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TKMH Tnh ton v thit k ly hp
TKMH Tnh ton v thit k ly hp2014
LI NI U Sau hn 25 nm i mi,t nc ta t c rt nhiu thnh tu trong pht trin kinh t -x hi, khoa hc- k thut. Ngnh cng nghip t cng ang trn pht trin vi vic lin doanh,lin kt vi nhng cng ty sn xut t hng u th gii nh TOYOTA, FORD, GM, HONDA... gp phn p ng nhu cu vn chuyn hng ha v i li ca ngi dn ngy mt tng.Hin nay,vic nng t l ni a ha cc cm tng thnh trong t lp rp ti Vit Nam c khuyn khch pht trin v mc tiu xa hn l chng ta s sn xut ra hng xe t mang thng hiu Made in Vit Nam . L sinh vin chuyn ngnh c kh t , vic tm hiu, nghin cu, tnh ton v thit k cc b phn, cm my, chi tit trong xe l rt thit thc v b ch. Trong khun kh gii hn ca n mn hc ny, em xin c trnh by thit k v tnh ton h thng ly hp trn xe khch. Cng vic ny gip cho em bc u lm quen vi cng vic thit k m em c hc trng ng dng cho thc t, ng thi n cn gip cho em cng c li kin thc sau khi hc cc mn l thuyt trc . Trong qu trnh hon thin n em xin chn thnh cm n s gip tn tnh ca thy Ths. Nguyn Hng Qun . Mc d c gng song do kh nng c hn nn n khng khi c nhng sai st mong thy c gp n tt hn.Em xin chn thnh cm n! Sinh vin thc hin Ng Tin Dng
MC LCLI NI UChng I: TNG QUAN4I.1. V TR4I.2. CNG DNG LY HP4I.3. PHN LOI LY HP 4I.4. YU CU LY HP 7I.5. TRNH T THIT K 7Chng II: TNH TON V THIT K8II.1. CC THNG S U VO 8II.2. LA CHN S 8II.2.1. S cu to ca ly hp loi a ma st kh 8II.2.2. Cu to chung ca loi a ly hp ma st kh 11II.2.3. Nguyn l lm vic ca loi a ly hp ma st kh 12II.3. PHN TCH V LA CHN KT CU 14II.4. TNH TON, THIT K CC THNG SCA LY HP 22II.4.1. Xc nh m men ma st ca ly hp 22II.4.2. Xc nh kch thc c bn ca ly hp 22II.4.3. Xc nh cng trt sinh ra trong qu trnh ng ly hp 24II.5. TNH TON SC BN MT S CHI TIT CA LY HP 27II.5.1. Tnh sc bn a b ng 27II.5.2. Tnh sc bn moay a b ng30II.5.3.Tnh ton sc bn ca l xo a 31II.5.4. Tnh sc bn trc ly hp39II.6. TNH TON H THNG DN NG LY HP 47II.6.1. Xc nh lc tc dng ln piston cng ha 47II.6.2. Xc nh hnh trnh ca bn p St50II.6.3. Tnh van iu khin51 Chng III: THIT LP BN V 52III.1. C S THIT LP BN V 52III.2. THIT LP BN V KT CU 53TI LIU THAM KHO55
Chng ITNG QUANI.1. V TRTrong h thng truyn lc c kh ,ly hp c b tr nm gia ng c v hp s. Ly hp nm ta trn bnh ca ng c v truyn m men ng c ti trc b ng.I.2. CNG DNG LY HPTrong h thng truyn lc ca t, ly hp l mt trong nhng cm chnh, n c cng dng l :- Ni ng c vi h thng truyn lc khi t di chuyn.- Ngt ng c ra khi h thng truyn lc trong trng hp t khi hnh hoc chuyn s.- m bo l c cu an ton cho cc chi tit ca h thng truyn lc khng b qu ti nh trong trng hp phanh t ngt v khng nh ly hp. h thng truyn lc bng c kh vi hp s c cp, th vic dng ly hp tch tc thi ng c ra khi h thng truyn lc s lm gim va p gia cc u rng, hoc ca khp gi, lm cho qu trnh i s c d dng. Khi ni m du ng c ang lm vic vi h thng truyn lc (lc ny ly hp c s trt) lm cho mmen cc bnh xe ch ng tng ln t t. Do , xe khi hnh v tng tc m.Cn khi phanh xe ng thi vi vic tch ng c ra khi h thng truyn lc, s lm cho ng c hot ng lin tc (khng b cht my). Do , khng phi khi ng ng c nhiu ln.I.3. PHN LOI LY HP Ly hp trn t thng c phn loi theo 4 cch :- Phn loi theo phng php truyn mmen.- Phn loi theo trng thi lm vic ca ly hp.- Phn loi theo phng php pht sinh lc p trn a p.- Phn loi theo phng php dn ng ly hp. I.3.1. Phn loi theo phng php truyn m menTheo phng php truyn mmen t trc khuu ca ng c n h thng truyn lc th ngi ta chia ly hp ra thnh 4 loi sau :Loi 1 : Ly hp ma st : l ly hp truyn mmen xon bng cc b mt ma st, n gm cc loi sau :- Theo hnh dng b mt ma st gm c :+ Ly hp ma st loi a (mt a, hai a hoc nhiu a).+ Ly hp ma st loi hnh nn.+ Ly hp ma st loi hnh trng.Hin nay, ly hp ma st loi a c s dng rt rng ri, v n c kt cu n gin, d ch to v khi lng phn b ng ca ly hp tng i nh. Cn ly hp ma st loi hnh nn v hnh trng t c s dng, v phn b ng ca ly hp c trng lng ln s gy ra ti trng ng ln tc dng ln cc cm v cc chi tit ca h thng truyn lc.- Theo vt liu ch to b mt ma st gm c :+ Thp vi gang.+ Thp vi thp.+ Thp vi phra hoc phra ng.+ Gang vi phra.+ Thp vi phra cao su.- Theo c im ca mi trng ma st gm c :+ Ma st kh.+ Ma st t (cc b mt ma st c ngm trong du).u im ca ly hp ma st l : kt cu n gin, d ch to.Nhc im ca ly hp ma st l : cc b mt ma st nhanh mn do hin tng trt tng i vi nhau trong qu trnh ng ly hp, cc chi tit trong ly hp b nung nng do nhit to bi mt phn cng ma st.Tuy nhin ly hp ma st vn c s dng ph bin cc t hin nay do nhng u im ca n.Loi 2 : Ly hp thy lc : l ly hp truyn mmen xon bng nng lng ca cht lng (thng l du).u im ca ly hp thy lc l : lm vic bn lu, gim c ti trng ng tc dng ln h thng truyn lc v d t ng ha qu trnh iu khin xe.Nhc im ca ly hp thy lc l : ch to kh, gi thnh cao, hiu sut truyn lc nh do hin tng trt.Loi ly hp thy lc t c s dng trn t, hin ti mi c s dng mt s loi xe t du lch, t vn ti hng nng v mt vi t qun s.Loi 3 : Ly hp in t : l ly hp truyn mmen xon nh tc dng ca t trng nam chm in. Loi ny t c s dng trn xe t.Loi 4 : Ly hp lin hp : l ly hp truyn mmen xon bng cch kt hp hai trong cc loi k trn (v d nh ly hp thy c). Loi ny t c s dng trn xe t.I.3.2. Phn loi theo trng thi lm vic ca ly hpTheo trng thi lm vic ca ly hp th ngi ta chia ly hp ra thnh 2 loi sau :Ly hp thng ng : loi ny c s dng hu ht trn cc t hin nay.Ly hp thng m : loi ny c s dng mt s my ko bnh hi nh C - 100 , C - 80 , MTZ2 ...I.3.3. Phn loi theo phng php pht sinh lc p trn a pTheo phng php pht sinh lc p trn a p ngoi th ngi ta chia ra cc loi ly hp sau :Loi 1 : Ly hp l xo : l ly hp dng lc l xo to lc nn ln a p, n gm cc loi sau :- L xo t xung quanh : cc l xo c b tr u trn mt vng trn v c th t mt hoc hai hng.- L xo trung tm (dng l xo cn).Theo c im kt cu ca l xo c th dng l xo tr, l xo a, l xo cn.Trong cc loi trn th ly hp dng l xo tr b tr xung quanh c p dng kh ph bin trn cc t hin nay, v n c u im kt cu gn nh, to c lc p ln theo yu cu v lm vic tin cy.Loi 2 : Ly hp in t : lc p l lc in t.Loi 3 : Ly hp ly tm : l loi ly hp s dng lc ly tm to lc p ng v m ly hp. Loi ny t c s dng trn cc t qun s.Loi 4 : Ly hp na ly tm : l loi ly hp dng lc p sinh ra ngoi lc p ca l xo cn c lc ly tm ca trng khi ph p thm vo. Loi ny c kt cu phc tp nn ch s dng mt s t du lch nh ZIN-110, POBEDA...I.3.4. Phn loi theo phng php dn ng ly hpTheo phng php dn ng ly hp th ngi ta chia ly hp ra thnh 2 loi sau :Loi 1 : Ly hp iu khin t ng.Loi 2 : Ly hp iu khin cng bc. iu khin ly hp th ngi li phi tc ng mt lc cn thit ln h thng dn ng ly hp. Loi ny c s dng hu ht trn cc t dng ly hp loi a ma st trng thi lun ng.Theo c im kt cu, nguyn l lm vic ca h thng dn ng ly hp th ngi ta li chia ra thnh 3 loi sau :- Dn ng bng c kh.- Dn ng bng thy lc v c kh kt hp.- Dn ng bng tr lc : c th bng tr lc c kh (dng l xo), tr lc bng kh nn hoc tr lc bng thy lc. Nh c tr lc m ngi li iu khin ly hp d dng, nh nhng hn.
I.4. YU CU LY HPLy hp l mt trong nhng h thng ch yu ca t, khi lm vic ly hp phi m bo c cc yu cu sau :- Truyn ht mmen ca ng c m khng b trt bt k iu kin s dng no. Mun vy th mmen ma st ca ly hp phi ln hn mmen cc i ca ng c (c ngha l h s d tr mmen ca ly hp phi ln hn 1).- ng ly hp phi m du, gim ti trng va p sinh ra trong cc rng ca hp s khi khi hnh t v khi sang s lc t ang chuyn ng.- M ly hp phi dt khot v nhanh chng, tch ng c ra khi h thng truyn lc trong thi gian ngn (v m khng dt khot s lm cho kh gi s c m du).- Mmen qun tnh phn b ng ca ly hp phi nh gim lc va p ln bnh rng khi khi hnh v sang s.- iu khin d dng, lc tc dng ln bn p nh.- Cc b mt ma st phi thot nhit tt.- Kt cu ly hp phi n gin, d iu chnh v chm sc, tui th cao. Ly hp lm b phn an ton trnh qu ticho h thng truyn lc.Tt c nhng yu cu trn, u c cp n trong qu trnh chn vt liu, thit k v tnh ton cc chi tit ca ly hp.I.5. TRNH T THIT K Phn tch kt cu chn phng n thit k ly hp. Xc nh mmen ma st ca ly hp. Xc nh cc kch thc c bn ca ly hp. Xac inh cng trt sinh ra trong qua trinh ong ly hp. Tnh ton sc bn mt s chi tit ch yu ca ly hp. Tnh ton dn ng ly hp. 02 bn v A1: Kt cu ca ly hp, h thng dn ng ly hp. 01 bn v A3: Bn v chi tit.
Chng IITNH TON V THIT KII.1. CC THNG S U VONhim v: Thit k ly hp ma st kh ca t vi s liu ban u :Loi tKhch
Loi ng cXng
Ga1 (KG)3570
Ga2 (KG)6770
Memax / nM (KGm/Vg/ph)41/1900
Nemax / nN (Ml/Vg/ph)150/3200
Ihj I07,44; 4,1; 2,29; 1,47; 1; 7,63
Bnh xe11- 20
Loi l xo pNn bin
Dn ngC kh tr lc kh nn
- Bn knh thit k: - Bn knh trung bnh ca bnh xe: rbx=.r0=533,4. 0,932 = 497 (mm) = 0,497 (m)(V l lp p sut thp nn ly =0,932)- trng lng ton b t Ga=Ga1 + Ga2 = 10340 (KG) =103400 (N)- Memax = 410 (N.m)
II.2. LA CHN S II.2.1. S cu to ca ly hp loi a ma st kh
Hnh 1.1 : S cu to ly hp mt a ma st1 - bnh ; 2 - a ma st; 3 - a p; 4 - l xo p;5 - v ly hp; 6 - bc m;7 - bn p;8 - l xo hi v bn p; 9 - n ko; 10 - cng m; 11 - bi "T"; 12 - n m; 13 - l xo gim chn.
Hnh1.2 : S cu to ly hp ma st hai a1 - bnh ; 2 - l xo a p trung gian; 3 - a p trung gian; 4 - a ma st; 5 - a p ngoi; 6 - bulng hn ch; 7 - l xo p; 8 - v ly hp; 9 - bc m; 10 - trc ly hp; 11 - bn p; 12 - l xo hi v bn p ly hp; 13 - thanh ko; 14 - cng m; 15 - bi "T"; 16 - n m; 17 - l xo gim chn.II.2.2.Cu to chung ca loi a ly hp ma st khi vi h thng ly hp, v mt cu to th ngi ta chia thnh 2 b phn :- C cu ly hp : l b phn thc hin vic ni v ngt truyn ng t ng c n h thng truyn lc.- Dn ng ly hp : l b phn thc hin vic iu khin ng m ly hp.Trong phn ny, ta xt cu to ca c cu ly hp, n gm 3 phn chnh : bnh , a ma st v a p.- Nhm cc chi tit ch ng gm bnh , v ly hp, a p, n m v cc l xo p. Khi ly hp m hon ton th cc chi tit thuc nhm ch ng s quay cng bnh .- Nhm cc chi tit b ng gm a ma st, trc ly hp. Khi ly hp m hon ton cc chi tit thuc nhm b ng s ng yn.Theo s cu to hnh 1.1 : v ly hp 5 c bt c nh vi bnh 1 bng cc bulng, a p 3 c th dch chuyn tnh tin trong v v c b phn truyn mmen t v 5 vo a p. Cc chi tit bnh 1, a p 3, l xo p 4, v ly hp 5 c gi l phn ch ng ca ly hp v chi tit a ma st 2 c gi l phn b ng ca ly hp. Cc chi tit cn li thuc b phn dn ng ly hp.i vi mt s t vn ti khi cn phi truyn mmen ln ngi ta s dng ly hp ma st kh hai a b ng. So vi ly hp ma st kh mt a b ng th ly hp ma st kh hai a b ng c nhng u nhc im sau : Nu cng mt kch thc a b ng v cng mt lc p nh nhau th ly hp hai a truyn c mmen ln hn ly hp mt a. Nu phi truyn mt mmen nh nhau th ly hp hai a c kch thc nh gn hn ly hp mt a. Ly hp hai a khi ng m du hn nhng khi m li km dt khot hn ly hp mt a. Ly hp hai a c kt cu phc tp hn ly hp mt a.Theo s cu to hnh 1.2 : cng bao gm cc b phn v cc chi tit c bn nh i vi ly hp mt a. im khc bit l ly hp hai a c hai a ma st 4 cng lin kt then hoa vi trc ly hp 10. V c hai a ma st nn ngoi a p 5 cn c thm a p trung gian 3. ly hp hai a phi b tr c cu truyn mmen t v hoc bnh sang a p v c a p trung gian. V nhc im ca ly hp hai a l m khng dt khot nn nhng loi ly hp ny th ngi ta phi b tr c cu to iu kin cho ly hp khi m c dt khot. Trn hnh 1.2 th c cu ny c thc hin bi l xo a p trung gian 2 v bu lng iu chnh 6. Khi m ly hp th l xo 2 s y a p trung gian 3 tch khi a ma st bn trong v khi a p trung gian chm vo u bu lng iu chnh 6 th dng li nn a ma st bn ngoi cng c t do. B phn dn ng iu khin ly hp gm : bn p ly hp, n dn ng, cng m ly hp, n m ly hp v bc m ly hp. Ngoi ra, ty theo tng loi ly hp m c th thm cc b phn dn ng bng thy lc, bng kh nn nh cc xilanh chnh v xilanh cng tc.II.2.3.Nguyn l lm vic ca loi a ly hp ma st khNguyn l lm vic theo hnh 1.1Trng thi ng ly hp : trng thi ny l xo 4 mt u ta vo v 5, u cn li t vo a p 3 to lc p p cht a b ng 2 vi bnh 1 lm cho phn ch ng v phn b ng to thnh mt khi cng. Khi ny mmen t ng c c truyn t phn ch ng sang phn b ng ca ly hp thng qua cc b mt ma st ca a b ng 2 vi a p 3 v l xo p 4. Tip mmen c truyn vo xng a b ng qua b gim chn 13 n moay ri truyn vo trc ly hp. Lc ny gia bi "T" 11 v u n m 12 c mt khe h t 3-4 mm tng ng vi hnh trnh t do ca bn p ly hp t 30-40 mm.Trng thi m ly hp : khi cn ngt truyn ng t ng c ti trc s cp ca hp s ngi li tc dng mt lc vo bn p 7 thng qua n ko 9 v cng m 10, bc m 6 mang bi "T" 11 s dch chuyn sang tri. Sau khi khc phc ht khe h bi "T" 11 s t vo u n m 12. Nh c khp bn l ca n m lin kt vi v 5 nn u kia ca n m 12 s ko a p 3 nn l xo 4 li dch chuyn sang phi. Khi ny cc b mt ma st gia b phn ch ng v b ng ca ly hp c tch ra v ngt s truyn ng t ng c ti trc s cp ca hp s.Nguyn l lm vic theo hnh 1.2Trng thi ng ly hp : trng thi ny cc l xo p 7 mt u ta vo v ly hp 8, u cn li t vo a p 5 to lc p p cht ton b cc a ma st 4 v a p trung gian 3 vi bnh 1 lm cho phn ch ng v phn b ng to thnh mt khi cng. Khi ny mmen t ng c c truyn t phn ch ng sang phn b ng ca ly hp thng qua cc b mt ma st ca cc a ma st 4 v a p trung gian 3 vi a p 5 v l xo p 7. Tip mmen c truyn vo xng a b ng qua b gim chn 17 n moay ri truyn vo trc ly hp. Lc ny gia bi "T" 15 v u n m 16 c mt khe h t 3-4 mm tng ng vi hnh trnh t do ca bn p ly hp t 30-40 mm.Trng thi m ly hp : khi cn ngt truyn ng t ng c ti trc s cp ca hp s th ngi li tc dng mt lc vo bn p 11 thng qua n ko 13 v ko cng m 14, bc m 9 mang bi "T" 15 s dch chuyn sang tri. Sau khi khc phc ht khe h bi "T" 15 s t vo u n m 16. Nh c khp bn l ca n m lin kt vi v 8 nn u kia ca n m 16 s ko a p 5 nn l xo 7 li dch chuyn sang phi to khe h gia cc a ma st vi cc a p, a p trung gian v bnh . Khi ny cc b mt ma st gia b phn ch ng v b ng ca ly hp c tch ra v ngt s truyn ng t ng c ti trc s cp ca hp s.Ngoi cc trng thi lm vic trn, th ly hp cn xut hin trng thi trt tng i gia cc b mt ma st ca ly hp. Hin tng ny thng xut hin khi ng ly hp (xy ra trong thi gian ngn) hoc khi gp qu ti (phanh t ngt m khng nh ly hp).II.3. PHN TCH V LA CHN KT CUII.3.1.La chn phng php dn ng ly hpII.3.1.1.Phng n 1: Dn ng ly hp bng c khy l h thng dn ng iu khin ly hp bng cc n, khp ni v c lp theo nguyn l n by. Loi dn ng iu khin ly hp n thun ny c kt cu n gin, d ch to v c tin cy lm vic cao. H thng dn ng ny c s dng ph bin cc t qun s nh xe ZIN-130, ZIN-131, ...Nhc im c bn ca h thng dn ng ny l : yu cu lc tc ng ca ngi li nn bn p ly hp phi ln, nht l i vi loi xe t hng nng.
Hnh 3.1. S h thng dn ng ly hp bng c kh1-Bc m; 2-Cng m ly hp; 3-Cn ngt ly hp; 4-Cn ca trc bn p ly hp; 5-Thanh ko ca ly hp; 6-L xo hi v; 8-Bn p ly hp
Nguyn l lm vic :Khi ngi li tc dng mt lc Q ln bn p ly hp 8 s lm cho cn ca trc bn p ly hp 4 quay quanh tm O1 ko thanh ko ca ly hp 5 dch chuyn sang phi (theo chiu mi tn). Lm cho cn ngt ly hp 3 v cng m ly hp 2 quay quanh O2 . Cng m gt bc m 1 sang tri (theo chiu mi tn) tc ng vo u n m ca ly hp, ko a p tch ra khi a ma st.Khi ngi li nh bn p 8 th di tc dng ca l xo hi v 6, bn p tr v v tr ban u duy tr khe h gia bc m vi u n m. Nh c cc l xo p p a p tip xc vi a ma st, ly hp c ng li.Hnh trnh ton b ca bn p ly hp thng t 130 150 mm. Trong qu trnh lm vic, do hin tng trt tng i gia cc b mt ma st, nn a ma st thng b mn, do hnh trnh t do ca bn p ly hp b gim xung. Khi cc b mt ma st mn ti mc no th hnh trnh t do ca ly hp gim ti mc ti a, s khng to c cm gic cho ngi li na, ng thi gy hin tng t ngt ly hp. Trong trng hp khc, khi hnh trnh t do ca bn p ly hp qu ln, lm cho ngi li p bn p ht hnh trnh ton b m ly hp vn cha m hon ton, cng to hin tng trt tng i gia cc b mt ma st, s gy mn cc b mt ma st mt cch nhanh chng.Trong c hai trng hp nu trn u khng c li, v vy phi iu chnh hnh trnh t do ca bn p ly hp trong mt min cho php.u im : Kt cu n gin, d ch to, c tin cy lm vic cao, d tho lp v sa cha.Nhc im : Kt cu ph thuc vo v tr t ly hp. Yu cu lc ca ngi li tc dng ln bn p ln. Hiu sut truyn lc khng cao.II.3.1.2. Phng n 2: Dn ng ly hp bng thy lcy l h thng dn ng iu khin ly hp bng cch dng p lc ca cht lng (du) trong cc xilanh chnh v xilanh cng tc.
Hnh 3.2. S h thng dn ng ly hp bng thy lc1-Bn p ly hp; 2-L xo hi v; 3-Xilanh chnh; 4-Piston xilanh chnh; 5-ng ng dn du; 6-Xilanh cng tc; 7-Cng m ly hp;8-Bc m ly hpCu to xi lanh chnh.
1-Xilanh; 2-Bnh cha du; 3-Nt du vo; 4-Tm chn du; 5-Piston;6-Cn piston; 7-L thp mng hnh sao;8-Pht lm kn; 9-L xo hi v piston;10-Van mt chiu; 11-L xo van mt chiu;12-Van hi du.a. L cung cp du b. L iu haNguyn l lm vic :Khi ngi li tc dng mt lc Q ln bn p ly hp 1, nh thanh y, y piston 4 ca xilanh chnh 3 sang tri, bt l b du b, lm du trong khoang D b nn li. Khi p lc du trong khoang D thng lc p ca l xo van mt chiu 11 van mt chiu 10 th van mt chiu m ra. Lc ny du t khoang D theo ng ng dn du 5 vo xilanh cng tc 6 y piston sang phi, lm cho cng m ly hp 7 quay quanh O, ng thi y bc m 8 sang tri (theo chiu mi tn). Bc m tc ng nn u di ca n m ly hp tch a p ra khi b mt ma st. Ly hp c m.Khi ngi th bn p ly hp 1 th di tc dng ca l xo hi v 2 v l xo p lm cc piston ca xilanh chnh v xilanh cng tc t t tr v v tr ban u. Lc ny du t xilanh cng tc 6 theo ng ng dn du 5 qua van hi du 12 vo khoang D.Khi ngi li nh nhanh bn p ly hp 1, th do sc cn ca ng ng v sc cn ca van hi du 12 lm cho du t xilanh cng tc 6 khng kp v in y vo khoang D. V th to ra chn khng khoang D, nn du t khoang C qua l cung cp du a vo khoang E, ri sau du qua l nh mt u piston p pht cao su 8 lt sang b sung du cho khoang D (trnh hin tng lt kh vo khoang D, khi khoang D c chn khng). Khi du khc phc c sc cn ca ng ng v van hi du 12 tr v khoang D, th lng du d t khoang D theo l b du b tr v khoang C, m bo cho ly hp ng hon ton.L b du b cn c tc dng iu ha du khi nhit cao. Lc nhit cao du trong khoang D n ra, lm p sut du tng ln, du qua l b du b v khoang C. V th khc phc c hin tng t m ly hp.u im : Kt cu gn, vic b tr h thng dn ng thy lc n gin v thun tin. C th m bo vic ng ly hp m du hn so vi h thng dn ng ly hp bng c kh. ng dn du khng c bin dng ln, nn h thng dn ng thy lc c cng cao. ng thi h thng dn ng bng thy lc c th dng ng m hai ly hp.Nhc im : Loi h thng dn ng bng thy lc khng ph hp vi nhng xe c my nn kh. Yu cu h thng dn ng ly hp bng thy lc cn c chnh xc cao.II.3.1.3.Phng n 3: Dn ng ly hp bng c kh c cng ha kh nny l h thng dn ng iu khin ly hp bng cc thanh n, khp ni. ng thi kt hp vi lc y ca kh nn.
Hnh 2.10. S h thng dn ng ly hp bng c kh c cng ha kh nn1-Bn p ly hp; 3, 5-Thanh ko; 2, 4, 7, 8, 18-n dn ng; 6-L xo hi v; 9-Mt bch ca xilanh phn phi; 10-Thn van phn phi; 11-ng dn kh nn vo; 12- Pht van phn phi; 13-ng dn kh nn; 14-Piston van phn phi; 15-Cn piston; 16-Cng m ly hp; 17-Xilanh cng tc;19-Bc m ly hp.Nguyn l lm vic :Khi ngi li tc dng mt lc Q ln bn p ly hp 1, lm cho n dn ng 2 quay quanh O1 , thng qua thanh ko 3 lm n 4 quay quanh O2 v qua thanh ko 5 lm n dn ng 7 quay quanh O3 . Nh c n dn ng 8 cng vi mt bch ca xilanh phn phi 9 v y thn van phn phi 10 sang phi (theo chiu mi tn). Khi mt phi ca thn van phn phi chm vo ai c hn ch hnh trnh np trn cn piston 15 th lm cho cng m ly hp 16 quay quanh O4 v y bc m ly hp 19 sang tri (theo chiu mi tn). Ly hp c m.ng thi vi vic khi np bn phi ca thn van phn phi t vo ai c hn ch hnh trnh ca cn piston 15 th u piston van phn phi 14 cng t vo pht van 12 v lm van 12 m ra. Kh nn lc ny t khoang A qua van 12 vo khoang B, ri theo ng dn kh nn 13 vo xilanh 17 v y xilanh lc dch chuyn lm n dn ng 18 quay quanh O4 . Kt hp vi cng m ly hp 16 quay v y bc m ly hp 19 sang tri. Ly hp c m.Khi ngi li thi tc dng vo bn p ly hp 1 th di tc dng ca l xo hi v 6 ko bn p tr v v tr ban u. ng thi thng qua n dn ng 8 ko thn van phn phi 10 sang tri, khi mt u bn phi ca piston 14 chm vo mt bch bn phi ca thn van th piston 14 c y sang tri, lm cng m ly hp 16 quay v y bc m ly hp 19 sang phi. Cng lc , di tc dng ca l xo hi v pht van phn phi 12 v y van ny ng kn ca van. Kh nn t xilanh lc 17 theo ng dn kh nn 13 vo khoang B v qua ng thng vi kh tri a thn piston 14 ra ngoi. Lc ny ly hp trng thi ng hon ton.u im : H thng dn ng lm vic tin cy, khi cng ha kh nn hng th h thng dn ng c kh vn c th iu khin ly hp c.Nhc im : Khi cng ha hng th lc bn p ln. Loi h thng dn ng ny ph hp vi nhng xe c my nn kh.II.3.1.4.Phng n 4: Dn ng ly hp bng thy lc c cng ha kh nny l h thng dn ng iu khin ly hp bng cc thanh n v p lc ca du trong cc xilanh lc. ng thi kt hp vi p lc ca kh nn ly t cc my nn kh.
Hnh 2.11. S h thng dn ng ly hp bng thy lc c cng ha kh nn1-Bn p ly hp; 2-L xo hi v; 3-Xilanh chnh; 4, 13-ng ng dn du; 5-Xilanh cng tc; 6-Piston xilanh; 7-Cn piston; 8-Xilanh thy lc; 9- Piston xilanh thy lc; 10-Cn piston xilanh thy lc; 11-Cng m ly hp; 12-Bc m ly hp; 14-Piston xilanh m van; 15-Cc van phn phi; 16-Mng ngn; 17-Van x; 18-Van np; 19-ng ng dn kh nn.Nguyn l lm vic :Khi ngi li tc dng mt lc Q ln bn p ly hp 1, lm cho tay n bn p quay quanh O1 v y cn piston ca xilanh chnh 3 i xung (theo chiu mi tn). Du t xilanh chnh 3 c piston nn li v theo ng ng dn du 4 vo xilanh thy lc 8. p lc du tc dng vo mt piston xilanh thy lc 9 v y n cng cn piston 10 sang phi. Lm cho cng m ly hp 11 quay quanh O2 v y bc m ly hp 12 sang tri (theo chiu mi tn). Ly hp c m.ng thi du c p sut theo ng ng dn du 13 tc dng ln piston xilanh m van 14 th y piston 14 cng cc van 15 v mng ngn 16 sang tri. ng van x 17 li v van np 18 c m ra. Kh nn t my nn kh theo ng ng dn kh nn 19 qua van np 18 vo khoang A, ri theo l thng xung khoang B v y piston xilanh 6 cng cn piston 7 sang phi. Kt hp vi lc y ca p lc du, y piston xilanh thy lc 9 cng cn piston 10 lm cho cng m ly hp 11 quay quanh O2 v y bc m ly hp 12 sang tri. Ly hp c m.Khi ngi li thi tc dng vo bn p ly hp 1 th di tc dng ca l xo hi v 2 ko bn p tr v v tr ban u. Piston ca xilanh chnh 3 dch chuyn ln pha trn v du t xilanh cng tc tr v xilanh chnh. ng thi van x 17 m, van np 18 ng li. Kh nn t khoang B qua l thng sang khoang A v qua van x 17 ri theo l trn cc van phn phi 15 thng vi kh tri ra ngoi. Ly hp ng hon ton.u im: H thng dn ng lm vic tin cy, khi cng ha kh nn hng th h thng dn ng bng thy lc vn hot ng bnh thng. Lc ca ngi li tc dng vo bn p ly hp nh. Hnh trnh ton b ca bn p khng ln. Loi h thng dn ng ny th m bo c yu cu ng ly hp m du, m dt khot v dng ph hp vi nhng xe c my nn kh.Nhc im: Kt cu phc tp, bo dng, iu chnh sa cha kh khn v yu cu chnh xc ca h thng dn ng cao.NHN XT:Qua phn tch, tm hiu kt cu, nguyn l hot ng, xem xt u im v nhc im ca tng phng n dn ng iu khin ly hp, ta thy phng n 3:Dn ng ly hp bng c kh c cng ha kh nnph hp p dng cho vic thit k h thng ly hp cho xe khch 10 tn.Phng n ny m bo nguyn tc :- Lc bn p phi ln c cm gic m ly hp.- S dng phi chc chn nh nhng.- D chm sc, bo dng v sa cha.II.4. TNH TON, THIT K CC THNG S C BN CA LY HPII.4.1.Xc nh m men ma st ca ly hp Cng thc tnh m men ma st ca ly hp : Ml = . Memax Trong : Ml : M men ma st ca ly hp (N.m) Memax : M men xon cc i ca ng c (N.m) : H s d tr ca ly hp Do xe l xe khch nn chn = 2 Vy m men ma st ly hp l : ML=2.41 = 82 (KGm) = 82.10 =820 ( Nm)II.4.2.Xc nh kch thc c bn ca a b ng S a b ng: n=1 nu Memax 465 N.m 03 n m n=2 nu Memax 465 N.m 04 n mTheo bi : Memax=410 (N.m ) nn ly hp thit k c 1 a b ng v 3 n m
Bn knh ngoi ca a b ng:
, cm Trong : Memax: M men xon ln nht ca ng c (N.m) C: h s kinh nghim ly theo loi tC=4,7 i vi t du lchC=3,6 i vi t vn tiC= 1,9 i vi t t Theo bi thit k t khch, ly C= 3,6
(cm) Vy R2=17 (cm) =170 (mm)
(D2 cn b gii hn bi ng knh ngoi ca bnh ) Bn knh trong ca a b ng:R1= (0,53 0,75) R2 = (0,53 0,75).170 = (90,1 127,5)Chn R1 =110 (mm) Bn knh trung bnh
(mm)
Lc p ln a ma st
Trong : Rtb: l bn knh trung bnh ca a ma st =2 h s d tr ly hp Memax=410 N.m i l s i bn mt ma st -i=2, ly hp c mt a b ng. -i=4, ly hp c 2 a b ng. : h s ma st, thng thng, i vi b ly hp t hin nay =0,25 0,3chn =0,28.
(N)
II.4.3. Xc nh cng trt sinh ra trong qu trnh ng ly hpQu trnh ng ly hp m du bao gi cng km theo s trt gia cc i bn mt ma st. S trt ca ly hp lm cho cc b mt ma st mn, ng thi sinh nhit nung nng cc chi tit tip xc vi cc b mt trt. Nu cng trt qu mnh s lm mn nhanh cc b mt ma st v nhit sinh ra s rt ln, c th lm chy cc b cc tm ma st, lm nung nng l xo p t c th lm gim kh nng p ca chng.V vy, cn xc nh cng trt, cng trt ring hn ch s mn, khng ch nhit cc i nhm m bo tui th cho ly hp l ht sc cn thit.
A: phn ch ngB: phn bi ng ca ly hp v cc phn c lin quan ti phn b ng ca ly hpMm : M mem ng c.Ml : M mem ca ly hp.Ma : m mem cn chuyn ng quy dn v trc ly hpm: tc ng gc ca trc khy.a : tc ng gc ca tr ly hpJm : mmem qun tnh ca bnh v cc chi tit ng c quy dn v bnh Ja : moomem qun tnh ca t v r mooc quy dn v trc ly hp
-Giai on 1: tng m mem ca ly hp khi ng ly hp t 0 n Ma (khi , t bt u khi ng ti ch) Cng ca ng c giai on u vi thi gian t1 s tiu tn cho s trt v nung nng ly hp. Cng trt L1 c tnh theo cng thc sau:
- Giai on 2: tng m mem ca ly hp n gi tr khng c s trt ca ly hpCng ca ng c giai on 2 ng vi thi gian t2 dng tng tc trc b ng ca ly hp v ni chng vi h cn chuyn ng ca t. Tnh L2
Vy cng trt ton b ca ly hp tnh theo cng thc:
( Jun)S trt ca ly hp din ra ngay sau khi gi s v thc hin ng ly hp. iu c th xy ra khi lc xe ang chy hoc khi bt u khi hnh. Trong , trng hp xe bt u khi hnh s c cng trt ln nht v lc ny s chnh lch tc gia bnh ng c v tc trc ly hp ( xe ang ng yn) l ln nht.Ta tnh cng trt trong trng hp xe bt u khi ng ti ch :
Ma: M mem cn chuyn ng quy dn v trc ca ly hp, c tnh theo cng thc:
(N.m)Trong : Trng lng ton b t Ga = 103400 (N) Trng lng ton b r mooc Gm = 0 (N) : h s cn tng cng ca ng, ly = 0,03 Lc cn gi P = 0 ( coi nh = 0 v xe ng yn ) rbx: bnh knh lm vic ca bnh xe rbx= 0,497 (m) t s truyn lc chnh i0= 7,63 t s truyn hp s ih ly ih1 = 7,44 t s truyn hp s ph ip = 1 tl hiu sut ca h thng truyn lc , ly tl = 0,9Tnh c Ma
(N.m) m : tc gc ca ng c khi ng ly hp, ly tc gc tng ng vi Memax. C nM = 1900 (v/ph)
vy: a :tc gc ca trc ly hp. tnh ton lc xe khi hnh nn a = 0 (rad/s)
ja : moomem qun tnh ca t v r mooc quy dn v trc ly hp
(kg.m2) Cc thng s bit
Vy, ta tnh c (kg.m2) t1, t2: thi gian ng ly hp giai on 1 v giai on 2 c xc nh theo cng thc:
Trong : k l h s t l k n nhp tang m mem Ml khi ng ly hp, xc nh theo thc nghim: i vi xe du lch: k = 50 150 Nm/s i vi xe vn ti: k = 150 750 Nm/s
chn k =200 Nm/s , ta tnh c t1, t2
(s)
(s)
Vy cng trt trong trng hp xe bt u khi hnh ti ch :
(J)
II.5 KIM TRA KH NNG LM VIC CA CHI TIT, TNG THNH, H THNGII.5.1 Kim tra kh nng lm vic ca ly hpII.5.1.1 Cng trt ring nh gi tui th ca ly hp theo iu kin trt, ngi ta dng ch tiu cng trt ring, c xc nh bng cng trt trn mt n v din tch lm vic ca cc b mt ma st, k hiu Lr (j/m2)
=202,155 (kJ/m2)Vi loi t khch, ti trng > 5 tn th cng trt cho php [L0] = 400 600 kJ/m2So snh vi gi tr cho php v cng trt ring Lr < [L0] Vy ly hp thit k t yu cu v tui th cho ly hpII.5.1.2 p sut trn b mt tm ma st
Trong :Pe=10029 (N) R,r : l bn knh ngoi v bn knh trong a ma sti=2 l s i b mt ma st[q]: p sut cho php, tra trong bng sau:
Nguyn liu ca cc b mt ma stH s ma st p sut cho php [p] (kN.m^-2)
Kh Trong du
Thp vi Ph-ra-ng vi Ph-ra-0,25 0,350,07 0,15100 - 250
Gang vi ph-ra-0,2100 - 250
Thp vi ph-ra- Cao su0,4 0,50,07 0,15100 - 250
< [q] (tha mn)
II.5.1.3 Nhit sinh ra do trt Cng trt sinh nhit lm nung nng cc chi tit nh a p, a p trung gian ( ly hp 2 a ma st), l xo Do phi kim tra nhit ca cc chi tit , bng cch xc nh nhit theo cng thc:
Trong : L: cng trt sinh ra khi ly hp b trt [J] : h s xc nh phn nhit nung nng chi tit cn tnh. Vi ly hp 1 a b ng th =0,5 c: nhit dung ring ca chi tit b nung nng, vi vt liu bng thp hoc gang c th ly c = 481,5 (J/kg0C) m: khi lng chi tit b nung nng tang nhit chi tit b nung nng [0C] tang nhit cho php ca chi tit tnh ton i vi mi ln khi hnh ca t ( ng vi h s cn ca ng =0,02) khng c vt qu 100C
T suy ra khi lng a p ti thiu phi l :
(kg)II.5.2 Tnh ton sc bn mt s chi tit ch yu ca ly hp II.5.2.1 Tnh sc bn a b ng gim kch thc ca ly hp, khi ly hp lm vic trong iu kin ma st kh th chn vt liu c h s ma st cao. a b ng gm cc tm ma st v xng a.Chn vt liu lm xng a l thp cc bon C50, chiu dy xng a thng chn t 2,0 mmChn vt liu lm tm ma st l ph ra , c chiu dy 5 mm.
Cu to a b ng ca xe tTm ma st c gn vi xng a b ng bng inh tn , vt liu lm inh tn bng nhm c ng knh 6 (mm)inh tn b tr hai dy trn a, tng ng vi cc bn knh vng trong l r1 = 12,5 (cm), vng ngoi l r2 = 15,5 (cm)
F2
F1 l
r2r1 d
S phn b lc trn inh tn
Lc tc dng ln mi dy inh tn c xc nh theo cng thc
F1 = Thay s vo ta c F1 = 65 (KG)
V: F2 = Thay s vo ta c F2 = 80 (KG)inh tn c kim tra theo ng sut ct v chn dp* ng sut ct v chn dp i vi inh tn vng trong:
Trong :+ c1 : ng sut ct ca inh tn vng trong+ cd1 : ng sut chn dp ca inh tn.+ n1: S inh tn b tr vng trong chn n1 = 8+ d: ng knh inh tn d = 5mm = 0,5cm+l: Chiu di b chn dp ca inh tn l=2mm =0,2cmThay vo cng thc trn ta c :c1 = 42KG/cm2 Fx25 = 2774 KG =>Fx23 = 3177,5-2774 = 403,5 KGXt mt phng (yOz) Fy = Fy23 - Fr2 + Fy25 = 0 (3)M3 (Fy) = Fr2 . l3 - Fy25 . (l3 + l4) = 0 (4)
(3) Fy23 + Fy25 = 1156,5 KG (4) 1156,5 . 275 - Fy25 . (275 + 40) = 0318037,5 - Fy25 . 315 = 0 =>Fy25 = 1009,6 KG=> Fy23 = 1156,5 - 1009,6 = 146,9 KGCc phn lc u dng nn chiu cc phn lc theo gi thit l ng. Tnh cc phn lc ti hai gi 0 v 1 trn trc ly hp :
Nhn xt : Nu ta gi hai lc do trc th cp tc dng ln trc ly hp ti v tr c bnh rng nghing l Fx13 v Fy13. Hai lc ny c gi tr tuyt i bng hai lc Fx23 v Fy23trn trc th cp, c im t vo bnh nghing lun n khp, c phng chiu ngc vi Fx23 v Fy23 .Nh vy ta c :Fx13 = Fx23 = 403,5KG Fy13 = Fy23 =146,9 KGTa c th coi ng tc dng lc ca hai lc Fx13 v Fy13 cng nm trong mt phng cha ng tc dng lc ca Pv1 v Pr1.Gi s cc phn lc c chiu nh hnh v. Ta c h phng trnh sau :Xt mt phng (xOz)Fx = Fx10 - Fx11 + Pv1 - Fx13 = 0 (5)Mo (Fx) = Fx11 . l1 - Pv1 . (l1 + l2) + Fx13 . (l1 + l2) = 0 (6) (5) Fx10 - Fx11 = Fx13 - Pv1 = 403,5 - 901 = - 497,5 KG (6) Fx11 . 200 - 901. (200 + 40) + 403,5. (200 + 40) = 0 => Fx11 . 200 216240 + 96840 = 0 => Fx11 = 597 KG => Fx10 = 597 - 497,5 = 99,5 KGXt mt phng (yOz)Fy = Fy10 - Fy11 + Pr1 + Fy13 = 0 (7)
Mo (Fy) = Fy11 . l1 - Pr1 . (l1 + l2) - Fy13 . (l1 + l2) + Pa1 = 0 (8)(7) Fy10 - Fy11 = - Pr1 - Fy13 = - 344,81 - 146,9 = - 491,71 KG
(8) Fy11 . 200 344,81. 240 - 146,9 . 240 +292,75. = 0 => Fy11 . 200 82754,435256 + 13320,1= 0 =>Fy11 = 523,5 KG =>Fy10 = 523,5- 491,71= 31,79 KG Cc phn lc u dng nn chiu ca cc phn lc theo gi thit l ng.II.5.4.5.Tnh cc mmen trn trc ly hp v v biu mmen Ta t trc ly hp trong h trc (Oxyz).Nh vy trc ly hp chu un theo phng Ox v Oy, xon quanh Oz. tit din mt ct m-m bn tri :Muy1 = Fy10 . l1 = 31,79 . 200 = 6358 KGmmMux1 = - Fx10 . l1 = - 99,5.200 = - 19900 KGmm tit din mt ct m-m bn phi :
Muy2 = Fy13 . l2 + Pr1 . l2 - Pa1
= 146,9 . 40 + 344,81. 40 - 292,75. = 6348,3 KGmmMux2 = Fx13 . l2 - Pv1 . l2 = 403,5. 40 - 901 . 40 = - 19900 KGmm
Mz = Pa1. =292,75. = 13320,1 KGmm
tit din mt ct n-n bn tri: Muy3 = Fy10 . (l1 + l2) - Fy11 . l2 = = 31,79. (200+ 40) 523,5. 40 = - 13310,4 KGmm Mux3 = - Fx10 . (l1 + l2) + Fx11 . l2 = = - 99,5 .240 + 597 .40 = 0 KGmmV biu mmen un v mmen xon.
Biu m mem un v m mem xon
II.5.4.6.Tnh sc bn trc ly hpTrc ly hp c ch to bng thp 40X, c ng sut cho php :[th] = 500 700 kG/cm2 ;[c] = 300 kG/cm2 ;[cd] = 250 kG/cm2
Ta c :th = [](KG/mm2)Trong :Mu - mmen un tc dng ln trc ly hp.
Mu = = = 20888KGmmMx - mmen xon tc dng ln trc ly hp.Mx = 13320KGmm d - ng knh trc ti tit din nguy him.d = 52 mm
th = = = 1,76 KG/mm2 = 176 KG/cm2Vyth = 176 KG/cm2< [] = 500 kG/cm2 nn m bo iu kin bn.II.5.3 TNH TON H THNG DN NG LY HP m ly hp (ly hp t l kiu thng ng bi lc p l xo) li xe phi tc dng lc vo bn p ly hp, thng qua h thng iu khin (ngy nay thng dng truyn ng bng thy lc), lc s c khuch i v truyn n a p mt lc ngc chiu vi lc p l xo v c gi tr bng lc nn l xo khi m ly hp. T s khuch i ca h thng iu khin cng ln, lc iu khin t bn p cng nh v gim nh c iu kin lm vic cho li xe. Tuy vy, t s truyn b gii hn bi hnh trnh dch chuyn ca bn p do tm vi chn li xe c hn.II.6.1. Xc nh lc tc dng ln piston cng hay l loi ly hp dn ng c kh kt hp c cng ho kh nn
Lc ca ngi li tc dng ln bn p khi cha c cng ha :
(kG)Trong : P' - tng lc p cc i ca cc l xo p tc dng ln a p - hiu sut ca c cu dn ng, thng chn = 0,75 0,80Ta chn = 0,8 ic - t s truyn chung ca h thng dn ng.
Theo s trn, ta c :ic = Trong :
= = 3,33 l t s truyn ca bn p ly hp v n dn ng.
= = 0,875 l t s truyn ca n dn ng.
= = 1,36 l t s truyn ca n dn ng.
= = 1,79 l t s truyn ca n quay v cng m ly hp.
= = 4,85 l t s truyn ca n m ly hp.
ic = = 3,33 . 0,875 . 1,36 . 1,79 . 4,85 = 34,4Tng lc p ca tt c cc l xo p tc dng ln a p khi ly hp lm vic c xc nh theo cng thc :P' = 1,2 Pe= 1,2 . 1031,1 = 1237,3 kGVy lc ca ngi li tc dng ln bn p khi cha c cng ha :
Qb = = KGKhi c cng ha, chn lc tc dng ln bn p l Qb . Lc ny va khc phc sc cn ca cc l xo ko bn p, l xo ca van phn phi kh, ma st trong cc khu khp dn ng, va gy cm gic m ly hp cho ngi li. Tra bng 6 Sch hng dn "Thit k h thng ly hp ca t", vi t ti th lc ca ngi li tc dng ln bn p l Qb = 8 20 kGTa chnQb = 20 kGDo , lc sinh ra bi cng ha phi thng c tng lc p ca cc l xo p v cc l xo hi v trong xilanh cng ha. Ta phi xc nh lc tc dng ln u ca n m khi cng ha lm vic vi lc cc i :P' = Qb . ic + Pc . i4(kG)Trong :Qb - lc ca ngi li tc dng ln bn p khi c cng ha (kG).Pc - lc sinh ra bi cng ha (kG).i4 - t s truyn t b phn cng ha n u trong ca bc m
i4 = = = 6,84 khc phc c nhng mt mt do tn tht ma st cc khu khp, xilanh, lc nn s b cc l xo,... ta phi tng lc Pc ln 20%, khi ta c :
Pc = = KGNh vy, vi lc ca b phn cng ha sinh ra l Pc = 96,4 kG th b phn cng ha phi m nhn mt lc Q'b = 45 - 20 = 25 kG gip cho ngi li .+ ng knh ca xilanh cng ha c xc nh theo cng thc :
D = (cm)Trong :D - ng knh ca xilanh cng ha (hoc piston ca xilanh cng ha).Pc - lc cn thit sinh ra bi cng ha.Pc = 96,4 kGpmax - p sut cc i ca kh nn tc dng vo piston xilanh cng ha.pmax = 0,8 p = 0,8 . 7 = 5,6 kG/cm2Vi p = 7 kG/cm2- p sut gii hn ca kh nn trong bung cha.
D = = cm = 46,8 mmII.6.2. Xc nh hnh trnh ca bn p St St = Slv+S0+ SvVi: Sv L hnh trnh ca bn p dng m van phn phi kh c xc nh theo cng thc Sv = i3.iv.(v + 0v )Trong :+ iv : L t s truyn ca n m van kh ,chn = 2+ 0v :Khe h gia cn y van v u n m van = 0,5mm+ v:Hnh trnh lm vic ca van = 2,5mm+ i3: T s truyn ca bn p i3 = a/b = 5,7 Sv = 34,2 mm S0 : L hnh trnh chy khng ca bn p khc phc khe h gia u n m v bc m S0 = .a/b.c/d. d22/d12Vi: L khe h gia u n m v bi t = 4mm S0 = 30,3mm+ Slv : L hnh trnh lm vic ca bn p khc phc khe h gia cc b mt ma st : Slv = l.icVi l :L khe h gia cc b mt ma st = 2,3mmSlv = 2,3 . 34,4 = 79,12 mmVy:St = 143,62 mm II.6.3.Tnh van iu khin.Khi tc dng lc ln bn p m van , lc p ca ngi li phi thng cc lc sau: Qc = Pk + Flx1 + Flx2Trong :*Pk: Lc kh nn tc dng vo mt van 3 (theo s hnh v) v c xc nh theo cng thc sau: Pk = p.d2/4Vi:+ d:L ng knh van ,d = 25mm+ p: p sut ca kh nn p = 8KG/cm2 Pk = 40KG* Flx1 L lc nn s b ca l xo gi van lun ng kn , khi khng lm vic lc ny c chn = 1,5KG* Flx2 l lc l xo hi v ca cn y van,chn = 2,5KGVy : Qc = 40 + 1,5 + 2,5 = 44KGChng III THIT LP BN VIII.1.C S THIT LP BN VIII.1.1.T l bn vT l l t s gia kch thc di ca 1 phn t thuc phn t thuc vt th biu din trong bn v gc v kch thc thc ca chnh bn v .Cc t l u tin s dng trong bn v k thut:-T l nguyn hnh: 1:1-T l thu nh: 1:2; 1:5; 1:10; 1:20; 1:50; 1:100; 1:200; 1:500; 1:1000; 1:2000; 1:5000; 1:10000-T l phng to: 2:1; 5:1; 10:1; 20:1; 50:1III.1.2.ng ntIII.1.2.1.Chiu rng nt vTy thuc vo loi v kch thc ca bn v, chiu rng d ca tt c cc nt v phi chn theo dy s sau:0,13; 0,18; 0,25; 0,35; 0,5; 0,7; 1; 1,4; 2 mmChiu rng cc nt rt m, m v mnh tun theo t l 4:2:1Chiu rng nt ca bt k ng no phi nh nhau trn sut chiu di ca ng .III.1.2.2.Cch v ng nt phi thng nht trn cng bn v.Khong cch ti thiu gia cc ng song song l 0,7 mm.Cc nt v ct nhau, tt nht l ct nhau bng nt gch.Th t u tin ca ng nt:-ng bao hay cnh thy-Cnh khut-Nt ct-ng trc, ng tm-ng ng
III.1.2.3.Cc loi ng nt thng gp:
III.1.3.Kiu chLoi nt trn, vit thng ng hoc nghing 75o so vi phng ngang.Chiu rng d ca cc nt ch u bng nhau.III.2.THIT LP BN V KT CU-Chn t l bi v l 1: 1-Chn chiu rng nt v l 0,5 mm.-Chiu rng cc nt rt m, m v mnh tun theo t l 4:2:1-Th t u tin ca ng nt:+ng bao hay cnh thy+Cnh khut+Nt ct+ng trc, ng tm+ng ng-Phng ch: Arial
TI LIU THAM KHO1. L TH VNGTi liu Hng dn thit k ly hp t 2. PGS.TS CAO TRNG HIN TS O MNH HNG L thuyt t Nh xut bn giao thng vn ti H Ni 20103. TRNG TT CH Chi tit my Tp 1 v tp 2. Nh xut bn giao thng H Ni nm 20014.TH.S NGUYN HNG MNH Bi ging cu to t5.TRNH CHT- L VN UYN Tnh ton thit k dn ng c kh tp 1Nh xut bn khoa hc v k thut nm 2002
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