Patent Abstract:
A tire condition monitoring system includes a transmission device, a receiving device, and a monitoring section. The transmitting device includes a sensor which detects, as tire information, a condition of gas in the tire cavity area surrounded with a tire and a rim, a transmitter which wirelessly transmits the tire information, and a housing having a wall surrounding the sensor and the transmitter and separating an inner space from the tire cavity area. The housing wall defines a communicating through hole which enables communication between the cavity area and inner space and a selectively non-communicating through hole having a member which is movable between blocking and unblocking positions to impede and enable communication, respectively, between the cavity area and inner space. The receiving device receives the tire information, and the monitoring section determines whether a tire anomaly exists based on the tire information and provides a result.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This U.S. National stage application claims priority under 35 U.S.C. §119(a) to Japanese Patent Application No. 2009-270924, filed in Japan on Nov. 30, 2009, the entire contents of Japanese Patent Application No. 2009-270924 are hereby incorporated herein by reference. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a transmission device provided in a tire cavity area to transmit tire information about a tire condition and a tire condition monitoring system for determining whether a tire anomaly is caused. 
     2. Background Information 
     Conventionally, a check and control of air pressure of a tire mounted to a vehicle are desired for improvement of tire durability, improvement of wear resistance, improvement of fuel economy, or improvement of ride quality, and improvement of handling performance. For this purpose, various systems for monitoring tire pressure have been proposed. In such a system, in general, information about the air pressure of the tire mounted to a wheel is detected, a transmission device for transmitting the information is provided in a tire cavity area of each wheel, and the information of the air pressure of each tire is obtained from the transmission device to monitor the air pressure of the tire. 
     On the other hand, when a tire goes flat, a puncture repair agent to be injected into a tire cavity area located between the tire and a rim is often used. Because the puncture repair agent is a liquid, the agent adheres to the transmission device provided in the tire cavity area as well as a tire inner surface facing the tire cavity area when the agent is injected into the tire cavity area. In some cases, the agent becomes solidified to close an opening portion formed in the transmission device to affect measurement of the air pressure. 
     To cope with this problem, a wheel condition detection device capable of maintaining a normal detection condition by preventing entry of foreign matter through a communication portion for detection has been proposed (Japanese Patent Application Laid-Open No. 2008-62730). 
     To put it concretely, a TPMS (Tire Pressure Monitoring System) valve of the wheel condition detection device is provided with a communication portion opening and closing mechanism for opening and closing a communication hole formed in a housing. At the time of puncture repair, entry of the puncture repair agent into a detection space through the communication hole is prevented. This communication portion opening and closing mechanism is made up of mechanical bodies including a lid body and a torsion coil spring and automatically opens and closes the communication hole by centrifugal force acting on a wheel. 
     Moreover, there are proposed a tire pressure monitoring system and a tire pressure sensor unit for informing an occupant that tire pressure may drop after a punctured tire is fixed by using a tire puncture repair agent (Japanese Patent Application Laid-Open No. 2007-196834). 
     To put it concretely, the tire pressure monitoring system is provided to each tire of a vehicle and is provided with a sensor unit having a tire pressure sensor and a transmitter, a receiving device for receiving a radio wave from the sensor unit, and a control ECU for giving an alarm when the air pressure of each tire becomes lower than or equal to a threshold value. The system is provided with a puncture determination means for determining puncture of each tire and a puncture repair agent use determination means for determining whether or not the punctured tire was repaired by using the puncture repair agent after it was determined that the tire blew out. When it was determined that the punctured tire was repaired by using the puncture repair agent, the control ECU continues the alarm even if the tire pressure value from the air pressure sensor is a normal value. 
     Because the communication portion opening and closing mechanism of the device described in Japanese Patent Application Laid-Open No. 2008-62730 is made up of the mechanical bodies including the lid body and the torsion coil spring, the device itself is complicated and expensive. In the system and the unit described in Japanese Patent Application Laid-Open No. 2007-196834, it is not certain whether or not the information about the tire pressure measured after the repair of the tire by using the puncture repair agent is correct. Therefore, it is impossible to determine whether a tire anomaly after the puncture repair is caused. 
     SUMMARY 
     Therefore, an object of the present invention is to provide a transmission device capable of appropriately detecting and transmitting tire information such as tire pressure information even after tire puncture repair by using a puncture repair agent and a tire condition monitoring system for determining whether a tire anomaly is caused. 
     According to a first aspect of the invention, there is provided with a transmitting device provided in a tire cavity area to transmit tire information about a condition of a tire. The device includes: a sensor which detects, as the tire information, a condition of gas filled in the tire cavity area surrounded with the tire and a rim;
     a transmitter which wirelessly transmits the detected tire information; and   a housing which has a wall surrounding the sensor and the transmitter, and an inner space separated from the tire cavity area by the wall.   

     The housing is provided with a plurality of through holes passing through the wall. The through holes include a non-communicating through hole which is out of communication between the tire cavity area and the inner space in the housing by blockage of a member, and a communicating through hole which is in communication between the tire cavity area and the inner space in the housing. The non-communicating through hole is made communicative between the tire cavity area and the inner space in the housing when the member is removed. 
     According to a second aspect of the invention, there is provided with a transmitting device provided in a tire cavity area to transmit tire information about a condition of a tire. The device includes:
     a sensor which detects, as the tire information, a condition of gas filled in the tire cavity area surrounded with the tire and a rim;   a transmitter which wirelessly transmits the detected tire information; and   a housing which has a wall surrounding the sensor and the transmitter, and an inner space separated from the tire cavity area by the wall.   

     The housing is provided with at least one through hole passing through the wall of the housing in order to connect the inner space and the tire cavity area and is further provided with means for forming a through hole, the means including a protrusion which protrudes from a face of the housing and a thin-walled portion which is formed in a position corresponding to a position of the protrusion on an opposite side of the wall of the housing from the protrusion and has a smaller wall thickness than a portion around the thin-walled portion. Then, a new through hole is formed in the position of the thin-walled portion by breaking off the protrusion. 
     According to a third aspect of the invention, there is provided with a tire condition monitoring system. The system includes a transmitting device; a receiving device; and a monitoring section. The transmitting device includes
     a sensor which detects, as tire information, a condition of gas filled in the tire cavity area surrounded with a tire and a rim,   a transmitter which wirelessly transmits the detected tire information, and   a housing which has a wall surrounding the sensor and the transmitter, and an inner space separated from the tire cavity area by the wall,   the housing is provided with a plurality of through holes passing through the wall.   

     The through holes include a non-communicating through hole which is out of communication between the tire cavity area and the inner space in the housing by blockage of a member, and a communicating through hole which is in communication between the tire cavity area and the inner space in the housing. The non-communicating through hole is made communicative between the tire cavity area and the inner space in the housing when the member is removed. The receiving device receives the tire information transmitted from the transmitter. The monitoring section determines whether a tire anomaly is caused based on the tire information and informs a determination result. 
     According to a fourth aspect of the invention, there is provided with a tire condition monitoring system. The system includes a transmitting device; a receiving device; and a monitoring section. The transmitting device includes
     a sensor which detects, as tire information, a condition of gas filled in the tire cavity area surrounded with the tire and a rim;   a transmitter which wirelessly transmits the detected tire information; and   a housing which has a wall surrounding the sensor and the transmitter, and an inner space separated from the tire cavity area by the wall.   

     The housing is provided with at least one through hole passing through the wall of the housing in order to connect the inner space and the tire cavity area and is further provided with means for forming a through hole. The means includes a protrusion which protrudes from a face of the housing and a thin-walled portion which is formed in a position corresponding to a position of the protrusion on an opposite side of the wall of the housing from the protrusion and has a smaller wall thickness than a portion around the thin-walled portion. Then, a new through hole is formed in the position of the thin-walled portion by breaking off the protrusion. 
     The receiving device receives the tire information transmitted from the transmitter. The monitoring section determines whether tire anomaly is caused based on the tire information and informs a determination result. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a general overview diagram of a tire pressure monitoring system which is a first embodiment of a tire condition monitoring system; 
         FIG. 2  is a drawing for explaining an example of a method of fixing a transmitting device illustrated in  FIG. 1  in a tire cavity area; 
         FIG. 3  is a perspective view of an entire device in which the transmitting device illustrated in  FIG. 2  is integrated with a tire valve; 
         FIG. 4  is a sectional view of the transmitting device taken along a direction of arrows A-A illustrated in  FIG. 3 ; 
         FIG. 5  is a circuit block diagram of the transmitting device illustrated in  FIG. 1 ; 
         FIG. 6  is a circuit block diagram of a monitoring device illustrated in  FIG. 1 ; 
         FIG. 7  is a perspective view for explaining another form of transmitting device different from the transmitting device illustrated in  FIG. 3 ; 
         FIG. 8  is a drawing for explaining another form of member used for the transmitting device and different from a member for closing a through hole illustrated in  FIG. 4 ; 
         FIG. 9  is a drawing for explaining another example of the member for closing the through hole and used for the transmitting device; 
         FIGS. 10A to 10C  are drawings for explaining yet another example of the member for closing the through hole and used for the transmitting device; 
         FIGS. 11A and 11B  are drawings for explaining yet another example of the member for closing the through hole and used for the transmitting device; and 
         FIGS. 12A and 12B  are drawings for explaining an example of a mechanism for forming the through hole in the transmitting device. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     A transmission device and a tire condition monitoring system of the present invention will be described below in detail. 
       FIG. 1  is a general overview diagram of a tire pressure monitoring system  10  which is an embodiment of the tire condition monitoring system. 
     The tire pressure monitoring system (hereafter referred to as “system”)  10  is mounted on a vehicle  12 . The system  10  includes air pressure information transmission devices (hereafter referred to as “transmission devices”)  16   a ,  16   b ,  16   c , and  16   d  provided in respective tire cavity areas in tires  14   a ,  14   b ,  14   c , and  14   d  of respective wheels of the vehicle  12  and a monitoring device  18 . 
     All of the transmission devices  16   a ,  16   b ,  16   c , and  16   d  detect information about pressure of air filled into the tire cavity areas surrounded with the tires and rims as tire information and wirelessly transmit the tire information to the monitoring device  18 . Hereafter, to explain all of the transmission devices  16   a ,  16   b ,  16   c , and  16   d  at a time, the transmission devices  16   a ,  16   b ,  16   c , and  16   d  will be collectively referred to as transmission devices  16 . 
       FIG. 2  is a drawing for explaining an example of a method for fixing the transmission device  16  in the tire cavity area.  FIG. 3  is a perspective view of an entire device in which the transmission device  16  illustrated in  FIG. 2  is integrated with a tire valve  20 . 
     The transmission device  16  is provided to an end portion of the tire valve  20  extending on a side of the tire cavity area and is fixed and disposed in the tire cavity area by mechanically fixing the tire valve  20  to the rim  19 . 
       FIG. 4  is a sectional view of the transmission device  16  along a line of A-A illustrated in  FIG. 3 . As illustrated in  FIG. 4 , the transmission device  16  includes a housing  22  and a circuit  24  provided in the housing  22 . The housing  22  includes a wall surrounding the circuit  24  and an inner space  38  separated from the tire cavity area by the wall. The circuit  24  includes a substrate  26  and a sensor unit  28 , a transmitter  30 , a processing unit  32 , a power supply section  34 , and an antenna  40  (see  FIG. 5 ) provided to the substrate  26 . 
       FIG. 5  is a circuit block diagram of the transmitting device  16 . 
     The sensor unit  28  includes an air pressure sensor  28   a  and an A/D converter  28   b . The air pressure sensor  28   a  senses the air pressure in the inner space  38  in the housing  22  and outputs a pressure signal. The inner space  38  in the housing  22  communicates with the space in the tire cavity area through one through hole  36  out of six through holes  36  passing through the housing  22 . The remaining five through holes  36  are closed with members  37  to be non-communicating through holes. In the sectional view in  FIG. 4 , the through holes  36   a ,  36   b , and  36   c  are illustrated. Out of the through holes  36   a ,  36   b , and  36   c , the through holes  36   a  and  36   b  are closed with the members  37  to be the non-communicating through holes and the through hole  36   c  connects the inner space  38  and the tire cavity area. The six through holes are collectively referred to as through holes  36 . 
     The A/D converter  28   b  carries out digital conversion of the pressure signal output from the air pressure sensor  28   a  and outputs pressure data. 
     The processing unit  32  includes a central processing section  32   a  and a memory section  32   b . The central processing section  32   a  operates based on a program stored in a semiconductor memory of the memory section  32   b . When the central processing section  32   a  is powered and driven, it carries out control so that the pressure data, which is information about the air pressure and sent from the sensor unit  28 , is transmitted to the monitoring device  18  via the transmitter  30  at predetermined time intervals, e.g., every five minutes. Identification information unique to the transmission device  16  is stored in advance in the memory section  32   b  and the central processing section  32   a  carries out control so that the identification information is transmitted to the monitoring device  18  together with the pressure data. 
     The memory section  32   b  includes a ROM for storing the program for operation of the central processing section  32   a  and rewritable nonvolatile memory such as an EEPROM. The identification information unique to the transmission device  16  is stored in an unwritable area in the memory section  32   b.    
     The transmitter  30  includes an oscillation circuit  30   a , a modulation circuit  30   b , and an amplifier circuit  30   c.    
     The oscillation circuit  30   a  generates a carrier signal, e.g., an RF signal belonging to a 315 MHz frequency band. 
     The modulation circuit  30   b  modulates the carrier signal by using the pressure data sent from the central processing section  32   a  and the identification information unique to the transmission device  16  to generate a transmitting signal. As a modulation method, a method such as amplitude shift keying (ASK), frequency modulation (FM), frequency shift keying (FSK), phase modulation (PM), and phase shift keying (PSK) can be used. 
     The amplifier circuit  30   c  amplifies the transmitting signal generated by the modulation circuit  30   b  and wirelessly transmits the transmitting signal to the monitoring device  18  via the antenna  40 . 
     A secondary battery, for example, is used as the power supply section  34  to almost permanently supply electric power to the sensor unit  28 , the transmitter  30 , and the processing unit  32 . 
     As described above, the six through holes  36  passing through a wall of the housing  22  are formed in the surface of the housing  22  which covers the circuit  24  as illustrated in  FIG. 3 . As the through holes  36 , the three through holes  36   a ,  36   b , and  36   c  are illustrated in  FIG. 4 . Out of the through holes  36   a ,  36   b , and  36   c , the through holes  36   a  and  36   b  are closed with the members  37 . In other words, through the two through holes  36   a  and  36   b , the tire cavity area and the inner space  38  in the housing  22  are separated from each other by the members  37  locked in the through holes  36 . Through the one through hole  36   c  not provided with the member  37 , the tire cavity area and the inner space  38  in the housing  22  communicate with each other. The member  37  has a columnar portion having substantially the same diameter as a hole diameter of the through hole  36  and is fixed by means of friction between the columnar portion and an inner peripheral face of the through hole  36 . 
     A purpose of providing the members  37  to some of the plurality of through holes  36  to make them the non-communicating through holes is to make it possible, when the communicating through hole  36  is closed with the puncture repair agent, to newly set a communicating through hole  36  by removing the member  37  provided in the non-communicating through hole. The number of through holes  36  provided with the members  37  and the number of through holes not provided with the members  37  are not especially restricted. However, in order to prevent the puncture repair agent from entering the inner space  38 , the number of through holes  36  not provided with the members  37  is preferably one. 
     An opening area of an opening portion of the through hole  36  in the surface of the housing  22  is preferably 0.4 mm 2  or smaller. This is because, even if the puncture repair agent adheres to the opening portion, the puncture repair agent does not enter the through hole  36  due to surface tension and the puncture repair agent attached to the opening portion is highly likely to be removed due to rolling of the tire before the agent solidifies. 
     The opening areas of the respective opening portions of the through holes  36  need not to be the same. An arrangement of the opening portions is not limited to that in  FIG. 3  in which the opening portions are arranged in two parallel rows but may be any arrangement. 
     Although the transmitting device  16  in the embodiment detects the pressure of the air filled in the tire cavity area as a condition of the tire, the target for the detection may be temperature of the air in the tire cavity area instead of the air pressure. 
     Moreover, the transmitting device  16  may not be fixed to the tire valve  20  but be fixed directly to an inner surface of the tire and facing the tire cavity area or a surface of the rim  19  and facing the tire cavity area. 
       FIG. 6  is a circuit block diagram of the monitoring device  18 . 
     The monitoring device  18  is installed in front of a position of a driver&#39;s seat of the vehicle  12 , for example, and informs a driver of the information about the air pressure. The monitoring device  18  includes an antenna  52 , a receiving section  54 , a receive buffer  56 , a central processing section  58 , a memory section  60 , an operation section  62 , a switch  64 , a display control section  66 , a display section  68 , and a power supply section  70 . 
     Frequency of the antenna  52  is matched to transmit frequency of the transmission device  16  and the antenna  52  is connected to the receiving section  54 . 
     The receiving section  54  receives the transmitting signal of a predetermined frequency and sent from the transmission device  16  and demodulates the signal to take out the pressure data and the data of the identification information. These pieces of data are output to the receive buffer  56 . The receive buffer  56  temporarily stores the pressure data and the data of the identification information output from the receiving section  54 . The stored pressure data and the data of the identification information are output to the central processing section  58  according to a direction of the central processing section  58 . 
     The central processing section  58  is mainly made up of a CPU and operates based on a program stored in the memory section  60 . The central processing section  58  monitors the air pressure of each of the tires  14   a  to  14   d  for each piece of identification information based on the received pressure data and data of the identification information. To put it concretely, the central processing section  58  determines whether a tire anomaly is caused based on the pressure data and informs a determination result. Determination of whether the tire anomaly is caused is to determine whether or not the air pressure dropped to an abnormally low level or dropped sharply in a short period of time to show that the tire blew out, for example. 
     The central processing section  58  outputs a determination result to the display control section  66  and causes the display section  68  to output the determination result through the display control section  66 . 
     Furthermore, the central processing section  58  initializes a communication method and the like with the transmission device  16  according to information from the operation section  62  and information from the switch  64 . Moreover, the central processing section  58  can set determination conditions for determining whether the tire anomaly is caused according to the information from the operation section  62 . 
     The memory section  60  includes a ROM for storing the program for operation of the CPU of the central processing section  58  and a nonvolatile memory such as an EEPROM. A table of the communication method with the transmission device  16  is stored in the memory section  60  during manufacture. The transmission device  16  and the monitoring device  18  communicate with each other by the above-described communication method at an early stage. The communication method table includes information such as a communication protocol, a transmission bit rate, and a data format corresponding to the identification information unique to the transmission device  16 . Settings of these pieces of information can be more freely changed by means of input from the operation section  62 . 
     The operation section  62  includes an input device such as a keyboard and is used to input various kinds of information and conditions. The switch  64  is used to direct the central processing section  58  to start initialization. 
     The display control section  66  controls the display section  68  to display the tire pressure corresponding to the mounted position of the tire according to the determination result from the central processing section  58 . At the same time, the display control section  66  carries out control to cause the display section  68  to display also the determination result that the tire has blown out, for example. 
     The power supply section  70  controls electric power supplied from a battery mounted to the vehicle  12  to suitable voltages and supplies them to respective portions of the monitoring device  18 . 
     The transmission device  16  and the monitoring device  18  are formed as described above. 
     As above described, some of the through holes  36  passing through the wall of the housing  22  are the non-communicating through holes which are closed by the members  37 . Even if the communicating through hole  36   c  is closed by the tire puncture repair agent, the through hole  36   a  or  36   b  can be made a communicating through hole by removing a member  37  provided in one of the non-communicating through holes. 
       FIG. 7  is a perspective view illustrating a modification of the transmitting device  16 . In the example in  FIG. 7 , four through holes  36  are provided to the housing  22 . The opening portions of the three through holes  36  are formed on a face  22   a  and the opening portion of the one through hole  36  is formed on a side face oriented in a different direction from the face  22   a . The two through holes  36  out of the three through holes  36  having the opening portions formed on the face  22   a  are closed with the members  37  to be the non-communicating through holes. The remaining one through hole  36  (the left hole on the face  22   a  in the drawing) is open and the inner space  38  and the tire cavity area communicate with each other through this through hole  36 . As described above, the housing  22  has a plurality of faces oriented in different directions from each other in the tire cavity area and the opening portions of the plurality of through holes  36  facing the tire cavity area are formed on the plurality of faces of the housing  22 . In this way, even if the puncture repair agent adheres to the opening portion of the through hole on one face, it is highly unlikely that the puncture repair agent adheres to the through hole formed on a different face, which keeps communication between the tire cavity area and the inner space in the housing  22 . One or more through holes  36  may be formed on each of the plurality of faces of the housing  22  and the two or more through holes  36  in total may be provided to the housing  22 . 
     It is the more preferable that the opening portions of the plurality of through holes  36  are formed on each of the plurality of faces of the housing  22  in order to keep the communication between the tire cavity area and the inner space  38  in the housing  22 . In this housing, some of the opening portions of the through holes  36  formed on each face may be the non-communicating through holes closed with the members  37 . Even if a through hole  36  is closed with the puncture repair agent, it is possible to reliably keep the communication between the inner space  38  in the housing  22  and the tire cavity area by using another through hole  36  formed on the same face. Therefore, even if the puncture repair agent is injected into the tire cavity area, the transmitting device  16  can appropriately measure and transmit the correct tire information. 
       FIG. 8  is a drawing which illustrates another embodiment (a second embodiment) of the member  37  for closing the housing  22  having the through holes  36  in the transmitting device  16 . 
       FIG. 8  illustrates examples of the member  37  having assist handles for helping attach and detach the member  37  to and from the non-communicating through hole. To put it concretely, an end portion (head portion) of the detachable member  37  protrudes from the opening portion of the non-communicating through hole when the member  37  is provided to the through hole  36 . The protruding end portion (head portion) of the member  37  is provided with the assist handle  37   a  for help attach and detach the member  37 . The assist handle  37   a  may be of various types as illustrated in  FIG. 8 . Some types may be a hook shape or an annular shape, for example, so that the member  37  can be easily pulled out of the through hole  36  by using string, wire rod such as wire, or a thin jig after detachment of the tire from the rim. Material of the member  37  may be resin or metal. 
       FIG. 9  is a drawing which illustrates a modification of the member  37  in the second embodiment. The member  37  is an external screw, an internal thread is formed in the non-communicating through hole  36 , and the member  37  is fixed by being screwed into the through hole  36 . By closing the through hole  36  with the external screw, airtightness is increased. Moreover, the member  37  can be removed by unscrewing the external screw with a screwdriver or the like, which improves workability. Furthermore, the external screw is used as the member  37 , which reduces cost. 
       FIG. 10A  is a drawing which illustrates another modification of the member  37  in the second embodiment. 
     The member  37  is a sheet-like film. The film is stuck on the face of the housing  22  around the opening portion of the through hole  36 . The member  37  may be an adhesive film. 
       FIG. 10B  is a drawing which illustrates another modification of the member  37 . 
     The plurality of through holes  36  are formed in the housing  22 . The members  37  are a plurality of sheet-like films and the plurality of films are separately stuck on the face of the housing  22  around the respective opening portions of the plurality of through holes  36 . Each member  37  is preferably printed with an instruction such as “Peel off one sheet after puncture repair” that encourages removal of the member  37 . Even if the communicating through hole  36  is closed with the puncture repair agent and brought into the non-communicating state, a worker can dismount the tire off the rim, see the instruction on the member  37 , and peel off the member  37  to thereby easily bring the non-communicating through hole  36  into the communicating state. 
       FIG. 11A  is a drawing which illustrates another modification of the member  37  in the second embodiment. 
     The member  37  is a rectangular plate member for sliding within a predetermined region on the face of the housing  22 . The through holes  36  are closed with the plate member to interrupt communication between the tire cavity area and the inner space  38  in the housing  22 . The member  37  (the member illustrated in a thick line in the drawing) which is the plate member is engaged with groove portions  39 . The groove portions  39  are formed on the surface of the housing  22 , corresponding to both side portions in a width direction of the member  37  and can freely slide in a left-right direction in the drawing. 
     Therefore, even if the through hole  36  is closed with the puncture repair agent and brought into the non-communicating state, it is possible to easily bring another non-communicating through hole  36  into the communicating state by dismounting the tire off the rim and sliding the member  37 . 
       FIG. 11B  is a drawing which illustrates another modification of the member  37  in the second embodiment. 
     The member  37  is a ring-shaped plate member which slides on a predetermined region of the face of the housing  22 . The through holes  36  are arranged in a circular pattern corresponding to the ring shape of the member  37 . The through holes  36  are closed with the member  37  to interrupt communication between the tire cavity area and the inner space  38  in the housing  22 . The member  37  which is a plate member is notched on a part of a circumference of the ring shape and at least one through hole  36  positioned at the notched portion is in a communicating state. 
     The member  37  is engaged with the groove portions  39  provided to correspond to an outer peripheral portion and an inner peripheral portion of the ring-shaped member  37  and can freely slide in the circumferential direction in the drawing. Therefore, even if the through hole  36  is closed with the puncture repair agent and brought into a non-communicating state, a worker will dismount the tire off the rim and can slide the member  37  in the circumferential direction of the ring shape to thereby easily bring one of the non-communicating through holes  36  into a communicating state. 
       FIGS. 12A and 12B  are drawings which illustrates yet another embodiment (a third embodiment) of the through hole  36  in the transmitting device  16 . 
     The housing  22  is provided with at least one through hole  36  passing through the wall of the housing  22  to communicate between the inner space  38  in the housing  22  and the tire cavity area as illustrated in  FIG. 12A . Furthermore, the housing  22  has protrusions  80  protruding from the face of the housing  22  and recessed portions  82  formed in a position corresponding to the positions of the protrusions  80  on an opposite side (on a side of the inner space  38 ) of the wall of the housing  22  from the protrusions  80 . The wall portions of the housing  22  in the positions of the recessed portions  82  are formed as thin-walled portions having smaller wall thickness than the portion around them. 
     By breaking off the protrusion  80  as illustrated in  FIG. 12A , the through hole  36  is formed in the position of the recessed portion  82 . In other words, the wall between a bottom portion of the protrusion  80  and a bottom face of the recessed portion  82  is thin and the thin-walled portion of the wall of the housing  22  is removed simultaneously with the protrusion  80  when the protrusion  80  is broken off to thereby form the through hole  36  as illustrated in  FIG. 12B . 
     Even if at least one through hole  36  in the communicating state is closed with the puncture repair agent and brought into the non-communicating state, a worker will dismount the tire off the rim and break off the protrusion  80  to thereby easily form a new communicating through hole  36 . Such a mechanism for forming the through hole by using the protrusion  80  and the recessed portion  82  can be added to the transmitting device  16  in the first embodiment and the second embodiment and their modifications described above. 
     Regions around the opening portions of all the through holes  36  in the first embodiment and the second embodiment and their modifications and the third embodiment are preferably water-repellent faces. Even if the puncture repair agent spatters on the water-repellent face, liquid drops of the spattered puncture repair agent are easily repelled from the water-repellent face and therefore it is highly unlikely that the puncture repair agent adheres to the opening portion of the through hole  36  and solidifies. As material of the water-repellent face, silicon-based resin, fluorine-based resin, a modified resin obtained by grafting an organosilyl group or a fluoroalkyl group, or the like is used, for example. The region around the opening portion of the through hole  36  may be provided with microscopic asperities that exert water repellency. 
     Moreover, the opening area of the opening portion of the through hole  36  is preferably 0.4 mm 2  or smaller. When the opening area of the opening portion is 0.4 mm 2  or smaller, the puncture repair agent is highly unlike to enter the through hole  36  due to the action of the surface tension even if the puncture repair agent adheres to the opening portion of the through hole  36 . 
     Although the transmission device and the tire condition monitoring system according to the invention have been described above in detail, the transmission device and the tire condition monitoring system according to the invention are not limited to the embodiments described above but may be improved or modified in various ways without departing from the gist of the invention.

Technology Classification (CPC): 1