KR100412715B1 - A method for diagnosing leakage of evaporated gas control system of a vehicle - Google Patents

Abstract

A method of diagnosing the leakage of the boil-off gas control system that supplies gas to the engine evaporated from the fuel tank to diagnose the leakage of the boil-off gas control system within a shorter time and more accurately. A low pressure maintaining step of maintaining the pressure at a set pressure below atmospheric pressure; A system blocking step of blocking the boil-off gas control system from the outside air and the engine when the vehicle speed becomes zero; And a leak diagnosis step of determining whether the boil-off gas control system is leaked based on a pressure change with time after the system shut-off step.

Description

A METHOD FOR DIAGNOSING LEAKAGE OF EVAPORATED GAS CONTROL SYSTEM OF A VEHICLE}

The present invention relates to a leak diagnosis method for detecting whether there is a leak in an evaporative gas control system of an automobile.

As is well known, an internal combustion engine is a device that generates power by burning fuel and air in an engine, and therefore, an automobile using the power of such an internal combustion engine has a fuel tank for storing fuel for supplying the engine. .

The fuel stored in the fuel tank will vary depending on the degree of volatility, but will evaporate as the evaporation evolves over time. Pollution is caused by the release of undesired gases.

Therefore, a modern vehicle has an evaporation gas control system for supplying an engine with boil-off gas generated from a fuel tank, and the evaporation gas control system is connected to a fuel tank for storing fuel of the vehicle and the fuel tank connected to a pipeline. And an evaporation gas collector for collecting the evaporated gas generated in the fuel tank, and a supply line for supplying the evaporated gas of the evaporative gas collector to the engine of the vehicle.

However, when leakage occurs in such an evaporative gas control system, pollution by the evaporated gas cannot be prevented, and thus, the automobile manufacturer is devising a method of detecting leakage of the evaporative gas control system.

For example, when the vehicle stops, the evaporation gas control system is disconnected from the outside air to form a vacuum, and then the evaporation gas control system is disconnected from the engine to leak based on a change in internal pressure as time passes. Diagnosing

1 is a graph showing the internal pressure of a fuel tank according to a process of performing a leak detection method of a conventional boil-off gas control system.

When the vehicle stops at a specific time P1 while driving, a leak diagnosis method according to the prior art is started to block the evaporation gas control system from the outside air and the engine.

When the internal pressure of the fuel tank increases to the set pressure due to the boil-off gas, it waits until the set pressure (P2), and when the internal pressure of the boil-off gas control system is reduced to the set pressure by starting to supply the boil-off gas to the engine ( To P3).

After that, the boil-off gas control system is shut off from the engine again to observe the change in the internal pressure of the fuel tank during the set time (40 sec). As a result, if the internal pressure change is large, it is determined that air has flowed into the boil-off gas control system from the outside air. It may be judged that there is a leak.

By the way, according to the prior art of this example, it takes about 20 seconds until the internal pressure increases (P2) after the future (P1), from about 20 seconds until the internal pressure is reduced (P3), Since it takes about 40 seconds to observe the change in the internal pressure over time, the total time is about 80 seconds.

As a result, it takes too much time to diagnose leakage, and it is not possible to properly detect leakage in the case of a vehicle that is continuously driven, and may reflect a state in which the internal pressure is inevitably increased, such as when fuel is injected after a stop. It can't be misdiagnosed.

Accordingly, the present invention has been made to solve this problem, and an object of the present invention is to provide a method for diagnosing leakage of an evaporative gas control system in a faster time and more accurately.

1 is a graph showing the internal pressure of a fuel tank according to a process of performing a leak detection method of a conventional boil-off gas control system.

Figure 2 shows an example of the leakage diagnosis apparatus is performed an example of the boil-off gas control system, and the leak diagnosis method of the boil-off gas control system of the present invention applied thereto.

3 is a flowchart illustrating a leak diagnosis method of an evaporative gas control system according to an exemplary embodiment of the present invention.

Figure 4 is a graph showing the internal pressure and the valve control timing of the boil-off gas control system during the leak diagnosis method of the boil-off gas control system of the embodiment of the present invention, Figure 4 (a) is the inside of the boil-off gas control system The pressure of the fuel tank as the pressure, Figure 4 (b) shows the open duty of the purge valve, Figure 4 (c) shows the open / closed operation state of the shut-off valve, Figure 4 (d) shows the vehicle speed state. .

In order to achieve the above object, a method of diagnosing a leak of a boil-off gas control system according to the present invention is a method of diagnosing a leak of a boil-off gas control system for supplying a gas evaporated from a fuel tank to an engine.

A low pressure maintaining step of maintaining the internal pressure of the boil-off gas control system at a set pressure of atmospheric pressure or less; A system blocking step of blocking the boil-off gas control system from the outside air and the engine when the vehicle speed becomes zero; And a leak determining step of determining whether the boil-off gas control system is leaked based on a pressure change with time after the system shut-off step.

The low pressure maintaining step may include a boil-off gas supplying step of supplying boil-off gas to the engine until the internal pressure is maintained at atmospheric pressure; An outside air blocking step of blocking the evaporation gas control system from outside air; And a gas supply adjusting step of adjusting an internal pressure to a set pressure below atmospheric pressure by adjusting the amount of boil-off gas supplied from the boil-off gas control system to the engine.

The boil-off gas supply step, the high-pressure judging step of determining whether the internal pressure of the boil-off gas control system is a high pressure state; And a maximum supply step of supplying the boil-off gas to the engine at maximum until the high pressure is released in the high pressure state.

The step of determining whether or not the high pressure is preferably determined to be in a high pressure state when a set time has elapsed since the last start-up or refueling.

The leak determining step may include: a first change amount detecting step of detecting a change amount (first change amount) of an internal pressure of the boil-off gas control system after a first predetermined time elapses; And a first change amount determining step of determining whether the first change amount is greater than or equal to the first set change amount, and when the first change amount is not equal to or greater than the first set change amount, it is determined that there is no leakage.

The leak determining step may include: an atmospheric pressure forming step of releasing the blocking of the evaporation gas control system and the outside air to form an internal pressure at atmospheric pressure when the first change amount is greater than or equal to the first set change amount in the first change amount determination step; A second change amount detecting step of detecting a change amount (second change amount) of an internal pressure of the boil-off gas control system after a second set time elapses; And a second change amount determining step of determining whether or not the second change amount is equal to or greater than a second set change amount. In the second change amount determining step, it is determined that there is no leakage when the second change amount is more than a second set change amount. If not, it is preferable to determine that there is leakage.

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

Figure 2 shows an example of the leakage diagnosis apparatus is performed an example of the boil-off gas control system, and the leak diagnosis method of the boil-off gas control system of the present invention applied thereto.

As shown in FIG. 2, a conventional evaporative gas control system includes a fuel tank 210 storing fuel of an automobile and a fuel pipe 210 connected to a pipeline to connect the evaporated gas generated from the fuel tank 210. An evaporation gas collector 215 to collect and a supply line 225 for supplying the evaporation gas of the evaporation gas collector 215 to the engine 220 of the vehicle.

Leakage diagnosis system of an embodiment of the present invention provided therein, the pressure sensor 230 is installed at the set position of the boil-off gas control system for detecting the internal pressure of the boil-off gas control system; An ignition switch sensor 235 for detecting whether the engine 220 is driven; A vehicle speed sensor 240 for detecting a driving speed of the vehicle; Shut-off valve (260) for selectively opening and closing the connection between the boil-off gas collector 215 and the outside air; A purge valve 270 interposed on the supply pipe 225 to adjust the amount of boil-off gas supplied from the boil-off gas collector 215 to the engine 220; And an electronic control unit 250 for controlling the shutoff valve 260 and the purge valve 270 and diagnosing leakage of the boil-off gas control system based on signals input from the sensors 230, 235, and 240. ECU "). In addition, the ECU 250 is provided with a clock 255 for detecting the passage of time.

In FIG. 2, although the pressure sensor 230 is shown to be installed in the fuel tank 210, the pressure sensor 230 may be installed at any position in the boil-off gas control system.

Although the example of the evaporative gas control system has been described as including an evaporative gas collector 215, even if it does not include the leak detection method of the present invention can be applied, in this case the shut-off valve 260 May be located at any position from which the outside air on the boil-off gas control system can be selected.

3 is a flowchart illustrating a leak diagnosis method of an evaporative gas control system according to an exemplary embodiment of the present invention.

That is, the leak diagnosis method of the boil-off gas control system of the embodiment of the present invention is a method of diagnosing the leakage of the boil-off gas control system 210, 215, 220, 225 for supplying the gas 220 evaporated from the fuel tank 210 to the engine 220.

After the internal pressure of the boil-off gas control system is maintained at a set pressure below atmospheric pressure (S310 to S345), and when the vehicle speed reaches 0, the boil-off gas control system is shut off from the outside air and the engine (S350, S355). It is determined whether the boil-off gas control system leaks based on the pressure change over time (S360 to S395).

Figure 4 is a graph showing the internal pressure and the valve control timing of the boil-off gas control system during the leak diagnosis method of the boil-off gas control system of the embodiment of the present invention, Figure 4 (a) is the inside of the boil-off gas control system The pressure of the fuel tank as the pressure, Figure 4 (b) is the open duty of the purge valve 270, Figure 4 (c) is the opening / closing operation state of the shut-off valve 260, Figure 4 (d) The vehicle speed is shown.

Hereinafter, a leak diagnosis method and its operation of an embodiment of the present invention will be described in detail with reference to FIGS. 3 and 4.

When the engine is started, such as by running (S310), the diagnostic method of the embodiment of the present invention is started, and first, it is determined whether the pressure in the boil-off gas control system is at high pressure (S315).

The high voltage judging may determine whether the set time has elapsed or is being oiled since the last start-up. If a long time passes after the start-up, a large amount of boil-off gas in the boil-off gas control system is included, and the discharge of the boil-off gas needs to be expedited.

The elapse of the set time may be detected by the clock 255 in the ECU 250, and the set time may be set to 24 hours. Lubrication can be determined based on the increase rate of the detection value of the pressure sensor (230).

Therefore, in this case, the purge valve 270 is opened to the maximum (S320) until the internal pressure is lowered (S325). Therefore, the boil-off gas in the boil-off gas control system is supplied to a large amount of engine so that the internal pressure is rapidly reduced. In the internal pressure determination step (S325), whether the internal pressure is large or small may be determined by an arbitrary reference value.

If it is not necessary to open the purge valve 270 to the maximum, the duty control is controlled (S330) until the internal pressure is maintained at atmospheric pressure for a set time (S335).

When the purge valve 270 is closed, the internal pressure will increase. In the case of the purge valve 270, since the internal pressure will be reduced by the inhalation of the boil-off gas of the engine, the duty control of the purge valve 270 is performed. It is obvious that atmospheric pressure can be maintained.

Therefore, the evaporation gas supply step (S310, S315, S320, S325, S330, S335) of supplying the boil-off gas to the engine until the internal pressure is maintained at atmospheric pressure by the driving process is implemented. This state corresponds to).

When the pressure in the boil-off gas control system is maintained at atmospheric pressure, the boil-off gas control system is blocked from the outside air (S340).

Blocking from outside air of the boil-off gas control system may be implemented by closing the shutoff valve 260.

Therefore, referring to FIG. 4, the pressure of the fuel tank 210 decreases from the time P1 to the time P2.

Then, by controlling the purge valve 270 to maintain the internal pressure in the boil-off gas control system to a set pressure of less than atmospheric pressure (S345). The set pressure can be arbitrarily set, but is preferably set to -14 hpa (hecto-pascal) based on atmospheric pressure.

Therefore, by the above process (S310 to S345) to maintain the internal pressure of the boil-off gas control system at a set pressure of less than atmospheric pressure. (See P2 to P3 in FIG. 4)

The pressure maintaining step (S345) is continued until the vehicle speed becomes 0 (S350), when the vehicle speed is 0 to block the evaporation gas control system from the outside air and the engine (S355). Since the shut-off valve 260 is already closed, the said shut-off S355 can be made to close the purge valve 270. FIG. (See P3 in Figure 4)

After the system shut-off (S355), it is determined whether the evaporative gas control system leaks based on the pressure change over time (S360 to S395). (See P3 to P4 in FIG. 4)

That is, the internal pressure change amount ΔP1 is detected after the first set time T1 has elapsed (S360), and it is determined whether the internal pressure change amount ΔP1 is greater than or equal to the first set change amount A1 (S365). If the pressure change amount? P1 is not equal to or larger than the first set change amount A1, it is determined that there is no leakage (S395).

If the internal pressure change amount? P1 is equal to or larger than the first set change amount A1, it is also possible to immediately determine that there is a leak. Preferably, it is determined that there is a leak by the following method.

That is, when the internal pressure change amount ΔP1 is equal to or larger than the first set change amount A1, the shutoff valve 260 is opened to release the shutoff of the evaporation gas control system and the outside air, thereby forming the internal pressure at atmospheric pressure ( S370). (See P4 of FIG. 4 (c) and P5 of FIG. 4 (a).)

Thereafter, the shutoff valve 260 is closed (S375), and after the second set time T2 has elapsed, the internal pressure change amount ΔP2 is detected (S380), and the internal pressure change amount ΔP2 is the second set change amount. It is determined whether or not (A2) is abnormal (S385), and when the internal pressure change amount ΔP2 is equal to or greater than the second set change amount A2, it is determined that there is a leak (S390).

The change after the second set time T2 has been detected in this case because it may be misjudged by sudden evaporation of the evaporated gas even if the internal pressure is temporarily lowered in a special case such as immediately after oiling. Since the internal pressure will increase rapidly after closing the shut-off valve 260 (S375) in this case, it is possible to prevent the misjudgment by prohibiting the leakage judgment, and in this case, even if the leakage judging is prohibited, This is because it can be judged normally.

As mentioned above, although the preferred embodiment regarding the leak diagnosis method of the evaporative gas control system of this invention was described, this invention is not limited to the said embodiment, The general knowledge in the technical field to which this invention belongs from the embodiment of this invention is described. It includes all changes to the extent that they are readily changed by the possessor and are considered equivalent.

According to the embodiment of the present invention, it is possible to diagnose whether the boil-off gas control system leaks quickly and accurately without incurring a disadvantage in driving performance of the vehicle.

Claims (6)

A method of diagnosing leakage of an evaporative gas control system that supplies an engine with gas evaporated from a fuel tank, A low pressure maintaining step of maintaining the internal pressure of the boil-off gas control system at a set pressure of atmospheric pressure or less; A system blocking step of blocking the boil-off gas control system from the outside air and the engine when the vehicle speed becomes zero; And And a leak determining step of determining whether the boil-off gas control system is leaked based on a change in pressure over time after the shut-off of the system. In claim 1, The low pressure maintaining step, An evaporation gas supplying step of supplying the engine with boil-off gas until the internal pressure is maintained at atmospheric pressure; An outside air blocking step of blocking the evaporation gas control system from outside air; And And a gas supply adjusting step of adjusting an internal pressure to a set pressure below atmospheric pressure by adjusting an amount of boil-off gas supplied to the engine from the boil-off gas control system. In claim 2, The boil-off gas supply step, A high pressure determining step of determining whether the internal pressure of the boil-off gas control system is high; And And a maximum supply step of supplying the boil-off gas to the engine at maximum until the high-pressure state is released in the high pressure state. In claim 3, The step of determining whether the high pressure is the evaporation gas control system leakage diagnostic method, characterized in that it is determined that the high pressure state when the set time has elapsed after the last start or refueling. In claim 1, The leak determining step, A first change amount detecting step of detecting a change amount (first change amount) of an internal pressure of the boil-off gas control system after a first predetermined time elapses; And A first change amount determining step of determining whether the first change amount is equal to or greater than a first set change amount, In the first change amount determining step, if the first change amount is not equal to or greater than the first set change amount, it is determined that there is no leakage. In claim 5, The leak determination step, An atmospheric pressure forming step of releasing the blocking of the boil-off gas control system and the outside air when the first change amount is equal to or greater than the first set change amount in the first change amount determining step to form the internal pressure at atmospheric pressure; A second change amount detecting step of detecting a change amount (second change amount) of an internal pressure of the boil-off gas control system after a second set time elapses; And And a second change amount determining step of determining whether the second change amount is equal to or greater than a second set change amount, In the second change amount determining step, when the second change amount is equal to or greater than the second set change amount, it is determined that there is no leakage, and when it is not abnormal, it is determined that there is a leakage.