Abstract:
A suspension system for a tilting vehicular chassis based on more than three wheels separates a tilting component of the chassis from a non-tilting component. The non-tilting component provides a means for powering the vehicle with automotive-type engine and drive train options, while the tilting component provides the turning stability necessary for a narrower wheel base. The narrower wheel base benefits fuel economy. The multiplicity of wheels, and the breadth of platform thus enabled, permits shelter and comfort features for the occupant not otherwise available on a typical two-wheel chassis.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This is a Continuation-in-Part of U.S. patent application Ser. No. 11/590,475, filed Nov. 1, 2006, claiming priority to Provisional Application 60/731,415, filed Oct. 31, 2005. 

   FIELD OF THE INVENTION 
   This invention relates to tilting chassis systems for vehicles, and more particularly to a suspension system for a tilting chassis having more than three wheels. 
   BACKGROUND OF THE INVENTION 
   Motorcycles exhibit handling characteristics which are superior in many ways over automobiles, and have less aerodynamic drag and reduced rolling resistance as compared with standard automobiles and automobile tires. Reduced aerodynamic and rolling resistance result in improved fuel economy and vehicle performance. The preferred embodiment of the invention has four tires and is therefore capable of carrying a higher gross weight than a typical motorcycle with two tires. The vehicle can accommodate a larger and heavier engine, heavier fuels and loads such as batteries, more cargo, and the weight of an enclosed aerodynamic body to protect the occupants from the elements and from crashes, while reducing aerodynamic drag. 
   A vehicle designed around this concept can be constructed as narrow as a motorcycle, which is important because frontal area and shape are significant determinates of aerodynamic drag. The combination of minimal frontal area, an enclosed aerodynamic passenger/cargo compartment, and low rolling friction (drag) motorcycle tires yields improved fuel economy. 
   Such a vehicle would not require computers, sensors, or mechanical systems to lean the vehicle or to keep it upright at speed. The only lean control mechanism required is a simple combination of bracing which will lock the vehicle in an upright position when parked or at slow speeds, such as when backing or otherwise maneuvering with feet on the ground. 
   The vehicle&#39;s suspension system can be softer and provide a smoother ride than motorcycles and many non-tilting vehicles such as autos, trucks, and ATVs. Typical motorcycle suspension systems are thirty to fifty percent stiffer than those of non-tilting vehicles because motorcycles experience all of the lateral acceleration or “G” force loading occurring during turning maneuvers. The proposed suspension system experiences none of the lateral acceleration of a motorcycle because the suspension system does not lean while turning. It remains in and acts only in the vertical like the suspension system of a typical non-leaning vehicle. Suspension systems of non-tilting vehicles must resist the forces causing the vehicle to lean to the outside of a turn and the resulting outward weight transfer. The proposed suspension system experiences no lateral weight transfer while turning because the vehicle&#39;s center of mass is moved to the inside of the turn similar to that of a motorcycle during a balanced turn. 
   Compared with a typical two-wheeled motorcycle, the preferred embodiment will have twice the traction, thereby promoting shorter braking distances, improved cornering, and the ability to accommodate more powerful engines. Due to the relatively smaller contact patch of motorcycles, the vehicle is less susceptible to hydroplaning than automobiles and trucks. Having the same overall width of a motorcycle makes a vehicle easier to maneuver, requires less parking space, and has access to car pool lanes. 
   With two front wheels, this design has inherently better front wheel traction, is more stable, and safer than vehicles with one tilting or fixed front wheel. As weight shifts forward as a vehicle slows and stops, front wheel traction is critical for stopping quickly, thus providing a major safety factor. 
   The prior art is replete with three-wheel tilting chassis. Two exemplary references are U.S. Patent Application 2007/0176384 to Brudeli and U.S. Patent Application 2006/0255550 to Pfeil. In both of these cases, which are typical of the genre, the drive system tilts with the rear, or driven, wheel. Such a tilt of the drive system, however, would not be compatible with an engine and drive train connected to driven wheels through a differential, as might be desirable for the reasons discussed above. If the differential were to be tiltable, the rotation of the drive shaft would bias the tilt attitude while creating complex angles with the driven axles. 
   Other references, such as U.S. Patent Application 2008/0238005 to James, disclose feedback mechanical systems to control lean. This may be an over-complication, however, considering the case of a motorcycle where no control other than that provided by the rider is needed. A motorcyclist, when provided with handlebar steering, will have a sense of balance while leaning and will know to counter-steer in order to initiate a turn. 
   U.S. Patent Application 2008/0197597 to Moulene discloses a four-wheel tilting chassis. All components of Moulene&#39;s chassis, however, also tilt. Moulene does not disclose sufficient detail of the drive mechanism to understand how it would operate in the context of a tilt. 
   What is missing in the prior art is a non-tilting component to a tilting chassis structure whereby a power transmission system comparable to an automobile is enabled for the benefits of the same combined with those of a motorcycle. 
   SUMMARY OF THE INVENTION 
   In view of the above-mentioned unfulfilled needs, the present invention embodies, but is not limited by, the following objects and advantages: 
   A first objective is to provide a tilting chassis having more than three wheels which can be used with a drive train using a differential gearbox. 
   A second objective is to provide improved fuel economy over non-tilting chassis systems. 
   A third objective is to provide a softer suspension and a smoother ride as compared to a two-wheel chassis system. 
   A fourth objective is to provide better traction and breaking control as compared to a two-wheel chassis system. 
   A fifth objective is to enable better passenger protection and comfort than is typically provided by a motorcycle. 
   A sixth objective is to provide for greater load-carrying capability as compared to a two-wheel chassis system. 
   A seventh objective is to simplify by eliminating sensors and feedback systems having the purpose of controlling the lean angle of a tilting chassis. 
   In a preferred embodiment of the present invention, a suspension system for a tilting vehicular chassis comprises a non-tilting frame of longitudinal extent having a first axis and a plurality of first horizontal members, the first horizontal members being rotatably attached in oppositely-disposed pairs about the first axis, at least, at each end. The non-tilting frame supports, at least, a means for motorizing. 
   The suspension system further comprises a tilting frame of longitudinal extent rotatably attached to the non-tilting frame about the first axis. The tilting frame has a second axis parallel to the first axis and a plurality of second horizontal members. The second horizontal members are rotatably attached in oppositely-disposed pairs about the second axis, each second horizontal member being rotatably attached to a corresponding first horizontal member by a vertical strut. The tilting frame supports, at least, one occupant. 
   The suspension system of the preferred embodiment additionally comprises a plurality of road-contact wheels rotatably attached to the vertical struts, at least one wheel of which is connected to the means for motorizing. Lastly, the suspension system comprises a means for suspending the paired first horizontal members to ride level with the road while providing for a smooth ride by absorbing road surface irregularities in the articulating recoil of individual wheels. 
   In a particular preferred embodiment, the means for suspending comprises a vertical beam rigidly attached to the non-tilting frame at the middle of each pair of first horizontal members. One of a pair of shock absorbers extend from the top of the vertical beam to each individual first horizontal member thereby forming a triangular brace. 
   Also, in a particular preferred embodiment, the means for motorizing is an engine with a power train connected to at least one of the wheels. The power train includes a differential joint and at least one differential drive shaft spur connecting the differential joint to at least one driven wheel. The differential drive shaft spur has an axis and a means for telescopically lengthening and shortening along said axis to accommodate varying distances from the at least one driven wheel to the differential joint caused by tilting or by articulating horizontal members responding to shock absorption. 
   In a second embodiment of the invention, the paired first horizontal members rotate about two axes flanking the first axis, the flanking axes parallel to and co-planar with the first axis. The second horizontal members similarly rotate about two axes flanking the second axis. The planes of the two sets of flanking axes are constrained to be parallel. In all other aspects, the second embodiment is structurally and functional the same as the preferred embodiment. 
   As this is not intended to be an exhaustive recitation, other embodiments may be learned from practicing the invention or may otherwise become apparent to those skilled in the art. 

   
     DESCRIPTION OF THE DRAWINGS 
     Various other objects, features and attendant advantages of the present invention will become fully appreciated as the same becomes better understood through the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein: 
       FIG. 1  is a perspective view of the tilting chassis of the invention; 
       FIG. 2  is a plan view of the tilting chassis of the invention; 
       FIG. 3  is a perspective view of the tilting frame; 
       FIG. 4  is a perspective view of the non-tilting frame; 
       FIG. 5  is a perspective view of the tilting chassis in a tilted turn; 
       FIG. 6  is a partial perspective view of the tilt lock mechanism; 
       FIG. 7  is a front elevation view of the tilting chassis in a neutral configuration; 
       FIG. 8  is a front elevation view of the tilting chassis under a shock-loading configuration; 
       FIG. 9  is a front elevation view of the tilting chassis in a tilting configuration; 
       FIG. 10  is a perspective view of a telescoping drive shaft spur; 
       FIG. 11  is a sectional view of the telescoping drive shaft spur of  FIG. 10 ; and 
       FIG. 12  is a half-sectional view of a shock absorber of the present invention 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A suspension system  1  for a tilting vehicular chassis is shown in a neutral posture, wherein the vehicle may be parked or moving directionally forward, in  FIGS. 1 and 2 .  FIG. 5  represents the suspension system  1  in the posture of a tilted turn. The articulation of suspension system  1  under certain road and steering conditions, as viewed frontally, is shown in  FIGS. 7-9 .  FIG. 7  represents the neutral posture;  FIG. 8  shows the suspension system encountering a shock load, as when traversing a road bump; and  FIG. 9  illustrates the chassis in a tilting posture, as when banking for a right-hand turn. 
   The details of suspension system  1  are best shown in  FIGS. 3 and 4 .  FIG. 4  illustrates a non-tilting frame  10 . Non-tilting frame  10  is comprised of a first longitudinal member  15  having a first axis  11 . First horizontal members  12  are disposed about the first axis  11  and are rotatably attached, in oppositely-directed pairs, at the front and rear of first longitudinal member  15 . In an alternate embodiment, first horizontal members  12  are disposed about a pair of first offset axes  14  (not shown), offset to each side from, and parallel to and planar with, the first axis  11 . In the preferred embodiment, first horizontal members  12  are first A-arms  13 . 
   Non-tilting frame  10  supports, at least, a means for motorizing  30 . In the preferred embodiment, the means for motorizing  30  is comprised of an engine  31  and a power train  32 . The power train  32  includes a differential (gear) joint  33  and at least one differential drive shaft spur  35  connecting the power train to the axle of a driven wheel  28  (see  FIG. 3 ). The differential drive shaft spur  35  connects through universal joints common in the art (represented by spheres in the drawings). 
   In a particular preferred embodiment, the differential drive shaft spur  35  provides a means for telescopically lengthening and shortening  36 , as best shown in  FIGS. 10 and 11 . The means for telescopically lengthening and shortening  36  is comprised of a splined shaft  37  which is slideably fitted to an internally-splined tube  38  to move along a spur axis  35 . This movement provides length adjustment of the drive shaft spur needed for varying positions of the axle to which it is connected as the axle is tilted or otherwise vertically displaced in response to shock absorption. The splines of the splined shaft  37  and the internally-splined tube  38  mesh to render the unit rotatable about spur axis  35 . Alternatively, in place of splines, the shaft and tube could be of angular geometry in cross-section, such as a square or polygonal. 
   A means for suspending  40  is mounted on first longitudinal member  15  at the median of each pair of first horizontal members  12 . In the preferred embodiment, the means for suspending  40  is comprised of vertical beams  41  braced by a pair of shock absorbers  42 . Shock absorbers  42  are attached at one end to the top of each vertical beam  41  and at the other, to each flanking horizontal member  12 , where they form a pair of mutually supporting triangular braces  43 . In a particular preferred embodiment, each shock absorber  42  is comprised of a shaft  44  slidingly fitted to a tube  45  (see  FIG. 12 ). A spring  46  housed within tube  45  biases shaft  44  to maintain the attached first horizontal member  12  substantially horizontal. In the case of a shock load, however, such as when the vehicle is traversing a bump or other surface disturbance, the spring  46  compresses to allow the first horizontal member  12  to flex upward and absorb the shock. In this manner, each of the first horizontal members  12  are independently suspended, but cooperatively buffered by mutually supporting triangular braces  43 . The shock absorbers  42  are connected at each end by hinge joints common in the art (represented by spheres in the drawings). 
     FIG. 3  shows a tilting frame  20 . Tilting frame  20  is rotatably connected to non-tilting frame  10  about first axis  11 . Tilting frame  20  is comprised of a second longitudinal member  29  and a second axis  21 . Similar to the case of first horizontal members  12 , second horizontal members  22  are disposed about the second axis  21  and are rotatably attached, in oppositely-directed pairs, at the front and rear of the second longitudinal member  29 . In the alternate embodiment discussed above, second horizontal members  22  are disposed about a pair of second offset axes  27  (not shown), offset to each side from, and parallel to and planar with, the second axis  21 . In the preferred embodiment, second horizontal members  22  are second A-arms  26 . Tilting frame  20  supports, at least, an occupant (not shown), which is represented in the figures by seat  24 . 
   Vertical struts  23  rotatably connect corresponding first and second horizontal members in a way that the paired members are constrained to rotate about the first and second axes together with the inclination of vertical struts  23  maintained constant (see  FIG. 7 ). Road wheels  25  are rotatably attached to vertical struts  23 . In the alternative embodiment, the planes of first offset axes  21  and second offset axes  14  must be maintained parallel in order to preserve parallelism in the road wheels  25 . In the preferred embodiment, there are four road wheels and four matched pairs of first and second horizontal members joined by a vertical strut. Two of the wheels are steering wheels and two, driven wheels. As shown in  FIGS. 5 ,  8 , and  9 , the road wheels are enabled to roll, to raise, to tilt, and, as structure dictates, to turn and all simultaneously. 
   Tilting frame  20  further comprises a means for steering  50 . The means for steering  50  includes handle bars  51  and steering arm  53 , both of which are rotatably mounted to the second longitudinal member  29 . A clockwise rotation of the handle bars  51 , for example, is translated into a clockwise rotation of the steering arm  53  urged by linkages  52  applying torque through lever arms  56 . Steering arm  53  is L-shaped, having vertical and horizontal legs. Horizontal leg  57  is rotatably connected at its distal end to tie rods  54 , which, in turn, are rotatably connected to control arms  55  at each of the steering wheels (see  FIG. 2 ). A clockwise rotation of steering arm  53  is thus translated into a clockwise rotation of the steering wheels, whereby a right turn is launched. If horizontal leg  57 , tie rods  54 , and control arms  55  are all coplanar with the hubs of the wheels, tilting frame  20  can tilt without substantially changing the steered angle of the wheels. Because the pivot point of the tie rods  54  and the pivot point of steering arm  53  is separated by the span of horizontal leg  57 , the distance between the control arms  55  will be shortened to the base of the triangle formed by tie rods as they rotate out of co-linear. This will produce a shortened turn radius for the inside wheel of the turn, as appropriate for a turning pair of “common axle” wheels. Tie rods  54  make connection by universal joints and linkages  52 , by pin-hinges, such mechanisms common in the art (represented by spheres in the drawings). 
   Tilting frame  20  also comprises a means for tilt control  60 , as best shown in  FIG. 6 . Tilt control  60  includes a crescent gear  61  rigidly mounted to first longitudinal member  15  (see  FIG. 7 ) to which worm gear  62  engages in meshing contact. Worm gear  62  is driven by worm gear motor  63 . Worm gear motor  63  is rotatably mounted to second longitudinal member  29  about motor axis  64 . When worm gear  62  is driven, it causes tilting frame  20  to rotate about first axis  11 . Because gear motor  63  is reversible, causing the tilt direction be reversible, tilt adjustment can be made subject to operator control through a control interface (not shown). When the worm gear  62  is idle, the tilt will be locked in place because worm gears cannot be driven in reverse by meshing spur gears. This is useful in the situation of speeds less than 5 mph, where in the gyroscopic effect of the rotating wheels has not yet created a righting moment. Above 5 mph, the worm gear  62  can be rotated out of meshing contact with crescent gear  61  by means of operator input directing a tilt of motor  63  about motor axis  64 . 
   In operation, the suspension system  1  resembles the dynamics of a motorcycle, except that the engine and power train do not rotate. Approaching a right turn, for example, the occupant/operator will initiate by a slight turn to the left, thereby causing an imbalance of forces which enable a lean to the right, followed by a steering turn to the right. The tilting frame of the chassis will tilt to the inside of the turn, the lean being controlled by steering input. The lean of the tilting frame, combined with the lateral shift of the non-tilting frame in response to the tilt of the wheel about an axis on the road surface, causes the combined center of mass to shift into balance with the centrifugal force resulting from the mean turn radius and the speed of the vehicle. The occupant/operator can then steer out of the turn and the tilt. 
   While a particular form of the invention has been illustrated and described, it will be apparent that various modifications can be made without departing from the spirit and scope of the invention. For example, the invention could be practiced with three road wheels, the third wheel being the steered wheel. Accordingly, it is not intended that the invention be limited, except as by the appended claims.