whether the value of the first tank pressure recovery slope S1 calculated in step S107 is less than a preset threshold value (for example, 0.1 hPa / s) (S108) If the value of the pressure recovery slope S1 is less than the preset threshold value, it is diagnosed that there is no fuel leakage (S109), and the diagnosis result is transmitted to the external tester (S110).

Otherwise, if the value of the first tank pressure recovery slope (S1) calculated in step S107 is equal to or greater than a predetermined threshold value, "A"

4, the value of the second tank pressure recovery slope S2 is calculated in a predetermined second tank pressure range (for example, about 0 hPa to 1 hPa) (S111) It is determined whether the value of the second tank pressure recovery slope S2 calculated in step S111 is less than a preset threshold value (e.g., 0.1 hPa / s) (S112).

On the other hand, if the value of the second tank pressure recovery slope S2 calculated in step S111 is equal to or greater than a preset threshold value, the result is regarded as no result (S113), and the flow proceeds to step S110 and the result is transmitted to the external tester.

Otherwise, if the value of the second tank pressure recovery slope S2 calculated in step S111 is less than the predetermined threshold value, the difference value S1-S2 of the first and second tank pressure recovery slope values is calculated, It is determined whether the value is less than a preset threshold value (e.g., 0.1 hPa / s) (S114).

If it is determined in step S114 that the difference (S1-S2) between the first and second tank pressure recovery slope values is less than the predetermined threshold value, it is diagnosed that there is no fuel leakage (S115) And transmits the diagnosis result to the external tester.

Otherwise, if the difference (S1-S2) between the first and second tank pressure recovery slope values is greater than or equal to a predetermined threshold value, the fuel leakage diagnosis is made (S116), the routine proceeds to step S110, Lt; / RTI &gt;

5, the switch information is received from the NVLD module 500 (S117), and it is determined whether the switch of the NVLD module 500 is closed (S118).

If it is determined in step S118 that the switch of the NVLD module 500 is closed, it is determined whether the tank pressure is equal to or greater than a predetermined threshold value (e.g., 1 hPa) (S119) (S120), and the process proceeds to step S110 and transmits the result to the external tester. Otherwise, if the tank pressure is less than the predetermined threshold value, it is diagnosed as fuel leakage (S121), and the process goes to step S110 and transmits the diagnosis result to the external tester.

If it is determined in step S118 that the switch of the NVLD module 500 is open, it is determined whether the tank pressure is equal to or greater than a predetermined threshold value (e.g., -4 hPa) (S122). If the tank pressure is less than a predetermined threshold value It is determined whether or not the purge valve 300 is abnormal (S123).

If it is determined in step S123 that there is an abnormality in the purge valve 300, the process proceeds to step S124, and the flow advances to step S110 to transmit the diagnosis result to the external tester. Otherwise, if there is no abnormality of the purge valve 300, the NVLD module 500 is diagnosed as being in the open state of the switch (S125), and the flow proceeds to step S110 and the diagnostic result is transmitted to the external tester. If it is determined in step S122 that the tank pressure is less than the preset threshold value, the flow advances to step S125 to diagnose that the NVLD module 500 is switched on.

Although the present invention has been described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And this also belongs to the present invention.

100: oxygen sensor, 200: tank pressure sensor,
300: purge valve, 400: canister,
500: NVLD module, 600: engine controller

Claims (6)

(a) receiving switch information from an NVLD (Natural Vacuum Leakage Detection) module through an engine controller of the vehicle, and determining whether a predetermined fuel leak diagnosis condition is satisfied;
(b) controlling the opening of the purge valve and the opening time of the purge valve after raising the RPM of the engine until the predetermined target RPM value is reached, when the fuel leak diagnosis condition is satisfied;
(c) when the tank pressure of the tank pressure sensor reaches a predetermined target pressure value within a predetermined threshold time, the purge valve is closed and the first tank pressure recovery slope value is calculated within the predetermined first tank pressure range, Calculating a second tank pressure recovery slope value within a predetermined second tank pressure range if the calculated first tank pressure recovery slope value is greater than or equal to a predetermined threshold value; And
(d) calculating a difference value of the first and second tank pressure recovery gradient values when the calculated second tank pressure recovery slope value is less than a predetermined threshold value, and diagnosing fuel leakage if the calculated second tank pressure recovery slope value is greater than a preset threshold value Wherein the fuel leakage diagnosis method comprises the steps of:
The method according to claim 1,
If the tank pressure does not reach a preset target pressure value within a predetermined threshold time, the switch information is received from the NVLD module and the switch is closed. If the tank pressure is less than the predetermined threshold value, And diagnosing the fuel leakage of the vehicle.
3. The method of claim 2,
Wherein when the switch information is received from the NVLD module and the switch is opened and the tank pressure is equal to or greater than a predetermined threshold value, the abnormality of the purge valve is checked, and if there is an abnormality, the purge valve is diagnosed .
The method of claim 3,
And if the purge valve is not abnormally diagnosed, the NVLD module is diagnosed as a switch-open fixation of the vehicle.
3. The method of claim 2,
Wherein when the switch information is received from the NVLD module and the switch is open and the tank pressure is less than a preset threshold value, the NVLD module is diagnosed as a switch open fixation of the vehicle.
The method according to claim 1,
Wherein the first tank pressure range is set to be lower than the second tank pressure range.

Images