Direct injection of fuels in internal combustion engines

Details Direct injection of fuels in internal combustion engines Direct injection of fuels in internal combustion engines

2002-05-28

2004-06-29

Solis, Erick (Department: 3747)

Internal-combustion engines

Combustion chamber means having fuel injection only

Combination igniting means and injector

C123S305000

Reexamination Certificate

active

06755175

ABSTRACT:

TECHNICAL FIELD
This invention relates to direct injection of fuels in internal combustion engines. More particularly, the invention relates to an apparatus and method for direct injection of fuels into spark-ignition internal combustion engines. The invention also relates to a combined fuel injection and ignition means for spark-ignition internal combustion engines.
BACKGROUND OF THE INVENTION
For a spark-ignition internal combustion engine having fuel directly injected into a combustion chamber, it is highly desirable to introduce the fuel into the combustion chamber in a form conducive to effect reliable and repeatable ignition. Typically, this requires that fuel droplets present at a spark gap in the combustion chamber are of a suitable size to provide favourable ignition conditions, and to avoid both quenching of either one or both of the electrodes which define the spark gap and insulation of either one or both of the electrodes by the fuel. This requirement can in certain applications be difficult to achieve, particularly where the fuel injector is combined into a single assembly with the ignition means.
Examples of arrangements involving combined fuel injection and ignition means are disclosed in U.S. Pat. No. 4,967,708 (Under et al), EP 0 632 198 (Suzuki), U.S. Pat. No. 5,497,744 (Nagaosa et al), and U.S. Pat. No. 5,730,100 (Bergsten).
Bergsten discloses an injector arrangement for injection of fuel and ignition of the resultant air-fuel mixture in the combustion chamber of a reciprocating-piston engine. The injector arrangement includes a valve housing, a valve needle and a valve element, all of which are made of electrically conductive material and which together form an electrode positioned centrally in the injector arrangement, so constituting a single-pole ignition plug. The second electrode is operatively attached to the piston or to the cylinder in which the piston reciprocates. With this arrangement, the injector delivers fuel into the combustion chamber, and co-operation between the electrode on the injector and the second electrode within the combustion chamber creates a spark gap at which an ignition spark can be established in timed sequence with operation of the engine. This arrangement enables fuel to be delivered into the combustion chamber as a single fluid in the form of a spray or cloud of fuel droplets, but not necessarily in a manner which regulates the dispersion and flow of fuel to the spark gap so as to facilitate a reliable ignition process and avoid quenching of the electrodes.
Further, due to physical limitations, it is often difficult if not impossible to arrange the spark gap of a suitable ignition means at the most optimum point within the combustion chamber. For example, in certain applications the optimum area for ignition may be ‘out of reach’ of a conventional ignition means. This may hence require the use of specially modified ignition means such as long reach spark plugs or unique orientations thereof within the cylinder head of an engine. In turn, this may result in increased cost and other engineering and durability issues which may be difficult to overcome.
It is against this background, and the problems and difficulties associated therewith, that the present invention has been developed. Specifically, it is an object of the present invention to provide a fuel delivery injector which delivers fuel to a spark gap in a manner which provides conditions conducive to effect reliable ignition.
SUMMARY OF THE INVENTION
The present invention provides a fuel delivery injector for a spark-ignition internal combustion engine, the fuel delivery injector comprising means defining a flow path for delivery of a fuel entrained in a gas to a combustion chamber of the engine, the flow path having a delivery port through which the fuel is delivered into the combustion chamber as a spray of fuel droplets and vapour, the delivery port being defined between a valve seat and a valve member movable with respect to the valve seat for opening and closing the delivery port, the delivery injector being configured to influence the trajectory of the fuel spray whereby smaller fuel droplets and vapour in the fuel spray are caused to flow towards a spark gap in close proximity to the downstream end of the delivery port and whereby larger fuel droplets are not so caused to flow towards the spark gap.
Preferably, the fuel delivery injector includes a flow control means disposed outwardly of the delivery port in the direction of issuance of the fuel spray, the flow control means being configured and positioned to influence the trajectory of the fuel spray whereby smaller fuel droplets and vapour in the fuel spray are caused to flow towards the spark gap in the vicinity of the control means.
With this arrangement, the spark gap is able to be located in the region downstream of the delivery port where the small fuel droplets and vapour are more prevalent, this area and such conditions being more favourable to reliable and repeatable ignition. In effect, the larger fuel droplets which are likely to inhibit the ignition process at the spark gap are separated from the smaller droplets in the gaseous stream, the larger droplets continuing to follow a trajectory established upon exit from the delivery port by virtue of their momentum.
Alternatively, or additionally, the flow control means may comprise or further comprise the delivery port.
Preferably, the flow control means comprises a flow control projection supported on the valve member and extending outwardly therefrom beyond the delivery port. The smaller droplets and vapour are guided by the profile of the projection in accordance with the Coanda Effect. That is, the small droplets and vapour are drawn inwards towards the surface of the projection such that a certain degree of ‘necking in’ of the fuel spray occurs. It should however be noted that, in certain applications, a similar effect may result even though there is no flow control projection provided downstream of the valve member. In such cases, it is believed that the small fuel droplets and vapour are drawn inwardly following their delivery into the combustion chamber due to the presence of a generally low pressure area immediately beneath the valve member of the fuel delivery injector.
The projection may, for example, have a profile as disclosed in U.S. Pat. No. 5,551,638, or U.S. Pat. No. 5,833,142, both of which have been assigned to the Applicant and the contents of which are incorporated herein by way of reference. The projection may be formed integrally with the valve member, or it may be detachable therefrom, such as for example, by way of a screw-threaded connection.
Where the injector forms part of a combined injection and ignition means, the control projection may define a first electrode which co-operates with a second electrode to define the spark gap. The first electrode defined by the control projection is preferably a primary electrode, in which case the second electrode defines a secondary electrode. The two electrodes can be so disposed relative to one another such that the spark gap defined therebetween can provide either a radial gap or an axial gap. If desired, there may be more than one said second electrode, in which case the second electrodes may conveniently be circumferentially spaced about the primary or central electrode defined by the control projection. In certain applications where a projection is not provided downstream of the valve member, or as an alternative arrangement where a control projection does exist, the valve member itself may be configured as the first electrode with the spark gap being provided between the valve member of the injector and the second electrode(s).
By having the spark gap defined by the projection or the valve member, the location of the spark gap within the region of small fuel droplets and vapour formed by the fuel delivery injector is effectively ensured. This is due to the effect of the delivery port and/or the flow control projection which facilitate the smaller fuel droplets and vapour in the

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