Abstract:
A wheel and sensor assembly includes a U-shaped bracket assembly mounting to and moving with a wheel assembly. One or more sensor device(s) such as camber angle and slip angle sensors mount to the bracket assembly for operatively measuring one or more wheel assembly parameter(s) during vehicle use. The bracket assembly mounts to the wheel assembly and turns therewith. The bracket assembly positions the sensor device(s) in operative optimal proximity to the road surface during vehicle use under actual operating conditions.

Description:
FIELD OF THE INVENTION 
     The invention relates generally to sensors for measuring tire operational parameters and generating tire-specific measurements data during vehicle use at high speed and, more specifically, to bearing assemblies for such wheel based sensors. 
     BACKGROUND OF THE INVENTION 
     In the operation of passenger cars and racecars, it is desirable to measure and test tires, wherever practical, in real time and under actual road conditions. For passenger cars, the venues of interest may be carefully selected road conditions while, for racecars, it is the operating conditions on a particular racetrack. The purpose for observing, testing, and measuring tire operating parameters in real time and under actual road conditions is to provide real world feedback on tire performance and to allow for the creation of more accurate tire durability test procedures and methods. 
     The specific tire parameters to be measured and evaluated may include tire slip and camber angles or tire deflection. Heretofore, the ability of the industry to test, measure, and evaluate tires for such tire parameters while the tire is at high speeds has not been available. Consequently, the tire testing procedures and methods utilized within the industry have been created without benefit of real time measurement of such tires under actual operating conditions. 
     SUMMARY OF THE INVENTION 
     An aspect of the invention embodies a wheel-based sensor assembly. The assembly includes a rotational wheel assembly, the wheel assembly including a wheel rim and a tire mounted thereto. One or more sensor device(s) are provided for operatively measuring one or more wheel assembly parameter(s) while the wheel assembly rotates during vehicle use. A bracket assembly mounts to the vehicle and operatively positions the sensor device(s). 
     In another aspect, the bracket assembly includes a first bracket arm segment extending at least partially along an outer sidewall of the tire in a radial direction and a sensor device adjustably repositionable along the arm segment. The bracket assembly may further include a second bracket segment extending at least partially along a tread region of the tire in an axial direction, preferably to a side of the tire opposite a normatively forward vehicular direction of travel. A secondary sensor device may be mounted to the second bracket arm segment adjacent the tread region of the tire. 
     In another aspect, the first and second bracket arm segments are relatively disposed at a ninety degree angle and include a channel along a tire-facing bracket side to operatively receive and route electrical wiring along the bracket assembly. The bracket assembly may be constructed in a U-shaped configuration connecting the second bracket member segment to an inner side of the wheel assembly by a third bracket arm segment. The sensor units may include a slip angle sensor mounted to the first bracket arm segment and a camber angle sensor mounted to the second bracket arm segment. 
     According to a further aspect, a remote end of the first bracket arm segment operatively connects to a bearing assembly; the bearing assembly including: a wheel plate; a stator housing affixed to an outward surface of the wheel plate; a stator shaft extending outward from the stator housing and connecting at an outward end to the first bracket arm; and multiple elongate extension members coupled to an inward side of the wheel plate and connecting at an inward end to a vehicle. The extension members are configured to have a length operative to position the stator shaft outward end in an optimal, substantially coplanar relationship, with the first bracket arm. 
     DEFINITIONS 
     “Aspect ratio” of the tire means the ratio of its section height (SH) to its section width (SW) multiplied by 100 percent for expression as a percentage. 
     “Asymmetric tread” means a tread that has a tread pattern not symmetrical about the center plane or equatorial plane EP of the tire. 
     “Axial” and “axially” means lines or directions that are parallel to the axis of rotation of the tire. 
     “Camber angle” means the angular tilt of the front wheels of a vehicle. Outwards at the top from perpendicular is positive camber; inwards at the top is negative camber. 
     “Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction. 
     “Equatorial Centerplane (CP)” means the plane perpendicular to the tire&#39;s axis of rotation and passing through the center of the tread. 
     “Footprint” means the contact patch or area of contact of the tire tread with a flat surface at zero speed and under normal load and pressure. 
     “Groove” means an elongated void area in a tread that may extend circumferentially or laterally about the tread in a straight, curved, or zigzag manner. Circumferentially and laterally extending grooves sometimes have common portions. The “groove width” is equal to tread surface area occupied by a groove or groove portion, the width of which is in question, divided by the length of such groove or groove portion; thus, the groove width is its average width over its length. Grooves may be of varying depths in a tire. The depth of a groove may vary around the circumference of the tread, or the depth of one groove may be constant but vary from the depth of another groove in the tire. If such narrow or wide grooves are substantially reduced depth as compared to wide circumferential grooves which the interconnect, they are regarded as forming “tie bars” tending to maintain a rib-like character in tread region involved. 
     “Inboard side” means the side of the tire nearest the vehicle when the tire is mounted on a wheel and the wheel is mounted on the vehicle. 
     “Lateral” means an axial direction. 
     “Lateral edges” means a line tangent to the axially outermost tread contact patch or footprint as measured under normal load and tire inflation, the lines being parallel to the equatorial centerplane. 
     “Net contact area” means the total area of ground contacting tread elements between the lateral edges around the entire circumference of the tread divided by the gross area of the entire tread between the lateral edges. 
     “Non-directional tread” means a tread that has no preferred direction of forward travel and is not required to be positioned on a vehicle in a specific wheel position or positions to ensure that the tread pattern is aligned with the preferred direction of travel. Conversely, a directional tread pattern has a preferred direction of travel requiring specific wheel positioning. 
     “Outboard side” means the side of the tire farthest away from the vehicle when the tire is mounted on a wheel and the wheel is mounted on the vehicle. 
     “Radial” and “radially” means directions radially toward or away from the axis of rotation of the tire. 
     “Rib” means a circumferentially extending strip of rubber on the tread which is defined by at least one circumferential groove and either a second such groove or a lateral edge, the strip being laterally undivided by full-depth grooves. 
     “Sipe” means small slots molded into the tread elements of the tire that subdivide the tread surface and improve traction, sipes are generally narrow in width and close in the tires footprint as opposed to grooves that remain open in the tire&#39;s footprint. 
     “Slip angle” means the angle of deviation between the plane of rotation and the direction of travel of a tire. 
     “Tread element” or “traction element” means a rib or a block element defined by having a shape adjacent grooves. 
     “Tread Arc Width” means the arc length of the tread as measured between the lateral edges of the tread. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described by way of example and with reference to the accompanying drawings in which: 
         FIG. 1  is a front perspective view of a wheel and sensor assembly configured using a mounted rotating load cell. 
         FIG. 2  is a side elevation view thereof. 
         FIG. 3  is a front elevation view thereof; and 
         FIG. 4  is an exploded perspective view of the bracket assembly. 
         FIG. 5  is a front perspective view of a wheel and sensor assembly configured using a bearing assembly in place of the load cell of  FIG. 1 . 
         FIG. 6  is an enlarged front perspective view of the bearing assembly. 
         FIG. 7  is a front exploded perspective view of the bearing assembly. 
         FIG. 8  is a rear perspective view of the bearing assembly. 
         FIG. 9  is a rear exploded perspective view of the bearing assembly. 
         FIG. 10  is a longitudinal section view through the bearing assembly taken along the line  10 - 10  of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1-4 , the subject wheel and sensor assembly  10  is shown to include a wheel assembly  12  in which a tire  16  is mounted to a rim  14  in conventional fashion. The assembly  10  is a component of a vehicle (not shown) such as a passenger car or truck. However, as will be explained, the invention has particular utility in conjunction with measuring tire set-up and performance on a race car. The tire  16  mounted to rim  14  is, accordingly, intended to be of a general depiction without regard to vehicle type or use. The tire  16  is of conventional construction having a sidewall  18  extending to a tread region  20 . 
     The assembly  10  further includes a bracket assembly  22  mounted as shown to the wheel assembly  12 . The bracket assembly  22  generally is of U-shape defined by a first bracket arm segment  24 , a second bracket arm segment  26  forming the bight of the assembly  22 , and a third bracket arm segment  26 . Each of the segments  24 ,  28  has a connector coupling at a remote end, the coupling of segment  24  being in the form of a sized C-clamp  30 . The segments forming bracket assembly  22  are formed from suitably sturdy material such as steel. The first segment  24  has an elongate narrow body  32  through which a longitudinal, medially located, slot  33  extends. Extending into an upper edge of the body  32  is a channel  34 . The channel  34  extends the length of the body  32  and is sized to admit electrical wiring (not shown) used for power transmission to sensor units mounted to the bracket assembly  22  as well as data transmission from the sensor units as will be explained. 
     The end segment  36  of the first segment  24  opposite the C-clamp  20  end angles inwardly to a remote flange  38  through which an assembly aperture  40  extends. The second segment  26  of the bracket assembly  22  attaches to the flange  38 . The second segment  26  is of elongate construction, generally L-shaped in transverse sectional configuration. The bracket segment  26  is formed by a horizontal elongate side  42  intersecting at a right angle along a longitudinal edge with a vertical side  44 . The sides  42 ,  44  extend between opposite triangular end flanges  46  through which assembly apertures  48  pass. Suitable assembly hardware is provided to affix the segment  26  to the first and third segments  24 ,  28  such as coupling screws and nuts  49 A, B respectively. Spaced apart apertures  50  extend through the side  44  and serve as mounting locations for sensor device(s) attaching to the side  44  as will be explained. Assembly hardware such as pins  51  are provided for the attachment of sensor units to the side  44 . 
     A mounting plate  52  is included within the bracket assembly  22  and attaches to the body  32  of the arm segment  24 . The plate  52  includes a vertical coupling tongue projection  53  having spaced apart elongate mounting slots  54  extending therethrough. A rectangular plate body  56  has appropriately located mounting through apertures  58  sized for attachment hardware such as pins  60 . A sensor device  62  mounts to the plate body  56  by means of extension of the pins  60  through the apertures  58 . The sensor device  62  is preferably but not necessarily of the type used to measure slip angle of a tire, such as the Commercial Unit Product No. SFII P, sold by Corrsys-Datron Co. located at 39205 Country Club Dr., No. C20, Farmington Hills, Mich. The slip angle sensor device  62  mounts to the mounting plate  52 . The plate  52  attaches by set screws  55  extending through plate slots  54  and through the slot  33  along the arm body  32 . So attached, the plate  52  and slip angle sensor device  62  affixed thereto depend from the arm body  32  and are repositionable along the arm slot  33  into an optimal location relative to the ground surface for tire slip angle measurement. 
     A camber angle sensor device is assembled to include a pair of spaced apart laser units  66 ,  68  that attach through the spaced apart apertures  50  in the second arm segment  26 . The sensor device  66 ,  68  measures camber angle of the tire  16  and are of a commercially available type such as Product Unit No. OADM 20145/405174 sold by Baumer Electric, Ltd., located at 122 Spring Street, Unit C-6, Southington, Conn. The laser units  66 ,  68  are provided with assembly holes  70  to facilitate attachment to the second arm segment  26 . The attachment of the slip angle sensor  62  and camber angle sensors  66 ,  68  to respective arm segments is preferably effected after the arm segments  24 ,  26 ,  28  are mutually assembled into the U-shaped configuration shown in  FIGS. 1 through 3 . To attach the completed bracket assembly  22  with the sensor units  62  and  66 ,  68  to the wheel assembly  12 , the U-shaped bracket assembly  22  is positioned in straddling relationship with the tire  16 . The ends of the segments  24 ,  28  attach to components of the wheel assembly  12  on opposite respective sides of the tire  16 . In the assembled position, the arm segments  24 ,  28  extend in a radial direction along opposite sidewalls  18  of the tire  16  and the arm segment  26  extends in an axial direction opposite the tread region  20  of the tire  16 . The spacing of the arm segments  24 ,  28  from respective sidewalls  18  is preferably closely adjacent, in the range of 0.5 to 3 inches to position the slip angle sensor  62  as close as possible to the tire sidewall. Minimizing the protrusion of the sensor  62  acts to minimize the potential for damaging contact between the sensor  62  and surrounding objects. The sensor  62  includes a downwardly directed laser element that measures the angle of the tire  16  relative to the ground surface during vehicle operation and thereby provides data for the calculation of the slip angle of the tire. 
     The location of the second arm segment  26  and the camber angle sensor  66 ,  68  is as shown to be closely adjacent the tread region  20  of the tire  16 , at a distance of 0.5 inches or more. The mounting of the arm segment  26  is preferable to the side of the wheel assembly  12  opposite the direction of forward vehicle travel  78  in order to protect the tire in the event of a bracket failure. The through passages  60  through the arm segment  26  reduces the bracket weight. The sensor units  66 ,  68  include downwardly directed laser elements that measure to the ground surface and the angular cant of the tire during vehicle operation, whereby providing data for the calculation of the camber angle of the tire. 
     While the subject bracket assembly  22  and sensor units mounted thereto can effect measurement from tires used in myriad vehicle applications, the assembly is particularly useful and effective in determining the wheel and tire set up in a race car in preparation for a race. The coupling C-clamp  30  of the assembly  22  may be affixed to the stator  74  of a load cell  72  within the wheel assembly  12  as shown. A load cell such as shown at  72  is commercially available under Product No. 77016-00A-E0000 from Sensor Development Inc., located at 1050 West Silverbell Road, Lake Orion, Mich. The opposite arm segment  28  of the bracket assembly  22  may attach to the brake assembly  76  on the opposite side of the wheel. So located and attached, the sensors  62  and  66 , 68  are located close to the tire  16  to generate accurate camber and slip angle data as well as to minimize the degree to which bracket and sensors protrude. Vehicles may be, in the course of normal operation, particularly in race cars, driven close to outside obstructions and other vehicles. The close proximity and location of the bracket and sensors of the invention to the tire minimizes the risk of contact with such outside influences. Location of the second arm segment and sensor behind the tire, on the opposite side of normatively forward direction of travel  78 , likewise protects the bracket and sensor assembly. 
     While the attach points of the bracket assembly to the wheel assembly  12  are preferably as shown, other means and locations of attachment of the bracket may be employed if desired. In addition, while slip angle and camber angle sensor units  62  and  66 ,  68  are described above, other types of sensors may be deployed through utilization of the bracket assembly  22  and deployment scheme. For example, without intent to delimit the invention, a tire deflection detector or camera may be mounted to the bracket arm segments  224 ,  26 ,  28  and utilized to detect and measure the existence, location, and geometry of tire anomalies during vehicle use. A thermal detector may also be mounted to the bracket assembly  22  to detect the thermal properties of a tire during vehicle use. Power to and data communication from such devices may be wired along the channel  34  of the arm segment  24 . The bracket assembly and deployment scheme described above allows for the measurement of the tire  16  while in actual use on a road surface. Such real time evaluation under actual working conditions results in a more thorough and accurate evaluation than laboratory testing. The bracket and sensors measure the tire under actual working conditions to provide not only information on tire performance but also tire response and reaction to a specific track or roadway. For a racecar, for example, specifically correlating tire response and conditional parameters to a particular racetrack is extremely important to the racecar setup. 
     In addition, mounting the bracket assembly  22  and sensor units to a steer wheel assembly  12  allows for tire evaluation through turns since the bracket assembly  22  and sensor units will turn with the tire. Such capability effects a more thorough and accurate evaluation of the tire and roadway surface than could otherwise be made by the mounting of slip angle and camber angle sensors on the body of the vehicle adjacent to a tire. The subject bracket and sensor assembly turns with the wheel to which it is mounted and measure the slip angle directly as opposed vehicle based sensors that measure the slip angle base on the entire car chassis. Improved accuracy therefore is achieved by the invention assembly. 
     The channel  34  formed within the arm segment  24  extends the length of the body  32  and is sized to admit electrical wiring (not shown) used for power transmission to sensor units  62  and  66 ,  68  as well as data transmission from the sensor units to a data storage or collection device. The electrical wiring is thus protected from interfering with the operation of the wheel assembly and from potential damage from contact with foreign objects. 
       FIGS. 1 through 4  illustrate the use of a load cell and stator shaft embodiment of the invention in which the load cell  72  has a dimensional configuration to place an outward end of the stator  74  in generally a coplanar relationship with the first bracket arm  24  to which the stator  74  is coupled. Thus, the stator extends outward to an extent enabling the bracket arm  24  to extend along the outward side of the tire  16  parallel with the tire sidewall  18  and couple to the stator  74 . 
     It may be preferable to configure the wheel and sensor assembly  10  in a manner which will enable the bracket  22  to be used in other wheel assemblies and not necessarily require the deployment of a rotating load cell. An alternative versatile bearing assembly  80  is shown in  FIGS. 5 through 10 . The assembly  80  allows the camber and slip angle bracket to be used in conjunction with regular track wheels and to take measurements while a racecar is operating at high-speeds. The heavy rotating load cell is thereby eliminated. 
     With reference to  FIGS. 5-10 , the bearing assembly  80  includes a stator shaft  82  having an outward shaft end  82  and an inward shaft end  86 . A stator housing  88  is provided having mounting threaded bores  89  and an internal chamber  90  dimensioned and of a geometric shape for admitting a pair of sealed ball bearings  92 ,  94 . An external snap ring  96  and an inward snap ring  98  are provided for securing the stator shaft in place within the housing  88 . A circular wheel standoff plate  100  is included having five spaced apart circumferential mounting apertures  102  extending through the plate  100  from an outward plate surface  104  to an inward facing surface  106 . Plate  100  has a large central through center hole  108 . 
     Continuing, the assembly  80  has spaced apart openings  110  therethrough. Five extender studs  112  are provided of generally elongate configuration circular in section. The studs  112  each have an outward segment  114 ; a hexagonal collar  116  to the rear of segment  114 ; a circular abutment flange  118  to the rear of the collar  116 ; and a rearward extender shaft  119  to the rear of collar  116 . Five locking nuts  120  are provided as well as five assembly screws  122 . The screws  122  are sized for close receipt through spaced apart mounting apertures  124  of the plate  100 . 
     Assembly of the bearing assembly proceeds as follows. The forward ends  114  of the extender studs  112  project through respective mounting apertures  102  of the plate  100  until the hexagonal collar  116  of each stud abuts the inward surface  106  of the plate  100 . The screws  120  affix to the outward stud ends  114  to secure the studs to the plate  100 . The stator housing  88  attaches to the outward surface  104  of the plate  100  as screws  122  project through plate apertures  124  and into the threaded bores  89  of the stator housing  88 . The stator shaft  82  extends through the bearings  92 ,  94 , the snap rings  96 , 98 , housing  88 , and plate center opening  88  with the snap rings  96 , 98  retaining the shaft  82  in place through the housing  88  and the bearings  92 ,  94  within the housing  88  as shown best by  FIG. 10 . 
     The completes assembly is illustrated by  FIGS. 6 ,  8 , and  10  and shown assembled to the tire assembly by  FIG. 5 . It will be seen that the extender studs  112  are configured having a length sufficient to place the plate  100  outward from the wheels a prescribed distance. The studs  112  of the bearing assembly  80  correspondingly move the outward end  84  of the stator shaft  82  outward into a coplanar relationship with the bracket arm  24  suitable to facilitate a coupling between the stator shaft end  84  and the bracket arm  24 . The bearing assembly  80  is relatively light weight compared to the load cell  72  which it replaces. The heavy rotating load cell  72  of  FIG. 1  may thus be eliminated. Moreover, the bearing assembly  80  is universal in the sense that it may be used with regular wheel units. Such versatility permits the bracket  22  through the implementation of bearing assembly  80  to be used in conjunction with regular track wheels, whereby allowing measurements to be taken while a racecar is operating at high-speeds on a track. The bracket can, through the use of the bearing assembly  80 , thus be used to measure tire camber and slip angle during actual operating conditions. 
     The nut extenders  112  fasten the wheel to a race car hub using female threads that of compatible configuration as the wheel studs. The taper of the nut extenders  112  match the wheel nuts. The stand off plate  100  is of suitable material composition such as steel or aluminum. The bolt holes through the plate are designed to mate with standard wheel nuts. The stator shaft  82  is of suitable composition such as aluminum. The shaft attaches to the plate  100  and presses into the bearing assembly within housing  88 . The shaft is retained in assembly by shoulders  83  and  86  respectively by snap rings  96 , 98 . The stator housing  88  is of suitable composition such as aluminum and houses  2  deep groove ball bearings  92 ,  94  by means of the snap rings  96 ,  98 . The bearings  92 ,  94  are of conventional configuration commercially available, such a single, double row angular contact ball bearings. 
     Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.