Abstract:
A receiver of a tire status monitoring apparatus which can specify tire mounting positions and does not require initial registration work. The tire status monitoring apparatus includes a plurality of transmitters which are provided on the respective tires of a vehicle and transmit data indicating statuses of the respective tires. The data includes an identification code to identify each tire, and the receiver is supplied with an activation signal to activate a drive source of the vehicle. The receiver includes a reception unit which receives the data from the transmitters, and a control circuit which is connected to the reception unit and collates the identification code included in the data upon detection of the activation signal and specifies, based on the identification code, each transmitter which has transmitted the data.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a wireless type tire status monitoring apparatus capable of checking the status of a tire, such as tire air pressure while the driver remains in the vehicle, and a receiver for such a tire status monitoring apparatus. More particularly, this invention relates to a tire status monitoring apparatus and a receiver for the tire status monitoring apparatus which specifies which one of transmitters provided on a plurality of tires is a data sender.  
           [0002]    Conventionally, a wireless type tire status monitoring apparatus has been used to enable the driver check the statuses of a plurality of tires provided on a vehicle while the driver remains inside the vehicle passenger compartment. Attached to the tires are respective transmitters which measure the air pressure statuses of the associated tires and transmit data by radio indicative of the measured statuses of the tires. The body of the vehicle is provided with a receiver which receives transmitted data from each transmitter.  
           [0003]    Each transmitter sends data indicating the status of the associated tire to a single receiver. The receiver should discriminate from which one of the transmitters on the tires has transmitted the data that was received. Therefore, each transmitter is assigned with an inherent ID code. Each transmitter transmits data indicating the status of the associated tire together with the ID code. Based on the ID code, therefore, the receiver can identify the transmitter which is the sender of the data (see Japanese Patent Laid-Open Publication No. 2000-103209).  
           [0004]    To allow the receiver to identify the transmitter which is the sender of data, however, the ID codes of the transmitters in the associated tires provided on the vehicle should be registered in the receiver beforehand. What is more, at the time of initial registration, it is necessary to associate the ID codes with the mounting positions of the tires to which the transmitters having the ID codes are respectively mounted. When new tires are mounted on a vehicle or the mounting positions of the tires with respect to the vehicle are changed, therefore, initial registration should always be performed. Such initial registration involving manual work is difficult and takes time.  
         SUMMARY OF THE INVENTION  
         [0005]    One aspect of the present invention is a receiver for a tire status monitoring apparatus that monitors statuses of a plurality of tires provided on a vehicle. The tire status monitoring apparatus includes a plurality of transmitters, provided on the tires respectively, for transmitting data indicating statuses of the respective tires. The data includes an identification code to identify each tire. The receiver is supplied with an activation signal to activate a drive source of the vehicle. The receiver includes a reception unit which receives the data from the transmitters. A control circuit is connected to the reception unit. Upon detection of the activation signal, the control circuit collates the identification code included in the data and specifies, based on the identification code, each transmitter which has transmitted the data.  
           [0006]    Another aspect of the present invention is a tire status monitoring apparatus for monitoring statuses of a plurality of tires provided on a vehicle. The tire status monitoring apparatus includes a plurality of transmitters provided on the tires respectively, which detect statuses of the associated tires and transmit data indicating the detected statuses of the tires. The data includes an identification code to identify each tire. A receiver is provided on the vehicle. The receiver receives the data from the plurality of transmitters and is supplied with an activation signal for activating a drive source of the vehicle. The receiver includes a control circuit. Upon detection of the activation signal, the control circuit collates the identification code included in the data and specifies, based on the identification code, each transmitter which has transmitted the data.  
           [0007]    Another aspect of the present invention is a method of monitoring statuses of a plurality of tires provided on a vehicle. The tires include a plurality of transmitters which generate data indicating statuses of the respective tires. The vehicle includes a receiver which receives the data from the transmitters. The data includes an identification code to identify each tire. The method includes detecting an activation signal for activating a drive source of the vehicle, transmitting a request signal for generating the data and transmitting the data to the receiver to the plurality of transmitters, when the activation signal is detected, receiving the data from the plurality of transmitters, collating the identification code included in the data, and specifying each transmitter which has transmitted the data, based on the identification code.  
           [0008]    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  
       [0009]    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:  
         [0010]    [0010]FIG. 1 is a schematic structural diagram of a tire status monitoring apparatus according to one embodiment of the present invention;  
         [0011]    [0011]FIG. 2 is a schematic block diagram of a transponder of the tire status monitoring apparatus in FIG. 1;  
         [0012]    [0012]FIG. 3 is a schematic block diagram of a transceiver of the tire status monitoring apparatus in FIG. 1; and  
         [0013]    [0013]FIG. 4 is a flowchart illustrating the operation of the transceiver in FIG. 3. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]    [0014]FIG. 1 is a schematic structural diagram of a vehicle  10  including a tire status monitoring apparatus  1  according to one embodiment of the present invention. As shown in FIG. 1, the tire status monitoring apparatus  1  includes four transponders (transmitters)  30  provided on respective tires  20  of the vehicle  10  and a single transceiver (receiver for the tire status monitoring apparatus)  40  provided on the body  11  of the vehicle  10 .  
         [0015]    Each transponder  30  is fixed inside the associated tire  20 , e.g., on the wheel  21  of the tire  20 . Each transponder  30  measures the status of the associated tire  20 , i.e., air pressure in the associated tire  20 , and transmits transponder data including air pressure data acquired by the measurement. The transponder data is wirelessly transmitted to the transceiver  40  from each transponder  30 .  
         [0016]    The transceiver  40  is provided at a predetermined location of the body  11  and operates on power from, for example, the battery (not shown) of the vehicle  10 . The transceiver  40  has four antennae (reception units)  41  respectively corresponding to the four transponders  30 . Each antenna  41  is connected to the transceiver  40  via a cable  42 . The transceiver  40  generates a request signal at a predetermined time interval and transmits the request signal from each antenna  41 . Each transponder  30  generates induced power based on the request signal and transmits transponder data using the induced power. The transceiver  40  receives the transponder data transmitted from each transponder  30  mainly via the associated antenna  41 .  
         [0017]    A display  50  is placed in a visible range of the driver of the vehicle  10 , such as in the passenger compartment. The display  50  is connected to the transceiver  40  via a cable  43 . An engine  60  or the drive source of the vehicle  10  is mounted in the front portion of the vehicle  10 .  
         [0018]    As shown in FIG. 2, each transponder  30  includes a controller  31 , a pressure sensor  32 , a transmission/reception circuit  33  and a coil antenna  34 . The controller  31  is, for example, a microcomputer including a CPU (Central Processing Unit), ROM (Read Only Memory) and RAM (Random Access Memory). Inherent ID codes are registered beforehand in the ROM. The ID codes are used to identify the four transponders  30  provided on the vehicle  10 .  
         [0019]    The pressure sensor  32  measures the air pressure in the tire  20  and supplies the controller  31  with air pressure data acquired by the measurement. The controller  31  generates transponder data including the air pressure data and the ID code registered in the internal memory, and supplies the transmission/reception circuit  33  with the transponder data.  
         [0020]    The transmission/reception circuit  33  encodes and modulates the transponder data, then transmits the encoded and modulated transponder data via the coil antenna  34 . The coil antenna  34  generates induced power based on, for example, the request signal sent from the associated antenna  41 .  
         [0021]    The transmission/reception circuit  33  supplies the induced power to the controller  31 . The controller  31  controls the transponder  30  with the supplied induced power. That is, the transponder  30  operates on the power induced in the coil antenna  34 . The controller  31  and the transmission/reception circuit  33  are formed on a single-chip semiconductor substrate and integrated into an IC  35 .  
         [0022]    As shown in FIG. 3, the transceiver  40  includes a controller  44  which processes transponder data received via the antenna  41  and a transmission/reception circuit  45 . The controller  44  is, for example, a microcomputer including a CPU, ROM and RAM. Inherent ID codes are registered in an internal memory, e.g., RAM, of the controller  44 .  
         [0023]    The transmission/reception circuit (reception unit)  45  receives the transponder data from each transponder  30  mainly via the associated antenna  41 . The transmission/reception circuit  45  demodulates and decodes the encoded and modulated transponder data, and then supplies the resultant transponder data to the controller  44 .  
         [0024]    Based on the received transponder data, the controller  44  determines the air pressure of the tire  20  associated with the sender transponder  30 . The controller  44  displays data about the air pressure on the display  50 . In the case where the air pressure is particularly abnormal, warning of the event is displayed on the display  50 . Further, the controller  44  receives from a key cylinder  80  a signal (activation signal) indicating the ON action of a key switch  70  which activates the drive source of the vehicle  10 , e.g., the engine  60 . In addition, the controller  44  stores an inherent ID code included in transponder data into its own internal memory, e.g., RAM, when a predetermined condition is met. Therefore, an inherent ID code indicating the sender transponder  30  is registered in the internal memory of the controller  44 .  
         [0025]    The controller  44  transmits a request signal to the transmission/reception circuit  45  from the antenna  41  at a predetermined time interval. Based on the request signal, induced power is generated in the coil antenna  34  of the transponder  30 . The pressure sensor  32  measures air pressure in the tire  20  using that power. The transponder  30  transmits transponder data including air pressure data via the coil antenna  34 . The transceiver  40  receives the transponder data transmitted from each transponder  30  mainly via the associated antenna  41 .  
         [0026]    The operation of the transceiver  40 , specifically, the controller  44  of the transceiver  40 , will be described next referring to the flowchart shown in FIG. 4.  
         [0027]    First, the controller  44  determines if the key switch  70  which activates the engine  60  is turned on by the driver (S 1 ). Specifically, the controller  44  determines if the activation signal from the key cylinder  80 , originated from the ON action of the key switch  70 , has been detected. When it is determined that the key switch  70  has been set to on (YES in S 1 ), the transceiver  40  generates a request signal and sequentially transmits the request signal from the individual antennae  41  (S 2 ). Then, induced power is generated in the coil antenna  34  of the transponder  30  corresponding to each antenna  41 . With the induced power, the pressure sensor  32  of the transponder  30  measures air pressure inside the associated tire. The transponder  30  transmits transponder data including the measured air pressure data via the coil antenna  34 .  
         [0028]    The transceiver  40  receives the transponder data, sent from the transponder  30 , via the associated antenna  41  (S 3 ). The controller  44  determines whether the ID code included in the received transponder data (hereinafter called a transponder ID code) matches with an ID code registered in the internal memory of the controller  44  (hereinafter called a registered ID code) (S 4 ). In the case where the transponder ID code matches with the registered ID code (YES in S 4 ), the transceiver  40  terminates the process.  
         [0029]    In the case where the transponder ID code does not match with the registered ID code (NO in S 4 ), on the other hand, the controller  44  determines if the transponder data has been received by a first predetermined number of times (e.g., n times) (S 5 ). In the case where the number of receptions of the transponder data has not reached the first predetermined number (NO in S 5 ), the controller  44  returns to the process of step S 2  and transmits the request signal.  
         [0030]    In the case where the number of receptions of the transponder data has reached the first predetermined number (YES in S 5 ) and the transponder ID codes received by the first predetermined number of times match with one another a second predetermined number of times or more (e.g., m times where m≦n) (YES in S 6 ), on the other hand, the controller  44  determines that the ID code has been changed. That is, the controller  44  determines that the tire  20  having the transponder  30  has been changed. Specifically, the controller  44  determines that a new tire  20  has been attached to the vehicle  10 . Alternatively, the controller  44  determines that the mounting position of the tire  20  with respect to the vehicle  10  has been changed. The controller  44  stores the changed ID code in the internal memory of the controller  44 . As a result, the changed ID code is newly registered in the internal memory of the controller  44  (S 7 ).  
         [0031]    In the case where the transponder ID codes do not match with one another the second predetermined number of times or more in step S 6 , on the other hand, the controller  44  executes other processes (S 8 ). One of the other processes possible may be a process which does not change the registered ID code considering that the transponder ID code has not been changed. In this case, the registered ID code is not changed and the ID code registered at that time remains as it is until the key switch  70  is set to on once again.  
         [0032]    The transceiver  40  of the tire status monitoring apparatus  1  according to this embodiment has the following advantages.  
         [0033]    (1) In the case where the key switch  70  of the vehicle  10  is set to on, the transceiver  40  transmits a request signal to the transponders  30  at predetermined time intervals. In response to the request signal, the controller  44  of the transceiver  40  determines whether the transponder ID code sent from the transponder  30  matches with an ID code registered in the controller  44 . In the case where the two ID codes do not match with each other and the transponder ID codes received by the first predetermined number of times match with one another the second predetermined number of times or more, the controller  44  determines that the ID code has been changed. In this case, the controller  44  determines that the tire  20  having the transponder  30  has been changed. The controller  44  stores the changed ID code into the internal memory, e.g., RAM. As a result, the changed ID code is registered in the internal memory of the controller  44 . Based on the ID code, therefore, the sender transponder  30  is specified. Even if the tire  20  has been changed, therefore, it is possible to specify the mounting position of the tire  20  and it is unnecessary to carry out the initial registration work for the ID code.  
         [0034]    (2) Only when the key switch  70  of the vehicle  10  is set to on, the controller  44  of the transceiver  40  determines whether an ID code has been changed or not. Therefore, the transceiver  40  can efficiently register the ID code into the internal memory of the controller  44 , e.g., RAM. That is, in the case where the controller  44  receives transponder data from the transponder  30  while the vehicle  10  is stopped or is running, the controller  44  need not make a determination on the ID code nor perform registration again. This can reduce the burden of the controller  44 .  
         [0035]    (3) When the transponder ID code matches with a registered ID code, the transceiver  40  terminates the process without overwriting the registered ID code. Even if the ID codes match with each other, therefore, the burden of the controller  44  can be relieved.  
         [0036]    (4) The transceiver  40  determines whether the ID code has been changed or not in accordance with the ON signal from the key switch  70  of the vehicle  10 . Therefore, no new signal is needed to determine if the ID code has been changed. That is, the transceiver  40  determines if the ID code has been changed by effectively using the existing activation signal. This can permit the transceiver  40  to be easily attached to the vehicle  10 .  
         [0037]    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.  
         [0038]    The above-described embodiment may be adapted to a tire status monitoring apparatus that includes a plurality of transmitters which are provided on the respective tires  20 , have batteries, measure the statuses of the associated tires  20  and transmit data indicating the statuses of the tires  20  acquired in the measurement, and a receiver which receives data from those transmitters.  
         [0039]    The transceiver  40  may have a single common antenna  41  with respect to the four transponders  30 , or may have two antennae  41  respectively provided at the front portion and rear portion of the vehicle  10 .  
         [0040]    The drive source may be a hybrid engine comprised of, for example, an engine and a motor, or may be a motor.  
         [0041]    The transponder  30  may have a temperature sensor which measures the temperature inside the associated tire  20  so that temperature data in the tire  20  is transmitted to the transceiver  40 .  
         [0042]    The air pressure data may be data specifically indicating the value of the air pressure, or data simply indicating whether the air pressure lies within an allowable range or not.  
         [0043]    In the case where the transponder ID code does not match with a registered ID code, the controller  44  may determine that the transponder ID code has been changed and the tire  20  associated with the changed transponder ID code has been changed.  
         [0044]    The vehicle may be a two-wheel bicycle or motorcycle, a multi-wheel bus or tractor, or an industrial vehicle or the like (e.g., a forklift) provided with tires  20 . In case where the transponders  30  are provided on the tires of a tractor, the transceiver  40  and the display  50  are placed on the tractor.  
         [0045]    The transceiver  40  may be activated in accordance with the ON action of the key switch  70  of the vehicle  10 . In this case, after the key switch  70  is set to on, the transceiver  40  transmits a request signal to the transponders  30  and executes the ID code determining process of the above-described embodiment.  
         [0046]    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.