JPH0136562B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high temperature strain gauge capable of measuring strain at high temperatures.

High-temperature strain gauges that have a sandwich structure in which a resistance element for detecting strain is sandwiched between ceramic materials, and those that use polyimide as a base material are known. As this ceramic material, for example, asbestos is specifically used, and as the resistance element material, for example, Karma (used when the temperature is below 300°C),
Alternatively, Nichrome V, Armoroy D, platinum-tungsten alloy (used when the temperature is 300° C. or higher), etc. are used. The strain detection resistive element is then bonded to a ceramic or polyimide base with an adhesive such as silicone. By the way, high-temperature strain gauges with such a configuration deteriorate at temperatures of 300° C. or higher, and the ceramic material no longer exhibits its original characteristics, resulting in a significant decrease in strength. One possible reason for this is that products using polyimide resin have problems with their own heat resistance, but especially when asbestos is used as the base material and silicone resin is used as the adhesive, silicone resin 400℃
When exposed to high temperatures of ~500°C, the three-dimensional network molecular structure of silicone decomposes and it no longer functions as a binder. That is, there is a problem in that the binder loses its ability to adhere to the base material and the resistance element, and the function of transmitting strain from the object to be measured to the resistance element is lost.

There are also strain gauges in which a resistance element is glued to polyimide and attached to asbestos or metal materials, but such strain gauges also suffer from the problem that the heat resistance of the polyimide resin itself is insufficient, and the resistance The problem is what adhesive to choose for bonding the element to the polyimide base. In other words, polyimide resin can be said to have one of the best heat resistance among plastic resins, but its heat resistance is inferior compared to materials such as ceramics, and polyimide resin is similar to polytetrafluoroethylene and polyolefin materials. Because it is a very difficult material to bond, there are significant restrictions on the adhesives that can be used to bond resistance elements to polyimide bases, and phenol, epoxy resin, etc. are generally used. It cannot be surpassed. Therefore, a high-temperature strain gauge having such a configuration has been unsuitable in terms of heat resistance.

Furthermore, some high-temperature strain gauges have a structure in which a resistance element is fixed to a metal base using a ceramic adhesive. This type of high-temperature strain gauge is superior to the above-mentioned ones in terms of heat resistance, and since it uses metal as the base, if the object to be measured is metal, the high-temperature strain gauge can be used as the object to be measured. It has the advantage that it can be fixed by spot welding.

However, this type of strain gauge has a structure in which a ceramic adhesive layer is placed on a metal base, and a resistance element is placed on this ceramic adhesive layer. Since it is interposed between the strain gauge and the element, there are disadvantages in that strain accumulates inside the strain gauge during the manufacturing process, leading to measurement errors, and it is easily destroyed during high-temperature heating. Also, since the base is made of metal and has high rigidity, there is no problem when measuring the strain of something with high rigidity like metal, but when measuring the strain of something with less rigidity than metal, such as a fire brick, for example. There is also the problem that strain cannot be effectively transferred to the resistive element.

Furthermore, when a strain gauge is fixed to an object to be measured such as a brick with adhesive, the gap between the strain-generating part, that is, the part where strain is to be detected, and the resistance element is large due to the presence of the adhesive. Therefore, there was a problem in that the strain transferability further deteriorated and the sensitivity further decreased.

The present invention has been made to address these problems, and an object of the present invention is to provide a high-temperature strain gauge that has excellent heat resistance, small measurement errors, and high measurement sensitivity, and a method for manufacturing the same.

Hereinafter, the present invention will be explained in detail according to embodiments shown in the drawings.

FIG. 1 is a vertical cross-sectional view showing the structure of a first embodiment of the high temperature strain gauge according to the present invention. A resistive element 3 for detecting strain and a part of a gauge lead 4 connected to the resistive element 3 to lead out the strain output of the resistive element 3 to the outside are embedded inside the shaped ceramic body 2.

Note that 5 is ceramic paper as a base used when manufacturing the high-temperature strain gauge 1, and is removed when used.

The high temperature strain gauge 1 having such a configuration is manufactured, for example, as follows.

(1) Prepare ceramic paper 5. This ceramic paper 5 is impregnated with an inorganic material such as silicone resin, water glass, etc. as a binder.
Select a material whose binder is destroyed when heated to a temperature of 500°C (various products are commercially available).

(2) Apply a thin layer of ceramic adhesive on the ceramic paper 5. Thereafter, precuring is performed to solidify the ceramic adhesive and form a first unfired ceramic layer.

(3) A heat-resistant alloy (e.g. Nichrome V,
A wire or foil-like resistance element 3 for strain detection, which is processed into an appropriate shape using Armoroy D, platinum-tungsten alloy, etc., is transferred. Then, the resistor element 3 is temporarily attached with ceramic adhesive as appropriate.

(4) Connect gauge lead 4 to resistance element 3 by spot welding.

(5) Apply a ceramic adhesive to the surface and cover the entire surface with the ceramic adhesive to form a second unfired ceramic layer.

(6) Then, it is fired in an electric furnace at a temperature of about 500°C. Through this firing process, as shown in FIG. 1, a resistive element 3 and a part of a gauge lead 4 connected to the resistive element and which leads the strain output of the resistive element to the outside are buried inside the ceramic body 2. A high-temperature strain gauge with a unique structure can be created.

(7) The ceramic paper 5 whose binder has been destroyed by the firing process remains in the form of fibers at the bottom of the strain gauge. and remove it.

Such a high-temperature strain gauge 1 is constructed only of ceramic with excellent heat resistance, except for the resistance element 3 and the gauge lead 4. Unlike strain gauges using silicone, etc., the high-temperature strain gauge 1 is composed of three-dimensional network molecules, etc. It has excellent heat resistance.
Since there is no risk of deterioration even at high temperatures of 500°C, there is no risk that strain transferability will decrease due to defects in the material.

In particular, in the above embodiment, the binder of the ceramic paper 5 as a base after being fired at high temperature is destroyed and can be completely removed. Since the strain is directly transmitted to the resistance element 3 only through the thin ceramic body formed by firing the ceramic layer, there is an advantage that strain sensitivity is increased. The high-temperature strain gauge 1 from which the ceramic paper 5 serving as the base has been removed can be made extremely thin as a whole, and the surface attached to the member to be measured (in FIG.
Since the lower surface of the ceramic body 2) and the resistance element 3 are very close to each other, especially when bending strain is applied when compressive or tensile strain is to be detected, it is hardly affected by the bending strain. There is an advantage that there is no

In addition, at the manufacturing stage, as mentioned above,
The manufacturing process is simple, as the process is relatively simple: applying and solidifying the ceramic adhesive on the ceramic paper 5, then transferring the resistive element 3, etc., and then applying and solidifying the ceramic adhesive on top of it. In particular, when connecting the resistance element 3 and the gauge lead 4, the resistance element 3 is transferred onto the first unfired ceramic, and the resistance element 3 is temporarily attached with ceramic adhesive. Since the gauge lead 4 is welded (spot welded) to the resistance element 3, it can be easily welded without changing the shape of the resistance element 3, improving work efficiency and minimizing the occurrence of defective products. Can be suppressed.

In addition, the strain gauge is made of ceramic with the same fired ceramic adhesive except for the resistance element 3 and the gauge lead 4. There is no possibility that strain will be accumulated inside due to heating during manufacturing due to differences in thermal expansion coefficients of two different materials. Therefore, measurement errors caused by internal strain can be significantly reduced.

Furthermore, since it is based on ceramic, which has lower rigidity than metal, it can have greater sensitivity, and can particularly measure strain in materials with low rigidity, such as refractory bricks, without any problems. By the way, the gauge factor of the conventional high temperature gauge is 1.4.
~1.6, but according to the present invention, the gauge factor is 2.0
It became possible to increase the size to a certain extent.

In addition, since the ceramic body 2 exhibits extremely low insulation deterioration at high temperatures and has an extremely high insulation resistance of several +MΩ, measurement errors due to current leakage hardly occur.

Note that, during use, the lowest layer of ceramic paper is removed, so that it can be adhered to the measurement point either on the bottom or the top surface. Furthermore, in order to bond this high-temperature strain gauge 1 to the object to be measured, the same adhesive as the ceramic material used in the above-mentioned manufacturing process is used.

FIGS. 2 and 3 show the configuration of another embodiment of the present invention. In addition to the active gauge, this embodiment uses a dummy to correct the apparent distortion that occurs based on the temperature rise of the resistance element. It has a built-in game.

In the drawing, 6 is a high temperature strain gauge;
A ceramic body 7, an active gauge resistance element 8 embedded in the ceramic body 7, a gauge lead 9 (consisting of an active gauge lead 9a, a dummy gauge lead 9b, and a common gauge lead 9c), and a ceramic paper 10 are dummy. It is composed of a resistance element 11 for gauge. The high-temperature strain gauge 6 having such a configuration can be manufactured, for example, as follows.

(1) First, prepare ceramic paper (not shown).

(2) A ceramic adhesive is thinly applied onto the ceramic paper and precured to solidify to form a first unfired ceramic layer.

(3) The active gauge resistance element 8 is transferred onto the first unfired ceramic layer and temporarily attached using a ceramic adhesive.

(4) Connect gauge leads 9a and 9c to active gauge resistance element 8 by spot welding.

(5) Apply a ceramic adhesive onto the first unfired ceramic layer so as to cover at least part of the active gauge resistance element 8 and gauge lead 9, and then perform pre-curing to solidify this adhesive. to form a second green ceramic layer.

(6) Ceramic paper 10 is placed on the second unfired ceramic layer and above the resistance element 8 for the active gauge.

(7) Apply a ceramic adhesive on the exposed portions of the ceramic paper 10 and the second unfired ceramic layer, and then perform precuring to harden the adhesive and apply the third unfired ceramic layer. Form.

(8) Transfer the dummy gauge resistance element 11 onto the third unfired ceramic layer, temporarily attach the ceramic adhesive, and arrange the gauge leads 9b. And gauge lead 9b and resistance element 11
The gauge lead 9 is connected to one terminal of the resistance element 11 by spot welding, and the other terminal of the resistance element 11 is connected to the gauge lead 9 by spot welding.
Connect c.

(9) Apply a ceramic adhesive so as to completely cover at least the dummy gauge resistance element 11 placed on the third unfired ceramic layer.
A green ceramic layer is formed.

(10) After that, a firing treatment is performed at a temperature of about 500°C in an electric furnace, for example.

(11) Finally, remove the bottom layer of ceramic paper (not shown).

The high temperature strain gauge 2 of the second embodiment manufactured in this manner has the following characteristics.

First, the ceramic paper 10 is interposed between the active gauge resistance element 8 and the dummy gauge resistance element 11, and when the ceramic paper 10 is fired, the binder is destroyed and only the fibers remain, and this part becomes strained. Acts as an insulator. Therefore, the strain transmitted to the active gauge resistive element 8 is transferred to the dummy gauge resistive element 11.
It is possible to perform more accurate temperature compensation.

Furthermore, by arranging the orientation of the gauge grid constituting the resistive element 8 for the active gauge and the orientation of the gauge grid constituting the resistive element 11 for the dummy gauge so as to be orthogonal to each other, and constructing a half bridge by both gauges. , it is possible to significantly reduce the occurrence of apparent strain due to wide temperature changes.

Furthermore, in the second embodiment, the first
Of course, the same effect as described in the explanation of the embodiment shown in the figure can be achieved.

As detailed above, according to the first invention recited in claim 1, it has excellent heat resistance and does not have a decrease in strain transmissibility even under high temperatures, and is suitable for conventional high temperature gauges of this type. In comparison, high-temperature strain gauges have a high gauge factor, are less susceptible to bending strain, do not accumulate internal strain, have low rigidity, and have little insulation deterioration, and can therefore perform highly accurate and sensitive strain measurements. It is possible to provide a method for manufacturing a high-temperature strain gauge that can be easily manufactured and can reduce the defective rate.

Further, according to the second and third inventions described in claims 2 and 3, in addition to the effects achieved by the first invention, it is possible to It is possible to provide a high-temperature strain gauge having a highly accurate temperature compensation function for an object to be measured, and a method for manufacturing the same.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of one embodiment of the present invention, and FIGS. 2 and 3 are sectional views and plan views showing the structure of other embodiments of the invention. 1, 6... High temperature strain gauge, 2, 7... Ceramic body, 3... Resistance element for strain detection, 4, 9
... Gauge lead, 5, 10 ... Ceramic paper, 8 ... Resistance element for active gauge, 11
...Resistance element for dummy gauge.

Claims (1)

[Claims] 1. Ceramic paper made of an inorganic material impregnated with silicone resin, water glass, etc. as a binder and whose binder is destroyed when heated to high temperature is used as a base, and a ceramic adhesive is applied on the ceramic paper. After applying a thin layer, precuring is performed to solidify it to form a first unfired ceramic layer, and on this first unfired ceramic layer, a wire or foil shaped strain detection material is pre-processed into an appropriate shape using a heat-resistant alloy. After transferring the resistor element and temporarily attaching the resistor element with a ceramic adhesive, a gauge lead is welded to the resistor element, and then the resistor element, a part of the gauge lead, and the first green ceramic layer are welded. A ceramic adhesive is applied to the exposed portion of the ceramic adhesive, the entire surface is covered with the ceramic adhesive to form a second unfired ceramic layer, and then a firing treatment is performed at a high temperature, and then the binder is removed by the firing treatment. By removing the ceramic paper as the base was destroyed,
A method for manufacturing a high-temperature strain gauge, characterized in that the resistance element and a part of a gauge lead connected to the resistance element and which leads the strain output of the resistance element to the outside are buried inside a ceramic body. 2. Inside the ceramic body, there is a resistive element for an active gauge for detecting strain, and a part of an active gauge lead that is connected to this resistive element for an active gauge and leads out the strain output of the resistive element for an active gauge to the outside. , a dummy gauge resistor that is appropriately spaced above the active gauge resistor and is connected to the dummy gauge resistor for correcting apparent strain generated based on a temperature rise of the active gauge resistor; A part of the dummy gauge lead for leading the output of the dummy gauge resistance element to the outside is directly buried between the active gauge resistance element and the dummy gauge resistance element by a firing process. A high-temperature strain gauge characterized by interposing a strain insulating layer made of ceramic paper in which the binder is destroyed and only fibers remain. 3 Based on a first ceramic paper made of an inorganic material impregnated with silicone resin, water glass, etc. as a binder and whose binder is destroyed when heated to a high temperature, and a ceramic adhesive is applied on this first ceramic paper. After applying a thin layer, precuring is performed to solidify it to form a first unfired ceramic layer, and a wire or foil-shaped strain that has been pre-processed into an appropriate shape using a heat-resistant alloy is applied onto the first unfired ceramic layer. After transferring a resistor element for an active gauge for detection and temporarily attaching it with a ceramic adhesive, an active gauge lead is welded to the resistor element, and then at least the resistor for an active gauge is placed on the first green ceramic layer. A ceramic adhesive is applied to cover the element, and then pre-curing is performed to solidify the ceramic adhesive to form a second unfired ceramic layer, and then at least an active gauge of the second unfired ceramic layer is formed. A second ceramic paper similar to the first ceramic paper is disposed above the resistive element, and the second ceramic paper and the second unfired ceramic layer are exposed. A ceramic adhesive is applied thereon, and then pre-curing is performed to solidify the ceramic adhesive to form a third unfired ceramic layer, and a third unfired ceramic layer is formed on the third unfired ceramic layer for use in the active gauge. After transferring a dummy gauge resistor element to correct the apparent strain that occurs due to the temperature rise of the active gauge resistor element above the resistor element, the dummy gauge is temporarily attached with ceramic adhesive. Gauge leads are welded to the dummy gauge resistance element, and then a ceramic adhesive is applied onto the third green ceramic layer so as to completely cover at least the dummy gauge resistance element, and a fourth green ceramic layer is formed. A method for manufacturing a high-temperature strain gauge, comprising: forming a ceramic paper, then performing a firing treatment at a high temperature, and finally removing the ceramic paper serving as the base in which the binder has been destroyed by the firing treatment.