Method for Controlling and/or Regulating a Metering Pump

Abstract

The present invention concerns a method of controlling and/or regulating a metering pump comprising a drive motor having a shaft driven by the motor and a displacement member arranged in a metering head, in which the rotary movement of the shaft is converted into an oscillating movement of the displacement member, wherein the displacement member, interacting with an outlet and inlet valve in alternate sequence, leads to a pump stroke (pressure stroke) and an intake stroke and thus to delivery of a medium to be metered. To provide a method of controlling and/or regulating a metering pump, which in principle manages without a position sensor on the thrust rod and can establish the metering behaviour of the pump with a high degree of precision, according to the invention it is proposed that at least one motor operating parameter, preferably a motor voltage U or a motor current I, is measured, at least one regulating parameter is calculated from the measured motor operating parameters and optionally further known motor characteristics, the at least one regulating parameter is compared to a predetermined guide parameter, and a comparison signal dependent on the result of the comparison is outputted, and can be used as a status, actuating and/or regulating signal.

1 . A method of controlling and/or regulating a metering pump comprising a drive motor having a shaft driven by the motor and a displacement member arranged in a metering head, in which the rotary movement of the shaft is converted into an oscillating movement of the displacement member, wherein the displacement member, interacting with an outlet and inlet valve in alternate sequence, leads to a pump stroke (pressure stroke) and an intake stroke and thus to delivery of a medium to be metered,
 characterised in that   at least one motor operating parameter, preferably a motor voltage U or a motor current I, is measured,   at least one regulating parameter is calculated from the measured motor operating parameters and optionally further known motor characteristics,   the at least one regulating parameter is compared to a predetermined guide parameter, and   a comparison signal dependent on the result of the comparison is outputted, and can be used as a status, actuating and/or regulating signal.   
     
     
         2 . A method according to  claim 1  characterised in that the actual torque M ACTUAL  and optionally the magnetic actual flux Φ ACTUAL  of the motor, preferably an asynchronous motor, is calculated as the regulating parameter. 
     
     
         3 . A method according to  claim 2  characterised in that a reference torque M LIM  is used as the guide parameter and a status and/or actuating signal is outputted if the regulating parameter deviates from the guide parameter more than a predetermined torque difference, wherein preferably the guide parameter varies in time. 
     
     
         4 . A method according to  claim 1  characterised in that as the regulating parameter the actual motor speed is measured preferably a plurality of times, particularly preferably at least five times, during a motor revolution, or is calculated from the motor operating parameters, preferably from the actual torque M ACTUAL  and the magnetic actual flux Φ ACTUAL  of the motor, and the difference between the actual motor speed and a predetermined reference motor speed is outputted as the comparison signal and the comparison signal is used as a regulating signal for adaptation of motor current I and/or motor voltage U to adapt the actual motor speed to the reference motor speed. 
     
     
         5 . A method according to  claim 1  characterised in that the metering pump is controlled and/or regulated, having a transmission for conversion of a rotary movement into a translatory movement, which connects the driven shaft of the motor to the displacement member, wherein the transmission preferably has an eccentric which runs on a contact element connected to the displacement member so that by rotation of the shaft the eccentric moves the displacement member in the direction of the metering head and thereby can perform a pump stroke. 
     
     
         6 . A method according to  claim 5  characterised in that a predetermined reference motor speed is used as the guide parameter wherein the reference motor speed is a periodic function having a period duration corresponding to the period duration of the displacement member. 
     
     
         7 . A method according to  claim 6  characterised in that the reference motor speed is established having regard to the transmission characteristic in a such a way that the translatory movement is effected substantially at a constant speed. 
     
     
         8 . A method according to  claim 5  characterised in that as the regulating parameter the actual motor magnetisation is calculated, preferably a plurality of times, particularly preferably at least five times during a motor revolution, from the actual torque M ACTUAL  and optionally from further motor operating parameters and/or known motor characteristics, and a predetermined reference motor magnetisation is selected as the guide parameter and the difference between the regulating parameter and the guide parameter is outputted as the comparison signal and the comparison signal is used as the regulating signal for the adaptation of motor current I and/or motor voltage U to adapt the actual motor magnetisation to the reference motor magnetisation, wherein preferably the reference motor magnetisation is a periodic function with a period duration corresponding to the period duration of the displacement member. 
     
     
         9 . A method according to  claim 1  characterised in that the actual torque M ACTUAL  and optionally the magnetic actual flux Φ ACTUAL  of the motor, preferably an asynchronous motor, is calculated as the regulating signal and the actual torque M ACTUAL  and optionally the magnetic actual flux Φ ACTUAL  of the motor is substantially continuously determined over at least one period duration and the time-dependent actual torque M ACTUAL  calculated in that way and optionally the time-dependent magnetic actual flux Φ ACTUAL  of the motor is compared to at least pre-determined pattern function as the guide parameter and the comparison signal represents the degree of similarity between the regulating parameter and the guide parameter and if the degree of similarity assumes a predetermined range of values the comparison signal is used as the status signal. 
     
     
         10 . A method according to  claim 1  characterised in that the metering pump has a displacement member with an at least partially elastic diaphragm, the metering amount is calculated as the regulating parameter from the time variation in the actual torque M ACTUAL  and optionally the magnetic actual flux Φ ACTUAL  of the motor having regard to further motor characteristics, wherein the influence to be expected by virtue of flexing of the elastic diaphragm on the metering amount is taken into consideration and the difference between the actual metering amount and a predetermined reference metering amount is outputted as the comparison signal and used as the regulating signal for the adaptation of motor current I and/or motor voltage U to adapt the actual metering amount to the reference metering amount. 
     
     
         11 . A method according to  claim 1  characterised in that an actual stroke length of the displacement member is calculated as the regulating parameter from the actual torque M ACTUAL  and optionally the magnetic actual flux Φ ACTUAL  and the difference between the actual stroke length and a predetermined reference stroke length is outputted as the comparison signal, wherein preferably the comparison signal is used as the regulating signal for the adaptation of motor current I and/or motor voltage U to adapt the actual stroke length to the reference stroke length. 
     
     
         12 . A method according to  claim 1  characterised in that the thrust rod position is calculated as the regulating parameter from the measured motor operating parameters and optionally further known motor characteristics. 
     
     
         13 . A metering pump comprising a drive motor having a shaft driven by the motor and a displacement member arranged in a metering head, in which the rotary movement of the shaft is converted into an oscillating movement of the displacement member by means of a transmission, wherein the displacement member, interacting with an outlet and inlet valve in alternate sequence, leads to a pump stroke (pressure stroke) and an intake stroke and thus to delivery of a medium to be metered, characterised in that the metering pump has a control and/or regulating device for carrying out a method according to one of  claims 1 ,  2 ,  4 ,  9 ,  10 ,  11 , and  12 . 
     
     
         14 . A metering pump according to  claim 13  characterised in that the pump is so adapted that it can operate in the pendulum stroke mode of operation, that is to say the direction of rotation of the motor can invert to end an intake stroke or a pump stroke.