Method for conveying hydraulic fluid, and electrohydraulic motor-pump unit therefor

Abstract

An electrohydraulic motor-pump unit comprises an unsteadily conveying displacement pump for conveying hydraulic fluid in a hydraulic system, an electric motor coupled with the displacement pump for driving the displacement pump, and an electrical control device coupled with the electric motor for controlling the electric motor. By way of a detector there is captured a pulsation parameter, which originates from a pulsation arising due to unsteady conveyance of hydraulic fluid in the hydraulic system, and by way of a modulator as part of the electrical control device the drive torque or the rotating speed of the electric motor for driving the displacement pump is modulated on the basis of the captured pulsation parameter. As a result the drive torque or the rotating speed of the electric motor is modulated in accordance with the conveying frequency of the displacement pump.

1 . An electrohydraulic motor-pump unit, comprising:
 an unsteadily conveying displacement pump which is arranged for conveying hydraulic fluid in a hydraulic system, an electric motor coupled with the displacement pump and arranged for driving the displacement pump, and an electrical control device coupled with the electric motor and arranged for controlling the electric motor, further comprising a modulator as part of the electrical control device, which is arranged for modulating a drive torque or a rotating speed of the electric motor for driving the displacement pump in accordance with a conveying frequency of the displacement pump.   
     
     
         2 . The motor-pump unit according to  claim 1 , wherein the displacement pump, the electric motor and the electrical control device are housed in a common housing block having hydraulic connections which are arranged for coupling the motor-pump unit to a hydraulic system, wherein the housing block preferably further comprises a hydraulic fluid tank for hydraulic fluid. 
     
     
         3 . The motor-pump unit according to  claim 1 , comprising a detector which is arranged for capturing a pulsation parameter which originates from a pulsation arising due to unsteady conveyance of hydraulic fluid in a hydraulic system, wherein the modulator is arranged for modulating the drive torque or a rotational speed of the electric motor on the basis of the captured pulsation parameter. 
     
     
         4 . The motor-pump unit according to  claim 3 , further comprising, as a detector, a pressure sensor which is arranged for capturing as the pulsation parameter a hydraulic pressure. 
     
     
         5 . The motor-pump unit according to  claim 3 , further comprising, as a detector, a pressure sensor on one of the hydraulic connections, which is arranged for capturing as the pulsation parameter a hydraulic pressure present on the hydraulic connection. 
     
     
         6 . The motor-pump unit according to  claim 3 , further comprising, as a detector, an evaluation circuit which is arranged for capturing as the pulsation parameter the drive torque of the electric motor, wherein the evaluation circuit is implemented in the electrical control device. 
     
     
         7 . The motor-pump unit according to  claim 1 , wherein the modulator comprises a circuit with an FPGA (field programmable gate array). 
     
     
         8 . A hydraulic system, comprising hydraulic lines and a motor-pump unit according to  claim 1  connected to said hydraulic lines. 
     
     
         9 . A method for conveying hydraulic fluid in a hydraulic system by an electrically driven, unsteadily conveying displacement pump, comprising:
 smoothing a pulsation of the hydraulic fluid in the hydraulic system, arising on due to the unsteady conveyance, by modulating a drive torque or a rotating speed of the electrical drive in accordance with a conveying frequency of the displacement pump.   
     
     
         10 . The method according to  claim 9 , wherein smoothing comprises a pulsation parameter wherein the pulsation is captured and the drive torque or the rotational speed of the electrical drive is modulated on the basis of the captured pulsation parameter. 
     
     
         11 . The method according to  claim 10 , wherein the drive torque or the rotational speed of the electrical drive is modulated on the basis of a pressure pulsation measured in the hydraulic fluid. 
     
     
         12 . The method according to  claim 10 , wherein the drive torque of the electrical drive is modulated on the basis of a torque pulsation measured on the electrical drive. 
     
     
         13 . The method according to  claim 10 , wherein the modulating of the drive torque or of the rotational speed of the electrical drive is effected via a circuit with an FPGA (field programmable gate array). 
     
     
         14 . The method according to  claim 9 , further comprising employing a motor-pump unit.