U.S. patent application number 11/990773 was filed with the patent office on 2009-04-02 for double wall structure.
This patent application is currently assigned to KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL LTD.). Invention is credited to Toshimitsu Tanaka, Kazuki Tsugihashi, Hiroki Ueda.
Application Number | 20090084627 11/990773 |
Document ID | / |
Family ID | 37835816 |
Filed Date | 2009-04-02 |
United States Patent
Application |
20090084627 |
Kind Code |
A1 |
Tsugihashi; Kazuki ; et
al. |
April 2, 2009 |
DOUBLE WALL STRUCTURE
Abstract
A double wall structure capable of suppressing an increase in a
sound transmission amount with regard to sound with a specified
frequency and stably exhibiting a sound insulation performance for
sound with various frequencies is provided. A double wall structure
1 is assumed to be a door serving as a part of an automobile. The
double wall structure 1 is provided with plate-like bodies 2 and 3
arranged in parallel and opposing to each other with leaving a
predetermined distance. The plate-like bodies 2 and 3 are formed in
a rectangular shape with one direction being slightly longer.
Between the two plate-like bodies 2 and 3 opposing to each other is
formed an internal chamber 4. Side plates 5 are provided so as to
connect the plate-like bodies 2 and 3 to each other, and thereby
the internal chamber 4 is almost closed. At a position where a
sound pressure is increased in the internal chamber 4 is provided a
sound absorbing chamber structure 6 having a porous surface 6a on
one surface in a rectangular parallelepiped.
Inventors: |
Tsugihashi; Kazuki; (Hyogo,
JP) ; Ueda; Hiroki; (Hyogo, JP) ; Tanaka;
Toshimitsu; (Hyogo, JP) |
Correspondence
Address: |
REED SMITH LLP
3110 FAIRVIEW PARK DRIVE, SUITE 1400
FALLS CHURCH
VA
22042
US
|
Assignee: |
KABUSHIKI KAISHA KOBE SEIKO SHO
(KOBE STEEL LTD.)
Hyogo
JP
|
Family ID: |
37835816 |
Appl. No.: |
11/990773 |
Filed: |
September 5, 2006 |
PCT Filed: |
September 5, 2006 |
PCT NO: |
PCT/JP2006/317546 |
371 Date: |
February 21, 2008 |
Current U.S.
Class: |
181/290 |
Current CPC
Class: |
B60J 5/04 20130101; B60R
13/0838 20130101; B60R 13/083 20130101; B60R 13/0815 20130101; B60J
5/00 20130101 |
Class at
Publication: |
181/290 |
International
Class: |
E04B 1/82 20060101
E04B001/82 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 8, 2005 |
JP |
2005-260887 |
Claims
1. A double wall structure having plate-like bodies opposing to
each other, a completely or almost closed internal chamber being
formed between said plate-like bodies, comprising: a sound
absorbing chamber forming shell forming a sound absorbing chamber
provided in at least one plate-like body among said plate-like
bodies, the sound absorbing chamber forming shell being adjacent to
said plate-like body and isolated from said internal chamber; and a
sound pressure reducing portion for reducing a sound pressure in
said internal chamber, the sound pressure reducing portion having a
number of through portions passing through said sound absorbing
chamber forming shell or said plate-like bodies so as to open said
sound absorbing chamber to said internal chamber.
2. The double wall structure according to claim 1, wherein said
sound absorbing chamber forming shell is provided in an inner
surface of said plate-like bodies, and said sound pressure reducing
portion is provided in at least a part of said sound absorbing
chamber forming shell.
3. The double wall structure according to claim 1, wherein said
sound absorbing chamber forming shell is provided in an outer
surface of said plate-like bodies, and said sound pressure reducing
portion is provided in at least a part of said plate-like
bodies.
4. The double wall structure according to claim 1, wherein at least
one plate-like body among said plate-like bodies is provided with a
perforated member in which an opening for opening said internal
chamber to the outside is formed, and a closing member attached to
said perforated member so as to close said opening, and said sound
absorbing chamber forming shell is provided in said closing
member.
5. The double wall structure according to claim 4, wherein said
closing member includes a vibration damping member formed of a
structure or a material having a vibration damping property.
6. The double wall structure according to claim 4, wherein said
closing member includes a concavity and convexity shape.
7. The double wall structure according to claim 4, wherein said
closing member includes a structure or a material having a sound
absorbing property.
8. The double wall structure according to claim 4, wherein said
closing member comprises a porous body.
9. The double wall structure according to claim 1, wherein a
plurality of said sound absorbing chamber forming shells are
provided in one of said plate-like bodies, and a plurality of sound
absorbing chambers are formed by said sound absorbing chamber
forming shells.
10. The double wall structure according to claim 1, wherein said
sound absorbing chamber forming shell is provided with a partition
member, and said sound absorbing chamber is partitioned into a
plurality of small chambers by said partition member.
11. The double wall structure according to claim 1, wherein said
sound absorbing chamber forming shell includes a concavity and
convexity shape.
Description
TECHNICAL FIELD
[0001] The present invention relates to a double wall structure for
insulating sound from a noise generating source for a part of a bag
structure in a vehicle body of an automobile such as a door, a hood
and a trunk lid.
BACKGROUND ART
[0002] Conventionally, there is a proposed technique that a double
wall structure is used for the door, the hood, the trunk lid or the
like serving as a part used in the automobile (for example, refer
to Patent Documents 1 and 2). A configuration of the above
conventional example is schematically shown in FIG. 26. A double
wall structure 1' of the above conventional example has a hollow
box shape in which between plate-like bodies 2 and 3 opposing to
each other with leaving a predetermined distance is formed an
internal chamber 4, and the internal chamber 4 is closed by side
plates 5.
[0003] However, in the double wall structure 1' shown in Patent
Document 1, (a) when a sound wave of a noise is incident from the
upper side and the noise includes a sound component with a
specified frequency, resonance in the internal chamber 4 (resonance
mainly in the direction parallel to the plate-like bodies 2 and 3)
is generated with regard to the sound component so that amplitude
of the plate-like body 2 on the lower side serving as a radiation
surface is increased, and hence an increase in a radiated sound
reduces a sound insulation performance; or (b) although the double
wall structure 1' constitutes a vibration system with three
elements of the plate-like body 2, the air in the internal chamber
4 (working as a spring) and the plate-like body 3, there is
sometimes a case where the resonance is generated in the vibration
system with regard to the noise with a specified frequency so that
the sound insulation performance is reduced.
Patent Document 1: Japanese Patent Laid-Open No. 2002-96636
Patent Document 2: Japanese Patent Laid-Open No. 2003-118364
DISCLOSURE OF THE INVENTION
[0004] The present invention is achieved in consideration to the
above point, and an object thereof is to provide a double wall
structure capable of suppressing an increase in a sound
transmission amount with regard to sound with a specified
frequency, and stably exhibiting a sound insulation performance for
sound with various frequencies.
[0005] The double wall structure according to the present invention
has plate-like bodies opposing to each other, a completely or
almost closed internal chamber being formed between the plate-like
bodies, the double wall structure comprising a sound absorbing
chamber forming shell forming a sound absorbing chamber provided in
at least one plate-like body among the plate-like bodies, the sound
absorbing chamber forming shell being adjacent to the plate-like
body and isolated from the internal chamber, and a sound pressure
reducing portion for reducing a sound pressure in the internal
chamber, the sound pressure reducing portion having a number of
through portions passing through the sound absorbing chamber
forming shell or the plate-like bodies so as to open the sound
absorbing chamber to the internal chamber.
[0006] In the double wall structure according to the present
invention, the sound pressure reducing portion having a number of
the through portions for opening the sound absorbing chamber to the
internal chamber is formed in the sound absorbing chamber forming
shell or the plate-like bodies. It should be noted that the
"closing" does not only mean strict sealing but also includes a
case where there is partially a clearance or an opening. The sound
absorbing chamber serving as a sound absorbing mechanism is
preferably formed in the vicinity of a part with a high sound
pressure in a resonance state of the internal chamber.
[0007] In the case where sound excitation is applied from one side
of the double wall structure, the resonance is generated within the
internal chamber. By a sound absorbing effect of the sound pressure
reducing portion, it is possible to effectively reduce the sound
pressure of the internal chamber. Thereby, since a sound excitation
force to the radiation surface of the other side of the double wall
structure is reduced, it is possible to reduce vibration amplitude
of the radiation surface and improve sound transmission loss. It
should be noted that the sound absorbing effect of the sound
pressure reducing portion is generated by energy dissipation due to
friction in an inner wall surface of the through portion when the
resonance is generated in a spring-mass system in which the air
within the sound absorbing chamber is the spring and the air inside
the through portion is a mass. Therefore, a size of the sound
absorbing chamber, a specification of the through portion (a
diameter and an aperture ratio) and the like have to be designed so
that a frequency of the resonance of the internal chamber to be
suppressed (that is, a frequency to improve sound transmission
loss) substantially corresponds to a resonance frequency of the
spring-mass system of the sound absorbing chamber and the through
portion. In the case where the through portion is minute, the
energy dissipation due to a vortex generated in the vicinity of the
through portion is added and hence a larger sound absorbing effect
is generated in a wider frequency range.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic perspective view of an embodiment 1-1
of a double wall structure according to the present invention.
[0009] FIG. 2 is a schematic perspective view of an embodiment
1-2.
[0010] FIG. 3 is a schematic perspective view of an embodiment
1-3.
[0011] FIG. 4 is a schematic perspective view of an embodiment
2-1.
[0012] FIG. 5 is a schematic perspective view of an embodiment
2-2.
[0013] FIG. 6 is a schematic perspective view of an embodiment
2-3.
[0014] FIG. 7 is a schematic perspective view of an embodiment
2-4.
[0015] FIG. 8 is a schematic perspective view of an embodiment
2-5.
[0016] FIG. 9 is a schematic perspective view of an embodiment
2-6.
[0017] FIG. 10 is a schematic perspective view of an embodiment
2-7.
[0018] FIG. 11 is a schematic perspective view of an embodiment
3-1.
[0019] FIG. 12 is a schematic view showing an example of a cross
section of a sound absorbing chamber structure.
[0020] FIG. 13 is a schematic view showing an example of the cross
section of the sound absorbing chamber structure.
[0021] FIG. 14 is a schematic view showing an example of the cross
section of the sound absorbing chamber structure.
[0022] FIG. 15 is a schematic view showing an example of the cross
section of the sound absorbing chamber structure.
[0023] FIG. 16 is a schematic view showing an example of the cross
section of the sound absorbing chamber structure.
[0024] FIG. 17 is a schematic view showing an example of the cross
section of the sound absorbing chamber structure.
[0025] FIG. 18 is a schematic view showing an example of the cross
section of the sound absorbing chamber structure.
[0026] FIG. 19 is a schematic view showing an example of the cross
section of the sound absorbing chamber structure.
[0027] FIG. 20 is a schematic view showing an example of the cross
section of the sound absorbing chamber structure.
[0028] FIG. 21 is a schematic view showing an example of the cross
section of the sound absorbing chamber structure.
[0029] FIG. 22 is a schematic view showing an example of the cross
section of the sound absorbing chamber structure.
[0030] FIG. 23 is a view showing an effect of the double wall
structure according to the present invention.
[0031] FIG. 24 is a view showing an effect of the double wall
structure according to the present invention.
[0032] FIG. 25 is a view showing an effect of the double wall
structure according to the present invention.
[0033] FIG. 26 is a schematic perspective view of a conventional
double wall structure.
BEST MODE FOR CARRYING OUT THE INVENTION
[0034] Next, a description will be given to embodiments of the
present invention. It should be noted that in the present
embodiments, a description will be given to a sound absorbing
chamber structure as an example of a sound absorbing chamber
forming shell. FIGS. 1 to 22 show embodiments of a double wall
structure respectively, and FIGS. 23 to 25 show the effects of the
double wall structure. Hereinafter, a description will be given in
order.
[0035] FIG. 1 is a schematic perspective view showing an example of
the double wall structure according to the present embodiment. A
double wall structure 1 of an embodiment 1-1 schematically shown in
FIG. 1 is assumed to be a door serving as a part of an
automobile.
[0036] The double wall structure 1 is provided with plate-like
bodies 2 and 3 arranged in parallel and opposing to each other with
leaving a predetermined distance. The plate-like bodies 2 and 3 are
formed in a rectangular shape with one direction being slightly
longer. Between the two plate-like bodies 2 and 3 opposing to each
other is formed an internal chamber 4. Side plates 5 are provided
so as to connect the plate-like bodies 2 and 3 to each other, and
thereby the internal chamber 4 is almost closed. In other words,
the double wall structure 1 of the present embodiment is formed in
a box shape in which the plate-like bodies 2 and 3 serving as
double walls and the side walls 5 surround the internal chamber
4.
[0037] In the present embodiment, at a position where a sound
pressure is high in the internal chamber 4 is provided a sound
absorbing chamber structure 6 having a porous surface (sound
pressure reducing portion) 6a in which a number of holes (through
portions) are formed on one surface in a rectangular
parallelepiped. As a material of the sound absorbing chamber
structure 6 having the porous surface 6a, all of materials capable
of forming the plate-like bodies such as iron, aluminum, resin and
paper, or porous foil-like bodies and the like can be used.
[0038] It should be noted that in the present embodiment, the sound
absorbing chamber structure 6 is formed in a rectangular
parallelepiped and has an independent internal chamber
(hereinafter, referred to as a sound absorbing chamber). Lower ends
of three sound absorbing chamber structures 6 are arranged within
the internal chamber 4 and in contact with a surface of the
plate-like body 2 on the radiation side. Specifically, the sound
absorbing chamber structure 6 and the plate-like body 2 are jointed
by adhering with an adhesive or the like. It should be noted that
the porous surface 6a is not necessarily be parallel to the
plate-like bodies 2 and 3. The present invention is not limited to
providing three sound absorbing structures 6 but may be provided
with one large sound absorbing chamber structure 6 and the inside
thereof may be partitioned into three.
[0039] It should be noted that when determining an installment
position of the porous surface 6a, a position where the sound
pressure is increased due to resonance in the internal chamber 4 is
determined by numerical calculation with the finite element method
or the boundary element method or by manufacturing and measuring an
actual structure, and the porous surface 6a is arranged at the
above position. However, there are many cases where the position
theoretically determined by calculation and the position where the
sound pressure is actually the highest do not strictly correspond
to each other and are different from each other. Therefore, the
position where the sound absorbing chamber structure 6 is actually
arranged is not strictly limited to the position where the sound
pressure is increased but may be a position in the vicinity of the
above position.
[0040] It should be noted that in the present embodiment, although
the sound absorbing chamber structure 6 is provided on the
plate-like body 2 side, the present invention is not limited to the
above but the sound absorbing chamber structure 6 may be provided
on the plate-like body 3 side.
[0041] When sound excitation is applied from the upper side to the
plate-like body 3 side in the above configuration, the plate-like
body 3 is vibrated so that the resonance is generated within the
internal chamber 4. However, the sound pressure of the internal
chamber 4 is reduced by a sound absorbing effect of the sound
absorbing chamber structure 6. Therefore, since vibration amplitude
of the plate-like body 2 on the lower side serving as a radiation
surface is reduced, it is possible to decrease a radiated sound
from the plate-like body 2 and improve sound transmission loss of
the double wall structure.
[0042] FIG. 2 shows an embodiment 1-2. In the above configuration,
four sound absorbing chamber structures 6 are arranged in the
lengthwise and crosswise directions (each two sound absorbing
chamber structures in the longitudinal direction and the lateral
direction respectively). That is, since the number of the sound
absorbing chamber structure 6 is increased from the case of the
embodiment 1-1, areas of the sound absorbing chamber and the porous
surface 6a are increased and hence it is possible to improve sound
transmission loss.
[0043] FIG. 3 shows an embodiment 1-3. In the above configuration,
porous surfaces 6a and 6b are formed in the sound absorbing chamber
structure 6. Therefore, since areas of the porous surfaces 6a and
6b of the four sound absorbing chamber structures 6 are increased,
it is possible to further improve sound transmission loss. It
should be noted that the number of the sound absorbing chamber
structure 6 is not limited to three or four, but the optimum number
may be determined in consideration to a resonance mode due to a
noise assumed within the internal chamber 4. Further, hole
diameters of the porous surfaces 6a and 6b may be optimally
adjusted respectively.
[0044] FIG. 4 shows an embodiment 2-1. In the above configuration,
an opening 2b is provided in a part of a plate-like body 2a on the
radiation side (a perforated member). A plate-like body 7 serving
as one of a closing member is provided so as to close the opening
2b. The sound absorbing chamber structure 6 is jointed to a surface
of the plate-like body 7. That is, the sound absorbing chamber
structure 6 and the plate-like body 7 are jointed with the adhesive
or the like. A description will be given later to other examples
and the like of the above joint state.
[0045] When the sound excitation is applied from the upper side to
the plate-like body 3 side in the above configuration, the
plate-like body 3 is vibrated so that the resonance is generated
within the internal chamber 4. The sound pressure of the sound
absorbing chamber is reduced by the sound absorbing chamber
structure 6. Therefore, since amplitude of the plate-like bodies 2a
and 7 on the lower side serving as the radiation surfaces is
reduced, it is possible to decrease the radiated sound from the
plate-like bodies 2a and 7 and improve sound transmission loss of
the double wall structure.
[0046] FIG. 5 shows an embodiment 2-2. The embodiment 2-2
corresponds to a combination of the embodiments 1-2 and 2-1. That
is, the four sound absorbing chamber structures 6 are arranged in
the lengthwise and crosswise directions (each two sound absorbing
chamber structures in the longitudinal direction and the lateral
direction respectively), and jointed to the surface of the
plate-like body 7. In the above configuration, since the number of
the sound absorbing chamber structure 6 is increased from the case
of the embodiment 2-1, the areas of the sound absorbing chamber and
the porous surface 6a are increased and hence it is possible to
improve sound transmission loss.
[0047] FIG. 6 shows an embodiment 2-3. The embodiment 2-3
corresponds to a combination of the embodiments 1-3 and 2-1. That
is, the sound absorbing chamber structure 6 has the porous surfaces
6a and 6b, and the four sound absorbing chamber structures 6 are
arranged in the lengthwise and crosswise directions (each two sound
absorbing chamber structures in the longitudinal direction and the
lateral direction respectively) and jointed in contact with the
surface of the plate-like body 7. In the above configuration, since
the areas of the porous surfaces 6a and 6b of the four sound
absorbing chamber structures 6 are increased, it is possible to
improve sound transmission loss. It should be noted that the number
of the sound absorbing chamber structure 6 is not limited to three
or four, but the optimum number may be determined in consideration
to the resonance mode due to the noise assumed within the internal
chamber 4.
[0048] FIG. 7 shows an embodiment 2-4. In the above configuration,
embossment having a concavity and convexity shape is provided on
the surface of the plate-like body 7 of the embodiment 2-3.
Therefore, it is possible to enhance rigidity of the plate-like
body 7. By using a plate-like body 7a provided with the embossment
in a concavity and convexity shape with enhanced rigidity, it is
possible to improve workability of the plate-like body 7a as well
as a sound absorbing property. It should be noted that although the
description is given to the embossment as a representative example
of the concavity and convexity shape in the present example, the
present invention is not limited to the above, and other arbitrary
concavity and convexity shapes may be formed.
[0049] FIG. 8 shows an embodiment 2-5. In the above configuration,
a vibration damping material 7b is adhered to the surface of the
plate-like body 7 of the embodiment 2-3. Therefore, the vibration
is reduced by the vibration damping material of the plate-like body
7b provided on the radiation surface side. As a result, it is
possible to improve sound transmission loss.
[0050] FIG. 9 shows an embodiment 2-6. In the above configuration,
a porous plate 7c is used instead of the plate-like body 7 of the
embodiment 2-3.
[0051] When the sound excitation is applied from the upper side to
the plate-like body 3 side in the above configuration, the
plate-like body 3 is vibrated so that the resonance is generated
within the internal chamber 4. The sound pressure of the internal
chamber 4 is reduced by the sound absorbing chamber structure 6 and
the porous plate 7c. Therefore, since amplitude of the plate-like
bodies 2a and 7c on the lower side serving as the radiation
surfaces is reduced, it is possible to decrease the radiated sound
from the plate-like bodies 2a and 7c and improve sound transmission
loss of the double wall structure.
[0052] FIG. 10 shows an embodiment 2-7. In the above configuration,
a material of the plate-like body 7 of the embodiment 2-3 is formed
of a porous body 7d. For example, an example of the porous body 7d
includes a sound absorbing material formed of a fiber system such
as grass wool and PET resin, or foam formed of open cells such as
urethane. It should be noted that although the entire plate-like
body 7 is formed of the porous body 7d, the present invention is
not limited to the above, and a part of a laminated thin film
structure may serve as the porous body 7d and be used in
combination with the porous plate.
[0053] In the above configuration, the sound absorbing property is
improved by the porous body 7d of the plate-like body 7. At the
time, the sound pressure of the internal chamber 4 is reduced by
the sound absorbing chamber structure 6 and the porous body 7d.
Therefore, since amplitude of the plate-like bodies 2a and 7d on
the lower side serving as the radiation surfaces is further
reduced, it is possible to further decrease the radiated sound from
the plate-like bodies 2a and 7d and improve sound transmission
loss.
[0054] Next, FIG. 11 shows an embodiment 3-1. In the above
configuration, a frame body 1c formed of a plate-like body 2c and
side walls 5c is attached from the lower side of the double wall
structure 1 of the embodiment 2-1. By attaching the frame body 1c,
the plate-like body 7 is sandwiched by the plate-like bodies 2a and
2c. It should be noted that the frame body 1c is attached so as to
provide a clearance between the plate-like bodies 2a and 7 and the
plate-like body 2c.
[0055] By the above configuration, in correspondence with the sound
excitation applied from the plate-like body 3 side, the plate-like
body 3 is vibrated so that the resonance is generated within the
internal chamber 4. However, the sound pressure of the internal
chamber 4 is reduced by the sound absorbing chamber structure 6
adhered and fixed to the plate-like member 7. Since amplitude of
the plate-like body 2c on the lower side serving as the radiation
surface is reduced, it is possible to improve sound transmission
loss of the double wall structure.
[0056] Next, a description will be given to the sound absorbing
chamber structure 6. FIGS. 12 to 15 are explanatory views on an
internal structure of the sound absorbing chamber structure 6.
[0057] FIG. 12 is a schematic sectional view showing the case where
the sound absorbing chamber structure 6 is formed in a part of the
plate-like body 2. In the above case, a lid member 61 is provided
along a surface of the plate-like body 2. In the case where the
configuration of FIG. 12 is applied to the embodiments 2-1 to 2-7
and 3-1, the sound absorbing chamber structure 6 is formed in a
part of the plate-like body 7 instead of the plate-like body 2.
[0058] FIG. 13 is a schematic sectional view showing the case where
the sound absorbing chamber structure 6 is formed in a part of a
sound absorbing chamber structure supporting member 6c.
[0059] In the above case, the sound absorbing chamber structure
supporting member 6c is provided in substantially parallel to the
plate-like body 2 or 7. In the above case, a clearance may be
provided between the sound absorbing chamber structure supporting
member 6c and the plate-like body 2 or 7, or conversely, no
clearance is provided.
[0060] FIG. 14 is a schematic sectional view showing the case where
the sound absorbing chamber structure 6 is formed in a container
shape with one surface thereof opened, and the surface of the sound
absorbing chamber structure 6 is substantially closed by the
plate-like body 2 or 7.
[0061] In the above case, a part of the sound absorbing chamber
structure 6 is screwed to the plate-like body 2 or 7. Therefore, it
is possible to enhance the rigidity of the sound absorbing chamber
structure 6.
[0062] Next, FIG. 15 is a schematic sectional view showing the case
where the sound absorbing chamber structure 6 is formed in a
rectangular parallelepiped container shape having the internal
chamber 4.
[0063] In FIG. 15, the sound absorbing chamber structure 6 is
jointed to the surface of the plate-like body 2 or 7 with an
adhesive 80.
[0064] In any case of FIGS. 12 to 15, the sound absorbing chamber
structure 6 is fixedly installed on the surface of the plate-like
body 2 or 7. Therefore, when the sound excitation is applied from
the upper side of the double wall structure 1 to the plate-like
body 3 side, the plate-like body 3 is vibrated so that the
resonance is generated within the internal chamber 4. At the time,
the sound pressure of the internal chamber 4 is reduced by the
sound absorbing chamber structure 6. Therefore, since amplitude of
the plate-like body 2 on the lower side serving as the radiation
surface is reduced, it is possible to decrease the radiated sound
from the plate-like body 2 and improve sound transmission loss of
the double wall structure.
[0065] Next, FIGS. 16 to 20 are schematic sectional views for
showing a shape of the sound absorbing chamber structure 6.
[0066] FIG. 16 is a schematic sectional view showing the case where
the sound absorbing chamber structure 6 is formed from a
rectangular parallelepiped.
[0067] As shown in FIG. 16, as well as the embodiment 1-1, the
porous surface 6a is preferably formed in substantially parallel to
the plate-like body 2. As in the embodiment 1-3, the porous surface
6b may be formed with the porous surface 6a substantially
perpendicularly to the plate-like body 2 (not shown).
[0068] FIG. 17 is a schematic sectional view showing the case where
the sound absorbing chamber structure 6 is formed in a shape in
which a cylinder is vertically divided.
[0069] In the above case, the porous surface 6a is formed on the
almost entire surface of the divided cylinder shape sound absorbing
chamber structure 6x. It should be noted that in FIG. 17, although
the description is given to the divided cylinder shape sound
absorbing chamber structure 6x, the present invention is not
limited to the above, and may be a sound absorbing chamber
structure formed of other arbitrary curved surfaces such as an
ellipse. Although the porous surface 6a is formed on the entire
surface, the present invention is not limited to the above, and the
porous surface 6a may be formed on a part thereof.
[0070] Next, FIG. 18 is a schematic sectional view showing the case
where the sound absorbing chamber structure 6 is formed in a
conduit shape forming a polygon cross section (a pentagon in the
figure) between the sound absorbing chamber structure 6 and the
plate-like body 2 or 7.
[0071] In the above case, the porous surface 6a is formed on the
almost entire surface of the polygon conduit shape sound absorbing
chamber structure 6y. It should be noted that in FIG. 18, although
the description is given to the polygon conduit shape sound
absorbing chamber structure 6y, the present invention is not
limited to the above, and a sound absorbing chamber structure may
be formed from a part of the polygon conduit shape sound absorbing
chamber structure 6y. Further, although the porous surface 6a is
formed on the entire surface, the present invention is not limited
to the above, and the porous surface 6a may be formed on a part
thereof.
[0072] FIG. 19 is a schematic sectional view showing the case where
the sound absorbing chamber structure 6 is formed in a conduit
shape with a V-shape cross-section.
[0073] In the above case, the porous surface 6a is formed on the
almost entire surface of the V conduit shape sound absorbing
chamber structure 6z. It should be noted that in FIG. 19, although
the description is given to the V conduit shape sound absorbing
chamber structure 6z, the present invention is not limited to the
above, and a sound absorbing chamber structure may be formed from a
part of the V conduit shape sound absorbing chamber structure 6z.
Although the porous surface 6a is formed on the entire surface, the
present invention is not limited to the above, and the porous
surface 6a may be formed on a part thereof.
[0074] FIG. 20 is a schematic sectional view showing the case where
the sound absorbing chamber structure 6 is formed in a cylindrical
shape.
[0075] In the above case, the porous surface 6a is formed in a part
of the cylindrical shape sound absorbing chamber structure 6R. The
cylindrical shape sound absorbing chamber structure 6R is adhered
and fixed to the plate-like body 2 or 7 with the adhesive 80.
[0076] It should be noted that in FIG. 20, although the description
is given to the cylindrical shape sound absorbing chamber structure
6R, the present invention is not limited to the above, and a sound
absorbing chamber structure may be formed from a part of the
cylindrical shape sound absorbing chamber structure 6R. Although
the porous surface 6a is formed in a part thereof, the present
invention is not limited to the above, and the porous surface 6a
may be formed on the entire surface.
[0077] In the above embodiment, although the description is given
to the configuration that the sound absorbing chamber structure 6
is arranged between the plate-like bodies 2 and 3 (within the
internal chamber 4), the sound absorbing chamber structure 6 can be
arranged at a position outside the plate-like body 2 or 3 as shown
in FIG. 21.
[0078] In an embodiment shown in FIG. 21, since the sound absorbing
chamber structure 6 is attached on a lower surface of the
plate-like body 2, the sound absorbing chamber is formed between
the sound absorbing chamber structure 6 and the plate-like body 2.
A porous surface (a sound pressure reducing portion) 2d in which a
number of holes (through portions) are formed is provided in the
plate-like body 2 so as to communicate with the internal chamber 4
between the plate-like bodies 2 and 3 and the sound absorbing
chamber.
[0079] When the sound excitation is applied from the upper side to
the plate-like body 3 side in the above embodiment, the plate-like
body 3 is vibrated so that the resonance is generated within the
internal chamber 4. However, the sound pressure of the internal
chamber 4 is reduced by the sound absorbing effect of the sound
absorbing chamber structure 6. Therefore, since vibration amplitude
of the plate-like body 2 on the lower side serving as the radiation
surface is reduced, it is possible to decrease the radiated sound
from the plate-like body 2 and improve sound transmission loss of
the double wall structure.
[0080] In the above embodiment, since the sound absorbing chamber
can be formed at positions outside both the plate-like bodies 2 and
3, it is possible to ensure a wide space (the internal chamber 4)
on the inside of both the plate-like bodies 2 and 3 while
exhibiting a sound pressure reducing effect mentioned above.
Therefore, according to the above embodiment, even in the case
where predetermined equipment is arranged within the internal
chamber 4, it is possible to maintain a high degree of freedom of
the arrangement so as to improve efficiency of an arrangement work
of the equipment, while exhibiting a high sound insulation
effect.
[0081] Further, as shown in FIG. 22, in the configuration provided
with the plate-like body 2a in which the opening 2b is provided and
the plate-like body 7 for closing the opening 2b, it is possible to
attach the sound absorbing chamber structure 6 on an outer surface
of the plate-like body 7.
[0082] In the above embodiment, the sound absorbing chamber is
formed between the sound absorbing chamber structure 6 and the
plate-like body 7. A porous surface (a sound pressure reducing
portion) 7e in which a number of holes (through portions) are
formed is provided in the plate-like body 7 so as to communicate
with the internal chamber 4 and the sound absorbing chamber.
[0083] In order to confirm effectiveness of the above embodiments,
the following experiments are conducted. That is, the double wall
structures 1 of the structures of the embodiments 1-1 to 1-3 and
2-1 to 2-7 are installed at positions between both a sound source
chamber and a sound receiving chamber in a reverberation chamber
formed of the sound source chamber and the sound receiving chamber.
On the basis of JIS A1416, a proper noise is generated from one
side of the double wall structures 1, and the sound pressure is
measured on the both sides sandwiching the double wall structures 1
with using a noise meter so as to determine sound transmission
loss.
[0084] Results thereof are shown in FIGS. 23 to 25. It should be
noted that results of similar experiments performed with regard to
the structure of the conventional example (FIG. 26) are also shown
in graphs of FIGS. 23 to 25. As shown in the graphs of the figures,
sound transmission loss is dropped in a frequency area around 315
Hz in the conventional example. It is assumed that the resonance is
generated in the above part.
[0085] Meanwhile, in the configuration of the embodiments of the
present invention, as a result of reducing the sound pressure by
the sound absorbing chamber structure 6 having the porous surface
6a at a position where the sound pressure is increased, or as a
result of reducing the resonance of a vibration system, it is found
that a sound insulation performance can be improved.
[0086] Although the preferred embodiments of the present invention
are shown above, a technical scope of the present invention is not
limited to the above embodiments, but can be changed and performed
in various ways.
[0087] For example, the double wall structure 1 according to the
present invention can be applied not only to the door of the
automobile, but also to a hood and a trunk lid for example. It is
needless to say that the shape of the plate-like bodies 2 and 3 is
not limited to the rectangle mentioned above, but can be variously
changed in accordance with a shape of parts required.
[0088] Although the sound absorbing chamber structure 6 is jointed
to the plate-like body 2 on the radiation side, the present
invention is not limited to the above, and the sound absorbing
chamber structure 6 may be jointed to the plate-like body 3 on the
incident side.
[0089] The direction of the porous surface 6a may be arbitrarily
determined in consideration to various situations such as a
positional relationship with a noise source.
[0090] Further, as the porous body 7d, it is possible to use for
example polyurethane, the foam formed of the open cells in addition
to the grass wool mentioned above, a felt and the like. Through
holes of the porous plate 7c are preferably minute so that a
viscous effect in the air passing through the holes can be
expected.
[0091] In the above embodiments, although the description is given
to an example that a number of holes (through portions) are formed
as the porous surfaces 2d, 6a and 7e, the through portions are not
limited to the holes, but can be slits for example.
[0092] The present invention is described in the above preferred
embodiments but is not limited to the above. It can be understood
that various other embodiments are performed without departing from
the spirit and the scope of the present invention. Further, in the
present embodiments, although operations and effects by the
configuration of the present invention are described, the
operations and effects are only examples and do not limit the
present invention.
[0093] That is, the present invention has the following
configuration at least.
[0094] (1) The double wall structure according to the present
invention has plate-like bodies opposing to each other, a
completely or almost closed internal chamber being formed between
the plate-like bodies, the double wall structure comprising a sound
absorbing chamber forming shell forming a sound absorbing chamber
provided in at least one plate-like body among the plate-like
bodies, the sound absorbing chamber forming shell being adjacent to
the plate-like body and isolated from the internal chamber, and a
sound pressure reducing portion for reducing a sound pressure in
the internal chamber, the sound pressure reducing portion having a
number of through portions passing through the sound absorbing
chamber forming shell or the plate-like bodies so as to open the
sound absorbing chamber to the internal chamber.
[0095] In the double wall structure according to the present
invention, the sound pressure reducing portion having a number of
the through portions for opening the sound absorbing chamber to the
internal chamber is formed in the sound absorbing chamber forming
shell or the plate-like bodies. It should be noted that the
"closing" does not only mean strict sealing but also includes a
case where there is partially a clearance or an opening. The sound
absorbing chamber serving as a sound absorbing mechanism is
preferably formed in the vicinity of a part with a high sound
pressure in a resonance state of the internal chamber.
[0096] In the case where sound excitation is applied from one side
of the double wall structure, the resonance is generated within the
internal chamber. By a sound absorbing effect of the sound pressure
reducing portion, it is possible to effectively reduce the sound
pressure of the internal chamber. Thereby, since a sound excitation
force to the radiation surface of the other side of the double wall
structure is reduced, it is possible to reduce vibration amplitude
of the radiation surface and improve a sound transmission loss. It
should be noted that the sound absorbing effect of the sound
pressure reducing portion is generated by energy dissipation due to
friction in an inner wall surface of the through portion when the
resonance is generated in a spring-mass system in which the air
within the sound absorbing chamber is the spring and the air inside
the through portion is a mass. Therefore, a size of the sound
absorbing chamber, a specification of the through portion (a
diameter and an aperture ratio) and the like have to be designed so
that a frequency of the resonance of the internal chamber to be
suppressed (that is, a frequency to improve sound transmission
loss) substantially corresponds to a resonance frequency of the
spring-mass system of the sound absorbing chamber and the through
portion. In the case where the through portion is minute, the
energy dissipation due to a vortex generated in the vicinity of the
through portion is added and hence a larger sound absorbing effect
is generated in a wider frequency range.
[0097] (2) The sound absorbing chamber forming shell can be
provided in an inner surface of the plate-like bodies, and the
sound pressure reducing portion is provided in at least a part of
the sound absorbing chamber forming shell.
[0098] In the above case, by providing the sound absorbing chamber
forming shell in the inner surface of the plate-like bodies, it is
possible to form the sound absorbing chamber at a position on the
inside of both the plate-like bodies.
[0099] (3) The sound absorbing chamber forming shell can be
provided in an outer surface of the plate-like bodies, and the
sound pressure reducing portion can be provided in at least a part
of the plate-like bodies.
[0100] In the above case, by providing the sound absorbing chamber
forming shell in the outer surface of the plate-like bodies, it is
possible to form the sound absorbing chamber at a position on the
outside of both the plate-like bodies. Therefore, it is possible to
ensure a wide space (the internal chamber) on the inside of both
the plate-like bodies, while exhibiting the sound pressure reducing
effect mentioned above. Consequently, according to the above
configuration, even in the case where predetermined equipment is
arranged within the internal chamber, it is possible to maintain a
high degree of freedom of the arrangement so as to improve the
efficiency of the arrangement work of the equipment, while
exhibiting a high sound insulation effect.
[0101] (4) At least one plate-like body among the plate-like bodies
can be provided with a perforated member in which an opening for
opening the internal chamber to the outside is formed, and a
closing member attached to the perforated member so as to close the
opening, and the sound absorbing chamber forming shell can be
provided in the closing member.
[0102] In the above configuration, the closing member provided with
the sound absorbing chamber forming shell is installed for the
opening formed in a part of the perforated member. It should be
noted that the "closing" does not only mean strict sealing but also
includes the case where there is partially the clearance or the
opening. The sound absorbing chamber serving as the sound absorbing
mechanism is preferably formed in the vicinity of the part with the
high sound pressure in the resonance state of the internal
chamber.
[0103] In the above case, since the internal chamber of the double
wall structure is closed, when the sound excitation is applied from
one side of the double wall structure, the resonance is generated
within the internal chamber. However, by the sound absorbing effect
of the sound pressure reducing portion, it is possible to
effectively reduce the sound pressure of the internal chamber.
Thereby, since the sound excitation force to the radiation surface
of the other side of the double wall structure is reduced, it is
possible to reduce the vibration amplitude of the radiation
surfaces and improve sound transmission loss.
[0104] (5) The closing member may include a vibration damping
member formed of a structure or a material having a vibration
damping property. It should be noted that the vibration damping
member includes a plate-like body in which a vibration damping
material is laminated, and a plate-like body in which a constraint
plate is laminated through the vibration damping material. It
should be noted that the closing member includes a plate-like
member or a sheet like body. The sheet like body means a body which
is thinner than a plate such as a coat, a foil and a film, and a
metal foil, a resin coat, cloth, a nonwoven fabric or the like can
be used.
[0105] Even in the case where the sound excitation is applied by
the above configuration, since the closing member itself has the
vibration damping property, it is possible to reduce amplitude of
the closing member itself and stably exhibit the sound insulation
performance. It should be noted that as means for providing the
vibration damping property of the closing member, the plate-like
member may be the vibration damping member (such as a vibration
damping steel plate, a vibration damping aluminum plate, and a
vibration damping resin), or the vibration damping material (such
as a vibration damping rubber, and the vibration damping resin) may
be adhered to the plate-like member.
[0106] (6) The closing member may include a concavity and convexity
member. It should be noted that an example of processing for
providing the concavity and convexity member includes
embossment.
[0107] In the above case, since the rigidity and the vibration
damping property of the closing member can be enhanced, it is
possible to reduce amplitude of the plate-like member itself and
stably exhibit the sound insulation performance.
[0108] (7) The closing member preferably includes a structure or a
material having a sound absorbing property. In the above case, the
sound absorbing property can be improved by not only the sound
pressure reducing portion but also the closing member and the
resonance of the internal chamber can be reduced. Therefore, it is
possible to stably exhibit the sound insulation performance.
[0109] (8) The closing member preferably comprises a porous body.
It should be noted that the number of the porous body is not
limited to one, but may be a plurality of porous bodies, or may be
formed by laminating the porous body and a porous plate.
[0110] In the above case, the sound absorbing property can be
improved by not only the sound pressure reducing portion but also
the closing member and the resonance of the internal chamber can be
reduced. Therefore, it is possible to stably exhibit the sound
insulation performance.
[0111] It should be noted that as a design condition of holes, it
is possible to use a design condition described in Japanese Patent
Laid-Open No. 2003-050586 for example. Specifically, the design
condition with regard to the porous plate of the above sound
pressure reducing portion can be set so that for example a plate
thickness, a hole diameter and an aperture ratio satisfy a design
condition for generating the viscous effect in the air passing
through the through portions.
[0112] As a result of facilitating conversion of air vibration due
to the viscous effect into thermal energy by the double wall
structure provided with the sound pressure reducing portion having
a number of the through portions, a sufficient sound absorbing
performance is surely exhibited in a wide frequency bandwidth.
Thereby, an excellent sound absorbing performance is obtained for
not only the noise of resonance frequency but also the noise of
other frequency.
[0113] Further, in a part of the double wall structure having a
number of the through portions, for example the frequency bandwidth
with a sound absorption coefficient of 0.3 or more may be set to
10% or more with regard to the resonance frequency of the sound
absorbing chamber. Further, the aperture ratio of a number of the
through portions may be 3% or less. Further, the diameter of the
through portions may be 3 mm or less, and a sound source of an
object to which the sound insulation is performed may be 70 dB or
more.
[0114] It should be noted that the diameter of the through portions
is preferably 1 mm or less. It should be noted that since the
diameter according to the present invention is provided in the
sound pressure reducing portion, even the diameter of the through
portions of 0.2 mm or less can be used.
[0115] (9) A plurality of the sound absorbing chamber forming
shells may be provided in one of the plate-like bodies, and a
plurality of sound absorbing chambers may be formed by the sound
absorbing chamber forming shells.
[0116] In the above case, since a plurality of the sound absorbing
chambers are formed by a plurality of the sound absorbing chamber
forming shells, a specification (the diameter of the through
portions, the thickness of the plate in which the through potions
are formed, a thickness of an air layer, the aperture ratio and the
like) can be changed for each of the sound absorbing chambers.
Therefore, it is possible to suppress a number of resonances and
improve sound transmission loss.
[0117] (10) The sound absorbing chamber forming shell may be
provided with a partition member, and the sound absorbing chamber
may be partitioned into a plurality of small chambers by the
partition member.
[0118] In the above case, since a plurality of the small chambers
are formed by the partition member, the specification (the diameter
of the through portions, the thickness of the plate in which the
through potions are formed, the thickness of the air layer, the
aperture ratio and the like) can be changed for each of the small
chambers. Therefore, it is possible to suppress a number of
resonances and improve sound transmission loss. The number of the
above plate in which the through portions are formed is not limited
to one, but a plurality of plates may be laminated or may be formed
in a multiple layer with leaving a space (a clearance).
[0119] (11) The sound absorbing chamber forming shell may include a
concavity and convexity shape.
[0120] In the above case, since the sound absorbing chamber forming
shell itself includes a concavity and convexity shape, it is
possible to improve a processing performance in processing such as
deep drawing, strength against the vibration and the like at the
time of forming the sound absorbing chamber forming shell. The
concavity and convexity shape may be included in a part of the
sound absorbing chamber forming shell, and the concavity and
convexity shape may be formed on the entire sound absorbing chamber
forming shell. It should be noted that the processing for providing
the concavity and convexity shape includes processing by the
embossment or the like.
INDUSTRIAL APPLICABILITY
[0121] According to the present invention, it is possible to
suppress an increase in a sound transmission amount with regard to
sound with a specified frequency, and stably exhibit the sound
insulation performance for sound with various frequencies.
* * * * *