Method and apparatus for diagnosing motor-operated valve

Abstract

A diagnostic method and apparatus for diagnosing a motor-operated valve capable of continuously measuring a preload of a spring cartridge at low costs, with high accuracy, and with ease, so that the elastic characteristics of the spring cartridge may be easily calibrated in a simple manner. The method and apparatus is for diagnosing a motor-operated valve including a valve disc 25 , a worm 12 rotatably driven by motor power, a link mechanism which opens and closes the valve disc 25 with the rotational driving force transmitted from the worm 12 , and a spring cartridge 13 containing disc springs 15 which expand or compress in response to reaction force acting on the worm 12 in its axial direction from the link mechanism. The method and apparatus calibrates the torque curve representing the elastic characteristics the spring cartridge 13 based on the load corresponding to a specific compression condition of the spring cartridge 13 , and based on the torque curve thus calibrated, produces a diagnosis of the motor-operated valve. Accordingly, an easy and quick diagnosis can be achieved on whether the torque-related characteristics of the motor-operated valve are appropriate or not.

1 . A motor-operated valve diagnostic method for diagnosing a motor-operated valve comprising a valve disc for opening and closing a given passage, a worm rotatably driven by motor power, a link mechanism which opens and closes the valve disc with rotational driving force transmitted from the worm, and a spring cartridge containing disc springs which expand or compress in response to reaction force, acting axially on the worm from the link mechanism said method comprising:
 calibrating a torque curve representing elastic characteristics of the spring cartridge with a spring pressing device mounted on the motor-operated valve, the spring pressing device pressing the disc springs axially within the spring cartridge while measuring a relationship between a pressing force applied to the disc springs and a displacement of the disc springs, and   diagnosing the motor-operated valve based on the calibrated torque curve.   
     
     
         2 . The motor-operated valve diagnostic method as claimed in  claim 1 , wherein the valve disc is moveable between a full open position and a full closed position, wherein the elastic characteristics of the spring cartridge show a hysteresis between when the valve disc moves from the full open position toward the full closed position and when the valve disc moves from the full closed position toward the full open position, and wherein the elastic characteristics of the spring cartridge for the valve disc opening movement from the full closed position toward the full open position are determined by means of the spring pressing device without the motor-operated valve in operation, while the elastic characteristics of the spring cartridge for the valve disc closing movement from the full open position are determined by the spring pressing device with the motor-operated valve in operation. 
     
     
         3 . A motor-operated valve diagnostic apparatus for diagnosing a motor-operated valve comprising a valve disc for opening and closing a given passage, a worm rotatably driven by motor power, a link mechanism which opens and closes the valve disc with rotational driving force transmitted from the worm, and a spring cartridge containing disc springs which expand or compress in response to reaction force acting on the worm from the link mechanism, said diagnostic apparatus comprising:
 diagnostic means for calibrating a torque curve representing elastic characteristics of the spring cartridge with a spring pressing device mounted on the motor-operated valve, the spring pressing device pressing the disc springs axially within the spring cartridge while measuring a relationship between a pressing force applied to the disc springs and a displacement of the disc springs, said diagnostic device diagnosing the motor-operated valve based on the calibrated torque curve.   
     
     
         4 . The motor-operated valve diagnostic apparatus as claimed in  claim 3 , wherein the spring pressing device is attached to the motor-operated valve through an adapter substituted for a cover covering the spring cartridge. 
     
     
         5 . The motor-operated valve diagnostic apparatus as claimed in  claim 3 , further comprising output means for outputting acceptance criteria relating to the diagnostic results or for the diagnostic data together with the diagnostic results and/or diagnostic data. 
     
     
         6 . The motor-operated valve diagnostic apparatus as claimed in  claim 3 , wherein the valve disc is moveable between a full open position and a full closed position, wherein the elastic characteristics of the spring cartridge shows a hysteresis between when the valve disc moves from the full open position toward the full closed position and when the valve disc moves from the full closed position toward the full open position, wherein the spring pressing device determines the elastic characteristics of the spring cartridge for the valve disc opening movement from the full closed position toward the full open position without the motor-operated valve in operation and the elastic characteristics of the spring cartridge for the valve disc closing movement from the full open position toward the full closed position with the motor-operated valve in operation. 
     
     
         7 . The motor-operated valve diagnostic apparatus as claimed in  claim 6 , wherein the spring pressing device is attached to the motor-operated valve through an adapter substituted for a cover covering the spring cartridge. 
     
     
         8 . The motor-operated valve diagnostic apparatus as claimed in  claim 6 , further comprising a worm position sensor for detecting a condition of compression of the spring cartridge, which results from the reaction force, as a worm axial displacement, and a stress sensor for detecting stress acting on the link mechanism or reaction stress generated in an area subjected to the stress acting on the link mechanism, wherein said diagnostic means detects a load corresponding to the preload of the spring cartridge based on the stress detected by the stress sensor when the spring cartridge is under compression, including at least a compression condition at the time the spring cartridge starts deforming, as detected by the worm position sensor. 
     
     
         9 . The motor-operated valve diagnostic apparatus as claimed in  claim 8 , wherein the spring pressing device is attached to the motor-operated valve exchangeably with the worm position sensor through an adapter substituted for a cover covering the spring cartridge. 
     
     
         10 . The motor-operated valve diagnostic apparatus as claimed in  claim 9 , wherein the worm position sensor comprises a laser sensor which detects the position of an object by irradiating a laser beam onto the object and detecting light reflected therefrom, wherein the object is an axial edge of the spring cartridge which is axially displaced together with said worm or a part connected to the axial edge for movement therewith. 
     
     
         11 . The motor-operated valve diagnostic apparatus as claimed in  claim 3 , further comprising a worm position sensor for detecting a condition of compression of the spring cartridge, which results from the reaction force, as a worm axial displacement, and a stress sensor for detecting stress acting on the link mechanism or reaction stress generated in an area subjected to the stress acting on the link mechanism, wherein said diagnostic means detects a load corresponding to the preload of the spring cartridge based on the stress detected by the stress sensor when the spring cartridge is under compression, including at least a compression at the time the spring cartridge starts deforming, as detected by the worm position sensor. 
     
     
         12 . The motor-operated valve diagnostic apparatus as claimed in  claim 11 , wherein the spring pressing device is attached to the motor-operated valve exchangeably with the worm position sensor through an adapter substituted for a cover covering the spring cartridge. 
     
     
         13 . The motor-operated valve diagnostic apparatus as claimed in  claim 12 , wherein the worm position sensor comprises a laser sensor which detects the position of an object by irradiating a laser beam onto the object and detecting light reflected therefrom, wherein the object is an axial edge of the spring cartridge which is axially displaced together with said worm or a part connected to the axial edge for movement therewith.