Patent ID: 7934377

Claim:
A method of controlling an apparatus for easing an impact on a boom of an excavator, including a boom cylinder connected to a hydraulic pump, a main control valve for controlling hydraulic fluid being supplied to the boom cylinder, an operation lever for generating an operation signal for driving the boom cylinder, operation lever detection means for detecting boom up and boom down signal pressures according to an amount of manipulation of the operation lever, boom cylinder pressure detection means for detecting pressures generated in a large chamber and a small chamber of the boom cylinder, a controller for receiving an input of detected signals from the boom cylinder pressure detection means and the operation lever detection means, and electro proportional pressure reducing valves for controlling the pilot signal pressure being supplied to the main control valve, the method comprising: receiving an input of the boom up and boom down signal pressures from the operation lever detection means and the operating pressures of the boom cylinder from the boom cylinder pressure detection means; obtaining a reduction rate of manipulation of the operation lever for a predetermined time in accordance with the received input of the boom up and boom down signal pressures, and judging that the operation lever has been suddenly stopped if the obtained value of the reduction rate is smaller than a predetermined value; receiving the pressure value of the compression chamber of the boom cylinder when the boom is stopped, comparing the received pressure value with a predetermined value, and predicting a boom vibration if the received pressure value is larger than the predetermined value; calculating and outputting a control value of the electro proportional pressure reducing valve so as to drive a spool of the main control valve if the boom vibration is predicted due to the sudden stop of the operation lever; and predicting an end of the boom vibration by checking a difference in pressure between the compression chamber and the expansion chamber of the boom cylinder when the boom is stopped, and controlling the output of the electro proportional pressure reducing valve to be stopped.