JPS596371B2 - force transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for converting force into frequency.

FIG. 1 is a diagram illustrating the basic configuration of an embodiment of a conventionally commonly used device for converting force into frequency.

In the figure, 1 is a rod with a uniform cross section fixed at both ends, and 2 is a base of, for example, a casing.

Now, assuming that an axial force S is applied to both fixed ends of the rod 1, there is a difference of I between the axial force S and the lateral vibration frequency f of the rod.
In the case of K2''S, there is a relationship as shown in equation (1).

t: Length of rod 1 E: Longitudinal elastic modulus of rod 1 ■: Second moment of area about the principal axis perpendicular to the vibration direction g: Gravitational acceleration ρ: Density of rod 1 A: Cross-sectional area of rod 1 S: Axial force ( Compressive force is positive) K1. 2: The constant resonance frequency ω determined by the support conditions and vibration mode of the rod 1 is expressed as 2πf, so if the resonance frequency ω of the rod 1 is measured, the corresponding axial force S can be measured.

In such a transducer, the following conditions must be satisfied in order to achieve highly accurate measurement.

(i) Good stability of frequency f.

In other words, the Q of the vibrator (= rod 1) is high.

(ii) Frequency change rate Δf/σ per unit stress is large.

That is, the good dust G of such a transducer can be expressed by the following equation.

In the structure shown in Fig. 1, the applied axial force S can be determined by making the rod 1 resonate and measuring its resonance frequency ω. When vibrating, a reaction force R is generated at the fixed end of the base 2, and this force is consumed as a loss if the base is not an ideal fixed end, which causes a decrease in the Q of the rod 1. Become.

The present invention solves the above problems.

An object of the present invention is to provide a force exchanger that has a simple structure, reduces vibration energy loss, and is highly efficient.

Another object of the present invention is to make the resonance frequencies of the symmetrical mode and the asymmetrical mode different, thereby stably oscillating the symmetrical mode.

FIG. 3 is a configuration explanatory diagram showing one embodiment of the present invention, in which 3A and 3B are two vibrating bodies arranged in parallel so as to be symmetrical with respect to the central axis, and 4A and 4B are these two vibrating bodies. Vibrating body 3
A bond that connects the ends of A and 3B, 5
is a connecting body that connects arbitrary positions of the vibrators 3A and 3B, and these constitute the vibrator main body (2).

6A and 6B are supports for fixing and supporting the combined bodies 4A and 4B of the vibrator main body V on the base 2, respectively.

EX is an exciter, DT is a detector, AMP is an amplifier,
The exciter EX is attached to the vibrating body 3A and the amplifier A
The detector DT is driven by the output of MP and is attached to the vibrating body 3B, and its output is applied to the amplifier AMP.

That is, an oscillation circuit is constituted by the vibrator main body (2), the exciter EX, the detector DT, and the amplifier AMP.

Note that a piezoelectric element, for example, can be used as the exciter EX1 detector DT.

In such a configuration, when the axial force S to be measured is applied in the direction of the arrow and the axial force S changes, the resonant frequency of the vibrator main body ■ changes as shown in equation (1) above, and the oscillation frequency of the oscillation circuit changes. will also change.

Here, by setting the oscillation mode of the vibrator main body (■) to a symmetric mode that vibrates symmetrically with respect to the central axis, as shown in FIG. The reaction force R and the moment M generated at the coupling portion are equal in magnitude in opposite directions and cancel each other out, so that the energy of the vibrator main body (2) is not consumed externally.

As a result, a vibrator main body with a high Q value and a large value of good dust G can be obtained.

Incidentally, the oscillation mode of the vibrator main body (2) also includes an asymmetric mode as shown in FIG.

However, according to the vibrator main body (■) according to the present invention, the length t2 of the vibrating body is dominantly involved in the case of symmetric mode oscillation as shown in FIG. 4, but in the case of asymmetric mode oscillation as shown in FIG. In this case, the length tl will be dominantly involved, and the resonance frequencies of the symmetric mode and the asymmetric mode will be different.

Therefore, according to the configuration shown in FIG. 3, the vibrator main body (2) can be stably oscillated in a symmetrical mode.

FIG. 6 is a configuration explanatory diagram showing main parts of a specific embodiment of the present invention, in which a is a front view and b is a side view, and parts equivalent to those in FIG. 3 are given the same reference numerals. ing.

In FIG. 6, the vibrator main body V and supports 6A, 6B
are integrated with a common member.

That is, this embodiment shows an example in which a single prismatic body is cut into a predetermined shape so as to be symmetrical with respect to a central axis perpendicular to each other.

The vibrating bodies 3A and 3B are formed by cut holes HC provided along the longitudinal direction.

The combined bodies 4A and 4B are formed by the remaining portions at both ends of the cut hole HC.

The connecting bodies 5A and 5B are formed by the remaining portion between the cut hole HO and the cut holes HA and HB provided in the combined bodies 4A and 4B, respectively.

Further, the supports 6A and 6B are plate-shaped flexures PA1 to FA3. which are perpendicular to each other. It is formed of FB1 to FB3, etc.

As a result, stresses such as bending due to attachment of the end portions are removed, and the vibrator main body V is vibrationally insulated from the base and the like.

By integrally molding in this way, it is possible to obtain a product with uniform characteristics.

In addition, in this embodiment, the exciter EX and the detector DT
is arranged on the side surface near the connecting body 6B.

This is based on the fact that stress acts on the coupling body 5 when the oscillation mode is a symmetric mode.

Furthermore, when oscillating in a symmetrical mode, the coupling body 5 also acts as a part of the vibrating body, so the mounting range of the exciter EX and the detector DT, which exhibit good Q characteristics, is the coupling body 5. It also has the effect of being wider than it would be without it.

Note that the exciter EX and the detector DT can also be directly formed as thin film piezoelectric elements on predetermined portions of the vibrator main body (2) by vapor deposition, sputtering, or the like.

According to this, a higher Q can be obtained and productivity can also be improved.

Alternatively, the vibrator main body (2) may be made of a magnetic material, and excitation and vibration detection may be performed in a non-contact manner using a coil.

Furthermore, the vibrator main body, the excitation means, and the detection means can be integrated using a piezoelectric material such as crystal.

For example, after the vibrator body (2) is made of crystal, electrodes may be deposited on the vibrator body (V) by vapor deposition or the like.

According to this, a device with a relatively simple configuration, low output impedance, and good characteristics can be obtained.

In this case, the cut of the crystal and the arrangement of the electrodes may be selected so that the vibrating bodies 3A and 3B undergo bending vibration.

Further, in the above embodiment, an example in which the vibrating body is shaped like a plate beam has been described, but the vibrating body is not limited to this, and may be shaped like a rod.

Further, in the above embodiment, an example was described in which the vibrator main body of a predetermined shape was cut out from a prismatic body and integrally molded, but individually configured parts may be combined.

As explained above, according to the present invention, it is possible to realize a force transducer with low loss of vibration energy, high conversion efficiency, and in which the asymmetric mode and the symmetric mode have different resonance frequencies.
It is suitable as a signal conversion element of a measuring device for physical quantities such as pressure (differential pressure), density, strain, and weight.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the basic configuration of the conventional device, and Figure 2 is the
3 is an explanatory diagram of the principle configuration of the device according to the present invention, FIGS. 4 and 5 are explanatory diagrams of the operation of FIG. 3, and FIG.
The figure is a configuration explanatory diagram showing main parts of a specific embodiment of the present invention. 2... Base, 3... Vibrating body, 4...
...combined body, 5...connected body, 6...
・Support, ■... Vibrator body, EX...
・Exciter, DT...Detector, AMP...
·amplifier.

Claims (1)

[Claims] 1. Two vibrating bodies arranged in parallel so as to be symmetrical with respect to a central axis, a coupling body that connects the ends of these vibrating bodies, and an arbitrary position between these vibrating bodies. a vibrator body including a coupling body that connects the vibrator body, an excitation means for causing the vibrator body to resonate, and a detection means for detecting the vibration of the vibrator body, and the vibrator body changes in accordance with the axial force acting on the vibrator body. A force transducer that makes the natural vibration frequencies of symmetric mode oscillation and antisymmetric mode oscillation of a vibrating body different. 2. The force transducer according to claim 1, wherein the vibrator main body is integrated with a common member. 3. The force transducer according to claim 1, characterized in that the excitation means and the detection means are provided at a connecting portion between the vibrating body and the connecting body. 4. The force transducer according to claim 1, characterized in that a piezoelectric element is used as the excitation means and the detection means. 5. The force transducer according to claim 4, wherein a thin film vapor-deposited piezoelectric element is used as the piezoelectric element. 6. The force transducer according to claim 1, wherein the vibrator body is made of a magnetic material, and a coil is used as the excitation means and the detection means. 7. The force transducer according to claim 1, wherein the vibrator body, the excitation means, and the detection means are integrated using a piezoelectric material.