GB2615808A

GB2615808A - Outboard motor with engine in vertically split casing

Info

Publication number: GB2615808A
Application number: GB2202287.5A
Authority: GB
Inventors: Pirault Jean-Pierre
Original assignee: JEAN PIERRE PIRAULT; Ospe Ltd
Current assignee: JEAN PIERRE PIRAULT; Ospe Ltd
Priority date: 2022-02-21
Filing date: 2022-02-21
Publication date: 2023-08-23
Also published as: GB202202287D0

Abstract

The invention, which is applicable to in-line 2-stroke and 4-stroke engines, is an outboard or outdrive marine propulsion unit in which the internal combustion engine is in the upper part (1000, figure 1) of the outboard or outdrive marine propulsion unit and which in use lies substantially above the waterline, and wherein the static components of the internal combustion engine, such as the crankcase, cylinder block and the packaging of the major engine systems are formed by the containment casings (60, figure 2) of the outboard or outdrive marine propulsion unit, said casings being split on a vertical plane of the outboard or outdrive marine propulsion unit. In one embodiment of the invention, the vertical split of the casing is on a plane passing through the longitudinal axis of the engine crankshaft 21 or the longitudinal axes of the engine crankshafts, said axis or axes being parallel to the axis of the propeller of the outboard or outdrive marine propulsion unit. In another embodiment of the invention, the vertical split of the casing is on a plane which is orthogonal to the longitudinal axis of the engine crankshaft or the longitudinal axes of the engine crankshafts, said axis or axes being orthogonal to the axis of the propeller of the outboard or outdrive marine propulsion unit.

Description

Outboard Motor with Engine in Vertically Split Casings

Introduction

This invention relates to the use of internal combustion engines for marine propulsion units which may either be of the "outboard type", usually mounted at the rear of the vessel, also known as the transom, or of the "outdrive" type, usually mounted within the hull but with the gearbox and propeller retractably exiting beneath the hull when in use.

The invention enables lighter, more compact and lower cost marine propulsion units in comparison to outboard marine power units or outdrive type marine power units in which the power unit is conventionally located in the uppermost part of the propulsion unit.

Some background and definitions are provided before describing the invention. Background As shown in Figure 1, state of art outboard marine (OM) propulsion units or engines can be considered as having two main parts, namely the upper part 1000 above the water line and the lower part 2000 below the water line, which contains the gearbox 7000 and the propeller 25. The lower part, which conunences at the submerged cavitation plate 6000, is also frequently termed the "gearbox" because it contains the gear drive to the propeller and neutral, forward and reverse drive options.

Steering of the boat is achieved by mounting the OM on a vertical pivot, allowing the engine and the connected propeller to be turned by a steering arm 4000 attached to a rotatable portion of the OM upper part. OMs are attached to the rear of the boat by adjustable and rotatable clamps which are part of the "saddle" 5000 section which may be rotatable about the vertical axis. These features enable OMs to be readily moved across the rear transom of the boat, or inclined to cope with shallower water, or removed from the rear of the boat for stowage, repairs or for use on another boat.

Inboard "outdrive", "keel drive" or "leg" type marine propulsion units are similar and almost identical to OMs in construction, but are mounted within the hull with a sealing arrangement so that the leg can protrude below the hull when in use and be retracted when not required. Ideally, these inboard OM engines can be rotated about a vertical axis to provide boat steerage.

The upper part of state of art OMs contains the shaft connection from the internal combustion engine to the gearbox and propeller. The upper part also acts as conduits for the exhaust of the engine, coolant to and from the engine and any shafts, cables or belts that may be used to actuate selection of the drives in the gearbox.

The mid-section of the upper part is that portion of the upper part (1000 in Figure 1) that is between the saddle 5000 and the cavitation plate 6000.

The invention is the symbiotic formation of the static parts of the internal combustion engine from the vertically split containment casing in the mid-section of the upper part of the propulsion unit.

The siting of the engine within either the OM mid-section, or in some cases the mid-section and the lower-section, is enabled by an engine architecture that is compatible with dimensional aspects to the OM mid-section and lower section, i.e. the engine shape must he implicitly elongated and prismatic, either substantially rectangular or cylindrical/ellipsoidal in section.

An opposed piston engine architecture, and in one embodiment an opposed piston engine that uses stepped pistons to provide the air supply to the power or combustion pistons, also known as a stepped opposed piston engine, facilitates this invention in some of the embodiments because this engine type is substantially elongated and prismatic. Opposed piston engines do not have cylinder heads and this enables the substantially prismatic cylindrical or rectangular architecture that is well suited to the shape of the OM mid-section.

The invention embodies 2-and 4-stroke engines with or without cylinder heads in opposed piston configurations, and single and multi-cylinder versions of these engines.

Definitions The following definitions and descriptions are provided to help the reader with this text; the definitions are in the context of this document and are not be universal. The definitions are listed alphabetically.

Aftertreament is the equipment fitted in the engine exhaust system which converts the engine's gaseous pollutants, except carbon dioxide, to harmless eases.

The "air" piston is the power piston which controls the opening and closing of the air ports of the combustion cylinder.

The air ports of a 2-stroke engine are those apertures or openings in the cylinder wall of the cylinder of the 2-stroke engine which control air entry to the combustion cylinder.

An air transfer piston is a piston used to pump air from the air intake system to the power piston and is usually only required for 2-stroke operation.

Blowby are products of combustion that escape the combustion chamber via leaks in the piston ring sealing and also escape via the valve guides in the exhaust ports. These blowhy gases are collected and recycled to the induction system of the engine. Blowby gases frequently contain engine oil which is entrained as the blowby circulates via the engine fluid transfer conduits; the oil is usually removed from the blowhy by means of static separators so that the blowhy does not introduce oil into the cylinders when it is recycled.

An exhaust aftertreatment catalyst in the context of an engine is a device which converts the pollutants in the exhaust gas to acceptable environmental eases.

A carburettor is a simpler device (compared to a fuel injector) for metering and mixing fuel to the air which is used for combustion in an engine.

Casings are rigid enclosures with an open side and a closed side, frequently arranged in pairs so that the two open sides are in contact with each other to form an enclosure or containment.

A cavity is volume in a surface which has at least one open side and may be used to secure a component when clamped to the open side of another cavity so that the combined cavities form either a containment or passage for gases, such as air or exhaust, or a liquid such as coolant water or oil.

Cetane based fossil fuels are liquid fuels that are readily ignited by compression temperatures without the need for electrical or other forms of ignition. Diesel is a commonly known cetanc biased fuel.

A check valve is a mechanism that allows flow in one direction only.

A compressor is a mechanical device which inducts gases, such as air, and transfers said gases from a first point to another, where the pressure at the second point is at a higher pressure than the pressure at the first point. During this gas transfer process, compressors reduce the volume of the gases as well as increasing the pressure of the gases.

A conduit is a passage for transferring fluid which may be a gas, such as air or exhaust, or a liquid such as coolant water or oil.

Containments refers to casings that are arranged to form at least one enclosure with contents such as the static and moving parts of an engine or other mechanical systems.

Contra-rotation of a body indicates rotation of that body in an opposite sense to the rotation of another body.

A crankcase is a static structure that contains the moving parts of an engine. The crankcase also contains conduits for oil, coolant and gases such as air and exhaust gases.

A crankpin is usually an integral part of a crankshaft which carries and is connected to the connecting rods that are in turn connected to the pistons via a rotatable joint called the gudgeon pin. Each engine cylinder usually has a piston, subjected to combustion gas pressure and connected via the gudgeon pin to the "small end" of the connecting rod. The other end of the connecting rod, called the "big-end", connects rotatably with the crankpin.

A crankshaft is usually a single part connecting crankpins and main journals via the crankthrows and may include balance masses.

A crankthrow of a crankshaft is usually an integral part of the crankshaft linking the main journal to the crankpin. There is usually at least one crankthrow connecting with each crankpin.

A crosshead arrangement in a reciprocating machine such as an engine or compressor is one in which the active piston is supported on a carrier piston or slider through which all, or most, of the side loads are transmitted. This has the principal advantage that little lubrication is required on the side surfaces of the active piston.

A cylinder block is a rigid structure that contains the engine cylinders, coolant passages, oil transfer passages and blowby passages.

A cylinder head is a rigid structure which closes and seals one end of a cylinder of an engine or compressor, and often is fitted with valves which handle the gas exchange process, and in the case of an internal combustion engine may be fitted optionally with a spark plug and injector.

A double diameter piston, also known as stepped piston, is a piston with two diameters, each of which separately engages one of two female cylinders, the diameters of said cylinders lying on a common axis. The two piston diameters are usually rigidly connected, with the smaller diameter piston being the power piston and the larger diameter being the air transfer piston. A stepped cylinder comprises a first cylinder which has a first diameter for a first length and which is joined to a second cylinder which has a second diameter for a second length, the axes of first and second cylinders lying on the same axis.

In one embodiment, the two piston diameters are immediately adjacent and may be monolithic and connected to the crankshaft by a single connecting rod; in this case, both piston diameters move in phase in terms of volumetric displacement. In another embodiment, the two piston diameters are spatially separated and may be connected to the crankshaft by a single or two connecting rods so that the two piston diameters move out of phase in terms of volumetric displacement.

The stepped piston and the stepped cylinder may comprise part of a compressor or an engine.

Downward refers to a direction vertically below the major axis, or datum, or plane of an object.

Drives are rotating connections from the main shaft of an engine, enabling the powering of auxiliaries, such as coolant pumps, oil pumps, electrical generators and compressors.

A duct is a conduit for transferring fluid which may he a gas, such as air or exhaust, or a liquid such as coolant water or oil.

An eccentric is a cylindrical solid of revolution, having its centre of geometry offset from the centre of rotation of the shaft to which it is connected, which rotates about the centre of rotation of the shaft.

The engine exhaust is the gaseous products of engine internal combustion which in OMs and ODs is usually routed below the water line and frequently the exhaust may be mixed with the outgoing coolant flow and exited near the propeller so as to be well mixed before dispersion in the water.

An exhaust system of an engine comprises essentially the conduits or pipes which transport the products of combustion, also known as the exhaust gases, from the engine working cylinder(s) to the environment, and certain other features such as catalysts and silencers. For ease of manufacture, exhaust systems are frequently cylindrical with an inner diameter which contains the exhaust gases and an outer diameter which provides adequate structural strength and containment of the hot gases that frequently have higher pressure than the ambient conditions.

The "exhaust" piston is the power piston which controls the opening and closing of the air ports of the combustion cylinder.

An expander is a mechanical device which inducts gases, such as air, and transfers said gases from a first point to another, where the pressure at the second point is at a lower pressure than the pressure at the first point. During this gas transfer process, expanders increase the volume of the gases.

Form-in-place gasket is a sealing method applied to two contacting surfaces whereby either the surfaces are coated with an anaerobic sealant which sets on compression between the two surfaces, or an elastomeric compound is pumped into a groove formed in at least one of the contacting surfaces and sets to form a continuous elastomeric bead.

Forward side of an air transfer piston is the side of the larger diameter of the stepped piston which acts in phase with the air piston or an exhaust piston of an opposed piston engine.

A fuel injector is a device for metering and mixing fuel to the air which is used for combustion in an engine.

Gas exchange is the process of air transfer from an environment into the cylinder of an engine and the ejection of exhaust gases, also known as products of combustion, from the engine cylinder volume to an environment.

An air induction system of an engine comprises essentially the conduits or pipes in which air from the environment is routed to the engine working cylinder(s), and certain other features such as check valves in the case of some 2-stroke engines, and throttle(s) in the case of spark ignition engines.

An internal combustion engine 2-stroke cycle is one that delivers power from each engine cylinder on each revolution.

An internal combustion engine 4-stroke cycle is one that delivers power from each engine cylinder on every second revolution.

In phase refers to an event that occurs in the same sequence as another event, or an event or component moving in the same direction as another event or component.

Left hand side refers to a part or portion or a whole unit which is disposed on the other side of an axis, datum line or plane of an object.

A linear guide is a substantially straight (but not necessarily flat) component fixed to ground and which has a groove or straight edge which engages with a moving component such that the this component is constrained to move with linear motion. An example of a linear guide could be a cylinder of an engine or compressor.

Longitudinal refers to the direction along the largest axis of a component or assembly of components.

The lower part of a marine propulsion unit is the portion of the unit which is below the water line.

A main journal is a solid of revolution and usually an integral part of the crankshaft and is arranged concentrically on the main axis of a crankshaft and is supported by a bearing in a crankcase.

Major Engine Systems include items such as the crankshaft(s), pistons), connecting rods(s), rectilinear drive components, gas exchange poppet valves, oil pump, cylinder bores, lubrication circuit, coolant circuit, air intake conduits, exhaust gas conduits, exhaust system, fuel circuit, channels for electrical wiring, crankcase scantlings including the main bearing, camshaft bearing and other bearing carriers, cylinder block scantlings to contain cylinder liners, cavities to contain dtive connections between the crankshaft, or crankshafts, other rotating parts of the engine and to rotating parts in the gearbox-section, a cavity to contain a cylinder head module, a cavity to contain any valvetrains including camshafts, blowby venting conduits and oil drain conduits, "Mid-section" is that portion of the upper part (1000 in Figure 1) that is between the saddle 5000 and the cavitation plate 6000.

Monolithic means a single part or component or object.

Octane based fossil fuels are liquid fuels that resist auto-ignition by compression temperatures alone and rely on electrical or other forms of ignition to start combustion. Gasoline, also known as petrol, is a commonly known octane biased fuel.

An opposed piston engine or compressor is an engine or compressor in which two pistons slide in a common cylinder compressing and expanding a common volume of air, so that the common cylinder does not need a cylinder head.

An opposed stepped piston engine is an opposed piston engine or compressor that has at least one stepped power and air transfer piston which is in connection with one power cylinder.

Orthogonal means at right angles to, or at ninety degrees to an axis, or datum or plane of an object.

An outboard marine (OM) unit is a portable or transferable self-contained mechanical, electrical or hybrid power propulsion system, usually fitted with a marine propeller and manual actuation systems for steering, power modulation and gear selection. The OM is readily attached to the outside of a boat in order to propel and steer the boat.

An inboard outdrive marine unit (OD) is a portable self-contained mechanical, electrical or hybrid power propulsion system, usually fitted retractably with a marine propeller and remote actuation systems for steering, power modulation and gear selection, which may be readily inserted through the hull or the inside of a boat in order to propel and steer the boat.

An "overhead valve" engine is a 4-cycle internal combustion power unit, also known as 4-stroke, in which the poppet valves that control the gas exchange are arranged in the cylinder head. The overhead valve arrangement enables higher compression ratios and easier Rowing gas exchange.

Paired discs, sometimes referred to as paired eccentrics, are a component of a rectilinear drive mechanism which consist of two eccentric discs rigidly fixed together and which A piston is the moving part of a positive displacement volumetric machine that acts on the fluid to displace, compress or expand the fluid. The piston is usually of a male shape which engages in a cylinder of a female shape with clearance, the motion of the piston moving the fluid to and from the cylinder.

A power piston is a piston which is used to compress and expand gases as part of the combustion process.

Prismatic means of a constant cross section such as a cylindrical or rectangular shape A reciprocating machine is a mechanism in which at least one component oscillates (travels along a single line with periodically reversing direction of motion) and which has a link between that reciprocating motion and the rotational motion of at least one shaft.

A rectilinear drive mechanism (RDM) is an assembly comprising a crankshaft fitted with paired discs (usually cylindrically shaped) which can rotate with clearance about the crankpin of the crankshaft, each disc of the pair being guided and constrained with clearance by at least one static linear rail and the static rail(s) of each disc being orthogonal to each other. For clarity, further description of rectilinear drive mechanisms is given with reference to diagrams, in the following sections.

The reverse side of an air transfer piston is the side of the larger diameter of the stepped piston which acts in anti-phase with the air piston or an exhaust piston of an opposed piston engine.

Right hand side refers to a part or portion or a whole unit which is disposed on the one side of an axis, datum line or plane of an object.

Scantlings are rigid structured enclosures, such as an engine crankcase or cylinder block, used A "side valve" engine is a 4-cycle internal combustion power unit, also known as 4-stroke, in which the poppet valves that control the gas exchange are arranged to be around the outer periphery of the cylinder liner instead of locating the valves in the cylinder head, which is known as an "overhead valve" arrangement. The side valve arrangement enables easier and more compact actuation of the poppet valves.

A "sleeve valve" is a means to control the gas exchange of internal combustion engines and comprises a sleeve with apertures that moves, with controlled clearance and lubrication, within the cylinder liner of the engine, the motion of the sleeve being arranged so that the apertures in the sleeve coincide with matching apertures in the cylinder liner when air is required to enter the cylinder space and when exhaust gases are required to be expelled.

A spark plug is a very voltage electrically powered ignitor for starting combustion and usually produces at least one extremely high temperature electrical discharge per combustion cycle in the combustion chamber of an engine.

A synchronous drive between at least two parallel or orthogonal shafts is a rotating connection that maintains the phasing of the at least two shafts for all rotational angles and speeds.

The transom is usually the rearmost portion of a small boat to which OMs are attached.

The upper part of a marine propulsion unit is that part above the water fine and contains the mid-section which is between the saddle 5000 and the cavitation plate 6000 of Figure 1.

Upward refers to a direction vertically above the major axis, or datum, or plane of an object.

The waterline is that the boundary around the boat hull below which there is water. This changes with boat loading, boat speed and water motion. The height of the upper part of OMs are sized according to the distance between the waterline and the attachment point of the OM to the boat hull.

A wet cylinder liner is a cylinder, fitted into the crankcase of an engine, in which the internal cylinder bore of the wet cylinder liner is finished to accept a sliding piston and piston rings and in which the outer substantially cylindrical surface is in contact with the engine coolant. A wet cylinder can be used with appropriate features for both 2 and 4-stroke applications.

A yoke is a substantially rigid link that joins two other parts, usually having some clearance with each of these other two parts so that there is some degree of rotational freedom between the link and the two parts.

Figures Figure la is a diagram showing the terminology of the main elements of outboard marine and outdrive marine propulsion units also known generally as outboard motors or outdrives.

Figure lb is a transverse vertical section through the central plane of an outboard or outdrive marine propulsion unit of the claimed invention as applied to a single cylinder opposed stepped piston 2-stroke engine with RDM cranktrains, with referencing numbers for some components.

Figure 2 is the same transverse vertical section shown in Figure lb through the claimed invention, but with other numbers referencing other components.

Figure 3 is a transverse vertical section, orthogonal to that shown in Figure 2, through the claimed invention, but with other numbers referencing other components or features.

Figure 4 is a part isometric section and view of the magneto connection to the engine crankshaft of the invention.

Figure 5 is an isometric view of both RDM crankshaft mechanisms and the inter-connecting drive of the invention shown in Figures lb. 2,3 and 4.

Figure 6 is an exploded view of the upper crankshaft mechanism shown in Figure 5.

Figure 7 is an isometric view of one side of the containment casing for the engine according to the first embodiment of the invention.

Figure 8 is a view of the other side of the containment casing for the engine according to the first embodiment of the invention.

Figure 9 shows the internal mechanism assembly of a second embodiment of the invention in which there is an orthogonal drive between the engine and the propeller shaft.

Figure 10 is an exploded view of the mechanism moving components shown in Figure 9.

Figure 11 is an isometric view of one side of the containment casing for the engine according to the second embodiment of the invention.

Figure 12 is a view of the other side of the containment casing for the engine according to the second embodiment of the invention.

Figurel3 is an exploded view of the invention when applied to a single cylinder 4-stroke engine with a cylindrical cylinder head and overhead poppet valves and overhead camshaft.

Figure 14 is a sectional isometric view on a vertical plane through the cylinder and crankshaft centreline of containment casing of the 4-stroke engine shown in Figure 13.

Figure 15 is a sectional isometric view on a vertical plane through the centrelines of the poppet valves of the 4-stroke engine shown in Figure 13.

Figure 16 is an exploded view of the invention when applied to a single cylinder opposed piston 4-stroke side valve engine, shown without the side casings, cylinder liners or air induction and air filtration systems.

Figure 17 is a partial exploded view of the invention when applied to an opposed piston 4-stroke side valve engine, with the side casings, cylinder liners, air induction and air filtration systems.

Figure 18 is a part sectional view of the upper and lower cylinder liners and pistons of the invention as depicted in Figures 16 and 17.

Figure 19 is a transverse section through the plane passing through the two sparking plugs fitted to the combustion chamber of the opposed piston side valve engine depicted in Figures 16, 17 and 18.

Figure 20 shows the two containment casings of the opposed piston side valve engine depicted in Figures 16, 17, 18 and 19 and fitted with an exhaust emission aftertreatment catalyst monolith with a retaining wire mesh.

Figure 21 is an isometric view of the internal parts of the invention when applied to a single cylinder 4-stroke opposed piston engine with sleeve valves.

Figure 22 is an exploded view of the internal parts of the invention when applied to a 4-stroke opposed piston engine with sleeve valves of Figure 21.

Figure 23 is a view of the assembled moving parts of the cranktrain and sleeve valves of the invention when applied to a 4-stroke opposed piston engine with sleeve valves of Figures 21 and 22.

Figure 24 is an exploded view of the internal parts and containment casings of the invention when applied to a 4-stroke opposed piston engine with sleeve valves of Figures 21,22 and 23.

Figure 25 is a sectional view of the cylinder liner arrangement with its central counterbore for sealing with the two sleeve valves of Figures 21-24.

Main Claim In the broadest sense, the invention is an outboard or outdrive marine propulsion unit in which the static parts of the internal combustion engine are formed by vertically split containment casings which are a portion of the upper part of the propulsion unit.

In one embodiment of the invention, the vertical split of the casing is on the plane passing through the longitudinal axis of the engine crankshaft or the longitudinal axes of the engine crankshafts, said axis or axes being parallel to the axis of the propeller of the outboard or outdrive marine propulsion unit.

In another embodiment of the invention, the vertical split of the casing is on the plane which is orthogonal to the longitudinal axis of the engine crankshaft or the longitudinal axes of the engine crankshafts, said axis or axes being orthogonal to the axis of the propeller of the outboard or outdrive marine propulsion unit.

The invention is applicable to 2 stroke and 4-stroke engines with single or multiple cylinders. These and other embodiments of the invention are outlined in the following description.

Description

Figure la, which is a diagram showing the terminology of the main elements of outboard marine and outdrive marine motor, has already been described in the first paragraph of the Background section.

Figure lb and Figure 2, are same pictures but they refer to different features. Figures lb and 2 are a transverse vertical section through the claimed invention which is an outboard marine unit 100 where the internal engine combustion engine, which in this embodiment is of an opposed stepped piston configuration, is in the upper section and lower section of the outboard unit. These two figures are used mainly to explain the overall layout of the invention; details of the crankshaft and stepped piston mechanism are explained with reference to Figures 5, 6, 7 and Figure 8.

With reference to Figure lb, Figure 2 and Figure 3 which are an embodiment of the invention 100 based on 2-stroke engines, air 250a (Figure 2) for combustion is drawn firstly through an air cleaner 47, then through an induction system which may contain a one-way flow valve 48 (Figure 2), and via a carburettor or fuel injection system 49 where fuel is metered to the air. The air is drawn into a volume 2 (Figure 1b), frequently known as an air transfer cylinder, by the motion of a piston 1 which is connected to the crankshaft 11 of the upper RDM cranktrain (see Definitions and Figures 5 and 6), so that as the upper crankshaft 11 rotates through 0-180 degrees of angular rotation, the piston moves firstly away from the air induction system, and then returns towards the air induction system as the crankshaft 11 rotates through 180-360 degrees of angular rotation, transferring the air 250b (Figure 2) to the air conduit pipe 6. The one-way flow valve 48 (Figure 2) prevents the air from being expelled backwards through the induction system. Piston rod 9 (Figure 3) connects power piston 8 to the same crankshaft 11 which drives the air transfer piston 1, and as will be explained later, piston 1 and piston 8 may be fitted to the same connecting rod 9, and form a monolithic "stepped piston" arrangement, explained with reference to Figure 6.

Continuing with reference to Figure lb, Figure 2 and Figure 3, the air 250c (Figure 2) for combustion is pumped by the upward movement of the stepped piston 1 (Figure lb) pushing the air through the conduit 6 and then via the cylinder air ports 7 into the combustion space 80 (Figure 2), formed by the piston crowns 8a and 18a of the pistons 8 and 18 (Figure lb). Piston 18 (Figure 3) is driven by crankshaft 21 of the lower RDM cranktrain, which is similar to crankshaft 11, the two crankshafts being connected and synchronously phased by a drive such as a toothed belt and toothed sprockets, or a chain and sprockets, or bevel gears and a shaft, or a spur or helical geartrain, or by eccentric drive connecting rods 90 and 91 as depicted, in Figures lb, 2 and S. The period and timing of the air transfer 250c being into the combustion space between the pistons 8 and 18 is controlled by the movement of the crown face of the air piston 8 (Figure lb).

Pistons 8 and 18 move within the cylinder liner 12 (Figure lb) which is rigidly clamped by at least the outboard or outclrive marine propulsion unit upper part containment casings 60 (Figure lb), and 61 (Figure 3). These upper part containment casings are the engine crankcase which house the engine components such as the crankshafts 11 and 21, the oil pump 50 and oil pickup up conduit or pipe 51 (Figure lb), the adjacent coolant pump 30 (Figure 2) for pumping coolant around the engine coolant jacket 33a, 33b, 33c and 33d and the coolant outlet pipe 34, and drives 23 and 24 (Figure lb) connecting the lower crankshaft 21 to the shafts and bearings supporting the propeller 25 and any gears for speed changes or reversing.

With further reference to Figure lb, Figure 2 and Figure 3, the air for combustion between the pistons 8 and 18a may be burned with a premixed octane based gasoline fuel from the fuelling system 49 (Figure 2) and ignited by at least one sparking plug located at positions such as 81 and 82 (Figure 3) in the cylinder 12 (Figure 1b). which are away from the split line of the containment casing. Alternatively, the air for combustion between the pistons 8 and 18a may be burned with a cetane based diesel fuel injected into the cylinder 12 from at least one fuel injector (not shown) located at either one or both apertures 81 and 82 in the cylinder 12. In another arrangement using octane based gasoline fuels, fuel may be injected by a gasoline fuel injector located at either positions such as 81 and 82 in the cylinder 12, and ignited with at least one sparking plug located at either positions such as 80 and 81 in the cylinder 12. The sparking plug(s) and injector(s) can also be used with carbon neutral fuels. Prechamber combustion systems connected to the cylinder liner may also be used for spark ignition of octane fuels or compression ignition of cetane fuels. The prechambers are screwed or clamped into the containment casings 60 and 61 or into the cylinder liner 12.

After combustion of the fuel and air in the combustion space 8a and 18a between the pistons 8 and 18 (Figure la), the products of combustion expand and push piston 8 upwards, turning crankshaft 11, and piston 18 downwards, turning crankshaft 21, the relative phasing of the crankshafts being maintained by the synchronous drive linking the crankshafts, such as the eccentric drive connecting rods 90 and 91 (Figure 2), also depicted in Figure 5. The burned gases expand until the crown face of the lower piston 18 uncovers the upper edge of the exhaust ports 17 (Figure 1 b) so that the combustion gases can be exhausted to the exhaust pipe 16 which is in connection with the marine water (not shown in Figures) via at least a non-reverse flow system, for example a siphon trap or a one-way check valve (not shown in Figures). The period and timing of the exhaust flow 51a (Figure 2) from the combustion space between the pistons 8 and IS is controlled by the movement of the crown face of the piston 18. The exhaust passage is formed in each of the upper and lower containment casings 60 (Figure lb, Figure 2 and Figure 7) and 61 (Figure 3 and Figure 8) so that the exhaust flows in a conduit to the marine water when the two casing portions are rigidly clamped together with fixings such as bolts and screws.

In the embodiment of Figure lb, a spur or helical gear 22 rigidly mounted on the axis of rotation of the lower crankshaft 21 engages with at least another gear 24 which is rigidly mounted on the axis of rotation of the propeller shaft 26 which drives the marine propeller 25. An idler, gear such 23, mounted with bearings on a supported shaft in the containment casings 60 (Figure lb, Figure 2) and 61 (Figure 3), allows the propeller shall to rotate in the same direction as the lower engine crankshaft 21 or allows the propeller shaft to be located deeper in the lower-section or gearbox portion of the outboard or outdrive propulsion unit. The connecting drive from the lower crankshaft 21 to the propeller shaft 26 may also he via a toothed belt and sprockets mounted on the crankshaft 21 and the propeller shaft 26, or via a chain and sprockets mounted on the crankshaft 21 and the propeller shaft 26, or via an eccentric rod drive similar to that shown in Figure lb and Figure 5 to connect the crankshafts 11 and 21.

With further reference to Figure lb and Figure 2, the oil pump 50 (Figure lb) takes oil via the oil pick-up pipe 51 from the sump 40 (Figure 2), which is formed from the two containment casements 60 and 61 (Figure lb and Figure 3) that also hold the crankshafts 11,21, and contain the pistons 8 and 18, the piston rods 9 and 19, the idler gear 23, the propeller shaft 26 and supporting bearings 27 and 28. The oil pump 50 (Figure lb) delivers the pressurised oil via channels, such as the channel 43 (Figure 2), in each or both halves of the containment casings 60 and 61 to the oil filter 44 and thence the oil leaves the filter via various channels to the parts and components of the engine requiring lubrication. For example, channel 45 connects the outlet of the oil filter to the lower crankshaft 21 and propeller shaft 26. Oil may drain from the upper part of the engine by routing the oil to collection points and galleries in the containment casings 60 and 61 that transfer the oil via enlarged channels formed either in one half or in both halves of the containment casings 60 and 61 to the oil sump 40. Oil drainage from the upper part of the engine to the sump 40 may also he achieved by allowing the oil to return via the gallery 65 (Figure lb) that contains the inter-crankshaft drives which in the embodiment of Figure lb, Figure 2 and Figure 5 are the eccentric drive connecting rods 90 and 91 (Figure 2 and Figure 5). The oil filter 44, whilst shown as an integral part of the containment casings, may be a cartridge element that can be mounted on any surface of the containment where there are drillings or connections with the oil gallery or passage 43 from the oil pump and where the filter may also supply the filtered oil to the galleries in connection with those parts of the engine needing lubrication, for example to the oil passage 45.

Continuing with reference to Figure lb and Figure 2, the engine coolant circuit takes marine water in to the coolant pump impeller 30, which in this embodiment is driven from the end of the lower crankshaft 21, but may be driven from any other convenient drive, such as the propeller shaft 26, or the gears 23 or 24. The coolant pump delivers to a gallery or channel 31 in the containment casing 60 or 61 which connects with one coolant gallery, such as 33a, of the coolant jacket surrounding the cylinder liner 12. Coolant gallery 33a is connected by surface cavities in the split faces of the containment casings 60 and 61 to the adjacent coolant gallery 33b, and thence in a similar fashion to the coolant galleries 33c and 33d. The depictions of the surface cavities in Figure lb and Figure 2 are diagrammatic as in reality oil transfer, coolant transfer, blowhy transfer and oil drain passages and conduits formed by surface cavities that cannot cross each other.

The cylinder liner 12 (Figure lb) is essentially an annulus of revolution in which the internal bore provides the running surface for the pistons and piston rings, and the external diameter and surfaces form the coolant jacket in conjunction with the mid-section containment casings, as shown in Figure lb, Figure 2 and Figure 3. The cylinder liner 12 extends sufficiently towards each crankshaft to support the piston skirts and piston rings. The outer surfaces of the cylinder liner will also have features to enable sealing of these surfaces which are in contact with the containment casings so that the coolant cannot leak through these sealing surfaces. For instance, the sealing features on the outer surfaces of the cylinder liner may comprise a well finished cylindrical surface that will make interference contact with elastomeric sealing rings fitted into peripheral grooves to the containment casings. For 2-stroke applications, the cylinder liner will have apertures, through the cylinder liner wall, that connect with the air inlet chest and the exhaust outlet chest. At these locations, the cylinder liner will have features to enable sealing of the outer surfaces of the cylinder liner which are in contact with the inlet air chest 7 (Figure lb) and exhaust outlet chest 117 (Figure lb) in the containment casings so that the coolant cannot leak through these sealing surfaces. The cylinder liner 12 and all sealing faces of the containment casings may use commonly known means for sealing contained systems such as setting and non-setting or setting sealants or glues, elastomeric sealing gaskets, 0-rings, injected formed-in-place elastomeric sealing beads and metallic gaskets or spring seals.

The cylinder liners for opposed piston 2-stroke applications also have features to enable fitment of sparking plugs, injectors and clecompressor valves.

With reference to Figure 4, which for simplicity is not shown in Figures lb, Figure 2 and Figure 3, the magneto 70 and starter (not shown), which serves as a flywheel and electrical generator for the engine electrics and ignition system, is mounted on a shaft and bearings which may be in the upper part containment casing 60 or 61 and connected via a drive, such as a multiple grooved belt 71 or a toothed belt, to a pulley or toothed sprocket 72 which is rigidly connected to the engine crankshaft 11. Although not shown in the Figures, the magneto can be rotated by commonly accepted methods, for instance with a cranking handle, or with a corded recoil pull starter, or via an electrical starter/alternator that engages directly with the magneto.

or a starter motor that can engage with a solenoid via a pinion to a ring gear mounted rigidly to the magneto. In this way, the engine can he started and can also he provided with electrical energy with the necessary low, moderate or high voltages via transformer coils or power electronics.

With reference to Figures 5 and 6, these pictures are included to explain a particular crankshaft arrangement, sometimes known as an eccentric crankshaft or a rectilinear drive mechanism (RDM, already partly explained in Definitions), that enable linear motion of the connecting rod with no angularity and also enables two pistons to be rigidly linked to the connecting rod. The RDM, covered by GB patent 2525213, is well suited to 2-stroke engines which use the reverse side of the combustion piston for providing scavenge air to engine whilst enabling the crankshaft and connecting rod components to be fully lubricated without the need of a total loss lubrication system. Air transfer piston 1, already shown in Figure lb, is rigidly joined to the connecting rod 9 which has a clearance fit with a first disc 101a (Figure 6) which is rigidly joined a second disc 102a, both discs having a common cylindrical bore 111b which has a clearance fit with the crankpin 20a of the crankshaft 11 (Figure 5). Connecting rod 9 is also rigidly linked to power piston 8, such that as the rotation of crankshaft 11 moves piston 1, cylinder volume 2 (Figure lb) changes in anti-phase with the combustion volume change between piston 8 and piston 18. Upward movement of piston 1 results in fresh air 250b (Figure 2) being transferred from piston 1 into the combustion space partially formed by piston 8 moving in cylinder liner 12 (Figure lb), and partially formed by piston 18 moving in cylinder liner 12, the two pistons 8 and 18 and the cylinder 12 founing the complete combustion chamber (Figure lb, Figure 2 and Figure 3).

With reference to Figures 3, 5 and 6, the linear motion of the connecting rod 9, which is associated with an eccentric crankshaft or a rectilinear drive mechanism, is generated by the motion of the two rigidly joined discs 101a and 102a (Figure 6) rotating about the crankpin 20a whilst connecting rod 9 is being constrained to move in a slot formed by vertical guides 74 and 75 (Figure 3) acting respectively on the connecting rod flanks 71 and 70 (Figure 6), and whilst the oscillating balance mass 103a is being constrained to move in a slot formed by horizontal guides 72 and 73 (Figure 3) acting respectively on the connecting rod flanks 76 and 77 (Figure 6). The vertical guides 74 and 75 (Figure 3) are arranged parallel to the motion of the connecting rod 9 above and below the centre of rotation of the crankshaft 11, whilst the horizontal guides 72 and 73 are arranged parallel to the motion of the balance mass 103a (Figure 6) and orthogonal to the major axis of the engine, above and below the centre of rotation of the crankshaft, and said guides 72 and 73 are part of the containment casing extensions 201a and 201b (Figure 3). Crankpin 20a is arranged to rigidly connect crankwebs 104 and 105 (Figure 6) by commonly practised methods, for instance arranging an interference fit between the male crankpin 20a and the female hole 20b in cranlcweb 105 and a corresponding hole in crankweb 104, which is not visible in Figure 6.

A similar RDM arrangement is used (Figures 2, 3, 5 and 6) for the piston 18 and oscillating balance of the crankshaft 21 (Figure 5), except connecting rod 19 of this lower cranktrain is only linked to power piston 18, i.e. in this arrangement it is not required to drive an air transfer piston such as 1 as the latter displaces enough air for the displacement of both power pistons of the engine. The oscillating balance masses, which reciprocate orthogonally to the power pistons, generate a reciprocating force that in combination with the power piston forces produces a constant rotating force that can be readily balanced with a counterweight on the crankshaft.

Figures 2, 5 and 6 also show optional seals 67 and 68 (Figure 5) which can allow volumetric pumping between the undersides of the pistons 8 and 18 and can also be used to exclude oil to the pistons 8 and 18, if dry piston operation is required.

With further reference to Figure 6, power piston 8 and air transfer piston 1 are rigidly connected by piston rod 9 and driven from the same crankshaft 11. In one embodiment, the diameter of air transfer piston 1 is sized so that its volumetric displacement is equal to the combined displacement of the power pistons 8 and 18. In another embodiment of the invention, the diameter of air transfer piston 1 is sized so that its volumetric displacement is greater than the combined displacement of the power pistons 8 and 18in order to supercharge the power pistons. The arrangement of a larger diameter piston which is rigidly connected to a smaller diameter piston is commonly known as a stepped piston. Usually, as indicated in the Definitions, the two piston diameters are immediately adjacent and may be monolithic and connected to the crankshaft by a single connecting rod; in this case, both piston diameters move in phase in terms of volumetric displacement. In the embodiment of the claimed invention depicted in Figures, lb, 2, 3, 5 and 6 the two piston diameters are spatially separated but rigidly connected by piston rod 9 and connected to the crankshaft 11 so that piston diameter 1 moves 180 degrees out of phase in terms of volumetric displacement with the volumetric displacements of pistons 8 and 18. This is therefore considered to be a stepped piston arrangement.

In Figures lb, 2, 3, 5 and 6, the axes of the crankshafts 11 and 21 are parallel with the axis of the propeller shaft 26 (Figure 1h) and the planes of the casing extensions 201a and 201h and 211a and 211b are orthogonal to the axis of the propeller shaft 26 (Figure 3). The split line of the upper part and lower part containment casings 60 (Figure lb and Figure 2) and its complementary casing (not shown) is on a plane through the crankshafts 11 and 21 and the propeller shaft 26 and parallel with the major axis of the cylinder liner.

Figures 7 and 8 show the upper and lower part containment casings 60 and 61 for the first embodiment of the invention as described with reference to Figures lb -6 in which the axes of the crankshafts 11 and 21 are parallel to the propeller shaft 26. The static features shown in Figures lb, 2 and 3 are formed by the assembly of the two containment casings, which in some embodiments are "mirror imaged". For instance, the cylinder liner 12 of Figures lb, 2 and 3 is contained by the half cylindrical cavities 12a and 12b of Figures 7 and 8. Similarly, the oil sump volume 40 of Figures lb, 2 and 3 is contained by the half cylindrical cavities 40a and 40b of Figures 7 and 8, and the air transfer pipe 6 of Figures lb, 2 and 3 is contained by the half cylindrical cavities 6a and 6b of Figures 7 and 8. Although not shown, the containment casings 60 and 61 are rigidly fixed to each other by commonly available methods so that the moving engine parts are appropriately supported and the engine air, coolant, lubrication circuits and exhaust are sealed from the external marine environment. For example the joint surfaces on the split faces between the casings 60 and 61 may be covered with a setting or non-setting sealant, or elastomeric gasket strips contained in grooves, or metallic seals and multiple bolts or screws are used to join casings 60 and 61.

The invention shown in Figures lb, 2, 3, 4, 5, 6, 7 and 8 is applicable to any multi-cylinder in-line 2-stroke engine configurations such as 2, 3, 4, 5 and 6 cylinder arrangements.

Figures 9 and 10 show the internal mechanism of another embodiment of the invention in which there is an orthogonal drive between the engine and the propeller shaft. It should he noted that in Figures 9 and 10, the axes of crankshafts 11 and 21 are orthogonal to the split line of the casings 60 (Figure lb and Figure 7) and 61 (Figure 8). With reference to Figures 9 and 10, the overall arrangement of the air induction, air transfer, fuelling and magneto systems is the same as the first embodiment shown in Figures la, 2, 3, 4, 5 and 6. For simplicity, the casings 60 and 61 containing the mechanisms shown in Figures 9 and 10 are removed and only the major differences of the two embodiments are shown, i.e. the first embodiment with crankshaft axes parallel to the propeller axis, and the second embodiment with crankshaft axes orthogonal to the propeller axis. It can therefore be seen that the air transfer piston 1, the crankshafts 11 and 21, the connecting rods 9 and 19, and the cylinder 12 of Figures 9 and 10 are almost identical to those shown in Figures la, 2, 3, 4, 5 and 6. However, crankshafts 11 and 21 are joined by a toothed belt drive 802 which engages with sprocket 801 on crankshaft 11 and with sprocket 803 on crankshaft 21. Other connecting drives between the crankshafts use bevel gears and a connecting shaft or the eccentric drive connecting rods such as those (90 and 91) shown with reference to Figures lb, 2 and 5. These crank to crank connecting drives would require an external chest and detachable scaled cover to the casings 60 and 61 to allow for assembly of the connecting chives that are not on the split line of the casings with the orthogonally disposed crankshafts of the embodiment shown in Figures 9,10,11 and 12.

Figures 11 and 12 show the containment casings 260 and 261 for the second embodiment of the invention as described with reference to Figures 9 and 10 in which the axes of the crankshafts 11 and 21 are orthogonal to the propeller shaft 26.

With reference to Figures 9,10, 11 and 12, toothed belt 804 engages with sprocket 808 on the lower crankshaft 21 and also with sprocket 805 which is rigidly attached to the lower bevel gear 806, said gear being supported on a bearing mounted in the casing 260. Bevel gear 806 is in engagement with an orthogonal bevel gear 807 with is rigidly fixed to the propeller shaft 26 to which the marine propeller 25 is attached. In this way, the axes of the crankshafts 11 and 21 may be orthogonal to the split line of the containment casings 260 and 261 (Figures 11 and 12) and the connecting rod guides 72 and 73 (Figure 3) are contained in the upper part casing extensions 201a and 201b (Figure 3) which are now parallel to the plane of the propeller shaft 26. This eases manufacturing of the guides 72 and 73 (Figure 3) and 172 and 173 (Figure 3).

With reference to Figures 11 and 12, as described with reference to the half casings shown in Figures 7 and 8, the cylinder liner 12 of Figures 9 and 10 is contained by the half cylindrical embossments (also known as cavities) 212a of Figure 11 and 212b of Figure 12. Similarly, the sump volume used in conjunction with the mechanisms shown in Figures 9 and 10 is contained by the half cylindrical embossments 240a of Figure 11 and 240b of Figure 12 and the air transfer pipe 6 of Figures lb, 2 and 3 is contained by the half cylindrical embossments 206a of Figure 11 and 206b of Figure 12. Although not shown, the casings 260 and 261 are rigidly clamped to each other by commonly available means so that the moving engine parts shown in Figures 9 and 10 are adequately supported and the engine air, coolant, lubrication circuits and exhaust conduits are sealed from the marine environment. For example the joint surfaces between the casings 260 and 261 are covered with a sealant, or elastomeric gasket strips contained in grooves, or metallic seals and multiple bolts or screws are used to join casings 260 and 261.

Although not shown in the figures, both previously described embodiments may have exhaust emission aftertreatment systems in the exhaust system conduit 16 (Figures lb and 2) and the casings of these aftertreatment systems may be cooled by the engine coolant before said coolant is discharged to the marine environment.

It should also be noted that Figures lb, 1 3, 4, 5, 6, 7, 8, 9 10, 11 and 12, and in particular Figures lb, 2 and 3, show the bulk of the engine systems are located in the outboard or outchivc propulsion unit left-hand and right-hand containment casings which are below the steering arm location (4000. Figure la), i.e. in the middle to lower portion of the upper part of the outboard marine unit.

Some ancillary engine items may be located above the steering arm; these may include the fuel tank 46 (Figure 2 and 3), the air cleaner (47), one-way flow valve(s) 48 (Figure 2), a carburettor or fuel injection system 49, a starting system, control electronics for the engine operation (not shown in Figures), an oil filling and dipstick cap (not shown in Figures), in some cases the magneto/electrical generator for the engine ignition and electrical power for electrical fuel pumps if used (but not shown in Figures), and gearbox controls for selection of neutral, forward and reverse drives.

To summarise, the invention is a marine outboard or outdrive propulsion unit, as described with reference to Figures lb, 2, 3, 4, 5, 6, 7, 8, 9 10, 11 and 12, in which the internal combustion engine is below the steering arm location of the outboard or outdrive marine propulsion unit, and in which static components of the internal combustion engine, such as the crankcase scantlings, cylinder block and the containment of some or all engine systems are formed by the vertically split casings of the outboard or outdrive marine propulsion unit. Figures lb, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 show two embodiments comprising a propeller, an internal combustion engine with at least one cylinder liner contained within the vertically split upper part and having a phased drive between the two crankshafts, engine starting means, an engine coolant pump, an engine oil pump, means for ignition and fuelling, a drive from the lower crankshaft to the propeller, wherein the containment casings of the vertically split upper part and lower part, when rigidly clamped together form the engine crankcase to carry the crankshafts and gear and propeller shafts, and with the wet cylinder liner forming the coolant jacket and air inlet port chest and exhaust outlet port chest, the engine lubricant containment also known as the oil sump, and forming the at least one conduit for the air induction, and forming the at least one conduit for exhaust and exhaust emission aftertreatment catalyst, and fanning the at least one conduit for electrical wiring, and forming the at least one conduit for the engine oil supply and the at least one conduit for oil return to the oil sump, and forming the gallery containing the phased drive between the crankshafts which may also serve as a blowby return conduit, with oil separation, to the intake system.

It will be obvious from Figures lb, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 that in these two embodiments of the invention the outboard or outdrive propulsion unit left-hand containment casing includes both the left-hand upper part and lower part as a monolithic unit, and right-hand containment casing includes both the right-hand upper part and lower part as another monolithic unit, avoiding the need for a separate lower unit for the gearbox. In these embodiments, the internal combustion engine is substantially in the mid-section of the upper part of the outboard or outdrive marine propulsion unit, but some elements of the engine may extend into in the lower part, also known as the gearbox-section, of the outboard or outdrive marine propulsion unit.

It should also be clear from Figures lb. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 that other embodiments of the outboard or outdrive marine propulsion unit invention may have the internal combustion engine entirely in the upper part of the outboard or outdrive marine propulsion unit, and connected by various means such as belt drives, spur gears, helical gears and bevel gears to the propeller shaft in the lower part. In this arrangement with the internal combustion engine entirely in the upper part of the outboard or outdrive marine propulsion unit, the upper part of the outboard or outdrive marine propulsion unit may be longer than outboard or outdrive marine propulsion units in which the engine is partially in the upper part and partially in the lower part. It is common for outboard or outdrive marine propulsion units to have optional upper part lengths in order to accommodate various boat transom heights.

In these embodiments and further embodiments to be described with reference to Figures 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 and 25, the containment casings of the outboard or outdrive marine propulsion unit are split on a vertical plane passing through the longitudinal axis of the engine crankshaft or the longitudinal axes of the engine crankshafts, said axis or axes being parallel to die axis of the propeller of the outboard or outdrive marine propulsion unit.

These embodiments also encompass arrangements in which the crankshaft axis or crankshaft axes is or are orthogonal to the propeller shaft axis and the containment casings of the outboard or outdrive marine propulsion unit are split through a vertical plane also passing through the longitudinal axis of the propeller shaft.

At risk of repetition, other aspects of the invention are now described specifically as Figures lb, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 may not show adequate detail.

The engine cylinder bore(s) are cylindrical wet liners which may be fitted in the upper part containment casings of the outboard or outdrive marine propulsion unit.

The exhaust system comprises a cylindrical pipe for the exhaust gas flow which fits at its upstream end into the exhaust outlet of the engine and fits at its downstream end to the engine coolant water outlet, said cylindrical exhaust pipe being contained with clearance on its outer diameter relative to cavities in the split containment casings of the upper part of the outboard or outdrive marine propulsion unit.

In another embodiment, the exhaust system comprises a cylindrical pipe for the exhaust gas flow which fits at its upstream end into the exhaust outlet of the engine and fits at its downstream end to the engine coolant water outlet, said cylindrical exhaust pipe being contained with clearance on its outer diameter relative to cavities in the split containment casings of the upper part and lower part of the outboard or outdrive marine propulsion unit.

The containment casings of said outboard or outdrive marine propulsion unit are rigidly clamped to each other by commonly used fixings such as for example set screws and bolts and the clamped containment casings firmly retain the static engine components including cylinder heads, cylinder liners, catalysts, bearings, exhaust pipes, check valves and blowby separators. By these means, the invention uses the containment casings of the outboard or outdrive propulsion unit to replace the conventional engine scantlings and therefore saves weight, reduces the number of parts, reduces the package size and reduces the unit manufacturing cost.

The combustion system of the 2-stroke opposed piston engines described in this invention may operate either by spark ignition combustion, jet ignition including pre-chambers, or by compression ignition combustion or by homogenous charge compression ignition combustion, all of these being commonly known methods of combustion for internal combustion engines, using either gasoline, diesel, carbon neutral fuels, zero carbon fuels or a blend of these fuels as is appropriate to the combustion system type.

Other embodiments of the invention are now described with respect to applications to 4-stroke and sleeve valve internal combustion engines.

Figure 13 shows the internal parts of a single cylinder single piston 4-stroke overhead valve engine which is contained in the left-hand and right-hand upper part casings of an outboard or outdrive propulsion unit. The piston 314 is connected to the crankshaft 349 by a connecting rod 348 and cap 347 and fixing bolts. The piston 314 slides with clearance in the wet cylinder liner 312 which is flanged at its upper end, said flange abutting with the lower outer periphery of a cylinder head assembly 313. This prismatic shaped cylinder head assembly contains at least one inlet poppet valve 344 and one exhaust poppet valve 346, springs 343a and 343b and valve spring retainers, the poppet valves being actuated by tappets from a camshaft 320 which is synchronously driven at half crankshaft rotational speed from the engine crankshaft 349 by a system of sprockets 331 and 332 and a toothed belt 334 with a belt tensioner 350. The inlet poppet valve is situated in an inlet port in the cylinder head assembly 313 and the exhaust poppet valve is situated in an exhaust port in the cylinder head assembly 313, said inlet port having a sealed connection with an air induction conduit formed in the two upper part containment casings (not shown) of the outboard or outdrive propulsion unit, and said exhaust port having a sealed connection with an exhaust conduit formed in the two upper part containment casings (not shown) of the outboard or outdrive propulsion unit. The cylinder head 313 is also fitted with a sparking plug 316 which is in connection with an electrical coil 315. Passages within the cylinder head receive coolant from the engine coolant pump 330 via at least one conduit formed in the two containment casings (not shown) and the warmed coolant is discharged via conduits formed in the two containment casings (not shown). In a similar fashion, the cylinder head receives oil from the engine oil pump and filter (not shown) via at least one conduit formed in the two containment casings (not shown) and the used oil is returned via conduits formed in the two containment casings (not shown). Fluid-tight connections between the cylinder head 313 and the containing casements (not shown) are made with seals which for example may be of the elastomerie form-in-place type or thin folded metallic cylindrical types. Oil spillage from the camshaft and valvetrain in the upper cylinder head is contained by a sealing plate 317. The cylinder head 313 and the wet cylinder liner 312 are each arranged to have at least one female circumferential groove with arcuate sections which substantially match a circumferential male rib with corresponding arcuate sections on the inner diameters in the containment casings so that closure of the upper part containment casings rigidly clamps the cylinder head and cylinder liner to prevent any movement between these parts and to act as a load path for the forces on the cylinder head and wet cylinder liner which arise from the gas forces. The containment casings are closed with fixings which for example may be set screws, bolts, or studs with nuts. In Figure 13, the engine may be started via any state of art starting system such as hand cranking, inertia starter, electric starter, cartridge starters, spring starters, and recoil pull starts; a gearing, in this case the toothed belt 340 and sprockets 341 and 332 and a clutch system (not shown) may be used to have advantageous starting ratios whilst avoiding over-speeding of any electrical driven parts such as starter, alternator and magneto 342.

With reference to Figure 14 which shows a single piece upper and lower containment casing for the 4-stroke engine described in Figure 13, this vertical section through the cylinder centre shows the crankshaft 349 is connected to the marine propeller 325 via any state of art driveline which in Figures 13 and 14 is a geartrain comprising gears 321, 322, 323 and 324. Simpler gear trains, for instance with fewer gears, are also feasible, as are drivelines using toothed belts, chains, eccentric rods and shafts with bevel gear connections. To reduce single cylinder engine vibration, this driveline may drive a shaft such as 326 which has a balance weight rotating at engine speed and in contra-rotation to the crankshaft 349. The driveline may also power a coolant pump 330 which passes marine water to the engine cooling system.

With further reference to Figure 14, the containment casing 360a is one of a pair of opposite handed casings which when fitted together contain at least the engine parts shown in Figures 13 and 14 and said containment casings also perform the critical functions of rigidly holding the wet cylinder liner 312, the prismatic shaped cylinder head 313 which in this embodiment is cylindrical on the axis of the cylinder liner, the crankshaft 349, the propeller 325 and the combined propeller and balance shaft 326, the shafts supporting the gears 322 and 323, the camshaft (320, Figure 15) and the shaft supporting the magneto and starting system 342. The containment casings 360a, and its opposite handed counterpart (not shown) also contain the oil filter 368, a cavity for the oil pump 367, and oil conduits, for example as shown by the half conduit 380 from the oil pump 367 to the oil filter and half conduit 369 from the oil filter to the cylinder head and the main bearings that support the crankshaft 349. Furthermore, the containment casings 360a, and its opposite handed counterpart (not shown) also contain the coolant flow passages to the cylinder liner 312 in the form of half conduits or cavities on the split line planes of each half containment casing, the coolant flow galleries 381 around the liner, and the coolant return conduits 370 from the cylinder head and wet cylinder liner. The induction air to the inlet ports in the cylinder head arrives via half conduits such as 373 in the half containment casings, the other matching half conduit being in the counterpart mid-section containment casing (not shown). The products of combustion leave the exhaust ports in the cylinder head via half conduits such as 371 in the half casings and exit the casings into the marine environment via the aperture 366, the other matching half conduit being in the corresponding other half containment casing (not shown). Alternatively, the exhaust conduit can be routed in the two parts of the containment casings to exit in a low pressure region near the propeller. The upper part cavity 378, with its counterpart in the other containment casing (not shown) provides a gallery for the synchronous timing belt 334 drive between the camshaft toothed sprocket 333 (Figure 14) and the crankshaft toothed sprocket 331 (Figure 14). The ignition coil 315 (Figure 13) is contained in a cavity formed by the two upper part casement halves and the low tension electrical wiring 390 (Figure 14) is routed in cavities in the casings to the ignition system. Similarly, the high tension wiring 391 (Figure 14), which connects the ignition coil to the sparking plug, is routed in cavities in the containment casings. As noted previously, the crankshaft 349 is supported by bearings which are clamped rigidly by the two upper part containment casings casing 360a (Figure 14), and its counterpart (not shown), and these two casings form the internal crankcase clearance volume wherein the crankshaft and the connecting rod rotates, the balance shaft rotates and the bulk of the lubricating oil is contained with connections to the suction side of the oil pump 367. The containment volume of the oil, which is part of the cavity 361, is effectively the traditional "engine sump" but symbiotically uses the containment casings of the lower part which are an extension of the upper part containment casings, i.e. in this embodiment each casing comprises a monolithic upper part and lower part.

With reference to Figure 15, this vertical sectional view, which is offset from the split line of the vertical symmetrical upper part and lower part containment casings, shows the poppet valves 344 and 346, and has a first male peripheral protrusion 393 in the containment casing 360a which engages, with interference, a first female peripheral groove in the cylinder head 313a, rigidly clamping the cylinder head to the containment casing and transferring the gas loads from the cylindrical cylinder head to the containment casings. A second male peripheral protrusion 394 in the containment casing 360a engages, with interference, a second female peripheral groove in the cylinder head 313b, rigidly clamping the cylinder head to the containment casing and transferring the gas loads from the cylinder head to the containment casings. In a similar fashion, another first male circumferential arcuate section rib 395 in the containment casing 360a engages, with interference, another first female circumferential arcuate groove in the wet cylinder liner 312, rigidly clamping the wet cylinder liner to the containment casing and transferring the piston side loads from the cylinder liner to the containment casings. Another second male circumferential arcuate section rib 396 in the containment casing 360a engages, with interference, another second female circumferential arcuate groove in the cylinder liner 312, rigidly clamping the cylinder liner to the containment casing and transferring the piston side loads from the wet cylinder liner to the containment casings. In this way, the static engine parts are rigidly held and the containment casings perform the function of the traditional engine crankcase as well as providing the structural upper and lower parts of the outboard or outdrive marine propulsion units.

With reference to male protrusions in the mid-section and the mating female grooves mentioned in the preceding paragraph for securing the cylinder head and cylinder liner to the containment casings, the locations of the protrusions and grooves maybe reversed such that the protrusions are on the cylinder head and cylinder liner, and the grooves located in the containment casings, or arranged as a mixture of grooves and protrusions on the cylinder head and cylinder liner, and vice-versa with respect to mating containment parts.

The arrangements described with reference to Figures 13, 14 and 15 may also he applied to a 4-stroke engine with a single crankshaft and with side valves in which the camshaft(s) for the valve actuation are driven from the crankshaft via a 2:1 speed reduction drivetrain, which for example could be a synchronous toothed belt and sprockets, or a gear drive or a chain and sprocket drive, as will be clearer from the following description for a similar embodiment. In this 4-stroke side valve arrangement, a clutched drive would be provided from the starting mechanism to the single crankshaft via a gallery formed in the containment casings. In a similar manner, a drive from the crankshaft would be provided to any required electrical generator mounted either in the upper part or the saddle section of the outboard or outdrive marine units, the drive being accommodated in a gallery formed in the containment casings.

With reference to Figures 16, 17, 18, 19 and 20, these show an alternative 4-stroke side valve embodiment of the invention which is also an opposed piston engine with a higher compression ratio capability, and therefore having higher thermal efficiency, than the 4-stroke side valve engine described in the immediately previous paragraph. This alternative 4-stroke side valve engine for marine outboard or outdrive propulsion units has a first crankshaft 449 (Figure 16), linked synchronously to a starting and ignition system 498, and also linked synchronously via a toothed sprocket and a toothed belt 434 and a second toothed sprocket to a second crankshaft 450, said first and second crankshafts each being connected respectively via connecting rods 462 and 463 to pistons 414 and 415, said pistons moving in cylinder liners 412a and 412b (Figure17). Actuation of the at least two poppet valves, such as 444a and 444b, is explained by the example of inlet poppet valve 444a, connected to the inlet port 481 (Figure 17) which is in connection with the induction and fuelling system of the engine. The inlet poppet valve is actuated by a tappet and camlobe 499 (Figure 16), rigidly linked by a camshaft to the gear 498 which is in mesh with gear 4970 on the crankshaft 449, said gear 4970 being sized to operate at twice the rotational speed of camshaft gear 498. The return motion of the valve 444a is arranged by a spring 4620 which is linked to the valve by the usual means of a spring retainer and cottars (not shown). The spring is housed in a spring cavity 4870 (Figure 18) which is also part of the cylinder liner 412a (Figures 17 and 18). The valve stem passes through a valve guide 487 in the upper cylinder liner (Figure 18), and the male conical valve head scats in a corresponding female conical counterbore 4810 (Figure 18) which is also part of the cylinder liner 412a. Said valve seat counterbore is outwardly facing, i.e. towards the joint face of the two wet cylinder liners, and is part of a volume 483, referred to as a "port bowl", on the outer periphery of each cylinder liner which enables a first valve 444a (Figure 16) to open and allows air to flow, with minimal restriction, from a first inlet port 481 (Figure 18) into the swept volume and combustion volume space between the two pistons 414 and 415 (Figure 18) respectively in the cylinder liners 412a and 412b. There is the same or similar arrangement for a first exhaust valve 444b (Figure 16) and its spring 4621 in the liner 412b and the valve head of valve 444b lifts into the same port bowl 483 (Figure 18) as the inlet valve 444a. With the inlet and exhaust valves are closed, which is during the compression, combustion and expansion phases, a first combustion chamber comprises the port bowl volume in combination with shaped volumes in the piston crowns, such as 485 (Figure 19) in piston 414 and a corresponding shape in piston 415 (Figure 18). The combustion chamber volume is in connection with a first sparking plug 4166 and the air motion from the inlet valve is arranged, by the shape of the inlet port 481 and bowl 483 and the interaction of the air as it enters the cylinder to have a bulk swirl pattern in the direction of the adjacent sparking plug 416b. As the pistons 414 and 415 move towards their inner dead centre (IDC) positions, the bulk swirl is displaced outwards towards the combustion chamber volume by the crown protrusions in the centre of the piston. During this transition of the bulk swirl, as is well known, said swirl is compressed into a higher speed vortex, based on the principle of conservation of momentum, because of the ratio of the cylinder bore diameter/combustion chamber diameter. As the combustion chamber, formed by the port bowl volume and the adjacent volume in the piston crown, is not circular and of a truncated combination of shapes, the accelerated bulk swirl in said combustion chamber is subject to many changes in flow direction and this gradually reduces the kinetic energy of the swirl by a process of smaller scale/higher frequency turbulence generation and subsequent degradation. This small scale turbulence, generated near the sparking plug, strongly increases the combustion burning rate which helps improve fuel efficiency, increases the engine power and reduces emissions.

With continued reference to Figures 16, 17, 18, 19 and 20, a second layout of an inlet valve 446a, exhaust valve 446b, inlet port 476, exhaust port 477, port bowl 484, piston combustion chamber 486, sparking plug 416a and valve actuation can be arranged diametrically opposite (across the piston diameter) the first inlet valve 444a and first exhaust valve 444b, so that first and second sets of inlet and exhaust ports and port bowls are arranged to be on the split line of the two containment casings 480a and 480b (Figures 17 and 19). Said arrangements of the ports and valves on the split line of the upper part and lower part containment casings enables the ports to be connected readily, with use of appropriate seals such as elastomeric or metallic gaskets and ring seals, to the inlet air conduit 4810 (Figure 18) and exhaust gas conduit 4770 (Figure 20) which are formed as matching half channels in the split of the upper part and lower part containment casings 480a and 480b. Figure 17 shows an example of the inlet port outlet 476 which engages with die inlet conduit 4810 (Figure 18) and the exhaust port outlet 477 which engages with the exhaust conduit (not shown). The presence of the second set of valves and combustion chamber enhances the rate of combustion and improves the fuel efficiency and the engine power and reduces the emissions of the engine.

In the prior discussion of the invention as applied to a 4-stroke side valve engine, the poppet valves for gas exchange are arranged with a least a first pair of inlet and exhaust valves, located co-axially on an axis through both valve sterns, and with the valve heads opening into a common port bowl. A third embodiment of this is to have the first pair of valves operating as inlet valves only, connected to the inlet ports and induction flow conduits, and the second pair of valves operating as exhaust valves only, connected to the exhaust ports and flow conduits, whilst still retaining the bulk swirl and twin combustion chamber arrangement previously described.

With reference to Figure 20, this view of the inside of one of the containment casings 480a shows a first female peripheral groove 4820 in the upper part and lower part containment casing 480a which engages, with interference. a first male peripheral protrusion (4824, Figure 17) in the cylinder liner 412a (Figure 17), and a second female peripheral groove 4821 in the containment casing 480a which engages. with interference, a second male peripheral protrusion (4824, Figure 17) in the cylinder liner 412a, the said arrangement rigidly clamping the cylinder liner 412a to the containment casing and transferring the side loading from the piston 414 from the cylinder liner 412a to the containment casing. Figure 20 also shows another first female peripheral groove 4822 in the containment casing 480a which engages, with interference, another first male peripheral protrusion (4825, Figure 17) in the cylinder liner 412b, and a second female peripheral groove 4821 in the containment casing 480a which engages, with interference, another second male peripheral protrusion (4826, Figure 17) in the cylinder liner 412a, the said arrangement rigidly clamping the cylinder liner 412b to the containment casing and transferring the side loading from the piston 415 from the cylinder liner 412b to the containment casing. Furthermore, the female groove 4821 in the centre of the containment casings for the cylinder liners is sized to take both the second male ribs 4824 and 4825 with radial interference. The abutting ends of the cylinder liners 412a and 4126 are arranged to also ensure axial, which is to say along the axis of the two cylinder liners, interference around the complete abutment contact area between the cylinder liners which includes the cylinder liner walls that encompass the port bowls. The axial interference between the two liners, which is required to ensure gas and coolant sealing, may be achieved by one of several means. For instance, a flexible gasket, which may be of a single or multiple layer steel type, may be inserted between the abutting end faces, each of which are orthogonal to the cylinder liner axis, of the upper cylinder liner 412a and the lower cylinder liner 412b; the gasket will be elastically compressed on insertion of the cylinder liners and closing of the two containing casings. Also shown in Figure 20 is an optional arrangement for the inclusion of an exhaust gas aftertreatment catalyst 493 which fits with a compliant support mesh 492 into appropriately sized half cavities in the two containment casings, such as half cavity 494 in containment casing 480a. The catalyst is connected at its entry to exhaust conduits, such as thc half conduit 4770, to the exhaust ports 477 and 482 of the cylinder 412b (Figures 18), and is connected at its exit to the exhaust outlet 495 (Figure 20) which discharges the exhaust to the marine environment or follows another conduit in the containment casings to exit by the propeller. The split line of the cavity 494 which retains the catalyst 493 and its support mesh 492 is arranged to be on the split line of the upper part and lower part containment casings 480a and 480h so that the catalyst and its support mesh can be readily assembled.

The sparking plugs 416a and 416b engage (Figure 16), for example with a gas tight threaded joint, into either one or other of the cylinder liners 412a and 412b (Figure 17) and connect with high tension electrical leads 497 and 496 to the ignition coil 495 (Figure 16), said high tension leads being contained in half conduits in the containment casings 480a and 480b (Figure 17). The sparking plugs 416a and 416b may he removed from access ports 4780 and 4790 (Figure 19) in the containment casings 480a and 480b, these access ports being closed by sealing plugs 478 and 479 (Figures 17 and 19).

With continued reference to Figures 16-20, at least one crankshaft, such as 450 (Figure 16), is connected via a driveline, such as geartrain comprising at least a first gear 455 on the crankshaft and a second meshing gear 458 on the shaft that drives the propeller 425. Intermediate gears 456 and 456 may also be used. Alternative drives between the crankshaft and the propeller shaft may be arranged with belts and appropriate pulleys or sprockets.

As the embodiment shown in Figures 16 -20 is a 4-stroke engine, there is no need for any phase angles between the crankshafts 449 and 450 and so this arrangement is fully balanced and it is not necessary to fit any balance shafts.

With reference to Figures 21, 22, 23, 24 and 25, this is another 4-stroke cycle engine embodiment of the invention, having sleeve valves instead of poppet valves for the functioning of the gas exchange. This embodiment also uses an opposed piston configuration with a first crankshaft 549, linked to a starting system 598 and ignition system 519 (Figure 21), and also linked synchronously via a toothed sprocket and a toothed belt 5219 and a second toothed sprocket 508, and a third toothed sprocket 507, a second toothed belt 509 and a fourth toothed sprocket 511, and a third belt 513 to a second crankshaft 550, said first and second crankshafts each being connected respectively via connecting rods 562 and 563 to pistons 534 and 535 (Figure 22), said pistons moving in rotating and oscillating sleeve valves 520 and 521 which themselves operate with clearance and lubrication in a static wet cylinder liner 501 (Figure 21). The sleeve valves 520 and 521 (Figure 22) are thin cylindrical liners each with a boss 5200 and 5210 (Figure 22) respectively at their outer ends and each boss being rigidly fitted with stiff and robust crankpins 537 and 523 respectively, said crankpins being rigidly joined to toothed sprockets 531 and 524 respectively, these sprockets being connected to the crankshaft sprockets 529 and 522 by toothed belts 530 and 525. The sprockets 531 and 524 are sized so that they operate at half the rotational speed of crankshaft sprockets 529 and 522, enabling the sleeve valves 520 and 521 to oscillate at half the frequency of the crankshaft rotational speed and therefore the sleeve valves can operate the induction and exhaust event timings for 4-stroke gas exchange operating cycles. As the crankshafts 549 and 550 rotate, the sleeve valve crankpins 537 and 523 (Figure 22) also rotate, imparting a predominantly reciprocating and partly rotating motion to the cylindrical sleeve valves, and this motion can be used to open and close ports 504 and 505 in the static cylinder liner 501 (Figure 21) so that air can he introduced into the cylinder and comhustion space contained within the cylindrical sleeves 520 and 521 (Figure 22), and exhaust gases can be displaced from the cylinder and combustion space contained within the cylindrical sleeves 520 and 521. Sleeve valves 520 and 521 have respectively male conical chamfers 5201 and 5211 (Figure 23) around their innermost end faces relative to the static cylinder liner 501 (Figure 21), and the latter has a smaller diameter bore 5011 at its inner end (Figure 25), which separates the sleeve valves from each other, provides part of the combustion chamber volume 5012 (Figure 25) and has a first female conical chamfer (not shown) which engages with the corresponding male conical chamfer 5201 (Figure 23) and has a second female conical chamfer (not shown) which engages with the corresponding male conical chamfer 5211. In this way, the sleeve valve liners can seal against combustion pressure. The effect of tolerances on the contact of the male conical chamfers with the female conical chamfers, as may occur with the variations of critical dimensions of the sleeve valves, the static liner and the crankpin attached to the sleeve, arc compensated by use of a compliant and tensioning element (not shown in Figures) in the sleeve valve, crankpin and sprocket assembly drive. Oil seals (not shown), secured to the static liner 501 and in sliding contact with the oscillating sleeve valves 520 and 521, prevent crankcase oil from entering the combustion chamber space 5019 or entering the inlet ports 504 or the exhaust ports 505. As with other embodiments, the static cylinder 501 is fitted rigidly to the upper part containment casings 580a and 580b (Figure 24), with clearance for coolant flow across thermally critical portions of the wet cylinder liner, particularly in the cylinder liner area adjacent to the combustion chamber zone 5019 and the sparking plug boss 503 (Figure 25). The bearings (not shown in Figures) that support the crankshaft main journals are also rigidly held in the midsection containment casings 508a and 508b (Figure 24), as well as the bearings that support the shafts for the gears 514, 515, 516 linking the crankshaft 550 to the propeller 525. In this 4-stroke sleeve valve embodiment of the invention, the upper part containment casings also have cavities and conduits, formed by half cavities and conduits in each containment casing, said cavities and conduits passing the induction air to the inlet ports 504 and receiving the exhaust gases from the exhaust ports 505. Similarly conduits are formed from half cavities in the upper part containment casings 580a and 580b for the coolant flow to cylinder liner 501 from the coolant pump 530 (Figure 21) , and from the wet cylinder liner to the coolant outlet in the marine environment. Likewise, conduits are formed from half cavities in the containment casings 580a and 580b for the passage of oil lubricant to the oil filter and thence to the crankshafts, the sleeve valve drives and the gears and gear shafts, and for drainage of the oil to the sump. As in other embodiments, the oil sump is also formed from half cavities in the lower part containment casings which in the embodiment of Figures 21-25 is monolithic with the upper part, hut can he an independent casing to the upper part casings.

With continued reference to Figures 21, 22, 23, 24 and 25, the sleeve valves 520 and 521 may be operated by other known methods, for example by camshafts with return springs acting on each liner, or the sleeve valves may be hydraulically driven with the return motion also by a spring acting on each liner, or may he hydraulically driven in both directions.

The upper part and lower part containment casings may also have auxiliary volumes formed by cavities in each containment casing for the flow and acoustic optimisation of the air induction process.

In all embodiments of the invention, the engine auxiliaries and peripheral items including the starting system, the electrical generator, the air cleaner, oil filler cap, fuel pumps, the engine throttle, the engine control system including any electronic management systems, are sited at the top of the upper part of the marine propulsion unit.

This invention covers outboard and outdrive marine propulsion units, as previously described, with at least one cylinder and is applicable to any number of in-line cylinders with compression ignition, spark ignition or controlled auto-ignition types of combustion, when used with diesel, gasoline, renewable and carbon neutral fuels such as ammonia and hydrogen.

Novelty and Inventive Steps The novel and non-obvious steps of the proposed inventions include: the use of the vertically split upper part of the outboard marine unit for the engine component containment and symbiotically forming the structural connection between the lower part and the saddle section and control arm of the outboard unit as generally defined in Figure la, the use of a unified vertically split upper part and lower part casing halves of the outboard marine unit for the engine containment, gearbox and propeller shaft containment and symbiotically forming the entire outboard structure beneath the saddle section and control arm depicted in Figure la, the use of open cavities on the split faces of the vertically split containment casings along the centrelines of the engine cylinder(s) enabling the containment of the engine cylinder liners, the engine main bearings and providing the main engine fluid flow conduits, for example the engine coolant flow and return passages, the oil feed and drain passages, the induction air conduits and the exhaust and catalyst conduits, and the gallery containing the drive connections between crankshafts and the gearbox which also provide the blowby return passages, the use of the opposed stepped piston architecture to enable two pistons and corresponding cylinders to be arranged co-axially along the vertical axis of the vertically split mid-section whilst allowing a convenient access for starting the engine from the upper crankshaft and connection to the propeller from the lower crankshaft, avoiding a separate drive shaft from the powerhead to the propeller, the symbiotic use of the Rectilinear Drive Mechanism (GB patent 2525213) for piston actuation in combination with the guidance of the connecting rod yokes of the RDM by the containment casing vertical and horizontal guides. The RDM in combination with the stepped piston technology also provides an inbuilt air scavenge supply for 2-stroke engine operation and enables the use of a closed circuit oil lubrication system for the engine components, avoiding the use of total loss oil system

Claims

Claims 1 An outboard or outdrive marine propulsion unit wherein the static parts of the internal combustion engine are formed by vertically split containment casings which are a portion of the upper part of the marine propulsion unit.
2 An outboard or outdrive marine propulsion unit, as in Claim 1, in which the vertical split of the casing portion the upper part is on the plane passing through the longitudinal axis of the engine crankshaft or the longitudinal axes of die engine crankshafts, said axis or axes being parallel to the axis of the propeller of the outboard or outdrive marine propulsion unit.
3 An outboard or outdrive marine propulsion unit, as in Claim 1, in which the vertical split of the casing portion of the upper part is on the plane which is orthogonal to the longitudinal axis of the engine crankshaft or the longitudinal axes of the engine crankshafts, said axis or axes being orthogonal to the axis of the propeller of the outboard or outdrive marine propulsion unit.
4 An outboard or outdrive marine propulsion unit, as in Claim 1, Claim 2 and Claim 3, in which both the upper part and the lower part containment casings of the outboard or outdrive marine propulsion unit are split through a vertical plane of the outboard or outdrive marine propulsion unit.
An outboard or outdrive marine propulsion unit, as in Claim 4, in which the right hand side vertically split section of the upper part containment casing is monolithic with the right hand side vertically split lower part containment casing, and in which the left hand side vertically split section of the upper part containment casing is monolithic with the left hand side vertically split lower part containment casing.
6 An outboard or outdrive marine propulsion unit, as in all preceding Claims, the internal combustion engine having at least one, several or all of the following static elements, systems, circuits, volumes, channels, conduits or cavities including, the oil sump, the oil pump cavity, the lubrication circuits, the air induction conduits, the auxiliary volumes for the flow and acoustic optimisation of the air induction process, the exhaust system volumes, the coolant circuit channels, the coolant pump volute cavity, the fuel circuit channels, the channels for electrical wiring, the crankcase including the main bearing, camshaft bearing and other bearing carriers, the cylinder block scantlings to contain cylinder liners, the cavities to contain drive connections between the crankshaft, or crankshafts, other rotating parts of the engine and to rotating parts in the gearbox-section, the cavities to contain a cylinder head module, the cavity or cavities to contain valvetrain components including camshafts, the blowby venting conduits, the oil drain conduits, of which at least one, several or all these static elements systems, circuits, volumes, channels, conduits or cavities are formed either in the mid-section of the upper part or in the mid-section of the upper part and in the lower part of the containment casings of the outboard or outdrive marine propulsion unit.
7 An outboard or outdrive marine propulsion unit, as in Claim 6, in which the exhaust system comprises a cylindrical pipe for the exhaust gas flow which fits at its upstream end into the exhaust outlet of the engine and fits at its downstream end to the engine coolant water outlet, said cylindrical exhaust pipe being contained with clearance on its outer diameter relative to cavities in the split containment casings of the midsection of the upper part of the outboard or outdrive marine propulsion unit.
8 An outboard or outdrive marine propulsion unit, as in Claim 6, in which the exhaust system comprises a cylindrical pipe for the exhaust gas flow which fits at its upstream end into the exhaust outlet of the engine and fits at its downstream end to the engine coolant water outlet, said cylindrical exhaust pipe being contained with clearance on its outer diameter relative to cavities in the split containment casings of the midsection of the upper part and lower part of the outboard or outdrive marine propulsion unit.
An outboard or outdrive marine propulsion unit, as in all preceding Claims, in which the engine cylinder bore(s) are cylindrical wet liners which are fitted in the midsection of the upper part of the containment casings of the outboard or outdrive marine propulsion unit.
An outboard or outdrive marine propulsion unit, as in all preceding Claims, in which the containment casings of said outboard or outdrive marine propulsion unit are rigidly clamped to each other by fixings.
11 An outboard or outdrive marine propulsion unit, as in all preceding Claims, in which the clamping forces of the fixings rigidly retain static engine components and assemblies including cylinder heads, cylinder liners, catalysts, hearings, exhaust pipes, check valves and blowby separators.
12 An outboard or outdrive marine propulsion unit, as in all preceding Claims, in which the clamped contacting faces of the right-hand and left-hand side vertically split containment casings use state-of-art means for sealing the contained systems including those listed in Claim 6, said sealing means including non-setting and setting sealants, elastomeric sealing gaskets and 0-iings, and injected formed-in-channel elastomeric sealing gaskets.
13 An outboard or outdrive marine propulsion unit, as in all preceding Claims, in which the internal combustion engine is an opposed piston 2-stroke engine with a first power piston and a second power piston.
14 An outboard or outdrive marine propulsion unit, as in Claim 13, in which the internal engine combustion engine is an opposed piston engine with two rectilinear drive mechanisms, the crankshafts of said mechanisms being joined by a synchronous drive.
An outboard or outdrive marine propulsion unit, as in Claim 14, in which at least one crankshaft drives an air transfer piston which supplies air for the power pistons.
16 An outboard or outdrive marine propulsion unit, as in Claim 15, in which at least one crankshaft drives a first power piston and a first air transfer piston which are joined by a single connecting rod yoke of a rectilinear drive mechanism.
17 An outboard or outdrive marine propulsion unit, as in Claim 15, in which the power piston and the air transfer piston are a monolithic stepped piston.
18 An outboard or outdrive marine propulsion unit, as in Claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12, in which the internal combustion engine is a 4-stroke overhead valve piston engine with at least one overhead camshaft.
19 An outboard or outdrive marine propulsion unit, as in Claim 18, in which the starting system engages with a camshaft.
An outboard or outdrive marine propulsion unit, as in Claims 18 and 19, in which the cylinder head is prismatic with its major axis parallel to the axis of the cylinder liner.
21 An outboard or outdrive marine propulsion unit, as in Claim 20, in which the cylinder head has at least two outer and continuous peripheral grooves that each engage in correspondingly shaped peripheral protrusions in each of the containment casings.
22 An outboard or outdrive marine propulsion unit, as in Claims 20 and 21, in which the prismatic cylinder head is circular in section.
23 An outboard or outdrive marine propulsion unit, as in Claims 18, 19. 20, 21 and 22, in which at least one shaft, which rotates in the opposite direction to the crankshaft and at the same rotational speed, is fitted with primary balance masses.
24 A marine propulsion unit, as previously described in all claims, in which the engine auxiliaries and peripheral items including the starting system, the electrical generator, the air cleaner, oil filler cap, fuel pumps, the engine throttle, the engine control system including any electronic management systems, are sited in the top portion of the upper part of the marine propulsion unit.