| 摘要 |
PROBLEM TO BE SOLVED: To prevent generation of noise in a stopper part of a rotor, form such a structure that a valve does not lock even if the valve is composed so as to be driven by a low torque, and prevent generation of a reversal noise of the rotor. SOLUTION: A male screw rod 7 is fixed on a rotor 18, and a driving male screw 31 of its front edge is screwed on a first female screw part 32 of a female member 10. A second female screw part 33 is provided on the female member 10, and is screwed on a lock release male screw 35 of a valve plug 34 whose pitch is larger than that of the driving male screw. The male screw member 10 and the valve element 34 are connected with a torsional coil spring 13, and a locking part of its lower end is engaged with a slit 12 of a locking ring fixed on a valve main body to form a detent. A ball 22 supported with a coil spring 23 is provided on an upper end part of the male screw rod 7 to form a stopper in an axial direction when all are shut.
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