JPH01113601A - High temperature strain gage and structure for attachment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (a) Technical Field The present invention relates to a high-temperature strain gauge and its attached structure, and more particularly, to stress, load, pressure, rotational force, etc. that acts on an object to be measured at high temperatures. A strain gauge element that converts a physical quantity into an electrical quantity, and a physical quantity to which the strain gauge is attached to the object to be measured itself or to the object to be measured.
This invention relates to an attachment structure attached to an object to be measured, such as a strain-generating part of an electrical quantity converter. .

(b) Conventional technology Electric resistance wire strain gauges have been used for a long time.

It can be said that the strain measurement technology at room temperature has been established. In addition, strain gauges that can be used at high temperatures have been developed.
Currently, it is widely used.

Some of the conventional examples will be explained using FIGS. 11 to 14.

The conventional examples shown in FIGS. 11 and 12 are improved strain gauges used at room temperature, using polyimide, asbestos, etc. as the base 26, Ni-Cr alloy as the resistance wire material 24, and using aromatic This is a strain gauge that is attached to the object to be measured 28 with a family resin and silicone resin adhesive 25 (hereinafter referred to as an "adhesive strain gauge").The resistance wire material 24 has a gauge lead 27.
are connected by spot welding etc. As described above, the resistance wire material (strain gauge element) 24 is bonded to the object to be measured 28 via the base 26 with the adhesive 25.

The conventional example shown in FIGS. 13(a) and 13(b) is as follows.

This is a type in which the strain gauge is attached to the object to be measured by spot welding, and is called a welded strain gauge. This type of strain gauge has a capsule 29 made of a stainless steel tube, and a resistance wire material 2 inside the capsule 29.
4 together with a metal oxide 30, and a base 26 made of stainless steel is attached to the object to be measured by spot welding.

The conventional example shown in FIG. 14 is a gauge called a free filament type strain gauge, and unlike the above two types of strain gauges, it is a gauge that uses only a very thin resistance wire material 24. Then, this resistance wire material 24 is connected to an object to be measured (not shown).
There are two methods for attaching the strain gauges: one is to use an adhesive, and the other is to spray alumina or the like. Particularly, the latter method is called a thermal spray strain gauge.

FIG. 14 shows the case of this free filament type strain gauge.

These strain gauges have many practical problems.

For example, in adhesive strain gauges, the base material has poor heat resistance, and furthermore, as shown in FIG. There was a problem that the transmission efficiency decreased.

On the other hand, the thermal spray strain gauge described above, in which alumina is applied by spraying, has the following drawbacks.

That is, (1) it is impossible to manufacture a free filament type gauge that is extremely small in size;

(2) In thermal spray strain gauges, the end of the filament (resistance wire material 24) does not come into close contact with the object to be measured, which is particularly noticeable when the object to be measured has a curved surface.

(2) The surface of the filament that the object to be measured (face '11) is a shadow part that is not sprayed by thermal spraying, so it does not bond to the object to be measured, reducing the strain transmission efficiency. (2) If the shape of the filament is small, the filament will be scattered by thermal spraying. ■Thermal spray equipment that performs thermal spraying becomes larger. ■
The filament cannot be applied to areas where the thermal spraying device cannot be inserted (for example, inside a cylinder), and therefore cannot be applied to complex structural members. The structure changes and residual stress occurs. ■When bonding a free filament type strain gauge with an adhesive, there were problems such as the need to repeatedly temporarily fasten and cure the filament, which was time-consuming.

Finally, the single-point welding method has the advantage that the properties are not greatly affected by the welding technique of the user, but there are some materials that cannot be welded, and there is also the risk that residual strain at the welding point may affect the measured values. There is.

The disadvantage is that it cannot be applied to thin plate structures.

(c) Purpose The present invention was made in view of the above-mentioned circumstances, and its purpose is to easily and inexpensively manufacture extremely small pieces without requiring large-scale equipment, and to measure objects without flatness. It can be easily and reliably attached to the body, regardless of the material of the object to be measured, and has extremely good strain transmission efficiency from the object to be measured to the strain gauge element, reducing the stress that acts on the object under high temperature. The object of the present invention is to provide a high-temperature strain gauge that can convert physical quantities such as load, pressure, and rotational force into electrical quantities corresponding thereto, and a structure for attaching the same.

(d) Structure In order to achieve the above object, the first invention (the invention set forth in claim 1) is based on the following features: A strain gauge element that converts a physical quantity into an electrical quantity is attached to the object to be measured, such as the object to be measured itself or a strain-generating part of a physical quantity-to-electrical quantity converter attached to the object to be measured. The gauge includes a foil-shaped strain gauge element that is flexible and whose electrical resistance changes in response to the above-mentioned physical quantity, and a surface of the strain gauge element opposite to the surface to be attached to the object to be measured under high temperature. A thin support layer made of a flexible material such as acrylic resin that is burnt away and dissolved by an organic solvent such as acetone, and a hole is formed near the part of the support layer corresponding to the gauge tab of the strain gauge element. comprising a gauge lead guided through a communication hole and connected to the gauge tab, and configured so that the strain gauge element can be directly bonded to the object to be measured with an adhesive;
The second invention (the invention set forth in claim 2) is a strain gauge element that converts physical quantities such as stress, load, pressure, and rotational force that act on an object to be measured at high temperatures into electrical quantities.
In the attachment structure of a high-temperature strain gauge attached to the object to be measured, such as the object to be measured itself or the strain-generating part of a physical quantity-to-electrical quantity converter attached to the object to be measured, the above-mentioned physical quantity is flexible. A foil-shaped strain gauge element whose electrical resistance changes when exposed to heat, and an organic solvent such as acetone that burns out at high temperatures and is coated on the surface of the strain gauge element opposite to the surface to be attached to the object to be measured. A thin support layer formed of a flexible material such as acrylic resin that is soluble in and a gauge lead connected to the strain gauge, the surface to be attached of the strain gauge is adhered to the object to be measured with an adhesive, and the supporting layer is burnt out by being exposed to high temperature. It is composed of

Hereinafter, the first and second inventions (hereinafter both inventions are collectively referred to as
Embodiments of a high temperature strain gauge and its attachment structure according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional side view partially omitting the configuration of a high temperature strain gauge and its attachment structure according to the present invention.

In FIG. 1, reference numeral 1 denotes an object to be measured consisting of the object to be measured itself or a strain-generating part of a physical quantity-to-electrical quantity converter attached to the object to be measured, 2 an adhesive, 3 a strain gauge element,
4 is a gauge tab of this strain gauge element 3; 5 is a surface to which the strain gauge element 3 is to be attached; 6 is a support layer; 7 is a communication hole drilled in the vicinity of a portion of this support layer 6 corresponding to the gauge tab 4; 8; Reference numeral 9 indicates a gauge lead whose tip end is inserted (introduced) into the communicating hole 7, and 9 indicates a welded portion where the gauge lead 8 and the gauge tab 4 are welded together. still.

Hereinafter, the attached structure having the support layer 6 as shown in FIG. 1 will be referred to as a quasi-attached structure.

The strain gauge element 3, the support layer 6, and the gauge leads 8 constitute a strain gauge 10.

Further, in FIG. 1, the thickness of each member is extremely exaggerated, and the same applies to the following drawings.

Furthermore, parts common to those in FIG. 1 are designated by the same reference numerals and redundant explanations will be omitted.

Figures 2 to 6 are diagrams showing the structure of the strain gauge in more detail, following the manufacturing process. Figure 2 is a partially cutaway perspective view showing the process of forming a support layer; 3 is a perspective view showing a preparation process for forming a strain gauge element, FIG. 4 is a perspective view showing a state in which the strain gauge element 3 is formed, and FIG. 5 is a perspective view showing a process of forming a communication hole. FIG. 6 is an enlarged perspective view partially omitted and cut away to show how the gauge lead is mounted.

In FIG. 2, 11 is a flat glass plate, 12 is a resistance material made of a foil material (about 5 μm), such as Ni-Cr, placed on this glass plate 11, and 13 is a high-temperature material such as acrylic resin. It is a thin acrylic film formed by applying a solution of a material that is burnt away on the resistive material 12 to a thickness of, for example, about 20 μm to 50 μm and drying it.

In FIG. 3, as already mentioned, 6 is a flexible support layer formed by adjusting the acrylic film 13 in FIG. 2 to the size of the resistive material 12. 6
The vertical relationship between the resistive material 12 and the resistive material 12 is shown reversed. Therefore, the above-mentioned surface to be attached 5 is located above here. 1
5, in order to form a strain gauge element by a well-known photo-etching method, a photo-etching resist is applied onto the surface 5 of the resistance material 12 to be attached and dried;
This is an exposure trace projected and exposed using a photomask.

In FIG. 4, reference numerals 16 and 17 denote gauge tabs formed at both ends of the strain gauge element 3 which was further formed from the state shown in FIG. The gauge tabs 4 shown in FIG. 1 are the same, but have different cross-sections. Reference numeral 18 denotes a portion where the communication hole 7 is to be formed in the support layer 6 and is approximately cylindrical or conical.

In FIG. 5, reference numeral 19 denotes an organic solvent such as acetone (hereinafter simply referred to as "acetone") that is dropped on the support layer 6 at a position corresponding to the gauge tab 16, that is, on the communication hole planned portion 18.

In FIG. 6, reference numeral 20 indicates a spot welding point forming a weld 9 for connecting the gauge tab 16 and the gauge lead 8.

7 and 8 are both cross-sectional views showing the quasi-attached structure, and the shape of the strain gauge 10 is taken along line BB' in FIG.
The cross section shown in the direction of the arrow is shown as an inverted shape, and FIG. 7 shows a case where the object to be measured 1 is made of a non-conductive material, and FIG. 8 shows a case where the object to be measured 1 is made of a conductive material.

In FIGS. 7 and 8, 21 is an inorganic adhesive used as a pure adhesive to bond the object to be measured 1 and the surface 5 to be attached of the strain gauge element 3, and is the same as the adhesive 2 in FIG. It is. Reference numeral 22 denotes glass beads as powder particles made of an insulating material mixed into the adhesive, and the glass beads 22 and the adhesive 21 constitute the mixed adhesive. Further, the glass beads 22 have a diameter of about 5 μm in this example.

FIG. 10 is a cross-sectional view showing a completed state of the attachment structure of the high-temperature strain gauge according to the present invention, and the dotted line shows the state before the support layer 6 disappears.

Next, the manufacturing method, attachment method, and operation of this embodiment configured as described above will be explained.

First, the manufacturing process of the strain gauge 10 itself will be explained. The steps from FIG. 2 to FIG. 4 are the same as described in the explanation of the configuration, and therefore will be omitted. As shown in FIG. 5, one drop of acetone 19 will soften the connecting hole portion 18 of the support layer 6 downward after a short period of time after the drop. Pick with a shaped jig and drill a communication hole 7 as shown in FIG. Then, the tip of the gauge lead 8 is inserted into the communicating hole 7 and brought into contact with the gauge tab 16, and spot welding is performed at the welding point 2o to join the gauge tab 16 and the gauge lead 8 (although not shown, the other gauge tab 17 is also However, as can be seen from the above description, the communication hole 7 is not a neat circle as shown in FIG. 6, but is actually irregular in shape.

For convenience of drawing, it is circular. The same applies to the inner wall of the communication hole 7.

Next, the quasi-attached structure of the strain gauge 10 manufactured in this way will be explained.

As shown in FIGS. 1 and 7, when the object to be measured 1 is made of a non-conductive material, an adhesive 21 (2) is applied to the object to be measured 1.
is applied, and the strain gauge 10 is bonded with the surface 5 of the strain gauge element 3 to be attached facing the object to be measured 1 side.

On the other hand, when the object to be measured 1 is made of a conductive material, the strain gauge 10 is bonded with an adhesive 21 mixed with glass beads 22, as shown in FIG.

When the quasi-attached structure shown in FIG. 8 manufactured in this way is exposed to high temperature to burn out the support layer 6, the structure shown in FIG.
The attached structure as shown in is completed.

In this way, according to this embodiment, the support layer 6 is formed on the resistive material 12, and then the strain gauge element 3 is formed from the resistive material 12 by the photoetching method. There is an advantage that the gauge element 3 can be manufactured, and since the strain gauge element 3 is supported by the support layer 6, it is easy to handle.

Further, the support layer 6 is easily softened by dropping acetone 19, and the communication hole 7 can be simply formed by simply picking thereafter, so that the strain gauge element 10 itself has the advantage of being easy to manufacture.

Furthermore, in the attachment structure, the strain gauge element 3 can be directly attached to the object to be measured 1 without using the base 26 as in the conventional case, and in addition to improving the strain transmission efficiency,
The support layer 6 that regulates the movement of the strain gauge element 3 has been burnt down and no longer exists.

There is an advantage that the sensitivity of the strain gauge element 3 is further improved.

Furthermore, when the object to be measured 1 is made of a conductive material, the insulating state is maintained by the glass beads 22 mixed into the adhesive 21, so even if a strong pressing force is applied to the strain gauge 1o during bonding, the strain gauge element 3 There is an advantage that each side of the device 1 is not short-circuited by the object 1 to be measured, and is not affected by insulation deterioration of the adhesive 21 at high temperatures.

Therefore, since the strain gauge element 3 and the support layer are flexible, they have the advantage of being applicable to complex objects to be measured without any problems, and can be applied to any material (metal, non-metal, etc.) of the object to be measured. There are advantages.

In addition, since adhesive is used, even the strain gauge element 3 having an extremely small shape will not be scattered, and the drawbacks of conventional welding methods will not be present.

Another advantage is that it does not require a particularly large device like the above-mentioned thermal spray strain gauge.

It should be noted that the present invention is not limited to the above-described embodiments, and can be modified in various ways without departing from the spirit thereof.

For example, as shown in FIG. 10, a protective film 23 may be formed using an inorganic adhesive. In this case, there is an advantage that the properties of the attached structure are more stable.

Further, in the above description, only one strain gauge 10 is attached, but a plurality of strain gauges 10 may be attached. Therefore, it can also be applied to so-called rosette type strain gauges.

In addition, although only a flat object to be measured 1 is illustrated,
The curved surface 1 can be easily applied to, for example, the inner peripheral surface and outer peripheral surface of a cylindrical member. Therefore, it can be attached directly to a bellows or attached to the inner surface of a diaphragm of a pressure gauge or the like.

(e) Effects As detailed above, according to the first and second inventions, large equipment is not required for installation, extremely small pieces can be manufactured easily and inexpensively, and flatness can be improved. It can be easily and reliably attached to objects to be measured that have complex surfaces such as curved surfaces, as well as objects to be measured that have complex surfaces such as curved surfaces, and can be attached regardless of the material of the object to be measured, such as ceramics, carbon, metal materials, etc. Moreover, it can be attached to strain gauge elements from objects to be measured to strain gauge elements. The strain transmission efficiency is extremely good, and the stress, load, and pressure that act on the measured object at high temperatures1
It is possible to provide a high-temperature strain and its attachment structure that can convert a physical quantity such as rotational force into a corresponding electrical quantity.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional side view showing a part of the configuration of a high temperature strain gauge and its attached structure according to the present invention, and FIGS.
The figure shows the structure of the strain gauge used in the embodiment shown in Fig. 1 in more detail, following the manufacturing process.
FIG. 2 is a partially cutaway perspective view showing the process of forming a support layer. FIG. 3 is a perspective view showing the preparation process for forming a strain gauge element, FIG. 4 is a perspective view showing the state in which the strain gauge element is formed, and FIG. 5 is a perspective view showing the process of forming a communication hole. Fig. 4 A-A' partial sectional view (inverted), No. 6
The figure is an enlarged perspective view partially omitted and cut away to show how the gauge leads are installed, and Figures 7 and 8 are cross-sectional views showing the quasi-attached structure, and the shape of the strain gauge is shown in Figure 8. 4
The cross section taken along the line B-B' in the figure is shown as an inverted shape. Of these, Fig. 7 shows the case where the object to be measured is made of a non-conductive material, and Fig. 8 shows the case where the object to be measured is made of a conductive material. FIG. 9 is a cross-sectional view showing the attachment structure in a state where the support layer of the quasi-structure shown in FIG. 8 has been burnt out;
FIG. 10 is a cross-sectional view showing the completed attachment structure of the high-temperature strain gauge according to the present invention, FIG.
2 is a plan view and a sectional view showing the configuration of a conventional bonded strain gauge, and FIGS. 13(a) and 13(b) are a front view and a longitudinal sectional view respectively showing the configuration of a conventional welded strain gauge. , FIG. 14 is a plan view showing the configuration of a conventional thermal spray strain gauge. 1...Object to be measured, 2...Adhesive, 3...Strain gauge element, 4.16, 17...Gauge tab, 5...・
・Planned attachment side. 6...Support layer, 7...Communication hole, 8...Gauge lead, 9...Welded part. 10...Strain gauge, 11...Glass plate. 12... Resistance material, 13... Acrylic film, 15... Exposure trace, 18... Connection hole planned area, 19...・Organic solvent (acetone), 21...
··glue. 22...Glass beads, 23...Protective film. Patent applicant Kyowa Dengyo Co., Ltd.

Claims (2)

[Claims] (1) A strain gauge element that converts physical quantities such as stress, load, pressure, rotational force, etc. that act on the measured object under high temperature into electrical quantities is attached to the measured object itself or to the measured object. High-temperature strain gauges attached to objects to be measured, such as strain-generating parts of physical quantity-to-electrical quantity converters, include a foil-like strain gauge element that is flexible and whose electrical resistance changes in response to the above-mentioned physical quantity; A thin support layer formed of a flexible material such as acrylic resin that burns out at high temperatures and dissolves in organic solvents such as acetone on the surface of the strain gauge element opposite to the surface attached to the object to be measured. and a gauge lead guided through a communication hole drilled in the vicinity of a portion of the support layer corresponding to the gauge tab of the strain gauge element and connected to the gauge tab, the strain gauge element being connected to the strain gauge element to be measured. A high temperature strain gauge characterized by being configured so that it can be directly attached to the body with an adhesive. (2) A strain gauge element that converts physical quantities such as stress, load, pressure, rotational force, etc. that act on the measured object under high temperature into electrical quantities is attached to the measured object itself or to the measured object. In the attached structure of a high-temperature strain gauge that is attached to a measured object such as a strain-generating part of a physical quantity-electrical quantity converter, a foil-like strain gauge element that is flexible and whose electrical resistance changes in response to the above physical quantity is used. , on the surface of this strain gauge element opposite to the surface to be attached to the object to be measured, is formed of a flexible material such as acrylic resin that burns out at high temperatures and dissolves in organic solvents such as acetone. A strain gauge comprising a thin support layer having a thin support layer, and a gauge lead connected to the gauge tab and guided through a communication hole bored in the vicinity of a portion of the support layer corresponding to the gauge tab of the strain gauge element. An attachment structure for a strain gauge for high temperature use, characterized in that the attachment surface of the gauge is adhered to the object to be measured with an adhesive, and the support layer is burnt out when exposed to high temperatures. .