GB2207463A

GB2207463A - I.C. engine petrol injector

Info

Publication number: GB2207463A
Application number: GB08718260A
Authority: GB
Inventors: John Herbert Kenning
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1987-08-01
Filing date: 1987-08-01
Publication date: 1989-02-01
Also published as: GB8718260D0

Abstract

An orifice plate 14 on one surface defines an annular sealing 18 for engagement by a plate-like valve member (16, Fig 1) of magnetic material which an be lifted away from the seating by magnetic force against the action of a spring (27). Formed in the orifice plate is a chamber 32 from which extends a pair of outlet orifices 31. The injector therefore delivers two sprays of petrol and is particularly suited to supply petrol to an engine having two inlet valves per cylinder. <IMAGE>

Description

"PETROL INJECTOR" This invention relates to petrol injectors for delivering petrol to a spark ignition engine, the injectors being of the kind comprising a valve member formed from magnetic material and movable by magnetic forces away from a seating against the action of a spring, to allow flow of petrol to an outlet orifice in an orifice plate, the jet of petrol leaving the outlet orifice forming a spray and mixing with air flowing to the engine.

It is the usual practice to provide one injector per engine cylinder and whilst this is satisfactory for engines having one inlet valve per cylinder, problems can arise when the engine is provided with two inlet valves per cylinder. It is found that if a single injector per cylinder is used that under certain conditions of operation the level of noxious gases in the engine exhaust can rise to an unacceptable value.

One solution is to provide two injectors per engine cylinder. However, this doubles the number of injectors which need to be provided on the engine and this itself is undesirable. In addition however each injector will supply a smaller volume of fuel leading to problems when minimum fuel flow is required. It is known to provide injectors with more than one outlet orifice and British patent specification 858966 discloses an injector which is provided with three outlet orifices each of which is surrounded by a sealing lip for engagement by the valve member. With this construction there must be at least three outlet orifices so as to ensure that the valve member can seat properly and therefore this arrangement is not suitable for an injector where two outlet orifices are required.

An alternative is to provide the orifice plate with inner and outer annular sealing lips and to position the outlet orifices so that they extend from between the sealing lips. This construction is more difficult to make since it is absolutely necessary to ensure perfect sealing in the closed position of the valve member. Moreover, it is difficult to ensure that the flow paths for the fuel to the outlet orifices are identical.

The object of the present invention is to provide an injector of the kind specified having a pair of outlet orifices and suitable for supplying fuel to engines having two inlet valves per cylinder.

According to the invention an injector of the kind specified comprises a pair of outlet orifices extending from a chamber formed in the orifice plate, said chamber opening onto the side of the orifice plate and receiving fuel when the valve member is lifted from the seating.

An example of a petrol injector 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 injector, and Figure 2 is a view to an enlarged scale of part of the injector seen in Figure 1.

The injector to be described is intended to be fitted to an engine having two inlet valves per engine cylinder in which the air inlet passages within the cylinder head of the engine merge in the cylinder head of the engine or open separately onto an external surface of the engine against which the air inlet manifold of the engine is secured. In both cases the injector to be described will be mounted on the air inlet manifold at a position so that jets of fuel are directed down the individual passages preferably so that the jets impinge upon the respective inlet valves.

Referring now to the drawings the injector comprises a hollow body 10 which is formed from magnetic material and which has a narrower end portion 11. Within the body there is defined an inwardly extending flange 12 and located against the flange is an annular spacer member 13 which is engaged by an orifice plate 14 held in position by a tubular outlet member 15 which is located within the portion 11 of the body. Slidable within the spacer member 13 is a plate-like valve member 16 which is provided with a central depression in its face remote from the orifice plate 14 and it is also provided with a plurality of openings 17 which extend between the opposite sides of the valve member.

As shown more clearly in Figure 2, the orifice plate 14 is provided with an inner annular sealing lip 18 which is engageable by the valve member under the action of a spring to be described. The orifice plate also defines an outer annular lip 19 which serves to stablise the valve member and to minimise the risk of tilting thereof.

The injector also includes a core member 20 which is of tubular form having intermediate its ends, a flange 21 which locates in the wider end of the body 10. The core member extends towards the valve member and is provided with a central passage 22 through which petrol can flow. Surrounding the portion of the core member which lies within the body is a former 23 upon which is wound an energising winding 24 the electrical connections to which are indicated at 25, being located within a moulding 26 which is secured about the portion of the core member which extends from the body.

The aforementioned depression in the valve member serves to locate one end of a coiled compression spring 27 the other end of which is engaged by a plug 28 which is an interference fit within the bore 22. The plug is provided with a central drilling to permit flow of fuel. The core member is also provided with a pair of outwardly extending drillings 29 which extend from the bore 22 into a space 30 adjacent the valve member 16.

In the closed position of the valve member as shown in Figure 1, the valve member engages the sealing lip 18 and there exists a small clearance between the end of the core member and the valve member and between the flange 12 and the valve member. When electric current is supplied to the winding 24, the core member and the aforementioned flange assume opposite magnetic polarity and the valve member is lifted away from the orifice plate 14 by the magnetic forces. Such movement is of course against the action of the spring 27 and when the flow of electric current ceases, the valve member is returned into sealing contact with the lip 18.

As shown in Figure 2, the orifice plate 14 is provided with a pair of outlet orifices 31 which open onto the face of the orifice plate remote from the valve member. As will be seen from Figure 2 the axes of the orifices are inclined relative to each other, in the particular example, at 200. The orifice plate has formed within it a chamber 32 which opens onto the face of the orifice plate presented to the valve member and the outlet orifices 31 extend from the chamber 32 so that when in use the valve member is lifted from the lip 18 fuel will flow into the chamber 32 and then through the outlet orifices 31 to form jets of fuel directed towards the respective inlet valves.

The formation of the chamber 32 together with the outlet orifices 31 has to be carried out with great care to ensure that equal flows of fuel occur through the orifices. In the particular example the entrance from the chamber to each orifice is of frusto-conical form and in the particular example, the cone angle is approximately 400. It is convenient to form the chamber 32 at the same time as the frusto-conical entrance portions to the orifices so that the chamber is formed by the merging of two conical sections.

Forming the chamber in this way produces a sharp edge 33 which ensures smooth flow of fuel.

The invention is also applicable to the form of injector in which the valve member co-operates with a seating formed on a member which is separate from the orifice plate.

Claims

1. A petrol injector for delivering petrol to a spark ignition engine, the injector comprising an orifice plate, a seating, a valve member formed from magnetic material, resilient means biasing the valve member into engagement with the seating, said valve member being lifted away from the seating by magnetic force when it is required to supply petrol to the associated engine, a chamber defined in the orifice plate and which is supplied with petrol under pressure when the valve member is lifted from the seating and a pair of outlet orifices formed in the orifice plate, said outlet orifices extending from the chamber.

2. An injector according to Claim 1 in which said valve member is of plate-like form and the seating is formed on the surface of the orifice plate presented to the valve member.

3. An injector according to Claim 1 in which each orifice has an entrance from the chamber of frusto-conical form.

4. An injector according to Claim 3 in which the chamber is formed by the merging of the fursto-conical entrances to the orifices.

5. A petrol injector for delivering petrol to a spark ignition engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings