| 摘要 |
PURPOSE:To enhance the operational reliablity of a parking brake, by arranging means for sealing liquid pressure in a wheel cylinder in assoication with a parking brake liver between each master cylinder and each wheel cylinder so that an auxiliary parhing brake device is formed. CONSTITUTION:Under the condition in which a parking brake 17 is not actuated, since a seating preventing member 11 in a pressure holding device 1 checks the seating of a ball valve 8 onto a valve seat 9, ports 4 through 6 and communicated together and therefore, brake action similar to normal brake operation may to obtained. Meanwhile, when the parking brake 17 is manipulated while a brake pedal is stepped in, a rotary shaft 14 is rotated in association with the pulling action of a cable 16, and the seating preventing member 11 is retracted into a hole 9a in the valve seat 9 by a cam part 14 on the rotary shaft 14. Therefore, the ball valve 8 seats on the value seat 9 so that liquid pressure on the wheel cylinder side adjacnent to an one-way valve 10 is confined, thereby liquid pressure upon the valve seating is maintained. Accordingly, the brake is maintained in its operating condition even if the brake pedal is released. |
