Automatic cushioning control apparatus for cylinder of working machine

An automatic cushioning control apparatus for a hydraulic cylinder, wherein said hydraulic cylinder is capable of extending movement and retracting movement as strokes in stroke directions along a stroke path in response to a lever signal from a lever device, the stroke path having a full stroke length and a stroke end, said automatic cushioning control apparatus comprising:

• said lever device for establishing said lever signal,
• a cylinder position detecting means for detecting a position of the hydraulic cylinder along the stroke path in a direction of a movement of the hydraulic cylinder as a stroke of the hydraulic cylinder along the stroke path and establishing a position signal representative thereof,
• a moving direction detecting means for detecting a direction of a movement of the hydraulic cylinder as a stroke along the stroke path and establishing a direction signal representative thereof,
• a lever gain computing means for computing a lever gain K in accordance with said position signal and said direction signal and outputting a lever gain signal representative thereof, the thus computed lever gain satisfying a relationship 0<K<1 and gradually changing from one toward zero in accordance with a distance from the hydraulic cylinder to said stroke end when the hydraulic cylinder is moving toward said stroke end,
• a multiplication element for multiplying the lever signal from the lever device by said lever gain signal and establishing an output signal representative of the multiplication product, and
• a cylinder control means for controlling the movement of the hydraulic cylinder along the stroke path in accordance with the output signal from the multiplication element.

A method for automatic cushioning of a hydraulic cylinder, wherein said hydraulic cylinder is capable of extending movement and retracting movement along a stroke path in response to a lever signal from a lever device, the stroke path having a full stroke length and a stroke end, said method comprising the steps of:

• establishing a lever signal,
• detecting a position of the hydraulic cylinder along the stroke path in a direction of a stroke of the hydraulic cylinder and establishing a position signal representative thereof,
• detecting the direction of a movement of the hydraulic cylinder along the stroke path and establishing a direction signal representative thereof,
• computing a lever gain K in accordance with said position signal and said direction signal and outputting a lever gain signal representative thereof, the thus computed lever gain satisfying a relationship 0<K<1and gradually changing from one toward zero in accordance with a distance from the hydraulic cylinder to said stroke end when the hydraulic cylinder is moving toward said stroke end,
• multiplying the lever signal by said lever gain signal and establishing an output signal representative of the multiplication product, and
• controlling the movement of the hydraulic cylinder along the stroke path in accordance with the output signal representative of the multiplication product.