Pumps – Three or more cylinders arranged in parallel – radial – or...
Utility Patent
1998-11-27
2001-01-02
Leung, Philip H. (Department: 3742)
Pumps
Three or more cylinders arranged in parallel, radial, or...
Utility Patent
active
06168389
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates in general to a swash plate type compressor and more particularly to a so-called semi-spherical shoe which is provided between a swash plate of the swash plate type compressor and a piston for reciprocating a piston in response to a rotation of the swash plate, and also relates to a piston joint using the shoe.
The swash plate type compressor has a swash plate and a reciprocal piston coupled to the swash plate by means of a piston joint. The swash plate is interlocked with and rotated by a rotational shaft.
The piston joint has, for example, a combination of a socket coupled to the piston and a shoe interposed between the socket and the swash plate. The shoe has a generally flat sliding surface which slides along the swash plate and will be called hereinunder a flat surface. The shoe further has a convex curved surface located on the opposite side of the flat surface. The socket has a concave spherical surface which receives the convex curved surface. The piston joint of the type is disclosed in Japanese Unexamined Publication Nos. 61-135990, 49-65509 and 56-138474.
During operation of the compressor, the shoe exhibits a swinging movement such as a wobble motion and the like relative to the socket of the piston in response to a rotational movement of the swash plate. Accordingly, it is strongly envisaged to provide and maintain a suitable lubricity between the convex spherical surface of the shoe and the concave spherical surface of the socket.
For example, U.S. Pat. No. 4,734,014 teaches to provide a shoe and a socket so that a radius curvature of the convex curved surface of the shoe is smaller than the radius curvature of the concave spherical surface of the socket and an apex or top of the spherical surface is formed flat. This structure will be advantageous since it permits to provide an oil reservoir between the flat surface of the shoe and the concave spherical surface of the socket so that a desired lubricity is obtained. In this structure, the contacting position where the shoe contact the concave spherical surface of the socket is located adjacent to the position of the above-stated oil reservoir and, in other words, the shoe contact the concave spherical surface of the socket at the position of an angular portion which lies on the boundary between the spherical curved surface of the shoe and the flat surface.
In general, some clearances or gaps are provided between the concave spherical surface of the socket and the spherical curved surface of the shoe, and between the flat surface of the shoe and the swash plate and, therefore, these clearances provide, during the operation of the compressor, both a relative vibration in an axial direction of the compressor and a relative vibration in a direction perpendicular to the axial direction. As a consequence of these relative vibrations and the aforementioned swinging movement (or wobble motion), it is assumed that there occurs an unexpected, unusual state that the boundary portion of the shoe contacts the concave spherical surface of the socket at the limited position only which surrounds the oil reservoir and no other place.
If this unexpected state occurs, the reactive force of the compression by the reciprocal movement of the piston is locally integrated to the contacted position, or in other words concentrated on only a part of the contacted position, and therefore it is likely that the conventional shoe structure in which the angular portion contacts the concave spherical surface of the socket as described above results in deformations on the concave spherical surface of the socket, due to plastic deformation, plastic flow and wear. Consequently, the possibility of generation of the relative vibrations described above will be increased.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved shoe for a swash plate type compressor, which permits an increased lubricity with less possibility of generation of deformations on a concave spherical surface which is for receiving the shoe.
It is another object of the present invention to provide a piston joint for the swash plate type compressor, to which the improved shoe is employed.
It is still another object of the present invention to provide an improved swash plate type compressor in which improvement is made about such a shoe.
Other objects of the present invention will become clear from the description proceeds.
A shoe to which the present invention is applicable is for a swash plate type compressor which comprises a swash plate rotatable on an axis and a reciprocal piston connected to the swash plate through the shoe and having a concave spherical surface at an end thereof, the shoe having a convex curved surface adaptable to the concave spherical surface of the piston. In the shoe, the convex curved surface has a cross sectional shape extending along a part of a predetermined ellipse.
A piston joint to which the present invention is applicable is for a swash plate type compressor which comprises a swash plate and a reciprocal piston, the piston joint comprising a socket connected to the piston and a shoe between the socket and the swash plate, the shoe having a sliding surface slidable along the swash plate and a convex curved surface opposite to the sliding surface, the socket having a concave spherical surface for receiving therein the convex curved surface of the shoe. In the piston joint, the convex curved surface has a specific portion extending along an oblate spheroid defined by a predetermined ellipse. The specific portion has a ring-like contact portion which is in contact with the concave spherical surface around a minor axis of the predetermined ellipse to surround a portion spaced from the concave spherical surface.
A swash plate type compressor to which the present invention is applicable comprises a swash plate rotatable on an axis, a reciprocal piston having a concave spherical surface at an end thereof, and a shoe interposed between the swash plate and the piston and having a convex curved surface adaptable to the concave spherical surface and a sliding surface slidable along the swash plate. In the swash plate type compressor, the convex curved surface has a specific portion extending along an oblate spheroid defined by a predetermined ellipse. The specific portion has a ring-like contact portion which is in contact with the concave spherical surface around a minor axis of the predetermined ellipse to surround a portion spaced from said concave spherical surface.
REFERENCES:
patent: 4568252 (1986-02-01), Hattori et al.
patent: 4662267 (1987-05-01), Kaku et al.
patent: 4734014 (1988-03-01), Ikeda et al.
patent: 4752191 (1988-06-01), Onomura et al.
patent: 4781539 (1988-11-01), Ikeda et al.
patent: 5495789 (1996-03-01), Ogura et al.
patent: 19830228 (1999-02-01), None
patent: 49-965509 (1974-06-01), None
patent: 56-138474 (1981-10-01), None
patent: 61-135990 (1986-06-01), None
Baker & Botts L.L.P.
Leung Philip H.
Robinson Daniel
Sanden Corporation
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