Abstract:
The invention relates to a hydraulic fan drive, comprising an adjustable hydraulic machine (10) having an adjusting device (32) for the displacement volume, a hydraulic motor (15) for driving a fan wheel (16), and a pressure line (14) which is connected to a pressure port (12) of the hydraulic motor and into which pressure medium is conveyed by the hydraulic machine. In order to recuperate energy, a hydraulic accumulator (17), which is connected to the pressure line, is provided, wherein the adjusting device of the hydraulic machine is suitable for setting the displacement volume of the latter depending on a setpoint signal, the hydraulic motor being adjustable. According to the invention, energy can be buffer-stored, on account of the hydraulic accumulator which is connected to the pressure line, by feeding in pressure medium beyond the quantity which is swallowed by the hydraulic motor, which energy is released for example during a braking operation or during the lowering of a load. The pressure changes associated therewith are compensated for by a change in the displacement volume of the hydraulic motor in such a way that the desired fan speed is reached.
Abstract:
The invention relates to a method for controlling lowering of an implement (3) of a working machine. The working machine has a hydraulic system (10) comprising a hydraulic cylinder (11) for moving the implement and a first control valve (12) for controlling the flow of hydraulic fluid from the piston side (13) of the hydraulic cylinder, and a recovery unit (14) connected to the control valve for recovering energy by receiving a return flow from the piston side of the hydraulic cylinder. The piston side (13) of the hydraulic cylinder and the control valve (12) are connected to each other, and the piston rod side (15) of the hydraulic cylinder is connected to the control valve (12) and to the recovery unit (14) in a point (16) between the control valve and the recovery unit. The method comprises the steps of identifying a requested lowering speed of the implement (3), and identifying a desired pressure at the piston side (13) of the hydraulic cylinder (11) and controlling the recovery unit (14) to provide a counter pressure resulting in the desired pressure at the piston side of the hydraulic cylinder, and enabling fluid communication between the piston side (13) of the hydraulic cylinder and the recovery unit (14), and between the piston side (13) of the hydraulic cylinder and the piston rod side (15) of the hydraulic cylinder (11), via the control valve (12), and controlling the control valve (12) in such a way that the flow through the control valve corresponds to the requested lowering speed of the implement (3).
Abstract:
A hydraulic system (46) is disclosed that has first and second passages (86, 88) connecting a pump (50) to an actuator (22) in closed-loop manner, and first and second load-holding valves (86, 88) within the first and second passages. The hydraulic system may also have a regeneration valve (78) connected to the first and second passages between the actuator and the first and second load-holding valves to selectively connect the first and second passages. The hydraulic system may further have a controller (54) configured to cause a control valve (132) to simultaneous move the first and second load-holding valves toward flow-blocking positions when pump displacement is about zero. The controller may also be configured to selectively cause the regeneration valve to connect the first and second passages when pump displacement is non-zero, and to cause only one of the first and second load-holding valves to move to its flow-blocking position when the regeneration valve connects the first and second passages.
Abstract:
First and second mechanical hydraulic valves (342, 340) are disposed between a pump (180) and the cap side chamber (170) of an actuator (132) and the pump (180) and the rod chamber (168) of the pump (180). The first and second valves (340, 342) are actuated as a result of respective pressure differentials applied across the valves (340, 342). A controller (320) controls flow from a pump (180) in response to a commanded motion to control movement of the actuator (132), and cause the valves (340, 342) to open. The valves (340, 342) are disposed in their no-flow positions when the pump (180) is not operative, and when the hydraulic system (104) of off or locked out to hold a load.
Abstract:
Offenbart wird ein hydraulischer Antrieb für einen hydraulischen Verbraucher oder für ein Hydrauliksystem mit einer verdrängungsvariablen Pumpe, die mechanisch mit einem vorzugsweise drehzahlvariablen Antriebsmotor gekoppelt ist und einer Steuerung zur Verstellung zumindest des Hubvolumens der Pumpe und optional der Drehzahl des Antriebsmotors. Erfindungsgemäß ist eine Drehmomenterfassungs-/ oder - bestimmungseinrichtung vorgesehen, die ein aktuelles Abgabedrehmoment des Antriebsmotors erfasst oder berechnet, wobei im Ansprechen darauf das Hubvolumen der Pumpe auf einen Wert eingestellt wird, bei dem das aktuelle Abgabedrehmoment auf oder unterhalb eines eingestellten Maximalwerts liegt.