Fluid working machines and methods

摘要

A fluid working machine, operable to carry out a motoring cycle under at least some circumstances, comprises a controller (12) and a working chamber (2) of cyclically varying volume. The working chamber has a high pressure valve (18) associated therewith to control the connection of the working chamber to a high pressure manifold (20), and an electronically controllable primary low pressure valve (14) to control the connection of the working chamber to a low pressure manifold. The controller is operable to actively control at least the primary low pressure valve, in phased relationship to cycles of working chamber volume, to determine the net displacement of fluid by the working chamber on a cycle by cycle basis. The fluid working machine is adapted to release pressurised fluid from the working chamber prior to the opening of the primary low-pressure valve, during a motoring cycle. This facilitates the opening of the primary low pressure valve.