Piston hydraulic motor

A hydraulic motor having pistons, some of which are in a working phase and some are in a non-working phase, whereby the pistons are adapted to rotate the piston hydraulic motor's shaft or casing. To the piston hydraulic motor there are at least two working pressure medium channels, whereby the piston hydraulic motor can be connected for full volume or partial volume. In full volume, all the pistons in the working phase can be brought into the working phase in the motor by a pump's working pressure, whereas in the case of partial volume flow only some pistons can be brought into the working phase by the working pressure. The piston hydraulic motor comprises an actuator, which can close one of the piston hydraulic motor's pressurized inlet channels when the pressure in the other pressure medium channel falls below a certain critical value.