AU4379501A - Improvement to opposed cylinders reciprocating piston engines - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATIONS Standard Patent IMPROVEMENTS TO OPPOSED CYLINDERS RECIPROCATING PISTON ENGINES The following is a full description of this invention, including the best method of performing it known to me.

Since their respective invention in 1891 and 1896, the two stroke and the four stroke internal combustion engine have been the object of constant and unrelenting effort from the part of many inventors, designers and engine manufacturers alike to improve the said internal combustion engine overall performances and characteristics. Those efforts have largely been successful and today's power plants are ingenious marvels of modem technology, each new model featuring significant improvements in the areas of specific fuel consumption and the control of emission level of harmful combustion gases together with a continuously improving power to weight ratio directly attributable to the formulation of new metal alloys together with the creation and adoption of new manufacturing techniques.

The size and bulk of today's piston engine is however the area of engine design left :°oooo S. most wanting due essentially to the geometrical and mechanical constraints associated with current engine layout preventing the designer from integrating the cylindrical pistons, cylinders, motion translating mechanism and crank shaft assembly in a package much smaller than the ones currently on offer. Further, those constraints lead to the geometric spread of the engine many moving elements whose sometimes large moment of inertia and associated vibrations have to be counteracted by way of .expansive and space taking balancing shafts which in turn add to the engine ooooi complexity, weight and cost.

It is a particular object of the present invention to dramatically reduce the size and bulk of the opposed cylinders reciprocating piston engine, pumps and compressors devices by way of: a) locating the mechanism translating the linear motion of the piston into the rotating motion of an output shaft within the peripheral wall of a double ended cylindrical or flat sided piston and cylinder assembly, in so doing sharing one motion translating mechanism between the two heads of the double ended piston and eliminating the need for a distinct and separate crank case.

b) Replacing the costly one piece forged crank shaft with suitably supported and located crank pin carriers enabling the adoption of a one piece engine block crank housing and the elimination of bulky split crank pin bearing housing.

The flat sided double ended piston and the cylindrical double ended piston are equally suited as the basis to the materialization of the present invention, the choice being between greater bulk reduction for the former and more conventional and proven S 10 sealing means for the latter, both however being identical in their working and achieving a power for power bulk reduction in excess of fifty per cent when compared to the current generation engines.

It is another object of this invention to significantly decrease the engine noise and vibration level and further decrease the engine weight and bulk by way of reducing the number of moving parts, locating the centre of mass of all moving elements as close as possible to the shaft centre of rotation while minimising their inertial momentum. To that effect, a Scotch yoke motion translating mechanism is integrated in the design of the double-ended piston(s). The attraction of this mechanism is that it renders otiose the articulated connecting rod, resulting in the true harmonic motion of the piston, the diminution of the piston side thrust and the reduction of the piston acceleration, both the consequence of the connecting rod troublesome angular swing.

Further, it allows an engine of any configuration to be balanced without consideration to secondary forces. It is a particularly attractive concept when embodied in an opposed cylinder layout of ultra short stroke. However, the advantages mentioned there above are to a great extent negated by the penalties in mechanical friction from the block that slides in the piston skirt or piston appendage cross way as well as severe shocks and vibrations caused by the running clearance between the cross way walls and the Scotch yoke block being taken up during the travel and load reversal of the reciprocating piston. At sliding speed in excess of 10m/second and high bearing loads, heat dissipation and the maintenance of an unbroken oil film between the piston cross way walls and the Scotch yoke sliding faces (a location that is hardly conducive to efficient lubrication) become an interesting challenge. To date, excepting some reciprocating oil pumps, few if any devices utilising a Scotch yoke have been commercially successful.

It is a further object of this invention to eliminate the backlash occurring between the Scotch yoke components during the travel and load reversal of the reciprocating piston and to improve the Scotch yoke's overall mechanical efficiency by way of placing and maintaining between the walls of the piston skirt cross way and the 15 sliding faces of the Scotch yoke, an adaptive, low friction and high load bearing, hydrodynamic sliding oil body, effecting a significant reduction in mechanical °-friction, heat build up and back lash generated shocks and vibrations, thus restoring to the Scotch yoke its perceived functional superiority when contrasted with the connecting rod/crank pin mechanism and the Scotch yoke of previous designs.

In practical terms, there is provided an integral crank pin-Scotch yoke block combination, each said Scotch yoke block sliding faces suitably machined to form, between raised peripheral edges, a shallow recess communicating with a centrally and axially located oil gallery by way of a cross gallery and ports, each fitted with a check valve, each said recesses further machined to feature a narrow groove of suitable depth contiguous to the raised edges inner walls, said grooves to receive a two part spring loaded metal strip seal, and the width of the Scotch yoke block measured between the two spring raised seals to be fractionally greater than the width of the double ended piston cross way, and the width of the double ended piston cross way to be fractionally greater than the width of the Scotch yoke block measured between the two sliding faces raised edges, and the spaces created between the Scotch yoke block sliding faces, their respective peripheral spring loaded metal strip seal inner walls and the double ended piston cross way wall to be filled with pressurised oil so that, upon starting the engine, the high pressure applied alternatively to each of the double ended piston heads by the expansion of the burning air-fuel charge is transmitted to the oil by the loaded side of the double ended piston causing the check valve on the loaded side of the Scotch yoke block to close and the body of oil trapped there between to become a low friction, high load bearing hydrodynamic pad while, on the off loaded side of the double ended piston, positive oil pressure in the oil gallery causes the 15 check valve on the off loaded side of the Scotch yoke block to open, enabling the 0ooo continuous maintenance of an optimum amount of oil in the space there between, thus eliminating the conditions for a backlash, and its associated shocks and vibrations, to occur during the travel and load reversal of the double ended piston.

An engine according to the invention may feature one or two double ended cylinders.

For the sake of simplicity, a single double ended cylinder engine will serve as the basis to the following description.

Broadly stated, there is provided a block of suitable material and of substantially square cross section, approximately twice as long as it is wide, said block, there after referred to as engine block, machined throughout in a length wise direction to form the cavity of a double ended cylinder, said engine block further machined transversally, centrally, and throughout to receive and seat the crank pin carrier bearings, said double ended cylinder to receive and house a double ended piston of monoblock fabrication, said piston suitably machined to feature longitudinally between its two heads two symmetrical elongated recesses with semicircular ends, said recesses of a length equal to the length of the piston stroke added to the crank pin carriers diameter and of a width sufficient for the said crank pin carriers to freely engage the recesses, said two symmetrical recesses delimitating between them a substantial rib, said rib machined centrally and in a transverse direction to form the double ended piston Scotch yoke cross way, said cross way to receive and retain the Scotch yoke block/crank pin combination, said Scotch yoke block of a substantially square cross section, each end turned down to a suitable diameter and length to S become the journaled section of the crank pin, said each crank pin end engaged and journaled in a bore machined in each of the crank pin carriers face engaged in the 15 double ended piston elongated recesses, said bores longitudinal axis laying off the oo crank pin carriers rotation centre by a distance equal to half the double ended piston stroke. Two shaft output support flanges and two cylinder heads complete the assembly.

•As the double ended piston slides to and fro within the confines of the double ended cylinder cavity, the spaces located between the cylinder ends and the double ended piston heads are made to increase from minimum to maximum capacity and vice versa allowing the device to be used either as a pump or as a gas compressor when energised externally by the rotation of a shaft or as an engine when internally energised by the combustion of a suitable liquid or gaseous fuel and when provided with suitably located air and fuel intakes together with exhaust ports, ignition and sealing means.

An engine according to the invention will function equally well as a two stroke, four stroke, diesel or petrol engine when provided with suitable porting or valves, timing and fuel injection mechanism. However, the quest for further bulk reduction, increase power to weight ratio and lesser part count on the one hand and significant all around improvement in supercharging and fuel injection technology on the other hand dictate in favour of the two stroke engine version of the invention featuring uniflow scavenging, direct fuel injection in the cylinder and positive pressurised induction.

o. In the two stroke version of the invention, a twin screw compressor/supercharger provides a continuous and non pulsing positive air base pressure for scavenging the .ooo exhaust gasses and pressurise the cylinder with fresh air before the compression commences. Various degrees of supercharging of the cylinders are obtained by way of *.-sizing the compressor/supercharger so as to deliver air to the cylinders at a rate greater than the swept volume of the engine would normally require and adjusting the compressor/supercharger air delivery pressure at between 2 and 5 bars. The belt driven compressor/supercharger is mounted directly on the engine by way of an .adapter plate and on top of air passages machined in the engine block. This eliminates a cumbersome delivery hose, improves the compactness of the engine while the air passages between the induction ports of each cylinder acts as a plenum chamber. It is to be noted that the volume of excess air flowing through the cylinder during the scavenging phase of the two stroke cycle contributes appreciably to the internal cooling of the cylinder wall and the piston head.

Fuel metering and supply is achieved by means of computerised electronic injection of the fuel in the cylinders following the closure of the induction and exhaust ports, by the sliding piston, avoiding the loss of unburned fuel vapor through the exhaust ports which is recognised to be the major drawback of many carburetted and ported two stroke engine designs.

Cold starting and idling characteristics as well as specific fuel consumption and low emission level of harmful exhaust gasses are all enhanced through the adoption of a simple, yet very effective fuel stratification system achieved by causing the inner sides of two low density fuel mist spray cones emanating from two suitably located and angled fuel injectors to overlap in the proximity of a centrally located spark plug, creating near the spark plug electrode, a zone of rich and readily ignited air fuel •mixture while a weak air fuel mixture prevails in the rest of the cylinder.

A preferred but not exclusive version of the invention will now be described with reference to the drawings in which: oo Figure 1 shows a simplified cross sectional view in a vertical and transversal direction of an engine according to the invention.

S" Figure 2 shows a simplified cross section view in an horizontal and longitudinal ooooo S•direction of an engine according to the invention.

Figure 3 shows a side view of a double-ended piston together with a transversal cross section of the Scotch yoke block.

Figure 4 is a simplified cross section through the piston cross way showing a side view of the Scotch yoke block/crank pin combination.

Figure 5 is a plan view of a double-ended piston showing a longitudinal cross section view of the Scotch yoke block/crank pin combination.

Figure 6 shows a longitudinal cross sectional view of the piston cross way/scotch yoke block assembly.

Figure 7 shows a transversal cross sectional view of the piston cross way/scotch yoke block assembly.

Figure 8 is a side view of the Scotch yoke block/crank pin combination.

Figure 9 is a schematic longitudinal and vertical cross sectional view of a single, double ended cylinder engine version of the present invention.

*o 10 Figure 10 is a schematic longitudinal and vertical cross sectional view of a twin, double ended cylinder engine version of the present invention.

Referring firstly to figure 1, there is shown therein an engine assembly featuring an integral engine block/crank case combination 1, a double ended cylinder 2 with its detachable cylinder heads 3 and 4, each fitted with one spark plug 5 and twin injectors 6, a one piece construction double ended piston 7 with its longitudinal recess 8, central rib 9, cross way passage 10 and Scotch yoke block 11. Figure 1 further shows o:oo0 S°schematically a crank pin carrier 12, an output shaft support flange 13, the belt driven twin screw type supercharger 14, the pressurised induction passages 15, induction ports 16, exhaust ports 17, exhaust passages and outlets 18, induction and exhaust passages separation blocks 19, ring gear 20, starter motor 21, alternator 22 and twin lubrication and cooling oil pumps 23 with their associated cooling oil galleries 24.

Considering now figure 2, there is shown therein a twin double ended cylinder engine version of the invention also featuring an integral engine block/crank case combination and illustrating, in addition to the components already shown in figure 1, the crank pin carriers/bearings assemblies 12, the output shaft support flanges 13, the double ended pistons cross ways walls, hard faced liners 26, the scotch yoke block/crank pin combination 11 with their oil supply galleries 27, check valves 28 and metal seals 29 and, the in the shaft, oil supply rotary union Figure 3 shows a side view of a double ended piston illustrating one of the two longitudinal recesses 8, the central rib 9, the cross way passage 10 with its hard faced liners 26 and the Scotch yoke block with its oil gallery 27, check valves 28 and metal seal 29.

oo S Figure 4 further illustrates one of the scotch yoke block/crank pin combination sliding face with its check valve (28) outlet and its metal seal 29.

•••got Figure 5 shows a plan view of a double ended piston illustrating the longitudinal recesses 8, the central rib 9, the cross way walls hard faced liners 26 and the Scotch yoke gallery 27, check valves 28, metal seals 29 and the sliding faces shallow recesses 31.

Figures 6 and 7 respectively show a longitudinal and a transversal cross section of a piston cross way/Scotch yoke block assembly illustrating the double ended piston cross way hard faced liners 26, the Scotch yoke block/crank pin combination 11 with its oil gallery 27, check valves 28, spring loaded metal seals 29 and the sliding faces, oil filled, shallow recesses 31, while figure 8 shows a side view of one of the Scotch yoke two sliding faces with its spring loaded metal seal 29 and the check valve (28) outlet.

Finally, figure 9 and 10 respectively show a single and a twin double ended cylinder engine illustrating, in vertical and longitudinal schematic cross sections, the crank pin carriers bearing assemblies 12, (Scotch yoke block/crank pin combination not shown) the output shaft support flanges 13, the belt driven compressor/supercharger 14, the pressurised induction passages 15, induction ports 16, exhaust ports 17, exhaust passages and outlets 18, induction and exhaust passages separation block 19, ring gear belt driven lubrication and cooling oil pumps 23 and the oil sump 32.

Leaving aside the improvements brought to the Scotch yoke mechanism and the fuel stratification system, the originality of an engine according to the invention resides 10 primarily in the piston/motion translating mechanism arrangement which permits the oo :construction of an engine based on known and proven technology (particularly in the sealing department) yet of very high power to weight ratio and exceptional compactness. It is believed that the resulting substantial production cost and c:ve. installation space savings will render this power plant universally attractive to the *to0 manufacturers of small to medium land, sea and air vehicles.

It is to be understood that many variations of the embodiment described are possible, those variations being none the less included within the scope of this invention.

So.