U.S. patent application number 11/985220 was filed with the patent office on 2008-08-07 for method of using syntactic foam to reduce noise and machine using same.
This patent application is currently assigned to Caterpillar Inc.. Invention is credited to Thomas J. Grabenstetter.
Application Number | 20080185220 11/985220 |
Document ID | / |
Family ID | 39675213 |
Filed Date | 2008-08-07 |
United States Patent
Application |
20080185220 |
Kind Code |
A1 |
Grabenstetter; Thomas J. |
August 7, 2008 |
Method of using syntactic foam to reduce noise and machine using
same
Abstract
A method of decreasing engine noise in machines, such as
internal combustion engines, by replacing metallic engine
components that serve as noise transmission pathways such as oil
pans, valve covers, gear covers with similar components made of
syntactic foam with a density of at least 0.5 g/cm.sup.3 and a
hardness at least about equal to that of an equivalent metallic
engine part which it is replacing. The syntactic foam is comprised
of fluid-filled microballoons in a foam matrix. The microballoons
have an outer shell harder than that of the surrounding foam
matrix, and a majority of the microballoons are out of contact with
one another.
Inventors: |
Grabenstetter; Thomas J.;
(Metamora, IL) |
Correspondence
Address: |
CATERPILLAR c/o LIELL, MCNEIL & HARPER
P.O. BOX 2417, 511 SOUTH MADISON STREET
BLOOMINGTON
IN
47402-2417
US
|
Assignee: |
Caterpillar Inc.
|
Family ID: |
39675213 |
Appl. No.: |
11/985220 |
Filed: |
November 14, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60858885 |
Nov 14, 2006 |
|
|
|
Current U.S.
Class: |
181/290 |
Current CPC
Class: |
G10K 11/165 20130101;
F02B 77/13 20130101 |
Class at
Publication: |
181/290 |
International
Class: |
E04B 1/84 20060101
E04B001/84 |
Claims
1. A machine comprising: a plurality of machine components being
attached to one another, and at least one of the components being
comprised of syntactic foam; the syntactic foam including a polymer
matrix and a plurality of fluid-filled microballoons, a density of
0.5 g/cm.sup.3 or greater, and a hardness of at least about Shore D
74; and a majority of the microballoons being out of contact with
one another, and each microballoon including fluid surrounded by a
shell more rigid than the matrix, and the fluid being a majority of
a volume of each microballoon.
2. The machine of claim 1 wherein the machine being an engine, and
the at least one component includes a valve cover.
3. The machine of claim 1 wherein the at least one component
includes a gear cover.
4. The machine of claim 1 wherein the at least one component
includes an oil pan.
5. An engine comprising: a plurality of engine components being
attached to one another and including a portion being metallic
components and a portion being comprised of a syntactic foam
component.
6. The engine of claim 5 wherein the syntactic foam component
includes a valve cover.
7. The engine of claim 5 wherein the syntactic foam component
includes a gear cover.
8. The engine of claim 5 wherein the syntactic foam component
includes an oil pan.
9. The engine of claim 5 wherein the syntactic foam includes a
density of 0.5 g/cm.sup.3 or greater.
10. The engine of claim 5 wherein the syntactic foam includes a
hardness of at least about Shore D 74.
11. The engine of claim 5 wherein the syntactic foam includes a
polymer matrix and a plurality of fluid-filled microballoons, and a
majority of the microballoons being out of contact with one
another.
12. The engine of claim 5 wherein the syntactic foam includes a
polymer matrix and a plurality of fluid-filled microballoons, and
each microballoon includes a fluid surrounded by a shell more rigid
than the matrix and the fluid being a majority of a volume of each
microballoon.
13. The engine of claim 12 wherein the syntactic foam components
include at least one of a valve cover, a gear cover, and an oil
pan; and the syntactic foam includes a density of 0.5 g/cm.sup.3 or
greater, a hardness of at least about Shore D 74, and a majority of
the microballoons being out of contact with one another.
14. A method of reducing sound emitted from a machine comprising a
step of: substituting a syntactic foam machine component for a
metallic machine component.
15. The method of claim 14 wherein the machine being an engine, and
the machine component including at least one of a valve cover, a
gear cover, and an oil pan.
16. The method of claim 14 wherein the syntactic foam component
includes a polymer matrix and a plurality of fluid-filled
microballoons, a density of 0.5 g/cm.sup.3 or greater, and a
hardness of at least about Shore D 74; and a majority of the
microballoons being out of contact with one another, and each
microballoon including fluid surrounded by a shell more rigid than
the matrix, and the fluid being a majority of a volume of each
microballoon.
Description
RELATION TO OTHER PATENT APPLICATION
[0001] This application claims priority from provisional
application No. 60/858,885, filed Nov. 14, 2006, with the same
title.
TECHNICAL FIELD
[0002] The present disclosure relates generally to substituting
equivalent syntactic foam for metal in engine component(s) to
reduce noise, and more specifically to replacing metallic engine
components such as oil pans or valve covers with comparable pieces
made from syntactic foam in order to reduce noise.
BACKGROUND
[0003] Internal combustion engines necessarily involve moving parts
and explosive combustion events, and these things necessarily
involve noise output. Governmental regulations require that this
noise output be below a certain level. This has led to complex
structures and "add-ons" to engines to try to reduce the noise
output from components that act as the prime transmission path of
sound such as valve covers, engine blocks, front and rear gear
covers, oil pans and other engine components known to those skilled
in the art. These add-ons can have the drawback of being bulky and
increasing total cost of production.
[0004] One solution to this problem that has been considered is
metallic components with isolation seals, however these have the
drawback in that they can increase total engine cost and can leak.
Another possible solution is laminated metal components such as
QuietSteel. Components using this material, however, are hard to
form and become quite difficult to weld. A related solution was
proposed in U.S. Pat. No. 5,566,721 which involved coating a
component, such as a driveshaft tube, with a sound deadening
material such as a urethane elastomer. This method adds an extra
production step and cost in terms of both capital and time. Other
solutions have included the use of polymeric composite components
with low density such as balsa wood, pvc foam or honeycomb inserts,
but these can suffer from the problem of low strength and be
damaged easily, which would make them difficult to use effectively
in engine components. A final solution has been to use gas-assisted
injection molded composite components, but this technology requires
very specific parameters in terms of the heat and pressure of the
surrounding environment. Thus it becomes difficult to achieve a
uniform density/size of voids in the foam, so thus far this
technology is only used in manufacturing relatively small pieces
such as car door handles.
[0005] This disclosure is directed toward one or more of the
problems set forth above.
SUMMARY OF THE INVENTION
[0006] In one aspect, a machine comprises a plurality of machine
components being attached to one another, where at least one of the
components is comprised of syntactic foam. The syntactic foam
includes a polymer matrix and a plurality of fluid-filled
microballoons which have a density of 0.5 g/cm.sup.3 or greater and
a hardness of at least about Shore D 74. A majority of the
microballoons are out of contact with one another, and each
microballoon is composed of a shell more rigid than the surrounding
matrix, and contains a fluid comprising a majority of the volume of
the microballoon.
[0007] In another aspect, an engine comprises a plurality of engine
components which are attached to one another. A portion of the
engine components are metallic components and the other portion of
the engine components comprise syntactic foam.
[0008] In still another aspect, a method of reducing sound emitted
from a machine is accomplished by substituting a syntactic foam
machine component for a metallic machine component.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is an enlarged cross section of the syntactic foam
according to the present disclosure;
[0010] FIG. 2 is an enlarged cross section of another syntactic
foam according to the present disclosure; and
[0011] FIG. 3 is a diagrammatic side view of engine components
which could be constructed of syntactic foam according to the
present disclosure.
DETAILED DESCRIPTION
[0012] Referring to FIG. 1, there is shown a syntactic foam 10
comprised of a plurality of microballoons 11a, b in a foam matrix
14, where the majority of microballoons are out of contact with one
another. One example of a production method for such a syntactic
foam is shown in U.S. Pat. No. 4,788,230, which teaches a specific
method for making a lightweight foam. In contrast, the focus of
this disclosure is to make a foam with sound deadening properties.
Each microballoon 11a, b has an outer shell 13a, b which is of
greater hardness than the surrounding foam matrix 14. It will be
understood that the microballoon shell 13a, b may be roughly 10% of
the total diameter of the microballoon 11a, b so that the
microballoons 11a, b can withstand the pressure put on them during
the manufacturing process, and other expected forces and stresses.
Each microballoon 11a, b encloses a volume 12a, b, wherein the
majority of said volume 12a, b is filled with some fluid, such as
any suitable gas. The microballoons may range from 1 micron to 1000
microns in diameter, as will be known to one skilled in the art. It
will further be understood that though FIG. 1 shows microballoons
of two different diameters 11a, b the scope of this disclosure is
intended to include syntactic foam containing solely one size of
microballoons or any combination of microballoons of different
sizes, dependant upon the specific heat, electric and sound
reduction properties and other criteria required for the specific
component to be manufactured as will be known by one skilled in the
art. Finally, it will be understood that though FIG. 1 only shows
the syntactic foam 10 and microballoons 11a, b, there may or may
not be any one of a number of filler materials or crosslink
additives in accordance with the desired characteristics of the
foam.
[0013] Referring to FIG. 2, another syntactic foam 110 magnified
cross section has a formulation similar to that of the foam 10 of
FIG. 1, but also includes fibers 118 for increased strength. The
FIG. 2 embodiment also differs in that the relative ratio of
microballoons to polymeric matrix is greater than that of the
syntactic foam of FIG. 1.
[0014] One set of materials proposed as components of the syntactic
foam 10 are bisphenol A epoxy as a matrix resin, aromatic amine as
a crosslink additive, glass fluid-filled microballoons and carbon
fiber as a fiber filler as necessary. A second example of the
syntactic foam 10 includes bisphenol F epoxy as a matrix resin,
aliphatic amine as a crosslink additive, ceramic fluid-filled
microballoons and basalt fiber as a fiber filler as necessary.
[0015] Other options for the matrix resin include but are not
limited to: epoxy phenolic, epoxy cresol, epoxy BPA, aromatic
epoxy, acrylic resins, bismaleimides maleic acid, isophthalic acid,
orthophthalic acid, terephthalic acid, furfuryl alcohol,
dicyclopentadiene diamines, or aromatic cyanate ester, or any
appropriate combination or accepted equivalent.
[0016] Some possible materials that could be used as crosslink
additives include but are not limited to: novolac polyamine,
novolac fumaric acid, novolac glycols, polyacrylate polyglycols,
styrene, acrylic acid, methacrylic acid, 1-4 butanediol, MOCA or UV
and EB cure systems, or any appropriate combination or accepted
equivalent.
[0017] One skilled in the art will understand that syntactic foam
10 necessarily involves the use of microballoons 11a, b, however
other fillers may be used to change the specifications or
properties of the foam as desired for the specific application.
Possible materials that could be used as fillers include but are
not limited to: expanded clay prills, glass fiber, perlite, wood
flour/fiber, expanded fly ash, corn stover/husk/cob, fly ash
cenospheres, rice hull, rice hull ash, expandable starch granules,
cotton wool/linters, hair or feather fiber, expanded thermoset such
as phenolic granules, hemp/jute/kenaf fiber, rock wool, graphite
fiber, aramid fiber, nylon fiber, other cellulosic or crop fiber,
thermoplastic fiber, thermoset fiber or other mineral fibers such
as asbestos, or any appropriate combination or accepted
equivalent.
[0018] It is finally envisioned that the syntactic foam 10 could
also be composed of: phenolic (phenol mixed with formaldehyde),
polyether polyols, polyester polyols, polyimide resins or high
heat-distortion thermoplastic resins, or any appropriate
combination or accepted equivalent.
[0019] One skilled in the art will understand that the above
examples are merely listed as exemplary options and are in no way
intended to specifically limit the scope of the materials used and
equivalent substitutes as defined by the current art may be used as
desired. Further, one skilled in the art will understand that some
combinations of the materials above may involve less ingredients,
such as thermoplastics which do not require a cross-linking
additive. The specific combinations of the materials listed above
will be recognized by one skilled in the art.
[0020] Referring to FIG. 3 with continued reference to FIGS. 1 and
2 there is shown an engine housing 22 including valve cover
components 20a-c as well as an oil pan 21, amongst various other
components. It is envisioned that according to the present
disclosure any number of components of the engine housing 22
including the valve cover components 20a-c or the oil pan 21 could
be composed of syntactic foam 10 as described above with a minimum
hardness at least equal to that of an equivalent metallic component
which it is replacing. The specific examples of FIGS. 1 and 2 have
hardness ranges of about Shore D 74 to about Shore D 80,
respectively. The term "about" means that when the number is
rounded off to the same number of significant digits, the numbers
are equal. For instance, 73.5 is about 74. Although syntactic foam
components having these hardness parameters may be suitable for the
identified engine compressions, higher and lower harnesses would be
attainable without difficulty. However, parts made at lower
durometers would likely not be as durable for engine component
applications, but higher durometers might be attractive, and would
certainly be attainable with a suitable polymer content. Further,
one skilled in the art will recognize that the description of the
valve cover or oil pan components is intended to be exemplary only
and other parts or components of the engine or engine housing 22
can be constructed from syntactic foam 10 in order to reduce noise.
The present disclosure might be especially applicable to covers and
the like that protect other machine components and include fastener
bores for receiving suitable fasteners, such as bolts or
screws.
INDUSTRIAL APPLICABILITY
[0021] One skilled in the art will recognize that the foam matrix
14 itself will have inherent sound reduction properties, but these
properties can be improved by adding fluid filled microballoons
11a, b. These microballoons 11a, b increase sound reduction in two
ways. The first is that they increase the complexity of the sound
path through the foam by adding internal reflection barriers into
the path once the sound enters the fluid-filled microballoons.
Additionally, each time the sound goes through a barrier into a
different medium, such as air to foam matrix 14, foam matrix 14 to
microballoon shell 13a, b, and microballoon shell 13a, b to
microballoon internal fluid 12a, b a portion of the sound is
scattered. By increasing the barrier changes in the sound path the
sound will be increasingly scattered throughout the foam, and the
sound emerging from the foam ultimately reduced.
[0022] As described above, it is envisioned that any number of
metallic engine parts may be replaced by syntactic foam 10 made of
fluid filled microballoons 11a, b in a foam matrix 14 in order to
reduce noise from the engine. Methods of part forming are various.
These could include compression molding, transfer molding and
injection molding. Since the syntactic foam composite material is
relatively incompressible, unlike most common foams, it may be
processed in normal pressure forming equipment. It may be necessary
to process the part like a similar solid composite material (based
upon the polymer content of the formulation), which may allow early
demolding, but also a relatively long open cure time.
[0023] One preferred low cost formulation of the foam involves a
foam comprised of 57% epoxy resin, 9% epoxy crosslinking agent, 22%
fibrous filler, 6% microballoons and 6% long-fiber filler. This
composite foam is roughly 30% lower density than comparable foam
involving glass-filled spheres, and has desirable acoustical and
physical properties for the intended application. This foam has a
specific gravity of roughly 1.04 g/cm.sup.3 and a Durometer
hardness of 80D (Shore D 80).
[0024] Another formulation involves a foam comprised of 59% epoxy
resin, 9% epoxy crosslinking agent, 23% fibrous filler, 6%
microballoons and 3% long-fiber filler as described above. This
compound is roughly 40% lower density than a comparable foam
involving glass-filled spheres, and also has desirable acoustical
and physical properties for the intended application. This foam has
a specific gravity of roughly 0.88 g/cm.sup.3 and a Durometer
hardness of 75D (Shore D 74).
[0025] Still another formulation for the foam involves a foam
comprised of 65% epoxy resin, 10% epoxy crosslinking agent, 13%
carbon fiber filler and 13% microballoons. This formulation may be
higher cost, but is 40% lower density than a comparable foam and
has excellent acoustical and physical properties. This formulation
of the foam has a Durometer hardness of 75D (Shore D 75) and a
specific gravity of 0.88 g/cm.sup.3.
[0026] Another formulation involves a syntactic foam comprised of
81% epoxy resin, 12% epoxy cross linking agent, 3% fibrous filler
and 4% microballoons. This foam has a specific gravity of roughly
1.94 g/cm.sup.3 and a durometer hardness of about Shore 74 D.
[0027] It should be understood that the above description is
intended for illustrative purposes only, and is not intended to
limit the scope of the present invention in any way. One skilled in
the art will recognize that although this disclosure focuses on
replacing metallic engine parts, especially non-structural
components, with syntactic foam to reduce noise, the scope includes
other machines with internal combustion engines such as lawn
mowers, leaf blowers, on-highway trucks and tractors, amongst other
examples which will be known to one skilled in the art. Thus, those
skilled in the art will appreciate that other aspects of the
invention can be obtained from a study of the drawings, the
disclosure and the appended claims.
* * * * *