Motor vehicles – Power – Having specific motor-to-body-frame relationship
Reexamination Certificate
2002-06-03
2004-06-08
Hurley, Kevin (Department: 3611)
Motor vehicles
Power
Having specific motor-to-body-frame relationship
C180S190000
Reexamination Certificate
active
06745862
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a snowmobile equipped with a four-cycle engine, in particular relating to an intake structure of a snowmobile engine.
(2) Description of the Prior Art
Conventionally, most snow vehicle such as snowmobiles and the like use two-cycle engines, which are relatively simple in structure, light and compact and yet powerful. Recently, however, because of regulation of exhaust gas or aiming at improvement of fuel consumption, there is a trend toward employing four-cycle engines. In contrast to two-cycle engines, which are compact and high in power, four-cycle engines need a camshaft and oil lubrication, inevitably tending towards large size.
Therefore, it is necessary to provide a contrived layout of the oil pan configuration, intake and exhaust systems and associated auxiliaries, in order to make the body and engine hood of a snowmobile equipped with a four-cycle engine having a similar size to that of a two-cycle engine.
In general, in order to improve the maneuverability of a snowmobile, it is preferred that the engine should be set as low as the steering tie-rod so that the center of gravity of the vehicle with the engine mounted is positioned at a low position while the engine should be set as close to the steering post as possible so that the center of gravity will be set at the center of the body.
Now, consider a configuration where the engine of an existing two-cycle snowmobile is replaced with a four-cycle engine and the crank center of the four-cycle engine is set at the same position as that of the original two-cycle engine. In this case, since a four-cycle engine has an oil pan at its bottom, it has a greater height than the two-cycle engine. Therefore, if the engine is arranged with its cylinders set upright, in some cases the engine may interfere with the steering rod, or in other cases the cylinder head and throttle body may interfere with the engine hood.
Further, the two-cycle snowmobile engine needs a large capacity expansion chamber for improving the performance. This chamber is generally routed on the side opposite to the drive clutch and connected to the muffler. The reason the exhaust system is thus laid out can be attributed to the necessity of providing a space for routing and for adjusting the weight balance between the left and right. A flywheel magneto, the chamber and muffler are arranged on the side opposite to the clutch which is heavy.
Electronic and electric parts such as an engine control unit (ECU), capacitive discharge ignition (CDI) unit and the like are attached on the top of the air cleaner, to the chassis or the engine in order to avoid breakage from vibrations.
However, if these electronic and electric parts are disposed away from the engine, the wires have to be tied up or clamped which is unpreferable from the viewpoint of layout.
A model with a starter motor needs a battery for electric supply, and the battery is usually disposed away from the clutch and muffler. Therefore, it is some distance from the engine so the lead wires have to be routed and clamped.
If the exit of the muffler is arranged near the rider, the noise becomes too large and harsh to the ear. If the exit of the muffler is offset to one side, either left or right, the exhaust noise during travel differs between the left and right of the vehicle, causing a noise problem.
Further, since snowmobiles are used in cold areas, there is a fear that the breather hose for releasing the pressure inside the head cover may be frozen because oil mixed with water circulates through the breather hose. Once it is frozen, the pressure inside the head cover increases, causing sealing deficiencies and lowering the power. Moreover, since snowmobiles travel on undulating courses, there is a fear that oil may leak out from the breather as the body moves to and fro.
SUMMARY OF THE INVENTION
The present invention has been devised in view of the above prior art problems, it is therefore an object of the present invention to provide a snowmobile equipped with a four-cycle engine, in which the four-cycle engine can be mounted with its center of gravity at a position low enough without interference with the engine hood, and which is improved in travelling performance by setting the centroid of the engine close to the centroid of the snowmobile body and lowering the center of gravity.
It is another object of the present invention to provide a four-cycle engine which is reduced in exhaust noise therefrom.
It is a further object of the present invention to provide an intake structure for a snowmobile engine, which is able to prevent oil leakage when the snowmobile body is tilted and which is able to prevent freezing inside the intake passage.
In order to achieve the above objects, the present invention is configured as follows:
In accordance with the first aspect of the present invention, a snowmobile having a four-cycle engine mounted on a front body thereof and enclosed by an engine hood located in front of a seat is characterized in that the four-cycle engine is mounted in such a manner that the crankshaft is arranged along the body width direction and the central axis of a cylinder(s) is tilted rearward with respect to the vertical direction of the snowmobile body, forming a rear tilted engine; at least part of the engine intake system including an air cleaner box and throttle body, located over the engine and connected to the intake port(s) at the rear part of the cylinder head is accommodated in the topmost space of the engine hood; and exhaust is led out to the front of the cylinder(s) by an exhaust system connected to the exhaust port(s) of the front part of the cylinder head.
In accordance with the second aspect of the present invention, the snowmobile equipped with a four-cycle engine, having the above first feature is characterized in that the engine hood has an upward projected portion formed at top thereof, a headlight is disposed at the front of the projected portion and an instrument panel for indicating the condition of the vehicle at the rear of the projected portion, and at least part of the intake system is accommodated in the space sandwiched between the headlight and instrument panel in the projected portion.
In accordance with the third aspect of the present invention, the snowmobile equipped with a four-cycle engine, having the above first feature is characterized in that the exhaust system includes an exhaust manifold connected to the exhaust port(s) at the front of the cylinder head and an exhaust muffler located in front of the engine and connected to the exit of the exhaust manifold by an exhaust pipe, both being arranged inside the engine hood, and the exhaust system further has an exhaust lead path from the muffler, with an opening formed in the body bottom at the center with respect to the body width so that exhaust will be discharged from the opening to the outside of the snowmobile body.
In accordance with the fourth aspect of the present invention, the snowmobile equipped with a four-cycle engine, having the above third feature is characterized in that the muffler is arranged at a level lower than the engine cylinder(s) and the exhaust pipe from the exhaust manifold is extended frontwards and downwards to the muffler.
In accordance with the fifth aspect of the present invention, the snowmobile equipped with a four-cycle engine, having the above third feature is characterized in that the muffler is of an overally cylindrical shape with its cylinder axis directed along the body width, and exhaust from the engine is led into the muffler via an exhaust pipe that is connected to the muffler at one side with respect to the body width.
In accordance with the sixth aspect of the present invention, the snowmobile equipped with a four-cycle engine, having the above first feature is characterized in that the four-cycle engine is arranged in the engine hood so that the lengthwise center of the crankshaft is off-centered to one side with respect to the center of the body width.
In accordance with the
Matsumura Hitoshi
Morii Hideshi
Sasaki Yutaka
Shibano Ken
Yatagai Yasuaki
Hurley Kevin
Nixon & Vanderhye P.C.
Suzuki Motor Corporation
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