Note: Descriptions are shown in the official language in which they were submitted.
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INTAKE M~NIFOLD FOR INTERNAL COMBUSTION ENGINE
HAVING EXHAUST GAS RECIRCULATION SYSTEM
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an internal
combustion engine equipped with an exhaust gas recircu
lation (EGR) system. More specifically, it relates to
an intake manifold for such an internal combustion
engine, capable of preventing the deposition of combus-
tion products around the EGR gas outlet of the exhaust
gas recirculation system.
2. Description of the Related Art
In an ordinary internal combustion engine,
unburnt hydrocarbons (abbreviated to "HC" hereinaterl
leak through the clearances between the piston and the
piston rings into the crankcase of the engine due to a
so~called pumping action of the piston rings during
reciprocating operation of the piston. The discharge of
HC (generally referred to as ~'the blow-by gas") into the
atmosphere causes air pollution. Therefore, it is usual
to feed the blow-by gas through the cylinder head into
the intake manifold, where the blow-by gas mixes with
the intake air or fuel-air mixture. A system for
introducing the blow by gas into the intake manifold is
generally referred to as a positive crankcase ventilation
system ~abbreviated to "PCV system" hereinafter).
On the other hand, in some internal combustion
engines, before discharging the exhaust gas into the
atmosphere, a part of the exhaust gas (EGR gas) is
circulated through the intake system to reduce the
concentration of nitrogen oxides (abbreviated to "NOx"
hereinafter3 in the discharged exhaust gas. In such an
exhaust gas recirculation systems, especially for a
Diesel engine, EGR gas contains relatively large amount
of combustion products, such as carbon particles. On the
other hand, in a PCV system as mentioned above, oil
vapor contained in the blow-by gas is brought from the
crankcase through the cylinder head and head cover into
the intake manifold in which the oil flows in a mist or
film-like condition. Under these circumstances, the
carbon particles contained in the EGR sas are trappe~ by
the oil flowing from the PCV system into the intake
` manifold and adhered to the inner surface or the intake
mani~old. These particles, hereinafter referred to as
"deposits", grow in the vicinity of the EGR pipe (the EGR
gas inlet of the intake manifold), thereby these deposits
may block the outlet of the EGR pipe. In an engine
equipped with a turbocharger, bearing lubrication oil
in a turbin housing will leak to the intake manifold,
so that the amount of oil flowing therein is increased,
thereby the above-mentioned problems will readily arise.
Techniques have been proposed to reduce the
collection of deposits around the outlet of the EGR pipe.
Such known techniques are, for example; projecting the
outlet of an EGR pipe into the interior of an intake
manifold (Japanese Unexamined Utility Model Publication
Nos. 56-88933 and 58-116748), disposing the outlet of an
EGR pipe and the outlet of the pipe of a PCV system
symmetrically with respect to the center axis of -the
throttle valve (Japanese Unexamined Patent Publication
No. 58-65922); providing a blow-by gas guide for guiding
the blow-by gas to the downstream of the outlet of the
EGR pipe (Japanese Unexamined Utility Model Publication
No. 56-8893~); or projecting a blow-by gas pipe of a
PCV system into the interior of an intake manifold
(Japanese Utility Model Publication No. 58-33713).
SUMMARY OF T~E IN~ENTION
An object of the present invention i5 to provide an
intake manifold having a simple construction for an
internal combustion engine equipped with an EGR system,
the interior of the manifold being provided with means
for preventing the oil vapor and the like from flowing
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into the EGR gas outlet of the EGR pipe, thereby prevent-
ing the deposition of deposits ar~und the exhaust gas
outlet to secure a necessary exhaust gas recirculating
rate (abbreviated to "EGR rate" hereinafter).
According to the present invention, an intake
manifold for an internal combustion engine is provided
eouipped with an EGR system for introducing a part of
the exhaus- gas from an exhaust passage through an
exhaust (EGR) gas outlet into the intake manifold~
characterized in that the exhaust (EGR) gas outlet is
provided in the upper section of the interior thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure lA is a partial cross-sectional view,
corresponding to a cross-sectional view taken along
line A-A of Fig. 6, but illustrating an embodiment of
the present invention;
Figure lB is a sectional view taken on line B-B of
Fig. lA;
Figures 2 and 3 are partial cross-sectional views,
corresponding to the cross-sectional view taken along
line A-A of Fig. 6, but illustrating further embodiments
of the present invention;
Figure 4 is a schematic illustration generally
showing an internal combustion engine equipped with an
EGR systemj
Figure 5 is a plan view of the internal combustion
engine as shown in Fig. 4;
Figure 6 is an enlarged fragmentary plan view of a
portion of Fig. 5 indicated by a symbol VI; and
Figure 7 is a partial cross-sectional view, corre-
sponding to a cross-sectional view taken along line A-A
of Fig. 6, but illustrating an exhaust (EGR~ gas outlet
and its vicinity, in a conventional EGR system.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be described hereinafter ~,
with reference to the preferred embodiments thereof in
conjunction with the accompanying drawings. First,
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re~erring to Fig. 4, indicated at 1 is an internal
combustion engine; 2, an intake manifold; and 3, an
exhaust manifold. The intake manifold 2 and the exhaust
manifold 3 are connected to each other by means of an
e~haust gas recirculation pipe 4 (abbreviated to
"EGR pipe" hereinafter) and an exhaust gas recirculation
valves (abbreviated to '7EGR valve" hereinafter). The
valve element 5c of the EGR valve 5 is operated to open
or close an inlet 5c by the mutual functions of the
intake manifold pressure and the resilient force of a
spring 5a. A part of exhaust gas (EGR gas) is fed
through an EGR gas outlet 10 into the intake manifold 2.
The intake manifold 2 is connected to the interior of a
cylinder head cover 6 by means of a positive crankcase
ventilation pipe (abbreviated to "PCV pipe" herein-
after) 7 which opens into the intake manifold 2 at a
positlon upstream of the EGR gas outlet 10. An air
cleaner 9 is connected to the intake manifold 2 by a
hose 8. Such an engine includin~ EGR and PCV systems is
already known in the prior art.
Figure 5 is a top plan view of the internal combus-
tion engine as mounted on a vehicle; Fig. 6 is a frag-
mentary enlarged view of a portion indicated by a
symbol VI in Fig. 5; and Fig. 7 is a sectional view of
an internal combustion engine equipped with a conven-
tional intake manifold and a conventional E&R system,
taken along line A-A of Fig. 6. As shown in Fig. 7 9 the
EGR gas outlet 10 of the conventional EGR system known
in the prior art is provided on the side wall of the
intake manifold 2. Consequently, the oil vapor contained
in ~he blow-by gas supplied to the intake manifold 2 by
the PCV system or leaked from a turbocharger into the
intake manifold 2 flows to a point downstream in the
intake manifold; however, the oil cannot be separated
properly from the EGR gas fed into the intake manifold 2,
and hence deposits are liable to collect around the
EGR gas outlet 10.
Figures lA, 2, and 3 are sectional views, each
corresponding to a sectional view taken along line A-A
of Fig. 6, of the intake manifold 2, but illustrating
embodiments o~~ the present invention, around the EGR gas
outlet o~ the EGR systemS respectively. Similar to the
EGR valve 5 of the conventional EGR svstem shown in
Fig. 7, e-ch of EGR valves 5 of these embodiments is
: disposed beside the side wall of the intake manifolds 2.
However, in each embodiment of the present invention,
the arrangement of an EGR gas supply passage 12 extending
from the EGR valve 5 to the intake manifold 2 and that
of an exhaust gas outlet 10 opened to the intake mani-
fold 2 are different from those in the conventional
EGR system including the intake manifold shown in Fig. 7.
In an embodiment shown Figs. lA and lB, when the
intake mani~old 2 is made by casting, the EGR ~as supply
passage 12 is ~ormed integrally with the intake mani-
fold 2 so as to extend into the interior of the intake
manifold 2. That is to say, a wall 13 ~or defining the
EGR gas supply passage 12 extends to the upper area of
the interior space of the intake manifold 2 to form an
EGR gas outlet 10 in the upper area within the intake
manifold 2. Preferably, the shape of the cross-section
of the EGR gas supply passage 12 is rectangular, as
shown in ~ig. lB, so that a sufficient sectional area of
the passage 12 is secured even if the EGR system needs
to be mounted on the internal combustion engine in a
narrow space. It is also preferable to form the EGR gas
outlet 10 as wide as possible so that deposits collected
around the EGR gas outlet 10 can be readily removed.
The upper end of the wall 13, namely, the edge of the
wall 13 defining the EGR gas outlet 10, is bent to form
a lip 14, as shown in Fig. lA. Preferably, the width w
of the lip 14 in the transverse cross-section of the
intake manifold 2 is in the range of 5 to 10 mm and the
angle ~ between the wall 13 and the lip 14 is 90 or
less. The preferable angle between the wall 13 and a
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substantially horizontal bottom wall 2a of the intake
manifold 2 is also 90 or less. The wall 13 and the
lip 14 thus formed cooperate to avoid oil from climbing
up along the inner surface (wall 13) of the intake
manifold 2.
In another embodiment of the present invention
shown in Fig. 2, an EGR gas supply passage 12 is made of
a pipe which is joined to an intake manifold 2 so as to
extend along the side wall to the top wall of the intake
manifold 2. The EGR gas outlet 10 of the EGR gas supply
passage 12 is located below the inner surface 2b of the
top wall of the intake manifold 2 by a small distance (5
to 10 mm) to prevent oil from flowing into the EGR gas
outlet 10. A portion 2c of the side wall of the intake
manifold 2, along which the EGR gas supply passage 12
extends, is concaved along the EGR gas supply passage 12
from the side wall 2d of the intake manifold 2 so as to
form a step 2e therebetween. Therefore, oil flowing
along the side wall 2d is stopped by the rising surface
of the s-tep 2e and is prevented from flowing into the
EGR gas outlet 10.
In a further embodiment shown in Fig. 3, an
EGR valve 5 is contiguous at one side thereof to the
side of the intake manifold 2. An ~GR gas supply
passage 12 is formed by a pipe 15 of a diameter in the
range of 20 to 25 mm. The pipe 15 is connected at one
end thereof to the other side of the EGR valve 5. The
other end of the pipe 15 is extended to the top wall of
the intake manifold 2 and protruded from the inner
surface 2b of the top wall into the interior of the
intake manifold 2 by a small distance (5 to 10 mm)/
similar to the relation between the EGR gas passage 12
and the top wall in the embodiment of Fig. 2. Conse-
quently, oil flowing along the inner wall of the intake
passage 2 is prevented from flowing into the EGR gas
outlet 10.
According to the present lnvention, the EGR gas
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outlet 10 is provided in the upper part of the intake
manifold 2 and the EGR gas supply passage is so con-
structed as to impede the oil from flowing into the
EGR gas outlet 10. Accordingly, the EGR gas introduced
through the EGR gas supply passage 10 into the intake
mzni.old 2 is well mixed with the intake air, and then
flows together with the oil which may be contained in
the blow-by gas supplied to the intake manifold 2 by the
PCV system or may be leaked into the intake manir-old 2
from the turbocharger. Consequently, deposits containing
carbon particles and impurities are neither produced nor
deposited within the intake manifold, and hence a
sufficient EGR rate is secured.
