Patent attributes
To provide a hydraulic drive system for a work machine capable of securing a favorable operability in the case where hydraulic fluid discharged from a hydraulic actuator is regenerated for driving other hydraulic actuator. The hydraulic drive system for a work machine includes: a regeneration line that connects a bottom-side hydraulic chamber of a hydraulic cylinder to a portion between a hydraulic pump and a second hydraulic actuator; a regeneration flow rate adjustment device that supplies at least part of the hydraulic fluid discharged from the bottom-side hydraulic chamber to a portion between the hydraulic pump and the second hydraulic actuator through the regeneration line; a differential pressure calculating section that reads a pressure in the bottom-side hydraulic chamber of the hydraulic cylinder detected by a first pressure sensor and a pressure between the hydraulic pump and the second hydraulic actuator detected by a second pressure sensor, and calculates a differential pressure, or a differential pressure sensor; and a control unit that controls the regeneration flow rate adjustment device such as to gradually increase the flow rate of the hydraulic fluid flowing through the regeneration line according to an increase in the differential pressure calculated by the differential pressure calculation section or in the differential pressure detected by the differential pressure sensor.
