A construction machine includes a bidirectionally tiltable type hydraulic pump 2, a hydraulic cylinder 1 having a cap chamber 1e and a rod chamber 1f, a first flow path 11 connecting the hydraulic pump 2 and the cap chamber 1e, a second flow path 12 connecting the hydraulic pump 2 and the rod chamber 1f, a discharge flow path 16 branched from the first flow path 11, a discharge valve 32 that is disposed in the discharge flow path 16 and controls a discharge rate of hydraulic working oil from the cap chamber 1e to the discharge flow path 16, an operation device 54 that instructs an action of the hydraulic cylinder 1, and a controller 56. The controller 56 controls the hydraulic pump 2 and the discharge valve 32 such that at least a part of hydraulic working oil discharged from the cap chamber 1e is discharged to the discharge flow path 16 when an operation amount of the operation device 54 lies within a fine operation region during a pulling action of the hydraulic cylinder 1 in a state that a load is applied in a contraction direction. Accordingly, operability improves during fine operation of the pulling action of the hydraulic cylinder in the state that the load is applied in the contraction direction.

A hydraulic drive device for a cargo vehicle includes a hydraulic cylinder supplying and discharging of hydraulic oil, an operation member that operates the hydraulic cylinder, a hydraulic pump, a lowering oil path connecting the hydraulic cylinder and the hydraulic pump, an operation valve disposed in the lowering oil path, a bypass oil path that branches off from the lowering oil path, a bypass flow rate control valve disposed in the bypass oil path and that controls a bypass flow rate, and a resistance element that is disposed closer to the hydraulic cylinder than the operation valve in the lowering oil path and that increases a fluid resistance. A pilot flow path of the bypass flow rate control valve is connected to a part of the lowering oil path between the hydraulic cylinder and the resistance element.

An emergency braking method for aircraft, comprising using a progressing parking brake controlled by a lever (10) that can be actuated by the pilot between a 0% position in which the brakes are connected to the return pressure of the aircraft, and a 100% position in which the brakes are connected to the feed pressure of the aircraft, the lever being blockable in the 100% position in order to provide parking braking when the aircraft is stationary. According to the invention, the emergency braking method being characterized in that it comprises: using a valve having an outlet port connected to the brakes, a return port, and a feed port, the valve presenting a state connecting the outlet port to the return port and a state connecting the outlet port to the feed port; and controlling the valve to occupy one or other of those states by pulse width modulation (PWM) having a duty ratio (R) that is a function of the position of the lever in order to deliver the brakes with pressure lying in the range return pressure to feed pressure, depending on the position of the lever.

A construction machine includes a bidirectionally tiltable type hydraulic pump 2, a hydraulic cylinder 1 having a cap chamber 1e and a rod chamber 1f, a first flow path 11 connecting the hydraulic pump 2 and the cap chamber 1e, a second flow path 12 connecting the hydraulic pump 2 and the rod chamber 1f, a discharge flow path 16 branched from the first flow path 11, a discharge valve 32 that is disposed in the discharge flow path 16 and controls a discharge rate of hydraulic working oil from the cap chamber 1e to the discharge flow path 16, an operation device 54 that instructs an action of the hydraulic cylinder 1, and a controller 56. The controller 56 controls the hydraulic pump 2 and the discharge valve 32 such that at least a part of hydraulic working oil discharged from the cap chamber 1e is discharged to the discharge flow path 16 when an operation amount of the operation device 54 lies within a fine operation region during a pulling action of the hydraulic cylinder 1 in a state that a load is applied in a contraction direction. Accordingly, operability improves during fine operation of the pulling action of the hydraulic cylinder in the state that the load is applied in the contraction direction.

A hydraulic drive device for a cargo vehicle includes a first hydraulic cylinder for raising and lowering, a second hydraulic cylinder for performing an operation different from the first hydraulic cylinder, a first operation member, a second operation member, a hydraulic pump, an electric motor, a lowering oil path, an operation valve, a bypass oil path that branches off from the lowering oil path, a bypass flow rate control valve in the bypass oil path, a command rotational speed setting unit that sets a command rotational speed of the electric motor, and an electric motor control unit. A command rotational speed deceleration which is a deceleration of the command rotational speed set by the command rotational speed setting unit is larger than an actual rotational speed deceleration which is a deceleration of an actual rotational speed of the electric motor by the controlling output of the electric motor control unit.

A first switching valve that switches between flow passages which allow communication between a first pressure-receiving chamber and a fluid supply device side and flow passages which allow communication between a second pressure-receiving chamber and the fluid supply device side, according to a change in a fluid pressure to be applied, and a second switching valve that is switched to flow passages which apply the fluid pressure to the first switching valve, are provided. The second switching valve includes return device, and is provided to be reciprocatable between an operation position to which the second switching valve is moved by a stroke of a piston and a return position to which the second switching valve is moved by the return device. The piston and the second switching valve are movable independently of each other.

A cylinder driving device includes: an electric motor; a pump; a main passage and a main passage; a hydraulic cylinder; an operation check valve and an operation check valve; and a restriction valve and a restriction valve configured to restrict a flow of the working oil directed to the operation check valve and an operation check valve, wherein an opening area of the restriction valve and the restriction valve is reduced in response to an increase in a flow rate of the working oil discharged from the hydraulic cylinder to the main passage and a main passage.

A hydraulic system, preferably for actuating and engaging a mobile slurry pump, includes a primary circuit, actuating a first hydraulic consumer, which circuit has a hydraulic drive assembly including at least one motor-driven hydraulic pump. The hydraulic system further includes a secondary circuit, actuating a second hydraulic consumer, which circuit has a second hydraulic drive assembly including at least one additional motor-driven hydraulic pump. In a first operating state, hydraulic oil from a common tank can be admitted to the hydraulic consumers arranged in the primary circuit and in the secondary circuit via the hydraulic drive assemblies thereof, independently of one another. In a second operating state, a portion of the hydraulic oil is supplied from the primary circuit to the secondary circuit to actuate the second consumer.

A hydraulic excavator drive system includes: a first pump connected to a head-side chamber of a boom cylinder; and a second pump that supplies hydraulic oil to one of, or both, an arm cylinder and a bucket cylinder. The first pump is driven by an electric motor. The drive system further includes a switching valve that is in a first position at a boom raising operation and in a second position at a vehicle body lifting operation. The first position is a position in which the switching valve brings a rod-side chamber of the boom cylinder into communication with a tank, and the second position is a position in which the switching valve brings the rod-side chamber into communication with the second pump.

A hydraulic unit includes an oil tank, a hydraulic pump, a first return pipe, and a first heat exchanger. The oil tank stores a hydraulic oil. The hydraulic pump supplies the hydraulic oil in the oil tank to an actuator. The first return pipe returns the hydraulic oil from a flow path between a discharge port of the hydraulic pump and the actuator to the oil tank. The first heat exchanger causes a coolant to exchange heat with the hydraulic oil returning to the oil tank through the first return pipe.