US3456884A

US3456884A - Liquid fuel supply systems

Info

Publication number: US3456884A
Application number: US728850A
Authority: US
Inventors: Basil Edward Knight; David Shufflebotham
Original assignee: CAV Ltd
Current assignee: CAV Ltd
Priority date: 1965-01-11
Filing date: 1968-05-13
Publication date: 1969-07-22
Anticipated expiration: 1986-07-22
Also published as: DE1526637A1; DE1526637B2; ES321886A1; FR1463387A; GB1060181A

Description

l July 22, 1969 B; E. KNIGHT Ef AL v 3,455,884

LIQUID FUEL SUPPLY SYSTEMS original Filed Jan. 1o, 1966' /ll/f/ i /7 y f. Zijll! ,if W

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f ma@ United States Patent O 3,456,884 LIQUID FUEL SUPPLY SYSTEMS Basil Edward Knight, Pinner, and David Shulilebotham, London, England, assignors to C.A.V. Limited, London, England, a British company Continuation of application Ser. No. 519,495, Jan. 10, 1966. This application May 13, 1968, Ser. No. 728,850 Claims priority, application Great Britain, Jan. 11, 1965, 1,133/65; July 27, 1965, 31,944/65 Int. Cl. F02m 45/04; B05b 1/32 U.S. Cl. 239-533 3 Claims ABSTRACT OF THE DISCLOSURE A liquid fuel supply system for internal combustion engines in which it is desirable to inject a predetermined quantity -of fuel through the injection nozzle at a restricted flow rate before injecting the main quantity of fuel through the nozzle at an unrestricted flow rate. This is accomplished by a device comprising in combination a valve member slideable in a cylinder, one end of said cylinder being in communication with a fuel pump and the other end of the cylinder being in communication with the nozzle through a restricted passage. Resilient means urge the valve member towards said one end of the cylinder, and a by-pass passage is arranged to be opened by the valve member when it has been moved a predetermined extent against the action of the resilient means. The movement of the valve member towards the said other end of the cylinder displaces a predetermined quantity `of fuel to the nozzle through the restricted passage at a restricted ow rate. The by-pass passage serves to by-pass the restricted passage so as to allow the main quantity of fuel to be injected through the nozzle at an unrestricted rate.

This application is a continuation of application Ser. No. 519,495, now abandoned.

This invention relates to liquid fuel supply systems for internal combustion engines and of the kind including an injection nozzle which is mounted in the body of the engine and through which fuel can be delivered to a combustion space of the engine and a fuel pump for supplying fuel to the nozzle in timed relationship to the engine, said nozzle incorporating a pressure -responsive valve for controlling the flow of fuel therethrough.

The object of this invention is to provide such a fuel system in an improved form.

According to the invention a fuel system of the kind specified includes in association with or adjacent to the s nozzle a device comprising in combination a valve member slidable in a cylinder, one end of said cylinder being in communication with the fuel pump and the other end of said cylinder being in communication with the nozzle through a restriction, resilient means urging the valve member towards said one end of the cylinder, and a bypass passage arranged to be opened by the valve member when the latter has been moved a predetermined extent against the action of the resilient means, the movement of the member towards said other end of the cylinder serving to displace a predetermined quantity of fuel to the nozzle at a restricted rate, said by-pass passage serving, when opened, to place said one end of the cylinder in communication with a point between said nozzle and said restriction.

According to a further feature of the invention the device includes a non-return valve which can be opened to permit fuel to flow from the nozzle to the pump, said non-return valve serving to permit the seating of the pressure responsive valve in the nozzle and also serving to maintain a predetermined residual pressure in the nozzle.

In the accompanying drawings:

FIGURE 1 is a view of one example of a fuel supply system in accordance with the invention and FIGURE 2 is a modification of the system shown in FIGURE 1.

Referring to the drawings there is provided an injection nozzle having a body 10 of generally cylindrical form and adapted for mounting in the cylinder head 11 of the engine so that a nozzle head 12 mounted on the body 10 forms part of the wall of a combustion space of the engine. The nozzle head is provided with an orifice 13 through which fuel can be directed into the combustion space and in the nozzle head is a spring loaded control valve 14 which is actuated by the pressure of fuel supplied to the injection nozzle by way of a pipe line 16 from a fuel pump 15 of any convenient form such, for example, as a pump of the rotary distributor type.

It has been found, by experiment, that it is desirable in order to improve the quiet running of a compression ignition engine, that the initial rate of injection of fuel should lbe closely controlled.`

In the present example a device, which is mounted eX- teriorly of the body of the injection nozzle will be described although it will Ibe understood that the device may be mounted within the body.

The device comprises a body which is formed of two parts 17, 18 which are in screw thread engagement with each other. In the part 18 is defined a cylindrical bore 19 which, at its end adjacent the nozzle is in communication with passages in the nozzle body through which fuel passes to the control valve 14 and orifice. The other end of the bore 19 opens into a chamber formed in the part 17 and slidably mounted in the bore is a valve element 20 a portion of which including a head 20a is accommodated in the chamber. The chamber is connected to the fuel pump by way of the pipeline 16 and the valve element 20 is loaded by a first coiled spring 21 in a direction towards the nozzle. Furthermore the head 20a and the adjacent end of the part 18 co-operate under the action of the spring 21 to form a seal so as to interrupt communication between the chamber and the bore.

Within the element is defined a cylinder which is defined by a bore 22 and which at its end disposed within the part 18 is closed by a plug 23 in which is formed a restricted passage 24. Within the bore 22 is mounted a cylindrical valve member 26 which is loaded by a spring 26a in a direction towards the part 17 of the body, the movement of the mem-ber being limited by a stop plate 27 which is retained bythe spring 21. Furthermore formed in the valve element 20 is a Iradially disposed passage 28 which is closed by the valve member 26 when the latter is against the stop plate 27, and the passage 28 communicates with a circumferential groove formed on the external periphery of the Valve element. This groove communicates with the end `of the bore 19 adjacent the nozzle by way of longitudinal grooves 29 formed in the periphery of the valve element and the circumferential groove and the passage 28 and longitudinal grooves 29 constitute a by-pass passage.

The action of the device is as follows, when fuel is delivered by the fuel pump the valve member 26 is first moved, by the initial quantity of fuel delivered by the pump, against the action of the spring 26a and during this movement fuel is displaced from the bore 22 and flows via the restricted passage 24 to the nozzle and causes the control valve 14 to be opened slightly to allow a predetermined quantity of fuel to be injected. After this predetermined quantity of fuel has been delivered the radial passage 28 is uncovered by the valve member 26 and fuel passes directly t-o the nozzle. Fuel continues to liow until the required quantity, as determined by the pump, is delivered and then the control valve 14 closes due to the lowered fuel pressure, and the valve member 26 moves to close the radial passage. Moreover, the valve element 20 and its head 20a will be moved against the action of the spring 21 and will act as a pressure relieving valve to permit the control valve to close quickly and also to maintain a predetermined residual pressure in the nozzle. In this sense, valve element 20, 20a acts as a non-return valve.

With the above arrangement it has been found that the return motion of the valve member 26 due to the action of the spring 26a is hindered by vfuel which becomes trapped in the chamber when the radial passage 28 is closed and also when the head of the element closes onto the end ofthe part 18 and also because fuel cannot enter the end of the bore 22 adjacent the nozzle. The result of this is that in the next injection stroke of the pump the amount of fuel initially delivered through the restriction 24 to the nozzle is reduced.

In order to overcome this and as shown in FIGURE 2 the valve member 26 is provided with an axial blind bore 30 which extends from the end of the valve member adjacent the spring 26a. Moreover, the blind end of the bore is in communication with the chamber through an orifice 31 which in the particular example has an effective size slightly larger than that of the restriction 24. Furthermore formed in the periphery of the valve member is a circumferential groove 32 which is in communication with the blind bore by way of transverse passages 33 formed in the wall of the valve member. The groove is arranged to be opened to a further port 34 in the wall of the bore 22, which port is in communication with the by-pass passage, before the .by-pass passage has been opened to the chamber by movement of the valve member 26 against the action of the spring 26a. The arrangement is such that towards the end of the movement of the valve member 26 the portion of the bore 22 which contains the spring 26a is progressively opened to the by-pass passage through the blind bore 30, the circumferential groove 32 and the further port 34 with which the edge of the groove 32 co-acts. Thus the hydraulic resistance to the motion of the valve member towards the other end of the cylinder is progressively lowered just before the by-pass passage is opened. Furthermore the return motion of the valve member under the inuence of the spring 26a is not hindered since fuel can iiow between the opposite ends of the bore 22 through the passage in the valve member.

Having thus described our invention what we claim as new and desire to secure by Letters Patent is:

l. A liquid fuel supply system for internal combustion engines and comprising an injection nozzle to which fuel is supplied in timed relationship to the engine by a fuel pump, a pressure responsivel valve in the nozzle for controlling the flow of fuel therethrough, a cylindrical bore dened in the nozzle or in a part which can be secured thereto, one end of said cylindrical bore being in communication with the fuel pump and the other end thereof being in communication with a conduit within the nozzle controlled by the pressure responsive valve, a valve element slidable in said cylindrical bore, a longitudinal groove defined in the valve element and serving to establish communication between said one end and said other end of the bore, a head formed on the end of the valve element at said one end of the bore, said head cooperating when the element has moved its fullest extent under the action 'of a resilient means, with a step for-med in the cylindrical bore, a cylinder formed in said valve element, one end of the cylinder being in communication with said fuel pump and the other end thereof being in communication with said conduit, a plug serving to close said other end lof the cylinder, a restricted passage formed in said plug, a valve member mounted in said cylinder, a further resilient means loading the valve member towards said one end of the cylinder, and a passage in the wall of the valve element communicating by way of said groove with said other end of the cylindrical bore, said passage being arranged to be uncovered by the valve member to permit fuel to ow to the nozzle as the valve member is moved by fuel under pressure delivered by the fuel pump, the movement of the member towards said other end of the cylinder serving to displace a predetermined quantity of fuel to the nozzle at a reduced rate.

2. A `fuel supply system as claimed in claim 1 including a passage formed in the valve member and through which fuel can ow to facilitate the return motion of the valve member under the action of its resilient means.

3. A fuel supply system as claimed in claim 2 in which said passage in the valve member is in communication with a groove formed in the periphery of the valve member, said groove being arranged to be opened by a progressively increasing amount as the valve member moves to a further port lformed in the wall of the valve element, the further port communicating with said groove in the valve element.

References Cited FOREIGN PATENTS 913,717 6/1954 Germany.

EVERE'IT W. KIRBY, Primary Examiner U.S. C1. X.R. 239--88