JPH01107109A - Dynamic quantity sensor - Google Patents

Abstract

PURPOSE:To measure dynamic quantity with high accuracy even when a severe mag netic field or heat source is present in the outside, by providing a layer composed of a superconductive material to the surface layer of a mechanical quantity/quantity-of- electricity converting sensor. CONSTITUTION:A ceramics layer 2 relatively inferior to heat conductivity is arranged to the inside of a layer composed of a superconductive material and a copper alloy 3 having good heat conductivity is subsequently fixed to the inside of said ceramics layer 2. Further, a holder 4 and two rectangular piezoelectric elements 5 having polariz ing axes in mutually opposite directions and bonded to each other are mounted therein. A U-shaped slit 6 by laser processing is formed to the center of this piezoelectric rectangular plate and the part surrounded thereby is set to a bending vibrator 7 having a cantilevered structure and output take-out electrodes are provided to both upper and lower surfaces thereof. The vibrator 7 vibrates at acceleration applied from the outside and acceleration can be measured on the basis of the voltages generated in the electrodes at this time. By this constitution, the resistance against the noise to the disturbing agitation of an external electromagnetic wave is enhanced and the effect of heat radiation is excluded even when there is a heat source in the vicinity.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is a mechanical quantity that detects force and acceleration by using the mechanical quantity (mechanical quantity) - electrical quantity conversion characteristic of magnetostrictive materials such as amorphous alloys and piezoelectric materials. It is related to sensors.

Conventional technology Conventionally, mechanical quantity sensors that utilize the mechanical quantity (mechanical quantity) - electrical quantity conversion characteristics of magnetostrictive materials such as amorphous alloys and piezoelectric materials have been manufactured as sensors for detecting mechanical quantities such as force and acceleration. There is. For example, in the former case, JP-A-61-14
As seen in Publication No. 1931, when an external force is applied to an amorphous alloy, stress-magnetic effect (magnetostrictive effect)
As a result, its magnetic properties change, and as a result, the impedance of the coil that constitutes the magnetic circuit changes, and this is electrically detected. On the other hand, JP-A-59-7092
Publication No. 3 describes an acceleration (vibration) sensor that utilizes the piezoelectric effect. It is a sensor that generates stress in a piezoelectric material due to acceleration such as vibration applied from the outside, and detects the electric charge generated in the piezoelectric material as an output.

Problems to be Solved by the Invention Sensors that detect mechanical quantities such as pressure using the stress-magnetic effect (magnetostrictive effect) of amorphous alloys have a magnetic circuit for detection, so a strong magnetic field is applied to the sensor from the outside. When applied, it creates an abnormal voltage,
This causes a large error in the detection of mechanical quantities. Further, in an acceleration sensor using a piezoelectric material as a transducer material, at the same time as detecting acceleration, if the material undergoes a temperature change due to the outside world, an electric charge is also generated. The generation of this pyroelectricity is given by the following equation.

dQ/d t=k −dT/d t (1) Here, Q is electric charge, T is temperature, t is time, and k is proportionality constant. That is, the generation of this charge cannot be distinguished from the charge generated by the acceleration to be detected, resulting in a large error in the measurement of acceleration. In this case, heat is transferred to the sensor not only through the air but also as radiation heat, and if a high-temperature heat source is nearby, the latter has a greater effect.In this way, in these mechanical quantity sensors, magnetic and There was a problem in that so-called electromagnetic waves such as radiant heat generated the output of the sensor, making it impossible to properly measure the mechanical quantities that were originally supposed to be measured.

Therefore, the present invention eliminates the influence of these electromagnetic waves.
Even in the presence of harsh external magnetic fields or heat sources,
The purpose is to provide a mechanical quantity sensor that can measure only mechanical quantities with high precision.

Means for Solving the Problems In a mechanical quantity sensor that converts mechanical quantities such as force and acceleration into electrical quantities, at least one layer made of a superconducting material is formed on the surface layer of the sensor housing.

By forming at least one layer made of a superconducting material on the surface layer of the sensor housing, it has the property of shielding electromagnetic waves when the material exhibits a superconducting state. As a result, by blocking all electromagnetic waves such as radio waves, magnetic fields, heat rays, etc., a mechanical quantity sensor that can accurately detect only the mechanical quantity to be measured can be obtained.

Example The present invention will be explained in detail with reference to examples.

Embodiment 1 FIG. 1 shows an acceleration sensor that is an embodiment of the present invention, and (a), (b), (C), and (d) are top sectional views, side sectional views, and cantilevered views, respectively. 1 shows a cross-sectional view and a perspective view of a bent piezoelectric sensor having a beam structure. 1 is a superconducting material, Y2O3, BaCO3 and CUO3, YBa
They were weighed and mixed to have a composition ratio of 2Cu2O7-d (d is a trace amount), calcined in the air at 900°C for 6 hours, and then ground. This pulverized powder was coated with an organic binder and dried to form a superconducting material layer that covered the sensor. A ceramic 2 having relatively poor heat conduction, such as alumina porcelain, is placed inside the layer, and a copper alloy 3 having good heat conduction is further fixed inside the layer. Further, it contains therein a holder 4 for holding a piezoelectric material, and two rectangular piezoelectric elements bonded to each other and having polarization axes in opposite directions in the thickness direction. A "U"-shaped slit (cutout) 6 is formed in the center of this piezoelectric rectangular plate by laser processing, and the portion surrounded by the slit 6 becomes a bending vibrator 7 having a cantilever structure. Electrodes are provided on the upper and lower surfaces of the electrodes, which serve as output extraction electrodes.

This vibrator vibrates due to externally applied acceleration, and the magnitude of the acceleration can be measured by the voltage generated across the electrodes. Acceleration sensors with such a configuration are resistant to noise from external disturbances caused by external electromagnetic waves (even if there is a heat source nearby, it is almost unaffected by the heat radiation, and the dT/dt of the piezoelectric material is extremely low (possible). Therefore, it is possible to output a signal containing only acceleration with high accuracy.

Embodiment 2 FIG. 2 is a sectional view of a torque sensor which is another embodiment of this patent. Reference numeral 11 denotes a layer of superconducting material provided in the outermost layer of the sensor in a cylindrical shape, and this layer was produced in the same manner as in Example 1. A coil 12 is disposed inside the shaft, and a magnetostrictive Fe-based amorphous alloy 14 is wound and bonded to the surface of the torque transmission shaft 13. Stress is generated inside the amorphous alloy through which torque is transmitted to the torque transmission shaft, which changes the impedance of the coil. Torque can be detected by detecting this change. A torque sensor with this structure is resistant to noise caused by external electromagnetic waves and can therefore output a torque-only signal with high accuracy.

Effects of the Invention According to the present invention, by providing one layer of superconducting material on the surface of a mechanical quantity-to-electrical quantity conversion sensor, the output induced by thermal changes and the noise induced by electromagnetic waves in the sensor can be increased. (This makes it possible to produce a highly accurate mechanical quantity sensor.

[Brief explanation of the drawing]

FIG. 1 shows an acceleration sensor according to an embodiment of the present invention, and (a), (b), (C) and (Company) are respectively a top sectional view, a side sectional view, a sectional view of a main part, and a perspective view of a main part. Figure, 1.
... superconducting material layer, 2 ... ceramics such as alumina porcelain, 3 ... copper alloy, 4 ... holder, 5 ... rectangular piezoelectric element, 6 ... "C-shaped" Slit (cutout), 7... Flexural vibrator, 11... Superconducting material layer, 12... Coil, 13... Torque transmission shaft, 14... Fe-based amorphous alloy. Name of agent: Patent attorney Toshio Nakao and 1 other person 1--1 super 4x special material layer Figure 1 3-Tsunaharu all 4-Holder 5 = -&7 shaped piezoelectric element c1 (ch

Claims (1)

[Claims] A mechanical quantity sensor that converts mechanical quantities such as force and acceleration into electrical quantities, characterized in that at least one layer made of a superconducting material is formed on the surface layer of the sensor housing.