CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Divisional of U.S. application Ser. No. 12/033,999, filed on 20 Feb. 2008, titled “Tilting Independent Suspension System for Motorcycle Trike,” which was a continuation of U.S. application Ser. No. 11/007,851, filed on 9 Dec. 2004, titled “Tilting Independent Suspension System for Motorcycle Trike,” which claimed the benefit of U.S. Provisional Application No. 60/528,041, filed 9 Dec., 2003, titled “Tilting Independent Suspension System for Motorcycle Trike,” and which claimed the benefit of U.S. Provisional Application No. 60/539,457, filed 27 Jan. 2004, titled “Tilting Independent Suspension System for Motorcycle Trike,” and which claimed the benefit of U.S. Provisional Application No. 60/558,006, filed 31 Mar. 2004, titled “Tilting Independent Suspension System for Motorcycle Trike,” all of which are hereby incorporated by reference for all purposes as if fully set forth herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to motorcycle trikes. In particular, the present invention relates to suspension systems for motorcycle trikes. 
         [0004]    2. Description of Related Art 
         [0005]    Motorcycles are turned by both turning the handlebars and leaning into the turn. At high speeds, motorcycles can be turned simply by leaning into the turn. The ability to lean into the turn makes the motorcycle easier to handle in the turns. 
         [0006]    However, when motorcycles are converted into three-wheeled trikes, this ability to lean into the turn is lost. This makes it difficult to handle the trike when turning, particularly at high speeds. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The novel features believed to be characteristic of the invention are set forth in the appended claims. However, the invention itself, as well as a preferred mode of use and further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein: 
           [0008]      FIG. 1  is a perspective view of a motorcycle trike having a tilting independent suspension system according to the present invention; 
           [0009]      FIG. 2  is a schematic of the suspension system according to the present invention, the suspension system being shown in a non-tilting mode; 
           [0010]      FIG. 3  is a schematic of the suspension system of  FIG. 2  shown in a tilting mode; 
           [0011]      FIG. 4  is a schematic of an alternative embodiment of a tilting independent suspension system for a motorcycle trike according to the present invention; 
           [0012]      FIG. 5  is a perspective view of a motorcycle trike having a tilting independent suspension system according to the present invention in which the trike has two front wheels and one rear wheel; 
           [0013]      FIG. 6  is a perspective view of a differential according to the present invention for the tilting independent suspension system of the invention; 
           [0014]      FIG. 7  is another perspective view of the differential of  FIG. 6  showing an alternate reduced size cover plate; 
           [0015]      FIG. 8  is a perspective view of the differential of  FIG. 6  shown with the cover plate removed; 
           [0016]      FIG. 9  is a perspective view of the differential of  FIG. 6  shown with the cover plate and one of the bevel gears removed; 
           [0017]      FIG. 10  is a perspective view of the differential of  FIG. 6  shown installed on a motorcycle having a shaft-drive transmission; 
           [0018]      FIGS. 11A-14F  are various views of several different adapter brackets used with the present invention; and 
           [0019]      FIG. 15  is a perspective view of a rolling chassis for a motorcycle trike and according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    Referring to  FIG. 1  in the drawings, a motorcycle trike, or trike  11 , having a tilting independent suspension system according to the present invention is illustrated. Trike  11  is three-wheeled motorcycle having a single front wheel  13 , and two rear wheels  15  and  17 . A frame  19  carries an engine  21  and a transmission  23 . Front wheel  13  is coupled to frame  19  via a front fork and suspension system  25 . Rear wheels  15  and  17  are coupled to frame  19  via a tilting independent suspension system  27 . 
         [0021]    Referring now to  FIGS. 2 and 3  in the drawings, tilting independent suspension system  27  is illustrated. Suspension system  27  is preferably a double control-arm suspension and is operable between a non-tilting mode, as is shown in  FIG. 2 , and a tilting mode, as is shown in  FIG. 3 . Trike  11  operates in the non-tilting mode when traveling in a straight direction, but transitions into the tilting mode when turning. This provides for better, safer, and more enjoyable handling of trike  11 . 
         [0022]    Transmission  23  includes a belt drive or drive shaft unit  30 , a differential  31 , at least one disk brake  32 , axles  33 , universal joints  35 , half shaft drive links  37 , wheel uprights  39 , and wheel hubs  41 . Wheels  15  and  17  are fastened to wheel hubs  41 . Uprights  39  are connected to frame  19  via upper and lower controls arms, shown in the figures as upper H-arms  43  and lower H-arms  45 , which cooperate to allow each upright  39  to move in a generally vertical path relative to frame  19  as H-arms  43 ,  45  pivot relative to frame  19 . Frame  19  includes towers  46  that extend generally upward from each side of frame  19 . The movement of each upright  39  is constrained and damped by a shock absorber  47 , which may be an air shock absorber or any other appropriate type of suspension damper. 
         [0023]    The unique tilting feature of the subject invention is facilitated by two opposing rotating rocker arms  51 . In the preferred embodiment, each rotating rocker arm  51  is V-shaped, having an interior leg  52  and an exterior leg  54 , such that interior legs  52  and exterior legs  54  meet at vertices  56  and rotate relative to frame  19  about pivot pins  58 . It will be appreciated that rotating rocker arms  51  may be of different shapes, sizes, and configurations. Rotating rocker arms  51  are pivotally connected to towers  46  at vertices  56 . The upper ends of shock absorbers  47  are pivotally coupled to exterior legs  54 , and the lower ends of shock absorbers  47  are pivotally coupled to lower H-arms  45 . Shock absorbers  47  and lower H-arms  45  form tilt angles A. The two rotating rocker arms  51  are rigidly and pivotally linked together by an adjustable connecting rod  53  that extends between interior legs  52 . 
         [0024]    Connecting rod  53  is selectively driven in opposing directions by a control actuator  55 . Control actuator  55  may be a pneumatic, hydraulic, electric, or magnetic device, and actuator  55  is controlled by a control system  57 . Actuator  55  may be a ball-screw device or other similar electro-mechanical device. Control system  57  is activated by one or more sensors  59  operably associated suspension system  27 . Sensors  59  preferably sense the orientation, speed, and/or acceleration of trike  11 , and may be pneumatic, hydraulic, electric, or magnetic devices, or any other suitable sensing apparatus. 
         [0025]    In the preferred embodiment, suspension system  27  allows free movement of uprights  39  until a selected tilt angle A is reached. When the selected tilt angle A is reached, such as during a turn, control system  57  is activated by sensor  59 . Control system  57  then actuates actuator  55 , thereby causing movement of connecting rod  53  and corresponding rotational movement of rotating rocker arms  51  about pivot pins  58 . The rotational movement of rotating rocker arms  51  causes frame  19  to tilt in the direction of the turn, thereby improving the handling of trike  11 . It will be appreciated that a full lean is not necessary. One purpose of suspension system  27  is to “break” the steering so that front fork and suspension system  25  “falls” into the turn more easily. 
         [0026]    Referring now to  FIG. 4  in the drawings, an alternate embodiment of trike  11  is illustrated. In this embodiment, control actuator  55  is disposed between one of towers  46  and one of rocker arms  51 . In this embodiment, it is preferred that one end of control actuator  55  be pivotally mounted to tower  46  at a pivot pin  58 , and the other end of control actuator  55  be pivotally mounted to rocker arm  51  at a second pivot pin  60 . As shown in the  FIG. 4 , control actuator  55  includes a housing  69  that defines two opposing fluid chambers  71  and  73  that are separated by a piston  75 . Piston  75  is connected to an elongated shaft  77 . Housing  69  is pivotally connected to pivot pin  58 , and elongated shaft  77  is pivotally connected to pivot pin  60 . Fluid chambers  71  and  73  are in fluid communication with a control box  79  via conduits  81  and  83 . Though shown in the figure as a pneumatic or hydraulic type, actuator  55  may be of any appropriate type, as described above. 
         [0027]    Control box  79  includes vent ports  85  and  87  that are operably associated with fluid chambers  71  and  73 , respectively. It will be appreciated that in applications in which the control fluid is air, vent ports  85  and  87  may be open to the environment; and that in applications in which the control fluid is a hydraulic fluid, vent ports  85  and  87  would be in fluid communication with a fluid reservoir. Control box  79  is in fluid communication with a source of pressurized fluid, such as pressurized tank  89 , via a conduit  91 . Pressurized tank  89  supplies pressurized fluid to control box  79  for controlling control actuator  55 . It is preferred that the fluid in control system  57  be air, and that tank  89  be maintained at about 80 psi. However, it should be understood that a wide variety of control fluids may be used over a wide range of pressures, depending upon the desired application, responsiveness, and cost. 
         [0028]    Tank  89  is in fluid communication with and pressurized by a compressor  93 . A one-way check valve  95  and a pressure switch  97  may be disposed between compressor  95  and tank  89 . One-way check valve  95  ensures that the fluid does not pass back through to compressor when compressor is in the off mode. Pressure switch  97  turns off compressor  95  when tank  89  has reached the desired pressure, and prevents compressor  95  from over-pressurizing control system  57 . 
         [0029]    In operation, when trike  11  is traveling straight, control actuator  55  is in a trim condition in which the pressures in chambers  71  and  73  are equalized. When trike  11  goes into a turn, sensors  59  send a signal to control box  79 . Control box  79  then selectively increases the pressure in one of chambers  73  or  75 , and correspondingly decreases the pressure in the other chamber. Vent ports  85  and  87  allow the fluid from the depressurized chamber to be appropriately vented. As a result, piston  75  moves in one direction or the other. Because housing  69  is pivotally mounted to tower  46 , movement of piston  75  causes a corresponding rotation of rocker arms  51 . The rotational movement of rotating rocker arms  51  causes frame  19  to tilt in the direction of the turn, thereby improving the handling of trike  11 . Control system  57  will maintain trike  11  in the tilted mode as long as sensors  59  sense that trike  11  is in the turn. As trike  11  leaves the turn and returns to straight travel, control box  79  causes the pressure in chambers  71  and  73  to again equalize and return control actuator  55  to the trim condition. 
         [0030]    It will be appreciated that control system  57  is preferably programmed or adjusted to provide a safe and smooth transition between tilting and straightening out. It should be understood that control system  57  may be operated manually or may be automated by computers, microprocessors, or any of a wide variety of automated control devices. For example, sensors  59  may be manual switches (not shown) disposed on the handlebars of trike  11  that are operated by the rider, or control system  57  may be configured to operate automatically without any input from the rider. In addition, it will be appreciated that trike  11  may include a means for manual or automatic override of control system  57 . 
         [0031]    Referring now to  FIG. 5  in the drawings, an alternate embodiment of the present invention is illustrated. In this embodiment, a trike  111  has two front wheels  113 ,  115  and one rear wheel  117 . In this embodiment, a suspension system  127 , which is similar in form and function to suspension system  27 , is operably associated with the front wheels instead of the rear wheels. Suspension system  127  allows front wheels  113 ,  115  to tilt when trike  111  turns, making trike  111  easier to handle. 
         [0032]    As is shown, trike  111  may include a body portion  119  that covers or encloses all or part of suspension system  127 . In those embodiments in which body portion  119  includes a main body  121  and separate fenders  123 ,  125 , it will be understood that suspension system  127  may be appropriately scaled down in size and shape, or relocated on trike  111  to fit within the confines of main body  121  and/or fenders  123 ,  125 . For example, the rotating rocker arms, the adjustable connecting rod, the control actuator, and the other components of suspension system  127  may be located beneath or in the same plane as the differential. One benefit of the present invention is that the components can be located in a wide variety of locations on the trike without adversely affecting the operation of the suspension system. 
         [0033]    Referring now to  FIGS. 6-10  in the drawings, differential  31  is shown in various views. In  FIG. 6 , differential  31  is shown installed in suspension system  27 . Differential  31  is fixed to and rotates with a drive pulley  154  for transmitting torque to the wheels of the trike. Differential  31  includes a base portion  151  and a cap portion  153  that encloses differential  31 . Base portion  151  includes two inserts  155 ,  157  that allow access to the interior of differential  31  for assembly and maintenance, and that provide internal operating surfaces for a pair of opposing bevel gears  159 ,  163 . Cap portion  153  also functions as a spacing means that allows differential  31  to be used to convert both shaft-drive and belt-drive motorcycles to trikes. In  FIGS. 6 and 7 , differential  31  is shown installed on a belt-drive trike. In  FIG. 10 , cap portion  153  of differential  31  has been replaced with an alternate, reduced size cap portion  156 . Cap portion  156  allows differential  31  to be used installed on a shaft-drive trike. Cap portions  153  and  156  are shown side-by-side in  FIG. 7  for comparative purposes. 
         [0034]    Differential  31  includes a plurality of internal bevel gears  159 ,  161 ,  163 ,  165  that allow the two wheels of the trike, whether located on the front or on the rear, to rotate at different speeds as the trike travels through turns. Gears  159  and  163  oppose each other and rotate on concave support surfaces located on the interior surfaces of inserts  155 ,  157 . Gears  159  and  163  are supported by a fixed shaft  169 . Gears  161  and  165  oppose each other and are coupled together via gears  159  and  163 . Gears  161  and  165  include internal splines  172  that are configured to matingly receive splined drive shafts (not shown) that extend outward from each side of differential  31  to continuously variable universal joints  171 ,  173 . Gears  159 ,  161 ,  163 ,  165  rotate with base portion  151  and cap portion  153  and do no rotate relative to each other unless the trike is turning. 
         [0035]    In  FIG. 10 , differential  31  is installed on a trike  189  having a shaft-drive transmission. Torque is transmitted to differential  31  from a drive shaft  191  through a 90° coupling member  193 . Thinner cap portion  156  is best suited for this embodiment, due to the thickness of coupling member  193 . In this embodiment, the splined shaft on the side of coupling member  193  is longer so that it can pass through coupling member  193  to the continuously variable universal joint on that side. In these shaft-drive embodiments, the suspension system is mounted to the motorcycle with an adapter bracket  195 , a mounting link  197 , and a second hatchet-shaped adapter bracket (see  FIGS. 11A-11G ). 
         [0036]    Referring now to  FIGS. 11A-14G  in the drawings, several different adapter brackets that are used to mount the suspension system to the motorcycle frame are illustrated. The adapter brackets shown in  FIGS. 11A-12G  are typically used to convert shaft-drive motorcycles to trikes. In  FIGS. 11A-11G , an adapter bracket  201  for converting a shaft-drive motorcycle to a trike is shown. Adapter bracket  201  includes a coupling end  203  and a shaft end  205  that is configured to be coupled to and/or telescopically mate with the frame of the motorcycle. Adapter bracket  195  is shown in  FIGS. 12A-12G . 
         [0037]    The adapter brackets shown in  FIGS. 13A-14F  are typically used to convert belt-drive motorcycles to trikes. Adapter bracket  301  shown in  FIGS. 13A-13  includes one or more arcuate slots  303  that allow the suspension system to rotate about a pivot point  305 . This allows the belt to be placed over the belt drive pulley and adjusted. Likewise, adapter bracket  401  shown in  FIGS. 14A-14F  includes one or more arcuate slots  403  that allow the suspension system to rotate about a pivot point  405 . The dashed lines indicate that the shape of that portion of bracket  401  may vary. 
         [0038]    In another embodiment of the present invention, the belt drive pulley includes a central, hollowed-out can-shaped portion. This can shaped portion allows the differential and bearings to be completely or partially recessed therein. This configuration allows longer drive shafts to be used, which in turn, allows the suspension system to have a greater range of tilting angles. 
         [0039]    The suspension system of the present invention is particularly well suited for use in a universal rolling chassis according to the present invention. Such a universal rolling chassis allows a user to install engines from a wide variety of manufacturers with little or no modification to the rolling chassis or suspension system.  FIG. 15  shows a rolling chassis  501  having a frame  503 , front suspension  505 , and rear tilting suspension  507 . A front wheel  509  is attached to front suspension  505 , and rear wheels  511 ,  513  are attached to rear suspension  507 . Frame rails  515 ,  517  support an engine installed within frame  503 . 
         [0040]    It is apparent that an invention with significant advantages has been described and illustrated. Although the present invention is shown in a limited number of forms, it is not limited to just these forms, but is amenable to various changes and modifications without departing from the spirit thereof. For example, the invention is described as being used in motorcycles, but it should be understood that the tilting suspension system may also be used for other types of vehicles.
A tilting suspension system is adapted for use with a vehicle having three wheels and a frame. The system has two sets of control arms, each set of control arms being pivotally connected to one side of the frame. An upright is pivotally connected to each set of control arms, each upright having a rotatable hub for allowing one of the wheels to be mounted thereto. Two rocker arms are pivotally connected to the frame, and a control link is pivotally connected to each of the rocker arms, such that pivoting of one rocker arm causes corresponding pivoting of the other rocker arm. A link member operably connects each rocker arm to a corresponding upright, such that pivoting of each rocker arm causes corresponding movement of the uprights. An actuator is configured to selectively pivot the rocker arms, such that actuation of the actuator pivots the rocker arms, thereby causing the frame to rotate about a generally longitudinal roll center and causing each upright to rotate about a generally longitudinal axis.