A digital pump axis control system having a circuit including an electric engine, powering first and second hydraulic machines connected in a rotationally locked manner to each other. At least one cylinder has a first chamber connected through a first pipeline to the first hydraulic machine and a second chamber of the cylinder is connected through a second pipeline to the second hydraulic machine. A first valve is arranged in the first pipeline; a second valve is arranged in the second pipeline; a third valve is arranged in a third pipeline, wherein the third pipeline connects a portion of the first pipeline between the first hydraulic machine and the first valve and a portion of the second pipeline between the second hydraulic machine and the second valve. An open tank provides hydraulic fluid to inlets of the first and second hydraulic machines. The first and second hydraulic machines are digital variable displacement pumps, each providing a positive and a negative displacement of hydraulic fluid.

A first required flow rate is calculated as a function of a first maximum allowable flow rate and a value of a first signal. A second required flow rate is calculated as a function of a value of the second signal. When the first maximum allowable flow rate is higher than a first capacity, the value of the first signal is a maximum level, and the value of the second signal is equal to or higher than a minimum level and equal to or lower than a maximum level, a first working fluid supply is controlled to discharge working fluid at a flow rate equal to the first capacity, and a second working fluid supply is controlled to discharge working fluid at a flow rate obtained by deducting the first capacity from the first maximum allowable flow rate, added to the second required flow rate.

A system for controlling hydraulic fluid flow within a work vehicle includes a pilot conduit configured to receive a pilot flow of hydraulic fluid from a fluid supply conduit such that the operation of a compensator valve is controlled based on a pressure of the pilot flow within the pilot conduit. Furthermore, a pilot conduit valve is configured to adjust the pressure of the pilot flow within the pilot conduit. In addition, the system includes a load sense conduit configured to receive a bleed flow of the hydraulic from the fluid supply conduit such that the operation of the pump is controlled based on a pressure of the bleed flow within the load sense conduit. Moreover, a load sense valve is configured to adjust the pressure of the bleed flow within the load sense conduit.

A first required flow rate is calculated as a function of a first maximum allowable flow rate and a value of a first signal. A second required flow rate is calculated as a function of a value of the second signal. When the first maximum allowable flow rate is higher than a first capacity, the value of the first signal is a maximum level, and the value of the second signal is equal to or higher than a minimum level and equal to or lower than a maximum level, a first working fluid supply is controlled to discharge working fluid at a flow rate equal to the first capacity, and a second working fluid supply is controlled to discharge working fluid at a flow rate obtained by deducting the first capacity from the first maximum allowable flow rate, added to the second required flow rate.

Some embodiments of the disclosure provide an advance and retreat automatic control method based on hydraulic sensing conversion and an advance and retreat automatic control system based on hydraulic sensing conversion, which includes an automatic advance and retreat device based on hydraulic sensing conversion, a motor, an oil cylinder, and/or an electric generator. When the digging motor encountered an overlarge resistance force, a pressure on the digging motor is instantaneously increased and exceeds a setting pressure value, hydraulic oil enters a hydraulic operated directional valve and pushes a valve rod to make the walking motor is reverse and retreat, an ultrahigh pressure state of the digging motor is released to restore to a normal pressure value to make reciprocated impact, the valve rod of the hydraulic operated directional valve is reset, and the walking motor is forwards rotated for advancing.

A hydraulic system for a working machine includes hydraulic actuators actuated with hydraulic fluid delivered from a hydraulic pump, control valves each of which is shiftable among shift positions to control a flowrate of hydraulic fluid flowing to the corresponding hydraulic actuator, a detection fluid passage, an interlocking control valve, and a pressure detection unit. Each control valve includes an input port, an output port, and a flowrate reduction section. One of the control valves includes a flowrate increase section. The interlocking control valve is configured to be shifted in accordance with a shift of the one of the control valves among the shift positions and to be shifted to a blocking position to block a pilot fluid introduced into the interlocking control valve from the detection fluid passage when the one of the control valves is shifted to the increase position.

A control device for at least one hydraulic working section (A, B), which can be connected to a pressure supply source (P) and a return flow (T) via a hydraulic supply circuit and to a control valve (34) supplied with a pilot pressure. The device includes an emergency shutdown system (32) having a pilot solenoid valve (16) and an additional valve (14). Both the hydraulic energy flow from the pressure supply source (P) to at least one of the respective working sections (A, B) and the pilot pressure supply to the control valve (34) can be suppressed by the pilot solenoid valve (16) via the additional valve (14).

A hydraulic drive device for an industrial vehicle includes a tank, a hydraulic pump, a capacity control valve, a plurality of hydraulic cylinders, a plurality of direction switching valves, a first hydraulic oil passage, a second hydraulic oil passages, a pilot line, a relief valve, a relief pressure setting portion, a plurality of operation detecting portions, and a control unit. The control valve controls the hydraulic pumps so that a differential pressure between a discharge pressure of the hydraulic pump and a pilot pressure of the pilot line is to be a predetermined pressure. The control unit controls the relief pressure setting portion.

A hydraulic system includes first and second valve assemblies connected to a common pump. The first valve assembly includes a main valve housed inside a manifold. A pressure compensator valve maintains a constant pressure drop across a variable orifice of the main valve. A pressure limiter valve is in communication with the main valve and the pressure compensator valve, and allows an actuator connected to the first valve assembly to operate independently of the second valve assembly so that fluid flow to a work port of the first valve assembly is not interrupted by operation of the second valve assembly.

A control device is disclosed for at least one hydraulic working section (A, B), which can be connected to a pressure supply source (P) and a return flow (T) via a hydraulic supply circuit and a control valve (34) supplied with a pilot pressure, the device comprising an emergency shutdown system (32) having a pilot solenoid valve (16) and an additional valve (14). Said control device is characterised in that both the hydraulic energy flow from the pressure supply source (P) to at least one of the respective working sections (A, B) and the pilot pressure supply to the control valve (34) can be suppressed by means of the pilot solenoid valve (16) via the additional valve (14).