JPH055756Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an ultrasonic ceramic sensor used particularly for detecting objects located at a short distance.

When detecting a nearby object by having a single ultrasonic sensor perform a transmitting action of emitting ultrasonic waves and a receiving action of receiving ultrasonic waves reflected from a nearby object, the ultrasonic sensor remains active even after emitting ultrasonic waves. If any vibration remains in the vibration case, this will prolong the reverberation (falling) time and will be superimposed on the ultrasound waves reflected from nearby objects and returned, making it impossible to detect the ultrasound waves that are being received.

Therefore, it is important to attenuate the vibration of the vibration case immediately after the ultrasonic wave is radiated.

The present applicant constructed the vibration case from a foamed plastic material with a low Q value instead of the conventional metal, and utilized its acoustic damping effect to reduce the reverberation (falling) time to 1.2 ms. We developed an ultrasonic ceramic sensor that could be shortened to
As a result of further experiments, it was discovered that the vibrations on the sides of the vibration case were not sufficiently damped and a small amount of vibration remained, making it impossible to further shorten the reverberation (falling) time. The reverberation time can be further shortened by removing reverberant vibrations, and the drawings will be explained below.

In Figures 1 and 2, 1 is a vibration case formed into a concave shape from a foamable plastic material, such as an epoxy resin in which glass microballoons of 50 to 100 microns are dispersed and mixed. Used as a transmitter and receiver. Reference numeral 2 denotes a plate-shaped piezoelectric element that is integrally attached to the inner surface of the closed end portion 1a of the vibration case 1, and has electrodes 2a and 2b on both sides. Reference numeral 3 denotes a cover plate fitted to seal the open end 1b of the vibration case, and 4a and 4b refer to the cover plate 3.
A pair of terminal pins are implanted so as to protrude upward and downward, respectively, and the thin metal wires 5a,
5b electrically conducts with each electrode 2a, 2b of the piezoelectric element. Reference numeral 6 denotes a sealing agent filled in a space formed between the outer surface of the cover plate 3 and the open end portion 1b of the case.Up to this point, the structure is the same as that of the ultrasonic microphone according to the prior art described above.

However, the structural feature of the present invention is that elastic rings 7, 7' are crimped onto either or both of the inner and outer surfaces of the side portion 1c of the vibration case 1.

Note that when the crimp ring 7 is fitted onto the outer surface of the side portion 1c of the vibration case as shown in FIG.
Using an elastic rubber tube (see Figure 3A) as
In addition, when the crimp ring 7' is fitted inside the inner surface of the side part 1c of the case as shown in Fig. 2, it is preferable to use an elastic metal cylinder with a slit 7'a (see B in the same figure) as the crimp ring 7'. .

Next, FIG. 4 shows the transmission pulse characteristics (a) of the ultrasonic ceramic sensor according to the prior art and the transmission pulse characteristics (b) of the ultrasonic ceramic sensor of the present invention shown in FIG. The figure shows that the reverberation (falling) time of the proposed ultrasonic sensor is as short as 1 mS or less, and that the elastic ring crimped to the side of the vibration case suppresses reverberant vibration on the side. Ru.

As described above, the closed end of the vibration case, which is formed into a concave shape from a foamed plastic material, is used as a sound wave transmitting and receiving part, and a piezoelectric element is attached to the inner surface of the vibration case, and a lid is embedded with a terminal pin that is electrically connected to the piezoelectric element. In a case in which a plate is sealed to the open end of the case, the present invention reduces the reverberation time by simply crimping an elastic ring to one or both of the inner and outer surfaces of the side part of the vibration case. Since it can be significantly shortened, it can be used in proximity switch sensors to great effect.

[Brief explanation of the drawing]

1 and 2 each show an ultrasonic ceramic sensor phon according to the present invention, each A is a partially cutaway plan view, and each B is a longitudinal sectional front view. 3A and 3B are perspective views of the crimp ring used in the embodiment of FIGS. 1 and 2. FIG. FIG. 4 shows a transmission pulse characteristic diagram A of the ultrasonic ceramic sensor according to the prior art and a transmission pulse characteristic diagram B of the ultrasonic sensor according to the present invention. Note that the same numbers in the figures indicate the same parts. 1... Vibration case, 1a... Closed end, 1b...
Open end, 1c... side part, 2... piezoelectric element, 3...
Cover plate, 4a, 4b... terminal pin, 7, 7'... crimp ring.

Claims (1)

[Scope of utility model registration request] The closed end of the vibration case, which is formed into a concave shape from a foamed plastic material, is used as a sound wave transmitting and receiving section, and a piezoelectric element is attached to the inner surface of the closed end, and a lid plate is installed with a terminal pin that is electrically conductive to the piezoelectric element. 1. An ultrasonic ceramic sensor sealed to an open end of a case, characterized in that an elastic ring is crimped to one or both of the inner and outer surfaces of the side part of the vibrating case.