Patent ID: 8657589

Claim:
A method of operating a hydraulic machine having at least one working chamber of cyclically changing volume, and a low-pressure valve to control a connection of each of the at least one working chamber to a low-pressure line, said low-pressure valve being an electromagnetically controlled valve that is open in its passive state, and a passive high-pressure check valve to control a connection of each of the at least one working chambers to a high-pressure line that is separate from said connection to the low-pressure line, the machine having (1) a normal idle mode, in which fluid at low pressure flows into and out of the working chamber via the low-pressure valve, (2) a working mode, in which the cylinder delivers fluid from the low-pressure line to the high-pressure line or vice-versa, and (3) a hibernation mode in which the low-pressure valve is held closed during expansion and contraction of the working cylinder, the hibernation mode being selected if it is foreseen that the working chamber will not be required to provide an output during two cycles of the chamber and, in the hibernation mode, the low-pressure valve being held closed during said two cycles, starting at minimum chamber volume, releasing air dissolved in liquid in the chamber from the liquid during expansions of the chamber volume and redissolving the air in the liquid during reductions in the chamber volume, wherein the selection of the hibernation mode is made based on a combination of a shaft speed of the machine and a viscosity of the liquid.