Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to an exhaust gas
purifier of an internal combustion engine. `-
This application is a divisional of Canadian Appli-
cation Serial ~o. 249,761 filed April 7, 1976.
Known internal combustion engines are provided with
exhaust gas purifiers which use catalytic converters for
eliminating harmful components from the exhaust gas, for
example unburned gases HC and C0. In conventional catalytic
converters of this type, a secondary air is fed to the
catalytic converter by means of the secondary air feed -
pump driven ~y the engine and thus the oxidation of unburned
HC and C0 is promoted in the catalytic converter, thereby
eliminating harmful components from the exhaust gas. Conse-
quently, conventional exhaust gas purifiexs need to be pro-
vided with the secondary air feed pump.
An object of the present invention is to provide an
improved exhaust gas purifier of a simple construction with-
out the above-mentioned`secondary air feed pump.
According to the present invention, an improved
exhaust gas purifer in a f~ur-stroke internal combustion
engine having a plurality of cylinders each having an
intake valve, an exhaust valve and an ëxhaust passage,
said cylinders being arranged in cylinder groups each of
; which group comprises at least two cylinders, the opening
durations of the exhaust valves in any one group not over-
lapping, wherein the improvement comprises:
at least ona air passage for connecting the
exhaust passages of the cylinders of one of said cylinder
groups with the atmosphere, and
a valve means disposed in said air passage and
arranged to open automatically in response to a decrease
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in pressure below a predeterminea value in the exhaust
passages of the cylinders of said one cylinder group to
permit the supply of an air into the exhaust passages of -
the cylinders of said one cylinder group.
The above-mentioned object of the invention may be
more fully understood from the following description of a
preferred embodim2nt of the invention and from the accom-
panying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
Fig. 1 is a schematic plane view of an internal
combustion engine having the exhaust gas purifier according
to the present invention;
Fig. 2 is a cross-sectional view taken along the
line II-II in Fig. l;
Fig. 3 is a view showing intake- and exhaust-
valve timing;
Fig. 4 is a view showing valve lifts of an
intake valve and an exhaust valve'~of each cylinder in a
four-cylinder engine;
Fig. 5 is a schèmatic plane view of an embodiment
showing the possible combinations of the cylinders which
the branch conduits should be connected to;
Fig. 6 is a view similar to Fig. 5, showing
another embodiment;
, Fig. 7 is a view similar to Fig. 5, showing the
oth~r embodiment;
Fig. 8 is a view showing valve lifts of an
intake valve and an exhaust valve of each cylinder in a
six-cylinder engine;
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Fig. 9 is a schematic plane view of an embodiment
showing the various possible combinations of cylinders
which the branch conduits should be connected to;
Fig. 10 is a view similar to Fig. 9, showing `
another embodiment, and;
Fig. 11 is a prospective view of the reed valve.
DESCRIPTION OF A PREFERRED EMBODIMENT
Fig. 1 shows a schematic plane view of the internal
combustion engine having the exhaust gas purifier according
to the present invention and Fig. 2 shows a cross-
sectional view of a part of the engine shown in Fig. 1.
Referring to Figs. 1 and 2, the internal combustion engine
comprises a cylinder block 1, a piston 3 reciprocatively
movable in the cylinder 2 formed in the cylinder block 1,
i5 a cylinder head 4 fixed onto the cylinder block 1, an
intake valve (not shown), an exhaust valve 6 for controlling
the opening and closing operation of an exhaust port 5, an
exhaust manifold 7 and an intake manifold 8 which are
fixed onto the cylinder head 4, an air cleaner 9 mounted
on`the intake manifold 8 and a catalytic converter 10.
The gas to be exhausted which has béen burned in a combustion
chamber 11 is delivered into the catalytic converter 10
through the exhaust manifold 7, and then, the gas cleaned
in the catalytic converter 10 is delivered to the atmosphere.
~25 Fig. 3 shows the intake- and exhaust-valve timing.
- In a conventional in,ternal combustion engine having the -
intake valve and the exhaust valve, a duration of overlap
between the intake valve and the exhaust valve occurs
during which both the intake and the exhaust valves are
each in an opened position immediately before the exhaust
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valve is closed. As in shown in Fig. 3, for example, the
exhaust valve A opens 50 before sDc (sottom dead center)
and closes 16 after TDC (Top dead center), and the intake
valve B opens 16 before TDC and closes 50 after sDC.
Consequently, as is shown by arrow C, a duration of overlap
occurs when both exhaust valve A and the intake valve B
are each in an opened position.
In Fig. 2, assuming that the engine is in an exhaust
stroke position during which the exhaust valve 6 is in an
opened position, the gas to be exhausted in the combustion
chamber 11 is delivered into the catalytic converter 10
via the exhaust valve port 5, the exhaust port 12 and the
exhaust manifold 7 as the piston 3 is moved upwords in the
cylinder 2. At this time, the pressure in the exhaust
port 12 and in the branch portion of the exhaust manifold
7 is greater than the atmospheric pressure. Then, when
the intake valve opens and piston 3 is further moved
upwards so as to reach its uppermost position (TDC), the
pressure in the exhaust port 12 and in the branch portion
of the exhaust manifold 7 becomes substantially the same
as the atmospheric pressure. Then, when the piston 3
begins to move downwards, the fuel mixture is sucked into
the combustion chamber 11 via the intake port (not shown).
; At this time, the exhaus~ valve 6 is still in an opened
-25 position. Thus, a part of the exhaust gas in the exhaust
port 12 is again sucked into the combustion chamber 11,
whereby the pressure in the exhaust port 12 and in the
branch portion of the exhaust manifold 7 becomes slightly
lower than the atmospheric pressure. As is aforementioned,
if both the intake valve and the exhaust valve 6 are in
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opened positions during the time when the piston has a
position at round TDC, the pressure in the exhaust port 12
and in the branch portion of the exhaust manifold 7 ap-
proaches that of a vacuum. According to the invention,
the internal combustion engine is provided with an auto-
matically opening and closing reed valve 13 known per se
in order to feed a secondary air for promoting the oxidation
of unburned gas into the exhaust port 12 by using said
vacuum, or by using the fluctuations of the exhaust gas
pressure, said fluctuations are created by the opening and
closing operation of the exhaust valve 6 and the intake
valve. The reed valve 13 is connected to the dust portion
of the air cleaner at a position opposite to the air inlet
opening in the air cleaner 9 via conduit 14, an air filter
15 for filterin~ the secondary air, a silencer 16 for
stopping a suction noise of the secondary air ana a conduit
17, on one hand; and to a predetermined number of exhaust
ports 12, as will be hereinafter explained, via an air
suction manifold 18, branch conduits 19, air suction
i 20 nozzles 20 disposed on the fron~ ends of the branch conduits
19 and passages 21 formed in the cy~inder head 4, on the
other hand. The reed valve 13 opens when the pressure in
; the branch conduits 19 becomes slightly lower than that in
the conduit 17, i.e~, the atmospheric pressure, or when a
- 25 decrease in the pressure greater than a predetermined
value takes place in the branch conduits 19. Consequently,
when the pressure in the exhaust port 12 becomes similar
to that in a vacuum or when the pressure drop takes place
in the exhaust port 12, air is sucked into the exhaust
port 12 from the air cleaner 9 via the conduit 17, the
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silencer 16, the air filter 15, the conduit 14, the reed
valve 13, the air suction manifold 18, the branch conduits
19, the air suction nozzles 20 and the passages 21.
An internal combustion engine used for an automobile,
for example, is generally provided with four, six or eight
cylinders. Of course, it is possible to provide the reed
valves and the air filters for every cylinder, however,
this causes an increase in costs and difficulties in
construction. Furthermore, it has been found that, for
example, in an internal combustion engine having four
cylinders, if the secondary air is fed into the exhaust
passages, i.e. the exhaust port 12 or the branch portion
of the exhaust manifold -? of only two of the four cylinders,
it is possible to supply the exhaust gas with a sufficient
amount of air which is needea for effectively promoting
the oxidation in the catalytic converter. Consequently,
consideration must be directed as to which exhaust passages
among those of the four cylinders the secondary air should
be fed into. `
As is shown in Figs. 5 through 7, assuming that an
internal combustion engine is provided with four cylinders
comprised of No.l cylinder, No.2 cylinder, No.3 cylinder
and No.4 cylinder, and the firing order in this engine is
1 ~ No.l-No.3-No.4-No.2, the exhaust- and intake-valve timing
L 25 in each cylinder is as shown in Fig. 4. In Fig. 4, the
'~ ~ abscissa indicates the crank angle eand the ordinate ~-
l indicates the valve lift of the exhaust valve and the
! intake valve in each cylinder. Each of the A curves
indicated by the hatched line shows the respective exhaust
valve lifts in No.l through No.4 cylinders, and each of
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the B curves shows the respective intake valve lifts in
No.l through No.4 cylinders. Furthermore, the duration of
an overlap between the exhaust valve and the intake valve
is shown by C.
It is assumed that branch conduits 19 which are
connected to a single reed valve 13 having the air filter
13 are connected to No.l and No.2 cylinders, respectively.
In this case, it is apparent from Fig. 4 that when the
intake valve and the exhaust valve of No.2 cylinder, are,
in a durational phase of an overlap and thus the pressure
in the exhaust port 12 of No.2 cylinder is similar to that
in a vacuum, the exhaust valve A of No.l cylinder is in an
opened position. Thus, the pressure in the exhaust port
12 of No.l cylinder is greater than the atmospheric pressure.
As a result, the reed valve 13 is closed by the action of
the pressure created in the exhaust port of No.l cylinder.
Consequently, in spite of the creation of the vacuum and
the occurrence of the pressure drop in the exhaust port of
No.2 cylinder, the secondary air cannot be fed into the
exhaust port of No.2 cylinder. That is to say, if the
branch conduits l9 are connected to said;two cylinders
that, when the intake valve and the exhaust valve of one
o$ the cylinders are in the durational phase of an overlap,
then, the exhaust valve of the other cylinder is in an
~;2~ opened position. In other words, when said two cylinders
are subjected to a condition wherein the opening durations
of the exhaust valves of both cylinders overlap with each
other, a secondary air cannot be fed into one of the two
cylinders under the influence of the other cylinder.
Consequently, in order to supply two cylinders with
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the secondary air, the branch conduits 19 must be connected
to said two cylinders such that the opening durations of
the exhaust valves of both cylinders do not overlap with
each other. Furthermore, it is considerably effective in
the operation of supplying the secondary air to divide an
exhaust manifold into two separate exhaust manifolds, one
of which is used for said two cylinders, the other exhaust
manifold being used for the remaining cylinders.
Referring to Fig. 5 while taking into consideration
the above, the possible combinations of two cylinders
which should be connected to the single reed valve 13 are
either the combination of No.l cylinder with No.4 cylinder
as shown in Fig.5, or the combination of No.2 cylinder ~-
with No.3 cylinder as shown in Fig. 6. In either case, as
a~orementioned, it is further effective to divide an
exhaust manifold into two separate exhaust manifolds as
shown in Fig. l and as shown by the broken line in Fig. 6.
Although the engine construction is made slightly com-
plicated, in order to supply all of the cylinders with the
secondary air, as shown in Fig. 7, the engine may be
provided with the branch conduits 19 connected to No.l
; cylinder and No.4 cylinder, the reed valve 13 connected to
the branch conduits 19, the branch conduits 19' connected
to No.2 cylinder and No.3 cylinder, the reed valve 13'
connected to the branch conduits 19' and the air filter 15
connected to the reed valves 13 and 13'.
Figs. 8 and 10 show another embodiment in the case
o~ applying the present invention to a six-cylinder engine.
In Figs. 8 through 10, the description of the components
is omitted because Fig. 8 ;s depicted in a similar manner
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as Fig. 4 and also Figs. 9 and 10 are depicted in a similar
manner as Figs. 5 through 7. Referring to Fig. 8, in a
six-cylinder engine, the possible combination of two
cylinders which should be connected to the single reed
valve 13 is, for example, the combination of No.l cylinder
with No.6 cylinder, or the combination of No.2 cylinder
with No.5 cylinder, or the combination of No.3 cylinder
with No.4 cylinder as shown in Fig. 9. Furthermore, in a
six-cylinder engine, three cylinders such as No.l, No.2
and No.3 cylinders or No.4, No.5 and No.6 cylinders can be
combined and connected to the single reed valve 13. That
is to say, it is possible to combine said three cylinders
in such a way that the crank angles of these three cylinders,
which cause the opening of the intake valves, are 240
apart from one another. In the case of combining the
above-mentioned three cylinders, these three cylinders are
affected much more by the remaining cylinders than would
the two cylinders ~e affected by the remaining cylinders
in the case of combining two cylinders, cran~ angies for
opening the intake valves of said two cyIinders being 360
apart from each other. However, when it is sufficient to
supply a small amount of a secondary air to the above-
mentioned three cylinders connected to the single reed
valve, the combination of three cylinders can be used. Of
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course, in Figs. 9 and 10, the engine is provided with a
-~ plurality of reed valves and with a single air filter as
- shown in Fig. 7, thereby feeding a secondary air into all
of the cylinders. Fig. 11 shows the reed valve. The reed
` valve comprises a reed valve body 22, a valve seat 24
forming thereon a pair of valve ports 23 and a pair of
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valves 25 normally closing the valve ports 23.
In the embodiment shown in Fig. 1, the passage 21
connectea to the branch conduit 19 opens into the exhaust
port 12. However, the branch conduit 19 may directly open
into the branch portion of the exhaust manifold 7.
As is described hereinbefore, according to the
present invention, the exhaust gas purifier of an extremely
simple construction ensures the feeding of a secondary air
into the exhaust passages.
Furthermore, as shown in Figs. 5 and 6, if the --
exhaust gas delivered from the cylinder which is not
connected to the reed valve 13 is recirculated into the
intake air system 28, for example the intake manifold 8
via an exhaust recirculation control valve 26 for controlling
the flow rate of the exhaust gas and an exhaust gas passage
; 27, said exhaust gas containing no air, that is to say,
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inert gas can be recirculated into the intake manifold, `
thereby bringing about an effective reduction of the
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`- harmful conponent NO in the exha~st gas. Furthermore, if
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the duration of an overlap betwèen the intake valve and
the exhaust valve in each cylinder which is connected to
the reed valve is extended compared with those durations
in the remaining cylinders not connected to the reed
valve, thereby increasing the feed amount of a secondary
air into the former cylinders, it is then possible to
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improve the purifying efficiency and also improve the
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engine performance.
In addition, the atmospheric side of the re~d valve
13 is connected to the dust portion of the air cleaner 9
` 30 at a position opposite to the air inlet opening in the air
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cleaner 9 via the air filter lS and the silencer 16.
Thus, when the occurrence of a malfunctioning of the reed
valve 13 causes the exhaust gas to flow reversely into the
air cleaner via the branch conduit 19, the conduits 18 and
17, the exhaust gas must not be delivered to the :
atmosphere; and said gas can be sucked again into the
combustion chamber.
The present invention is hereinbefore described
with a reference to the preferred embodiment in which the
engine is provided with a catalytic ronverter in its
exhaust system. However, the catalytic converter can be
replaced by a manifold reactor or an after-burner.
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