DELIVERY UNIT

Delivery units are already known, having a drive rotor and an output rotor driven by the drive rotor, which are rotatably mounted in a rotor housing and interact in a meshing manner via spur toothing in each case, at least one of the two rotors being axially adjustable and, on the rear side thereof, facing away from the other rotor, having a compensating pressure applied via a compensation channel. The compensating pressure acts firstly counter to the axial compressive forces which arise in the working chambers formed between the rotors, and secondly compensates for the forces which would force the two rotors apart. This ensures that the distance between the rotors does not change. The compensating pressure frequently corresponds to the pressure on the pressure side of the delivery unit, which means that the forces on the rotors are considerably higher than necessary. This leads to increased friction in the bearings and between the rotors. The rear side of the rotors can also be supplied via slot flows. This has the disadvantage that an undefined compensating pressure is established, which depends on the leakage flows which flow into the space or out of the space behind the rotor. In addition, in this embodiment the compensating pressure does not have the ideal value for low-friction operation. In the delivery unit according to the invention, a defined compensating pressure is established on the rear side of the axially adjustable rotors. The invention provides for a control valve (14) to be provided, which sets the compensating pressure to a predetermined value between a pressure on the pressure side and a pressure on the suction side.