DD287080A5 - COMBUSTION ENGINE - Google Patents

Abstract

An internal combustion engine has a pair of first and second cylinders communicating with a combustion chamber, the first cylinder having a larger displacement than the second cylinder. In the cylinders, first and second pistons are provided. In the first cylinder, an intake passage is provided for supplying a charge of unthrottled fuel, while a fuel injection valve is controlled by means of a controller to supply a fuel charge to the second cylinder as soon as possible after the start of a suction stroke of the second piston. The movement of the fuel / air mixture from the second cylinder into the combustion chamber is prevented until the second piston is at or near its inward dead center position. The second piston may be formed as a projection on the top of the first piston and is an extension of the first cylinder with the second cylinder. The engine may be a compression-ignition engine in which the ignition takes place automatically in the combustion chamber, or alternatively in the combustion chamber a Zuendeinrichtung be provided with a catalyst or hot surface. Fig. 1 {internal combustion engine; Cylinder; Piston; Einlaszkanal; Fuel; Fuel injection valve; Control means; Fuel charge; intake stroke; Fuel / air mixture; dead center; compression-; Combustion chamber; ignition device}

Description

For this 4 pages drawings

Field of application of the invention The present invention relates to internal combustion engines.

-3- 287 080 characteristic of the known state of the art

An internal combustion engine system may be subdivided into a number of interrelated subsystems that operate together to provide desired performance in terms of speed, output, fuel consumption and exhaust emissions of the engine system. These subdivisions are the following:

a) Ignition device

b) Handling the fuel inlet

c) Handling of the gas flow within the engine cylinder and the combustion chamber. The diesel engine system additionally has the following subsystems:

d) segregation mechanisms

e) mixing the fuel and the air in a combustion chamber.

Segregation is the term used to describe the exclusion of fuel from the combustion chamber of the engine during the intake and compression strokes of the engine to prevent pre-ignition when there is a permanently operable ignition device in the combustion chamber. Segregation gives the advantage of considerable efficiency in an internal combustion engine for the following reasons: (i) the engine compression ratio can be selected without reference to the fuel used, since compression by compression can be prevented;

(ii) at partial load, the fuel inlet may be reduced without intentional reduction of the air inlet; (iii) at partial load there is also no need for any mechanical interference in the airflow during the air intake, such as that caused by a throttle valve resulting in delivery losses leads. The diesel engine is the only combustion engine available anywhere that uses segregation in its operation. During operation, air is drawn into a cylinder of the engine and compressed to a high volumetric ratio (14: 1 to 25: 1), as a result of which the air is heated to a high temperature between 300 ^° C. and 400 ° C. The fuel becomes Because of the high temperature of the air, the fuel ignites itself, but the combustion does not take place immediately upon injection of the fuel, the fuel enters the cylinder in the form of liquid droplets must intimately mix and vaporize with the air in the cylinder before they can ignite to initiate the combustion process.This inherent delay in combustion makes the combustion process a relatively slow process which limits the efficient operation of the diesel engine to relatively low speeds. The segregation, which refers to the above, is in the Mechanically caused by the fuel injection pump whose injection nozzle mechanically separates the fuel from the cylinder or the combustion chamber until the moment of injection.

Object of the invention The aim of the invention is to largely avoid the aforementioned disadvantages. Explanation of the essence of the invention The present invention has for its object to provide an improved internal combustion engine. According to the invention

the object is achieved in that the internal combustion engine comprises:

at least one first and second cylinders communicating with a combustion space, said first cylinder having a larger displacement than said second cylinder, first means for providing a charge consisting essentially of air into the engine said first cylinder,

a second means for supplying a charge of liquid fuel into said second cylinder, corresponding first and second pistons movable in said cylinders, a continuously operating ignition device in said combustion chamber, control means for controlling said second means to communicate with said second means Distributing said fuel charge in said second cylinder during movement of said second piston between a first position in which said piston is at the beginning of its intake stroke and a second position at which said piston is not less than 10 ° travel angle from the end of its Compression stroke is to start and stop the supply of said fuel charge when said second piston reaches a third position which is not later than the internal dead center position of the piston at the end of the compression stroke, and means for delay Be movement of the fuel / air mixture from said second cylinder in said

Combustion chamber, before said second piston reaches a fourth position, in which said piston at least

has substantially completed 80% of its compression stroke length, and means for inducing a swirling motion in the air coming from said first cylinder into said combustion space to promote rapid mixing in said combustion space of the fuel / air mixture from said second cylinder and Air supplied from said first cylinder during combustion

The present invention also provides a motoi ^>; t Compression ignition, characterized by at least one A pair of first and second cylinders communicating with a combustion chamber, wherein said first cylinder engages

has a larger displacement than said second cylinder, first means for delivering a charge consisting essentially of air into said first cylinder,

second means for delivering a charge of liquid fuel into said second cylinder, corresponding first and second pistons movable in the genannton cylinders,

Control means for controlling said second means to interfere with the supply of said fuel charge in the

said second cylinder during movement of said second piston between a first position, in which said piston is at the beginning of its suction stroke, and a / wide position, in which said

Pistons not less than 10 ° movement angle! from the end of its compression stroke, to begin and terminate delivery of said fuel charge when said second piston reaches a third position not later than the internal dead center position of the piston at the end of the compression stroke, and means for retarding fuel flow. / Air mixture from said second cylinder into said combustion space before said second piston reaches a fourth position in which said piston has substantially 80% of its compression stroke length terminated, and means for inducing a swirling motion in the air resulting from said first cylinder is supplied into the genannton combustion chamber for assisting rapid mixing in said combustion space of the fuel / air mixture from said second cylinder and air from said first cylinder during combustion.

An internal combustion engine according to the present invention relies on the movement of the gases between two cylinders of unequal displacement connected by a common combustion chamber in which the ignition takes place to promote segregation. It has been determined that as both pistons of the engine move toward their internal dead center positions, the gas flows from the larger cylinder through the combustion chamber and into the smaller cylinder during most of the compression stroke. The fuel is introduced during the intake stroke of the smaller cylinder and / or a portion of the compression stroke in the smaller cylinder Zy, up to a piston position at which the gas flow reverses and the contents of the smaller cylinder enters the combustion chamber. The liquid fuel may be introduced into the smaller cylinder, starting at any part or the total stroke of the piston of the second cylinder from the inner dead center (IOC ·) position of the second piston at the beginning of the intake stroke up to not less than 10% before internal dead center position at the end of the compression stroke, ending over the full range of fuel takeover states from full load to idle and no later than at the inner dead center position at the end of the compression stroke.

The introduction of the liquid fuel into the smaller cylinder during a preselected part of the pre-ignition cycle allows the fuel to be vaporized in time in the smaller cylinder in gas so that when it enters the combustion chamber to be ignited, the Following combustion process contains gaseous fuel and takes place much faster compared to the combustion process in the diesel engine. The "allows the engine according to the present invention to operate at much higher speeds than is possible with the diesel engine. In essence, the engine according to the present invention combines the efficiency of the diesel engine as a segregation engine with the ability of fast running a gasoline engine.

A number of features in a preferred embodiment of the invention contribute to effective segregation. This includes:

a) a combination of a cylinder with a large displacement, which contains only air (or air with such a small amount of fuel that it is not ignitable by the ignition means in the combustion chamber, the upper limit of any such fuel / air mixture ratio below the lower (lean) flammability limit for such a mixture) with a cylinder of smaller stroke volume in which the fuel is introduced. The two cylinders are connected to each other by means of a common combustion chamber.

b) The introduction of the fuel into the smaller cylinder in the liquid form cools the gases in the smaller cylinder by evaporation, so that there the pressure with respect to the pressure in the larger cylinder at any given piston positions during the compression stroke up to reduces the end of the compression stroke. This effectively promotes gas flow from the larger cylinder through the combustion chamber into the smaller cylinder.

c) A freely selectable feature is that the phase difference between the positions of the pistons in the larger and smaller cylinders can be selected to adjust the crank angle at which the contents of the smaller cylinder enter the combustion chamber to ignite and burn trigger.

d) the combustion chamber communicates with the smaller cylinder via an opening which confines gas flow into the smaller cylinder during the intake stroke; this acts on the pressure in the smaller cylinder at the beginning of the compression stroke to maintain the pressure at a lower value than the pressure in the larger cylinder.

Ausführungsbelsplelo

The present invention will be further described below by way of example with reference to the accompanying drawings. Show in it

1 shows a partial section through part of a first embodiment of an internal combustion engine according to the present invention

Invention; Fig. 2 is a view similar to Fig. 1 of a second embodiment of an internal combustion engine according to the present invention

Invention; Fig. 3 is a view similar to Figs. 1 and 2 of a third embodiment of an internal combustion engine according to the present invention

4, a section through a modified form of a combustion space 1 for an internal combustion engine according to the present invention.

First, reference is made to FIG. 1. This is a section through part of a preferred form of an internal combustion engine ntr'.i of the present invention. For a better understanding and in the interests of a complete description of the engine and its operation, reference should be made to the earlier British applications Nos. 2155 546 and 2186913. In the accompanying drawings, the same reference numerals are used as in the aforementioned earlier patent specifications to identify like parts.

The engine of Figure 1 has one or more pairs of cooperating first and second cylinders 12; 14, the corresponding first and second pistons 16; 18 included. Dio cylinder 12; 14 are interconnected by a combustion chamber 20 in the engine cylinder head. The two cylinders are formed by a large cylinder 12 which is a cylindrical one

Has expansion that forms a smaller cylinder 14. The larger cylinder has a larger displacement than the smaller one Cylinder. The axes of the two cylinders are parallel, and although the cylinder 14 with respect to the larger cylinder 12th

Off-center positioned, it may be in any position, including a central one of the

Cylinder 12. The larger cylinder 12 is equipped with a first piston 16, which also at its upper End carries a cylindrical extension which projects into the smaller cylinder 14 and the piston 18 for the smaller Cylinder forms. The lifting height of the first piston 16 is set such that the second piston 18 projects into the cylinder 14,

even in his sweeter dead center.

Both cylinders 12; 14 are connected to the combustion chamber 20 through respective openings 40; 44 in connection. The Combustion space is preferably spherical, although other suitable shapes may be used, and is with

a suitable ignition device 22, as described below equipped. The fuel is in the smaller cylinder 14 with

Assisted by a fuel injector 36 and controlled by a control device 37, while in the larger Cylinder air is introduced through an inlet opening 25. The air introduced into the larger cylinder is preferable

unthrottled, that is, for example, it is not controlled by means of a throttle valve, as in the case with known gasoline engines. In the smaller cylinder 14, an exhaust port is provided. As an alternative you can

Exhaust and air inlet openings 27 '; 25 'open into the larger cylinder 12, as it by the dashed lines

is shown. The channels can be opened and closed by valves, such as drain valves or through the

Piston itself when the channels are in the sidewalls of the cylinders. Starting the engine can be done with appropriate Means are supported, such as a spark plug or electrode 52, which a continuous spark current or

can generate an arc to assist the starting process, or a hot surface, such as a

Glow plug or a preheated surface area in the combustion chamber. Fig. 2 is a view similar to that of Fig. 1, illustrating a modified form of the engine. At this Embodiment, the combustion chamber 20 is actually formed within the second piston 18. The second piston 18

can be operated without piston rings, since the air flows only from the larger cylinder to the smaller cylinder 14, while between the two cylinders a small pressure difference occurs.

The smaller cylinder 14 is also provided with a projection 100, μ elcher is formed on the end wall to the

displace most of the volume in the opening 40, at or near the inner dead center. The

Projection is positioned so that it enters the opening 40 as soon as the piston 18 reaches the inner dead center. this will

Described in detail below.

In the modified engine of Fig. 3, the top ends of the cylinders 12; 14 through the combustion chamber 20 in constant Connection. The pistons in both cylinders are mechanically coupled together. The pistons can be coupled in phase and up

they move coincidentally, that is, they reach the inner dead center (IDC) and the outer dead center (ODC) simultaneously, but the engine is slightly lagging or slightly advanced with respect to the first piston 16 with the second piston 18.

Preferably, there is no change in the phase difference between the two pistons as the engine speed increases or decreases

decreases.

The air cylinder 12 communicates with an air intake passage and an exhaust port of the respective intake and exhaust ports Exhaust pipes (exhaust 28 is shown). The piston 18 is also provided with a projection 100 'formed on its head part to be the largest To displace volume fraction in the cooperating opening 40, at or near the inner dead center. The combustion chamber in each of the described embodiments includes a perpetual ignition means, i. H. on Igniter, which is continuously operable. The term "continuously operable * is hereby referring to

use the ignition medium that is active or capable of being used over the entire engine cycle or over a preselected one

Time period, which is an essential part (i.e., greater than 26%) of the period of time necessary for the termination of the period Engine revolution is required. The following forms of igniter may be used.

1. A part or the entire wall of the combustion chamber may be formed or coated with a ceramic material, which is a heat insulator and reaches very high temperatures during operation of the engine, so as to form a hot surface igniter. The fuel / air mixture ignites on contact with the hot ceramic surface.

2. As an alternative to the ceramic material, some or all of the combustion chamber wall may be a metal wall which may also reach temperatures suitable for ignition during engine operation.

3. The ignition agent may be in the form of a catalyst, typically platinum and / or palladium, preferably in the form of a film or coating on a part or all or part of the interior wall or walls of the combustion chamber.

4. Any of the above-mentioned combinations may be used.

5. Compressor firing. Where the hot gases suddenly fill the combustion chamber. Ignites the fuel at the end of the compression stroke with or without the aid of the above mentioned igniter.

During an intake stroke, air is drawn into the larger cylinder 12 through the intake port, and a part of the intake air is drawn into the smaller cylinder 14 through the combustion chamber. The fuel is also injected or introduced into the cylinder 14 over a preselected angle (length) of bolt travel. The fuel is sufficiently introduced into the smaller cylinder prior to the internal dead center at the end of the compression stroke to allow a substantial portion of the power flow to evaporate before the second piston reaches internal dead center. The range of movement of the second piston, within which the beginning of the injection takes place, takes place from the inner dead center of the piston at the beginning of the intake stroke to approximately 10 ° movement angle before the inner dead center at the end of the compression stroke. The preferred range in which the injection begins is from the internal dead center at the beginning of the intake stroke to the point where the piston has completed 90% (equivalent to an angle of movement of approximately 144 °) of its compression stroke length. The injection of the fuel does not end later than the internal dead center at the end of the compression stroke. L..4 Fuel injection may be to any toe within this range above the preselected angle, but ideally the injection is made as early as possible in the intake stroke to provide as much time as possible to the fuel for its vaporization. In a preferred embodiment of the invention, the force injection occurs immediately after the beginning of the suction stroke.

After reaching the outer dead center, both pistons begin the compression stroke. During the compression stroke is

supplied by the piston 16 air in the combustion chamber 20; this inevitably leads to a whirling movement within the

Combustion chamber. Although the drawings illustrate that both openings 40 and 44 open tangentially in the combustion chamber to a In an alternative embodiment, only the opening 44 opens tangentially into the chamber. The term tangential * is not used herein in its strict mathematical sense, but excludes the arrangement

one in which an opening in the chamber opens in a direction having a relatively large tangential component. The air also travels into the cylinder 14 to mix in this cylinder 14 with the LufWFstoffstoffgemisch.

During the compression stroke, both pistons 16 and 18 deliver their gases into the combustion chamber 20, in the case of the piston 18

this is done at the end of the compression stroke. The entry of the rich fuel / air mixture into the combustion chamber is combined with rapid mixing, preferably by suitable means and means, as pointed out in the above-referenced patent applications.

Where a catalyst or hot surface is used as the ignition agent, the combustion is catalyzed

or hot surface upon contact of the fuel / air mixture with the surface. Where the ignition means is compression ignition, the fuel / air mixture in the combustion chamber itself ignites.

Air Mixture In dsm smaller cylinder does not ignite before mixing with the air from the larger cylinder, because

it is too rich (or too lean). Since the fuel / air mixture that is forced out of the smaller cylinder 14 into the combustion chamber is completely or partially vaporized, there is no delay in ignition as opposed to

Diesel engine in which the fuel is injected to the internal dead center in the form of fuel droplets, which in the Combustion chamber must first be mixed with the air and then heated and evaporated,

before they can be burned.

Although the fuel in the present invention in a concentrated form (a method known as stratification Is) is introduced into the combustion chamber, since the fuel was preferably introduced into the smaller cylinder 14,

it is at least partially vaporized as soon as it is introduced into the combustion chamber, so that the ignition delay is reduced. The combustion increases the temperature and promotes the ignition of the remaining gases. As combustion commences, the chemical reaction that takes place requires additional oxygen to continue, and this results in increased mixing. In hot surface catalytic or hot-surface ignition, the fuel is ignited on a surface of the combustion chamber and the burning fuel causes the gases to expand and move radially inward, with strong interaction with the air flow in the combustion chamber producing a reactive mixing action.

The spinning vortex motion in the combustion chamber continues during the ignition period and secures one

prolonged contact with the catalyst or hot surface over a period of time to promote rapid and complete combustion. Both pistons are then piloted away from internal dead center so that it is possible to expand combusted gases and deliver work from the pistons to the engine crankshaft or crankshafts.

The projections 100 respectively located on the piston 18 and the cylinder wall (FIGS. 2 and 3); 100 'ensure that the fuel

/ Air mixture in the small cylinder 14 is transferred into the combustion chamber 20 when the piston 18 to the inner

Dead center moves. The projection enters the opening 40 as soon as the piston 18 approaches the inner dead center, so that

the fuel-air mixture, the between the head of the piston 18 and the coated top wall of the cylinder 14th

is pressed through the narrower part of the opening 40 in the combustion chamber. This also increases the

Speed of the fuel / air mixture and intensifies mixing within the combustion chamber. The shape of the projection 100; 100 'is such that a gap 102 between the projection and the side wall of

Opening 40 remains to allow access to the combustion chamber for the gases that exist between the head of the

Piston 18 and the coated head wall of the cylinder 14 are included. This space 102 may over the

Whole circumference of the projection 100 or over a part of the circumference to be extended.

The cross-sectional shape of the projection 100 may correspond to that of the opening 40 or it may be a different one Be cross-sectional shape, which may also be different along the width or length of the projection. In the latter In this case, this would result in a gap 102 which changes as the piston 18 approaches the inner dead center

emotional.

The opening 40 may have any cross-sectional shape, for example, rectangular, curved, for example

circular or in the form of an ellipsoid or an irregular shape, such as the cross-sectional shape of the protrusion 100

The length of the protrusion 100 may be greater than, equal to or less than the length of the opening 40. A similar projection can also be formed on the head of the piston 16, as in the aforementioned Descriptions is disclosed. In Fig. 3, a projection 66 is shown, which is formed at the top of the piston 16 and which in

is arranged close to an edge of the piston. This allows large intake and exhaust ports in the with the

Cylinder 12 connected cylinder head are provided. The use of a projection for the second piston ensures the delivery of almost the entire fuel / air Mixture in the combustion chamber. When used for both pistons, it extends the time of almost constant Volumenerbrennung, which can promote the engine in his fast-acting combustion process and allows

larger openings, which must be used to the transfer of air from the inlet valve and through the

To facilitate combustion chamber in the smaller cylinder 14 during the intake stroke. Hereinafter, reference is made to FIG. This figure shows a section through a preferred form of the Combustion chamber 20. In this combustion chamber is the general shape of the cross section of a combustion chamber

circular (although other effectively curved shapes may be used) with a radius R |. Both

Intake ports 40 and 44 open tangentially into the combustion chamber to cause swirling of the gas in the combustion chamber Combustion chamber during the compression stroke of the engine to produce. The radius of curvature of the chamber becomes

however, decreases over part of the circumference immediately before the openings 40 and 44 (in the direction of movement of the gases in the combustion chamber). The radii of curvature immediately before the openings 40 and 44 are corresponding to Rj and R ₂ . The radii R ₂ and R ₃ may be the same or different.

It is of course estimated that both or only one of the radii R ₂ and R ₃ differ from the radius Rt. The effect of the change in curvature is to displace the circulating gas flow in the combustion space with respect to the flows entering the combustion space through the openings 40 and 44. This allows for improved mixing of the gases and reduces any tendency of the circulating gases in the combustion chamber to hinder the entry of the gases through the openings 40 and 44.

The main advantage of the above-described embodiments of a segregation engine over the diesel · segregation engine is that the liquid fuel can be introduced into the smaller cylinder 14 much earlier, i. H. at any time from the beginning of the intake stroke to 10 ° angular movement from the inner dead center at the end of the compression stroke. This allows the fuel to have much more time to evaporate before being forced to enter the combustion chamber. Ignition and combustion of the gaseous fuel occur much faster than with a liquid fuel with the elimination of spark retard and longer combustion time of a diesel engine, and lend the present invention suitability for high speed, well-functioning operation.

The liquid fuel injected during the intake stroke can be injected at relatively low pressures compared to a diesel engine. Low volatile liquid fuels can also be preheated, for example, by heat exchange with engine cooling water or exhaust gases. The low volatility liquid fuels may also be injected at higher pressures to facilitate finer atomization of the fuel, which in turn aids vaporization.

The fuel in the form of a gas may be used in the engine on a dual fuel basis. A small amount of fuel in gaseous form may be mixed with air as the air enters the larger cylinder 12 (the mixture is below the lean flammability limit) while the greater part of the fuel is injected in liquid form into the smaller cylinder 14. A small amount of the gaseous fuel may remain in the combustion chamber in a larger amount of the air unaffected by the ignition means.

It will be appreciated by those skilled in the art that the embodiments disclosed in FIGS. 1 and 2 may be used together or separately in a motor and combined with any of the embodiments discussed in the aforementioned earlier descriptions.

Although each combustion chamber relating to the above is described as having a curved surface or a curved cross-sectional shape, it will be appreciated that the term "curved" includes such surfaces defined by a number of straight or curved portions a combination of both are formed, for example a combustion chamber in the form of a polyhedron.

The head of the first piston 16 or a part thereof may be equipped with or formed of ceramic material which forms a hot surface during operation of the engine and promotes combustion. The ceramic material may preferably be coated with catalytic material.

When a multi-cylinder engine of this type receives fuel over the full range of fuel demand, a condition may be achieved under light loads as the fuel air-to-air ratio of the mixture in the smaller cylinder falls within the ignition limits by igniting the mixture in the smaller cylinder caused by the compression ignition. This can be avoided by controlling the amount of fuel injected so that, for example, when the fuel / air ratio of the mixture falls below the range of a preselected value above the enriched fuel flammability limit, the fuel injected into a plurality of cylinders, is increased to a set amount to keep the mixture above the enriched fuel flammability limit, while the fuel injected into the other cylinders is immediately reduced to restore the fuel / air ratio of the other mixtures below the lean flammability limit. This ensures that the engine continues to run at the required full load without the risk of unwanted ignition during the engine cycle. Once the fuel demand of the engine is such that the fuel / air ratio of the mixture in each cylinder should be below the lean flammability limit, the amount of fuel injected into each cylinder is set to the same value to such air / fuel ratio to create in each cylinder. It is estimated that the reverse operation occurs as the fuel / air ratio of the mixture in each cylinder increases, within a preselected magnitude below the lean exhaustibility limit. The above applies to the use of a catalytic igniter suitable for igniting mixtures below the lean fuel flammability limit.

Claims (20)

An internal combustion engine characterized by a pair of first and second cylinders (12; 14) communicating with a combustion chamber (20), said first cylinder (12) having a larger displacement than said second cylinder (14), first means (25; 25 ') for supplying a substantially air filling into said first cylinder, second means (36) for providing a charge of liquid fuel to said second cylinder, respective first and second pistons (16; a continuously operable ignition means (22) in said combustion space, control means (37) for controlling said second means (36) to control the delivery of said fuel charge into and out of said cylinders (12; 14) said second cylinder (14) during movement of said second piston (18) between a first position at which said piston is at the beginning of its intake stroke det, and a second position in which said piston is not less than 10 ° of the Bewegungswinkelf from the end of its compression stroke to initiate, and to stop the supply of said fuel charge when said second piston (18) reaches a third position not later than the internal dead center position of the piston at the end of the compression stroke, and means for retarding movement of the fuel / air mixture from said second cylinder (14) into said combustion space (20) before said second piston (12). 18) reaches a fourth position, said piston having terminated at least substantially 80% of its compression stroke length, and means for inducing a swirling movement in air into said combustion space (20) from said first cylinder (12) to assist a rapid Mixture of the fuel / air mixture from said second cylinder (14) and air from said ers cylinder (12) is supplied in said combustion chamber during combustion. 2. Engine according to claim 1, characterized in that the continuously operable ignition means is a compression ignition. 3. Engine according to claims 1 or 2, characterized in that said second cylinder (14) comprises an extension of said first cylinder (12) and said second piston (18) has a projection on the top of said first piston (16 ),. and that the stroke of said first piston is such that said second piston (18) projects into said second cylinder in its outer dead center position. 4. Motor according to claim 3 _t characterized in that said combustion chamber (20) is formed in said second piston (18) and corresponding first and second opening means (44; 40), which (in said first and second cylinders 12, 14) to allow a flow of air and air / fuel mixture from said cylinders into said combustion space (20). An engine according to claim 4, characterized in that said second cylinder (14) has a projection (100) disposed on a top wall thereof to project into said second aperture (40) and displacing the air cylinder. To assist fuel mixture in said combustion chamber (20) when said second piston (18) approaches its internal dead center position. An engine according to any one of claims 1 to 3, characterized in that the second piston (18) has a projection (100 ') disposed thereon for projecting into an opening (40) of said combustion space (20) said second cylinder (14) is in communication to assist the displacement of the air-fuel mixture into said combustion space when said second piston (18) reaches its inner dead center position. 7. Engine according to one of claims 1 to 6, characterized in that said piston (18) reaches its second position when it has finished more than 90% of its compression stroke length. An engine as claimed in any of claims 1 to 7, characterized in that said pistons (16; 18) move toward and away from their internal dead center positions over at least 70% of their stroke length of the engine cycle. 9. Motor according to claims 1 to 8, characterized in that said control means (37) working Jet. to cause the second means (36) to begin delivering said fuel charge to said second cylinder (14) during the intake stroke of said second piston (18). An engine according to claim 9, characterized in that said control means (37) is operative to cause said second means (36) to begin delivering said fuel charge immediately to said second cylinder (14) said second piston (18) begins its intake stroke. 11. Motor according to claims 1 to 10, characterized in that said first piston (16) has an upper part which is at least partially formed of ceramic material. 12. Motor according to claim 11, characterized in that there is a catalytic material over said ceramic material. An engine according to claims 1 to 12, characterized in that said first means (25) is operative to supply a charge of unthrottled air to said first cylinder (12). An engine according to claims 1 to 13, characterized in that said first means (25) is operative to deliver a fuel-vapor mixture charge to said first cylinder (12), said mixture being below the lean flammability limit located. 15. Motor according to claims 1 to 14, characterized in that said ignition means (22) comprises a hot surface ignition means. 16. Engine according to claim 15, characterized in that the hot surface ignition means (22) comprises at least a portion of a wall of the combustion chamber (20) formed of ceramic material. 17. Motor according to claims 1 to 16, characterized in that said ignition means (22) comprises a catalytic material. 18. Motor according to claims 1 to 17, characterized in that the combustion chamber (20) has a substantially curved cross section with first and second inlet openings (44; 40) for entry of the air or the fuel / air mixture, and in that the radius (R) of the curvature of the cross-section of the combustion space (20) is immediately reduced over a part of the volume, at least in front of one of said openings in a circulation means of the gases in said combustion space. 19. Motor according to claims 1 to 18, characterized by a plurality of said first and a plurality of said first and second pistons (16, 18), said control means (37) being operable to adjust the fuel / air mixture ratio in each of said second cylinders (14) monitor 2U and adjust the amount of fuel injected into at least one of said second cylinders (14) to maintain the fuel-air mixture therein above the enriched-fuel flammability limit and adjust the amount of fuel remaining in the remaining second cylinders (14) is injected to restore a fuel / air mixture ratio below the lean fuel flammability limit as the fuel / air ratio in said second cylinders decreases to a preselected value above the enriched fuel flammability limit to prevent unwanted ignition during the engine cycle. An engine according to claim 19, characterized in that said control means (37) is operative to adjust the amount of fuel injected into at least one of said second cylinders (14) to increase the air-fuel ratio therein above To restore the flammability limit of the enriched fuel and adjust the amount of fuel injected into the remaining second cylinders (14) so as to restore the fuel / air ratio below the lean fuel flammability limit when the fuel / air mixture Ratio in said second cylinders increases to a preselected value below the lean flammability limit to prevent undesirable ignition during the engine cycle.