Cap for master cylinder reservoir

A cap for a master cylinder reservoir in which a cover cap and a body cap are connected to each other, a passage communicating with an inside and an outside of the reservoir is formed in a space formed between the cover cap and the body cap, and a diaphragm is disposed in said space to provide a valve function, wherein

• said cover cap has a cylindrical portion extending downward at a center portion on a lower surface and an annular protrusion which is formed downward on an outer side of said cylindrical portion, a groove traversing said annular protrusion being formed,
• said body cap has a funnel portion with a small-diameter side opening to a fluid storing chamber vertically at a center portion and a notch passage on an upper portion of a large-diameter side, a groove being formed in an outer surface and a flat surface on said large-diameter side,
• said diaphragm has an annular fixed portion at a center portion in a radial direction, an annular lip portion yieldingly urged against an outer surface of said cylindrical portion of said cover cap inside of said annular fixed portion, and an annular valve portion yieldingly urged against said flat surface of said body cap outside of said annular fixed portion,
• said annular fixed portion of said diaphragm is fitted between an inner periphery of said annular protrusion of said cover cap and an outer periphery of said funnel portion of said body cap,
• said annular lip portion forms a suction valve together with said outer surface of said cylindrical portion of said cover cap, and
• said annular valve portion forms an exhaust valve together with a lower surface of said body cap.