Apparatus and method of belt dynamic tension measurement

Abstract

A method and apparatus for measuring an operating front end accessory belt tension using a hubload transducer and a torque transducer. The hubload transducer comprises concentric rings with a strainable member disposed in a coplanar fashion between an inner and outer ring. The hubload transducer is used with a non-torque transmitting idler pulley. The torque transducer comprises a strainable cylindrical member connected to a belt bearing surface and a rotating shaft. The torque transducer will transmit a torque to a driven accessory. It is used on accessories such as an air conditioner compressor or power steering pump. Signals from the hubload transducer and torque transducer as used to calculate a drive efficiency as well as belt span tensions between the driver and driven accessories.

We claim:  
     
         1 . A transducer comprising; 
 an outer ring member having at least one aperture;    a hub member having at least one aperture;    an arcuate sensor member;    the arcuate sensor member connected between the outer ring member and the hub member, the arcuate sensor member is connected to the outer ring member by a connecting member having a arcuate form for dispersing a stress; and    the outer ring member and the hub member are coplanar.    
     
     
         2 . The transducer as in  claim 1  further comprising: 
 at least one strain gage disposed on a surface of the arcuate sensor member.  
 
     
     
         3 . The transducer as in  claim 1  wherein the arcuate sensor member and the outer ring member and the hub member are coplanar.  
     
     
         4 . The transducer as in  claim 1  wherein the inner ring member describes a means for connecting the hub member to a mounting surface.  
     
     
         5 . The transducer as in  claim 1  wherein the outer member and the hub member are concentric.  
     
     
         6 . A transducer comprising; 
 an outer member having an aperture;    an inner hub member having an aperture;    an arcuate strainable member;    the arcuate strainable member connected to the outer member at a first location and connected to the inner hub member at a second location;    the first location and the second location disposed on substantially opposing sides of the arcuate strainable member; and    the outer member and the inner hub member are coplanar.    
     
     
         7 . The transducer as in  claim 6  further comprising: 
 at least one strain gage disposed on each side of the arcuate strainable member.  
 
     
     
         8 . The transducer as in  claim 6  wherein the arcuate strainable member and the outer member and the inner hub member are coplanar.  
     
     
         9 . The transducer as in  claim 6  wherein the inner hub member describes a bore for receiving a fastener.  
     
     
         10 . The transducer as in  claim 6  wherein the outer member and the inner hub member are concentric.  
     
     
         11 . The transducer as in  claim 6 , wherein the arcuate strainable member is connected to the outer member by a connecting member having a arcuate form for dispersing a stress concentration.  
     
     
         12 . A transducer comprising; 
 an arcuate outer member having an aperture;    an arcuate inner member having an aperture;    an arcuate strainable member;    the arcuate strainable member connected between the arcuate outer member and the arcuate inner member;    at least one strain gage disposed on a surface of the arcuate strainable member;    the arcuate outer member and the arcuate inner member are coplanar; and    the arcuate inner member comprising a bore offset from a transducer center, the transducer thereby eccentrically rotatable about the transducer center.    
     
     
         13 . The transducer as in  claim 12  wherein the arcuate strainable member and the arcuate outer member and the arcuate inner member are coplanar.  
     
     
         14 . The transducer as in  claim 12  wherein the arcuate inner member describes a bore.  
     
     
         15 . The transducer as in  claim 12  wherein the arcuate outer member and the arcuate inner member are concentric.  
     
     
         16 . The transducer as in  claim 12  further comprising an arcuate connecting member between the arcuate strainable member and the arcuate outer ring.  
     
     
         17 . The transducer as in  claim 12  further comprising a bearing disposed in the offset bore for engaging a fastener.  
     
     
         18 . A torque transducer comprising: 
 a cylindrical strainable member having a surface and a first portion and a second portion;    the first portion connectable to a shaft;    the second portion connected to a belt bearing portion;    a low-friction bearing disposed between the belt bearing portion and the cylindrical strainable member for substantially isolating a torque induced strain on the surface; and    at least one strain gage mounted on the surface, the strain gage generating a signal proportional to the torque induced strain.    
     
     
         19 . The torque transducer as in  claim 18  further comprising: 
 a slip ring engaged with the cylindrical strainable member for receiving the signal; and  
 a signal conditioner electrically disposed between the strain gage and the slip ring.  
 
     
     
         20 . The torque transducer as in  claim 18 , wherein the low-friction bearing comprises a ball bearing.  
     
     
         21 . The torque transducer as in  claim 18 , wherein the belt bearing portion comprises a multiple-ribbed profile.  
     
     
         22 . The torque transducer as in  claim 18  further comprising a plurality of strain gages mounted to the surface and disposed in a full bridge electrical configuration.  
     
     
         23 . The torque transducer as in  claim 18 , further comprising a second strain gage mounted to the surface and cooperatively connected to the strain gage.  
     
     
         24 . The torque transducer as in  claim 18 , wherein a strain gage axis is disposed at an angle in the range of approximately 40-50 degrees to a cylindrical strainable member rotational axis (R-R).  
     
     
         25 . The torque transducer as in  claim 18  further comprising a damping member disposed between the belt bearing portion and cylindrical strainable member.  
     
     
         26 . The torque transducer as in  claim 25  wherein the damping member comprises an elastomeric material.  
     
     
         27 . A method of measuring a belt dynamic tension in an operating belt drive system comprising the steps of: 
 engaging a belt about a driver pulley and a driven pulley;    driving the belt and the driven pulley with the driver pulley;    measuring a hubload on an idler pulley using a hubload transducer;    measuring a driven pulley torque on a driven pulley using a torque transducer;    measuring a driven pulley rotational speed; and    calculating a belt span tension using the measured driven pulley torque and the measured hubload.    
     
     
         28 . The method as in  claim 27  further comprising the step of: 
 instrumenting (n−1) pulleys using the hubload transducer and torque transducers where (n) is the total number of pulleys.  
 
     
     
         29 . The method as in  claim 27  further comprising the step of: 
 calculating a drive efficiency using the driven pulley torque and driver rotational speed.