JP6732370B2 - Vehicle approach alarm - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle approach notification device, and more particularly to a vehicle approach notification device that can generate a vehicle approach notification sound having a flat frequency characteristic using a piezoelectric element sounding body.

Although hybrid vehicles and electric vehicles have become popular due to environmental considerations, these vehicles have a problem that pedestrians cannot easily notice approaching due to their quietness at low speeds. Therefore, in the device described in Patent Document 1, the environmental sound around the vehicle and the traveling sound of the vehicle are acquired and frequency analysis is performed, and filter coefficients are set so that the target volume ratio between the environmental sound and the traveling sound becomes appropriate. A vehicle approaching alarm device has been proposed in which the amplification factor is adjusted so that the traveling sound can be maintained at an appropriate level relative to the environmental sound.

JP2012-166662A

By the way, there is an attempt to use a piezoelectric element as a sounding body in order to reduce the size and extend the life of the approaching vehicle alarm, but the piezoelectric element often has a resonance frequency at a predetermined frequency. This is preferable in that a large output sound can be obtained with a relatively small input when an alarm sound in a specific frequency range is emitted, but vehicle approach notification sounds such as motor quasi-noise are spread over a relatively wide frequency band. It is preferable that the flat sound pressure is output.

Therefore, the present invention solves such a problem, and provides a vehicle approaching notification device capable of obtaining a vehicle approaching notification sound having a flat frequency characteristic in a wide frequency band by using a piezoelectric element sounding body. The purpose is to

To achieve the above object, in the first aspect of the present invention, the piezoelectric element sounding body (3) having a frequency characteristic having a resonance frequency at a predetermined frequency and the frequency characteristic of the piezoelectric element sounding body (3) are canceled. A filter means (11) for inputting a vehicle approach notification signal having a frequency band including the resonance frequency and filtering the vehicle approach notification signal with the inverse frequency characteristic; and a filter means (11). Output means (13, 14) for outputting the output signal (11a) to the piezoelectric element sounding body (3), and the inverse frequency characteristic of the filter means (11) is the frequency of the piezoelectric element sounding body (3). Among the characteristics, only a predetermined band including the resonance frequency is inverted, and the remaining band has a constant shape.

According to the first aspect of the present invention, since the frequency characteristic of the piezoelectric element sounding body which has the maximum at the resonance frequency is canceled by the inverse frequency characteristic of the filter means, the sound pressure of the vehicle approach notification sound output from the piezoelectric element sounding body is reduced. It becomes flat over a wide frequency band, and natural motor and engine artificial sounds are output as vehicle approach notification sounds. In particular, the frequency characteristics of the piezoelectric element sounding body, which has a maximum at the resonance frequency, are canceled out, and the sound pressure of the vehicle approaching notification sound output from the piezoelectric element sounding body has no maximum and minimum parts, which is sufficient as a vehicle approaching sound. It is possible to output a natural motor dummy sound and engine dummy sound, and it is possible to simplify the configuration of the filter means.

In the second aspect of the present invention , an alarm signal generating means (12) for generating an alarm signal (12a) when the alarm means (15) is operated is further provided, and the output means (13, 14) is the vehicle approach notification signal. In addition to the above, the alarm signal is set to be output to the piezoelectric element sounding body.

According to the second aspect of the present invention , since the vehicle approach notification sound and the warning sound can be output by the single piezoelectric element sounding body, the vehicle approach notification device that can also be used as a horn is realized more compactly.

The reference numerals in parentheses refer to corresponding relationships with specific means described in the embodiments described later.

As described above, according to the vehicle approach notification device of the present invention, the piezoelectric device sounding body is used to achieve a small size and a long life, and a vehicle approach notification sound having a constant flat frequency characteristic in a wide frequency band. Can be obtained.

It is a block block diagram of the electric circuit of the vehicle approaching alarm in a reference example . It is a wave form diagram which shows an example of an alarm signal. It is sectional drawing of a vehicle approach notification device main body. It is a figure which shows the frequency characteristic of the output sound pressure of a piezoelectric element sounding body. It is a figure which shows the frequency characteristic of the gain of a filter circuit. It is a figure which shows the frequency characteristic of the output sound pressure of a piezoelectric element sounding body when inputting the output signal of a filter circuit. It is a figure which shows the frequency characteristic of the gain of a filter circuit in embodiment of this invention. It is a figure which shows the frequency characteristic of the output sound pressure of a piezoelectric element sounding body when inputting the output signal of a filter circuit.

The embodiment described below is merely an example, and various design improvements made by those skilled in the art are also included in the scope of the present invention without departing from the scope of the present invention.

(Reference example)
FIG. 1 shows a block diagram of an electric circuit (alarm circuit) of a vehicle approaching alarm device according to a reference example . The alarm circuit 1 includes a filter circuit 11 as a filter means, an alarm signal generation circuit 12, an amplifier circuit 13 to which the output signals 11a and 12a of the circuits 11 and 12 are input, and a boosting drive to which the output signal of the amplifier circuit 13 is input. It is composed of a circuit 14. The amplifier circuit 13 and the boost drive circuit 14 form an output means.

The vehicle approach notification signal 1a is input to the filter circuit 11 from an external computer. The vehicle approach notification signal 1a is a signal of, for example, a motor dummy sound or an engine dummy sound in a wide frequency band, and is input to the filter circuit 11 from an external computer under the condition that the vehicle is running quietly at low speed. The frequency characteristic of the filter circuit 11 will be described later.

A horn switch 15 serving as an alarm means is input and connected to the alarm signal generating circuit 12, and when the horn switch 15 is operated, an alarm signal 12a is generated and output by the alarm signal generating circuit 12. An example of the alarm signal 12a is shown in FIG. The alarm signal 12a is, for example, a signal obtained by adding the treble modulated wave 12ah shown in FIG. 2(2) and the bass modulated wave 12al shown in FIG. 2(3). Here, the waveform of the signal 12ah is a rectangular wave, and the region X1 of 3600 Hz and the region Y2 of 2800 Hz, which are up and down by 400 Hz around the frequency 3200 Hz of the first basic rectangular wave, are 2.5 ms (=1/400 (Hz)). ) Is repeated alternately. In addition, the waveform of the signal 12al is a rectangular wave, and the region X2 of 3200 Hz and the region Y2 of 2400 Hz which are up and down by 400 Hz from the frequency 2800 Hz of the second fundamental rectangular wave are 2.9 ms (=1/350 (Hz)). It alternates with the cycle.

In FIG. 1, the output signal 11 a of the filter circuit 11 and the alarm signal 12 a generated by the alarm signal generation circuit 12 are input to the amplifier circuit 13, amplified to a predetermined level, and input to the boost drive circuit 14. The booster drive circuit 14 boosts each of the signals 11a and 12a to a voltage necessary for driving the piezoelectric element sounding body 3 which is connected to the circuit 14 and has a structure described below. It is output to the piezoelectric element sounding body 3 as a drive signal and an alarm drive signal.

FIG. 3 shows the structure of the main body of the horn (vehicle approaching alarm) including the piezoelectric element sounding body 3. The horn body includes a metal plate housing 4 in the shape of a circular open container, and a stay 41 for mounting is bolted to the center of the bottom wall of the housing 4. An open container-shaped resin holder 42 is inserted along the inside of the housing 4, and a circuit board 5 provided with the alarm circuit 1 is arranged on the bottom wall of the holder 42 in parallel therewith. It is set up. The circuit board 5 is fitted and supported by a pin portion 421 erected on the bottom wall of the holder 42. The circuit components and the like of the audible alarm circuit 1 are not shown.

A metal diaphragm plate 31 constituting a piezoelectric element sounding body 3 together with a piezoelectric body 32 described below is stretched in parallel with the circuit board 5 by closing the opening of the holder 42, and the diaphragm plate 31 has an outer peripheral edge thereof. Are sandwiched between the opening edge of the holder 42 and the outer peripheral edge of the resin resonator 43 covered by the opening of the holder 42. The resonator 43 is provided with sound output ports 431 at a plurality of locations on the outer peripheral portion (four locations at equal intervals in the circumferential direction in this embodiment).

A circular piezoelectric body 32 is attached to the center of the back surface (lower surface of FIG. 3) of the diaphragm plate 31, and an example of the frequency characteristics of the piezoelectric element sounding body is, as shown in FIG. 4, a low frequency of 500 Hz to 800 Hz. It has a first resonance frequency f1 in the side band and a second resonance frequency f2 in the high frequency side band of 2 KHz to 5 KHz. Output lines 33 and 34 extend from the circuit board 5 to one electrode (not shown) of the piezoelectric body 32 and a diaphragm plate 31 that communicates with the other electrode (not shown) of the piezoelectric body 32. Further, one end of the power supply connector 51 extending to the outside of the housing 4 is connected to one end of the circuit board 5. The outside of the resonator 43 is covered with a metal cover body 6 having a long hole-shaped sound output port 61.

Here, an example of the frequency characteristic of the filter circuit is shown in FIG. As is clear from FIG. 5, the frequency characteristic of the filter circuit 11 is an inverse frequency characteristic in which the frequency characteristic of the piezoelectric element sounding body 3 is inverted as it is in the entire frequency band. That is, the gain of the filter circuit becomes minimum at the resonance frequencies f1 and f2 at which the output sound pressure of the sounding body 3 becomes maximum, and the gain gradually decreases toward the high frequency side in the remaining frequency range. When the output signal 11a that has passed through the filter circuit 11 having such an inverse frequency characteristic is input to the piezoelectric element sounding body 3 as the vehicle approach notification drive signal through the amplifier circuit 13 and the boost drive circuit 14, the resonance frequencies f1 and f2 are obtained. The frequency characteristics of the maximum piezoelectric element sounding body 3 are canceled out, and the frequency characteristic of the sound pressure of the vehicle approach notification sound output from the piezoelectric element sounding body 3 is substantially constant over a wide frequency band as shown in FIG. Will be flat. As a result, a natural motor dummy sound or engine dummy sound is output as the vehicle approach notification sound.

When the horn switch 15 is operated, an alarm drive signal having the same waveform as the alarm signal 12a (FIG. 2(1)) is output to the piezoelectric element sounding body 3. When the alarm drive signal is input, the piezoelectric element sounding body 3 causes the frequency spectrum of the alarm sound output from the conventional high-tone electromagnetic flat horn and the frequency of the alarm sound output from the low-tone electromagnetic horn. It emits a warning sound with a greatly improved timbre, which has a frequency spectrum with spectrum added.

(Embodiment)
In the above reference example , the inverse frequency characteristic of the filter circuit 11 is the frequency characteristic of the piezoelectric element sounding body 3 inverted, but as shown in FIG. 7, the output sound pressure of the piezoelectric element sounding body 3 is the maximum. The gain is minimized by inverting the frequency characteristic of the piezoelectric element sounding body 3 only in a predetermined band including the resonance frequencies f1 and f2, and the gain is flat in the remaining frequency region. When the piezoelectric element sounding body 3 is driven by the vehicle approach notification drive signal based on the output signal 11a that has passed through the filter circuit 11 having such an inverse frequency characteristic, the vehicle output from the piezoelectric element sounding body 3 as shown in FIG. The frequency characteristics of the output sound pressure of the approach notification sound gradually increase toward the high frequency side as a whole, but the frequency characteristics of the piezoelectric element sounding body, which becomes maximum at the resonance frequencies f1 and f2, are offset, and there is no maximum or minimum portion. Becomes Therefore, it is possible to output a sufficiently natural motor dummy sound and engine dummy sound as the vehicle approach notification sound, and it is possible to simplify the configuration of the filter circuit 11 as compared with the first embodiment.

DESCRIPTION OF SYMBOLS 1... Alarm circuit, 11... Filter circuit (filter means), 11a... Vehicle approach notification signal, 12... Warning signal generation circuit (warning signal generation means), 12a... Warning signal, 13... Amplifier circuit (output means), 14 ... boost driving circuit (output means), 15... horn switch (alarm means), 3... piezoelectric element sounding body, f1... first resonance frequency, f2... second resonance frequency.

Claims (2)

A piezoelectric element sounding body having a frequency characteristic having a resonance frequency at a predetermined frequency, and a vehicle approach notification signal in a frequency band including the resonance frequency and having an inverse frequency characteristic that cancels the frequency characteristic of the piezoelectric element sounding body. And a filter means for filtering the vehicle approach notification signal with the inverse frequency characteristic, and an output means for outputting the output signal of the filter means to the piezoelectric element sounding body, and the inverse frequency characteristic of the filter means is A vehicle approach alarm having a shape in which only a predetermined band including a resonance frequency in the frequency characteristics of the piezoelectric element sounding body is inverted and the remaining band is constant . An alarm signal generating unit for generating an alarm signal when the alarm unit is operated is further provided, and the output unit is set to output the alarm signal to the piezoelectric element sounding body in addition to the vehicle approach notification signal. The vehicle approach notification device according to claim 1 .

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