GB2141173A

GB2141173A - I. C. Engine fuel injection nozzle

Info

Publication number: GB2141173A
Application number: GB08410701A
Authority: GB
Inventors: Peter Howes
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1983-06-08
Filing date: 1984-04-26
Publication date: 1984-12-12
Also published as: GB8410701D0; GB2141173B

Abstract

A valve member 16 has a head 15 biased into contact with a seating 14 by a coiled spring 20 and fuel under pressure applied to the valve member lifts the head from the seating to allow fuel flow through an outlet 17. The valve member has a spring retainer 21 connected to it and which forms a piston slidable in a skirt member 25 which forms a cylinder into and out of which fuel can flow through a port 32. The port is positioned to be progressively covered by the retainer or a valve stem enlargement (Fig. 2) to form a hydraulic spring inside the skirt member which assists the action of the coiled spring 20, as the valve head is lifted from the seating. <IMAGE>

Description

SPECIFICATION Fuel injection nozzles This invention relates to fuel injection nozzles through which fuel can be supplied to a combustion chamber of an internal combustion engine, the nozzle being of the so-called outwardly opening type and comprising a valve member slidable in a bore, the valve member having a head shaped to co-operate with a seating and resilient means biasing the valve member to a closed position in which the head is in sealing engagement with the seating and in which flow of fuel from an inlet to an outlet is prevented.

The form of fuel spray required to be produced by a fuel injection nozzle depends on the type of combustion chamber and in one example the injection nozzle is required to supply a low energy spray during the initial delivery of fuel but finishing with a high energy spray. The energy of the fuel spray is dependent upon the pressure drop across the orifice which produces the spray and forms the outlet.

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

According to the invention a fuel injection nozzle of the kind specified comprises means defining a piston slidable within a cylinder, a port through which fuel can flow into and out of said cylinder, said port in use being progressively closed as the valve head lifts away from the seating, the fuel in said cylinder forming a liquid spring acting to assist the action of said resilient means.

Two examples of fuel injection nozzles in accordance with the invention will now be described with reference to the accompanying drawings in which: Figures 1 and 2 show the two nozzles respectively in sectional side elevation.

Referring to Fig. 1 of the drawings the nozzle is generally indicated at 10 and comprises a valve assembly generally indicated at 11. The valve assembly comprises a flanged body 1 2 in which is defined a bore 1 3. The bore 1 3 has an enlarged portion at the narrower end of the body, the enlarged portion defining a seating 1 4 of truncated conical form with which co-operates a valve head 1 5 which is carried upon a stem 16, the stem and the valve head forming a valve member.

The valve head has an outer cylindrical portion which defines with the enlarged end portion of the bore an annular outlet 1 7 through which fuel can flow. The valve head has a tapered portion so that as the head emerges from the enlarged end of the bore the area of the annular outlet increases.

The main portion of the stem 1 6 is smaller than the bore but it is provided with an intermediate enlargement 1 8 to guide the movement of the stem. The stem extends beyond the end of the body and located about the stem is a spring abutment 1 9 between a step defined on which and the flange of the body 1 2 is a coiled compression spring 20.

The abutment 1 9 is. retained in position on the stem by means of a retainer 21 which is itself held in position by a fastening 22. In the closed position of the valve member as shown, a clearance exists between the adjacent ends of the abutment 1 9 and the body 1 2 and this clearnace diminishes as the valve member moves to the open position, movement of the valve member being halted by the contact of the abutment with the body.

The valve assembly is located within a hollow housing 23, the reduced end portion of the body 1 2 extending through an aperture in the base wall of the housing. The housing is closed by a closure member 24 which is in screw thread engagement with the housing and intermediate the closure member 24 and the flange of the body is a hollow skirt member 25. The portion of the skirt member 25 adjacent the closure member 24 is of right cylindrical form and constitutes a cylinder the piston of which is constituted by the retainer member 21.

The closure member 24 defines a fuel inlet 26 which is connected in use to an injection pump generally indicated at 27 and the fuel inlet by way of a passage 28, communicates with the space defined on the side of the retainer member remote from the spring. In addition, the passage 28 communicates by way of a radial passage or passages 29, with an annular space 30 defined between the skirt member 25 and the interior surface of the housing. The body 1 2 is provided with a plurality of ports 31 which connect the space 30 with the annular space intermediate the enlargement 1 8 and the head 1 5 and defined between the bore 1 3 and the reduced portion of the stem 16.In addition, the skirt portion 25 is provided with ports 32 which connect the space 30 with the chamber or cylinder disposed between the retainer member 21 and the flange of the body 1 2. The ports 32 are so positioned that they will be progressively covered by the retainer member 21 as the valve head lifts from the seating.

In operation, when fuel under pressure is supplied by the injection pump 27 the fuel pressure acting on the valve assembly will move the valve member against the action of the spring 20 and fuel will flow through the ports 31 from the space 30 and through the outlet 1 7. The effective area over which the pressure acts is substantially equal to the area of the valve head 1 5. During the initial stages of delivery of fuel by the pump 27 the fuel pressure will be comparatively low so that the fuel spray which is generated at the outlet 1 7 will have a comparatively low energy. As the pressure continues to increase, the valve member will move further against the action of the spring 20 until the ports 32 are covered.When this occurs the fuel contained in the space which is bounded by the retainer member 21, the flange of the body 12 and the skirt member 25 will act as an hydraulic spring to assist the coiled compression spring 20 in resisting movement of the valve member. The pressure of fuel supplied by the injection pump will tend to increase but owing to the action of the fluid spring, the additional movement of the valve member will be comparatively small. The pressure drop across the outlet will therefore increase and the resulting spray will have a higher energy.

In the arrangement which is shown in Fig.

2, the ports 32 are omitted but their function is taken over by ports 33 which are formed in the body 1 2 and communicate with the annular clearance defined between the stem 1 6 of the valve member and the bore 1 3. In this example the enlargement 1 8 on the stem of the valve member acts to close the ports 33 as the valve head is lifted from the seating.

When the ports 33 are closed the fuel in the aforesaid space will act as an hydraulic spring and will assist the action of the coiled compression spring.

Claims

1. A fuel injection nozzle through which fuel can be supplied to a combustion chamber of an internal combustion engine, the nozzle being of the so-called outwardly opening type and comprising a valve member slidable in a bore, the valve member having a head shaped to co-operate with a seating, resilient means biasing the valve member to a closed position in which the head is in sealing engagement with the seating and in which the flow of fuel from an inlet to an outlet is prevented, means defining a piston slidable within a cylinder, a port through which fuel can flow into and out of said cylinder, said port in use being progressively closed as the valve head lifts away from the seating, the fuel in said cylinder forming a liquid spring acting to assist the action of said resilient means.

2. A nozzle according to Claim 1 in which the means defining the piston comprises a retainer which is mounted upon a stem of the valve member.

3. A nozzle according to Claim 2 in which said retainer is slidable within one end of a hollow skirt member, said skirt member at its other end engaging a flange formed on a valve body in which the valve member is mounted, the retainer member engaging an abutment for one of a coiled compression spring forming said resilient means, the other end of the spring engaging said flange.

4. A nozzle according to Claim 3 in which said port is formed in said skirt member at a position to be progressively covered by said retainer member as the valve head is lifted from the seating.

5. A nozzle according to Claim 3 in which said port is formed in said valve body and opens into a bore in the valve body in which the stem of the valve member is located, said stem having an enlargement which co-operates with the wall of the bore to guide the stem, said port being progressively covered by said enlargement as the valve head is lifted from the seating.

6. A fuel injection nozzle through which fuel can be supplied to a combustion chamber of an internal combustion engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawings.

7. A fuel injection nozzle through which fuel can be supplied to a combustion chamber of an internal combustion engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Fig. 2 of the accompanying drawings.