JP5522081B2 - Vehicle approach warning device - Google Patents

Description

  The present invention relates to a vehicle approach warning device that warns the surroundings that a vehicle is approaching by generating sound from the vehicle.

  Conventionally, a vehicle approach warning device that warns the surroundings that a vehicle is approaching has been proposed (see, for example, Patent Documents 1 to 3). In this vehicle approach warning device, as a sound generation method, data such as PCM (Pulse Code Modulation) data stored in a memory, that is, data obtained by converting the volume of a voice into a data code and encoding it is D / A for each sampling period. A method of generating sound by setting in a converter or PWM output device is used.

  Some vehicle approach warning devices control the sound pressure generated according to the vehicle speed or the accelerator opening / closing operation for the purpose of reminding the surrounding people of the running state of the vehicle. Specifically, the PWM output from the PWM output device is changed in accordance with the vehicle speed and the accelerator opening / closing operation, and the sound pressure generated based on this is controlled.

  In addition, when sounding is started from the sounding stopped state, the sounding at the desired sound pressure is suddenly changed from 0% to 100%, or conversely, when the sounding state is changed to the sounding stopping state, the desired sound is If the pressure sound is suddenly changed from 100% to 0%, there is a concern that surrounding pedestrians may be surprised. For this reason, fade-in / fade-out control is performed in which the sound pressure change is made fine and the sound pressure is smoothly changed. In this case as well, the PWM output from the PWM output device is changed, and the sound pressure generated based on this is controlled.

JP 2005-215544 A JP 2007-38937 A JP 2009-101895 A

  However, when the sound pressure control corresponding to the running state of the vehicle is performed based on the change in the PWM output from the PWM output device, the pulse width of the PWM output becomes extremely small, and as a result, S / N (Signal / Noise). The ratio decreases, the pronunciation becomes insufficient, and it may become impossible to pronounce.

  On the other hand, as a measure for improving the S / N ratio, it is possible to raise the carrier frequency of the PWM output device, but there is a contradiction that radiation noise increases.

  In view of the above points, an object of the present invention is to provide a vehicle approach warning device that can suppress a decrease in S / N ratio while suppressing an increase in radiation noise when lowering a sound production sound pressure.

  In order to achieve the above object, according to the first aspect of the present invention, in the vehicle approach warning device for warning the approach of the vehicle by controlling the sound pressure of the sound from the sounding body (3) mounted on the vehicle, The vehicle has a memory for storing the relationship of the sound pressure level corresponding to the traveling state in association with the traveling state of the vehicle, inputs a traveling state detection signal indicating the traveling state of the vehicle, and the traveling of the vehicle indicated by the traveling state detection signal A sound pressure level corresponding to the state is calculated, and a control signal output unit (21a) for outputting a control signal corresponding to the sound pressure level, and a PWM output for generating sound by the sounding body (3) are generated. Based on the control signal from the microcomputer (21) having the PWM output device (21b) and the control signal output section (21a), the voltage level of the PWM output from the PWM output device (21b) is changed and output. Electric It corresponds to the output of the control means (22), the filter means (23) for removing the noise component from the PWM output whose voltage level has been changed by the voltage control part (22), and the output of the filter means (23). And an amplifier (24) for supplying a current to the sounding body (3).

  As described above, the voltage level of the PWM output is changed by the voltage control unit (22) in accordance with the sound pressure level generated. Therefore, as in the case where the sound pressure level is controlled only by the pulse width of the PWM output, the S / N ratio is lowered and the sound pressure becomes insufficient because the pulse width of the PWM output becomes extremely small. Can be prevented. In such a control mode, as a measure for improving the S / N ratio, it is not necessary to increase the carrier frequency of the PWM output device (21b), and the conventional S / N ratio is inevitably lowered. As in the case where the carrier frequency is increased, the problem of radiation noise due to the contradiction can be prevented from occurring. For this reason, the effect that the countermeasure circuit of a radiation noise can be simplified compared with the former is also acquired.

  Specifically, as described in claim 2, the control signal output unit (21a) increases the sound pressure level as the approach of the vehicle becomes faster based on the traveling state of the vehicle indicated by the traveling state detection signal. The power control unit (22) decreases the voltage level of the PWM output from the PWM output device (21b) as the sound pressure level decreases.

  Further, as described in claim 3, the PWM output device (21b) changes the pulse width of the PWM output based on the sound pressure level corresponding to the running state of the vehicle, and the PWM output becomes smaller as the sound pressure level becomes smaller. The pulse width may be reduced.

  Thus, not only the voltage level control in the voltage controller (22) is performed, but also the pulse width of the PWM output in the PWM output device (21b) may be changed according to the running state.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

1 is a block diagram of a vehicle approach warning system including a vehicle approach warning device according to a first embodiment of the present invention. It is the figure which showed the voltage waveform after controlling the voltage level of a PWM output with a voltage control part, and the waveform of the electric current sent through a speaker through AMP. It is a figure which shows the voltage waveform of the PWM output in the case of controlling the electric current sent through a speaker only by the pulse width modulation by PWM control like the past, and the waveform of the electric current sent through a speaker.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram of a vehicle approach warning system including a vehicle approach warning device according to the present embodiment. With reference to this figure, the vehicle approach warning system including the vehicle approach warning device concerning this embodiment is demonstrated.

  As shown in FIG. 1, the vehicle approach alarm system includes various sensors 1 a and 1 b, a vehicle approach alarm device 2, and a speaker 3. In the vehicle approach warning system, the vehicle approach warning device 2 generates a sound from the speaker 3 which is a sounding body based on the running state detection signals transmitted from the various sensors 1a and 1b, thereby detecting the approach of the vehicle to the surrounding pedestrians. Alarm. Here, the vehicle approach warning device 2 is separated from the speaker 3, but the speaker 3 may be integrated with the vehicle approach warning device 2.

  The various sensors 1a and 1b constitute vehicle running state acquisition means. As the various sensors 1a and 1b, a vehicle speed sensor 1a and an accelerator opening sensor 1b are provided. The vehicle speed sensor 1a outputs a detection signal indicating the vehicle speed as a vehicle traveling state detection signal, and the accelerator opening sensor 1b outputs a detection signal indicating the accelerator opening as a vehicle traveling state detection signal. For this reason, the vehicle approach warning device 2 inputs a detection signal indicating the vehicle speed and the accelerator opening as a traveling state detection signal, and controls sound generation according to the traveling state of the vehicle such as the vehicle speed and the accelerator opening.

  The vehicle approach warning device 2 includes a microcomputer 21, a voltage control unit 22, a low-pass filter (hereinafter referred to as LPF) 23, and a power amplifier (hereinafter referred to as AMP) 24.

  The microcomputer 21 has a memory (not shown) and a digital / analog converter (hereinafter referred to as DAC) 21a and a PWM output device 21b. In the memory, in addition to data such as a sound generation control program and PCM, for example, a calculation formula or a map of a sound pressure level associated with the running state of the vehicle indicated by the running state detection signal, a PWM corresponding to the sound pressure level The output pulse width and the like are stored. Using this stored content, the microcomputer 21 calculates the sound pressure level corresponding to the traveling state of the vehicle indicated by the traveling state detection signal, for example, by reading it at every sampling period, and the calculated sound pressure level is output to the PWM output device 21. The PWM output corresponding to the sound pressure level is output from the PWM output device 21b. Basically, the sound pressure level is set so as to increase as the vehicle speed increases and as the accelerator opening increases. That is, as the vehicle approaches the pedestrian or the like faster, the sound pressure level is increased so that the approach of the vehicle to the pedestrian or the like is easily detected.

  The microcomputer 21 outputs a control signal for controlling the voltage generated by the voltage control unit 22 from the DAC 21a. Specifically, the control signal output from the DAC 21a is changed according to the sound pressure level calculated as described above, and is generated by the voltage control unit 22 when the sound pressure level to be generated increases. The control signal is changed so that the voltage level generated by the voltage control unit 22 decreases as the voltage level increases and the sound pressure level to be generated decreases.

  The voltage control unit 22 changes the voltage level of the PWM output based on the control signal transmitted from the DAC 21a, and changes the voltage level of the PWM output to the voltage level indicated by the control signal. Therefore, for example, the lower the sound pressure level that is generated, the lower the voltage level of the PWM output, and the voltage control unit 22 outputs the voltage level.

  The LPF 23 corresponds to filter means, and removes high frequency noise components and generates an output corresponding to the output of the PWM output device 21 b transmitted via the voltage control unit 22. For example, the LPF 23 stores a voltage corresponding to the output of the voltage control unit 22 in a built-in capacitor and outputs it to the AMP 24.

  The AMP 24 supplies a current corresponding to the output of the LPF 23 to the speaker 3 based on voltage application from a constant voltage source (not shown). The sound pressure generated by the speaker 3 is determined according to the magnitude (amplitude) of the current supplied from the AMP 24, and the magnitude of the current supplied from the AMP 24 is determined by the output waveform of the LPF 23 corresponding to the PWM output. For this reason, the current flowing through the AMP 24 is changed based on the adjustment of the voltage level in the voltage control unit 22. At this time, if the voltage control unit 22 does not adjust the voltage level, the current flowing through the AMP 24 is changed only by the pulse width of the PWM output of the PWM output device 21b. The pulse width becomes too small. However, since the voltage level of the PWM output is made variable by the voltage control unit 22, even when the current flowing through the AMP 24 is small, the pulse width of the PWM output does not need to be extremely reduced.

  FIG. 2 is a diagram illustrating a voltage waveform after the voltage level of the PWM output of the present embodiment is controlled by the voltage control unit 22 and a waveform of a current flowing through the speaker 3 through the AMP 24. FIG. 3 is a comparative example, and shows a voltage waveform of a PWM output and a waveform of a current flowing in the speaker when the current flowing in the speaker is controlled only by pulse width modulation by PWM control as in the prior art. is there. FIG. 2 shows the state when the sound pressure level changes according to the running state. In practice, the pulse width of the PWM output also changes according to the running state. The pulse width of the PWM output is not changed so that the image of the voltage level control at 22 is easy.

  When the current flowing through the speaker is controlled only by pulse width modulation by PWM control as shown in FIG. 3, the speaker is reduced as the sound pressure level decreases from 100% to 50%, 25%, and 12.5%. The current flowing through the current decreases, and the pulse width of the PWM output for generating the current gradually decreases. When the sound pressure level is reduced to, for example, 25% or less, the pulse width of the PWM output becomes extremely small, and the current waveform flowing through the speaker does not become smooth, but changes in a stepped manner. . That is, since the pulse width of the PWM output becomes extremely small and the S / N ratio decreases, such a phenomenon occurs. For this reason, the pronunciation becomes insufficient, and there is a possibility that the pronunciation cannot be performed.

  On the other hand, when control as in this embodiment is performed, as shown in FIG. 2, even if the sound pressure level drops from 100% to 50%, 25%, and 12.5%, the voltage of the PWM output By reducing the level by the voltage control unit 22, the pulse width of the PWM output can be prevented from becoming extremely small. For this reason, the waveform of the current flowing through the speaker 3 becomes smooth and can have a desired amplitude. That is, since the pulse width of the PWM output does not become extremely small, it is possible to suppress a decrease in the S / N ratio, and the current waveform passed through the speaker 3 can be kept smooth. For this reason, it is possible to prevent the sound generation from becoming insufficient, and the sound from the speaker 3 can reliably warn the vicinity of a pedestrian or the like of the approach of the vehicle.

  Also, when performing fade-in / fade-out control, the sound generation at a desired sound pressure is gradually changed from 0% to 100% when sound generation is started from the sound generation stop state. When the sound generation at the desired sound pressure is gradually changed from the 100% state to the 0% state when changing from the state to the sound generation stop state, the voltage level of the output of the voltage control unit 22 is gradually increased or decreased. In this way, a control signal is sent to the voltage control unit 22. Thereby, also when making a sound pressure extremely small in fade-in / fade-out control, it can suppress that S / N ratio falls, and the said effect can be acquired.

  As described above, according to the present embodiment, the voltage level of the PWM output is changed by the voltage control unit 22 in accordance with the generated sound pressure. Therefore, as in the case where the sound pressure level is controlled only by the pulse width of the PWM output, the S / N ratio is lowered and the sound pressure becomes insufficient because the pulse width of the PWM output becomes extremely small. Can be prevented. In the case of such a control mode, it is not necessary to increase the carrier frequency of the PWM output device 21b as a measure for improving the S / N ratio. The problem of radiation noise due to the contradiction can be prevented from occurring as in the case of increasing the value. For this reason, the effect that the countermeasure circuit of a radiation noise can be simplified compared with the former is also acquired.

(Other embodiments)
In the above embodiment, FIG. 2 is shown as a case where it is assumed that the voltage control unit 22 changes the output voltage level in the range of 0 to a predetermined voltage. However, when the voltage lower limit value at which the voltage level can be controlled by the voltage control unit 22 is a value larger than 0, it may be performed within the range of the voltage lower limit value to the voltage upper limit value.

  In the above embodiment, the pulse width of the PWM output from the PWM output device 21b is changed according to the running state. However, only the voltage level control in the voltage control unit 22 may be performed. .

DESCRIPTION OF SYMBOLS 1a Vehicle speed sensor 1b Accelerator opening sensor 2 Vehicle approach warning device 3 Speaker 21 Microcomputer 21a DAC
21b PWM output device 22 Voltage control unit 23 LPF
24 AMP

Claims (3)

In the vehicle approach warning device that warns the approach of the vehicle by controlling the sound pressure of the sound from the sounding body (3) mounted on the vehicle,
A memory for storing a relationship of sound pressure levels corresponding to the driving state in association with the driving state of the vehicle, and a driving state detection signal indicating the driving state of the vehicle are input, and the driving state detection signal indicates the A control signal output unit (21a) for calculating a sound pressure level corresponding to the running state of the vehicle and outputting a control signal corresponding to the sound pressure level, and for generating sound by the sounding body (3) A microcomputer (21) having a PWM output device (21b) for generating a PWM output;
A voltage controller (22) for changing and outputting a voltage level of the PWM output from the PWM output device (21b) based on a control signal from the control signal output unit (21a);
Filter means (23) for removing and outputting a noise component from the PWM output whose voltage level has been changed by the voltage control unit (22);
A vehicle approach alarm device comprising: an amplifier (24) for causing a current corresponding to the output of the filter means (23) to flow through the sounding body (3). The control signal output unit (21a) outputs the control signal indicating that the sound pressure level is increased as the approach of the vehicle becomes faster based on the traveling state of the vehicle indicated by the traveling state detection signal;
2. The vehicle approach warning device according to claim 1, wherein the power supply control unit (22) decreases the voltage level of the PWM output from the PWM output device (21 b) as the sound pressure level decreases. .   The PWM output device (21b) changes the pulse width of the PWM output based on the sound pressure level corresponding to the running state of the vehicle, and decreases the pulse width of the PWM output as the sound pressure level decreases. The vehicle approach alarm device according to claim 2.

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