Vent valve

Abstract

The invention relates to a vent valve (1) for controlling the internal tank pressure of a fuel tank, having at least one valve housing (2) having at least one first connection (3) to the fuel tank and at least one second connection (4), which can be connected to a vent line leading to a fuel vapor filter. The vent valve (1) comprises at least one valve element, which is held in a valve seat (8) in a position in which it closes the first connection (3) by the force of gravity and/or by spring loading and, after a given pressure threshold is exceeded, is raised from the valve seat (8) and, when a given pressure threshold is undershot, returns to the initial position. The valve element and/or the valve element guide has/have at least one relief opening (10), which forms a bypass for a gap flow which arises, for example, during a return movement of the valve element.

Claims

1. A vent valve to control internal tank pressure of a fuel tank, comprising: at least one valve housing having at least one first connection configured to provide fluid communication with the fuel tank and at least one second connection configured to provide fluid communication with a fuel vapour filter, at least one valve element seated by at least one of gravitational force and spring force in a valve seat in a position which completely closes the first connection, wherein the vent valve is operable such that, when a pressure from the fuel tank rises above a threshold pressure, the valve element is unseatable from the valve seat and, when the pressure from the fuel tank lowers below the threshold pressure, the valve element is returnable to the seated position, wherein the valve element is arranged to move within a valve element guide, wherein the valve element and the valve element guide are configured to permit a gap flow between the valve element and the valve element guide, wherein the valve element has at least one first relief opening, which forms a bypass for said gap flow, and wherein the first relief opening is arranged approximately at a level of the valve seat or below the valve seat in relation to the direction of flow through the valve, and wherein the valve element has at least one second relief opening, which is closed by a nonreturn valve acting counter to a direction of closing of the vent valve.

2. The vent valve according to claim 1, wherein the valve element comprises a ball, a piston or a plate.

3. The vent valve according to claim 1, wherein the valve element guide comprises at least one cylinder in which the valve element is arranged to move axially.

4. The vent valve according to claim 1, wherein the first relief opening is provided in a sealing surface of the valve element.

5. The vent valve according to claim 1, wherein the valve element has at least one second relief opening, which is open permanently.

6. The vent valve according to claim 1, wherein the valve element guide is formed by a portion of the valve housing.

Description

(1) The invention is explained below with reference to two illustrative embodiments illustrated in the drawings, in which:

(2) FIG. 1: shows a schematic sectional view through a vent valve according to a first illustrative embodiment of the invention,

(3) FIG. 2: shows a schematic sectional view through a vent valve according to a second illustrative embodiment of the invention,

(4) FIG. 3: shows a schematic representation of a vent valve according to a third illustrative embodiment of the invention,

(5) FIG. 4: shows a schematic representation of a vent valve according to a fourth illustrative embodiment of the invention, and

(6) FIGS. 5 and 6: show schematic representations of a vent valve according to a fifth illustrative embodiment of the invention.

(7) The vent valve 1 according to the invention can be designed as a pure pressure holding valve or, alternatively, as part of a normal service vent valve with a roll-over function on a fuel tank. It comprises, for example, a valve housing 2 having a first connection 3 to a fuel tank (not shown) and a second connection 4, which can be connected to a vent line leading to a fuel vapour filter. The first connection 3 comprises a vent opening 5, which is either connected directly to the compensating volume of a fuel tank or to a vent line from the fuel tank. The valve housing 2 of the vent valve 1 can, for example, be connected directly to the tank wall of a fuel tank or can be welded thereto.

(8) A valve element in the form of a ball 6 (first illustrative embodiment) is arranged within the valve housing 2, for example.

(9) In the illustrative embodiment shown in FIG. 1, the ball 6 is arranged so as to be able to move freely in a tube section 7, which forms a valve element guide.

(10) An encircling collar around the vent opening 5 is provided as a valve seat 8, and is closed by the ball 6 in the rest position. As the valve element, the ball 6 is held in the position in which it closes the vent opening 5 purely by virtue of its mass, i.e. by the force of gravity. The mass of the ball determines the closing force of the valve. The clear width of the tube section 7 is larger than the diameter of the ball 6 by an amount such that, when the fuel tank or the motor vehicle in which the latter is installed is in a tilted position or due to driving dynamics, deflection of the ball 6 out of the centre of the vent opening 5 as defined by the valve seat 8 is possible. By virtue of this possibility, the ball 6 partially exposes the cross section of the vent opening 5 when the vehicle is in a tilted position or when there is deceleration or acceleration of the vehicle, thus enabling pressure compensation to take place between the fuel tank and the surroundings.

(11) In order to minimize the pressure loss in the event of a response of the vent valve 1 when the valve element, i.e. the ball 6, returns to the initial position thereof, in which it completely closes the vent opening 5, first relief openings (10) are provided at the edge in the tube section 7, approximately at the level of the valve seat 8, forming a flow bypass for the pressure loss caused by the valve element or ball 6, irrespective of the tilted position of the vehicle.

(12) Owing to this simple and effective measure, the switching hysteresis of the vent valve 1 is significantly reduced.

(13) In the variant of the vent valve 1 shown in FIG. 2, in which parts which are the same are provided with the same reference signs, the valve element is designed as a piston 9. The piston 9 is likewise arranged with play in the tube section 7, allowing it to perform a slight wobbling/tilting movement within the tube section 7. Since deflection of the piston 9 in a manner corresponding to that in the illustrative embodiment shown in FIG. 1 is not desired and not necessary, the size of the gap between the piston 9 and the tube section 7 is somewhat smaller than in the first illustrative embodiment. As a result, the pressure loss due to the valve element would normally be greater in the illustrative embodiment according to FIG. 2. Owing to the first relief opening 10 provided in the tube section 7, the switching behaviour of the piston is essentially independent of the gap flow which arises between the piston 9 and the tube section 7.

(14) In the illustrative embodiment according to FIG. 2 too, the piston 9 can be held in the position in which it closes the vent opening 5 purely by the force of gravity.

(15) As an alternative, it is possible to hold the piston 9 in the closed position by spring loading.

(16) The piston 9 and the tube section 7 have mutually complimentary circular cross sections but, of course, the invention is not restricted to such a cross-sectional geometry.

(17) It is also possible for a plate to be provided as a valve element instead of a piston 9.

(18) In the variant of the vent valve 1 shown in FIG. 3, it is arranged in a vent line 11 as a pure pressure holding valve. Accordingly, the valve element is designed as a piston 9 loaded by a spring 13. The piston 9 has a conical sealing surface 12, which interacts with a funnel-shaped valve seat 8. In the region of the encircling sealing surface 12, the piston 9 is provided with first relief openings 10 in the form of bores, through which gas can flow as long as the sealing surface 12 is not in the valve seat 8, ensuring that the pressure losses associated with the piston 9 moving in the valve seat 8 are minimal. Another variant of the vent valve 1 according to the invention is shown in FIG. 4. The variant of the vent valve 1 illustrated in FIG. 4 corresponds to the variant of the vent valve shown in FIG. 3. Components which are the same are provided with the same reference signs. The variant of the vent valve 1 shown in FIG. 4 differs from that shown in FIG. 3 in that a second relief opening 14 is provided in the end face of the piston 9 and is permanently open. This relief opening 14 is embodied as a somewhat smaller relief bore and allows an intended small amount of leakage through the vent valve 1. Such leakage ensures that the liquid column in the feed pipe of the fuel tank falls after a certain time once the fuel pump nozzle is switched off. The delay is set in such a way that the user cannot immediately add more fuel. Moreover, the second relief opening 14 serves to compensate for any vacuum in the tank.

(19) A fifth variant of the vent valve 1 according to the invention is illustrated in FIGS. 5 and 6. This fifth variant of the vent valve 1 corresponds essentially to the variant illustrated in FIG. 4, with the difference that a nonreturn valve element 15 is inserted into the second relief opening 14. This opens the second relief opening 14 if there is a vacuum in the tank, and closes it when there is excess pressure.

REFERENCE SIGNS

(20) 1 vent valve 2 valve housing 3 first connection 4 second connection 5 vent opening 6 ball 7 tube section 8 valve seat 9 piston 10 first relief opening 11 vent line 12 sealing surface 13 spring 14 second relief opening 15 nonreturn valve element