Expansible chamber devices – Piston – With ported chamber in piston part for circulating heat...
Reexamination Certificate
1999-08-16
2001-09-11
Ryznic, John E. (Department: 3745)
Expansible chamber devices
Piston
With ported chamber in piston part for circulating heat...
C123S193600, C092S238000
Reexamination Certificate
active
06286414
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to a piston for an internal combustion engine and more particularly to a one piece welded closed cooling gallery piston having a compact compression height and a method of producing such a 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 compact one piece piston with a piston body having a top surface and a longitudinal axis is provided. A support portion extending in a direction longitudinally from the piston body 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 preselected compression height distance “CH”. A flange portion extends in a direction radially from the piston body at a preselected location between the top surface and the pin bore. A piston ring belt portion having a preselected diameter “D” 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 piston body, flange portion and ring belt portion define a closed piston cooling gallery. The compression height distance “CH” is within a magnitude of between 55 percent and 70 percent the magnitude of diameter “D”.
In another aspect of the present invention, a method of producing a compact one piece piston having a top surface and a longitudinal axis is provided. The method includes the step of forging a one piece piston body having a head portion, a flange portion, and a support portion. The flange and support portions are connected to the head portion. The head portion has a top surface and the support portion has a pin bore axis spaced a preselected compression height distance “CH” from the top surface. The method further includes the steps of providing a cooling gallery disposed annularly about the piston body, and connecting a piston ring belt portion to the piston body and closing off the cooling gallery. The ring belt has a preselected diameter “D” and the compression height distance “CH” being within a magnitude of between 55 percent and 70 percent the magnitude of the diameter “D”.
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Caterpillar Inc.
Hickman Alan J.
Ryznic John E.
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