WO2002008597A1

WO2002008597A1 - Valve for controlling the fuel vapor pressure in a tank system

Info

Publication number: WO2002008597A1
Application number: PCT/IL2001/000420
Authority: WO
Inventors: Asaf Halamish; Zohar Moalem; Moshe Ehrman; Daniel Ostraich
Original assignee: Raval - Agriculture Cooperative Societies Ltd.
Priority date: 2000-07-26
Filing date: 2001-05-11
Publication date: 2002-01-31
Also published as: DE10196452T1; AU2001256634A1; IL137529A0

Abstract

A fuel vapor pressure control valve (20) comprising a housing (22) fitted with a first port (26) connectable to a fuel tank (12) and a second port (36) connectable to a fuel vapor recovery device (16), a valve assembly (20) for admitting vapor flow in a first direction from the first port to said second port when pressure within the tank rises to a first threshold, or for admitting vapor flow in a second, opposite direction when pressure within the tank drops bellow the pressure at the fuel vapor recovery device.

Description

VALVE FOR CONTROLLING THE FUEL VAPOR PRESSURE IN A TANK SYSTEM

FIELD OF THE INVENTION

The present invention is in the field of fluid flow control valves and in particular it is concerned with fuel vapor recovery valves which are typically mounted between a vehicle's fuel tank and a fuel vapor recovery device, e.g. a canister.

BACKGROUND OF THE INVENTION

A fuel tank of the type typically mounted in a vehicle, is subject to varying pressure owing to several changing parameters, e.g. fuel consumption during operation of the engine (resulting in pressure decrease within the tank), rise of temperature and refueling (resulting in pressure increase within the tank), etc.

Such pressure changes within the fuel tank may have an overall effect on the engine's performance owing to unsteady fuel supply to the engine and, in some extreme cases, may result in deformation of the fuel tank.

In modern vehicles there is typically provided a vapor control system wherein the fuel vapor is transferred from the fuel tank to a recovery device such as a carbon canister, as known per se. For that purpose, it is known to provide a control pressure valve in flow communication between the fuel tank and the vapor recovery device for selectively evacuating fuel vapor from the fuel tank. However, it is desired not to evacuate unnecessary fuel vapors in order to reduce fuel consumption. Some vapor control valves are pressure responsive whereby they open or close in response to pressure condition at the filling pipe inlet. Other pressure responsive valves respond to vapor pressure within the fuel tank itself. Still another type of fuel vapor control valves respond to the level of the fuel within the fuel tank.

The fuel vapor developing within the fuel tank is collected and transferred to the carbon canister in which air supplied to the engine is enriched by the fuel vapor, thus, on the one hand enriching the injected gas mixture injected to the engine and, on the other hand, reducing or eliminating fuel vapor escaped to the atmosphere, as this is becoming an ever-growing environmental requirement and which within a few years will become a compulsory requirement by environment control authorities.

However, in order to reduce the evacuation of fuel vapor from the tank, thus reducing overall fuel consumption, it is required that evacuation of fuel vapor to the carbon canister shall take place only upon increase of fuel vapor pressure within the fuel tank over a predetermined pressure threshold.

It is thus an object of the present invention to provide a fuel vapor control valve for controlling the flow of fuel vapor to a fuel recovery apparatus and for venting the fuel tank and fuel recovery apparatus of a vehicle.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a fuel vapor pressure control valve fittable between a vehicle's fuel tank and a fuel vapor recovery device, the control valve having the following features:

I. while filling the fuel tank the valve remains closed so as to facilitate spontaneous shut-off of the fuel pump upon pressure within the fuel tank;

II. venting the fuel tank under the regular course of operation, so as to prevent excessive pressure rise within the fuel tank;

III. venting the fuel tank upon pressure drop within the fuel tank; IV. when a pressure within piping extending between the control valve and the fuel vapor recovery device, is smaller than the atmospheric pressure, the control valve prevents fuel vapor flow from the tank, so as to prevent pressure drop within the tank. According to the present invention there is provided a fuel vapor pressure control valve comprising a housing fitted with a first port connectable to a fuel tank and a second port connectable to a fuel vapor recovery device, a valve assembly for admitting vapor flow in a first direction from said first port to said second port when pressure within the tank rises to a first threshold, or for admitting vapor flow in a second, opposite direction when pressure within the tank drops bellow the pressure at the fuel vapor recovery device.

According to the design of the control valve the housing is partitioned by a diaphragm into a first chamber associated with the first port, and a second chamber associated with the second port; said diaphragm comprising an aperture establishing a fuel vapor flow path between said chambers. The valve assembly within the first chamber comprises a first flow path in the first direction, said first flow path remains sealed by the diaphragm as long as the pressure within the fuel tank remains below the first pressure threshold; and a second flow path in the second direction, forming a unidirectional valve admitting flow only in said second direction when the pressure within the tank drops bellow the pressure within the fuel vapor recovery device.

The valve of the present invention has several modifications whereby forming one or more apertures in components of the housing gives rise to one or more respective flow paths which influence the behavior of the control valve to obtain different control effects.

BRIEF DESCRIPTION OF THE DRAWINGS

For better understanding the invention and to see how it may be carried out in practice, one embodiment will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: Fig. 1 is a schematic illustration of a vehicle fuel system fitted with a fuel vapor recovery device and a control valve in accordance with the present invention;

Fig. 2 A is an exploded view of the control valve of the present invention;

Fig. 2B is an elongated view of the diaphragm; Fig. 3 is a longitudinal cross-sectional view of the valve in rest;

Fig. 4 is a longitudinal cross-sectional view of the valve in a tank-venting state;

Fig. 5 is a longitudinal cross-sectional view of the valve in an airing state, admitting vapor flow into the fuel tank; and Fig. 6 is a longitudinal cross-sectional view of the valve illustrating airing of the vapor fuel treating device.

DETAILED DESCRIPTION OF A SPECIFIC EMBODIMENT

Fig. 1 schematically illustrates a vehicle's fuel system generally designated 10 comprising a fuel tank 12 fitted with an inlet pipe 14 and a fuel vapor recovery device 16, typically a carbon canister. Fitted intermediate tank 12 and fuel vapor recovery device 16 there is a fuel vapor pressure control valve 20 in accordance with the present invention, shown in an exploded view of Fig. 2.

The control valve 20 comprises a housing 22 formed with a first housing member 24 fitted with a first port 26 connectable via tube portion 28 to tank 12 (Fig. 1). A second housing member 30 is fitted with a second port 36, connectable via cubing 38 to recovery device 16 (Fig. 1).

With further reference being made now also to Fig. 3, the assembly of the valve 20 will now be illustrated. A diaphragm 40 is formed with a peripheral rib 42, clampingly fitted between mating flanged portions 44 and 46 of the first and second housing members 24 and 30, respectively. Housing member 24 defines a first chamber 50, and a second chamber 52 is defined within the second housing member 30 by a cylindrical wall 54 extending therewimin, and a control chamber 55 has an annular shape extending between wall 54 and the external wall of the second housing 30. Diaphragm 40 is formed with an annular groove portion 58 serving as a receptacle for a biasing spring 60 bearing at one end against wall portion 62 of the second housing member 30, and at an opposite end thereof received within the receptacle groove 58. Diaphragm 40 is further formed with an annular rib 66 which is clampingly received within a corresponding groove 70 of a support member 72. The arrangement is such that diaphragm 40 is fixedly clamped between the end of the cylindrical wall 54 and the receptacle groove 70 of support member 72.

Diaphragm 40 is formed with a central aperture 76, which as can best be seen in Fig. 2A is formed with a plurality of radially extending slits 78 forming a weakened zone deformable for increasing flow upon pressure change, as will be explained hereinafter in more detail.

It is appreciated that the effective sectional area of diaphragm 40 at a face thereof corresponding with the first chamber 50 is greater than a face thereof corresponding with the second chamber 52. Support member 72 is formed with an annular skirt portion 80 engaged at perimetric edge 82 by a corresponding portion of diaphragm 40 displaceable between a sealing and unsealing position as will become apparent hereinafter.

Fitted at an opposed end of support member 72 there is a unidirectional mushroom-type valve 86 formed with a central hub 88 which snapingly engages into opening 90 of support member 72. Peripheral portion 89 at valve 91 sealingly rests over perimetric edge 93 of support member 72.

In Fig. 3 it is also seen that the second housing member 30 comprises an airing aperture 94 being in flow communication with an aperture 96 formed in cylindric wall 54 of the second chamber 52. Fig. 4 illustrates the valve in a position in which the fuel tank (not shown) is pressurized, e.g. during a fueling process.

Pressurized fuel vapor enters the first chamber 50 through first inlet port 26 and encounters diaphragm 40, forcing it to deform against the biasing effect of spring 60, into the position seen in Fig. 4. At this state, a first flow path is established in a direction from the first chamber 50 towards the second chamber 52, as indicated by arrows 97, whereby the pressurized fuel vapor flows between edge 82 of skirt portion 80 and the diaphragm 40, and then through opening 76 which deforms to allow easy flow of vapor into second chamber 52 and then through second port 36 towards the fuel vapor recovery device 16 (not seen).

As the pressure within the fuel tank drops below a predetermined threshold which is governed by the elasticity of biasing spring 60, the diaphragm displaces into its closed, sealing position of Fig. 3 whereby the first flow path shuts and no further vapor flows in direction from the first chamber 50 towards the second chamber 52. Furthermore, it is appreciated that the unidirectional valve 86 remains closed as long as the pressure within the first chamber 50 exceeds the pressure within the second chamber 52.

The position illustrated in Fig. 5 discloses a state in which a vacuum develops in the fuel tank (not shown) e.g. as a result of fuel consumption. In this position unidirectional valve 86 opens whereby the peripheral portion 91 disengages from peripheral edge 93 of support member 72, giving rise to a second flow path marked by arrows 98, whereby vapor flows from the fuel vapor recovery device (not shown) via second port 36, into second chamber 52, and then through aperture 76 of diaphragm 40 into the first chamber 50 and via first port 26 to the fuel tank (not shown). As soon as the pressure between the first and second chamber equalizes, namely when the pressure within the fuel tank reaches equilibrium with the fuel vapor recovery device, the unidirectional valve 86 spontaneously seals. It is appreciated, that the unidirectional valve 86 requires a minimal force to open or close as no biasing means are provided. In the figures of the embodiment disclosed hereinbefore, chamber 55 is vented to the atmosphere via aperture 94 whereby the pressure in the first chamber 50 has to overcome the combined force of spring 60 and the pressure on the annular portion of diaphragm 40 (which is maintained at atmospheric pressure). However, by restricting the size of aperture 94 or by sealing this aperture, the diaphragm 40 encounters a high resistance at chamber 55 in addition to the biasing force of spring 60, whereby the diaphragm 40 will displace into its open position only when the pressure within the first chamber 50 is significantly higher than the pressure in the second chamber 52. In this embodiment, the control device 55 generates pneumatic resistance to displacement of the diaphragm. This arrangement however, has the advantage that the valve is entirely sealed and there is no leak of fuel vapor to the atmosphere.

By still another embodiment (not illustrated in the figures) aperture 94 does not exist whilst aperture 96 extending between the second chamber 52 and chamber 55 is formed. In this position, when the canister generates a vacuum (owing to operation of the motor) the pressure within the second chamber 52 is lower than the pressure within the first chamber 50 and accordingly, the pressure within chamber 55 is essentially similar to that within chamber 52, i.e., lower than the pressure within the first chamber 50. In this situation, the force required for displacing the diaphragm into its open position is significantly lower than in the previous embodiments and this embodiment appears to be useful in particular for low flow rates.

In accordance with another embodiment illustrated in Fig. 6, the second housing 30 is formed with two apertures 94 and 96 wherein aperture 94 is significantly larger than the aperture 96 (say, for example, about 10 times larger). In this embodiment, the diaphragm 40 displaces into its open position when the pressure in the first chamber 50 is larger than atmospheric pressure and can overcome the biasing effect of spring 60. When, however, the pressure within the fuel tank and accordingly in the first chamber 50, drops below atmospheric pressure and simultaneously the pressure at the second chamber 52 is at atmosphere pressure, then air is admitted to flow into the first chamber 50 and into the tank. When now the first chamber 50 and the second chamber 52 are below atmospheric pressure, the diaphragm will close so as to prevent exhausting vapor from the fuel tank which might cause collapse of the tank. In this position the pressure at the chamber 55 (which is essentially at atmospheric pressure) together with the biasing effect of spring 60, acts to displace diaphragm 40 into its closed position. This position is possible only when aperture 96 is significantly smaller than aperture 94. Whilst an embodiment has been shown and described in detail, it is to be understood that it is not intended thereby to limit the disclosure of the invention, but rather it is intended to cover all modifications and arrangements falling within the spirit and the scope of the invention, mutatis mutandis.

Claims

CLAIMS:

1. A fuel vapor pressure control valve comprising a housing fitted with a first port connectable to a fuel tank and a second port connectable to a fuel vapor recovery device, a valve assembly for admitting vapor flow in a first direction from said first port to said second port when pressure within the tank rises to a first threshold, or for admitting vapor flow in a second, opposite direction when pressure within the tank drops bellow the pressure at the fuel vapor recovery device.

2. A fuel vapor pressure control valve according to Claim 1, wherein the housing is partitioned by a diaphragm into a first chamber associated with the first port, and a second chamber associated with the second port; said diaphragm comprising an aperture establishing a fuel vapor flow path between said chambers.

3. A fuel vapor pressure control valve according to Claim 2, wherein the valve assembly within the first chamber comprises a first flow path in the first direction, said first flow path remains sealed by the diaphragm as long as the pressure within the fuel tank remains below the first pressure threshold; and a second flow path in the second direction, forming a unidirectional valve admitting flow only in said second direction when the pressure within the tank drops bellow the pressure within the fuel vapor recovery device.

4. A fuel vapor pressure control valve according to Claim 2, wherein the sectional area of the diaphragm at a face thereof associated with the first chamber is larger then a face thereof associated with the second chamber.

5. A fuel vapor pressure control valve according to Claim 2, wherein the diaphragm is biased to sealingly bear against a perimetric support member at the first chamber.

6. A fuel vapor pressure control valve according to Claim 2, wherein the diaphragm is formed with radial slits extending from the aperture.

7. A fuel vapor pressure control valve according to Claim 2, wherein the second chamber is vented to the atmosphere.

8. A fuel vapor pressure control valve according to Claim 3, wherein the unidirectional valve enables free flow only in the direction.

9. A fuel vapor pressure control valve according to Claim 4, wherein at least a portion of the face of the diaphragm facing the second port is vented to the atmosphere.

10. A fuel vapor pressure control valve according to Claim 5, wherein the support member is cylindrical and where the diaphragm bears against a circular edge thereof.

11. A fuel vapor pressure control valve according to Claim 5, wherein the support member is formed with a coaxial shoulder, whereby the diapliragm is clamped between said shoulder and a corresponding wall extending from the second chamber.

12. A fuel vapor pressure control valve according to Claim 7, wherein the second chamber is in flow communication with vented to the atmosphere via a third, control chamber having an aperture which is significantly larger than the aperture between the second chamber and the control chamber.

13. A fuel vapor pressure control valve according to Claim 2, wherein the housing further comprises a control chamber at a side of the diaphragm corresponding with the second chamber.

14. A fuel vapor pressure control valve according to Claim 13, wherein the control chamber is an annulus surrounding the second chamber.

15. A fuel vapor pressure control valve according to Claim 12, wherein the control chamber is vented to the atmosphere.

16. A fuel vapor pressure control valve according to Claim 12, wherein the control chamber is in flow communication with the second chamber.

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