JP3867990B2 - Mechanical quantity sensor - Google Patents

Description

  The present invention relates to a mechanical quantity sensor that measures a mechanical quantity such as a load, a pressure, a displacement, and the like, and a change amount thereof by a change in electric resistance of a resistance element.

In recent years, a mechanical quantity sensor that detects a load, a pressure, and the like is widely used to measure a stress and a magnitude of a load generated in each part of a machine, a ship, an automobile, and the like. Various sensors of this type have been proposed depending on the type of substrate and the type of strain-sensitive material used for the resistance element.
As a representative example,
(1) A film made of a resin such as polyester, epoxy, polyimide, etc. is used as a substrate, and a thin film resistive element made of Cu—Ni alloy, Ni—Cr alloy or the like is formed on this surface by vapor deposition or sputtering,
(2) Using a glass plate instead of the above resin film (Patent Document 1), and (3) Using a metal substrate whose surface is covered with a crystallized glass layer as a substrate, applying a paste to this surface, A device in which a resistive element is formed by firing has been proposed (see Patent Document 2).

The magnitude of the mechanical quantity is measured as follows. When an external force or load is applied to the mechanical quantity sensor, the resistance element formed on the surface of the substrate is deformed together with the substrate. The applied mechanical quantity is detected by measuring a change in electrical resistance due to a change in the length and cross-sectional area of the resistance element between a pair of electrodes formed connected to the resistance element.
By the way, as one of the markets where the demand for mechanical quantity sensors is great, there is a vehicle suspension used for automobiles and the like. In a vehicle suspension, for example, a mechanical quantity sensor is attached to the surface of a shaft of a shock absorber with an adhesive or the like, and a change in load applied to the vehicle body is detected from a change in electrical resistance of the mechanical quantity sensor.

However, a mechanical quantity sensor using a resin film as a substrate can be used in a wide range of environmental temperatures from −50 ° C. to 150 ° C., as in a vehicle suspension, and under severe environmental conditions where the maximum load reaches 2 tons. When used for a period, there is a problem that the adhesive strength is lowered and the mechanical quantity sensor is peeled off from the member.
Further, in a mechanical quantity sensor using a glass plate as a substrate, a resistance element formed by vapor deposition or sputtering has difficulty in adhesion to the substrate. Furthermore, when the glass plate is welded to a curved surface such as a shaft, the adhesiveness is poor, so that strong adhesion is difficult and easy to peel off.
On the other hand, in a mechanical quantity sensor using a metal substrate with a crystallized glass layer formed on the surface as a substrate, each component element is mutually connected between the metal substrate and the crystallized glass layer, and between the crystallized glass layer and the resistance element. Since they are diffused, the adhesion between them is very strong, making it ideal as a sensor for use in harsh environmental conditions. As a resistance element of this type of mechanical quantity sensor, a resistance element formed by applying a resistance paste obtained by adding glass powder and a vehicle to ruthenium oxide, which is a resistance material, and then drying and firing is known. Since the element contains components other than the resistive material, the sensitivity of the obtained sensor to distortion is low and has not yet been put into practical use. Therefore, development of a mechanical quantity sensor using a resistance paste capable of forming a highly sensitive resistance element has been awaited.
Japanese Patent Publication No. 3-20682 JP-A-5-93659

  An object of the present invention is to solve the above-described problems and to provide a highly sensitive mechanical quantity sensor including a resistance element having high sensitivity to strain.

  By applying a resistance paste containing copper-containing composite oxide, glass frit, organic vehicle and diluent to the surface of the insulating substrate, followed by drying and firing, a mechanical quantity sensor using a highly sensitive resistance element can be obtained. .

  According to the present invention, it is possible to obtain a mechanical quantity sensor including a highly sensitive strain-sensitive resistance element that exhibits a high rate of change in resistance.

The resistance paste used for manufacturing the mechanical quantity sensor of the present invention contains a copper-containing composite oxide, a glass frit, an organic vehicle, and a diluent.
Furthermore, the copper-containing composite oxide is preferably a composite oxide containing Bi, Sr and Ca.
Further, the copper-containing composite oxide is Bi: Pb: Sr: Ca: Cu = 2-x: x: 2: 2: 3 (0 ≦ x ≦ 2) in a molar ratio of Bi, Pb, Sr, Ca and Cu. It is preferable to contain in the ratio.

The mechanical quantity sensor of the present invention includes an insulating substrate, a strain sensitive resistor element formed on the surface of the insulating substrate, and a pair of electrodes for detecting a change in electric resistance of the strain sensitive resistor element. Includes a copper-containing composite oxide and glass. A highly sensitive mechanical quantity sensor can be obtained by firing a mixture of copper-containing composite oxide powder and glass frit to form a resistance element. In particular, when the above-described resistance paste is used, the organic vehicle and diluent in the paste are scattered during drying and firing, and an excellent mechanical quantity sensor can be obtained.
Moreover, it is preferable that an insulating substrate consists of a metal base material which coat | covered the layer which consists of crystallized glass on the surface.
Further, the crystallized glass is SiO ₂ : 7 to 33% by weight, B ₂ O ₃ : 5 to 31% by weight, MgO: 16 to 50% by weight, CaO: 0 to 20% by weight, BaO: 0 to 50% by weight. La ₂ O ₃ : 0 to 40% by weight, P ₂ O ₅ : 0 to 5% by weight and MO ₂ : 0 to 5% by weight (wherein M is at least one element of Zr, Ti and Sn) It is preferable.

The insulating substrate used for the mechanical quantity sensor of the present invention will be described.
(A) Metal base material As the metal base material, various alloy materials such as horo steel, stainless steel, silicon steel, nickel-chromium-iron, nickel-iron, kovar, invar, and cladding materials thereof are selected. Stainless steel SUS430 is most preferable from the viewpoint of adhesion to the insulating layer.
Once the material of the metal substrate is determined, it is processed into a desired shape by normal machining, etching, laser processing, or the like. As the shape, a cylindrical shape, a plate shape (including a foil shape), or the like is selected depending on the magnitude and application of the load.
For the purpose of improving the adhesion of the insulating layer, these metal substrates are subjected to surface defatting and then subjected to sand blasting treatment, various plating treatments such as nickel and cobalt, or thermal oxidation treatment for forming an oxide coating layer. Is done.

(B) Insulating layer The insulating layer formed on the metal substrate is preferably made of crystallized glass. In particular, from the viewpoint of insulation and heat resistance, non-alkali crystallized glass (for example, MgO-based by firing). It is preferable that the crystal phase is precipitated.
Examples of the method of coating the crystallized glass layer on the metal substrate include a printing method, a spray method, a powder electrostatic coating method, and an electrophoretic electrodeposition method. The electrophoretic electrodeposition method is most preferable from the viewpoints of the denseness of the coating, electrical insulation, and the like.

The electrophoresis electrodeposition method is performed, for example, as follows.
Alcohol and a small amount of water are added to the glass, and the mixture is pulverized and mixed in a ball mill for about 20 hours, so that the glass has an average particle size of about 1 to 5 μm and is slurried. The obtained slurry is put into an electrolytic cell and the liquid is circulated. A metal base material is immersed in this slurry, a voltage of 100 to 400 V is applied between the metal base material as a negative electrode and a counter electrode, and glass particles are coated on the surface of the metal base material. This is dried and then fired at 850 to 900 ° C. for 10 minutes to 1 hour to melt the fine particles of the glass and form a crystallized glass layer. At this time, the glass melts and the glass component and the metal material component sufficiently interdiffuse, so that a strong adhesion between the crystallized glass layer and the metal substrate can be obtained.
During firing, by gradually raising the temperature from room temperature to the above temperature, an infinite number of fine needle crystals are precipitated, and the anchor effect improves the mechanical strength of the glass layer itself and the adhesion to the resistance element. Can be made.

Next, specific examples of the present invention will be described in detail.
First, the following examination was performed about the composition of this crystallized glass.
In accordance with the above-described insulating layer forming step, No. 1 shown in Tables 1 to 7 were formed on the surface of a metal base made of stainless steel (SUS430) having a length of 100 mm, a width of 100 mm and a thickness of 0.5 mm. Crystallized glass having a composition of 1 to 42 was electrodeposited by the above-described electrophoresis method and baked at 880 ° C. for 10 minutes to form a crystallized glass layer having a thickness of 100 μm. Various characteristics such as surface properties such as surface roughness and waviness and heat resistance of the obtained samples were examined.

The surface roughness is expressed by Talysurf surface roughness meter to measure the surface average roughness Ra, waviness resistance was expressed by the difference R _max of peaks and valleys of the undulation obtained at this time.
For heat resistance, the sample is placed in an electric furnace at 850 ° C. for 10 minutes, removed from the furnace, and then subjected to a spalling test in which the sample is naturally cooled at room temperature for 30 minutes. Examined. The crack was determined by immersing the sample in red ink, wiping off the ink on the sample surface, and visually observing whether the red ink remained on the surface of the sample. ○, Δ and × in the table indicate that no abnormality is observed even if ○ is performed for 10 cycles or more, Δ indicates that an abnormality has occurred in 5 to 9 cycles, and × indicates that an abnormality has occurred in 4 cycles or less. Indicates.
Adhesiveness is determined by conducting a bending test on an insulating substrate, where the crystallized glass layer is peeled off and the metal part is exposed x, when the metal part is only partially exposed Δ, when the metal part is not exposed Was marked as ○.
Comprehensive evaluation was performed based on the above evaluations, and the results were indicated by ○, Δ, and ×.

No. shown in Table 1. 1 to 8 are obtained by changing the ratio of SiO ₂ and B ₂ O ₃ while keeping other components constant.

As is apparent from these figures, when SiO ₂ is increased, the heat resistance is improved, but the surface properties and adhesion are deteriorated. On the contrary, when the amount of B ₂ O ₃ is increased, surface properties and adhesion are improved, but heat resistance is lowered.
Considering these, it is preferable that the composition ratio of SiO ₂ is 7 to 33% by weight and the composition ratio of B ₂ O ₃ is 5 to 31% by weight.

No. shown in Table 2 In Nos. 9 to 15, SiO ₂ / B ₂ O ₃ is made substantially constant and the amount of MgO is changed.

  If the added amount of MgO exceeds 50% by weight, crystals are likely to precipitate and crystallize easily when the glass is melted. Therefore, it is difficult to obtain a homogeneous glass, and the surface roughness is increased. The amount of MgO correlates with crystallinity, and if it is less than 16% by weight, crystal precipitation is insufficient and heat resistance is poor. Therefore, the composition ratio of MgO is preferably in the range of 16 to 50% by weight.

No. shown in Table 3 Nos. 16 to 19 are obtained by making SiO ₂ / B ₂ O ₃ substantially constant and changing the amount of CaO. No. shown in Table 4 Similarly, 20 to 24 are obtained by changing the BaO amount. In addition, as shown in Table 5, No. Similarly, 25 to 29 are obtained by changing the amount of La ₂ O ₃ .

When the amount of CaO added exceeds 20% by weight, the surface property is deteriorated, which is not preferable. Therefore, the addition amount of CaO is preferably 0 to 20%.
When the addition amount of BaO exceeds 50% by weight, the heat resistance and adhesion are deteriorated, which is not preferable. Therefore, the addition amount of BaO is preferably 0 to 50%.
When the addition amount of La ₂ O ₃ exceeds 40% by weight, the heat resistance is deteriorated, which is not preferable. Therefore, the addition amount of La ₂ O ₃ is preferably 0 to 40%.

No. shown in Tables 6-8. 30 to 44 are obtained by changing the amount of ZrO ₂ , TiO ₂ , SnO ₂ , P ₂ O ₅ and ZnO added.
ZrO ₂ , TiO ₂ , SnO ₂ , P ₂ O ₅ and ZnO can be added up to 5% by weight.

Example 1
Based on the manufacturing method described above, a mechanical quantity sensor was manufactured as follows.
A 1.2-mm-thick metal substrate processed into a predetermined pattern was subjected to degreasing, water washing, pickling, water washing, nickel plating, and water washing as pretreatments. Next, this is changed to the above-mentioned No. The surface of the metal substrate 1 was coated with the glass particles by immersing in a slurry containing glass particles having the composition shown in 7 and applying a constant voltage between the counter electrode and the metal substrate. The metal substrate 1 is heated from room temperature to 880 ° C. over 2 hours, and further subjected to a baking treatment for 10 minutes at this temperature. A crystallized glass layer having a thickness of 100 μm is formed on the surface of the metal substrate 1 as an insulating layer. 2 was formed to obtain an insulating substrate. Next, the electrode 3 was formed by screen-printing Ag—Pd-based conductive paste in a predetermined pattern on the surface of the crystallized glass layer 2 and firing at 850 ° C. for 10 minutes.

Next, Bi ₂ O ₃ , SrO, CaO and CuO were weighed so that the molar ratio was 1: 2: 2: 3, and these were sufficiently mixed in a mortar. The mixed powder was subjected to a solid phase reaction by heat treatment at 1000 ° C. for 24 hours to synthesize a copper-containing composite oxide. The obtained copper-containing composite oxide was pulverized to an average particle size of 0.3 μm.
In addition, Pb ₃ O ₄ , SiO ₂ , H ₃ BO ₃ and Al (OH) ₃ were weighed in predetermined amounts and sufficiently mixed in a mortar. This mixed powder is heated and melted at 1300 ° C. and poured onto a plate to synthesize a glass containing PbO, SiO ₂ , B ₂ O ₃ and Al ₂ O ₃ in a molar ratio of 52: 25: 10: 1. did. This glass was pulverized to an average particle size of 1 μm.
The obtained copper-containing composite oxide and glass are weighed and mixed so that the weight ratio is 1: 1, and an appropriate amount of organic vehicle and diluent is added thereto and mixed in a mortar. Resistive paste was prepared by mixing. The paste was screen-printed on an insulating substrate on which the electrode 3 had been formed in advance, and then baked at 830 ° C. in air to form the resistance element 4 to obtain the mechanical quantity sensor for a washing machine shown in FIG.

Example 2
Bi ₂ O ₃ , PbO, SrO, CaO and CuO were weighed in a molar ratio of 0.9: 0.2: 2: 2: 3 and mixed well in a mortar. Next, this was heat treated at 1000 ° C. for 24 hours to cause a solid phase reaction, thereby synthesizing a copper-containing composite oxide. The obtained copper-containing composite oxide was pulverized to an average particle size of 0.3 μm. The copper-containing composite oxide and the same glass as used in Example 1 were weighed and mixed so that the weight ratio was 1: 1, and an organic vehicle and a diluent were added in an appropriate amount and mixed in a mortar. Thereafter, a resistance paste was prepared by thoroughly mixing with three rolls. Using this resistance paste, a mechanical quantity sensor was fabricated in the same manner as in Example 1.

<< Comparative Example 1 >>
A glass similar to that used in Example 1 and ruthenium oxide (RuO ₂ ) having an average particle diameter of 0.3 μm are weighed and mixed at a weight ratio of 1: 1, and an organic vehicle and a diluent are added thereto. After adding an appropriate amount and mixing in a mortar, a resistance paste was prepared by thoroughly mixing with three rolls.
This paste was printed on an insulating substrate on which electrodes had been formed in the same manner as in the example and baked to form a resistance element, thereby obtaining a mechanical quantity sensor.

The mechanical quantity sensor 10 obtained as described above was attached to a washing machine as shown in FIG. The outer tub 6 accommodated inside the outer frame 9 is suspended by a plurality of support bars 7. As shown in FIG. 3, the mechanical quantity sensor 10 is connected and arranged between the support bar 7 and the support fixing member 8, and when clothes or the like is put into the dehydration tank 5, the tension applied to the support bar 7 increases. Then, the mechanical quantity sensor 10 is deformed. This mechanical quantity sensor 10 detects the amount of cloth thrown in due to a change in electrical resistance of the resistance element 4 due to deformation.
The electrical resistance of the sensor with respect to the amount of cloth put into the dewatering tank 5 was measured.
FIG. 4 shows the relationship between the amount of cloth input and the electrical resistance of the mechanical quantity sensor. As described above, by using the resistance paste of the example, it is possible to obtain a resistance element and a mechanical quantity sensor having higher sensitivity to distortion as compared with the case of using the resistance paste of the comparative example.

In addition, even when PbO, SrO, CaO and CuO are mixed so that the molar ratio is 2: 2: 2: 3, and a copper-containing composite oxide synthesized in the same manner as in the above example is used, the sensitivity is also improved. A high mechanical quantity sensor was obtained.
In addition, Bi _2-x Pb _x Sr ₂ Ca ₂ Cu ₃ O _y exhibiting metal conductivity has been described as an example of the copper-containing composite oxide used for the resistance element. The same effect can be obtained when a copper-containing composite oxide is used for the resistance element.
In this embodiment, the weight sensor used in the washing machine is described as an example of the mechanical quantity sensor. However, the present invention can be applied to various products such as an acceleration sensor, a pressure sensor, and a pointing device sensor for personal computers. Needless to say.

  The mechanical quantity sensor of the present invention can be used for a weight sensor, an acceleration sensor, a pressure sensor, and the like.

It is a figure which shows the mechanical quantity sensor of the Example of this invention, (a) is a perspective view, (b) is a longitudinal cross-sectional view. It is a longitudinal cross-sectional view of the principal part of the washing machine which attached the same mechanical quantity sensor. It is a longitudinal cross-sectional view of the attachment location of the same mechanical quantity sensor. It is a characteristic view which shows the electrical resistance value with respect to the amount of cloth thrown into the washing machine of the mechanical quantity sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal base material 2 Crystallized glass layer 3 Electrode 4 Resistance element 5 Dehydration tank 6 Outer tank 7 Support rod 8 Support fixing member 9 Outer frame 10 Mechanical quantity sensor

Claims (3)

  An insulating substrate, a strain sensitive resistor formed on the surface of the insulating substrate, and a pair of electrodes for detecting a change in electrical resistance of the strain sensitive resistor, the strain sensitive resistor being a copper-containing composite Mechanical quantity sensor containing oxide and glass.   The mechanical quantity sensor according to claim 1, wherein the insulating substrate is made of a metal substrate having a surface coated with a layer made of crystallized glass. The crystallized glass, SiO _2: seven to thirty-three wt%, B ₂ O _3: 5~31 wt%, MgO: 16 to 50 wt%, CaO: 0 to 20 wt%, BaO: 0 to 50 wt%, From La ₂ O ₃ : 0 to 40% by weight, P ₂ O ₅ : 0 to 5% by weight and MO ₂ : 0 to 5% by weight (provided that M is at least one element of Zr, Ti and Sn) The mechanical quantity sensor according to claim 2.

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