GB2240587A

GB2240587A - I.c. engine fuel injection nozzle

Info

Publication number: GB2240587A
Application number: GB9002448A
Authority: GB
Inventors: John William Stevens
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1990-02-03
Filing date: 1990-02-03
Publication date: 1991-08-07
Also published as: GB9002448D0

Abstract

The valve member 17 passes through a flanged guide bush 33 which is allowed limited lateral movement in the body. When the alignment of the valve member is correct the flange 34 of the guide bush is clamped to the adjacent end of the body to achieve a seal. Fuel pressure acting on an inner bush 35 may assist initial valve opening. <IMAGE>

Description

FUEL INJECTION NOZZLE This invention relates to a fuel injection nozzle for supplying fuel to a compression ignition engine and comprising an elongated nozzle body, a bore defined in the body, a seating defined at one end of the bore, a valve member located in the bore and shaped at one end for cooperation with the seating, a fuel inlet communicating with the bore, resilient means biasing the valve member into contact with the seating, the valve member being movable away from the seating to permit flow of fuel from the bore through an outlet, a bush mounted in the body and through which the other end of the valve member passes, the bush acting to guide the movement of the valve member and a guide collar formed on the valve member intermediate its ends, the guide collar cooperating with the wall of the bore.

With such an arrangement it is necessary to ensure that in the closed position of the valve member the engagement of the valve member with the seating is fuel tight otherwise fuel will dribble from the outlet. It is therefore necessary to ensure that the aforesaid bush is correctly positioned in the body during assembly of the nozzle. In GB 1019011 there is described an injection nozzle in which the bush is mounted in loose screw thread relationship within the nozzle body with the clearance between the threads being filled during assembly, with a hardenable material. When hardened the material secures and locates the bush and prior to hardening the valve member is utilised to locate the bush. The hardening process takes place with the valve member in position and in the example the hardening is accomplished by the application of heat.The provision of the screw threads involves considerable expense and the insertion of the hardenable material has to be carried out with care.

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

According to the invention in a nozzle of the kind specified the bush is provided with a flange and the main portion of the bush is allowed limited lateral movement within the body, the nozzle including means for clamping the bush in the body so that the flange of the bush forms a seal with the end of the body.

Examples of fuel injection nozzle 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 and Figure 2 is a similar view of another example.

Referring to Figure 1 of the drawings the nozzle comprises a multi-part body 10 comprising a main cylindrical portion 11 within one end of which is located an insert 12 which extends from the cylindrical portion 11. The body also includes a mounting 13 which extends about the cylindrical portion 11 and is secured thereto in any convenient manner such as by brazing, adhesive or by virtue of an interference fit. The mounting 13 defines a hollow cylindrical boss 14 which is formed with a peripheral screw thread.

Extending within the portion 11 and the insert 12 is a bore 15 and communicating with the bore is a fuel inlet 16 which in use is connected to the outlet of a fuel injection pump.

There is defined in the portion of the bore 15 extending within the insert, a seating 18. Located within the bore is a valve member 17 which is shaped at one end for cooperation with the seating. In the closed position of the valve member flow of fuel from the inlet 16 through an outlet orifice 19 is prevented.

The valve member 17 extends out of the bore 15 and the extended portion 20 of the valve member is of enlarged diameter and is slidably located within a guide bush 21 having a flange 22 which overlies the end of the boss 14. The diameter of the main portion of the guide bush 21 is slightly smaller than the internal diameter of the boss.

The valve member is also guided for movement intermediate its ends by the provision of a fluted collar 23 which is in slidable engagement with a portion of the wall of the bore lying in the insert 12.

Engaged with the boss 14 is a tubular member 25 in the internal surface of which there is defined a step 26 and located against the step is a thrust plate 27 engageable with the flanged end of the bush 21. The thrust plate is provided with a central aperture through which extends into contact with the portion 20 of the valve member, a spring abutment 28 against which is located one end of a coiled compression spring 29. The other end of the spring engages an adjuster 30 which is adjustably mounted in the tubular member 25 and the adjuster carries a stop member 31 which extends within the spring 29 and is engageable by the spring abutment 28 to limit the extent of movement of the valve member in the use of the nozzle.

In use, when fuel under pressure is admitted to the bore 15, the fuel pressure will act upon the valve member to move the valve member against the action of the spring 29 and when the valve member is lifted from the seating 18 fuel will flow through the outlet orifice 19.

As previously stated the extent of movement of the valve member away from the seating is limited by the engagement of the spring abutment 28 with the stop 31. The valve member is guided at two spaced positions and in the closed position of the valve member it is essential that it forms a fuel tight seal with the seating. In order to accommodate any misalignment the bush can move laterally a limited extent within the boss 14 and therefore during assembly of the nozzle the valve member is inserted into position and engaged with the seating following which the tubular member is tightened on the boss. The clamping force which is generated, urges the thrust plate 27 against the flanged end of the bush and the flange of the bush is urged against the end wall of the boss 14. A fuel tight seal is obtained, this being facilitated by the provision of a soft metal washer 32.The alignment of the bush is therefore readily achieved during assembly of the nozzle and following the tightening of the tubular member the adjuster 30 can be adjusted to set the nozzle opening pressure and the stop member 31 set to determine the maximum lift of the valve member.

A modification of the nozzle is seen in Figure 2 and in this Figure it will be seen that the guide bush is formed in two parts, the parts comprising an outer bush 33 having a flange 34 and an inner bush 35 also having a flange 36 which is accommodated within an enlarged portion of the bore in the bush 33. As in the example of Figure 1, the bush 33 is allowed limited lateral movement in the boss 14 prior to tightening the tubular member 25.

The flange of the bush 35 is engageable with the spring abutment 28 but its extent of movement is limited by its abutment with the thrust plate 27. In operation, when fuel under pressure is supplied to the bore 15 the fuel pressure acts upon the valve member 17 and also upon the end surface of the bush 35. The fuel pressure acting on the bush 35 will therefore assist the movement of the valve member towards the open position but since the movement of the bush 35 is limited, the initial movement of the valve member will also be limited. The limited extent of movement of the valve member permits fuel flow to the associated engine at a restricted rate but as the fuel pressure at the inlet increases, the valve member will eventually move its maximum extent against the action of the spring so that the fuel flow to the associated engine is at a substantially unrestricted rate. The initial movement of the valve member is critical and this movement can be adjusted by controlled tightening of the tubular member 25 so as to deform the washer 32. As in the example of Figure 1, the bush 33 is aligned by the valve member when the latter is in contact with the seating, prior to tightening the tubular member.

By the arrangement described a simple method of achieving correct alignment of the guide bush is obtained.

Claims

1. A fuel injection nozzle for supplying fuel to a compression ignition engine comprising an elongated nozzle body, a bore defined in the body, a seating defined at one end of the bore, a valve member located in the bore and shaped at one end for cooperation with the seating, a fuel inlet communicating with the bore, resilient means biasing the valve member into contact with the seating, the valve member being movable away from the seating to permit flow of fuel from the bore through an outlet, a bush mounted in the body and through which the other end of the valve member passes, the bush acting to guide the movement of the valve member, a guide collar formed on the valve member intermediate its ends, the guide collar cooperating with the wall of the bore, a flange formed on the bush, the main portion of the bush being allowed limited lateral movement within the body, the nozzle including means for clamping the bush in the body so that the flange of the bush forms a seal with the end of the body.

2. A nozzle according to Claim 1 in which said clamping means includes a tubular member in screw thread engagement about said end of the body, the tubular member defining an internal step against which is located a thrust plate engagable with the flange of the bush.

3. A fuel injection nozzle for supplying fuel to a compression ignition engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

4. A fuel injection nozzle for supplying fuel to a compression ignition engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.