CA1054004A

CA1054004A - Internal combustion engine

Info

Publication number: CA1054004A
Application number: CA259,449A
Authority: CA
Inventors: Yasuo Sakai; Hiroaki Miyazaki; Yoji Ito; Kazuya Kunii
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1975-08-20
Filing date: 1976-08-19
Publication date: 1979-05-08
Also published as: DE2636938A1; GB1525185A; JPS5412563B2; JPS5224629A; AU496827B1

Abstract

ABSTRACT OF THE DISCLOSURE:
A spark ignition internal combustion engine comprising a cylinder; a reciprocating piston in the cylinder; a cylinder head closing one end of the cylinder; a main section of a com-bustion chamber formed in the cylinder between the piston and cylinder head; an auxiliary section of the combustion chamber communicating only with the main section through a connecting passage; the cylinder head formed with an intake passage opening to the main section and with an exhaust passage opening to the main section; an intake valve to open and close the intake pas-sage; an exhaust valve to open and close the exhaust passage;
means for supplying an air fuel mixture to the intake passage;
means for supplying a portion of exhaust gas discharged from the exhaust valve through the exhaust passage to the intake passage.
The volume of the auxiliary section is from 3 percent to 20 per-cent of the volume of the main section and the cross-sectional area of the connecting passage being from 0.1cm2 to 2.0cm2 so that in operation of the engine a proportion of the amount of residual gas within the auxiliary section to the volume of the auxiliary section is higher than a proportion of the amount of residual gas within the main section to the volume of the main section; and that during the compression cycle part of the com-bustible charge within the main section is forced through the connecting passage into the auxiliary section. A spark plug is provided to produce a spark within the auxiliary section.

Description

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The preserlt invention relates to an internal com-bustion ensinc nnd rnore particularly to arl lnterrlal comhllstlorl erlgirle in whicll combustible mixture in a mnirl section of a combustion chamber is ignited by a torch flame r~sulted from combustion of combustible mixture in an auxiliary section of the combustion chamber.
Among toxic exhaust emissions, carbon monoxide (C0) and hydrocarbons (~IC) are relatively aasy to be oxidized with an exhaust converter provided in an ex-haust system and reduced sufficiently, while nitrogen oxides (NOx) are very difficult to be treated in the :`
exhaust system and thus formation of NOx must be sup-pressed in a combustion chamber. There is the tendency that NOx formation will increase as combustion peak temperatures and pressures increase. In other words as combustion state improves NOx formation increases. -~
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suppressing NOx formation to deteriorate the combustion ~ -state. This results in a loss in power output and a loss in fuel economy, deteriorating the performance of an engine. ~ ~;
~; The present invention aims at solving the above~
mentioned problem in the prior art regarding the suppression of NOx formation and it is a main object ~
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~ ' ~54~[)fls oE ~he l~resent il~VC ~ ion t:o p.roYic1e G~n inte~nal combust.ion en~;ne irl which a considcrabl~ reducti.on in NOx emissions is achi.eved w;.thout a~y cleteriora-t.ion in the perfo:rmance of the e~g-i.ne and red~lc~i.orls in CO and HC em:i.ssions are achieved at the same tlme.
There;Eore, according to -the present invention -there is provided a spa:rk ignition i.nternal combustion engine com-prising: a cylinder; a reciprocating piston in the cylinder; -a cylinder head closing one end of the` cylinder; a main section . .:
~ 10 of a combustion chamber formed in the cylinder between -the ~ ~
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piston and cylinder head; an auxiliary section of the combustion ~ .

:; chamber communicating only with the main sect;.on tJIrough a con- ~

`~ necting passa.ge; the cylinder head being forrned with an intake ~`

passage opening to the main section and with an exhaust passage ~ .

.-. opening to the main section; an intake valve -to open and close ..
~:~ the intake passage; an exhaust valve -to open and close -the exhaust passage; means for supplying an air Euel mixture to the intake passage; means for supplying a portion of exhaust gas dis-charged from the exhaust valve through the exhaust passage to the ~' 20 intake passage. The volume of the auxiliary section being from .:` 3 percent to 20 percent of the volume of the main section and ~',`: ~ :- '.
the cross-sectional area of the connecting passage ~eing from -~; 0.1cm2 to 2.0cm2 so that in operation of the engine a proportion . . . . .
`~ of the amount of resi.dual gas within the auxiliary section to .:~ the volume of the auxiliary section is higher than a proportion :~
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.~ of the amount of residual gas within the main section to the ~.. . . ::

,~ volume of the main section; and that during the compression :~

~ cycle part of the combustible charge within the main section is `~ forced through the connecting passage into the auxiliary section. ~ ~:
. ,j ., A spark plug is proYided to produce a spark within the auxiliary :' section. .

The other objects and advantages o~ the present ' `' . '

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invcnt;on wiL1 }-ec(~ne apparent frosn the .follo~inc~ description in connection with the accompallying dra~in~s, in which:-F;g. 1 is a schernatic diagram st~owing a firste]nbodiTnent of ~n i?l ~erllal comhustion enylne according to the present invelltion;
F:ig. 2 is a flagrnentary scction of the engine shown in I~'ig. l;
Fi.g. 3 is a section taken through line III-III sho~m in Fig. 2;
Fig. 4 is a schematic diagram showing a second embodiment of ~n internal combustion engine according to the present invention; -~
Fig. 5 is a graph showing Cycle by Cycle Variability in an internal combustion engine according to the present ;
invention against air fuel ratio and that of a conventional in-ternal cornbustion engine against air fuel ratio; and -~' Fig. 6 is a graph showing a pressure history of the ~; ' , ' , . ~
engine according to the present invention and that of the ~;~
conventional engine.
-~ 20 Referring to Fig. 1 of the accompanying drawings, ;'~ there is shown a schematic layout of the engine according to the present inventionr in which reference numeral l designated ;~;
an air c]eaner, 2 a car~uretor, 3 an intake ~
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plssllgc~ly, ll Ul c~lgille block~ 5 n thcrnlal reactor~
l 6 111 cxl~ t l~l~Sils l ! \~' c l y .
~s best .secll ;n l~ .s. ~ alld 3, tlle ellgine block /I coml)li;es a cylillclcr 7, a cyl;lldcr llcacl 8 closing ~; 5 onc clld of ~lle cylil~(lcr 7 alld a recil7rocntillg piston :, 9 in the cylindcr 7. The cylirlde~ 7, the cylinder ; head 8 nlld the pis-ton 9 cooperating to form a main - section 10 of a coolbustion chamber in the cylinder 7. ;
Commllrlicating only ~ith tl1e milin section 10 tllroush a connect1nS nozzle t1 is an nuxilialy section 12 of the combustion ch~ ber.
The main section 10 of the combustion chamber is i providcd ~ith an intake valve 13 and an exhaust valve .,. ~ , ~ ' -14 to o~)en alld close an intake port 15 and an exhaust ~ ~
`; 15 port lG, respectively, ~llile the auxiliary scction 12 ~ -: :, . . .
:~ is not l>rovided with such valves and ports and th1ls ;~ scavenging of the auxi]iary section 12 is performed ; through the connecting nozzle 11 at the same time as .: ................................................................... . . ..
;; that of the main section 10.
-~ 20 PrefeI-ably, the auxiliary section 12, the main section 10 arld the connectinS nozzle 11 shoulA be so designed that after scavengillg of the auxiliary section ;~ 12 the ratio of rcsidl~al gas to the combustible charge in the auxiliary section 12 ranses from 5 to 20 per 25 cent. Describing in detail, the vol~lme of the auxiliary ~; _ '' ~:' ~ i, :~54004 .';eCt:i()n 12 :is hetlieer1 ~ to ~.0 per ccnt of t1~e volume of t}l~ 111;1i11 .s~ctiol1 lO ~11~] t:11c cross s~c~ A1 dt't'A

is l~cl~ce~1 O.l cm ar1d 2.0 cm . By so cor1.YLructi.l1g the e~llgille, tlle rat;o 0~ r es:idlltl ga9 to ~11c combw~;l:i.blo .
c11n~ge ill the allxi.1.;ary sectiol1 :i~s greater t~1arl ~he ratio of reYic1ual gas to the combllsti.ble charge in the , . . .
... ; inain section. Thi s results in a considerable reduction :~
in NOx. .
The auxili.ary section 12 is provicled with a spark lO plug 19 and after ignition with the spark plug 19 ].snition flame rllshes into the main section lO throu$h ~` the connectil1s no~.zle ll to ignite the cornbustible ~:, cha:r$e in the main section 10.
:~ Having surveyed the distribution state of NOx 15 formation in the combustion chamber, NOx formation is ;
.~ great at elevated temperature area in the combustion :-`.i chamber. Thus most of the NOx is formed within a . -.
;,~ srnall area arow1d the spark plug.
In the engine according to the present invel1tion : .
'. ' . , 20 an appropriate amow1t of residual gas will remain in .
t}-e auxiliary sectio11 12 in WhiC}I the spark plug 19 is pl.aced and thus forll1ation of NOX is greatly suppressed ,`-i because the presence of the residual gas in t}1e auxilia,- ~ :
ry section 12 has the same effect as recirculating the :i ; -`~, 25 exhaust gas concentrically to the area around the spark :~ ~

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plug 19 at high rate. It i8 to be noted that increasins the EGR rate will result in a corresponding redllction i~ NOx emissions.
Although the presence of the residual gas in the auxiliary section 12 will hinder the combustion in the auxiliary section 12 to some extent, Cycle by Cycle Variability in the engine as a whole is small and stable combustion is assured because the combustible :
mixture in the auxiliary section 12 is surely ignited due to the fact that the volume of the auxiliary is small and the combustible mixture in the main section 10 which occupies most of the volume of the combustion chamber is subsequerltly ignited by a torch flame re- ~
~ ~ulted from the combustion in the auxiliary section 12. ~ ;
- 15 As a result, considerably reduction in NOx emissions wlthout deteriorations in engine power output and fuel -r economy is achieved.
If more stable combustion in the auxiliary section .. ~ . , .
~`~ 12 15 desired,~the center line of the connecting nozzle 11 should be tangential to walls of the auxiliary : .
section 12 so that during the compression cycle part of :; - :
`~ the combustible charge rushes into the auxiliary section 12, causing great turbulence therein. The use of great turbulence make pos~ible rapid completion of the com-bustion in the auxiliary section although there is ~ . , . ~ :
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~ubst~ntial amourlt of residual gas in the a~xiliary section 12. Thus more stable and stronger torch flame ~, is provided by ~rranging the center line of thc con-necting noY.~le 11 in tangential relation to the wall of the auxiliary ~ection 12. It will thus be under-stood that more stable combustion in the engine is ; achieved owing to this more stable and stronger torch flame.
Greater reduction in NOx emissions can be achieved by the use of exhaust gas recirculation (EGR). -~
A system effecting the EGR comprises an EGR conduit ~ 20 interconnecting the exhaust passageway 6 and the .'.'`' ., intake passageway 3 and an EGR valve 21 provided in the ~ ;
; EGR conduit 20 to control flow of exhaust gas passing , `~ 15 through the EGR conduit 20.

`~ The EGR valve 21 is operatively connected with a ',`'A diaphragm device 22 such that the flow rate of th~

,~ e~haust gas passing through the EGR conduit 20 is ' controlled in proportion to the flow rate of intake -~

air.

The diaphragm device 22 includes a~diaphragm 23 a vacuum chamber 24 above the diaphragm, a return ;~

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~`~ spring 25 in the vacuum chamber 24, and a vacuum line `' connecting the vacuum chamber 24 to a vacuum port provided in the intake passageway 3.

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~ en EGR is employed, the combustible charge diluted by th~ recirculated exhaust gag is supplied to the mairl s~ction 10 of the combu~tiorl chamber.
E~ecause the recirculated exhaust gas flows into botl the main section 10 and the auxiliary section 12, formation of NOx in the main section is suppressed as well as the formation of NOx in the auxiliary section is suppressed. The air fuel ratio of the combustible charge may be set at richer value that the stoichiometry : :
to improve the combustion stability of the engine with ~`~
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` . EGR.
Although the EGR rate should be a value within the range from 0 percent EGR to 30 percent EGR. The `: ' ;
value will vary with desired emission standard for NOx.

For the purpose of reducing C0 and HC contents of ` the exhaust gas the thermal reactor 5 together with a :: .
secondary air supply system 28 is provided in the engine ~xhaust system in the case of this embodiment.
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To promote oxidation reaction in the thermal reactor 5, tha air fuel ratio of the combustible charge should be set to a value within a range from 11 to 15 -`` to provide an appropriate strength of C0 in the exhaust . :. , - :
~ gas to be fed to the thermal reactor 5 and the amount ,, ~` of the secondary air supplied by the secondary air `

supply system 28 should be controlled so that the total ~`
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~0~0~4 . air fuel ratio that is tho air fuel ratio o.f the com-.
: bustible charse actually fed -to the combustion chamber ..
under the operation of the .secondary air supply system 28 should be from 16 to 18.
:~ 5 The secondary air supply system 28 comprises an air injectiorl nozzle 29, a check valve 3t an air . . ~, .
~upply conduit 31, a relief valve 32, and an air pump 33. The air pump 33 is driven by the engine crank shaft and the system should be calibrated so that the flow rate of the secondary air injected through the air ~ injection nozzle 29 varies in approximately proportion -: to the flow rate of the intake air. In this embodiment :~
:.:. the secondary air is pushed into the flow of exhaust gase~ passing through the exhaust system by the air .:: 15 pump 33. The secondary air may be drawn into the ex-: ,'. .
:` haust system by the use of exhaust pulsation. -~
` As the exhaust converter the thermal reactor 5 is .. : employed in the preceding embodiment, a catalytic con~
... : .verter ;5 may, instead of the thermal reactor, be . 20 provided in the exhaust passageway 6 as shown in Fig. 4.
.
'~hen the catalytic converter 35 is employed, the air fuel ratio of the combustible charge provided by ~ the carburetor 2 should be from 13 to 18. Preferably ... the air fuel ratio should be from 14 to 18. The use 25 of catalytic converter 35 makes possible the operation -., ' .
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l~S4~04 of the engine on relatively leaner air fuel ratio as compared to the case in which the thermal reactor 5 is ~Isrd~ thus improving the fuel economy.
W~len tlle air fuel ratio range is from 13 to 15 it is of course desirable to supply the secondary air ~ :
into the flow of exhaust gas. : .
~ It is to be noted that the use of the catalytic :~ converter 35 is advantageous over the use of the ther-mal reactor 5 in the fuel economy because wllen the exhaust temperature is low it is not necessary to ~ . enrich the air fuel ratio in the case of the catalytic :~ converter due to the fact the catalyst promote oxidation of C0 and HC even under the low temperature conditions, whereas in the case of the thermal reactor the air fuel :
ratio must be enriched to sustain appropriate oxidation reaction speed in the thermal reactor when the exhaust .
temperature is low.
, . :
It will now be appreciated from the preceding de~
scription that according to the present invention NOx, ; 20 HC and C0 emission reduction is achieved without ~:
deteriorating the engine performance. Comparing the -engine according to the present invention with a con-ventional spark ignition internal combustion engine, ~, it has been revealed that Cycle by Cycle Variability in the engine according to the present invention is .
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smaller th~rl that in the conventional engine, as shown in Fig. 5. Also reve~led is that combustion pressure variability in the engine ~ccording to the present invention is smaller than that in the conventional ~ 5 ongine, as shown in Fig. 6.
;; It will be understood that with small Cycle by Cycle Variability engine stability, power output and fuel economy are improved and enhanced.
It is to be noted that the carburetor 2 may be . . : .
replaced with a fuel injection apparatus (not shown) . with the same result.
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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A spark ignition internal combustion engine comprising:
a cylinder;
a reciprocating piston in said cylinder;
a cylinder head closing one end of said cylinder;
a main section of a combustion chamber formed in said cylinder between said piston and cylinder head;
an auxiliary section of the combustion chamber com-municating only with said main section through a connecting passage;
said cylinder head formed with an intake passage opening to said main section and with an exhaust passage opening to said main section;
an intake valve to open and close said intake passage;
an exhaust valve to open and close said exhaust passage;
means for supplying an air fuel mixture to said intake passage;
means for supplying a portion of exhaust gas discharged from said exhaust valve through said exhaust passage to said intake passage;
the volume of said auxiliary section being from 3 percent to 20 percent of the volume of said main section and the cross-sectional area of said connecting passage being from 0.1cm2 to 2.0cm2 so that in operation of the engine a proportion of the amount of residual gas within said auxiliary section to the volume of said auxiliary section is higher than a proportion of the amount of residual gas within said main section to the volume of said main section; and that during the compression cycle part of the combustible charge within said main section is forced through said connecting passage into said auxiliary section; and a spark plug to produce a spark within said auxiliary section.

2. A spark ignition internal combustion engine as claimed in claim 1, in which the proportion of the amount of residual gas within said auxiliary section to the volume of said auxiliary section is from 5 percent to 20 percent.

3. A spark ignition internal combustion engine as claimed in claim 1 or 2, in which said connecting passage is constructed and arranged with respect to said main section and auxiliary section such that part of the combustible charge within said main section which is forced through said connecting passage into said auxiliary section during the compression cycle creates turbulence within said auxiliary section.

4. A spark ignition internal combustion engine as claimed in claim 2, in which part of fresh charge is admitted through said connecting passage into said auxiliary section during the intake cycle.

5. A spark ignition internal combustion engine as claimed in claim 4, in which said connecting passage is arranged and directed so as to provide an arrangement in which during the intake cycle part of fresh charge admitted to said main section through said intake passage is directed by the valve head of said intake valve to enter through said connecting passage into said auxiliary section.

6. A spark ignition internal combustion engine as claimed in claim 2, in which the air fuel mixture has an air fuel ratio less than the stoichiometry.