Note: Descriptions are shown in the official language in which they were submitted.
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VEHICLE BODY
FIELD OF THE INVENTION
The present invention relates to an internal combustion engine.
BACKGROUND OF THE INVENTION
There has been conventionally known an internal combustion engine having a
structure in which an oil supply passage extending across a cylinder block and
a
cylinder head branches at a wall portion of the cylinder head into an oil
supply
passage communicating with a support portion of a rocker shaft and an oil
supply
passage communicating with a support portion of a camshaft (see Japanese
Patent
Application Publication No. 2009-215923).
An internal combustion engine according to Japanese Patent Application
Publication
No. 2009-215923 is a diesel engine and a fuel injection valve is attached to
communicate with a substantial center (top portion) of each of combustion
chambers.
Moreover, this internal combustion engine is a four-valve engine and multiple
intake
and exhaust valves and multiple intake and exhaust rocker arms are arranged
side by
side in an axial direction of each of camshafts.
In the internal combustion engine, a space for forming the oil supply passage
is limited
because the shape of the cylinder head is complex and multiple members are
provided
in the cylinder head. Accordingly, when an oil supply passage capable of
securing a
sufficient amount of lubricating oil for the rocker shaft and the camshaft is
to be
formed, the oil supply passage becomes complicated and the passage length
becomes
long. Moreover, the wall portion of the cylinder head needs to be made thick
to secure
the space for forming the oil supply passage. The internal combustion engine
thus
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has a problem that securing the sufficient amount of lubricating oil and
reducing the
size and the like at the same time is difficult.
Specifically, as in Japanese Patent Application Publication No. 2009-215923,
when the
internal combustion engine has a configuration in which the fuel injection
valve is
attached to the substantial center of the combustion chamber and the multiple
rocker
arms and the like are provided side by side in the axial direction of the
camshaft, the
oil supply passage branches to extend to a bearing portion of the camshaft and
four
points in support portions of the intake and exhaust rocker shafts located on
both sides
of the bearing portion in the axial direction of the camshaft. The oil supply
passage is
thus complicated and is long depending on portions to which the oil is
supplied.
Moreover, the support portions of the rocker shafts are relatively thick in
the axial
direction of the camshaft.
Furthermore, although the internal combustion engine of Japanese Patent
Application
Publication No. 2009-215923 is a SOHC (Single OverHead Camshaft) engine, a
DOHC
(Double OverHead Camshaft) engine requires that the oil supply passage should
be
formed while avoiding the fuel injection valve or a similar measure needs to
be taken.
Accordingly, the oil supply passage may become more complicated.
Moreover, in an internal combustion engine using gasoline as fuel, an ignition
plug is
generally provided at the aforementioned position where the fuel injection
valve is
attached. As in the aforementioned diesel engine, this case also has a problem
that
securing the sufficient amount of lubricating oil and reducing the size and
the like at
the same time is difficult when an oil supply passage capable of securing a
sufficient
amount of lubricating oil for the rocker shaft and the camshaft is formed.
The present invention has been made in view of such circumstances, and an
object
thereof is to provide an internal combustion engine which can secure a
sufficient
amount of lubricating oil for rocker shafts with a shape of an oil supply
passage to the
rocker shafts being simple and thereby reducing the size and the like while
securing
sufficient amount of lubricating oil for rocker shafts.
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SUMMARY OF THE INVENTION
For the purpose of solving the above-mentioned problems, a first aspect of the
present
invention provides an internal combustion engine including: a plurality of
valves
provided in a valve chamber formed in a cylinder head; a cam holder provided
in the
valve chamber; a camshaft rotatably supported by the cam holder and having
cams
configured to open and close the plurality of valves via rocker arms; an
attachment
hole for an ignition plug or a fuel injection valve, the attachment hole
formed to
communicate with a substantial center of a combustion chamber; and rocker
shafts
configured to support the rocker arms, the rocker shafts being parallel to a
direction
of an axis of the camshaft and arranged in a distributed manner on one side
and
another side of the attachment hole, the internal combustion engine
characterized in
that the cam holder extends from a wall portion of the cylinder head toward
the
attachment hole, a downstream rocker shaft oil supply passage formed in a
cross
shape by causing two linear portions to intersect each other is formed inside
the cam
holder, and in the downstream rocker shaft oil supply passage, one of the
linear
portions extends toward the one side of the attachment hole and communicates
with
a support hole located on the one side of the attachment hole and configured
to
support the corresponding rocker shaft, while the other one of the linear
portions
extends toward the other side of the attachment hole and communicates with a
support hole located on the other side of the attachment hole and configured
to
support the corresponding rocker shaft.
A second aspect of the present invention provides the internal combustion
engine
according to the first aspect, characterized in that the rocker shafts support
the rocker
arms on one side and another side of the attachment hole in the direction of
the axis
of the camshaft in such a way that the rocker arms are swingable, and the
rocker arms
are in contact with the plurality of valves arranged on the one side and the
other side
of the attachment hole in the direction of the axis of the camshaft, an
upstream rocker
shaft oil supply passage extending in the direction of the axis of the
camshaft is formed
in the wall portion of the cylinder head, and the downstream rocker shaft oil
supply
passage extends from the upstream rocker shaft oil supply passage.
According to the first and second aspects of the present invention, it is
possible to
distribute and supply the lubricating oil to the rocker shafts located on the
one side
and the other side of the attachment hole for the fuel injection valve or the
ignition
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plug in the direction of the axis of the camshaft by using the simple-shaped
downstream rocker shaft oil supply passage which is formed inside the cam
holder
and which has the cross shape. Moreover, since the downstream rocker shaft oil
supply passage has the cross shape, it possible to make the passage lengths of
the
linear portions extending toward the one side and the other side of the
attachment
hole uniform and short, and to supply the lubricating oil to the rocker shafts
located
on the one side and the other side.
Due to this, in the internal combustion engine, while the shape of the oil
supply
passage to the rocker shafts is simple, it is possible to secure a sufficient
amount of
lubricating oil for the rocker shafts. Accordingly, size reduction and an
improvement
in production efficiency can be achieved while securing a sufficient amount of
lubricating oil for the rocker shafts.
A third aspect of the present invention provides the internal combustion
engine
according to the first or second aspect, characterized in that the rocker
shafts are
arranged in a distributed manner on one side and another side of the
attachment hole
in the direction of the axis of the camshaft, the attachment hole is provided
to extend
from the cam holder to the combustion chamber, at least part of the attachment
hole
is located between a connection portion between the support hole on the one
side of
the attachment hole in the direction of the axis of the camshaft and the
downstream
rocker shaft oil supply passage and a connection portion between the support
hole on
the other side and the downstream rocker shaft oil supply passage.
According to the third aspect of the present invention, the downstream rocker
shaft
oil supply passage can be connected to the support holes without interfering
with the
attachment hole. Moreover, providing the attachment hole closer to the rocker
shafts
can reduce a dimension of the cam holder in the extending direction thereof
and
reduce the size.
A fourth aspect of the present invention provides the internal combustion
engine
according to any one of the first to third aspects, characterized in that a
bearing portion
of the camshaft is formed above a cross portion of the downstream rocker shaft
oil
supply passage in the cam holder, and a cam oil supply passage extending from
the
cross portion to the bearing portion is formed in the cam holder.
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According to the fourth aspect of the present invention, the cam oil supply
passage is
formed to extend from the cross portion of the downstream rocker shaft oil
supply
passage where a cross-sectional area of the oil supply passage becomes
smaller. This
causes the lubricating oil to be evenly distributed to portions branching from
the cross
portion and extending downstream in the downstream rocker shaft oil supply
passage
and also facilitates supplying of the lubricating oil to the bearing portion.
Hence, the
camshaft can be preferably lubricated.
A fifth aspect of the present invention provides the internal combustion
engine
according to the second aspect, characterized in that an upstream oil supply
passage
is formed at least in the cylinder head, the upstream oil supply passage
extending
along a fastening member provided to extend across a crankcase, a cylinder
block
standing upright from the crankcase, and the cylinder head standing upright
from the
cylinder block, the upstream rocker shaft oil supply passage is connected to a
downstream end portion of the upstream oil supply passage, and the upstream
rocker
shaft oil supply passage and the downstream rocker shaft oil supply passage
are
formed on a plane orthogonal to the cylinder center axis.
According to the fifth aspect of the present invention, since the shapes of
the upstream
rocker shaft oil supply passage, the downstream rocker shaft oil supply
passage, and
the upstream oil supply passage upstream of these oil supply passages are
simple, the
oil supply passages can be easily formed with the number of processing steps
suppressed to few steps.
A sixth aspect of the present invention provides the internal combustion
engine
according to the first aspect, characterized in that the internal combustion
engine is a
four-valve engine in which the plurality of valves configured to open and
close a
single one of the combustion chamber include two intake valves and two exhaust
valves, and the rocker arms corresponding to the single combustion chamber
include
two intake rocker arms configured to open and close the intake valves and two
exhaust rocker arms configured to open and close the exhaust valves, the
camshaft
includes an intake camshaft configured to swing the intake rocker arms and an
exhaust camshaft configured to swing the exhaust rocker arms, the intake
rocker arms
and the exhaust rocker arms are each orthogonal to a direction of an axis of
the intake
camshaft or the exhaust camshaft and are arranged in a distributed manner on
one
side and another side of the attachment hole in a direction orthogonal to a
cylinder
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center axis, and the downstream rocker shaft oil supply passage includes an
intake-
side downstream rocker shaft oil supply passage and an exhaust-side downstream
rocker shaft oil supply passage.
According to the sixth aspect of the present invention, in the DOHC internal
combustion engine, the lubricating oil can be preferably supplied from the
cross-
shaped downstream rocker shaft oil supply passage to the intake rocker shafts
and the
exhaust rocker shafts.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are shown in the drawings, wherein:
Fig. 1 is a left-side view of an internal combustion engine in an embodiment
of the
present invention;
Fig. 2 is a view of a cylinder head of the internal combustion engine from
above in a
cylinder center axis direction;
Fig. 3 is a bird's-eye-view in which a vertical cross section of the internal
combustion
engine along a front-rear direction is viewed downward from above;
Fig. 4 is a bird's-eye-view in which a cross section of the internal
combustion engine
taken along an axis direction of valves arranged on a front side of the
internal
combustion engine is viewed downward from above;
Fig. 5 is a view of the cylinder head of the internal combustion engine from
above in
the cylinder center axis direction with camshafts and rocker arms being
removed; and
Fig. 6 is a cross-sectional view taken along the I-I line of Fig. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment of the present invention is described below by using the
drawings.
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Fig. 1 shows an internal combustion engine 1 in the embodiment of the present
invention. In Fig. 1 and the drawings used in the below-mentioned description,
FR
shows a front side of the internal combustion engine 1, UP shows an upper side
of the
internal combustion engine 1, and LH shows a left side of the internal
combustion
engine 1. Note that these directions are specified for the convenience of
description
of the embodiment and the present invention is not limited by the directions
of the
embodiment.
The internal combustion engine 1 includes a crankshaft 2 arranged to extend in
a left-
right direction, a crankcase 3 housing, as an integral unit, a transmission
configured
change the speed of rotational motion transmitted from the crankshaft 2, a
cylinder
block 4 standing upright from an upper portion of the crankcase 3 to extend
forward
and upward, a cylinder head 5 standing upright from an upper portion of the
cylinder
block 4, and a head cover 6 covering an upper portion of the cylinder head 5
from
above. In the embodiment, the crankcase 3, the cylinder block 4, and the
cylinder head
5 are formed by casting.
Moreover, in the embodiment, the internal combustion engine 1 is assumed to be
mounted on a motorcycle. However, the internal combustion engine of the
present
invention is not limited to an engine mounted on the motorcycle.
The internal combustion engine 1 is a four-valve four-cycle single cylinder
DOHC
engine and one cylinder bore 7 is formed in the cylinder block 4. Note that
reference
numeral Si in the drawing denotes a cylinder center axis passing through the
center
of a circular cross section of the cylinder bore 7.
A piston omitted in the drawings is fitted to the cylinder bore 7 to be
capable of
reciprocating. One end of a connection rod omitted in the drawings is
connected to
the piston and the other end of the connection rod is connected to the
crankshaft 2. A
combustion chamber 8 which is recessed upward, for example, in a dome shape is
formed on a bottom surface of a bottom wall portion (not illustrated) of the
cylinder
head 5 which comes into contact with and faces the upper portion of the
cylinder block
4.
A valve chamber 9 in which a valve train V is housed is formed above the
bottom wall
portion of the cylinder head 5 and the combustion chamber 8 described above is
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located below the valve chamber 9. The cylinder head 5 includes a front wall
portion
5F, a rear wall portion 5B, a left wall portion 5L, and a right wall portion
5R and is
formed to have a rectangular horizontal cross section (cross section in a
direction
orthogonal to the cylinder center axis Si). The front wall portion 5F, the
rear wall
portion 5B, the left wall portion 5L, and the right wall portion 5R are
located outside
the cylinder center axis Si as viewed in the cylinder center axis Si
direction. The
aforementioned bottom wall portion of the cylinder head 5 is formed inside a
space
surrounded by the front wall portion 5F, the rear wall portion 5B, the left
wall portion
5L, and the right wall portion 5R. Note that, in Fig. 1, the reference sign of
the right
wall portion 5R not illustrated in the drawing is shown in parentheses for the
sake of
convenience.
In the drawings, reference sign 5In denotes an intake port and reference sign
5Ex
denotes an exhaust port. The intake port 5In extends from the rear wall
portion 5B of
the cylinder head 5 toward the combustion chamber 8 through the bottom wall
portion of the cylinder head 5, and communicates with the combustion chamber 8
at
two portions. Air-fuel mixture supplied to the combustion chamber 8 when the
internal combustion engine 1 is driven passes through the intake port 5In.
Meanwhile, the exhaust port 5Ex extends from the front wall portion 5F of the
cylinder
head 5 toward the combustion chamber 8 through the bottom wall portion of the
cylinder head 5, and communicates with the combustion chamber 8 at two
portions.
Exhaust gas exhausted from the combustion chamber 8 when the internal
combustion
engine 1 is driven passes through the exhaust port 5Ex.
In the embodiment, since the internal combustion engine 1 is a four-valve
engine, each
of the intake port 5In and the exhaust port 5Ex has two open ends
communicating
with the combustion chamber 8. Note that the bottom wall portion of the
cylinder
head 5 is formed to have a relatively large thickness in the cylinder center
axis Si
direction because the combustion chamber 8 is formed in the bottom wall
portion to
be recessed and the intake port 5In and the exhaust port 5Ex are formed to
penetrate
the bottom wall portion.
Fig. 2 shows the inside of the cylinder head 5. Inside the cylinder head 5, a
cam chain
chamber forming wall portion 5C extending along the left wall portion 5L is
formed
on the right side of the left wall portion 5L. The cam chain chamber forming
wall
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portion 5C extends between the front wall portion 5F and the rear wall portion
5B in
the front-rear direction. As viewed in the cylinder center axis Si direction,
the inside
of the cylinder head 5 is partitioned into the valve chamber 9 and a cam chain
chamber
11 respectively on the right side and the left side of the cam chain chamber
forming
wall portion 5C.
In other words, the valve chamber 9 is formed of the front wall portion 5F,
the rear
wall portion 5B, the right wall portion 5R, and the cam chain chamber forming
wall
portion 5C and a rectangular space is formed by a horizontal cross section
(cross
section in a direction orthogonal to the cylinder center axis Si) of the valve
chamber
9. Meanwhile, the cam chain chamber 11 is formed of the front wall portion 5F,
the
rear wall portion 5B, the left wall portion 5L, and the cam chain chamber
forming wall
portion 5C.
The cam chain chamber 11 communicates with the crankcase 3 through the
cylinder
block 4 and houses a not-illustrated cam chain. The bottom wall portion of the
cylinder head 5 is open in a portion where the cam chain chamber 11 is formed.
Moreover, paired front and rear left fastening boss portions 60 are formed
integrally
with the cam chain chamber forming wall portion 5C by casting in the cam chain
chamber 11, on the left side of the cam chain chamber forming wall portion 5C,
inside
the cylinder head 5. Moreover, paired front and rear right fastening boss
portions 61
are formed integrally with the right wall portion 5R by casting on the right
side of the
right wall portion 5R, outside the cylinder head 5. A through hole extending
along
the cylinder center axis Si is formed in each of the left fastening boss
portions 60 and
the right fastening boss portions 61.
A stud bolt 62 which is a fastening member shown in Fig. 1 is inserted into
each of the
paired front and rear left fastening boss portions 60 and the paired front and
rear right
fastening boss portions 61 and the cylinder head 5 is thus fastened to the
cylinder
block 4 and the crankcase 3 by the stud bolts 62. The four stud bolts 62 are
each
provided to extend across the crankcase 3, the cylinder block 4, and the
cylinder head
5. When the cylinder head 5 is fastened to the cylinder block 4, the stud
bolts 62 are
fixed to the crankcase 3 to stand upright from the crankcase 3, and then
sequentially
inserted into the cylinder block 4 and the cylinder head 5 (the aforementioned
fastening boss portions 60, 61).
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Returning to Fig. 2, a cam holder 10 extending between the front wall portion
5F and
the rear wall portion 5B in the front-rear direction is formed in the valve
chamber 9 at
a substantially center position thereof in the left-right direction. The cam
holder 10 is
formed integrally with the front wall portion 5F and the rear wall portion 5B
by
casting.
An intake camshaft bearing portion 10In and an exhaust camshaft bearing
portion
10Ex are formed in the cam holder 10 to be arranged side by side in the front-
rear
direction. The intake camshaft bearing portion 10In is formed behind the
exhaust
camshaft bearing portion 10Ex. The intake camshaft bearing portion 10In and
the
exhaust camshaft bearing portion 10Ex are each formed in an arc shape
protruding
downward.
Referring to both of Figs. 1 and 2, the valve train V includes an intake
camshaft 12In
supported by the intake camshaft bearing portion 10In described above, an
exhaust
camshaft 12Ex supported by the exhaust camshaft bearing portion 10Ex described
above, paired intake rocker arms 13In configured to swing according to
rotation of the
intake camshaft 12In, paired exhaust rocker arms 13Ex configured to swing
according
to rotation of the exhaust camshaft 12Ex, paired intake valves 14In configured
to
operate according to the swinging of the intake rocker arms 13In, and paired
exhaust
valves 14Ex configured to operate according to the swinging of the exhaust
rocker
arms 13Ex.
Note that, in Fig. 2, the intake camshaft 12In, the exhaust camshaft 12Ex, the
intake
rocker arms 13In, and the exhaust rocker arms 13Ex are illustrated by two-dot
chain
lines for the sake of convenience.
The intake camshaft 12In and the exhaust camshaft 12Ex are supported by the
cam
holder 10 while extending across the valve chamber 9 and the cam chain chamber
11
in the left-right direction. To be more specific, the intake camshaft 12In and
the
exhaust camshaft 12Ex are held down from above by a not-illustrated holding
member
in which arc-shaped bearing portions are formed, while being placed on the
intake
camshaft bearing portion 10In and the exhaust camshaft bearing portion 10Ex,
and are
rotatably supported by the cam holder 10 and the holding member in a sliding
bearing
state.
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Here, in the drawings, the reference sign Cl denotes the center axis of the
intake
camshaft 12In and the reference sign C2 denotes the center axis of the exhaust
camshaft 12Ex. Note that, hereafter, the center axis Cl of the intake camshaft
12In is
simply referred to as the axis Cl of the intake camshaft 12In and the center
axis C2 of
the exhaust camshaft 12Ex is simply referred to as the axis C2 of the exhaust
camshaft
12Ex.
The cam chain described above is wound around portions of the intake camshaft
12In
and the exhaust camshaft 12Ex which are located inside the cam chain chamber
11.
The cam chain transmits rotation of the crankshaft 2 to the camshaft 12In and
the
exhaust camshaft 12Ex, and the intake camshaft 12In and the exhaust camshaft
12Ex
rotate 1/2 revolution per one revolution of the crankshaft 2.
Moreover, paired intake cams 15In arranged side by side in the camshaft axis
direction
(left-right direction) are formed in a portion of the intake camshaft 12In
which is
located inside the valve chamber 9, and paired exhaust cams 15Ex arranged side
by
side in the camshaft axis direction (left-right direction) are formed in a
portion of the
exhaust camshaft 12Ex which is located inside the valve chamber 9. To be more
specific, the paired intake cams 15In and the paired exhaust cams 15Ex are
formed in
a distributed manner on left and right sides of the cam holder 10.
The intake rocker arms 13In are in contact with the intake cams 15In and swing
according to profiles of the intake cams 15In when the intake cams 15In
rotate.
Meanwhile, the exhaust rocker arms 13Ex are in contact with the exhaust cams
15Ex
and swing according to profiles of the exhaust cams 15Ex when the exhaust cams
15Ex
rotate.
Referring to Figs. 2 to 5, a rocker arm holder portion 16 extending between
the right
wall portion 5R and the cam chain chamber forming wall portion 5C in a
direction
orthogonal to the cam holder 10 (left-right direction) is formed in the valve
chamber
9. The intake rocker arms 13In and the exhaust rocker arms 13Ex are swingably
supported by the rocker arm holder portion 16. Note that the rocker arm holder
portion 16 is formed integrally with the right wall portion 5R, the cam chain
chamber
forming wall portion 5C, and the cam holder 10 by casting.
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The rocker arm holder portion 16 extends in the left-right direction in a
space between
the intake camshaft 12In (intake camshaft bearing portion 10In) and the
exhaust
camshaft 12Ex (exhaust camshaft bearing portion 10Ex) as viewed in the
cylinder
center axis Si direction. A left housing support groove 17L and a right
housing
support groove 17R which are recessed downward and are opened toward the
intake
camshaft 12In (rearward) and the exhaust camshaft 12Ex (forward) are formed
respectively in sections of the rocker arm holder portion 16 which are on left
and right
sides of the cam holder 10.
Referring to both of Figs. 2 and 5, one of the paired intake rocker arms 13In
arranged
on the left side is supported with one end portion thereof housed in a rear
portion of
the left housing support groove 17L and the other end portion thereof
extending
rearward. Meanwhile the other one of the paired intake rocker arms 13In
arranged
on the right side is supported with one end portion thereof housed in a rear
portion
of the right housing support groove 17R and the other end portion thereof
extending
rearward.
Specifically, as shown in Fig. 5, a left intake-side support hole 18L
extending in the
left-right direction across the left housing support groove 17L is formed in
an intake
camshaft 12In side portion of the section of the rocker arm holder portion 16
on the
left side of the cam holder 10. Meanwhile, a right intake-side support hole
18R
extending in the left-right direction across the right housing support groove
17R is
formed in an intake camshaft 12In side portion of the section of the rocker
arm holder
portion 16 on the right side of the cam holder 10. The left intake-side
support hole 18L
penetrates the cam chain chamber forming wall portion 5C and the right intake-
side
support hole 18R penetrates the right wall portion 5R.
Then, referring to Fig. 2, a left intake-side rocker shaft 20L extending in
the left-right
direction is inserted into the left intake-side support hole 18L through the
cam chain
chamber forming wall portion 5C, and is inserted into the aforementioned one
end
portion of the intake rocker arm 13In arranged on the left side in such a way
that the
intake rocker arm 13In is supported to be swingable about the axis of the left
intake-
side rocker shaft 20L.
Moreover, a right intake-side rocker shaft 20R extending in the left-right
direction is
inserted into the right intake-side support hole 18R through the right wall
portion 5R,
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and is inserted into the aforementioned one end portion of the intake rocker
arm 131n
arranged on the right side in such a way that the intake rocker arm 131n is
supported
to be swingable about the axis of the right intake-side rocker shaft 20R. The
left intake-
side rocker shaft 20L and the right intake-side rocker shaft 20R extend
parallel to the
intake camshaft 12In.
Furthermore, referring to Fig. 5, a left exhaust-side support hole 19L
extending in the
left-right direction across the left housing support groove 17L is formed in
an exhaust
camshaft 12Ex side portion of the section of the rocker arm holder portion 16
on the
left side of the cam holder 10. Meanwhile, a right exhaust-side support hole
19R
extending in the left-right direction across the right housing support groove
17R is
formed in an exhaust camshaft 12Ex side portion of the section of the rocker
arm
holder portion 16 on the right side of the cam holder 10. The left exhaust-
side support
hole 19L penetrates the cam chain chamber forming wall portion 5C and the
right
exhaust-side support hole 19R penetrates the right wall portion 5R.
Then, referring to Fig. 2, a left exhaust-side rocker shaft 21L extending in
the left-right
direction is inserted into the left exhaust-side support hole 19L through the
cam chain
chamber forming wall portion 5C, and is inserted into the aforementioned one
end
portion of the exhaust rocker arm 13Ex arranged on the left side in such a way
that the
exhaust rocker arm 13Ex is supported to be swingable about the axis of the
left
exhaust-side rocker shaft 21L.
Moreover, a right exhaust-side rocker shaft 21R extending in the left-right
direction is
inserted into the right exhaust-side support hole 19R through the right wall
portion
5R, and is inserted into the aforementioned one end portion of the exhaust
rocker arm
13Ex arranged on the right side in such a way that the exhaust rocker arm 13Ex
is
supported to be swingable about the axis of the right exhaust-side rocker
shaft 21R.
The left exhaust-side rocker shaft 21L and the right exhaust-side rocker shaft
21R
extend parallel to the exhaust camshaft 12Ex.
Here, as shown in Figs. 1 and 2, in the left wall portion 5L in the cylinder
head 5, an
intake-side work hole 50 is formed to be coaxial to the left intake-side
support hole
18L while an exhaust-side work hole 51 is formed to be coaxial to the left
exhaust-side
support hole 19L. In assembly of the left intake-side rocker shaft 20L and the
left
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exhaust-side rocker shaft 21L, work is performed through the intake-side work
hole
50 and the exhaust-side work hole 51.
Next, description is given of the intake valves 14In and the exhaust valves
14Ex with
reference to Fig. 1. Each of the intake valves 14In and the exhaust valves
14Ex includes
a valve head and a stem portion extending from the valve head. Each of the
intake
valves 14In advances and retreats in an axis direction of the stem portion
thereof
according to the swinging of the corresponding intake rocker arm 13In and each
of the
exhaust valves 14Ex advances and retreats in an axis direction of the stem
portion
thereof according to the swinging of the corresponding exhaust rocker arm
13Ex.
In each of the intake valves 14In, the aforementioned valve head is formed in
a lower
end portion and is disposed in the combustion chamber 8. In addition, an upper
end
portion of the stem portion is disposed in the valve chamber 9 and brought
into
contact with the aforementioned other end portion (end portion on a swinging
side)
of the corresponding intake rocker arm 131n. The intake valve 14In is disposed
such
that the stem portion is spaced away from the cylinder center axis Si to the
rear side
as extending upward. The valve head of one of the paired intake valves 14In is
configured to open and close one of the two open ends of the intake port 5In
on the
combustion chamber 8 side while the valve head of the other one of the paired
intake
valves 14In is configured to open and close the other one of the two open ends
of the
intake port 5In on the combustion chamber 8 side.
Moreover, similarly, in each of the exhaust valves 14Ex, the aforementioned
valve
head is formed in a lower end portion and is disposed in the combustion
chamber 8.
In addition, an upper end portion of the stem portion is disposed in the valve
chamber
9 and brought into contact with the aforementioned other end portion (end
portion on
a swinging side) of the corresponding exhaust rocker arm 13Ex. The exhaust
valve
14Ex is disposed such that the stem portion is spaced away from the cylinder
center
axis Si to the front side as extending upward. The valve head of one of the
paired
exhaust valves 14Ex is configured to open and close one of the two open ends
of the
exhaust port 5Ex on the combustion chamber 8 side while the valve head of the
other
one of the paired exhaust valves 14Ex is configured to open and close the
other one of
the two open ends of the exhaust port 5Ex on the combustion chamber 8 side.
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In the internal combustion engine 1, the engine is driven by repeating an
intake stroke,
a compression stroke, a combustion stroke, and an exhaust stroke. In the valve
train
V, when the intake stroke is started, the intake rocker arms 13In are swung
downward
by the intake cams 15In of the intake camshaft 12In to open the intake valves
14In.
Moreover, in the valve train V, when the exhaust stroke is started, the
exhaust rocker
arms 13Ex are swung downward by the exhaust cams 15Ex of the exhaust camshaft
12Ex to open the exhaust valves 14Ex.
In the internal combustion engine 1, ignition of air-fuel mixture compressed
in the
compression stroke is performed between the compression stroke and the
combustion
stroke and a cycle proceeds to the combustion stroke after the ignition. As
shown in
Figs. 1 and 2, in the internal combustion engine 1 of the embodiment, an
ignition plug
22 configured to ignite the air-fuel mixture at a predetermined timing is
provided to
communicate with a substantial center of the combustion chamber 8.
The substantial center of the combustion chamber 8 refers to a substantially-
center
portion of the substantially-circular combustion chamber 8 as viewed in the
cylinder
center axis Si direction. In the embodiment, the substantial center of the
combustion
chamber 8 is located in a top portion of the combustion chamber 8 in the
cylinder
center axis Si direction.
As shown in Figs. 2 to 4, an attachment hole 23 for the ignition plug 22 is
formed in a
center portion of the cam holder 10 in the front-rear direction. The
attachment hole 23
extends from a top surface of the cam holder 10 to the combustion chamber 8
along
the cylinder center axis Si and communicates with the substantial center of
the
combustion chamber 8. In a case of attaching the ignition plug 22, the
ignition plug
22 is inserted into the attachment hole 23 from above to face the combustion
chamber
8.
Description is given of arrangement relationships among the attachment hole 23
and
the parts forming the valve train V. The left intake-side rocker shaft 20L is
arranged
on the left side of the attachment hole 23 in the direction of the axis Cl of
the intake
camshaft 12In and the right intake-side rocker shaft 20R is arranged on the
right side
of the attachment hole 23 in the direction of the axis Cl. On the left side of
the
attachment hole 23 in the direction of the axis Cl of the intake camshaft
12In, the left
intake-side rocker shaft 20L supports one of the paired intake rocker arms
13In
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arranged on the left side in such a way that the intake rocker arm 13In is
swingable.
The intake rocker arm 13In arranged on the left side is in contact with the
intake valve
14In located on the left side of the attachment hole 23.
Meanwhile, on the right side of the attachment hole 23 in the direction of the
axis Cl
of the intake camshaft 12In, the right intake-side rocker shaft 20R supports
one of the
paired intake rocker arms 13th arranged on the right side in such a way that
the intake
rocker arm 13th is swingable. The intake rocker arm 13th arranged on the right
side
is in contact with the intake valve 14In located on the right side of the
attachment hole
23.
Furthermore, the left exhaust-side rocker shaft 21L is arranged on the left
side of the
attachment hole 23 in the direction of the axis C2 of the exhaust camshaft
12Ex and the
right exhaust-side rocker shaft 21R is arranged on the right side of the
attachment hole
23 in the direction of the axis Cl. On the left side of the attachment hole 23
in the
direction of the axis C2 of the exhaust camshaft 12Ex, the left exhaust-side
rocker shaft
21L supports one of the paired exhaust rocker arms 13Ex arranged on the left
side in
such a way that the exhaust rocker arm 13Ex is swingable. The exhaust rocker
arm
13Ex arranged on the left side is in contact with the exhaust valve 14Ex
located on the
left side of the attachment hole 23.
Meanwhile, on the right side of the attachment hole 23 in the direction of the
axis C2
of the exhaust camshaft 12Ex, the right exhaust-side rocker shaft 21R supports
one of
the paired exhaust rocker arms 13Ex arranged on the right side in such a way
that the
exhaust rocker arm 13Ex is swingable. The exhaust rocker arm 13Ex arranged on
the
right side is in contact with the exhaust valve 14Ex located on the right side
of the
attachment hole 23.
Returning to Fig. 1, an oil pan 24 which is a separate body is provided in a
lower
portion of the crankcase 3 and an oil pump 25 configured to pump up
lubricating oil
accumulated in the oil pan 24 is provided inside the lower portion of the
crankcase 3.
Moreover, an oil cooler 26 is provided in a front portion of the crankcase 3.
In the
internal combustion engine 1, the lubricating oil pumped up by the oil pump 25
is
supplied to the cylinder head 5 to lubricate the intake and exhaust camshafts
12th,
12Ex and the intake and exhaust-side rocker shafts 20L, 20R, 21L, 21R which
are
described above.
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In Fig. 1, an oil supply passage T extending from the oil pump 25 to the
cylinder head
is illustrated by a bold dotted line and a bold one-dot chain line. In the oil
supply
passage T, a portion illustrated by the bold dotted line is a crankcase-side
oil supply
5 passage Ti formed in the crankcase 3 and a portion illustrated by the
bold one-dot
chain line is a cylinder-side oil supply passage T2 formed in the cylinder
block 4 and
the cylinder head 5. Description is given below of the crankcase-side oil
supply
passage Ti and the cylinder-side oil supply passage T2.
First, the crankcase-side oil supply passage Ti has a portion which extends
forward
and upward from an outlet of the oil pump 25 in the crankcase 3 and is open to
the
outside of the crankcase 3 to be connected to the oil cooler 26. The portion
of the
crankcase-side oil supply passage Ti extending from the oil pump 25 to the oil
cooler
26 is formed of a hole formed in the crankcase 3. Note that the lubricating
oil passing
through the oil cooler 26 is cooled and flows downstream.
Next, the crankcase-side oil supply passage Ti has a portion which returns to
the
upper portion of the crankcase 3 through a hose 27 connecting the oil cooler
26 and
the upper portion of the crankcase 3 to each other, extends rearward and
downward
from a connection portion of the hose 27, extends upward along the cylinder
center
axis Si from a portion on the front side of the crankshaft 2 immediately
therebehind,
and reaches a connection surface (upper surface) of the crankcase 3 with the
cylinder
block 4 to be opened upward.
The portion of the crankcase-side oil supply passage Ti which extends from the
oil
cooler 26 to the connection surface of the crankcase 3 with the cylinder block
4 is
formed of the aforementioned hose 27, a hole formed in the crankcase 3 to
extend
rearward and downward from the connection portion of the hose 27, a hole
formed in
the crankcase 3 to extend upward from a rear end portion of the hole extending
rearward and downward.
Lastly, the crankcase-side oil supply passage Ti has a portion which extends
rearward
from an open end of the aforementioned hole extending upward in the crankcase
3
and being open on the connection surface of the crankcase 3 with the cylinder
block 4
and which is connected to an upstream end portion of the cylinder-side oil
supply
passage T2. The portion of the crankcase-side oil supply passage Ti which
connects
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the aforementioned open end and the upstream end portion of the cylinder-side
oil
supply passage T2 to each other is formed of a groove formed on the connection
surface of the crankcase 3 with the cylinder block 4 by being recessed
downward. The
groove is formed in an arc shape as viewed in the cylinder center axis Si
direction to
avoid the cylinder bore 7.
Note that the portion of the crankcase-side oil supply passage Ti which
connects the
open end of the hole extending upward in the crankcase 3 and being open on the
connection surface of the crankcase 3 with the cylinder block 4 and the
upstream end
portion of the cylinder-side oil supply passage T2 to each other may be formed
of a
groove formed on a connection surface of the cylinder block 4 with the
crankcase 3 by
being recessed upward.
Meanwhile, in the embodiment, the cylinder-side oil supply passage T2 has: a
main
upstream oil supply passage T3 which is connected to the crankcase-side oil
supply
passage Ti and extends upward along the stud bolt 62 to reach a portion below
the
intake camshaft 12In; and a sub upstream oil supply passage 14 which branches
off
from the middle of the main upstream oil supply passage T3, extends forward,
and
then extends upward to reach a portion below the exhaust camshaft 12Ex.
The main upstream oil supply passage T3 is formed to overlap, in a side view,
the stud
bolt 62 provided on a rear left side and is formed at a position on the right
side of this
stud bolt 62.
The sub upstream oil supply passage T4 extends forward substantially
orthogonal to
an extending direction of the main upstream oil supply passage T3 in a portion
in the
bottom wall portion of the cylinder head 5 which is located above the
combustion
chamber 8 and the ignition plug 22, and then extends upward from the front
wall
portion 5F.
The main upstream oil supply passage T3 is formed of a hole extending from a
bottom
surface of the cylinder block 4 to reach an top surface thereof and a hole
formed
upward from a bottom surface of the cylinder head 5.
Meanwhile, the sub upstream oil supply passage 14 is formed of a hole formed
to
extend forward from the rear wall portion 5B of the cylinder head 5 and a hole
formed
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to extend upward from the bottom surface of the cylinder head 5. Although not
illustrated, a lower end of an oil supply passage formed by the hole formed to
extend
upward from the bottom surface of the cylinder head 5 in the sub upstream oil
supply
passage T4 is closed by a plug member and the top surface of the cylinder
block 4.
Accordingly, no lubricating oil leaks from the lower end.
The main upstream oil supply passage T3 extends to a position at a
substantially the
same height as positions where the left and right intake-side rocker shafts
20L, 20R are
supported, and is connected to an intake-side upstream rocker shaft oil supply
passage 30 extending along the direction of the axis Cl of the intake camshaft
12In.
Moreover, the sub upstream oil supply passage T4 extends to a position at
substantially the same height as positions where the left and right exhaust-
side rocker
shafts 21L, 21R are supported, and is connected to an exhaust-side upstream
rocker
shaft oil supply passage 31 extending along the direction of the axis C2 of
the exhaust
camshaft 12Ex.
Accordingly, in the internal combustion engine 1, the intake camshaft 121n,
the left
intake-side rocker shaft 20L, and the right intake-side rocker shaft 20R are
lubricated
by the lubricating oil supplied to the intake-side upstream rocker shaft oil
supply
passage 30 while the exhaust camshaft 12Ex, the left exhaust-side rocker shaft
21L,
and the right exhaust-side rocker shaft 21R are lubricated by the lubricating
oil
supplied to the exhaust-side upstream rocker shaft oil supply passage 31.
Description is given below of configurations of the intake-side upstream
rocker shaft
oil supply passage 30, the exhaust-side upstream rocker shaft oil supply
passage 31,
and oil supply passages downstream of these oil supply passages.
As shown in Figs. 5 and 6, the main upstream oil supply passage T3 extends in
an up-
down direction in a left end portion of the rear wall portion 5B and is
connected to a
left end portion (upstream end portion) of the intake-side upstream rocker
shaft oil
supply passage 30. Meanwhile, the sub upstream oil supply passage T4 extends
in
the up-down direction in a left end portion of the front wall portion 5F and
is
connected to a left end portion (upstream end portion) of the exhaust-side
upstream
rocker shaft oil supply passage 31.
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The intake-side upstream rocker shaft oil supply passage 30 is formed of a
hole
extending leftward from the right wall portion 5R, inside the rear wall
portion 5B. The
exhaust-side upstream rocker shaft oil supply passage 31 is foruted of a hole
extending
leftward from the right wall portion 5R, inside the front wall portion 5F.
Note that the rear wall portion 5B is located outside the intake valves 141n
(exterior
side of the cylinder head 5) in a radial direction of the intake camshaft 121n
and the
front wall portion 5F is located outside the exhaust valves 14Ex in a radial
direction of
the exhaust camshaft 12Ex.
An intake-side downstream rocker shaft oil supply passage 32 formed in a cross
shape
by causing two linear portions 32A, 32B to intersect each other is connected
to a
portion of the intake-side upstream rocker shaft oil supply passage 30 which
passes
through a connection portion between the rear wall portion 5B and the cam
holder 10.
An exhaust-side downstream rocker shaft oil supply passage 33 formed in a
cross
shape by causing two linear portions 33A, 33B to intersect each other is
connected to
a portion of the exhaust-side upstream rocker shaft oil supply passage 31
which passes
through a connection portion between the front wall portion 5F and the cam
holder
10.
The lubricating oil is supplied to the left and right intake-side rocker
shafts 20L, 20R
from the intake-side downstream rocker shaft oil supply passage 32.
In the embodiment, in the intake-side downstream rocker shaft oil supply
passage 32,
the linear portion 32A extends toward the right side of the attachment hole 23
from a
portion of the intake-side upstream rocker shaft oil supply passage 30 which
is located
on the left side of the attachment hole 23 in the direction of the axis Cl of
the intake
camshaft 12In, and communicates with the right intake-side support hole 18R.
Moreover, in the intake-side downstream rocker shaft oil supply passage 32,
the linear
portion 32B extends toward the left side of the attachment hole 23 from a
portion of
the intake-side upstream rocker shaft oil supply passage 30 which is located
on the
right side of the attachment hole 23 in the direction of the axis Cl of the
intake
camshaft 12In, and communicates with the left intake-side support hole 18L.
The lubricating oil can be thus supplied from the intake-side downstream
rocker shaft
oil supply passage 32 to the left and right intake-side rocker shafts 20L,
20R.
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Moreover, as apparent from Fig. 6, in the embodiment, the intake-side upstream
rocker shaft oil supply passage 30 and the intake-side downstream rocker shaft
oil
supply passage 32 are formed on the same plane orthogonal to the cylinder
center axis
Si. The intake-side downstream rocker shaft oil supply passage 32 is formed of
a hole
extending obliquely rightward and forward from the rear wall portion 5B and a
hole
extending obliquely leftward and forward from the rear wall portion 5B.
Moreover, as shown in Fig. 5, the intake camshaft bearing portion 10In is
located
above a cross portion Cr1 of the intake-side downstream rocker shaft oil
supply
passage 32 in the cam holder 10, and an intake-side cam oil supply passage 34
extending upward from the cross portion Cr1 to the intake camshaft bearing
portion
10In is formed in the cam holder 10.
Part of the lubricating oil flowing into the intake-side downstream rocker
shaft oil
supply passage 32 thereby flows into the intake-side cam oil supply passage 34
from
the cross portion Cr1. The lubricating oil can be thus supplied to the intake
camshaft
bearing portion 10In.
Note that description of the exhaust-side downstream rocker shaft oil supply
passage
33 on the exhaust side is omitted because the configuration thereof is front-
rear
symmetric to the configuration of the intake-side downstream rocker shaft oil
supply
passage 32. In the drawing, reference sign Cr2 denotes a cross portion of the
exhaust-
side downstream rocker shaft oil supply passage 33 and reference numeral 35
denotes
an exhaust-side cam oil supply passage extending from the cross portion Cr2.
Moreover, in the embodiment, as is apparent from Figs. 5 and 6, the attachment
hole
23 is provided to extend from the center portion of the cam holder 10 in the
front-rear
direction to the combustion chamber 8 and part of the attachment hole 23 is
located
between a connection portion between the left intake-side support hole 18L on
the left
side of the attachment hole 23 in the direction of the axis Cl of the intake
camshaft
12In and the linear portion 32B of the downstream rocker shaft oil supply
passage 32
and a connection portion between the right intake-side support hole 18R on the
right
side of the attachment hole 23 and the linear portion 32A of the downstream
rocker
shaft oil supply passage 32.
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Note that description of a positional relationship among the left exhaust-side
support
hole 19L, the right exhaust-side support hole 19R, and the attachment hole 23
on the
exhaust side is omitted because the positional relationship is similar to that
on the
intake side and is front-rear symmetric thereto.
As described above, in the internal combustion engine 1 of the embodiment, the
intake-side upstream rocker shaft oil supply passage 30 extending in the
direction of
the axis Cl of the intake camshaft 121n is formed in the rear wall portion 5B
which is
located outside the intake valves 141n in the radial direction of the intake
camshaft
12In in the cylinder head 5 and which is located outside (behind) the cylinder
center
axis S1 as viewed in the cylinder center axis Si direction. Moreover, the
exhaust-side
upstream rocker shaft oil supply passage 31 extending in the direction of the
axis C2
of the exhaust camshaft 12Ex is formed in the front wall portion 5F which is
located
outside the exhaust valves 14Ex in the radial direction of the exhaust
camshaft 12Ex
in the cylinder head 5 and which is located outside (in front of) the cylinder
center axis
Si as viewed in the cylinder center axis Si direction.
Moreover, the cam holder 10 extends from the rear wall portion 5B and the
front wall
portion 5F toward the attachment hole 23 as viewed in the cylinder center axis
Si
direction. In addition, the cam holder 10 extends orthogonally to the intake
camshaft
12In and the exhaust camshaft 12Ex as viewed in the cylinder center axis Si
direction.
Furthermore, inside the cam holder 10, there are formed the intake-side
downstream
rocker shaft oil supply passage 32 formed in the cross shape by causing the
two linear
portions 32A, 32B to intersect each other and the exhaust-side downstream
rocker
shaft oil supply passage 33 formed in the cross shape by causing the two
linear
portions 33A, 33B to intersect each other.
In the intake-side downstream rocker shaft oil supply passage 32, the linear
portion
32B out of the linear portions 32A, 32B extends from the intake-side upstream
rocker
shaft oil supply passage 30 toward the left side of the attachment hole 23 in
the
direction of the axis Cl of the intake camshaft 12In, and communicates with
the left
intake-side support hole 18L which is located on the left side of the
attachment hole
23 and which supports the left intake-side rocker shaft 20L. Moreover, the
linear
portion 32A out of the linear portions 32A, 32B extends from the intake-side
upstream
rocker shaft oil supply passage 30 toward the right side of the attachment
hole 23 in
the direction of the axis Cl of the intake camshaft 12In, and communicates
with the
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right intake-side support hole 18R which is located on the right side of the
attachment
hole 23 and which supports the right intake-side rocker shaft 20R.
Moreover, in the exhaust-side downstream rocker shaft oil supply passage 33,
the
linear portion 33B out of the linear portions 33A, 33B extends from the
exhaust-side
upstream rocker shaft oil supply passage 31 toward the left side of the
attachment hole
23 in the direction of the axis C2 of the exhaust camshaft 12Ex, and
communicates with
the left exhaust-side support hole 19L which is located on the left side of
the
attachment hole 23 and which supports the left exhaust-side rocker shaft 21L.
Moreover, the linear portion 33A out of the linear portions 33A, 33B extends
from the
exhaust-side upstream rocker shaft oil supply passage 31 toward the right side
of the
attachment hole 23 in the direction of the axis C2 of the exhaust camshaft
12Ex, and
communicates with the right exhaust-side support hole 19R which is located on
the
right side of the attachment hole 23 and which supports the right exhaust-side
rocker
shaft 21R.
In the internal combustion engine 1 described above, it is possible to
distribute and
supply the lubricating oil to the rocker shafts (20L, 20R, 21L, 21R) located
on the left
and right sides of the attachment hole 23 for the ignition plug 22 in the
directions of
the axis Cl of the intake camshaft 121n and the axis C2 of the exhaust
camshaft 12Ex
by using the simple-shaped intake-side downstream rocker shaft oil supply
passage
32 and exhaust-side downstream rocker shaft oil supply passage 33 which are
formed
inside the cam holder 10 and which have the cross shapes. Moreover, since the
intake-
side downstream rocker shaft oil supply passage 32 and the exhaust-side
downstream
rocker shaft oil supply passage 33 each have the cross shape, it possible to
make the
passage lengths of the two linear portions (32A, 32B, 33A, 33B) extending
toward the
left and right sides of the attachment hole 23 uniform and short, and to
supply the
lubricating oil to the rocker shafts (20L, 20R, 21L, 21R) located on the left
and right
sides of the attachment hole 23.
Due to this, in the internal combustion engine 1, while the shape of the oil
supply
passages to the rocker shafts is simple, it is possible to secure a sufficient
amount of
lubricating oil for the rocker shafts. Accordingly, size reduction and an
improvement
in production efficiency can be achieved while securing a sufficient amount of
lubricating oil for the rocker shafts.
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The embodiment of the present invention has been described above. However, the
present invention is not limited to the embodiment described above and various
changes can be made within a scope not departing from the scope of the present
invention as set out in the appended claims.
For example, in the aforementioned embodiment, description is given of the
case
where the left intake-side rocker shaft 20L and the right intake-side rocker
shaft 20R
are arranged on the left and right sides of the attachment hole 23 in a
distributed
manner and the left exhaust-side rocker shaft 21L and the right exhaust-side
rocker
shaft 21R are arranged on the left and right sides of the attachment hole 23
in a
distributed manner. However, as a modified example, a rocker shaft may extend
on
both of the left and right sides of the attachment hole 23.
Moreover, in the aforementioned embodiment, description is given of an example
in
which the intake-side upstream rocker shaft oil supply passage 30 and the
intake-side
downstream rocker shaft oil supply passage 32 are provided on the intake side
and
the exhaust-side upstream rocker shaft oil supply passage 31 and the exhaust-
side
downstream rocker shaft oil supply passage 33 are provided on the exhaust
side. As
a modified example, the intake-side upstream rocker shaft oil supply passage
30 and
the intake-side downstream rocker shaft oil supply passage 32 may be provided
only
on the intake side or the exhaust-side upstream rocker shaft oil supply
passage 31 and
the exhaust-side downstream rocker shaft oil supply passage 33 may be provided
only
on the exhaust side.
Moreover, in the aforementioned embodiment, description is given of the
configuration in which the ignition plug 22 is provided in the substantial
center of the
combustion chamber 8. However, the internal combustion engine of the present
invention may be a diesel engine in which a fuel injection valve is provided
in the
substantial center of the combustion chamber 8. Moreover, although description
of
the DOHC internal combustion engine 1 is given in the aforementioned
embodiment,
the internal combustion engine of the present invention may be a SOHC internal
combustion engine.
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