| 摘要 |
<p>[Problem] To increase the turning efficiency of a turbine and also prevent negative pressure from occurring inside a turbine chamber due to inertial rotation of turbine blades when use of a handpiece comes to an end and air suction is halted. [Solution] A handpiece comprising: a head part which has rotatable turbine blades disposed therein; a neck part which is provided extending to the head part and is held by an operator; and a grip part which is provided extending backward from the neck part, the handpiece further comprising an air supply pipeline which supplies air to drive the turbine blades and an air discharge pipeline which discharges air after the turbine blades are rotated, wherein a discharge-air return flow pipeline (16) is formed in the air discharge pipeline (12) and comprises: a return flow inlet (19) which opens at one end of the discharge-air return flow pipeline (16); and a discharge outlet (17) which opens in the turbine chamber (15) at the other end of the discharge-air return flow pipeline (16). The value obtained by dividing the diameter of the return flow outlet (17) of the return flow pipeline (16) by the diameter of an air supply inlet (14) of the air supply pipeline (11) is set to 1 or less, and the return flow outlet (17) of the return flow pipeline opens in the turbine chamber (15) that is close to the air supply inlet and is between the air supply inlet (14) and the discharge outlet (17).</p> |
