JP2003042860A - Stress impedance element and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-cost stress impedance element whose reliability is satisfactory. SOLUTION: In the stress impedance element, when an AC current is applied, an impedance is changed by depending on an external stress, a core is formed as a core wire 11 composed of a conductive material, and its outer circumferential part is formed as a magnetostrictive layer 12 comprising magnetostriction. The magnetostrictive layer is formed of any material from among an Fe-Ni material, a Co-Ni material, a Co-Fe material and an Ni material by an electrolytic plating method. The method is performed in such a way that the core wire is connected to a cathode, that a weight of a nonconductive material is installed at its lower end, and that the weight is surrounded with an anode plate so as to make the distance between the core wire and the anode plate definite.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stress impedance element for detecting stress such as tension, compression force and torque of a solid.

[0002]

2. Description of the Related Art Conventionally, strain gauges have been widely used as sensors for detecting stress such as tension, compression force and torque of solids. The strain gauge has a resistance wire strain gauge and a semiconductor strain gauge, and the resistance change rate (gauge ratio) per unit strain is about 2 for the resistance wire strain gauge and 100 to 200 for the semiconductor strain gauge.
Is. The resistance wire strain gauge utilizes a change in electric resistance due to deformation of a NiCr-based resistance wire having a diameter of several tens of μm. The semiconductor strain gauge uses the piezoresistive effect of the semiconductor, and by a sensor that integrates a bridge circuit of a gauge element and an amplifier on a silicon diaphragm by microfabrication technology,
Minute pressure can be detected. On the other hand, for a tactile sensor of a robot or a new medical drawing sensor for medical use, a strain sensor with higher sensitivity is required for more advanced intelligent robot control and higher accuracy of diagnosis. In order to cope with such an application, a stress impedance element having a gauge factor of 1200 or more with respect to tension was found by applying a high frequency current to a CoSiB amorphous magnetostrictive wire having a diameter of 30 μm to generate a skin effect ( IEEE Tran
s.Magn., 33, p. 3355, 1997). FIG. 5 is a structural diagram of a stress impedance element using this amorphous wire. Reference numeral 51 is an amorphous wire, 52 is the direction of the easy axis of magnetization of the core portion, and 53 is the direction of the easy axis of magnetization of the outer peripheral portion.
This stress impedance element is obtained by subjecting an amorphous wire produced by the quenching method to a special heat treatment. The core has an easy axis of magnetization in the longitudinal direction of the wire and the surface layer has an easy axis of magnetization in the circumferential direction of the wire. It has a double structure. When stress is applied to the wire while a high-frequency current is applied to both ends of the wire, the magnetostriction effect changes the magnetization vector of the wire surface layer, so that the impedance at both ends of the wire changes. This impedance change is used for stress detection.

[0003]

However, since the amorphous wire produced by this method has an oxide layer formed on the surface, the solderability is poor. Therefore, it has been a factor that impairs the yield and reliability in manufacturing a sensor head using the stress impedance element. In addition, the quenching method requires large-scale equipment and thus requires a large amount of capital investment. Therefore, an object of the present invention is to provide a stress impedance element which has good solderability and does not require large-scale manufacturing equipment.

[0004]

In order to solve the above problems, the present invention provides a stress impedance element whose impedance changes when an alternating current is applied depending on external stress. , And a magnetostrictive layer provided on the outer periphery thereof. The magnetostrictive layer is made of Fe-Ni, Co-Ni, Co-F.
The magnetostrictive layer is formed by electrolytic plating using either e or Ni. In addition, the electrolytic plating is performed by connecting a core wire to a cathode, providing a weight of a non-conductive material at the lower end thereof, and enclosing the core wire with an anode plate so that the distance between the core wire and the positive electrode is constant. is there. Further, the electrolytic plating, the electrolytic bath using nickel sulfate and ferrous sulfate,
The total metal ion concentration in the bath is 1 mol / L, the pH is adjusted with sulfuric acid or sodium hydroxide so that the magnetostrictive layer has a predetermined Fe / Ni concentration ratio, and the current density is 5 to 20 A.
This is done at / dm ² . In the electrolytic plating, the electrolytic bath is a sulfamic acid bath, nickel sulfamate and cobalt sulfamate are used, the total metal ion concentration in the bath is 1 mol / L, and the magnetostrictive layer has a predetermined Ni / Co concentration ratio. Adjust the pH using sulfamic acid or sodium hydroxide to
This is performed at 20 A / dm ² . In the electrolytic plating, the electrolytic bath is a sulfamic acid bath, cobalt sulfamate and ferrous sulfamate are used, the total metal ion concentration in the bath is 1 mol / L, and the magnetostrictive layer has a predetermined Co / Fe concentration. The pH was adjusted using sulfamic acid or sodium hydroxide so as to obtain a ratio, and the current density was 5 to 20 A / dm ² . According to this structure, only the surface layer that requires the magnetostrictive effect is the magnetic layer, and the core is a conductive material with good solderability, so the solderability as an element is good, and the production A highly reliable stress impedance element can be obtained. Further, the stress impedance element can be manufactured at low cost without using a large-scale device such as a vacuum device or a quenching device.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. An embodiment of the present invention is shown in FIG. Figure 1
Is an explanatory view of the stress impedance element of the present invention,
(A) is a schematic diagram showing a structure, and (b) is a schematic diagram showing a magnetic domain structure of an element. This stress impedance element 10
Is composed of a core wire 11 made of a copper wire and a magnetostrictive layer 12, and the magnetostrictive layer 12 has an easy axis 13 of magnetization oriented in the circumferential direction of the core wire 11. The manufacturing method is 80μ in diameter
A copper wire having a length of 30 mm and a length of 30 mm was used as the core wire 11, and the magnetostrictive layer 12 was formed on the surface of the core wire 11 by using the plating apparatus shown in FIGS. 2 is a sectional view of the plating apparatus, and FIG. 3 is a top view thereof. In the figure, 21 is an anode plate, 22 is a cathode terminal, and 23
Is an anode terminal, 24 is a weight, 25 is an electrolytic bath, 26 is an electrolytic bath, 27 is a constant temperature bath, and 28 is a DC power supply. A copper core wire 11 pickled and alkali-electrolytically degreased was connected to the cathode, and a non-conductive material weight 24 was attached to the lower end of the core wire 11. The core wire 11 and the anode plate 21 were surrounded by a constant distance. The core wire 11 was connected to the cathode terminal 22 of the DC power supply 28, and the anode plate 21 was connected to the anode terminal 23 of the DC power supply 28. (First Embodiment) In the first embodiment of the present invention, the magnetostrictive layer 12 has a composition of Fe-Ni system. The thickness of the magnetostrictive layer 12 is about 1 μm. As the anode plate 21, a Ni plate was used. The electrolytic bath 26 uses nickel sulfate and ferrous sulfate, and the total metal ion concentration in the bath is 1.
It was kept constant at 0 mol / L. In order to change the Fe / Ni ratio, a predetermined amount was dissolved in distilled water and the pH was adjusted using sulfuric acid or sodium hydroxide. The electrolysis was performed using a constant temperature bath 27 to keep the bath temperature at 40 ° C. and using a direct current power source 28 at a current density of 5 to 20 A / dm ² . Table 1 shows the composition of the magnetostrictive layer 12 when the current density is 10 A / dm ² . As a comparative example, a Co-Si-B system amorphous wire and a semiconductor strain gauge were added. With this fabrication, the magnetostrictive layer 12 formed by the magnetic field in the circumferential direction of the core wire 11 created by the current flowing through the core wire 11 serving as the cathode is easy to magnetize in the circumferential direction like the amorphous wire shown in FIG. The axis 13 is aligned. Next, the characteristics of the produced stress impedance element were examined. FIG. 4 is a schematic diagram of an apparatus for measuring stress characteristics. Reference numeral 42 is an electrode terminal for supplying high frequency current and measuring impedance. The stress impedance element 1 of the present invention is mounted on the plastic plate 43, one end of which is fixed to the fixing jig 44, through the electrode terminal 42.
0 is pasted. Further, lead wires from a power source and a signal processing circuit (not shown) are connected to the electrode terminals 42 at both ends of the stress impedance element 10, and the weight 45 is lowered on one side of the plastic plate 43 in a state where a high frequency current is applied to bend the plastic plate 43. However, when the relationship between the weight of the weight 45 and the output was examined, it was found that the output tended to increase as the saturation magnetostriction constant of the magnetostrictive layer 12 formed on the outer circumference increased. Table 1 shows the result of calculating the gauge factor based on this result. Sample Nos. 1 to 8 are stress impedance elements manufactured in this example, Comparative example 1 is an amorphous stress impedance element, and Comparative example 2 is a semiconductor strain gauge.

[0006]

[Table 1]

As can be seen from these results, the gauge factor is
Although the Ni content is low at a concentration of 30 mass% or less and near 80 mass%, the Ni content is 40 to 50 mass% and 90 ma.
At concentrations above ss%, good results comparable to the gauge factor of stress impedance devices using amorphous wires were shown. (Second Embodiment) In the second embodiment of the present invention, the magnetostrictive layer 12 has a composition of Co-Ni system. A Pt plate was used as the anode plate 21. As the electrolytic bath 26, a sulfamic acid bath of Ni and Co is used so that the total metal ion concentration in the bath is constant at 1.0 mol / L, and Co /
In order to change the Ni ratio, a predetermined amount is dissolved in distilled water, and p-amine is dissolved with sulfamic acid or sodium hydroxide.
H was adjusted. The bath temperature is kept at 40 ° C. by using a constant temperature bath 27, and the current density is 5-20 A / dm ² by using a DC power source 28.
It went in the range of. The thickness of the Co—Ni magnetostrictive layer 12 is about 1 μm.
m. Magnetostrictive layer 12 when current density is 10 A / dm ^2.
The composition of is shown in Table 2. As a comparative example, Co-Si
-B-based amorphous wire, semiconductor strain gauge, and Co alone were added. Next, Table 2 shows the result of calculation of the gauge factor as in the first embodiment.

[0008]

[Table 2]

As can be seen from these results, the gauge factor is
At Co concentrations of 5 to 10 mass% and concentrations of 30 mass% or more, good results comparable to the gauge ratio of the stress impedance element using the amorphous wire of the comparative example were shown. In addition, the gauge ratio of Co alone of Comparative Example was as low as 20. (Third Embodiment) In the third embodiment of the present invention, the magnetostrictive layer 12 has a composition of Co--Fe system. A Pt plate was used as the anode plate 21. As the electrolytic bath 26, a sulfamic acid bath of Co and Fe is used so that the total metal ion concentration in the bath is constant at 1.0 mol / L, and Co /
In order to change the Fe ratio, a predetermined amount is dissolved in distilled water, and p is added using sulfamic acid or sodium hydroxide.
H was adjusted. The electrolysis condition and the thickness of the magnetostrictive layer 12 are the second
Is almost the same as the embodiment of. Table 3 shows the composition of the magnetostrictive layer 12.
Shown in. As a comparative example, a Co—Si—B system amorphous wire, a semiconductor strain gauge, and a simple substance of Fe were added. Next, Table 3 shows the result of calculation of the gauge factor in the same manner as in the first embodiment.

[0010]

[Table 3]

As can be seen from these results, the gauge factor is
At a concentration of Co of 10 to 30 mass%, good results were obtained, which reached several times the gauge factor of the stress impedance element using the amorphous wire of the comparative example. In the comparative example, Fe alone has a gauge factor of 200, which is a relatively good value comparable to that of a semiconductor strain gauge. In addition, although Cu wire was used for the core wire in the present embodiment, Cu alloy, Al, Ag
Similar results can be obtained by using a conductive material such as.

[0012]

As described above, according to the present invention, the magnetic layer is provided on the surface layer which needs the magnetostrictive effect, and the core portion is made of the conductive material having good solderability. The solderability is good, and there is an effect that a stress impedance element having high productivity and high reliability can be provided. Moreover, since a large-scale device such as a quenching device is not required, there is an effect that the stress impedance element can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a stress impedance element of the present invention.

FIG. 2 is a sectional view of a plating apparatus used in an embodiment of the present invention.

FIG. 3 is a top view of FIG.

FIG. 4 is a schematic diagram of an evaluation device for evaluating the characteristics of the stress impedance element of the present invention.

FIG. 5 is a schematic diagram showing a conventional stress impedance element.

[Explanation of symbols]

10 Stress impedance element 11 core wire 12 Alloy layer 21 Anode plate 22 Cathode terminal 23 Anode terminal 24 weights 25 electrolyzer 26 Electrolysis bath 27 bath 28 DC power supply 41 Stress impedance element 42 electrode terminals 43 plastic plate 44 Fixing jig 45 weights 51 amorphous wire 52 Direction of easy axis of magnetization of core 53 Orientation of easy axis of magnetization on outer periphery

Claims (7)

[Claims] 1. A stress impedance element in which impedance changes depending on external stress when an alternating current is applied, wherein a core portion is composed of a conductive material, and a magnetostrictive layer is provided on an outer peripheral portion of the core wire. Is a stress impedance element. 2. The magnetostrictive layer is Fe—Ni, Co—N
The stress impedance element according to claim 1, wherein the stress impedance element is made of any one of i, Co-Fe, and Ni. 3. A method for manufacturing a stress impedance element in which impedance changes when an alternating current is applied depending on an external stress, wherein a core is a thin wire made of a conductive material, and a magnetostrictive layer is formed on the outer circumference by electrolytic plating. A method for manufacturing a stress impedance element, which is characterized by being formed. 4. The electrolytic plating is performed by connecting a core wire to a cathode, providing a weight of a non-conductive material on the lower end of the core wire, and enclosing the core wire with an anode plate so that the distance between the core wire and the positive electrode is constant. The method for manufacturing a stress impedance element according to claim 3, which is characterized in that. 5. In the electrolytic plating, nickel sulfate and ferrous sulfate are used as an electrolytic bath, and the total metal ion concentration in the bath is 1 m.
The pH is adjusted with sulfuric acid or sodium hydroxide so that the magnetostrictive layer has a predetermined Fe / Ni concentration ratio, and the current density is 5 to 20 A / dm ^2. A method for manufacturing the stress impedance element according to claim 1. 6. In the electrolytic plating, a sulfamic acid bath is used as an electrolytic bath, nickel sulfamate and cobalt sulfamate are used, and a total metal ion concentration in the bath is 1 mol / mol.
L, the pH was adjusted using sulfamic acid so that the magnetostrictive layer had a predetermined Ni / Co concentration ratio, and the current density was 5 to 5
The stress impedance element manufacturing method according to claim 3, wherein the stress impedance element is manufactured at 20 A / dm ² . 7. In the electrolytic plating, a sulfamic acid bath is used as the electrolytic bath, cobalt sulfamate and ferrous sulfamate are used, and the total metal ion concentration in the bath is 1 mol / L.
5. The pH is adjusted using sulfamic acid or sodium hydroxide so that the magnetostrictive layer has a predetermined Co / Fe concentration ratio, and the current density is 5 to 20 A / dm ^2. A method for manufacturing the stress impedance element according to claim 1.