Fluid-working machine

A valve arrangement for controlling fluid flow from a high-pressure line to a working chamber of cyclically varying volume of a hydraulic or pneumatic motor or pump, the working chamber having a piston that is movable to cyclically vary a volume of the working chamber, the valve arrangement comprising:

• a main valve having a valve element arranged to provide sealing contact with a valve seat, and
• an auxiliary valve comprising an electromagnetically-movable valve member for equalising pressure on either side of the main valve by placing the working chamber in direct fluid communication with the high pressure line,
• wherein
• the valve element has an internal conduit communicating with an opening defined by the valve seat, and
• the electromagnetically-movable valve member is adapted to place the internal conduit in direct fluid communication with a space surrounding said valve element such that the internal conduit connects the working chamber with the high pressure line,
• wherein
• the valve element is a poppet valve having a poppet shank, and
• the electromagnetically-moveable member is a moving pole ring slidable on the poppet shank, and
• wherein
• a pole compression spring is configured to act on the pole ring and the poppet shank.

A hydraulic or pneumatic motor or pump, comprising:

• a high-pressure line;
• a working chamber having a piston that is movable to cyclically vary a volume of the working chamber;
• and
• a valve arrangement disposed between the high-pressure line and the working chamber for controlling fluid flow from the high-pressure line to the working chamber, the valve arrangement comprising
• a main valve having a valve element arranged to provide sealing contact with a valve seat, and
• an auxiliary valve comprising an electromagnetically-movable valve member for equalising pressure on either side of the main valve by placing the working chamber in direct fluid communication with the high-pressure line, the main and auxiliary valves being integrated,
• wherein
• the valve element has an internal conduit communicating with an opening defined by the valve seat,
• the electromagnetically-movable valve member is adapted to place the internal conduit in direct fluid communication with a space surrounding said valve element such that the internal conduit connects the working chamber with the high pressure line, and
• the valve arrangement further comprises
• a main biasing element for biasing the valve element towards the valve seat, and
• an auxiliary biasing element for biasing the electromagnetically-movable valve member to a position in which the internal conduit is isolated from the space surrounding said valve element.

A valve arrangement for controlling fluid flow from a high-pressure line to a working chamber of cyclically varying volume of a hydraulic or pneumatic motor or pump, the working chamber having a piston that is movable to cyclically vary a volume of the working chamber, the valve arrangement comprising:

• a main valve having a valve element arranged to provide sealing contact with a valve seat,
• an auxiliary valve comprising an electromagnetically-movable valve member for equalising pressure on either side of the main valve by placing the working chamber in direct fluid communication with the high pressure line, the main and auxiliary valves being integrated,
• wherein
• the valve element has an internal conduit communicating with an opening defined by the valve seat,
• the electromagnetically-movable valve member is adapted to place the internal conduit in direct fluid communication with a space surrounding said valve element such that the internal conduit connects the working chamber with the high pressure line, and
• the valve arrangement further comprises
• a main biasing element for biasing the valve element towards the valve seat, and
• an auxiliary biasing element for biasing the electromagnetically-movable valve member to a position in which the internal conduit is isolated from the space surrounding said valve element.