Expansion machine

Abstract

An expander is provided in which spherical projections (61a) formed at the forward end of pistons (42) of an axial piston cylinder group abut against spherical depressions (31a) formed in a swash plate (31), and an elliptical contact point locus (T) of contact points (p) between the spherical depressions (31a) and the spherical projections (61a) is offset toward the expansion stroke side of the axial piston cylinder group. As a result, in a middle region of the expansion stroke where the speed of the piston (42) is high and the surface pressure of the contact point (p) is high, the position of the contact point (p) can be made as close as possible to an axis (L3) of the spherical depression (31a) and an axis (L2) of the piston (42), thus reducing a bending moment and a radially biased load exerted on the piston (42) and minimizing any increase in sliding resistance and any occurrence of abnormal wear.

Description

FIELD OF THE INVENTION [0001] The present invention relates to an expander in which an axial piston cylinder group is arranged annularly in a rotor so as to surround an axis of the rotor, the rotor being rotatably supported in a casing, and spherical projections formed at the forward end of pistons of the axial piston cylinder group abut against spherical depressions formed in a swash plate. BACKGROUND ART [0002] A hydraulic device in which a spherical projection formed at the forward end of a piston of an axial piston cylinder group abuts against a spherical depression formed in a swash plate is known from Japanese Patent Application Laid-open No. 61-274166. By making the spherical projection abut against the spherical depression it is possible to reduce the surface pressure in the area where the two abut against each other and prevent relative rotation between the swash plate and the piston, thereby contributing to a reduction in wear of the swash plate and the piston. Moreover, s...

AI Technical Summary

Benefits of technology

[0004] The present invention has been achieved under the above-mentioned circumstances, and it is an object thereof to reduce the bending moment or the radially biased load exerted on the piston of the expander by the swash plate, thereby minimizing any increase in sliding resistance and any occurrence of abnormal wear.

[0006] In accordance with this arrangement, with regard to the expander that includes the axial piston cylinder group, since the locus of the contact points between the spherical depressions of the swash plate and the spherical projections of the pistons is offset toward the expansion stroke side of the axial piston cylinder group, in a middle region of the expansion stroke where the speed of the piston is high and the surface pressure at the contact point between the piston and the swash plate is large, the position of the contact point between the spherical depression of the swash plate and the spherical projection of the piston is made to be as close as possible to an axis of the spherical depression and an axis of the piston, thus reducing the bending moment and the radially biased load acting on the piston and thereby minimizing any increase in sliding resistance and any occurrence of abnormal wear.

[0008] In accordance with this arrangement, by employing a simple arrangement in which the axis of the swash plate is offset toward the exhaust stroke side of the axial piston cylinder group relative to the axis of the rotor, it is possible to offset the locus of the contact points between the spherical depressions of the swash plate and the spherical projections of the pistons toward the expansion stroke side of the axial piston cylinder group.

Problems solved by technology

As a result, the piston receives a bending moment or a radially biased load, and the bending moment or radially biased load causes galling on sliding faces of the piston and the cylinder, thus giving rise to the problems of increased sliding resistance and the occurrence of abnormal wear.

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