GB2200948A

GB2200948A - I.C. engine fuel injection nozzle

Info

Publication number: GB2200948A
Application number: GB08801569A
Authority: GB
Inventors: David John Gaskell
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1987-02-05
Filing date: 1988-01-25
Publication date: 1988-08-17
Also published as: GB8801569D0

Abstract

A valve member 13 carries a first spring abutment 19 engaged with one end of a first spring 17. The other end of the spring engages a second spring abutment 21 adjustable in a body 10. A second spring 18 is located between third and fourth spring abutments 23, 26, the third abutment engaging with the second abutment to prevent relative rotation but being axially movable relative thereto. The fourth abutment is adjustably mounted in the second abutment and a peg 24 is adjustably mounted on the third abutment. The peg is engaged by the first abutment after a predetermined movement of the valve member against the action of the first spring, continued movement of the valve member being against the action of both springs. The drilling 29 in the abutment 26 provides access to the adjustment slot 25 in the peg 24. <IMAGE>

Description

"FUEL INJECTION NOZZLE" This invention relates to a fuel injection nozzle for supplying fuel to an internal combustion engine, the nozzle being of the so-called inwardly opening type and comprising a valve member movable by fuel under pressure away from a seating to allow fuel flow from an inlet to an outlet and first and second springs for urging the valve member into contact with the seating, the first spring acting directly upon the valve member and the second spring acting upon the valve member only when the valve member has moved a predetermined distance away from the seating.

A problem w-ith known arrangements of nozzle of the aforesaid type is the difficulty of adjusting the nozzle following assembly such adjustment comprising setting the nozzle opening pressure, the lift of the valve member away from its seating before the second spring is brought into operation and the force exerted by the second spring.

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

According to the invention a fuel injection nozzle of the kind specified comprises a hollow body defining a chamber into which extends the end of the valve member remote from the seating, a first spring abutment mounted on said end of the valve member and supporting one end of said first spring, a hollow cylindrical second spring abutment adjustably mounted in the chamber and engaging the other end of said first spring, a third spring abutment carried within the second spring abutment and mounted for axial non-rotational movement therein, said second spring being positioned between said third spring abutment and a fourth spring abutment adjustably mounted within said second spring abutment, said third spring abutment being urged into engagement with a stop surface defined by the second spring abutment and carrying an adjustable peg engageable by the first spring abutment after the valve member has moved said predetermined distance away from the seating.

An example of a fuel injection nozzle in accordance with the invention will now be described with reference to the accompanying drawing which shows the nozzle in sectional side elevation.

The nozzle comprises a hollow body 10 to which is secured a nozzle body 11 in which is defined a bore 12, the bore mounting a valve member 13. In known manner for an inwardly opening injector, the valve member is shaped to co-operate with a seating to control fuel flow from a fuel inlet 14 to an outlet not shown. The inlet 14 is connected by means of a passage 15 in the bodies 10 and 11 to a chamber defined about the valve member, the valve member defining a surface against which pressure in the chamber can act to lift the valve member from its seating to allow fuel flow through the outlet.

Formed in the body 10 is a chamber 16 which houses first and second coiled compression springs 17, 18.

One end of the spring 17 is mounted on a first spring abutment 19 which is carried upon an extension 20 of the valve member 13, the extension extending with clearance through a base wall of the body 10. The other end of the spring 17 is engaged with a second spring abutment 21 which is of cup shaped form and which extends within the chamber 16. At its end remote from the valve member 13, the second spring abutment 21 is provided with a peripheral screw thread for engagement with a complementary thread formed in the side wall of an enlarged portion of the chamber 16.

The second spring abutment 21 carries a third spring abutment 23 and this in turn carries an adjustable stop 24 which extends towards the abutment 19. The stop 24 is adjustably mounted within the abutment 23 and the latter is of flanged tubular form with the tubular portion defining a non-circular outer peripheral surface which extends through a non-circular opening formed in the base wall of the second abutment 21, the opening being shaped to co-operate with the outer peripheral surface of the third abutment so as to allow relative axial movement therebetween but to prevent angular movement. The stop member 24 at its end facing the open end of the chamber 16 is provided with a non-circular aperture 25.The spring 18 is sandwiched between the flange of the third spring abutment 23 and a fourth spring abutment 26 which is mounted in screw thread engagement within the second spring abutment. The spring 18 therefore exerts a force acting to urge the flange of the third spring abutment 23 into contact with a stop surface 27 defined by the second spring abutment.

In operation, when fuel under pressure is applied to the valve member 13 a force will be developed on the valve member acting to urge the valve member against the action of the spring 17. When the force attributable to the fuel pressure exceeds the force exerted by the spring 17, the valve will move to a partly open position determined by the distance between the end of the stop 24 and the abutment 19. At this point the fuel pressure must increase substantially to overcome the additional force exerted by the spring 18 and when the force attributable to the fuel pressure is sufficient, the valve member will move a further amount against the action of both springs. The extent of such further movement is limited by the abutment of a shoulder 28 on the valve member, with the base wall of the body 10.

The initial opening pressure of the nozzle is determined by the force exerted by the spring 17 and this can be adjusted by adjustment of the second spring abutment 21 within the body 10. Following such adjustment the lift of the valve member against the action of the spring 17 only, can be determined by adjustment of the stop 24 this being achieved by inserting a tool into the aperture 25 through an axial drilling 29 formed in the abutment 26. Following the setting of the stop the fourth abutment 26 can be adjusted to determine the force exerted by the spring 18. It is thus possible to adjust all the operating parameters of the nozzle without having to disassemble the nozzle following its assembly. The various threaded components can be locked in position by suitable locking agents or by the provision of locking rings and it will be appreciated that the sequence of adjustment described need not necessarily be followed.

Claims

1. A fuel injection nozzle for supplying fuel to an internal combustion engine, the nozzle being of the inwardly opening type comprising a valve member movable by fuel under pressure away from a seating to allow fuel flow from an inlet to an outlet, first and second springs for urging the valve member into contact with the seating, the first spring acting directly upon the valve member and the second spring acting upon the valve member only when the valve member has moved a predetermined distance away from the seating, a hollow body defining a chamber into which extends the end of the valve member remote from the seating, a first spring abutment mounted on said end of the valve member and supporting one end of said first spring, a hollow cylindrical second spring abutment adjustably mounted in the chamber and engaging the other end of said first spring, a third spring abutment carried within the second spring abutment and mounted for axial non-rotational movement therein, said second spring being positioned between said third spring abutment and a fourth spring abutment adjustably mounted within said second spring abutment, said third spring abutment being urged into engagement with a stop surface defined by the second spring abutment and carrying an adjustable peg engageable by the first spring abutment after the valve member has moved said predetermined distance away from the seating.

2. A nozzle according to Claim 1 in which said second spring abutment is of cup-shaped form and has a bore formed in the base wall thereof, said third spring abutment being of flanged tubular form, the shape of the wall of the bore and the outer peripheral surface of the tubular portions being such that relative axial movement of the abutments can take place but relative angular movement is prevented.

3. A nozzle according to Claim 2 in which said peg its mounted.in screw thread engagement within the tubular portion of the third spring abutment, said peg defining a non-circular recess in its end presented to the fourth spring abutment, the fourth spring abutment defining a drilling through which can be passed a tool engageable within said recess to permit adjustment of said peg.

4. A 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 drawing.