METHOD FOR OPERATING A DRIVE UNIT OPERATED WITH GASEOUS FUEL

Abstract

A method for operating a drive unit operated with gaseous fuel. The gaseous fuel is provided under high pressure in a plurality of pressure tanks that can be connected via a supply line and with a metering valve via which the gaseous fuel can be dispensed to the drive unit. One of the pressure tanks is designed as a high-load pressure tank which is only connected to the supply line when the drive unit is under high load, the pressure tanks in which a lower gas pressure prevails than in the high-load pressure tank simultaneously being disconnected from the supply line.

Claims

1-10. (canceled)

11. A method for operating a drive unit operated with gaseous fuel, the gaseous fuel being provided under high pressure in a plurality of pressure tanks that can be connected via a supply line and with a metering valve via which the gaseous fuel can be dispensed to the drive unit, the method comprising the following steps: providing one of the pressure tanks as a high-load pressure tank, which is connected to the supply line only at high load of the drive unit; simultaneously disconnecting from the supply line the pressure tanks in which a lower gas pressure than in the high-load pressure tank prevails.

12. The method according to claim 11, wherein the high-load pressure tank is connected to the supply line only when the gas pressure in the remaining pressure tanks is no longer sufficient to supply the drive unit at high load.

13. The method according to claim 11, wherein each of the pressure tanks can be connected to the supply line via a connecting line, wherein a shut-off valve is arranged in each connecting line.

14. The method according to claim 13, wherein the shut-off valves are controlled electrically.

15. The method according to claim 11, wherein several high-load pressure tanks are present, at least one of which is connected to the supply line when the drive unit is at high load.

16. The method according to claim 15, wherein all of the high-load pressure tanks are always connected together to the supply line.

17. The method according to claim 15, wherein only one of the high-load pressure tanks is connected to the supply line when the drive unit is at high load, until the one of the high-load pressure tanks has the same gas pressure as the remaining pressure tanks, and a next one of the high-load pressure tanks is subsequently connected to the supply line when the drive unit is at high load.

18. The method according to claim 11, wherein the drive unit operated with gaseous fuel is an internal combustion engine or a fuel cell including an electric motor powered by the fuel cell.

19. The method according to claim 11, wherein a pressure reducer is arranged in the supply line between the pressure tanks and the metering valve.

20. The method according to claim 11, wherein several metering valves are connected to the supply line.

Description

BRIEF DESCRIPTION OF EXAMPLE EMBODIMENTS

[0014] The figures show various exemplary embodiments of devices that can be operated using the method according to example embodiments of the present invention.

[0015] FIG. 1 shows a schematic representation of a drive unit operated with gaseous fuel, together with a pressure tank assembly for supplying this drive unit, according to an example embodiment of the present invention.

[0016] FIG. 2 shows a further exemplary embodiment of a pressure tank assembly with alternative circuitry of the individual pressure tanks, according to an example embodiment of the present invention.

[0017] FIG. 3 shows a flow chart for illustrating the method according to the present invention, according to an example embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0018] In order to explain the method according to the invention, a drive unit, which is operated with gaseous fuel, is schematically shown in FIG. 1. The drive unit 11 is designed as an internal combustion engine here and comprises four combustion chambers 14, into each of which a metering valve 12 opens. Gaseous fuel can be metered via the metering valve 12 into the respective combustion chamber 14, where the gaseous fuel combusts and in each case moves a piston in a conventional manner. A pressure tank assembly 1 is provided to supply gaseous fuel to the drive unit 11. The pressure tank assembly 1 comprises several pressure tanks 3, 3a, 3b, 3c, of which the pressure tank 3 is used as a high-load pressure tank 3, wherein the high-load pressure tank 3 is otherwise not structurally different from the remaining pressure tanks 3a, 3b and 3c. The pressure tanks 3, 3a, 3b, 3c are substantially formed in the form of high-pressure gas cylinders, wherein the gas pressure within the pressure tanks 3, 3a, 3b, 3c is measured by a respective pressure sensor 15, 15a, 15b, 15c, which transmit their measured values to a control unit 9, which is schematically shown in FIG. 1.

[0019] In order to supply the drive unit 11 with the gaseous fuel, all pressure tanks 3, 3a, 3b, 3c are connected via connecting lines 4, 4a 4b, 4c to a supply line 7, which branches toward the individual metering valves 12. In the connecting lines 4, 4a, 4b, 4c, a respective shut-off valve 5, 5a, 5b, 5c is arranged, which can be controlled electrically and are connected to the control unit 9 via an electrical connecting line 8. The individual shut-off valves 5, 5a, 5b, 5c can thus be opened and closed independently of one another. In the supply line 7, a pressure reducer 10 is arranged, by means of which the required pressure of the gaseous fuel at the metering valves can be adjusted if the gaseous fuel delivered from the pressure tanks has too high a gas pressure.

[0020] The method according to the present invention for operating the drive unit and for supplying the drive unit with gaseous fuel is explained in more detail with reference to the flow chart of FIG. 3. In a first step 100, the drive unit is put into service, i.e., the combustion engine is started, for example. In a second step 200, the shut-off valve of at least one pressure tank 3a, 3b, 3c is opened; generally, when the combustion engine is at a normal load state, one of the shut-off valves 5a, 5b, 5c is opened, while the shut-off valve 5 of the high-load pressure tank 3 remains closed.

[0021] In a next step 300, it is checked whether the pressure threshold value of the pressure tanks 3a, 3b, 3c has decreased below a predetermined threshold value at which the supply of the drive unit 11 is no longer ensured at maximum load. This takes place on the basis of the pressure that the individual pressure sensors 15a, 15b, 15c measure and transmit to control unit 9. If the pressure in the pressure tanks 3a, 3b, 3c is sufficient (branch “N”), the shut-off valve 5 remains closed (step 600) and the shut-off valves 5a, 5b, 5c remain open so that the drive unit, here the internal combustion engine, continues to be supplied with the gaseous fuel from the pressure tanks 3a, 3b, 3c. If, however, the pressure in the pressure tanks 3a, 3b, 3c drops below a threshold value (branch “Y”), it is checked in the following step 400 whether the drive unit 11 is in a high-load state. If not (branch “N”), the shut-off valves 5a, 5b, 5c remain open and the shut-off valve 5 remains closed. If yes (branch “Y”), in a step 500, the shut-off valves 5a, 5b, 5c are closed and the shut-off valve 5 is opened so that gaseous fuel now flows under high pressure from the high-load pressure tank 3 into the supply line 7 and from there to the metering valves 12. The pressure reducer 10 is only used if the gas pressure is too high. Subsequently, the method steps of testing the pressure threshold value in the pressure tanks 3a, 3b, 3c in step 300 and the subsequent steps are passed through again until the control unit detects that the drive unit 11 is no longer at full or maximum load. If this is determined, in a step 600, the shutoff valve 5 of the high-load pressure tank is closed and the shutoff valves 5a, 5b, 5c of the pressure tanks 3a, 3b, 3c are reopened.

[0022] FIG. 2 shows an alternative circuitry of the pressure tanks 3a, 3b, 3c. Instead of directly connecting each connecting line 4a, 4b, 4c with a shut-off valve 5a, 5b, 5c to the supply line, the connecting lines 4a, 4b, 4c here open into a further connecting line 4′, in which a normal shut-off valve 6 is arranged. In this case, the connection of the pressure tanks 3a, 3b, 3c to the supply line 7 can be interrupted by the normal shut-off valve 6, while the shut-off valves 5a, 5b, 5c can remain constantly open even in full-load cases.

[0023] In the pressure tank assembly 1 shown here, four pressure tanks 3, 3a, 3b, 3c are provided, one of which is formed as a high-load pressure tank 3. It does not have to be structurally different from the remaining pressure tanks 3a, 3b, 3c but only becomes a high-load pressure tank as a result of its use and assumes supplying the drive unit at full load. It may also be provided to use a greater number of pressure tanks and to operate more than one of the pressure tanks as a high-load pressure tank. For example, if two pressure tanks are provided as high-load pressure tanks, one of the high-load pressure tanks can first assume the task of providing the necessary gaseous fuel pressure when the drive unit is at full load, until the pressure level in this high-load pressure tank is no longer sufficient. Then, the second high-load pressure tank can be used, which then ensures the supply of the drive unit 11 even at full load and, if the drive unit is a combustion engine, at very high rotational speeds.