JP3640738B2 - Method for forming amorphous alloy thin film layer and method for attaching magnetic sensor to base material - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming an amorphous alloy thin film layer on a base material and a method for attaching a magnetic sensor, for example, a magnetic non-contact torque sensor, to the base material by this method.
[0002]
[Prior art]
Amorphous alloys have a Villari effect, and it is known to use this effect to detect strain, and also to detect rotational torque applied to the rotating shaft by twisting torque → strain conversion.
That is, when the rotational torque T acts on the shaft of the diameter d, the shear stress τ represented by the formula (1) is generated on the shaft surface,
τ = 16T / (πd ³ ) (1)
Further, as is apparent from the stress circle of the mole, main stress is generated in the direction of 45 ° with respect to the shear direction.
[0003]
Thus, when the amorphous alloy thin film is fixed to the shaft surface, uniaxial magnetic anisotropy is exhibited in the principal stress direction, and the anisotropic energy Ku has a saturation magnetostriction constant of λs and the amorphous alloy thin film. Assuming that the torsional Young's modulus is Ga and the torsional Young's modulus of the shaft is Gs,
Ku = 48λsGa / (πd ³ Gs) (2)
Given in.
Therefore, it is possible to detect the torque T from the change in the relative magnetic permeability μr given from the magnetic resistance of the magnetic circuit passing through the amorphous alloy thin film by applying a magnetic field to the shaft.
[0004]
Of course, if an amorphous alloy thin film is fixed to the surface of a base material that generates strain due to external force, uniaxial magnetic anisotropy is exhibited in the direction of the force. It can be measured from the change in specific magnetic permeability μr given by the magnetic resistance of the magnetic circuit that passes through the amorphous alloy thin film. Furthermore, it can be used as a sensor for mass, pressure, etc. by grasping in advance the relationship between the amount of strain and external force. It is.
[0005]
[Problems to be solved by the invention]
Conventionally, in order to detect torque and strain by the above-described method, a previously formed amorphous alloy thin film is adhered to an axis of rotation with an adhesive such as an epoxy resin.
Therefore, due to the bending strain at the time of sticking and the processing strain at the time of thin film forming, the accompanying uniaxial magnetic anisotropy is unavoidable, and the anisotropic energy of the accompanying uniaxial magnetic anisotropy is inevitable. Kb is superimposed on the anisotropic energy -Ku in the main stress direction based on the torque, and the variability of the superimposed anisotropic energy with respect to the torque becomes gradual. As Kb increases, the detection sensitivity is inevitably lowered.
[0006]
An object of the present invention is to fix an amorphous alloy thin film layer to a base material, and to detect a strain generated in the base material by the Villari effect of the amorphous alloy thin film. An object of the present invention is to provide a method for forming an amorphous alloy thin film layer capable of ensuring high-sensitivity strain detection by eliminating the influence, and a method for attaching a magnetic sensor to a base material.
[0007]
[Means for Solving the Problems]
In the method for forming an amorphous alloy thin film layer according to the present invention, an amorphous alloy piece is brought into contact with a base material, the amorphous alloy piece is melted by instantaneous energization with a contact electrode, and after the energization is cut off, the molten metal is removed from the electrode. A structure characterized by rapid solidification by heat dissipation and amorphization again, or non-amorphous alloy material is used in place of the amorphous alloy piece, and the non-amorphous alloy material is melted by instantaneous energization with a contact electrode to cut off the energization Thereafter, the molten metal is rapidly cooled and solidified by heat radiation from the electrode to be amorphous, and in any structure, the amorphous alloy is Co ₇₀ . ₅ B ₁₅ Si ₁₀ Fe ₄ . _In the case of the composition of ₅ , it is appropriate that the instantaneous current application time is 300 μs or less.
A method for attaching a magnetic sensor to a base material according to the present invention includes the above amorphous alloy using an amorphous alloy thin film layer as a magnetic sensor (for example, a magnetic non-contact torque sensor) on the base material (for example, a rotating shaft). The thin film layer is provided by a method for forming a thin film layer.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In order to carry out the present invention, first, as shown in FIG. 1A, an amorphous alloy piece 2 is brought into contact with the base metal material 1, and further, the base metal material 1 and the amorphous alloy piece 2 are brought into contact with each other. The electrodes 31 and 32 are brought into pressure contact with each other.
Next, current is instantaneously applied to melt the amorphous alloy piece as shown in FIG. Reference numeral 20 denotes a molten metal.
[0009]
In this case, the electrical resistance of the amorphous alloy piece 2 (the electrical resistance including the contact resistance with the base metal material 1) is sufficiently higher than that of the base metal material 1 and the electrodes 31 and 32. -The heat of the heat is substantially generated only in the amorphous alloy piece 2 (including the contact interface with the base metal material 1). Further, the energization time of the current is sufficiently short, and the amount of heat that escapes from the amorphous alloy piece in which the Joule heat is generated within this energization time can be ignored. Therefore, if the heat capacity of the amorphous alloy piece is C, the electrical resistance of the amorphous alloy piece is R, the average current value is I, and the energization time is Δt, the temperature rise ΔT of the amorphous alloy piece is approximately ΔT = RI ² Δt / C. ▲ 3 ▼
Given, if the melting point of the amorphous alloy flakes Tm, the normal temperature T _0, energization current I is approximately I = _{[C (Tm-T 0) /} (RΔt) ] ^1/2 ▲ 4 ▼
Given in.
[0010]
During the energization of the current value I for Δt time, the amount of heat transfer from the amorphous alloy piece 2 in which the Joule heat is generated to the electrode 32 or the base metal material 1 is substantially zero. Since the metal material 1 (the majority of the base metal material excluding the contact interface with the amorphous alloy piece) is held at almost normal temperature, the heat of the amorphous alloy piece is rapidly increased after the energization is cut off. The molten metal 20 is cooled and solidified by escaping to the base metal material 1.
In this cooling of the molten metal, the solidified metal can be amorphized again if it is quenched so as to prevent crystal growth, that is, depriving the latent heat of aggregation and preventing diffusion of atoms to become crystals. An amorphous alloy thin film layer can be formed on the material surface.
Therefore, in the present invention, the amorphous alloy pieces are energized and melted in a short time, and during this time, the temperature of the electrode and the base metal material is substantially reduced without transferring the amount of generated heat to the electrode 32 and the base metal material 1. Since it can be kept at room temperature, the heat of the molten metal rapidly moves to the electrode 32 and the base metal material 1 after the current supply is cut off, and the molten metal is rapidly cooled to ensure re-amorphization.
[0011]
In the present invention, the alloy composition of the amorphous alloy piece is an alloy of a transition metal such as Fe or Co and a nonmetal such as B or Si and is limited to a composition system having a nonmetal content of 10 to 30 atomic%, for example, Co ₇₀ . ₅ B ₁₅ Si ₁₀ Fe ₄ . ₅ (subscript indicates atomic%; the same applies hereinafter) and Fe ₇₅ Si ₁₀ B ₁₅ are advantageous in terms of re-amorphization because the critical cooling rate for crystallization is relatively slow.
[0012]
Instead of an amorphous alloy piece, a non-amorphous alloy material, for example, a mixed material of Co powder 70.5%, B powder 15%, Si powder 10%, Fe powder 4.5%, or Fe powder 75%, Si powder 10 In addition to a mixed powder material that becomes an amorphous alloy by melting and quenching, such as a mixed material of 15% or B powder, a laminate of elemental foils can also be used.
Furthermore, the energization time is set to 300 μs or less, and the energization current is set to a current value or less that does not cause evaporative flying due to excessive melting.
[0013]
In the above-described embodiment of the present invention, one electrode is brought into contact with the amorphous alloy piece or the non-amorphous alloy material, and the other electrode is brought into contact with the base metal material so that the amorphous alloy piece or the non-amorphous alloy material is energized. -Although it is melted by the knurling heat, both the electrodes can be brought into contact with the amorphous alloy piece or the non-amorphous alloy material, and the amorphous alloy piece or the non-amorphous alloy material can be melted by the joule heat by energization. In the latter case, if the distance between the electrodes is too wide, it becomes difficult to weld the intermediate portion of the amorphous alloy piece between the electrodes to the base metal material. It is preferable to sequentially perform melting, quenching, and re-amorphization by bringing the entire surface into contact with each other.
[0014]
In the present invention, an amorphous alloy thin film layer is formed on a rotating shaft, and a change in magnetic anisotropy energy based on a principal stress strain of a stress generated on the surface of the rotating shaft by a rotating torque acting on the rotating shaft is measured. It can be suitably used for forming an amorphous alloy thin film layer when detecting the rotational torque by detecting the change in the magnetic resistance.
In addition, the present invention forms an amorphous alloy thin film layer on a base material that generates a strain due to an external force, and changes the magnetic anisotropy energy based on the strain of the stress generated in the base. It can be used suitably for the formation of an amorphous alloy thin film layer in the case where the strain is measured by detecting the change in the magnetic resistance.
[0015]
In addition, an amorphous alloy piece is used as a magnetic field sensor (by applying a minute high-frequency current to the amorphous alloy piece and the impedance changes sensitively by an external magnetic field due to the skin effect. For use as an external magnetic field), a ceramic film is provided with a high permeability metal film, and an amorphous alloy thin film layer is formed on the metal film, or an amorphous alloy thin film layer is formed on the high permeability metal. Thus, it can also be used when manufacturing a magnetic field sensor.
In the present invention, the magnetic sensor is a general term for a sensor that detects a change in magnetic characteristics due to the above-described distortion using a magnetic field and a sensor that detects an external magnetic field from a change in magnetic characteristics of the sensor.
[0016]
【Example】
〔Example〕
For amorphous alloy pieces, Co ₇₀ . ₅ B ₁₅ Si ₁₀ Fe ₄ . _Five fine wire cut pieces were used, and the base metal material was an Fe—Co—Ni alloy plate having a thickness of 0.2 mm. The energization time was 60 μs and the energization peak current was 700 amperes.
[Comparative example]
The same as the example except that the energization time was 950 μs and the energization peak current was 500 amperes.
When the uniaxial magnetic anisotropy was inspected for these Example products and Comparative Example products, the Examples had uniaxial magnetic anisotropy, but in the Comparative Examples, the cooling rate was slow and the amorphization was satisfactorily achieved. No uniaxial magnetic anisotropy was observed.
[0017]
【The invention's effect】
In the method for forming an amorphous alloy thin film layer according to the present invention, an amorphous alloy piece or a non-amorphous alloy material is melted and rapidly amorphized, so that even if processing strain remains in the amorphous alloy piece, To be removed. Further, unlike the case where the amorphous alloy thin film is bent and stuck, bending strain can be eliminated.
However, heat shrinkage strain is accompanied by rapid cooling, but the strain can be sufficiently reduced as compared with the total amount of bending strain and thin film processing strain.
Furthermore, since no special apparatus for amorphization by rapid cooling is required, the apparatus is simple.
[0018]
Therefore, according to the present invention, an amorphous alloy thin film layer capable of ensuring high sensitivity and simple strain detection by eliminating the influence of incidental strain other than strain to be detected can be attached to the base material as a magnetic sensor ( For example, it can be attached to the rotating shaft as a magnetic non-contact torque sensor).
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a method for forming an amorphous alloy thin film layer according to the present invention, where FIG. 1 (a) shows the state before the amorphous alloy is melted, and FIG. 1 (b) shows the state after the melt. Respectively.
[Explanation of symbols]
1 Base metal material 2 Amorphous alloy piece 31 Electrode 32 Electrode

Claims (4)

The amorphous alloy piece is brought into contact with the base material, the amorphous alloy piece is melted by instantaneous energization with a contact electrode, and after the energization is cut off, the molten metal is rapidly cooled and solidified by heat radiation from the electrode, and is made amorphous again. A method for forming an amorphous alloy thin film layer. A non-amorphous alloy material is brought into contact with a base material, the non-amorphous alloy material is melted by instantaneous energization with a contact electrode, and after the energization is cut off, the molten metal is rapidly cooled and solidified by heat radiation from the electrode to become amorphous. A method for forming an amorphous alloy thin film layer. The amorphous alloy composition is Co ₇₀ . ₅ B ₁₅ Si ₁₀ Fe ₄ . _The method for forming an amorphous alloy thin film layer according to claim 1, wherein an instantaneous energization time of current is 300 μs or less. 4. A method for attaching a magnetic sensor to a base material, comprising the step of providing an amorphous alloy thin film layer as a magnetic sensor on the base material according to the method for forming an amorphous alloy thin film layer according to claim 1. .

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