Piston compressor and method for operating a piston compressor

Abstract

In order to avoid over-lubrication of the cylinders (2) in a piston compressor (1) and to reduce the amount of lubricant to a level required for operation, according to the invention, a lubricating system having a lubricating system control unit (14) is provided, in which system at least one lubricant sensor (15) is provided for detecting a lubricating film measurement variable (S) representative of a lubricating film thickness of a lubricating film (11) on the cylinder surface of the cylinder (2), the lubricating system control unit (14) being designed to operate the lubricating system at least once in a predetermined calibration operating mode during operation of the piston compressor (1) and to determine a lubricating film state value (SZ) on the basis of the lubricating film measurement variable (S) detected during execution of the calibrating operating mode and the lubricating system control unit (14) being designed, after the end of the calibration operating mode during operation of the piston compressor (1), to control the amount of lubricant to be introduced depending on the determined lubricating film state value (SZ).

1 . Lubricating system for a piston compressor for introducing a lubricant onto a cylinder surface of a cylinder of the piston compressor in which a piston can be moved in a reciprocating manner, the lubricating system comprising:
 a lubricating system control unit configured to control an amount of lubricant to be introduced,   at least one lubricant sensor configured to detect a lubricating film measurement variable representative of a lubricating film thickness of a lubricating film on the cylinder surface of the cylinder,   wherein the lubricating system control unit is further configured to
 operate the lubricating system at least once in a predetermined calibration operating mode during operation of the piston compressor, 
 determine a lubricating film state value on the basis of the lubricating film measurement variable detected during execution of the calibrating operating mode, and 
 after the end of the calibration operating mode, during operation of the piston compressor, control the amount of lubricant to be introduced depending on the determined lubricating film state value. 
   
     
     
         2 . The  1  lubricating system according to  claim 1 , characterized in that the lubricant sensor is an ultrasonic sensor. 
     
     
         3 . The lubricating system according to  claim 1 , characterized in that the lubricating system control unit is further configured to use a sensor value of the lubricating film measurement variable to determine the lubricating film state value, the sensor value is detected during a piston stroke of the piston at a point in time at which a piston ring of the piston is in the sensor region of the lubricant sensor. 
     
     
         4 . The lubricating system according to  claim 1 , characterized in that the lubricating system is configured for an intermittent introduction of the lubricant into the cylinder, and
 the lubricating system control unit is further configured to control the amount of lubricant by changing a frequency and/or an injection amount of each injection of the intermittent introduction of the lubricant.   
     
     
         5 . The lubricating system according to  claim 1 , wherein the lubricating system control unit is further configured to repeat the calibration operating mode in a specified cycle in order to update the lubricating film state value and to adapt the amount of lubricant to the updated lubricating film state value. 
     
     
         6 . The lubricating system according to  claim 1 , characterized in that a duration of the calibration operating mode is at least ten, crankshaft revolutions of the piston compressor or an equivalent time. 
     
     
         7 . The lubricating system according to  claim 1 , wherein the lubrication system control unit is further configured and arranged to operate the lubricating system in at least two consecutive time ranges with different amounts of lubricant in the calibration operating mode, determine a maximum value and a minimum value in a time profile of the lubricating film measurement variable detected during the at least two time ranges and to determine therefrom the lubricating film state value for controlling the amount of lubricant. 
     
     
         8 . The lubricating system according to  claim 7 , wherein the lubrication system control unit is further configured and arranged to operate the lubricating system in
 a first time range having a predetermined duration and a subsequent second time range having a predetermined duration, wherein the amount of lubricant introduced during the first time range is defined such that a completely wetted lubricating film sets on the cylinder surface, and   the amount of lubricant introduced during the second time range is set such that dry running occurs on the cylinder surface.   
     
     
         9 . The lubricating system according to  claim 7 , characterized in that the lubricating system control unit is further configured to
 determine a difference value between the determined maximum value and the determined minimum value,   determine a lubricating film limit value from the maximum value and the determined difference value,   use the lubricating film limit value as a lubricating film state value and   during operation of the piston compressor after the end of the calibration operating mode, introduce the lubricant when the lubricating film measurement variable lies in a lubricating system activation range between the minimum value and the lubricating film limit value.   
     
     
         10 . The lubricating system according to  claim 1 , further including a lubricant amount detection unit configured to detect an amount of lubricant supplied to a lubrication point and in that the lubricating system control unit is configured to compare the lubricating film measurement variable obtained from the lubricating film sensor and the amount of lubricant obtained from the lubricant amount detection unit in order to check the two values for consistency and/or to detect a leak in the lubricating system. 
     
     
         11 . A piston compressor comprising:
 a number of cylinders,   a number of pistons, each piston arranged in one of the cylinders and configured to move in a reciprocating manner within the respective cylinder,   at least one lubrication point provided on each of the number of cylinders, and configured to introduce the lubricant onto a cylinder running surface of the cylinder, and   a lubricating system in accordance with  claim 1  configured to supply the number of cylinders with the lubricant.   
     
     
         12 . The piston compressor according to  claim 11 , characterized in that a plurality of lubrication points and/or a plurality of lubricant sensors are provided on at least one cylinder. 
     
     
         13 . Method for operating a piston compressor having at least one cylinder in which a piston is moved in a reciprocating manner, wherein a lubricant is supplied to a cylinder surface of the at least one cylinder by means of a lubricating system and an amount of lubricant of the supplied lubricant being controlled by a lubricating system control unit, the method including the following steps:
 using at least one lubricant sensor to detect a lubricating film measurement variable representative of a lubricating film thickness of a lubricating film on the cylinder surface of the cylinder,   operating the lubricating system at least once by the lubricating system control unit in a predetermined calibration operating mode during operation of the piston compressor,   determining a lubricating film state value on the basis of the lubricating film measurement variable detected during execution of the calibrating operating mode, and   in that the lubricating system control unit, after the end of the calibration operating mode during operation of the piston compressor, controls the amount of lubricant to be introduced depending on the determined lubricating film state value.   
     
     
         14 . The method according to  claim 13 , characterized in that an ultrasonic sensor is used as the lubricant sensor. 
     
     
         15 . The method according to  claim 13 , characterized in that a sensor value of the lubricating film measurement variable is used to determine the lubricating film state value, the sensor value is detected during a piston stroke of the piston at a point in time at which a piston ring of the piston is in the region of the lubricant sensor. 
     
     
         16 . The method according to  claim 13 , characterized in that the lubricant is intermittently introduced into the cylinder and in that the lubricating system control unit controls the amount of lubricant by changing a frequency and/or an injection amount of each injection of the intermittent introduction of the lubricant. 
     
     
         17 . The method according to  claim 13 , characterized in that the calibration operating mode is repeated in a specified cycle in order to update the lubricating film state value and to adapt the amount of lubricant to the updated lubricating film state value and/or in that the calibration operating mode is executed over at least ten, crankshaft revolutions of the piston compressor or an equivalent time. 
     
     
         18 . The method according to  claim 13 , characterized in that in the calibration operating mode, different amounts of lubricant are introduced into the cylinder in at least two consecutive time ranges and in that the lubricating system control unit determines a maximum value and a minimum value in a time profile of the lubricating film measurement variable detected during the at least two time ranges and determines therefrom the lubricating film state value for controlling the amount of lubricant. 
     
     
         19 . The method according to  claim 18 , characterized in that a first time range having a predetermined duration and a subsequent second time range having a predetermined duration are defined and in that the amount of lubricant introduced during the first time range is defined such that a completely wetted lubricating film forms on the cylinder surface and the amount of lubricant introduced during the second time range is defined such that dry running occurs on the cylinder surface, the duration of the first time range and the amount of lubricant introduced during the first time range being 90-200% of an amount of lubricant predetermined by the compressor manufacturer and the duration of the second time range and the amount of lubricant introduced during the second time range being 0% of the amount of lubricant predetermined by the compressor manufacturer. 
     
     
         20 . The method according to  claim 18 , characterized in that a difference value between the determined maximum value and the determined minimum value is determined,
 a lubricating film limit value is determined from the maximum value and the determined difference value, and   the lubricating film limit value is used as a lubricating film state value and in that the lubricating system control unit, after the end of the calibration operating mode, controls the lubricating system for introducing the lubricant when the lubricating film measurement variable lies in a lubricating system activation range between the minimum value and the lubricating film limit value.   
     
     
         21 . The lubricating system according to  claim 8 , wherein the duration of the first time range and the amount of lubricant introduced during the first time range being 90-200% of an amount of lubricant predetermined by the compressor manufacturer and the duration of the second time range and the amount of lubricant introduced during the second time range being 0% of the amount of lubricant predetermined by the compressor manufacturer. 
     
     
         22 . The piston compressor according to  claim 12 , wherein the plurality of lubrication points and/or lubricant sensors being provided in the circumferential direction of the at least one cylinder and/or a plurality of lubrication points and/or lubricant sensors being provided in the axial direction of the at least one cylinder. 
     
     
         23 . The method according to  claim 15 , wherein a minimum value of the lubricating film measurement variable (S) detected during the piston stroke. 
     
     
         24 . The method according to  claim 19 , the duration of the first time range being at least five crankshaft revolutions and the amount of lubricant introduced during the first time range being 90-200% of an amount of lubricant predetermined by the compressor manufacturer and the duration of the second time range being at least five crankshaft revolutions and the amount of lubricant introduced during the second time range being 0% of the amount of lubricant predetermined by the compressor manufacturer.