Abstract:
An isolating pulley comprising a hub comprising an inertia carrier, the inertia carrier having an inner surface, a spring carrier journalled to the hub, the spring carrier having a releasable driving engagement with the inertia carrier, a pulley journalled to the hub, a spring drivingly engaged between the spring carrier and the pulley, a clutch spring having a frictional engagement with the inner surface, and which frictional engagement is partially releasable upon a temporary, pressing contact of the pulley upon the clutch spring.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to an isolating pulley, and more particularly, to an isolating pulley having a clutch spring releasably engaged with an inertia carrier inner surface upon a pressing contact of the pulley with the clutch spring. 
       BACKGROUND OF THE INVENTION 
       [0002]    Diesel engine use 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 and to also control belt chirp. 
         [0005]    Representative of the art is U.S. Ser. No. 13/541,216 which discloses an isolator decoupler having a pulley temporarily engagable with an end of the wrap spring one way clutch in an unwinding direction whereby a temporary contact between the wrap spring one way clutch end and the pulley will temporarily diminish the frictional engagement of the wrap spring one way clutch from the shaft. 
         [0006]    What is needed is an isolating pulley having a clutch spring releasably engaged with an inertia carrier surface upon a pressing contact of the pulley with the clutch spring. The present invention meets this need. 
       SUMMARY OF THE INVENTION 
       [0007]    The primary aspect of the invention is an isolating pulley having a clutch spring releasably engaged with an inertia carrier surface upon a pressing contact of the pulley with the clutch spring. 
         [0008]    Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings. 
         [0009]    The invention comprises an isolating pulley comprising a hub comprising an inertia carrier, the inertia carrier having an inner surface, a spring carrier journalled to the hub, the spring carrier having a releasable driving engagement with the inertia carrier, a pulley journalled to the hub, a spring drivingly engaged between the spring carrier and the pulley, a clutch spring having a frictional engagement with the inner surface, and which frictional engagement is partially releasable upon a temporary, pressing contact of the pulley upon the clutch spring. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    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. 
           [0011]      FIG. 1  is a front perspective view of the inventive device. 
           [0012]      FIG. 2  is a cross-section view of the device. 
           [0013]      FIG. 3  is an exploded view of the device. 
           [0014]      FIG. 4   a  is a front elevation view of the spring carrier. 
           [0015]      FIG. 4   b  is a rear elevation view of the spring carrier. 
           [0016]      FIG. 5   a  is a front elevation view of the pulley. 
           [0017]      FIG. 5   b  is a rear elevation view of the pulley. 
           [0018]      FIG. 6  is an elevation view of the interior of the device. 
           [0019]      FIG. 7   a  is an elevation view of the front of the inertia mass. 
           [0020]      FIG. 7   b  is an elevation view of the rear of the inertia mass. 
           [0021]      FIG. 8  is an elevation view of the interior of the inertia carrier. 
           [0022]      FIG. 9   a  is a detail of the spring. 
           [0023]      FIG. 9   b  is a detail of the spring. 
           [0024]      FIG. 9   c  is a detail of the spring. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]      FIG. 1  is a front perspective view of the inventive device. The device is typically attached to the crankshaft of an internal combustion engine (not shown). 
         [0026]      FIG. 2  is a cross-section view of the device. The inventive device comprises hub  1 . Hub  1  further comprises a crankshaft sprocket  110  having a toothed surface. Crankshaft sprocket  110  can be used to drive an engine timing belt  900 . Timing belt  900  is referred to as a toothed or synchronous belt. 
         [0027]    Thrust bearing  2  engages shoulder  60  on hub  1 . Pulley  3  is journalled to hub  1  on bushing  11 . Pulley  3  comprises a profile  300  for engaging a multi-ribbed belt  800 . The multi-ribbed belt may be used to drive an engine accessory system (not shown). Spring  4  is engaged between pulley  3  and spring carrier  14 . Clutch spring  5  is engaged between spring carrier  14  and inertia carrier  16 . Spring carrier  14  bears upon thrust bearing  6 . Spring carrier  14  is journalled to hub  1  upon bushing  7 . Inertia mass  17  is mounted to inertia carrier  16  by rubber member  8 . Rubber member  8  comprises a natural or synthetic elasotmeric or polymeric resilient material suitable for damping axial and torsional vibrations which arise from operation of the engine. Fasteners  9  attach inertia carrier  16  to hub  1 . 
         [0028]      FIG. 3  is an exploded view of the device. Hub  1  is fixedly attached to an engine crankshaft (not shown). Dowel pin  10  is fixedly attached to hub  1 . Thrust bearing  2  is located between pulley  3  and hub  1 . Bushing  11  is fixed to pulley  3 . 
         [0029]      FIG. 4   a  is a front elevation view of the spring carrier.  FIG. 4   b  is a rear elevation view of the spring carrier. Spring carrier  14  comprises a spring receiving portion  140 . Spring end  45  is received by slot  141 . Spring surface  46  engages with spring receiving portion  140 . Spring surface  46  interfaces with spring carrier portion  140 . 
         [0030]    Clutch spring  5  engages slot  142 . End  56  of clutch spring  5  engages slot  141  whereby clutch spring  5  is retained. 
         [0031]    Pulley  3  comprises a spring receiving portion  30 , see  FIG. 5   a .  FIG. 5   a  is a front elevation view of the pulley.  FIG. 5   b  is a rear elevation view of the pulley. Slot  31  receives an end  40  of spring  4 . Spring surface  41  interfaces with spring receiving portion  30 . 
         [0032]      FIG. 6  is an elevation view of the interior of the device. Release  13  is engaged with slot  32  of pulley  3  and is fastened in place via fastener  12 . The position of release member  13  can be adjusted in slot  32  to adjust the release torque. Slot  32  comprises an arc having a constant radius centered on the axis of rotation A-A. 
         [0033]    Bumper  15  comprises elongate portion  151  and elongate portion  152  joined by connecting member  153 . Bumper  19  comprises elongate portion  191  and elongate portion  192  joined by connecting member  193 . 
         [0034]      FIG. 7   a  is an elevation view of the front of the inertia mass.  FIG. 7   b  is an elevation view of the rear of the inertia mass. Connecting member  153  of bumper  15  nests in slot  167  and around tab  161 . Elongate member  151  and elnongate member  152  are disposed on opposing sides of tab  161 . Connecting member  193  of bumper  19  nests in slot  166  and around tab  160 . Elongate member  191  and elongate member  192  are disposed on opposing sides of tab  190 . Bumper  15  and bumper  19  comprise any suitable resilient, compliant or compressible material for absorbing the force of engagement with tabs  33  and  34 . Tabs  33 ,  34  comprise projecting members. 
         [0035]      FIG. 8  is an elevation view of the interior of the inertia carrier. Inertia carrier  16  has tab  160  and tab  161 . Tab  160  and tab  161  are configured with slot  166  and slot  167  respectively. Tab  160  comprises face  162  and face  163 . Tab  161  comprises face  164  and face  165 . Spring carrier tabs  33  and  34  engage bumpers  15  and  19 . 
         [0036]      FIG. 9   a  is a detail of the spring. Spring  4  comprises a tab  45  at a first end and a tab  40  at a second end. Flat surface  46  allows more of the spring coil to seat on the spring carrier and thereby avoid distortion. Flat surface  41  allows more of the spring coil to seat on the pulley and thereby avoid distortion. Each of flat surface  41  and  46  causes the respective end of spring  4  to have a tapered form. 
         [0037]      FIG. 9   b  is a detail of the spring.  FIG. 9   c  is a detail of the spring. Spring  4  comprises a coil spring. Spring  4  may be loaded in either the winding or unwinding direction. The torsional spring rate is in the range of approximately 2 Nm/deg to approximately 5 Nm/deg. 
         [0038]    In normal operation the engine drives the accessory drive with torque flowing from pulley  3  to the accessory drive belt and system. The system can comprise an alternator, water pump, AC compressor or power steering. During normal operation an operational condition known as overrun also occurs. Overrun occurs when there is a deceleration of the engine from a higher rpm, such as slowing or approaching a stop light. Although engine speed decreases the accessories will momentarily continue operating at a higher speed of rotation due to their combined inertia. The overrun condition causes the accessory belt to reverse its loading on the crankshaft such that it temporarily drives the crankshaft. 
         [0039]    In driving operation torque transmission in the inventive device is from hub  1  to inertia carrier  16 , to tabs  160  and  161 , to bumpers  15  and  19 , then to spring carrier  14  through spring  4  to pulley  3  and then to a belt to drive the accessories (not shown). Spring  4  is typically driven in an unwinding direction, but may also be driven in a winding direction with equal success. Tabs  160  and  161  apply force to bumpers  15  and  19  which in turn apply force to spring carrier  14  through tabs  33  and  34 . Tabs  33 ,  34  project from spring carrier  14 . Spring carrier  14  applies force to spring  4  through tab  45  engaged with slot  141 . Spring  4  applies force to pulley  3  via engagement of tab  40  with slot  31 . 
         [0040]    In the overrun condition torque transmission reverses. Torque transmission is from pulley  3  to spring  4  to spring carrier  14  to clutch spring  5  to inertia carrier  16  to hub  1 . 
         [0041]    During overrun conditions the device limits overrun torque applied to pulley  3  to levels that do not exceed a predetermined release amount, for example, 15 Nm. Pulley  3  applies torque to spring  4 . Spring  4  applies the torque to spring carrier  14  which applies it to clutch spring  5  which in turn applies it to inertia carrier  16 . Reverse rotation of pulley  3  allows release member  13  to rotate toward clutch spring tab  55  until contact is made. Overrun protection is then accomplished through the release of engagement of clutch spring  5  from inner surface  168  of inertia carrier  16 . Inner surface  168  has a cylindrical form and faces radially inward toward the axis of rotation. 
         [0042]    Clutch spring  5  is released from surface  168  upon pressing contact of release  13  with clutch spring tab  55  because clutch spring  5  is thereby wound in a winding direction which causes clutch spring  5  to radially contract, which in turn causes clutch spring  5  to disengage from surface  168  of inertia carrier  16 . Disengagement allows pulley  3 , spring  4 , spring carrier  14  and clutch spring  5  to rotate in unison relative to inertia carrier  16 . This in turn causes spring carrier tabs  33  and  34  to lose contact with bumper  15  and bumper  19 . However, clutch spring  5  does not completely disengage from inertia carrier  16 . Through frictional drag there continues to be overrun or release torque applied to inertia carrier  16  through clutch spring  5 . If the torque drops below the predetermined release torque, spring  5  locks to surface  168  and the relative rotational motion stops. 
         [0043]    The position of release member  13  is adjustable within slot  32 . The position of release member  13  determines the torque at which the release member  13  engages end  55 . Adjustment can be used to either increase or decrease the torque threshhold at which release of clutch spring  5  occurs. 
         [0044]    If the overrun torque continues, pulley  3 , spring  4 , spring carrier  14  and clutch spring  5  rotate with respect to inertia carrier  16 . Relative motion can continue until spring carrier tab  33  and tab  34  come into contact with the opposite sides of bumpers  15  and  19  after approximately 180° of rotation from the drive position. Contact between the tabs  33 ,  34  and bumpers  15 ,  19  limits the amount of overrun rotation in the inventive device. 
         [0045]    Upon return to normal operation wherein the engine is driving the accessories, inertia carrier  16  rotates relative to pulley  3 , spring  4 , spring carrier  14  and clutch spring  5  until spring carrier tab  33  and tab  34  come back into contact with bumpers  15  and  19 . This represents approximately 180° of rotation from the overrun position. 
         [0046]    An advantage of the device is control of the effective inertia torque of all driven components on the crankshaft pulley due to engine deceleration so that system problems such as noise and vibration are significantly reduced. Further, dynamic belt slip, span vibration and tensioner arm vibration are reduced or eliminated. Further, controlled overrun reduces the crankshaft rotational vibration or speed fluctuation which is the primary excitation of the belt drive system. 
         [0047]    Numerical information is provided by way of example and is not intended to limit the scope of the invention. 
         [0048]    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.