Internal-combustion engines – Free piston – Single chamber; one piston
Reexamination Certificate
1999-02-22
2001-04-17
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Free piston
Single chamber; one piston
C123S0460SC
Reexamination Certificate
active
06216647
ABSTRACT:
TECHNICAL FIELD
The present invention relates to free piston internal combustion engines, and, more particularly, to piston and cylinder configurations within such engines.
BACKGROUND ART
Free piston internal combustion engines include one or more pistons which are reciprocally disposed within corresponding combustion cylinders. Each piston is typically rigidly attached to a plunger rod which provides a desired work output. For example, the plunger rod may be used to provide electrical power output by inducing an electrical current, or fluid power output such as pneumatic or hydraulic power output.
Pistons used in free piston internal combustion engines typically include a piston head which is entirely constructed from a metallic material such as aluminum or steel. Metals such as aluminum and steel have a relatively high coefficient of thermal expansion. Thus, during operation of the free piston engine, the metallic piston head expands considerably in the radial direction toward the inside surface of the combustion cylinder. Each piston head used in the free piston engine is thus formed with an outside diameter which provides a considerable radial clearance with the inside surface of the combustion cylinder to accommodate the relatively large radial expansion during operation. To prevent blow-by of combustion products past the piston head during operation, the outside peripheral surface of the piston head is formed with one or more piston ring grooves which receive corresponding piston rings therein. The piston rings allow for radial thermal expansion and contraction of the piston head, while at the same time effectively preventing blow-by of combustion products past the piston head.
Although piston rings provide valuable functionality as indicated above, it would be desirable to eliminate the use of piston rings to reduce manufacturing and assembly costs.
Moreover, to prevent excessive wear between the piston rings and the inside surface of the combustion cylinder, it is necessary to lubricate the piston rings with a suitable lubricant. The lubrication system for lubricating the piston rings may require additional porting and/or other structure to effect proper lubrication, which in turn increases the size and complexity of the engine. Additionally, the lubricating oil may increase undesirable emissions from the engine.
Another problem with using conventional piston and cylinder arrangements including a metallic combustion cylinder and metallic piston head with piston rings is that suitable fluid cooling channels must be provided within the combustion cylinder to effect the proper cooling of the combustion cylinder and piston head. These cooling fluid channels again increase the size and complexity of the engine.
The present invention is directed to overcoming one or more of the problems as set forth above.
SUMMARY OF THE INVENTION
The present invention provides a free piston internal combustion engine with a piston head having a non-metallic radially outside bearing surface with low friction, low thermal expansion and high temperature resistance properties.
In one aspect of the invention, a free piston internal combustion engine includes a combustion cylinder having an inside surface. A piston is reciprocally disposed within the combustion cylinder. The piston includes a piston head and a plunger rod attached to the piston head. The piston head has a cylindrical outside surface lying closely adjacent to and defining a bearing surface with the inside surface of the combustion cylinder. The bearing surface consists essentially of a non-metallic material.
An advantage of the present invention is that the need for lubricating oil and cooling fluid in the free piston engine is eliminated, thereby eliminating the increased physical size and decreased efficiency losses associated with such structure.
Another advantage is that the radial clearance between the piston head and cylinder inside surface is substantially reduced or eliminated, thereby eliminating the need for piston ring grooves and piston rings in the piston head.
Yet another advantage is that the portion of the piston head defining the bearing surface is constructed from a material having low friction, low thermal expansion and high temperature resistance properties.
REFERENCES:
patent: 4020804 (1977-05-01), Bailey
patent: 4589380 (1986-05-01), Coad
patent: 4724800 (1988-02-01), Wood
patent: 4736676 (1988-04-01), Taylor
patent: 4867119 (1989-09-01), Cooper et al.
patent: 4986234 (1991-01-01), Bell
patent: 5437821 (1995-08-01), Diberardino et al.
patent: 5483869 (1996-01-01), Bock et al.
patent: 5540194 (1996-07-01), Adams
patent: 5724933 (1998-03-01), Silvonen et al.
patent: 5740788 (1998-04-01), Atmur et al.
patent: 5816211 (1998-10-01), Atmur et al.
patent: 5975040 (1999-11-01), Silvonen et al.
patent: 38 20 240 A1 (1989-01-01), None
patent: 195 45 397 A1 (1997-06-01), None
patent: 0 108 475 A1 (1980-11-01), None
patent: 2 602 273 (1988-05-01), None
TU Dresden—publication date unknown—earliest date 1993—Dresden University in Germany.
Argenbright Tony M.
Benton Jason
Caterpillar Inc.
Taylor Todd T.
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