Vehicle approach notification device

Abstract

To reduce a sense of discomfort felt by a person around an electric vehicle and an occupant due to a stop of an approach notification sound output from the electric vehicle.SOLUTION: In a speed range equal to or lower than a legal maximum vehicle speed Vc which is the highest vehicle speed among a plurality of vehicle speeds stipulated by a law, an ECU 18 performs control such that a sound pressure of an approach notification sound increases as a vehicle speed increases, so as to satisfy the law. Further, when a vehicle speed of an electric vehicle EV is higher than a vehicle speed V1 which is a vehicle speed equal to or higher than the legal maximum vehicle speed Vc, the ECU 18 performs control such that the sound pressure of the approach notification sound gradually decreases as the vehicle speed of the electric vehicle EV increases.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This specification discloses an improvement to a vehicle approach notification device. [Background technology]

[0002] Electric vehicles, such as electric cars and hybrid cars, run on the driving force of a motor when traveling at low speeds. Unlike internal combustion engine vehicles, electric vehicles do not emit much noise when traveling at low speeds, which can make it difficult for people around the electric vehicle (e.g., pedestrians) to notice that an electric vehicle is nearby. Therefore, electric vehicles have traditionally emitted an approaching warning sound to the outside of the vehicle when traveling at low speeds to alert people around the vehicle that an electric vehicle is nearby. The requirement that electric vehicles emit an approaching warning sound to the outside of the vehicle when traveling at low speeds is stipulated in the laws and regulations of each country.

[0003] Conventionally, techniques for controlling the output of approach warning sounds have been proposed. For example, Patent Document 1 discloses a vehicle approach warning device that includes a speaker that outputs an approach warning sound toward the outside of the vehicle, and that changes the pitch (frequency, i.e., interval) of the approach warning sound output from the speaker according to the vehicle speed of the electric vehicle, and also changes the output level of the approach warning sound according to the pitch of the approach warning sound. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-121518 Summary of the Invention [Problem to be solved by the invention]

[0005] As the speed of an electric vehicle increases, the noise (background noise) emitted from the electric vehicle increases. Therefore, the laws and regulations of each country require that electric vehicles output an approach warning sound when traveling at low speeds. In other words, the laws and regulations do not require electric vehicles to output an approach warning sound when traveling at high speeds. Therefore, as the speed of an electric vehicle increases, there is no legal requirement to output an approach warning sound, and the electric vehicle stops outputting the approach warning sound when its speed reaches or exceeds a predetermined speed.

[0006] If the approach warning sound stops, a problem may occur in that people around the electric vehicle or the occupants may feel uncomfortable (startled, etc.) This will be described in detail with reference to FIG.

[0007] FIG. 4 is a graph showing the relationship between vehicle speed and sound pressure of the approach warning sound in a conventional electric vehicle. In the graph in FIG. 4, the horizontal axis represents the vehicle speed of the electric vehicle, and the vertical axis represents the sound pressure of the approach warning sound or background noise output from the electric vehicle. A vehicle speed less than 0 indicates that the electric vehicle is backing up. In the example in FIG. 4, the unit of sound pressure is [dBA], i.e., the sound pressure is expressed as an A-weighted sound pressure level. The sound pressure here refers to the sound pressure at a predetermined position from the electric vehicle as defined by law. For example, the law defines sound pressure as the sound pressure at two positions, 2 m to the left and 2 m to the right of the front end and center of the electric vehicle in the width direction, both at a height of 1.2 m. Therefore, the sound pressure in FIG. 4 also indicates the sound pressure at those positions.

[0008] Points Pa, Pb, and Pc shown in FIG. 4 represent the vehicle speed and sound pressure of the approach warning sound as stipulated by the law. For example, the law represented by points Pa, Pb, and Pc stipulates that when the electric vehicle has a vehicle speed Va (when the electric vehicle is reversing at a vehicle speed Va because Va<0), the approach warning sound must be output at a sound pressure La or higher; when the electric vehicle has a vehicle speed Vb, the approach warning sound must be output at a sound pressure Lb or higher; and when the electric vehicle has a vehicle speed Vc, the approach warning sound must be output at a sound pressure Lc or higher. The vehicle speed Vc is higher than the vehicle speed Vb, and the sound pressure Lc is higher than the sound pressure Lb. In other words, the law requires that the higher the vehicle speed of the electric vehicle, the higher the sound pressure at which the approach warning sound must be output.

[0009] The solid line in Figure 4 shows the relationship between the vehicle speed of the electric vehicle and the sound pressure of the approach warning sound output from the electric vehicle. For example, the electric vehicle outputs an approach warning sound with a sound pressure that corresponds to the vehicle speed so as to satisfy the regulations represented by points Pa, Pb, and Pc. Specifically, when the vehicle speed of the electric vehicle is Va, the approach warning sound is output with a sound pressure of La or higher, when the vehicle speed of the electric vehicle is Vb, the approach warning sound is output with a sound pressure of Lb or higher, and when the vehicle speed of the electric vehicle is Vc, the approach warning sound is output with a sound pressure of Lc or higher. In accordance with the regulations, when the vehicle speed of the electric vehicle is greater than 0, the sound pressure of the approach warning sound increases as the vehicle speed of the electric vehicle increases.

[0010] In this specification, the highest vehicle speed among multiple vehicle speeds defined by regulations is referred to as the legal maximum vehicle speed. In the example of FIG. 2, the legal maximum vehicle speed is vehicle speed Vc (in this case, it will be written as "legal maximum vehicle speed Vc"). The regulations do not require the output of a proximity warning sound when the vehicle speed of the electric vehicle is greater than the legal maximum vehicle speed Vc. Therefore, when the vehicle speed of the electric vehicle is greater than the legal maximum vehicle speed Vc, the electric vehicle may stop outputting the proximity warning sound. In the example of FIG. 4, the electric vehicle stops outputting the proximity warning sound (the sound pressure of the proximity warning sound is set to 0 dBA) at a vehicle speed Vp1 that is a small margin above the legal maximum vehicle speed Vc (Vp1 > legal maximum vehicle speed Vc).

[0011] If the output of the approach warning sound is stopped at vehicle speed Vp1, the approach warning sound, which had been output at a sound pressure equal to or greater than Lc, will suddenly stop, which may cause discomfort to people around the electric vehicle.

[0012] The dashed line in Figure 4 shows the relationship between the vehicle speed of the electric vehicle and the sound pressure of the background noise. Here, background noise refers to sounds other than the approach warning sound emitted by the electric vehicle, including, for example, the motor sound of the electric vehicle and road noise. As shown in Figure 4, the sound pressure of the background noise increases as the vehicle speed increases. Even if the approach warning sound suddenly stops, the presence of background noise makes it less likely that people around the electric vehicle will feel uncomfortable. In other words, the background noise acts to reduce the sense of discomfort felt by people around the electric vehicle when the approach warning sound stops. However, if there is a large difference ΔL1 between the sound pressure of the approach warning sound at vehicle speed Vp1 (just before stopping) and the sound pressure of the background noise at vehicle speed Vp1, people around the electric vehicle will still feel uncomfortable.

[0013] The object of the vehicle approach notification device disclosed in this specification is to reduce the discomfort felt by people around the electric vehicle when the approach notification sound output from the electric vehicle is stopped. [Means for solving the problem]

[0014] The vehicle approach warning device disclosed in this specification is characterized by comprising a sound pressure control unit that controls the sound pressure of an approach warning sound output from a sound generator provided in an electric vehicle toward the outside of the vehicle in accordance with the vehicle speed of the electric vehicle, and when the vehicle speed of the electric vehicle is greater than a threshold vehicle speed, the sound pressure control unit controls the sound pressure of the approach warning sound so that it gradually decreases as the vehicle speed of the electric vehicle increases.

[0015] The sound pressure control unit may stop output of the approach warning sound from the sound generator when the sound pressure of the approach warning sound gradually decreases as the vehicle speed of the electric vehicle increases, and as a result, the difference between the sound pressure of the approach warning sound and the sound pressure of background noise becomes equal to or less than a threshold sound pressure. [Effects of the Invention]

[0016] According to the vehicle approach notification device disclosed in this specification, the discomfort felt by people around the electric vehicle can be reduced by stopping the approach notification sound output from the electric vehicle. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram illustrating the configuration of a vehicle approach notification device according to an embodiment of the present invention. [Figure 2] 10 is a diagram showing the content of a sound pressure control function showing the relationship between vehicle speed and sound pressure of an approach notification sound in this embodiment. FIG. [Figure 3] 10 is a flowchart showing the flow of a process for creating a sound pressure control function. [Figure 4] 10 is a graph showing the relationship between vehicle speed and sound pressure of an approach warning sound in a conventional electric vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0018] 1 is a schematic diagram of a vehicle approach notification device 10 according to this embodiment. The vehicle approach notification device 10 is provided in an electric vehicle (EV), such as an electric vehicle or hybrid vehicle, that runs on the driving force of a motor at least when traveling at low speeds. The vehicle approach notification device 10 includes a vehicle speed sensor 12, a memory 14, a speaker 16, and an ECU 18. The ECU 18 is connected to the vehicle speed sensor 12, the memory 14, and the speaker 16 so as to be able to communicate with them.

[0019] The vehicle speed sensor 12 is a sensor that detects the vehicle speed of the electric vehicle EV. For example, the vehicle speed sensor 12 detects the vehicle speed by detecting the rotation speed of the output shaft of the transmission. The vehicle speed sensor 12 may be any sensor as long as it can detect the vehicle speed of the electric vehicle EV. The vehicle speed detected by the vehicle speed sensor 12 is input to the ECU 18.

[0020] The memory 14 includes a solid state drive (SSD), an embedded multi media card (eMMC), a read only memory (ROM), a random access memory (RAM), or the like. The memory 14 stores a vehicle approaching notification program for operating each unit of the vehicle approaching notification device 10. The vehicle approaching notification program can also be stored in a computer-readable non-transitory storage medium such as a USB (Universal Serial Bus) memory or an SD card. The vehicle approaching notification device 10 can read and execute the vehicle approaching notification program from such a storage medium.

[0021] The memory 14 stores a sound source file 14a and a sound pressure control function 14b. The sound source file 14a is sound data representing an approach warning sound. The sound pressure control function 14b is a function that indicates the relationship between the vehicle speed of the electric vehicle EV and the sound pressure of the approach warning sound output from the electric vehicle EV. The sound pressure control function 14b will be described in detail later.

[0022] The speaker 16 as a sound generator outputs an approach warning sound to the outside of the vehicle under control of the ECU 18 at a sound pressure according to the control of the ECU 18. In this embodiment, the speaker 16 outputs sound obtained by playing the sound source file 14a to the outside of the vehicle as the approach warning sound. Note that the sound generator is not limited to the speaker 16 as long as the sound pressure of the output approach warning sound can be changed under control of the ECU 18, and may be, for example, a piezoelectric sounder or a buzzer.

[0023] The ECU 18 is composed of, for example, a processor and its peripheral components. The ECU 18 controls the sound pressure of the approach warning sound output from the speaker 16 in accordance with a vehicle approach warning program stored in the memory 14. Specifically, the ECU 18 controls the sound pressure of the approach warning sound output from the speaker 16 by controlling the amplitude of the voltage of an audio signal, which is an electrical signal, supplied to the speaker 16. In particular, the ECU 18 controls the sound pressure of the approach warning sound output from the speaker 16 in accordance with the vehicle speed of the electric vehicle EV detected by the vehicle speed sensor 12. In other words, the ECU 18 functions as a sound pressure control unit.

[0024] 2 is a diagram showing the contents of a sound pressure control function 14b that indicates the relationship between the vehicle speed and the sound pressure of the approach warning sound in this embodiment. In this embodiment, the ECU 18 controls the sound pressure of the approach warning sound output from the speaker 16 in accordance with the sound pressure control function 14b. The sound pressure control function 14b is created in advance by a designer of the vehicle approach warning device 10 or the like, and is stored in the memory 14. Note that, in this embodiment, the sound pressure control function 14b is a graph as shown in FIG. 2, but the sound pressure control function 14b may be any type of function as long as it indicates the relationship between the vehicle speed of the electric vehicle EV and the sound pressure of the approach warning sound.

[0025] As with Figure 4, the horizontal axis in Figure 2 represents the vehicle speed of the electric vehicle EV, and the vertical axis represents the sound pressure of the approach warning sound or background noise output from the electric vehicle EV. The sound pressure in Figure 2 also represents the sound pressure at predetermined positions relative to the electric vehicle EV as defined by regulations (for example, two positions 2 m to the left and 2 m to the right of the front end and center of the vehicle width direction of the electric vehicle EV, both at a height of 1.2 m).

[0026] As in the past, ECU 18 controls the sound pressure of the approach warning sound according to the vehicle speed so as to satisfy the legal regulations represented by the multiple points Pa, Pb, and Pc. At least in the speed range below the legal maximum vehicle speed Vc, ECU 18 controls the sound pressure of the approach warning sound so that the sound pressure increases as the vehicle speed increases, so as to satisfy the legal regulations.

[0027] In a speed range higher than the legal maximum vehicle speed Vc, the ECU 18 performs control of the sound pressure of the approach warning sound differently from conventional methods. Conventionally, as shown in Fig. 4, the output of the approach warning sound is stopped at a vehicle speed Vp1 that is higher than the legal maximum vehicle speed Vc. In contrast, in this embodiment, when the vehicle speed of the electric vehicle EV is higher than a threshold vehicle speed V1 that is equal to or higher than the legal maximum vehicle speed Vc, the ECU 18 controls the sound pressure of the approach warning sound so that it gradually decreases as the vehicle speed of the electric vehicle EV increases (between vehicle speeds V1 and V2 in Fig. 2).

[0028] Furthermore, as the vehicle speed of the electric vehicle EV increases from vehicle speed V1, the sound pressure of the approach warning sound gradually decreases, and as a result, when the difference between the sound pressure of the approach warning sound and the sound pressure of the background noise (ΔL2 in FIG. 2) becomes equal to or less than the threshold sound pressure (when the vehicle speed of the electric vehicle EV reaches vehicle speed V2 in FIG. 2), ECU 18 stops output of the approach warning sound from speaker 16. Thereafter, in a speed range greater than vehicle speed V2, ECU 18 does not cause speaker 16 to output the approach warning sound.

[0029] Below, with reference to Figure 2 and in accordance with the flowchart of Figure 3, we will explain the details of the sound pressure control function 14b (i.e., the details of the control of the sound pressure of the approach warning sound by the ECU 18 in accordance with the vehicle speed of the electric vehicle EV) along with the flow of the process of creating the sound pressure control function 14b.

[0030] In step S10, in the speed range below the legal maximum vehicle speed Vc, the relationship between the speed of the electric vehicle EV and the sound pressure of the approach warning sound is determined so as to satisfy the legal regulations, as in the past. Specifically, the sound pressure of the approach warning sound is increased as the speed of the electric vehicle EV increases.

[0031] In step S12, a vehicle speed V1 greater than the legal maximum vehicle speed Vc is determined. As shown in FIG. 2, in the sound pressure control function 14b, the vehicle speed V1 is a vehicle speed with a margin relative to the legal maximum vehicle speed Vc (V1 > legal maximum vehicle speed Vc), but it is sufficient for the vehicle speed V1 to be greater than the legal maximum vehicle speed Vc. Then, a sound pressure L1 of the approach warning sound at the vehicle speed V1 is determined. The sound pressure L1 is set to be equal to or greater than the sound pressure Lc at the legal maximum vehicle speed Vc (L1 ≧ Lc). The point represented by the vehicle speed V1 and the sound pressure L1 in the sound pressure control function 14b is called point P1.

[0032] In step S14, a candidate value for vehicle speed V2, which is a vehicle speed greater than vehicle speed V1 and at which the approach warning sound is stopped, and a candidate value for sound pressure L2 of the approach warning sound at vehicle speed V2 are determined. The candidate value for vehicle speed V2 needs only to be greater than vehicle speed V1. However, if the difference between vehicle speed V2 and vehicle speed V1 is small, the sound pressure of the approach warning sound will rapidly decrease from sound pressure L1 as the vehicle speed of the electric vehicle EV increases from vehicle speed V1 to vehicle speed V2, and the output of the approach warning sound will be stopped at vehicle speed V2, thereby reducing the effect of the present invention. Therefore, the candidate value for vehicle speed V2 is determined so that the difference between vehicle speed V2 and vehicle speed V1 is equal to or greater than a predetermined value. In this embodiment, the candidate value for vehicle speed V2 is determined so that the difference between vehicle speed V2 and vehicle speed V1 is, for example, approximately 15 to 20 km / h.

[0033] Next, a candidate value for the sound pressure L2 is determined. The candidate value for the sound pressure L2 is a sound pressure that is smaller than the sound pressure L1. In particular, the candidate value for the sound pressure L2 is determined so that the difference ΔL2 between the candidate value for the sound pressure L2 and the sound pressure of background noise at vehicle speed V2 is equal to or smaller than a threshold sound pressure. The threshold sound pressure may be, for example, 5 dBA.

[0034] As mentioned above, background noise refers to sounds other than the approach warning sound emitted by the electric vehicle EV, including, for example, the motor noise of the electric vehicle EV and road noise. In Figure 2, the relationship between the vehicle speed of the electric vehicle EV and the sound pressure of the background noise is also shown by the dashed line. The sound pressure of the background noise increases as the vehicle speed increases. Therefore, the higher the vehicle speed V2, the larger the candidate value for sound pressure L2; conversely, the lower the vehicle speed V2, the smaller the candidate value for sound pressure L2.

[0035] In step S16, the approach warning sound is stopped using the candidate values ​​for vehicle speed V2 and sound pressure L2 determined in step S14, and a sensory test is conducted to determine whether a person (examiner) actually feels uncomfortable around the electric vehicle EV. If the examiner feels uncomfortable as a result of the sensory test (NG in step S16), the process returns to step S18, and the candidate value for sound pressure L2 is adjusted. Specifically, the candidate value for sound pressure L2 is adjusted to be smaller so as to reduce the difference ΔL2. Also, in step S18, the candidate value for vehicle speed V2 may be adjusted in addition to the candidate value for sound pressure L2 so as to reduce the difference ΔL2. If the examiner does not feel uncomfortable as a result of the sensory test (OK in step S16), the process proceeds to step S20.

[0036] In step S20, the vehicle speed V2 and sound pressure L2 candidate values ​​determined in step S14 or the vehicle speed V2 and sound pressure L2 candidate values ​​adjusted in step S18 are determined as the vehicle speed V2 and sound pressure L2. The point represented by the vehicle speed V2 and sound pressure L2 in the sound pressure control function 14b is called point P2.

[0037] In step S22, the relationship between the vehicle speed and the sound pressure of the approach warning sound between point P1 and point P2 is determined. Specifically, the relationship between the vehicle speed and the sound pressure of the approach warning sound is determined so that the sound pressure of the approach warning sound gradually decreases as the vehicle speed increases from vehicle speed V1 to vehicle speed V2. In the example of Fig. 2, the sound pressure of the approach warning sound decreases linearly as the vehicle speed increases from vehicle speed V1 to vehicle speed V2, but this does not necessarily have to be the case.

[0038] 4, whereas in the past the approach warning sound was stopped when the vehicle speed of the electric vehicle EV reached vehicle speed Vp1, in this embodiment the approach warning sound is not stopped even when the vehicle speed of the electric vehicle EV reaches vehicle speed V1, and the sound pressure of the approach warning sound gradually decreases as the vehicle speed increases from vehicle speed V1. This reduces, at least compared to the past, the difference between the sound pressure of the approach warning sound immediately before it is stopped and the sound pressure of background noise, thereby reducing the discomfort felt by people around the electric vehicle EV and its occupants when the approach warning sound is stopped.

[0039] In particular, in this embodiment, the difference ΔL2 between the sound pressure L2 of the approach warning sound (at vehicle speed V2) just before the approach warning sound stops and the sound pressure of the background noise at vehicle speed V2 is controlled to be equal to or less than the threshold sound pressure, thereby more reliably reducing the discomfort felt by people around the electric vehicle EV and by occupants.

[0040] The above describes an embodiment of the vehicle approach notification device according to the present disclosure, but the vehicle approach notification device according to the present disclosure is not limited to the above embodiment, and various modifications are possible as long as they do not deviate from the spirit of the device. [Explanation of symbols]

[0041] 10 vehicle approach notification device, 12 vehicle speed sensor, 14 memory, 14a sound source file, 14b sound pressure control function, 16 speaker, 18 ECU.

Claims

1. a sound pressure control unit that controls the sound pressure of an approach notification sound that is output to the outside of the vehicle from a sound generator provided in the electric vehicle in accordance with the vehicle speed of the electric vehicle, and that, when the vehicle speed of the electric vehicle is higher than a threshold vehicle speed, controls the sound pressure of the approach notification sound so that the sound pressure gradually decreases as the vehicle speed of the electric vehicle increases; A vehicle approach notification device comprising:

2. the sound pressure control unit stops output of the approach notification sound from the sound generator when the sound pressure of the approach notification sound gradually decreases as the vehicle speed of the electric vehicle increases, and as a result, the difference between the sound pressure of the approach notification sound and the sound pressure of background noise becomes equal to or less than a threshold sound pressure.

2. The vehicle approach notification device according to claim 1.

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