Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a method of casting ~;
of cylinder head for an internal combustion engine. ~; ;
Among various measures to reduce air pollutants,
- such as hydrocarbon (HC) and carbon monoxide (CO), within
exhaust gas discharged from automobiles, it is known to fit an -~
internal combustion engine with a thermal reactor in its exhaust
system to oxidize the air pollutants. The~efficiency of the ;`
thermal reactor depends on the temperature of the exhaust
gas and it is necessary to minimize a heat loss in the exhaust
system to maintain the exhaust gas at elevated temperature.
A conventional internal combustion engine is installed
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; with a port liner within an axhaust port passage formed through
a cast body of its cylinder head. The port liner is pressed in-to
the exhaust port passage according to the conventional method i`
; of installing a port liner in an exhaust port passage of a cylin- ~
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der head. This conventional method has a problem in that machin-
ing of an inner wall defining the exhaust port passage is
required before the port liner is pressed into the exhaust
port passage, and if the exhaust port passage has a complicated
curvature, the port liner can not fully enter the exhaust port
passage. Another problem resides in that the port liner can not
ex-tend from an exhaust valve to a discharge end o the passage
to which one of manifold passages of an exhaust manifold is
connected, because usually an exhaus-t port passage leading from `
the exhaust valve to the discharge end is curved and thus the
temperature gradient along the exhaust port passage does not
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reduce sufficiently.
The main object of the present invention is to solve ;~
the~above mentioned problems encountered in the conventional
method and to provide a method by which productivity of a
cylinder head having a port liner increases.
' J A further object of the present invention is to provide
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a simple method of casting a port liner in an exhaust port ..
passage of a cylinder head, which eliminates the above mentioned ..
problems.
These objects are achieved with a method comprising
the steps of~
. forming a port liner by a metal tube, said port liner :
having an exhaust intake end and an opposite exhaust discharge . ;:
end;
forming on an exterior surface of s'aid port liner a ;
layer of a moulding material, said layer ~mcovering an area on :~
said exterior surface of said por.t liner which is disposed adjacent `~: '
to said exhaust intake end of said port liner,'said layer
. uncovering an area on said ex-terior surface or said port liner which'
. is disposed adjacent said opposite exhaust discharge end of said
port liner to ~orm a plurality of grooves running toward said
` opposite discharge end o:E said port liner;
forming a valve seat; ~:
engaging said exhaust intake end of said port liner in `' :'
said valve seat;
casting material on an outer periphery of said valve ; : ~:
seat, said layer and said exterior surface of said port liner ' `.~:
at those areas which are uncovered by said layer; and
removing said moulding material after the step of ' '~ .`
. . casting is completed. . '`~
'' The present invention will be more clearly described . " ~'
.hereinafter-by reference to'the accompanying drawlngs, in which~
Fig. 1 is a sectional view of a cylinder head showing '
an exhaust port passage provided with a port liner;
Fig. 2 is a plan view of the port liner before
'` 30 casting; . ' ~`~
~ Fig~ 3 is a sectional view taken through line III-
.-' III in Fig. 4 showing the liner and land for the exhaust port
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passage;
Fig. 4 is a sectional view taken through line I~l-IV
in Fig. 3;
Fig. 5 is a plan view of a port liner for a Siamese
exhaust port passage; and
; Fig. 6 is a similar view to Fig. 4 showinga ~ore for the
Siamese exhaust port passage.
Fig. 1 shows a cast cylinder head embodying the present ~ ~
invention. The cylinder head is formed by a casting operation, a ~;
valve seat 10 for an intake valve, a valve seat 12 for an exhaust
valve and a port liner 14 is placed in their proper positions
with respect to a flask (not shown~ for the cylinder head. The
cylinder head is formed with a combustion space 16, an intake `
port passage 18 and an exhaust port passage 20. Valve guides 22
and 24 for intake and exhaust valves (not shown) are pressed into
the ~ody o~ the cylinder head ancl directed to the valve seats
10 and 12, respectively.
The port liner 14 comprises a metal tube 14a made of a
heat resisting steel with one end 14b inserted into an annular
shoulder 12a formed in the exhaust valve seat 12 and the opposite
end 14c terminating in a lateral side of the body of the cylinder
head. The one and the opposite ends 14b and 14c serve as an
exhaust intake and a exhaust discharge respectively, the dischar- `
ge end being for connection to one of manifold passages of an
exhaust manifold (not shown). A space 26 is formed between the
liner 14 and an inner wall 28 of the body of the cylinder head
defining the exhaust port passage 20 and serves as an insulating
layer.
The shape of the intake port passage 18 is determined by
configuration of a core made of a moulding material, such as green `~
moulding sandwich is a mixture of sand grains, clay, water and
other materials to improve properties of the core, while the liner
14 and a land 30 which act as a core during casting determine
the shape of the exhaust port passage 20.
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The Land 30 is adhered to the outer periphery of -
the metal tube 14a and is made of the green moulding sand and
corresponds in shape to the space 26 serving as an insulating ~ ,
layer. Figs. 3 and 4 show the llner 14 ancl the land 30 which
act as the core of the exhaust port passage 20 during casting.
The shape of the land 30 is formed by removing a portion of green
moulding sand within an area which is disposed adjacent to the one
end 14b and by removing a portion of green moulding sand to ;~
form a plurality of grooves 32 within an area which is disposed
adjacent to the opposite end 14c after adhering a layer of green
moulding sand to all of the area of the outer periphery of the
metal tube 14a with even depth. The core for the exhaust port i
passage 20 is placed in its proper position with its other
end 14c suitably supported by the flask (not shown) for the
cylinder head.
Means for preventing the port liner 14 from slipping ~ ;
out of its proper position within the exhaust port passage 20 ~;
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is provided. The preventing means is in the form of a projection
14d integrally formed on the outer periphery and adjacent
to the one end 14b of the metal tube 14a. As there is no green ~
~moulding sand within an area where the projection 14d is ,~ -
formed, the projection 14d will be embedded in the body of
the cylinder head after the casting operation is over. '
After the casting operation is over, the green
, moulding sand forming the land 30 can be removed through sand
, filled spaces formed between grooves 32 which are the filled `
with metal. As a result the space 26 is formed. If desired
', the land 30 filling the space 26 may be left as it is because
the green moalding sand serves as an insulating material.
Turning to Fig, 1 because the port liner 14 is
installed within the exhaust port passage 20 with the
: space 26 therearound the amount of heat transfer from the port
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liner 14 to the body of the cylinder head, which depends on
amount of contact area between the por-t liner 14 and the body
of the cylinder head, is reduced. Thus the cooling effect due
to cooling liquid within a passage 3~ on exhaust gas flowing ~
through the metal tube 14a is reduced, and the temperature -~ ;
gradient along the exhaust port passage 20 emanating from the
exhaust intake to the exhaust discharge is also reduced. It
will therefore be appreciated that with the engine head shown
; in Fig. 1 the temperature of the exhaust gas is maintained
high.
Fig. 5 shows a port liner 14' for a Siamese exhaust
port passage. Since this port liner 14' is basically similar
to the port liner 14 shown in Fig. 2 except that two such
port liners 14 join with each other to form a common end, the
similar parts shown in Figs. 5 and 5 to those shown in Figs.
1 to 4 are designated by the same references, but with primes,
respectively.
The port liner 14' is integral with the body of
a cylinder head during casting operation after forming a
land 30' on the outer periphery of each of two metal tubes
20 14'a in the same manner as preceedly described in connection ;
with Figs. 1 to 4.
It will be appreciated as one of the advantages of
the present invention that irrespective of the shape of
an exhaust port passage, a port liner can be installed ~ -
in the exhaust port passage and an insulating-space or layer
between an interior surface defining the exhaust port passage
and an exterior surface of the port liner may take any
~` desired shape.
It will also be appreciated that because the port
liner is placed in its proper position during the casting
operation, high quality on mass production basis can be
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37
maintained. :
It will also be appreciated that a conventional
core, which is made of green moulding sand only, for the ;-
exhaust port passage is no longer necessary.
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