Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B33/00—Engines characterised by provision of pumps for charging or scavenging
  • F02B33/02—Engines with reciprocating-piston pumps; Engines with crankcase pumps
  • F02B33/06—Engines with reciprocating-piston pumps; Engines with crankcase pumps with reciprocating-piston pumps other than simple crankcase pumps
  • F02B33/10—Engines with reciprocating-piston pumps; Engines with crankcase pumps with reciprocating-piston pumps other than simple crankcase pumps with the pumping cylinder situated between working cylinder and crankcase, or with the pumping cylinder surrounding working cylinder

Definitions

• This invention relates to internal combustion engines operating on the two-stroke cycle, and particularly to high compression two-stroke engines, including such engines operated with diesel fuels.
• One of the problems with two-stroke engines is the restriction on the mass of air in the combustion chamber at the time of combustion due in part to low pressure of that air delivered to the engine during the intake stroke. It has been proposed to obtain higher compression pressures by the use of supercharging, however these have limitations, particularly in regard to the fact that they only operate efficiently at relatively high engine speeds.
• a two-stroke cycle internal combustion engine comprising first and second co-axial chambers with a division wall therebetween, first and second piston members mounted in the respective first and second chambers to reciprocate in unison therein and coupled to a crankshaft to rotate the crankshaft in response to said reciprocation of the piston members, a cylinder head closing the end of the first chamber remote from the division wall, whereby a combustion chamber is formed between the cylinder head and the first piston member and a first compressor chamber is formed between the first piston member and the division wall, said second piston member forming with the division wall a second compressor chamber, first means responsive to a predetermined pressure differential between the first and second compressor chambers to communicate said chambers to permit gas to pass from the second compressor chamber to the first compressor chamber, and second means to permit gas to pass from the first compressor chamber for admission to the combustion chamber when the pressure in the first compressor chamber is above a first predetermined pressure, said first means being adapted to terminate communication between the first and second compressor chambers when the pressure in the first compressor chamber is at
• Inlet ports are provided to communicate the first and second compressor chambers with atmosphere when the pressure in the relevant chamber falls below atmospheric pressure.
• the inlet ports communicate with the respective compressor chambers through or adjacent to the division wall. In this location, air may enter the respective chambers as the respective piston members commence to move in a direction away from the division wall, that is commence their suction stroke.
• the inlet ports are valve controlled so as to open at pressures in the respective compressor chambers below atmospheric pressure and at or above atmospheric pressure the ports are automatically closed.
• the valve may be of the reed, poppet or disc type appropriately spring-loaded.
• the second means is arranged to communicate the first compressor chamber with a transfer chamber when the pressure in the first compressor chamber is above said first predetermined pressure.
• the transfer chamber is selectively communicated with the combustion chamber in timed relation to the reciprocation of the first piston member, conveniently by a port in the wall of the first compressor chamber controlled by the movement of the first piston member.
• a third means is provided to permit gas to pass from the second compressor chamber to the transfer chamber when the pressure in the second compressor chamber is a predetermined amount above the pressure in the transfer chamber.
• the second chamber at the end remote from the division wall may conveniently be in communication with an engine crankcase in which the crankshaft is journalled.
• fourth means may be provided to communicate the crankcase with the transfer chamber when the pressure in the crankcase is above the pressure in the transfer chamber.
• the crankcase is provided with an inlet port that will open when the pressure in the crankcase falls below atmospheric pressure.
• the fourth means may be a port in the wall of the second compressor chamber that is controlled by the movement of the second piston member.
• the second, third and fourth means may be arranged so that the first and second compressor chambers and the crankcase are respectively communicated with the transfer chamber when the pressure in the transfer chamber is below that in the respective chamber by a relatively small amount, such as 5 to 10 kpa.
• the first, second, third and fourth means may be valve controlled ports, such as ports controlled by reed, poppet or disc valves, appropriately spring loaded.
• the engine as described above has multiple compressors to increase the mass of air available for combustion of the fuel. Also due to multi-stage compression of at least some of the air, the pressure of the air available for admission to the combustion chamber may be raised. These increases in mass and pressure of the air are achieved with a relatively simple engine construction and minimal increase in physical size and weight of the engine.
• the engine comprises a cylinder 10 mounted on or integral with a crankcase 11 and having a detachable cylinder head 12 fitted thereto.
• the crankshaft 13 is journalled in bearings 14 and has an eccentric crank pin 15 within the crankcase 11.
• the cylinder 10 defines a uniform internal bore divided into upper and lower cylinders 16 and 17 formed by the division wall 18.
• Piston 20 is mounted in the upper cylinder 16 and piston 21 is mounted in the lower cylinder 17.
• Pistons 20 and 21 are rigidly connected by the rod 22 which is formed integral with the lower piston 21 and has a spigoted end 23 received in a central bore in the upper piston 20 and the co-operating bolt 24.
• the conventional connecting rod 25 is rotatably mounted on the eccentric journal 15 of crankshaft 13 and is journalled on the bearing pin 26 attached by the bolts 27 to the lower piston 21. It will thus be appreciated that the upper and lower pistons 20 and 21 reciprocate in unison in the upper and lower cylinders 16 and 17 as the crankshaft 13 rotates.
• the pistons 20 and 21 have been shown to be of equal diameter, it is to be understood that it is not essential for these diameters to be equal, and the diameter of one or both may be varied in accordance with the final compression pressure required in the combustion chamber.
• the upper piston 20 divides the upper cylinder 16 into a combustion chamber 60 above the piston 20 and an upper compressor chamber 16a below the piston 20.
• the lower piston 21 divides the lower compressor chamber 17a from the crankcase 11.
• the division wall 18 is provided with a seal assembly 30 to permit reciprocation of the rod 22 relative thereto, whilst maintaining a seal against the passage of gas under pressure between the rod 22 and the division wall 18.
• the division wall 18 is also fixed in a sealed relation to the cylinder 10 so as to prevent any uncontrolled passage of gas between the periphery of the division wall 18 and the internal surface of the cylinder 10.
• a number of spaced transfer ports 32 are provided in the division wall 18 to provide communication between the upper compressor chamber from the lower compressor chamber. These ports 32 are provided with respective reed valves 33 so that gas above a predetermined pressure may pass from the lower compressor chamber to the upper compressor chamber 16 but gas cannot at any time pass in the reverse direction.
• the inlet port 40 communicating with the upper compressor chamber 16a towards the lower end thereof, the inlet port 41 communicating with the lower compressor chamber 17a near the upper end thereof and the inlet port 42 communicating with the crankcase 11.
• Each of the inlet ports 40, 41 and 42 are each provided with reed valves 40a, 41a and 42a respectively and arranged so that ambient air will only enter the respective chambers when the pressure in that chamber is lower than ambient pressure.
• Transfer port 46 communicates the interior of the crankcase with the transfer passage 45 and transfer port 47 communicates the transfer passage 45 with the lower compressor chamber 17a. Transfer port 47 is opened and closed by the lower piston 21 as it reciprocates in the lower cylinder 17.
• the transfer port 48 communicates the transfer passage 44 with the lower end of the upper compressor chamber 16a.
• the final transfer port 49 communicates the transfer passage 44 with the combustion chamber 60 and this communication is controlled by the reciprocation of the upper piston 20 in the cylinder 16
• the exhaust port 50 is provided in the wall pf the upper cylinder 16 and is opened and closed in response to the reciprocating movement of the upper piston 20.
• the reed valves 33 associated with the ports 32 in the division wall 18 are set to open at a higher pressure than the reed valve in the inlet port 40 so that on the upstroke of the pistons 20 and 21 air will first enter the upper compressor chamber 16a through the inlet port 40, and air will be transferred from the lower compressor chamber 17a to the upper chamber 16a only when the pressure in the lower compressor chamber 17a is raised sufficiently to open the reed valves 33. This ensures that during each cycle of the engine a proportion of the engines air intake is atmospheric air drawn into the upper compressor chamber 16a.
• the piston 21 will correspondingly move down and air will enter the lower compressor chamber 17a through the opening of the reed valve in the inlet port 41.
• the reed valve in the inlet port 42 in the crankcase 11 will be closed as a result of the rising pressure in the crankcase.
• the location of the transfer ports 47 and 49 relative to the stroke of the respective pistons 21 and 20 determine the timing in the engine cycle of the admission of air from the crankcase 11 to the lower compressor chamber 17a and from the upper compressor chamber 16a to the combustion chamber 60. Because of the relationship between the opening of the transfer ports and the position of the respective piston within its stroke, the pressure of the air available on opening of the transfer ports is related to the position of the transfer ports. Alternatively, or in addition, valves set to open at respective selected pressures may be associated with each of the transfer ports.
• the engine as illustrated incorporates a spark plug 61 and the required fuel may be supplied to the combustion chamber 60 by a suitable fuel injector which delivers the fuel directly into the combustion chamber 60 or into the transfer passage 44 or 45.
• a suitable form of carburation may be provided to meter the fuel into the air being drawn into the engine through the inlet port 42 in the crankcase and/or through the inlet ports 40 and 41 in the upper and lower compressor chambers, respectively.
• fuel could be metered by an injection system into the air passing to one or more of the above referred to three inlet ports.
• the engine may be operated on the diesel cycle with diesel fuel being injected directly into the combustion chamber 60 after the compression of the gas in the combustion chamber has raised the temperature thereof sufficiently to ignite the diesel fuel during delivery.
• the engine as above described enables the compression pressure in the combustion chamber 60 at the time of combustion to be substantially higher than that normally achieved with a crankcase compression type two-stroke cycle engine.
• the inlet ports 40 and 41 increase the mass of air delivered to the combustion chamber in relation to that which would be delivered in a simple multi-stage compression of the air. This increases the air mass and higher degree of compression improves the overall efficiency of the engine.
• the provision of the inlet ports 40 and 41 so that ambient air may enter the upper and lower compressor chambers immediately the suction stroke of the respective pistons commence reduces substantially the "pumping losses" which would normally occur in conventional two-stroke engines.
• the various components and manner of construction of the engine is in accordance with substantially conventional engine manufacturing techniques and the design can therefore be readily adopted by engine manufacturers without major difficulties.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Combustion Methods Of Internal-Combustion Engines (AREA)

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• 1987
  • 1987-02-17 WO PCT/AU1987/000041 patent/WO1987005073A1/en unknown
  • 1987-02-17 EP EP19870901281 patent/EP0263117A1/de not_active Withdrawn

Non-Patent Citations (1)

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