AU2012100364A4 - An internal combustion engine - Google Patents

Abstract

An internal combustion engine is disclosed which comprises a cylinder, a piston which can move inward and outward relative to the cylinder, a moving component located and movable in the cylinder between a head end of the cylinder and the piston, wherein when the piston moves inward, a stationary part which is fixed relative to the cylinder becomes positioned at least partially in an cavity in the piston causing gas in the cavity to be forced out between the piston and the stationary part into a space between the piston and the moving component, inlet means operable to allow gas to enter the cavity, between the piston and the stationary part when/as the piston moves outward, pressure reduction means for reducing pressure between the piston and the stationary part when the piston moves inward, sealing means for sealing between the stationary part and the piston to trap gas in the space between the piston and the moving component upon reduction in pressure between the piston and the stationary part by the pressure reduction means, injecting means for injecting fuel into the space between the piston and the moving component, wherein the fuel combusts in the said space increasing pressure between the piston and the moving component forcing the piston outward, and exhaust means operable to allow gas (combusted fuel etc) to escape. Figure 1

Description

AN INTERNAL COMBUSTION ENGINE TECHNICAL FIELD [00011 The present invention relates to internal combustion engines. BACKGROUND [0002] Piston-cylinder type internal combustion engines are well-known and are used to provide power in a wide range of applications. For example, they are used to power automobiles, pumps, generators and the like. [0003] The principal components of most piston-cylinder type internal combustion engines are the piston(s), the cylinder(s) and the crank shaft. In general, each cylinder comprises a blind cylindrical bore that is open at one end. The cylinder bore also has openings or "ports" which allow fuel to enter the cylinder and spent combustion gases to exit the cylinder. The piston comprises a plug-like component that is inserted into the cylinder through the open end of the bore to fit snugly within the bore. The piston is connected to an eccentric portion of the crankshaft by a connecting rod such that rotation of the crank shaft causes the piston to reciprocate linearly back and forth within the cylinder bore along the longitudinal axis of the cylinder. [0004] The side of the piston typically has piston rings to seal against the internal wall of the cylinder bore. Hence, the open region between the piston and the closed end of the cylinder bore generally forms a combustion chamber. The volume of the combustion chamber increases and decreases with the respective outward and inward reciprocating movement of the piston. [00051 Piston-cylinder internal combustion engines are fuelled by a combustible fluid fuel, typically a vapour mixture of air and another hydrocarbon or petrochemical fuel product. This combustible fuel enters the combustion chamber at a particular time during the engine's cycle. [00061 One common form of piston-cylinder internal combustion engine operates on a four stroke cycle. The four strokes of the cycle are conventionally known as (1) the inlet or "intake" stroke, (2) the compression stroke, (3) the combustion or "power" stroke, and (4) the exhaust stroke. These four strokes are illustrated schematically in Figure I. [00071 With reference to Figure I, it can be seen that at the beginning of the intake stroke, the piston 1 is located at its most inward position within the cylinder 2 (called "top dead centre"). Then, during the intake stroke, the rotation of the crank shaft (not pictured in Figure I) causes the piston 1 to move outwardly from top dead centre towards its most outward position (called "bottom dead centre"). This outward movement causes the volume of the combustion chamber 3 to increase. The increase in volume results in a drop in the relative pressure within the chamber 3 (compared with the pressure outside the chamber), and this drop in relative pressure helps to suck the fuel mixture into the chamber. A range of other mechanisms may also be provided for injecting the fuel into the combustion chamber, for example, under pressure. The fuel mixture enters the chamber 3 through one or more intake valves 4 near the closed end of the cylinder 2. The intake valves 4 are open to allow fuel to enter the combustion chamber 3 during the intake stroke (or a part thereof), but they are closed for the other strokes in the cycle. 100081 The intake stroke is completed when the piston 1 reaches bottom dead centre, whereupon further rotation of the crank shaft causes the piston 1 to again commence moving back inwardly within the cylinder 2. This starts the compression stroke. During the compression stroke, all of valves in the cylinder bore (i.e. the intake valves 4 and the "exhaust valves" 5) are closed so that the inward movement of the piston 1 within the cylinder 2 compresses the vapour fuel. Just before the piston 1 reaches top dead centre, a spark plug 6 located in the closed end of the cylinder 2 introduces an electric spark into the combustion chamber igniting the compressed fuel. Alternatively, in other "diesel" style engines, the heat generated by the compression of the fuel causes the fuel to "auto-ignite", in which case no spark plug is required. In either case, the ignition of the fuel increases the pressure and temperature within the combustion chamber 3 so that after the piston 1 passes top dead centre the increased pressure forces the piston I outwardly within the cylinder 2. This pressure driven outward movement of the piston 1 constitutes the "power" stroke. This is what drives the continued rotation of the crank shaft. [0009] The power stroke is completed when the piston I again reaches bottom dead centre, whereupon further rotation of the crank shaft causes the piston I to commence moving back inwardly within the cylinder. This commences the exhaust stroke. During the exhaust stroke, the one or more exhaust valves 5 in the cylinder 2 open to allow the spent combustion gases to be expelled. Therefore, as the piston 1 continues to move inwardly (driven by the continued rotation of the crank shaft), the combustion chamber volume decreases and the spent combustion gases are forced out of the combustion chamber 3 through the exhaust valves 5. The exhaust stroke is completed when the piston 1 reaches top dead centre, whereupon the exhaust valves. close, the intake valves open and the continued rotation of the crank shaft causes the piston 1 to again commence moving outwardly. This recommences the intake stroke and therefore the four strokes of the cycle repeat.

100101 It is quite common for internal combustion engines that operate on the four stroke cycle to have more than one cylinder. In these multiple cylinder engines, all of the cylinders operate on the four stroke cycle described above, but some of the cylinders are typically out of phase with others of the cylinders so as to achieve staggered firing of the cylinders (i.e. so that the power stroke for each of the cylinders occurs at different times). This allows the engine to run more smoothly, and it can also help to balance the engine against vibrations caused by the rotation of the eccentric mass of the crank shaft. The amount of phase difference between the cylinders depends on the number of cylinders present. The most common multi-cylinder engine configurations comprise 2, 4, 6, 8, 10 or 12 cylinders (although other arrangements with a greater number of cylinders, or with an odd number of cylinders, have also been devised). [00111 One problem with existing piston-cylinder engines such as the ones described above and shown schematically in Figure 1, is that the maximum volume in the combustion chamber available for the expansion of the combusting fuel gases is the same as the maximum intake volume of the combustion chamber. In these existing engines this maximum volume is the volume defined when the piston is at bottom dead centre. This limited volume available for the expansion of the combusting fuel gases limits the amount of energy that can be extracted from the engine for each piston power stroke. This in turn restricts the fuel and energy efficiencies that can be achieved with such four stroke piston-cylinder engines. [00121 Another problem with existing four stroke piston-cylinder engines is that each cylinder provides only one power stroke for every two revolutions of the crank shaft. Therefore, for example, with conventional six-cylinder four stroke engines there are only 3 power strokes per revolution of the crank shaft. This can mean that high engine speeds (i.e. high "revs") are required in order to achieve useful amounts of torque and/or power from existing four stroke engines. [00131 Another common form of piston-cylinder internal combustion engine operates on a two-stroke cycle. This form of engine is commonly referred to as a "two-stroke engine". Two stroke engines generally have one "power stroke" for every revolution of the crankshaft. [0014] Figures II-V show a two-stroke engine 10 having a single cylinder and a single piston therein. Two-stroke engines can also operate with multiple cylinders each having a single piston. In these multi-cylinder engines, the multiple pistons all connect to and drive a single crankshaft, and they generally operate (i.e. reciprocate) in their respective cylinders simultaneously at the same speed, but out of phase with each other in order to balance the engine. In any event, it is convenient to refer to the single cylinder engine 10 in Figures II-V for the purposes of explanation. [00151 The two strokes in a two-stroke engine cycle are commonly referred to as (1) the power stroke, and (2) the compression stroke. In the drawings, Figures II and III show the engine during the power stroke, Figure IV shows the engine near the beginning of the compression stroke, and Figure V shows the engine during the compression stroke. [00161 In Figures 1I-V, the blind internal bore that defines the cylinder bore is designated by reference numeral 20. The piston 30 forms a plug-like component which inserts snugly into the cylinder bore 20. The piston 30 is connected via a connecting rod 40 to an eccentric point 50 on the crankshaft 60. Consequently, when the crankshaft 60 rotates, the eccentric point 50 where the connecting rod 40 attaches to the crankshaft 60 also moves in a circular fashion. This circular motion is then transmitted via the connecting rod 40 to cause the piston 30 to move up and down in a linear reciprocating manner within the cylinder. [0017] For the purposes of explanation, it is convenient to consider the engine cycle to begin with the power stroke which starts when the piston is located as far into the cylinder as it can go (i.e. at top dead centre). Figure Il shows the piston slightly after top dead centre. During this period in the engine cycle there is a compressed mixture of air and fuel located in the combustion chamber 70 between the blind top of the cylinder bore 20 and the top of the piston 30. The power stroke commences when the compressed air/fuel mixture ignites. This ignition creates an increase in the pressure inside the combustion chamber 70 which forces the piston to move downwards within the cylinder. The downward force on the piston 30 is transmitted via the connecting rod 40 to drive rotation of the crankshaft 60. It is this downward force created by the combusting fuel that drives the engine (hence the name "power" stroke). This is how the engine converts the energy derived from the combustion of the fuel into "work" in the form of usable rotational energy which is delivered via the crankshaft. [00181 Also, at the beginning of the power stroke as shown in Figure II, an uncompressed mixture of air and fuel enters the region below the piston 30 via carburettor 90. The region below the piston 30 (i.e. in and around the crankshaft) is commonly referred to as the "crankcase" 80. The crankcase 80 is sealed off when the piston starts moving downwards and the downward movement of the piston in the cylinder towards the crankcase effectively compresses the air/fuel mixture in the crankcase.

j [0019] Referring next to Figure III, it can be seen that as the piston 30 moves downwards in the cylinder 20, the top of the piston passes by an open "port" I1 in the side of the cylinder. The port 11 is the "exhaust" port. When this happens, the mixture of air and fuel (most of the fuel has been burnt by this point in the cycle and so the mixture is more one of air and spent combustion products) is allowed to vent out through the exhaust port 11. [0020] Referring next to Figure IV, it can be seen that as the piston continues to move down, the top of the piston then passes by another open port 12 in the other side of the cylinder. This port is called the "transfer" port. The transfer port 12 is in fluid communication with the crankcase 80. Therefore, when the top of the piston 30 moves down past the transfer port so that the transfer port opens up, the fresh air/fuel mixture in the crankcase (which was compressed by the downward movement of the piston described above) flows from the crankcase up into the combustion chamber 70. Soon after the transfer port 12 opens, the piston 30 reaches its lowermost point (i.e. bottom dead centre). When the piston reaches bottom dead centre, the power stroke ends and the compression stroke commences. [00211 It will be appreciated that the rotating crankshaft 60 carries a considerable amount of angular momentum. Because of this angular momentum, the crankshaft continues to rotate even after the end of the power stroke, and this continued rotation in turn causes the piston 30 to move back upwards in the cylinder as illustrated in Figure V. As the piston 30 moves up, it first moves up past the transfer port 12 closing the transfer port, and then moves up past the exhaust port I1 closing the exhaust port. After the two ports have been closed, the un-combusted air/fuel mixture from the crankcase becomes trapped in the combustion chamber 70, and the upward movement of the piston 30 in the cylinder compresses the air/fuel mixture therein. The upward movement of the piston 30 also creates a relative vacuum inside the crankcase which helps to draw more air and fuel into the crankcase when it is allowed to enter by the carburettor 90. [0022] Finally, the piston 30 continues to move upwards in the cylinder until it reaches top dead centre whereupon the compressed air/fuel mixture in the combustion chamber ignites and the engine cycle commences again. The ignition of the compressed air fuel mixture can be triggered by "auto-ignition", or alternatively the compressed air/fuel mixture in the combustion chamber 70 can be ignited using a spark (delivered via a spark plug or something similar). [0023] One of the problems with existing two-stroke engines is that the fresh un-combusted air/fuel mixture from the crankcase enters the combustion chamber at the same time as spent combustion products are leaving the combustion chamber. This can be seen in Figure III which shows that the transfer port 12 is opening to allow new air/fuel to flow into the combustion V chamber at the same time as exhaust port 11 is open to allow spent combustion products to be expelled. This can lead to new air/fuel passing directly from transfer port 12 out through exhaust port 11 uncombusted. Fuel that is expelled uncombusted in this way is wasted because it is not used to drive the engine, and it therefore reduces the fuel efficiency of the engine. [00241 Another problem with existing two-stroke engines is that the simultaneous inflow of new air/fuel and outflow of spent combustion products allows the spent combustion products to mix with the new air/fuel as it enters. This can lead to some spent combustion products remaining in the combustion chamber even after the piston moves up to seal the ports. Consequently, some spent combustion products can remain inside the combustion chamber during compression and during the power stroke. However, because these already spent combustion products generally cannot combust further, their presence reduces the amount of combustion occurring during the power stroke and hence the amount of energy or "work" that can be produced by the engine. The extent to which the energy produced by the engine is reduced in this way depends on the proportion of spent combustion products relative to new air/fuel that remains in the combustion chamber during the power stroke. The more spent combustion products that remain, the lower the amount of energy that will be produced by the engine every cycle. [00251 It is an object of the present invention to provide an internal combustion engine that may partially ameliorate one or more of the above problems, or which at least provides an alternative to existing internal combustion engines. [00261 It is to be clearly understood that mere reference herein to previous or existing products, practices, publications or other information, or to any associated problems or issues, does not constitute an acknowledgement or admission that any of those things individually or in any combination formed part of the common general knowledge of those skilled in the field or are admissible prior art. SUMMARY OF THE INVENTION [00271 In one form, the invention resides broadly in an internal combustion engine having a cylinder and a piston which can move inward and outward relative to the cylinder, the engine having a two-stroke cycle whereby combustion is associated with each outward stroke of the piston, and wherein combustion occurs in a space inside the cylinder, and during combustion, the said space is sealed relative to the region into which new air/gas flows when entering the engine thus preventing combusting/combusted gases mixing with new air/gas.

[00281 In another form, the invention resides broadly in an internal combustion engine comprising a cylinder, a piston which can move inward and outward relative to the cylinder, a moving component located and movable in the cylinder between a head end of the cylinder and the piston, wherein when the piston moves inward, a stationary part which is fixed relative to the cylinder becomes positioned at least partially in a cavity in the piston causing gas in the cavity to be forced out into a space between the piston and the moving component, inlet means operable to allow gas to enter the cavity when/as the piston moves outward, pressure reduction means for reducing pressure between the piston and the stationary part when the piston moves inward, sealing means for sealing between the stationary part and the piston to trap gas in the space between the piston and the moving component upon reduction in pressure between the piston and the stationary part by the pressure reduction means, injecting means for injecting fuel into the space between the piston and the moving component, wherein the fuel combusts in the space increasing pressure between the piston and the moving component forcing the piston outward, and exhaust means operable to allow gas to escape. Further explanations will be given primarily with reference to this form of the invention. [00291 Engines in accordance with the present invention incorporate at least one cylinder, and possibly multiple cylinders. Where an engine includes multiple cylinders, there will be multiple other components (e.g. pistons, inlets, etc) associated with the respective cylinders. Each cylinder may be similar, at least in general terms, to cylinders used in other piston cylinder internal combustion engines. Therefore, each cylinder will comprise a bore that is substantially blind at one end (the head end). The bore will usually have a circular cross-section that remains constant in diameter along at least a substantial portion of its length. As in many conventional piston-cylinder internal combustion engines, the cylinder bore may be formed as an internal bore in the body of the engine. The engine body is commonly called the "engine block". The engine block may be formed from any material that is suitably robust and resistant to heat/thermal/pressure and related failures (for example cracking due to rapid thermal expansion/contraction etc). Ferrous metal alloys and some aluminium alloys are considered to 0 be suitable. In any event, suitable materials for the engine block will be well known to those skilled in the art. [00301 The engine may be provided with a cooling system. A range of cooling systems are used with existing piston-cylinder type internal combustion engines, and any such cooling system may be used with engines of the present invention. For example some or all of the cylinders, or the engine block as a whole, may be provided with cooling fins which may help to dissipate heat by giving the cylinder(s)/engine block increased surface area to more effectively dissipate heat through convection/radiation. Alternatively, or additionally, the engine may be provided with a piped cooling system. The working fluid in such a cooling system could be a gas (e.g. air) or liquid (e.g. water or some other liquid coolant). In any event, the system may circulate the working fluid through fluid conduit passageways in the engine block to absorb heat from the engine block. A radiator may also be provided for dissipating heat from the working fluid before the fluid is recirculated through the engine block. These are just examples, and other cooling systems known to those skilled in the art could also be used. [00311 Each cylinder bore is substantially blind at one end (the head end). It is said that the head end of each cylinder bore is "substantially" blind because the head end of each bore may incorporate the inlet means which allows gas/air to enter the engine. The stationary part which is fixed relative to the cylinder may also be incorporated in, connected to, or part of, the head end. This is discussed further below. [00321 In some embodiments, the inside of the cylinder may be formed by a cylindrical through-bore extending through the engine block, and the substantially blind head end may be formed by securing a lid-type component (often called a "cylinder head" or "head") on the engine block. The connection between the engine block and the head may be sealed using a "head gasket". In alternative embodiments, the head of the cylinder may be formed integrally with the rest of the cylinder. [00331 As mentioned above, the head end of each cylinder bore may incorporate the inlet means which allows gas to enter the engine, and the stationary part which is fixed relative to the cylinder may also be incorporated in, connected to, or part of, the head end. In some embodiments, the stationary part may be a part of the head which extends from the head end into the cylinder. In other words, the stationary part may be part of the head which itself projects into the region within the internal cylindrical wall of the cylinder. The projecting stationary part may also have an aperture or passage communicating between the inside of the cylinder and the outside of the engine. This communicating aperture/passage may form the inlet means. Thus, gas (e.g. air) from outside the engine may flow into the engine (and more specifically into the cavity in the piston, between the piston and the stationary part, as described below) through the aperture/opening in the stationary part. The inlet means (which may be the communicating aperture in the stationary part, as described above) may be openable and closable/sealable. This may be achieved in any suitable way, for example through the use of a conventional poppet valve. [00341 Associated with each cylinder of the engine there is a piston which can move inward and outward relative to the cylinder. The piston may be similar, at least in general terms, to pistons used in other piston-cylinder type internal combustion engines. For example, the piston may be a round, generally "plug"-like component the outside of which seals against the inside of the cylinder. Conventional piston rings may be used to provide this seal. [00351 However, unlike pistons used in most conventional engines, the piston in the present invention includes a cavity which can, in effect, receive the stationary part (recall that the stationary part is fixed relative to the cylinder) when the piston moves inward within the cylinder. As explained above, in some embodiments, the stationary part may project into the inside of the cylinder from the head end of the cylinder. Accordingly, in these embodiments, the cavity in the piston may be formed, e.g., as a recess or hole or gap in part of the piston which points towards the head end of the cylinder. The cavity (part of the piston) may also be aligned with the stationary part (which may be part of, or connected to, the cylinder), and the cavity may be slightly larger than the stationary part. Hence, when the piston moves inward towards the head end of the cylinder, this may cause the cavity to effectively move over and around the stationary part such that the stationary part becomes positioned at least partially within the cavity in the piston. It should also be noted that the valve (or other means) used for sealing the inlet means (recall that the inlet means may be an aperture through the stationary part) should be closed when/as the piston moves inwards. This is so that, as the stationary part becomes positioned progressively more and more within the cavity in the piston as the piston moves inward, the volume between the stationary part and the piston in the vicinity of the cavity reduces. This causes gas in the cavity to be forced out between the cavity wall and the stationary part and into a space between the piston and the moving component. [00361 As explained above, the engine also includes a moving component which is located in the cylinder, between the head end of the cylinder and the piston, and which is movable therein. In many embodiments, the moving component will be round so that the external edge/surface thereof seals against the inside wall of the cylinder. Rings similar to piston rings IU may also be provided to create this seal. The moving component may also have a gap or hole therein extending through its full thickness. The gap or hole may be shaped or configured so as to enable the moving component to be mounted on and/or around the stationary part which is fixed relative to the cylinder. Therefore, the movable component may slide back and forth (or up and down) relative to the stationary part when it moves within the cylinder in the region between the cylinder head and the piston. In some embodiments, the external shape of the stationary part may be substantially cylindrical, the stationary part may be centrally located relative to the cylindrical internal war the cylinder, and it may extend into the cylinder from the head end. In such embodiments, the gap or hole in the movable component may comprise a round hole through the centre of the moving component which is the same size or very slightly larger than the diameter of the stationary part, such that the stationary part is received in the round hole thereby mounting the moving component on the stationary part, and the moving component may therefore slide up and down the stationary part when it moves inside the cylinder. However, it is to be clearly understood that the invention is not necessarily limited to the particular configuration of the stationary part and the moving component described in this paragraph. A wide range of other configurations are also possible. [00371 The engine also includes pressure reduction means for reducing pressure between the piston and the stationary part when the piston moves inwards. For the avoidance of doubt, any means or mechanisms suitable or able to allow a reduction in pressure between the piston and the stationary part when the piston moves inwards could be used. In some embodiments, the pressure reduction means may comprise one or more holes in the piston and one or more corresponding holes in the cylinder. In these embodiments, the hole(s) in the piston may communicate between the cavity in the piston and the outside of the piston. The hole(s) in the cylinder may communicate between the inside of the cylinder and the outside of the engine. The positioning of the hole(s) in the piston, and the positioning of the hole(s) in the cylinder, may be such that the hole(s) in the piston come into register with the corresponding hole(s) in the cylinder when the piston reaches a certain position relative to the cylinder during its inward and outward travel. The said position of the piston relative to the cylinder may be somewhere between top dead centre and bottom dead centre. The alignment of the hole(s) in the piston with the hole(s) in the cylinder may create a flow path between the inside of the cavity within the piston and the outside of the engine. Accordingly, when the hole(s) are thus aligned, gas between the piston and the stationary part (which it will be recalled is compressed by the movement of the stationary part into the cavity in the piston) is allowed to escape/vent to the S1I outside of the engine, thus causing a reduction in pressure in the cavity (and between the piston and the stationary part). [00381 The engine further incorporates sealing means for sealing between the stationary part and the piston upon the reduction in pressure between the piston and the stationary part, to thereby trap gas between the piston and the moving component. For the avoidance of doubt, any means or mechanisms suitable or able to seal between the stationary part and the piston could be used. In some embodiments, the sealing means may comprise a bevelled ring or collar which is mounted on the stationary part and which can engage with both the piston and the stationary part so as to create a seal therebetween upon the reduction in pressure between the piston and the stationary part caused by the pressure reduction means (in other words, when the pressure in the cavity drops in relation to pressure between the piston and the moving part). [00391 Similar sealing means may also be provided for sealing between the stationary part and the moving component, and again, any suitable means or mechanisms suitable for or able to achieve this seal could be used. 100401 The engine further includes exhaust means for allowing gas (e.g. spent combustion products etc) to escape. Any means or mechanisms suitable for or able to allow gas to escape from the engine at the appropriate time may be used. In some embodiments, the exhaust means may be provided by one or more holes in the cylinder (e.g. in the cylinder wall) which communicate between the inside of the cylinder and the outside of the engine. Said one or more holes may be (although need not necessarily be) the same as the one or more holes that (together with the one or more holes in the piston) provide the pressure reduction means in the embodiments described above. 100411 Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS [00421 Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows: 100431 Figure I illustrate a conventional four stroke engine cycle.

IL4 [00441 Figures II-V together illustrate a conventional two stroke engine cycle. [00451 Figures 1-10 illustrate an engine cylinder, and its associated power generating components, in accordance with one embodiment of the invention at different points during the engine cycle. [00461 Figure 11 illustrates a pair of engine cylinders, each of the kind described with reference to Figures 1-10, connected in a manner so as to enable electricity to be generated through magnetic induction. [0047] Figure 12 also illustrates a pair of engine cylinders, again each of the kind described with reference to Figures 1-10, connected and linked to a Scotch yolk arrangement such that the reciprocating motion is converted into rotary motion. [00481 Figure 13 illustrates a configuration wherein four engine cylinders, each of the kind described with reference to Figures 1-10, are arranged generally in a line parallel to a rotatable shaft such that operation of the cylinders causes rotation of the shaft. 100491 Figure 14 illustrates a configuration wherein eight engine cylinders, each of the kind described with reference to Figures 1-10, are arranged in two linear sets of four, both sets being in a line parallel to a rotatable shaft, and with the respective sets on opposite sides of the shaft, such that operation of the cylinders causes rotation of the shaft. [00501 Figure 15 and 16 show alternative "a radial" configurations of engine cylinders arranged to generate rotation. [00511 Figure 17 shows an arrangement whereby a number of cylinders are arranged around a swage plate. DETAILED DESCRIPTION OF THE DRAWINGS [00521 Figure 1 illustrates an engine cylinder, and its associated components, in accordance with one possible embodiment of the invention. More specifically, Figure 1 illustrates a metal cylinder 100 with a plurality of external cooling fins 102. In this particular embodiment, the cooling fins 102 horizontally encircle the cylinder 100. Near the bottom of the cylinder 100, away from the head 104, there are a number of holes 106 through the wall of the cylinder 100 (see Figures 2 and 3). These holes 106 are exhaust ports.

I -) 100531 There is a metal plate affixed to cover the top of the cylinder 100, or this plate could be cast as part of the cylinder. The said plate forms the cylinder head 104. Protruding through the cylinder head 104 into the bore within the cylinder 100 is a stationary part in the form of a hollow cylindrical component 108. This component will be referred to hereafter as the stationary piston 108 or the static piston 108 (these two terms are interchangeable). [00541 As mentioned above, the static piston 108 is hollow. Furthermore, its internal end is machined to allow a conventional poppet valve 110 to be installed within the static piston 108. The inner end of the poppet valve 110 can seal against the internal end of the static piston 108. Mounted on the external end of the stationary piston (outside the cylinder 100) is a spring 109. The spring functions to bias the poppet valve 110 to the closed position where the inner end of the poppet valve seals against the inner end of the stationary piston 108. Of course, the poppet valve 110 can also be caused to move against the bias of the spring 109 such that the inner end of the poppet valve separates from the inner end of the stationary piston 108, thus opening the poppet valve (e.g. see Figure 3). This can occur when the poppet valve is subject to pressure below atmospheric pressure, as discussed below. 100551 The external end of the stationary piston may also have an air filter attached thereto (not illustrated). The air filter functions to clean the air as it is admitted into the compression chamber 122 through the stationary piston 108 when the poppet valve 110 is open. This will also be discussed further below. [00561 Near the top of the cylinder 100, and extending horizontally through the wall thereof, is an injector 112. Fuel can be injected under pressure into the engine's cylinder 100 through the injector 112. [00571 A round moving component in the form of a movable flat plate 114, referred to hereafter as the sweeper 114, has a concentric central hole through it. The hole in the sweeper 114 is of the same diameter as the stationary piston 108, and the outer diameter of the sweeper 114 is the same as the internal diameter of the engine cylinder 100. The sweeper 114 is mounted on, and can slide along, the stationary piston 108 (i.e. it can slide up and down on the stationary piston 108, inside the cylinder 100, below the engine cylinder head 104). The sweeper 114 has, machined in one side of the hole, on the side facing away from the head 104, a concentric bevel to accommodate a collar seal 116 that also slides up and down the static piston 108. This collar seal 116 is bevelled to fit into the sweeper bevel such that, when the collar seal 116 and the sweeper 114 come together, gases are prevented from passing between the sweeper 114 and the stationary piston 108. The outer edge of the sweeper has conventional piston rings (not shown) I't to prevent gases from passing between the outer edge of the sweeper 114 and the inside of the cylinder 100. In other embodiments, the collar ring 116 may be replaced by alternative sealing devices. 100581 The collar seal 116 is essentially a bevelled collar (ring) with a gap in the collar (as in piston rings). The collar and gap are machined such that, when under pressure, the collar 116 is driven by gas pressure into the bevel of the sweeper 114 so that the matching bevels are pushed together and the gap is closed, thus preventing gas from passing between the sweeper 114 and the stationary piston 108. 100591 A movable piston 118, referred hereafter to as the work piston 118, inserts through the open end of the cylinder 100 and has conventional piston rings (not shown) near the top to prevent the passage of gases between the work piston 118 and the cylinder wall. The work piston 118, at the outer end 120 thereof relative to the cylinder, may operate with little friction against a concave or convex moving surface by means of a roller or the like. This is discussed further below. 100601 The inner end of the work piston 118 (the end facing the sweeper 114) has a cavity shaped as a cylindrical hollow blind bore formed therein. This blind bore is hereafter referred to as the intake chamber 122 or the compression chamber 122. In the side of the work piston 118, near the bottom of the compression chamber 122, there are holes 124 which pass through the walls of the work piston. At a position just before TDC, these holes 124 align with the exhaust ports 106 thereby allowing air under compression to vent from the compression chamber 122 through the exhaust ports 106. The work piston 108 has additional rings (not shown) fitted on either side of (i.e. above and below) these holes 124 to prevent unwanted leaking of compressed air from the compression chamber 122 (between the work piston 118 and the walls of the cylinder 100). [0061] The diameter of the blind bore that forms the compression chamber 122 is slightly greater than the diameter of the stationary piston 108 to allow compressed air to move from the compression chamber 122 into the combustion space 123 during the upstroke (e.g. see Figure 4). During the operation of the engine, as the work piston 118 is pushed up towards the head 104, the stationary piston 108, in effect, moves into the compression space 122. The end of the compression chamber 122 facing the sweeper 114 is bevelled so as to accommodate a movable sealing collar ring 126 similar to the collar seal 116 associated with the sweeper. This collar ring 126 also encircles the stationary piston 108 and can move up and down on the stationary piston 108 (the collar seal 126 is positioned in between the collar seal 116 and the work piston 118).

The collar seal 126 provides sealing between the combustion space 123 and the intake/compression chamber 122 when it is pushed into engagement with the bevelled top of the work piston 118 by pressure difference between the combustion space 123 and the compression chamber 122. 100621 As the air is being compressed in the compression chamber 122 during the upstroke, the said air is able to pass into the combustion space 123 by passing between the work piston 118 and stationary piston 108 (during this part of the engine cycle the collar seal 126 is not sealed against the top of the work piston 118). During compression, the poppet valve 110 in the end of the stationary piston 108 is forced shut (by the spring 109 and by the pressure in the compression chamber 122) and thus prevents air from escaping through the static piston 108. Near the end of the upstroke, the holes 124 in the compression chamber briefly align with the exhaust ports 126. This allows pressurised air still in the compression chamber 122 to vent to the atmosphere, which in turn causes the pressure in the compression chamber 122 to drop. When the pressure in the compression chamber 122 drops, the collar seal 126 between the combustion space 123 and the compression chamber 122 closes (i.e. the collar seal 126 moves into sealing engagement with the bevelled top of the work piston 118). This is due to the fact that the pressure above the collar seal 126 in the combustion space 123 is then higher than the pressure in the compression chamber 122 (which is vented to atmosphere). After the collar seal 126 closes, further movement of the work piston 118 inwards into the cylinder causes the air in the combustion space 123 to be further compressed. Fuel is then injected through the injector 112 and ignites (this particular embodiment relies on auto ignition due to the temperature/pressure in the combustion space 123). Importantly, the combustion caused by the ignition is contained within the combustion space 123, which is then sealed off from the compression space 122 by the collar seal 126. 100631 In each cylinder of the engine according to this embodiment, there is therefore no combustion chamber in the conventional sense. Combustion takes place between the sweeper 114 and the work piston 118. The space between the sweeper 114 and a work piston 118 varies in volume during the combustion cycle. This is why it is referred to herein as the combustion space 123. [00641 The way in which the engine cycle operates in this embodiment, and aspects of its operation, will now be described in more detail, beginning with the work piston 118 at the end of its stroke at bottom dead centre (BDC).

IlU [00651 As shown in Figure 2, when the work piston 118 is at the end of its stroke, the top of the work piston 118 is located a short distance below the exhaust ports 106. The distance between the top of the work piston 118 and the exhaust ports 106 is slightly larger than the thickness of the sweeper 114. At this time, the sweeper 114 is also descending down the static piston 108 towards the top of the work piston 118. As the sweeper 114 moves past the exhaust ports 106, the pressure behind the sweeper 114 (i.e. in the space 125 between the sweeper 114 and the cylinder head 104) is able to vent to, and equalise with, the atmosphere. This prevents build-up of gases behind the sweeper 114 in the space 125. [00661 As the sweeper 114 moves further towards the work piston 118, a small amount of gas is entrapped between the sweeper 114 and the work piston 118 and the pressure of that small amount of trapped gas rapidly rises (at this time the exhaust ports 106 are no longer exposed as the sweeper has moved down past, and is located beneath, the exhaust ports).The entrapped gas cushions the impact of the sweeper 114 as it is about to contact the work piston 118. [00671 The work piston 118, with the sweeper 114 then upon or just above it, then begins to move up towards the head 104. As the work piston 118 (and the sweeper 114) move up past the exhaust ports 106 any gas entrapped between the work piston 118 and the sweeper 114 is exhausted and the sweeper finally comes fully (if it hasn't already) into contact with the upper face of the work piston 118. The work piston 118, with the sweeper 114 then riding upon it, then continues upward. [0068] Meanwhile, as the work piston 118 moves up, the stationary piston 108 is, in effect, moving into the compression chamber 122 compressing the air therein. The compressed air in the compression chamber 122 is in turn forced between the stationary piston 108 and the walls of the compression chamber 122, through the collar seal 126 and into the space 123 between the sweeper 114 and the work piston 118 (see Figure 4). Essentially, the combustion space 123 and the compression chamber 122 are (during this part of the engine cycle) united/linked. As the work piston 118 continues to rise the air in the linked spaces 122, 123 is further compressed (increasing in pressure). This pressure increase forces the collar seal 116 to seal against the sweeper 114 and in turn pushes the seal 116 and sweeper 114 upwards, thus increasing the volume of the combustion space 123. The air which is entrapped in the space 125 above the sweeper 114 (i.e. between the sweeper 114 and the head 104) is therefore also compressed. As the sweeper 114 (and its seal 116) are free to move along the stationary piston 108, at any instant during this part of the engine cycle, the sweeper 114 and seal 116 will generally be naturally moved (by the pressure above and below) to a position such that the pressure above the sweeper I / is the same (or roughly the same) as the pressure below the sweeper. In other words, such that the pressure between the sweeper 114 and the head 104 is roughly the same as the pressure in the combustion and compression spaces (which are linked during this part of the engine cycle). [0069] Very near the highest point of travel of the work piston 118 (i.e. very near TDC) the holes 124 in the compression chamber 122 briefly align with the exhaust ports 106 (see Figure 6). This allows venting from the compression chamber 122 and causes a rapid drop in pressure in the compression chamber 122. This in turn causes the work piston's collar seal 126 to close due to the large difference in pressure in the compression space 123 compared with the now atmospheric (or near atmospheric) pressure in the compression chamber 122. This was also described above. [0070] Figure 7 shows that when the work piston 118 reaches TDC, the sweeper 114 is above the injector 112, and fuel is injected below the sweeper 114 into the combustion space 123 (between the sweeper 114 and the work piston 118). When the fuel is injected, it ignites due to the temperature and pressure within the combustion space, and the pressure in the combustion space 123 then rapidly increases further due to the combustion. This pressure increase caused by combustion also causes the sweeper 114 to rise even further up towards the head 104. [00711 The work piston 118 is forced back down in the cylinder by the pressure increase caused by combustion, thus doing work, and the sweeper 114 then follows. (The distance of the sweeper 114 from the work piston 118 at any given instant in this part of the engine cycle is determined by the expansion of the combustion gases between the sweeper 114 and the work piston 118 and also by the expansion of compressed air in the space 125 between the sweeper 114 and the head 104. In other words, it is determined by the balancing of the pressures above and below the sweeper 114, as discussed above. 100721 As the work piston 118 moves down during the power stroke, air is drawn into the compression chamber 122 through the poppet valve 110. Note that, during this part of the engine cycle, the combustion in the combustion space 123 forces the collar seal 126 to seal against the top of the work piston 118. The compression chamber 122 is therefore sealed off from the combustion space 123. Accordingly, as the work piston 118 moves down, the volume of the compression chamber 122 increases resulting in a drop in pressure within the compression chamber 122. This drop in pressure is sufficient to cause the poppet valve 110 to open (it is sucked/drawn open against the bias of spring 109) allowing air to be drawn into the compression chamber 122 through the poppet valve 110. See Figure 8.

10 100731 Eventually the work piston 118 moves down such that the top of the work piston moves past the exhaust ports 106. This therefore exposes the combustion space 123 to the exhaust ports 106 whereupon the combustion gases mostly escape. When the pressure in the combustion space 123 drops to (approximately) atmospheric pressure, the residual pressure behind the sweeper 114 (i.e. pressure in the space 125 between the sweeper 114 and the head 104) pushes the sweeper 114 down towards the work piston 118 thus "sweeping" any remaining gases (spent combustion gases and byproducts, etc) in the combustion space 123 out through the exhaust ports 106. The sweeper 114 eventually catches up with the work piston 118 and the engine cycle is ready to begin again. (The combustion space 123 is closed, the air behind the sweeper 114 in the space 125 is at atmospheric pressure and the intake/compression chamber 122 is recharged with air drawn in through the poppet valve 110.) [00741 Further reference will now be made to Figures 3-10 which illustrate different stages of the engine cycle. [00751 Figures 3 and 4 illustrate successive points in time during the upstroke. In this part of the engine cycle, the inlet valve 110 closes (compare Figures 3 and 4) and upward movement of the work piston 118 causes the stationary piston 108 to, in effect, move into the compression chamber 122. This causes the air within the compression chamber 122 to be forced from the compression chamber 122 through the space between the stationary piston 108 and the walls of the compression chamber 122 and into the combustion space 123 between the work piston 118 and the sweeper 114 (as illustrated in Figure 4). The compression chamber collar seal 126 is also pushed open (as illustrated in Figures 3 and 4) by the pressure of the air such that air is allowed to pass from the compression chamber 122 into the combustion space 123. The sweeper 114 (sealed relative to the static piston 108 by the collar seal 116) is thus pushed upwards. During this part of the engine cycle, the pressure in the compression chamber 122 and also in the combustion space 123 is increasing, although at any given instant the pressure in the two spaces is the same as they are linked/connected. [00761 Referring next to Figures 5 and 6, as the work piston 118 nears TDC, the holes 124 in the walls of the work piston 118 align with the exhaust ports 106 (see Figure 6) bringing the compression chamber 122 into communication with the atmosphere, whereupon the pressure in the compression chamber 122 falls rapidly as the air is vented. This sudden drop in pressure causes the collar seal 126 associated with the work piston 118 to close and prevent any further communication between the compression chamber 122 and the combustion space 123.

[00771 Referring next to Figure 7 which shows the work piston 118 at TDC, it can be seen that at this time the sweeper 114 is located above the injector 112. Fuel is injected under high pressure into the compression space 123 between the sweeper 114 and the work piston 118, and due to the temperature/pressure therein the fuel ignites, as in conventional diesel engines. After ignition the pressure in the combustion space 123 rises further which pushes the sweeper 114 further up to the point where the pressure above the sweeper 114 (in the space 125) and the pressure in the combustion space 123 are equal. The high pressure in the combustion space 123 forces the working piston down, doing work. [0078] Next, as illustrated in Figure 8, the high pressure caused by combustion in the combustion space 123 forces the work piston 118 down. As the work piston 118 is moving down, the pressure in the intake chamber 122 drops, causing the poppet valve 110 to open and thereby allow air to be drawn in through the hollow static piston 108 to fill the compression chamber 122. This therefore functions essentially as the "intake stroke". However, unlike conventional four stroke engines, this "intake stroke" occurs during/at the same time as the "work stroke"/"power stroke". In other words, intake and expansion occur at the same time. [00791 Referring next to Figure 9 which shows the work piston 118 towards the end of the "power stroke", it can be seen that the work piston 118 has moved down past the exhaust ports 106 thereby allowing gases (spent combustion gases etc) in the combustion space 123 to vent to the atmosphere. With the resultant drop in pressure in the combustion space 123 the pressure in the space 125 behind the sweeper 114 causes the sweeper 114 to rapidly advance down towards the work piston 118, exhausting/forcing out any remaining gases in the combustion space 123. [00801 Figure 10 shows the work piston 118 towards the end of the "power stroke" (i.e. towards the end of the engine cycle). In Figure 10, the sweeper 114 has almost moved down onto the work piston 118 and the space 125 behind the sweeper is exposed to the exhaust ports which means that the space 125 drops to atmospheric pressure. This prevents gases building up behind the sweeper. Also, at the end of the power stroke, the top of the work piston 118 is positioned a little below the exhaust ports 106. This allows a small amount of gases to be trapped between the work piston 118 and the sweeper 114 as the sweeper completes its descent. The rapid increase in pressure of this trapped gas as the sweeper 114 nears the work piston 118 decelerates the sweeper 114 and prevents it from colliding with the work piston. As the work piston 118 begins to rise with the commencement of the next engine cycle, the space between the work piston 118 and the sweeper 114 is momentarily exposed to the exhaust ports allowing the trapped gases to escape and the sweeper 114 to finally contact the work piston 118. This arrangement prevents the sweeper from colliding too heavily with the work piston at the end of each stroke thus preventing undue wear and tear on the components, etc. [0081] One beneficial aspect of the engine cylinder configuration, as described with reference to the embodiment above, is that there is no necessity to pull/draw the work piston 118 down. The work piston 118 is pushed down by the pressure in the combustion space 123 caused by combustion, but this downward movement of the work piston 118 also causes the intake stroke (i.e. the inflow of air into the compression chamber 122 through the poppet valve 110) to be performed simultaneously. This means that it is not necessary (as it is in conventional engines) to have a connecting rod or a crank shaft which pulls/draws the piston down in the cylinder to perform the intake stroke. [0082] Other beneficial aspects of the invention, as described with reference to the embodiment above, include the following: - apart from the seals 116 and 126 and the poppet valve 110, the only other moving parts inside the cylinder 100 are the work piston 118 and the sweeper 114. - The ratio of the intake volume (the volume of the compression chamber 122) to the expansion volume (the volume of the combustion space 123) can be readily altered during manufacture. For instance, the engine could be designed/dimensioned such that the maximum volume attained by the combustion space 123 during the engine cycle is considerably larger than the volume of the compression chamber 122, thereby allowing for greater expansion of the combusting fuel/air than is possible with conventional engines (in conventional engines the volume available for expansion is generally the same as the intake volume). The ability to vary the ratio of intake volume to expansion volume may allow the power vs. efficiency of the engine to be control led/improved/optimised. = The configuration provides, in effect, a two-stroke engine in that, for each cylinder, there is a power stroke for every single "in-out" cycle of the work piston 118. In contrast, in conventional four stroke engines, a power stroke only occurs during every second "in out" cycle of the piston. In other words, in the present engine configuration, for each cylinder, the power stroke occupies 50% of the cycle time as compared with 25% of the cycle time for conventional four stroke engines.

L I " Also, whilst the present engine configuration provides a form of two-stroke cycle, it does not suffer from the problems of conventional two stroke engines with regards to, for example: o new air/fuel passing directly from transfer port out through exhaust port uncombusted, or o mixing of new fuel/air with spent combustion products due to the simultaneous inflow of new air/fuel and outflow of spent combustion products. m There is no exhaust 'stroke' as such since expulsion of spent combustion products occurs almost instantaneously at the end of the power stroke (the power stroke being simultaneous with the intake stroke). - The simplicity of the engine configuration may help to minimise manufacturing costs. [00831 Certain ways in which the engine, as described with reference to the embodiment above, might be used to drive motion or generate energy are explained by way of example below. In general, work done during the power stroke may often be recovered by mechanical or electrical means. The mechanical means could be, for example, a conventional crankshaft, a Scotch yoke, a reversed multi lobed reverse cam drive or an arrangement of multiple of the above cylinders in an orbital fashion. Some such possible configurations are discussed below. 100841 Cams are commonly used to convert rotary motion into linear reciprocal motion. With the embodiment of the present invention described above, the reciprocal motion of the work piston 118 may be converted into rotary motion by using an elliptical cam (not shown) connected to a drive shaft (not shown). In such arrangements, the roller which is shown on the bottom end of the work piston in Figures 1-10 engages with the elliptical surface of the cam such that during the power stroke the roller pushes against the elliptical surface of the cam causing the cam to turn, thereby causing rotation of the shaft. [00851 Figure 11 illustrates a pair of engine cylinders, each of the kind described with reference to Figures 1-10 above, but connected end to end such that the heads of the respective cylinders are at opposed ends and the two work pistons are formed effectively as a single component that oscillates within the connected cylinders. In this particular configuration, the single component which forms the work pistons also contains one or more permanent magnets 200, and there is a solenoid or coil of conducting wires 202 wrapped around the cylinders, L around where the magnet(s) 200 are (within the magnets' magnetic field), such that movement of the permanent magnet(s) 200 relative to the coils 202 (caused by the oscillating movement of the work piston component within the cylinders) causes a flow of electrical charge in the wires of the coil. [00861 Figure 12 also illustrates a pair of engine cylinders, again each of the kind described with reference to Figures 1-10 above, and again connected end to end such that the heads of the respective cylinders are at opposite ends with the two work pistons formed effectively as a single component that oscillates within the cylinders. However, in this configuration, the oscillating movement of the work piston component within the cylinders is converted into rotational motion of an associated shaft 204 using a Scotch yolk arrangement. A Scotch yolk is a very common arrangement for converting reciprocating linear motion into rotary motion (or vice versa) and this therefore need not be explained in detail. [00871 Figure 13 illustrates a configuration wherein four engine cylinders, each of the kind described with reference to Figures 1-10 above, are arranged generally in a line parallel to a rotatable shaft 206. The shaft has a series of cams 208 connected thereon, and the rollers on the respective outer ends of the work pistons each bear against the respective cams 208 to drive the cams in the manner described above. In this particular configuration, the cams and the cylinders are arranged so that each cylinder is out of phase with the other cylinders (i.e. at any given time, the different cylinders are at a different stage in their engine cycle). This may assist to achieve smoother operation and delivery of rotation of the shaft, and it may also assist to balance the engine, etc. [0088] The arrangement in Figure 14 is similar to the arrangement in Figure 13 except that, whereas Figure 13 has a series of four cylinders arranged in single line on one side of the shaft, the arrangement in Figure 14 has two sets of four cylinders, each set arranged in a line with the two sets on opposite sides of the shaft. In this arrangement, a given cam 208 on the shaft is shared by one cylinder on either side. In Figure 14, the arrangement is like a "boxer" engine arrangement in that the two sets of cylinders are arranged directly opposite each other relative to the shaft. In an alternative configuration, the two sets of cylinders could be arranged to form a "V" (it would be a V8 in this case as there are eight cylinders, but of course other arrangements are also possible, e.g., V6, V12, etc, depending on the number of cylinders.) [00891 Figure 15 illustrates a radial arrangement wherein the reciprocal motion of the work pistons 118 is converted into rotary motion by using an elliptical cam 210 connected to a drive shaft 212. The rollers on the ends of the respective work pistons engage with the elliptical surface of the cam 210 such that during the power stroke of each cylinder the roller pushes against the elliptical surface of the cam causing the cam turn, thereby driving rotation of the shaft. [00901 Figure 16 shows an arrangement where six cylinders are arranged with their respective work pistons pointing outwards such that the roller on each work piston engages with the inside of an elliptically shaped casing. In this "rotary" arrangement, during the power stroke of respective cylinders, the rollers on the ends of the respective work pistons push against the casing with a rolling, camming action, such that there is a force vector at an angle to the radial vector thus causing the illustrated rotation. In this arrangement, the shape of the casing (encircling track) can be so formed that each stroke can have its period determined by the curve that the piston is constrained to take. In fact the "intake" and "exhaust" periods (i.e. the periods in the engine cycle when intake and exhaust/venting occur) can be reduced to small fractions of the combustion cycle. It is envisaged that the intake and exhaust time could be reduced, perhaps to less than 5% of the cycle time. This would mean that the power stroke, for instance, occupies proportionally more of the engine cycle time. [00911 Figure 17 shows an arrangement whereby a number of cylinders are arranged around a plate. The plate is known as a swage plate and is affixed to a shaft at an angle other than 900. The arrangement shown allows the reciprocal movement of each of the pistons to be converted to a rotary motion of the shaft. [0092] In the present specification and claims (if any), the word "comprising" and its derivatives including "comprises" and "comprise" include each of the stated integers but does not exclude the inclusion of one or more further integers. [0093] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations. [0094] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.

Claims (5)

1. An internal combustion engine comprising a cylinder, a piston which can move inward and outward relative to the cylinder, a moving component located and movable in the cylinder between a head end of the cylinder and the piston, wherein when the piston moves inward, a stationary part which is fixed relative to the cylinder becomes positioned at least partially in a cavity in the piston causing gas in the cavity to be forced out between the piston and the stationary part into a space between the piston and the moving component, inlet means operable to allow gas to enter the cavity, between the piston and the stationary part, when/as the piston moves outward, pressure reduction means for reducing pressure between the piston and the stationary part when the piston moves a certain distance inward, sealing means for sealing between the stationary part and the piston to trap gas in the space between the piston and the moving component upon reduction in pressure between the piston and the stationary part by the pressure reduction means, injecting means for injecting fuel into the space between the piston and the moving component, wherein the fuel combusts in the said space increasing pressure between the piston and the moving component forcing the piston outward, and exhaust means operable to allow gas to escape.

2. An internal combustion engine as claimed in claim 1 wherein the external edge/surface of the moving component seals against the inside wall of the cylinder, the moving component also has a gap or hole shaped to enable the moving component to be mounted on or around the stationary part such that the movable component can slide relative to the stationary part when it moves in the region between the cylinder head and the piston.

3. An internal combustion engine as claimed in claim I or 2 wherein the pressure reduction means comprises one or more holes in the piston and one or more corresponding holes in the cylinder, the hole(s) in the piston communicate between the cavity in the piston and the outside of the piston, the hole(s) in the cylinder communicate between the inside of the cylinder and the outside of the engine, and the positioning of the hole(s) in the piston, and the positioning of the hole(s) in the cylinder, is such that the hole(s) in the piston come into register with the hole(s) in LO the cylinder when the piston reaches a certain position relative to the cylinder creating a flow path between the inside of the cavity and the outside of the engine.

4. An internal combustion engine as claimed in claim 3 wherein the said one or more holes in the cylinder also provide the exhaust means.

5. An internal combustion engine having a cylinder and a piston which can move inward and outward relative to the cylinder, the engine having a two-stroke cycle whereby combustion is associated with each outward stroke of the piston, and wherein combustion occurs in a space inside the cylinder, and during combustion, the space is sealed relative to the region into which new air/gas flows when entering the engine thus preventing combusting/combusted gases mixing with new air/gas.