GB2232202A

GB2232202A - C.i. engine fuel injector

Info

Publication number: GB2232202A
Application number: GB8912648A
Authority: GB
Inventors: Graham Rhys Lewis
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1989-06-02
Filing date: 1989-06-02
Publication date: 1990-12-05
Also published as: GB8912648D0

Abstract

One of the springs 20, 29 acts to urge the valve member 15 into engagement with the seating 14 and the other acts to oppose the movement of the valve member away from the seating after the valve member has been lifted a predetermined amount from the seating. <IMAGE>

Description

FUEL INJECTION NOZZLE This invention related to a fuel injection nozzle for supplying fuel to a compression engine.

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 sectional side elevation of the nozzle.

and Figure 2 is a side view showing part of a modified form of the nozzle.

Referring to Figure 1 of the drawings there is provided an elongated hollow body 10 which conveniently is formed in two parts, the one part being a tubular member 11 and the other part being a nozzle head 12. The nozzle head is secured within the tubular member and has an enlargement 13 which defines a step against which the tubular member is located. The nozzle head defines a blind bore at the blind end of which is formed a seating 14 of frusto conical form leading in a well known manner, into a sac volume from which extends an outlet orifice.

The nozzle head is formed from a wear resisting material whereas the tubular member 11 can be formed from a relatively cheap material, the tubular member and the nozzle head being secured together in any convenient manner such as for example, by electron beam welding, the usual form of cap nut or by rolling a portion of the tubular member around a step defined on the nozzle head.

Extending within the tubular member and the nozzle head is a valve member 15. The valve member is shaped for engagement with the seating 14 and the portion thereof which lies within the nozzle head does so with clearance. The intermediate portion of the valve member which lies within the tubular member is of reduced member and the portion of the valve member remote from the seating is slidable located within a bore 16 formed in a part 17 which is secured within the tubular member.

The valve member conveniently adjacent the end of the nozzle head remote from the seating, is provided with an enlargement 18 against which is located a plate 19 forming a spring abutment for a coiled compression spring 20 which is accommodated within the space defined between the intermediate portion of the valve member and the wall of the tubular member 11. The spring 20 at one end engages the plate 19 and at its opposite end engages the part 17. The spring biases the valve member into contact with the seating.

Communicating with the space within the tubular member occupied by the spring is a fuel inlet 24 and in use when fuel under pressure is supplied to the inlet the fuel pressure is applied to the valve member to lift same against the action of the spring, from the seating. Fuel can then flow through the aforesaid space, and clearance between the valve member and the nozzle head, and through the sac volume to the outlet orifce. When the pressure of fuel at the inlet decreases, the valve member is returned to the closed position by the action of the spring 20.

The part 17 is secured within the tubular member and may be so secured after adjustment of the preload of the spring 20, by welding the part to the tubular member.

Alternatively, a threaded connection can be used between the tubular member and the part 17 and a shoulder provided on the part. In this case a shim would be interposed between the spring and the part to allow adjustment by selection of the thickness of the shim, of the force exerted by the spring.

In order to provide two stages of lift of the valve member 15 from the seating 14 the valve member has an extension 25 which extends from the bore 16 in the member 17. The extension 25 extends into an opening formed in the face wall of a hollow insert 27 which is secured within an extended portion 28 of the tubular member 11.

Within the insert there is located a further coiled compression spring 29 which at its end adjacent the base wall engages a plate 30 and at its other end engages a tubular abutment 31 which is adjustably mounted in the insert. The abutment carries an elongated stop member 32 extending within the spring 29.

The initial movement of the valve member under the action of the fuel under pressure supplied to the inlet 24 is determined by the clearance between the extension 25 and the plate 30. When in use and this clearance has been taken up, fuel will flow through the outlet orifice at a restricted rate. As the pressure of fuel at the inlet increases continued movement of the valve member will take place against the action of both springs until the movement of the valve member is arrested by engagement of the plate 30 with the stop member.

In the example described the nozzle opening pressure is determined by the force exerted by the spring 20.

In the alternative arrangement shown in Figure Zthe roles of the springs are reversed. In this case the spring which determines the nozzle opening pressure, is located in the space occupied by the spring 29 of Figure 1. The extension 25 therefore is in engagement with the plate 30 and the latter is clear of the base wall of the hollow insert 27. The spring 33 which is located in the space occupied by the spring 20 of Figure 1 bears against the abutment plate 19 but in the closed position of the valve member the plate rests against the end of the nozzle head 12 and a gap exists between the plate 19 and a step 34 of the valve member. It is this gap which determines the initial movement of the valve member when fuel under pressure is supplied to the inlet.

Claims

1. A fuel injection nozzle for supplying fuel to a compression ignition engine comprising a tubular nozzle body, a seating defined at one end of the body, a bearing part secured in the body, a valve member slidable in the bearing part and shaped to engage the seating, a fuel inlet to an annular space defined between the bearing part and the seating, a first spring located in said annular space and a second spring located in a chamber located on the remote side of the bearing part from said seating, one of said springs acting on the valve member to urge it into engagement with the seating and the other spring resisting the movement of the valve member away from the seating after the valve member has been lifted away from the seating by a predetermined amount.

2. A nozzle according to Claim 1 in which said one spring is defined by said first spring, one end of the first spring engaging said bearing part and the other end of the first spring engaging a plate which is located against a step defined on the valve member.

3. A nozzle according to Claim 2 in which the second spring engages a further plate positioned to be engaged by said valve member after the latter has moved said predetermined amount away from the seating.

4. A nozzle according to Claim 1 in which said one spring is defined by said second spring, the second spring acting on a portion of said valve member which extends through said bearing part, the first spring having one end engaging said bearing part and the other end engaging a further plate which is engaged by a step on the valve member often the latter be moved away from the seating by said predetermined amount.

5. A nozzle according to any one of the preceding Claims including a stop member extending within said chamber and acting to limit the total movement of the valve member away from the seating.

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

7. A fuel injection nozzle for supplying fuel to a compression ignition engine comprising the combination and arrangement of parts substantially as described with reference to Figure 1 as modified by Figure 2 of the accompanying drawings.