JP2014173988A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure sensor capable of detecting pressure fluctuation in a low-frequency band, and capable of detecting fine change of pressure even right after abrupt pressure fluctuation occurs.SOLUTION: A pressure sensor 1 detecting pressure fluctuation adjusts pressure in a cavity 10 by circulating inside and outside air of the cavity 10, and has a pressure adjustment mechanism 8 including a communication opening 11b, a switch 6 and an opening/closing controller 7.

Description

  The present invention relates to a pressure sensor that detects minute pressure fluctuations based on a pressure difference.

  Conventionally, as a pressure sensor for detecting pressure fluctuation (also referred to as “differential pressure sensor”), for example, a substrate having a through hole or a recess, a storage container having a vent hole, and a storage container disposed in the storage container, There is known a pressure sensor including a piezoelectric element that is cantilevered on a substrate so as to vibrate in a recess (see, for example, Patent Document 1).

  According to the pressure sensor configured as described above, according to the magnitude of the pressure difference between the pressure fluctuation transmitted into the storage container via the vent hole and the pressure inside the through hole or the recess that follows the pressure fluctuation. The piezoelectric element vibrates. As a result, the pressure sensor can detect a pressure fluctuation transmitted to the storage container based on a voltage change generated in the piezoelectric element.

JP-A-4-208827

  By the way, in this type of pressure sensor (including the pressure sensor disclosed in Patent Document 1), the specification is determined according to the application, and the sensor is designed to satisfy the specification. At this time, factors that determine the specifications of the pressure sensor include, for example, the shape of the piezoelectric element, the volume of the through hole or the recess, the shape of the gap between the piezoelectric element and the through hole or the recess, and the inside and outside of the through hole or the recess. The flow rate that goes in and out is mentioned.

  One factor that determines the performance of the pressure sensor is, for example, a frequency band in which pressure fluctuations can be detected. The upper limit frequency of pressure fluctuation that can be detected by the pressure sensor is considered to be in the vicinity of the resonance frequency of the piezoelectric element.

On the other hand, as for the lower limit frequency, it has been found that the lower the frequency, the easier it is to lower the frequency as the volume of the through hole or recess is increased and the flow rate between the inside and outside of the through hole or recess is reduced.
That is, when the volume of such a through-hole or a recessed part is made large, the delay time of the pressure fluctuation inside a through-hole or a recessed part becomes long with respect to the pressure fluctuation outside the said through-hole or recessed part.

  In other words, even if the pressure inside the through hole or the concave portion changes very slowly, if the pressure inside the through hole or the concave portion fluctuates more slowly than the pressure fluctuation, the difference between the external pressure and the pressure inside the through hole or the concave portion Pressure is obtained and the output of the pressure sensor can be obtained.

However, such a pressure sensor configured to detect a very slow pressure fluctuation causes a problem when it receives a sudden pressure fluctuation or a large pressure change.
For example, if the pressure outside the through-hole or the recess suddenly fluctuates, the pressure inside the through-hole or the recess also changes with a delay following the external pressure fluctuation.

  Immediately after sudden pressure fluctuation is applied, the differential pressure between the pressure outside the through hole or the recess and the internal pressure is very large, and the differential pressure gradually decreases. In the process of decreasing the differential pressure, the pressure sensor forms a state in which the sensor output can be obtained despite the constant pressure state in which the external pressure does not fluctuate.

  Therefore, whether the output of the pressure sensor immediately after the sudden pressure fluctuation is actually due to the pressure fluctuation outside the through hole or the concave portion, or the pressure inside the through hole or the concave portion caused by the sudden pressure fluctuation and the external pressure There was a problem that it was impossible to determine whether it was due to the differential pressure.

  Accordingly, an object of the present invention is to provide a pressure sensor capable of detecting a minute pressure change even immediately after a sudden pressure fluctuation occurs.

The present invention provides the following means in order to solve the above problems.
(1) A pressure sensor according to the present invention is a pressure sensor for detecting pressure fluctuations, and is disposed so as to face a sensor main body having a cavity and the cavity, and is supported in a cantilever manner. A pressure measuring cantilever that bends and deforms due to a pressure difference between the inside of the cavity and the outside of the cavity, a displacement measuring unit that measures displacement according to the bending deformation of the pressure measuring cantilever, and air inside and outside the cavity is circulated And a pressure adjusting mechanism for adjusting the pressure in the cavity.

The pressure sensor according to the present invention has a pressure adjustment mechanism that adjusts the pressure inside the cavity by circulating air inside and outside the cavity, so that when the pressure outside the cavity suddenly or very greatly fluctuates, However, it is possible to almost eliminate the differential pressure inside and outside the cavity (in other words, return to zero).
As a result, it is possible to accurately detect a minute pressure fluctuation immediately after the sudden or very large pressure fluctuation outside the cavity.

(2) In the pressure sensor according to the present invention, the pressure adjusting unit may include a communication opening that penetrates the sensor body and a switch that opens and closes the communication opening.

Thus, by having a communication opening that penetrates the sensor body and a switch that opens and closes the communication opening, air inside and outside the cavity can be circulated when the pressure outside the cavity suddenly or very greatly fluctuates. Thus, the pressure difference inside and outside the cavity can be almost eliminated.
As a result, pressure fluctuations can be detected in the low frequency band, and minute pressure changes can be detected immediately after a sudden pressure fluctuation occurs.

(3) In the pressure sensor according to the present invention, the pressure adjusting unit is arranged around the atmospheric pressure measurement cantilever and is supported in a cantilever manner, and pressure between the inside of the cavity and the outside of the cavity. A pressure adjusting cantilever that bends and deforms due to the difference may be included.

As described above, the pressure adjustment cantilever is arranged around the atmospheric pressure measurement cantilever and is supported in a cantilevered manner and is bent and deformed by the pressure difference between the inside of the cavity and the outside of the cavity. In the case where the pressure of the air pressure changes suddenly or very greatly, the air inside and outside the cavity can be circulated so that the differential pressure inside and outside the cavity can be almost eliminated.
As a result, pressure fluctuations can be detected in the low frequency band, and minute pressure changes can be detected immediately after a sudden pressure fluctuation occurs.
Also, by arranging the pressure adjustment cantilever around the atmospheric pressure measurement cantilever, it becomes possible to collectively form the atmospheric pressure measurement cantilever and the pressure adjustment cantilever, thereby simplifying the manufacturing process of the pressure sensor. it can.

(4) In the pressure sensor according to the present invention, the pressure adjusting unit includes a pressure adjusting cantilever that bends and deforms due to a pressure difference between the inside of the cavity and the outside of the cavity, and the pressure adjusting cantilever includes You may arrange | position so that the said cantilever for atmospheric | air pressure measurement may be opposed through a cavity.

In this way, when the pressure measuring cantilever and the pressure adjusting cantilever are arranged to face each other through the cavity, the air inside and outside the cavity is changed when the pressure outside the cavity suddenly or very greatly fluctuates. It is possible to eliminate the pressure difference between the inside and outside of the cavity.
As a result, pressure fluctuations can be detected in the low frequency band, and minute pressure changes can be detected immediately after a sudden pressure fluctuation occurs.
Further, the pressure sensor can be downsized as compared with the case where the pressure measuring cantilever and the pressure adjusting cantilever are arranged on the same side of the sensor body.

(5) In the pressure sensor according to the present invention, the pressure adjusting unit is supported in a cantilever manner with first and second communication openings penetrating a lid portion disposed on the sensor body, A first preload cantilever that opens and closes the first communication opening by bending and deforming due to a pressure difference between the inside of the cavity and the outside of the cavity, and is disposed outside the cavity and is supported in a cantilever manner. And a second preloading cantilever that opens and closes the second communication opening by being bent and deformed by a pressure difference between the inside of the cavity and the outside of the cavity, and the first preloading When the pressure outside the cavity becomes higher than the pressure inside the cavity, and the pressure difference between the inside and outside the cavity exceeds a predetermined value, the cantilever for the first cantilever The second preload cantilever is opened, and when the pressure inside the cavity becomes higher than the pressure outside the cavity, and the pressure difference inside and outside the cavity exceeds a predetermined value, the second preload cantilever A communication opening may be opened.

Thus, when the pressure outside the cavity becomes higher than the pressure inside the cavity and the pressure difference between the inside and outside of the cavity exceeds a predetermined value, the first preloading cantilever that opens the first communication opening, A second preload cantilever that opens the second communication opening when the pressure inside the cavity becomes higher than the pressure outside the cavity and the pressure difference between the inside and outside of the cavity exceeds a predetermined value. When the pressure outside the cavity changes suddenly or very greatly, air inside and outside the cavity can be circulated so that the differential pressure inside and outside the cavity can be almost eliminated.
As a result, pressure fluctuations can be detected in the low frequency band, and minute pressure changes can be detected immediately after a sudden pressure fluctuation occurs.

(6) In the pressure sensor according to the present invention, the first preload cantilever has a tip portion that closes the first communication opening, and the second preload cantilever includes the second communication opening. You may have the front-end | tip part which plugs up.

  As described above, the first preload cantilever has a tip portion that closes the first communication opening, and the second preload cantilever has a tip portion that closes the second communication opening, so that the pressure of the outside air rapidly increases. In this case, the first preload cantilever is used, and the second preload cantilever can be used when the outside air pressure suddenly drops. Therefore, even if the outside air pressure fluctuates positively or negatively, Can be performed.

(7) In the pressure sensor according to the present invention, the atmospheric pressure measurement cantilever may be disposed inside the second preload cantilever.

  As described above, the pressure measuring cantilever is arranged inside the second preloading cantilever, so that the second preloading cantilever and the pressure measuring cantilever can be collectively formed. The process can be simplified.

(8) In the pressure sensor according to the present invention, the pressure adjusting unit may include an opening / closing control unit that controls an opening / closing operation of the switch.

  Thus, by having the opening / closing control part which controls the opening / closing operation | movement of a switch, the timing which performs the opening / closing operation | movement of a switch can be appropriately controlled by the opening / closing control part.

(9) In the pressure sensor according to the present invention, the opening / closing control unit may output a control signal for opening the switch when the output of the displacement measuring unit exceeds a predetermined range. .

In this way, when the switching control unit outputs a control signal for opening the switch when the output of the displacement measuring unit exceeds a predetermined range, the pressure change over the predetermined range is detected. Since the sensor output can be reset, a minute pressure fluctuation can be accurately detected immediately after detection of a pressure fluctuation exceeding a predetermined range.
Further, the pressure range for resetting the sensor output by opening and closing the switch can be freely set.

(10) In the pressure sensor according to the present invention, the open / close control unit includes a detector that detects a pressure outside the cavity, and the open / close control unit has a pressure outside the cavity exceeding a predetermined value. When the detector detects this, a control signal for opening the switch may be output.

  As described above, when the detector detects that the pressure outside the cavity exceeds a predetermined value, the change amount of the actual pressure fluctuation outside the cavity is output by outputting a control signal for opening the switch. Therefore, it is possible to reset the output of the pressure sensor based on the above, so that a minute pressure fluctuation can be accurately detected.

(11) In the pressure sensor according to the present invention, the open / close control unit outputs a control signal for closing the switch after a predetermined time has elapsed since the output of the control signal for opening the switch. May be.

  In this way, after a predetermined time has elapsed since the output of the control signal for opening the switch, the control signal for closing the switch is output after the predetermined time has elapsed, so that the switching operation of the switch is performed by the control signal of the switch controller. Can be controlled. As a result, the differential pressure inside and outside the cavity can be reliably eliminated, so that a minute atmospheric pressure immediately after the pressure fluctuation can be accurately detected.

(12) In the pressure sensor according to the present invention, the switching controller outputs a control signal for opening the switch, and then closes the switch based on the output signal of the displacement measuring unit. You may output the control signal which performs.

In this way, after outputting the control signal for opening the switch, the control signal for closing the switch is output based on the output signal of the displacement measuring unit. Based on this, it is possible to control the opening / closing operation of the switch, so that even if a sudden or very large pressure fluctuation is applied, the differential pressure inside and outside the cavity can be reliably eliminated.
As a result, a minute atmospheric pressure can be accurately detected even immediately after a sudden or very large pressure fluctuation.

(13) In the pressure sensor according to the present invention, the displacement measuring unit may include a piezoresistor provided at a proximal end portion of the atmospheric pressure measuring cantilever.

  In this way, by having a piezoresistor that can convert the stress applied to the proximal end of the cantilever into a change in electrical resistance value at the proximal end of the cantilever, it is possible to easily detect the electrical resistance value of the piezoresistor. Since it is possible to detect the displacement of the cantilever, it is possible to accurately detect the pressure fluctuation.

(14) In the pressure sensor according to the present invention, the displacement measurement unit may include a piezoelectric thin film provided at a proximal end portion of the cantilever.

  In this way, by having a piezoelectric thin film at the base end of the cantilever that can convert the stress applied to the base end of the cantilever into an electromotive force, the electromotive force of the piezoelectric thin film is detected, and the displacement of the cantilever is easily detected. It becomes possible to do. Thereby, pressure fluctuations can be detected accurately.

(15) In the pressure sensor according to the present invention, an outer shape of the pressure adjusting cantilever may be larger than an outer shape of the atmospheric pressure measuring cantilever.

  In this way, by making the outer shape of the pressure adjustment cantilever larger than that of the atmospheric pressure measurement cantilever, only when the pressure adjustment cantilever receives a large pressure, the pressure adjustment cantilever is deformed, and the inside and outside of the cavity are deformed. Differential pressure can be eliminated.

(16) In the pressure sensor according to the present invention, a piezoelectric thin film may be provided on the pressure adjusting cantilever.

  As described above, by providing the pressure adjusting cantilever with the piezoelectric thin film, the pressure adjusting cantilever can be provided with the function of an actuator.

(17) In the pressure sensor according to the present invention, an outer shape of the first and second preloading cantilevers may be larger than an outer shape of the atmospheric pressure measuring cantilever.

  Thus, by making the outer shape of the first and second preloading cantilevers larger than the outer shape of the atmospheric pressure measurement cantilever, only when the first and second preloading cantilevers receive the first and second preloading cantilevers. Any one of the second preload cantilevers can be deformed to eliminate the pressure difference inside and outside the cavity.

(18) In the pressure sensor according to the present invention, the first and second preloading cantilevers may include a piezoelectric thin film.

  As described above, since the first and second preload cantilevers include the piezoelectric thin film, the first and second preload cantilevers can be warped (in other words, preload).

  According to the pressure sensor of the present invention, it is possible to detect a slow pressure fluctuation in a low frequency band, and it is possible to detect a minute pressure change immediately after the sudden pressure fluctuation by resetting the output immediately after the sudden pressure fluctuation.

It is a top view which shows schematic structure of the pressure sensor which concerns on the 1st Embodiment of this invention. It is sectional drawing of the pressure sensor along the AA line shown in FIG. It is a figure which shows typically an example of the output of the pressure sensor shown in FIG. 1, (A) is a figure which shows the time-dependent change of the pressure inside and outside a cavity, (B) is a figure which shows the time-dependent change of the output of a pressure sensor. It is. It is sectional drawing which shows typically an example of operation | movement of the pressure sensor shown in FIG. 1, (A) has shown sectional drawing of the pressure sensor of an initial state, (B) is the pressure outside a cavity from internal pressure. A cross-sectional view of the pressure sensor when the pressure is high is shown, and (C) shows a cross-sectional view of the pressure sensor when the pressure inside and outside the cavity returns to an equal pressure. It is a figure which shows typically an example of the output when a sudden pressure fluctuation arises in the pressure sensor shown in FIG. 1, (A) is a figure which shows the time-dependent change of the pressure inside and outside a cavity, (B) is a pressure It is a figure which shows the time-dependent change of the output of a sensor, (C) is a figure which shows the time-dependent change of the output signal of an opening / closing control part. It is sectional drawing which shows schematic structure of the pressure sensor which concerns on the modification of the 1st Embodiment of this invention. It is sectional drawing which shows schematic structure of the pressure sensor which concerns on the 2nd Embodiment of this invention. It is a top view of the principal part of the pressure sensor shown in FIG. 7, and is a figure for demonstrating the positional relationship of the cantilever for atmospheric pressure measurement, and the cantilever for pressure adjustment. It is sectional drawing which shows schematic structure of the pressure sensor which concerns on the 3rd Embodiment of this invention. It is a perspective view which shows schematic structure of the pressure sensor which concerns on the 4th Embodiment of this invention. It is sectional drawing of the pressure sensor along the BB line shown in FIG. It is a figure which shows typically the displacement of the 1st cantilever for preload and the cantilever for atmospheric pressure measurement when the pressure difference of the pressure outside a cavity and the pressure in a cavity becomes large. It is the perspective view which decomposed | disassembled the pressure sensor which concerns on the modification of the 4th Embodiment of this invention. It is sectional drawing of the pressure sensor along the JJ line shown in FIG. It is sectional drawing which shows schematic structure of the pressure sensor which concerns on the 5th Embodiment of this invention. FIG. 17 is a plan view of the main part of the pressure sensor shown in FIG. 16 for explaining the positional relationship between the atmospheric pressure measurement cantilever and the second preload cantilever. It is sectional drawing (the 1) which shows the other example of the cantilever for preloads. It is sectional drawing (the 2) which shows the other example of the cantilever for preloads. It is sectional drawing (the 3) which shows the other example of the cantilever for preloads.

  Embodiments to which the present invention is applied will be described below in detail with reference to the drawings. The drawings used in the following description are for explaining the configuration of the embodiment of the present invention, and the size, thickness, dimensions, etc. of each part shown in the drawings are different from the dimensional relationship of an actual pressure sensor. There is a case.

(First embodiment)
<Description of Configuration of Pressure Sensor According to First Embodiment>
FIG. 1 is a plan view showing a schematic configuration of a pressure sensor according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the pressure sensor along the line AA shown in FIG.

1 and 2, the pressure sensor 1 according to the first embodiment is a sensor that detects pressure fluctuations in a predetermined frequency band (for example, 0.05 Hz to 10 kHz). , A pressure measuring mechanism 8 including a pressure measuring cantilever 4, a lid 12, a displacement measuring unit 5, a communication opening 11 b, a switch 6, and an opening / closing control unit 7.
The pressure adjusting mechanism 8 is a mechanism for adjusting the pressure in the cavity 10 by circulating the air inside and outside the cavity 10 (air chamber) (specifically, to eliminate the pressure difference between the inside and outside of the cavity 10). is there.

  The sensor body 3 has a cavity 10. The sensor body 3, for example, defines the cavity 10 and is disposed on the first portion 3-1 made of resin, the first portion 3-1, and the silicon support layer 2 a and the silicon oxide film. And a second portion 3-2 made of the oxide layer 2b.

The atmospheric pressure measurement cantilever 4 can be formed, for example, by processing the SOI substrate 2 in which the silicon support layer 2a, the oxide layer 2b such as a silicon oxide film, and the silicon active layer 2c are thermally bonded.
The atmospheric pressure measurement cantilever 4 is formed by cutting out a gap 13 formed of a silicon active layer 2c on the SOI substrate 2 and formed in a U-shape in plan view from the flat silicon active layer 2c.

Thus, the atmospheric pressure measuring cantilever 4 has a cantilever structure in which the base end portion 4a is a fixed end and the tip end portion 4b is a free end.
The atmospheric pressure measurement cantilever 4 is disposed so as to surround the upper surface of the cavity 10 formed in the sensor body 3. That is, the atmospheric pressure measuring cantilever 4 substantially closes the opening of the cavity 10.

The barometric pressure measuring cantilever 4 is cantilevered by being integrally fixed to the sensor body 3 with respect to the second portion 3-2 via the base end portion 4a.
Thereby, the cantilever 4 for atmospheric pressure measurement can be bent and deformed according to the pressure difference between the inside and the outside of the cavity 10 with the base end portion 4a as the center.
The base end portion 4a of the atmospheric pressure measuring cantilever 4 is formed with a U-shaped through hole 15 in a plan view, and the atmospheric pressure measuring cantilever 4 is designed to be easily bent and deformed. However, the shape of the through-hole 15 is not limited to the U-shape, and can be appropriately changed to a shape that facilitates bending deformation of the atmospheric pressure measurement cantilever 4.

  The lid 12 is arranged around the atmospheric pressure measurement cantilever 4 via the gap 13. The lid 12 is composed of a silicon active layer 2c. The lid portion 12 is disposed above the cavity 10.

  The displacement measuring unit 5 detects the displacement of the piezoresistor 20 provided on the upper surface of the base end part 4 a of the atmospheric pressure measuring cantilever 4, the wiring unit 21 connected to the upper part of the piezoresistor 20, and the atmospheric pressure measuring cantilever 4. And a detection circuit 22.

The piezoresistor 20 is a resistance element whose electrical resistance value changes according to the amount of deflection (displacement) of the atmospheric pressure measurement cantilever 4. As shown in FIG. 1, the piezoresistors 20 are arranged in pairs on both sides of the through hole 15 in the short direction of the atmospheric pressure measurement cantilever 4.
The pair of piezoresistors 20 are electrically connected to each other via a wiring portion 21 made of a conductive material.

  The overall shape including the wiring portion 21 and the piezoresistor 20 can be, for example, a U shape in plan view. The piezoresistor 20 is electrically connected to a detection circuit 22 that measures the displacement of the atmospheric pressure measuring cantilever 4 based on a change in the electric resistance value of the piezoresistor 20.

In the displacement measuring unit 5 configured as described above, a current generated when a predetermined voltage is applied to the piezoresistor 20 through the detection circuit 22 wraps around the through hole 15 so that the wiring unit 21 is connected to the piezoresistor 20. To the other piezoresistor 20 via.
For this reason, the detection circuit 22 can take out an electrical resistance value change of the piezoresistor 20 that changes in accordance with the displacement (deflection deformation) of the atmospheric pressure measurement cantilever 4 as an electrical output signal.

  Therefore, since the displacement measuring unit 5 can measure the displacement of the atmospheric pressure measuring cantilever 4 based on this output signal (sensor output), it detects the differential pressure between the inside and the outside of the cavity 10. Can do.

The piezoresistor 20 is formed by doping the silicon active layer 2c with a dopant (impurity) such as phosphorus by various methods such as an ion implantation method and a diffusion method.
In addition, the pair of piezoresistors 20 is configured to be electrically connected only by the wiring portion 21. For this reason, although not shown, the silicon active layer 2 c located around the atmospheric pressure measuring cantilever 4 is etched so that both the piezoresistors 20 are not conductive except at the wiring portion 21.

Further, a piezoelectric thin film may be used in place of the piezoresistor 20.
In this case, an electromotive force is generated according to the stress applied to the base end 4b of the atmospheric pressure measurement cantilever 4, and the displacement of the atmospheric pressure measurement cantilever 4 can be detected by detecting the electromotive force. .

  The communication opening 11 b is provided separately from the gap 13 of the atmospheric pressure measurement cantilever 4. The communication opening 11 b is provided so as to penetrate the bottom of the sensor body 3. The communication opening 11 b is a cylindrical outside air circulation port whose one end is in contact with outside air and whose other end is in communication with the cavity 10.

  The diameter of the communication opening 11b may be set so that the opening area is larger than the opening area of the gap 13. In this way, by configuring the diameter of the communication opening 11 b so that the opening area is larger than the opening area of the gap 13, even if a pressure difference between the cavity 10 and the outside air is applied, the communication opening 11 b than the gap 13. Thus, the air flow rate between the cavity 10 and the outside air can be increased.

  The switch 6 is attached to a communication opening 11b provided in the sensor body 3, and has a function of opening and closing the communication opening 11b. As the switch 6, for example, a small solenoid valve can be used.

  The opening / closing control unit 7 is electrically connected to the detection circuit 22 and the switch 6 of the displacement measuring unit 5. The opening / closing control unit 7 outputs a control signal to the switch 6 to cause the switch 6 to sequentially execute an opening / closing operation. The specific operation control of the switch 6 by the switching control unit 7 will be described in detail later.

<Description of the operation of the pressure sensor according to the first embodiment>
FIG. 3 is a diagram schematically showing an example of the output of the pressure sensor shown in FIG. 1, (A) is a diagram showing the change over time of the pressure inside and outside the cavity, and (B) is the time course of the output of the pressure sensor. It is a figure which shows a change.
4 is a cross-sectional view schematically showing an example of the operation of the pressure sensor shown in FIG. 1. (A) shows a cross-sectional view of the pressure sensor in the initial state, and (B) shows the pressure outside the cavity. A cross-sectional view of the pressure sensor when the pressure is higher than the internal pressure is shown, and (C) shows a cross-sectional view of the pressure sensor when the pressure inside and outside the cavity returns to the equal pressure.
In FIG. 4, the same components as those of the pressure sensor 1 shown in FIG. Further, in FIG. 4, illustration of the opening / closing control unit 7 and the detection circuit 22 constituting the pressure sensor 1 is omitted.

Next, with reference to FIG. 3 and FIG. 4, the operation of the pressure sensor 1 in the case of detecting minute pressure fluctuations using the pressure sensor 1 described above will be described.
First, as in period A shown in FIG. 3A, the pressure between the pressure outside the cavity 10 (hereinafter referred to as “external pressure Pout”) and the pressure inside the cavity 10 (hereinafter referred to as “internal pressure Pin”). When the difference is zero, as shown in FIG. 4A, the pressure measuring cantilever 4 is not bent and deformed.

Here, as in the period B after time t1 shown in FIG. 3A, for example, when the external pressure Pout rises stepwise, a differential pressure is generated between the outside and the inside of the cavity 10, so that FIG. As shown in B), the atmospheric pressure measurement cantilever 4 is bent and deformed toward the inside of the cavity 10.
Then, distortion occurs in the piezoresistor 20 according to the bending deformation of the atmospheric pressure measuring cantilever 4, and the electric resistance value changes, so that the output signal of the pressure sensor 1 increases as shown in FIG.

  Further, after the increase of the external pressure Pout, the pressure transmission medium flows from the outside to the inside of the cavity 10 through the gap 13. For this reason, as shown in FIG. 3A, the internal pressure Pin rises with time and with a response that is slower than the external pressure Pout and slower than the fluctuation of the external pressure Pout.

  As a result, the internal pressure Pin gradually approaches the external pressure Pout, so that the pressure between the outside and the inside of the cavity 10 starts to be in an equilibrium state, and the deflection of the atmospheric pressure measuring cantilever 4 gradually decreases, as shown in FIG. As described above, the output signal gradually decreases.

  When the internal pressure Pin becomes equal to the external pressure Pout as in the period C after time t2 shown in FIG. 3A, the bending deformation of the atmospheric pressure measuring cantilever 4 is eliminated as shown in FIG. 4C. It returns to the original state, and the output signal of the pressure sensor 1 becomes zero again as shown in FIG.

Thus, by monitoring the fluctuation of the output signal based on the displacement of the atmospheric pressure measuring cantilever 4, the pressure fluctuation outside the cavity 10 can be detected.
In particular, since the barometric pressure measuring cantilever 4 can be formed by a semiconductor process technique using the silicon active layer 2c of the SOI substrate 2, it is easy to make it thinner (for example, several tens to several hundreds nm) than a conventional piezoelectric element. Therefore, it is possible to detect minute pressure fluctuations with high accuracy.

FIG. 5 is a diagram schematically illustrating an example of an output when a sudden pressure fluctuation occurs in the pressure sensor illustrated in FIG. 1, and FIG. 5A is a diagram illustrating a temporal change in pressure inside and outside the cavity. FIG. 4B is a diagram showing a change with time of the output of the pressure sensor, and FIG. 4C is a diagram showing a change with time of the output signal of the opening / closing control unit.
In FIG. 5B, the output signal of the pressure sensor 1 when the switch 6 and the switching control unit 7 are operated is a solid line, and the switch 6 and the switching control unit 7 are not operated (that is, the conventional one) The output signal of the pressure sensor is indicated by a broken line.

Next, the operation of the pressure sensor 1 when a sudden pressure fluctuation is applied will be described with reference to FIG.
First, the case where the switch 6 and the switching controller 7 are operated will be described. When the external pressure Pout rises significantly at time t3 shown in FIG. 5A, a pressure difference between the outside and the inside of the cavity 10 is generated as described above, and the pressure measuring cantilever 4 is deformed. As shown in FIG. 5B, the output signal of the pressure sensor 1 increases.

  Here, when the output signal of the pressure sensor 1 exceeds the threshold value Vc, the switching control unit 7 outputs a control signal to the switch 6, and opens the switch 6 for a predetermined time (period t3c to t4). Then, outside air is introduced into the cavity 10 through the communication opening 11b.

  Since the opening area of the communication opening 11b is larger than the opening area of the gap 13 as described above, the flow amount of the switch 6 (in other words, the flow amount of the communication opening 11b) is the gap 13 around the pressure measuring cantilever 4. And the differential pressure between the outside and inside of the cavity 10 returns to almost zero.

For this reason, the deformation of the atmospheric pressure measuring cantilever 4 is eliminated and the output signal is also reset to zero, so that the pressure sensor 1 is again in a state where it can detect a minute pressure fluctuation.
Here, the threshold Vc of the output signal and the predetermined time for opening the switch 6 are for basic performance of the pressure sensor 1 (for example, pressure resolution, etc.), volume of the cavity 10 constituting the pressure sensor 1, and pressure measurement. This value is determined appropriately depending on the rigidity of the cantilever 4, the width of the gap 13, the air flow rate through the switch 6, and the like.

  For example, the pressure sensor 1 passes through a pressure measuring cantilever 4 whose tip is displaced by 0.1 μm with a pressure difference of 1 Pa, a gap 13 having a width of 5 μm, a cavity 10 having a volume of 1 mL, and a communication opening 11b having a diameter of 1 mm. It is assumed that a pressure difference of 30 Pa occurs inside and outside the cavity 10 when the threshold Vc is 1 V.

In this case, the flow rate of air flowing through the communication opening 11b and the switch 6 with a pressure difference of 30 Pa is about 5.5 mL / sec. Then, in order to cancel the pressure difference 30 Pa inside and outside the cavity 10 and make the pressure difference zero, about 0.3 μL of air needs to enter and exit the cavity 10.
For this reason, when the switch 6 is opened for about 1 msec, a pressure difference of about several tens of Pa inside and outside the cavity 10 can be offset. Therefore, the predetermined time is about several milliseconds.

  If the volume of the cavity 10 is further increased, the amount of air that cancels out the pressure difference increases, so that it is necessary to lengthen the predetermined time. Further, if the diameter of the communication opening 11b and the air flow rate of the switch 6 are increased, the pressure difference can be offset even if the predetermined time is shorter than several msec.

  Further, the threshold value Vc and the predetermined time may be values set in advance in the open / close control unit 7, or a display unit or an operation input unit (not shown) is provided in the pressure sensor 1 as necessary. It is good also as what a user can input / set.

  Thereafter, when the external pressure Pout decreases slightly as shown at time t5 in FIG. 5A, a differential pressure is generated again between the outside and the inside of the cavity 10. Due to this differential pressure, the atmospheric pressure measuring cantilever 4 is deformed toward the outside of the cavity 10 and the output signal of the pressure sensor 1 decreases.

Next, the case where the switch 6 does not open / close will be described. In this case, after a large pressure increase at time t3 in FIG. 5A, the sensor output signal gradually decreases in the period B in FIG.
For this reason, in the process in which the differential pressure decreases, the pressure sensor 1 is in a state in which the sensor output can be obtained even though the external pressure Pout does not fluctuate. I can't.

  Further, when the external pressure Pout is slightly decreased at time t5 in FIG. 5A, the decreasing gradient of the sensor output signal is changed. Although it can be determined that the external pressure Pout has decreased even if the change in the decreasing gradient at this time is captured, it is difficult to accurately detect how much the pressure has decreased. Further, as the change in the external pressure Pout is rapid and large, the period B during which the sensor output signal decreases is longer, and therefore the period during which accurate detection cannot be performed becomes longer.

According to the pressure sensor of the first embodiment, the sensor body 3 having the cavity 10 and the cavity 10 are disposed so as to face the cavity 10 and are supported in a cantilever manner. A pressure measuring cantilever 4 that bends and deforms due to a pressure difference with the outside, a displacement measuring unit 5 that measures displacement according to the bending deformation of the pressure measuring cantilever 4, and air inside and outside the cavity 10 circulates inside the cavity 10. The pressure adjustment mechanism 8 including the communication opening 11b, the switch 6, and the switching control unit 7 is operated, so that the switch 6 and the switching control unit 7 operate, so that the outside of the cavity 10 can be operated. Even when the pressure suddenly or fluctuates greatly, the pressure difference between the inside and outside of the cavity 10 is almost eliminated (in other words, the pressure is reset to zero. ) It becomes possible.
Thereby, even if the external pressure Pout has an extremely sudden and large fluctuation, the pressure sensor 1 can accurately detect a minute pressure change immediately after the fluctuation.

In addition, by reducing the width of the gap 13 (for example, several μm or less), it is possible to limit the air flow rate between the cavity 10 and the outside air very small.
As a result, the pressure difference between the cavity 10 and the outside air can be maintained for a long time, so that the pressure fluctuation in the low frequency band can be detected.

In the first embodiment, as an example, the method in which the switch 6 is opened only for a predetermined time has been described as an example. However, the switching control unit 7 determines whether the difference is based on the measurement value of the displacement measuring unit 5. When it is determined that the pressure can be eliminated, a control signal for closing the opened switch 6 may be output.
In this configuration, the pressure difference is eliminated without necessarily waiting for the set opening time, the deformed barometric pressure measuring cantilever 4 is restored, and the switch 6 is closed, so that the pressure fluctuation can be detected again.

And the pressure sensor 1 of 1st Embodiment is applicable to the following various uses. The pressure sensor 1 of 1st Embodiment is applicable to the navigation apparatus for motor vehicles, for example.
In this case, for example, the pressure difference based on the height difference can be detected using the pressure sensor 1, so that the elevated road and the elevated road can be accurately determined and reflected in the navigation result. Furthermore, it is possible to accurately detect the slope immediately after leaving the parking lot.

  The pressure sensor 1 of the first embodiment can also be applied to a portable navigation device, for example. In this case, for example, it is possible to detect the pressure difference based on the height difference using the pressure sensor 1, so that it is possible to accurately determine the floor in which the user is located in the navigation result. It can be reflected.

In addition, it is possible to accurately detect a step up and down immediately after moving a plurality of floors by an elevator, a step up and down immediately after entering and leaving a building controlled by air conditioning, and the like.
Furthermore, since it is possible to detect a pressure change in the room, the present invention can be applied to a crime prevention device that detects opening and closing of a door of a building or a car, for example.
As described above, the pressure sensor 1 according to the first embodiment can be applied to various applications, and when applied to such applications, an unexpected sudden pressure change that occurs during use is applied. However, it is possible to reset immediately and detect a fine pressure change again.

  FIG. 6 is a sectional view showing a schematic configuration of a pressure sensor according to a modification of the first embodiment of the present invention. In FIG. 6, the same components as those of the pressure sensor 1 of the first embodiment are denoted by the same reference numerals.

  Referring to FIG. 6, the pressure sensor 25 according to the modification of the first embodiment is an absolute pressure which is a detector instead of the opening / closing control unit 7 constituting the pressure sensor 10 of the first embodiment. The configuration is the same as that of the pressure sensor 1 except that the open / close control unit 27 including the sensor 26 is provided.

  The absolute pressure sensor 26 is electrically connected to the detection circuit 22. The absolute pressure sensor 26 is a sensor that covers one surface of a vacuum cavity (not shown) with a thin film and detects an external pressure (absolute pressure) based on a deformation amount of the thin film. In general, a method is known in which absolute pressure is detected by a semiconductor thin film in which a piezoresistor is formed, a metal thin film in which a strain gauge is formed, or a thin film incorporating a crystal or silicon oscillator.

Such an absolute pressure sensor 26 can detect an absolute pressure, which is a differential pressure from a vacuum, and has a wide detectable pressure range.
Here, when the external pressure Pout changes suddenly, the open / close control unit 7 outputs a control signal to the switch 6 when determining that the output change of the absolute pressure sensor 26 exceeds a predetermined threshold value. 6 is opened for a predetermined time (for example, a period of several to several tens of msec).

When the switch 6 is opened, the differential pressure between the outside and the inside of the cavity 10 becomes almost zero, and the output of the pressure sensor 25 returns to near zero. Thereafter, even if the external pressure Pout changes minutely, the pressure sensor 25 can accurately detect the minute change.
As described above, according to the pressure sensor 25 according to the modification of the first embodiment, the output of the pressure sensor 25 can be restored based on the output of the absolute pressure sensor 26 even if a large pressure change is applied. Therefore, a minute pressure change immediately after a large pressure change can be accurately detected.

(Second Embodiment)
FIG. 7 is a cross-sectional view showing a schematic configuration of a pressure sensor according to the second embodiment of the present invention. FIG. 8 is a plan view of the main part of the pressure sensor shown in FIG. 7, for explaining the positional relationship between the atmospheric pressure measuring cantilever and the pressure adjusting cantilever.
7 and 8, the illustration of the displacement measuring unit 5 shown in FIG. 1 constituting the pressure sensor 30 of the second embodiment is omitted.

7 and 8, the pressure sensor 30 of the second embodiment has a pressure adjustment mechanism 31 instead of the pressure adjustment mechanism 8 constituting the pressure sensor 1 of the first embodiment. Other than that, the configuration is the same as that of the pressure sensor 1.
The pressure adjustment mechanism 31 includes a pressure adjustment cantilever 32 and a gap 33. The pressure adjusting cantilever 32 is disposed around the atmospheric pressure measuring cantilever 4 and is supported in a cantilever manner, and bends and deforms due to a pressure difference between the inside of the cavity 10 and the outside of the cavity 10. The pressure adjustment mechanism 31 has a through portion 35 that houses the atmospheric pressure measurement cantilever 4.

  The outer shape of the pressure adjusting cantilever 32 is configured to be larger than the outer shape of the atmospheric pressure measuring cantilever 4. Thus, by making the outer shape of the pressure adjusting cantilever 32 larger than the outer shape of the atmospheric pressure measuring cantilever 4, the pressure adjusting cantilever 32 is deformed only when the pressure adjusting cantilever 32 receives a large pressure, The differential pressure inside and outside the cavity 10 can be eliminated.

Further, the width W2 of the gap 33 disposed between the pressure adjusting cantilever 32 and the lid portion 12 is larger than the width W1 of the gap 13 disposed between the pressure adjusting cantilever 32 and the atmospheric pressure measuring cantilever 4. It is good to make it small (to make it as small as possible).
When the deformation of the pressure adjusting cantilever 32 and the atmospheric pressure measuring cantilever 4 is small, the gap 33 can make the air flow rate between the cavity 10 and the outside air smaller than the gap 13. As a result, the pressure fluctuation in the detectable range of the atmospheric pressure measurement cantilever 4 can restrict the air flow rate between the outside air and the cavity 10 to be small, so that the pressure fluctuation in the low frequency band can be detected. .

  On the other hand, when a large pressure fluctuation occurs, the pressure adjusting cantilever 32 is deformed larger than the atmospheric pressure measuring cantilever 4, so that the width W 2 of the gap 33 is much larger than the width W 1 of the gap 13, and the outside air and the gap 10 Therefore, the differential pressure between the outside air and the cavity 10 can be eliminated in a short time.

  Further, a piezoelectric thin film may be provided on the pressure adjusting cantilever 32. Thus, by providing the pressure adjusting cantilever 32 with the piezoelectric thin film, the pressure adjusting cantilever 32 can be provided with the function of an actuator.

According to the pressure sensor of the second embodiment, the pressure sensor is disposed around the atmospheric pressure measuring cantilever 4 and is supported in a cantilever manner, and is bent and deformed by a pressure difference between the inside of the cavity 10 and the outside of the cavity 10. By having the pressure adjusting cantilever 32 to be operated, when the pressure outside the cavity 10 suddenly or very greatly fluctuates, the air inside and outside the cavity 10 can be circulated so that the differential pressure inside and outside the cavity 10 can be almost eliminated. It becomes.
As a result, pressure fluctuations can be detected in the low frequency band, and minute pressure changes can be detected immediately after a sudden pressure fluctuation occurs.

  Further, by arranging the pressure measuring cantilever 4 and the pressure adjusting cantilever 32 on the same plane, it becomes possible to form the pressure measuring cantilever 4 and the pressure adjusting cantilever 32 at a time. The process can be simplified.

  Furthermore, since the switch 6 and the switching controller 7 described in the first embodiment are not necessary, the configuration of the pressure sensor 30 can be simplified.

(Third embodiment)
FIG. 9 is a cross-sectional view showing a schematic configuration of a pressure sensor according to a third embodiment of the present invention. 9, the same components as those of the pressure sensor 30 according to the second embodiment shown in FIG.
In FIG. 9, the illustration of the displacement measuring unit 5 shown in FIG. 1 constituting the pressure sensor 40 of the third embodiment is omitted.

  Referring to FIG. 9, the pressure sensor 40 of the third embodiment has a pressure adjustment mechanism 41 in place of the pressure adjustment mechanism 31 constituting the pressure sensor 30 of the second embodiment. The configuration is the same as that of the pressure sensor 30.

The pressure adjustment mechanism 41 is replaced with a pressure adjustment cantilever 43 disposed opposite to the atmospheric pressure measurement cantilever 4 via the cavity 10 instead of the pressure adjustment cantilever 32 constituting the pressure adjustment mechanism 31. The adjustment mechanism 31 is configured similarly.
The pressure adjusting cantilever 43 is configured in the same manner as the pressure adjusting cantilever 32 except that the pressure adjusting cantilever 43 does not have the penetrating portion 35 (see FIG. 8) formed in the pressure adjusting cantilever 32.

  According to the pressure sensor of the third embodiment, the pressure sensor is disposed so as to face the atmospheric pressure measurement cantilever 4 through the cavity 10, and is bent and deformed by a pressure difference between the inside of the cavity 10 and the outside of the cavity 10. By having the pressure adjusting cantilever 43 to be operated, when the pressure outside the cavity 10 suddenly or very greatly fluctuates, the air inside and outside the cavity 10 can be circulated so that the differential pressure inside and outside the cavity 10 can be almost eliminated. It becomes. As a result, pressure fluctuations can be detected in the low frequency band, and minute pressure changes can be detected immediately after a sudden pressure fluctuation occurs.

  Further, the pressure sensor 40 and the barometric pressure measuring cantilever 4 are disposed to face each other, so that the pressure sensor 40 is compared with the case where the pressure adjusting cantilever 43 and the barometric pressure measuring cantilever 4 are disposed on the same plane. Can be miniaturized.

(Fourth embodiment)
FIG. 10 is a perspective view showing a schematic configuration of a pressure sensor according to the fourth embodiment of the present invention. FIG. 11 is a cross-sectional view of the pressure sensor along the line BB shown in FIG. In FIG.10 and FIG.11, the same code | symbol is attached | subjected to the same component as the pressure sensor 1 of 1st Embodiment shown in FIG.
10 and 11, the illustration of the displacement measuring unit 5 shown in FIG. 1 constituting the pressure sensor 50 of the fourth embodiment is omitted. In FIG. 10, the first support member 54 and the first preload cantilever 56 constituting the pressure sensor 50 of the fourth embodiment are not shown.

  Referring to FIGS. 10 and 11, the pressure sensor 50 of the fourth embodiment has a pressure adjustment mechanism 51 instead of the pressure adjustment mechanism 8 constituting the pressure sensor 1 of the first embodiment. Other than that, the configuration is the same as that of the pressure sensor 1.

  The pressure adjustment mechanism 51 includes a first communication opening 52, a second communication opening 53, a first support member 54, a second support member 55, a first preload cantilever 56, and a second preload cantilever 56. A preload cantilever 57.

  The first and second communication openings 52 and 53 are provided so as to penetrate the lid portion 12. The first and second communication openings 52 and 53 are arranged so as to face each other via the atmospheric pressure measurement cantilever 4. The shape of the first and second communication openings 52 and 53 can be, for example, a groove shape. The first and second communication openings 52 and 53 function as openings for circulating air into and out of the cavity 10.

The first support member 54 is fixed in the cavity 10 on the bottom of the sensor body 3 located at the end. As the first support member 54, for example, an adhesive or an SOI substrate serving as a base material of the first preload cantilever 56 can be used.
The second support member 55 is fixed on the end of the lid portion 12 located on the side opposite to the position where the first support member 54 is disposed. As the second support member 55, for example, an adhesive or an SOI substrate serving as a base material of the second preload cantilever 57 can be used.

The base end portion 56 a of the first preloading cantilever 56 is fixed to the first support member 54 or is integrated with the first support member 54. The first preload cantilever 56 has a warp caused by the preload. When there is no pressure difference between the inside and the outside of the cavity 10, the tip 56b is brought into contact with the inner surface of the lid 12. (See FIG. 11).
The first preload cantilever 56 is composed of, for example, a cantilever body (not shown) formed by processing an SOI substrate, and a piezoelectric thin film (not shown) that covers one surface of the cantilever body. Can do.
The outer shape of the first preload cantilever 56 is configured to be larger than the outer shape of the atmospheric pressure measurement cantilever 4. Thus, the first preload cantilever 56 can be displaced only when a large pressure is applied from the outside of the cavity 10.

FIG. 12 is a diagram schematically showing displacement of the first preloading cantilever and the pressure measuring cantilever when the pressure difference between the pressure outside the cavity and the pressure inside the cavity increases.
In FIG. 12, D indicates the transition of the displacement of the cantilever without preload, and C indicates the transition of the displacement of the first preload cantilever 56.
In FIG. 12, E indicates the transition of the displacement of the atmospheric pressure measurement cantilever 4 when the first preload cantilever 56 does not exist, and F indicates the case where the first preload cantilever 56 exists. The displacement of the atmospheric pressure measurement cantilever 4 is shown.

  Here, with reference to FIG. 12, the displacement of the first preloading cantilever 56 and the atmospheric pressure measurement cantilever 4 when the difference between the pressure outside the cavity 10 and the pressure inside the cavity 10 increases will be described. Since the first preload cantilever 56 is displaced when the pressure outside the cavity 10 becomes larger than the pressure inside the cavity, this case will be described.

  Referring to FIG. 12, an initial stage where the pressure difference between the pressure outside the cavity 10 and the pressure inside the cavity 10 is small (the range of the region G shown in FIG. 12, in other words, the stage where the pressure difference is smaller than the predetermined value H). ), The front end portion 56a and the lid 12 are in contact with each other due to the preload of the first preload cantilever 56. Therefore, as shown in FIG. 12C, the first preload cantilever 56 is not displaced by the pressure difference.

  On the other hand, the atmospheric pressure measuring cantilever 4 has a smaller outer shape than the first preloading cantilever 56 and is thus displaced by the differential pressure. However, when the differential pressure is small, since the displacement of the atmospheric pressure measurement cantilever 4 due to the differential pressure is small, a fine pressure fluctuation can be detected without any problem.

  Thereafter, when the pressure difference between the inside and outside of the cavity 10 exceeds a predetermined value H, the first preloading cantilever 56 is pressed by the pressure from the outside of the cavity 10 and pushed downward. Thereby, the front-end | tip part 56b spaces apart from the cover body 12, the 1st communication opening 52 is opened, the air inside and outside the cavity 10 distribute | circulates, and the pressure difference (differential pressure) inside and outside the cavity 10 is almost lost.

As a result, as shown in FIG. 12F, the displacement of the atmospheric pressure measurement cantilever 4 is gradually reduced and almost no displacement is detected, so that a minute pressure change can be detected immediately after a sudden pressure fluctuation occurs. Can do.
On the other hand, when the first preload cantilever 56 does not exist, the displacement of the atmospheric pressure measurement cantilever 4 becomes larger as shown by E, so that a minute pressure change cannot be detected.

Referring to FIG. 11, the base end portion 57 a of the second preload cantilever 57 is fixed to the second support member 55, or is integrated with the second support member 55. The second preload cantilever 57 has the same configuration as the first preload cantilever 56 described above.
The second preload cantilever 57 is arranged so that the tip end portion 57b closes the second communication opening 53 in a state where the first preload cantilever 56 shown in FIG.

  When the pressure inside the cavity 10 becomes higher than the pressure outside the cavity 10 and the pressure difference inside and outside the cavity 10 exceeds a predetermined value H (see FIG. 12), the second preload cantilever 57 The same displacement as that of the first preloading cantilever 56 described above with reference to FIG. 12 is performed except that 57b is separated from the lid 12 and the second communication opening 53 is opened.

According to the pressure sensor of the fourth embodiment, the first and second communication openings 52 and 53 penetrating the lid portion 12 disposed on the sensor body 3 and the pressure outside the cavity 10 are applied to the cavity 10. When the pressure difference between the inside and outside of the cavity 10 exceeds a predetermined value H, the first preloading cantilever 56 that opens the first communication opening 52 and the pressure inside the cavity 10 are By having a second preloading cantilever 57 that opens the second communication opening 53 when the pressure difference outside the cavity 10 becomes higher than the pressure outside the cavity 10 and the pressure difference inside and outside the cavity 10 exceeds a predetermined value, the cavity 10 When the external pressure is sudden or very large, the air inside and outside the cavity 10 is circulated so that the differential pressure inside and outside the cavity 10 is almost eliminated. It can become.
As a result, pressure fluctuations can be detected in the low frequency band, and minute pressure changes can be detected immediately after a sudden pressure fluctuation occurs.

FIG. 13 is an exploded perspective view of a pressure sensor according to a modification of the fourth embodiment of the present invention. FIG. 14 is a cross-sectional view of the pressure sensor along the line JJ shown in FIG.
13 and 14, the same components as those of the pressure sensor 50 according to the fourth embodiment shown in FIGS. 10 and 11 are denoted by the same reference numerals.
Moreover, in FIG.13 and FIG.14, illustration of the displacement measurement part 5 shown in FIG. 1 which comprises the pressure sensor 60 which concerns on the modification of 4th Embodiment is abbreviate | omitted. Further, in FIG. 13, illustration of the first support member 64 and the first preload cantilever 66 constituting the pressure sensor 60 is omitted.

  Referring to FIGS. 13 and 14, a pressure sensor 60 according to a modification of the fourth embodiment is replaced with a pressure adjustment mechanism 51 instead of the pressure adjustment mechanism 51 constituting the pressure sensor 50 of the fourth embodiment. Except having 61, it is comprised similarly to the pressure sensor 50. FIG.

The pressure adjusting mechanism 61 includes a first communication opening 62, a second communication opening 63, a first support member 64, a second support member 65, a first preload cantilever 66, and a second preload cantilever 66. A preload cantilever 67.
The first communication opening 62 is provided so as to penetrate one wall of the sensor body. The second communication opening 63 is provided so as to penetrate the other wall facing the first communication opening 62.

The first support member 64 is fixed in the cavity 10 on the bottom of the sensor body 3 located at the end. As the material of the first support member 64, the same material as that of the first support member 54 described above can be used.
The second support member 65 is disposed outside the cavity 10 and on the side opposite to the position where the first support member 64 is disposed. As the material of the second support member 65, the same material as that of the second support member 55 described above can be used.

  The base end portion 66 a of the first preload cantilever 66 is fixed to the first support member 64 or is integrated with the first support member 64. The first preload cantilever 66 has the same configuration as that of the first preload cantilever 56 described above, except that the first preload cantilever 66 has a distal end portion 66 b that closes the first communication opening 62.

  The base end portion 67 a of the second preload cantilever 67 is fixed to the second support member 65 or is integrated with the second support member 65. The second preload cantilever 67 has the same configuration as the second preload cantilever 56 described above, except that the second preload cantilever 67 has a distal end portion 67 b that closes the second communication opening 63.

  The pressure sensor 60 according to the modification of the fourth embodiment having the above-described configuration includes a first preloading cantilever 66 having a tip portion 66b that closes the first communication opening 62, and a second communication opening 63. And a second preload cantilever 67 having a leading end portion 67b for closing, the first preload cantilever 66 is used when the pressure of the outside air suddenly rises, and the second when the pressure of the outside air suddenly drops. Since the preload cantilever 67 can be used, a predetermined operation can be performed regardless of whether the pressure of the outside air fluctuates positively or negatively.

(Fifth embodiment)
FIG. 15: is sectional drawing which shows schematic structure of the pressure sensor which concerns on the 5th Embodiment of this invention. FIG. 16 is a plan view of the main part of the pressure sensor shown in FIG. 15, for explaining the positional relationship between the atmospheric pressure measurement cantilever and the second preload cantilever.
In FIG.15 and FIG.16, the same code | symbol is attached | subjected to the same component as the pressure sensor 50 of 4th Embodiment shown in FIG.
15 and 16, the illustration of the displacement measuring unit 5 shown in FIG. 1 constituting the pressure sensor 70 of the fifth embodiment is omitted.

  Referring to FIGS. 15 and 16, the pressure sensor 70 of the fifth embodiment includes a second communication opening 53 and a second communication opening 53 constituting the pressure adjustment mechanism 51 of the pressure sensor 50 of the fourth embodiment. Instead of the preload cantilever 57, the pressure sensor 50 is configured in the same manner as the pressure sensor 50 except that the pressure adjusting mechanism 71 includes a second communication opening 72 and a second preload cantilever 73.

The second communication opening 72 penetrates the lid portion 12 and is sized to accommodate the atmospheric pressure measurement cantilever 4.
The second preload cantilever 73 is configured in the same manner as the second preload cantilever 57 described above, except that the second preload cantilever 73 has a through-hole 75 that can accommodate the atmospheric pressure measurement cantilever 4. The atmospheric pressure measurement cantilever 4 is integrated with the second preload cantilever 73.

According to the pressure sensor of the fifth embodiment, the barometric pressure measuring cantilever 4 and the second preloading cantilever 73 are physically configured so that the barometric pressure measuring cantilever 4 and the second preloading cantilever 73 are provided. Since it can be formed in a lump, the manufacturing process of the pressure sensor 70 can be simplified.
In addition, the pressure sensor 70 configured as described above can obtain the same effects as the pressure sensor 50 of the fourth embodiment.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to such specific embodiments, and within the scope of the present invention described in the claims, Various modifications and changes are possible.

Specifically, for example, in the pressure sensor 1 according to the first embodiment and the pressure sensor 25 according to the modification of the first embodiment, as an example, only one communication opening 11 b is provided at the bottom of the sensor body 3. Although the case where it provided was mentioned as an example and demonstrated, the arrangement | positioning position and number of the communication openings 11b are not limited to the structure shown in FIG.2 and FIG.6. For example, a plurality of communication openings 11 b may be provided, or may be provided on the side wall of the sensor body 3.
However, when providing the some communication opening 11b, it is necessary to provide the switch 6 with respect to each communication opening 11b.

In the pressure sensors 1 and 25 described above, the cylindrical opening arranged in the cylindrical member is described as an example of the communication opening 11b. However, the communication opening 11b has a cavity 10 side. You may make it the curved shape (funnel shape) which expanded the shape of the located part.
By providing the communication opening 11b having such a shape, the pressure sensors 1 and 25 can promote the introduction of outside air into the cavity 10 when the switch 6 is opened. The time (specifically, the time required until a minute pressure fluctuation can be detected again after a rapid pressure fluctuation) can be further shortened.

 When the communication opening 11b is provided at the bottom of the sensor body 3 as in the pressure sensors 1 and 25 described above, the communication opening 11b is disposed closer to the base end 4a in the longitudinal direction of the atmospheric pressure measurement cantilever 4. Is preferable from the viewpoint of preventing a transient response of the pressure sensors 1 and 25.

Furthermore, in the first embodiment, a solenoid valve is illustrated as an example of the switch 6, but the switch 6 is not limited to a valve that opens and closes electromagnetically.
As the switch 6, for example, a mechanical valve that expands and contracts according to a differential pressure between the external pressure Pout and the internal pressure Pin and mechanically switches between opening and closing may be used. In this case, since the pressure sensors 1 and 25 can reset the output immediately after the sudden pressure fluctuation without providing the opening / closing control unit 7, the pressure sensors 1 and 25 can be reduced in size (simplified configuration). Effects such as power saving and manufacturing cost reduction can be expected.

Also, first preload cantilevers 56 and 66 and second preload cantilevers 57 and 67 constituting the pressure sensors 50 and 70 of the fourth and fifth embodiments are shown in FIGS. The structure shown may be applied.
17 to 18 are sectional views showing other examples of the preload cantilever. 17 to 18, the same components as those of the pressure sensor 50 shown in FIG. In FIG. 18, the same components as those of the structure shown in FIG.

As shown in FIG. 17 (A), a preload cantilever 81 that is integrated with the second support member 55 and includes a piezoelectric thin film 83 on one surface of a cantilever main body 82 obtained by processing an SOI substrate is prepared. Thereafter, as shown in FIG. 17B, the second support member 55 is attached to the lid 12 so that the preload cantilever 81 faces the second communication opening 53, and the preload cantilever 81 is straightened. The leading end portion 81a of the preload cantilever 81 may be supported by the support member 85 that is supported in this manner.
Further, by adjusting the thickness of the support member 85 with respect to the second support member 55, the pressure when the second communication opening 53 is opened and closed can be adjusted.

As shown in FIG. 18 (A), a preload cantilever 90 integrated with the second support member 55 and made of a cantilever main body 82 (at this stage, there is no preload and the cantilever main body 82 shown in FIG. 17). 18), and then, as shown in FIG. 18B, cover the second support member 55 so that the preload cantilever 90 faces the second communication opening 53. The tip 90a of the preload cantilever 90 is supported by a support member 91 (a member thicker than the second support member 55) that is attached to the portion 12 and supports the preload cantilever 90 so as to warp upward. Also good.
With such a configuration, it is possible to give a preload.
Further, by adjusting the thickness of the support member 91 with respect to the second support member 55, the pressure when the second communication opening 53 is opened and closed can be adjusted.

As shown in FIG. 19A, the cantilever main body 96, a frame 97 that is integral with the cantilever main body 96, and sandwiches the cantilever main body 96 in a separated state, and is disposed on both sides of the cantilever main body 96. A preload cantilever 95 having a spring portion 98 connecting 96 and the frame body 97 and a protruding tip portion 99 is prepared, and as shown in FIG. The second support member 55 may be disposed on the lid 12 so that the leading end 99 closes the communication opening 101 formed in the extending support member 102.
With such a structure, it is possible to adjust the pressure when the second communication opening 53 is opened and closed by the spring portion 98.
In addition, you may comprise the pressure sensors 50, 60, and 70 combining the structure shown in FIGS.

  The present invention can be applied to a pressure sensor that detects minute pressure fluctuations based on a pressure difference.

  DESCRIPTION OF SYMBOLS 1, 25, 30, 40, 50, 60, 70 ... Pressure sensor, 2 ... SOI substrate, 2a ... Silicon support layer, 2b ... Oxide layer, 2c ... Silicon active layer, 3 ... Sensor main body, 3-1 ... 1st 3-2 ... 2nd part, 4 ... Barometric pressure measurement cantilever, 4a, 56a, 57a, 66a, 67a ... Base end part, 4b, 56b, 57b, 66b, 67b, 81a, 90a, 99 ... Tip , 5 ... Displacement measuring unit, 6 ... Switch, 7, 27 ... Open / close control unit, 8, 31, 41, 51, 61, 71 ... Pressure adjusting mechanism, 10 ... Cavity, 11b ... Communication opening, 12 ... Lid , 13, 33 ... gap, 15 ... through hole, 20 ... piezoresistor, 21 ... wiring part, 22 ... detection circuit, 26 ... absolute pressure sensor, 32, 43 ... pressure cantilever, 35, 75 ... penetrating part, 52 62 ... 1st communication opening, 53, 6 72, second communication opening, 54, 64 ... first support member, 55, 65 ... second support member, 56, 66 ... first preload cantilever, 57, 67, 73 ... second preload. For cantilever, 81, 90, 95 ... cantilever for preloading, 82, 96 ... main body of cantilever, 83 ... piezoelectric thin film, 85, 91, 102 ... support member, 97 ... frame, 98 ... spring part, 101 ... communication opening, G ... area, W1, W2 ... width

Claims (18)

A pressure sensor for detecting pressure fluctuations,
A sensor body having a cavity;
A cantilever for pressure measurement that is disposed so as to face the cavity, is supported in a cantilever manner, and is bent and deformed by a pressure difference between the inside of the cavity and the outside of the cavity;
A displacement measuring unit for measuring a displacement according to the bending deformation of the barometric pressure measuring cantilever;
A pressure adjusting mechanism for adjusting the pressure inside the cavity by circulating air inside and outside the cavity;
A pressure sensor comprising:   The pressure sensor according to claim 1, wherein the pressure adjusting unit includes a communication opening that penetrates the sensor body, and a switch that opens and closes the communication opening.   The pressure adjusting unit includes a pressure adjusting cantilever disposed around the barometric pressure measurement cantilever, supported in a cantilever manner, and flexibly deformed by a pressure difference between the inside of the cavity and the outside of the cavity. The pressure sensor according to claim 1. The pressure adjusting unit includes a pressure adjusting cantilever that bends and deforms due to a pressure difference between the inside of the cavity and the outside of the cavity,
The pressure sensor according to claim 1, wherein the pressure adjusting cantilever is disposed so as to face the atmospheric pressure measuring cantilever through the cavity. The pressure adjusting unit includes first and second communication openings penetrating a lid portion disposed on the sensor body,
A first cantilever for preload that is supported in a cantilever shape and is bent and deformed by a pressure difference between the inside of the cavity and the outside of the cavity, thereby opening and closing the first communication opening;
A second preload that is disposed outside the cavity and is supported in a cantilevered manner and opens and closes the second communication opening by being deformed by a pressure difference between the inside of the cavity and the outside of the cavity. For cantilevers,
Have
The first preload cantilever opens the first communication opening when a pressure outside the cavity becomes higher than a pressure inside the cavity and a pressure difference between the inside and outside of the cavity exceeds a predetermined value. ,
The second preload cantilever opens the second communication opening when the pressure inside the cavity becomes higher than the pressure outside the cavity and the pressure difference inside and outside the cavity exceeds a predetermined value. The pressure sensor according to claim 1. The first preload cantilever has a tip portion that closes the first communication opening;
The pressure sensor according to claim 5, wherein the second preloading cantilever has a tip portion that closes the second communication opening.   The pressure sensor according to claim 5 or 6, wherein the pressure measuring cantilever is disposed inside the second preloading cantilever.   The pressure sensor according to claim 2, wherein the pressure adjusting unit includes an opening / closing control unit that controls an opening / closing operation of the switch.   The pressure sensor according to claim 8, wherein the opening / closing control unit outputs a control signal for opening the switch when the output of the displacement measuring unit exceeds a predetermined range. The opening / closing control unit includes a detector that detects a pressure outside the cavity,
9. The opening / closing controller outputs a control signal for opening the switch when the detector detects that the pressure outside the cavity exceeds a predetermined value. The pressure sensor described in 1.   11. The switch control unit according to claim 8, wherein the switch control unit outputs a control signal for closing the switch after a predetermined time has elapsed since the output of the control signal for opening the switch. The pressure sensor according to any one of the above.   The switch control unit outputs a control signal for performing the closing operation of the switch based on an output signal of the displacement measuring unit after outputting a control signal for performing the opening operation of the switch. The pressure sensor according to any one of claims 8 to 10.   The pressure sensor according to any one of claims 1 to 12, wherein the displacement measuring unit includes a piezoresistor provided at a base end portion of the atmospheric pressure measuring cantilever.   The pressure sensor according to any one of claims 1 to 12, wherein the displacement measuring unit includes a piezoelectric thin film provided at a base end of the barometric pressure measuring cantilever.   The pressure sensor according to claim 3 or 4, wherein an outer shape of the pressure adjusting cantilever is larger than an outer shape of the atmospheric pressure measuring cantilever.   16. The pressure sensor according to claim 3, wherein a piezoelectric thin film is provided on the pressure adjusting cantilever.   8. The pressure sensor according to claim 5, wherein an outer shape of the first and second preloading cantilevers is larger than an outer shape of the atmospheric pressure measurement cantilever. 9.   18. The pressure sensor according to claim 5, wherein each of the first and second preloading cantilevers includes a piezoelectric thin film.

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