GAS METERING VALVE

Abstract

A gas metering valve. The gas metering valve includes a housing, in which a gas chamber is formed, which can be filled with gaseous fuel via an inlet opening and from which gaseous fuel can be discharged in a metered manner via an outlet opening. A valve element is longitudinally moveably arranged in the gas chamber, and has a valve seal surface which cooperates with a valve seat for opening and closing the outlet opening. A magnet armature is connected to the valve element. A bellows is connected in a gas-tight manner to the valve element at one end and to the housing at the other end. The gas-tight connection with the housing is formed along a sealing line. The diameter of the sealing line is greater than the diameter of the valve seat.

Claims

1-9. (canceled)

10. A gas metering valve, comprising: a housing in which a gas chamber is formed, which can be filled with gaseous fuel via an inlet opening and from which gaseous fuel can be discharged in a metered manner via an outlet opening; a valve element which is longitudinally moveably arranged in the gas chamber, wherein the valve element has a valve seal surface which cooperates with a valve seat for opening and closing the outlet opening; a magnetic armature which is connected to the valve element and can be moved by an electromagnet; a bellows which is connected in a gas-tight manner to the valve element at one end and to the housing at the other end, wherein the gas-tight connection with the housing is formed along a sealing line; wherein a diameter of the sealing line is greater than a diameter of the valve seat, such that, using pressure in the gas chamber, a resulting pneumatic longitudinal force is exerted on the valve element in a closing direction.

11. The gas metering valve according to claim 10, wherein the diameter of the sealing line is at least 5% larger than the diameter of the valve seat.

12. The gas metering valve according to claim 10, wherein a valve disk is formed at an outlet end of the valve element, the valve seal surface being formed on the valve disk and facing the housing.

13. The gas metering valve according to claim 12, wherein the valve seal surface is conical in shape.

14. The gas metering valve according to claim 10, wherein the magnet armature is a plunger armature.

15. The gas metering valve according to claim 14, wherein the magnet armature is sealed in a gas-tight manner against the gas chamber by the bellows.

16. The gas metering valve according to claim 10, wherein a closing spring is arranged in the gas chamber, the closing spring being arranged under a pressure bias between a shoulder on the housing and the valve element and exerts a closing force in a longitudinal direction on the valve element.

17. The gas metering valve according to claim 10, wherein the magnet armature is arranged in a magnet armature chamber which can be filled with gas and in which a lower pressure prevails during operation of the gas metering valve than in the gas chamber.

18. The gas metering valve according to claim 17, wherein the magnet armature chamber is connected to ambient air via a compensating line.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0015] FIG. 1 shows a longitudinal cross section through a gas metering valve according to the present invention, wherein only main features are shown.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0016] FIG. 1 shows a gas metering valve according to the present invention in longitudinal cross section. The gas metering valve has a housing 1 in which a gas chamber 2 is formed. The lower end region of the housing 1 in FIG. 1 has a cylindrical shape and opens into a circular outlet opening 5. The gas chamber 2 can be filled with a gaseous fuel via a connection 3 formed in the housing 1, which fuel flows into the gas chamber 2 via an inlet opening 4. A piston-shaped valve element 8 is longitudinally moveably arranged in the gas chamber 2 for opening and closing the outlet opening 5 and therefore for metered discharge of the gaseous fuel. At its outlet end, the valve element 8 has a valve disk 9 which has a conical valve seal surface 10. The valve seal surface 10 faces the housing 1 and cooperates with a valve seat 11 formed at the outlet end of the housing 1 for opening and closing the outlet opening 5 so that when the valve seal surface 10 is in contact with the valve seat 11, the outlet opening 5 is closed in a gas-tight manner. At the opposite end of the valve element 8 remote from the outlet opening 5, said element merges into a piston rod 108 which is connected to a magnet armature 18 so that the magnet armature 18 always moves synchronously together with the piston rod 108 and the valve element 8. The magnet armature 18 is designed as a plunger armature and is longitudinally moveably arranged in a magnet armature chamber 17. To move the magnet armature 18 and therefore the valve element 8, an electromagnet 20 is arranged in the housing 1 in the region of the magnet armature chamber 17.

[0017] In order to keep the gas metering valve closed when the electromagnet 20 is switched off, a closing spring 12 is arranged in the gas chamber 2, which spring is arranged between a shoulder 13 in the housing 1 and a ring shoulder 14 on the valve element 8 under a pressure bias, and presses the valve element 8 with the valve disk 9 against the valve seat 11. The piston rod 108 which forms part of the valve element 8 is surrounded by a bellows 25. The bellows 25 is connected in a gas-tight manner to a disk 26 which is firmly connected to the valve element 8, and a sealing ring 27 which rests against the housing 1 or is connected to the housing 1. As a result, the bellows 25 seals the gas chamber 2 against the magnet armature chamber 17. The magnet armature chamber 17 is filled with air under ambient pressure, wherein a compensating line 21 formed in the housing 1 establishes a connection with the environment for pressure compensation. Alternatively, it is also possible to fill the magnet armature chamber 17 with an inert gas; in this case, the compensating line 21 is closed after filling.

[0018] When the valve seal surface 10 is in contact with the valve seat 11, the gas chamber 2 is sealed along a circular sealing line that has a diameter D.sub.V. This means that a pneumatic force acts on parts of the valve disk 9 due to the pressure in the gas chamber 2, which is directed in the opening direction of the valve element 8, i.e. out of the housing 1. On the opposite side of the valve element 8, a pneumatic force acts on the disk 26 in the opposite direction, i.e. in the closing direction of the valve element 8, wherein the seal on the sealing ring 27 is along a circular sealing line 28 with a diameter D.sub.W. The gas-tight sealing of the bellows 25 on the sealing ring 27 yields a resulting closing force on the valve element 8 if the diameter D.sub.W is greater than the sealing diameter D.sub.V on the valve seat. The resulting pneumatically effective surface is then the difference between the surfaces that are bounded by the sealing line 28 and the sealing line on the valve seat 11. Since both surfaces are circular, this results in a differential area of A.sub.Diff=/4.Math.(D.sub.W.sup.2D.sub.V.sup.2), so that the resulting pneumatic force F on the valve element 8 in the closing direction is given by F=A.Math.p if p is the differential pressure between the gas chamber 2 and the magnet armature chamber 17, and ambient pressure acts on the lower side of the valve disk 9 like it also prevails in the magnet armature chamber 17. In an advantageous way, the diameter D.sub.W is at least 5% larger than the diameter D.sub.V, so that a pneumatic closing force on the valve element 8 results which is sufficient to always keep the valve element 8 sealed, even with higher pressures in the gas chamber 2.

[0019] Since the pressure in the gas chamber 2 generates a closing force on the valve element 8, the force of the closing spring 12 does not need to be high in order to always keep the gas metering valve sealed, even when the electromagnet 20 is switched off. Given a corresponding design of the bellows 25, the closing spring 12 can also be dispensed with since the low closing force still required can be achieved via the tension-biased bellows 25.