Abstract:
An apparatus for the static testing of a vehicle tire to determine displacement as a function of force of the tire. A tire is placed upon several cross members that are vertically adjustable where the cross members are vertically adjusted to simulate a particular road bed profile. A tire is then forced down upon the cross members and the force created upon the cross members is measured against the displacement of the tire.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to a static testing device for testing automobile components. More particularly, the present invention pertains to a device for testing and measuring the forces created by road imperfections on automobile tires under particular loads and a related method. 
     BACKGROUND 
     Efforts to measure the forces created by various road surfaces upon a tire tread have been addressed by several prior devices. Generally, these prior devices disclose methods of quantifying the forces placed upon the tire tread and the reaction of the tire and tread to these forces. The forces measured include the lateral displacement of the tread and spring force of the tread during use. Such conventional testing is done to evaluate the integrity of the tire under use conditions when the vehicle to which they are attached is maneuvered under normal and extreme situations. However, these prior devices evaluate only specifics of the tire and the reaction of the tire tread to particular motions. 
     U.S. Pat. No. 4,986,118 discloses one attempt to evaluate the force of the tire on the road bed. The device disclosed by this patent measures the force of a particular footprint of a tire on a road bed. However, the road bed disclosed is flat and the measuring is performed through needles placed in holes in the base plate of the device. Neither this nor other known devices are capable of evaluating the entire footprint of the tire for a road bed that is variable. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a device that allows for the measurement of force created by a tire during the application of a known force on the tire. 
     It is a further object of this invention to measure these forces for particular road bed topographies. In this way, the forces produced and experienced by the tire may be determined for road surfaces that are variable. 
     In one form, the present invention provides an apparatus for static testing of a vehicle tire. The apparatus includes a support structure and at least one pair of guide members vertically extending from the support structure. At least one pair of guide members includes first and second vertical guide members spaced a distance apart and disposed generally parallel to one another. At least one cross member is slidably interconnected with the first and second vertical guide members of at least one pair of guide members such that the first cross member is vertically adjustable along the first pair of guide members. A first drive member is associated with the first cross member for moving the first cross member in a vertical direction. A tire mounting member receives the tire and displaces the tire vertically relative to the first cross member. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
     FIG. 1 is perspective view of an apparatus constructed in accordance with the teachings of a preferred embodiment of the present invention. 
     FIG. 2 is a perspective view of the apparatus of the present invention shown operatively associated with a tire and force producing member. 
     FIG. 3 is a perspective view of a portion of the apparatus of the present invention shown partially exploded. 
     FIG. 4 is cross-sectional view taken along the line  4 — 4  of FIG.  3 . 
     FIG. 5 a  is schematic view of a tire on a model road contour. 
     FIG. 5 b  is a schematic view of a tire shown on a portion of apparatus of the present invention that represents the model road contour of FIG. 5 a.    
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to the drawings, a static tire testing apparatus constructed in accordance with the teachings of the preferred embodiment of the present invention is illustrated and generally identified at reference number  10 . The apparatus  10  is illustrated generally to include a support structure  11  having a base plate  12  which rests upon a support member or frame  14 . The support structure  11  of the testing apparatus  10  may be formed of numerous separate pieces or may be formed of one piece. In either case, the entire testing apparatus  10  must be of solid construction in order to resist the testing forces. 
     The support structure  11  is shown resting upon a scale  16 . The scale  16  is present to measure the downward forces produced during a testing cycle (described further below). A force is transferred through the support structure  11  to the scale  16  and measured on a meter  21  attached to the scale  16  through a cable  23 . The force  15  applied to scale  16 , however, may be measured by several means, which are not particular to this invention, as long as an accurate measure of the force applied to the scale  16  can be known from time to time. 
     Upwardly extending from a top surface of the base plate  12  are a plurality of guide rods or bars  17 . The guide bars  17  are arranged in spaced apart pairs and slidably pass through a corresponding pair of apertures  19  provided in a plurality of cross members  20 . In a manner discussed below, the cross members  20  are vertically transposable along the associate guide bars  17 . Each of the cross members  20  is shown to preferably include an upper portion having a pyramidal shape. The pyramidal shape provides a more accurate and precise representation of a road surface as further described herein. 
     With particular reference to FIGS. 3 and 4, the particulars of the base plate  12  and the cross members  20  may be further seen. The base plate  12  can been seen to generally contain several rows of holes  40 ,  42 ,  44 . The holes  40 ,  42 ,  44  are generally concealed by the cross members  20 , however, the holes  40 ,  42 ,  44  perform critical functions. The guide bar holes  40 , positioned on the outer edge of the base plate  12 , receive the guide bars  17 . The guide bars  17  are press fit into the guide bar holes  40  and communicate with the cross members  20  in a manner to allow only vertical adjustment. Furthermore, there are two threaded jack screw holes  42  associated with each cross members  20 . The jack screw holes  42  threadably receive jack screws  46 . The jack screws  46  are in communication with the cross members  20  and may be adjusted upwardly or downwardly to reposition the cross members  20 . Finally, a measuring hole  44  is associated with each of the cross members  20  for accurate measuring of the displacement of the cross members  20  from the base plate  12 . As can be seen from FIG. 2, once a wheel  31  is placed upon the testing apparatus  10  access to the base plate  12  is limited to approach from below. 
     A pair of stop bars or members  22  are illustrated which define an upper limit of travel for the cross members  20 . The pair of stop bars  22  are stock portions of metal that are suitably attached, including welding or threaded attachment, to one or a plurality of the guide bars  17 . The stop bars  22  ensure that the cross members  20  do not disengage the guide bars  17 . Additionally, the stop bars  22  may assure that the wheel  31  does not become free of the testing apparatus  10 . 
     The wheel  31 , shown operatively associated with the testing apparatus  10 , conventionally includes a tire  34  and a rim  38 . The wheel  31  is affixed to a force-creating member  36  through the rim  38 . The force-creating member  36  creates a downwardly directed force in the direction of Arrow A which is parallel to guide members  17  and perpendicular to the scale  16 . The force Arrow A is translated to the tire  34  through the rim  38  and onto the testing apparatus  10 . 
     The tire  31  rests upon the cross members  20  which may be independently adjusted vertically with jack screws  46  (shown in FIG.  4 ). The force Arrow A from the tire  34  is translated through the cross members  20  to the support structure  11  is finally measured by the scale  16 . The displacement of the wheel  31  is measured by the vertical displacement measuring device  30 , preferably a linear variable placement transducer. The vertical displacement measuring device  30  is shown attached to rod  32  to hold it steady throughout a cycle of the test (described further below). The vertical displacement and the force measured on the scale are measured simultaneously throughout a test cycle. 
     With particular reference to the schematic views of FIGS. 5 a  and  5   b , an explanation of a test cycle will follow. A tire  34  becomes misshapen from round when it encounters a road bed  50 . The area of the tire  34  that is misshapen is said to envelope the imperfections  51  of the road bed  50 . It is desirous to gain knowledge as to the forces that the tire  34  encounters while enveloping the imperfections  51  of the road bed  50 . To learn of the forces from road bed  50  imperfections  51  they may be transferred to the testing apparatus  10 . The cross members  20  may be adjusted by the jack screws  46  to match the dimensions of the road bed  50  to create a simulated road bed. The simulated road bed  52  can create nearly the same envelope on the tire  34  as it becomes misshapen from round  57  as would the real road bed  50 . When this simulated road bed  52  is created upon the testing apparatus  10  and the tire  34  is forced upon the testing apparatus  10  by the force-creating member  36  then the forces may be measured. 
     The scale  16  measures the force created by the tire  34  while the vertical displacement measuring device  30  measures the vertical distance that the wheel  31  has traveled. These two measurements are taken simultaneously at set intervals of time. A cycle of the test occurs when the force Arrow A has gone through the steps of (1) no force created to (2) maximum testing force and finally returned to (3) no force created. The force measured by the scale  16  and the vertical displacement measured by the vertical displacement measuring device  30  over time are then used to produce a graph of displacement versus force for evaluation. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.