JPH0112480Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention consists of two bridge-shaped support parts each having a concave portion on the upper surface having an opening width equal to the width of a rectangular piezoelectric vibrator having a vibration form bent in the length direction. This is a vibrator support stand integrally formed with a soft elastic body whose lower surface is connected to the bottom part with a substantially equal distance between the nodes of vibration of the piezoelectric vibrator.

Aerial ultrasonic devices are used for security intrusion detectors, visitor alarms, and remote controllers for electronic devices. The transmitters and receivers of these ultrasonic devices are required to be high performance and inexpensive.

For devices that utilize the Doppler effect, in which ultrasonic waves continuously emitted from a transmitter are reflected from a moving object to be detected and the frequency received by the receiver changes, the transmitter/receiver It is necessary that the sensitivity is high and the resonant frequency is small with respect to temperature changes.
In addition, if the ultrasonic signal emitted from the transmitter in the form of a pulse waveform is reflected from the object to be detected and uses the time difference between when it reaches the receiver, the transmission and
It is necessary that the pulse waves to be received have steep rise and fall characteristics, and that the transmitting and receiving signals of the transmitter and receiver have a wide frequency bandwidth.

Conventionally, this type of aerial ultrasonic transmitter/receiver has a ring-shaped support 2 made of silicone rubber glued to the vibration nodes of a circular ceramic bimorph vibrator 1, as shown in the example in FIG. Fix it to the bottom of case 3. In addition, a circular reflection plate 4 is arranged on the upper surface of the case 3 at a constant distance from the ultrasonic emission surface of the transducer 1, and an electric signal is applied to the transducer 1 from the terminal 5, and the ultrasonic wave is radiate. Therefore, in this structure, since the vibration nodes of the vibrator 1 are supported, a highly sensitive transmitter/receiver with a high mechanical Q and a narrow frequency bandwidth can be obtained. Further, as shown in the example of FIG. 2, a conical resonator 6 is bonded to the center of the circular ceramic bimorph vibrator 1, an electric signal is applied to the vibrator 1 from the terminal 5, and an ultrasonic wave is emitted from the resonator 6. Let it radiate. A transmitter/receiver having this type of structure can radiate vibrations in a wide frequency bandwidth without reducing sensitivity due to the effect of the conical resonator 6. In this type of transmitter/receiver, the ceramic bimorph vibrator 1 may be square instead of circular. However, these conventional transmitters and receivers all have one vibrator.
Since two ceramic vibrating pieces are bonded together, it is necessary that the characteristics of each vibrating piece be the same, and there is also the disadvantage of bonding the vibrator 1 and the support 2, and the process required for bonding is expensive. becomes.

The present invention overcomes these drawbacks of the conventional method and provides stable support by supporting the position of the vibration node of a single rectangular piezoelectric vibrator using interdigital electrodes, and by changing the supporting dimensions, the Q different shipping/
A vibrator support base from which a wave receiver can be obtained is provided.

Hiroshi Shimizu of Tohoku University and others presented ``Piezoelectric bending oscillator using interdigitated electrodes'' (paper number 1-7-11) at the Autumn Conference of the Acoustical Society of Japan held in October 1982.
Cross electrodes parallel to the length direction are formed on at least one surface of a rectangular piezoelectric body, the piezoelectric body is polarized using the cross electrodes, and the bending vibration in the length direction is generated using the same electrodes. Tsutsumi's idea was to enable efficient excitation.
Since this bending vibrator is composed of a single piezoelectric material, it does not require adhesive as required in a bimorph vibrator.
Therefore, variations in characteristics are reduced and costs are reduced.

The present invention relates to a support for a rectangular bending vibrator obtained in this way, and examples thereof will be described with reference to the drawings.

The vibrator used in this invention has interdigitated electrodes parallel to the length direction formed on at least one surface of a single rectangular piezoelectric material such as ceramic, and the piezoelectric material is polarized by these electrodes to achieve the same result. Efficient bending vibration can be caused in the length direction using electrodes. As shown in the embodiment of FIG. 3, this type of support for a piezoelectric vibrator vibrates two bridge-shaped support parts 8 each having a recess 7 at the top having an opening width equal to the width of a rectangular piezoelectric vibrator. The internodal spacing is equal to that of the child 1, and the lower part 9 is integrally formed of a soft elastic material such as silicone rubber. A fourth
As shown in the figure, a rectangular vibrator 1 that performs bending vibration as shown by dotted lines in the longitudinal direction is placed at the vibration node position, and a conical resonator 6 for ultrasonic radiation is bonded to the center.
Therefore, in the support stand of the present invention, since the support part 8 and the bottom part 9 are integrally formed, the positioning of the vibrator 1 is easy, and the entire stand is made of a soft elastic material such as silicone rubber. Therefore, by reducing the thickness of the upper part of the support part 8, the vibration characteristics are less affected by the support, and a transmitter/receiver with less deviation can be obtained.

In another embodiment of the present invention, the thickness of the upper part of the support part 8 of the support base is increased to reduce the Q
By reducing , an aerial ultrasonic transmitter/receiver with excellent pulse characteristics can be obtained. Note that the value of Q of the transmitter/receiver can be easily controlled not only by changing the thickness of the support portion 8 but also by changing the hardness of the forest material of the soft elastic body.

As mentioned above, the support base of the present invention
rectangular vibrator 1 without joining it to the support base.
There is an advantage that not only can the support part 8 be stably supported, but also transmitters and receivers with different Q values can be obtained by changing the dimensions of the support part 8 and the hardness of the forest material of the soft elastic body.

[Brief explanation of the drawing]

Fig. 1 is a plan view and a side vertical sectional view of an example of a conventional aerial ultrasonic transmitter/receiver, Fig. 2 is a plan view and a side longitudinal sectional view of another conventional example, and Fig. 3 is a plan view and a side longitudinal sectional view of an example of a conventional aerial ultrasonic transmitter/receiver. FIG. 4 is a perspective view of an embodiment of the support base, FIG. 4 is a perspective view of an aerial ultrasonic transmitter/receiver in which a transducer is mounted on the support base of FIG. 3, and FIG. 5 is another implementation of the support base of the present invention A perspective view of an example, FIG. 6 is a perspective view of an aerial ultrasonic transmitter/transducer in which a vibrator is mounted on the support base of FIG. 4. The symbols in the drawings are 1... vibrator, 6... resonator, 7... recess, 8... support part, 9... bottom part.

Claims (1)

[Scope of utility model registration request] The lower surfaces of two bridge-like supports are provided with a concave portion having an opening width equal to the width of a rectangular piezoelectric vibrator with a vibration form bent in the length direction, and the vibration nodes of the piezoelectric vibrator are approximately equal to each other. A rectangular plate-shaped bending piezoelectric vibrator support stand formed integrally with a soft elastic body connected to the bottom part at intervals.