GB2223799A

GB2223799A - I.C. engine fuel injection nozzle

Info

Publication number: GB2223799A
Application number: GB8823847A
Authority: GB
Inventors: Buckley Paul
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: GB8823847D0

Abstract

An elongated hollow body 11 has a seating 14 at one end and a part 17 mounted in the other end. The part 17 defines a bore 16 which serves to guide the movement of an elongated valve member 15 which is shaped to cooperate with the seating 14 and which extends with clearance within the body. The valve member has an enlargement 18 against which bears a plate 19 engaged by one end of a coiled compression spring 20 the other end of which engages the part 17. A fuel inlet 23 is connected to the clearance and the end of the bore 16 remote from the seating defines a stop for the valve member (Fig. 4) or contains an adjustable stop (24, 25, Figs. 2 and 3) and is connected to a drain outlet. <IMAGE>

Description

FUEL INJECTION NOZZLES This invention relates to a fuel injection nozzle for supplying fuel to a compression ignition engine and of the kind comprising a valve member which is resiliently biased into contact with a seating to prevent flow of fuel through an outlet from an inlet, the valve member defining a surface against which fuel under pressure can act to lift the valve member from the seating thereby to allow fuel flow through the outlet.

A known form of such a nozzle has an elongated valve member located with clearance within an elongated body, the body defining at one end a frusto conical seating with the adjacent end of the valve member being shaped for co-operation with the seating. The valve member adjacent its end remote from the seating is slidably located in an extends through a guide bush. A spring abutment is engaged with the end of the valve member remote from the seating and a coiled compression spring has one end engaging the abutment, the spring being located within a chamber which in use is connected to a drain. The fuel inlet of the nozzle is connected to the clearance defined between the valve member and the body.The inlet can be in the form of a pipe union secured to the body directly or by way of a short length of pipe and in use the body extends within a bore in the cylinder head of an engine with the inlet being located outside the bore. Since the inlet must lie on the opposite side of the bush to the spring, the nozzle has a considerable length exterior of the bore.

The advantage of this type of injector is that its diameter is smaller than a conventional nozzle but there is a considerable length of injector projecting from the bore and this can cause problems when trying to accomodate the injector in the engine.

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

According to the invention a fuel injection nozzle of the kind specified comprises a hollow elongated body with the seating defined at one end of the body, an elongated valve member located with clearance within said body and shaped at one end for engagement with the seating, the other end portion of the valve member being slidable within and guided by the wall of a bore defined in a part secured relative to the other end of the body, a spring abutment carried by the valve member intermediate its ends, a coiled compression spring located about the valve member in the annular space defined between the valve member and the body, one end of said spring engaging said abutment and the other end of the spring being supported by said part and a fuel inlet connected to said space.

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 Figures 2, 3 and 4 show modifications to parts of the nozzle.

Referring to 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 to 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 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 diameter and the end portion of the valve member remote from the seating is slidably 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 accomodated 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 abutment 19 and at its opposite end engages the part 17. The spring biases the valve member into contact with the seating.

The bore 16 in the part 17 extends beyond the end of the tubular member and is connected to a laterally extending nipple 21 which in use is connected to a drain. Moreover, the part defines an inlet passage 22 which at one end communicates with the aforesaid space and at its other end it is shaped to define a fuel inlet 23 which in use is connected to the outlet of a fuel injection pump. The inlet in the particular example extends axially, however, if desired, and as shown in Figure 2, the inlet 23A may be laterally disposed with the end of the bore connected to an axial drain outlet. The inlet in this case can be formed in a lateral extension formed integrally with the part 17 or as shown, it can be a simple frusto conical recess in which the pipe which conveys fuel to the nozzle can be clamped. The recess can lead directly into the chamber containing the spring.

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 along the passage 22 through the aforesaid space and the clearance between the valve member and the nozzle head, through the sac volume to the outlet orifice. 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. It will be appreciated that where a threaded connection is used, some method has to be used which will ensure that the connection is a fuel tight connection. A suitable locking compound can be used for this purpose.

It is necessary to limit the extent of movement or lift of the valve member 15 against the action of the spring and thus can be achieved in a number of ways depending upon the configuration of the fuel inlet 23 and the drain connection. With the construction shown in the drawing, the movement of the valve.member can be arrested by engagement of the end of the piston portion of the valve member with the end surface of the bore 16. With this arrangement the end portion of the bore 16 as shown in Figure 4, must be slightly enlarged with the drain connection 21A extending from the enlarged portion of the bore. This arrangement does not however provide for adjustment of the lift once assembly of the nozzle has been effected. Adjustment can be provided as shown in Figure 3, by inclining the axis of the drain connection in the part 17 and locating therein an adjustable stop member 24 which extends into the bore 16 to be engaged by the end surface of the piston portion of the valve member. The stop member is provided with a channel to ensure that the fuel leaking past the piston portion of the valve member can escape.

In the case where the fuel inlet is laterally disposed as shown in Figure 2, and the drain outlet is axially disposed the latter can mount an adjustable stop member 25 which extends into the end of the bore 16. Again the stop member must be provided with a flow channel for fuel leaking past the piston portion of the valve member With the arrangement described the overall diameter of the injection nozzle will be slightly larger than in the form of nozzle described in the second paragraph of this specification, however, the overall length of the nozzle is considerably shorter than is the case with the known nozzle thereby facilitating the installation of the nozzle in an engine.

Claims

1. A fuel injection nozzle for supplying fuel to a compression ignition engine comprising a hollow elongated body having a seating defined at one end of the body, an elongated valve member located with clearance within the body and shaped at one end for engagement with the seating to prevent flow of fuel through an outlet, the other end portion of the valve member being slidable within and bering guided by the wall of a bore defined in a part secured relative to the other end of the body, a spring abutment carried by the valve member intermediate its ends, a coiled compression spring located about the valve member in the annular space defined between the valve member and the body, one end of said spring engaging said abutment and the other end of the spring being supported by said part and a fuel inlet connected to said space, said valve member defining a surface against which fuel under pressure can act to lift the valve member from the seating.

2. A nozzle according to Claim 1 in which said part defines a chamber into which the other end of the valve member extends, and a drain outlet from said chamber.

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.