Hydraulic brake booster

摘要

In a proportional booster valve V, a primary reaction piston 37 and a secondary reaction piston 38 are provided between a control piston 23 which faces at one end thereof toward a control pressure chamber 25 into which hydraulic pressure outputted from a primary master cylinder is inputted a boost pressure chambers 44 connected to secondary master cylinders, the primary reaction piston 37 being adapted to transmit at all times to the control piston 23 a reaction force corresponding to hydraulic pressure of the boost pressure chamber 44, the secondary reaction piston 38 being adapted to transmit to the control piston 23 a reaction force corresponding to the hydraulic pressure of the boost pressure chamber 44 as the hydraulic pressure of the boost pressure chamber 44 exceeds a set hydraulic pressure. <IMAGE>