Motorcycle provided with an engine having a supercharger

A motorcycle provided with an engine having a supercharger wherein the engine integrally formed with an engine body and a transmission case is mounted on a body frame, said transmission case having an upper case and a lower case integrally connected with each other, which are separable into upper and lower portions, and a supercharger for compressing suction air of said engine is mounted on the rear surface of said transmission case.

BACKGROUND OF THE INVENTION 
The present invention relates to a motorcycle provided with an engine 
having a supercharger which compresses suction air of the engine to 
enhance the filling efficiency thereby increasing the output thereof. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a motorcycle of the 
kind described which can enhance the cooling property of a supercharger 
heated to a high temperature and prevent the supercharger in an exposed 
state from being interfered with other parts. 
It is a further object of the present invention to provide a motorcycle of 
the kind described in which a supercharger is mounted on a body frame 
without hindering the mounting and operation of existing devices. 
It is another object of the present invention to provide a motorcycle of 
the kind described in which a supercharger is mounted at a position as low 
as possible to prevent the raise of gravity of the vehicle resulting from 
the provision of the supercharger while the connection of an exhaust pipe 
to the outer periphery of a turbine housing of the supercharger will not 
lower the minimum level of the vehicle from the ground. 
The above and other objects, features and advantages of the present 
invention will become apparent from the following detailed description of 
a few preferred embodiments when taken in conjunction with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the following, some embodiments of the present invention will be 
described in conjunction with the attached drawings, and in which 
description and drawings, same reference numerals are given to the similar 
or corresponding elements. 
First, FIGS. 1 and 2 illustrate a first embodiment. In FIG. 1, suspended 
and supported on a body frame F of a motorcycle is an engine E integrally 
formed with an engine body 1 and a transmission case 2. The transmission 
case 2 includes an upper case 2a and a lower case 2b separated into upper 
and lower portions which are integrally connected with each other, and a 
turbo-supercharger S is mounted on the rear surface of the lower case 2b. 
Above the turbo-supercharger S, the forward end of a rear fork 4 is 
pivotally connected at 5 to a center tube 3 of the body frame F for upward 
and downward swinging movement, and a rear wheel W is rotatably supported 
on the rear end of the rear fork in a conventional manner. 
A rear damper 6 suspended at 7 from the body frame F for lateral swinging 
movement has a lower end connected to the rear fork 4 through a link 
mechanism L. The link mechanism L is designed so that free ends of a first 
link 9 pivotally mounted at 11 at one end to the lower end of the body 
frame F and a second link 10 pivotally mounted at 12 at one end to a 
middle portion of the rear fork 4 are rotatably connected with each other 
at 13. The rear damper 6 has the lower end connected at 14 to the middle 
portion of the first link 9. In the link mechanism L, as the rear fork 4 
swings upwardly, that is, as the rear wheel W moves upwardly, the rate of 
increase in flexure amount of the rear damper 6 increases and that flexure 
amount relative to the upward movement amount of the rear wheel W changes 
in a curve-like fashion. 
Next, the structure of the engine E provided with the aforementioned 
turbo-supercharger S will be explained principally referring to FIG. 2. 
The engine body 1 conventionally comprises a cylinder block 16 slidably 
receiving therein a piston 18 and a cylinder head 17 secured thereon. The 
cylinder head 17 and piston 18 constitute a combustion chamber 19 to which 
is open at a suction port 20 and an exhaust port 21 which ports 20 and 21 
are alternately opened and closed by means of a suction valve 22 and an 
exhaust valve 23. 
The suction port 20 and exhaust port 21 have their respective outer ends 
connected to a suction passage 24 and an exhaust passage 25, between which 
passages is provided the turbo-supercharger S. This turbo-supercharger S 
comprises a turbine T provided in the midst of the exhaust passage 25 and 
a compressor C provided in the midst of the suction passage 24. The 
turbine T is constructed such that a turbine disc 27 is accommodated 
within a turbine chamber 26 formed in the midst of the exhaust passage 25. 
The compressor C is constructed such that a compressor disc 29 is 
accommodated within a compressor chamber 28 provided in the midst of the 
suction passage 24. The turbine chamber 26 and the compressor chamber 28 
are integrally connected by means of a bearing holder 30. The turbine disc 
27 and the compressor disc 29 are connected for integral rotation by means 
of a rotary shaft 33 supported within the bearing holder 30 through 
bearings 31 and 32. 
The suction passage 24 has a fuel jet nozzle 37 mounted adjacent to the 
suction port 20, a throttle valve 34 is mounted on the upstream side of 
the jet nozzle, and a prechamber 35 provided on the upstream side of the 
throttle valve 34 and formed by enlarging a sectional area of a part of 
the suction passage 24. 
The exhaust passage 25 has a waste gate 36 which by-passes the turbine T, 
and a flow of exhaust gas from the engine E is partly permitted to be 
escaped into the waste gate 36 so that inlet pressure of the turbine T may 
be adjusted. 
An air cleaner A is connected to the inlet of the suction passage 24, and a 
muffler M is connected to the outlet of the exhaust passage 25. 
The exhaust gas discharged from the combustion chamber 19 to the exhaust 
passage 25 during the exhaust stroke of the engine E principally passes 
through the turbine T to impart exhaust energy to the turbine disc 27. 
This causes the turbine disc 27 to rotate to drive the compressor disc 29 
through the rotary shaft 33, and therefore, air sucked into the suction 
passage 24 from the air cleaner A is pressurized by the compressor C and 
fed to the prechamber 35. The sucked air is adjusted in flow rate by the 
throttle valve 34, thereafter mixed with injected fuel from the jet nozzle 
37 and is fed to the combustion chamber 19 during the suction stroke of 
the engine E. In this manner, a high filling efficiency in air-fuel 
mixture may be obtained in the combustion chamber 19, and upon combustion 
of the mixture, the engine E provides a high output. 
When pressure pulsations are brought forth within the suction passage 24 
resulting from the intermittent operation of the suction valve 22 during 
engine operation, the pressure pulsations are damped by the prechamber 35 
to prevent a surging phenomenon of the compressor C. In the drawings, 
reference character P designates an oil pump provided on the upper case 
2a. 
According to the aforementioned embodiment, the engine E integrally formed 
with the engine body 1 and the transmission case 2 is mounted on the body 
frame F, the transmission case 2 is composed of the upper case 2a and the 
lower case 2b separated into upper and lower portions integrally connected 
with each other, and the supercharger S is mounted on the lower case 2b. 
With this arrangement, even if the supercharger S is heated to a high 
temperature, such heat is promptly transmitted to the lower case 2b in 
which lubricating oil is stored as having a relatively low temperature, 
thus effectively cooling the supercharger S to prevent inconvenience due 
to the overheat thereof. 
Moreover, if the supercharger S is attached to the rear surface of the 
lower case 2b, the fore part of the supercharger is protected by the 
engine so as not to interfere with obstacles from the front, during the 
running of the motorcycle, to be kept from damage. 
FIG. 3 illustrates a second embodiment of the present invention. In this 
embodiment, the supercharger S is mounted on the rear surface of the upper 
case 2b of the transmission case 2, and the rear fork 4 rotatably 
supporting a rear wheel Wr is below the supercharger S and has its forward 
end pivotally supported at 5 on the body frame F for upward and downward 
swinging movement. Thus, the supercharger S is covered at its forward 
portion with the engine body and at its lower portion with the pivoted 
portion of the rear fork 4 so that during the running of the motorcycle, 
an obstacle coming from the front of the supercharger S is blocked by the 
engine body and an obstacle from the lower portion, that is, from the 
running surface blocked by the pivoted portion of the rear fork 4 to 
protect the supercharger S as a whole from any obstacles to prevent it 
from being damaged. The construction and operation of this embodiment 
other than those noted above are substantially similar to the 
aforementioned first embodiment. 
FIGS. 4 and 5 illustrate a third embodiment of the present invention. 
In FIG. 4, the engine E provided with a crank case and transmission case 2 
at the lower end of the engine block 1 substantially stood upright is 
suspended and supported on the body frame F of the motorcycle halfway 
between front and rear wheels Wf, Wr. The transmission case 2 includes an 
upper case 2a and a lower case 2b separated into upper and lower portions 
which are integrally connected with each other, and a turbo-supercharger S 
is mounted on the rear surface of the lower case 2b. 
Above the turbo-supercharger S, the forward end of a rear fork 4 is 
pivotally connected at 5 to a center tube 3 of the body frame F for upward 
and downward swinging movement, and the rear wheel Wr is rotatably 
supported on the rear end of the rear fork in a conventional manner. 
Next, the construction of the engine E with the turbo-supercharger S 
mounted thereon will be described with reference to FIGS. 4 and 5. The 
engine block 1 is formed with four cylinders 16, and corresponding to 
these cylinders 16, the engine block 1 has four independent suction pipes 
15 connected to the rear surface thereof and four independent exhaust 
pipes 25 connected to the forward surface thereof, said independent 
suction pipes 15 each having a throttle valve 34 and a fuel jet nozzle 37 
positioned at a downstream of said valve 34. The four independent suction 
pipes 15 have their respective upstream ends connected to the forward 
surface of a single prechamber 35 disposed above the transmission case 2, 
and the prechamber 35 is connected to an air cleaner A through a common 
suction pipe 24. Also, the four independent exhaust pipes 25 have their 
respective downstream ends connected to a single exhaust manifold box 44 
disposed on one side of the lower portion of the engine E (on the right 
side of the lower portion of the transmission case 2 in FIG. 5). The 
exhaust manifold box 44 is connected to a muffler M disposed on one side 
of the rear wheel Wr through a common exhaust pipe 45, and the 
turbo-supercharger S is provided between the common exhaust pipe 45 and 
the common suction pipe 24. 
The turbo-supercharger S comprises a turbine T disposed in the midst of the 
common exhaust pipe 45 and a compressor C disposed in the midst of the 
common suction pipe 24. The turbine T is designed to accommodate a turbine 
disc 27 within a turbine housing 26 formed in the midst of the common 
exhaust pipe 45 while the compressor C is designed to accommodate a 
compressor disc 29 within a compressor housing 28 formed in the midst of 
the common suction pipe 24. Both the housings 26 and 28 are integrally 
connected through the bearing holder 30, and both the discs 27 and 29 are 
integrally rotatably connected with each other through a rotary shaft 33 
supported on the bearing holder 30. 
In mounting the turbo-supercharger S on the transmission case 2, the 
turbine T and compressor C are disposed in a lateral direction of the 
vehicle, under which condition the bearing holder 30 is secured to the 
rear surface of the lower case 2b of the transmission case 2 so as to be 
deviated laterally from the center of the case 2 toward the exhaust 
manifold box 44, whereby the turbine T is placed in a position close to 
the outer surface of the transmission case 2 near the exhaust manifold box 
44. 
An upstream side half 45a of the common exhaust pipe 45 extending from the 
exhaust manifold box 44 to the turbine housing 26 rises from the upper 
surface of the exhaust manifold box 44 and is connected to the upper 
portion of the outer periphery of the turbine housing 26 from an upward 
oblique direction. A downstream side half 45b of the exhaust pipe 45 
extending from the turbine housing 26 to the muffler M projects from the 
central part of the outer surface of the turbine housing 26 and extends 
substantially along the extended axis of the independent exhaust pipe 25 
and is connected to the muffler M. A web-like style strip 47, which covers 
each of outer surfaces of the exhaust manifold box 44 and a part of the 
common exhaust pipe 45 with a vent gap 43 therebetween, is disposed 
extending from the rear end of the outermost independent exhaust pipe 25 
to the forward end of the muffler M. The style strip 47 is fastened to the 
bracket (not shown) projectingly provided on the exhaust manifold box 44 
and Muffler M. This style strip 47 has its forward end outwardly bended so 
as to facilitate introduction of running air into the vent gap 43. 
During the operation of the engine E, power thereof is removed from an 
output shaft 38 of the transmission system to drive the rear wheel Wr 
through a chain transmission device 39 in a conventional manner. The chain 
transmission device 39 is disposed through the rear wheel Wr opposite the 
exhaust system such as the exhaust manifold box 44, turbine T and muffler 
M. 
During the exhaust stroke of the engine E, exhaust gases discharged from 
the cylinders 16 into the independent exhaust pipes 25 are merged at the 
exhaust manifold box 44, after which the gases pass through the turbine T 
via the common exhaust pipe 45 to impart exhaust energy to the turbine 
disc 27. This causes the turbine disc 27 to rotate to drive the compressor 
disc 29 through the rotary shaft 33 whereby air sucked into the common 
suction pipe 24 from the air cleaner A is compressed by the compressor C 
and fed into the prechamber 35, from which the air is distributed into the 
independent suction pipes 15 and then adjusted in flow rate by the 
throttle valves 34, after which the air is mixed with jet fuel from the 
jet nozzle 37 and during the suction stroke of the engine E, is supplied 
to the cylinders 16. In this manner, the filling efficiency high in 
air-fuel mixture may be obtained in the cylinders 16 and by the combustion 
of the mixture the engine E exhibits a high output. 
When, during the aforesaid operation, the intermittent operation of the 
suction valve causes pressure pulsations within the independent suction 
pipes 15, the pressure pulsations are damped by the prechamber 35 to 
prevent a surging phenomenon of the compressor C. 
In the drawings, reference numeral 46 designates an oil pan integrally 
formed on the bottom of the transmission case 2. 
In the above-mentioned embodiment, the exhaust manifold box 44 in 
communication with the plurality of independent exhaust pipes 25 
associated with the cylinders 16 is disposed on the side of the engine 
block 1 and the common exhaust pipe 45 extended from the exhaust manifold 
box 44 is connected to the outer periphery of the turbine housing 26 of 
the turbo-supercharger S so that the exhaust gases from the cylinders 16 
of the engine E are permitted to continuously act on the turbine T of the 
turbo-supercharger S through the exhaust manifold box 44 to drive the 
turbine in a well stabilized manner, as a consequence of which the filling 
effect of the cylinders 16 may be enhanced effectively. 
Furthermore, the connected portion of the common exhaust pipe 45 extended 
from the exhaust manifold pipe 44 to the outer periphery of the turbine 
housing 26 is located above the housing 26 so that the turbo-supercharger 
S can be arranged at a sufficiently low level position around the lower 
portion of the vehicle without lowering a predetermined minimum height of 
the vehicle from the ground by the common exhaust pipe 45 to prevent the 
center of gravity of the vehicle from being raised by the 
turbo-supercharger S. 
FIGS. 6 and 7 illustrate a fourth embodiment of the present invention. 
In this embodiment, on the substantially same axis as of the 
turbo-supercharger S mounted on the rear surface of the lower case 2b of 
the transmission case 2, the rear fork 4 has a base end pivotally 
supported for upward and downward swinging movement through a pivot 5 on a 
support bracket B fixedly mounted on the lower end of a center tube 3 of 
the body frame F. 
The above-mentioned structure will be further described in detail. The rear 
fork 4 is composed of a pair of fork legs 4a disposed on left and right 
sides of the rear wheel Wr, and a cross member 4b for integrally 
connecting these fork legs 4a immediately before the rear wheel Wr. On the 
other hand, the support bracket B is integrally provided with two pairs of 
support legs B1 which extend downwardly to sandwich the turbo-supercharger 
S between those paired legs, and between the pairs of support legs B1 are 
bridged and fastened the pivots 5 arranged on the substantially same axis 
as of the turbo-supercharger S. The paired pivots 5 pivotally support the 
base ends of both the fork legs 4a for upward and downward swinging 
movement. The rear wheel Wr is rotatably supported between the rear ends 
of both the fork legs 4a in a conventional manner. 
The lower end of the rear damper 6 pivotally supported at 7 for forward and 
rearward swinging motion on the body frame F is connected to the rear fork 
4 through the link mechanism L in a manner similar to the case of the 
aforementioned first embodiment. 
In accordance with this embodiment, the supercharger S for pressurizing 
suction air of the engine E is disposed at the rear of the engine body 1 
and between the pair of fork legs 4a, and therefore, the forward portion 
of the supercharger S is protected by the engine body 1 and both the left 
and right sides thereof are protected by the pair of fork legs 4a so as 
not to interfere with obstacles from the front or side during the running 
of the motorcycle preventing the damage thereof. In addition, even if the 
pivot point 5 at the forward end of the rear fork 4 is brought to a 
position close to the center of gravity of the motorcycle, that is, to the 
engine body 1, the rear fork 4 will not interfere with the supercharger S. 
Moreover, since the supercharger S is disposed between the paired pivots 5 
of both the fork legs 4a of the rear fork 4, the supercharger S is not 
displaced from the position between both the fork legs 4a in any swinging 
position of the rear fork 4 to enhance the protective effect of the rear 
fork 4 with respect to the supercharger S and to avoid interference 
between the supercharger S and the pivots 5. 
The construction and operation of this embodiment other than those noted 
above is substantially similar to the case of the aforementioned third 
embodiment. 
While the case in which a turbo-supercharger S is employed as a 
supercharger has been described in the above-described embodiments, it 
should of course be noted that any type of supercharger may be employed.