JPS58160831A - Electrostatic capacity type pressure sensor - Google Patents

Abstract

PURPOSE:To decrease a secular change by using alumina for a base supporting part and a diaphragm and to reduce the inclination of the output of a pressure sensor with temperature by forming branch-shaped electrodes closely to a sealing member in the middle of the electrode lead-out part of an electrode for detecting electrostatic capacity. CONSTITUTION:An electrode 2 is formed at the base supporting part 1 where when pressure (p) is applied to the diaphragm 4, the diaphragm 4 deforms most, and an electrode 3 is formed where the diaphragm deforms a little against variation in the pressure; and conductive layer of a couple of left and right branch-shaped electrodes 9 and 10 are formed in the middle of the electrode lead-out part 11 of the electrode 2 which senses pressure, said electrode 3 is made concentrically near a glass layer 7, and the electrode lead-out part 12 is formed. When the electrode is formed near the sealing member (glass layer 7), the additional amount of floating capacity from alumina and the glass sealing member as materials constituting a detection capsule part increases in addition to original electrostatic capacity generated between the electrodes under a vacuum.

Description

[Detailed description of the invention] The present invention relates to a capacitive pressure sensor.

Conventionally, an electrostatic tolerance type pressure sensor has a diaphragm and a base support, a conductive layer formed on the diaphragm and the base support and arranged to face each other, and a conductive layer iml.
The sealing member is disposed between the diaphragm and the base support to maintain a constant gap and seal around the diaphragm and the base support.

Therefore, the principle of pressure detection of the C1 static KW type pressure sensor is as follows:
When gas pressure is applied from the diaphragm side and the diaphragm deforms, the capacitance between the conductive layers changes, and this is converted into voltage by an electric circuit. Generally, pressure sensors detect the pressure! In reality, output drift due to temperature, especially temperature, was a major problem, making it difficult to obtain a highly accurate pressure detection device.

A capacitive pressure sensor is mainly composed of a capacitive sensing capsule section and a sensing circuit section.

Figure 1 shows the configuration of the detection capsule part of a conventional pressure sensor.
1 Pressure-sensitive volume jIL (Cp) t A provided at k
(2) The conductive layer and the reference volume wax (Cr
) Electrode (3) C7-) Conductive! Jl+, t, diaphragm (
4) The common electrode provided on the surface faces the conductive layer of the pole (5) and C
In his own book, the static [capacitance Cp, Cr
occurs, and 'C' is obtained by passing eight lead wires (6)... Also, the diaphragm (4) is made of a ceramic thin plate,
Around the base support part (if), a C seal is fixed by the glass layer (7). The inside of the capsule part is sealed with solder (8) in a reduced pressure state, and depending on the pressure applied to the diaphragm (4), the C1 common terminal is connected to the pole (5) and the pressure valley electrode (2).
The distance between the two changes, and the corresponding pressure capacity can be obtained.

Figure 2 shows the principle of the detection circuit section of a capacitive pressure sensor.
r indicates the reference valley area of the detection capsule portion. Here, Cp and Cr are charged ['a is discharged through resistor R, and 9
The discharge follows a curve as shown in Figure 82. When the discharge curve reaches a certain voltage Vref, a switch is activated and C
A pulse with a width proportional to the time difference between p and Cr discharges is generated. The width of this pulse is smoothed over the entire family 1 hour,
1η current voltage Vo. According to this principle, the relationship between the output voltage and pressure of C is expressed as follows.

Vout -A (1-Cr/(p J -J' P
Here, Vout is the output voltage, A, B1 . is a constant, Cp is the static weight of the sensing capsule section, and Cr is the base 111W weight of the sensing capsule section. In terms of shape, the humidity coefficients of Cp and Cr are as shown in Figure 4, and the rate of change of f(ru.(1-''/Cp) due to temperature is Cp.
In the case of the conventional example shown in Fig. 1, the temperature change rate of I Cr/c is large, and when combined with the detection circuit #11, the leakage occurs as shown in Fig. 6. On the other hand, it is not possible to maintain sufficient C detection illumination over a wide range of m degrees, and the large slope of the output with respect to temperature, as shown in the curve in Figure 6, is due to the fact that the detection capsule part This is due to temperature 1f resistance. To change the temperature characteristics of the detection capsule part by 1 times, that is, 1-C of the detection capsule part.
To improve the temperature characteristics of r/c, Cp and C
11 of r! It is necessary to bring the pt coefficients closer together.

Now, if the temperature coefficients of Cp and Cr are α and β, respectively, and the range of change of 7M degrees is △T, then if the temperature change of △T is α x β, the value of ICr/C9 is the temperature will change, and 'C will not change at all. The present invention was made in order to make the temperature coefficients of Cp and Cr as close as possible. The first, second . an eighth conductive layer, and a sealing member interposed between the base support and the diaphragm, the first conductive layer and the second conductive layer. The eighth conductive layer is rotated relative to the sealing member to maintain a constant gap, and the second conductive layer is attached to the branched conductive layer near the sealing part and the electrode lead-out part connected thereto. However, the eighth conductive layer is separated from the second conductive layer and formed in a ring shape so as to surround the conductive layer 1- of the C part 2, and has an electrode extraction part.

In the electrostatic four-edge pressure sensor according to the present invention, the vertical section of the horizontal θ bushel part is the same as that of the conventional example shown in FIG. The structure is as shown in FIG. 8(U). In the drawings, the same members as in FIG. 1 are indicated by the same symbols ff and C. That is, when a pressure p is applied to the diaphragm (4), the diaphragm (4) is deformed the most at the point where the deformation of the diaphragm (4) is the greatest fC, and the VL, pole (2) and L edge formed on the base support (1) are It consists of an electrode (3) formed on the base support part curvature in a place where C does not deform much due to changes in C, and is shown in Fig. 8 (]).
As shown in Figure 4, a pair of left and right branch-like electrodes (9) ul O) are placed in the middle of the electrode extraction part uO of the electrode (2).
! - is formed, and furthermore, the electrode (3) formed in the part where C does not change much due to pressure is formed in the same 8-circle shape at a position close to the glass layer (7). 1
4 is formed and C is present.

Here, the electrode (2) formed in the part of the C diaphragm 14) where the deformation is large due to pressure is the static wL valley that occurs between it and the electrode (5) on the C diaphragm (4) side. It is provided to detect NtCp and is called a Cp electrode. -10,000, The ring-shaped electrode (3) provided in the part where C does not deform much due to changes in pressure is for the reference capacitance Cr, and is called the Cr city pole.

With the configuration of the present invention, the conventional example is improved! Difference from capital punishment letter 1.17. The dot is the branch lane 191 installed in the middle of the Cp''#L repair takeout section.
It is in tlJ. This branch shape [tJli
+91 ud is formed [7, C' and Cp of the prepared sample
The results are shown in Figure 6.As is clear from this figure, the temperature If coefficient of Cp is larger than the temperature coefficients of Cr and Cp in Figure 4, and the temperature coefficient of sCr is When considered from the perspective of the temperature change of lCr//c, this means that there is a smaller temperature change (not less than 7), and the influence of the temperature on pressure sensor This is a more preferable direction when considering λ.C
By forming the branch electrode 1111) (111) on the p-electrode (2), the reason why the warm coefficient of Cp shifts in the direction of increasing and approaches the temperature coefficient of cr can be explained as follows. That is, vt , the pole is on the glass side of the seal member r (7)
], C faces each other through the original vacuum! In addition to the static troughs and troughs that occur between the poles, the additional amount t of floating shrimp from the alumina and glass sealing members that constitute the sensing capsule section increases. This added t:
The temperature coefficient of static electricity is larger than that of the original ideally generated electrostatic change. Therefore, CCpl [There is one sealing member [glass By forming a branch increase city fIiIi1113 in a position close to layer (7)], the temperature coefficient of Cp becomes branch-like [pole 19]
[C is larger than the one without 113. As a result, C
The coefficient of p approaches the temperature coefficient of Cry.

From the above explanation, we can see that the Cp city pole (2) has a branched electrode, and the pole (9) (
By forming 10, the temperature relationship coefficient between Cr and Cp becomes approximately close to each other, and the value 1- is proportional to the output Vout.
It is possible to reduce the turbidity lf change of Cr/Cp. In addition, the branched electrode #j19) tll added to the Cp'li pole (2) is located at the base support part +11.
The effect can be obtained by being close to the periphery of the branch-shaped electrode, and regarding the positional relationship of the shape and arrangement of the branch-like electrode 1), the branch-shaped electrode is located near the base support part + 1). As far as this goes, the effect will not be lost. The material for the base support part (1) and the diaphragm (4) should preferably be one that has chemically and mechanically stable properties and excellent electrical insulation. Alumina is an extremely stable material both chemically and mechanically. Since it is easy to obtain, it is an excellent material for the base support part (it) and diaphragm (4) of the static II@quantity type liquid sensor.

Next, a specific example of the present invention will be explained in C#. Base support part 1
Alumina is used as the material for 1) and the diaphragm (4). The diameter of the diaphragm (4) on which the common electrode +5) is formed is 88ff and the thickness is 0.5ff, and the diameter of the base support a11) is 881m+, j! I! Mi was 6 favors. An Au--Pt thin film electrode is formed as a common electrode (5) on the diaphragm (4), and a circular electrode with a diameter of 25 fl is formed. -10,000, base support SF! In u), a circular electrode (2) for Cp is formed in the center, and in the middle of the electrode extraction point 91, there is a circular electrode (2) at the same circumference as the Cr.
Form a branch-shaped electrode (9) with a wide angle.

Also, as jL pole (3) for Cr, C1 base support +t) l
It is formed concentrically on 11 sides, and the outer diameter is a glass layer (7
) from 1wxllJ. These electrodes 12) (3
) (The relationship between Ilf and Kawaaki is the same as that shown in Figure 8 (b). As mentioned above, the base support part (1) on which the electrode is formed is removed, and the diaphragm (4) is removed from the seal part shrine. The material of the glass layer (7) of the sealing member 1 is Pb, -B20. low melting point glass is used for the base support part. +1) and the diaphragm (4) were manufactured so that the distance between them was 20 μm. After vacuum-sealing the inside of this gear Y-tube, the lead wire (6
)... was connected to form the detection capsule section for the a'JJ sensor. When we measured the temperature relationship coefficient between Cp and Cr in this detection θ bushel part, we found a relationship as shown in Figure 6 of the ship.
The temperature coefficient of r took a value extremely close to C. The temperature characteristic when this sensing capsule section is connected to the sensing circuit section is shown by the curve in FIG. 6a. FIG. 6 also shows the temperature characteristic when the branch shape tm is not formed, and the curve is b.

The temperature characteristics shown in Figure 6 are the amount of drift of the output voltage from the set center value expressed in wllHl, and the pressure is 46
What is shown for the case of 0flHg? Also, the settings were made at 25°C, and the drift at 26°C is 0.
It is. As is clear from this figure, the branched tI pole19)
It can be seen that by forming Q13, the slope of the output of the pressure sensor due to temperature is extremely small.

As mentioned above, the capacitive pressure sensor according to the present invention has an extremely excellent temperature coefficient, and also has excellent resistance to aging due to the use of alumina, for example, as the material for the base support and the diaphragm. The present invention provides a capacitive pressure sensor that is industrially extremely advantageous because it exhibits excellent characteristics.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are longitudinal and cross-sectional views of the detection capsule used in a conventional capacitive pressure sensor, and Figure 2
Figures (4) and (B) are schematic diagrams and discharge state curve diagrams showing the principle of the detection circuit section, and Figures (6) and (B) are longitudinal cross-sectional views of the detection capsule section in an example of implementation of the present invention. Figure 4 is a graph showing the relationship between the temperature coefficient and pressure of Cp and Cr when no branch electrode is formed in the middle of the electrode lead-out part of Cp. A graph showing the relationship between temperature coefficient and pressure when branched electrodes are formed. Figure 6 is a graph showing the relationship between temperature coefficient and pressure when branched electrodes are formed.
It is a graph showing the temperature characteristics when the ``b cell part is set as the detection circuit part. (1)... Base support part, (ri)... Electrode,
(4)...Diaphragm, 16)...Common electric 1fi
, +7)...Glass connection, 19>(1G...branch electrode, (111(b)...Electric field extraction section Yoshihiro Morimoto Fig. f(/1) (Rono Fig. 2(4) ) (mouth 2

Claims (1)

[Scope of Claims] 1. A pair of base support parts and a diaphragm foot having electrical insulation properties, and a first base support part and a diaphragm foot formed on the base support parts and the diaphragm. , 2nd. The eighth (J) is composed of a conductive layer, and a sealing member interposed between the base support portion and the diaphragm, and the eighth (J) conductive layer includes the first conductive layer and the second conductive layer. The eighth conductive layer faces each other and is maintained at a constant gap of °C by the seal member, and the second conductive layer has a branch-like conductive layer near the seal portion and an electrode lead-out portion connected thereto. , the eighth conductive layer is the second conductive layer
A capacitance type pressure sensor having an electrode extraction portion that is separated from the second conductive layer and formed in a ring shape so as to surround the second conductive layer. 2. The capacitive pressure sensor according to claim 1, wherein the material of the base support portion and the diaphragm is alumina. 8. The electrostatic valley type pressure sensor according to claim 1, wherein the gas inside the seal portion is removed.