KR20180044116A - System of leak diagnosis of fuel supply system for vehicle and method of leak diagnosis thereof - Google Patents

Abstract

Disclosed is a leak diagnosis system for a vehicular fuel supply system including: a shut-off valve operated to open and close a first flow path connecting a fuel tank and a canister; a first valve provided in a second flow path connecting the first flow path and the fuel pump, the first valve operating to open and close the second flow path; a solenoid valve provided on a return passage connecting the fuel pump and the fuel tank, the solenoid valve being operated to open and close the return passage; a second valve provided in an air discharge passage which is another flow passage for connecting the fuel pump and the fuel tank, the second valve being operated to open and close the air discharge passage; a canister closing valve operated to open and close the connection between the canister and the atmosphere; and a control unit for individually controlling opening and closing operations of the shutoff-valve, the solenoid valve, the first and second valves, and the canister closing valve.

Description

TECHNICAL FIELD [0001] The present invention relates to a leak diagnosis system and a leakage diagnosis method for a fuel system for a vehicle,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a leakage diagnosis system and leak diagnosis method for a fuel system for a vehicle for determining whether a fuel tank and a canister are leaks in a plug-in hybrid electric vehicle (PHEV).

Generally, in the case of a vehicle that can be driven by an engine, a fuel system (system) for supplying fuel to the engine is provided. The fuel system includes a fuel tank for storing fuel, a fuel pump for supplying fuel of the fuel tank to the engine, a canister for collecting fuel vapor of the fuel tank, And a purge control solenoid valve (PCSV) disposed between the intake manifold of the engine and the canister for transferring the fuel system to the engine. The fuel system has an open system.

In recent years, however, plug-in hybrid vehicles have been produced which allow the vehicle to travel through electric energy to the engine. In the case of a plug-in hybrid vehicle, the hybrid vehicle can be driven in a 100% EV mode without the help of an engine. However, even if the engine is driven in the 100% EV mode, a fuel tank may be provided to store the fuel in case the engine needs to be driven only with the engine or in the engine mode. Even when the plug-in hybrid vehicle is traveling in the EV mode, the fuel in the fuel tank is evaporated by the external environment or the like, and the fuel evaporation gas is continuously generated. When the fuel evaporation gas is continuously supplied to the engine in a situation where the engine is not driven, the supply of the fuel evaporation gas becomes saturated in the engine. However, when the fuel evaporation gas is not sent to the engine, the pressure of the fuel tank continuously increases. Therefore, in the case of the plug-in hybrid vehicle, the fuel tank is provided with a Fuel Tank Isolate Valve so that the fuel tank maintains the closed system. When the pressure in the fuel tank becomes high due to the fuel evaporation gas, The shutoff valve of the fuel tank is appropriately opened or closed by reducing the pressure in the fuel tank by discharging the gas so that the pressure inside the fuel tank is not overpressured.

Further, the fuel system is provided with an electric leak check module for detecting leakage of the fuel system. The leak detection module detects a leak of the fuel system by forming a negative pressure in the fuel tank and the canister at a time when the temperature and pressure in the fuel tank are stabilized after the vehicle is turned off. However, when such leak detection module is used, the structure is complicated and the cost is increased.

It should be understood that the foregoing description of the background art is merely for the purpose of promoting an understanding of the background of the present invention and is not to be construed as an admission that the prior art is known to those skilled in the art.

KR 10-2009-0105010 A

The present invention has been proposed in order to solve such a problem, and provides a leak diagnosis system and a leak diagnosis method for a fuel system for a vehicle, which can confirm the leaks of a vehicle fuel system more accurately, It has its purpose.

According to an aspect of the present invention, there is provided a leak diagnosis system for a fuel system for a vehicle, including: a shut-off valve operative to open and close a first flow path connecting a fuel tank and a canister; A first valve provided in a second flow path connecting the first flow path and the fuel pump, the first valve operating to open and close the second flow path; A solenoid valve provided in a return passage connecting the fuel pump and the fuel tank, the solenoid valve being operated to open and close the return passage; A second valve which is provided in an air discharge passage which is another flow passage for connecting the fuel pump and the fuel tank, and which operates to open and close the air discharge passage; A canister closing valve operable to open and close the connection between the canister and the atmosphere; And a control unit for separately controlling opening and closing operations of the shutoff valve, the solenoid valve, the first and second valves, and the canister closing valve.

The second flow path branches off from the first flow path, and a branch point can be located between the canister and the shutoff valve.

The second flow path may further include a third flow path branched from the second flow path and connected to the fuel tank, and the first valve may be installed at a branch point between the second flow path and the third flow path.

The first valve may selectively open only one of the second flow path and the third flow path depending on the movement of the plunger.

The first valve can open the third flow path so that fuel in the fuel tank is moved to the fuel pump by the plunger being moved and closed by the pressure of the fuel and the pressure of the elastic member when the vehicle travels.

The first valve closes the third flow path and opens the second flow path by pressing the plunger of the first valve by the pressure of the fuel in the return flow path when the fuel system is diagnosed, So that air can be introduced into the fuel pump through the flow path.

The return channel may further include a regulator.

The control unit may open the return flow passage so that a part of the fuel in the fuel pump is moved to the fuel tank through the return flow passage by controlling the solenoid valve to open when the vehicle travels.

The control unit may close the return flow passage so that a part of the fuel in the fuel pump can not be moved to the fuel tank through the return flow passage by controlling and closing the solenoid valve at the time of diagnosis of the fuel system.

The second valve is provided between the return flow path and the air discharge flow path so that only one of the return flow path and the air discharge flow path can be selectively opened by the hydraulic pressure in the return flow path.

The second valve is capable of closing the air discharge passage by pressing the plunger by the elastic member when the vehicle is running and closing it.

The second valve opens the plunger by the pressure of the fuel in the return flow path when the fuel system is diagnosed and opens the air discharge flow path so that the air moved into the fuel pump flows along the air discharge flow path, It can be moved into the tank.

According to another aspect of the present invention, there is provided a leak diagnosis method for a leak diagnosis system for a fuel system for a vehicle, the leak diagnosis system for a fuel system for a fuel system for a vehicle according to claim 1, A fuel pump driving step of closing the shut-off valve provided in the fuel tank, closing the solenoid valve, and driving the fuel pump when the reference time input to the control unit is exceeded; Wherein when the fuel tank is driven in the fuel pump driving step, the first valve and the second valve are opened by the fuel pressure and air is introduced through the second flow path, and the specified pressure, A fuel pump stopping step of opening the solenoid valve and stopping driving of the fuel pump if it is determined that the fuel pump is formed; And when the driving of the fuel pump is stopped in the step of stopping the fuel pump, the first valve and the second valve are closed by the fuel pressure, and the pressure inputted to the control unit by the detection means is inputted to the control unit And a leak checking step of confirming whether or not the reference value is satisfied.

In the fuel pump driving step, after the start-off signal of the vehicle is inputted, the canister closing valve can be closed if the reference time input by the control unit is exceeded.

Wherein the control unit is operable to determine whether the pressure of the fuel tank delivered to the control unit through the detection unit is within a range in which leak diagnosis of the fuel tank is possible, Step;

If it is determined that the pressure of the fuel tank is within the leak diagnosis range of the fuel tank, it is possible to check whether the fuel tank and the canister are leaked.

If it is determined that the pressure of the fuel tank is not within the leak diagnosis range of the fuel tank in the tank pressure checking step, only the leakage of the canister can be checked.

According to the leak diagnosis system and the leak diagnosis method for a fuel system for a vehicle having the above-described structure, it is possible to more accurately diagnose the leak of the fuel tank or the canister through only a pressure factor which is at least one factor.

In particular, since the parts for diagnosis are mounted in the fuel tank or the canister, the space can be reduced without occupying a separate space, and the configuration and control are simple and the cost is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a leak diagnosis system for a fuel system for a vehicle according to an embodiment of the present invention; FIG.
2 is a view showing a flow of fuel in a fuel tank when the vehicle is running;
Figs. 3 to 5 are diagrams showing states in the fuel tank when the fuel system is diagnosed. Fig.
6 is a block diagram illustrating a method of diagnosing a leak of a leak diagnosis system for a fuel system for a vehicle according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a leak diagnosis system and a leak diagnosis method for a fuel system for a vehicle according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a view showing a leak diagnosis system for a fuel system for a vehicle according to an embodiment of the present invention, FIG. 2 is a view showing the flow of fuel in the fuel tank 200 when the vehicle is running, 5 is a view showing the state in the fuel tank 200 at the time of the fuel system diagnosis. And FIG. 6 is a block diagram showing a leak diagnosis method of a leak diagnosis system for a fuel system for a vehicle according to an embodiment of the present invention. The leak diagnosis system and the leak diagnosis method for a vehicle fuel system of the present invention can be applied to a fuel system having a closed system applied to a plug-in hybrid vehicle (PHEV) particularly in a vehicle. Here, reference numeral 220 denotes a top plate of the fuel tank 200, and 240 denotes a bottom plate.

A leak diagnosis system for a fuel system for a vehicle according to a preferred embodiment of the present invention includes a shut-off valve 230 for opening and closing a first flow path 600 connecting a fuel tank 200 and a canister 300; A first valve 510 provided in a second flow path 700 connecting the first flow path 600 and the fuel pump 210 to open and close the second flow path 700; A solenoid valve 400 provided on a return passage 810 connecting the fuel pump 210 and the fuel tank 200 to open and close the return passage 810; A second valve 530 provided in the air discharge passage 850, which is another flow passage connecting the fuel pump 210 and the fuel tank 200, to operate to open and close the air discharge passage 850; A canister closing valve 310 operable to open and close the connection between the canister 300 and the atmosphere; And a control unit 900 for individually controlling opening and closing operations of the shutoff valve 230, the solenoid valve 400, the first and second valves, and the canister closing valve 310.

As shown in FIG. 1, the vehicle is provided with the fuel tank 200 for supplying fuel to the engine 100. The fuel tank 200 is provided with the fuel pump 210 for supplying fuel to the engine 100. The fuel tank 200 is provided with the shut-off valve 230 for isolating the fuel tank 200 and a vent valve 250 for discharging the air in the fuel tank 200 when the fuel is injected, Detection means 270 for detecting the state of the fuel tank 200 is provided. In particular, the detection means 270 may be a pressure sensor capable of detecting the pressure in the fuel tank 200. The pumped fuel is supplied to the engine 100 through the injector 130 provided in the intake line 110 of the engine 100 through the high pressure pump 290 through the fuel pump 210 do.

The fuel tank 200 is connected to the canister 300. The canister 300 collects the fuel vapor generated in the fuel tank 200 and supplies the collected fuel vapor to the engine 100 through the intake line 110 through the return line 370 do. The return line 370 is provided with a purge control solenoid valve 390 that operates to open and close the return line 370. The canister 300 is provided with the canister closing valve 310 connected to the atmosphere. When the canister closing valve 310 is opened and the atmospheric air flows into the canister 300, the canister air filter 310 for filtering the impurities contained in the air, And a detection unit 350 for detecting the state of the canister 300 is also provided. The detection means 350 may be a pressure sensor for detecting the pressure of the canister 300.

The fuel tank 200 and the canister 300 are connected by the first flow path 600 and the first flow path 600 is connected to the shutoff valve 230, . The shutoff valve 230 is preferably located on the first flow path 600 and is located between the vent valve 250 of the fuel tank 200 and the canister 300 .

In the first flow path 600, the second flow path 700 connecting the first flow path 600 and the fuel pump 210 is branched. The second flow path 700 branches from the first flow path 600 and a branch point is located between the canister 300 and the shutoff valve 230. The second flow path 700 is provided with the first valve 510 for opening and closing the second flow path 700. The first valve 510 is located at the fuel pump 210 side and branched at the second flow path 700 and branched at a branching point of the third flow path 800 connected to the fuel tank 200 Respectively. Accordingly, the first valve 510 can selectively open only one of the second flow path 700 and the third flow path 800 according to the movement of the plunger 511.

The fuel pump 210 is provided with a return flow path 810 connecting the fuel pump 210 and the fuel tank 200. The return flow path 810 is provided with the solenoid valve 400 that operates to open and close the return flow path 810. Further, the return flow path 810 further includes a regulator 550. Therefore, when the fuel pump 210 is driven at the time of diagnosis of the fuel system of the vehicle, the regulator 550 generates the hydraulic pressure in the return channel 810.

Further, the fuel pump 210 is provided with an air discharge passage 850, which is another passage through which the fuel pump 210 and the fuel tank 200 are connected. The second valve 530 is provided between the return flow passage 810 and the air discharge passage 850 and is connected to the return passage 810 and the air discharge passage 850 by the hydraulic pressure in the return passage 810. [ And selectively opens any one of them. Therefore, when the fuel system of the vehicle is diagnosed, the air pumped through the fuel pump 210 flows through the second flow path 700 into the fuel tank 200 by the second valve 530 So that the pressure inside the fuel tank 200 is increased.

The control unit 900 individually controls opening and closing operations of the shutoff valve 230, the solenoid valve 400, the first and second valves and the canister closing valve 310, and controls various components of the fuel system .

The operation of the fuel tank 200 will be described with reference to FIGS. 2 to 5 at the time of driving the vehicle and diagnosing the fuel system of the vehicle.

2 is a view showing the operation of the first valve 510, the second valve 530 and the solenoid valve 400 when the vehicle is running.

The first valve 510 is moved and closed by the pressure of the fuel and the pressure of the elastic member 513 when the vehicle is traveling so that the fuel in the fuel tank 200 is discharged to the fuel pump 200. [ The third flow path 800 is opened so as to be moved to the second flow path 210. That is, the elastic member 513 of the first valve 510 presses the plunger 511 to block the second flow path 700, opens the third flow path 800, So that the fuel in the fuel pump 210 is transferred to the fuel pump 210.

The control unit 900 controls the solenoid valve 400 to open the fuel pump 210 so that a part of the fuel in the fuel pump 210 flows into the fuel tank 200 through the return flow path 810, The return flow path 810 is opened. The second valve 530 closes the air discharge passage 850 when the plunger 531 is pressed and closed by the elastic member 533 when the vehicle is running.

The fuel in the fuel tank 200 is supplied to the fuel pump 210 along the third flow path 800 by the first valve 510 closed from the fuel tank 200 . A part of the fuel of the fuel pump 210 is transferred to the high pressure pump 290 through the fuel valve 291 opened along the high pressure passage 830 and is moved to the engine 100, A portion of the fuel is returned to the fuel tank 200 through the return channel 810 through the regulator 550 and the solenoid valve 400.

3 is a view showing the operation of the first valve 510, the second valve 530, and the solenoid valve 400 in the fuel system diagnosis first step.

The control unit 900 closes the shutoff valve 230 and the canister closing valve 310 and closes the solenoid valve 400 to close the return flow path 810 when the fuel system is diagnosed. Then, the fuel pump 210 is driven. Fuel is then transferred from the fuel tank 200 to the fuel pump 210 via the first valve 510 and the fuel in the fuel pump 210 is returned to the high- 810). However, since the solenoid valve 400 is closed and the engine 100 is not driven, the pressure in the third passage 800, the high-pressure passage 830, and the return passage 810 is gradually increased .

4 is a view showing the operation of the first valve 510, the second valve 530 and the solenoid valve 400 in the fuel system diagnosis second stage.

The pressure in the return flow path 810 equipped with the above-described return line is gradually increased by the continuous driving of the fuel pump 210. Accordingly, the first valve 510 of the first valve 510 is opened by the pressure of the fuel in the return flow path 810. Therefore, the third flow path 800 is closed, the second flow path 700 is opened, and the air flowing through the second flow path 700 is moved to the fuel pump 210.

The plunger 531 is also pressed by the pressure of the fuel in the return passage 810 so that the second valve 530 is opened to open the air discharge passage 850 to move into the fuel pump 210 Thereby allowing the air to flow into the fuel tank 200 along the air discharge path 850.

5 is a view showing the operation of the first valve 510, the second valve 530 and the solenoid valve 400 in the fuel system diagnosis 3 stage. When the prescribed pressure for leak diagnosis is generated in the fuel tank 200, the control unit 900 opens the solenoid valve 400 and stops driving the fuel pump 210. The plungers 511 and 531 are moved by the elastic members 513 and 533 of the first valve 510 and the second valve 530 to close the second flow path 700 and the air discharge path 850, do. In this state, the controller 900 performs leak diagnosis.

6, a leakage diagnosis method for a leak diagnosis system for a fuel system for a vehicle according to an embodiment of the present invention will be described. The leakage diagnosis method for a leak diagnosis system for a fuel system for a vehicle according to the present invention comprises: When the reference time inputted to the control unit 900 is exceeded after the start-off signal of the vehicle is input, the leak diagnosis system diagnoses the leak, the shutoff valve 230 provided in the fuel tank 200 is closed A fuel pump driving step S100 for driving the fuel pump 210 after the solenoid valve 400 is closed; When the fuel tank 200 is driven in the fuel pump driving step S100, the first valve 510 and the second valve 530 are opened by the fuel pressure and the air flows in through the second flow path 700 And when it is determined that the predetermined pressure input to the control unit 900 is formed in the fuel tank 200, the solenoid valve 400 is opened and the fuel pump 210 stops stopping the fuel pump 210 Step S300; The first valve 510 and the second valve 530 are closed by the fuel pressure when the fuel pump 210 stops driving in the fuel pump stopping step S300, (S500) for checking whether the pressure input to the controller 900 by the controller 900 satisfies the reference value input to the controller 900. [

When the start time of the vehicle is turned off and the reference time input to the control unit 900 is exceeded after the start-off signal of the vehicle is inputted to the control unit 900, the control unit 900 controls the fuel tank 200 are in a stable state. Here, the reference time may be five hours. If the reference time is exceeded, the controller 900 closes the canister closing valve 310. The controller 900 closes the shut-off valve 230 installed in the fuel tank 200 and closes the solenoid valve 400 and then drives the fuel pump 210 (S100).

The control unit 900 controls the pressure of the fuel tank 200 transferred to the control unit 900 through the detection unit 270 before driving the fuel pump 210 in the fuel pump driving step S100. (S700) of confirming whether or not the leak diagnosis of the fuel tank 200 is within the allowable range.

The range for judging whether leak diagnosis of the fuel tank 200 is possible may be < tank pressure &lt; 37 hpa. The pressure of the fuel tank 200 may be expressed using an absolute value so as to include both a positive pressure and a negative pressure. If it is determined in S700 that the pressure of the fuel tank 200 is within the above range, the control unit 900 determines whether or not the fuel tank 200 and the canister 300 are leaked All checked.

However, if it is determined that the pressure of the fuel tank 200 is not within the above range in the tank pressure check step S700, the control unit 900 does not check whether the fuel tank 200 is leaking, Only whether or not the canister 300 is leaking is checked. The reason why the fuel tank 200 is formed as described above is that when the pressure of the fuel tank 200 is excessively formed, even if a predetermined pressure is added through the fuel pump 210, In the diagnosis, the leak diagnosis of the fuel tank 200 is skipped, and if it is within a possible range next time, a willingness to check again is reflected.

When the fuel pump 210 is driven by the control unit 900 in the fuel pump driving step S100, the return flow path 810 is closed because the solenoid valve 400 is closed, The pressure in the return flow path 810 is gradually increased by the regulator 210 and the regulator 550. Accordingly, the first valve 510 and the second valve 530 are pressed and opened by the pressure of the fuel in the return flow path 810. That is, the first valve 510 is opened and the third flow path 800 is closed and the second flow path 700 is opened so that air is introduced into the fuel pump 210 from the rear end of the shut- &Lt; / RTI &gt; The air that has been transferred into the fuel pump 210 is discharged into the fuel tank 200 through the air discharge line since the air discharge line is opened by the second valve 530. Accordingly, the pressure in the fuel tank 200 is gradually increased.

If the control unit 900 determines that the fuel tank 200 is driven in the fuel pump driving step S100 and the predetermined pressure input into the control unit 900 is formed in the fuel tank 200, (S300) of opening the solenoid valve (400) and stopping the driving of the fuel pump (210).

 After the fuel pump stopping step S300 is performed, the pressure applied to the return flow path 810 is removed, so that the first valve 510 and the second valve 530 are closed, (S500) for confirming whether the pressure inputted to the controller 900 by the controller (270, 350) satisfies the reference value input to the controller (900).

A method for checking leakage of the fuel tank 200 and the canister 300 will be described in more detail. The control unit 900 can determine leakage by using the pressure factor of the fuel tank 200 and the canister 300 as basic data in the leak checking step S500. In some cases, So that it is possible to judge whether or not the leak occurs.

The method of determining the leak of the fuel tank 200 is a method in which when the predetermined pressure (positive pressure) input into the control unit 900 is formed in the fuel tank 200, the shutoff valve 230 is closed If the pressure in the fuel tank 200 is not changed or is within a predetermined range during the test time input to the controller 900 when the pressure in the fuel tank 200 is checked, It can be judged that there is no leakage.

When the predetermined pressure (positive pressure) input into the control unit 900 is formed in the fuel tank 200, the shutoff valve 230 and the canister closing valve A low pressure or a negative pressure is formed on the side of the canister 300 while the fuel pump 210 is driven, because the fuel pump 310 is in a closed state. If the shutoff valve 230 is in the closed state and the canister close valve 310 is closed when the time exceeds 5 hours after the start-off, if there is no supply of pressure from other components, the canister- ), The canister 300, the first flow path 600, and the shutoff valve 230, the negative pressure is reduced at a predetermined rate per hour and equilibrated with the atmospheric pressure. At this time, if the rate at which the negative pressure is released in the interval is within the range of the negative pressure inputted to the controller 900, it is determined that there is no leakage in the canister 300.

If the control unit 900 determines that there is no leakage from the fuel tank 200 or the canister 300 through the leak checking step S500, the leak diagnosis control of the leak diagnosis system for the fuel system for the vehicle ends. However, if it is determined that leakage has occurred in the fuel tank 200 or the canister 300 in the leak checking step S500, when the user turns ON the control unit 900 may use a warning sound or an instrument panel And an alarm system 910 that warns a user through an instrument panel (not shown).

In the diagnosis of the canister 300, peripheral lines and components of the canister 300 other than the canister 300 may be included in the leak diagnosis.

Therefore, according to the leak diagnosis system and leak diagnosis method for a fuel system for a vehicle according to the present invention, it is possible to more accurately diagnose the leak of the fuel tank 200 or the canister 300 through only a pressure factor which is at least one factor There are advantages.

In particular, since the parts for diagnosis are mounted in the fuel tank 200 or the canister 300, the space can be reduced without occupying a separate space, and the configuration and control are simple and the cost is reduced .

While the present invention has been particularly shown and described with reference to specific embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims It will be apparent to those of ordinary skill in the art.

100: engine 110: intake line
130: Injector 200: Fuel tank
210: fuel pump 220: top plate
230: shutoff valve 240: lower plate
250: vent valve 270: detection means
290: high pressure pump 291: fuel valve
300: Canister 310: Canister closing valve
330: canister air filter 350: detection means
370: Return line 390: Purge control solenoid valve
400: Solenoid valve 510: First valve
511: plunger 513: elastic member
530: second valve 531: plunger
533: elastic member 550: regulator
600: first flow path 700: second flow path
800: Third Euro 810: Return Euro
830: High pressure passage 850: Air discharge passage
900: control unit 910: warning system
S100: Step of driving the fuel pump
S300: Step of stopping the fuel pump
S500: Leak check step
S700: Tank Pressure Verification Step

Claims (17)

A shut-off valve operative to open and close a first flow path connecting the fuel tank and the canister;
A first valve provided in a second flow path connecting the first flow path and the fuel pump, the first valve operating to open and close the second flow path;
A solenoid valve provided in a return passage connecting the fuel pump and the fuel tank, the solenoid valve being operated to open and close the return passage;
A second valve which is provided in an air discharge passage which is another flow passage for connecting the fuel pump and the fuel tank, and which operates to open and close the air discharge passage;
A canister closing valve operable to open and close the connection between the canister and the atmosphere; And
And a control unit for individually controlling opening and closing operations of the shutoff valve, the solenoid valve, the first and second valves, and the canister closing valve. The method according to claim 1,
Wherein the second flow path is branched from the first flow path, and the branch point is located between the canister and the shut-off valve. The method according to claim 1,
Further comprising a third flow path branched from the second flow path and connected to the fuel tank, wherein the first valve is provided at a branch point between the second flow path and the third flow path. System leak diagnosis system. The method of claim 3,
Wherein the first valve selectively opens either the second flow path or the third flow path in accordance with the movement of the plunger. The method of claim 3,
Wherein the first valve opens the third flow path so that the fuel in the fuel tank is moved to the fuel pump by the plunger being moved and closed by the pressure of the fuel and the pressure of the elastic member when the vehicle travels Leak diagnosis system for fuel system of vehicle. The method of claim 3,
The first valve closes the third flow path and opens the second flow path by pressing the plunger of the first valve by the pressure of the fuel in the return flow path when the fuel system is diagnosed, So as to allow air to flow into the fuel pump through the flow path. The method according to claim 1,
Wherein the return flow path further includes a regulator. The method according to claim 1,
Wherein the control unit opens the return flow passage so that a part of the fuel in the fuel pump is transferred to the fuel tank through the return flow passage by controlling the solenoid valve when the vehicle travels, Leak diagnosis system. The method according to claim 1,
Wherein the control unit closes the return flow passage so that a part of the fuel in the fuel pump can not be moved to the fuel tank through the return flow passage by controlling and closing the solenoid valve at the time of diagnosis of the fuel system, System leak diagnosis system. The method according to claim 1,
Wherein the second valve is provided between the return flow path and the air discharge flow path and selectively opens only one of the return flow path and the air discharge flow path by the hydraulic pressure in the return flow path. . The method of claim 10,
Wherein the second valve closes the air discharge passage when the plunger is pressed and closed by the elastic member when the vehicle is running. The method of claim 10,
The second valve opens the plunger by the pressure of the fuel in the return flow path when the fuel system is diagnosed and opens the air discharge flow path so that the air moved into the fuel pump flows along the air discharge flow path, And to move the fuel system into the tank. A leak diagnosis system for a fuel system for a vehicle according to claim 1,
A fuel pump driving step of closing the shut-off valve provided in the fuel tank, closing the solenoid valve, and driving the fuel pump when the reference time input to the control unit after the start-off signal of the vehicle is inputted is exceeded;
Wherein when the fuel tank is driven in the fuel pump driving step, the first valve and the second valve are opened by the fuel pressure and air is introduced through the second flow path, and the specified pressure, A fuel pump stopping step of opening the solenoid valve and stopping driving of the fuel pump if it is determined that the fuel pump is formed; And
Wherein when the driving of the fuel pump is stopped in the fuel pump stopping step, the first valve and the second valve are closed by the fuel pressure, and the pressure input to the control unit by the detection means is lower than the reference value And a leak checking step of checking whether or not the leakage diagnosis of the leakage diagnosis of the vehicle fuel system satisfies the condition. 14. The method of claim 13,
Wherein the fuel pump driving step closes the canister closing valve when the reference time input to the control unit is exceeded after the start-off signal of the vehicle is inputted. 14. The method of claim 13,
Wherein the control unit is operable to determine whether the pressure of the fuel tank delivered to the control unit through the detection unit is within a range in which leak diagnosis of the fuel tank is possible, The method of claim 1, further comprising the step of: 16. The method of claim 15,
Wherein when the pressure of the fuel tank is judged to be within a range capable of diagnosing leakage of the fuel tank in the tank pressure checking step, it is checked whether or not the fuel tank and the canister are leaked. Leak diagnosis method. 16. The method of claim 15,
Wherein when the pressure of the fuel tank is judged not to be within the allowable range of leak diagnosis of the fuel tank in the tank pressure checking step, only the leak of the canister is checked. .

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