JPS5856405B2 - crystal transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crystal transducer that converts strain, density, etc. into frequency.

An object of the present invention is to provide a crystal transducer that is easy to manufacture and vibrates efficiently in the planar direction.

FIG. 1 is an explanatory view of the principle structure when a crystal resonator is used as a strain gauge, and A is a front view and B is a side view.

In the figure, 1 is a long plate-shaped crystal resonator with both ends fixed, and 2 is a base of, for example, a casing.

Now suppose that a strain ε occurs in the vibrator 1 in the direction of the arrow X, and if the spring constant of the crystal is weaker than that of the base 2, then
A stress as shown in equation (1) is generated in the vibrator 1.

σ=ε・E(1) E: Equivalent Young's modulus of crystal resonator 1 If resonator 1 is vibrating in the vibration mode in the direction of arrow Y in this state, its vibration frequency f is ( 2) As shown in the equation, it changes depending on the strain ε.

Since the resonant frequency ω can be expressed as 2πf, by measuring the resonant frequency ω of the vibrator 1, the corresponding distortion can be measured.

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

(:) Good stability of frequency f.

In other words, the Q of the vibrator 1 is high.

(11) Frequency change rate Δf/ε per unit strain is large.

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

In the structure shown in Fig. 1, if the vibrator 1 is caused to resonate and its resonant frequency ω is measured, the applied strain ω can be determined.
can be known.

FIG. 2 is an explanatory diagram of the configuration of an embodiment of the present invention, where A is a front view, B is a sectional view taken along line A-A' of A, and in the case of a three-terminal configuration, C is a cross-sectional view taken along line A-A' of A. , shows the case of a two-terminal configuration.

In the figure, 1 is a long plate-shaped crystal resonator.

As shown in FIG. 3, the vibrator 1 has cutting angles α and β of 190° with respect to the y-axis and the 2' axis.

It is within the range of 10°<β<85°.

2 is, for example, a base such as a housing.

Reference numeral 3 denotes an electrode provided on the surface of the vibrator 1, which is mainly provided on both fixed end sides I having a length of ]/4 of the effective total length l of the vibrator 1, and is composed of electrodes 31, 32, 33, and 34. .

The electrodes 31 and 32 are provided along the fixed end side 1/4t of the left and right edges of the vibrator 1 in the figure, respectively.

Electrodes 33 and 34 connect the electrodes 31 and 32, with the electrode 33 connecting the electrode 31 and the electrode 34 connecting the electrode 32.

In the case of a two-terminal configuration, on the back side of the vibrator 1,
As shown in Figure 0, electrodes with the same pattern as in Figure A are provided.

In addition, in the case of a three-terminal configuration, as shown in Figure B, the vibrator 1
An electrode 35 is provided on the entire back surface.

As shown in FIG. 4, the electrodes 31 and 32 are connected to an externally provided amplifier 4, and the vibrator 1 and the amplifier 4 constitute an oscillation circuit A.

5 is a frequency measuring device.

In the above configuration, when wires are connected as shown in FIG. 2B, for example, an electric field is applied to the vibrator 1 in the direction of arrow 2.

In this case, the transducer 1 is -900〈α〈90° as mentioned above.
, 100<1β1<85°, the vibrator 1 vibrates in the direction of arrow Y.

(FIG. 5 shows a schematic diagram illustrating the relationship between the crystal axis, the vibrator 1, and the applied electric field.

) Therefore, the moment 1 generated by the applied electric field
Since the distribution takes the form shown in FIG. 6B, a desired vibration mode can be efficiently excited.

FIG. 6A shows the displacement of the vibrator 1 during vibration, and FIG. 6B shows the bending moment diagram at that time.

Furthermore, since the vibrator 1 and the electrodes 3 are configured in a flat plate shape, they are extremely easy to manufacture, and at the same time, it is possible to use not only machining but also etching, etc., so that an inexpensive product can be obtained.

FIG. 1 is an explanatory diagram of the configuration of another embodiment of the present invention, in which A is a front view, B is a cross-sectional view taken along A-A', and C is a cross-sectional view taken along B-B' of A, showing a three-terminal configuration. Indicate the case.

In this embodiment, t on the center side in the longitudinal direction of the vibrator 1
The portion H having a length of /2 is also provided with an electrode portion (in this case, the electrode 31) that directly participates in the excitation action.

However, in the area of part H, as shown in Figure 0, the electrode 32 is provided along the right edge of vibration 1 so that the direction of application of the electric field is opposite to part I shown in Figure B. It is being

As a result, a vibrator 1 is obtained in which the central portion H of the vibrator 1 can also be actively excited, and a vibrator with good vibration efficiency is obtained.

When used in a two-terminal configuration, electrodes 3 having the same pattern as in the front view A may be provided on the back surface of the vibrator 1, and the wiring may be connected in the same manner as in FIG. 2C.

FIG. 8 is a configuration explanatory diagram of another embodiment of the present invention, A is a front view, B is a sectional view taken along line AA' of A, and in the case of a three-terminal configuration, C
1 is a sectional view taken along line AA' of A, and shows the case of a two-terminal structure.

In the figure, reference numeral 1 denotes a flat crystal oscillator, which consists of a oscillator 11 and a coupling portion 12, as shown in FIG.

The vibrating section 11 is provided symmetrically in parallel to the central axis 0-0' and consists of two plate beam-shaped vibrating sections 11a and 11b.

The coupling portion 12 has both ends coupled to one end of each of the vibrating portions 11, and the vibrating portion 11 and the coupling portion 12 form a mouth shape.

Returning to FIG. 8, 3 is an electrode provided on the surface of the vibrator 1.
It consists of electrodes 31, 32 and 33°34.

The electrodes 31, 32, 33, and 34 have the same pattern as shown in FIG. 2 in the vibrating portion 11a.

11b, respectively.

Therefore, for example, if the wires are connected as shown in FIG. 8B and C, an electric field is applied to the vibrator 1 in the direction of arrow 2,
As shown in FIG. 10, the two vibrating parts 11atllb vibrate symmetrically about the central axis 0-0'.

In this case, the fixed end of the vibrator 1 to the base 2 is subjected to a reaction force R generated at the connection point between the vibrating part 11 and the coupling part 12.
, moment) are equal in magnitude and in opposite directions, so they cancel each other out at the joint 12, and no force is generated at all. Even when the support is not ideal, energy is not transferred from the vibrator 1 to the outside. never consumed.

As a result, it is possible to obtain a vibrator main body with a high Q (a large value of the goodness level G).

FIG. 11 is a configuration explanatory diagram of another embodiment of the present invention, in which A is a front view, B is a sectional view taken along line AA' of A, and C is a sectional view taken along line B-8' of A.

In this embodiment, the vibrator 1 is composed of vibrating parts 11a, 11b and a coupling part 12, as in the embodiment in FIG. Electrodes with similar patterns are formed in each of the vibrating parts 11a and 11b.

In such a transducer, as explained in the embodiment of FIG. 8, vibration energy is not lost in the base 1, and as in the embodiment of FIG. It is possible to actively excite, and a product with good vibration efficiency can be obtained.

Next, in the embodiment shown in FIG. 2, when the transducer 1 is placed in the fluid to be measured, the relationship between the density ρ0 of the fluid to be measured and the transverse plane vibration frequency f' of the transducer is expressed by the equation (3). There is a relationship as shown in

Since the resonance frequency can be expressed as 2πf, by measuring the resonance frequency ω of the vibrator 1, the density ρO of the target fluid can be measured.

Therefore, the device of this embodiment can also be used as a density conversion transducer.

As shown in FIG. 12, the surface of the electrode 3 can be coated with a coating 6 of glass such as quartz glass (Si02) to resist adhesion of dust or the like or to prevent corrosion of the electrode 3 due to the atmosphere. .

As explained above, according to the present invention, it is easy to manufacture,
A crystal transducer that efficiently vibrates in the flat direction can be realized.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the principle of the present invention, A is a front view, B is a side view, and FIG. 2 is a diagram explaining the configuration of one embodiment of the present invention, A is a front view, and B is A-A of A. In the cross-sectional view, in the case of a double-sided pattern, C is the A-A' cross-sectional view of A; in the case of a single-sided pattern, Figure 3 is an explanatory diagram of the cutting direction of the vibrator, and Figure 4 is an explanatory diagram of the configuration of the oscillation circuit. , Fig. 5 is a diagram of the relationship between the crystal axis, the vibrator, and the applied electric field, Fig. 6 is an explanatory diagram of the operation of the embodiment of Fig. 2, A is the displacement, B is the bending moment diagram, and Fig. 7 is the diagram. FIG. 2 is a configuration explanatory diagram of another embodiment of the present invention, where A is a front view and B is an A of A.
-A' sectional view, C is a B-8' sectional view of A, showing the case of a three-terminal configuration; FIG. 8 is a diagram illustrating the configuration of another embodiment of the present invention; B is an AA' cross-sectional view of A, in the case of a three-terminal configuration; C is a cross-sectional view of A, showing the case of a two-terminal configuration; FIG. 9 is an explanatory diagram of the main part of FIG. 8. , FIG. 10 is an explanatory diagram of the operation of FIG. 8, and FIG. 11 is an explanatory diagram of the configuration of another embodiment of the present invention, where A is a front view, B is a sectional view taken along line AA' of A, and C is a cross-sectional view of A The BB' sectional view and FIG. 12 are explanatory diagrams of the main part configuration of the electrode portion. DESCRIPTION OF SYMBOLS 1... Vibrator, 11... Vibrating part, 12... Coupling part, 2... Base, 3, 31-35... Electrode, 4...
・Amplifier, 5... Frequency measuring device, A... Oscillation circuit,
0...0'...Central axis.

Claims (1)

[Scope of Claims] 1. A crystal resonator that is fixed at both ends and cut into a substantially long plate shape, and an applied electric field that is perpendicular to the longitudinal direction of the resonator, applied at right angles to the flat plate direction, and applied in the longitudinal direction. electrodes arranged on the vibrator so that electric fields are applied in substantially opposite directions at approximately both fixed end side 1/4 and central side 1/2 of the total length, and perpendicular to the longitudinal direction. A crystal transducer that generates vibrations in the direction of the plane of the plate. 2. A patent claim characterized in that the vibrator includes a substantially long plate-shaped vibrating section that is symmetrically arranged on the same plane and parallel to a central axis, and a connecting section that connects one end of each of the vibrating sections. The crystal lance dusa described in item 1.