BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
[0001] The present invention relates to an internal combustion engine with a valve operating
system, 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 stationary support shaft 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 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 ART
[0002] Document DE 196 40 520 A1 describes a valve operating system, including a cam shaft
provided with a valve operating cam, a first rocker arm supported on a cranked lever
and in contact with the cam shaft via a roller provided on the first rocker arm, a
tappet in contact with an abutment surface on the first rocker arm, and a second rocker
arm which is in contact with the underside of the tappet via a roller provided on
the second rocker arm and which is directly connected to an intake valve stem.
[0003] During movement of the cam shaft, the first rocker arm moves the tappet backwards
and forwards, which brings different areas of the shaped underside of the tappet in
contact with the roller of the second rocker arm and thus moves the second rocker
arm up and down, thus opening and closing the intake valve. The cranked lever supporting
the first rocker arm can be moved in order to bring the roller of the first rocker
arm into contact with different areas of the cam shaft and at the same time bring
the roller of the second rocker arm in contact with different areas of the shaped
underside of the tappet. Thus, different intake valve opening and closing regimes
can be achieved at different positions of the cranked support lever.
[0004] However, this known valve operating system does include a large number of moving
parts, does not ensure a high rigidity of the rocker arms and does not allow for a
spark plug insertion tube to be placed in close proximity to the valve operating system.
SUMMARY OF THE INVENTION
[0005] Accordingly, it is an object of the present invention to provide an internal combustion
engine with a valve operating system, wherein the rigidity of each of the rocker arms
is increased, while avoiding an increase in size of the rocker arm and which allows
for a spark plug insertion tube to be placed in close proximity to the valve operating
system without increasing the size demands on the cylinder head.
[0006] To achieve the above object, there is provided an internal combustion engine with
a valve operating system comprising the features of claim 1.
[0007] With the arrangement as claimed, the base ends of the pair of support wall portions
are connected to each other by the lower connecting wall. Therefore, the rigidity
with which the support shaft is supported by the support wall portions is increased,
and the rigidity of the entire rocker arm is also increased. The lower connecting
wall is arranged so that it effectively utilizes the 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. Due to the provision of the notch at a central position
of the swinging support portion of the free rocker arm, a spark plug insertion tube
can be placed in close proximity to the valve operating system without increasing
size demands on the cylinder head.
[0008] According to a second aspect and feature of the present invention, in addition to
the first feature, the radius of curvature of the notch is set larger than the radius
of the outer surface of the spark plug insertion tube. With such an arrangement, it
is ensured that the swinging support portion of the free rocker arm does not touch
the spark plug insertion tube when the free rocker arm is moving.
[0009] According to a third aspect and feature of the present invention, in addition to
the first or second feature, the spark plug tube is circular in cross section. With
such an arrangement, the spark plug insertion tube allows for optimum access to the
spark plug.
[0010] According to a fourth aspect and feature of the present invention, in addition to
any of the preceding features, arcuate bulged portions bulged outwards are formed
at opposite ends of the swinging support portion along the axis of the support member
in such a manner that the notch is sandwiched between the bulged portions. With such
an arrangement the loss of rigidity in the swinging support portion due to the provision
of the notch can be somewhat balanced by the provision of the bulged portions.
[0011] According to a fifth 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 wall and the roller. With
such an 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 roller and the support shaft to reduce the
resistance to the rotation of the roller.
[0012] According to a sixth aspect and feature of the present invention, in addition to
the first or fifth feature, the rocker arm is formed from metal by injection molding.
With such an 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.
[0013] According to a seventh aspect and feature of the present invention, in addition to
any one of the preceding 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 projectingly 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 an arrangement, the rigidity of the
receiving portion receiving a load from the urging means can be increased by the lower
connecting wall.
[0014] According to an eighth aspect and feature of the present invention, in addition to
the first feature, the support shaft is supported between the support wall portions
with opposite 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 porting 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, which is rotatably 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.
[0015] With the arrangement of the eighth 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.
[0016] According to a ninth aspect and feature of the present invention, in addition to
the eighth feature, an oil passage is 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 an 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 provision of the
receiving portion.
[0017] According to a tenth aspect and feature of the present invention, in addition to
the eighth or ninth feature, the rocker arm is formed from metal by injection molding.
With such an 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.
[0018] According to an eleventh aspect and feature of the present invention, in addition
to the first feature, 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 an arrangement, 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.
[0019] The above and other objects, features and advantages of the invention will become
apparent from the following description of the preferred embodiments taken in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020]
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 in Fig.1;
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.5 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 caulking 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.10 is a sectional view taken along a line 10-10 in Fig.4;
Fig.11 is a sectional view taken along a line 11-11 in Fig.10;
Fig.12 is a plan view of intake-side and exhaust-side valve operating systems;
Fig.13 is a sectional view taken along a line 13-13 in Fig.12;
Figs.14 and 15 show a second embodiment of the present invention, wherein
Fig.14 is a sectional view of a free rocker arm; and
Fig.15 is a sectional view taken along a line 15-15 in Fig.14.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] A first embodiment of the present invention will now be described with reference
to Figs.1 to 13. Referring first to Fig.1, 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.
[0022] 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.
[0023] Fixed to the cam shaft 18 are a high-speed valve operating 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.
[0024] 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.
[0025] 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.
[0026] Each of the first and second driving rocker arms 19 and 20 is integrally provided
with a swinging support portion 19a, 20a swingably supported on the rocker shaft 22,
a first support wall portion 31
1, 32
1 connected at a base end thereof to the swinging support portion 19a, 20a, a second
support wall portion 31
2, 32
2 connected to the swinging support portion 19a, 20a with its base end opposed to the
first support wall portion 31
1, 32
1 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 31
1, 31
2 and 32
1, 32
2 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 33
1 connected at its base end to the swinging support portion 21a, a second support wall
portion 33
2 connected at its base end to the swinging support portion 21a in an opposed relation
to the first support wall portion 33
1 in a direction along the axis of the rocker shaft 22.
[0027] 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 31
1 and 31
2. A cylindrical roller 28 is rotatably supported on the first driving rocker arm 19
to come into rolling contact with the low-speed valve 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 32
1 and 32
2. 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 33
1 and 33
2, 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.
[0028] A bottomed fitting bore 37
1, which opens at an end adjacent the free rocker arm 21, is provided in the first
support wall portion 31
1 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 37
2, which opens at opposite ends thereof, is provided in the second support wall portion
31
2 coaxially with the first fitting bore 37
1. A first fitting bore 38
1, which opens at opposite ends thereof, is provided in the first support wall portion
32
1 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 38
2, which opens at an end adjacent the free rocker arm 21, is provided in the second
support wall portion 32
2 coaxially with the first fitting bore 38
1. A first fitting bore 39
1, which opens at opposite ends thereof, is provided in the first support wall portion
33
1 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 39
2, which opens at opposite ends thereof, is provided in the second support wall portion
33
2 coaxially with the first fitting bore 39
1.
[0029] One end of a cylindrical support shaft 41 is fitted into the first fitting bore 37
1 in the first driving rocker arm 19, until it abuts against a closed end of the first
fitting bore 37
1, and the other end of the support shaft 41 is fitted into the fitting bore 37
2. One end of a cylindrical support shaft 42 is fitted into the first fitting bore
38
1 in the second driving rocker arm 20, and the other end of the support shaft 42 is
fitted into the second fitting bore 38
2, until it abuts against a closed end of the second fitting bore 38
2. Further, opposite ends of a cylindrical support shaft 43 are fitted into the first
and second fitting bores 39
1 and 39
2 in the free rocker arm 21, respectively.
[0030] Referring also to Fig.5, an insertion bore 44 is provided in the second support wall
portion 31
2 of the first driving 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 37
2 to lead to an inner surface of the second fitting bore 37
2. The following recesses are also provided in the second support wall portion 31
2: 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 31
2, 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 31
2. The first and second recesses 80 and 81 are formed with their diameters larger than
that of the insertion bore 44.
[0031] 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 37
2, 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.
[0032] 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 the insertion bore 44, whereby the support
shaft 41 is fixed to the first driving rocker arm 19.
[0033] The support shaft 42 is fixed to the first support wall portion 32
1 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 32
1 of the second driving rocker arm 20 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 38
1.
[0034] Further, the support shaft 43 is fixed to the first support wall portion 33
1 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 33
1 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 39
1.
[0035] 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 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.
[0036] The hardness of at least those portions of the pins 47 to 49 which are engaged in
the engage grooves 50 to 52, e.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, e.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
v 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
v.
[0037] Needle bearings 53 are interposed between the roller 28 and the support shaft 41
and between the first and second support wall portions 31
1 and 31
2 of the first driving rocker arm 19. Needle bearings 54 are interposed between the
roller 29 and the support shaft 42 and between the first and second support wall portions
32
1 and 32
2 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
33
1 and 33
2 of the free rocker arm 21.
[0038] 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.
[0039] 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 33
2 in such a manner that the pin 49 is inserted into and fixed in one 33
1 of the first and second support wall portions 33
1 and 33
2 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 perpendicular to the axis of the support shaft 43.
[0040] Moreover, the receiving portion 62 is integrally provided on the second support wall
portion 33
2 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 33
2. In other words, because the second fitting bore 39
2, into which the support shaft 43 is fitted, is provided in the second support wall
portion 33
2 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 33
2. In this embodiment, the receiving portion 62 extending over the substantially entire
width of the second support wall portion 33
2 is integrally provided at a lower portion of the second support wall portion 33
2 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.
[0041] The receiving portion 62 is integrally provided at the lower portion of the second
support wall portion 33
2 in such a manner that it is disposed between (1) a straight line L
2 extending through the axis of the rocker shaft 22 in a direction perpendicular to
a straight line L
1 extending through the axis of the rocker shaft 22 and the axis of the support shaft
43 and (2) a straight line L
3 extending through the axis of the support shaft 43 in a direction perpendicular to
the straight line L
1.
[0042] Referring carefully to Figs.1 to 5, a lower connecting wall 85 interconnecting lower
portions of base ends of the first and second support wall portions 31
1 and 31
2 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 31
1 and 31
2 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.
[0043] Moreover, the lower connecting wall 85 is connected to the lower portion of the second
support wall portion 31
2 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 outer peripheral surface of the roller 28.
[0044] 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.
[0045] 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.
[0046] Referring carefully to Fig.7, a lower connecting wall 87 interconnecting lower portions
of base ends of the first and second wall portions 33
1 and 33
2 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 33
1 and 33
2 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 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.
[0047] Moreover, the lower connecting wall 87 is connected to the lower portion of the first
support wall portion 33
1 at a location corresponding to the second recess 81 for accommodating the caulked
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 33
2 at a location corresponding to a receiving portion 92 which is projectingly provided
at the lower portion of the second support wall 33
1 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.
[0048] 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 adjacent each other,
a cylindrical switching piston 64 capable of switching 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.
[0049] 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 37
1 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 33
1 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.
[0050] 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 31
1 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 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.
[0051] 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.
[0052] 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 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.
[0053] 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.
[0054] 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
38
2 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 38
2.
[0055] 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; 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.
[0056] 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.
[0057] Referring also to Figs.10 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 33
1 and 33
2 of the free rocker arm 21 in which the receiving portion 62 is provided, i.e., in
the second support wall portion 33
2, in such a manner one end of the lubricating oil passage 76 opens into the inner
surface of the second fitting bore 39
2. A groove 77 is provided in the inner surface of the second fitting bore 39
2. 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.
[0058] The lubricating oil passage 76 is provided in the second support wall portion 33
2 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.
[0059] 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.
[0060] 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 subjecting 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.
[0061] 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.
[0062] The intake-side valve operating system 171 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 tube 93 are sandwiched
between the systems. 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 intake-side and exhaust-side valve operating systems
17I and 17E are only shown in Figs.12 and 13 with the same reference characters affixed
thereto, and a detailed description of the exhaust-side valve operating system 17E
is omitted.
[0063] 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.
[0064] 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.e., the axis of the rocker shaft 22.
[0065] In addition, the notch 94 is provided in the swinging support portion 21a within
the width of the opening 36 provided in the free rocker arm 21, i.e., in a section
corresponding to a portion between the first and second support walls 33
1 and 33
2 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.
[0066] A lubricating oil passage 76 is provided in the second support wall 33
2 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 39
2. 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.
[0067] Further, lower portions of the base ends of the support walls 33
1 and 33
2 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 33
1 and 33
2 are interconnected by an upper connecting wall 88. At least a portion of the notch
94 (the whole in this embodiment) 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.e., the axis of the rocker shaft 22.
[0068] Vertically extending grooves are provided in outer surfaces of those portions of
support walls 33
1 and 33
2 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.
[0069] 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 37
1, 38
1 and 39
1 and the second fitting bores 37
2, 38
2 and 39
2 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 31
2 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 32
1 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 33
1 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 axes and hence, the support shafts 41 to 43 can be fixed to the rocker
arms 19 to 21 in a simple structure.
[0070] 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 caulked.
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.
[0071] 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.
[0072] The opposite ends of each of the pins 47 to 49 are caulked by the flat punches 82
and 83 and hence, even if the caulking positions of the flat punches 82 and 83 relative
to the pins 47 to 49 are slightly displaced, the opposite ends of the pins 47 to 49
can be caulked 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 caulked portions due to the displacement of the caulking 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 caulking the opposite ends of the pins 47
to 49 within the recesses 80, 81, it is ensured that the caulked 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 caulking
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.
[0073] Further, since the hardness of at least those portions of the pins 47 to 49 which
engage the engage grooves 50 to 52 (the areas subjected to the high-frequency hardening)
is relatively high (e.g., in the range of 579 to 832 in unit of H
v), 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 subjected
to the high-frequency hardening) is relatively low (e.g., in the range of 180 to 260
in unit of H
v), the caulking operation is facilitated, and the caulking accuracy is also enhanced.
[0074] 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.
[0075] Moreover, in the first driving rocker arm 19, one end of the support shaft 41 is
fitted into the first fitting bores 37
1 in the first support wall portion 31
1, 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 31
1. 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
31
1 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 37
1 in the first support wall portion 31
1 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.
[0076] 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.
[0077] Provided on the outer surface of the first driving rocker arm 19 at one end thereof
in the axial direction of the rocker 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.
[0078] Further, the communication passage 70 is provided in the first driving rocker arm
19 on the side of the first support wall portion 31
1, and the insertion bore 44 for fixing the support shaft 41 is provided in the second
support wall portion 31
2 with the roller 28 sandwiched between the first and second support wall portions
31
1 and 31
2. 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.
[0079] 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 39
2 and leads to the oil passage 68 in the rocker shaft 22. The groove 77 is provided
in the inner surface of the second fitting bore 39
2, 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. 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 39
2. 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.
[0080] 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.
[0081] 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 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.
[0082] In the free rocker arm 21, the lubricating oil passage 76 is provided in the second
support wall portion 33
2, and the insertion bore 46 for fixing the support shaft 43 is provided in the first
support wall portion 33
1. 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.
[0083] 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 33
2 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 33
2. In other words, the receiving portion 62 is integrally provided on the second support
wall portion 33
2 in such a manner that at least a portion of the area of the support shaft 43, which
is fitted in the second support wall portion 33
2, 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 39
2 with the support shaft 43 fitted therein is provided in the second support wall portion
33
2 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 33
2 and integrally provided at the lower portion of the second support wall 33
2 to abut against the lifter 60 of the lost motion mechanism 58 disposed below the
free rocker arm 21.
[0084] 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.e., the 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.
[0085] The provision of the receiving portion 62 enhances the support rigidity of the support
shaft 43 on the second support wall portion 33
2.
[0086] Further, the receiving portion 62 is integrally provided at the lower portion of
the second support wall 33
2 in such manner that it is disposed between (1) the straight line L
2 extending through the axis of the rocker shaft 22 in a direction perpendicular to
the straight line L
1 extending through the axis of the rocker shaft 22 and the axis of the support shaft
43 and (2) the straight line L
3 extending through the axis of the support shaft 43 in a direction perpendicular to
the straight line L
1. 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 33
2 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 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.
[0087] Moreover, the support shaft 43 is fixed by the pin 49 on the side of the first support
wall 33
1, and the receiving portion 62 is provided on the second support wall 33
2. 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 33
2, it is possible to avoid a reduction in rigidity of the second support wall 33
2, despite the provision of the lubricating oil passage 76 which is the cavity in the
second support wall 33
2, and to compensate for a reduction in weight of the second support wall 33
2 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 33
1 and 33
2.
[0088] Further, the free rocker arm 21 is supported on the rocker shaft 22 in such manner
that the first support wall portion 33
1 provided with the insertion bore 46 for fixing the support shaft 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 32
1 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.
[0089] 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 37
1 and 37
2 and the insertion bore 44 can be defined simultaneously with the formation of the
first driving rocker arm 19, and the fitting bores 38
1 and 38
2, 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 39
1 and 39
2 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 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.
[0090] 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 31
1, 31
2, 32
1, 32
2, 33
1 and 33
2 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 projectingly
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 31
1, 31
2, 32
1, 32
2, 33
1 and 33
2 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 projectingly 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 to increase the rigidities of supporting
of the support shafts 41 to 43 by the support walls 31
1, 31
2, 32
1, 32
2, 33
1 and 33
2 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.
[0091] 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.
[0092] 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
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 31
1, 31
2, 32
1, 32
2, 33
1 and 33
2 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 31
1, 31
2, 32
1, 32
2, 33
1 and 33
2.
[0093] 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.
[0094] Yet further, in the rocker arms 19 to 21, the second recess 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 31
2, 32
1 and 33
1 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 31
2, 32
1 and 33
1 due to the provision of the second recess 81 to the utmost.
[0095] 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 33
2 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.
[0096] 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 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.
[0097] 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.
[0098] 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 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.
[0099] 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 33
1 and 33
2 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.
[0100] 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 94.
[0101] 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.
[0102] Figs.14 and 15 show a second embodiment of the present invention. A lubricating oil
passage 76 is provided in the second support wall portion 33
2 in such a manner that a center line L
4 is disposed at a location displaced toward the receiving portion 62 from a straight
line L
1 extending through the axis of the rocker shaft 22 and the axis of the support shaft
43, i.e., below the straight line L
1. 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.
[0103] With the second embodiment, although the width of the second support wall portion
33
2 in the first embodiment is as shown by a dashed line in Fig. 15, the width of the
second support wall portion 33
2 can be decreased as shown by a solid line in Fig. 15. Moreover, even if the width
of the second support wall portion 33
2 is decreased, the rigidity of the second support wall portion 33
2 cannot be reduced, because the width of the lubricating oil passage 76 is also small.
Therefore, the width of the second support wall portion 33
2 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 33
2.
[0104] 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.
[0105] 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 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.
[0106] 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.
[0107] A valve operating system in an internal combustion engine includes 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 and which are 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
so as to be in rolling contact with the valve operating cam. A lower connecting wall
interconnecting lower portions of the base ends of the support wall portions is projectingly
provided on the swinging support portion in a manner opposed to an outer peripheral
surface of a lower portion of the roller. Thus, it is possible to increase the rigidity
of the rocker arm, while avoiding an increase in size of the rocker arm.