Pressure detector with improved deterioration protection

Abstract

A pressure detector includes a first board with a first pressure inlet, a first groove, and a first board electrode; a second board with a second pressure inlet, a second groove, and a second board electrode; and a sensing unit arranged therebetween with a diaphragm. The first groove is in communication with the first pressure inlet so as to prevent the formation of a closed space between the first board and the diaphragm when they contact with each other. The second groove is in communication with the second pressure inlet so as to prevent the formation of a closed space between the second board and the diaphragm when they contact each other.

Claims

1. A pressure detector comprising: a sensing unit comprising a plate-shaped diaphragm, a first diaphragm electrode provided on one surface of the diaphragm, a second diaphragm electrode provided on the other surface of the diaphragm, and a bonding portion provided on a peripheral portion of the diaphragm; a first board comprising a first board body shaped in a plate and bonded to one surface of the bonding portion of the sensing unit and a first board electrode provided on a surface of the first board body facing the first diaphragm electrode; and a second board comprising a second board body shaped in a plate and bonded to the other surface of the bonding portion of the sensing unit and a second board electrode provided on a surface of the second board body facing the second diaphragm electrode, wherein the first board body comprises a first pressure inlet penetrating through the first board body and a first groove that is a groove recessed in the surface of the first board body facing the first diaphragm electrode, the first groove being in communication with the first pressure inlet, and the second board body comprises a second pressure inlet penetrating through the second board body and a second groove that is a groove recessed in the surface of the second board body facing the second diaphragm electrode, the second groove being in communication with the second pressure inlet.

2. The pressure detector according to claim 1, wherein the first groove is covered with the first board electrode, and the second groove is covered with the second board electrode.

3. The pressure detector according to claim 1, wherein the first groove linearly extends from the first pressure inlet to a portion of the first board bonded with the bonding portion, and the second groove linearly extends from the second pressure inlet to a portion of the second board bonded with the bonding portion.

Description

BRIEF EXPLANATION OF DRAWINGS

(1) FIG. 1 is a cross-sectional view schematically showing a pressure detector according to an exemplary embodiment.

(2) FIG. 2 is another cross-sectional view schematically showing the pressure detector according to the exemplary embodiment.

(3) FIG. 3 is a perspective view schematically showing a first board according to the exemplary embodiment.

(4) FIG. 4 is a cross-sectional view schematically showing a typical pressure detector.

(5) FIG. 5 is another cross-sectional view schematically showing the typical pressure detector.

DESCRIPTION OF EMBODIMENT(S)

Exemplary Embodiment

(6) An exemplary embodiment of the invention will be described below with reference to the attached drawings.

(7) FIGS. 1 and 2 are cross-sectional views schematically showing a pressure detector 1 according to the exemplary embodiment.

(8) As shown in FIGS. 1 and 2, the pressure detector 1 according to the exemplary embodiment is a capacitance pressure detector, which includes a first board 2, a second board 3, and a sensing unit 4.

(9) First Board 2

(10) FIG. 3 is a perspective view schematically showing the first board 2. It should be noted that the perspective view of FIG. 3 shows the first board 2 seen from an inner side (the side facing the sensing unit 4) of the pressure detector 1. It should also be noted that the second board 3 is symmetric with the first board 2 across the sensing unit 4.

(11) As shown in FIGS. 1 to 3, the first board 2 includes a first board body 21 and a first board electrode 22.

(12) The first board body 21 is a plate-shaped component made of an insulating material (e.g. glass). The first board electrode 22, which is configured to generate capacitance between the sensing unit 4 and the first board electrode 22, is provided on a surface of the first board body 21 facing the sensing unit 4. In the exemplary embodiment, the first board electrode 22 is a metal vapor deposition film patterned by photolithography.

(13) Further, a first pressure inlet 23 penetrating through the first board body 21 is provided at the center of the first board body 21. In the exemplary embodiment, the first pressure inlet 23, which is trapezoidal in cross section, is tapered from an outer side to the inner side.

(14) Further, in the exemplary embodiment, a first groove 24 in communication with the first pressure inlet 23 is formed on the surface of the first board body 21 facing the sensing unit 4. Specifically, the first groove 24 linearly extends from the first pressure inlet 23 to a portion bonded with a later-described bonding portion 44 of the sensing unit 4. The first groove 24 is formed in the first board body 21 through some kind of processing (e.g. etching by photolithography), for instance.

(15) In the exemplary embodiment, the first pressure inlet 23 and the first groove 24 are covered with the first board electrode 22.

(16) Second Board 3

(17) As described above, the second board 3, which is symmetric with the first board 2 across the sensing unit 4 as described above, includes a second board body 31 and a second board electrode 32.

(18) The second board body 31 is a plate-shaped component made of an insulating material (e.g. glass). The second board electrode 32, which is configured to generate capacitance between the sensing unit 4 and the second board electrode 32, is provided on a surface of the second board body 31 facing the sensing unit 4. In the exemplary embodiment, the second board electrode 32 is a metal vapor deposition film patterned by photolithography.

(19) Further, a second pressure inlet 33 penetrating through the second board body 31 is provided at the center of the second board body 31. In the exemplary embodiment, the second pressure inlet 33, which is trapezoidal in cross section, is tapered from an outer side to the inner side.

(20) Further, in the exemplary embodiment, a second groove 34 in communication with the second pressure inlet 33 is provided on the surface of the second board body 31 facing the sensing unit 4. Specifically, the second groove 34 linearly extends from the second pressure inlet 33 to the portion bonded with the later-described bonding portion 44 of the sensing unit 4. The second groove 34 is formed in the second board body 31 by some kind of processing (e.g. etching by photolithography), for instance.

(21) In the exemplary embodiment, the second pressure inlet 33 and the second groove 34 are covered with the second board electrode 32.

(22) Sensing Unit 4

(23) The sensing unit 4 is a component made of an electro-conductive silicon material of a predetermined thickness, a central part of which is thinned by a processing (e.g. etching by photolithography) to form a diaphragm 41. Specifically, the sensing unit 4 includes the diaphragm 41, a first diaphragm electrode 42 defined on a surface of the diaphragm 41 facing the first board 2, and a second diaphragm electrode 43 defined on another surface of the diaphragm 41 facing the second board 3. With this arrangement, capacitance is generated between the first board electrode 22 of the first board 2 and the first diaphragm electrode 42 of the sensing unit 4, and capacitance is generated between the second board electrode 32 of the second board 3 and the second diaphragm electrode 43 of the sensing unit 4. The pressure detector 1 according to the exemplary embodiment is configured to detect a change in the capacitance between the first and second board electrodes and first and second diaphragm electrodes to detect a pressure applied on the diaphragm 41.

(24) A thickened peripheral portion of the diaphragm 41 of the sensing unit 4 defines the bonding portion 44 bonded with the first board 2 and the second board 3. Specifically, the first board body 21 of the first board 2 is bonded to one surface of the bonding portion 44 of the sensing unit 4, and the second board body 31 of the second board 3 is bonded to the other surface of the bonding portion 44 of the sensing unit 4 in the exemplary embodiment.

(25) It should be noted that the sensing unit 4 is not necessarily configured as described above. For instance, the sensing unit 4 is optionally made of insulative silicon or the like and is optionally provided with the first diaphragm electrode 42 on one side of the diaphragm 41 facing the first board 2, and the second diaphragm electrode 43 on the other side of the diaphragm 41 facing the second board 3. In other words, it is only necessary for the sensing unit 4 to be provided with the first diaphragm electrode 42 on the side of the diaphragm 41 facing the first board 2 and the second diaphragm electrode 43 on the side of the diaphragm 41 facing the second board 3.

(26) Operation of Sensing Unit 4

(27) Next, an operation of the sensing unit 4 will be described below.

(28) When an excessive pressure or negative pressure is applied upward (in the figure) on the diaphragm 41 of the pressure detector 1 shown in FIG. 1, the diaphragm 41 is brought into contact with the first board electrode 22 provided on the first board body 21 as shown in FIG. 2. The diaphragm 41 is thus not excessively deformed, so that a damage on the diaphragm 41 is restrained.

(29) Further, in the exemplary embodiment, the first board body 21 is provided with the first groove 24, which is in communication with the first pressure inlet 23, on the surface facing the first diaphragm electrode 42. Accordingly, the first groove 24 is kept in communication with the first pressure inlet 23 even when the diaphragm 41 and the first board electrode 22 are in contact as shown in FIG. 2, so that a closed space is restrained from being formed between the first diaphragm electrode 42 and the first board electrode 22. Thus, this restraint of the formation of the closed space can avoid the tight contact of the diaphragm 41 and the first board electrode 22 and consequent failure in immediate separation therebetween that are caused by the pressure difference between the closed space and an outside generated when the excessive pressure or negative pressure applied on the diaphragm 41 is released.

(30) Similarly, the second groove 34 in communication with the second pressure inlet 33 is provided on the surface of the second board body 31 facing the second diaphragm electrode 43 in the exemplary embodiment. Accordingly, the tight contact of the diaphragm 41 and the second board electrode 32 and consequent failure in immediate separation therebetween, which are caused by the pressure difference between the closed space and an outside generated when the excessive pressure or negative pressure applied on the diaphragm 41 is released, can be prevented.

Advantage(s) of Exemplary Embodiment

(31) The following advantages can be achieved by the above-described present exemplary embodiment.

(32) (1) In the exemplary embodiment, the first board body 21 is provided with the first groove 24, which is in communication with the first pressure inlet 23, on the surface facing the first diaphragm electrode 42. Thus, even when an excessive pressure or negative pressure is applied on the diaphragm 41 through the first pressure inlet 23 or the second pressure inlet 33 to bring the first diaphragm electrode 42 of the diaphragm 41 into contact with the first board electrode 22 of the first board 2, the closed space between the first diaphragm electrode 42 and the first board body 21 provided with the first board electrode 22 can be prevented from being formed. Accordingly, failure in immediate separation of the first diaphragm electrode 42 from the first board electrode 22 and consequent deterioration in responsiveness can be restrained.

(33) Similarly, in the exemplary embodiment, since the second groove 34 in communication with the second pressure inlet 33 is formed on the surface of the second board body 31 facing the second diaphragm electrode 43, the closed space between the second diaphragm electrode 43 and the second board body 31 provided with the second board electrode 32 can be prevented from being formed. Accordingly, failure in immediate separation of the second diaphragm electrode 43 from the second board electrode 32 and consequent deterioration in responsiveness can be restrained.

(34) Further, in the exemplary embodiment, since the presence of a plurality of pressure inlets in each of the first board 2 and the second board 3 is not required, decrease in an effective electrode area by the plurality of pressure inlets and consequent deterioration in detection sensitivity can be restrained.

(35) In addition, in the exemplary embodiment, the presence of the plurality of pressure inlets is not required, a sufficient bonding area is ensured even when the pressure detector 1 is miniaturized.

(36) (2) In the exemplary embodiment, since the first groove 24 and the second groove 34 of the first board 2 and the second board 3, respectively, are covered with respective electrodes, the parts corresponding to the first groove 24 and the second groove 34 are also effective usable. Accordingly, decrease in effective electrode area due to the presence of the first groove 24 and the second groove 34 can be restrained.
(3) Since the first groove 24 and the second groove 34 of the exemplary embodiment are linearly formed, the formation of the first groove 24 and the second groove 34 is easy.

(37) Modifications

(38) It should be noted that the present invention is not limited to the above-described embodiment but includes modifications, improvements, and the like as long as an object of the invention can be achieved.

(39) The first groove 24, which is a single groove formed in the first board body 21 in the exemplary embodiment, is not necessarily configured as described in the exemplary embodiment. For instance, the first groove is optionally a plurality of radial grooves formed in the first board body.

(40) Similarly, the second groove 34, which is a single groove formed in the second board body 31 in the exemplary embodiment, is not necessarily configured as described in the exemplary embodiment. For instance, the second groove is optionally a plurality of radial grooves formed in the second board body.

(41) Further, the groove is optionally formed in only one of the first board body and the second board body.

(42) The first groove 24, which is a linear groove in the exemplary embodiment, is not necessarily configured as described in the exemplary embodiment. For instance, the first groove is curved in some embodiments. In other words, the first groove is configured in any manner as long as the first groove serves as a flow path capable of restraining the formation of the closed space between the first diaphragm electrode and the first board body when the first diaphragm electrode is in contact with the first board electrode.

(43) Similarly, the second groove 34, which is a linear groove in the exemplary embodiment, is not necessarily configured as described in the exemplary embodiment. For instance, the second groove is curved in some embodiments. In other words, the second groove is configured in any manner as long as the second groove serves as a flow path capable of restraining the formation of the closed space between the second diaphragm electrode and the second board body when the second diaphragm electrode is in contact with the second board electrode.

(44) The first pressure inlet 23, which is trapezoidal in cross section and is tapered from the outer side to the inner side in the exemplary embodiment, is not necessarily configured as described in the exemplary embodiment. For instance, the first pressure inlet is rectangular in cross section in some embodiments.

(45) Similarly, the second pressure inlet 33, which is trapezoidal in cross section and is tapered from the outer side to the inner side in the exemplary embodiment, is not necessarily configured as described in the exemplary embodiment. For instance, the second pressure inlet is rectangular in cross section in some embodiments.

(46) The first pressure inlet 23 and the first groove 24, which are covered with the first board electrode 22 in the exemplary embodiment, are not necessarily configured as described in the exemplary embodiment. For instance, the first pressure inlet and/or the first groove is not covered with an electrode in some embodiments of the invention.

(47) Similarly, the second pressure inlet 33 and the second groove 34, which are covered with the second board electrode 32 in the exemplary embodiment, are not necessarily configured as described in the exemplary embodiment. For instance, the second pressure inlet and/or the second groove is not covered with an electrode in some embodiments of the invention.