GB2108581A - Fuel injection stratified charge internal combustion engine - Google Patents

Abstract

Charge stratification is provided by a swirl-forming valve shroud 23 and timed port fuel injection into the cylinder 12 during the latter portions of the piston intake stroke. Enriched fuel-air mixture is concentrated near the cylinder inlet end, adjacent the spark plug 26, while lean portions of the charge remain at the lower end of the cylinder 12 adjacent the piston 14. <IMAGE>

Description

SPECIFICATION Fuel injection stratified charge internal combustion engine This invention relates to piston type spark ignition internal combustion engines with cylinder charge stratification and more particularly to engines having fuel injection with means for creating stratification of the cylinder charge.

It is known in the art relating to spark ignition internal combustion engines that provision of a stratified charge wherein the mixture near the spark plug is richer than the average charge mixture permits operation of an engine with overall leaner mixtures offering relatively higher efficiency and lower exhaust emissions while retaining good ignition characteristics. Many methods of charge stratification have been proposed; however, all involve some degree of complication in engine design and/or control and limitations as to the engine operating characteristics which may be obtained.

The present invention provides a relatively simple but effective system and arrangement for achieving axial stratification of the intake charge in each cylinder of a piston type internal combustion engine. The system requires means for inducting an air charge into each cylinder in a swirling motion around the cylinder axis and means for providing timed fuel injection into the cylinder intake port so as to direct the fuel charge into the cylinder during the latter portion of the piston intake stroke. The swirling cylinder charge together with addition of the fuel late in the intake stroke provides axial stratification of the cylinder charge with enriched fuel-air mixture lying towards the inlet end of the cylinder, near the location of the spark plug while a lean mixture or pure air resides in the lower end of the cylinders near the piston.

Any suitable means for causing swirl of the inlet air charge may be used, but the system should preferably provide smooth rotation of the charge around the cylinder axis with a minimum of random nonswirling motion parallel to the cylinder axis. While various arrangements of timed fuel injection systems may be utilized, the injector for each cylinder should be located to spray fuel into the respective intake port in a manner to direct the fuel charge into the cylinder with a minimum of delay due to wall wetting or condensation of fuel on the intake port walls. Preferably the injector is located to spray fuel directly through the inlet port into the cylinder.Alternatively, however the fuel spray may be directed at the inlet valve or against the port walls immediately adjacent to the opening into the cylinder, so that the fuel charge engaging these surfaces is immediately thereafter swept into the cylinder. The injection of fuel is terminated before the end of the intake event so that none of the injected fuel remains in the intake port after closing of the intake valve. In this way, the mixing of fuel with the initial air charge admitted on the next intake stroke is avoided.

These and other features and advantages of the invention will be more fully understood from the following description of a preferred embodiment chosen for purpose of illustration taken together with the accompanying drawings, in which: Figure 1 is a fragmentary pictorial view partially in cross section showing one cylinder of a multicylinder spark ignition internal combustion engine having charge stratification means in accordance with the present invention; Figure 2 is a transverse cross-sectional view through the cylinder of the engine of Figure 1 and showing the engine operation during the early portion of an intake stroke; Figure 3 is a view similar to Figure 2 showing the engine operation near the end of an intake stroke, and Figure 4 is a view similar to Figures 2 and 3 showing the engine operation near the end of a compression stroke.

Referring now to the drawings in detail, numeral 10 indicates an internal combustion engine having a cylinder biock 11 containing a plurality of cylinders 12, only one of which is illustrated. Each of the cylinders contains a piston 14 arranged for reciprocation within the cylinder through connection by a connecting rod 1 5 with a crankshaft, not shown. The ends of the cylinder are closed by a cylinder head 1 6 which, together with the piston and cylinder walls, defines a variable volume combustion chamber 1 8 at the closed end of each cylinder.

The cylinder head defines for each cylinder an intake port 1 9 and an exhaust port, not shown, which communicate with the end of the cylinder for respectively admitting intake charges to and discharging exhaust products from the combustion chamber at predetermined times of the engine operating cycle. An intake valve 20, reciprocably mounted in the cylinder head, is operative to engage a valve seat 22 at the entrance to the cylinder so as to control communication of the intake port with the cylinder and thereby the admission of intake charges to the combustion chamber, A shroud 23 provided on the intake valve directs the flow of inducted air and fuel in a circumferential direction around the cylinder axis to create a swirling charge in the cylinder when the valve is opened during the piston intake stroke.

An exhaust valve 24 is operable in conventional fashion to control communication of the cylinder with the exhaust port and thereby provide for the discharge of exhaust products at predetermined portions of the engine cycle. A spark plug 26 mounted in the cylinder head and extending into the combustion chamber provides for ignition of the cylinder charge.

The cylinder head also carries fuel injection means including an injector 27 for each cylinder.

The injector is preferably mounted with a spray tip nozzle 28 arranged to discharge fuel into the intake port near the location of the intake valve with a fuel spray pattern directed through the opening of the intake port into the cylinder when the intake valve is open. Alternatively, the injector may be located so as to discharge the fuel spray directly on the inlet valve and/or on the intake port walls as close as possible to the opening of the port into the cylinder so that fuel sprayed upon these surfaces is swept into the cylinder without deiay during the intake stroke.In any case, the positioning of the injector nozzle and its arrangement and spray pattern within the intake port must be such as to permit precise timing of the admission of the fuel charge into the cylinder so that the charge may be admitted as close as possible to the end of the intake stroke without any substantial amounts of residual fuel remaining in the intake port after closing of the intake valve.

In operation, the system of the illustrated engine embodiment utilizes a conventional 4-stroke cycle including intake, compressiori, expansion and exhaust strokes, although other suitable engine cycles could be substituted. During the initial part of each intake stroke, as shown in Figure 2, the open intake valve allows downward motion of the piston to draw a charge of air into the engine cylinder through the intake port. The charge is directed in a swirling pattern around the axis of the cylinder by the shrouded intake valve. If desired, a swirl type port or other suitable means could be used instead of the shrouded valve to generate a swirl pattern of the intake charge within the engine cylinder.

As the piston 14 moves further downward on the intake stroke, the fuel injector 27 is actuated, as shown in Figure 3, to spray a fuel charge through the port opening into the cylinder 12 during the latter part of the intake stroke. The timing of the beginning of injection may be variable depending upon the amount of fuel required to obtain the desired power output.

However, the ending of injection is timed as close to the end of the intake stroke as possible so that the terminal portion of the fuel charge is admitted just before the intake valve closes. In this manner, a rich portion of the cylinder charge is created which, by reason of the swirling pattern of the charge within the cylinder, causes the last inducted fuel containing portions of the charge to be stratified near the upper (inlet) end of the cylinder adjacent the spark plug 26.

Subsequently, the piston moves upwardly on the compression stroke compressing the stratified charge of mixture which containues to maintain its swirling pattern. As the piston 14 nears its top dead center position at the end of the compression stroke, the spark plug 26 is fired, as shown in Figure 4, igniting the relatively rich mixture at the upper end of the combustion chamber 18 within the cylinder 12. Thereafter, burning of the mixture increases pressure on the piston 14 as it moves downward on its expansion stroke to thereby provide power to the engine crankshaft. The burned gases are then exhausted during the upward exhaust stroke of the piston 14, during which time the exhaust valve 24 is open.

Tests of several embodiments of axiaily stratified charge engines with timed fuel injection in accordance with the invention have shown the capability of the system to provide the desired axial stratification of rich fuel-air mixture in the engine combustion chamber. The tested systems have differed from the illustrated embodiment in that the injector fuel spray has been directed against the surface of the inlet valve and/or on the intake port walls near the opening to the cylinder.

These tested arrangements showed a significant capability of fuel injection timing for late admission of fuel to the cylinder to provide the desired charge stratification and it is considered that the preferred embodiment illustrated would be even more effective in this regard. Therefore, while the invention has been described by reference to a specific embodiment shown for purposes of illustration, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited except by the language of the following claims.

Claims (4)

1. A fuel injection stratified charge internal combustion engine having in combination: a cylinder having a closed end and carrying a piston reciprocable in a cycle including an intake stroke and defining with the cylinder a variable volume combustion chamber at the cylinder closed end; spark ignition plug means in the cylinder at its closed end; induction means including an intake port through the cylinder closed end and an intake valve in the port movable to open or close communication of the port with the combustion chamber, said induction means being formed to direct induction charges delivered to the cylinder during the piston intake stroke in a swirling pattern around the cylinder axis, and fuel injection means mounted to supply fuel to the intake port for timed delivery to the combustion chamber, said fuel injection means being operative to time the delivery of fuel to the combustion chamber towards the end of the intake stroke under less than full load operation of the engine and to complete the delivery of fuel just prior to closing of the intake valve on each piston intake stroke, whereby significant axial stratification of part load cylinder charges is accomplished with substantial enrichment of fuelair mixtures at the cylinder closed end adjacent the spark plug.

2. A fuel injection stratified charge internal combustion engine according to claim 1, in which said induction means is formed to direct induction charges delivered to the cylinder during the piston intake stroke in said swirling pattern around the cylinder axis with a minimum of random nonswirling motion parallel to the cylinder axis, and said fuel injection means supplies fuel to the intake port for timed delivery to the combustion chamber with a minimum of contact of fuel spray with the inlet port walls.

3. A fuel injection stratified charge internal combustion engine according to claim 1, in which the intake valve is a shrouded valve, said shrouded valve being formed to direct induction charges delivered to the cylinder during the piston intake stroke in said swirling pattern around the cylinder axis with a minimum of random non-swirling motion parallel to the cylinder axis.

4. A fuel injection stratified charge internal combustion engine substantially as hereinbefore particularly described and as shown in Figures 1 to 4 of the accompanying drawings.