Hydraulic circuit and method for controlling the same

Abstract

A hydraulic circuit includes a pump driven by a motor, an inverter for controlling the motor, and an accumulator. The inverter controls rotational speed of the motor such that the pump always discharges hydraulic fluid at a fixed flow rate, which is the sum of an average necessary flow rate and an adjustment flow rate. The accumulator operates, when the fixed flow rate and a necessary flow rate differ, in order to accumulate or discharge the hydraulic fluid to thereby secure the necessary flow rate.

1 . A hydraulic circuit which comprises:
 a pump driven by a motor;   an inverter for controlling the motor; and   an accumulator;   wherein the inverter controls rotational speed of the motor such that the pump always discharges hydraulic fluid at a fixed flow rate, which is the sum of an average necessary flow rate and an adjustment flow rate; and   wherein the accumulator operates, when the fixed flow rate and a necessary flow rate differ, in order to accumulate or discharge the hydraulic fluid to thereby secure the necessary flow rate.   
     
     
         2 . A hydraulic circuit according to  claim 1 , wherein the accumulator comprises a plurality of accumulators which differ in accumulation pressure from one another. 
     
     
         3 . A hydraulic circuit according to  claim 2 , wherein the plurality of accumulators are comprised of a low pressure accumulator, an intermediate pressure accumulator whose accumulation pressure is higher than that of the low pressure accumulator, and a high pressure accumulator whose accumulation pressure is higher than that of the intermediate pressure accumulator. 
     
     
         4 . A method for controlling a hydraulic circuit which comprises a pump driven by a motor, an inverter for controlling the motor, and an accumulator, the method comprising the steps of:
 causing the inverter to control rotational speed of the motor such that the pump always discharges hydraulic fluid at a fixed flow rate, which is the sum of an average necessary flow rate and an adjustment flow rate; and   causing the accumulator to operate, when the fixed flow rate and a necessary flow rate differ, in order to accumulate or discharge the hydraulic fluid to thereby secure the necessary flow rate.