JPH0136098Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field This invention relates to a thermocouple protection tube used for temperature detection in temperature control in a furnace, etc.

Conventional technology For temperature detection in a furnace where the temperature inside the furnace is 1000 to 1700℃,
Primarily platinum-platinum rhodium thermocouples are used.

Conventionally, a protective tube for a thermocouple used in the above-mentioned temperature environment has a structure as shown in FIGS. 1a and 1b.

In Fig. 1, 1 indicates a pair of insertion holes 1a and 1b.
is an inner tube body which is axially penetrated, and each metal wire 2a, 2b of the thermocouple 2 is inserted into each of the above-mentioned insertion holes 1.
a, 1b, pull out the non-thermal contact side ends from one end of the inner tube 1, and attach the thermocouple 2 so that the hot junction 2c is exposed at the other end of the inner tube 1. be done. The inner tube 1 is inserted into an outer tube 3 with one end closed, and the outer tube 3 is configured to cover the thermocouple 2 and the inner tube 1 entirely. As the material for the inner tubular body 1 and the outer tubular body 3, a high alumina magnetic material is used.

FIG. 1a shows a thermocouple 2 covered with a protective tube 4 consisting of the inner tube body 1 and outer tube body 3, inserted through a through hole in the furnace shell insulation material 5 so that its hot junction 2c side faces the inside of the furnace. 5a is a cross-sectional view showing a state where the device is attached to the device 5a, and 6 is an electric heating element.

However, in the protective tube 4 having the above structure, when the temperature inside the furnace exceeds 1000°C, the electrical insulation properties of the inner tube body 1 and the outer tube body 3 decrease significantly, and the electrical insulation properties of the furnace shell insulation material 5 also decrease. As a result, electromagnetic induction occurs in the thermocouple 2 due to the influence of electricity flowing through the heating element 6, and dielectric charge is generated, which prevents the temperature regulator and temperature recorder connected to the thermocouple 2 from operating accurately. A problem arises in which it stops working.

One possible solution to the conventional electrical insulation problem is to cover the thermocouple 2 with a protective tube 4' having the structure shown in FIGS. 2a and 2b, for example.

In the proposed example shown in FIG. 2, Inconel metal (trademark for heat-resistant steel material) is used instead of the magnetic material of the conventional example to form an inner tube 1' with one end closed.
The thermocouple 2 is inserted into this inner tube 1', and the insulating powder 7 is filled, and the thermal junction of the thermocouple 2 is
The insulation between the metal wires 2a and 2b except for the wires 2a and 2b is the same as that of the conventional example shown in FIG. 1 with respect to the outer tube body 3.

In the case of the structure of the proposed example, although the deterioration of electrical insulation, which is a drawback of the conventional example, can be prevented, the inner tube body 1' made of Inconel metal has the disadvantage that the metal element evaporates under high temperature conditions. As a result, a new problem arises in that the thermocouple 2 itself is corroded by this evaporated element and becomes unusable after a short period of time, making it impossible to put it into practical use.

Purpose This invention eliminates the above-mentioned drawbacks of conventional methods, prevents adverse electrical effects such as electromagnetic induction and dielectric charge generation from electric heating elements in the furnace, and improves accuracy. The purpose of the present invention is to provide a thermocouple protection tube that can perform accurate temperature measurements and has excellent heat resistance.

Overview The thermocouple protection tube of this invention has a platinum shield covering the outer periphery of the inner magnetic tube body, which has a pair of insertion holes extending in the axial direction through which each metal wire of the thermocouple is inserted.
A ground wire that is electrically connected to this shielding material is pulled out from the base end of the inner magnetic tube corresponding to the non-thermal junction side of the thermocouple, and an outer magnetic tube with one end corresponding to the thermal junction side of the thermocouple closed. The inner magnetic tube body and the shield material are entirely covered by the body.

Embodiment An embodiment of this invention will be described based on FIGS. 3a and 3b. Reference numeral 8 denotes an inner magnetic tube body made of high alumina magnetic material, which has a pair of through holes in the axial direction. 8a and 8b are provided through the plate. For each insertion hole 8a, 8b of this inner magnetic tube 8, platinum
The metal wires 9a and 9b of the platinum-rhodium thermocouple 9 are inserted, and their non-thermal contact side ends are pulled out of the tube from one end of the inner magnetic tube 8, and the hot contact 9 is inserted at the other end.
The thermocouple 9 is attached so that c is placed.

10 is a platinum-made 10 on the outer periphery of the inner magnetic tube 8.
10a made of platinum is pulled out in the same direction as the direction in which each metal wire 9a, 9b of the thermocouple 9 is pulled out, and is used as a ground wire 11.

Reference numeral 12 denotes an outer magnetic tube with one end closed, which is made of a high alumina magnetic material.The inner magnetic tube 8 covered with the shielding material 10 enters the tube from the open end side, and connects the thermocouple 9. This outer magnetic tube 12 is inserted with the end side corresponding to the hot junction 9c first.
Almost the entire inner magnetic tube 8 and shielding material 10 are covered by this. The outer magnetic tube 12 has its open end fixed to an insulating substrate 13, and the inner magnetic tube 8 is attached to the inner magnetic tube 8 through a mounting hole 13a formed in the insulating substrate 13.
is held concentrically with the outer magnetic tube 12.
The ground wire 11 is connected to the mounting hole 13 of the insulating board 13.
It is drawn out of the tube through the gap between a and the inner magnetic tube 8.

FIG. 3a shows a protective tube 1 consisting of the inner magnetic tube 8, the shielding material 10 and the outer magnetic tube 12.
4, the thermocouple 9 is inserted into the mounting hole 15a of the furnace shell insulation material 15, and the hot junction 9c of the thermocouple 9 is exposed near the electric heating element 16 in the furnace. The metal wires 9a and 9b of the thermocouple 9 drawn out of the furnace from one end of the protective tube 14 are connected to a temperature regulator or a temperature recorder, and the shielding material 10 is also grounded via a ground wire 11. .

In the case of the protective tube 14 described above, even if the electrical insulation of the inner magnetic tube 8 and the outer magnetic tube 12 decreases under high-temperature conditions, electromagnetic waves generated from the electric heating element 16 and the like and leakage from the outer magnetic tube 12 occur. Since the current flowing into the inner magnetic tube body 8 side is shielded by the grounded shielding material 10, the adverse effects of electromagnetic waves and current will not affect the thermocouple 9.

In the case of the above embodiment, the shielding effect of the shielding material 10 depends on the number of turns of the platinum wire 10a, and the closer the number of turns of the coil is, the more the shielding effect increases. Therefore, instead of the above embodiment in which the shielding material 10 is formed by winding the platinum wire 10a into a coil, a cylindrical body made of platinum that can be fitted onto the inner magnetic tube 8 is formed, and this is used as the shielding material. For example, it becomes possible to further improve the shielding effect. However, forming a cylindrical body using expensive platinum as a material poses problems in terms of cost and requires time and effort in processing.

Figures 3a, b, and c show other embodiments in which the shielding material 10' has a coil shape different from that described above. The shielding material 10' of this embodiment is a platinum thin film (film thickness 5 to 70μ) on the outer periphery of the inner magnetic tube 8.
10'a is wound and tied to the inner magnetic tube 8 at multiple locations (three locations in the embodiment) with platinum wires 10'b, and at the same time, another platinum wire 10'
c is connected to the platinum thin film 10'a and the platinum wire 10'b, and the platinum wire 10'c is drawn out to the insulating substrate 13 side.
One end is a ground wire 11', and the other configurations are the same as in the previous embodiment.

In the case of the protective tube 14' of this embodiment, a platinum thin film 10'a is wound around the inner magnetic tube body 8, and the shielding material 10'a is wrapped around the inner magnetic tube body 8.
0', the shielding effect of the shielding material 10' can be sufficiently enhanced without using too much platinum. Since this is done by winding the platinum wire 10'b and tying the platinum wire 10'b, it is possible to reduce costs in terms of both materials and processing.

Effects According to the thermocouple protection tube of this invention, a platinum shielding material is covered on the outer periphery of the inner magnetic tube body, which has a pair of insertion holes extending in the axial direction through which each metal wire of the thermocouple is inserted. A ground wire that is electrically connected to the platinum shield material is pulled out from the base end of the inner magnetic tube corresponding to the non-thermal contact side of the thermocouple, and one end corresponding to the hot contact side of the thermocouple is closed to the outside. Since the inner magnetic tube and the platinum shielding material are entirely covered by the magnetic tube, the shielding effect of the shielding material can be maintained even under conditions where a source of electromagnetic waves or leakage current exists near the installation part of the thermocouple. This has the effect that it is possible to completely prevent any adverse electrical influence from being exerted on the thermocouple, and that it is possible to perform accurate temperature measurements.

[Brief explanation of the drawing]

Figures 1a and b are longitudinal and cross-sectional views, respectively, of the conventional example, Figures 2a and b are longitudinal and cross-sectional views, respectively, of the proposed example, and Figures 3a and b are views of the proposed example, respectively. FIGS. 4A, 4B, and 4C are a longitudinal sectional view, a lateral sectional view, and a main part perspective view showing other embodiments, respectively. 8, 8'... Inner magnetic tube body, 8a, 8b... Insertion hole, 9... Thermocouple, 9a, 9b... Metal wire, 9
c...Hot junction, 10,10'...Shield material, 1
0a, 10'b, 10'c...Platinum wire, 10'a...
...Platinum thin film, 11,11'...Earth wire, 12...
...Outer magnetic tube, 13... Insulating substrate, 13a...
Mounting hole, 14, 14'...Protection tube.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A platinum shielding material is coated on the outer periphery of an inner magnetic tube body in which a pair of insertion holes for passing each metal wire of the thermocouple are inserted in the axial direction. An outer magnetic tube body in which a ground wire that is electrically connected to the shielding material is pulled out from the base end side of the inner magnetic tube body corresponding to the non-thermal junction side of the thermocouple, and one end portion corresponding to the hot junction side of the thermocouple is closed. A protective tube for a thermocouple, characterized in that the inner magnetic tube body and the platinum shielding material are entirely covered. (2) The thermocouple protection tube according to claim 1, wherein the shielding material is a coiled platinum wire wound around the outer periphery of the inner magnetic tube. (3) The thermocouple protection tube according to claim 1, wherein the shielding material is a platinum cylindrical body fitted onto the inner magnetic tube. (4) The thermocouple protection tube according to claim 1, wherein the shielding material is a platinum thin film wrapped around the outer circumference of the inner magnetic tube.