JP2010125984A - Road surface condition detection device and road surface condition monitoring system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a road surface condition detection device and a road surface condition monitoring system, for reducing introduction costs, and for precisely detecting road surface conditions at a vehicle side. <P>SOLUTION: This road surface condition monitoring system 1 is provided with: a transponder 3 installed in a tire; and a controller 4 which is installed in a vehicle body and can communicate with the transponder 3. The transponder 3 is provided with: a piezoelectric element 13 which is fixed to the tire and converts the vibration of the tire traveling on a road surface into an electric signal; and an antenna 11 for wirelessly transmitting the electric signal converted by the piezoelectric element 13 to a controller 4. The controller 4 is configured to acquire road surface condition information based on the frequency of the electric signal received from the transponder 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a road surface state detection device and a road surface state monitoring system that detect a road surface state of a road surface on which an automobile or the like travels.

2. Description of the Related Art Conventionally, as a road surface state detection device that detects a road surface state of a road surface on which an automobile travels, a device that detects the road surface state while being fixed to the road surface is known (see, for example, Patent Document 1). This road surface condition detection device installs a microphone inside a road, detects contact sound between a road and a tire of an automobile into an electric signal using the microphone, and extracts a frequency spectrum from the detected electric signal. Then, the road surface condition is detected by comparing the extracted frequency spectrum with frequency spectra corresponding to a plurality of types of road surface conditions registered in the apparatus in advance.
JP 2002-256521 A

  However, in the road surface condition detection device described in Patent Document 1, since the road surface state is detected by a device fixed inside the road, only local information can be obtained, and overall information is obtained. For this purpose, there is a problem that it is necessary to provide all the roads and the introduction cost increases. In this case, in order to obtain overall information, a configuration in which a microphone is provided on the vehicle body and the road surface condition is detected while traveling is considered, but unlike the structure provided inside the road, the road surface condition is correctly corrected by noise propagating in the air. There was a problem that it could not be detected.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a road surface state detection device and a road surface state monitoring system capable of reducing the introduction cost and accurately detecting the road surface state on the vehicle side. And

  The road surface condition detection device of the present invention is a piezoelectric element that converts vibration of the tire that is fixed on a tire and travels on a road surface into an electric signal, and a vehicle-side device that is provided on a vehicle body. And a communication unit that wirelessly transmits the converted electrical signal.

  The road surface condition monitoring system of the present invention is the road surface condition monitoring system provided with a road surface condition detection device provided on a tire and a vehicle side device provided on a vehicle body and capable of communicating with the road surface state detection device. The situation detection device includes a piezoelectric element that is fixed to the tire and that converts vibrations of the tire traveling on a road surface into an electrical signal, and a communication unit that wirelessly transmits the electrical signal converted by the piezoelectric element to the vehicle-side device. The vehicle-side device acquires road surface status information based on the frequency of the electrical signal received from the road surface status detection device.

According to this configuration, the tire is vibrated in accordance with the road surface condition during traveling and the tire vibrates, and the piezoelectric element vibrates at a cycle corresponding to the vibration of the tire, and the electric cycle having the period information including the road surface information is obtained. A signal is generated. Since the electrical signal generated by the piezoelectric element is wirelessly transmitted to the vehicle-side device by the communication unit, the vehicle-side device on the vehicle body side can acquire road surface condition information based on the electrical signal and monitor the road surface state. it can. Therefore, the introduction cost can be reduced as compared with a configuration in which a device for detecting a road surface condition is provided on a road.
In addition, since the vibration of the tire that is vibrated according to the road surface condition is directly converted into an electric signal, the contact sound between the road surface and the tire is converted into an electric signal and compared with a configuration that detects the road surface condition. Since noise that propagates in the air does not occur, the road surface condition can be detected with high accuracy.

  In the road surface condition detection apparatus according to the present invention, the communication unit transmits power to the vehicle side device using electric power of an electric signal converted by the piezoelectric element.

  According to this configuration, since the power of the electric signal is transmitted autonomously, a modulation circuit for modulating the carrier wave with the electric signal becomes unnecessary, and a simpler circuit configuration can be achieved.

  According to the present invention, in the road surface condition detection device, the communication unit modulates and transmits a carrier wave received from the vehicle side device with an electric signal converted by the piezoelectric element.

  According to this configuration, since the carrier wave modulated by the electric signal is transmitted to the vehicle side device, the electric signal can be stably transmitted to the vehicle side device.

  Further, the road surface condition detection device of the present invention uses a piezoelectric element that is fixed to a tire and converts vibration of the tire traveling on the road surface into an electric signal, and the frequency of the electric signal converted into the piezoelectric element is road surface condition information. A control circuit for converting and a power storage unit that rectifies and stores an electrical signal converted by the piezoelectric element, and the control circuit is operated by a voltage of the power storage unit.

  According to this configuration, since the electric signal generated from the piezoelectric element is rectified and stored in the power storage unit and used as the power supply voltage of the control circuit, the road surface condition can be calculated in the road surface condition detection device without providing a battery. Can do.

  According to the present invention, the introduction cost can be reduced, and the road surface condition can be accurately detected on the vehicle side.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
(First embodiment)
FIG. 1 is an overall configuration diagram of a road surface condition monitoring system according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating a fixed state of the piezoelectric element. In the road surface condition monitoring system according to the present embodiment, the present invention is applied to an automobile. However, the present invention is not limited to an automobile, and is not limited to an automobile. As long as it travels, it may be applied to any thing.

  As shown in FIG. 1, a road surface condition monitoring system 1 is used to detect a road surface condition on which a tire of an automobile travels and to monitor the road surface condition on the vehicle body side, and a road surface provided in the tire. It comprises a transponder 3 as a situation detection device and a controller 4 as a vehicle side device provided in the vehicle body and wirelessly connected to the transponder 3. The road surface condition monitoring system 1 is provided with a piezoelectric element 13 that vibrates in a cycle corresponding to the vibration of the tire in the transponder 3 and monitors the road surface condition based on an electric signal that is a voltage change generated by the vibration of the piezoelectric element 13. Yes.

  The controller 4 identifies the road surface condition where the tire is running and evaluates it for a warning message to the driver. The controller 4 transmits an unmodulated carrier wave of about 2.4 GHz from the antenna 7 to the transponder 3 and also does not modulate it. The carrier wave modulated by the electrical signal of the piezoelectric element 13 is received from the transponder 3. Further, the controller 4 extracts the modulation component of the carrier wave modulated by the transponder 3, and calculates tire road surface condition information based on the extracted modulation component.

  The transponder 3 converts the vibration of the tire into an electric signal, modulates an unmodulated carrier wave transmitted from the controller 4 by this electric signal, and sends it back to the controller 4. An antenna 11 and an antenna serving as a communication unit 11 has a FET 12 (Field Effect Transistor) connected to 11. The FET 12 is of the MOS type, the power supply point of the antenna 11 is connected to the drain, one electrode of the piezoelectric element 13 is connected to the gate, and the other electrode of the piezoelectric element 13 is connected to the source. A bias resistor 14 is connected between the gate and source of the FET 12 in parallel with the piezoelectric element 13.

  In the FET 12, an electric signal that changes in accordance with the vibration period output from the piezoelectric element 13 is applied to the gate to change the resistance between the gate and the source. The transmitted unmodulated carrier wave is modulated. In this way, the carrier wave is modulated by the electric signal generated from the piezoelectric element 13.

  As shown in FIG. 2, the piezoelectric element 13 is located in a space defined by a tire 21 and a wheel 22, and is fixed to the back side of the tread surface 21 a of the tire 21 via a pedestal 24. That is, the piezoelectric element 13 vibrates in accordance with the vibration period of the natural vibration of the tire 21 at this time because the tire 21 is vibrated and vibrated according to the road surface condition while the automobile is running.

  The piezoelectric element 13 is a bimorph type, and is configured by joining both surfaces of an elastic plate 16 from both sides by a pair of piezoelectric plates 17a and 17b, and between the piezoelectric plate 17a and the elastic plate 16 by vibration, and A voltage is generated between the piezo plate 17b and the elastic plate 16 respectively. At this time, the vibration period of the vibration of the piezoelectric element 13 and the vibration period of the electric signal are the same.

で与えられる。 Therefore, the road surface condition can be specified by measuring the frequency of the natural vibration of the tire 21 (frequency of the electric signal). In FIG. 1, the impedance R _DS between the source and the drain of the FET 12 is V (t)> V _P where V (t) is the voltage generated in the piezoelectric element 13, V _{P is} the pinch-off voltage, and I _DSS is the saturation drain current. When

Given in.

となる。 Looking at Figure 1, FET 12 is turned on the load of the antenna 11, the backscattered cross section sigma _B, the impedance of the antenna 11 R, the wavelength of the carrier wave lambda, when the gain of the antenna 11, _{G A,}

It becomes.

となり、圧電素子１３で発生する電圧変化から、コントローラ４の受信電力が変化することがわかる。このことから、コントローラ４の受信電力の変調成分を抽出し、変調成分の周波数を測定することで、路面状況がわかることとなる。 Using this backscattering cross section sigma _B, the received power P _R of the controller 4, the transmission power P _T of the transponder _3, gain G _T antennas 7 of the controller _4, the distance from the antenna 11 of the transponder 3 d Then,

Thus, it can be seen from the voltage change generated in the piezoelectric element 13 that the received power of the controller 4 changes. From this, the road surface condition can be understood by extracting the modulation component of the received power of the controller 4 and measuring the frequency of the modulation component.

  In the road surface condition monitoring system 1 using such a measurement principle, an unmodulated carrier wave transmitted from the controller 4 to the transponder 3 is modulated by an electric signal generated by the piezoelectric element 13 of the transponder 3 and transmitted to the controller 4. The From the modulated carrier wave received by the controller 4, the modulation component is extracted by a filter (not shown).

  The extracted modulation component represents the vibration frequency of the piezoelectric element 13. The control unit calculates the road surface condition information with reference to a table in which the extracted vibration frequency of the piezoelectric element 13 and the road surface state information are associated with each other. In the present embodiment, the table in which the vibration frequency of the piezoelectric element 13 and the road surface information are associated with each other is referred to. However, a map in which the vibration frequency of the piezoelectric element 13 and the road surface state information are associated with each other The road surface condition information may be calculated by a calculation formula incorporated in the program.

  The road surface condition information may be information indicating specific road surface conditions such as a dry road surface, a wet road surface, a frozen road surface, a snowy road surface, and an uneven road surface, or information indicating a road surface state indirectly such as a friction coefficient. May be.

As described above, according to the road surface condition monitoring system 1 according to the present embodiment, the tire is vibrated in accordance with the road surface condition during traveling, and the tire vibrates, and the piezoelectric element has a period according to the vibration of the tire. 13 vibrates, and an electric signal having a cycle including road surface condition information is generated. Since the electric signal generated by the piezoelectric element 13 is wirelessly transmitted from the transponder 3 to the controller 4, the controller 4 on the vehicle body side can acquire road surface condition information based on the electric signal and monitor the road surface condition. . Therefore, the introduction cost can be reduced as compared with a configuration in which a device for detecting a road surface condition is provided on the road.
In addition, since the vibration of the tire that is vibrated according to the road surface condition is directly converted into an electric signal, the contact sound between the road surface and the tire is converted into an electric signal and compared with a configuration that detects the road surface condition. Since noise that propagates in the air does not occur, the road surface condition can be detected with high accuracy.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. The road surface condition monitoring system according to the second embodiment of the present invention differs from the road surface condition monitoring system according to the first embodiment described above in that no carrier wave is used. Therefore, only differences will be described in particular, and the same reference numerals are used for the same components, and repeated descriptions are omitted. FIG. 3 is an overall configuration diagram of the road surface condition monitoring system according to the second embodiment of the present invention.

  As shown in FIG. 3, the transponder 33 includes an antenna 11 and a piezoelectric element 13 connected to the antenna 11 as a communication unit. The piezoelectric element 13 has one electrode connected to the feeding point of the antenna 11 and the other electrode grounded. In this road surface condition monitoring system 31, when the piezoelectric element 13 vibrates at a period that matches the vibration period of the tire, a radio wave having a frequency that the electric signal has is emitted from the antenna 11 using the electric power of the electric signal itself. The vibration frequency of the radio wave received by the controller 34 is measured in a control unit (not shown). A control part calculates the road surface condition information of a tire with reference to the table which matched the vibration frequency of the piezoelectric element 13, and the road surface condition information in a tire.

  As described above, according to the road surface condition monitoring system 31 according to the present embodiment, radio waves are independently transmitted using the power of the electrical signal output from the piezoelectric element 13, so that a carrier wave is transmitted to the transponder 33. This eliminates the need for a modulation circuit for modulating with this output signal, and allows a simpler circuit configuration.

(Third embodiment)
Next, a third embodiment of the present invention will be described. The road surface condition monitoring system according to the third embodiment of the present invention is different from the road surface condition monitoring system according to the first embodiment described above in that the road surface condition information in the tire is calculated in the transponder. Therefore, only differences will be described in particular, and the same reference numerals are used for the same components, and repeated descriptions are omitted.

  FIG. 4 is an overall configuration diagram of a road surface condition monitoring system according to the third embodiment of the present invention. FIG. 5 is a diagram illustrating output waveforms of an electric signal and a power supply voltage. FIG. 6 is an explanatory diagram of an increase cycle of the power supply voltage in FIG. In FIG. 5, the waveform W1 indicates the vibration waveform of the electric signal of the piezoelectric element, the waveform W2 indicates the waveform of the power supply voltage of the electrolytic capacitor, and the line L1 indicates the specified voltage. The waveform W3 in FIG. 6 shows the vibration waveform of the electric signal of the piezoelectric element, and the waveform W4 shows the waveform of the power supply voltage of the electrolytic capacitor.

  As shown in FIG. 4, the road surface condition monitoring system 41 includes a control circuit 46 that calculates road surface condition information in a transponder 43, converts it into a pulse signal, and outputs the pulse signal. The control circuit 46 is generated from the piezoelectric element 13. The road surface condition is monitored by operating with a direct current power source charged with electricity.

  The controller 44 transmits an unmodulated carrier wave of about 2.4 GHz from the antenna 7 to the transponder 43, and receives the unmodulated carrier wave modulated by the pulse signal output from the control circuit 46 from the transponder 43. In addition, the controller 44 extracts a modulation component from the carrier wave modulated by the transponder 43, and acquires road surface condition information from the extracted modulation component.

  The transponder 43 includes an antenna 11 and an FET 12 connected to the antenna 11 as a communication unit. A feed point of the antenna 11 is connected to the drain of the FET 12, a control circuit 46 is connected to the gate, and a control circuit 46 is connected to the source via the bias resistor 14. In the FET 12, a voltage corresponding to the period of the pulse signal output from the control circuit 46 is applied to the gate to change the resistance between the gate and the source. Unmodulated carrier waves are modulated.

  A frequency measurement unit 47 that measures the frequency of the electrical signal output from the piezoelectric element 13 is connected to the control circuit 46, and the output terminal of the operational amplifier 51 is connected to the frequency measurement unit 47. The operational amplifier 51 has an inverting input side input terminal connected to one electrode of the electrolytic capacitor 52, and a non-inverting input side input terminal connected to the other electrode of the electrolytic capacitor 52.

  A pair of electrodes of the piezoelectric element 13 is connected between the two input terminals of the operational amplifier 51 in parallel with the electrolytic capacitor 52, and between the inverting input terminal of the operational amplifier 51 and one electrode of the piezoelectric element 13. A DC cut capacitor 56 is provided, and a DC cut capacitor 57 is provided between the non-inverting input terminal of the operational amplifier 51 and the other electrode of the piezoelectric element 13. Between the piezoelectric element 13 and the electrolytic capacitor 52, a rectifier circuit 53 including four rectifier diodes 54 is provided.

  As shown in FIG. 5, when the piezoelectric element 13 vibrates at a period corresponding to the tire vibration, the electric signal W <b> 1 is stored in the electrolytic capacitor 52 through the rectifier circuit 53. When the power supply voltage W2 of the electrolytic capacitor 52 reaches the specified voltage L1 due to the storage, the operations of the control circuit 46, the frequency measuring unit 47, and the operational amplifier 51 are started. More specifically, as shown in FIG. 6, the piezoelectric element 13 vibrates in accordance with the rotation of the tire, and the power supply voltage W4 rises periodically.

  Returning to FIG. 4, a storage unit 48 is connected to the control circuit 46. The storage unit 48 stores a control program of the control circuit 46, a table in which the vibration frequency of the piezoelectric element 13 and road surface condition information are associated with each other, and these are read by the control circuit 46 as appropriate.

  The control circuit 46 operates when the power supply voltage supplied from the electrolytic capacitor 52 reaches a specified voltage, reads the table from the storage unit 48, and based on the vibration frequency of the piezoelectric element 13 measured by the frequency measurement unit 47, the road surface condition. Information is calculated, converted into a pulse signal, and output to the FET 12. The pulse signal output to the FET 12 is used for carrier wave modulation as described above. In addition, the electrical storage part as described in a claim is comprised from the electrolytic capacitor 52 and the rectifier circuit 53 which concern on this Embodiment.

  In such a road surface condition monitoring system 41, the unmodulated carrier wave transmitted from the controller 44 to the transponder 43 is modulated by the pulse signal output from the control circuit 46 and transmitted to the controller 44. The controller 44 extracts a modulation component from the received modulated carrier wave using a filter, and generates road surface condition information from the extracted modulation component.

  As described above, according to the road surface condition monitoring system 41 according to the present embodiment, the electrical signal generated from the piezoelectric element 13 is rectified by the rectifier circuit 53 and stored in the electrolytic capacitor 52, and used as the power supply voltage of the control circuit 46. Therefore, the road surface condition information can be calculated by driving the control circuit 46 and the like in the transponder 43 without providing a battery.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. The road surface condition monitoring system according to the fourth embodiment of the present invention is different from the road surface condition monitoring system according to the third embodiment described above in that an oscillation circuit is provided in the transponder. Therefore, only differences will be described in particular, and the same reference numerals are used for the same components, and repeated descriptions are omitted. FIG. 7 is an overall configuration diagram of a road surface condition monitoring system according to the fourth embodiment of the present invention.

  As shown in FIG. 7, the road surface condition monitoring system 61 according to the present embodiment is different in that an oscillation circuit 66 is provided instead of the FET 12 and the bias resistor 14 of the transponder 43 according to the third embodiment. . The oscillation circuit 66 oscillates according to the period of the pulse signal output from the control circuit 46. Then, the controller 64 generates road surface condition information from the oscillation frequency of the oscillation circuit 66 received by a control unit (not shown).

  As described above, according to the road surface condition monitoring system 61 according to the present embodiment, the electric signal generated from the piezoelectric element 13 is rectified by the rectifier circuit 53 and stored in the electrolytic capacitor 52 as the power supply voltage of the control circuit 46. Therefore, the road surface condition information can be calculated by driving the control circuit 46 and the like in the transponder 63 without providing a battery. Further, a step for transmitting a carrier wave from the controller 64 to the transponder 63 is not required, and the time for calculating the road surface condition information in the controller 64 can be saved, so that the measurement time can be shortened and the controller 64 can be simplified. A circuit configuration can be obtained.

(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described. The road surface condition monitoring system according to the fifth embodiment of the present invention is an existing tire air pressure which monitors the air pressure in the tire with the structure for detecting the road surface condition and the road surface condition monitoring system according to the first embodiment described above. It differs in that it is incorporated into a monitoring system (TPMS: Tire Pressure Monitoring System). Therefore, only differences will be described in particular, and the same reference numerals are used for the same components, and repeated descriptions are omitted. FIG. 8 is an overall configuration diagram of a road surface condition monitoring system according to a fifth embodiment of the present invention.

  As shown in FIG. 8, the road surface condition monitoring system 71 is configured by providing an existing TPMS with a piezoelectric element 13 for road surface condition detection, and is based on an electrical signal of the piezoelectric element 13 whose frequency changes according to tire vibration. To monitor road surface conditions. Since the TPMS has a known configuration, the details thereof will not be described. However, the TPMS is connected in parallel to the first crystal unit 76 and the first crystal unit 76, and the capacity is variable according to the pressure in the air. The air pressure in the tire is detected by the capacitive element 78, and the detected air pressure is corrected by the temperature in the tire detected by the second crystal resonator 77.

  The controller 74 switches the presence / absence of modulation of the carrier wave, and transmits the carrier wave modulated by the resonance frequency (excitation signal) of the first crystal resonator 76 and the second crystal resonator 77 to the transponder 73 for a certain period. After the first crystal unit 76 and the second crystal unit 77 are excited, the modulation is stopped and an unmodulated carrier wave is transmitted to the transponder 73.

  On the other hand, when the carrier wave modulated by the excitation signal is transmitted from the controller 74, the transponder 73 detects the excitation signal by the diode 79, and the first crystal resonator 76 and the second crystal resonator 77 are detected by this excitation signal. Exciting. At this time, the first crystal resonator 76 and the second crystal resonator 77 continue to vibrate for about 1 msec or more after the modulation is stopped. In this state, when an unmodulated carrier wave is transmitted from the controller 74 to the transponder 73, the unmodulated carrier wave is a resonance signal of the first crystal resonator 76 and the second crystal resonator 77 and an electric signal of the piezoelectric element 13. In response, the signal is modulated by the diode 79 at each frequency and transmitted to the controller 74.

  The controller 74 receives the carrier wave modulated by the resonance frequency of the first crystal resonator 76 and the second crystal resonator 77 from the transponder 73 and also receives the carrier wave modulated by the electric signal of the piezoelectric element 13. Each modulation component is extracted. At this time, as shown in FIG. 9, the resonance signal of the first crystal resonator 76 is located at about ± 11 MHz from the carrier wave, and the resonance signal of the second crystal resonator 77 is located at about ± 10 MHz from the carrier wave, Since the electrical signal of the piezoelectric element 13 is located at about ± 100 Hz from the carrier wave, a plurality of modulation components can be extracted from the modulated carrier wave. The controller 74 calculates tire air pressure information from the extracted resonance frequency of the first crystal resonator 76 and the extracted resonance frequency of the second crystal resonator 77, and calculates road surface condition information from the vibration frequency of the piezoelectric element 13.

  As described above, according to the road surface condition monitoring system 71 according to the present embodiment, the road surface condition monitoring system 71 can be configured by adding the piezoelectric element 13 to the existing TPMS. The introduction cost can be reduced.

  In each of the above-described embodiments, the bimorph piezoelectric element 13 is used. However, the present invention is not limited to this configuration as long as the vibration is converted into a voltage with a period corresponding to the vibration of the tire. For example, a configuration using a monomorph type or multilayer type piezoelectric element may be used.

  Further, in each of the above-described embodiments, the piezoelectric element 13 is fixed to the back side of the tread surface 21a of the tire 21 via the pedestal 24. However, as long as the structure vibrates at a cycle according to the vibration of the tire. For example, a configuration embedded in the tire 21 may be used. In the above-described embodiments, the road surface condition is determined based on the frequency of the electric signal received from the road surface condition detection device. However, it is possible to receive the frequency and amplitude of the electric signal and determine the road surface condition from them. In this case, it is possible to judge a more precise road surface condition. This modification can be realized by associating the vibration frequency and amplitude of the piezoelectric element with the road surface condition information, but this can be easily implemented by applying the above-described embodiment.

  The embodiment disclosed this time is illustrative in all respects and is not limited to this embodiment. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims for patent.

  As described above, the present invention has the effect of reducing the introduction cost and accurately detecting the road surface condition on the vehicle side, and in particular, detecting the road surface condition of the road surface on which an automobile or the like travels. It is useful for a situation detection device and a road surface situation monitoring system.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows 1st Embodiment of the road surface condition monitoring system which concerns on this invention, and is a whole block diagram of a road surface condition monitoring system. It is a figure which shows 1st Embodiment of the road surface condition monitoring system which concerns on this invention, and is a figure which shows the fixed state of a piezoelectric element. It is a figure which shows 2nd Embodiment of the road surface condition monitoring system which concerns on this invention, and is a whole block diagram of a road surface condition monitoring system. It is a figure which shows 3rd Embodiment of the road surface condition monitoring system which concerns on this invention, and is a whole block diagram of a road surface condition monitoring system. It is a figure which shows 3rd Embodiment of the road surface condition monitoring system which concerns on this invention, and is a figure which shows the output waveform of an electric signal and a power supply voltage. It is a figure which shows 3rd Embodiment of the road surface condition monitoring system which concerns on this invention, and is explanatory drawing of the increase cycle of the power supply voltage in FIG. It is a figure which shows 4th Embodiment of the road surface condition monitoring system which concerns on this invention, and is a whole block diagram of a road surface condition monitoring system. It is a figure which shows 5th Embodiment of the road surface condition monitoring system which concerns on this invention, and is a whole block diagram of a road surface condition monitoring system. It is a figure which shows 5th Embodiment of the road surface condition monitoring system which concerns on this invention, The resonance signal of a 1st crystal oscillator, the resonance signal of a 2nd crystal oscillator, the electrical signal of a piezoelectric element, and a carrier wave It is a figure which shows a relationship.

Explanation of symbols

1, 31, 41, 61, 71 Road surface monitoring system 3, 33, 43, 63, 73 Transponder (road surface detection device)
4, 34, 44, 64, 74 Controller (vehicle side device)
11 Antenna (communication part)
12 FET (communication part)
DESCRIPTION OF SYMBOLS 13 Piezoelectric element 46 Control circuit 47 Frequency measurement part 48 Memory | storage part 51 Operational amplifier 52 Electrolytic capacitor (electric storage part)
53 Rectifier circuit (power storage unit)
54 Rectifier diode 66 Oscillator circuit

Claims (5)

A piezoelectric element that is fixed to the tire and converts the vibration of the tire traveling on the road surface into an electrical signal;
A road surface condition detection apparatus comprising: a communication unit that wirelessly transmits an electric signal converted by the piezoelectric element to a vehicle side device provided in a vehicle main body.   The road surface condition detection device according to claim 1, wherein the communication unit transmits the electric signal power converted by the piezoelectric element to the vehicle side device.   The road surface condition detection device according to claim 1, wherein the communication unit modulates and transmits a carrier wave received from the vehicle-side device with an electric signal converted by the piezoelectric element. A piezoelectric element that is fixed to the tire and converts the vibration of the tire traveling on the road surface into an electrical signal;
A control circuit for converting the frequency of the electric signal converted into the piezoelectric element into road surface condition information;
A power storage unit that rectifies and stores the electrical signal converted by the piezoelectric element;
The road surface condition detection device, wherein the control circuit is operated by a voltage of the power storage unit. In a road surface condition monitoring system provided with a road surface condition detection device provided on a tire and a vehicle side device provided on a vehicle body and capable of communicating with the road surface condition detection device,
The road surface condition detection device is
A piezoelectric element that is fixed to the tire and that converts vibration of the tire traveling on a road surface into an electrical signal;
A communication unit that wirelessly transmits an electrical signal converted by the piezoelectric element to the vehicle-side device,
The road surface condition monitoring system, wherein the vehicle side device acquires road surface condition information based on a frequency of an electric signal received from the road surface condition detection device.

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