GB2203795A

GB2203795A - I.C. engine fuel injection nozzle

Info

Publication number: GB2203795A
Application number: GB08709713A
Authority: GB
Inventors: David John Gaskell
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1987-04-24
Filing date: 1987-04-24
Publication date: 1988-10-26
Also published as: GB8709713D0

Abstract

A valve 30 is opened by a pin 31 after a predetermined lift of the valve member 21 away from the seating 14 to allow fuel under pressure from the inlet to act on an area of the valve member in the chamber 28 to assist the action of the spring 27. This results in at least partial closure of the valve member which is then moved away from the seating as the fuel pressure at the inlet continues to increase. The seat (32, Fig. 2) of the valve 30 may be adjustable to vary the predetermined valve member lift. <IMAGE>

Description

"FUEL INJECTION NOZZLE" This invention relates to a fuel injection nozzle for supplying fuel to a compression ignition engine, the nozzle being of the so-called inwardly opening type and comprising a nozzle body in which is defined a bore, a seating at one end of the bore, a valve member slidable in the bore and shaped at one end for co-operation with the seating to control fuel flow from an inlet to an outlet which is disposed downstream of the seating, the valve member defining an area which is exposed to the fuel pressure at the inlet, the fuel pressure acting on said area causing the valve member to lift from the seating against the force exerted by a spring, when the pressure at the inlet attains a predetermined value.

In order to improve the operating characteristics of some compression ignition engines it is desirable to be able deliver a pilot quantity of fuel followed by the main quantity of fuel and the object of the present invention is to provide a fuel injection nozzle of the kind specified in a form in which this desideratum can be achieved.

According to the invention a fuel injection nozzle of the kind specified comprises valve means operable upon a predetermined movement of the valve member away from the seating to apply fluid under pressure to a further area of the valve member to assist the action of the spring thereby to temporarily close said valve member onto the seating, the valve member being reopened upon an increase of pressure at the inlet.

Two examples of fuel injection nozzle in accordance with the invention will now be described with reference to the accompanying drawings each of which shows a sectional side elevation of part of the nozzle. Referring to Figure 1 of the drawings the nozzle includes a stepped nozzle body 10 which in use, is secured as shown in Figure 2, to a nozzle holder 1l, the method of securement being by means of the well known cap nut.

Within the nozzle body there is formed a stepped bore which includes a guide portion 12 intermediate tbe ends of the bore. The bore further includes a reduced portion 13 which extends within the narrower portion of the nozzle body, to a seating 14 from downstream of which extend outlet orifices 15. Intermediate the portions 12 and 13 of the bore there is formed an enlargement 16 which is connected by means of a fuel inlet passage 17 and a passage in the holder 11, to a fuel inlet. The fuel inlet is connected in use to a fuel supply pump 18 which is operated in timed relationship with the associated engine.

Located within the bore is a valve member 19, the valve member having a narrower portion 20 which extends with clearance within the narrower portion of the bore and which at its end is shaped for co-operation with the seating 14. Adjacent the narrower portion 20 of the valve member is an enlarged portion 21 which is a sliding fit within the guide portion 12 of the bore At the end of the enlarged portion 21 of the valve member is a flange 22 which is accommodated within an enlarged portion 23 of the bore. Fixed within the enlarged portion 23 is a sleeve 24 within which is slidable a portion 25 of the valve member which extends in an extension 26, beyond the body and sleeve and mounts a spring abutment (not shown) against which bears a coiled compression spring 27. The spring 27 biases the valve member into contact with the seating 14.Moreover, a clearance exists between the flange 22 and the adjacent end of the sleeve 24 so as to form an annular chamber 28. The diameter of the portion 25 of the valve member is less than that of the enlarged portion 21.

Valve means 29 is provided to admit fuel under pressure from the fuel pump 18 to the chamber 28, the valve means comprising a spring loaded ball 30 which can be lifted from its seating by means of a pin 31 which is engageable by the flange 22 after the valve member has moved away from its seating by a predetermined amount.

In operation, when fuel under pressure is supplied by the pump 18 the fuel pressure acts upon an area of the valve member represented by the difference in the diameters of the enlarged portion 21 and the seat 14.

The fuel pressure acting upon this area generates a force acting to lift the valve member against the action of the spring 27 and when the force becomes sufficient the valve member will lift to allow fuel flow through the outlet orifices 15. As the valve member lifts, a position will be reached at which the flange engages the pin 31 to lift the ball 30 from its seating and when lifted fuel from the inlet will be admitted to the chamber 28. The fuel pressure in the chamber 28 acts upon an area of the valve member represented by the difference in the diameters of the portions 21 and 25, to produce a force acting on the valve which will assist the action of the spring so that the valve member will be returned at least towards and possibly into contact with its seating to restrict or to halt the supply of fuel through the orifices 15.As the pressure of fuel delivered by the pump 18 continues to increase, a pressure will be reached at which the valve member is again moved away from the seating to allow an increased or a further supply of fuel through the outlet orifices. When the flange of the valve member again contacts the pin 31, the fuel pressure in the chamber 28 will be raised again but it is anticipated that whilst there may be a tendency for the valve member to move once again towards the closed position, the rate of rise of fuel pressure will be such as to maintain the valve member clear of the seating thereby to allow continued flow to the associated engine until such time as the pressure of fuel delivered by the pump falls. When the pressure falls the valve member will return to the closed position and it is anticipated that leakage of fuel along the working clearance between the portion 25 of the valve member and the sleeve 24, will cause a reduction in the pressure within the chamber 28 before the next delivery of fuel by the pump.

The nozzle which is shown in Figure 2 is essentially the same as that shown in Figure 1, the exception being that the valve means is adjustable so that the position at which the valve member lifts the ball 30 from its seating can be adjusted. For this purpose the seating is defined in an insert 32 which is adjustably mounted within the nozzle body 10.

Claims

1. A fuel injection nozzle for supplying fuel to a compression ignition engine, the nozzle being of the inwardly opening type and comprising a nozzle body in which is defined a bore, a seating at one end of the bore, a valve member slidable in the bore and shaped at one end for co-operation with the seating to control fuel flow from an inlet to an outlet which is disposed downstream of the seating, the valve member defining an area which is exposed to the fuel pressure at the inlet, the fuel pressure acting on said area causing the valve member to lift from the seating against the force exerted by a spring, when the pressure at the inlet attains a predetermined value, and valve means operable upon a predetermined movement of the valve member away from the seating, to apply fluid under pressure to a further area of the valve member to assist the action of the spring thereby to move said valve member towards the seating, the valve member being moved away from the seating upon an increase of fuel pressure at said inlet.

2. A nozzle according to Claim 1 in which said further area of the valve member is defined by an annular step defined by an intermediate portion of the valve member which is slidable in the bore and a reduced portion of the valve member which is slidable in a sleeve mounted in the bore, the reduced portion of the valve member being disposed at the end of the intermediate portion remote from the seating.

3. A nozzle according to Claim 1 in which said step, the bore and the sleeve define a chamber to which fuel under pressure from the inlet is supplied by said valve means.

4. A nozzle according to Claim 1 in which said valve means comprises a spring loaded ball, and a seating for the ball, the ball being lifted from its seating to apply fluid under pressure to said further orifice, by means of a pin engageable by a part of the valve member.

5. A nozzle according to Claim 4 in which the seating for the ball is adjustably mounted in the nozzle body.

6. 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.

7. 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.