Patent Abstract:
A method of securing a tire-based unit ( 24 ) of a tire condition sensing system ( 12 ) to a rim ( 60 ) and an associated apparatus ( 62 ) are provided. The method comprising the steps of: positioning a mounting bracket ( 124 ) on the rim ( 60 ); positioning a self-pierce rivet ( 140, 200 ) against the mounting bracket ( 124 ), so that a portion of the mounting bracket ( 124 ) is interposed between the self-pierce rivet ( 140, 200 ) and the rim ( 60 ); pressing the self-pierce rivet ( 140, 200 ) against the mounting bracket ( 124 ) and toward the female mold portion of the press, so as to pierce a portion of the mounting bracket and to deep draw a portion of the rim into the female mold portion to secure the mounting bracket relative to the rim; removing the rim and secured mounting bracket from the press; and attaching the tire-based unit ( 24 ) to the mounting bracket ( 124 ).

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority to European Patent Application 05291027.0, filed May 12, 2005, which is incorporated herein by reference in its entirety. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a method of securing a tire-based unit of a tire condition sensing system to a rim and to an associated apparatus. More particularly, the present invention relates to a method of securing a tire-based unit to a rim using a self-pierce rivet and an associated apparatus. 
   2. Description of the Related Art 
   A typical tire condition sensing system for a vehicle includes a vehicle-based unit and a plurality of tire-based units. Each tire of the vehicle has an associated tire-based unit. Each associated tire-based unit senses a condition of its tire and provides a signal to the vehicle-based unit indicative of the sensed parameter. Common tire conditions that are sensed by the tire-based unit include tire pressure and tire temperature. 
   It is common to secure an associated tire-based unit to the rim upon which its tire is mounted. One known method for securing the tire-based unit to the rim includes extending a strap circumferentially around the rim and securing the tire-based unit to the strap. A potential drawback to the use of the strap, however, is that the strap may slip relative to the rim. This slipping of the strap may affect the balance of the tire. 
   It is also known to secure a tire-based unit to a rim using an adhesive. Adhesives, however, typically degrade over time, especially when subjected to the temperatures common in a vehicle tire. Also, special surface preparation of the rim may be required for the adhesive to property adhere to the rim. 
   Another known method attaches a mounting bracket to the rim using rivets. The tire-based unit is secured to the mounting bracket. A drawback of using rivets is that each rivet is associated with a hole that extends through the rim. Air may escape the tire through the associated rivet holes. As a result, the associated rivet holes must be sealed to prevent air leaks. 
   SUMMARY OF THE INVENTION 
   The present invention relates to a method of securing a tire-based unit of a tire condition sensing system to a rim. The method comprises the steps of: positioning a mounting bracket on the rim; disposing the rim and the mounting bracket in a press between a female mold portion and a self-pierce rivet; pressing the self-pierce rivet against the mounting bracket and toward the female mold portion of the press, so as to pierce a portion of the mounting bracket and to deep draw a portion of the rim into the female mold portion to secure the mounting bracket relative to the rim; removing the rim and secured mounting bracket from the press; and attaching the tire-based unit to the mounting bracket. 
   In accordance with another aspect, the present invention relates to an apparatus for a vehicle having a tire condition sensing system. The apparatus comprises a rim upon which a tire of the vehicle is mounted. The apparatus also comprising a tire-based unit of the tire condition sensing system. The tire-based unit includes electronics for sensing a condition of the tire and for transmitting a signal indicative of the sensed condition. The apparatus further comprises a mounting bracket to which the tire-based unit is attachable. The mounting bracket is positioned on the rim. The apparatus still further comprises a self-pierce rivet for securing the mounting bracket to the rim. The self-pierce rivet, when positioned against the mounting bracket and pressed against the mounting bracket, pierces a portion of the mounting bracket and deep draws a portion of the rim so that the self-pierce rivet secures the mounting bracket and the deep drawn portion of the rim. 
   In accordance with yet another aspect, the method of the present invention uses advantageously a self-piercing rivet comprising a shank with a first end, a second, free, end and an outer periphery; and an enlarged head at the first end of the shank with a non-circular outer periphery, wherein the second end of the shank is provided with a bifurcating slot extending in an axial direction of the shank, from the second end thereof and transversely therethrough; and wherein the outer periphery of the head does not extend in the transverse direction (d) of extension of the slot, substantially beyond the outer periphery of the shank of the rivet on at least one side of the shank. 
   Preferably, the self-pierce rivet is disposed with the transverse direction (d) of extension of the slot oriented in the axial direction of the rim. 
   The use of such a slotted self-pierce rivet allows placing the rivet at a significantly smaller distance of the flanges of the drop well without deep drawing the material of the drop well portion in the axial direction. This is very advantageous in the case of steel wheel comprising a rim and a disk assembled under the drop well of the rim. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other features of the present invention will become apparent to those skilled in the art to which the present invention relates, upon reading the following description with reference to the accompanying drawings, in which: 
       FIG. 1  schematically illustrates a vehicle having a tire condition sensing system and apparatuses constructed in accordance with the method of the present invention; 
       FIG. 2  illustrates an exemplary apparatus of  FIG. 1 ; 
       FIG. 3  is exploded view of a portion of the apparatus of  FIG. 2 ; 
       FIG. 4  illustrates a portion of the apparatus of  FIG. 2  located in a press during formation of the apparatus; and 
       FIG. 5  is an enlarged view of a portion of the apparatus of  FIG. 2  constructed in accordance with the method of the present invention. 
       FIG. 6  is a section of a conventional rim, with assembly below the rim well. 
       FIGS. 7-9  illustrate a preferred slotted self-pierce rivet. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  schematically illustrates a vehicle  10  including a tire condition sensing system  12 . For illustrative purposes, the vehicle  10  of  FIG. 1  is an automobile having four tires  16 ,  18 ,  20 , and  22 . Vehicles having a number of tires other than four are also contemplated by the present invention. 
   The tire condition sensing system  12  of  FIG. 1  includes four tire-based units  24 ,  26 ,  28 , and  30  and a vehicle-based unit  32 . Each tire  16 ,  18 ,  20 , and  22  of the vehicle  10  includes an associated tire-based unit  24 ,  26 ,  28 , and  30 , respectively. Each of the associated tire-based units  24 ,  26 ,  28 , and  30  includes electronics for sensing at least one condition of the tire and for transmitting a tire condition signal indicative of the sensed condition(s) to a vehicle-based unit  32  of the tire condition sensing system  12 . The sensed tire condition(s) may include one or both of inflation pressure and temperature, as well as various other conditions. The transmitted tire condition signals for the tire-based units  24 ,  26 ,  28 , and  30  are indicated in  FIG. 1  as tire condition signals  38 ,  40 ,  42 , and  44 , respectively. 
   As shown in  FIG. 1  with reference to tire-based unit  24 , the electronics of tire-based unit  24  include a power source  34  for providing the tire-based unit with electrical energy, a sensor  36  for sensing tire conditions, transmitter electronics  46  for providing the associated tire condition signals  38 , and an antenna  48  from which the tire condition signals  38  are transmitted. Preferably, the tire condition signals  38  that are transmitted by the tire-based unit  24  are a radio frequency (“RF”) signals. Tire-based units  26 ,  28 , and  30  include electronics similar to those of tire-based unit  24 . 
   The vehicle-based unit  32  includes an antenna  50  that is connected to a receiver  52 . Tire condition signals  38 ,  40 ,  42 , and  44  received by the antenna  50  are demodulated in the receiver  52 . Each demodulated tire condition signal is then transferred to a controller  54  of the vehicle-based unit  32 . The controller  54  of the vehicle-based unit  32  operates an algorithm for determining whether the received tire condition signal under consideration originated from one of the tire-based units  16 ,  18 ,  20 , and  22  associated with the vehicle  10 . The algorithm operated by the controller  54 , upon determining that the received tire condition signal originated from one of the tire-based units  24 ,  26 ,  28 , and  30  associated with the vehicle  10 , also determines from which of the tire-based units the tire condition signal originated. 
   The controller  54  of the vehicle-based unit  32  is operatively connected to a display  56  or other device for providing a vehicle operator with tire condition information. Preferably, the display  56  is located within the occupant compartment of the vehicle  10  and provides the vehicle operator with visual information regarding the tires  16 ,  18 ,  20  and  22  of the vehicle. 
   Each of the tires  16 ,  18 ,  20 , and  22  of the vehicle  10  is mounted on an associated rim.  FIG. 2  illustrates tire  16  mounted on rim  60 . The tire-based unit  24  that is associated with tire  16  is secured to the rim  60 . The method for securing the tire-based unit  24  to the rim  60  will be discussed in detail below. An apparatus in accordance with the present invention is formed from an assembly of a tire, its associated rim, and its associated tire-based unit. For example,  FIG. 2  illustrates apparatus  62  formed from an assembly of tire  16 , rim  60 , and tire-based unit  24 . 
   For purposes of brevity, the present application will only specifically discuss the method of securing tire-based unit  24  to rim  60 , which is associated with fire  16 . It should be understood that tire-based units  26 ,  28 , and  30  may be secured to the associated rims of tires  18 ,  20 , and  22  using the same method as is used for securing tire-based unit  24  to rim  60 . 
     FIG. 2  is a cross-sectional view of the apparatus  62 . As shown in  FIG. 2 , the tire-based unit  24  is secured to the rim  60  at a location within tire  16 . In the embodiment illustrated in  FIG. 2 , the rim  60  is formed from metal. The rim  60  may be formed from any malleable material that is suitable for use as a vehicle rim. The rim  60  includes an annular base wall  64 . Inner and outer bead flanges  66  and  68  are located on opposite sides of the base wall  64 . A drop well  72  extends into the base wall  64  and toward a center (axis A) of the rim  60 . The drop well  72  extends circumferentially around the rim  60  and includes a lower wall  74  and opposite side walls  76  and  78 . 
   The sidewalls  84  and  86  of the tire  16  terminate at ends opposite the tread portion  82  with bead portions  88  and  90 , respectively. When the tire  16  is mounted on the rim  60 , bead portion  88  seats in bead flange  66  and bead portion  90  seats in bead flange  68 . Also, when the tire  16  is mounted on the rim  60 , an annular chamber  92  is formed within the tire. The rim  60  defines an interior edge of the annular chamber  92 . 
     FIG. 3  illustrates a portion of the lower wall  74  of the drop well  72 . The lower wall  74  has a curved profile that is centered at the center (axis A) of the rim  60 . The lower wall  74  includes inner and outer surfaces  102  and  104 , respectively. The inner surface  102  is located nearer the center (axis A) of the rim  60  than the outer surface  104 . The lower wall  74  has a generally uniform thickness, measured between the inner and outer surfaces  102  and  104 . 
   As shown in  FIG. 3 , the tire-based unit  24  associated with tire  16  includes a protective housing  108 . The protective housing  108  includes a metallic lower portion  110  and a plastic upper portion  112 . The lower portion  110  has opposite ends  114  and  116 , respectively. A rectangular lock tooth  118  extends outwardly of each of the ends  114  and  116 . A cavity (not shown) is formed in the protective housing  108  between the lower portion  110  and the upper portion  112 . The electronics of the tire-based unit  24  are located within the cavity. The cavity of the protective housing  108  is subject to the same environmental conditions as the annular chamber  92 . For example, the air pressure within the cavity of the protective housing  108  is equal to the air pressure within the annular chamber  92 . 
   A mounting bracket  124  is associated with the tire-based unit  24 . The mounting bracket  124  secures the protective housing  108  of the tire-based unit to the rim  60 . As is shown in  FIG. 2 , the tire-based unit  24  is secured to the lower wall  74  of the drop well  72 . When secured to the lower wall  74  of the drop well  72 , the protective housing  108  of the tire-based unit  24  is located below, or nearer to the center (axis A) of the rim  60 , than the annular base wall  64 . As a result, when the tire  16  is mounted on the rim  60 , the bead portions  88  and  90  of the tire  16  may pass along the annular base wall  64  and over the drop well  72  without contacting the tire-based unit  24 . 
   The mounting bracket  124  is formed from metal or another resilient material. The mounting bracket  124  includes a base portion  126  and opposite end portions  130  and  132 , respectively. The base portion  126  of the mounting bracket  124  has a curved profile. The curved profile of the base portion  126  of the mounting bracket  124  corresponds to the curved profile of the lower wall  74  of the drop well  72  of the rim  60 , as is illustrated in  FIG. 3 . The base portion  126  preferably has a width, measured into the paper as viewed in  FIG. 3 , that is less than half a width of the lower wall  74 , measured in a direction parallel to axis A between opposite side walls  76  and  78  of the drop well  72 . 
   The end portions  130  and  132  of the mounting bracket  124  extend from opposite ends of the base portion  126  in a direction radially outward relative to a center of the curved profile of the base portion. A rectangular opening  136  extends through each of the end portions  130  and  132 . Each rectangular opening  136  is sized for receiving a rectangular lock tooth  118  of the lower portion  110  of the protective housing  108  of the tire-based unit  24  for securing the tire-based unit to the mounting bracket  124 . 
     FIG. 3  also illustrates two self-pierce rivets  140 . The two self-pierce rivets  140  illustrated in  FIG. 3  are identical to one another. Each self-pierce rivet  140  is formed as a monolithic body and not from multiple structures secured together. Each self-pierce rivet  140  is formed from hardened steel. 
   Each of the self-pierce rivets  140  includes upper and lower portions  142  and  144 , respectively. The upper portion or head  142  includes a flat, circular-shaped upper surface  150 . A frustoconical side surface  152  of the head  142  narrows as it extends away from the upper surface  150 . The lower portion or shank  144  of the self-pierce rivet  140  is tubular and presents a central hole  154  and a tapered mouth  156 . The diameter of the shank is identical to the diameter of the neck  162  of the head  142 . The surface  156  is the lower end of shank  144 . 
   The two self-pierce rivets  140  are used for piercing the mounting bracket  124  and deep drawing the rim  60  to secure the mounting bracket relative to the rim. A number of self-pierce rivets  140  other than two may be used. By using the self-pierce rivets  140  in accordance with the method of the present invention, the mounting bracket  124  may be secured to the rim  60  without the rim being penetrated and without the rim requiring special surface preparation. 
   To secure the mounting bracket  124  to the rim  60 , the base portion  126  of the mounting bracket  126  is positioned on the outer surface  104  of the lower wall  74  of the drop well  72  of the rim  60 . Preferably, the mounting bracket  124  is positioned at equal distances from each of the side walls  76  and  78  of the drop well  72 . The rim  60  and the mounting bracket  124  are then positioned in a press  168  ( FIG. 4 ) having a female mold portion  170  and a plunger portion  172 . The rim  60  and the mounting bracket  124  are positioned in the press  168  at a location between the female mold portion  170  and the plunger portion  172 .  FIG. 4  illustrates the lower wall  74  of the drop well  72  and the mounting bracket  124  being interposed between the female mold portion  170  and the plunger portion  172 . 
   The female mold portion  170  of the press  168  includes an upper surface  178  upon which the inner surface  102  of the lower wall  74  of the drop well  72  is positioned. Preferably, the upper surface  178  of the female mold portion  170  has a curved profile that corresponds to the curved profile of the inner surface  102  of the lower wall  74  of the drop well  72  of the rim  60 . A cavity  180  extends into the upper surface  178  of the female mold portion  170 . The cavity  180  is generally cylindrical and is defined by an annular side surface or recess  182  and a centrally disposed upstanding anvil  184 . A curved shoulder  186  connects the annular side surface  182  to the surface of the anvil  184 . The cavity  180  has a depth, measured generally in the vertical direction as viewed in  FIG. 4 , that is approximately equal to the height of the self-pierce rivet  140 . The height of the self-pierce rivet  140  is a distance between the upper surface  150  and the lower surface  156  of the shank  144  of the self-pierce rivet  140 . The cavity  180  has a width, measured generally horizontally as viewed in  FIG. 4 , that is larger than the diameter of the tubular shank  144  of the self-pierce rivet  140 . 
   The self-pierce rivet  140  is positioned on the base portion  126  of the mounting bracket  124  at a location above the cavity  180  of the female mold portion  170 . When positioned on the mounting bracket  124 , the lower surface  156  of the self-pierce rivet  140  abuts the base portion  126  of the mounting bracket  124  and the upper surface  150  of the self-pierce rivet is engaged by the plunger portion  172  of the press  168 . Thus, as shown in  FIG. 4 , the rim  60 , the mounting bracket  124 , and the self-pierce rivet  140  are interposed between the female mold portion  170  and the plunger portion  172  of the press  168 . 
   Next, the press  168  is actuated so that the plunger portion  172  presses the self-pierce rivet  140  against the mounting bracket  124  and toward the cavity  180  of the female mold portion  172 . As shown in  FIG. 5 , as the self-pierce rivet  140  is pressed toward the cavity  180  of the female mold portion, it acts initially as a piercing punch so that a slug  128  of material defined by the piercing of the material of the base portion  126  of the mounting bracket  124  by the rivet  140  lies within the hollow  158  of the rivet. Thereafter the slug  128  is driven forwardly with the rivet  140  and the combined slug and rivet act as a drawing punch on the lower wall  74  of the drop well  72  of the rim  60  on their path. This material displaced by the forward movement of the combined slug and rivet is drawn into the cavity  180  of the female mold portion  170 . As the displaced lower wall  74  of the drop well  72  of the rim  60  reaches the anvil  184  of the female mold  170  it is trapped between the advancing rivet  140  and the anvil  184 . Further forward movement of the rivet and slug causes the tubular portion of the rivet  140  to roll radially outwardly. The tubular portion of the rivet is thus spread radially outwardly and the material displaced is trapped by the recess  182  of the female mold portion  170  as can be seen with reference to  FIG. 5 . 
   After the base portion  126  of the mounting bracket  124  is secured to the lower wall  74  of the drop well  72  of the rim  60 , the rim  60  and mounting bracket  124  are removed from the press  168 . The method of the invention is repeated for securing the mounting bracket  124  to the rim  60  with additional self-pierce rivet  140 . 
   After all of the self-pierce rivets  140  have been pressed into positions securing the mounting bracket  124  to the rim  60 , the protective housing  108  of the tire-based unit  24  is attached to the mounting bracket. To attach the protective housing  108  to the mounting bracket  124 , the rectangular lock tooth  118  on the end  114  of the lower portion  110  of the protective housing  108  is inserted through the rectangular opening  136  in the end portion  130  of the mounting bracket  124 . The protective housing  108  is then pressed downward toward the base portion  126  of the mounting bracket  124  so that the rectangular lock tooth  118  on the end  116  of the lower portion  110  of the protective housing  108  snaps into the rectangular opening  136  in the other end portion  132  of the mounting bracket  124 . The tire  16  is then mounted on the rim  60  in a known manner. The apparatus  62 , which includes the rim  60 , the tire  16 , and the secured tire-based unit  24 , is then ready for assembly onto the vehicle  10  having the tire condition sensing system  12 . 
   The previous self-pierce rivet, which is axisymmetrical, is appropriate in all the cases where the thickness of the drop well portion of the wheel is regular.  FIG. 6  presents a section of a steel wheel rim  60  assembled to a disk  61  under the lower wall  74  of the drop well  72 . In this case the tire-based unit is preferably placed in the portion of the drop well adjacent the disk. The axial width L of this portion is limited and it is advantageous to use a slotted self-pierce rivet  200  which will expand substantially only in the circumferential direction of the rim. 
   Such a slotted self-pierce rivet  200  is presented in the  FIGS. 7 to 9 . The slotted self-pierce rivet  200  differs from that shown in  FIGS. 3-5  mainly in two respects. First, the head  210  of the slotted rivet is modified by removing two opposing sectors of the head up to the shank  220  of the rivet. Thus, the head  210  of the rivet has two opposed arcuate portions defining there between a major dimension D and two opposed straight portions defining there between a minor dimension d, the straight portions being parallel to each other and being substantially tangential to the shank  220 , giving rise to a head which has a major dimension D which extends beyond the shank  220  of the rivet  200  and a minor dimension d, perpendicular to the major dimension, which does not extend beyond the shank  220  of the rivet. Second, the shank  220  of the rivet is formed with, in addition to a central hole  222  extending the length of the shank of the rivet and a tapered mouth  224 , a slot  226  positioned substantially perpendicular to the straight portions of the head and extending from the mouth  224  or the central hole  222  towards the closed end thereof. The geometry of the female mold portion of the press is adapted to the geometry of the slotted self-pierce rivet in order to guide the displaced material in the appropriate circumferential direction. 
   The use of such a slotted self-pierce rivet allows placing the rivet at a significantly smaller distance of the flange  78  on one side and of the axial end of the disk  63  on the other side. The bifurcated slot allows securing the mounting bracket and the drop well portion of the rim by deep drawing the drop well portion mainly in the circumferential direction of the rim. A circumferential section of the tire-based unit mounted on the rim is very similar to  FIG. 5 . 
   The slotted rivet  200  described here is just an example of the numerous versions possible. Other examples are presented, for example, in U.S. Pat. No. 6,263,560, which is incorporated herein by reference. 
   From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.

Technology Classification (CPC): 1