GB2223798A

GB2223798A - I.C. engine fuel injector

Info

Publication number: GB2223798A
Application number: GB8823844A
Authority: GB
Inventors: Stuart William Nicol
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1988-10-11
Filing date: 1988-10-11
Publication date: 1990-04-18
Also published as: GB8823844D0

Abstract

The spring 24 is permanently coupled to the valve member 13 through an abutment 33 and a second spring abutment 31 is engaged by the valve member after the latter has moved a pre-determined extent. The abutment 33 has a spigot 35 which is slidable within a bore in the abutment 31. <IMAGE>

Description

FUEL INJECTION NOZZLE This invention relates to a liquid fuel injection nozzle for supplying fuel to an internal combustion engine and of the kind comprising a valve member movable by fuel under pressure away from a seating defined in a nozzle body, to allow fuel flow through an outlet and resilient means for biasing the valve member into contact with the seating, said resilient means comprising a first spring which acts on the valve member after the valve member has moved a predetermined distance away from the seating and a second spring which is permanently coupled to the valve member.

A nozzle of the kind specified is particularly useful for use with certain types of compression ignition engines the operation of which benefits by supplying the initial quantity of fuel at a restricted rate.

Nozzles of the aforesaid kind are known in which the springs are positioned in chambers respectively defined in a nozzle holder, the chambers being located in end to end relationship. This results in a nozzle of substantial length. It is also known, see for example British patent specification 1594174, to mount the springs one within the other. In such an arrangement care has to be taken to ensure that in use, the coils of the two springs do not engage with each other since this can lead to early failure of the springs. In the aforesaid specification the sizes of the springs are such that in assembly, there is a substantial gap between the outer peripheral surface of the inner spring and the inner peripheral surface of the outer spring to ensure that the coils of the two springs do not engage with each other. This gap adds to the overall diameter of the nozzle.If the springs are located at their opposite ends the gap can be made much smaller resulting in:a reduction. in the overall diameter of the nozzle.

The object of the invention is to provide a nozzle of the kind specified in a simple and convenient form.

According to the invention a nozzle of the kind specified comprises a first spring abutment shaped to locate the end of the first spring nearer the valve member, said first spring abutment defining a central bore in which is slidably located a reduced end portion of the valve member, a second spring abutment shaped to locate the end of the second spring which is located within the first spring, said second spring abutment defining a spigot slidable in said central bore of the first spring abutment so that the ends of said springs adjacent the valve member are guided in their movement relative to each other.

An example of a fuel injection nozzle in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a section) side elevation of the nozzle, and Figure 2 is a view to an enlarged scale of part of the nozzle seen in Figure 1.

Referring to the drawings the nozzle comprises a nozzle body 10 of stepped cylindrical form within which is formed a blind bore 11, the bore extending from the wider end of the body. At the blind end of the bore there is a formed a seating 12which surrounds an outlet opening. Moreover, the inner end of the bore is of enlarged diameter. Slidable within the bore is a valve member 13, the valve member with the enlarged portion of the bore defining a supply chamber 14 and the valve member being shaped to co-operate with the seating 12. In the particular example the valve member is provided with a projection 15 which extends through the outlet opening. The chamber 14 is connected by way of a passage 16 to a circumferential groove 17 which is formed in the wider end face of the body.

The nozzle also includes a holder 18 and a spacer 19 which is positioned between the holder 18 and the valve body 10. The body 10 and the holder 18 are held in assembled relationship by means a cap nut 20. The spacer member defines passages which connect with the groove 17 and the passages in the spacer member connect with a fuel inlet 21 formed in the holder by way of a supply passage formed therein.

The holder defines a spring chamber 22 within which is located a first coiled compression spring 23 and located within the spring 23 is a second coiled compression spring 24. The end of the spring 23 is located against an annular spacer 25 which engages a shoulder 26 defined in the spring chamber and the end of the spring 24 remote from the valve member engages an annular spacer 27 which locates against a head 28 from which extends a stop member 29.

The valve member 13 is provided with a reduced portion 30 at its end remote from the seating and slidably mounted about the reduced portion is a first spring abutment 31, the reduced portion of the valve member being located within a central bore 32 formed in the abutment. The spring abutment 31 is of stepped form and defines an annular surface 32A against which is locatted-the spring 23. The abutment also defines an annular projection extending upwardly from the; surface 32A, the projection serving to locate the end of the spring 23 against lateral movement.

The nozzle also includes a second spring abutment 33 which defines a surface for engagement by the spring 24 the abutment 33 also having a projection 34 which extends within the spring 24 to locate the latter against lateral movement. In addition, the abutment 33 defines a spigot 35 slidable in the bore 32 and in the closed position of the valve member as shown, the spigot 35 engages with the reduced portion 30 of the valve member. As will be observed from Figure 2, a small gap exists between the spring abutment 31 and the step defined on the valve member 13. This gap is determined by contact of the abutment 31 with a stop surface 36 defined in the spacer member 19.

In operation, when fuel under pressure is supplied to the space 14, the fuel pressure acts upon the valve member 13 against the action of the spring 24. When the fuel pressure is high enough, the valve member moves against the action of the spring until it engages with the spring abutment 31. In so doing the valve member lifts a predetermined distance from the seating 12 to allow restricted flow of fuel to the associated engine. As the pressure of fuel supplied to the inlet 21 increases, the force acting on the valve member due to the fuel pressure will eventually cause movement of the valve member against the action of both springs and the maximum extent of such movement is limited by the engagement of the stop member 29 with the projection 34 on the spring abutment 33.Fuel can flow to the engine at an increased rate and when the supply of fuel under pressure to the inlet 21 ceases, the valve member is returned to the position shown in Figure 1 of the drawings. The forces exerted by the springs 23 and 24 can be adjusted by varying the thicknesses of the spacers 25 and 27 respectively. It will be noted that the ends of the springs remote from the valve member are located against lateral movement by their engagement with the walls of the chamber. A gap is arranged between the outer surface of the spring 23 and the wall of the chamber and the gap between the two springs can be made very small by virtue of the fact that the ends of the springs adjacent the valve member are located by the two spring abutments, the two spring abutments being guided for relative movement by the spigot 35 and the wall of the bore 32.In addition, the abutment 31 is guided about the reduced portion of the valve member, this in turn being guided by the wall of the bore 11.

The extent of movement before the valve member 13 engages the spring abutment 31 is extremely small for example, 0.05 mm and this gap can be set in a variety of ways for example, if the step on the valve member is made flush with the end surface of the body 10, the end surface of the spring abutment 31 can be ground to provide the required degree of lift of the valve member before it engages the abutment. Alternatively, the spacer 19 and the spring abutment may be clamped together with the abutment engaging the stop surface 36.

The face of the spacer which engages the valve body 10 and the face of the abutment which is engaged by the valve member can then be ground. The movement of the valve member before it engages the abutment 31 can then be determined by grinding the valve member or the end face of the body.

The spring abutment 31 has a substantial area of contact with the stop surface 36 and the valve member and the spring abutment 31 also have a substantial area of contact. Variation of the setting of. the gap due to wear is therefore minimised.

Claims

1. A liquid fuel injection nozzle for supplying fuel to an internal combustion engine and of the kind comprising a valve member movable by fuel under pressure away from a seating defined in a nozzle body thereby to allow fuel flow through an outlet, resilient means for biasing the valve member into contact with the seating, said resilient means comprising a first spring which acts on the valve member after the valve member has moved a predetermined distance away from the seating and a second spring which is permanently coupled to the valve member, a first spring abutment shaped to locate the end of the first spring nearer the valve member, said first spring abutment defining a central bore in which is slidabley located a reduced end portion of the valve member, a second spring abutment shaped to locate the end of the second spring which is located within the first spring, said second spring abutment defining a spigot slidable in said central bore of the first spring abutment so that the ends of said springs adjacent the valve member are guided in their movement relative to each other.

2. A nozzle according to Claim 1 including a stop member extending within the second spring and being engageable by the second spring abutment to limit the movement of the valve member against the action of the springs.

3. A liquid fuel injection nozzle for supplying fuel to an internal combustion engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.