There is provided a driving device for a work machine, having a closed hydraulic circuit system for driving cylinders with hydraulic pumps, the driving device making the speed of operation substantially the same in both directions of piston rod extension and contraction. The driving device includes: a first hydraulic pump that has flow rate control device for controlling the flow rate and direction of hydraulic fluid to be delivered; a single rod hydraulic cylinder that is driven with the hydraulic fluid to drive one of work members of a work device on the work machine; a closed hydraulic circuit that connects the first hydraulic pump with the single rod hydraulic cylinder to form a closed circuit using flow lines through which the hydraulic fluid flows; a branch line that branches from the flow line between the first hydraulic pump and the single rod hydraulic cylinder; a first flow line of which one end is connected to the branch line; a tank to which the other end of the first flow line is connected; and a hydraulic fluid flow rate control device attached to the first flow line to control the flow rate of the hydraulic fluid flowing from the branch line to the tank or from the tank to the branch line.

A downforce control system for an agricultural ground engaging unit provides individual control of each agricultural ground engaging row unit by providing a proportional pressure control valve connected to the retracting chamber of a double acting cylinder which varies the upward force produced by the retracting chamber of the cylinder against a constant counteracting downward force produced by an extending chamber of the cylinder, the valve control based on a comparison of a sensed resultant downward force on the agricultural ground engaging row unit and a predetermined target downward force.

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 system for braking a displacement-controlled drive system (10), which can be driven by means of an inflow pressure and an outflow pressure at an inflow end and an outflow end thereof, respectively, for a motion, characterized in that by means of an electro-proportional adjustment of at least one valve element (26, 28, 126, 128) an outflow volume flow of the drive system (10) is controlled such that the outflow pressure is decoupled from the motion of the drive system and can be freely preset and coupled to the inflow pressure, which can in that way be lowered to the extent necessary for the motion of the drive system (10).

A hydraulic valve arrangement (1) is provided comprising comprising a supply port arrangement having a high pressure port (2) and a low pressure port (4), a working port arrangement having two working ports (6, 7), a first valve (13) arranged between said high pressure port (2) and said working port arrangement (6, 7), a second valve (14) arranged between said low pressure port (4) and said working port arrangement (6, 7), a controller (19) for controlling said first valve (13) and said second valve (14), said controller (19) having an input connection (20) for receiving a signal of an operator input device, and a regenerative flow path which can be established by means of at least one of said first valve (13) and said second valve (14). The function of such a hydraulic valve arrangement should be enhanced. To this end said controller (19) said controller interrupts said regenerative flow path when a feed pressure at said working port arrangement (6, 7) exceeds a predetermined pressure level.

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.

To reduce an increase in the electric power consumption of an electric motor according to the state of an electric power source at the start of driving of an actuator, and make it possible to use devices in an appropriate state in an electrically driven hydraulic construction machine including a driving system that drives a hydraulic pump by using the electric motor. For this purpose, a controller 50 sets a target relief pressure of a relief valve 3 to a normal relief pressure Pn (first relief pressure) when an operation lever device 44 is not being operated and a storage amount SOC(t) of a battery 62 (the state quantity of an electric power source) is equal to or larger than a threshold S1, and sets the target relief pressure to a reduced relief pressure Pr(t) (second relief pressure) lower than the normal relief pressure Pn (first relief pressure) when the operation lever device 44 is not being operated, and the storage amount SOC(t) of the battery 62 (the state quantity of the electric power source) is smaller than the threshold S1.

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.

A hydraulic actuating device for a friction clutch and a gear setting element has a power unit for pressure generation by use of an electrically driven pump. Gear setting and clutch actuating sections are hydraulically connected to the power unit. A detenting device with a blocking element is associated with a piston of the clutch setting cylinder, which is operatively connected with the friction clutch and can be hydraulically loaded on opposite sides. The blocking element is resiliently biased into a blocking setting preventing piston movement and is movable by an actuator from the blocking setting into a release setting permitting piston movement. The pump is reversible in order to load the piston on one or the other side for an actuating movement. The control unit coordinates activation of the pump and actuator in order to disengage or engage the friction clutch.

A hydraulic arrangement for supplying a consumer or actuator includes a first supply device that has at least one pump with an adjustable delivery volume. The hydraulic arrangement further includes a second supply device that is connected in parallel to the first supply device. The second supply device includes a loadable accumulator and a digitally regulated switching valve arrangement.