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JP2012253568

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DESCRIPTION JP2012253568
The present invention provides a vehicle presence notification device capable of suppressing
power consumption and avoiding the increase in size and cost of parts. Inductive speaker driving
means (7) is switching means (9) for switching on / off of the conductive state of the inductive
speaker (2) by PWM sound signal (A) for inductive speaker. The control circuit 5 includes a
smoothing circuit 10 for smoothing the surge voltage generated by the switching of the
switching means 9. The capacitive speaker driving unit 8 is a class D amplifier, and drives the
capacitive speaker 3 using the secondary voltage C ′ smoothed by the smoothing circuit 10.
The surge energy generated by the switching of the switching means 9 is used for driving the
capacitive speaker 3 without discarding it. For this reason, power consumption can be
suppressed. In addition, it is possible to avoid the increase in size and cost of parts required to
discard the surge energy. Furthermore, the surge voltage can be added to the power supply
voltage to increase the drive voltage of the capacitive speaker 3. [Selected figure] Figure 1
Sound equipment
[0001]
The present invention comprises an inductive speaker (for example, an electromagnetic vehicle
horn etc.) that generates a sound wave by a change in generated magnetic force, and a capacitive
speaker (for example a piezoelectric speaker etc.) that generates a sound wave by a change in
stored charge. The present invention relates to a sound device used, and relates to a technology
suitable for use in a vehicle presence notification device which notifies the presence of a vehicle
to the surroundings by notification sound.
[0002]
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1
(Background Art) Background art will be described using a vehicle presence notification device.
There has been proposed a vehicle presence notification device for notifying the surroundings of
the presence of a quiet vehicle (such as an electric vehicle) by a notification sound (a pseudo
engine sound or the like) (see, for example, Patent Document 1). The vehicle presence
notification device disclosed in Patent Document 1 generates a notification sound from a
dynamic speaker (a speaker that directly emits an audible sound). The audible sound produced
directly by the dynamic speaker has the property of spreading to the surroundings. For this
reason, when an alarm sound is generated far from the traveling direction of the vehicle, an
alarm sound of a large sound pressure arrives in a direction (including the vehicle interior)
different from the traveling direction of the vehicle, and the alarm sound It becomes a factor of
noise.
[0003]
To solve this problem, a technique using a parametric speaker in place of the dynamic speaker
has been proposed (for example, Patent Document 2). The parametric speaker performs
ultrasonic modulation (sound modulation of the original sound) of the notification sound (audible
sound) and emits it from the ultrasonic speaker into the air, and the modulation component
included in the ultrasonic wave (sound wave that can not be heard by the ear) By selfdemodulating in the air on the way of propagation, a notification sound is generated at a place
away from the ultrasonic speaker. Since this parametric speaker is a technology that uses an
ultrasonic wave with high directivity (straight line), it is possible to generate a notification sound
only in front of the vehicle, and to avoid the problem that the notification sound causes noise it
can.
[0004]
However, the technology for generating an alarm sound using a parametric speaker generates an
alarm sound only in front of the vehicle, so no alarm sound is generated except in front of the
vehicle, and there is a vehicle other than in front of the vehicle Can not be notified by a
notification sound. Therefore, as a means for avoiding the above problems, a vehicle presence
notification device has been proposed which generates notification sound from both of the
dynamic speaker and the parametric speaker and complements the two defects (this is not a
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known technique).
[0005]
(Problem 1) Problem 1 will be described with reference to FIG. 12 and FIG. In addition, the same
reference numerals are given to the related items in the "embodiments for carrying out the
invention" and the "example" described later. Further, the technology shown in the following
problems is a technology disclosed to explain the difference from the present invention, and is
not a known technology.
[0006]
As a dynamic speaker, an inductive speaker 2 which is easy to drive a vibration system having a
large mass is generally used. In addition, as an ultrasonic speaker for generating an ultrasonic
wave in a parametric speaker, a capacitive speaker 3 in which a vibration system can be easily
provided is generally used.
[0007]
FIG. 12 shows an example of the control circuit 5 that performs energization control of the
inductive speaker 2 and the capacitive speaker 3; (a) PWM audio signal A for inductive speaker
as a drive signal of the inductive speaker 2 Two-channel PWM sound source 6 that generates an
audible sound PWM signal) and a capacitive speaker PWM audio signal E (ultrasonic wave PWM
signal) serving as a drive signal for the capacitive speaker 3; (b) for an inductive speaker
Inductive speaker drive means 7 for generating inductive speaker drive signal C by PWM audio
signal A; (c) Capacitive speaker drive means 8 for generating capacitive speaker drive signal F by
PWM audio signal E for capacitive speaker Equipped with.
[0008]
FIG. 13 shows the waveforms of the respective parts associated with the operation of the control
circuit 5, and from the top of FIG. 13 to the lower side, a PWM audio signal A for inductive
speaker which becomes a drive signal for the inductive speaker 2; Inductive speaker drive signal
C applied to the inductive speaker 2 Output waveform D of the inductive speaker 2 PWM audio
signal E for a capacitive speaker serving as a drive signal of the capacitive speaker 3 Provided to
the capacitive speaker 3 Capacitive speaker drive signal F, and output waveform G of the
capacitive speaker 3, and waveform signal H of a parametric reproduction sound in which an
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ultrasonic waveform is self-demodulated in air are shown.
[0009]
In FIG. 12, the battery 4 of 12 V is used as the main power supply, but as shown in FIG. 13, it is
assumed that the maximum amplitude of the capacitive speaker drive signal F applied to the
capacitive speaker 3 is. +-. 30 V. explain.
The capacitive speaker drive means 8 mounted in the control circuit 5 of FIG. 12 is the capacitive
speaker 3 according to the PWM audio signal E for the capacitive speaker, as in the
“embodiment to carry out the invention” and the “embodiment” described later. It is a pushpull class D amplifier that switches between positive and negative voltages.
And the coil which is not shown in figure is provided in the output part of capacitive speaker
drive means 8 (class D amplifier), it operates as a series resonance circuit by a coil and capacitive
speaker 3, and resonance frequency is selected by the choice of the inductance of a coil. By
adjusting the carrier frequency of the capacitive speaker 3 (for example, 40 kHz) to obtain a
voltage width (. +-. 30 V) five times the supply voltage (12 V). Note that five times is a specific
example for explanation and can be changed.
[0010]
Here, the inductive speaker driving means 7 of FIG. 12 is a switching means 9 for switching on /
off of the conductive state of the inductive speaker 2 by the PWM audio signal A for inductive
speaker as in the present invention. As described above, by using the switching means 9 as the
inductive speaker driving means 7, (i) the notification sound can be generated from the horn for
the vehicle by intermittently controlling the switching means 9 with the PWM signal in a short
time. (Ii) A warning sound (warning sound) can be generated from the horn for a vehicle by
continuing the ON of the switching means 9. That is, both the notification sound and the alarm
sound can be generated from the vehicle horn. Further, since the switching means 9 has a simple
circuit configuration, the control circuit 5 can be simplified and the cost can be suppressed.
[0011]
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However, when the inductive speaker 2 is intermittently switched by the switching means 9, a
peak-like surge occurs in the inductive speaker drive signal C. In particular, when an
electromagnetic type vehicle horn is used as an example of the inductive speaker 2, a large surge
energy is generated in the inductive speaker drive signal C because the coil of the vehicular horn
has a large inductance.
[0012]
This surge generates hundreds of volts, which affects the surrounding vehicle electronics as radio
noise. Therefore, in order to prevent radio noise from being generated from the vehicle horn, it is
required to suppress the surge to several tens of volts. As means for removing the surge, it is
conceivable to provide a snubber circuit 100 as shown in FIG. However, the snubber circuit 100
dissipates the generated surge as heat. As a result, the power of the battery 4 can not be used
effectively, and the power consumption of the battery 4 increases.
[0013]
Furthermore, since the snubber circuit 100 is required to have a performance to discard the
surge energy as heat, a large and expensive component is required, and mounting the snubber
circuit 100 results in an increase in cost. In particular, when an electromagnetic type vehicle
horn is used as an example of the inductive speaker 2, the snubber circuit 100 needs a
particularly large, high-cost component in order to dispose the large surge energy as heat by the
snubber circuit 100. It causes the deterioration of the mountability of the control circuit 5 and
the cost increase.
[0014]
In the above, the problem in the case of using the switching means 9 for the inductive speaker
driving means 7 has been described. However, even if another means different from the
switching means 9 is used for the inductive speaker driving means 7, the same problem as
described above occurs. A specific example will be described in Problems 2 and 3.
[0015]
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(Problem 2) The inductive speaker driving means 7 of FIG. 14 is a class B amplifier 102 which
converts the inductive speaker PWM audio signal A into a voltage change by the filter 101 and
drives the inductive speaker 2. When the inductive speaker 2 is driven by the class B amplifier
102, although the above-described surge does not occur, electric energy corresponding to the
surge energy is consumed by the power amplification element (transistor or the like) configuring
the class B amplifier 102. That is, the power amplification element generates heat. For this
reason, the heat generation needs to be discarded using the heat sink 103.
[0016]
As described above, even if the B-class amplifier 102 is used as the inductive speaker driving
means 7, since the heat generation of the power amplification element is dissipated using the
heat sink 103, a part of the electric energy is wastefully consumed as heat. Further, the use of the
heat sink 103 causes the control circuit 5 to be upsized and causes an increase in cost.
[0017]
(Problem 3) The inductive speaker driving means 7 of FIG. 15 is a push-pull class D amplifier
104 which switches positive and negative voltages to the inductive speaker 2 by the inductive
speaker PWM audio signal A and applies the same. Since the class D amplifier 104 is excellent in
energy efficiency, the heat sink 103 (see the problem 2) may not be used. However, in order to
drive the inductive speaker 2 by the class D amplifier 104, it is necessary to provide a filter 105
composed of a coil and a capacitor at the output portion of the class D amplifier 104. In
particular, when an electromagnetic type vehicle horn is used as an example of the inductive
speaker 2, a large and expensive coil and capacitor corresponding to a large current are
necessary because the inductance of the coil mounted on the vehicle horn is large. The size of the
circuit 5 is increased and the cost is increased.
[0018]
JP, 2005-289175, A JP, 2011-050184, A
[0019]
The present invention has been made in view of the above problems, and an object thereof is to
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drive a capacitive speaker without discarding surge energy generated when switching on and off
the conductive state of the inductive speaker. It is an object of the present invention to provide
an acoustic device capable of suppressing power consumption by consuming electricity and
avoiding enlargement of parts and cost increase required for discarding surge energy.
[0020]
The inductive speaker driving means for driving the inductive speaker is a switching means, and
interrupts the conduction state of the inductive speaker by the PWM signal (PWM audio signal
for the inductive speaker).
A surge is generated in the conductive circuit of the inductive speaker as the switching means
switches on and off the conductive state of the inductive speaker.
Capacitive speaker driving means for driving the capacitive speaker drives the capacitive speaker
using a DC secondary voltage obtained by smoothing a surge voltage generated due to switching
of the switching means.
[0021]
(Effect 1 of the Invention) As described above, surge energy generated when switching on and off
the conductive state of the inductive speaker is utilized for driving the capacitive speaker without
discarding it. Thereby, the power consumption used to drive the capacitive speaker can be
suppressed, and as a result, the power consumption of the acoustic device can be suppressed.
[0022]
(Effect 2 of the Invention) In addition, since it consumes by driving a capacitive speaker without
discarding surge energy, it is possible to avoid upsizing and cost increase of parts required when
discarding surge energy. become.
[0023]
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(Effect 3 of the Invention) Furthermore, since the secondary voltage is a voltage obtained by
adding the surge voltage to the power supply voltage, the drive voltage of the capacitive speaker
is increased.
As a result, the sound pressure of the capacitive speaker can be increased. Alternatively, it is
possible to reduce the number of capacitive speakers used.
[0024]
[Means of claim 2] The switching means of claim 2 is a low side type that intermittently connects
between an inductive speaker connected to the positive potential of the main power supply (for
example, a battery etc.) and the earth potential {see FIG. a) see a.] The surge voltage due to the
switching of the switching means is generated on the positive potential side of the amplifier
circuit in the capacitive speaker driving means (see the waveform signal C in FIG. 3).
[0025]
[Means of claim 3] The switching means according to claim 3 is a high side type for switching
between the positive potential of the main power supply (for example, a battery etc.) and the
inductive speaker (see FIG. 4). Intermittent surge voltage is generated on the negative potential
side of the amplifier circuit in the capacitive speaker driving means (see the waveform signal C in
FIG. 5).
[0026]
According to a fourth aspect of the present invention, there is provided an acoustic device
according to the fourth aspect, wherein the PWM for a capacitive speaker is generated in
response to a change in secondary voltage caused by a change in a PWM voice signal for
inductive speaker (drive signal for the inductive speaker). A secondary voltage increase /
decrease correction means is used to correct the audio signal (drive signal of the capacitive
speaker) directly or indirectly.
As a result, it is possible to avoid the problem that fluctuation occurs in the reproduced sound by
the capacitive speaker due to the fluctuation (fluctuation) of the secondary voltage.
[0027]
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8
[Means of claim 5] The capacitive speaker according to claim 5 is a piezoelectric speaker using a
piezoelectric element displaced by a change in stored charge, and this piezoelectric speaker is an
ultrasonic speaker that generates an ultrasonic wave in a parametric speaker. It is used.
Thereby, it can utilize with a parametric speaker, without throwing away surge energy, and can
suppress the power consumption of a parametric speaker.
[0028]
[Means of claim 6] The inductive speaker according to claim 6 is a dynamic speaker using a coil
whose generated magnetic force changes according to a change in applied voltage, and this
dynamic speaker is an alarm sound when the horn switch is operated. This is an electromagnetic
vehicle horn that generates (warning noise). Since the vehicle horn is used as the inductive
speaker, the cost can be reduced, and the mountability to the vehicle can be enhanced.
[0029]
[Means of Claim 7] The acoustic device of Claim 7 is used for a vehicle presence notification
device which generates a notification sound to the outside of a vehicle to notify the presence of a
vehicle.
[0030]
It is a schematic block diagram (basic block diagram of the invention) of an electric circuit of an
acoustic device using switching means as inductive speaker driving means.
(A) Schematic block diagram of low side type booster circuit, (b) Schematic block diagram of
booster circuit used for comparison (Embodiment 1). It is a time chart for operation explanation
using a waveform signal (Embodiment 1). It is a schematic block diagram of a high side type
booster circuit (Embodiment 2). It is a time chart for operation explanation using a waveform
signal (Embodiment 2). It is the schematic of a vehicle presence alerting | reporting apparatus
(Example 1). It is a vehicle mounting view of an ultrasonic speaker and the horn for vehicles
(Example 1). (A) Sectional drawing which shows the structure of the horn for vehicles, (b) It is a
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9
perspective view of the horn for vehicles in which the ultrasonic speaker was mounted (Example
1). It is the schematic of a vehicle presence alerting | reporting apparatus (Example 2). It is the
schematic of a vehicle presence alerting | reporting apparatus (Example 3). It is the schematic of
a vehicle presence alerting | reporting apparatus (Example 4). It is a schematic block diagram of
an electric circuit of an acoustic device using switching means as inductive speaker driving
means (Example 1). It is a time chart for operation explanation using a waveform signal
(reference example 1). It is a schematic block diagram of an electric circuit of an acoustic device
using a class B amplifier as inductive speaker driving means (Example 2). It is a schematic block
diagram of an electric circuit of an acoustic device using a push-pull class D amplifier as
inductive speaker driving means (Example 3).
[0031]
An embodiment of the present invention will be described with reference to FIGS. The acoustic
device 1 of the present invention comprises: (a) an inductive speaker 2 that generates a sound
wave by a change in generated magnetic force; (b) a capacitive speaker 3 that generates a sound
wave by a change in stored charge; And a control circuit 5 for controlling operation of the
inductive speaker 2 and the capacitive speaker 3 using the power supplied from the control unit.
[0032]
The control circuit 5 includes (d) a PWM audio signal A for inductive speaker which is a drive
signal for the inductive speaker 2 and a PWM audio signal E for capacitive speaker which is a
drive signal for the capacitive speaker 3. (E) drive the capacitive speaker 3 by the inductive
speaker drive means 7 for driving the inductive speaker 2 by the PWM sound signal A for the
inductive speaker, (f) drive the capacitive speaker 3 by the PWM sound signal E for the
capacitive speaker Capacitive speaker driving means 8.
[0033]
And the inductive speaker drive means 7 is switching means 9 which performs on-off of the
energized state of the inductive speaker 2 by PWM sound signal A for inductive speakers which
carries out PWM modulation of the audible sound signal.
The control circuit 5 further includes a smoothing circuit 10 for smoothing a surge voltage
generated by the switching of the switching means 9. Further, the capacitive speaker driving
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means 8 uses the voltage smoothed by the smoothing circuit 10 (a secondary voltage C 'of direct
current obtained by smoothing a surge voltage generated by switching on and off the switching
means 9). To drive.
[0034]
Thus, it is used for driving of the capacitive speaker 3 by utilizing for the drive of the capacitive
speaker 3 without discarding the surge energy generated when the conduction state of the
inductive speaker 2 is interrupted by the switching means 9. Power consumption can be reduced.
In addition, since the capacitive speaker 3 is consumed by driving the capacitive speaker 3
without discarding the surge energy, it becomes possible to avoid the increase in size and cost of
parts necessary for discarding the surge energy, and thus the control circuit 5 can realize
miniaturization and cost reduction.
[0035]
Furthermore, since the secondary voltage C '(voltage smoothed by the smoothing circuit 10) is a
voltage obtained by adding the surge voltage to the power supply voltage, the drive voltage of
the capacitive speaker 3 is increased. As a result, the sound pressure of the capacitive speaker 3
can be increased. Alternatively, when a plurality of capacitive speakers 3 are used, the number of
capacitive speakers 3 used can be reduced. A specific example in which the drive voltage of the
capacitive speaker 3 is increased by the surge voltage will be described using “first and second
embodiments”. The first embodiment shows an example of boosting on the low side, and the
second embodiment shows an example of boosting on the high side.
[0036]
Embodiment 1 Embodiment 1 will be described with reference to FIGS. 2A and 3. The switching
means 9 according to the first embodiment is a low side type switching between the inductive
speaker 2 connected to the positive potential (12 V as a specific example) of the battery 4 (an
example of the main power supply) and the ground potential. The surge voltage due to the
intermittent operation of 9 is generated on the positive potential side of the amplifier circuit in
the capacitive speaker driving means 8.
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[0037]
Here, FIG. 3 shows a specific example of the waveform of each part along with the operation of
the control circuit 5, and from the top of FIG. PWM voice signal A, Inductive speaker drive signal
C given to the inductive speaker 2, Output waveform D of the inductive speaker 2, Secondary
voltage C '(Battery voltage + B smoothed voltage α for positive side surge Applied voltage), PWM
audio signal E for capacitive speaker serving as a drive signal of capacitive speaker 3, capacitive
speaker drive signal F (ultrasonic drive signal) applied to capacitive speaker 3, capacitive speaker
3 The output waveform G of {circle around (1)} indicates the waveform signal H of a parametric
reproduction sound whose ultrasonic waveform is self-demodulated in air.
[0038]
By switching on and off the conduction state of the inductive speaker 2 by the PWM audio signal
A for inductive speaker by the switching means 9, the surge voltage generated on the positive
potential side is added to the battery voltage + B without being discarded.
As a result, the secondary voltage C ′ smoothed by the smoothing circuit 10 is boosted, and the
drive voltage of the capacitive speaker 3 is increased. Thereby, the sound pressure of the
capacitive speaker 3 can be increased. Alternatively, the number of capacitive speakers 3 used
can be reduced.
[0039]
(Comparative Description) In addition, unlike the present invention, it is conceivable to use a
booster circuit as a means for increasing the drive voltage of the capacitive speaker 3. A specific
example of a general booster circuit is shown in FIG. 2 (b). In FIG. 2B, the choke coil (inductance)
X1 disposed in the voltage supply circuit is intermittently switched by the switching means 9,
and a symbol X2 in the figure indicates an intermittent signal (PWM for boosting) to the
switching means 9. It is a switching signal generation unit that provides a signal A ′).
[0040]
When the drive voltage of the capacitive speaker 3 is increased using the existing booster circuit
shown in FIG. 2B, it is necessary to separately mount a dedicated booster circuit, which causes a
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cost increase. On the other hand, in the present invention, since the drive voltage of the
capacitive speaker 3 is increased by using the surge voltage without discarding it, it is not
necessary to separately mount a dedicated booster circuit. That is, according to the present
invention, the drive voltage of the capacitive speaker 3 can be increased without separately
mounting a dedicated booster circuit.
[0041]
In addition, although secondary voltage C 'is about 18V, it demonstrates that the largest
amplitude of the capacitive speaker drive signal F given to the capacitive speaker 3 is +/- 45V.
The capacitive speaker driving means 8 in this embodiment is a push-pull class D amplifier which
applies positive and negative voltages to the capacitive speaker 3 by switching the capacitive
speaker PWM audio signal E. And the coil which is not shown in figure is provided in the output
part of capacitive speaker drive means 8 (class D amplifier), it operates as a series resonance
circuit by a coil and capacitive speaker 3, and resonance frequency is selected by the choice of
the inductance of a coil. Is adjusted to the carrier wave frequency (for example, 40 kHz) of the
capacitive speaker 3 to obtain a voltage width (. +-. 45 V) five times the secondary voltage C '(18
V). In addition, 5 times shows a specific example and can be changed suitably.
[0042]
Second Embodiment A second embodiment will be described with reference to FIGS. 4 and 5. The
switching means 9 of the second embodiment is a high side type that intermittently connects
between the plus potential (12 V as a specific example) of the battery 4 (an example of the main
power supply) and the inductive speaker 2. A voltage is generated on the negative potential side
of the amplifier circuit in the capacitive speaker driving means 8.
[0043]
Here, FIG. 5 shows a specific example of the waveform of each part according to the operation of
the control circuit 5, and from the top of FIG. PWM voice signal A, Inductive speaker drive signal
C applied to the inductive speaker 2, Output waveform D of the inductive speaker 2, Secondary
voltage C '(battery voltage + B and smoothing voltage of negative side surge-α (A differential
voltage of the capacitive speaker 3), a PWM voice signal E for a capacitive speaker serving as a
drive signal of the capacitive speaker 3, a capacitive speaker drive signal F given to the capacitive
speaker 3, an output waveform G of the capacitive speaker 3, The ultrasonic waveform shows the
waveform signal H of the parametric reproduction sound self-demodulated in air.
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[0044]
By interrupting the conduction state of the inductive speaker 2 by the switching means 9 with
the PWM audio signal A for inductive speaker, the surge voltage generated on the negative
potential side is added to the negative side of the battery voltage (12 V) without being discarded
Ru.
As a result, the voltage width of the secondary voltage C ′ smoothed by the smoothing circuit
10 is increased, and the drive voltage of the capacitive speaker 3 is increased. Thereby, the sound
pressure of the capacitive speaker 3 can be increased. Alternatively, the number of capacitive
speakers 3 used can be reduced.
[0045]
In the following, a specific example (embodiment) in which the present invention is applied to the
vehicle presence notification device 1 will be described with reference to the drawings. It is
needless to say that the following examples show specific examples, and the present invention is
not limited to the examples. In the following examples, the same reference numerals as those in
the above-described “embodiment of the present invention” denote related items.
[0046]
Example 1 Example 1 will be described with reference to FIGS. 6 to 8. The vehicle presence
notification device 1 notifies presence of a vehicle by a notification sound (audible sound: pseudo
engine sound etc.), for example, a vehicle (electric car, fuel cell car etc.) not equipped with an
engine (internal combustion engine), running Even when the vehicle is a vehicle that may stop
the engine during a stop (such as a hybrid vehicle), a vehicle that may stop the engine during a
stop (such as an idle stop vehicle), or even an engine vehicle It is to be installed on vehicles such
as
[0047]
This vehicle presence notification device 1:-Vehicle horn 2 (an example of an inductive speaker)
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using as a dynamic speaker that emits notification sound in the audible band directly toward the
outside of the vehicle;-Ultrasonic modulation of a waveform signal that forms notification sound
And a control circuit 5 for controlling the operation of the vehicle horn 2 and the parametric
speaker 11.
[0048]
(Description of Vehicle Horn 2) The vehicle horn 2 is an electromagnetic horn that generates an
alarm when the horn switch 12 (for example, a horn button of the steering wheel) is operated by
an occupant, as shown in FIG. Thus, it is fixedly disposed between the front grille 13 provided at
the front of the vehicle and the heat exchanger 14 (radiator, air conditioner heat exchanger, etc.)
disposed therein.
[0049]
A specific example of the vehicle horn 2 will be described with reference to FIG. 8 (a).
The horn 2 for a vehicle: a coil 21 generating a magnetic force by energization; a fixed iron core
22 (magnetic attraction core) generating a magnetic attraction force by the magnetic force of the
coil 21; and a central portion of a diaphragm 23 (diaphragm) Movable iron core 24 (movable
core) supported and supported movably toward fixed iron core 22; · Fixed by moving movable
iron core 24 toward fixed iron core 22 in conjunction with the movement of movable iron core
24 A movable contact 26 which is separated from the contact 25 and de-energizes the coil 21;
[0050]
Then, a self-excitation voltage (voltage of 8 V or more) equal to or higher than a threshold value
is applied as a direct current to the conduction terminal (terminal connected to both ends of the
coil 21) of the vehicle horn 2 The movable core 24 is magnetically attracted to the fixed core 22,
and the movable contact 26 moves away from the fixed contact 25 to stop the energization of the
coil 21. (ii) The diaphragm 23 moves the action of the return spring by the energization stop. The
movable core 24 is returned to the initial position by being applied to the iron core 24, and the
fixed contact 25 and the movable contact 26 come into contact, and the restoring operation in
which the energization of the coil 21 is resumed is continuously repeated.
[0051]
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That is, the fixed contact 25 and the movable contact 26 constitute a current interrupter 27 for
interrupting the conduction circuit of the coil 21.
As described above, the intermittent operation of the coil 21 (intermittent generation of the
magnetic attraction force of the fixed iron core 22) occurs, so that the diaphragm 23 vibrates
together with the movable iron core 24 and the vehicle horn 2 generates an alarm sound.
[0052]
On the other hand, the vehicle horn 2 can be used as a dynamic speaker by giving the coil 21 a
drive signal of a separately excited voltage (for example, a voltage of less than 8 V) lower than
the self-excitation voltage.
Alternatively, even if it is a self-excitation voltage, the vehicular horn 2 is used as a dynamic
speaker by quickly controlling the energization of the coil 21 (PWM control etc.) within a short
period of time in which no interruption occurs in the current interrupter 27. be able to. In this
embodiment, the latter (using the self-excitation voltage to quickly control the coil 21
intermittently) is employed, and the vehicle horn 2 is used as a dynamic speaker.
[0053]
The vehicle horn 2 shown in this embodiment is provided with a spiral horn 28 (spiral-shaped
trumpet member: spiral-shaped acoustic tube) that emits an alarm sound due to the vibration of
the diaphragm 23 and enhances the alarm sound. It is mounted on the vehicle so that the
opening of the spiral horn 28 faces downward (road surface) so that the notification sound
generated from the horn 2 reaches the periphery of the vehicle substantially equally. The vehicle
horn 2 is not limited to the one provided with the spiral horn 28 and may be a disc-type horn not
using the spiral horn 28.
[0054]
(Description of Parametric Speaker 11) The ultrasonic speaker 31 used for the parametric
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speaker 11 generates air vibration of a frequency (20 kHz or higher) higher than the human
audible range, and emits ultrasonic waves toward the front of the vehicle To be installed in the
vehicle. Specifically, the ultrasonic speaker 31 of this embodiment is provided on the front
surface of the vehicle horn 2 (the surface facing the front of the vehicle when mounted on the
vehicle, for example, the spiral horn 28), and the front grille 13 and the heat exchanger 14 are
provided. By mounting the vehicle horn 2 therebetween, the ultrasonic speaker 31 is mounted on
the vehicle in a state where the radiation direction of the ultrasonic wave is directed to the front
of the vehicle.
[0055]
As shown in FIG. 7, the ultrasonic speaker 31 of this embodiment is equipped with a plurality of
piezoelectric speakers 3 (an example of a capacitive speaker) for generating ultrasonic waves,
and the plurality of piezoelectric speakers 3 are housings. It is mounted on a vehicle in a state of
being housed inside the 32. The plurality of piezoelectric speakers 3 are mounted on a support
plate 33 fixedly disposed inside the housing 32, and collectively arranged as a speaker array.
Each piezoelectric speaker 3 includes a piezoelectric element (piezoelectric element) which is
expanded and contracted in response to a change in applied voltage (stored charge), and a
diaphragm which is driven by the expansion and contraction of the piezoelectric element to
generate compression waves in air. It is configured to use.
[0056]
The housing 32 may be provided integrally with the member forming the vehicle horn 2 or may
be provided separately and attached to the vehicle horn 2. The ultrasonic radiation port of the
housing 32 is provided with a waterproof means for preventing rainwater from intruding into the
mounting portion of each piezoelectric speaker 3. As an example of this waterproofing means, in
this embodiment, an ultrasonic-permeable waterproof sheet 34 covering the ultrasonic wave
radiation port and a louver 35 disposed on the front surface of the waterproof sheet 34 are
provided {FIG. In a), the waterproof sheet 34 and the louver 35 are omitted.
[0057]
(Description of Control Circuit 5) The control circuit 5 is configured using a microcomputer 41
(abbreviated to a microcomputer) as shown in FIG. 7, and for example, as shown in FIG. 7, the
control circuit 5 is a vehicle. It arrange | positions inside the horn 2 for horns (specifically, inside
of a horn housing) (it is not limited).
09-05-2019
17
[0058]
The control circuit 5 will be specifically described with reference to FIG.
The microcomputer 41 operates with 5 V (voltage suitable for the operation of the
microcomputer 41) generated by step-down from the battery voltage. The microcomputer 41 is
supplied with a vehicle speed signal (vehicle speed pulse etc.) from the operation signal of the
horn switch 12 or the ECU 42 (abbreviation of engine control unit) etc. A control program for
changing the tone of the notification sound (for example, the tone according to the vehicle speed
of the pseudo engine sound) according to the vehicle speed or the like is provided.
[0059]
Specifically, the main part configuration of the microcomputer 41 will be described. The
microcomputer 41 includes the functions of the two-channel PWM sound source 6 described
above, and includes a period measurement unit 51, a timer counter 52, a voice memory 53, an
inductive speaker PWM modulation unit 54, and a capacitive speaker PWM modulation unit 55.
It is configured with. The cycle measurement unit 51 measures the cycle of the vehicle speed
signal (vehicle speed pulse or the like) given from the ECU 42 to calculate the vehicle speed.
[0060]
In the voice memory 53, voice data forming a notification sound according to the vehicle speed
(specifically, a pseudo engine sound according to the vehicle speed) is stored. Then, voice data
corresponding to the vehicle speed is selected and sequentially output by the timer counter 52.
Specifically, the timer counter 52 outputs the audio data of the audio memory 53 to both the
inductive speaker PWM modulator 54 and the capacitive speaker PWM modulator 55 at the
same rate as the sampling rate at the time of recording. That is, the “waveform signal forming
the notification sound” corresponding to the vehicle speed is output to the inductive speaker
PWM modulator 54 and the capacitive speaker PWM modulator 55.
[0061]
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18
The inductive speaker PWM modulation unit 54 generates an inductive speaker PWM sound
signal A (a drive signal of the vehicle horn 2) formed by PWM-modulating the “waveform signal
forming the notification sound”. Here, a frequency of 20 kHz or more is used as the frequency
(pulse generation frequency) of the PWM modulation in the inductive speaker PWM modulation
unit 54 so that the sound of the frequency used for the PWM modulation is not reproduced from
the vehicle horn 2 It is done.
[0062]
The capacitive speaker PWM modulation unit 55 performs PWM modulation on the capacitive
speaker PWM audio signal E (the ultrasonic speaker 31) by PWM-modulating “the DSBmodulated waveform signal forming the notification sound” using PWM modulation technology.
Drive signal). Here, as the frequency (generation frequency of the pulse) of PWM modulation in
the PWM modulation unit 55 for capacitive speaker, a frequency obtained by multiplying the
resonance frequency of the piezoelectric speaker 3 by a positive number is used. It is provided to
occur.
[0063]
In addition to the microcomputer 41 described above, the control circuit 5 also includes: an
inductive speaker drive means 7 for driving the vehicle horn 2 (inductive speaker); and each
piezoelectric speaker 3 in the ultrasonic speaker 31 (capacitive speaker And a smoothing circuit
10 for smoothing a surge voltage generated by the switching of the switching means 9.
[0064]
The inductive speaker driving means 7, as described in the “embodiment of the invention,”
intermittently interrupts the conduction state of the vehicle horn 2 by the PWM audio signal A
for inductive speaker formed by PWM modulation of an audible sound signal. Switching means 9
(semiconductor switching elements such as bipolar transistors and FETs) which perform the
above-described process, and may be the low side type shown in the “first embodiment” or the
high side type shown in the “second embodiment” Also good.
[0065]
The capacitive speaker driving means 8 is a push-pull class D amplifier (a capacitive speaker
PWM audio signal E for each piezoelectric speaker 3 for switching between positive and negative
09-05-2019
19
voltages applied to each piezoelectric speaker 3 by the capacitive speaker PWM audio signal E).
Amplifier that includes a piezo charging switching unit that turns on and off one pole, and a
piezo discharging switching unit that turns on and off the other pole of each piezoelectric
speaker 3 by the reverse signal obtained by inverting the capacitive speaker PWM audio signal E)
It is.
[0066]
As described above, the smoothing circuit 10 smoothes the surge voltage generated by the
switching of the switching means 9 and includes at least a diode 56 for preventing backflow and
a capacitor 57 for suppressing voltage fluctuation (reference numeral , Figure 2 and Figure 4).
Then, the secondary voltage C 'smoothed by the smoothing circuit 10 is applied to the capacitive
speaker driving means 8 (class D amplifier).
The capacitive speaker driving means 8 (class D amplifier) controls charging and discharging of
the respective piezoelectric speakers 3 using the secondary voltage C ′ smoothed by the
smoothing circuit 10.
[0067]
In the microcomputer 41, while the horn switch 12 is turned on, the switching means 9 is
continuously turned on to apply the battery voltage to the vehicle horn 2 and generate an alarm
sound from the vehicle horn 2 Is provided.
Further, the microcomputer 41 is provided with a function of giving priority to "ON of the horn
switch 12" over "informing sound generation condition", and always generating an alarm sound
from the vehicle horn 2 when the horn switch 12 is turned ON. It is done.
[0068]
(Operation of Vehicle Presence Informing Device 1) When the driving state of the vehicle
conforms to the generation condition of the notification sound, “waveform signal forming
notification sound (simulated engine sound etc.) according to the vehicle speed is extracted from
09-05-2019
20
the voice memory 53, i) The inductive speaker PWM audio signal A formed by PWM-modulating
the "waveform signal forming the notification sound" from the inductive speaker PWM
modulator 54 is applied to the switching means 9, and (ii) the capacitive speaker PWM A
capacitive speaker PWM audio signal E obtained by ultrasonically modulating “waveform signal
forming notification sound” from the modulation unit 55 by PWM modulation is applied to the
capacitive speaker driving means 8.
[0069]
Since the switching means 9 is interrupted by the inductive speaker PWM audio signal A, the
"announcement sound" of the audible sound is directly emitted from the vehicle horn 2 around
the vehicle.
On the other hand, when the capacitive speaker drive means 8 drives the respective piezoelectric
speakers 3 of the ultrasonic speaker 31 by the capacitive speaker PWM audio signal E, an
ultrasonic wave formed by DSB modulating the notification sound is emitted forward of the
vehicle . As the ultrasonic waves emitted to the front of the vehicle propagate through the air, the
ultrasonic waves having a short wavelength are distorted and blunted due to the viscosity of the
air and the like. As a result, the modulation component contained in the ultrasonic wave is selfdemodulated in the air on the way of propagation, and as a result, the "announcement sound" is
reproduced in front of the vehicle.
[0070]
(Effect 1 of Embodiment 1) When the vehicle presence informing apparatus 1 of this
embodiment generates an alarm sound from the vehicle horn 2, the surge energy generated
when the vehicle horn 2 is interrupted by the switching means 9 Is used as a power source of the
capacitive speaker driving means 8 (class D amplifier), and is utilized for driving each
piezoelectric speaker 3 in the ultrasonic speaker 31. As a result, the power consumption used to
drive the ultrasonic speaker 31 can be suppressed, and as a result, the battery consumption
accompanying the operation of the vehicle presence notification device 1 can be suppressed.
[0071]
(Effect 2 of Embodiment 1) The vehicle presence notification device 1 of this embodiment
consumes by driving the ultrasonic speaker 31 without discarding the surge energy, and
09-05-2019
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therefore, the parts necessary for discarding the surge energy It becomes possible to avoid
upsizing and cost increase, and the control circuit 5 can be miniaturized and cost-reduced, and
the mountability to a vehicle can be improved.
[0072]
(Effect 3 of Embodiment 1) Since the secondary voltage C ′ smoothed by the smoothing circuit
10 is a voltage obtained by adding the surge voltage smoothed to the battery voltage, the drive
voltage of the ultrasonic speaker 31 is increased.
Thereby, the sound pressure (sound pressure of an ultrasonic wave) which ultrasonic speaker 31
generates can be enlarged. Alternatively, the number of piezoelectric speakers 3 used for the
ultrasonic speaker 31 can be reduced, and the cost of the ultrasonic speaker 31 can be
suppressed.
[0073]
Since the secondary voltage C 'is boosted using the surge voltage, the microcomputer 41 has a
function of adjusting the secondary voltage C' by offsetting the pulse width of the PWM audio
signal A for inductive speaker. It may be provided.
[0074]
(Effect 4 of Embodiment 1) In this embodiment, the vehicle horn 2 that generates an alarm sound
(warning sound) when the horn switch 12 is pressed is used as the “inductive speaker that
generates an alarm sound”.
For this reason, it is not necessary to separately mount the "inductive speaker that generates a
notification sound" on the vehicle, and the cost can be suppressed, and the vehicle mountability
can be ensured.
[0075]
09-05-2019
22
Second Embodiment A second embodiment will be described with reference to FIG. As described
above, the secondary voltage C 'used for the power supply of the capacitive speaker driving
means 8 utilizes the surge voltage generated by the switching of the switching means 9 due to
the inductive speaker PWM audio signal A. For this reason, fluctuation (fluctuation) occurs in the
secondary voltage C 'in accordance with the change of the "waveform signal forming the
notification sound (simulated engine sound etc.)". Fluctuation occurs in the secondary pressure C
', which causes fluctuation in the sound pressure generated by the ultrasonic speaker 31, and as
a result, fluctuation occurs in the parametric reproduction sound by the parametric speaker 11.
[0076]
This defect is explained concretely. When the booster circuit shown in FIG. 2 (b) of the second
embodiment is used, the boosted secondary voltage C 'is fed back to the switching signal
generator X2, and the boosting PWM signal A intermittently switching the switching means 9
The boosted voltage can be controlled to be constant by changing the duty ratio of '. However, in
the vehicle presence notification device 1, the PWM signal for switching the switching means 9
intermittently is the PWM audio signal A for the inductive speaker for generating the notification
sound from the vehicle horn 2, so the secondary voltage C ' There is a problem that the duty ratio
of the PWM audio signal A for inductive speaker can not be changed by feedback control in
order to make constant.
[0077]
With respect to the above problems, in the vehicle presence notifying apparatus 1 according to
the second embodiment and the third embodiment and the fourth embodiment described later,
fluctuation in the parametric reproduction sound by the parametric speaker 11 occurs due to the
fluctuation of the secondary voltage C '. To avoid. Specifically, the control circuit 5 corrects the
capacitive speaker PWM audio signal E directly or indirectly according to the change of the
secondary voltage C 'generated with the change of the inductive speaker PWM audio signal A.
The secondary voltage increase / decrease correction means 61 is used.
[0078]
The secondary voltage increase / decrease correction means 61 of the second embodiment will
be described. The secondary voltage increase / decrease correction means 61 of the second
09-05-2019
23
embodiment real-time "waveform signal forming notification sound" output from the voice
memory 53 to the capacitive speaker PWM modulator 55 according to the fluctuation of the
secondary voltage C '. To make a feedback correction.
[0079]
Specifically, the secondary voltage increase / decrease correction means 61 of the second
embodiment monitors the secondary voltage C 'smoothed by the smoothing circuit 10 with the
microcomputer 41, and (i) the monitored secondary voltage C' rises Correct the sound pressure
component (voltage) of the “waveform signal that forms the notification sound” given from the
voice memory 53 to the capacitive speaker PWM modulation unit 55 small (ii) conversely, the
monitored 2 When the next voltage C 'falls, the sound pressure component (voltage) of the
"waveform signal forming the notification sound" given from the voice memory 53 to the
capacitive speaker PWM modulator 55 is largely corrected, and the secondary voltage It cancels
out the variation of the parametric reproduction sound caused by the variation of C '.
[0080]
In order to perform this correction, the microcomputer 41 of the second embodiment (a) AD
converter 62 (abbreviation of analog-digital converter) for reading the secondary voltage C ′
smoothed by the smoothing circuit 10 by the microcomputer 41 (B) A correction value for
canceling the fluctuation of the secondary voltage C 'read by the AD converter 62 is calculated,
and this correction value is used as the sound pressure component of the "waveform signal
forming an alarm sound" output from the voice memory 53. And a mixing unit 63 to be added.
[0081]
In the second embodiment, the secondary voltage C ′ is monitored to correct the “waveform
signal forming the notification sound” applied to the capacitive speaker PWM modulator 55 in
real time. The output signal of the speaker driving means 8 (the driving signal given to the
ultrasonic speaker 31) may be monitored to correct in real time the "waveform signal forming a
notification sound" given to the capacitive speaker PWM modulation unit 55. .
[0082]
Third Embodiment A third embodiment will be described with reference to FIG.
The secondary voltage increase / decrease correction means 61 of the second embodiment needs
09-05-2019
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to calculate the correction value in real time according to the fluctuation of the secondary voltage
C '.
For this reason, the microcomputer 41 is required to have a high processing capability.
On the other hand, the secondary voltage increase / decrease correction means 61 of the third
embodiment does not calculate the correction value in real time according to the fluctuation of
the secondary voltage C ', and To overwrite the “waveform signal that makes up the corrected
notification sound” in anticipation of an increase or decrease in the secondary voltage C ′,
eliminating real-time correction and adopting an inexpensive microcomputer 41 with low
processing capacity It is
[0083]
An example of the procedure for overwriting the voice memory 53 with the “waveform signal
forming the corrected notification sound” will be described with reference to FIG. When an
instruction to start the correction is given to the microcomputer 41 by the mixing switch 64
which can be operated arbitrarily, the control circuit 5 sequentially generates an alarm sound (a
pseudo engine sound etc.) corresponding to the vehicle speed stored in the sound memory 53.
And reproduce from the ultrasonic speaker 31.
[0084]
At this time, as in the second embodiment, the AD converter 62 is used to monitor the secondary
voltage C ′ smoothed by the smoothing circuit 10. Then, “the waveform signal (pre-correction
signal) forming the notification sound” given from the voice memory 53 to the capacitive
speaker PWM modulation unit 55 using the mixing unit 63 and “increase / decrease change of
the monitored secondary voltage C ′” (I) correct the sound pressure component (voltage) of
the “waveform signal forming the notification sound” of the audio memory 53 to a smaller
value when the monitored secondary voltage C ′ rises, and (ii) reversely When the monitored
secondary voltage C 'falls, the sound pressure component (voltage) of the "waveform signal
forming the notification sound" of the audio memory 53 is largely corrected to cause the
variation of the secondary voltage C'. Create a “waveform signal that forms a corrected
notification sound” that cancels out the variation of the parametric reproduction sound. Then,
the “waveform signal forming the corrected notification sound” corresponding to the vehicle
09-05-2019
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speed obtained by this work is overwritten and stored in the voice memory 53.
[0085]
As a result, when the vehicle presence notification device 1 is driven, a “waveform signal that
forms a corrected notification sound” according to the vehicle speed is given from the voice
memory 53 to the capacitive speaker PWM modulator 55. For this reason, the microcomputer 41
does not need to calculate the correction value in real time according to the fluctuation of the
secondary voltage C ', and an inexpensive microcomputer 41 with low processing capacity can be
adopted.
[0086]
In the third embodiment, an example in which the secondary voltage C ′ is used when
overwriting the “waveform signal forming the corrected notification sound” has been
described. However, the output signal of the capacitive speaker driving means 8 The “waveform
signal forming the corrected notification sound” may be calculated using the drive signal of the
sound wave speaker 31 and the overwrite processing may be performed.
[0087]
Fourth Embodiment A fourth embodiment will be described with reference to FIG.
In the third embodiment, the microcomputer 41 is provided with the AD converter 62 and the
mixing unit 63, and the "waveform signal forming the notification sound" is made "the waveform
signal forming the corrected notification sound" based on the fluctuation of the secondary
voltage C '. An example of overwrite processing is shown. Therefore, using the AD converter 62
and the mixing switch 64 causes an increase in cost. On the other hand, the secondary voltage
increase / decrease correction means 61 of the fourth embodiment stores the "waveform signal
forming a corrected notification sound" in anticipation of the increase / decrease of the
secondary voltage C 'from the beginning in the voice memory 53. This eliminates the need for
the AD converter 62 and the mixing switch 64.
[0088]
09-05-2019
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A procedure for obtaining the “waveform signal forming the corrected notification sound” to
be stored in the voice memory 53 will be described with reference to FIG. First, a notification
sound (a pseudo engine sound or the like) according to the vehicle speed is sequentially
generated from the vehicle horn 2 and the ultrasonic speaker 31. At this time, the parametric
reproduction sound from the ultrasonic speaker 31 is converted into an electric signal by the
microphone 65 and taken into a personal computer 66 (abbreviation of personal computer).
[0089]
In the personal computer 66, the "waveform signal (information before correction) forming the
notification sound" is compared with the "waveform signal of parametric reproduction sound"
taken in by the microphone 65. (i) Parametric reproduction sound due to the rise of the
secondary voltage C ' The sound pressure component (voltage) of the “waveform signal forming
the notification sound” of the voice memory 53 is corrected to be small when the sound
pressure of the sound pressure rises, and (ii) the parametric reproduction sound is The sound
pressure component (voltage) of the “waveform signal forming the notification sound” of the
audio memory 53 is largely corrected when the sound pressure of the sound pressure drops, and
the variation of the parametric reproduction sound due to the variation of the secondary voltage
C ′ is A "waveform signal forming a corrected notification sound" to be canceled is calculated.
[0090]
The “waveform signal forming the corrected notification sound” obtained in this manner is
used as master data.
Then, the master data (waveform signal forming a corrected notification sound) is written in the
sound memory 53 of each microcomputer 41 using the programmer 67.
[0091]
As a result, when the vehicle presence notification device 1 is driven, a “waveform signal that
forms a corrected notification sound” according to the vehicle speed is given from the voice
memory 53 to the capacitive speaker PWM modulator 55. For this reason, as in the third
embodiment, the microcomputer 41 does not have to calculate the correction value in real time
according to the fluctuation of the secondary voltage C ', and an inexpensive microcomputer 41
09-05-2019
27
with low processing capacity can be adopted. Further, unlike the second and third embodiments,
the AD converter 62 and the mixing switch 64 become unnecessary, so that the cost of the
control circuit 5 can be suppressed.
[0092]
In the fourth embodiment, an example is shown in which “waveform signal forming a corrected
notification sound” is obtained based on the parametric reproduction sound captured by the
microphone 65, but the secondary voltage C smoothed by the smoothing circuit 10 is shown.
Alternatively, the output signal of the capacitive speaker driving means 8 (the driving signal of
the ultrasonic speaker 31) may be taken into the personal computer 66, and a "waveform signal
forming a corrected notification sound" may be obtained and used as master data.
[0093]
Although the example which applies this invention to the vehicle presence alerting | reporting
apparatus 1 was shown in said Example, you may apply this invention to the other sound device
different from the vehicle presence alerting | reporting apparatus 1. FIG.
[0094]
In the above embodiment, an example of using the electromagnetic vehicle horn 2 as an example
of the inductive speaker is shown, but another dynamic speaker (which generates a
magnetomotive force in the magnetic pole generated by the magnet to drive the diaphragm) A
cone speaker or the like may be used.
[0095]
In the above embodiment, the piezoelectric speaker 3 is used as an example of the capacitive
speaker. However, another capacitive speaker such as a capacitor type speaker that generates a
sound wave by a change of the accumulated charge may be used.
In addition, an inductive speaker with low power consumption such as a ribbon speaker may be
used regardless of the capacitive speaker.
[0096]
09-05-2019
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In the above embodiment, an example of generating an ultrasonic wave from the capacitive
speaker 3 has been described, but the capacitive speaker 3 is not limited to the use of the
parametric speaker 11, and the high loudness of the audible band from the capacitive speaker 3
is It may be generated.
Specifically, the capacitive speaker 3 may be used as a tweeter, the midrange bass may be
generated from the inductive speaker 2, and the high-pitched sound may be generated by the
capacitive speaker 3.
That is, the present invention may be applied to other applications such as a vehicle audio
apparatus.
[0097]
DESCRIPTION OF SYMBOLS 1 vehicle presence alerting apparatus (sound apparatus) 2 horn for
vehicles (inductive speaker: dynamic speaker) 3 piezoelectric speaker (capacitive speaker) 4
battery (main power supply) 7 inductive speaker drive means 8 capacitive speaker drive means 9
switching means DESCRIPTION OF SYMBOLS 10 Smoothing circuit 11 Parametric speaker 12
Horn switch 21 Coil which generate | occur | produces a magnetic force in an inductive speaker
31 Ultrasonic speaker 61 Secondary voltage increase / decrease correction means
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