Nguyn l hot ng ca h thng li (1) Ngi gi: bmnhy Khi bn xoay vnh tay li i, ng nhin chic xe ca bn s chuyn hng theo pha m bn mun. Th nhng quan h nhn qu ca chng nh th no? Chc chn s c nhiu iu th v khi bn tm hiu v nguyn l lm vic ca h thng li trn xe t. Sau y s l mt s kin thc c bn nht v h thng chuyn hng ca xe. Chng ta s cng nghin cu v nguyn l lm vic, mt s h thng chuyn hng c bn v nh hng ca n n tnh kinh t nhin liu ca xe. Chng ta hy cng xem xt ci g lm cho chic xe chuyn hng. Chc chn n khng n gin nh bn ngh!.

Hnh 1: S b tr h thng li trn xe hi

u tin, bn s rt ngc nhin v khi chuyn hng, cc bnh xe trc khng i theo cng mt hng. Ti sao vy? chic xe chuyn hng m du, mi bnh xe cn phi i theo mt ng trn khc nhau. Bi v bnh xe bn trong chuyn ng theo mt vng trn c bn knh nh hn, vic quay vng kh khn hn so vi bnh xe pha ngoi. Nu bn v mt ng thng vung gc vi tng bnh xe, cc ng thng s giao nhau ti tm quay vng. S hnh hc di y cho bit bnh xe bn trong s phi quay nhiu hn bnh xe ngoi.

Hnh 2: S m phng bn knh quay vng

T trc n nay tn ti mt cp c cu li khc nhau. C th tm tt chung nht l c cu bnh rng - thanh rng (Rack-and-pinion) v trc vt bnh vt (recirculating ball). Trc ht chng ta cng xem xt nguyn l ca h thng bnh rng thanh rng. C cu li bnh rng thanh rng xut hin v rt nhanh c s dng ph bin trn cc xe t du lch v xe ti nh, xe SUV. N l mt c cu c kh kh n gin. Mt bnh rng c ni vi mt ng kim loi, mt thanh rng c gn trn mt ng kim loi. Mt thanh ni (tie rod) ni vi hai u mt ca thanh rng. Bnh rng trn c ni vi trc tay li. Khi bn xoay vnh tay li, bnh rng quay lm chuyn ng thanh rng. Thanh ni hai u thanh rng c gn vi mt cnh tay n trn mt trc xoay (hnh 3).

Hnh 3: H thng li vi bnh dn hng trong h thng treo c lp

Cp bnh rng thanh rng lm hai nhim v: - Chuyn i chuyn ng xoay ca vnh tay li thnh chuyn ng thng cn thit lm i hng bnh xe. - N cung cp mt s gim tc, tng lc lm i hng cc bnh xe d dng v chnh xc hn. Trn a s xe hi hin nay ngi ta thng phi xoay vnh tay li ba n bn vng chuyn hng bnh xe t cui cng bn tri sang tn cng bn phi v ngc li. T s truyn ca hp tay li l t s biu th mi quan h ca gc quay vnh tay li vi gc m bnh xe i hng. V d, nu vnh tay li quay cmt vng (360 ) m chic xe i hng 20 , th khi t s li l 360 chia 20 bng 18: 1. Mt t s cao ngha l bn cn phi quay vnh tay li nhiu hn bnh xe i hng theo mt khong cch cho trc. Tuy nhin, mt t s truyn cao s khng hiu qu bng t s truyn thp. Nhn chung, nhng chic t hng nh v th thao c t s ny thp hn so vi cc xe ln hn v cc xe ti hng nng. T s thp hn s to cho tay li phn ng nhanh hn, bn khng cn xoay nhiu vnh tay li khi vo cua gp, v y chnh l mt c im c li cho cc xe ua. Cc t loi nh ny kh nh nn ch cn loi tay li c t s thp, cc loi xe ln thng phi dng loi hp tay li c t s cao hn n gim lc tc ng ca ngi li khi iu khin xe vo cua. Mt s chic xe c hp s vi t s thay i c, vn s dng b bnh rng thanh rng nhng c bc rng phn gia v phn bn ngoi khc nhau (bc rng l s rng trn mt n v di). iu ny lm cho chic xe c phn ng nhanh hn khi bc ti bt u nh li nhng li gim c lc khi cc bnh xe gn v tr hn ch. H thng li bnh rng-thanh rng c tr lc

Hnh 4: S h thng li c tr lc

h thng li ny, thanh rng c thit k hi khc so vi loi thng mt cht. Mt phn ca thanh rng c cha mt xi lanh v mt piston lun v tr gia. Piston c ni vi thanh rng. C hai ng ng dn cht lng hai bn ca piston. Mt dng cht lng (thng l du thu lc) c p sut cao s c bm vo mt u ng ng y piston dch chuyn, h tr thanh rng chuyn dch. Nh vy, khi bn nh li sang bn no th cng c s h tr ca h thng thu lc sang bn . C cu li trc vt-cu-bi-cung rng C cu ny hin ang c s dng trn hu ht cc xe ti v SUV. S lin kt ca cc chi tit trong c cu hi khc vi c cu li kiu bnh rng thanh rng.

Hnh 5: S b tr cc chi tit trong h thng li Bn c th tng tng rng c cu c hai phn. Phn th nht l mt khi kim loi c mt ng ren rng trong . Bn ngoi khi kim loi ny c mt vi rng n khp vi mt vnh rng (c th dch chuyn mt cnh tay n). Vnh tay li c ni vi mt trc c ren (ging nh mt ci cu ln) v n khp vi cc rnh ren trn khi kim loi nh cc vin bi trn (xem hnh). Khi xoay vnh tay li, cu quay theo. ng l khi vn chic cu ny, n phi i su vo trong khi kim loi ng theo nguyn tc ren nhng n b gi li nn khi kim loi phi di chuyn ngc li. iu ny lm cho bnh rng n khp vi khi kim loi ny quay v dn n di chuyn cc cnh tay n lm cc bnh xe chuyn hng.

Hnh 6: C cu li trc vt-cu-bi-cung rng

Nh trn hnh v th hin, chic cu n khp vi khi kim loi nh cc vin bi trn. Cc bi ny c hai tc dng: mt l n gim ma st gia cc chi tit. Th hai, n lm gim r ca c cu. r xut hin khi i chiu tay li, nu khng c cc vin bi, cc rng s ri nhau ra trong chc lt gy nn d ca tay li. H thng tr lc ca c cu li ny cng tng t nh ca c cu li bnh rng thanh rng. Vic h tr cng c thc hin bng cch a dng cht lng p sut cao vo mt pha ca khi kim loi. Nguyn l hot ng ca h thng li (2) Chuyn Relay Nhp mn mch in in t nng cao: Lp LabVIEW online Chuyn vi iu khin AVR

iu khin t ng trong t Anh vn k thut cng ngh t: Thut ng, Ng php Gii thiu v cng ngh X-by-wire VAGAM TP Tham kho - Auto Fundamentals: How and Why of the Design, Construction, and Operation of Automobiles : Applicable to All Makes and Models, by Martin T. Stockel (Author), Chris Johanson (Author) - Wiki - Howstuffworks - Autonet.com.vn