Delivery unit

Abstract

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.

1 . A conveying assembly with a driving rotor ( 3 ) and with a driven rotor ( 3 ) driven by the driving rotor ( 2 ), said rotors being mounted rotatably in a rotor housing ( 4 ) and cooperating in a meshing manner in each case via a spur toothing ( 5 ), at least one of the two rotors ( 2 ,  3 ) being axially adjustable and being acted upon, on a rear side ( 2 . 1 ,  3 . 1 ) facing away from the other rotor ( 2 ,  3 ), by a compensating pressure, characterized in that a control valve ( 14 ) sets the compensating pressure at a predetermined value between a pressure on a delivery side and a pressure on a suction side. 
     
     
         2 . The conveying assembly as claimed in  claim 1 , characterized in that the control valve ( 14 ) has a control piston ( 15 ) and first, second and third control chambers ( 16 ,  17 ,  18 ) separated from one another via the control piston ( 15 ), the first control chamber ( 16 ) of the control valve ( 14 ) being acted upon by the pressure on the delivery side and the second control chamber ( 17 ) by the pressure on the suction side, the third control chamber ( 18 ) being flow-connectable to the first control chamber ( 16 ) or to the second control chamber ( 17 ) via a control duct ( 19 ) formed on the control piston ( 15 ). 
     
     
         3 . The conveying assembly as claimed in  claim 2 , characterized in that an inlet cross section of the control duct ( 19 ) is variable as a function of the position of a control piston ( 15 ). 
     
     
         4 . The conveying assembly as claimed in  claim 3 , characterized in that the control piston ( 15 ) projects through a passage duct ( 22 ) between the first and the second control chamber ( 16 ,  17 ), the variable inlet cross section of the control valve ( 14 ) being achieved by a partial overlap of the inlet cross section by a wall of the passage duct ( 22 ). 
     
     
         5 . The conveying assembly as claimed in  claim 1 , characterized in that the control duct ( 19 ) issues at an end facing away from the inlet cross section into the third control chamber ( 18 ). 
     
     
         6 . The conveying assembly as claimed in  claim 1 , characterized in that the control valve ( 14 ) is a proportional valve. 
     
     
         7 . The conveying assembly as claimed in  claim 1 , characterized in that the control piston ( 15 ) is acted upon by two valve springs ( 23 ) counteracting one another. 
     
     
         8 . The conveying assembly as claimed in  claim 1 , characterized in that the control valve ( 14 ) is fastened to the rotor housing ( 4 ) of the conveying assembly. 
     
     
         9 . The conveying assembly as claimed in  claim 1 , characterized in that a pressure of the third control chamber ( 18 ) is conducted via a flow connection ( 24 ) onto a rear side ( 2 . 1 ,  3 . 1 ) of the rotors ( 2 ,  3 ). 
     
     
         10 . The conveying assembly as claimed in  claim 1 , characterized in that the driving rotor ( 2 ) and the driven rotor ( 3 ) have a cycloidal toothing. 
     
     
         11 . The conveying assembly as claimed in  claim 1 , characterized in that the control valve ( 14 ) is integrated in the rotor housing ( 4 ). 
     
     
         12 . The conveying assembly as claimed in  claim 1 , characterized in that the driving rotor ( 2 ) and the driven rotor ( 3 ) have a trochoidal toothing.