Method of determining the shape of spiral elements for scroll type

Abstract

The surface of a central section of a spiral element formed on a stationary or a movable scroll unit of a scroll type compressor is determined through the steps of locating an outer wall surface changing point G in a first polar coordinate system X, Y having a first origin O, drawing a circle Cs with its center at the first origin O and with a diameter corresponding to the orbital radius e of the orbiting motion of the movable scroll unit, locating a contact point P at a desired contact angle .beta. on the circle Cs, drawing a straight line m passing through the contact point P and the first origin O, drawing a straight line I passing the outer wall surface changing point G and inclined at a predetermined angle .alpha. to the X-axis, determining the intersection point C of the straight lines m and I, and determining a section of the contact curve in a second polar coordinate system having its second origin at the intersection point C by determining a smooth curve interconnecting the outer wall surface changing point G and the contact point P, and smoothly merging into an outer curve at the outer surface changing point G. The compression clearance formed between the scroll elements can be substantially reduced to zero at the final stage of a compression cycle so that the compression efficiency can be improved, the vibration and noise are reduced, and that the operation reliability can be improved.