GB2237325A

GB2237325A - I.c. engine fuel injection nozzle

Info

Publication number: GB2237325A
Application number: GB8924343A
Authority: GB
Inventors: Graham Rhys Lewis; John William Stevens
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1989-10-28
Filing date: 1989-10-28
Publication date: 1991-05-01
Also published as: GB8924343D0

Abstract

A deep drawn casing 14 surrounds a tubular member 15 and secures a nozzle tip 10. A valve guide bush 16 is spaced from the tubular member 15 and a collar 22 providing or supporting a fuel inlet surrounds the casing and overlaps the tubular member and the bush. <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 kind comprising an elongated tubular body having a nozzle tip secured to one end thereof, a seating formed in the nozzle tip and surrounding an outlet opening in the tip, an axially movable valve member located with a clearance within the body and shaped at one end for co-operation with the seating to prevent flow of fuel along the clearance and through the outlet opening, a guide bush secured in the body at a positioned removed from said seating, said guide bush defining a bore the wall of which guides the movement of the valve member, a fuel inlet communicating with said clearance, the valve member defining a surface against which the fuel under pressure in said clearance can act to lift the valve member from the seating against the action of resilient means acting on the valve member.

Such nozzles are known in the art, the body being machined from solid material and the nozzle tip being secured to the body by means of a conventional cap nut or by for example, welding. The bush is secured within a recess in the body and the fuel inlet is formed in a projection on the body or is secured thereto as by brazing or welding.

It is expensive to produce the body since it must be formed from material which is sufficiently strong to withstand the high pressure of fuel and the conventional practice is to machine the body from solid. The object of the present invention is to provide fuel injection nozzle of the kind specified in a form enabling a reduction in the cost of manufacture of the nozzle.

According to the invention in a fuel injection nozzle of the kind specified said body comprises a thin wall outer tubular case, one end of said case being secured to said tip, a tubular member located in said case, one end of said tubular member abutting said tip, said bush being secured in said case in axial spaced relationship relative to the opposite end of the tubular member and a collar secured about the case, said collar defining said fuel inlet and having an axial length such that its opposite ends overlap said other end of the tubular member and said bush respectively.

Examples of fuel injection nozzles in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation of one example of the nozzle, Figure 2 is a view similar to Figure 1 showing a modification to the nozzle of Figure 1, Figure 3 is a view similar to Figure 1 showing an alternative arrangement of the nozzle and Figure 4 shows a modification to the nozzle shown in Figure 3.

Referring to Figure 1 of the drawings the nozzle comprises an elongated nozzle tip 10 in which is formed a blind bore 11 at the blind end of which is formed a seating 12 which surrounds an outlet orifice 13. The end portion of the nozzle tip remote from the blind end of the bore is provided with a peripheral step and this portion of the nozzle tip is located within one end of a thin walled outer tubular case 14. The case is conveniently formed as a deep drawn pressing and conveniently the case is rolled about the enlarged portion of the tip in order to secure the tip within the case.

Mounted within the case and abutting the tip is a tubular member 15 and this is secured within the case in any convenient manner for example by gluing, brazing, welding or it may simply be a press fit.

Also mounted within the case is a guide bush 16.

The presented end faces of the bush and tubular member 15 are spaced so as to define a chamber 17. The bush is secured within the case in any convenient manner and it serves to guide an enlarged portion 18 of a valve member 19 which extends with clearance through the opening in the tubular member 15 and also the blind bore 11. At its end adjacent the seating the valve member is shaped for co-operation with the seating and a clearance exists between the wall of the bore 11 and the wall of the bore in the tubular member 15, the clearance communicating with the chamber 17. The portion 18 of the valve member forms a working clearance with the bore in the bush and the working clearance is such as to minimise leakage of fuel from the chamber 17.

The case is provided with an opening 20 into the chamber and the opening communicates with a fuel inlet 21 which in use is connected to the outlet of a fuel injection pump. Conveniently the inlet 21 is formed as a lateral extension to a collar 22 which is mounted about the case 14 and is secured thereto in a fuel tight manner. The axial length of the collar is such that it overlaps at its opposite ends respectively, the bush 16 and the tubular member 15 and it therefore serves to support the portion of the case defining the outer wall of the chamber 17, against the fuel pressure within the chamber.

The portion 18 of the valve member extends through the bush and engages a spring abutment 23 against which is located one end of a coiled compression spring 24.

The other end of the spring bears against a shim 25 which in turn bears against a support plate 26 which engages a ledge defined by the case. Also provided is a cap 28 which has an outwardly extending flange located against the plate 26 and the cap and the plate are secured against the ledge defined by the case, by a rolled over portion 29 of the case. The cap provides an outlet for fuel which leaks along the working clearance and the support plate mounts an adjustable stop member 30 whereby the extent of movement of the valve member can be adjusted.

In operation, when fuel under pressure is supplied to the chamber 17 the fuel pressure acts upon the stepped surfaces of the valve member to generate a force acting to lift the valve member from the seating 12 against the action of the spring 24. Once the valve member has moved, fuel flows along the clearance between the valve member 19 and the tubular member and the wall of the bore and through the outlet orifice 13.

As stated the case is formed as a deep drawn pressing and it will be noted that its internal and external surfaces are stepped to provide location for the tubular member, the bush and also the collar. The tubular member can be formed from proprietary stock cut to the appropriate length.

In a modification of the arrangement shown in Figure 1, the plate 26 is replaced by a flanged bush against which the spring 24 bears and the bush is adjustably mounted in the cap 26 and also carries the adjustable stop 30. With this arrangment there is no need for the shim.

In the modification shown in Figure 2 the spring 24 A is a conical spring and the contour of the case 14A is shaped in an appropriate manner. Moreover, Figure 2 shows how the adjustable stop may be replaced by a fixed stop 31 which is formed as a pressing and replaces the support plate 26.

in the arrangement shown in Figure 3 the nozzle tip 31 is provided with a flange 32 at its end remote from the seating, the flange having a size which corresponds to the outer diameter of the tubular member 15. Figure 3 also shows the replacement of the fixed stop in the same manner as is shown in Figure 2 but with a straight coiled spring.

Figures 2 and 3 also show the inlet 21A constructed as a separate item from the collar 22.

In Figure 4 a construction is shown which provides for two stage lift of the valve member. A first spring abutment 33 corresponding to the abutment 23 is provided and this is engaged by a first spring 34 the opposite end of which engages a support plate 35. A second spring abutment 36 is provided and this has a peripheral flange 37 which engages the side of the support plate remote from the spring 34 under the action of a further spring 38. The spring abutment 36 is positioned to be engaged by the spring abutment 33 after a pre-determined movement of the valve member and the spring abutment 36 is allowed limited movement against the action of the spring 38 before it engages a stop surface 39 defined by the cap 40. The initial movement of the valve member is therefore against the action of the spring 34 until the abutment 33 engages the abutment 36. Only when the fuel pressure in the chamber 17 has risen to a higher value can the valve member move further against the action of both springs.

In the various constructions described it is necessary to prevent fuel at high pressure flowing between the case 14 and 14A and the tubular member 15 and the bush 16. It is therefore necessary to ensure that the presented surfaces of those components are secured together using the adhesive ot the weld or braze. It is also necessary to prevent fuel leakage from the joint between the nozzle tip 10 and the member 15.

Claims

1 A fuel injection nozzle for supplying fuel to an internal combustion engine the nozzle being of the kind comprising an elongated tubular body having a nozzle tip secured to one end thereof, a seating formed in the nozzle tip and surrounding an outlet opening in the tip, an axially movable valve member located with a clearance within the body and shaped at one end for co-operation with the seating to prevent flow of fuel along the clearance and through the outlet opening, a guide bush secured in the body at a position removed from said seating, said guide bush defining a bore the wall of which guides the movement of the valve member, a fuel inlet communicating with said clearance, the valve member defining a surface against which the fuel under pressure in said clearance can act to lift the valve member from the seating against the action of resilient means acting on the valve member, the body comprising a thin wall outer tubular case, one end of said case being secured to said tip, a tubular member located in said case, one end of said tubular member abutting said tip, said bush being secured in said case in axial spaced relationship relative to the opposite end of the tubular member and a collar secured about the case, said collar defining said fuel inlet and having an axial length such that its opposite ends overlap said other end of the tubular member and said bush respectively.

2 A nozzle according to Claim 1 including means for preventing fuel flow between the case and the tubular member and between the tubular member and the tip.

3 A fuel injection nozzle for supplying fuel to an internal combustion engine substantially as hereinbefore described with reference to the accompanying drawings.