Patent ID: 6907732

Claim:
A master cylinder device for a brake comprising: a master cylinder body formed along a longitudinal axis, the master cylinder body having an upper end and a lower end, and a cylindrical cylinder bore formed in the master cylinder body such that the cylinder bore opens to the lower end, the master cylinder body being oriented such that the longitudinal axis is substantially vertical; a reserve tank provided integrally with the master cylinder body so as to have a fluid reserving portion for feeding hydraulic fluid for the brake; a fluid passing port provided in the fluid reserving portion of the reserve tank, the fluid passing port having an opening area smaller than an opening cross-sectional area of the fluid reserving portion; and a communicating passage connecting the fluid passing port to the cylinder bore, wherein the communicating passage is formed on the side portion of the master cylinder body to extend substantially in parallel with an axis of the master cylinder body and configured to open into the reserved tank; wherein the reserve tank is disposed on an upper end of the master cylinder body; and wherein a piston is provided in the cylinder bore of the master cylinder body, and the piston is configured to be vertically slidable along the longitudinal axis of the master cylinder body within the cylinder bore.