JP2013187814A - Ultrasonic wave transmitting and receiving apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which ones having wide variations in sensitivity property and low sensitivity property are frequently found in ultrasonic wave transmitting and receiving apparatuses in which an unimorph oscillator is constituted by sticking a piezoelectric element to a bottom center of a bottomed cylindrical case.SOLUTION: It is found that a hole diameter of a sound absorption material significantly contributes to a factor determining a sensitivity property. An ultrasonic transmitting and receiving apparatus having a stable sensitivity property is provided in which a diameter of a hole of the sound absorption material is larger than a maximum diameter of a lead wire so that a gap between the periphery of the lead wire and an inner edge of a through hole is filled with a sound absorption material hole filling silicone, and is less than a maximum diameter in a horizontal direction of solder of a piezoelectric element so that a sealing silicone filled in a bottomed cylindrical case is prevented from contacting the piezoelectric element.

Description

  The present invention relates to an ultrasonic transducer that transmits and receives an ultrasonic frequency band.

In the ultrasonic transducer according to the conventional embodiment, when an ultrasonic transducer is embedded in a vehicle bumper or the like and an obstacle around the vehicle is to be detected, pulse burst electrical is applied to the ultrasonic transducer. By inputting a signal, an ultrasonic signal corresponding to the input pulse burst electric signal is transmitted from the ultrasonic transducer, the transmitted ultrasonic signal reaches the obstacle, and the ultrasonic signal that hits the obstacle Is reflected by the obstacle, and a part of the reflected ultrasonic signal returns to the same ultrasonic transducer. The ultrasonic transducer detects an obstacle by receiving the reflected signal.

  FIG. 3 is a schematic longitudinal sectional view of an ultrasonic transducer according to a conventional embodiment. In FIG. 3, the piezoelectric element 1 is bonded inside the bottom surface of the bottomed cylindrical case 2 made of an aluminum material or the like to constitute a unimorph vibrator. The input / output lead wire 5a is taken out from the surface opposite to the bonding surface side of the piezoelectric element 1 with the bottomed cylindrical case 2, and the input / output lead wire 5b is taken out from the bottomed cylindrical case 2 by soldering or the like. Here, a solder fillet portion that can be soldered to the input / output lead wire 5 a is referred to as element solder 7. The bonding surface side of the piezoelectric element 1 with the bottomed cylindrical case 2 and the bottomed cylindrical case 2 are electrically connected. Furthermore, the piezoelectric element 1, the input / output lead wire 5 a, and the bottomed cylindrical case 2 and the input / output lead 5b are electrically connected. As shown in FIG. 4, a sound absorbing material 3 made of silicon foam or the like in which holes for passing the input / output lead wires 5 b are formed is placed on the upper surface of the piezoelectric element 1, and the holes of the sound absorbing material 3 are filled. The sound absorbing material hole-filled silicone 6 is filled. Further, the bottomed cylindrical case 2 is filled with a sealing silicone 4 made of a silicon material, a urethane material, or the like.

However, the ultrasonic transducer having such a structure has a large variation in sensitivity characteristics, and it has been a problem that some have low sensitivity characteristics. However, it is unclear what caused this.
The present invention relates to an ultrasonic transducer that performs transmission and reception of an ultrasonic frequency band.

JP-A-8-237796

Tanikoshi Shinji “Ultrasound and its usage-Ultrasonic transducer and ultrasonic motor” Nikkan Kogyo Shimbun 1994

Conventionally, it has been unclear what causes low sensitivity characteristics.

This time, it was found that the sensitivity characteristic depends on the hole diameter of the sound absorbing material. Further, as a result of the present invention, the diameter of the hole of the sound absorbing material is made larger than the maximum diameter of the lead wire so that the gap between the periphery of the lead wire and the inner edge of the through hole is filled with the sound absorbing material hole filled silicone, and the element solder By preventing the silicone material for sealing filled in the bottomed cylindrical case from being smaller than the maximum diameter in the horizontal direction from contacting the piezoelectric element, high sensitivity characteristics can be maintained.

According to the present invention, it is possible to provide an excellent product that does not generate low sensitivity characteristics and has little variation in sensitivity characteristics.

1 is a schematic longitudinal sectional view of an ultrasonic transducer according to an embodiment of the present invention. Schematic diagram of a sound absorbing material according to an embodiment of the present invention Schematic longitudinal sectional view of an ultrasonic transducer according to a conventional embodiment Schematic diagram of sound-absorbing material according to conventional embodiments Relationship between hole diameter of sound-absorbing material and sensitivity of ultrasonic transducer according to the embodiment of the present invention

FIG. 5 shows values of sensitivity characteristics when the diameter of the through hole of the sound absorbing material 3 is changed. In this experiment, a piezoelectric element 1 having a diameter of 5.3 mm is bonded to the bottom surface of a bottomed cylindrical case 2 made of an aluminum alloy having an outer diameter of 12 mm and a height of 8 mm. The input / output lead wire 5a soldered to the piezoelectric element 1 is perpendicular to the piezoelectric element 1, and the input / output lead wire 5a has a diameter of 0.25 mm. The size of the solder element 7 is produced under the condition that the diameter of the solder fillet is 1.5 mm, and the contact area with the piezoelectric element 1 is approximately 1.77 square mm. The sound absorbing material 3 used in the experiment had a thickness of 1.5 mm, and a through hole having a diameter of 0.25 mm to 2.5 mm. The table of FIG. 5 shows that when the diameter of the through hole of the sound-absorbing material 3 exceeds 2 mm, the sensitivity characteristic starts to rapidly decrease. The area when the diameter of the through hole is 2 mm is 3.14 square mm, which is 178% with respect to the contact area of the element solder 7 with the piezoelectric element 1. Here, when an ultrasonic transducer using a sound absorbing material 3 having a hole diameter of 2.1 mm or more was disassembled and the inside was observed, the piezoelectric element 1 and the sound absorbing material-filled silicone 6 were bonded. In the case of .8 mm to 2.0 mm or less, contact with the piezoelectric element 1 was recognized, but adhesion was not performed. Further, when the thickness was 1.8 mm or less, the element solder 7 on the piezoelectric element 1 was adhered, but the piezoelectric element 1 was not even contacted. That is, it has been found that the sensitivity characteristics are adversely affected by the sound absorbing material-filled silicone 6 being bonded to the piezoelectric element 1. Although it has been empirically known that the position and size of the element solder 7 have a great influence on the sensitivity characteristic, manual soldering has been the mainstream in the past, and there is a large variation in the position and size of the element solder. The through holes of the sound absorbing material 3 have been made with a size that emphasizes workability. For this reason, it is considered that the influence of the element solder 7 is large even if the sensitivity characteristic is lowered, and the size of the through hole of the sound absorbing material 3 has not been examined in detail. However, recently, by introducing an automatic machine for soldering, the position and size of the solder element 7 can be easily controlled and the variation is reduced. The effect on sex is considered to be small. From the above, the diameter of the through hole of the sound absorbing material 3 is made larger than the maximum diameter of the lead wire so that the gap between the periphery of the lead wire and the inner edge of the through hole is filled with the sound absorbing material hole filled silicone, and the element solder It is possible to maintain high sensitivity characteristics by preventing the sealing silicone material filled in the bottomed cylindrical case from having a diameter less than the horizontal maximum diameter in contact with the piezoelectric element. As long as the shape of the through hole is large enough to create a gap between the lead wire and the inner edge of the through hole, and the maximum inner edge diameter of the through hole is less than the horizontal diameter of the element solder, it is a triangle / quadrangle.・ It does not matter as polygonal shape such as pentagon

FIG. 1 is a schematic longitudinal sectional view of an ultrasonic transducer according to an embodiment of the present invention. In FIG. 1, a piezoelectric element 1 is bonded to the inside of the bottom surface of a bottomed cylindrical case 2 made of an aluminum material and having a cylinder diameter of Φ12 mm to Φ18 mm to constitute a unimorph vibrator. The input / output lead wire 5a is taken out from the surface opposite to the bonding surface side of the piezoelectric element 1 with the bottomed cylindrical case 2, and the input / output lead wire 5b is taken out from the bottomed cylindrical case 2 by soldering or the like. The bonding surface side of the piezoelectric element 1 with the bottomed cylindrical case 2 and the bottomed cylindrical case 2 are electrically connected. Furthermore, the piezoelectric element 1, the input / output lead wire 5 a, and the bottomed cylindrical case 2 and the input / output lead 5b are electrically connected. On the upper surface of the piezoelectric element 1, a sound absorbing material 3 made of silicon foam or the like and having a hole diameter of 2 mm or less and larger than the diameter of the input / output lead wire 5a as shown in FIG. After filling the sound absorbing material hole-filled silicone 6, a sealing silicone 4 made of a silicon material, a urethane material or the like is filled into the bottomed cylindrical case 2 from above.
Incidentally, as a molding method of the sound absorbing material 3, the dimensional tolerance of the hole of the sound absorbing material when it is punched out from a sheet-like silicon foam or the like with a mold is about ± 0.2 mm even when the dimensional aim is Φ2.0 mm. There is a variation that can easily occur, and when the input / output lead wires are passed through the conventional structure, workability is emphasized. When aiming for Φ2.0 mm, a sound absorbing material with a hole diameter larger than Φ2.0 mm is used. There is a possibility that the ultrasonic transducer was manufactured. Therefore, the aim of the size of the sound absorbing material 3 is Φ1.8 mm when the dimensional tolerance is ± 0.2 mm.

DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 Bottomed cylindrical case 3 Sound absorbing material 4 Silicone for sealing 5a Input / output lead wire 5b Input / output lead wire 6 Sound absorbing material filling silicone 7 Element solder

Claims (1)

A bottomed cylindrical case, a piezoelectric element bonded and fixed to the inner bottom surface of the bottomed cylindrical case, and a lead soldered to a surface opposite to the surface fixed to the bottomed cylindrical case of the piezoelectric element A sound absorbing material having a through hole through which the lead wire laid on the piezoelectric element passes, and a sound absorbing material filled silicone filled in the through hole of the sound absorbing material,
In the ultrasonic wave transmitter / receiver made of sealing silicone filled inside the bottomed cylindrical case, the diameter of the through hole of the sound absorbing material is in the gap between the periphery of the lead wire and the inner edge of the through hole. The maximum horizontal dimension of the solder soldered to the surface opposite to the surface fixed to the bottomed cylindrical case of the piezoelectric element is larger than the maximum diameter of the lead wire because the sound absorbing material-filled silicone is filled The ultrasonic transducer according to claim 1, wherein the sound absorbing material-filled silicone does not contact the piezoelectric element by being less than the diameter.

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