JPS58124922A - Pressure sensor - Google Patents

Abstract

PURPOSE:To obtain a titled sensor of high sensitivity by molding part or the whole of a core with a pressure transmitting medium. CONSTITUTION:An energizing winding 24 and an output winding 25 are wound around a core 22 consisting of a magnetostrictive material and a coating layer or embedding layer 23 of a pressure transmitting medium is applied thereon.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a pressure sensor.

[Technical background of the invention and its problems]

This is a magnetic pressure transducer that uses the magnetostrictive effect, and the pressure sensor that uses a small core is embedded in materials such as thermosetting plastics and prestressed concrete, and when they harden, the internal pressure that occurs in such materials It is known that stress can be measured.

These internal stress measurements are made due to the significant side effect of the presence of a core embedded in the material. Fourth, the additional internal stresses that occur in these materials, such as due to radiation expansion and contraction of the materials, can be readily measured using these cores.

FIG. 1 shows an example of a known magnetic pressure transducer, in which an excitation winding 14 (primary coil) is arranged around a core 12 made of magnetostrictive material.
Signal generator connected via 1! Schematic illustration of a circuit diagram illustrating the method used to determine the stress ia+ of a microtransducer 4 with a core 12 and an output winding 15 (secondary coil) excited by 2° excitation winding (primary coil) and an output winding (secondary coil).
The number of turns in the secondary coil can be selected as appropriate; by increasing the number of turns in the secondary coil, -J(3) greater output can be obtained. In some applications, this can eliminate the noise associated with the output signal. In a typical application, the pressure sensor 13 is embedded within the epoxy resin, and the internal stress generated within the epoxy resin during curing is
This is observed by monitoring the output signal induced in the output winding 15 (secondary coil) located in the core 12. The output signal is fed to an amplifier 16 and displayed on a conventional electrometer 17 or the like.

Such an application example is used to analyze the internal stress caused by curing shrinkage during the process of changing from a liquid state to a solid state and during the process of cooling from a high temperature to room temperature during resin casting of a cast insulator.

On the other hand, these cast insulators have coils, conductors,
In many cases, it has a structure in which an iron core or the like is embedded and integrated with resin. For this reason, temperature distribution occurs within the insulating layer as the equipment starts and stops, and thermal stress is generated due to the difference in coefficient of thermal expansion and modulus of elasticity between the resin and the embedded material. If the magnitude of the leftward stress or thermal stress exceeds the strength of the insulator, peeling or cracking will occur in the insulating layer, so it is used to measure the magnitude and distribution of internal stress and thermal stress.

Conventionally, attempts have been made to improve magnetostrictive materials as a means of improving the sensitivity of such pressure sensors.

In other words, a highly sensitive gas pressure sensor is required to improve the accuracy of resin internal stress measurement, and sensitivity has been improved by improving the material constants such as the amount of magnetostriction of the ferrite material used in the core of the pressure sensor. Ta.

However, such methods have limitations, such as sensitivity,
The accuracy is not sufficient either, and a pressure sensor with higher sensitivity is desired.

[Purpose of the invention]

The present invention improves the problems of the conventional pressure sensor described above, and aims to provide a high-sensitivity pressure sensor.

[Summary of the invention]

The present invention is a pressure sensor having a cuff core made of magnetostrictive material and having an excitation winding and an output winding, characterized in that the core is partially or entirely molded with a pressure transmission medium.

The pressure transmission medium used in the present invention includes plastics,
Examples include silicone rubber and glass, but other pressure transmission media may also be used.

Furthermore, in the present invention, molding means covering or partially embedding the entire structure.

The thickness of the covering layer or the embedding layer may be 0.05 to 3.5 mm, but preferably the thickness is 0.1 to 0.5 mm.

That is, according to the present invention, if a part or the whole of the sensing portion including the core and excitation winding and output winding of the conventional pressure sensor is coated or embedded with a pressure transmission medium, the sensitivity is higher than that of the conventional pressure sensor. It is an enhanced pressure sensor.

Hereinafter, the present invention will be explained in detail with reference to Examples.

[Embodiments of the invention]

FIG. 1 shows an outline of a conventional pressure sensor.

The core 12 made of magnetostrictive material is provided with, for example, a four-turn excitation winding 14 and an eight-turn output winding 15 . The excitation winding 14 is connected to a signal generator 11, and the output winding 15 is connected to an electrometer 17 via an AC amplifier 16 to detect pressure. In this case, increasing the number of turns in the output winding 15 can provide a larger output voltage, which in some applications has the advantage of eliminating noise associated with the output signal.

FIG. 2 schematically shows the pressure sensor of the present invention.

Core 22 made of magnetostrictive material (outer diameter 1.3 mm, inner diameter 0.7
The excitation winding 24, the output winding 25, the signal generator 21, the AC amplifier 26, the electrometer 27, and the detection method are the same as those of conventional pressure sensors. Core 22 made of magnetostrictive material
is provided with a covering layer or buried layer 23 of pressure transmission medium. In this example, as the pressure transmission medium,
Although epoxy resin was used, similar effects can be obtained using other pressure transmitting media such as other plastics or silicone rubber and glass. The epoxy resin is Stycastna 2651 manufactured by Emerson & Cuming.
-MM was used.

The thickness of the coating layer for the coated type (partially molded type) is approximately 0.25 tan, and for the embedded type (partially molded type).
The thickness of the buried layer (completely molded) is 0.2 to 0.
It was 5+nm. In the partial mold, the epoxy resin is fully coated on the center and outside of the core 22. The epoxy resin was cured for 24 hours at room temperature. FIG. 3 shows a comparison of the sensitivity characteristics of the conventional pressure casserole juice and the present invention. In the figure, curve a represents the sensitivity characteristic of a conventional pressure sensor, curve A represents the sensitivity characteristic of the partially molded pressure sensor of the present invention, and curve C represents the sensitivity characteristic of the fully molded pressure sensor of the present invention. These sensitivity characteristics vary from O to 50 in silicone oil under certain excitation conditions.
It represents the output voltage induced in the output winding 25 when a hydrostatic pressure of 0 to /- is applied.

As is clear from the figure, the pressure sensor of the present invention exhibited approximately five times the sensitivity as compared to the conventional pressure sensor. In particular, fully molded pressure sensors exhibited much better force sensitivity than partially molded pressure sensors.

〔Effect of the invention〕

According to the present invention, a highly sensitive pressure sensor can be provided by simply molding a conventional pressure sensor with a pressure transmission medium. In particular, it is possible to improve the accuracy of resin internal stress measurement, which is a typical application example.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a conventional magnetic pressure transducer, Fig. 2 is a schematic diagram of a magnetic pressure transducer using a pressure sensor of the present invention, and Fig. 3 is a schematic diagram of a conventional pressure sensor and a pressure transducer of the present invention. FIG. 3 is a diagram showing a comparison of sensor sensitivities. In FIG. 3, curve a represents the sensitivity characteristics of the conventional pressure sensor, curve C represents the sensitivity characteristics of the partially molded pressure sensor of the present invention, and curve C represents the sensitivity characteristics of the fully molded pressure sensor of the present invention. 11.21... Signal generator, 12.22... Core,
13...Pressure sensor, 14.24...Excitation winding,
15.25... Output winding, 16.26... AC amplifier, 17.27... Electrometer (potential meter), 2
3...Covering layer or embedding layer (mold layer). Figure 3 Pressure (Kg/cm2)

Claims (1)

[Claims] 1. A pressure sensor having a core made of a magnetostrictive material and having an excitation winding and an output winding, the core being partially or entirely molded with a pressure transmission medium.