Abstract:
The present invention relates to a control unit (24) for a hydraulic system (16), the hydraulic system (16) comprising a hydraulic actuator (18) which in turn comprises an actuator chamber (26), the hydraulic actuator (18) comprising a first actuator portion (30) and a second actuator portion (32) wherein the first actuator portion (30) can move relative to the second actuator portion (32), the actuator chamber (26) being in fluid communication with a flow rate control arrangement (34) adapted to control a rate of flow from the actuator chamber (26). According to the present invention, the control unit (24) is adapted to: -receive a load signal indicative of the magnitude of the load (L) applied to the hydraulic actuator (18), which load (L) is determined to impart a pressure in the actuator chamber (26); -receive a requested speed signal indicative of a desired relative speed of movement between the first actuator portion (30) and the second actuator portion (32) in a direction that reduces the chamber volume, and - on the basis of the load signal and the requested speed signal, issue a control signal to the flow rate control arrangement (34) indicative of a desired flow rate from the actuator chamber (26).
Abstract:
A closed-loop hydraulic circuit (164) associated with a swing mechanism (105) of a machine is controlled to obtain both a pressure control during acceleration and deceleration of the swing mechanism (105) and a velocity control during coasting. In this manner, a system pressure in closed-loop hydraulic circuit (164) is maintained below a maximum allowable pressure during acceleration and deceleration, and the swing mechanism (105) can be rotated at a desired constant speed during coasting. This is achieved by controlling a hydraulic actuator (142) adjusting the displacement of a variable displacement pump (140) in different control modes, depending on a comparison between a desired displacement of the pump and an actual displacement of the same.
Abstract:
Eine Ablaufdruckwaage (30), bestehend aus mindestens einem Venti lgehäuse (41 ) mit mindestens drei Fluid-Anschlussstel len in Form eines Nutzanschl usses (A), eines Rücklaufanschlusses (T) und eines Steueranschlusses (28), in dem entgegen der Wirkung eines Energiespeichers (42) ei n Venti lkolben (52) längsverfahrbar geführt, von einer jewei ligen Öffnungs- oder Regelstel lung ausgehend, gegen einen Ventilsitz (94) in eine Schließstel l ung verfährt, bei der Steuer(28)- und Rück- laufanschluss (T) voneinander getrennt sind, ist dadurch gekennzeichnet, dass mittels einer Druckausgleichseinrichtung (70) der am Steuer- anschl uss (28) anstehende Fl uiddruck derart auf eine druckwi rksame Fläche (A 1 *) des Ventilkolbens (52) geführt ist, dass dieser druckausgeglichen aufgrund der Kraft des Energiespeichers (42) in seine jeweilige Öffnungs- oder Regelstellung gelangt.
Abstract:
Modular directional valve with two or more crossing elements (E1.. En) fed by a variable displacement (PA), negative control or load sensing pump. A pressure regulator (5) is placed in the entry side and only on the bypass line and upstream of the first element (E1..En). In the single drive, it makes the flow rate to the utility independent of the load and allows setting a maximum flow rate at the end of the stroke; in multiple drives, it ensures that the sum of the required flow rates is independent of the loads.