PROBLEM TO BE SOLVED: To provide an air motor and a medical handpiece, preventing leakage of pressure fluid and providing sufficient rotating torque even at low speed.SOLUTION: In this air motor 13, a valve member 60 includes a first air supply passage outlet 65 formed in an end surface 61 opposed to a fixed member 50. The fixed member 50 has a second air supply passage inlet 57 formed in an end surface 56 opposed to the valve member 60. The end surface 61 of the valve member 60 has a double sealing member, that is, an inner sealing member 68 and an outer sealing member 69 which surround the first air supply passage outlet 65. In the air motor, it is possible to employ, based on the rotation of the valve member 60, a state where only an inner area 80 surrounded by the inner sealing member 68 is opposed to the second air supply passage inlet 57, a state where an outer area 81 surrounded by the inner sealing member 69 and outer sealing member 69 is opposed to the second air supply passage inlet 57 together with the inner area 80, and a state where only the outer area 81 is opposed to the second air supply passage inlet 57.COPYRIGHT: (C)2011,JPO&INPIT【課題】圧力流体の漏れを防止し、低速時にあっても十分な回転トルクが得られるエアモータ及び医療用ハンドピースを提供する。【解決手段】エアモータ13において、弁部材60は、固定部材50に対向する端面61に第1給気路出口65を有する。固定部材50は、弁部材60に対向する端面56に第2給気路入口57を有する。弁部材60の端面61は、第1給気路出口65の周りを囲む二重の内側シール部材68と外側シール部材69を有する。このエアモータでは、弁部材60の回転に基づいて、内側シール部材68に囲まれた内側領域80のみが第2給気路入口57に対向する状態と、内側シール部材69と外側シール部材69に囲まれた外側領域81が内側領域80と共に上記第2給気路入口57に対向する状態と、外側領域81のみが第2給気路入口57に対向する状態を採り得るようにした。【選択図】図12
