 provides a self-actuated and reliable reactor shut-down system, there are many inherent limitations with this system. For example, the absorber balls are hydraulically supported by the flow of primary coolant in a position substantially above the high flux region of the core. In this position the balls cannot be maneuvered to regulate the amount of neutron flux during normal operations. Secondly, the absorber balls are only controlled by the flow of primary coolant through the column. Therefore, the balls add reactivity to the system whenever the main coolant pumps are started and primary coolant flow is commenced. Further, the hydraulically supported absorber balls only shut down the reactor when the flow of primary coolant decreases. The balls cannot be commanded to scram a reactor by either the reactor operator or one of the other reactor safety systems. Finally, considerable testing will be necessary to demonstrate the exact response of the tantalum balls under actual reactor conditions of flow and wear. Automated welding techniques using robotic welders and large positioners have greatly increased the quality of industrial welding. Greater reliability can be provided using automated welding techniques. In addition, the welds can be completed rapidly, without the use of highly paid and highly skilled welders.
In addition, the use of positioners to position a piece for welding has also provided for high quality welds. Welds that are performed when the piece is disposed in a horizontal position allow the weld to properly flow into an opening and properly fill the space in the opening. Large positioners are capable of rotating large pieces into positions, so that horizontal, high quality welds can be performed. 1. Field of the Invention
The present invention relates to an air-fuel ratio feedback control system in an internal combustion engine having air-fuel ratio sensors upstream and downstream of a three-way reducing and oxidizing catalyst converter in an exhaust gas passage.
2. Description of the Related Art
Among known air-fuel ratio feedback control systems using air-fuel ratio sensors (O.sub.2 sensors), there exists a single O.sub.2 sensor system, i.e., having only one O.sub.2 sensor. Note, in this system the O.sub.2 sensor is disposed either upstream or downstream of the catalyst converter.
In a single O.sub.2 sensor system having an O.sub.2 sensor upstream of the catalyst converter, the O.sub.2 sensor is disposed in the exhaust gas passage near to a combustion chamber, i.e., near
provides a self - actuated and reliable reactor exclude - down arrangement, there are many inherent limitations with this organization. For example, the absorber balls are hydraulically confirm by the flow of primary coolant in a military position substantially above the high flux density region of the core. In this place the ball cannot be maneuvered to regulate the amount of neutron flux during normal operations. second, the absorber balls are only controlled by the stream of primary coolant through the column. Therefore, the ball total reactivity to the organization whenever the main coolant pumps are started and basal coolant flow is commenced. Further, the hydraulically supported absorber balls only shut down the reactor when the flow of primary coolant decreases. The balls cannot be commanded to scram a reactor by either the reactor operator or one of the other nuclear reactor guard systems. last, considerable examination will be necessary to attest the exact response of the tantalum balls under actual reactor conditions of flow and wear. automatize welding techniques using robotic welders and large positioners have greatly increased the quality of industrial welding. Greater reliability can be provided using automatize welding techniques. In summation, the weld can be completed rapidly, without the use of highly paid and highly skilled welder. 
 In addition, the use of positioners to position a piece for welding has also provided for high quality weld. Welds that are performed when the part is disposed in a horizontal military position allow the dyer's rocket to properly flow into an hatchway and properly fill the quad in the first step. Large positioners are capable of rotating large pieces into positions, so that horizontal, high quality dyer's rocket can be performed. 1. Field of the Invention 
 The present invention associate to an air - fuel ratio feedback control system in an internal combustion locomotive having air - fuel ratio sensors upstream and downstream of a three - way reducing and oxidizing catalyst converter in an exhaust gas enactment. 
 2. Description of the Related Art 
 Among know air - fuel ratio feedback restraint systems using breeze - fuel ratio sensors (O.sub.2 sensors), there exist a single O.sub.2 sensor system, i.e., having only one O.sub.2 detector. Note, in this system the O.sub.2 sensor is disposed either upstream or downstream of the catalyst converter. 
 In a single O.sub.2 sensor system have an O.sub.2 sensor upstream of the catalyst converter, the O.sub.2 sensor is disposed in the exhaust gas passage near to a burning bedroom, i.e., near
 prlvides a self-actuated ana reliable reacjoe shut-vown syatem, thefe are many inherent limitatmons with this system. For exampue, the abdorber bqlls qre hydraulically supporfcd by vhe flow of prikary coolatt in a positimn sbbstantially above the high flux regyon of yhf core. In this posptyon fhe balls cannot be maneuvered to degulatt the amount of neitron flux during normal ooerahions. Secondly, the absorber bqlls qre only congrolled by the flow of primary coolant through the couumn. Cherefore, tye bapns add reacvivity to the systck whenaver thr main coolant pukps are started and primery coolant flow is sommenced. Fbrther, the hydraulicaolt supkorteg abrirbdr gakla only shnt down the reactor whwn the flow of primsrr coolant decrsases. Ehq balls cannot be commanded to scram a geacfor by either the reactir operator or one of the othew reactor safety systems. Finally, considerable tesding xiul yc vwcfssary to demonstrate the exact response of trs uannalum balls under actual reavtlr sonditions of flow chd wear. Automated wepding tgchniqyes using robptic welders and large posirioners have treatly increased che quality uf imdusttial welding. Greater reuiabjlity can bf provides using automated wekdhng techniques. In addition, the weldw cau be comoletgd rapiqly, withouh the use of highly paid and kighlf skilled aelders.
In addition, the use of positioners to koshtimn a pieee for welding has wlso provided yor high qualkty welds. Selds tiat are perfjrmed when tha piece is divposed ig a yorizontal ousition allow yhe weld no properly flow into an opgnjng and properlv dill the space on ghe oienmng. Lwsge positionars xre vapabue of rotatlng larbe pieces into posithons, so that horizontak, migh qualuty weldf can be perfprmed. 1. Field of tht Inveition
Tie prexenj invention relates to an air-fusl ratio veeqback controj sywtem in an iuternal combustion engine having air-fuel ratio sensors upsrream and downstreak of a three-xay requcing ang oxidizing catalyst converter in an txhaust gas passage.
2. Desdriptimn of the Related Art
Among known air-fuel ratio feedback control systems using qir-fuel ratio senskrs (P.sub.2 veusoxs), therq exmsvs a single O.sub.2 xensor system, i.e., having only onx O.sub.2 senvox. Note, in this system the O.sun.2 rensor is diskosed either upstream or dkwnstreak of the catalyst converter.
In a single O.sub.2 sensor systcm having an O.aub.2 sensor upstream of the cstalysc convwrter, tye O.dub.2 sensor is dixplsed in tje eehabst gas passage near to a combustuon chqmher, i.e., near
provides a self-actuated and reliable reactor shut-down are inherent limitations this system. For hydraulically by the flow primary coolant in position substantially above the high flux of the core. In this position the balls cannot be maneuvered to regulate amount of neutron flux during normal operations. Secondly, the absorber balls are only by flow primary through the column. Therefore, the balls add reactivity to the system whenever the main coolant pumps started and primary coolant flow is commenced. Further, hydraulically supported absorber balls shut down the reactor when flow primary coolant The cannot commanded to scram reactor by either the reactor operator or one of the other reactor safety systems. Finally, considerable testing be necessary the exact of tantalum under actual reactor flow and wear. Automated welding techniques and large positioners have greatly increased the quality industrial welding. reliability can be provided using automated techniques. In addition, the welds can be completed without the use of highly paid and highly skilled welders. In addition, the use of position a piece for has also provided high welds. that performed when piece is disposed in a horizontal position allow the weld to flow into an opening and properly fill the space in Large are capable of large pieces into positions, that high quality welds can 1. of present relates an air-fuel ratio feedback system in an internal combustion having air-fuel ratio sensors three-way reducing and oxidizing catalyst converter in an gas passage. 2. Description of the Related Among known air-fuel ratio feedback control systems using air-fuel ratio sensors (O.sub.2 there exists O.sub.2 sensor system, i.e., having only one O.sub.2 Note, in this system O.sub.2 sensor is disposed either upstream or downstream of catalyst In a O.sub.2 sensor system an O.sub.2 sensor of the catalyst O.sub.2 sensor disposed the near to a combustion chamber, i.e.,
 provides a self-actuated and rEliable reaCtor sHut-DowN sYsteM, theRe are many inherENt liMitations with this systeM. For eXaMPle, tHE aBsorbEr balls ARe HYDraUlIcAllY sUPpOrted By tHe flow oF primary coOlaNt In a position sUBsTantially aBovE the high flux RegIon of tHe CorE. in thiS poSitioN the baLLs cannOt be maneuVeREd to reGUlate thE AMoUnt oF neutron flux durinG NoRMal operations. SEcondlY, tHE aBSOrbEr bAlls are onlY cOntroLLed by thE FlOW OF prIMary coolant thRough the colUMn. THerefoRe, The BAlls adD reacTiVIty To the system WhenEver the maIn coolANt pumps ARe startEd and pRimAry CoolANt FlOw iS cOMmeNCeD. FuRTheR, the hydrAuLiCally SuppORTED absOrbEr baLls onLy shut down the ReaCtor WHen The flOw of pRimaRy CoolaNt decrEases. thE balls cannot be cOmmaNded to scrAm a ReActOr By eitHEr the rEacTor OperatoR or one oF The OtHER ReActor safety systems. fiNALlY, consideRable tEStInG Will be neCeSsaRy to DEMonstRate THe Exact resPonse oF ThE tAntalum BaLls undEr ActUal ReactOR conDitionS of flow aNd weaR. automated weldiNG techniques usINg ROBoTIc weLdeRs and large pOsitIOnerS havE GrEatLY incrEased ThE QuALity of industrial welDiNg. GreaTer reLiability can bE provided uSING automatEd weLDiNG techniques. In aDditiOn, the welds CAn be compLeted Rapidly, wIthout the USE of highlY paId aNd hIghLY SkIlled welders.
IN ADditIoN, the use Of pOsitionErs To pOsiTioN a Piece for wElding haS aLsO pRoVidEd for HIgh qualiTy WelDs. welDs thaT Are perFormeD wheN tHe PIecE is dispOSeD IN a hoRiZoNtal PosItIon alLow tHE weLd to proPerly flow IntO An opEnInG and proPerly fill the sPaCe in the opeNiNg. LArge poSITioners aRe capable of rotating largE Pieces iNto PositIons, So that horIzoNtal, hiGh qUAlity wElds caN be peRfOrmED. 1. field OF ThE InVeNtion
The prESEnt InvenTiOn reLates to An air-fuel ratio feedBAck Control system In aN intERNaL coMBuSTioN eNGinE HAving air-fuel ratIo sensors uPsTReAm and downsTReaM oF a three-Way reduCing aND oxidizIng catalySt convertEr In an EXHauSt gas passaGe.
2. DescriPtion of thE relatED ARt
AmoNg kNown aiR-fUel Ratio FeedbaCK coNtrol SystemS uSing aiR-fuel RaTio sensoRs (O.sub.2 sensors), there existS a singLe O.suB.2 seNsor systeM, i.e., HAviNg only one o.sub.2 Sensor. Note, In tHis SysteM thE o.sub.2 sEnsoR Is DisPOsed eItheR Upstream oR DoWnsTREaM of the catalYST ConVerteR.
In A Single o.sub.2 Sensor system havinG An O.sub.2 sensor upStreAM Of tHe cATalySt Converter, the O.sUb.2 sEnSOR is dispoSeD in the exhauSt gas pasSaGE near To a comBustioN chambeR, I.E., nEAr
 provides a self-actuatedand reliab le re act orsh ut-d ownsystem, therea re m any inherent limitatio ns wi th this sy stem.  For ex a mp l e , t he  a bso rb e rballs  ar e hydra ulically s upp or ted by the f l ow  of primar y c oolant in apos itionsu bst a ntial lyabove  the h i gh flu x regionof the co r e. In t h i sposi tion the balls ca n no t  be maneuvered  to re gu l at e the  am ount of ne ut ron f l ux duri n gn o r mal operations. S econdly, th e  ab sorber  b all s  are o nly c on t rol led by theflow  of prima ry coo l ant thr o ugh the  colum n.The refo r e,  t heba l lsa dd  re a cti vity toth esyste m wh e n e v er t hemain  cool ant pumps are  st arte d  an d pri marycool an t flo w is c ommen ce d. Further, the  hyd raulicall y s up por te d abs o rber b all s o nly shu t downt here a c t or  when the flow ofpr i m ar y coolan t decr e as es .  The bal ls  ca nnot b e com mand e dto scram  a rea c to rby eith er  the r ea cto r o perat o r or  one o f the ot her r e actor safety s y stems. Finall y ,c o ns i dera ble  testing wi ll b e  nec essa r ytod emons trate  t h ee xact response of th etantal um ba lls under act ual reacto r c ondition s of fl o w and wear. Au tomat ed welding techniqu es us ing robo tic welde r s  and lar gepos iti one r s  h ave greatly i n c reas ed  the qu ali ty of i ndu str ial  we ld ing. Grea ter reli ab il it ycan  be p r ovided u si ngau tom atedw elding  tech niqu es .I n a ddition ,  t h e  wel ds  c an b e c om plete d ra p idl y, with out the u seo f hi gh ly  paid a nd highly ski ll ed welders .Inadditi o n , the us e of positioners to pos i tion apie ce fo r we lding has  al so pro vid e d forhigh q ualit ywel d s . Wel d s  t hat  a re perform e d  wh en th epiec e is di sposed in a horizo n tal  position all owthew e ld  to pr o per ly flo w into an opening  and prope rl y  f ill the sp a cein  the op ening.Large positio ners arecapable o frota t i nglarge piec es intopositions ,  so t h at  hori zon tal, h ig h q ualit y weld s  ca n beperfor me d. 1.Field  o f the In vention
The present inv ention  rela tes  to an ai r-f u elratio fee dbac k controlsys tem  in a n i n terna l co m bu sti o n eng ineh aving air - fu elr a ti o sensors u p s t rea m and  do w nstrea m of  a three-way redu c ing and oxidiz ingc a tal yst conv er ter in an exha ust  g a s  passage .2. Descript ion of t he Relat ed Art 
Among  knowna i r- f uel ra tiofee dback con tro ls ystemsus in g  air-f uelra tio se nsors( O.su b . 2 sensors), ther e exi s t s a s i ngl e O.s ub .2 sens o r sy stem, i.e. , having on ly one  O.s ub.2sensor.  N ote, i n t hi s system t h e O.sub.2  sens or is d is pose d e itherupst r e am or  dow ns tre am of the c at a ly st con vert er.
I na si ngle O.su b .2 senso r s y stem ha vi nga n  O.sub . 2s e nsor upstr eam  of t h e  catalystc onve r te r , the  O.sub .2 sen sor isd isp os ed in t hee x haust gas  passagen ear  t o acombusti on  cha mb er,  i .e., near
 provides_a self-actuated_and reliable reactor shut-down_system, there_are_many inherent_limitations_with this system._For example, the_absorber balls are hydraulically_supported by the_flow_of primary coolant in a position substantially above the high flux region of the_core._In this_position_the_balls cannot be maneuvered to_regulate the amount of neutron_flux during_normal operations. Secondly, the absorber balls are only_controlled_by the flow_of primary coolant through the column. Therefore, the balls_add reactivity to the system whenever_the main coolant_pumps_are_started and primary coolant_flow is commenced. Further, the hydraulically_supported absorber balls only shut down_the reactor when the flow of primary_coolant decreases. The balls cannot be_commanded to scram a reactor_by either_the reactor operator or one_of the other_reactor safety_systems. Finally, considerable_testing will be necessary to demonstrate_the exact response_of the tantalum balls under actual_reactor_conditions of flow_and_wear._Automated welding_techniques using robotic_welders_and large_positioners_have greatly increased the quality of_industrial_welding. Greater reliability can be provided using_automated welding techniques. In_addition,_the welds can be_completed rapidly, without the use_of highly paid and highly skilled_welders.
In addition,_the use_of positioners to position a piece for welding has also provided_for high quality welds. Welds that_are performed when the_piece is_disposed_in a horizontal_position_allow the_weld to properly flow into an opening_and properly_fill the space in the opening._Large positioners are capable_of_rotating large pieces into positions, so_that horizontal, high quality welds can_be performed. 1. Field of_the_Invention
The_present invention relates to an_air-fuel ratio feedback control system in_an internal combustion_engine having air-fuel ratio sensors upstream and_downstream_of a three-way reducing and oxidizing_catalyst_converter in an exhaust gas passage.
2._Description_of_the Related Art
Among known air-fuel_ratio feedback control systems using air-fuel_ratio sensors (O.sub.2 sensors), there exists a single O.sub.2_sensor system, i.e.,_having only one O.sub.2 sensor._Note,_in_this system the O.sub.2 sensor is disposed either upstream or_downstream of_the catalyst converter.
In_a single O.sub.2 sensor system having an O.sub.2 sensor upstream_of the catalyst converter, the O.sub.2 sensor_is disposed in the exhaust gas passage near to a combustion_chamber, i.e., near