Oil-flooded screw compressor with axial-thrust balancing device

Abstract

In an arrangement on an oil-flooded screw compressor with two rotors, a male rotor having essentially convex lobe flanks and a female rotor having essentially concave flank portions, with the male rotor having a drive-shaft end and an oil-pressure loaded balancing piston supplied with oil via a pressure line, both rotors are enclosed in housing sections, with a regulating device arranged either on or in the compressor the inputs of which are at least connected to measuring means for the pressure on the suction side and measuring means for determination of the input power, wherein according to the invention means for changing the pressure in the pressure line to the balancing piston are arranged with said means having a control interconnection to the regulating device, with the latter having an algorithm between operating parameters representing input variables for the regulating device and the pressure in the pressure line to the balancing piston.

1 . Arrangement on an oil-flooded screw compressor with two rotors, a male rotor having essentially convex lobe flanks and a female rotor having essentially concave flank portions, with the male rotor having a drive-shaft end and an oil-pressure loaded balancing piston supplied with oil via a pressure line, both rotors are enclosed in housing sections, with a regulating device arranged either on or in the compressor the inputs of which are at least connected to measuring means for the pressure on the suction side and measuring means for determination of the input power, wherein means for changing the pressure in the pressure line to the balancing piston are arranged with said means having a control interconnection to the regulating device, with the latter having an algorithm between operating parameters representing input variables for the regulating device and the pressure in the pressure line to the balancing piston. 
   
   
       2 . Arrangement on an oil-flooded screw compressor according to  claim 1  with a regulating device wherein a pressure-regulating valve is arranged in the oil-supply line to the balancing piston, with control interconnection between the regulating device and the pressure-regulating valve, with the regulating device having an algorithm containing a relationship between the drive torque at the drive shaft of the compressor, the pressure on the compressor suction side and the pressure on the balancing piston. 
   
   
       3 . Screw compressor according to  claim 1  wherein the relationship of the control algorithm is designed so that the pressure on the oil-pressure loaded balancing piston will increase when the driving torque rises or when the pressure on the compressor suction side rises or when in combination of rising driving torque and rising pressure on the suction side there will occur changes. 
   
   
       4 . Screw compressor according to  claim 1  wherein the relationship of the control algorithm is designed so that the pressure on the oil-pressure loaded balancing piston will decrease when the driving torque decreases or when the pressure on the compressor suction side decreases or when in combination of decreasing driving torque and decreasing pressure on the suction side there will occur changes. 
   
   
       5 . Oil-flooded screw compressor according to  claim 1 , wherein at least one output of the regulating device has a control interconnection to the pressure-regulating valve. 
   
   
       6 . Screw compressor according to  claim 5 , wherein the output signal of the regulating device modulates the pressure on the oil-pressure loaded balancing piston. 
   
   
       7 . Screw compressor according to  claim 1  wherein a pressure-measuring point is located in the supply line between the proportional pressure-regulating valve and the connection for admission of pressure to the balancing piston the output signal of which is connected to a three-position controller. 
   
   
       8 . Screw compressor according to  claim 7 , wherein the output signal of the regulating device is set value and the output signal of the pressure-measuring point is actual value, with both values being inputs to the three-position controller, and the output of the three-position controller has a control interconnection to the pressure-regulating valve. 
   
   
       9 . Screw compressor according to  claim 1  wherein a speed-controlled oil pump is arranged in the supply line for admission of pressure to the balancing piston with the speed of the pump depending on the result of comparison of the three-position controller.