Valve mechanism for discharging fluid from a valve port

Abstract

A flow rate adjusting valve includes: a casing including an inlet and an outlet and also including a channel connecting the inlet and the outlet to each other; a cylindrical valve port member disposed in the channel and having a valve port penetrating the valve port member in an upstream-downstream direction; and a valve body configured to move forward and backward to the valve port from a downstream side to thereby adjust an opening degree of a downstream opening of the valve port. The valve port includes a narrowing portion whose opening diameter is smaller than an opening diameter of an upstream opening, the valve body includes a tapered portion that enters the valve port when the valve body moves forward and a flange portion disposed at a downstream end of the tapered portion and having a contact surface that is parallel to an end surface of the valve port member and is brought into surface contact with the end surface while the valve port is fully closed, and when the downstream opening is at a predetermined opening degree, a passage area of the fluid in the valve port is at minimum in the narrowing portion.