JPS6034687B2 - Pressure electronic conversion element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure-electric transducer, and particularly to a capacitive pressure-electric transducer used while being connected to an electric circuit.

It is generally necessary to know the pressure of a liquid or gas for measurement or control purposes, and there is now a need to provide a device for sensing the pressure of a liquid or gas, particularly in prime movers and other mechanical devices.

Various pressure measuring devices have been proposed in the past in response to such needs. A piezo element having a piezo effect is used as one type of these devices. When a pressure to be measured is applied to a device having a piezo element, a voltage proportional to the applied pressure is generated from the device. A device having such a piezo element can measure pressure, but this pressure measurement is only used to measure the amount of change in pressure and is not used to measure static pressure. The device suffers from relatively low sensitivity and low accuracy. A strain gauge element is known as another element used for pressure measurement.

A strain gauge element is a resistance element whose resistance value changes depending on the applied pressure, and this strain gauge element can measure static pressure. However, this element has the drawback of being able to obtain only a small change in output in response to a large change in pressure, and also having low stability against changes in temperature and over time. In addition to the above-mentioned elements, capacitive elements whose electric capacity changes with changes in pressure are known. This capacitive element has better stability over temperature and time than the previously described elements, and has better sensitivity than strain gauge elements. However, this type of device requires an extremely complicated manufacturing process;
Therefore, it is extremely expensive. Furthermore, since this type of element is generally obtained by combining a plurality of different materials, it has the disadvantage of low reproducibility due to different coefficients of thermal expansion. This type of capacitive element is disclosed in US Pat. No. 2,999 No. 5, US Pat. The present invention has been made in view of the above-mentioned conventional problems, and its main purpose is to provide a capacitive pressure-electric transducer that is easy to manufacture and inexpensive. Another object of the present invention is to provide a capacitive pressure-electric transducer that has a high degree of accuracy and stability over a long period of time and over a wide temperature range.

Still another object of the present invention is to provide a capacitive pressure-electric transducer having good sensitivity to changes in pressure. According to the invention, the above objects and other objects are achieved by providing a pair of electrically non-conductive members having essentially zero hysteresis characteristics, at least one of the electrically non-conducting members being constituted by an elastic diaphragm; a pair of non-conductive members, the opposing surfaces of which are substantially flat over their entire surface; a sealing portion comprising a glass frit at the outer periphery of the opposing surfaces of the pair of non-conductive members; are provided, whereby the central portions of the opposing surfaces of the pair of non-conductive members, other than the outer periphery green, are fixed in a parallel relationship with a certain space between them: a flat layer of electrically conductive material is affixed to each of the opposing surfaces; an outer conductive layer portion extending outwardly from the center conductive layer portion of the opposing surface; This is achieved by providing a piezoelectric transducer element characterized in that a diaphragm forms an element whose capacitance changes substantially by deflection relative to the other of the non-conductive members.

When pressure is applied to the non-conductive member in the element of the present invention,
The non-conductive member deforms, resulting in a change in the capacitance of the piezoelectric transducer.

This change in capacitance is detected by an electric circuit, and the indicated value corresponds to the value of pressure applied to this capacitive pressure-electric transducer. Hereinafter, with reference to the drawings, a preferred embodiment of the present invention (FIG. 3) and first to fifth aspects (FIG. 1, 2, 4 to 8) will be explained.

First, with reference to FIGS. 1 and 2, a first aspect that can be referred to when constructing a pressure-electric conversion element according to the present invention will be described.

The capacitive piezoelectric transducer of the first embodiment shown in FIGS. 1 and 2 includes two disks 2 and 4 made of non-conductive or insulating material.

A flat layer of conductive material (conductive layer) is fixed to each of the surfaces of these two disks 2 and 4 that face each other with a space between them, and this conductive layer is connected to the central conductive layer portions 6 and 8. outer conductive layer portions 10 and 12. The central conductive layer portions 6 and 8 have a substantially circular shape. Outer conductive layer section 10
and 12 form conductive paths extending from the central conductive layer portions 6 and 8 towards the outer ends of the disks 2 and 4. External leads 14 and 16 are connected to the outer conductive layer parts 10 and 12, respectively, to maintain electrical connection.
One surface of both disks 2 and 4 is connected to a spacer 18 made of a non-conductive or insulating material to form a capacitive piezoelectric transducer 21, and the central conductive layer portions 6 and 8 are opposed to each other and are formed using a suitable material. separated by a gap.

In practice, disks 2 and 4 and spacer 18 may be formed from any non-conductive material, but these materials are preferably selected so that each part is formed from the same or substantially similar material.

In a preferred embodiment, the non-conductive or insulating material is selected from alumina, fused silica or a glass such as Pyrex, which has near zero hysteresis characteristics.
"Zero hysteresis" or "zero hysteresis" used in the present invention
The term "near drop hysteresis" means that the value is minimal or negligible in the particular state of use. Additionally, the guiding layer can be formed by plating, etching, sputtering, screen printing, baking, or other various commonly used means. Also, in devices where absolute pressure measurements are required, the gap between the central conductive layer parts 6 and 8 forming the counter electrodes of the capacitor is evacuated. Furthermore, the disks 2 and 4 can be coupled and fixed to the baser 18 in the following manner, for example. That is, after a small amount of glass frit (vitreous pottery raw material) is interposed between the disks 2 and 4 and the spacer 18, the space between each part is heated to melt the glass frit while they are combined as a pressure-electric transducer. Seal it. In a preferred embodiment, the conductive layer is screen printed onto the disks 2 and 4 using a conductive paste, and a small amount of sealing material is inserted between the disks 21 and 4 and the spacer 18. The pressure-electric conversion element assembled in this manner is heated to complete the element. This type of element provides the following effects.

That is, when pressure is applied to the capacitive pressure-electric conversion element 21, one or both disks act as a diaphragm, and the gap between the disks changes. As the disk deforms, the capacitance of the element changes. In this way, the capacitance changes as a function of pressure, and the element can be configured to correspond to a particular pressure applied to the element at any value of its capacitance. This change in capacitance can be measured by electrical circuits of various configurations well known in the art. A conventionally well-known AC Wheatstone reactance bridge circuit is suitable as an example of such a device. FIG. 3 shows a preferred embodiment of the capacitive pressure-electric transducer according to the present invention.

The embodiment of FIG. 3 is similar to the embodiment shown in FIGS. 1 and 2, so only a cross-sectional view thereof is shown. In FIG. 3, parts similar to those in FIGS. 1 and 2 are designated by the same reference numerals. In FIG. 3, substantially circular central conductive layer portions 6 and 8 are provided on disks 2 and 4. In FIG.

Furthermore, outer conductive layer portions 10 and 12 are provided on the disks 2 and 4 to form conductive paths extending from the central conductive layer portions 6 and 8 toward the outer ends of the disks 2 and 4, respectively. There is. Similarly, external leads 14 and 16 are connected to the outer conductive layer portions 10 and 12, respectively. The capacitive pressure-electric transducer 31 according to this embodiment is assembled as follows.

A glass frit 32 is disposed close to the periphery of one or both of the surfaces of the disks 2 and 4, which have previously been provided with the central conductive layer portions 6 and 8. Thereafter, the disc 2 is placed on top of the disc 4 such that the central conductive layer portion 6 faces the central conductive layer portion 8 and is separated by a gap. The capacitive pressure-electric transducer 31 that has been assembled in its initial state is heated, and the glass frit 32 is melted.
When glass frit 32 is melted, not only are disks 2 and 4 bonded together, but a seal is formed between them around their circumference. Further, in this embodiment, any type of spacer such as the spacer 18 in the embodiments of FIGS. 1 and 2 is not required, and as a result, the number of parts constituting the pressure-electric conversion element 31 can be reduced. The material for the disks 2 and 4 shown in FIG. 3 is a material with essentially zero hysteresis and non-conductive properties, such as alumina, fused silica, glass such as Pyrex.

Furthermore, the piezoelectric transducer 31 is preferably formed by screen printing and baking a conductive layer onto the disks 2 and 4 using a conductive paste, and then a glass frit is provided around one or both of the disks 2 and 4. and the disc 2 is placed on top of the disc 4 and, after being thus assembled, is formed by heating. FIG. 4 shows a second embodiment that can be referred to when constructing a capacitive pressure-electric transducer according to the present invention.

The second embodiment of FIG. 4 is similar to the first embodiment shown in FIGS. 1 and 2, so only a cross-sectional view thereof is shown. Fourth
In the figures, members similar to those in the embodiments of FIGS. 1 and 2 are given the same reference numerals. In FIG. 4, a capacitive piezoelectric transducer 41 of this embodiment includes two non-conductive plates which, when arranged in combination, form a gap 46 having a substantially circular cross section between the plates 42 and 44. It is configured to be formed between.

Circular central conductive layer portions 6 and 8 are provided on the circular surfaces of plates 42 and 44. Furthermore, outer conductive layer portions 10 and 12 are provided on each plate 42, 44, respectively, thereby providing a central conductive layer portion 6 towards the outer ends of the plates 42, 44.
A conductive path extending from and 8 is formed. External leads 14 and 16 are connected to the outer conductive layer portions 10 and 12, respectively. Capacitive pressure-electric conversion element 4 of this embodiment
1 is assembled as follows.

First, a small amount of glass frit is attached to the inner peripheral surface of the plate 44. The plate 42 then connects the central conductive layer section 6 to the central conductive layer section 8.
They are arranged on the plate 44 so as to face each other. The capacitive pressure electric transducer 41 assembled in this initial state is heated and the glass frit is melted. Once the glass frit is melted, the plates 42 and 44 are bonded to each other by a thin glass seal formed around them. . This embodiment also does not require any type of smoother, such as the smoother 18 in the embodiment of FIG. Moreover, only a very thin glass seal is formed between the two sheets 42 and plate 44. In this embodiment, the seal thickness is 0.0254
It is set in a range from microns to 0.0254 millimeters (1 microinch to 1 milliinch). As with other embodiments, plates 42 and 44 are preferably comprised of a non-conductive material with fog hysteresis, such as alumina, fused silica or glass such as Pyrex. Furthermore, in a preferred embodiment of the pressure-electric transducer element 41, conductivity is achieved by using conductive paste on the plates 42 and 44.
A small amount of glass frit is then placed near the periphery of plate 44, plate 42 is then placed on top of plate 44, and the piezoelectric transducer thus assembled is heated. The glass frit is melted to form a seal. Furthermore, the shapes of plates 42 and 44 can be configured in a variety of shapes with a gap 46 formed between their inner surfaces.

Plates 42 and 44 may be thicker at one end than the other, as shown in FIGS. 4 and 5, or may be dished or concave, or may be curved on at least one of the plates. It can also have a formed shape. FIG. 5 shows a third embodiment that can be referred to when configuring the pressure-electric conversion element according to the present invention.

The embodiment of FIG. 5 is similar to the embodiments shown in FIGS. 1, 2, and 4, so only a cross-sectional view thereof is shown.
In FIG. 5, parts similar to other embodiments are designated by the same reference numerals. In FIG. 5, plates 42 and 44, central conductive layer sections 6 and 8, and outer conductive layer sections 10 and 12 are formed substantially as described above.

External leads 52 and 54 are provided on the outer conductive layer portions 10 and 12.
is connected. To assemble this capacitive pressure-electric transducer 51, the plates 42 and 44 are arranged so that the central conductive layer parts 6 and 8 are adjacent to each other and face each other, and the external leads 52 and 54 are arranged along the periphery of the plate 44. It is bent and arranged so that an electrical connection point can be made from the bottom surface of the plate 44.

A glass frit 56 is then placed on the outer edge of the disk and heated to melt the glass frit.
In this embodiment, the external leads 52 and 54 extend downwardly along the sides of the plate 44, and the external leads 52 and 54
It is clear that the can be soldered to the outer conductive layer parts 10 and 12 laterally. Square or rectangular plates are acceptable as a variant of this embodiment. FIG. 6 shows a fourth embodiment that can be referred to when constructing a pressure-electric transducer according to the present invention.

The embodiment of FIG. 6 is similar to the embodiment shown in FIG. 4, so only a cross-sectional view thereof is shown. In FIG. 6, members similar to other embodiments are given the same reference numerals. In FIG. 6, a through hole 62 is provided in the plate 42, and the inside of the capacitive pressure-electric transducer 61 is communicated with the pressure medium around its outer periphery.

An external medium is passed through the through hole 62 through a filter 64. This configuration can prevent dust from entering the gap between the plates 42 and 44. This capacitive pressure-electric transducer 61 has the structure and function of the fourth
It can be provided exactly like the element 41 shown in the figure. Furthermore, in practice, the external pressure medium can be air, oil or other media in various applications. FIG. 7 shows a fifth embodiment that can be referred to when configuring the pressure-electric conversion element according to the present invention.

The embodiment of FIG. 7 is similar to the embodiment of FIG. 4, so only its cross section is shown. In FIG. 7, members similar to other embodiments are given the same reference numerals. The capacitive pressure electric transducer 71 shown in FIG. 7 includes two plates 42 and 72 made of non-conductive members, and these plates 42 and 72 form a circle with the plate 42 when placed at predetermined positions relative to each other. A gap 46 having a substantially circular cross section is formed between the columnar plate 72 and the columnar plate 72 .

The cylindrical plate 72 is configured to be substantially thicker than the plate 42. On the inner surfaces of the plate 42 and the cylindrical plate 72, circular central conductive layer portions 6 and 8 are provided. Furthermore, each board 4
2 and cylindrical plate 72, respectively, plates 42 and 7
Outer conductive layer portions 10 and 12 are formed extending from the central conductive layer portions 6 and 8 toward the outer ends of the conductive layer portions 2 . External leads 14 and 16 are connected to the outer conductive layer portions 10 and 12, respectively. This capacitive pressure-electric transducer 71 is assembled by substantially the same method as the capacitive pressure-electric transducer 41 shown in FIG.

Since the cylindrical plate 72 is considerably thicker than the plate 42, only the plate 42 acts as a diaphragm in this capacitive pressure-electric transducer 71, so that the pressure is transferred to the capacitive pressure-electric transducer 71.
When applied to the central conductive layer section 8, only the plate 42, and therefore the central conductive layer section 6, deforms relative to the central conductive layer section 8, changing its capacitance.

8 is substantially the same as FIG. 7 except that a hybrid circuit 82 is provided in the capacitive pressure-electric transducer according to the embodiment of FIG. 7, and each member corresponds to the one shown in FIG. 7. The same reference numerals as the members are given. In FIG. 8, a cylindrical plate 72 is provided with a hybrid circuit 82 on its outer surface.

The hybrid circuit 82 is manufactured separately and then attached to the cylindrical plate 7.
2, or may be formed on the cylindrical plate 72 using it as a substrate. This hybrid circuit 32 can be placed on any surface with sufficient available area. Note that it is preferable to provide the hybrid circuit 82 near the electrode of the capacitor formed on the cylindrical plate 72. This is because within the cavity of the capacitor it is protected from outside elements. In the capacitive pressure-electric transducer according to the present invention, the gap formed between the plates is preferably approximately 0.00254 to 0.508 mm (0.1 to 20 mm).

Typically, the thickness of the bent portion of the plate is approximately 0.0254 mm (0.00 mm) if the plate is made of alumina.
1 inch) to 12.7 mm (0.500 inch). Further, the shape of the plate does not limit the present invention in any way, and the piezoelectric transducer can be easily formed from a square or rectangular plate made of a non-conductive material. Furthermore, the central conductive layer portion need not be circular, but may be square, rectangular or any other desired shape. As mentioned above, an embodiment of the invention is shown in FIG. 3, which represents a typical example of a configuration according to the invention. The present invention includes, for example, FIG.
Various modifications and changes can be made in accordance with the teachings of the configurations shown in FIGS. 2, 4 to 8. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a first aspect that can be referred to when constructing a pressure-electric transducer according to the present invention. FIG. 2 shows a cross section taken along line 2-2 in FIG. 1. figure.

FIG. 3 is a cross-sectional view of a pressure-electric transducer according to a preferred embodiment of the present invention. FIG. 4 is a cross-sectional view of a second embodiment that can be referred to when constructing a pressure-electric transducer according to the present invention. FIG. 5 is a cross-sectional view of a third embodiment that can be referred to when constructing a pressure-electric transducer according to the present invention. FIG. 6 is a cross-sectional view of a fourth embodiment that can be referred to when constructing a pressure-electric conversion element according to the present invention. 7th
The figure shows that when configuring the pressure-electric conversion element according to the present invention,
A sectional view of a fifth aspect that can be used as a reference. FIG. 8 is a sectional view showing a state in which an electric circuit is provided in the embodiment of FIG.
2, 4... Disc (non-conductive part), 6, 8...
Central conductive layer portion, 10, 12...Outer conductive layer portion, I4,
16...External lead, 32...Glass frit.

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Claims (1)

[Claims] 1 A pair of non-conductive members having essentially zero hysteresis, at least one of the non-conductive members being constituted by an elastic diaphragm, and opposing surfaces of the pair of non-conducting members having an essentially zero hysteresis characteristic; a pair of non-conductive members that are substantially flat over their entire surfaces; a sealing member made of glass frit is provided at the outer periphery of opposing surfaces of the pair of non-conductive members, thereby sealing the pair of non-conductive members; The central portions of opposing surfaces of the pair of members other than the outer periphery are fixed in a parallel relationship with a certain space between them; each of the surfaces of the pair of non-conductive members that face each other with a space therebetween is provided with a flat layer of a conductive material. each planar layer of conductive material has a central conductive layer portion and an outer conductive layer portion extending outwardly from the central conductive layer portion that connects to an external lead; The central conductive layer portions of the opposing surfaces are arranged parallel to each other with a gap therebetween, and the elastic diaphragm is deflected relative to the other of the non-conductive members in response to pressure applied to the elastic diaphragm of the non-conductive member. 1. A pressure-electric transducer, characterized in that the element has a substantially variable capacitance.