JPH06180262A - Magnetostrictive strain sensor - Google Patents

Abstract

PURPOSE:To provide a magnetostrictive strain sensor which suppresses temperature drift and has large outputting and high noise-resistance regardless of the material quality of power transmitting member. CONSTITUTION:At least two pairs of coil pairs 6 consisting of exciting coils 7 and 8 and detecting coils 9 and 10 are arranged on the periphery of a power transmitting member 3 consisting of a magnetic material having reverse magnetostrictive effect or a power transmitting member 3 consisting of a non- magnetic material where a magnetic film having reverse magnetostrictive effect is formed on the surface thereof. Further, the changes in magnetic permeability caused by the strain generating on the surface of the member 3 are recognized as impedance change in a detecting coil, and a part where no power is transmitted thereto is arranged in a part of or adjacent to the power transmitting member for a magneto-strictive strain sensor for detecting strain in the power transmitting member, wherein at least one pair of two pairs of coil pairs is arranged in the part with no power transmitted or in the periphery of the magnetic film formed in the part with no power transmitted and another pair is arranged in the periphery of the power transmitting member, while respective coils 7 and 8 are connected in series.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetostrictive strain sensor utilizing the inverse magnetostrictive effect of a magnetic material, and more particularly to a strain sensor for measuring liquid pressure and wire tension.

[0002]

2. Description of the Related Art Recently, the performance of die cast machines and actuators utilizing hydraulic pressure has been improved. For example, in a die cast machine, the defect rate of the die cast material can be reduced by accurately controlling the hydraulic pressure. Also, in the actuator, it leads to accurate control of the operation. In this sense, pressure sensors are being developed, and pressure sensors that utilize the piezoelectric effect of semiconductors and pressure sensors that utilize magnetostriction are being developed. Of these, the latter is excellent in heat resistance and is therefore advantageous for high temperatures. Figure 5
The structure is shown in. The pressure sensor uses a titanium pipe to form a pressure receiving portion 1 and an atmospheric pressure portion 2, a magnetic film 4 is formed on the outer peripheral surface of the pipe, and excitation coils 22 to 25 and detection coils 26 to 29 are wound around the magnetic film 4. ing. The two sets of exciting coils 24 and 25 of the pressure receiving unit 1 are connected in series. Also,
The exciting coils 22 and 23 of the atmospheric pressure section 2 are also connected in series. The pressure receiving portion 1 is connected to the high pressure pipe and directly receives the hydraulic pressure, but the other one does not receive the hydraulic pressure. When the hydraulic pressure changes, the magnetic film 4 of the pressure receiving portion 1 is distorted and the magnetic characteristics change. Along with this, the impedances of the detection coils 28 and 29 change in the opposite directions, so that when the outputs of the detection coils are differentiated, the final output is increased and the noise is reduced.
On the other hand, since the detection coils 26 and 27 do not change, the difference between the pressure receiving portion and the atmospheric pressure portion is detected and measured as a change in hydraulic pressure.

[0003]

However, the structure of the conventional pressure sensor cannot have the same structure when the force transmitting member is a magnetic body. Further, even in the case of a pressure sensor made of a non-magnetic material, there is a problem that a temperature drift occurs because the temperature characteristics of a portion with a magnetic film and a portion without a magnetic film are different due to temperature change. Therefore, the present invention reduces the temperature drift regardless of the material of the force transmitting member, and
It is an object of the present invention to provide a magnetostrictive strain sensor which has a large output and is resistant to noise.

[0004]

In order to solve the above problems, the present invention provides a force transmitting member made of a magnetic material having an inverse magnetostrictive effect or a force made of a non-magnetic material having a magnetic film having an inverse magnetostrictive effect formed on its surface. Around the transmission member, at least two sets of coil pairs consisting of an excitation coil and a detection coil are arranged, and the change in magnetic permeability based on the strain generated on the surface of the force transmission member is detected as the change in impedance of the detection coil, In a magnetostrictive strain sensor for detecting the strain of a force transmitting member, a part where the force is not transmitted is formed in a part of or near the force transmitting member, and one of the at least two coil pairs is not transmitted with the force. Another set is arranged around the force transmitting member around the magnetic film formed in the portion or the portion where the force is not transmitted, and each exciting coil is connected in series. There.

[0005]

[Function] Since a part where the force is not transmitted is formed in a part of the force transmitting member, and the structure of the magnetic member of the part where the force is transmitted is the same as that of the part where the force is not transmitted, and it is arranged in the vicinity.
The temperature changes of both magnetic members and the coil are the same.
Therefore, it is possible to eliminate the temperature change by taking the differential between both outputs, and moreover, the output can be made large and the noise is reduced as in the conventional case.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings. First Embodiment FIG. 1 is a sectional view of a pressure sensor showing a first embodiment of the present invention. In the figure, 1 is a pressure receiving portion, 3 is a force transmitting member, 5 is a non-force transmitting member, 7 to 8 are exciting coils, and 9 to 10 are detecting coils. The pressure receiving portion 1 is composed of a force-transmitting member 3 which is formed by processing a magnetic pipe made of maraging steel into concentric steps and which senses pressure. The non-force transmission member 5 is a member that is provided on the stepped portion of the force transmission member 3 and has the same outer shape that does not feel pressure. A coil pair 6 including an exciting coil 7 and a detection coil 9 is provided around the force transmitting member 3, and a coil pair 6 including an exciting coil 8 and a detecting coil 10 is provided around the non-force transmitting member 5. Coil specifications are 2 for each excitation coil 7 and 8.
00 turns, and the detection coils 9 and 10 were each 400 turns. The exciting coils 7 and 8 are connected in series as shown in the equivalent circuit of the electric circuit in FIG. Reference numeral 19 is an AC power source, 20 is a DC conversion circuit for converting an AC voltage into a DC voltage, and 21 is a differential amplifier. Now, the pressure receiving part 1 was connected to a high-pressure oil pipe, the ambient temperature was changed from zero to 100 ° C., and the temperature drift was examined. With respect to a temperature change of 10 ° C., the pressure sensor of the conventional method is 1% and the pressure sensor of the present invention is 0.01
%, Which is very small and a good result was obtained. Second Embodiment FIG. 3 is a sectional view of a pressure sensor showing a second embodiment of the present invention. In this configuration, a pipe made of a Ti alloy is used, and two pairs of coil pairs 6 are added to the atmospheric pressure section 2 in addition to the configuration of the pressure receiving section 1. In the figure, 4 is a magnetic film, 11-14 are excitation coils, and 15-18 are detection coils. Both the pressure receiving portion 1 and the atmospheric pressure portion 2 are made of Ti alloy pipe with stepped portions, and a non-force transmission member 5 that does not feel pressure is provided. Then, the periphery of the transmission member 3 and the non-force transmission member 5 is coated with a 50% Ni-Fe film by the ion plating method. As shown in the equivalent circuit of the electric circuit in FIG.
, 12, 13 and 14 are connected in series. The specifications of the coil are 200 turns for each exciting coil and 400 turns for each detecting coil as in the first embodiment. Now, similarly to the first embodiment, the pressure receiving portion 1 was connected to a high-pressure oil pipe and the ambient temperature was changed from zero to 100 ° C. to examine the temperature drift. With respect to the temperature change of 10 ° C., the pressure sensor of the conventional method was 1%, and the pressure sensor of the present invention was 0.02%, which were very small and good results were obtained. Although only the ion plating method is used for forming the magnetic film in the embodiments of the present invention, the same effect can be obtained by using another magnetic film forming method such as a sputtering method or a method of adhering an amorphous magnetic material. It is obvious that Further, although the example in which only the tension when the pressure is applied acts has been described, it is also clear that the same effect can be obtained when only the compression force acts. .

[0007]

As described above, according to the present invention, since the detecting portion of the non-force transmitting portion has the same magnetic material structure as that of the force transmitting portion, the temperature drift is very small and the strain against the strain is large. There is an effect that a large output can be obtained and a strain sensor that is strong against noise can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view of a magnetostrictive strain sensor showing a first embodiment of the present invention.

FIG. 2 is a diagram showing an equivalent circuit of the first exemplary embodiment of the present invention.

FIG. 3 is a sectional view of a magnetostrictive strain sensor showing a second embodiment of the present invention.

FIG. 4 is a diagram showing an equivalent circuit of a second embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a conventional pressure sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressure receiving part 2 Atmospheric pressure part 3 Force transmission member 4 Magnetic film 5 Non-force transmission member 6 Coil pair 7-8, 22-25 Excitation coil 9-10, 26-29 Detection coil 19 AC power supply 20 DC conversion circuit 21 Differential amplifier

Claims (1)

[Claims] 1. A coil comprising an exciting coil and a detection coil around a force transmitting member made of a magnetic material having an inverse magnetostrictive effect or a force transmitting member made of a non-magnetic material having a magnetic film having an inverse magnetostrictive effect formed on the surface. At least two pairs are arranged, the change in magnetic permeability based on the strain generated on the surface of the force transmission member is detected as an impedance change of the detection coil, and in the magnetostrictive strain sensor that detects the strain of the force transmission member, A part of the force transmission member or a part thereof in the vicinity where a force is not transmitted is formed, and one set of the at least two coil pairs is formed of a magnetic film formed in a part where force is not transmitted or a part where force is not transmitted. A magnetostrictive strain sensor, characterized in that another set is arranged around the force transmitting member and each exciting coil is connected in series.