Note: Descriptions are shown in the official language in which they were submitted.
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The present application is a division of application
No. 206,947 :Eil,ed on August 13r~ 1974.
The present invention relates to a system Por reducing
concentrations o~ harmful substances ln multicylinder internal
combustion enyine exhaust gases, in which system two differently
composed exhaust gases, one rich in unburned fuel and the other
in air~ are supplied alternately to a thermal reactor.
Concentrations of harmful substances in an internal
combustion engine exhaust gas are greatly dependent on the air
to fuel ratio (A/F) of a combustible mixture fed to the engine.
When an A/F near the stoichiometric ratio is employed, the
maximum concentration of nitrogen oxides (NOx) is produced
and concentrations of carbon monoxide (CO) and unburned hydro-
carbone (HC) are also considerably high through not maximum.
A lower A/F, or a rich mixture, causes HC and CO to increase, and
a higher A/F or a lean mixture causes these two substances to
decrease, particularly CO, while NOx is decreased in both cases.
It is, however, very hard to reduce concentrations
of HC and CO in the exhaost gas to values low enough to meet
current requirements merely by employment of either a considera- ;~
bly rich or lean mixture. Accordingly, a thermal reactor of
after-burner is frequently used to convert the discharged HC
and CO into harmless oxides even when A/F is deviated from the
stoichiometric value. It may seem quite favorable in such a case
to use a lean mixture putting the above facts together, but CO
shows an extremely poor reactivity with air in low concentrations
and/or at relatively low temperatures. Thus, a rich mix-ture is
more favorable because the resulting large amounts of HC and CO
can be more easlly oxidi~ed in a suitable thermal reactor while
NOx is inherently decreased as mentioned above. For practical
application, however, a rich mixture is quite unfavorable from
the viewpoint of fuel economy.
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It is therefore a major object of the ~resent invention
to pxovide a system for ef~ctively xed~lcing concent~ations o~
harmful substances in an exhaust gas from a typical internal
combustion engine having an even number o~ combustion chambers
accompanied w~th substantially no increase in fuel consumption.
It is another object of the invention to provide such
a system which maintains its function even when the engine is
operated at such a low load as to cause the exhaust gas temperature
to fall.
In brief, and in the li~ht of the above comments, the
present invention relates to an engine sys-tem comprising an ?
internal combustion engine having an even number of combustion
chambers; an exhaust manifold, in communication with the com-
bustion chambers, this manifold having an outlet; a thermal
reactor made up of an inner body, forming a reaction chamber and
having an inlet connected with the outlet of the exhaust mani~old,
and an outer body arranged to enclose the inner body with a space
therebetween. This outer body is provided with a discharge port
inits peripheral wall and the aforesaid space communicates with
the reaction chamber only through holes formed in end regions of `
the inner body. The system of the invention further comprises
carburation means on the engine capable of causing the exhaust gas
to have alternately two different compositions at the same
- frequency as the sequential firing of the combustion chambers
when the exhaust gas is discharged from the exhaust manifold.
These two compositions are such that a first exhaust having one
- of the two compositions contains more carbon monoxide and
unburned uel and less oxygen than a third exhaust gas which is
- produced by the combustion of a stoichiometric air-fuel mixture
in the same combustion chamber~ while a second exhaus-t gas having
the other composition contains less carbon monoxide and
unburned fuel and more oxygen than the thixd exhaust gas so that ~ ~ 7,
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~(337~2
the first an~ second exhaust gases readily mix with each other
in the thermal xeactor to cause e~ective oxidation o~ carbon
monoxide and unburned fuel contained therein by the oxygen con-
tained therein.
The invention in the parent application is restricted
to the situation wherein the carburation means include a combi-
nation of two differently adjusted air-fuel mixture supply systems
arranged to feed the combustion chambers alternately with two
di~ferently concentrated air-fuel mixtures. Also, the carbura-
tion means form and supply a first air~fuel mixture and an
air/fuel ratio below the stoichiometric ratio of a first group
of combustion chambers consisting of one half of the combustion
chambers and a second air-fuel mixture of an air/fuel ratio above
the stoichiometric ratio to a second group consisting of the other
half of the combustion chambers, these first and second groups
being formed in such a manner that eac~ combustion chamber of the
first group is fired alternately in sequence with a combustion
chamber of the second group.
The invention in the instant divisional application is
restricted to the case wherein the carburation means comprise
an air-fuel mixture supply system arranged to feed the combustion
chambers with an air-fuel mixture having an air/fuel ratio above
a stoichiometric ratio and a secondary fuel supply sustem
arranged to introduce the fuel into the exhaust manifold at
locations close to a first group of combustion chambers consisting
of one half of the combustion chambers selected in such a manner
that each combustion chamber of the first group is fired
alternately in sequence with one of the remaining combustion
chambers form~ng ~ second group.
Other features and advantages of the invention will
become clear from the following detailed description of
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preferred embodiments the~eof taken with the accompanying
drawings, i~ which:
Fig. 1 is a plan view, partially in section, of a
four-cylinder engine provided with a system of the invention
Fig. 2 is a longitudinal sectional view of a thermal
reactor similar to that shown in Fig. 1 but incorporating
a small modification; and
Fig. 3 is a plan view similar to Fig. 1, but showing
a six-cylinder engineO
In Fig. l, an engine 10 has ~our cylinders or
combustion chambers 11, 12, 13 and 14 provided with, respect-
ively, intake ports 21-24 and exhaust ports 31-34. An exhaust
manifold 40 having four branches 41-44 is connected to the ~;
exhaust ports 31-34, and an outlet 45 thereof is connected -
to a thermal reactor 50. The thermal reactor S0 essentially ~ -
consists of a cylindrical inner body 51 and a cylin~rical
outer body 52 enclosing the former 51 to form a space 53
between the two bodies 51 and~52! An interior space or reaction ~-
chamber 54 in the inner bod~ 51 communicates with the exhaust ;~
manifold 40 through an inlet 55 formed in the middle of the
peripheral wall of the inner body 51. The inlet 55 extends
across the space 53 and through the wall of the outer body 52
in a manner as to be isolated from the space 53. The reaction
chamber 54 communicates with the exterior space 53 through a
plurality of holes 56 formed through the wall of the inner ;~
- body 51 at both ends 57 and peripheral regions close thereto.
Two partitions 58 are preferably disposed in the reaction
- chamber 54 at locations between the inlet 55 and the ends 57
to divide the reaction chamber 54 into three sections. A
plurality of through holes 59 in the partitions 58 allows the
thus formed central section 54A to communicate with the
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remainder sections of the reaction chamber 54. The outer body
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52 has a discharge port 60 in the middle of the peripheral
wall thereof, which is connected to an exhaust pipe 61.
In the engine 10, the firing sequence of the four
cylinders 11-14 is 11-12-14-13 as is customarily employed.
According to the present invention ar~ exhaust gas from, fo~
example, the combustion chamber :Ll is caused to differ in
composition from another exhaust gas from the com~ustion chamber
12 which is fired next. For that purpose, a relatively rich
air/fuel mixture having a low A/F of, for example, 12/1 is
supplied to the cylinders 11 and 14 from a carburetting system
25, a'nd another carburetting system 26 supplies a relatively
lean mixture of, for example, an A/F of 18/1 to the remaining
cylinders 12 and 13.
In operation, the cylinder 11 discharges a first :~
type of exhaust gas aontaining large amounts of C0 and unburned
fuel or HC into the central section 54A of the reaction chamber -:~
54 through the exhaust manifold 40. The cylinder 12 is fired ~. :-
next, and a second type of exhaust gas containing air in large ;;
excess but only small amounts of CO and HC flows into the
central section 54A. Subsequently the first type of exhaust
gas is again discharged from the cylinder 14, thus the two
differently composed exhaust gases are alternately supplied
to the thermal reactor 40
Due to retardation of the exhaust.gas flow by the
partitions 58, the two different composed exhaust gases mix
- with each other in the central section 54A. Upon mixing, C0
and HC in the first exhaust gas begin to react with the excess
and heated air in the second exhaust gas. The burning reactions
proceed during the subsequent flow of the mixed exhaust gas
from the central or mixing section 54A to the main sections of
the reaction chamber 54 through the holes 59. The mixed ..
exhaust gas then flows into the space 53 surrounding the inner
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~103 ~3~Z
body 51 throu~h the holes 56 in the end re~ion and rounds
towards the middle of the reactor 40, where the discharge
port 60 is disposed. It is to be noted that the burning
of large amounts of HC and CO in the react~ion chamber 54
allows the fractional amount of ~0 which is contained original-
ly in the second exhaust gas to he oxi~ized without difficulty.
Such a long route in the thermal reactor 50 allows
the mixed e`xhaust gas to remain therein for a period long
enough to accomplish oxidation of almost whole Co and HC
contained initially therein. Besides a~foring a long
reaction time, the passage of the heated exhaust gas, either -
burning or burnt, around the inner body 51 causes the reaction
chamber 54 to be maintained at elevated temperatures, so that
the oxidation reactions can be initiated with ease and proceed
smoothly.
Thus, an extremely clean exhaust gas is discharged
into the exhaust pipe 61 aa the result of efficient oxidation
of C0 and ~C in the thermal reactor 50 and the inherent low
; concentration of NOx due to the initial deviations of A/F values
from the stoichiometric ratio.
The provision of the partitions 58 is usually prefer~
able as mentioned above, but similar results may be obtained
without them if the length to diameter ratio of the reaction
chamber 54 and the arrangement of the holes 56 are designed
appropriately.
~t will be self-evident that the firing sequence of
the cylinders 11-14 is not limited to 11-12-14~13 but may
alternatively be 11-13-14-12 and that the apportionment of
the rich air/fuel mixture to the pair of the cylinders 11 and
14 and the lean mixture to the other pair 12 and l3 may be
reversed. T'ne firing sequence and the apportionment of the
mixtures may be combined in any way so long as the above
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described two di~ferent composed ~xhaust gases ar~ pro~uced
alternately in accordance with the sequential firing of the
cylinders 11~14~
Referring now to Fig. 2, a thermal reactor 50A
essentially similar to the reactor 50 of Figq 1 has a
dividing wall 62 transversely disposed in the center of
the reaction chamber 54 to divide the central section 54A
thereof into two halves. The dividi~g wall 62 extends through
the inlet 55 dividing it also into two halves. Also the
outlet 45 of the exhaust manifold 40 is divided into two
sections by a dividing wall 63.
In this arrangement, the first type of exhaust gas
from the cylinder 11 is mixed with only the second exhaust
gas from the cylinder 12 in the left side region of the
mixing section 54A, and the exhaust gases from the cylinders
13 and 14 are similarly mixed with each other in the right
side. Consequently, the mixing of the two differently composed
~ exhaust gases can be accomplished more efficiently and
; achieving a more`accurate mixing ratio. ~;
Il will be apparent that the thermal reactor 50A
and/or the exhaust manifold 40 may be provided with two
inlets 55 and/or two outlets 45, respectively, in place of
the extension and/or provision of the dividing walls 62 and/or
63.
Referring again to Fig. 1, the two sets of carbu~
retting systems 25 and 26 for producing the two types of
air/fueL mixtures may be replaced with a fuel injection
system (not shown) controlled to supply the cylinder pairs
11, 14 and 12, 13 with different quantities of fuel.
The two types of exhaust gases may alternatively
be produced as follows. In place of feeding the engine 10
with the two types of air/fuel mixtures, all the cylinders
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11-14 are fed with the above second or lean mixture. The two
branches 41 and 44 of the exhaust manifold 40 are equipped with
secondary fuel injection nozzles 71 at locations close to the
exhaust ports 31 and 34, respectively, which fuel nozzles 71
are connected to a fuel supply system (not shown) through a
secondary fuel duct 72. With the enric~ment of the exhaust
gas ~rom the cylinders 11 and 14 with unburned fuel by means
of the fuel nozzles 71 it is easy to initiate and sustain the
burning reaction of the resulting gas with the air-rich.exhaust
gas from the cylinders 12 and 13 in the reaction chamber 54O
Thus the low concentration of C0 can be oxidized almost entirely. .
The amount of the fuel supply from the fuel nozzles 71 is prefer-
ably regulated proportionally to the amount of air induction
to the intake ports 21-24 of the engine 10. ~ .
. The branches 41 and 44 of the exhaust manifold 40
are preferably equipped with auxiliary air nozzles 81 at loca-
:,. ;
tions close to the exhaust ports 31 and 34,respectively. An . ~;
air duct 82 for these nozzles 81 is governed by a solenoid .
valve 83, which is normally closed and is energized to its
open position by a control unit 84 having means to sense
the engine load and a switch. When the load on the engine 10
falls to such a value that the temperature of the first exhaust
gas from the cylinders 11 and 14 becomes too low to achieve :.
the expected reactions in the thermal reactor 50, the control
unit 84 opera~es the valve 83 to feed secondary or auxiliary
air into the first exhaust gas through the air duct 82 and the
nozzles 81. As a result, a portion of the unburned fuel .in
the first exhaust gas is burned within the exhaust manifold 40,
allowing the exhaust gas temperature to rise sufficiently prior
to entrance of the exhaust gas into the reactor 50.
In addition to the auxiliary air, the first exhaust
gas is preferably enriched with fuel during such a low-load
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~0373WZ
operation of the engine 10 to promote the above de~cribed
after-burning in the exhaust mani~old 40. The enrichment may
be accomplished by controlling the A/F of the combustible
mixture to be fed to the combust:ion chambers 11 and 14. When
the aforementioned fuel nozzles 71 are employed, such fuel
enrichment can be accomplished simply by regulating the fuel
supply rate from the secondary fuel nozzles 71. For example,
a solenoid valve 73 is provided in the fuel duct 72, and the
control unit 84 is arranged to operate the two valves 83 and
73 simultaneously~ The valve 73 to the fuel duct 72 is
normally kept partially open, and the opening thereof is
enlarged by a power from the control unit 84 in response to
the engine load reduction.
A system of the invention is applicable to various
internal combustion engines having an even number of cylinders
other than the four-cylinder engine 10. For example, a six-
cylinder engine 110 of Fig. 3 is provided with a system
identical with that of Fig. 1 except that an exhaust manifold
140 with six branches 141-146 is employed. A customary firing
sequence of six combustion chambers 111-115-113-116-112-114
is employed in this engine 110. Accordingly, a relatively ~ -
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rich air/fuel mixture is fed to a set of the cylinders 111,
.
112 and 113, and a relatively lean mixture to the remainder
cylinders 114, 115 and 116. The reverse apportionment is
of course permissible. Consequently, the aforementioned
first and second exhaust gases flow alternately into the thermal
reactor 50 and react with each other in exactly the same way as
in the case of Fig. 1. The dividing wall 62 of Fig. 2, however,
- is unnecessary in this case since the first and second exhaust
gases flow always through the left side and right side of the
exhaust manifold 140, respectively.
The exhaust manifold 140 may be equipped with the
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~V373~
auxiliary air nozzles 81 and the secondary fuel nozzles 71
~imilarly to the exhaust manifolcl 40 of Fig. 1 except for
the growth in number.
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