Abstract:
A transmitter has a valve stem, an electronic element, a casing and a coupler. The valve stem permits flow of air into the tire. The electronic element transmits a data representing the condition of the tire. The casing accommodates the electronic element. The coupler couples the valve stem to the casing such that an angle of the casing relative to the valve stem is adjustable be controlled. This can be attached to wheels having different cross-sectional shape.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a wireless tire condition monitoring apparatus that permits a driver in a vehicle passenger compartment to check the conditions of tires, such as the air pressure. More specifically, the present invention relates to a transmitter in a tire condition monitoring apparatus. 
   Some transmitters for tire condition monitoring apparatus have a valve stem that is formed integrally with a casing and functions as a transmission antenna. The casing accommodates electronic elements for transmitting data, which data represents the condition of a tire. Such a casing includes a flange extending outward from the bottom and triangular reinforcing ribs between the flange and the outer surface of the casing. Therefore, when the tire is replaced, the tire beads are overlaid on the casing. Therefore, the tire is replaced without damaging the casing (Japanese Laid-Open Patent Publication No. 2000-081358). 
   However, the construction disclosed in the publication cannot be applied to all the types of vehicle wheels. That is, there are many different types of cross-sectional shapes in wheels. The cross-sectional shapes in wheels include a deep rim, a shallow rim, a wide flat rim, and wide deep rim. Therefore, the angle defined by a valve stem and a casing is determined by the cross-sectional shape of a wheel. As a result, to attach a casing to a drop center of a wheel, a valve for a transmitter in a tire condition monitoring apparatus must correspond to the cross-sectional shape of the wheel. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an objective of the present invention to provide a transmitter in a tire condition monitoring apparatus, which valve can be attached to wheels having different cross-sectional shape. 
   To achieve the above object, the present invention provides a transmitter. The transmitter has a valve stem, an electronic element, a casing and a coupler. The valve stem permits flow of air into the tire. The electronic element transmits a data representing the condition of the tire. The casing accommodates the electronic element. The coupler couples the valve stem to the casing such that an angle of the casing relative to the valve stem is adjustable be controlled. 
   Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
     FIG.  1 ( a ) is a perspective view illustrating a valve stem; 
     FIG.  1 ( b ) is a perspective view illustrating an odd shaped washer; 
     FIG.  1 ( c ) is a perspective view illustrating a housing member; 
       FIG. 2  is a partially cross-sectional perspective view illustrating the valve stem and the odd shaped washer attached to the housing member; and 
       FIG. 3  is a partially cross-sectional view illustrating a valve for a transmitter in a tire condition monitoring apparatus attached to a wheel. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A transmitter in a tire condition monitoring apparatus according to one embodiment will now be described with reference to the drawings. 
   As shown in FIG.  1 ( a ), a valve stem  10  has a threaded cap receiving portion  11  and a threaded fixing portion  12  for fixing the valve stem  10  to a wheel. The diameter of the cap receiving portion  11  is less than the diameter of the fixing portion  12 . An engaging groove  13  is formed at a portion below the fixing portion  12 . Below the engaging groove  13 , that is, at a lower portion of the valve stem  10  that is embedded in a tire, a pair of arcuate grooves  14 . A through hole for filling the tire with air extends through the valve step  10 . An air valve is provided in the through hole. 
   As shown in FIG.  1 ( b ), an odd shaped washer  20  has an circular projecting edge  21  at an upper inside circumference. A pair of arcuate recesses  22  are formed at the lower part of the odd shaped washer  20 . The radius of curvature of the recesses is substantially the same as the grooves  14  shown in FIG.  1 ( a ). 
   As shown in FIG.  1 ( c ), a coupler, which is a housing member  30 , has a pair of flat plate portions  31 , rising portion  32 , and a pair of arcuate projections  33 . The flat plate portions  31  are fixed to a casing  40  (see  FIG. 3 ) that accommodates electronic elements. The rising portion  32  is located between the flat plate portions  31 . The projections  33  extend from the rising portion  32 . The radius of curvature of the projections  33  is substantially the same as the arcuate recesses  22  shown in FIG.  1 ( b ). The thickness of the projection  33  is substantially the same as an axial size  14   a  of the grooves  14 . A space  34  having an open end is defined between the projections  33 . A width  34   a  of the space  34  is substantially the same as the distance  14   b  between the grooves  14 . 
   A procedure for attaching a transmitter in the tire condition monitoring apparatus to a wheel  2  will now be described. The casing  40  for accommodating electronic element has been fixed to the flat plate portions  31  of the housing member  30  through insert molding in advance. 
   As shown in  FIG. 2 , an O ring  15  is engaged with the engaging groove  13  of the valve stem  10 . The valve step  10  is fitted to the odd-shaped washer  20 . The grooves  14  formed at a lower portion of the valve stem  10  are fitted to the projections  33  having an open end. That is, the groove  14  of the valve stem  10  is fitted to the projections  33  to arrange the valve stem  10  in the space  34 . At this time, the odd-shaped washer  20  is arranged such that no gap is created between the arcuate recesses  22  formed at the lower side of the washer  20  and the projections  33 . 
   Subsequently, the valve stem  10  is put through the valve hole  3  from the inside of the wheel  2  so that the O ring  15  engaged with the engaging groove  13  of the valve stem  10  to contact the valve hole  3 . Also, the projecting edge  21  formed on the upper inside of the odd-shaped washer  20  contacts the valve hole  3 . Accordingly, the O ring  15  is stopped in the valve hole  3  to ensure the airtightness of the tire. 
   As shown in  FIG. 3 , when the casing  40  is pressed against the drop center  4  of the wheel  2 , the projections  33  are moved along the arcuate grooves  14  of the valve stem  10 . As a result, an installment angle θ defined by the valve stem  10  and the casing  40  is changed according to the cross-sectional shape of the wheel  2 . In this state, the washer  50  is fitted to the valve stem  10  from the outside of the wheel  2 . Then, a valve nut  60  is threaded to the fixing portion  12  of the valve stem  10  from the outside of the wheel  2 . 
   When threading the valve nut  60 , the grooves  14  of the valve stem  10  are engaged with the projections  33  of the housing portion  30 . Further, the casing  40  is pressed against the drop center  4  of the wheel  2 . Thus, when threading the valve nut  60 , the valve stem  10  receives a force toward the outside of the wheel  2 . As a result, the odd-shaped washer  20  is pressed by the wheel  2  and the housing portion  30 . In other words, threading the valve nut  60  to the fixing portion  12  of the valve stem  10  determines the arrangement of the odd-shaped washer  20  relative to the housing portion  30 . Accordingly, the position of the casing  40  is determined relative to the valve stem  10 . 
   That is, the valve stem  10  is attached to the wheel  2  simply by threading the valve nut  60  to the fixing portion  12  of the valve stem  10 . At the same time, the threading of the valve nut  60  determines the installment position of the casing  40 . In this manner, the transmitter of the tire condition monitoring apparatus is attached to the wheel  2 . Thereafter, a valve cap  70  is threaded to the cap receiving portion  11  to complete the installment of the transmitter of the tire condition monitoring apparatus. 
   This embodiment has the following advantages. 
   (1) The grooves  14  formed at a lower portion of the valve stem  10  are fitted to the projections  33  having an open end. That is, the valve stem  10  is arranged in the space  34  defined by the projections  33 . Therefore, when the casing  40  is pressed against the drop center  4  of the wheel  2 , the projections  33  are moved along the arcuate grooves  14  of the valve stem  10 . As a result, an installment angle θ defined by the valve stem  10  and the casing  40  is changed according to the cross-sectional shape of the wheel  2 . Thus, the transmitter of the tire condition monitoring apparatus can be installed in wheels  2  having various cross-sectional shapes. 
   (2) The valve stem  10  is attached to the wheel  2  simply by threading the valve nut  60  to the fixing portion  12  of the valve stem  10 . At the same time, the threading of the valve nut  60  determines the installment position of the casing  40 . Therefore, the transmitter for the tire condition monitoring apparatus is easily attached to the wheel  2 . Further, by adjusting the fastening amount of the valve nut  60 , the installment angle θ of the valve stem  10  and the casing  40  can be readjusted. 
   (3) Also, the transmitter for the tire condition monitoring apparatus may be removed from the wheel  2  and attached to a wheel having a different cross-sectional shape. That is, the present invention provides a highly versatile transmitter for tire condition monitoring apparatus. 
   (4) The transmitter for the tire condition monitoring apparatus is attached to the drop center  4  of the wheel  2 . This prevents the beads of a tire from contacting the casing  40  when attaching the tire to the wheel  2 . Therefore, unlike the prior art, a plurality of reinforcing triangular ribs need not be provided between the flange and the outer surface of the casing  40 . It is needless to say that reinforcing ribs may be provided on the assumption that beads can contact the casing  40 . 
   It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the invention may be embodied in the following forms. 
   In the illustrated embodiment, the O ring  15  is provided at the engaging groove  13  of the valve stem  10 . However, instead of the O ring  15 , a grommet may be provided at the engaging groove  13  of the valve stem  10 . 
   The data representing the condition of the tire may include the pressure and the temperature of the tire. 
   The illustrated embodiment may be applied to any vehicle having tires. That is, the illustrated embodiment may be applied not only to four-wheel and two-wheel vehicles, but also to multi-wheel vehicles such as a bus and a truck. 
   In the illustrated embodiment, the arcuate grooves  14  of the valve stem  10  are engaged with the projections  33  of the housing portion  30 . However, the valve stem  10  may have projections and the housing portion  30  may have arcuate grooves. 
   Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.