Seal for a joint or juncture – Seal between relatively movable parts – Piston ring or piston ring expander or seat therefor
Reexamination Certificate
1999-02-04
2001-07-10
Mah, Chuck Y. (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Piston ring or piston ring expander or seat therefor
C277S448000, C277S460000, C029S888070
Reexamination Certificate
active
06257590
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosed contents of Japanese Patent Applications Nos. HEI 10-39264 filed on Feb. 20, 1998, HEI 10-151568 filed on Jun. 1,1998, and HEI 10-238940 filed on Aug. 25, 1998 including the specifications, drawings and abstracts are incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sealing structure for sealing a space between a piston and a cylinder that are in sliding contact with each other and, more particularly, relates to a sealing structure in the form of a piston ring for an internal combustion engine wherein an outer ring made of a resinous material is pressed toward a sliding face by urging means via an inner ring. The present invention also relates to a method of mounting a piston ring structural body for use in the sealing structure.
2. Description of the Related Art
A sealing structure is widely employed to seal a space between a piston and a cylinder that are in sliding contact with each other.
For example, an internal combustion engine has a so-called piston ring disposed within a piston ring groove. Conventionally, in many cases, this piston ring is made of a metal. However, a resinous piston ring has also been developed.
For example, Japanese Patent Application Laid-Open No. HEI 9-280373 discloses usage of a resinous piston ring. In this publication, there is disclosed a piston ring structural body wherein an outer ring that is continuously formed of polytetrafluoroethylene (PTFE) as a fluororesin without being provided with an abutment is pressed radially outwards by a ring tensile force applying member composed of a metal coil expander via an inner ring that is also continuously formed of PTFE without being provided with an abutment.
In the piston ring structural body disclosed in the aforementioned publication, the ring is divided into the inner and outer rings. While the inner ring ensures sealability around a ring groove, the outer ring ensures sealability between a sliding portion thereof and a cylinder wall.
It is to be noted herein that the piston ring structural body disclosed in the aforementioned publication uses PTFE for both the inner and outer rings. However, PTFE has a low threshold value of PV (a product of a real pressure P and sliding speed V) and cannot provide the sliding portion that slides on the cylinder wall with sufficient durability. Furthermore, PTFE has a large coefficient of thermal expansion. Thus, when the temperature rises, the pressing force applied to the cylinder wall due to an elastic force of the coil expander becomes larger and increases a frictional loss of the engine, which raises a serious problem in relation to the outer ring.
Furthermore, when the temperature rises during operation of the engine, the coil expander cuts into the inner ring and causes permanent distortion. This results in a problem, for example, of deterioration in the sealability around the ring groove.
SUMMARY OF THE INVENTION
In view of the aforementioned problems, it is an object of the present invention to enhance durability of a sealing structure wherein a resinous sliding-contact ring is pressed against one of opposed sliding faces of a piston and a cylinder by urging means via an urging force receiving ring.
It is another object of the present invention to provide a method of mounting a piston ring structural body for use in such a sealing structure to a piston easily and reliably.
A first aspect of the present invention provides a sealing structure that is disposed in a groove formed in one of opposed sliding faces of a piston and a cylinder that are in sliding contact with each other and is urged toward and brought into sliding contact with the other sliding face where no groove is formed. This sealing structure includes a sealing member composed of a plurality of radially laminated rings and urging means for urging the sealing member toward a side where no groove is formed. A sliding-contact ring of the sealing member is disposed on a side most remote from the urging means and contains the aforementioned sliding-contact face. This sliding-contact ring is made of polyimide resin. An urging force receiving ring of the sealing member is adjacent to the urging means and receives an urging force from the urging means. This urging force receiving ring is provided with an abutment and made of a material that has a hardness equal to or greater than polyimide resin.
In the thus-constructed sealing structure, the sliding-contact ring is made of polyimide resin, and the urging force receiving ring is provided with an abutment and made of a material that is as hard as or harder than polyimide resin. Therefore, both the sliding-contact face and the urging force receiving face exhibit high durability.
In addition to the features of the first aspect of the present invention, the present invention may further be specified according to a second aspect thereof. That is, the aforementioned sealing structure is a piston ring disposed within a piston ring groove formed in a piston for an internal combustion engine, and the sealing member is a double-structure ring composed of an outer ring serving as the sliding-contact ring disposed on the side closest to the cylinder and an inner ring serving as the urging force receiving ring disposed on the side closest to the piston.
In the thus-constructed sealing structure, the outer ring, which is disposed within the piston ring groove as the piston ring and made of polyimide resin, is pressed against the cylinder by the urging means via the inner ring.
In the second aspect of the present invention, the aforementioned outer ring can be continuously formed without being provided with an abutment.
In the thus-constructed piston ring structural body, the outer ring continuously formed of polyimide without being provided with an abutment is pressed against the cylinder by the urging means via the inner ring.
In the second aspect of the present invention, the aforementioned outer ring can also be provided with an abutment.
In the thus-constructed piston ring structural body, the outer ring made of polyimide and provided with an abutment is pressed against the cylinder by the urging means via the inner ring.
In addition, the abutment of the outer ring may be an inclined abutment that has been formed by cutting the outer ring when the outer ring is in the shape of a perfectly round circle at a room temperature. Also, the width of the outer ring in a piston-axis direction during operation can be set smaller than the width of a groove of the piston in the piston-axis direction during operation.
In the thus-constructed sealing structure, the outer ring having the inclined abutment, which has been formed by cutting the outer ring when the outer ring is in the shape of a perfectly round circle at a room temperature, is pressed against the cylinder by the urging means via the inner ring. When the outer ring thermally expands during operation, opposed end faces of the inclined abutment are displaced relative to each other.
Furthermore, in the second aspect of the present invention, the width of the outer ring in the piston-axis direction during operation can be set smaller than the width of the inner ring in the piston-axis direction during operation, and the width of the inner ring in the piston-axis direction during operation can be set smaller than the width of a ring groove of the piston in the piston-axis direction during operation.
In the thus-constructed sealing structure, the inner ring moves in a piston-axis direction in accordance with the movement of the outer ring in the piston-axis direction. Accordingly, the inner ring first hits top and bottom faces of a piston groove, whereby the outer ring is inhibited from being abraded.
In the second aspect of the present invention, at least a lower face of the outer ring may be coated with titanium nitride, chrome nitride or diamond-like carbon.
In the thus-constructed sealing structure, the lower face of the outer ring of the piston ring structural body, which has a
Kumai Teruo
Masuda Yoshihiko
Okamoto Michio
Mah Chuck Y.
Peavey Enoch E
Pillsbury & Winthrop LLP
Toyota Jidosha & Kabushiki Kaisha
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