Drain valve device, flush water tank device equipped with this flush valve device, and flush toilet equipped with this flush water tank device

摘要

PROBLEM TO BE SOLVED: To provide a drain valve device capable of effectively restraining reduction in an instantaneous flow rate of washing water.SOLUTION: A drain valve device 8 includes: a body part 18 having a drain port part 14 attached to a drain port 6b formed on a washing water tank 6, and a valve element for opening and closing the drain port part; and a cylindrical body 20 attached to the body part. The cylindrical body includes a lower opening part 46 attached to the drain port part of the body part attached to the washing water tank, a bottom surface part 48 protruding to an outer peripheral side from the lower opening part and forming a bottom surface of the cylindrical body, a side wall part 50 protruding upward from the bottom surface part and surrounding the body part, and an upper opening part 52 continued to an upper end of the side wall part. A curved surface is formed on the upper opening part of the cylindrical body in such a manner of separating from the body part toward the upper end from the lower end.SELECTED DRAWING: Figure 4