U.S. patent application number 09/745992 was filed with the patent office on 2001-08-23 for valve operating system in internal combustion engine.
Invention is credited to Iwamoto, Junichi, Nakamura, Hiromu, Tanaka, Chikara, Yamada, Noriyuki.
Application Number | 20010015188 09/745992 |
Document ID | / |
Family ID | 18497684 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010015188 |
Kind Code |
A1 |
Tanaka, Chikara ; et
al. |
August 23, 2001 |
Valve operating system in internal combustion engine
Abstract
In a valve operating system in an internal combustion engine, a
rocker arm has a plurality of valve abutments provided thereon and
capable of being individually put into abutment against upper ends
of a plurality of engine valves cam abutments, and also has cam
abutments provided thereon to come into contact with a valve
operating cam. Wall-removed portions are formed in the rocker arm
at locations corresponding to the cam abutments and open at
opposite sides of the rocker arm. Thus, it is possible to provide a
reduction in weight of the rocker arm.
Inventors: |
Tanaka, Chikara; (Wako-shi,
JP) ; Nakamura, Hiromu; (Wako-shi, JP) ;
Yamada, Noriyuki; (Wako-shi, JP) ; Iwamoto,
Junichi; (Haga-gun, JP) |
Correspondence
Address: |
ARMSTRONG,WESTERMAN, HATTORI,
MCLELAND & NAUGHTON, LLP
1725 K STREET, NW, SUITE 1000
WASHINGTON
DC
20006
US
|
Family ID: |
18497684 |
Appl. No.: |
09/745992 |
Filed: |
December 26, 2000 |
Current U.S.
Class: |
123/90.44 ;
123/90.27; 123/90.39 |
Current CPC
Class: |
Y10T 74/20882 20150115;
F01L 1/26 20130101; F01L 1/18 20130101 |
Class at
Publication: |
123/90.44 ;
123/90.27; 123/90.39 |
International
Class: |
F01L 001/02; F01L
001/18 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 1999 |
JP |
11-370835 |
Claims
What is claimed is:
1. A valve operating system in an internal combustion engine
comprising a swinging support section provided at a base end of a
rocker arm and swingably carried on an arm support portion provided
in a cylinder head, a plurality of valve abutments provided at a
tip end of said rocker arm and capable of being individually put
into abutment against respective upper ends of a plurality of
engine valves, and cam abutments provided on said rocker arm in an
intermediate portion between said swinging support section and said
respective valve abutments to come into contact with a valve
operating cam, wherein said rocker arm has wall-removed portions
formed therein at locations corresponding to said cam abutments,
said wall-removed portions opening at opposite sides of said rocker
arm.
2. A valve operating system in an internal combustion engine
according to claim 1, wherein said rocker arm includes an opening
in which a roller which is said cam abutment is accommodated, and a
pair of coaxially disposed shaft insertion bores with its inner
ends thereof opening into said opening and with its outer ends
thereof opening outwards and sideways of said rocker arm for
fitting and fixing of opposite ends of a roller shaft for rotatably
supporting said roller, said roller shaft being fitted and fixed in
inner ends of said shaft insertion bores, with portions of said
shaft insertion bores axially outer than the opposite ends of said
roller shaft being left as the hollow wall-removed portions.
3. A valve operating system in an internal combustion engine
according to claim 2, wherein each of said shaft insertion bores
comprises a first insertion bore portion adjacent to said opening,
a second insertion bore portion connected at an inner end thereof
to an outer end of said first insertion bore portion, and a step
formed between the outer end of said first insertion bore portion
and the inner end of said second insertion bore portion and facing
on a side opposite to said opening, and the opposite ends of said
roller shaft fitted respectively in said first insertion bore
portions of said shaft insertion bores are disposed in caulked
engagement with said step.
4. A valve operating system in an internal combustion engine
according to claim 2, wherein said rocker arm has a pair of support
walls provided thereon to extend from said swinging support section
in such a manner that said valve abutments individually
corresponding to the pair of engine valves are provided at tip ends
of the support walls, and the opposite ends of said roller shaft
formed at a length shorter than a distance between both of said
support walls are fitted and fixed in said shaft insertion bores
such that said wall-removed portions can be formed in said rocker
arm at locations axially outer than the opposite ends of said
roller shaft.
5. A valve operating system in an internal combustion engine
according to claim 4, wherein said rocker arm has a pair of
cylindrical shaft support portions provided thereon over said first
and second support walls and said opening to define said shaft
insertion bores, respectively.
6. A valve operating system in an internal combustion engine
according to any of claims 2 to 5, wherein each of portions of said
shaft insertion bores left as the wall-removed portions is formed
into such a shape that it is enlarged gradually as approaching the
side of said rocker arm.
7. A valve operating system in an internal combustion engine
according to claim 1, wherein said rocker arm has a pair of support
walls provided thereon to extend from said swinging support section
in such a manner that said valve abutments are provided at tip ends
of said support walls; a cam slipper which is said cam abutment is
provided on said rocker arm between both of said support walls; and
said wall-removed portions are formed within a pair of connecting
tubes which interconnect said support walls and said cam slipper.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a valve operating system in
an internal combustion engine comprising a swinging support section
provided at a base end of a rocker arm and swingably carried on an
arm support portion provided in a cylinder head, a plurality of
valve abutments provided at a tip end of the rocker arm and capable
of being individually put into abutment against upper ends of a
plurality of engine valves, and cam abutments provided on the
rocker arm in an intermediate portion thereof between the swinging
support section and the valve abutments to come into contact with a
valve operating cam.
[0003] 2. Description of the Related Art
[0004] Such a valve operating system is conventionally known, for
example, from Japanese Patent Application Laid-open
No.6-185322.
[0005] In a valve operating system which is designed such that a
plurality of engine valves are driven by a single rocker arm, the
width of the rocker arm cannot help increasing, thereby bringing
about increases in size and weight of the rocker arm. In the
mentioned known system, however, a structure for reducing the
weight of the rocker arm is not disclosed.
SUMMARY OF THE INVENTION
[0006] Accordingly, it is an object of the present invention to
reduce the weight of the rocker arm for driving the plurality of
engine valves.
[0007] To achieve the above object, according to a first aspect and
feature of the present invention, there is provided a valve
operating system in an internal combustion engine comprising a
swinging support section provided at a base end of a rocker arm and
swingably carried on an arm support portion provided in a cylinder
head, a plurality of valve abutments provided at a tip end of the
rocker arm and capable of being individually put into abutment
against respective upper ends of a plurality of engine valves, and
cam abutments provided on the rocker arm in an intermediate portion
between the swinging support section and the respective valve
abutments to come into contact with a valve operating cam, wherein
the rocker arm has wall-removed portions formed therein at
locations corresponding to the cam abutments, the wall-removed
portions opening at opposite sides of the rocker arm.
[0008] With such arrangement of the first feature, the weight of
the entire rocker arm can be reduced by the wall-reduced portions
provided at the locations corresponding to the cam abutments.
[0009] According to a second aspect and feature of the present
invention, in addition to the first feature, the rocker arm
includes an opening in which a roller which is the cam abutment is
accommodated, and a pair of coaxially disposed shaft insertion
bores with its inner ends thereof opening into the opening and with
its outer ends opening outwards and sideways of the rocker arm for
fitting and fixing of opposite ends of a roller shaft for rotatably
supporting the roller, the roller shaft being fitted and fixed in
inner ends of the shaft insertion bores, with portions of the shaft
insertion bores axially outer than the opposite ends of the roller
shaft being left as the hollow wall-removed portions.
[0010] With the arrangement of the second feature, the portions of
the shaft insertion bores axially outer than the opposite ends of
the roller shaft are left as the hollow wall-removed portions,
whereby the weight of the entire rocker arm can be reduced and
moreover, the length of the roller shaft can be reduced. Thus, it
is possible to facilitate the assembling of the roller shaft to the
rocker arm and to make the roller shaft difficult to deform,
thereby ensuring the proper swinging operation of the rocker
arm.
[0011] According to a third aspect and feature of the present
invention, in addition to the second feature, each of the shaft
insertion bores comprises a first insertion bore portion adjacent
to the opening, a second insertion bore portion connected at an
inner end thereof to an outer end of the first insertion bore
portion, and a step formed between the outer end of the first
insertion bore portion and the inner end of the second insertion
bore portion and facing on a side opposite to the opening, and the
opposite ends of the roller shaft fitted respectively in the first
insertion bore portions of the shaft insertion bores are disposed
in caulked engagement with the step.
[0012] With such arrangement of the third feature, the size of each
of the wall-removed portions of the shaft insertion bores left as
the hollow form can be increased, thereby further reducing the
weight of the entire rocker arm. Moreover, the roller shaft can be
fixed to the rocker arm by caulking and hence, it is possible to
further facilitate the assembling of the roller shaft to the rocker
arm.
[0013] According to a fourth aspect and feature of the present
invention, in addition to the second feature, the rocker arm has a
pair of support walls provided thereon to extend from the swinging
support section in such a manner that the valve abutments
individually corresponding to the pair of engine valves are
provided at tip ends of the support walls, and the opposite ends of
the roller shaft formed at a length shorter than a distance between
both of the support walls are fitted and fixed in the shaft
insertion bores such that the wall-removed portions can be formed
in the rocker arm at locations axially outer than the opposite ends
of the roller shaft.
[0014] With the fourth feature, loads from the engine valves are
applied to the support walls, but the roller can be supported by
the roller shaft disposed at a location kept away from portions to
which the loads are applied and hence, the rigidity of supporting
of the roller can be enhanced.
[0015] According to a fifth aspect and feature of the present
invention, in addition to the fourth feature, the rocker arm has a
pair of cylindrical shaft support portions provided thereon over
the first and second support walls and the opening to define the
shaft insertion bores, respectively. With such arrangement of the
fifth feature, the pair of the cylindrical shift support portions
interconnected through the roller shaft are connected to the
support walls and hence, the rigidity of support walls and the
rigidity of supporting of the roller can be enhanced.
[0016] According to the sixth aspect and feature of the present
invention, in addition to any of the second to fourth features,
each of portions of the shaft insertion bores left as the
wall-removed portions is formed into such a shape that it is
enlarged gradually as approaching the side of the rocker arm.
[0017] With such arrangement of the sixth feature, it is possible
to facilitate an operation for fitting and fixing the roller shaft
in the inner ends of the shaft insertion bores, leading to an
enhanced assemblability.
[0018] According to the seventh aspect and feature of the present
invention, in addition to the first feature, the rocker arm has a
pair of support walls provided thereon to extend from the swinging
support section in such a manner that the valve abutments are
provided at tip ends of the support walls; a cam slipper which is
the cam abutment is provided on the rocker arm between both of the
support walls; and the wall-removed portions are formed within a
pair of connecting tubes which interconnect the support walls and
the cam slipper.
[0019] With the arrangement of the seventh feature, the cam slipper
is continuously formed with the pair of support walls through the
pair of the connecting tubes. Therefore, it is possible to reduce
the weight of the rocker arm, while avoiding reductions in rigidity
of the support walls and the rigidity of supporting of the cam
slipper.
[0020] The above and other objects, features and advantages of the
invention will become apparent from the following description of
the preferred embodiments taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIGS. 1 to 7 show a first embodiment of the present
invention.
[0022] FIG. 1 is a partially vertical sectional view of an internal
combustion engine;
[0023] FIG. 2 is a plan view taken in a direction of an arrow 2 in
FIG. 1;
[0024] FIG. 3 is a plan view of an exhaust-side rocker arm;
[0025] FIG. 4 is a sectional view taken along a line 4-4 in FIG.
2;
[0026] FIG. 5 is a sectional view taken along a line 5-5 in FIG.
2;
[0027] FIG. 6 is a sectional view taken along a line 6-6 in FIG.
5;
[0028] FIG. 7 is a sectional view taken along a line 7-7 in FIG.
6;
[0029] FIG. 8 is a partially vertical sectional view of an internal
combustion engine, similar to FIG. 1, but according to a second
embodiment of the present invention;
[0030] FIG. 9 is a plan view of an exhaust-side rocker arm, similar
to FIG. 3, but according to the second embodiment;
[0031] FIG. 10 is a sectional view taken along a line 10-10 in FIG.
9;
[0032] FIG. 11 is a sectional view similar to FIG. 10, but
according to a third embodiment; and
[0033] FIG. 12 is a plan view of an exhaust-side rocker arm,
similar to FIG. 3, but according to a fourth embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] A first embodiment of the present invention will be
described with reference to FIGS. 1 to 7. Referring first to FIGS.
1 and 2, a multi-cylinder internal combustion engine includes a
cylinder block 15, and a cylinder head 16 coupled to an upper
portion of the cylinder block 15 through a gasket 17. A piston 19
is slidably received in each of cylinders 18 provided in the
cylinder block 15. A combustion chamber 20 is defined in each of
the cylinders by the cylinder block 15, the cylinder head 16 and
each of the pistons 19.
[0035] Provided in the cylinder head 16 for every cylinder are a
pair of intake valve bores 21 facing one side of a ceiling surface
of the combustion chamber 20, an intake port 22 which opens into
one side (a right side in FIG. 1) of the cylinder head 16 and
connected commonly to the intake valve bores 21, a pair of exhaust
valve bores 23 facing the other side of the ceiling surface of the
combustion chamber 20, and an exhaust port 24 which opens into the
other side (a left side in FIG. 1) of the cylinder head 16.
[0036] Stems 25 of intake valves VI, VI capable of opening and
closing the intake valve bores 21 are slidably received in guide
tubes 26 mounted in the cylinder head 16, and valve springs 28 for
biasing the intake valves VI, VI upwards, i.e., in valve closing
directions are mounted between the cylinder head 16 and retainers
27, 27 mounted at upper ends of the stems 25 protruding upwards
from the guide tubes 26. Stems 29 of exhaust valves VE, VE as
engine valves capable of opening and closing the exhaust valve
bores 23 are slidably received in guide tubes 30 mounted in the
cylinder head 16, and valve springs 32 for biasing the exhaust
valves VE, VE upwards, i.e., in valve closing directions are
mounted between the cylinder head 16 and retainers 31, 31 mounted
at upper ends of the stems 29 protruding upwards from the guide
tubes 30.
[0037] The intake valves VI, VI are opened and closed by an
intake-side valve operating device 33, and the exhaust valves VE,
VE are opened and closed by an exhaust-side valve operating device
34. A plug insertion tube 36 is disposed to extend vertically, so
that a spark plug 35 mounted in the cylinder head 16 to face a
central portion of the combustion chamber 20 is inserted into the
plug insertion tube 36. The plug insertion tube 36 is attached at
its lower end to the cylinder head 16.
[0038] The intake-side valve operating device 33 includes a pair of
intake-side rocker arms 37 and 38 individually corresponding to the
pair of intake valves VI, VI, an intake-side rocker shaft 39 on
which the intake-side rocker arms 37 and 38 are swingably carried,
and an intake-side camshaft 40 which is rotatable about an axis
parallel to the rocker shaft 39.
[0039] The intake-side rocker shaft 39 is fixedly supported by
holder walls 41 provided on the cylinder head 16 between the
cylinders, and intake-side rocker arms 37 and 38 are swingably
carried at their base ends on the intake-side rocker shaft 39.
Tappet screws 42A and 42B are threadedly fitted at tip ends of the
intake-side rocker arms 37 and 38 to abut against upper ends of the
corresponding intake valves VI, VI, i.e., upper ends of the stems
25, so that their advanced and retracted positions can be adjusted.
The intake-side camshaft 40 is operatively connected at a reduction
ratio of 1/2 to a crankshaft (not shown) and rotatably carried by
the holder walls 41 and cam holders 43 fastened to upper ends of
the holder walls 41.
[0040] The intake-side camshaft 40 is provided with a high-speed
valve operating cam 44 corresponding to one of the intake-side
rocker arms 37, and a low-speed valve operating cam 45
corresponding to the other intake-side rocker arm 38. A roller 46
supported on the one intake-side rocker arm 37 is in rolling
contact with the high-speed valve operating cam 44, and a roller
(not shown) supported on the other intake-side rocker arm 38 is in
rolling contact with the low-speed valve operating cam 45.
[0041] Moreover, an interlocking-motion switchover means (not
shown) is provided between the intake-side rocker arms 37 and 38
and capable of switching over the interlocking motion of the rocker
arms 37 and 38 and the releasing of the interlocking motion one
from another, so that the rocker arms 37 and 38 are swung
independently from each other during operation of the engine at a
low speed and the rocker arms 37 and 38 are swung operatively from
each other in an interlocking motion during operation of the engine
at a high speed. Therefore, during operation of the engine at the
low speed, the one intake-side rocker arm 37 is swung to open and
close one of the intake valves VI in an operational characteristic
corresponding to a cam profile of the high-speed valve operating
cam 44, while the other intake-side rocker arm 38 is swung to open
and close the other intake valves VI in an operational
characteristic corresponding to a cam profile of the low-speed
valve operating cam 45. During operation of the engine at the high
speed, both of the intake-side rocker arms 37 and 38 are swung to
open and close the intake valves VI, VI in the operational
characteristic corresponding to the high-speed valve operating cam
44.
[0042] The exhaust-side valve operating device 34 includes a single
exhaust-side rocker arm 50A which is common to the pair of exhaust
valves VE and VE, an exhaust-side rocker shaft 51 serving as an arm
support portion on which the exhaust-side rocker arm 50A is
swingably carried and an exhaust-side cam shaft 52 which is
rotatable about an axis parallel to the rocker shaft 51.
[0043] The exhaust-side rocker shaft 51 has an axis parallel to the
intake-side rocker shaft 39 and is fixedly supported by the holder
wall 41, as is the intake-side rocker shaft 39. The exhaust-side
rocker arm 50A is swingably carried at its base end on the
exhaust-side rocker shaft 51, and first and second tappet screws
53A and 53B as valve abutments are threadedly fitted at tip ends of
the exhaust-side rocker arm 50A to abut against upper ends of the
corresponding exhaust valves VE, VE, i.e., upper ends of the stems
29, so that their advanced and retracted positions can be adjusted.
The exhaust-side camshaft 52 is operatively connected at a
reduction ratio of 1/2 to the crankshaft (not shown) rotatably
carried by the holder walls 41 and cam holders 54 fastened to the
upper ends of the holder walls 41.
[0044] A valve operating cam 55 is provided on the exhaust-side
camshaft 52 in correspondence to the exhaust-side rocker arm 50A,
and a roller 56 as a cam abutment axially supported on the
exhaust-side rocker arm 50A is in rolling contact with the valve
operating cam 55.
[0045] Referring to FIG. 3, the exhaust-side rocker arm 50A is
provided at its base end with a cylindrical swinging support
section 57 through which the exhaust-side rocker shaft 51 is
inserted and which is swingably carried on the rocker shaft 51. The
exhaust-side rocker arm 50A is further provided with first and
second support walls 58 and 59, and a connection wall 60 connecting
tip ends of the first and second support walls 58 and 59 to each
other.
[0046] First and second boss portions 58a and 59a each having a
circular outer peripheral surface are integrally formed on
respective tip ends of the first and second support walls 58 and
59, so that they are arranged parallel to the axis of the
exhaust-side rocker shaft 51. It is preferable that the first and
second support walls 58 and 59 are provided to extend from opposite
ends of the swinging support section 57 along a plane perpendicular
to the axis of the exhaust-side rocker shaft 51, and that the first
and second boss portions 58a and 59a and the swinging support
section 57 are interconnected by the first and second support walls
58 and 59 perpendicular to the axis of the exhaust-side rocker
shaft 51.
[0047] The boss portions 58a and 59a are provided with threaded
bores 61A and 61B into which the first and second tappet screws 53A
and 53B are threadedly engaged. The roller 56 is supported on the
exhaust-side rocker arm 50A in a location intermediate between the
swinging support section 57 and the tappet screws 53A and 53B,
i.e., at a location displaced from the axis of the exhaust-side
rocker shaft 51.
[0048] A first straight line L1 extends through (1) the center of
one 53A of the first and second tappet screws 53A and 53B which is
disposed on axially one side (a lower end side in FIG. 3) of the
exhaust-side rocker shaft 51, i.e., the center of the threaded bore
61A in the first boss portion 58a, and (2) an area of contact (an
area indicated by intersecting oblique lines in FIG. 3) of the
valve operating cam 55 with the roller 56. A second straight line
L2 extends through (1) the center of the other 53B of the first and
second tappet screws 53A and 53B which is disposed on the axially
other side (an upper end side in FIG. 3) of the exhaust-side rocker
shaft 51, i.e., the center of the threaded bore 61B in the second
boss portion 59a, and (2) an area of contact of the valve operating
cam 55 with the roller 56. The first and second straight lines L1
and L2 and the axis C of the exhaust-side rocker shaft 51 intersect
together at intersection points P1 and P2 as viewed in the plane of
the exhaust-side rocker arm 50A. The intersection points P1 and P2
are disposed at locations inside axially opposite sides of the
swinging support section 57. In other words, the swinging support
section 57 is formed to have such a length that their opposite ends
faces are disposed outside the first and second intersection points
P1 and P2. It is desirable that the first and second straight lines
L1 and L2 pass through the center of the area of contact of the
valve operating cam 55 with the roller 56.
[0049] Moreover, the swinging support section 57 is formed at a
length longer than a distance between the centers of the first and
second tappet screws 53A and 53B, and third and fourth straight
lines L3 and L4 passing through the centers of the first and second
tappet screws 53A and 53B and intersecting the axis C of the
exhaust-side rocker shaft 51 at right angles are disposed inside
the axially opposite ends of the swinging support section 57.
[0050] Referring also to FIGS. 4 to 6, a rectangular opening 62 for
accommodation of the roller 56 is provided in the exhaust-side
rocker arm 50A between the first and second support walls 58 and
59. A roller shaft 63, which has a length shorter than a distance
between the first and second support walls 58 and 59 and has an
axis parallel to the exhaust-side rocker shaft 51, extends across
the opening 62 and is fixed to the exhaust rocker arm 50A, and the
roller 56 is rotatably carried on the roller shaft 63 with a needle
bearing 64 interposed therebetween.
[0051] A pair of shaft support portions 65, 65 which are formed
into a cylindrical shape are provided over the first and second
support walls 58 and 59 and the opening 62 respectively to extend
in parallel to the exhaust-side rocker shaft 51. Shaft insertion
bores 66, 66 are coaxially provided in the shaft support portions
65, 65, respectively, with its inner end opening into the opening
62 and with its outer end opening outwards and sideways of the
exhaust-side rocker arm 50A, i.e., outwards and sideways of the
first and second support walls 58, 59.
[0052] The shaft insertion bore 66 comprises a first insertion bore
portion 66a adjacent the opening 62, a second insertion bore
portion 66b connected at its inner end to an outer end of the first
insertion bore portion 66a, and a step 66c formed between the outer
end of the first insertion bore portion 66a and the inner end of
the second insertion bore portion 66b and facing on a side opposite
from the opening 62. It is desirable that the first and second
insertion bore portions 66a and 66b are formed as coaxial circular
bores, so that the annular step 66c is formed between both of the
insertion bore portions 66a and 66b. If the first and second
insertion bore portions 66a and 66b are formed as described above,
it is easy to carry out a boring for forming them. Alternatively,
the first insertion bore portion 66a may be circular in cross
section, while the second insertion bore portion 66b may be
non-circular in cross section. Namely, the second insertion bore
portion 66b may be of any cross-sectional shape, if the step 66c is
formed between the first and second insertion bore portions 66a and
66b to face on the side opposite from the opening 62. Moreover, it
is desirable that the second insertion bore portion 66b is of such
a shape that it is enlarged gradually as approaching a side of the
exhaust-side rocker arm 50A. In the present embodiment, the second
insertion bore portion 66b is defined as a tapered bore with its
end adjacent to the exhaust-side rocker arm 50A being of a larger
diameter.
[0053] The roller shaft 63 is fitted in and fixed to inner ends of
the shaft insertion bores 66, 66 with each of portions of the shaft
insertion bores 66 axially outer than opposite ends of the roller
shaft 63 being left in a hollow form. For such fitting and fixing,
outer peripheral edges of the opposite ends of the roller shaft 63
fitted in the first insertion bore portions 66a, 66a are brought
into caulked engagement with the steps 66c, 66c. Thus, wall-removed
portions 67, 67 are formed in the exhaust-side rocker arm 50A at
locations axially outside the opposite ends of the roller shaft 63
in a state in which the roller shaft 63 has been fixed to the
exhaust-side rocker arm 50A.
[0054] The cylindrical swinging support section 57 comprises a
thinner cylindrical portion 57a surrounding the exhaust-side rocker
shaft 51, and thicker cylindrical portions 57b, 57b thicker than
the thinner cylindrical portion 57a and continuously and integrally
formed at opposite ends of the thinner cylindrical portion 57a,
respectively. The first and second support walls 58 and 59 are
formed continuously with the thicker cylindrical portions 57b,
57b.
[0055] Referring also to FIG. 7, grooves 68, 68 capable of
accumulation of an oil between the grooves and the outer surface of
the exhaust-side rocker shaft 51 are provided in an arcuate shape
in lower portions of inner surfaces of the thicker cylindrical
portions 57b, 57b corresponding to connections of the first and
second support walls 58 and 59, respectively.
[0056] Recesses 69 and 70 capable of supplying the oil to the
roller 56 within the opening 62 are defined in portions of the
upper surface of the exhaust-side rocker arm 50A, which are
surrounded by the first and second support walls 58 and 59, the
connection wall 60 and the swinging support section 57.
[0057] One of the recesses 69 is defined in the exhaust-side rocker
arm 50A between the shaft support portions 65, 65 and the swinging
support section 57, and the other recess 70 is defined in the
exhaust-side rocker arm 50A between the shaft support portions 65,
65 and the connection wall 60.
[0058] An axially central portion of the swinging support section
57, i.e., an axially intermediate portion of the thinner
cylindrical portion 57a is disposed at a location corresponding to
the plug insertion tube 36. Notches 71 and 72 connected to each
other are provided in the swinging support section 57 and the
exhaust-side rocker shaft 51 at the location corresponding to the
plug insertion tube 36 and formed into such an arcuate shape that
they are recessed on a side opposite to the plug insertion tube 36,
and a portion of the plug insertion tube 36 is accommodated in the
notch 71. Moreover, the notches 71 and 72 are provided in the
swinging support section 57 and the exhaust-side rocker shaft 51
between connections of the first and second support walls 58 and 59
to the swinging support section 57.
[0059] An oil injection bore 73 is provided, with its outer end
opening into the opening 62, in the swinging support section 57 on
a side opposite to the notch 71 with respect to the axis C of the
exhaust-side rocker shaft 51. An oil supply passage 74 is provided
in the exhaust-side rocker shaft 51 to extend along the axis C of
the exhaust-side rocker shaft 51, and an oil supply bore 75 is also
provided in the exhaust-side rocker shaft 51 to communicate with
the oil supply passage 74, and is capable of communicating at its
outer end with an inner end of the oil injection bore 73. The oil
supply passage 74 is connected to an oil supply source which is not
shown. Therefore, it is possible to supply the oil through the oil
supply passage 74 within the exhaust-side rocker shaft 51 via the
oil supply bore 75 and the oil injection bore 73 to the roller 56
to lubricate the roller 56. The communication between the oil
supply bore 75 and the oil injection bore 73 may be cut off
depending on a swung state of the exhaust-side rocker arm 50A, bat
in the cut-off state, the oil supplied from the oil supply bore 75
is used for the lubrication between the swinging support section 57
and the exhaust-side rocker shaft 51, and the oil is also supplied
to the grooves 68, 68 in the inner surface of the swinging support
section 57.
[0060] The connection wall 60 interconnecting the tip ends of the
first and second support walls 58 and 59, i.e., the first and
second boss portions 58a and 59a comprises first and second wall
portions 60a and 60b intersecting each other at right angles in a
plane perpendicular to the axis C of the exhaust-side rocker shaft
51, i.e., the swinging axis of the exhaust-side rocker arm 50A. The
wall portions 60a and 60b intersect each other to form, for
example, a substantially L-shape in such plane.
[0061] Moreover, the second wall portion 60b is formed to extend in
parallel to the axis of the exhaust-side rocker shaft 51 with its
outer surface connected flush to outer surfaces of the first and
second boss portions 58a and 59a at their tip ends. One side of the
opening 62 is defined by a portion of an inner surface of the first
wall portion 60a.
[0062] The operation of the first embodiment will be described
below. In the exhaust-side rocker arm 50A, the intersection points
P1 and P2, at which (a) the first straight line L1 extending
through (1) the center of one 53A of the first and second tappet
screws 53A and 53B arranged in parallel to the axis C of the
exhaust-side rocker shaft 51, which is disposed on the axially one
side of the exhaust-side rocker shaft 51 and (2) the area of
contact of the valve operating cam 55 with the roller 56,
preferably the center of such area, (b) the second straight line L2
extending through (1) the center of the other 53B of the first and
second tappet screws 53A and 53B which is disposed on the axially
other side (an upper end side in FIG. 3) of the exhaust-side rocker
shaft 51 and (2) the area of contact of the valve operating cam 55
with the roller 56, preferably the center of such area, and (c) the
axis C of the exhaust-side rocker shaft 51 intersect together as
viewed in the plane of the exhaust-side rocker arm 50A, are
disposed inside the axially opposite ends of the cylindrical
swinging support section 57 swingably carried on the exhaust-side
rocker shaft 51.
[0063] Therefore, even if a difference is produced between the
tappet clearances in the first and second tappet screws 53A and
53B, and a large load is produced on the first or second straight
line L1, L2 to act so as to incline the exhaust-side rocker arm
50A, the exhaust-side rocker arm 50A can be supported stably,
because the swinging support section 57 is supported on the
exhaust-side rocker shaft 51 on the first and second straight lines
L1 and L2. As a result, it is also possible to prevent an uneven
wear from being produced in the swinging support section 57 and the
roller 56.
[0064] In addition, the swinging support section 57 is formed at
the length longer than the distance between the centers of the
first and second tappet screws 53A and 53B, and the third and
fourth straight lines L3 and L4 passing the centers of the first
and second tappet screws 53A and 53B and intersecting the axis C of
the exhaust-side rocker shaft 51 at the right angles are disposed
inside the axially opposite ends of the swinging support section
57. Therefore, the exhaust-side rocker shaft 52 is supported on the
exhaust-side rocker shaft 52 over the length longer than the
distance between the tappet screws 53A and 53B, and the
exhaust-side rocker arms 50A is supported more stably.
[0065] The roller shaft 63 is fitted and fixed in the exhaust-side
rocker arm 50A, and the roller 56 in rolling contact with the valve
operating cam 55 is rotatably carried on the roller shaft 63.
However, the roller shaft 63 is shorter than the distance between
the first and second support walls 58 and 59 provided to extend
from the opposite ends of the swinging support section 57, and is
fitted and fixed at the inner ends of the pair of shaft insertion
bores 66, 66 which are coaxially provided in the exhaust-side
rocker arm 50A with their portions axially outer than opposite ends
of the roller shaft 63 being left as the hollow wall-removed
portions 67, 67.
[0066] Thus, the portions of the shaft insertion bores 66 which are
axially outer than the opposite ends of the roller shaft 63 are
left in the hollow forms and hence, the weight of the entire
exhaust-side rocker arm 50A can be reduced, and it is also possible
to confirm, from the opposite sides of the exhaust-side rocker arm
50A, the state of the roller shaft 63 fixed to the rocker arm 50.
Moreover, the roller shaft 63 can be formed at a relatively small
length, whereby the assembling of the roller shaft 63 to the
exhaust-side rocker arm 50A is facilitated. In addition, the roller
shaft 63 can be formed so that it is difficult to deform, thereby
ensuring a proper swinging movement of the exhaust-side rocker arm
50A. Loads from the exhaust valves VE, VE are applied to the first
and second support walls 58 and 59, but the roller 56 can be
supported by the roller shaft 63 disposed at the location kept away
from the load-applied portions and hence, the rigidity of
supporting of the roller 56 can be enhanced.
[0067] The shaft insertion bore 66 comprises the first insertion
bore portion 66 adjacent to the opening 62 with the roller 56
accommodated therein, and the second insertion bore portion 66b
connected at its inner end to the outer end of the first insertion
bore portion 66 to form the step 66c facing on the side opposite
from the opening 62 between the first and second insertion bore
portions 66a and 66b. The opposite ends of the roller shaft 63
fitted in the first insertion bore portions 66a, 66a of the shaft
insertion bores 66, 66 are in caulked engagement with the steps
66c, respectively, whereby the roller shaft 63 is fitted and fixed
in the shaft insertion bores 66, 66. Therefore, the portions of the
shaft insertion bores 66, 66 left in the hollow forms, i.e., the
wall-removed portions 67, 67 can be formed at large areas as the
second insertion bore portions 66b, 66b, and the weight of the
entire exhaust-side rocker arm 50A can be further reduced. Further,
since the roller shaft 63 is fixed in the caulked manner to the
exhaust-side rocker arm 50A, the assembling of the roller shaft 63
to the exhaust-side rocker arm 50A is further facilitated.
[0068] Additionally, the portion of the shaft insertion bore 66
left as the wall-removed portion 67, i.e., the second insertion
bore portion 66b, is of such shape that it is enlarged gradually as
approaching the portion adjacent to the side of the exhaust-side
rocker arm 50A. Therefore, an operation is facilitated for fitting
and fixing the roller shaft 63 in the inner end of the shaft
insertion bore 66, whereby the assemblability of the roller shaft
can be enhanced.
[0069] Further, the pair of cylindrical shaft support portions 65,
65 defining the shaft insertion bores 66, 66 respectively are
provided on the exhaust-side rocker arm 50A over the first and
second support walls 58 and 59 and the opening 62, and the pair of
cylindrical shaft support portions 65, 65 interconnected through
the roller shaft 63 are connected to the support walls 58 and 59.
Therefore, the rigidity of the support walls 58 and 59 and the
rigidity of supporting of the roller 56 can be further
enhanced.
[0070] The cylindrical swinging support section 57 provided at the
base end of the exhaust-side rocker arm 50A so that it is swingably
supported by the exhaust-side rocker shaft 51, comprises the
thinner cylindrical portion 57a surrounding the exhaust-side rocker
shaft 51, and the thicker cylindrical portions 57b, 57b thicker
than the thinner cylindrical portion 57a surrounding the
exhaust-side rocker shaft 51 and integrally connected to the
axially opposite ends of the thinner cylindrical portion 57a,
respectively. Therefore, the central portion of the swinging
support section 57 can be formed at a smaller thickness to avoid an
increase in weight of the exhaust-side rocker arm 50A, while the
opposite ends of the swinging support section 57 having a
possibility that a large load may be applied, can be formed at a
larger thickness to enhance the rigidity of supporting of the
exhaust-side rocker arm 50A and the durability of the latter.
[0071] In addition, the grooves 68, 68 capable of accumulation of
an oil between the grooves and the outer surface of the
exhaust-side rocker shaft 51 are provided in the inner surfaces of
the opposite ends of the swinging support section 57 along the axis
of the exhaust-side rocker shaft 51, i.e., in the inner surfaces of
the thicker cylindrical portions 57b, 57b, respectively. Therefore,
the oil can be accumulated between the opposite ends of the
swinging support section 57 and the exhaust-side rocker shaft 51,
and even if the exhaust-side rocker arm 50A is inclined, an uneven
wear can be prevented to the utmost from being produced, leading to
an enhanced durability. Moreover, the grooves 68, 68 are merely
provided in the inner surface of the swinging support section 57 at
its opposite ends and hence, the weight of the exhaust-side rocker
arm 50A cannot be increased, and a reduction in rigidity of the
swinging support section 57 can be inhibited.
[0072] Furthermore, the first and second support walls 58 and 59,
at the tip ends of which the first and second tappet screws 53A and
53B are mounted to abut against the upper end of the exhaust valves
VE, VE, are provided to extend from the opposite ends of the
swinging support section 57 at the locations corresponding to the
grooves 68, 68. Therefore, a slight reduction in rigidity of the
opposite ends of the swinging support section 57 due to the
provision of the grooves 68, 68 can be made up for by the first and
second support walls 58 and 59.
[0073] The outer periphery of the exhaust-side rocker arm 50A is
formed by the swinging support section 57, the first support wall
58, the second support wall 59 and the connection wall 60, and the
recesses 69 and 70 are defined at least in the upper surface of the
exhaust-side rocker arm 50A by the portions surrounded by the
swinging support section 57, the first support wall 58, the second
support wall 59 and the connection wall 60. Therefore, it is
possible to provide a reduction in weight of the exhaust-side
rocker arm 50A, while avoiding a reduction in rigidity of the
exhaust-side rocker arm 50A.
[0074] Moreover, one of the recesses 69 is disposed between the
pair of shaft support portions 65, 65 and the swinging support
section 57, and the oil can be supplied to the roller 56
accommodated in the opening 62. Therefore, the oil scattered within
the valve operating chamber can be reliably accumulated at a
portion of the exhaust-side rocker arm 50A which is swung in a
relatively small amount, thereby lubricating the roller 56, and
hence, it is unnecessary to provide a passage for supplying the oil
to the roller 56 in the exhaust-side rocker arm 50A, thereby
reducing the number of steps of processing the exhaust-side rocker
arm 50A.
[0075] The other recess 70 is defined in the exhaust-side rocker
arm 50A between the shaft support portions 65, 65 and the
connection wall 60 to enable the supplying of the oil to the roller
56 and hence, the weight of the tip end of the exhaust-side rocker
arm 50A can be reduced to alleviate the inertial weight, while
performing the lubrication of the roller 56.
[0076] The axially central portion of the swinging support section
57 in the exhaust-side rocker arm 50A is disposed at the location
corresponding to the plug insertion tube 36 mounted in the cylinder
head 16, and the notches 71 and 72 connected smoothly to each other
and formed into the arcuate shape recessed on the side opposite to
the plug insertion tube 36 are provided in the swinging support
section 57 and the exhaust-side rocker shaft 51 at the location
corresponding to the plug insertion tube 36. Therefore, it is
possible not only to reduce the weight of the exhaust-side rocker
arm 50A, but also the exhaust-side rocker shaft 51 and the plug
insertion tube 36 can be disposed in the proximity to each other in
such a manner that a portion of the plug insertion tube 36 is
accommodated in the notch 71, and the limitation of the layout of
the exhaust-side rocker arm 50A within the valve operating chamber
can be moderated to contribute to the compactness of the entire
engine.
[0077] Moreover, the notches 71 and 72 are provided in the swinging
support section 57 and the exhaust-side rocker shaft 51 between the
connections of the first and second support walls 58 and 59 to the
swinging support section 57 and hence, the notches 71 and 72 can be
disposed at the portions to which a relatively small stress is
applied during driving of the exhaust valves VE, VE, thereby
reducing the influence to the rigidity due to the provision of the
notch 71 in the exhaust-side rocker arm 50A to reduce the weight of
the exhaust-side rocker arm 50A.
[0078] The oil is supplied from the oil supply passage 74 in the
exhaust-side rocker shaft 51 through the oil supply bore 75 and the
oil injection bore 73 to the roller 56, and the oil injection bore
73 is provided in the swinging support section 57 on the side
opposite to the notch 71, with respect to the axis C of the
exhaust-side rocker shaft 51, which notch is provided in the
swinging support section 57 in such a manner that an outer surface
of a portion of the exhaust-side rocker shaft 71 provided with the
notch 72 faces the notch 71. Therefore, it is possible to conduct a
boring for the oil injection bore 73 from the side of the notch 71,
thereby facilitating the boring for the oil injection bore 73.
[0079] The first and second boss portions 58a and 59a, in which the
first and second tappet screws 53A and 53B are threadedly fitted to
abut against the upper ends of the exhaust valves VE, VE, are
disposed at the tip ends of the exhaust-side rocker arm 50A and
arranged in the direction along the axis C of the exhaust-side
rocker shaft 51, but they are interconnected by the connection wall
60. Therefore, the rigidity of the tip end of the exhaust-side
rocker arm 50A driving the pair of exhaust valves VE, VE can be
enhanced sufficiently and moreover, the connection wall 60
comprises the first and second wall portions 60a and 60b
intersecting each other at the right angles in the plane
perpendicular to the axis C of the exhaust-side rocker shaft 51,
i.e., the swinging axis of the exhaust-side rocker arm 50A.
Therefore, it is possible to suppress the increase in weight of the
exhaust-side rocker arm 50A due to the connection wall 60 to the
minimum, while maintaining the sufficient connection rigidity. In
addition, the second wall portion 60b of the connection wall 60 is
formed to extend in parallel to the axis of the exhaust-side rocker
shaft 51, so that its outer surface is connected flush to the outer
surfaces of the tip ends of the first and second boss portions 58a
and 59a. Therefore, it is possible to eliminate the concentration
of a stress on the connections between the connection wall 60 and
the boss portions 58a and 59a, thereby enhancing the durability of
the exhaust-side rocker arm 50A, while sufficiently enhancing the
rigidity of the tip end of the exhaust-side rocker arm 50A.
[0080] Further, one side of the opening 62 provided in the
exhaust-side rocker arm 50A to accommodate the roller 56 is formed
by the inner surface of the first wall portion 60a of the
connection wall 60, and the connection wall 60 can be disposed in
proximity to the roller 56, thereby enhancing the rigidity of
supporting of the roller 56.
[0081] FIGS. 8 to 10 show a second embodiment of the present
invention, wherein portions or components corresponding to those in
the first embodiment are designated by like reference
characters.
[0082] In the exhaust-side rocker arm 50B of the exhaust-side valve
operating device 34, a cam slipper 76 as a cam abutment is provided
integrally or by securing by another member, in an intermediate
portion between the swinging support section 57 and the valve
abutments 53A and 53B, and is in contact with the valve operating
cam 55 on the exhaust-side camshaft 52.
[0083] The cam slipper 76 is disposed in an intermediate portion
between the first and second support walls 58 and 59, and the
support walls 58 and 59 and the cam slipper 76 are interconnected
by connecting tubes 77, 77 extending in parallel to the
exhaust-side rocker shaft 51. Moreover, a recess having a circular
sectional shape is coaxially provided in each of the connecting
tubes 77, 77 with its outer end opening into the outer surface of
the exhaust-side rocker arm 50B, i.e., the outer surface of each of
the first and second support walls 58 and 59. Thus, wall-removed
portions 78, 78 are coaxially defined in the exhaust-side rocker
arm 50B at locations corresponding to the cam slipper 76, and open
into opposite sides of the exhaust-side rocker arm 50B,
respectively. A through-bore 79 is provided in the exhaust-side
rocker arm 50B at a location corresponding to the cam slipper 76 to
coaxially connect inner ends of the wall-removed portions 78, 78 to
each other, and is defined at a diameter smaller than those of the
wall-removed portions 78, 78.
[0084] In the second embodiment, the wall-removed portions 78, 78
are formed in the exhaust-side rocker arm 50B at the locations
corresponding to the cam slipper 76 provided in sliding contact
with the valve operating cam 55, and open into the opposite sides
of the exhaust-side rocker arm 50B, i.e., the sides of the first
and second support walls 58 and 59, and therefore, the weight of
the entire exhaust-side rocker arm 50B can be reduced.
[0085] Moreover, the wall-removed portions 78, 78 are defined
within the connecting tubes 77, 77 interconnecting the cam slipper
76 and the first and second support walls 58 and 59. Therefore, it
is possible to reduce the weight of the exhaust-side rocker arm
50B, while avoiding reductions in rigidity of the first and second
support walls 58 and 59 and in rigidity of supporting of the cam
slipper 76.
[0086] The weight of the exhaust-side rocker arm 50B can be reduced
further by the interconnection of the wall-removed portions by the
through-bore 79, and the reduction in wall thickness of the
exhaust-side rocker arm 50B at the location corresponding to the
cam slipper 76 can be suppressed to the minimum by defining the
through-bore 79 disposed at the location corresponding to the cam
slipper 76 at the diameter smaller than those of the wall-removed
portions 78, 78 on the opposite sides of the through-bore 79,
thereby inhibiting the reduction in rigidity of the exhaust-side
rocker arm 50B at the location corresponding to the cam slipper
76.
[0087] FIG. 11 shows a third embodiment of the present invention.
In the third embodiment, inner ends of wall-removed portions 78, 78
may be spaced at a distance by a partition wall 80 from each other.
If the wall-removed portions 78, 78 are formed in the above manner,
the wall thickness of an exhaust-side rocker arm 50C can be
increased at a location corresponding to the cam slipper 76,
whereby the rigidity of the exhaust-side rocker arm 50C at the
location corresponding to the cam slipper 76 can be maintained.
[0088] FIG. 12 shows a fourth embodiment of the present invention.
In the fourth embodiment, reinforcing ribs 81 and 82 are provided
on an exhaust-side rocker arm 50D with the cam slipper 76
sandwiched therebetween to extend a first straight line L1 passing
through the center of the first tappet screw 53A, i.e., the center
of the threaded bore 61A in the first boss portion 58a and the
center of the cam slipper 76, and reinforcing ribs 83 and 84 are
also provided on the exhaust-side rocker arm 50D with the cam
slipper 76 sandwiched therebetween to extend a second straight line
L2 passing through the center of the second tappet screw 53B, i.e.,
the center of the threaded bore 61B in the second boss portion 59a
and the center of the cam slipper 76.
[0089] According to the fourth embodiment, it is possible to
further enhance the rigidity of the exhaust-side rocker arm 50D,
and it is also possible to further effectively prevent an uneven
wear from being produced in the swinging support section 57 and the
cam slipper 76.
[0090] Although the embodiments of the present invention have been
described in detail, it will be understood that the present
invention is not limited to the above-described embodiments, and
various modifications in design may be made without departing from
the spirit and scope of the invention defined in claims.
[0091] For example, the present invention is applicable to a valve
operating system for an intake valve.
* * * * *