PURPOSE: A fluid pressure revolution system of an excavator is provided to recycle a rotating motion energy in the rotation deceleration an upper rotating body. CONSTITUTION: A fluid pressure revolution system of an excavator comprises a hydraulic pump(30), a capacity variable pivot motor(35), an accumulator(36), a first flow control valve(37), a second flow control valve(38), a third flow control valve(40), and a fourth flow control valve(42). The hydraulic pump is connected to an engine. The pivot motor is connected to the discharge path of the hydraulic pump through a first path and a second path. The accumulator is installed in the discharge path and the intersection of first and second paths. The first flow control valve is installed in the first path. The fourth flow control valve is switched according to the input signal from outside when supplying the working fluid to the capacity variable pivot motor through the first flow control valve.
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