CN201264489Y - Automotive tire pressure monitoring method based on tyre impedance - Google Patents

Abstract

The utility model discloses a vehicle tire pressure monitoring device based on the tire impedance. A sound surface wave resonator is embedded into the inside of the tire, and the tire capacity and the resistance which are made of tire rubber and steel wire are taken the external impedance load of the sound surface wave resonator. The changed of the tire impedance is caused by the change of the tire status, and the change of the resonance frequency of the sound surface wave resonator is caused by the change of the tire impedance. The resonance of the sound surface wave resonator is generated and the signal of resonance frequency is sent out without power and wire through an external pulse excitation, and therefore the testing of the tire status without power and wire can be achieved. In the testing process of the tire status, different steel wires and a plurality of sound surface wave resonators are connected and a plurality of sound wave resonators with different external impedance loads are formed. The status testing of tire pressure, temperature, wear, aging and so are can be achieved by using the combination of the resonance frequency of a plurality of sound surface wave resonators.

Description

Vehicle tire pressure monitoring device based on tire impedance

(1) Technical field:

The utility model relates to an automobile safety running monitoring device, in particular to an automobile tire pressure monitoring device based on tire impedance.

(two) background technology:

In the driving of a car, tire burst is the most worrying and most difficult to prevent for all drivers, and it can cause or induce serious traffic accidents. Especially when running at high speed, tire burst will be more dangerous. Safety experts pointed out that when the speed of the car exceeded 160 kilometers per hour, the death rate caused by tire burst was almost close to 100%. According to theoretical analysis, before the tire bursts, the tire pressure will be abnormal, so the danger caused by the tire burst can be fundamentally avoided by monitoring the tire pressure and alarming the abnormal situation. In addition, if the inflation pressure of the tire is insufficient, the rolling resistance of the tire will increase, the fuel consumption of the car will increase, and the abnormal wear of the tread will intensify, resulting in early scrapping of the tire. Performance, economy and stability are of great significance.

Existing tire pressure measurement methods, such as the patent of "automotive tire low air pressure alarm" in the CN209245 announcement number, this patent is to fix the sensor on the wheel hub to realize the direct contact and measurement of tire pressure and temperature, but this The installation process is more complicated, and the tire needs to be removed from the steel ring to fix the sensor. The fixed sensor is prone to loosening or falling off during the long-term rotation and vibration of the tire. High temperature and humid environment can easily reduce the performance of the sensor or even damage the sensor. In addition, since this measurement method installs the sensor inside the tire, it needs a power supply that can supply power for a long time. Generally, a high-performance lithium battery is used for power supply, but the life of the lithium battery is limited, and it is very inconvenient to replace the battery. The volume and weight are relatively large, which increases the dynamic load of tire rotation, easily destroys the dynamic balance of the tire, and discarded batteries will also cause environmental pollution.

In order to avoid the installation problems of the above-mentioned sensors, in 2005, R.Matsuzakia and A.Todoroki published an article on page 323-31 of the 119th issue of "Sensors and Actuators" in 2005, "Using Capacitance and Oscillating Circuits for Wireless Tire Deformation Measurement (Wireless Strain Monitoring of Tires Using Electrical Capacitance Changes with an Oscillating Circuit), for the first time converts the change of tread capacitive impedance caused by the change of tire pressure into frequency change and transmits it wirelessly, that is, the tread rubber and steel wire of the tire are regarded as capacitive elements, The rubber is a dielectric material, the steel wire is a conductive material, and the rubber and the steel wire between adjacent steel wires can form a tire capacitance element together. In the tire module, the change of tire pressure causes the deformation of the tire tread, the distance between the tread steel wires changes, the capacitance of the capacitor composed of the tread steel wire and rubber changes, and the change of capacitance is converted into frequency by the CR oscillator The change is transmitted through the antenna of the transmitter. The frequency signal emitted by the transmitter is received by the external module receiver, which is calculated by the frequency counter and sent to the computer for processing, and the change of the obtained measurement frequency signal is converted into the change of tire pressure, thereby realizing the wireless measurement of tire pressure. Although this can save the conventional tire pressure sensor and avoid various troubles when installing the conventional sensor, when using the tire capacitive impedance and CR oscillator for wireless measurement of tire pressure, the measurement signal needs a power supply when it is transmitted. Generally, a high-performance lithium battery is used for power supply, so this tire condition measurement method still has various problems in using battery power supply. In addition, the CR oscillator and transmitter are composed of electronic components such as resistors and amplifiers, and are embedded in the tread. It is very difficult and will affect the tire's tread elasticity and stiffness after installation.

(3) Contents of utility model:

The technical problem to be solved by the utility model is to provide an automobile tire pressure monitoring device based on tire impedance that does not need to be powered by a battery and is easy to install.

The utility model is an automobile tire pressure monitoring device based on tire impedance designed to realize the above method, including a tire module that converts the change of tread capacitance and resistance impedance caused by tire pressure into frequency change and wirelessly transmits it, and according to the received An external module that solves tire pressure changes for frequency changes. The external module is constituted by the external module commonly used in the prior art, and each tire module includes at least one surface acoustic wave resonator embedded in the tire rubber, a proximal antenna and a matching impedance; one end of the surface acoustic wave resonator The matching impedance is connected to the common steel wire G in the tire tread rubber, and the other end is connected to the tire steel wire _Sn different from the common steel wire G through a wire, and a near-end antenna is connected between the surface acoustic wave resonator and the matching impedance. The surface acoustic wave resonator of the tire module is excited by the radio frequency pulse signal sent by the external module, and resonates under the influence of tire pressure, and returns the resonant frequency to the external module through the near-end antenna for frequency calculation, and then solves the tire's pressure.

Since the change of tire temperature will cause the shift of the central resonance frequency of the surface acoustic wave resonator, in order to eliminate the influence of these factors and make the measurement result of tire pressure more accurate, it is necessary to compensate the measurement error. As an improvement, a surface acoustic wave resonator group formed by connecting two surface acoustic wave resonators with the same structure and the same central resonance frequency can also be embedded in the tire rubber of the tire module. One end of the two surface acoustic wave resonators is connected to the common steel wire G through matching impedance, and the other two ends of the surface acoustic wave resonator group are connected to the common steel wire G through a wire, and the other end is connected to a tire different from the common steel wire G through a wire. The steel wire S _n is connected, and the near-end antenna is also connected between the surface acoustic wave resonator and the matching impedance. Since temperature changes have the same influence on the central resonant frequency of the two SAW resonators, the influence of temperature on the central resonant frequency of the SAW resonator can be eliminated by using the resonant frequencies of the two SAW resonators, and the correct tire pressure measurements.

Multiple SAW resonators and/or SAW resonator groups located in the same tire module share a matching impedance and a near-end antenna.

Different surface acoustic wave resonators and/or surface acoustic wave resonator groups in the same tire module are connected to different tire steel wires _Sn , that is, the external tire impedance is different, so as to solve those factors that can affect the tire pressure measurement results Other tire parameters, such as tire temperature, wear and aging, etc. The number of surface acoustic wave resonators and/or surface acoustic wave resonator groups is selected according to the number of parameters to be solved, and each surface acoustic wave resonator and/or surface acoustic wave resonator groups have different center resonant frequency. Using the resonant frequencies of 2n surface acoustic wave resonators in n (n≥3) surface acoustic wave resonator groups, according to tire parameters (such as pressure, and/or temperature, and/or wear and aging, etc.) and tire impedance and the relationship between the tire impedance and the resonant frequency of the surface acoustic wave resonator, and the information of various parameters (such as pressure, and/or temperature, and/or wear and aging, etc.) of the tire can be obtained simultaneously through the method of data fusion.

The external module includes an interconnected remote antenna and radio frequency transceiver, a frequency counter, a microcontroller, and a power supply;

Remote Antenna and RF Transceiver: Used to transmit RF pulse signals to SAW resonators and/or SAW resonator groups, and to receive resonant frequencies returned by SAW resonators and/or SAW resonator groups Pulse signal;

Frequency counter: used to calculate the received resonance frequency and send the calculation result to the microcontroller;

Microcontroller: used to control the working state of the remote antenna and radio frequency transceiver, and/or the time and frequency of transmitting radio frequency pulse signals, and/or the time of receiving resonance frequency signals, and according to the tire status (such as pressure, and (or temperature, and/or wear and aging degree, etc.)

The number of sets of radio frequency transceivers and remote antennas is the same as the number of tire modules, and each set of radio frequency transceivers and remote antennas corresponds to a tire module.

Described micro-controller is also connected with memory, and/or warning device, and/or display device, and memory is used for storing the safe pressure range of tire, the pressure-frequency of tire, and/or temperature-frequency, and/or wear and tear and Aging-frequency relationship and each measured tire pressure value, and/or temperature, and/or wear and aging degree; the alarm device is used to send an alarm signal when the pressure of the tire is too high or too low; the display device is used to display The pressure value of the tire, and/or the state of the tire, and/or the type of failure.

According to the specific state of the tire (such as temperature, and/or wear and aging degree, etc.), the external module uses the pressure safety range of the tire stored in the memory under different states (such as temperature, and/or wear and aging degree, etc.), through intelligent Reasoning, to make a correct judgment on the safety state of the tire pressure in the current state, if the tire pressure is too high or too low, the microcontroller sends a signal to the alarm device and the display device, if the tire pressure state is normal, the microcontroller The controller only sends signals to the display unit.

The utility model realizes the passive wireless detection of the tire pressure according to the relationship between the tire pressure and the capacitance and resistance impedance of the tire tread and the relationship between the tire tread impedance and the resonant frequency of the surface acoustic wave resonator, saving conventional sensors, The cost is reduced; the tire module of the monitoring system is small in size, and the surface acoustic wave resonator of the tire module has good anti-electromagnetic interference and heat resistance performance, and can be directly embedded in the tread steel wire layer of the tire during the tire production process. In the rubber, it avoids the problems of installation, fixation and performance impact of the tire module installed in the valve part or hub part of the current tire pressure monitoring system; the tire module adopts passive working mode, which avoids the current tire pressure monitoring system. The source sensor needs to be powered by a battery to limit the service life of the monitoring system and battery pollution. It also avoids the dynamic load of the tire rotation and the impact on the tire due to the large volume and weight of the tire module when the active sensor is used in the current tire pressure monitoring system. The problem of dynamic balance.

(4) Description of drawings:

The utility model will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is a schematic structural view of an embodiment of the present invention.

FIG. 2 is a work flow chart of the external module corresponding to FIG. 1 .

FIG. 3 is a schematic structural diagram of a SAW resonator group Mn according to another embodiment of the present invention.

FIG. 4 is a schematic diagram of embedding multiple SAW resonator groups Mn as shown in FIG. 3 in the same tire and connecting them.

FIG. 5 is a workflow diagram of the external module corresponding to FIG. 4 .

Description of drawings: 1. External module; 2. Tire module; 3. Substrate; 4. Surface acoustic wave resonator; 5. Surface acoustic wave resonator group.

(5) Specific implementation methods:

Example 1:

An embodiment of an automobile tire pressure monitoring device based on tire impedance may consist of at least one tire module 2 and an external module 1 as shown in FIG. 1 . The tire module 2 located in different tires includes a surface acoustic wave resonator 4 embedded in the steel wire layer rubber of the tire tread, a steel wire connected thereto, a near-end antenna and a matching impedance. The surface acoustic wave resonator 4 is composed of a substrate 3 and an interdigital transducer on the surface of the substrate 3 and two identical reflectors, and the reflectors are completely symmetrically arranged on both sides of the interdigital transducer. One end of the interdigital transducer of the surface acoustic wave resonator 4 is connected with the matching impedance, and this end is also connected with the near-end antenna in addition, and the other end of the interdigital transducer of the surface acoustic wave resonator 4 is connected with the tread wire S _n connected. One end of the matching impedance is connected with the near-end antenna, and the other end is connected with the common steel wire G. The common wire G is another wire different from the tread wire _Sn to which the IDT of the surface acoustic wave resonator 4 is directly connected. The steel wire is a conductive material, and the rubber is a dielectric material. In addition, the carbon black contained in the rubber is a conductive material. In this way, the tread steel wire S _n , the common steel wire G, and the rubber between them can form the capacitance and resistance impedance of the tire. The tire capacitance and resistance impedance can be regarded as the external tire impedance load of the surface acoustic wave resonator 4 . When the pressure of the tire changes, the distance between the tire steel wire S _n and the public steel wire G changes, the capacitance and resistance of the impedance element composed of the tire steel wire S _n , the public steel wire G and rubber change, and the impedance of the surface acoustic wave resonator 4 As the load changes, the resonance frequency of the surface acoustic wave resonator 4 changes.

The external module 1 is composed of a remote antenna, a radio frequency transceiver, a frequency counter, a microcontroller, a memory, an alarm display device and a power supply, and the power supply is generally the power supply of a car. Since there are multiple tire modules 2, in order to distinguish the tire modules 2, the external module 1 can be provided with multiple sets of radio frequency transceivers and remote antennas, the number of sets of which is the same as the number of tire modules 2, each set of transceivers and remote antennas The antenna corresponds to a tire module 2, and the radio frequency transceiver and the antenna are installed on the dust shield on the upper part of the tire. The frequency counter, microcontroller, memory and display alarm device are installed in the cab, and each set of remote antenna and transceiver is connected to the frequency counter and microcontroller of the external module 1 through wires, and the microcontroller and frequency counter, transceiver The device is connected with the display alarm device, and the memory can store the safe pressure range of the tire and the tire pressure values measured several times before.

When the microcontroller of the external module 1 sends a command to transmit a pulse to a certain radio frequency transceiver, the radio frequency transceiver sends a radio frequency pulse signal with the same central resonance frequency as the surface acoustic wave resonator 4 to the tire module 2 through the remote antenna . The proximal antenna of the tire module 2 is directly connected to the interdigital transducer of the surface acoustic wave resonator 4, and the surface acoustic wave resonator 4 uses the interdigital transducer to convert the received radio frequency signal into the substrate of the surface acoustic wave resonator 4 3 surface acoustic wave, the surface acoustic wave propagates between the interdigital transducer and the reflector of the surface acoustic wave resonator 4 and resonates. The external tire impedance connected to the surface acoustic wave resonator 4 is the capacitance and resistance impedance of the tire. The capacitance and resistance impedance of the tire are affected by factors such as the pressure of the tire. The resonant frequency of the surface acoustic wave resonator 4 is affected by the external tire impedance. Therefore, the tire pressure and other states can be reflected by the resonant frequency of the SAW resonator 4 . The resonant frequency signal of the surface acoustic wave resonator 4 is converted into an electromagnetic pulse signal of the same frequency through the interdigital transducer of the surface acoustic wave resonator 4 , and the electromagnetic pulse signal is transmitted through the near-end antenna of the tire module 2 .

After the transceiver of external module 1 transmits the pulse signal, it enters the receiving state after receiving the receiving pulse command sent by the microcontroller of external module 1. Once it receives the pulse signal sent by the corresponding tire module 2, it will receive the pulse signal Send it to the frequency counter to calculate the pulse frequency. The calculated pulse frequency is sent to the micro-controller, and the micro-controller calculates the tire pressure according to the relationship between the change of the tire pressure and the change of the resonant frequency of the surface acoustic wave resonator 4, and then compares the calculated tire pressure with the memory stored The tire module 2 compares the previous tire pressure signals and the safe range of tire pressure changes, and uses an intelligent algorithm to determine whether the tire pressure state is too high, too low or normal. If the tire pressure status is too high or too low, the microcontroller sends a signal to the alarm device, and the alarm device sends out an alarm signal; at the same time, the microcontroller sends a signal to the display device to display the status of the tire and the type of failure, otherwise the microcontroller only Send a signal to the display unit to display the tire pressure value.

The microcontroller of the external module 1 controls the working state of the radio frequency transceiver and the remote antenna, as well as the time and frequency of transmitting pulse signals and the time of receiving pulse signals. Each transmit or receive command can only be sent to one transceiver, that is, only one transceiver can work at a time. After all the pressure measurement data of the tire module 2 are received, the microcontroller determines the start time of the next measurement according to the tire pressure situation. When the pressure of the tire is abnormal, the time between two measurements should be shortened, otherwise, the time between two measurements can be increased.

When there are m (m>1) tire modules 2, as shown in Figure 2, the workflow of the external module 1 in this embodiment is as follows:

a) Initialize the time T1 of transmitting pulses and the time T2 of receiving pulses, define the number of transceivers as i (i=1～m, m is the number of tire modules 2), and initialize i=1, go to step b) ;

b) judge whether i exceeds m+1, that is, whether all tire modules 2 have been detected, if not, go to step c), otherwise go to step d);

c) The microcontroller of the external module 1 sends a transmit pulse command to the i-th transceiver, and the i-th transceiver sends a radio frequency pulse signal through the remote antenna after receiving the transmit pulse command. The transmit time is T1, and then the external module 1 The microcontroller of the i-th transceiver sends a receive pulse command to the i-th transceiver. After the i-th transceiver receives the receive pulse command, the remote antenna of the i-th transceiver is in the state of receiving pulse signals, waiting to receive the resonance returned by the tire module 2 Frequency signal pulse, the receiving time is T2, and finally, the i-th transceiver sends the received pulse signal to the frequency counter for frequency calculation, and the calculation result is sent to the microcontroller, and the microcontroller resonates with the surface acoustic wave according to the pressure change of the tire Relation between the frequency variation of device 4 solves the pressure of tire, i=i+1, changes over to step b);

d) The microcontroller of the external module 1 uses an intelligent algorithm to perform m tire pressure changes based on the received pressure change signals of the m tire modules 2 and the previous tire pressure signals of each tire module 2 stored in the memory and the safety range of tire pressure changes. Intelligent judgment of the tire pressure state, if the pressure state of a certain tire is abnormally high or the pressure is too low, go to step e), if the pressure state of all tires is normal, go to step f);

e) The microcontroller of the external module 1 sends an alarm command to the alarm device, and the alarm device sends an alarm signal. The microcontroller sends tire pressure status information and pressure values to the display device, and the display device displays the pressure status of each tire. If the pressure is abnormal , to display the specific status of the abnormality, if the pressure is normal, only the pressure value is displayed, wait for the measurement interval time T3, and then go to step a);

f) The microcontroller of the external module 1 sends the specific pressure value of each tire to the display device, and the display device displays the pressure value of each tire, then waits for the measurement interval T4, T4 can be greater than T3, and turns to step a).

Example 2:

In this embodiment, by embedding a plurality of surface acoustic wave resonator groups 5 inside the tire, not only the pressure, temperature, wear and aging information of the tire can be obtained at the same time, but also the tire pressure can be calculated according to the obtained tire pressure, temperature, wear and aging information. The correct judgment of the security status.

The structure of the external module 1 of this embodiment is the same as that of Embodiment 1, and the structure of its tire module 2 is more complex than that of Embodiment 1, that is, each tire module 2 is mainly composed of a surface acoustic wave resonator group 5, a near-end antenna and a matching impedance. . The surface acoustic wave resonator group 5 is formed by connecting two surface acoustic wave resonators 4 with exactly the same structure. A near-end antenna is also connected between the surface wave resonator 4 and the matching impedance. One of the other two ends of the surface acoustic wave resonator group 5 is connected to the common steel wire G through a wire, that is, not connected to the external tire impedance; the other is connected to the tire steel wire _Sn different from the common steel wire G through a wire, that is, connected to the external tire impedance, such as Figure 3 shows.

When the temperature inside the tire changes, the temperature change will cause a change in the central resonant frequency of the surface acoustic wave resonator 4, thereby causing measurement errors. The utility model can also use the surface acoustic wave resonator 4 not connected to the external tire impedance to compensate the measurement error, because the change of temperature will also affect the central resonant frequency of the surface acoustic wave resonator 4 connected to the external tire impedance. In addition, the structures of these two surface acoustic wave resonators 4 are exactly the same as the central resonant frequency, and the environment they are in is also exactly the same, therefore, the frequency changes caused by temperature changes on the two surface acoustic wave resonators 4 should be the same . Therefore, the measurement error caused by the temperature change can be eliminated by utilizing the frequency change of the two surface acoustic wave resonators 4 , so as to obtain correct tire pressure state information.

In addition, when the surface acoustic wave resonator group 5 is used to measure tire pressure, since the safe pressure range of the tire is different at different temperatures, the safe pressure range of the tire is also different under different degrees of wear and aging. Therefore, the external module 1 is for To be able to correctly judge the safety state of the tire pressure, it is also necessary to obtain the temperature information inside the tire and the wear and aging state information of the tire. At this time, in order to obtain the pressure, temperature, wear and aging state information of the tire at the same time and to compensate the influence of the temperature change on the central resonant frequency of the surface acoustic wave resonator 4, this embodiment embeds n (n≥3) resonators in the same tire SAW resonator groups 5 with different center resonant frequencies are realized. As shown in Figure 4, in order to obtain more tire information at the same time, this implementation can embed multiple SAW resonator groups 5 in the same tire, and the connected ends of these SAW resonator groups 5 are all connected through the same matching The impedance is connected to the common steel wire G, and the common steel wire G and the matching impedance are connected to the same near-end antenna. Of the two remaining ends of each SAW resonator group 5 , one end connected to an external impedance is connected to a different tire steel wire S _n , and the end not connected to a tire impedance is connected to a common steel wire G. The tire steel wires S _n connected to the external tire impedance terminals connected to each surface acoustic wave resonator group 5 are different, and their center resonant frequencies are also different, but they are not connected to the external tire impedance terminals and are always connected to the common steel wire G. The changes of the resonant frequencies of the two SAW resonators 4 of each SAW resonator group 5 are measured respectively, and then the measured information is fused to obtain the required tire pressure, temperature, wear and aging status information. The external module 1 can use the pressure safety range of the tire stored in the memory at different temperatures, different degrees of wear and aging according to the specific wear and aging state of the tire, as well as the temperature inside the tire, and through intelligent reasoning, the current temperature and current wear Make a correct judgment on the pressure safety state of the tire under the aging degree. If the pressure of the tire is too high or too low, the microcontroller sends a signal to the alarm device, and the alarm device sends out an alarm signal; at the same time, the microcontroller sends a signal to the display device to display the status of the tire and the type of failure. If the tire pressure status is normal , the microcontroller only sends a signal to the display device to display the pressure value of the tire.

Assuming that each SAW resonator group 5 embedded in the automobile tire is connected to the tire steel wire S _j (j=1, 2, 3... n) respectively at the external tire impedance end, each SAW resonator group 5 has a different The central resonant frequency f _j0 (j=1, 2, 3...n), and there must be a certain difference between the central resonant frequencies of each surface acoustic wave resonator group 5, that is, the center resonance frequency of each surface acoustic wave resonator group 5 The difference between the frequencies must be greater than the change in the resonant frequency of the surface acoustic wave resonator 4 caused by the maximum change in the external tire impedance. According to the central resonant frequency of surface acoustic wave resonator group 5, design surface acoustic wave resonator group 5, matching impedance and near-end antenna under each frequency, the matching impedance connected with surface acoustic wave resonator group 5 and the near-end antenna are both It is optimized design, under the conditions of SAW resonator 4, matching impedance and near-end antenna tread embedded installation, the energy utilization rate, frequency stability, insertion loss and quality factor of SAW resonator group 5 The overall performance is the best, and the transmitting and receiving performance of the near-end antenna is the best.

When the microcontroller of the external module 1 sends a command to transmit a pulse to a certain transceiver, the transceiver first sends a radio frequency pulse signal with a frequency f ₁₀ through the remote antenna, and f ₁₀ is the first acoustic surface of the tire module 2 The central resonant frequency of the wave resonator group 5M1, that is, the central resonant frequency of the two surface acoustic wave resonators 4 of _M1 . The near-end antenna of the tire module 2 corresponding to the transceiver and the remote antenna receives the transmitted radio frequency pulse signal, and the near-end antenna of the tire module 2 is directly connected to the two surface acoustic wave resonators 4 of each surface acoustic wave resonator group 5 , the interdigital transducer of the surface acoustic wave resonator 4 converts the received radio frequency pulse signal into a surface acoustic wave and propagates on the surface of the substrate 3 of the surface acoustic wave resonator 4, due to the first surface acoustic wave of the tire module 2 Since the center resonance frequency of the two SAW resonators 4 of the wave resonator group _5M1 matches the frequency of the received pulse signal, the two SAW resonators 4 of the SAW resonator group 5 resonate. Assume that the resonant frequency of a SAW resonator 4a not connected to the tire impedance in the same SAW resonator group 5 is _f11 , and the resonant frequency of the other SAW resonator 4b connected to the tire impedance is f ₁₂ . Among them, the surface acoustic wave resonator a will be affected by _f12 to the temperature inside the tire, and the temperature will cause the deviation of the central resonance frequency of the surface acoustic wave resonator 4a, assuming that the caused deviation is Δf _T1 , so its resonance frequency is:

f ₁₁ =f ₀₁ +Δf _T1 1

The surface acoustic wave resonator 4b connected to the impedance of the tire, the pressure, temperature, wear and aging of the tire will cause the change of the external tire impedance, and the change of the external tire impedance will cause the change of the resonant frequency of the surface acoustic wave resonator 4b, assuming is f ₁ (P, T, W). In addition, the tire temperature also causes the shift Δf _T1 of the central resonance frequency of the SAW resonator 4b, therefore, the resonance frequency of the SAW resonator 4b is:

f ₁₂ = f ₀₁ + f ₁ (P, T, W) + Δf _T1 2

The surface acoustic wave resonator 4 a and the surface acoustic wave resonator 4 b respectively convert their own resonant frequency signals into electromagnetic pulse signals of the same frequency, and the electromagnetic pulse signals are transmitted through the antenna of the tire module 2 . After the transceiver of external module 1 transmits the pulse signal, it enters the receiving state after receiving the receiving pulse command sent by the microcontroller of external module 1. After receiving the pulse signal sent by the corresponding tire module 2, it will receive the pulse signal Send to the frequency counter to calculate the pulse frequency, use the frequency counter to obtain the frequencies f ₁₁ and f ₁₂ respectively, and then send the obtained frequencies to the microcontroller.

Next, the microcontroller of the external module 1 sends a command to transmit pulses again to the same transceiver, which sends a radio frequency pulse signal with a frequency f ₂₀ through the remote antenna, where f ₂₀ is the second acoustic signal of the tire module 2. The center resonant frequency of the surface wave resonator group 5. According to the same principle, the external module 1 can obtain the resonance frequencies f ₂₁ and f ₂₂ of the two SAW resonators 4 of the SAW resonator group 5M ₂ .

Then, the resonance frequency signals of the two SAW resonators 4 of other SAW resonator groups 5 can be obtained in the same way, and the microcontroller of the external module 1 solves the following formula on the basis of the obtained frequency signals:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;f</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\\ {\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 12</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;f</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\\ {\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;f</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; twenty\; two</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;<figure-callout\; id="2"\; label="f\; T"\; filenames="Y200820301175E00172.png"\; state="\{\{state\}\}">f</figure-callout></span><figure-callout\; id="2"\; label="f\; T"\; filenames="Y200820301175E00172.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; \&Greater\; Equal;</span>\mathrm{<span\; class="notranslate">\; 3</span>}\\ <span\; class="notranslate">\; \&Center\; Dot;</span>\\ <span\; class="notranslate">\; \&Center\; Dot;</span>\\ <span\; class="notranslate">\; \&Center\; Dot;</span>\\ {\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\; f</span>}}_{\mathrm{<span\; class="notranslate">\; Tn</span>}}\\ {\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&Delta;\; f</span>}}_{\mathrm{<span\; class="notranslate">\; Tn</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 3</span>}$

The solution method can adopt data fusion and intelligent algorithm, therefore, the external module 1 can obtain tire pressure, temperature, wear and aging state information. When using this method to measure tire pressure, temperature, wear and aging information, the calibration method is to use standard tire pressure, temperature sensors and LCR testers to measure the impedance of tires at different pressures, different temperatures, different degrees of wear and aging. Measure, then compare the result of the measurement with the frequency measured by the measuring method of the present invention, obtain the corresponding relationship of pressure-frequency, temperature frequency, wear and aging frequency, then store the corresponding relationship into the memory of the external module 1, According to these corresponding relationships, the microcontroller of the external module 1 can calculate the specific tire pressure, temperature, wear and aging degree according to the obtained frequency signal.

According to the obtained tire pressure, temperature, wear and aging status information, the micro-controller of the external module 1 utilizes the pressure safety range of the tire at different temperatures, different wear and aging degrees stored in the memory, and uses an intelligent algorithm to determine the current temperature and aging status of the tire. Under the current wear and aging degree, the pressure safety state of the tire is judged. If the pressure of the tire is too high or too low, the microcontroller sends a signal to the alarm device, and the alarm device sends an alarm signal; at the same time, the microcontroller sends a signal to the display device. signal to display the status of the tire and the type of fault. If the pressure status of the tire is normal, the microcontroller only sends a signal to the display device to display the pressure value of the tire.

The microcontroller of the external module 1 controls the working state of the radio frequency transceiver and the remote antenna, as well as the time and frequency of transmitting pulse signals and the time of receiving pulse signals. Each transmit or receive command can only be sent to one transceiver, that is, only one transceiver can work at a time. After all the measurement signals of the tire module 2 are received, the microcontroller determines the start time of the next measurement according to the pressure state of the tire. When the pressure of the tire is abnormal, the time between two measurements should be shortened, otherwise, the time between two measurements can be increased.

When there are m (m>1) tire modules 2 and each tire module 2 has n (n≥3) surface acoustic wave resonator groups 5, as shown in Figure 5, the workflow of the external module 1 in this embodiment is as follows:

a) Initialize the time T1 of transmitting pulses and the time T2 of receiving pulses, define the number of transceivers as i (i=1～m, m is the number of tire modules 2), and initialize i=1, go to step b) ;

b) judge whether i exceeds m+1, that is, whether all tire modules 2 have been detected, if not, go to step c), otherwise go to step g);

c) Define the number of the surface acoustic wave resonator group 5 as j (j=1～n, n is the number of the surface acoustic wave resonator group 5), and initialize j=1, then go to step d);

d) judging whether j exceeds n+1, that is, whether the measurement information of all SAW resonator groups 5 of the tire module 2 has been obtained, if not, proceed to step e), otherwise proceed to step f);

e) The microcontroller of the external module 1 sends a transmit pulse command to the i-th transceiver, and the i-th transceiver sends a radio frequency pulse signal through the remote antenna after receiving the transmit pulse command. The transmit time is T1, and the transmit frequency is the tire module The central resonant frequency f _0j of the jth surface acoustic wave resonator group 5 of 2, then, the microcontroller of the external module 1 sends a receive pulse command to the i-th transceiver, and the i-th transceiver receives the receive pulse command , the remote antenna of the i-th transceiver is in the state of receiving the pulse signal, waiting to receive the resonant frequency signal pulse returned by the tire module 2, and the receiving time is T2. Finally, the i-th transceiver sends the received pulse signal to the frequency counter Carry out frequency calculation, calculation result is sent into microcontroller, j=j+1, changes over to step d);

f) Utilize the corresponding relationship of pressure-frequency, temperature frequency, wear and aging frequency stored in the memory, according to the relationship between the measurement frequency of the n surface acoustic wave resonator groups 5 of the tire module 2 and the pressure, temperature, wear and aging degree of the tire The relationship between, solve the concrete pressure of tire, temperature, wearing and aging degree by the method for data fusion, i=i+1, turn over to step b);

g) According to the received pressure, temperature, wear and aging state information of the m tire modules 2, the microcontroller of the external module 1 utilizes the pressure safety range of the tire stored in the memory at different temperatures, different wear and aging degrees, through intelligent The algorithm judges the pressure safety state of m tires under the current temperature and the current degree of wear and aging. If the pressure state of a tire is abnormally high or the pressure is too low, go to step h), if all The pressure state of tire is all normal, changes to step i);

h) The microcontroller of the external module 1 sends an alarm command to the alarm device, and the alarm device sends an alarm signal. The microcontroller sends tire pressure status information and pressure values to the display device, and the display device displays the pressure status of each tire. If the pressure is abnormal , to display the specific status of the abnormality, if the pressure is normal, only the pressure value is displayed, wait for the measurement interval time T3, and then go to step a);

i) The microcontroller of the external module 1 sends the specific pressure value of each tire to the display device, and the display device displays the pressure value of each tire, then waits for the measurement interval T4, T4 can be greater than T3, and turns to step a).

The utility model is not limited to the above-mentioned embodiments, as long as the surface acoustic wave resonator 4 or the surface acoustic wave resonator group 5 is embedded in the tire rubber, and the tire's own capacitance and resistance composed of tire steel wire and rubber are used as its external impedance, it belongs to this utility model. Protection scope of utility model.

Claims (6)

1. [claim 1] is based on the automobile tire pressure monitor of tire impedance, comprise external module (1) and at least one tire module (2), it is characterized in that: described each tire module (2) comprises at least one SAW resonator (4), near-end antenna and the matched impedance that is embedded in the rubber for tire; One end of SAW resonator (4) links to each other with public steel wire G in the tire protector rubber by matched impedance, the other end links to each other with the bead wire Sn that is different from public steel wire G by lead, also is connected to the near-end antenna between SAW resonator (4) and matched impedance.
2. [claim 2] automobile tire pressure monitor based on the tire impedance according to claim 1, it is characterized in that: described tire module (2) also comprises at least one SAW resonator group (5), this SAW resonator group (5) interconnects by two SAW resonators (4) with same structure and identical central resonant frequency and forms, the end that two SAW resonators (4) join links to each other with public steel wire G by matched impedance, also be connected to the near-end antenna between SAW resonator (4) and matched impedance, one at the other two ends of SAW resonator group (5) link to each other with public steel wire G by lead, and one links to each other with the bead wire Sn that is different from public steel wire G by lead.
3. [claim 3] automobile tire pressure monitor based on the tire impedance according to claim 1 and 2 is characterized in that: described different SAW resonators (4) and/or shared matched impedance of SAW resonator group (5) and the near-end antenna that is positioned at same tire module (2).
4. [claim 4] automobile tire pressure monitor based on the tire impedance according to claim 1 and 2, it is characterized in that: describedly be positioned at the different SAW resonators (4) of same tire module (2) and/or bead wire Sn that SAW resonator group (5) is connect has nothing in common with each other, promptly each SAW resonator (4) and/or SAW resonator group (5) have different external tire impedances.
5. [claim 5] automobile tire pressure monitor based on the tire impedance according to claim 1 and 2 is characterized in that: described external module (1) comprises at least one interconnective far-end antenna and RF transceiver, frequency counter, microcontroller and power supply;

   Far-end antenna and RF transceiver: be used for to SAW resonator (4) and/or SAW resonator group (5) emission RF pulse signal, and receive the resonant frequency impulse singla that SAW resonator (4) and/or SAW resonator group (5) are returned;

   Frequency counter: be used for the resonant frequency that receives is calculated, and result of calculation is sent into microcontroller;

   Microcontroller: be used to control the time and the frequency size of the mode of operation of far-end antenna and RF transceiver and/or emission RF pulse signal and/or receive the time of resonant frequency signal and change the pressure of finding the solution tire according to survey frequency.
6. [claim 6] automobile tire pressure monitor based on the tire impedance according to claim 5, it is characterized in that: the tricks of described RF transceiver and far-end antenna is identical with the number of tire module (2), the corresponding tire module (2) of every suit RF transceiver and far-end antenna.

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