Aligning drive mechanism and positioning apparatus having this mechanism

An aligning drive mechanism, comprising:

• a guide hole (10) as a reference surface for aligning is formed in a housing (6),
• an output member (13) is inserted into the guide hole (10) axially movably,
• the output member (13) is provided with a plurality of guided portions (21, 22) axially at intervals,
• an annular aligning space (31, 32), which narrows in either one axial direction, is formed between at least one of the guided portions (21, 22) and the guide hole (10),
• a shuttle member (41, 42), which is diametrically expandable and contractible, is inserted into the aligning space (31, 32), the shuttle member (41, 42) is supported on either one of the guide hole (10) or the guided portion (21, 22) axially movably, and configured to make a tapering engagement with the other of the guided portion or the guide hole (21, 22 or 10),
• the shuttle member (41, 42) is urged by an urging means (51, 52) in such a direction as to tighten the tapering engagement,
• the output member (13) is configured to be axially reciprocatable by
• a driving means (D).