SU934389A1 - Piezoelectric accelerometer - Google Patents

Description

(5) PIEZOELECTRIC ACCELEROMETER

The invention relates to a technique for measuring vibration parameters on various objects with low-frequency vibration displacements, where a large transducer factor is required.

In this area of instrumentation, the perfection of a piezo accelerometer is largely determined by the charge conversion coefficient, which determines its suitability for measuring the motion parameters of an object.

In addition, a number of other important requirements are imposed on a piezo accelerometer: small dimensions and weight, wide frequency range, strength and reliability.

Known constructions of piezoaccelerometers have a non-bending bending element made in the form of a metal plate cantilever-mounted in a support and a piezoelectric plate glued to it.

on face faces of which the load С l} is fixed.

The main disadvantage of this design is the inefficient distribution of stiffness along the elastic reinforcement and the piezoplates, which leads to a decrease in the conversion coefficient.

The irrational stiffness distribution along the console appears in

The fact that ceramic plates in any section are underloaded to the maximum allowable stress.

"five

Closest to the present invention is a piezoaccelerometer, which contains a cantilever sensor in the form of two rectangular piezoplates, separated by

Claims (2)

20 by a metal plate of an elastic connection of constant thickness, and fixed on the end faces of the plates of the inertial load C2. However, this design does not allow an increase in the conversion coefficient by charge, since it implements a known method of redistributing the rigidity of the console, which assumes a linear decrease in the generated charge. The purpose of the invention is to increase the conversion coefficient of a piezraxelerometer. This goal is achieved by the fact that, in the construction of a piezoaccelerometer, an elastic reinforcement is made in the form of an isosceles p1 | hegonum with a base clamped in the support, and a height that ensures a mechanical bending along the piezoplate length. FIG. 1 shows a piezo accelerometer circuit; in fig. 2 - section A-A on ({mg. 1; in Fig. 3 - stress diagram. The piezo accelerometer contains a metal plate 1 of elastic support, piezoplates 2 and inertial load 3. The law of width variation, the plates of elastic reinforcement are determined by the ratio PU - x) h-4y GbR3 1-, A,. (where Cp3 is the mechanical stress of the proportionality limit of the material of piezoplates; t is the length of the salt;% N is the thickness of the piezoceramic and metal plates; P is the inertia force; :) is half the width of the plate in the pinch zone; , 2. elastic moduli; . h "- - h h, -i .; "I -Vz-f A plate that satisfies this ratio (I) of dimensions. Has the shape of an isosceles triangle with a base clamped in the support (Fig. 2 The principal difference of the proposed design of RT is that the change according to the formula (1) the width of the elastic reinforcement plate makes it possible to create a zone of constant mechanical april along the length of the piezoplate. The stress puree in the proposed contraction in piezoplates along the axis is shown in Fig. 3 (continuous line). The length X. of the constant mechanical section The voltage (Fig. 3) is calculated from the following ratio under the condition (G - LGfiJ const, - Pth - 1Ph width of piezoplates, and consequently the area of the electrodes does not decrease. As a result, there is an increase in the charge conversion factor. If for the conversion factor for charge in the known structure is:., M (h hz) d3 21 + Е Z with 2b 2b b 6 / x-О 6pJ. then in the proposed construction se f (x + e). Using the proposed design Piezo Accelerometer provides, in comparison with known constructions, the following advantages Properties: the possibility of increasing the conversion coefficient in charge without increasing mass and size, as well as reducing the frequency of the first resonance and strength; rational use of the mechanical properties of piezoplates by creating a zone of constant mechanical stress, not exceeding the maximum permissible value; rational use of the electrical properties of piezoplates by obtaining a zone of uniformly distributed electric charge proportional to the measured value, which will significantly increase the technical level of the piezo-accelerometer sensor. The cavities between the piezor plates, the elastic reinforcement plate and the load are filled with glue (КЗОО, VK20, VKAKO), which improves the solidity of the structure, increases its strength and reliability. In addition, the introduction of glue increases attenuation and, thus, allows for expansion. frequency range of measurements at 2030%. Claims of the Invention A piezoelectric accelerometer comprising a cantilever sensing element in the form of two rectangular piezoplates separated by a metal plate of elastic reinforcement of constant thickness and fixed on the face faces of the plates of inertial load, which also that, in order to increase the conversion rate of the piezo accelerometer, the elastic reinforcement is made in the form of an isosceles one fug. g of a triangle with a base clamped in a support and a height ensuring a mechanical stress constant bending along the length of the piezoplates. Sources of information taken into account in the examination 1. USSR author's certificate number, cl. G 01 R 15/09, 25.09.63. 2. Sinani I. B. From the experience of designing piezoelectric devices for changing vibration. L., LDNTP TEH, with. 15-16 (prototype).