JPH0993780A - MI cable terminal structure - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A terminal structure of an MI cable is desired, which does not lower the insulation resistance even when left in the air, and which is easily incorporated into equipment. SOLUTION: The end of the MI cable 1 is inserted through a cable hole 12 formed at one closed end of a connecting member 10 and the outer periphery of the MI cable 1 and the cable hole 12 are airtightly fixed, while the core wire is provided from the other end. The sealing plate 20 from which 2a and 2b were pulled out was fitted into the inside of the connecting member 10 and fixed airtightly, and the terminal was sealed inside the connecting member 10 airtightly.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an MI (Miner) in which a core wire is disposed in a thin-walled cylindrical metal sheath and an inorganic substance (mineral insulator) powder is filled between the sheath and the conductor.
al Insulated) cable end structure.

[0002]

2. Description of the Related Art MI cables are used as devices such as sensors that are exposed to high temperatures because they have high heat resistance and high insulation, for example, as lead wires of acceleration sensors for extracting acceleration signals in a steam cooler of a nuclear power plant. ing.

FIG. 2 is a cross-sectional view showing a terminal structure of a conventional MI cable, and the terminal of the MI cable 100 is a sheath 1.
01 is brazing metal on the side of the device case 1
The core wires 104a and 104b are directly fixed to each other at 03, and are connected to a conversion unit or the like of the device.

In the MI cable 100, an insulating layer 105 formed by packing an inorganic substance, for example, MgO (magnesium oxide) powder in a sheath 101 and solidifying the same is formed.
In the middle of 05, the core wires 104a and 104b are separated from each other and held so as not to come into contact with the sheath 101.

[0005]

In the terminal structure of the MI cable described above, when the MI cable before being assembled is left in a normal atmosphere (air), the insulating layer is an inorganic powder having high hygroscopicity. Since it is formed from, the moisture in the air is absorbed over time, and the insulation resistance is reduced.

Therefore, before assembling, it is necessary to store the MI cable in a dry atmosphere with little water content, and the terminal is exposed in the atmosphere even when the terminal is fixed to the case, so that the terminal is exposed in the atmosphere. Similarly, it is necessary to carry out in a dry atmosphere, and when carrying out in a normal atmosphere, the work must be completed in a short time so that the insulating layer absorbs as little water as possible, which is troublesome.

[0007]

In order to solve the above problems, a terminal structure according to the present invention has a shape in which a connecting member is airtightly attached to one end of an MI cable and the other end of the connecting member can be connected to another member. Further, a sealing plate that defines an airtight space where the tip of the MI cable is exposed is fixed in the connecting member, and the core wire of the MI cable is led out through a lead hole formed in this sealing plate. At least the lead hole portion was hermetically sealed with a sealing material.

According to the above structure, the end of the MI cable can be hermetically sealed by using the sealing plate in the connecting member, and the insulating member can absorb moisture even if the MI cable is left in a high humidity atmosphere. At the same time, the connecting member can increase the strength of the MI cable pull-out portion. Also,
It becomes possible to easily connect to the equipment to which the MI cable is connected.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing a terminal structure of an MI cable according to the present invention, in which the MI cable 1 is fixed to a terminal with a connecting member 10 having one end closed and the other end opened. Core wires 2a and 2b that extend through the fitted sealing plate 20 and extend to a device (not shown) in the case 30 indicated by a two-dot chain line are drawn out. The other end of the MI cable 1 is already hermetically sealed by an appropriate means.

As described above, the MI cable 1 tends to absorb moisture in a normal atmosphere and its insulation resistance lowers. Therefore, when the terminal treatment is performed, the MI cable 1 is cut into a predetermined length in advance and placed in a drying furnace for insulation. The moisture absorbed in 4 is released to improve the insulating property.

Further, as the sheath 3 and the core wires 2a and 2b, for example, Inconel which is a heat-resistant metal of Fe-Ni-Cr can be used, and as the insulating member 4, for example, powder-like high-purity MgO is used as in the conventional case. To use.

The connecting member 10 is formed of a metal material such as Inconel into a cylindrical shape with one end open, and the one end side has an outer periphery, for example, a step portion 11 having a spring action.
And a shape matching the mounting hole 31 of the case 30 accommodating the device to which the MI cable 1 is connected, and the other end side has a predetermined length having an inner diameter substantially the same as the outer diameter of the MI cable 1. Cable hole 12 is formed. Further, the connecting member 10 has a step portion 13 formed therein for supporting the sealing plate 20.

The sealing plate 20 is made of an insulating material that can withstand high temperatures, such as ceramics, and is formed into a disk shape that can be fitted into the opening 14 of the connecting member 10, and is fixed to the step portion 13 of the connecting member 10. The sealing plate 20 has core wires 2a, 2
Lead holes 21a and 21b corresponding to the number of b are formed. The lead holes 21a and 21b are at least MI.
A taper surface is formed on the side of the cable 1 facing the terminal to facilitate the work of inserting the core wires 2a and 2b.

Next, the manufacturing procedure of the terminal structure of the MI cable according to this embodiment will be described. MI of the connecting member 10
For fixing to the cable 1, the MI cable 1 is connected to the connecting member 10
The thin cylindrical sheath 3 made of a metal member, which is the outer circumference of the MI cable 1, and the periphery of the cable hole 12 are inserted into the cable hole 12 of No. 2 and brazed with metal 5, for example, silver brazing.

By adopting this brazing, not only the MI cable 1 and the connecting member 10 can be connected airtightly, but also stable electrical conduction can be obtained between the sheath 3 and the connecting member 10.

As the fixing method, an adhesive for high temperature can be used in addition to the brazing 5, but brazing is preferable from the viewpoint of durability and electrical conduction.

Next, after inserting the core wires 2a and 2b through the lead holes 21a and 21b, the sealing plate 20 is connected to the connecting member 10.
It fits in the stepped part 13 of. By doing this, the core wire 2
The core wires 2a, 2b are not contacted with each other or the core wires 2a, 2b are not contacted with the connecting member 10 or the case 30.
b can be guided to the device in the case 30.

After that, the heat-resistant adhesive 22 is applied to the entire other surface of the sealing plate 20, and the sealing plate 20 is connected.
0 It sticks inside. In this way, the adhesive 22 is applied to the sealing plate 20.
The lead holes 21a and 21b are also covered with the heat-resistant adhesive 22 by coating the entire surface of the above, and the end of the MI cable 1 is sealed in the connecting member 10.

It is sufficient that the adhesive 22 can seal the end of the MI cable 1 without applying the adhesive 22 to the entire surface of the sealing plate 20 as described above.
You may apply only the contact part with the inside and the lead holes 21a and 21b part.

By performing the above work in a dry atmosphere, the terminal structure of the heat-resistant and high-insulation MI cable 1 in which the terminals are hermetically sealed can be obtained, and the MI cable 1 is placed in a humid atmosphere before being incorporated into a device. Even if it is left inside, the moisture does not enter the insulating layer, and the insulation resistance can be prevented from lowering.

The MI cable 1 having the above terminal structure is
Equipment stored in the case 30 (for example, in the case of an acceleration sensor, an acceleration conversion unit including a charge amplifier)
After connecting the core wires 2a and 2b to the output end of the
The opening 14 is press-fitted and connected until the step 11 hits the mounting hole 31 of the device case 30. After press-fitting, the peripheral edge of the stepped portion 11 and the case 30 are laser-welded together to form the case 30.
Is hermetically sealed.

At this time, since the MI cable 1 maintains high insulation, the work must be completed in a short time in order to prevent deterioration of the insulation when proceeding with the connection work with the equipment. Is released from.

The connection method adopted in the above embodiment is as follows.
Since the MI cable is not directly fixed to the case as in the conventional case, the method is not limited to press fitting as long as it can be surely connected, and screwing can be adopted, which widens the design range. Although the above embodiment shows the case where there is one MI cable, it is needless to say that the same structure can be applied when there are a plurality of MI cables.

In the terminal structure of the MI cable of this embodiment, since the case and the terminal of the MI cable are fixed to both ends of the metallic connecting member, the joint strength between them is increased, which is convenient for an acceleration sensor to which repeated vibration is applied. However, it can also be applied to the terminals of MI cables of various devices exposed to high temperatures. In particular, it is suitable for devices having a high output impedance in which cable insulation is likely to be a problem, for example, sensors that output the output of the piezoelectric element directly to the outside via the cable, and are less susceptible to noise.

[0025]

As described above, the MI according to the present invention
The terminal structure of the cable is such that the end of the MI cable is airtightly inserted into one end of the tubular connecting member, and the other end of the connecting member is connectable to another member. Further, the end of the MI cable is inside the connecting member. A sealing plate that defines an airtight space where is exposed is fixed, the core wire of the MI cable is led out through a lead hole formed in this sealing plate, and at least the portion of the lead hole is made of a sealing material. Since it is hermetically sealed, the end of the MI cable can be hermetically sealed, and M
Even if the I cable is left unattended, the insulating member does not absorb moisture, and the work of connecting the device to which the MI cable is connected to the device must be completed in a short time. Further, the strength of the MI cable pull-out portion can be increased by the connecting member, and a high-strength MI cable terminal structure can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a terminal structure of an MI cable according to the present invention.

FIG. 2 is a sectional view showing a terminal structure of a conventional MI cable.

[Explanation of symbols]

1 ... MI cable, 2a, 2b ... Core wire, 3 ... Sheath, 4
... Insulating member, 5 ... Brazing, 10 ... Connecting member, 11, 13
... step, 12 ... cable hole, 14 ... opening, 20 ... sealing plate, 21a, 21b ... lead hole, 22 ... heat resistant adhesive, 3
0 ... Case, 31 ... Mounting hole.

Claims (1)

[Claims] 1. A terminal structure of an MI cable in which a core wire is inserted into a metal sheath filled with a powdery insulating material, the terminal structure including a tubular connecting member, the connecting member comprising: The tip of the MI cable is airtightly inserted at one end,
The other end has a shape that can be connected to another member, and further, a sealing plate that defines an airtight space where the tip of the MI cable is exposed is fixed in the connecting member, and a lead hole formed in this sealing plate is used. A terminal structure of the MI cable, characterized in that the core wire of the MI cable is led out to the outside and at least the portion of the lead hole is hermetically sealed with a sealing material.