A hydraulic driving apparatus provided in a work machine including a working device to hydraulically drive the working device, the working device including a boom capable of being raised and lowered, an arm connected to a tip of the boom so as to be capable of rotational movement, and a tip attachment attached to a distal end of the arm, the hydraulic driving apparatus comprising:
- a boom actuator configured to receive supply of hydraulic fluid to thereby raise and lower the boom;
- an arm actuator configured to receive supply of hydraulic fluid to thereby bring the arm into rotational movement;
- an attachment actuator configured to receive supply of hydraulic fluid to thereby actuate the tip attachment;
- a pump power source configured to generate power;
- a first hydraulic pump that is a variable displacement pump to be connected to a first main actuator that is selected from the boom actuator and the arm actuator, the first hydraulic pump being configured to be operated by the power provided from the pump drive source so as to discharge hydraulic fluid to supply the hydraulic fluid to the first main actuator;
- a second hydraulic pump that is a variable displacement pump connected to a second main actuator and the attachment actuator, the second main actuator being one of the boom actuator and the arm actuator and different from the first main actuator, the second hydraulic pump being configured to be operated by the power provided from the pump drive source so as to discharge hydraulic fluid to supply the hydraulic fluid to the second main actuator and the attachment actuator;
- a first main control valve interposed between the first hydraulic pump and the first main actuator, the first main control valve being operable to change a flow rate of hydraulic fluid supplied from the first hydraulic pump to the first main actuator;
- a second main control valve interposed between the second hydraulic pump and the second main actuator, the second main control valve being operable to change a flow rate of hydraulic fluid supplied from the second hydraulic pump to the second main actuator;
- an attachment control valve interposed between the second hydraulic pump and the attachment actuator, the attachment control valve being operable to change a flow rate of hydraulic fluid supplied from the second hydraulic pump to the attachment actuator;
- a first main operation device configured to receive a first main operation for moving the first main actuator and to operate the first main control valve in accordance with the first main operation;
- a second main operation device configured to receive a second main operation for moving the second main actuator and to operate the second main control valve in accordance with the second main operation;
- an attachment operation device configured to receive an attachment operation for moving the attachment actuator and to operate the attachment control valve in accordance with the attachment operation;
- a first merging selector valve provided between the first hydraulic pump and the second main actuator, the first merging selector valve being configured to be opened, on condition that the second main operation for operating the second main actuator at least in a raising direction is applied to the second main operation device, to allow hydraulic fluid discharged from the first hydraulic pump to merge with hydraulic fluid discharged from the second hydraulic pump to be supplied to the second main actuator;
- and
- a power distribution control device configured to operate first pump displacement that is displacement of the first hydraulic pump and second pump displacement that is displacement of the second hydraulic pump to thereby control distribution of the power provided from the pump power source to the first hydraulic pump and the second hydraulic pump;
- wherein:
- the power distribution control device is configured to operate the first pump displacement and the second pump displacement so as to make the distribution of the power from the pump drive source to the second hydraulic pump be smaller and to make the distribution of the power from the pump drive source to the first hydraulic pump be larger when a specified combined operational action is performed on the second main operation device and the attachment operation device than when a second main single operational action is performed on the second main operation device;
- the specified combined operational action is an action of applying the second main operation for operating the second main actuator in the raising direction to the second main operation device to thereby open the first merging selector valve while simultaneously applying the attachment operation to the attachment operation device;
- the second main single operational action is an action of applying the second main operation to the second main operation device while not applying the attachment operation to the attachment operation device;
- the power distribution control device includes:
- a flow rate ratio calculation section configured to calculate a flow rate ratio, based on the first main operation, the second main operation, and the attachment operation, the flow rate ratio being a ratio between a first main flow rate that is a flow rate of hydraulic fluid to be supplied from the first hydraulic pump to the first main actuator, a second main flow rate that is a flow rate of hydraulic fluid to be supplied from the second hydraulic pump to the second main actuator, an attachment flow rate that is a flow rate of hydraulic fluid to be supplied from the second hydraulic pump to the attachment actuator, and a first merging flow rate that is a flow rate of hydraulic fluid to be supplied from the first hydraulic pump to the second main actuator through the first merging selector valve;
- a power distribution calculation section configured to calculate a power distribution of the first hydraulic pump and the second hydraulic pump based on the flow rate ratio calculated by the flow rate ratio calculation section, the power distribution being the distribution of respective powers to be provided to the first hydraulic pump and the second hydraulic pump;
- and a pump displacement operation section configured to operate the first pump displacement and the second pump displacement so as to obtain the calculated power distribution, and
- the flow rate ratio calculation section is configured to reduce a ratio of the attachment flow rate in accordance with the second main operation applied to the second main operation device in the specified combined operational action.