JPS58731A - Electrostatic capacity type pressure sensor - Google Patents

Abstract

PURPOSE:To reduce floating capacity, and also to elevate both adjustment and a mass-production property, by forming an electrode on a surface where a substrate and a diaphragm are opposed to each other, storing it in a metallic case holding its airtightness, and forming a capsule part. CONSTITUTION:A capsule part 1 is formed byproviding thin film electrodes 13 which are both opposed to one surface of an alumina substrate 11 and one surface of an alumina substrate 12 forming a diaphragm, printing glass layers 14, joining together and seal-sticking them between said surfaces, subsequently, covering them with an aluminum case 2 through a silicone rubber ring 3, and caulking them mechanically. After that, it is incorporated in a housing 21 together with a circuit part 22 for converting the capacity to voltage, by which an electrostatic capacity type pressure sensor is formed. Accordingly, since the capsule part 1 is cased in advance, its floating capacity can be reduced, also durability of its structure is elevated, and its adjustment and mass production can be executed easily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a capacitive pressure sensor that detects displacement of a diaphragm due to pressure as a change in capacitance.

The so-called capacitive pressure sensor, which detects the displacement of a diaphragm due to pressure as a change in capacitance through opposing electrodes, has excellent durability due to its fundamental stability and the stability of the materials used. ing. For this reason, it is widely used as a pressure sensor for automatic applications, which have particularly severe usage conditions.

FIG. 1 is a cross-sectional view showing the structure of such a conventional capacitive mouse type sensor, and in the figure, 11 is an insulating substrate;
12Lri diaphragm; 13 is an electrode for detecting capacitance formed on the inner surface of the substrate 11 and the diaphragm 12; 14 is a predetermined gap provided between the guiaphragm 12 and the substrate 11, and maintains confidentiality from the outside world; a glass layer 22ij for converting a capacitance change into an electrical signal (generally a DC voltage); 21 is a housing that accommodates the capsule part 1 and the circuit part 22; The capsule portion 1 is electrically connected to the circuit portion 22 by a lead wire 4, and is kept airtight from the outside world by a ring 16.

The conventional capacitance sensor described above does not directly detect pressure changes as electrical signals, but converts pressure into capacitance and then converts this into electric rFE (DC voltage corresponding to 1,000 volts). It consists of a capsule section 1 that converts pressure into volume and a circuit section 22 that converts pressure into volume f k 'R[E.
Generally, they are assembled independently from each other, and then the two are brought together at the end. In other words, in terms of manufacturing, the capsule part 1j11
At this stage, the capacitance of the body was measured, a certain degree of selection was made, and the circuit part 22 was assembled into the housing, and then the function of the circuit part 220 had to be modified, which was a relatively complicated process. In particular, since the capacitance variation range of this pressure sensor is extremely small, at several tens of pF, it is sensitive to the effects of stray capacitance when measuring capsule capacitance, and stray capacitance when incorporating ). For these reasons, in the conventional pressure sensor, a pressure sensor that satisfies the specifications can only be obtained through complicated selection and adjustment of the capsule portion 1 and the circuit portion 22.

Furthermore, when viewed structurally, the conventional pressure sensor described above has
As shown in FIG. 1, the airtightness between the measured pressure and the circuit section (for the atmosphere) was maintained only by, for example, the O-ring 15, which caused several problems. For example, the confidentiality of the measured pressure is easily lost due to misalignment with the O-ring when the capsule 10 is installed, deterioration of the O-ring, and the like. There was also a risk that the circuit would deteriorate due to the contamination cloud percentage (gasoline vapor, humidity) of the measured pressure.

As described above, conventional pressure sensors currently have major problems in terms of manufacturing and structure.6 The present invention is a capacitive sensor [d By casing the side surface of the capsule part and the housing separately, it provides a force sensor that is easy to adjust, suitable for mass production, and highly reliable.

Hereinafter, one embodiment of the present invention will be described in detail using the drawings. FIG. 2 shows a sectional view of the IFE sensor according to an embodiment of the present invention after it is assembled into a housing. Parts having the same functions as those in FIG. 1 are given the same numbers. 3. Example 1 The manufacturing process of the capsule portion of this pressure sensor will be specifically explained below. A circular thin film electrode 13 was placed on one side of a 96% alumina substrate 11 with a diameter of 30 mm and a thickness of 21 yb, and on the other side of the same alumina substrate 12 with a diameter of 30 m and a thickness of 0.58. The entire glass layer 14 was printed on the same side with a predetermined gap, and both were brought together and sealed. Here, the glass layer 14 may be printed on both sides. The glass sealing temperature at this time varies depending on the substrate material and glass material used, but it is suitable to carry out the sealing at a temperature of 400 to 70° C. for about 10 to 30 minutes. After the capsule portion 1 is shaped 11y in this manner, lead wires 4 for electrical connection to the electrodes are provided. , then covered with an aluminum case 2 via a silicone rubber ring 3,
The rubber ring was mechanically caulked. Furthermore, it was incorporated into the housing 21 together with the circuit 22 to obtain an FE force sensor.

Embodiment 2 FIG. 3 is a cross-sectional view of a capsule portion of a force sensor according to another embodiment of the present invention.Hereinafter, the capsule portion of the 11-teca sensor shown in FIG. 3 will be specifically explained according to the manufacturing process. The substrate 11 and the diaphragm 12 are prepared in the same manner as in Example 1.
A circular electrode 13 is provided on one side of each, and then a Py-based thick film conductor 5 is printed in a ring shape with a width of 2M on each side of I, ', and the other side without electrodes, and dried. Then, it was baked at 850°C for 10 minutes. Furthermore, Example 1
Using the same method as 11 (Ci), a seal 11' glass layer 14 was provided, a capsule part 1 was obtained, and a lead wire 4 was provided.Next, solder paste was printed on the thick i layer 5 on both sides of the capsule, and a copper The thick film layer 5 was covered with a casing 2/, and the hang was melted to attach the thick film layer 5 to the casing.Furthermore, in the same manner as in Example 1, it was assembled into a housing part [r] to obtain a sensor.

In the pressure sensor of the present invention described above, since the capsule portion is shielded in advance with a metal case, it is less susceptible to the influence of stray capacitance of the measurement system. Table 1 shows the capacitance value of the capsule alone and the capacitance value when assembled into the housing: (△C)
shows. From this table, it can be seen that the capsule part of the force sensor of the present invention is completely shielded, so it is difficult to fully receive the influence of stray capacitance between the cover and housing when the circuit is installed, and This further facilitates characteristic adjustment. In other words, the capsule part can be handled as if it were a part with a complete change in capacity, which facilitates management during production. In addition, the structure of the present invention makes the capsule part completely independent, that is,
The durability of the sensor is greatly improved because the measurement [-1] and the third secrecy are double-layered. In addition, since the capsule part with the metal case part can be freely handled as a single component, the structure of the Uzing can also be easily installed.

As described above, since the capacitive 1F capacitive sensor of the present invention has the capsule part cased in advance, it is possible to reduce the stray capacitance of the capsule part and improve the durability between the structures. Compared to secondary pressure sensors, it is possible to provide a sensor that is superior in mass production and has stable performance.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional pressure sensor, and FIGS. 2 and 3 are sectional views of an example of a force sensor according to an embodiment of the present invention. 1... Capsule portion , 2 and 2'...
Metal case, 3...Rubber ring, 4...
・Lead wire, 6... Thick film baking is layer, 11...
...Porcelain substrate, 12...Diaphragm, 13
・-・-・Electrode, 14...Sealing glass layer, 2
1...Housing, 22...Circuit board. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 @31m

Claims (1)

[Scope of Claims] (1) A ceramic substrate and a diaphragm made of an insulating thin plate arranged at a predetermined distance between one of the substrates, and the displacement due to the pressure of the diaphragm is controlled by the substrate. and a metal case configured to detect a change in capacitance toward a counter electrode provided opposite to the diaphragm, and to maintain airtightness of at least the side surface of the substrate and the diaphragm. Characteristic capacitance pressure sensor. (2. A capacitive pressure sensor according to claim 1, characterized in that a receiving port for attaching a pipe for introducing measurement pressure is provided on the diamond rubber surface side of the metal case. (3) Patent In claim 1 or 2,
A capacitive pressure sensor characterized by having a metal case caulked to the same side of a substrate and a diaphragm via a rubber ring. 1sa4t-7 - Claims 1st item tt<+1 In the 2nd item, the electrostatic charger is characterized by having a metal case soldered to the periphery of the substrate and the diaphragm through a thick film baking layer. Capacitive pressure sensor.