PURPOSE: To improve the smooth relative rotation of valve members and the smooth flow of pressure oil by providing both edges that run along the axial directions of extension recessed portions to be formed at the outer periphery of a second valve member, between the peripheral directions of both edges that run along the axial directions of pressure oil discharge recessed portions.

CONSTITUTION: Extension recessed portions 38 are provided respectively and extendingly from the respective end portions of three pressure oil discharge recessed portions T formed at mutually peripheral equal intervals at the outer periphery of a second valve 25 toward the axial outer part. Each extension recessed portion 38 is formed with s first portion 38a extending from one end of a pressure oil discharge recessed portion T and a second portion 38b extending from the other end. The end portion of the first portion 38a is provided extendingly to the upper part of a first valve member and is connected to an outlet port and in addition to a tank through the upper part space of the first valve. The end portion of the second portion 38b is provided extendingly to the chamfering portion 25c of the tip outer periphery edge of the second valve 25, and is connected to the tank through the lower part space of the second valve member 25.