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JP2008042324

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2008042324
To provide a vibration generating device capable of obtaining a strong excitation force even in a
low frequency region to be excited, and a speaker device capable of increasing the sound
pressure in a low frequency region using the vibration generating device. An excitation force
generating unit (60) constituting a speaker device (10) operates an actuator (20) that vibrates an
output shaft (78) with respect to a yoke (66) fixed to a diaphragm (18) by operation; The
actuator 20 applies a reaction force accompanying the vibration of the weight 80 to the
diaphragm 18 as a forcing force. [Selected figure] Figure 1
Vibration generating device and speaker device
[0001]
The present invention relates to a vibration generating device and a speaker device.
[0002]
There is known a flat speaker which applies a forced displacement to a flat diaphragm using a
giant magnetostrictive element as a drive source and vibrates the diaphragm to generate an
acoustic wave (see, for example, Patent Document 1).
JP, 2005-244804, A JP, 11-143476, A
04-05-2019
1
[0003]
However, since the giant magnetostrictive element has a small amount of expansion and
contraction, that is, the amount of displacement of forced displacement, in order to secure the
sound pressure in the low frequency range, the dimensions of the giant magnetostrictive element
must be increased to secure the excitation amplitude. There is room for improvement on this
point.
[0004]
In view of the above facts, the present invention provides a vibration generating device capable
of obtaining a strong excitation force even in a low frequency region to be excited, and increasing
the sound pressure in the low frequency region using the vibration generating device. The object
is to obtain a speaker device that can
[0005]
The vibration generating apparatus according to the invention of claim 1 comprises an actuator
for vibrating an output portion with respect to a main body fixed to a vibration target by being
operated, and a weight provided on the output portion of the actuator. Have.
[0006]
In the vibration generator according to claim 1, when the actuator is operated, the weight
provided at the output portion of the actuator is vibrated.
For this reason, the reaction force accompanying the vibration of the weight is input as an
excitation force (forcing force) to the excitation target to which the main body of the actuator is
fixed.
That is, the vibration of the vibration target is forced vibration by force.
Since this excitation force can be increased in proportion to the acceleration of the weight, it is
possible to obtain a large excitation force even if the vibration frequency of the vibration target is
a low frequency.
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2
[0007]
As described above, in the vibration generating apparatus according to the first aspect, it is
possible to obtain a strong excitation force even in the low frequency region to be excited.
[0008]
The vibration generating apparatus according to the invention of claim 2 is the vibration
generating apparatus according to claim 1, wherein the actuator vibrates the output unit with
respect to the main body by periodically changing the applied magnetic field. A magnetostrictive
element is included.
[0009]
In the vibration generating apparatus according to claim 2, the actuator excites the weight by the
expansion and contraction of the magnetostrictive element accompanying the change of the
applied magnetic field.
Since the magnetostrictive element generates a large stress for changing the magnetic field, it
can vibrate a relatively large mass at high speed, and can obtain a large excitation force acting on
the vibration target along with the oscillation of the mass. .
Thus, the vibration amplitude of the vibration target can be reliably increased.
[0010]
The vibration generating apparatus according to the invention of claim 3 is the vibration
generating apparatus according to claim 2, wherein the actuator changes a magnetic field which
changes in a time shorter than a cycle of an output vibration to be generated in the vibration
target. It is comprised including the excitation apparatus provided to the said magnetostriction
element by the period of an output vibration.
[0011]
In the vibration generating device according to claim 3, the excitation device of the actuator
causes the magnetic field fluctuation for a time shorter than the period of the output vibration to
04-05-2019
3
occur only once in one period of the output vibration to be generated in the vibration target.
As a result, the weight repeatedly performs the movement driven with a large acceleration due to
the magnetic field fluctuation in a short time at the frequency of the output vibration described
above. As described above, since the weight moves with a large acceleration, the excitation force
(the reaction force of the movement of the weight) of the frequency of the output vibration input
to the vibration target becomes large. Thus, the vibration amplitude of the vibration target can be
further increased.
[0012]
In the speaker device according to the invention of claim 4, a flat diaphragm and the diaphragm
are fixed to the main body of the actuator as the vibration target. And a vibration generator.
[0013]
In the speaker device according to the fourth aspect, the diaphragm can be vibrated with a large
amplitude by using the above-described vibration generating device, so that the sound pressure
in the low frequency range of the generated sound wave can be increased.
[0014]
As described above, the vibration generating apparatus according to the present invention has an
excellent effect of being able to obtain a strong excitation force even in a low frequency range to
be excited.
Furthermore, the speaker device according to the present invention has an excellent effect that
the sound pressure in the low frequency range can be increased using the above-described
vibration generating device.
[0015]
A speaker device 10 to which a vibration generating device according to an embodiment of the
present invention is applied will be described based on FIG. 1 to FIG.
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4
First, the overall configuration of the speaker device 10 will be described, and then, the excitation
force generation unit 60 as a vibration generating device in the present invention will be
described in detail.
[0016]
(Overall Configuration of Speaker Device) FIG. 5 (A) shows a plan view of the speaker device 10,
and FIG. 5 (B) shows a side cross section taken along line 5B-5B of FIG. 5 (A). A diagram is
shown, and a bottom view of the speaker device 10 is shown in FIG. 5 (C). As shown in FIGS. 5A
and 5B, the speaker device 10 includes a case 12. The case 12 is configured mainly with a
substantially rectangular flat bottom wall (bottom plate) 14 and a rectangular frame-like
peripheral wall 16 erected from the periphery of the bottom wall 14 all around. In this
embodiment, the bottom wall 14 is formed in a substantially square shape, and the peripheral
wall 16 is formed in a square frame shape. The open end of the case 12 is closed by a diaphragm
18 as a cover.
[0017]
Specifically, the diaphragm 18 is formed in a rectangular flat shape substantially corresponding
to the bottom wall 14 in a front view, and the peripheral portion 18A is an end of the peripheral
wall 16 opposite to the substantially rectangular flat bottom wall 14 It is joined to the part. In
this embodiment, the case 12 and the diaphragm 18 are each made of a metal material, and the
peripheral portion 18A of the diaphragm 18 is an end 16A of the peripheral wall 16 (open end of
the case 12) over the entire circumference. Are joined by welding. As a metal good which
comprises case 12 and diaphragm 18, the stainless steel etc. which are heat-resistant favorable,
for example are used.
[0018]
As described above, in the speaker device 10, the sealed space R surrounded by the bottom wall
14 and the diaphragm 18 facing each other and the peripheral wall 16 connecting them is
formed between the case 12 and the diaphragm 18. . In the enclosed space R, an actuator 20
constituting a main part of the excitation force generating unit 60 in the present invention is
disposed. As will be described in detail later, the actuator 20 is attached to the diaphragm 18,
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5
and vibrates the diaphragm 18 in the thickness direction by receiving power from the power
supply lead wire 20A to operate. The speaker device 10 is configured to be used for an
application (for example, an exhaust sound active muffling device 30 described later as an
example) that generates a sound wave outward of the sealed space R by the vibration of the
diaphragm 18.
[0019]
As shown in FIGS. 5 (B) and 5 (C), a bead 26 as a rigidity change portion is formed on the
diaphragm 18. The bead 26 is formed in an annular shape substantially coaxial with the actuator
20 in a front view as shown in FIG. 5C, and surrounds the actuator 20 between the actuator 20
and the rectangular frame-like peripheral wall 16. It is located in Further, as shown in FIG. 5B,
the bead 26 is formed in a corrugated plate (convex-concave) shape that is sinusoidally curved in
the thickness direction of the diaphragm 18 in a cross-sectional view.
[0020]
Therefore, the bead 26 is a low rigidity portion (spring portion) of the diaphragm 18 and
functions as a vibration blocking portion which makes it difficult to transmit the dynamic
displacement and load input to the central portion of the diaphragm 18 to the peripheral portion
18A side. It is supposed to Therefore, in the diaphragm 18 fixed to the end 16A of the peripheral
wall 16 at the peripheral portion 18A, the inner portion of the bead 26 vibrates more than the
outer portion (the peripheral portion 18A side portion) of the bead 26 by the operation of the
actuator 20. It is set as the structure which is easy to vibrate in the thickness direction of the
board 18 (it is easy to produce a division | segmentation vibration).
[0021]
The size and shape of the bead 26 are determined according to the vibration mode (mode of
divided vibration of the diaphragm 18) required for the speaker device 10. That is, in the speaker
device 10, the size and shape of the bead 26 are determined such that the sound wave in the
frequency band to be generated becomes the plane wave Wf shown in FIG. 6A. In this
embodiment, the speaker device 10 applied to the exhaust sound active noise reduction device
30 described later has the diaphragm 18 in the frequency band (idle rotation speed to maximum
rotation speed) of the rotational secondary component of the internal combustion engine 32. The
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6
bead 26 is provided so that the plane wave Wf is output from the above.
[0022]
The speaker device 10 further includes a sound absorbing material 28 filled in the enclosed
space R. The sound absorbing material 28 is made of, for example, glass wool, and is filled in the
closed space R to absorb (attenuate) air vibration, that is, sound generated in the closed space R
along with the vibration of the diaphragm 18. It has become.
[0023]
Furthermore, a rib 22 is formed on the bottom wall 14 of the case 12. As shown in FIG. 5A, the
ribs 22 are orthogonal to a plurality of (three in this modification) longitudinal ribs 22A along
two opposing sides of the bottom wall 14 in a plan view and the longitudinal ribs 22A. A plurality
of (three in this modification) transverse ribs 22B along the line intersect with the grid and
project from the outer surface of the bottom wall 14. The rib 22 functions as a means of
reinforcing (stiffening) the bottom wall 14 and the bending rigidity of the bottom wall 14 is
enhanced.
[0024]
(Detailed Configuration of Excitation Force Generating Unit) As shown in FIG. 1, the speaker
device 10 includes an excitation force generation unit 60 as a vibration generating device for
vibrating the diaphragm 18 at a predetermined frequency. The excitation force generation unit
60 is configured with an actuator 20 and a weight 80 as a weight excited by the actuator 20 as
main components.
[0025]
The actuator 20 includes a yoke 66 as a main body fixed to the diaphragm 18 via the bracket 64.
The yoke 66 has a cylindrical wall 66A formed in a substantially cylindrical shape, one end in the
axial direction of the cylindrical wall 66A closed, and the bottom plate 66B facing the diaphragm
18, and the other axial end of the cylindrical wall 66A closed. And a top plate 66C. A through
04-05-2019
7
hole 66D is formed in an axial center portion of the top plate 66C. On the bottom plate 66B in
the cylindrical wall portion 66A of the yoke 66, a disc-shaped magnet 68 for setting a magnetic
bias described later is disposed.
[0026]
A magnetostrictive element (super magnetostrictive element) 70 is disposed on the magnet 68.
The magnetostrictive element 70 is formed in a cylindrical shape having a sufficiently smaller
diameter than the inner diameter of the cylindrical wall portion 66A, and is coaxially disposed at
the axial center portion of the yoke 66. As shown in FIG. 3, the magnetostrictive element 70 is
designed to be expanded and contracted in its longitudinal dimension in accordance with the
strength of the applied magnetic field. The vertical axis of the diagram shown in FIG. 3 can be
grasped as a displacement amount of the other end 70B with respect to one end (bottom plate
66B side) 70A of the magnetostrictive element 70. A spacer 72 is interposed between the
magnetostrictive element 70 and the magnet 68 as necessary.
[0027]
The magnetostrictive element 70 is covered with a coil 74 as an excitation device from the outer
peripheral side (radially outside). The coil 74 is wound around a bobbin 76 held by a yoke 66, so
that a magnetic field generated by energization is applied to the magnetostrictive element 70.
That is, the other end 70B of the magnetostrictive element 70 is displaced with respect to the
one end 70A depending on the magnitude of the magnetic field applied from the coil 74.
[0028]
An output shaft 78 as an output portion is fixed to the other end 70B of the magnetostrictive
element 70 described above. Specifically, one end 78A of the output shaft 78 is fixed to the other
end 70B of the magnetostrictive element 70, the middle portion 78B is inserted into the through
hole 66D of the yoke 66, and the other end 78C protrudes outside the yoke 66. There is. A bolt
portion 78D is integrally formed on the other end 78C side of the output shaft 78.
[0029]
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8
The excitation force generator 60 is provided with a weight 80 fixed to the other end 78 C of the
output shaft 78 constituting the actuator 20. More specifically, the weight 80 is formed in a short
cylindrical shape in this embodiment, and the nut 82 is screwed into the bolt portion 78D of the
output shaft 78 inserted through the through hole 80A formed in the axial center portion. By
doing this, the other end 78C of the output shaft 78 is fixed.
[0030]
Further, from the portion of the output shaft 78 located in the yoke 66, the flange 84 is formed
to project radially outward. A preload setting spring 86 is disposed in a compressed state
between the flange 84 and the top plate 66C of the yoke 66. The preload setting spring 86
applies an initial compression displacement to the magnetostrictive element 70 by its biasing
force. Thus, in the actuator 20, the magnetostrictive element 70 to which the magnetic field from
the coil 74 is applied is expanded and contracted mainly in the range of compressive
deformation.
[0031]
Furthermore, the actuator 20 is provided with a control unit 88 for energizing (energizing) the
coil 74. In this embodiment, the control unit 88 controls the frequency and phase of power
supply (voltage application) to the coil 74 so that the diaphragm 18 is vibrated at a
predetermined frequency and phase by the actuator 20. . The control unit 88 and the coil 74
constitute an excitation device in the present invention.
[0032]
In the excitation force generation unit 60 configured as described above, the magnetostrictive
element 70 energized in a predetermined cycle by the coil 74 of the actuator 20 causes the
weight 80 to vibrate with respect to the yoke 66 via the output shaft 78. The reaction force
associated with the vibration of the weight 80 is transmitted to the diaphragm 18 as a forcing
force, that is, an excitation force via the yoke 66 and the bracket 64, so that the diaphragm 18
vibrates at the frequency of the excitation force. It has become. That is, the excitation force
generation unit 60 is not a device for inputting a displacement (for example, a displacement with
respect to the case 12) to the diaphragm 18, but inputs the excitation force F as schematically
04-05-2019
9
shown in FIG. The device is configured as a device that generates forced vibration by force.
[0033]
Supplementally referring to FIG. 3, the displacement characteristic of the magnetostrictive
element 70 with respect to the strength of the magnetic field is the same (symmetrical) whether
the direction of the magnetic field is positive or negative, and displacement occurs in accordance
with the scalar quantity of the magnetic field It has hysteresis corresponding to the change
direction of the magnetic field. In this embodiment, the magnetic bias is set by the abovedescribed magnet 68 so that the displacement of the magnetostrictive element 70 is used in the
magnetic field region B of FIG. 3 showing a relatively linear characteristic. Therefore, with
respect to the sinusoidal input magnetic field M shown in FIG. 3, the displacement y of the other
end 70B (weight 80) of the sine wave can be obtained.
[0034]
Assuming that the mass of the weight 80 is m [kg] and the acceleration of the weight 80 by the
actuator 20 is α [m / s <2>], F of the excitation force (fluctuating load) that can be generated by
the excitation force generator 60. , F = m × α [N], and when the weight 80 vibrates in a sine
wave, the amplitude is A [m] and the frequency (frequency of the input magnetic field to the
magnetostrictive element 70 by the coil 74) is f [Hz] Assuming that αmax = A × (2πf) <2>, the
maximum value (instantaneous value) of the excitation force F is Fmax = m × A × (2πf) <2>. On
the other hand, the force Fm that can be generated by the magnetostrictive element 70 is Fm = S
× σ, where the cross-sectional area of the magnetostrictive element 70 is S [m <2>] and the
generated stress of the magnetostrictive element 70 is σ [Pa]. Fmax <Fm = S × σ.
[0035]
Therefore, in the excitation force generation unit 60, the excitation force F (Fmax) is obtained
according to the mass m of the weight 80, the excitation amplitude A, and the excitation
frequency f in the range of the force Fm that the magnetostrictive element 70 can generate. be
able to. That is, in the excitation force generation unit 60, a large excitation force F can be
obtained by applying a magnetic field having a high variation rate to the magnetostrictive
element 70 to increase the expansion / contraction acceleration and driving the weight 80 with a
large acceleration. For this reason, the control unit 88 of the excitation force generation unit 60
04-05-2019
10
performs an operation of driving the magnetostrictive element 70 at a frequency f70 higher than
the frequency f18 at which the vibration plate 18 to be excited is vibrated. The coil 74 is
configured to be energized (voltage application) so as to repeat at the frequency f18. More
specifically, as shown in, for example, FIG. 4A, control unit 88 has a period shorter than period
T18 during period T18 (= 1 / f18) of vibration frequency f18 of diaphragm 18. The coil 74 is
configured to generate a fluctuating magnetic field of a frequency f70 (= 1 / T70) higher than the
frequency f18 by T70.
[0036]
For example, in consideration of the fact that the frequency range required for the speaker device
10 is approximately 20 Hz to 500 Hz, that is, the minimum period T18 min of the vibration
(sound generation) of the diaphragm 18 is 2 ms. Thus, the drive frequency f70 of the
magnetostrictive element 70 can be f70 = 1 [kHz]. In this case, for example, assuming that the
weight m of the weight 80 is 0.1 kg, the excitation amplitude A is 0.0001 m, and the excitation
frequency f is f70 = 1 kHz, then Fmax 395 395 N. It can be seen that a sufficient excitation force
F can be obtained without increasing the excitation amplitude A. The magnetostrictive element
70 has responsiveness of 100 [kHz] or more, and can follow the limit frequency of the magnetic
field change. Therefore, by exciting the weight 80 at a higher acceleration (high frequency), a
larger excitation force can be obtained, and the performance is sufficient for use in, for example,
phase control of sound waves described later.
[0037]
The mass m of the weight 80 is determined in accordance with the dimensional shape of the
diaphragm 18 (in the rectangular diaphragm 18, the vertical and horizontal dimensions a and b
shown in FIG. 2B) and the sound pressure to be generated. In the example which constitutes the
exhaust noise active muffling apparatus 30 (main muffler 42) described later, the mass m of the
weight 80 and the magnetostrictive element for driving the weight 80 so as to generate a sound
pressure substantially equal to the exhaust noise of each frequency. 70 dimensions are
determined.
[0038]
The control unit 88 is configured to apply a sine wave voltage application of the frequency f70 as
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11
shown in FIG. 4A, and as shown in FIG. In the example of (1), a pulse wave of 1 (ms) may be
input. Also in the configuration in which the pulse wave is input, a large excitation force F can be
obtained as in the case of inputting the above-described sine wave.
[0039]
Next, the operation of the present embodiment will be described.
[0040]
In the speaker device 10 configured as described above, when the coil 74 of the actuator 20 is
energized, the actuator 20 vibrates the weight 80 in the contact / separation direction with the
diaphragm 18 at a frequency corresponding to the energization frequency.
The reaction force accompanying the vibration of the weight 80 acts on the diaphragm 18 as an
excitation force, and the diaphragm 18 vibrates at the frequency of the excitation force. Due to
this vibration, in the speaker device 10, a sound wave is generated outward (opposite to the
sealed space R).
[0041]
Here, since the speaker device 10 is configured to vibrate the diaphragm 18 by using a reaction
force generated by the actuator 20 vibrating the weight 80 as a vibrating force, it depends on the
amplitude that the actuator 20 can generate. Instead, a large excitation force can be applied to
the diaphragm 18. In particular, since the actuator 20 uses the magnetostrictive element 70 as a
drive source of the weight 80, it can drive the weight 80 having a large possible load Fm = S ×
σ and a relatively large mass m at a high frequency (high acceleration) Since it is possible, it has
been realized to obtain a large excitation force F while having a compact configuration. Thereby,
in the speaker device 10, a large sound pressure can be secured in a low frequency range (for
example, 20 Hz to 500 Hz), and flat frequency characteristics can be obtained.
[0042]
In particular, in the excitation force generating unit 60 that constitutes the speaker device 10,
the control unit 88 applies a fluctuating magnetic field having a period T70 shorter than the
period T18 of the sound wave output from the diaphragm 18 to the magnetostrictive element 70.
04-05-2019
12
The acceleration of the weight 80 is increased, and the diaphragm 18 can be reliably oscillated
with a large constant excitation force without relying on the excitation amplitude A or the mass
m (make it larger than necessary).
[0043]
As described above, in the speaker device 10 according to the present embodiment, the weight
80 is excited using the magnetostrictive element 70 having a large generated stress σ and a
good response although the obtained excitation amplitude A is relatively small. By using the
reaction force that accompanies, it was possible to realize a sufficient sound pressure at low
frequency with a compact configuration.
In addition, other effects of the speaker device 10 will be supplemented below.
[0044]
In the speaker device 10, since the end portion 16A of the peripheral wall 16 of the peripheral
wall 16 constituting the case 12 and the peripheral portion 18A of the diaphragm 18 are joined
over the entire circumference, waterproofness and dust resistance to the enclosed space R are
achieved. Is secured. Further, since the case 12 and the diaphragm 18 are made of a metal
material such as stainless steel, the heat resistance is good. Further, since the metal case 12 and
the diaphragm 18 are joined to the end 16A and the peripheral edge 18A of the peripheral wall
16 over the entire circumference as described above, the mechanical strength against external
force and the like including the junction is high. . As described above, since the speaker device 10
does not include components made of rubber or resin in its component parts, such as a speaker
device used in a favorable environment such as indoors, and does not use an adhesive or the like
for bonding the components, There are few restrictions on the usage environment.
[0045]
Here, in the speaker device 10, since the flat diaphragm 18 is vibrated to generate a sound wave,
a plane wave having a high directivity in the sound wave transmission direction is easily output.
For this reason, there is little attenuation to the distance of sound pressure. In addition, low
frequency sound can be generated without depending on the capacity of the case 12 (the
04-05-2019
13
enclosed space R), and as described above, the plane wave has less attenuation with respect to
the distance of the sound pressure. Can get a large sound wave). That is, as described above, it is
possible to propagate the sound wave of the large sound pressure obtained by the large
excitation force F which is a reaction force accompanying the excitation of the weight 80 without
attenuating. Thus, the speaker device 10 can be miniaturized as compared with, for example, the
cone-type speaker 100 that generates the diffusion wave Wd as illustrated in FIG. 6B. In
particular, in the speaker device 10, since the bead 26 is formed on the diaphragm 18, a plane
wave can be reliably generated in a required frequency band.
[0046]
Furthermore, in the speaker device 10, since the sealed space R is formed by the case 12 and the
diaphragm 18, the sound generated by the vibration of the diaphragm 18 to the inside of the
sealed space R leaks to the outside of the sealed space R. hard. Further, the case 12 having a
closed cross-section structure with the diaphragm 18 has a predetermined rigidity and the
bottom wall 14 is reinforced by the ribs 22. Therefore, the bending determined depending on the
rigidity (mainly of the bottom wall 14) Transmission of sound of a frequency component lower
than the limit frequency of vibration (flexural vibration) to the outside of the enclosed space R is
effectively prevented. Further, since the sound absorbing material 28 is filled in the enclosed
space R, the middle and high frequency components of the sound generated by the vibration of
the diaphragm 18 toward the inside of the enclosed space R (components whose frequency is
higher than the above-mentioned limit frequency) Is absorbed by the sound absorbing material
28 and prevented from permeating the outside of the closed space R (case 12).
[0047]
In the above embodiment, an example in which the annular bead 26 is provided to set the
divided vibration mode of the diaphragm 18 to output a plane wave in a required frequency band
has been described, but the present invention is limited to this. Alternatively, for example, the
diaphragm 18 may be provided with a concavo-convex shape instead of the bead 26 or together
with the bead 26. The uneven shape may be formed, for example, in an annular shape like a bead
26 and may be formed to have a rectangular wave-like cross section, or may be formed
intermittently in, for example, the circumferential direction of the diaphragm 18.
[0048]
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14
(Exhaust Sound Active Silencer) Next, an exhaust noise active silencer 30 as a noise suppression
device to which the above-described speaker device 10 is applied will be described based on
FIGS. 7 to 9. Arrows FR appropriately shown in the respective drawings indicate the front side in
the longitudinal direction of the vehicle body to which the exhaust noise silencer 30 is applied,
arrow UP indicates the upper side in the vertical direction of the vehicle body, and arrow W
indicates the vehicle width direction. I assume.
[0049]
In FIG. 9, an exhaust system 34 of an internal combustion engine 32 provided with an exhaust
noise active silencer 30 to which the speaker device 10 is applied is shown in a schematic plan
view. As shown in this figure, the exhaust system 34 includes an exhaust pipe 36 for guiding the
exhaust gas exhausted by the internal combustion engine 32 out of the system, and the upstream
end 36 A of the exhaust pipe 36 is an exhaust manifold of the internal combustion engine 32.
Connected to 32A. On the other hand, the downstream end of the exhaust pipe 36 is an air
release portion 36B. Between the upstream end 36A of the exhaust pipe 36 (the exhaust system
path formed by the exhaust pipe 36) and the atmosphere opening portion 36B, a catalytic
converter 38 for purifying the exhaust gas and an exhaust noise are reduced in order from the
upstream side. A sub muffler 40 and a main muffler 42 are provided. And, in this embodiment,
the speaker device 10 is applied to the main muffler 42. That is, the main muffler 42
corresponds to the exhaust system component and separator in the present invention.
[0050]
As shown in FIGS. 7A to 7C, the main muffler 42 is a peripheral portion of each diaphragm 18 of
the speaker device 10 provided in a pair in the vertical direction of the vehicle body and the
upper and lower diaphragms 18 opposed to each other. A muffler chamber (an expansion
chamber or a resonance chamber) 46, which is a closed space, is formed by the muffler side
surface member 44 having a substantially rectangular frame shape in plan view and welded over
the entire circumference to 18A. An inlet pipe 48 connected to the exhaust pipe 36 on the
upstream side and an outlet pipe 50 whose end is the air release portion 36B of the exhaust pipe
36 are connected to the muffler side surface member 44 having a substantially rectangular
frame shape in plan view. .
[0051]
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15
As described above, the main muffler 42 is configured such that a part of its outer wall is formed
by the diaphragm 18 of the speaker device 10, and the diaphragm 18 is directly connected to the
exhaust gas flowing (diffused and discharged) flowing through the inside thereof. It is designed
to emit sound waves. Further, as shown in FIGS. 7A to 7C, the muffler side surface member 44
has a flat main muffler 42 whose size in the vertical direction of the vehicle body is smaller than
the upper and lower ones in the vehicle longitudinal direction and the vehicle width direction. It
is dimensioned to be formed between the loudspeaker devices 10.
[0052]
The control unit 88 of each speaker device 10 is shown in FIG. 8A based on the output of, for
example, a microphone provided in the main muffler 42 or an engine tachometer that outputs a
signal according to the rotational speed of the internal combustion engine 32. The voltage
applied to the coil 74 of each actuator 20 (a frequency f18 of the output vibration output from
the diaphragm 18 (period T18) so that a sound wave Sa having a substantially equal sound
pressure and an opposite phase to the exhaust sound Se is output. , Phase, a cycle to be added for
each cycle of the output vibration, a voltage application pattern of pulse width T70, and the like)
are controlled.
[0053]
In the exhaust noise active muffling apparatus 30 configured as described above, as the exhaust
gas of the internal combustion engine 32 flows through the exhaust system 34, for example, with
respect to relatively low frequency exhaust noise generated due to pulsation of the exhaust gas,
The actuator 20 is driven so that the diaphragm 18 generates sound waves of substantially equal
sound pressure in opposite phase.
For this reason, as shown in FIG. 8B, the exhaust noise Se and the sound wave Sa generated by
the diaphragm 18 cancel each other, and the exhaust noise is reduced. The frequency band of the
exhaust noise of the rotational secondary component of the internal combustion engine 32 is
approximately 20 Hz to 500 Hz corresponding to the idle rotation to the maximum rotation
speed.
[0054]
04-05-2019
16
Here, since the exhaust sound active muffling apparatus 30 includes the above-described speaker
device 10, it can be used in a high temperature environment and exposed to the outside of the
vehicle to exhibit a required muffling performance. That is, the speaker device 10 configured by
welding and joining the metal case 12 and the diaphragm 18 is excellent in environmental
resistance, and is deteriorated by high temperature exhaust gas as in a configuration using
rubber or resin parts. Since it does not occur, stable muffling performance is exhibited over a
long period of time. Further, even if the speaker device 10 is disposed under the vehicle body
floor, intrusion of rain water, splashing from the road surface and the like into the case 12 (the
enclosed space R) such as water or dust is prevented, and the actuator 20 (electric system) Is
protected. Furthermore, since the metal case 12 has the required mechanical (destructive)
strength, the speaker device 10 is prevented from being damaged by stepping stones or the like.
[0055]
Here, in the exhaust noise active muffling apparatus 30, the diaphragm 18 of the speaker device
10 constitutes the outer wall (partition) of the main muffler 42, and the diaphragm 18 is an
exhaust gas in the main muffler 42, ie, a vibration source. On the other hand, in order to directly
output a sound wave, that is, to directly cancel the exhaust sound of the exhaust gas having a
large acoustic energy, for example, the structure to output the sound wave toward the relatively
low energy exhaust gas open to the atmosphere. In comparison, the effect of suppressing exhaust
noise is large. Further, since the sound wave is output into the main muffler 42 which is a closed
space, the transmission loss of the sound wave generated by the speaker device 10 is small
compared to the configuration in which the sound wave is output toward the exhaust gas open to
the atmosphere. Sound can be canceled more effectively, and the effect of suppressing exhaust
noise can be improved.
[0056]
And the speaker apparatus 10 which comprises the exhaust sound active muffling apparatus 30
produces the sound wave Sa which is a plane wave of a big sound pressure in a low frequency
area by driving the weight 80 by the actuator 20, and the exhaust sound is efficient. Can be
canceled out. In particular, since the speaker device 10 is set to generate a plane wave by the
bead 26 up to the frequency band (idle rotation to maximum number of revolutions) of the
exhaust sound of the rotational secondary component of the internal combustion engine 32, It
can cancel more efficiently.
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[0057]
Furthermore, in the speaker device 10 in which the diaphragm 18 is covered by the case 12,
leakage of the sound emitted outward of the main muffler 42 by the diaphragm 18 is suppressed
to the outside. In particular, components lower in frequency than the limit frequency of the case
12 block transmission to the outside of the enclosed space R, and components higher in
frequency than the limit frequency are absorbed by the sound absorbing material 28, so that
vibration of the diaphragm 18 is generated. The accompanying noise generation is prevented.
[0058]
Further, since the main muffler 42 is formed in a flat shape that is flat in the vertical direction,
the height in the vertical direction of the vehicle body is kept low even if the speaker device 10 is
disposed above and below. On the other hand, since the upper and lower diaphragms 18
constitute a flat surface of the main muffler 42, that is, a wall having a large contact area with the
exhaust gas, the sound output of the diaphragms 18 more effectively suppresses the exhaust
noise of the exhaust gas. can do.
[0059]
Although the above-mentioned embodiment showed an example where speaker device 10 was
applied to exhaust sound active muffling device 30, the present invention is not limited to this,
and speaker device 10 can be applied to various uses. In addition, the excitation force generating
unit 60 that constitutes the speaker device 10 can be applied to various applications other than
the speaker application.
[0060]
In the above embodiment, the exhaust noise active muffling apparatus 30 includes the pair of
upper and lower speaker devices 10. However, the present invention is not limited to this. For
example, either the upper or lower speaker device 10 may be provided. You may
[0061]
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18
Furthermore, in the above embodiment, the exhaust noise active muffling apparatus 30 has an
example including the pair of upper and lower speaker devices 10. However, even if the speaker
device 10 is disposed on the side surface of the main muffler 42 in the vehicle width direction
good.
Furthermore, for example, the diaphragm 18 of the speaker device 10 may be formed in an
elliptical shape corresponding to the end surface of the winding muffler in the longitudinal
direction, and the end surface in the longitudinal direction of the wound muffler may be
configured by the elliptical diaphragm 18. In this case, the exhaust noise active silencer 30 can
be easily applied to the existing muffler.
[0062]
It is a sectional side view which shows the excitation force generation part which comprises the
principal part of the speaker apparatus which concerns on embodiment of this invention. It is a
figure which shows typically the speaker apparatus based on embodiment of this invention,
Comprising: (A9) is a side view, (B) is a top view. It is a diagram which shows the magnetic fielddisplacement characteristic of the magnetostrictive element which comprises the speaker
apparatus which concerns on embodiment of this invention. (A)は。 It is a diagram which
shows the magnetic field generation | occurrence | production pattern by the control part which
comprises the speaker apparatus which concerns on embodiment of this invention, (B) is a
diagram which shows the modification of a magnetic field generation | occurrence | production
pattern. It is a figure which shows the speaker apparatus based on embodiment of this invention,
Comprising: (A) is a top view, (B) is a sectional side view along 5B-5B line of FIG. 5 (A), (C) is a
bottom face. FIG. (A) is explanatory drawing which shows typically the plane wave which the
speaker apparatus which concerns on embodiment of this invention generate | occur | produces,
(B) is explanatory drawing which shows typically the diffusion wave which the cone-type speaker
which concerns on a comparative example generate | occur | produces. . It is a figure showing an
exhaust sound active muffling device to which a speaker device concerning an embodiment of
the present invention was applied, and (A) is a side sectional view, (B) is a top view, and (C) is a
rear view. It is a figure for demonstrating the muffling principle by the exhaust sound active
muffling apparatus to which the speaker apparatus which concerns on embodiment of this
invention was applied, Comprising: (A) is a diagram which shows separately the exhaust sound
and the sound wave to cancel. (B) is a diagram synthesized with the exhaust sound and the sound
wave to be canceled. FIG. 1 is a plan view of an exhaust system to which an exhaust noise active
muffling apparatus to which a speaker device according to an embodiment of the present
invention is applied is applied.
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Explanation of sign
[0063]
DESCRIPTION OF SYMBOLS 10 Speaker apparatus 18 Diaphragm (excitation object) 20 Actuator
60 Excitation force generation part (vibration generation apparatus) 66 yoke (body) 70
Magnetostrictive element 74 Coil (excitation apparatus) 78 Output shaft (output part) 80 Weight
(weight) 88 Control unit (excitation device)
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