In a crop harvesting machine there is provided a pair of hydraulic float cylinders for a header relative to a vehicle, where a float pressure to the cylinders is directly controlled by an electronic control supplying a variable control signal to a PPRR valve arrangement to maintain the float pressure at a predetermined value. At the set pressure a predetermined lifting force is provided to the header. A position sensor is used to generate an indication of movement and/or acceleration. The electronic control is arranged, in response to changes in the sensor signal, to temporarily change the control signal to vary the lifting force and thus change the dynamic response of the hydraulic float cylinder. In order to reduce static friction so that the system can react quickly, an arrangement is provided for causing relative reciprocating movement in an alternating wave pattern between the piston and cylinder.

A work machine includes: a hydraulic actuator that is driven by a hydraulic fluid from a hydraulic pump; an open-center directional control valve that is arranged on a center bypass line, and controls a flow of the hydraulic fluid to be supplied to the hydraulic actuator; a CB cut valve arranged between a directional control valve and a hydraulic working fluid tank on the center bypass line; and a machine controller that controls an opening of the CB cut valve. The machine controller restricts the opening of the CB cut valve when operation on the hydraulic actuator is in a fine operation state in which the operation on the hydraulic actuator is within a predetermined range representing a region of fine operation, and the fine operation state is continued longer than a predetermined period, and fully opens the CB cut valve otherwise.

At least some embodiments of the present disclosure are directed to distributed pump architectures used in control systems for multifunctional machines. In some cases, a control system for a multifunctional machine includes three or more control circuits. At least two of the control circuits each has a hydraulic fluid pump and each of the pumps is controlled by a different control circuit. At least two of the hydraulic fluid pump have different flow rates.

A hydraulic control system for linear actuation that provides a bypass flow during startup of a lifting command, provides a split flow between a cylinder and a reservoir once a minimum operating speed of a pump has been reached, and provides complete flow to a cylinder after the minimum operating speed of the pump has been reached. This is achieved through control of a flow control valve and a proportional flow control valve by a processor.

A hydraulic system is provided for controlling one or more piston-cylinders of an implement. An implement valve includes at least one spool operable to transition between a neutral position and an open position. A variable displacement pump is operable to move a fluid from a reservoir into a supply conduit and to the at least one spool. A flow control valve, distinct and separate from the at least one spool is located in-line with the supply conduit between the variable displacement pump and the at least one spool, and is operable to simultaneously provide the fluid to the implement valve and to a bypass pathway. The bypass pathway extends from the flow control valve to the reservoir without intervening valving. Each of the at least one spool is operable to permit increased fluid flow to a corresponding piston cylinder of the implement when in the open position. The variable displacement pump is operable to vary a flow rate to maintain a predetermined pump margin across the flow control valve.

An object of the present invention is to provide a work machine that can increase the operation speed of an actuator by a regenerating function while ensuring accuracy of position control of the actuator. For this purpose, a controller computes a target actuator supply flow rate by subtracting a regeneration flow rate from a target actuator flow rate, computes a target flow control valve opening amount on the basis of the target actuator supply flow rate, computes a target pump flow rate equal to or more than the sum of a plurality of the target actuator supply flow rates, controls flow control valves according to the target flow control valve opening amount, and controls a hydraulic pump according to the target pump flow rate.

A safety valve which has two fluidically interconnected safety valves, each of which has a 4/2-way valve function. Each safety valve has a first connecting port and a second connecting port, which are connected to each other in such a way that a fluid flow through the two safety valves, controlled by means of a control valve, to a fluid-actuated drive is prevented if the two safety valves simultaneously adopt a first switching position and such a fluid flow is possible if both valves simultaneously have a second switching state. One safety aspect results from the fact that the above-mentioned fluid flow is also prevented if the two safety valves adopt different switching states.

Systems and apparatuses include a primary hydraulic pump including a primary displacement actuator and a primary pressure port, a primary load sense system fluidly coupled to the primary displacement actuator, a secondary hydraulic pump including a secondary displacement actuator and a secondary pressure port, a secondary load sense system fluidly coupled to the secondary displacement actuator, and a crossover pressure controller coupled between the primary pressure port and the secondary pressure port and including: a selectively energizable crossover pressure solenoid, and a crossover pressure spool movable by the crossover pressure solenoid between a combined pressure position providing fluid communication between the primary pressure port and the secondary pressure port, and a separate pressure position inhibiting fluid communication between the primary pressure port and the secondary pressure port.

A control system of a hybrid construction machine includes fluid pressure pumps, a regeneration motor, a rotating electric motor coupled to the regeneration motor, a storage battery configured to store electric power generated by the rotating electric motor, an assist pump provided coaxially to the regeneration motor to be driven by the rotating electric motor, the assist pump being configured to supply a working fluid to a fluid pressure actuator, and load adjusting units configured to change a load of the assist pump in accordance with a state of the storage battery.

A control system of a hybrid construction machine includes fluid pressure pumps configured to supply a working fluid to a fluid pressure actuator, a regeneration unit having a regeneration motor for regeneration to be rotated by the working fluid discharged from a load side pressure chamber of the fluid pressure actuator, a rotating electric motor coupled to the regeneration motor, and a storage battery configured to store electric power generated by the rotating electric motor, and a variable throttle configured to bleed a portion of the working fluid obtained by excluding a flow rate of the working fluid guided to the regeneration motor from the working fluid discharged from the load side pressure chamber.