GB2192944A

GB2192944A - Fuel pump

Info

Publication number: GB2192944A
Application number: GB08717541A
Authority: GB
Inventors: Antonio Navarro Trevino
Original assignee: RE CON SA
Current assignee: RE CON SA
Priority date: 1986-07-24
Filing date: 1987-07-24
Publication date: 1988-01-27
Anticipated expiration: 2007-07-24
Also published as: DE3724603A1; FR2602007B1; FR2602007A1; IT8721440A0; GB8717541D0; GB2192944B; IT1228438B

Abstract

A diaphragm fuel pump for supplying fuel from a fuel tank to a carburettor comprises an induction chamber (17) and a superposed pressure chamber (10) of larger capacity. A vent hole (19) is provided in the upper region of the pressure chamber for venting fuel vapour, so that liquid fuel only is supplied to the carburettor. A further chamber (8) is formed between the induction chamber and the pressure chamber, constituting an auxiliary fuel tank which is full of liquid in and after use so that the pump is effectively primed and ready for re-use, even after a long period without use. <IMAGE>

Description

SPECIFICATION Fuel pump Field of invention This invention relates to a fuel pump, particularly a diaphragm fuel pump, eg for supplying fuel from a fuel tank to a vehicle engine carburettor.

Summary of the invention In one aspect the present invention provides a diaphragm fuel pump comprising an induction chamber and a superposed pressure chamber of larger capacity, a vent hole being provided in the upper region of the pressure chamber for venting fuel vapour.

Such a pump can thus evacuate fuel vapours, which are formed by the fuel being exposed to high temperatures in fuel-carrying ducts in an engine and also inside the pump, with the vapours conveniently being conveyed back to the fuel tank for condensation and recirculation in liquid form. The presence of fuel vapour is undesirable as it slows the passage of fuel through an engine, and represents an increasing problem because of the prevailing trend in engine design of reducing the housing frame of vehicle engines, with consequent limitation on the cooling flow effect of such enclosures, in order to obtain a lower aerodynamic co-efficient, because of the high resolution and large flows these feeding members are required to provide. Further, in transverse engines pumps are more sensitive to the heat energy discharged by the engine radiatior, resulting in further heating.The present invention thus provides a pump that can cope with such conditions.

In a further aspect of the present invention provides a diaphragm fuel pump comprising an induction chamber and a superposed pressure chamber of large capacity, with a further chamber between the induction chamber and the pressure chamber constituting an auxiliary fuel tank which is full of liquid in and after use.

Because the further chamber remains full of liquid after use, the pump effectively remains Primed and ready for use, even after a long period without use. In this way, virtually instant filling up of the carburretor is possible (even though the rest of the pump and fuel supply system may be unprimed). This is because the effective path along which fuel has to run is between the pump and the carburettor, and not, as occurs in conventional pumps, from the fuel tank to the pump. Thus starting of the vehicle engine is possible in a period of time shorter than time required when using a conventional pump, even when the vehicle has been parked for several days.

The pump preferably includes a pressure or outlet duct which is vertically oriented and which is extended into the pressure chamber in such a way that its free end terminates in the lower half of the chamber (ie the length of the duct portion within the chamber is greater than half the height of the chamber), with the chamber being constructed such that the duct intake will always remain dipped in the liquid present in the pressure chamber, while vapours are eliminated through a small hole drilled in the side wall, near the upper wall or roof of the pressure chamber. In this way liquid fuel, without vapour, is supplied by the pump.

The pump conveniently includes a member delimiting the induction chamber and that forms a part of the intercommunication duct with the pressure chamber, located immediately thereabove. Such a member desirably forms leak-tight seals in two separate regions: one with an annular shoulder of a stepped cylindrical shell of the pump, and the other (of smaller diameter) with an annular flange extending outwardly from a truncated conical member which forms an end part of the inter chamber duct, the conical member being closed at its upper end by an inlet valve to the upper, pressure chamber.

The two aspects of the invention may be used separately or in combination.

The invention also includes within its scope a vehicle engine incorporating a fuel pump embodying the invention.

The invention will be further described, by way of example, with reference to the accompanying drawing, the single Figure of which is a vertical section through the upper part of one illustrative embodiment of a fuel pump embodying the invention.

Detailed description of the drawing The illustrated fuel pump comprises a stepped cylindrical shell 2 in which is located a member 1 having an inner cylindrical portion and upper and lower annular portions. The member 1 generally divides the pump into an induction or inlet chamber 17 and a pressure or delivery chamber 10 which is co-axial with and above the induction chamber and which has a larger volume than the induction chamber.

Member 1 is retained in the shell by a clamping arrangement around the periphery of the lower annular portion, the clamping arrangement also serving to secure pump membrane or diaphragm 16, which is of conventional construction. The diaphragm 16 has associated therewith a conventional pull rod and return spring, which function in conventional manner.

The periphery of the upper annular portion of member 1 sealingly engages the shoulder between the cylindrical parts of shell 2, with an O-ring seal 3 forming a leak-proof seal.

This annular portion defines the base of pressure chamber 10.

A truncated cone shaped bushing 4 is lo cated in the upper part of the shell 2, being fitted into the open upper end of the inner cylindrical portion of member 1 and being sealingly secured thereto by means of an 0ring seal 5.

The bushing 4 and inner cylindrical portion of member 1 together define a central duct 8 which links the induction chamber and pressure chamber.

A one way valve 7 is located at the upper end of bushing 4 to permit passage of fluid to the pressure chamber. The valve comprises a washer 13 supported at the upper ends of four walls 12 surrounding the upper portion of bushing 4, the washer in turn supporting a return spring 14 which biases a valve member to a closed position (as shown) in which it is sealing seated against the upper periphery of the bushing 4. A clearance gap 1 5 is provided between walls 12 and the shell end face for passage of vapours and liquid.

A further one way valve 6 of similar construction but inverted orientation is located in the lower part of member 1, to permit passage of fluid into the induction chamber 17.

The vertical spacing of valves 6 and 7 is designed to be as large as possible, so that the volume of duct 8 is as large as possible.

The pump further comprises a horizontally oriented fuel inlet pipe 18, extending outwardly from a lower portion of shell 2, for supplying fuel to the induction chamber of the pump from a fuel tank (not shown).

A vertically oriented fuel outlet pipe or duct 9 for supplying fuel from the pump to a carburettor (not shown) is associated with the pressure chamber. The pipe 9 extends in to the pressure chamber to such an extent that the lower end of the pipe 9 is always immersed in liquid in use, as shown.

A small aperture 19 is provided in the upper part of shell 2 defining the pressure chamber, with a horizontally oriented vent pipe or duct 11 surrounding aperture 19 and extending outwardly from shell 2. Duct 19 leads to the fuel tank and is for venting fuel vapour from the pressure, as will be described.

The remaining, lower portion of the pump is of conventional construction and is not illustrated or described.

In use, valve diaphragm 16 is reciprocated in conventional manner, causing fuel to be drawn into the induction chamber 17 from the fuel tank, via inlet pipe 18 and valve 6. As pumping continues, the induction chamber fills with fuel, which flows upwardly and fills the central duct 8. When duct 8 is full, the fuel passes via valve 7 to the pressure chamber 10 to be passed via duct 9 to the carburettor.

In use, the central duct 8 is always full and functions as an auxiliary fuel tank, defined between the valves 6 and 7. After use, duct 8 remains full, so that the pump is effectively primed and ready for re-use, even after a long period without use of the engine. This is in contrast to conventional pumps, which do not remain primed in this way between use.

This arrangement permits virtually instant supply of fuel to and filling of the carburettor on re-starting of the pump (even though the rest of the system may be unprimed), because the effective path along which fuel has to be supplied is from the auxiliary tank formed by duct 8 to the carburettor, and not the conventional longer path from the fuel tank to the carburettor via the pump (once this is primed).

Thus the priming time is reduced virtually to zero.

This arrangement thus assists in supplying fuel to the carburettor in minimum time on restarting of the engine, even after a long period, eg several days, without use. This means that an engine, eg of a vehicle, can be started in a shorter period of time than is possible when using a conventional pump which does not remain primed in the same way between use.

Further, in use of the pump any fuel vapour formed due to heating rises and accumulates in the top of the pressure chamber 10, where it is vented via aperture 19 and duct 11 and returned to the fuel tank where it condenses.

Liquid fuel, without vapour, is expelled (by the action of vapour pressure) from pressure chamber 10 via duct 9 the lower end of which is always immersed in liquid fuel as shown. In this way an even supply of liqiud fuel only, without vapour, is fed smoothly to the carburettor.

Claims

1. A diaphragm fuel pump comprising an induction chamber and a superposed pressure chamber of larger capacity, a vent hole being provided in the upper region of the pressure chamber for venting fuel vapour.

2. A diaphragm fuel pump comprising an induction chamber and a superposed pressure chamber of larger capacity, with a further chamber between the induction chamber and the pressure chamber constituting an auxiliary fuel tank which is full of liquid in and after use.

3. A diaphragm fuel pump comprising an induction chamber and a superposed pressure chamber of larger capacity, a vent hole being provided in the upper region of the pressure chamber for venting fuel vapour, and a further chamber between the induction chamber and the pressure chamber which constitutes an auxiliary fuel tank which is full of liquid in and after use.

4. A fuel pump according to claim 1 or 3, comprising a vertical outlet duct leading from the pressure chamber for supplying fuel to a carburettor, the duct extending into the pressure chamber so that the lower end is immersed in liquid in use.

5. A fuel pump according to claim 1, 3 or 4, wherein a tubular duct is associated with the vent hole for supplying vented vapour to the fuel tank.

6. A fuel pump according to claim 2 or 3, wherein the further chamber is defined between two vertically spaced valves for admitting fuel to the induction chamber and pressure chamber, respectively.

7. A fuel pump according to claim 6, wherein the valves have a maximum vertical spacing.

8. A fuel pump according to any one of the preceding claims, wherein the induction chamber and pressure chamber are coaxial with respect to each other.

9. A fuel pump according to any one of the preceding claims, wherein an inlet for supplying fuel to the pump from a fuel tank is located close to the bottom of the pump.

10. A fuel pump according to claim 3, wherein an inlet valve to the pressure chamber is located near the central upper part of such chamber, closing in one of its operative positions the end of a manifold that is introduced into said chamber and by its opposite end communicates with the area close to the pump membrane or diaphragm, whose access is achieved through inlet valve to the induction chamber arranged in vertical alignment with the former valve.

11. A fuel pump according to claim 3, wherein a member delimiting the induction chamber and forming a part of a duct intercommunicating with the pressure chamber, presents two separate annular profiles of leaktight shutoff, one of them peripheral, corresponding to the frame wall of the pump, and the second one, coaxial with the former, at the joint area of such part with a truncatedcone-shaped pipe forming the end part of the interchamber communication duct, closed at its upper part by an inlet valve to the pressure chamber.

12. A fuel pump according to claim 10, wherein an annular plate supporting a spring of an inlet valve to the pressure chamber supports and is retained in four radial walls surrounding the interchamber communication manifold, the walls presenting a slight clearance in the vicinity of the upper part of the pressure chamber.

13. A fuel pump according to claim 3, comprising an outlet duct oriented vertically, passing through the roof of the pressure chamber and extending inward until its end is under half the height of such chamber.

14. A fuel pump according to claim 3, wherein the vapours outlet is defined by a reduced passage hole, drilled close to the upper part of the pressure chamber, communicating with the side manifold, parallel to the induction chamber.

15. A membrane type fuel pump characterised by the fact its two working chambers are coaxial, located superposed, the pressure chamber having a larger capacity than the induction chamber, and being located at the upper part of the assembly, the intake for fuel supply being close to the bottom of such cavity and having near the top of such pressure chamber a passage hole communicating with a tubular duct, to evacuate the fuel vapours and the feedback of same to the fuel tank, being located the two valves it has available, induction and pressure valves, at a maximum gap, in such a way a large enclosure is developed between them and the membrane plane, such enclosure constituting a tank to store fuel, that will in use always remain filled with same.

16. A diaphragm fuel pump substantially as herein described with reference to, and as shown in, the accompanying drawing.

17. A vehicle engine incorporating a fuel pump in accordance with any one of the preceding claims.