Abstract:
A tire pressure-monitoring (TPM) system includes a TPM device directly mounted onto an air-pumping inlet on a tire. The TPM device further includes a mechanical triggering mechanism engaged to an air pressure through the air-pumping inlet pushing from an air filled in the tire. The triggering mechanism is triggered by a low tire pressure to turn on a micro-controller unit of the TPS device to send a radio frequency (RF) signal for warning a low tire-pressure of the tire. The tire pressure monitoring (TPS) system further includes a signal receiving system near a vehicle driver for receiving and processing the RF signal.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention is generally related to device configuration and method of a tire pressure-sensing (TPS) and low-pressure warning system. More particularly, this invention is related to system configuration and mechanical pressure switch design for implementing a compact tire pressure monitoring system. 
         [0003]    2. Description of the Related Art 
         [0004]    Conventional technologies and devices for measuring the changes of tire pressure are still faced with the difficulties that the signals of tire pressure measurements can only transmit to a limited distance and furthermore, the tire pressure measurement devices do not effective antitheft mechanisms. 
         [0005]    Generally there are two types of tire pressure monitoring systems (TPMS). The first type of TPMS is an indirect tire pressure monitoring system that monitoring the changes of tire pressures by monitoring the rotational speed differences as that detected and transmitted through the ABS speed transmitter. This type of TPMS has a limitation that the tire pressure monitoring operation would become ineffective when there are simultaneous tire-pressure changes occur in more than one tires. Also, the TPMS become unreliable when a vehicle is traveling at a speed more than one hundred kilometers per hour. A second type of tire pressure monitor system is a direct tire pressure monitoring system implemented with tire pressure measurement devices directly mounted on the tire. The tire pressures are measured and monitored continuously. Once the tire pressure in a tire is lower or higher than a threshold value, an alarm signal is generated. The direct type of TPMS has definite advantages of higher accuracy and reliability over the indirect type of TPMS. However, a discussed above, the direct TPMS devices still have limit capability to effectively transmit pressure monitoring signals and furthermore, there still lacks an antitheft device mechanism with the tire pressure monitoring devices directly mounted onto the tires. Practical application of the direct TPMS devices would still have the concerns that such devices may often be stolen and lost due to such limitations. 
         [0006]    Therefore, there is still need to design and manufacture a tire pressure monitor device and system that would enable those of ordinary skill in the art to overcome such difficulties and limitations. 
       SUMMARY OF THE INVENTION 
       [0007]    Accordingly, it is an aspect of the present invention to provide a tire-pressure monitoring system (TPMS) that includes a tire pressure signal transmission system that is automatically activated only when a tire pressure is lower than a threshold voltage to transmit a low tire pressure signal to a receiver such that the battery power of the TPMS of a sensing and signal transmitting system directly mounted on the tires can be preserved for long term operation. 
         [0008]    It is another aspect of this invention that the present invention provides a tire-pressure monitoring system (TPMS) that has an improved accuracy in detecting a low-pressure condition to transmit a warning signal such that the low-pressure condition can be accurately detected and timely corrected. 
         [0009]    It is another aspect of this invention that the present invention provides a tire-pressure monitoring system (TPMS) that has a low battery-power detection and reporting capability to send a warning signal to the user of the TPMS to alert the use that the battery power is low. The user of the TPMS system therefore can timely change the battery to maintain the battery power above a low battery power threshold and to continuously keep the TMPS in a good working condition. 
         [0010]    It is another aspect of this invention that the present invention provides a tire-pressure monitoring system (TPMS) that has a periodical signal transmission function. A signal transmission system mounted on each tire with tire pressure detection function is programmed to send a periodical signal to a signal receiving system mounted in the main panel near a driver. The user of the TPMS system is therefore kept informed about the operational condition of the tire-pressure monitor function when the periodical signals are received from each tire pressure monitoring devices mounted on the tires. 
         [0011]    Specifically, this invention discloses a method for monitoring a tire pressure of a tire on a car. The method includes a step of mounting a tire-pressure monitoring (TPM) device directly onto an air-pumping inlet on a tire. The method further includes a step of mechanically triggering a switch-on of a micro controller unit (MCU) of the TPM device to send an RF signal for warning a low tire-pressure of the tire when a tire-pressure of said tire is lower than a threshold tire-pressure. 
         [0012]    These and other objects, features and advantages of the present invention will no doubt become apparent to those skilled in the art after reading the following detailed description of the preferred embodiments that are illustrated in the several accompanying drawings. 
     
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         [0013]    The present invention can be better understood with reference to the following drawings. The components within the drawings are not necessarily to scale relative to each other, emphasis instead being placed upon clearly illustrating the principles of the present invention. 
           [0014]      FIG. 1  is a functional block diagram of a tire-pressure signal transmission system of this invention. 
           [0015]      FIG. 2  is a circuit diagram of the tire-pressure signal transmission system of  FIG. 1 . 
           [0016]      FIG. 3  is a functional block diagram of a tire-pressure signal receiver system of this invention. 
           [0017]      FIG. 4  is a circuit diagram of an RF signal receiver implemented in the tire-pressure signal receiver system of  FIG. 3 . 
           [0018]      FIG. 5  is a circuit diagram of the MCU signal processor implemented in the tire-pressure signal receiver system of  FIG. 3 . 
           [0019]      FIG. 6  is a circuit diagram of a signal display device implemented in the tire pressure signal receiver system of  FIG. 3 . 
           [0020]      FIG. 7  is a diagram for showing the detail structural configuration of the tire pressure-monitoring device as an exemplary embodiment of this invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    The tire pressure monitoring system of this invention is a direct tire pressure-monitor system with a tire pressure sensor installed as part of a tire pressure sensing-signal transmission system that is mounted directly on each tire. The tire pressure monitoring system continuously monitors the pressure in each fire and the tire pressure sensing-signal transmission system is activated to transmit a “tire pressure low” warning signal when a low-pressure threshold is reached in anyone of the tires of a vehicle. Referring to  FIG. 1  for a functional block diagram of a tire pressure sensor (TPS) signal transmission system  100  of this invention. The TPS signal transmission system includes a tire pressure-sensing device  110  that includes an oscillator for providing tire pressure-sensing signal with a specific frequency to a micro-controller unit (MCU processor  120 ) that carries out all the functions of signal processing and control. The MCU signal processing and control processor  120  further receives signals from an ID address encoder  125  to generate a tire pressure-monitoring signal for inputting to a signal transmitter  130  to transmit the signals to a receiver through an antenna  135 . 
         [0022]      FIG. 2  is a diagram for showing the circuit configuration of the signal transmission system  100 . The signal transmission system is operated with a low voltage of three volts thus consumes only small amount of electrical energy during the operation. The signal transmission system  100  includes a chip U 2  as a microprocessor to perform all the functions a MCU signal processor  120 , i.e., a micro controller unit. An input port JP 1  is connected to the MCU signal processor chip U 1  to write the ID specifically for a particular user. Another microprocessor chip U 1  is a surface acoustic oscillator and Q 1  as a transistor to function as a high frequency oscillating circuit. The signal transmission system  100  includes the MCU signal processor  120  is turned when the tire pressure sensing device  110  detects a low tire pressure lower than a threshold tire pressure. The low-pressure signal processed by the MCU signal processor U 1  is transmitted through resistor R 3  and R 1  to the high frequency oscillating transistor Q 1  with the transistor Q 1  functions with an inductor L 1 , a capacitors C 1  and C 2  as a three-point capacitor-type oscillator. The capacitor C 6  connecting to the high voltage Vcc to perform a filtering function for the oscillator while capacitor C 7  also connected to the high voltage Vcc to perform a filtering function for the MCU microprocessor U 1 . The capacitors C 3  a C 4  combined with the inductor L 2  forms a π shaped network and coupled through the capacitor C 5  to filter out the DC components of the signal to work with the antenna J 1 . 
         [0023]    In a specific exemplary embodiment, the antenna J 1  is provided to transmit signals of a frequency at approximately 433.92 MHZ. The signal transmission is carried out during a time when the tire is making a continuously rotational movement. In an exemplary embodiment, the antenna is formed as a screw-shaped antenna taking into consideration of the rotational movement thus generating blind spots due to the dynamic changes of the antenna&#39;s locations. However, even there are blind spots of signal transmission projected from the antenna that is rotating with the tire when the vehicle is moving, sufficient intensity of signals are received by a signal receiver to provide low pressure warning signals to a driver when a low pressure condition is detected by the tire-pressure sensing device. 
         [0024]    Referring to  FIG. 2  again, wherein the microprocessor U 2  combines with the capacitor C 7  and the input terminal JP 1  carries out the functions of the micro-controller unit (MCU). The capacitor C 7  functions as a filtering capacitor and JP 1  is an input port for receiving the ID-address from the encoder  125 . A battery provides power to the microprocessor U 2  with a negative potential electrode of the battery  13  connected to the ground terminal of the capacitor C 7  and a positive terminal of the battery  13  connected to an opposite terminal of the capacitor C 7  as a power source for providing power to the microprocessor U 2 . The connection of the positive terminal of the battery  13  to the capacitor C 7  is from the opposite side of the signal transmitting system shown in  FIG. 7 . As the tire pressure drops below a threshold, the switch to the battery is turned on and the MCU starts the functions of detecting the voltage of the battery and also sends a low tire pressure warning signal that includes an TPS ID-address for identifying the tire-pressure monitoring signal transmission system to the signal receiving system. The circuit components 
         [0025]    R 3 , R 1 , Q 1 , U 1 , L 1 , R 2 , C 6 , C 1 , C 2 , C 3 , L 2 , C 4 , C 5  and the antenna function as signal processing functional circuitry. The microprocessor U 1  performs a function of a surface acoustic wave oscillator to provide a basic RF frequency for carrying out the function of signal transmission. The combined circuits of Q 1  and R 3 , R 1 , Q 1 , L 1 , R 2 , C 1 , C 2  function as a waveform amplifier to amplify the signal received from the MCU. The amplified signals are then filtered through the filtering circuit comprised of C 3 , L 2 , C 4 , C 5  for transmitting through the antenna. 
         [0026]    According to the circuit diagram shown in  FIG. 2  above, the signal transmission system  100  as that implemented in the tire-pressure monitoring system (TPMS) of this invention has a low battery-power detection and reporting capability to send a warning signal to the user of the TPMS to alert the use that the battery power is low. A microcontroller unit (MCU) U 2  performs a function of checking the voltage of the battery. A battery low-voltage warning signal is generated by U 2  when output voltage of a battery is lower than a threshold voltage. The user of the TPMS system therefore can timely change the battery to maintain the battery power above a low battery power threshold and to continuously keep the TMPS in a good working condition. 
         [0027]    According to above circuit diagram it is another aspect of this invention that the present invention provides a tire-pressure monitoring system (TPMS) that has a periodical signal transmission function. A signal transmission system mounted on each tire with tire pressure detection function is programmed to send a periodical signal to a signal receiving system mounted in the main panel near a driver. The user of the TPMS system is therefore kept informed about the operational condition of the tire-pressure monitor function when the periodical signals are received from each tire pressure monitoring devices mounted on the tires. Specifically, the signal transmission system of  FIG. 2  includes a microprocessor U 2  that functions as a micro-controller unit (MCU) to periodically send a signal to a signal receiver mounted inside the car. The signal includes data to indicate whether the tire is operated within a normal tire pressure range and the output voltage of the battery. The signal generated by the U 2  as a micro-controller unit (MCU) is transmitted through R 3 , R 1 , Q 1 , L 2 , and C 5  to the antenna for transmitting to the signal receiving system mounted inside the car. A driver of the vehicle is therefore informed of the operational condition of the signal transmission system mounted on each tire. 
         [0028]    Another aspect of this invention is the assignment of a unique ID to each tire pressure signal transmitting system  100 . A specific ID identified with an “ID-address” is coded by the use of an ID address encoder  125  and the ID-address generated by the ID address encoder  125  is inputted to the MCU  120  through an ID-address input port JP 1  and stored into an EPROM (Erasable Programmable Read Only Memory) of the controller U 2 . The encoded ID address once stored in the EPROM of the controller U 2  is programmed into a firmware for transmitting output signal to include this ID-address in the outgoing signals transmitted from the TPS signal transmitting signals. The signal transmitted from each TPS signal transmitting system  100  is transmitted with a header that includes the ID-address of a specific TPS signal transmitting system mounted on a specific tire. The tire pressure signal receiving system once receives a signal from a specific TPS signal transmitting system  100  is able to identify a specific TPS signal transmitting system mounted on a specific tire by using this unique ID address that identifies this TPS signal transmitting system  100 . 
         [0029]    Referring to  FIG. 3  for a functional block diagram of a tire pressure signal receiver system  200  of this invention. The tire pressure signal receiver system includes an antenna  235  to receive the tire pressure signals sent from the tire pressure signal transmission system  100 . The tire pressure signals received through the antenna  235  is then sent to an RF signal receiver  230  and processed by a MCU signal processor  220 . Then the signal processed and outputted from the MCU signal processor are display in a LED or LCD signal display system  210 . 
         [0030]      FIG. 4  is a circuit diagram of the RF signal receiver  230  that receives the tire pressure signals through the antenna  235  connected to the circuit implemented as an Integrated circuit as shown. The second leg of the surface acoustic filter F 1  and the fifth leg of the filter F 1  are respectively the input and the out terminals. The first and the sixth legs of the filter F 1  are connected to a ground potential. A crystal oscillator X 2  is connected to the filter F 1  and the 26 th  leg of the transistor U 3 . The third, fourth, seventh and eighth legs of the filter F 1  are connected to ground with resistor R 3  and capacitor C 7  connected in series between the third leg of the filter F 1  and the 29 th  leg of the receiver chip U 1 . The inductor L 2  and the capacitor C 6  are connected in series between the fifth leg of the filter F 1  and the thirty-first leg of the filter F 1  and the thirty-first leg of the chip U 3 . The inductor L 1  and the capacitor C 5  are connected in series between the second and the eighth legs of the filter F 1  for transmitting a signal outputted from the fifth leg of the filter F 1  to the thirty-first leg of the chip U 1 . The first, fifth, tenth, twenty-second and the second leg of the chip U 3  are connected to the ground while the eighth, seventeenth, twenty-seventh and thirty-second legs of the U 3  chip are connected to VDD. The twenty-eighth leg is connected to the twenty-seventh leg of the chip U 3 . The capacitors C 10 , C 11 , C 12  and C 13  are connected in series between the fourth and the seventh legs of the chip U 3  and the inductor L 3  is connected in parallel to both sides of the capacitor C 10 . The resistor R 18  and R 19  are connected respectively to the sixth and the seventh legs of the chip U 3  with a common node connected to a voltage VDD. The capacitor C 8  and C 9  are connected across the thirty, twenty-seventh and the thirty-second legs of the chip U 3 . A mid-frequency filter F 2  includes a first and third legs connected across the eleventh and the ninth legs for inputting a mid-frequency from the chip U 1 . Capacitors C 14 ,  15 , and  16  are connected to the twelfth and the thirteen legs of the chip U 3 . The resistor R 20  is connected across between the twelfth and the thirteen legs and the eleventh and the thirteen legs of the chip U 3 . The common node of the capacitors C 15  and C 16  and the second leg of the filter F 2  are connected to the ground. The capacitor C 19  and C 20  are connected in series to the seventeenth and the fourteenth legs of the chip U 3 . The eighteenth, nineteenth, and twentieth legs are amplification terminals and the nineteenth and the twentieth legs are connected to capacitors C 17  and C 18  respectively. A resistor R 22  is connected across the capacitors C 17  and C 18 . The common node between the capacitors C 17  and C 18  is connected to the ground. The eighteenth leg of the chip U 3  provides an output terminal of an amplified signal. The amplified signals are transmitted through the eighteenth leg to the controller of the receiver chip. 
         [0031]    More specifically, the circuit shown in  FIG. 4  is to provide a signal interface to the display device to carry out the functions of a graphic user interface. The switch SW 1  and SW 2  are two reset buttons for providing a learning function. The resistors R 28  and R 29  are current limiting resistors. LS 1  is an alarming device and R 50  is a current limiting resistor for the LS 1  device. A combination of D 25 , D 26  and D 26  is to carry out a function of providing a low-battery power warning display through a LED light and the resistors R 25 , R 26  and R 27  are current-limiting resistors. The diodes D 1  to D 24  are connected to 24 LEDs for indicating the functional conditions of the tire pressure-monitoring signal transmitting systems and the resistors R 1 -R 24  are the corresponding current-limiting resistors. The circuit J 1 ,  2 , J 4 , and J 5  are provided to receive and process the signals from the MCU for displaying the signals through the graphic user interface. 
         [0032]    Referring to  FIG. 5  for a circuit diagram of the MCU signal process  220 . The voltage supply receives a twelve volts voltage input to a three-leg voltage stabilizer U 1  and through capacitor C 1 , C 2 , C 3 , and C 4  and also a diode D 10  to covert to a five volts Vcc voltage supply. The tire pressure signals are received and sent to RA 4  terminal to output an audio warning signal from the RA 5  terminal and a low-pressure warning signal is outputted from a RA 0  terminal. A battery-low warning signal is outputted from the RZ 1  terminal. RC 0  to RC 5  terminal output the warning signals for the detected signals at corresponding locations. The input from a learning key is inputted through an input terminal RA 2  and the twenty-fourth, twenty-seventh and twenty-eighth legs of the chip U 2  are connected to the input terminal J 2  of an encoder. 
         [0033]    Specifically, the  FIG. 5  shows the circuits that provide the function of a micro-controller unit (MCU)  220  of the signal receiving system  200  of  FIG. 3 . The MCU  220  processes the RF signals received and processed by the RF signal receiver  230 . The MCU  220  further processes the user interface signals through the push buttons as shown in  FIG. 4  to confirm the display and control status as displayed through the LED lights. A microprocessor IC 1  is programmed to perform the MCU functions and to work with C 4 , C 5 , Y 1 , and R 7  as an oscillator. The IC 1  further combines with R 8 , R 12 , R 14 , R 15  as another signal processing functional block. The input terminal J 6  serves the function of programming the microprocessor IC 1  to perform different functions of the MCU  220 . The terminals J 1 , J 2 , J 4 , and J 5  are connected the corresponding terminals J 1 , J 2 , J 4 , and J 5  of the circuits shown in  FIG. 4  to monitor and control the signal and status display functions. A DC input voltage of  12  volts is plugged in through the input port J 11  to provide power for the display device of the signal receiving system  200 . The input voltage is transmitted through CR 3 , CR 4 , C 1 , C 28 , U 1 , C 24  to provide a high voltage and the terminal J 10  is a high voltage output (USART) terminal. The input voltage is processed through CR 1 , C 16 , U 2 , C 25 , C 15 , and C 23  to provide a low voltage of five volts as power source of the signal receiver. 
         [0034]    Referring to  FIG. 6  for the circuit diagram of the LED or LCD signal display system  210 . Corresponding to the location of each tire, the display system  210  includes six light emitting diodes (LED) for each tire. Three LEDs are employed to indicate a condition of low battery power, power supply connectivity, and low tire pressure (D 7  to D 9 ). The display system further includes an audio warning device B 1 , and two buttons SW 1  and SW 2 . Each of the six resistors R 1  to R 6  are connected in series respectively to each of the six LEDs, D 1  to D 6 , and a common node of the six LEDs is connected to a high voltage terminal VCC. The other ends for each of the six resistors R 1  to R 6  are connected to a connector J 1 . The LEDs D 7  to D 9  are connected to resistors R 7  to R 9  respectively and the other ends of the resistors R 7  to R 9  are connected to a common node with a voltage VCC. The audio alarm device B 1  is connected directly to a transistor Q 1  with another end connected to the ninth leg of the connector J 1 . The first and the ninth legs of the connector J 1  are connected to the ground and VCC respectively and the third leg of the connector J 1  is connected to resistor R 10  and recovery button SW 1 , and the fourth leg of the connector J 1  is connected to resistor R 11 , the learning button SW 1 , and the common ground node of the buttons SW 1  and SW 2 . 
         [0035]    In  FIG. 6 , the signals received from antenna J 5  are processed and filtered through C 5 , L 1 , F 1 , and L 2  and then processed by microprocessor U 1  to amplify, demodulate and compare to generate high and low multi-voltage level signals for transmitting to the MCU  220  for further process as described above. 
         [0036]    Referring to  FIG. 7  for the detail structural configuration of the tire pressure-monitoring device  100  as an exemplary embodiment of this invention. One electrode of the battery  13  is engaged to and contacting a metallic adjusting screw  15  that in turn is engaged to a spring  16 . The other end of the spring  16  pushes onto a bottom of a receiving cup  17  and the receiving cup  17  has a bottom surface pressing onto a pressing ring  4 . The pressing ring  4  has a screw interface edge that is screwed onto the base core  2 The base core  2  is tightly engage to a copper ring  6  and the cooper ring has a back surface that supports circuits connected to the printed circuit board (PCB)  11 . The PCB  11  is connected to another electrode of the battery  13  through a battery spring plate  19 . A complete electric current conducting path is therefore formed according to above configuration. In a normal operation condition, a normal tire pressure pushes up the film plate  3  that pushes up the receiving cup  17  thus disconnected the connection of the PCB to the battery to save the battery power in a normal tire pressure condition. When the tire pressure is lower than a threshold, the receiving cup  17  is pushed back by the spring  16  thus contact to the base core  2  and a complete electric current conducting path is formed to the circuit supported on the PCB. Then a low tire pressure signal is transmitted. A pressure adjustment screw  15  carries out a function for adjusting the length of the spring  16 . By accurately adjusting the length of the spring  16 , the pressure measurements can be more accurately calibrated and pressure drop can be more accurately detected. 
         [0037]    With a structural configuration as shown in  FIG. 7 , the tire pressure-monitoring device  100  further has a waterproof structural feature. The base core  2  is attached securely to a tire pressure-pumping stem and sealed by a ring  20  to prevent water or moisture to enter into the internal space of the tire pressure-monitoring device  100 . The front cover assembly  1  is securely attached to the core base  2  and seal with another ring  18  to prevent water or moisture to enter into the internal space of the tire pressure-monitoring device  100 . The back cover assembly is screwed onto the front cover assembly  1  through an O-ring that again seal the interface to prevent water or moisture to enter into the internal space of the tire pressure-monitoring device  100 . 
         [0038]    Furthermore, one aspect of this invention is to enable the tire pressure monitoring system to more accurately detect a low-pressure condition. According to above structural features, improved accuracy for detecting a low-pressure condition is achieved because an elongated rod is placed through the central portion of the receiving cup  17  that penetrates through the pressure measurement adjustment screw  15 . The receiving cup  17  is engaged against the pressure measurement adjustment screw  15  instead of floating freely along the central rod. The length of the spring therefore is adjusted immediately with fixed regularity with the change of the tire pressure to accurately detect the tire pressure changes. The inaccuracies that could be induced due to the changes of the position of a freely movable floating receiving cup  17  caused by external vibrations or outside pressures that leads to a variation of the lowest contact position to the pressure cup  4  are therefore eliminated. For these reasons, the accuracy of pressure drop measurements is significantly improved. 
         [0039]    Although the present invention has been described in terms of the presently preferred embodiment, it is to be understood that such disclosure is not to be interpreted as limiting. Various alternations and modifications will no doubt become apparent to those skilled in the art after reading the above disclosure. Accordingly, it is intended that the appended claims be interpreted as covering all alternations and modifications as fall within the true spirit and scope of the invention.