JPH0228563A - Vibration sensor - Google Patents

Abstract

PURPOSE:To obtain an extremely lightweight, small-sized, and thin vibration sensor which can be formed of a thin plate by detecting an electromotive current flowing to a coil by the electromagnetic induction by enclosure vibration. CONSTITUTION:A U-shaped slit 12 is cut by etching in a displacement detection body 10 made of an amorphous silicon film to form a cantilever 13 which can be displaced in the film thickness direction. Then when a lever 13 which is excited by the enclosure vibration moves up and down about the coil 17 of a base plate body 11, a magnetic body 14 formed on the reverse surface of the lever 13 faces the coil 17 and a magnetic field passing through the coil 17 varies with the vibration to male a current to the coil 17 by the electromagnetic induction. For the purpose, this electromotive current is measured to detect the speed component of vibration applied to the sensor and this component is integrated to detect the acceleration and displacement. Thus, the vibration state is detected. The sensor consisting of the detection body 10 and base plate body 11 has the base plate body 11 constituted in film or thin plate structure and is reduced in weight extremely and in size and thickness.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an electromagnetic induction type vibration sensor.

2. Description of the Related Art Conventionally, as a vibration sensor (acceleration sensor, speed sensor), there is a piezoelectric element type as shown in FIG. 5, for example. This is achieved by adding a mass inertia body 4 to a piezoelectric element 3 installed in a cover 1 via a support 2, converting the acceleration obtained by vibration into force by the mass inertia body 4, and using the piezoelectric element 3 to generate force. It detects the amount. Although this is a piezoelectric method, the method shown in Japanese Utility Model Application Laid-Open No. 63-17460 also uses a mass inertial body.

Furthermore, as shown in FIG. 6, there is also an electromagnetic induction type vibration sensor consisting of a coil 5 and a magnet 6.

Problems to be Solved by the Invention However, according to the former, a mass inertial body is required to detect vibrations, and according to the latter, a coil 5 and a magnet 6 are required. It becomes something big. Therefore, when measuring the vibration of a lightweight object, it adds mass, which is undesirable, and it also lacks mass productivity.

Means for Solving the Problems A displacement detecting body is provided, which includes a cantilever made of amorphous silicon and displaced in response to ambient vibration, and a magnetic material formed in a layered or laminated manner on at least one surface of the cantilever. At the same time, a substrate body is provided in which opposing coils are formed on the magnetic material so that the magnetic flux density changes according to the direction of displacement of the cantilever.

When the surrounding vibration acts, the cantilever of the displacement detection body vibrates and displaces in response. Then, the magnetic field passing through the coil facing the magnetic body of the cantilever changes, and current flows through the coil due to electromagnetic induction. Therefore, by detecting this current flowing through the coil, the vibration situation is detected. In other words, it is lightweight and does not involve heavy objects such as inertial mass bodies.
It becomes a small vibration sensor.

Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 to 3. First, the vibration sensor of this embodiment is of an electromagnetic induction type, and basically consists of a displacement detection body 10 and a substrate body 11.
Consists of pieces. First, the displacement detector 10 is a rectangular plate-shaped film formed of an amorphous silicon (a-5i) film, and by etching a portion of the substantially U-shaped slit 12, A cantilever 13 displaceable in the thickness direction is formed, and a magnetized layered or film-like magnetic material 14 is laminated or film-formed on the entire or part of the lower surface of the free displaceable end of the cantilever 13. This magnetic body 14 has magnetic flux directed in the vertical direction. Further, the substrate body 11 side includes a substrate portion 15 and support portions 16 which are formed high on both sides and to which the lower surfaces of both ends of the displacement detecting body 10 are fixed. A pattern is formed by etching or the like. Here, this coil 17 is formed at a position facing the magnetic body 14 formed on the cantilever 13.

In a configuration like 2, when the cantilever 13 excited by the surrounding vibration moves up and down with respect to the coil 17,
Since the magnetic body 14 on the lower surface of the cantilever 13 and the coil 17 face each other, the magnetic field (magnetic flux density) passing through the coil 17 changes with the vibration, and current flows through the coil 17 due to electromagnetic induction.

Therefore, by measuring this electromotive current flowing through the coil 17, the velocity component of the vibration applied to the sensor can be detected. Then, by differentiating or integrating this velocity component, acceleration or displacement can be detected. In this way, the vibration state is detected.

According to the electromagnetic induction vibration sensor of this embodiment having such a configuration and principle, it is easy to make the substrate body 11 side have a film structure or a thin plate structure, and since it does not have a mass body,
It can be made into an ultra-lightweight, small, and thin sensor. Furthermore, the entire structure can be manufactured by etching technology, and it is highly suitable for mass production.

Regarding the cantilever 13, by appropriately changing the shape of the slit 12 as illustrated in FIGS. 4(a), (b), and (c), the natural frequency of the cantilever 13 relative to the surrounding vibration can be changed. The measurement sensitivity can be improved by changing the shape according to the measurement frequency band of the target vibration.

Effects of the Invention As described above, the present invention provides a displacement detection body comprising a cantilever made of amorphous silicon and displaced in response to ambient vibration, and a magnetic material formed in a layered or laminated manner on at least one surface of the cantilever. At the same time, a substrate body was provided in which a magnetic body was formed with opposing coils whose magnetic flux density changed according to the direction of displacement of the cantilever.
When external vibration is applied, the vibration status can be detected by the current flowing through the coil due to electromagnetic induction according to the vibration displacement of the cantilever.It is ultra-lightweight and compact and can be formed from a thin plate, etc., without heavy objects such as inertial masses. - It can be made into a thin vibration sensor, and it can also be manufactured by etching technology, making it a highly mass-producible sensor.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing one embodiment of the present invention, FIG. 2 is a perspective view, FIG. 3 is a longitudinal front view, FIG. 4 is a perspective view showing a modification of the displacement detector, and FIG. Side view showing the conventional example, No. 6
The figure is a side view showing a different conventional example. 10...Displacement detection body, 11...Substrate body, 13...Cantilever 14...Magnetic material, 17...Coil output
Figure 16

Claims (1)

[Claims] a displacement detection body comprising a cantilever formed of amorphous silicon and displaced in response to ambient vibration; a magnetic material formed in a layered or laminated manner on at least one surface of the cantilever; 1. A vibration sensor comprising: a substrate body on which coils are formed to face each other in a state where the magnetic flux density changes according to the state of the vibration sensor;