Patent Document ID: 20110168011
Application ID: 12998114
Patent Flag: 0

Claim One:
1. A device for controlling the stroke of an actuator driven by a working fluid, wherein: said device for controlling the stroke comprises a flow rate control valve for controlling the amount of the working fluid in said actuator, a valve actuator for operating a valve body of said flow rate control valve, a stroke sensor for detecting a real stroke of said actuator, a target stroke-setting means for setting a target stroke of said actuator, and a flow rate control valve control device for controlling said valve actuator depending upon a feedback operation amount operated based on a deviation between the real stroke of said actuator and the target stroke; wherein said flow rate control valve is connected to a communication passage communicated with said actuator, to a pressure source passage communicated with a working fluid pressure source, and to a discharge passage for discharging the working fluid from said actuator, and is so constituted that, at the neutral position of said valve body, said communication passage is cut off from said pressure source passage and said discharge passage, and said flow rate control valve control device learns, as the operation amount at the neutral position, an operation amount of said valve actuator at a moment when a rate of change in the detection signal of said stroke sensor becomes smaller than a predetermined value, and controls said valve actuator by correcting said feedback operation amount by the operation amount at the learned neutral position.