| 摘要 |
PURPOSE:To facilitate the sensing of a trouble, by disposing a resilient plug in a discharge hole communicating a closed air chamber in a master cylinder with the outside so that the plug expands when the pressure in the air chamber is increased exceeding a predetermined value, and piercing a hole in the plug when the latter expands so as to easily discharge leakage oil. CONSTITUTION:When either one of seal members 301, 302, 311, 312 fitted respectively on right and left pressure receiving pistons 91, 92 or valve moving pistons 111, 112 in master cylinder M, is worn or damaged, and therefore, hydraulic leaks into an air chamber 8 from input hydraulic chambers 181, 182, the pressure in the air chamber is increased. When this pressure exceeds a predetermined value, the outer wall of a resilient plug 34 expands, and therefore, the tip of a needle pierces into the expanding part of the plug 34 so that a hole is formed in the latter. Thereby, hydraulic oil pooled in the air chamber 8 is made to flow out to the outside through the hole opened by the needle. The flow-out of hydraulic oil causes the oil level of an oil tank R to abnormally lower so that an oil level sensor S is actuated to energize an alarm.
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