JP2008128724A - Pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure sensor capable of improving airtightness of the pressure sensor, and facilitating structure and a manufacturing process of the pressure sensor. <P>SOLUTION: In this pressure sensor 1, the first circular electrode 4 enclosing a vibrator 3 fixed to the inner surface 2a of a diaphragm 2 is formed. A coupling electrode 5 is formed inside the first electrode 4. The first electrode 4 and the coupling electrode 5 are connected to the vibrator 3. The coupling electrode 5 is electrostatically coupled with the second electrode 6 placed on the outer surface 2b of the diaphragm 2. Therefore, anode joint of a casing 7 to the diaphragm 2 becomes possible by using the surface of the first electrode 4 having no irregularities as a circular joint surface. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pressure sensor, and more particularly, to a pressure sensor that can be suitably used for a direct type TPMS (tire pressure monitoring system).

  Pressure sensors are used in various places and devices. For example, in a direct TPMS that measures the air pressure of an automobile tire, the pressure sensor is used to directly measure the air pressure by incorporating the pressure sensor in the tire.

  As an example, the conventional pressure sensors 101A and 101B include a diaphragm 102, a vibrator 103, extraction electrodes 104 and 105, and a casing 107 as shown in FIG. 4 or FIG. As the vibrator 103, a quartz crystal vibrator or SAW (Surface Acoustic Wave) filter having a constant width in a plan view is selected, and the vibrator 103 is disposed on the inner surface 102a of the diaphragm 102 that is elastically deformed. It is pasted.

  In addition, lead electrodes 104 and 105 are connected to both ends of the vibrator 103 for connection to a wireless reception circuit or an acceleration sensor and other circuits (not shown) provided together with the pressure sensors 101A and 101B. The lead electrodes 104 and 105 are extended from both ends of the vibrator 103 to the outer edge of the diaphragm 102 on the inner surface 102a of the diaphragm 102 as shown in FIG. 4, or via the columnar wiring 111 and the via hole 112 as shown in FIG. Thus, the vibrator 103 is extended from both ends via the inside of the housing 107.

  Then, as shown in FIG. 4 or FIG. 5, in order to prevent the vibrator 103 from being affected by changes in temperature and humidity, the flat bottom 108 and the side wall 109 having the circular through hole 109a are joined. A container-like casing 107 obtained in this manner is joined to the diaphragm 102 so as to enclose the vibrator 103 (see Patent Document 1).

  When these conventional pressure sensors 101A and 101B are built in a tire (not shown) of a car, when the air pressure of the tire changes, the diaphragm 102 of the pressure sensors 101A and 101B elastically deforms according to the change of the air pressure. Accordingly, since pressure is applied to the vibrator 103, the oscillation frequency or resonance frequency of the vibrator 103 changes. By converting the frequency change of the vibrator 103 into an electric signal, the wireless transmission / reception circuit outside the tire can measure the change in the tire air pressure.

JP 2005-208043 A

  However, as shown in FIG. 4, when the extraction electrodes 104 and 105 according to the conventional pressure sensor 101 </ b> A are extended from both ends of the vibrator 103 to the outer edge of the diaphragm 102 on the inner surface 102 a of the diaphragm 102, The extraction electrodes 104 and 105 exist in a part of the bonding surface (shaded portion in FIG. 4). For this reason, irregularities are formed on the joint surface, which makes it difficult to improve the airtightness between the diaphragm 102 and the housing 107.

  Further, as shown in FIG. 5, when the extraction electrodes 104 and 105 according to the conventional pressure sensor 101B are extended from both ends of the vibrator 103 to the outside of the casing 107 through the columnar wiring 111 and the via holes 112, FIG. The columnar wiring 111 and the via hole 112 that do not exist in the pressure sensor 101A shown in FIG. For this reason, the structure of the pressure sensor 101B and the manufacturing process thereof are complicated, and there is a problem that the manufacturing cost of the pressure sensor 101B increases. Further, when the structure of the pressure sensor 101B is complicated, there is a problem that the reliability of the pressure sensor 101B with respect to a failure is also lowered.

  In addition, regardless of the extraction method of the extraction electrodes 104 and 105, the diaphragm 102 and the casing 107 are usually formed using the same material (for example, glass), so that the diaphragm 102 and the casing 107 are hermetically sealed. There was a problem that highly reliable anodic bonding could not be used. Here, as an example of the joining means other than anodic bonding, low-melting glass bonding may be mentioned. However, low-melting glass bonding has a drawback that it is difficult to control the amount of glass to be bonded. For this reason, there is a problem that the airtightness of the pressure sensors 101A and 101B may be lowered and the measurement accuracy may be adversely affected.

  Accordingly, the present invention has been made in view of these points, and provides a pressure sensor that can improve the airtightness of the pressure sensor and simplify the structure and manufacturing process of the pressure sensor. Is the object of the present invention.

  In order to achieve the above-described object, a pressure sensor according to the present invention has, as a first aspect thereof, a vibrator fixed to one surface of an elastically deforming diaphragm, and surrounds the vibrator on one surface of the diaphragm. A first electrode connected to one end of the vibrator and formed inside the ring of the first electrode on one surface of the diaphragm, and the other end of the vibrator A joined electrode connected to the diaphragm, a second electrode that is electrically coupled to the joined electrode by facing the joined electrode on the other face of the diaphragm facing the one face, and joined to the diaphragm And a housing that is joined to the diaphragm via the first electrode with the surface of the first electrode as an annular joining surface. It is characterized by a door.

  According to the pressure sensor of the first aspect of the present invention, since the first electrode is formed in an annular shape and the surface thereof is used as a joint surface with the housing, the joint surface between the diaphragm and the housing is formed in a smooth annular shape. can do. In addition, since the first electrode, the coupling electrode, and the second electrode, which are conventional extraction electrodes, are formed on one of the surfaces facing each other and the other surface of the diaphragm, They can be formed more easily than forming a three-dimensional wiring such as a hole.

  The pressure sensor according to a second aspect of the present invention is the pressure sensor according to the first aspect, wherein the first electrode is formed using metal, and the bonding surface of the housing with the first electrode is made of glass. The case is characterized in that the case is bonded to the diaphragm by anodically bonding the surface of the first electrode and the bonding surface of the case to the first electrode.

  According to the pressure sensor of the second aspect of the present invention, the airtightness of the pressure sensor can be enhanced by anodic bonding of the diaphragm and the casing, as compared with bonding methods other than bonding with an adhesive or other anodic bonding. .

The pressure sensor according to a third aspect of the present invention is the pressure sensor according to the first or second aspect, wherein the diaphragm is formed using SiO ₂ and the vibrator is a quartz crystal formed using SiO _2. It is characterized by being a vibrator.

  According to the pressure sensor of the third aspect of the present invention, since the diaphragm and the vibrator are made of the same material, the thermal expansion coefficients of the diaphragm and the vibrator are equal. As a result, it is possible to reduce only one of the diaphragm and the vibrator from being greatly distorted by thermal expansion and adversely affecting the electrical signal obtained from the vibrator.

A pressure sensor according to a fourth aspect of the present invention is the pressure sensor according to the first or second aspect, wherein the diaphragm and the casing are formed using SiO ₂ , and the vibrator is made of SiO ₂ . It is characterized by being a crystal resonator formed by using.

  According to the pressure sensor of the fourth aspect of the present invention, since the diaphragm, the casing, and the vibrator are all made of the same material, the thermal expansion coefficients of the diaphragm, the casing, and the vibrator are equal. As a result, it is possible to reduce only one of the diaphragm, the casing, and the vibrator from being greatly distorted by thermal expansion and adversely affecting the airtightness of the pressure sensor.

  A pressure sensor according to a fifth aspect of the present invention is the pressure sensor according to any one of the first to fourth aspects, wherein the casing is larger than the bottom surface portion serving as a lid and the ring related to the first electrode. It is formed in a container shape having a bottomed hole by separately forming a side wall portion having a smaller through-hole and joining the bottom surface portion and the side wall portion so that the side wall portion stands up from the periphery of the bottom surface portion. It is characterized by that.

  According to the pressure sensor of the fifth aspect of the present invention, for example, a housing can be formed by forming a through hole in only one of two flat plates and joining them together. The manufacturing process of the casing and the pressure sensor can be simplified as compared to manufacturing the casing by integrally forming the side wall portion.

  The pressure sensor according to a sixth aspect of the present invention is the pressure sensor according to any one of the first to fifth aspects, wherein the second electrode includes at least a vibrator, a first electrode, and a coupling on the other surface of the diaphragm. The ground electrode is formed as a single flat plate facing all of the electrodes.

  According to the pressure sensor of the sixth aspect of the present invention, the vibrator, the first electrode, and the coupling electrode are all covered with the second electrode serving as the ground electrode, and are electrically shielded from external noise. Therefore, the electrical signal obtained from the pressure sensor can be protected from external noise. In addition, since the coupling electrode is covered with the second electrode, the facing area between the coupling electrode and the second electrode becomes equal to the area of the coupling electrode, so that the capacitance between the coupling electrode and the second electrode is increased. Can be maximized.

  A pressure sensor according to a seventh aspect of the present invention is the pressure sensor according to any one of the first to sixth aspects, further comprising a ground electrode that covers all or part of the outer surface of the casing. It is said.

  According to the pressure sensor of the seventh aspect of the present invention, since the ground electrode exhibits a shielding effect, the vibrator, the first electrode, and the coupling electrode can be electrically isolated from external noise. It is possible to protect the electric signal obtained from the external noise.

  According to the pressure sensor of the present invention, since the first electrode is formed in an annular shape, the joint surface between the diaphragm and the casing is formed in a smooth annular shape, so that the airtightness of the pressure sensor can be improved. In addition, since the first electrode, the coupling electrode, and the second electrode have a planar shape to facilitate their structure and formation, the structure and manufacturing process of the pressure sensor can be simplified. As a result, the measurement accuracy and reliability of the pressure sensor can be improved, and the manufacturing cost can be reduced.

  Hereinafter, the pressure sensor of the present invention will be described with reference to FIG. 1 and FIG. Here, FIG. 1 shows an exploded perspective view of the pressure sensor 1 of the present embodiment, and FIG. 2 shows a plan view taken along arrow 2-2 of FIG. The hatched area in FIGS. 1 and 2 indicates the joint surface between the housing 7 and the diaphragm 2.

  As shown in FIGS. 1 and 2, the pressure sensor 1 of the present embodiment includes a diaphragm 2, a vibrator 3, a first electrode 4, a coupling electrode 5, a second electrode 6, and a housing 7.

As shown in FIGS. 1 and 2, the diaphragm 2 is formed in a flat plate shape (for example, a rectangular flat plate shape as shown in FIGS. 1 and 2) using a material that elastically deforms according to changes in the external air pressure. . As the elastically deformable material in the present embodiment, SiO ₂ is selected from the viewpoint of thermal expansion matching with respect to the vibrator 3 and the housing 7.

As shown in FIGS. 1 and 2, the vibrator 3 is fixed to the inner surface (one surface) 2 a of the diaphragm 2. As this vibrator 3, an element that changes the frequency of the input signal by pressurization such as a crystal vibrator, a SAW filter, or the like can be selected. As the vibrator 3 of the present embodiment, a quartz crystal vibrator (SiO ₂ ) is selected from the viewpoint of thermal expansion matching with the diaphragm 2 and the housing 7.

  As shown in FIGS. 1 and 2, the first electrode 4 is formed by sputtering or plating in an annular shape (for example, an annular shape as shown in FIGS. 1 and 2) surrounding the vibrator 3 on the inner surface 2 a of the diaphragm 2. Has been. The first electrode 4 is connected to one end 3a of the vibrator 3 fixed inside. As a material used for the first electrode 4, a metal having good conductivity such as Cu, Ag, or Au is used. Further, as shown in FIG. 1, in order to connect the first electrode 4 to another circuit (not shown) outside the pressure sensor 1, the lead-out pattern 4 a extends from the first electrode 4 to the housing 7. The side wall 9 is extended to the side of the notch 9b provided at one corner.

  As shown in FIGS. 1 and 2, the coupling electrode 5 has a smooth circular shape having a U-shaped opening 5 a on the inner surface 2 a of the diaphragm 2 and on the inner surface of the ring related to the first electrode 4. Sputtered or plated. The vibrator 3 is arranged inside the U-shaped opening 5 a related to the coupling electrode 5, and the coupling electrode 5 is connected to the other end 3 b of the vibrator 3. As a material used for the coupling electrode 5, a metal having good conductivity such as Cu, Ag, Au or the like is used.

  The reason why the coupling electrode 5 is formed in a circular shape having the U-shaped opening 5a is that the coupling electrode 5 is not brought into contact with the portion other than the other end 3b of the vibrator 3 and the first electrode 4 is concerned. This is because the area of the coupling electrode 5 is maximized on the inner surface of the ring. Therefore, about the shape of the coupling electrode 5 of this embodiment, it does not deny that the shape becomes shapes other than the circular shape which has the U-shaped opening part 5a.

  As shown in FIGS. 1 and 2, the second electrode 6 is formed by sputtering or plating on the other surface facing the inner surface 2 a of the diaphragm 2, that is, the outer surface 2 b of the diaphragm 2, and faces the coupling electrode 5. As a result, the coupling electrode 5 is electrically coupled (capacitive coupling). The shape of the second electrode 6 may be at least a flat plate shape facing the coupling electrode 5. As shown in FIG. 2, the second electrode 6 of the present embodiment is formed in one wide flat plate shape facing the vibrator 3 and the first electrode 4 in addition to the coupling electrode 5. At the same time, it is a ground electrode. The single flat plate shape may be a rectangle as shown in FIG. 2 or may be a polygon or a circle other than the rectangle although not shown.

  The casing 7 is formed in a container shape that seals the vibrator 3 when joined to the diaphragm 2. As shown in FIG. 1, the housing 7 of the present embodiment has a bottom surface portion 8 and a side wall portion 9 that are separately formed. The bottom surface portion 8 is formed in a rectangular flat plate shape and serves as a lid. The side wall portion 9 has a shape in which a through hole 9a larger than the vibrator 3 and smaller than the ring related to the first electrode 4 is formed on a rectangular flat plate having the same size as the bottom surface portion 8, and serves as a spacer. As described above, the side wall 9 has the notch 9b at one corner. And the bottom face part 8 and the side wall part 9 are joined so that the side wall part 9 stands up from the periphery of the bottom face part 8. Thereby, the housing | casing 7 of this embodiment is formed in the container shape which has the bottomed hole 7a.

Here, as the material used for the bottom surface portion 8 and the side wall portion 9, SiO ₂ is selected from the viewpoint of thermal expansion consistency, like the diaphragm 2 and the vibrator 3. Moreover, as joining of these bottom face parts 8 and side wall parts 9, low melting glass joining, joining by an adhesive agent, or anodic joining is used. When anodic bonding is selected, a metal dummy electrode necessary for anodic bonding is formed by sputtering on one of the bonding surfaces of the bottom surface 8 and the side wall 9 formed using SiO _2. Plating is performed.

The casing 7 is joined to the diaphragm 2 via the first electrode 4 with the surface of the first electrode 4 as an annular joining surface. A side wall portion 9 of the housing 7 which is a joint portion with the first electrode 4 in the housing 7 is formed in a rectangular flat plate shape having a through hole 9a, and is formed on the inner surface 2a of the diaphragm 2 having the rectangular flat plate shape. Since the first electrode 4 has a smooth surface, the joint surface between the housing 7 and the diaphragm 2 is smooth. In order to join these smooth joint surfaces, as the pressure sensor 1 of the present invention, various bonding means such as bonding with an adhesive can be employed. In the pressure sensor 1 of the present embodiment, the housing 7 is used. By utilizing the fact that the surface of the side wall portion 9 is made of SiO ₂ (glass) and the first electrode 4 is made of metal, the bonding surface of the housing 7 (the bonding surface of the side wall portion 9) and the first electrode 4 The case 7 is bonded to the diaphragm 2 by anodic bonding to the surface of the diaphragm 2.

  Further, in the casing 7 of the present embodiment, as shown in FIG. 1, the ground electrode 10 that covers a part of the outer surface of the casing 7 by covering the entire outer surface of the bottom surface portion 8 is formed in a flat plate shape. Yes. As with the second electrode 6, the ground electrode 10 is preferably formed so as to face at least all of the vibrator 3, the first electrode 4, and the coupling electrode 5.

  Next, the operation of the pressure sensor 1 of the present embodiment will be described with reference to FIGS. 1 to 3. Here, FIG. 3 shows an equivalent circuit diagram of the pressure sensor 1 of the present embodiment.

  In the pressure sensor 1 of the present embodiment, as shown in FIGS. 1 and 2, a vibrator 3 is fixed to an inner surface 2a of a diaphragm 2 that is elastically deformed. As shown in FIGS. 2 and 3, the first electrode 4 is connected to one end 3 a of the vibrator 3, and the coupling electrode 5 is connected to the other end 3 b of the vibrator 3. The coupling electrode 5 is electrically coupled to the second electrode 6 formed on the outer surface 2 b of the diaphragm 2.

  Since the coupling capacitance 21 between the coupling electrode 5 and the second electrode 6 may be about 1 pF depending on the size of the pressure sensor 1, for example, a large value may not be desired. However, the internal series capacitance 3c of the vibrator 3 is about several fF, which is only about 1/100 to 1/1000 times the coupling capacitance when a large value cannot be expected. Therefore, electrical coupling between the coupling electrode 5 and the second electrode 6 can be sufficiently realized.

  In addition, as shown in FIG. 3, a parasitic capacitance 20 is generated between the first electrode 4 and the second electrode 6, and this parasitic capacitance 20 is generated by the vibrator 103 according to the conventional pressure sensor 101. The circuit is equivalent to an external parallel capacitor (not shown) provided in parallel with the vibrator 103 in order to adjust the parallel resonance frequency. Therefore, the parasitic capacitance 20 does not adversely affect the parallel resonance frequency of the vibrator 3. From the above, the first electrode 4 and the second electrode 6 serve as extraction electrodes.

  When the external pressure of the diaphragm 2 is changed, the diaphragm 2 is elastically deformed, and accordingly, pressure is applied to the vibrator 3 fixed to the inner surface 2a of the diaphragm 2, so that the oscillation frequency of the vibrator 3 is increased. Or the resonance frequency changes. The change in the external pressure of the diaphragm 2 can be measured by the change in the frequency of the vibrator 3.

  Here, the vibrator 3 serving as a measuring element of the pressure sensor 1 is easily affected by a change in humidity. That is, the measurement accuracy of the pressure sensor 1 depends on the airtightness of the pressure sensor 1. Therefore, as shown in FIG. 1 and FIG. 2, the first electrode 4 is formed in an annular shape, and the coupling electrode 5 formed inside the first electrode is electrically coupled to the second electrode 6. Yes. As a result, regardless of the presence of the coupling electrode 5 and the second electrode 6, the first electrode 4 can be formed in a smooth closed ring surrounding the vibrator 3. By using the surface of the first electrode 4 as an annular bonding surface and bonding the housing 7 to the diaphragm 2 via the first electrode 4, the unevenness is removed from the bonding surface between the diaphragm 2 and the housing 7. Therefore, the airtightness of the pressure sensor 1 can be improved.

Further, in the pressure sensor 1 of the present embodiment, the first electrode 4 is formed using metal, and the bonding surface with the first electrode 4 in the housing 7 (the surface facing the diaphragm 2 in the side wall portion 9). ) Is formed using SiO ₂ (glass). The casing 7 of this embodiment is bonded to the diaphragm 2 by anodic bonding the surface of the first electrode 4 and the bonding surface of the casing 7 to the first electrode 4. By using anodic bonding, the first electrode 4 and the housing 7 can be bonded without using an adhesive, and therefore the possibility that a slight gap is generated in the bonded portion by the adhesive can be eliminated. it can. That is, by adopting anodic bonding, the airtightness of the pressure sensor 1 can be enhanced as compared with bonding methods other than anodic bonding such as bonding with an adhesive.

Furthermore, in the pressure sensor 1 of the present embodiment, in addition to the improvement in its airtightness, the thermal expansion of the vibrator 3, the diaphragm 2, and the housing 7 that degrades the measurement performance of the pressure sensor 1 is prevented. It is preventing. That is, in the pressure sensor 1 of the present embodiment, a quartz crystal resonator (SiO ₂ ) is selected as the vibrator 3, and SiO ₂ is used for the diaphragm 2 and the casing 7 in accordance with the material of the vibrator 3. . As a result, the vibrator 3, the diaphragm 2, and the housing 7 are made of the same material and have the same thermal expansion coefficient, so that only one member of the vibrator 3, the diaphragm 2, or the housing 7 is heated. It is possible to reduce a large distortion caused by the expansion and an adverse effect on the electric signal obtained from the vibrator 3.

Here, since the diaphragm 2 is formed in a flat plate shape, it is not difficult to form the diaphragm 2 using SiO ₂ . However, since the housing 7 needs to be formed in a container shape, it may be difficult to form the housing 7 using SiO ₂ depending on the shape of the housing 7 employed such as a hollow hemisphere or a cup shape. . Therefore, in the pressure sensor 1 of the present embodiment, as shown in FIG. 1, by separately forming and joining the rectangular flat plate-like side wall portion 9 having the rectangular flat plate-like bottom surface portion 8 and the through hole 9 a, The housing 7 is formed in a container shape having a bottomed hole 7a. Thus, it is possible to form the housing 7 by joining them after forming the only one in the through-hole 9a of the rectangular flat plate formed using SiO _2, for example, the bottom surface in a hollow hemispherical portion 8 And the manufacturing process of the housing | casing 7 and the pressure sensor 1 can be simplified rather than manufacturing the housing | casing which formed the side wall part 9 integrally.

  Further, in the pressure sensor 1 of the present embodiment, countermeasures are taken against the mixing of external noise and the formation of unnecessary capacitance. In other words, in the pressure sensor 1 of the present embodiment, the second electrode 6 is one flat grounding that faces at least all of the vibrator 3, the first electrode 4, and the coupling electrode 5 on the outer surface 2 b of the diaphragm 2. It is an electrode. Since all of the vibrator 3, the first electrode 4, and the coupling electrode 5 are covered with the second electrode 6 serving as the ground electrode, they can be electrically shielded from external noise.

  In addition, since the vibrator 3, the first electrode 4 and the coupling electrode 5 are all electrically cut off by the second electrode 6, the vibrator 3, the first electrode 4 or the coupling electrode 5 is externally connected to the outside. No unnecessary capacitance is formed with circuit elements (not shown) arranged in the circuit. Therefore, the electrical signal obtained from the pressure sensor 1 can be protected from the introduction of external noise and the formation of unnecessary capacitance.

  Further, the entire surface of the coupling electrode 5 is covered with the second electrode 6 by covering all of the vibrator 3, the first electrode 4 and the coupling electrode 5 with the second electrode 6. Therefore, since the facing area between the coupling electrode 5 and the second electrode 6 becomes equal to the area of the coupling electrode 5, the capacitance between the coupling electrode 5 and the second electrode 6 can be maximized.

  Since the second electrode 6 can be formed into a thin film by sputtering, the influence of the second electrode 6 on the diaphragm 2 on the pressure accuracy can be almost ignored.

  In addition, in the pressure sensor 1 of the present embodiment, the ground electrode 10 is formed on the entire outer surface of the bottom surface portion 8. Like the second electrode 6, all of the vibrator 3, the first electrode 4, and the coupling electrode 5 are covered with the ground electrode 10 of the housing 7, so that the electric signal obtained from the pressure sensor 1 is mixed with external noise and It is possible to protect against the formation of unnecessary capacitance.

  That is, according to the pressure sensor 1 of the present embodiment, since the airtightness inside the pressure sensor 1 is increased, the vibrator 3 can transmit an accurate electric signal without being affected by the outside. Further, since the thermal expansion strains of the casing 7, the diaphragm 2, and the vibrator 3 are made equal, adverse effects due to thermal expansion on the pressure sensor 1 can be mitigated. Furthermore, since the grounded second electrode 6 and ground electrode 10 are disposed on the outer surface of the diaphragm 2 and the housing 7, it is possible to eliminate the formation of external noise and unnecessary electrostatic capacitance. By these actions, there is an effect that the measurement accuracy of the pressure sensor 1 can be improved.

  Further, according to the pressure sensor 1 of the present embodiment, the first electrode 4, the coupling electrode 5 and the second electrode 6 are formed in a planar shape to facilitate their structure and formation. Therefore, it is not necessary to form the three-dimensional columnar wiring 111 and the via hole 112 as in the conventional pressure sensor 101B (see FIG. 4), and the structure and manufacturing process of the pressure sensor 1 can be simplified. Thereby, there exists an effect that the manufacturing cost of the pressure sensor 1 becomes low.

  In addition, this invention is not limited to embodiment mentioned above etc., A various change is possible as needed.

For example, in the pressure sensor according to another embodiment, in order to reduce the manufacturing cost, the diaphragm 2 and the vibrator 3 are formed using glass having a thermal expansion coefficient similar to that of SiO _2, and the casing 7 is made of SiO ₂ than You may form using a cheap nonelectroconductive material.

  When the housing 7 is integrally formed in a hollow hemispherical shape or a cup shape, the ground electrode 10 is preferably formed so as to cover the entire outer surface of the housing 7.

The disassembled perspective view which shows one Embodiment of the pressure sensor of this invention 2-2 arrow plan view of FIG. Equivalent circuit diagram showing pressure sensor of this embodiment An exploded perspective view showing an example of a conventional pressure sensor A longitudinal sectional view showing another example of a conventional pressure sensor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pressure sensor 2 Diaphragm 3 Vibrator 4 1st electrode 5 Coupling electrode 6 2nd electrode 7 Case 8 Bottom face part 9 Side wall part 9a Through-hole

Claims (7)

A vibrator fixed to one surface of the elastically deforming diaphragm;
A first electrode that is formed in an annular shape surrounding the vibrator on one surface of the diaphragm and connected to one end of the vibrator;
A coupling electrode formed on one side of the diaphragm on the inner side of the ring of the first electrode and connected to the other end of the vibrator;
A second electrode that is electrically coupled to the coupling electrode by facing the coupling electrode on the other surface facing the one surface of the diaphragm;
It is formed in a container shape that seals the vibrator when bonded to the diaphragm, and is bonded to the diaphragm via the first electrode with the surface of the first electrode as an annular bonding surface. A pressure sensor comprising a housing. The first electrode is formed using a metal,
The joint surface with the first electrode in the housing is formed using glass,
The said housing | casing is joined to the said diaphragm by carrying out anodic bonding of the surface of the said 1st electrode, and the joint surface of the said 1st electrode in the said housing | casing. The described pressure sensor. The diaphragm is formed using SiO ₂ ;
The pressure sensor according to claim 1, wherein the vibrator is a crystal vibrator formed using SiO ₂ . The diaphragm and the casing are formed using SiO ₂ .
The pressure sensor according to claim 1, wherein the vibrator is a crystal vibrator formed using SiO ₂ . The housing separately forms a bottom surface portion serving as a lid and a side wall portion having a through-hole that is larger than the vibrator and smaller than the ring related to the first electrode, and the side wall portion extends from the periphery of the bottom surface portion. The pressure according to any one of claims 1 to 4, wherein the bottom surface part and the side wall part are joined so as to stand to form a container having a bottomed hole. Sensor. The second electrode is a ground electrode formed in a single plate shape facing at least the vibrator, the first electrode, and the coupling electrode on the other surface of the diaphragm. The pressure sensor according to any one of claims 1 to 5. The pressure sensor according to claim 1, wherein the housing includes a ground electrode that covers all or a part of an outer surface of the housing.

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