Cooled one piece piston and method

Internal-combustion engines – Cooling – Internal cooling of moving parts; e.g. – hollow valves,...

Reexamination Certificate

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C092S222000

Reexamination Certificate

active

06223701

ABSTRACT:

TECHNICAL FIELD
This invention relates generally to a piston for an internal combustion engine and more particularly to a cooled one piece piston having a closed piston cooling gallery and a method of producing such a cooled one piece piston.
BACKGROUND ART
An efficient, light weight, compact, increased horsepower internal combustion engine is sought after by those involved in the industry. To achieve this it is necessary to push the engine design toward its mechanical limits. Increasing combustion pressures in the combustion chamber requires higher combustion temperatures, faster piston speeds and increased mechanical forces. As a result, the piston and associated components are placed under greater stress.
In order to perform satisfactorily and live in such an environment it is necessary to provide a piston that has improved cooling capabilities, increased strength, and a short compression height for reduced mass and light weight. It is also important that such a piston is easy to manufacture with a high level of quality.
It is known to provide a piston with a closed piston cooling gallery. An example of this is shown in U.S. Pat. No. 4,581,983, dated Apr. 15, 1986, to Horst Moebus. The closed piston cooling gallery of Moebus is provided by welding a top portion of the piston to a bottom portion of the piston along a planar surface. The top and bottom portions of the piston each have a portion of the cooling gallery disposed therein. This piston has an excessively tall compression height making it heavy and unsuitable for high speed operation. This piston is also difficult to manufacture and does not have the strength to withstand the increased stresses of the higher combustion pressures. The closed piston cooling gallery as configured in Moebus does not provide a height sufficient to permit adequate shaking of the cooling fluid within the closed piston cooling gallery. Therefore, the efficiency of cooling of the piston is inadequate.
It is also known to provide a piston with decreased mass by reducing height. An example of this is shown in U.S. Pat. No. 4,727,795, dated Mar. 1, 1988, to Edward J. Murray. The short piston height is achieved by intersecting the ring band with the pin bores. This ring band intersection is unacceptable in a high piston speed engine, as leakage and wear in the region of the ring band would be excessive. Additionally, such a piston would not survive the high piston speeds because of insufficient cooling of the piston top portion. Further, the piston skirt, when welded to the piston top, does not permit removal of a pin in the pin bore and therefore makes assembly difficult and would not be a suitable choice. Additionally, providing a piston skirt that is removably attached to the piston reduces strength and further restrict the possibility of use in the proposed high speed, high temperature and high combustion pressure environment.
U.S. Pat. No. 5,78,846, dated Jul. 14, 1998, to Siegfried Mielke discloses a forged or cast piston head of an articulated (two piece) piston. The ring band of the piston is welded to a top portion of the piston. Because this piston does not have a closed cooling gallery or a supported ring band it would not be suitable for use in a high piston speed, high temperature and high compression pressure environment. The higher forces applied to the piston would cause the unsupported ring band to deflect. This would result in unacceptable blowby leakage and premature stress failure of the piston. Further, the piston cooling would be inadequate and would result in a thermal related structural failure of the piston.
The present invention is directed to overcoming one or more of the problems set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention, a cooled one piece piston has a piston body, a top surface and a longitudinal axis. A support portion extends in a direction longitudinally from the piston body and defines a pair of spaced apart pin bosses. The pin bosses have a pin bore and a pin bore axis oriented transverse the longitudinal axis. The pin bore axis is spaced from the top surface. A flange portion extends in a direction radially outwardly from the piston body at a preselected location between the top surface and the pin bore. A piston ring belt portion is disposed about the piston body. The piston ring belt portion is connected to the piston body and to the flange portion by welding. The a piston cooling gallery is disposed annularly in and about the piston body. The piston cooling gallery is located between the top surface and the pin bore. The piston cooling gallery is closed to form a closed piston cooling gallery by the ring belt and the flange portions. The closed piston cooling gallery is adapted to carry a cooling fluid therein. The closed piston cooling gallery has first and second spaced apart extreme end locations defining a preselected gallery length “L” sufficient to provide a preselected maximum amount of cooling fluid shaking space.
In another aspect of the present invention, a method of producing a cooled one piece piston having a closed piston cooling gallery and a longitudinal axis, includes forging a piston body having a head portion, a flange portion, and a support portion. The flange and support portions being connected to the head portion. Providing a cooling gallery disposed annularly about the piston body. Machining a plurality of spaced apart cooling fluid passing passageways radially inwardly in the piston body toward the longitudinal axis from an outward location. Connecting a piston ring belt portion to the piston body and closing off the piston cooling gallery.


REFERENCES:
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patent: 3323503 (1967-06-01), Grosshans et al.
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patent: 4517930 (1985-05-01), Nakano et al.
patent: 4581983 (1986-04-01), Moebus
patent: 4662047 (1987-05-01), Berchem
patent: 4727795 (1988-03-01), Murray et al.
patent: 4838149 (1989-06-01), Donnison et al.
patent: 5040454 (1991-08-01), Ballheimer et al.
patent: 5778846 (1998-07-01), Mielke
patent: 6003479 (1999-12-01), Evans

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