Abstract:
A fluid coupled speed retarder generating a restraining torque on a vehicule wheel system comprises a restraining shaft ( 50 ) coupled by a viscous fluid to a wheel ( 32 ) and axle ( 54 ) system through a coupling ( 30 ) which includes an impeller ( 48 ) with radial vanes ( 77 ) connected to the restraining shaft and a housing ( 44 ) with further radial vanes ( 46 ), the housing connected for rotation with the wheel ( 34 ). A braking force is developed upon demand by a selective locking of the restraining shaft ( 50 ) from motion, the relative motion between the impeller and housing in the viscous coupling generating the barking force.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to devices for coupling one rotating shaft to another rotating shaft. The present invention relates more specifically to a fluid coupled retarding device between a high speed rotating shaft and a lower speed or nonrotating shaft in a manner that may be utilized in conjunction with braking systems on on-road and off-road vehicles.  
           [0003]    2. Description of the Related Art  
           [0004]    There are currently many different devices and systems whose purpose it is to slow, retard or stop the motion of a vehicle across a surface by directly or indirectly impeding the rotation of the wheels for such a vehicle. These vehicle retarding systems generally fall into four different categories; (1) engine based systems where the engine is operated in a compression mode and linked to the rotating wheels of the vehicle, (2) engine exhaust based systems where manifold pressure is increased, typically through an engine exhaust valve, (3) eddy current coupling based systems where magnetic forces provide a retarding coupling to the metallic components of the rotating wheels or the rotating drive train, and (4) a general class of retarding systems that rely on the use of viscous fluids to provide a retarding coupling. All of these various retarding systems are generally used to provide additional braking forces above and beyond that which is provided by the foundation brakes.  
           [0005]    Brake failure, especially for larger tractor trailer vehicles, often occur when excessive braking is experienced on downhill grades. With conventional brake pads, excessive braking will quite rapidly overheat the surfaces of the pads and cause the pads to lose their friction holding capability. It is known that under extreme conditions, conventional brake pads can slip dramatically as superheated layers of gas can form immediately over the surface of the brake pads causing, in some instances, complete failure of the brakes to hold. In such circumstances little or no braking is available to the vehicle operator. Under conditions where the vehicle is running downhill there may be no way to stop the vehicle except through the use of specifically designed and installed road run-offs. It is precisely because of the problems associated with conventional brake failure under high heat conditions that highway systems often install such road run-offs for large tractor-trailer vehicles in downhill terrain.  
           [0006]    Some efforts have been made in the past to implement heat removal systems from conventional brake pads so as to reduce the likelihood of the overheating condition described. Other efforts have been made, as mentioned above, to supplement the conventional braking system in such a manner to place less work on the conventional brake pads and diminish the likelihood that they will overheat. Unfortunately, many of the back-up or supplemental systems designed suffer from an overcomplexity that results in their failure more frequently than desired.  
           [0007]    It would be desirable to have an auxiliary braking system or vehicle retarder that provided a controlled restraining torque on the wheel system of a vehicle that is in addition to the normal braking system using conventional brake pads. Such a system could be used to retard the motion of a vehicle in the event of a failure of the primary brake system, generally known as the foundation brakes, and additionally would take much of the load off of the primary brake system to prevent its failure in the first place.  
           [0008]    Some efforts have been made in the past to utilize fluid couplings for vehicle drive trains that utilize interleaved discs and the like containing highly viscous fluids that couple a variety of rotating shafts. Examples of these efforts are included in U.S. Pat. Nos. 5,363,498, 5,414,260, 5,431,603, and 5,593,012. These referenced patents generally describe concepts that use a highly viscous fluid to strongly couple two rotating systems in a manner that provides slip between the rotating systems only when a predetermined brake away torque is exceeded. These systems therefore act as rotational shock absorbers to allow slippage between the rotating shafts as a means of preventing the overstress and subsequent failure of the drive train components. An example of this can be found when a rotating wheel leaves the ground surface for a period of time, increases its rotational speed and then suddenly comes back into contact with the ground surface creating a shock on the rotating shaft members. A viscous coupling, such as described in the above-referenced patents, can absorb much of the shock by releasing the coupling when excessive torque is experienced.  
           [0009]    Contrary to the purpose of the systems described in the above-referenced patents, the present invention addresses the use of a viscous coupling that does not “break away” when a given torque is experienced. Rather, the present concerns are addressed by a system that maintains a fluid coupling between two rotating shafts but exerts a counter rotational force on the higher speed shaft that over time facilitates the reduction in speed of the higher speed rotating shaft. The structures of such a system, as well as the nature of the viscous fluid, are therefore quite distinct from those described above with the referenced patents.  
           [0010]    It would be desirable to have an auxiliary braking system for wheeled vehicles that utilizes a viscous fluid to provide fluid shear between rotating components in the drive train of the vehicle in a manner that slows the relative motion between the components. It would be desirable if the system incorporated a fluid that could be used as a medium to extract heat energy generated by the operational braking or retarding of the speed of the vehicle. It would be important for such a system to provide a controlled restraining torque on the wheel system of the vehicle that is in addition to the normal foundation braking system.  
         SUMMARY OF THE INVENTION  
         [0011]    It is therefore an object of the present invention to provide an auxiliary speed retarding system for a wheeled vehicle that may supplement the braking force provided by the foundation braking system of the vehicle.  
           [0012]    It is a further object of the present invention to provide an auxiliary braking system for a wheeled vehicle that not only supplements the foundation braking system but also serves to prevent the foundation braking system from failing.  
           [0013]    It is a further object of the present invention to provide a speed retarding system that utilizes a viscous fluid to provide fluid shear between rotating components in the wheel and axle system of a vehicle so as to provide an opposing rotational torque to the higher speed rotating components of the system.  
           [0014]    It is a further object of the present invention to provide a viscous fluid coupled speed retarder to slow the relative motion between two rotating components in a vehicle wheel and axle system, and further to provide, by said viscous fluid, a medium for the extraction of heat energy generated by the process of braking or retarding the speed of the vehicle.  
           [0015]    In fulfillment of these and other objectives, the present invention provides a fluid coupled vehicle speed retarder that generates a controlled restraining torque on the wheel system of a moving vehicle that is in addition to the normal foundation braking system on the vehicle. The fluid coupled vehicle speed retarder comprises a restraining shaft system coupled by means of a viscous fluid to a wheel and axle shaft system rigidly coupled to one or more of the rotating wheels of the vehicle. Under normal operational conditions the restraining shaft system rotates in conjunction with the wheel and axle shaft system by means of the viscous fluid coupling. In the event of braking, the restraining shaft system is locked to prevent its rotation with respect to the vehicle and with respect to the wheel and axle shaft system. The viscous fluid coupling, which is established within an impeller vane and disc enclosure, serves to create a counter rotational force on the wheel and axle shaft system connected to the wheels of the vehicle. In this manner the viscous fluid and the impeller vane and disc device both retard the speed of the rotating wheels and serve to remove the energy associated with such rotation, and the braking of such rotation, away from the vehicle wheel system. The impeller enclosure comprises a plenum through which a radial array of impeller vanes and impeller discs rotate adjacent to a radial array of impeller ribs that, by counter rotation, serve to force a circulation of the viscous fluid within the impeller enclosure. The impeller enclosure case is connected to the wheel system of the vehicle and rotates at wheel speed. The impeller vane and impeller disc components of the system are rigidly connected to the restraining shaft system and respond to the fixed or rotating condition of the restraining shaft. In this manner a viscous fluid contained within the impeller case serves to couple the two rotating systems so as to cause them to rotate together under normal conditions and to experience the fluid drag caused by the viscous fluid moving through the system when the restraining shaft system is locked under braking conditions. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a schematic diagram that shows the basic rotating systems of a vehicle utilizing the device and system of the present invention.  
         [0017]    [0017]FIG. 2 is a partial cross sectional view of one wheel of a vehicle utilizing the system of the present invention.  
         [0018]    [0018]FIG. 3 is a detailed cross sectional view of the components of the system of the present invention.  
         [0019]    [0019]FIG. 4 is a detailed side view, in partial cross section, showing the internal components of the system of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]    One goal of the present invention is to provide a speed retarding system that may be readily installed in a retrofit manner on existing wheeled vehicles. The design of the system, therefore, is such that the primary components may be fixed to the external rotating face of one or more wheels of the vehicle. Minor modifications to the balance of the existing axle structure are required to position the restraining system of the present invention and to install a mechanism for locking the restraining shaft upon activation of the foundation brakes. The following description, therefore, involves an embodiment where the primary components of the present invention are positioned on the outside face of the wheels of the vehicle. It is understood, however, that other placements of these components are anticipated, especially where the system might be manufactured as original equipment on a vehicle. The system could, for example, be placed directly between the rotating axle shaft and a fixed position on the vehicle should access to the rotating axle shaft be available. The following description, however, conveys the basic concepts of the present invention and gives one example of an appropriate placement of the system&#39;s components.  
         [0021]    Reference is made first to FIG. 1 for a brief description of the basic rotating systems of a vehicle utilizing the device of the present invention. FIG. 1 is a schematic diagram that is not intended to show geometric structures so much as the functional relationship between the components of the present invention. Restraining shaft system  10  is shown in FIG. 1 coupled to wheel shaft system  12  by way of viscous coupling fluid  24 . Wheel shaft system  12  is comprised of rotating wheel/tire  14  and wheel shaft  16  which are connected by rigid wheel coupling  18  as is well known in the art. Wheel shaft coupling face  20  engages viscous coupling fluid  24  and by such engagement is coupled to restraining shaft coupling face  22 .  
         [0022]    Restraining shaft system  10  is compromised of rotating restraining shaft  26  that is rigidly attached to restraining shaft coupling face  22 . Restraining shaft  26  is operably engaged to locking mechanism  28  as indicated. Locking mechanism  28  may be any of a number of devices known in the art that are operable to lock or stop the rotation of the rotating shaft. Viscous fluid coupling  24  permits locking mechanism  28  to be any of a number of devices which may gradually or quite abruptly stop the rotation of restraining shaft  26 .  
         [0023]    Under normal operating conditions, restraining shaft system  10  rotates in conjunction with wheel shaft system  12  through viscous coupling fluid  24 . When braking is applied to the vehicle, locking mechanism  28  stops the rotation of restraining shaft system  10 . Viscous coupling fluid  24  then experiences the rotational shear forces that, because of the structure of the retarding impeller system of the present invention, provides a counter rotational torque to wheel shaft system  12 . In this manner, the rotational speed of wheel shaft system  12  is reduced in response to the counter rotational torque produced.  
         [0024]    Reference is now made to FIG. 2 for a detailed description of the specific components of the present invention that together effect the above-described function. Speed retarding system  30  is positioned on the outside face of wheel/tire combination  32 . In FIG. 2, tire  34  is shown in cross sectional configuration as it would be positioned on wheel rim  36 . Wheel rim  36  is attached to the vehicle by way of attachment to axle shaft flange  38 . Wheel lug nuts/bolts  40  are positioned through wheel rim  36  to rigidly attach it to axle shaft flange  38 .  
         [0025]    Speed retarder system  30  is attached to wheel  36  by way of impeller case wheel bolts  42 . These bolts are positioned, in the preferred embodiment, immediately over wheel lug nuts/bolts  40  and attached thereto in a manner well known in the art. The placement of impellar case wheel bolts  42  and their attachment to wheel lug nuts/bolts  40  rigidly attach impeller case  44  to wheel/tire combination  32 . Impeller case  44  therefore rotates in conjunction with wheel/tire combination  32 .  
         [0026]    Within impeller case  44  are positioned impeller case ribs  46  which are rigidly attached to the inside wall surfaces of impeller case  44 , as well as impeller vanes  48  and impeller discs  77  which are free to rotate within impeller case  44  between impeller case ribs  46 . This structure is described in more detail below.  
         [0027]    Impeller vanes  48  and impeller discs  77  are rigidly positioned on restraining shaft  50  which passes through impeller case  44  and additionally through the center of rotating axle shaft  54 . Restraining shaft bearings  52  position and allow the rotation of restraining shaft  50  within axle shaft  54 .  
         [0028]    Axle shaft  54  is positioned within axle housing  56  which itself is rigidly positioned on the vehicle by means of axle mount  58 . The axle shaft and axle housing structures are typical of trailered vehicles and the like. Axle shaft bearings  16  stabilize the rotating axle shaft  54 .  
         [0029]    At the end of restraining shaft  50  is positioned locking mechanism  62  which is shown generically in FIG. 2 since it may be any of a number of known mechanisms for stopping the rotation of a rotating shaft. Lock activator  64  is positioned adjacent to locking mechanism  62  and responds to the activation of the foundation braking system of the vehicle as described above. It should be noted that the foundation braking system of the vehicle is not shown in FIG. 2 for clarity but would typically be positioned behind axle shaft flange  38  with either a braking disc or drum configuration.  
         [0030]    Reference is now made to FIG. 3 for a detailed description of the internal structures of the impeller case component of the present invention. Various wheel/tire components are not shown in FIG. 3 for clarity. Speed retarding system  30  is shown positioned on axle shaft flange  38  in the same manner as described above. Wheel  36  is attached to axle shaft flange  38  by means of wheel lug nuts/bolts  40 . Impeller case  44  is attached to axle shaft flange by way of impeller case wheel bolts  42  which are attached to wheel lug nuts/bolts  40  in the preferred embodiment.  
         [0031]    Impeller case  44  is a hollow disc-shaped enclosure, symmetrical about the axis formed by restraining shaft  50 . Only an upper portion of impeller case  44  is shown in FIG. 3 as the balance of the component is symmetrically identical. Attached to the inside walls of impeller case  44  and positioned in a radial array described in more detail below, are impeller case ribs  46 . Impeller case ribs  46  are positioned internally on both an outside inner face of impeller case  44  and an inside inner face. Between these two radial arrays of impeller case ribs  46  are positioned impeller vanes  48  and impeller discs  77  which are attached one to the other and are free to rotate with respect to impeller case  44  but for the viscous fluid  70  contained within impeller case  44 . Outside impeller case bearing  66  and inside impeller case bearing  68  permit the rotation of impeller vanes  48  and impeller discs  77  with respect to impeller case ribs  46 . These bearings  66  and  68  operate in conjunction with sealing devices as are well known in the art in order to contain viscous fluid  70  within impeller case  44 .  
         [0032]    The arrangement of impeller vanes  48  and impeller discs  77  with respect to impeller case ribs  46 , and the rotation of restraining shaft  50  with the resultant rotation of impeller vanes  48  and impeller discs  77 , forces the movement of viscous fluid  70  in a circulatory manner within impeller case  44 . Impeller vanes  48  are bounded on either side by impeller discs  77 . Impeller discs  77  are circular discs attached to restraining shaft  50  and to impeller vanes  48  to form what is essentially a fluid circulation chamber between the vanes and the discs. At least two arrays of apertures are positioned through impeller discs  77  to facilitate and direct a circulation of viscous fluid  70  therein. Apertures  73  are sized, shaped, and positioned to draw viscous fluid  70  through impeller discs  77  from between vanes  48  outward to ribs  46 . Apertures  75  are sized, shaped, and positioned to draw viscous fluid  70  from between ribs  46  back into the “circulation chamber” described above. In this manner viscous fluid  70  is “pumped” through apertures  73  and  75  when shaft  50  is held stationary with respect to the rotating wheel. Fluid flow within the ribs is shown at  72  while fluid flow within the impeller vanes is shown at  74 . The geometry of the impeller vanes, the impeller discs (and the apertures therein) and the impeller ribs, together with the fluid characteristics of viscous fluid  70 , provide the necessary fluid shear between the two rotating systems to effect a counter rotational torque on the rotating wheel system.  
         [0033]    The balance of the rotating mechanism disclosed in FIG. 3 includes restraining shaft  50  positioned within axle shaft  54  by means of restraining shaft bearings  52 . Axle shaft  54  is itself positioned within axle housing  56  and may rotate with respect thereto by means of axle shaft bearing  60 .  
         [0034]    Reference is now made to FIG. 4 for a profile view of the primary components of speed retarding system  30 . In FIG. 4, a two level partial cut away view of impeller case  44  is shown. In this view a plurality of mounting eyes  76  for receiving impeller case wheel bolts  42  are disclosed. These mounting eyes  76  are positioned in symmetrical arrangement as would be appropriate for a six lug wheel. Other mounting eye configurations based on other wheel configurations are of course anticipated.  
         [0035]    The left hand side of FIG. 4 is cut away to show in profile the rotating impeller vanes  48  and impeller discs  77 , while the right hand side of FIG. 4 is cut away to show the “fixed” impeller case ribs  46  with impeller discs shown in dashed lines. It is understood by reference to FIG. 3 how impeller vanes  48  and impeller discs  77  rotate within the confines defined by impeller case ribs  46  and thereby cause the flow of viscous fluid  70  through apertures  73  and  75  as shown. In FIG. 4 rotating restraining shaft  50  is shown with its radial array of impeller vanes  48 . By reference again to FIG. 3 it is seen that impeller vanes  48  may be offset one from the next in alternating fashion so as to provide impeller vane eye  78  close to restraining shaft  50 . In other words, the width of each impeller vane  48  does not completely bridge the gap between the opposing impeller discs  77  on either side. Impeller vanes  48  are alternatively offset one from the next so as to provide a channel by way of impeller vane eye  78  that receives the return flow of viscous fluid  70  as shown. This return flow is facilitated by the open plenum in the outward section of impeller case  44 . The flow of viscous fluid  70  is shown at  72  and  74  in FIG. 4 in response to the rotation of restraining shaft  50 , also as indicated in FIG. 4.  
         [0036]    Once again, operation of the system of the present invention can be understood best by reference to FIGS. 1 and 2. Locking mechanism  28  ( 62  in FIG. 2) may be activated electrically, mechanically, or hydraulically in response to the activation of the foundation braking system of the vehicle. Alternately, if such concurrent activation is not desired, a separate means for activating locking mechanism  28  may be provided on the vehicle. In either case, activation of the locking mechanism serves to stop the rotation of the restraining shaft system of the present invention. An important characteristic of locking mechanism  28  is that it not degrade with temperature. The shock of the locking of shaft  26  should be readily absorbed by the viscous fluid in the system. Prior to such activation the restraining shaft system is rotating in conjunction with the rotation of the wheel axle system by means of the viscous fluid coupling described. As there is little or no resistive torque between the two systems prior to activation, the restraining shaft system rotates at approximately the same speed as the wheel axle system.  
         [0037]    Once activated, however, the rotation of the restraining shaft is quickly brought to a stop. It is understood that the composition of the viscous fluid within the system should not be such as to create a sudden excessive counter rotational torque on the wheel axle system of the vehicle. A viscous fluid made of long chain polymer compounds with a viscosity rating ranging from 500,000 centipoise to 30,000,000 centipoises is appropriate for such operation. The arrangement shown for the internal structure of the impeller disc of the present invention provides a thrust balance along the axis of the restraining shaft which eliminates the need for large thrust bearings or wear plates. Impellers with vanes on one internal surface of the impeller disc component can provide equivalent retarding torque by using vanes of a greater depth than that shown in the preferred embodiment.  
         [0038]    Once the restraining shaft is locked, the retarder system begins to act as a pump for the viscous fluid. The viscous fluid is pumped through the apertures in the impeller discs positioned near the impeller eye adjacent to the rotating axis of the restraining shaft and then radially outward towards the case plenum. In this process power is extracted from the system and converted to heat. The viscous fluid provides a smooth transition of speed between the restraining shaft system and the impeller case that is connected to the rotating wheel system. Additionally, the viscous fluid provides a mechanism for carrying heat from the friction surfaces (impeller and case walls) by pumping the fluid from the impeller center outward through the apertures at the perimeters of the impeller discs to the plenum where the heat may be dissipated. The viscous fluid returns through return ducts between the radial case ribs. These return ducts provide an additional large surface area from which heat may be extracted by convection and radiation. Convective heat transfer from the case to the external environment will occur as a result of the high velocity air flow that surrounds the rotating and translating wheels of the vehicle.  
         [0039]    Once again, it is anticipated that operation of the system of the present invention reduces the load on the foundational brake components of the vehicle. In this manner, not only does the system of the present invention facilitate the braking process but generally assists in preventing the failure of the foundation brakes due to overheating as a result of excessive load.  
         [0040]    Once again, it should be mentioned that the specific positioning of the components of the system of the present invention lend themselves to a retrofit installation on existing vehicle trailers and the like. Alternative placement of the components will be recognized by those skilled in the art when alternative vehicle structures are encountered. It is further anticipated that installation of the system of the present invention on original equipment might be better served by an internal positioning (between the wheels) of the system components. The only critical elements necessary to the proper positioning of the system components involve attachment of the impeller case to some part of the rotating wheel system of the vehicle/trailer and some access to an opposing end of the restraining shaft for the purposes of locking and stopping its rotation.  
       Component Identification List  
       [0041]    [0041] 10 . RESTRAINING SHAFT SYSTEM  
         [0042]    [0042] 12 . WHEEL SHAFT SYSTEM  
         [0043]    [0043] 14 . ROTATING WHEEL/TIRE  
         [0044]    [0044] 16 . WHEEL SHAFT  
         [0045]    [0045] 18 . RIGID WHEEL COUPLING  
         [0046]    [0046] 20 . WHEEL SHAFT COUPLING FACE  
         [0047]    [0047] 22 . RESTRAINING SHAFT COUPLING FACE  
         [0048]    [0048] 24 . VISCOUS COUPLING FLUID  
         [0049]    [0049] 26 . RESTRAINING SHAFT  
         [0050]    [0050] 28 . LOCKING MECHANISM  
         [0051]    [0051] 30 . SPEED RETARDING SYSTEM  
         [0052]    [0052] 32 . WHEEL/TIRE COMBINATION  
         [0053]    [0053] 34 . TIRE  
         [0054]    [0054] 36 . WHEEL  
         [0055]    [0055] 38 . AXLE SHAFT FLANGE  
         [0056]    [0056] 40 . WHEEL LUG NUTS/BOLTS  
         [0057]    [0057] 42 . IMPELLER CASE WHEEL BOLTS  
         [0058]    [0058] 44 . IMPELLER CASE  
         [0059]    [0059] 46 . IMPELLER CASE RIBS  
         [0060]    [0060] 48 . IMPELLER VANES  
         [0061]    [0061] 50 . RESTRAINING SHAFT  
         [0062]    [0062] 52 . RESTRAINING SHAFT BEARINGS  
         [0063]    [0063] 54 . AXLE SHAFT  
         [0064]    [0064] 56 . AXLE HOUSING  
         [0065]    [0065] 58 . AXLE MOUNT  
         [0066]    [0066] 60 . AXLE SHAFT BEARINGS  
         [0067]    [0067] 62 . LOCKING MECHANISM  
         [0068]    [0068] 64 . LOCK ACTIVATOR  
         [0069]    [0069] 66 . OUTSIDE IMPELLER CASE BEARING  
         [0070]    [0070] 68 . INSIDE IMPELLER CASE BEARING  
         [0071]    [0071] 70 . VISCOUS FLUID  
         [0072]    [0072] 72 . FLUID FLOW WITHIN RIBS  
         [0073]    [0073] 73 . CENTRAL APERTURES  
         [0074]    [0074] 74 . FLUID FLOW WITHIN IMPELLER  
         [0075]    [0075] 75 . PERIMETER APERTURES  
         [0076]    [0076] 76 . MOUNTING EYES  
         [0077]    [0077] 77 . IMPELLER DISCS  
         [0078]    [0078] 78 . IMPELLER VANE EYE