Patent ID: 7497080
Filing Date: 2009-03-03
Classification: E02F

Abstract:
1. A hydraulic controlling device of a working machine, comprising: a lower traveling body; an upper rotating body mounted on the lower traveling body; a working attachment mounted to the upper rotating body; hydraulic actuator groups including left and right travel motors and working actuators that are actuators other than the left and right travel motors, the hydraulic actuator groups being divided into a first group and a second group, the first group including one of the left and right travel motors, the second group including the other of the left and right travel motors; first and second pumps serving as hydraulic sources that are driven by an engine; and a straight travel valve adapted to switch flow paths of oil discharged from the pumps, wherein, when performing a single operational process in which a travel operation and a working operation, which is an operation other than the travel operation, are performed separately, the straight travel valve is at a neutral position and supplies the oil discharged from the separate pumps to the first and second groups, wherein, when performing a combined operational process in which the travel operation and the working operation are performed at the same time, the position of the straight travel valve is switched to a straight travel position and the straight travel valve supplies the oil discharged from the separate pumps to both of the travel motors and the working actuators, wherein, when the neutral position of the straight travel valve is switched to the straight travel position, pump lines of both of the pumps are connected to each other by a connection path, and wherein the hydraulic controlling device further comprises controlling means for performing an opening controlling operation that reduces an opening amount of the connection path at a low-rotational-speed side in accordance with a rotational speed of the engine when performing the combined operational process.