| 摘要 |
PURPOSE:To enable slit-shaped oil paths to be formed in a cylinder main unit, when it is cast, so as to improve productivity, by forming a recessed groove, which communicates with a reservoir, on a piston slide contact surface of the cylinder main unit and the plural slit-shaped oil paths communicating with said recessed groove. CONSTITUTION:A tandem type master cylinder, which forms a secondary pressure chamber 12 in the end part of a cylinder main unit 1 increasing a pressure by moving a secondary piston 17 to the left against a return spring 18 through a primary piston 20 by depressing force of a brake pedal, outputs that increasing boost pressure as the brake force. Here the cylinder main unit 1 forms on its secondary piston slide contact surface a plurality of slit-shaped oil paths 2 connected to a recessed groove 4 communicating with a reservoir tank 6 through a supply port 3. These oil paths 2 are formed into a trapezoidal shape opened to a side of the slide contact surface. In this way, the cylinder main unit 1, when it is cast, enables the slit-shaped oil paths 2 to be formed by a core.
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