| 摘要 |
<p>A hydraulic driving system in a construction machine, comprising: a variable capacity type hydraulic pump (1); a pump regulator (2) for controlling the discharge flowrate of this hydraulic pump; a plurality of hydraulic actuators (7) driven by pressure oil from the hydraulic pump; a plurality of directional changeover valves (4A - 4D) for controlling flows of pressure oil supplied from the hydraulic pump to the plurality of hydraulic actuators; a center bypass line (23) for serially connecting the center bypasses of the plurality of directional changeover valves (4A - 4D) to a low pressure circuit (22); a plurality of throttles (26) for bleedoff provided on the center bypass line, for operating in cooperation with the associated directional changeover valves, respectively, to change the opening degrees; a fixed throttle (5) provided on the center bypass line, for generating control pressure (PZ); and a pressure detecting device (8) for detecting control pressure to output an associated electric signal (E); wherein the system further comprises: a memory device (9c) for previously setting a plurality of pump flowrate characteristics (40, 41, 42) for specifying the relationship between a value of the electric signal (E) output from the pressure detecting device (8) and a discharge flowrate (Q) of the hydraulic pump (1); a selecting device (12) for outputting a command signal (ES) for selecting one of the plurality of pump flowrate characteristics (40, 41, 42) set in the memory means; and an operation device (9b) for obtaining the discharge flowrate (Q) associated with the value of the electric signal (E) output from the pressure detecting means (8) in accordance with the pump flowrate characteristics selected by the command signal (ES) and outputting a driving signal (ED) corresponding to the discharge flowrate; whereby the pump regulator is driven in response to this driving signal.</p> |
