Rotary expansible chamber devices – Working member has planetary or planetating movement – With relatively movable partition member
Patent
1996-04-03
1997-12-02
Vrablik, John J.
Rotary expansible chamber devices
Working member has planetary or planetating movement
With relatively movable partition member
F04C 18324
Patent
active
056928874
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention refers to a rotary compressor presenting a fixed vane and, more particularly, to a new construction for the piston-vane assembly of this type of compressor, in which the piston performs a circular translational motion inside the cylinder.
BACKGROUND OF THE INVENTION
In rotary hermetic compressors with a fixed vane, the separation inside the cylinder between a high pressure, or discharge, chamber and a low pressure or suction chamber occurs according to a contact line between the rolling piston and the cylinder and between the rolling piston and the fixed vane, as the top of said vane follows the displacement of the rolling piston when said top is forced against the external surface of said piston, by the action of an impelling means, such as a spring.
Also due to the high pressure differential existing between the internal part of the compressor case (which is maintained at a high discharge pressure of the system) and the inside of the cylinder, which is maintained at a lower pressure during most of the compression cycle, the fixed vane is forced against the external surface of the rolling piston. The action of said forces, together with the shape of the vane top causes, between the rolling piston and the fixed vane, a limit lubrication, i.e., an intermediate phase between the formation of a hydrodynamic wedge and the metallic contact between the parts. As a result, such lubrication becomes insufficient, allowing the metallic contact between the parts, causing wear on the top of the fixed vane and on the external contact surface of the rolling piston, resulting in alterations on the diameter of said piston, impairing its useful life and consequently affecting the reliability of the compressor.
Such contact, besides generating friction noise, which is difficult to attenuate, increases the energy loss of the compressor, thus impairing its efficiency. Moreover, the profile of the contact between the rolling piston and the fixed vane causes leakages between the compression and suction chambers of the compressor, reducing the volumetric capacity of said compressor.
The known solutions to minimize the problem of wear between the rolling piston and fixed vane make use of materials that are more resistant to wear in the manufacture of fixed vanes. Compound materials may also be used, which, besides high durability, present the advantages of low specific weight and low friction coefficient. Nevertheless, the solution that uses special materials to construct the contact parts, such as the one described in the Brazilian Patent Application PI 9102901 of the same applicant, in which the fixed vane is provided at the free end thereof with an insert, which is designed to contact the rolling piston and is made of a material that is more resistant to wear, increases the cost of the compressor, due to the high costs of said materials.
These solutions, although reducing the problem of wear in the vane and rolling piston, do not minimize the problems of noise and energetic loss of the compressor.
DISCLOSURE OF THE INVENTION
Thus, it is a general object of the present invention to reduce the metallic contact and the wear between the top of the vane and the external surface of the piston of a rotary compressor, without causing losses in the energy efficiency of the compressor.
Another object of the present invention is to present a solution to the above cited problem, which does not require the use of special materials for constructing the contact parts presenting relative movement to each other, without altering the normal running conditions of the compressor.
It is also a specific object of the present invention to present a vane-piston assembly, which allows the formation of a permanent sealing oil film between the contact surfaces of said vane and piston, thereby minimizing the leakages between the compression and suction chambers of the compressor, besides reducing the friction noises.
The rotary compressor used in the present invention is of the type including a piston,
REFERENCES:
patent: 2344159 (1944-03-01), Meeks
patent: 2929550 (1960-03-01), Sadler
patent: 3554676 (1971-01-01), Porteous
Krueger Manfred
Puff Rinaldo
Empresa Brasileira de Compressores S/A-Embraco
Vrablik John J.
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