JP2011013063A - Pressure sensor and pressure-detecting method for pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure sensor and a pressure detecting method for the pressure sensor which suppress the degradation with time, of the accuracy of detection of pressure and also enable improvement in the characteristics, such as, the speed of detection of the pressure.SOLUTION: The pressure sensor 1 includes a crystal oscillation piece 10 which has oscillating arm portions 12; a base part 20 whereon the crystal oscillation piece 10 is mounted; a diaphragm part 40 which covers the crystal oscillation piece 10 being in parallel with main faces 12a of the oscillating arm portions 12 of the crystal oscillation piece 10 and having a prescribed interval h from the main faces 12a; and a package 70, which is so constituted as to include the base part 20 and the diaphragm part 40 and has an internal space 30 sealed airtightly. The crystal oscillation piece 10 is held together with inert gas in the internal space 30 of the package 70, while the diaphragm part 40 is displaced, according to the pressure applied from the outside, and the prescribed interval h from the main face 12a of the crystal oscillation piece 10 is changed.

Description

  The present invention relates to a pressure sensor using a pressure-sensitive element, and more particularly, to a pressure sensor configured with a diaphragm and a pressure detection method for the pressure sensor.

  2. Description of the Related Art Conventionally, there has been known a pressure sensor that includes a diaphragm, a container, and a pressure sensitive element such as a double tuning fork vibrator (hereinafter referred to as a double tuning fork element) mounted on a support provided in the diaphragm. (For example, refer to Patent Document 1).

JP 2007-333452 A

The pressure sensor is configured to transmit the displacement of the diaphragm due to the pressure applied from the outside to the pressure sensitive element and detect the pressure based on the amount of change in the resonance frequency of the pressure sensitive element.
For this reason, the pressure sensor gradually deteriorates due to the stress generated due to repeated pressure applied to the support part of the diaphragm with the fixing part that fixes the base part of the pressure sensitive element with a bonding member such as an adhesive. There is.
As a result, the pressure sensor may deteriorate in pressure detection accuracy over time.

In addition, when the pressure sensor detects pressure, it is necessary to count the resonance frequency of the pressure-sensitive element for a certain time (gate time) in order to grasp the amount of change in the resonance frequency of the pressure-sensitive element. There may be a time lag before outputting.
Thus, since the pressure sensor requires a certain time from detection of pressure to output of the detection result, there is room for improvement in the pressure detection speed in an environment where the pressure changes every moment.

In addition, the pressure sensor has a structure in which a pair of base portions at both ends of the pressure sensitive element are rigidly fixed to the diaphragm support portion at both ends rigidly. It is easy to leak into a package including a diaphragm. When the container itself starts to vibrate due to the leaked vibration and the resonance frequency related to the natural vibration of the container exists in the vicinity of the resonance frequency of the pressure-sensitive element, the resonance frequency of the pressure-sensitive element and the container The resonance frequency may be coupled, thereby changing the resonance frequency of the pressure sensitive element.
As a result, the pressure sensor may change the resonance frequency even when there is no change in the pressure applied from the outside, so that the pressure detection accuracy may be reduced.

  In addition, since the pressure sensor has a structure in which a pair of bases at both ends of the pressure sensitive element are fixed to the support part of the diaphragm, stress caused by a difference in expansion and contraction between the pressure sensitive element and the diaphragm due to a change in ambient temperature. In order to suppress the occurrence of (thermal stress), there is a restriction that the material of the diaphragm must be selected from materials whose linear expansion coefficient approximates that of the pressure sensitive element.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A pressure sensor according to this application example includes: a pressure-sensitive element having a vibration part; a base part on which the pressure-sensitive element is mounted; and a main surface of the vibration part of the pressure-sensitive element. A package that includes a diaphragm portion that covers the pressure-sensitive element at a predetermined distance from a main surface; and a package that includes the base portion and the diaphragm portion, and whose internal space is hermetically sealed. The pressure sensitive element is accommodated together with gas in the internal space, the diaphragm portion is displaced according to the pressure applied from the outside, and the predetermined distance from the main surface of the pressure sensitive element changes. Features.

According to this, the pressure sensor includes a base portion and a diaphragm portion (synonymous with a diaphragm), and the pressure-sensitive element is accommodated together with the gas inside the package in which the internal space is hermetically sealed. The portion is displaced according to the pressure applied from the outside, and the predetermined distance between the diaphragm portion and the vibration surface of the pressure sensitive element changes.
As a result, in the pressure sensor, the gas viscous resistance with respect to the vibration part of the pressure-sensitive element changes as the predetermined distance between the diaphragm part and the main surface of the pressure-sensitive element changes.
In the pressure sensor, as the viscous resistance of the gas increases, the degree of inhibition of the vibration of the pressure sensitive element increases, and the series equivalent resistance value (hereinafter referred to as CI (Crystal Impedance) value) of the pressure sensitive element increases. Become.
From this, the pressure sensor detects a change in the viscous resistance of the gas as a change in the CI value of the pressure sensitive element, so that the correlation between the change amount of the predetermined interval and the change amount of the CI value, and the diaphragm The pressure applied from the outside can be detected based on the correlation between the pressure applied to the part and the amount of displacement of the diaphragm part.

The pressure sensor has a pressure-sensitive element mounted on the base part. When pressure is applied from the outside, the diaphragm part is displaced and the base part is hardly displaced. ) Can be prevented from generating stress.
Thereby, since the pressure sensor can suppress the deterioration of the support part of the pressure sensitive element, it is possible to avoid the possibility that the pressure detection accuracy deteriorates with time.

In addition, the pressure sensor has a pressure-sensitive element mounted on the base, and the vibration of the pressure-sensitive element is less likely to leak into the package compared to the conventional case where it is supported (fixed) on the diaphragm. Therefore, it is possible to suppress a change in CI value and the like due to vibration leakage of the pressure sensitive element.
Thereby, the pressure sensor can improve the pressure detection accuracy as compared with the conventional configuration.
In addition, since the pressure sensor can instantly grasp the amount of change in the CI value of the pressure sensitive element, for example, as the amount of change in the voltage value, the pressure sensor is compared with the conventional configuration that counts the resonance frequency (oscillation frequency) of the pressure sensitive element. Thus, the detection speed of the pressure applied from the outside can be improved.

  In addition, since the pressure sensor has a pressure-sensitive element mounted on the base part, there is no restriction of approximation of the linear expansion coefficient with the pressure-sensitive element when selecting the material of the diaphragm part. The choice of material can be increased.

  Application Example 2 In the pressure sensor according to the application example, it is preferable that the pressure is detected by a resistance value of the pressure sensitive element.

  According to this, since the pressure sensor detects the pressure based on the resistance value of the pressure-sensitive element, the effect described in the application example can be obtained.

  Application Example 3 In the pressure sensor according to the application example, the vibration portion of the pressure-sensitive element includes at least one columnar beam that vibrates in a bending vibration mode in a direction along the main surface. It is preferable that

  According to this, since the vibration part of the pressure-sensitive element has at least one columnar beam that vibrates in the bending vibration mode in the direction along the main surface, the other vibrations Compared with the mode pressure-sensitive element, a change in the viscous resistance of the gas can be detected with high sensitivity as a change in the CI value of the pressure-sensitive element.

  Application Example 4 In the pressure sensor according to the application example, it is preferable that the gas is an inert gas.

According to this, since the gas accommodated in the inside of the package is an inert gas, a chemical reaction with a component such as a pressure sensitive element hardly occurs.
From this, the pressure sensor can suppress deterioration of components such as a pressure sensitive element.

  Application Example 5 In the pressure sensor according to the application example described above, the amplifier is configured to oscillate the pressure sensitive element, and is output from the terminal connected to the input terminal side of the amplifier among the terminals of the pressure sensitive element. A filter circuit that removes a direct current component of the input signal, a rectifier circuit that half-wave rectifies the output signal of the filter circuit, and an integrated signal obtained by integrating the output signal of the rectifier circuit It is preferable that the potential of the integration signal is a pressure detection signal.

  According to this, since the pressure sensor replaces the change in the CI value of the pressure-sensitive element due to the change in the viscous resistance of the gas with the change in the potential of the integration signal by the above circuit configuration, Compared with the conventional configuration in which the resonance frequency of the pressure sensitive element is counted, the detection speed of the pressure applied from the outside can be dramatically improved.

  Application Example 6 A pressure detection method for a pressure sensor according to this application example includes a pressure-sensitive element having a vibration part, a base part on which the pressure-sensitive element is mounted, and a main surface of the vibration part of the pressure-sensitive element. A package that includes a diaphragm portion that covers the pressure-sensitive element at a predetermined interval from the main surface, and includes a base portion and the diaphragm portion, and an internal space is hermetically sealed. A pressure detection method of a pressure sensor in which the pressure sensitive element is accommodated together with gas in the internal space of the package, wherein the diaphragm portion is displaced according to a pressure applied from the outside, and the pressure sensitive element The pressure is detected based on a change in resistance value of the pressure-sensitive element when the predetermined distance from the main surface changes.

  According to this, the pressure detection method of the pressure sensor is based on the resistance value of the pressure sensitive element when the diaphragm portion is displaced according to the pressure applied from the outside and the predetermined distance from the main surface of the pressure sensitive element changes. Since the pressure is detected based on the change in (CI value), the effect described in Application Example 1 can be achieved.

The schematic diagram which shows schematic structure of the pressure sensor of this embodiment. The graph shown about an example of the correlation of the change of CI value with respect to the change of the space | interval of a diaphragm part and a quartz crystal vibrating piece. The schematic circuit diagram which shows an example of the pressure detection circuit of a pressure sensor. The schematic diagram which shows the signal in each circuit. The model perspective view which shows the variation of a pressure sensitive element. The schematic diagram explaining the viscous resistance concerning a quartz crystal vibrating piece and a fluid.

Hereinafter, embodiments of a pressure sensor and a pressure detection method of the pressure sensor will be described with reference to the drawings.
(Embodiment)
FIG. 1 is a schematic diagram showing a schematic configuration of the pressure sensor of the present embodiment. FIG. 1A is a plan view seen from the diaphragm side, and FIG. 1B is a cross-sectional view taken along the line AA in FIG.
In the plan view, the diaphragm portion is omitted for easy understanding, and the outer shape of the diaphragm portion is indicated by a two-dot chain line. Further, circuit elements are omitted.

  As shown in FIG. 1, the pressure sensor 1 includes a crystal vibrating piece 10 as a pressure sensitive element, a base portion 20 on which the crystal vibrating piece 10 is mounted, and a diaphragm portion that covers the crystal vibrating piece 10 and is joined to the base portion 20. 40, a base portion 20 and a diaphragm portion 40, and a package 70 in which the internal space 30 is hermetically sealed.

The quartz crystal resonator element 10 includes a base portion 11 having a substantially rectangular planar shape, and a pair of prismatic vibrating arm portions 12 (vibrating portions) as columnar beams extending substantially in parallel with each other from one end portion of the base portion 11. It is a tuning fork type crystal vibrating piece. Note that an excitation electrode (not shown) is formed on the crystal vibrating piece 10.
The crystal vibrating piece 10 vibrates in a flexural vibration mode in which the vibrating arm portion 12 is displaced alternately in the direction of the arrow B and the direction of the arrow C, which are directions along the main surface 12 a of the vibrating arm portion 12, according to the drive signal.

The base portion 20 includes a flat bottom substrate 21 having a substantially rectangular planar shape, and a frame-shaped frame substrate 22 that surrounds the crystal vibrating piece 10 mounted on the bottom substrate 21 and is stacked on the bottom substrate 21. Yes.
For the bottom substrate 21 and the frame substrate 22, an aluminum oxide sintered body formed by firing a ceramic green sheet is used.

Internal electrodes 21b and 21c are formed on the inner bottom surface 21a of the base portion 20, and the base portion 11 of the quartz crystal vibrating piece 10 is supported (fixed) via a conductive adhesive 50 such as epoxy, silicon, or polyimide. The crystal vibrating piece 10 is mounted. For mounting the crystal vibrating piece 10, a bonding material such as solder or bump may be used instead of the conductive adhesive 50.
The crystal vibrating piece 10 is mounted so that a mount electrode (not shown) as a terminal electrically connected to the excitation electrode is formed on the base 11, and each mount electrode is overlapped with the internal electrodes 21b and 21c. As a result, in the pressure sensor 1, the excitation electrode of the crystal vibrating piece 10 and the internal electrodes 21b and 21c are electrically connected.

On the outer bottom surface 23 of the base portion 20, mounting terminals 24 and 25 that are terminals when the pressure sensor 1 is mounted on a substrate or the like are provided.
The internal electrodes 21b and 21c are electrically connected to the mounting terminals 24 and 25 by internal wiring (not shown), respectively. For example, the internal electrode 21 b is connected to the mounting terminal 24, and the internal electrode 21 c is connected to the mounting terminal 25.
Thereby, the mounting terminals 24 and 25 are electrically connected to the crystal vibrating piece 10.
The internal electrodes 21b and 21c and the mounting terminals 24 and 25 are made of a metal film in which a film made of nickel, gold or the like is laminated on a metallized layer such as tungsten by plating or the like.

The diaphragm portion 40 has flexibility, is formed from a flat crystal substrate having a substantially rectangular planar shape and the like.
The diaphragm portion 40 covers the crystal vibrating piece 10 with a predetermined interval h (hereinafter also simply referred to as an interval h) from the main surface 12a in parallel with the main surface 12a of the vibrating arm portion 12 of the crystal vibrating piece 10. Yes.
The diaphragm portion 40 is joined to the joining surface 22a of the frame substrate 22 of the base portion 20 via a joining member 60 such as low melting point glass or brazing material.

  The interior of the package 70 is hermetically sealed. In the internal space 30 of the package 70, the crystal vibrating piece 10 is accommodated together with an inert gas such as nitrogen, argon, or helium as a gas.

Next, the operation of the pressure sensor 1 as a pressure detection method will be described.
First, a dynamic model of the vibration of the quartz crystal vibrating piece 10 in the internal space 30 filled with an inert gas and the inert gas as a fluid will be described with reference to FIG.
FIG. 6 is a schematic diagram for explaining the viscous resistance related to the quartz crystal vibrating piece and the fluid. FIG. 6 schematically shows a cross section of the pressure sensor 1 by a straight line orthogonal to the AA line in FIG.

In FIG. 6, since the inert gas as the fluid in contact with the diaphragm portion 40 that is the fixed surface tries to maintain the position as it is, the velocity of the inert gas is zero. On the other hand, the inert gas in contact with the surface of the vibrating arm portion 12 of the crystal vibrating piece 10 tries to move at a velocity U.
The inert gas moves between the surface of the diaphragm part 40 and the surface of the vibrating arm part 12 at a speed u proportional to the distance y from the surface of the diaphragm part 40.
u = U × y / h (1)
The force to move the surface of the vibrating arm portion 12 of the quartz crystal vibrating piece 10 is equal to the force required to fix the surface of the diaphragm portion 40, both of which are proportional to the speed U and are at a distance (interval) h. Inversely proportional.
The force τ0 acting per unit area on the surface of the vibrating arm 12 in contact with the inert gas can be expressed as follows.
τ0 = μ × U / h (2)
Here, the proportionality constant μ is called the viscosity coefficient of the inert gas (fluid).
Therefore, when the distance (interval) h between the diaphragm 40 and the crystal vibrating piece 10 changes due to the diaphragm 40 receiving pressure and bending, the force τ0 changes according to the equation (2). Become.

Here, the force τ0 per unit area acting on the surface of the vibrating arm portion 12 is referred to as viscous resistance, and the viscous resistance suppresses (inhibits) the vibration of the vibrating arm portion 12 of the crystal vibrating piece 10. A change occurs in the electrical characteristics of the crystal vibrating piece 10.
Therefore, the inventors of the present application can detect a change in the CI value that is the resistance value of the crystal vibrating piece 10 by using the change in the viscous resistance acting on the surface of the crystal vibrating piece 10 caused by the change in the interval h. This makes it possible to realize a detection device that detects the pressure and force to be measured.

FIG. 2 is a graph showing an example of a correlation of a change in a CI (crystal impedance) value, which is a series equivalent resistance value of the crystal vibrating piece, with respect to a change in the distance between the diaphragm portion and the crystal vibrating piece.
As shown in FIG. 2, when pressure is applied from the outside, the pressure sensor 1 is displaced in the direction of arrow D (when it is bent) as shown in FIG. The CI value increases as the distance h between the diaphragm portion 40 and the main surface 12a of the vibrating arm portion 12 of the quartz crystal vibrating piece 10 decreases.

This is because the viscosity resistance of an inert gas such as nitrogen, argon or helium as a fluid (gas) acting on the surface (main surface 12a) of the vibrating arm 12 is inversely proportional to the interval h, and as the interval h becomes narrower. This is because the degree to which the bending vibration of the vibrating arm portion 12 of the crystal vibrating piece 10 is hindered increases.
As a result, in the pressure sensor 1, as the interval h becomes narrower, the electrical characteristics of the quartz crystal vibrating piece 10 change, and the CI value increases (it becomes difficult to vibrate).

Using this phenomenon, the pressure sensor 1 detects the pressure based on the change in the CI value of the crystal vibrating piece 10 with respect to the change in the interval h due to the displacement (deflection) of the diaphragm portion 40 according to the pressure from the outside.
It is assumed that the correlation between the pressure applied to the diaphragm unit 40 and the amount of displacement of the diaphragm unit 40 is known in advance.
As shown in FIG. 2, in the case of this example, the interval h is preferably set to 0 μm <h <150 μm where the correlation with the CI value is established.

Here, a pressure detection method based on a change in the CI value will be described from the circuit configuration.
FIG. 3 is a schematic circuit diagram illustrating an example of a pressure detection circuit of the pressure sensor.
As shown in FIG. 3, the pressure detection circuit 80 of the pressure sensor 1 includes an oscillation circuit 81, a filter circuit 82, a rectification circuit 83, an integration circuit 84, and a DC amplification circuit 85.
FIG. 4 is a schematic diagram showing signals in each circuit. In FIG. 4, the horizontal axis represents time (T), and the vertical axis represents voltage (V).

The oscillation circuit 81 includes inverters 121, 122, and 123 as amplifiers for causing the crystal resonator element 10 to oscillate (resonate), a resistor R1 including a circuit in which resistors RA, RB, and RC are connected in series, and capacitors C1 and C2. And have.
The inverters 121, 122, and 123 are connected in series between both terminals of the crystal vibrating piece 10.
The first stage inverter 121 has an input terminal connected to one terminal of the crystal vibrating piece 10 and an output terminal connected to an input terminal of the second stage inverter 122. The output terminal of the second stage inverter 122 is connected to the input terminal of the third stage inverter 123. The third-stage inverter 123 has an output terminal connected to the other terminal of the crystal vibrating piece 10.

The resistor R <b> 1 is connected between both terminals of the crystal vibrating piece 10. The terminal of the resistor RA, which is one terminal of the resistor R1, is connected to the input terminal of the inverter 121.
The terminal of the resistor RC, which is the other terminal of the resistor R1, is connected to the output terminal of the inverter 123. A connection midpoint between the resistor RA and the resistor RB is connected to the output terminal of the inverter 121. A connection midpoint between the resistor RB and the resistor RC is connected to the output terminal of the inverter 122. In addition, a resistor RD for phase control is connected between the terminal of the resistor RC, which is the other terminal of the resistor R1, and the other terminal of the crystal vibrating piece 10.

The capacitor C1 is connected between the input terminal of the inverter 121 and the ground potential. The capacitor C2 is connected between the output terminal of the inverter 123 and the ground potential.
As a result, the oscillation circuit 81 outputs an oscillation signal OUT obtained by oscillating the crystal vibrating piece 10 from the output terminal of the inverter 123.

The filter circuit 82 has a capacitor C3 and a resistor R3. One terminal of the capacitor C <b> 3 is connected to the input terminal of the inverter 121 and one terminal of the crystal vibrating piece 10, and the other terminal is connected to the input terminal of the rectifier circuit 83.
The resistor R3 is connected between the other terminal of the capacitor C3 and the ground potential.

As shown in FIG. 4A, the filter circuit 82 is a part of the vibrator current as the current output from the terminal connected to the input terminal side of the inverter 121 among the terminals of the crystal vibrating piece 10. The signal a is input as an input signal.
Here, the signal a is a sinusoidal AC signal on which a DC component is superimposed. The amplitude (voltage) Vpp1 of the signal a changes in proportion to the magnitude of the CI value. If the CI value is large (the pressure is high), the amplitude Vpp1 is output large, and if the CI value is small (the pressure is low). For example, the amplitude Vpp1 is output small.
Then, as shown in FIG. 4B, the filter circuit 82 removes the DC component of the signal a and outputs it as a signal (output signal) b.

The rectifier circuit 83 has a diode D1. The diode D 1 has one terminal connected to the other terminal of the capacitor C 3 of the filter circuit 82 and the other terminal connected to one terminal of the resistor R 4 of the integrating circuit 84.
The rectifier circuit 83 receives the signal b output from the filter circuit 82, and outputs a signal (output signal) c obtained by half-wave rectifying the signal b as shown in FIG. 4C.

The integrating circuit 84 has a resistor R4 and a capacitor C4. The resistor R4 has one terminal connected to the output terminal of the diode D1 of the rectifier circuit 83, and the other terminal connected to the plus terminal side of the comparison circuit 85a of the DC amplifier circuit 85. The capacitor C4 is connected between the other terminal of the resistor R4 and the ground potential.
The integration circuit 84 receives the signal c output from the rectification circuit 83 and outputs a signal (integration signal) d obtained by integrating the signal c as shown in FIG.

The DC amplification circuit 85 includes a comparison circuit 85a and resistors R5, R6, and R7. The resistor R5 has one terminal connected to the other terminal of the resistor R4 of the integrating circuit 84, and the other terminal connected to the plus terminal of the comparison circuit 85a.
The resistor R6 has one terminal connected to the ground potential and the other terminal connected to the minus terminal of the comparison circuit 85a. The resistor R7 has one terminal connected to the minus terminal of the comparison circuit 85a and the other terminal connected to the output terminal of the comparison circuit 85a.

The DC amplification circuit 85 receives the signal d output from the integration circuit 84, amplifies the potential of the signal d, and outputs the signal e as a pressure detection signal (Vout), as shown in FIG.
For example, when the external pressure is a reference pressure (100 kpa as an example), the potential of the signal e is about ½ of the reference voltage of the pressure detection circuit 80. It is preferable to adjust so as to achieve good pressure detection.

With the circuit configuration as described above, the pressure detection circuit 80 detects the potential of the signal e based on the change in the CI value of the quartz crystal vibrating piece 10 in accordance with the change in the interval h (see FIG. 1), thereby providing an external signal. Can be detected.
The potential of the signal e can be detected instantaneously (for example, at a level of several msec).

In the pressure detection circuit 80, the circuit elements other than the crystal vibrating piece 10 may be externally attached around the package 70, and at least a part of the circuit elements is accommodated in the internal space 30 of the package 70. It may be.
In the present embodiment, an example in which the amplifier of the oscillation circuit 81 has three stages has been described. However, the number of stages is not limited to this and may be one, and the number of stages may be appropriately set according to the design conditions of the oscillation circuit 81.
Further, since the pressure detection circuit 80 can detect the pressure from the outside by basically detecting the potential of the signal d output from the integration circuit 84, the DC amplification circuit 85 may be omitted.

As described above, in the pressure sensor 1, the viscosity of the inert gas (gas) with respect to the crystal vibrating piece 10 is changed by changing the distance h between the diaphragm portion 40 and the main surface 12 a of the vibrating arm portion 12 of the crystal vibrating piece 10. Resistance changes.
The pressure sensor 1 detects the change in the viscous resistance of the inert gas as the change in the CI value of the quartz crystal vibrating piece 10, thereby correlating the change amount of the interval h and the change amount of the CI value, and the diaphragm portion. The pressure applied from the outside can be detected based on the correlation between the pressure applied to 40 and the amount of displacement of the diaphragm 40.

In the pressure sensor 1, the crystal vibrating piece 10 is mounted on the base portion 20. When pressure is applied from the outside, the diaphragm portion 40 is displaced and the base portion 20 is hardly displaced. It can suppress that a stress generate | occur | produces in the support part.
Thereby, since the pressure sensor 1 can suppress deterioration of the support part of the crystal vibrating piece 10, it can avoid the possibility that the pressure detection accuracy will deteriorate over time.

Further, the pressure sensor 1 has one end portion of the crystal vibrating piece 10 mounted on the base portion 20 by cantilever support, and the other end portion is opened to be a free end. Compared to the case where a pair of base parts of a double tuning fork element are rigidly supported at the diaphragm 40 on both ends, the vibration of the crystal vibrating piece 10 is less likely to leak into the package 70, resulting in vibration leakage of the crystal vibrating piece 10. Changes in the CI value and the like can be suppressed.
Thereby, the pressure sensor 1 can improve the pressure detection accuracy as compared with the conventional configuration.
In addition, the pressure sensor 1 instantaneously (several msec) from the potential of the signal e output as a pressure detection signal by rectifying, integrating, and amplifying the change amount of the CI value of the quartz crystal vibrating piece 10 by the pressure detection circuit 80. Can grasp.
From this, the pressure sensor 1 dramatically improves the detection speed of the pressure applied from the outside as compared with the above-described conventional configuration in which the resonance frequency of the quartz crystal resonator element 10 is counted for a certain time (a few hundred msec as the gate time). Can do.

In addition, since the quartz vibrating piece 10 is mounted on the base portion 20 of the pressure sensor 1, when selecting the material of the diaphragm portion 40, there is a restriction of approximation of the linear expansion coefficient with the quartz vibrating piece 10 as in the prior art. Therefore, the choice of the material of the diaphragm 40 can be increased.
Thereby, the material of the diaphragm part 40 may use a glass substrate, a ceramic substrate, a metallic substrate, etc. other than said quartz substrate.

  Further, since the pressure sensor 1 is mounted on the base portion 20 only at one end portion (base portion 11) of the crystal vibrating piece 10, thermal stress due to a difference in linear expansion coefficient between the crystal vibrating piece 10 and the base portion 20 can be obtained. Generation can be suppressed.

  Further, in the pressure sensor 1, the vibrating arm portion 12 of the quartz crystal vibrating piece 10 as the pressure sensitive element is composed of at least one columnar beam that vibrates in the bending vibration mode in the direction along the main surface 12a. Compared with other vibration mode pressure-sensitive elements, the change in the viscous resistance of the inert gas can be detected with high sensitivity as the change in the CI value of the quartz crystal vibrating piece 10.

Further, in the pressure sensor 1, since the gas accommodated in the internal space 30 of the package 70 is an inert gas such as nitrogen, argon, or helium, a chemical reaction occurs with a component such as the crystal vibrating piece 10. It is hard to do.
From this, the pressure sensor 1 can suppress deterioration of components such as the crystal vibrating piece 10.

The pressure sensor 1 can be used not only in a gas but also in a liquid because the internal space 30 of the package 70 is hermetically sealed.
The quartz crystal vibrating piece 10 is hermetically sealed in the internal space 30 and is isolated from an object to be measured such as gas or liquid, and the surface of the vibrating arm portion 12 of the quartz crystal vibrating piece 10 may be contaminated. Therefore, there is no possibility that the detection sensitivity of the pressure sensor 1 is deteriorated.

  Further, the pressure detection method of the pressure sensor 1 is that the diaphragm portion 40 is displaced according to the pressure applied from the outside, and the predetermined distance h between the main surface 12a of the vibrating arm portion 12 of the crystal vibrating piece 10 changes. Since the pressure is detected based on the change in the CI value of the quartz crystal vibrating piece 10, the pressure sensor 1 having the above-described effects can be provided.

(Modification)
Here, the modification of the said embodiment is demonstrated.
FIG. 5 is a schematic perspective view showing variations of the pressure sensitive element.
The pressure sensor 1 includes, as pressure-sensitive elements, for example, a pair of prismatic vibrating arms (columnar beams) 112 that are substantially parallel to each other as vibrating portions, as shown in FIG. You may use the double tuning fork element 110 which has a pair of substantially rectangular base 111 connected to both ends.

The double tuning fork element 110 is mounted on the base portion 20 by supporting (fixing) both or one of the base portions 111 on the base portion 20. In the double tuning fork element 110, the vibrating arm portion 112 vibrates in the bending vibration mode in the direction along the main surface 112a of the vibrating arm portion 112, similarly to the crystal vibrating piece 10 of the above embodiment.
The double tuning fork element 110 is disposed at a position where the most displaced portion of the diaphragm portion 40 overlaps with the substantially central portion of the vibrating arm portion 112 in a plan view.

Further, the pressure sensor 1 is a pressure-sensitive element, for example, as shown in FIG. 5B, a vibrating arm portion 212 as a vibrating portion is composed of one columnar beam (also referred to as a single beam). A tuning fork element 210 having a pair of base portions 211 connected to both ends of the same may be used.
The tuning fork element 210 is mounted on the base portion 20 by supporting (fixing) both or one of the base portions 211 on the base portion 20. In the tuning fork element 210, the vibrating arm portion 212 vibrates in the bending vibration mode in the direction along the main surface 212a of the vibrating arm portion 212, similarly to the crystal vibrating piece 10 of the above-described embodiment.
The tuning fork element 210 is disposed at a position where the most displaced portion of the diaphragm portion 40 overlaps with the substantially central portion of the vibrating arm portion 212 in plan view.

  As a result, the pressure sensor 1 using the pressure-sensitive element according to the modification can obtain the same effects as those of the embodiment. In the above modification, if the base part 20 of the double tuning fork element 110 and the tuning fork element 210 is supported by both bases, the pressure sensor 1 can measure the acceleration to the double tuning fork element 110 and the tuning fork element 210 during movement. The influence can be suppressed.

  In the above embodiment, the parallelism between the diaphragm portion 40 and the main surface 12a of the vibrating arm portion 12 of the quartz crystal vibrating piece 10 may not be completely parallel, and the change amount of the interval h and the CI value Based on the correlation with the amount of change, any error within a range in which the pressure applied from the outside can be detected is allowed. The same applies to the modified example.

  Further, the base material of the pressure sensitive element is not limited to quartz, and may be a piezoelectric substrate such as lithium tantalate or lithium niobate.

  DESCRIPTION OF SYMBOLS 1 ... Pressure sensor, 10 ... Quartz vibrating piece as pressure-sensitive element, 11 ... Base part, 12 ... Vibrating arm part as columnar beam, 12a ... Main surface of vibrating arm part, 20 ... Base part, 21 ... Bottom substrate, 21a ... inner bottom surface, 21b, 21c ... internal electrode, 22 ... frame substrate, 22a ... bonding surface, 23 ... outer bottom surface, 24, 25 ... mounting terminal, 30 ... internal space, 40 ... diaphragm part, 50 ... conductive adhesive, 60 ... joining member, 70 ... package.

Claims (6)

A pressure-sensitive element having a vibrating part;
A base portion on which the pressure sensitive element is mounted;
A diaphragm portion that covers the pressure sensitive element at a predetermined distance from the principal surface in parallel with the principal surface of the vibration part of the pressure sensitive element;
A package including the base portion and the diaphragm portion, and having an internal space hermetically sealed;
In the internal space of the package, the pressure sensitive element is accommodated together with a gas,
The pressure sensor, wherein the diaphragm portion is displaced according to a pressure applied from the outside, and the predetermined distance from the main surface of the pressure sensitive element changes.   The pressure sensor according to claim 1, wherein the pressure is detected by a resistance value of the pressure sensitive element.   3. The pressure sensor according to claim 1, wherein the vibration part of the pressure-sensitive element includes at least one columnar beam that vibrates in a bending vibration mode in a direction along the main surface. A pressure sensor.   The pressure sensor according to any one of claims 1 to 3, wherein the gas is an inert gas. The pressure sensor according to any one of claims 1 to 4, an amplifier for oscillating the pressure sensitive element;
Among the terminals of the pressure sensitive element, a filter circuit that removes a direct current component of the input signal, using a part of the current output from the terminal connected to the input terminal side of the amplifier as an input signal;
A rectifier circuit for half-wave rectifying the output signal of the filter circuit;
An integration circuit that outputs an integration signal obtained by integrating the output signal of the rectifier circuit,
A pressure sensor, wherein the potential of the integration signal is a pressure detection signal. A pressure-sensitive element having a vibrating part;
A base portion on which the pressure sensitive element is mounted;
A diaphragm portion that covers the pressure sensitive element at a predetermined distance from the principal surface in parallel with the principal surface of the vibration part of the pressure sensitive element;
A package including the base portion and the diaphragm portion, and having an internal space hermetically sealed;
A pressure detection method of a pressure sensor in which the pressure sensitive element is housed together with a gas in the internal space of the package,
Based on a change in the resistance value of the pressure sensitive element when the diaphragm portion is displaced according to the pressure applied from the outside and the predetermined distance from the main surface of the pressure sensitive element changes. A pressure detection method for a pressure sensor, characterized in that:

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