CA1048355A - Spark-ignition internal combustion engine capable of preventing noxious gas emissions - Google Patents
Spark-ignition internal combustion engine capable of preventing noxious gas emissionsInfo
- Publication number
- CA1048355A CA1048355A CA76262521A CA262521A CA1048355A CA 1048355 A CA1048355 A CA 1048355A CA 76262521 A CA76262521 A CA 76262521A CA 262521 A CA262521 A CA 262521A CA 1048355 A CA1048355 A CA 1048355A
- Authority
- CA
- Canada
- Prior art keywords
- air
- combustion chamber
- spark
- fuel
- exhaust
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D21/00—Controlling engines characterised by their being supplied with non-airborne oxygen or other non-fuel gas
- F02D21/06—Controlling engines characterised by their being supplied with non-airborne oxygen or other non-fuel gas peculiar to engines having other non-fuel gas added to combustion air
- F02D21/08—Controlling engines characterised by their being supplied with non-airborne oxygen or other non-fuel gas peculiar to engines having other non-fuel gas added to combustion air the other gas being the exhaust gas of engine
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
- F02B23/08—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D35/00—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for
- F02D35/0015—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for using exhaust gas sensors
- F02D35/0046—Controlling fuel supply
- F02D35/0053—Controlling fuel supply by means of a carburettor
- F02D35/0061—Controlling the emulsifying air only
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
- F02F1/00—Cylinders; Cylinder heads
- F02F1/24—Cylinder heads
- F02F1/242—Arrangement of spark plugs or injectors
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
- F02B23/08—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition
- F02B2023/085—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition using several spark plugs per cylinder
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
- Ignition Installations For Internal Combustion Engines (AREA)
- Combustion Methods Of Internal-Combustion Engines (AREA)
- Output Control And Ontrol Of Special Type Engine (AREA)
Abstract
Abstract of the Disclosure An electronically controlled carburetor and an E.G.R. system produce a stoichimetric mixture contain-ing large quantities of exhaust gas. A "three-way"
converter optimally treats the noxious gases after the charge is ignited in each cylinder with a dual spark plug ignition system.
converter optimally treats the noxious gases after the charge is ignited in each cylinder with a dual spark plug ignition system.
Description
~ 835~ ~
This invcn-ti.on rel.ates to a spark-ignition internal combustion engine of the type wherein two spark plugs are disposed within a combustion chamber of the engine to reliably igni.te an air-fuel mixture mixed with inert gases.
In connection with purification of the exhaust gases discharged from the combustion chambers of spark-ignition internal combustion engine, it has been already ::~
proposed that an air-fuel mixture is combusted in the combustion chamber in the presence of inert gases such .~
as exhaust gases recirculated into the combustion - :
chamber and combusted gases remaining in the combustion chamber, by ignition with two spark plugs disposed within .
the combustion chamber (dual spark-ignition system), ::
~5 thereby achieving a considerable decrease in the emis- `~
: ~ .
sion level of nitrogen oxides (NOx) without deterioration :~ --~ . ,.
of stable engine operation.
This NOx decreasing effect results from the fact .
that, according to the dual spark-ignition system, the combustion volume alotted to each spark plug is con-siderably decreased compared with prior art spark ::
ignition system whsre only one spark plug is disposed ~
within a combustion chamber. Accordingly, combustion ~ ~:
of the air-fuel mixture is accomplished within an extremely short period of time and therefore stable -
This invcn-ti.on rel.ates to a spark-ignition internal combustion engine of the type wherein two spark plugs are disposed within a combustion chamber of the engine to reliably igni.te an air-fuel mixture mixed with inert gases.
In connection with purification of the exhaust gases discharged from the combustion chambers of spark-ignition internal combustion engine, it has been already ::~
proposed that an air-fuel mixture is combusted in the combustion chamber in the presence of inert gases such .~
as exhaust gases recirculated into the combustion - :
chamber and combusted gases remaining in the combustion chamber, by ignition with two spark plugs disposed within .
the combustion chamber (dual spark-ignition system), ::
~5 thereby achieving a considerable decrease in the emis- `~
: ~ .
sion level of nitrogen oxides (NOx) without deterioration :~ --~ . ,.
of stable engine operation.
This NOx decreasing effect results from the fact .
that, according to the dual spark-ignition system, the combustion volume alotted to each spark plug is con-siderably decreased compared with prior art spark ::
ignition system whsre only one spark plug is disposed ~
within a combustion chamber. Accordingly, combustion ~ ~:
of the air-fuel mixture is accomplished within an extremely short period of time and therefore stable -
- 2 -:
8355 `:
combustion of the air-fuel mixture is carried out in the combustion chamber even if a relatively large amount Or the inert gas is present with the air-fuel mixture in the combustion chamber. The combustion carried out in the presence of the large amount of the inert gases lowers the maximum temperature of combustion and consequently suppresses NOx generation durlng same.
However, it is now required to further improve the NOx generation suppressing effect and to increase the post combustion NOx reduction of same in order to further decrease the overall NOx emission level of ths engine. Additionally, it is also required to decrease the emission levels of carbon monoxide (C0) and hydro~
carbons (HC) which are generated by incomplete combustion ~5 of fuel.
It is, therefore, a general object of the present -invention is to provide a spark-ignition internal combustion engine capable of producing very low concen-:.
trations of NOx, C0, and HC.
Another object of the prcsent invention is to provide a spark-ignition internal combustion engine in which the NOx emission level is decreased firstly by combusting the air-fuel mixture in the presence of inert gases and thereafter reducing NOx in the three-way catalytic converter, whereas C0 and HC emission ~ 3 ~
:
~4B3~5 :
levels are decreased firstly by comb~lsting an approxi-mately stoichiometric air-fue~ mixture and thereafter by oxicli~ing them in the three-way catalytic converter.
A further object of the present invention is provide a spark-ignition internal combustion engine of the type where an air-fuel mixture mi~sd with inert gases is ignited with a dual spark-ignition system, which is further equipped with a three-way catalytic - converter for reducing NOx and oxidi~ing CO and HC, and with an air-fuel ratio control device for controlling the air-fuel ratio of the mixture supplied to the com- ;
bustion chamber so as to feed the three-way catalytic converter with exhaust gases most suited for achieving the highest mutual conversion efficiencies in thc three- ;~
way converter.
:, :
Other objects, features, and advantages of the ,. ~
- spark-ignition internal combustion engine in accordance .
~ with *he present invention will become more apparent - as the following description of preferred embodiments ,~ , thereof progresses, taken in conjunction with the ac- ;
companying drawings, in which~
Fig. 1 is a schematic plan yiew of a preferred ~, embodiment of a spark-ignition internal combustlon -engine in accordance with the present invention;
Fig. 2 is a vertical section view of a carburetor , ~
- 4 ~ ~
'~
~, ~.
.
.
employed in the engine oI` ~ig. 1;
~ig. 3 is a v~rtical section view of a cylinder portion Or the engine of Fig. 1;
Fig. Il is a plan view of a cylinder head portion defined by the cylinder of Fig. 3;
Fig. 5 is a graph showing the characteristics of a three-way catalytic converter employed in the engine of Fig. 1, in terms of conversion efficiency and air-fuel ratio of the mixture supplied to the combustion chamber of the engine of Fig. 1; and Fig. 6 is a schematic plan view of another pre-ferred embodiment of the spark~ignition internal combustion engine in accordance with the present invention Y5 Referring now to Fig. 1, 2, 3 and 4 of the drawings, a preferred embodiment of a spark~ignition internal com-bustion engine in accordance with the present invention is shown, in which the engine is generally designated by ,~
the reference numeral 10. The engine of this instance -~
is an in-line, four cylinder type and therefore the engine proper 11 has four aligned combustion chambers C1 to C4 therein. As clearly shown in Fig. 3, each com-bustion ~hamber is defined by the cylindrical inner wall of a cylinder 12 formed in a cylinder block 13, the inner wall of a cylinder head 14 closing the one (upper) end of ~;
~ : ~ . :
:: ~ , ,- . : . .
.
~0~335~i the cylinder 12 and the crown of a piston 16. Each combustion chamber is commllnicabLe through each intake port 18 with an intake mani~old 20 of the intake system (no n~mleral) which manifold communicates with a carbu-retor 22 formirlg part of air-fuel mixture supply means 24. Reference numeral 25 indicates intake valves.
Furthermore, each combustion chamber communicates through each exhaust port 26 with an exhaust manifold 28 which connects to a connecting pipe 30 forming part of an exhaust passage 31 of the exhaust system (no numeral). The reference numeral 27 indicates exhaust valves. The connecting pipe 30 is connected to a so-called three-way catalytic converter 32 capable of reducing nitrogen oxides (NOx) and oxidizing carbon ~5 monoxide (CO) and hydrocarbons (HC). The three-way catalytic converter 32, in turn, communicates with the atmosphere to discharge the exhaust gases purified ;
in the converter 32 into the atmosphere.
As best seen in Fig. 2, the carburetor 22 has a throttle valve 34 rotatably disposed within the air-fuel mixture induction passage 36 thereof. A main venturi portion 38 is located upstream of the throttle valve 34, and a secondary venturi portion 40 is located adjacent the main venturi portion 38. Opened to the secondary venturi portion 40 is a main discharge nozzle - 6 _ ;
' ,; ' , , "' . ,". ' ' . . ' ~ ' ' ' "' '~ ', . ', ' ' ' ' ' ' ' ; ' ... .: :
~L~4~5~i l~2 of a main circuit (no numeral) which nozzle 42 is communicated with a main well 44 which is in turn commllnica-ted w:ith a float bowl 46 through a main fuel passage 48 having therein a main jet 50. The main well 41l has a main air bleed 52 and a firs-t auxiliary ~:
air bleed 51l. The main well 44 is further communicated through a jet or a restrictor 56 with a fuel passage 58 of a low-speed circuit (no numeral) which passage 58 is communicated with a slow port 60 opened to the air-fuel mixture induction passage 36 downstream of the main venturi portion 38. The fuel passage 58 has a low-speed circuit air bleed 62 and a second auxiliary air bleed 64.
A first solenoid valve 66 or first air flow amount control means is disposed for opening or closing the first auxiliary air bleed 54 and arranged to take a ; first state wherein the actuating rod or member 66a thereof is moved with respect to the first auxiliary air bleed 54 to increase the flow amount of air inducted `
through the first auxiliary air bleed 54 into the main well 44 above a predetermined level, and take a second state wherein the actuating rod 66a thereof is moved . ~.
with respect to the first auxiliary air bleed 54 to decrease the flow amount of the air inducted through the auxiliary air bleed 54 into the main well 44 below ~ :
,:
.
~, ':, ' , . : ' ~a34133S~
the predetermined level. A second sol0noid valve 68 or second air flow contro]. means is electrically con-nectecl in parallel with the first solenoid valve 66 and arrangec~ to be operated similarly to the first solenoid valve 66. The first and second solenoid -;
valves 66 and 68 form part of air-fuel ratio control ~ .
means 70 and electrically connected to a control circuit 72. ~ :
The control circuit 72 is arranged to generate a ~ ~
10 first command signal for placing the first and second :
solenoid valves 66 and 68 into the first state and a ; :
second command signal for placing the first and second solenoid valves 66 and 68 into the second state. The control circuit 72 is electrically connected to an 15 exhaust gas sensor 74 which is disposed within the connecting pipe 30 upstream of the catalytic converter 32. The exhaust gas sensor 74 is arranged to generate :~
a first information signal (which may be a voltage signal) for causing the control circuit 72 to generate ~ :
20 the first command signal when the exhaust gases passing .~
through the connecting pipe 30 have a first composition ~.
indicating that the combustion chambers are fed with an ~:
air-fuel mixture richer than that having the stoichio~
metric air-fuel ratio (14.8:1), and a second information ~;
25 signal for causing the control circuit 72 to generate ' . ' :' ~
:, ., ~ . ~: . .
the second conun~nd signal when the exhaust gases passing through the connect.ing p:ipe 30 have a second composition indicating that the combustion chambers 18 are fed with an air-fuel mixture leaner than that having the stoichi-ometric ratio. The exhaust gas sensor 74 lllay be oxygen (2) sensor, a nitrogen oxides ~NOx) sensor, a carbon monoxide (C0) sensor, a carbon dioxide (C02) sensor or a hydrocarbon (HC) sensor which respectively detect the ; ~:~
concentrations of 2~ NOx, C0, C02 or ~IC contained in the exhaust gases discharged from the combustion chambers.
In order to operate the first and second air flow amount control means 66 and 68 in the above discussed manner, the control circuit 72 may be arranged to set, as a reference voltage, a specified voltage signal generated ~-by the exhaust gas sensor 74 when the air-fuel mixture having stoichiometric air-fuel ratio is supplied into :~
the combustion chambers, and to generate the first com- :~
mand signal when the level of the voltage signal from - :
the sensor 74 is lower than that of the specified voltage signal., indicating that the combustion chambers ~ :
are fed with the air-fuel mixture leaner than the stoi-chiometric mixture and the second command signal when ~:
the level of the voltage signal from the sensor 74 is ~ higher than that of the specified voltage signal, indi- : :
: 25 cating that the combustion chambers are fed with the :
_ g _ ' ' ~.' `'' ', ~.
, .
, .
air-fuel mi~ture r:icher than the stoichiometric mix-ture.
Connected to the exhaust manifold 28 and the intake manifold 20 is a conduit 76 or conduit means for recirculating or suppJ,ying a portion of the exhaust gases passing through the exhaust manifold 28 into the combustion chambers C1 to C~ through the intake manifold 20. The concluit 76 forms part of exhaust gas recirculat- `-' : ' ing means 78 or an exhaust gas recirculation system. A :
control valve 80 is disposed in the conduit 76 and is ' arranged to control the amount of the recirculated exhaust gases with respect to the amount of the intake ',~
air induced through the intake system in response, for , example, to the venturi vacuum which is a function of , : :
the amount of the intake air. The venturi vacuum is ~' ~
generated at the venturi portion of the carburetor 22. ~,' ~ . .
The exhaust gas recirculating means 78 functions to ~:
- add substantially inert gaS to the air-fuel mixture in the combustion chamber by only itself or in combination with other measures such as, for example, controlling . ~ ' so-called valve overlap of the intake and exhaust valves :,~
25 and 27. It will be appreciated that addition of a ' ,,'`
`: relatively large amount of the substantially inert gas ',' . to the air-fuel mixture in the combustion chamber ,~
results in lowering the maximum temperature of the ':~' "
- 10 _ , ..
,.
.. . .
835~i combustion carried out in the combustion chamber, causing a recluction of the NOx emission level. The substantially inert gas consists of mixed gases which substantially clo not par-ticipate or remain substantially iner-t in the com-bustion in the combustion chamber and therefore include residual gas or combustion gas which is not discharged from the combustion chamber during the exhaust stroke and remains in the combustion chamber, recirculated exhaust gas which is recirculated or supplied into the combustion chamber by exhaust gas recirculation system 78, nitrogen gas (N2) contained in the intake air. It will be under-stood thai the residual gas and the recirculated exhaust gas contain amongst other things carbon dioxide (C02), water vapour (1~20) and nitrogen gas. With respect to the residual gas, when the valve overlap of the intake and exhaust valves 25 and 27 is set, for instance, at about 35 to 60 degrees of crank angle of the engine, 20 ~-to 30% of the residual gas remains in the combustion chamber during low engine speed operating range. Accord~
ing to the present invention, the weight ratio of the fuel substantially combusted in the combustion chamber ~ ~;
or the fuel in the air-fuel mixture in the combustion chamber and the substantially inert gas added to the air-fuel mixture supplied to the combustion chamber, is selected to be within the range from 1:13.5 to - 11 - : ' '~
' ' : , . . . : -: : . :
, . . . . . .
~.~4~; ~S~
1:22.5 (this weight ratio will be referred to as "fuel-inert gas ratio" hereinafter) during normal engine operation.
i In order to reliably ignite the air-fuel mixture mixed with such a larse amount of the substantially inert gas, two spark plugs 82a and 82b, as best seen in Figs. 3 and 41 are disposed in each combustion chamber in such a manner that the two spark plugs 82a and 82b are installed through the cylinder head 14 and ~ ~-their electrodes are projected into each combustion ~ ~
chamber. The two spark plugs 82a and 82b are located ~ ;
, ~.
spaced oppositely from the center axis Xc of the cyl~
inder 12 and near the periphery of the combustion -. .
chamber. The locations of the two spark plugs 82a and 82b are preferably such that an intermediate point ; of the spark gap or the distance between the two elec- ` ;;-trodes of the spark plug 82a and an intermediate point of the spark gap of the spark plug 82b constitute an .~
angle ranging from 110 to 180 degrees with respect to the center axis Xc of the cylinder 12, and the shortest distance L between the intermediate point of the spark gap of each spark plug and the center axis Xc is 0.15 to 0.45 times of the diameter D of the cylinder bore.
With this location of the two spark plugs 82a and 82b, the combustion volume alotted to each spark plug ;~
.
,~ , `
: ~ . :
- 12 _ ;` ' ''~ '' '.
.. . .
:.:. : ,:... .. . ...
.:-:: : - :
:::: -is approximate:ly one half Or the combustion chamber volume causins shortening of flame propasation distance per spark plug and therefore the combustion time. In general, shortened combus-tion time results in an im-provement in the efficiency of converting combustion energy or pressure into mechanical work, thereby achiev-ing improvement in fuel consumption characteristics and engine power output performance. Additionally, even when the above-mentioned fuel-inert gas ratio is as high as 1:13.5 to 1:22.5, reliable ignition and stable ;~
combustion of the air-fuel mixture in the combustion chamber achieved. If the locations of the two spark plugs 82a and ~2b are excessively close to each other, the ignition effect -thereof is similar to that in the ,15 combustion chamber with only one spark plug. It will be appreciated from the foregoing that the above-men-tioned locations of the two spark plugs contribute to reliable ignition and stable combustion of the air-fuel ~-mixture in the combustion chamber.
With respect to the selected fuel-inert gas ratio range: if the ratio of the inert gas is lower than its lower limit 1:13.5, the NOx decreasing effect is reduced~
whereas if it is higher than its upper limit 1:22.5, stable combustion in the combustion charnber is not possible even with the most effective ignition with ~ -~' . .
~` .
: :.
~4i~
the two spark plugs 82a and 82b. Additionally, the NOx clecrcasin$ effect is not improved to any extent by doing same. Unstable combustion in the combustion chamber inevitably causes noticeable deterioration of the fuel economy characteristics and the engine outpu-t power performance.
In this connection, the fuel-inert gas ratio is calculated as follows: since the weight ratio of the ; fuel (gasoline or petrol) and the atmospheric air in the stoichiometric air-fuel mixture is 1:14.7 and the volume ratio of oxygen gas (2) and nitrogen gas (N2) is 21:79, the weight ratio of the fuel and nitrogen gas is obtained to be 1:11.3. Given the above facts, ~ -assuming that the exhaust gases containing the residual i5 gases occupy X% by volume of the amount of intake air, the weight ratio of the fuel and total inert gas in the combustion chamber is represented as 1-(11.3+14.7x1oo) since the weight ratio of the air and the exhaust gases or the residual gases is about 1:1~ Accordingly when the amount of the exhaust gas recirculated into the combustion chamber is 10% with respect to the amount of intake air and the residual gases occupy 20% of the volume of the intake air, the fuel-inert gas ratio is 1:(11.3+14.7xloo)=1:15.7. ~ ~;
Fig. 5 shows the characteristics of the three-way ~ ~
,, ;" : ~ "
::
.. . . ... ..
.~ , : ~ : , , -catalytic converter 32, in which ~he conversioT1 effi-ciencies of NOx, CO and 11C are respectively represented by lines a, b and c, in term of air-fuel ratio of the air-fuel mixture supplied to the combustion chamber of`
the engine. As is apparent from this figure, it is necessary for obtaining the highest mutual conversion efficiencies of NOx, C0 and 11C to supply the combustion chamber of the engine with the air-fuel mixture having a narrow air-fuel ratio range including the stoichio-metric air-fuel ratio. Accordingly, if an air-fuel mixture leaner or richer than the stoichiometric air-fuel mixture is supplied to the combustion chamber, the efficiency of at least one of NOx, C0 and HC abruptly drops. It will be understood from the foregoing that the air-fuel ratio of the air-fuel mixture supplied to ~ -the combustion chamber must be strictly controlled at approximately stoichiometric or within the narrow air-fuel ratio range, in order to produce the highest mutual conversion efficiencies in the three-way catalytic ;~
converter 32. -With the arrangement hereinbefore described, during operation of the engine lO, a considerably large amount Or the inert gas containing the recirculated exhaust gases through the exhaust gas recirculating means 78 and the residual gas remaining in the combustion chamber :
:, - 15 ~ ~
~ ., .: .: : , :, :
~48355 ~:~
is mixed with the air-fuel mixture inducted into the combustion chambers. The air-fuel mixture mixed with the inert gas is ignited and effectively burned by the two spark plugs ~2a and 82b disposed within each the combustion chamber. With these spark plugs arrangement, when the air~fuel mixture in the combustion chamber is ;
ignited, two flame fronts are produced adjacent the inner wa]l surface of the combustion chamber, or quench area. These flame fronts move toward the centre of the ~;
combustion chamber, heating it to a high temperature.
Therefore, the distance of flame propagation is shortened compared with a conventional engine using only one spark ~ ;
plug. Thus combustion, as a result of the plurality of spark plugs, is faster and completed at the central portion of the combustion chamber thereby accomplishing stable and smooth combustion even though such a large amount of the inert gas is mixed with the air-fuel mixture to be combusted in the combustion chamber. Due to the effect of the inert gas, the maximum temperature within the combustion chambers is lowered and accordingly the - emission level of NOx is reduced as compared with the engine without the exhaust gas recirculating means.
Now, when the combustion chambers are fed with the air fuel mixture richer than that having stoichiometric air-fuel ratio, the first and second solenoid valves 66 - .
~ ~ "' '' ' '' ' , ..
.,: . . .
8355 `:
combustion of the air-fuel mixture is carried out in the combustion chamber even if a relatively large amount Or the inert gas is present with the air-fuel mixture in the combustion chamber. The combustion carried out in the presence of the large amount of the inert gases lowers the maximum temperature of combustion and consequently suppresses NOx generation durlng same.
However, it is now required to further improve the NOx generation suppressing effect and to increase the post combustion NOx reduction of same in order to further decrease the overall NOx emission level of ths engine. Additionally, it is also required to decrease the emission levels of carbon monoxide (C0) and hydro~
carbons (HC) which are generated by incomplete combustion ~5 of fuel.
It is, therefore, a general object of the present -invention is to provide a spark-ignition internal combustion engine capable of producing very low concen-:.
trations of NOx, C0, and HC.
Another object of the prcsent invention is to provide a spark-ignition internal combustion engine in which the NOx emission level is decreased firstly by combusting the air-fuel mixture in the presence of inert gases and thereafter reducing NOx in the three-way catalytic converter, whereas C0 and HC emission ~ 3 ~
:
~4B3~5 :
levels are decreased firstly by comb~lsting an approxi-mately stoichiometric air-fue~ mixture and thereafter by oxicli~ing them in the three-way catalytic converter.
A further object of the present invention is provide a spark-ignition internal combustion engine of the type where an air-fuel mixture mi~sd with inert gases is ignited with a dual spark-ignition system, which is further equipped with a three-way catalytic - converter for reducing NOx and oxidi~ing CO and HC, and with an air-fuel ratio control device for controlling the air-fuel ratio of the mixture supplied to the com- ;
bustion chamber so as to feed the three-way catalytic converter with exhaust gases most suited for achieving the highest mutual conversion efficiencies in thc three- ;~
way converter.
:, :
Other objects, features, and advantages of the ,. ~
- spark-ignition internal combustion engine in accordance .
~ with *he present invention will become more apparent - as the following description of preferred embodiments ,~ , thereof progresses, taken in conjunction with the ac- ;
companying drawings, in which~
Fig. 1 is a schematic plan yiew of a preferred ~, embodiment of a spark-ignition internal combustlon -engine in accordance with the present invention;
Fig. 2 is a vertical section view of a carburetor , ~
- 4 ~ ~
'~
~, ~.
.
.
employed in the engine oI` ~ig. 1;
~ig. 3 is a v~rtical section view of a cylinder portion Or the engine of Fig. 1;
Fig. Il is a plan view of a cylinder head portion defined by the cylinder of Fig. 3;
Fig. 5 is a graph showing the characteristics of a three-way catalytic converter employed in the engine of Fig. 1, in terms of conversion efficiency and air-fuel ratio of the mixture supplied to the combustion chamber of the engine of Fig. 1; and Fig. 6 is a schematic plan view of another pre-ferred embodiment of the spark~ignition internal combustion engine in accordance with the present invention Y5 Referring now to Fig. 1, 2, 3 and 4 of the drawings, a preferred embodiment of a spark~ignition internal com-bustion engine in accordance with the present invention is shown, in which the engine is generally designated by ,~
the reference numeral 10. The engine of this instance -~
is an in-line, four cylinder type and therefore the engine proper 11 has four aligned combustion chambers C1 to C4 therein. As clearly shown in Fig. 3, each com-bustion ~hamber is defined by the cylindrical inner wall of a cylinder 12 formed in a cylinder block 13, the inner wall of a cylinder head 14 closing the one (upper) end of ~;
~ : ~ . :
:: ~ , ,- . : . .
.
~0~335~i the cylinder 12 and the crown of a piston 16. Each combustion chamber is commllnicabLe through each intake port 18 with an intake mani~old 20 of the intake system (no n~mleral) which manifold communicates with a carbu-retor 22 formirlg part of air-fuel mixture supply means 24. Reference numeral 25 indicates intake valves.
Furthermore, each combustion chamber communicates through each exhaust port 26 with an exhaust manifold 28 which connects to a connecting pipe 30 forming part of an exhaust passage 31 of the exhaust system (no numeral). The reference numeral 27 indicates exhaust valves. The connecting pipe 30 is connected to a so-called three-way catalytic converter 32 capable of reducing nitrogen oxides (NOx) and oxidizing carbon ~5 monoxide (CO) and hydrocarbons (HC). The three-way catalytic converter 32, in turn, communicates with the atmosphere to discharge the exhaust gases purified ;
in the converter 32 into the atmosphere.
As best seen in Fig. 2, the carburetor 22 has a throttle valve 34 rotatably disposed within the air-fuel mixture induction passage 36 thereof. A main venturi portion 38 is located upstream of the throttle valve 34, and a secondary venturi portion 40 is located adjacent the main venturi portion 38. Opened to the secondary venturi portion 40 is a main discharge nozzle - 6 _ ;
' ,; ' , , "' . ,". ' ' . . ' ~ ' ' ' "' '~ ', . ', ' ' ' ' ' ' ' ; ' ... .: :
~L~4~5~i l~2 of a main circuit (no numeral) which nozzle 42 is communicated with a main well 44 which is in turn commllnica-ted w:ith a float bowl 46 through a main fuel passage 48 having therein a main jet 50. The main well 41l has a main air bleed 52 and a firs-t auxiliary ~:
air bleed 51l. The main well 44 is further communicated through a jet or a restrictor 56 with a fuel passage 58 of a low-speed circuit (no numeral) which passage 58 is communicated with a slow port 60 opened to the air-fuel mixture induction passage 36 downstream of the main venturi portion 38. The fuel passage 58 has a low-speed circuit air bleed 62 and a second auxiliary air bleed 64.
A first solenoid valve 66 or first air flow amount control means is disposed for opening or closing the first auxiliary air bleed 54 and arranged to take a ; first state wherein the actuating rod or member 66a thereof is moved with respect to the first auxiliary air bleed 54 to increase the flow amount of air inducted `
through the first auxiliary air bleed 54 into the main well 44 above a predetermined level, and take a second state wherein the actuating rod 66a thereof is moved . ~.
with respect to the first auxiliary air bleed 54 to decrease the flow amount of the air inducted through the auxiliary air bleed 54 into the main well 44 below ~ :
,:
.
~, ':, ' , . : ' ~a34133S~
the predetermined level. A second sol0noid valve 68 or second air flow contro]. means is electrically con-nectecl in parallel with the first solenoid valve 66 and arrangec~ to be operated similarly to the first solenoid valve 66. The first and second solenoid -;
valves 66 and 68 form part of air-fuel ratio control ~ .
means 70 and electrically connected to a control circuit 72. ~ :
The control circuit 72 is arranged to generate a ~ ~
10 first command signal for placing the first and second :
solenoid valves 66 and 68 into the first state and a ; :
second command signal for placing the first and second solenoid valves 66 and 68 into the second state. The control circuit 72 is electrically connected to an 15 exhaust gas sensor 74 which is disposed within the connecting pipe 30 upstream of the catalytic converter 32. The exhaust gas sensor 74 is arranged to generate :~
a first information signal (which may be a voltage signal) for causing the control circuit 72 to generate ~ :
20 the first command signal when the exhaust gases passing .~
through the connecting pipe 30 have a first composition ~.
indicating that the combustion chambers are fed with an ~:
air-fuel mixture richer than that having the stoichio~
metric air-fuel ratio (14.8:1), and a second information ~;
25 signal for causing the control circuit 72 to generate ' . ' :' ~
:, ., ~ . ~: . .
the second conun~nd signal when the exhaust gases passing through the connect.ing p:ipe 30 have a second composition indicating that the combustion chambers 18 are fed with an air-fuel mixture leaner than that having the stoichi-ometric ratio. The exhaust gas sensor 74 lllay be oxygen (2) sensor, a nitrogen oxides ~NOx) sensor, a carbon monoxide (C0) sensor, a carbon dioxide (C02) sensor or a hydrocarbon (HC) sensor which respectively detect the ; ~:~
concentrations of 2~ NOx, C0, C02 or ~IC contained in the exhaust gases discharged from the combustion chambers.
In order to operate the first and second air flow amount control means 66 and 68 in the above discussed manner, the control circuit 72 may be arranged to set, as a reference voltage, a specified voltage signal generated ~-by the exhaust gas sensor 74 when the air-fuel mixture having stoichiometric air-fuel ratio is supplied into :~
the combustion chambers, and to generate the first com- :~
mand signal when the level of the voltage signal from - :
the sensor 74 is lower than that of the specified voltage signal., indicating that the combustion chambers ~ :
are fed with the air-fuel mixture leaner than the stoi-chiometric mixture and the second command signal when ~:
the level of the voltage signal from the sensor 74 is ~ higher than that of the specified voltage signal, indi- : :
: 25 cating that the combustion chambers are fed with the :
_ g _ ' ' ~.' `'' ', ~.
, .
, .
air-fuel mi~ture r:icher than the stoichiometric mix-ture.
Connected to the exhaust manifold 28 and the intake manifold 20 is a conduit 76 or conduit means for recirculating or suppJ,ying a portion of the exhaust gases passing through the exhaust manifold 28 into the combustion chambers C1 to C~ through the intake manifold 20. The concluit 76 forms part of exhaust gas recirculat- `-' : ' ing means 78 or an exhaust gas recirculation system. A :
control valve 80 is disposed in the conduit 76 and is ' arranged to control the amount of the recirculated exhaust gases with respect to the amount of the intake ',~
air induced through the intake system in response, for , example, to the venturi vacuum which is a function of , : :
the amount of the intake air. The venturi vacuum is ~' ~
generated at the venturi portion of the carburetor 22. ~,' ~ . .
The exhaust gas recirculating means 78 functions to ~:
- add substantially inert gaS to the air-fuel mixture in the combustion chamber by only itself or in combination with other measures such as, for example, controlling . ~ ' so-called valve overlap of the intake and exhaust valves :,~
25 and 27. It will be appreciated that addition of a ' ,,'`
`: relatively large amount of the substantially inert gas ',' . to the air-fuel mixture in the combustion chamber ,~
results in lowering the maximum temperature of the ':~' "
- 10 _ , ..
,.
.. . .
835~i combustion carried out in the combustion chamber, causing a recluction of the NOx emission level. The substantially inert gas consists of mixed gases which substantially clo not par-ticipate or remain substantially iner-t in the com-bustion in the combustion chamber and therefore include residual gas or combustion gas which is not discharged from the combustion chamber during the exhaust stroke and remains in the combustion chamber, recirculated exhaust gas which is recirculated or supplied into the combustion chamber by exhaust gas recirculation system 78, nitrogen gas (N2) contained in the intake air. It will be under-stood thai the residual gas and the recirculated exhaust gas contain amongst other things carbon dioxide (C02), water vapour (1~20) and nitrogen gas. With respect to the residual gas, when the valve overlap of the intake and exhaust valves 25 and 27 is set, for instance, at about 35 to 60 degrees of crank angle of the engine, 20 ~-to 30% of the residual gas remains in the combustion chamber during low engine speed operating range. Accord~
ing to the present invention, the weight ratio of the fuel substantially combusted in the combustion chamber ~ ~;
or the fuel in the air-fuel mixture in the combustion chamber and the substantially inert gas added to the air-fuel mixture supplied to the combustion chamber, is selected to be within the range from 1:13.5 to - 11 - : ' '~
' ' : , . . . : -: : . :
, . . . . . .
~.~4~; ~S~
1:22.5 (this weight ratio will be referred to as "fuel-inert gas ratio" hereinafter) during normal engine operation.
i In order to reliably ignite the air-fuel mixture mixed with such a larse amount of the substantially inert gas, two spark plugs 82a and 82b, as best seen in Figs. 3 and 41 are disposed in each combustion chamber in such a manner that the two spark plugs 82a and 82b are installed through the cylinder head 14 and ~ ~-their electrodes are projected into each combustion ~ ~
chamber. The two spark plugs 82a and 82b are located ~ ;
, ~.
spaced oppositely from the center axis Xc of the cyl~
inder 12 and near the periphery of the combustion -. .
chamber. The locations of the two spark plugs 82a and 82b are preferably such that an intermediate point ; of the spark gap or the distance between the two elec- ` ;;-trodes of the spark plug 82a and an intermediate point of the spark gap of the spark plug 82b constitute an .~
angle ranging from 110 to 180 degrees with respect to the center axis Xc of the cylinder 12, and the shortest distance L between the intermediate point of the spark gap of each spark plug and the center axis Xc is 0.15 to 0.45 times of the diameter D of the cylinder bore.
With this location of the two spark plugs 82a and 82b, the combustion volume alotted to each spark plug ;~
.
,~ , `
: ~ . :
- 12 _ ;` ' ''~ '' '.
.. . .
:.:. : ,:... .. . ...
.:-:: : - :
:::: -is approximate:ly one half Or the combustion chamber volume causins shortening of flame propasation distance per spark plug and therefore the combustion time. In general, shortened combus-tion time results in an im-provement in the efficiency of converting combustion energy or pressure into mechanical work, thereby achiev-ing improvement in fuel consumption characteristics and engine power output performance. Additionally, even when the above-mentioned fuel-inert gas ratio is as high as 1:13.5 to 1:22.5, reliable ignition and stable ;~
combustion of the air-fuel mixture in the combustion chamber achieved. If the locations of the two spark plugs 82a and ~2b are excessively close to each other, the ignition effect -thereof is similar to that in the ,15 combustion chamber with only one spark plug. It will be appreciated from the foregoing that the above-men-tioned locations of the two spark plugs contribute to reliable ignition and stable combustion of the air-fuel ~-mixture in the combustion chamber.
With respect to the selected fuel-inert gas ratio range: if the ratio of the inert gas is lower than its lower limit 1:13.5, the NOx decreasing effect is reduced~
whereas if it is higher than its upper limit 1:22.5, stable combustion in the combustion charnber is not possible even with the most effective ignition with ~ -~' . .
~` .
: :.
~4i~
the two spark plugs 82a and 82b. Additionally, the NOx clecrcasin$ effect is not improved to any extent by doing same. Unstable combustion in the combustion chamber inevitably causes noticeable deterioration of the fuel economy characteristics and the engine outpu-t power performance.
In this connection, the fuel-inert gas ratio is calculated as follows: since the weight ratio of the ; fuel (gasoline or petrol) and the atmospheric air in the stoichiometric air-fuel mixture is 1:14.7 and the volume ratio of oxygen gas (2) and nitrogen gas (N2) is 21:79, the weight ratio of the fuel and nitrogen gas is obtained to be 1:11.3. Given the above facts, ~ -assuming that the exhaust gases containing the residual i5 gases occupy X% by volume of the amount of intake air, the weight ratio of the fuel and total inert gas in the combustion chamber is represented as 1-(11.3+14.7x1oo) since the weight ratio of the air and the exhaust gases or the residual gases is about 1:1~ Accordingly when the amount of the exhaust gas recirculated into the combustion chamber is 10% with respect to the amount of intake air and the residual gases occupy 20% of the volume of the intake air, the fuel-inert gas ratio is 1:(11.3+14.7xloo)=1:15.7. ~ ~;
Fig. 5 shows the characteristics of the three-way ~ ~
,, ;" : ~ "
::
.. . . ... ..
.~ , : ~ : , , -catalytic converter 32, in which ~he conversioT1 effi-ciencies of NOx, CO and 11C are respectively represented by lines a, b and c, in term of air-fuel ratio of the air-fuel mixture supplied to the combustion chamber of`
the engine. As is apparent from this figure, it is necessary for obtaining the highest mutual conversion efficiencies of NOx, C0 and 11C to supply the combustion chamber of the engine with the air-fuel mixture having a narrow air-fuel ratio range including the stoichio-metric air-fuel ratio. Accordingly, if an air-fuel mixture leaner or richer than the stoichiometric air-fuel mixture is supplied to the combustion chamber, the efficiency of at least one of NOx, C0 and HC abruptly drops. It will be understood from the foregoing that the air-fuel ratio of the air-fuel mixture supplied to ~ -the combustion chamber must be strictly controlled at approximately stoichiometric or within the narrow air-fuel ratio range, in order to produce the highest mutual conversion efficiencies in the three-way catalytic ;~
converter 32. -With the arrangement hereinbefore described, during operation of the engine lO, a considerably large amount Or the inert gas containing the recirculated exhaust gases through the exhaust gas recirculating means 78 and the residual gas remaining in the combustion chamber :
:, - 15 ~ ~
~ ., .: .: : , :, :
~48355 ~:~
is mixed with the air-fuel mixture inducted into the combustion chambers. The air-fuel mixture mixed with the inert gas is ignited and effectively burned by the two spark plugs ~2a and 82b disposed within each the combustion chamber. With these spark plugs arrangement, when the air~fuel mixture in the combustion chamber is ;
ignited, two flame fronts are produced adjacent the inner wa]l surface of the combustion chamber, or quench area. These flame fronts move toward the centre of the ~;
combustion chamber, heating it to a high temperature.
Therefore, the distance of flame propagation is shortened compared with a conventional engine using only one spark ~ ;
plug. Thus combustion, as a result of the plurality of spark plugs, is faster and completed at the central portion of the combustion chamber thereby accomplishing stable and smooth combustion even though such a large amount of the inert gas is mixed with the air-fuel mixture to be combusted in the combustion chamber. Due to the effect of the inert gas, the maximum temperature within the combustion chambers is lowered and accordingly the - emission level of NOx is reduced as compared with the engine without the exhaust gas recirculating means.
Now, when the combustion chambers are fed with the air fuel mixture richer than that having stoichiometric air-fuel ratio, the first and second solenoid valves 66 - .
~ ~ "' '' ' '' ' , ..
.,: . . .
3~
and 68 are operated to increase the amounts of air inducted respectively -through the first and second auxiLiary air bleeds 54 and 61 into the main well 41 and the ruel passage 58 of the low-speed circuit.
Thus, the amount of fuel flowing through the main nozzle 42 and the slow port 60 is decreased and accordingly the air-fuel mixture fed into the com-bustion chambers is made leaner. On the con-trary, when -the combustion chambers are fed with the air-fuel mixture leaner than that having stoichiometricair-fuel ratio, the first and second solenoid valves 66 and 68 are operated to decrease the amount of air inducted respectively through the first and second auxiliary air bleeds 511 and 64 into the main well 44 ~5 and the fuel passage 58 of the low-speed circuit.
Thus, the amount of fuel through the main nozzle 42 ` and the slow port 6~ is increased and accordingly, the air-fuel mixture fed into the combustion chambers is enriched. As discussed above, the air-fuel ratio of the mixture supplied into the combustion chambers ~- can be always maintained accurately at the stoichio-metric air-fuel ratio or near same. ~ ;
Now~ in addition to less generation of CO and HC because of combustion of stoichiometric air-fuel mixture, the generated CO and ~IC are further oxidized - l7 - ;`
' ' ' ~ . :
:- ' : :. ' : .
:.:
s~ :~
in the three-way catalyt.ic converter 32 to even further reduce the emission levels of C0 and HC. The relative].y small amount of NOx contained in the exhaust gases discharged from the combustion chambers is also further reduced in the three-way catalytic converter 32 to more reduce the emissibn level thereof~ .
It will be understood that since the ai.r-fuel ratio of the air-fuel mixture supplied to the combustion chamber is always accurately controlled at approximately stoichiometric, variation or change in the emission level of NOx, C0 and HC is minimized providing more accurate :~
and improved control of noxious constituents contained .~ :~
~ in the exhaust gases. ;~
: While the solenoid valves 66 and 68 have been shown ,: '~
~5 and described to control the air amount inducted from ; ~ ;
the auxiliary air bleeds 54 and 64, it will be understood ~ ~ -that similar solenoid valves may be alternately or addi-tionally disposed in the main fuel passage 48 and the ., ;
low-speed circuit fuel passage 58 in order to directly control the amount of fuel supplied from the main dis-charge noz,zle 42 and the slow port 60. '~
Fig. 6 illustrates another preferred embodiment of .~ ~;
the spark-ignition internal combustion engine 10' in accordance with the present invention, in which descrip- ~.
tion of similar parts to that of the embodiment in Fig. 1 .
....
. . .
' ' ' " . ' , ' ,. ;~': ' ' ~ ; .: . , , 3~i5 will be omitted for the purpose of sil~plicity of explanat:ion by deslgnating Iike parts at like refer-ence numeraIs. This engine 10' is similar to that of I~`ig. 1 except for an electrically controlled fuel injection system emp1oyed in place of carburetor 22 of Fig. 1.
As shown, the engine 10' is equipped with intake passage means 84 fluidly communicating with a conduit 85 which defines therein a throttle chamber 85a in which a throttle valve 86 is movably disposed. The intake passage means 84 is formed with four branch passages (no numerals)which are respectively communicable with the four combustion chambers C1 to C4. Disposed respec-tively at the four branch passages are fuel injectors 90a, 90b, 90c and 90d forming part of an electronically controlled fuel injection system. The injectors extend ~ -, into the branch passages of the intake passage means B~ ~ .
to inject a fuel mist into the air stream passing through the branch passages. Accordingly, the fuel mist from the injectors is inducted into the combustion chambers with air and recirculated exhaust gas to form the air-fuel mixture within the combustion chambers.
~ ach fuel injector is arranged to take the first state wherein the injection time for injecting the fuel is decreased below a predetermined level to decrease the _ I9 _ ~' ,, , . -. - , . , : .
' ,,:, . . , .. '' , ::
~4~3355 :
:.
amount of fuel inje~-tecl by one in;jection and a second ~, j~ state wherein the i,njectioJl time is increased above the precletermined level to increase the amount of fuel ~'- .
injected by one injection. The each fuel injector is ;~
electrically connected to the control circuit 72' forming part of the air-fuel ratio control means (no -' numeral ) . The circuit is arranged to generate a first ';
command signal to place each fuel injector into the `
~; first state and a second command signal to place each fuel injector into the second state. The control circuit ~ ~ , 72' is, in turn, electrically connected to the exhaust ~ - -gas sensor 74 located within an exhaust manifold 92 '' ~ -serving as a thermal reactor or reactor means forming , part of the exhaust passage 31. The exhaust manifold '~
~ 15 92 is communicable with the four combustion chambers C~
', to C4 through so-called siamesed exhaust ports 94 each ~ .
- of which is formed in the cylinder head 14 such that the outlets of the exhaust ports of two adjacent combustion ,~ ', ' chambers are combined to form an only one outlet. Refer- "
ence numeral 96 indicates port liners which cover the ,, inner surface of the siamesed exhaust ports 94. The ., exhaust manifold 92 'communicates through the connecting pipe 30 with the,three-way catalytic converter 32. '~
;; ' The, control circuit 72' is designed to supply the '; '`
'`25 fuel injectors 90a to 90d with command sigDals for - 20- , ' . :
~483~iS ``: ~ ~
causing the fuel injectors to inject -the optimum amounts of fucl at the optirnum timings in response no-t only to the inforn~ation signals from the exhaust gas serlsor 74 but also to the infortl~ation signals from an intake air temperature sensor, a throttle position (opening degree) sensor, an air flow amount sensor, and an engine coolant temperature sensor.
It is to be noted that since the temperature of the exhaust gases discharged from the combustion chambers, ~0 in this instance, is maintained relatively high because of the siamesed exhaust ports and the port liners 96, HC and C0 contained in the exhaust gases discharged from the combustion chambers are effectively burned within the exhaust manifold 92 serving as a thermal reactor, making it possible to decrease the capacity or volume of the three-way catalytic converter 32. Additionally, if the outer surface of the exhaust passage 31 is heat- ~ ;
insulated, the noxious gas decreasing effect of the three-way catalytic converter 32 may be furthermore improved.
With the engine 10' of this instance, the fuel ;
injection from the fuel injectors provides improved fuel distribution to respective combustion chambers.
Improved volumetric efficiency is also realized and therefore more stable operation of the engine and - 21 - '~
-:
: ~
- :. . , , . , , :
.~ : ' ' ,. .. .
~4~3355 improved engine power output performance are obtained.
I~Thile on1y rour cy]inder eng:ines have been shown ancl described here:inbefore, it will be understood that the principle of the present invention may be applied to engines having any other number of cylinders.
It will be appreciated that the stoichiometric air-fuel ratio of the mixture supplied to the combustion chamber may be somewhat modified during engine warm-up period or high engine speed and load operation in order to obtain more stable engine operation and high engine output power.
As is apparent from the foregoing discussion that, according to the present invention, NOx emission is effectively prevented firstly by suppressing NOx generation in the combustion chamber and thereafter :-by reducing the relatively small amount of NOx in the three-way catalytic converter. While, C0 aDd HC emis-sions are also effectively prevented firstly by supplying the combustion chamber with stoichiometric air-fuel mixture and thereafter by oxidi7ing the C0 and HC in the three-way catalytic converter. Therefore~ the noxious constituents in the exhaust gases discharged from the combustion chamber are almost completely removed to discharge the harmless exhaust gases into the atmosphere. Additionally, since the air-fuel ratio - 2? _ : .
' -', ' ' . : ~
~.: - ' ' , ' ' of the air-fuel mixture sul)plied to the combustion chambers of the engine is controlled with a high degree of accuracy a-t approximately stoichiometric, the fuel consumption of the engine is improved, con-tributing to ruel economy.
, ~, .
'~''' ' ~:
.
" ,'~
- 23 ~
' ~:
'''` ' ', ~
?
. .
- . . .
and 68 are operated to increase the amounts of air inducted respectively -through the first and second auxiLiary air bleeds 54 and 61 into the main well 41 and the ruel passage 58 of the low-speed circuit.
Thus, the amount of fuel flowing through the main nozzle 42 and the slow port 60 is decreased and accordingly the air-fuel mixture fed into the com-bustion chambers is made leaner. On the con-trary, when -the combustion chambers are fed with the air-fuel mixture leaner than that having stoichiometricair-fuel ratio, the first and second solenoid valves 66 and 68 are operated to decrease the amount of air inducted respectively through the first and second auxiliary air bleeds 511 and 64 into the main well 44 ~5 and the fuel passage 58 of the low-speed circuit.
Thus, the amount of fuel through the main nozzle 42 ` and the slow port 6~ is increased and accordingly, the air-fuel mixture fed into the combustion chambers is enriched. As discussed above, the air-fuel ratio of the mixture supplied into the combustion chambers ~- can be always maintained accurately at the stoichio-metric air-fuel ratio or near same. ~ ;
Now~ in addition to less generation of CO and HC because of combustion of stoichiometric air-fuel mixture, the generated CO and ~IC are further oxidized - l7 - ;`
' ' ' ~ . :
:- ' : :. ' : .
:.:
s~ :~
in the three-way catalyt.ic converter 32 to even further reduce the emission levels of C0 and HC. The relative].y small amount of NOx contained in the exhaust gases discharged from the combustion chambers is also further reduced in the three-way catalytic converter 32 to more reduce the emissibn level thereof~ .
It will be understood that since the ai.r-fuel ratio of the air-fuel mixture supplied to the combustion chamber is always accurately controlled at approximately stoichiometric, variation or change in the emission level of NOx, C0 and HC is minimized providing more accurate :~
and improved control of noxious constituents contained .~ :~
~ in the exhaust gases. ;~
: While the solenoid valves 66 and 68 have been shown ,: '~
~5 and described to control the air amount inducted from ; ~ ;
the auxiliary air bleeds 54 and 64, it will be understood ~ ~ -that similar solenoid valves may be alternately or addi-tionally disposed in the main fuel passage 48 and the ., ;
low-speed circuit fuel passage 58 in order to directly control the amount of fuel supplied from the main dis-charge noz,zle 42 and the slow port 60. '~
Fig. 6 illustrates another preferred embodiment of .~ ~;
the spark-ignition internal combustion engine 10' in accordance with the present invention, in which descrip- ~.
tion of similar parts to that of the embodiment in Fig. 1 .
....
. . .
' ' ' " . ' , ' ,. ;~': ' ' ~ ; .: . , , 3~i5 will be omitted for the purpose of sil~plicity of explanat:ion by deslgnating Iike parts at like refer-ence numeraIs. This engine 10' is similar to that of I~`ig. 1 except for an electrically controlled fuel injection system emp1oyed in place of carburetor 22 of Fig. 1.
As shown, the engine 10' is equipped with intake passage means 84 fluidly communicating with a conduit 85 which defines therein a throttle chamber 85a in which a throttle valve 86 is movably disposed. The intake passage means 84 is formed with four branch passages (no numerals)which are respectively communicable with the four combustion chambers C1 to C4. Disposed respec-tively at the four branch passages are fuel injectors 90a, 90b, 90c and 90d forming part of an electronically controlled fuel injection system. The injectors extend ~ -, into the branch passages of the intake passage means B~ ~ .
to inject a fuel mist into the air stream passing through the branch passages. Accordingly, the fuel mist from the injectors is inducted into the combustion chambers with air and recirculated exhaust gas to form the air-fuel mixture within the combustion chambers.
~ ach fuel injector is arranged to take the first state wherein the injection time for injecting the fuel is decreased below a predetermined level to decrease the _ I9 _ ~' ,, , . -. - , . , : .
' ,,:, . . , .. '' , ::
~4~3355 :
:.
amount of fuel inje~-tecl by one in;jection and a second ~, j~ state wherein the i,njectioJl time is increased above the precletermined level to increase the amount of fuel ~'- .
injected by one injection. The each fuel injector is ;~
electrically connected to the control circuit 72' forming part of the air-fuel ratio control means (no -' numeral ) . The circuit is arranged to generate a first ';
command signal to place each fuel injector into the `
~; first state and a second command signal to place each fuel injector into the second state. The control circuit ~ ~ , 72' is, in turn, electrically connected to the exhaust ~ - -gas sensor 74 located within an exhaust manifold 92 '' ~ -serving as a thermal reactor or reactor means forming , part of the exhaust passage 31. The exhaust manifold '~
~ 15 92 is communicable with the four combustion chambers C~
', to C4 through so-called siamesed exhaust ports 94 each ~ .
- of which is formed in the cylinder head 14 such that the outlets of the exhaust ports of two adjacent combustion ,~ ', ' chambers are combined to form an only one outlet. Refer- "
ence numeral 96 indicates port liners which cover the ,, inner surface of the siamesed exhaust ports 94. The ., exhaust manifold 92 'communicates through the connecting pipe 30 with the,three-way catalytic converter 32. '~
;; ' The, control circuit 72' is designed to supply the '; '`
'`25 fuel injectors 90a to 90d with command sigDals for - 20- , ' . :
~483~iS ``: ~ ~
causing the fuel injectors to inject -the optimum amounts of fucl at the optirnum timings in response no-t only to the inforn~ation signals from the exhaust gas serlsor 74 but also to the infortl~ation signals from an intake air temperature sensor, a throttle position (opening degree) sensor, an air flow amount sensor, and an engine coolant temperature sensor.
It is to be noted that since the temperature of the exhaust gases discharged from the combustion chambers, ~0 in this instance, is maintained relatively high because of the siamesed exhaust ports and the port liners 96, HC and C0 contained in the exhaust gases discharged from the combustion chambers are effectively burned within the exhaust manifold 92 serving as a thermal reactor, making it possible to decrease the capacity or volume of the three-way catalytic converter 32. Additionally, if the outer surface of the exhaust passage 31 is heat- ~ ;
insulated, the noxious gas decreasing effect of the three-way catalytic converter 32 may be furthermore improved.
With the engine 10' of this instance, the fuel ;
injection from the fuel injectors provides improved fuel distribution to respective combustion chambers.
Improved volumetric efficiency is also realized and therefore more stable operation of the engine and - 21 - '~
-:
: ~
- :. . , , . , , :
.~ : ' ' ,. .. .
~4~3355 improved engine power output performance are obtained.
I~Thile on1y rour cy]inder eng:ines have been shown ancl described here:inbefore, it will be understood that the principle of the present invention may be applied to engines having any other number of cylinders.
It will be appreciated that the stoichiometric air-fuel ratio of the mixture supplied to the combustion chamber may be somewhat modified during engine warm-up period or high engine speed and load operation in order to obtain more stable engine operation and high engine output power.
As is apparent from the foregoing discussion that, according to the present invention, NOx emission is effectively prevented firstly by suppressing NOx generation in the combustion chamber and thereafter :-by reducing the relatively small amount of NOx in the three-way catalytic converter. While, C0 aDd HC emis-sions are also effectively prevented firstly by supplying the combustion chamber with stoichiometric air-fuel mixture and thereafter by oxidi7ing the C0 and HC in the three-way catalytic converter. Therefore~ the noxious constituents in the exhaust gases discharged from the combustion chamber are almost completely removed to discharge the harmless exhaust gases into the atmosphere. Additionally, since the air-fuel ratio - 2? _ : .
' -', ' ' . : ~
~.: - ' ' , ' ' of the air-fuel mixture sul)plied to the combustion chambers of the engine is controlled with a high degree of accuracy a-t approximately stoichiometric, the fuel consumption of the engine is improved, con-tributing to ruel economy.
, ~, .
'~''' ' ~:
.
" ,'~
- 23 ~
' ~:
'''` ' ', ~
?
. .
- . . .
Claims (13)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A spark-ignition internal combustion engine comprising:
means for defining a combustion chamber;
air-fuel mixture supply means for producing an air-fuel mixture by mixing fuel and intake air and supplying it into the combustion chamber;
means for adding substantially inert gas to the air-fuel mixture in the combustion chamber, said substantially inert gas consisting of mixed gases which remain substantially inert in the combustion carried out in the combustion chamber, said inert gas adding means including control means for controlling the ratio of the fuel in the air-fuel mixture, sub-stantially combusted in the combustion chamber, and the substantially inert gas in the range from 1 : 13-5 to 1 : 22.5 by weight during normal engine operation;
two spark plugs disposed in the combustion chamber for reliably igniting the air-fuel mixture mixed with the substantially inert gas;
a three-way catalytic converter capable of reducing nitrogen oxides and oxidizing carbon monoxide and hydrocarbons, communicable with the combustion chamber for receiving the exhaust gases discharged from the combustion chamber, said three-way catalytic con-verter being most effective when supplied with the exhaust gases which are produced by supplying the combustion chamber with the air-fuel mixture having stoichiometric air-fuel ratio; and air-fuel ratio control means for controlling the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber at the stoichiometric air-fuel ratio in accordance with the composition of the exhaust gases discharged from the combustion chamber.
means for defining a combustion chamber;
air-fuel mixture supply means for producing an air-fuel mixture by mixing fuel and intake air and supplying it into the combustion chamber;
means for adding substantially inert gas to the air-fuel mixture in the combustion chamber, said substantially inert gas consisting of mixed gases which remain substantially inert in the combustion carried out in the combustion chamber, said inert gas adding means including control means for controlling the ratio of the fuel in the air-fuel mixture, sub-stantially combusted in the combustion chamber, and the substantially inert gas in the range from 1 : 13-5 to 1 : 22.5 by weight during normal engine operation;
two spark plugs disposed in the combustion chamber for reliably igniting the air-fuel mixture mixed with the substantially inert gas;
a three-way catalytic converter capable of reducing nitrogen oxides and oxidizing carbon monoxide and hydrocarbons, communicable with the combustion chamber for receiving the exhaust gases discharged from the combustion chamber, said three-way catalytic con-verter being most effective when supplied with the exhaust gases which are produced by supplying the combustion chamber with the air-fuel mixture having stoichiometric air-fuel ratio; and air-fuel ratio control means for controlling the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber at the stoichiometric air-fuel ratio in accordance with the composition of the exhaust gases discharged from the combustion chamber.
2. A spark-ignition internal combustion engine as claimed in claim 1, in which said substantially inert gas includes residual gas which is not discharged out of the com-bustion chamber during the exhaust stroke to remain in the combustion chamber, exhaust gas which is supplied from the exhaust system of the engine to the combustion chamber, and nitrogen gas contained in the intake air.
3. A spark-ignition internal combustion engine as claimed in claim 1, in which said inert gas adding means includes exhaust gas recirculating means for supplying the exhaust gas of the engine into the combustion chamber through the intake system of the engine.
4. A spark-ignition internal combustion engine as claimed in Claim 3, in which said exhaust gas recirculating means includes conduit means connecting a portion of the exhaust system of the engine and a portion of the intake system of the engine for intro-ducing the exhaust gases into the intake system, and a control valve disposed in said conduit means for controlling the amount of the exhaust gases passing through the conduit means.
5. A spark-ignition internal combustion engine as claimed in Claim 1, in which said combustion chamber is defined by the cylindrical inner wall of the cylinder of the engine, the inner wall of a cylinder head closing the one end of the cylinder, and the crown of a piston reciprocally disposed within the cylinder.
6. A spark-ignition internal combustion engine as claimed in Claim 5, in which said two spark plugs are located such that an intermediate point of the spark gap of the two electrodes of a spark plug and all intermediate point of the spark gap of the two electrodes of another spark plus constitute an angle ranging from 110 to 180 degrees with respect to the center axis of the cylinder.
7. A spark-ignition internal combustion engine as claimed in Claim 6, in which said two spark plugs are located such that the shortest distance between the intermediate point of the spark sap of each spark plug and the center axis of the cylinder is 0.15 to 0.45 times of the diameter of the cylinder bore.
8. A spark-ignition internal combustion engine as claimed in Claim 1, in which said air-fuel mixture supply means includes a carburetor having a main dis-charge nozzle opened into the venturi portion of the carburetor, a main well communicated through a main fuel passage with the main discharge nozzle and communicated with the float bowl of the carburetor, a main air bleed communicated with the main well for introducing therethrough the atmospheric air into the main well, and a first auxiliary air bleed communicated with the main well for introducing therethrough the atmosphere air into the main well.
9. A spark-ignition internal combustion engine as claimed in Claim 8, in which said air-fuel ratio control means includes:
first air flow amount control means for eon-trolling flow amount of air inducted through the first auxiliary air bleed into the main well, said first air flow amount control means being operated electrically and arranged to take a first state wherein the flow amount of the air is increased above a predetermined level and a second state wherein the flow amount of the air is decreased below the predetermined level;
control circuit electrically connected to said air flow amount controls means and arranged to generate a first command signal to place said air flow amount control means into the first state and a second command signal to place said air flow amount control means into the second state;
an exhaust gas sensor disposed within the exhaust gas passage of the exhaust system communicable with the combustion chamber of the engine and electri-cally connected to said control circuit, said exhaust gas sensor being arranged to generate a first information signal for causing said control circuit to generate the first command signal when the exhaust gases passing through the exhaust passage have a first composition representing that the combustion chamber is fed with an air-fuel mixture richer that that having stoichio-metric air-fuel ratio, and a second information signal for causing said control circuit to generate the second command signal when the exhaust gases passing through the exhaust passage have a second composition repre-senting that the combustion chamber is fed with an air-fuel mixture leaner than that having the stoichio-metric air-fuel ratio.
first air flow amount control means for eon-trolling flow amount of air inducted through the first auxiliary air bleed into the main well, said first air flow amount control means being operated electrically and arranged to take a first state wherein the flow amount of the air is increased above a predetermined level and a second state wherein the flow amount of the air is decreased below the predetermined level;
control circuit electrically connected to said air flow amount controls means and arranged to generate a first command signal to place said air flow amount control means into the first state and a second command signal to place said air flow amount control means into the second state;
an exhaust gas sensor disposed within the exhaust gas passage of the exhaust system communicable with the combustion chamber of the engine and electri-cally connected to said control circuit, said exhaust gas sensor being arranged to generate a first information signal for causing said control circuit to generate the first command signal when the exhaust gases passing through the exhaust passage have a first composition representing that the combustion chamber is fed with an air-fuel mixture richer that that having stoichio-metric air-fuel ratio, and a second information signal for causing said control circuit to generate the second command signal when the exhaust gases passing through the exhaust passage have a second composition repre-senting that the combustion chamber is fed with an air-fuel mixture leaner than that having the stoichio-metric air-fuel ratio.
10. A spark-ignition internal combustion engine as claimed in Claim 9, in which said air flow amount control means includes a first solenoid valve having an actuating member which is arranged to be movable with respect to the first auxiliary air bleed to in-crease the flow amount of air inducted through the first auxiliary air bleed into the main well above the predetermined level upon receiving the first command signal from the control circuit, and movable with respect to the first auxiliary air bleed to decrease the flow amount of the same air below the predetermined level upon receiving the second command signal from said control circuit.
11. A spark-ignition internal combustion engine as claimed in Claim 1, in which said air-fuel mixture supply means includes an intake air passage means for introducing air into the combustion chamber, and a fuel injector disposed in said intake air passage means for injecting fuel into the upstream portion of the combustion chamber, said fuel injector being arranged to take a first state wherein the injection time of the injection is decreased below a predetermined level, and a second state wherein the injection time of the injector is increased below -the predetermined level.
12. A spark-ignition internal combustion engine as claimed in Claim 11, in which said air-duel ratio control means includes:
a control circuit electrically connected to said fuel injector and arranged to generate a first command signal to place said fuel injector into the first state and a second command signal to place said fuel injector into the second state; and an exhaust gas sensor disposed within the exhaust passage of the exhaust system communicable with the combustion chamber of the engine and electrically connected to said control circuit, said exhaust gas sensor being arranged to generate a first information signal for causing said control circuit to generate the first command signal when the exhaust gas passing through the exhaust passage have a first composition representing that the combustion chamber is fed with an air-fuel mixture richer than that having stoichiometric air-fuel ratio, and a second command signal for causing said control circuit to generate the second command signal when the exhaust gases passing through the exhaust passage have a second composition representing that the combustion chamber is fed with an air-fuel mixture leaner than that having stoichiometric air-fuel ratio.
a control circuit electrically connected to said fuel injector and arranged to generate a first command signal to place said fuel injector into the first state and a second command signal to place said fuel injector into the second state; and an exhaust gas sensor disposed within the exhaust passage of the exhaust system communicable with the combustion chamber of the engine and electrically connected to said control circuit, said exhaust gas sensor being arranged to generate a first information signal for causing said control circuit to generate the first command signal when the exhaust gas passing through the exhaust passage have a first composition representing that the combustion chamber is fed with an air-fuel mixture richer than that having stoichiometric air-fuel ratio, and a second command signal for causing said control circuit to generate the second command signal when the exhaust gases passing through the exhaust passage have a second composition representing that the combustion chamber is fed with an air-fuel mixture leaner than that having stoichiometric air-fuel ratio.
13. A spark-ignition internal combustion engine as claimed in Claim 11, further comprising reactor means for oxidizing the unburned constituents contained in the exhaust gases discharged from the combustion chamber, said reactor means being disposed between the combustion chamber and said three-way catalytic converter to receive the exhaust gases from the combustion chamber and introduce the exhaust gases passing therethrough into said three-way catalytic converter.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP50120049A JPS5244337A (en) | 1975-10-03 | 1975-10-03 | Exhaust gas purification device used for a two-point ignition type eng ine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1048355A true CA1048355A (en) | 1979-02-13 |
Family
ID=14776615
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA76262521A Expired CA1048355A (en) | 1975-10-03 | 1976-10-01 | Spark-ignition internal combustion engine capable of preventing noxious gas emissions |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS5244337A (en) |
| CA (1) | CA1048355A (en) |
| DE (1) | DE2644203A1 (en) |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5131324B2 (en) * | 1971-11-29 | 1976-09-06 | ||
| JPS5213268B2 (en) * | 1973-06-05 | 1977-04-13 |
-
1975
- 1975-10-03 JP JP50120049A patent/JPS5244337A/en active Pending
-
1976
- 1976-09-30 DE DE19762644203 patent/DE2644203A1/en active Pending
- 1976-10-01 CA CA76262521A patent/CA1048355A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| AU1829776A (en) | 1978-02-09 |
| DE2644203A1 (en) | 1977-04-14 |
| JPS5244337A (en) | 1977-04-07 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP2580823B2 (en) | Stratified combustion internal combustion engine | |
| US4445468A (en) | 2-Stroke internal combustion engine and an ignition-combustion method of an internal combustion engine | |
| EP1389679A1 (en) | Compression ignition internal combustion engine | |
| US4071001A (en) | Stratified combustion engine with prechamber | |
| US4004563A (en) | Spark ignition engine using lean air-fuel mixture | |
| US4742804A (en) | Spark-ignition engine | |
| EP0249286B1 (en) | Combustion engine | |
| US4350129A (en) | Spark-ignition internal combustion engine capable of preventing noxious gas emissions | |
| US4038952A (en) | Internal combustion engine | |
| US4133322A (en) | Internal combustion engine | |
| CA1050369A (en) | Internal combustion engine and method of operating same | |
| US4325346A (en) | Four-cycle internal combustion engine | |
| CA1061205A (en) | Multiple spark-ignition internal combustion engine | |
| US4111161A (en) | Engine operated on hydrogen-supplemented fuel | |
| US4459804A (en) | Multiple spark ignition internal combustion engine with exhaust gas recirculation | |
| CA1055337A (en) | Internal combustion engine | |
| CA1048355A (en) | Spark-ignition internal combustion engine capable of preventing noxious gas emissions | |
| US4100736A (en) | Spark-ignition internal combustion engine equipped with exhaust gas recirculation system | |
| GB2271808A (en) | Pre-combustion chamber spark-ignition engine. | |
| GB1581689A (en) | Internal combustion engine | |
| JPH0670368B2 (en) | Spark ignition engine | |
| US4213430A (en) | Spark-ignition internal combustion engine capable of reducing noxious constituents in exhaust gases | |
| CA1060295A (en) | Spark-ignition internal combustion engine capable of reducing noxious constituents in exhaust gases | |
| US4210104A (en) | Internal combustion engine | |
| CA1062102A (en) | Multiple spark ignition internal combustion engine equipped with exhaust gas recirculation system |