Abstract:
A valve device attachable to a wheel including a tire in a state where the valve device penetrates through an opening of the wheel. The valve device includes a transmitter unit for detecting a condition of the tire and generating a transmission signal indicating the detected condition of the tire, a valve stem extending from the transmitter unit and an elastic member disposed to surround the valve stem. The elastic member has an annular attaching portion having a diameter greater than the diameter of the opening. The valve stem is attached to the wheel by passing the attaching portion through the opening by compressively deforming the attaching portion. The attaching portion includes a recessed portion for facilitating compressively deforming the attaching portion.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a valve attachable to a wheel of a vehicle, and more particularly, to a valve functioning as a transmitter for a tire condition monitoring system.  
         [0002]     A wireless type tire condition monitoring system has been proposed for monitoring from the passenger compartment, the condition of a tire attached to a vehicle. The system includes a transmitter installed in the interior of the tire and a receiver. The transmitter detects the condition of the tire such as the pneumatic pressure and temperature within the tire. The transmitter transmits information regarding the tire condition to the receiver and the receiver displays the information on a display provided in the passenger compartment, when necessary.  
         [0003]      FIG. 11  shows a transmitter described in U.S. Pat. No. 6,005,480. The transmitter is configured as a snap-in valve device including a transmitter unit  112  and a valve unit  100  connected to the transmitter unit  112 . The valve unit  100  includes a stem  116  connected to the transmitter unit  112 , a valve body  117  incorporated in the stem  116  for supplying air to the interior of the tire, and an elastic member  111  encompassing the stem  116 . The transmitter unit  112  is received in the interior of the tire, which is defined by the tire (not shown) and a vehicle wheel  115 . For attaching the valve unit  100  to the wheel  115 , the valve unit  100  is inserted into an opening  115   a  defined in the wheel  115 . The valve unit  100  is then pressed toward the exterior of the wheel  115  until an annular engaging portion  111   a  of the elastic member  111  is fully exposed from the opening  111   a . Since the annular engaging portion  111   a  has a diameter larger than that of the opening  115   a , the engaging portion  111   a  is deformed in a compressed manner while it is passed through the opening  115   a . The engaging portion  11   a  is released from pressing force when fully released from the opening  115   a , such that the engaging portion  111   a  is enlarged radially outward. The valve unit  100  is thus prevented from falling from the opening  115   a.    
         [0004]     For stabilizing the connection between the transmitter unit  112  and the valve unit  100 , the stem  116  extending through the valve unit  100  must be formed of hard material such as metal. The transmitter unit  112  is thus secured to the stem  116 , which is relatively hard. However, if the stem  116  is formed of the hard material, compressive deformation of the elastic member  111  encompassing the stem  116  is hampered. It is thus necessary to increase the force for pressing the annular engaging portion  111   a  into the opening  115   a  for deforming the engaging portion  111   a  radially inward as compressed. This makes it difficult to attach the valve unit  100  to the wheel  115 .  
         [0005]     According to the aforementioned patent, a space  120  is defined between the transmitter  112  and the elastic member  111  for facilitating the compressive deformation of the elastic member  111 . When the valve unit  110  is inserted into the opening  115   a  of the wheel  115 , a portion of the elastic member  111  is deformed and thus received in the space  120 . However, the space  120  is relatively spaced from the annular engaging portion  111  that is deformed in a compressed manner when passing through the opening  115   a . Accordingly, the attachment of the valve unit  100  to the wheel  115  still requires relatively great force.  
         [0006]     The elastic member  111  is formed of rubber and thus deteriorates relatively quickly. However, since the elastic member  111  of the aforementioned device is fixed to the stem  116  in an inseparable manner, at least the entire portion of the valve unit  100  must be replaced when the elastic member  111  is deteriorated, and the cost for replacement is increased.  
       SUMMARY OF THE INVENTION  
       [0007]     Accordingly, it is an objective of the present invention to provide a snap-in valve device that is easily attached to a wheel of a vehicle. Another objective of the present invention is to provide a cost-saving snap-in valve device.  
         [0008]     To achieve the foregoing and other objectives and in accordance with the purposes of the present invention, the invention provides a valve device attachable to a wheel including a tire in a state where the valve device penetrates through an opening of the wheel. The valve device comprises a transmitter unit for detecting a condition of the tire and generating a transmission signal which indicates the detected condition of the tire, a valve stem extending from the transmitter unit and an elastic member disposed to surround the valve stem. The elastic member has an annular attaching portion that has a diameter greater than the diameter of the opening. The valve stem is attached to the wheel in a state where the attaching portion is attached to a portion of the wheel around the opening by passing the attaching portion through the opening by compressibly deforming the attaching portion. The attaching portion includes a recessed portion for facilitating compressibly deforming the attaching portion.  
         [0009]     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  
       [0010]     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:  
         [0011]      FIG. 1  is a side view showing a snap-in valve device according to an embodiment of the present invention;  
         [0012]      FIG. 2  is a cross-sectional view showing the device of  FIG. 1 ;  
         [0013]      FIG. 3  is an enlarged, cross-sectional view showing a portion of  FIG. 2 ;  
         [0014]      FIG. 4 ( a ) is a partially broken bottom view showing the snap-in valve device of  FIG. 1 ;  
         [0015]      FIG. 4 ( b ) is a plan view showing the device of  FIG. 1 ;  
         [0016]      FIG. 5  is a side view showing the device of  FIG. 1  with an elastic member separated from the device;  
         [0017]      FIG. 6 ( a ) is a cross-sectional view taken along line  6   a - 6   a  of  FIG. 5 ;  
         [0018]      FIG. 6 ( b ) is a cross-sectional view showing a modification of grooves in the elastic member of  FIG. 6 ( a );  
         [0019]      FIG. 7  is a side view showing a snap-in valve device including an elastic member according to another embodiment of the present invention;  
         [0020]      FIG. 8  is a cross-sectional view showing the device of  FIG. 1  with a transmitter module removed from the device;  
         [0021]      FIG. 9  is a rear view showing the device of  FIG. 1  with the transmitter module  1  attached to the device;  
         [0022]      FIG. 10  is an enlarged perspective view showing an engagement structure between the transmitter module and a casing; and  
         [0023]      FIG. 11  is a cross-sectional view showing a prior art snap-in valve device. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     An embodiment of the present invention will now be described.  
         [0025]      FIG. 1  shows a snap-in valve device  10  in a state attached to a wheel  15  of a vehicle.  FIG. 2  is a cross-sectional view showing the snap-in valve device  10 . The snap-in valve device  10  includes a valve unit  19  and a transmitter unit  12 .  
         [0026]     The valve unit  19  has a hollow cylindrical valve stem  16  extending from the transmitter unit  12 . A valve body  17  is incorporated in a distal end of the valve stem  16  such that the valve body  17  is accommodated in an air introduction hole  16   a  of the valve stem  16 . Through the valve body  17  and the air introduction hole  16   a , air is supplied to the interior of a tire (not shown) attached to the wheel  15 . The distal end of the valve stem  16  is covered and protected by a cap  14 . The valve stem  16  configures the main structure for the valve unit  19  and is formed of relatively hard material such as metal. A hollow and cylindrical elastic member  11  encompasses the valve stem  16 . The elastic member  11  is formed of an elastically deformable material, preferably, rubber. The elastic member  11  is fitted into an opening  15   a  defined in the wheel  15  as deformed in a compressed manner, such that the valve unit  19  is secured to the wheel  15 .  
         [0027]     The transmitter unit  12  includes a resin casing  30  connected to the valve stem  16  and a transmitter module  13  received in the casing  30  in a removable manner. Since the snap-in valve device  10  must be secured to the wheel  15  stably, the transmitter unit  12  must be connected securely to the valve unit  19 , which is directly engaged with the wheel  15 . It is therefore desirable that the valve stem  16  be of hard material, or that the main structure of the valve unit be formed integrally with the resin casing  30  of the transmitter unit  12 . In this case, it is preferable that the casing  30  be molded with the proximal end of the valve stem  16  placed in a mold, through so-called insert molding. A connecting flange  25  is formed at the proximal end of the valve stem  16 . The connecting flange  25  is embedded in the casing  30  and thus improves the connection strength between the valve stem  16  and the casing  30 . However, as long as the transmitter unit  12  is connected securely to the valve unit  19 , the transmitter unit  12  and the valve unit  19  may be fabricated separately. The transmitter unit  12  and the valve unit  19  are then connected to each other in a separable or inseparable manner.  
         [0028]     With reference to FIGS.  1  to  4 ( b ), the elastic member  11  includes a base  22 , a groove-like annular attaching portion  23 , and an annular engaging portion  20 , which are arranged in this order from the proximal end to the distal end of the elastic member  11 . As illustrated in  FIGS. 1 and 2 , the snap-in valve device  10  is attached to the wheel  15  in a state in which the attaching portion  23  is fitted into the opening  15   a  and an area of the wheel  15  around the opening  15   a  is supported by the base  22  and the engaging portion  20 . In a state where the snap-in valve device  10  is separated from the wheel  15 , the diameter of the attaching portion  23  is larger than that of the opening  15   a . Therefore, with the snap-in valve device  10  attached to the wheel  15 , the attaching portion  23  receives pressing force acting radially inward from the inner circumferential wall of the opening  15   a.    
         [0029]     The annular engaging portion  20  is shaped in a tapered manner toward the distal end of the elastic member  11 . The maximum diameter of the engaging portion  20  (the outer diameter of the section of the engaging portion  20  adjacent to the annular attaching portion  23 ) is larger than the diameter of the opening  15   a . For attaching the snap-in valve device  10  to the wheel  15 , the valve unit  19  is inserted into the opening  15   a  from the distal end of the valve unit  19 . The valve unit  19  is then pressed toward the exterior of the wheel  15  until the annular engaging portion  20  is fully exposed from the opening  15   a . When passing through the opening  15   a , the annular engaging portion  20  is pressed by the inner circumferential wall of the opening  15   a  and thus deformed radially inward in a compressed manner. When the engaging portion  20  is fully exposed from the opening  15   a , the engaging portion  20  is released from the pressing force of the inner circumferential wall of the opening  15   a . The engaging portion  20  is thus enlarged radially outward, such that the engaging portion  20  is engaged with the portion of the wheel  15  corresponding to the opening  15   a . Accordingly, the valve unit  19  is prevented from falling from the opening  15   a.    
         [0030]     For securely engaging the valve unit  19  with the opening  15   a , it is preferred that the diameter of the annular engaging portion  20  (particularly, the diameter of the section of the engaging portion  20  adjacent to the attaching portion  23 ) be enlarged to the possible maximum margin with respect to that of the opening  15   a . However, if the diameter of the engaging portion  20  is excessively large as compared to that of the opening  15   a , the compressive deformation of the engaging portion  20 , which allows the engaging portion  20  to pass through the opening  15   a , is hampered when the snap-in valve device  10  is attached to the wheel  15 . Also, since the valve stem  16  located radially inward from the elastic member  11  has relatively high rigidity, the valve stem  16  hampers the compressive deformation of the annular engaging portion  20 .  
         [0031]     Accordingly, in the illustrated embodiment, for facilitating the compressive deformation of the annular engaging portion  20 , a plurality of recessed portions, or grooves  21 , are defined in the surface of the engaging portion  20 . The grooves  21  extend along the axis of the elastic member  11  as spaced at equal angular intervals about the axis of the elastic member  11 . If compressive force is applied to the annular engaging portion  20  in a radial inward direction, the annular engaging portion  20  is deformed such that the deformed portion is received by the spaces defined by the grooves  21 . This facilitates the compressive deformation of the engaging portion  20 , as compared to the case in which the grooves  21  are not provided. It is thus easy to pass the annular engaging portion  20  through the opening  15   a.    
         [0032]     In the illustrated embodiment, as shown in  FIG. 6 ( a ), each of the grooves  21  has a V-shaped cross section. In terms of cross sections extending perpendicular to the axis of the elastic member  11 , the proportion of the total cross-sectional area of the grooves  21  to the cross-sectional area of the solid portion of the elastic member  11  corresponding to the engaging portion  20  is preferably not less than 5 percent but not more than 15 percent. In other words, if the cross-sectional area of the solid portion of the elastic member  11  corresponding to the engaging portion  20  is indicated as A, the cross-sectional area of each groove  21  is indicated as B, and the number of the grooves  21  is indicated as n, it is desired that the proportion represented by the equation (B×n)/A×100, is not less than 5 percent but not more than 15 percent. If such proportion is less than 5 percent, passing of the annular engaging portion  20  through the opening  15   a  is not sufficiently facilitated. In contrast, if the proportion exceeds 15 percent, the rigidity of the engaging portion  20  becomes excessively low. In this case, the elastic member  11  is easily separated from the opening  15   a . That is, the aforementioned range of proportion, 5 to 15 percent, is preferred for easily fitting the valve unit  19  into the opening  15   a  and then preventing the valve unit  19  from the opening  15   a.    
         [0033]     The recessed portions for facilitating the compressive deformation of the engaging portion  20  are not restricted to the grooves  21 . The recessed portions may be shaped and arranged in any other suitable manner, as long as the solid portion of the annular engaging portion  20  is reduced. For example, the cross-sectional shape of each groove  21  may be rectangular, as shown in  FIG. 6 ( b ), rather than the V-shape. Alternatively, each groove  21  may have a U-shaped cross section. Further, the dimensions (the axial dimension, the lateral dimension, and the depth) of each groove  21 , the extending direction of the groove  21 , and the number of the grooves  21  may be modified as needed. In addition, as shown in  FIG. 7 , a plurality of recesses  28  each having an arched cross-sectional shape may be defined in the surface of the annular engaging portion  20 , instead of the grooves  21 .  
         [0034]     In the illustrated embodiment, the elastic member  11  is attached to the valve stem  16  in a separable manner, referring to  FIG. 5 . Although the elastic member  11  is exposed to the external environment, the elastic member  11  is formed of a material that is relatively easily deteriorated, such as rubber. The life of the elastic member  11  is thus relatively short, as compared to the remaining components of the snap-in valve device  10 . If the elastic member  11  is inseparable from the valve stem  16 , the snap-in valve device  10  as a whole must be replaced every time the elastic member  11  becomes unusable. This increases replacement cost for the snap-in valve device  10 . However, if the elastic member  11  is attached to the valve stem  16  in a separable manner, as in the illustrated embodiment, the elastic member  11  is replaceable independently from the remainder of the device  10 . The cost for the snap-in valve device  10  is thus saved.  
         [0035]     As shown in FIGS.  1  to  5 , the valve stem  16  includes a first holding flange  26  with a relatively large diameter and a second holding flange  27  with a relatively small diameter. The first holding flange  26  is formed near the proximal end of the valve stem  16 . The second holding flange  27  is spaced from the first holding flange  26  in the axial direction of the valve stem  16  toward the distal end of the valve stem  16 . The second holding flange  27  is shaped in a tapered manner toward the distal end of the valve stem  16 . The maximum outer diameter of the second holding flange  27  is larger than the inner diameter of the elastic member  11 . The elastic member  11  is held by the first and second holding flanges  26 ,  27  with respect to the axial direction of the elastic member  11 .  
         [0036]     For attaching the elastic member  11  to the valve stem  16 , the valve stem  16 , with the cap  14  removed from the valve stem  16 , is inserted into the elastic member  11  from the distal end of the valve stem  16 . When reaching a position beyond the second holding flange  27 , the elastic member  11  is held between the first holding flange  26  and the second holding flange  27 . The tapered shape of the second holding flange  27  makes it easy for the elastic member  11  to proceed along and beyond the second holding flange  27 .  
         [0037]     As shown in  FIG. 3 , the valve stem  16  includes an annular recess  18  defined in a portion between the first and second holding flanges  26 ,  27 , or a portion of the valve stem  16  to which the elastic member  11  is attached. The annular recess  18  corresponds to a potion of the valve stem  16  between the first and second holding flanges  26 ,  27  having a reduced diameter, as compared to the remainder of the valve stem  16 . The annular recess  18  is located at an axial position corresponding to the opening  15   a  with the valve stem  16  attached to the wheel  15 . The annular recess  18  is located at a position offset from the annular engaging portion  20  with respect to the axial direction of the elastic member  11 .  
         [0038]     When the engaging portion  20  is passed through the opening  15   a  for attaching the valve stem  16  to the wheel  15 , a portion of the elastic member  11  is deformed such that the portion is received in the space defined by the annular recess  18 . This further facilitates the attachment of the snap-in valve device  10  to the wheel  15 .  
         [0039]     As has been described, the annular attaching portion  23 , which diameter is larger than that of the opening  15   a , is pressed by the inner circumferential wall of the opening  15   a  with the snap-in valve device  10  attached to the wheel  15 . In this state, a portion of the elastic member  11  is deformed and thus received by the space defined by the annular recess  18 , as shown in  FIG. 3 , such that the deformed portion is engaged with the annular recess  18 . Therefore, regardless of that the elastic member  11  is separable from the valve stem  16 , the elastic member  11  is fixed to the valve stem  16  securely and stably, while restricted from axial movement with respect to the valve stem  16 .  
         [0040]     In the illustrated embodiment, the snap-in valve device  10  is configured such that the transmitter module  13  is separable from the casing  20 , as illustrated in  FIG. 8 . Referring to FIGS.  4 ( a ),  8  and  9 , the transmitter module  13  includes a resin case  35  having a square box-like shape and a circuit unit  36 , which is accommodated in the case  35 . The circuit unit  36  includes a circuit board  37  and a plurality of electronic elements formed on the circuit board  37 , a controller  38 , a pressure sensor  39 , and a transmission circuit  40 , each of which is formed as a chip. Also, a battery  41  is provided on the circuit board  37  for supplying power to the electronic elements on the circuit board  37 .  
         [0041]     The pressure sensor  39 , serving as a tire condition sensor, detects the pneumatic pressure in the interior of the tire and provides the controller  38  with pneumatic pressure data obtained from the detection. The controller  38  sends data including the pneumatic pressure data to the transmission circuit  40 . The transmission circuit  40  generates a transmission signal from the received data and transmits the signal wirelessly through a transmission antenna (not shown).  
         [0042]     The resin case  35  is filled with potting material such that the circuit unit  36  in the case  35  is covered by the potting material except for a pressure sensing surface of the pressure sensor  39 . In the illustrated embodiment, the resin case  35  has a downward opening. The potting material is thus filled in the case  35  with the circuit unit  36  accommodated in the case  35  from the downward opening of the case  35 .  
         [0043]     An engagement mechanism is deployed between the casing  30  and the transmitter module  13  for engaging the casing  30  and the transmitter module  13  with each other in a separable manner. In other words, with reference to FIGS.  8  to  10 , the casing  30  has an accommodating portion  31  having an opening facing the opposite direction with respect to the valve unit  19 . The transmitter module  13  is selectively inserted into or removed from the opening of the accommodating portion  31 . At opposing sides of the casing  30  near the opening of the accommodating portion  31 , a pair of engaging pieces  32  are formed. Correspondingly, a pair of receiving members  33  each having a square flame-like shape are formed at opposed sides of the resin case  35  of the transmitter module  13 .  
         [0044]     For installing the transmitter module  13  in the casing  30 , the transmitter module  13  is inserted into the accommodating portion  31  of the casing  30 , such that each of the engaging pieces  32  is passed through the corresponding one of the receiving members  33 . At this stage, each engaging piece  32  is elastically deformed in an inward direction by the corresponding receiving member  33 . When the transmitter module  13  is fully received in the accommodating portion  31 , each engaging piece  32  restores the original shape and is thus engaged with the corresponding receiving member  33 . In contrast, for separating the transmitter module  13  from the casing  30 , each of the engaging pieces  32  is elastically deformed in the inward direction such that the engaging piece  32  is released from the engagement with the corresponding receiving member  33 . The transmitter module  13  is then removed from the accommodating portion  31 .  
         [0045]     The engagement mechanism between the casing  30  and the transmitter module  13  is not restricted to the illustrated structure but may be modified as needed.  
         [0046]     When the battery  41  is completely drained or a certain electronic element of the circuit board  37  has failed, only the transmitter module  13  must be separated from the snap-in valve device  10  for replacement. That is, the remaining portion of the snap-in valve device  10 , other than the transmitter module  13 , may be continuously used without replacement. This structure saves replacement costs.  
         [0047]     Further, replacement of the transmitter module  13  may be accomplished with the snap-in valve device  10  maintained as attached to the wheel  15 . This simplifies such replacement.  
         [0048]     As shown in  FIG. 1 , with the snap-in valve device  10  attached to the wheel  15 , the opening of the accommodating portion  31  of the casing  30  is oriented parallel with the rotational axis of the wheel  15 . This structure reduces the force acting parallel with the rotational axis of the wheel  15  when the vehicle is moving. The transmitter module  13  is thus prevented from falling from the casing  30 . Even if the snap-in valve  10  is subjected to centrifugal force produced by rotation of the wheel  15 , the transmitter module  13  is supported by an upper wall of the casing  30 . Further, even if the snap-in valve device  10  is subjected to force produced in the rotational direction of the wheel  15 , the transmitter module  13  is supported by opposing side walls of the casing  30 . Accordingly, in the illustrated embodiment, in which the transmitter module  13  is removable from the snap-in valve device  10 , the parallel orientation of the opening of the accommodating portion  31  with the rotational axis of the wheel  15  is effective in preventing the transmitter module  13  from falling therefrom.  
         [0049]     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.