Abstract:
An isolating decoupler comprising a pulley having a pulley inner surface, a hub having a radially extending arm, the radially extending arm having a frictional surface slidingly engaged with the pulley inner surface, a spring fixed to the pulley, the spring intermittently engageable with the radially extending arm, an elastomeric member disposed between the spring and the radially extending arm; and the radially extending arm intermittently engageable with a pulley stop.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to an isolating decoupler having an arm having a frictional surface slidingly engaged with a pulley inner surface, a spring having an intermittent engagement with the arm, and the radially extending arm intermittently engageable with a pulley stop. 
       BACKGROUND OF THE INVENTION 
       [0002]    Diesel engines used for passenger car applications 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. 
         [0003]    Due to increased crankshaft vibration plus 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. 
         [0004]    Crankshaft isolators/decouplers 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. 
         [0005]    An alternator decoupler/isolator can eliminate belt slipping at an alternator pulley, but it cannot resolve belt slip taking place at the crankshaft pulley. For some engines, a crankshaft isolator/decoupler and an alternator decoupler/isolator have to be used together. Unfortunately, this can add significant cost to the accessory drive system. 
         [0006]    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. 
         [0007]    What is needed is an isolating decoupler having an arm having a frictional surface slidingly engaged with a pulley inner surface, a spring having an intermittent engagement with the arm, and the radially extending arm intermittently engageable with a pulley stop. The present invention meets this need. 
       SUMMARY OF THE INVENTION 
       [0008]    The primary aspect of the invention is an isolating decoupler having an arm having a frictional surface slidingly engaged with a pulley inner surface, a spring having an intermittent engagement with the arm, and the radially extending arm intermittently engageable with a pulley stop. 
         [0009]    Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings. 
         [0010]    The invention comprises an isolating decoupler comprising a pulley having a pulley inner surface, a hub having a radially extending arm, the radially extending arm having a frictional surface slidingly engaged with the pulley inner surface, a spring fixed to the pulley, the spring intermittently engageable with the radially extending arm, an elastomeric member disposed between the spring and the radially extending arm; and the radially extending arm intermittently engageable with a pulley stop. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    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. 
           [0012]      FIG. 1  is a front perspective view of the isolator decoupler. 
           [0013]      FIG. 2  is a front exploded view of the isolator decoupler. 
           [0014]      FIG. 3  is a rear exploded view of the isolator decoupler. 
           [0015]      FIG. 3   a  is a cross-sectional view of the damping members. 
           [0016]      FIG. 4  is a front view of the isolator decoupler. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]      FIG. 1  is a front perspective view of the isolator decoupler. The device comprises a shaft  10 . Shaft  10  is used to connect the device to an engine crankshaft (not shown). Torque is transmitted from the crankshaft through shaft  10  to a hub  20 . Shaft  10  can be press fit into hub  20  so that shaft  10  and hub  20  rotate together. 
         [0018]    Hub  20  comprises radially extending arms  21 ,  22 ,  23 . The radial extension is with respect to the axis of rotation A-A of shaft  10 , see  FIG. 2 . Although the preferred number of arms  21 ,  22 ,  23  is three, any number of radially extending arms may be used with equal success for this device. The range of motion of the device is a function of the number of arms. Three radially extending arms allow a range of relative movement of approximately 120° between the hub  20  and pulley  30 . For four radially extending arms the range of relative movement is approximately 90° and so on. 
         [0019]    The end of each arm comprises a friction plate member  210 ,  220 ,  230 . A friction member  211 ,  212 ,  213  is fixed on the end of each respective frictional plate member  210 ,  220 ,  230 . Each friction member frictionally contacts an inner surface  300  of pulley  30 . Inner surface  300  is a cylindrical section. Each frictional plate member  210 ,  220 ,  230  comprises an arcuate shape for engaging the inner surface  300 . 
         [0020]    The friction plate members allow relative motion between the pulley and the shaft during decoupling and re-coupling. Pulley  30  comprises a belt engaging surface  31  for contacting a belt. Belt engaging surface  31  may comprise a multi-ribbed profile as shown, or may also comprise any other profile known in the art such as toothed, flat, or a single v notch. 
         [0021]    A spring member  41 ,  42 ,  43  extends from a mounting member  301 ,  302 ,  303  respectively. Each spring member  41 ,  42 ,  43  engages a radially extending arm  21 ,  22 ,  23  respectively. Each spring member  41 ,  42 ,  43  is loaded in a substantially cantilever manner. Each mounting member  301 ,  302 ,  303  also acts as a stop to stop a rotation of each radially extending arm during operation. 
         [0022]    Each radially extending arm engages its respective spring during operation thereby allowing the transfer of torque from the crankshaft to the pulley while engine is in operation. The spring members  41 ,  42 ,  43  cushion and damp engine vibrations and isolate them from the pulley, and therefore, from the rest of the belt drive system. 
         [0023]    For example, in a shaft  10  driving direction D 1  friction plate member  210  will contact mounting member  301 . In a shaft driving direction D 2  friction plate member  210  will contact mounting member  302 . Driving direction D 1  is typically associated with engine deceleration. Driving direction D 2  is typically associated with engine acceleration. 
         [0024]    Each spring member comprises an arm  41   a ,  42   a ,  43   a  that bends in a cantilever bending mode. Each spring member also comprises an end  41   b ,  42   b ,  43   b  that has an accordion-like shape, or multiple bends, that are used in compression mode. 
         [0025]    Each spring member shape can be varied in the bending area  41   a ,  42   a ,  43   a  by comprising various curves as well as in the accordion area by having different number of compression folds. Flexibility in the spring member design allows isolating of engine vibration to be designed and tuned according to the needs of any given engine. In addition to the many shapes that the spring member can have in its bend and compression areas, the thickness of it can also be varied to adjust the spring rate as needed. The simplest way of changing the spring member thickness is doubling or tripling its thickness in the desired areas. 
         [0026]      FIG. 2  is a front exploded view of the isolator decoupler. Friction ring  50  damps a relative movement of the pulley  30  with respect to the hub  20 . Friction ring  50  comprises materials known in the art. 
         [0027]    Each radially extending arm  21 ,  22 ,  23  is attached to a plate  400 , which plate also serves to enclose the interior of the device, thereby protecting it from debris. 
         [0028]      FIG. 3  is a rear exploded view of the isolator decoupler. Friction ring  51  damps a relative movement of the pulley  30  with respect to the hub  20 . Friction ring  50  comprises materials known in the art. 
         [0029]      FIG. 3   a  is a cross-sectional view of the damping members. Damping members  61 ,  62 ,  63  cushions the impacts between each spring member  41 ,  42 ,  43  and the respective radially extending arm  21 ,  22 ,  23 . The lower level  601 , which is attached to each radially extending arm, is an energy absorbing material known in the art to prevent a “knocking” sound and shock, and the second (top) layer  600 , which contacts the end of the spring member, is a wear resistant elastomer or polymer also known in the art. 
         [0030]    In an alternate embodiment, the points of contact points of each radially extending arm and spring under the damping members  61 ,  62 ,  63  is magnetized using a permanent magnet. This feature will keep the system always coupled. The amount of magnetization can be adjusted to enable de-coupling at the desired decoupling force for the system. The decoupling force should overcome the magnetic force and separate the radially extending arm from the respective contact point. For example, this feature reduces unnecessary decoupling and re-coupling when engine is turned off, or with minute decoupling forces. 
         [0031]      FIG. 4  is a front view of the isolator decoupler. The contact areas of metal-to-metal that are four points times the number of arms are all covered by at least two layers of elastomers or polymers. This results in a smooth decoupling action. 
         [0032]    Upon deceleration of the engine, the arms and springs simply separate from each other and the arms move backwards over their friction plate contacts on the internal diameter of the pulley. This creates a very simple and efficient decoupling. Since most engines require about 15 degrees of decoupling, this device provides much more degrees of decoupling than required. 
         [0033]    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.