U.S. patent application number 11/882210 was filed with the patent office on 2008-01-24 for vibration-damping device for vehicles and method of manufacturing the same.
This patent application is currently assigned to TOKAI RUBBER INDUSTRIES, LTD.. Invention is credited to Kouichi Maeda, Yoshinori Yasumoto.
Application Number | 20080018032 11/882210 |
Document ID | / |
Family ID | 35308666 |
Filed Date | 2008-01-24 |
United States Patent
Application |
20080018032 |
Kind Code |
A1 |
Yasumoto; Yoshinori ; et
al. |
January 24, 2008 |
Vibration-damping device for vehicles and method of manufacturing
the same
Abstract
A vehicle vibration-damping device including a rigid housing and
an independent mass member housed in the housing and having a
metallic mass of circular shape in section and a rubber elastic
body layer adhered to the metallic mass. A distance of a gap
between opposing surfaces of the housing and the metallic mass in
the radial direction, with the housing and metallic mass disposed
coaxially, is set to between 0.5 and 2 mm. The rubber elastic body
layer is formed around an entire outer peripheral surface of the
metallic mass by a vulcanization molding of a rubber material
filling the gap, and thermal contraction is used both to cause the
rubber elastic body layer to peel from the housing and to cause it
to adhere onto the outer peripheral surface of the metallic mass to
thereby fabricate a small gap of no more than 0.1 mm. A method of
manufacturing the same is also disclosed.
Inventors: |
Yasumoto; Yoshinori;
(Kasugai-shi, JP) ; Maeda; Kouichi;
(Nishikamo-gun, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
TOKAI RUBBER INDUSTRIES,
LTD.
Komaki-shi
JP
|
Family ID: |
35308666 |
Appl. No.: |
11/882210 |
Filed: |
July 31, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11125115 |
May 10, 2005 |
7267740 |
|
|
11882210 |
Jul 31, 2007 |
|
|
|
Current U.S.
Class: |
267/141.2 |
Current CPC
Class: |
Y10T 29/49615 20150115;
F16F 7/108 20130101 |
Class at
Publication: |
267/141.2 |
International
Class: |
F16F 7/00 20060101
F16F007/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 14, 2004 |
JP |
2004-145348 |
Claims
1. A vehicle vibration-damping device adapted to be installed on a
vibrating member to damp vibrations excited therein, comprising: a
rigid housing having a cylindrical inner peripheral surface, that
is adapted to be attached to the vibrating member; and an
independent mass member including a metallic mass having a circular
shape in cross section, and a rubber elastic body layer adhered to
an outer peripheral surface of the metallic mass, the independent
mass member being housed within the housing with a gap therebetween
in a radial direction corresponding to a primary vibration input
direction so that the independent mass member is movable relative
to the housing in the primary vibration input direction, the
vibration-damping device being capable of exhibiting a
vibration-damping effect based on the independent mass member
moving relative to the housing, and striking the housing, when a
vibration is applied, wherein a distance between opposing surfaces
of the inner peripheral surface of the housing and the outer
peripheral surface of the metallic mass in the radial direction,
when the housing and metallic mass are disposed coaxially, is set
to between 0.5 and 2 mm, and wherein the rubber elastic body layer
is formed around an entire outer peripheral surface of the metallic
mass by a vulcanization molding of a rubber material filling the
gap between the inner peripheral surface of the housing and the
outer peripheral surface of the metallic mass, and thermal
contraction is used both to cause the rubber elastic body layer to
peel from the housing and to cause the rubber elastic body layer to
adhere onto the outer peripheral surface of the metallic mass to
thereby fabricate a small gap of no more than 0.1 mm, between the
opposing surfaces, when the rubber elastic layer member and the
housing are disposed coaxially, so that a natural frequency of the
independent mass member is set to a frequency band that is higher
than a natural frequency of the vibrating member so that the
metallic mass repetitively strikes the inner surface of the housing
on both sides in the primary vibration input direction through the
rubber elastic body layer when a vibration is applied.
2. A vehicle vibration-damping device according to claim 1, wherein
the vibration-damping device is disposed in a state where the
primary vibration input direction is approximately vertically
oriented, and when the vibration-damping device is subjected to at
least 2G input vibration, the independent mass member undergoes
repetitive strike against the inner peripheral surface of the
housing on both sides in the primary vibration input direction.
3. A vehicle vibration-damping device according to claim 1, wherein
at least one through hole is fabricated in the housing in a
position that avoids the part wherein the independent mass member
strikes the housing when a vibration is applied in the primary
vibration input direction.
4. A vehicle vibration-damping device according to claim 1, wherein
an outer peripheral surface of the rubber elastic body layer and
the inner peripheral surface of the housing are fabricated so as to
extend in the axial direction with approximately uniform cross
sections so that the small gap that is fabricated between the outer
peripheral surface of the rubber elastic body layer and the inner
peripheral surface of the housing is approximately uniform along
the entire length in the axial direction.
Description
INCORPORATED BY REFERENCE
[0001] This is a Division of application Ser. No. 11/125,115 filed
May 10, 2005, which claims priority of Japanese Application No.
2004-145348 filed May 14, 2004. The entire disclosure of the prior
application is hereby incorporated by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a vibration-damping device
for use in a vehicle, which reduces vibrations excited in vibrating
members of the vehicle, and more particularly to a vehicle
vibration-damping having a novel structure capable of exhibiting
effective vibration-damping performance when being applied to
vibrating members such as transmission cases, suspension arms,
sub-frames, body panels, engine units, mount brackets, exhaust
system components, and so forth.
[0004] 2. Description of the Related Art
[0005] Conventional known means for reducing vibration that are
problematic in vehicles, such as automobiles, includes: (1) mass
dampers wherein masses are affixed to the vibrating members, (2)
dynamic dampers wherein masses are connected to the vibrating
member, and supported by, a spring, and (3) vibration-damping
materials wherein sheet-shaped elastic materials are adhered to the
surfaces of the vibrating members. However, the (1) mass dampers
and (2) dynamic dampers not only have problems in that they require
large masses, but also that the range of frequencies over which
there is effective vibration-damping is narrow. Moreover, the (3)
vibration-damping materials have a problem in that not only is a
large adhesive surface area required, but the mass is large as
well. Furthermore, the (2) dynamic damper and (3) vibration-damping
materials have temperature dependencies in the vibration-damping
effect, and hence there is a problem in that it is difficult to
obtain the desired stability in the vibration-damping effect.
[0006] In order to address problems such as those described above,
JP-A-2001-241493 and JP-A-2002-213423, for example, disclose
vibration-damping devices for vehicles of an attenuation-impact
type wherein an independent mass member is disposed within a
housing affixed to the vibrating member, with a gap of a specific
size interposed therebetween, and without being adhesive to the
housing, so that the independent mass can move relative to the
housing. Upon input of vibrations, the independent mass member is
forced to move relative to the housing in the vibration input
direction to strike the housing through an elastic member, whereby
vibration-damping effect is obtained through the use of energy loss
due to sliding friction and collision when there are impacts
between the independent mass member against the housing. This type
of vehicle vibration-damping device affords the advantage of
smaller mass when compared to the various types of conventional
vibration-damping devices described above (such as the dynamic
damper), but also that it is possible to obtain excellent
vibration-damping effect relative to many different and broad
ranges of vibration through tuning the resonant frequency of the
vibration-damping device by appropriately changing the settings of,
for example, hardness or modulus of elasticity of the elastic
member, or the gap between the elastic member and either the mass
member or the housing, depending on the resonant frequency of the
objective vibrating member for which the vibration is to be
controlled.
[0007] However, in recent years, this type of attenuation
impact-type vibration-damping device for automobiles have been
subjected to calls for even more sophisticated anti-vibration
characteristics. In particular, there are cases wherein there are
calls for improvements in the vibration-damping effects for
vibrations in even higher frequency bands.
[0008] With this regards, the extensive studies conducted by the
inventors have discovered that the attenuation impact-type
vibration-damping device described above suffers from a problem
that the vibration-damping effect is greatly reduced for vibrations
in high frequency bands higher than the resonant frequency at which
the independent mass member undergoes jumping displacement relative
to the housing.
[0009] In order to cope with these problems, one may consider, for
example, increasing the spring constant of the elastic member at
the striking part of the mass member against the housing to
increase the resonant frequency of the independent mass member.
However, in order to increase the resonant frequency to several
hundred hertz or above, the elastic member will be extremely hard,
due to the increase in the spring constant of the elastic member.
This results in a tendency for the striking noise and the shock to
be problematic when the elastic member strikes the housing, and
thus this is not always an effective approach.
SUMMARY OF THE INVENTION
[0010] It is therefore one object of this invention to provide a
vibration-damping device for use in a vehicle with a novel
structure that effectively exhibiting the desired vibration-damping
effect through the setting of the natural frequencies of the
independent mass members to higher frequency bands than the natural
frequencies of the vibrating members for which the vibrations are
to be controlled, while maintaining the spring component of the
rubber elastic body layer in the independent mass members.
[0011] The above and/or optional objects of this invention may be
attained according to at least one of the following modes of the
invention. Each of these modes of the invention is numbered like
the appended claims and depending from the other mode or modes,
where appropriate, to indicate possible combinations of elements or
technical features of the invention. It is to be understood that
the principle of the invention is not limited to these modes of the
invention and combinations of the technical features, but may
otherwise be recognized based on the teachings of the present
invention disclosed in the entire specification and drawings or
that may be recognized by those skilled in the art in the light of
the present disclosure in its entirety.
[0012] A first aspect of the present invention relates to a vehicle
vibration-damping device. According to a first mode of the first
aspect of the invention, provided is a vehicle vibration-damping
device adapted to be installed on a vibrating member to damp
vibrations excited therein, comprising: a rigid housing having a
cylindrical inner peripheral surface, that is adapted to be
attached to the vibrating member; and an independent mass member
including a metallic mass having a circular shape in cross section,
and a rubber elastic body layer adhered to an outer peripheral
surface of the metallic mass, the independent mass member being
housed within the housing with a gap therebetween in a radial
direction corresponding to a primary vibration input direction so
that the independent mass member is movable relative to the housing
in the primary vibration input direction, the vibration-damping
device being capable of exhibiting a vibration-damping effect based
on the independent mass member moving relative to the housing, and
striking the housing, when a vibration is applied, wherein a
distance between opposing surfaces of the inner peripheral surface
of the housing and the outer peripheral surface of the metallic
mass in the radial direction, when the housing and metallic mass
are disposed coaxially, is set to between 0.5 and 2 mm, and wherein
the rubber elastic body layer is formed around an entire outer
peripheral surface of the metallic mass by a vulcanization molding
of a rubber material filling the gap between the inner peripheral
surface of the housing and the outer peripheral surface of the
metallic mass, and thermal contraction is used both to cause the
rubber elastic body layer to peel from the housing and to cause it
to adhere onto the outer peripheral surface of the metallic mass to
thereby fabricate a small gap of no more than 0.1 mm, between the
opposing surfaces, when the rubber elastic layer member and the
housing are disposed coaxially, so that a natural frequency of the
independent mass member is set to a frequency band that is higher
than a natural frequency of the vibrating member so that the
metallic mass is repetitively strike the inner surface of the
housing on both sides in the primary vibration input direction
through the rubber elastic body layer when a vibration is
applied.
[0013] In a vehicle vibration-damping device of construction
according to this mode, the use of the cylindrically-shaped inner
peripheral surface of the housing and metallic mass that is
circular in its cross section makes it possible to stabilize and
cause the independent mass member to strike the housing when a
vibration is applied in the radial direction. In addition, the
small gap that is formed between the facing surfaces of the rubber
elastic body layer and the inner peripheral surface of the housing
in the radial direction, is no more than 0.1 mm. As a result,
reduced is the amount of movement required for the independent mass
member to come to impact against the inner surfaces on both sides
of the housing in the vibration input direction, causing desirable
impacts of the independent mass member against the inner surface of
the housing on both sides of the housing in the vibration input
direction. This makes it possible to tune the independent mass
member to the high frequency band, which ultimately could not be
achieved by the prior technology.
[0014] The vibration-damping device of this mode is able to set the
resonant frequency of the independent mass member to an adequately
high frequency band through the structure described above, without
having the dynamic spring constant of the rubber elastic body layer
be extremely large. With this arrangement, it is possible to avoid
problems with striking noises, impacts, and the like, accompanying
the striking of the independent mass member that would result from
the rubber elastic body layer being too hard due to the high spring
constant, making it possible to exhibit an extremely effective
vibration-damping performance over an extremely broad frequency
band, ranging from low frequency bands through high frequency
bands.
[0015] While the technological theory that makes it possible to
achieve the results described above is not yet fully clear, the
following may be considered: In a state wherein the independent
mass members are dislocated so as to be off of the housing, and are
in an essentially floating state, since the rubber elastic body
layer spring does not operate in this state, it may be that
increase in the hardness of the spring of the rubber elastic body
layer will have very little contribution to increasing the
resonance frequency. In the vibration-damping device of
construction according to the present mode of the invention, on the
other hand, it is possible to use effectively the spring effect of
the rubber elastic body layer, since the independent mass member
can be brought into impact against the housing at both ends of the
movement. Additionally, by having an extremely small gap, i.e., a
gap of no more than 0.1 mm in the radial direction between the
facing surfaces of the outer peripheral surface of the independent
mass member and the inner peripheral surface of the housing, the
amount of float time wherein the independent mass member is off of
the housing can be reduced substantially, making it possible for
the spring effect of the rubber elastic body layer to be effective
over a longer period of time. Accordingly, it may be possible to
increase substantially the resonance frequency of the independent
mass member through using effectively the spring effect of the
rubber elastic body layer without increasing the spring constant of
the rubber elastic body layer as much.
[0016] Also, in this embodiment of the invention, the size of the
small gap and the distance between the surfaces that are facing
each other in the radial direction, those being the inner
peripheral surface of the housing and the outer peripheral surface
of the metallic mass, under the condition that the housing and the
metallic mass are disposed coaxially, are not limited in any way,
but rather it is possible to change both settings independently, as
appropriate, depending on the required vibration-damping results,
required manufacturability and so forth. Moreover, meant by the
size of the small gap and the distance, in the radial direction,
between opposing surfaces those being the inner peripheral surface
of the housing and outer peripheral surface of, the metallic mass,
is the size of the small gap and the distance between opposing
surfaces on each of the individual small gaps and distances between
opposing surfaces that are produced on both sides, with the central
axis there between, on radial lines that pass through the central
axis of the housing and of the independent mass members under the
condition that the housing and the independent mass members are
coaxial. Furthermore, the small gap should be formed at at least
one part of the surfaces that oppose each other in the radial
direction, those being the inner peripheral surface of the housing
and the outer peripheral surface of the rubber elastic body layer,
under the condition that the housing and the rubber elastic body
layer member are disposed coaxially. Preferably, in consideration
of stabilizing the impacts of the independent mass members with the
housing, the small gap is fabricated along the entirety of the
space between the opposing surfaces.
[0017] A second mode of the first aspect of the invention provides
a vehicle vibration-damping device according to the first mode,
wherein in the case where the vibration-damping device is disposed
in a state where the primary vibration input direction is
approximately vertically oriented and is subjected to at least 2G
input vibration, the independent mass member undergoes repetitive
strike against the inner peripheral surface of the housing on both
sides of the housing in the primary vibration input direction.
[0018] A third mode of the first aspect of the invention provides a
vehicle vibration-damping device according to the first or second
mode, wherein at least one through hole is fabricated in the
housing in a position that avoids the part wherein the independent
mass member strikes the housing when a vibration is applied in the
primary vibration input direction.
[0019] A fourth mode of the first aspect of the invention provides
a vehicle vibration-damping device according to any one of the
first through third modes, wherein an outer peripheral surface of
the rubber elastic body layer and the inner peripheral surface of
the housing are fabricated so as to extend in the axial direction
with approximately uniform cross sections so that the small gap
that is fabricated between the outer peripheral surface of the
rubber elastic body layer and the inner peripheral surface of the
housing is approximately uniform along the entire length in the
axial direction.
[0020] A second aspect of the present invention relates to a method
of manufacturing a vehicle vibration-damping device. According to a
first mode of the second aspect of the invention, provided is a
method of manufacturing a vehicle vibration-damping device
comprising: (a) a gap fabricating process that fabricates a gap of
0.5-2 mm between an inner peripheral surface of a rigid housing and
an outer peripheral surface of a metallic mass, by rigidly
positioning the housing having an inner peripheral surface of
cylindrical shape and the metallic mass having a cylindrical cross
section, relative to a vulcanization fabrication mold for
fabricating a rubber elastic body layer, while by disposing the
metallic mass coaxially disposed within the housing; (b) a rubber
elastic body layer fabricating process wherein a rubber material is
filled into the gap, and then is vulcanized to mold the rubber
material within a mold cavity that is formed between the housing
and the metallic mass in order to fabricate the rubber elastic body
layer; and (c) a small gap fabricating process that fabricates a
small gap of no more than 0.1 mm between the outer peripheral
surface of the rubber elastic body layer and the inner peripheral
surface of the housing that are opposed to each other in a radial
direction, under a condition of the metallic mass being disposed
coaxially within the housing, by utilizing a thermal contraction of
the rubber elastic body layer to both peel the rubber elastic body
layer from the housing and to adhere the rubber elastic body layer
by means of reduction of an diameter thereof towards the metallic
mass, wherein a natural frequency of the independent mass member
that is formed by a tight adherence of the rubber elastic body
layer to the outer peripheral surface of the metallic mass is set
to be at a frequency band that is higher than a frequency of a
target vibration that is to be damped for a vibrating member so
that, upon application of the target vibration, the independent
mass member repetitively strikes the inner surfaces of the housing
on both sides in a primary vibration input direction.
[0021] A second mode of the second aspect of the invention provides
a method of manufacturing a vehicle vibration-damping device
according to the first mode, further comprising a preliminary
process that performs at least one of an adhesion treatment for
ensuring an adhesion of the rubber elastic body layer to the
metallic mass, and a non-adhesion treatment for ensuring a
non-adhesion of the rubber elastic body layer to the housing, prior
to the rubber elastic body layer fabricating process.
[0022] A third mode of the second aspect of the invention provides
a method of manufacturing a vehicle vibration-damping device
according to the first or second mode, further comprising a release
process that forcibly causes a relative movement between the rubber
elastic body layer and the housing, in at least one of a
circumferential direction and an axial direction, and that is
executed posterior to the rubber elastic body layer fabricating
process.
[0023] As will be apparent from the aforementioned explanation, by
using a cylindrical housing and a metallic mass that has a circular
cross section in the vibration-damping device for a vehicle that is
structured according to the present invention, it is possible to
stabilize the impact of the independent mass member on the housing.
Also, the gap that is formed between the opposing surfaces of the
rubber elastic body layer and the housing in the radial direction,
is fabricated as a small gap of no more than 0.1 mm, thereby
permitting the independent mass member to strike the inner surface
of the housing in a desirable way on both sides of the housing in
the primary vibration input direction, owing to the reduced amount
of movement needing for the independent mass member to come to
impact against the inner peripheral surface of the housing, on both
sides thereof in the primary vibration input direction.
Additionally, the small gap makes it possible to set the natural
frequency of the independent mass member to be effectively at a
higher frequency band than the natural frequency of the
target-vibrating member whose vibration to be damped. Therefore,
the vibration-damping device of construction according to the
present invention is capable of exhibiting highly improved
vibration-damping effect in comparison with vibration-damping
devices with conventional structures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The forgoing and/or other objects features and advantages of
the invention will become more apparent from the following
description of a preferred embodiment with reference to the
accompanying drawings in which like reference numerals designate
like elements and wherein:
[0025] FIG. 1 is an elevational view in axial or vertical cross
section of a vehicle vibration-damping device of construction
according to a first embodiment of the invention;
[0026] FIG. 2 is a fragmentary enlarged view in vertical cross
section of a principle part of the vibration-damping device of FIG.
1;
[0027] FIG. 3 is a vertical cross sectional view showing one
process of a manufacturing method of the vibration-damping device
of FIG. 1;
[0028] FIG. 4 is a vertical cross sectional view showing another
process of the manufacturing method of the vibration-damping device
of FIG. 1;
[0029] FIG. 5 is a vertical cross sectional view showing yet
another process of the manufacturing method of the
vibration-damping device of FIG. 1;
[0030] FIG. 6 is a fragmentary enlarged cross sectional view
showing a principle part in the process in shown in FIG. 5;
[0031] FIG. 7 is a vertical cross sectional view showing a further
process of the manufacturing method of the vibration-damping device
of FIG. 1;
[0032] FIG. 8 is a vertical cross sectional view showing a still
further process of the manufacturing method of the
vibration-damping device of FIG. 1;
[0033] FIG. 9 is a perspective view showing a vehicle engine mount
of construction according to a second embodiment of the present
invention;
[0034] FIG. 10 is a front elevational view of the engine mount of
FIG. 9;
[0035] FIG. 11 is a cross sectional view taken along line 11-11 of
FIG. 10;
[0036] FIG. 12 is an enlarged cross sectional view showing one
process of a manufacturing method of the engine mount of FIG. 9;
and
[0037] FIG. 13 is an fragmentary enlarged view in vertical cross
section of the engine mount of FIG. 9.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0038] Referring first to FIG. 1, there is shown a
vibration-damping device 10 for use in a vehicle according to a
first embodiment of the present invention. This vibration-damping
device 10 has a structure wherein an independent mass member 16 is
housed within a housing space 14 formed by a housing 12, and is
installed at, for example, the free end of an automobile
transmission case 18, such as shown by the double dotted lines in
FIG. 1. In the explanation hereinbelow, the "up/down direction" or
"vertical" direction, "axis-perpendicular direction," "radial
direction," and so forth shall refer to the vertical direction in
FIG. 1, unless otherwise specified, and the "left/right direction"
or "horizontal direction," "axial direction," and so forth shall
refer to the horizontal direction in FIG. 1.
[0039] More specifically, the housing 12 has approximately the
shape of a cylinder that is closed at the bottom, where the
cylinder wall part 20 extends in the axial direction with an
approximately uniform circular cross-sectional shape extending from
the bottom part side on one side in the axial direction (to the
left in FIG. 1) to the opening part side in the axial direction on
the other side (to the right in FIG. 1). Moreover, the housing 12
is fabricated from a hard material with a modulus of elasticity of
at least 5.times.10.sup.3 Mpa, and when the hard material is a
metallic material such as an aluminum alloy, the housing 12 may be
fabricated using a drawing process or a press process using a metal
pipe or a metal plate. Alternatively, if the hard material is a
synthetic resin material such as FRP, the housing 12 may be
fabricated using injection molding, or the like.
[0040] The housing 12 is further provided with a through hole 22
perforated in the axial direction at the center of the bottom part
of the housing 12. A male screw part 24 is formed at the outer
circumferential surface of the bottom part of the housing 12.
[0041] A cover member 26 is fastened to an opening part of the
housing 12. The cover member 26 has a shape that is approximately a
hollow cylinder with a bottom, and the inner diameter dimension
thereof is approximately the same as, or slightly larger than, the
outer diameter dimension of the housing 12. On the inner
circumferential surface of the cylinder wall part in the vicinity
of the bottom part of the cover member 26, there is formed a
housing groove 28, which opens towards the inner radial direction,
and extends circumferentially over the entire circumference of the
cover member 26.
[0042] The cover member 26 is press fit onto the housing 12,
whereby the opening part of the housing 12 is provided with a
fluid-tight sealing, causing the housing space 14 of the housing 12
to be a substantially sealed structure. When press fastening the
cover member 26 onto the housing 12, a stop ring 30 is fitted into
the housing groove 28 of the cover part 26. This stop ring 30 is
formed by a ring-shaped spring metal, or the like, which extends
discontinuously in the circumferential direction, and the inner
diameter dimension thereof is smaller than the outer diameter
dimension of the housing 12. With this arrangement, at the time of
the press fit, the stop ring 30 that fits into the housing groove
28 is flattened in the outer radial direction of the housing 12,
and based on the elastic effect, the stop ring 30 contracts in its
diameter in the inner radial direction and is supported with a
tight seal relative to the outer peripheral surface of the housing
12. Consequently, the mating in the axial direction of the stop
ring 30 and the housing groove 28 effectively prevents the cover
member 26 from falling off of the housing 12. The independent mass
member 16 is disposed within the housing space 14 of the housing
12.
[0043] The independent mass member 16 comprises a metallic mass 32
and a striking rubber layer 34 as the rubber elastic body layer.
The metallic mass 32 may be fabricated from a ceramic, a synthetic
resin, or the like, or from an appropriate composite. However, in
the present embodiment, it is fabricated from a metal with a high
specific gravity, such as iron. Moreover, the metallic mass 32 has
approximately a true cylindrical shape overall, extending in the
axial direction with what is an approximately uniform circular
cross-sectional shape. Furthermore, the outer diameter dimension of
the metallic mass 32 is smaller than the inner diameter dimension
of the housing 12 by a specific amount. The metallic mass 32 is
formed with a large-diameter indentation 36 open in a central
portion of one axial end face thereof on the cover member 26-side
(i.e., the right in FIG. 1), and a small-diameter indentation 38
open in a central portion of the other axial end face (i.e., the
left in FIG. 1) on the side of the bottom part of the housing
12.
[0044] In this embodiment, the metallic mass 32 is disposed within
the housing space 14 of the housing 12, and also is placed so that
the inner peripheral surface of the cylinder wall part 20 of the
housing 12 and the outer peripheral surface of the peripheral wall
part of the metallic mass 32 face each other with a specific gap
distance (the distance between the facing surfaces) of d.sub.1 (mm)
in the radial direction along the entire length (see FIG. 2), in a
state wherein the metallic mass 32 and the housing 12 are disposed
so as to be coaxial. In other words, between the surfaces that face
each other in the radial direction, those being the cylindrical
wall part 20 of the housing 12 and the metallic mass 32, there is
formed a gap 40 of a specific dimension. The dimension of this gap
40, or in other words, the distance in the radial direction between
the inner peripheral surface of the cylindrical wall part 20 of the
housing 12 and the outer peripheral surface of the peripheral wall
part of the metallic mass 32, is d.sub.1, where d.sub.1=(dimension
of the inner radius of the cylindrical wall part 20 of the housing
12-the outer radius dimension of the metallic mass 32)/2. It should
be appreciated that the distance between facing surfaces d.sub.1 is
not limited in any way, and in the present embodiment,
0.5.ltoreq.d.sub.1.ltoreq.2, and preferably, d.sub.1 should be set
so that 0.8.ltoreq.d.sub.1.ltoreq.1.5. Furthermore, the small
diameter indentation 60 is disposed coaxially with the through hole
22 that is perforated through the bottom part of the housing 12,
and in a position facing thereto in the axial direction.
[0045] Moreover, on the surface of the metallic mass 32, except for
at the large indentation 36 and the small indentation 38, there is
a thin striking rubber layer 34 adhered with an essentially uniform
thickness. In other words, the striking rubber layer 34 is adhered,
with an essentially uniform thickness, to the outer peripheral
surface of the peripheral wall part of the metallic mass 32 that is
positioned facing, in the radial direction, the cylinder wall part
20 of the housing 12, the outer peripheral surface of the one axial
end of the metallic mass 32 that is positioned facing, in the axial
direction, the bottom part of the cover member 26 (i.e., to the
right in FIG. 1), and to the outer peripheral surface of the other
axial end of the metallic mass 32 that is positioned facing, in the
axial direction, the bottom part of the housing 12 (i.e., to the
left in FIG. 1). The striking rubber layer 34 that covers the outer
peripheral surface of the axial end of the metallic mass 32 that is
positioned facing, in the axial direction, the bottom part of the
cover 26 has a smaller thickness dimension than the striking rubber
layer 34 in the other positions.
[0046] The striking rubber layer 34, in consideration of durability
and the reduction of the noise of impact when the metallic mass 32
strikes the housing 12, as will be described below, and in
consideration of thermal contraction characteristics, and so forth.
Preferably, the striking rubber layer 34 is fabricated from a
rubber material such as natural rubber, a butyl rubber, or the
like, with a shore D hardness of not greater than 85 according to
the ASTM standard D2240, and more preferably with a shore D
hardness, according to the same specification, between 55 and
80.
[0047] The thickness dimension t (mm) of the striking rubber layer
34 is expressed in terms of t=(outer diameter dimension of the
striking rubber layer 34-inner diameter dimension of the metallic
mass 32)/2, and there are no particular constraints on this
thickness. In this embodiment, preferably, the thickness dimension
t (mm) is determined to meet 0.4.ltoreq.t.ltoreq.1.99, more
preferably, 0.7.ltoreq.t.ltoreq.1.49, where this thickness is less
than the distance d.sub.1 in the radial dimension between the
opposing surfaces of the metallic mass 32 and the housing 12, as
described above. As a result, under the condition that the striking
rubber layer 34 and the housing 12 are disposed coaxially, a small
gap 42, which extends in the axial direction with an approximately
uniform ring-shaped cross section will be formed, as shown in the
expanded view in FIG. 2, in the space wherein the outer peripheral
surface of the striking rubber layer 34 faces the inner peripheral
surface of the cylinder wall part 20 of the housing 12 in the
radial direction.
[0048] The dimension d.sub.2 (mm) of this small gap 42, or in other
words, the distance d.sub.2 between the facing surface of the outer
peripheral surface of the striking rubber layer 34 and the inner
peripheral surface of the cylindrical wall part 20 of the housing
12 is expressed in terms of d.sub.2=(inner diameter dimension of
the cylindrical wall part 20 of the housing 12-outer diameter
dimension of the striking rubber layer 34)/2, or expressed
differently, d.sub.2=d.sub.1 (which is the distance between the
facing surfaces in the radial direction of the outer peripheral
surface of the metallic mass 32 and the inner peripheral surface of
the cylindrical wall part 20 the housing 12)-t (which is the
thickness dimension of the striking rubber layer 34). Moreover, the
dimension d.sub.2 of the small gap 42, while having no particular
constraints, is such that 0.01.ltoreq.d.sub.2.ltoreq.0.1 in the
present embodiment or preferably such that
0.02.ltoreq.d.sub.2.ltoreq.0.08, or even more preferably set such
that 0.02.ltoreq.d.sub.2<0.05. Consequently, in the present
embodiment, 0.02.ltoreq.2d.sub.2.ltoreq.0.2, or preferably
0.04.ltoreq.2d.sub.2.ltoreq.0.16, or more preferably
0.04.ltoreq.2.sub.2.ltoreq.0.1 should be set as the total small gap
dimension (2d.sub.2) in the radial direction equipped in the
vibration-damping device 10. Although it is not shown in the
figure, it should be appreciated that this small gap 42 is formed
also in the gap between facing surfaces in the axial direction
between the outer peripheral surface of the striking rubber layer
34 that is coated onto the outer peripheral surface of the one
axial end of the metallic mass 32 (i.e., towards the left in FIG.
1) and the inner peripheral surface of the bottom part of the
housing 12.
[0049] Consequently, in the present invention, the axial-direction
dimension of the independent mass member 16, comprising the
metallic mass 32 and the striking rubber layer 34, is smaller than
the axial-direction dimension of the housing space 14 of the
housing 12, and the small gap 42, with its dimension d.sub.2 is
fabricated across the entire periphery between the facing surfaces
of the outer peripheral surface of the striking rubber layer 34 and
the inner peripheral surface of the cylindrical wall part 20 of the
housing 12. With this arrangement, the independent mass member 16
is disposed within the housing space 14 of the housing 12 so as to
be able to move relative to the housing 12 in the axial direction,
in the axis-perpendicular direction (the radial direction) and in
the circumferential direction.
[0050] The small gap 42 is formed in the space between the facing
surfaces in the radial direction of the outer peripheral surface of
the independent mass member 16 (i.e., of the striking rubber layer
34) and the inner peripheral surface of the housing 12, thereby
ensuring an adequately large spring constant in the independent
mass member 16 based on the desirably arranged amount of relative
movement in the independent mass member 16 relative to the housing
12 in the radial direction, which is a primary vibration input
direction. This arrangement permits that the natural frequency of
the independent mass member 16 will be set to a frequency band that
is higher than the natural frequency of the transmission case 18,
which is the vibrating member whose vibration to be damped, at a
frequency band of, for example, 400 to 1,000 Hz. Furthermore, when
a vibration of 2G or more is applied, the metallic mass 32
undergoes jumping like displacement relative to the housing 12, via
the striking rubber layer 34, to thereby repetitively strike the
inner peripheral surfaces on both sides (i.e., both top and bottom
in FIG. 1) in the primary vibration input direction. Preferably,
the vibration-damping device 10 is arranged by utilizing a
vibration multiplier (based on the resonance effect, etc.) in a
mass-spring system comprising a mass of the independent mass member
16 and the spring of the striking rubber layer 34, so that when a
1G vibration is applied in the target frequency of vibration to be
damped, the independent mass member 16 undergoes jumping like
displacement, with the gap creation and impacts repeatedly
performed on both sides of the independent mass member 16 in the
vibration input direction.
[0051] Next there will be an explanation regarding a specific
example of a method for manufacturing the vehicle vibration-damping
device 10, including, for example, the method of forming the small
gap 42, as described above. It should be appreciated that the
present invention is in nowise limited to this specific
example.
[0052] Initially, the housing 12, the metallic mass 32, and the
cover member 26 are formed as individual units. As shown in FIG. 3,
the metallic mass 32 is inserted into the housing 12 from an
axial-direction end part wherein a small-diameter indentation 38
has been provided. Then, as shown in FIG. 4, the metallic mass 32
and the housing 12 are placed on a fabrication mold 44. The
fabrication mold 44 includes a female mold 46 and a male mold 48.
The female mold 46 and the male mold 48 fit together in the axial
direction (the left and right in FIG. 4). On the inside of each
mold, there are protrusions, indentations, and so forth that are
fabricated appropriately according to the external geometries of
the housing 12 and the metallic mass 32.
[0053] The metallic mass 32 and the housing 12 fit into
indentations in the female mold 46 and the male mold 48. A support
pin 47 that is fabricated on the female mold 46 is inserted into
the through hole 22 of the housing 12 and the small-diameter
indentation 38 of the metallic mass 32. Further, a support
protrusion 49, fabricated on the male mold 48 is fitted into the
large-diameter indentation 36 of the metallic mass 32. With this
state, the female and male molds 46 and 48 are mated together to
thereby form the gap 40 between the inner peripheral surface of the
cylindrical wall part 20 of the housing 12 and the outer peripheral
surface of the peripheral wall part of the metallic mass 32. In
this state, the positioning of the metallic mass 32 and the housing
12 is maintained coaxially within the fabrication mold 44 to set
the distance d.sub.1 between the facing surfaces in the radial
direction, to 0.5.ltoreq.d.sub.1.ltoreq.2, and the gap 40 is
partitioned by the fabrication mold 44 to fabricate a mold cavity
50.
[0054] Under the conditions of mating and clamping the molds in
this way, as shown in FIG. 5, a rubber material 34', such as
natural rubber, butyl rubber, or the like is injected into the mold
cavity 50 through an injection gate (not shown) formed in the
fabrication mold 44. The rubber material 34' is subjected to a
specific vulcanization molding process, to thereby form the
striking rubber layer 34.
[0055] As shown in FIG. 6, the result is that the rubber material
34', which has a thickness dimension of t' that is substantially
the same as the distance d.sub.1 between the radially facing
surfaces, i.e., the outer peripheral surface of the metallic mass
32 and the inner peripheral surface of the housing 12, undergoes
thermal contraction along with the vulcanization molding process,
causing not only peeling thereof away from the inner peripheral
surface of the housing 12, but also contract in terms of the radius
towards the metallic mass 32, which is on the inside in the radial
direction, until the thickness dimension of t, as shown in FIG. 2,
is reached. With this arrangement, the striking rubber layer 34,
with the thickness dimension of t, as shown in FIG. 1, is
fabricated adhering to the surface of the metallic mass 32, forming
the independent mass member 16, and forming the small gap 42, with
the dimension d.sub.2, between the outer peripheral surface of the
independent mass member 16 and the inner peripheral surface of the
housing 12.
[0056] The rate of thermal contraction of the striking rubber layer
34 in the vulcanization molding process may be adjusted as
appropriate through, for example, changing the settings of the
aforementioned shore D hardness according to the size required for
the small gap 42, and thus it is not particularly limited. In the
present embodiment, the thermal contraction ratio is set to between
1 and 5%, or preferably, is set to between 2 and 3%.
[0057] In the present embodiment, an adhesive agent is coated onto
the outer peripheral surface of the metallic mass 32, onto which
the striking rubber layer 34 will be adhered and fabricated, prior
to the filling of the mold cavity 50 with the rubber material 34'
in order to perform an adhesive treatment on the metallic mass 32
for the striking rubber layer 34. This treatment permits the
striking rubber layer 34 to adhere more securely to the metallic
mass 32.
[0058] The fabrication mold 44 is opened and the housing 12 housing
the independent mass member 16 within the housing space 14, is
removed. As shown in FIG. 7, for example, a push rod 52 is inserted
into the through hole 22 of the housing 12 in order to place the
tip part of this rod 52 in contact with the small-diameter
indentation 38 of the metallic mass 32. With the housing is held
immovable, a pushing force is applied against the independent mass
member 16, based on the movement of the push rod 52 from one axial
direction (the left in FIG. 7) towards the other axial direction
(the right in FIG. 7) to force the independent mass member 16 and
the housing 12 to move relative to each other in the axial
direction. As a result, the outer peripheral surface of the
striking rubber layer 34 can be peeled off from the inner
peripheral surface of the housing 12 with more certainty.
[0059] Furthermore, as is shown in, for example, FIG. 8, the push
rod 52 is removed from the through hole 22, at which time the
independent mass member 16 is moved towards the bottom part of the
housing 12 and is disposed within the housing space 14. On the
other hand, the stop ring 30 is fitted into the housing groove 48
of the cover member 26, establishing the relative positioning of
the cover member 26 and a housing 12 in the axial direction. In a
state where the cover member 26, etc., are held immovable, the
housing 12 is press fitted into the cover member 26. The result is
that the stop ring 30 is stretched in the outer radial direction by
the housing 12, and is maintained tightly fitted onto the outer
peripheral surface of the cylindrical wall part 20 of the housing
12 by the elastic effect of the stop ring 30. Thus, there is
produced the vehicle vibration-damping device 10 as shown in FIG.
1.
[0060] In the vibration-damping device 10 of construction as
described above, the male screw part 24 of the housing 12 is
screwed tightly onto the female screw part (not shown) which is
fabricated in the transmission case 18. Thus, the vibration-damping
device 10 is fastened onto the free end of the transmission case 18
so that the axial direction of the vibration-damping device 10
extends in approximately the horizontal direction. In other words,
the vibration-damping device 10 is installed on the transmission
case 18 in a state where the primary vibration input direction,
i.e., the primary direction in which vibrations are applied to the
housing 12 is approximately the vertical direction (i.e., the
radial direction of the casing 12).
[0061] In the state where the vibration-damping device 10 is
equipped on the free end of the transmission case 18, when the
transmission of vibrations from the automobile engine causes the
transmission case 18 to apply a vibration in a direction that is
perpendicular to the axial direction (i.e., the radial direction of
the housing 12), which is the primary vibration input direction,
then the housing 12 is vibrated together with the transmission case
18. As a result, the housing 12 and the independent mass member 16
move relative to each other in the direction in which the vibration
is applied. Accordingly, the metallic mass 32 of the independent
mass member 16 repetitively strikes, through the striking rubber
layer 34, the inner peripheral surface of the housing 12 on both
sides thereof in the direction of the vibration. At the time of
this striking, the force of the shock that is applied to the
transmission case 18 from the housing 12 exhibits an offsetting
vibration-damping effect, based on the phase difference of the
vibrations that derive from the transmission case 18.
[0062] In the vibration-damping device 10 according to the present
embodiment, the cylindrical housing 12 and the metallic mass 32
with a circular cross section are used to cause the independent
mass member 16 to be stable in striking the housing 12, while
forming a small gap 42 wherein the gap in the radial direction
between the facing surfaces of the striking rubber layer 34 and the
housing 12 is no more than 0.1 mm. This arrangement creates a
desirable striking of the independent mass member 16 against the
inner peripheral surface of the housing 12 on both sides in the
vibration input direction, with the help of the reduced amount of
movement needed for the independent mass member 16 to come to
impact against the inner peripheral surface of the housing 12 on
both sides in the vibration input direction. Also, this arrangement
makes it possible to effectively set the natural frequency of the
independent mass member 16 to be in a frequency band that is higher
than the natural frequency of the transmission case 18. Thus, it is
possible to exhibit effectively vibration-damping performance even
for vibrations in high frequency bands that were difficult to
handle using vibration-damping devices with conventional
structures.
[0063] Moreover, in the present embodiment, the rubber material 34'
is filled into the gap 40 of 0.5 to 2 mm formed between the outer
peripheral surface of the metallic mass 32 and the inner peripheral
surface of the housing 12 in a state where the metallic mass 32 is
disposed coaxially with the housing 12. With this arrangement, the
outer peripheral side of the rubber material 34' is supported by
the cylindrical housing 12, and the thermal contraction effect
caused by the vulcanization molding process can be exerted on the
striking rubber layer 34 (the rubber material 34') in a state where
the metallic mass 32 of cylindrical cross section is embedded in
the center of the rubber material 34'. This arrangement makes it
possible for the striking rubber layer 34 to contract approximately
uniformly around the entire periphery from the housing 12 that is
on the outside in the radial direction towards the metallic mass
32, which is on the inside in the radial direction. Thus, a
superior dimensional precision can be given to the small gap 42
which is fabricated between the outer peripheral surface of the
striking rubber layer 34 and the inner peripheral surface of the
housing 12.
[0064] Accordingly, it is possible to produce, beneficially, the
vibration-damping device 10 equipped with the small gap 42, of the
aforementioned 0.1 mm or less, having superior manufacturing
efficiency and cost performance, and the like, of a degree not
achieved in vibration-damping devices of conventional structures,
and possible to obtain benefits in mass production as well. Namely,
in the vibration-damping device of the conventional structure, for
example, (1) a gap was formed between the outer peripheral surface
of the striking rubber layer and the inner peripheral surface of
the housing through positioning within the housing a metallic mass
onto which a striking rubber layer had been adhered after
fabricating the striking rubber layer and the metallic mass
together in vulcanization molding. Alternatively, (2) only the
rubber material that forms the rubber elastic member would be
filled into the housing and then the thermal contraction that
accompanies vulcanization molding of a single rubber elastic member
would be used to dispose within the housing an independent mass
member comprising the rubber elastic member but not equipped with a
metallic mass, so as to form a gap between the outer peripheral
surface of the independent mass member and the inner peripheral
surface of the housing. However, the conventional devices of these
structures have suffered from inherent problems. For instance, in
the vibration-damping device of (1) it is difficult to fabricate a
small gap of no more than 0.1 mm when there are minor shifts in
dimensional tolerances of the housing, metallic mass, or striking
rubber layers. Further, since the fabrication of these small gaps
using sophisticated fabrication molds led to increased costs, there
has been a problem that mass production could not be achieved at a
fully practical level. Additionally, in the vibration-damping
device of (2) the inside of the rubber material is not maintained
by a metallic mass when the vulcanization molding of the rubber
elastic member is performed within the housing. Therefore, when
there would be external forces, such as vibrations, applied to the
housing, or when the housing was at an angle relative to the
horizontal direction, it was difficult to stabilize and maintain
the rubber material within the housing, making it difficult to have
a contraction that is uniform in the radial direction across the
entirety of the rubber material, leading to a problem in that it is
difficult to set the small gap to the target dimensions.
[0065] In the present embodiment, since the vibration-damping
device 10 is disposed in a state where the primary vibration input
direction will be approximately the vertical direction, when these
are vibrations applied in excess of 2G, the independent mass member
16 will repetitively strike the inner peripheral surface of the
housing 12 on both sides in the vibration input direction. This
causes the benefits of the independent mass member 16 striking both
sides of the housing 12 even when a relatively small vibration has
been applied, thereby making it possible for the target
vibration-damping effects to exhibit even greater benefits.
[0066] Moreover, in the present embodiment, the push rod 52 is
pushed against the independent mass member 16 through insertion
through the through hole 22 of the housing 12 when performing the
vulcanization molding of the striking rubber layer 34 between the
inner peripheral surface of the housing 12 and the outer peripheral
surface of the metallic mass 32. This therefore forcedly causes a
relative movement between the housing 12 and the independent mass
member 16 in the axial direction, causing the outer peripheral
surface of the striking rubber layer 34 to peel more reliability
from the inner peripheral surface of the housing 12 in order to
fabricate more reliably the required small gap 42. Thus, it is
possible to improve the reliability of the target vibration-damping
effects more beneficially.
[0067] Furthermore, in the present embodiment, the through hole 22
is provided along the central axial direction at the bottom part of
the housing 12 to be formed in a position that avoids the places
wherein the independent mass member 16 strikes when a vibration is
applied to the housing 12 in the main direction of vibration.
Therefore, the shock force based on the independent mass member 16
striking the inner surface of the housing 12 is transmitted
efficiently to the vibrating member for which the vibration is to
be controlled (the transmission case 18 in the present example
embodiment), thus making it possible for the vibration-damping
effect to exhibit greater benefits.
[0068] Moreover, in the present embodiment, the outer peripheral
surface of the striking rubber layer and the inner peripheral
surface of the housing 12 are fabricated so as to extend in the
axial direction with essentially uniform cross sections, and thus
the small gap 42, formed between these inner and outer peripheral
surfaces, extends across the entire length in the axial direction
with an approximately uniform cross-sectional shape. Therefore,
when a vibration is applied in the primary vibration input
direction, the independent mass member 16 strikes against the
housing 12 across approximately the entire length in the axial
direction. Thus, it is possible to reduce or avoid the
concentration of stresses in the independent mass member 16 and/or
housing 12 that stem from one part of the independent mass member
16 striking a focused place on the inner surface of the housing 12,
and it is possible to have a stabilized vibration-damping effect
over extended periods of time.
[0069] Further, the fabrication of the striking rubber layer 34
over the outer peripheral surface of both axial-direction ends of
the metallic mass 32 as well makes it possible to exhibit superior
vibration-damping effects even regarding vibrations in the axial
direction based on the striking of the inner surface of the bottom
part of the cover member 26 and the inner surface of the bottom
part of the housing 12 by the metallic mass 32 through the striking
rubber layer 34 in the independent mass member 16 when a vibration
is applied in the axial direction.
[0070] According to the manufacturing method of this embodiment of
the present invention, not only is the distance d.sub.1 between the
opposing surfaces of the outer peripheral surface of the metallic
mass 32 and the inner peripheral surface of the housing 12 set to
between 0.5 and 2 mm in a state wherein the metallic mass 32 and
the housing 12 are disposed coaxially, but also the thermal
contraction accompanying the vulcanization molding of the striking
rubber layer 34 is used to easily and reliably fabricate a small
gap 42, of 0.1 mm or less, between the radially opposing surfaces,
i.e., the outer peripheral surface of the independent mass member
16 (of the striking rubber layer 34) and the inner peripheral
surface of the housing 12. As a result, it is not necessary to use,
in particular, fabrication molds, or the like, with complicated
structures or geometries, effectively reducing the manufacturing
cost and the overhead in the manufacturing process, making it
possible to provide superior mass production characteristics.
[0071] Next, an engine mount 60 for an automobile is shown in FIGS.
9 through 11 as a second embodiment according to the present
invention. This engine mount 60 has a structure wherein a metallic
inner cylinder 62, as a first attachment member, and a metallic
outer cylinder 64, as a second attachment member, are elastically
connected by a rubber elastic member 66. Either the inner cylinder
62 or the outer cylinder 64 is attached to the power unit side (not
shown), and the other cylinder is attached to the body side, so
that the power unit is supported on the body in a vibration-damping
fashion. The overall structure of this engine mount 60 is
substantially the same structure as for the engine mount disclosed
in, for example, JP-A-2002-227921, and thus detailed explanations
thereof are omitted. In the description hereinbelow, the same
numerals are assigned in the figures for those members and
components that have substantially the same structures as in the
first embodiment, and no detailed explanations thereof are
provided.
[0072] In the engine mount 60, the inner cylinder 62 according to
the present embodiment has a small-diameter inner cylinder shape,
and is in a form wherein it can be securely attached to a body or
power unit (not shown) by a bolt passing through an inner hole 68.
In the outer radial direction of the inner cylinder 62 is disposed
an outer cylinder 64, essentially coaxially with the inner cylinder
62.
[0073] The outer cylinder 64 has a large diameter approximately
cylindrical shape. The outer cylinder 64 is formed so as to be able
to be attached securely to an automobile body or power unit (not
shown) through press fitting, or the like, to an attachment member
that is securely attached to the automobile body or power unit.
[0074] Between the surfaces of the inner and outer cylinders 62 and
64, which oppose each other in the radial direction, is disposed
the rubber elastic body 66. This rubber elastic body 66 has an
essentially cylindrical shape in its wall, and it fabricated as an
integrated vulcanization molded product equipped with the inner
cylinder and outer cylinder 62 and 64, with the inner peripheral
surface thereof bonded by vulcanization to the outer peripheral
surface of the inner cylinder 62, and the outer peripheral surface
thereof bonded by vulcanization to the inner peripheral surface of
the outer cylinder 64.
[0075] The rubber elastic body 66 is equipped with a pair of slits
70 and 72 in the axial direction on both sides of the inner
cylinder 62 in a primary vibration input direction in which the
load is applied (the top and the bottom in FIG. 10). While the slit
70 has a crescent shape in its cross section, extending around
essentially half of the periphery, the slit 72 has a fan-shaped
cross sectional shape.
[0076] In other words, the rubber elastic body 66 exists only
between the pair of slits 70 and 72 in the inner and outer
cylinders 62 and 64. Thus, the inner and outer cylinders 62 and 64
is substantially connected via the pair of elastic linking parts 74
and 74 that are fabricated so as to extend in the axial direction
between the inner and outer cylinders 62 and 64. Moreover, in a
state where this rubber elastic body 66 is equipped between the
inner and outer cylinders 62 and 64, a static load is applied in
the radial direction, and when the static load is applied,
substantially a V shape is formed by the spreading of the elastic
linking parts 74 and 74 that is wider in the direction in which the
inner cylinder 62 moves relative to the outer cylinder 64. As a
result, the tensile stress on the elastic linking parts 74 and 74
when a load is applied from the outside is reduced.
[0077] Further, stopper parts 76 and 78 are provided on the
circumferential central portions of the inner peripheral surfaces
of the slits 70, 72, respectively so as to protrude towards the
inner cylinder 62 from the outer cylinder 64. These stopper parts
76 and 78 are integrally formed with the rubber elastic body 66.
With this arrangement, since the inner cylinder 62 and the outer
cylinder 64 striking each other through these stopper parts 76 and
78, the amount of relative movement in one of the axial directions
that is the primary vibration input direction (the vertical
direction in FIG. 10) is limited in a cushion-wise manner.
[0078] A housing 12 is equipped in the central area in the linking
direction of each of the elastic linking parts 74, or in other
words, in the central area between the radially opposing surfaces
of the inner and outer cylinders 62 and 64. The housing 12
according to the present embodiment has an approximately
cylindrical shape that is long in the axial dimension, and is
disposed so as to extend substantially parallel to the axial
direction of the mount (in the vertical direction in FIG. 11),
while the outer peripheral surface thereof is vulcanized and
adhered to the rubber elastic body 66.
[0079] An independent mass member 16, comprising a metallic mass 32
and a striking rubber layer 34, is disposed within the housing 12.
The metallic mass 32 in the present embodiment has an approximately
cylindrical shape that is long with a small diameter, disposed
within the housing 12 with a distance d.sub.1 between the radially
opposing surfaces, i.e., the outer peripheral surface of the
metallic mass 32 and the inner peripheral surface of the housing
12, under the conditions where the metallic mass 32 is disposed
coaxially with the housing 12. Both axial end parts of the metallic
mass 32 protrude to the outside in the axial direction from each of
the opening parts in the housing 12. Also, at both tip parts, there
are attached ring-shaped retainer members 80 that have external
diameter dimensions that are larger than the diameter dimensions of
the opening parts of the housing 12. As a result, the metallic mass
32 is prevented from falling out of the housing 12. Well-known
speed nuts, push nuts, snap retainers, clip retainers, or the like
may be used as appropriate as the retainer members 80.
[0080] Further, a thin striking rubber layer 34 covers essentially
the entirety of the outer peripheral surface of the metallic mass
32. The striking rubber layer 34 has a thickness dimension (t) that
is sustained as in the first embodiment, described above. In a
state where the metallic mass 32 is disposed coaxially with the
housing 12, the striking rubber layer 34 faces the housing 12 so
that over the entire periphery there is a radial-direction distance
d.sub.2 between the facing surfaces of the outer peripheral surface
of the striking rubber layer 34 and the inner peripheral surface of
the housing 12. With this arrangement, a small gap 42 with a small
dimension (d.sub.2) is formed between the radially opposing
surfaces, i.e., the external peripheral surface of the striking
rubber layer 4 and the inner peripheral surface of the housing (See
FIG. 13).
[0081] In the present embodiment, a runner 82 for the injection of
a rubber material 34' is formed at at least one of the axial ends
of the metallic mass 32 as shown in FIGS. 12 and 13. This runner 82
for injection extends in the axial direction from the axial end
surface of the metallic mass 32 with a specific depth dimension,
and extends in the radial direction to open in the outer peripheral
surface of the metallic mass 32.
[0082] The inner cylinder 62 and the outer cylinder 64 are placed
in the fabrication mold 84 for molding the rubber elastic body 66
as shown in FIG. 12. When molding the rubber elastic body 66 by
means of vulcanization of a suitable rubber material, the housing
12 with the metallic mass 32 coaxially housed therein, is placed at
a predetermined position located in the central portion in the
linking direction of each of the elastic linking parts 74 between
the inner cylinder 62 and the outer cylinder 64. The rubber
material for the rubber elastic body 66 is filled into the radial
space between the inner cylinder and the outer cylinder through an
injection gate (not shown) that is formed in the injection mold 84.
After filling a portion of the rubber material through the
injection runner 82 of the metallic mass 32 from the injection mold
84 into a mold cavity 50 that is formed between the
radial-direction opposing surfaces of the metallic mass 32 and the
housing 12, a specific vulcanization molding process may be
performed.
[0083] As shown in FIG. 13, for example, the thermal contraction
that accompanies vulcanization fabrication of the striking rubber
layer 34, is used to have the striking rubber layer 34 peeled off
of the housing 12 as well as to have the striking rubber layer
contracted towards the metallic mass 32 and adhered firmly to the
outer peripheral surface of the metallic mass 32. Thus, the small
gap 42 between the radially opposing surfaces, i.e., the outer
peripheral surface of the striking rubber layer 34 and the inner
peripheral surface of the housing 12, will be fabricated together
with the rubber elastic body 66. Namely, in the present embodiment,
not only is an adhesive material coated onto the outer peripheral
surface of the housing 12, but also, in the same manner as in the
embodiment described above, an adhesive material is also coated
onto the outer peripheral surface of the metallic mass 32, in
advance, when performing the vulcanization molding of the striking
rubber layer 34. In the present embodiment, the release of the
striking rubber layer 34 from the housing 12 can be performed more
reliably by forcibly moving the independent mass member 16 and the
housing 12 relative to each other in the axial direction and/or
peripheral direction, if necessary, after the vulcanization molding
of the striking rubber layer 34.
[0084] The engine mount 60 of construction according to this
embodiment is installed between the power unit and the vehicle body
in a state where the primary vibration input direction will be
approximately the vertical direction (the direction that is
approximately perpendicular to the axial direction of the mount
60). In the engine mount 60, a vibration is applied between the
inner cylinder 62 and the outer cylinder 64, and when there is no
surging phenomenon in the elastic linking part 74, the elastic
linking part 74 will be vibrated with a large amplitude vibration
in the shear direction. Thus, the external forces in the direction
perpendicular to the axial direction of the independent mass member
16 from the elastic linking part 74 relative to the independent
mass member 16 will be large, and the independent mass member 16
will become independent from the inner peripheral surface of the
housing 12 and bounced within the housing 12 so as to repetitively
strike the housing 12 in the direction of the shear deformation of
the elastic linking part 74, which is the primary vibration input
direction. In other words, the independent mass member 16 exhibits
a vibration amplitude control effect and/or a vibration-damping
effect relative to the elastic displacement of the rubber elastic
body 66 accompanying the application of vibrations based on the
metallic mass 32 repetitively striking the inner peripheral surface
of the housing 12 at both sides, in the vibration input direction
through the striking rubber layer 34, to thereby suppress the
surging in the rubber elastic body 66.
[0085] Consequently, in the engine mount 60, structures as
described above, there is minimized or avoided reduction in the
anti-vibration function stemming from the surging phenomenon of the
rubber elastic body 66 at specific frequency ranges. As a result,
the anti-vibration effects based on the elastic characteristics of
the rubber elastic body 66 can exhibit stability relative to
vibrations in a broad range of frequencies.
[0086] In the present embodiment, particularly, the small gap 42 is
fabricated in the same manner as in the first embodiment between
the radially opposing surfaces of the inner peripheral surface of
the housing 12 and the outer peripheral surface of the metallic
mass 32. Therefore, it is possible to set with ease the natural
frequency of the independent mass member 16 to a frequency band
that is higher than the natural frequency of the vehicle body or
the like, for which the vibrations are to be controlled. Also, it
is possible to produce the mount 60 with superior mass production
properties wherein the surging suppression effects exhibit their
benefits because the gap 42 can be produced easily and with high
precision.
[0087] While presently preferred embodiments of the invention have
been described in detail hereinabove, for illustrative purpose
only, it is to be understood that the present invention is not
limited to the details of the illustrated embodiments, but may be
otherwise embodied with various other changes, modifications and
improvements, which may occur to those skilled in the art, without
departing from the spirit and scope of the invention.
[0088] For instance, in the illustrated embodiments, there is
employed a process wherein the independent mass member 16 and the
housing 12 are moved in the axial direction relative to each other
using the push rod 52 after vulcanization molding of the striking
rubber layer 34 in order to caused the striking rubber layer 34 to
peel more reliably from the housing 12. However, there is no need
to perform this process when, for example, the striking rubber
layer 34 peels reliably from the housing 12 when the initial
vibration is applied.
[0089] In the first embodiment, the push rod 52 prepared separately
was used to move the independent mass member 16 and the housing 12
relative to each other. Instead, a stop part may be fabricated in
the large-diameter indentation part 36 of the metallic mass 32 and
a stop member fabricated separately may be stopped by the stop part
to move the stop member in the rotational direction or the axial
direction. Alternatively, a stop member is formed by utilizing the
support protrusions 49 of the male mold 48 of the fabrication mold
44, and during opening the fabrication mold 44 after the
vulcanization molding process, the independent mass member 16 is
moved together with the mold 48 so that the independent mass member
16 and the housing 12 undergoes relative movement in the axial
direction. Yet alternatively, a structure may be used wherein there
can be stretching and/or compression of the support pin 47 of the
fabrication mold 44 that is inserted into the insertion hole 22 of
the housing 12, and then to move the support pin 47 in the axial
direction to force relative motion, in the rotational direction
and/or axial direction, of the independent mass member 16 and the
housing 12.
[0090] In the illustrated embodiments, while the process of
adhering the striking rubber layer 34 onto the metallic mass 32 is
performed, the non-adhesion process for the striking rubber layer
34 on the housing 12 was not performed. However, in addition to, or
instead of, the adhesion process for the metallic mass 32, a
non-adhesion process may be performed on the housing 12 by coating
a releasing agent onto the inner peripheral surface of the housing
10 when performing the vulcanization molding of, for example, the
striking rubber layer 34.
[0091] In the second embodiment, the rubber material 34' for the
striking rubber layer 34 is filled into the mold cavity 50 through
the runner 82 for injection fabricated in the metallic mass 32.
However, instead the rubber material 34' may be filled into the
mold cavity 50 through a separate runner, or the like, fabricated
in the fabrication mold 84 that opens directly into the space
between the radially opposing surfaces of the metallic mass 32 and
the housing 12.
[0092] Furthermore, in the second embodiment, the rubber elastic
body 66 and the striking rubber layer 34 were integrated. However,
the fabrication of the striking rubber layer 34 may be performed in
a separate process from the fabrication of the rubber elastic body
66. Specifically, after the vulcanization molding of the rubber
elastic body 66, the inner cylinder 62 and outer cylinder 64, and
housing 12 may be placed on a fabrication mold that has been
prepared separately from the integrally vulcanized product of the
rubber elastic body 66, the metallic mass 32 may be disposed within
the housing 12 so that the housing 12 and the metallic mass 32 are
disposed coaxially, and then the striking rubber layer 34 may be
vulcanization molded. Conversely, prior to the vulcanization
molding of the rubber elastic body 66, the metallic mass 32 may be
disposed within the housing 12 so that the housing 12 and the
metallic mass 32 are disposed coaxially and the striking rubber
layer 34 may be molded by vulcanization. After the vulcanization,
the independent mass member 16, having the striking rubber layer 34
fabricated covering the metallic mass 32, is removed from the
housing 12 in the axial direction and then. After vulcanization
molding of the inner and outer cylinders 62 and 64 and the housing
12 to integrate with the rubber elastic body 66, the independent
mass member 16 that had been removed may be then disposed within
the housing 12.
[0093] Moreover, the shape, size, and so forth of the metallic mass
32, the housing 12, and the small gap 42 may be changed as
appropriate depending on the required anti-vibration
characteristics and product characteristics, and the like, and are
not limited to the illustrative cases presented herein.
[0094] In addition to the engine mount 60 for an automobile or the
vibration-damping device 10 that are attached to the transmission
case 18 of an automobile as in the illustrated embodiment, the
present invention may be similarly applied to body mounts and
member mounts, cab mounts, strut bar cushions, etc., or to
fluid-filled cylindrical mounts.
* * * * *