JPS622876Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to the structure of a piezoelectric alarm device that generates sound by bending and vibrating a piezoelectric vibrator, and its purpose is to efficiently obtain a large sound volume.

In order for a piezoelectric horn to be used as an automobile horn, it is necessary to create a tone that includes low-frequency components in terms of audibility. A method of generating sound by applying amplitude-modulated signals to a piezoelectric vibrator is considered, and the piezoelectric vibrator for this purpose has a structure in which a piezoelectric element is bonded to the outer bottom of a cylindrical diaphragm with one end open. is convenient. However, it is difficult to obtain a value of 105 dB at a position 2 m in front of the horn with the sound pressure generated from this piezoelectric vibrator alone.

Therefore, in this invention, the structure of the horn is devised so as to obtain a large sound volume while using the above-mentioned vibrator. This will be explained below using figures.

Reference numeral 1 denotes a piezoelectric vibrator, which is constructed by adhering, with an adhesive, a circular piezoelectric element 4 smaller than a metal plate 3 that is smaller than the bottom surface of the diaphragm 2 and has an irregular shape to the outer bottom 2a of a diaphragm 2 that has one open end. The sound pressure frequency characteristic of this piezoelectric vibrator exhibits a plateau while maintaining a high level of sound pressure.

Reference numeral 5 denotes a housing, which has a sound wave reflecting section 5a and a recessed section 5b that accommodates an electric circuit 6 that bends and vibrates the piezoelectric vibrator 1. Reference numeral 7 denotes a cap for sealing the recess 5b, and when the cap is attached, its upper surface is flush with the sound wave reflection part 5a of the housing, and the sound wave reflection part and the sound wave reflection part 8 are flush with each other.
Configure. The piezoelectric vibrator 1 is supported by an elastic support 9 such as a sponge at a suitable position in front of the sound wave reflector 8 with the opening of the diaphragm 2 facing forward. still,
As a supporting method, the flange portion 2c of the diaphragm may be elastically supported at several locations. 10 has 1 sound emitting port on the front
The open end of the cylindrical case 10 is connected to the outer edge of the sound wave reflector 8 so as to surround the cylindrical portion 2b of the diaphragm, and a sound path 11 is formed between the cylindrical diaphragm 2 and the cylindrical diaphragm 2. It is configured.

When an amplitude-modulated signal is applied to the piezoelectric horn having the above structure, the piezoelectric vibrator 1 makes a bending vibration forming a nodal circle near the outer diameter of the metal plate 3. If we observe the vibration state of each part at this time, there is a phase difference of about 180° between the center of the inner bottom of the diaphragm 2 and the outer circumference of the inner bottom.
The center part of the inner bottom and the outer periphery of the outer bottom of the diaphragm 2 radiate sound into the air in substantially the same phase. This invention has a structure in which the sound emitted from the outer periphery of the outer bottom of the diaphragm 2 is radiated to the front of the horn via the detailed sound path 11, thereby increasing the sound pressure in front of the horn. be able to.

To explain the embodiment using numerical examples, the outer diameter dimension
Cylindrical diaphragm with 90mmφ, cylindrical part height 10mm, outer diameter 36
When a modulated wave with a carrier frequency of 2200 Hz, a modulation frequency of 150 Hz, and a voltage of 120 VPP is applied to a piezoelectric vibrator (natural frequency of 2200 Hz) consisting of a mmφ piezoelectric element, etc., the sound pressure is 103 dB (2 m). . When this is configured as the above-mentioned alarm (distance between the sound wave reflector and the bottom of the diaphragm is 5 mm, the inner diameter of the cylindrical case is 95 mm)
mm, and the height of the cylindrical part (5 mm) is 2 m in front.
I was able to raise the sound pressure by 108dB and 5dB. In addition, the tone at this time is a sound that includes low frequency components that makes the difference tone (150Hz) created by the carrier frequency and both upper and lower band waves, that is, the modulation frequency, feel as if it were the fundamental frequency. can.

As described above, according to this invention, a large volume of sound can be obtained efficiently, so that the piezoelectric horn can also be provided as a car horn, for example.

[Brief explanation of the drawing]

The figure is a sectional view showing an embodiment of the piezoelectric alarm according to the present invention. 1...Piezoelectric vibrator, 2...Cylindrical diaphragm, 4...
...Piezoelectric element, 8...Sound wave reflector, 10...Cylindrical case, 10a...Sound emitting port, 11...Sound path.

Claims (1)

[Scope of utility model registration request] In a piezoelectric alarm device that generates sound by bending a piezoelectric vibrator, a piezoelectric element is bonded to the outer bottom of a cylindrical diaphragm with one end open to form a piezoelectric vibrator, and the piezoelectric vibrator is used as a sound wave reflector. The opening of the diaphragm is placed in front of the diaphragm with the opening facing forward, and a cylindrical case with a sound emitting port on the front is connected to the outer edge of the sound wave reflector so as to surround the cylindrical part of the diaphragm. A piezoelectric alarm device characterized by forming a sound path between the