BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a tire pressure sensing device and a tire pressure sensing method, and more particularly to a wireless tire pressure sensing device and a wireless tire pressure sensing method to facilitate setting and modifying a standard tire pressure of the wireless tire pressure sensing device after the wireless tire pressure sensing device is mounted in a tire. 
         [0003]    2. Description of the Related Art 
         [0004]    With reference to  FIG. 7 , a conventional wireless tire pressure monitoring system (WTPMS) has multiple wireless tire pressure sensors  71 ˜ 74  and a monitoring unit  70 . The wireless tire pressure sensors  71 ˜ 74  are respectively mounted in tires of a vehicle. The monitoring unit  70  is mounted inside the vehicle. Each wireless tire pressure sensor  71 ˜ 74  has a battery, a sensing element, a control unit with embedded or external memory, a high-frequency transmitting circuit and a low-frequency circuit. Each wireless tire pressure sensor  71 ˜ 74  is configured with one set of dedicated code having at least 8 bits when shipped out of the factory. 
         [0005]    When the WTPMS is activated, each wireless tire pressure sensor  71 ˜ 74  regularly or irregularly transmits detected information and the dedicated codes to the monitoring unit  70  through the high-frequency transmitting circuit by means of a fixed coding method. After receiving data, the monitoring unit  70  compares the received data with the dedicated codes to determine if the received data are transmitted from one of the wireless tire pressure sensors  71 ˜ 74  of the vehicle or from other vehicles. After determining that the data are transmitted from one of the wireless tire pressure sensor  71 ˜ 74  mounted in one of the tires of the vehicle, the monitoring unit  70  further decodes tire pressure, tire temperature and other detected relevant values of the tire. 
         [0006]    Manufacturers normally store standard tire pressure, low pressure threshold, and other relevant threshold values in a memory of the monitoring unit  70  before delivering the WTPMS. Hence, after comparing the received tire pressure and other relevant values with the preset threshold values, the monitoring unit  70  determines if the tire is in an abnormal condition. 
         [0007]    Although most WTPMSs store data such as standard tire pressure or threshold values in the memory of the monitoring unit  70 , some wireless tire pressure sensors have relevant tire pressure pre-stored prior to delivery so that the wireless tire pressure sensors can intensively transmit data to inform the monitoring unit  70  of variation and irregularity of abnormal tires for alerting drivers ahead of time when the detected tire pressure or other detected values exceed the preset threshold values. 
         [0008]    However, tire pressure has not been standardized yet for various vehicles on the road or for sales. Vehicles varying in model, weight or tire type may have different tire pressure values for their tires. For example, certain car owners prefer to replace original tires of their vehicles with high speed tires requiring much higher standard tire pressure than that of the original tires. If the threshold values remain the same, malfunction or misjudgment of the WTPMS easily arises. As a result, when the desired tire pressure is different from the preset tire pressure, service personnel of a service center or a tire store must manually adjust the threshold valves in the monitoring unit  70 . As the threshold value calculation method varies from WTPMS to WTPMS and the procedure for adjusting the threshold values in the monitoring unit is complicated, the adjusting procedure is not easy to be correctly conducted. 
         [0009]    To cope with the foregoing problems, the tire pressure sensor can be mounted in a tire and wirelessly transmits detected tire pressure values to a master control unit for drivers to understand current tire pressure condition. The master control unit computes an average tire pressure value of the two front wheels and the two rear wheels and stores the value therein as a pressure warning value upon detecting tire pressure of the front wheels and the rear wheels. It is unnecessary for such solution to set up the pressure warning values for different types of vehicle models prior to their delivery. The tire pressure sensors of the solution can be universally applied to any kind of vehicle model or tire. 
         [0010]    However, the above solution only tackles the setup issue of the monitoring unit  70  while leaving the setup issue of the wireless tire pressure sensors unresolved. 
         [0011]    Additionally, as certain wireless tire pressure sensors are pre-stored with threshold values or standard tire pressure therein and are mounted and sealed in tires prior to their shipment, the threshold values in the wireless tire pressure sensors cannot be adjusted after their delivery. Accordingly, manufacturers of the wireless tire pressure sensors need to produce various wireless tire pressure sensors having different threshold values to meet the need of different threshold values, and inevitably build up the stocking pressure on inventory management for the manufacturers. 
       SUMMARY OF THE INVENTION 
       [0012]    A first objective of the present invention is to provide a wireless tire pressure sensing method to facilitate setting and modifying a standard tire pressure of a wireless tire pressure sensing device after the wireless tire pressure sensing device is mounted in a tire. 
         [0013]    To achieve the foregoing objective, the method for setting a standard tire pressure of a wireless tire pressure sensing device is performed in a tire pressure setup mode and has steps of: 
         [0014]    counting time until a time period ends; 
         [0015]    detecting a current tire pressure; and 
         [0016]    setting the current tire pressure as the standard tire pressure. 
         [0017]    Preferably, the wireless tire pressure sensing device is adapted to be mounted in each tire of a vehicle, the tire pressure in each tire is adjusted to the standard tire pressure according to a requirement of the vehicle, the tire is maintained at the standard pressure for the time period, and after the time period is over, the wireless tire pressure sensing device detects the current tire pressure and automatically sets the current tire pressure as the standard tire pressure of the tire. 
         [0018]    To achieve the foregoing objective, an alternative method for setting a standard tire pressure of a wireless tire pressure sensing device is performed in a tire pressure setup mode and has steps of: 
         [0019]    determining if a setup instruction is received; 
         [0020]    if positive, sensing a current tire pressure; and 
         [0021]    setting the current tire pressure as a standard tire pressure. 
         [0022]    Preferably, the wireless tire pressure sensing device is adapted to be mounted in each tire of a vehicle, the tire pressure of each tire is adjusted to the standard tire pressure according to a requirement of the vehicle, the setup instruction is externally transmitted to the wireless tire pressure sensing device, and the wireless tire pressure sensing device senses and sets the current tire pressure as the standard tire pressure after receiving the setup instruction. 
         [0023]    Preferably, the wireless tire pressure sensing device further transmits out data having the standard tire pressure. 
         [0024]    A second objective of the present invention is to provide a wireless tire pressure sensing device for easily setting a standard tire pressure thereof. 
         [0025]    To achieve the foregoing objective, a wireless tire pressure sensing activation device has a micro-controller, a low-frequency transmitting circuit, a high-frequency receiving circuit and a power supply. The low-frequency transmitting circuit is connected to an output terminal of the micro-controller for transmitting a setup instruction to the wireless tire pressure sensing device. The high-frequency receiving circuit is connected to an input terminal of the micro-controller for receiving data having the standard tire pressure from the wireless tire pressure sensing device. The power supply supplies an operating power to the micro-controller, the low-frequency transmitting circuit and the high-frequency receiving circuit. 
         [0026]    After a wireless tire pressure sensing device is mounted in a tire and activated, an operation personnel first inflates the tire to a desired tire pressure and employs the wireless tire pressure sensing activation device to transmit a setup instruction to the wireless tire pressure sensing device. The wireless tire pressure sensing device senses and sets up a current tire pressure as the standard tire pressure, and transmits out data having the standard tire pressure. 
         [0027]    A third objective of the present invention is to provide a wireless tire pressure sensing device to facilitate entering a setup mode by means of external activation. 
         [0028]    To achieve the foregoing objective, a wireless tire pressure sensing device has a micro-controller, at least one sensing chip, a high-frequency transmitting circuit, a sensing element and a power supply. The at least one sensing chip is respectively connected to at least one input terminal of the micro-controller, and detects tire pressure and temperature inside a tire. The high-frequency transmitting circuit is connected to an output terminal of the micro-controller. The sensing element is respectively connected to an input terminal of the micro-controller for receiving a setup instruction. The power supply supplies an operating power to the micro-controller, the at least one sensing chip, the high-frequency transmitting circuit and the sensing element. 
         [0029]    The above wireless tire pressure sensing device can be externally activated to set up the standard tire pressure. After a driving element externally approaches and is continuously sensed by the sensing element for a period of time, the wireless tire pressure sensing device starts sensing and setting up a standard tire pressure. 
         [0030]    Based on the foregoing features, the present invention has the following advantages. 
         [0031]    1. Manufacturers do not need to stock wireless tire pressure sensing devices having various standard tire pressures or threshold values so as not to build up the stocking pressure on inventory management. 
         [0032]    2. The standard tire pressure or threshold value can be easily customized and modified by the foregoing method based on customer&#39;s demand. 
         [0033]    Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]      FIG. 1A  is a functional block diagram of a first embodiment of a wireless tire pressure sensing device in accordance with the present invention; 
           [0035]      FIG. 1B  is a functional block diagram of a second embodiment of a wireless tire pressure sensing device in accordance with the present invention; 
           [0036]      FIG. 2  is a flow chart of a first embodiment of a method for setting a standard tire pressure in accordance with the present invention; 
           [0037]      FIG. 3  is a flow chart of a second embodiment of a method for setting a standard tire pressure in accordance with the present invention; 
           [0038]      FIG. 4A  is a functional block diagram of a first embodiment of a wireless tire pressure sensing activation device communicating with a second embodiment of a wireless tire pressure sensing device in accordance with the present invention; 
           [0039]      FIG. 4B  is a functional block diagram of a second embodiment of a wireless tire pressure sensing activation device communicating with the wireless tire pressure sensing device in  FIG. 4A ; 
           [0040]      FIG. 5  is a flow chart of a first embodiment of a method for modifying a standard tire pressure in accordance with the present invention; 
           [0041]      FIG. 6  is a flow chart of a second embodiment of a method for modifying a standard tire pressure in accordance with the present invention; and 
           [0042]      FIG. 7  is a schematic view of a conventional wireless sensing system mounted in a vehicle. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0043]    With reference to  FIGS. 1A and 1B , a wireless tire pressure sensing device  10  in accordance with the present invention has a micro-controller  11 , at least one sensing chip  12 , a high-frequency transmission circuit  13  and a power supply  15 . The at least one sensing chip  12  is respectively connected to at least one input terminal of the micro-controller  11 , and detects tire pressure and other relevant sensed values, such as tire temperature and the like. The high-frequency transmission circuit  13  is connected to an output terminal of the micro-controller  11 , and transmits the sensed values of tire pressure and others to a monitoring unit. The power supply  15  supplies an operating power to the foregoing components. The high frequencies used by the wireless tire pressure sensing device  10  may be 315 MHz, 433 MHz, 447 MHz and other open frequencies designated by local governments. The low frequencies used by the wireless tire pressure sensing device  10  are lower frequencies relative to the high frequencies, and may be 125 kHz, 13.56 MHz or other open frequencies designated by local governments. The sensing chip  12  may be further integrated with other sensing function or sensing element, such as an acceleration sensor  16 A as shown in  FIG. 1A  or a magnetic sensor  16 B as shown in  FIG. 1B , to detect the sensed values other than tire pressure and tire temperature. 
         [0044]    With reference to  FIG. 2 , a first embodiment of a method for setting a standard tire pressure of a wireless tire pressure sensing device in accordance with the present invention enables the micro-controller  11  to perform the following steps of: 
         [0045]    starting  201 ; 
         [0046]    counting time  202 ; 
         [0047]    determining if a time period ends  203 ; 
         [0048]    if positive, detecting a current tire pressure  204 ; and 
         [0049]    setting the current tire pressure as a standard tire pressure  205 . 
         [0050]    Instead of before delivery, the method for setting a standard tire pressure can be carried out after delivering the wireless tire pressure sensing device  10  in accordance with the characteristics and actual requirements of each tire. The method can be substantially implemented as follows. 
         [0051]    The wireless tire pressure sensor preset with none of any standard tire pressure is mounted in each tire of a vehicle. If the wireless tire pressure sensing device  10  is deactivated, the wireless tire pressure sensing device  10  is activated to enter a setup mode. In accordance with the actual demand of a vehicle, the tire pressure is adjusted to a standard value and the tire pressure is maintained at the standard value for the pre-defined time period. The pre-defined time period is a time period within which the tire pressure should be stable, and may be 30 minutes or longer or shorter in duration. After the micro-controller determines that the pre-defined time period ends, the sensing chip  12  senses a current tire pressure, and automatically sets the tire pressure as the standard tire pressure. 
         [0052]    Given the above procedure, the standard tire pressure of the wireless tire pressure sensing device  10  can be easily set up. 
         [0053]    In the foregoing method, the wireless tire pressure sensor  10  automatically sets the detected tire pressure as the standard tire pressure after the pre-defined time period ends. Besides the automatic set up means, the wireless tire pressure sensing device  10  can be activated by an external signal to passively set up a detected tire pressure as a standard tire pressure. With reference to  FIG. 3 , a second embodiment of a method for setting a standard tire pressure in accordance with the present invention has the following steps of: starting  301 ; 
         [0054]    determining if a setup instruction is received  302 ; 
         [0055]    if positive, sensing a current tire pressure  303 ; and 
         [0056]    setting the current tire pressure as a standard tire pressure  304 . 
         [0057]    The passive tire pressure set up method can be substantially implemented as follows. 
         [0058]    The wireless tire pressure sensing device  10  preset with none of any standard tire pressure is mounted in a tire. The wireless tire pressure sensing device  10  is activated to enter a setup mode. In accordance with the actual demand of a vehicle, the tire pressure is adjusted to a standard value. Then, a setup instruction is transmitted externally to the wireless tire pressure sensing device  10 . The micro-controller  11  senses a current tire pressure through the sensing chip  12  and automatically sets the current tire pressure as the standard tire pressure. 
         [0059]    Furthermore, besides actively or passively setting the sensed tire pressure as the standard tire pressure, the wireless tire pressure sensor  10  can further transmit the standard tire pressure out  305  to an external device to serve as a critical value for the monitoring unit to compute and set alerts accordingly. 
         [0060]    With reference to  FIG. 4A , a first embodiment of a wireless tire pressure sensing activation device communicating with a second embodiment of a wireless tire pressure sensing device in accordance with the present invention is shown. The wireless tire pressure sensing device has a micro-controller  11 , a sensing chip  12 , a high-frequency transmitting circuit  13 , a low-frequency receiving circuit  14  and a power supply  15 . The low-frequency receiving circuit  14  is connected to an input terminal of the micro-controller  11  and receives a setup instruction from the wireless tire pressure sensing activation device. 
         [0061]    The wireless tire pressure sensing activation device has a micro-controller  21 , a low-frequency transmitting circuit  22  and a power supply  23 . The low-frequency transmitting circuit  22  is connected to an output terminal of the micro-controller  21 , and transmits a setup instruction to the wireless tire pressure sensing device  10  under the control of users. The power supply supplies an operating power to the micro-controller  21  and the low-frequency transmitting circuit  22 . 
         [0062]    With reference to  FIG. 4B , a second embodiment of a wireless tire pressure sensing activation device communicating with the wireless tire pressure sensing device is shown. Besides transmitting the setup instruction to the wireless tire pressure sensing device  10 , the wireless tire pressure sensing activation device further receives data of the standard tire pressure transmitted from the wireless tire pressure sensing device  10 . In the present embodiment, the wireless tire pressure sensing activation device additionally has a high-frequency receiving circuit  24 . The high-frequency receiving circuit  24  is connected to an input terminal of the micro-controller  21  and receives data transmitted from the wireless tire pressure sensing device  10 . 
         [0063]    The wireless tire pressure sensing activation device  20  can serve as a standalone device dedicated to transmit the setup instruction to and receive the standard tire pressure from the wireless tire pressure sensing device  10 , and may be a handheld device, embedded in the monitoring unit of a WTPMS or mounted in the vicinity of a wheel of a vehicle. 
         [0064]    As mentioned, the wireless tire pressure sensing activation device  20  can transmit the setup instruction to the wireless tire pressure sensing device  10  through the low-frequency transmitting circuit  22  so that the wireless tire pressure sensing device  10  senses and sets up the standard tire pressure in response to the setup instruction. Besides externally activated by the low-frequency signal, the wireless tire pressure sensing device  10  can be activated by other external means. The external means is a sensing element that is mounted inside the wireless tire pressure sensing device  10 . The sensing element detects a signal of a setup instruction in collaboration with a control procedure of the micro-controller  11  after a driving element externally approaches and is continuously sensed by the sensing element for a period of time, such as 1 to 3 seconds. The sensing element then starts sensing and setting up a standard tire pressure. The sensing element may be a magnetic sensing element, and the driving element may be a magnetic activation device, such as a magnet. 
         [0065]    As the wireless tire pressure sensing device is mounted and sealed in a tire before the shipment of the tire, the standard tire pressure of the wireless tire pressure sensing device should be adjusted through a contactless method. 
         [0066]    With reference to  FIG. 5 , a contactless method for modifying a standard tire pressure in accordance with the present invention has the following steps of: 
         [0067]    starting  501 ; 
         [0068]    determining if a tire pressure is zero or below a critical value  502 ; 
         [0069]    when the tire pressure is zero or below the critical value, counting time  503 ; 
         [0070]    determining if a first time period ends  504 ; 
         [0071]    if positive, detecting a current tire pressure  505 ; 
         [0072]    counting time  506 ; 
         [0073]    determining if a second time period ends  507 ; and 
         [0074]    when the second time period ends, setting the detected tire pressure as a standard tire pressure  508 . 
         [0075]    The above method can be substantially implemented as follows. After a tire is deflated and the wireless tire pressure sensing device in the tire stays at a pressure-free condition for over a preset first time period, for example 3 minutes, the tire is inflated to a standard tire pressure to be set up. The wireless tire pressure sensing device in the tire is maintained at the standard tire pressure for over a preset second time period, for example 5 minutes. After the second time period is over, the wireless tire pressure sensing device automatically sets the detected tire pressure as the standard tire pressure. 
         [0076]    With reference to  FIG. 6 , a second embodiment of a contactless method for modifying a standard tire pressure in accordance with the present invention has the following steps of: 
         [0077]    entering a standard tire pressure modification mode  601 ; 
         [0078]    determining if receiving a resetting instruction  602 ; 
         [0079]    after receiving the resetting instruction, detecting a current tire pressure  603 ; and 
         [0080]    setting the current tire pressure as a standard tire pressure  604 . 
         [0081]    The above method can be substantially implemented as follows. A tire is inflated to a standard tire pressure to be set up. The wireless tire pressure sensing activation device outside the tire is employed to transmit the resetting instruction to the wireless tire pressure sensing device. After the wireless tire pressure sensing device receives the resetting instruction, the wireless tire pressure sensing device sets the detected current tire pressure as the standard tire pressure, or further transmits out data of the standard tire pressure to the monitoring unit for computation. 
         [0082]    Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
A wireless tire pressure sensing device, a method for setting a standard tire pressure thereof and a wireless tire pressure sensing activation device adjust the tire pressure of each tire in a vehicle to a standard tire pressure according to a requirement of the vehicle after the wireless tire pressure sensing device is mounted in each tire, maintain each tire at the standard tire pressure for a preset time period or employ the wireless tire pressure sensing activation device to transmit a setup instruction to the wireless tire pressure sensing device to set a current tire pressure as the standard tire pressure. The wireless tire pressure sensing device can be set up with the standard tire pressure and conveniently modified. As no threshold value of tire pressure needs to be pre-stored, wireless tire pressure sensing devices with different threshold values are not necessarily prepared beforehand, thereby effectively lowering the stocking pressure on inventory management.