HTNL Dong Co Diesel
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Transcript of HTNL Dong Co Diesel
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http://www.ebook.edu.vn 130
I- CHC NNG, NHIM V, YU CU V S CU TO H THNG
NHIN LIU NG C DIESEL.
1.1.Chc nng:
Lc sch nhin liu ri phun vo bung t theo nhng yu cu ph hp vi
c im cu to v tnh nng ca ng c.
T y , ta thy rng h thng nhin liu c cc chc nng chnh sau:
1.1.1.Chc nng nh lng:
Cung cp nhng lng nhin liu chnh xc ph hp vi ch lm vic ca
ng c , theo cng thc sau :
nlee
ct inZgNg ...60...1000=
Trong :
gct : Tng s nhin liu c phun vo bung t trong thi gian mt chu
trnh (mm3/ct).
Ne: Cng sut c ch ca ng c (Kw).
ge: Sut tiu hao nhin liu ring c ch (g/Kw.h).
Z: H s ph thuc vo s k ca ng c
Z=1 i vi ng c 2 k .
Z=2 i vi ng c 4 k.
n: Tc quay ca ng c (v/p).
i: S xylanh ca ng c.
nl : Khi lng ring ca nhin liu (kg/m3). T cng thc trn ta thy rng lng nhin liu c phung vo bung
tph thuc vo cng sut v tc quay ca ng c
H THNG NHIN LIU NG C DIESEL
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1.1.2. nh thi:
Phun nhin liu vo bung t ng thi im, theo quy lut ph hp vi c
im t chc qu trnh chy.
Thi im to hn hp chy do thi im phun nhin liu quyt nh. Nu
hn hp chy ng lc th qu trnh chy s din ra v kt thc ng lc vi tr s pz
v wtb va phi.
Thng s nh gi thi im to hn hp chy l gc phun sm ( fs). Trong qu trnh s dng ng c fs b thay i do cc nguyn nhn ch yu sau:
Cc chi tit chuyn ng b hao mn (cc khp ni trc i vi bm, cc con ln...)
Cc cam nhin liu b hao mn. c tnh ca cc cp lp ghp chnh xc khc nhau. Cp lp ghp piston xylanh BCA b hao mn. S iu chnh ban u b thay i hoc cn sai st trong cc h thng truyn
ng (con i, ni ghp b lng...).
1
2
3
C 1 3 3 2
1
C T
P
C 1 2C 1 1
ng
s 1-Thi im
phun qu sm.
ng
s 2-Thi im
phun ng lc.
ng
s 3-Thi im
phun qu tr.
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Hnh1.1: nh hng ca thi im phun nhin liu n cht lng ca
qu trnh chy.
Trn Hnh1.1 biu th nh hng ca thi im phun nhin liu n qu trnh
chy. Khi phun nhin liu qu sm, giai on chy tr tng v p sut v nhit
khng kh lc bt u phun thp. Tc tng p sut cng nh p sut chy cc i
do tp trung mt lng nhin liu ln trong bung chy n thi im bc chy v
1 phn ln nhin liu chy gn CT khi th tch cng tc xylanh nh v nng
xy ln (ng 1_Hnh 2.1).
qu trnh chy gin n, tc tng p sut v p sut chy cc i cn tr s nh
(ng 3- hnh1.1).
1.1.3 ui lut phun:
1
p
1 2
12
T
z ' 1e fz 1
z 2 z ' 2
e e 1 e e 2
C fC i
g c t
C f C i e f Hnh1.2: nh hng ca quy lut phun nhin liu n qu trnh chy.
Cu trc cc tia nhin liu v quy lut phun ph hp vi c im cu to v
tnh nng ca ng c.
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H thng nhin liu khng ch cn nhim v a vo bung chy mt lng
nhin liu (gct) thch hp vi ch lm vic m lng nhin liu phi c
phun vo bung chy ng thi im v ng quy lut ph hp vi c im cu
to ca ng c.
Trn hnh 1.2 Biu th quy lut phun nhin liu n qu trnh chy trong iu
kin cc yu t khc gi nguyn. Quy lut phun nhin liu l quy lut bao gm 2 yu
t:
S phn b tc phun v thi im phun. Nu cng mt lng cp nhin
liu chu trnh gct m rt ngn thi gian phun s lm tng tc phun giai on
chy tr dn n lng nhin liu tp trung giai on ny g1 l ln. Chnh v vy
m qu trnh chy ca ng c cn tr s pz v wtb ln, tuy nhin qu trnh chy s
kt thc sm hn (ng 1). Ngc li vi thi im phun ko di dn n qu
trnh chy ca ng c cn tr s pz v wtb nh hn, ng c lm vic m hn. Do
thi im kt thc phun mun hn nn qu trnh chy phi ko di sang ng gin
n (ng 2) lm gim cng sut v hiu sut ca ng c.
1.2. Nhim v:
9D tr nhin liu : m bo cho ng c c th lm viclin tc trong mt thi gian nht nh, khng cn cp thm nhin liu, lc sch nc v tp cht c
hc ln trong nhin liu, gip nhin liu chuyn ng thng thong trong h thng.
9Cung cp nhin liu cho ng c : o lng nhin liu cp cho mi chu trnh ph hp vi ch lm vic ca
ng c
o phun nhin liu vo ng thi im v ng quy lut mong mun o lng nhin liu vo cc xilanh phi ng u 9Cc tia nhin liu vo xilanh ng c phi m bo kt hp tt gia s
lng ,phng hng , hnh dng kch thc ca tia phun vi kch thc v hnh
dng ca bung chy.
1. 3.Yu cu:
H thng nhin liu ng c diesel phi tha mn cc yu cu sau:
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- Hot ng lu bn , c tin cy cao.
- D dng v thun tin trong s dng , bo dng v sa cha.
- D ch to , gi thnh h .
Cc b phn c bn:
9Thng nhin liu: Bao gm thng nhin liu hng ngy v thng nhin liu d tr. Thng nhin liu hng ngy cn cn dung tch bo m cha nhin liu
cho ng c hot ng lin tc trong mt khong thi gian nh trc.
9Bm thp p (bm cung cp): Cn chc nng ht nhin liu t thng cha hng ngy ri y ti BCA. H thng nhin liu cn th khng cn bm thp p nu
thng cha nhin liu hng ngy c t v tr cao hn ng c.
9Lc nhin liu:Trong h thng nhin liu ng c cn cc b phn c ch to vi chnh xc rt cao nh : Cp piston xylanh ca BCA VP, cc b
phn ny rt d b h hng nu trong nhin liu cn tp cht c hc.V th nhin
liu cn phi c lc sch trc khi n BCA.
9ng dn nhin liu: Gm c ng cao p v ng thp p.ng cao p dn nhin liu cn p sut cao t BCA ti vi phun. ng thp p dn nhin liu t thng
cha n bm thp p v dn nhin liu v thng cha.
9Bm cao p(BCA): Cn chc nng sau: Nn nhin liu n p sut cao ri y n vi phun.
o iu chnh lng nhin liu cung cp vo bung t ph hp vi ch lm vic ca ng c (chc nng nh lng).
o nh thi im bt u v kt thc qu trnh phun nhin liu (chc nng nh thi).
o Vi phun nhin liu (VP): C chc nng phun nhin liu cao p vo bung t vi cu trc tia nhin liu ph hp vi phng php t chc qu trnh
chy.
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Hnh1.3: S cu to
h thng nhin liu ng c
Diesel.
a). vi bm cao p cm;
b). vi bm cao n;
1.thng nhin liu;
2. bm thp p;
3. bc nhin liu;
4.bm cao p;
5.ng cao p; 6.vi phun
7.b iu tc;
8.b iu chnh gc
phun sm
9.ng thp p; 10.ng
du hi
II. PHN LOI, CU TO H THNG NHIN LIU NG C
DIESEL:
Bng1.1. Phn loi tng qut h thng phun nhin liu ca ng c Diesel
TIU CH PHN LOI PHN LOI
Phng php phun nhin
liu
H thng phun nhin liu
bng kh nn
H thng phun nhin liu
bng thy lc
Phng php to v duy tr
p sut phun
H thng phun trc tip
H thng phun gin tip
Phng php iu chnh qu
trnh phun
H thng iu chnh kiu c
kh
H thng iu chnh kiu in
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2.1. Theo phng php phun nhin liu.
2.1.1. H thng phun nhin liu bng khng kh nn:
c im ca h thng ny gm mt my nn kh p sut khong 60 atm
chuyn nhin liu vo xylanh.
Nguyn l hot ng: Bm chuyn nhin liu 1 a nhin liu t kt 8 vo
khng gian 2 ca Vi phun. Khi cam 4 y n gnh 5 nht kim 6 ln khi l nhin
liu lp tc c phun vo xi lanh. Khi cam 4 cha quay n phn li kim phun
t
Cch thc t hp cc thnh
t ca h thng
H thng phun c in
H thng phun vi BCA-VP
lin hp
H thng phun vi BCA-VP
phn phi
Loi Vi phun
H thng phun vi Vi phun
h
H thng phun vi Vi phun
kn
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ng kn l phun nh l xo 7.
Hnh1.4: S h
thng phun nhin liu bng
khng kh nn.
1.Bm chuyn nhin
liu;
2.Khng gian phun;
3.My nn kh; 4.Cam;
5.n gnh; 6.Kim
phun;
7.L xo; 8.Kt nhin
liu
u, nhc im :
H thng ny t c s dng v lng nhin liu ph thuc vo p sut kh
nn v s phn p trong xi lanh, nn cn cn mt my nn kh v mt b phn phn
phi kh nn lm cho kt cu ca h thng phc tp, thiu an ton, iu khin kh
khn v phi tiu hao cng sut cho my nn kh t 5 n 10% lm cho cng sut
ng c gim.
2.1.2. H thng phun nhin liu bng thy lc:
Nhin liu c phun vo bung t do s chnh lch p sut ca nhin liu
trong vi phun v p sut kh trong xylanh, di tc dng ca kh ban u trong tia
nhin liu v lc cn ca kh ng ca kh trong bung t, cc tia nhin liu s b
x thnh nhng ht c kch thc ng knh rt nh ha hi nhanh v ha trn
vi khng kh. Cc l phun c b tr v sp t sao cho khi nhin liu c phun
vo cn dng hnh nn to thnh hn hp chy d dng hn.
2.2. Theo phng php to v duy tr p sut phun.
2.2.1. H thng phun nhin liu trc tip:
Nguyn l hot ng:
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Hnh1.5: S h thng phun nhin liu trc tip.
1,3,11,12,14. ng dn du; 2. bu lc th; 4. vt iu chnh;
5. b khp ni; 6.bm nhin liu; 7.ng x du; 8.b iu tc;
9. ng cao p; 10. vi phun; 13.bu lc tinh; 15. BCA Cm;
Nguyn l hot ng:
Nhin liu t kt theo ng ng 1 n bu lc th 2 n bm chuyn nhin
liu 6, t bm chuyn nhin liu n bu lc tinh 13, sau theo ng ng 14 n
bm cao p bm vo ng nhin liu cao p 9 n vi phun 10 phun vo xi lanh di
dng sng m tng thi im v tng thi gian nht nh. Nhin liu tha vi
phun theo ng ng 11 tr v ng 3 v tip tc chuyn n bm nhin liu 6.
u, nhc im:
9So vi h thng phun nhin liu gin tip th h thng ny gn nh, cn th sa cha ring tng bm cao p cho tng xylanh khi ng c ang hot ng.
9S dng d dng, kt cu phc tp nn t tin. Phm vi ng dng :
Hin nay h thng ny c ng dng rng ri v ph bin , ln n 90% .
Ni chung h thng nhin liu trc tip c phn loi nh sau: oC in :Bm cao p: iu chnh lng nhin liu bng piston-xilanh ca
bm cao p.nh thi : bng bin dng cam. Hnh dng tia nhin liu : ph thuc
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vo l phun.
oin t: - Vi phun iu khin in t:
-Bm cao p iu khin bng in t
b. b. HH thngthng iuiu chnhchnh khiukhiu inin tt
c/ Bm phn phi
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2.2.2. H thng phun nhin liu gin tip:
Hnh1.6: S h thng phun nhin liu gin tip.
1. bm chuyn nhin liu; 2. b khng ch p lc; 3. ng du vo;
4. vi phun; 5.tay ga; 6.n gnh; 7.con i; 8. thc iu chnh p lc ;
9. l xo; 11. ng du ra; 12. khoang nhin liu; 13. kt nhin liu
Nguyn l hot ng:
Bm chuyn nhin liu 1 a nhin liu t kt 13 n b khng ch p lc 2.
Nhin liu theo tng ng ng 3 n vi phun 4 ca cc xylanh. Tay ga 5 iu
khin lng nhin liu chung ca tt c cc vi phun. Nu tay ga 5 y v pha bn
tri cng nhiu th kim phun nhc ln cng cao, nhin liu vo cc xylanh cng nhiu
v ngc li.
u, nhc im :
9 u im ca phng php ny l kt cu n gin, trong sut qu trnh phun nhin liu p sut nhin liu khng thay i, khng ph thuc vo tc
ca ng c
9 Nhc im l b truyn ng nhin liu chng mn, d hng hc, kim phun lun c bao bc lp nhin liu cn p lc ln, trnh r r, kim phun phi
tip xc tt. h thng ny c dung trong cc ng c ln.
2.3.Phn loi theo phng php iu chnh lng nhin liu cung cp
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4
3
2
1
1 0
9
5
6
7
8
chu trnh (gct):
a. BCA iu chnh bng cam dc :
1. Piston
2. Xylanh
3. Rng ng cao p
4. ng cao p
5. Van trit hi
6. Van np ;
7. L xo kh hi
8. Con i
9. Cam nhin liu
10. Thn bm
Nguyn l hot ng :
Loi iu chnh bng cam dc(cam di ng dc trc). y cam c hnh
dng na cn.Ta iu chnh lng cung cp nhin liu bng cch iu chnh trc
cam dc,chnh l phn iu chnh phn cam dn n lm thay i hnh trnh piston
bm t lm thay i lng nhin liu n vi phun.Khi trc cam di ng lm
con i piston bm tip xc v lm vic phn cam ln s lm tng hnh trnh piston
do s lm tng lu lng nhin liu phun.Ngc li khi con i piston bm tip
xc v lm vic phn cam nh s lm gim hnh trnh piston bm do s lm
gim lu lng nhin liu phun .
Phng php ny hin nay t c s dng .
b. BCA iu chnh bng van tit lu :
Nguyn l hot ng :
9Khi vu cam 11 tc dng vo con i 10 y con i v piston 1 i ln nn nhin liu n p sut nh mc n khi thng c lc cn ca l xo 3, m van
nhin liu theo ng ng cao p 4 i ti vi phun.Khi vu cam thi tc dng th l
xo 8 ko piston 1 i xung, kt thc qu trnh phun nhin liu v to ra khng gian
ht nhin liu vo tip tc cho qu trnh sau.
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4
3
2
1
1 2
1 0
1 1
9
87
6
5
9 iu chnh lng nhin liu cung cp cho chu trnh, ta vn van tit lu 5. Nu mun tng lng nhin liu cung cp cho vi phun ta iu chnh cho tit lu
5 dch chuyn ra ngoi, m ng du np thm vo khoang nn nhin liu. Do
nhin liu c cung cp thm cho qu trnh phun.
9BCA iu chnh bng van tit lu ch c s dng rng ri trn cc ng c tnh ti hoc ng c tu thy c nh,c va nh ng c D6 hoc bm cao p
PMY.
Cu to:
1.Piston ;
2.Xylanh ;
3.Rng ng cao p ;
4.ng cao p ;
5.Van tit lu ;
6. L np ;
7. Chm iu chnh gc phun sm ;
8. L xo kh hi
9. Thn BCA ;
10. Con i ;
11. Cam nhin liu
12. Cn bm tay.
2.4. Theo cch thc t hp cc thnh t ca h thng.
2.4.1. Bm cao p Vi phun lin hp.
i Vi BCA Vi phun lin hp cn 4 nhim v sau:
9 n nh s lng nhin liu phun nhin liu vo xylanh. 9 To mt p lc phun nhin liu cao. 9 Phn tn nhin liu di dng sng. 9 Cho nhin liu lu thng lm ngui thn Vi phun. Cu to v nguyn l hot ng :
H thng phun nhin liu Vi BCA VP lin hp l mt hnh thi bin
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tng ca h thng phun nhin liu c in. loi h thng phun nhin liu kiu
ny, BCA v Vi phun c t hp thnh mt cm chi tit gi l BCA VP lin
hp, thc hin chc nng ca ba b phn : BCA, Vi phun v ng cao p. Trong
BCA VP lin hp, nhin liu sau khi c nn n p sut rt cao v c nh
lng s c a trc tip vo vi phun m khng cn cn ng dn nhin liu cao
p.
BCA VP lin hp do hng General Motors thit k l kiu in hnh v
c s dng ph bin nht hin nay trn cc ng c.
Khi ng c lm vic n thi im phun, vu cam iu khin m y i
ln qua a y, c m i xung p m y, kim bm y piston i xung p
nhin liu phun vo xylanh. Khi cam ht y l xo m y bung ra ko piston bm
i ln ch thi im phun khc hot ng( u c m v a y cn vt hiu
chnh iu chnh kim bm ).
Hnh1.9: Bm cao p Vi phun lin hp ca hng GM
1. thn kim; 2. m y; 3. l xo; 4. lc du; 5. l xo; 6. np y;
7. xylanh; 8. piston; 9. thanh rng; 10. vnh rng; 11. vng cn du;12. kim
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phun; 13. xupap thot v b;14. l xo xupap ht ; 15. b ta l xo;
16. van an ton; 18. ng cha l xo.
Khi cam cha i piston v tr cao nht, nhin liu n kim bm nh p lc
bm chuyn, theo ng du trong thn bm n xylanh bm ni cn vng cn
du. Nhin liu np vo xylanh bng c hai l vo cc khe h ri theo ng du v
thng cha. Du lu chuyn trong bm cn tc dng lm mt, bi trn, sy nng v
loi b cc bt kh gip vic nh lng du tt hn.
Khi n giai on bt u phun th cam i c m, y piston i xung, l
du ra pha di xylanh ng trc, du tip tc b y ra l du vo pha trn,
khi cnh vt ca piston va ng l du vo, nhin liu bt u b p trong xylanh
(gi l thi im bt u phun).
Piston tip tc i xung, p nhin liu gy p lc cao, m xupap nhin liu
vo trong xylanh. Khi cnh ngang ca piston bm va h m l du v pha di
xylanh, nhin liu s theo l khoan gia tm v l ngang ra ngi xylanh bng l du
v (gi l thi im kt thc phun).
Piston tip tc i xung cho ht hnh trnh, l du v m hon ton do
nhin liu ra khoang cha nhin liu xung quanh xylanh ni vng cn du.
Khi cam khng cn i na, l xo m y ko piston i ln chun b cho
chu trnh k tip.
Mun tng hay gim lu lng nhin liu tu theo yu cu hot ng ca
ng c, ta ch cn iu khin thanh rng cho piston xoay qua li tu theo v tr rnh
vt piston ti l du ra v vo m lu lng thay i.
u im :
9 Bm cao p v kim phun c thit k mt cm duy nht. 9 Loi b hn ng ng cao p 9 Gn nh, d thay th v sa cha. Phm vi s dng :
H thng nhin liu BCA- VP lin hp c s dng trn cc ng c 2 th
GM General Motors (M), 2 th 9A 3 204 (Lin X), ng c Murphy 4 th
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(M), bm kim lin hp Bendix .
2.4.2. H thng nhin liu bm cao p phn phi :
Khc vi h thng nhin liu khc, h thng nhin liu bm cao p phn
phi cn bm cao p t nm ngang v b iu tc c kh (cc loi bm cao p t
thng ng cn b iu tc thy lc). Bm cao p loi phn phi c chia lm 2
nhm c bn l bm cao p kiu piston v bm cao p kiu rto.
Trn bm cao p kiu piston cn chc nng l y nhin liu vo phn t
phn phi nhin liu, tng chu k lm thng khoang trn piston bm vi cc vi
phun ca xylanh ng c tng ng vi th t n.
Trn hnh 1.10 di y: H thng nhin liu bm cao p phn phi kiu
piston cn c im l piston bm ca n va chuyn ng tnh tin lm nhim
v y nhin liu va thc hin chuyn ng xoay phn phi nhin liu cho cc
xylanh ng c.
H thng ny c s dng trn ng c Reo II, III, GMC, ONAN.
Hnh1.10: H thng nhin liu BCA phn phi.
1. bm cao p phn phi; 2. lc nhin liu;
3. thng cha nhin liu; 4.Bm thp p; 5. vi phun
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69
8
7 5
4
3
2 10
11
12
1
Hnh1.11: S cu to BCA
phn phi.
1. piston ngn ko;
2. ngn ko iu chnh;
3.l khoan ngang
4,5,7. ng nhin liu;
6. bulng;
8.van cao p
9. ng van cao p;
10. trc lch tm;
11.con i;
12. mu cam
20
BOSCH19
IOC
1817
10
16
8
7
9
62
54
1
3
15141312
11
Hnh1.12: H thng phun nhin liu trang b bm cao p PE
iu khin bng in t.
1. bnh nhin liu; 2. bm tip vn; 3. lc th cp; 4. bm cao p PE;
5. c cu kim st thi im phun nhin liu; 6. c cu iu tc;
7.vi phun nhin liu; 8,18. ng dn du v; 9. buji xng my v b phn kim
st;
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10. b phn iu khin trung tm; 11. n bo kt qu chun on;
12. cng tc ca b phn li hp; 13. b cm bin v tr bn p;
14. b cm bin tc ng c; 15. b cm bin nhit ;
16. b cm bin p sut kh np; 17. tuabin tng p; 19. c quy;
20. cng tc buji xng my v khi ng
Trn ng c Diesel th h mi, b iu tc c nng hay chn khng ca
bm cao p PE c thay th bng h thng iu tc in t. H thng ny gm cc
b phn sau y:
1.B phn tc ng tc ng ( b phn chp hnh) hot ng do mt xlnoy
tc ng.
2.Mt cm bin khong dch chuyn ca thanh rng.
3.Mt b cm bin vn tc trc khuu ng c.
4.B s l v iu khin in t trung tm ECU.
Cc b cm bin cng phi hp vi b phn tc ng iu tc ng c
Diesel.
Hnh1.12 gii thiu h thng iu tc loi ny. Kiu iu tc ny phc tp
hn nhiu so vi b iu tc c nng. Tuy nhin kh nng iu tc v hot ng ca
n rt phong ph, bao gm cc cng vic sau y:
9 Bo m vic khi ng / ngng my. 9 c bit c kh nng iu tc n nh p ng mi ch ng c. 9 Thc hin vic iu tc ng c cn c vo cc thng tin v nhit
khng kh np, nhit ca nhin liu v ca nc lm mt ng c. Gii hn v
iu tit lng nhin liu bm i ty theo khi lng khng kh c np vo
xylanh cng nh vn tc ca trc khuu.
9 m bo cung cp tt nhin liu ch cm chng khng ti. 9 Kim sot vn tc trung bnh v gii hn vn tc ti a. 9 Pht tn hiu v tnh hnh cng sut, vn tc ca ng v v kt qu chun
on.
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Hot ng ca h thng iu tc in t c th tm tt nh sau:
1.nh lng nhin liu ( Fuel metering):
iu khin thay i lng nhin liu bm i, ngi trang b mt c cu
tc ng hot ng nh in t (xlnoy), c cu ny dch chuyn thanh rng bm
cao p lm xoay cc piston bm n nh nhin liu bm i.
2.Thu nhn thng tin v d liu (Operating-data acquisition):
Mt lot cc thng tin v nhiu ch lm vic khc nhau ca ng c c
ghi nhn v thu nhn nh cc b phn sau y:
9Mt b cm bin ghi nhn v tr ca thanh rng. S khc bit ca v tr thanh rng so vi v tr chun (setpoint) s hnh thnh tn hiu i vi b iu tc.
9Mt b cm bin vn tc trc khuu c chc nng theo di v c a tn hiu (pulse ring) gn trn u trc cam. Cn c vo nhng ngt qung tn hiu ca
a ny, vi tnh s quyt on c vn tc thc t ca ng c.
9Mt b cm bin nhit ghi nhit nhin liu ni mch np vo bm cao p.
9B cm bin v tr bn p gia tc s ghi nhn v tr ca bn p np. 9Cc b phn cm bin v tnh hnh khng np c chc nng ghi nhn p
sut lung khng kh np t bm tng p, ghi nhn nhit lung khng kh np.
9My pht in xoay chiu cng tham gia cung cp tn hiu v vn tc quay. 9Tc k ca xe cung cp thng tin v vn tc c th ca xe. 9Thng tin v v tr bn dp ly hp c ch nh do mt cng tc. 9Cng tc n stop cung cp thng tin v v tr bn p thng. 3.X l cc thng tin thu c(Operating-data processing):
B vi s l v iu khin trung tm ECU thu nhn tt c thng tin tt c
thng tin cn thit ni trn. Cn c theo v tr bn p gia tc, cn c vn tc thc t
ca ng c, vo mt lot cc i lng iu chnh my vi tnh phi hp vi b
nh, phn tch, so snh cc thng tin nhn c vi d liu lu tr trong b nh.
Cui cng ECU quyt nh iu khin thanh rng bm i mt lng nhin liu
ti u cho ch ang lm vic ca ng c.
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4.C cu tt my (Shutoff device):
Mun tt ng c Diesel, ngi ta phi ngt mch nhin liu bm nhin liu
ln cc kim phun. Thng thng trn bm cao p PE, c trang b c cu tt my dn
ng bng c kh, bng hi v bng t, c cu ny s ko thanh rng v v tr stop.
Nhm nng cao cht lng qu trnh to hn hp chy trong ng c Diesel,
khc phc nhng nhc im m h thng nhin liu c iu khin bng c kh vn
cn tn ti nh vic nh lng, nh thi im phun cha chnh xc, tnh t ng
iu chnh v t ng ha cn hn ch nht l cc ch lm vic khng n nh
nh: khi ng, tng tc, gim tc...v cc c cu h thng (iu tc, thay i gc
phun sm...) lm vic cha nhy lm. Vic p dng cc thit b in t vo h thng
nhin liu ng c Diesel nhm mc ch gii quyt nhng vn ny, ngoi ra n
cn gp phn gim bt tnh c hi cho mi trng do qu trnh chy ca nhin liu
c chy hon ton hn.
H thng gm cc b phn sau:
9B phn cm bin: Gm cc bin tc , ti trng p sut kh np, cm bin LambdaCc cm bin ny cn nhim v ghi nhn cc hot ng ca ng c
cung cp thng tin cho khi thit b iu khin trung tm (CPU).
9B iu khin trung tm (CPU): y l b phn cn nhim v tip nhn thng tin do cc cm bin cung cp. Cc tn hiu c a n t cc cm bin s
c chuyn i thnh cc tn hiu s. B phn x l phi hp nh cc b phn tch
so snh cc thng tin nhn c vi cc d liu lu tr sn trong b nh. T b
iu khin trung tm s cho ra tn hiu lm nhim v iu khin cc c cu phn
chp hnh.
9B phn chp hnh: Cn nhim v thc hin lnh iu khin, ch huy vic nh lng, thi im phun nhin liu, cng nh ch huy 1 s c cu v thit b khc
nh lun hi kh x, ngng hot ng mt s xylanh, hiu chnh hn hp chy khi
ng c lm vic tc caoNhm m bo s lm vic ti u ca ng c.
So snh gc phun nhin liu thc t vi gc phun nhin liu sm quy nh
cn sn trong b nh. Cui cng CPU s a dng in n xlnoy iu khin t
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dch chuyn sao cho im bt u phun nhin liu thc t ging im bt u phun
quy nh.
u im: Lm vic n nh v tin cy Nhc im: Gi thnh cao, cng knh, phc tp Phm vi ng dng: Hin nay c s dng ph bin trn cc ng c
hin i.
Hnh1.13: S nguyn l hot ng ca h thng nhin liu vi
bm cao p PE trang b h thng in t.
Cam bien khac
Nhiet o ong c
Ap suat nap khong kh
Cung cap thong tin
Bo phan kiem soat v tr thanh rang
BO PHAN CAM BIEN
iem khi phun thc
te
BO IEU KHIEN TRUNG TAM CPU
V tr thc te cua thanh rang
Bo phan kiem soat iem bat aunhien lieu
V tr truc khuyu
Toc o ong c
Xolenoy ieu khien thanh rang
Xolenoy ieu khien t
Kim phun vi bo cam bien tac ong van kim
BM CAO AP PE THE HE MI
III- CU TO, THO LP, KIM TRA V SA CHA CC B
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PHN CA H THNG
3.1. Bm cao p.
3.1.1. BCA c in (Bosch) loi n.
a/ Chc nng , yu cu , nhim v:
9Chc nng, nhim v: bm nhin liu vi p sut caovo trong khoang cao p
9Yu cu: nhin liu phi c bm ng lng cn cung cp, ng thi im, v hnh n tia phun ph hp.
b/ iu kin lm vic:
9Lm vic trong mi trng p sut nhin liu cao, thay i thng xuyn v c chu k.
9Chu lc nn cao. c/ Cu to v nguyn l hot
ng:
9Cu to:
1. thanh rng ; 2. vnh rng; 3.
u ni ng; 4. l xo;
5. van cao p; 6. van; 7.
xylanh; 8. g x nhin liu ;
9 v 11. vt; 10. piston ;12. ng
xoay; 13. a trn ;
14. l xo bm cao p; 15. a
di ;16. bulng iu chnh ;
17. con i; 18. con ln ; 19.
cam. Hnh 2.1:BCA c in loi n
Nguyn l lm vic:
hiu r nguyn l lm vic ca bm PF, ta chia ra ba giai on: Np
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nhin liu, khi s bm v dt bm.
9Np nhin liu: hnh.2.1.b.I, II, III cho thy piston bm xung im cht di v cam cha i v b l xo ko xung. Hai l np v thot du a, b m, nhin
liu trn vo xylanh b
9Bt u bm: hnh 2.1.b.IV,V cam i piston ln, n lc mt phng trn piston ng kn hai l du a, b, p sut trong xylanh tng. Van thot du cao p m,
piston tip tc i ln bm nhin liu n vi phun vo bung t.
9Kt thc bm: hnh.2.1.b .VI qu trnh bm nhin liu n lc cnh xin ca piston bm m l thot nhin liu. Lc ny nhin liu tt xung theo rnh ng
n rnh ngang theo l b v bng cha du quang xylanh. p sut trong bm gim
xung ngay v cao p ng tc thi.
a. Piston im cn trn; b. Np nhin liu vo khoang bm;
c. Piston im cn di; d. Bt u bm hnh hc;
e. Kt thc bm hnh hc; f. Kt thc chu trnh cng tc
Hnh 2.11: Cp piston-xylanh ca BCA Bosch c in
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9 Nguyn l thay i lng nhin liu cung cp chu trnh (hnh.2.1.c): X dch thanh rng xoay piston bm cho rnh xin ca n m sm hay
m tr l thot du.
Khi xoay piston bm qua tri cnh xin m tr l thot du, nhin liu bm
i nhiu; Ngc li, xoay piston bm qua phi, cnh xin piston bm s m sm l
thot (b), nhin liu bm i t.
Nu xoay piston bm tn cng pha phi rnh ng ca piston s i din vi
l thot b, lng nhin liu bng 0, tt my.
Hnh 2.8: Cc phng n iu chnh lng cung cp chu trnh.
a. Thay i thi im kt thc cung cp.
b. Thay i thi im bt u.
c. Thay i hn hp.
- Quan st, kim tra chi tit bm.
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+ Cp piston v xylanh bm. Dng knh lp quan st tnh trng sy st ca
piston nht l ni vng du v rnh xin. Nu b sy st l do nhin liu bn.
Nu sy st nh th xoy li vi m r c bit, tuyt i khng c dng
ct r. Try xc nng th phi phc hi hoc thay mi cp piston v xylanh.
+ Van v van cao p. Dng knh lp quan st tnh hnh tip xc gia van
v van. Try xc nh th xoy, nng th thay mi cp van v van.
+ L xo van cao p, vng rng, thanh rng.
Nu nu l xo van thot cao p b cong, r phi thay mi. Rng ca vng
rng v thanh rng mn th lm sai lu lng, do phi thay mi.
Hnh 2.2: Ch mi mn ca cp piston v v tr mi mn trn b mt cng tc ca van cao p a. van ; b. van; c thay i hnh dng cc mt cng tc A. rnh thot ti; B. u cn t; C ui van; D. g cn; . mt tip xc vi rnh; G. l dn hng
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d/ hao mn , h hng:
*B mi mn do:
- ma st gia cam v con i lm cho lng nhin liu cung cp khng cn
c chnh xc.
- ma st gia cp piston v xilanh bm cao p, v do p sut du ln nn
cng b mn khi nhin liu chy qua.
*L xo BCA lm vic lu ngy khng cn n hi tt.
Sa cha
i vi mn do cam c th nng cao con i iu chnh lng nhin liu
cho ng .
L xo c th thay .
i vi cc cp chi tit trong BCA thng l cc cp chi tit siu chnh xc
nn thng khi b h l thay mi,
- Ngoi ra khi c nhiu cp piston-xilanh cng mt lc, c th dng tnh cht
lp ln tn dng c nhng cp cn li.
Tho bm cao p PF cn lu :
+ Mt bn th v hm bn kp phi c bc kim loi mm nh nhm, ch
trnh lm try xc chi tit bm.
+ Ra sch bn ngoi trc khi tho bm.
+ Cc chi tit tho ra phi ngm trong du sch.
+ Khng c dng cc dng c sc bn nh st, thp co sch chi tit
bm.
+ Trc khi lp phi ngm cc chi tit bm vo trong du sch. Tuyt i
khng dng vi lau, v si bng trong vi cn th lm kt hng piston, xylanh v
cc chi tit tinh xc khc.
u tin tho khoen chn y bm, ly ng dn l xo, piston bm, vng
rng, chn rng. Sau cng tho rc co ly van cao p, vt chn xylanh v xylanh
bm ra.
Qui trnh lp chi tit bm.
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Th t ngc li vi tho. Lu my im sau y:
+ Rnh nh v xylanh bm phi thng vi l ren vt gi.
+ Trn rnh kp ca vng rng c nh du. Trn mt ngnh chn piston
cng cn du. Khi lp, hai du ny phi thng nhau. Nu lp ngc 1800 ng c s
lun lun chy mc ti a khng gim tc c, v cng nguy him.
Cch hiu qu nht l cnh xin ca ty bm phi hng qua pha vt gi
xylanh bm.
Du thanh rng phi thng vi du ca vng rng.
Trc khi lp chng phi nhng chng trong du sch.
Kim tra p sut ca bm v kn van cao p.
- Kim tra sau khi phc hi sa cha, tin hnh kim tra kh nng bm
du ca bm cao p v Van cao p nh sau:
+ Gn vo rc co ng dn cao p ca bm cao p ca bm mt p k c kh
nng chu c 500 kG/cm2.
+ a thanh rng ln v tr ga ti a (lu lng ti a).
+ Xeo piston khong 5 ln.
+ Nu p sut t c 250kG/cm2 l tt.
+ Duy tr p sut ny trong 10 giy nu p sut ny khng tt xung qua 20
KG/cm2 l van cao p cn kn tt.
c/ Cn bm cao p PF.
- Cn ng lng cp ca cc bm cao p. Trn ng c diesel nhiu
xylanh, nu cc bm cao p hot ng khng ng lng ngha l lng du bm i
ca cc bm khng ng u nhau, ng c s g v b nhiu hu qu khc. V vy
trc khi gn bm ln ng c, phi tin hnh cn ng lng cc bm PF.
+ Cn ng lng trn bng th. V d mi bm bm ra c 10cc trong
100 hnh trnh ca piston vn tc 600 vng/pht.
* Gn bm PF s 1 ln bng th.
* Cho bng th quay, x gi trong bm, chnh vn tc bng th 600
vng/pht.
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* Dch thanh rng hng 10cc trong 100 ln phun, ta thy mi ch v tr
50 mm trn thanh rng.
* Tho bm s 1, gn bm s 2 ln bng th. Cho bng th quay 600
vng/pht, dch thanh rng th no hng 10cc trong 100 ln phun.
* iu chnh mi ch n mc 50 mm trn thanh rng.
Nh vy trn c hai bm PF1, PF2, lc ta t thanh rng ca chng mc 50
mm chng s bm ra mt lng nhin liu bng nhau mt tc nht nh.
+ Cn ng lng trn ng c khng n.
* Tho cc vi phun ra khi quy lt ng c.
* Gn cc ng nhin liu hng du.
* X sch gi trong h thng nhin liu v cc bm PF.
* Dng maniven quay trc khuu mt vn tc v s vng quay no .
* X dch iu chnh mi ni gia cc thanh rng PF1 v PF2 th no cho
tng lng nhin liu phun ra gia hai bm cho ng u.
+ Cn ng lng trn ng c khi ang vn hnh.
* Cho ng c chy cm chng t n nhit vn hnh sau tng n
vn tc bnh thng cn ti.
* Dng nhit k o nhit ng x tng xylanh.
* Ty theo nhit ni mi ng x, ta iu chnh thanh rng nhit cc
ng ng u. Nu nhit cao, chnh thanh rng bt lu lng. Nu nhit thp,
iu chnh thanh rng thm nhin liu. iu chnh x dch thanh rng ti mi ni
cc thanh rng.
- Cn bm cao p PF vo ng c.
Cn bm cao p vo ng c l gn bm vi ng c sao cho bm phun
nhin liu vo bung t ng thi im cn thit (vo cui th nn ng gc phun
sm quy nh).
Trn ng c cn nh sn du phun sm cn thit, bm cao p PF cn ca
s cn bm (1) ghi im khi s bm. Trng hp bm khng cn du ta cng phi
bit cch x l nh sau:
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+ Trng hp cn du thn bm PF.
* Chi sch cc mt lp ghp bm.
* Quay trc khuu ng chiu cho m y bm cao p xung im cht
di.
* Gn bm cao p PF vo ng c, xit u hai ai c,
* Quay bnh t t ng chiu tm im phun du cui th nn, du
phun du ghi trn bnh trng du c nh trn thn my.
* Lc ny du vch ng y piston phi thng du ca s cn bm,
Nu vch ng y cao hn du trn ca s cn bm l phun du sm phi
chnh vt u con i xung.
Ngc li, vch ng y piston bm nm di du ca s cn bm l phun
tr, phi xoay vt ln.
Kim tra bng cch quay bnh hai vng n im khi phun, cc du cn
bm cao p ti bm cao p phi thng nhau.
+ Cn bm theo phng php ngng tro
Nhng bm cao p c nh thng khng cn ca s cn bm hoc du cn
bm khng r, ta p dng phng php ngng tro. Ni dung ca phng php ny
l: Lc piston m cc l a, b du s tro ra ni rc co lp van thot cao p ( tho
van ra). Khi piston tin ln bt l a,b khi s bm th du bt u ngng tro.
* Quay trc khuu ng chiu cho piston (ng c mt xylanh) cui th
Hnh 2.3: Cn BCA n vo ng c theo phng php ngng tro
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nn cch im cht trn khong 300.
* Tho l xo v van cao p ra khi bm PF, gn thay vo ng nghim ch
U.
* y thanh rng n v tr lu lng ti a, m van thng nhin liu (cp
du bng trng lc), du s tro ra khi ng U.
* Tho ng U, lp li l xo v van cao p.
Trong trng hp con i bm cao p khng c vt iu chnh, ta phi thm
hay bt cc ming chm mng di gn bm.
- X gi trong h thng nhin liu bm PF
Nu trong h thng nhin liu ng c diesel cn ln khng kh (gi), ng
c khng vn hnh c. Khng kh ng trong bnh lc th cp, bnh lc s
thiu nhin liu. Nu cn khng kh cn trong bm cao p, trong ng dn cao p v
trong kim phun, nhin liu s khng phun c. V vy phi tin hnh x gi.
Khng kh thng vo trong h thng nhin liu trong cc trng hp: Ht nhin
Hnh 2.4: Phng php x gi trong h thng BCA n A. Vt x gi ni bu lc
B. Rc co ni ng cao p ti kim phun 2.vt x gi ni BCA
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liu trong thng cha, sau khi sc ra cc thit b h thng nhin liu.
Thao tc x gi nh sau:
- Np y nhin liu vo bnh cha.
- Ni lng vt x gi a trn np bu lc th cp, nhin liu t thng cha s
chy vo bu lc v thot ra ni vt ny cn ln bt khng kh.
- n khi du thot ra ngoi khng cn bt kh trong bu lc, kha vt
x gi.
- Tin hnh x gi ti bm cao p PF nh sau:
+ Ko thanh rng n v tr Stop.
+ Ni lng vt x gi (2), du ln bt trn ra n khi ht bt trong bm l sch
gi. Kha vt x gi.
- X gi vi phun nhin liu bng cch ni ni lng rc co B ca vi phun,
ko thanh rng bm cao p n v tr lu lng ti a, quay my hoc bm tay bm
cao p cho nhin liu bm ln vi phun. Lc nhin liu v gi tro ra ch rc co
ang ni lng, ht bt kh l c. Sit cng rc co.
- Bm tay hay via my vi ln, nghe ting mykt kt l khi ng
c.
3.1. 2 Bm cao p loi cm:
a/ Cu to v nguyn l hot ng :
Bm cao p Bosch loi P.E hay cn gi l bm cao p piston ngn ko
Piston 7 c cam 24 y ln qua con i 4 v vt iu chnh. Hnh trnh i
xung ca piston l nh l xo 16 v ta di 6.
Nguyn l hot ng ca bm cao p loi cm cng tng t nh bm loi
n, thc cht n l nhiu bm n c chung mt thanh rng.
So vi bm cao p n loi ny ch dng cho my c cng sut nh.
Sau khi kt thc qu trnh phun, piston vn tip tc chuyn ng i ln
cho ht hnh trnh danh ngha ca n (Sd).
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Hnh2.5: BCA
kiu piston ngn ko
loi cm.
1. v thn van
cao p; 2. trc con ln; 3.
con ln; 4. vng rng; 5.
l xo nn; 6. piston; 7.
con ln, con i; 8. bi;
9. trc cam ; 10. thn
bm; 11. v tr lp bm
tip vn; 12. vt nh v xylanh ; 13. vt nh v xylanh ; 14. vt nh v x
Vi loi bm ta ang xt th hnh trnh danh ngha (Sd) bng chiu cao ca
cam cn hnh trnh c ch (Si) c xc nh nh trn bnh khai trin u piston va
chm gp mp vt iu chnh.
Lng cung cp 1 ln bm c tnh theo cng thc:
Trong :
d: ng knh piston ngn ko bm; Si Hnh trnh c ch.
Gi nguyn hnh trnh danh ngha (Sd) nhng nu dch chuyn thc nhin
liu (19) th piston ngn ko s xoay quanh ng tm ca n xoay phi gim hnh
trnh c ch - gim cung cp. Xoay tri, tng hnh trnh c ch - tng cung cp.
V tr tng i ca piston ngn ko so vi cc l ca xylanh cc mc cung
cp ti a, trung bnh, cm chng v tt my (khng cung cp) trnh by trn tng
ng vi hnh trnh c ch l Std, Stb, Sc, v S0 .
Nh vy, loi bm cn piston ngn ko ct vt pha di, khi xoay piston
cho php thay i thi im kt thc phun cn thi im bt u phun th vn c
gi nguyn.
ip S
dq .
4=
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Hnh 2.6: Hnh trnh c ch ca piston cc ch .
Cng l gii nh vy, u piston c ct pha trn hoc c pha trn ln pha
di th khi xoay piston, ta cn th iu chnh lng cung cp chu trnh bng cch
thay i thi im bt u (hnh b) hoc thay i c thi im bt u c thi im
kt thc cung cp (hnh c)
p sut cung cp du ln ng cao p do cng ca l xo van cao p (13)
quyt nh. Nh vy, bm piston ngn ko cho php ta to p sut nhin liu theo
yu cu, ng thi cho php ta thay i thi im v lng cung cp tu - ph
hp vi ch lm vic ca ng c.
c im cu to ca BCA ngn ko loi cm:
Khng gian c hnh thnh gia mt trong xylanh v vng c khot su
thm u piston c gi l ngn ko ca bm. piston trn hnh 2.8.a ngn ko
bm c thng vi khoang trn nh piston nh l khoan ngang v l khoan chnh
tm. Cn cc piston th rnh khng c x dc pha ngoi. Nh cn ngn ko v
ng thng gia n vi khoang nh nn khi ngn ko thng vi ca x cung cp
Hnh 2.7: V tr tng i ca piston trong xylanh cc ch .
a- Cung cp ti a; b-Trung bnh; b- Cm chng; d-Tt my;
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nhin liu c kt thc v khi n khng cn thng vi khoang nh ca piston na,
s cung cp mi c bt u.
Vic khot ngn ko bn trong u piston nh trn lm cho n b y v
pha i din bi p lc nhin liu trong khoang ko lc bm tng p. Pha piston
v xylanh b c st vo nhau mnh hn, gy ra hao mn nhiu hn, lm cho chng
khng cn dng tr xoay ban u na. khc phc nhc im ny, ngi ta
khot thm mt ngn ko v mt rnh thng na pha i din ca u piston. s
i xng ny s trit tiu p lc ca du ln piston trong mt phng vung gc vi
ng sinh piston xylanh.
*/ Vic sa cha bm cao p loi cm gn ging vi bm cao p loi n.
3.1.3.Bm cao p kiu phn phi:
a. Cu to :
Hnh 2.9: Dng ct iu chnh u piston BCA ngn ko v
quy lut thay i lng cung cp theo gc xoay ca piston.
a - Ct xon c 1/3 Vng;b - 1 Vng; c- Ct thng; d - ng gCT=f().
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b/ iu kin lm vic:
- Lm vic trong mi trng p sut nhin liu cao, thay i thng xuyn
v c chu k.
- Chu lc nn cao.
c/ nguyn l hot ng :
1.Xilanh; 2.Piston; 3.ai c m; 4.u ni vi ng cao p; 5.L xo valve tng p; 6.Van tng p; 7.ng du ra;
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69
8
7 5
4
3
2 10
11
12
1
*/ Hao mn, h hng , sa cha:
- Hao mn: +/mn do ma st gia cp piston- xilanh ca bm phn phi,
+/ mn do ma st gia cam v con i.
+/ l xo van tng p b r, khng cn cng lm vic.
- Sa cha: +/ i vi l xo c th thay mi,
+/ cp piston-xilanh nu mn t th c th r li bng m r c bit. Nu b
mn nhiu th phi thay mi
3.1.4 - Con i ca BCA; khc vi con i dng c cu phn phi kh l
n cn th iu chnh chiu cao bng bulng 4 v c hm 3 (h2.10).
Nh thay i chiu cao ca con i, ta c th thay i thi im cung
cp, ngha l nu lng nhin liu cp cho BCA khng , ta c th vn bulng 4
cao ln
Khi con i c cam y v tr cao nht, s lm cho piston cua bm cao p nng ln, c im ca piston loi ny l c th xoay c, nn n va tnh tin bm nhin liu ng thi va xoay c phn phi nhin liu cho cc bm.
Hnh 2.10: Con i BCA. 1. con i 2. con ln 3. c hm 4. bulng iu chnh
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Khi tng chiu cao con i, p sut cui k nn trong BCA cn th
tng qu gii hn cho php. V vy BCA loi n ngi ta vch du gii hn trn
cho s dch chuyn ca piston .
3.2. Vi phun (bc du). 3.2.1. Cu to, nguyn l hot ng Cu to:
Kt cu chung ca mt vi phun nhin liu gm ba phn chnh:
Thn : trn thn kim c ng du dn n, ng dn v v vt x gi. Trong thn c l xo, cy y, pha trn c ai c chn hiu chnh sc cng ca l xo,
trn cng l chp y ai c hiu chnh.
u (t kim):c ni lin vi thn kim bng mt khu ni (cu trng) bn trong c ng du cao p, khoang cha du cao p v cha van kim. Phn
di u VP c mt hay nhiu l phun du rt b.
Khu ni: dng ni thn v u VP. Vi phun c lp vo np quy lt nh gujon v mt bch
.
Hnh 2.16: Vi phun kn.
3.2.2. Phn loi vi phun.
Cn c vo van kim v t kim, ngi ta phn ra hai loi vi phun: vi phun
kn v vi phun h.
- Vi phun kn. Vi phun kn chia thnh: vi phun kn tiu chun, vi phun
kn c cht trn mi kim v vi phun kn dng van.
Hin nay, hu ht cc ng c Diesel u dng Vi phun kn.
1. l phun; 2. mt cn ta ca kim; 3 v
19. kim phun; 4. cu trng;
5 v 16. ng dn nhin liu; 6. a
y; 7. a l xo; 8. l xo ;
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+ Vi phun kn tiu chun (hnh 2.16) gm hai chi tit chnh xc l xi lanh
kim phun 17 v kim phun 3, khe h trong phn dn hng ca hai chi tit ny
khong 23m. Mt cn ta 2 ca kim t ln van trong thn kim phun v ng kn ng thng ti cc l phun. Cc l phun cn ng knh 0,34mm phn b u
quanh chu vi u vi phun. ng tm cc l phun v ng tm u vi phun to
thnh gc 750. cu trng 4 dng bt cht u vi phun ln thn.
Nguyn l lm vic :
Nhin liu cao p c bm cao p a qua li lc 14, qua cc ng 16
trong thn kim phun ti khng gian bn trn mt cn ta ca van kim. Lc do p
sut nhin liu cao p to ra tc dng ln din tch hnh vnh khn ca van kim
chng li lc p ca l xo. Khi lc ca p sut nhin liu ln hn lc p ca l xo
th van kim b y bt ln m ng thng cho nhin liu ti l phun. p sut nhin
liu lm cho van kim bt u bt m c gi l p sut bt u phun nhin liu p.
i vi Vi phun kn tiu chun p = 15 25MN/m2. Trong qu trnh phun, p sut nhin liu cn th ti 50 80MN/m2, trong mt vi trng hp cn th cao hn na.
Mun gim bt nhin liu r r qua khe h phn dn hng ca kim phun,
i khi trn kim phun cn cn rnh hnh vnh khn. Hnh trnh nng kim phun
c xc nh bi khe h gia mt trn ca kim vi mt phng di ca thn vi
phun. Khe h ny thng vo khong 0,3 0,5mm. + Vi phun kn loi van.
Trong loi vi phun
ny ch cn mt tit din
tit lu bin i t phn
l phun. Tit din tit lu
ny do van thun ( chiu
Hnh 2.17: Vi kn dng van
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m van trng vi chiu lu ng ca nhin liu ) hoc van nghch iu khin.
+ Vi phun c cht trn kim.
c im ca vi phun ny l cn mt vi tit din bin i phn l phun.
Trn thn kim phun 16 cn mt l phun ng knh khong 1,5 2mm. Mt cn ta ca van kim 4 che kn tit din trn cng ca l phun. u di ca kim cn mt
cht hnh tr. Phn ui ca cht tr lm thnh dng hai mt cn cn chung mt
y nh. Khi lp vo u vi phun, cht ca kim phun nh ra ngoi l khong
0,40,5mm.
Trong qu trnh m kim phun, phn cht ca kim phun chuyn dch trong l
phun hnh tr. Lc y xung quanh cht to thnh mt ng thng nhin liu hnh
vnh khn vi 3 mt tit lu: mt th nht ti mt cn ta ca kim, cn hai mt
khc ti hai y ln ca hai mt cn.
Tia nhin liu ca loi vi phun c cht trn kim c dng hnh cn rng, nh
cn l cn. Gc cn ca tia nhin liu ph thuc vo hnh dng phn ui ca
Hnh 2.18: Vi phun c cht trn kim phun 1. L phun ; 2. Mt cn ta ca van kim ; 3 v 5. ng dn nhin liu;
4.kim phun; 6. a y; 7. l xo; 8. a l xo; 9. cc ;
10. m iu chnh; 11. bulng ; 12. vt iu chnh; 13. chp;
14. Thn vi phun; 15. cu trng; 16 .thn kim phun;
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cht v vo hnh trnh ca van kim. Gc cn bin ng trong phm vi rt rng ( t
00 n 500600), hnh trnh ca van kim cng c hn ch nh trong vi phun kn tiu chun.
+ Vi phun kn loi van l phun. Trong vi phun ny cng ging vi phun
tiu chun l cn hai mt tit lu: Mt th nht l mt khng bin i ti l phun v
mt th hai l mt thay i gia van v van. c im vi phun kn loi van l
phun khc vi vi phun tiu chun l ch chiu m van cng chiu vi chiu
chuyn ng ca nhin liu. V vy trn van ch dng l xo mm cng sc p
cht van ln , ngoi lc l xo cn c lc kh th trong xylanh ng c cng tc
dng p van t ln van. Phn u vi phun cn th c mt hoc nhiu l phun.
u, nhc im :
u im chnh ca loi vi phun ny l kch thc nh gn, cu to n
gin, d ch to.
Nhc im chnh ca n l u vi phun tip xc vi kh nng trong xylanh
cn th b nng qu mc cho php, lm thay i cc khe h trong u vi phun
khin phun b cong vnh, lm knh van gy nh hng xu n cht lng phun.
- Vi phun dn ng c kh.
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11
34
5
2
1
6
8
10
9
7
Hnh 2.19: Vi phun dn ng c kh.
Cu to v nguyn l hot ng : Khi qu o 10 con i 8, a y 6 th tay
n 5 quay quanh khp bn l p l xo 4 nng kim phun 2 ln, m van phun cho
nhin liu t khoang cao p 11 qua cc l phun vo bung t.
Vo lc cam khng i, l xo 4 p kim phun vo b ca n, ng kim
van phun.Thi im bt u phun du ca loi vi phun ny, do v tr tng i ca
trc cam vi trc khuu quyt nh. Lng phun du do v tr nm 9 quyt nh. p
sut du trong khoang 11 c gi lun lun khng i nh mt b tch tr chung
cho tt c cc vi phun ca ng c. B ny c mt BCA chung cung cp.Vi
phun ny nm trong h thng tch phun.
u, nhc im :
u im chnh l trong thi gian phun, p sut phun hu nh khng i.
Nhc im chnh l cu to phc tp, nhiu chi tit.
-
Vi phun kiu thy lc.
Cu to v nguyn l hot ng :
1.kim phun; 2.khoang phun; 3.thn vi phun;
4.l xo; 5.tay n;
6.a y; 7.tay quay; 8.con i; 9.nm;
10.qu o; 11.khoang cha
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Trong thn s 2 khng cha cc chi tit dng p kim phun thng
thng m c thay th bng hc cha hn hp du s 1 cn p sut khong 180 200 KG/cm2. Vic cung cp hn hp vo khoang ny do mt h thng thy lc thc
hin. Thay i p sut phun ca vi phun thy lc thc hin mt cch d dng bng
cch thay i van x 6 (khng cn tho vi phun ra)
Tui th ca cp kim b ca vi phun ny ln. Tuy nhin, khi dng vi
phun thy lc cn cn h thng cung cp du kim phun, lm cho ng c
phc tp hn.
- Vi phun ca hng Cummins.
Cu to v nguyn l hot ng :
Hnh trnh i ln ca kim (nh l xo 3), ht mt lng kh nng t bung
chy qua l phun vo cc. Lc m l nh lng 12 cng l lc m ng kn ng
du hi, t lc nhin liu c qua l nh lng np vo cc, hn hp vi kh
nng trong cc. Hnh trnh i xung ca kim (nh vu cam), lc kim che kn l
nh lng bt u bm, cng l lc m thng ng du hi, t lc nhin liu
v kh nng trong cc b nn v c phun qua l phun vo xylanh ng c di
Hnh 2.20: Vi phun kiu thy lc. 1. hc cha du; 2. thn bm; 3. bm piston; 4. van mt chiu;5,7. bnh cha ; 6. van x; 8. van an ton; 9. ng dn cao p
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dng nh tng (bt nhin liu). Do dc ca mt cam tng lin tc khi phun nn
cng v cui tc phun cng ln lm cho bt c x rt ti v ha trn u vi
khng kh trong bung chy, lc a y 3 v tr cao nht th mi kim va t st
ln mt cn ca cc, kt thc phun. Sau im cao nht mt cam c h thp cht t
gim ti trng tip xc gia cam v cc. Do s lng nhin liu c nn (trong
cc phun) t nn p sut nhin liu dao ng rt t.
ng c diesel Cummins, dng h thng nhin liu phn phi p sut thp.
Trong , bm nhin liu n b kim bm lin hp, nh lng v phn phi nhin
liu c tin hnh di p sut thp. B kim phun lin hp gn trn np quy lt
ca mi xylanh ng c s c to p sut cao phun nhin liu vo bung t
ng c.
3.2.3. Hao mn v h hng ca vi phun:
* Do ma st khi chuyn ng v khi nhin liu khng sch, mt dn hng
b mn, v va p c chu k v v nhin liu phun qua vi tc ln, phn b mt
kn st, ni kim v b tip xc nhau, b dp nt, trc r nn van y khng kn v
gy ra s r r nhin liu ming phun . Ti y nhin liu chy km, to mui than
, lm nng u phun v thng lm tt l phun.
* Nu nhin liu c nhiu cn cn hoc ln nc , kim phun kh chuyn
ng , lm chy xm b mt kim hoc lun trng thi ng nn khng phun nhin
liu c, hoc lun m lm nhin liu b r r.
Vi phun ca hng Cummins.
1. cn piston; 2. a l xo; 3. l xo; 4. thn bm; 5.
li lc; 6. l a du vo; 7. cu trng; 8. xylanh;
9. u vi phun; 10. piston;11. rnh nhin liu
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a/ Phng php xc nh h hng vi phun trn ng c.
Mt ng c c nhiu VP ang hot ng, nu mun xc nh chnh
xc vi phun vo h, ta tin hnh cc thao tc nh sau:
- Cho ng c lm vic tc cm chng.
- Dng mt cha kha ming thch hp vi khu ni, ni ng cao p vi vi
phun.
- Ni rc co ni ra khong 1 1.5 vng khi no thy du x ra y th dng
li.
- Lng nghe ting n ca ng c. Nu my khng, ting n thay i chng
t vi phun con tt. Nu tnh trng lm vic ca ng c v ting n khng thay i
chng t vi phun h. Sit li rc co cao p.
- Ln lt ni lng cc rc co kim tra cc VP cn li .
b/ Phng php kim tra kim phun trn bn th
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- Dng c.
+ Cl ni lng rc co ng du v u VP (kch thc thch hp).
+ Cl vng tho np chp l xo (kch thc thch hp).
+Tuc n vt
- Thao tc kim tra
Sau khi xc nh VP h hng (hoc cn kim tra) lp VP ln bn th v thc
hin cc bc sau:
+ X gi:
Kha van dn du ln ng h p lc.
n mnh cn bm tay vi ln x gi n khi no thy nhin liu phun.
+ Kim tra v iu chnh p lc phun:
* M van cho du ln ng h p lc khong vng.
* n mnh cn tay bm cho ng h p lc tng ln n khi no VP phun.
* So snh p lc trn ng h vi gi tr cho ca nh ch to. Nu khng
c l lch my c th ly gi tr 115- 120 kG/cm2 vi VP kiu kim cht, 175 kG/cm2
vi VP kn nhiu l.
* Nu p lc thp hn gi tr qui nh ta vn c hiu chnh p lc hoc thm
tm m. Nu p lc cao hn th lm ngc li.
+ Kim tra r r u VP .
Hnh 2.23: Bn th vi phun 1. lc nhin liu 2. van kim tra 3. vt x kh 4. vi phun 5. bm tay 6. ng h hin th p sut 7. ng ng cao p 8. vt iu chnh p sut 9. ai c nh v
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n cn bm tay cho p lc ln khong 4 5 kG/cm2 di p lc qui nh. V
d : 110 kG/cm2 cho p lc qui nh 115 kG/cm2.
Vi p lc ny du khng c r ra u VP.
Nu c r r l do mi kim (ch cn nh) v b trn cha kn. Nu r ra
khu ni l do sit khu ni cha ng lc, mt tip xc khng tt ta phi tho kim
ra xoy li bng ct r v du nhn.
+ Kim tra phun rt
Kha van du ln ng h. Dng giy mm lau kh sch du u VP, n
mnh cn bm tay cho du phun ra nu thy kh u kim l kim tt, nu t th
VP phun rt. Nguyn nhn c th l do d bn hay try xc cn tho ra, r thn
kim du bi trn.
+ Kim tra cht lng phun
* Vn kha van du ln ng h p lc.
* n mnh cn bm tay.
* Quan st tnh trng phun du phi tht ti sng, ng gc nn chm tia.
* Dng ming giy di u VP khong 3 cm. Xem s l tia c khng
. Nu nght th dng cy xoi thng, cn thn trnh cy xoi gy trong l.
+ Kim tra s mn ca kim v b:
* M van cho du ln ng h p lc.
* n cn bm tay cho p lc gn bng p lc phun. Gi cn bm v quan
st s st p trn ng h. Nu s st p khng qu 15kG/cm2 trong vng 15 giy
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th VP cn tt
Ch : Khng dng vi lau, ch dng du gasoil ty, ra sch cc chi tit.
Dng c, bn kp, tay ca ngi thao tc phi tht sch.
* Sa cha vi phun:
V y l mt trong nhng cp chi tit i hi tnh chnh xc rt cao nn thng
thng khi b mn hoc h hng th ta thay b i kim-b phun.
Trong trng hp thiu ph tng thay th th ta c th khi phc bng cch r .
3.3 Cc loi bm nhin liu thp p:
3.3.1 Bm piston:
a/ cu to v nguyn l hot ng:
Khi trc trc cam (10) ca BCA quay n v tr thp , th piston (8) s c
l xo hi v (7) y xung khng gian pha di . Lc ny do chn khng to ra
pha trn nn van tng p (2) ng li, van np (6) m ra.Nhin liu t thng cha
c ht vo khong khng gian pha trn piston qua van np (6) . ng thi khi
piston chuyn ng xung pha di , khng gian pha di hp li v nhin liu
c nn vo ng du (3) n bnh lc tinh. Nh vy piston (7) ng vai tr
quyt nh trong vic bm nhin liu.
Khi trc piston quay n v tr cao , lm y con i (9) , dn n y piston
(8) i ln, lm khng gian pha trn hp li, p sut nhin liu tng ln, lm cho
van(2) m ra v van (6) ng li, dn nhin liu n ng lc tinh (3)
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Bm tay dng bm nhin liu ln bm cao p khi ng c ngng lm
vic lu trc khi khi ng hoc dng bm nhin liu khi x e trong h thng
trc khi cho ng c lm vic.
* u im: -gi cho p sut bm lun khng i
* Nhc im: khi piston b mn , cc van b h th bm khng u , l xo hi v
gy hay yu cng lm cho bm lm vic khng tt.
b/ Sa cha, lp rp v iu chnh bm cp nhin liu
Nhng h hng ch yu ca cc bm cung cp nhin liu kiu piston l mn
piston v xi lanh, mn cc mt t ca cc van nn v ca chng, mn van bi ca
piston ca bm tay v ca n, mn con i v l dn hng ca n trong v
bm. Cc l xo ca van v piston mt n hi, chn ren ca bm tay hoc cc
bulng .
Phc hi piston bm cp nhin liu kiu piston bng phng php m Crm
ti kch thc sa cha, cn xi lanh th doa va tin hnh r theo kch thc ca
piston.
B mt van b mn th gia cng phay ti ht mn. Nu sau khi gia
cng phay m trn lng ca cc van khng t yu cu th tin hnh r.
Phc hi cc van hnh nm bng cch r trn mt mt trn bn r bng
1.Thn bn, 2.van tng p, 3.ng dn du n bnh lc tinh 4. ng thot nhin liu , 5.ng np nhin liu 6. Van np nhin liu, 7.l xo piston, 8.piston, 9. con i, 10.trc lch tm, 11.cn piston
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gang ph lp bt r.
Kh mn van (mt vt) lp vi vin bi trong bm tay trn my tin.
Nu khe h piston v xylanh bm vt qu gii hn cho php th tin
rnh theo ng knh ngoi ca piston ri lp vo mt pht bng cao su chu
c du (nu nh trc y cha c).
Nu b t hay mn ren ch lp nt ren ca van th khoan rng, ri
ct ren mi v lp vo trong v bm ming tp c ng knh tiu chun; nu hng
ren lp bulng hoc ca u ni ng th lp vo v bm ng ni chuyn i.
Cc l xo van v piston khng p ng c yu cu k thut ca nh
ch to th cn thay mi.
- Nu khe h piston v xilanh bm vt qu gii hn cho php th tin rnh
theo ng knh ngoi ca piston ri lp vo mt pht bng cao su chu c
du,
3.3.2. Bm hi chuyn (bm phin trt). 2 3
4
5
6
7
1 8
Hnh 2.24: Bm phin trt.
1. nhin liu vo; 2.v bm; 3.vt iu chnh; 4. l xo; 5. nhin liu ra ca;
6. cm kn nhin liu; 7. a; 8. van an tn; 9. rto; 10. trc;
Nguyn l hot ng :
Bm c 2 cnh 3 bng gang, t trong rto thp, c p vo v 2 nh lc l
xo 4 v lc ly tm ca bn thn n khi rto ang quay.
Nhin liu vo ca 1, ra ca 5. Khi p sut khoang 5 vt qu 4
KG/cm2 th van an ton 8 m ra. Trc ca rto chuyn ng qua a 7 v c lm
kn bi cm kn du s 6.
3.4. Bnh lc nhin liu.
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3.4.1. Lc th nhin liu.
Hnh 2.27 l lc th nhin liu, b phn chnh ca lc l li lc 2 hnh
phu nm trong cc 1. Nhin liu i vo bnh lc th theo ng ng 6, do thay i
t ngt hng chuyn ng, nhin liu sch qua li lc ln rnh trong ng ni
gia. Cn cc cn c hc vng ra, ri xung y cc. cn ny khng xo trn
trong cc lc trn y cc c lm mt cnh lm lng 7 hnh phu.
Chm sc bnh lc th, ngi ta thng k x cn v ra bnh lc. X
cn sau 50 gi lm vic ng c. Ra bnh lc sau 960 gi. Tho li lc. Ra cn
thn cc lc 1, cnh lm lng 7 v li lc 2. Ra li lc trong nhin liu diesel
n khi ht cn bn.
Sa cha, lp v th bu lc th nhin liu
Cc h hng chnh ca cc chi tit bu lc nhin liu l nt rn v b mt bt
vo thn ng c; nt, t, mn ren. Cc vt nt ngoi c hn hoc dn bng
nha pxt. Sau khi hn dn th kim tra kn ca cc chi tit.
Ra cc li lc th nhin liu bng cch nhng chng vo chu du ha t 10
- 15 pht. C sau 3 4 pht lc mt lt. Sau khi ra kim tra cc phn t nhn thy
c bng mt v hn cc ch b hng. Tng din tch hn trn li lc cho php
khng qu 1cm2.
Nhng cc li lc bn vo trong du ha sch, dch trt cc bn lc vi
nhau v lc cc phn t cc mui bn bm gia cc bn lc ri ra.
Hnh2.27:Lc th nhin liu. 1. cc 2. li lc v li lc 3. vng p 4. thn bu lc 5. ng nhin liu vo 6. ng nhin liu ra 7. cnh lm lng 8. nt x cn
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3.4.2. Lc tinh nhin liu.
Bnh lc c hai cc 5. Bn trong mi cc li c mt phn t lc 9. Phn t
lc gm c mt ng cc tng vi nhiu l bn cho nhin liu i qua, c hai np
cng hai u v bn trong l mt hp giy lc c bit ch to theo kiu n xp,
hai cc lc c chung mt np. Trong np c van ba ng 19, cho php ra cc khng
cn tho. Hai cc lm vic song song. Khi van ba ng v tr lm vic nhin liu
i t bm thp, qua van ba ng ng thi vo c hai cc, qua hp giy lc i vo
bm cao p.
Nguyn tc lm vic : nhin liu s trc tip thm t t theo hng t ngoi
vo trong qua li lc, cn cn s c gi li li lc.
*/ Nhng h hng thng gp v cch sa cha:
- li lc lu ngy b mc hoc cn cn bm nhiu.- cn thay li lc mi.
- c th b nt do anh hng nhit ca ng c i vi b mt ang tip
xc ca bnh lc.- cn hn kn li. Mun ra bnh lc bn tri, dng cl xoay van ba ng cho cnh gia ca van
hng v cc bn phi. Ni c di y cc bn trai vi vng. Cho ng c lm
vic s vng quay ln nht. Lc ny nhin liu ch i qua cc bn phi, sau khi
thm vo hp giy lc bn trong mt phn ln tip tc i vo bm cao p, cn mt
phn thm vo bn trong hp giy lc ca cc bn tri ri t bn trong thm chy ra
bn ngoi, nh vy m lm sch c cn bn bm bn trong hp giy lc. ra
Hnh 2.28: Bu lc tinh 1. l x cn; 2, 3, 11, 16. bulng 4. van bi; 5 Cc; 6. l xo 7. a vng bt du; 8. vng bt du 9. li lc; 10, 12, 23. m 13, 14. ai c; 15. vt cy 17. ng lt; 18. bch ca van 19. nt ren ca van 20, 22. vng pht 21. vng hm
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cc bn phi, xoay van ba ng theo chiu ngc li.
3.5. B iu chnh tc (b iu tc).
Chc nng, yu cu, nhim v:
Chc nng, nhim v: t ng thay i lng nhin liu ph hp khi c s
thay i tc ca ng c.
Yu cu: - phi thay i lng nhin liu sao cho ph hp nht.
- c cu phi n gin, d s dng, gi c hp l, d bo dng.
iu kin lm vic:
Lm vic trong iu kin tc ng c thay i, c khi tng tc, c khi
gim tc.
3.5.1. B iu tc chn khng.
Cu to :
12
1011 9 8
7
14
13
15
16
5
6
34
2
1
Nguyn l hot ng :
Khi ng c chy, khng kh qua bnh lc 1 v hng 3 i vo ng ng
ht 5. Khi bm gi v tr nht nh, nu thay i s vong quay ca ng c th
tc khng kh s thay i theo v do lm thay i chn khng ca hng.
Khi cng tng s vng quay ca ng c th chn khng trong ngn 14 cng tng
B iu tc chn khng nhiu ch .
1. bnh lc khng kh; 2. tay iu khin tc ;
3. hng; 4. bm gi;
5. ng ng ht ca ng c; 6. nt ko ;
7. thanh rng bm cao p
8. l thng vi kh tri;
9. ngn bn phi ca b iu tc
10. l xo iu tc; 11. l xo ; 12. cht ta;
13. vt iu chnh, 14.ngn tri ca b iu tc,
15.mng mng, 16.ng ni.
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lm cho mng 15 cng p l xo 10 ko thanh rng bm cao p sang tri v pha
gim nhin liu. Nu gim s vng quay ca ng c th chn khng s gim
theo v l xo 10 s y mng 15 ra v thanh rng bm cao p sang phi v pha tng
nhin liu.
Mi v tr ca bm gi do tay n 12 iu khin s tng ng vi mt ch
tc ca ng c. Cng m rng bm gi th ch tc ca ng c cng
ln.
L xo 11 cn tc dng lm tng n nh ca b iu tc khi ng c chy
chm ch khng ti hoc t ti. Vt 13 dng iu chnh lc cng ca l xo
11. trong qu trnh thanh rng bm cao p chuyn v pha gim nhin liu, khi ti v
tr no , thanh rng s t ln cht ta 12 qua p l xo 11. Nu chuyn v pha
tng nhin liu thanh rng cng s t ln cht hn ch lng nhin liu t nht. Nt
ko 6 dng ct nhin liu khi tt my. Nt ko 6 keo thanh rng s p cc l xo
10 v 11 chuyn v v tr ct nhin liu.
- u, nhc im :
u im chnh ca b iu tc ny l cu to n gin kch thc nh, lc
dng iu khin ch tc ca ng c tng i nh khng cn cc chi tit
mi mn.
Nhc im chnh ca b iu tc chn khng l phi lp hng v lp bm
gi trn ng ng ht do lm gim bt 20 30% tit din lu thng ca ng ng, lm gim h s np v do gim cng sut ca ng c.
-Phm vi s dng :
Ngi ta thng lp b iu tc chn khng trn cc ng c Diesel vn ti
cao tc hot ng trong mt phm vi tc tng i rng.
H hng v sa cha:
L xo iu tc lu ngy b gin, cng khng cn ph hp - cn thay mi.
Mng chn khng b rch, vic to chn khng khng ng theo yu
cu.- thay mi.
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3.5.2. B iu tc c kh.
Cu to v nguyn l hot ng :
Hnh 2.30: B iu tc c kh.
1. vt gii hn; 2. tay n; 3. trc b iu tc; 4. ln ta;
5. bnh rng truyn ng; 6. bi; 7. qu vng; 8. chc ch thp; 9. thanh ko;
10. trc ming vt nghing; 11. ming vt nghing; 12. vt m c; 13. na; 14. l xo
ngoi;15 l xo trong; 16; trc qu vng;17. bc trt;
18.bulng gii hn; 19. l xo kp; 20. vnh ta.
Nguyn l hot ng:
B iu tc thuc loi ly tm, mi ch . Trc iu tc 3 quay nh
bnh rng truyn ng 5 vi bnh rng trn trc bm cao p. Khi trc 3 quay, qu
vng 7 vng ra, chn ca n y bc trt 17 v na 13, ko thanh ko 9 v do
ko tay thc bm cao p v pha gim hay tng cung cp nhin liu, l im bt
u tc ng b iu tc.
Ngha l: khi ko thc nhin liu ra xa th nhin liu s c tng ln, v
khi thc nhin liu ko v gn th gim lng nhin .
u, nhc im :
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u im chnh ca b iu tc ny l lc l xo iu tc v lc ly tm ca qu vng ch tc dng ln khp trt v bi ca khp trt, cn li tt c cc c
cu khc u khng chu tc dng ca hai lc y. Do tui th v tin cy ca
b iu tc ny tt hn. Ngoi ra tc dng ca ngi iu khin trn tay iu khin
rt nh.
Nhc im chnh ca b iu tc ny l cu to hi phc tp, kch thc hi ln v cn nhiu chi tit, ngi ra cc ch tc thp, khng ng u
ca b iu tc cng tng i ln.
H hng v sa cha:
Do y l b iu tc kiu c kh nn hao mn do ma st l kh trnh khi,
rng ca bnh rng truyn ng b mn, bi b mn, l xo khng cn cng.
i vi l xo c th thay mi.
3.5.3. B iu tc thy lc.
Nguyn l hot ng :
Nu tng s vng quay ca trc khuu, s lm tng s vng quay ca bm
chuyn nhin liu 4, do lm tng p sut nhin liu trn ng ng C, mt khc
van trt ly tm 2 cng chy xa tm quay lm tng p sut nhin liu trong xylanh
cng tc 6 ca b iu tc. Do p sut nhin liu tng, nn piston 9 b y sang phi
p l xo 10 v lm xoay van 7 v pha gim nhin liu. C th dng tay iu khin
12 thay i bin dng ban u ca l xo 10. V vy b iu tc ny l b iu tc
nhiu ch . Khi nht ca nhin liu thay i, van trt ly tm 1 cn th t
ng thay i tit din ng B v ng C sao cho p sut nhin liu trong khng
gian A ch ph thuc vo s vng quay ca ng c.
B iu tc thy lc. A. Khng gian trong ca rto; B.
ng nhin liu ra;
C. ng nhin liu vo; D. ng
nhin liu ;
1. rto; 2. van trt ly tm; 3. l xo;
4. bm chuyn nhin liu;
5. van trn ; 6. xylanh b iu tc; 7.
van; 8. cht ko; 9. piston;
10. l xo; 11. bm cao p ; 12. tay
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u, nhc im :
-u im chnh ca b iu tc thy lc l cu to n gin, kch thc nh,
cc chi tit vn ng u c bi trn tt nn t mn.
-Nhc im :
1. H s lu lng ti van tit lu ph thuc vo nht ca nhin liu,
m nht li thay i theo nhit , v vy nu trng thi nhit ca ng c thay
i s lm thay i ch tc v do lm s vng quay iu chnh ln nht
ca ng c khng n nh.
2. Nu trong thng ht nhin liu hoc b tc ng ng t thng cha
ti bm chuyn nhin liu th s vng quay ca ng c s tng vt ln v ng c
c th tip tc s dng nhin liu d tr trong bnh lc chy thm mt thi gian
na.
3.6. B t ng iu chnh gc phun sm: Chc nng, nhim v: phun lng nhin liu ng thi im, ng lng
cn cung cp sao cho to c hn hp chy l ti u ng thi gim c lng
nhin liu d tha khi phun khng ng thi im.
Yu cu: c cu n gin, lm vic an ton, d dng sa cha v bo
dng.
3.6.1. B t ng iu chnh gc phun sm kiu ly tm.
a/ cu to :
76 8
910
D
54
1112
2A3C B 1
6
5
7
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b/ nguyn l hot ng :
Khi tng s vng quay trc cam, qu vng 3 vung ra quanh trc 2, lc
y chn qu vng a y ng then hoa 8 sang tri.
Nu gim s vng quay, l xo 1 s y ng then hoa sang phi. ng then hoa
8 dng then hoa xon, mt u xon tri, cn u kia xon phi.
V vy khi chuyn dch ng then hoa 8 s lm cho gc phun sm tng ln
hoc gim xung.
Thng thng nng lng ca qu vng khng y ng then hoa di
chuyn. V vy thng phi lp thm mt b khuych i nhm tng lc y .
Hin nay thng dng khuch i thy lc.
3.6.2. B t ng iu chnh gc phun sm thy lc.
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1
3
2
4
6
5
7
EBD
A9 8
Hnh 2.34: B t ng iu chnh gc phun sm thy lc.
A. Khng gian hnh vnh khn; B, C. L dn du;
D. Khng gian cha du; E. L ;
1. bnh rng dn ng bm cao p; 2. gi qu vng; 3. qu vng;
4. van ca b khuch i; 5. l xo ca ng trt; 6. l xo ca piston;
7. piston ca b khuch i; 8. u then hoa ca trc dn ng ; 9. ng then
hoa
Nguyn l hot ng :
Gi ca hai qu vng 3 c bt cht trn bnh rng 1 ca trc cam dn
ng bm cao p. Hai qu vng 3 ng thi tc dng ln ng trt 4. Bn thn ng
trt li l mt van iu khin c cu khuch i. Piston 7 ca c cu khuch i
c p cht ln ng then hoa 9. Mt ngoi ca ng then hoa l then hoa thng, cn
mt trong l ng then hoa xon, ng then hoa ny lp vo ng then hoa 8 ca trc
dn ng bm. Cn mt ngoi ca ng then hoa li n khp vi tang bnh rng 1.
Gi 2 ca qu vng c dng lm xylanh ca piston 7.
Du ca h thng bi trn ca ng c i vo khng gian hnh vnh khn A
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sau qua l B, l C vo khng gian D ri qua l E ti xylanh.
Khi tc ca ng c tng ln, qu vng y ng trt sang phi.
M l E v du nhn t khng gian D i vo xylanh khuch i. Lc y, lc do p
sut du tc dng ln piston ln hn lc n hi ca l xo nn piston 7 chuyn dch
sang phi.
Chuyn dch ca piston ko theo chuyn dch ca ng then hoa v thng qua
rnh then hoa n khp vi tang bnh rng lm cho trc bm c quay tng i so
vi v tr ca bnh rng nh lm tng gc phun sm. Khi l E b che kn th ng
trt i ti mt v tr n nh mi v piston dng li, khng chuyn dch na. Nu
gim s vng quay ca ng c, l xo 5 s y ng trt sang tri ti v tr mi ng
kn l du E, lc y gc phun sm s gim.
Vi gc nghing ca then hoa l 170 v ng knh ngoi ca trc cam l 35
mm th c chuyn dch ca piston khuch i i 5 mm s ng vi gc quay ca trc
cam l 50.
3.7. Van iu p.
Hnh 2.35: Kt cu v hot ng ca van iu p.
1 l trn; 8 l gia; 2 l xo; 9 l thot
3 l xo iu p; 10 rcco; 4 xylanh; 11 li lc nylon
5 piston; 12bu lng; 6 l xo mi; 13 chn chn
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7 l np; 14 m kn cao su
Van iu p gn trong np y ca bm chuyn ca bm cao p cm gm
c: Xylanh (4) cha piston (5). L xo mi (6) lun lun nng piston (5) i ln. Bn
trn piston c l xo iu p (3), trn van iu p c rcco (10) nhn nhin liu np
vo t bu lc th cp. Rcco ny vn ren vo v van iu p, n ln l xo (2) v
chn chn (13) gi cht xylanh (4). Bu lc nhin liu bng li nylon dy (10)
bao ngoi l xo (2) v phn xylanh (4) lc nhin liu ln cui cng.
Bn hng van iu p c 2 l: L thot (9) thng vi mch vo ca bm
chuyn vn, l np (7) thng vi mch thot ca bm chuyn vn, cht nh v (12)
dng nh v vng lch tm ca bm chuyn vn.
Van iu p m trch 2 vic:
Cho nhin liu lu thng x gi.
Duy tr p sut nhin liu chuyn vn c nh cn thit khi ng c hot
ng.
Hot ng ca van iu p gm 3 giai on:
Giai on ngng: Giai on ng c ngng, bm tay ca bm chuyn
ng yn. Piston (5) xung st y xylanh (4), c l xo mi (6) ln ng kn
l (7) chn khng cho nhin liu trong bm tt v thng cha.
Giai on bm tay x gi: x gi trong ton b h thng, ta tc ng
cn bm tay ca bm chuyn nhin liu chui vo rcco (11) qua lp li lc cui
cng chui vo l trn (1) ni xylanh (4) n piston (5) m l (7) nhin liu vo
u du gi.
Giai on ng c vn hnh: Lc ny trc cam bm cao p quay, bm
chuyn vn y nhin liu vo l (7) ca b iu p chui xung mt di piston (5)
v nng piston ny ln. Nu vn tc trc cam tng, p sut chuyn vn ca nhin
liu vt mc n nh, piston (5) s b nng ln cao hn, p l xo iu p (3) v m
l (8) ni xylanh (4) cho nhin liu v l trn (9) tr li mch np ca bm tip vn,
p sut chuyn vn gim ngay. Nu ngc li piston (5) i xung, y t hn hoc t
hn. S di chuyn ca piston u do p sut nhin liu, ph thuc vo tc ca
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ng c.
IV. Cc bin php kt cu nhm ci thin cht lng to hn hp chy:
4.3. Cc yu t nh hng ti cht lng hn hp chy:
C hai yu t c bn:
-Nhin liu.
- H thng to hn hp chy:
. i vi ng c xng: b ch ha kh hoc h thng phun xng.
.i vi ng c diesel: h thng phun nhin liu
.Ngoi ra cu hnh ca bung t , h thng np x c nh hng ln n cht
lng qu trnh to hn hp chy.
4.4.Cc bin php kt cu nhm ci thin cht lng hn hp chy
A/ Theo hng c in:
4.4.1. p sut phun:
- t c s lm vic tin cy, kinh t ca ng c cn phi phun
vo xilanh lng nhin liu cp cho chu trnh vi gc phun sm cho v phun
sng.
- Mt trong cc yu t quan trng nh hng n cht lng phun
nhin liu l p sut ca n trc vi phun gi l p sut phun
- Khi ch to ng c c hnh trnh piston ln , ngi ta c xu hng
tng p sut phun ln cao(130MPa) vi mc ch rt ngn thi k phun v ci thin
cht lng nhin liu
* c tnh thay i p sut phun ph thuc vo :
- ch lm vic ca ng c
- cc thng s kt cu ca h thng cp nhin liu
- tnh cht vt l ca nhin liu
- Nu gi thit khng c s r lt nhin liu qua cc khe h vi phun v b
qua nht , co gin ng ng cao p th sut tiu hao nhin liu th thch
qua vi phun bng lng cp nhin liu th tch bm .
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- Tc nng piston BCA ph thuc vo bin dng cam ca bm, tc ln nht
t c khi nng ca piston bm t mt na ng vi phn dc nht ca bin
dng cam. Nhin liu c cp vo xilanh trong thi gian ny c p sut cao v bo
m phun tt.
Ngi ta dng h s Co lm thng s c trng cho mi dng cam .Hnh
trnh cp nhin liu ca piston bm cao p c t ti khu vc c Co ln nhm
m bo tnh dt khot ca th im bt u cng nh kt thc cp nhin liu,
ng thi duy tr p sut phun tng i cao trong sut thi gian cp nhin liu.
Ngt nhin liu khi tc piston cao cui thi k phun s m bo gim
nhanh p sut phun v ng dt khot thi im phun s m bo gim nhanh p
sut phun v ng dt khot kim phun, iu ny rt quan trng v nu p sut phun
gim t t lm kim phun ng chm nn s c th xy ra hin tng ng git
nhin liu lm cht lng phun xu i nh hng xu n qu trnh chy.
- Hin tng phun rt l hin tng m do dao ng mnh p sut nhin liu
sau khi ng, kim phun c kh nng m tr li sau khi ng. Phun rt lm tng
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thi k chy trn ng gin n nh hng n qu trnh chy. Ngha l p sut
phun ln vi mc ph hp l tt nhng cn phi trit tiu dao ng sng ca
nhin liu trnh hin tng phun rt. Gii php: t trong vi phun van trit hi
ngn cch vi ng ng cao p gim phn x sng p sut
4.4.2. Cht lng phun nhin liu:
- Cht lng nhin liu c c trng bng nhiu ch s, quan trng nht
trong cc ch s l mn v ng nht. mn c nh gi bng ng
knh ht , cn ng nht c nh gi bng s ging nhau ca cc ng knh
ht.
Yu cu l mn v ng nht tng th cht lng phun c ci thin. Vi ng c thp tc th ng knh trung bnh ca ht nhin liu l 15-25m
, cao tc l5-10m.
- nh gi ng thi tn x v ng nht phun , ta dng th biu
din s ph thuc gia ng knh ht v s lng ht tng i.
ng c tnh phun nhin liu cng gn trc tung, phm vi ng knh ht
cng hp th mn v ng nht cng tt
Vd: phun mn v ng nht tt (qua 4 l ng knh 0,4mm) ngs vi
ng c tnh 1, phun th nht ( qua 1 l 0,8mm) ng vi ng c tnh 3 ,
ng c tnh 2 ng vi phun qua 2 l ng knh 0,57mm.
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Khi cc ht c kch thc nh, ng u nn s tng c b mt tip xc
ca khng kh vi nhin liu, dn n tng tc qu trnh trao i nhit v do cht
lng cng tc trong xilanh ng c tt hn, cgn vi tng vng quay trc khuu v
mc cng ho, gim kch thc xilanh th cht lng phun nhin liu s c
tng ln.
4.4.3. nh hng ca kt cu l phun
Qu trnh phun nhin liu c thi gian ri lon nn tnh c bit kt cu thit
b phun c kh nng to ri dng nhin liu khi lu ng qua ; tn x ,
ng nht tng khi tng nhn mp vo, nhm b mt pha trong l phun.
- ng knh l phun l mt trong cc yu t kt cu quan trng nh hng
r rt n cht lng phun; Theo thc nghim khi gim ng knh vi phun v
tng s l phun , vi cc yu t khc c gi nguyn th cht lng phun c
tng ln.
- T s gia chiu di Lpo vi ng knh l phun Dpo nh hng n cht
lng to hn hp , phun v tn x nhin liu tt nht khi Lpo/Dpo =3 l tt , vi
iu kin ny th nhin liu ra khi l phun t ti tc ri lon ln nht.
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T hnh v thy r , khi gim ng knh l phun nhin liu c phun mn
hnv ng nht hn.
4.4.4. Cch t vi phun nhin liu
- Kt hp vi cc dng bung chy khc nhau, s c cc cch t v tr vi
phun khc nhau sao cho qu trnh to hn hp chy l thch hp nht
a/ i vi bung chy thng nht:
Thng th vi phun t trc tip vo bung chy v thng gc.
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Khi kt hp vi ng kh phun vo tia nhin liu s c nhng chuyn ng
hp l nhin liu c x tan.
b/ i vi bung chy khot su trn nh piston :
Thng th vi phun dt xin, khi c dng xoy khng kh t sng tia thi
phun phn nhin liu bay hi ra ngoi , khin nhng ht nhin liu cn li trong
tia d bay hi , tng tc hnh thnh ho kh.
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c/ i vi bung chy xoy lc:
Vi phun c t bung xoy lc v t xin, nhin liu c
phun vo cung hng vi dng xoy lc, lc cc ht nhin liu nh, nh v tia
b cun theo dng xoy lc , c sy nng , bay hoi cng khng kh nng to ra
ho kh v bc chy khu vc ming ng thng, iu nay lm cho vic chay
c din ra tt hn.
Nu tia nhin liu c phun hng tm hoc lch tm nhng
ngc chiu dng xoy th mng la u tin s xut hin tm bung chy mc d
c li cho vic khi ng nhng d to ra kho nhit nn khng tt tia nhin lieu phun theo chieu dong xoay.
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d/ i vi bung chy d b:
- Vi phun c t trong bung d b.
B. Theo hng hin i :
Nhm nng cao cht lng qu trnh to hn hp chy trong ng c Diesel,
khc phc nhng nhc im m h thng nhin liu c ien iu khin bng c
kh vn cn tn ti nh vic nh lng, nh thi im phun cha chnh xc, tnh t
ng iu chnh v t ng ha cn hn ch nht l cc ch lm vic khng n
nh nh: khi ng, tng tc, gim tc...v cc c cu h thng (iu tc, thay i
gc phun sm...) lm vic cha nhy lm. Vic p dng cc thit b in t vo h
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thng nhin liu ng c Diesel nhm mc ch gii quyt nhng vn ny, ngoi
ra n cn gp phn gim bt tnh c hi cho mi trng do qu trnh chy ca
nhin liu c chy hon ton hn
H thng gm cc b phn sau:
* B phn cm bin: Gm cc cam bin tc , ti trng p sut kh np,
cm bin LambdaCc cm bin ny cn nhim v ghi nhn cc hot ng ca
ng c cung cp thng tin cho khi thit b iu khin trung tm (CPU).
* B iu khin trung tm (CPU): y l b phn co nhim v tip nhn
thng tin do cc cm bin cung cp. Cc tn hiu c a n t cc cm bin s
c chuyn i thnh cc tn hiu s. B phn x l phi hp nh cc b phn tch
so snh cc thng tin nhn c vi cc d liu lu tr sn trong b nh. T b
iu khin trung tm s cho ra tn hiu lm nhim v iu khin cc c cu phn
phoi chp hnh.
* B phn chp hnh: Cn nhim v thc hin lnh iu khin, ch huy vic
nh lng, thi im phun nhin liu, cng nh ch huy 1 s c cu v thit b khc
nh lun hi kh x, ngng hot ng mt s xylanh, hiu chnh hn hp chy khi
ng c lm vic tc caoNhm m bo s lm vic ti u ca ng c.
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Cam bien khac
Nhiet o ong c
Ap suat nap khong kh
Cung cap thong tin
Bo phan kiem soat v tr thanh rang
BO PHAN CAM BIEN
iem khi phun thc
te
BO IEU KHIEN TRUNG TAM CPU
V tr thc te cua thanh rang
Bo phan kiem soat iem bat aunhien lieu
V tr truc khuyu
Toc o ong c
Xolenoy ieu khien thanh rang
Xolenoy ieu khien t
Kim phun vi bo cam bien tac ong van kim
BM CAO AP PE THE HE MI
S nguyn l hot ng ca h thng nhin liu
vi bm cao p PE trang b h thng in t
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H thng phun nhin liu trang b bm cao p PE iu khin bng in
t.
1.Bnh nhin liu; 2.Bm tip vn;3.Lc th cp; 4.Bm cao p PE; 5.C cu kim st thi im phun nhin liu; 6.C cu iu tc; 7.Vi phun nhin liu; 8.ng dn du v; 9.Buji xng my vb phn kim st; 10.B phn iu khin trung tm; 11n bo kt qu chun on; 12.Cng tc ca b phn li hp; 13B cm bin v tr bn p; 14.B cm bin tc ng c; 15.B cm bin nhit ; 16.B cm bin p sut kh np; 17.Tuabin tng p; 19.Ac quy; 20.Cng tc buji xng my v khi ng
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*/ Cc loi cm bin
a.Cm bin lu lng gi: c nhiu kiu: cnh trt ,Karman ,dy t
Sau y l cm bin kiu cnh trt:
Hot ng:
Dng kh qua lu lng k s tc dng mt lc t l vi lu lng kh ln ca o
3,lm ca ny quay i 1 gc a cho n khi cn bng vi lc l xo xon. Gc a t l
vi in p U sinh ra
Thit b c mi quan h lgarit gia a v th tch khng kh
Nn c nhy cao d lng khng kh nh .
Cnh b tr 4 c tc dng n nh gc ca thit b o v cc sng p sut trong
ng np do ng c hot ng khng lin tc.
Trn cm bin cn c gn cng tt bm nhin liu(c lp trn bin tr)
L mt trong
nhng cm bin quan
trng nht
Cnh o gi
c gi cn bng bi
1 l xo hon lc
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b.Cm bin nhit kh np:
Cung cp thng tin v nhit khng kh np.
Cu to: l mt nhit in tr
c. Cm bin nhit nc lm mt :
Cung cp thng tin v nhit ng c :
-Khi ng c lnh :ECU tng lng nhin liu phun vo
-Khi ng c qu nng : gim lng nhin liu
Kt cu v ng c tnh ca cm bin nhit nc lm mt
d/B cm bin vn tc trc khuu: c cc nng theo v c a tn hiu
(pulse ring) gn trn u trc cam . Cn c vo nhng ngt qung tn hiu ca a
ny, vi tnh s quyt on c vn tc thc t ca ng c.
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e/ B cm bin ghi nhn v tr thanh rng: s khc bit ca v tr thanh rng so vi v
tr chun (set point) s thnh tn hiu vi b iu tc.
f/ Cm bin Lamda
Xc nh nng oxi trong kh thi,sau a tn hiu v ECU kt hp
vi thng tin t cm bin ghi nhn v tr thanh rng cung cp lng nhin liu
cho ln tip theo
*/Lm m trong v sau khi khi ng
Trong qu trnh lm m ny s tng lng phun, ph thuc vo
nhit nc lm mt (lng phun s ln khi nhit nc lm mt thp), nng
cao kh nng khi ng v ci thin tnh n nh hot ng trong mt khong thi
gian nht nh sau khi ng c khi ng. Lng phun s gim dn n lng
phun c bn.
*/ Hiu chnh tng gim lng nhin liu
Khi tc ng c vt qu gi tr nh trc hoc khi xe xung dc tn
hiu c truyn t cm bin tc v ECU, sau ralnh cho b iu tc gim
li lng nhin liu, nn nhin liu chy ht v sch hn, t gy nhim mi
trng.
*/Hiu chnh m khi tng tc
Lc cn vt qua mt t lu thng cng chiu, phi iu khin cho xe tng
tc tc th. trong ch ny cn phi phun thm nhin liu kp thi tng tc t
nhanh chng. Hp ECU nhn c tn hiu tng tc nh b cm bin lu lng
dng kh np. Khi bm ga m ln t xut, khi lng kh np tng vt ln, mm
o ca b cm bin dng kh np xoay dch chuyn mt gc ln hn. Hp ECU
nhn c tn hiu ny s ch huy phun thm nhin liu, iu chnh t l kh hn
hp c h s d lng khng kh phu hp
Lm giu hn hp ch ton ti
ch tn ti, ng c pht huy cng sut ti a, v vy cn phi cung cp
cho ng c mt lng nhin liu hn so vi ch ti mt phn. Trong ch ti
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mt phn, lng nhin liu dng nh mc ti thiu, mc c hi trong kh
thi tng i thp. Tuy nhin ch tan ti, bt buc lng nhin liu phi nhiu
hn hn. Vic iu chnh nhin liu cn thit ny c lp trnh sn trong b s l vi
iu khin in t ECU.