Note: Descriptions are shown in the official language in which they were submitted.
CA 02496716 2001-09-05
1
A SNOWMOBILE ENGINE ARRANGEMENT HAVING AN IMPROVED HEAT
EXCHANGER CONFIGURATION
This application is a division of Canadian Patent
Application Serial No. 2,356,599, filed September 5, 2001.
In view of division enforced by the Canadian
Intellectual Property Office the claims of this application
are directed to a snowmobile engine arrangement having an
improved heat exchanger configuration. However, for the
purpose of facilitating an understanding of all objects and
features of the development which are inextricably bound-up
in ane and the same inventive concept as taught and claimed
in the parent application, the objects and teachings of
those features claimed in the parent Canadian Application
Serial No. 2,356,599 are retained herein.
Accordingly, in view of enforced division required by
the Examiner in the prosecution of the aforesaid parent
application, object clauses and features have been retained
for the purposes of facilitating and understanding of the
overall development. However, the retention of any clauses
or features which may be more particularly related to the
parent application or a separate divisional thereof should
not be regarded as rendering the teachings and claiming
ambiguous or inconsistent with the subject matter defined
in the claims of the divisional application presented
herein when seeking to interpret the scope thereof and the
basis in this disclosure for the claims recited herein.
CA 02496716 2001-09-05
la
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to an engine
arrangement, and in particular relates to an arrangement
of a four-cycle engine mounted on a snowmobile.
(2) Description of the Prior Art
Conventionally, small snow vehicles such as
snowmobiles have mainly used two-cycle engines. A two-
cycle engine is characterized by a relatively simple engine
configuration having the advantages of being lightweight
and compact and still providing high power. However, two-
cycle engines have drawbacks, when compared with four-
cycle engines, of emitting a greater amount of exhaust and
louder noise with greater vibrations.
The recent worldwide trend demands a silent, clean and
environment-conscious engine. Snow vehicle engines are no
exception and clean and silent engines have been desired.
To fulfill this demand, development of engines for
snowmobile into a four-cycle configuration has been
studied.
Brief Description of Prior Art Drawings 1 & 2
Figure 1 is a conventional snowmobile with a
normal engine arrangement; and
Figure 2 is a snowmobile with an engine inclined
forwardly.
CA 02496716 2001-09-05
2
As shown in Fig. l, a typical conventional snowmobile
200 has a body frame 210 in a monocoque frame configuration,
wherein an engine 202 is mounted in a space formed between
a track housing 211c and a front suspension housing 211b -in
the front frame ( engine mounting frame ) 211. For a two-cycle
engine, engine 202 is mounted upright in an engine compartment
206.
If a four-cycle engine is attempted to be put into use
for a snowmobile in the same manner as above, the upright
mounting has been difficult because a four-cycle engine has
a greater full height compared to a two cycle engine due to
its bulky cylinder head and the necessity of an oil pan.
Further, since a four-cycle engine needs additional parts
unique to it such as an alternator, supercharger, intercooler,
oil filter and the like, it has been very difficult to lay
out all these parts in a limited engine compartment space.
To overcome the above space difficulty, there has been
a layout proposal as shown in Fig.2 in that an engine 202
to be mounted on a snowmobile 201 is set inclined forwards
in an engine compartment 206 so as to reduce the full height
of engine 202 while the aforementioned components are laid
out in the space created by the inclined arrangement of the
engine.
On the other hand, in order to enhance the power of a
four-cycle engine which is relatively low in power compared .
CA 02496716 2001-09-05
3
to a two-cycle engine, it is generally known that a
supercharger(so-called turbocharger) is provided on the
intake side of the engine so as to increase the amounts of
air and fuel to be supplied to the combustion chamber, to
thereby enhance the engine power.
When the engine has a supercharger, provision of an
intercooler in the intake line is effective in improving the
intake efficiency. However, the position at which the
intercooler is attached needs careful thought as to the cooling
efficiency of the engine and is affected by the attached
position of the supercharger, so that it has been very difficult
to design the layout and allot mounting spaces for these
components in the engine compartment.
For example, when the intercooler is arranged on the
top of the engine, the full height of the engine becomes high
so that the center of gravity as well as the body height of
the snowmobile becomes high, hence the result is not
preferable .
On the other hand, when the intercooler is arranged in
front of the engine, the heavy part is located away from the
center of gravity, so that the maneuverability lowers.
Further, there is another drawback in that if the snowmobile
is collided, the front part of the engine compartment will
crush so that damage to the engine will become serious.
For a four-cycle engine, the oil pan, designated at 238,
CA 02496716 2001-09-05
4
needs to be positioned at the engine bottom. If the engine
is of a wet sump type, a large oil pan 238 is needed, which
will cause difficulty of interference with the steering shaft ,
designated at 224, as shown in Fig.2.
Further, for a snowmobile, the underside of the engine
compartment serves as a sled sliding over snow, hence needs
to be closed, which makes maintenance work such as changing
oil difficult.
Moreover, when a four-cycle engine with a V-belt type
automatic transmission is used for a snowmobile, the engine
is used at higher speeds compared to that of a four-wheel
vehicle. Therefore, the engine oil increases in temperature
due to increased amount of heat from the engine, whereby oil
film starvation may occur, leading to damage to the engine.
SUMMARY OF THE INVENTION
The present invention has been devised in view of the
above conventional difficulties, it is therefore an object
of the present invention to provide a snowmobile four-cycle
engine arrangement with which space saving in the engine
compartment is achieved and the workability of maintenance
is improved. It is another object of the present invention
to provide a snowmobile four-cycle engine arrangement with
which cooling performance of the air and engine oil supplied
to the engine is improved and space saving is achieved without
CA 02496716 2001-09-05
any loss of maneuverability.
In order to achieve the above object, the present
invention is configured as follows:
5 In accordance with the first aspect of the present
invention, a snowmobile four-cycle engine arrangement
includes : a four-cycle engine having a cylinder head on the
top thereof and arranged in an engine compartment formed
in the front body of a snowmobile with its crankshaft laid
substantially parallel to the body width and its engine
body inclined forwards with respect to the vehicle's
direction of travel; and an intake path on the upper face
of the engine body, and is characterized in that a heat
exchanger for cooling the engine cooling water, engine oil
or air to be supplied to the engine is arranged in the
tunnel created inside the body frame for accommodating a
track for driving
In accordance with the second aspect of the present
invention, the snowmobile four-cycle engine arrangement
having the above first feature is characterized in that the
heat exchanger is disposed in front of the track, with
respect to the vehicle's direction of travel, inside the
tunnel.
In accordance with the third aspect of the present
invention, the snowmobile four-cycle engine arrangement
having the above first feature is characterized in that an
intercooler for cooling the air to be supplied to the
engine is put into use as the heat exchanger.
CA 02496716 2001-09-05
6
In accordance with the fourth aspect of the present
invention, the snowmobile four-cycle engine arrangement
having the above second feature is characterized in that
an intercooler for cooling the air to be supplied to the
engine is put into use as the heat exchanger.
In accordance with the fifth aspect of the present
invention, the snowmobile four-cycle engine arrangement
having the above first feature is characterized in that an
oil cooler for cooling the engine oil is put into use as
the heat exchanger.
In accordance with the sixth aspect of the present
invention, the snowmobile four-cycle engine arrangement
having the above second feature is characterized in that
an oil cooler for cooling the engine oil is put into use
as the heat exchanger.
In accordance with the seventh aspect of the present
invention, the snowmobile four-cycle engine arrangement
having the above first feature is characterized in that a
radiator for cooling the engine cooling water is put into
use as the heat exchanger.
In accordance with the eighth aspect of the present
invention, the snowmobile four-cycle engine arrangement
having the above second feature is characterized in that
a radiator for cooling the engine cooling water is put into
use as a heat exchanger.
In accordance with the ninth aspect of the present
invention, the snowmobile four-cycle engine arrangement
CA 02496716 2001-09-05
6a
having the above first feature is characterized in that an
integrated configuration comprised of an oil cooler for
cooling the engine oil and a radiator for cooling the
engine cooling water is put into use as the heat exchanger.
In accordance with the tenth aspect of the present
invention, the snowmobile four-cycle engine arrangement
having the above second feature is characterized in that
an integrated configuration comprised of an oil cooler for
cooling the engine oil and a radiator for cooling the
engine cooling water is put into use as the heat exchanger.
In accordance with the eleventh aspect of the present
invention, the snowmobile four-cycle engine arrangement
having the above fifth feature is characterized in that a
thermostat is interposed in the oil path of the oil cooler.
In accordance with the twelfth aspect of the present
invention, the snowmobile four-cycle engine arrangement
having the above sixth feature is characterized in that a
thermostat is interposed in the oil path of the oil cooler.
In accordance with the thirteenth aspect of the
present invention, the snowmobile four-cycle engine
arrangement having the above ninth feature is characterized
in that a thermostat is interposed in the oil path of the
oil cooler.
In accordance with the fourteenth aspect of the
present invention, the snowmobile four-cycle engine
arrangement having the above tenth feature is characterized
CA 02496716 2001-09-05
6b
in that a thermostat is interposed in the oil path of the
oil cooler.
According to the present invention, since the heat
exchanger for cooling the engine cooling water, engine oil
or air to be supplied to the engine is arranged in the
tunnel created inside the body frame for accomodating a
track for driving, it is possible to provide a snowmobile
four-cycle engine arrangement in which the heat exchanger
will not receive any thermal influence from the engine
compartment and can be cooled markedly efficiently by snow
powder stirred up during running. Further, provision of
the heat exchanger outside the engine compartment makes it
possible to reduce the engine height so realize deployment
of a four-cycle engine. Further,
CA 02496716 2001-09-05
7
this configuration enhances space saving in the engine
compartment and is markedly effective in reducing the body
height so avoid any loss of maneuverability.
Since the heat exchanger is disposed in front of the
track, with respect to the vehicle's direction of travel,
in the tunnel, it is possible to arrange it close to, and
approximately below, the engine. Therefore, the connections
such as pipes, etc. , can be shortened, thus making it possible
to simplify the communication paths so reduce the cost.
Since the intercooler for cooling the air to be supplied
to the engine is put into use as the heat exchanger, it is
possible to efficiently cool the air which has been compressed
and sent from the supercharger and hence is high in temperature
to thereby improve the engine power.
Since the oil cooler for cooling the engine oil is put
into use as the heat exchanger, it is possible to efficiently
cool the engine oil which is high in temperature. Therefore,
it is possible to prevent oil film starvation hence prevent
damage to the engine to thereby maintain the engine in a good
running state.
Since the radiator for cooling the engine cooling water
is put into use as the heat exchanger, it is possible to
ef ficiently cool the cooling water which is high in temperature .
Therefore, it is possible to prevent the engine from
overheating so keep the engine in a good running state.
CA 02496716 2001-09-05
8
Since the oil cooler for cooling the engine oil and the
radiator for cooling the engine cooling water are integrated
as the heat exchanger, it is possible to eliminate the necessity
of providing an oil cooler and radiator separately hence
achieve space saving and reduce the number of parts.
Since a thermostat is interposed in the oil path of the
oil cooler, the engine oil can be kept at a proper temperature .
Therefore, it is possible to prevent the engine oil from being
excessively cooled, hence keep the engine in a good running
state.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig.l is a partially sectional side view showing an
overall configuration of a snowmobile having a conventional
four-cycle engine mounted thereon;
Fig.2 is an illustrative view showing an overall
configuration of a conventional snowmobile four-cycle engine:
Fig.3 is a partially sectional side view showing an
overall configuration of a snowmobile employing a snowmobile
four-cycle engine arrangement in accordance with the
present invention;
Fig.4 is a partially sectional plan view showing an
overall configuration of a snowmobile of a first variational
example of the present invention;
Fig.5 is a sectional side view showing the bottom
CA 02496716 2001-09-05
9
arrangement of an engine compartment of a second variational
example of the present invention;
Fig.6 is a bottom view showing the bottom arrangement
of the engine compartment;
Fig.7 is a sectional side view showing the bottom
arrangement of an engine compartment of a third variational
example of the present invention;
Fig.8 is a bottom view showing the bottom arrangement
of the engine compartment;
Fig.9 is a partially sectional side view showing an
overall configuration of a snowmobile four-cycle engine in
accordance with the first embodiment of the present
invention;
Fig.lO is a partially sectional plan view showing an
overall configuration of a snowmobile four-cycle engine of
the first embodiment;
Fig.ll is a partially sectional side view showing an
overall configuration of a snowmobile four-cycle engine of
the second embodiment; and
Fig.l2 is a partially sectional plan view showing an
overall configuration of a snowmobile four-cycle engine of
the second embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention will hereinafter
CA 02496716 2001-09-05
be described in detail with reference to the accompanying
drawings.
Fig.3 is a partially sectional side view showing an
overall configuration of a snowmobile employing a snowmobile
5 four-cycle engine arrangement in accordance with the
present invention.
A snowmobile four-cycle engine according to the
invention is arranged as shown in Fig. 3. That is, a
four-cycle engine 2 having a cylinder head 3 at the top thereof
10 is arranged in an engine compartment 6 enclosed by a front
cover 4 on the front body side of a snowmobile 1 and is inclined
forwards with respect to the vehicle's direction of travel
with its crankshaft(not shown) laid substantially parallel
to the body width and an intake path 5 on the top thereof .
Engine 2 employs a dry sump oil supplying system therein.
Now, the configuration of snowmobile 1 will be explained
in detail.
Snowmobile 1 has a body frame 10 extending front to rear
as shown in Figs.3 and 4 with a pair of steerable, ski-type
runners 13 arranged on the left and right under the front
frame, designated at il, so as to be turned to the left and
right . Arranged under the rear frame, designated at 12 , is
a tractive crawler 16 including a circulating continuous track
belt 15. This crawler 16 comprises a drive wheel 17 arranged
at the front end of rear frame 12, an idle wheel 18 arranged
CA 02496716 2001-09-05
11
at the rear end and a multiple number of middle wheels 19,
a suspension mechanism 20 and the track belt 15 wound around
these wheels and driven circulatively.
Body frame 10 has a monocoque frame configuration . The
front frame ( engine mount frame ) 11 on which engine 2 is mounted
is comprised of a main part lla as a middle part, a front
suspension housing llb projectively formed upward in front
of the main part for accommodating the upper part of front
suspension 13a for supporting steerable ski-type runners 13,
and a track housing llc raised upwards and rearwards from
the main part lla for accommodating the upper part of drive
wheel 17 of crawler 16 . This track housing llc is continuously
and integrally formed with rear frame 12.
The rear frame 12 is extended to the rear with respect
to the vehicle's direction of travel and also functions as
the cover for accommodating the whole crawler 16 under it .
A saddle type seat 22 is arranged on the top of rear
frame 12 with steps 23 disposed below on both sides of seat
22.
A steering shaft 24 is provided extending upward
substantially in the center of the body between seat 22 and
front cover 4 while handlebars 26 extending horizontal to
the left and right and inclined rearwards are attached at
the top of steering shaft 24.
Disposed upright in front of handlebars 26 is awindshield
CA 02496716 2001-09-05
12
28, from the base of which front cover 4 is formed in a
substantially streamline shape, or in a substantially
hull-bottom shape gradually lowering to the front.
Steerable ski-like runners 13 are adapted to be steered
via steering shaft 24 by handlebars 26.
Next, the configuration of engine 2 will be described
in detail.
As shown in Fig. 3 , engine 2 is a four-cycle engine and
is arranged at the approximate center of engine compartment
6 inside front cover 4 with its crankshaft(not shown) laid
substantially parallel to the body width and its cylinder
head 3 inclined at a large angle forwards in the vehicle's
direction of travel.
An intake path 5 including a carburetor and throttle
body is arranged on the upper side of the engine 2 body, an
alternator 31 and air cleaner 32 being arranged to the rear,
downstream of the intake path.
A flywheel (not shown) is disposed afi one end (on the
lef t side with respect to the vehicle' s direction of travel )
of the crankshaft and a V-belt type stepless transmission(not
shown ) incorporating a centrifugal clutch is arranged on the
outer side of this flywheel. This stepless transmission is
configured so as to transmit drive power to track belt 15
via gears etc., on the receiving side. A brake(not shown)
is fitted at the other end of the receiving shaft of the stepless
CA 02496716 2001-09-05
13 '
transmission.
Arranged at the other end of the crankshaf t ( on the right
side with respect to the vehicle's direction of travel) is
a pulley 34 functioning as a transmission for driving auxiliary
equipment so as to drive alternator 31 and a water pump 35.
A starter motor(not shown) is arranged in proximity to
the flywheel on the top of the engine 2 body and under intake
path 5 such as carburetor, throttle body etc. Disposed on
the top of the engine 2 body is an intake manifold 37 which
~ branches the intake path 5 from carburetor 36 into the intake
ports of the individual cylinders. The intake system of
carburetor 36 and air cleaner 32 from intake manifold 37 is
coupled and arranged above the top position of cylinder head
3 and extended to the rear.
This intake system is located under front cover 4 behind
the base of windshield 28 from where it extends upward. The
top part of cylinder head 3 is accommodated, without
interference with other components , in the front inner side
o:E front cover 4 where it gradually lowers toward the front .
As the exhaust system, an unillustrated exhaust manifold
is extended from the cylinder case , designated at 39 , to the
front of engine 2 and is connected to a supercharger 7. An
exhaust path is created rearwards along the engine 2 body
from this supercharger 7 located at the engine 2 front . That
is, supercharger 7 is connected by way of the exhaust path
CA 02496716 2001-09-05
14
to an unillustrated muffler arranged on one side in the rear
of the engine.
As shown in Fig. 3, engine 2 is inclined forwards in engine
compartment 6 and mounted on, and along, front frame 11 with
an oil pan 38 arranged adjacent to inclined track housing
llc and cylinder case 39 arranged adjacent to front suspension
housing llb.
An oil tank 40 is arranged on the top of front suspension
housing llb in front of and separately from, engine 2.
The engine oil distributed to parts of the engine returns
into oil pan 38 and goes to the oil tank 40 via an oil strainer
41 and is re-supplied appropriately to the parts of the engine.
In main part lla constituting part of engine compartment
bottom 6a, an opening port 50 for maintenance which establishes
communication between engine compartment 6 and the external
space and a lid element 51 for opening and closing the opening
port 50 are provided at a position opposing the bottom of
o:Ll pan 38 of engine 2.
Thisopening port 50 is approximately rectangular-shaped
and has a size which allows for maintenance of oil pan 38
from the underside of engine compartment 6.
The one side of lid element 51 is engaged at one side
of opening port 50 with a connecting means 52 such as a hinge
etc . , so that the lid element will be able to pivotally open .
A .lock mechanism 53 is provided on the other side of lid element
CA 02496716 2001-09-05
51 so that lid element 51 can be positively fixed to engine
compartment bottom 6a when opening 50 is closed.
Thus, since engine 2 of a dry sump type is arranged
inclined forwards with the oil pan 38 at the bottom of
5 engine 2 close to main part lla, it becomes possible to
arrange engine 2 in engine compartment 6 in a compact
manner.
Since oil tank 40 is arranged in front of cylinder head
3 of engine 2, on the upper surface of front suspension housing
10 lib, which is projected into engine compartment 6, it is
possible to provide a space saving engine arrangement by making
the best use of the front space of engine 2. Further, this
arrangement allows the oil tank to receive little thermal
influence from the engine and makes it possible to cool the
15 engine oil effectively from the air flow during travel.
Further, since opening port 50 for maintenance is formed
at a position opposing oil pan 38 of engine compartment 6a
so as to allow maintenance work such as changing oil etc.,
to be performed outside engine compartment 6, the maintenance
performance can be markedly improved.
Provision of opening port 50 in an openable and closable
configuration has the advantage of not affecting the travel
performance of the snowmobile.
Though the invention shows engine 2 arranged inclined
forwards inside engine compartment 6, the present
CA 02496716 2001-09-05
16
invention should not be limited to this. For example, as a
first variational example, an engine 102 may be mounted
substantially upright in engine compartment 6 as shown
information Fig.4 with an oil tank 141 arranged on the top
surface of front suspension housing llb located in front of
the engine. It is understood that this arrangement is a simple
extension of the present invention.
Further, oil tank 40 is arranged on the top surface
of front suspension housing llb in front of engine 2.
However, the present invention should not be limited to
this. For example, an oil tank 140 may be arranged on the
top face of track housing llc behind engine 2 as is
indicated by a broken line in Figs. 3 and 4. In this case,
it is possible to provide a space saving arrangement by
making effective use of the space over track housing llc
behind engine 2. Further, since the oil tank is located
apart from the heat source of the engine and can be cooled
by snow powder stirred up during running, the engine oil
can be cooled efficiently.
Though, hinged lid element 51 is provided so as to
open and close the opening port 50 formed at engine
compartment bottom 6a, the present invention should not be
limited to this. For example, as a second variational
example, a lid element 151 having an approximately
congruent shape with an opening port 150 formed at the
engine compartment bottom 6a can be provided separately.
CA 02496716 2001-09-05
17
That is, the lid element my be fitted to the opening port
150 and integrally fixed to engine compartment bottom 6a
with fasteners 152 such as fastening bolts or the like.
In the drawing, reference numeral 153 denotes a threaded
hole to secure screw fastener 152.
In this case, opening port 150 may be depressedly formed
into the engine compartment 6 by a height approximately equal
to the thickness of lid element 151. This makes it possible
to arrange the lid element 151 substantially flush with the
engine compartment bottom 6a, providing a refined appearance
as well as reducing air drag during travel.
As a third variational example, as shown in Figs . 7 and
8, an opening port 250 with its inner periphery formed with
a thread 250a may be formed on engine compartment bottom 6a
so as to be pro jected into engine compartment 6 while a lid
element 251 with a thread 251a, mating the thread 250a, formed
on. its outer periphery may be provided separately. In this
case, since no other fastener is needed when lid element 251
is attached to opening port 250, it is possible to improve
work performance as well as to use fewer components so reduce
the cost.
Next, the first embodiment of the present invention
will be described in detail with reference to the drawings.
Fig.9 is a partially sectional side view showing an
overall configuration of a snowmobile four-cycle engine in
CA 02496716 2001-09-05
18
accordance with the first embodiment of the present
invention. Fig. LO is a partially sectional plan view
showing an overall configuration of the same snowmobile
four-cycle engine.
A snowmobile four-cycle engine according to the first
embodiment of the present invention is arranged as shown
in Figs. 9 and 10. That is, similar to what is previously
described, a four-cycle engine 2 (to be referred to herein-
below as engine) having a cylinder head 3 at the top
thereof is arranged in an engine compartment 6 enclosed by
a front cover 4 on the front body side of a snowmobile 1
and inclined forwards with respect to the vehicle's
direction of travel with its crankshaft (not shown) laid
substantially parallel to the body width and an intake path
5 on the top of the inclined engine 2 body. A supercharger
(turbocharger) 7 is arranged separately from the engine 2
body while an intercooler 8 for cooling intake air sent
from this supercharger 7 to the engine 2 body is arranged
at the front side, with respect to the vehicle's direction
of travel, inside the tunnel that is formed on the inner
side of a body frame 10 in which an aftermentioned drive
track belt 15 is accommodated.
Here, the configuration of snowmobile 1 is generally
the same as previously described except that the rear
frame, designated at 12, has a tunnel-like configuration
from the body front to the rear, i.e., with the inner side
depressed upwards from the bottom, so as to function as a
CA 02496716 2001-09-05
19
cover accommodating the whole track belt 15 under it.
Next, the configuration of engine 2 will be described
in detail.
As shown in Figs.9 and 10, engine 2 is a four-cycle
three-cylinder engine having its cylinder head 3 on top and
is arranged at the approximate center of engine compartment
6 inside front cover 4 with its crankshaft(not shown) laid
substantially parallel to the body width and its cylinder
head 3 inclined at a large angle ( a . g. , more than 45 degrees
forwards) in the vehicle's direction of travel. Other
arrangement is the same as ;previously described.
Next, the intake system will be described.
In the arrangement of the intake system, the parts to
be disposed on the upper side of engine 2 are positioned under
front cover 4 behind the base of windshield 28 from where
it extends upward while the parts to be disposed in front
of cylinder head 3 are accommodated, so as not to interfere
with other components, on the front inner side of front cover
4 where it gradually lowers toward the front.
Disposed on the top of engine 2 is an intake manifold
3? which branches the intake path 5 from carburetor 36 .into
the intake ports of the individual cylinders.
A supercharger 7 is arranged in front the engine 2 and
an air cleaner 32 is disposed at the frontmost space in engine
compartment 6.
CA 02496716 2001-09-05
An intercooler 8 is arranged in proximity to engine 2
at its rear bottom, but outside engine compartment 6 and on
the inner side of body frame 10.
One end of supercharger 7 is connected to an intake passage
5 7a extended forwards so that the supercharger is connected
to air cleaner 32 via this intake air passage 7a.
The other end of supercharger.? is connected to
intercooler 8 via an intake air passage 7b which starts from
the front side of engine 2 and is bent along the side face
10 of engine 2, in an L-shape as viewed from the top, extended
to the rear and bent downwards, in a sectional view, near
the engine crankshaft.
An intake air passage 8a is connected to the outlet side .
of the intercooler 8. This intake air passage 8a extends
15 upwards approximately vertically from the engine Z bottom
and is connected to carburetor 36 arranged over the engine
2.
For air supply to engine 2, air is introduced from the
body front via air cleaner 32 into supercharger 7 , where the
20 air is compressed and sent to intercooler 8. In the
intercooler 8, the air which has become high in temperature
through supercharger 7 is cooled and sent to carburetor 36 ,
from where air is supplied to individual cylinders in engine
2 via intake manifold 37.
On the other hand, the exhaust path starts from cylinder
CA 02496716 2001-09-05
21
case 39 toward the front side of engine 2 and is connected
to the inlet side of supercharger 7 via an exhaust manifold
41. The outlet side of supercharger 7 is connected to an
exhaust passage 42, which is extended from the front side
of the engine 2 body to the rear along the engine 2 body and
connected to a muffler 43 arranged at one side behind the
engine.
Next, mounting of engine 2 will be described.
As shown in Fig . 9 , engine 2 is inclined forwards in engine
compartment 6 and mounted on, and along, front frame 11 with
an oil pan 38 arranged adjacent to inclined track housing
llc and cylinder case 39 arranged adjacent to suspension
housing llb.
The engine 2 is attached to track housing llc by a pair
of oil-pan side brackets 45 on the rear side and to suspension
housing llb by a pair of cylinder-case side brackets 46 on
the front side. Both the oil-pan side brackets 45 and
cylinder-case side brackets 46 are angled fittings and
arranged left and right . Shock absorbers 47 such as cushion
rubber are interposed at the fastening sites to front frame
11 so that the engine is supported floatingly on front frame
11.
According to the first embodiment as above, since intake
path 5 is arranged on the upper side of engine 2 , supercharger
7 and air cleaner 32 are disposed in front of the engine in
CA 02496716 2001-09-05
22
engine compartment 6 while intercooler 8 is placed outside
engine compartment 6 and inside body frame 10, it is possible
to realize a compact engine layout and markedly improve the
cooling performance of intercooler 8 by eliminating any
thermal effect from engine 2 and cooling it by snow powder
stirred up during running, to thereby enhance the charging
efficiency of intake air.
By arranging the intake path and exhaust path from the
front side toward the rear of engine 2 along its body side,
it is possible to improve the cooling effect on the intake
and exhaust path by air flow during travel.
Next, the second embodiment will be described in
detail with reference to the drawings.
Fig. 11 is a partially sectional side view showing an
overall configuration of a snowmobile four-cycle engine of
the second embodiment. Fig. 12 is a partially sectional
side view showing an overall configuration of the
snowmobile four-cycle engine. Here, the parts
corresponding to those in the first embodiment are allotted
with the same reference numerals without description.
A snowmobile four-cycle engine according to the second
embodiment is arranged as shown in Figs. il and 12. That
is, a four-cycle engine 102 (to be referred to hereinbelow
as engine) having a cylinder head 3 at the top thereof is
arranged in an engine compartment 6 enclosed by a front
cover 4 on the front body aide of a snowmobile 100 and
CA 02496716 2001-09-05
23
with respect to the vehicle's direction of travel with its
crankshaft (not shown) laid substantially parallel to the
body width and an intake path 5 on the top of the inclined
engine 2 body.
An oil cooler 108 is arranged at the front side, with
respect to the vehicle's direction of travel, in the tunnel
that is formed on the inner side of a body frame 10. This
oil cooler 108 has a thermostat valve(not shown) between its
inlet and outlet oil paths.
An intake path 5 including a carburetor and throttle
body is arranged on the upper side of the engine 102 body,
an alternator 31 and air cleaner 132 being arranged to the
rear, downstream of the intake path.
According to the second embodiment as above, since
intake path 5 and air cleaner 132 are arranged on the upper
side of engine 102, oil cooler 108 is placed outside engine
compartment 6 and in the front inner side of body frame 10,
it is possible to realize a compact engine layout. Further,
since oil cooler 108 is arranged at the front side, with
respect to the vehicle's direction to travel, in the tunnel
that is formed on the inner side of body frame 10 so that it
will not receive any thermal influence from engine 102, it is
possible to efficiently cool the engine oil which is high in
temperature by snow powder stirred up during travel.
CA 02496716 2001-09-05
24
Therefore, it is passible to prevent oil film starvation hence
prevent damage to the engine to thereby maintain the engine
in a good running state.
Further, since a thermostat is interposed in the oil
path of the oil cooler 108, it is possible to prevent the
engine oil from being excessively cooled so keep the engine
in a good running state.
In the above embodiments, intercooler 8 or oil cooler
108 is put into use as a heat exchanger and arranged inside
the tunnel-like hollow inside body frame 10. However, the
present invention should not be limited to this arrangement .
Far example, the radiator may be arranged inside body frame
10. In this case, the engine cooling water can be efficiently
cooled so that the engine can be prevented from overheating,
thus making it possible to keep the engine in a good running
state.
Further, in the present invention, the oil cooler for
cooling the engine oil and the radiator for cooling the engine
cooling water may be configured integrally and is put into
use as the heat exchanger. In this case, it is possible to
provide a space saving arrangement and reduce the number of
parts because of being needless of providing an oil cooler
and radiator separately.
As has been described heretofore, according to the
snowmobile four-cycle engine arrangement of the present
CA 02496716 2001-09-05
invention, since the oil tank is arranged in the engine
compartment, separately from the engine, it is possible to
make the use of a four-cycle engine feasible as well as realizing
space saving by making efficient use of the space inside the
5 engine compartment.
Further, since an openable/closable maintenance opening
is provided at the bottom of the engine compartment, this
arrangement is markedly effective in improving the workability
of maintenance when changing oil and the like.
10 Since a heat exchanger for cooling the engine cooling
water, engine oil or air to be supplied to the engine is disposed
inside the tunnel that is formed inside the body frame, instead
of arranging it inside the engine compartment, it is possible
to achieve space saving inside the engine compartment and
15 reduce the engine height, whereby it is possible to realize
deployment of a four-cycle engine, which is
environment-conscious.
Finally, according to the present invention, it is
possible to provide a snowmobile four-cycle engine which is
20 markedly improved in its cooling performance by snow powder
stirred up during running.
