Rack & Pinion Steering Systems

8/3/2019 Rack & Pinion Steering Systems

1/19

FOREWORDTh ' 'Ir' , , o f - ' 'th k . " .. I I......... -' ,I 'd -' " ", -I'th_ I e 1 P l ! _pose __":> manu;u ID IV prO\! ' " ,e } f O W l 'iN IIn form ation on th e rack-and-plnlon steer i ingsystems used on certain Chevro le t passengeriI;a!'S. Inclucred ,I s a n e xp ra na tio n , o f the ,operat lon l

'T AB 'LE O ,F CONTENTSINTRODUCTION , . "_' __ ._._" _._"'. :2OPERATION' , , , , .... , , ... " , "... , , ... ,',. 2GENERAL _ , .. ,. __._, ,'_,_'" __._" 2

M AN UA L RA C IK AN D PI N ION " ... ," " ... " : 2End Take~Off S-ystam .. , ,.. .. ,.. _ 3,Center Tak~'-Qff System ... " , " , , " : 5POVV ER RA CK A~ 'D PI N ION . ," , " ," 6Power Ftack'-and~PiiFllion'Components. __, , __.. , , .... , , ... " , '" 7Powe r A6a i8t Vslving Opera tion .. , , " 11Po lNer S t .ee ri ing P ump .. .. , .. ,... 1,2

DtA'GNOSIS _" '" " , " '" " ,' '" 19GENERA1. ." ,'" ,", ,", " ," 19MANUAL RACK.AND PINION _.. __,., 19Exoo!S8lve Play or l.eosenese inSteering By,stem " .. ,... , ,.. .. . , 9Rattle or C ,h uck iln IRack and P in ion , ... , 1 9P()W ER STEER IrN lG R AC K AN DP1NION AND PUMP .., .. , __,_ .. _ 20Hissing Ndsa in .F1ack ,and P ln 'roo " , , , 20R attle or ChllJckle Noise in Rack.and !?inion __.. .. , ., , . ..,_,_ 20P oo r R e tu rn of S t ee rl1 ng W hee lto Cenlter .... , " ... " , .... , , .. _.. " , , . __ 2 0E){C1: ! iSSivS Whee l KIc< i< tJad


2/19

Ste;e!l1ng a oar Seems Iike a very ~imple th iog todo If you are the driver. All you do IS tum t h > esteering wt1ee~in the direction that you want to~o an d t h e : car goBS that way. But as ' Y _ O ' U know.lt's not qUite that s lmp le . In order for the oar' totum when the steering whee,1is turned, there area numoor of Com p on en ts h rrv ol'Y ed belwee n thesteer ing whee,1and th e w hlee.ls. AI~these com-ponents m ake up the steeri ng sy.s. tem.lhere is more than one type of :st~e.n'ng systemavai' lab le, on C8.r.5 today. The on-e that yo u areprobably most familiar with lis the integral steering~m _ The other system that is be. com1lng rno repopular, ~ooia.l~y on front~wh~el drive cam, is,'fhe rack-and-pinion s'le.~rlng, system,

A rack -and-pi nion st.eering system, e:speci; i~:l i ty thelinKagel is simIPle"r than an intEl9ral steeringS , y : 6 1 e m . U is also ligl'!t9r In wag h~ which r ; s . a nimportant taotor lin todayls IUorts to make lightercars, Chevrolet now has five car Ii r i l e s , Citation,Cef.ebrity, Cavalier, CheveUe, and CQ rv ette ." th atare equ ipped! with ra.ak.~a.nd-p:il'!,iolF1teering,SySt-ems. Three are t rent -wh !e !J d r ive and tw oere l'eap'wheei dl ' iVa.li n th is m a n ua l, 'We C Q \ I ! S I r the operation of thareck-and-pi l '1Iionstooring system used onCheVirol'et passenger cars. In add lUoo , you will alsoflndl in this manual! diagnoais of the steering'system and some servioE!' information to hefp youprovide better Servi08' on 'ona of thesesteering systems.

____________ O PERA T IO NGENERALThe steerl ng wheel is the. fl rs t in l ine yn the s81nies.o f components be,tween the driver and the. ca rwheels. 'The steeri ng whe~1 is connected to aat ,eer i l l1g 'colum n, whloh Is OOJi !nec: ted to an inter-medilate steenng .shatt The sresriog shaft Iseonneeteo by a steering coupling to thesteering gear. .When the steering wheel Is turned. the rotationis transm iUed dow.n througlh the. steeri ng collumnand irtt~m1ediatt!, Bteering shaH to the ~teering~-ear. 'The fu nctlen of 'the s-tee'ring gear rs to con-'vert the ro'tary motion, it has received frorn th e,s te erin g wh ee l into. the lF8qui'red la t ,eml mot ion tothe wheels to tum thi ear in the di Faction de-S!.ired ,b y the drr 'Y"er.After a tum is completed', ali ,gni ng forces betwoonthe tirl3$ and the, r : o a d tend to hel p' re alig 'n th ev-ehlcle baok to a straight-ahead position.On the' rack"~andipinionsteering system , th erack etind'the rPin:ion ars the two components thatconvert the rotarv motion of the steerinq wheal'into the. late ra l mo tio n rreqlllir,edfor tum,1ngrthe wheels,

Bath manual and power-asslst raok-and-pl nion,steering ,systems are available 01 1 Chev.Fol~tpassenqer ca rs, B oth types halt@the serne basicmechan ism and work the same way..

MA'NUAL RACK AND PINIONA very siimlPle' ste an ng g ea r', usi ng a singleme-chan ism. is provid:ad in th is ~.tetrl., The steer-ing allaft ends it:'ia hallcaJl gear ,oaliiedthe ,pin ion.,M shown in simplif ied form in figl,l re 1, the pin ion,connected through the steering eolu mn andsteeriing shaft, rotates dl,reetly ' with the stear-if1lgwheel.

FIQ.1 Steen ng Gear Pinion


3/19

OPERATION_ ---3The rP~nionis supported in the ,ra,ck-ai1d-pi n ionIhousing by a 1 00 0a rbe aring th at is press-ed intoth e h ou sin g" It is , also supported by an upperbearing' assembly that I s pos l t k>noo I-engthWloo,o n th e p ~n .io !'1 l.T he upper bearing assembly ish e kjl o n the p in ion Iby' a retajina;r that. is sta ke d tn to8.g rom '' !? on th e pin ion. The uppe r b e slJ lin \gas-sembly sl ides into the housing ' lNith the pi nlonO nce th e pinion is positioned inlhe h o us l'n ~, I~ I sheld firm I~tin pl'aca by a beveled retain ing ningwhich m e into a groOV8' in the housl ng. Ther'l Is ,also a rubber i~p&ea;1V llh l'c h p re& .OOs in to th eh ous ing and seals between th e housing and thepin io n , ( f ig . 2 } .

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fig. 2 Steenng Gear AsOOimblyTh:e'rack i s : a long round bar which has a numberof ,gear teeth in a' strai'ght I~ ne" lh 9 'ge ar teeth enthe f ow ,e lr pa rt , o f the pin io n mesh with the geaJ[teeth On the, rack Therefore, as th e pi nion rotates,th e' m es h iog of : th a gear teeth causes the rackto move back and forth :sideways. {fig. 3),.Thus, therotary motion of the steeri ngl 'W h e al Is,convertedby' th e stoonrlg gear Into the ~a. teral movementof the rack.

Fig,.a Rack"a.nd-Pinion Movement

The , movement of the rack 1$t ransmi t ted by t he - trods to ' th e st 'Ger lng a rm s a nd w ile er:s. There aiftw o different ways that th a He rod s connect to thrack on .C;havrolet c ars" O n a is c e . : I I e d th e endta lk e -o ff s yS tem and t he , other is the center takeoff system,,End Tak'eOff SysteimThe end take,-otf ~ck-and-pinion syStem isused by Chevro le t on Citation, Cel'ebrity, Chevet t 'and Corvette '- .Basic:aI ' ly! the end tat.;a~oU ra ck , a ss emb:ly ' is comprised of th~ fo llow l ng m al n components, A racbush ing fa pressed 'into the h~usinQ~and is heldln place bya retajilli.r1lg r ing_ The ;steer ing rack the,s l id:es baek and forth throug h i the bushing ~ t i g _ 4

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R A C K .. ... . . __, .. . . -- .... :.. . ,

".. . .... . . . - , ~ - Jfig. 4 Rac~ Bushing a nd H ou singA raCik bearingl elides into the hO~isl"9a nd ~~re ot lSU lPpo rt s. t hB ' ste;enng raek A s ph ln g 1 9 p oS lb orn edbE: tweal 'l l t he boorl ,ng ,aJ rl dan a .d jlJ . i:S t~ , r: 1 1 l , J : g , h l o ht hll' 9S ids , Into the hiousing. The adjust,a,r plug issecured in position by a IocklnlUt ( f tg, 5).

VIEWM ~_ HOUS I NG. - EIIEAFUNG

~ ' N GADJuSTER... ua ~J\, L .O C K I N U T

HOUS!NG'Fig, 5 Rack ,Bearing" Spr1 lng a nd A d ju ste r Plug


4/19

The Inner ' t l\e rod a .s .seren ib lies are thr::eadEid and:s ta ke d to the steenirng rack . , A s hoCk , ,~m "p e'n eralso ,snaps over each Inner tie rod. The damp -e ne r ,m in im i%e$ no is e at the end of ra ck tra ve land also stops t h . E I ra ck tra ve l. Boots. are securedto tha housing with clam1ps. On some models,th e boots. are a lso secured to tha inlller t ie rod swith ~arnP9. On other models, th~ boots rr t t i ' g h 1 J l yo ve r th e inner tie rods wlthou~' requir ing l dam P$.

An outer tie rod a,se.embly threads O'V~reach frnnertie rod and ls held in place with a ~ookn:IJt (f,lg. 5).F"gure 7 is an exploded V 1 i E r W of a 'M l lca ! en dt ake-o t f rack-and~pl rJlOIiI steer i lng Maembly . Thera~k housing may be !S~ightlydifferent iin somem od els fro m what is sho.wn h ere , d epend lng onthe mqdel and year ' lJ9hicle you a re 8e rv ic~ng .

'RACKt___' .. . - - - . _ - - . . . . ,"~J\

~F i' g. 6 j;le iRod Assembl1ie.s- E 'x plo de d V ie w

1 . H I ;J o .LQ i Il iE i. Ra c k , & Pii'liGI'I~ , B siH II1 !iJ A ~'_ " F h:..:lillt l"3.FI~II'I.0i'IIA~'_ . lBN!1ns &4. Fill1g. ~!'1~IliS6 .. S.Ii!I; ~llI1g PIIl'iKII!i$., Ai:lm~e,. SMi~7_ I ! II 1 !1 ~ r il 1 ll il , ~EI,iSl ' l r .Jns.Mjl ; l iE!t9riii. Plug, Adjuoat l ! l r10\. t,lIL:lt; Adji.il!jll~:'1 PluglLook11".~ 1 r i 1 J , Shock, Dampenerl:it. F lDd AE i ~ . , 11lIi'lM'T~13_ Clf l i' I fI [ ; :I ' . Eliflltn1 ~ _ ! l i l ; l l ; l t ; F t I ! ~ . . . " P l i n i ' o nj~. N~, Heoc" J i llm16. Rod AMy., Oi:J ihH Tie17. FiMiiiCil, L U ~ 1 i 1

1I ! I . 8.ITliIl!l FtW'1t. N !.It H~ L.o~k. 10 . i 5 I1B11 'l f' I ~ , IiIIKt:.21 . Rii'l!il, Bi; l i I i ;hi l ! igFI.b!ln!!1!g22,. Flm~k, St&9rlll!lll

Fig.,7 End Take~Olf Rack '- and -P~n i on Steer ing ' A ssem bly - Ex ;pkJded View


5/19

The center t ake-o f system tunetions in a si milarm anner to the e nd ta ke ~c lf s.~ te :m but . is.de-signed 8. b it d lf fe re_n tt y. c ava l ier IS the OIl. IyC nevrolet m od el with a OSIn le r t ak e -- of f s yS tem ,Show! " ! in fi:gura 8 is the ra ck . a nd h o us in g to r th eOOn1'e1f teke~of ' f aye.tem. Th , is s y st em ; also haseIbush~ng pressed i.'I1Itoitle housingl thmug h whichth ~ rack c:a n $~ Id a, A rack bea rIn g, sp rin .g and& d~ uiS te rp lu g a re p os ltlo ne d in th is system thesame 'Way as for the end take-off: sYStem. Noticethe front of the housing, It ils not se Ud lik e the oneused fo r end take-.oHr b ut ra th e r has an open slot

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Is secu red t o . each end , o f th e h ou sin g winhclamps ( "ig . 9 ).

'F i g. 8 Center rake-Off Rad k en d H ous l ngWhen the rack is pogi1!ionedlin the housinq, a rackguide. is positiol'l~d 'In th e fron t ope.n l'ng of 'th ehousing. A boo t cove rs m ost of the Ih o u si in g, in ~cl udiillg 1the op8n.ingl and the rack guide. The boot

! " IO IJ ISING

Fi 'g_ 9 Rac k G uid e and Housing Boo tT he inner tie rod ! assemblies are connected to thrack at a,ppro}(imat.errv ' the o o n t e w ' of th e hOUSi!'i!gW h ere th e o pe n.in g 'is locate d. T he bolts connect-ingthE! i.rnnertie reds pa.s.;s through and: alsoconnect the rank g' lJ lde to the rack, The outer troo essem b li :e s c onnec t to th e inner tie rods hya bo!t, or stud, that t h reads unto both the inneran d ou ter tie. rod . This is a lso an ,ad j'lJstling boD :thais used tor toe adjustment during a front-enda l ignment {flg- 110) - ,.E xc ep t fo r th e differences in a om e of th e ir components, the center tak.&-OUand end fake-oftsystems ,functlon ' t h e . s ,a m s , . Figure, 1! i~. an - e ' ~ -ploded View of th e entirecenter ta lke of f rackand -pin ion steering assembly,

F: ig . 1 . 0 R ack and T ie Rodl Assemblies


6/19

6 0PERATION

3!}. FMlt'I!ijI. Lubricirticllo31_,&81, Till!! FtQd$ ; : ; : . 1 I ! ! . I t , i - I ' m c SIo~ecl- 3 : ; ; . F - ' i M, r C ' O t t & r,34. BU91l1llg, Fhill:1i:3 5 . F tl i' l5 ). I ri h~ !I 1I '1 Z1 IFhil i i1! lnlng:Mi. BuJill1!l9, e Q l O ' l ; R~lIill1"lng!~. Grommet, Mo:unllng ~FlH)3 6 . R i Bc k " S lh !I I!l I' Ii r. g39, COiii!lt. Houirn!iJ End40. Chimp. ~~41 . 1e,,,,8l1~l"ig,,Boot Retaining42:. Boot" Fli!I !=:1i:& : Piniell4;3. Clamp . 1 3 ! l J o C 1 t :

~~" , ao, , '

-(; '""!

~ '~r31)@ti .;e - - - ~

1,5.GrcmlMM, Mounllng ( I , J - I I )11fLCent'. Hj)iu.,ing EnQ1 1'f.G ! ,I jd . . R41ck '1 - : 1 ; . , G!.Ik:le. ~r,ll!'l!ill19. ~!!Il'I i!I~. C!!iiflhir Hi;g C l I ; I f I ' l i I r:20. [RDd. 11lI1I!ir' TII ! iI ~W}2.1. iBiutl!l! '!g, ~nn(lf PlVf!I'2 : 2 : , I F i Q d " Inl ier T Ie . ~ Fl Hl23 . ! Ph ! il 'e , 1 6011SU ,l ). p oi 't:24. PIl!lli!I, l U J o i : i k:26. BDIt. 'jl'llN!lr T ! i ! i I R od2$


7/19

OPERATION 7Basi icall~, povi."!rsteeriing is accomplished byadding a prston 'to th e rack , a n d ' sealilllg I~vvi th inth hOlJl6' in.g.This, in effect , ereates a h y d ra u li ecylinder; When oil ls sent under pres:sulf'e from a'P um p a nd throl,Jlgh a valve to one end of the hy.-drauHc c yU nd er, it exerts a force th at. tend s to pushth e ra ck . in one d:irection_ mrec~iillgl th e (IIi! to thetrimer end of th ~ hy d rau,l~Gynndief pushes theraek in the oth er d l rection ( f ig. " 1 2} .

'FUUP

P FtE :S SU F U 5 ,O I L 1R~I , j IRNO!!" ,

Power Rack"and-PinionCo,mponentsBooth th e end l8ik :e-otf and ! center take-oft mck. ,8l1 id" lp in i ion steering systems are' availabl'e wipower assist, E> l:c ap t f or some , d IJ fe r~ '!'i !C !9 ncom conente , both ,system s are ve ry 5imii lar andfu nctlon in a simil!ar manner, For the ,o;perationexplanation p:ro.vildad ,In t h Is m anual, th e endtak.e~off'system i s c ove red .FigUre 13, Is an exploded view of a typical ,pr.wrack -anc ~ f:linion , steerl ng ~e '!ib ly w ith ,e :nd .take-off. !I f you compare this with figure 7" whichis th e menual ~ck and p in ion wltlh end ta iKe-myou can see the difference between the twos,ystems" A s . y ou 'J I n fJ tlc e. , 'th e p ll1mary differenoe:I s lin th e ~ousing, rack and steering ' gear (p in, iobecause of the addit::ional components 'for thepO'INer assist.N,OTE:' The housi ng shown in tigu re. 1: 3 may dif'fSfrom one 'y ou :a re servlol ng, depending on modeand year o f v eh ic le .

HY DFU i& JU C P ISiI"O NCYi.IINDE:FI:Fig. 1 2 RocK wirth Power A s s l : . s , t

F ig., 1 3 P ow er R ack -a nt:l ~ Pijn io n S te elin g A ssemb ly ' (End Ta ke ,..Q ;ff} - Explod:ed V1iew


8/19

8 , OPERATIONIn orde r fo r th e pow er s tee ring to wor ,k , a hydm l. i1 1 iccy1 lnder is created ~n the raCk- -and~p~n ion ' hous-I ng . I f t h e hO l. lls l, ng is a o ne -p ie ce d esig n; a eyl i .noortube Is preMed into the, h O U S i n g and is no1 'Y 1 l S i i b l efrom th e outside o f th e housi ng (f Ig. ' 14) .

F IQ .14 H ousl ng and CjI1 i ;nder Tube(One ,~PreC8 Hous ing )Il f th e hou~ng Is a tw o~ pie ce dOO :lg n, t h e tu be :I sno l necessa ry s ince one part o f th e h ousing ante :as a ,cylinder. 'A prstoo is attached t o . the s te erl n g rack andsJr~e$ Ib ae k a nd forth in the cyl ' inder. A tetron r1inga cts a s a se al ibe tw ,e en ~h e p isto n and the c-yt lnder. ,A I 'ip s i3 al, caned! th e inne r rack sea!, i ~ ,pressedin to th e h O O B in g ' t o act as a seal be"lw een thehotl:! i l ing and th e s te er, in g rackAn inner bu'khead tits in to th e hous ing and lslo ca t.e d a t the end of t h e , c y l~nde r. Ano.u ter bulk~head Hts into Uta houSing outooalrd i[lf the . innerbu lkhead . The outer buUd'1ead has a lip sea lpressed in to ~ wh lot i- provides a ssa l between th eouter bulkhead and the rack (figl. l'5). In add it io n ,a mbber -a-r ing acts as a seal l betvveen th e QUt' i3' iFbu lkhead and the hous ing . A U th ese p arts a re h e.I'd,i~ place ln th e ~ousing by a re ta in ing ring w h ichfits, In to a h o .u smg g rc >O \lle (fig'_ ~ 6 )-OUTeR aU L.I


9/19

OPERAT' ION ~9

Fig . 1 8 C yI~n der lines and Tie F tod Ass .emb j i: es

Fl ig . .11:9Cylinder L ines and T ie R od Assemblies -Exp loded V i e " i N 'T h e re i's o ne o ompoiflem in this area t ha t is notprovid ed on th e manual rack and pin Ion. A breathertube r . . s connec ted l to Ulle tvvo boo t seals lor thein ne r t ie , md'S (fig. .20 ) . This breather t J l J O e is ; veryimportant. aince it transfers a ir belv ioo


10/19

10'------------OPERATIONThe top end o ,f the pinim is attached to a.vajve.a ss emb ly " T h e v alv e body' ro ta te s w ith in th e h ous-ingbore. Then;! a re a nn u lar g l"OO\ i's on t he- outs ideof th e v alv e body whlCh connec t with o il h o Je a in Ith e ihQusi ng, The p utrp os e. of th e se h o le s is forsupp.lyin9 o il from lhle pump and directi'ng it to!91~herend o f th e steer ing eyli n de r b ore , TeftonIir i lga,provide a seal be' lw~n the vatve bod andthe housi~_ T here a re a lso h o le s th ro ug h t t l & -wall of th e valve body whioh con nect th e :O 'utaide.g moves with this long itud l na l B iota on th e insidesurtace. Th'etsa f.nne:r surface slots form Qne-ihallfof th e 'IIa Mn g inf .eri .a.c;:e {where th e o t r va lv ing isdone , (fig, 2~).

iFig..2,3 Valve BodlyA tor slo n D a F ii s pressed and s taked in to th e t op ,end o f the' piniort, !heire lis also a pin in th! head oft he ' p l' ni on w hich fits intn.a.hole in 'the valva body .Th is then ~,together t he . va lve body. , tne IowB.F, snoot the to~r .s .' lonbar an d th e pinion, aI IO'wl.~t hem t o . rotate as,though they 'were one oolldcom ponen t (U g_24) -

F,igL24 V alve ' Body., Torsion B ar and Pinion

The S(Poolsha f t ( ,I f! IP u t : S !h a . f t ) of the gear assemblyis at tached 1'.0the I!J pper end o f the to rs io n ba rw ith a p i n {f ig . 25). This. allows th e s ce ol shaft andthe u pp er a nd ! . o f the. tors ion bar to rotate togethera s th ou Q h they ' JNereone solid compollant

II] ~ I Iis

~;~fig. 25 Spoo f Slhatt and Tcrslon BarLo.ng1l tud inal slots are curl into the outsi'dediamete.rof th e spool shaft and interact with the , Iongi-tudinal sto ts on th e IMide surface of the valvebodry. Thls rinteraction folTTlS the other lhallf o t t h e .valv;ing int'armeS',-Holes that go through the s p O O i l shaft wan al lowthe o il to n o w back to the : :pum p. T he re a re sena -t ioos I:n th ,a bottom of the spoom shaft which allowth e spo ol sh att to . fit 1~1y into se rra tio ns In fh atop,of the pinion (fig. . 26) . Ther 'a -Is a c erta ln am ou ntof ro tanonal moveme nt a vaiilab le lin the serra- .t lOM of the spoo.l shaft and' pinion. Thi's mtivernootIS called valve t ravel .

Fig.:26 Spool Shaft VaMI'I9 Intertace Slots andPinion Conlnection SerrationsThese then a.r;a the. eomeonents of th e p ow .-e rr::ack"ano-pl 'nion sy.stem" HOw th es e o omp on ;G i ntswork together to provide the dttver - with power.,assist is e.xp!ained In th e next section.


11/19

OPERATION '1 1Power Assist ValvingOperationThe am ount o f hyd r.au l ie a.ss~t th at [!s provMed ~n,a power stee rl ng system is,directly related to , andcontrolled by~h e, driver, This is because as thedr iver turns 'the s.tooriing w~eer, h e controls theop em tfrO n of t :he s tee r ir ig gear valve, T he vah.! ', intu rn , is a very innportant component. in control-:Iing the hyd r .~u ,J IUCssoonse to th e driver's fiulI'11lngof the steering wheel. The actual operatlon ofthe wive is as fol loW'S.In the previous s e c t l ' O r 1 l , n t ' was shewn th at th espool shaft and uppar and o f the torsion barmlate as one part. lhe. valve body, p i n l on and[ower end of the torsion bar act as another solidipart, One part is thl;l 'n o.o:ns idered th e ae tlo n side-and the othe r part is oons ldered the reeletance:side, The torsion ba r, 'iN h ich is a rntatina I spri ngjis 'the con nectlon between t h e e ' tw o parts (fig,~ln

T O RS IO :N B AR// 0 0Fig. 27 Stee\p lng Gear ,Assembly- Action andReslstanoo S id les .Wh~n the dr iver tumlS th e steeting wheel, th eact ion side o f th e , st ee ri ng gear " whiich ie : th e s:poolshaft and upper end ' o f _ the torsion bar! rotateswit"h t he - steering wheet The 'r es is tance' s id a ,wh ioh is t h ; e ' val'\l'e body, pln lon, and lewer end ofthe torni:on bar, does. not move at first but doessense fihe rlsista:l'iIceto turning at th e ti'res. Sh~oothe' va IV - G ' body is no t rotating, -valvlng begins totake pla ce an d a n is sent under pressu re to the:appropriate and of the rack c,y!lnder ,

I

M th e SIi'!erllng lwhee l ! and speol shaft oonUnue trotate Ithe o'il pressure i nereases and th e hydraulie toree actl rig on the steer i1ng ra'Ckpiston is large n r u g 1 h to o ' i / : f 'C io m e ' the t u rnl ing , r e S I s . t . E U " ! OE ; ! ' a tt hE ! till"SS. Wh~n th is happens" the piston, F&~ tiro ds ,an d tlre s start to mO'lJH,If th e dr iver cootlnues rotatl rng th e ,M eer,11l9 wheelt he - , spoo l shaft wil,l rotat' i;:l 'wjlhin the valve body'on ly as much as I s re qu 'llra d t o overcome th e :turning resistance at the tires. T he spbQ li shan withern maimai'n tha.t position relative to the va I\i ',body , evan though both parts, actlon and resis-tance; of the s,teenng gear a!SBemb:ly. are , rm atl nwithi'n the gEtar I~Qusing.When the driver releaf!!S the :s.toolring whe~l, thetorsion bar unwinds and returns the sp oo l sh ato a cemral posiltiol1 'iNilhin the valve body. If theca r is m o.vin g, th e a ,ligning torces from th e t i resh c E l l p both the action and reslstance sldes q .f thestearlng g~ar assambl~ to rotate to the straight-a h ea d p os it io n.IFlgura 28. is ;a cutaway view O o f a valve assemblys hO 'N l!n g th e s pC>O lshaft a nd va lva body. When thvalve is i'na centered position, oiil from th e pum pflO\iVSiinto t h e . vatve ~hl1 'OUgh fou r : sup'p ly ho lie sth e v alv e o o d y . Thl' :s va , I ' ( i ' e is an open cen ter va lvemean ing fhat the oll is freely' ported to both Bideof t h e eylinder an d to t h ; e n;lt lU rn flow baok 'to' "the pump.

Iil'FlEss.uF[~RETURN

VIEW"- "


12/19

1 2 ' _ , OPERATI 'ONr

When a car is tu med right, the.-steer ing wheeJ and,spool shaft rotate clockwl~, restricting oil f,lowto th e lef t cyi i ,nder ! )Ort . on that is h om the pumiPand unde r iPreMuwe i s d i re t: 'tad to th e r ight c.y~indlrport and to the outer sid'e of the cyli ndsr, AlSo,8.6 the stee,ring ra Cik m oves, Q il at the Ermer side ofthe CjI1i nd er Is push ed out th ro.l!. lghth e retu F n Ipor t ing :and back to the pu~p (fi'g. 29,)..For a . carturn ing feftl jus.t the reverse happens. (ffg_ 30').

,mE55I:.1FCE:~~;-F lU U F IIN

~.AI:OHTTlIRN

Fig. 29 Oil Row During a Right Turn

~E'SSURE. ; . ~RETURN !

L.EFT1UIUtfig. 30 Oil Flow Dur. ing a Left Turn

Power Steering PumpTypes 0 - 1 P u mops~ 1 1 1 the section' on valving, we covered the f low ofhyd ra . u l l o ~ij that is neede .d to move the rack fo .r aright or leU tu rn IH 'owever, the hyd rau lic aU willno t m ove by rrta.elf, it must be p y m : p o o . In thP ssec tion , w e wi I I cove r th e pum p w hich is the corn-ponem that cal!. lSElSth e o i l' f ll ow thF"Q l .Jg lhoutthesteering sy,stem. .Depending on the model of car, C heyro let use:stwo different types ,o f PU!TIps.. One is a sub-merged type- and the. other is a nQnsu lbm-ergedtype. T i lla s u lbme rged "tiypa' means that the r e -servoir for conta in in .g th e 0 . 1 1 is attached d i rectly 'to the pump, A noosubi 'i J e rged type of pu mD hast h e r :e sa rv olo rs ep ara te " ,rom t h e , p u n n p ' . .This , is a l s ocall'ed a remote type w ith the reaervoir beingattached away from tl"le, pump and con nected to ..ti le pump wltl"l hoaes or tubes.Operation 0 ' PumpExcept 'for ths extemal tubing requ ired for theoperation of a remote pump; th I3 oil flO'lNfrom the,re se rvo ir a nd thlroug,h the pl;Jmp is s lm i le r forboth types, Figure 31 sl"low.s a remote pu miD illlthe p ow er ste eri,n g sy :s tem_ Th@ o.Ureservoir ismoun ted a .way fro m th e IPu 'mp , u su ally a t the bulk~head. Oil flow [\S from the remote reservoir th roug iiian In take h ose to the belt-drtvsn power steeri ln'glpump which is rnou r n~edon t he engi ne, Oil ' fkYI,iy.ingfrom th e pu m lP Is dehlvemd thmlllgh a pressurehose to the. steering. gear. This. is an open centertype of st' i3@ ri:ng:system which meansthat' l iVhenaver th e eng in e is ru nniilllgl, the pump Ispurn p ing and oF Ifl'aws to and througl"l tne 'valve inthe- st.earing Q ~ ar a nd back. to the reservoir vnacont inuous man n e r o 'When the st.eel ing wheel ' is .tu rn ed , th e oil fkiw throug h the s.ys~em Is restrlctedcreati ng h yd ra ullo P f !s au re that acts on one- endof the oyflnd er in the steering gear to h yd ra u~Uosl ly assist. the driver in p erform In g th e d esiredsteen rng man-euver. 'One! th e steering rnaneuver ;~$com pleted, th e o i I agavn flo w s th ro ug h th e:s ys tem , !3 J tnormal back pressure . -


13/19

O PERAT IO N _RESERVOIR

INTAiu~:HOSE

"

~---------.- _JF Ig .3 1 P ow er Steering' S yStem w l1h R em oteRes !SNo l r' T o .h~1P you better tmde~a ,t 1 !d 1 how the powerSieer.lllg syStern works" we willi cover in th is sectionexactly h O ' ! N the pump worl


14/19

T he p u !rip 's in ta kes are fed l from tih a pump reser-voir. Thi \S is,cal led th e lo vv p re ss ure side of thepUlmp, The o i~that is discharg'ed from the pumpf lOwS to th e steeiri"ng gear '~'Odo Ua.efLd work. Th islis caMl 'edthe h,igh pressure side of : t h a pump .l O IN ' pressu re oi~ exerts very smaU fo:rces in theintake qua( jmrr t of the pump, Howe ve r, 't he highpressure oil ln the diS'Charge ,quad!rant o f th epump ,exerts large terees, Th IS produces a largeu:nbal 'anoed force trying to P\l~h the rotor sfde-ways , which results in noise ' , a n d : mqui res anU IiIU. s u a II:!,. t r > o n & support f(J( the shaft that turnsth ~~ It: ..,'"' e - , lJ~or \n9. -Lt;:I,'

Fi'g,.:35 Unbalanced Force Acti i ilg on R otori . : : ; . , . . . ' .T o avoid th ese problems associa ted 'W i th anIL l rnbalanced ro ta ting teree . the vane pum p. usedby Ch evrd et .h as been d 'e s i'g n ed slight ly dmeren t .The, pum p still has a r :( ) tat ingl ' ro tor with V81')!EI in1ih8 rotor ,s lo ts. bu t 1 he , IMide eontou r ot the pumpring :hM been' changed. It has t w ' O nsilf!9 portionsand tw.o fal!~ng port ions instead of just one each,Th-erefore, there are two intake- ports and twodischarge ports { f i g _ 36}-

I"TAKEPORT

,A s th e ro to r .ro ta tes, each pum ping ca.v i ty intakeso i~ and d i :s cha rge s it twice fo r each revolution o fthe


15/19

-F~g.38 ~reMure G.elher.a1l1nga Force.If a.spr ing Is a d de d to . the l i ight sitE o f the pis lon,then the Sum of' th!' spring force end the hydrslI.J li efon::::e.n th e r ig :h t s ide opposes the h yd rau lic .fo rc a a ctin g on the left side. of the p ls ton. If thehydr :aulk : force on th e left s ide of the ~ton issmal ler th an 'th e. o ombin ed hydraulEc an d :sprlFi!9 i' r o . r o o o ~ l" Ig on the I~ h~s ide ~f ttle _lpi 'sto.n,thePIston WIll move t o . th e left However, if the hy-d ra u lie to m e. o n th e le ft side rs ~a"ller th an th ecombi ned ' foll 'CS's on the ,r ig'ht aide; the piston wi IImo ve . to th e r lght (fig. 39 ) . .

Fig. 39 H yd ra ul ie Force va ~prl'ng Force P IusH y d ra ul, ic F o rc eIf ofl flows th rough a pipe of uni form diameter,then the pressure is unilform throughout th eentire. pipe (flg. 4O-A) . H~Ir, ~fan erltlce, orn o w r .estr ioti 'on, is added to the. center of the pilpewhi le keep ing f low th e same , the orifice providesE ll re sl. st an ce t o the flOW an d th ere is a. h igherpressure . before the o nllce , T h e pressu re aft.erfhe orIffoe I s I 'e s s fh!ID before I t (f ig'. 4o . B )" I f in the

sam e pu pa; . th e oil 'flo w cont lnues to I remai ! '1 !th esame and the ormce is m ade ave .n smaller, th el '9ai!S1:anceto flow beoornea 'even greater. T h ~pressure ahe ' l of the oriffee goes eYein 1 "1 igherand the dl:fferenoe iri ' ~re- betw,een the: i3J~$ahead and after the orifloe becom es la rger(ffg . 4 0 -c ). T h e d lffe -re nc e ~I':I pressure a cross an' Q ( r l f lc e is 'known as the differential pressure.

EVENHJa iHERPReSSURE' IN PFlESSUIFliEF tQ .40 C re at in g 0 11 P re ss ureti t o li l i s pumped throug h a unifo rm pipe a t a certainf.low ra te ' V L i ' i l h o l ! J t an orifice and then the flow Is .i ncreased, t he . re slsta .n ce to f low b.eoom.es. g'reaer and the prsssu re goos up ( f l ! Q . 41 , . .T h i s type. opressure is often caned back pre$Sm'e.


16/19

16 O PERAT IO N

To avoid th ~ situation! it j:g necessary to p ro vid eadequate ro w speed 'flO\lVand avoid high outputf low to the hoses and steer ing gear va-Ivlng_Th 'Gway 'to do th is is 3i process called flow co nti'ol'ling.,O il COmes . from the- fl'uid reservoir and enters th eintake ports in to the p u rn p, The on Is, then dlls-placed from the pu mp and f lO ' tNB up into the. cavityin from of the floYJ control v ah /;e . F rom there it ,g o es , t h ro :u g ii i a flow restriction ca lled th e nowcontrol orif'ic9 and out to the steering gear, From -,-, --, ---. ---_ --- ~Jth e steerln,g gear, it agai n re tu rn s to th e I"e Oe l"V O ir. . y . Fig. ,43 Pump Op!3;rating a t low Speed of';' ~~~..;.!.-./it...... ~~

] 1 As th e s ce e d incr,aa.:ses and m ore and m ore pumpo r& ::h arg e is d ire cte d to the flow qrlntrol otitice,the resistance to floW' i"CreMes. ihis causes thedifference in presSure acro-ss the orifice and valve.to increase and the 'Valve to mO'IJ e further to therig!lt, f inally opening t h e: va lv .e bare to th e eu per-charge oole (fig. 4 4}. T he a m l ; : M , u ' ! t ' of oil flowing toth e s 'w erb 1Q lgear ~8'Vels off V!lith th e re ma in d& r ofthe oil oom i I'lIg from th e pump racircula.f l lngttl rough the supercharge ho:le back , into t l i i . . s ' pUm p~fltakes.T his type of flow diM'sien is ca Jre d flowcontrol. Suff ic ient flow is d&l iv 'eraa to the ,steer,lng'gear to ,aOCOmpUsih the desi ,red steen!ll9 rneneu-ve rB whilB kaeplng : !! rys tem back iP~lJre and~temperat~ re.sunder control by recirculating theSUlP.!~s with In th e ' pump .

Wt !e .n ' t h er e ls oil u n d e r ersssu re in a pipe andther.e is no flow occu r ,r ,l n:g"the pressure Js the sameon all i! lIwmaf. surfaces regardless, of siz e o r sh ap e.IEven if the pipe contahllS an orifice, as llong asthere is no f l - o . w " th e p re ss u r e willi remain un~tormthrOI.lQ hcut the pipe.lLooking again at th e pump; w e ' 1 1 1 se e' h ow t he p ri, n-clples oonCe1rn ing pre ss ,U r& are pu t t o, u s e dur ingp u m p operation. A t ,low speeds, the pu rnp .ispumpi inQ' a vo~um e that can be aasli ly hand led inth e stee'rLng ,system, H,~e '\ . .. if '"at h ig hwa y speeds,the o il f low is so leu]'G that resistenee to fl'ow inthe hoses a,ndisteeri ing gear valvilflg wl il l cause highb ac k p re ss ure . Tih~sresults ~nexcessi ' l l ,ely highoperatJng t e rn pe.ra tures and reducedPU i 'i I 'I , p durabiJny.

Re fe r to figu re 42 snd you Can see that the pres-su re a.head of th e fl'ow control o rlflo o a c1 s en th eta.oe o :f the 'Valve ; I n d that th e preesure alter thaorifice is, portedl around to act on the back o f thevalve., The re i e . also a spMing pushl ng against theback of the v a l V f ! ! _ Ther:e{ote, ,there is . a hydraulicforce on the f t tOO of the valve opPOSing th e sumo :f ['Ower presaure hiydr.aUlI~corce and springforce on the b e l , c k of the valve.

: t - . Ag. 42 flow Control Orifice. . . . . . , r ')

Figure 43 s n O 'W ' S th e- p ump operating at lo wspoods before it begi ns flow contr.pllinQ_Thedtscharge flow thr 'oug!h the. flow contro l orlifice islow enough 00 that the pre.swr ,e and 'fofCe dif-fe re ntia l a cro ss th e va l'lJ e h ,ss on I :t compressed ithe flaw control spr ing a small amount . T he frontface of th e va lve sti II clo se s o ff th e su plS 'rch arg eho fe ,opening into the varve bore and a ll of thedi.scharge 011flowa out th rough th e llO 'W control'orffloo aM to th~ steer ing ,gear.

FLOW CONTROl!.: S PR INGTOSl'l:ER INGGiEAR


17/19

.OPERATION . 1 7S U i P . ~ J l i C H A R G i EHOLE ,

TO ,STEE !R IN i 3G~A'

FLOW C O N T R O LVALVe

FIg . 4.4 Flow Control Operation ~ F ig ., 4 5 F IO 'INCon tr ol Valve Parts..J I I . J l : . _ - r . :. . . . . There is a b en eficia l b y-p ro du ct o f" fI.ow c,ontrol l ! lng I ;; Whe n a d lriv e'r Is .park. ing ,81Car o r d lliv d ng , a t l OW "wh li ch r ela te -s to the pump i n t a l < e . s . Unti l f ! o Y . t ron- speed and he turns tne steer ing whee l '1'0thetrdJ beg ins, 011tmUfl .t be pul led ' Into the pu mpi ng . r ight OF left as fa r as i t w i ll i go, he causes th e va lvecavliUes II ' l l the. intake quadrant. Without flow' in th-s, s te.e rl ng gea r to . be closed off, resu ItIng inctmtrolUngj it becomes ' Ve ry ' d i ff ic iJ I t to putll in . t ct al r es is ta nce 1 ' . 0 flow fro.m the pum p. T his Causes .' la1rge qjlJlQntl.tl.\esof ,O ' il 'when the car ls moving a1' the' pressure o n th e d io oh arge side of the pumph ig lh sPee(H~,'and thiBpu mp Is nmnlng "fast. By re - to rise rap id ly . If this pressure is not re lie ve d, itcirc;ulatili~ 'the su ! 'P lus 0'11flOw and c:lel~ering the can burst the pum p , p ra ssu re hose or .BfeeMingre tedned energy in tha t f t I ( )W to th e in tak e area , th e gear. This, 'I s wh y t h e , pr es slllr ~ rel ief o.rifice Is sointake c arv ~t y b e come s s llg h tlfy pressurized; lm portant iin the syStem: u t ' acts as a eafu ty vailvepush ing th e 011 to fili i the pumpin.g cavities mom by Iimmng the m axim urn pressu r@ in the' powe refficiently as they ,pass ttl ro.ugh the steer,lng sya,telll' l"i il lt a k e quad ran ts .

Figure 45 shows the parts. I ns :id e t he now controlv .a lv e . . A r o u n d bal l h e hek l tig!htly agaiinst the seatIn 1ha . vaJ lve body . by a spring ~nsklethe valV. Thespring pushes the ball to 1he right Hlydraul icpressure beh, lnd the.valve acts on t h . - e ' exposedarea of th e b al:l~try,ing te push the balll off itS seat tothe lef t . U"de..aUoondi t io l i ls other than pressurerel ief, the spr:ing force iis larger than the hydraukIDros on the ball: and the ball I remains. sea ted ,,o oa lln g th e h ole ,in the back of 1h e v~ll iJe,.There. is a smal l ,o . ri fi ice in the ho'le connecting the,d ownstream sid le of the How 00ntrol orlt lce tothe cavity beh ind the valrve. This, is tne p rs ss u rerel ief orl'floe and is , Hili important part o f fhe powe rs te e rin g s ys tem .

T he O pelr:aU on of th e pressure reliief system is asfollows. Imme.d ia t@i iy af ter the stee.r lngl g ea r va lveis dosed off, them Is no f low any.whelfS on ths _d i schar~e . s ide of the pump, S in ce . t h erE ! is nofllow, liiffither the 'flow control unfree nor f h ! 3 - pr@ssure rel ief ornl'oo, is effective at this time. Thepressure is th e Same ,evSlrywhere on , the discha.rge:Sidle of the pUmlp. 11ncl lud i ingthe cavity bshl ndth e wlva and on the ;8XpOSOO surface of th e ballin th e valV.


18/19

18 ,O PERAT IO NT he pump shatt and rotor and v an es c on tin uerntati'ng; trying to pum p m ore h ydMu irc o f! in toth e s ys tam .~ S in c e there li s no place for the oJ I t ogo! the, resistance to th e pUmping l inCflaSea andthe pre:s.wret r , lses.A s th e ~ising pressure a cts onth e e :x po ae dl a re a o f the ball, the hydrau lie forootryi rn g to push t h e . ,be.l i o il its , se at also i ncreases(fig, 46) "

01 L FlE$~Ii


19/19

ION .... 19D'lui rig p re ss ure re lie f" the ban in th e va lve . staySoH th a seat only as long , as I s required to ,keep theva lve in the fuU f low recirculation posit ion. Thi ls iswhat dtctates the. maxi mum pressu re sustaineddur ing pressure re~ief.~f.h ow eve r, th e sp r'in g loadon the ba ll Is greater, this, maxirnu m .a .llowed~u re will aleo be higher .Since du ring p r e s s u r e relief, on:ly a smal l a l l T J i O U I lf ! tof o i I i s r ec ir cu lating insiae the pUl!lIl p, and s~ncethe pump Is ,worki.ng cor l ' t i inuous:1y aga.l 'nsti ' max i -mum p re ss ure , th e ol~ ta m perature ris es 'V e ryqu ic k J " I f' tihe steering whee l is held lin ful'l travel

pcsltlon fo r too long a , timel th e pump can o'verheatand D e d am aged . For th is ' reason , the pumpeh ou ld ne t be ha' id 'in p re ss ure re lie f. fo r m o re thath e ti me re qu iire d fli'-FQ pa.rking O f" steeringmaneuver ..I f you are se.rvlclng a pow er ~er'ing ,systemwhere the pump has been damaged by hea.tlcau tlon th e oustom er m ot to exceed short per iodof time, when. keepl ing the steering wheel In fulltr ,a,vel. ~plaln to ' hiimwhat car'llh appen and whyiii happens.

GENERALThe im -o rm a tlo n' presented in t ln i js sect ion appl iesto the ChevrOle t mooe l' :s 9Qu ipp&d with rack-and-p in I on steer ing systems, Some . of' th e Info.rrnationappli ie .s only t o Che 'i le tt e since it is a rear-wheeldrlv"G model W f fi h rack and pin ion. As you 'gothrough llh i s e e ct lo n , it s ho uld , b e ,o bvio us, t o . youwhich Informatio.n does ,apply only to Chevette.Compla in ts ot ta u Ity s te erin g a re fre qu ;e ntly therssu It 0.1problems o th er th an the steering gear orpum p O ' T hose ar.ws o f the s te erin g B ya tem w h'lchcan be easi Iy ohecked and quick l ,y correctedV!.r tH~outd~mbly and overhau l o f any m ajo rcQm p on en ts sh ou r.d be attempted "f irstMan y fa cto rs CS!f' l affect proper operatlon ofthe steering , s .ys tem. Among the most com rnon are, the followi ng~ lO 'lN ' tire p'res.aurn. . R ad ia l t ire lead.. Front-end al ignment.II' F :lu id le ve l a nd o on cH lio nII' D r 1 f 1 J e H : : l i 6 1 t tension.. L .oo .se component rnounUngs Coupl in g ru bbing on g ea r h o us in g.

J \ J I . N a y s che!k and correct these f ,ac t .p rs , ~mrm ak ing any furt ihar dlagno:sis of th e a te erln gsYStem. Als~ I f " C l I E I i d test t h e car wheneve r IT i spractica l. T he need fu r [proper d ia gno sis ca rl n otbe overemphaa lz ,ed . .After you've di l l .oovere.d th e so urc e o . f th e prob lemdeterm ine the cause. M ake sure . ttl'.Edthere iSnltmora , than one cause' i so that y o u d o nit c orre ctone p ro ble m a nd ;ijt ll~ h a ve anot'her reme i n in g.MANUAL RACK ANID P~N'IONExcessive Play or looseness i:Steering SystemCheck the fo l~owlng: F la c k- a nd -p ln lo n adjustment W h ee l[ baari'ngs incorrecfly ad jus ted or worn ''. Tie rod end looseII' Rack~and~pl nion mounting loose uRattle or Chu,ck in Rackand PinionChock fo r a loose r ac k -Qnd~p in iQn a tt a chmen t .

Rack & Pinion Steering Systems

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Transcript of Rack & Pinion Steering Systems