Tank leakage diagnosis having a fuel tank as a pressure store

Abstract

The invention relates to a system (1) and to a corresponding method for tank leakage diagnosis. The system (1) comprises a fuel tank (3), a pressure source (5, 9), and a pressure sensor (7). The pressure source (5, 9) is configured to increase the pressure in the fuel tank (3). The pressure sensor (7) is configured to detect the pressure progression at the fuel tank (3). The system (1) is configured to seal the fuel tank (3) in a gas-tight manner such that the fuel tank (3) can be used as a pressure store. Furthermore, the system (1) is configured to conclude, independently of a current operation of the pressure source (5, 9) based on the determined pressure progression at the fuel tank (3), that a leak is present.

Claims

1. A system for tank leakage diagnosis, the system comprising: a fuel tank; a pressure source, which is configured to increase a pressure in the fuel tank; and a pressure sensor, which is configured to detect a pressure progression at the fuel tank, wherein the system is configured to seal the fuel tank in a gas-tight manner such that the fuel tank can be used as a pressure store, wherein the system is configured to conclude, independently of a current operation of the pressure source, based on a detected pressure progression at the fuel tank, that a leak is present, wherein the fuel tank is configured to be connected to the pressure source via a first line, wherein a first electric valve is provided on the first line, wherein the system further comprises an adsorption filter, wherein the fuel tank is configured to be connected to the adsorption filter via a second line, wherein a second electric valve is provided on the second line, and wherein, when detecting a pressure progression at the fuel tank, the first valve and the second valve seal the fuel tank in a gas-tight manner.

2. The system according to claim 1, wherein the pressure source is a turbocharger.

3. The system according to claim 1, wherein the adsorption filter is configured to be connected to a surrounding environment via a fourth line; wherein a third electric valve is provided on the fourth line; wherein the adsorption filter is configured to be connected via a fifth line to an intake manifold in order to be flushed with fresh air; wherein a fourth electric valve is provided on the fifth line; and wherein, when detecting a pressure progression at the adsorption filter, the second electric valve is open, whereas the first electric valve, the third electric valve and the fourth electric valve are closed in a gas-tight manner.

4. The system according to claim 1, wherein the fuel tank is configured to be connected to the adsorption filter via a third line; wherein a first pressure relief valve is provided on the third line; and wherein the first pressure relief valve is designed to open in the direction of the adsorption filter as soon as a predefinable pressure threshold value has been exceeded in the fuel tank.

5. The system according to claim 1, further comprising: an adsorption filter; wherein the pressure source is configured to be connected to the adsorption filter via a first line; wherein a first electric valve is provided on the first line; wherein the fuel tank is configured to be connected to the adsorption filter via a second line; wherein a second electric valve is provided on the second line; and wherein, when detecting a pressure progression at the fuel tank, the second valve seals the fuel tank in a gas-tight manner.

6. The system according to claim 5, wherein the adsorption filter is configured to be connected to a surrounding environment via a fourth line; wherein a directional control valve is provided between the first line, the fourth line and the adsorption filter; wherein the directional control valve is configured in a first position to connect the adsorption filter to the first line; and wherein the directional control valve is configured in a second position to connect the adsorption filter to the fourth line.

7. The system according to claim 6, wherein the adsorption filter is configured to be connected to an intake manifold via a fifth line in order to be flushed with fresh air; wherein a fourth electric valve is provided on the fifth line; and wherein, when detecting a pressure progression at the adsorption filter, the second electric valve is open, whereas the first electric valve and the fourth electric valve are closed in a gas-tight manner and the directional control valve is disposed in the first position.

8. The system according to claim 7, wherein the adsorption filter is configured to be connected to the intake manifold via a sixth line in order to be flushed with fresh air; wherein a second pressure relief valve is provided on the sixth line; and wherein the second pressure relief valve is designed to open in the direction of the intake manifold as soon as a predefinable pressure threshold value at the adsorption filter has been exceeded.

9. A method for carrying out a tank leakage diagnosis on a system according to claim 1, the method comprising the following steps: connecting the fuel tank to the pressure source; increasing the pressure in the fuel tank by means of the pressure source; sealing the fuel tank in a gas-tight manner; using the fuel tank as a pressure store; and detecting a presence of a leak independently of the current operation of the pressure source and based on a detected pressure progression at the fuel tank.

10. A system for tank leakage diagnosis, the system comprising: a fuel tank; a pressure source, which is configured to increase a pressure in the fuel tank; a pressure sensor, which is configured to detect a pressure progression at the fuel tank; and an adsorption filter, wherein the pressure source is configured to be connected to the adsorption filter via a first line, wherein a first electric valve is provided on the first line, wherein the fuel tank is configured to be connected to the adsorption filter via a second line, wherein a second electric valve is provided on the second line, wherein, when detecting a pressure progression at the fuel tank, the second valve seals the fuel tank in a gas-tight manner, wherein the fuel tank is configured to be connected to the adsorption filter via a third line, wherein a first pressure relief valve is provided on the third line, and wherein the first pressure relief valve is designed to open in the direction of the adsorption filter as soon as a predefinable pressure threshold value has been exceeded in the fuel tank.

11. A method for carrying out a leakage diagnosis on a portion of a fuel system, the method comprising the following steps: communicating a fuel tank with a pressure source; increasing a pressure in the fuel tank by means of the pressure source; sealing the fuel tank in a gas-tight manner; detecting a presence of a leak independently of a current operation of the pressure source and based on a determined pressure progression at the fuel tank; after the detecting, opening a valve connecting the fuel tank with an adsorption filter; and after the opening, detecting a presence of a leak independently of a current operation of the pressure source and based on a determined pressure progression at either 1) a space including both the fuel tank and the adsorption filter or 2) the adsorption filter only.

12. The method of claim 11, wherein detecting a presence of a leak independently of the current operation of the pressure source and based on a determined pressure progression at a space including both the fuel tank and the adsorption filter includes detecting with a pressure sensor positioned in the fuel tank.

13. The method of claim 11, wherein detecting a presence of a leak independently of the current operation of the pressure source and based on a determined pressure progression at a space including both the fuel tank and the adsorption filter includes detecting with a pressure sensor positioned in the adsorption filter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the present invention will become apparent to the person skilled in the art from the following description of exemplary embodiments, which are not to be interpreted so as to limit the invention, with reference to the attached drawings. In the drawings:

(2) FIG. 1 shows a system for tank leakage diagnosis according to a first exemplary embodiment of the invention;

(3) FIG. 2 shows a system for tank leakage diagnosis according to a second exemplary embodiment of the invention.

(4) All of the figures are only schematic depictions of inventive devices or components thereof according to exemplary embodiments of the invention. Spacings and size relations are not depicted true to scale in the figures. In the different figures, corresponding elements are provided with the same reference numbers.

DETAILED DESCRIPTION

(5) In FIG. 1, a first exemplary of the system 1 for tank diagnosis is depicted. The system 1 comprises a fuel tank 3, a pressure source 5 and a pressure sensor 7. The pressure source 5 is designed as a turbocharger 9 in the exemplary embodiments shown. The turbocharger 9 is disposed on the intake manifold 11 and compresses the air which is supplied to an internal combustion engine 13. The pressure source 5 could, for example, alternatively be designed as an air pump.

(6) The pressure source 5, 9 can increase the pressure in the fuel tank 3 via the first line 17, if a first electric valve 29 that is disposed on the first line 17 is in an open position. The pressure sensor 7 detects the pressure progression at the fuel tank 3 and transmits the measured values, for example, to a control device. In order to carry out the tank leakage diagnosis, the system 1 is configured to seal all supply and discharge lines of the fuel tank 3 in such a manner that the fuel tank 3 can be used as a pressure store. The system 1 is furthermore configured to conclude, independently of a current operation of the pressure source 5, 9 based on the determined pressure progression at the fuel tank 3, that a leak is present. That means that an overpressure is initially stored in the fuel tank 3 and subsequently all of the shut-off valves on supply and discharge lines of the fuel tank 3 are sealed in a gas-tight manner. If the pressure sensor 7 thereupon detects a substantially constant pressure progression, it can then be concluded that a leak is not present at the fuel tank 3. If, on the other hand, the pressure drops considerably, it can then be concluded that a leak is present.

(7) The subspace checked in the process is indicated by dashed lines on the left in FIG. 1. The subspace in which the check takes place comprises, for example, the fuel tank 3 and the lines 17, 19, 21 up to the valves 29, 31, 37.

(8) In addition, the tank leakage diagnosis can be expanded to a further subspace of the system 1. This is likewise indicated with a dashed line in FIG. 1 and comprises an adsorption filter 15. The adsorption filter 15 can be connected via a second line 19 to the fuel tank 3 if the electric valve 31 provided on the second line 19 is in an open position. The adsorption filter 15 can furthermore be connected via a fourth line to a surrounding environment if a third electric valve 33 is in an open position. In addition, the adsorption filter 15 can be connected via a fifth line 25 to the intake manifold 11 in order to be flushed with fresh air if a fourth electric valve 35 is in an open position.

(9) When detecting a pressure progression at the fuel tank 3, i.e. for conducting the tank leak diagnosis in the first subspace, the first valve 29 and the second valve 31 are closed in a gas-tight manner. When detecting a pressure progression at the adsorption filter 15, i.e. for conducting the tank leakage diagnosis in the second subspace, the second electric valve 31 is opened, whereas the first electric valve 29, the third electric valve 33 and the fourth electric valve 35 are closed in a gas-tight manner.

(10) When using the fuel tank 3 as a pressure store, a tank leak diagnosis is advantageously possible at any point in time after completing the pressurization. In so doing, a tank leakage diagnosis in the after-run period can be omitted; thus enabling energy to be saved. A further advantage can be seen therein that an outgassing of the fuel in the fuel tank 3 is reduced due to the stored overpressure. This in turn makes a lower flush rate of the adsorption filter 15 possible.

(11) In order to prevent the overpressure in the fuel tank 3 from becoming too large, a third line 21 is provided which connects the fuel tank 3 to the adsorption filter 15. A first pressure relief valve 37 is provided on the third line 21 which is designed to open in the direction of the adsorption filter 15 as soon as a predefinable pressure threshold value has been exceeded in the fuel tank 3.

(12) As a further component of the system 1, a charge air cooler 43 can be provided at a channel area between turbocharger 9 and internal combustion engine 13. Furthermore, an air-flow sensor 45, in particular a hot-film air-flow sensor (HFS), can be provided at the intake manifold 11. In addition, the fifth line 25 extending between the adsorption filter 15 and the intake manifold 11 can branch off. A first section of the fifth line 25 then extends directly to the intake manifold 11. A second section of the fifth line 25 is connected to the channel area between turbocharger 9 internal combustion engine 13. In this way, fuel vapors 15 flushed from the adsorption filter 15 can be directly fed to the internal combustion engine. In addition, a first check valve 47 can be provided in the first section of the fifth line 25 and a second check valve 49 in the second section of the fifth line 25. The check valves 47, 49 can prevent gases from flowing back to the adsorption filter 15. For example, the first line 17 is flow-connected to a line section between the turbocharger 9 and the charge air filter 43.

(13) A second exemplary embodiment of the system 1 for tank leakage diagnosis is depicted in FIG. 2. The system 1 is constructed similarly to the system 1 depicted in FIG. 1. In contrast to the system 1 of FIG. 1, the lines 17, 19, 27 in the system 1 depicted in FIG. 2 are arranged or configured differently. In this case, the fuel tank 3 cannot be directly connected to the pressure source 5, 9 via the first line 17 but can be connected to said pressure source via the combination of second line 19, adsorption filter 15 and first line 17. To this end, the first line 17, for example originating from the line section between the turbocharger 9 and the charge air cooler 43, is flow-connected directly to the adsorption filter 15. In order to generate an overpressure in the fuel tank 3, the first electric valve 29 as well as the second electric valve 31 has to be open. In order to detect a pressure progression at the fuel tank 3 and to carry out a tank leakage diagnosis, only the second electric valve 31 has to be closed. Hence, the number of shut-off valves required for the tank leakage diagnosis can be reduced in comparison to the exemplary embodiment in FIG. 1.

(14) A directional control valve 41 is furthermore provided in FIG. 2 between the first line 17, the fourth line 23 and the adsorption filter 15. In a first position, the directional control valve 41 connects the adsorption filter 15 to the first line 17. In a second position, the directional control valve 41 connects the adsorption filter 15 to the fourth line 23. When detecting a pressure progression at the adsorption filter 15, i.e. in the second subspace of the system 1, the second electric valve 31 is open, whereas the first electric valve 29 and the fourth electric valve 35 are closed in a gas-tight manner and the directional control valve 41 is disposed in the first position.

(15) A sixth line 27 is furthermore provided in the exemplary embodiment of FIG. 2, which connects the adsorption filter 15 to the intake manifold 11 for flushing with fresh air. A second pressure relief valve 39 is provided on the sixth line 27, said pressure relief valve preventing the pressure in the region of the adsorption filter 15 from increasing too much. To this end, the second pressure relief valve 39 is configured to open in the direction of the intake manifold 11 as soon as a predefinable pressure threshold value has been exceeded at the adsorption filter 15. In addition, a further pressure sensor 51 is provided in a channel area between intake manifold 11 and adsorption filter 15. The further pressure sensor 51 can be configured to carry out a component test, i.e. to, e.g., detect the switching of the tank vent valves 35.

(16) In closing, it is noted that expressions such as comprising or something similar do not exclude other elements or steps from being provided. In addition, it should be noted that a or one do not exclude a plurality. Furthermore, features described in connection with the different embodiments can be combined with each other in an arbitrary fashion. It is further noted that the reference signs in the claims are not to be interpreted so as to limit the scope of the claims.