U.S. patent application number 09/974873 was filed with the patent office on 2002-04-25 for valve gear of internal combustion engine.
Invention is credited to Nomura, Akifumi, Shimura, Yasuo, Takemoto, Kazuhisa, Tokito, Akira.
Application Number | 20020046719 09/974873 |
Document ID | / |
Family ID | 18793400 |
Filed Date | 2002-04-25 |
United States Patent
Application |
20020046719 |
Kind Code |
A1 |
Nomura, Akifumi ; et
al. |
April 25, 2002 |
Valve gear of internal combustion engine
Abstract
In an internal combustion engine, a pair of suction ports are
formed on left and right sides of the rear of the cylinder head
with respect to the vehicle body. A pair of exhaust ports is formed
on left and right sides on the front side of the cylinder head.
Suction poppet valves and exhaust poppet valves for opening and
closing the suction ports and the exhaust ports are slidably fitted
in guide tubes, respectively. In addition, a valve gear includes a
camshaft and a rocker arm pivotally supported on a rocker arm
shaft. The rocker arm is formed with a bifurcated end, which
crosses an ignition plug on the exhaust poppet valve side. The
suction poppet valves are directly driven to open and close by the
camshaft.
Inventors: |
Nomura, Akifumi; (Saitama,
JP) ; Shimura, Yasuo; (Saitama, JP) ;
Takemoto, Kazuhisa; (Saitama, JP) ; Tokito,
Akira; (Saitama, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
18793400 |
Appl. No.: |
09/974873 |
Filed: |
October 12, 2001 |
Current U.S.
Class: |
123/90.22 ;
123/90.27; 123/90.44 |
Current CPC
Class: |
F01L 2305/00 20200501;
F01L 1/022 20130101; F01L 1/181 20130101; F01L 1/26 20130101; F01L
1/047 20130101 |
Class at
Publication: |
123/90.22 ;
123/90.27; 123/90.44 |
International
Class: |
F01L 001/26; F01L
001/02; F01L 001/18 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 13, 2000 |
JP |
2000-314086 |
Claims
What is claimed is:
1. A valve gear for an internal combustion engine, the engine
including at least two valves on one side thereof and at least one
valve on an opposite side thereof, said valve gear comprising: a
rocker arm, said rocker arm being formed with a bifurcated end for
avoiding an ignition plug of the engine, said bifurcated end being
located on said one side for driving the at least two valves; and a
camshaft, said camshaft for directly driving the at least one valve
on the opposite side of the engine.
2. The valve gear according to claim 1, further comprising: a
camshaft holder, said camshaft being fitted in said camshaft
holder; and a rocker arm shaft, said rocker arm being pivotally
supported on said rocker arm shaft.
3. The valve gear according to claim 1, wherein said bifurcated end
of said rocker arm is contactable with top ends of each of the at
least two valves.
4. The valve gear according to claim 1, wherein said rocker arm
further comprises: a pair of brackets on left and right sides
thereof; and a roller, said roller being rotatably mounted between
said pair of brackets.
5. The valve gear according to claim 4, wherein said camshaft
further comprises left and right cam crests and a central cam crest
located therebetween, said roller being in contact with said
central cam crest for pivoting said rocker arm about said rocker
arm shaft.
6. The valve gear according to claim 5, wherein said camshaft
further comprises a mounting hole, said mounting hole serving as an
oil passage for lubricating said left and right cam crests and said
central cam crest.
7. The valve gear according to claim 2, wherein said bifurcated end
of said rocker arm is contactable with top ends of each of the at
least two valves.
8. The valve gear according to claim 2, wherein said rocker arm
further comprises: a pair of brackets on left and right sides
thereof; and a roller, said roller being rotatably mounted between
said pair of brackets.
9. The valve gear according to claim 8, wherein said camshaft
further comprises left and right cam crests and a central cam crest
located therebetween, said roller being in contact with said
central cam crest for pivoting said rocker arm about said rocker
arm shaft.
10. The valve gear according to claim 9, wherein said camshaft
further comprises a mounting hole, said mounting hole serving as an
oil passage for lubricating said left and right cam crests and said
central cam crest.
11. An internal combustion engine, comprising: at least two exhaust
or suction ports formed on one side thereof and at least one
exhaust or suction port formed on an opposite side thereof; at
least two valves on said one side thereof for opening and closing
said at least two exhaust or suction ports and at least one valve
on said opposite side thereof for opening and closing said at least
one exhaust or suction port; an ignition plug; and a valve gear,
said valve gear comprising: a rocker arm, said rocker arm being
formed with a bifurcated end for avoiding said ignition plug, said
bifurcated end being located on said one side for driving said at
least two valves; and a camshaft, said camshaft for directly
driving said at least one valve on said opposite side.
12. The engine according to claim 11, further comprising: a
camshaft holder, said camshaft being fitted in said camshaft
holder; and a rocker arm shaft, said rocker arm being pivotally
supported on said rocker arm shaft.
13. The engine according to claim 11, wherein said bifurcated end
of said rocker arm is contactable with top ends of each of said at
least two valves.
14. The engine according to claim 11, wherein said rocker arm
further comprises: a pair of brackets on left and right sides
thereof; and a roller, said roller being rotatably mounted between
said pair of brackets.
15. The engine according to claim 14, wherein said camshaft further
comprises left and right cam crests and a central cam crest located
therebetween, said roller being in contact with said central cam
crest for pivoting said rocker arm about said rocker arm shaft.
16. The engine according to claim 15, wherein said camshaft further
comprises a mounting hole, said mounting hole serving as an oil
passage for lubricating said left and right cam crests and said
central cam crest.
17. The engine according to claim 12, wherein said bifurcated end
of said rocker arm is contactable with top ends of each of said at
least two valves.
18. The engine according to claim 12, wherein said rocker arm
further comprises: a pair of brackets on left and right sides
thereof; and a roller, said roller being rotatably mounted between
said pair of brackets.
19. The engine according to claim 18, wherein said camshaft further
comprises left and right cam crests and a central cam crest located
therebetween, said roller being in contact with said central cam
crest for pivoting said rocker arm about said rocker arm shaft.
20. The engine according to claim 19, wherein said camshaft further
comprises a mounting hole, said mounting hole serving as an oil
passage for lubricating said left and right cam crests and said
central cam crest.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The present invention claims the benefit of Japanese Patent
Application No. 2000-314086, filed Oct. 13, 2000, the entirety of
which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a valve gear for an
internal combustion engine, wherein one side of the engine includes
at least two poppet valves. The valve gear includes a rocker arm
having a bifurcated end for driving the at least two poppet
valves.
[0004] 2. Description of Background Art
[0005] A conventional valve gear for a 4-stroke cycle internal
combustion engine is known, wherein one suction or exhaust valve is
driven to open and close through a rocker arm from a camshaft. The
other of the suction or exhaust valve is directly driven to open
and close from the camshaft (Japanese Patent Application Laid-Open
No. 5-133207 Publication).
[0006] In the aforementioned valve gear, three suction poppet
valves and two exhaust poppet valves are disposed per cylinder. A
camshaft is provided with five cam crests per cylinder
corresponding 1:1 to each poppet valve. Top ends of the three
suction poppet valves are placed in contact with three cam crests
of the camshaft to be directly driven to open and close by the cam
crests. The other two exhaust poppet valves are driven to open and
close by two cam crests of the camshaft through respective rocker
arms. Therefore, many cam crests are necessary, two rocker arms are
necessary to avoid the ignition plug, the number of parts
increases, and the construction becomes complex. Accordingly, there
is a disadvantage in terms of productivity and costs.
SUMMARY OF THE INVENTION
[0007] The present invention relates to an improvement in a valve
gear of an internal combustion engine, which overcomes the above
drawbacks. In an internal combustion engine, at least one side of
the engine includes not less than two poppet valves. A valve gear
includes a rocker arm formed with a bifurcated end which crosses an
ignition plug on the valve side having not less than two poppet
valves. The other valve is directly driven to open and close from a
camshaft.
[0008] With the above construction according to the present
invention, with regard to the poppet valves on the side driven to
open and close by the rocker arm, one cam crest is sufficient and
one rocker arm is sufficient. Furthermore, the number of assembling
steps is reduced, the valve gear is decreased in weight, the
construction is simplified, the productivity is enhanced
considerably, and lower cost is achieved.
[0009] Furthermore, since the rocker arm is bifurcated or branched
into the shape of a U to avoid the ignition plug, a nipping angle
between one poppet valve and the other poppet valve is small, a
combustion chamber enabling higher compression and higher
combustion efficiency is easily constructed, and the performance of
the internal combustion engine is materially enhanced.
[0010] Further scope of applicability of the present invention will
become apparent from the detailed description given hereinafter.
However, it should be understood that the detailed description and
specific examples, while indicating preferred embodiments of the
invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the
invention will become apparent to those skilled in the art from
this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present invention will become more fully understood from
the detailed description given hereinbelow and the accompanying
drawings, which are given by way of illustration only, and thus are
not limitative of the present invention, and wherein:
[0012] FIG. 1 is a longitudinal sectional side view of an internal
combustion engine provided with a valve gear according to the
present invention;
[0013] FIG. 2 is a longitudinal sectional front view of the
internal combustion engine shown in FIG. 1;
[0014] FIG. 3 is a top view of the internal combustion engine with
a cylinder head cover removed; and
[0015] FIG. 4 is an enlarged perspective view of main parts of the
valve gear.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] One embodiment of the present invention will now be
described with reference to FIGS. 1 to 4.
[0017] In a water-cooled overhead valve spark ignition type single
cylinder 4-stroke internal combustion engine 1, a crankshaft 6 is
mounted on a motorcycle (not shown) so as to be directed in a width
direction of the motorcycle. A cylinder block 3, a cylinder head 4
and a cylinder head cover 5 are sequentially placed on a crankcase
2 as shown in FIG. 1. The crankcase 2, the cylinder block 3, the
cylinder head 4 and the cylinder head cover 5 are connected
integrally with one another by means of bolts or the like (not
shown) extending therethrough. The crankshaft 6 is pivotally
supported on the crankcase 2. A piston 8 is vertically slidably
fitted in a cylinder bore 7 of the cylinder block 3. The ends of a
connecting rod 11 are pivotally mounted on a piston pin 9 of the
piston 8 and a crank pin 10 of the crankshaft 6, respectively. The
piston 8 is pressed downward by combustion gases ignited
intermittently by an ignition plug 13 (see FIG. 3) in the vicinity
of a top dead center of the piston 8 within a combustion chamber 12
defined by a generally triangular (in section) depressed surface in
the central part of the lower surface of the cylinder head 4, the
cylinder bore 7 and the top surface of the piston 8. The crankshaft
6 is driven in rotation by the pressing force.
[0018] A pair of left and right suction or intake ports 14 are
formed on the rear side (right side in FIG. 1) of the vehicle body
of the cylinder head 4. A pair of left and right exhaust ports 15
are formed on the front side (left side in FIG. 1) of the vehicle
body of the cylinder head 4. A suction poppet valve 16 and an
exhaust poppet valve 17 for opening and closing openings of the
suction port 14 and the exhaust port 15 are slidably fitted in a
guide tube 18 at a small valve nipping angle. Valve springs 20 are
disposed between lifters 37 (on the side of the suction poppet
valve 16) and retainers 19 (on the side of the exhaust poppet valve
17) provided on the top ends of the suction poppet valve 16 and the
exhaust poppet valve 17, and the top surface of the cylinder head
4. The suction poppet valve 16 and the exhaust poppet valve 17 are
always closed by the spring force of the valve springs 20.
[0019] Furthermore, as shown in FIG. 2, a diecast camshaft holder
25 pivotally supports the camshaft 21 through a rolling bearing 39
so that the camshaft 21 is parallel with the crankshaft 6. The
camshaft holder 25 is mounted integrally with the cylinder head 4
by bolts (not shown). The camshaft holder 25 has a plane shape
formed in the general shape of a U. A drive sprocket 26 is fitted
integrally on the left end of the camshaft 21 (See FIG. 1). An
endless cam chain 28 extends between a drive sprocket 27 fitted on
the left side of the crankshaft 6 and the drive sprocket 26. The
number of teeth of the drive sprocket 27 and the drive sprocket 26
is set to 2:1. Accordingly, when the crankshaft 6 is rotated, the
camshaft 21 is rotated at a rotational speed of 1/2.
[0020] One mounting hole of the camshaft holder 25 with respect to
the cylinder head 4 serves as an oil passage. Lubricating oil is
discharged towards the cam crests 22, 23 and 24 of the camshaft 21
from the oil passage formed in the camshaft holder 25.
[0021] As shown in FIG. 1, a rocker arm shaft 29 is positioned
downwardly on a front side of the vehicle body (left side) with
respect to the camshaft 21. The rocker arm shaft 29 is fitted in
the camshaft holder 25. Furthermore, the rocker arm shaft 29 is
partly stopped by bolts to prevent the rocker arm shaft from
slipping out and interfering with bolts (not shown) for mounting
the camshaft holder 25 to the cylinder head 4. A rocker arm 30 is
pivotally supported on the rocker arm shaft 29. A roller 33 is
supported rotatably through a shaft 32 on a pair of left and right
brackets 31 on one end (vehicle body rear side) of the rocker arm
30. The other end of the rocker arm 30 is branched or bifurcated
toward left and right sides to form a U-shape. The bifurcated ends
are respectively placed in contact with the top end of the two
exhaust poppet valves 17 positioned forward of the vehicle body
(left side in FIG. 1). Furthermore, a roller 33 on one end of the
rocker arm 30 is placed in contact with the cam crest 22 in the
central part of the camshaft 21 at a forward position with respect
to the vehicle body.
[0022] As shown in FIG. 1, a bottom part 35 is formed to extend
obliquely, forwardly and upwardly from the lower end of a wall part
34 at the rear of the body of the camshaft holder 25. The bottom
part 35 is formed with a tube part 36 which is capable of loosely
receiving a lifter 37 of the suction poppet valve 16.
[0023] The cam crests 23 and 24 positioned on left and right sides
of the body of the central cam crest 22 are placed in contact with
the top end of two suction poppet valve 16 positioned at the rear
(right side in FIG. 1) of the body through the lifter 37. The cam
crests 22, 23 and 24 of the camshaft 21 are respectively formed in
a fixed shape so as to impart suction and exhaust characteristics
to the suction poppet valve 16 and the exhaust poppet valve 17,
which are adapted to the fixed operating circumstances of the
water-cooled overhead valve spark ignition type single cylinder
4-stroke internal combustion engine 1.
[0024] Furthermore, as shown in FIG. 1, an ignition plug guide tube
38 is formed integrally with the cylinder head 4 positioned in the
approximately central position of the suction poppet valve 16 and
the exhaust poppet valve 17 as viewed from the side. The ignition
plug guide tube 38 is somewhat inclined forwardly. The ignition
plug 13 is detachably mounted on the lower end of the ignition plug
guide tube 38. It is noted that the ignition plug guide tube 38 may
be integrally pressed into the cylinder head 4 or may be integrally
cast into the cylinder head 4.
[0025] In the embodiments shown in FIGS. 1 to 4, as mentioned
above, the suction poppet valve 16 has a large diameter and weight
and is directly driven to be opened and closed by the cam crests 23
and 24 of the camshaft 21. The exhaust poppet valve 17 has a light
weight and is indirectly driven to be opened and closed by the cam
crests 22 through the rocker arm 30. Therefore, the equivalent
weight of the suction system and exhaust system is uniform, and the
valve operating and closing characteristics in the high-speed
rotational region is excellent.
[0026] Furthermore, a single camshaft 21 is used, and the rocker
arm 30 is bifurcated or branched into the shape of a Uto avoid the
wall part 34 in which the ignition plug 13 is enveloped. Therefore,
a nipping angle between the suction poppet valve 16 and the exhaust
poppet valve 17 is set at a small value. As a result, a combustion
chamber that has a high compression ratio, and a high combustion
efficiency is easily constructed to obtain a high performance
water-cooled overhead valve spark ignition type single cylinder
4-stroke internal combustion engine 1.
[0027] Furthermore, one camshaft 21 is sufficient, the single
camshaft holder 25 pivotally supports the camshaft 21 and the
rocker arm shaft 29, and two exhaust poppet valves 17 are driven to
open and close by the single rocker arm 30. Therefore, the number
of parts is materially reduced, the construction is simplified, and
the cost and weight are considerably reduced.
[0028] Furthermore, as shown in FIG. 1, the camshaft holder 25 is
formed with the wall part 34 at the rear thereof. The bottom part
35 is somewhat inclined forwardly and upwardly and is formed at the
lower edge of the bottom part 34. Therefore, the comers of the wall
part 34 and the bottom part 35 serve as a lubricating oil reservoir
for lubricating the contact part between the cam crest 22 and the
lifter 37 sufficiently.
[0029] In addition, the lifter 37 for the suction poppet valve 16
is in contact with the cam crests 23 and 24, and the position of
the roller 33 of the rocker arm 30 for the exhaust poppet valve 17
is in contact with the cam crest 22. Accordingly, the lifter 37 and
the roller 33 are shifted away from each other by approximately
90.degree. about the center axis of the camshaft 21. The opening
timing of the suction poppet valve 16 and the exhaust poppet valve
17 is separated by 180.degree. of a rotational angle of the
crankshaft 6 and by 90.degree. of a rotational angle of the
camshaft 21. In view of this, the cam crests of the cam crest 22
and the cam crests 23 and 24 are at approximately the same phase
angle.
[0030] Furthermore, the direction of the opening reaction of the
suction poppet valve 16 and the direction of the opening reaction
of the exhaust poppet valve 17 are different from each other by
approximately 90.degree.. Therefore, a large valve opening reaction
is not exerted on the camshaft 21. Accordingly, a large rigidity of
the camshaft 21 is not required, the weight is reduced, and higher
speeds are possible.
[0031] Furthermore, since the roller 33 is pivotally supported on
one end of the rocker arm 30, the rotational friction force of the
camshaft 21 is reduced, and the cam crest 22 experiences less
friction.
[0032] Furthermore, since the camshaft 21 is fitted in the camshaft
holder 25 through the rolling bearing 39, which is larger in
diameter than the cam crests 22, 23 and 24 of the camshaft 21, the
camshaft 21 can be mounted from the side of the camshaft holder 25
to considerably enhance the mounting properties.
[0033] The invention being thus described, it will be obvious that
the same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims.
* * * * *