Patent ID: 7127888
Filing Date: 2006-10-31
Classification: E02F,F15B

Abstract:
1. A hydraulic drive unit arranged on a construction machine and provided with a main hydraulic pump, a first hydraulic cylinder and second hydraulic cylinder each of which has a rod chamber and a bottom chamber, a first directional control valve for controlling a flow of pressure oil to be fed from said main hydraulic pump to said first hydraulic cylinder, a second directional control valve for controlling a flow of pressure oil to be fed from said main hydraulic pump to said second hydraulic cylinder, a first control device for performing switching control of said first directional control valve, and a second control device for performing switching control of said second directional control valve, wherein: said hydraulic drive unit is provided with a communication control system which brings said rod chamber of said first hydraulic cylinder and said bottom chamber of said second hydraulic cylinder into communication with each other when a pressure in said rod chamber of said first hydraulic cylinder has risen to a high pressure of at least a predetermined pressure.