Note: Descriptions are shown in the official language in which they were submitted.
CA 02293000 1999-12-21
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1
VALVE OPERATING SYSTEM IN INTERNAL COMBUSTION ENGINE
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
The present invention relates to a valve operating system
in an internal combustion engine, including a cam shaft provided
with a valve operating cam, a rocker arm having a pair of support
wall portions which are integrally connected at their base ends
to a swinging support portion swingably supported on a support
member mounted on a cylinder head, the support wall portions
being opposed to each other at a distance in a direction along
the swinging axis of the swinging support portion, a support
shaft supported between the support wall portions , and a roller
which is rotatably supported on the support shaft with a bearing
interposed therebetween, the roller being in rolling contact
with the valve operating cam.
2. DESCRIPTION OF THE RELATED AR's
Such valve operating system is already known from
Japanese Patent Application Laid-open No.63-230916.
The rocker arm in the above known valve operating system
is comprised of a swinging support portion swingably supported
by a pivot serving as a support member, a pair of support wall
portions connected at their base ends to the swinging support
portion, and a tip-end connecting portion which connects tip
ends of the support wall portions to each other . An engine valve
is operatively connected to the tip-end connecting portion ,
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and a roller is rotatably supported on a support shaft supported
between the support wall portions to come into rolling contact
with the valve operating cam. That face of the swinging support
portion, which is opposed to the roller, is formed as a flat
surface extending along a plane intersecting a straight line
connecting a point at which the swinging support portion is
swingably supported by the pivot, to the axis of rotation of
the roller. It is difficult to say that the rigidity of the
rocker arm of this system is excellent, and desirably the
rigidity of the rocker arm should be increased. Moreover, it
should be avoided that the size of the rocker arm is increased
when its rigidity is increased.
~ITMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to
provide a valve operating system in an internal combustion
engine, wherein the rigidity of each of the rocker arms is
increased, while avoiding an increase in size of the rocker arm.
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 cam shaft provided with a valve operating cam, a rocker arm
having a pair of support wall portions which are integrally
connected at base ends thereof to a swinging support portion
swingably supported on a support member mounted on a cylinder
head, the support wall portions being opposed to each other at
a distance in a direction along a swinging axis of the swinging
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support portion, a support shaft supported between the support
wall portions , and a roller which is rotatably supported on the
support shaft with a bearing interposed therebetween, the
roller being in rolling contact with the valve operating cam,
wherein a lower connecting wall interconnecting lower portions
of the base ends of the support wall portion is projectingly
provided on the swinging support portion so as to be opposed
to an outer peripheral surface of a lower portion of the roller.
With the arrangement of the first feature, the base ends
of the pair of support wall portions are connected to each other
by the lower connecting wall. Therefore, the rigidity of
supporting the support shaft by the support wall portions is
increased, and the rigidity of the entire rocker arm is also
increased. The lower connecting wall is disposed while
effectively utilizing space between the roller and the swinging
support portions , and the size of the rocker arm is not increased
due to the lower connecting wall.
According to a second aspect and feature of the present
invention, in addition to the first feature, the lower
connecting wall is located in proximity to and opposed to the
outer peripheral surface of the lower portion of the roller to
such an extent that oil can be once retained between the lower
connecting walls and the rollers. With such arrangement, the
oil can be once retained between the lower connecting wall and
the roller, and the oil retained between the lower connecting
wall and the roller can be guided to the bearing between the
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roller and the support shaft to reduce the resistance to the
rotation of the roller.
According to a third aspect and feature of the present
invention, in addition to the first or second feature, the
rocker arm is formed from metal by injection molding. With such
arrangement , it is possible to simply form the rocker arm having
a relatively complicated structure in which the lower
connecting wall protrudes from the swinging support portion.
Thus , it is possible to easily form the rocker arm to be of an
optimal shape while taking an increase in rigidity and a
reduction in weight into consideration.
According to a fourth aspect and feature of the present
invention, in addition to any one of the first, second and third
features, the valve operating system further includes an urging
means for biasing the rocker arm in a direction to bring the
roller into rolling contact with the valve operating cam, the
urging means being put in abutment against a receiving portion
which is pro jectingly provided at a lower portion of one of the
support wall portions and connected to one end of the lower
connecting wall in an axial direction of the support shaft.
With such arrangement, the rigidity of the receiving portion
receiving a load from the urging means can be increased by the
lower connecting wall.
According to a fifth aspect and feature of the present
invention, in addition to the first feature, the support shaft
is supported between the support wall portions with its opposite
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. 5
ends of the support shaft being fitted in the support wall
portions, at least one of the support wall portions having a
receiving portion integrally provided thereon in a range
corresponding to at least a portion of that area of the support
shaft which is fitted into the one support wall portion, the
receiving portion being disposed at a location radially outside
the support shaft , and wherein an urging means is provided for
exhibiting a spring force for urging the rocker arm in a
direction to bring the roller rotatably, which is supported on
the support shaft with the bearing interposed therebetween,
into rolling contact with the valve operating cam, the urging
means being put in abutment against the receiving portion.
With the arrangement of the fifth feature, it is possible
to simplify the structure of the rocker arm in such a manner
that the receiving portion is provided radially outside the
roller. At the same time, the receiving portion does not
protrude from the rocker arm in the axial direction of the
support shaft . Therefore , it is possible to avoid an increase
in size of the rocker arm in the axial direction of the support
shaft, and the inertial weight is decreased. Therefore, it is
possible to conveniently accommodate the high-speed rotation
of the internal combustion engine. In addition, the rigidity
of supporting the support shaft on the one support wall portion
can be increased by the provision of the receiving portion.
According to a sixth aspect and feature of the present
invention, in addition to the fifth feature, an oil passage is
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provided in the one support wall portion to extend along a plane
which extends perpendicular to the axis of the support shaft
and through an abutment point between the receiving portion and
the urging means. With such arrangement, it is possible to
compensate for a decrease in weight of the one support wall
portion due to the provision of the oil passage which is a cavity,
by the receiving portion, thereby improving the balance in
weight between the support wall portions. Moreover, it is
possible to avoid a reduction in rigidity of the one support
wall portion due to the provision of the oil passage by the
providing the receiving portion.
According to a seventh aspect and feature of the present
invention, in addition to the fifth or sixth feature, the rocker
arm is formed from metal by injection molding. With such
arrangement, a fitting bore for fitting the support shaft
therein can be defined in the rocker arm simultaneously with
the formation of the rocker arm, and the number of post-
processings can be decreased to contribute to an enhancement
in productivity. Moreover, when the rocker arm has the oil
passage provided therein, even if the cross sectional shape of
the oil passage is out of round, it is possible to define the
oil passage simultaneously with the formation of the rocker arm,
thereby providing an enhancement in productivity and increasing
the degree of freedom of design of the cross sectional shape
of the oil passage.
According to an eighth aspect and feature of the present
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invention, in addition to the first feature, a notch
recessed on a side opposite to a spark plug insertion tube
mounted in the cylinder head is provided in that portion of
the swinging support portion of the rocker arm, which is
opposed to the spark plug insertion tube, and at least a
portion of the lower connecting wall and at least a portion
of the notch are disposed in the same plane perpendicular to
a swinging axis of the rocker arm. With such arrangement,
the spark plug insertion tube and the rocker arm can be
disposed in close proximity to each other to contribute to a
reduction in weight of the rocker arm and a reduction in
size of a valve operating chamber defined in the internal
combustion engine in such a manner to accommodate the valve
operating system in the engine. Moreover, it is possible to
compensate for the reduction in rigidity of the swinging
support portion due to the provision of the notch by the
lower connecting wall.
According to another aspect of the present
invention, there is provided a valve operating system in an
internal combustion engine, comprising a cam shaft provided
with a valve operating cam, a rocker arm having a pair of
support wall portions which are integrally connected at base
ends thereof to a swinging support portion swingably
supported on a support member mounted on a cylinder head,
said support wall portions being opposed to each other at a
distance in a direction along a swinging axis of said
swinging support portion, a support shaft supported between
said support wall portions, and a roller which is rotatably
supported on said support shaft with a bearing interposed
therebetween, said roller being in rolling contact with said
valve operating cam, wherein said swinging support portion
has a surface portion opposed to said roller and extending
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between said pair of support wall portions, and a lower
connecting wall interconnecting lower portions of the base
ends of said support wall portions is projectingly provided
on said surface portion of said swinging support portion so
as to be opposed to an outer peripheral surface of said
roller, said lower connecting wall being closest to said
outer peripheral surface of the roller in said surface
portion.
According to yet another aspect of the present
invention, there is provided a valve operating system in an
internal combustion engine, comprising: a cam shaft provided
with a valve operating cam, a rocker arm having a pair of
support wall portions which are integrally connected at base
ends thereof to a swinging support portion swingably
supported on a support member mounted on a cylinder head,
said support wall portions being opposed to each other at a
distance in a direction along a swinging axis of said
swinging support portion, a support shaft supported between
said support wall portions, a roller which is rotatably
supported on said support shaft with a bearing interposed
therebetween, said roller being in rolling contact with said
valve operating cam, a surface portion of said swinging
support portion opposed to said roller and extending between
said pair of support wall portions, a lower connecting wall
interconnecting lower portions of the base ends of said
support wall portions and projecting from said surface
portion of said swinging support portion so as to be opposed
to an outer peripheral surface of a lower portion of said
roller, said lower connecting wall being located closest to
and opposed to the outer peripheral surface of the lower
portion of said roller in said surface portion to such an
extent that oil can be once retained between said lower
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connecting wall and said roller, and urging means for
biasing said rocker arm in a direction to bring said roller
into rolling contact with said valve operating cam, said
urging means being put in abutment against a receiving
portion which is projectingly provided at a lower portion of
one of said support wall portions and connected to one end
of said lower connecting wall in an axial direction of said
support shaft.
According to yet another aspect of the present
invention, there is provided a valve operating system in an
internal combustion engine, comprising a cam shaft provided
with a valve operating cam, a rocker arm being formed from
metal by injection molding and having a pair of support wall
portions which are integrally connected at base ends thereof
to a swinging support portion swingably supported on a
support member mounted on a cylinder head, said support wall
portions being opposed to each other at a distance in a
direction along a swinging axis of said swinging support
portion, a support shaft supported between said support wall
portions, a roller which is rotatably supported on said
support shaft with a bearing interposed therebetween, said
roller being in rolling contact with said valve operating
cam, a surface portion of said swinging support portion
opposed to said roller and extending between said pair of
support wall portions, a lower connecting wall
interconnecting lower portions of the base ends of said
support wall portions and projecting from said surface
portion of said swinging support portion so as to be closest
to and opposed to an outer peripheral surface of a lower
portion of said roller in said surface portion, and urging
means for biasing said rocker arm in a direction to bring
said roller into rolling contact with said valve operating
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cam, said urging means being put in abutment against a
receiving portion which is projectingly provided at a lower
portion of one of said support wall portions and connected
to one end of said lower connecting wall in an axial
direction of said support shaft.
According to yet another aspect of the present
invention, there is provided a valve operating system in an
internal combustion engine, comprising a cam shaft provided
with a valve operating cam, a rocker arm having a pair of
support wall portions which are integrally connected at base
ends thereof to a swinging support portion swingably
supported on a support member mounted on a cylinder head,
said support wall portions being opposed to each other at a
distance in a direction along a swinging axis of said
swinging support portion, a support shaft supported between
said support wall portions, a roller which is rotatably
supported on said support shaft with a bearing interposed
therebetween, said roller being in rolling contact with said
valve operating cam, and a surface portion of said swinging
support portion opposed to said roller and extending between
said pair of support wall portions, a lower connecting wall
interconnecting lower portions of the base ends of said
support wall portions and projecting from said surface
portion of said swinging support portion so as to be closest
to and opposed to an outer peripheral surface of a lower
portion of said roller in said surface portion, wherein said
support shaft is supported between said support wall
portions with opposite ends of the support shaft being
fitted in said support wall portions, at least one of said
support wall portions having a receiving portion integrally
provided thereon in a range corresponding to at least a
portion of that area of said support shaft which is fitted
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into said one support wall portion, said receiving portion
being disposed at a location radially outside said support
shaft, and wherein an urging means is provided for
exhibiting a spring force for urging said rocker arm in a
direction to bring said roller, which is rotatably supported
on said support shaft with the bearing interposed
therebetween, into rolling contact with said valve operating
cam, said urging means being put in abutment against said
receiving portion.
According to yet another aspect of the present
invention, there is provided a valve operating system in an
internal combustion engine, comprising a cam shaft provided
with a valve operating cam, a rocker arm having a pair of
support wall portions which are integrally connected at base
ends thereof to a swinging support portion swingably
supported on a support member mounted on a cylinder head,
said support wall portions being opposed to each other at a
distance in a direction along a swinging axis of said
swinging support portion, a support shaft supported between
said support wall portions, a roller which is rotatably
supported on said support shaft with a bearing interposed
therebetween, said roller being in rolling contact with said
valve operating cam, a surface portion of said swinging
support portion opposed to said roller and extending between
said pair of support wall portions, a lower connecting wall
interconnecting lower portions of the base ends of said
support wall portions and projecting from said surface
portion of said swinging support portion so as to be closest
to and opposed to an outer peripheral surface of a lower
portion of said roller in said surface portion; wherein a
notch recessed on a side opposite to a spark plug insertion
tube mounted in the cylinder head is provided in that
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portion of the swinging support portion of said rocker arm,
which is opposed to said spark plug insertion tube, and at
least a portion of said lower connecting wall and at least a
portion of said notch are disposed in the same plane
perpendicular to a swinging axis of said rocker arm.
According to yet another aspect of the present
invention, there is provided a valve operating system in an
internal combustion engine, comprising a cam shaft provided
with a valve operating cam, a rocker arm having a pair of
support wall portions which are integrally connected at base
ends thereof to a swinging support portion swingably
supported on a support member mounted on a cylinder head,
said support wall portions being opposed to each other at a
distance in a direction along a swinging axis of said
swinging support portion, a support shaft supported between
said support wall portions, and a roller which is rotatably
supported on said support shaft with a bearing interposed
therebetween, said roller being in rolling contact with said
valve operating cam, wherein a lower connecting wall
interconnecting lower portions of the base ends of said
support wall portions is projectingly provided on said
swinging support portion so as to be opposed to and spaced
apart from an outer peripheral surface of a lower portion of
said roller at a first distance and an upper connecting wall
interconnecting upper portions of the base ends of said
support wall portions is projectingly provided on said
swinging support portion so as to be opposed to and spaced
apart from the outer peripheral surface of an upper portion
of said roller at a second distance being larger than the
first distance.
The above and other objects, features and
advantages of the invention will become apparent from the
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following description of the preferred embodiments taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figs. 1 to 13 show a first embodiment of the
present invention, wherein
Fig. 1 is a vertical sectional view taken along a
line 1-1 in Fig. 2 and showing a portion of a valve
operating system;
Fig. 2 is a plan view taken in a direction of an
arrow 2
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in Fig. l;
Fig.3 is a sectional view taken along a line 3-3 in Fig.2;
Fig.4 is a sectional view taken along a line 4-4 in Fig.3;
Fig.S is an enlarged sectional view taken along a line
5-5 in Fig.2;
Fig.6 is a sectional view similar to Fig.5, but in a state
before swaging of a pin;
Fig.7 is a sectional view taken along a line 7-7 in Fig.2;
Fig.8 is a sectional view taken along a line 8-8 in Fig.4;
Fig.9 is a sectional view taken along a line 9-9 in Fig.2;
Fig.lO is a sectional view taken along a line 10-10 in
Fig.4;
Fig.ll is a sectional view taken along a line 11-11 in
Fig.lO;
Fig. l2 is a plan view of intake-side and exhaust-side
valve operating systems;
Fig.l3 is a sectional view taken along a line 13-13 in
Fig. l2;
Figs. l4 and 15 show a second embodiment of the present
invention, wherein
Fig.l4 is a sectional view of a free rocker arm; and
Fig.l5 is a sectional view taken along a line 15-15 in
Fig. l4.
A first embodiment of the present invention will now be
described with reference to Figs.l to 13. Referring first to
r CA 02293000 1999-12-21
. 9
Fig. l, a pair of intake valve bores 12 are provided for each
of cylinders in a cylinder head 11 of a multi-cylinder, e.g.,
serial-4-cylinder internal combustion engine. The intake
valve bores 12 are opened and closed individually by intake
valves VI as engine valves, whose stems 13 are slidably fitted
in guide tubes 14 provided in the cylinder head 11. Valve
springs 16 are mounted between retainers 15 mounted at upper
ends of the stems 13 protruding upwards from the guide tubes
14 and the cylinder head 11 to surround the stems 13 , so that
the intake valves VI are biased by the valve springs 16 in the
direction to close the intake valve bores 12.
Referring also to Figs.2 to 4, an intake-side valve
operating system 17I is connected to the pair of intake valves
VI, VI, and includes a cam shaft 18 operatively connected to
a crankshaft (not shown) at a reduction ratio of 1/2, a first
driving rocker arm 19 operatively connected to one of the intake
valves VI , a second driving rocker arm 20 operatively connected
to the other intake valve VI , a free rocker arm 21 capable of
becoming free relative to the intake valves VI, a stationary
rocker shaft 22 as a support member for commonly supporting the
rocker arms 19, 20 and 21 for swinging movement and having an
axis parallel to the cam shaft 18, and an associative operation
switching means 23 for switching the associative operation and
the release of the associative operation of the rocker arms 19 ,
20 and 21.
Fixed to the cam shaft 18 are a high-speed valve operating
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cam 26 and low-speed valve operating cams 25, 25 which are
disposed on opposite sides of the high-speed valve operating
cam 26 in correspondence to the intake valves VI, respectively.
The high-speed valve operating cam 26 has a cam profile
which enables the intake valves VI to be opened and closed in
a high-speed operational range of the engine, and includes a
base-circle portion 26a which is arcuate about an axis of the
cam shaft 18, and a cam lobe 26b protruding radially outwards
from the base-circle portion 26a. The low-speed valve
operating cam 25 has a cam profile which enables the intake
valves VI to be opened and closed in a low-speed operational
range of the engine, and includes a base-circle portion 25a
which is formed into an arcuate shape about the axis of the cam
shaft 18, and a cam lobe 25b which protrudes radially outwards
of the cam shaft 18 from the base-circle portion 25a over a range
of center angle smaller than that of the cam lobe 26b and in
an amount smaller than the amount of cam lobe 26b protruding
from the base-circle portion 26a in the high-speed valve
operating cam 26.
The first driving rocker arm 19 , the second driving rocker
arm 20 and the free rocker arm 21 are carried swingably and
commonly on the rocker shaft 22 and disposed adjacent one
another in such a manner that the free rocker arm 21 is sandwiched
between the first and second driving rocker arms 19 and 20.
Each of the first and second driving rocker arms 19 and
20 is integrally provided with a swinging support portion 19a,
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20a swingably supported on the rocker shaft 22, a first support
wall portion 311, 321 connected at a base end thereof to the
swinging support portion 19a, 20a, a second support wall portion
312, 322 connected to the swinging support portion 19a, 20a with
its base end opposed to the first support wall portion 311, 321
in a direction along the axis of the rocker shaft 22, and a
tip-end connecting portion 19b, 20b which interconnects tip
ends of the support wall portions 311, 312 and 321, 322 forming
a pair. Tappet screws 27, 27 are threadedly inserted in the
tip-end connecting portions 19b and 20b for advancing and
retreating movements to abut against upper ends of the stems
13 of the intake valves VI . The free rocker arm 21 is integrally
provided with a swinging support portion 21a swingably
supported on the rocker shaft 22, a first support wall portion
331 connected at its base end to the swinging support portion
21a, a second support wall portion 332 connected at its base
end to the swinging support portion 21a in an opposed relation
to the first support wall portion 331 in a direction along the
axis of the rocker shaft 22.
An opening 34 which opens vertically is provided between
the swinging support portion 19a and the tip-end connecting
portion 19b of the first driving rocker arm 19 in such a manner
that opposite sides of the opening 34 are delimited by the first
and second support wall portions 311 and 312. A cylindrical
roller 28 is rotatably supported on the first driving rocker
arm 19 to come into rolling contact with the low-speed valve
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operating cam 25 in such a manner that it is disposed in the
opening 34. An opening 35 which opens vertically is provided
between the swinging support portion 20a and the tip-end
connecting portion 20b of the second driving rocker arm 20 in
such a manner that opposite sides of the opening 35 are delimited
by the first and second support wall portions 321 and 322. A
cylindrical roller 29 is rotatably supported on the second
driving rocker arm 20 to come into rolling contact with the
low-speed valve operating cam 25 in such a manner that the
cylindrical roller 29 is disposed in the ,opening 35 . Further,
an opening 36, which opens on a side opposite to the rocker shaft
22 and vertically, is provided in the free rocker arm 21 in such
a manner that opposite sides of the opening 36 are delimited
by the first and second support wall portions 331 and 332, and
a cylindrical roller 30 is rotatably supported on the free
rocker arm 21 to come into rolling contact with the high-speed
valve operating cam 26 in such a manner that it is disposed in
the opening 36.
A bottomed fitting bore 371, which opens at an end adjacent
the free rocker arm 21, is provided in the first support wall
portion 311 of the first driving rocker arm 19 opposite to the
free rocker arm 21 in parallel to the axis of the rocker shaft
22, and a second fitting bore 372, which opens at opposite ends
thereof, is provided in the second support wall portion 312
coaxially with the first fitting bore 371. A first fitting bore
381, which opens at opposite ends thereof, is provided in the
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first support wall portion 321 of the second driving rocker arm
20 adjacent the free rocker arm 21 in parallel to the axis of
the rocker shaft 22, and a second bottomed fitting bore 382,
which opens at an end ad j acent the free rocker arm 21, is provided
in the second support wall portion 322 coaxially with the first
fitting bore 381. A first fitting bore 391, which opens at
opposite ends thereof, is provided in the first support wall
portion 331 of the free rocker arm 21 adjacent the first driving
rocker arm 19 in parallel to the axis of the rocker shaft 22,
and a second fitting bore 392, which opens at opposite ends
thereof, is provided in the second support wall portion 332
coaxially with the first fitting bore 391.
One end of a cylindrical support shaft 41 is fitted into
the first fitting bore 371 in the first driving rocker arm 19,
until it abuts against a closed end of the first fitting bore
371, and the other end of the support shaft 41 is fitted into
the fitting bore 372. One end of a cylindrical support shaft
42 is fitted into the first fitting bore 381 in the second driving
rocker arm 20, and the other end of the support shaft 42 is fitted
into the second fitting bore 382, until it abuts against a closed
end of the second fitting bore 382. Further, opposite ends of
a cylindrical support shaft 43 are fitted into the first and
second fitting bores 391 and 392 in the free rocker arm 21,
respectively.
Referring also to Fig.5, an insertion bore 44 is provided
in the second support wall portion 312 of the first driving
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rocker arm 19, and extends rectilinearly in a direction
intersecting a straight line interconnecting axes of the rocker
shaft 22 and the second fitting bore 372 to lead to an inner
surface of the second fitting bore 372. The following recesses
are also provided in the second support wall portion 312: a first
recess 80 which leads to an upper end of the insertion bore 44
and opens into an upper surface of the second support wall
portion 312, and a second recess 81 which leads to a lower end
of the insertion bore 44 and opens into a lower surface of the
second support wall portion 312. The first and second recesses
80 and 81 are formed with their diameters larger than that of
the insertion bore 44.
On the other hand, an engage groove 50 is provided in an
outer surface of the support shaft 41 in correspondence to an
opening in the insertion bore 44 leading to the inner surface
of the second fitting bore 372, and extends along a direction
tangent to a phantom circle C about the axis of the support shaft
41. A pin 47 extending rectilinearly is inserted into the
insertion bore 44 and engaged at its intermediate portion into
the engage groove 50, as shown in Fig.6.
Opposite ends of the pin 47 inserted in the insertion bore
44 are caulked by flat punches 82 and 83 having outside diameters
smaller than inside diameters of the recesses 80 and 81, as shown
in Fig.5, and caulked portions 47a, 47a formed by crushing the
opposite ends into a disk shape by such caulking are brought
into engagement with steps between the recesses 80 and 81 and
' CA 02293000 1999-12-21
the insertion bore 44, whereby the support shaft 41 is fixed
to the first driving rocker arm 19.
The support shaft 42 is fixed to the first support wall
portion 321 of the second driving rocker arm 20 in a structure
similar to the structure in which the support shaft 41 is fixed
to the first driving rocker arm 19. More specifically, a pin
48 , which is inserted into an insertion bore 45 provided in the
first support wall portion 321 of the second driving rocker arm
and which is caulked at its opposite ends , is engaged into
an engage groove 51 provided in an outer surface of the support
shaft 42 fitted into the first fitting bore 381.
Further, the support shaft 43 is fixed to the first support
wall portion 331 of the free rocker arm 21 in a structure similar
to the structure in which the support shaft 41 is fixed to the
first driving rocker arm 19 as well as the structure in which
the support shaft 42 is fixed to the second driving rocker arm
20. More specifically, a pin 49, which is inserted into an
insertion bore 46 provided in the first support wall portion
331 of the free rocker arm 21 and which is caulked at its opposite
ends, is engaged into an engage groove 52 provided in an outer
surface of the support shaft 43 fitted into the first fitting
bore 391.
Each of the depths of the engage grooves 50, 51 and 52
is set at a value which is smaller than one half of the radius
of each of the pins 47, 48 and 49 corresponding to the engage
grooves 50, 51 and 52, preferably, set at a value which is close
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' 16
to one half of the radius of each pin 47, 48, 49. By setting
the depths as described above, not only the processing for
defining the engage grooves 50, 51 and 52 in the support shafts
41, 42 and 43 is facilitated, but also it is possible to avoid
a reduction in rigidity of the support shafts 41, 42 and 43 due
to the provision of the engage grooves 50 to 54 to the utmost .
The hardness of at least those portions of the pins 47
to 49 which are engaged in the engage grooves 50 to 52 , a . g . ,
those portions of the pins 47 to 49 which are inserted in the
insertion bores 44 to 46 in this embodiment, is set higher than
the hardness of opposite ends of the pins 47 to 49 , a . g. , those
ends of the pins 47 to 49 which protrude from the insertion bores
44 to 46 in this embodiment . Each of the pins 47 to 49 is made
of , for example, JIS SUJ2 , but the hardness of a portion of the
outer surface of each of the pins 47 to 49 is increased by
subjecting an axial intermediate portion of each of the pins
47 to 49, for example, to a high-frequency hardening. Thus,
the hardness of at least those portions of the pins 47 to 49
which are engaged in the engage grooves 50 to 52 assumes a value,
for example, in a range of 579 to 832 in unit of H~ by the
high-frequency hardening, and the hardness of the opposite ends
of the pins 47 to 49, which are un-hardened areas, assumes a
value in a range of 180 to 260 in unit of H~.
Needle bearings 53 are interposed between the roller 28
and the support shaft 41 and between the first and second support
wall portions 311 and 312 of the first driving rocker arm 19.
CA 02293000 1999-12-21
17
Needle bearings 54 are interposed between the roller 29 and the
support shaft 42 and between the first and second support wall
portions 321 and 322 of the second driving rocker arm 20. Needle
bearings 55 are interposed between the roller 30 and the support
shaft 43 and between the first and second support wall portions
331 and 332 of the free rocker arm 21.
Referring to Fig. 7, a lost motion mechanism 58 is provided
in the cylinder head 11 below the free rocker arm 21, and serves
as an urging means for applying a spring force to the free rocker
arm 21 in a direction to bring the roller 30 of the free rocker
arm 21 into rolling contact with the high-speed valve operating
cam 26 . The lost motion mechanism 58 is comprised of a bottomed
cylindrical lifter 60 which is slidably fitted in a bottomed
slide bore 59 provided in the cylinder head 11 and which opens
at its upper portion, and a spring 61 mounted under compression
between a closed end of the slide bore 59 and the lifter 60.
On the other hand, the free rocker arm 21 includes a
receiving portion 62 which is in contact with an upper end of
the lifter 60 to receive the spring force from the lost motion
mechanism 58. The receiving portion 62 is integrally provided
on the second support wall portion 332 in such a manner that
the pin 49 is inserted into and fixed in one 331 of the first
and second support wall portions 331 and 332 included in the
free rocker arm 21 to fix the support shaft 43, and the receiving
portion 62 is disposed in a position radially outside the
support shaft 43 on a diagram of projection onto a plane
CA 02293000 1999-12-21
18
perpendicular to the axis of the support shaft 43.
Moreover, the receiving portion 62 is integrally provided
on the second support wall portion 332 in a region corresponding
to at least a portion of that section of the support shaft 43
which is fitted in the second support wall portion 332. In other
words, because the second fitting bore 392, into which the
support shaft 43 is fitted, is provided in the second support
wall portion 332 over the entire width of the support shaft 43
along its axis in this embodiment , the receiving portion 62 may
be disposed within the width of the second support wall portion
332. In this embodiment, the receiving portion 62 extending
over the substantially entire width of the second support wall
portion 332 is integrally provided at a lower portion of the
second support wall portion 332 in the position radially outside
the support shaft 43 so as to bulge downwards to abut against
the lifter 60 of the lost motion mechanism 58 disposed below
the free rocker arm 21.
The receiving portion 62 is integrally provided at the
lower portion of the second support wall portion 332 in such
a manner that it is disposed between (1) a straight line L2
extending through the axis of the rocker shaft 22 in a direction
perpendicular to a straight line L1 extending through the axis
of the rocker shaft 22 and the axis of the support shaft 43 and
( 2 ) a straight line L3 extending through the axis of the support
shaft 43 in a direction perpendicular to the straight line L1.
Referring carefully to Figs.l to 5, a lower connecting
CA 02293000 1999-12-21
19
wall 85 interconnecting lower portions of base ends of the first
and second support wall portions 311 and 312 is projectingly
provided at the swinging support portion 19a of the first
driving rocker arm 19 in such a manner that it is in proximity
to and opposed to an outer peripheral surface of a lower portion
of the roller 28. An upper connection wall 86 interconnecting
upper portions of the base ends of the first and second support
wall portions 311 and 312 is also projectingly provided at the
swinging support portion 19a of the first driving rocker arm
19 in such a manner that it is in proximity to and opposed to
an outer peripheral surface of an upper portion of the roller
28. The distance between the lower connecting wall 85 and the
roller 28 is set smaller than the distance between the upper
connecting wall 86 and the roller 28 . The lower connecting wall
85 is in proximity to and opposed to the outer peripheral surface
of the lower portion of the roller 28 to such an extent that
an oil can be once retained between the lower connecting wall
85 and the roller 28.
Moreover, the lower connecting wall 85 is connected to
the lower portion of the second support wall portion 312 at a
location corresponding to the second recess 81 for
accommodating the caulked lower end of the pin 47 for fixing
the support shaft 41 to the first driving rocker arm 19. The
face of the swinging support portion 19a, which is opposed to
the roller 28 between the lower and upper connecting walls 85
and 86 , is formed into a curved-face shape corresponding to the
' CA 02293000 1999-12-21
outer peripheral surface of the roller 28.
The face of the tip-end connecting portion 19b, which is
opposed to the roller 28, is formed into a curved-face shape,
so that the distance between the face and the roller 28 becomes
smaller at a lower location. Thus, in an area corresponding
to the axially lower half of the tappet screw 27, the thickness
of the tip-end connecting portion 19b in a direction
perpendicular to the axis of the tappet screw 27 is larger than
that in an area corresponding to the axially upper half of the
tappet screw 27.
The face of the swinging support portion 20a of the second
driving rocker arm 20 which is opposed to the roller 29 and the
face of the tip-end connecting portion 20b which is opposed to
the roller 29, are formed as in the swinging support portion
19a and the tip-end connecting portion 19b in the first driving
rocker arm.
Referring carefully to Fig.7, a lower connecting wall 87
interconnecting lower portions of base ends of the first and
second wall portions 331 and 332 is projectingly provided on
the swinging support portion 21a of the free rocker arm 21 in
such a manner that it is in proximity to and opposed to an outer
peripheral surface of a lower portion of the roller 30 . An upper
connecting wall 88 interconnecting upper portions of the base
ends of the first and second wall portions 331 and 332 is also
projectingly provided on the swinging support portion 21a of
the free rocker arm 21 in such a manner that it is in proximity
' CA 02293000 1999-12-21
70488-153 21
to and opposed to an outer peripheral surface of an upper portion
of the roller 30. The distance between the lower connecting
wall 87 and the roller 30 is set smaller than the distance between
the upper connecting wall 88 and the roller 30. The lower
connecting wall 87 is in proximity to and opposed to the outer
peripheral surface of the lower portion of the roller 30 to such
an extent that the oil can be once retrained between the lower
connecting wall 87 and the roller 30.
Moreover, the lower connecting wall 87 is connected to
the lower portion of the first support wall portion 331 at a
location corresponding to the second recess 81 for
accommodating the swaged lower end of the pin 47 for fixing
the support shaft 43 to the free rocker arm 21, and is also
connected to the second support wall portion 332 at a location
corresponding to a receiving portion 92 which is pro,~ectingly
provided at the lower portion of the second support wall 331
to abut against the lost motion mechanism 58. The face of the
swinging support portion 21a, which is opposed to the roller
30 between the lower and upper connecting walls 87 and 88, is
formed into a curved-face shape corresponding to the outer
peripheral surface of the roller 30.
The associative operation switching means 23 includes a
timing piston 63 capable of switching the associative operation
and the release of the associative operation of the first
driving rocker arm 19 and the free rocker arm 21 ad j acent each
other, a cylindrical switching piston 64 capable of switching
CA 02293000 1999-12-21
' 22
the associative operation and the release of the associative
operation of the free rocker arm 21 and the second driving rocker
arm 20 adjacent each other, a bottomed cylindrical limiting
member 65 which is in contact with the switching piston 64 on
a side opposite to the timing piston 63, and a return spring
66 for biasing the limiting member 65 toward the switching
piston 64.
The timing piston 63 is slidably fitted in the support
shaft 41 in the first driving rocker arm 19, and a hydraulic
pressure chamber 67 is defined between the closed end of the
fitting bore 371 with one end of the support shaft 41 fitted
therein and one end of the timing piston 63. An oil passage
68 is provided, for example, coaxially within the rocker shaft
22 and connected to a hydraulic pressure source through a
control valve ( both not shown ) , and a communication bore 69 is
provided in the rocker shaft 22 to ensure that a communication
passage 70 provided in the first support wall portion 331 of
the first driving rocker arm 19 with one end leading to the
hydraulic pressure chamber 67 is normally in communication with
the oil passage 68.
Referring also to Fig.8, the communication passage 70 is
provided in the first driving rocker arm 19 on the side of the
first support wall portion 311 to extend along a plane
substantially perpendicular to a direction of the arrangement
of the rocker arms 19, 20 and 21, i.e., in a direction along
the axis of the rocker shaft 22 in this embodiment , and has such
' CA 02293000 1999-12-21
23
a cross sectional shape with a length longer in a direction
perpendicular to the direction of arrangement of the rocker arms
19, 20 and 21 than the length in the direction substantially
parallel to the direction of arrangement of the rocker arms 19 ,
20 and 21. The communication bore 69 is provided in the rocker
shaft 22 in a range larger in a circumferential direction of
the rocker shaft 22 than a range in which the communication
passage 70 faces the outer surface of the rocker shaft 22, in
order to ensure that the oil passage 68 is normally in
communication with the communication passage 70, irrespective
of the swinging state of the first driving rocker arm 19.
Moreover, the other end of the communication passage 70 opens
into a side of the first driving rocker arm 19, and an
intermediate portion of the communication passage 70 is blocked
by the rocker shaft 22.
Referring also to Fig.9, a bulge portion 19c bulging
outwards to define the communication passage 70 is provided on
an outer surface of the first driving rocker arm 19 at one end
in the direction of arrangement of the rocker arms 19 to 21.
A plurality of, e.g., two ribs 71, 71 are provided between a
side edge 19d and the bulge portion 19c on the outer surface
of the first driving rocker arm 19.
The communication passage 70 is provided in the first
driving rocker arm 19 in such a manner that a portion thereof
is disposed closer to the roller 28 than one end of the support
shaft 41 in a direction parallel to the axis of the rocker shaft
' CA 02293000 1999-12-21
24
22. A notch 72 having a shape corresponding to the
communication passage 70 is provided in that area of the one
end of the support shaft 41 which corresponds to the
communication passage 70 . Thus , a working oil flowing through
the communication passage 70 is conducted to the hydraulic
pressure chamber 67, so that its flow cannot be obstructed.
The switching piston 64 is slidably fitted in the support
shaft 43 in the free rocker arm 21, so that one end thereof is
in contact with the other end of the timing piston 63 for sliding
movement relative to each other.
The limiting member 65 is formed into a bottomed
cylindrical shape and slidably fitted in the support shaft 42
in the second driving rocker arm 20, so that a closed end of
the limiting member 65 is in contact with the other end of the
switching piston 64 for being capable of sliding movement
relative to each other. A stop ring 73 is mounted to an inner
surface of the support shaft 42 to abut against the limiting
member 65 to inhibit the falling-off of the limiting member 65
from the support shaft 42. The return spring 66 is mounted
between the closed end of the second fitting bore 38z in the
second driving rocker arm 20 and the limiting member 65, and
an open bore 74 is formed in the closed end of the second fitting
bore 382.
In such associative operation switching means 23 , in the
low-speed operational region of the engine, the hydraulic
pressure in the hydraulic pressure chamber 67 is relatively low;
' CA 02293000 1999-12-21
contact faces of the timing piston 63 and the switching piston
64 are at a location corresponding to between the first driving
rocker arm 19 and the free rocker arm 21; and contact faces of
the switching piston 64 and the limiting member 65 are at a
location corresponding to between the free rocker arm 21 and
the second driving rocker arm 20. Therefore, the rocker arms
19 , 20 and 21 are in relatively swingable states , such that the
intake valves VI are opened and closed at a timing and in a lift
amount depending on the low-speed valve operating cams 25 , 25 .
In the high-speed operational region of the engine, a
relatively high hydraulic pressure is applied to the hydraulic
pressure chamber 67, whereby the timing piston 63 is fitted into
the support shaft 43 in the free rocker arm 21, while urging
the switching piston 64 , and the switching piston 64 is fitted
into the support shaft 42 in the second driving rocker arm 20,
while urging the limiting member 65 . Therefore, the rocker arms
19, 20 and 21 are brought into an integrally connected state,
such that the intake valves VI are opened and closed at a timing
and in a lift amount depending on the high-speed valve operating
cam 26.
Referring also to Figs.l0 and 11, a lubricating oil
passage 76, which normally leads to the oil passage 68 in the
rocker shaft 22 , is provided in one of the support wall portions
331 and 332 of the free rocker arm 21 in which the receiving
portion 62 is provided, i . a . , in the second support wall portion
332, in such a manner one end of the lubricating oil passage
CA 02293000 1999-12-21
26
76 opens into the inner surface of the second fitting bore 392.
A groove 77 is provided in the inner surface of the second fitting
bore 392. One end of the groove 77 leads to one end of the
lubricating oil passage 76 , and the other end of the groove 77
opens toward the bearings 55.
The lubricating oil passage 76 is provided in the second
support wall portion 332 to extend along a plane S extending
perpendicular to the axis of the support shaft 43 and through
an abutment point P between receiving portion 62 and the lifter
60 of the lost motion mechanism 58.
Moreover, the lubricating oil passage 76 is formed to have
such a cross sectional shape with the length longer in the
direction substantially perpendicular to the direction of
arrangement of the rocker arms 19 to 21 than the length in the
direction substantially parallel to the direction of
arrangement of the rocker arms 19 to 21. A communication bore
78 is provided in the rocker shaft 22 in a range larger in the
circumferential direction of the rocker shaft 22 than a range
in which the lubricating oil passage 76 faces the outer surface
of the rocker shaft 22, in order to ensure that the oil passage
68 is normally in communication with the lubricating oil passage
76, irrespective of the swinging state of the free rocker arm
21. The other end of the lubricating oil passage 76 opens into
a side of the free rocker arm 21, and an intermediate portion
of the lubricating oil passage 76 is blocked by the rocker shaft
22.
CA 02293000 1999-12-21
27
Each of the rocker arms 19, 20 and 21 is formed from metal
by injection molding. In carrying out the metal injection
molding, the following steps may be sequentially conducted: a
step of kneading a starting powder material and a binder such
as wax and the like, a step of granulating a compound produced
in the kneading step to provide a pellet , a step of sub jecting
the pellet to injection molding in a mold to shape the pellet,
a step of heating the shaped product to remove the binder, and
a step of subjecting the resulting product to a sintering
treatment.
Referring to Figs . 12 and 13 , a spark plug 91 is mounted
in the cylinder head 11 to face the central portion of a
combustion chamber 90 in each of the cylinders. The cylinder
head 11 is provided with a mounting bore 92 for mounting of the
spark plug 91, and a spark plug insertion tube 93 is mounted
in the cylinder head 11 to extend upwards through the mounting
bore 92.
The intake-side valve operating system 17I for driving
the pair of intake valves VI , VI to open and close them and the
exhaust-side valve operating system 17E for driving the pair
of exhaust valves VE, VE to open and close them are disposed
above the cylinder head 11 in such a manner that the spark plug
insertion tube93aresandwiched between thesystems. Moreover,
the exhaust-side valve operating system 17E is constructed in
the same manner as is the intake-side valve operating system
17I, and hence, mutually corresponding portions of the
' CA 02293000 1999-12-21
28
intake-side and exhaust-side valve operating systems 17I and
17E are only shown in Figs. l2 and 13 with the same reference
characters affixed thereto, and a detailed description of the
exhaust-side valve operating system 17E is omitted.
The spark plug insertion tube 93 is disposed between the
free rocker arms 21, 21 included in the intake-side and
exhaust-side valve operating systems 17I and 17E . A notch 94
recessed on the opposite side to the spark plug insertion tube
93 is provided in that portion of the swinging support portion
21a of each of the free rocker arms 21, which is opposed to the
spark plug insertion tube 93.
The notch 94 is formed so that it is curved in
correspondence to the outer peripheral surface of the spark plug
insertion tube 93 which is circular in cross section, and the
radius of curvature of the notch 94 is set larger than the radius
of the outer surface of the spark plug insertion tube 93.
Moreover, the notch 94 is provided at the central portion of
the swinging support portion 21a as viewed in a direction along
the axis of the rocker shaft 22. The deepest portion of the
notch 94 ( the center of the spark plug insertion tube 93 ) and
a portion of the roller 30 supported on the free rocker arm 21
(preferably, the axially central portion of the roller 30 as
in this embodiment ) are disposed in the same plane perpendicular
to the axis of turning movement of the free rocker arm 21, i . a . ,
the axis of the rocker shaft 22.
In addition, the notch 94 is provided in the swinging
CA 02293000 1999-12-21
29
support portion 21a within the width of the opening 36 provided
in the free rocker arm 21, i . a . , in a section corresponding to
a portion between the first and second support walls 331 and
332 in the free rocker arm 21 to accommodate the roller 30.
Arcuate bulged portions 95, 95 bulged outwards are formed at
opposite ends of the swinging support portion 21a along the axis
of the rocker shaft 22 in such a manner that the notch 94 is
sandwiched between the portions 95, 95.
A lubricating oil passage 76 is provided in the second
support wall 332 of the free rocker arm 21 to normally lead to
the oil passage 68 in the rocker shaft 22 in such a manner that
one end of the oil passage 76 opens into the inner surface of
the second fitting bore 392. The other end of the lubricating
oil passage 76 is disposed at a location deviated from the notch
94 along the axis of the rocker shaft 22, and opens into the
outer surface of one of the bulged portions 95, 95.
Further, lower portions of the base ends of the support
walls 331 and 332 of the free rocker arm 21 are interconnected
by a lower connecting wall 87 , and upper portions of the base
ends of the support walls 331 and 332 are interconnected by an
upper connecting wall 88. At least a portion of the notch 94
(the whole in this embod3.ment) and at least a portion of the
lower connecting wall 87 (central portions of the lower and
upper connecting walls 87 and 88 in this embodiment) are
disposed in the same plane perpendicular to the axis of swinging
movement of the free rocker arm 21, i . a . , the axis of the rocker
CA 02293000 1999-12-21
shaft 22.
Vertically extending grooves are provided in outer
surfaces of those portions of support walls 331 and 332 of the
free rocker shaft 22 which are closer to the swinging support
portion 21a. These grooves define oil grooves 96, 96, with
their upper ends opening in the upper portion of each of the
rocker arms 19, 20 and 21, between the adjacent first driving
rocker arm 19 and free rocker arm 21 as well as between the
adjacent second driving rocker arm 20 and free rocker arm 21.
The operation of the first embodiment will be described
below. The support shafts 41 to 43 for rotatably supporting
the rollers 28 to 30 for alleviating the valve operating load
are fixed to the rocker arms 19 to 21, but the opposite ends
of each of the support shafts 41 to 43 are fitted in the first
fitting bores 371, 381 and 391 and the second fitting bores 372,
382 and 392 in the rocker arms 19, 20 and 21, respectively. The
pin 47 inserted in the insertion bore 44 provided in the second
support wall portion 312 of the first driving rocker arm 19 is
engaged in the engage groove 50 in the support shaft 41; the
pin 48 inserted in the insertion bore 45 provided in the first
support wall portion 321 of the second driving rocker arm 20
is engaged in the engage groove 51; and the pin 49 inserted in
the insertion bore 46 provided in the first support wall portion
331 of the free rocker arm 21 is engaged in the engage groove
52. This inhibits the axial movement of the support shafts 41
to 43 and the rotation of the support shafts 41 to 43 about the
CA 02293000 1999-12-21
70488-153 31
axes and hence, the support shafts 41 to 43 can be fixed to the
rocker arms 19 to 21 in a simple structure.
In fixing the pins 47 to 49 to the corresponding rocker
arms 19 to 21, the opposite ends of each of the pins 47 to 49
inserted in the insertion bores 44 to 46 are swaged. Therefore,
even if each of the pins 47 to 49 is of a small diameter, the
fixing is easy, as compared with a case where the pin is
press-fitted, thereby enhancing the operability to ensure that
the pins 47 to 49 can be reliably fixed to the rocker arms 19
to 21.
Moreover, the pins 47 to 49 are inserted into the insertion
bores 44 to 46 rather than being press-fitted into the bores ,
respectively. The inside diameters of the insertions bores 44
to 46 may be set with relatively large margins , relative to the
outside diameters of the pins 47 to 49 , and the widths of the
engage grooves 50 to 52 may be also set with relatively large
margins, relative to the diameters of the pins 47 to 49. In
this case, even if the circumferential positions of the support
shafts 41 to 43 are not established exactly, it is easy to insert
the pins 47 to 49 into the insertion bores 44 to 46 to bring
them into engagement in the engage grooves 50 to 52, thereby
facilitating the operation of fixing the pin 47 to 49 to the
rocker arms 19 to 21.
The opposite ends of each of the pins 47 to 49 are swaged
by the flat punches 82 and 83 and hence, even if the swaging
positions of the flat punches 82 and 83 relative to the pins
CA 02293000 1999-12-21
70488-153 32
47 to 49 are slightly displaced, the opposite ends of the pins
47 to 49 can be swaged reliably by setting the diameters of
the flat punches 82 and 83 larger than the diameters of the pins
47 to 49 and hence, a reduction in rigidity of each of the swaged
portions due to the displacement of the swaging positions
cannot be produced. Moreover, the inside diameters of the
recesses 80, 81 are set larger than the outside diameters of
the flat punches 82 and 83, so that the flat punches 82 and 83
can be accommodated in the recesses 80, 81 leading to the
opposite ends of the insertion bores 44 to 46. Therefore, by
swaging the opposite ends of the pins 47 to 49 within the
recesses 80 , 81, it is ensured that the swaged portions cannot
protrude from the outer surfaces of the rocker arms 19 to 21.
Moreover, the lengths of the insertion bores 44 to 46 and thus,
of the pins 47 to 49, can be reduced by amounts corresponding
to the provision of the recesses 80, 81, and the it is possible
to prevent the intermediate portions of the pins 47 to 49 from
being deformed due to the swaging to the utmost, thereby
enhancing the accuracy of positioning of the support shafts 41
to 43 by the pins 47 to 49, and at the same time, providing
reductions in entire weights of the rocker arms 19 to 21 to
alleviate the inertial weights of the rocker arms 19 to 21. Thus ,
it is possible to conveniently accommodate the high-speed
rotation of the internal combustion engine.
Further, since the hardness of at least those portions
of the pins 47 to 49 which engage the engage grooves 50 to 52
70488-153 CA 02293000 1999-12-21
33
(the areas subjected to the high-frequency hardening) is
relatively high (e.g., in the range of 579 to 832 in unit of
H~), it is possible to prevent the wearing and deformation of
the pins 47 to 49 to the utmost to enable the reliable positioning
of the support shafts 41 to 43. In addition, since the hardness
of the opposite ends of the pins 47 to 49 ( the areas not sub jected
to the high-frequency hardening) is relatively low (e.g., in
the range of 180 to 260 in unit of H~) , the swaging operation
is facilitated, and the swaging accuracy is also enhanced.
The communication passage 70 is provided in the first
driving rocker arm 19 to extend in the plane substantially
perpendicular to the direction of arrangement of the rocker arms
19 to 21 to connect the oil passage 68 in the rocker shaft 22
and the hydraulic pressure chamber 67 in the associative
operation switching means 23 to each other. The communication
passage 70 has a cross sectional shape with a length longer in
the direction substantially perpendicular to the direction of
arrangement of the rocker arms 19 to 21 than the length in the
direction substantially parallel to the direction of
arrangement of the rocker arms 19 to 21. Therefore, it is
possible to reduce, to the utmost, the space occupied in the
direction substantially parallel to the direction of
arrangement of the rocker arms 19 to 21 by the communication
passage 70, and to correspondingly reduce the size of the first
driving rocker arm 19.
Moreover, in the first driving rocker arm 19, one end of
CA 02293000 1999-12-21
34
the support shaft 41 is fitted into the first fitting bores 371
in the first support wall portion 311, whereby the support shaft
41 is fixed to the first driving rocker arm 19, but the
communication passage 70 is provided in the first driving rocker
arm 19 on the side of the first support wall portion 311.
Therefore, the communication passage 70 can be disposed in the
first driving rocker arm 19, while avoiding an increase in
thickness of the first support wall portion 311 for fixing the
support shaft 41 supporting the roller 28. Moreover, since the
notch 72 having the shape corresponding to the communication
passage 70 is provided in the area of the one end of the support
shaft 41 which corresponds to the communication passage 70, it
is possible to dispose the communication passage 70 in more
proximity to the roller 28 , while ensuring a sufficient contact
area of the support shaft 41 with the first fitting bore 371
in the first support wall portion 311 included in the first
driving rocker arm 19 to ensure the support strength of the
support shaft 41 in the first driving rocker arm 19. Thus, it
is possible to more reduce the size of the first driving rocker
arm 19.
In the multi-cylinder internal combustion engine as
applied in this embodiment, it is possible to remarkably reduce
the size of the cylinder head 11 by enabling the reduction in
size of the first driving rocker arm 19, as described above.
Provided on the outer surface of the first driving rocker
arm 19 at one end thereof in the axial direction of the rocker
CA 02293000 1999-12-21
shaft 22 is the bulge portion 19c bulging outwards to define
the communication passage 70, and the ribs 71, 71 connecting
the side edge portion 19d and the bulge portion 19c on the outer
surface to each other. Therefore, it is possible to reduce the
weight of the first driving rocker arm 19, while ensuring the
rigidity of the bulge portion 19c defining the communication
passage 70.
Further, the communication passage 70 is provided in the
first driving rocker arm 19 on the side of the first support
wall portion 311, and the insertion bore 44 for fixing the
support shaft 41 is provided in the second support wall portion
312 with the roller 28 sandwiched between the first and second
support wall portions 311 and 312. Therefore, it is possible
to avoid an increase in size of the first driving rocker arm
19 to ensure a space for provision of the insertion bore 44,
and additionally, the provision of the insertion bore 44 at a
location relatively spaced apart from the communication passage
70 which is cavity, is convenient for the rigidity of the first
driving rocker arm 19.
The lubricating oil passage 76 is provided in the free
rocker arm 21, so that it opens at one end thereof into the inner
surface of the second fitting bore 392 and leads to the oil
pas s age 6 8 in the rocker shaf t 2 2 . The groove 7 7 is provided
in the inner surface of the second fitting bore 392, so that
one end thereof leads to one end of the lubricating oil passage
76 and the other end opens toward the needle bearings 55.
CA 02293000 1999-12-21
36
Therefore, the lubricating oil is supplied from the oil passage
68 through the lubricating oil passage 76 and the groove 77 to
the needle bearings 55 . Thus , the supplying of the oil to the
needle bearings 55 can be performed in a simple structure in
which the lubricating oil passage 76 is provided in the free
rocker arm 21 and the groove 77 is provided in the inner surface
of the second fitting bore 392. Therefore, it is unnecessary
to bore the support shaft 43 for the purpose of introduction
of the lubricating oil and hence, there is no possibility that
a reduction in rigidity of the support shaft 43 is brought about,
and the number of processing steps is decreased.
The free rocker arm 21 follows the high-speed valve
operating cam 26 having the cam profile for the high-speed
operation of the engine, and has a relatively large inertial
weight, and the load to the needle bearings 55 is relatively
large. However, the lubricating oil can be supplied
effectively to the needle bearings 55 in the simple structure
as described above, the load applied to the needle bearings 55
can be alleviated.
Moreover, the lubricating oil passage 76 is formed to have
a cross sectional shape with the length longer in the direction
substantially perpendicular to the direction of arrangement of
the rocker arms 19 to 21 than the length in the direction
substantially parallel to the direction of arrangement of the
rocker arms 19 to 21. Thus , the space occupied in the direction
parallel to the direction of arrangement of the rocker arms 19
CA 02293000 1999-12-21
37
to 21 by the lubricating oil passage 76, and the size of the
free rocker arm 21 can be reduced, whereby the size of the
cylinder head 11 of the multi-cylinder internal combustion
engine can be reduced.
In the free rocker arm 21, the lubricating oil passage
76 is provided in the second support wall portion 332, and the
insertion bore 46 for fixing the support shaft 43 is provided
in the first support wall portion 331. Therefore, it is
possible to ensure the space for provision of the insertion bore
46, while avoiding an increase in size of the free rocker arm
21. In addition, the provision of the insertion bore 44 at the
location relatively spaced apart from the lubricating oil
passage which is the cavity, is convenient for the rigidity of
the free rocker arm 21.
The free rocker arm 21 includes the receiving portion 62
which is in contact with the lifter 60 of the lost motion
mechanism 58. The receiving portion 62 is disposed at the
position radially outside the support shaft 43 in the diagram
of projection onto the plane perpendicular to the axis of the
support shaft 43, and is integrally provided on the second
support wall portion 332 in the range corresponding to at least
a portion of the area of the support shaft 43 which is fitted
in the second support wall portion 332. In other words, the
receiving portion 62 is integrally provided on the second
support wall portion 332 in such a manner that at least a portion
of the area of the support shaft 43, which is fitted in the second
CA 02293000 1999-12-21
38
support wall portion 332, exists on the plane perpendicular to
the axis of the support shaft 43 and extending through the
abutment point P between the receiving portion 62 and the lost
motion mechanism 58. In this embodiment, the second fitting
bore 392 with the support shaft 43 fitted therein is provided
in the second support wall portion 332 over the entire width
along the axis of the support shaft 43. Therefore, the
receiving portion 62 is disposed radially outside the support
shaft 43 within the width of the second support wall portion
332 and integrally provided at the lower portion of the second
support wall 332 to abut against the lifter 60 of the lost motion
mechanism 58 disposed below the free rocker arm 21.
Therefore, the receiving portion 62 can be disposed
axially outside the roller 30, thereby simplifying the
structure of the free rocker arm 21. Since the receiving
portion 62 cannot protrude from the free rocker arm 21 along
the axial direction of the support shaft 43, it is possible to
avoid an increase in size of the free rocker arm 21 in the axial
direction of the support shaft 43, and the inertial weight is
decreased. Thus, it is possible to conveniently accommodate
the high-speed rotation of the internal combustion engine.
Especially, when the plurality of rocker arms 19, 20 and 21 are
disposed adjacent one another in the axial direction of the
rocker shaft 22 for each of the cylinders in the multi-cylinder
internal combustion engine as in this embodiment, the space in
the direction along the axis of the rocker shaft 22 , i . a . , the
CA 02293000 1999-12-21
39
axes of the support shafts 41, 42 and 43 is limited, but a surplus
space is provided in the direction perpendicular to the axes
of the support shafts 41 to 43. Thus, the receiving portion
62 and the lost motion mechanism 58 can be disposed utilizing
an unoccupied.. space effectively.
The provision of the receiving portion 62 enhances the
support rigidity of the support shaft 43 on the second support
wall portion 332.
Further, the receiving portion 62 is integrally provided
at the lower portion of the second support wall 332 in such manner
that it is disposed between ( 1 ) the straight line L2 extending
through the axis of the rocker shaft 22 in a direction
perpendicular to the straight line L1 extending through the axis
of the rocker shaft 22 and the axis of the support shaft 43 and
(2) the straight line L3 extending through the axis of the
support shaft 43 in a direction perpendicular to the straight
line L1. Therefore, it is possible to avoid an increase in size
of the free rocker arm 21 due to the provision of the receiving
portion 62, and to increase the rigidities of the supported
portion of the free rocker arm 21 on the rocker shaft 22 and
the supported portion of the free rocker arm 21 on the support
shaft 43. Namely, the lower portion of the second support wall
332 can be formed into an upward recessed shape, if the receiving
portion 62 is not provided, but the receiving portion 62 is
disposed, effectively utilizing an unoccupied space produced
by the recessed portion. Therefore, it is possible to avoid
CA 02293000 1999-12-21
the increase in size of the free rocker arm 21. In addition,
the rigidities of the supported portion of the free rocker arm
21 on the rocker shaft 22 and the supported portion of the free
rocker arm 21 on the support shaft 43 are increased by the
provision of the receiving portion 62 with such recessed portion
eliminated.
Moreover, the support shaft 43 is fixed by the pin 49 on
the side of the first support wall 331, and the receiving portion
62 is provided on the second support wall 332. Therefore, the
size and disposition of the insertion bore 46 for insertion and
fixing of the pin 49 cannot be limited by the receiving portion
62, and it is possible to ensure that the load from the lost
motion mechanism 58 is difficult to be applied to the pin 49,
thereby increasing the fixing strength of the support shaft 43.
In addition to this, since the receiving portion 62 is provided
on the second support wall 332, it is possible to avoid a
reduction in rigidity of the second support wall 332, despite
the provision of the lubricating oil passage 76 which is the
cavity in the second support wall 332, and to compensate for
a reduction in weight of the second support wall 332 caused by
the lubricating oil passage 76 being the cavity, by the
receiving portion 62, thereby improving the balance of the
weight of the support wall portions 331 and 332.
Further, the free rocker arm 21 is supported on the rocker
shaft 22 in such manner that the first support wall portion 331
provided with the insertion bore 46 for fixing the support shaft
CA 02293000 1999-12-21
41
43 is disposed on the side of the first driving rocker arm 19.
The second driving rocker arm 20 is supported on the rocker shaft
22 in such manner that the first support wall portion 321
provided with the insertion bore 45 for fixing the support shaft
42 is disposed. on the side of the first driving rocker arm 19 .
The support shafts 43 and 42 are fixed to the free rocker arm
21 and the second driving rocker arm 20 on the side where the
timing piston 63 and the switching piston 64 of the associative
operation switching means 23 are inserted. Therefore, the
insertion of the pistons 63 and 64 into the support shafts 43
and 42 is smooth and thus , the associative switching operation
of the associative operation switching means 23 is smooth.
Each of the rocker arms 19 to 21 is formed from metal by
injection molding. The communication passage 70 which is out
of round, the fitting bores 371 and 372 and the insertion bore
44 can be defined simultaneously with the formation of the first
driving rocker arm 19 , and the fitting bores 381 and 382 , the
insertion bore 45 and the open bore 74 can be defined
simultaneously with the formation of the second driving rocker
arm 20. The lubricating oil passage 76 which is out of round,
the fitting bores 391 and 392 and the insertion bore 46 can be
defined simultaneously with the formation of the free rocker
arm 21. Therefore, the number of post-processings of the rocker
arms 19 to 21 can be decreased to the utmost to provide an
enhancement in productivity. It is possible to simply form the
relatively complicated structure in which the lower connecting
CA 02293000 1999-12-21
42
walls 85 , 87 and the upper connecting walls 86 , 88 protrude from
the swinging support portions 19a to 21a, and to easily form
the rocker arms 19 to 21 each having an optimal shape with an
increase in rigidity and a reduction in weight taken into
consideration. Further, the free rocker arm 21 has the
receiving portion 62 integrally provided thereon, and it is
possible to easily form the free rocker arm 21 having the
receiving portion 62 integrally provided thereon by the metal
injection molding.
In the rocker arms 19 to 21, the lower connecting walls
85, 87, which interconnect the lower portions of the base ends
of the pair of support walls 311, 312, 321, 322, 331 and 332
included in the rocker arms 19 to 21 and which are in proximity
to and opposed to the outer peripheral surfaces of the lower
portions of the rollers 28 to 30 , are pro jectingly provided on
the swinging support portions 19a to 21a swingably supported
on the rocker shaft 22 , and the upper connecting walls 86 , 88 ,
which interconnect the upper portions of the base ends of the
support walls 311, 312, 321, 322, 331 and 332 and which are in
proximity to and opposed to the outer peripheral surfaces of
the upper portions of the rollers 28 to 30 , are also pro jectingly
provided on the swinging support portions 19a to 21a. Therefore,
in cooperation with the formation of those faces of the swinging
support portions 19a to 21a, which are opposed to the rollers
28 to 30, into the curved faces between the lower connecting
walls 85, 87 and the upper connecting walls 86, 88, it is possible
CA 02293000 1999-12-21
43
to increase the rigidities of supporting of the support shafts
41 to 43 by the support walls 311, 312, 321, 322, 331 and 332 and
the same time, to increase the rigidities of the entire rocker
arms 19 to 21, and it is possible to avoid an increase in weight
due to the increases in the rigidities to the utmost by the
formation of the curved faces.
Moreover, the lower connecting walls 85, 87 and the upper
connecting walls 86, 88 are disposed, effectively utilizing the
spaces between the rollers 28 to 30 and the swinging support
portions 19a to 21a, and the sizes of the rocker arms 19 to 21
cannot be increased due to the lower connecting walls 85, 87
and the upper connecting walls 86, 88.
In addition, since the lower connecting walls 85, 87 are
in proximity to and opposed to the lower portions of the rollers
28 to 30, the oil can be once retained between the lower
connecting walls 85, 87 and the rollers 28 to 30, and the oil
retained between the lower connecting walls 85, 87 and the
rollers 28 to 30 can be conducted to the needle bearings 53 to
55 between the rollers 28 to 30 and the support shafts 41 to
43 to reduce the resistance to the rotation of the rollers 28
to 30. In this case, the oil from the above can be conducted
effectively to between the lower connecting walls 85, 87 and
the rollers 28 to 30, because the distances between the lower
connecting walls 85 , 87 and the rollers 28 to 30 are set smaller
than distances between the upper connecting walls 86, 88 and
the rollers 28 to 30. Additionally, the beaten loads received
CA 02293000 1999-12-21
44
from the valve operating cams 25 and 26 disposed above the
support shafts 41 to 43 are larger at the lower portions than
at the upper portions of the support shafts 41 to 43. The lower
portions of the support walls 311, 312, 321, 322, 331 and 332
supporting the lower portions of the support shafts 41 to 43
are reinforced by the lower connecting walls 85 and 87
protruding in the amount larger than the amount of protrusion
of the upper connecting walls 86 and 88. This is convenient
for increasing the rigidities of the support walls 311, 312,
321, 322, 331 and 332.
Further, in the first and second driving rocker arms 19
and 20 , those faces of the tip-end connecting portions 19b and
20b which are opposed to th rollers 28 and 29 are formed into
the curved shapes corresponding to the outer peripheral
surfaces of the rollers 28 and 29 , so that the distances between
those faces and the rollers 28 and 29 become smaller at a lower
location. Therefore, the oil can be also retained effectively
in lower portions of the areas between the rollers 28 and 29
and the tip-end connecting portions 19b and 20b, thereby further
reducing the resistance to the rotation of the rollers 28 and
29 and at the same time, increasing the thickness of the tip-end
connecting portion 19b in a direction perpendicular to the axis
of the tappet screw 27 in an area corresponding to the axially
lower half of the tappet screw 27 to increase the support
rigidity of the tappet screw 27.
Yet further, in the rocker arms 19 to 21, the second recess
CA 02293000 1999-12-21
81 faced by the lower ends of the pins 47 to 49 for fixing the
support shafts 41 to 43 opens into the lower surfaces of the
support wall portions 312, 321 and 331 at locations corresponding
to the connections to the lower connecting walls 85 and 87.
Therefore, it is possible to suppress reductions in rigidities
of the support wall portions 312, 321 and 331 due to the provision
of the second recess 81 to the utmost.
On the other hand, the receiving portion 62 provided on
the free rocker arm 21 to abut against the lost motion mechanism
58 is disposed on the second support wall 332 and connected to
one end of the lower connecting wall 87. Therefore, it is
possible to increase the rigidity of the receiving portion 62
to which the load applied from the lost motion mechanism 58,
by the lower connecting wall 87.
The notch 94 recessed on the opposite side to the spark
plug insertion tube 93 is provided in that portion of the
swinging support portion 21a of each of the free rocker arms
21, which is opposed to the spark plug insertion tube 93.
Therefore, the spark plug insertion tube 93 and the free rocker
arm 21 can be disposed in close proximity to each other to
contribute to a reduction in weight of the free rocker arm 21
and a reduction in size of the valve operating chamber defined
in the internal combustion engine in such a manner to
accommodate the intake-side and exhaust-side valve operating
systems 17I and 17E in the engine. Moreover, at least a portion
of the notch 94 (the whole in this embodiment) and at least a
CA 02293000 1999-12-21
46
portion of the lower connecting wall 87 ( the central portions
of the lower and upper connecting walls 87 and 88 ) are disposed
in the same plane perpendicular to the axis of the rocker shaft
22. Therefore,. it is possible to compensate for the reduction
in rigidity of the swinging support portion 21a due to the
provision of the notch 94 by the lower and upper connecting walls
87 and 88.
The notch 94 is formed so that it is curved in
correspondence to the outer peripheral surface of the spark plug
insertion tube 93 which is circular in cross section, and hence,
the free rocker arm 21 can be disposed in more proximity to the
spark plug insertion tube 93 , while avoiding the reduction in
rigidity of the free rocker arm 21 to the utmost. Moreover,
the radius of curvature of the notch 94 is set larger than the
radius of the outer surface of the spark plug insertion tube
93 and hence, the free rocker arm 21 can be disposed in further
proximity to the spark plug insertion tube 93, while avoiding
the interference of the swinging free rocker arm 21 and the spark
plug insertion tube 93 with each other, and it is possible to
suppress the reduction in rigidity of the free rocker arm 21
due to the provision of the notch 94 to a small level.
The deepest portion of the notch 94 and a portion of the
roller 30 supported on the free rocker arm 21 (preferably, the
axially central portion of the roller 30 as in this embodiment )
are disposed in the same plane perpendicular to the axis of the
rocker shaft 22, and moreover, the notch 94 is provided in the
CA 02293000 1999-12-21
47
swinging support portion 21a within the width of the opening
36 provided in the free rocker arm 21 to accommodate the roller
30. Therefore, the notch 94 is disposed at a location deviated
from sites where a load from the intake valve VI or the exhaust
valve VE and a load from the high-speed valve operating cam 26
are applied to the free rocker arm 21, and even if a reduction
in rigidity of the free rocker arm 21 due to the provision of
the notch 94 is generated, the sufficient rigidity of the entire
free rocker arm 21 can be maintained.
The arcuate bulged portions 95, 95 bulged outwards are
formed at the opposite ends of the swinging support portion 21a
along the axis of the cam shaft 22, so that the notch 94 is
sandwiched therebetween. Therefore, it is possible to
compensate for the reduction in rigidity due to the notch 94
by the bulged portions 95 , 95 , and the rigidity of the support
walls 331 and 332 to which the load from the intake valve VI
or the exhaust valve VE and the load from the high-speed valve
operating cam 26 are applied, can be increased by the bulged
portions 95, 95.
The lubricating oil passage 76 normally leading to the
oil passage 68 in the rocker shaft 22 opens into the outer surface
of the swinging support portion 21a, but is disposed at the
location deviated from the notch 94 along the axis of the rocker
shaft 22. Therefore, a reduction in rigidity of the swinging
support portion 21a cannot be produced even by the provision
of the opening in the lubricating oil passage 76 and the notch
CA 02293000 1999-12-21
48
94.
Further, the oil grooves 96, 96 with their upper ends
opening in the upper portion of each of the rocker arms 19 , 20
and 21 are defined between the adjacent first driving rocker
arm 19 and free rocker arm 21 as well as between the adjacent
second driving rocker arm 20 and free rocker arm 21. Therefore,
the provision of a special oil passage is not required, and
sections between the rocker arms 19 and 21 as well as the arms
20 and 21 can be lubricated by a scattered oil within the valve
operating chamber.
Figs. l4 and 15 show a second embodiment of the present
invention. A lubricating oil passage 76 is provided in the
second support wall portion 332 in such a manner that a center
line L4 is disposed at a location displaced toward the receiving
portion 62 from a straight line L1 extending through the axis
of the rocker shaft 22 and the axis of the support shaft 43,
i . a . , below the straight line L1. The lubricating oil passage
76 is defined to have such a cross sectional shape that it extends
long along a plane 80 which is perpendicular to the axis of the
support shaft 43 and which extends through an abutment point
between the receiving portion 62 and the lost motion mechanism
58.
With the second embodiment, although the width of the
second support wall portion 332 in the first embodiment is as
shown by a dashed line in Fig .15 , the width of the second support
wall portion 332 can be decreased as shown by a solid line in
CA 02293000 1999-12-21
49
Fig.lS. Moreover, even if the width of the second support wall
portion 332 is decreased, the rigidity of the second support
wall portion 332 cannot be reduced, because the width of the
lubricating oil passage 76 is also small. Therefore, the width
of the second support wall portion 332 can be decreased to
contribute to a reduction in size of the valve operating system,
while avoiding the reduction in rigidity of the second support
wall portion 332.
For example, the valve operating system including the
rocker arms swingably supported on the rocker shaft 22 has been
described in the above embodiments. The present invention is
applicable to a valve operating system in which each of rocker
arms is swingably supported at one end thereof by a pivot , as
disclosed in Japanese Patent Application Laid-open No.63-
230916 , and also widely applicable to a valve operating system
in an internal combustion engine, in which each of a plurality
of rocker arms 19 to 21 is operatively connected to a valve
operating cam, irrespective of the presence or absence of an
associative operation switching means 23 capable of switching
the associative connection and the release of the associative
operation of the rocker arms 19 to 21.
In addition, the present invention is applicable to a
valve operating system in which pins 47 to 49 for fixing support
shafts 41 to 43 are press-fitted into rocker arms 19 to 21. In
this case, the connection of lower connecting walls to lower
fixed portions of the pins 47 to 49 can contribute to an increase
CA 02293000 1999-12-21
in rigidities of the rocker arms 19 to 21 receiving press-fit
loads upon the press-fitting of the pins 47 to 49. Further,
the support member 22 may be mounted directly on the cylinder
head 11 and may be supported on a holder mounted on the cylinder
head 11.
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 may be made without departing from
the spirit and scope of the invention defined in claims.
