GB1575643A

GB1575643A - Diesel engine fuel system

Info

Publication number: GB1575643A
Application number: GB1006177A
Authority: GB
Original assignee: Ford Motor Co Ltd; Ford Motor Co
Current assignee: Ford Motor Co Ltd; Ford Motor Co
Priority date: 1977-03-10
Filing date: 1977-03-10
Publication date: 1980-09-24

Description

(54) DIESEL ENGINE FUEL SYSTEM (71) We, FORD MOTOR COMPANY LIM ITED, of Eagle Way, Brentwood, Essex CM13 3BW, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following state ment:- This invention relates to fuel systems for diesel engines.

It has been found that, in cold ambient conditions, diesel engines will stall shortly after satisfactory starts due to a process known as "waxing." This occurs when the ambient temperature is sufficiently low to precipitate wax in the fuel, the wax being deposited on the fuel filter element and progressively blocking fuel flow. Waxing has been found to occur when the fuel CFPP value is equal to or up to 5"C below ambient temperature.

An object of the present invention is to provide a fuel system in which waxing is eliminated or is substantially mitigated.

Another object is to assist in purging air from the system.

The present invention provides a fuel system for a diesel engine, including a fuel tank, a filter, a first conduit connecting the fuel tank to the filter, a pump having an inlet, one or more outlets for supplying fuel to an engine, and a fuel return outlet, a second conduit connecting the filter to the pump inlet, and a reservoir comprising a container, an inlet discharge into the container intermediate the top and bottom thereof, and connected to receive fuel from the fuel return outlet of the fuel pump a main outlet in the bottom of the container, arranged to discharge into the first conduit, the main outlet being provided with valve means arranged to open when a predetermined minimum level of fuel is present in the container, and an overflow outlet adjacent the top of the container and communicating with the fuel tank.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a block diagram of a fuel system embodying the invention, and Figure 2 is a diagrammatic cross-sectional view of a reservoir in accordance with the invention.

Referring to Figure 1, a diesel engine 10 is supplied with fuel by an injection pump 12 of known type. Fuel is supplied to the inlet of the pump 12 from a tank 14 via a fuel filter 16; In known manner, the pump 12 normally draws more fuel than is required by the engine and discharges the excess fuel from a return outlet.

In accordance with the invention, fuel from the return outlet is fed to a reservoir 18, to be described, the reservoir 18 being connected to the tank 14 and to a point intermediate the tank 14 and filter 16.

Turning to Figure 2, the reservoir 18 comprises an upright cylindrical container 20. An inlet 22 connected to the return outlet of the pump 12 discharges at the mid-point of the height of the container 20. A main outlet 24 is formed in the bottom wall of the container 20 and is provided with a valve seat 26. The outlet 24 discharges into the fuel line between the tank 14 and the filter 16. An overflow outlet 28 adjacent the top of the container 20 communicates with the fuel tank 14. The top of the container 20 is closed by a transparent cover plate 30, e.g. of "Perspex", and sealed by a resilient gasket 32.

A float 34 is free to move vertically within the container 20 and carries a valve needle 36 shaped to cooperate with the valve seat 26.

Peripheral spacers 38 on the float 36 guide the latter within the container 20 while leaving spaces for fluid flow there-around.

In use, the operation of the pump 12 causes considerable heating of the fuel discharged.

Tests with a standard low pressure fuel system have shown a typical temperature difference between fuel tank and fuel pump outlet, after 30 minutes running at constant speed, of the order of 20"C at idle (650 r.p.m.) and 35"C at maxium speed (4,000 r.p.m.). Hence, quantities of relatively hot fuel are fed to the reservoir 18 and thence to the main fuel flow upstream of the filter, thus preventing waxing in any circumstances likely to be found in practice. The valve formed by the needle 36 and seat 26 ensures that the conduit from the reservoir 18 to the main fuel path is filled with liquid fuel at all times.

The reservoir 18 also acts to purge air from the fuel system. The volume and depth of fuel present and the fact that the container 20 is vented to tank pressure allows any air present in the incoming fuel to escape past the float 34 and thence to the tank 14 via the outlet 28.

(The outlet 28 also acts to overflow excess fuel to the tank if necessary). The release of air is assisted by the relatively high temperature of the fuel in the reservoir 18. It has been found that this action of the reservoir 18 is sufficient to eliminate the need to bleed the fuel system after disturbing any of its connections.

WHAT WE CLAIM IS 1. A fuel system for a diesel engine, including a fuel tank, a filter, a first conduit connecting the fuel tank to the filter, a pump having an inlet, one or more outlets for supplying fuel to an engine, and a fuel return outlet, a second conduit connecting the filter to the pump inlet, and a reservoir comprising a container, an inlet discharging into the conainer intermediate the top and bottom thereof, and connected to receive fuel from the fuel return outlet of the fuel pump, a main outlet in the bottom of the container, arranged to discharge into the first conduit, the main outlet being provided with valve means arranged to open when a predetermined minimum level of fuel is present in the container, and an overflow outlet adjacent the top of the container and communicating with the fuel tank.

2. A fuel system according to claim 1, in which the valve means comprises a valve seat at said main outlet and a float carrying a valve needle arranged to cooperate with the valve seat.

3. A fuel system according to claim 1 or claim 2, in which the top of the container comprises a transparent member.

4. A fuel system for diesel engine, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. practice. The valve formed by the needle 36 and seat 26 ensures that the conduit from the reservoir 18 to the main fuel path is filled with liquid fuel at all times. The reservoir 18 also acts to purge air from the fuel system. The volume and depth of fuel present and the fact that the container 20 is vented to tank pressure allows any air present in the incoming fuel to escape past the float 34 and thence to the tank 14 via the outlet 28. (The outlet 28 also acts to overflow excess fuel to the tank if necessary). The release of air is assisted by the relatively high temperature of the fuel in the reservoir 18. It has been found that this action of the reservoir 18 is sufficient to eliminate the need to bleed the fuel system after disturbing any of its connections. WHAT WE CLAIM IS

1. A fuel system for a diesel engine, including a fuel tank, a filter, a first conduit connecting the fuel tank to the filter, a pump having an inlet, one or more outlets for supplying fuel to an engine, and a fuel return outlet, a second conduit connecting the filter to the pump inlet, and a reservoir comprising a container, an inlet discharging into the conainer intermediate the top and bottom thereof, and connected to receive fuel from the fuel return outlet of the fuel pump, a main outlet in the bottom of the container, arranged to discharge into the first conduit, the main outlet being provided with valve means arranged to open when a predetermined minimum level of fuel is present in the container, and an overflow outlet adjacent the top of the container and communicating with the fuel tank.