JPH06103230B2 - Strain gauge - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of a strain gauge used for a pressure sensor that converts a physical quantity such as pressure, load, displacement, velocity, acceleration, or torque into an electric signal. is there.

(Prior Art) Conventionally, as pressure sensors, those shown in FIGS. 13 to 15 are known.

In all of these, the semiconductor strain gauge 2 is attached to the pressure detection cylinder 1 connected to the object inlet 3, and when the semiconductor strain gauge 2 is distorted by an external force, the resistance change is detected.

(Problems to be Solved by the Invention) However, although the semiconductor strain gauge 2 is suitable for mass production, there are problems that the temperature characteristic is poor and the sensitivity is low.

Therefore, an object of the present invention is to provide a strain gauge that solves the above problems and improves the temperature characteristics and the sensitivity.

(Means for Solving the Problem) In order to achieve such an object, the present invention has the following configuration.

That is, according to the present invention, an input converter for converting an input signal into a surface acoustic wave and an output converter for converting a surface acoustic wave propagating on the surface of the piezoelectric substrate into an electric signal are provided at predetermined intervals on the piezoelectric substrate. The piezoelectric substrate has a pressure detecting portion between the two transducers, and the pressure detecting portion is formed with a surface acoustic wave adjuster that increases or decreases the passage amount of the surface acoustic wave according to its deformation. .

(Operation) In the present invention thus configured, the input converter converts an input signal into a surface acoustic wave.

When the surface acoustic wave passes through the pressure detecting portion, the amount of passage of the surface acoustic wave adjuster is increased or decreased according to the deformation of the pressure detecting portion.

That is, when the pressure detection unit is deformed by external pressure,
The surface acoustic wave modulator increases or decreases the passage amount of the surface acoustic wave according to this deformation.

Therefore, the output converter outputs an electric signal which changes abruptly due to a slight deformation of the pressure detecting portion.

Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a plan view showing a first embodiment of the present invention.

The first embodiment is a piezoelectric substrate 4 made of crystal or LiNbO _9.
An input transducer 5 for converting an input signal into a surface acoustic wave and an output transducer 6 for converting a surface acoustic wave propagating on the surface of the piezoelectric substrate 4 into an electric signal are formed at predetermined intervals on the left and right sides above. .

The input converter 5 includes a comb-shaped electrode 5A and a comb-shaped electrode 5B,
It is formed of an aluminum thin film or the like so that the combs are arranged alternately and in parallel. Here, the distance between the combs arranged in parallel is λ / 2, where λ is the wavelength of the input signal. In the output converter 6, the comb-shaped electrode 6A and the comb-shaped electrode 6B are formed by vapor deposition of aluminum or the like, like the input converter 5.

A portion of the piezoelectric substrate 4 between the input transducer 5 and the output transducer 6 is used as a pressure detecting portion 7, and the surface of the pressure detecting portion 7 passes through a surface acoustic wave in accordance with deformation of the pressure detecting portion 7 due to an external force. The surface acoustic wave modulator 8 is formed to reduce

The surface acoustic wave adjuster 8 forms a plurality of conductor patterns 9 in parallel with each other on the piezoelectric substrate 4 in a direction perpendicular to the propagation direction of the surface acoustic waves with a thin film of aluminum or the like, and electrically connects both ends of each conductor pattern 9 to each other. Connect to each other. Here, the distance between the conductor patterns 9 arranged in parallel is λ / 2−Δλ, where λ is the wavelength of the input signal.

The strain gauge configured as described above is arranged in a detection cylinder 11 having an object inlet 10 as shown in FIG. 2, for example, and constitutes a pressure sensor.

Next, an operation example of the first embodiment configured as above will be described.

Now, when an input signal of wavelength λ is input to the input converter 5, the input converter 5 converts the input signal into a surface acoustic wave.

When the surface acoustic wave passes through the pressure detector 7, the amount of passage of the surface acoustic wave adjuster 8 increases or decreases according to the deformation of the pressure detector 7.

That is, when the conductor pattern 9 side of the pressure detecting portion 7 is deformed into a convex state by the external pressure, the intervals between the conductor patterns 9 are increased from λ / 2−Δλ to λ / 2 in accordance with this deformation, which causes the surface elasticity. As the wave attenuation increases, the output signal from the output converter 6 decreases.

Therefore, as shown in FIG. 6, the output converter 6 outputs an electric signal that changes abruptly due to a slight deformation of the pressure detecting portion 7, and is extremely sensitive.

Next, a second embodiment of the present invention will be described with reference to FIG.

The second embodiment is the surface acoustic wave modulator 8 of the first embodiment.
The conductor pattern 9 has an interval of λ / 2.

With this configuration, when the conductor pattern 9 side of the pressure detecting portion 7 is deformed into a convex state due to the external pressure, the intervals of the conductor pattern 9 are increased from λ / 2 to λ / 2 + Δλ in accordance with this deformation, which causes the surface elasticity. Wave attenuation is reduced. Therefore, an output signal as shown in FIG. 7 is obtained from the output converter 6 in response to an increase in pressure applied to the pressure detecting section 7.

Next, a third embodiment of the present invention will be described with reference to FIG.

The third embodiment is a surface acoustic wave modulator 8 according to the first embodiment.
The conductor pattern 9 has an interval of λ / 2 + Δλ.

In this way, when the conductor pattern 9 side of the pressure detecting portion 7 is deformed into a concave state by the external pressure, the intervals between the conductor patterns 9 are decreased from λ / 2 + Δλ to λ / 2 in accordance with this deformation, which results in surface elasticity. Wave attenuation increases. Therefore, an output signal as shown in FIG. 8 is obtained from the output converter 6 in response to an increase in pressure applied to the pressure detecting section 7.

Next, a fourth embodiment of the present invention will be described with reference to FIG.

The fourth embodiment is the surface acoustic wave modulator 8 of the first embodiment.
Are replaced by surface acoustic wave modulators 8A and 8B having different properties. That is, the distance between the conductor patterns 9 in the surface acoustic wave modulator 8A is set to λ / 2−Δλ.
Then, the distance between the conductor patterns 9 in the surface acoustic wave modulator 8B is set to λ / 2 + Δλ.

With this configuration, when the pressure detection unit 7 is deformed by the external pressure on the conductor pattern 9 side, for example, in a concave state, the intervals of the conductor patterns 9 of the surface acoustic wave modulator 8A from λ / 2−Δλ are further increased according to this deformation. As the length becomes shorter, the intervals between the conductor patterns 9 of the surface acoustic wave modulator 8B decrease from λ / 2 + Δλ to λ / 2. Therefore, the output converter 6 outputs an electric signal as shown in FIG. 9 in response to a change in pressure to the pressure detector 7.

Next, a pressure sensor related to the present invention will be described with reference to FIG.

In this pressure sensor, a strain gauge 13 as shown in FIG. 11 is attached to the outer frame 12. This strain gauge 13 has the surface acoustic wave modulator 8 omitted from the one shown in FIG.

The hemispherical elastic body 15 attached to the tip of the cylindrical body 14 is in point contact with the pressure detecting portion 7 of the strain gauge 13, and the elastic body 15 is configured to be expandable and contractible according to the pressure in the cylindrical body 14. .

With this configuration, the elastic body 15 expands and contracts according to the external pressure to increase or decrease the passage amount of the surface acoustic waves propagating through the pressure detection unit 7. Therefore, the output converter 6 outputs the output as shown in FIG. The signal is obtained.

(Effects of the Invention) As described above, in the present invention, the surface acoustic wave passing through the pressure detecting unit is increased or decreased according to the deformation of the pressure detecting unit. An electric signal that changes abruptly due to the deformation of is output. Therefore, the present invention can improve the sensitivity and the temperature characteristics.

[Brief description of drawings]

FIG. 1 is a plan view of a first embodiment of the present invention, FIG. 2 is a diagram showing a configuration of a pressure sensor to which the embodiment is applied, and FIG. 3 is a plan view of a second embodiment of the present invention, and FIG. FIG. 5 is a plan view of a third embodiment of the present invention, FIG. 5 is a plan view of a fourth embodiment of the present invention, and FIGS. 6 to 9 are views showing the relationship between pressure and output signal of each embodiment. , Fig. 10 is a sectional view of the pressure sensor, Fig. 11 is a plan view of a strain gauge used for the pressure sensor, and Fig. 12
The figure shows the relationship between the pressure and the output signal, Figs. 13 to 15
Each of the figures is a diagram for explaining a conventional technique. Reference numeral 4 is a piezoelectric substrate, 5 is an input converter, 6 is an output converter, 7 is a pressure detector, 8 is a surface acoustic wave modulator, and 9 is a conductor pattern.

Claims (1)

[Claims] 1. An input converter for converting an input signal into a surface acoustic wave on a piezoelectric substrate and an output converter for converting a surface acoustic wave propagating on the surface of the piezoelectric substrate into an electric signal at predetermined intervals. A strain detecting element is formed between the two transducers of the piezoelectric substrate, and a surface acoustic wave modulator that increases or decreases the amount of surface acoustic wave passing according to the deformation is formed in the pressure detecting portion. gauge.