CN112746899A

CN112746899A - Internal combustion engine

Info

Publication number: CN112746899A
Application number: CN201911036985.2A
Authority: CN
Inventors: G·H·方丹; R·T·坦巴; D·普索尼斯; E·卡瓦尔诺斯
Original assignee: Saide Power Technology Guangdong Co ltd
Current assignee: Saide Power Technology Guangdong Co ltd
Priority date: 2019-10-29
Filing date: 2019-10-29
Publication date: 2021-05-04

Abstract

An internal combustion engine comprising a piston, a cylinder and an output shaft, wherein the piston is arranged to be driven by combustion to reciprocate within the cylinder and the piston is coupled to the output shaft by a coupling such that the reciprocating movement of the piston drives the output shaft to rotate, the coupling being arranged such that the piston has a sinusoidal motion when plotted against the angle of rotation of the output shaft.

Description

Internal combustion engine

Technical Field

The present invention relates to internal combustion engines. More particularly, but not exclusively, the invention relates to an internal combustion engine having improved piston motion characteristics.

Background

It is known to provide an internal combustion engine for powering equipment such as vehicles, generators, machinery and the like. Conventional internal combustion engines use a crankshaft, crankpin, and connecting rod. However, applicants have discovered that conventional internal combustion engines have limitations and deficiencies with respect to noise, smoothness, efficiency, and emissions.

Examples of the invention seek to avoid or at least ameliorate the disadvantages of existing internal combustion engines.

Disclosure of Invention

According to one aspect of the present invention there is provided an internal combustion engine comprising a piston, a cylinder and an output shaft, wherein the piston is arranged to be driven by combustion to reciprocate within the cylinder and the piston is coupled to the output shaft by a coupling such that said reciprocating movement of the piston drives the output shaft to rotate, the coupling being arranged such that for a constant rotational speed of the output shaft (or when plotted against the rotational angle of the output shaft), the piston has a sinusoidal motion.

Preferably, the engine is in the form of a scotch yoke engine.

In a preferred form, the coupling includes a sliding bearing. More preferably, the engine comprises a pair of opposed pistons rigidly fixed to each other.

Preferably, the engine is arranged such that the movement of the piston after top dead centre has a lower acceleration when compared to a conventional crank mechanism engine having the same bore and stroke, such that the volume difference in the cylinder peaks between 10% and 20% between top dead centre and bottom dead centre when compared to a conventional crank mechanism engine.

More preferably, the engine is arranged such that the movement of the piston after top dead centre has a lower acceleration when compared to a conventional crank mechanism engine with the same bore and stroke, such that the difference in volume in the cylinder peaks between 15% and 17% between top dead centre and bottom dead centre.

Even more preferably, the engine is arranged such that the movement of the piston after top dead centre has a lower acceleration when compared to a conventional crank mechanism engine of the same bore and stroke, such that the difference in volume in the cylinder peaks between 40 and 80 degrees of output shaft rotation after top dead centre.

In one form, the engine is arranged such that the movement of the piston after top dead centre has a lower acceleration when compared to a conventional crank mechanism engine of the same bore and stroke, such that the difference in volume in the cylinder peaks between 50 and 70 degrees of output shaft rotation after top dead centre.

Preferably the engine is arranged such that the movement of the piston after top dead centre has a lower acceleration when compared to a conventional crank mechanism engine of the same bore and stroke, such that the volumetric difference in the cylinder peaks between 50 and 60 degrees of output shaft rotation after top dead centre.

In one form, the engine includes a combustion chamber, and the combustion chamber and/or the coupling are arranged to achieve a target volume difference characteristic as compared to a conventional crank mechanism engine.

According to an aspect of the invention, there is provided a method of engineering an engine as described above, comprising:

measuring and/or modeling charge density in the cylinder to obtain data; and

the data is used to optimize one or more parameters of the engine to extend maintenance of a gas state having a higher charge density near top dead center.

Preferably, the method comprises the steps of: using the data to optimize one or more parameters of the engine, the one or more parameters including one or more of a coupling, a piston, a cylinder, a combustion chamber, and a valve.

More preferably, the method comprises the steps of: the data is used to optimize one or more parameters of the engine to extend the maintenance of a gas state with a higher charge density near top dead center for better fuel mixing.

According to another aspect of the present invention there is provided an internal combustion engine comprising a pair of opposed pistons, a pair of opposed cylinders, and an output shaft, wherein each piston is arranged to be driven by combustion to reciprocate within a respective one of the cylinders, and the pistons are coupled to the output shaft by a coupling such that said reciprocating movement of the pistons drives the output shaft to rotate, wherein the coupling comprises a connecting rod coupled to said opposed pistons, said connecting rod being formed from a pair of similar components fastened together, one of said similar components being reversed relative to the other of said similar components prior to fastening.

Preferably, the connecting rod may have a side guide for guiding the sliding bearing positioned for reciprocating movement relative to the connecting rod, and the coupling may further include a crankshaft rotatably mounted within the sliding bearing.

According to another aspect of the present invention there is provided an internal combustion engine comprising a pair of opposed pistons, a pair of opposed cylinders and an output shaft, wherein each piston is arranged to be driven for reciprocation by combustion within a respective one of the cylinders, and the pistons are coupled to the output shaft by a coupling such that said reciprocation of the pistons drives rotation of the output shaft, wherein the coupling comprises a connecting rod coupled to the opposed pistons, the connecting rod having side guides for guiding sliding bearings positioned for reciprocation relative to the connecting rod, and the coupling further comprises a crankshaft rotatably mounted within the sliding bearings, wherein the internal combustion engine comprises an air intake system arranged to induce cyclonic air flow in a plenum chamber of the air intake system.

Preferably, the firing order of the cylinders may be 1-2-4-3. More preferably, the intake system is arranged such that the intake conduits leading to the cylinders meet at the plenum and are arranged in a generally circular configuration around the plenum in the firing order of the cylinders.

Drawings

The invention is further described by way of non-limiting example only with reference to the accompanying drawings, in which:

FIG. 1 illustrates a perspective view of an engine according to one example of the invention;

FIG. 2 illustrates a graph of piston speed of an engine according to an example of the invention compared to the motion of the piston of a conventional engine before and after zero speed at top dead center;

FIG. 3 illustrates a graph depicting total operating unit cylinder volume versus crank angle for an engine according to one example of the present invention and a conventional engine;

FIG. 4 illustrates simulation results for an engine according to an example of the present disclosure;

fig. 5 to 17 illustrate tables and graphs for explaining advantages of the internal combustion engine according to one example of the invention with respect to a conventional internal combustion engine;

FIG. 18 shows a schematic diagram illustrating a combined coaxial camshaft and balance shaft;

FIGS. 19-28 illustrate schematic diagrams relating to an angle block, oil pump arrangement, piston cooling nozzle, and lubrication circuit;

FIGS. 29-31 illustrate schematic diagrams of a two-stage bleed valve and bleed (intermediate) regulator;

fig. 32 to 35 depict a guide shoulder arrangement;

FIGS. 36 and 37 show the crank assembly in isometric and exploded views;

FIGS. 38 and 39 show the crank, slide and link assembly in isometric and exploded views;

FIG. 40 illustrates an exploded view of an internal combustion engine including an air intake system; and

figure 41 shows a schematic view of cyclonic airflow in a plenum chamber by means of an arrangement of an air intake system.

Detailed Description

Fig. 1 to 4 depict the operation of an internal combustion engine according to one example of the invention.

More specifically, according to one example of the present invention, applicants have developed an internal combustion engine 10, the internal combustion engine 10 including a cylinder 12, a piston 14, and an output shaft 16, wherein the piston 14 is arranged to be driven by combustion to reciprocate within the cylinder 12, and the piston 14 is coupled to the output shaft 16 by a coupling. The internal combustion engine 10 is configured such that the reciprocating motion of the pistons 14 drives the output shaft 16 to rotate. The form of the piston and spindle connection is arranged so that the piston 14 has a sinusoidal motion when plotted against the angle of rotation of the output shaft 16.

In the example shown in the drawings, the internal combustion engine 10 is in the form of a scotch yoke engine (as shown in fig. 1) and the coupling includes sliding bearings. The example internal combustion engine 10 includes a pair of opposed pistons 14 rigidly fixed to one another such that movement of one piston in a first direction causes movement of the other piston in a second direction opposite the first direction.

Referring to fig. 2 and 3, the internal combustion engine 10 is arranged such that the movement of the piston 14 after top dead center has a lower displacement, velocity and acceleration when compared to a conventional crank-link engine having the same bore and stroke, such that the difference in volume of the cylinder 12 peaks between 10% and 20% between top dead center and bottom dead center when compared to the conventional crank-link engine. In fig. 2, the speed of the piston 14 of an internal combustion engine 10 according to an example of the invention is illustrated by curve 18, while the speed of the piston of a conventional engine having the same bore and stroke (as the internal combustion engine 10) is illustrated by curve 20. In fig. 3, the total working unit cylinder volume of an internal combustion engine 10 according to an example of the invention is illustrated by curve 22, while the total working unit cylinder volume of a conventional engine having the same bore and stroke (as the internal combustion engine 10) is illustrated by curve 24. With respect to fig. 3, the motion of piston 14 is sinusoidal such that the speed of piston 14 is greater near top dead center 26 (than in a conventional engine) and the speed of piston 14 is less near bottom dead center 28 (than in a conventional engine).

Referring specifically to fig. 3, internal combustion engine 10 is arranged such that the motion of piston 14 after top dead center 26 has a lower acceleration when compared to a conventional crank-link engine with the same bore and stroke, such that the volumetric difference in cylinder 12 peaks between 15% and 17% between top dead center 26 and bottom dead center 28. In the example shown, the internal combustion engine 10 is arranged such that the movement of the piston 14 after top dead centre 26 has a lower acceleration when compared to a conventional crank mechanism engine with the same bore and stroke, such that the volumetric difference in the cylinder 12 peaks between 40 and 80 degrees of output shaft rotation after top dead centre 26. More specifically, the peak value may be between 50 and 70 degrees of output shaft rotation after top dead center. Even more specifically, the peak may be between 50 and 60 degrees of output shaft rotation after top dead center 26.

Internal combustion engine 10 includes a combustion chamber 30 for charge combustion, and combustion chamber 30 and/or a coupling are arranged to achieve a target volume difference characteristic as compared to a conventional crank mechanism engine.

Applicants have advantageously discovered a method of engineering (and specifically designing) an internal combustion engine 10 comprising the steps of: measuring and/or modeling charge density in the cylinder 12 to obtain data; and using the data to optimize one or more parameters of the internal combustion engine 10 to extend the maintenance of a gaseous state having a higher charge density near top dead center 26. The method may include the step of using the data to optimize one or more parameters of the internal combustion engine 10, including one or more of the coupling, the piston 14, the cylinder 12, the combustion chamber 30, and the valve 32.

The method may comprise the steps of: this data is used to optimize one or more parameters of the internal combustion engine 10 in order to prolong the maintenance of the gaseous state with higher charge density near top dead center 26, thereby achieving better fuel mixing.

As described above, with reference to fig. 3, the motion of the piston 14 in the internal combustion engine 10 is sinusoidal. As shown by the sinusoidal curve of line 22 in fig. 3, the motion of piston 14 relative to crank angle is the same at Top Dead Center (TDC)26 and Bottom Dead Center (BDC) 28.

In contrast, the crank and connecting rod mechanism of a conventional engine produces unequal piston motion in the region of Top Dead Center (TDC)26 and BDC28 (compare line 22 with line 24). In the region of Top Dead Center (TDC)26, the pistons of a conventional engine move faster than in the inventive internal combustion engine 10, while in the region of BDC28, the pistons of a conventional engine move slower than in the inventive internal combustion engine 10. The difference in the two positions for a given engine stroke depends on the length of the connecting rod. The shorter the link, the greater this difference.

The power level for a given piston displacement is largely dependent on the amount of air inducted per cycle, which affects the volumetric efficiency of the engine. Volumetric efficiency depends on several engine design parameters, namely cam profile, valve timing, manifold adjustment length, forced induction (turbo/mechanical boost), etc., which are optimized for the pressure fluctuation dynamics set by any given piston motion. Therefore, the processes to be influenced by the piston motion can be divided into two categories: an air intake process and a post-air intake process.

The present invention is concerned with post-induction processes, i.e. compression, combustion and expansion, which are influenced by the motion of the piston. The applicant has found that of particular note is the NOx emissions produced during the combustion process and expansion stroke (post combustion) in producing useful work. To understand the advantages of the internal combustion engine 10 of the present invention, and in particular the advantages of the movement of the piston 14 over conventional engines, we must first compare the same volumetric efficiency and bore diameter and stroke to have the same intake conditions for the internal combustion engine 10 of the present invention and conventional engines.

In the graph shown in fig. 2, two engines with different piston movements but otherwise identical (with the same volumetric efficiency and the same bore and stroke) are compared at the same engine speed, load (full power) and air-fuel ratio.

Piston speed in (millimeters/crank angle) is independent of engine speed and is therefore characteristic of piston motion over the entire speed range. It is apparent that the pistons 14 of the internal combustion engine 10 approach and move away from Top Dead Center (TDC)26 at a lower acceleration (rate of change) than conventional pistons. This means that the internal combustion engine 10 will have a lower rate of change of cylinder volume near Top Dead Center (TDC)26, and therefore will contribute to maintaining the gas state having a higher charge density near Top Dead Center (TDC) 26. Applicants have found that higher charge densities contribute to flame acceleration. The lower piston acceleration continues for a substantial portion of the gas expansion duration.

When calculated over the entire speed range, it was found that at most speeds, the cylinder peak pressure in internal combustion engine 10 was lower than in a conventional engine, except for the lower speeds 1500 and 2500r/min where the peak pressures were very similar. However, the cylinder pressure in the internal combustion engine 10 remains higher during the gas expansion process (i.e., after the mass fraction burned has reached 1.0) as compared to conventional engines, providing more useful work (and higher in-cylinder average effective pressure) to the internal combustion engine 10.

Combustion problems require more intensive treatment due to other complex engine related parameters, namely extrusion speed (including extrusion surface geometry) and heat loss through the surfaces (influenced by combustion chamber geometry, piston-connecting rod connections affecting the homogeneity of the temperature of the piston crown near the joining surfaces, cooling water circuits, etc.). It is important, however, that all of these factors contribute to the development of the final cylinder pressure (profile) that affects the power levels and emissions achieved.

As shown in fig. 4, simulation results of an internal combustion engine 10 according to one example of the present invention are shown, demonstrating near perfect airflow tumble as the intake airflow enters and fills the cylinders 12, resulting in a homogeneous fuel mixture that produces cleaner combustion, high torque, and lower emissions.

With both engines having the same stroke and bore, the piston 14 approaches and moves away from Top Dead Center (TDC)26 at a lower acceleration than conventional pistons. This means that the internal combustion engine 10 will have a lower rate of change of cylinder volume near Top Dead Center (TDC)26, and applicants have found that this helps to maintain a gaseous state with a higher charge density near Top Dead Center (TDC)26, resulting in a homogeneous fuel mixture that produces cleaner combustion, better engine knock resistance, high flexibility of exhaust gas recirculation (exhaust gas recirculation), high torque, and lower emissions.

In one example, applicants have discovered that internal combustion engine 10 may be used to drive an electric generator in a hybrid vehicle. More specifically, applicants have discovered that the internal combustion engine 10 may be used to drive a generator in a series hybrid vehicle, where the engine may be operated at a constant rotational speed during generator operation, which may be located at discrete locations on the vehicle, such as in the trunk/trunk. The efficiency, balance, low vibration, and quietness of the internal combustion engine 10 may make the internal combustion engine 10 particularly suitable for such applications.

Targeted engine lubricating oil and oil pump apparatus

In many conventional engines, an oil pump driven by a crankshaft generates oil pressure. When the oil pump reaches too high an oil pressure and flow at higher engine speeds, this excess oil is redirected back to the pump suction port by the pressure regulating device or to the oil sump by the drain passage. Generally, in a range extender engine, when the engine is at a low engine speed, the engine has a low oil pressure but is also at a low load. As engine speed increases, load also increases and, correspondingly, oil pressure and flow also increase to the point where the pump produces excess oil that is typically not used and redirected back to the engine sump or back to the pump suction port.

Referring to fig. 19-31, the following invention outlines several methods of targeted delivery of lubricating oil to the areas of the engine where it is most needed, and methods of using this excess oil to advantage in the engine by: excess oil is first redirected to other areas of the engine and then only in this case can the oil be redirected back to the pump suction port or sump if the pump still has excess oil available.

This aspect of the patent specification covers the following key areas:

using angle blocks and bearings resulting in uninterrupted sliding bearing surfaces

Depositing the bearing-type material directly onto the uninterrupted sliding bearing surface of the slider

Two-stage regulator in the pump-lube circuit, with primary and secondary spill functions, whereby the primary spill generates oil pressure and flow targeted to specific regions of the engine under high engine load conditions

Targeted piston cooling using nozzles on the slide

Targeted piston cooling using primary spill oil from the regulator via a nozzle inside the engine

Targeted piston cooling using surplus lubrication at the linear sliding bearing via nozzles on the connecting rod

Individually controlled lubrication from the bearing shell to the side of the slide using recesses or indentations or controlled surface finish and leakage

-a preset regulator in the lubricating oil circuit which redirects oil targeted to a specific region of the engine under high engine load conditions

The results were:

reducing the oil consumption in an oil pump

Redirecting normally wasted oil to critical areas of the engine and bringing benefits in a controlled manner

Reduction of engine oil foam

-improving engine efficiency

-improving engine performance

To facilitate piston cooling

Reduced friction, since targeted lubrication can lead to smaller bearing surfaces

In addition, the use of sliders in scotch yoke engines requires specific and targeted lubrication to maintain a boundary layer of oil on the sliding bearing surfaces.

Referring to fig. 25, the piston cooling injection in the engine block is supplied by excess oil from the slide. The slider oil passage is aligned with the nozzle and supplies oil to the nozzle at top and bottom dead centers of each stroke (the nozzle is closed in this view). Turning to fig. 26, piston cooling injection in the engine block is supplied by excess oil from the slide. The slider oil passage is aligned with the nozzle and supplies oil to the nozzle at top and bottom dead centers of each stroke (the top nozzle is open in this view).

Fig. 27 shows notches (6 are shown) in the edge of the bearing surface to allow oil to leak past the bearing surface and out the sides of the bearing to lubricate the sides of the bearing and associated bearing surfaces. This also applies to the crank flange guide surface.

Coaxial camshaft and balance shaft

In many conventional engines, a balance shaft is used to reduce engine vibration. These balance shafts rotate at a certain speed relative to the engine and are driven by the crankshaft. This speed is typically twice the engine speed, and a conventional inline four cylinder engine requires two balance shafts. These axles dampen engine vibrations by causing an imbalance (commonly referred to as a second order force) that opposes the engine-induced vibrations.

Referring to fig. 18, with the aid of the seider engine design, the second order forces are minimal, so only one balance shaft is needed, and the balance shaft rotates at the engine speed instead of twice the engine speed. The following invention outlines a balance shaft located inside an engine camshaft. For reference, the camshaft rotates at half the engine speed. This kind of camshaft and balance shaft coaxial axle combination have many benefits to engine design, include:

-if the camshaft and the balance shaft rotate in opposite directions, the rotational inertia of the assembly can be reduced

Reduced space requirements, since the invention allows the same positioning of the camshaft and the balance shaft in the same assembly, thus achieving optimum assemblability

Reduced assembly costs due to reduced machining requirements on the cylinder block

The camshaft and the balance shaft can be preassembled as a module before being assembled into the engine

In a V-engine, the recess between the cylinder heads can be used to position the combined camshaft/balance shaft, thereby reducing the size of the engine, and to reposition the balance shaft outside the engine oil pan, where it typically causes oil agitation and foaming

The results were:

reduced machining requirements for the cylinder block

Reduced costs due to the use of low-cost bearings (reduced speed difference of the parts), thus reducing costs

Reduced accumulation of cylinder block alignment errors, resulting in lower cost and easier manufacturing of the cylinder block

Reduction of friction previously caused by balancing the higher rotational speed of the shaft support (bearing)

Easy assembly and reduced assembly costs

To take full advantage of the invention, the camshaft and balance shaft will rotate in the same direction to minimize bearing differentials between the parts.

Scotch yoke type piston connecting rod and crankshaft guide

Referring to fig. 32-35, the seider engine is an engine that relies on the scotch yoke operating principle for a horizontally opposed inline cylinder arrangement. Typically, these engines require the two opposing cylinders to have very close tolerances in the cylinder block to ensure alignment and not cause side loading of the pistons or excessive restraint and loading of the slide on the crankshaft. This results in very tight tolerances and manufacturing costs for:

cylinder bore

-a cylinder block

Crankshaft positioning

-reciprocator alignment

Conventional engines must incorporate a rotatable wrist pin between the connecting rod and the piston to allow the connecting rod to follow the crankshaft connecting rod journal in a circular motion. The wrist pin is typically not required for a Sade engine because the piston and connecting rod move only in a linear direction and therefore have no lateral forces.

To reduce the sensitivity to manufacturing tolerances and reduce the need for "mating" half blocks, it is desirable to provide a floating connection between the connecting rod and the piston and to transfer the guidance and alignment of the piston from the cylinder bore to the crankshaft.

This means that:

guiding the sliding bearing on the crankshaft with a thrust ring

Guiding the sliding bearing in the connecting rod by means of the sliding bearing and the lateral bearing surfaces

The piston is free to find its own centre in the cylinder bore, independent of the rigid connection between the piston and the connecting rod

This will allow a wider tolerance band for the cylinder bores, which are only aligned with respect to the crankshaft, without the need for the centers of the left and right cylinder bores to be aligned. The piston can self-center within the cylinder bore with its smaller piston skirt, regardless of the positional tolerances of the connecting rod. The results were:

the fully floating piston may operate according to a Saeder (SYTECH) sinusoidal piston motion

Cylinder block production without mating

Reduced tolerance requirements between opposed and adjacent cylinder bores

Reducing the cumulative alignment tolerance requirements of the cylinder block and the respective cylinder bores, so that the cylinder block is manufactured more easily and at lower cost

This design reduces friction in the original design due to misalignment of the left and right cylinder bores

Easy assembly

Crank mechanism assembly

With reference to fig. 36 to 39, an arrangement is illustrated in which the connecting rod of the internal combustion engine is formed of two similar parts, each in the form of an identical C-shaped claw. More specifically, an internal combustion engine is presented that includes a pair of opposed pistons, a pair of opposed cylinders, and an output shaft, wherein each piston is arranged to be driven by combustion to reciprocate within a respective one of the cylinders, and the pistons are coupled to the output shaft by a coupling such that the reciprocating motion of the pistons drives the output shaft to rotate. The coupling comprises a connecting rod coupled to the opposed pistons, the connecting rod being formed of a pair of

similar parts

524, 526 fastened together, one 526 of said similar parts being inverted with respect to the other 524 of said similar parts prior to fastening.

The connecting rod may have a side guide for guiding a sliding bearing positioned for reciprocating movement relative to the connecting rod, and the coupling may further include a crankshaft rotatably mounted within the sliding bearing.

Cyclonic airflow

Referring to fig. 40 and 41, the seider engine may have an air induction system 530, the air induction system 530 promoting cyclonic airflow in the plenum chamber to the same effect as pulse air induction. In particular, an internal combustion engine is presented comprising a pair of opposed pistons, a pair of opposed cylinders, and an output shaft, wherein each piston is arranged to reciprocate within a respective one of the cylinders driven by combustion, and the pistons are coupled to the output shaft by a coupling such that said reciprocating movement of the pistons drives rotation of the output shaft, wherein the coupling comprises a connecting rod coupled with the opposed pistons, the connecting rod having side guides for guiding sliding bearings positioned to reciprocate relative to the connecting rod. The coupling further includes a crankshaft rotatably mounted within the sliding bearing. The internal combustion engine comprises an air intake system 530, the air intake system 530 being arranged to induce cyclonic airflow in a plenum chamber of the air intake system.

The firing order of the cylinders may be 1-2-4-3. The intake system may be arranged such that the intake conduits leading to the cylinders meet at the plenum and are arranged in a generally circular configuration around the plenum in the firing order of the cylinders.

The described construction has been modified by way of example only and many modifications and variations may be made without departing from the spirit and scope of the invention which includes each and every novel feature and combination of features disclosed herein.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as, an acknowledgment or admission or any form of suggestion that prior publication (or information derived from it) or known matter forms part of the common general knowledge.

Benefits associated with the invention

The invention can be used in a wide variety of applications, particularly as a low cost and unique solution to modern range extenders.

The inventors have developed a new modern opposed-piston gasoline engine family, referred to as a Sayd engine, based on the Scotch yoke crankshaft coupling principle. The engine family is made up of modular twin cylinder units which are joined together to form an engine family. Due to the configuration of the engine, the engine may be modularized into an even number of cylinders, i.e., 2 cylinders, 4 cylinders, 8 cylinders, etc. In this way, common engine parts and architectures can be employed to reduce engine cost and weight. The first engine in the series, a 1.5 liter four cylinder engine identified as 415 (where 4 represents cylinder number and 15 represents 1.5 liter engine displacement), is of primary interest herein. During the combustion system analysis phase, the FEV is responsible for developing a conceptual design with a tailored set of engine geometric parameters that can best utilize the advantages of the Scotch yoke mechanism. To this end, 1D engine modeling software (GT-Power) and 3D computational fluid dynamics software Star CCM + were used to accurately simulate the effect of unique piston motion on selected combustion chamber concepts, respectively. After this step is performed and the engine combustion is modeled, the next step is to determine the necessary technology and cost to be employed on scotch yoke mechanism based engines to meet legal and customer requirements. The new family of seider engines is briefly introduced here, with emphasis on detailed results of combustion system analysis and engine recommendations leading to the prototype manufacturing stage and upcoming engine tests.

1. Introduction to modern Saide (SYTECH) Engine series

Background of the new engine family is the development of a common core engine architecture in crankshaft and piston connections that can be applied to a variety of engine configurations. This enables the engine to be adapted to various power outputs with maximum versatility while protecting other technology applications in the future. The advantage of this strategy is that it allows for implementation of various engine variants that comply with legal regulations, while using as many common parts as possible in the required technical package.

To determine the optimal architecture of the engine, we first model the engine configuration. The piston motion of a Sade engine is very different from that of a conventional crank/connecting rod engine. Due to the connecting rod arrangement, the piston of the Saeder engine moves in a uniform manner following a pure sinusoidal movement. Figure 5 shows a SYTECH linkage with a slider.

The piston motion of a conventional engine is very short/severe at top dead center of the stroke during combustion, which is a function of the relationship between the connecting rod and the crank stroke length. The SYTECH mechanism results in a pure sine wave piston motion regardless of the connecting rod length, as shown in fig. 2 and 3.

Although this difference appears to be small, the net effect is that the combustion process has more time to complete at the end of the compression stroke. Theoretically, this will result in more fuel burn time, more uniform piston motion, more uniform piston pressure/force, less peak ignition force, and lower emissions.

A next advantage of the piston arrangement of the seider engine is that two opposed pistons share the same crank journal. This makes the engine much shorter than conventional engines and conventional horizontally opposed engines. When comparing only the bore pitch without regard to the front and rear engine mounts, the four cylinder Saddy engine is up to 50% shorter than a conventional inline four cylinder engine. When comparing a four-cylinder Sade opposed-piston engine with a four-cylinder horizontally opposed engine, the Sade engine is up to 33% shorter. This makes the Sade engine very easy to install in most engine compartments and has advantages when installing the engine in other areas of the vehicle, like behind rear seats, under the vehicle, etc.

Fig. 6 shows a comparison of engine lengths for a (in-line 4), B (opposite 4), and C (SYTECH 4).

A third advantage of the engine is that there is little imbalance force and little piston side force due to the scotch yoke mechanism and slider arrangement. This results in a quiet, well-balanced engine. FIG. 7 (for imbalance force comparison) shows the imbalance forces of a Saddy engine compared to other engines. Fig. 8 (for NVH test results) shows test results performed on an early prototype of the engine developed several years ago. Among these results, the advantage of NVH is very evident, which is crucial for range extender vehicles, mainly battery electric vehicles with on-board generators. The generator needs to be quiet and vibration free so that it is as unobtrusive as possible and does not adversely affect the comfort of the vehicle driver when in operation.

The advantages of the sayde engine make it an attractive solution for the range extender market, and we decided that we wished to manufacture some engines to test, but provided that the engines were able to meet performance and emissions targets, especially in the chinese market and in chinese 6b emissions.

The first step in designing an engine is to set a target for engine performance and then model the engine, particularly where the SYTECH technique is employed, using the SYTECH piston motion and resulting combustion to optimize cylinder bore, stroke, compression ratio, valve size, valve overlap, valve timing and injector requirements to meet the target performance and emission levels. Initial target parameters were set for engine design and analysis based on a 1.5 liter low cost minimum package engine.

The key design parameters are as follows:

satisfies the emission (regulation) of China's nation 6b

RON 92 fuel

At 4500rpm, the natural suction power rating is 60kW

Optimum fuel economy

The design process followed is intended to suggest a combustion system concept that enables us to have a family of engines based on the same core internal design, where all engines in the family will share the same bore, stroke, compression ratio, crankshaft bearing diameter, connecting rod, piston, slider, valve size/angle, and be modular. The expected output will then be similar to that shown in the "engine series" table of fig. 9.

As a result, if successful, these three engine variants will share:

the same bore

Identical combustion chambers

The same valve size

Identical oil injection devices

Identical pistons

Identical connecting rods

Identical timing drives

Identical slides

And many other basic engine components. This reduces manufacturing complexity, increases the amount of common parts, improves reliability, reduces manufacturing/machining costs, and reduces overall engine cost.

2. Saide (SYTECH) Combustion System analysis

The conventional four-cylinder engine has a firing order of 1-3-4-2, while the Saeder opposed-piston engine has a firing order of 1-2-4-3. This change in combustion sequence is not as important in modeling individual combustion chamber performance, but is critical in modeling the intake manifold, plenum and exhaust system to determine the length of these intake and exhaust systems and adjust them to optimize the final engine performance.

Figure 10 shows the ignition sequence for a saybolt engine as 1-2-4-3.

3. Combustion analysis of hydromechanical design of charging process via FEV

The concept and layout phase of the new engine family is supported by the inflation process hydromechanical design CFD flow of the FEV. The process analyzes and compares the geometry of the air-guiding surfaces in the cylinder head and combustion chamber to predict the best combination of engine parameters to achieve the design objective. It also takes into account the interaction between the in-cylinder flow field and the fuel injection to improve and optimize fuel homogeneity.

A conceptual research model is used to determine the optimal cylinder diameter and stroke of the seidel engine. After several simulation simulations in a mathematical model, the optimal cylinder diameter and stroke were determined to be 85mm stroke and 75mm cylinder diameter, which resulted in we obtaining a 1.5L four cylinder engine. The model is then iterated, modified, and repeated sufficiently to determine the optimal arrangement of combustion chambers using a data-driven approach.

After these modeling iterations are performed, the engine architecture that decides to push forward is:

4 valve combustion chambers, 2 intake and 2 exhaust without camshaft phaser

-a centrally placed spark plug

Port fuel injection (non-DI)

-flat piston

Compression ratio of 11.0:1

Further modeling iterations and engine analysis yield valve sizes and angles that best match the piston motion of the Saeder engine and are good inputs for the next step of engine modeling. Finally, the parameters proposed for the engine are shown in the table of FIG. 11.

After selecting the proposed parameters, several iterations are performed using a detailed CFD modeling method to evaluate and optimize flow planes in the combustion system. After these analyses, we determined an iteration that demonstrated a good compromise between inflation fluid mechanics and flow restriction.

Fig. 4 shows static port flow simulation results, while fig. 12 shows a charge centered to the spark plug. Fig. 4 and 12 show two important illustrations of the pneumatic process fluid mechanics design process. Fig. 4 depicts a simulated intake flow field in the valve cut plane of cylinder No. 1 in the middle of the intake stroke. It can be seen that the high velocity tumble flow created at the intake port results in a strong airflow (jet) into the combustion chamber. Within the combustion chamber, the jet is directed by the exhaust side of the combustion chamber ceiling to be converted into tumble motion. The flat geometry of the piston crown ensures less interference in the early stages of the intake and compression strokes. This conserves tumble motion well until the end of the compression cycle, allowing the charge to be well centered around the centrally located spark plug, as shown in fig. 12.

All modeling performed on the engine was performed with RON 92 fuel. It has been determined that this is an important consideration for range extender engines, since range extender engines must be flexible and capable of fueling even at the most remote locations.

Fig. 13 shows the mass flow distribution over the two intake valves.

In comparing the engine analysis results, the selected model iteration was found to lie above the performance lines of the other 30 similar engines included in the FEV scatter band, as shown in fig. 14 (evaluation of charge hydrodynamics versus engine scatter band). This demonstrates an optimal compromise between the flow performance required to achieve rated power and tumble flow to achieve a high efficiency charge-fluid-mechanical response throughout the engine map.

The table in fig. 15 (engine design attributes) shows an abstraction of the techniques obtained that are necessary to achieve the engine parameters that have been set for engine performance. It can be seen that the heart of the proposed seidel engine family includes low cost, readily available common engine technology features such as fixed intake and exhaust camshaft timing (well suited for non-transient REX applications), port fuel injection and catalytic converters incorporating GPF. Therefore, the engine should be a low cost engine with maximum reliability.

Although the engine architecture sounds relatively simple, it is still able to implement all of the design parameters set for the REX application, based on modeling. Additionally, in the design and analysis stages, spaces may be incorporated for the DI injectors and combustion chambers designed to protect the turbocharger from future common cylinder head base designs. For any future supercharging application the inlet duct must be optimised for TC applications and also tooling for the DI injector must be considered, but importantly the design of the cylinder head takes these options into account. While we add these features to the size, shape, weight and vibration advantages inherent in engines, applicants will provide a good solution for range extender vehicles, especially those requiring high power output.

With relatively basic (universal, advanced) technology, we can achieve a light weight, cost effective, low risk engine that can be less changed when a DI injector and/or turbocharger is later installed.

The table in fig. 16 shows the values of the performance parameters for a 1.5 liter saybolt engine, while fig. 17 shows the engine performance. Figures 16 and 17 show simulation results for a seidend model 1.5 liter engine with a peak power of 62kW at 4500 rpm. As previously mentioned, the engine design may provide high power output even with the RON 92 fuel naturally aspirated. This target is represented by 140Nm peak torque at 3000rpm engine speed.

To achieve this development, FEVs and ASFTs apply advanced engineering methods to ensure fast, stable and efficient combustion while maintaining low friction, good NVH and lightweight design.

4. Basic design of engine

The basic design of the seidel 1.5 liter engine must be capable of withstanding the forces and loads generated by combustion while being reliable, lightweight, low cost and low friction. Friction is a major consideration in designing high efficiency engines. Since the piston-to-crank connection of a Saddy engine is unique, during FEV analysis and modeling, we must assume a friction level based on previous Saddy engines. The seider engine should generally have a lower friction rating because it has only 3 main bearings and 2 rod bearings for four cylinders, as opposed to 5 main bearings and 4 rod bearings in the case of most conventional inline four cylinder engines. The seider engine does have an additional sliding bearing but the sliding bearing causes the piston to have little lateral force and therefore lower overall piston friction. After prototyping is complete, the focus of engine development will be to adjust engine emissions and power, correlate the analytical model and analyze overall engine friction, which will improve our efficiency and reduce losses. The small bearing diameter with the low pre-load ring set and the light weight piston set help reduce friction in the crank drive and have been incorporated into engine designs.

Belts have been selected for timing drives to combine the benefits of ultra-high robustness and advanced NVH behavior with good durability. At the same time, the overall timing drive layout is optimized in close cooperation with the belt drive system supplier to achieve extremely low friction and minimize belt harmonics and whiplash.

The valve train uses roller Rockers (RFFs) and Hydraulic Lifters (HLAs) to achieve low friction and maintenance free operation. Valve spring designs are analyzed and optimized in detail through kinematics and dynamic valvetrain simulations to ensure safe operation over the entire speed range. The balance shaft on the Saede engine runs at engine speed and is directly driven by the crankshaft chain. The oil pump is located around the crankshaft and therefore does not need to take into account the friction losses associated with the drive.

5. Combustion research and development

Several engines have been manufactured and are currently being prepared, installed and prepared for testing in the FEV testing facility to verify the concept, layout and design steps. The engine will be equipped with water cooled in-cylinder pressure sensors on all cylinders, exhaust and intake pressure indicators on cylinder number 1, and comprehensive exhaust gas analysis and thermocouples and pressure sensors at all relevant locations on the engine.

The combustion model used in the conceptual design study will be used for verification purposes and to help further determine any areas of combustion system optimization after the first thermodynamic test round.

6. Conclusion and conclusions

ASFT has successfully worked with FEV to develop a new modern seidel gasoline engine family. The principal engine developed in tandem is the seidel new 1.5 liter opposed-piston engine, which provides excellent performance and good fuel efficiency at low cost using RON 92 fuel.

To achieve target performance using RON 92 fuel, FEV and ASFT have focused on developing modern sayde engines with stable combustion performance.

FEV's inflation Process hydrodynamics design Process has been successfully applied to establish high inflation hydrodynamics levels, good flow maintenance until late in the compression Stroke, and optimized turbulence localization at the end of compression

The basic engine is optimized to withstand the loads and forces of combustion, while achieving a light, compact design and low total friction

Simulation results indicate that the Saider engine should be a low cost solution that can meet the requirements of the Chinese 6b emissions legislation with minimal technology.

The Sade engine approach creates a modular engine that can reuse paired cylinders to achieve a series of engines with the same core design and components, thereby minimizing cost and infrastructure.

The seidel new engine family not only provides excellent performance with minimal technology, but also provides protection for the application of more sophisticated advanced technologies such as cooled exhaust gas recirculation, direct injection and turbocharging.

Thus, the new 1.5 liter Sade engine according to one example of the invention is a low cost unique solution to modern range extenders.

List of features and reference numerals of the drawings

10 internal combustion engine

12 cylinder

14 piston

16 output shaft

Performance curve of 18 engine (fig. 2)

Performance curve of 20 conventional engine (FIG. 2)

22 performance curve of engine (figure 3)

24 Performance Curve of a conventional Engine (FIG. 3)

26 top dead center

28 bottom dead center

30 combustion chamber

32 air valve

34 both the exemplary Saede (SYTECH) and conventional engines of the present invention have the same stroke and bore

36 conventional (R) to

38 SYTECH

Before 40 Top Dead Center (TDC)

42 bottom dead center later (BDC)

44 piston velocity, mm/degree

46 crank angle, degree

48 Combustion Chamber Volume (CV)

50 cylinder volume

52 scavenging air (Cylinder capacity)

54 total working unit cylinder volume

56 crank (degree before TDC)

58 crank angle, degree

60 percent combustor speed Difference (conventional > SYTECH), ((conventional-SY)/CV) 100

62 conventional

64 sine curve (SYTECH)

66 (percent) conventional > SY, ((conventional-SY)/SY) 100

68 crank (degree after TDC)

70 (percent) volume difference

72 Saide (SYTECH) and conventional

74 horizontal arbitrary section

76 vertical arbitrary section

78 Preview

Sectional view of 80 valve 1

Cross-sectional view of 82 valve 2

84 Preview

86 connecting rod

88 crankshaft

90 sliding block

92 piston

94 conventional engine

96 opposed engine

More than 98 out-of-balance forces

More than 100 unbalanced forces

102 Saide (SYTECH) Horizontally opposed Engine

104 almost free of unbalance forces

106 fully balanced smooth quiet operation

108 full load conventional engine

110 full load Sade engine

112 acceleration (meters per second)

114 frequency (Hz)

116 running noise comparison: 75-80db Saide engine and 90-95db conventional engine

Full open cabin noise at 118 throttle, second gear

120 conventional engine (four cylinders)

122 Saide (SYTECH) engine (four cylinders)

124 noise level (db) (A)

126 engine speed in rpm

128 parameter

130 cylinder number

132 Engine Displacement

134 power estimation

136 strokes

138 cylinder diameter

140 inner angle

142 inner diameter

144 outer corner

146 outer diameter

148 Dv/D

150 CR

152 Sierra FEV-3

154 Sierra FEV-4

156 TKE/m^2/s^2

720 degrees after TDC (158 CA)

160 air outlet

162 air inlet

164 air outlet

166 air inlet

168 Mass flow distribution intake valve 2/[ kg/h ]

170 Mass flow distribution intake valve 1/[ kg/h ]

Flow coefficient of 172 port

174 αK＝12.8％

176 inflation fluid mechanics generation

178 required filling performance (rated power)

180 CMD trend line for IV angle 21 degrees, S/D1.14

182 Sierra FEV-2

184 Sierra FEV-4

186 scattering NA

188 CMD Trend line for IV Angle 16 degrees, S/D0.9, D0.56

190 flow coefficient (alpha K)/1

192 first tumble Peak/1

194 Engine technology

196 aluminum crankcase

198 forged steel crankshaft

200 targeted lubrication

202 NVH optimized base engine

204 NVH and friction optimized synchronous belt

206 low-friction roller rocker valve mechanism with maintenance-free automatic hydraulic clearance adjusting function

208 fixed intake and exhaust timing

210 high-aeration hydromechanical tumble air inlet

212 port fuel injection

214 close coupling catalysts, including GPF

216 electric water pump

218 optimized low friction piston ring

220 balance shaft (first order)

222 technical protection

224 protection against external HP exhaust gas circulation

226 protection against turbocharging

228 protection of ISG

230 protection against direct injection

232 SYTECH

Performance parameters of 234 SYTECH 415 Engine

236 rated power @4500rpm

238 low end torque @1500rpm

240 specific power output

242 minimum BSFC @3020rpm and 11.65BMEP

244 emission level

246 nominal fuel

248 performance

250 New DoE

252 old DoE

254 brake power/kW

256 BSFC/g/kWh

258 engine speed/rpm

260 residual gas fraction/%)

262 braking torque/Nm

264 cam lobe

266 camshaft support

268 balance shaft

270 camshaft

272 balance shaft bearing (between camshaft and balance shaft)

274 camshaft drive sprocket

276 balance shaft driving sprocket

278 sliding support

280 bolt

282 sliding support

284 crankshaft bearing

286 bolt

288 angle block with uninterrupted slide bearing surfaces using separate slide bearings

290 sliding bearing material deposited on the slider

292 bolt

294 sliding bearing material deposited on the slider

296 crankshaft bearing

298 bolt

300 angle block with uninterrupted sliding bearing surface using bearing material deposited directly on the face of the block

302 oil filter

304 to engine bearings and the like

306 pressurized oil

308 oil pump

310 pressure regulator

312 excess oil returning to the suction opening

314 oil suction port

316 oil pan

318 oil filter

320 to engine bearings or the like

322 oil under pressure

324 engine oil pump

326 pressure regulator

328 two-stage governor diverts excess oil to piston cooling nozzles or other areas and then returns the oil to the pump or sump

330 then returns any other excess oil to the oil intake or sump

332 oil pan

334 piston cooling nozzle on slide block

336 piston

338 connecting rod

340 sliding block

342 connecting rod

344 piston

346 piston-cooled nozzle in an engine block supplied by a two-stage pressure regulator

348 piston

350 connecting rod

352 sliding block

354 connecting rod

356 piston

358 piston

360 connecting rod

362 slide block

364 connecting rod

366 piston

368 piston cooling nozzles in an engine block that are supplied with excess oil from the slide. The slider oil passages are aligned with the nozzles and supply oil to the nozzles at top and bottom dead centers of each stroke (nozzles closed in this view)

370 the piston in the engine block, which is supplied with excess oil from the slide, cools the nozzle. The slide oil gallery is aligned with the nozzle and supplies oil to the nozzle at top and bottom dead centers for each stroke (top nozzle open in this view)

372 piston

374 link

376 sliding block

378 connecting rod

380 piston

382 recesses (6 are shown here) in the edge of the bearing surface to allow oil to leak past the bearing surface and out the sides of the bearing to lubricate the sides of the bearing and associated bearing surfaces. This also applies to the sides of the crank flange faces

384 sliding support

386 bolt

388 sliding support

390 crankshaft bearing

392 bolt

394 angle block with side recesses in all bearings for side lubrication

396 preset regulator in the lube circuit

398 oil filter

400 sent to engine bearings and the like

402 preset regulator

404 at a preset pressure flow rate, this regulator diverts the filtered oil to a piston cooling nozzle or the like.

406 main pressure regulator

408 excess oil returning to the suction port

410 oil pan

412 pressurized oil

414 oil pump

416 typical Standard valve

418 lubricating oil to engine parts

420 filter

422 pressure

424 pump

426 suction

428 oil filter

430 return

432 oil pan

434 regulating valve

436 two-stage bleed

438 lubricating oil to engine parts

440 filter

442 pressure

444 pump

446 suction

448 oil filter

450 oil pan

452 return to

454 to piston nozzle (Main discharge path)

456 two-stage regulator

458 secondary discharge paths

460 bleed (intermediate) regulator

462 lubricating oil to Engine parts

464 filter

466 pressure

468 Pump

470 suction

472 oil filter

474 oil pan

476 return

478 Main regulator (45psi)

480 to piston nozzle, etc

482 30psi

484 intermediate adjuster

486 torsion

488 offset

490 axial spacing

The 492 pin allows for misalignment and twisting of the cylinder bore in all directions, including crank-to-cylinder bore misalignment. Crankshaft shoulder allowing self-centering of piston connecting rod

494 guide shoulders for the sliding support on the crank (both ends/sides of the slider)

496 axial spacing

498 dislocation

500 turn round

Sliding bearing side guide in 502 connecting rod

504 guide shoulder on crank

506 crank assembly

508 Gear-crankshaft

510 keys

512 crankshaft

514 plug-crankshaft

516 pin-pin

518 trigger-roller

520 Pin-dowel

522 screw-trigger wheel

524C-shaped claw of connecting rod

526 connecting rod reverse C-shaped claw

528 slide block assembly

530 air intake system

532 injection system

534 cooling system

536 cylinder cover

538 valve mechanism

540 timing transmission

542 exhaust system

544 cooling system

546 throttle body

548 Cylinder cover

550 cylinder cover

Cyclonic airflow in 552 chamber

554 intake air

556 SYTECH ignition sequence

Claims

1. An internal combustion engine comprising a piston, a cylinder and an output shaft, wherein the piston is arranged to be driven by combustion to reciprocate within the cylinder and the piston is coupled to the output shaft by a coupling such that the reciprocating movement of the piston drives the output shaft to rotate, wherein the coupling is arranged such that the piston has a sinusoidal motion for a constant rotational speed of the output shaft when plotted against the rotational angle of the output shaft.

2. The engine of claim 1, wherein the engine is in the form of a scotch yoke engine.

3. An engine according to claim 1 or 2, wherein the coupling comprises a sliding bearing.

4. An engine according to any one of claims 1 to 3, wherein the engine is arranged such that the movement of the piston after top dead centre has a lower acceleration when compared to a conventional crank mechanism engine with the same bore and stroke, such that the difference in volume in the cylinder peaks between 10% and 20% between top dead centre and bottom dead centre when compared to a conventional crank mechanism engine.

5. An engine according to claim 4, wherein the engine is arranged such that the movement of the piston after top dead centre has a lower acceleration when compared to a conventional crank mechanism engine with the same bore and stroke, such that the volume difference in the cylinder peaks between 15% and 17% between top dead centre and bottom dead centre.

6. An engine according to claim 4 or claim 5, wherein the engine is arranged such that the movement of the piston after top dead centre has a lower acceleration when compared to a conventional crank mechanism engine of the same bore and stroke, such that the difference in volume in the cylinder peaks between 40 and 80 degrees of output shaft rotation after top dead centre.

7. An engine according to claim 6, wherein the engine is arranged such that the movement of the piston after top dead centre has a lower acceleration when compared to a conventional crank mechanism engine of the same bore and stroke, such that the volume difference in the cylinder peaks between 50 and 70 degrees of output shaft rotation after top dead centre.

8. An engine according to claim 7, wherein the engine is arranged such that the movement of the piston after top dead centre has a lower acceleration when compared to a conventional crank mechanism engine of the same bore and stroke, such that the volume difference in the cylinder peaks between 50 and 60 degrees of output shaft rotation after top dead centre.

9. An engine according to any of claims 4 to 8, wherein the engine comprises a combustion chamber, and wherein the combustion chamber and/or the coupling are arranged to achieve a target volume difference characteristic.

10. A method of manufacturing an engine according to any one of claims 1 to 9, comprising:

measuring and/or modeling charge density in the cylinder to obtain data; and

using said data to optimize one or more parameters of said engine to prolong maintenance of a gas state having a higher charge density near top dead centre.

11. The method of manufacturing an engine of claim 10, comprising the steps of: using the data to optimize one or more parameters of the engine, the parameters including one or more of the coupling, the piston, the cylinder, a combustion chamber, and a valve.

12. A method of manufacturing an engine according to claim 10 or 11, comprising the steps of: the data is used to optimize one or more parameters of the engine so as to prolong maintenance of a gaseous state having a higher charge density near top dead center for better fuel mixing.

13. An internal combustion engine comprising a pair of opposed pistons, a pair of opposed cylinders, and an output shaft, wherein each piston is arranged to be driven by combustion to reciprocate within a respective one of the cylinders, and the pistons are coupled to the output shaft by a coupling such that said reciprocating movement of the pistons drives rotation of the output shaft, wherein the coupling comprises a connecting rod coupled to said opposed pistons, said connecting rod being formed from a pair of like parts fastened together, one of said like parts being reversed relative to the other of said like parts prior to fastening.

14. The internal combustion engine of claim 13, wherein the connecting rod has side guides for guiding a sliding bearing positioned for reciprocating movement relative to the connecting rod, and the coupling further comprises a crankshaft rotatably mounted within the sliding bearing.

15. An internal combustion engine comprising a pair of opposed pistons, a pair of opposed cylinders, and an output shaft, wherein each piston is arranged to reciprocate within a respective one of the cylinders driven by combustion, and the pistons are coupled to the output shaft by a coupling such that said reciprocating movement of the pistons drives rotation of the output shaft, wherein the coupling comprises a connecting rod coupled to the opposed pistons, the connecting rod having side guides for guiding sliding bearings positioned to reciprocate relative to the connecting rod, and the coupling further comprises a crankshaft rotatably mounted within the sliding bearings, wherein the internal combustion engine comprises an air intake system arranged to induce cyclonic airflow in a plenum of the air intake system.

16. The internal combustion engine of claim 15, wherein the firing order of the cylinders is 1-2-4-3.

17. An internal combustion engine according to claim 15 or claim 16, wherein the air intake system is arranged such that the intake conduits leading to the cylinders meet at the plenum and are arranged in a generally circular configuration around the plenum in the firing order of the cylinders.

18. An internal combustion engine substantially as hereinbefore described with reference to the accompanying drawings.

19. A method of manufacturing an engine substantially as hereinbefore described with reference to the accompanying drawings.