U.S. patent number RE31,724 [Application Number 06/475,835] was granted by the patent office on 1984-11-06 for motorcycle exhaust systems.
This patent grant is currently assigned to Yamaha Hatsudoki Kabushiki Kaisha. Invention is credited to Yoshiharu Isaka.
United States Patent |
RE31,724 |
Isaka |
November 6, 1984 |
Motorcycle exhaust systems
Abstract
A motorcycle has an engine with two banks of cylinders. One bank
is forward of the other, and its exhaust pipe or pipes passes
forwardly, downwardly, and outwardly of the frame, and then
rearwardly beneath the side of the engine to reach a muffler and
tailpipe. The frame includes a pivoted fork-like rear section with
a power transmission. The rear exhaust pipe or pipes extends
rearwardly and downwardly between the arms of the rear section, and
makes connection with the muffler. In another embodiment for
engines with multiple cylinders in each bank, the rear exhaust
pipes cross over one another, and extend downwardly outside of the
arms. They may also be elongated inside the muffler so the lengths
of the forward and rear exhaust pipes are equal. They can connect
with one another so as to share outlets into the muffler.
Inventors: |
Isaka; Yoshiharu (Shizuoka,
JP) |
Assignee: |
Yamaha Hatsudoki Kabushiki
Kaisha (Iwata, JP)
|
Family
ID: |
26339391 |
Appl.
No.: |
06/475,835 |
Filed: |
March 16, 1983 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
110468 |
Jan 8, 1980 |
04327811 |
May 4, 1982 |
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Current U.S.
Class: |
180/219;
123/54.4; 180/225; 180/227; 180/296; 181/238; 60/313 |
Current CPC
Class: |
B62M
7/06 (20130101); F01N 13/08 (20130101); F01N
2590/04 (20130101); F01N 2340/04 (20130101) |
Current International
Class: |
B62M
7/06 (20060101); B62M 7/00 (20060101); F01N
7/08 (20060101); B62M 007/06 (); F01N 007/08 () |
Field of
Search: |
;180/219,225,226,227,229,296,297 ;280/284 ;123/55VF,56AA,56BA
;60/313 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Mitchell; David M.
Assistant Examiner: McGiehan; Donn
Attorney, Agent or Firm: Beutler; Ernest A.
Claims
I claim:
1. In combination with a motorcycle of the type having a front
frame portion mounting a front wheel and an engine, and a rear
frame portion mounting a rear wheel, said portions being pivotally
connected by a horizontally disposed pivot, said rear frame portion
comprising a pair of laterally spaced-apart arms, said engine
comprising two banks of cylinders, one disposed forwardly of the
other, an exhaust system comprising:
a front bank exhaust pipe extending from said front bank,
downwardly and to the side of the said frame and rearwardly;
a rear bank exhaust pipe extending rearwardly and downwardly
between the planes of said arms and between the rear portion of
said engine and the pivot of said arms;
a muffler having a substantial lateral extent mounted to said frame
at an elevation beneath that of said engine, all of said exhaust
pipes discharging into said muffler; and
a tailpipe discharging rearwardly from said muffler.
2. A combination according to claim 1 in which there is a pair of
each of said front and rear pipes, disposed one pipe of each pair
at each side of the centerline of the motorcycle.
3. A combination according to claim 2 in which there is one of said
tailpipes at each side of said rear wheel.
4. In combination with a motorcycle of the type having a front
frame portion mounting a front wheel and an engine, and a rear
frame portion mounting a rear wheel, said portions being pivotally
connected by a horizontally disposed pivot, said rear frame portion
comprising a pair of laterally spaced-apart arms, said engine
comprising two banks of cylinders, one disposed forwardly of the
other, an exhaust system comprising:
a pair of front bank exhaust pipes extending from said front bank,
downwardly and to respective sides of said frame and
rearwardly;
a pair of rear bank exhaust pipes extending rearwardly, crossing
each other laterally, and then extending downwardly outside of the
planes of said arms and forward of the pivot and rearwardly of the
rear portion of said engine;
a muffler having a substantial lateral extent mounted to said frame
at an elevation beneath that of said engine all of said exhaust
pipes discharging into said muffler; and
a tailpipe discharging rearwardly from said muffler.
5. A combination according to claim 4 in which there is one of said
tailpipes at each side of the said rear wheel.
6. A combination according to claim 4 in which all of said exhaust
pipes extend in said muffler to such an extent that all of their
lengths are substantially equal.
7. A combination according to claim 6 in which said front and said
rear exhaust pipes join in pairs, and each pair discharges through
a single opening into said muffler. .Iadd.
8. In combination with a motorcycle of the type having a frame
portion, a front wheel dirigibly supported by said frame, a V-type
engine supported by said frame with its crankshaft axis extending
transversely to said frame, trailing arm means pivotally connected
to said frame for pivotal movement about a transversely extending
pivot axis, and a rear wheel journaled by said trailing arm means,
an exhaust system comprising an exhaust device extending
transversely across said frame for substantially the entire width
of said frame and juxtaposed at a level below that of said engine
and in proximity to said trailing arm pivot axis, a front bank
exhaust pipe extending from the front bank of said engine
downwardly and terminating in said exhaust device, a rear bank
exhaust pipe extending downwardly into said exhaust device, said
rear bank exhaust pipe being positioned ahead of the said rear
wheel and ahead of said pivot axis, and a tailpipe discharging
rearwardly from said exhaust device. .Iaddend. .Iadd.9. A
combination according to claim 8 wherein the engine overlies at
least in part the exhaust device. .Iaddend. .Iadd.10. A combination
according to claim 8 wherein the front bank exhaust pipe enters the
exhaust device at one side thereof and the rear bank exhaust pipe
enters the exhaust device at a central position therein. .Iaddend.
.Iadd.11. A combination according to claim 10 wherein there is a
second front bank exhaust pipe extending from said front bank
rearwardly and entering the other side of said exhaust device and a
second rear bank exhaust pipe extending rearwardly and downwardly
forwardly of the rear wheel and
entering said exhaust device at the center thereof. .Iaddend.
.Iadd.12. A combination according to claim 11 wherein the engine
overlies at least in part the exhaust device. .Iaddend. .Iadd.13. A
combination according to claim 11 wherein the engine drives a drive
shaft that extends to one side of said frame for driving said rear
wheel, one of the rear bank exhaust pipes being offset relative to
the other of said rear bank exhaust pipes away from said drive
shaft for providing clearance therebetween. .Iaddend. .Iadd.14. A
combination according to claim 13 wherein a pair of tailpipes
extend from the opposite sides of the exhaust device and rearwardly
on opposite sides of the rear wheel. .Iaddend.
Description
FIELD OF THE INVENTION
This invention relates to motorcycle exhaust systems.
BACKGROUND OF THE INVENTION
Motorcycle engines with two banks are generally mounted to the
motorcycle frame with their crankshaft axis arranged laterally of
the forward direction, and with one bank of cylinders located
forwardly of the other. In such installations, it is a simple
matter to locate the exhaust pipe or pipes from the forward bank so
it is not readily contacted by the rider. However, placing of the
exhaust pipe or pipes from the rear bank presents difficult
problems. Because of the engine construction, if the rear bank
pipes are directly connected with the front bank pipes at the side
of the engine, there is risk of contact by the leg of the rider. If
they extend directly rearward, the risk exists that their heat may
deteriorate the rear tire.
Furthermore, in V-type engines with four cylinders, there is an
advantage if all of the pipes can be the same length.
It is an object of this invention to locate the rear exhaust pipes
in a location not threatening to the rider or to the rear tire.
It is another object of this invention to enable the four exhaust
pipes to be made the same length.
This invention is carried out with a motorcycle frame which
includes a forward section which carries an engine and a front
wheel, and a fork-like rear section which is pivoted to the forward
section and carries the rear wheel, and a transmission from the
engine to the rear wheel. The engine has two banks, the cylinder or
cylinders of the front bank being forwardly of the cylinder or
cylinders of the rear bank. The foward exhaust pipe or pipes
extends forwardly, downwardly and outwardly, and then rearwardly
beneath the side of the engine. In one embodiment of the invention,
the rear exhaust pipe or pipes extends rearwardly and downwardly
between the engine and the pivot axis of the arms of the rear
section between the planes of the arms. All pipes communicate with
a muffler, and the muffler exhausts to atmosphere.
In another embodiment of the invention, in which a V-type four
cylinder engine is used, the rear pipes cross one another, and
descend outside of the planes of the arms and forward of the pivot
axis of the arms to enter the muffler, and extend in the muffler
for such a length that the lengths of all pipes are equal.
The above and other features of this invention will be fully
understood from the following detailed drawings, in which:
FIG. 1 is a side elevation showing the major portions of a
motorcycle provided with one embodiment of this invention;
FIG. 2 is a perspective view of a portion of FIG. 1;
FIG. 3 is an enlarged plan view showing portions of FIG. 1;
FIG. 4 is a fragmentary side elevation view of a motorcycle with
another embodiment of the invention;
FIG. 5 is a perspective view of a portion of FIG. 4;
FIG. 6 is an enlarged plan view showing portions of FIG. 4;
FIG. 7 is a fragmentary cross-section taken at line 7--7 in FIG. 4;
and
FIG. 8 is a cross-section taken at line 8--8 in FIG. 7.
DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a portion of a motorcycle using the exhaust system
according to the present invention. In this motorcycle, a power
unit 20 equipped with a four cylinder V-type engine 20a is mounted
on a body 10. The output of the power unit 20 is transmitted
through a drive shaft to a rear wheel 11. The V-type four cylinder
engine 20a forming a part of the power unit 20 is composed, as is
apparent especially from FIG. 2, of two front cylinders 21 and 21
and two rear cylinders 22 and 22.
Each of the front cylinders 21 and 21 has its exhaust port
connected to one end of each paired first right and left exhaust
pipes 31 and 31, as is apparent especially from FIG. 3. Those first
exhaust pipes 31 and 31 are constructed to extend from the front of
the body 10 downwardly and then rearwardly below the side of the
same until their other (rear) ends are both connected at respective
sides of the front portion of a muffler 32 which is disposed below
the power unit 20. The muffler forms a noise-silencing chamber.
On the other hand, the sides of the rear portion of the muffler 32
are connected to respective one ends of one pair of second right
and left exhaust pipes 33 and 33 which thus form a part of the
exhaust pipes of the front cylinders 21 and 21. Said second exhaust
pipes 33 and 33 are constructed to extend along the lower sides of
the body 10 at the sides of the rear wheel 11, and their other ends
are opened backward of the body 10. Second exhaust pipes 33 and 33
are sometimes referred to as "tail pipes".
The exhaust ports of the rear cylinders 22 and 22 are connected, as
shown in FIGS. 2 and 3, to the respective one ends of one pair of
third right and left exhaust pipes 34 and 34. These third exhaust
pipes 34 and 34 are constructed to extend downward through the
space which is formed between the rear portion 201 of the power
unit 20 and a pair of rear wheel supporting arms 13 connected
pivotally to the body 10 through a pivot pin 12. The rear wheel is
journaled to these arms, and the arms thereby form a rear frame
portion. On the other hand, the rear portion 321 of the muffler 32
extends below that particular space so that the other ends of the
third exhaust pipes 34 and 34 are connected to the upper side of
the rear portion 321. Thus, the third exhaust pipes 34 and 34 are
connected in a communicating manner to the exhaust pipe assembly of
the front cylinders 21 and 21, which are composed of the first
exhaust pipes 31 and 31 and the second exhaust pipes 33 and 33.
Incidentally, reference numerals 40 and 40 appearing in FIGS. 1 and
2 indicate intake branches connecting the respective cylinders 21,
21, 22 and 22 of the engine 20a to a not-shown carburetor.
In the motorcycle thus constructed, since the exhaust pipes (i.e.,
the third exhaust pipes 34 and 34) of the rear cylinders 22 and 22
of the engine 20a are constructed to extend downwardly through the
space, which is formed between the rear portion 201 of the power
unit 20 and the base 131 of the rear arms 13, and are connected
through the muffler 32 to the exhaust pipes (i.e., the first
exhaust pipes 31 and 31 and the second exhaust pipes 33 and 33) of
the front cylinders 21 and 21, the third exhaust pipes 34 and 34
can be prevented from being exposed to the sides of the body 10. As
a result, there is neither a danger that the legs of the motorcycle
driver may contact with the third exhaust pipes 34 and 34 nor a
fear that the tire of the rear wheel 11 may be burnt.
Although the foregoing embodiment is directed to the construction,
in which the exhaust pipes of the front cylinders 21 and 21, i.e.,
the first exhaust pipes 31 and 31 and the second exhaust pipes 33
and 33 are connected through the muffler 32, and in which the
exhaust pipes (i.e., the third exhaust pipes 34 and 34) of the rear
cylinders 22 and 22 are connected through the muffler 32 to those
exhaust pipes of the front cylinders 21 and 21, the present
invention can be modified to a construction, in which each of the
exhaust pipes of the front cylinders 21 and 21 is composed of a
single pipe and in which the exhaust pipes of the rear cylinders 22
and 22 are guided downward through the space between the rear
portion 201 of the power unit 20 and the base 131 of the rear arms
13 and are then bent sideway so that they are connected directly to
the inner sides of the exhaust pipes of the front cylinders 21 and
21. Moreover, the present invention can be applied to a variety of
motorcycles of the type, in which the power unit is equipped with
an engine having at least two cylinders arranged in a longitudinal
direction of the motorcycle body.
As has been described hereinbefore, this embodiment of the present
invention has its constructional characteristics in that the
exhaust pipe having its one end connected to the rear cylinder of
said engine is arranged to extend downward through the space, which
is formed between the rear portion of said power unit and the base
of the rear wheel supporting arms, and to have its other end
connected to the exhaust pipe which in turn has its one and
connected to the front cylinder of said engine and which is
disposed below the side of said body. As a result, the arrangement
of the exhaust pipe of the aforementioned rear cylinder can be made
such that there is neither danger that the exhaust pipe may contact
with the leg of the driver nor a fear that the rear wheel tire may
be burnt.
FIGS. 4, 5 and 6 show a motorcycle 300 with a forward frame portion
301 for supporting a front wheel (not shown), and a rear frame
portion 302 as in FIGS. 1-3. A four cylinder V-type engine 20a is
shown, together with exhaust tailpipes 33, 33, front bank exhaust
pipes 303, 304 and rear bank exhaust pipes 305, 306 from front bank
cylinders 21 and rear bank cylinders 22.
The rear frame portion is joined to the front frame portion by
pivot 12, as in FIG. 3. In fact, except for the configurations of
the exhaust pipes 303, 304, 305 and 306, the motorcycles are
indentical.
In this embodiment, an objective is to make all of the exhaust
pipes 303-306 of equal length. Obviously the arrangements of FIGS.
1-3 cannot provide this advantage.
As best seen in FIGS. 5 and 6, pipes 305 and 306 extend rearwardly,
then have sidewise portions 307, 308 that cross over one another,
past and over arms 13, and downward into the muffler. Then, as best
shown in FIGS. 7 and 8, they have portions 309, 310 inside the
muffler, which join to the front pipes at intersections 314, 315
inside the muffler, and they discharge into the muffler through
common openings 312, 313. The lengths to the intersections 314, 315
are all equal.
This invention is not to be limited by the embodiments shown in the
drawings and described in the description, which are given by way
of example and not of limitation, but only in accordance with the
scope of the appended claims.
* * * * *