JP4415945B2 - Horn - Google Patents

Description

  The present invention relates to a horn that expands the transmission range of ultrasonic waves transmitted from an ultrasonic transducer.

  Conventionally, an in-vehicle obstacle that detects the movement of an object by detecting the frequency component that changes due to the Doppler effect by transmitting an ultrasonic wave to the space and receiving a reflected wave from the object existing in the space Ultrasonic sensors for detection are known, for example, as disclosed in Patent Document 1. As shown in FIG. 2, the ultrasonic transmitter used in this type of ultrasonic sensor includes an ultrasonic transducer 2 that transmits ultrasonic waves and receives reflected waves from obstacles, and an ultrasonic vibration. It comprises a horn 1 ′ that accommodates the child 2 and widens the transmission range of ultrasonic waves transmitted from the ultrasonic transducer 2.

  The ultrasonic transducer 2 is formed in a substantially cylindrical shape, and is provided with a wave transmitting portion 20 formed of a substantially disk-shaped piezoelectric element that transmits ultrasonic waves on one end face in the axial direction, and 2 on the other end face. Two leads 21 are provided. The ultrasonic vibrator 2 applies an alternating voltage between the leads 21 to vibrate the wave transmission unit 20 and transmits ultrasonic waves.

The horn 1 ′ is formed in a bottomed cylindrical shape with one open end, and accommodates the ultrasonic transducer 2 in a form in which the wave transmitting unit 20 is opposed to the bottom 11 at the other end. An approximately circular opening 10 ′ in plan view that penetrates in the axial direction of the bottom 11 is provided at the approximate center of the bottom 11. As shown in FIG. 2B, the opening 10 ′ is formed with a diameter smaller than the diameter of the wave transmitting part 20 of the ultrasonic transducer 2, and ultrasonic wave transmission is performed by utilizing diffraction of sound waves. The range is expanding.
JP 2001-238286 A

  Here, FIG. 2C shows the result of measuring the sound pressure level of the ultrasonic wave at a certain distance from the opening 10 ′ of the horn 1 ′ in the conventional example. In the drawing, the vertical axis represents the sound pressure level of the ultrasonic wave, and the horizontal axis represents the ultrasonic wave transmission angle when the normal direction of the opening 10 'is 0 degree. As can be seen from the drawing, the sound pressure level of the ultrasonic wave is lowered in front of the opening 10 '. Thus, in the above conventional example, the ultrasonic wave to be transmitted is not efficiently output in front of the opening 10 ′ of the horn 1 ′, and the directivity of the ultrasonic wave in front of the opening 10 ′ is deteriorated. there were.

  The present invention has been made in view of the above points, and an object thereof is to provide a horn that can efficiently transmit ultrasonic waves.

In order to achieve the above object, the invention according to claim 1 is a horn that expands a transmission range of ultrasonic waves transmitted from an ultrasonic transducer, and is at least one of ultrasonic transmission surfaces of the ultrasonic transducer. An opening that exposes the portion, the opening is formed so that the opening surface is narrow along the ultrasonic wave transmission direction, and the inner peripheral surface is inclined along the wave transmission direction, The peripheral surface is composed of a portion parallel to the transmission direction .

  According to the first aspect of the present invention, the ultrasonic transducer includes the opening that exposes at least part of the ultrasonic wave transmission surface of the ultrasonic transducer, and the opening has a narrow opening surface along the ultrasonic wave transmission direction. And at least a part of the inner peripheral surface is inclined along the transmission direction, so that ultrasonic waves transmitted from the transmission unit are collected and efficiently transmitted to the front of the opening. Therefore, the directivity of the ultrasonic wave in front of the opening can be increased.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, since the basic configuration in this embodiment is the same as that of the conventional example, common portions are denoted by the same reference numerals, description thereof is omitted, and only portions that are characteristic of this embodiment will be described in detail.

  In the present embodiment, as shown in FIG. 1A, the opening 10 has a substantially cylindrical shape with the cylindrical portion 10 a and the bottom 11 extending in the axial direction from the middle in the axial direction to the wave sending surface of the wave sending portion 20. And it is formed in the form which combined the truncated cone shape part 10b of the substantially truncated cone shape whose inner peripheral surface inclines. That is, the opening surface is formed so as to narrow from the transmission surface of the transmission unit 20 along the transmission direction of the ultrasonic waves, and the inner peripheral surface of the opening unit 10 extends from the periphery of the opening surface on the transmission unit 20 side to the other side. It inclines toward the periphery of the opening surface. Here, similarly to the conventional example, the result of measuring the sound pressure level of the ultrasonic wave at a certain distance from the opening 10 of the horn 1 is shown in FIG. In the figure, the vertical axis represents the ultrasonic sound pressure level, and the horizontal axis represents the ultrasonic wave transmission angle when the normal direction of the opening 10 is 0 degree. As can be seen from the figure, the sound pressure level of the ultrasonic wave in front of the opening 10 does not drop compared to the result of the conventional example (see FIG. 2C).

  The above results were obtained because the exposed area of the transmission surface of the transmission unit 20 was increased, the opening surface was narrowed along the ultrasonic transmission direction, and the inner peripheral surface was in the transmission direction. It is presumed that the ultrasonic waves can be collected by inclining along, and therefore, the waves can be efficiently transmitted in front of the opening 10.

  Further, by widening the opening surface on the side of the transmission unit 20, the contact area between the transmission unit 20 and the horn 1 is reduced, and therefore, interference that occurs in a slight gap between the transmission unit 20 and the horn 1 is reduced. It is speculated that you can.

It is a figure which shows the horn of embodiment of this invention, (a) is sectional drawing, (b) is the figure seen from the front of an opening part, (c) is a graph showing the directional characteristic of an ultrasonic wave. It is a figure which shows the conventional horn, (a) is sectional drawing, (b) is the figure seen from the front of an opening part, (c) is a graph showing the directional characteristic of an ultrasonic wave.

Explanation of symbols

1 Horn 10 Opening

Claims (1)

A horn that widens the transmission range of ultrasonic waves transmitted from an ultrasonic transducer, and includes an opening that exposes at least a part of an ultrasonic wave transmission surface of the ultrasonic transducer, The opening surface is narrowed along the direction of sound wave transmission, and the inner peripheral surface is formed of a portion inclined along the transmission direction, and the inner peripheral surface is formed of a portion parallel to the transmission direction. Horn characterized by.

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