Patent ID: 7387061

Claim:
A control apparatus for a hydraulic cylinder, comprising: the hydraulic cylinder including a piston slidably disposed in a cylinder tube and a pair of oil chambers defined by the piston; a cushion chamber disposed in the vicinity of each end of the hydraulic cylinder to throttle inflow or out flow of an operating oil caused by the piston moving close to a piston stroke end; a pressure sensor to detect pressure of the cushion chamber; a control valve assembly disposed in a passage to supply/drain the operating oil to and from the oil chambers of the hydraulic cylinder for varying a flow amount of the operating oil, wherein the control valve assembly includes a first flow control valve and second flow control valve which are interposed in the supply/drain passage respectively, and further comprises a control valve disposed in the supply/drain passage in series with both the first flow control valve and the second flow control valve, wherein operation of the control valve determines a direction that the piston moves within the cylinder tube; and a controller to determine a piston stroke end range based upon a output of the pressure sensor, and vary an opening degree of the control valve assembly to lower a moving speed of the piston at the piston stroke end range.