WO2015145659A1 - Electronic alarm - Google Patents

Abstract

[Problem] To provide a compact, lightweight, low-cost and long-standing electronic alarm capable of making a sound similar to that of a conventional flat electromagnetic horn. [Solution] An electronic alarm makes a warning sound by vibrating a diaphragm (4) with a piezoelectric body (6), the electric alarm comprising: a modulated wave generation circuit (84) for generating a modulated rectangular wave for a fundamental frequency of the warning sound; a fundamental rectangular wave generation circuit (85) for generating a fundamental rectangular wave for a harmonic frequency of the fundamental frequency; a frequency modulation and deviation circuit (83) for modulating the fundamental rectangular wave with the modulated rectangular wave and setting the frequency deviation during modulation within a prescribed range with respect to the frequency of the fundamental rectangular wave; and a drive circuit (81) for driving the piezoelectric body (6) with a modulated wave that has been modulated.

Description

Electronic horn

The present invention relates to an electronic audible alarm used for a vehicle or the like.

A so-called electromagnetic flat horn is often used as a sound alarm used for vehicles. An example is shown in FIG. In FIG. 6, the sound alarm has an open container-like circular housing 91, and a fixed iron core 92 is provided at the center of the housing 91. A movable iron core 93 is provided so as to face the fixed iron core 92. The movable iron core 93 is fixed to the center of the back surface of the metal diaphragm plate 94 that is stretched so as to close the opening of the housing 91, and is opposed to the fixed iron core 92 at a certain interval by the spring force of the diaphragm plate 94. Is located. A resonance plate 95 is provided in front of the diaphragm plate 94 (upward in FIG. 6), and its center is fixed to the center of the surface of the diaphragm plate 94.

An electromagnetic coil 96 is disposed in a housing 91 portion surrounding the fixed iron core 92. One end of the electromagnetic coil 96 is electrically connected to a power supply terminal 98 provided in the housing 91 via a contact 97. The other end of the electromagnetic coil 96 is electrically connected to an earth terminal 99 provided on the housing 91. The contact 97 is composed of a fixed contact 971 and a movable contact 972. The fixed contact 971 is conductively fixed to the power supply terminal 98, and the movable contact 972 is provided on the spring plate 973 and is conductively connected to the fixed contact 971. ing. The tip of the spring plate 973 is in contact with the stepped surface of the movable iron core 93.

When the alarm is energized, current flows from the power supply terminal 98 to the fixed contact 971, the movable contact 972, the electromagnetic coil 96, and the earth terminal 99, and the movable iron core 93 magnetized by the electromagnetic coil 96 as shown in FIG. It is attracted to the fixed iron core 92 and collides with it, and the impact at the time of collision is transmitted to the resonance plate 95 and sounded. When the movable iron core 93 moves toward the fixed iron core 92, the spring plate 973 is deformed, the movable contact 972 is separated from the fixed contact 971, and the current is interrupted. Thereby, the movable iron core 93 is returned to the original position shown in FIG. 6 by the spring force of the diaphragm plate 94 and is separated from the fixed iron core 92.

Therefore, the electromagnetic coil 96 is energized again, and the movable iron core 93 is attracted to the fixed iron core 92 again. By repeating this operation, an alarm sound having a desired tone color (frequency band) is generated. An example of such an electromagnetic flat horn is disclosed in Patent Document 1.

JP 2013-25078 A

However, the electromagnetic flat horn has a problem of life due to wear and the like because there are many mechanical working parts, and there is a problem that the whole is enlarged due to the installation of the electromagnetic coil and the iron core. Therefore, an electronic horn (sounder) using a piezoelectric element as a vibrating body has been proposed (for example, Japanese Patent Application Laid-Open No. 59-79294). Because it is difficult to realize the electronic horn, the electronic horn has not been generally adopted particularly for the vehicle horn.

Therefore, the present invention solves such a problem, and can provide a timbre similar to that of a conventional electromagnetic flat-type horn, and is a small, lightweight, low cost and long-life electronic horn. The purpose is to do.

[Correction based on Rule 91 03.04.2014]
In order to achieve the above object, according to the first aspect of the present invention, in the electronic sounding device that vibrates the diaphragm (4) by the piezoelectric body (6) and outputs an alarm sound, the fundamental frequency of the alarm sound is modulated. Means (84) for generating a rectangular wave, means (85) for generating a fundamental rectangular wave having a harmonic frequency of the fundamental frequency, means (83) for modulating the fundamental rectangular wave with the modulating rectangular wave, A means (83) for setting a frequency shift at the time of modulation within a predetermined range with respect to the frequency of the basic rectangular wave, and a means (81) for driving the piezoelectric body (6) with the modulated wave modulated by each means. ).

In the first aspect of the invention, when the fundamental frequency is set to be the same as or close to the fundamental frequency of the alarm sound of the conventional electromagnetic flat horn, the alarm sound of the electronic sound alarm is the same as that of the electromagnetic flat horn. A tone is obtained. In addition, the electronic horn according to the first aspect of the present invention is small, light and low in cost.

In the second invention, the resonance frequency of the diaphragm is set as the frequency of the basic rectangular wave.

According to the second aspect of the invention, sufficient sound pressure can be applied to the alarm sound of the electronic sound alarm.

In the third invention, the frequency of the basic rectangular wave is set to 4 to 10 times the frequency of the modulated rectangular wave.

In the fourth invention, the frequency of the basic rectangular wave is set between 1800 and 3550 Hz, preferably between 2200 and 3150 Hz, and the frequency of the modulated rectangular wave is set between 290 and 580 Hz, preferably between 310 and 440 Hz, The frequency deviation is set between −11 and −25 dB, preferably −15 to −21 dB with respect to the frequency of the fundamental rectangular wave.

The symbols in the parentheses indicate the correspondence with specific means described in the embodiments described later.

As described above, according to the electronic audible alarm of the present invention, a tone similar to that of a conventional electromagnetic flat horn can be realized, and it is small, light, and low in cost.

It is a whole sectional view of an electronic horn. It is a block diagram which shows the structure of a warning sound circuit. It is a figure which shows an example of the frequency spectrum of the alarm sound of the conventional electromagnetic flat type horn. It is a wave form diagram which shows an example of the drive voltage signal applied to a piezoelectric material. It is a figure which shows an example of the frequency spectrum of the warning sound of an electronic horn. It is a whole sectional view of the conventional electromagnetic flat type horn. It is a whole sectional view at the time of operation of the conventional electromagnetic flat type horn.

FIG. 1 shows an overall cross-sectional view of the electronic sounding device of the present invention. The electronic sound alarm includes a metal plate housing 1 having a circular open container shape, and a mounting stay 11 is bolted to the center of the bottom wall of the housing 1. An open container-like resin holder 2 is inserted in the housing 1 along this, and a circuit board 3 is disposed on the bottom wall of the holder 2 in parallel therewith. The circuit board 3 is fitted and supported by a pin portion 21 erected on the bottom wall of the holder 2, and a warning circuit described later is provided on the circuit board 3. Note that the circuit components and the like of the alarm circuit are not shown.

A metal diaphragm plate 4 as a diaphragm is stretched in parallel with the circuit board 3 with the opening of the holder 2 closed, and the outer peripheral edge of the diaphragm plate 4 is the opening edge of the holder 2 and the opening of the holder 2. Between the outer periphery of the resin resonator 5 covered with the The resonator 5 is provided with sound output ports 51 at a plurality of locations on the outer peripheral portion (in this embodiment, four locations at regular intervals in the circumferential direction). A circular piezoelectric body 6 is joined to the diaphragm plate 4 at the center of the back surface (the lower surface in FIG. 1). Output lines 31 and 32 extend from the circuit board 3 to one electrode (not shown) of the piezoelectric body 6 and to the diaphragm plate 6 leading to the other electrode (not shown) of the piezoelectric body 6. In addition, one end of a power supply connector 33 extending to the outside of the housing 1 is connected to one end of the circuit board 3. The outer side of the resonator 5 is covered with a metal cover body 7 in which a long hole-like sound emission port 71 is formed.

FIG. 2 shows the configuration of the alarm circuit 8 provided on the circuit board 3. Both electrodes of the piezoelectric body 6 are connected to a drive circuit 81, and a drive voltage is supplied to the drive circuit 81 from a voltage generation circuit 82. A frequency modulation / shift circuit 83 is connected to the drive circuit 81, and a modulation rectangular wave generation circuit 84 and a basic rectangular wave generation circuit 85 are connected to the frequency modulation / shift circuit 83. The basic rectangular wave generated by the basic rectangular wave generating circuit 85 is frequency-modulated at a predetermined frequency deviation by a frequency modulating / shifting circuit 83 by a modulating rectangular wave output from the modulating wave rectangular wave generating circuit 84 as described later. Then, a drive voltage signal corresponding to the modulated wave is applied to the piezoelectric body 6 via the drive circuit 81, and the piezoelectric body 6 is vibrated. The frequency modulation / shift circuit 83, the modulation rectangular wave generation circuit 84, and the basic rectangular wave generation circuit 85 may be realized by software instead of hardware.

Here, an example of the frequency spectrum of the alarm sound of the conventional electromagnetic flat horn is shown in FIG. In the example shown in FIG. 3, the fundamental frequency of the alarm sound is 350 Hz, and there are a plurality of harmonics a to k having a frequency that is an integral multiple of the fundamental frequency. Then, the resonance plate resonated at the 8th harmonic g (2800 Hz) of the fundamental frequency, and the sound pressure became the highest, and the sound pressure was in the range of 105 to 118 dB.

Therefore, the frequency of the fundamental rectangular wave to be modulated was set to 2800 Hz, the frequency of the modulating rectangular wave was set to 350 Hz, and the frequency shift was set to 440 Hz (absolute value). When this frequency shift is expressed in dB, 20 log (frequency shift / basic rectangular wave frequency) = 20 log (440/2800) = − 16 dB. The reason why the frequency shift is set to -16 dB is that the tone color of the alarm sound can be improved as will be described later.

FIG. 4 shows the waveform of the drive voltage signal when the frequency of the basic rectangular wave is set to 2800 Hz, the frequency of the modulated rectangular wave is set to 350 Hz, and the frequency shift is set to 440 Hz (absolute value) as described above. The waveform is a square wave that changes positively and negatively. The 2360 Hz region X and the 3240 Hz region Y, which are up and down by 440 Hz around this, are alternately repeated every 2.9 ms (= 1/350 (Hz)). Become.

FIG. 5 shows a frequency spectrum of an alarm sound generated by the diaphragm plate 4 oscillated by the piezoelectric body 6 to which such a drive voltage is applied. An alarm sound output from the conventional electromagnetic flat horn shown as an example, with the sound pressure of the 8th harmonic g of the fundamental frequency having the fundamental frequency of 350 Hz, a plurality of its harmonics, and 2800 Hz being the highest. Is similar to the frequency spectrum of.

As for the sound pressure, for example, the diaphragm plate 4 is composed of a SUS plate having a plate thickness of 0.3 mm and φ64, and a piezoelectric member 6 having a plate thickness of 0.3 mm and φ40 is used as the vibration plate. If the drive voltage that changes positively and negatively at an absolute value of 62.5 V is applied, a sufficient sound pressure of about 110 dB can be obtained when the drive frequency is close to the resonance frequency of the diaphragm plate 4. The resonance frequency of the diaphragm plate 4 can be changed by changing the plate thickness and outer diameter.

Here, according to a sensory test with five subjects, as shown in Table 1, when the frequency of the fundamental rectangular wave is set in the range of 1800 to 3550 Hz (the range with a single circle in Table 1), the electromagnetic flat type A timbre close to the timbre of the alarm sound output from the horn is obtained, and the range of 2000 to 3350 Hz is particularly preferable (the range indicated by the double circle in Table 1). At 1600 Hz, it may deviate from the tone color of the electromagnetic flat horn, and at 1400 Hz or less, sufficient sound pressure cannot be obtained. At 3750 Hz, the sound is slightly higher than that of the electromagnetic flat horn, and above 3950 Hz, the sound is high.

As shown in Table 2, the frequency of the modulated rectangular wave is close to the timbre of the alarm sound output from the electromagnetic flat horn when set in the range of 290 to 580 Hz (the range with a single circle in Table 2). A tone color is obtained, and a range of 310 to 440 Hz is particularly preferable (a range indicated by a double circle in Table 2). At 270 Hz, a slight beat may be felt, and at 250 Hz or less, a beat can be felt. At 600 Hz, the sound is somewhat monotonous with respect to the electromagnetic flat horn, and at 620 Hz or more, it is completely monotonous.

As shown in Table 3, when the frequency deviation is set within the range of -11 to -25 dB, a tone similar to the tone of the alarm tone output from the electromagnetic flat horn can be obtained (see the single circle in Table 3). The range of −15 to −21 dB is particularly preferable (the range with a double circle in Table 3). At -7 dB, the sound is slightly broken, and at -3 dB or less, the sound is broken. At -29 dB, the sound is somewhat monotonous with respect to the electromagnetic flat horn, and at -33 dB or more, it is close to a single sound.

DESCRIPTION OF SYMBOLS 1 ... Housing, 2 ... Holder, 3 ... Circuit board, 4 ... Diaphragm board (diaphragm), 6 ... Piezoelectric body, 8 ... Warning sound circuit, 81 ... Drive circuit, 83 ... Frequency modulation / shift circuit, 84 ... Modulation Wave generation circuit, 85... Basic rectangular wave generation circuit.

Claims (4)

In an electronic horn that oscillates a diaphragm with a piezoelectric body and outputs an alarm sound, means for generating a modulated rectangular wave of the fundamental frequency of the alarm sound, and a harmonic frequency of the fundamental frequency of the alarm sound Means for generating a fundamental rectangular wave; means for modulating the fundamental rectangular wave with the modulation rectangular wave; means for setting a frequency shift during modulation within a predetermined range with respect to the frequency of the fundamental rectangular wave; Means for driving the piezoelectric body with the modulated wave modulated by each means. The electronic horn according to claim 1, wherein a resonance frequency of the diaphragm is set as the frequency of the basic rectangular wave. The electronic horn according to claim 1 or 2, wherein the frequency of the basic rectangular wave is set to 4 to 10 times the frequency of the modulated rectangular wave. The frequency of the fundamental rectangular wave is set between 1800 and 3550 Hz, preferably between 2000 and 3150 Hz, the frequency of the modulated rectangular wave is set between 290 and 580 Hz, preferably between 310 and 440 Hz, and the frequency shift is set 4. The electronic sounding device according to claim 1, wherein the electronic sounding device is set within a range of −11 to −25 dB, preferably −15 to −21 dB with respect to the frequency of the fundamental rectangular wave.

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