FR2747758A1 - VALVE FOR TANK AND RESERVOIR THUS EQUIPPED - Google Patents

Abstract

The invention relates to a valve for a fuel tank, comprising a shutter sensitive to gravity, movable in a valve body between a rest position allowing gas flow from the inside of the tank to an external duct, through a valve body. 'an orifice of the valve body, and a closed position in which the shutter closes said orifice. Said orifice (12) has an axial dimension which is sufficiently small to prevent a gas flow passing through said orifice from generating a fluid stream of high speed. Said orifice (12) also opens into a back-pressure chamber (13) whose section offered to the passage of the gas flow is chosen sufficiently large so that the depression downstream of said orifice, due to the speed of the flow gas in the back pressure chamber, remains negligible.

Description

The present invention relates to a valve for a fuel tank.

  having a gravity-responsive shutter movable in a valve body between a rest position allowing a gas flow from the interior of the tank to an outer conduit, through an orifice of the valve body, and a position of sealing

  wherein the shutter closes said orifice.

  Such a valve is used on motor vehicles to firstly communicate the interior of the tank with the outer conduit when the tank is in a normal position of use and allow the degassing of the latter and secondly close the access to the external duct when the tank is tilted beyond a predetermined limit of its normal position of use, in the event of accidental overturning of the vehicle by

example.

  It has been found that the shutter of a known valve of this type has a tendency, for a flow of gas of high flow and under a certain pressure, to be sucked by the orifice of the valve body until it comes into position. shutter although the tank is in

a normal position of use.

  This malfunction hinders the evacuation of fuel vapors and may result in excessive overpressure

in the tank.

  In order to remedy this drawback, it has been proposed to move the shutter away from the orifice of the valve body so as to make it more

difficult his aspiration.

  However, the inclination from which the shutter closes the orifice of the valve body increases with the distance separating the shutter in its rest position and said orifice, and this solution is not satisfactory when one wish that the valve responds to low inclinations of the reservoir relative to its

normal position of use.

  It has further been proposed to make the pressure drop experienced by the gas flow sufficiently high so that the flow rate of the latter remains low under all circumstances and does not generate. when passing through the orifice of the valve body, a depression capable of sucking the shutter or keeping it in a closed position following a

  momentary uplift by a wave of fuel.

  2- However, this solution is incompatible with certain specifications established by car manufacturers, which require the evacuation of fuel vapors with a minimum flow rate for a given overpressure, for example a flow rate greater than 1300 1 / h when the overpressure in the tank is 30 mbars and that the vehicle

moves.

  The object of the invention is to remedy the aforementioned drawbacks. It achieves this by the fact that the orifice of the valve body has an axial dimension sufficiently small to prevent a gas flow passing through said orifice generates a high velocity fluid vein and by the fact that said orifice opens into a chamber of counterpressure, the section of which is provided for the passage of the gas flow is chosen to be large enough for the depression downstream of said orifice, due to the flow velocity

  gaseous in the backpressure chamber, remains negligible.

  In a preferred embodiment of the invention, the orifice is circular and has a constant diameter. But in other examples of embodiments, the geometry of the orifice may be different, the latter may be in the form of a rectangular slot in particular, and it must be understood that the axial dimension of the orifice is sufficiently small within the meaning of the invention when it is at most equal to one and a half times the smallest

  transverse dimension of the orifice.

  Thanks to the invention, the passage through the gaseous flow of the orifice of the valve body does not generate a high velocity fluid vein, unlike what would happen if the orifice was axially extended by a reentrant nozzle. or outgoing length

  large compared to the smallest transverse dimension of the orifice.

  In a particular embodiment, the orifice of the valve body has a circular section whose diameter is between 3 and 5 mm, and it is constituted by a bore formed through a partition separating the interior of the valve body and said chamber counterpressure. Preferably, the thickness of this partition is included

between 2 and 4 mm.

  The counterpressure chamber extends axially over a height preferably greater than five times the axial dimension of the orifice. In a particular embodiment of the invention, the counterpressure chamber is delimited laterally by a cylindrical wall of revolution, whose internal diameter is advantageously greater

or equal to 15 mm.

  Advantageously, the shutter has a conical end

  shaped to engage at its top in the orifice of the valve body.

  The conical end of the shutter allows the gas flow to gain relatively easily said orifice and avoid the occurrence of turbulence that could affect the

valve operation.

  The subject of the invention is also a fuel tank of

  motor vehicle equipped with a valve as aforesaid.

  Other features and benefits of this

  invention will emerge from a reading of the detailed description which will

  follow, an exemplary non-limiting embodiment of the invention, and in view of the accompanying drawing in which Figure 1 is a schematic view. in

  axial section, a valve according to the invention.

  This valve 1 shown in Figure 1 is intended to be mounted in an orifice 2 through the upper wall 3 of a reservoir

  of motor vehicle fuel.

  The valve 1 comprises an elongated lower body 4 which is generally cylindrical of revolution about a longitudinal axis X, in which a shutter 5 can be displaced in translation along the axis X. The lower body 4 is closed at its lower end by a wall transverse 6 provided on its internal face. of a 7 serving barrel

  guide at the lower end of a spring 8.

  This spring 8 bears on the inner face of the wall 6 and engages at its upper end in an annular groove 9

  arranged in the lower part of the shutter 5.

  The lower body 4 is closed at its upper end by a transverse partition 11 extending radially outwardly beyond the cylindrical wall of the lower body 4 to form a flange 10 for fixing the valve 1 on the outer face

of the wall 3 of the tank.

  In the example described, the collar 10 and the wall 3 are made of polyethylene and the fixing of the valve on the reservoir

can be done by welding.

  The partition 11 has at its center a thickness e and P is traversed by a circular orifice 12 of diameter D P communicating the interior of the body 4 with a chamber of

back pressure 13.

  This counter-pressure chamber 13 is delimited radially by a tubular wall 14, cylindrical in revolution about the X axis, of diameter D and height H, connecting cc below on the partition 11 and closed topally by a transverse wall 15 A tubular endpiece 16 with a longitudinal axis perpendicular to the X axis is laterally connected to the tubular wall 14 in the upper part of the backpressure chamber 13 and tangentially to the wall 15. for mounting a conduit

  outside 17 of venting the tank.

  The lower body 4 is crossed laterally. in the lower part, by slots 18 making it possible to communicate constantly

  inside the tank with the inside of the lower body of the valve.

  The shutter 5 has a conical upper end 19,

converging upwards.

  When the reservoir is in a normal position of use, the X axis is oriented substantially vertically and the shutter 5 compresses by its weight the spring 8. The orifice 12 is released and establishes a communication between the inside of the body

  lower part 4 of the valve and the outer conduit 17.

  In case of overpressure in the tank, typically an overpressure of the order of 30 to 50 mbar, and when the tank is in a normal position of use. a flow is established

gaseous degassing.

  E is indicated by such a gas flow, passing through the slots 18 and then the annular space formed between the internal face of the cylindrical wall of the lower body 4 and the lateral external surface 20, cylindrical of revolution, of the shutter 5, along the conical surface 19 towards the orifice 12, passing through the latter, then gaining the back pressure chamber 13 and the outer conduit 17 which communicates through a filter designed to trap

  the fuel vapors with the atmosphere.

  - The section offered to the passage of the gas flow through the back-pressure chamber 13 is chosen to maintain the dynamic pressure in it negligible. Specifically, we seek to have: 1/2 V2 p << P o denotes the density of the fuel vapor, of the order of 1 kg / m3, V designates the speed of the gas flow in the chamber of

  back pressure 13, and P is the pressure in the tank.

  The dimensions D, e of the orifice 12 are chosen

P P

  to avoid the formation at its crossing of a fluid vein oriented almost exclusively parallel to the X axis, as it would be the case

a nozzle coming in or out.

  The gas flow therefore does not acquire a high speed along the X axis and no depression is formed upstream of the orifice 12 which is strong enough to suck the shutter 5. The

  mass is typically a few grams.

  As an indication, in the particular example described, the diameter D of the orifice 12 is 5 mm, the thickness e of the partition 11 is 2 mm in its region bordering the orifice 12, the internal diameter of the body 4 is 23 mm, the inner diameter of the tip 16 is mm. the internal diameter D of the back-pressure chamber is C

  mm and its height H is substantially equal to its diameter.

  For a gas flow whose flow is equal to 1300 1 / h.

  corresponding to an overpressure of 30 mbar inside the tank, we have 1/2 p V close to 2 N / m, or about 10'2 mbar, which is negligible compared to the pressure in the reservoir. The particular valve 1 is provided not to close the orifice 12 for a flow rate up to 1500 l / h, corresponding to an overpressure of 50 mbar in the tank. even if the vehicle is moving and therefore subject to vibrations or waves of fuel

  capable of displacing the shutter 5 slightly along the X axis.

  When the fuel tank is tilted beyond a predetermined value of its normal position of use, ie when the X axis is at a certain angle to the vertical, the weight component of the shutter on the X axis decreases and the spring 8 tends to move the shutter 5 closer to the orifice 12. For a certain value of the inclination, the shutter 5 thus comes into contact

  of the partition 11 to close the orifice 11.

  This is particularly the case in case of accidental rollover of the vehicle, the shutter 5 thus making it possible to isolate the outer conduit 17 from the inside of the tank and to prevent fuel

  liquid gains the latter then the outside of the vehicle.

  Of course, the invention is not limited to the example of

  realization which has just been described.

  In particular, without departing from the scope of the invention, it is possible to modify the geometry of the orifice 12 or of the counterpressure chamber 13 and adopt a non-circular cross section.

for example.

-7-

Claims (8)

RVENDICATIONS   A fuel tank valve having a gravity-responsive shutter movable in a valve body between a rest position allowing a gas flow from the interior of the reservoir to an outer conduit through a body orifice valve, and a closed position in which the shutter closes said orifice, characterized in that said orifice (12) has an axial dimension sufficiently small to prevent a gas flow passing through said orifice generates a fluid stream of high speed, and in that said orifice (12) opens into a counterpressure chamber (13) whose section offered to the passage of the gas flow is chosen to be sufficiently large so that the depression downstream of said orifice, due to the velocity of the gas flow in the backpressure chamber remains negligible.   2. Valve according to claim 1, characterized in that said orifice is circular and in that the shutter has a conical end (19) adapted to engage in said orifice   (12) in the closed position of the latter.   3. Device according to one of claims 1 and 2,   characterized in that the counterpressure chamber (13) is delimited radially by a tubular wall (14) whose diameter   internal is greater than or equal to 15 mm.   4. Device according to one of claims 1 to 3,   characterized in that said orifice (12) is circular of   diameter (D) between 3 and 5 mm.   5. Device according to any one of claims 1 to   4. characterized in that said counterpressure chamber extends over a height (H) at least equal to five times the axial dimension of said orifice.   6. Device according to any one of the claims   preceding, characterized in that said orifice (12) is constituted by a bore passing through a partition (11) formed in part upper body valve.   7. Device according to claim 6, characterized in that the thickness (e) of said partition (11) in the region   bordering said orifice (12) is between 2 and 4 mm.   bordering said orifice (12) is between 2 and 4 mm.   - 8 - 8. Fuel tank of a motor vehicle, characterized in that it is equipped with a valve as defined in one of the   any of the preceding claims.