A valve for a circuit for recovering fuel vapours coming from a motor vehicle fuel tank

Abstract

 The valve (10) can be fitted between a fuel vapour container (7) connected to a fuel tank (1) of a motor vehicle and a device (2) for controlling the flow of air supplied to the engine; the valve comprises an electro-magnetically actuated movable shutter member (14) operable to control the passage of fuel vapours between an inlet (15) and an opening (16) and is characterised in that it is provided with coupling surfaces (17a, 17b, 17c) which can be coupled to corresponding surfaces of a seat (18) formed in a body (13) of the said mixture-forming device and which is in communication with the duct (4) of the body itself through which the said mixture flows. The outlet (16) of the valve opens into a region surrounded by the said coupling surfaces (17a, 17b, 17c) in such a way as to be in communication with the said seat (18) of the body.

Description

[0001] The present invention relates to a valve which can be located in a circuit for the recovery of fuel vapour coming from a motor vehicle fuel tank.

[0002] A circuit of this type substantially comprises a duct which puts the fuel tank into communication with a fuel-and-air mixture-forming device; along the said duct there is located a container in which there is normally disposed a material capable of absorbing fuel vapours, normally active carbon, and an electromagnetically actuated valve located in that part of the duct which runs from the said container to the above-mentioned mixture-forming device.

[0003] Vapours which form in the fuel tank, in particular when the vehicle is stationary and at high temperature, are absorbed by the active carbon in the above-mentioned container and, during operation of the engine these are drawn in by the fuel-and-air mixture-forming device; to this end the said valve, which is disposed between the fuel vapour container and the mixture-forming device, is opened by applying to it suitable excitation pulses generated by an electronic central control unit of the device.

[0004] The said valve is normally fixed to the motor vehicle body and is put in communication both with the fuel vapour container and with the mixture-forming device, by suitable lengths of tubing.

[0005] Valves utilised in recovery circuits of the above described type have several disadvantages.

[0006] Above all, they require lengthy operations for fixing the valve itself to the motor vehicle body and to form the connections between the valve and the length of tubing which put it in communication with the fuel vapour container and with the mixture-forming device. Moreover, the reliability of the circuit in which valves of this type are fitted is rather modest because of the risk, in particular after extended use of the motor vehicle, of leakages in the connections between the valve and the lengths of tubing, as well as between these latter and the fuel vapour container and the mixture-forming device.

[0007] Moreover, in order to allow a simple mounting and dismounting of the said valves there is normally required a space which cannot be utilised for housing other components of the fuel supply device and which can be found only with difficulty in many types of vehicles.

[0008] The object of the present invention is that of providing a valve of the type briefly described above, which can be fitted in a circuit for the recovery of fuel vapours coming from the fuel tank of a motor vehicle and the above described disadvantages of which can be eliminated.

[0009] According to the present invention there is provided a valve which can be fitted between a fuel vapour container connected to a motor vehicle fuel tank and a fuel-and-air mixture-forming device intended to supply an internal combustion engine, the said valve comprising an electro-magnetically actuated movable shutter member operable to control the passage of the said vapour between an inlet and an outlet of the valve, and the said mixture-forming device including at least one body in which there is formed a duct though which the mixture passes, characterised in that the said valve is provided with coupling surfaces which can be coupled to corresponding surfaces of a seat formed on the said body of the said mixture-forming device and which is in communication with the said duct through which the said fuel-and-air mixture passes, the said outlet of the said valve opening into a region surrounded by the said coupling surfaces in such a way as to be in communication with the said seat of the said body.

[0010] For a better understanding of the structure and the mode of operation of the valve of the invention, a particular embodiment of the valve itself will be described with reference to the attached drawings in which:

Figure 1 is a schematic view of a circuit for the recovery of fuel vapour coming from a fuel tank of a motor vehicle, in which the valve of the invention is fitted;

Figure 2 is a partially sectioned side view of a part of the circuit of figure 1 in which a fuel-and-air mixture-forming device is shown and the valve of the invention is shown mounted on the device itself; and

Figure 3 is an axial section of the valve of the invention.

[0011] The fuel vapour recovery circuit in which the valve of the invention is fitted, as shown in figure 1, is adapted to connect a fuel tank 1 of a motor vehicle with a device 2 for controlling the flow of air supplied to the motor. The device can include, as has been shown in figure 1, a body 3 provided with an axial duct 4 the opening of which is controlled by a butterfly valve 5. Along the said duct can conveniently be located an electro-magnetically actuated fuel metering and atomization valve (not shown), which is adapted to inject a pre-determined quantity of fuel into the duct 4 in order to form, with the air which flows through the duct itself, a mixture of fuel-and-air which is supplied, for example, to a mixture manifold 6.

[0012] The circuit for the recovery of fuel vapours coming from the fuel tank 1 further includes a fuel vapour container 7 which is connected to the tank 1 via a length of tubing 8; the valve of the invention, generally indicated 10, forms part of this circuit and is interposed, in a manner which will be explained, between another length of tubing 9 which extends from the container 7 and the body 3 of the mixture-forming device 2.

[0013] Within the fuel vapour container 7 is disposed any suitable material 12 capable of absorbing the vapours themselves, for example active carbon; furthermore, the internal cavity within the container itself is also in communication with the atmosphere through a connector 13.

[0014] As can be seen from figure 3, the valve of the invention substantially comprises a movable shutter member, generally indicated 14, actuated electro-magnetically and operable to control the passage of fuel vapours between an inlet 15 and an outlet 16. The valve 10 is provided with coupling surfaces 17a, 17b, 17c which can be coupled to corresponding surfaces of a seat 18 (figure 2) which is formed on the body 3 of the fuel-and-air mixture-forming device 2; the seat 18 is in turn in communication with the end of the duct 4 of the device 1 via a suitable duct 19 formed, in part, within the body 3 and, in part, within the mixture manifold 6 or another part of the engine. Furthermore, on the basis of the invention, the outlet 16 (figure 2) of the valve 10 opens into a zone which is located within the coupling surfaces 17a, 17b, 17c in such a way as to be in communication with the duct 19 formed in the interior of the body 3. As is clearly seen in Figures 2 and 3, the coupling surfaces can include a first substantially cylindrical surface portion 17a, a second flat annular surface portion 17b, and finally, a third cylindrical surface portion 17c within which the outlet 16 is located.

[0015] According to the invention the valve substantially comprises an axial duct 24 (Figure 3), which extends longitudinally through the valve and the ends of which define the inlet 15 and the outlet 16 mentioned above; along the said duct there is disposed a disc 25 which constitutes the shutter member 14 of the valve and which is normally held against an annular seat 26 by the action of a coil spring 27 housed in the duct itself.

[0016] The shutter member 14 is fixed to a movable armature 28 which can be attracted by a core 29 of an electromagnet 30 having an annular form which is disposed around the above-mentioned axial duct 24.

[0017] As is seen from figure 3, the valve substantially comprises a body 33 of substantially cylindrical form which is provided with an axial bone 34 within which is housed the core 29 and within which a metal bush 36, also of tubular form, is movable to constitute the above defined armature 28. The bush 36 is connected to the disc 25 and for this purpose this latter is fixed to a support element 37 which is provided with a plurality of ribs 38 which are force fitted within the bush itself; furthermore this latter is provided with an internal annular projection 39 forming a shoulder for one end of the spring 27, whilst an elastically deformable ring 40 is housed within the tubular metal element 35 and constitutes a shoulder for the other end of the spring.

[0018] The body 33 of the valve further has a first sleeve 43 in communication with the axial bone 34 of the body and defining the inlet 15 of the valve, as well as a second sleeve 44, which can be fitted in the seat 18 (Figure 2) of the body 3 of the fuel-and-air mixture-forming device 1; finally, the body 33 has an annular groove 45 which is adapted to house the electromagnet 30.

[0019] As is clearly seen in Figure 3 the axial bone 34 in body 33 is conical and convergent towards the sleeve 43; within the bone 34 is formed a first series of axial ribs 46 which constitute contacts for the tubular metal element 35, and a second series of axial ribs 47 which constitute guides for the bush 36. The outer diameter of the tubular metal element 35 is greater than the outer diameter of the bush 33 because of the conical shape of the axial bone 34.

[0020] Conveniently the body 33 of the valve is made of plastics material, whilst the casing 23 is made of sheet metal; this latter substantially encloses all the parts of the valve and, in particular, also the end sleeve 44.

[0021] The valve is provided with an electrical connection element 48 connected to the electromagnet 30 and housed within a projection 49 forming part of the body 33 of the valve.

[0022] In use the valve described functions in the following way.

[0023] The valve is mounted on the body 3 of the fuel-and-air mixture-forming device by introducing the end of the valve into the interior of the seat 18 formed on the body. During this operation the coupling surfaces 17a, 17b, 17c come into contact with the corresponding surfaces of the seat; in particular the diameter of the surface 17a can be slightly greater than the corresponding surface of the seat in such a way that the mounting of the valve takes place with a certain interference and, therefore, once mounting has taken place, pressures of predetermined value are exchanged between the surface 17a and the corresponding surface of the seat. Moreover, conveniently, there is disposed a sealing ring 15 (Figure 2) on the coupling surface 17c housed in a corresponding seat in the body. Finally, the casing 23 of the valve can conveniently be provided with an annular projection 51 able to contact against a corresponding abutment surface of the body 3 as is seen in Figure 2.

[0024] The sleeve 43 is connected by means of a length of tubing 9 to the container 7 in the manner shown in figure 1.

[0025] When fuel vapours form within the tank 1, in particular when the vehicle is stationary in the sun, these are absorbed by the active carbon contained in the tank itself. During operation of the engine, a certain depression exists in the section of the duct 4 of the device 1 located downstream of the butterfly valve 5 and therefore, when the electromagnet 33 is activated, by means of a suitable control signal, the core 29 is able to control the displacement of the armature 28 towards the core itself overcoming the resilient reaction of the spring 27; consequently the disc 25 of the shutter member 14 is moved away from the seat 26 and therefore fuel vapours which are contained within the container 7 are drawn in and added to the mixture which passes through the duct 4 of the mixture-forming device 2.

[0026] It is therefore evident that by utilising the valve of the invention in a circuit for the recovery of fuel vapours numerous advantages are achieved.

[0027] Above all the mounting of the valve in the circuit is extremely easy since it is sufficient to fit it in the manner just described onto the body 3 of the mixture-forming device 2 and connect the length of tubing 9 to the sleeve 43 of the valve. This therefore becomes an integral part of the device itself and therefore does not have to be fixed to the motor vehicle body by complex and difficult operations. Moreover, the dimensions of the circuit can be very modest since the valve is closely connected to the mixture-forming device and does not require lengths of tubing for connecting the valve to the device as occurred in prior art circuits. Finally, a circuit such as that shown in Figure 1 which utilises the valve of the invention is very reliable (only tube sections 8 and 9), both because there are short sections of duct for connecting the components of the circuit together and because the valve itself has a very simple structure and secure operation. In fact the flow path for the aspirated vapours through the valve is perfectly rectilinear and coincides with the axis of the valve.

[0028] The second series of ribs 47 form an effective guide for the movement of the armature 18 and perfect centring of this with respect to the associated core 29.

[0029] Moreover, since the outer diameter of this latter is greater than the corresponding diameter of the armature, the magnetic flux linkage between the armature and core is not substantially affected by small eccentricities between the armature and the core due to assembly errors.

[0030] Finally, the closure force of the shutter member 14 exerted by the spring 27 can easily be varied by axially displacing the ring 40.

[0031] The embodiment of the present invention described can have modifications and variations introduced thereto without departing from the invention itself.

Claims

1. A valve adapted to be fitted between a fuel vapour container (7) connected to a motor vehicle fuel tank (1) and a fuel-and-air mixture-forming device (2) intended to supply an internal combustion engine, the said valve including an electro-magnetically actuated movable shutter member (14) operable to control the passage of the said vapours between an inlet (15) and an outlet (16) of the valve and the said mixture-forming device including at least one body (3) in which is formed a duct (4) through which the mixture passes, characterised in that the said valve (10) is provided with coupling surfaces (17a, 17b, 17c) which can be coupled with corresponding surfaces of the seat (18) formed on the said body (3) of the said mixture-forming device which is in communication with the said duct (4) through which the said fuel-and-air mixture passes, the said outlet (16) of the said valve opening into a region surrounded by the said coupling surfaces (17a, 17b, 17c), in such a way as to be in communication with the said seat (18) of the said body (3).

2. A valve according to claim 1, characterised in that the said coupling surfaces (17a, 17b, 17c) are formed on a cylindrical end of a casing (23), which externally delimits the said valve, the said outlet (16) opening substantially into the central part of the said end.

3. A valve according to any preceding claim, characterised in that it includes an axial duct (24) which passes through the valve and the ends of which define the said inlet (15) and the said outlet (16), a disc (15) being disposed in the said axial duct to form the said shutter member (14) of the valve, which is normally held against an annular seat (26) formed in the said axial duct (24) by the action of a spring (27) housed in the duct itself, the said shutter member (14) being fixed to a movable armature (28) which can be attracted by a core (29) of an annular electromagnet (30) disposed around the said axial duct (24).

4. A valve according to claim 3, characterised in that the said valve (10) comprises a body (33) of substantially cylindrical form provided with an axial bone (34) within which is housed a tubular metal element (35) forming the said core (29) and within which a metal bush (36), also of tubular form, is movable, to form the said armature (28) connected to the said disc (25), the said valve body (33) having a first sleeve (43) in communication with the said axial hole (34) of the said body defining the said inlet (15) of the valve and a second sleeve (44) which can be fitted into the said seat (18) of the said body (3) of the fuel-and-air mixture-forming device, and the said valve body (33) further having an annular groove (45) to house the said electromagnet (30).

5. A valve according to Claim 4, characterised in that the said disc (25) is fixed to a ribbed support (37) which can be fitted within the said bush (36), the said bush having an axial internal shoulder (39) to constitute a stop for one end of the said spring (27), a radially deformable ring (40) being fitted within the said tubular metal element (35) to form a shoulder for the other end of the said spring (27).

6. A valve according to any preceding claim, characterised in that the said axial bone (34) in the said body is conical and convergent towards the said first sleeve (43) and within the said conical bone there is formed a first series of axial ribs (46) constituting contacts for the said tubular metal element (35), and a second series of axial ribs (47) constituting guides for the said bush (36).

7. A valve according to claim 6, characterised in that the outer diameter of the said tubular metal element (35) is greater than the outer diameter of the said bush (36).

8. A valve according to any preceding claim characterised in that the said body (33) of the valve is made of plastics material and the said casing (23) is made of sheet metal and substantially encloses the parts of the valve.

Drawing