JPH04188001A - Electrostatic capacity detector - Google Patents

Abstract

PURPOSE:To completely prevent a foreign material from entering at a detection part and stably hold high precision by providing the detector with a rubber ring guided in a ring-shaped groove part. CONSTITUTION:After ring-like packing members 32, 33 composed of a thin sheet material previously formed so as to nearly fit in the form of ring-like groove parts 30a, 31b provided on a case nut 30 and a shaft nut 31 which become the fixing member of a detection part housed in a case 2 are arranged for a moisture-proof film 21, the opening end of the case 2 from upward of these is placed to blockade, further rubber rings 34, 35 rich in the resilience of a rubber system fitted in the groove parts 30a, 31a are arranged so as to be guided by the groove parts 30a, 31a, by tightening a case nut 36 and a shaft nut 37, the rubber rings 34, 35 are resiliently deformed in the groove parts 30a, 31b of the case nut 30 and the shaft nut 31 and a moisture-proof film 21 is pushed to hold.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to the structure of a capacitive detector that converts a minute mechanical displacement into an electrical signal as a change in capacitance. In particular, it relates to the improvement of its moisture-proof structure.6 <Prior Art> A conventional detector of this type is disclosed in a patent application filed on March 29, 1990 by a friend of the applicant.

As shown in FIG. 4, this detector is constructed by housing a detection part A having a parallel plate spring structure in a cylindrical case 2 made of a metal material. A parallel plate spring 4.6 made of two metal materials installed in the cylindrical case 2, and a metal supported by the above-mentioned parallel plate spring 4.6 so as to be movable approximately on the axial center line of the cylindrical case 2. A core shaft 5 made of a ceramic material and an insulating spacer 7 made of a ceramic material are attached to the core shaft 5 between the parallel plate springs.
．． Insulating spacers 10, 11 and 12 are attached to the inner circumferential wall of the cylindrical case 2 between the leaf springs with a certain gap between the core electrode made of a cylindrical metal material attached through the core electrode 9 and the outer circumferential surface of the core electrode 9. A pair of ring-shaped identification voltages ff113.
3.degree. 14 to differentially convert the amount of change in capacitance into an electrical signal.

The fixed electrodes 13 and 14 of this detection part A are connected to the cylindrical case 2.
The spacer 15, 16 made of a metal material is used to position the ring-shaped protrusion 2a below the inner circumferential wall of the case 2 as a reference, and the outer circumferential threaded portion is connected to the threaded portion provided on the inner circumferential surface of the entrance of the opening 2b of the case 2. The core electrode 9, which is sandwiched and fixed between the first case nut 17 to be fitted and the protrusion 2a of the case 2, is made of a metal material with reference to the upper surface of the lower step 5a of the core shaft 5. The core axis 5 is positioned by one spacer 18° consisting of
The first shaft nut 20 coupled to the threaded portion on the tip side of the core I! It is sandwiched and fixed between the step part a of No.5.

2, after the detection part A is inserted into the case 2 and fixed by the first case nut 17 and the first shaft/upper 20, foreign matter (moisture, polishing powder,
In order to prevent the intrusion of dust, etc.), a moisture-proof film 21 made of highly visible and chemically stable thin polyethylene film is installed to cover the opening of the cylindrical case 2 on the inner peripheral wall of the case and the core. On the shaft side, they are sandwiched between thin ring-shaped packings 22, 23 and 24, 25 made of a material such as Teflon, which has a small coefficient of friction and is chemically extremely stable, with the moisture-proof film 21, respectively. It is inserted between the first case nut 17 and the second case nut 26 on the inner peripheral wall side of the case, and is fixed between the second case nut 26 and the first case nut 17, and the second case nut 27 on the core shaft side.
It is sandwiched and fixed between the first shaft nut 20 and the first shaft nut 20.

That is, focusing on the detection part A in the above structure, this detection part A is connected to the moisture-proof film 21 and the fixing members of the gaskets 22 to 25 (the second case nut 26 and the second shaft 2
7) is fixed in the case 2 at the front stage of the moisture-proof film 21 and packings 22 to 25 by fixing members (first case nut 17 and first shaft slot 20) that are different from 7), so it is not affected by changes in ambient temperature. In contrast, the coefficient of linear expansion of iron is 10
This is designed to avoid the effect on the inside of the detection part A of the expansion and contraction of the moisture-proof film 21 and packing 22 made of polyethylene and Teflon 25 times from 20 times to 20 times due to temperature changes.

<Problems to be Solved by the Invention> It is true that with the above structure, good results can be obtained with very little influence on the detection part A due to ambient temperature changes, but the second Casena Soto 26 When the second shaft nut 27 is tightened, the moisture-proof film 21 is formed between the first case nut 17 and the first shaft nut 20 which are opposite to the second case nut I and the second shaft nut 20. It has also been found that it is surprisingly difficult to press and hold the gaskets 22 to 25 uniformly and elastically over the entire circumference. That is, the thickness of the moisture-proof film and packing is 0.
．． Because it is thin (1 mm or less), if you tighten the second case nut 26 and the second shaft latch 27 too strongly, the gasket 22 will break.
~25 easily plastically deforms and loses its so-called elasticity as a pankin, and in some cases, a part of the pachinko 22~25 and the film 21 breaks, and you don't know it. There was a risk of assembling the 6-prong, but on the other hand, if you give up too much, foreign matter, especially moisture, will naturally enter through the minute gap and have an adverse effect on the detection part A. 2 case nand 2
6 and the second shaft nut 27 are delicately adjusted, the assembly workability is poor, and the reliability is poor. Therefore, attempts were made to increase the thickness of the packings 22 to 25 by two or three times, but the expected backing effect could not be obtained and workability and reliability could not be satisfied.

Therefore, in the present invention, a ring-shaped groove is formed on the opposing surfaces of the moisture-proof film of the first case nut and the first shaft nut, and the moisture-proof film is inserted through a rubber ring that almost fits into this groove. By elastically pressing and holding the first case nut and the second case nut, and the first shaft nut and the second shaft nut, it is possible to completely prevent foreign matter from entering the detection part A, making it more reliable. The purpose of the present invention is to provide a highly accurate capacitive detector with high performance.

<Means for Solving the Problems> The n$ capacitive detector of the present invention includes a cylindrical case, and a cylinder movably supported on the center side of the darkness by two parallel plates via a core axis. a detection unit housed in a case, the detection unit having a core electrode having a shape of a plate spring, and a pair of fixed electrodes having a shape of a link facing the outer peripheral surface of the second core electrode with a constant angle of a flat spring; A moisture-proof film is disposed through a packing member so as to close one open end of the sensor.
In a capacitance type detector fixed in the case in front of the moisture-proof film and the barrier member, another identification member is used. A ring-shaped groove is formed on the surface facing the moisture-proof film, and the packing member is installed so that it is inserted into this groove. It is characterized by

Function> This capacitance type detector has a link-shaped part formed in another fixing member that fixes the detection part in front of the moisture-proof film, and is guided by this ring-shaped groove part together with the packing member. It has at least one com ring. Therefore,
When the fixing member that fixes the moisture-proof film and the packing member is tightened and pushed one inch, the rubber ring deforms sufficiently elastically within the groove to evenly press and hold the moisture-proof film, completely preventing foreign matter from entering the detection section. This makes it possible to prevent this and maintain stable high accuracy.

<Example> The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a capacitance type detector according to a preferred embodiment of the present invention. The same parts as those of the capacitance type detector shown in FIG. 4 have the same reference numerals. is attached.

The detector in this embodiment is the same as the detector shown in FIG. 4 except for the fixing structure of the moisture-proof film 21 and the constituent members.

That is, the moisture-proof film 21 in FIG.
The ring-shaped grooves 30a and 31a are provided in the first case nut 30 and the first shaft nut 31, which are the identification members of the detection unit A housed in the case 2, respectively. After a ring-shaped padding member 3233 made of a thin sheet material such as Teflon is placed in advance, these padding members 32
It is placed from above ゜33 so as to close the open end of the case 2,
Furthermore, a highly elastic comb ring 34, 35 made of rubber and fitted into the grooves 30a and 31a is arranged so as to be guided by the grooves 30a and 31a, and the second case nut 36 and the second shaft By tightening the bolt 37, the rubber rings 34 and 35 are elastically deformed within the grooves 30a and 31a of the first case nut 30 and the first shaft nut 31, thereby holding the moisture-proof film 21 under pressure.

In this way, by providing the ring-shaped grooves 30a and 31a in the first case nut 30 and the first shaft nut 31, it is possible to make the ring-shaped grooves 30a and 31a thick enough to correspond to the thickness of the punching member, and the elastic range relative to displacement can be increased. Furthermore, since the deformation range of the packing member is almost limited by the grooves 30a and 31a and the lower surfaces of the second case nut 36 and the second shaft nut 37, the elastic Rubber rings 34 and 35, which are link-shaped rubber backings extremely rich in water, form the groove portion 30a.

It deforms almost uniformly within 31a, and presses and holds the portion of the moisture-proof film 21 within the groove almost uniformly.

FIG. 2 is an enlarged partial sectional view showing another embodiment of the first case nut 30 and the first shaft y)-31 in the actual cotton example diagram of FIG. are given the same reference numerals.

The first case nut 40 and the first shaft No. 1 to 1 in FIG. 11 is a protrusion/10b and 41b that protrudes from the entrance surface of the ring-shaped grooves 40a and 41a toward the second case nut 6 and the second shaft nand 37 side.
is formed, and when the second case nut 36 and the second shaft nut 37 are assembled, the lower surfaces of the second case nut 36 and the second shaft nut 37 abut on the protrusions 40b and 41b, respectively. Due to this contact, the amount of compressive deformation of the rubber rings 34 and 35 is always constant, eliminating variations during one assembly, and improving work efficiency.

In addition, in FIG. 1 and FIG. 2I2t, the groove portion 30a.

The sheet-like punching members 32 and 33 disposed in the grooves 30a, 40a
, 31a and 41a are relatively good and there is no risk of the moisture-proof film 21 being tlI (P4) during assembly, it may be omitted.

FIG. 3 is a plan view of notches 30c and 40c provided in the first case nuts 30 and 40, which are formed continuously from the inner circumferential surface of the first case nuts 30 and 40 toward the outer circumference. First case nuts 30 and 40
When assembling into case 2, this notch 3'OC and 40
It is used when inserting a special tool into c and screwing it in.

In addition, in the explanation so far, sealing of the threaded part of the case 2 and the threaded part of the core shaft 5 was not mentioned.
After the case nut of WI41, the first shaft nut, the second case nut, and the second shaft nut are assembled, it goes without saying that they are sealed with adhesive or seal cutting.

Furthermore, the cross-sectional shapes of the grooves 30a, 3ja, 40a, and 41a are not limited to the illustrated example, and the inserts can have various colors.

<Effects of the Invention> According to the present invention, a ring-shaped groove is formed in each of the first case nand and the first shaft nand, and a rubber ring made of extremely elastic rubber is used as the punching member. As a result, the anti-11v film can be evenly pressed and held within the groove, which not only completely prevents substances from entering the detection area, but also improves the ease of assembly. I-5 Moreover, stable high accuracy can be ensured over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a capacitance heat detector according to an embodiment of the present invention. FIG. 2 is a partially enlarged half-section cross-sectional view of a capacitance type detector incorporating another first case nut and first shaft I of the present invention, and FIG. Figure 4 is a cross-sectional view of a conventional static capacitance type detector.2 Case, 4.6 Parallel plate spring. 5...Core N- 9-Core T4. Poles 13.14...Fixed [L 3o, 40...1st case nand, 31.41 - 1st shaft, 30a, 31 a, 40a, 41. a ・Groove portion 40
b, 41b・Protrusion, 34.35 Rubber ring, 36・Second case nand, 37・Second shaft nut. 30c, 40c...notch. Figure 1 Figure 2 Figure 3

Claims (3)

[Claims] (1) A cylindrical case, a cylindrical core electrode movably supported via a core shaft on the center side between two parallel leaf springs, and an outer peripheral surface of this core electrode within the space between the leaf springs. and a pair of ring-shaped fixed electrodes facing each other with a certain gap, and housed in the case, and disposed through a packing member so as to close one open end of the case. and a moisture-proof film fixed in the case in front of the moisture-proof film and the packing member by a fixing member different from the fixing member of the moisture-proof film and the packing member. In the capacitive detector, the another fixing member has a ring-shaped groove formed on a surface facing the moisture-proof film, and the packing member includes at least one rubber ring guided by the groove. A capacitance type detector characterized by: (2) The capacitance type detector according to claim 1, wherein the other fixing member includes a protrusion that protrudes upward from the entrance surface of the ring-shaped groove. (3) The case-side fixing member of the other fixing member is provided with at least one notch extending from the inner circumferential surface toward the outer radial direction and continuous with the inner circumferential surface. Or the capacitance type detector according to 2.