Construction machine
The construction machine includes: a work implement driven by a first hydraulic actuator and a second hydraulic actuator; a first directional control valve controlling a flow rate and a direction of a hydraulic fluid supplied to the first hydraulic actuator; a first speed-up directional control valve provided in a second pump line and controlling a flow rate and a direction of a hydraulic fluid supplied to the first hydraulic actuator; a second directional control valve controlling a flow rate and a direction of a hydraulic fluid supplied to the second hydraulic actuator; an excavation load sensor that detects an excavation load imposed on the work implement; and a first speed-up control section that drives the first speed-up directional control valve, and the first speed-up control section is configured to control a driving amount of the first speed-up directional control valve in response to the excavation load.
1. A construction machine comprising:
a first hydraulic actuator;
a second hydraulic actuator;
a work implement driven by the first hydraulic actuator and the second hydraulic actuator;
a first hydraulic pump;
a second hydraulic pump;
a first directional control valve provided in a first pump line that is a delivery hydraulic line of the first hydraulic pump and controlling a flow rate and a direction of a hydraulic fluid supplied to the first hydraulic actuator;
a first speed-up directional control valve provided in a second pump line that is a delivery hydraulic line of the second hydraulic pump and controlling a flow rate and a direction of a hydraulic fluid supplied to the first hydraulic actuator; and
a second directional control valve provided in the second pump line that is the delivery hydraulic line of the second hydraulic pump and controlling a flow rate and a direction of a hydraulic fluid supplied to the second hydraulic actuator, wherein
the construction machine includes:
an excavation load sensor that detects an excavation load imposed on the work implement; and
a first speed-up control section that drives the first speed-up directional control valve, and
the first speed-up control section is configured to control a driving amount of the first speed-up directional control valve in response to the excavation load detected by the excavation load sensor.
2. The construction machine according to claim 1 , wherein
the work implement includes a boom and an arm,
the first hydraulic actuator is a boom cylinder that drives the boom,
the second hydraulic actuator is an arm cylinder that drives the arm,
the excavation load sensor is an arm cylinder bottom-chamber-side pressure sensor that measures a pressure of a bottom-side hydraulic chamber of the arm cylinder, and
the first speed-up control section is configured to control the driving amount of the first speed-up directional control valve in response to the pressure of the bottom-side hydraulic chamber of the arm cylinder measured by the arm cylinder bottom-chamber-side pressure sensor.
3. The construction machine according to claim 1 , wherein
the work implement includes a boom and an arm,
the first hydraulic actuator is a boom cylinder that drives the boom,
the second hydraulic actuator is an arm cylinder that drives the arm,
the excavation load sensor is an arm cylinder bottom-chamber-side pressure sensor that measures a pressure of a bottom-side hydraulic chamber of the arm cylinder and a boom cylinder bottom-chamber-side pressure sensor that measures a pressure of a bottom-side hydraulic chamber of the boom cylinder, and
the first speed-up control section is configured to control the driving amount of the first speed-up directional control valve on the basis of a deviation between the pressure of the bottom-side hydraulic chamber of the boom cylinder measured by the boom cylinder bottom-chamber-side pressure sensor and the pressure of the bottom-side hydraulic chamber of the arm cylinder measured by the arm cylinder bottom-chamber-side pressure sensor.
4. The construction machine according to claim 3 , wherein
the first speed-up control section is configured to exercise control such that an opening area of the first speed-up directional control valve is made smaller as the deviation between the pressure of the bottom-side hydraulic chamber of the boom cylinder and the pressure of the bottom-side hydraulic chamber of the arm cylinder is smaller, and such that the opening area of the first speed-up directional control valve is made larger as the pressure of the bottom-side hydraulic chamber of the arm cylinder is higher.
5. The construction machine according to claim 1 , further comprising
a target surface distance acquisition section that measures or computes a target surface distance that is a distance between a target surface subjected to work conducted by the work implement and the work implement, wherein
the first speed-up control section is configured to exercise control such that the driving amount of the first speed-up directional control valve is corrected in response to the target surface distance.
6. The construction machine according to claim 1 , wherein
the first directional control valve and the first speed-up directional control valve are driven by a pilot hydraulic fluid generated by a pilot hydraulic fluid source,
the first directional control valve and the first speed-up directional control valve each include a meter-out opening that communicates a discharge-side hydraulic chamber of the first hydraulic actuator with a hydraulic tank, and
a value of the pilot pressure at which the meter-out opening of the first speed-up directional control valve starts to open is set lower than a value of the pilot pressure at which the meter-out opening of the first directional control valve starts to open.