Abstract:
An isolator decoupler comprising a shaft having a shaft projection, a pulley having a pulley projection, the pulley journalled to the shaft, a member pivotally connected to the shaft, the member alternatively engagable with the shaft projection or with the pulley projection, engagement with the pulley by the member causes locked rotation of the shaft with the pulley, and a viscous fluid between the shaft and the pulley, the member immersed in said viscous fluid.

Description:
FIELD OF THE INVENTION 
     The invention relates to an isolator decoupler, and more particularly, to a hydraulic isolator decoupler comprising a member pivotally connected to the shaft, the member alternatively engagable with the shaft projection or with the pulley projection, engagement with the pulley by the member causes locked rotation of the shaft with the pulley, and a viscous fluid between the shaft and the pulley, the member immersed in said viscous fluid. 
     BACKGROUND OF THE INVENTION 
     Overrunning decouplers for serpentine drives used on internal combustion engines are well known. They operate to reduce torsional vibrations in the serpentine drive caused by operation of the engine. 
     Decouplers typically include a one way clutch, which operates so the decoupler only transmits torque in one rotational direction. They also include an isolation spring which operates to dampen the torsional vibrations between the decoupler pulley and the accessory device driven by the pulley. 
     Decouplers are typically installed on the alternator or crankshaft of an internal combustion engine because the alternator has the highest inertial load of the accessories driven by the serpentine drive. 
     Use of an isolating decoupler involves advantages such as increasing the life of the serpentine belt and decreasing the spring force requirements of the belt tensioner for the serpentine system. It can also increase the operating life of the alternator. 
     Representative of the art is U.S. Pat. No. 8,006,819 which discloses an overrunning accessory decoupler with a locking mechanism which provides the desired overrunning accessory decoupler functionality and also permits torque to be transferred from the accessory to which the decoupler is installed to the drive of the engine when desired. In one embodiment, the decoupler includes a locking mechanism that is controlled by centrifugal forces developed in the decoupler to lock the decoupler to permit the accessory to transfer torque to the drive to start or boost the engine. 
     What is needed is an isolator decoupler comprising a member pivotally connected to the shaft, the member alternatively engagable with the shaft projection or with the pulley projection, engagement with the pulley by the member causes locked rotation of the shaft with the pulley, and a viscous fluid between the shaft and the pulley, the member immersed in said viscous fluid. The present invention meets this need. 
     SUMMARY OF THE INVENTION 
     An aspect of the invention is to provide an isolator decoupler comprising a member pivotally connected to the shaft, the member alternatively engagable with the shaft projection or with the pulley projection, engagement with the pulley by the member causes locked rotation of the shaft with the pulley, and a viscous fluid between the shaft and the pulley, the member immersed in said viscous fluid. 
     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 shaft having a shaft projection, a pulley having a pulley projection, the pulley journalled to the shaft, a member pivotally connected to the shaft, the member alternatively engagable with the shaft projection or with the pulley projection, engagement with the pulley by the member causes locked rotation of the shaft with the pulley, and a viscous fluid between the shaft and the pulley, the member immersed in said viscous fluid. 
    
    
     
       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 cutaway view of the inventive device. 
         FIG. 2  is a cross-sectional view through  2 - 2  in  FIG. 1 . 
         FIG. 3  is a cross-sectional view. 
         FIG. 4  is a cross-sectional view. 
         FIG. 5  is a cross-sectional view. 
         FIG. 6  is a cross sectional view of an alternate embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  is a perspective cutaway view of the inventive device. The inventive hydraulic isolator decoupler comprises shaft  10  and pulley  20 . Pulley  20  is journalled to shaft  10  by a bearing  30  and bearing  40 . A belt (not shown) engages an outer surface  24  of pulley  20 . The inventive device may be used on an alternator shaft in a belt driven accessory drive for an internal combustion engine (not shown), or may also be used on an engine crankshaft. 
     A plurality of gate mechanisms  50  are disposed about the outer circumference of shaft  10  in hinged attachment to shaft  10 . A gate member  51  is hinged by pin  53  to a base  52 . Base  52  is attached to shaft  10 . Gate  51  freely pivots about pin  53 . Gates  51  may comprise metal, plastic or any other suitably rigid material. 
     Radial projections or protrusions  54  protrude radially outward from shaft  10 . A radial projection  54  is disposed on each side of a gate base  52  in order that a gate  51  may bear upon and be supported by a radial projection  54  during shaft rotation in a predetermined direction. The number of projections  54  can be varied and will influence the time required for each gate  51  to “lay down” and thereby effect decoupling. The radial height of each projection  54  can be varied and will also influence the timing and effect of decoupling of each gate  51 , that is, the time required to “lay down” when decoupling is occurring. “Decoupling” occurs when shaft  10  overruns pulley  20  and each gate  51  is disengaged from each projection  22 . 
     The inventive device will operate without projections  54  wherein each gate simply contacts shaft  10  or an adjacent base  52  in the overrun condition. 
     Radial projections or protrusions  22  protrude radially inward from pulley surface  21 . The number of projections  22  may vary. The greater the number of gates  51  the more quickly the device will “lock-up” during a load reversal since the angular spacing between each gate is a function of the number of gates divided by 360°. Projections  22  are aligned to engage a gate  51  when the device is transmitting torque from pulley  20  to shaft  10 . Typically, a belt (not shown) will engage pulley  20 . 
     The length of a gate  51  is greater than the radial distance (R) from pin  53  to inner surface  21 , see  FIG. 3 . This prevents gate  51  from overrotating past pulley  20  and thereby allowing shaft  10  to freely rotate more than 360 degrees with respect to pulley  20  in either direction. Namely, shaft  10  is only allowed to rotate with respect to pulley  20  through only a partial rotation in one direction (during the locked or lock up condition) and through greater than 360 degrees in a second direction (during the overrun condition). This mechanism and its operation may also be operationally referred to as a one-way clutch. 
     Each gate  51  may be smaller in surface area than each projection  54  or  22 . Each gate  51  may comprise a triangular cross section while each projection  54 ,  22  comprises a rectangular shape. The size and surface area of each gate member  51  can be varied depending on the speed with which the re-engagement is intended to occur. Gate  51  may comprise any suitable material including metallic and polymeric, or plastic. A metallic gate may be covered with a layer of elastomeric material which will then diminish the landing impact as the gate engages a projection. 
     In an alternate embodiment, a plurality of gate mechanisms  50  are disposed about the inner surface  21  of pulley  20  in hinged attachment to pulley  20 . Each gate member  51  is hinged by pin  53  to a base  52 . Gate  51  freely pivots about pin  53 . In operation each gate  51  pivots as described elsewhere in this specification. Further, upon a load reversal each gate  51  pivots into engagement with a shaft radial projection  54 , thereby causing locked rotation, namely, no rotational movement of the pulley with respect to the shaft. 
       FIG. 2  is a cross-sectional view through  2 - 2  in  FIG. 1 . Gate  51  is shown in the fully retracted position. This position is typical when pulley  20  is overrotating or overrunning shaft  10  in direction D 1 . Gates  51  bears upon a radial projection  54 . Space  60  between shaft  10  and pulley  20  is filled with a viscous fluid  61  which immerses each gate  51 . Depending on the degree of vibration isolation desired, any viscous fluid from low viscosity hydraulic oils to medium and high viscosity oils and greases such as Krytok™ Grease (a high viscosity DuPont high temperature grease) or silicon fluids and silicon grease can be used. The higher the viscosity, the more “cushioned” or “damped” the motion of the viscous fluid  61  and each gate member  51  will be, and subsequently more damping of vibrations will be realized. Higher viscosity fluids also allow a less elaborate sealing system to be used on the outer sides of the bearings  30  and  40 . As an example here and not by way of limitation, a grease similar to a grease used in bearings  30 ,  40 , or a silicon fluid can be used, for example, automotive grade lithium grease having NLGI Grade 2, or NLGI Grade 1, or NLGI Grade 1.5. By the nature of the curvature and the presence of the projections  54 ,  22 , gates  51  do not open fully in the drive condition, so that when the reverse flow of the grease starts (overrun condition) it pushes the gates closed. “Open fully” refers to the situation wherein each gate extends along a radial directly away from shaft  10 . As shown in  FIG. 5 , in the drive condition each gate  51  is not fully radially extended because each gate  51  engages a projection  22 . Projection  22  may also be coated with an elastomeric material which will diminish the landing impact when a gate  51  engages a projection  22 , thereby decreasing wear and noise of operation. 
     During a reversal each projection  54  and  22  imparts a shear force on the viscous fluid in space  60 . The shear force on the viscous fluid damps and cushions operation of the device upon a reversal of the pulley  20  with respect to shaft  10 . 
       FIG. 3  is a cross-sectional view. In  FIG. 3  shaft  10  is beginning to drive, thereby causing shaft  10  to rotate past pulley  20 . As shaft  10  overrotates pulley  20 , gate  51  is engaged with the viscous fluid  60 . This causes gate  51  to rotate radially outward toward pulley  20  (see arrow). Gate  51  pivots about pin  53 . In this embodiment there are three gates, all of which rotate or pivot radially outward in unison. 
       FIG. 4  is a cross-sectional view. Each gate  51  has rotated radially outward to engage surface  21 . Shaft  10  continues to overrotate pulley  20 . 
       FIG. 5  is a cross-sectional view. Each gate  51  now engages a projection  22 . Once each gate  51  engages a projection  22  the relative rotation of shaft  10  is halted. Shaft  10  now drives pulley  20  through each gate  10 , thereby causing shaft  10  to rotate in locked relation with pulley  20 . 
     The inventive device is operable to transmit torque from shaft  10  to pulley  20 , or, from pulley  20  to shaft  10 . The preceding description considers torque transmission from shaft  10  to pulley  20 . It is also operationally possible for pulley  20  to drive shaft  10 , for example, when shaft  10  is connected to an alternator (not shown). 
     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.