JPH06137805A - Strain gauge and its manufacture - Google Patents

Abstract

PURPOSE:To provide a strain gauge being less in the dispersion of resistance by coating a metallic elastic body with a glass-ceramic insulated layer, forming a gel layer or a glass layer on the surface of this insulated layer, and forming an element whose resistance alters according to a strain on this gel or glass layer. CONSTITUTION:The crystal glass is prefered to be non-alkaline, for instance the glass-ceramic having such composition as SiO2 7 to 30%, B2O3 5 to 34%, MgO 16 to 50%, CaO 0 to 20%, BaO 0 to 50%, ZrO2 0 to 50%, P2O5 0-5%, and La2O3 0 to 4% (all in weight %) to strengthen adherence to a metallic substrate. After the metallic substrate is covered by spray, powder electrostatic coating and electric induction electrocoating and dried, the glass-ceramic layer is baked at 850 to 900 deg.C for about 10 to 60 minutes. Glass component and metallic substrate component are thereby mutually diffused to form strong mutual adherence. In addition, the surface roughness of the substrate therefore becomes small to reduce the dispersion of resistance in forming a resistance element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strain gauge for detecting stress and strain and a method for manufacturing the strain gauge, and more particularly to a vehicle suspension used in an automobile.

[0002]

2. Description of the Related Art Conventionally, strain gauges have been used to detect stresses generated in various parts of machines, ships, automobiles and the like, the magnitude of loads, and the like. This strain gauge has a configuration in which a resistive element of Cu-Ni, Ni-Cr foil is arranged on a resin or ceramic base material such as polyester, epoxy, or polyimide, and at the time of measurement, the strain gauge is used as an object to be measured. It is fixed with an adhesive. There is also a strain gauge in which a resistance element is formed on a metal core substrate in which a metal base material is covered with a crystallized glass layer.

[0003]

However, when the above-mentioned adhesive strain gauge is used by adhering it to a portion such as a shaft of a suspension of an automobile where a repeated strain amount is measured, the adhesive layer is formed in tens of thousands of cycles. It could not be used because it may peel off. Further, when the strain measurement site is exposed to a high temperature atmosphere of 150 ° C. or higher, the adhesive strength of the adhesive becomes weak and the strain gauge is easily peeled off.

In addition, although there is no possibility of peeling, the strain gauge using a metal core substrate has a high degree of crystallinity for precipitating crystals in order to provide heat resistance, so that the surface becomes rough to some extent. When resistors are formed on such a crystallized glass layer having poor surface properties, the variations in the resistance increase.

The present invention solves the above problems, and provides a strain gauge and a method for manufacturing the strain gauge in which the surface roughness of the substrate surface can be reduced and the resistance variation of the resistance element formed thereon can be reduced. That is the purpose.

[0006]

In order to solve the above-mentioned problems, the strain gauge of the present invention and a method for manufacturing the same are provided with a gel layer or glass on the surface of an insulating layer made of crystallized glass coated on a metal elastic body. A layer is formed, and an element whose resistance changes with strain is formed on the gel layer or the glass layer.

[0007]

With the above structure, the strain gauge substrate of the present invention comprises a gel layer or a glass layer further formed on the electrical insulating layer. By providing the gel layer or the glass layer, the surface of the substrate surface is provided. The roughness is reduced, and it is improved to the level of a high-purity alumina substrate. Therefore, variations in resistance when the resistance element is formed are reduced.

[0008]

EXAMPLE An example of the present invention will be described below. First, the crystallized glass layer which is the insulating layer of the present invention will be described. The crystallized glass is preferably alkali-free in consideration of heat resistance, substrate strength, and insulation. The crystallized glass composition, SiO ₂ 7 to 30 wt% B ₂ O ₃ 5~34 wt% MgO 16 to 50 wt% CaO 0 to 20 wt% BaO 0 to 50 wt% ZrO ₂ 0 to 5 wt% P ₂ O ₅ is 0-5% by weight La ₂ O ₃ 0 to 40 wt%. The reason why the glass having the above composition range is selected is that the adhesion between the metal substrate and the crystallized glass layer needs to be strong. If the amount exceeds the above range, the adhesion is deteriorated, which is not preferable.

Further, as a method for coating the above-mentioned crystallized glass layer on a metal substrate, a spray method, a powder electrostatic coating method,
Electrophoretic electrodeposition method and the like. The electrophoretic electrodeposition method is the most preferable from the viewpoints of the denseness of the coating film, the electric insulating property, and the like.

According to this method, glass, alcohol and a small amount of water are added, and the mixture is ground in a ball mill for about 20 hours and mixed to make the average particle diameter of glass about 1 to 5 μm. The obtained slurry is put in an electrolytic cell and the liquid is circulated. A previously washed metal substrate is dipped in this slurry and
Glass particles are deposited on the surface of the metal substrate by performing negative polarization at 0 to 400V. After drying this, 850-9
Bake at 00 ° C. for 10 minutes to 1 hour. As a result, the glass fine particles are melted, and the glass component and the metal material component are sufficiently diffused to each other, so that strong adhesion between the glass hollow layer and the metal material can be obtained.

Next, a concrete embodiment will be described. (Example 1) Crystallized glass as shown in composition numbers 1 to 42 of (Table 1) to (Table 5) was synthesized. In addition, according to the above process, SUS430 base material (100 mm x 100 mm x
(0.5 mm), a 100 μm thick crystallized glassy layer was electrophoretically electrodeposited and baked at 880 ° C. for 10 minutes to prepare a sample, and the surface roughness and waviness of the sample as shown in the table were obtained. The results of various properties such as heat resistance and heat resistance were obtained.

The surface roughness was measured with a Talysurf surface roughness meter and indicated by the surface center line average roughness Ra. The waviness was expressed by the difference Rmax between the peak and the valley obtained by a Talysurf surface roughness meter. Regarding the heat resistance, a sample was put in an electric furnace at 850 ° C. for 10 minutes, taken out of the furnace, and allowed to stand for 30 minutes to perform a spalling test in which a cycle of natural cooling was repeated to examine the state of cracks and peeling of the sample. The cracks were immersed in the red ink, the surface was wiped off, and the presence or absence of the cracks was checked by visual observation. In the table, ◯, Δ, and × indicate that no abnormality was observed even if ◯ was performed for 10 cycles or more,
The symbol Δ indicates that it occurred in 5 to 9 cycles, and the symbol x indicates that it occurred in 4 cycles or less. Adhesion was measured by conducting a bending test on the substrate and removing the holo layer to expose the metal part.
The case where only a part of the metal part was exposed was evaluated as Δ, and the case where the metal part was not exposed was evaluated as ○.

Based on the above evaluations, a comprehensive evaluation was performed, and the results are shown by ◯, Δ, and x. Nos. 1 to 8 are obtained by changing SiO ₂ and B ₂ O ₃ while keeping other components constant, N
o 9 to 15 make SiO ₂ / B ₂ O ₃ almost constant and M
No. 16 to 19 in which the amount of gO was changed was the same as C
A change in aO amount. No20 ~ 24,
The amount of BaO was changed. Similarly, Nos. 25 to 29 are those in which the amount of La ₂ O ₃ was changed. No. 30 to 42 are ZrO ₂ , TiO ₂ , SnO ₂ , P ₂ O ₅ , and
This shows the effect of ZnO.

As is clear from the table, when the SiO ₂ content is increased, the heat resistance is improved, but the surface property and the adhesion are deteriorated. On the contrary, when the amount of B ₂ O ₃ is increased, the surface property and the adhesion are improved, but the heat resistance is decreased. Considering these, in the present invention, SiO ₂ is 7 to 30% by weight, B
₂ O ₃ is preferably in the range of ₅ to 34% by weight.

The amount of MgO has a correlation with the crystallinity, and if it is 16% by weight or less, the precipitation of crystals is insufficient and the heat resistance is poor. Also,
If it is 50% by weight or more, crystals are likely to precipitate, it is difficult to crystallize when the glass melts, it is difficult to obtain a homogeneous glass, and the surface roughness becomes large.

If the CaO content is 20% by weight or more, the surface property is deteriorated, which is not preferable. BaO content is 50% by weight
Above, it is not preferable because the heat resistance and the adhesion are deteriorated.

When the amount of La ₂ O ₃ is 40% by weight or more, heat resistance is deteriorated, which is not preferable. Other additives can be component of _{ZrO 2, TiO 2, SnO 2} , P 2 O 5, but including ZnO and the like, can be added if up to 5% by weight or less.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

[Table 4]

[0022]

[Table 5]

A strain sensor manufactured by forming crystallized glass based on the above method will be described. Outer diameter 20
After performing the steps of degreasing, washing with water, pickling, washing with water, nickel plating, and washing with a cylindrical metal elastic body having a diameter of 18 mm, an inner diameter of 18 mm, and a length of 20 mm as pretreatments, (No. 1 in Table 1). 5 (surface roughness 0.05 μm) was immersed in a slurry consisting of glass particles having a composition shown in FIG. 5, and a DC voltage was applied between the counter electrode and the cylindrical metal to coat the glass particles on the side surface of the cylindrical metal, It was baked at 900 ° C. for 10 minutes to form an insulating layer made of a crystallized glass layer. Next, the crystallized glass layer, silicon tetraethoxide _{Si (O-C 2 H 5} ) 4, titanium tetraisopropoxide _{Ti (O-isoC 3 H 7} ) 4,
An alkoxide solution containing water, ethanol and hydrochloric acid was applied. The metal element in the alkoxide solution had a silicon element to titanium element ratio of 8: 2. The application was performed by the dip coating method. After coating, it was dried at room temperature for 5 hours and heat-treated at 500 ° C. for 10 minutes. By drying and heat treatment, the applied metal alkoxide solution undergoes hydrolysis and dehydration condensation reaction to form a gel layer or a glass layer containing a silicon element and a titanium element, thereby improving the surface properties of the substrate. The Ag-Pd type electrode paste is printed on the gel layer or the glass layer by screen printing and heat-treated at 850 ° C for 15 minutes, and then the RuO ₂ type resistance paste is printed and heat-treated at 760 ° C for 30 minutes to make resistance. A strain gauge was manufactured by forming an element.

The gel layer or glass layer is made of Si, G
Any oxide containing at least one element of e, Ti, Zr, B, Al and P may be used. (Example 2) In Example 1, the ratio of the silicon element and the titanium element in the alkoxide solution was set to 8.5: 1.5.

Example 3 In Example 1, the ratio of silicon element to titanium element in the alkoxide solution was set to 10: 0 without adding titanium alkoxide. (Example 4) In Example 1, the glass particles in the slurry were changed to No. 2 (surface roughness 0.5 μm). Other conditions are the same.

Based on the above-mentioned examples and the comparative examples shown below, the average value of the surface roughness before forming the electrode layer and the resistance layer, and the average value of the surface roughness after forming the electrode layer and the resistance layer were respectively set for 10 pieces. The resistance value was measured, and the average value and standard deviation were measured. The results are shown in (Table 6).

[0027]

[Table 6]

As shown in (Table 6), when a glass layer is provided on a metal core substrate having a poor surface roughness (Example 4), variations in resistance (standard) are better than those of a metal core substrate having a good surface roughness (Comparative Example 1). Deviation) has become smaller. That is, according to the present invention, it is possible to manufacture a sensor having a small variation in resistance value even on a substrate having a poor surface roughness. However, it can be seen that the degree of variation reflects the surface roughness of the original substrate as shown by the results of Examples 1 and 4. However,
It can be seen that if the composition of the alkoxide solution for coating is not properly selected, the surface roughness of the substrate will deteriorate.

Comparative Example 1 In Example 1, an electrode and a resistance layer were directly formed on the crystallized glass layer without forming the glass layer on the crystallized glass layer. Comparative Example 2 In Example 1, the ratio of silicon element to titanium element in the alkoxide solution was 2.5: 7.5. The surface roughness was 0.06 μm, and the surface property was poor.

[0030]

As described above, the strain gauge of the present invention can reduce the surface roughness of the substrate surface by forming the gel layer or the glass layer on the insulating layer, and easily reduce the variation in resistance. Therefore, it can withstand a high temperature atmosphere of about 200 ° C.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiko Yoshida 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. An insulating layer made of crystallized glass coated on a metal elastic body, a gel layer or a glass layer formed on the surface of the insulating layer, and a strain formed on the gel layer or the glass layer. A strain gauge with an element whose resistance changes with respect to. 2. The composition of the crystallized glass is wt% MgO;
16-50%, BaO; 0-50%, CaO; 0-20
_{%, La 2 O 3; 0~40} %, B 2 O 3; 5~34%,
SiO ₂ ; 7 to 30%, MO ₂ (M is Zr, Ti, Sn
0% to 5%, P ₂ O ₅ ; 0 to 5%. The strain gauge according to claim 1. 3. The gel layer or glass layer is Si, Ge, T
3. An oxide containing at least one element selected from i, Zr, B, Al and P. 3.
Strain gauge as described. 4. A step of providing an insulating layer composed of a crystallized glass layer on at least a metal elastic body, a step of providing a gel layer or a glass layer on the surface of the insulating layer, and a strain on the gel layer or the glass layer. A method of manufacturing a strain gauge, comprising the step of forming a resistance element whose resistance changes with respect to. 5. The step of providing a gel layer or a glass layer,
The method for manufacturing a strain gauge according to claim 4, which is a step of applying a solution containing a metal alkoxide that becomes gel or glass by heat treatment and heat-treating. 6. The method of manufacturing a strain gauge according to claim 5, wherein the metal alkoxide contains silicon alkoxide and / or titanium alkoxide, and the composition ratio thereof is in the range of 10: 0 to 8: 2.