JP2012083338A - Vibrator, and oscillator and gas detector including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase resonance frequency variation responding to deformation of a beam member.SOLUTION: A gas sensor 1 includes first and second beam members 2, 3 which are coupled with each other and driven by vibration. The first beam member 2 has deformable gas sensitive films 4. The first beam member 2 is deformed with an aspect different from that of the second beam member 3, by deformation of the gas sensitive films 4.

Description

  The present invention relates to a vibrator including a beam member, and an oscillator and a gas detection device including the vibrator.

  Conventionally, an apparatus including a vibrator having a beam member is known. For example, Patent Document 1 discloses a gas sensor including a vibrator having a beam member supported in a cantilever manner. This gas sensor detects the gas by utilizing the bending of the beam member as the gas is adsorbed on the surface of the beam member. Specifically, the gas sensor vibrates the vibrator at a resonance frequency in advance, and detects the gas adsorbed on the beam member by a change in the resonance frequency caused by the bending of the beam member.

  Thus, a vibrator that utilizes a change in resonance frequency caused by deformation of a beam member is known.

Japanese Patent Laid-Open No. 2000-214072

  However, the conventional configuration has a problem that the amount of change in the resonance frequency with respect to the deformation of the beam member is small. For example, if the beam member is passively deformed and a change in the resonance frequency due to the deformation is detected like a gas detection device, if the amount of change in the resonance frequency relative to the deformation of the beam member is small, Detection capability will be lowered.

  It is also conceivable to use such a vibrator as an oscillator that can adjust the resonance frequency of the vibrator to a desired value by actively deforming the beam member. If the amount of change in frequency is small, the amount of deformation of the beam member required to change the resonance frequency of the vibrator becomes large.

  The technique disclosed herein has been made in view of such a point, and an object thereof is to increase the amount of change in the resonance frequency with respect to the deformation of the beam member.

The technology disclosed herein is directed to a vibrator, and the vibrator includes first and second beam members that are coupled to each other and driven to vibrate, and at least the first beam member has a shape change. Possible deformable portions are provided, the base end portions of the first and second beam members are fixed ends, and the tip portions of the first and second beam members are connected to each other and are free ends. The first and second beam members are deformed in different manners so that the distance between the first and second beam members is increased by the deformation of the deformation portion.

  According to the above configuration, the first beam member that changes due to the deformation of the deforming portion is connected to the second beam member and is different from the second beam member so that the interval between the first beam member and the second beam member is widened. Due to the deformation, the amount of change in the bending rigidity (in other words, the bending elastic modulus) of the first and second beam members as a whole with respect to the deformation of the first beam member is larger than that when the first beam member is deformed alone. And get bigger. As a result, the amount of change in the resonance frequency with respect to the deformation of the beam member increases.

  The technique disclosed herein is directed to an oscillator, and the oscillator includes the vibrator and a driving unit that drives the vibrator to vibrate, and the deforming unit responds to a signal from the outside. It shall be comprised so that it may deform | transform.

  According to said structure, the said deformation | transformation part is actively deformed according to the signal from the outside, and the said 1st beam member deform | transforms in connection with it. When the first beam member is deformed, the second beam member connected to the first beam member is also deformed. Thus, the resonance frequency of the vibrator changes as the first and second beam members are deformed. That is, this oscillator can change the resonance frequency of the vibrator. Here, since the first beam member is connected to the second beam member and deforms in a different manner from the second beam member, the bending rigidity of the first and second beam members as a whole against the deformation of the first beam member. (In other words, the amount of change in the flexural modulus) is greater than when the first beam member is deformed alone. As a result, the resonance frequency can be greatly changed by only slightly deforming the beam member.

  Further, the technology disclosed herein is directed to a gas detection device, and the gas detection device includes a vibrator and a drive unit that drives the vibrator to vibrate, and the deformation unit has a gas attached thereto. It is assumed that the gas sensitive part is deformed by the above.

  According to said structure, the said deformation | transformation part is a gas sensitive part, and deform | transforms passively, when gas adheres. The first beam member is deformed along with the deformation of the deforming portion. When the first beam member is deformed, the second beam member connected to the first beam member is also deformed. Thus, the resonance frequency of the vibrator changes as the first and second beam members are deformed. Thus, the gas detection device can detect gas based on the change in the resonance frequency of the vibrator. Here, since the first beam member is connected to the second beam member and deforms in a different manner from the second beam member, the bending rigidity of the first and second beam members as a whole against the deformation of the first beam member. (In other words, the amount of change in the flexural modulus) is greater than when the first beam member is deformed alone. As a result, even if a little gas is attached to the deformed portion, the resonance frequency changes greatly.

  According to the vibrator, the amount of change in the resonance frequency with respect to the deformation of the beam member can be increased.

  Further, according to the oscillator, the resonance frequency can be greatly changed by slightly deforming the beam member, and thus the adjustment range of the resonance frequency can be increased.

  Further, according to the gas detection device, the resonance frequency can be greatly changed even if a little gas is attached to the deformed portion, and the detection capability can be improved. Further, since it can be detected with a simple circuit, the cost can be reduced.

It is a perspective view of the gas sensor before a deformation | transformation which concerns on Embodiment 1. FIG. It is a perspective view of the gas sensor after a deformation | transformation. It is a perspective view of the gas sensor which performs the vertical vibration of a primary mode. It is a perspective view of the gas sensor which performs the vertical vibration of a secondary mode. It is a perspective view of the gas sensor which performs the vertical vibration of a tertiary mode. It is a top view of the gas sensor used for simulation. It is an example of the change characteristic of the resonant frequency of the vertical vibration of a secondary mode with respect to the deformation amount of a gas sensor. It is a perspective view of the gas sensor which performs the horizontal vibration of a primary mode. It is a perspective view of the gas sensor which performs the horizontal vibration of a secondary mode. It is a perspective view of the gas sensor which performs the horizontal vibration of a tertiary mode. It is an example of the change characteristic of the resonant frequency of a horizontal vibration with respect to the deformation amount of a gas sensor. 6 is a plan view of a gas sensor according to Modification Example 1. FIG. It is a top view of the gas sensor which concerns on the modification 2. It is a top view of the gas sensor which concerns on the modification 3. It is a perspective view of the gas sensor before a deformation | transformation which concerns on the modification 4. FIG. It is a top view of the gas sensor after the deformation | transformation which concerns on the modification 4. It is a perspective view of the gas sensor before a deformation | transformation which performs the vertical vibration of a primary mode. It is a perspective view of the gas sensor before a deformation | transformation which performs the vertical vibration of a secondary mode. It is a perspective view of the gas sensor before a deformation | transformation which performs the vertical vibration of a tertiary mode. It is a perspective view of the gas sensor after a deformation | transformation which performs the vertical vibration of a primary mode. It is a perspective view of the gas sensor after a deformation | transformation which performs the vertical vibration of a secondary mode. It is a top view of the gas sensor after a deformation | transformation which performs a horizontal vibration. It is a top view of the gas sensor before a deformation | transformation which performs a horizontal vibration. It is a perspective view of the gas sensor before a deformation | transformation which concerns on the modification 5. FIG. 10 is a perspective view of a gas sensor after deformation according to Modification Example 5. FIG. It is a top view of the gas sensor used for simulation. It is an example of the change characteristic of the resonant frequency of the 3rd-order mode vertical vibration with respect to the deformation amount of a gas sensor. It is a block diagram of a gas detection apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment 1 of the Invention
1 is a perspective view of a gas sensor before deformation according to Embodiment 1, and FIG. 2 is a perspective view of the gas sensor after deformation.

  The gas sensor 1 includes a first beam member 2 and a second beam member 3. The gas sensor 1 is manufactured by a known MEMS process (semiconductor process). The first and second beam members 2 and 3 are formed in a plate shape. The first and second beam members 2 and 3 have a line-symmetric shape. This gas sensor 1 constitutes a vibrator.

  Specifically, the first beam member 2 has a beam body 20 made of silicon. The beam body 20 includes a first extending portion 21 that extends linearly, a folded portion 22 that bends at a right angle from the tip of the first extending portion 21, and a first extending portion that extends in parallel with the first extending portion 21 from the folded portion 22. It has the 2nd extending | stretching part 23 extended | stretched linearly to the base end side of the part 21, and the connection part 24 bent at right angle from the front-end | tip part of the 2nd extending | stretching part 23. FIG. These 1st extending | stretching part 21, the folding | returning part 22, the 2nd extending | stretching part 23, and the connection part 24 are located on the same plane so that a plate | board thickness direction may face the same direction.

  On the other hand, the second beam member 3 has a beam body 30 made of silicon. The beam main body 30 includes a first extending portion 31 that extends linearly, a folded portion 32 that bends at a right angle from the tip of the first extending portion 31, and a first extending portion that extends from the folded portion 32 in parallel with the first extending portion 31. It has the 2nd extending | stretching part 33 extended | stretched linearly to the base end side of the part 31, and the connection part 34 bent at right angle from the front-end | tip part of the 2nd extending | stretching part 33. FIG. The first extending portion 31, the turned-up portion 32, the second extending portion 33, and the connecting portion 34 are located on the same plane so that the plate thickness direction faces the same direction.

  And the connection part 24 of the 1st beam member 2 and the connection part 34 of the 2nd beam member 3 are mutually connected. At this time, the first beam member 2 and the second beam member 3 are located on the same plane so that the plate thickness directions are in the same direction. The first and second extending portions 21 and 23 of the first beam member 2 and the first and second extending portions 31 and 33 of the second beam member 3 are arranged in parallel to each other. Thus, the first and second beam members 2 and 3 are formed in an M shape in plan view as a whole. The base end portion of the first beam member 2, that is, the base end portion of the first extension portion 21, and the base end portion of the second beam member 3, ie, the base end portion of the first extension portion 31, are supported by the support portion 11. It is connected to. Thus, in the first and second beam members 2 and 3, the base ends of the first extending portions 21 and 31 are fixed ends, while the distal ends of the first extending portions 21 and 31 (that is, the folded portions 22 and 32). ) And the distal end portions of the second extending portions 23 and 33 (that is, the connecting portions 24 and 34) constitute a cantilever.

  In this specification, for convenience of explanation, the thickness direction of the first and second beam members 2 and 3 is the Z direction, the first and second extending portions 21 and 23 of the first beam member 2, and the second beam member. The first and second extending portions 31 and 33 of the first beam member 2 in the Y direction, the first and second extending portions 21 and 23 of the first beam member 2, and the first and second extending portions 31 of the second beam member 3. , 33 is defined as the X direction.

  The first beam member 2 further includes gas sensitive films 4 and 4 made of palladium. The gas sensitive film 4 is laminated on one surface 2 a of the beam body 20. Here, the surface of the beam main body 20 is a surface whose normal direction is directed to the plate thickness direction and is a surface directed to the Z direction. Specifically, the gas sensitive film 4 is provided on the surfaces 2 a of the first and second extending portions 21 and 23 of the first beam member 2. Palladium is a material that expands by adsorbing hydrogen. The gas sensitive film 4 constitutes a gas sensitive part, that is, a deformed part. The second beam member 3 is not provided with the gas sensitive film 4.

  In the gas sensor 1 configured as described above, when hydrogen is adsorbed to the gas sensitive film 4 of the first beam member 2, the gas sensitive film 4 is expanded and deformed. As a result, in the first beam member 2, the gas sensitive films 4 and 4 extend in the longitudinal direction, and as shown in FIG. Curve with 4 on the outside. Here, since the base end part of the 1st extending | stretching part 21 is a fixed end, the folding | turning part 22 of the 1st extending | stretching part 21 is displaced to a Z direction with a curve. On the other hand, since the gas sensitive film 4 is not provided, the second beam member 3 maintains a flat shape. As a result, in the gas sensor 1, the folded portion 22 of the first beam member 2 is separated from the folded portion 32 of the second beam member 3, that is, the interval between the first beam member 2 and the second beam member 3 is widened. It deforms as follows.

  By deforming in this way, the resonance frequency of the gas sensor 1 changes. Hereinafter, the resonance in the case where the gas sensor 1 is vibrated (hereinafter also referred to as “vertical vibration”) in the bending deformation direction of the first and second beam members 2 and 3 (that is, the plate thickness direction and the Z direction). A change in frequency will be described.

  When the gas sensor 1 is vertically vibrated, the gas sensor 1 resonates in various vibration modes. Each vibration mode is referred to as a primary mode, a secondary mode, a tertiary mode,. 3 is a perspective view of the gas sensor 1 that performs vertical vibration in the primary mode, FIG. 4 is a perspective view of the gas sensor 1 that performs vertical vibration in the secondary mode, and FIG. 5 performs vertical vibration in the tertiary mode. A perspective view of gas sensor 1 is shown.

  In the primary mode vertical vibration, as shown in FIG. 3, the gas sensor 1 includes the first beam member 2 and the first beam member 2, and the folded portion 22 of the first beam member 2 and the second beam member. The third folded portion 32 vibrates in the Z direction so as to become a vibration antinode. That is, the first beam member 2 and the second beam member 3 vibrate in the Z direction in the same phase.

  In the vertical vibration in the secondary mode, as shown in FIG. 4, the gas sensor 1 has the folded portion 22 of the first beam member 2 and the folded portion 32 of the second beam member 3 substantially serving as vibration nodes. The connecting portion 24 of the beam member 2 and the connecting portion 34 of the second beam member 3 vibrate in the Z direction so as to become antinodes of vibration. That is, the second extending portion 23 of the first beam member 2 and the second extending portion 33 of the second beam member 3 vibrate like a single beam as a whole.

  In the tertiary mode vertical vibration, the gas sensor 1 vibrates in the Z direction with the first beam member 2 and the second beam member 3 using the folded portions 22 and 32 as antinodes as shown in FIG. . That is, the first and second extending portions 21 and 23 of the first beam member 2 vibrate like a single beam as a whole, and are in phase opposite to the first and second extending portions of the second beam member 3. 31 and 33 vibrate like one beam as a whole.

  When the gas sensor 1 is deformed as described above, the resonance frequency of the gas sensor 1 changes significantly, particularly in the vertical vibration of the secondary mode. Specifically, when the gas sensor 1 is deformed as described above, the folded portion 22 of the first beam member 2 and the folded portion 32 of the second beam member 3 are separated from each other. The next moment increases and the bending rigidity (in other words, the flexural modulus) increases. As described above, in the vertical vibration of the secondary mode, the bending rigidity of the vibration-side portion of the second extending portions 23 and 33 that vibrate like a single beam increases, so the resonance frequency of the gas sensor 1 is It changes significantly in the direction of increasing. Therefore, the amount of change in the resonance frequency of the gas sensor 1 before and after deformation increases. As described above, when the first beam member 2 connected to the second beam member 3 is deformed in a mode different from that of the second beam member 3, the resonance frequency of the gas sensor 1 may be changed before and after the deformation depending on the vibration mode and the vibration mode. It changes a lot.

  Even in vibration modes other than the secondary mode, there may be a vibration mode in which the resonance frequency of the gas sensor 1 changes significantly before and after deformation.

  Below, the simulation result of the change characteristic of the resonant frequency of the secondary mode vertical vibration with respect to the deformation when the gas sensor 1 is bent and deformed will be described. FIG. 6 shows the dimensions of the gas sensor used for the simulation, and FIG. 7 shows the simulation result of the change characteristic of the resonance frequency of the secondary mode vertical vibration with respect to the deformation amount of the gas sensor. The gas sensor used for this simulation is only an example, and the present invention is not limited to this.

  In the gas sensor 1, the first beam member 2 and the second beam member 3 are made of silicon having a thickness of 10 μm, and the surface 2 a of the first extending portion 21 and the second extending portion 23 of the first beam member 2 Palladium having a thickness of 100 nm is laminated as the gas sensitive film 4. On the other hand, silver 35 having a thickness of 100 nm is laminated on the surface 3 a of the first extending portion 31 and the second extending portion 33 of the second beam member 3 in order to balance the first beam member 2.

The analysis code used for the simulation is ANSYS 11.0 Product Launcher, and the element type used is solid185. The mesh size was a hexahedron with a side of 10 μm. As material properties, the Young's modulus of silicon is 130.8 GPa, the density is 2.33 g / cm ³ , the Poisson ratio is 0.26, the Young's modulus of palladium and silver is 110 GPa, the density is 12.02 g / cm ³ , Poisson. The ratio was 0.3. In the simulation, static analysis was performed with hydrogen storage expansion of palladium as temperature expansion. The resonance frequency of the vertical vibration of the secondary mode of the gas sensor 1 was obtained while changing the expansion of palladium from 0 to 0.5% and updating the shape of the gas sensor 1. Further, in the gas sensor 1, the base end portion of the first extending portion 21 of the first beam member 2 and the base end portion of the first extending portion 31 of the second beam member 3 are fixed ends that restrict all degrees of freedom.

  As a comparative example, a simple beam composed of only the first extending portion 21 of the first beam member 2 (hereinafter referred to as “simple beam”) was also simulated. The first extending portion 21 is made of silicon having a thickness of 10 μm, and palladium having a thickness of 100 nm is laminated on the surface thereof. Other dimensions and simulation conditions are the same as those of the gas sensor 1. While changing the amount of bending deformation of the simple beam by changing the expansion of palladium from 0 to 0.5%, the resonance frequency of the primary mode vertical vibration of the simple beam was obtained.

  7 shows that the resonance frequency of the secondary mode vertical vibration of the gas sensor 1 increases as the amount of bending deformation increases. The deformation amount is the deformation amount in the Z direction of the folded portion 22 of the first beam member 2 shown in FIG. On the other hand, in the case of a simple beam, the resonance frequency hardly changes even if the amount of bending deformation increases. That is, it can be seen that the gas sensor 1 configured in this way has a large amount of change in the resonance frequency of the secondary mode vertical vibration with respect to the bending deformation.

  Subsequently, the gas sensor 1 is vibrated in the direction perpendicular to the direction of bending deformation of the first and second beam members 2 and 3 and the extending direction of the first and second beam members 2 and 3 (that is, the X direction) (hereinafter referred to as the X direction). The change of the resonance frequency in the case of “also referred to as“ horizontal vibration ”) will be described.

  When the gas sensor 1 is vibrated horizontally, the gas sensor 1 vibrates in various vibration modes. Each vibration mode is referred to as a primary mode, a secondary mode, a tertiary mode,. 8 is a perspective view of the gas sensor 1 that performs horizontal vibration in the primary mode, FIG. 9 is a perspective view of the gas sensor 1 that performs horizontal vibration in the secondary mode, and FIG. 10 performs horizontal vibration in the tertiary mode. A perspective view of gas sensor 1 is shown.

  In the primary mode horizontal vibration, as shown in FIG. 8, the gas sensor 1 includes the first beam member 2 and the first beam member 2, and the folded portion 22 of the first beam member 2 and the second beam member. The third folded portion 32 vibrates in the X direction so as to become an antinode of vibration.

  In the secondary mode horizontal vibration, as shown in FIG. 9, in the gas sensor 1, the folded portion 22 of the first beam member 2 and the folded portion 32 of the second beam member 3 respectively become antinodes of vibration, and the connecting portion 24. , 34 vibrate in the X direction so that they become vibration nodes. That is, the folded part 22 and the folded part 32 vibrate in the X direction with opposite phases.

  As shown in FIG. 10, in the third mode horizontal vibration, the gas sensor 1 includes three portions of the folded portion 22 of the first beam member 2, the folded portion 32 of the second beam member 3, and the connecting portions 24 and 34. It vibrates in the X direction so that it becomes an antinode of vibration. That is, the folded portion 22 and the folded portion 32 are in the same phase, and the connecting portions 24 and 34 are oscillating in the X direction in the opposite phase.

  When the gas sensor 1 is deformed as described above, the resonance frequency of the gas sensor 1 changes significantly, particularly in the third-order horizontal vibration. Specifically, in this vibration, the bending rigidity of the U-shaped portion formed by the second extending portion 23 of the first beam member 2, the second extending portion 33 of the second beam member, and the connecting portions 24 and 34 of both is The resonance frequency is greatly affected. Then, when the gas sensor 1 is deformed as described above, the distal end portion of the second extending portion 23 and the distal end portion of the second extending portion 33 that are the proximal end side of the U-shaped portion are deformed so as to be separated in the Z direction. Therefore, the bending rigidity changes greatly. As a result, the resonance frequency also changes greatly. As described above, when the first beam member 2 connected to the second beam member 3 is deformed in a mode different from that of the second beam member 3, the resonance frequency of the gas sensor 1 may be changed before and after the deformation depending on the vibration mode and the vibration mode. It changes a lot.

  Further, in the case of horizontal vibration, air damping is reduced, so that the Q value can be increased compared to vertical vibration.

  Even in vibration modes other than the tertiary mode, there may be a vibration mode in which the resonance frequency of the gas sensor 1 changes significantly before and after deformation.

  Below, the simulation result of the change characteristic of the resonant frequency of the horizontal vibration of the third mode with respect to the deformation when the gas sensor 1 is bent and deformed will be described. FIG. 11 shows the simulation result of the change characteristic of the resonance frequency of the horizontal vibration with respect to the deformation amount of the gas sensor.

  The gas sensor 1 used for the simulation is the same as that for the vertical vibration simulation, and only the vibration direction is different.

  From the simulation result of FIG. 11, it can be seen that the resonance frequency of the horizontal vibration of the third-order mode of the gas sensor 1 increases as the amount of bending deformation increases. The deformation amount is the deformation amount in the Z direction of the folded portion 22 of the first beam member 2 shown in FIG.

-Modification 1-
Next, the gas sensor 201 according to the first modification will be described. FIG. 12 shows a plan view of the gas sensor 201.

  In the gas sensor 201, the gas sensitive film 4 is also provided on the second beam member 3. Specifically, gas sensitive films 4 and 4 are laminated on the surface 3 b of the first extending portion 31 and the second extending portion 33 of the second beam member 3, respectively. That is, the gas sensitive films 4 and 4 are provided on the surface of the second beam member 3 on the side opposite to the first beam member 2.

  With this configuration, when hydrogen is adsorbed to the gas sensitive films 4, 4,..., The first beam member 2 is curved with the first and second extending portions 21 and 23 on the inside and the gas sensitive films 4 and 4 on the outside. On the other hand, the second beam member 3 bends the first and second extending portions 31 and 33 inward and the gas sensitive films 4 and 4 outward. Here, the first beam member 2 and the second beam member 3 are provided with gas sensitive films 4, 4,... On different surfaces 2a, 3b, respectively. It curves in the opposite direction. As a result, the gas sensor 201 is configured so that the folded portion 22 of the first beam member 2 and the folded portion 32 of the second beam member 3 are separated from each other, that is, the distance between the first beam member 2 and the second beam member 3. Deforms to spread. As described above, by providing the gas sensitive films 4, 4,... On the first beam member 2 and the second beam member 3, the gas sensor 1 in which the gas sensitive films 4, 4 are provided only on the first beam member 2. As a result, the amount of bending deformation can be increased, and as a result, the amount of change in resonance frequency with respect to the concentration of hydrogen gas can be increased.

  In addition, any one of the gas sensitive film | membrane 4 of the 1st extending | stretching part 21 of the 1st beam member 2 and the gas sensitive film | membrane 4 of the 2nd extending | stretching part 23, and the gas sensitive film | membrane of the 1st extending | stretching part 31 of the 2nd beam member 3 are used. 4 and the gas sensitive film 4 of the second extending portion 33 may be omitted. Even in such a configuration, when hydrogen is adsorbed on the gas sensitive films 4 and 4, the gas sensor 201 is configured so that the folded portion 22 of the first beam member 2 and the folded portion 32 of the second beam member 3 are separated from each other. That is, the first beam member 2 and the second beam member 3 are deformed so that the distance between them increases.

-Modification 2-
Next, the gas sensor 301 according to Modification 2 will be described. FIG. 13 shows a perspective view of the gas sensor 301.

  In the gas sensor 301, the first beam member 302 and the second beam member 303 are connected in a state where the surface 302b and the surface 303b face each other. The connecting portion 324 of the first beam member 302 bends from the tip of the second extending portion 323 to the surface 302b side in the plate thickness direction, while the connecting portion 334 of the second beam member 303 is the second extending portion 333. Bending from the tip to the surface 303b side in the plate thickness direction. And the connection part 324 of the 1st beam member 302 and the connection part 334 of the 2nd beam member 303 are mutually connected. The gas sensitive films 4 and 4 are laminated on the surface 302 b of the first extending portion 321 and the second extending portion 323 of the first beam member 302. That is, the gas sensitive films 4 and 4 are provided on the surface 302 b of the first beam member 302 facing the second beam member 303.

  In such a configuration, when hydrogen is adsorbed on the gas sensitive films 4 and 4, the gas sensor 301 causes the folded portion 322 of the first beam member 302 to be separated from the folded portion 332 of the second beam member 303, that is, the first sensor. It deform | transforms so that the space | interval of the beam member 302 and the 2nd beam member 303 may spread.

  The gas sensor 301 configured as described above is vibrated in the thickness direction of the first and second beam members 302 and 303, that is, vertically vibrated. The gas sensor 301 resonates in various vibration modes. In the primary mode vertical vibration, the gas sensor 301 uses the folded portion 322 of the first beam member 302 and the folded portion 332 of the second beam member 303 as vibration antinodes, and the first and second beam members 302 and 303 as a whole. Vibrates like a single beam. In the vertical vibration in the secondary mode, the gas sensor 301 uses the folded portion 322 of the first beam member 302 and the folded portion 332 of the second beam member 303 as nodes of substantial vibration, and the first and second beam members 302 and 303. The connecting portions 324 and 334 are vibrated as vibration antinodes. In the vertical vibration of the tertiary mode, the gas sensor 301 vibrates using the first beam member 302 as a vibration node at the base end portion of the first extending portion 321 and the connecting portion 324 and the folded portion 322 as a vibration antinode. In the opposite phase, the second beam member 303 vibrates with the proximal end portion of the first extending portion 331 and the connecting portion 334 as vibration nodes and the folded portion 332 as vibration antinodes. And if the gas sensor 301 deform | transforms as mentioned above, the resonant frequency of the vertical vibration of a secondary mode will change a lot.

  The gas sensitive film 4 may be further provided on the surface 303b of the second beam member 303.

-Modification 3-
Next, the gas sensor 401 according to Modification 3 will be described. FIG. 14 is a perspective view of the gas sensor 401.

  The gas sensor 401 includes a first beam member 402 and a second beam member 403. The first beam member 402 includes a first extending portion 421, a second extending portion 423, and a third extending portion 425 that extend in parallel to each other. The first extending portion 421, the second extending portion 423, and the third extending portion 425 are arranged in this order. The 1st extending | stretching part 421 and the 3rd extending | stretching part 425 are the same length, and the 2nd extending | stretching part 423 is short compared with them. The first to third extending portions 421, 423, and 425 are formed on the same plane with the plate thickness directions facing the same direction. The leading end portion of the first extending portion 421 and the leading end portion of the third extending portion 425 are connected by a turn-back portion 422. And the base end part of the 2nd extending | stretching part 423 is also connected with the folding | returning part 422. FIG. A connecting portion 424 is provided at the tip of the second extending portion 423. The connecting portion 424 is provided to be bent from the tip end portion of the second extending portion 423 to the surface 402b side in the plate thickness direction. The second beam member 403 has the same shape as the first beam member 402. The first beam member 402 and the second beam member 403 are connected to each other with the connecting portion 424 and the connecting portion 434 in a state where the surface 402b and the surface 403b face each other. Further, the base end portions of the first and third extending portions 421 and 425 of the first beam member 402 and the base end portions of the first and third extending portions 431 and 435 of the second beam member 403 are the support portion 11. To the fixed end. Gas sensitive films 4, 4, 4 are laminated on the surface 402 b of the first to third extending portions 421, 423, 425 of the first beam member 402.

  The thus configured gas sensor 401 is vibrated in the thickness direction of the first and second beam members 402 and 403, that is, vertically vibrated. The gas sensor 401 resonates in various vibration modes. In the primary mode vertical vibration, the gas sensor 401 uses the folded portion 422 of the first beam member 402 and the folded portion 432 of the second beam member 403 as vibration antinodes, and the first and second beam members 402 and 403 as a whole. Vibrates like a single beam. In the vertical vibration in the secondary mode, the gas sensor 401 uses the folded portion 422 of the first beam member 402 and the folded portion 432 of the second beam member 403 as nodes of substantial vibration, and the first and second beam members 402 and 403. The connecting portions 424 and 434 are vibrated as vibration antinodes. In the vertical vibration of the tertiary mode, the gas sensor 401 uses the first beam member 402 as the vibration end at the base end portions of the first and third extending portions 421 and 425 and the connection portion 424, and the folded portion 422 as the antinode of vibration. The second beam member 403 vibrates with the base end portions of the first and third extending portions 431 and 435 and the connecting portion 434 as vibration nodes and the folded portion 432 as an antinode of vibration.

-Modification 4-
Next, a gas sensor 501 according to Modification 4 will be described. 15 shows a perspective view of the gas sensor 501 before deformation, and FIG. 16 shows a perspective view of the gas sensor 501 after deformation.

  The gas sensor 501 has a first beam member 502 and a second beam member 503. The first beam member 502 includes a plate-like beam body 521 that extends linearly. Similarly to the first beam member 502, the second beam member 503 is also composed of a plate-like beam body 531 that extends linearly. The first beam member 502 and the second beam member 503 are arranged on the same plane so as to constitute one flat plate. Further, the first beam member 502 and the second beam member 503 are disposed in parallel to each other. The proximal end portions of the first and second beam members 502 and 503 are connected to a support portion (not shown) to become a fixed end, while the distal end portions of the first and second beam members 502 and 503 are connected to the connection portion 524. And are connected to each other through a free end. The gas sensitive film 4 is laminated on the surface 502 a of the beam main body 521.

  In the gas sensor 501 configured as described above, when hydrogen is adsorbed to the gas sensitive film 4 of the first beam member 502, the gas sensitive film 4 is expanded and deformed. As a result, as shown in FIG. 16, the first beam member 502 is curved with the gas sensitive film 4 extending in the longitudinal direction and the beam main body 521 on the inside and the gas sensitive film 4 on the outside. Here, since the second beam member 503 is connected to the first beam member 502, the second beam member 503 is deformed along with the deformation of the first beam member 502. Specifically, the second beam member 503 curves to the opposite side to the first beam member 502. That is, in the second beam member 503, the surface 503a on the same side as the surface 502a on which the gas sensitive film 4 of the first beam member 502 is provided shrinks, and the gas sensitive film 504 of the first beam member 502 is not provided. Curved so that surface 503b on the same side as surface 502b extends. As a result, the first and second beam members 502 and 503 are curved so that their intermediate portions are separated in the thickness direction.

  By deforming in this way, the resonance frequency of the gas sensor 501 changes. Hereinafter, resonance in the case of causing the gas sensor 501 to vibrate (hereinafter also referred to as “vertical vibration”) in the direction of bending deformation of the first and second beam members 502 and 503 (that is, the plate thickness direction and the Z direction). A change in frequency will be described.

  FIG. 17 shows a perspective view of the gas sensor 501 before deformation that performs vertical vibration in the primary mode, FIG. 18 shows a perspective view of the gas sensor 501 before deformation that performs vertical vibration in the secondary mode, and FIG. The perspective view of the gas sensor 501 before a deformation | transformation which performs the vertical vibration of a tertiary mode is shown.

  In the primary mode vertical vibration, as shown in FIG. 17, the gas sensor 501 uses the base ends of the first and second beam members 502 and 503 as vibration nodes, while the first and second beam members 502. , 503, the first and second beam members 502, 503 are vibrated in the Z direction integrally with the tip of the vibration as the antinode. That is, the first beam member 502 and the second beam member 503 vibrate in the Z direction in the same phase.

  In the secondary mode vertical vibration, as shown in FIG. 18, the gas sensor 501 includes a base end portion of the first and second beam members 502 and 503 and a portion separated by about 80% of the total length from the base end portion. On the other hand, the first and second beam members 502, 503 are used as vibration nodes, with the tip portions of the first and second beam members 502, 503 being approximately 45% of the entire length from the base end portions as vibration antinodes. 503 integrally vibrates in the Z direction. That is, the first beam member 502 and the second beam member 503 vibrate in the Z direction in the same phase.

  In the vertical vibration of the third mode, the gas sensor 501 uses the first and second beam members 502 and 503 as the vibration nodes, while the proximal and distal ends of the first and second beam members 502 and 503 are used as shown in FIG. The beam member 502, 503 vibrates in the Z direction with the middle part of the beam as a vibration antinode. At this time, the first beam member 502 and the second beam member 503 vibrate in the Z direction with opposite phases.

  When the gas sensor 501 is deformed as described above, the resonance frequency of the gas sensor 501 changes significantly, particularly in vertical vibrations in the first and second modes. Specifically, when the gas sensor 501 is deformed as described above, the first beam member 502 and the second beam member 503 are separated from each other in the Z direction, whereby the first and second beam members 502 and 503 as a whole are rotated about the X axis. The cross-sectional second moment increases. In particular, in the first and second mode vertical vibrations, the first and second beam members 502 and 503 vibrate integrally in the same phase, so that the bending rigidity is greatly increased and the resonance frequency is greatly increased.

  Below, the simulation result of the change characteristic of the resonant frequency with respect to the deformation when the gas sensor 501 is bent and deformed will be described. FIG. 20 shows a perspective view of the deformed gas sensor 501 that performs vertical vibration in the primary mode, and FIG. 21 shows a perspective view of the deformed gas sensor 501 that performs vertical vibration in the secondary mode.

  In this gas sensor 501, the first beam member 502 and the second beam member 503 are made of silicon having a thickness of 10 μm. The dimension of the first and second beam main bodies 502 and 503 in the Z direction is 760 μm excluding the connecting portion 524, and is 780 μm when the connecting portion 524 is included. The X direction width of each of the first and second beam members 502 and 503 is 30 μm. The same applies to the dimension of the second beam member 503 in the Z direction. The distance in the X direction between the first beam member 502 and the second beam member 503 is 10 μm.

The analysis code used for the simulation is ANSYS 12.0, and the element type used is solid186. The mesh size was a hexahedron with a side of 10 μm. As material properties, the Young's modulus of silicon was 130.8 GPa, the density was 2.33 g / cm ³ , and the Poisson's ratio was 0.26. In the gas sensor 501, the base end portion of the first extending portion 21 of the first beam member 2 and the base end portion of the first extending portion 31 of the second beam member 3 are fixed ends that restrict all degrees of freedom. In the simulation, the distance between the first beam member 502 and the second beam member 503 in the Z direction (hereinafter referred to as deformation amount) at the intermediate point in the Y direction of the portion excluding the connecting portion 524 of the first and second beam bodies 502 and 503. The resonance frequency of the vertical vibration of each mode of the gas sensor 501 was obtained for the case of 0) and 35 μm.

  The resonance frequency of the primary mode vertical vibration of the gas sensor 501 before the deformation was 19743 Hz. On the other hand, the resonance frequency of the primary mode vertical vibration of the gas sensor 501 after deformation was 26507 Hz. In this way, by bending and deforming the first and second beam members 502 and 503 of the gas sensor 501, the resonance frequency of the primary mode vertical vibration can be significantly changed.

  Further, the resonance frequency of the vertical vibration of the secondary mode of the gas sensor 501 before the deformation was 123770 Hz. On the other hand, the resonance frequency of the secondary mode vertical vibration of the gas sensor 501 after deformation was 346550 Hz. In this way, by bending and deforming the first and second beam members 502 and 503 of the gas sensor 501, the resonance frequency of the secondary mode vertical vibration can be significantly changed.

  Even in vibration modes other than the first and second modes, there may be vibration modes in which the resonance frequency of the gas sensor 501 changes significantly before and after deformation.

  Subsequently, the gas sensor 501 is vibrated in the direction perpendicular to the direction of bending deformation of the first and second beam members 502 and 503 and the extending direction of the first and second beam members 502 and 503 (that is, the X direction) (hereinafter referred to as the X direction). The change of the resonance frequency in the case of “also referred to as“ horizontal vibration ”) will be described. FIG. 22 shows a plan view of the gas sensor 501 after deformation that performs horizontal vibration in the primary mode, and FIG. 23 shows a plan view of the gas sensor 501 before deformation that performs horizontal vibration in the primary mode.

  In the horizontal vibration of the gas sensor 501, the first beam member 502 and the second beam member 503 are arranged on the same plane and have a flat shape before the deformation, as shown in FIG. Bending deformation in which one of the first and second beam members 502 and 503 contracts and the other extends is unlikely to occur. For this reason, the gas sensor 501 before being deformed undergoes bending deformation having one inflection point as shown in FIG. 23 during horizontal vibration. On the other hand, as described above, when the first and second beam members 502 and 503 are bent and deformed, the first and second beam members 502 and 503 are easily expanded and contracted in the longitudinal direction. That is, in order for the flat first and second beam members 502 and 503 before deformation to expand and contract in the longitudinal direction, the first and second beam members 502 and 503 themselves have to be distorted. The deformed curved first and second beam members 502 and 503 can be easily expanded and contracted in the longitudinal direction by changing the amount of bending deformation. Therefore, as shown in FIG. 22, the deformed gas sensor 501 is likely to bend and deform such that one of the first and second beam members 502 contracts and the other extends. Thus, the resonance frequency of the horizontal vibration of the gas sensor 501 is reduced by changing from the vibration mode shown in FIG. 23 to the vibration mode shown in FIG. 22 before and after the deformation of the gas sensor 501.

  Here, the resonance frequency of the horizontal vibration of the primary mode of the gas sensor 501 was obtained by simulation.

  The resonance frequency of the horizontal vibration of the primary mode of the gas sensor 501 before the deformation was 85239 Hz. On the other hand, the resonance frequency of the horizontal vibration of the primary mode of the gas sensor 501 after deformation was 60536 Hz. In this way, by bending and deforming the first and second beam members 502 and 503 of the gas sensor 501, the resonance frequency of the primary mode horizontal vibration can be significantly changed.

  As described above, even in the gas sensor 501 in which the tip portions of two simple beams are connected, the resonance frequency is greatly changed by deforming the first beam member 502 and the second beam member 503 differently. Can do.

-Modification 5-
Next, a gas sensor 601 according to Modification 5 will be described. FIG. 24 shows a perspective view of the gas sensor 601 before deformation, and FIG. 25 shows a perspective view of the gas sensor 601 after deformation.

  In the gas sensor 601, the configuration of the first and second beam members 2 and 3 is the same as that of the gas sensor 1, and the place where the gas sensitive film 4 is provided is different. Specifically, in the gas sensor 601, gas sensitive films 4 and 4 are laminated on the surface 2 a of the second extending portion 23 of the first beam member 2 and the surface 3 a of the second extending portion 33 of the second beam member 3, respectively. . The gas sensor 601 is a type of gas sensor driven by a piezoelectric element, unlike the second embodiment described later. Specifically, a driving piezoelectric element 26 is laminated on the base end portion of the first extending portion 21 of the first beam member 2. A piezoelectric element 36 for detection is laminated on the base end portion of the first extending portion 31 of the second beam member 3.

  In this configuration, when hydrogen is adsorbed to the gas sensitive films 4, 4, the first beam member 2 is curved with the second extending portion 23 inside and the gas sensitive film 4 outside, and the second beam member 3 is The second extending portion 33 is curved with the gas-sensitive film 4 on the outside and the gas-sensitive film 4 on the outside. At this time, the first extending portion 21 of the first beam member 2 and the first extending portion 31 of the second beam member 3 are hardly deformed. Since the gas sensitive films 4 and 4 are provided on the surfaces 2a and 3a on the same side in the first beam member 2 and the second beam member 3, the second extending portions 23 and 33 are curved in the same direction. As a result, the first beam member 2 of the gas sensor 601 is arranged so that the distal end portion of the second extending portion 23 is separated from the proximal end portion of the first extending portion 21, that is, the first end portion of the second extending portion 23 and the first extending portion 23. It deform | transforms so that the space | interval with the base end part of the extending | stretching part 21 may spread. Similarly, the second beam member 3 of the gas sensor 601 is arranged so that the distal end portion of the second extending portion 33 is separated from the proximal end portion of the first extending portion 31, that is, the first extending portion 33 and the first extending portion 33. It deform | transforms so that the space | interval with the base end part of the extending | stretching part 31 may spread.

  By deforming in this way, the resonance frequency of the gas sensor 601 changes. In particular, the resonant frequency of the vertical vibration of the third-order mode changes significantly. In the vertical vibration of the third mode, the first and second extending portions 21 and 23 of the first beam member 2 are formed as one beam as a whole, and the folded portion 22 vibrates in the Z direction as the vibration antinode. However, the first and second extending portions 31 and 33 of the second beam member 3 are formed as a single beam as a whole, and vibrate in the Z direction with the folded portion 32 as an antinode of vibration. . Therefore, as described above, the distance between the distal end portion of the second extending portion 23 and the proximal end portion of the first extending portion 21 is widened in the first beam member 2, and the distal end of the second extending portion 33 is expanded in the second beam member 3. When the first and second extending portions 31 are deformed so that the distance between the first extending portion 31 and the base end portion of the first extending portion 31 is widened, the first and second extending portions 21 and 23 that vibrate like a single beam and the first portion on the node side of the vibration And the bending rigidity with the part by the side of vibration of the 2nd extension parts 31 and 33 becomes large. Thereby, the resonance frequency of the gas sensor 601 changes significantly in the direction of increasing. Therefore, the amount of change in the resonance frequency of the gas sensor 601 before and after the deformation increases.

  In addition, in a sensor that performs driving and detection using a piezoelectric element, by providing the piezoelectric element in a portion where a large stress is generated, driving can be easily performed and detection ability can be improved. Here, in the vertical vibration of the third mode, the proximal end portion of the first extending portion of the first beam member 2 and the proximal end portion of the second extending portion of the second beam member serve as vibration nodes, and a large stress is generated. Arise. That is, in the gas sensor 601 in which the vertical vibration in the third mode is effective, the driving and detection piezoelectric elements 26 and 36 are connected to the base end portion of the first extending portion 21 of the first beam member 2 and the second beam member first. By disposing the base end portion of the one extending portion 31, driving and detection performance can be improved. Thus, when the piezoelectric elements 26 and 36 are disposed at the proximal end portion of the first extending portion 21 of the first beam member 2 and the proximal end portion of the first extending portion 31 of the second beam member, these proximal end portions are supported. Since it is close to the portion 11, wiring of the wiring to the piezoelectric elements 26 and 36 can be simplified. For example, when a piezoelectric element is disposed in the folded portions 22 and 32, it is necessary to construct the wiring from the support portion 11 through the first extending portions 21 and 31 to the folded portions 22 and 32. Becomes complicated. On the other hand, in the configuration in which the piezoelectric elements 26 and 36 are disposed at the proximal end portion of the first extending portion 21 of the first beam member 2 and the proximal end portion of the first extending portion 31 of the second beam member, the piezoelectric element 26 is provided. , 36 can be shortened, and the routing of the wiring can be simplified.

  Furthermore, in the case of a sensor that is driven and detected by a piezoelectric element, the viscous resistance of air does not matter so much. That is, in a sensor that performs detection by electrostatic drive and capacitance as in the second embodiment described later, in order to improve drive and detection performance, the sensor may be brought close to the drive electrode and the detection electrode. In this case, the sensor is close to the substrate on which the drive electrode and the detection electrode are provided, and the influence of the viscous resistance due to air between the sensor and the substrate is increased. As a result, the vibration of the sensor may be hindered. That is, the sensor by electrostatic drive is restricted by the viscous resistance of air. On the other hand, in a sensor driven by a piezoelectric element, it is not necessary to bring the sensor close to the substrate in order to improve driving and detection performance, so that the influence of the viscous resistance of air is less likely to be a problem.

  Therefore, by providing the gas sensitive films 4 and 4 on the second extending portions 23 and 33 located in the center of the first and second beam members 2 and 3 formed in an M shape in a plan view, It is possible to realize a gas sensor in which the resonance frequency of the vertical vibration of the third-order mode varies greatly according to the amount of adsorption. The driving and detecting performance can be improved by driving and detecting the gas sensor 601 configured in this way by the piezoelectric elements 26 and 36 provided at the base ends of the first extending portions 21 and 31. At the same time, the routing of the wiring to the piezoelectric elements 26 and 36 can be simplified. Furthermore, by driving and detecting the gas sensor 601 with the piezoelectric elements 26 and 36, the influence of the viscous resistance of air can be reduced.

  However, the configuration for greatly changing the resonance frequency of the third-order mode vertical vibration before and after the deformation is not limited to the above-described configuration. For example, a gas sensitive film may be further provided on the surface 2 b of the first extending portion 21 of the first beam member 2 and the surface 3 b of the first extending portion 31 of the second beam member 3. By doing so, the first beam member 2 is deformed so that the distance between the distal end portion of the second extending portion 23 and the proximal end portion of the first extending portion 21 is further widened, and the second beam member 3 is It deform | transforms so that the space | interval of the front-end | tip part of the extending | stretching part 33 and the base end part of the 1st extending | stretching part 31 may spread further. Or you may provide a gas sensitive film in the 1st extending | stretching parts 21 and 31, without providing the gas sensitive films 4 and 4 in the 2nd extending | stretching parts 23 and 33. FIG. Even in this case, the first beam member 2 is deformed so that the distance between the distal end portion of the second extending portion 23 and the proximal end portion of the first extending portion 21 is widened, and the second beam member 3 is 2 Deformation is performed so that the distance between the distal end portion of the extending portion 33 and the proximal end portion of the first extending portion 31 is widened.

  Even in vibration modes other than the tertiary mode, there may be vibration modes in which the resonance frequency of the gas sensor 601 changes significantly before and after deformation.

  The simulation result of the change characteristic of the resonant frequency of the third-order mode vertical vibration with respect to the deformation amount when the gas sensor 601 is bent and deformed will be described below. FIG. 26 shows the dimensions of the gas sensor used for the simulation, and FIG. 27 shows the simulation result of the change characteristic of the resonance frequency of the vertical vibration with respect to the deformation amount of the gas sensor. The gas sensor used for this simulation is only an example, and the present invention is not limited to this.

  In this gas sensor 601, the first beam member 2 and the second beam member 3 are made of silicon having a thickness of 15 μm, and the first extending portion 21 of the first beam member 2 and the first extending portion of the second beam member 3 are configured. PZT (lead zirconate titanate) 27 having a thickness of 3 μm is laminated on the surfaces 2 a and 3 a of 31. The PZT 27 is a substitute for the gas sensitive film 4, and a bending deformation is caused in the gas sensor 601 by applying a voltage to the PZT 27.

The analysis code used for the simulation is ANSYS 11.0 Product Launcher, and the element type used is solid45 for silicon and solid5 for PZT. The mesh size was a hexahedron with sides of 3 to 20 μm. As the material properties, silicon is linear isotropic, Young's modulus is 130.8 GPa, density is 2.33 g / cm ³ , and Poisson's ratio is 0.28. PZT has linear anisotropy, density of 7.534 g / cm ³ , elastic stiffness {c _ij ^E }, piezoelectric stress constant {e _ij }, and relative dielectric constant {ε _ij } are set as follows: did.

  In the simulation, static analysis was performed by deforming the gas sensor 601 by applying a voltage to the PZT 27. The applied voltage was changed between 0 to 20 V, the shape of the gas sensor 601 was updated, and the resonance frequency of the vertical vibration of the third-order mode of the gas sensor 601 was obtained. Further, in the gas sensor 601, the base end portion of the first extending portion 21 of the first beam member 2 and the base end portion of the first extending portion 31 of the second beam member 3 are fixed ends that restrict all degrees of freedom. In FIG. 26, a deformation amount corresponding to the applied voltage is added.

  From the simulation result of FIG. 27, it can be seen that the resonance frequency of the vertical vibration of the third-order mode of the gas sensor 601 increases as the applied voltage increases (that is, the amount of bending deformation increases). The deformation amount is the deformation amount in the Z direction of the connecting portions 24 and 34 shown in FIG.

<< Embodiment 2 of the Invention >>
Next, the gas detection device 5 including the gas sensor 1 will be described. FIG. 28 shows a block diagram of the gas detection device.

  The gas detection device 5 includes a gas sensor 1 and a control device 50 that controls the gas sensor 1. The gas sensor 1 is formed on a silicon substrate (not shown), and the support portion 11 is connected to the silicon substrate. The first and second beam members 2 and 3 are opposed to the silicon substrate with a predetermined gap. A drive electrode 12 and a detection electrode 13 are provided on a portion of the silicon substrate facing the connecting portions 24 and 34 between the first beam member 2 and the second beam member 3 of the gas sensor 1. An appropriate voltage is applied to the gas sensor 1.

  The control device 50 includes a control circuit 51, a variable frequency generation circuit 52 that outputs a pulse voltage to the drive electrode 12, a detection voltage from the detection electrode 13, and a pulse voltage (drive voltage) from the variable frequency generation circuit 52. A phase detection circuit 53 that detects a phase difference, a frequency counter 54 that detects a frequency of a detection voltage from the detection electrode 13, and a frequency-concentration conversion circuit 55 that calculates a gas concentration from the frequency detected by the frequency counter 54. ing. The control device 50 constitutes a drive unit.

  The variable frequency generation circuit 52 can output a pulsed driving voltage having an arbitrary frequency, and outputs a driving voltage having a frequency corresponding to an output signal from the control circuit 51. When a drive voltage is applied to the drive electrode 12, an electrostatic force acts between the drive electrode 12 and the connecting portions 24 and 34 of the first beam member 2 and the second beam member 3 of the gas sensor 1, and the gas sensor 1 The first and second beam members 2 and 3 vibrate in the thickness direction. When the gas sensor 1 vibrates, the distance between the gas sensor 1 and the detection electrode 13 changes. Then, the capacitance between the gas sensor 1 and the detection electrode 13 changes. A detection voltage from the detection electrode 13 and a drive voltage from the variable frequency generation circuit 52 are input to the phase detection circuit 53. Then, the phase detection circuit 53 obtains the phase difference between the detection voltage and the drive voltage, and outputs the result to the control circuit 51. The control circuit 51 outputs an output signal for adjusting the frequency of the drive voltage to the variable frequency generation circuit 52 so that the phase difference is 90 °. When the gas sensor 1 is resonating, the phase difference is 90 °.

  As described above, the control circuit 51, the variable frequency generation circuit 52, and the phase detection circuit 53 feed back the phase difference between the drive voltage and the detection voltage so that the phase difference becomes 90 °, that is, the gas sensor 1 resonates. Thus, the frequency of the drive voltage is controlled. For example, the gas sensor 1 is resonated by the secondary mode vertical vibration.

  The frequency counter 54 monitors the frequency of the detection signal from the detection electrode 13. Since the gas sensor 1 is resonated by the control circuit 51 as described above, the frequency counter 54 basically monitors the resonance frequency of the gas sensor 1. The frequency-concentration conversion circuit 55 has a calibration curve for the hydrogen gas concentration with respect to the resonance frequency of the gas sensor 1. The resonance frequency of the gas sensor 1 changes according to the deformation amount of the first beam member 2 as described above. The deformation amount of the first beam member 2 changes according to the expansion amount of the gas sensitive film 4, that is, the hydrogen gas adsorption amount. Further, the adsorption amount of hydrogen gas correlates with the gas concentration of hydrogen gas. Therefore, the resonance frequency of the gas sensor 1 and the gas concentration of hydrogen gas are correlated, and the calibration curve can be obtained in advance. The frequency-concentration conversion circuit 55 converts the resonance frequency of the gas sensor 1 input from the frequency counter 54 into a gas concentration based on the calibration curve. The frequency counter 54 and the frequency-concentration conversion circuit 55 constitute a gas detection unit that detects gas based on a change in the resonance frequency of the gas sensor 1.

  That is, when hydrogen gas is adsorbed to the gas sensitive film 4, the gas sensitive film 4 expands and the first beam member 2 is deformed. Thereby, when the resonance frequency of the gas sensor 1 changes, the frequency of the drive voltage is adjusted to the same frequency as the resonance frequency by feedback control of the control circuit 51. As a result, the gas sensor 1 is resonated at the changed resonance frequency. At this time, the changed resonance frequency is detected by the frequency counter 54 and converted into a gas concentration by the frequency-concentration conversion circuit 55. Thus, the gas concentration is detected. Since the gas sensor 1 has the above-described configuration, the change in the resonance frequency with respect to the deformation of the gas sensitive film 4 can be increased, so that the gas detection capability can be improved. In addition, since the circuit can be configured with a simple circuit, the cost can be reduced.

  In the above embodiment, the gas sensor is driven and detected using electrostatic force and capacitance, but the present invention is not limited to this. Instead of the drive electrode 12 and the detection electrode 13, a drive and detection piezoelectric element may be provided in the gas sensor as in the sixth modification. In this case, the drive voltage from the control device 50 is applied to the drive piezoelectric element, and the detection voltage from the detection piezoelectric element is input to the control device 50.

<< Other Embodiments >>
The present invention may be configured as follows with respect to the above embodiment.

  Although the gas sensor has been described in the above embodiment, the present invention is not limited to this. For example, an oscillator and a vibrator used therefor may be used. In such a case, a piezoelectric layer may be provided in place of the gas sensitive film 4. Then, a voltage may be applied to the piezoelectric layer from the outside, for example, from the control circuit 51, and thereby the vibrator may be bent and deformed. The shape of the vibrator and the installation location of the piezoelectric layer can be appropriately set with reference to the embodiment. According to this configuration, the deformation of the vibrator can be adjusted by adjusting the voltage applied to the piezoelectric layer, and thereby the resonance frequency of the vibrator can be adjusted. At this time, an output signal from the frequency counter 54 may be input to the control circuit 51, and the control circuit 51 may be configured to feedback control the voltage applied to the piezoelectric layer according to the resonance frequency. In this way, a vibrator and an oscillator that can change the resonance frequency to a desired value can be configured. The frequency-density conversion circuit 55 is not necessary. When the relationship between the voltage applied to the piezoelectric layer by the control circuit 51 and the resonance frequency of the vibrator corresponding to the voltage is known, the frequency counter 54 may be omitted.

  Moreover, in the said embodiment, although the palladium which adsorb | sucks hydrogen is employ | adopted as the gas sensitive film | membrane 4, it is not restricted to this. Any substance can be used as the gas sensitive film 4 as long as it is a substance whose shape changes (expands or shrinks) by adhering gas (not limited to adsorption or occlusion). In the above embodiment, the gas sensitive film 4 is used as the deforming portion, but the present invention is not limited to this. For example, you may employ | adopt the deformation | transformation part comprised with the material from which a linear expansion coefficient differs from a 1st beam member. According to such a vibrator, the first beam member and the deformed portion are thermally deformed with different strain amounts according to the ambient temperature, and the first beam member and the deformed portion are bent and deformed. As a result, the first beam member and the second beam member are deformed in different modes, the bending rigidity of the first and second beam members as a whole changes, and the resonance frequency changes. By detecting this change in resonance frequency, the ambient temperature can be detected. That is, a temperature sensor can be configured.

  Further, the shape, vibration mode and vibration mode of the gas sensor are not limited to the above embodiment. As long as the first beam member and the second beam member are deformed differently, and the resonance frequency can be changed greatly before and after the deformation, any shape, vibration mode and vibration mode can be adopted. .

  Moreover, in the said embodiment, although the beam main body is flat shape before a deformation | transformation, specifically, it is flat form, it is not restricted to this. The beam main body may have a shape curved in advance before deformation. For example, when the gas sensor 501 is deformed, the first beam member 502 and the second beam member 503 need to bend to the opposite side. Since the gas sensitive film 4 exists in the first beam member 502, the bending direction at the time of deformation (which surface of the first beam member 502 is the inside and which surface is the outside) is determined. However, since the gas sensitive film 4 is not provided in the second beam member 503, it is not known in which direction the second beam member 503 is bent when the first beam member 502 is bent and deformed. Therefore, the second beam member 503 may be formed in a slightly curved state in a desired direction in advance. The gas sensitive film 4 may be provided on the surface of the second beam member 503 opposite to the surface on which the gas sensitive film 4 of the first beam member 502 is provided.

  In the gas detection device 5, the gas concentration is detected by resonating the gas sensor 1 by feedback control and detecting the resonance frequency at that time, but the present invention is not limited to this. For example, even if the vibrator (that is, the gas sensor 1) is deformed, the driving frequency of the vibrator may not be changed. In this case, since the resonance frequency of the vibrator moves away from the drive frequency, the amplitude of the vibrator becomes small. Therefore, by monitoring the amplitude of the vibrator, it is possible to detect a change in the resonance frequency, and hence deformation of the vibrator. That is, any method can be employed as long as it can detect a change in the resonance frequency of the vibrator.

  In addition, the above embodiment is an essentially preferable illustration, Comprising: It does not intend restrict | limiting the range of this invention, its application thing, or its use.

  As described above, the present invention is useful for a vibrator including a beam member, an oscillator including the same, and a gas detection device.

1 Gas sensor (vibrator)
2 1st beam member 21 1st extending part 22 Folding part 23 2nd extending part 3 2nd beam member 31 1st extending part 32 Folding part 33 2nd extending part 4 Gas sensitive film (deformation part, gas sensitive part)
5 Gas detection device 50 Control device (drive unit)

Claims (17)

First and second beam members connected to each other and driven to vibrate,
At least the first beam member is provided with a deformable portion whose shape can be changed,
The base ends of the first and second beam members are fixed ends,
The tip portions of the first and second beam members are connected to each other and are free ends,
The first and second beam members are transducers that are deformed in different manners so that a distance between the first and second beam members is increased by deformation of the deformable portion. The vibrator according to claim 1,
A vibrator whose bending elastic modulus is changed by deformation of the deforming portion. The vibrator according to claim 1,
Each of the first and second beam members includes a first extending portion extending from the proximal end side, and a second extending portion extending from the distal end portion of the first extending portion as a folded portion and extending toward the proximal end side. And the ends of the second extending portion are connected to each other,
The base end portion of the first extending portion of the first and second beam members is a fixed end,
The tip end portions of the second extending portions of the first and second beam members are free ends,
The first beam member and the second beam member are deformed so that a space between the folded portions is widened by deformation of the deformation portion. The vibrator according to any one of claims 1 to 3,
The deforming portion is provided on both the first and second beam members,
The second beam member is a vibrator that is deformed to the opposite side to the first beam member by deformation of the deformation portion. The vibrator according to claim 1,
Each of the first and second beam members includes a first extending portion extending from the proximal end side, and a second extending portion extending from the distal end portion of the first extending portion as a folded portion and extending toward the proximal end side. And the ends of the second extending portion are connected to each other,
The base end portion of the first extending portion of the first and second beam members is a fixed end,
The tip end portions of the second extending portions of the first and second beam members are free ends,
The first and second beam members are deformed so that a distance between a base end portion of the first extending portion and a distal end portion of the second extending portion is widened by deformation of the deforming portion. The vibrator according to any one of claims 1 to 5,
The transducer is configured to be deformed in accordance with an external signal. The vibrator according to any one of claims 1 to 5,
The deforming portion is a vibrator that is a gas sensitive portion that is deformed by the attachment of gas. A vibrator according to claim 3;
A drive unit that vibrates and drives the vibrator,
The deformation portion is configured to be deformed according to an external signal,
The drive unit is an oscillator that vibrates the first and second beam members so that a tip end portion of the second extending portion becomes a vibration antinode. A vibrator according to claim 5;
A drive unit that vibrates and drives the vibrator,
The deformation portion is configured to be deformed according to an external signal,
The drive unit vibrates the first beam member so that the folded portion becomes an antinode of vibration, and the second beam member is different from the first beam member so that the folded portion becomes an antinode of vibration. An oscillator that vibrates in opposite phase. A vibrator according to claim 6;
An oscillator comprising: a drive unit that vibrates and drives the vibrator. The oscillator according to claim 10, wherein
The drive unit is an oscillator that vibrates the vibrator in a direction parallel to a deformation direction of the first beam member. The oscillator according to claim 10, wherein
The drive unit is an oscillator that vibrates the vibrator in a direction orthogonal to a deformation direction of the first beam member. A vibrator according to claim 3;
A drive unit that vibrates and drives the vibrator,
The deformation part is a gas sensitive part that is deformed by the adhesion of gas,
The drive unit is a gas detection device that vibrates the first and second beam members so that a tip end portion of the second extending portion becomes an antinode of vibration. A vibrator according to claim 5;
A drive unit that vibrates and drives the vibrator,
The deformation part is a gas sensitive part that is deformed by the adhesion of gas,
The driving unit vibrates the first beam member so that the folded portion becomes an antinode of vibration, and the second beam member is different from the first beam member so that the folded portion becomes an antinode of vibration. Gas detector that vibrates in reverse phase. A vibrator according to claim 7;
A gas detection apparatus comprising: a drive unit that vibrates and drives the vibrator. The gas detection device according to claim 15, wherein
The drive unit is a gas detection device that vibrates the vibrator in a direction parallel to a deformation direction of the first beam member. The gas detection device according to claim 15, wherein
The drive unit is a gas detection device that vibrates the vibrator in a direction orthogonal to a deformation direction of the first beam member.

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