Note: Descriptions are shown in the official language in which they were submitted.
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OVERHEAD VALVE TYPE ENGINE
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1) Field of the Invention:
This invention relates in genera:L to an overhead
valve type internal combustion engine and, in more par-
ticular, to the intake and exhaust system arrangement
for such engines.
2) Description of the Prior Art:
Overhead valve type internal combustion engines
characterized by their arrangements that the intake and
exhaust valves are disposed in the top portion of the
combustion chamber, are universally applied in rolling
stock and other work vehicles for agriculture and public
engineering.
Work vehicles normally employ general-purpose engines,
which can he broadly classified into two groups depending
on the disposition of the crankshaft. In the first group,
the crankshaft is vertically suported with horizontally
placed cylinders. Those belonging to the other group
have theix crankshafts horizontally arranged, with the
cylinders being vertically held.
For application particularly in lawn mowers and
mowing machines, vertical crankshaft types having their
output sha~t provided at a lower end thereof are more
popular due to less overall engine height and the greater
stability of the equipped machine.
In the cylinder heads of those conventional overhead
val~e type internal combustion engines, the inlet ports,
which are connected to the carburetor and air cleaner,
are bored at locations opposite the corresponding exhaust
ports to which the exhaust duct and muffler are joined
for exhaust gas emission.
A fan is generally mounted at the remotest end of
the crankshaft from the output shaft, which is provided
for cooling the cylinders and cylinderhead by supplying
cooling air to them through an air duct.
3~5;~:
A representative such engine is disclo~ed in U.S.
patent No. 4,570,584
However, those prior art overhead val~e type engines
have been found to pose problems. First, because of
their designs that the inlet port is located opposite
the exhaust port in the cylinder head, the bores them-
selves and their portions enclosing the push rods stand
in the way of air streams from the coo:Ling fan, so that
no suf~icient cooling of the cylinder head cannot be
achieved.
Moreover, since insufficient cool:Lng of a cylinder
head tends to result in abnormal combustion problems
such as knocking, the engine cannot enhance output and
insure high fuel economy, one of the expected advantages
of the overhead valve type inkernal combustion engine.
The valve guide is normally pressure itted into
the exhaust or intake valve bore and is usually made of
iron since it is more likely to pose heat problems.
In overhead valve type engines, the exhaust valve guides
are normally mounted in the cylinder head on the crank-
shaft output side. Another problem with them is that
; ~ great difficulty is encountered in cooling the exhaust
valve guides in particular by a cooling fan. As result,
exhaust valve guides, exposed to the high temperatures
of exhaust gaseS~ tend to slip out of places in the
cylinder head, which are normally made of cast aluminum.
SUMMARY OF THE INVENTION
The present invention has been proposed to solve
the drawback of the above-mentioned problems with the
3G prior art.
It is therefoxe a primary objective of the present
invention to provide an overhead val~e type internal
combustion engine which can provide for efficient cooling
of its cylinder head so that engine performance and relia-
bility can be greatly enhanced.
The above and other objectives, features and advan-
tages of the present invention is accomplished by the
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cylinder h ad design that the intake port formed in the
cylinder head has its outlet side opening with the com-
bustion chamber that is substantially perpendicular with
the side in which the intake port has its inlet opening,
with the carburetor connected to the i:ntake port being
located on the opposite side of the cylinder head to the
muffler connected through the exhaust duct to the exhaust
port.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. l is a side cross sectional view of a preferred
embodiment of the overhead type internal combustion engine
according to the present invention;
FIG. 2 is a cross-sectional view taken along the line
II-II of FIG. l; and
FIG. 3 is a cross-sectional view taken along the line
III-III of FIG. 1.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The preferred embodiment of the present invention
: will be described in conjunction with the accompanying
drawings.
; Referring first FIGS. l and 2, which depict diferent
views of an overhead ~alve t~pe internal combustion engine
with a vertically disposed cra~kshaft constructed in
accordance with the present invention, a crankcase l is
shown to carry a vertically disposed crankshaft 2, which
i5 connected to a connecting rod 4 thorugh a crankpin 3.
: Connected to the other end of the connecting rod 4 is a
reciprocating piston 6 that is movably inserted into a
cylinder 5. In this particular embodiment, the cylinder
5 is disposed on a horizontal plane and made integral
with the crankcase 1.
A cylinder head 7 is joined in airtight to the top
surface of the cylinder 5 defining a combustion chamber
8 between the cylinder body and cylinder head 7. In the
upper portion o~ the combustion chamber 8 are provided
: an intake valve 9 and an exhaust valve 10, which both
are movably disposed to move against their respective
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valve seat in the same direction of movement of the piston
6 Each of the valves 9 and 10 is inserted into a valve
guide 11, which may be pressure fitted in the cylinder
head 7.
As shown in the drawing, an intake port 12 is formed
in the cylinder head 7 to open at one end thereof into
the combustion chamber 8 to supply it with fuel/air mix-
ture. The intake port 12 is closed by the intake valve 9
which controls the supply of fuel/air mixtures to the
combustion chamber 8. Also, an exhaust port 13 is defined
to open into the combustion chamber 8 to permit discharge
of exhaust gases generated as a result of combustion of a
fuel/air mixture, controlled by the timed reciprocation
of exhaust valve 10, shown above the intake valve 9 in
the drawing~
As shown in FIGS. 1 and 2, the intake port 12 and
exhaust port 13 are boxed to eixtend in a direction sub-
stantially perpendicular with each other in the cylinder
head 7.
In the cylinder head 7 are pivotally disposed a pair
: of rocker arms 14 which are connected to the intake and
exhaust valves 9 and 10, respectively, as shown in FIG. 2,
in such a ma~ner that motion of the rocker arm 14 in one
direction (clockwise, in the drawing in which thei intake
valve 9 alone i5 shown, although the descrlption should
also refer to the exhaust valve) causes the intake valve
9 to open against a return spring, which urges the intake
valve 9 in a direction that closes it.
A cylinder heiad cover 15 is provided mounted on top
of the cylinder head 7 enclosing the rocker arms 14 in
a rocker arm chamber 16 defined between the cylinder head
cover 15 and cylinder head 7.
Within the crankcase 1 is provlded a camshaft 17
: that extends parallelly with the crankshaft Z, which is
driven to rotate at a rate twice the speed of the crank-
shaft 2. Connected to the camshaft 17 are a pair of
valve drives each consisting of a cam, which is directly
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carried by the camshaft 17, a tappet 18 and a push rod
19 to reciprocate the intake and exhaust valves 9 and 10,
respectively, in timing relationship wlth the rotation
of the crankshaft 2 through their respective associated
rocker arm 140
In this particular embodiment, the push rods 19 are
lined up parallelly with the exhaust pvrt 13. Thus, the
relative location of the valve drives to the valves allows
one of the push rods 19, the one for the intake valve 9
as shown in FIG~ 3, to extend right through the intake
port 12. In order to protect the push rod 19 from expo
sure to the flow of fuel/air mixture passed through the
intake port 12, the push rod 19 may preferably be encased
in a hollow cylinder such as a pipe 20 whose hollow inside
is large enough to permit free reciprocation of the push
rod 19 but narrow enough not to cause obstruction to
streams of Euel/air mixture through the intake port 12.
Preferably, the pipe 20 may be pressure fitted in the
cylinder head 7.
As a consequence of the location of the push rods
19 in the cylinder head 7, the rocker arms 14, along with
rocker arm shaft 21, are located nearer the intake port
12 than the intake and exhaust valves 9 and 10, as illus-
: trated in FIG. 2
Connected to the intake port 12 is a carburetor 22
through an intake pipe (which is omitted in the drawing
for brevity of illustration) to supply fuel/air mixture
to the combustion chamber 8. The carburetor 22 is con-
nected at its inlet side to an air cleaner ~not shown).
As depicted in FIGS. 2 and 3, a muffler 23 is
- provided on the opposi~e side of the cylinder head 7
to the carburetor 22, which is connected to the exhaust
port 13 through an exhaust duct 24.
An output shaft 25 is connected to the crankshaft
: 35 2 at the bottom side of the cxankcase 1, which is placed
on a base 26 for mounting on the floor of a work vehicle,
to transmi-t engine torque to the road wheels of the
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vehicle through a transmission system. Owing to this
arrangement, the exhaust port 13 i~ formed to open on
the bottom side of the crankcase 1.
The crankshaft 2 protrudes above the top surface
of the crankcase 1 for connection to a flywheel 27 and
a cooling fan 28. In the embodiment shown, a combined
flywheel with a cooling fan is employed in place of them.
Also, a recoil starter 29 is provided for starting the
engine.
A fan housing 30 is provided covering half part of
the top surface of the crankcase 1 to enclose the cooling
fan 28. The fan houseing 30 is constructed in such a
manner as to guide the cooling air from the cooling fan
28 to flow along -the surfaces of the cylinder 5 and
cylinder head 7.
Furthermore, between the cylinder head 7 and muf-
fler 23 is disposed a baffle 31 which directs cooling
air from above to flow along the surfaces of the cylinder
5 and cylinder head 7 then downward along the bottom of
the cylinder head 7 in the vicinity of the exhaust port
13.
The surfaces of the cylinder 5 and cylinder head 7
may preferably be shaped into fins~ as shown in FIG. 1
and 2, to increase outside cooling surface.
Thls arrangement enables the cylinder head 7 to be
formed on its side opposite the intake port 12 with a
sufficiently corrugated fin centering around the valve
guides 11 for the intake and exhaust valves 9 and 10 to
provide for enhanced cooling, as shown in FIG. 2. Thus,
the cooling air from the cooling fan 28 is allowed to
flow smoothly in a desired direction, as indicated by
the arrows in FIG. 3, cooling that part of the cylinder
head 7 surfaces which encircling the valve guides 11
where proper cooling is most required. The baffle 31
helps guide the cooling air along a direction that
further optimize cooling efficiency.
The side of the cylinder head 7 adjacent to the
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intake port 12 is far less exposed to cooling.air, blocked
by the push rod 19, in addition to physical impossibility
to form a proper fin in the surface. ~loweve~, this area
is almost unlikely to cause heat problems and some degree
of cooling is provided by the passage of fuel/air mixtures
through the intake port 12. ~ cooling passage 32 opened
to vertically run through the cylinder head 7, illust~
rated in FIG. 2, will suffice to provide effectlve cooling
of the intake port 12.
1~ With respect to F~G. 3, cooling air flowing around
the left side of the cylinder head 7 will be allowed to
move uninterrupted into the area below its bottom side
so that the exhaust port 13, together with part of the
exhaust duct 2~, will be cooled~ The baffle 31 will help
enhance the cooling effect of the air flow thus directed.
The air flow, after exposure to the heated exhaust port 13
by high-temperature gases flowing in its inside, is then
permitted to exit downward.
In this particular embodiment, although the baffle
31 and the fan housing 30 are separate parts, this is a
matter of choice and they may be built in-to a single
component putting together their features.
It will be appreciated from the above tha-t the pre-
sent invention provides efficient cooling, in addition
to the engine layout where uniform cooling can be obtain-
able.
Furthermore, since the cooling air, after increase
in temperature through contact with the heated cylinder
head 7 and other associated parts, is caused to leave
the cylinder 5 on its exhaust port side, without flowing
in the vicinity of the carburetor 22, problems such as
percoration in the fuel system will be eliminated~
In addition, the layout of the intake port 12 extend-
ing perpendicular with the exhaust port 13 within the
cylinder head 7, with the carburetor 22 connected to the
intake port 12 on the opposite side of the cylinder 5 to
the muffler 23 connected through the exhaust duct 24 to
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the exhaust port 13, as can best be illustrated in FIG. 3,
enables both the width W and the height H of the engine
to be reduced~ contributing much to easing the mounting
and handling of an overhead valve type internal combus-
tion engine. It is important to note that minibuariza-
tion can be achieved while insuring a sufficient length
of the exhaust duct 24, as will be apparent from FIG~ 3.
Furthermore, as can be best shown in FIG. 3, the
intake and exhaust valves 9 and 10, together with their
intake and exhaust ports 12 and 13, can be put to one
side in the cylinder head 7 so that the en~ine designer
can have the greater freedom in selecting the location
~nd angle of the spark plug in a fairly wide space oppo-
site the valves within the combustion chamber 8.
Although the above description refers to an internal
combustion engine of the type in which the camshaft 17 is
disposed wlthin the crankcase 1, the present invention
can also be applied to overhead camshaft engines having
their camshafts encased in a rocker arm
2~ Furthermoref the present invention has been described
with respect to a vertical crankshaft type of internal
combustion engine with a horizontal cylinder~ However,
it should be understood that the invention is applicable
for engines with tilted (V-type) or vertical cylinders
as well.
Additionally, in the above description of the embodi-
ment, although the exhaust port 13 and the exhaust duct
24 are each placed at right angles with respect to the
axis of the crankshaft 2, as shown in FIG. 3, this is a
matter of choice and they can take any angle of position,
for example 45, to the crankshaft.
