In some scroll compressors the crankshaft is supported at one end and near the other end such that an eccentric drive pin is overhung or cantilevered with respect to the bearing support. The drive pin coacts with the orbiting scroll of the compressor through a slider block or bushing which permits the drive pin to rotate while the orbiting scroll is held to an orbiting motion through an anti-rotation mechanism such as an Oldham coupling. The coaction between the drive pin and slider block is complicated by the nature of the force transmission. If the contacting members are not aligned, there will be edge loading, but there is a deflection of the cantilevered drive pin and/or crankshaft under load which produces a change in the nature and location of the contact between the drive pin and slider block. This change, in turn, produces changes in the nature and location of the contact between the slider block or bushing and the orbiting scroll which can also produce edge loading.
In U.S. Pat. No. 4,836,758 this deflection of the drive pin and/or crankshaft under load is addressed by having the desired contact take place as a result of the deflection under load. In one example the canting or deflection of the crankshaft causes the drive pin to go from a line contact to an area contact with the slider block or bushing. In a second example the drive pin deflects or cants causing it to go from a line contact to an area contact with the slider block or bushing. In a third example, there is area contact between the drive pin and bushing, but only a line contact between the bushing and hub of the orbiting scroll until deflection of the crankshaft takes place. In each case, the line contact is at the point closest to the orbiting scroll which is the point of greatest overhang. As a result, the forces act at the greatest lever arm until area contact is achieved. Presumably, at forces greater than the design load there will be a line contact at the point farthest from the orbiting scroll if there is continued deflection. These designs overcompensate in that the desired contact surface must deform to obtain an even contact with the bushing or slider block which is actually applying the load. However, it is only at one load, with tolerances, in which the parts align for surface contact.
Commonly assigned U.S. patent application Ser. No. 734,009 filed Jul. 22, 1991 provides a curved surface on the drive pin or bore of the slider block such that linear contact occurs between the two members. Upon flexure or canting of the drive pin and/or crankshaft under load, the line of contact moves relative to the surfaces but remains at essentially the same axial position. The foregoing solutions do not address the coaction between the slider block and orbiting scroll relative to edge loading due to misalignment due to clearances and tolerances.