JPH11326068A - Protecting tube and thermocouple using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a short circuit generated between element wires constituting a thermocouple even in an atmosphere in which a conductive dust such as metal flutters by lengthening the shortest distance of a No.1 hole and a No.n hole along an edge surface of a protecting tube than a specific length. SOLUTION: This protecting tube for a thermocouple accommodating two element wires is provided with a stepped portion 6 at an intermediate area of holes 3a, 3b into which the thermocouple is inserted or drawn at an end. Thereby, the shortest distance of a first hole 3a and a second hole 3b can be lengthened than L-R1 -R2 (L represents a space between a center of the hole 3a and a center of the hole 3b and R1 and R2 represent a radius of the holes 3a, 3b, respectively). Accordingly, a distance along a surface of the two holes 3a, 3b can have a longer distance than that of a usual protecting tube. Therefore, a short circuit between the element wire passed through the hole 3a and the element wire passed through the hole 3b can be prevented even in an atmosphere in which a conductive dust such as metal and carbon flutters.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a protection tube and a thermocouple using the same. More specifically, the present invention relates to a protective tube capable of preventing a short circuit occurring between wires constituting a thermocouple even in an atmosphere in which a conductive substance dances, and a thermocouple capable of performing stable and accurate temperature measurement.

[0002]

2. Description of the Related Art As a means for measuring an object in a high temperature state,
Conventionally, thermocouples have been widely used. Figure 1
As shown in FIG. 1, the ends of two wires 2a and 2b made of different materials are welded, and the other ends are connected to a voltmeter V for use. The voltage measured by the voltmeter is the temperature T1 and T2 at both ends of each strand.
2 is determined. At that time, in order to prevent a measurement error from occurring due to contact between the wires, a general thermocouple uses the wires through a protective tube.

FIG. 12 shows two strands 2 shown in FIG.
(a), a side view (b) showing one end face of the protection tube, and a side view showing the other end face of the protection tube (a). c). Such a protective tube 1 is formed of a highly insulating heat-resistant material such as a ceramic, for example, and has two holes 3a and 3b extending in the longitudinal direction inside the protective tube 1. Since it is necessary to measure the temperature by bending the thermocouple depending on the temperature measurement target, the protection tube in FIG. 12 is connected and used as shown in FIG. 13 in that case.

FIG. 13 is a schematic diagram showing a tip shape of a general thermocouple. On the other hand, when the tip 4 of the thermocouple is attached to an object to be measured (not shown), the measurement error is reduced.
A protective tube for a thermocouple tip that incorporates various structural ideas has been proposed. FIGS. 14 to 16 are cross-sectional views of thermocouples manufactured using the protection tube 1 ′ for a thermocouple tip having various structures. In the case of FIGS. 14 and 16, the outer peripheral portion 5 of the thermocouple tip protective tube 1 ′ protrudes from the thermocouple tip 4 toward the device under test (not shown).
This is suitable for measuring the temperature of a conductive object to be measured because it does not directly contact the object to be measured. On the other hand, in the case of FIG. 15, the tip 4 of the thermocouple projects from the outer peripheral portion 5 of the protection tube 1 ′ for the tip of the thermocouple toward the measured object (not shown). It is suitable for measuring with high accuracy.

Japanese Patent Application Laid-Open No. 08-075562 discloses a protective tube shown in FIG. 17A is a longitudinal sectional view of the protection tube, and FIG. 17B is a side view showing one end surface of the protection tube. This protection tube is
It has a shape provided with four holes for passing two sets of thermocouples (that is, four wires) through one protection tube, and is used for a thermocouple having a wire protruding from its tip. Has a structure in which the distal end shape forms a concave portion. The protective tube having this structure makes it possible to provide a thermocouple having excellent durability by improving abrasion when the thermocouple is inserted.

[0006] Any of the above-mentioned thermocouples could be used in a vacuum or in the air without any problem.

However, when a thermocouple provided with a protective tube shown in FIG. 13 is used for a long time in an atmosphere where conductive dust such as metal or carbon flies, as shown in FIG.
Conductive dust adheres to the surface of the unit and the end of the protection tube. As a result, a short circuit occurs between the wires at the connection portion B of the protection tube. Furthermore, in the case of a protective tube having a small surface area, the resistance of the surface of the protective tube is reduced, and a short circuit may be caused not only by a direct short circuit between the wires but also by dust adhering to the surface.

For example, in a protective tube having an outer diameter of φ3 mm, the dimension of the end of the protective tube shown in FIG. 19 is r1 = r2 = 0.8.
mm, d = 0.5 mm, and a short circuit occurred even with a small amount of dust.

Alternatively, even if the short circuit is not completely made, if the insulation property decreases and the resistance between the wires decreases, the circuit of FIG. 20 is formed, and the temperature of T3 is affected in addition to T1 and T2. There was a problem that a value different from the temperature to be measured was measured.

[0010]

SUMMARY OF THE INVENTION The present invention provides a protective tube capable of preventing a short circuit between wires constituting a thermocouple even in an atmosphere in which conductive dust such as metal or carbon flies. It is an object of the present invention to provide a thermocouple capable of measuring temperature with high accuracy.

[0011]

The protective tube of the present invention is characterized in that the shape of the end of the thermocouple protective tube having n holes is formed with the first hole along the end face of the protective tube. the shortest distance between the holes in the n-th, wherein the longer than L-R ₁ -R _n.

Here, n is a positive number of 2 or more, L is the distance between the center of the first hole and the center of the n-th hole, R ₁ is the radius of the first hole, and R _n is the n-th hole. Is the radius of

According to the above configuration, the distance between the first hole and the n-th hole along the end face of the protection tube of the present invention is longer than that of the conventional protection tube. Therefore, a short circuit between the strand passing through the first hole and the strand passing through the n-th hole is less likely to occur.

Further, by using the protective tube having the above-described structure, a thermocouple capable of performing stable and accurate temperature measurement can be obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a protection tube and a thermocouple using the same according to the present invention will be described in detail.

FIG. 1 shows a first embodiment of the present invention.
FIG. 1 is a longitudinal sectional view (a) of a protection tube used to store two strands 2a and 2b, a side view (b) showing one end face of the protection tube, and the other of the protection tube. It is a side view (c) which shows the end surface.

The protection tube of FIG. 1 differs from the conventional protection tube (for example, FIG. 12) in that the shape of the end portion is such that a step portion 6 is provided in an intermediate region between the holes 3a and 3b for inserting or removing a thermocouple. different. With the provision of the stepped portion 6, it is possible to have a structure in which the distance along the surface of the two holes is longer than that of a normal protective tube.

FIG. 2 is a cross-sectional view of a thermocouple manufactured using the thermocouple protection tube having the structure shown in FIG. The connecting portion of the protective tube shown in FIG. 2 has a longer distance between the two strands and a longer distance along the surface of the protective tube as compared with the case where a protective tube having a conventional structure is used. A short circuit between the wires is less likely to occur, and a thermocouple capable of measuring the temperature with high accuracy can be obtained.

In this example, the case where the length of two holes formed inside one protection tube is equal to the length of the protection tube in the longitudinal direction is shown. However, as shown in FIG. Even if protection tubes with different lengths are used in combination as shown in FIG.
It goes without saying that the operation and effect of the present invention can be obtained.
Here, FIG. 3 is a longitudinal sectional view (a) of a protection tube used to store two strands 2a and 2b according to the second embodiment, and one end face of the protection tube. FIG. 6B is a side view showing the other end surface of the protective tube, and FIG. 7C is a side view showing the other end surface of the protective tube, wherein the length of the protective tube storing one of the wires is longer than the length of the protective tube storing the other of the wires. Show the case. FIG. 4 is a cross-sectional view of a thermocouple manufactured using a thermocouple protection tube having the structure of FIG.

FIGS. 5 to 10 are longitudinal sectional views of protective tubes used to store two strands 2a and 2b according to the third to eighth embodiments.

The protection tube of FIG. 5, which is a third embodiment,
The shape of the end is a hole 3 for inserting or removing a thermocouple.
The stepped portion 7 is provided in the middle region between a and 3b, and the surface of the stepped portion 7 is corrugated. Therefore, a structure in which the shortest distance between the two holes along the end face of the protection tube is longer than that of the protection tube of FIG.

The protection tube of FIG. 6 according to the fourth embodiment is as follows.
This is a case where a concave portion 8 is provided in an intermediate region between two holes on the end face. In this case, a structure in which the shortest distance between the two holes along the end face of the protection tube can be longer than that of the conventional protection tube (for example, FIG. 12) by the amount of the recess 8.

The protection tube of FIG. 7 of the fifth embodiment is
This is a case where the projection 9 is provided in an intermediate region between two holes on the end face. In this case, compared to a conventional protection tube (for example, FIG. 12), the structure in which the shortest distance between the two holes along the end surface of the protection tube is longer by the protrusion 9 can be adopted.

The protection tube of FIG. 8 according to the sixth embodiment
One end face is provided with a recess 8 in the middle area of the two holes, and the other end face is provided with a projection 9 in the middle area of the two holes.
Is provided. In this case, in addition to the effect that the shortest distance between the two holes along the end face of the protective tube can be increased, the effect that the degree of connection of the thermocouple can be improved by combining the concave portion 8 and the convex portion 9 is obtained.

The protection tube shown in FIG. 9 according to the seventh embodiment comprises:
As in the case of FIG. 7, this is a case in which the convex portion 10 is provided in the intermediate region between the two holes on the end face of the protective tube, and the cross-sectional shape of the convex portion 10 has a shape expanding outward. In such a structure, since the side surface of the convex portion 10 is shadowed by dust, short-circuiting is more difficult than in the structure of FIG.
A thermocouple capable of high-precision measurement can be formed. In FIG.
Although the cross-sectional shape of the convex portion 10 is trapezoidal, it goes without saying that the operation and effect of the present embodiment can be obtained as long as the shape expands outward.

The protection tube shown in FIG. 10 according to the eighth embodiment is a case where the cross-sectional shape of the end face is oblique to the longitudinal direction of the protection tube. As a result, an oblique portion 11 is obtained in the intermediate region between the two holes on the end face of the protective tube. In the protective tube having such a structure, the shortest distance between the two holes along the end surface of the protective tube cannot be made much longer than that of the protective tube shown in FIGS. There is an advantage that the tube can be easily manufactured.

In the above-described embodiment, the protection tube having two holes in one protection tube has been described. However, as shown in FIG. 17, two or more holes are formed in one protection tube. The operation and effect of the present invention are effective even for an empty protective tube. Further, in the above description, the case where the outer shape of the protective tube is round is used, but it goes without saying that the present invention can be applied to an elliptical shape.

[0028]

As described above, in the protective tube according to the present invention, the shape of the end is such that the shortest distance between the first hole and the n-th hole along the end face of the protective tube is L. -R ₁ -R _n (where n is a positive number of 2 or more, L is the distance between the center of the first hole and the center of the n-th hole, R ₁ is the radius of the first hole, and R _n is (Radius of the n-th hole), the distance between the first hole and the n-th hole is longer than that of the conventional protection tube. As a result, a protection tube that can prevent a short circuit between the strand through the first hole and the strand through the nth hole is obtained. In the protective tube having such a configuration, the short circuit hardly occurs even in an atmosphere in which conductive dust such as metal or carbon flutters.

Further, by using the protective tube having the above-described structure, it is possible to provide a thermocouple capable of stably and accurately measuring a temperature even in an atmosphere where conductive dust such as metal or carbon flies.

[Brief description of the drawings]

FIGS. 1A and 1B are schematic diagrams of a protection tube according to a first embodiment, in which FIG. 1A is a longitudinal sectional view of the protection tube, FIG. 1B is a side view showing one end face of the protection tube, and FIG. () Is a side view showing the other end face of the protection tube.

FIG. 2 is a schematic cross-sectional view of a thermocouple manufactured using a thermocouple protection tube having the structure of FIG.

3A and 3B are schematic views of a protection tube according to a second embodiment, in which FIG. 3A is a longitudinal sectional view of the protection tube, FIG. 3B is a side view showing one end surface of the protection tube, and FIG. () Is a side view showing the other end face of the protection tube.

4 is a schematic cross-sectional view of a thermocouple manufactured using a thermocouple protection tube having the structure of FIG.

FIG. 5 is a schematic cross-sectional view in a longitudinal direction of a protection tube according to a third embodiment.

FIG. 6 is a schematic cross-sectional view in a longitudinal direction of a protection tube according to a fourth embodiment.

FIG. 7 is a schematic cross-sectional view in a longitudinal direction of a protection tube according to a fifth embodiment.

FIG. 8 is a schematic cross-sectional view in a longitudinal direction of a protection tube according to a sixth embodiment.

FIG. 9 is a schematic cross-sectional view in a longitudinal direction of a protection tube according to a seventh embodiment.

FIG. 10 is a schematic cross-sectional view in a longitudinal direction of a protection tube according to an eighth embodiment.

FIG. 11 is a schematic view showing the principle of a thermocouple.

FIG. 12 is a schematic diagram of a protection tube according to a conventional example, and (a).
FIG. 3 is a longitudinal sectional view of the protective tube, FIG. 3B is a side view showing one end surface of the protective tube, and FIG. 3C is a side view showing the other end surface of the protective tube.

FIG. 13 is a schematic diagram showing a tip shape of a thermocouple according to a conventional example.

FIG. 14 is a schematic cross-sectional view showing an example of a thermocouple manufactured using a protection tube for a thermocouple tip according to a conventional example.

FIG. 15 is a schematic cross-sectional view showing another example of a thermocouple manufactured using a thermocouple tip protection tube according to a conventional example.

FIG. 16 is a schematic cross-sectional view showing another example of a thermocouple manufactured using a protection tube for a thermocouple tip according to a conventional example.

FIG. 17 is a schematic view of a conventional protection tube having four holes for passing two sets of thermocouples (that is, four strands) through one protection tube, and (a). FIG. 2 is a longitudinal sectional view of the protection tube, and FIG. 2B is a side view showing one end surface of the protection tube.

FIG. 18 is a schematic diagram of a thermocouple provided with a protection tube according to a conventional example, and is a view showing a state where conductive dust adheres to a surface of the protection tube and an end of the protection tube.

FIG. 19 is a side view used to explain the dimensions of each component at the end of the protective tube in the conventional protective tube.

FIG. 20 is a schematic view showing the principle of the thermocouple shown in FIG. 11; as a result of conductive dust adhering to the surface of the protective tube and the end of the protective tube, the insulation of the protective tube is reduced, and 5 is a drawing showing a case where the resistance of the has decreased.

[Explanation of symbols]

1 thermocouple protection tube, 1 'thermocouple tip protection tube, 2a, 2b thermocouple wire, 3a, 3b thermocouple insertion or removal hole, 4 thermocouple tip, 5 thermocouple tip 6 Outer peripheral portion of protective tube 1 ', 6 Surface stepped portion, 7 Surface corrugated stepped portion, 8 Concave portion, 9 Convexed portion, 10 Convex portion having cross-sectional shape expanding outward. 11 Oblique B, the connecting portion of the protection tube, L the distance between the center of the first hole and the center of the n-th hole (however,
n is 2 or more positive), R ₁ radius of the first bore, the radius of the hole of the R _n the n (where, n is 2 or more positive number), T1, T2 the temperature of both ends of the wires, T3 Temperature at the part where the insulation of the protection tube has decreased and the resistance between the wires has dropped, V voltmeter.

Claims (8)

[Claims] An end of a thermocouple protection tube having n holes is formed with a first hole and an n-th hole along an end surface of the protection tube.
The shortest distance between the holes, the protective tube, characterized in that greater than L-R ₁ -R _n (where, n is 2 or more positive number, L is the center of the hole of the first n of the first bore distance between centers, R ₁ is the radius of the first bore, the R _n is the radius of the holes of the n). 2. The protective tube according to claim 1, wherein a peripheral region of the first hole and a peripheral region of the n-th hole forming an end face of the protective tube are stepped. 3. The protection according to claim 1, wherein a recess is provided between a peripheral region of the first hole and a peripheral region of the n-th hole, which form an end face of the protective tube. tube. 4. The projection according to claim 1, wherein a convex portion is provided between a peripheral region of the first hole and a peripheral region of the n-th hole, which form an end surface of the protection tube. Protection tube. 5. The protection tube according to claim 1, wherein one end face of the protection tube is provided with the concave portion according to claim 3, and the other end face is provided with the projection portion according to claim 4. Protection tube as described. 6. The protection tube according to claim 4, wherein a cross-sectional shape of the convex portion provided on an end face of the protection tube is a shape expanding outward. 7. The protection tube according to claim 1, wherein a sectional shape of an end face of the protection tube is oblique to a longitudinal direction of the protection tube. 8. A thermocouple using the protection tube according to claim 1.