To perform a work with the same operability under a dead weight of a front work equipment in any of a float work and a normal work, when a bucket descends in the air, and after contacting the ground, to perform a work with the operability being maintained as it is when performing the float work, and to perform a work while pressurized hydraulic fluid is supplied from a hydraulic pump when performing the normal work. A lower-ing control during a float working mode is performed in a valve passage state in a first region at which the lowering control is performed under the dead weight of the from work equip-ment without being supplied with hydraulic fluid from the hydraulic pump, regardless of whether or not the bucket is in contact with the ground, and the lowering control during a normal working mode is performed in a valve passage state at the first region in a non-ground-contacting state and at a second region in which the hydraulic fluid can be supplied from the hydraulic pump n a ground-contacting state.

A work machine (1) comprises at least one structural element (21), at least one pressure medium operated actuator 22) for establishing at least one operation of the work machine, and at least one detection device (23) to determine the position of the structural element (21) of the work machine. An arrangement for controlling at least one operation of the work machine (1) comprises: a control valve arrangement (24) for controlling the actuator (22), and a control device (25) for controlling the control valve arrangement (24). The control device (25) is adapted to control said control valve arrangement (24) for adjusting the pressure and/or volume flow on the return line of the actuator (22) as dependent on the position of the structural element (21).

A method for closed-loop controlling, in particular closed-loop pressure controlling, a piezo valve device, including the steps: calculating a control error integral signal representing a time integral of a control error of the closed-loop control of the piezo valve device, adjusting, based on the control error integral signal, at least one control opening voltage value defining within the closed-loop control an opening voltage value of a piezo valve of the piezo valve device, and using the adjusted at least one control opening voltage value, providing at least one drive voltage for driving the piezo valve within the closed-loop control.

A control device controls movement of a valve body of a valve device and estimates a flow rate of the valve device; determines, on the basis of an input target flow rate value and the flow rate estimate, whether or not the flow of an operating fluid in the valve device is in a transient flow state; calculates an opening command on the basis of the target flow rate value and an upstream-downstream pressure difference of the valve device; and controls the movement of the valve body. When the control device determines that the flow is not in the transient flow state, it controls the movement of the valve body on the basis of the opening command, and when the control determines that the flow is in the transient flow state, it controls the movement of the valve body on the basis of the target flow rate value.

A fixed displacement hydraulic pump match flow demand control system that includes a spool valve, a plurality of fixed displacement pumps and a control valve is provided. The spool valve includes a spool. The spool is configured to shuttle within a chamber of a housing based at least in part on a pressure difference between a first end and the second end of the chamber. A fluid flow from each fixed displacement pump of the plurality of fixed displacement pumps is in fluid communication with an associated input port to the spool valve. At least one output port of the spool valve is in fluid communication with a hydraulically operated device and at least one of another output port is in fluid communication with a return. The control valve is configured to adjust the location of the spool in the chamber to regulate fluid flow to the hydraulically operated device.

Techniques involve a hydraulic valve module having at least one hydraulic valve with a valve slide which can be adjusted by way of an electric actuator in order to supply hydraulic lines with hydraulic liquid by way of the hydraulic valve. The hydraulic valve module has a controller and an electric energy store. The controller and the electric energy store are set up to move the valve slide out of every possible valve slide position into a deactivation position by way of the electric actuator and energy which is stored in the electric energy store. This allows the safe operation of hydraulic valves without a restoring spring, wherein valves of this type and the actuators thereof can be of smaller and less expensive construction than in the case of conventional valves with a restoring spring.

To achieve improvement of operability and reduction of energy loss, when controlling so that an upper limit pressure of a discharge line becomes a pressure corresponding to an manipulation tool manipulation amount by controlling an increase or decrease of a bypass amount, in a hydraulic control circuit equipped with a bypass valve for controlling a bypass amount flowing from a hydraulic pump to an oil tank. By using a bypass valve control map representing a relationship between a manipulation tool manipulation amount and a spool stroke, the spool stroke of a bypass valve is controlled, and an upper limit pressure of the discharge line is set so that an opening area of the bypass valve is fully closed by a manipulation amount which is larger than a manipulation tool manipulation amount at which the maximum pressure of the discharge line is reached.

A method for preventing prime mover stall for a work machine including a hydraulic system having a plurality of control valves served by a hydraulic pump. The method can include determining an actual required flow rate value for the plurality control valves and a total maximum flow rate to the plurality of control valves that will enable the prime mover to operate without stalling. The method can also include operating the plurality of control valves such that the combined total flow of the plurality control valves is at or below the total maximum flow rate such that the pump operates at a condition below which prime mover stall will occur. The method can also include setting a flow sharing allocated specific criteria in which the flow reduction takes place during a flow saturation condition for each of the plurality of control valves such that the total sum of the flow rates (calculated based on the criteria) is equal to or less than the total maximum flow rate.

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.

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.