JP2020040496A - Vehicle approach notification apparatus - Google Patents

Abstract

To provide a vehicle approach notification apparatus capable of suppressing a frequency dip within a given distance from a vehicle regardless of an outside temperature.SOLUTION: A vehicle approach notification apparatus is mounted on a vehicle and issues an approach notification sound to a vehicle surroundings. The vehicle approach notification apparatus includes: an outside temperature obtainment part for obtaining an outside temperature; a frequency change amount calculation part for calculating a change amount of frequency in order to make a sound wavelength contained in the approach notification sound constant against changes in the outside temperature on the basis of the outside temperature obtained by the outside temperature obtainment part; and a sound issuance part for changing a frequency of a sound contained in the approach notification sound on the basis of a correction amount calculated by the frequency change amount calculation part and issuing the post-change approach notification sound.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a vehicle approach notification device that is mounted on a vehicle and emits a sound indicating the approach of the vehicle to the surroundings.

  Since vehicles such as electric vehicles and hybrid vehicles have low noise, a vehicle approach notification device that emits an approach notification sound that indicates the approach of the vehicle is provided around the vehicle.

  Various proposals have been made to more appropriately sound the approach notification sound. Patent Literature 1 discloses a vehicle approach notification device that outputs a vehicle approach notification sound to be reflected on a running road surface, and determines a road surface condition based on information from devices such as a video camera, a raindrop sensor, a temperature sensor, and an ABS system. It discloses that the sound pressure and frequency of the approach notification sound are set according to the result. Patent Literature 2 discloses that the sound pressure and the frequency of the approach notification sound are set in accordance with the noise and the temperature characteristics of a speaker based on the noise acquired by a microphone and the outside air temperature acquired by a temperature sensor.

JP 2012-123730 A JP-A-2005-80992

  The approach notification sound is typically generated by a sound generator such as a speaker mounted inside the vehicle body, and spreads from each part of the vehicle to the periphery of the vehicle. Therefore, depending on the shape of the vehicle and the characteristics and arrangement of the sound emitting device, approach notification sounds arriving on different routes at specific positions around the vehicle interfere with each other, and sound of a specific wavelength included in the approach notification sound is generated. There is a possibility that a phenomenon called frequency dip in which the pressure decreases will occur.

  The approach notification sound is required to sound good near the vehicle (in an area within a predetermined distance from the vehicle) for the purpose. Therefore, it is not preferable that a frequency dip occurs within a predetermined distance. One of the conditions under which a frequency dip occurs at a particular location is the wavelength of the sound. The sound wavelength depends on the temperature when the frequency is constant. For this reason, even the same approach notification sound may be heard near the vehicle depending on the outside temperature, and there is room for improvement in order to ensure that the sound can be heard more reliably.

  The present invention has been made in view of the above problems, and has as its object to provide a vehicle approach notification device that can suppress a frequency dip within a predetermined distance from a vehicle regardless of an outside air temperature.

  In order to solve the above-described problem, one aspect of the present invention is a vehicle approach notification device that is mounted on a vehicle and emits an approach notification sound around the vehicle, and includes an outside temperature acquisition unit that acquires an outside temperature, A frequency change amount calculation unit that calculates a frequency change amount for keeping a wavelength of a sound included in the approach notification sound constant with respect to a change in the outside air temperature based on the outside air temperature acquired by the air temperature acquisition unit; A sound-producing unit that changes the frequency of the sound included in the approach notification sound based on the correction amount calculated by the amount calculation unit and that emits the changed approach notification sound. .

  According to the present invention, it is possible to provide a vehicle approach notification device that can suppress a frequency dip within a predetermined distance from a vehicle regardless of an outside air temperature.

The top view which shows typically the vehicle which concerns on one Embodiment of this invention, and the example of a frequency dip position. Graph showing an example of a frequency dip FIG. 1 is a diagram showing functional blocks of a vehicle approach notification device according to an embodiment of the present invention. Flowchart showing processing according to an embodiment of the present invention

(Embodiment)
The vehicle approach notification device according to the present invention changes the frequency based on the acquired outside temperature so as to keep the wavelength of the sound included in the approach notification sound constant with respect to the change in the outside temperature. Thus, the frequency dip can be suppressed within a predetermined distance from the vehicle regardless of the outside air temperature, and the approach notification sound can be stably heard.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

<Structure>
FIG. 1 is a top view schematically illustrating a vehicle 1 according to the present embodiment and an example of a frequency dip position. The vehicle 1 is, for example, an electric vehicle or a hybrid vehicle that can travel by the output of a motor. The vehicle approach notification device 10 mounted on the vehicle 1 provides an approach notification having a predetermined frequency and sound pressure distribution while the vehicle 1 satisfies a predetermined condition such as running by a motor at a predetermined speed or less. Produce sound. FIG. 1 also shows an example of a position of a microphone for acquiring an approach notification sound in a test of a vehicle approach notification sound device based on regulations. FIG. 2 is a graph in which frequency is plotted on the horizontal axis and sound pressure is plotted on the vertical axis, and shows an example of frequency dip. In the example shown in FIG. 2, due to the frequency dip, the sound pressure is significantly reduced in a certain range including the frequency F1. When the position of such a frequency dip is at a position P1 that is more than a predetermined distance from the vehicle, there is no problem for the purpose of the approach notification sound, but it moves to, for example, a position P2 within a predetermined distance from the vehicle due to a change in outside air temperature. Is not preferred. In the example shown in FIG. 1, the position P2 overlaps the position of the microphone in the test, and the test fails.

  FIG. 3 is a functional block diagram of the vehicle approach notification device 10 according to the present embodiment. The vehicle approach notification device 10 obtains an ambient temperature (outside air temperature) near the outside of the vehicle, an outside temperature acquisition unit 11, a frequency change amount calculation unit 12 that calculates an amount of change in the frequency of the approach notification sound, and generates an approach notification sound. And a control unit 14 for appropriately controlling these.

<Process>
FIG. 4 is a flowchart illustrating an example of a process executed by the vehicle approach notification device 10. The process of the vehicle approach notification device 10 will be described with reference to FIG. This flow is started when the vehicle 1 starts running by, for example, a motor and a predetermined condition is satisfied, and the control unit 14 causes the sound generation unit 13 to start generating a predetermined approach notification sound. The predetermined approach notification sound is, for example, a suitable sound designed as a sound in which a frequency dip does not occur within a predetermined distance from the vehicle 1 at a predetermined outside temperature.

  (Step S101): The outside temperature acquisition unit 11 acquires the outside temperature.

  (Step S102): The control unit 104 determines whether or not the outside temperature acquired by the outside temperature acquisition unit 11 has changed from the previously acquired outside temperature. In consideration of the error, it may be determined that the outside air temperature has changed when the outside air temperature has increased or decreased by a predetermined value or more, and otherwise, it may be determined that the outside air temperature has not changed. When this step is first executed after the start of this flow, the previously obtained outside temperature may be compared with the above-mentioned predetermined outside temperature, or the last obtained outside air temperature when the previous flow was executed. May be stored and compared with this. If the outside air temperature has changed, the process proceeds to step S103. If the outside air temperature has not changed, the process proceeds to step S101.

  (Step S103): The frequency change amount calculation unit 12 calculates a frequency change amount with respect to the sound included in the approach notification sound based on the outside air temperature. This change amount is a change amount for keeping the wavelength of the sound included in the approach notification sound constant with respect to the change in the outside air temperature. Here, an example of a method of calculating the amount of change will be described.

If the sound speed v [m / s] at the outside air temperature T [unit ° C] is represented as v (T), v (T) can be approximated by the following (Equation 1) using constants a and b.
v (T) = a × T + b (where a = 0.6, b = 331.5) (Equation 1)

Assuming that the wavelength of the sound having the frequency f [Hz] at the outside temperature T is λ [m], λ is represented by the following (Equation 2).
λ = (a × T + b) / f (T) (Equation 2)

When the outside air temperature changes to T ′, the frequency f (T ′) of the sound having the same wavelength λ is obtained from (Equation 2) by the following (Equation 3).
f (T ′) = (a × T ′ + b) / (a × T + b) × f (T) (Equation 3)

For example, when the wavelength of a sound having a frequency of 800 Hz at an outside air temperature of 20 ° C. is kept constant even when the outside air temperature changes to T ′ [° C.], a specific value is substituted into (Equation 3) and the frequency f (T ′ ) Can be calculated by the following (Equation 4).
f (T ′) = (0.6 × T ′ + 331.5) / (0.6 × 20 + 331.5) × 800
= 1.397T '+ 772.5 (Equation 4)

From (Equation 4), when the outside air temperature changes from 20 ° C. by ΔT [° C.], the amount of frequency change Δf required to keep the wavelength of the sound at the frequency of 800 Hz constant can be calculated by the following (Equation 5). .
Δf = 1.397 × ΔT (Equation 5)

  As in the above example, in this step, for example, the change amount ΔT = T′−T of the outside air temperature and the change amount of the frequency for keeping the wavelength of the sound included in the approach notification sound constant are calculated.

  (Step S104): The control unit 104 causes the sounding unit 13 to change the frequency of the sound included in the approach notification sound by the amount of change calculated in step S103, and emit the changed approach notification sound. The above steps S101 to S104 are repeatedly executed, but when the vehicle 1 stops running or the engine is started in the case of a hybrid vehicle, and the predetermined condition for generating the approach notification sound is not satisfied. In this case, the flow ends, and the sounding of the approach notification sound also stops.

<Effect>
According to the vehicle approach notification device 10 according to the above embodiment, since the wavelength of the sound included in the approach notification sound does not depend on the outside temperature, the position where the frequency dip occurs does not change even if the outside temperature changes. For example, the vehicle 1 does not move from a distant position to a near position. As a result, it is possible to suppress the possibility that the frequency dip occurs within a predetermined distance from the vehicle 1 due to the influence of the outside air temperature, so that the approach notification sound can be stably and well heard within the predetermined distance of the vehicle 1 irrespective of the outside air temperature. And stably pass the performance test.

  In the above-described flow, when the approach notification sound includes sounds of a plurality of wavelengths, if the occurrence of a frequency dip within a predetermined distance from the vehicle 1 due to a change in the outside air temperature can be suppressed to a certain extent, some wavelengths may be used. The frequency of the sound may be changed to keep the wavelength constant, or the frequency of the sound of all wavelengths may be changed to keep each wavelength constant. Further, in the above-described flow, when the outside air temperature changes, the change amount of the frequency for keeping the wavelength constant based on the outside air change amount ΔT is calculated by (Equation 5). Each time it is acquired, a frequency corresponding to a certain wavelength may be calculated based on the outside air temperature T by (Equation 3).

  Although the present invention has been described above, the present invention is applicable not only to a vehicle approach notification device, but also to a method for generating an approach notification sound executed by a computer of the vehicle approach notification device, a program, and a computer-readable non-temporary program storing the program. Recording media, vehicles, etc.

  The present invention is useful for a vehicle approach notification device mounted on a vehicle or the like.

REFERENCE SIGNS LIST 1 vehicle 10 vehicle approach notification device 11 outside temperature acquisition unit 12 frequency change amount calculation unit 13 sound generation unit 14 control unit

Claims (1)

A vehicle approach notification device that is mounted on a vehicle and emits an approach notification sound around the vehicle,
An outside temperature acquisition unit for acquiring an outside temperature;
Based on the outside air temperature acquired by the outside air temperature acquisition unit, a frequency change amount calculation unit that calculates a change amount of a frequency for keeping a wavelength of a sound included in the approach notification sound constant with respect to a change in the outside air temperature. When,
Based on the correction amount calculated by the frequency change amount calculation unit, the sound included in the approach notification sound to change the frequency, comprising a sounding unit that emits the approach notification sound after the change, Vehicle approach notification device.

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