This invention relates to scroll fluid apparatus suitable for use as a compressor, expander or liquid pump, and, more particularly, to an oil feeding device for such scroll fluid apparatus.
A scroll fluid apparatus is disclosed, for example, in U.S. Pat. No. 3,885,599 which comprises an orbiting scroll member including an end plate and a wrap of an involute or substantially involute form located in an upright position on the surface of the end plate and a stationary scroll member including an end plate, a wrap of the same construction as that of the orbiting scroll member and an outlet port, the orbiting scroll member and the stationary scroll member being arranged in contact with each other with the respective wraps in meshing engagement with each other and the two scroll members housed in the interior of a housing formed with a suction port. An Oldham's ring is interposed between the orbiting scroll member and the housing or the stationary scroll member to keep the orbiting scroll member from rotating on its own axis, and a crank shaft is in engagement with the orbiting scroll member for moving the orbiting scroll member in orbiting movement while keeping same from apparently rotating on its own axis, so as to cause a fluid in sealed spaces defined between the two scroll members to perform a pumping action or to supply pressure fluid through the exhaust port to expand the pressure fluid to impart a force of rotation to the crank shaft. In, for example, U.S. Pat. No. 4,065,299 and Japanese Patent Application Laid-Open No. 148994/80, a scroll fluid apparatus is provided wherein the elements are located in a sealed vessel.
In the scroll fluid apparatus of the construction wherein the elements thereof are located in a sealed vessel, a crank shaft is generally arranged vertically and includes a shaft portion and a crank portion. The shaft portion is journalled by two upper and lower bearings while the crank shaft is engaged in a plain bearing provided to the orbiting scroll member. A device for feeding lubricant to these bearings usually comprises oil feeding passages formed in the crank shaft for supplying, by centrifugal forces, the bearing lubricant stored in the lower portion of the sealed vessel.
In the case of a scroll fluid apparatus comprising an intermediate chamber having an internal pressure which is intermediate in level between the suction pressure and the exhaust pressure located between the undersurface of the orbiting scroll member and a frame supporting the shaft portion of the crank shaft as disclosed in Japanese Patent Application Laid-Open No. 148994/80, the aforesaid oil feeding device has been found to have some disadvantages. For example, the pressure in the intermediate chamber affects the operation of the oil feeding device, so that variations are caused to occur in the volume of lubricants fed to the plain bearings. More specifically, the volume of lubricant fed to the plain bearing of the orbiting scroll member and the upper bearing of the shaft portion differs from the volume of lubricant fed to the lower bearing of the shaft portion. The result of this is that each bearing is unable to produce a lubricant film reaction commensurate with the load applied by the fluid pressure, thereby causing wear and seizure to occur.