EP0344063A1 - Degassing device for the fuel feeding of an internal combustion engine - Google Patents

Abstract

The invention relates to a fuel degassing device which comprises a settling tank (11) and a cover body (12) fastened sealingly to the settling tank, the said cover body being equipped with a fuel inlet connection (20), with a return connection (24) to the gas and vapour reservoir and with an outlet connection (22) which discharges the degassed liquid fuel towards the carburettor and in which is mounted a valve (64) loaded by a calibrated spring. The inlet connection (20) has a portion of narrowed diameter (36) in which the fuel experiences an acceleration and which is extended by a portion (38) causing the fuel to enter the settling tank (11) tangentially to the wall of the latter. Mounted in the return connection is a nozzle (62), towards which some of the incident flow of fuel is diverted by a channel (60), in order to generate a vacuum at the entrance of the return connection. <IMAGE>

Description

In internal combustion engines, the supply fuel must reach the carburetor free of any vapor or gas and at a temperature compatible with the fuel metering organ with the intake air.

This requirement is becoming problematic these days, mainly due to the fact that today's gasolines are more volatile, and also due to the very high temperatures reached under the engine hood, especially after short stops.

By French patent application No. 87 10 385, a fuel degassing device is already known which comprises a decantation tank and a cover body tightly fixed on the decantation tank, said cover body being provided with a fuel inlet pipe, a gas and vapor return pipe to the tank, located in an upper part of the cover and an outlet pipe for the evacuation of the degassed liquid fuel towards the carburetor, and in which is mounted a valve loaded by a calibrated spring, which keeps the valve applied against a first seat as long as the settling tank contains gas, this then escaping towards the return pipe to the tank through low-loss passages load which by-pass the valve, while, when the settling tank is completely filled with liquid fuel, the valve is biased against the force of the spring, towards a closed position on a second seat o where it closes the return line to the tank.

A first separation between the liquid phase and the gas phase of the fuel takes place under the effect of the impact of the incident flow of fuel on a deflector, then the fuel gets rid of another part of the gases which it contains by passing through a cylindrical filter cartridge.

However, experience has shown that degassing with such a device is still insufficient because gases are recreated when the fuel passes through the filter cartridge. In addition, the latter introduces an important pressure drop, which requires using a more powerful feed pump.

On the other hand, from patent DE-A-1 235 067 a fuel supply system for an internal combustion machine is known, which comprises a gas separator, a recycling duct connected to the pressure outlet of a circulation pump and a Venturi tube arranged in the recycling duct to create a positive pressure drop between the interior space of the gas separator and the recycling duct, so that the gas coming from said space is sucked by the Venturi.

However, such a system is of a relatively complicated construction since the separator comprises at least four connections with the neighboring elements.

In addition, the separator according to said patent is connected between the tank and the pump, its main function being to send gas-free fuel to the pump. But as we know, this can cause the formation of gases or emulsions at the outlet.

On the other hand, GB-A-2 157 803 discloses a gas separator which comprises a valve constituted by a ball which, when in the high position, completely closes the orifice of the return pipe to the tank.

The present invention provides a degassing device according to the preamble of claim 1, and which is much simpler, more effective and economical than the devices of the technique described above. This device is characterized by the following points:
- the inlet manifold has in said cover a portion of narrowed diameter in which the fuel undergoes an acceleration, and which is extended by a portion which makes the fuel penetrate into the settling tank tangentially to the wall thereof,
- downstream of the valve and in the return pipe to the tank is mounted a nozzle to which part of the incident fuel flow is derived by a channel connected to the inlet tubing, said nozzle creating a vacuum at the inlet of the return tubing.

The settling tank according to the invention is much simpler and economical than the separator according to patent DE-A-1 235 067 since it only has three connections instead of four. Another important difference is that the settling tank is mounted between the pump and the engine and therefore sends liquid fuel to the latter free of air bubbles and gases.

According to another advantageous characteristic of the invention, the settling tank is divided into two superposed stages, by a separating element in the form of an overturned funnel, the conical part of which defines with the internal wall of the tank a small interval for the 'flow of fuel from the inlet manifold, and the tubular part of which adapts to the upper part of the cover body, orifices being provided at the end of the tubular part to allow the evacuation of the gases s' accumulating in the upper stage towards the return pipe to the tank.

Said separating element is closed at its narrowed end by a wall pierced with a calibrated hole for the evacuation of gases accumulating in the lower stage.

At the lower part of the settling tank is mounted a filter with suitable mesh intended to separate the last gas bubbles from the fuel, the degassed fuel being under the filter being sucked towards the outlet pipe by a cannula whose lower end crosses the filter tightly and dives into the fuel.

Advantageously, the valve is pierced with a calibrated orifice allowing a low rate of fuel leakage towards the return pipe when the valve is in the closed position.

The device according to the invention therefore performs degassing in three stages:
- a first separation due to the acceleration of the die bit of fuel, then when it relaxes in the settling tank, where it is projected tangentially to the wall. The fuel undergoes a thermal shock by cicuring on said wall, which promotes the separation of gases;
- the suction of gases by the vacuum created by the nozzle;
- the residual gases and vapors are channeled through the funnel towards the return pipe to the tank.

• La figure 1 est une vue en coupe axiale d'un disposi­tif de dégazage;
• La figure 2 est une vue en plan par le haut du dispo­sitif, et partiellement en coupe;
• La figure 3 est une vue à plus grande échelle du cla­pet monté dans la tubulure de retour au réservoir;
• La figure 4 représente un clapet anti-retour monté dans la tubulure de sortie; et
• La figure 5 est une vue en coupe du clapet selon la ligne V-V de la figure 4.

The invention will be better understood on reading the following description of a preferred embodiment, with reference to the appended drawings in which:

• Figure 1 is an axial sectional view of a degassing device;
• Figure 2 is a plan view from above of the device, and partially in section;
• Figure 3 is an enlarged view of the valve mounted in the return pipe to the tank;
• FIG. 4 represents a non-return valve mounted in the outlet pipe; and
• FIG. 5 is a sectional view of the valve along the line VV in FIG. 4.

With reference to Figures 1 and 2, the degassing device 10 comprises a settling tank 11 and a cover body 12, made of a light metal or a synthetic material capable of withstanding the temperatures prevailing under the engine hood.

The tank and the cover body can be assembled in various ways. For example, if the tank is made of metal, assembly can be carried out, as shown in FIG. 1, by crimping its upper edge 14 on a flange 16 formed on the periphery of the edge of the cover body, an O-ring 18 sealing. If the tank and the cover are made of synthetic material, they can be welded edge to edge, for example by the rotary process.

With the cover body there comes molding an inlet pipe 20 through which the fuel which is discharged by the fuel pump enters the device. degassing, an outlet pipe 22 for the delivery of the degassed fuel to the carburetor and a pipe 24 by which the excess fuel or the gases and vapors are brought back to the tank.

In the upper part of the settling tank there is a dome-shaped element 26 intended to recover the gases and vapors inside the tank and to bring them back to the tube 24 back to the tank. To this end, said dome-shaped element is constituted by a disc having a concave lower face 28, for example with a slight taper centered on the axis of the tank. Said element 26 is pierced in its center with an axial orifice 30 which communicates with the return pipe 24. It has a flat upper face 32 which bears against the internal face of the cover body, and a projecting peripheral edge 34 which is clamped between the edge 16 of the cover and a shoulder formed on the upper edge of the settling tank.

The inlet pipe 20 has a vertical portion 36 of narrowed diameter drilled in the element 26, in which the fuel accelerates. The portion 36 is extended by a substantially horizontal portion 38 oriented so that the outgoing jet of fuel strikes the internal wall of the tank under a substantially tangential incidence.

The interior of the settling tank is divided into two stages by a deflector 40 in the form of an inverted funnel and of the same axis as the tank. The deflector comprises a frustoconical part 42 whose flared edge leaves a slight clearance with the inner wall of the tank. Said edge comprises for this purpose a plurality of protrusions 44 regularly spaced in contact with the wall of the tank, and which define with the latter narrow passages 46 in the form of an arc. The frustoconical part is extended by a tubular part 48 provided at its upper end with hooks 50 which snap onto shoulders provided in the axial orifice 30 of the element 26. The deflector 40 thus defines a stage upper annular 52 and a lower stage 54.

The vapors and gases being in the upper stage can flow towards the return orifice 24 by several calibrated tangential orifices 56 formed at the upper end of the tubular part 48 of the deflector. The latter is closed by a wall pierced with an orifice 58 through which the vapors and gases forming in the lower stage are discharged.

According to the invention, a small portion of the effluent fuel flow is diverted from the inlet pipe 20 through a narrow channel 60 to a nozzle 62 which is mounted in the return pipe 24. The fuel mixture jet leaving the nozzle creates a depression at the inlet of the return pipe which sucks the gases and vapors forming in the two stages of the tank.

In a manner known per se, in the orifice of the return pipe, a valve 64 is slidably mounted between a low position (right part of FIG. 3) where it is applied against a first seat 66 secured to the element 26 and a high position (left part of FIG. 3) where it is applied against a second seat 68 located at the entrance to the return pipe. The valve struggles in a bore 70 provided with vertical grooves 72 which by-pass the valve when the latter is in the low position. These grooves offer different pressure drop passages for the liquid and gas phases. The valve is calibrated by a spring 74 which keeps it normally applied against the seat 66 as long as the pressure downstream of the valve is less than a predetermined pressure. It has a central orifice calibrated 76 through which a low flow rate of liquid fuel leakage can escape when the valve is in its high position.

In the lower part of the tank is fixed a filter 78 with a suitable mesh, used to separate the last gas bubbles which may remain. The degassed fuel flows to the bottom of the tank and is sucked in through a tube 80 connected to the outlet pipe.

The operation of the degassing device according to the invention will now be explained. The fuel pushed by the pump enters the device through the inlet manifold 20. Part of the flow is diverted to the nozzle 62 via the channel 60, from where it returns to the tank via the return manifold 24. By leaving at high speed of the nozzle, this fraction of the flow creates a depression which sucks the gases and vapors forming in the upper stages 52 and lower 54. The rest of the fuel undergoes a deceleration in the vertical pipe, then a sudden increase in speed in the portion horizontal 38 of smaller diameter, which creates a gas mixture which expands in the upper stage 52. A first gas separation takes place at this level.

The gaseous mixture is projected tangentially to the hot wall of the tank where it undergoes a thermal shock which still releases gases and vapors contained in the fuel. This separation continues under the effect of the vortex movement of the fuel and the centrifugal force. The gases accumulate towards the highest part of the concave element 26 and are evacuated through the orifices 56 and the valve 64 towards the return pipe 24.

The liquid fuel, practically free of gas, continues its rotational movement and passes to the lower stage 54. The last fraction of gas accumulates in the deflector and is discharged through the orifice 58 towards the valve 64 and the return pipe. .

Due to the calibration of the valve, the gas pressure is insufficient to lift the valve. The latter therefore remains applied against its lower seat 66, the gases passing through the grooves 72. The liquid fuel cannot escape by the same path because the grooves oppose it with great resistance. Liquid fuel continues to fill the device and when the pressure it exerts counterbalances the force of the spring 74, the valve 64 is lifted and applied against the other seat 68. The return pipe is then closed, only a small flow of leak flowing through the calibrated hole 76. The valve reopens only when a gas mat of sufficient thickness has reformed under the valve.

As shown in FIG. 4, a non-return valve 82 can be integrated in the outlet pipe 22, in the case where the height or the distance between the carburetor and the device is large. The valve has a triangular section with rounded ends (Figure 5) and struggles in a cylindrical bore 84 circumscribed to the valve, so that passages 86 are defined for the flow of liquid fuel. At rest, the valve is supported under the action of its own weight on a first seat 88 (left part of Figure 5), while when degassed fuel flows, it is lifted and applied against a second seat 90 (right part of Figure 5) located at the entrance to the return pipe 22 which it only partially closes.

It goes without saying that the element 26 can be made in one piece with the body of the cover. In this case, the underside of the cover is concave.

Claims (7)

1.- Fuel degassing device which comprises a decantation tank and a cover body tightly fixed on the decantation tank, said cover body being provided with a fuel inlet pipe, a fuel pipe return to the gas and vapor reservoir, located in an upper part of the cover and of an outlet pipe for the evacuation of the degassed liquid fuel towards the carburetor, and in which is mounted a valve charged by a calibrated spring, which maintains the valve applied against a first seat as long as the settling tank contains gas, this then escaping towards the return pipe to the tank through passages with low pressure drop which by-pass the valve, while, when the settling tank is completely filled with liquid fuel, the valve is biased against the force of the spring, towards a closed position on a second seat where it closes the return pipe to the tank, characterized é in that:
- the inlet pipe (20) has in said cover (12) a portion of narrowed diameter (36) in which the fuel undergoes an acceleration, and which is extended by a portion (38) which makes the fuel penetrate into the tank decantation (11) tangential to the wall thereof,
- downstream of the valve (64) and in the return pipe to the tank is mounted a nozzle (62) to which part of the incident fuel flow is diverted by a channel (60) connected to the inlet pipe (20 ), said nozzle creating a vacuum at the inlet of the return pipe. 2.- degassing device according to claim 1, characterized in that in the upper part of the settling tank is fitted a dome-shaped element (26) intended to recover the gases and vapors inside the tank and bring them back to the tubing (24) back to the tank, said element being pierced in its center of an axial orifice (30) which communicates with the return pipe, said element being pinched along its edge between the body of the cover and the edge of the settling tank. 3.- degassing device according to one of claims 1 and 2, characterized in that the settling tank (11) is divided into two superposed stages (52, 54), by a separating element (40) in the form of upside-down funnel, the conical part (42) of which defines with the internal wall of the tank a small gap (44) for the flow of fuel coming from the inlet nozzle, and the tubular part (48) of which adapts at the upper part of the cover body or of the dome-shaped element (26), orifices (56) being provided at the end of the tubular part to allow the evacuation of gases accumulating in the stage upper (52) towards the return pipe to the tank. 4.- degassing device according to claim 3, characterized in that said separating element (40) is closed at its narrowed end by a wall pierced with a calibrated hole (58) for the evacuation of gases accumulating in the lower floor (54). 5.- degassing device according to one of the preceding claims, characterized in that at the lower part of the settling tank (11) is mounted a suitable mesh filter (78) intended to separate the last gas bubbles from the fuel, the degassed fuel located under the filter being sucked towards the outlet pipe by a cannula (80) the lower end of which passes through the filter with sealing and plunges into the fuel. 6.- degassing device according to one of the preceding claims, characterized in that a non-return valve (82) of substantially triangular section is slidably mounted in a cylindrical bore (84) circumscribed to the valve formed in the outlet pipe. (22), so that passages (86) remain free for the liquid fuel, said valve being held in abutment at rest, under the action of its own weight, on a first seat (88), while in operation, it is lifted and applied against a second seat (90) located at the entrance to the return pipe (22) which it only partially closes. 7 - degassing device according to claim 1, characterized in that the valve (64) is pierced with a calibrated orifice (76) allowing a low flow rate of fuel leakage to the return pipe when the valve is in the closed position.

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