GB2102878A

GB2102878A - Pre-combustion chamber internal combustion engine

Info

Publication number: GB2102878A
Application number: GB08123624A
Authority: GB
Inventors: Richard Furneaux Kinnersly
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-08-01
Filing date: 1981-08-01
Publication date: 1983-02-09
Also published as: ZA825514B

Abstract

A rotary intake and exhaust valve member mounted for rotation in the cylinder head (12) or the cylinder head is provided with a supplementary chamber (14) which is periodically brought into communication with the engine cylinder (6), and an igniter (22) is operative to ignite combustible fluid in the supplementary chamber (14). Conveniently combustible fluid is delivered to the supplementary chamber (14) from the engine cylinder (6) prior to operation of the igniter, but may be supplied to the supplementary chamber (14) by an injector 18. <IMAGE>

Description

SPECIFICATION Improvements relating to internal combustion engines This invention is concerned with improvements relating to internal combustion engines, particularly of the kind comprising a cylinder, a piston in the cylinder, means alternately operable to deliver to the cylinder a combustible fluid (usually a mixture of petrol fuel and air) and to exhaust said cylinder, and ignition means operable at stage in the cycle of operation of the engine to ignite the combustible fluid delivered to the cylinder.

Conventionally used in an internal combustion engine of the kind specified is ignition means located in the cylinder, and operable to provide a high voltage discharge (hereinafter termed a "spark") in the cylinder. This system has manifest disadvantages: for example, it is necessary for the spark to be generated at a precise moment in the cycle of the engine, and it is necessary for the spark to produce very fast combustion of the fuel in the engine.

It is one of the various objects of the present invention to provide an improved combustion initiation system in an internal combustion engine.

According to this invention there is provided an internal combustion engine of the kind specified, comprising a supplementary chamber which is periodically brought into communication with the cylinder, and wherein the ignition means is operative to ignite combustible fluid in the supplementary chamber.

Preferably the supplementary chamber is also delivered of combustible fluid prior to or in consequence upon such communication. Such supply may be effected by separate delivery means to deliver combustible fluid to the supplementary chamber, or combustible fluid may be delivered to the supplementary chamber from the engine cylinder prior to ignition of the combustible fluid in the supplementary chamber, or a combination of these may be used.

Thus by (for example) igniting a small quantity of combustible fluid in the supplementary chamber, some of the conflicting requirements encountered in conventional internal combustion engines of the kind specified may be circumvented.

An ignition means may be thus utilised, which ensures that combustion of the fuel in the supplementary chamber takes place, whilst the timing of the initiation of combustion in the cylinder is determined by the bringing of the supplementary chamber into communication with the engine cylinder.

The ignition means may thus be one which more reliably and/or more conveniently produces combustion in the supplementary chamber, by virtue of the reduced need to produce very fast combustion of the fuel therein. For example, the ignition means may be a heated coil, although of course it may be adapted to provide a spark.

Additionally, it is possible by the use of the present invention to deliver to the engine cylinder a weaker mixture of combustible fluid, and/or to use combustible fluid of a lower octane rating, and/or to use combustible fluid without any preignition inhibitor such as lead tetraethyl.

For example, a combustible fluid may be delivered to the supplementary chamber which is different from that delivered to the engine cylinder, particularly being a "richer" mixture of fuel and air. Indeed, feasibly a different fuel may be delivered to the supplementary chamber, from that delivered to the engine cylinder.

Preferably as distinct from the ignition means being in the supplementary chamber, the ignition means may be located in an ignition chamber which is itself periodically brought into communication with the supplementary chamber.

In this manner, the extent to which the ignition means is subjected to the extreme conditions of temperature and pressure existing in the engine cylinder may be reduced.

On igniting the combustible fluid in the supplementary chamber, the pressure therein will increase, and with the supplementary chamber in communication with the engine cylinder, there will be a rapid migration of hot gas from the supplementary chamber into the engine cylinder which will produce a very rapid combustion of the fuel in the engine cylinder over a large volume.

Ignition of the combustible fluid in the engine cylinder may be effected by the direction action of flame travelling from the supplementary chamber into the engine cylinder, but the construction and arrangement may be such if desired, that the flame is extinguished and incomplete combustion products migrate into the engine cylinder to produce cascade, or avalanche activation of combustion in the engine cylinder by chemical kinetic initiation.

However in either event, by the use of the present invention it is possible to arrange for such ignition of the combustible fluid in the engine cylinder to be initiated at a point in the engine cycle closer to top dead centre than would otherwise be practical.

However, if desired, the time in the cycle of the engine at which such communication occurs in relation to the engine cycle may be varied.

Preferably the supplementary chamber is afforded by a rotary valve member which also provides inlet and exhaust ports which are moved into periodic communication with the engine cylinder by rotation of the valve member, Where combustible fluid is delivered to the supplementary chamber by fuel delivery means which injects combustible fluid into the supplementary chamber independent of the delivery of combustible fluid to the engine cylinder, a "richer" mixture of fuel and air may be delivered to the supplementary chamber compared with that delivered to the engine cylinder. However this is not wholly necessary, since the combustible fluid may readily be caused to rotate within the supplementary chamber, producing "stratification" of the fuel components thereof, allowing a "richer" mixture to be provided in the immediate vicinity of the ignition means.

Thus where fuel delivery means is used which is operative to deliver fuel to the supplementary chamber from the engine cylinder, although that mixture so delivered to the supplementary chamber may be "weaker" than in theory is desirable, the "stratification" of the fluid so delivered can ensure acceptable combustion conditions as the supplementary chamber moves into communication with the ignition means, Alternatively the supplementary chamber may be stationary relative to the cylinder, e.g. in a housing in which the rotary valve member is mounted, the valve member affording a duct to bring the supplementary chamber into periodic communication with the engine cylinder.

There will now be given descriptions, to be read with reference to the accompanying drawings, of seven embodiments of this invention which have been selected to illustrate the invention by way of example.

In the accompanying drawings: FIGURE 1 is a schematic sectional view of the first embodiment of this invention; FIGURE 2 is a schematic sectional view of the second embodiment of this invention; FIGURE 3 is a schematic sectional view of a third embodiment of this invention; FIGURE 4 is a sectional view taken on the line A-A of Figure 3; FIGURE 5 is a sectional view taken on the line B-B of Figure 3; and FIGURES 6, 7, 8 and 9 are, respectively, schematic sectional views of the fourth, fifth, sixth and seventh embodiments of this invention.

In the embodiment illustrated in Figure 1, a cylinder 6 is afforded in an engine block 8 and a rotary valve member 10 is mounted in a cylindrical bore 11 of a cylinder head 1 2. In this embodiment the valve member is provided with inlet and exhaust ports (not shown) which are respectively brought into communication with the cylinder 6, to allow respectively a combustible fluid, consisting of a mixture of fuel and air, to enter the cylinder, and burned gases to be ducted from the cylinder, in conventional manner.

However, whilst in a conventional engine ignition of the combustible fluid is effected by an ignition device which extends into an uppermost part of the cylinder, or which is located in a chamber in the cylinder head opening permanently into the uppermost part of the cylinder, in the embodiment illustrated in Figure 1 the valve member 10 is afforded with a supplementary chamber 14 which opens into a circumferential face of the valve member 10.

Also provided in the cylinder head 12 is an injection chamber 1 6 into which a low pressure fuel injection nozzle 1 8 is secured which is preferably intermittently operative, and an ignition chamber 20, within which an ignition device 22 is secured, both chambers 1 6 and 20 opening into the cylindrical bore 11 of the head 12.

As the valve member 10 rotates in the direction shown, the supplementary chamber 14 passes across, in communication with, firstly the injection chamber 16, at which combustible fluid is injected into the chamber 14. Continued rotation of the valve member 10 moves the chamber 14 out of communication with the chamber 16, and into communication with the ignition chamber 18.

On continued rotation of the valve member 10, the supplementary chamber moves into communication with the uppermost part of the engine cylinder, shortly before top dead centre of the piston 7 therein. Compressed gases within the uppermost part of the engine cylinder flow into the supplementary chamber 14 somewhat tangentially, producing a vigorous swirling movement therein, causing a high degree of stratification of the fuel constituent of the gases, presenting to the element 23 of the ignition device 22 a "rich" fuel.

At or shortly after the point shown in Figure 1, the ignition device 22 ignites the fuel in the chamber 14 by virtue of the "richness" of the mixture presented to the element 23, and by virtue of the turbulence in the supplementary chamber, combustion of the contents of the chamber 14 taking place relatively quickly.

Consequently, burning or hot gases migrate from the chamber 14 into the cylinder 6 to cause combustion of the combustible fluid in the cylinder 6.

In view of the richness of the mixture presented to the element 23 before ignition, the turbulence thereof, and the fact that the chamber 14 is not subjected to high pressure until just before combustion is required, the ignition device 22 may be in the form of a continuous or semi-continuous glow plug or a hot coil ignition device. In this manner the high tension distribution system commonly utilised in internal combustion engines may be dispensed with, and fouling of the spark plug or electrical linkages avoided. In the application illustrated in Figure 1 , the hot coil ignition device may be supplied with a voltage sufficient at starting to cause the coil temperature to ignite the fuel in the chamber 14. However once the engine is running it is envisaged that the voltage supplied to the coil may be reduced accordingly, whilst maintaining a necessary residual voltage to ensure a sufficiently high coil temperature to continue the initiation of combustion in each succeeding cycle.

This partial dependence on current may ensure that the cessation of ignition can be utilised to stop the engine by switching off such residual current.

It is also envisaged that the residual supply voltage to the hot coil ignition device may automatically be varied with respect to engine speed and load, to optimise the hot coil temperature.

By use of the invention described above and illustrated in Figure 1, in view of the significantly higher reliability of ensuring combustion of the fuel within the cylinder 6, significant reductions may be made to the ratio of liquid fuel to air, to the octane rating of the fuel used, and to the use of "anti-knock" additives such as lead tetraethyl.

It is envisaged that the injection device 1 8 may be omitted, in which circumstances the total amount of combustible fluid in the chamber 14 at the point of activation of the ignition device 22 will be effected by flow therein from the engine cylinder 6. In such circumstances the charge stratification produced by the swirling movement of the combustible fluid in the chamber 14 will in itself be desirably sufficient to enable combustion to be initiated by the device 22, despite fuel having been delivered to the engine cylinder at less than stoichiometric strength.

It is additionally envisaged that the valve member 10 may be mounted on a drive shaft (not shown) with provision therebetween for angular rotative variation whereby variation of the prechamber events with respect to the crank angle may be achieved by such relative rotational movement. For example, such mounting of the valve member 10 on such a shaft may be effected by the use of helical splining, whereby axial movement of the valve driving member relative to such shaft will simultaneously Droduce relative rotational movement therebetween.

Alternatively, the chamber 14 may extend longitudinally of the valve member 10 somewhat in the form of a helix, whereby the reiationship, between the point at which the chamber 14 first communicates with the cylinder 6, and the position of the piston 7 within the cylinder 6, may be progressively varied by axial movement of the valve member 10 within the cylinder 11.

Additionally it is envisaged that thermal conduction between the exhaust port in the valve member 10 and the walls defining the chamber 14 may be utilised to heat said pre-chamber: for example the internal surface of the chamber 14 may be provided with an hermetically sealed, removable or integral, thin-section walling adjacent to and forming a division between the exhaust port and said chamber 14, whereby part of, most of, or possibly all of said chamber 14 may be heated by a varying degree of communication with said exhaust port.

Whilst in the first embodiment above described the supplementary chamber 14 is of a lesser volume that that of the engine cylinder at top dead centre of the piston, it is possible for the supplementary chamber 14 to constitute a majority of the volume of the main chamber under compression. Thus in the second embodiment of this invention shown in Figure 2, a valve member 10 is utilised, having a supplementary chamber 14 which is larger than that shown in Figure 1.

Additionally in the second embodiment, the total combustible fluid presented by the supplementary chamber 14 to the ignition device 22 for combustion is supplied thereto from the engine cylinder. Convenientiy, to avoid unduly high pressures, and to permit a slightly longer time for stratification of the combustible fluid in the supplementary chamber 14, said chamber 14 opens into the main cylinder 6 somewhat before top dead centre of the piston 7. Thus, a fuel mixture of less than stoichiometric strength may be delivered to the engine cylinder, and by virtue of the stratification produced in the chamber 14, a mixture of strength equal to or greater than stoichiometric is presented to the ignition device, and at a pressure and turbulence sufficient to cause ignition to be induced by a heated coil ignition device.

In the third embodiment of this invention, illustrated in Figures 3, 4 and 5, fuel is delivered to the supplementary chamber 14 by a high pressure delivery device 18, delivering fuel through a feed passage 30 which is displaced relative to the supplementary chamber 14 in an axial direction, delivery of such fuel to the chamber 14 being effected by alignment of said feed passage 30 with a transfer duct in the valve member 10, opening into the chamber 14.

Thus during rotation of the valve member 1 0, combustible fluid, conveniently consisting of a mixture of fuel and air, passes from the delivery device 18 into the chamber 14 as the transfer duct 36 passes the feed passage 30. On continued rotation of the valve member 10, the transfer duct 36 moves out of engagement with the feed passage 30, and the chamber 1 4 passes across the ignition chamber 18, a combustible fluid within the chamber 14 is ignited by the ignition device 20.High temperatures and pressures develop within the supplementary chamber 14 whilst the valve member continues to rotate, until the establishment of communication between the chamber 14 and the uppermost part of the engine cylinder 6, whereupon a jet of flame sweeps from the supplementary chamber into the cylinder, causing very fast combustion of the fuel therein.

Thus in the third embodiment of this invention, initiation of combustion of the combustible fluid in the engine cylinder 6 may take place very quickly, allowing such initiation to occur at a point very close to the top dead centre position of the piston.

This embodiment provides a significant advantage, in that a very small charging piston need be utilised to deliver combustible fluid to the supplementary chamber, and that this charging piston may be supplied by a small carburettor.

Alternatively, the use of such a charging cylinder may be avoided, and a pressurised gas (such as propane) mixed with air under pressure may be delivered through the feed passage 30 by the injection device 1 8.

In the fourth embodiment of the invention illustrated in Figure 6, in place of the injection device 18, a delivery passage 28 extends from the uppermost portion of the cylinder 6, and opens into the cylindrical bore 11 of the head 1 2 at the point occupied in the embodiment illustrated in Figure 1, by the injection chamber 16. Thus with the rotor 10 and supplementary chamber 14 in the relative positions shown in Figure 6, in which fuel and air have been delivered to the cylinder 6, with the piston 7 rising towards top dead centre, part of the fuel and air delivered to the cylinder 6 is forced through the delivery port 28 into the chamber 14.

Preferably the delivery port 28 opens into the cylindrical bore 11 of the head in an orientation such as to ensure the creation of a swirling movement of combustible fluid delivered to the supplementary chamber 14 when such communication occurs. In this manner the fuel within the chamber 14 stratifies, producing a higher concentration of petrol to air in the radially outermost region of the chamber 14, allowing the mixture in the chamber 14 to be readily ignited by the ignition device 22 notwithstanding that the fuel delivered to the engine cylinder is less than stoichiometric.

In the fifth embodiment illustrated in Figure 7, a short passage 40 extends from the leading face of the supplementary chamber 14, and opens into the circumferential surface of the valve member 10. Thus, fuel is delivered under relatively low pressure to the chamber 14 from the device 18, and as the passage 40 opens into communication with the engine cylinder 6, gases under pressure flow through the passage 40, pressurising the chamber 14 causing a swirling movement of gases therein, and ignition of the contents of the chamber 14 by the device 22.

Advantageously, the passage 40 is also arranged so as to cause hot gases to pass from the supplementary chamber 14 through said passage 40, and enter the cylinder 6 generally tangentially, to swirl around the uppermost part of said cylinder.

The passage 40 (of which there may be more than one) may be of a dimension sufficient to cause quenching of the flame travelling therealong from the supplementary chamber 14, whereby chemical kinetic initiation of combustion of the fuel in the cylinder 6 takes place, or may be sufficient merely to produce a jet of flame which produces rapid combustion of said fuel.

The embodiment illustrated in Figure 8 shows an arrangement alternative to that shown in Figure 7, in which a passage 42, corresponding to the passage 40 of the fifth embodiment, is provided in the engine housing.

As a modification of the sixth embodiment, the passage 42 could be arranged to establish communication between the engine cylinder and the supplementary chamber 14 subsequent to the delivery of fuel thereto by the delivery device 1 8, and prior to the establishment of communication between the chamber 14 and the ignition device 22. In this manner, initiation of combustion of the fluid within the chamber 14 may take place at a point where there is no communication between the chamber 14 and the cylinder 6, permitting such combustion to be initiated at leisure, and allowing pressure to build up within the chamber 14 prior to the re-establishment of communication thereof with the cylinder 6, producing a very rapid migration of flame from the chamber 14 into the cylinder 6 as will produce very fast combustion of the fuel within the cylinder 6.

In the seventh embodiment illustrated in Figure 9, the supplementary chamber 1 4b is not afforded by the rotary valve member 10, but it provided in the head 12 of the engine. The valve member 10 is afforded with two ducts, namely a fuel delivery duct 44, and an ignition duct 46. During rotation of the valve member 10, the delivery duct affords communication between the injection device 1 8 and the chamber 1 4b, allowing fuel to be delivered to the chamber 1 4b. When the duct 30 has moved to a circumferential position at which the chamber 1 4b is no longer in communication with the chamber 16, the ignition device 22 operates to ignite the fuel within the chamber 1 4b.The ignition duct 46 then affords communication between the supplementary chamber 1 4b and the cylinder 6, causing the ignited fuel within the chamber 1 4b to effect ignition of the fuel within the cylinder 6.

Alternatively, where the ignition device is afforded by a continuously or semi-continuously powered heating coil, combustion can be initiated automatically when the communication established between the chamber 1 4b and the engine cylinder 6 establishes adequate pressure and turbulence within the chamber 1 4b.

As an alternative expedient to that shown in Figure 9, fuel may be delivered to the chamber 1 4b from the cylinder 6, by the use of a supplementary duct similar to that numbered 28, Figure 6.

With the embodiments illustrated in Figures 6 to 9, there may be provided a plurality of ducts 28, or 40, or 42, or 44 and/or 46.

In all the various embodiment described above, if desired the supplementary chamber 14 may be divided axially into one or more subcompartments. Additionally, if desired the valve member may be provided with two or more supplementary chambers axially or angularly disposed relative to the valve member.

If desired, the supplementary chamber may be helically disposed, and/or may be afforded with tapered ports, to permit variability in the time at which the supplementary chamber opens into communication with the cylinder 6, in relation to the engine cycle, for axial movement of the valve member within the axial bore 11. Alternatively such adjustment may be obtained by the mounting of the valve member, or the valve drive shaft, in relation to the valve driving mechanism.

It is to be appreciated that the embodiments of this invention have been illustrated in the accompanying drawings schematically, which are not to be taken as indicating precise periods in the engine cycle.

In particular, it is envisaged that the valve member will rotate at one quarter speed, and will comprise two supplementary chambers 14, and two inlet and two exhaust ports, producing combustion in the engine cylinder twice for each rotation of the valve member 10.

Additionally whilst the ignition device 22 is shown as comprising a single element, if desired more than one such ignition elements may be utilised, as is permitted and desired.

Claims

1. An internal combustion engine of the kind specified, comprising a supplementary chamber which is periodically brought into communication with the engine cylinder, and wherein the ignition means is operative to ignite combustible fluid in the supplementary chamber.

2. An internal combustion engine according to claim 1 wherein combustible fluid is delivered to the supplementary chamber prior to the establishment of communication between the supplementary chamber and the engine cylinder.

3. An internal combustion engine according to claim 2 wherein communication is established between the supplementary chamber and the engine cylinder subsequent to ignition of combustible fluid in the supplementary chambers

4. An internal combustion engine according to any one of claims 1,2 and 3 wherein communication between the supplementary chamber and the engine cylinder is established prior to the ignition of the combustible fluid in the supplementary chamber, and gases under pressure flow from the engine cylinder into the supplementary chamber in consequence of such communication.

5. An internal combustion engine according to claim 4 wherein the flow of gases from the engine cylinder to the supplementary chamber is arranged to produce a cyclic or swirling movement within the supplementary chamber.

6. An internal combustion engine according to claim 5 wherein such cyclic or swirling movement of combustible fluid within the supplementary chamber produces stratification of the fuel constituent of fluid.

7. An internal combustion engine according to any one of the preceding claims wherein the supplementary chamber is periodically brought into communication with the engine cylinder by means of a member mounted for rotation relative to the engine cylinder.

8. An internal combustion engine according to claim 7 wherein sd member is rotated in dependence upon the cycle of operation of the engine.

9. An internal combustion engine according to claim 7 wherein said member may be adjusted rotationally to vary the point at which it establishes such communication in relation to the cycle of operation of the engine.

1 0. An internal combustion engine according to any one of claims 7, 8 and 9 wherein said member is operative periodically to bring a plurality of such supplementary chambers into communication with the engine cylinder.

11. An internal combustion engine according to any one of claims 7 to 10 wherein the said member also provides an inlet port through which combustible fluid is delivered to the engine cylinder, and/or an exhaust port through which exhaust gases are ducted from the engine cylinder.

12. An internal combustion engine according to any one of claims 7 to 11 wherein the supplementary chamber is provided in the said member.

1 3. An internal combustion engine according to any one of claims 7 to 11 wherein the supplementary chamber is provided in a housing of the engine in a fixed position relative to the engine cylinder, and periodic communication between the supplementary chamber and the engine cylinder is afforded by the communication passage in said member.

14. An internal combustion engine according to any one of the preceding claims wherein the construction and arrangement is such as to cause, after the establishment of such communication and after the ignition of combustible fluid in the supplementary chamber, to cause a flame to travel from the supplementary chamber into the engine cylinder.

1 5. An internal combustion engine according to any one of claims 1 to 1 3 wherein the construction and arrangement is such as to cause, after the establishment of such communication and after the ignition of combustible fluid in the supplementary chamber, to cause incomplete combustion products to migrate from the supplementary chamber into the engine cylinder to produce cascade, or avalanche activation or combustion in the engine cylinder by chemical kinetic initiation.

1 6. An internal combustion engine according to any one of the preceding claims wherein the ignition means is afforded in the supplementary chamber.

1 7. An internal combustion engine according to any one of claims 1 to 1 5 wherein the ignition means is afforded in an ignition chamber which is periodically brought into communication with the supplementary chamber to effect ignition of combustible fluid therein.

18. An internal combustion engine according to any one of the preceding claims wherein the ignition means is of the kind adapted to deliver a high voltage discharge periodically.

19. An internal combustion engine according to any one of claims 1 to 1 7 wherein the ignition means comprises an electrically powered heating coil.

20. An internal combustion engine according to claim 19 wherein the heating coil is continuous or semi-continuously powered, ignition of the combustible fluid in the supplementary chamber occurring in consequence of the establishment in said chamber of appropriate conditions.

21. An internal combustion chamber according to claim 20 wherein said conditions are established by bringing the supplementary chamber into communication with the engine cylinder whereby to establish in the supplementary chamber a sufficiently high pressure to allow combustion to be initiated by the heating coil.

22. An internal combustion engine constructed and arranged substantially as hereinbefore described with reference to any of the accompanying drawings.

23. Any novel feature or novel combination of features hereinbefore described and/or shown in the accompanying drawings.