An electrically-operated hydraulic work machine drives an actuator with a hydraulic pump driven by an electric motor and exercises load sensing control by controlling the rotation speed of the electric motor. The useful life of an electrical storage device, which is an electrical power source for the electric motor, is increased by suppressing the horsepower consumption of the hydraulic pump. This prolongs the operating time of the electrically-operated hydraulic work machine, and reduces the size of the electric motor. A controller exercises load sensing control over a variable displacement main pump by controlling the rotation speed of the electric motor, and provides the main pump with a torque control device that reduces the delivery rate of the main pump when the delivery pressure of the main pump increases, or provides the controller with a control algorithm that performs the same function as the torque control device.

A pressure compensation unit includes: a control valve controlling hydraulic fluid supply and discharge to and from an actuator, the control valve including a pump port, a pair of relay and supply/discharge ports, and a tank port; a pressure compensation valve connected to the relay ports by an upstream and downstream-side relay lines, the pressure compensation valve moving in accordance with a pressure difference between upstream-side relay line and signal pressure; a load pressure detection line branching from the downstream-side relay line; a relief line connected to the downstream-side relay line and having a relief valve; and a switching valve leading: a maximum load pressure to the pressure compensation valve as the signal pressure when the hydraulic fluid does not flow through the relief line; and a pump pressure to the pressure compensation valve as the signal pressure when the hydraulic fluid flows through the relief line.

A control device, in particular for hydraulically controlling components of mobile working machines, has a pressure supply connection (P) and a tank or return connection (T) in addition to two user connections (A, B). Control and/or regulating valves (10, 14, 16, 18) are connected between the individual connections (P, T, A, B). Two control lines (C, Z) can control at least one of the control and/or regulating valves. A modular-type functional block (24, 26) is connected to at least one of the control lines (C, Z).

In a hydraulic driving system for construction machines, when track motors 3f and 3g are operated and the delivery pressure of a main pump 2 increases to a second value PS2 of the set pressure of a main relief valve 14, the set pressure of a signal pressure relief valve 16 increases from a third value PA1 to a fourth value PA2, which is smaller than the second value PS2 of the set pressure of the main relief valve 14, the difference between the second value PS2 and the fourth value PA2 being smaller than the target LS differential pressure. With such a structure, even if one of actuators reaches the stroke end and the delivery pressure of the hydraulic pump rises to the set pressure of the main relief valve, the other actuators do not stop, and further when the main relief valve is configured to increase the set pressure during operation of a specific actuator, the load pressure of the specific actuator does not increase to the increased set pressure of the main relief valve.

A pressure compensated load sense hydraulic system and method is disclosed where a first pressure compensated valve controls flow between a pump and a first function based on a highest function load; and a second pressure compensated valve controls flow between the pump and a second function based on the highest function load. First and second operator controls activate the first and second functions, respectively. When the first function is stalled and the second function is activated, the controller closes the first valve to remove the first function load from the load sense circuit and prevent flow to or from the first function. The controller can determine the first function is stalled when a timer exceeds an initialization period. When the controller closes the first valve, it can cycle the first valve between a shutoff period where the valve is closed, and a refresh period where the valve is opened.

Pressure compensating valves not fully closing at the stroke end are employed, and upon the operator's operation for the traveling, pilot primary pressure is reduced and supplied to remote control valves 34c-34h of non-travel operating devices. Thus, the inflow of the hydraulic fluid into non-travel actuators is suppressed and a necessary amount of hydraulic fluid for travel motors is secured in travel combined operation. Accordingly, when saturation occurs in a construction machine's hydraulic drive system performing the load sensing control due to combined operation with a great load pressure difference between two actuators, deceleration/stoppage of an actuator on the low load pressure side is prevented by preventing full closure of the pressure compensating valve on the low load pressure side, while also preventing deceleration/stoppage of a high load pressure actuator by securing a necessary amount of hydraulic fluid for the high load pressure actuator.

A hydraulic system for a feed delivery unit according to the present disclosure may include a pump configured to supply a total flow, the pump including at least one suction port configured to be connected to a reservoir and at least one outlet port configured to be connected to a supply line, a control valve fluidly coupled to the pump and including a plurality of valve sections, the control valve being coupled to the pump such that the total flow supplied by the pump is distributed among the plurality of valve sections, and wherein each valve section of the plurality of valve sections is configured to control a direction of flow of a portion of the total flow, and a plurality of hydraulic motors fluidly coupled to the pump via the control valve, each of the motors being configured to drive a respective auger of the feed delivery unit.

A valve block includes a plurality of control valve disks that form a first block part and a second block part. A supply pressure for the control valve disks of the first block part is limited by a common pressure-limiting valve. The common pressure-limiting valve is arranged such that a prevailing load pressure registered by the control valve disks does not exceed a specific value. The supply pressure for the control valve disks of the second block part is not limited.

A hydraulic load-sensing control arrangement for a first and second hydraulic consumer has a variable displacement pump having load-sensing regulation, to which the highest respective load-sensing pressure of consumers is reported. The first consumer has the highest load pressure in normal operation and therefore the highest load-sensing pressure dependent on the load pressure. A pressure reducing valve is arranged in the pressure medium flow path between the variable displacement pump and the first consumer. A spring force from a regulating spring and a regulating pressure dependent on the load pressure of the first consumer are applied in the opening direction of a valve gate in this pressure reducing valve and pressure is applied directly downstream from the pressure reducing valve in the closing direction thereof. A pressure equivalent of the spring force of the regulating spring and the regulating pressure are greater than a pressure of the variable displacement pump.

A load-controlled hydraulic supply for an attachment attached to an agricultural tractor includes a hydraulic high-pressure source providing a volume flow in a supply line, a pressure-compensated control valve including an actuation device for adjusting the volume flow in the supply line, a return line leading to a hydraulic reservoir, and a load-indicating line. The volume flow is adjusted based on pressure feedback prevailing at the load-indicating line.