A motorcycle having an improved frame and fuel tank arrangement that define a ram air inlet channel for delivering cooling air to the engine induction system.
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1. A motorcycle having a frame comprised of a head pipe, a pair of box section main frame members having inwardly facing side surfaces depending from respective upper surfaces, said main frame members being fixed at their front ends to said head pipe and extending rearwardly and downwardly therefrom, said inwardly facing side surfaces and said main frame members diverging from each other in the vicinity of their connection to said head pipe, a front wheel dirigibly supported by said head pipe, an engine carried by said frame and positioned at least in substantial part below said main frame members, said engine having a charge forming system including a rearwardly extending air inlet positioned at least in substantial part below said upper surfaces of said main frame members, a rear wheel suspended from said main frame member at the rear end thereof, and a fuel tank supported upon said main frame members and having a lower surface extending above said engine and said air inlet, said lower surface of said fuel tank and said inwardly facing side surfaces of said main frame members defining a forwardly opening air inlet channel for delivering ram air to said air inlet.
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This invention relates to an engine cooling system for motorcycles and more particularly to an improved system for directing cool air to the air induction system of a motorcycle engine.
The compactness of motorcycles is well known. Because of their extremely compact nature, there are a number of problems to be overcome in designing a successful motorcycle. One of the main problems is designing the engine mounting and air flow system in such a way as to insure that a good supply of clean cool fresh air is provided to the engine induction system. Recently, it has been the practice to position the carburetors or induction system for the engine to the rear of the engine so that the air cleaners and air inlet devices are positioned in the area of the rider's seat so that they will be protected from the intrusion of foreign matter. However, such a location makes it difficult to provide an adequate supply of cool air to the engine induction system.
It is, therefore, a principal object of this invention to provide an improved motorcycle engine cooling system.
It is another object of this invention to provide an improved motorcycle arrangement for permitting a rearwardly positioned air inlet and yet insuring adequate air supply to the engine.
It is another object of this invention to design the motorcycle frame and associated components so that they act as a ram air inlet device for the engine induction system.
This invention is adapted to be embodied in a motorcycle having a frame that is comprised of a head pipe and a pair of main frame members that have a box section configuration and which are fixed at their forward ends to the head pipe. The main frame members extend rearwardly and downwardly from the head pipe and diverge from each other in the vicinity of their connection to the head pipe. A front wheel is dirigibly supported by the head pipe and an engine is carried by the frame and positioned at least in substantial part below the main frame member. The engine has a charge forming system including a rearwardy extending air inlet positioned at least in substantial part below the upper surfaces of the main frame members. A fuel tank is supported upon the main frame members and above the engine and the engine air inlet. The fuel tank lower surface and the side surfaces of the main frame members define a ram air inlet channel for directing ram air to the engine air inlet.
FIG. 1 is a side elevational view of a motorcycle constructed in accordance with an embodiment of the invention.
FIG. 2 is an enlarged side elevational view, with portions broken away and other portions shown in section, showing the engine air induction system.
FIG. 3 is a top plan view of the frame and engine relationship with certain components removed so as to more clearly show the construction.
FIG. 4 is a view taken in the direction of the arrow 4 in FIG. 2.
FIG. 5 is a cross-sectional view taken along the line 5--5 of FIG. 2.
A motorcycle constructed in accordance with an embodiment of the invention is identified generally by the reference numeral 11. The motorcycle 11 includes a frame assembly, indicated generally by the reference numeral 12, which is a welded up assembly that includes a head pipe 13. Affixed to the head pipe 13 are a pair of main frame members 14 that have a generally box like configuration in cross-section and which may be conveniently formed by welding a pair of stamped sections together. The main frame members 14 diverge from each other in the area where they are affixed to the head pipe 13 and then extend parallel for a substantial portion of their length as may be best seen in FIGS. 3 through 5. In addition, the main frame members 14 extend generally rearwardly and downwardly from the head pipe 13.
The main frame members 14 are joined together at their rearward ends by welding them to a casting 15. In addition, a pair of down tubes 16 are connected to the main frame members 14 by means of a briding reinforcing member 17. The down tubes 16 are connected at their other ends to the casting 15 in an appropriate manner.
A pair of seat rails 18 extend rearwardly from the main frame members 14 and are integrally connected at their rear ends. The seat rails 18 are supported at each side of the frame assembly 12 by means of seat pillar rails 19 that extend between the casting 15 and the rearward portions of the seat rails 18.
A front wheel 21 is dirigibly supported from the frame 12 and specifically from the head pipe 13 by means of a front fork 22. A handlebar assembly 23 is connected to the front fork 22 for steering of the front wheel 21 in a known manner.
A rear wheel 24 is supported by a trailing arm assembly 25 which is, in turn, pivotally journaled by the frame casting 15 by means of a pair of pivot shafts 26.
An engine, indicated generally by the reference numeral 27, is supported by the frame assembly 12 in a location that is substantially beneath the main frame members 14 so as to provide a low center of gravity. The engine 27 includes a cylinder block and head assembly 28 that defines a pair of aligned cylinders that extend transversely across the width of the frame 12 in the area between the main frame members 14 and beneath them. The engine 27 and specifically the cylinder block, cylinder head assembly 28 is provided with a pair of forwardly facing exhaust ports 29 that cooperate with an exhaust manifold, muffler arrangement 31 that discharges the exhaust gases rearwardly of the motorcycle 11.
The engine 27 is also provided with a charge forming and induction system in the form of a pair of carburetors 32 As may be seen from FIG. 2, a portion of the air flowing through the air inlet channel 41 passes through the radiator 39 while another portion, as already noted, passes over the radiator. The air flowing through the radiator is indicated in this figure by solid line arrows while the air flowing around the radiator is noted by broken line arrows. This air is supplied to the engine induction system.
The frame assembly 12 may be formed from any suitable material but preferably is formed from either aluminum castings and stampings or from steel.
It is to be understood that the foregoing description is that of a preferred embodiment of the invention and that various changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.
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| Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
| Apr 01 1992 | Yamaha Hatsudoki Kabushiki Kaisha | (assignment on the face of the patent) | / |
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