| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve a constitution of a communication passage (communication passage provided on a cap) for making a reservoir connection port communicate with a first pressure chamber in a brake master cylinder. SOLUTION: In the brake master cylinder, a first pressure chamber R1 communicates with a reservoir connection port 11b through a piston port 31a, a first communication passage (communication groove 26a) and a second communication passage provided on a cap 12 at a retreat position of a first piston 31. The first communication passage is provided near a rear side of a seal cup 24. The second communication passage is constituted by an annular groove 12b having a larger diameter than an outer diameter of the seal cup 24, formed near a rear side of the seal cup 24, opened to an inner periphery of the cap 12 and communication with the first communication passage; and a communication hole provided toward from an outer periphery of the cap 12 to a front outer periphery portion of the annular groove 12d, making the annular groove 12d communicate with the reservoir connection port 11b and upwardly toward the reservoir connection port 11b.</p> |
