Patent ID: 6898932
Filing Date: 2005-05-31
Classification: E02F,F15B

Abstract:
1. A hydraulic driving unit mounted on a construction machine and provided with a main hydraulic pump, a first hydraulic cylinder and second hydraulic cylinder driven by pressure oil delivered from said main hydraulic pump, a first directional control valve for controlling a flow of pressure oil to be supplied from said main hydraulic pump to said first hydraulic cylinder, a second directional control valve for controlling a flow of pressure oil to be supplied from said main hydraulic pump to said second hydraulic pump, a first control device for selectively controlling said first directional control valve, and a second control device for selectively controlling said second directional control valve, wherein: said hydraulic driving unit is provided with a communication controller to bring a rod chamber of said first hydraulic cylinder and a bottom chamber of said second hydraulic cylinder into communication with each other when a bottom pressure of said second hydraulic cylinder has increased to a high pressure equal to or higher than a predetermined pressure.