JP2004163134A - Pressure sensor, pressure measuring apparatus, and pressure measurement system using them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure measurement system using a pressure detection sensor that has a simple configuration and is inexpensive and a pressure measuring apparatus. <P>SOLUTION: The pressure measurement system 1 comprises the pressure sensors 50a-50d and the pressure measuring apparatus 10. The pressure sensors 50a-50d are composed as a radio tag having a resonance circuit, where a resonance frequency changes depending on pressure. The pressure measuring apparatus 10 detects the resonance frequency of the resonance circuit and specifies the pressure of the radio tag, based on the detected resonance frequency, by transmitting or receiving radio waves to and from the pressure sensors 50a-50d. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pressure detection sensor for detecting pressure, a pressure detection device, and a pressure detection system using the same.
[0002]
[Prior art]
In recent years, various pressure detection sensors, pressure detection devices, and pressure detection systems using these have been developed in order to meet the demand for automatic pressure detection. By the way, the air pressure of an automobile tire naturally drops due to so-called air bleeding or the like, but sufficient performance is exhibited only when an appropriate air pressure is charged. On the other hand, it is desired that the driver measures with a pneumatic gauge before traveling whether or not the tire air pressure is at an appropriate value, but such work is complicated. Under such circumstances, systems in the field of car electronics have been devised in the past to respond to the demand for automatic air pressure checking of automobile tires.
[0003]
A conventional system includes, for example, a tire-side alarm device mounted in a tire, a vehicle-side alarm device, and a notification device.
The tire-side alarm device detects whether there is an abnormality in the tire air pressure (low air pressure, puncture) when the tire vibrates, and wirelessly transmits a signal indicating the abnormality to the vehicle body-side alarm device when the abnormality is detected, In addition to a pressure sensor for detecting tire pressure, a temperature sensor for detecting tire temperature, a vibration sensor for detecting tire vibration, active components such as a transmission circuit and a control circuit, a battery for supplying power to the active components, a transmission antenna, and the like. Consists of
[0004]
The vehicle-side alarm device includes a receiving antenna, a band-pass filter, an amplifier circuit, a detection / demodulation circuit, and a control circuit, and includes a content of an abnormal signal (low air pressure / puncture) transmitted from the tire-side alarm device. , Etc.), and the notification device is driven (for example, see Patent Document 1).
[0005]
[Patent Document 1]
JP-A-2000-355203 (specification, FIG. 1)
[0006]
[Problems to be solved by the invention]
However, in order to detect the air pressure in the tire, the conventional system requires an active component, a battery, and the like in addition to the pressure sensor. Therefore, there has been a problem that the configuration of the device for detecting the pressure is complicated and the cost is increased.
[0007]
An object of the present invention is to solve the above-mentioned problems, and to provide a pressure detection sensor, a pressure detection device, and a pressure detection system using the same that are simple and inexpensive.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a pressure sensor according to the present invention is configured as a wireless tag having a resonance circuit whose resonance frequency changes depending on pressure.
[0009]
Here, the resonance circuit may include an antenna coil for receiving a detection radio wave from the outside and a capacitor, and may include a capacitance changing unit that changes the capacitance of the capacitor according to a pressure change.
[0010]
Here, the capacitance changing means is constituted by an inter-electrode distance changing means for changing an inter-electrode distance of the capacitor according to a pressure change, or the inter-electrode distance changing means is formed of an elastic body, The reversible elastic material can be constituted by a sponge material or a spring, or the interelectrode distance changing means can be constituted by an airtight chamber for sealing the electrodes of the capacitor. .
[0011]
In addition, the above-described pressure measuring device may further include a correction unit that corrects the table according to a value of the specific pressure input by the user when the wireless tag is at a specific pressure.
[0012]
Here, the pressure measurement device further includes a control unit that controls the pressure to be periodically specified by the detection unit and the specification unit, and a recording unit that records the periodically specified pressure as a history in a memory. It may be.
[0013]
Further, the pressure measuring device further includes a control unit that controls the pressure to be periodically specified by the detection unit and the specifying unit, and transmits the periodically specified pressure to the wireless tag, and stores the pressure in a memory in the wireless tag. And a transmission unit for recording as a history.
[0014]
Further, the pressure measuring device of the present invention transmits and receives radio waves to and from the wireless tag, thereby detecting means for detecting the resonance frequency of the resonance circuit, and specifies the pressure of the wireless tag based on the detected resonance frequency. And a specifying means for performing the operation.
[0015]
Further, the pressure measuring device of the present invention includes a transmitting unit for transmitting and receiving a radio wave of a specific frequency to and from a wireless tag including a resonance circuit whose resonance frequency changes depending on pressure, and a reception level of a reflected wave of the transmission radio wave. And a determining means for determining the pressure of the wireless tag according to the above.
[0016]
Here, the transmitting unit sets the resonance frequency corresponding to the monitoring pressure input by the user as the specific frequency, and the determining unit determines that when the reception level is smaller than the threshold, the wireless tag almost reaches the monitoring pressure. You may judge that there is.
[0017]
Note that the present invention can be realized as a pressure measurement system including the pressure sensor and the pressure measurement device, or can be realized as a pressure measurement method including, as steps, characteristic means constituting the pressure measurement device. It goes without saying that the characteristic means and steps constituting the apparatus can be realized as a pressure measurement program for causing the CPU to execute the steps.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0019]
(Embodiment 1)
FIG. 1 is a diagram showing an overall configuration in a case where the pressure measurement system 1 according to the first embodiment is applied to measurement of air pressure of a tire of an automobile.
[0020]
As shown in FIG. 1, the pressure measurement system 1 includes a pressure measurement device 10 and a plurality (four in the drawing) of pressure sensors 50a to 50d. The pressure sensors 50a to 50d are attached to the inner surfaces of the tires 4a to 4d of the automobile. Each of the pressure sensors 50a to 50d is a wireless tag including a resonance circuit including two passive elements, an antenna coil L and a capacitor C connected in parallel to the antenna coil L. The configuration is such that the resonance frequency changes. The pressure sensors 50a to 50d are configured to have different resonance frequency pressure characteristics in order to identify which sensor. That is, each of the pressure sensors 50a to 50d is configured such that its resonance frequency is different as f1 <f2 <f3 <f4 even at the same pressure.
[0021]
The pressure measuring device 10 emits radio waves for measuring pressure to the pressure sensors 50a to 50d, resonates the resonance circuits of the pressure sensors 50a to 50d in a non-contact manner by electromagnetic induction by the radio waves, and sets a value of the resonance frequency. This measures the pressure of the pressure sensors 50a to 50d, that is, the air pressure of each of the tires 4a to 4d. And an in-vehicle speaker 23 for notifying a warning or the like by sound.
[0022]
2 is an external view of the pressure sensors 50a to 50d shown in FIG. 1, FIG. 3 is a plan view of the pressure sensors 50a to 50d shown in FIG. 2, and FIG. FIG. 5 is an exploded perspective view of the pressure sensors 50a to 50d when the periphery of the pressure sensors 50a to 50d shown in FIG. 3 is cut away. Since the pressure sensors 50a to 50d have the same configuration except that the resonance frequency is different, the configuration of the pressure sensor 50a will be described as a representative.
[0023]
As shown in FIGS. 2 to 5, the pressure sensor 50 a is a substantially gourd-shaped flat body, and includes an antenna coil 51 constituting the above L, a pair of electrodes 52 and 53 constituting the above C, and an electrode An elastic body 54 interposed between 52 and 53, a base material 55 on which the antenna coil 51 is formed, and a surrounding pressure while sealing the antenna coil 51, the electrodes 52 and 53, the elastic body 54 and the base material 55. And a sealing and wrapping member 56 for applying voltage above and below the electrodes 52 and 53.
[0024]
The base material 55 on which the antenna coil is formed is a thin sheet material having electrical insulation and is formed in a substantially square shape having a convex portion on one side. A land 55a for electrically connecting the upper surface and the lower surface of the base material 55 is formed substantially at the center of the base material 55.
[0025]
The sealing and wrapping member 56 is made of a thin material such as a rubber material having electric insulating properties and a property of expanding and contracting according to pressure. Applied above and below 52 and 53.
[0026]
The antenna coil 51 is formed by winding one strip wire a plurality of times. One end 51 a of antenna coil 51 is electrically connected to electrode 52. The other end of the antenna coil 51 is electrically connected to a connection terminal 51b provided at a position corresponding to the land 55a.
[0027]
The electrodes 52 and 53 are each formed in a square shape, and are arranged to face each other with the elastic body 54 interposed therebetween.
The elastic body 54 has the same shape as the electrodes 52 and 53 and is formed to a predetermined thickness, and has a characteristic that the thickness changes according to pressure. As the elastic body 54, a reversible elastic material containing a gas therein (for example, a sponge material such as a porous rubber material or a urethane material, or a spring) is used. If the space between the electrodes 52 and 53 has a hermetic chamber structure and one of the electrodes 52 and 53 (for example, the electrode 53) has a flange structure, the reversible elastic material can be replaced with this hermetic chamber. Moreover, since the electrode 53 can directly receive the ambient pressure, the sealing and packaging member 56 can be omitted.
[0028]
Here, in this embodiment, a case where a sponge material is used as the elastic body 54 will be described assuming that a change in the relative permittivity εr can be ignored even if the thickness changes. As a result, the capacitor C is constituted by the pair of electrodes 52 and 53.
[0029]
On the other hand, the electrode 53 is electrically connected to the connection terminal 53b provided at a position corresponding to the land 55a via the lead wire 53a. The two connection terminals 51b and 53b are electrically connected at the position of the land 55a by caulking or pressing. As a result, the capacitor C is connected in parallel to the antenna coil 51, and a resonance circuit is formed by the two. In this resonance circuit, the distance between the electrodes 52 and 53 changes according to the pressure, and the capacitance of the capacitor C changes, so that the resonance frequency also changes according to the pressure. Therefore, radio waves are emitted from the pressure measuring device 10 to detect the resonance frequencies of the pressure sensors 50a to 50d, and specify the pressure corresponding to the resonance frequencies.
[0030]
The elastic body 54 has a characteristic that the thickness changes according to the pressure. Since the thickness of the elastic body 54 changes depending on the pressure, the interval between the electrodes 52 and 53 changes accordingly, and the capacitance of the capacitor C also changes depending on the pressure.
[0031]
FIG. 6 is a diagram showing the pressure characteristics of the thickness (distance between electrodes) of the elastic body 54 formed of a sponge material.
The elastic body 54 changes the distance d between the electrodes 52 and 53 according to the pressure applied to the electrodes 52 and 53 from above and below. That is, as the pressure applied to the electrodes 52 and 53 from above and below increases, the thickness (distance between the electrodes) d decreases.
[0032]
In the figure, the thickness d increases under pressure of 100 kPa, for example, when the elastic body 54 is formed of a sponge material and has a thickness of 0.525 mm, increases to approximately 0.55 mm when decreasing to 0 kPa, and increases to approximately 0.55 mm when increasing to 200 kPa. It can be seen that it decreased to 0.5 mm and changed according to the pressure. When the same material is formed to a thickness of 0.625 mm under a pressure of 100 kPa, the thickness (distance between electrodes) d increases to about 0.65 mm when the pressure drops to 0 kPa, and increases to about 0. 65 mm when the pressure increases to 200 kPa. It can be seen that it decreased to 0.6 mm and changed according to the pressure. When the same material is formed to a thickness of 0.725 mm under the pressure of 100 kPa, the thickness (distance between electrodes) d increases to about 0.75 mm when the pressure decreases to 0 kPa, and increases to about 0.75 mm when the pressure increases to 200 kPa. 0.7 mm, and it can be seen that it changes according to the pressure. Further, when the same material is formed to a thickness of 0.825 mm under a pressure of 100 kPa, the thickness (distance between electrodes) d increases to about 0.85 mm when the pressure decreases to 0 kPa, and increases to about 0. It can be seen that it decreased to 0.8 mm and changed according to the pressure.
[0033]
FIG. 7 is a diagram showing the pressure characteristics of the capacitance of the capacitors C1 to C4 having the pressure characteristics of FIG.
However, the electrodes 52 and 53 of the capacitor C are squares of 20 mm square, the distance between the electrodes is 0.525, 0.625, 0.725, and 0.825 mm under a pressure of 100 kPa, respectively. It is set to 1.
[0034]
In the figure, for example, the capacitance of the capacitor C1 is 6.439 pF at a pressure of 0 kPa, 6.746 pF at a pressure of 100 kPa, and 7.083 pF at a pressure of 200 kPa. The capacitance of the capacitor C2 is 5.449 pF at a pressure of 0 kPa, 5.667 pF at a pressure of 100 kPa, and 5.902 pF at a pressure of 200 kPa, and it can be seen that the capacitance changes according to the pressure. The capacitance of the capacitor C3 is, for example, 4.722 pF at a pressure of 0 kPa, 4.885 pF at a pressure of 100 kPa, and 5.059 pF at a pressure of 200 kPa. Further, the capacitance of the capacitor C4 is, for example, 4.167 pF at a pressure of 0 kPa, 4.293 pF at a pressure of 100 kPa, and 4.427 pF at a pressure of 200 kPa.
[0035]
FIG. 8 is a diagram illustrating an example of a pressure characteristic of a resonance frequency of a resonance circuit including the antenna coil L and the capacitor C of the pressure sensors 50a to 50d. However, the inductance of the antenna coil L is 3 μH.
[0036]
In the figure, the pressure sensors 50a to 50d have resonance frequency ranges of about 33 to 36 MHz, about 36 to 39 MHz, about 39 to 42 MHz, and about 42 to 45 MHz, respectively, in a pressure range of 0 kPa to 400 kPa.
[0037]
This difference in pressure characteristics can be easily realized in this embodiment by providing a difference in the distance between electrodes (thickness of elastic body 54) of capacitor C in pressure sensors 50a to 50d (that is, a difference in capacitance). it can. Such a difference in pressure characteristics makes it possible to distinguish which of the pressure sensors 50a to 50d is resonating by one pressure measuring device 10. In this case, it is possible to distinguish which of the pressure sensors 50a to 50d is resonating by a difference in the distance between electrodes (thickness of the elastic body 54). (I.e., differences in capacitance) and the number of turns and diameter of the antenna coil L (i.e., differences in inductance).
[0038]
Accordingly, the pressure sensors 50a to 50d have different resonance frequency pressure characteristics. That is, the pressure sensors 50a to 50d are configured to have different resonance frequencies even at the same pressure.
[0039]
For example, as shown by the solid line in FIG. 9, when the pressure is the same, the resonance frequencies of the pressure sensors 50a to 50d are f1, f2, f3, and f4, respectively. Further, the pressure sensors 50a to 50d have a pressure characteristic such that the resonance frequency ranges within the pressure range used (for example, 100 to 300 kPa) do not overlap.
[0040]
FIG. 10 is a diagram showing an external configuration of the pressure measuring device 10 shown in FIG.
An operation unit 21 including a plurality of buttons, an antenna 25 for wirelessly transmitting and receiving data to a host or the like (not shown), and the like are provided on the surface of the device main body 11 of the pressure measurement device 10. The operation unit 21 includes, for example, a measurement button 21a for instructing pressure measurement, a monitoring button 21b for monitoring pressure and instructing to warn when a specific pressure is reached, A history button 21c for instructing recording of the pressure, a correction button 21d for correcting the measured pressure, a set button 21e for setting pressures such as monitoring pressure and correction pressure, a reset button 21f for resetting, and the like. Is done.
[0041]
The LCD unit 22 displays an operation menu, a measured pressure, a warning, and the like. For example, in the monitoring mode described later, the LCD unit 22 displays the air pressures of the front, rear, left, and right tires, whether the air pressures are appropriate, if the air pressures are not appropriate, a warning of refilling air, a warning of tire puncture, and the like. Is displayed.
[0042]
FIG. 11 is a diagram showing an electrical configuration of the pressure sensors 50a to 50d and the pressure measuring device 10.
Each of the pressure sensors 50a to 50d is a wireless tag having an LC resonance circuit including an antenna coil L and a capacitor C whose capacity changes depending on the pressure by each part shown in FIG.
[0043]
The pressure measuring device 10 is roughly divided into an input / output unit 20, a control unit 30, and an antenna unit 40.
The input / output unit 20 includes an operation unit 21, an LCD unit 22, a speaker 23 for notifying the completion of the measurement by sound, a vibrator motor 24 for notifying the completion of the measurement by vibration, history information of the measured pressure, and other data. An antenna 25 for wirelessly transmitting and receiving commands and commands to a host computer (not shown) installed at a gas station or the like, and a level converter 26 for transmitting and receiving data to and from the host computer.
[0044]
The control unit 30 has a ROM in which a program is stored in advance, a memory for temporarily storing data such as a button type operated by the operation unit 21, a memory for providing a work area when the program is executed, and time measurement. A microcomputer unit 31 composed of one chip including a timer, a CPU for executing a program, and the like, a D / A conversion unit 32, and a VCO (Voltage-Controlled Oscillator) that is an oscillator that outputs a high-frequency signal having an oscillation frequency according to an applied voltage ) 33, a demodulation unit 34 for demodulating radio waves received by the antenna unit 40, an A / D conversion unit 35, a pressure table 36a indicating the frequency versus pressure characteristics of the pressure sensors 50a to 50d, and a pressure history. And a non-volatile memory 36 for storing a history table 36b and the like.
[0045]
The antenna unit 40 includes an amplifier 41 for amplifying a signal output from the VCO 33, a transmitting antenna coil 42 for emitting a signal amplified by the amplifier 41, and a receiving antenna coil 43 for receiving radio waves from the pressure sensors 50a to 50d. And an amplifier 44 for amplifying the electric signal received by the receiving antenna coil 43.
[0046]
FIG. 12 is a diagram illustrating an example of the pressure table 36a.
This drawing is created based on the frequency versus pressure characteristics shown in FIG. 8, is stored at the time of shipment from a factory, and is appropriately corrected by the user. In the figure, the pressure intervals are irregular for the sake of convenience, but may be once or less. Note that, instead of the pressure table 36a, a table indicating the correspondence between the digital value of the input voltage of the VCO 33 (that is, the input data of the D / A converter 32) and the pressure may be used.
[0047]
FIG. 13 is a flowchart showing various operations in the pressure measuring device 10 that measures pressure under the control of the microcomputer unit 31 shown in FIG. In FIG. 13, steps S102, S104, S109, and S114 are the same subroutine.
[0048]
First, the microcomputer unit 31 receives an operation for designating an operation mode from the user via the operation unit 21 and determines which operation mode is selected (S101). The operation modes include (A) a measurement mode for measuring the pressure at that time, (B) a history mode for periodically measuring the pressure and accumulating the measured pressure as a history, and (C) whether the specified pressure is reached. And (D) a correction mode for correcting an error in the measured pressure.
[0049]
(A) When the operation of starting the measurement mode is performed, the microcomputer unit 31 measures the current pressure Pc of the pressure sensors 50a to 50d (S102), and displays the measured pressure Pc on the LCD unit 22 (S103). .
[0050]
The process of measuring the current pressure Pc is performed according to a subroutine shown in FIG.
In the figure, the microcomputer 31 sweeps the frequency of the detected radio wave emitted from the transmitting antenna coil 42 by gradually changing the voltage applied to the VCO 33 via the D / A converter 32 (S120). The frequency at which the reception level of the radio wave received by the receiving antenna coil 43 becomes the lowest is specified (S121, see FIG. 12A), and the pressure corresponding to the specified frequency is read out from the pressure table 36a to obtain the current value. (P122).
[0051]
Here, the sweep of the transmission frequency is performed, for example, by gradually increasing the digital value output from the microcomputer unit 31 within the frequency range of the pressure table 36a, thereby gradually increasing the voltage input to the VCO 33 and outputting the voltage from the VCO 33. This is done by gradually increasing the frequency of the signal. When the frequency is swept in this manner, the reception level of the radio wave received by the reception antenna coil 43 rapidly decreases from a constant value slightly before the resonance frequency of the pressure sensors 50a to 50d (see FIG. 15A). ), Minimum at the resonance frequency, above which it rapidly increases again and returns to a constant value. That is, a dip occurs. Therefore, the resonance frequency can be easily specified from the digital value output from the microcomputer unit 31 at the time of receiving the dip, and the current pressure Pc can be specified based on the pressure table 36a.
[0052]
Further, the pressure measurement device 10 notifies the user of the current pressure Pc in the measurement mode. Since the current pressure is measured in a non-contact manner, it is possible to know the current pressure (air pressure) Pc of each of the tires 4a to 4d without having to measure the air pressure of each of the tires 4a to 4d with a user or a pressure gauge. it can.
[0053]
Note that the measurement completion may be notified to the user by the speaker 23 and the vibrator motor 24 at the same time when the measured pressure is displayed on the LCD unit 22.
(B) When the operation of starting the history mode is performed, the microcomputer unit 31 measures the current pressure Pc of the pressure sensors 50a to 50d (S104), and measures the measured pressure together with the accompanying data such as date and time in the nonvolatile memory 36. Is recorded (appended) in the history table 36b (S105), and it is determined whether or not a certain time (here, three minutes) has elapsed (S106). When it is determined that the time has elapsed, the process returns to S104, and the above measurement and the above additional writing are performed in the same manner. As described above, in the history mode, the pressure information is recorded in the history table 36b as the history of the measurement at regular time intervals together with the attached information.
[0054]
As an application example of the history mode, a pressure history can be used as a part of a record of air replenishment at the time of tire replacement or a part of a maintenance storage record.
(C) When the operation of starting the monitoring mode is performed, the microcomputer unit 31 first receives an operation of setting an arbitrary pressure by the user, holds the received pressure internally as the monitoring pressure Pt (S107), and performs the predetermined time. It is determined whether (one minute in this case) has elapsed (S108). When one minute has elapsed, the microcomputer unit 31 measures the current pressure Pc (S109), calculates a difference ΔP between the measured pressure Pc and the held monitoring pressure Pt (S110), and calculates the difference ΔP. It is determined whether it is smaller than the threshold value P1a (S111a). Here, the threshold value P1a is a predetermined value, for example, P1a = 190 kPa.
[0055]
When the difference ΔP is not smaller than the threshold value P1a (S111a: no), the microcomputer unit 31 determines that the current pressure has not yet reached the monitoring pressure (see FIG. 12B), and proceeds to step S108. Return.
[0056]
When the difference ΔP is smaller than the threshold value P1a (S111a: yes), the microcomputer unit 31 determines whether the difference ΔP is smaller than the threshold value P1b (S111b). Here, the threshold value P1b is a predetermined value, for example, lower than P1a, such as P1b = 150 kPa.
[0057]
If the difference ΔP is not smaller than the threshold value P1b (S111b: no), the microcomputer unit 31 determines that the current pressure Pc has reached the monitoring pressure Pt for air supplementation, A warning to that effect is given by sound, vibration by the vibration motor 24, wireless communication from the antenna 25 to the host (S112a), and the process returns to step S108.
[0058]
Further, when the difference ΔP is smaller than the threshold value P1b (S111b: yes), the microcomputer unit 31 determines that the current pressure Pc has reached the monitoring pressure Pt for tire puncture detection, and the speaker unit 23 A warning is given by sound, vibration by the vibrating motor 24, wireless communication from the antenna 25 to the host, or the like (S112b).
[0059]
As described above, in the monitoring mode, when the pressure measuring device 10 reaches the monitoring pressure arbitrarily set by the user, the pressure measuring device 10 warns of the monitoring pressure.
As an application example of the monitoring mode, if the user sets a pressure deviating from the appropriate pressure as the monitoring pressure Pt for replenishing air, the air can be replenished to the tires 4a to 4d at a gas station or the like after a warning, and the appropriate level is again determined. Can be kept at pressure.
[0060]
Further, as another application example of the monitoring mode, if the user sets a pressure slightly lower than the monitoring pressure for replenishing air, for example, a pressure of about 150 kPa, as the monitoring pressure, when the tire air pressure reaches the monitoring pressure, You will be warned of a tire puncture. In this case, the tire can be replaced with a spare tire without damaging the tire, and the punctured tire can be reused with a small repair. Since the values of these monitoring pressures are arbitrarily determined by the user, they can be set to air pressures suitable for the user's preferences.
[0061]
Further, as another application example of the monitoring mode, when a pressure sensor having the same configuration as the pressure sensors 50a to 50d and different only in the resonance frequency is attached to a spare tire, the spare tire is replaced when the air pressure of the spare tire reaches the monitoring pressure. You will be warned of tire refilling. As a result, the performance of the spare tire can be fully exhibited from the time of tire replacement.
[0062]
(D) When the operation of starting the correction mode is performed, the microcomputer unit 31 first receives the operation of inputting the actual pressure Pa of the pressure sensors 50a to 50d by the user, and internally holds the received pressure as the monitoring pressure Pt. (S113). For example, the user sets the pressure sensors 50a to 50d to a known pressure and inputs the pressure as the actual pressure Pa.
[0063]
Here, as the known pressure, for example, if the air pressure of the tires 4a to 4d is set to the appropriate air pressure of the automobile (for example, 200 kPa) at a gas station or the like, the appropriate pressure can be corrected.
[0064]
Next, the microcomputer unit 31 measures the current pressure Pc (S114), calculates a difference ΔP between the measured pressure Pc and the actual pressure Pa (S115), and the difference ΔP is larger than the threshold value P2. It is determined whether or not. Here, the threshold value P2 is a value that is allowable as an error and is a predetermined value.
[0065]
If the difference ΔP is equal to or smaller than the threshold value P2, that is, if the measured pressure Pc is within the allowable range of the error (S116: no), the microcomputer unit 31 ends the correction mode. In this case, the pressure table 36a does not need to be corrected.
[0066]
When the difference ΔP is larger than the threshold value P2, that is, when the difference exceeds the allowable range of the error (S117), the microcomputer unit 31 corrects the pressure table 36a (S118). The correction here is the simplest method, in which the pressure value in each column of the pressure table 36a may be updated to a value obtained by subtracting ΔP.
[0067]
As described above, in the correction mode, the pressure table 36a is corrected to a more correct value even if the resonance frequency is shifted from the initial value due to repeated use of the pressure sensors 50a to 50d, aging, and the like, and the error ΔP becomes unacceptable. Therefore, the current pressure can be measured without deteriorating the accuracy.
[0068]
As described above, according to the pressure measurement system 1 of the first embodiment, the pressure of the measurement target to which the pressure sensors 50a to 50d are attached can be measured in a non-contact manner.
[0069]
The microcomputer unit 31 is different from the monitoring mode process (S107 to 112a, 112b) shown in FIG. 13 in that the processing load on the microcomputer unit 31 is small and another process shown in FIG. Monitoring mode processing may be performed.
[0070]
In FIG. 16, after receiving the monitoring pressure Pt (S130), the microcomputer unit 31 determines the frequency corresponding to the monitoring pressure Pt with reference to the pressure table 36a (S131), and a predetermined time (here, one minute) elapses. Each time the radio wave is transmitted, the radio wave is transmitted at the frequency via the D / A conversion unit 32, the VCO 33, and the antenna unit 40 (S133), and transmitted via the antenna unit 40, the demodulation unit 34, and the A / D conversion unit 35. The reception level at that time is measured (S134), and if the reception level is equal to or lower than the threshold value V1 (S135: yes), a warning is issued (S136). This is because, when the pressures of the pressure sensors 50a to 50d are different from the monitoring pressure Pt, the reception level is relatively large (see the dashed line and the broken line in FIG. 17), and the pressure sensors 50a to 50d reduce the monitoring pressure Pt. Utilizing the fact that the reception level becomes minimum when it reaches (see the solid line in FIG. 14). The threshold value V1 may be a value slightly larger than the minimum reception level in FIG.
[0071]
As described above, in the monitoring mode process of FIG. 16, the frequency sweep in FIG. 13 is unnecessary, and the radio wave is transmitted at one frequency corresponding to the monitoring pressure Pt, so that the process (S133 to S135) every fixed time is required. It can be greatly reduced. Therefore, the monitoring mode processing of FIG. 16 is more suitable when the pressure change of the measurement target is fast.
[0072]
In the history mode, a start condition and an end condition for taking a history may be set. For example, the start condition or the end condition may be that the time set by the user has come, and that the pressure or pressure range has been set by the user.
[0073]
Further, in S105 of FIG. 13, a condition for adding a history may be set. For example, additional recording may be performed in the history only when the measured pressure Pc is within (or out of) the pressure range set by the user in advance.
[0074]
In the history mode, a warning in the monitoring mode may be issued (called a composite mode). In that case, the configuration may be such that the steps of S110 to S112 in FIG. 13 are added immediately after S105.
[0075]
(Embodiment 2)
Although the pressure sensors 50a to 50d according to the first embodiment include only passive elements, the present embodiment describes a configuration in which the pressure sensor itself records the pressure history as a wireless tag.
[0076]
FIG. 18 is a diagram illustrating an appearance of the pressure sensors 70a to 70d according to the second embodiment.
The pressure sensors 70a to 70d in the figure are wireless tags to which an IC chip 60 is added, as compared with the pressure sensors 50a to 50d shown in FIGS.
[0077]
FIG. 19 is a block diagram illustrating a functional configuration of the pressure sensors 70a to 70d. Since the pressure sensors 70a to 70d have the same configuration except that the resonance frequency is different, the configuration of the pressure sensor 70a will be described as a representative.
[0078]
As shown in the figure, the pressure sensor 70a includes an antenna coil L, a capacitor C, and an IC chip 60. The antenna coil L and the capacitor C have the same configuration as in FIG.
[0079]
The IC chip 60 includes a power generation unit 71, a clock reproduction unit 72, a demodulation unit 73, a modulation unit 74, a microcomputer unit 75, and a memory 76, and is configured to wirelessly receive power from the outside and transmit and receive data. I have.
[0080]
The power generation unit 71 generates an induced power by an electromagnetic induction method or an electromagnetic coupling method while receiving a power carrier wave from the external pressure measuring device 80 via the antenna unit (the antenna coil L and the capacitor C). Thus, DC power is supplied to the inside of the IC chip 60. Therefore, the power generation unit 71 includes a diode that internally rectifies the induced power, a capacitor that smoothes the voltage of the rectified induced power or stores DC power, and a regulator that stabilizes the voltage to a constant value (Vcc). Prepare. Here, the power carrier radio wave is a high-frequency signal such as the power carrier A and the ASK modulated wave B shown in FIG.
[0081]
The clock recovery unit 72 recovers a clock signal from the received power carrier and supplies the clock signal to the microcomputer unit 75.
The demodulation unit 73 extracts data by demodulating a high-frequency signal received via the antenna unit. For example, an ASK modulation wave B as shown in FIG. 20 is demodulated, and the result is output to the microcomputer unit 75 as data C.
[0082]
The modulator 74 modulates a high-frequency signal based on data input from the microcomputer 75. For example, the data D shown in FIG.
The microcomputer unit 75 interprets the data C demodulated by the demodulation unit 73 and, if the command is an interpretation result command, executes a response or a process corresponding to the command. The commands include a write command instructing to write received data into the memory 76, a read command instructing to read data from the memory 76 and transmit the data via the modulator 74 and the antenna.
[0083]
The memory 76 is a non-volatile memory that does not disappear even when power is not supplied by the power generation unit 71.
FIG. 21 is a block diagram showing a functional configuration of pressure measuring device 80 in the present embodiment.
[0084]
11 differs from the pressure measurement device 10 shown in FIG. 11 in that a control unit 81 is provided instead of the control unit 30. Commands and data are exchanged between the pressure measurement device 80 and the pressure sensor 70. Is transmitted and received. Hereinafter, the description of the same components will be omitted, and different components will be mainly described.
[0085]
The control unit 81 is different from the control unit 30 in that a modulation unit 82 is newly added and a demodulation unit 83 is provided instead of the demodulation unit 34. Also, the programs stored in the ROM in the microcomputer unit 31 are different.
[0086]
The modulator 82 modulates the high-frequency signal from the VCO 33 based on the data C from the microcomputer 31 and outputs the modulated signal to the antenna 40. Here, it is assumed that the modulator 82 performs the ASK modulation shown in FIG. If the modulating section 82 performs the non-modulation operation, the power carrier A shown in FIG. 20 is transmitted. Similarly, no modulation is performed in the frequency sweep.
[0087]
The demodulation unit 83 demodulates a radio wave received from the pressure sensor 70 via the antenna unit 40. Here, it is assumed that BPSK demodulation is performed.
By executing the program stored in the ROM, the microcomputer unit 31 executes (1) a process of recording the measured pressure as history information inside the pressure sensors 70a to 70d in addition to the functions of the first embodiment, and (2) A) reading the pressure history recorded inside the pressure sensors 70a to 70d.
[0088]
(1) Processing for recording history information inside pressure sensors 70a to 70d
FIG. 22 is a sequence diagram showing a process of recording the pressure history inside the pressure sensors 70a to 70d under the control of the microcomputer unit 31.
[0089]
The process of FIG. 14 starts and ends according to a user operation. In response to the start operation, the microcomputer unit 31 in the pressure measuring device 80 first measures the current pressure Pc of the pressure sensors 70a to 70d (S190). In the measurement of the current pressure Pc, the microcomputer unit 31 performs a frequency sweep (S191) to determine a frequency at which the reception level is the minimum, and determines the pressure based on the frequency, similarly to the processing of FIG. 11 described in the first embodiment. The current pressure is obtained from the table 36a.
[0090]
Next, the microcomputer unit 31 performs a process of transmitting the current pressure Pc measured to the pressure sensors 70a to 70d as pressure information (S192). Specifically, the microcomputer unit 31 starts transmission of the power carrier (S193), and after the power is supplied to the pressure sensors 70a to 70d, sends a write command via the modulation unit 82 and the antenna unit 40. Then, pressure information (current pressure Pc, date and time, etc.) is transmitted (S195), and transmission of the power carrier is stopped after a predetermined time has elapsed (S196). Here, the predetermined time refers to a time sufficient for completing the memory writing operation inside the pressure sensors 70a to 70d. The command and data (pressure information) are transmitted as ASK-modulated serial data, and the ASK-modulated wave at the time of this transmission also functions as a power carrier, so that the pressure sensors 70a to 70d are in a state where power is supplied. I have.
[0091]
Further, the microcomputer unit 31 in the pressure measuring device 80 performs the above-described measurement of the current pressure Pc and the pressure information transmission process when a predetermined time (10 minutes in the figure) has elapsed (S200). Thereby, the pressure information at regular time intervals (10 minutes) is transmitted to the pressure sensor 70.
[0092]
On the other hand, in the pressure sensor 70, the microcomputer unit 75 receives the command after the power is supplied (S197). Since the command is interpreted as a write command, the microcomputer unit 75 continuously receives data (S198). The pressure information is recorded (appended) as a history in the memory 76 (S199). Since the additional writing to the memory 76 is repeated at the above-mentioned fixed time intervals, the pressure information is accumulated in the memory 76 as a history.
[0093]
(2) Processing for reading the pressure history recorded inside the pressure sensor 70
FIG. 23 is a sequence diagram illustrating a process of transmitting the pressure history recorded inside the pressure sensor 70 to the pressure measuring device 80 under the control of the microcomputer unit 31.
[0094]
The process of FIG. 11 also starts and ends according to a user operation. In response to the start operation, the microcomputer unit 31 in the pressure measuring device 80 performs a pressure history reading process (S201). Specifically, the microcomputer unit 31 starts transmission of the power carrier signal A (see FIG. 18) (S202), and after the power supply of the pressure sensor 70 is supplied, the modulation unit 82 and the antenna unit 40 Then, a read command is transmitted (S203), and a pressure history transmitted from the pressure sensor 70 is received (S204). After completion of the reception, the transmission of the power carrier signal is stopped (S205). As a result, the pressure history stored in the pressure sensor 70 is transferred to the pressure measuring device 80. The transferred pressure history is further wirelessly transmitted from the pressure measuring device 80 to an external host computer via the antenna 25, and is used for, for example, transport management of the pressure measurement target.
[0095]
As described above, according to the pressure measurement system 2 of the present embodiment, it is possible to record the pressure history in the internal memory of the pressure sensor 70 itself and to transfer the pressure history to the pressure measurement device 80. .
[0096]
In addition, in addition to the pressure history, the ID (product ID) of the pressure measurement object, the date and time of replacement of the product (tire), and the traveling distance may be recorded as additional information in the memory 76 in the pressure sensor 70, In the case of an automobile, these additional information may be recorded after acquiring such additional information from the control device of the engine.
[0097]
Further, the command from the pressure measuring device 80 to the pressure sensor 70 is not limited to the above-described write command and read command, but may be a reset command, a memory clear command, or the like.
[0098]
Further, prior to transmission or reception of a command or data between the pressure measurement device 80 and the pressure sensor 70 in FIGS. 22 and 23, the authentication sequence may be configured to be performed in one direction or two directions.
[0099]
Further, a configuration may be adopted in which encrypted data is transmitted and received. In this way, when the pressure sensor 70 is used as a wireless tag, items relating to trade secrets can also be safely recorded.
[0100]
Further, in the present embodiment, the pressure of pressure sensor 70 is measured by the frequency sweep from pressure measurement device 80, but pressure sensor 70 itself may be configured to measure the pressure by the frequency sweep. As a configuration example in that case, in addition to the configuration in FIG. 19, a power supply unit such as a button battery or a solar cell, a transmission antenna for transmitting a radio wave by performing a frequency sweep after the modulation unit 74, and the 14 may be added so that the microcomputer unit 75 performs the pressure measurement process shown in FIG. At this time, the microcomputer unit 75 may specify the resonance frequency at the time when the induced current in the resonance circuit becomes the maximum, instead of specifying the resonance frequency with the frequency with the lowest reception level. Alternatively, a control circuit may be provided which detects the resonance frequency of the resonance circuit at the time when the induced current becomes maximum, and specifies the pressure based on the detected resonance frequency.
[0101]
(Embodiment 3)
In pressure sensors 50a to 50d according to the first embodiment, antenna coil 51 is formed planarly on one surface.
[0102]
In such a configuration, the maximum communication distance is obtained when the antenna surface of the pressure measuring device 10 and the tag surface formed by the antenna coil 51 are parallel. In other words, under a certain distance, the maximum electromagnetic induction occurs when the antenna surface and the tag surface are parallel, and there is direction dependency in the detection sensitivity. For this reason, if the tag is tilted, electromagnetic induction is reduced, and it may be difficult to specify the resonance frequency during pressure measurement.
[0103]
Thus, in the pressure sensor according to the third embodiment, the above-described direction dependency is eliminated by forming the antenna coil three-dimensionally.
FIG. 24 is a diagram showing a configuration of a pressure sensor 50A according to the present embodiment. In particular, FIG. 24A is a perspective view of a mechanical configuration of the pressure sensor 50A, and FIG. Circuit diagrams of a typical configuration are shown. Here, since the main focus is on the description of the three-dimensional configuration of the antenna coil, the electrodes 52 and 53, the elastic body 54 and the like constituting the capacitor are not shown in FIG.
[0104]
The pressure sensor 50A is formed by forming antenna coils Lx to Lz on three adjacent surfaces of a cube 61 formed small, for example, several mm on a side, and connecting the antenna coils Lx to Lz in series. ing. The cube 61 is formed of an insulator material.
[0105]
When the antenna surfaces of the pressure measuring devices 10 and 80 are parallel to the surface formed by the antenna coil Lx, electromagnetic induction occurs most between the antenna surface and the antenna coil Lx. When the antenna surfaces of the pressure measuring devices 10 and 80 are parallel to the plane formed by the antenna coil Ly or the antenna coil Lz, the most electromagnetic induction occurs between the antenna coil Ly and the antenna coil Lz. On the other hand, when the antenna surface of the pressure measuring device 10 is inclined from the plane formed by the antenna coils Lx to Lz, electromagnetic induction occurs by adding the parallel components of the antenna coils Lx to Lz with respect to the antenna surface. That is, under a certain distance, no matter what angle the antenna surface and the tag surface make, electromagnetic induction of almost the same value as when the antenna surface of the pressure measuring device 10 is parallel to an antenna coil always occurs. For this reason, the reduction of the electromagnetic induction and the direction dependency that occur in the case of the first embodiment are eliminated, and the resonance frequency can be reliably detected. Further, the antenna coil shown in the figure can be similarly applied to the pressure sensor 70 in the second embodiment.
[0106]
In the above embodiment, the antenna coils Lx to Lz are formed only on the three surfaces of the cube, however, antenna coils may be formed on the remaining three surfaces.
In the third embodiment, the three-dimensional antenna coil is formed by combining the antenna coils Lx to Lz formed on the plane, respectively. However, as shown in FIG. A three-dimensional antenna coil may be formed by forming one antenna coil L1. It goes without saying that a three-dimensional antenna coil may be formed by forming one antenna coil L1 on the convex surface. Even with such a simple antenna coil L1, substantially the same effects as those of the antenna coils Lx to Lz can be obtained.
[0107]
Further, as shown in FIG. 25B, antenna coils L2, L3, and L4 are formed on the surface of the sphere around the X, Y, and Z axes having the center of the sphere 62 as the origin of the three-dimensional orthogonal coordinates. The coils L2 to L4 may be connected in series.
[0108]
Also in this case, similarly to the case of the antenna coils Lx to Lz, the decrease in the electromagnetic induction that occurs in the first and second embodiments is eliminated, and the resonance frequency can be reliably detected.
[0109]
Further, in each of the above-described embodiments, an example has been described in which the resonance circuit in which the resonance frequency changes depending on the pressure is realized by the capacitor C whose capacitance changes depending on the pressure. May be configured to use a coil L whose inductance changes depending on the current. In that case, the shape memory alloy may be used as the material and a coil having a different spacing or diameter between the windings at a specific pressure and a different coil at other pressures may be used. Further, a resonance circuit may be configured by combining this coil with a capacitor C whose capacity changes depending on pressure. In this case, the change in the resonance frequency at a specific pressure can be made steep.
[0110]
It should be noted that the flowcharts or sequence diagrams shown in FIGS. 13, 14, 16, 22, and 23 in each embodiment are realized as a program in the microcomputer in the pressure measuring devices 10, 80 or the pressure sensor 70. Nor. This program can be distributed and distributed through a recording medium such as a CD or a telecommunication line.
[0111]
In addition, as shown in FIG. 26, the pressure sensors 50a to 50d have one surface of the fastener (for example, a loop material 59a) adhered to the lower surface of the sealed packaging member 56, and are attached to the mounting position (the inner surface side of the tire 4). The other of the fasteners (e.g., hook material 59b) may be attached so that the pressure sensors 50a to 50d can be easily attached and detached. The same applies to the pressure sensors 70a to 70d.
[0112]
In the above-described embodiment, the pressure sensors 50a to 50d and 70a to 70d are used as sensors for detecting the air pressure of the tires 4a to 4d. it can. Further, in combination with the pressure measuring devices 10 and 80, medical devices such as a barometer, an altimeter, an altitude correction meter, a depth gauge, and a sphygmomanometer can be realized. In addition, when used in combination with a general wireless tag in addition to the pressure sensors 50a to 50d, pressure management based on pressure history can also be performed in combination with pressure-related product management / distribution management, manufacturing container / pallet management, and the like. Can be. Further, as another application example of the history mode, when the pressure sensors 50a to 50d are attached to an instrument such as a test tube for a chemical experiment, when performing an experiment of a chemical reaction involving heat generation in the container, the pressure history is measured. It is useful for calculating the reaction speed under pressure.
[0113]
【The invention's effect】
The pressure sensor of the present invention is configured as a wireless tag having a resonance circuit whose resonance frequency changes depending on pressure.
[0114]
According to this configuration, a slight improvement of a general wireless tag is sufficient, and the pressure measuring device wirelessly identifies the resonance frequency of the resonance circuit, and identifies the pressure of the wireless tag based on the resonance frequency, thereby reducing the pressure. Measurement can be performed, and there is an effect that a pressure sensor can be formed by applying a wireless tag.
[0115]
Here, the resonance circuit may include an antenna coil for receiving a detection radio wave from the outside and a capacitor, and may include a capacitance changing unit that changes a capacitance of the capacitor according to a pressure change.
[0116]
According to this configuration, according to this configuration, since the resonance circuit is formed of a passive circuit including a coil and a capacitor, it is possible to reduce the size and cost with a simple configuration. In addition, in the conventional system, complicated battery replacement work was required in a device for detecting pressure.However, in the present invention, since it can be configured only with passive components, complicated battery replacement work is unnecessary, and maintenance-free and permanent. It becomes possible to use it effectively.
[0117]
Further, the capacitance changing means is constituted by an inter-electrode distance changing means for changing an inter-electrode distance of the capacitor according to a pressure change, the inter-electrode distance changing means is constituted by an elastic body, or the elastic body is reversible. Or the reversible elastic material may be formed of a sponge material or a spring, or the inter-electrode distance changing means may be formed of an airtight chamber for airtightly sealing the electrodes of the capacitor.
[0118]
According to this configuration, various frequency-pressure characteristics suitable for the application of the pressure sensor or the range of the measured pressure can be easily realized depending on the type of the capacitance changing unit.
In addition, the above-described pressure measuring device may further include a correction unit that corrects the table according to a value of the specific pressure input by the user when the wireless tag is at a specific pressure.
[0119]
According to this configuration, the reliability of the measured pressure can be increased without deteriorating the accuracy of the pressure measurement.
Here, the pressure measurement device further includes a control unit that controls the pressure to be periodically specified by the detection unit and the specification unit, and a recording unit that records the periodically specified pressure as a history in a memory. It may be.
[0120]
According to this configuration, since the pressure history is recorded in the memory in the pressure measuring device, it is suitable for managing the pressure history in real time.
Further, the pressure measuring device further includes a control unit that controls the pressure to be periodically specified by the detection unit and the specifying unit, and transmits the periodically specified pressure to the wireless tag, and stores the pressure in a memory in the wireless tag. And a transmission unit for recording as a history.
[0121]
According to this configuration, since the pressure history is recorded in the internal memory of the pressure sensor itself, it is suitable for managing the pressure history ex post facto.
Further, the pressure measuring device of the present invention includes a transmitting unit for transmitting and receiving a radio wave of a specific frequency to and from a wireless tag including a resonance circuit whose resonance frequency changes depending on pressure, and a reception level of a reflected wave of the transmission radio wave. And a determining means for determining the pressure of the wireless tag according to the above.
[0122]
Here, the transmitting unit sets the resonance frequency corresponding to the monitoring pressure input by the user as the specific frequency, and the determining unit determines that when the reception level is smaller than the threshold, the wireless tag almost reaches the monitoring pressure. You may judge that there is.
[0123]
According to this configuration, instead of transmitting the radio wave while changing the frequency, the radio wave of the specific frequency corresponding to the monitoring pressure is transmitted and the reception level of the reflected wave is determined. Response time can be made faster.
[0124]
As described above, according to the present invention, a user using a pressure measurement system including a pressure sensor having a simple configuration, a small size and an inexpensive pressure, and a pressure measurement device can quickly perform a pneumatic operation by detecting a decrease in tire pressure or a puncture. By replenishing and replacing tires, you can spend a car life that maximizes the performance of the car. Therefore, the present invention expands the application range of the wireless tag, dramatically improves the value provided by the pressure sensor, the pressure measuring device, and the pressure measuring system, and has a very high practical value.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration in a case where a pressure measurement system 1 according to a first embodiment is applied to air pressure measurement of an automobile tire.
FIG. 2 is an external view of the pressure sensors 50a to 50d shown in FIG.
FIG. 3 is a plan view of the pressure sensors 50a to 50d shown in FIG.
FIG. 4 is a sectional view as viewed from AA shown in FIG. 3;
FIG. 5 is an exploded perspective view of the pressure sensors 50a to 50d when the periphery of the pressure sensors 50a to 50d shown in FIG. 3 is cut away.
FIG. 6 is a diagram showing a pressure characteristic of a thickness (distance between electrodes) of an elastic body 54;
FIG. 7 is a diagram showing the pressure characteristics of the capacitance of the capacitors C1 to C4 having the pressure characteristics of FIG.
FIG. 8 is a diagram illustrating an example of a pressure characteristic of a resonance frequency of the pressure sensors 50a to 50d.
FIG. 9 is a diagram showing reception levels and resonance frequencies of the pressure sensors 50a to 50d.
10 is a diagram showing an external configuration of the pressure measuring device 10 shown in FIG.
11 is a diagram showing an electrical configuration of the pressure sensors 50a to 50d and the pressure measuring device 10. FIG.
FIG. 12 is a diagram illustrating an example of a pressure table 36a.
13 is a flowchart showing various operations in the pressure measuring device 10 that measures pressure under the control of the microcomputer unit 31 in FIG.
FIG. 14 is a flowchart showing a subroutine of measurement processing of a current pressure Pc.
FIG. 15A is a diagram showing a frequency to be swept and a reception level.
(B) is a diagram showing the frequency and the reception level at the current pressure and the monitoring pressure.
FIG. 16 is a flowchart showing another monitoring mode process.
FIG. 17 is a diagram showing a frequency and a reception level corresponding to a monitoring pressure.
FIG. 18 is a diagram illustrating an appearance of pressure sensors 70a to 70d according to the second embodiment.
FIG. 19 is a block diagram showing a functional configuration of pressure sensors 70a to 70d.
FIG. 20 is a diagram showing various signal waveforms transmitted and received by the pressure sensors 70a to 70d and the pressure measuring device 80.
FIG. 21 is a block diagram showing a functional configuration of the pressure measuring device 2.
FIG. 22 is a sequence diagram showing a process of recording a pressure history inside a pressure sensor IC chip under the control of a microcomputer unit.
FIG. 23 is a sequence diagram showing a process of transmitting a pressure history recorded on a pressure sensor IC chip to a pressure measurement device under the control of a microcomputer unit.
FIG. 24A is a diagram illustrating a perspective view of a mechanical configuration of a pressure sensor.
FIG. 3B is a circuit diagram of an electrical configuration of the pressure sensor.
FIG. 25 is a perspective view of another mechanical configuration of the pressure sensor.
FIG. 26 is an external view of a pressure sensor having a fastener on a lower surface.
[Explanation of symbols]
1,2 pressure measurement system
4a-4d tire
10,80 Pressure measuring device
20 input / output unit
21 Operation unit
21a Measurement button
21b Monitoring button
21c History button
21d Correction button
21e Set button
21f Reset button
22 LCD unit
23 Speaker
24 vibe motor
25 Antenna
26 level converter
30, 81 control section
31,75 microcomputer section
32 D / A converter
33 VCO
34, 73, 83 demodulation unit
35 A / D converter
36 Non-volatile memory
36a pressure table
36b history table
40 Antenna part
41,44 Amplifier
42 transmitting antenna coil
43 Receiving antenna coil
50a-50d, 70a-70d Pressure sensor
51 Antenna coil
52,53 electrodes
54 Elastic body
55 substrate
56 Sealed packaging material
59a Loop material
59b hook material
60 IC chip
71 Power generation unit
72 Clock recovery unit
74, 82 modulation section
76 memory

Claims (50)

A pressure sensor for detecting pressure,
A pressure sensor comprising a wireless tag having a resonance circuit whose resonance frequency changes depending on pressure. The resonance circuit includes an antenna coil and a capacitor for receiving a detection radio wave from the outside,
2. The pressure sensor according to claim 1, further comprising capacitance changing means for changing the capacitance of the capacitor according to a pressure change. 3. The pressure sensor according to claim 2, wherein the capacitance changing unit is an inter-electrode distance changing unit that changes an inter-electrode distance of the capacitor according to a pressure change. 4. The pressure sensor according to claim 3, wherein said inter-electrode distance changing means is an elastic body. The pressure sensor according to claim 4, wherein the elastic body is a reversible elastic material. The pressure sensor according to claim 5, wherein the reversible elastic material is a sponge material. The pressure sensor according to claim 5, wherein the reversible elastic member is a spring. 4. The pressure sensor according to claim 3, wherein said inter-electrode distance changing means is an airtight chamber for air-tightly connecting the electrodes of said capacitor. The pressure sensor according to any one of claims 2 to 8, wherein the pressure sensor is a flat body. The pressure sensor according to claim 9, wherein the pressure sensor further includes a planar fastener attached to the flat body. The pressure sensor according to any one of claims 2 to 10, wherein the antenna coil is formed three-dimensionally. The pressure sensor according to claim 11, wherein the antenna coil is formed by spirally winding one coil. The pressure sensor according to claim 11, wherein the antenna coil is configured such that winding surfaces of two or more coils are connected to be orthogonal to each other. The pressure sensor according to claim 2, wherein the pressure sensor further includes a memory and a microcomputer, and the microcomputer records the pressure measured based on a resonance frequency of the resonance circuit in the memory. The pressure sensor further has communication means,
The pressure sensor according to claim 14, wherein the microcomputer records pressure information received via a communication unit in a memory. The pressure sensor according to claim 15, wherein the microcomputer stores the pressure information as a history. 16. The pressure sensor according to claim 15, wherein the microcomputer reads out the pressure information recorded in the memory according to a command received through the communication unit and transmits the read pressure information through the communication unit. The pressure sensor further has a memory and a microcomputer,
The pressure sensor according to claim 2, wherein the microcomputer detects a resonance frequency of the resonance circuit, specifies a pressure based on the detected resonance frequency, and records the specified pressure in a memory. The pressure sensor further includes a memory, a communication unit, and a microcomputer,
The memory stores a resonance frequency versus pressure characteristic in the resonance circuit as a table,
The microcomputer specifies a resonance frequency of the resonance circuit by transmitting and receiving a radio wave while changing a frequency through a communication unit, and specifies a pressure corresponding to the resonance frequency by referring to a table. The pressure sensor according to claim 2, wherein 20. The pressure sensor according to claim 19, wherein the microcomputer records the specified pressure in a memory. 20. The pressure sensor according to claim 19, wherein the microcomputer periodically specifies the resonance frequency and the pressure, and records the specified pressure as a history in a memory. 22. The pressure sensor according to claim 21, wherein the microcomputer reads a pressure history recorded in a memory and transmits the pressure history via a communication unit according to a command received via the communication unit. Detecting means for detecting the resonance frequency of the resonance circuit by transmitting and receiving radio waves to and from a wireless tag including a resonance circuit whose resonance frequency changes depending on pressure;
A specification unit for specifying the pressure of the wireless tag based on the detected resonance frequency. The detection means,
Transmitting means for transmitting radio waves while changing the frequency,
Measuring means for measuring the level of the reflected wave from the wireless tag;
24. The pressure measuring apparatus according to claim 23, further comprising: a determination unit configured to determine a frequency at which the measured level is minimum as a resonance frequency. The specifying means includes:
Memory means for storing a resonance frequency versus pressure characteristic in the resonance circuit as a table,
25. The pressure measuring device according to claim 24, further comprising: specifying means for specifying a pressure corresponding to the detected resonance frequency based on the table. 26. The pressure according to claim 25, wherein the pressure measuring device further includes an output unit that outputs the specified pressure by any one of display, vibration, sound, wireless communication, or a combination of two or more thereof. measuring device. 26. The pressure measurement device according to claim 25, wherein the pressure measurement device further includes a correction unit that corrects the table according to a value of the specific pressure input by a user when the wireless tag is at a specific pressure. The pressure measuring device further includes control means for controlling the pressure to be periodically specified by the detection means and the specification means,
24. The pressure measuring device according to claim 23, further comprising: a recording unit that records periodically specified pressures as a history in a memory. The pressure measuring device further includes control means for controlling the pressure to be periodically specified by the detection means and the specification means,
24. The pressure measuring device according to claim 23, further comprising: a transmitting unit that periodically transmits the specified pressure to the wireless tag and records the pressure as a history in a memory in the wireless tag. The transmitting means transmits a command instructing the wireless tag to transmit a pressure history,
The pressure measurement device according to claim 29, wherein the pressure measurement device further includes a receiving unit that receives a pressure history transmitted from a wireless tag in accordance with a command. The pressure measuring device further includes a receiving unit that receives a setting of a monitored pressure by a user,
Control means for controlling the pressure to be periodically specified by the detection means and the specification means,
Determining means for determining whether the specified pressure has reached the monitoring pressure,
The pressure measuring device according to claim 23, further comprising a warning unit that issues a warning when it is determined that the pressure has been reached. A pressure measuring device including a microcomputer, a memory, and a communication unit that wirelessly communicates with a wireless tag including a resonance circuit whose resonance frequency changes depending on pressure,
The memory stores a resonance frequency versus pressure characteristic in the resonance circuit as a table,
The microcomputer specifies a resonance frequency of the resonance circuit by transmitting and receiving a radio wave while changing a frequency through a communication unit, and specifies a pressure corresponding to the resonance frequency by referring to a table. Pressure measuring device. 33. The pressure measuring apparatus according to claim 32, wherein the microcomputer further specifies the resonance frequency and the pressure periodically and records the specified pressure as a history in the memory. The microcomputer further specifies the resonance frequency and the pressure periodically, transmits the specified pressure to the wireless tag via the communication unit, and records the pressure as a history in a memory in the wireless tag. The pressure measuring device according to claim 32. The microcomputer transmits a command instructing the wireless tag to transmit the pressure history via the communication unit,
35. The pressure measurement device according to claim 34, wherein the pressure measurement device receives a pressure history transmitted from the wireless tag via the communication unit in accordance with the command. The microcomputer further receives a setting of the monitoring pressure by the user, periodically specifies the resonance frequency and the pressure, determines whether the specified pressure has reached the monitoring pressure, and when it is determined that the monitoring pressure has been reached. The pressure measuring device according to claim 32, wherein a warning is output. 33. The pressure measuring device according to claim 32, wherein the microcomputer further corrects the table according to a value of a specific pressure input by a user when the wireless tag is at a specific pressure. Transmitting means for transmitting and receiving radio waves of a specific frequency to and from a wireless tag having a resonance circuit whose resonance frequency changes depending on pressure;
A pressure measuring device comprising: a determination unit configured to determine a pressure of the wireless tag according to a reception level of a reflected wave of the transmission radio wave. The transmitting means, as the specific frequency resonance frequency corresponding to the monitoring pressure input by the user,
39. The pressure measuring apparatus according to claim 38, wherein the determination unit determines that the wireless tag is substantially at the monitoring pressure when the reception level is smaller than a threshold value. A detecting step of detecting a resonance frequency of the resonance circuit by transmitting and receiving a radio wave to and from a wireless tag including a resonance circuit whose resonance frequency changes depending on pressure;
A specifying step of specifying the pressure of the wireless tag based on the detected resonance frequency. A pressure measurement system comprising a pressure sensor and a pressure measurement device,
The pressure sensor is configured as a wireless tag having a resonance circuit whose resonance frequency changes depending on pressure,
The pressure measuring device,
Detecting means for detecting the resonance frequency of the resonance circuit by transmitting and receiving radio waves to and from the wireless tag,
Specifying means for specifying the pressure of the wireless tag based on the detected resonance frequency. A pressure measurement system comprising a plurality of pressure sensors and a pressure measurement device,
Each of the pressure sensors is configured as a wireless tag having a resonance circuit whose resonance frequency changes depending on pressure,
The pressure measuring device,
Detecting means for detecting the resonance frequency of the resonance circuit by transmitting and receiving radio waves to and from the wireless tag,
Identification means for identifying the pressure of the wireless tag and the wireless tag based on the detected resonance frequency,
The plurality of wireless tags have different frequency ranges for the same pressure range. Each of the pressure sensors is respectively mounted in a plurality of tires of the vehicle,
43. The pressure measuring system according to claim 42, wherein the specifying unit specifies a state of air pressure of each tire. The detection means sweeps the frequency of the radio wave periodically or intermittently,
44. The pressure measuring system according to claim 43, wherein the specifying unit specifies the wireless tag attached to the tire based on the detected resonance frequency. The pressure measuring device further includes a receiving unit that receives a setting of a monitored pressure by a user,
Control means for controlling the pressure to be periodically specified by the detection means and the specification means,
Determining means for determining whether the specified pressure has reached the monitoring pressure,
Warning means for issuing a warning when it is determined that the time has been reached,
45. The pressure measuring system according to claim 44, wherein the warning means notifies the driver of the condition of the tire pressure. 46. The pressure measurement system according to claim 45, wherein the warning includes at least one of replenishing the tire and puncturing the tire. Each of the pressure sensors further includes a memory, a microcomputer, and communication means,
47. The pressure measurement system according to claim 46, wherein the microcomputer records pressure information received from the pressure measurement device via communication means and information unique to each tire in a memory. 48. The pressure measurement system according to claim 47, wherein at least one of an ID of each tire, a replacement date and time, and a traveling distance of the vehicle at the replacement date and time is included. The determining means determines the tire replacement time based on the pressure information recorded in the memory and the unique information,
49. The pressure measurement system according to claim 48, wherein the warning unit notifies a driver of a time for replacing each of the tires. A program for a pressure measurement device including a microcomputer, a memory, and a communication unit that wirelessly communicates with a wireless tag including a resonance circuit whose resonance frequency changes depending on pressure,
Identifying the resonance frequency of the resonance circuit by transmitting and receiving radio waves while changing the frequency via communication means,
And a step of specifying a pressure based on the resonance frequency.

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