Scroll compressor

Abstract

An orbital scroll wrap and a fixed scroll wrap of a scroll compressor include respective scroll start portions each having a bulbous shape defined by connecting an involute start point of an outer-surface involute curve and an involute start point of an inner-surface involute curve to each other with a plurality of arcs. At least one of the scroll start portions has a tiered shape wherein an n number (where n≥2) of tiers each having the bulbous shape are stacked in an axial direction of a main shaft. Letting involute-start-point angles of the outer-surface involute curves in respective tiers of the scroll start portion having the tiered shape be φos(1), φos(2), φos(3), . . . , and φos(n) in order from tip to base of the scroll start portion, the following is satisfied: φos(1)>φos(2)>φos(3)> . . . >φos(n); and 0.3π<φos(1)-φos(n)<0.7π.

1 . A scroll compressor configured to compress a working medium in a plurality of compression chambers defined between an orbital scroll wrap of an orbiting scroll and a fixed scroll wrap of a fixed scroll that are made to mesh with each other, the working medium being compressed when the orbiting scroll driven through a main shaft undergoes an orbital motion about the fixed scroll,
 wherein the orbital scroll wrap and the fixed scroll wrap include respective scroll start portions each having a bulbous shape defined by connecting an involute start point of an outer-surface involute curve and an involute start point of an inner-surface involute curve to each other with a plurality of arcs, at least one of the scroll start portions having a tiered shape in which an n number (where n≥2) of tiers each having the bulbous shape are stacked in an axial direction of the main shaft, and   wherein letting involute-start-point angles of the outer-surface involute curves in the respective tiers of the scroll start portion having the tiered shape be φos(1), φos(2), φos(3), . . . , and φos(n) in order from a tip toward a base of the scroll start portion, the following relationships are satisfied:
   φ os (1)>φ os (2)>φ os (3)> . . . >φ os ( n ); and
 
   0.3π<φ os (1)-φ os ( n )<0.7π.
 
   
     
     
         2 . A scroll compressor configured to compress a working medium in a plurality of compression chambers defined between an orbital scroll wrap of an orbiting scroll and a fixed scroll wrap of a fixed scroll that are made to mesh with each other, the working medium being compressed when the orbiting scroll driven through a main shaft undergoes an orbital motion about the fixed scroll,
 wherein the orbital scroll wrap and the fixed scroll wrap include respective scroll start portions each having a bulbous shape defined by connecting an involute start point of an outer-surface involute curve and an involute start point of an inner-surface involute curve to each other with a plurality of arcs, at least one of the scroll start portions having a tiered shape in which an n number (where n≥2) of tiers each having the bulbous shape are stacked in an axial direction of the main shaft,   wherein the orbiting scroll and the fixed scroll are made of respective materials having different coefficients of linear expansion, and   wherein letting the tiers of the scroll start, portion be defined as a first tier, a second tier, . . . , and an n-th tier in order from a tip toward a base of the scroll start portion; and   a situation where the orbital scroll wrap and the fixed scroll wrap go out of contact with each other in the n-th tier of the scroll start portion and, among the compression chambers, two compression chambers that are not made to communicate with each other before the scroll wraps go out of contact with each other are made to communicate with each other be expressed as the n-th tier is opened,   a relief is provided in the orbital scroll wrap or the fixed scroll wrap such that while the orbiting scroll is undergoing the orbital motion from a crank angle at which the first tier is opened to a crank angle at which the n-th tier is opened, the outer-surface involute of the scroll wrap of the scroll that is made of the material having the greater coefficient of linear expansion and the inner-surface involute of the scroll wrap of the scroll that is made of the material having the smaller coefficient of linear expansion are out of contact with each other at least at an outermost one of a plurality of contact points where the two involutes are to come into contact with each other.   
     
     
         3 . The scroll compressor of  claim 2 ,
 wherein letting involute-start-point angles of the outer-surface involute curves in the respective tiers of the scroll start portion having the tiered shape be φos(1), φos(2), φos(3), . . . , and φos(n) in order from a tip toward a base of the scroll start portion, the following relationships are satisfied:
   φ os (1)>φ os (2)>φ os (3)> . . . >φ os ( n ); and
 
   0.3π<φ os (1)-φ os ( n )<0.7π.
 
   
     
     
         4 . The scroll compressor of  claim 2 , wherein the relief is provided in the orbital scroll wrap or the fixed scroll wrap such that the two involutes are out of contact with each other at the contact points excluding an innermost contact point. 
     
     
         5 . The scroll compressor of  claim 2 , wherein the orbiting scroll is made of aluminum, and the fixed scroll is made of cast iron. 
     
     
         6 . The scroll compressor of  claim 2 , wherein a ratio of a total height of the first to (n−1)-th tiers of the scroll start portion to a total height of the first to n-th tiers is 25% to 50%. 
     
     
         7 . The scroll compressor of  claim 2 , wherein a curvature radius R at a base of each of the first to (n−1)-th tiers is greater than a curvature radius at a base of the n-th tier.