Abstract:
An isolator decoupler comprising a first tapered portion for connecting to a driving shaft, a second tapered portion cooperatively engaging the first tapered portion, the second tapered portion having a frictional engagement with a pulley, and an elastomeric member operatingly disposed between the second tapered portion and the pulley.

Description:
FIELD OF THE INVENTION 
     The invention relates to an isolator decoupler, and more particularly, to an isolator decoupler comprising first and second cooperating tapered members. 
     BACKGROUND OF THE INVENTION 
     Diesel engine usage for passenger 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 decoupler/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 can not resolve belt slip taking place at the crankshaft pulley. For some engines, both a crankshaft isolator and alternator decoupler/isolator have 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 having 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 an isolator decoupler comprising first and second cooperating tapered members. The present invention meets this need. 
     SUMMARY OF THE INVENTION 
     The primary aspect of the invention is to provide an isolator decoupler comprising first and second cooperating tapered members. 
     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 an isolator decoupler comprising a first tapered portion for connecting to a driving shaft, a second tapered portion cooperatively engaging the first tapered portion, the second tapered portion having a frictional engagement with a pulley, and an elastomeric member operatingly disposed between the second tapered portion and 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 cut away perspective view of the isolator decoupler. 
         FIG. 2  is a front exploded view of the isolator decoupler in  FIG. 1 . 
         FIG. 3  is an exploded view of an alternate embodiment. 
         FIG. 4  is an exploded view of yet another alternate embodiment. 
         FIG. 5  is a cut away cross section of the embodiment in  FIG. 4 . 
         FIG. 6  is a cut away perspective view of an alternate embodiment. 
         FIG. 7  is a exploded view of the alternate embodiment in  FIG. 6 . 
         FIG. 8  is a perspective view of the alternate embodiment in  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  is a cut away perspective view of the isolator decoupler. The isolator decoupler eliminates belt slip due to engine deceleration and also filters out reverse vibration during engine start up/shut down. 
     Isolator decoupler  100  comprises a compact design. The components of the isolator decoupler are contained within the pulley  50 . Wedge disk  10  is cooperatively engaged with wedge disk  20 . Wedge disk  20  is attached to a hub  30 . 
     Wedge disk  10  comprises a plurality of tapered portions  11  which are disposed about the circumference of disk  10 . Each tapered portion  11  cooperatively engages a tapered portion  21  of wedge disk  20 . Each tapered portion extends along an axis of rotation A-A having an included angle α. The number of tapered portions  11 ,  21  and the angle α of each tapered portion is selected based on the torque load requirements of the accessory drive and disengagement response time. Angle α is determined with reference to a normal plane which extends normal to an axis of rotation. Angle α is situated normal to the normal plane. The normal plane is substantially parallel to surface  13 . 
     Springs  60  are disposed between each wedge disk  10  and wedge disk  20 . Springs  60  are used to resiliently maintain a predetermined relationship between wedge disk  10  and wedge disk  20 , namely, keeping wedge disk  10  in contact with isolator plate  40 . The spring shape or number of springs can be varied as well depending upon the operating requirements, for example using leaf springs, rubber members, coil springs and so on. 
     Wedge disk  10  can comprise plastic material, or plastic combined with metal, or any other suitable molding material having like strength. Wedge disk  20  can comprise stamped sheet metal, cast iron, flow formed aluminum, plastic or similar material. 
     Wedge surfaces  12 ,  22  are in sliding contact with each other. Each wedge surface  12 ,  22  comprise a very low coefficient of friction (COF) of less than approximately 0.2 to facilitate ease of relative movement. On the other hand, surface  13  is coated or molded with a high COF material in the range of approximately 0.5 to approximately 3.0. Surface  13  is made of a durable material such as metal or plastic. 
     Wedge disk surface  13  is slidingly engaged with isolator plate  40 . Disposed between isolator plate  40  and pulley  50  is a resilient spring member  70 . Spring member  70  is attached to pulley  50  and isolator plate  40 . Spring member  70  comprises either natural rubber or synthetic polymers or a metal spring, each known in the art, or a combination of two or more of the foregoing. Spring member  70  isolates and absorbs crankshaft pulses that would otherwise be transmitted to the pulley and thereby to the belt driven accessories (not shown). 
     Hub  30  is connected to an engine crankshaft (not shown) using fasteners such as bolts (not shown) through holes  31 . Hub  30  can be press fit to engage hub member  32 . 
     The following table illustrates an example design: 
     Number of tapered portions ( 11 ,  21 ): 4 
     Wedge Angle (α): 25° 
     Spring Rate: 3 to 10 N/mm 
     Number of Springs ( 60 ): 4 
     Torque Load Requirement: 100 Nm 
     Wedge Disk Disengagement Response Time: &lt;0.1 second 
     On engine start-up as the crankshaft turns wedge disk  20  in the engine rotation direction wedge disk  10  is pushed toward isolator plate  40  by interaction of the tapered portions  11 ,  21 . Wedge disk  10  drives pulley  50  through friction force imparted to the isolator plate  40  and thereby through elastomeric member  70  to pulley  50 . Pulley  50  then drives the engine accessory system through a belt engaged with surface  51 , see  FIG. 2 . 
     During engine deceleration or engine shut down, pulley  50  will be driven in the reverse direction by the momentum of the belt drive system through the belt. Wedge disk  10  and wedge disk  20  move axially toward each as tapered portions  11 ,  21  slide together. Relative axial movement of wedge disk  10  with respect to wedge disk  20  causes surface  13  to disengage from isolator plate  40 , thereby temporarily disengaging the pulley from the crankshaft. This instantaneous reversal of torque flow direction allows the pulley to temporarily overrun the crankshaft rotation. Springs  60  allow for a soft engagement between wedge disk  10  and isolator plate  40  during reverse running or stop events. 
       FIG. 2  is a front exploded view of the isolator in  FIG. 11 . Wedge disk  20  is nested within hub  30 . Wedge disk  10  is cooperatively engaged with wedge disk  20 . Springs  60  are disposed at an end of each tapered portion  11 ,  21 , between each wedge disk  10 ,  20 . 
     Surface  13  is frictionally engaged with isolator plate  40 . Spring member  70  is attached to isolator plate  40  and to pulley  50 . A low friction bushing  80  is disposed between hub  30  and pulley  50  to hold alignment and to allow relative instantaneous movement between them. Pulley  50  has a surface  51  suitable for engaging a belt (not shown). 
     Hub member  32  is attached to hub  30  using fasteners  33 , or by other suitable means such as staking, welding or riveting. Rim  34  of member  32  captures pulley  50 , bushing  80 , elastomeric member  70 , isolator plate  40 , bushing  82 , wedge disk  20 , wedge disk  10  between member  32  and hub  30 . A low friction bushing  81  is disposed between member  32  and pulley  50  to hold alignment and to allow relative movement between them. Bushing  82  is disposed between pulley  50  and isolator plate  40  to hold alignment and to allow relative movement between them. Bushing  83  is disposed between isolator plate  40  and hub  30  to hold alignment and to allow relative movement between them. The bushings may comprise any low friction bushing or bearing suitable for the service. 
       FIG. 3  is an exploded view of an alternate embodiment. The components in this alternate embodiment are as described for  FIGS. 1 and 2  with the exception of springs  61 . In this embodiment each spring  61  comprises a coil spring which is compressed between the wedge disk  10  and wedge disk  20  during operation. Recesses  62  receive each spring  61 . 
       FIG. 4  is an exploded view of yet another alternate embodiment. In this alternate embodiment wedge disk  10  and wedge disk  20  are replaced with cooperating wedge circular portions  200  and  300 . Each wedge circular portion  200 ,  300  has a tapered shape. Disposed between each wedge circular portion  200 ,  300  is a spring  700 . Each spring  700  bears upon a portion  200  and urges each portion  300  into contact with a hub plate surface  403 . 
     Each wedge portion comprises an angle (α). Angle α is situated parallel to a plane which extends normal to an axis of rotation A-A. Hub portion  320  is attached to hub  301  using fasteners  330 . Elastomeric member  402  is attached to pulley  500  and to hub plate  400 . Bushing  401  is disposed between hub plate  400  and hub portion  301 . Bushing  404  is disposed between hub portion  301  and pulley  500 . Bushings  601 ,  602  and  603  are each low friction to allow relative movement between adjacent components. 
     Each wedge surface  304  is coated or molded in with a high COF in the range of approximately 0.5 to approximately 3.0 and made of durable material such as metal or plastic. The number of wedge portions  200 ,  300  and the angle α of each portion is selected based on the torque load requirements of the accessory drive and disengagement response time. The surface of each wedge portion  200 ,  300  each have a coefficient of friction of less than approximately 0.2. 
     Wedge circular portions  200  are fixedly attached to and/or form a part of hub  301 . Portions  300  are not attached to hub  301 . Each portion  300  “floats” between and is constrained by each adjacent portion  200  and surface  403 . With the wedge circular portions, a frictional driving force is generated between surface  304  of portion  300  and outer diameter surface  401  as a result of the relative movement (wedging) between portion  200  and portion  300 . As a result of movement of portion  200  with respect to portion  300  caused by rotation of hub  301 , portion  300  is pressed radially inward upon surface  403  of the isolator to transfer the torque from the hub  301 , through portions  300  to the isolator plate  400 . Torque is then transmitted through elastomeric member  402  and thereby to pulley  500  during normal, non-accelerating running condition. Pulley  500  drives a belt (not shown). 
     During engine deceleration, which is also the overrunning state, wedge portion  300  moves relative to portion  200  to disengage portion  300  from the surface  403 . This releases the frictional force between portion  300  and surface  403 , thereby allowing isolator to decouple the belt from the crankshaft and thereby to overrun the crankshaft during deceleration (shut-down) or start up. 
       FIG. 5  is a cut away cross section of the embodiment in  FIG. 4 . Hub portion  301  is omitted from this figure for reasons of clarity. Spring member  501  holds each wedge portion  300  away from hub portion  301 . Since hub portion  301  has some small amount of relative movement with respect to the wedge members  300 , the spacing effect of spring member  501  prevents undue rubbing, wear, frictional heating and damping between wedge members  300  and hub portion  301 . 
       FIG. 6  is a cut away perspective view of an alternate embodiment. In this alternate embodiment, the resilient spring member  70  is not used. The components in this alternate embodiment are as described in  FIGS. 1 through 5  except as specifically provided for in this  FIG. 6 . 
     A low friction bushing  502  is disposed between flange  501  and pulley flange  503 . Flange  501  is fixedly connected to end  301  of hub  3000 , for example, by a press fit. Wedge disk  20  is fixedly engaged within hub  3000 . Wedge disk  20  does not rotate with respect to hub  3000 . Tapered portions  11  and wedge disk  20  operate as described in  FIGS. 1 through 5 . Surface  13  of tapered portions  11  frictionally engage wedge disk  20  and flange  503 . Belt engaging surface  504  is for engaging a belt (not shown). 
       FIG. 7  is an exploded view of the alternate embodiment in  FIG. 6 . Hub  3000  is fixedly attached to a shaft, such as an alternator shaft (not shown). Wedge disk  20  rotates with hub  3000 . Wedge disk  10  and wedge disk  20  and tapered portions  11  operate as described for  FIGS. 1-5 . 
       FIG. 8  is a perspective view of the alternate embodiment in  FIG. 6 . Notches  201  engage cooperating tabs  301  in hub  3000 , which assures that wedge disk  20  fixedly rotates with hub  3000 . 
     Although forms of the invention have 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.