Hydraulic energy recovery apparatus for working machine

A hydraulic energy recovery apparatus for a working machine comprising:

• a main pump that is driven by a prime mover mounted on a working machine and delivers a hydraulic fluid as pressurized oil;
• a hydraulic actuator that is driven by the pressurized oil delivered from the main pump;
• and
• an accumulator that recovers a part or all of returned oil from the hydraulic actuator, wherein the hydraulic energy recovery apparatus for the working machine includes:
• a pressure sensor that detects a pressure of the accumulator;
• a temperature sensor that detects a temperature of the hydraulic fluid;
• a reset device that is reset at a time of a replacement of the accumulator;
• and
• a controller to which signals from an operation lever device configured to operate the hydraulic actuator, the pressure sensor, the temperature sensor, and the reset device are input, and wherein the controller includes:
• an elapse time measuring section that measures a time elapsed since an initial use of the accumulator based upon a signal from the reset device;
• a number-of-operations measuring section that measures a number of operations of the accumulator based upon a signal from the pressure sensor;
• a gas permeation amount estimating section that estimates a gas permeation amount of the accumulator based upon outputs from the elapse time measuring section, the pressure sensor, and the temperature sensor;
• a sealed gas pressure estimating section that estimates a sealed gas pressure of the accumulator from a rising state of an accumulator pressure in a case of starting accumulation from a state where the accumulator pressure is equal to a tank pressure, based upon the signal from the pressure sensor;
• and
• an accumulator degradation determining section that determines a degradation condition of the accumulator based upon at least one output of outputs from the elapse time measuring section, the number-of-operations measuring section, the gas permeation amount estimating section, and the sealed gas pressure estimating section, and outputs the determination result.