JPH04112598U - Airborne ultrasonic transducer - Google Patents

Abstract

(57) [Summary] [Purpose] To provide an airborne ultrasonic transducer that does not cause deterioration of reverberation characteristics and does not malfunction even at low temperatures. [Structure] In this aerial ultrasonic transducer, a sound absorbing material 20 is pasted and fixed to the inner surface of a metal case 4 or a resin case 7 in which a piezoelectric sounding body 1 is housed.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention is applicable to airborne ultrasound, which is widely used in the frequency range of 20KHz to 50KHz. Techniques for improving the reverberation characteristics of wave transmitters and receivers, especially at low temperatures. Regarding the technique.

0002

[Conventional technology]

Traditionally, they have been placed near automatic doors and used for purposes such as detecting human bodies. As an example of an aerial ultrasonic transducer, one having the structure shown in Figure 5 is known. ing. In other words, this aerial ultrasonic transducer is called an integrated horn type. A bimorph vibrator 1, which is a piezoelectric sounding body, and a protrusion 2 for placing the vibrator are formed. In addition to comprising a terminal plate 3 made of resin and a metal case 4 containing these, A horn 6 is formed facing the sound collection hole 5 of the metal case 4, and a metal The structure includes a resin case 7 surrounding the outer periphery of the case 4.

0003 Note that the reference numeral 8 in the figure is an elastic adhesive for fixing the bimorph vibrator 1 to the protrusion 2; 9 is a funnel-shaped resonator fixed at the center position on the surface side of the bimorph resonator 1; 10 is a funnel-shaped resonator; 11 is a terminal pin that penetrates the terminal plate 3 and is pulled out to the outside, and 11 is a bimorph vibration Lead wire connecting the electrode (not shown) formed on the child 1 and the terminal pin 10 It is.

0004

[Problem that the idea aims to solve]

By the way, when using the airborne ultrasonic transducer with the conventional configuration, this If the environmental temperature in the area where the device is located is low, a human body may be detected even when no one is present. This airborne ultrasonic transducer seems to have detected a human body, even though it should not have been possible. Malfunctions such as this could occur. And such malfunctions occur due to low temperature. As a result, a standing wave is generated within the metal case 4, which results in ultrasonic interference. As a result, it is thought that this is caused by the deterioration of the reverberation characteristics of the airborne ultrasonic transducer. It will be done.

[0005] The present invention was devised in view of these inconveniences, and it To provide an airborne ultrasonic transducer with a configuration that does not cause deterioration of reverberation characteristics even when The purpose is

[0006]

[Means to solve the problem]

In order to achieve this purpose, the present invention has developed a metal case with a built-in piezoelectric sounding element. A sound absorbing material is pasted and fixed to the inner surface of the case or resin case. It is something.

[0007]

[Effect]

According to the above configuration, even if the environmental temperature around the aerial ultrasonic transducer becomes low, , due to the sound-absorbing material installed inside the metal case or resin case, The generation of waves will be suppressed.

[0008]

【Example】

Hereinafter, embodiments of the present invention will be described based on the drawings.

[0009] Figure 1 is a cross-sectional view showing the schematic structure of the aerial ultrasonic transducer according to this embodiment, and Figure 2 is FIG. 3 is an explanatory diagram showing the temperature characteristics of transmission and reception sensitivity in this aerial ultrasonic transducer. is an explanatory diagram showing the temperature characteristics of reverberation time. Furthermore, the basis of this aerial ultrasonic transducer is Since this configuration is not different from the conventional example, FIG. 1 is the same as or equivalent to FIG. 5. The same parts and parts are given the same reference numerals.

0010 This aerial ultrasonic transducer has a structure called an integrated horn type, A bimorph vibrator 1 as a piezoelectric sounding body and a protrusion 2 for placing the vibrator are formed. In addition to being equipped with a terminal plate 3 made of resin and a metal case 4 containing these, this A horn 6 is formed facing the sound collection hole 5 of the metal case 4 and is formed on the outside of the metal case 4. A resin case 7 surrounding the sides is provided. And inside this metal case 4 A sound absorbing material 20 of a predetermined thickness made of felt, cloth, sponge, etc. is attached to the surface with adhesive ( (not shown). In addition, in the figure 8 is an elastic adhesive, 9 is a funnel-shaped resonator, 10 is a terminal pin, and 11 is the lead wire.

By the way, the inventors of the present invention have developed an airborne ultrasonic transducer (hereinafter referred to as an example product) in which a sound absorbing material 20 is provided in a metal case 4 and an airborne ultrasonic transducer in which a sound absorbing material 20 is provided in a metal case 4 . According to experiments conducted using a conventional aerial ultrasonic transducer (conventional example product) that has not been developed, the experimental results shown in the explanatory diagrams of FIGS. 2 and 3 were obtained. . The operating frequency of both of these aerial ultrasonic transducers is set to 40 KHz, and the vertical axis in Figure 2 is the transmitting and receiving sensitivity (mV _{O P} ), and the vertical axis in Figure 3 is the transmitting and receiving sensitivity of 9 mV. The reverberation time (ms) in the case of _O/P is shown, and the horizontal axes of FIGS. 2 and 3 both show the temperature (° C.). In addition, the example product 1 in these figures is the one in which the inner diameter of the proximal opening 6a of the horn 6 shown in FIG. The diameter d is set to 8.0 mm.

According to FIG. 2, the transmitting and receiving sensitivity of the conventional example product in the temperature range of -20° C. to +60° C. varies greatly from 45 mV _{O · P} to 60 mV _{O · P} , whereas the example product 1, It can be seen that the changes in transmitting and receiving sensitivity for both cases are good, ranging from 38 mV _O·P to 50 mV _O·P . Furthermore, according to FIG. 3, the reverberation time of the conventional example product is particularly large at 2.0 ms at around 0°C, while the reverberation time of Example products 1 and 2 at around the same temperature is 1.0 ms. It is clear that it is very small. Note that the reverberation time of the conventional example product at around 25°C is 1.1 ms, and that of the example products 1 and 2 is 1.0 ms, so the example products 1 and 2 can be used throughout the generally required temperature range. This means that it has good reverberation characteristics throughout. By the way, in this experiment, no difference in characteristics between Example products 1 and 2, which is considered to be based on the difference in the incident diameter d, was found.

[0013] Note that this invention is applicable only to the aerial ultrasonic transducer with the above structure. For example, a horn 6 and a resin case configured as shown in FIG. The present invention is also applicable to an airborne ultrasonic transducer having a structure that does not include the base 7. In addition, the aerial ultrasonic transducer shown in Fig. 1 is not equipped with a metal case 4 and is made of sound absorbing material. It goes without saying that 20 may be directly pasted and fixed on the inner surface of the resin case 7. not.

[0014]

[Effect of the idea]

As explained above, according to the aerial ultrasonic transducer according to the present invention, piezoelectric sound A sound-absorbing material is attached and fixed to the inner surface of the metal case or resin case that contains the body. Therefore, the generation of standing waves due to the lower temperature inside the metal case is suppressed. As a result, the reverberation characteristics will be greatly improved, and the air super The effect is that malfunctions of the acoustic wave transducer can be effectively prevented.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a schematic structure of an airborne ultrasonic transducer according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the temperature characteristics of transmission and reception sensitivity in an airborne ultrasonic transducer.

FIG. 3 is an explanatory diagram showing the temperature characteristics of reverberation time in an airborne ultrasonic transducer.

FIG. 4 is a sectional view showing a schematic structure of an aerial ultrasonic transducer according to another embodiment.

FIG. 5 is a sectional view showing a schematic structure of an airborne ultrasonic transducer according to a conventional example.

[Explanation of symbols]

1 Bimorph vibrator (piezoelectric sounding body) 4 Metal case 7 Resin case 20 Sound absorbing material

──────────────────────────────────────────────── ─── Continuation of front page (72) Creator Masaharu Oda 2-26-10 Tenjin, Nagaokakyo City, Kyoto Prefecture Stocks Inside the company Murata Manufacturing Co., Ltd.

Claims (1)

[Scope of utility model registration request] [Claim 1] A sound absorbing material (2) is attached to the inner surface of the metal case (4) or resin case (7) containing the piezoelectric sounding body (1).
An aerial ultrasonic transducer characterized in that 0) is pasted and fixed.