Catalytic converter having improved supporting members for monolithic catalyst

The catalytic element is supported at its both longitudinal ends by two supporting members which are secured to the inner surface of a casing. Each supporting member is formed with a plurality of slits for releasing thermal stresses generated therein due to a high temperature within the casing when used.

This invention relates generally to a catalytic converter for use in an 
exhaust system of an automotive internal combustion engine and, more 
particularly to a catalytic converter of the type in which a monolithic 
catalytic element is secured within a casing thereof. 
It is a main object of the present invention to provide an improved 
catalytic converter having a monolithic catalytic element therein, which 
converter is constructed so that the catalytic element is not damaged or 
broken by the application of local mechanical force thereto due to the 
thermal deformation of the supporting members supporting the catalytic 
element. 
It is another object of the present invention to provide an improved 
catalytic converter having supporting members for securely supporting a 
monolithic catalytic element within a casing, in which the supporting 
members are formed with slits to release the thermal stresses generated 
therein in order to prevent thermal deformation of the supporting members, 
thereby preventing the application of local mechanical force and 
accordingly damage to the monolithic catalytic element.

With reference to FIG. 1, there is shown a prior art catalytic converter 10 
of a type in which a cylindrical monolithic type catalytic element 12 is 
located within a cylindrical casing 14. In general, such a type of 
catalytic element 12 is made of a brittle material such as ceramics and 
accordingly is liable to be damaged by severe vibration and local 
mechanical force applied thereto. Accordingly, the catalytic element 12 is 
supported, within the casing 14, in its radial direction by a supporting 
member 16 which is disposed between the inner surface of casing 14 and the 
outer surface of the catalytic element 12, and at its both ends by two 
opposite similar supporting members 18a and 18b. As shown, each of the 
supporting members 18a and 18b is formed of cylindrical flange portions 20 
secured to the inner surface of the casing 14 and radial annular disc 
portions 22 integral with the flange portions 20. The radial annular disc 
portions 22 are in contact with the end portions of the opposite and 
parallel annular planes 12a and 12b of the catalytic element 12, 
respectively. 
It is to be noted that the radial length l of the radial annular disc 
portion 22 is designed to be relatively small to provide a relatively 
large area of the opening 24 defined by the annular disc portion 22 in 
order to obtain an increased flow amount of the exhaust gases passing 
through the converter 10 and an increased contacting area of the catalytic 
element 12 with the exhaust gases flowing into the converter 10. 
Additionally, the radial annular disc portion 22 of the supporting member 
20 is generally designed to be small in its thickness t. 
Since the prior art converter 10 is constructed as described above, 
particularly in its supporting members 18a and 18b for supporting the 
catalytic member 12 at its both ends, it has encountered problems in which 
the radial annular disc portions 22 of the supporting members 18a and 18b 
are thermally warped by a high temperature of the exhaust gases passing 
through the converter 10, applying severe local mechanical force to the 
peripheral portions at the annular planes 12a and 12b of the catalytic 
element 12. Therefore, the peripheral portions of the annular planes 12a 
and 12b of the catalytic element 12 are liable to be damaged or destroyed. 
In order to overcome the above-described problems encountered in the prior 
art, the present invention contemplates to present warping of the radial 
annular disc portions of the supporting members supporting the catalytic 
element in its longitudinal direction, by forming a plurality of radial 
slits in the radial annular disc portion. 
Referring now to FIGS. 2 to 4, a preferred embodiment of a catalytic 
converter 30 in accordance with the present invention is shown. The 
catalytic converter 30 comprises a metal casing 32 which is formed of 
frusto-conical end closure portions 34a and 34b integral with a 
cylindrical portion 36. The frusto-conical end closure portion 34a has at 
its central portion a gas inlet 38 communicable with the combustion 
chambers of an automotive internal combustion engine (they are not shown). 
The frusto-conical end closure portion 34b has at its central portion a 
gas outlet 40 communicable with the atmosphere to emit purified exhaust 
gases into the atmosphere. Additionally, the frusto-conical portion 34a is 
so dimensioned as to enable distribution or passage of the exhaust gases 
over the entire or substantially entire cross-sectional area of the 
cylindrical portion 36 of the casing 32. The other frusto-conical portion 
34b is of similar dimensions as the frusto-conical portion 34a as shown, 
and of such dimensions as to enable free passage of gas out of the 
converter without causing substantial back pressure. 
Disposed within the cylindrical portion 36 of the casing 32 is a catalytic 
element or catalyst 42 which is made of a refractory material such as 
ceramics and is generally cylindrical and of unitary solid skeletal 
structure (honeycomb type) having a plurality of gas flow channels or 
paths 44 therethrough. The catalytic element 42 has two opposite and 
parallel end planes 42a and 42b. The plane 42a faces the gas inlet 38 to 
introduce the exhaust gases from the gas inlet 38 into the gas flow 
channels 44 of the catalytic element 42, and the end plane 42b faces the 
gas outlet 40. A catalytic material such as a platinum group metal is 
carried on the inner surfaces of the channels 44. Within a cylindrical 
space (no numeral) defined between the inner surface of the cylindrical 
portion 36 of the casing 32 and the outer surface of the catalytic element 
42, a supporting member 46 is disposed to support the catalytic element 42 
in its radial direction and concentrically to the cylindrical portion 36 
of the casing 32. The cylindrical space extends completely around the 
catalytic element 42 along the entire length of the catalytic element 42. 
The supporting member 46 is formed to prevent the exhaust gases from 
by-passing the catalyst and is accordingly formed of packed asbestos or 
ceramic fibers to serve as a sealing member. 
Reference numerals 48a and 48b indicate two opposite metal supporting 
members or first and second supporting members for supporting the 
catalytic element 42. The supporting member 48a is composed of an annular 
flange portion 50 and a radial annular disc portion 52 integral with the 
flane portion 50. The supporting member 48a is secured at its flange 
portion 50 to the inner surface of the cylindrical portion 36 of the 
casing 32 and contacts at its annular disc portion 52 the peripheral 
portion of the annular plane 42 of the catalytic element 42. As clearly 
shown, the supporting member 48b is of similar construction to the 
supporting member 48a and accordingly the annular flange portion 50 of the 
supporting member 48b is secured to the inner surface of the cylindrical 
portion 36 of the casing 32, and the radial annular disc portion 52 is in 
contact with the peripheral portion of the annular plane 42b of the 
catalytic element 42. It will be understood that the radial annular disc 
portions 52 of the supporting members 48a and 48b define openings 54a and 
54b, respectively. 
As best seen in FIGS. 3 and 4, the radial annular disc portion 52 of the 
supporting member 48a is formed with a plurality of radial slits which may 
be slits 52a which define considerable openings as indicated in FIG. 3, or 
be slits 52a' which do not define any openings therethrough as indicated 
in FIG. 4. The slits 52a or 52a' are, as shown, formed suitably spaced 
from each other to extend radially from the inner peripheray 52b to the 
outer periphery 52c of the radial annular disc portion 52. The annular 
disc portion 52 is integral at the outer periphery with the flange portion 
50. It is to be noted that the radial annular disc portion 52 of another 
supporting member 48b is also formed with the slits 52a or 52a' similar to 
the supporting member 48a, though not shown. 
With the catalytic converter arrangement hereinbefore described, the 
exhaust gases discharged from the automotive internal combustion engine 
are introduced through the gas inlet 38 into the gas flow channels 44 of 
the monolithic catalytic element 42. Then, the noxious constituents 
contained in the exhaust gases are converted into harmless compounds by 
contacting the catalytic material carried on the surfaces of the gas flow 
channels 44. At this time, if the radial annular disc portions 52 of the 
supporting members 48a and 48b are subjected to an excessively high 
temperature, thermal stresses generated by the high temperature are 
released from the radial annular disc portions 52 because the annular disc 
portion 52 is separated into a plurality of small pieces. Accordingly, the 
annular disc portions 52 do not warp or deform to apply local mechanical 
force at the peripheral portions of the annular planes 42a and 42b of the 
catalytic element 42, and consequently the catalytic element 42 is not 
damaged or broken at all. It will be understood that although the slits 
52a or 52a' extend to the outer periphery of the radial annular disc 
portion 52, the exhaust gases introduced through the gas inlet 38 is not 
allowed to flow from the upstream side into the downstream side of the 
catalytic element 42 through the slits 52a or 52a' and the supporting 
member 46 because the supporting member 46 serves as a sealing member. 
FIG. 5 illustrates another preferred embodiment of the catalytic converter 
10' according to the present invention, which converter 10' is similar to 
the embodiment of FIG. 2 except for the radial direction supporting member 
46 and the shape of the slits 52a and 52a' of the radial annular disc 
portions 52. In this instance, the supporting member 46 is formed of 
coiled wires, corrugated metal meshes or wound metal mesh fabrics which 
are poor in sealing effect of the exhaust gases and allow the exhaust 
gases to pass therethrough. In order to prevent the gas flow through the 
supporting member 46 of the poor gas sealing effect, each slit 52a and 
52a' is not formed to reach the outer periphery of the radial annular disc 
member 52, but is formed to extend from the inner periphery 52b of the 
annular portion 52 to a predetermined point which does still not reach the 
level corresponding to the outer periphery of the cylindrical catalytic 
element 42. It will be appreciated that the exhaust gases containing 
unreacted noxious constituents are prevented from by-passing the catalytic 
element 42. 
As is apparent from the foregoing discussion, according to the present 
invention, the monolithic honeycomb type catalytic element is prevented 
from damage due to warp of the supporting member 46 merely by forming a 
plurality of slits 52a and 52a' in the radial annular disc portions 52 in 
the supporting members 46. Accordingly, this improves the durability of 
the catalytic element 42.