JP2909277B2 - Plate transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a plate-shaped transducer.

[0002]

2. Description of the Related Art FIGS. 6A and 6B show a conventional plate transducer. Note that FIG. 6A is a cross-sectional view, and FIG. 6B is a top view of FIG.

[0003] Reference numeral 1 in the drawing denotes a housing having a pressure-resistant structure with an open top. A flat plate 2 is attached to an upper opening of the housing 1. The back surface (lower surface) side of the flat plate 2, the upper and lower
A piezoelectric body 4 having electrodes 3a and 3b attached to the surface is attached. Here, when an AC voltage is applied to the piezoelectric body 4 via the electric wire 5, a stretching strain (L) is generated in the piezoelectric body 4, exciting the vibration (V) of the flat plate 2, and the sound wave P is generated in the fluid 6. Is transmitted.

Conversely, when the sound wave P is incident on the flat plate 2, the vibration (V) of the flat plate 2 is excited, and a stretching strain L is generated on the piezoelectric body 4, and the electrodes 3 a and 3 b on the upper and lower surfaces of the piezoelectric body 4 are applied. Generates a voltage and can detect a received sound wave.

[0005]

However, the conventional transmitter / receiver shown in FIG. 6 utilizes a flat plate resonance phenomenon in order to transmit and receive waves efficiently. Is limited only near the resonance frequency of the flat plate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a plate-shaped transducer that can widen a range of a used frequency, which has been conventionally limited only near a resonance point of a flat plate. I do.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a flat plate.
A shape memory alloy wire rod with both ends constrained, a flat plate-shaped piezoelectric body attached to the flat plate and provided with electrodes on both sides to generate stretching strain, and a current provided at both ends of the shape memory alloy wire rod A plate-shaped transducer comprising: a power supply circuit for flowing a current; and an electric circuit for exciting or detecting vibration of the electrode of the piezoelectric body.

FIGS. 4 and 5 are characteristic diagrams showing the temperature dependence of the elastic modulus of the shape memory alloy wire. From the figure,
In general, it can be seen that the shape memory alloy has the property that the elastic modulus increases several times when the temperature increases. The figure shows a titanium-nickel-based product name Nitinol, but all shape memory alloys have this property.

FIG. 3 is a diagram showing a restoring stress characteristic of the shape memory alloy wire rod, wherein the horizontal axis represents temperature and the vertical axis represents restoring stress. From FIG. 3, when the initial strain is applied in a low temperature state and heat is applied, the shape memory alloy wire tries to return to the original shape, but when the displacement of both ends of the shape memory alloy wire is restrained, Causes tension in the wire. In addition, since the shape memory alloy wire has electric resistance, the temperature can be increased only by passing an electric current.

Accordingly, if current is applied to the shape memory alloy wire rod while restraining its displacement at both ends in the structure shown in FIG. 2, the temperature rises and the elastic modulus of the shape memory alloy increases and the tension increases, so that the out-of-plane characteristic of the flat plate is increased. The frequency rises.

[0011]

In the plate-like transducer of the present invention, when a voltage is applied to the piezoelectric body, the resonance vibration of the flat plate is excited by the expansion and contraction of the piezoelectric body, and a sound wave is emitted into the fluid. Conversely, when a sound wave is incident on a flat plate, the vibration of the flat plate is excited to cause stretching distortion in the piezoelectric body, a voltage is generated in the electrode of the piezoelectric body, and the received sound wave can be detected. Since the resonance phenomenon of the flat plate is used, transmission and reception are performed only near the natural frequency of the flat plate.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A plate-like transducer according to one embodiment of the present invention will be described below with reference to FIGS. 1 (A) and 1 (B). Here, FIG. 1A is a cross-sectional view, and FIG. 1B is a top view of FIG.

Reference numeral 11 in the drawing denotes a housing having a pressure-resistant structure with an open top. A plate-shaped transducer 12 is attached to the housing 11. Here, the transducer 12 is attached to an opening of the housing 11 and has shape memory alloy wires 13a, 13a therein.
b, 13c, 13d, 13e, and 13f, and a flat plate 14 on the rear surface (lower surface) of the flat plate 14, and electrodes 15 on the upper and lower surfaces.
a, a power source circuit provided at both ends of the shape memory alloy wires 13a to 13f, and excitation or detection of vibration to the electrodes 15a, 15b of the piezoelectric body 16. And an electric circuit for performing the operation.

Both ends of each of the shape memory alloy wires 13a to 13f are attached to the housing 11, and displacement of both ends is restrained. The power supply circuit is a power supply V _a ~V _f and the switch S
_a to S consists _f, if necessary the shape memory alloy wire 13
A current can flow through a to 13f.
The electric circuit is a driving power supply 18 connected between the electrodes 15a and 15b of the piezoelectric body 16 via electric wires 17. That is,
A driving power supply 18 is attached when transmitting a wave, and detects a voltage generated between the electrodes 15a and 15b when receiving a wave. In addition, reference numeral 19 in the drawing denotes a fluid in contact with one surface (upper surface) of the flat plate 14.

When a voltage V ₀ is applied to the piezoelectric body 16 in the plate-like transducer of this configuration, the expansion and contraction (L) of the piezoelectric body 16
As a result, the resonance vibration (V) of the flat plate 14 is excited, and the sound wave P is emitted into the fluid 19.

On the contrary, when the sound wave P is incident on the flat plate 14,
The vibration V of 14 is excited, and a stretching strain (L) is generated in the piezoelectric body 16, a voltage is generated in the electrodes 15 a and 15 b of the piezoelectric body 16, and the received sound wave P can be detected. Since the resonance phenomenon of the flat plate 14 is used, transmission and reception are performed only near the natural frequency of the flat plate.

[0017] Thus, in this way according to the plate-shaped transducer arrangement, by controlling the current supplied to the shape memory alloy wire 13a~13f turning the switch S _a to S _f, by turning off,
The configuration is such that the rise of the natural frequency of the flat plate 14 is controlled by adjusting the number of shape memory alloy wires whose elastic modulus and tension increase. Therefore, as compared with the related art, the range of the frequency used for the transmission and reception using the flat plate 14 can be expanded.

[0018]

As described above in detail, according to the present invention, it is possible to provide a plate-shaped transducer which can widen the range of operating frequencies conventionally limited only near the resonance point of a flat plate.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a plate transducer according to one embodiment of the present invention.

FIG. 2 is a perspective view of a flat plate which is one configuration of the plate-shaped transducer shown in FIG.

FIG. 3 is a diagram showing a restoring stress characteristic of a shape memory alloy wire rod.

FIG. 4 is a joining diagram of acceleration cells in step A according to the second embodiment of the present invention.

FIG. 5 is a joining diagram of acceleration cells in step B according to the second embodiment of the present invention.

FIG. 6 is an explanatory view of a conventional plate transducer.

[Explanation of symbols]

11: housing, 12: transducer, 13a to 13f: shape memory alloy wire, 14: flat plate, 15a, 15b: electrode, 16
... Piezoelectric body, 18 ... Power supply for driving piezoelectric body, 19 ... Fluid.

Claims (1)

(57) [Claims] 1. A shape in which at least both ends are restrained by a flat plate
A memory alloy wire rod, a flat-plate-shaped piezoelectric body attached to the flat plate and provided with electrodes on both sides thereof, which generates stretching strain, and a power supply circuit provided at both ends of the shape memory alloy wire for flowing current, An electric circuit for exciting or detecting vibrations on the electrodes of the piezoelectric body.