Note: Descriptions are shown in the official language in which they were submitted.
'
~064399
BACKGROUND OF THE INVENTION
....
The present invention relates to a catalytic converter
for cleansing the exhaust gases of an internal combustion en-
gine, and to the method for assembling such apparatus.
In general 7 catalytic converters are formed of one or
more catalyst bodies, through which air or exhaust gases can
flow. The catal~tic bodies are mounted in a tubular metal
housing connected at one end to the outlet of the cylinder
blocks and, at its other end, to the exhaust manifold. The
catalytic bodies generally consist of brittle ceramic materials,
such as aluminum oxide, silicon dioxide, magnesiu~ oxide,
zirconium silicate,, or the like, all of which require a shock-
,~:
proof support within the tubular housing. This has causedgreat difficulty and has heretofore been affected only by the
use of expensive surrounding jackets or by the use of additional
axial supports located within the catalyst body itself. Refer-
ence can be made, for example, to the German patent publication
(~uslegeschrift 2,213,540). m e systems are generally expensive,
complex and far from efficient.
. ~ . .
` SUMMARY OF THE INVENTION
~1
According to the present invention, an effective shock-
, absorbing mounting of the catalyst bodies of a catalytic conver-
ter is achieved in a simple and inexpensive manner by locating
, ! .
l' ~ 2 - ` ~ .
.. . .
............................................................ .
:
1064399
the catalyst bodies within a tubular housing, and by enveloping
the circumferential surface of the body, parallel to the direc-
tion of air flow, with a material which expands under the action
of heat to a greater extent than the metal of the housing, but
contracts during subsequent cooling of the converter to the
ambient temperat~re, to a lesser extent than the metal of the
housing. In this manner, the catalyst body is held solely through
the radial pressure exerted by the material of the envelope.
.
~; As a result, shocks both in the axial flow direction
and in the radial dixection, that îs to say shocks which occur
transversely to the 10w direction, are a~sorbed as a result
of the elastic characteristic of the en~elope material.
.
~ refera~ly, materials which expand ~y foaming when
heated are particularly suitable and desirable as the envelope
material. A suita~le ~aterial which can be used is the commer-
` cially available Thermex ~a trademark of the 3M Company, Technical
Ceramic Products Division, Chattanooga, Tennessee2~ Thermex is
a composition consisting substantially of heat~resistant mineral
fibers containing organic binding agents and includes a component
; that oams and expands upon heating. This material is obtainable
in the form of a paste or as a fiber mat, which can easily be
i applied about the circumferential surface of the catalyst body.
.. ~ .
. .
~l ~ 3 -
.`, . .
~ ~ ' ' ' ~' . '
.. ~ .
1064399
An~r elastic material w'nich has the characterized thermal
expansion property, and ~hich does not lose its elasticity under
the action of heat during the e~ended operation of the catalys t
converter, is suitable for use 2S the envelope material. Pre-
ferably, material having an enclosed cell structure, which foams
under the action of heat, can be used since it comprises, due
to the high proportion of gas, an elastic compressibility re-
quired due to the radial pressure increase on the surface of the
catalyst body.
The present invention enables the construction of
catalytic converters in ~Jhich a plurality of catalyst b~dies are
arranged in tande~ witnin the interior o the housing. In such
COnstructiQnS, it is preferable, in accordance with the present
invention, to fo~n the catalyst bodies narrower in the axial
direction than heretofore usual, and to arrange between adjacent
bodies, a diaphragm conically taperi.ng in the flow direction.
The tapering diaphragm concentrates the gas flow on the rnore
acti~e central cross-section of the catalyst body and serves to
protect the surrounding envelope from the gases.
~''. ' ' .
Further, according to the present invention, a method
for securing the catalyst body ~Jithin the interior of the housing
'.
~.
. - - .. .. .. : .
1064399
is provided, comprising the step o~ subjecting the device
to pre-heating prior to installation, whereby a permanent pre-
tensioning of the envelope about the catalyst body is achieved.
This procedure eliminates the need for any additional fastening
elements for the support of the catalytic body concentrically
within the ~ubular housing, before the converter is affected
by heat in the vehicle of use for the first time, that is while
the envelope surrounding it is still soft. The pre-heating
step, which is carried out during the manufacturing process and
assembly of the converter, causes the hardening or curing of
the envelope material, together with simultaneous build-up of
radial pretensioning of the envelope about the catalyst body. The
!foregoing is sufficient to tension the catalyst body relative
to the housing unit until the catalyst converter is put into
operation on the vehicle and during the warming-up period of
the motor.
~; Full details o~ this pre9ent invention are set forth
in the following disclosure, and are illustrated in the accom-
panying drawings.
.~ .
~'
`':
., .
- 5 -
,~,
:,
.. ~ ,.
,'` .
~ .
~064399
~RIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
Fig.l is a sectional ~iew of the upper half of a
catalytic conYerter, formed in accord~nce with the present
invention, intersecting the central a~is, and
- Fig.2 is a s~milar view through a portlon of a
catalytic conYerter employing a plurality of catalyst bodies,
in accordance with the present inventîon.
DESCRIPTION OF THE INYENTION
.
; .
! As seen in ~ig,l, a monolithic unitary catalyst body
formed o~ conventional ceramic m~terial, such as that here-
tofore described, is located within a tubular metal housing 2.
The catalyst body is porous, comprising in conventional manner
a hard thin framework inner support 3 (skeleton~ covered by a re-
latively thin layer of catalyst material and ha~ing a plurality of
fine axial ducts, channels or openings extending through the body,
through which the exh~ust air or gases may flow, as shown by the
directional arrow R. The catalyst body is surrounded for its pro-
textion ~y a cement-like protective coating 4 of hard binding
material such as that sold under the Trademark "Beton". The me-
~"~, .
tallic housing 2, is made of highl~ heat-resistant metal, preferab-
~;~ ly of suitable ferric or stainl~ss steel, because o its relatively
low coefficient of expansion.
.,
. .; .
:, . .
1~64399
Interposed between the catalyst body 1, and the hous-
ing 2 is the surrounding envelope 5 formed, of material, for example
the aforementioned Ther~ex, which when heated, expands at a rate
and to an e~tent greater than that of the metal material orming the
housing and wh~ch contracts, when cooled as to the cooling temperature
of t~e ambient air when the engine is closed, at a rate and to a
lesser extent than that of the metal from which the housing is made.
The envelope 5, may be formed by coating, painting, or laying a
laminate ~at a~out the circumferential surface o~ the catalyst
body to an appropriate thickness. The layer forming the envelope 5
should contact bot~ the circumferential surface of the catalyst
body and the inner surface of the housing adhering thereto under
tension or radial pressure. Depending on the specific envelope
material, the lower li~it of thickness is chosen by its facility to
withstand shock action, while its upper limit of thickness is chosen
by its resistance to axial deformation, which of course should be
prevented~ A thickness between 1 - 3 mm will generally suffice for
the conventional materials.
Under operation of the catal~st converter, the envelope
5 seryes to absorb shocks in both the radial and axial dimen~
sion, and is caused to abut under tension created by the rela-
tively fixed outer housing, against the outer surface of the
protectiye coating 4 about the catalyst body, thereby exerting
a radially inward pressure on the catalyst body~ Because of the
relative hardness and essentially small dimensions of the envelope
5 the catalyst body is thus fixed firmly in place within the housing
2. The thickness of the envelope 5, and its material is so chosen
; that the envelope is proportioned to be such that its displacement
'
~064399
in the axial direction relative to the housing, or to the catalyst
body, is impossible, even under the greatest possible shock
action in the flow direction. A thickness of 1.5 mm for the
Thermex material has been found to be suitable. Other thick-
nesses may vary depending on material used for the envelope,
the catalyst bodies, and the forces to which the device is to
be put.
., .
Secured to the motor end of the housing 2 is a rad-
ially extending flange fitting 6 having one or more axial holes,
permitting the connection of the housing to the outward end
of the cylinder block of the engine. The opposite end of the
housing 2 is welded to a manifold pipe 7. In this manner, the
catalytic converter can be inserted directly at the outlet of
the cylinder block prior to the remainder of the exhaust system
thereby cleansing the exhaust gases before passing through the
conventional mu1er.
`' , ' .
In Fig. 2, a catalytic converter is illustrated in
which a plurality of catalytic bodies 11 are arranged in tandem,
one behind the other, in the direction of flow, indicated by
the arrow R within a metallic tubular housing. The catalyst
bodies 11 are relatively narrow, that is, have a small length
in the axial direction and thus have a low weight. Each is
supported within the housing 12 by an envelope 15 formed of the
. ' , :
~ - 8 -
~064399
type of material heretofore mentioned. The catalyst bodies may
even be of the size approximately gi~en in the drawings. The
housing 12 is shown as being thermally insulated on its exterior sur-
face by means of the use of a conventional thermal insulating layer
16 formed of mineral fihers, as~estos fibers, rock wool or the like,
the form of which is well known and will depend upon where the
catalyst con~erter apparatus is installed. Positioned between
each o the adjacent catalyst bodies is a diaphragm 13 comprising
a tubular body haYing a conical section and a cylindrical section.
The cylîndrical section is welded as indicated to the housing 13
to fi~ it in position. The conical section tapers inwardly in the
direction of air flow, so as to deflect the gases from the prece-
ding catalyst body ln jet fashion on the central cross sectional
portion of the succeeding body. The catalyst bodies and the
diaphragm 13 are secured in place with a small space between each.
The outer ho~sing 12 can be formed as a single tubular
section, or as shown in ~ig 2, can ~e formed as a plurality
of sections welded together at their ends in a position where
the diaphragm 13 is also welded.
. .
; In manufacturing the catalyst conYerter, it is pre-
; ~era~le, in accordance with the present inYention to preheat the
catalyst body and enyelope prior to assem~ly within the housing
and prior to installation in the vehicle, to a predetermined
.
'1064399
.
temperature. Thls c~uses t~e enYelope to expand and by this
means strengt~ens the envelope material gi~ing it a set with re-
spec~ to its elastîcity crea~ing a permanent pre-tensioning of
the envelope about the catalyst body before being subject to use.
After cooling the catalyst body and envelope are inserted in the
housing, In this manner, the elastic envelope can be fixed in
place in permament position within the housing and with permanent
pre-tension upon the catalyst body, prior to any installation in
the vehicle of use,
; yarious modi~ications, changes and embod~ments have
1 been descxibed herein. Othexs ~ill be o~Yious-to those skilled
in the present art. It is therefoxe intended that the present
disclosure be taken as illustxati~e only o~ the invention and
;- not limited o~ the scope.
. .
.; .
/ .
.
.
.` 10 `
-. . .. .
