Background to the Invention With direct fuel injection into a combustion chamber of an internal combustion engine there are problems associated with delivering an adequately atomised charge to be compressed and then combusted.

Valve timing which allows ingress of the injector charge is required to be matched with the injector pulse and piston motion.

Currently proposed direct injectors fire a fuel charge into the intake tract or manifold upstream of or adjacent a valve, such as a poppet valve, controlled by a cam or engine management system. The valve not only opens and closes the combustion chamber at appropriate times but also seals off the air intake tract and injector nozzle from the high temperature and pressure of combustion as would occur if the injector nozzle were in fluid communication with the combustion chamber at all times.

Summary of the Invention The present invention provides a poppet valve for controlling direct injection of a fuel charge into a combustion chamber wherein a face of the valve is, in use, exposed to combustion products within the combustion chamber, said poppet valve including an elongate valve stem slidably movable within a bore of a valve body between a seating position wherein the bore of the valve is closed and an open position wherein the valve stem is unseated, biasing means biasing the valve to its closed position, a longitudinal bore within the valve stem for directing fluid flow therealong from a fuel injector adapted to be mounted to the valve distal the valve face, a plurality of transverse bores radiating from the longitudinal bore and opening into a radial space between the valve stem and the valve body, said space being formed as a stepwise expansion zone in the valve body to a location

at least adjacent the seating surfaces between the valve stem and the valve body, and further wherein there is at least one stepwise expansion within the longitudinal bore in the direction toward the valve face.

The operation of a valve in accord with the present invention is, because of its direct exposure to the combustion chamber, controlled in its opening and closing by the pressure within that chamber and within the injector as balanced against the magnitude of the biasing force. Preferably the biasing force is extremely low, say, of the order of 5 psi so as to provide a positive seating between the valve stem and body under ambient conditions.

The stepwise expansion zones within the valve stem bore and the valve body function to reduce film adherence of the fuel charge from the injector as it travels through the valve to the combustion chamber and to maintain the atomization quality of that charge.

A direct injection valve of the present invention has applicability to 2-and 4-stroke cycle engines. It is also particularly well suited to our existing injector disclosed in United States Patent 5735468, the contents of which are incorporated herein by reference. In use, the induced air charge necessary for complete combustion of the fuel charge enters the combustion chamber/cylinder through valving separate from valving of the present invention.

Brief Description of the Drawings The present invention will now be described by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a longitudinal cross-sectional view of an embodiment of the present invention in situ; Figure 2 is a longitudinal cross-sectional view of the Figure 1 embodiment of the present invention in situ in combination with a pulsed fuel injector of US 5735468 in the form shown in Figure 4 of Australian provisional patent application PP 8022/99;

Figure3A is a cutaway view of the layout of Figure 2; Figure3B is a magnified view of"Detail A"of Figure 3A; and Figure3C is a magnified view of"Detail B"of Figure 3A Best Modes Figure 1 shows a fuel injector 10 feeding a valve 11 of one embodiment of the present invention. Valve 11 comprises extended valve body 12 connected by threads 13 to the outlet zone 14 of injector 10 which leads to inlet 15 of valve body 12. Valve guide 16 within extended valve body 12 comprises a contracting inlet 17 to bore 18 within double step valve stem 19 fitted within valve stem 20. Valve stem 20 is connected to valve guide 16 via pin 21. Between valve guide 16 and valve body 22 is positioned coil spring 23 which biases valve stem 20 so that spring 23 moves to seat valve stem 20 against valve body 22.

As a fuel charge leaves injector 10 it passes through outlet 14 to inlet 15 and into bore 18.

A first minor expansion step 24 between valve guide 16 and stem 19 leads into bore 18.

A second larger step 25 is formed between stems 19 and 20 is followed by transverse bores 26 into radial space 27 between body 22 and stem 20.

Five expansion steps 28 are formed in valve body 22 immediately upstream of valve seating surfaces 29,30 between body 22 and stem 20, respectively. The bias force of spring 23 can be, say, of the order of 5 psi to provide sufficient force to seat stem 20 against body 22 at engine"off"conditions. The effect of this low bias force is that positive pressure applied from the injector side or negative pressure from the combustion chamber side readily opens valve 11 to allow ingress of a fuel charge into combustion chamber 31.

In Figure 2 combustion chamber 31 contains a spark plug 32 while injector 40 mounted atop valve 11 is a double solenoid pulse injector as described in International patent application PCT/AU00/0001, the contents of which are incorporated herein by reference, with solenoid 41 controlling fuel flow to the injector while solenoid 42 is operable to feed pulses of air to atomise each fuel charge fed to valve 11.

For Figure 3 like parts are referenced by the same numerals as shown in Figures 1 and 2, as appropriate.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing form the spirit or scope of the invention as broadly described. The present invention embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.