KR102644367B1 - Diagnostic apparatus of fuel leakage of fuel supply system and diagnostic method thereof - Google Patents

Abstract

The present invention relates to a method for diagnosing a fuel leak in a fuel system of a vehicle using negative pressure inside an engine, comprising the steps of: determining whether conditions for diagnosing a fuel leak in the fuel system of a vehicle are satisfied; If the conditions for fuel leak diagnosis are satisfied, controlling the factors affecting the formation of negative pressure inside the engine to satisfy a predetermined negative pressure formation condition: If the predetermined negative pressure formation condition is satisfied, supplying negative pressure inside the fuel system steps; It is characterized in that it includes the step of diagnosing a leak in the fuel system by detecting a change in pressure inside the fuel system due to negative pressure supply.

Description

Fuel leak diagnosis method of fuel system {DIAGNOSTIC APPARATUS OF FUEL LEAKAGE OF FUEL SUPPLY SYSTEM AND DIAGNOSTIC METHOD THEREOF}

The present invention relates to a method for diagnosing a fuel leak in a fuel system of a vehicle, and more specifically, to a method for diagnosing a fuel leak by forming a suitable match for diagnosing a fuel leak in the fuel system of a hybrid vehicle.

When gasoline vapor generated from a fuel system such as a fuel tank leaks from the fuel system and is released into the air, it causes air pollution due to hydrocarbons contained in the gasoline vapor. In particular, as the number of automobiles has increased recently and interest in environmental pollution has increased, measures against leaking fuel evaporation gas have been required, and accordingly, the development of technology that can accurately diagnose fuel leakage from the fuel system is also required.

As an apparatus and method for diagnosing a fuel leak in a conventional fuel system, as disclosed in Patent Document 1, the pressure change inside the fuel system is measured while the negative pressure inside the engine intake system is applied to the fuel system, There are ways to check the tightness of the fuel system.

Specifically, as shown in FIG. 6, the canister purge solenoid valve (PSV) and canister shut-off valve (Canister Shut-Off Valve) of the canister purge line of the fuel system (fuel tank and fuel supply line) When SOV) is closed, the space inside the fuel system is sealed and fuel vapor is generated inside the fuel system for a predetermined time (T1). Afterwards, when the purge solenoid valve is opened, the negative pressure inside the fuel intake system (the difference between atmospheric pressure and intake manifold pressure) is supplied to the fuel system, and the vapor inside the fuel system is discharged into the fuel intake system. At this time, by measuring the change in pressure (measured by the fuel tank pressure sensor (DTP)) inside the fuel system (the area indicated by the dashed line), it is possible to determine whether there is a fuel leak inside the fuel system or whether the tank cap is missing. .

Meanwhile, with regard to leak standards when diagnosing fuel leaks, the laws and regulations are different for each country, and the diagnosis system and its control method are applied differently accordingly. In particular, in the case of a hybrid vehicle, when the negative pressure generated during driving is supplied to the fuel system, if the pressure inside the fuel system decreases above a certain level, it is determined that there is no leak.

Patent Document 1: Republic of Korea Patent Publication No. 10-2008-0000036 (January 2, 2008)

In the fuel leak diagnosis method of the prior art described above, cases where a misdiagnosis occurs as a fuel leak even though there is no fuel leak, or cases where the diagnosis is canceled when it is determined that conditions suitable for diagnosis are not met, frequently occur.

As a misdiagnosis, a fuel leak diagnosis was performed using negative pressure for a certain period of time, but if the negative pressure inside the fuel intake system was not sufficiently formed, the pressure inside the fuel system did not fall below a certain level when diagnosing the leak. Therefore, there are cases where a fuel leak is incorrectly diagnosed when there is no actual fuel leak.

In addition, in the case of canceling the diagnosis, a certain negative pressure condition must be created to diagnose a fuel leak, but if a negative pressure condition suitable for the diagnosis is not created, the diagnosis is judged to be unsuitable and the diagnosis is canceled. In particular, in the case of hybrid vehicles, the driving mode is frequently switched, which causes the engine to stop frequently, and satisfactory negative pressure is often not formed inside the engine's intake system, which can lead to many cases where the diagnosis is canceled. there is. In this case, there are cases where the various national laws and regulations related to fuel leak diagnosis are not satisfied.

As described above, misdiagnosis or cancellation of fuel leak diagnosis mainly occurs due to failure of an appropriate amount of negative pressure to be formed inside the fuel intake system.

The present invention was developed to solve the problems of the prior art described above. When diagnosing a fuel leak, it is possible to accurately and stably detect a fuel leak in the system by creating an appropriate level of negative pressure suitable for the diagnosis. The purpose is to provide a diagnostic method that can be used.

The amount of negative pressure inside the engine's intake system, which is needed to diagnose fuel leakage within the fuel system, corresponds to the difference between atmospheric pressure and intake manifold pressure. However, since the level of atmospheric pressure cannot be artificially adjusted, it is necessary to lower the pressure inside the intake manifold in order to ultimately form a negative pressure of a size suitable for diagnosis. Therefore, in the present invention, factors affecting negative pressure formation inside the engine are controlled to satisfy predetermined negative pressure formation conditions.

Meanwhile, according to the present inventors' research, the main factors affecting intake manifold pressure are ① the amount of EGR supplied to the intake system in a vehicle equipped with an EGR device, ② the valve timing of the intake cam, and ③ the canister purge solenoid valve. There are also dogs, etc. Among these, the opening degree of the canister purge solenoid valve is a factor for determining whether there is a fuel leak in the fuel system, and since it is a factor that directly affects whether there is a fuel leak, it is difficult to control it for forming negative pressure. Therefore, in the present invention, by adjusting the EGR amount and the timing of the intake valve, negative pressure of a size suitable for diagnosing a fuel leak in the fuel system can be formed.

More specifically, the method for diagnosing a fuel leak in a fuel system of a vehicle according to the present invention for solving the above problems includes the steps of determining whether conditions enabling fuel leak diagnosis in the fuel system of a vehicle are satisfied; If the conditions for fuel leak diagnosis are satisfied, controlling factors affecting the formation of negative pressure inside the engine to satisfy a predetermined negative pressure formation condition: If the predetermined negative pressure formation condition is satisfied, supplying negative pressure inside the fuel system steps; It is characterized in that it includes the step of diagnosing whether there is a leak in the fuel system by detecting a change in pressure inside the fuel system due to negative pressure supply.

Additionally, preferably, the vehicle is equipped with an EGR device that returns a portion of the engine's exhaust to the engine's intake, and in the step of controlling the factors affecting the formation of negative pressure inside the engine, when diagnosing a fuel system leak. Then, the EGR device is stopped to ensure that a predetermined negative pressure formation condition is satisfied.

In addition, preferably, the vehicle is equipped with an EGR device that returns a part of the engine exhaust to the engine intake, and in the step of controlling the factors affecting the formation of negative pressure inside the engine, diagnosis of leaks in the fuel system is performed. In this case, the EGR amount of the EGR device is reduced to satisfy a predetermined negative pressure formation condition.

Also, preferably, in the step of controlling factors affecting the formation of negative pressure inside the engine, the valve timing of the intake valve is advanced to ensure that a predetermined condition for forming negative pressure is satisfied.

Additionally, the method may further include measuring the amount of negative pressure formed inside the engine using a pressure sensor installed inside the intake manifold.

Also preferably, in the step of supplying negative pressure inside the fuel system, a canister shut off valve (SOV) formed in the atmospheric connection part of the canister is closed and a canister purge solenoid communicates between the intake system of the engine and the canister. Opens the canister purge solenoid valve to supply negative pressure inside the fuel system.

Also preferably, the method for diagnosing a fuel leak in a fuel system according to the present invention can be used for diagnosing a fuel leak in a hybrid vehicle.

According to the method for diagnosing a fuel leak in a fuel system of a vehicle according to the present invention, by creating a negative pressure environment suitable for diagnosis, in particular, it is difficult to perform diagnosis in a timely manner because the engine is frequently turned off, and it is difficult to form a negative pressure suitable for diagnosis. Even in hybrid vehicles, accurate and stable fuel leak diagnosis can be performed. Therefore, it is possible to easily satisfy various laws and regulations of each country related to fuel leak diagnosis.

1 is a diagram illustrating a fuel system of a vehicle to which the fuel leak diagnosis method according to the present invention can be applied.
2 is a diagram showing a fuel system and an intake system of a vehicle engine.
Figure 3 is a diagram showing the valve timing of the intake valve and exhaust valve.
4 is a diagram showing a fuel system and an EGR device of a vehicle.
5 is a flowchart showing a fuel leak diagnosis method according to the present invention.
Figure 6 is a diagram showing changes in valve control signals and internal pressure of the fuel system when diagnosing a fuel leak in the fuel system.

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

Hereinafter, with reference to FIG. 1, a fuel system to which the fuel leak diagnosis method according to the present invention can be applied will be described.

1 is a diagram illustrating a fuel system of a vehicle to which the fuel leak diagnosis method according to the present invention can be applied. The fuel system includes a fuel tank (8), a fuel tank pressure sensor (DTP) (6) that detects the pressure of the fuel tank (8), a canister (2) that stores the boil-off gas evaporating within the fuel tank (8), The canister closing valve (SOV) (5) is connected to the atmospheric connection of the canister (2) and changes the on/off state of the valve in accordance with the control signal from the ECU (3), this canister (2) and the intake system of the engine ( 1) is connected, and the on/off state of the valve changes according to the control signal from the ECU (3) to guide the evaporative gas stored in the canister (2) to the engine's intake system (1). PSV)(4), etc.

When diagnosing a fuel leak in the fuel system, as shown in FIG. 6, when the canister purge solenoid valve (4) and the canister closing valve (5) are closed, the space inside the fuel system is sealed and the fuel system is closed for a predetermined time (T1). Fuel vapor is generated inside. Afterwards, when the canister purge solenoid valve 4 is opened, the negative pressure inside the fuel intake system (the difference between atmospheric pressure and intake manifold pressure) is supplied to the fuel system, and the vapor inside the fuel system is discharged into the fuel intake system. At this time, the fuel tank pressure sensor 6 measures the change in pressure inside the fuel system to diagnose whether there is a fuel leak inside the fuel system. Therefore, in order to determine whether there is a leak in the fuel system, a negative pressure of a size suitable for diagnosis must be formed inside the engine's intake system (1), and for this, a pressure inside the intake manifold (10) of a certain size or more must be formed. .

Hereinafter, with reference to FIGS. 2 and 3, the effect of the valve timing of the intake valve on the internal pressure of the intake manifold 10 will be described.

FIG. 2 is a diagram illustrating a fuel system and an intake system of a vehicle engine, and FIG. 3 is a diagram illustrating valve timing of intake valves and exhaust valves.

According to the illustration in FIG. 2, the outside air of the vehicle flows into the intake system 1 of the engine according to the opening degree of the throttle valve 17, and the introduced outside air has a negative pressure inside the intake system 1 of the engine. As a result, the fuel injected by the injector 18 passes through the intake manifold 10 and is supplied into the cylinder 13 of the engine at the opening timing of the intake valve 14. The mixture of fuel and air introduced into the cylinder 13 is combusted by spark ignition by the igniter 19 or compression ignition by rotation of the engine piston, and the exhaust gas after combustion is released at the opening timing of the exhaust valve 15. It is discharged to the outside of the vehicle through the exhaust system (9). At this time, the oxygen concentration in the exhaust gas discharged through the exhaust system 9 is measured by the oxygen sensor 7 and used to control the air-fuel ratio. Here, the negative pressure inside the intake system 1 of the engine is determined by the difference between the atmospheric pressure of the outside air and the pressure inside the intake manifold 10 of the engine, and preferably, the internal pressure of the intake manifold 10 is the intake pressure. Measured by the manifold pressure sensor (16).

As described above, in order to detect a fuel leak in the fuel system, negative pressure inside the engine's intake system 1 must be supplied into the fuel system. To this end, when the canister purge solenoid valve (4) connecting the canister (2) and the engine's intake system (1) is opened, the canister ( 2) The internal evaporative gas is supplied into the intake system (1) of the engine, and accordingly, as shown in FIG. 6, the pressure inside the fuel system, that is, measured by the fuel tank pressure sensor (DTP) (6) The pressure decreases.

Meanwhile, in Figure 3, the valve timing of the intake valve 14 and the exhaust valve 15 is shown. As shown in FIG. 3, valve overlap occurs in an area (overlap angle) where the valve operating angles of the intake valve 14 and the exhaust valve 15 overlap each other. When valve overlap occurs, both the intake valve (14) and the exhaust valve (15) are opened, and the new air component supplied through the intake valve (14) directly passes through the exhaust valve (16) and enters the exhaust system (9). A scavenging state occurs where the discharge is released. Meanwhile, as shown in FIG. 3, when the valve opening timing of the intake valve 14 is advanced, the amount of valve overlap increases, and as a result, the air supplied to the cylinder 13 of the engine at that point due to the scavenging phenomenon. The amount increases, and as a result, the pressure inside the intake manifold 10 of the engine is reduced. Therefore, by advancing the valve timing of the intake valve 14, the amount of negative pressure inside the intake system 1 of the engine can be increased. Therefore, in the present invention, when negative pressure is not formed at a size suitable for fuel leak diagnosis, the valve timing of the intake valve 14 is advanced to form negative pressure at a size suitable for diagnosis.

Hereinafter, with reference to FIG. 4, the effect of the EGR amount of the EGR device on the internal pressure of the intake manifold 10 will be described.

4 is a diagram showing a fuel system and an EGR device of a vehicle. Recently, as part of efforts to improve fuel efficiency, EGR devices, which are exhaust gas recirculation devices, have been widely used. When an EGR device is applied, engine efficiency can be increased by improving the knocking characteristics of the fuel and advancing the ignition timing, thereby improving fuel efficiency. In the case of a vehicle employing the EGR device shown in FIG. 4, the outside air filtered by the air cleaner 11 flows into the intake manifold 10 according to the opening degree of the throttle valve 17. At this time, the amount of incoming external air is measured by the air mass sensor (HFM) (12). The outside air flowing into the intake manifold 10, along with fuel supplied by a fuel supply device (not shown), is supplied into the cylinder 13 of the engine at the opening timing of the intake valve 14, and the cylinder 13 The mixture of external air and fuel introduced inside is combusted in the combustion chamber and discharged to the exhaust system (9) at the opening timing of the exhaust valve (15). Meanwhile, in vehicles employing an EGR system, a portion of the exhaust gas discharged from the exhaust system 9 is extracted and supplied to the engine intake system 1, thereby recirculating the exhaust gas. At this time, the EGR amount, which is the recirculation amount of exhaust gas from the exhaust system 9 to the intake system 1, is determined by the EGR valve 20.

Meanwhile, as shown in FIG. 2, in order to detect whether there is a fuel leak in the fuel system, when the canister purge solenoid valve 4 connecting the canister 2 and the engine intake system 1 is opened, the inside of the fuel system The evaporated gas inside the canister (2) is supplied into the engine's intake system (1) by the pressure difference between the pressure and the pressure inside the engine's intake system (1).

However, when the recirculated exhaust gas flows from the exhaust system 9 to the intake system 1 due to the operation of the EGR device, the internal pressure of the intake manifold 10 increases. As a result, the negative pressure inside the engine's intake system 1 becomes small, and as described above, there is a risk of misdiagnosing a fuel leak or frequent cancellation of the diagnosis. Therefore, in the present invention, when diagnosing a fuel leak, the operation of the EGR device is stopped or the EGR amount is reduced by adjusting the opening degree of the EGR valve 20, thereby forming a negative pressure of a size suitable for diagnosis.

Figure 5 is a flowchart showing a preferred embodiment of the fuel leak diagnosis method according to the present invention.

As shown in FIG. 5, after the vehicle is driven, the ECU 3 first determines whether the fuel leak diagnosis conditions of the fuel system are satisfied (S10). Conditions that can diagnose a fuel leak include, for example, the vehicle's ignition-on state, the engine driving state on level ground, the normal operation state of various sensors mounted on the vehicle, the normal pressure state of the fuel tank 8, and the canister purge solenoid valve 4. These include the normal state of control operation, whether purge control of the canister is applied for a certain period of time, and whether the degree of evaporation gas saturation in the canister does not exceed the standard value. If the relevant state is satisfied, the conditions for fuel leak diagnosis are satisfied. can judge

If it is determined in step S10 that the conditions for fuel leak diagnosis are satisfied, the ECU 3 determines whether negative pressure inside the engine suitable for fuel leak diagnosis is formed (S20). Preferably, for this purpose, the internal air pressure of the intake manifold 10 is measured using the intake manifold pressure sensor 16, and the difference between the measured internal air pressure value of the intake manifold 10 and atmospheric pressure is determined. Compare with the standard value of Alternatively, instead of using the measured value from the intake manifold pressure sensor 16, it is also possible to estimate the negative pressure inside the engine's intake system 1 using the engine speed and the opening degree of the throttle valve 17.

If it is determined in step S20 that the negative pressure inside the engine's intake system 1 has not reached a negative pressure of a size appropriate for fuel leak diagnosis, the ECU 3 determines a factor affecting the negative pressure so that a negative pressure of an appropriate size is formed. control. To this end, as described above, control (S40) can be performed to reduce the amount of EGR by stopping the operation of the EGR device or adjusting the opening degree of the EGE valve so that the pressure inside the intake manifold 10 decreases. Or, as described above, control (S50) to lower the pressure inside the intake manifold 10 by advancing the valve timing of the intake valve 14 to increase the amount of air supplied into the cylinder 13 of the engine. It can also be implemented. In order to form a negative pressure of a size suitable for fuel leak diagnosis, either the control of the EGR device described above or the valve timing control of the intake valve 14 may be performed, and the target negative pressure can be formed only with either control. If this does not work, two controls can be performed simultaneously.

After performing the control in step S40 or step S50, the ECU 3 again determines whether negative pressure inside the engine suitable for fuel leak diagnosis is formed (S60). If it is determined in step S20 that a negative pressure of an appropriate size has been formed, or if it is determined in step 60 that a negative pressure of a size appropriate for fuel leakage diagnosis has been formed through control of factors affecting the negative pressure, the ECU (3) begins to supply fuel in earnest. Start leak diagnosis.

As described above, for fuel leakage diagnosis, the ECU (3) closes the canister purge solenoid valve (4) and canister closing valve (5) of the fuel system to seal the inside of the fuel system, including the fuel tank (8). . As shown in period T1 of FIG. 6, a change in internal pressure occurs inside the sealed fuel system due to the generation of fuel evaporation gas. Thereafter, the ECU (3) controls the canister purge solenoid valve (4) to be opened while the canister closing valve (5) is closed in order to depressurize the inside of the fuel system. Accordingly, the negative pressure inside the intake system 1 of the engine is supplied to the inside of the fuel system (S70), and the evaporative gas inside the canister 2 is supplied to the intake system 1 of the engine, as shown in FIG. 6. , the pressure inside the fuel system is reduced. At this time, the change in pressure inside the fuel system is measured using the fuel tank pressure sensor 6, etc. to diagnose fuel leakage (S80). If a fuel leak occurs inside the fuel system, as shown by the broken line in FIG. 6, when negative pressure is supplied to the engine's intake system 1, the inside of the fuel system is not depressurized by a predetermined amount and quickly returns to its original state. It is restored by pressure. Therefore, when negative pressure is supplied to the engine's intake system 1, it is possible to determine whether there is a fuel leak by observing the pressure change inside the fuel system.

As described above, according to the present invention, by controlling the factors affecting the negative pressure of the engine intake system 1, a negative pressure of a size suitable for fuel leak diagnosis is formed, so that frequent engine stops such as hybrid vehicles are prevented. Even if a sufficient amount of negative pressure is not formed, fuel leakage can be diagnosed at the appropriate timing. In addition, by securing a sufficient level of negative pressure, misdiagnosis due to lack of negative pressure can be prevented, allowing more accurate diagnosis of fuel leakage.

1: Engine intake system 2: Canister
3: ECU 4: Canister purge solenoid valve (PSV)
5: Canister closing valve (SOV) 6: Fuel tank pressure sensor
7: Oxygen sensor 8: Fuel tank
9: Engine exhaust system 10: Intake manifold
11: Air cleaner 12: Air mass sensor (HFM)
13: engine cylinder 14: intake valve
15: Exhaust valve 16: Intake manifold pressure sensor
17. Throttle valve 18: Fuel injector
19.: Igniter

Claims (7)

Determining whether conditions for diagnosing a fuel leak in a fuel system of a vehicle are satisfied;
If the conditions for fuel leak diagnosis are satisfied, controlling factors affecting negative pressure formation inside the engine to satisfy predetermined negative pressure formation conditions:
supplying negative pressure inside the fuel system when a predetermined negative pressure forming condition is satisfied;
Diagnosing whether there is a leak in the fuel system by detecting a change in pressure inside the fuel system due to the supply of negative pressure,
The vehicle is equipped with an EGR device that returns part of the engine exhaust to the engine intake,
The step of controlling factors affecting the formation of negative pressure inside the engine is,
A method of diagnosing a fuel leak in a fuel system of a vehicle, wherein when diagnosing a leak in the fuel system, a predetermined negative pressure formation condition is satisfied by stopping the EGR device. Determining whether conditions for diagnosing a fuel leak in a fuel system of a vehicle are satisfied;
If the conditions for fuel leak diagnosis are satisfied, controlling factors affecting negative pressure formation inside the engine to satisfy predetermined negative pressure formation conditions:
supplying negative pressure inside the fuel system when a predetermined negative pressure forming condition is satisfied;
Diagnosing whether there is a leak in the fuel system by detecting a change in pressure inside the fuel system due to the supply of negative pressure,
The vehicle is equipped with an EGR device that returns part of the engine exhaust to the engine intake,
The step of controlling factors affecting the formation of negative pressure inside the engine is,
A method of diagnosing a fuel leak in a fuel system of a vehicle, wherein when diagnosing a leak in the fuel system, a predetermined negative pressure formation condition is satisfied by reducing the EGR amount of the EGR device. Determining whether conditions for diagnosing a fuel leak in a fuel system of a vehicle are satisfied;
If the conditions for fuel leak diagnosis are satisfied, controlling factors affecting negative pressure formation inside the engine to satisfy predetermined negative pressure formation conditions:
supplying negative pressure inside the fuel system when a predetermined negative pressure forming condition is satisfied;
Diagnosing whether there is a leak in the fuel system by detecting a change in pressure inside the fuel system due to the supply of negative pressure,
The step of controlling factors affecting the formation of negative pressure inside the engine is,
A method for diagnosing a fuel leak in a fuel system of a vehicle, wherein a predetermined negative pressure formation condition is satisfied by advancing the valve timing of the intake valve of the engine. In claim 1,
A method for diagnosing a fuel leak in a fuel system of a vehicle, further comprising measuring the amount of negative pressure formed inside the engine using a pressure sensor installed inside the intake manifold. In claim 1,
In the step of supplying negative pressure inside the fuel system, the canister shut off valve (SOV) formed in the atmospheric connection part of the canister is closed and the canister purge solenoid valve (canister purge solenoid) communicates between the intake system of the engine and the canister. A method of diagnosing a fuel leak in a vehicle's fuel system, characterized by supplying negative pressure inside the fuel system by opening a valve. In claim 1,
A method for diagnosing a fuel leak in a fuel system of a vehicle, wherein the vehicle is a hybrid vehicle. delete

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