Mounting structure for diaphragm and retainer

A mounting structure comprising:

• a diaphragm that is formed to have a disc shape and includes a fixation part positioned in an outer circumferential part of the diaphragm, a movable part positioned in a central part of the diaphragm, and a linking part linking the fixation part and the movable part together, wherein a side of the diaphragm facing a pump chamber is defined as a front side and a side of the diaphragm opposite from the pump chamber is defined as a rear side;
• a movable shaft that has an insert member attached at a tip end of the movable shaft and that drives the movable part to reciprocate in an axial direction while a tip end part of the insert member is inserted in the movable part of the diaphragm;
• and
• a retainer that has an annular shape, is attached to the tip end of the movable shaft coaxially with the movable shaft, supports the rear side of the movable part of the diaphragm, and reciprocates, together with the movable part, in an advancement/retreat direction to and from the pump chamber, wherein
• the diaphragm has a first curved part recessed toward the pump chamber and provided over an entire circumference of the diaphragm in the circumferential direction, on the rear side of a boundary section between the movable part and the linking part,
• the retainer includes an abutment part that abuts against the rear side of the diaphragm and a second curved part that is formed in an outer circumferential position of the abutment part so as to protrude farther toward the pump chamber than the abutment part and provided over an entire circumference of the retainer in the circumferential direction, and that mates with the first curved part, and
• a part of the movable part of the diaphragm is sandwiched and held between an inner circumferential part of the second curved part and the abutment part of the retainer and the tip end part of the insert member, and reciprocates in the axial direction together with the movable shaft.