JP4048237B2 - Sheath type thermocouple and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sheath type thermocouple that can be easily bent and has few breaks due to bending, and a method for manufacturing the same.
[0002]
[Prior art]
When both ends of the two kinds of metal wires are joined and the temperature at both junctions is kept different, an electromotive force is generated in this closed circuit. A combination of two types of metal wires is called a thermocouple. The thermoelectromotive force of a thermocouple is determined by the type of metal wire combined and the temperature at both junctions. When one junction of the thermocouple is kept at a constant reference temperature, the electromotive force is determined by the temperature of the other junction. Therefore, the temperature can be known by measuring the thermoelectromotive force.
FIG. 4 shows an example of the measurement circuit. The compensating conductor has approximately the same thermoelectric characteristics as the thermocouple used, and this connects between the thermocouple terminal and the reference junction to compensate for errors caused by temperature changes in the thermocouple terminal. use.
[0003]
Thermocouple strands are generally thin and may break during use. For this reason, as illustrated in FIG. 5, a sheath type thermocouple in which a thermocouple element wire is housed in a metal protective tube (sheath tube) called a sheath is widely used. The sheath type thermocouple is used by appropriately bending the sheath tube in accordance with the device configuration at the time of installation on the measurement target part. For this reason, ceramic powder is used as an insulating material for sheathed thermocouples so that bending can be performed, and ceramic powder is densely packed to ensure insulation between the wires of the thermocouple and between the wires and the sheath tube. Filled.
[0004]
[Problems to be solved by the invention]
In the production of the above-described sheath type thermocouple, it is difficult to fill a thin sheath tube with ceramic powder at a high density, and therefore a production method called a drawing annealing method has been conventionally used. In this method, a ceramic powder compact and a thermocouple wire are set in a starting tube having a diameter larger than the product diameter, and the entire diameter is simultaneously reduced while repeating heating and tension, thereby reducing the diameter of the thermocouple. This increases the filling rate of the insulating material.
[0005]
However, the sheath-type thermocouple manufactured by such a manufacturing method has a problem that the wire breaks frequently in the protective tube during bending. In other words, in the conventional manufacturing method, the insulating material is rubbed against the surface of the strand in the process of stretching the strand, and innumerable scratches are formed on the surface of the strand, so that the strand in the completed sheath type thermocouple is apparent. The ductility is reduced. In addition, since the insulating material is compressed by the sheath tube and strongly pressed against the strands during the stretching process, the extension range of the strands when bending the completed sheath type thermocouple is limited to the vicinity of the bend. Yes. Therefore, there has been a problem that the strands are likely to break due to a decrease in ductility and local elongation of the strands.
[0006]
The present invention has been made to solve such problems. That is, the object of the present invention is to prevent the ductility of the thermocouple strands from decreasing and to avoid local elongation of the thermocouple strands when the sheath tube is bent. An object of the present invention is to provide a sheath-type thermocouple that can be cut and that is not easily broken by bending, and a method for manufacturing the same.
[0007]
[Means for Solving the Problems]
According to the present invention, a plurality of relatively high strength insulating members (2) that hold a pair of thermocouple wires (1) spaced apart from each other, and a high strength insulation adjacent in the length direction. A sheath comprising a plurality of low strength insulating members (4) sandwiched between members and having relatively low strength, and a high strength insulating member and an elongated sheath tube (6) surrounding the low strength insulating member. A mold thermocouple is provided.
[0008]
According to the configuration of the present invention, the sheath tube (6) and the thermocouple wire (1) are separately processed to a predetermined product diameter, and the high strength member (2) and the low strength member (4) are alternately used as the insulating member. It becomes the structure arranged repeatedly. Unlike the conventional ceramic powder, the high strength member (2) of the insulating member can be relatively easily inserted into a thin protective tube (sheath tube). Further, since the low-strength member (4) can be deformed by collapsing with an external force, it can easily follow the bending process of the thermocouple sheath tube. Furthermore, since the thermocouple wires are held at a predetermined interval by the repeatedly disposed high strength member (2), there is no fear of a short circuit even if the density of the low strength member (4) is low. Therefore, with this configuration, it is possible to avoid both the decrease in ductility of the thermocouple element and the compression of the thermocouple element by the insulating member.
[0009]
According to a preferred embodiment of the present invention, the high-strength insulating member (2) and the low-strength insulating member (4) are both cylindrical ceramic members, and the pair of thermocouple wires (1) are spaced from each other. A pair of through-holes (2a, 4a) that pass through in the lengthwise direction are provided.
With this configuration, for example, by designing the diameter of the through hole (2a, 4a) through which the thermocouple element (1) passes slightly larger than the element diameter, the constraint of the thermocouple element by the insulating member is further reduced. . For this reason, when bending is performed, the thermocouple strands are stretched in a wide area, and durability against bending is improved. The strength of the insulating members (2, 4) can be controlled, for example, by changing the density of the ceramic parts.
[0010]
The high-strength insulating member (2) is a cylindrical ceramic member, and has a pair of through-holes (2) through which two thermocouple wires are passed in the longitudinal direction with a space therebetween. The low-strength insulating member (4) may be a ceramic adhesive that is filled and cured between high-strength insulating members.
By filling the space between the high-strength insulating members (2) with a ceramic adhesive and performing a curing process, a structure substantially the same as when a ceramic member is used as the low-strength insulating member (4) can be obtained. Since the ceramic adhesive becomes a fine powder when it is broken by an external force, the risk of damage to the thermocouple wire during bending of the thermocouple sheath tube is reduced.
[0011]
In addition, according to the present invention, (a) a plurality of cylindrical ceramic members (2) having a pair of longitudinal through holes (2a) spaced apart from each other are prepared, and (b) each through-hole of the ceramic member. Each of the pair of thermocouple wires (1) is passed through the holes, (c) each ceramic member is positioned at a predetermined interval, and a ceramic adhesive (4) is filled between them to be cured. Manufacturing a thermocouple component (8) comprising a ceramic member, a ceramic adhesive and a thermocouple wire, and (d) then inserting the thermocouple component into an elongated sheath tube (6) A method of manufacturing a mold thermocouple is provided.
[0012]
This manufacturing method makes it easy to make a sheathed thermocouple that secures insulation between the wires of the thermocouple and between the wires and the sheath tube without causing a drop in the ductility of the thermocouple wires as in the conventional drawing annealing method. And local elongation of the thermocouple wire can be avoided when the sheath tube is bent.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to a common part and the overlapping description is abbreviate | omitted.
FIG. 1 is a configuration diagram of a sheathed thermocouple according to the present invention. As shown in this figure, the sheath-type thermocouple of the present invention includes a plurality of high-strength insulating members 2 having relatively high strength that hold a pair of thermocouple wires 1 at intervals, and a length direction. A plurality of low-strength insulating members 4 sandwiched between adjacent high-strength insulating members and a relatively low strength, and an elongated sheath tube 6 surrounding the high-strength insulating member and the low-strength insulating member.
[0014]
FIG. 2 is a perspective view of the high-strength insulating member or the low-strength insulating member of the present invention. As shown in this figure, both the high-strength insulating member 2 and the low-strength insulating member 4 are cylindrical ceramic members, and a pair of thermocouple wires 1 are passed through the pair of thermocouple strands 1 in the length direction at intervals. Through-holes 2a and 4a.
[0015]
As schematically shown in FIG. 2, the outer diameter D of the insulating members 2 and 4 is designed to be slightly smaller than the inner diameter of the sheath tube 6. The diameter d of the hole through which the thermocouple wire 1 passes is made larger than the wire diameter. The larger the clearance, the easier the manufacture of the thermocouple. However, in consideration of the sheath diameter and the repeated pitch of the high-strength member 2 and the low-strength member 4, the thermocouple sheath tube 6 can be insulated even if it is bent. It must be designed so as to ensure an interval between the thermocouple wires or between the thermocouple wires and the sheath so that no defect occurs.
[0016]
The length B of the high-strength insulating member 2 is defined by the bending radius to be guaranteed. If the length B is too wide, the high-strength insulating member 2 becomes a core material and bending with a small radius cannot be performed.
[0017]
As the low-strength member 4, a ceramic member having the shape shown in FIG. The length B of the low-strength insulating member 4 needs to be determined in consideration of followability to the bending process and insulation. If the length of the low-strength insulating member 4 is too short compared to the length of the high-strength insulating member 2, the followability to a small bending radius is deteriorated. On the other hand, if the length of the low-strength insulating member 4 is too long, there is a risk of contact between the thermocouple wires or between the thermocouple wires and the sheath tube when the low-strength insulating member 4 is broken by bending. Further, since the low-strength insulating member 4 does not need a function of holding the thermocouple element, it is preferable that the strength is as low as possible within the range that can be handled.
[0018]
The high-strength insulating member 2 and the low-strength insulating member 4 manufactured in consideration of the above are alternately passed through the pair of thermocouple wires 1 to manufacture a structure as shown in FIG. 1 to a predetermined length. The sheath-type thermocouple according to the present invention is obtained by inserting this into a sheath tube 6 that has been cut to a predetermined length in advance and forming a hot junction and connecting a compensating lead wire by a conventional method.
[0019]
Next, the case where a ceramic adhesive is used for the low strength portion of the insulating member will be described. In this case, as described above, the high-strength insulating member 2 is a cylindrical ceramic member and has a pair of through-holes 2 through which two thermocouple wires are passed in the length direction with a distance from each other. However, the low-strength insulating member 4 is a ceramic adhesive that is filled and cured between the high-strength insulating members 2.
[0020]
This sheath type thermocouple is manufactured in the following steps.
(A) First, a plurality of cylindrical ceramic members 2 having a pair of longitudinal through-holes 2a spaced from each other are prepared.
(B) Next, each of the pair of thermocouple wires 1 is passed through each through hole 2 a of the ceramic member 2.
(C) Next, the ceramic members 2 are positioned at a predetermined interval, and the ceramic adhesive 4 is filled between them to be hardened. Thereby, the thermocouple component 8 which consists of the ceramic member 2, the ceramic adhesive agent 4, and the thermocouple strand 1 is completed.
(D) Next, the thermocouple component 8 is inserted into the elongated sheath tube 6 to complete the sheath type thermocouple according to the present invention.
[0021]
That is, first, the high-strength insulating member 2 having the shape of FIG. 2 is passed through the pair of thermocouple wires 1 and arranged at a predetermined interval. Next, the space between the high strength insulating members 2 is filled with a ceramic adhesive to form a low strength portion. Note that the dimensions of the high-strength member 2 and the low-strength member 4 are both determined in the same manner as when a ceramic member is used. In addition, a ceramic adhesive that does not generate gas and does not react with the constituent material of the thermocouple within the range up to the service temperature of the thermocouple must be selected. When the ceramic adhesive is sufficiently dried, the excess adhesive is removed so that the outer diameter is equal to or smaller than the outer diameter of the high-strength insulating member 2 by using sandpaper or the like. Thereafter, the curing treatment specified for the used adhesive is performed, and gas generation associated with the curing reaction is completely terminated.
[0022]
The structure of the thermocouple component 8 obtained in this way is substantially the same as the structure shown in FIG. 2 in which the high-strength member 2 and the low-strength member 4 are both ceramic members. This can be used as a sheathed thermocouple by inserting it into the sheath tube 6 and forming a hot junction and connecting a compensating lead wire as in the conventional case.
[0023]
The sheath-type thermocouple according to the present invention has a structure in which the high-strength member 2 and the low-strength member 4 are repeatedly arranged, and is not limited to the above manufacturing method. In addition, when the bending portion at the time of actual use is limited, a portion where bending is not performed may be formed by a high-strength ceramic two-hole straight pipe, and the structure of the present invention may be used only in the vicinity of the bending portion.
[0024]
【Example】
Below, the Example of this invention at the time of using a ceramic adhesive agent for the low intensity | strength insulating member 4 is described.
The manufactured sheath-type thermocouple is a Ta-sheath W-Re thermocouple having an outer diameter of 1 mm, the sheath inner diameter is 0.7 mm, and the thermocouple wire diameter is 0.2 inch. The high-strength insulating member 2 was formed of an alumina sintered body having a relative density of 97% or more and a purity of 99% or more with the length B of the insulating member in FIG. The thermocouple element wire 1 was passed through this and arranged at intervals of 0.55 mm, and a low-strength insulating member 4 was formed using an alumina-based ceramic adhesive 4. After 120 mm of this structure was produced and allowed to air dry for 24 hours or longer, excess adhesive was removed using sandpaper. The low-strength member 4 formed of an adhesive can be moved along the thermocouple wire 1 as an independent structure, and has substantially the same structure as the case where a ceramic member is used as the low-strength member. .
[0025]
The 120 mm thermocouple internal structure (thermocouple component 8) thus produced was dried at about 90 ° C. for 2 hours and then cured at about 150 ° C. for 1 hour. Further, this was inserted into a 120 mm Ta sheath tube 6 to obtain a sheath type thermocouple. It can be used in the same manner as a normal thermocouple by forming a hot junction and connecting a compensating lead wire.
[0026]
Furthermore, in order to verify the effect of the present invention, a bending test was performed on a 120 mm body structure manufactured as described above. The bending shown in FIG. 3 with a bending radius of R1 mm was subjected to bending at six places in the order of the numbers in the figure, but no breakage of the thermocouple wire 1 occurred. On the other hand, when a conventional sheath type thermocouple was cut out by 120 mm and subjected to the same bending test, the thermocouple element was broken when the fifth bending in FIG. 4 was performed. Thereby, it was confirmed that the sheath type thermocouple according to the present invention has superior bending resistance as compared with the conventional sheath type thermocouple.
[0027]
In addition, a 150 mm sheathed thermocouple was prepared by the same method as described above, and after forming a hot junction and connecting a compensating lead wire by a conventional method, the operation was confirmed and the sheathed thermocouple of the present invention was used. Was confirmed to have the same temperature measuring function as the conventional product.
[0028]
It should be noted that the present invention is not limited to the above-described embodiments and examples, and can of course be changed without departing from the gist of the present invention. For example, the sheath-type thermocouple of the present invention is not limited to the W-Re thermocouple shown in the examples, and it is obvious that the effect can be expected for all sheath-type thermocouples.
[0029]
【The invention's effect】
As described above, the sheathed thermocouple according to the present invention has the following excellent functions.
{Circle around (1)} Even if the sheath diameter is small, it is possible to arrange the insulating material reliably, so that it is not necessary to take a step of reducing the ductility of the thermocouple wire as in the prior art. As a result, there is little risk of disconnection during bending.
(2) Since the thermocouple element is not restrained by the insulating member, changes in the length of the thermocouple element during bending can be absorbed by a wide area, and there is little risk of disconnection.
[0030]
As described above, the sheath-type thermocouple and the manufacturing method thereof according to the present invention can avoid the local elongation of the thermocouple wire without bending the duct of the thermocouple wire and bending the sheath tube. Thus, there are excellent effects such that bending can be easily performed and disconnection due to bending is less likely to occur.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a sheathed thermocouple according to the present invention.
FIG. 2 is a perspective view of a high-strength insulating member or a low-strength insulating member according to the present invention.
FIG. 3 is a bent view showing an embodiment of the present invention.
FIG. 4 is a diagram showing an example of using a thermocouple.
FIG. 5 is a structural diagram of a conventional sheathed thermocouple.
[Explanation of symbols]
1 Thermocouple Wire 2 High Strength Insulating Member 2a Through Hole 4 Low Strength Insulating Member (Ceramic Adhesive)
4a Through hole 6 Sheath tube 8 Thermocouple component

Claims (4)

It is sandwiched between a plurality of high strength insulating members (2) having relatively high strength and holding a pair of thermocouple wires (1) spaced apart from each other and a high strength insulating member adjacent in the length direction. A sheath type thermocouple comprising a plurality of low strength insulating members (4) having relatively low strength and a high strength insulating member and an elongated sheath tube (6) surrounding the low strength insulating member. The high-strength insulating member (2) and the low-strength insulating member (4) are both cylindrical ceramic members, and pass a pair of thermocouple wires (1) in the lengthwise direction at a distance from each other. The sheath-type thermocouple according to claim 1, wherein the sheath-type thermocouple has a through hole (2 a, 4 a). The high-strength insulating member (2) is a cylindrical ceramic member, and has a pair of through-holes (2) through which two thermocouple wires are spaced apart from each other in the length direction. The sheath-type thermocouple according to claim 1, wherein the strength insulating member (4) is a ceramic adhesive filled and cured between high strength insulating members. (A) preparing a plurality of cylindrical ceramic members (2) having a pair of longitudinal through holes (2a) spaced apart from each other;
(B) Each of the pair of thermocouple wires (1) is passed through each through hole of the ceramic member, (c) each ceramic member is positioned at a predetermined interval, and the ceramic adhesive (4) is interposed therebetween. Fill and cure, thereby producing a thermocouple component (8) comprising a ceramic member, a ceramic adhesive and a thermocouple strand,
(D) Next, a method of manufacturing a sheath type thermocouple, wherein the thermocouple component is inserted into an elongated sheath tube (6).

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