A construction machine that precisely enables derivation of the operation characteristics of hydraulic actuators in a high-velocity area with less calibration operation is provided. A controller (10) has a calibration mode in which the controller (10) derives operation characteristics (α(xs)) representing a relation among a spool position (xs) of a meter-in valve (8a1), an operation velocity (Va) of a hydraulic actuator (4a), and a differential pressure (ΔP) across the meter-in valve (8a1), and is configured to, in a case where the spool position (xs) of the meter-in valve (8a1) has changed in a direction to increase the opening area of the meter-in valve (8a1) in the calibration mode, output a command signal to increase the opening area of a bleed-off valve (8b1) to a bleed-off solenoid proportional pressure-reducing valve (8b2) as a command signal to reduce the differential pressure (ΔP).

A hydraulic excavator drive system includes: a first pump connected to a boom main control valve and an arm auxiliary control valve by a first pump line; a second pump connected to a boom auxiliary control valve and an arm main control valve by a second pump line; and a controller that does not move the arm auxiliary control valve when arm crowding operation boom raising operations are performed concurrently. The boom auxiliary control valve moves together with the boom main control valve when the boom raising operation is performed. A boom raising second supply line, which connects the boom auxiliary control valve to a boom raising first supply line between the boom main control valve and a boom cylinder, is provided with a check valve that allows a flow from the boom auxiliary control valve toward a head side of the boom cylinder, but prevents a reverse flow.

A hydraulic excavator drive system includes: a first pump connected to a boom main control valve and an arm auxiliary control valve by a first pump line; a second pump connected to a boom auxiliary control valve and an arm main control valve by a second pump line; and a controller that does not move the arm auxiliary control valve when arm crowding operation boom raising operations are performed concurrently. The boom auxiliary control valve moves together with the boom main control valve when the boom raising operation is performed. A boom raising second supply line, which connects the boom auxiliary control valve to a boom raising first supply line between the boom main control valve and a boom cylinder, is provided with a check valve that allows a flow from the boom auxiliary control valve toward a head side of the boom cylinder, but prevents a reverse flow.

A shovel includes a lower traveling structure, an upper swing structure swingably mounted on the lower traveling structure, a first hydraulic pump provided on the upper swing structure, an attachment attached to the upper swing structure, a first actuator, a second actuator, a first directional control valve corresponding to the first actuator, a second directional control valve corresponding to the second actuator, a first conduit connecting the first hydraulic pump and the first directional control valve, a second conduit connecting the first conduit and the second directional control valve, a control valve installed in the second conduit, and processing circuitry configured to control the opening area of the control valve according to information on work details.

An open center hydraulic system (100) includes a tank configured to hold hydraulic fluid, a pump configured to provide pressurized hydraulic fluid from the tank, and a shunt valve configured to adapt a first opening area between a first input port and a first output port of the shunt valve dependent on a first control signal. The first input port is coupled to the pump, and the first output port is coupled to the tank. A first actuator valve is coupled to the first input port and configured to adapt a second opening area of the first actuator valve dependent on a second control signal. A hydraulic valve control unit is configured to determine a first opening area value and a second opening area value based on user input data and a predetermined relation dependent on the user input data, sending the first control signal, indicative of the first opening area value and sending the second control signal indicative of the second opening area value.

An open center hydraulic system (100) includes a tank configured to hold hydraulic fluid, a pump configured to provide pressurized hydraulic fluid from the tank, and a shunt valve configured to adapt a first opening area between a first input port and a first output port of the shunt valve dependent on a first control signal. The first input port is coupled to the pump, and the first output port is coupled to the tank. A first actuator valve is coupled to the first input port and configured to adapt a second opening area of the first actuator valve dependent on a second control signal. A hydraulic valve control unit is configured to determine a first opening area value and a second opening area value based on user input data and a predetermined relation dependent on the user input data, sending the first control signal, indicative of the first opening area value and sending the second control signal indicative of the second opening area value.

A valve arrangement for supplying pressure medium to a hydraulic consumer has two utility ports (A, B) for fluid connection to the consumer and has a first control valve. The first control valve (20) has a first intake (24) via which a first intake flow from the first utility port (A) to the consumer (10) is controllable, has a first return control orifice (26) via which a first return flow (28) from the consumer (10) via the second utility port (B) is controllable simultaneously with the first intake (24), has a second intake (34) via which a second intake flow from the second utility port (B) to the consumer (10) is controllable, and having a second return control orifice (36), via which a second return flow (38) from the consumer (10) via the first utility port (A) is controllable simultaneously with the second intake (34). A second control valve (40) has an intake control orifice (42) used to control the respective intake (24, 34) of the first control valve (20).

This hydraulic drive system includes: a hydraulic pump capable of changing a discharge flow rate of a working fluid; a meter-in control valve that controls a meter-in flow rate of the working fluid flowing from the hydraulic pump to a hydraulic actuator; a meter-out control valve that is provided separately from the meter-in control valve and controls a meter-out flow rate of the working fluid being drained from the hydraulic actuator into a tank; an operation device that outputs an operation command; a first pressure sensor that detects a drainage pressure of the hydraulic actuator; and a control device that sets a target meter-out flow rate according to the operation command from the operation device and controls an opening degree of the meter-out control valve on the basis of the drainage pressure detected by the first pressure sensor and the target meter-out flow rate.

This hydraulic drive system includes: a hydraulic pump capable of changing a discharge flow rate of a working fluid; a meter-in control valve that controls a meter-in flow rate of the working fluid flowing from the hydraulic pump to a hydraulic actuator; a meter-out control valve that is provided separately from the meter-in control valve and controls a meter-out flow rate of the working fluid being drained from the hydraulic actuator into a tank; an operation device that outputs an operation command; a first pressure sensor that detects a drainage pressure of the hydraulic actuator; and a control device that sets a target meter-out flow rate according to the operation command from the operation device and controls an opening degree of the meter-out control valve on the basis of the drainage pressure detected by the first pressure sensor and the target meter-out flow rate.

This hydraulic drive system includes: first and second circuit systems; first and second hydraulic pumps; a merge valve that opens and closes a merge passage connecting the hydraulic pumps; an operation device that outputs an operation command corresponding to an amount of operation specifying an amount of actuation of first and second hydraulic actuators; and a control device that controls the merge valve according to the operation command from the operation device. The first circuit system includes: a first meter-in control valve that controls a meter-in flow rate of the working fluid that flows to the first hydraulic actuator; and a first meter-out control valve that controls a meter-out flow rate of the working fluid that is drained from the first hydraulic actuator into a tank. The control device controls an opening degree of the first meter-in control valve and an opening degree of the first meter-out control valve.