Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to improvements in exhaust cooling systems for
recreational vehicles, and particularly, although not exclusively, to a new or
improved exhaust cooling system which is helpful in combating excessive heat
build-up within the engine compartment under the cab o-f a snowmobile
Although recreational vehicles such as snowmobiles are intended
primarily for cold weather operation, problems can be encountered in providing
satisfactory dissipation o:f tlle heat generated by operation of the sno~mobile
engine. Recreational sno~mobiles are o necessity of fairly compact form, and
the design considerations are such that it becomes almost imperitive to posi-
tion the exhaust muffler under the cab at the forward end of the machine so
that it is, in effect, located in a common housing with the engine. This con
figuration can lead to undesirable build-up of heat under the snowmobile cab,
and while such heat build-up can be alleviated to a certain extent by the pro-
vision o large ventilation apertures in the snowmobile cab, this is not a
satisfactory solu~ion since such large apertures often conflict with styling
requirements of the vehicle design. Furthermore, in recent years progress
ively more stringen~ requirements have been imposed upon snowmobile manufac-
turers as regards operating noise levels. Since a major part of the noise
produced by a snowmobile in operation emanates from the engine, one means of
reducing operating noise levels which has been widely adopted has been to pro-
vide a more complete enclosure of the engine within the cab of ~he snowmobile.
However, this tends to aggravate the problems of heat build-up.
A partial solution to the problems discussed above is provided in
United States Patent 3,795,287 Rose wherein the muffler is located trans-
~ersely at the forward end of the en~ine compartment and is substantially
isolated from the engine compartment by two opposed semi-cylindrical members
which form a shield spaced around the muffler. The shield reduces heat
; ra~iation from the muffler into the engine compartment, and also guides a
flow of cooling air ~produced from the forward motion of the sno~nobile~ over
the muf-fler
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:
According to the present invention there is provided a recreational
vehicle powered by an internal combustion engine having an exhaust system
comprising a muffler, an exhaust manifold connected to deliver exhaust gases
from the engine to the muffler, and an exhaust duct adapted to deliver exhaust
gases from the muf:Eler to atmosphere, said engine and said muffler being
positioned within a common housi.ng in the vehicle, said muffler being enclosed
within a jacket which defines a cooling chamber around the wall of the muffler,
and cooling means for directing a flow of cooling air through said chamber
and for ducting said flow to atmosphere on the exterior of said housing there- `
10 b.y to inhibit transfer of heat from said exhaust system into said housing,
said cooling means comprising an engine-driven fan.
Pre:Eerably, in a recreational vehicle such as a snowmobile having
an air-cooled engine, the engine-driven fan is also employed to drive a
flow of air within a shroud over the cooling fins of the engine. In this
arrangementJ a duct is connected to the shroud close to the fan so that the .:
flow of air directed over the muffler is relatively cool and has not been
appreciably heated through contact with the engine cooling fins.
~le invention will further be described, by way of example only,
with reference to the accompanying drawings, wherein:
Figure 1 is a schematic diagram of an exhaust muffler cooling system
in accordance with the invention;
Figure 2 is a perspective view of an exhaust muffler cooling system
as provided in a snowmobile; and
Figure 3 is a perspective view of an alternative arrangement of
exhaust muffler cooling s~stem for a snowmobile.
In Figure 1 a two-cylinder air-cooled snowmobile engine is illus-
trated in broken lines at 10, the engine having an exhaust manifold 11 which
: directs exhaust gas from the engine through an exhaust pipe 12 to a muffler 13,
and from there to atmosphere through a tail pipe 1~. The muffler 13 is of
.~0 cylindrical form and is enclosed within a jacket 15 which defines an annular
`. .'A'~I -- 2
.
.
cooling chamber 16 completely surrounding the muffler.
The engine 10 is enclosed within a shroucL 17 which is spaced from
the ellgine cooling fins, and which has an inlet opening 1~ in which is located
an engine-driven fan ]9. When the engine is operating ~he fan 19 is driven
to direct a current of air over the engine cooling fins in the direction of
the arrows 20. A duct 21 communicates between the interior of the shroud 17
and the annular cooling chamber 16, and is designed to deliver a flow of air
driven by the fan 19 through the chamber 16, extracting heat rom the muffler
13 and delivering to atmosphere through a pipe 22, thus greatly reducing the
amount of heat released by the muffler 13 to its surroundings.
The duct 21 opens from the shroud 17 at a location close to the fan
19, so that the flow o air passed through this duct is relatively cool and
has not been appreciably heated by contact with the engine 10 or exhaust
manifold 11. If desired, a de:~lector (not shown~ may be provided on the
shroud 17 adjacent the inlet to the duct 21 to ensure an adequate flow of
cooling air.
~igure 2 shows the exhaust cooling system as mounted in a snowmobile,
the latter being indicated in broken lines at 23. The snowmobile 23 has a
housing 24 which together with the conventional upper housing structure or cab
(not shown) defines a substantially closed engine compartment 25 at the for-
ward end of the snowmobile. Within this compartment the snowmobile engine is
enclosed within a shroud 17a and is coupled through a transmission 26 shown
~ot
in broken lines to drive the snowmobile track (~2w shown). At the inlet end
, ~
of ~he shroud 17a an engine-driven fan l9a is located which in operation is
adapted to deliver a flow of cooling air over the engine. If desired, duct-
ing ~not shown~ may be provided to deliver the spent cooling air to the ex--
terior of the engine compartment. The muffler (not shown) is positioned with-
; in the engine compartment, transversely at the or~ard end thereof and is
enc:Losed within a jacket 15a, exhaust gases being delivered rom the engine
to the mufler through an e~haust pipe 12a and Erom the muEfler to atmosphere
-3~
through a tailpipe l~la which passes to an opening 27 on the underside of the
snowmobile housing 2~.
A duct 21a is connected between the shroud 17a and the jacket 15a to
deliver a flow of cooling air generated by the fan l9a into the cooling chamber
~not shown) surrounding the muffler within the jacket 15a. The spent flow of
cooling air is delivered from the jacket 15a through the pipe 22a; and is
passed to atmosphere through the opening 27.
With the above described muffler cooling arrangement, very little
heat generated by the muffler is released within the engine compartment, and
accordingly problems of heat build-up within the engine compartment are greatly
reduced.
Various configurations of the exhaust cooling system are possible
within the scope of the invention. For example as shown in ~igure 3 the jacket
l5b is not positioned transversely at the front of the engine compartment, but
rather is inclined towards the rear end of the machine, the exhaust gases in
this case being released at the rear of the engine compartment, in the neighbor-
hood o the track tunnel. The shroud 17b, exhaust pipe 12b and duct 21b are
modified as required to suit this configuration.
