Patent Application
20080271715
The present invention relates generally to internal combustion engines, and more specifically to a two stroke barrel engine.
A barrel engine is a type of reciprocating engine that replaces the common crankshaft with a circular plate (the swashplate). Pistons press down on a circular plate in a circular sequence, forcing it to nutate around its center. The plate, also known as a wobble plate, is typically geared to produce rotary motion.
Barrel engines are differentiated from other engines in that the cylinders are arranged in parallel around the edge of the plate, and possibly on either side of it as well, and are aligned with the output shaft rather than at 90 degrees as in crankshaft engines. This design results in a very compact, cylindrical engine, ideally suited for use in aircraft engines.
One or more embodiments are illustrated by way of example, and not by limitation, in the figures of the accompanying drawings, and wherein:
Each cylinder comprises a power cylinder comprising power sleeve 3 and a stepped charging cylinder comprising stepped sleeve 4. Disposed within each power cylinder are opposing piston 1 and 2. At a top stroke, a piston position encloses minimum cylinder volume; at a bottom stroke a piston position encloses maximum cylinder volume. Piston 1 is a power piston whose reciprocating motion drives power shaft 13. Piston 2, however, includes both a power piston and a stepped charging piston portion.
The cylinders operate in pairs opposite each other, wherein the stepped charging piston portion of piston 2 compresses inlet air to charge the two stroke power cylinder of the opposing paired cylinder.
At opposite ends of the power cylinder and at the bottom of the stroke, one of the power pistons 1 actuates an inlet port 8b and the stepped power piston 2 actuates an exhaust port. The ports are configured such that exhaust port 8a opens slightly before the inlet 8a port. On the opposite side of wobbleplate 9, stepped piston 2 opens an inlet port 6 from the carburetor at the bottom of it's stroke. At the top of it's stroke there is an always open outlet port 5 leading into a transfer passage 7 that connects with inlet port 8b of the power piston it pressurizes.
The stepped piston 2 pressurizes the inlet air to charge the power cylinder of its paired cylinder. When the power piston's inlet port 8b has opened for inlet, at the bottom of the stroke, the stepped piston 2 opposite is at the top of it's stroke, having compressed the fuel/air mixture.
The stepped charging piston 2 of one cylinder pressurizes the power cylinder of its paired cylinder. Accordingly, each stepped piston 2 moves in the opposite direction from its paired power piston 1. The stepped piston can be large enough to produce more piston displacement than the power piston's displacement producing excess air for supercharging.
Intake port 5 is an input to the power cylinder by transfer passage 7, and the stepped charging cylinder comprises intake port 6 from a carburetor. Transfer passage 7 connects the charging cylinder to a port 8b of the power cylinder. The cylinder block further includes four split radial shaft main bearings 18, a cooling water jacket 21, a starter ring gear 22, an accessory drive gear 23, an end housing 24, a split bore 26 in cylinder block 25 to assemble power shaft 13 into it's main bearings, spark plug bore 27, and a shaft thrust bearing 17.
The pistons disposed within each power cylinder include a power piston 1 and a combination power piston and stepped charging piston 2. Connecting rods 14 connect each piston 1, 2 to wobbleplates 9 via carden type two-pin universal joints at both ends of the connecting rod 14. Because all of the pins handle the same load, the diameter of the pins is determined by the diameter of the piston wrist pins. Unlike a crankshaft connecting rod that experiences a violent lateral oscillation due to rotation of the crank, the connecting rods 14 do not need to be of the strong I-beam shape of crankshaft connecting rods. Accordingly, in one embodiment, connecting rods 14 are comprised of lightweight tubes having thick ends, the ends flattened and bored, wherein the hole for the pin goes through the thicker part of the flattened rod end. No welding or riveting is required.
As disclosed herein, wobbleplate 9 eliminates the need of piston rollers of previous wobbleplate designs and is designed according to a fatigue life determined by factors including the material used, stress in the shaft, and the number of its cycles experienced in its lifetime. Stress is based upon the value of the bending moment, caused by the spread of the main bearings 10 that straddle the wobbleplate 9 and the offset of the connecting rods 14 from the shaft center and the number of cycles experienced. The greater the bearing spread, the higher the bending moment value.
Wobbleplates 9 are restricted from rotating and receive force from each piston 1, 2 equally spaced around the periphery of wobbleplate 9 by a connecting rod 14 having swiveled ends that cause wobbleplate 9 to wobble, thereby transferring the piston's reciprocating motion into rotary motion of power shaft 13.
Each wobbleplate 9 is mounted via wobbleplate mounting bearing 10 to a slug 11 with a skewed bore, and is configured to transfer reciprocating motion from pistons 1, 2 into rotary motion of power shaft 13 passing through slug 11. Pin 12 secures slug 11 to power shaft 13. Connecting rod 14 includes hinged ends mounted to hinged double pin carden joints. The hinged connection 15 of wobbleplate 9 to the connecting rod 14 allows angular motion of connecting rod 14 at the wobbleplate 9. Hinged carden joint 16 includes a piston wrist pin.
Wobbleplates 9 are non-rotating. In the embodiment illustrated in
Rotation restraint pin 31, mounted to the periphery of wobbleplate 9, oscillates, rotating twice the angle of wobbleplate 9 twice every revolution of shaft 13 as pin 31 slides back and fourth with the wobble. Furthermore, rotation restraint pin 31 carries the load of wobbleplate 9 from connecting rods 14. Accordingly rotation restraint pin 31 is preferably lubricated by the surrounding load-carrying bushings.
In one embodiment, shaft 13 is hollow and contains oil under pressure. A groove disposed all the way around the inside bearing 10 allows oil to flow from skewed slug 11 through wobbleplate 9 to rotation restraint pin 31 or anti-rotator rod 19.
In an alternate embodiment, a non-wobbling oil disc 28 is mounted on power shaft 13 between the wobbleplate 9 and the cylinder block. Unlike oil being dispersed from wobbleplate 9, non-wobbling oil-disk 28 has an advantage of directing oil with greater accuracy without squirting oil in a trajectory determined by the wobble.
