JP5101356B2 - Pressure sensor and pressure measuring device having the same - Google Patents

Description

  The present invention relates to a pressure sensor using a surface acoustic wave and a pressure measuring device including the pressure sensor.

  In recent years, a tire pressure monitoring system (TPMS) for monitoring the air pressure of tires such as automobiles has been developed. In such a tire pressure monitoring system, a pressure sensor capable of accurately detecting air pressure is indispensable.

As a pressure sensor for detecting a gas pressure such as air pressure, a pressure sensor as shown in the following Patent Document 1 is known. The pressure sensor disclosed in Patent Document 1 includes a pressure detection resonator and a local oscillation resonator each including a comb electrode pair (interdigital transducer) that oscillates a surface acoustic wave. According to the pressure sensor having such a configuration, it is possible to detect the gas pressure using the resonance frequency of the pressure detection resonator while compensating for the influence of the temperature using the resonance frequency of the local oscillation resonator.
JP-A-2005-181305

  However, in the above pressure sensor, since two comb electrode pairs are alternately connected to an external communication antenna, there is a problem in that the pressure sensor must be provided with a power supply for a switching circuit. It is desirable that a pressure sensor used in a tire pressure monitoring system or the like transmits a wireless signal without power supply without providing a power source therein.

  The present invention has been made to solve the above-described problems. Accordingly, an object of the present invention is to provide a pressure sensor capable of detecting a gas pressure without power supply while compensating for the influence of temperature, and a pressure measuring device including the pressure sensor.

  The above object of the present invention is achieved by the following means.

The pressure sensor of the present invention includes a piezoelectric substrate, a comb electrode portion, a pressure detecting reflector, a diaphragm portion, and a temperature compensating reflector. The piezoelectric substrate propagates surface acoustic waves. The comb electrode portion is provided on the piezoelectric substrate, receives a radio signal from the outside, and excites surface acoustic waves on the piezoelectric substrate, while receiving surface acoustic waves propagating on the piezoelectric substrate. Wave and convert to response signal. The reflector for pressure detection is provided on the propagation path of the surface acoustic wave, and reflects the surface acoustic wave excited by the comb electrode part toward the comb electrode part. The diaphragm portion is provided between the comb electrode portion and the pressure detecting reflector, and is propagated by the surface acoustic wave by being deformed according to a pressure difference between the cavity portion inside the piezoelectric substrate and the outside. Change the path length of the path. The temperature compensating reflector is provided on the comb electrode part side with respect to the diaphragm part on the surface acoustic wave propagation path, and the surface acoustic wave excited by the comb electrode part is applied to the comb electrode. Reflects towards the part. The temperature compensating reflector is provided on the anti-diaphragm portion side of the comb electrode portion, and reflects the surface acoustic wave excited by the comb electrode portion toward the comb electrode portion. And while reflecting a part of the surface acoustic wave provided between the first reflector and the comb electrode part and excited by the comb electrode part toward the comb electrode part, A part of the surface acoustic wave that is provided between the second reflector that passes the remaining surface acoustic wave, and between the comb electrode portion and the diaphragm portion and is excited by the comb electrode portion A third reflector that reflects toward the electrode portion and allows the remaining surface acoustic waves to pass therethrough.

  The pressure measuring device of the present invention has the pressure sensor, reading means, and calculating means. The reading means receives a response signal from the pressure sensor while transmitting a radio signal to the pressure sensor. The calculation means calculates a gas pressure based on a time change of the response signal received by the reading means.

  According to the pressure sensor and the pressure measuring device of the present invention, the surface acoustic wave reflected by the pressure detecting reflector and the temperature compensating reflector is converted into a response signal by one comb electrode portion. It is possible to detect the gas pressure without power supply while compensating for the above.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol was used for the same member in the figure.

  FIG. 1 is a diagram showing a schematic configuration of a pressure measuring device according to an embodiment of the present invention. The pressure measuring device according to the present embodiment measures gas pressure using surface acoustic waves.

  As shown in FIG. 1, the pressure measurement device according to the present embodiment includes a pressure sensor 10, a reading device 20, and a computer 30. The pressure sensor 10 is disposed away from the reading device 20 and the computer 30. The reading device 20 and the computer 30 are connected via a communication cable.

  The pressure sensor 10 detects gas pressure (for example, air pressure). The pressure sensor 10 is a non-powered sensor that does not have a power source therein, and operates by receiving a radio signal (hereinafter referred to as a call signal) transmitted from the reading device 20. The pressure sensor 10 detects the gas pressure using surface acoustic waves, and returns a response signal whose response time changes according to the change of the gas pressure to the reading device 20. A detailed description of the pressure sensor 10 using surface acoustic waves will be described later.

  The reading device 20 transmits and receives an electrical signal (electromagnetic wave) to and from the pressure sensor 10 as a reading unit. The reading device 20 receives a response signal from the pressure sensor 10 while transmitting a call signal to the pressure sensor 10. The response signal is transmitted to the computer 30 through the communication cable.

  The computer 30 calculates gas pressure based on the time change of the response signal received by the reading device 20 as calculation means. The computer 30 of this embodiment calculates the gas pressure by detecting the phase of the response signal from the pressure sensor 10 received by the reading device 20.

  Next, the pressure sensor 10 of the present embodiment will be described in detail with reference to FIG.

  2A is a top view of the pressure sensor in the pressure measuring device shown in FIG. 1, and FIG. 2B is a cross-sectional view taken along the line II-II 'of FIG. As described above, the pressure sensor 10 of the present embodiment is a non-powered sensor that detects a gas pressure using surface acoustic waves.

  As shown in FIG. 2, the pressure sensor 10 of this embodiment includes a piezoelectric substrate 11, a comb electrode portion 12, a pressure detection reflector 13, a diaphragm portion 14, and a temperature compensation reflector 15. The comb electrode portion 12, the pressure detection reflector 13, and the temperature compensation reflector 15 are provided on the surface of the piezoelectric substrate 11, and the diaphragm portion 14 is provided on the same plane as the surface of the piezoelectric substrate 11. ing.

The piezoelectric substrate 11 propagates surface acoustic waves. The piezoelectric substrate 10 is formed of a piezoelectric material such as lithium niobate (LiNbO ₃ ), and forms a propagation path of the surface acoustic wave excited by the comb electrode portion 12. Inside the piezoelectric substrate 11, a hollow portion for constituting the diaphragm portion 14 is provided.

  The comb-tooth electrode part 12 mutually converts a surface acoustic wave and an electric signal. The comb electrode unit 12 receives a call signal from the reading device 20 and excites a surface acoustic wave on the piezoelectric substrate 11, while receiving a surface acoustic wave propagating on the piezoelectric substrate 11 to generate a response signal. Convert. The comb-tooth electrode part 12 is comprised from a pair of comb-tooth-shaped electrode, and each comb-tooth-shaped electrode is formed from aluminum (Al), for example. Of the pair of comb-like electrodes, one comb-like electrode is electrically connected to the communication antenna through an electrode pad, and the other comb-like electrode is grounded. The call signal and the response signal are transmitted / received to / from the reading device 20 via the communication antenna.

  The pressure detecting reflector 13 is provided on the propagation path of the surface acoustic wave, and reflects the surface acoustic wave excited by the comb electrode portion 12 toward the comb electrode portion 12. The pressure detecting reflector 13 is composed of a plurality of band-shaped protrusions extending perpendicularly to the propagation path of the surface acoustic wave, and reflects the surface acoustic wave propagating on the surface of the diaphragm portion 14. The band-shaped protrusion is made of aluminum, for example.

  Diaphragm part 14 changes the length of the propagation path of a surface acoustic wave by changing according to gas pressure. The diaphragm portion 14 is provided between the comb-teeth electrode portion 12 and the pressure detecting reflector 13, and is deformed in accordance with a pressure difference between the cavity portion inside the piezoelectric substrate 11 and the outside, whereby propagation of surface acoustic waves is performed. Change the path length of the path.

  The temperature compensating reflector 15 is provided on the comb electrode portion 12 side with respect to the diaphragm portion 14 on the surface acoustic wave propagation path, and the surface acoustic wave excited by the comb electrode portion 12 is applied to the comb electrode portion 12. Reflected toward the. The temperature compensating reflector 15 in the present embodiment includes first to third reflectors 15a, 15b, and 15c. The distances from the comb electrode portion 12 to the reflectors 13, 15a, 15b, and 15c are different from each other.

  The first reflector 15 a is provided on the anti-diaphragm part 14 side of the comb electrode part 12, and reflects the surface acoustic wave excited by the comb electrode part toward the comb electrode part 12. The first reflector 15a is formed of the same number of band-like protrusions as the pressure detecting reflectors 13, and reflects the surface acoustic waves that have passed through the second reflector 15b.

  The second reflector 15 b is provided between the first reflector 15 a and the comb electrode part 12, and a part of the surface acoustic wave excited by the comb electrode part 12 is directed toward the comb electrode part 12. The remaining surface acoustic waves are allowed to pass through while reflecting. The second reflector 15b is formed from a number of band-shaped protrusions that are fewer than the pressure detecting reflector 13 so as to pass a part of the surface acoustic wave.

  The third reflector 15 c is provided between the comb electrode portion 12 and the diaphragm portion 14, and reflects part of the surface acoustic wave excited by the comb electrode portion 12 toward the comb electrode portion 12. On the other hand, the remaining surface acoustic waves are passed. The third reflector 15c is formed from a number of band-shaped protrusions that are fewer than the pressure detection reflector 13 so as to pass a part of the surface acoustic wave.

  Next, a manufacturing method of the pressure sensor shown in FIG. 2 will be described with reference to FIG.

  FIG. 3 is a cross-sectional view for explaining a manufacturing process of the pressure sensor shown in FIG. The pressure sensor 10 of the present embodiment is formed by directly joining two piezoelectric substrates.

  First, the base substrate 11a is prepared, and a photoresist is formed on the base substrate 11a. Then, by patterning the photoresist, the mask layer 16 provided with the opening 16h is formed on the base substrate 11a (see FIG. 3A).

  Next, a portion of the base substrate 11a exposed from the opening 16h of the mask layer 16 is cut using a sand blast method, thereby forming a recess 11c in the base substrate 11a (see FIG. 3B).

  Next, a thin film substrate 11b made of the same piezoelectric material as the base substrate 11a is prepared, and the base substrate 11a provided with the recess 11c and the thin film substrate 11b are directly bonded using a direct bonding method, an anodic bonding method, or the like. (See FIG. 3C). If it does in this way, a cavity part is formed by the recessed part 11c and the thin film substrate 11b of the base substrate 11a, and a part of thin film substrate 11b comprises the diaphragm part 14. FIG. The hollow portion is filled with an inert gas such as argon gas, and airtightness is maintained. Alternatively, unlike the present embodiment, the cavity can be maintained in a vacuum.

  Then, the comb electrode part 12, the pressure detecting reflector 13, and the temperature compensating reflector 15 are formed on the thin film substrate 11b (see FIG. 3D). The comb electrode part 12, the pressure detecting reflector 13, and the temperature compensating reflector 15 are formed by using a lift-off method or an etching method.

  In the pressure sensor 10 of the present embodiment configured as described above, the comb electrode portion 12 receives the calling signal and excites the surface acoustic wave. The excited surface acoustic wave propagates on the piezoelectric substrate 11. The surface acoustic wave propagating on the piezoelectric substrate 11 is reflected toward the comb electrode portion 12 by the reflectors 13, 15a, 15b, and 15c. The comb electrode portion 12 receives the surface acoustic waves reflected by the reflectors 13, 15a, 15b, and 15c and converts them into response signals.

  At this time, if the gas pressure around the pressure sensor 10 changes, the diaphragm portion is deformed according to the gas pressure. If the diaphragm portion 14 is deformed, the path length of the propagation path of the surface acoustic wave propagating between the comb electrode portion 12 and the pressure detecting reflector 13 changes. Further, if the temperature around the pressure sensor 10 changes, the surface acoustic wave propagating between the comb electrode portion 12 and each of the reflectors 13, 15 a, 15 b and 15 c due to thermal deformation of the piezoelectric substrate 11. The path length of the propagation path changes. If the path length of the propagation path of the surface acoustic wave changes, the time until the surface acoustic wave is reflected by each reflector 13, 15a, 15b, 15c and returns to the comb electrode portion 12 changes. The pressure measurement device according to the present embodiment calculates the gas pressure by detecting the phase change (phase lag or phase advance) of the response signal corresponding to such a change in the response time of the surface acoustic wave. Hereinafter, the pressure measurement process performed by the pressure measurement device according to the present embodiment will be described.

  In the pressure measurement process of the present embodiment, the computer 30 calculates the gas pressure based on the phase of the response signal from the pressure sensor 10.

More specifically, first, from the response signal from the pressure sensor 10, the response signal corresponding to the surface acoustic wave reflected by the pressure detection reflector 13 and the surface elasticity reflected by the temperature compensation reflector 15. A response signal corresponding to the wave is extracted. Next, the phase phi ₁ of the response signal from the phase phi _P and temperature compensation reflector 15 of the response signal from the pressure detecting reflector _13, phi _2, phi ₃ is obtained, respectively.

Then, the phase φ _P of the response signal of the pressure detecting reflector 13 affected by both the pressure and the temperature is changed to the phase φ ₁ of the response signal of the first to third reflectors affected only by the temperature. , Φ ₂ , φ ₃ , the phase φ _{t_comp} after temperature compensation is calculated. Then, based on the calibration data indicating the relationship between the phase and the pressure, a pressure value corresponding to the phase φ _{t_comp} after temperature compensation is calculated.

  Hereinafter, the pressure measurement process performed by the pressure measurement device according to the present embodiment will be described in detail with reference to FIGS. 4 to 7.

  First, with reference to FIG. 4, processing for extracting a response signal from the pressure detection reflector 13 and a response signal from the temperature compensation reflector 15 from the response signal from the pressure sensor 10 will be described.

  FIG. 4 is a diagram showing waveform data of a response signal from the pressure sensor in the pressure measuring device shown in FIG. The waveform data shown in FIG. 4 is obtained by inverse Fourier transforming waveform data in the frequency domain into waveform data in the time domain. As shown in FIG. 4, the response signal from the pressure sensor 10 corresponds to the surface acoustic wave that is multiple-reflected between the reflectors in addition to the response signal corresponding to the surface acoustic wave first reflected by each reflector. Response signal. In the present embodiment, by setting a time slot in the vicinity of the first response time from each reflector predicted from the design value of the pressure sensor 10, 1 from each reflector is selected from a plurality of response signals. The response signal of the second time is extracted.

  Next, a pressure calculation process for calculating the gas pressure from the phase of the response signal will be described with reference to FIG. FIG. 5 is a flowchart for explaining a pressure calculation process in the pressure measuring apparatus shown in FIG. In the present embodiment, even if the phase of the response signal exceeds a set range (for example, −π to π), the gas pressure is calculated while the phase is updated so that the pressure value continuously changes.

As shown in FIG. 5, in the pressure calculation process of the present embodiment, first, reading of the phase change data is started, and the phases φ _P , φ ₁ , φ ₂ , φ ₃ of the response signals from the reflectors 13, 15 are started. Is acquired (steps S101 and S102).

Next, it is determined whether or not the phases φ _P , φ ₁ , φ ₂ , and φ _{3 of} the acquired response signals are within a set range (−π to π) (step S103).

  When the phase of the response signal is within the set range (step S103: YES), the phase is temporarily stored without being updated (step S106). On the other hand, when the phase of the response signal is out of the set range (step S103: NO), it is determined whether the phase is advanced or delayed, and the phase is updated according to the determination result (steps S104, S105). In the present embodiment, first, the phase advance or phase lag is determined by comparing the magnitude with the phase immediately before being acquired at a predetermined sampling interval. Then, the phase is updated so that the corresponding pressure value changes continuously according to the phase advance or phase lag. The updated phase is temporarily stored (step S106).

Next, based on the stored phases φ _P , φ ₁ , φ ₂ , and φ ₃ from the reflectors 13 and 15, the phase φ _{t_comp} after temperature compensation is calculated (step S 107). In the present embodiment, from the following equation (1), the phase φ _P of the response signal of the pressure detecting reflector 13 that is affected by both pressure and temperature is affected by the temperature. The phase φ ₁ , φ ₂ , φ ₃ of the response signal of the three reflectors 15 is corrected, and the phase φ _{t_comp} after temperature compensation is calculated.

Here, l _P is the distance between the pressure detecting reflector 13 and the comb electrode part 12, and l ₁ , l ₂ , and l ₃ are the first to third reflectors 15 and the comb electrode part. 12 distance.

Next, the temperature φ-compensated phase φ _{t_comp} is compared with the calibration data, and the pressure value corresponding to the temperature compensated phase φ _{t_comp} is calculated (steps S108 and S109). The calibration data is stored in the computer 30 in advance.

  Then, it is determined whether all phase change data has been acquired (step S110). In the present embodiment, it is determined whether or not phase change data for a predetermined measurement time has been acquired. If all the data has not been acquired (step S110: NO), the processes in and after step S103 are repeated until all the data is acquired. On the other hand, when all the data has been acquired (step S110: YES), the process ends.

As described above, according to the processing of the flowchart shown in FIG. 5, the phases φ _P , φ ₁ , φ ₂ , and φ ₃ of the response signals from the reflectors 13 and 15 are acquired, and the acquired phases φ _P and φ are acquired. _A pressure value is calculated based on ₁ , φ ₂ , and φ ₃ . At this time, each phase is updated so that the pressure value continuously changes even if the phase φ _P , φ ₁ , φ ₂ , φ _{3 of} the response signal exceeds the set range (−π to π), A value is calculated.

  Next, with reference to FIG. 6 and FIG. 7, the pressure measurement result of the gas pressure by the pressure measuring apparatus of this Embodiment is demonstrated.

  FIG. 6A is a diagram showing the pressure measurement result of the gas pressure by the pressure measuring device shown in FIG. 1, and FIG. is there. Moreover, FIG. 7 is a figure which shows the response with respect to the gas pressure of the pressure sensor in the pressure measuring apparatus shown in FIG.

  The solid line in FIG. 6A is the phase of the response signal from the pressure detecting reflector 13, and the broken line is the phase of the response signal from the temperature compensating reflector 15. The one-dot chain line is a phase after temperature compensation in which the phase of the response signal from the pressure detecting reflector 13 is corrected by the phase of the response signal from the temperature compensating reflector 15, and the two-dot chain line is a pressure sensor for reference. The gas pressure measured in

  As described above, the phase change of the response signal from the pressure detection reflector 13 indicated by the solid line is caused by the temperature change and pressure change around the pressure sensor 10. The phase change of the response signal from the temperature compensating reflector 15 indicated by the broken line is caused only by the temperature change around the pressure sensor 10. Response signals from the first to third reflectors 15a, 15b, and 15c exhibit substantially the same phase.

As shown in FIG. 6A, the phase after temperature compensation is obtained by correcting the phase φ _P of the response signal of the pressure detecting reflector 13 with the phases φ ₁ , φ ₂ , and φ ₃ of the temperature compensating reflector 15a. φ _{t_comp} shows a change similar to the reference pressure. Therefore, the gas pressure can be calculated from the temperature compensated phase φ _{t_comp} by using the calibration data.

  On the other hand, in FIG. 6B, since the phase is acquired without being updated, an accurate value cannot be calculated for a pressure exceeding the set range, and the measurement range is limited.

  As shown in FIG. 7, the measured values of the gas pressure by the pressure measuring device are distributed on a logical curve, and the pressure measuring device of the present embodiment calculates the gas pressure while compensating for the influence of temperature. You can see that you can.

  As described above, in the pressure measuring apparatus according to the present embodiment described above, the gas pressure is calculated based on the phase of the response signal from the pressure sensor that is delayed or advanced due to the influence of pressure and temperature. More specifically, by correcting the phase of the response signal from the pressure detecting reflector affected by both pressure and temperature by the phase of the response signal from the temperature compensating reflector affected only by the temperature. The pressure value corresponding to the phase after temperature compensation can be calculated.

  And in the pressure sensor 10 of this Embodiment, the one comb-tooth electrode part 12 can convert the surface acoustic wave reflected in the reflector 13 for pressure detection, and the reflector 15 for temperature compensation into a response signal. Therefore, a pressure sensor with a temperature compensation function that detects the gas pressure without power supply is realized.

  In the above-described embodiment, the temperature sensor is provided with three temperature compensating reflectors. However, if the distance between the pressure sensor 10 and the reading device 20 is maintained constant, only one temperature compensating reflector may be provided. In this case, from the viewpoint of minimizing the temperature difference between the temperature compensating reflector and the pressure detecting reflector, the temperature compensating reflector is preferably provided in the vicinity of the diaphragm portion.

  As described above, the described embodiment has the following effects.

  (A) The pressure sensor of the present embodiment includes a piezoelectric substrate, a comb electrode portion, a pressure detection reflector, a diaphragm portion, and a temperature compensation reflector. The comb electrode part is provided on the piezoelectric substrate, receives a radio signal from the outside and excites surface acoustic waves on the piezoelectric substrate, and receives and responds to surface acoustic waves propagating on the piezoelectric substrate. Convert to signal. The pressure detecting reflector is provided on the propagation path of the surface acoustic wave, and reflects the surface acoustic wave excited by the comb electrode part toward the comb electrode part. The diaphragm part is provided between the comb electrode part and the pressure detecting reflector, and is deformed according to the pressure difference between the cavity part inside the piezoelectric substrate and the outside, thereby reducing the path length of the propagation path of the surface acoustic wave. Change. The temperature compensating reflector is provided on the comb electrode portion side with respect to the diaphragm portion on the surface acoustic wave propagation path, and reflects the surface acoustic wave excited by the comb electrode portion toward the comb electrode portion. . Therefore, the surface acoustic wave reflected by the pressure detecting reflector and the temperature compensating reflector is converted into a response signal by one comb electrode part, so that the gas pressure is supplied without power supply while compensating for the influence of temperature. Can be detected. In addition, the pressure sensor can be reduced in size.

  (B) The temperature compensating reflector includes a plurality of reflectors. Therefore, the noise included in the response signal from the pressure sensor can be canceled by taking the difference between the response signals from the plurality of reflectors. As a result, the measurement accuracy of the gas pressure is improved.

  (C) The temperature compensating reflector includes first to third reflectors. Therefore, the noise included in the response signal from the pressure sensor can be canceled by taking the difference between the response signals from the plurality of reflectors. As a result, the measurement accuracy of the gas pressure is improved.

  (D) The temperature compensating reflector is provided in the vicinity of the diaphragm portion. Therefore, the temperature difference between the temperature compensating reflector and the pressure detecting reflector is minimized. As a result, the measurement accuracy of the gas pressure is improved.

  (E) The piezoelectric substrate is formed by bonding a thin film substrate to a base substrate provided with a recess. Therefore, the controllability of the thickness of the diaphragm portion is good, and further, the back surface of the diaphragm portion facing the cavity portion can be smoothed, so that the characteristics and quality of the pressure sensor can be made constant.

  (F) The base substrate and the thin film substrate are made of the same piezoelectric material, and are directly bonded at the contact surface. Therefore, since no adhesive is used, it is not necessary to consider the difference in thermal expansion coefficient between the adhesive and the piezoelectric substrate. In addition, the occurrence of measurement errors due to the difference in thermal expansion coefficient between the substrates is prevented. As a result, the pressure sensor can be used in a high temperature environment.

  (G) The pressure measurement device according to the present embodiment includes a pressure sensor, a reading device, and a computer. The reading device receives a response signal from the pressure sensor while transmitting a wireless signal to the pressure sensor. The computer calculates the gas pressure based on the time change of the response signal received by the reading device. Therefore, the surface acoustic wave reflected by the pressure detecting reflector and the temperature compensating reflector is converted into a response signal by one comb electrode part, so that the gas pressure is supplied without power supply while compensating for the influence of temperature. Can be detected. Further, since only one response signal is received, the circuit configuration of the reading device can be simplified.

  (H) When the phase of the response signal is out of the set range, the computer determines whether the phase of the response signal is advanced or delayed, so that the pressure value calculated from the phase of the response signal changes continuously. The gas pressure is calculated while updating the phase. Therefore, the measurement range of the pressure measuring device can be expanded to the endurance limit of the pressure sensor.

  As described above, in the above-described embodiment, the pressure sensor and the pressure measuring device of the present invention have been described. However, it goes without saying that the present invention can be appropriately added, modified, and omitted by those skilled in the art within the scope of the technical idea.

It is a figure which shows schematic structure of the pressure measuring apparatus in one embodiment of this invention. 2A is a top view of the pressure sensor in the pressure measuring device shown in FIG. 1, and FIG. 2B is a cross-sectional view taken along the line II-II 'of FIG. It is sectional drawing for demonstrating the manufacturing process of the pressure sensor shown in FIG. It is a figure which shows the waveform data of the response signal from the pressure sensor in the pressure measuring device shown in FIG. It is a flowchart which shows the pressure calculation process in the pressure measuring device shown in FIG. FIG. 6A is a diagram showing the pressure measurement result of the gas pressure by the pressure measuring device shown in FIG. 1, and FIG. is there. It is a figure which shows the responsiveness with respect to the gas pressure of the pressure sensor in the pressure measuring apparatus shown in FIG.

Explanation of symbols

10 Pressure sensor,
11 Piezoelectric substrate,
11a base substrate,
11b thin film substrate,
11c recess,
12 comb electrode part,
13 Pressure sensing reflector,
14 Diaphragm part,
15 Temperature compensating reflector,
15a first reflector,
15b second reflector,
15c third reflector,
20 Reading device (reading means),
30 Computer (calculation means).

Claims (5)

A piezoelectric substrate that propagates surface acoustic waves;
Provided on the piezoelectric substrate, receives external radio signals and excites surface acoustic waves on the piezoelectric substrate, while receiving surface acoustic waves propagating on the piezoelectric substrate and converts them into response signals A comb-tooth electrode portion,
A pressure detecting reflector that is provided on a propagation path of the surface acoustic wave and reflects the surface acoustic wave excited by the comb electrode portion toward the comb electrode portion;
A path length of the surface acoustic wave propagation path is provided between the comb electrode portion and the pressure detecting reflector, and is deformed according to a pressure difference between the cavity portion inside the piezoelectric substrate and the outside. A changing diaphragm part,
Temperature compensation that is provided on the comb electrode part side with respect to the diaphragm part on the surface acoustic wave propagation path and reflects the surface acoustic wave excited by the comb electrode part toward the comb electrode part possess and use reflectors, the,
The temperature compensating reflector is:
A first reflector that is provided on the anti-diaphragm portion side of the comb electrode portion and reflects the surface acoustic wave excited by the comb electrode portion toward the comb electrode portion;
A part of the surface acoustic wave provided between the first reflector and the comb electrode portion and excited by the comb electrode portion is reflected toward the comb electrode portion, while the rest A second reflector that passes surface acoustic waves;
A portion of the surface acoustic wave provided between the comb electrode portion and the diaphragm portion and excited by the comb electrode portion is reflected toward the comb electrode portion, while the remaining surface acoustic waves are reflected. A pressure sensor comprising: a third reflector that passes through the pressure sensor. The pressure sensor according to claim 1 , wherein the piezoelectric substrate is formed by bonding a thin film substrate to a base substrate provided with a recess corresponding to the cavity. The pressure sensor according to claim 2 , wherein the base substrate and the thin film substrate are made of the same piezoelectric material and are directly bonded at a contact surface. The pressure sensor according to any one of claims 1 to 3 ,
Reading means for receiving a response signal from the pressure sensor while transmitting a wireless signal to the pressure sensor;
A pressure measuring device comprising: a calculating unit that calculates a gas pressure based on a time change of a response signal received by the reading unit. When the phase of the response signal is out of a setting range, the calculation unit determines whether the phase of the response signal is advanced or delayed, and the pressure value calculated from the phase of the response signal continuously changes. The pressure measuring device according to claim 4 , wherein the gas pressure is calculated while the phase is updated.

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