Patent ID: 6971859

Claim:
A diaphragm unit comprising: a diaphragm having a center point and an outer peripheral portion; and a diaphragm case comprising: a fixing surface for supporting the diaphragm at the outer peripheral portion thereof, thereby defining a fluid chamber in the diaphragm case, inflow of fluid into the fluid chamber and outflow of the fluid from the fluid chamber being accomplished as the diaphragm is deformed; and a regulating surface for forming an inner surface of the fluid chamber, thereby providing a limit of deformation of the diaphragm, the regulating surface comprising: a convex surface region formed continuously with the fixing surface for supporting the diaphragm at a portion thereof adjacent to the outer peripheral portion; and a concave surface region formed continuously with the convex surface region for supporting the diaphragm at a portion thereof adjacent to the center point, wherein curvatures of the convex surface region and the concave surface region are the same.