Fluid pressure control system with an accumulator responsive to a loss of system pressure

A fluid pressure control system, comprising:

• an operational reaction force generating means for reducing a volume of a pressure chamber in response to an operation of an operating member, said operational reaction force generating means having a piston which includes a front surface facing said pressure chamber and is operatively connected to said operating member;
• a fluid pressure control valve means for adjusting and outputting an output pressure from a fluid pressure supply source which outputs a constant fluid pressure in accordance with an amount in which said operating member operates;
• and
• a stroke accumulator connected to said pressure chamber,
• wherein said stroke accumulator comprises a casing, an accumulator piston slidably received in said casing so as to define an accumulating chamber leading to said pressure chamber between said accumulator piston and said casing, a back-up piston slidably received in said casing to define a pilot chamber leading to the fluid pressure supply source between said back-up piston and said casing such that a movement of the back-up piston in a direction to reduce a volume of the pilot chamber corresponds to a movement of the back-up piston toward the accumulator piston, a first biasing means for resiliently biasing the accumulator piston in a direction to reduce a volume of said accumulating chamber, and a second biasing means having a load larger than a load of said first biasing means for resiliently biasing said back-up piston in a direction so as to reduce the volume of said pilot chamber, and wherein the resilient biasing force acting on said accumulator piston by the movement of said back-up piston toward said accumulator piston with the abnormal reduction in fluid pressure in said pilot chamber is increased more than the resilient biasing force acting on said accumulator piston when the fluid pressure in said pilot chamber is normal.