JPS638581A - Bulk material sensor - Google Patents

Abstract

PURPOSE:To stabilize the sensitivity characteristic of a sensor for bulk material or the like, by a method wherein a groove is arranged at an opening peripheral portion of a support to have a step at an internal circumference-side edge portion with respect to an open surface and a piezo-electric vibrator is elastically bonded on the edge. CONSTITUTION:A circumferential groove 14 is formed at an opening peripheral portion of one end of a support case 11 in such a manner as to have a step at an internal circumference-side edge portion 12 with respect to an open surface 13 of the case 11. The groove section 14 is filled with an elastic adhesive 15 comprising silicone resin or the like and a diaphragm 17 of a piezo-electric vibrator 16 is placed on the edge portion 12 with the peripheral portion 18 extending over the groove section 14 and fastened elastically.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a powder sensor that detects the presence or absence of powder, granules, etc. using a piezoelectric vibrator.

Conventional technology In recent years, a piezoelectric vibrator that vibrates in response to an oscillation voltage from an oscillator circuit has been developed using the principle that when an object to be detected, such as powder or granules, comes into contact with the vibrator, the vibrator stops vibrating and the oscillation output disappears. Sensors have come to be used to detect the presence or absence of powder and granules ("Piezoelectric Buzzer/Sounding Body Latest Technology '85 Edition" Editorial Committee Cotton "Piezoelectric Buzzer/Sounding Body Latest Technology '85 Edition 4198
Published by Sogo Gijutsu Shuppan, December 26, 2015, pages 2 to 15)
.

An example of a conventional powder sensor is shown in Figures 2 to 4 below.
This will be explained using figures.

As shown in FIGS. 2 to 4, in the powder sensor, a piezoelectric vibrator 1 includes a thin disk-shaped diaphragm 2 made of non-magnetic metal and a plate-shaped piezoelectric ceramic attached to the thin disk-shaped diaphragm 2. The vibration plate 3 also serves as one electrode, and an electrode is provided on the free surface of the piezoelectric element 3. A peripheral portion 4 of the diaphragm 2 is supported and fixed to a step formed in the opening of the support case 6 with an adhesive 6.

Regarding the conventional powder sensor configured as above,
The operation will be explained below.

By supporting and fixing the peripheral portion 4 of the diaphragm 2 of the piezoelectric vibrator 1, the vibration nodes are moved toward the outer circumference.
When a secondary resonance higher than this primary resonance occurs while the piezoelectric vibrator 1 is oscillating at the fundamental frequency by the oscillation circuit, vibration nodes also occur in the outer circumferential portion and the inner circle portion.

Problems to be Solved by the Invention For this reason, the above sensor has a phase difference of 1800 degrees between the vibrations of the outer peripheral part and the inner part, so the vibration may become unstable or if powder or granules come into contact with the piezoelectric vibrator. There has been a problem in that characteristics vary, such as vibrations at frequencies other than the fundamental frequency, resulting in large changes in sensitivity.

The present invention aims to solve the problems of conventional sensors and provide a powder sensor with stable sensitivity characteristics that does not generate secondary resonance.

Means for Solving the Problems The powder sensor of the present invention is provided with a groove portion in the opening peripheral portion of the support body, the inner peripheral side ridgeline portion of which is stepped with respect to the opening surface,
A piezoelectric vibrator is placed on the inner circumferential ridgeline of this groove and bonded with an elastic adhesive.

A groove portion in which a ridgeline near the inner circumference has a step with respect to the opening surface is provided in the opening periphery of the action support case, and a piezoelectric vibrator is placed on the ridgeline and adhesively held with an elastic adhesive. Therefore, this portion can be used as a node of the piezoelectric vibrator.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 shows an enlarged cross-sectional view of a main part of a piezoelectric vibrator mounting part of a powder sensor according to an embodiment of the present invention. In the figure, a diagonal groove portion 14 is formed in the peripheral edge of the opening at one end of the support case 11 so that the ridgeline portion 12 near the inner circumference has a step with the opening surface 13.

This groove portion 14 is filled with an elastic adhesive 15 made of, for example, silicone resin, and the diaphragm 17 of the piezoelectric vibrator 16 is placed on the ridge portion 12 and held by adhesive. At this time, the peripheral edge portion 18 of the diaphragm 17 is disposed so as to extend over the groove 14 and is resiliently fixed by the adhesive 16, so that the peripheral edge portion 16 of the diaphragm 17 absorbs the vibrations of the piezoelectric vibrator 16. It will be held flexibly. Note that 19 is a plate-shaped piezoelectric vibrating element.

Furthermore, since the vibration node 20 of the diaphragm 17 is on the ridgeline portion 12, the center portion and the peripheral portion 18 of the piezoelectric vibrator 16
The piezoelectric vibrator 16
Only the resonance of the in-phase part at the center of the sensor functions as a sensor.

Note that the ridgeline portion 12 is not limited to a shape that is formed continuously on the opening peripheral edge portion, but may be one in which a plurality of protruding portions are arranged and formed on the same circumference.

Effects of the Invention The present invention provides a groove portion in which the ridgeline near the inner circumference has a step with respect to the opening surface in the opening peripheral portion of the support case, places the piezoelectric vibrator on the ridgeline, and applies an elastic adhesive. Since it is adhesively held, this part can be used as a node of the piezoelectric vibrator, and it is possible to realize an extremely excellent powder sensor that can maintain stable sensitivity characteristics.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view of a main part of a powder sensor according to an embodiment of the present invention, FIG. 2 is a perspective view of a conventional powder sensor, and FIG. 3 is a sectional view taken along line A-A in FIG. FIG. 4 is an enlarged sectional view of the main part. 11...Support case, 12...Ridge line portion, 14...Groove portion, 15...Adhesive, 1
6... Piezoelectric vibrator, 17... Vibration plate, 18
...Peripheral portion, 19...Piezoelectric vibration element. Name of agent: Patent attorney Toshio Nakao and 1 other person//
-=Case I Figure 2 Figure 3 Figure 4

Claims (3)

[Claims] (1) A groove is formed in the opening periphery of the support case, and the ridgeline near the inner periphery has a step with respect to the opening surface, and the piezoelectric vibrator is placed on the ridgeline, and the elastic adhesive is applied to the groove. A particle sensor characterized by being bonded. (2) A patent characterized in that the peripheral edge portion of the piezoelectric vibrator extends from above the ridgeline portion near the inner circumference onto the groove portion, and is adhesively held by an elastic adhesive filled in the groove portion. A powder sensor according to claim 1. (3) The powder sensor according to claim 1 or 2, wherein the ridgeline portion near the inner circumference is formed of a plurality of protruding portions.