GB1573703A

GB1573703A - Fuel system

Info

Publication number: GB1573703A
Application number: GB1145976A
Authority: GB
Original assignee: Plumbly S J
Current assignee: Plumbly S J
Priority date: 1977-03-10
Filing date: 1977-03-10
Publication date: 1980-08-28

Description

(54) FUEL SYSTEM (71) We, STUART JOHN PLUMBLY of 7, Usborne Close, Staplehurst, Kent and KEVFN JOSEPH COLLINS of 14 Pen sharst Close, Farleigh Road, Canterbury, Kent, formerly of 8 Orchard Glade, Headcorn, Kent, both British Subjects, 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 statement: The present invention relates to fuel systems, for example, for internal combustion engines.

It is useful to be able to meter the quantity of fuel being fed to a fuel consumer such as an engine and this is relatively simple in the case of, for example, petrol engines in which petrol is drawn from the petrol tank and fed to the engine and consumed. However, in the case of diesel engines, it is conventional for fuel to be drawn from the diesel fuel tank and to be passed to the injection system in a greater quantity than is required at any one time, the overflow being passed back to the tank. This, of course, creates problems with metering the fuel since if the meter is placed in the line from the tank to the engine, it will record more than the amount of fuel being used. Various, means have been proposed to overcome this problem.

The problcm, however, is particularly acute in the case of some engines in which the fuel in, cctors in ect Icss than OCGOf the total amount of fuel passed to the injection system so that 80% of the fuel is returned and in some cases, the returned fuel is aerated and at an elevated temperaturc.

The present invention provides a fuel system for metering the fuel flow to a fuel consumer such as an engine including a fuel tank, a fuel flow meter, a first line connecting the fuel tank and the meter, a second line connecting the meter and the consumer, a buffer tank, a third return line for returning excess fuel from the consumer to the buffer tank, and a fourth line for passing fuel from the buffer tank to the second line. Although such an arrangement may be used with any engine which requires an excess of fuel to be passed to the engine, it is particularly useful in the case of those engines in which the excess of fuel from the engine is aerated since the air may be allowed to pass out of the fuel in the buffer tank.

In such a case, the air removed from the buffer tank should be vented and it is particularly preferred to vent this air through a vent line to the fuel tank.

Furthermore, to prevent the buffer tank from being overfilled, it is preferred to arrange that the consumer draws its fuel supply from the buffer tank in preference to the fuel tank and so the fluid resistance between the fuel tank and the second line should be greater than the resistance in the fourth line.

This may be arranged by incorporating, ad- acent the meter, a fluid tlow resistance which may comprise a non-return vade.

In order to cool the fuel passing from the consumer to the buffer tank, the third line may incorporate a cooler.

Filters may, of course, be provided in the various lines to filter the fuel tlowing therethrough.

A fuel system incorporating a preferred embodiment of the invention wi) i now he described by way of example only and with reference to the accompanying drawings in which: Figure 1 shows the fuel system in diag- rammatic form, and Figures 2 and 3 are front and side views respectively of a preferred arrangement of part of the system of Figure 1.

The fuel system illustrated in thc drawings is intended for use with a heavv commercial vehicle engine a ! though it is suitab) e for other engines, particularly internal combustion engmes of the type which have fuel injection systems which require a gallery full of fuel for proper operation.

The fuel system comprises a fuel tank 10, a fuel flow meter 12, a first fuel line 13 connecting the fuel tank to the flow meter 12, the first fuel line 13 including a fuel filter 14 and non return valve 15. An injector/pump assembly 16 for the engine is connected to the meter 12 by a second fuel line 17 which includes a T-piece 18, a fuel filter 19 and a second fuel filter 20. As is illustrated diag rammatically in the drawing, six fuel injection lines 21, extend from the injector/pump assembly 16 to the engine.

A third, return, fuel line 22 is provided connecting the iniector/pump assembly 16 to buffer tank 23 whereby excess fuel can pass from the injector/pump assembly to the buffer tank 23. The third return line 22 incorporates a cooler 24.

The buffer tank 23 is illustrated diagram maticallv. As can be seen, the return line 22 passes into the top of the buffer tank above a baffle plate 25 down which the fuel can flow to the lower half of the buffer tank. An air vent line 26 is provided passing from the upper surface of the buffer tank 23 back to the fuel tank 10. A fuel outlet 27 is provided in the base of the buffer tank 23 the opening of which is controlled by a float valve 28, the outlet 27 being connected to the T-piece ; unction 18 by means of a fourth, return, fuel line 30.

A fifth. return, fuel line is provided for removing excess fuel from the iniection lines 21 to the third return fuel line 22. A by-pass line 32 is provided interconnecting the filter 20 and the third return line 22. The line 32, which is not present in all heavy commercial vehicles, is used as a flushing line for the filters.

The mode of operation of the apparatus described is as follows. The apparatus is par ticularly adapted, as has been previously described, for use with diesel engines of the tvpe wherein a maximum of about 20% of the fuel provided to the in ector/pump assemblv 16 is utilise. 80icof the fuel being returned. If a metering arrangement is not required, this fuel is normallv returned direct) y to the fuel tank 10. However, in the present instance where metering is required, fuel is drawn from the fuel tank 10 through the filter 14 and non return valve 15 to the meter 12 which records the total amount of fuel used. The fuel then passes along the second fuel line 17 via filters 19 and 20 to the in ; ector/pump assembly 16. Excess fuel from the injector pump assembly 16 passes along the third return line 22. and excess fuel from the injection tines 21 passes along line 31 both then passing through the coller 24.

This excess fuel is frequently at an elevated temperature and contains a considerable quantity of air. The cooler 24 cools the fuel.

Any suitable conventional cooler can be used.

The fuel then passes into the buffer tank 23 and during its passage down the baffle plate 25, the air trapped in the fuel is readily released. This air passes along the vent line 26 back to the fuel tank 10, and the fuel then passes into the lower part of the buffer tank 23. Providing there is more than a minimum amount of fuel in the buffer tank 23, the float valve 28 opens the outlet 27 to allow fuel to be returned from the buffer tank to the T-piece 18 and second line 17 via the fourth return line 30.

To prevent the buffer tank 23 overfilling, it is arranged that fuel is preferentially drawn from the buffer tank rather than from the fuel tank 10. This is arranged by virtue of the inclusion of the non-return valve 15 which provides a resistance in the first fuel line 13.

In view of this resistance, the injector pump assembly 16 draws fuel from the buffer tank 23 in preference to fuel from the first line 13 until the float valve 28 closes when further supplies of fuel will be drawn along the first fuel line 13.

Installation of the metering arrangement in a conventional fuel supply in which the return line 22 is directlv connected to the fuel tank 10 can be provided by breaking the return fuel line 22 to incorporate the cooler 24, buffer tank 23 (the vent line 26 being provided by part of the original return line 22) and by inserting into the line connecting the fuel tank 10 and the filter 19, the filter 14, the non-return valve 15 and meter 12 together with the line 30 and T-piece 18.

A preferred arrangement of part of the system is shown in Figures 2 and 3. In this arrangement, the components 12, 5 18 23.

25,27,28,30 are incorporated in a single structure.

As is illustrated in Figures 2 and 3, there is provided a tank 40 having a front panel 41, the tank incorporating in the front panel 41 the meter 12. Within the tank 40, which corresponds to the buffer tank 43. there is incorporated the float valve 28. In practice, it has been found that is is not normally necessary to incorporate in the present arrangement the baffle plate 25.

As can be clearly seen. the front panel 41 incorporates a connection 43 for the line 13.

(the filter 14 being mounted outside the tank 40 in the line 13) and a connection 44 for the line 17. The top of the tank incorporates a connection 45 for the line 26. and a connection 46 for the line 22.

As will be clear, the connection 45 simply allows air from the top of the tank 40 to be vented to line 26, and the connection 46 allows fuel to pass into the tank 40. The connection 43 is connected with a line within the tank 40 in which the non return valve 15 is incorporated and is connected to the input side of the meter 12. The connection 44 is connected by a line inside the tank to the T-piece 18 one side of which is connected to the output side of the meter 12, and the other side of which is connected to the output side of the float valve 28. It will be understood, therefore, that the apparatus of Figures 2 and 3 operates in the same way as that of Figure 1 except that a neater and more practical structure has been provided.

The invention is not restricted to the details of the foregoing example. In particular, the resistance in the first fuel line 13 may be provided by some kind of choke rather than the non-return valve 15. Some of the filters may be deleted or other filters added in other parts of the circuit as required. When used in engine systems in which the return fuel is not heated, the cooler 24 need not be incorporated.

There has thus been described a particularly simple metering arrangement which is capable of coping with engines which return a large proportion of the fuel provided to the engine in the form of heated and aerated fuel. The system described is suitable for more conventional engines also in which the fuel returned is not of an elevated temperature nor particularly aerated and this allows a single system to be used for almost all engines.

WHAT WE CLAINI IS: 1. A fuel system for metering the fuel flow to a fuel consumer including a fuel tank, a fuel flow meter, a first line connecting the fuel tank and the meter, a second line connecting the meter and the consumer, a buffer tank, a third return line for returning excess fuel from the consumer to the buffer tank, and a fourth line for passing fuel from the buffer tank to the second line.

Claims

2. A fuel system as claimed in claim 1 in which the buffer tank is vented.

3. A fuel system as claimed in claim 2 in which a vent line connects the buffer tank and the fuel tank to vent air from the buffer tank.

4. A fuel system as claimed in any of claims I to 3 arranged so that the consumer will draw its fuel supply from the buffer tank in preference to the fuel tank.

5. A fuel system as claimed in claim 4 in which the fluid resistance between the fuel tank and the second line is greater than the resistance in the fourth line.

6. A fuel system as claimed in claim 5 in which there is provided adjacent the meter a fluid flow resistance in the form of a nonreturn valve.

7. A fuel system as claimed in any of claims 1 to 6 in which the third line incorporates a cooler.

8. A fuel system as claimed in any of claims 1 to 7 in which the meter is mounted in the buffer tank.

9. A fuel system as claimed in claim 1 substantially as hereinbefore described with reference to Figure 1 or as modified in Figures 2 and 3 of the accompanying drawings.