A hydraulic system for a work machine includes a hydraulic bump to output an operation fluid, a hydraulic switch valve to be switched among switching positions in accordance with a pressure of the operation fluid, a proportional valve to change the pressure of the operation fluid applied to the hydraulic switch valve, a travel hydraulic device to change a thrust power in accordance with the switching positions of the hydraulic switch valve. And, the hydraulic system includes a controller to control the proportional valve in accordance with a state of the travel hydraulic device.

A method of controlling a float function of a cylinder 25 having a first side and a second side includes connecting the second side of the cylinder to a reservoir 15; connecting the first side of the cylinder to an output of a pump 20 and to the reservoir; and supplying an amount of flow from a pump less than an amount supplied by the pump under loaded conditions. A three-position directional control valve 30 having a pump port, a reservoir port, a first cylinder port, and a second cylinder port may be provided to effectuate aspects of this method.

A method of controlling a float function of a cylinder 25 having a first side and a second side includes connecting the second side of the cylinder to a reservoir 15; connecting the first side of the cylinder to an output of a pump 20 and to the reservoir; and supplying an amount of flow from a pump less than an amount supplied by the pump under loaded conditions. A three-position directional control valve 30 having a pump port, a reservoir port, a first cylinder port, and a second cylinder port may be provided to effectuate aspects of this method.

A hydraulic system (40) for a work machine comprising a priority circuit (41) including at least a first priority actuator (47, 48) and a priority control valve (58) for controlling the supply of hydraulic fluid to the first priority actuator (47, 48) and for providing a load sense signal indicative of the load acting on the first priority actuator (47, 48); an auxiliary circuit (42) including at least a first auxiliary actuator (51) and at least a first auxiliary control valve (80) for controlling the supply of hydraulic fluid to the first auxiliary actuator (51); at least a first pump (46) for producing a flow of hydraulic fluid; and a priority valve (74) for distributing the flow from the pump (46) to the priority circuit (41) and auxiliary circuit (42) for operating the respective actuators thereof, with priority being given to the priority circuit (41) as a function of the load sense signal.

A hydraulic system (40) for a work machine comprising a priority circuit (41) including at least a first priority actuator (47, 48) and a priority control valve (58) for controlling the supply of hydraulic fluid to the first priority actuator (47, 48) and for providing a load sense signal indicative of the load acting on the first priority actuator (47, 48); an auxiliary circuit (42) including at least a first auxiliary actuator (51) and at least a first auxiliary control valve (80) for controlling the supply of hydraulic fluid to the first auxiliary actuator (51); at least a first pump (46) for producing a flow of hydraulic fluid; and a priority valve (74) for distributing the flow from the pump (46) to the priority circuit (41) and auxiliary circuit (42) for operating the respective actuators thereof, with priority being given to the priority circuit (41) as a function of the load sense signal.

A servovalve (15) comprising a motor (16), a motor bias mechanism (20), a first stage valve member (22) adapted to be moved from a first position to a first off-null position, a second stage member (29) adapted to be moved from a first position to a second position with movement of the first valve member (22), a transfer link (34) acting between the first (22) and second (29) valve members, an eccentric drive member (35) acting between the motor (16) and the transfer link (34), the transfer link (34) and drive member (35) configured such that selective movement of the motor (16) causes the transfer link (34) to move the first valve member (22), movement of the first valve member (22) causes the second valve member (29) to move, and movement of the second valve member (29) causes the transfer link (34) to move the first valve member (22) from the first off-null position back to the null position.

An oil pressure control device controls a supply pressure of oil supplied to an oil pressure chamber of a friction element having a first engagement board and a second engagement board engaged with or disengaged from each other between a non-engagement state and a non-sliding engagement state via a sliding engagement state. The oil pressure control device includes: an electromagnetic valve that controls the supply pressure using a spool which reciprocates according to an energizing amount; and a control part that defines a first oscillatory wave part in which the energizing amount is controlled by making a first waveform with a first frequency to superimpose on a second waveform with a second frequency higher than the first frequency during a first period while the sliding engagement state and an instruction value of the supply pressure are kept constant.

A jet pipe arrangement for a servo valve, the jet pipe arrangement including a jet pipe, at least two receivers in operable communication with the jet pipe. The jet pip arrangement further includes an electromagnet in direct magnetic communication with the jet pipe such that, in use, the jet pipe is movable in response to changes in a magnetic field created by the electromagnet to distribute flow from the jet pipe asymmetrically between the at least two receivers.

A jet pipe arrangement for a servo valve, the jet pipe arrangement including a jet pipe, at least two receivers in operable communication with the jet pipe. The jet pip arrangement further includes an electromagnet in direct magnetic communication with the jet pipe such that, in use, the jet pipe is movable in response to changes in a magnetic field created by the electromagnet to distribute flow from the jet pipe asymmetrically between the at least two receivers.

The present disclosure relates to a system for monitoring a solenoid operated valve including at least one coil and at least one spool. The system compares a normalized current signature and a normalized current signature comparator to determine a spool fault condition.