Abstract:
A decoupling isolator comprising a pulley, a hub member comprising a stop, a flat wire spiral spring having an end fixedly connected to the pulley, the flat wire spiral spring having another end engageable with the stop to limit a rotation of the pulley.

Description:
FIELD OF THE INVENTION 
     The invention relates to a decoupling isolator and more particularly, to a decoupling isolator having a flat wire spiral spring engagable with a stop to limit a rotation of the pulley. 
     BACKGROUND OF THE INVENTION 
     Diesel engine usage for passenger car application is increasing due to the benefit of better fuel economy. Further, gasoline engines are increasing compression ratios to improve the fuel efficiency. As a result, diesel and gasoline engine accessory drive systems have to overcome the vibrations of greater magnitude from crankshafts due to above mentioned changes in engines. 
     With increased crankshaft vibration in addition to high acceleration/deceleration rates and high alternator inertia the engine accessory drive system is often experiencing belt chirp noise due to belt slip. This will also reduce the belt operating life. 
     Crankshaft isolators and alternator decouplers/isolators have been widely used for engines with high angular vibration to filter out vibration in engine operation speed range. However, although a crankshaft isolator can function very well in engine running speed range; it still presents problems during engine start-up or shut-down due to the natural frequency of the isolator itself. 
     An alternator decoupler/isolator can eliminate the belt slipping issue at an alternator pulley, but it cannot resolve belt slip taking place at the crankshaft pulley. For some engines, both a crankshaft isolator and alternator decoupler/isolator has to be used together. Unfortunately, this adds to the cost of the accessory drive system significantly and often vehicle manufacturers are not willing to pay for it. 
     Representative of the art is U.S. Pat. No. 6,044,943 which discloses a crankshaft decoupler has a mounting hub, a pulley rotatably mounted on the mounting hub, an annular carrier mounted within said pulley, a biasing device mounted therebetween, and a one way clutch mounted between the annular carrier and the pulley. The biasing device cushions the belt drive from crankshaft impulses and lowers the angular resonant frequency of the belt system. The one way clutch prevents sudden reversal of the belt tension in the drive due to start/stop of the engine or sudden deceleration of the engine and prevents momentary reverse slip belt squeal as a result of the tensioners&#39; inadequate output for the reverse mode. The one way clutch limits the maximum amount of torque which may be transmitted preventing belt slippage during momentary overload. 
     What is needed is a decoupling isolator having a flat wire spiral spring engagable with a stop to limit a rotation of the pulley. The present invention meets this need. 
     SUMMARY OF THE INVENTION 
     The primary aspect of the invention is to provide a decoupling isolator having a flat wire spiral spring engagable with a stop to limit a rotation of the pulley. 
     Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings. 
     The invention comprises a decoupling isolator comprising a pulley, a hub member comprising a stop, a flat wire spiral spring having an end fixedly connected to the pulley, the flat wire spiral spring having another end engageable with the stop to limit a rotation of the pulley. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and form a part of the specification, illustrate preferred embodiments of the present invention, and together with a description, serve to explain the principles of the invention. 
         FIG. 1  is a perspective view of the decoupling isolator. 
         FIG. 2  is an exploded view of the decoupling isolator in  FIG. 1 . 
         FIG. 3  is a cross-sectional perspective view of the decoupling isolator in  FIG. 1 . 
         FIG. 4  is a perspective view of an alternate embodiment of the decoupling isolator. 
         FIG. 5  is an exploded view of the decoupling isolator in  FIG. 4 . 
         FIG. 6  is a cross-sectional perspective view of the decoupling isolator in  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a perspective view of the decoupling isolator. Decoupler  100  comprises a pulley  10 . A radial bushing  11  is engaged with an inner surface  13  of pulley  10 . Bushing  11  is engaged with surface  13 . Hub member  20  is omitted for clarity, see  FIG. 2 . 
     A hub plate  12  is cooperatively engaged with pulley  10 . Hub plate  12  is not fixedly connected to pulley  10 . Instead, hub plate  12  is fixedly connected to hub stop member  20 , see  FIG. 2 . 
     A flat wire spiral spring  14  is connected to the pulley  10  by end  16 . An end  15  of spring  14  is engaged with a spring support  17 . Spring support  17  engages a stop  21  in hub member  20 . Spiral spring  14  may comprise either a flat wire or round wire. 
     Disposed between volutes of spring  14  is a plastic spring support  18 . 
       FIG. 2  is an exploded view of the decoupling isolator in  FIG. 1 . Surface  17   a  of spring support  17  slidingly engages an inner surface  23  of hub member  20 . Axial bushing  25  is disposed between hub member  20  and pulley  10 . Bushing  25  slidingly facilitates movement between the hub member  20  and pulley  10 . Axial bushing  26  is disposed between hub plate  12  and pulley  10 . Bushing  26  slidingly facilitates movement between the hub member  20  and the pulley  10 . 
     Spring  14  is fixedly connected to pulley  10  by fasteners  30 , see  FIG. 3 . Hub plate  12  is fixedly connected to hub member  20  by fasteners  31 . The decoupler is connected to an engine crankshaft (not shown) by use of fasteners through hub plate  12 . Spring support  17  engages stop  21  on hub member  20 . 
     Pulley  10  can rotate relative to the hub member  20 , limited by stop  21 . Spring  14  winds and contacts stop  21  to absorb the angular vibration in a first direction (drive direction). During periods of deceleration spring  14  (and thereby pulley  10 ) will simply decouple from stop  21  and turn freely in the opposite direction for 360 degrees, 180 degrees, 120 degrees, etc. until spring support  17  again contacts stop  21 . The range of free motion depends on the number of spiral springs  14  and the number of stop tabs  21 . 
     Support  18  prevents the volutes from collapsing on each other causing support  17  to “ratchet” past stop  21  during periods of hard drive. Support  18  also allows some sliding movement of the volutes with respect to each other. 
       FIG. 3  is a cross-sectional perspective view of the decoupling isolator in  FIG. 1 . Fasteners  30  fixedly connect end  16  to pulley  10 . Support  17  is shown engaged with stop  21 . 
     The range of relative rotational movement of the pulley with respect to the hub member is approximately 360°. This is because one spring and one stop are used. 
       FIG. 4  is a perspective view of an alternate embodiment of the decoupling isolator. With the exception of the following described differences, the decoupler in  FIGS. 4 ,  5 ,  6  is the same as described in  FIGS. 1 ,  2 ,  3 . In this alternate embodiment instead of a single flat wire spiral spring there are two flat wire spiral springs  140  and  141 . 
       FIG. 5  is an exploded view of the decoupling isolator in  FIG. 4 . An end of each spring is connected to a spring support  170  and  171  respectively. Springs  140  and  141  are each connected to pulley  10 . Each spring support  170 ,  171  engages a stop  210 ,  211  respectively. 
     The range of rotational movement of the pulley with respect to the hub member is approximately 180°. This is because two springs and two stops are used. The stops are located 180° from each other. 
       FIG. 6  is a cross-sectional perspective view of the decoupling isolator in  FIG. 4 . In a drive direction, spring support  170  will contact stop  210  and spring support  171  will contact stop  211 . 
     In the opposite direction, for example during deceleration of an engine, pulley  10  will rotate through approximately 180° causing support  171  to contact stop  210  and support  170  to contact stop  211 . 
     Although a form of the invention has been described herein, it will be obvious to those skilled in the art that variations may be made in the construction and relation of parts without departing from the spirit and scope of the invention described herein.