RU2247993C2 - Resonator pickup - Google Patents

Abstract

FIELD: measuring engineering.

SUBSTANCE: pickup has base made of monocrystal and provided with through slots to form a sensor and sensor suspension made of at least two rods and rod resonator. One ends of the rods are connected with the sensor which is freely mounted inside the hollows made in the lids arranged on both sides of the base and connected with them over periphery. The rods of the suspension are provided with the flexible pivots for allowing the sensor to move with respect to the base in the direction of the measuring axis. The sensor comprises at least two interconnected members, one flexible member, and one nonflexible member which can move one with respect to the other.

EFFECT: enhanced reliability of pickup under the action of vibration.

6 dwg

Description

The invention relates to the field of measuring mechanical parameters. A known sensor (see US patent No. 5.165.279, class G 01 P 15/10 dated 06/06/1989, published 11/24/92), which is the closest in technical essence to the claimed device and is taken as a prototype. The sensor is made of a flat monocrystalline base with the formation of a sensitive element in it in the form of a rectangular plate connected to it through elastic hinges, and contains a resonator freely placed in its slot. The resonator is electrically and mechanically connected to an electromechanical converter, providing excitation of mechanical vibrations and their reverse conversion into an electrical signal. In addition, the base is closed on both sides by covers, which are fastened around its perimeter and have recesses for the free movement of the sensing element.

The disadvantage of the prototype is the need to use an external mechanical filter to reduce the intensity of the oscillation of the sensitive element when it falls into its own frequency range of vibrations.

The technical result of the proposed sensor is to ensure its operability under the action of vibration by reducing the intensity of oscillation of the sensing element.

The technical result is achieved by the fact that the sensor is a resonator containing a single crystal base in which through slots are made with the formation of a sensitive element and its suspensions in the form of at least two rods and a rod resonator, one ends of which are connected to a sensitive element freely placed in the recesses of the covers located on both sides of the base and connected with them along the perimeter, elastic hinges are made on the suspension rods to move the sensitive element relative to the base In the direction of the measuring axis, the rod resonator is electrically and mechanically connected with the electromechanical transducer, characterized in that the sensitive element consists of two parts with the possibility of moving them relative to each other and interconnected by elastic joints and an inelastic element filling the gap formed between the parts of the sensitive item.

Figure 1 shows the primary Converter without a cover.

Figure 2 is an equivalent mechanical diagram.

Figure 3 is a graph of the movement of the first sensor element.

Figure 4 is a graph of the movement of the second sensor element.

In Fig.5 - the primary Converter with covers.

Figure 6 - sensor resonator Assembly.

The device comprises a base 1 and a sensing element connected to it by means of two elastic hinges 5 and a rod resonator 2, made, for example, in the form of a two-branch tuning fork. The sensitive element consists of two parts 3 and 4, interconnected by elastic hinges 6 and an inelastic element, which fills the gap B formed between the parts of the sensitive element (figure 1).

Cover 7 (FIG. 5) limits the stroke of the sensitive element, protecting the suspension and the resonator from damage under the action of shock loads.

The resonator sensor operates as follows. The mechanical force acting in the direction of the measuring axis, perpendicular to the plane of the parts of the sensing element 3, 4, causes a moment M _AND equal to:

M _AND = F · L,

where: F - mechanical force,

L is the shoulder between the point of application of mechanical force and the elastic suspension.

The moment M _{I is} balanced by the reactive moment caused by the pair of forces applied to the resonator and the suspension rods and the moment of the elastic hinge 6. The elongation of the resonator 2 causes an angular displacement θ _{1 of the} sensing element 3 relative to the axis of the hinges 6. In the kinematic diagram of FIG. 3, the total rigidity of the hinges 6 suspension taking into account the stiffness of the resonator 2 is denoted as C ₁ and the hinges 7 as C ₂ . In this case, the parts of the sensing element 3, 4 move relative to each other with different angular velocities, determined by their dynamic properties (stiffness of the hinges 6, 7, the moment of inertia of the parts of the sensing element 3, 4), interacting through an inelastic element 9, which has a certain viscosity coefficient, which causes the loss of mechanical energy in the oscillatory system (consisting of sensitive elements 3, 4 and elastic joints 6, 7), reducing its quality factor and decreasing the amplitude of oscillations of elements 3, 4, dampen informative element as a whole. As the damping element 9, an elastic (rubber-like) compound with the required viscosity can be used. In a particular case, the length of the rigid part of the suspension rods of the sensing element can have a minimum (zero) value and the role of the suspension in this case will be performed by elastic hinges. The law of motion of the sensitive elements 3, 4 is described by the following system of differential equations (see figure 3):

where: θ ₁ , θ ₂ is the angular displacement of the suspension relative to the base;

,

,

,

- угловые скорости и угловые ускорения соответственно;

,

,

,

- angular velocities and angular accelerations, respectively;

ω is the angular frequency;

t is the time;

J ₁ , J ₂ - moment of inertia, respectively, of the first and second sensitive elements;

m ₁ , m ₂ - mass of the first and second sensitive elements;

l ₁ - the distance between the elastic joints 6,7 (the distance between the conditional axes of rotation of the elastic joints);

C ₁ - equivalent stiffness of the joints 5 taking into account the resonator 2;

C ₂ - the stiffness of the hinges 7 connecting the parts 3 and 4 of the sensing element;

η is the coefficient of losses introduced by the inelastic element 9;

L _ЦМ1 , L _ЦМ2 - center of mass of the first and second sensitive elements;

and - acceleration.

We represent the solution of system (1) in dimensionless form

Where

,

,

,

,

=2,11. Добротность первой части чувствительного элемента - 3,0 и второй - 2,0. Добротность системы без демпфирования достигает значения 400. Введение предлагаемого демпфирования позволит снизить добротность до единиц, что обеспечит работоспособность датчика при воздействии вибрации.Figure 4, 5 presents graphs of the relative amplitudes of the parts of the sensing element. Calculations were given for a design with the following characteristics: δ = 0.668, β = 1.41, μ = 0.7,

= 2.11. The quality factor of the first part of the sensing element is 3.0 and the second is 2.0. The quality factor of the system without damping reaches 400. The introduction of the proposed damping will reduce the quality factor to units, which will ensure the operability of the sensor when exposed to vibration.

Claims (1)

A resonant sensor containing a single crystal base in which through slots are made to form a sensitive element and its suspensions in the form of at least two rods and a rod resonator, one ends of which are connected to a sensitive element freely located in the recesses of the covers located on both the sides of the base and the perimeter connected to them, elastic hinges are made on the suspension rods to move the sensitive element relative to the base in the direction of the measuring axis, erased the reed resonator is electrically and mechanically connected to an electromechanical transducer, characterized in that the sensitive element consists of two parts with the possibility of moving them relative to each other and interconnected by elastic hinges and an inelastic element filling the gap formed between the parts of the sensitive element.

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