RU2057400C1 - Pressure gradient head - Google Patents

Abstract

FIELD: acoustics. SUBSTANCE: pressure gradient head has case, cover in the form of truncated cone, inertia element, piezoids of capacity C₁ and C₂ mounted on opposite sides of inertia element, reinforcing member in the form of stud made of material having Young's modulus of (19-21)10¹⁰ N/sq.m, one of its ends being fixed within case and other connected to cover through threaded joint. All these components are arranged coaxially. Head also incorporates four capacitors of values C₁₁, C₂₁, C₁₂, C₂₂, respectively, mounted in case. Case and cover are symmetrical to plane crossing center of inertia element perpendicular to heat axis. Ratio of height of cover side wall over generating line to its thickness is 8-9. Capacitors C₁₁ and C₁₂ are connected in parallel with piezoids and two other capacitors are connected to them in series. Capacitances are selected from equation

.

EFFECT: improved design. 1 dwg

Description

 The invention relates to acoustic and seismic measuring techniques and can be used in the design of acoustic receivers and receivers of seismic signals.

A known piezoelectric accelerometer containing a housing in the form of a base and a cover, fixed at one end to the base, the other on the cover a rod on which an annular piezoelectric element and a spring-loaded inertial mass are placed, and a source follower installed in the base along the periphery of the piezoelectric element, the ratio of the thickness of the base to the thickness the walls of the cover and the diameter of the base to the diameter of the rod are in the range of 15-25 and 7-13, respectively [1]
The disadvantages of this transducer include its asymmetry with respect to the phase center, as well as the presence of a heavy base, which facilitates the measurement of vibrations, but makes it almost impossible to measure the parameters of acoustic fields.

Closest to the invention is a piezoelectric tender-sensor containing two identical piezoceramic washers or a package of washers with a common inertial element. Piezoceramic washers or washer packages are clamped in a common housing symmetrically on opposite sides of a common inertial element. In this case, depending on the direction of polarization of the piezoceramics, the washers are connected to each other in parallel or sequentially so that the charges from them are summed. Spurious (in direction) vibrations cause the appearance of electrical signals of opposite signs, which are mutually destroyed [2]
However, in this receiver only those charges will be mutually annihilated, the occurrence of which is associated with spurious oscillations symmetric about the center of the inertial element of the sensor.

 The problem to which the invention is directed is to increase the orthogonal vibration protection of the receiver and to create the possibility of unifying the electro-acoustic parameters of a series of receivers.

и отношение высоты боковой стенки крышки по образующей к ее толщине равно 8-9.This is achieved by the fact that in the receiver of the pressure gradient, comprising a housing with a cover, an inertial element located in the housing and piezoelectric elements with a capacitance C ₁ and C ₂ mounted on opposite sides of the inertial element and electrically connected to each other with the possibility of summing signals, and the housing, the cover, the inertial element and the piezoelectric elements are installed coaxially, a reinforcing element is introduced in the form of a hairpin made of a material with a Yurga module (19.0-21.0) · 10 ¹⁰ N / m ² , one end of which is rigidly fixed in the housing, and the other is connected to lid with a threaded connection, and four correction capacitors with capacities C ₁₁ , C ₁₂ , C ₂₁ , C _22, respectively, installed in the housing, and the lid is made in the form of a truncated cone, the ratio of the diameters of the larger and smaller bases of which is 1.7-2.9, moreover, the pin is installed along the axis of the receiver, the housing and the cover are symmetrically relative to the plane passing through the center of the inertial element perpendicular to the axis of the receiver, capacitors with capacities C ₁₁ and C ₁₂ are electrically connected to the piezoelectric elements, and the capacitor s with a capacity of C ₂₁ and C _{22 in} series, while the capacitance values are selected from the condition

and the ratio of the height of the side wall of the cover along the generatrix to its thickness is 8-9.

 The drawing schematically shows the proposed device.

 The device comprises a housing 1 with a cover 2, a reinforcing element 3, piezoelectric elements 4 and an inertial element (inertial mass) 5. The electric capacitors and the electrical connections of the piezoelectric elements introduced into the housing are not shown in the drawing. The reinforcing element 3 is made in the form of a stud. Cover 2 is a truncated cone. The reinforcing pin is rigidly fixed at one end in the housing 1. Its other end is fixed by means of a threaded connection in the cover 2. The device is symmetrical about the axis of the pin and relative to the plane located perpendicular to the axis of the reinforcing element and passing through its middle.

 The device operates as follows.

 The sound pressure gradient determines the magnitude of the force under which the body 1 and the pin move relative to the inertial element 5. In this case, the inertial element 5 acts on the piezoelectric elements 4, deforming them. The electrical signal taken from the piezoelectric elements is proportional to the mechanical stress arising in them and, consequently, the sound pressure gradient. This takes into account that the dimensions of the receiver are small compared to the sound wavelength. Piezoelectric elements are installed on both sides of the inertial element, so some of them under its influence are compressed relative to their initial state, others are stretched. If the polarization directions of the piezoelectric elements in the assembly, located on opposite sides of the inertial element, coincide, their output signals are summed with different signs, i.e. deductible. In the event that the polarization directions of the piezoelectric elements are opposite, the signals from them are summed, while in the amount of one of the electrodes an inertial element or a housing can serve.

 Oscillations of acoustic or vibrational origin acting on the receiver, the direction of which does not coincide with the direction of the measurement axis, can be decomposed into two, one of which coincides with the direction of the measurement axis, and the other perpendicular to it. The latter excites in the receiver oscillations orthogonal to its axis of symmetry.

 The introduction of a reinforcing pin into the receiver and making it symmetrical with respect to a plane perpendicular to its axis and passing through the center of the inertial element eliminates cantilever oscillations and ensures that the piezoelectric elements are affected only by those orthogonal oscillations that are symmetrical either with respect to the indicated plane or with respect to the phase center of the receiver, coinciding with the center of the inertial element.

 The electrical signals at the output of the piezoelectric elements corresponding to the indicated oscillations are mutually destroyed when the signals from the piezoelectric elements located on opposite sides of the inertial mass are added. This is true for the case when the piezoelectric elements are identical in their parameters.

Since the spread in the parameters of commercially available piezoelectric transducers usually lies within 20%, to reduce the contribution of these signals to the resulting signal at the output of the receiver, it is necessary to minimize the amplitude of orthogonal oscillations. This can be achieved by selecting the material of the stud and the degree of stretching. The Young's modulus of the material E should be (19.0-21.0) · 10 ¹⁰ N / m ² .

In addition, the magnitude of the considered spurious signals is significantly influenced by the geometric and mechanical parameters of the housing and the cover in which the reinforcing stud is mounted. The results of experimental modeling showed that the truncated cone with the following geometric parameters is the optimal shape of the cover: the ratio of the diameters of the larger and smaller bases of the cone is in the range 1.7-2.9, the ratio of the height of the side wall of the cover along the generatrix to its thickness is 8-9, the angle at the base of the cone is 45 ^about .

 Such a cover has sufficient rigidity to protect the converter from mechanical influences, to remove the natural frequencies of the cover from the frequency range of the converter, to minimize the arrow deflection of the cover, which is especially important when the stud is stretched to achieve the required value of E.

;

+

C_o где С₁, С₂ емкости пьезоэлементов, расположенных по разные стороны от инерционного элемента;
С₁₁, С₂₁ емкости конденсаторов, включенных параллельно С₁ и С₂ соответственно;
С₁₂, С₂₂ емкости конденсаторов, включенных последовательно С₁ и С₂;
С_о результирующая емкость пьезоэлементов, входящих в состав приемников унифицируемой серий.In order to unify the acoustoelectric parameters of a series of receivers and further equalize the parameters of the piezoelectric elements in the receivers, correction is used with the help of electric capacitors located inside the receiver case. In parallel and sequentially with each piezoelectric element, capacitors are included, the capacities of which are determined based on the formulas

;

+

C _o where C ₁ , C ₂ capacitance of piezoelectric elements located on different sides of the inertial element;
C ₁₁ , C ₂₁ capacitance capacitors connected in parallel with C ₁ and C _2, respectively;
C ₁₂ , C ₂₂ capacitance capacitors connected in series With ₁ and C ₂ ;
With _{about the} resulting capacity of the piezoelectric elements that make up the receivers of the unified series.

 The use of the indicated capacitive correction makes it possible to substantially equalize both the parameters of the piezoelectric elements that make up a single receiver and the electro-acoustic parameters of a series of receivers.

Claims (1)

PRESSURE GRADIENT RECEIVER, comprising a housing with a cover, an inertial element located in the housing and piezoelectric elements with capacitances C ₁ and C ₂ mounted on opposite sides of the inertial element and electrically connected to each other with the possibility of summing signals, the housing, the cover, the inertial element and the piezoelectric elements mounted coaxially, characterized in that a reinforcing element is introduced into it in the form of a hairpin made of a material with a Young's modulus (19 - 21) • 10 ^{1 0} N / m ² , one end of which is rigidly fixed in the housing and the other is connected n with a cap threaded connection, and four correction capacitors with a capacity of C _{1 1} , C _{2 1} , C _{1 2} , C _{2 2,} respectively, installed in the housing, and the cap is made in the form of a truncated cone, the ratio of the diameters of the larger and smaller bases of which is 1, 7 - 2.9, with the pin installed along the axis of the receiver, the housing and the cover are symmetrically relative to the plane passing through the center of the inertia element perpendicular to the axis of the receiver, capacitors with a capacity of C _{1 1} and C _{1 2 are} connected electrically to the piezoelectric elements, and the condenser capacitors C _{2 1} and C _{2 2} - sequentially, while the capacitance values are selected from the condition

and the ratio of the height of the side wall of the cover along the generatrix to its thickness is 8 - 9.

Images