JPS63122926A - Piezoelectric pressure detector - Google Patents

Abstract

PURPOSE:To reduce the number of the seal parts relative to the piezoelectric element of a housing member, by forming the bottom wall of a cylindrical body constituting a pressure receiving part in integral relation to the residual part of the cylindrical body. CONSTITUTION:This detector is constituted of a floating type piezoelectric type pressure detector 10, a holding member 20 and a connector. The detector 10 has a cylindrical body 11 formed of a metal material so as to having a C-shaped cross-section. An annular thin wall part 11b is formed to the outer peripheral edge part of the bottom wall 11a of the cylindrical body 11 by forming an annular groove to the bottom wall 11a from the inner surface side thereof. Further, the detector 10 is equipped with the seal member 12 incorporated in the cylindrical body 11, spacers 13, 14 and a piezoelectric element 15. Furthermore, the holding member 20 is formed of a metal material so as to have a longitudinal shape and the annular boss part 21 provided to the leading end part of the member 20 is fixed to the opening part 11c of the cylindrical body 11 by a welding part 21a. Then, the cylindrical body 11 is evacuated or substituted with dry nitrogen.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a pressure detector, and in particular to a piezoelectric pressure sensor that is used to detect various pressures such as engine cylinder pressure by the piezoelectric conversion action of a piezoelectric element. Regarding the detector.

[Prior art]

Conventionally, in this type of piezoelectric pressure detector,
As shown in Publication No. 0-68449, the pressure receiving part is housed in the case so that the pressure receiving surface of the plate-like pressure receiving part is exposed outward from the opening at the tip of the cylindrical case, and the piezoelectric element is The charge generating section is housed in the case so that the charge generating section having the structure overlaps with the back surface of the pressure receiving section, and the base of the case is arranged so that the tip of the cylindrical bushing member overlaps the back surface of the charge generating section. The tip of the bushing member is coaxially fitted into the end opening, and an inner elastic insulating material is inserted from the open end into a large diameter cylindrical part formed at the base of the bushing member.
By sequentially inserting the terminal and the outer elastic insulating material and curling the open end of the large diameter cylindrical portion of the bushing member, each joint portion between the both elastic insulating materials and the terminal and the bushing member is crimped. There is a device in which both the elastic insulating materials electrically insulate the terminal and the bushing member and seal the charge generating portion.

[Problem that the invention seeks to solve]

However, in such a configuration, in addition to sealing the charge generating section by curling as described above, sealing between the outer circumferential surface of the pressure receiving section and the inner circumferential surface of the tip opening of the case, and the sealing of the bushing member. The seal between the outer circumferential surface of the distal end and the inner circumferential surface of the proximal opening of the case must also be achieved by welding or the like. Therefore, this results in extra work, and also causes welding distortion in the pressure receiving portion and a decrease in airtightness within the case. In addition, although the bushing member serves not only as a sealing member for the case but also as a holding member, for example, when installing it in a deep part of the engine, it is necessary to extend the bushing member appropriately. More parts must be added.

Therefore, in view of the above, the present invention provides a piezoelectric pressure sensor that minimizes the sealing part for the piezoelectric element of the housing member that houses the piezoelectric element and has a compact external dimension. This is what I am trying to do.

[Means for solving problems]

In order to solve this problem, the present invention has a structure including a cylinder made of a metal material and having a U-shaped cross section, a spacer made of an insulating elastic material superposed on the bottom wall of the cylinder,
A heat insulating sealing member airtightly fitted into the opening of the cylindrical body and a pair of mutually parallel electrodes are arranged within the cylindrical body so that each electrode is positioned parallel to or at right angles to the peripheral wall of the cylindrical body. a piezoelectric element held between the spacer and the sealing member, an annular thin wall portion is formed on the bottom wall of the cylindrical body, and the inside of the cylindrical body is evacuated or replaced with dry nitrogen. There is a particular thing.

[Effect]

However, by configuring the present invention as described above,
Since the bottom wall of the cylindrical body constituting the pressure receiving part is formed integrally with the remaining part of the cylindrical body, the sealing point inside the cylindrical body from the outside is the sealing member for the opening of the cylindrical body. Only the seal part is included. Therefore, the sealing work inside the cylinder becomes easy, and the degree of sealing inside the cylinder with respect to the outside can be maintained at a sufficiently high level. Also, within the cylinder. In order to create a vacuum around the piezoelectric element or to replace it with nitrogen, it is only necessary to create a vacuum or replace the cylinder with nitrogen, which has a small volume, when the cylinder is sealed by the sealing member. The work or nitrogen replacement work can be easily and easily performed. Further, since the inside of the cylinder is independently sealed as described above, it becomes easy to assemble the amplifier to the pressure detector. Furthermore, since the external shape of the pressure sensor is determined only by the cylinder and has a simple shape, the structure of the holding member required when the pressure sensor is installed in a deep part of the engine, for example, becomes simple.

Furthermore, when the pressure detector according to the present invention detects, for example, the internal cylinder pressure of an engine, the transmission of this internal cylinder pressure to the piezoelectric element via the bottom wall of the cylindrical body and the spacer is caused by the action of the annular thin wall portion. Since the detection is performed with high sensitivity, the cylinder pressure can be detected with high accuracy. In such a case, the interior of the cylinder is maintained in a vacuum state due to the sufficient sealing function of the seal member, so that the atmosphere inside the cylinder will not have an adverse effect on the piezoelectric element under any adverse conditions. I won't give anything. Further, since the sealing portion of the cylinder body is separated from the bottom wall thereof, welding strain at the sealing portion does not affect the bottom wall. Further, since the spacer and the sealing member maintain the piezoelectric element in an insulated state from the cylindrical body force, the piezoelectric element can be properly protected from external heat.

〔Example〕

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a pressure detection device to which the present invention is applied.
This pressure detection device includes a floating piezoelectric pressure detector 10, a holding member 20, and a connector 30, which constitute the main parts of the present invention. Pressure detector 10
As shown in FIGS. 1 and 2, it has a cylindrical body 11, and this cylinder 11 is made of a metal material and has a U-shaped cross section as shown in FIG. , an annular thin wall portion 11b is provided at the outer peripheral edge of the bottom wall 11a of the cylinder 11.
It is formed by forming an annular groove from the inner surface side of the bottom wall 11a, and this annular thin wall portion 11b
This enables elastic deflection of a in the thickness direction.

The pressure detector 10 also includes a seal member 12 assembled in the cylinder 11, spacers 13, 14, and a piezoelectric element 15, and the seal member 12 is made of a sealing metal material such as Kovar iron. The cylindrical body 11 is composed of a disk portion 12a and insulating portions 12d and 12e made of glass material that are hermetically fitted into a pair of through holes 12b and 12C formed in the disk portion 12a. The cylindrical body 11 is airtightly fitted into the opening 11c by welding or the like while the inside of the cylindrical body 11 is evacuated. The spacer 13 is formed into a disk shape from a heat insulating elastic material, and is superposed and fixed to the inner surface of the bottom wall 11a of the cylinder 11. On the other hand, the spacer 14 is made of a heat insulating elastic material like the spacer 13. The seal member 12 is formed into a disk shape, and is superposed and fixed to the inner surface of the seal member 12.

The piezoelectric element 15 has a plate-like element body 1 made of Y-cut crystal.
5a, and electrodes 15b and 15c formed on both surfaces of the element body 15a.As shown in FIG. It is held between both spacers 13 and 14 at both ends.

This means that the piezoelectric element 15 converts the pressure applied to both ends of the element body 15a into an amount of electric charge, and the piezoelectric element 15 converts the pressure applied to both ends of the element body 15a into an amount of electric charge.

15c. Each electrode 15b, 15c of the piezoelectric element 15 is wire-bonded to each lead wire 16°17 at each tip thereof, and the lead wire 16 is connected to the through hole 14a formed in the spacer 14 and the insulation of the sealing member 12. The lead wire 17 is inserted airtightly into the portion 12d and extends outward.
It is inserted airtightly inside and extends outward. This means that both electrodes 15b and 15c of the piezoelectric element 15 are maintained in a floating state.

The holding member 20 is formed of a metal material and has a longitudinal cross-sectional shape as shown in FIG.
The annular boss portion 21 provided at the tip of the annular boss portion 21 is fixed to the opening portion 11c of the cylindrical body 11 inserted therein by welding 21a. Further, both lead wires 16 and 17 extending from the sealing member 12 of the pressure detector 10 are inserted into a stepped insertion hole 22 formed in the axis of the holding member 20 . The connector 30 has a connector main body 31 formed of a metal material and having a T-shaped cross section, and the connector main body 31 is coaxially attached to the base end 23 of the holding member 20 by welding 23c at its disk portion. It is fixed.

A pair of connector pins 33° 33 (only one is shown in FIG. 1) is fitted into the annular insulating portion 32 which is fitted concentrically into the leg portion of the connector main body 31. Each inner end of the connector pin 33.33 has both lead wires 1
The outer ends of 6.17 are each soldered. In addition, in FIG. 1 and FIG. 2, the code|symbol 24 shows a male thread part.

In this embodiment configured in this way, the pressure detector 1
The bottom wall 11a of the cylindrical body 11 constituting the pressure receiving part of the cylindrical body 1 is
Since it is formed integrally with the remaining part of cylindrical body 1
The only part of the cylinder 1 that is sealed to the outside is the part sealed by the seal member 12 to the opening 11c of the cylindrical body 11. Therefore, the sealing work inside the cylindrical body 11 becomes easy.
Moreover, a sufficiently high degree of sealing from the inside of the cylindrical body 11 to the outside can be ensured. In addition, when creating a vacuum around the piezoelectric element 15, it is only necessary to evacuate the inside of the cylinder 11, which has a small volume, when sealing with the sealing member 12 inside the cylinder 11, so this kind of vacuum work can be done easily and easily. Easy to do.

Further, as described above, since the inside of the cylinder 11 is independently sealed, the external shape and dimensions of the pressure detector 10 are determined only by the cylinder 11. Therefore, by appropriately changing the external dimensions of the holding member 20, the pressure sensor 10 can be easily installed, for example, in a deep part of the engine, using only the holding member 20. In this case, since the external shape of the cylinder 11 is simple, the shape of the part of the holding member to be assembled with the cylinder 11 is simple and does not require troublesome machining.

Further, when the pressure detection device configured as in this embodiment is attached to, for example, a cylinder of an engine to detect the pressure inside the cylinder, the bottom wall 11b of the cylinder body 11 in the pressure detector 10 receives the cylinder pressure. It is elastically deflected and applies pressure to the piezoelectric element 15 from one end to the other end through the spacer 13.

Then, the piezoelectric element 15 generates the cylinder pressure as a charge amount in both electrodes 15b and 15c by its piezoelectric conversion action. Therefore, if the amount of charge generated in both electrodes 15b and 15c is taken out from both lead wires 16.17 and both connector pins 33.33 of connector 30, the cylinder pressure can be detected.

In this case, since the annular thin wall portion 11b is formed around the bottom wall 11a of the cylinder 11, the bottom wall 11a is elastically deflected with good response to the cylinder pressure, and serves as a pressure receiving portion with high precision and high sensitivity. It can work. Furthermore, since the inside of the cylinder 11 is in a vacuum state due to the sufficient sealing function of the sealing member 12, no matter how bad the atmosphere is in which the pressure detector 10 is placed, Pressure that would adversely affect the piezoelectric element 15 is not generated in the space inside the cylinder 11. Further, since the welded portion of the cylinder body 11 and the seal member 12 is separated from the bottom wall 11a, the bottom wall 11a is not distorted by the welding and can function as a highly accurate pressure receiving portion. Further, since both spacers 13 and 14 reliably maintain the piezoelectric element 15 in a thermally insulated state from the cylindrical body 11 and the sealing member 12, the external temperature of the pressure detector 10 is transferred as heat to the piezoelectric element 15.
As a result, the adverse effects of external thermal energy on the piezoelectric element 15 can be appropriately removed.

A modification of the first embodiment will be described with reference to FIG. 3. In this modification, a grounded piezoelectric pressure sensor 40 is used in place of the pressure detector lO described in the first embodiment. The pressure sensor 40 is characterized by the fact that the seal member 1 is used in the pressure sensor 10.
The same pressure detector 10 except that a sealing member 41 and a lead terminal 42 are used in place of the lead wires 16 and 17.
It has a similar configuration. The sealing member 41 includes a metal disc portion 41a having a lead terminal 41b, and a metal disc portion 41a having a lead terminal 41b.
The insulating part 41c made of a glass material is fitted airtightly into the through hole 1a, and the opening 11c of the cylindrical body 11 is hermetically sealed by welding or the like while the inside of the cylindrical body 11 is evacuated. It is fitted.

Further, the lead terminal 41b of the sealing member 41 is connected to the spacer 1.
The electrode 15 of the piezoelectric element 15 extends through the tube 4 and into the cylindrical body 11.
This electrode 15C is grounded to the cylindrical body 11 by elastic pressure contact with the electrode 15C. On the other hand, the lead terminal 42 is made of a metal material,
This lead wire 52 has its tip connected to the electrode 1 of the piezoelectric element 15.
The insulating portion 41 of the seal member 41 is elastically pressed against the seal member 5b.
c, and is connected to the connector 30 via the holding member 20 by an appropriate lead wire extending outward in an airtight manner.

Therefore, this modified example configured as described above is different from the first embodiment except that the lead wire connection structure is simplified by changing the pressure sensor from the floating type in the first embodiment to the grounded type. The same effect can be achieved.

Next, a second embodiment of the present invention will be described with reference to FIG. 4. In this second embodiment, in place of the pressure detector 10 described in the first embodiment, a floating piezoelectric type Its structural feature lies in the adoption of the pressure detector 50. This pressure detector 50 has a cylindrical body 51, which is similar to the cylinder body 1 described in the first embodiment.
Similar to 1, it is made of a metal material and has a U-shaped cross section.

Further, an annular thin wall portion 51b is formed in an annular portion of the circumferential wall of the cylinder body 51 adjacent to the bottom wall 51a by forming an annular groove from the inner surface side of the cylinder body 51. 51b allows elastic deviation of the bottom wall 51a in the thickness direction thereof.

The pressure detector 50 also includes a seal member 52 assembled into the cylindrical body 51. The sealing member 52 has a spacer 53, 54 and a piezoelectric element 55, and the sealing member 52 is constructed in the same manner as the sealing member 12 described in the first embodiment. The body 51 is airtightly fitted by welding or the like while the inside of the body 51 is evacuated. In such a case, the disc part 5
2a and the respective insulating parts 52b and 52C correspond to the disk part 12a and the respective insulating parts 12b and 12G, respectively. Spacer 5
3 is made of an elastic material having heat insulating and electrically insulating properties and has the cross-sectional shape shown in FIG.
On the other hand, the spacer 54 is formed into a disk shape from the same material as the spacer 53, and is superimposed and fixed on the inner surface of the sealing member 52. There is.

The piezoelectric element 55 has a plate-like element body 5 made of X-cant crystal.
5a, and electrodes 55b and 55C formed on both surfaces of the element body 55a, and as shown in FIG. Both spacers 53. through pieces 56a and 56b.
It is held between 54. This means that the piezoelectric element 55 converts the pressure applied to both electrodes 55b, 55c into an amount of charge, which is generated in each electrode 55b, 55c.

Each lead wire 57.5 is attached to the end of each conductive piece 56a, 56b.
8 are welded at each tip thereof, and the lead wire 57 is connected to the spacer 54 and the insulating part 52b of the seal member 52.
The lead wire 58 is inserted into the spacer 54 and the insulating part 52 of the sealing member 52 in an airtight manner and extends outward.
It is hermetically inserted into C and extends outward. This means that both electrodes 55b and 55c of the piezoelectric element 55 are maintained in a floating state. Note that each lead wire 57, 58 passes through the holding member 20 and is connected to each connector pin 33, 33 of the connector 30, instead of each lead wire 16, 17 described in the first embodiment.

In the second embodiment configured as above, the bottom wall 51a of the cylinder 51 constituting the pressure receiving part of the pressure detector 50 is formed integrally with the remaining part of the cylinder 51. The sealing location inside the cylinder 51 to the outside is the same as the cylinder 51.
Only the seal member 52 seals the opening 51c.

Therefore, the sealing work inside the cylindrical body 5 becomes easy, and a sufficiently high degree of sealing inside the cylindrical body 51 to the outside can be ensured. In addition, when creating a vacuum around the piezoelectric element 55, it is only necessary to create a vacuum inside the cylinder 51, which has a small volume, when sealing with the sealing member 52 inside the cylinder 51. This makes this type of vacuum work easy and convenient. Easy to do. Also,
As described above, since the inside of the cylindrical body 51 is sealed independently, the external shape and external dimensions of the pressure detector 50 are
It is determined only by the cylindrical body 51. Therefore, the holding member 20
By appropriately changing the external dimensions of the holding member 2,
By using only 0, the pressure sensor 5° can be easily installed, for example, in a deep part of the engine. In such a case, since the outer shape of the cylinder 51 is simple, the cylinder 5 of the holding member 20
The shape of the part to be assembled with 1 is simple and does not require complicated machining.

Furthermore, when the pressure detection device configured as in the second embodiment is attached to a cylinder of an engine to detect the pressure inside the cylinder, the bottom wall 51b of the cylindrical body 51 in the pressure detection 850 receives the pressure inside the cylinder. The piezoelectric element 55 is elastically deflected and pressure is applied to the piezoelectric element 55 from its electrode 55b to its electrode 55c via the spacer 53. Then, the piezoelectric element 55 transforms the cylinder pressure into a charge amount by its piezoelectric conversion action, and converts both types of tfi5 into electric charges.
5 b.

55c. Therefore, both these electrodes 55b, 5
If the amount of electric charge generated at 5c is extracted from both lead wires 57 and 58 and both connector pins 33 and 33 of connector 30, the cylinder pressure can be detected.

In this case, since the annular thin wall portion 51b is formed around the bottom wall 51a of the cylinder 51, the bottom wall 51a is elastically deflected with good response to the cylinder pressure, and serves as a pressure receiving portion with high precision (high sensitivity). Furthermore, since the interior of the cylinder 51 is in a vacuum state due to the sufficient sealing function of the seal member 52, the pressure sensor 50 can be placed in any adverse atmosphere. Even if the piezoelectric element 55 is closed, pressure that would adversely affect the piezoelectric element 55 is not generated in the space inside the cylinder 51.Furthermore, the welded portion of the cylinder 51 with the sealing member 52 is separated from the bottom wall 51a. Therefore, the bottom wall 51a is not distorted by the welding and can function as a highly accurate pressure receiving part.In addition, both spacers 53 and 54 ensure that the piezoelectric element 55 is insulated from the cylinder 51 and the seal member 52 and is electrically isolated. Since the insulated state is maintained, the external temperature of the pressure detector 50 is not transmitted as heat to the piezoelectric element 55, and the cylindrical body 51
No charge flows into the piezoelectric element 55, and as a result, the adverse effects of external thermal energy and electrical energy on the piezoelectric element 55 can be appropriately removed.

FIG. 5 shows a modification of the second embodiment, in which a ground-type pressure detector 60 is used in place of the pressure detector 50 described in the second embodiment. has its compositional characteristics. This pressure detector 60 has a cylindrical body 61, which is made of a metal material and has a U-shaped cross section, similar to the cylinder body 51 described in the second embodiment. There is. Further, an annular thin wall portion 61b is formed in an annular portion of the peripheral wall of the cylinder body 61 adjacent to the bottom wall 61a by forming an annular groove from the inner surface side of the cylinder body 61. allows elastic deflection of the bottom wall 61a in the thickness direction.

Further, the pressure detector 60 includes a seal member 62, a spacer 63, a conductive member 64, and the piezoelectric element 55 described in the second embodiment, which are assembled into the cylinder body 61. Ring 62a made of sealing material such as Kovar iron
and an insulating part 62b made of a heat insulating glass material attached to one surface of the ring 62a and the hollow part in a T-shape, and when the inside of the opening 61c of the cylinder 61 is evacuated, the opening 61c is closed. It is hermetically fitted to the portion 61c by welding or the like.

The spacer 63 is made of an electrically insulating elastic material and has a T-shaped cross section.
3a is fitted into the center of the bottom wall 61a of the cylindrical body 61 as shown in FIG. The conductive member 64 has a T-shaped cross section,
The leg portion 64a of the conductive member 64 extends outwardly in an airtight manner through the insulating portion 62b of the seal member 62, and is connected to the connector 30 via the holding member 20 by a suitable lead wire.

Further, the disk portion 64b of the conductive member 64 is seated on the insulating portion 62b, and together with the disk portion 63b of the spacer 63, the piezoelectric element 5
Holding 5. Therefore, this modified example configured as described above is different from the second embodiment except that the lead wire connection structure is simplified by changing the pressure sensor from the floating type in the second embodiment to the grounded type. Substantially the same effects can be achieved.

FIG. 6 shows another modification of the first or second embodiment, in which an amplifier 70 is attached to the holding member 20 instead of the connector 30. There are structural characteristics. The amplifier 70 has a cylindrical body 71, and one end of the cylindrical body 71 is coaxially and airtightly fitted to the base end portion 23 of the holding member 20 by welding or the like. An amplifying section 72 is housed within the cylinder 71, and the amplifying section 72 is connected at its input terminal to a lead wire extending from the pressure detector 10 or 50 into the holding member 20. .

At the other end of the cylinder 71, a cylinder 73 is coaxially and airtightly fitted to the other end of the cylinder 72 by welding or the like.
A disc-shaped sealing member 74 is hermetically fitted into each fitting portion of both cylindrical bodies 71, 73. A plurality of feedthrough capacitors 75 to 75 for noise prevention are hermetically fitted into the sealing member 74, and each of these feedthrough capacitors 75 to
75 is connected at one end to each output terminal of the amplifying section 72, respectively. In addition, each feedthrough capacitor 75 to 75
The other end is connected to the connection end of each lead wire 76 to 76, and each of these lead wires 76 to 76 is connected to the cylindrical body 73.
It extends outward from the other end.

Therefore, in this modified example configured in this way, the inside of the pressure detector 10 or 50 is completely airtight from the outside in a vacuum state independently as described in the first or second embodiment. Therefore, when assembling the amplifier 70 to the holding member 20, the amplifier 70 can be assembled without the troublesome work of evacuating the inside of the amplifier 70 together with the inside of the pressure detector. The mounting work can be easily performed, and the original function and durability of the pressure detector itself will not be degraded by the mounting of the amplifier 70.

In carrying out the present invention, the inside of each pressure detector described in each of the above embodiments and modifications is not limited to being in a vacuum state, and may be replaced with dry nitrogen, for example.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a schematic cross-sectional view of a pressure detection device according to the present invention;
2nd TI! J is a cross-sectional view of the pressure detector in FIG. 1, FIG. 3 is a cross-sectional view showing a modification of the same pressure sensor, FIG. 4 is a cross-sectional view of main parts showing another embodiment of the present invention, and FIG. is a cross-sectional view showing a modification of the pressure detector in FIG. 4, and FIG. 6 is a cross-sectional view of essential parts showing another modification of each of the embodiments. Explanation of symbols 10.40.50.60...Pressure detector, 11°51
．． 61...Cylinder, 1lal sia, 61a...
Bottom wall, llb, 51b, 61b... annular thin wall portion, 11
c, 51 c, 61 c... opening, 12
．． 41.52.62...Seal member, 13°53.6
3... Spacer, 15.55... Piezoelectric element.

Claims (1)

[Claims] A cylindrical body made of a metal material and having a U-shaped cross section, a spacer made of a heat insulating elastic material that is polymerized on the bottom wall of the cylindrical body, and a heat insulating seal that is airtightly fitted into the opening of the cylindrical body. a piezoelectric element having a member and a pair of electrodes parallel to each other and sandwiched between the spacer and the sealing member within the cylinder so that each electrode is positioned parallel to or at right angles to the peripheral wall of the cylinder. A piezoelectric pressure sensor comprising: an annular thin wall portion formed on the bottom wall of the cylindrical body; and the inside of the cylindrical body is evacuated or replaced with dry nitrogen.