chamber 84 the elastic valve body member 76 may be a leaf spring which is soft in the axial direction and is rigid movement of the first elastic plate shaped portion 76 a with respect to the valve hole 72 is shown by broken lines in fig3 the elastic valve body member 76 operates as a valve body which can be elastically displaced so as to open and close the valve hole 72 the first elastic plate shaped portion 76 a and the second elastic plate shaped portion 76 b form an integral member that is elastic valve body member 76 which is continuous to each other for example in a case where the elastic valve body member 76 has a circular plate shape the first elastic plate shaped portion 76 a may be a semicircular portion alternatively a fan shaped region or an arc shaped region which is positioned on one side of the circular plate and the second elastic plate shaped portion 76 b may be a semicircular portion alternatively a fan shaped region or an arc shaped region positioned on a side opposite to the first elastic plate shaped portion 76 a in addition the elastic valve body member 76 includes a slit 76 c which is positioned between the first elastic plate shaped portion 76 a and the second elastic plate shaped portion 76 b the elastic pressing member 78 is disposed along the second elastic plate shaped portion 76 b so as to be elastically deformed along with the elastic valve body member 76 the elastic pressing member.