In order to simultaneously generate pressure and negative pressure with a single-stage rotary piston machine, said machine has a chamber (18) that is formed in a housing and that is provided with a suction connection, a pressure port and a charging port. In the pump chamber (18), there are two three-blade rotors (30, 32) that work with internal compression and internal expansion and that rotate in opposite directions around parallel spaced axes and these rotors intermesh so as to be free of contact so that, together with the peripheral wall of the pump chamber (18), they define cells (60, 62a, 62b, 64) that are separate from each other.