FR2686048A1 - System for venting a tank with a shut-off and restriction (choke) device with variable flow rate - Google Patents

Abstract

The present invention relates to a system for venting a fuel tank of a motor vehicle. This system, which comprises a box forming a valve (140) which connects the upper part of the tank (14) to the atmosphere (A), and in which a bob weight (141) and a stopper (142) can respectively move between an up position and a down position so as to be able to shut off the connection of the box with the tank (10) and with the atmosphere, at least partially, is characterised in that the bob weight (141) is generally cylindrical and slides longitudinally between a lower chamber and an upper chamber so that the length of a restriction passage decreases in step with the penetration of the bob weight into the upper chamber. This invention applies to fuel tanks of motor vehicles of any type.

Description

 The present invention relates to a ventilation system of a fuel tank for a motor vehicle.

 Various ventilation systems for fuel tanks have been known for a long time, such as fuel tanks for vehicles powered by internal combustion engines. For safety reasons in particular, these ventilation systems include a valve housing, connected by means of an ventilation duct on the one hand to the upper part of the interior of the tank and on the other hand to ambient air or atmosphere. Generally, a counterweight such as a ball for example and a capsule or the like acting as a plug are respectively mounted movable between a high position and a low position in the housing.

 The housing thus constitutes a shutter and throttling device by which the fuel vapors or gases are braked by the counterweight which partially obstructs the connection of the housing with the tank when it is in the low position, and limiting the flow fuel in the event of the tank overturning, since the cap is then in a position where it closes the connection between the housing and the atmosphere.

 However, the aeration systems of the prior art do not make it possible to control the rate of evaporation of the gases coming from the tank, in order to satisfy both the requirements of safety and respect for the environment, and to guarantee a excellent transfer of fuel from the tank to the vehicle engine.

 Also, the invention aims to solve the drawbacks mentioned above, by proposing an aeration system with which not only the fuel leaks in the event of the vehicle overturning are reduced, but also making it possible to limit evaporation as well as possible. fuel and maintain optimal pressure in the tank for the engine's fuel system.

To this end, the subject of the invention is an aeration system for the fuel tank of a motor vehicle, of the type comprising a valve housing, connected using an aeration duct on the one hand at the upper part of the tank and on the other hand at the atmosphere, a counterweight and a plug being respectively mounted movable between an upper position and a lower position in said housing, so that in the lower position the counterweight partially blocks the connection of the housing with the reservoir, and that the plug blocks the connection of the housing with the atmosphere in its high position,
characterized in that the counterweight which is displaceable under the effect of the gases coming from the tank, is generally cylindrical and capable of sliding along its longitudinal axis from a lower chamber where it is housed in the low position towards an upper chamber whose cross section is longer, so that the length of a throttle passage defined by the annular space between the lower chamber and the counterweight decreases as the latter enters said upper chamber.

 According to another characteristic of the invention, the aforementioned gas throttling passage comprises fins, the edges of which constitute baffles capable of creating turbulence in the flow of gases through the valve housing.

 Depending on the case, the aforementioned fins are integral with the internal wall of the lower chamber of the housing, or are integral with the external wall of the sliding counterweight.

 The invention is also characterized in that the fins comprise at least one helical thread.

 Furthermore, the fins include at least two superimposed rings.

 According to the embodiments of the invention, these fins came integrally with the wall of which they are integral, or are constituted by a piece such as a wire wound around the counterweight and interposed between the outer wall thereof and the inner wall of the lower chamber.

 It will be noted here that the reservoir has an integrated expansion chamber, connected to the aforementioned housing by an intake pipe itself connected to the chambers of the housing by a restricted passage when the counterweight is in the low position.

 The ventilation system according to the invention preferably comprises, bypassing the valve, a vacuum valve capable of connecting the atmosphere and the upper part of the tank under the effect of a determined vacuum in the latter.

However, other advantages and characteristics of the invention will emerge more clearly from the detailed description of several embodiments, given solely by way of example which follows and refers to the appended drawings and in which
- Figure 1 is a schematic view of the ventilation system according to the invention
- Figure 2 is a longitudinal sectional view through the shutter and throttling device according to the invention;
- Figure 3 is an enlarged view of a detail designated in III in Figure 2
- Figure 4 is a view along arrow IV of Figure 2
- Figure 5 is a top view of a cap-forming capsule for the closure device of Figure 2
- Figure 6 shows in elevation a sliding weight according to a second embodiment of the invention;
- Figure 7 is a view similar to Figure 6, but showing yet another embodiment of sliding shoe
- Figure 8 illustrates a detail of a fourth embodiment of the invention; and
- Figure 9 is an enlarged view of a detail designated at IX in Figure 1.

 Referring first to Figure 1, we see a tank 10 of a motor vehicle 1 shown schematically by a part of its body where is formed an orifice 11 for filling the reservoir 10. The orifice 11 opens out of the vehicle 1 in the atmosphere or ambient air which is designated here by the reference A.

A filling line 12 which connects the orifice 11 inside the tank 10 makes it possible to pour into the latter any liquid fuel 20 such as petrol or diesel. As illustrated in dotted lines in FIG. 1, the gasoline 20 can be conventionally delivered as indicated by the arrow
F, using a fuel pump valve 30.

 The tank 10 comprises an upper partition 14 which comprises an upper part 14a and a lower part 14b. The pipe 12 opens into the tank 10 substantially below the part 14b, that is to say below a flap 14c called overflow, opposite which opens the lower end of a pipe overflow -full 16. The overflow pipe 16 extends from its end opposite the flap or deflector 14c to a part of the filling pipe 12 which forms an expansion chamber 18 connected to the atmosphere A by l orifice 11 in particular.

 The tank 10 is also equipped with an aeration system 100 as well as an expansion chamber 24. This is constituted by a free space inside the tank 10, which is located between the lower end of the flap 14c and the upper part 14a, that is to say between the maximum level 20a of fuel and the top 14a of the tank 10. This chamber 24 allows the expansion of the fuel contained in the tank, for example when the temperature s' raises, and also facilitates the filling of the latter.

 The ventilation system 100 comprises at least one valve housing 140 connected on the one hand to the expansion chamber 24 (the interior of the upper part of the tank 10) and on the other hand to the atmosphere A, preferably by means of a filter 150 capable of adsorbing the fuel vapors 20.

 More precisely, the housing 140 is mounted on an aeration duct 160 connected to the reservoir 10 and to the ambient air A, so as to form a shutter and throttling device, as explained below.

 To this end, a counterweight 141 and a cap forming cap 142 are respectively mounted movable between an upper position and a lower position, inside the housing 140. Thus, the counterweight 141 can partially close the connection of the housing with the reservoir 10 when it is in the low position, and the capsule 142 can close the connection of the housing with the atmosphere A when it is in the high position.

 According to the invention, the counterweight 141 is vertically displaceable under the effect of the gases coming from the tank 10; for this purpose, it is relatively light, for example made of plastic and containing a metal tare, and it is generally cylindrical (cf. FIG. 2) and capable of sliding along its longitudinal axis XX 'from a lower chamber 144a where it is housed in the low rest position, towards an upper chamber 144b whose cross section is greater, so that the length of a gas throttling passage defined by the annular space between the lower chamber and 144a and the counterweight 141 decreases at as the latter enters said upper chamber 144b.

 According to the embodiment of Figure 2, the valve housing 140 is constituted by two generally cylindrical bodies fixed to one another. The reference numeral 140a designates a lower cylindrical body at one end of which is mounted an upper cylindrical body 140b. The bodies 140a and 140b are preferably obtained by molding an appropriate rigid plastic material. The fixing of the bodies 140a and 140b can be carried out using any conventional means, for example by elastic stapling or the like.

The lower body of the housing 140 generally extends along the axis XX 'and has an internal space which defines the two lower chambers 144a and upper 144b, whose cross section at the axis
XX 'is substantially circular. The end of the body 140a which is opposite to the upper chamber 144b has the form of a generally cylindrical pipe 145a formed integrally with the body 140a proper. This pipe 145a is a pipe for admitting the gases into the housing 140, which comprises at its free end a ring made of material and tapered 146a, projecting from this pipe to allow the fixing on the body 140a of a part of the pipe ventilation 160 connected to the tank 10.

 It can be seen in FIGS. 2 and 8 that this pipe 145a opens out at the center of the lower chamber 144a, the latter opening into the upper chamber 144b. In other words, the two chambers 144a, 144b constitute, with the interior of the intake pipe 145a, the internal space of the lower body 140a of the housing.

 The reference numeral 143a designates in FIGS. 2 and 8 a generally cylindrical jacket, the length of which corresponds substantially to the length "1" of the counterweight 141. This jacket is housed in a bore and constitutes the internal peripheral wall of the chamber 144a, of so as to form a sliding guide bearing for the counterweight 141. Thus, the lower chamber 144a has a cross section smaller than that of the chamber 144b, and greater than that of the interior of the intake pipe 145a. In fact, the internal space of the lower body 140a has a first shoulder 143b and a second shoulder 145b, respectively formed at one end of the lower chamber 144a.

 As shown in Figure 2, the upper body 140b of the valve housing 140 also has an internal space which defines a chamber 144c disposed opposite the chamber 144b of the lower body 140a, when these two bodies are assembled. The chamber 144c is separated from the chamber 144b by a rigid diaphragm 143c. This diaphragm 143c which is fixed at an upper edge of the body 140a, for example by elastic stapling or any other suitable means, is of substantially conical shape with its tapered part directed towards the chamber 144b of the lower body 140a. This diaphragm 143c can be made of plastic or metal and has gas passage orifices 145c formed at its periphery to connect or put the chambers 144b and 144c in permanent communication.

 At its end opposite to the diaphragm 143c, the upper body 140b comprises a so-called exhaust pipe 145b made integrally with this body. The pipe 145b extends along the axis XX ′ and comprises at its free end an integrated conical ring 146b, similar to that which has been described above. The ring 146b allows the fixing of a part of the ventilation duct 160 which connects the housing 140 to the atmosphere A.

 The body 140a of the housing 140 has on its external peripheral wall a protruding medallion 101.

As illustrated in FIG. 4, this medallion 101 came integrally with the lower body 140a and has a raised sign lOîx which indicates the direction of flow of the fuel gases 20 in the bowl 140 during filling of the tank, in order to '' avoid any assembly error of this box on the ventilation system 100.

 Seeing Figure 2, we understand that the conical shape of the diaphragm 143c stabilizes in the rest position a ball 132, which is enclosed in the chamber 144c of the boltier 140 so as to be able to move inside the latter when the bolt bowl 140 is overturned, but has a mass sufficient to remain substantially immobile under the effect of the passage of gases through the orifices 145c of the diaphragm 143c.

A cap-forming capsule 142 is mounted above the ball 132 in the cylindrical chamber 144c of the housing 140, so as to be movable along the axis
XX 'between a low position (in strong lines) and a high or high position as shown in dotted lines in FIG. 2.

 Referring to Figure 5, we see that the plug 142 has the shape, in a plane perpendicular to the longitudinal axis XX ', of an eight-pointed star.

Among these, there are four branches 142a whose free ends are in contact with the internal peripheral wall or bore of the chamber 144c, and four branches 142b alternately and whose length is less than that of the branches 142a. The branches 142a are used to guide the sliding plug 142 in the chamber 144c, between its high and low positions.

 The plug 142 has a central part which interconnects the branches 142a, 142b and which comprises a flat lower face 142c and an upper protrusion 142d. This has a generally hemispherical shape and projects from the ring 142c opposite the open end of the exhaust duct 145b, so as to be able to seal it hermetically when the plug 142 is in its high position shown in dotted lines. in figure 2.

 As explained above, the counterweight 141 is generally cylindrical and is slidably mounted in the lower body 140a, so that in the low or rest position, it is entirely inside the chamber 144a, with its lower end. in abutment against the intake pipe 145a to close it at least partially.

 More specifically, the counterweight 141 is mounted with a certain lateral clearance in the jacket 143a, so that an annular space E is defined between the jacket 143a and the counterweight 141. This space E acts as a throttle passage for the gases. passing through the housing 140. Here, it will be noted that the lower end 141a of the counterweight 141 is hemispherical so that the contact between the latter and the pipe 145a is well centered and sealed. However, so that the intake duct 145a is never hermetically sealed by the counterweight 141, a bevelled radial groove 135 is formed in the lower body 140a, between the duct 145a and the shoulder 145b against which the counterweight rests, as this is illustrated in detail in FIG. 3. The radial groove 135 is formed with a depth chosen as a function of a minimum desired flow rate through the housing 140. As a variant, the body 140a does not have a groove 35 and the pipe 145a , is closed by the counterweight 141 in the low position; a valve 170, described below, then allows air to enter the tank when its expansion chamber 24 is under vacuum.

 Note in FIGS. 2,6,7 and 8 that the walls of the throttle passage E are not smooth, but have fins, the edges of which constitute baffles capable of creating turbulence in the flow of gases through the valve housing 140.

 Obviously, the fins for braking the flow can be either integral with the counterweight 141, or integral with the internal wall of the lower chamber 144a. In the latter case, the fins can come in one piece with the jacket 143a, in the form of propellers, superimposed rings or the like.

 However, in all of the embodiments described, the fins forming baffles are integral with the counterweight 141. According to the embodiment illustrated in FIG. 2, the fins of the counterweight 141 are in the form of a helix or helical thread. More precisely, a first propeller 141b extends over substantially two thirds of the length of the counterweight 141 and a second propeller 141c with reduced pitch is formed over the remaining third of its length. The propellers 141b and 141c came in one piece with the flyweight 141 and have a V-shaped section. By "not reduced" is meant that the edges of the upper helical thread 141c are closer to each other in comparison with those of the thread lower 141b.

This makes it possible to make the sliding of the counterweight 141 between its high and low positions more progressive.

 FIG. 6 represents a counterweight 141 whose fins consist of superimposed rings 141d. These superimposed rings 141d came integrally with the counterweight 141 and are formed over the entire length of the latter, with a pitch "pl" between each edge forming a baffle.

 For its part, FIG. 7 represents a counterweight 141 similar to that of FIG. 6 and comprising an axial channel 147 allowing, like groove 135, a small flow of gas through the valve when the counterweight 141 rests on the orifice of the conduit 145a. It also goes without saying that the counterweight 141 may include both helical fins and superimposed rings, with different pitches.

 FIG. 8 illustrates an embodiment of a counterweight 141 whose fins forming a baffle did not come from one material but consist of at least one insert. Here, the counterweight 141 is cylindrical and a wire 141e is interposed between the counterweight and the housing 140. The wire 141e is wound in a helix between the chamber 143a and the counterweight 141, so as to form a "helical thread" integral with the latter .

 A vacuum valve 170 is mounted on the upper wall of the expansion chamber 18 of the filling pipe 12. This valve 170 visible in FIG. 1 allows when a conventional sealed plug (not shown) closes the orifice 11, d '' admit air into the lines 12 and 16 so that there is optimal pressure in the tank 10 for the fuel supply system (not shown) 20 of the vehicle 1. In other words, the vacuum valve 170 is capable of connect the atmosphere A and the upper part of the tank 10, under the effect of a determined vacuum in the latter.

 The valve 170 represented in FIG. 9 is housed in a neck 18b of the chamber 18 and comprises a fixing jacket 171 of generally cylindrical shape, and a pair of lips 172a, 172b elastically deformable, contiguous at rest and deviating during '' a depression in the tank.

 Such a vacuum valve 170 can also be arranged between the inlet pipe of the valve housing 140 and the settling filter 150 through which the exhaust pipe of the housing 140 is connected to the atmosphere A, so that the housing can be bypassed by the opening of this vacuum valve 170, in order to increase the air supply to the tank 10 and to allow a return into the latter, by gravity and by vacuum, of the fuel adsorbed in the filter 150.

 Referring again to FIG. 2, it is understood that if a positive pressure develops in the tank 10, the gases will tend to escape through the system 100. Such a pressure will gradually raise the counterweight 141 so that the ratio between the length 1 of the lower chamber 144a and the length of the counterweight 141 inside this chamber will tend towards zero. Thus, as the counterweight 141 moves along XX 'from the chamber 144a towards the chamber 144b, the length of the constriction passage E will decrease, thereby progressively reducing the resistance opposed by the housing 140 to the circulation of gas from the reservoir 10, in the direction of the arrows F in FIGS. 1 and 2.

When the counterweight 141 is in the high position, the gases can then pass almost freely through the housing 140.

 As regards the plug 142, its operation is easily understood under the effect of gravity between its low position in strong lines in FIG. 2 where the exhaust pipe is released, and the high shutter position illustrated in dotted lines. .

 Similarly, it is understood that it is under the effect of gravity and when the latter is greater than the lifting pressure of the counterweight 141 that the latter returns from its high position to its low position for partially closing the intake pipe 145a.

 Of course, the invention is in no way limited to the embodiments described above, and includes all the equivalents of the technical means described as well as their combinations, if these are in its spirit.

Claims (10)

 1. Ventilation system for the fuel tank of a motor vehicle (1), of the type comprising a valve housing (140), connected by means of an ventilation duct (160) on the one hand at the upper part of the tank and on the other hand at the atmosphere (A), a counterweight (141) and a plug (142) being respectively mounted movable between a high position and a low position in said case (140), so that in the low position the counterweight (141) at least partially closes the connection of the housing with the reservoir (10), and that the plug (142) closes the connection of the bootmaker with the atmosphere in its high position, characterized in that that the counterweight (141) which is displaceable under the effect of the gases coming from the tank, is generally cylindrical and capable of sliding along its longitudinal axis (X-X ') from a lower chamber (144a) where it is housed in the low position to an upper chamber (144b) whose cross section is greater, so that the length of a gas throttling passage (E) defined by the annular space between the lower chamber (144a) and the counterweight (141) decreases as the latter enters said superior room (144b).  2. Aeration system according to claim 1, characterized in that the gas throttling passage (E) comprises fins (141b, 141c, 141d, 141e) whose edges constitute baffles capable of creating turbulence in the gas flow through the valve housing (140).  3. System according to claim 2, characterized in that the aforementioned fins are integral with the internal wall of the lower chamber (144a) of the housing (140).  4. System according to claim 2, characterized in that the aforementioned fins (141b, 141c, 141d) are integral with the external wall of the sliding counterweight (141).  5. System according to one of claims 2 to 4, characterized in that the fins (141b, 141c, 141e) comprise at least one helical thread.  6. System according to one of claims 2 to 5, characterized in that the fins comprise at least two rings (141d) superimposed.  7. System according to one of claims 3 to 6, characterized in that the fins have come integrally with the wall (141) of which they are integral.  8. System according to one of claims 3 to 6, characterized in that the fins are constituted by a part (141e) such as a wire interposed between the outer wall of the counterweight (141) and the inner wall (143a) of the lower chamber (144a).  9. System according to one of claims 1 to 8, characterized in that the reservoir (10) comprises an integrated expansion chamber (24) connected to the housing (140) by an intake pipe (145a) itself connected to the chambers (144a, 144b) of the housing by a restricted passage (135,147) when the counterweight (141) is in the low position.  10. System according to one of claims 1 to 9, characterized in that it comprises a vacuum valve (170) capable of connecting the atmosphere and the upper part (14) of the tank (10) under the effect of 'a determined vacuum in the latter, and a filter (150) capable of absorbing the fuel vapors emanating from this part (14).