A hydraulic machine is provided. A boom actuator includes a large chamber and a small chamber. A recovery unit receives fluid discharged from the large chamber and then recovers energy. A recovery line connects the large chamber and the recovery unit. An accumulator is connected to the recovery line. A jack-up assist line connects the accumulator and the small chamber. A jack-up assist valve is disposed on the jack-up assist line to block flow of fluid from the accumulator to the small chamber in a first position and allow the flow of fluid from the accumulator to the small chamber in a second position. A controller controls movement of the jack-up assist valve. The controller may determine whether or not the hydraulic machine is in a jack-up condition, and when the hydraulic machine is determined to be in the jack-up condition, moves the jack-up assist valve to the second position.

A hydraulic machine. A boom actuator includes a large chamber and a small chamber. A recovery unit receives fluid discharged from the large chamber and then recovers energy. A recovery line connects the large chamber and the recovery unit. An accumulator is connected to a first point on the recovery line. A discharge valve is disposed on the recovery line between the first point and the recovery unit. A first sensor measures a pressure in the accumulator. A controller controls opening and closing of the discharge valve. The controller performs anti-bouncing control of: determining a target pressure in the accumulator corresponding to a load pressure applied to fluid in the large chamber by a load according to a predetermined correspondence; and controlling the opening and closing of the discharge valve such that the pressure in the accumulator measured by the first sensor reaches the target pressure.

A swing motion control system for an earth-moving machine may include a closed loop hydraulic circuit including a hydrostatic swing pump fluidly coupled to at least one hydraulic swing motor configured to control a swing mechanism of the earth-moving machine, a pressure control device configured to control the pressure of fluid supplied to the hydrostatic swing pump for control of the pressure output by the pump, and a controller. The controller may be configured to monitor and process signals received from sensors and operator input, wherein the signals received from the sensors are indicative of machine position and pose, and inertia mass of swing components and a payload being moved by the swing mechanism of the machine, and control at least one of an offset amount for desired pump displacement by the hydrostatic swing pump or an offset amount for pump output pressure from the hydrostatic swing pump based on at least one of an amount of slope on which the machine is operating or the inertia mass of the swing components and payload.

A control valve assembly for indirect pneumatic control and method for controlling a working fluid pressure, which enable precise, sensitive and speed-variable controlling. The assembly includes two valve units, a working fluid inlet, and a control fluid inlet. A working fluid channel connects the working fluid inlet through the two valve units to an outlet. A valve piston arranged within a valve cylinder of the valve units is movable between open and closed positions. A spring element biases the valve piston toward the closed position, and a control pressure chamber applies a control pressure counteracting the spring element's bias. When a control pressure is applied in the first chamber, the first valve piston is moved to the open position. Two opposite valve surfaces form a valve opening opened at varying widths when the valve piston is moved in the valve cylinder because of a changing control pressure, and the working pressure can be finely adjusted corresponding to the valve opening width depending on the control pressure.

Provided is a construction vehicle including: a rolling-use hydraulic pump coupled to an output shaft of an engine and supplying hydraulic oil to a rolling-use hydraulic circuit; a task-use hydraulic pump coupled to the output shaft of the engine and supplying the hydraulic oil to a task-use hydraulic circuit; and an overspeed suppression mechanism configured to activate the task-use hydraulic pump to suppress overspeed of the engine when a load equal to or greater than allowable rotation speed is applied from the rolling-use hydraulic pump to the output shaft of the engine.

The object of the present invention resides in provision of a construction machine in which a hydraulic cylinder can be driven in a high efficiency by an accumulator. To this end, the construction machine including: a hydraulic cylinder; a first accumulator that accumulates return fluid from the hydraulic cylinder with a first set pressure; a tank that stores hydraulic fluid therein; a first hydraulic pump that delivers the hydraulic fluid sucked from the tank; a hydraulic actuator that is driven by the first hydraulic pump; and a second accumulator that accumulates return fluid from the hydraulic actuator with a second set pressure, includes a first control valve placed in a first hydraulic line that connects the first accumulator and the hydraulic cylinder to each other, and a second control valve placed in a second hydraulic line that connects the second accumulator and the hydraulic cylinder to each other. The second set pressure is set to a value higher than that of the first set pressure.

A hydraulic machine. A boom actuator includes a large chamber and a small chamber. A recovery unit receives fluid discharged from the large chamber and then recovers energy. A recovery line connects the large chamber and the recovery unit. An accumulator is connected to a first point on the recovery line. A discharge valve is disposed on the recovery line between the first point and the recovery unit. A first sensor measures a pressure in the accumulator. A controller controls opening and closing of the discharge valve. The controller performs anti-bouncing control of: determining a target pressure in the accumulator corresponding to a load pressure applied to fluid in the large chamber by a load according to a predetermined correspondence; and controlling the opening and closing of the discharge valve such that the pressure in the accumulator measured by the first sensor reaches the target pressure.

A hydraulic circuit includes a pump connected to a tank for supplying hydraulic liquid under pressure to a component via a directional control slide valve provided with a feed port connected to an inlet of the component and with a return port connected to an outlet of the component. The hydraulic circuit further includes a pressure limiter connected to the inlet of the component and the tank, and a feed control system for the hydraulic component including a pressure sensor installed upstream of the hydraulic component downstream of the feed port for supplying information about the pressure of the hydraulic liquid and a setpoint pressure. The feed control system further including an actuator for controlling the movement of the directional control slide valve, and a control unit for generating a control signal for the actuator based on information about the pressure measured at the feed port.

A hydraulic machine. A high pressure line allows working fluid to flow into a hydraulic motor. A low pressure line allows working fluid to flow out of the hydraulic motor. High pressure line valves open and close the high pressure line. Low pressure line valves open and close the low pressure line. An operator input device inputs a command to control movement of the hydraulic motor. A control unit controls the high pressure line valves and the low pressure line valves to be opened and closed by receiving the command from the operator input device. The control unit controls the high pressure line valves to have a normalized flow factor K.sub.vHP, and controls the low pressure line valves to have a normalized flow factor K.sub.vLP, where K.sub.vLP<K.sub.vHP when a normalized flow factor K.sub.vcmd corresponding to the command is 0<K.sub.vcmd<1.

A rotary actuator may include a first holder in which a fluid injecting portion is formed, a second holder rotatably coupled to the first holder, a flexible body fixed to the first holder and the second holder and configured to expand as a fluid is injected through the first holder, and a plurality of fibers radially disposed in a spiral shape at the flexible body and configured to rotate the flexible body when the flexible body expands.