Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: Valve System For OHV-Type Four-Cylinder Internal
Combustion Engine
FIELD OF THE INVENTION
The present invention relates to a valve system
suited for use with light-weight small OHV-type four-
cycle internal combustion engines, particularly,
horizontal opposed type and V-type internal combustion
engines applicable to vehicles, to ships, to airplanes,
to stationary use, and so on.
BACKGROUND OF THE INVENTION
OHV (overhead valve)-type four-cycle internal
combustion engines have been widely used for vehicles,
for ships, for airplanes, for stational use, and so on
because of such advantages as excellent thermal
efficiency, low emission of HC and the like harmful
components, low exhaust noise, and excellent drivability
in a wide range of operation (See, for example, Japanese
Patent Laid-open No. 2000-110516).
This type of internal combustion engines,
however, have the problem that valve camshafts large in
weight and valve mechanisms operating in connection
therewith are disposed collectively at cylinder heads,
namely, at head portions of the engine, leading to heavy
head portions and large size, which tendency increases as
the number of intake and exhaust valves is increased for
raising the output of the engine. The above-mentioned
publication discloses an example of application of an
OHV-type valve mechanism to a horizontal opposed type
four-cycle internal combustion engine. In the example
disclosed, however, valve camshafts and valve systems are
disposed in head portions located at left and right
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extreme ends farthest from a crankshaft and, necessarily,
the left and right head portions are large in weight and
size.
The present invention has been made in
consideration of the above-mentioned circumstances.
Namely, a principal purpose of the invention is to make
it possible to dispose the large-weight valve camshafts
as near to the crankshaft as possible, to thereby
contrive reductions in weight and size of the head
portions of the internal combustion engine, thus
providing a novel valve system for OHV-type four-cycle
internal combustion engine.
SUt~lARY OF THE INVENTION
In order to attain the above-mentioned object,
the present invention is characterized in that, in an
OHV-type four-cylinder internal combustion engine
comprising a pair of cylinder banks disposed
symmetrically on opposite sides of an imaginary line
orthogonal to the axis line of a crankshaft, each of the
cylinder banks comprises integrally a crankcase portion
for rotatably supporting the crankshaft, a cylinder block
portion on the outside of the crankcase portion, and a
cylinder head portion on the outside of the cylinder
block portion, valve camshafts operating in connection
with the crankshaft are rotatably supported at the
crankcase portions, while valve-operating members for
operating intake and exhaust valves for opening and
closing intake and exhaust ports of combustion chambers
are provided at the cylinder head portions, and
oscillating arms operating in connection with the valve
camshafts are connected with the valve-operating members
through pull rods disposed on lateral sides of the
cylinder banks. The characteristic feature makes it
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possible to reduce greatly the weight and size of the
head portions of the engine, and the adoption of the pull
rods enables to narrow the valve mechanism as a whole
notwithstanding that the valve camshafts are located away
from the cylinder heads.
Besides, in order to attain the above object,
in an aspect, the invention is characterized in that the
intake and exhaust valve camshafts are disposed
respectively on both sides of the crankcase portions with
the crankshaft therebetween, and the oscillating arms
operating in connection with the valve camshafts and the
valve-operating members for operating the intake and
exhaust valves are respectively connected to each other
through the pull rods disposed on both sides of the
cylinder banks. This characteristic feature makes it
possible, in a system having valve camshafts disposed on
both sides of a crankcase, to reduce greatly the weight
and size of the head portions of the engine, and the
adoption of the pull rods enables to narrow the valve
mechanism as a whole notwithstanding that the valve
camshafts are located away from the cylinder heads.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are
shown in the drawings, wherein:
Fig. 1 is a sectional view taken along line 1-1
of Fig. 2 of a horizontal opposed type internal
combustion engine according to the first embodiment of
the invention.
Fig. 2 is a sectional view taken along line 2-2
of Fig. 1.
Fig. 3 is a sectional view taken along line 3-3
of Fig. 2.
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Fig. 4 is a sectional view taken along line 4-4
of Fig. 3.
Fig. 5 is a sectional view taken along line 5-5
of Fig. 1.
Fig. 6 is an enlarged sectional view taken
along line 6-6 of Fig. 1.
Fig. 7 is a vertical sectional view of a V-type
internal combustion engine according to the second
embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now, modes for carrying out the present
invention will be described based on the embodiments of
the invention illustrated by the attached drawings.
First, referring to Figs. 1 to 6, a first
embodiment of the invention will be described. The first
embodiment pertains to application of the valve system
for OHV-type four-cycle internal combustion engine of the
invention to a horizontal opposed type four-valve four-
cylinder engine. Fig. 1 is a sectional view taken along
line 1-1 of Fig. 2 of the horizontal opposed type
internal combustion engine according to the first
embodiment; Fig. 2 is a sectional view taken along line
2-2 of Fig. 1; Fig. 3 is a sectional view taken along
line 3-3 of Fig. 2; Fig. 4 is a sectional view taken
along line 4-4 of Fig. 3; Fig. 5 is a sectional view
taken along line 5-5 of Fig. 1; and Fig. 6 is an enlarged
sectional view taken along line 6-6 of Fig. 1.
In the description below, of a pair of cylinder
banks disposed on opposite sides of a crankshaft 1, the
one on the left side in Fig. 1 will be called left
cylinder bank, and the other on the right side will be
called right cylinder bank.
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In Fig. 1, a pair of left and right cylinder
banks CB1, CB2 are disposed symmetrically on the left and
right sides of a vertical imaginary line L2-L2 orthogonal
to the axis line L1-L1 of the crankshaft 1 which is
disposed roughly horizontally in a direction orthogonal
to the surface of paper. The left and right cylinder
banks CB1 and CB2 have the same configuration, and are
extended roughly horizontally in the left-right
direction. Each of the cylinder banks CB1, CB2 comprises
a crankcase portion 2L, 2R for receiving and rotatably
supporting the crankshaft 1, a cylinder block portion 3L,
3R connected integrally to an outside surface of the
crankcase portion 2L, 2R by a plurality of connecting
bolts 5, and a cylinder head portion 4L, 4R provided
integrally on the outside of the cylinder block portion
3L, 3R. The left and right crankcase portions 2L and 2R
are coupled integrally to each other by coupling means
such as coupling bolts.
The crankcase portion 2L, 2R and the cylinder
block portion 3L, 3R may be formed integrally with each
other, while the cylinder block portion 3L, 3R and the
cylinder head portion 4L, 4R may be formed as separate
bodies and connected integrally by known connecting
means.
As shown in Figs. 2 and 3, the crankshaft 1 has
a portion thereof formed hollow in order to contrive a
reduction in weight. Journal shaft portions 1j of the
crankshaft 1 are rotatably supported by a plurality of
bearing halves provided respectively at the crankcase
portions 2L, 2R of the left and right cylinder banks CB1,
CB2. Large end portions of connecting rods 8 are
rotatably connected to four crank pins of the crankshaft
1, namely, first to fourth crank pins 1p-1 to 1p-4.
Concretely, as shown in Fig. 2, small end portions of the
connecting rods 8 connected to the first and third crank
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pins 1p-1, 1p-3 are connected to pistons 9 on the side of
the left cylinder bank CB1, whereas small end portions of
the connecting rods 8 connected to the second and fourth
crank pins 1p-2, 1p-4 are connected to pistons 9 on the
side of the right cylinder bank CB2.
As shown in Figs. 1 and 2, the left and right
cylinder block portions 3L, 3R are each provided with two
cylinder barrels disposed side by side. The cylinder
barrels of the left cylinder block portion 3L are
provided with first and third cylinders 10-1 and 10-3,
whereas the cylinder barrels of the right cylinder block
portion 3R are provided with second and fourth cylinders
10-2 and 10-4. The pistons 9 connected with the small
end portions of the connecting rods 8 are slidably fitted
in the cylinders.
As clearly shown in Figs. 1 and 2, the cylinder
head portions 4L, 4R formed integrally with the left and
right cylinder block portions 3L, 3R are respectively
provided with combustion chambers 11 corresponding to the
first and third cylinders 10-1, 10-3 and the second and
fourth cylinders 10-2, 10-4. Two intake ports 12 and two
exhaust ports 13 which are communicated to the combustion
chambers 11 via valve ports are respectively communicated
with each of the combustion chambers 11. The two intake
ports 12 and two exhaust ports 13 are opened and closed
respectively by intake and exhaust valves 14, 15 which
are provided slidably in the cylinder head portions 4L,
4R. In addition, the intake and exhaust valves 14, 15
are energized in a closing direction by valve springs 17
as usual. The cylinder head portions 4L, 4R comprise
valve-operating members, namely, swing arms 18i and 18e
on the intake and exhaust sides, which are supported
swingably through shafts. Slipper surfaces at tip ends
of the swing arms 18i, 18e are disposed adjacently to end
faces of the intake and exhaust valves 14 and 15. Pull
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rods 20i and 20e which will be detailed later are
respectively connected by connection pins 22 to the tip
ends of the swing arms 18i and 18e on the intake and
exhaust sides. The intake and exhaust valves 14 and 15
are respectively opened when the swing arms 18i and 18e
are swung to the inside against the springy force of the
valve springs 17 by the pulling operation of the pull
rods 20i and 20e.
The intake ports 12 are each connected to an
intake system In disposed on the upper side of the left
and right cylinder banks CB1 and CB2 collectively,
whereas the exhaust ports 13 are each connected to an
exhaust system Ex disposed on the lower side of the left
and right cylinder banks CB1 and CB2 collectively. As
shown in Fig. 1, fuel injection valves V are connected to
downstream portions of the intake system In. An ignition
plug P is screwed to a central portion of an upper wall
of each of the combustion chambers 11.
Portions of the valve mechanism described later
are provided on the left and right cylinder head portions
4L, 4R, and the portions of the valve mechanism are
covered by head covers 24 disposed on top surfaces of the
cylinder head portions 4L, 4R.
As shown in Figs. 1 and 3 to 5, on the vertical
imaginary line L2-L2 orthogonal to the axis line L1-L1 of
the crankshaft 1 mentioned above, two valve camshafts 26i
and 26e on the intake side and exhaust side parallel with
the crankshaft 1 are rotatably supported at an upper
portion and a lower portion of the left and right
crankcase portions 2L, 2R. The valve camshaft 26i on the
intake side is rotatably supported at an upper portion of
the left and right crankcase portions 2L, 2R by a
plurality of bearing halves 28 which are provided at the
faying surface of the crankcase portions 2L, 2R and a
bearing cap 29 which is fixed to flat top surfaces of the
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left and right crankcase portions 2L, 2R by a plurality
of bolts 30. On the other hand, the valve camshaft 26e
on the exhaust side is also rotatably supported at a
lower portion of the left and right crankcase portions
2L, 2R by a plurality of bearing halves 32 which are
provided at the faying surface of the crankcase portions
2L, 2R and a bearing cap 33 which is fixed to flat top
surfaces of the left and right crankcase portions 2L, 2R
by a plurality of bolts 30. The two valve camshafts 26i,
26e on the intake and exhaust sides are each rotationally
driven by the crankshaft 1 through a timing gear
transmission mechanism T. Namely, as clearly shown in
Fig. 4, driven gears 35 are respectively fixed to end
portions (a right end portion in Fig. 5) of the two valve
camshafts 26i, 26e, while a driving gear 37 is fixed to
an end portion of the crankshaft 1, and idle reduction
gears 36 respectively meshed with the gears 35, 37 are
rotatably supported on the left and right crankcase
portions 2L, 2R. Therefore, when the crankshaft 1 is
rotated, the upper and lower valve camshafts 26i and 26e
can be driven to rotate in the same direction with a
speed reduction rate of 1/2 through the driving gear 37,
the idle reduction gears 36 and the driven gear 35.
As shown in Figs. 1 and 5, on the left and
right sides of the bearing cap 29 supporting the intake
side valve camshaft 26i disposed at upper portions of the
left and right cylinder banks CB1 and CB2, base ends of a
plurality (two for each cylinder) of forked oscillating
arms 39i are oscillatably supported with supporting
shafts 40 at intervals along the direction of the
crankshaft 1. One free end of each of the oscillating
arms 39i is provided with a slipper, which is in contact
with an intake cam formed on the valve camshaft 26i on
the intake side. The other free end of each of the
oscillating arms 39i is connected by a connection pin 41
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with one end of the pull rod 20i. In Fig. 1, the left
and right pull rods 20i penetrate through the crankcase
portions 2L, 2R of the left and right cylinder banks CB1,
CB2, and are extended downward toward the head portions
of the cylinder banks CB1, CB2, namely, the cylinder head
portions 4L, 4R. Tips of the left and right pull rods
20i are connected by connection pins 22 to free ends of
the intake-side swing arms 18i which are shaft-supported
on the cylinder head portions 4L, 4R. Those portions of
the pull rods 20i which are exposed outside the cylinder
banks CB1, CB2 are covered by tubular rod covers 42
bridgingly connected between the crank case portions 2L,
2R and the cylinder head portions 4L, 4R. Also, on the
left and right sides of the bearing cap 33 supporting the
exhaust-side valve camshaft 26e disposed at lower
portions of the left and right cylinder banks CB1 and
CB2, base ends of a plurality (two for each cylinder) of
forked oscillating arms 39e are oscillatably supported
with supporting shafts 40 at intervals along the
direction of the crankshaft 1. Slippers of the
oscillating arms 39e are in contact with exhaust cams
formed on the valve camshaft 26e on the exhaust side.
The left and right pull rods 20e connected by connection
pins 41 to the other free ends of the oscillating arms
39e penetrate through the crankcase portions 2L, 2R of
the left and right cylinder banks CB1, CB2, and are
extended upward toward the head portions of the cylinder
banks CB1, CB2, namely, the cylinder head portions 4L,
4R. Tips of the left and right pull rods 20e are
connected by connection pins 22 to free ends of the
exhaust-side swing arms 18e which are shaft-supported on
the cylinder head portions 4L, 4R. The intake-side
bearing cap 29 supporting the oscillating arm 39i by the
supporting shaft 40 is covered by a cover 43 fixed to an
upper surface of the faying part of the crankcase
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portions 2L, 2R, while the exhaust-side bearing cap 33
supporting the oscillating arm 39e by the supporting
shaft 40 is covered by an oil pan 44 fixed to a lower
surface of the faying part of the crankcase portions 2L,
2R. Incidentally, numeral 45 in the figure denotes an
oil filter supported on the oil pan 44.
The oscillating arms 39i, 39e, the pull rods
20i, 20e, and the swing arms 18i, 18e as valve-operating
members constitute the valve mechanism.
Now, the operation of the first embodiment will
be described. When the crankshaft 1 is rotated by
operation of the internal combustion engine, the upper-
lower pair of the intake-side and exhaust-side valve
camshafts 26i, 26e are respectively rotated in the same
direction with a reduction ratio of 1/2 through the
timing gear transmission mechanism T composed of a group
of gears. Then, the intake-side and exhaust-side
oscillating arms 39i, 39e in adjacent contact with cam
surfaces of valve cams of the valve camshafts 26i, 26e
are respectively forcedly oscillated. When the pull rods
20i, 20e in connection with the oscillating arms 39i, 39e
are pulled toward the valve camshafts 26i, 26e, the
intake and exhaust valves 14, 15 are opened through the
swing arms 18i, 18e functioning as the valve-operating
members. On the other hand, when pulling of the pull
rods 20i, 20e is released, the intake and exhaust valves
14, 15 are closed by springy force of the valve springs
17. When rotation of the intake-side and exhaust-side
valve camshafts 26i, 26e is continued, the intake and
exhaust valves 14, 15 are opened and closed with
predetermined timings, whereby the engine operation is
continued repeating predetermined intake, compression,
expansion and exhaust strokes.
According to the valve system, the valve
camshafts 26i, 26e which are large in weight and mounting
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of which requires space for mounting bearings and other
component members are provided at the crankcase portions
2L, 2R near the crankshaft 1. As a result, cylinder head
portions 4L, 4R, i.e. the head portions, of the cylinder
banks CB1, CB2 can be formed as light and small as
possible.
Next, a second embodiment of the invention will
be described.
Fig. 7 is a vertical sectional view of a V-type
internal combustion engine according to the second
embodiment of the invention, wherein the same elements as
those in the first embodiment are denoted by the same
symbols as above. The second embodiment is application
of the valve system of the invention to an OHV-type four
cycle and V-type four-cylinder internal combustion
engine. In Fig. 7, a pair of left and right cylinder
banks CB1, CB2 are disposed symmetrically on the left and
right sides of an imaginary line L2-L2 orthogonal to the
axis line L1 of the crankshaft 1 disposed in a roughly
horizontal direction orthogonal to the surface of paper.
The structures of the left and right cylinder banks CB1,
CB2 are the same as those of the left and right cylinder
banks CB1, CB2 in the first embodiment above, except for
the V-type layout; and, accordingly, description of the
same structures will be omitted.
A single valve camshaft 26 is rotatably
supported by left and right crankcase portions 2L, 2R on
the imaginary line L2-L2 directly below the crankshaft 1.
Pull rods 20i, 20e connected with intake-side and
exhaust-side oscillating arms 39i, 39e in adjacent
contact with intake and exhaust cams of the valve
camshaft 1 are extended upward respectively on the
lateral sides of the left and right crankcase portions
2L, 2R, and top ends of the pull rods 20i, 20e are
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connected to valve-operating members, i.e. swing arms
18i, 18e on the intake and exhaust sides.
When the pull rods 20i, 20e are pulled via
oscillating arms 39i, 39e by rotation of the valve
camshaft 1, intake and exhaust valves 14, 15 in the left
and right cylinder banks CB1, CB2 are opened with
predetermined timings. When the pulling of the pull rods
20i, 20e is released due to continued rotation of the
valve camshaft 26, the intake and exhaust valves are
closed by springy force of valve springs with
predetermined timings, as usual.
The system according to the second embodiment
makes the same effects as the system according to the
first embodiment above. It is possible to largely reduce
the weight and size of the cylinder head portions 4L, 4R,
i.e. head portions, of the pair of cylinder banks CB1,
CB2 disposed in a V-type configuration.
Incidentally, the left and right crankcase
portions 2L, 2R may be split into upper and lower
portions with respect to a line in a direction
intersecting the imaginary line L2-L2, or may be split
into left, right, front and rear portions in forward and
rearward directions with respect to the surface of paper.
Although the embodiments of the present
invention have been described above, the invention is not
limited to or by the embodiments, and various embodiments
can be made within the scope of the invention. For
example, although the above embodiments have been
described as application of the invention to horizontal
opposed type and V-type internal combustion engines, the
invention can also be applied to other types of internal
combustion engines. Further, although the invention has
been described referring to application to four-valve
type internal combustion engines, the invention can
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naturally be applied to other valve types of internal
combustion engines, e.g. two- or three-valve type.
As has been described above, according to the
invention as set forth in the claims, it is possible to
largely reduce the weight and size of the head portions
of an internal combustion engine. In addition, adoption
of pull rods for operating intake and exhaust valves
promises narrowing of the valve mechanism for connecting
the operation of the valve camshaft and the operations of
intake and exhaust valves.
Although various preferred embodiments of the
present invention have been described herein in detail,
it will be appreciated by those skilled in the art, that
variations may be made thereto without departing from the
spirit of the invention or the scope of the appended
claims.
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