GB2496099A

GB2496099A - Reciprocating internal combustion engine

Info

Publication number: GB2496099A
Application number: GB1117263.2A
Authority: GB
Inventors: Paul Protopapa
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-10-06
Filing date: 2011-10-06
Publication date: 2013-05-08
Anticipated expiration: 2031-10-06
Also published as: GB2496099B; GB201117263D0

Abstract

An i.c. engine has a piston 2 having two sections 23, 24 of different cross-sectional profile reciprocating inside a cylinder 1 having a complementary profile so that each section 23, 24 of the piston has a combustion surface 4, 5 partly defining respective combustion chambers 8, 9 which are not in fluid communication with one another, eg piston rings 3 prevent egress of gases from one combustion chamber into the other. The engine can thus perform isolated cycles in respective chambers, eg 180 degrees out of phase. The piston 2 and cylinder 1 may each have a stepped profile. The combustion chambers 8, 9 may have respective sets of gas exchange valves 13, 14. The engine may have a double-ended stepped cylinder and piston (51, 52, fig.4) in which the combustion surfaces (5, 5a) of the middle sections are bevelled and its valves are actuated by a rotating cam ring (30, fig.5). The engine may have plural cylinders and may be spark-ignited or diesel, four-stroke or two-stroke. The engine may be used as a compressor.

Description

Title: Split Volume Cylinder Descrirtion of Invention THE PRESENT INVENTION relates to cylinders for reciprocating engines, and more specifically to engine cylinders having a split volume.

In general, two-and four-stroke engines are known in the art which include at least one cylinder with a combustion chamber of a generally cylindrical shape.

Inside such a cylinder, a substantially cylindrical piston may reciprocate. These engines generally operate at a low efficiency, and particularly in the case of two-stroke engines, are polluting and noisy.

Split-cycle engines are also known in the art which employ two linked cylinders, one cyHnder used for intake, mixture and compression of the air-fuel mixture, the other for ignition, expansion and exhaust of the air-fuel mixture.

These engines go some way to addressing the unbalanced nature of a reciprocating engine.

However, there exists a need for a reciprocating engine which operates more efficiently, with the ability to deliver more power whilst occupying a small space. Such an engine would allow for the development of less polluting, smaller and more efficient vehicles. Furthermore, an engine that is more balanced would produce less noise and likely waste less energy.

The present invention seeks to provide an improved engine cylinder.

Accordingly, the present invention provides a cylinder for a reciprocating engine, the cylinder having an internal volume and a piston located therein, the piston being movable inside the cylinder, constrained to move along an axis of motion, wherein a first section of the piston has a first substantially constant cross-sectional profile and terminates in a first end surface which has a first area, substantially perpendicular to the axis of motion, a second section of the piston, connected to the first section, has a second substantially constant cross-sectional profile and terminates in a second end surface which has a second area substantially perpendicular to the axis of motion, the cylinder has a unitary internal volume having a first section with an internal cross-sectional profile which is complimentary to the cross-sectional profile of the first section of the piston and a second section with an internal cross-sectional profile which is complimentary to the cross-sectional profile of the second section of the piston, and respective first and second combustion chambers are defined between the first and second end surfaces of the piston and one or more walls of the cylinder, the chambers not being in fluid communication with one another.

Preferably, the end surfaces of the first and second sections have substantially the same surface area.

Alternatively, the end surfaces of the first and second sections have different surface areas.

Conveniently, the piston moves along the axis of motion between end points of a working range of motion, and when the piston is at any point within this working range, the combustion chambers have substantially the same internal volume.

Alternatively, the piston moves along the axis of motion between end points of a working range of motion, and when the piston is at any point within this working range, the combustion chambers have differing internal volumes.

Advantageously, the exterior profile of the piston is that of two cylinders, a larger cylinder and a smaller cylinder arranged so the combustion surfaces are substantially annular and circular respectively.

Preferably, there is a fuel supply connected to each of the combustion chambers.

Conveniently, there is an ignition source in or connected to each of the combustion chambers.

Advantageously, there is an air intake associated with each of the combustion chambers.

Alternatively, a third section of the piston, connected to the second section of the piston, has a third substantially constant cross-sectional profile and terminates in a third end surface which has a third area, substantially perpendicular to the axis of motion, and a fourth section of the piston, connected to the third section, has a fourth substantially constant cross-sectional profile and terminates in a fourth end surface which has a fourth area substantially perpendicular to the axis of motion, the cylinder further including a third section with an internal cross-sectional profile which is complimentary to the cross-sectional profile of the third section of the piston and a fourth section with an internal cross-sectional profile which is complimentary to the cross-sectional profile of the fourth section of the piston, and respective third and fourth combustion chambers are defined between the third and fourth end surfaces of the piston and one or more walls of the cylinder, the chambers not being in fluid communication with each other or the first and second combustion chambers.

Preferably, the third and fourth end surfaces face in a substantially opposite direction to the first and second end surfaces.

Conveniently, at least one of the second and third end surfaces is formed on opposite sides of a portion of the piston which has a generally constant cross-sectional profile.

Advantageously, the exterior profile of the piston is substantially that of three cylinders, a first smaller cylinder, a larger cylinder and a second smaller cylinder arranged co-axially such that the combustion surfaces are a first, substantially circular surface, a second, substantially annular surface, a third, substantially annular surface and a fourth, substantially circular surface, respectively.

Preferably, the combustion chambers are each associated with at least one valve.

Conveniently, the at least one valve is actuated by way of a rotating ring, the rotating ring including a surface which includes protrusions extending therefrom.

Advantageously, when the ring is rotated, the protrusions make contact with a stem section of the at least one valve and causes the valve to move.

Preferably, a wall of the cylinder incorporates a coolant channel.

Conveniently, the pistons are lubricated by way of oil rings on the outer of the pistons and inner of the cylinders and oil pockets and oil tubes in the walls of the cylinder.

Another aspect of the present invention provides an engine incorporating a cylinder according to the first aspect of the present invention.

Preferably, the engine is a four-stroke.

Conveniently, the engine is a two-stroke.

Advantageously, the engine is diesel.

Preferably, the engine incorporates two cylinders, wherein the cylinders are 900 out of phase with each other A yet further aspect of the present invention provides a vehicle incorporating the engine of the second aspect of the present invention.

The embodiments of the present invention will now be described, by way of example only, with reference to the figures, in which: FIGURE 1 shows an example of a pair of engine cylinders embodying the present invention; FIGURE 2 shows an alternate view of the cylinders of figure 1; FIGURE 3 shows a piston for use inside the cylinders of figure 1; FIGURE 4 shows an alternative engine cylinder which also embodies the present invention; FIGURE 5 shows an yet further engine cylinder embodying the present invention, similar to the cylinder shown in figure 4; FIGURE 6 shows a piston for use inside the cylinder of figure 5; FIGURE 7 shows a cam ring for use with an engine cylinder embodying the present invention; and FIGURE 8 shows an alternative view of the cam ring of figure 7.

Turning firstly to figure 1, a partial view of a reciprocating engine 100 according to the present invention is shown. The engine 100 includes two cylinders 1 which each accommodate a piston 2. The pistons 2 are connected to a crank shaft 6 by way of connecting rods 7, in a known fashion. An engine including cylinders which embody the present invention may however include only one or more than two cylinders 1, each with a piston 2 associated therewith.

The pistons 2 shown in figure 1 each have a stepped" outer profile, and take the form of two substantially cylindrical sections one atop another, with a relatively wide lower section 23 and a relatively narrow upper section 24, which are substantially coaxial with one another. However, it is to be understood that the pistons 2 may take any suitable form. For instance, the pistons 2 may be L"-shaped or "U-shaped, or any suitable shape having a first section and a second section, with the first section having a substantially constant cross section and the second section having a different, but still substantially constant cross section.

The cylinders 1 shown in figure 1 have a region with an internal profile which is at least substantially complimentary to the outer profile of the pistons 2, having a "stepped" profile, with a narrow upper section 25 and a wide lower section 26. However, the cylinders 1 may take any suitable internal shape, that is generally complimentary to the outer profile of the pistons 2 being used, for instance a "U-shape or "L"-shape, in dependence upon the shape of the pistons 2 as discussed above.

Following the outer profile of the pistons 2 discussed above, the cylinders 1 have an upper section 25 having a substantially constant circular cross section and a lower section 26 having a larger substantially constant circular cross section. The cylinders 1 may be formed by way of machining, casting or any other suitable method.

Each piston 2 is received in a respective cylinder so that the upper section 24 thereof fits into the upper section 25 of the cylinder 1, and the lower section 23 of the piston 2 fits into the lower section 26 of the cylinder 1. It will therefore be understood that the piston 2 is constructed to move within the cylinder 1 along an axis of motion A. Each section 23, 24 of the piston 2 defines a combustion surface 4, 5, with the combustion surfaces 4, 5 in the example shown in figure 1 being a first, circular combustion surface 4 (of the upper section 24) and a second, annular combustion surface 5 (of the lower section 23) respectively. The combustion surfaces 4, 5 face generally towards the upper, closed end of the cylinder 1.

The pistons 2 may be manufactured by casting or machining, or any other suitable method, and could be formed as one single section or from two or more separate pieces affixed together.

The outer profiles of each piston 2 and the inner profile of its associated cylinder 1, when combined, define two discrete combustion chambers 8, 9 inside each cylinder 1. The shape of cylinders 1 and pistons 2 may take any suitable form to define the two combustion chambers 8, 9.

The upper combustion chamber 9 is defined between the combustion surface 4 of the upper section 24 and the internal walls of the upper section 25 of the cylinder 1. The lower combustion chamber 8 is defined between the combustion surface 5 of the lower section 23 of the piston 2, the outer surface of the upper section 24 of the piston 2, and the internal walls of the lower section 26 of the cylinder 1.

As the pistons 2 oscillate within the cylinders 1, the combustion chambers 8, 9 increase and decrease in volume and hence capacity. The two combustion chambers 8, 9 are not in fluid communication with one another, as piston rings 3 prevent an egress of gases from either combustion chamber 8, 9 into the other. Therefore each of the combustion chambers 8, 9 may be used for full independent combustion cycles.

It is also envisaged that the combustion chambers 8, 9 could be separated not just by way of a stepped piston or pistons 2, but also by way of the cylinder walls or other, potentially additional, dividing walls or similar obstructions, as the skilled person will appreciate.

The engine 100, as per a standard four-stroke engine, also includes a cam-shaft 20, which carries cams 12. Also shown in figure 1 are first and second set of valves 13, 14, which are actuated by rockers 22 (not shown in figure 1) by way of cams 12 through rotation of camshaft 20. Springs 15 are provided to maintain the valves 13, 14 in a closed position when not opened by the cams 12.

The first valves 13 open into the second combustion chamber 8 and the second valves 14 open into the first combustion chamber 9. It will be understood that the valves 13, 14 deliver air and fuel into the combustion chambers and allow exhaust gases to escape.

Turning now to figure 2, another partial view of the engine 100 of figure 1 is shown. The engine 100 is shown end-on, and therefore only one cylinder 1 and piston 2 can be seen. At the top of the engine 100, an alternative view of the camshaft 20 and a rocker 22, along with cams 20, valves 13, 14 and springs 15 can be seen.

The crank shaft 6 and the connecting rod 7 can be seen, along with a gudgeon pin 25 which affixes the connecting rod 7 to the piston 2. The coolant channels 16 are also shown in more detail.

In the engine 100 shown in figures 1 and 2, the combustion chambers 8, 9 each have the same internal capacity, but the combustion chambers 8, 9 do not need to have the same internal capacity.

Returning to figure 1, the first valves 13 are longer than the second valves 14, so they may reach from the top of the engine 100 to the lower combustion chamber 8. Also, given the reduced width of the lower combustion chamber 8 when compared to upper combustion chamber 9, the longer first valves 13 are narrower, but it is envisaged that twice the number of first valves 13 than second valves 14 will be provided. It is appreciated that varying strategies are available for movement of cams 12 and rockers, including multiple camshafts 20, hydraulic tappets or similar and any suitable method may be used. Also, the layout of the valves 13, 14 will depend upon the layout of the cylinders 1 and the pistons 2.

The valves 13 of the lower chamber 8 may be triggered to open horizontally or vertically and the upper surfaces of the valve seats of the lower combustion chamber 8 may be suitably inclined to allow practical positioning of the valves 13.

Turning now to figure 4, an alternative engine 101 according to the present invention is shown. The engine 101 works in a similar overall fashion to the engine 100 discussed above, but employs a double-ended stepped piston 52 as opposed to the single-ended stepped piston 2 of engine 100.

The double-ended piston 52 shown in figure 4 has a similar outer profile to the piston 2 shown in figure 1 and discussed above, with a "stepped" outer profile.

In this case, however, the piston 52 generally takes the form of three substantially cylindrical sections, generally aligned end-to-end and substantially co-axial with each other, with a relatively narrow lower section 75, a relatively wide mid-section 74 (which gives the piston a "shoulder" section) and a relatively narrow upper section 73.

In a similar way to the piston 2 shown in figure 1, the piston 52 shown in figure 4 has a first, circular combustion surface 4 and a second, annular combustion surface 5. In addition, however, the opposing end of the piston 52 has a corresponding third, circular combustion surface 4A and a fourth, annular combustion surface 5A. The third and fourth combustion surfaces 5A, 4A are substantially similar to the first and second surfaces 4, 5, respectively, but the outermost diameter of the third combustion surface 4A may be larger than the outermost diameter of the first combustion surface 4 to take account of a connecting rod 57 passing through the third combustion surface 4A and into piston 52. The piston 52 of figure 4 fits inside and is accommodated by the cylinder 51. The second and fourth combustion surfaces 5, 5A are part of the wide mid-section 74 of the piston 52, with the second combustion surface 5 forming a "shoulder" atop the mid-section 74, and the fourth combustion surface 5A forming a "shoulder" on the underside of the mid-section 74.

The cylinder 51 shown in figure 4 is similar to the cylinders 1 shown in figure 1, but with the notable difference that the cylinder 51 is configured to accommodate the double-ended piston 52. In a similar fashion to the cylinders 1 of figure 1, the cylinder 51 of figure 4 may have an upper section 25 and a lower section 26 corresponding to cylinder 1 shown in figure 1. However, the lower section 26 of the cylinder 51 of figure 4 is divided into two sections, with a first lower section 26A and a second lower section 26B, to correspond with the second and third combustion surfaces 5 and 5A. Cylinder 51 also includes a base section 27 to correspond with fourth combustion surface 4A of the piston 52. The lower section 26 of the cylinder may be wider than the upper and base sections 25, 27, and has "shoulder" surfaces, complementary to the second and fourth combustion surfaces 5, 5A on the piston 52. Valves 13, iSA, 14, 14A may pass through the shoulder surfaces, as well as top and bottom surfaces of the cylinder 52, these valves 13, 13A, 14, 14A will be discussed later.

Otherwise, the cylinder 51 of engine 101 may be of a similar spatial configuration to those of engine 100, with regions of the internal profile at least substantially complimentary to a portion the outer profile of the piston 52. The internal configuration of the cylinder 51 is such that it may accommodate a double-ended piston 52, and in doing so, describes four independent combustion chambers, a topmost combustion chamber 59, an upper anular combustion chamber 58, a lower annular combustion chamber 58A and a lowermost combustion chamber 59A. These combustion chambers 58, 58A, 59, 59A are defined between the first, second, third and fourth surfaces of the piston 4, 4A, 5, 5A and one or more walls of the cylinder 51, and are all preferably of the same internal cross-sectional area, but may of course, if required, be of differing internal cross-sectional areas.

A double ended piston 52 and corresponding cylinder 51 are also shown in figure 5. It is to be noted that the piston 52 and cylinder 51 arrangement shown in figure 5 is substantially similar to that shown in figure 4, with the notable difference that the second and fourth combustion surfaces 5, 5A of the piston 52 and the shoulder surfaces of the cylinder 51 are bevelled, the combustion surfaces 5, 5A sloping away from the first and fourth combustion surfaces 4, 4A.

Figure 6 shows a close-up view of the double-ended piston 52 of figure 4.

It is to be understood that the piston 52 may take any suitable form to achieve four combustion chambers 58, 58A, 59, 59A. For instance, the piston 52 may be "I-shaped (an upper case "T" viewed in a 9Q0 rotated orientation) or "H"-shaped, or any suitable shape having a first section, a second section and a third section, with the first section 75 having a substantially constant cross section, the second section 74 having a different, but still substantially constant cross section and the third section 73 having a different, but still substantially constant cross section. It is, of course, to be understood that the cross-sectional profiles of the first and third sections 73, 75 may be identical.

Similarly, the cylinder 51 may take any suitable internal shape that is generally complimentary to the portion outer profile of the pistons 52 being used, for instance a "U-shape or "L"-shape, in dependence upon the shape of the piston 52 as discussed above. The overall shape of the cylinder 51 may be "+" or "H" shaped, or may take the form of a rotated "T". Of course, any suitable shape may be used.

The piston 52 may oscillate within the cylinder 51, causing the combustion chambers 58, 58A, 59, 59A to increase and decrease in volume and hence capacity. The four chambers 58, 58A, 59, 59A are not in fluid communication with one another, as piston rings 53 prevent an egress of gases from one combustion chamber into another, allowing each chamber to be used for full combustion cycles. However, the combustion chambers do include valves 13, iSA, 14, 14A to allow controlled ingress and egress of fuel, air and combustion products, the valves 13, 13A, 14, 14A passing from outside the engine 101 into the combustion chambers 58, 58A, 59, 59A. The annular combustion chambers 58, 58A may include multiple valves 13, iSA spaced around the annulus of the chambers 58, 58A, as discussed earlier in connection with engine 100. Engine 101 may have valves 13, 13A, 14, 14A associated with each combustion chamber 58, 58A, 59, 59A, and the lower combustion chambers 58A, 59A may include valves 13A, 14A that are oriented at substantially 180° to the valves 13, 14 in the upper combustion chambers 58, 59.

In fact, each combustion chamber 58, 58A, 59, 59A is capable of undertaking one of the four stages of a standard four-stroke combustion cycle, with each independent combustion chamber 58, 58A, 59, 59A undertaking one of intake, compression, combustion and exhaust. In the case of the cylinder 51 shown in figure 4, the topmost combustion chamber 59 may be undertaking intake, the upper annular combustion chamber 58 may be undertaking combustion (and subsequent expansion), the lower annular combustion chamber 58A may be undertaking exhaust and the lowermost combustion chamber 59A may be undertaking compression.

Another notable difference between engine 100 shown in figures 1 and 2 and engine 101 shown in figures 4 and 5 is the use of a rotating cam ring 30 to actuate the valves 13, 1 3A, 14, 1 4A, as opposed to standard cams 12. As can be seen in more detail in figure 7, the cam ring 30 may be annular, and generally flat, with sections 31, 32 having an increased depth. Figure 8 shows an alternative view of the cam ring 30, showing the sections 31, 32 of increased depth. The cam ring 30 may also be divided into an inner and outer ring, each of the inner and outer rings may have a section of increased depth 31, 32 which may be in different regions of the circumference of the cam ring 30. The inner and outer ring sections may be configured in this way to actuate different valves 13, 13A, 14, 14A in the engine at different times. This will be discussed in more detail later.

The regions of increased depth 31, 32 may have a chamfered edge at each end of the section to allow for smooth actuation of valves 13, 13A, 14, 14A during rotation of the cam ring 30, although it is to be understood that, if required, the chamfered edge may be replaced with an alternative shape profile.

As can be seen in figure 5, the cam ring 30 may be positioned in a circular orbit around the cylinder 51 in a location which may allow the cam ring 30 to actuate the valves 13, 13A, 14, 14A. As discussed previously, the cylinder 51 shown in figure 4 may have "shoulders", above which the cam ring 30 may be placed, to activate the valves 13 of the upper annular combustion chamber 58.

A corresponding cam ring 30, associated with the valves 13A of the lower annular combustion chamber 58A may be placed below the lower shoulders.

The cam ring 30 may rotate about a central axis (the axis that passes through the centre-line of the cylinder 51 shown in figure 4). As the cam ring 30 is rotated, the inner section and outer section pass above valves 13, 13A, 14, 14A, and the inner and outer sections may be associated with a particular valve 13, 13A, 14, 14A. As can be seen in figure 4, the valves 13, 13A, 14, 14A are generally biased towards a closed position and may be moved into an open position by way of a section of increased depth 31, 32 of the cam ring 30 contacting the top of each valve 13, 13A, 14, 14A as the cam ring 30 rotates and applies a downward force upon the valve 13, 13A, 14, 14A, moving it momentarily from a closed position to an open position. However, it is to be understood that any suitable method may be employed to operate the valves 13, 1 3A, 14, 1 4A, depending upon the application sought.

Returning to a more general discussion of an engine 100, 101, the camshaft or cam ring 30 and the crank shaft 6 are connected by way of a timing system (not shown), such that rotation of the crank shaft 6 and the camshaft or cam ring 30 are linked, ensuring that the valves 13, 13A, 14, 14A are in the correct position when compared to the position of pistons 2, 52 within cylinders 1, 51 at any time during operation of the engine 100, 101.

Considering the engine 100, 101 shown in figures 1, 2, 4 and 5, lubrication of the pistons 2, 52 is preferably achieved by oil rings (not shown) on the outer surface of the pistons 2, 52 and inner surfaces of the pistons 1, 51, and by way of oil pockets fed by oil tubes (not shown) in the walls of the cylinders 1, 51. To lubricate the piston 52 of engine 101, lubrication ducts 81, 82 may be provided within the connecting rod 57 to provide lubricant to the outer surfaces of the piston 52. Lubrication of the piston 52 is of particular importance because due to the shape and spatial arrangement of the piston 52, when the engine is in use, the piston 52 will be subject to high temperatures and thermal stress, and will be in very close sliding contact with the wall of the cylinder 81.

Lubricant may be supplied to the piston 2, 52, or indeed to any part of the engine 100, 101 under pressure. However, with respect to the piston 52, the lubricant may be supplied through one of the ducts 81 in the connecting rod 57 and retrieved through another of the ducts 82 in the connecting rod 57.

The lubricant employed in lubricating the piston 2, 52 and indeed the engine 100, 101 in general may be filtered and re-used, Of course, any suitable lubrication method may be employed.

Also present in the engine 100, 101 but not shown are spark plugs, positioned near the top of each of the combustion chambers 8, 9, 58, 59 and at the bottom of combustion chambers 58A, 59A, the spark plugs capable of igniting a compressed air-fuel mixture. Cylinders 1, 51 of this type, providing two or four combustion chambers 8, 9, 58, 58A, 59, 59A, could be used with a diesel engine, and it is to be appreciated that glow plugs or similar may be used instead of spark plugs to ignite an air-fuel mixture in the combustion chambers 8, 9, 58, 58A, 59, 59k In the outer combustion chambers 8, 58, 58A two spark plugs may be used, evenly spaced inside the annular cross-sectional shape of these combustion chambers 8, 58, 58A so as to ensure even combustion of the air-fuel mixture. It is envisaged that the spark plugs will be positioned spaced 1 80° from each other, but any suitable configuration may be employed.

Of course, the engine 100, 101 may be used with any other combustible or pressurised means, and may utilise Liquefied Petroleum Gas (LPG), Compressed Natural Gas (CNG), steam or any other suitable material or means. Further, the engine 100, 101 may be used as a compressor.

Coolant channels 16 are provided in the upper part of the engine 100, 101, passing near to the cylinders 1, 51 (not shown in figure 4 or 5) through which liquid coolant may flow to cool the engine 100, 101 during use. These coolant channels 16 would be attached to a coolant system (not shown) likely including a water pump and radiator, but alternative cooling systems may be used, including air-cooling. Additionally, the isolated surfaces of the piston 52 may be cooled by way of further coolant channels (not shown) which pass through the connecting rod 57. It is important to carry the heat energy generated damp combustion that is transferred into the cylinder 1, 51 and piston 2, 52 away, to avoid thermal stresses causing damage to the engine 100, 101, and to promote smooth and efficient running of the engine 100, 101.

A working cycle of one of the cylinders 1 will now be described.

In normal operation of the engine 100, combustion of an air-fuel mixture in the upper combustion chamber 9 of the cylinder 1 would cause expansion of the mixture, exerting pressure upon the upper combustion surface 4 which in turn drives the piston 2 downwardly away from the top of the cylinder 1. In doing so, the lower combustion chamber 8 would complete an intake stroke, as the piston 2 moves downwards, thus increasing the volume of the lower combustion chamber 8.

While the piston 2 moves downwards, the connecting rod 7 also moves downwards, causing the crank shaft 6 to rotate. Once at the bottom of the stroke, the piston 2 would begin to move upwards in the cylinder 1. This enables the lower and upper combustion chambers 8, 9 in the cylinder 1 to complete a compression stroke and an exhaust stroke respectively, ready for ignition of an air-fuel mixture in the lower combustion chamber 8 of the cylinder 1.

Thus, it will be appreciated that the cycle of the lower combustion chamber 8is 1 80° out of phase with that of the upper combustion chamber 9.

In a standard four-stroke engine including two cylinders (not shown), the cylinders are configured to be 1800 out of phase, such that when the piston 2 in one cylinder 1 is moving upwards, the piston 2 in the other cylinder 1 is moving downwards, resulting in two volumes, each at a different stroke during the four-stroke cycle. For instance, one cylinder 1 could be compressing the air-fuel mixture whilst the other could be undergoing the expansion stroke.

However, the cylinders 1 in the engine 100 shown in figure 1 are 90° out of phase with each other and the combustion chambers 8, 9 of each cylinder 1 are 180° out of phase. This allows the combustion chambers 8, 9 in one cylinder 1 to compress and exhaust simultaneously, as per the right-hand cylinder 1 shown as part of the engine 100 of figure 1. The left-hand cylinder 1 shown in figure 1 is undergoing simultaneous intake and ignition/expansion.

The engine 100 shown in figure 1 could be used to replace a four-cylinder engine, using two cylinders 1 but providing an engine having four combustion chambers 8, 9 of the same cubic capacity (cc") as a standard four-cylinder engine. If more cylinders 1 are to be used, it is to be understood that the phase difference between the cylinders and combustion chambers may be different, to accommodate the differing positions of the pistons 2 during the four-stroke cycle.

A working cycle of one an engine 101 including a cylinders 51 is very similar, with the notable difference that at any one instance, each of the combustion chambers 58, 58A, 59, 59A may be undergoing one of the four strokes of a combustion cycle. Additionally, the cams and valves of the engine 101 may operate in an alternative fashion, with valves 13, 13A, 14, 14A actuated by a cam ring 30.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

<claim-text>Claims: 1. A cylinder for a reciprocating engine, the cylinder having an internal volume and a piston located therein, the piston being movable inside the cylinder, constrained to move along an axis of motion; wherein a first section of the piston has a first substantially constant cross-sectional profile and terminates in a first end surface which has a first area, substantially perpendicular to the axis of motion; a second section of the piston, connected to the first section, has a second substantially constant cross-sectional profile and terminates in a second end surface which has a second area substantially perpendicular to the axis of motion; the cylinder has a unitary internal volume having a first section with an internal cross-sectional profile which is complimentary to the cross-sectional profile of the first section of the piston and a second section with an internal cross-sectional profile which is complimentary to the cross-sectional profile of the second section of the piston; and respective first and second combustion chambers are defined between the first and second end surfaces of the piston and one or more walls of the cylinder, the chambers not being in fluid communication with one another.</claim-text> <claim-text>2. The cylinder of claim 1, wherein each of the end surfaces of the first and second sections have substantially the same surface area.</claim-text> <claim-text>3. The cylinder of claim 1, wherein each of the end surfaces of the first and second sections have different surface areas.</claim-text> <claim-text>4. The cylinder of claim 1 or 2, wherein the piston moves along the axis of motion between end points of a working range of motion, and when the piston is at any point within this working range, the combustion chambers have substantially the same internal volume.</claim-text> <claim-text>5. The cylinder of claim 1 or 3, wherein the piston moves along the axis of motion between end points of a working range of motion, and when the piston is at any point within this working range, the combustion chambers have differing internal volumes.</claim-text> <claim-text>6. The cylinder of any preceding claim, wherein the exterior profile of the piston is that of two cylinders, a larger cylinder and a smaller cylinder arranged so the combustion surfaces are substantially annular and circular respectively.</claim-text> <claim-text>7. The cylinder of any preceding claim, wherein there is a fuel supply connected to each of the combustion chambers.</claim-text> <claim-text>8. The cylinder of any preceding claim, wherein there is an ignition source in or connected to each of the combustion chambers.</claim-text> <claim-text>9. The cylinder of any preceding claim, wherein there is an air intake associated with each of the combustion chambers.</claim-text> <claim-text>10. The cylinder of any preceding claim, wherein: a third section of the piston. connected to the second section of the piston, has a third substantially constant cross-sectional profile and terminates in a third end surface which has a third area, substantially perpendicular to the axis of motion; and a fourth section of the piston, connected to the third section, has a fourth substantially constant cross-sectional profile and terminates in a fourth end surface which has a fourth area substantially perpendicular to the axis of motion; the cylinder further including a third section with an internal cross-sectional profile which is complimentary to the cross-sectional profile of the third section of the piston and a fourth section with an internal cross-sectional profile which is complimentary to the cross-sectional profile of the fourth section of the piston; and respective third and fourth combustion chambers are defined between the third and fourth end surfaces of the piston and one or more walls of the cylinder, the chambers not being in fluid communication with each other or the first and second combustion chambers.</claim-text> <claim-text>11. A cylinder according to claim 10 wherein the third and fourth end surfaces face in a substantially opposite direction to the first and second end surfaces.</claim-text> <claim-text>12. A cylinder according to claim 10 or 11 wherein at least one of the second and third end surfaces is formed on opposite sides of a portion of the piston which has a generally constant cross-sectional profile.</claim-text> <claim-text>13. A cylinder according to any one of claims 10-12 wherein the exterior profile of the piston is substantially that of three cylinders, a first smaller cylinder, a larger cylinder and a second smaller cylinder arranged co-axially such that the combustion surfaces are a first, substantially circular surface, a second, substantially annular surface, a third, substantially annular surface and a fourth, substantially circular surface, respectively.</claim-text> <claim-text>14. A cylinder according to any preceding claim wherein the combustion chambers are each associated with at least one valve.</claim-text> <claim-text>15. A cylinder according to claim 14, wherein the at least one valve is actuated by way of a rotating ring, the rotating ring including a surface which includes protrusions extending therefrom.</claim-text> <claim-text>16. A cylinder according to claim 15, wherein when the ring is rotated, the protrusions make contact with a stem section of the at least one valve and causes the valve to move.</claim-text> <claim-text>17. The cylinder of any previous claim, wherein a wall of the cylinder incorporates a coolant channel.</claim-text> <claim-text>18. The cylinder of any previous claim, wherein the pistons are lubricated by way of oil rings on the outer of the pistons and inner of the cylinders and oil pockets and oil tubes in the walls of the cylinder.</claim-text> <claim-text>19. An engine incorporating a cylinder according to any previous claim.</claim-text> <claim-text>20. The engine of claim 17 wherein the engine is a four-stroke.</claim-text> <claim-text>21. The engine of claim 17 wherein the engine is a two-stroke.</claim-text> <claim-text>22. The engine of claim 17 wherein the engine is diesel.</claim-text> <claim-text>23. A vehicle incorporating the engine of claim 17-20.</claim-text> <claim-text>24. A cylinder according to any one of claims 1-11 wherein the cylinder is operable to perform isolated cycles in the first and second combustion chambers.</claim-text> <claim-text>25. A cylinder according to claim 22 wherein the cycles are 1800 out of phase with each other.</claim-text> <claim-text>26. An engine incorporating two cylinders according to one of claims 1-11, 23 or 24, wherein the cylinders are 90° out of phase with each other.</claim-text> <claim-text>27. A cylinder for a reciprocating engine as hereinbefore described, with reference to the accompanying drawings.</claim-text> <claim-text>28. Any novel feature or combination of features described herein.</claim-text>