H thng nhin liu v t ng iu chnh tc C T

H THNG NHIN LIU V T NG IU CHNH TC NG C T TRONG

Ngi dy: TS. KHNG V QUNG

B mn ng c t trong Vin C kh ng lc Trng HBK H Ni---------*****---------

Bi ging:

H thng nhin liu v t ng iu chnh tc C T

1.7. HTNL ca ng c phun xng

1.7.1. u nhc im so vi b CHK

1.7.2. Phn loi

-Sut tiu hao nhin liu nh

-Cng sut lt ca ng c cao hn

- cc ch chuyn tip ca ng c th ng c lm vic tt hn

-Kh thi t c hi

-ng c lm vic tt mi iu kin thi tit v a hnh

Nhc im: Cu to phc tp, gi thnh cao

H thng nhin liu v t ng iu chnh tc C T

1.7.2. Phn loi

-Phn loi theo s vi phun

-Phn loi theo bin php iu khin phun xng

-Phn loi theo cch o lu lng kh np

H thng nhin liu v t ng iu chnh tc C T

H thng nhin liu v t ng iu chnh tc C T

1. Pedal-treval sensor, 2. Motronic ECU, 3. Throttle-valve-angle sensor, 4. Throttle-valve drive, 5. Throttle valve.

Electronic throttle control (ECT) system

H thng nhin liu v t ng iu chnh tc C T

Development of fuel-injection systems

Year System Features

1967 D-Jetronic Analog-technology multi-point injection system Intermittent fuel injection Intake-manifold-controlled

1973 K-Jetronic Mechanical-hydraulic multi-point injection system Continuous fuel injection

1973 L-Jetronic Electronic multi-point injection system (initially analog,

later digital technology) Intermittent fuel injection Air-flow sensing

1981 LH-Jetronic Electronic multi-point injection system Intermittent fuel injection Air-mass sensing

1982 KE-Jetronic K-Jetronic with electronically controlled additional functions

1987 Mono-Jetronic Single-point injection system Intermittent fuel injection Air-flow calculation via throttle-valve angle and engine

speed

H thng nhin liu v t ng iu chnh tc C T

D-Jetronic system schematic

H thng nhin liu v t ng iu chnh tc C T

K-Jetronic system schematic

H thng nhin liu v t ng iu chnh tc C T

L-Jetronic system schematic

H thng nhin liu v t ng iu chnh tc C T

Mono-Jetronic system schematic

H thng nhin liu v t ng iu chnh tc C T

H thng nhin liu phun xng1. H thng nhin liu phun xng gin tip v trc tip

- Khc vi h thng nhin liu dng b ch ho kh- xng c phun vo ng np hay vo xy lanh ho trn vi khng kh to thnh hn hp.- Mt s ng c my bay hoc xe ua trc y tng s dng h thng phun xng trc tip (Gasoline Direct Injection- GDI) vo trong xy lanh cui k nn tng t nh ng c diesel. Nhng do xng l loi nhin liu nh, nht nh nn to p sut phun ln phi gii quyt nhiu vn k thut lin quan nh ch to bm cao p v vi phun vi khe h cc nh, bi trn bm cao p, tch khng kh cha trong nhin liu trc khi vo bm cao p, phi hp iu chnh c nhin liu v khng kh iu chnh ti... V vy, ng c rt phc tp v gi thnh cao nn khng c s dng ph bin trong thc t. Tuy nhin, ng c phun xng trc tip vo xy lanh c mt s u im ca ng c diesel nh h s d lng khng kh ca cc xy lanh rt ng u, h s np ln... Ngoi ra, t s nn c th ln hn so vi trong ng c dng b ch ho kh m khng b kch n. - Hin nay h thng phun xng gin tip vo ng ng np c s dng rt rng ri v sau y chng ta ch kho st h thng ny. n gin, t y tr i chng ta s ch gi vn tt l h thng nhin liu phun xng.

H thng nhin liu v t ng iu chnh tc C T

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2. Phn loi h thng nhin liu phun xng

1: khng kh np, 2: thit b o lu lng khng kh, 3: bm hn hp, 4: xu pp np, 5: vi phun, 6: tn hiu iu khin phun, 7:

b iu khin phun xng, 8: cc tn hiu cm bin vo b x l, 9: xng t bm

chuyn.

V nguyn tc, nhin liu t thng cha qua bm dn n vi phun thng qua tn hiu ca b iu khin s c phun vo ng np.Trong h thng phun a im (Multi - Point) mi xy lanh c mt vi phun b tr ngay trc xu pp np. Cn h thng phun n im(Single - Point) hay cn gi l h thng phun trung tm, ton b ng c ch c mt vi phun ng ng np chung cho tt c cc xy lanh.

H thng phun nhiu im so vi h thng phun trung tm c u im l xng c phun vo xu pp l ni c nhit cao nn iu kin bay hi tt hn v trnh c hin tng ng bm xng trn thnh ng np. Tu theo tnh cht phun ngi ta cn phn bit h thng phun xng lin tc hay gin on. Ngoi ra, theo thit b iu khin c th phn bit h thng phun xng iu khin c kh, in thay hn hp c kh- in t.

H thng nhin liu v t ng iu chnh tc C T

H thng nhin liu v t ng iu chnh tc C T

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1: van l bp bnh, 2: profil iu chnh, 3: i trng, 4: piston, 5: ca thot, 6: vi phun, 7: b hng chnh p, 8: bm, 9: b iu chnh p sut, 10: b d tr p sut, 11: van-r le gim p, 12: van-r le b sung khng kh (by pass), 13: gc l gim chn, 14: bm ga, 15: vt iu chnh khng ti, 16: thng xng, 17: lc xng, 18: xu pp.

3. Mt s h thng nhin liu phun xng thng dng1) K- Jetronic (y l h thng phun xng nhiu im, lin tc v iu

khin bng c kh).

H thng nhin liu v t ng iu chnh tc C T

- Xng c bm 8 to p sut chuyn n b d tr p sut 10, sau khi qua lc tinh n b iu khin thu- c ri c dn n vi phun 6. B d tr p sut gi cho p sut ca h thng cn tn ti sau mt thi gian sau khi dng ng c sau khi ng li trng thi nng c d dng. B iu chnh p sut 9 gi cho p sut ca h thng mt gi tr nht nh trong qu trnh lm vic.

- B iu khin lu lng phun kiu thu- c lm vic theo nguyn tc sau. Trong ng ng np chung ca ng c c b tr c cu van l 1 kiu bp bnh. V tr ca van l ny c xc nh bi trng thi cn bng gia p lc ca dng kh np trn b mt van l 1 v p lc ca nhin liu ln b mt bn trn piston 4. V tr ca piston 4 do c xc nh s quyt nh din tch thng qua ca l thot 5, tc l quyt nh lu lng xng qua vi phun 6. cho lu lng xng ch ph thuc tit din thng qua ca ca thot 5, chnh p trc v sau ca thot c gi khng i nh b iu chnh 7 gm mng n hi v l xo hi v. Cc van tit lu 13 c tc dng gim chn cho h thng. Vi phun kiu van l xo m vi p sut khong 4 bar c th x rt ti xng ngay c vi lu lng rt nh.

H thng nhin liu v t ng iu chnh tc C T

- Trong qu trnh ng c chuyn tip t trng thi ngui khi khi ng n nhit n nh (gi l qu trnh hm nng my), do nhit du bi trn thp nn ma st trong ng c ln. Van 11 khi s hot ng c tc dng lm gim p sut trn piston 4, do van trt m rng thm ca thot 5 lm tng lu lng xng n vi phun. ng thi, van 12 m thng thm ng khng kh. Kt qu l lng hn hp np tng v do tng cng sut ng c thng ma st trong qu trnh chuyn tip. C hai van 11 v 12 u l cc r le nhit kiu bimetall.

- Trn b iu khin thu c c vt 15 c th thay i v tr tng quan gia piston 4 v van l 1 nhm iu chnh ch khng ti.

- Hnh dng profil 2 quyt nh ch lm m ton ti ng c pht ra cng sut cc i.

- Khi khi ng ng c t trng thi ngui, thng qua cng tc in khi ng, trn ng ng np chung ca ng c b tr mt vi phun b tr phun thm xng lm m hn hp trong qu trnh khi ng.

H thng nhin liu v t ng iu chnh tc C T

H thng nhin liu v t ng iu chnh tc C T

2) L- Jetronic (H thng phun xng L- Jetronic l h thng phun xng nhiu im, phun gin on v iu khin bng in t. )

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1: l van lt, 2: b iu khin in t, 3: l cn gim chn, 4: vi phun in t, 5: thng xng, 6: bm , 7: lc, 8: b iu chnh p sut, 9: cng tc, 10: r le nhit- thi gian, 11: vi phun khi ng, 12: cm bin nhit ng c, 13: bm hn hp, 14: r le nhit, 15: ng b sung khng kh.

H thng nhin liu v t ng iu chnh tc C T

- Nguyn tc ca h thng ny l lng khng kh np c o trc tip. Trn ng ng np chung c van lt 1, van c gi bng l xo xon. Tn hiu gc lch ca van lt- t l vi lng khng kh np- c mt vn k (trn hnh v th hin tm quay ca van lt) ghi nhn v truyn n b iu khin 2. L cn 3 c tc dng gim dao ng cho van lt. Xng t thng cha 5 qua bm in 6, lc tinh 7 dn n vi phun 4. Vi phun l mt van in t. B iu chnh p sut 8 gi cho chnh p trc v sau vi phun khng i. Do , lng nhin liu phun ra ch ph thuc vo thi gian m ca vi phun m thi.

- Tt c vi phun ca ng c nhn tn hiu xung t b iu khin v phun ng thi. Tn hiu ny thng ly t mt c cu to xung b tr cng vi b chia in. Do phun ng thi nn gia cc xy lanh c s khc bit v pha lm vic ti thi im phun. iu nh hng n tnh lm vic ng u gia cc xy lanh. gim bt s khc bit ny, qu trnh phun c thc hin hai ln trong mt chu trnh ca ng c.

- khi ng d dng, cng ging nh h thng trnh by trn, vi phun 11- thng qua cng tc khi ng 9 phun thm mt lng xng vo ng ng np chung. R le nhit - thi gian 10 iu khin thi gian ng-m vi phun khi ng 11 theo tn hiu nhit ng c, do iu chnh lng nhin liu phun thm h tr khi ng.

H thng nhin liu v t ng iu chnh tc C T

- Trong qu trnh hm nng my, cng nh h thng trnh by trn, thng qua tn hiu nhit ng c ca cm bin nhit 12, b iu khin 2 s tng thi gian m vi phun 4 tng lng xng phun ra. ng thi, b iu khin 2 cng ch th cho r le nhit 14 m thm ng khng kh 15. Kt qu l tng lng hn hp trong qu trnh qu .

- Trn bm ga 13 b tr mt cng tc. Khi ng c b ko, v d trong trng hp t xung dc, bm ga v tr khng ti nhng tc vng quay ng c lc ln hn tc vng quay khng ti. Tn hiu v m bm ga v tn hiu tc c dn n b iu khin ct hon ton nhin liu. Khi ng c lm vic ch ti ln, bm ga m to, cng chnh nh cng tc ny hn hp s c lm m ng c pht ra cng sut cao.

- Do lng khng kh np c do trc tip nn cht lng hn hp khng ph thuc tnh trng hao mn ca ng c cng nh s sai khc gia cc ng c trong phm vi dung sai khi ch to.

H thng nhin liu v t ng iu chnh tc C T

H thng nhin liu v t ng iu chnh tc C T

3) Mono Jetronic (y l h thng phun n im)

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1: bm, 2: lc, 3: b n p, 4: vi phun in t, 5: nhit in tr o lu lng khng kh, 6: van b sung khng kh (by pass), 7: cm bin gc m bm ga, 8: b iu khin in t, 9: bm ga, 10: tn hiu tc vng quay ng c, 11: tn hiu nhit ng c, 12: cm bin thnh phn hn hp .

H thng nhin liu v t ng iu chnh tc C T

- y l h thng phun n im. Theo phng n ny, xng c phun vo ng np chung cung cp hn hp cho cc xy lanh. V mt nguyn tc c th s dng cc phng php phun lin tc hay phun gin on. Vi phun c b tr ngay trn bm tit lu, ti y vn tc dng khng kh ln nht to iu kin tt cho qu trnh x ti xng v ho trn vi khng kh.

- B iu khin in t 8 nhn tn hiu t cc cm bin khc nhau trn ng c, trong thng s iu khin chnh l lu lng khng kh np qua thit b o 5 kiu nhit - in tr. Cm bin y l mt si dy in tr bng platin c dng in chy qua. Dng khng kh np bao quanh s lm mt si dy v do lm thay i in tr ca n. gi nhit dy dn khng thay i, dng in chy qua dy phi tng ln mt gi tr nht nh. Tn hiu dng in t l vi lu lng khng kh np s phn nh n b iu khin, qua iu khin lng nhin liu phun vi phun 4. Ngoi ra, b iu khin cn nhn cc tn hiu khc nh trnh by trn hnh v thc hin cc chc nng nh lm m khi hm nng my, khi tng tc, khng ti... Ni chung, v mt gi thnh v v mc hon thin cc chc nng, h thng phun trung tm l trng thi trung gian gia h thng dng b ch ho kh v h thng phun nhiu im.

H thng nhin liu v t ng iu chnh tc C T

4) So snh h thng phun xng v h thng dng b ch ho kh

HTNL dng CHK (kiu c kh thng thng) c u im l n gin, gi thnh thp v lm vic chc chn. Tri li, HTNL phun xng c cc u im ni bt sau:

- v cao hn v khng c ch tht nh hng khuych tn gim p sut nh BCHK v khng phi sy nng ng ng np.

- Trong h thng phun nhiu im, h s d lng khng kh gia cc xy lanh ng u hn. ng thi, phn ln lng xng phun ra bay hi trong xy lanh c tc dng gim nhit mi cht do khi thit k c th tng t s nn.

Hai u im ch yu trn dn ti tng tnh hiu qu (pe ln) v tnh kinh t (genh) ca ng c. Ngoi ra tnh kinh t cao cn do nhng nguyn nhn khc nh xng khng ng bm trn ng np khi ng c khi ng v khi ng c b ko nhin liu b ct hon ton.

Khng cn h thng tng tc ring r do b iu khin phn ng tc thi tng lng nhin liu phun ph hp vi lng khng kh np.

H thng nhin liu v t ng iu chnh tc C T

ng c c tnh tch ng cao trong cc iu kin s dng khc nhau d l tnh ti nh trm pht in hay di ng nh trn t, xung my, my bay...

H s d lng khng kh c iu chnh chnh xc nn c th gim c thnh phn c hi trong kh thi, gim nhim mi trng (xem chng X).

V nhng u im quan trng ny, ng c phun xng ngy cng c dng ph bin. Hin nay, hu ht xe hi du lch ca cc hng t ni ting trn th gii u lp ng c phun xng.

H thng nhin liu v t ng iu chnh tc C T

1.7.3. Nguyn tc hot ng ca cc h thng phun xng

H thng nhin liu v t ng iu chnh tc C T

1.7.4. Kt cu, nguyn tc hot ng ca h thng phun xng nhiu im

H thng nhin liu v t ng iu chnh tc C T

1.7.5. c im ca h thng phun xng in t mt im

H thng nhin liu v t ng iu chnh tc C T

1.7.6. c im ca h thng phun xng c kh nhiu im

H thng nhin liu v t ng iu chnh tc C T

1.7.7. iu chnh Lamda

H thng nhin liu v t ng iu chnh tc C T