Cdng nghiep rimg NGHIEN ClTU GIAI PHAP HOAN THIEN XE ALL STAR 2017 - VNUF THEO H U N G GIAM TIEU HAO NHIEN LIEU Dang Thi Ha, Le Van Thai Trudng Dai hgc Ldm nghiep TOM TAT Bing phu'ong phap nghien cuu ly thuySt, bin bao trinh bay ca set khoa hoc ciia viec dua cac giai phap cai tiSn dpng CO xe may Wave Anpha lOcc theo huong giam tieu hao nhien li^u Tinh toan lua chgn he thong truyen luc voi ty s6 truygn hop ly, dap iing yeu ciiu vk dieu kien keo, bam ciia xe chuySn dong dong thoi dam bao v6 t6c cua cuoc thi theo quy dinh Thiet ke khop noi tu dong mot chieu de truyen mo men xoan cho banh xe chu dong nh5m nang cao hieu suit truygn lite Thiet ke hinh dang dong hpc cua xe cho luc can khong tac dung len xe ta nho nhat nham giam lupmg nhien lieu tieu hao xe chuyen dpng tren duong vai dp dai nhat dinh KSt qua nghien cuu dat dugc lam co so cho viec cai tien hoan thi?n xe All Star 2017 - VNUF theo huong tiet kiem nhien lieu nham nang cao tich cua xe phuc vu cupc thi "Lai xe sinh thdi, tiet kiem nhien liiu" Honda to chuc hang nam tai Viet Nam Tu khoa: All Star 2017, he thong truyen lyc, khdp noi tu dong mpt chieu, Ui xe sinh thai - tiet kiem nhi^n lieu, tiSu hao nhien lieu D^T VAN BE Cuoc thi "Lai xe sinh thai, tiet kiem nhien lieu" dugc Honda Nhat Ban bat dau to chiic tu nam 1981, den nam 2010 cuoc thi dugc to chuc lan dau tai Viet Nam voi 10 dgi tham gia Cugc thi da tao co hgi quy bau cho sinh vien cac truang ky thuat phat huy tu sang tao ve ky thuat, cong nghe, dua cac y tucmg vao thuc te, gop phan vao viec day manh phong trao tiet kiem nhien lieu va bao ve moi truang song Honda Viet Nam cung cap cho cac dgi tham gia cugc thi dgng co Wave Anpha llOcc kieu mai, tiet kiem nhien lieu va dang dugc sir dung tren cac dong xe so Honda Viet Nam san xuat Cac dgi tham gia se su dung dgng ca de che tao xe theo y tuong cua minh nhimg phai tuan thu theo quy dinh cugc thi Day se la su canhtt-anhlanh manh ca v6 y tuong thi^t kk, ky thuat che tao va ky nang lai xe Trong cugc thi, cac thi sinh se phai van hanh xe tren quang duong dai 9,5 km vai yeu cm van tfic trung binh cua xe phai dat toi thi8u 25 km/li Hieu suat tieu hao nhien lieu (km/lit) se dugc tmh toan dira hen lugng nhien lieu tieu hao thuc t^ h-en chieu dai duong dua theo quy dinh va dpi nao dat tich cao nhat se la dgi chign th^ng Tnrdng Dai hgc Lam nghiep da tham gia cugc thi lan dau tien vao nam 2017 voi muc dich la dua sinh vien nganh ky thuat ca va 112 nganh cong nghe ky thuat to hoi nhap voi sinh vien cac truang ky thuat nuoc va tao CO hgi cho sinh vien tu sang tao, ap dung nhiing y tuong thiet ke moi vao thuc te va hgc hoi sinh vien tir cac truong khac De chuan hi cho cupc thi, truang da lap hai dpi tuyen, la KTCK - VNUF va dpi All Star 2017 VNUF Cac dpi da tich cue nghien ciiu dua y hrong thiet ke, che tao va lap rap cong hai mau xe tu che de tham gia cugc thi dugc to chuc Ket qua la ca hai man xe deu hoan cugc thi voi tich kha khiem ton De huong tai tich cao hon cua Truang Dai hgc Lam nghiep tham gia o cac cugc thi nhung nam tiep theo thi viec "Nghien cdu hodn thien xe All Star 2017 - VNUF theo hwdng gidm tieu hao nhien lieu" la can thiet va co y nghia thuc tien cao PHUONG PHAP NGHIEN CUtJ 2.1 Phirffng phap k§ thiia Thu thap, suu tam cac tai lieu chuyen mon lien quan toi cac cugc thi xe tiet kiem nhien lieu va ly thuyet dpng co dot trong, ly thuyet to may leo de lam ca so cho viec nghien ciiu ly thuyet de xuat giai phap thiet ke cai tien xe 2.2 Phuffng phap nghien ciru Iy thuyit Su dung ly thuyet ve dgng co d6t trong, ly thuyet to may keo de dua cac giai phap thiet k6 cai tien dpng co theo huang nang cao TAP CHI KHOA HOC VA C N G NGHE LAM NGHIEP SO - 2019 Cdng nghiep rirng hieu suat tieu hao nhien lieu K E T QUA VA THAO LUAN 3.1 Nghien cihi cai tign nang cao hieu suat cho dong Cff 3.L1 Hgn che truyen nhiet mdi trudng xung quanh nhdm tgo diiu kien thudn lgi cho viec hinh thdnh hdn hgp chdy cung cdp cho ddng Cff Doi vai dpng co xang thi viec tao hSn hgp chay dupe tien hanh ben ngoai xi lanh nho bg che hoa (dgng co dimg che hoa khi) hoac nho voi phun phun nhien lieu o dang suong mu de hoa trpn voi khong a truoc van nap (loai phun xang dien hi) De tao di6u kien thuan lpi cho viec hinh hon hgp chay (xang hoa hon voi khong sach a dang hoi) thi dpng co, phai tich san mgt nhiet luong de tao dieu kien cho xang de hoa hoi nap vao buong dot Khi dgng co dot lam viec lien tuc thai gian dai thi viec thoat nhiet cho dgng CO la rat can thiet vi nhiet buong dot CO the len den ngan Neu nhiet dp qua cao thi nhien lieu se bi hoc chay truac thai diem can thiet, anh huong rat 1cm tai sy sinh cong va kha nang lam viec ciia dpng co Nhiet cao se lam cac chi tiet von bang kim Ioai cua dpng CO no ra, lam giam khe ho, tang ma sat, gay bo ciing pit tong long xi lanh Vi the de giam nhiet dp dpng co xuong thap hon nhiet dp giai han, ban than dgng co da dugc thiet ke he thong lam mat bang khong vol cac canh tan nhiet Tuy nhien voi dac thu van hanh xe cugc thi lai xe sinh thai tiet kiem nhien lieu la cho dpng CO no va tang toe dat toi toe dp cao, sau tat dpng co cho xe tha troi theo quan tinh ve toe dp nho nhat theo quy dinh cua cugc thi (V = 25 km/h) Sau lai de no tang toe roi lai tat may va cii lap di lap lai nhu the cho den xe thi dau di dii so kilomet quang duong dua ciia cugc thi theo quy dmh (khoang hon 20 phut) Voi thai gian ngSn nhu vay thi nhiet dp dgng ca chua cao vay de Ipi dung nhiet ciia dgng ca tao hon hop chay chk lugng t6t thi chn thiSt phai han chg truygn nhiet tir dpng co moi trucmg xung quanh bang cac giai phap: - Ckt loai bo toan bg cac canh tan nhiet tren than dpng co dk han ch^ thoat nhiet dgng CO moi trucmg xung quanh; - Lpi dung nhiet dp ciia luong thai de lam nong duang 6ng nap, tao dieu kien thuan lpi cho viec tao h6n hgp chay truoc nap vao xi lanh 3.L2 Gidi phdp ddt chdy hodn todn hdn hgp chdy Khac voi dgng co diezel ve phucmg phap d6t chay h6n hgp xi lanh, dpng co xang dung phuong phap dot chay cuang biic, nghTa la sir dung bugi bat tia lua dien tai thoi diem cuoi ky nen va each diem chet tren mpt goc danh lua som Vi the, de tao dugc tia liia dien manh de dot chay hoan toan hon hpp chay xi lanh, giai phap la sir dung hai bugi noi song song voi cuon day cao ap ciia bo bin danh lira 3.1.3 Ndng cdo dp sudt cudi thdi ky nen Ap suat va nhiet dp hon hgp chay cuoi ky nen xi lanh tang lam cho cong suat dpng CO tang, chi phi nhieu Heu rieng va hao ton mat mat ma sat dgng co se giam Mat khac, ap suat va nhiet hon hpp chay cuoi ky nen xi lanh phu thupc dang ke vao ty so nen cua dpng ca va dupe xac dinh theo cong thiic (Nguyin Diic Phu, 1979): P^ =P^.£"' va T^ =?;.£"'"' (1) Trong do: Pa, Ta - ap suat va nhiet dp cuoi ky nap; £• - ty so nen cua dpng co; ni - chi so ducmg nen Nhu vay, de tang ap suat va nhiet dp hdn hgp chay cuoi ky nen nham phat huy cong suat dpng CO va giam chi phi nhien lieu rieng can thiet la nang cao ty so nen len cao nhat co the Ti so nen s cua dpng ca la ti so the tich cua khong gian xi lanh pit tong di xuong diem chet duoi (the tich toan phan) voi the tich khong gian xi lanh pit long di len diem chet tren (the tich buong dot) va dugc xac dinh theo cong thiic: K + K -\ + v,^ TAP CHI KHOA HOC VA CONG NGHE LAM NGHIEP SO - 2019 (2) 113 Cdng nghiep rirng Trong do: Vtp - the tich toan phan; Vc - the tich buong dot; Viv - the tich lam viec Tit cong thirc (2) ta thay: Muon tang ty so nen e ta co the tang the tich lam viec cua xi lanh hoac giam the tich buong dot xi lanh Tuy nhien ta khong the tang the tich lam viec cua xi lanh kich thuoc tay bien, tay quay true khuyu dpng ca la khong the thay doi Vi vay ta chi c6 the tac dgng bien phap ky thuat de giam the tich buong dot xi lanh ciia dpng CO (giam Vc) bSng nhung giai phap sau: - Giam chieu cao buong dot nap xi lanh bang each phay mat dau nap xi lanh mpt lop kim loai voi chieu day la 0,5 mm - Giam chieu cao buong dot xi lanh bang each phay mat dau xi lanh mgt lap kim loai voi chieu day la 1,0 mm 3.1.4 Cdi tien he thdng cung cdp nhien lieu cho dgng ca He thong nhien lieu lam nhiem vu cung cap hon hop chay (gom hon hgp xang va khong sach) dong deu ve so lugng va co phan phii hop voi cac che dp lam viec cua dpng co, dam bao dot chay hoan toan nham phat huy cong suat cao nhat, tiet kiem nhien lieu va han che nhiem moi truong sinh thai Hien nay, he thong cung cap nhien lieu dgng CO xang tren xe may dupe su dung gom hai loai: He th6ng cung cAp nhien lieu dung bp che hoa va he thfing cung cap nhien lieu phun xang dien hr Dgng CO Wave Anpha 110 cc sir dung trgn xe All Star 2017 - VNUF la loai dimg bp che hoa nen tich ciia xe cugc thi "Lai xe sinh thdi tiet kiem nhien lieu" nam 2017 chua cao Sau tim hieu ve uu, nhugc diem cua he thSng cung cap nhien lieu dung bp che hoa va he thong cung cap nhien lieu phun xang dien tii, vai muc tieu la nang cao hieu suat tieu hao nhien lieu cho xe phuc vu thi dau nham nang cao tich, chiing toi de xuat nghien cuu thay the he thong cung cap nhi^n lieu diing bp che hoa bang he thong phun xang dien hi Tuy nhien, theo quy dinh cua cugc thi, nSu cac dgi su dung he thong phun xang dien tii cho dgng co Wave Anpha 11 Occ thi bit buoc phai sir dung bom mang Ban to chitc cugc thi cung cap Do vay, can thiet phai nghien cihi xay dyng so he thong phun xang dien tu cho dgng co sir dyng bom mang Honda cung cap, ket qua the hien o hinh va so dh dau noi cac phan tir he thong cung cap nhien lieu phun xang dien hi a hinh Hinh I Sff he thong phun xang di£n tu sd dung bom mang Honda cung cap / Binh chua nen; Van cdp khi; Van dieu dp; Van dieu chinh dp sudt; Bam mdng; Van mot chieu; Binh xang (BTC cdp); Voi phun xang; Dong ca 114 TAP CHI KHOA HOC VA CONG NGHE LAM NGHIEP SO - 2019 Cdng nghifp rirng V u I U B cluak i p • IM hatk chm k U D3y BUtu bfiogU day kit not voi ^r- / ['' i T C m s t i c diMli I n ^ đ Ac.ôiv 12V J Hinh So' dau n6i cac phan tu* he thong phun xang diln tu' sir dyng bom mang 3.2 Nghien ciru cai tien he thong truyen lyc 3.2.1 Thiet ke ly hap mot chieu truyen md men xoan td tr^fc dia xich bi dgng den moay ffbdnhxe Muc dich cua viec che tao xe phyc vu cugc thi "Lai xe sinh thdi tiet kiem nhien lieu" vai khau hieu la: "/ lit xang xe di duac bao nhieu ki Id met" Nhu vay giam tieu hao nhien lieu nham nang cao tich dat dugc thi can thiet phai nhien cim tim giai phap giam mat mat ma sat he thong truyen lyc xuong nho nhat CO the Tuy nhien, hien trang ciia he thong truyen luc toi banh xe All Star 2017 - Vnuf la dimg khap mgt chieu giira dia xich bi dpng voi moay o banh xe la dung lip xe dap nen gay mat mat ma sat lan Khi xe dang chuyen dpng, neu ta tat dpng co (ngat mo men chii dpng), vanh lip khong quay theo quan tinh banh xe, cot lip ciing ca lip quay theo chieu kim dong ho, quay ca lip trugt tren rang ciia vanh lip, ep 16 xo xuong gay hao ton ma sat dang ke De khac phyc hien tupng nay, nhom nghien ciiu de xuat cai tien he thong truyen luc xe All Star 2017 bang each thay the bp khap mgt chieu diing lip xe dap bang ly hgp ty dgng van rang mgt chieu Ly hgp ty dgng dong mo phu thupc vao lyc tren nhanh xich chil dpng cua truyen dpng xich, nghia la khong truyen mo men xoan cho banh chii dpng (tat may) thi ly hgp tu dpng tach truyen dpng lam cho banh xe quay tron tren true nen giam dupe ma sat qua trinh chuyen dpng Bg ly hpp dupe thiet ke theo nguyen ly chep hinh tir bg ly hgp mpt chieu cua he thong khoi dpng bang chan dgng co xe may (kich thuac va dang rang khong doi, chieu nghieng ciia rang ly hpp va true xoan dupe thiet ke theo huong ngupc lai) nhu a hinh Hinh Ly hop ty d^ng mot chi^u lap tren banh sau ciia xe tiet kiem TAP CHI KHOA H O C VA CONG NGHE LAM NGHIEP SO - 2019 115 Cdng nghiep rimg Trong do: Vtp - the tich toan phan; Vc - the tich buong dot; VK, - the tich lam viec Tir cong thiic (2) ta thay: Muon tang ty so nen B ta co the tang the tich lam viec cua xi lanh hoac giam the tich buong dot xi lanh Tuy nhien ta khong the tang the tich lam viec cua xi lanh kich thuac tay bien, tay quay true khuyu dgng ca la khong the thay doi Vi vay ta chi co the tac dpng bien phap ky thuat de giam the tich buong dot xi lanh cua dgng CO (giam Vc) bang nhirng giai phap sau: - Giam chieu cao buong dot nap xi lanh bang each phay mat dau nap xi lanh mpt lop kim loai voi chieu day la 0,5 mm - Giam chieu cao buong dot xi lanh bang each phay mat dau xi lanh mpt lop kim loai voi chieu day la 1,0 mm 3.1.4 Cdi tien he thdng cung cdp nhien lieu cho dgng cff He thong nhien lieu lam nhiem vu cung cap hon hop chay (gom hon hgp xang va khong sach) dong deu ve so lugng va co phan phii hgp vai cac che lam viec cua dpng co, dam bao dot chay hoan toan nham phat huy cong suat cao nhat, tiet kiem nhien lieu va han che nhiem moi truong sinh thai Hien nay, he thong cung ckp nhien lieu dgng CO xang tren xe may dugc sir dyng gom hai loai: He thong cung cap nhien lieu diing bg che hoa va he th6ng cung cap nhien heu phun xang dien tu Dgng CO Wave Anpha 110 cc su dung tren xe All Star 2017 - VNUF la loai diing bg chg hoa nen tich cua xe cupc thi "Lai xe sinh thdi tiet kiem nhien lieu" nam 2017 chua cao Sau tim hieu ve uu, nhugc diem cua he thong cung cap nhien lieu dimg bg ch^ hoa va he thong cung cap nhien lieu phun xang dien tir, voi myc tieu la nang cao hieu suat tieu hao nhien lieu cho xe phyc vu thi dau nhSm nang cao tich, chiing toi de xuat nghien ciiu thay the he thong cung cap nhien lieu dung bg che hoa bang he thong phun xang dien hi Tuy nhien, theo quy dinh ciia cupc thi, neu cac dpi sir dung he thdng phun xang dien hi cho dpng CO Wave Anpha 11 Occ thi bat bugc phai su dyng bom mang Ban to chirc cugc thi cung cap Do vay, can thiet phai nghien ciiu xay dung so he thong phun xang dien tu cho dpng CO sii dyng bom mang Honda cung cap, ket qua the hien o hinh va so dau noi cac phan tit he th6ng cung cSp nhien Heu phun xang dien hi hinh Hinh Sff he thong phun xang dign tir su dung bom mang Honda cung cap L Binh chua nen, Van cdp khi; Van diiu dp; Van dieu chinh dp sudt, Bam mdng; Van mgt chieu; Binh xang (BTC cdp); Voi phun xang; Dong ca TAP CHI KHOA HOC VA C O N G NGHE LAM NGHIEP SO - 2019 Cong nghiep rimg VuSUsdiakip > Diyiniu hdngU d^lcit noi voi cdt^tic danhlOi ' / © ^ r~ ^ L Caag lie I n k id* ""* ® e-mv 12V J Hinh Sff d^u n6i c^c phan tu hf thSng phun xang dien tu su dung bffm mang 3.2 Nghien ciru cai tien he th6ng truyen lyc 3.2.1 Thiet k& ly hgp mgt chieu truyen md men xoan tir tr^c dia xich bi dgng den moay ffbanh xe Myc dich ciia viec che tao xe phuc vu cupc thi "Lai xe sinh thdi tiet kiem nhien lieu" voi khau hieu la: "1 lit xang xe di duac bao nhieu ki 16 met" Nhu vay giam tieu hao nhien lieu nham nang cao tich dat dupe thi can thiet phai nhien ciiu tim giai phap giam mat mat ma sat he thong truyen lyc xuong nho nhat CO the Tuy nhien, hien trang ciia he thong truyen lyc tai banh xe All Star 2017 - Vnuf la dimg khap mpt chieu giira dia xich bi dpng voi moay o banh xe la diing lip xe dap nen gay mat mat ma sat Ion Khi xe dang chuyen dgng, neu ta tat dpng ca (ngat mo men chii dpng), vanh lip khong quay theo quan tinh banh xe, cot lip ciing ca lip quay theo chieu kim dong ho, quay ca lip trugt tren rang cua vanh lip, ep 16 xo xuong gay hao ton ma sat dang ke De khac phuc hien tupng nay, nhom nghien ciiu de xuat cai tien he thong truyen luc xe All Star 2017 bang each thay thg bg khop mpt chieu dung lip xe dap bang ly hpp tu dpng vau rang mpt chieu Ly hpp tu dgng dong mo phy thugc vao luc tren nhanh xich chu dgng ciia truyen dgng xich, nghTa la khong truyen mo men xoan cho banh chii dgng (tat may) thi ly hpp tu dpng tach truyen dpng lam cho banh xe quay tron tren true nen giam dugc ma sat qua trinh chuyen dgng Bp ly hpp dupe thiet ke theo nguyen ly chep hinh tir bg ly hgp mgt chieu cua he thong khoi dgng bang chan dgng co xe may (kich thuac va dang rang khong doi, chieu nghieng cua rang ly hpp va true xoan dugc thiet ke theo huong ngupc lai) nhu a hinh Hinh Ly hop ty dong mfit chigu \ip tren banh sau eiia xe tiet kiem TAP CHI KHOA HOC VA CONG NGHE L A M NGHIEP SO - 2019 115 Cdng nghiep rdng 3,2.2 Ndng cao hieu sudt chung he thong truyen lire Hieu suat chung ciia he thong truyen lyc ciia xe dugc xac dinh theo cong thiic: _ W, _ N, =1 (3) '7, ~ AT, ~ Trong do: Ni - cong suat hieu dung truyen den banh xe chu dpng; N, - cong suat mat mat ma sat va khuay dau; Ne - cong suat chi thi cua dpng co Tir cong thiic (3) cho thay, voi cong suat chi thi ciia dpng co khong doi (N^ = const), d& nang cao hieu suat chung cua he thong truyen lyc bang cac giai phap nham giam toi da cong suat mat mat ma sat va khuay dau De giam cong suat mat do ma sat va khuay dau bang each nghien ciiu loai bo hop so khoi dpng co dong thoi thiet ke he thong boi tron tryc tiep cho cac chi tiet dgng ca co chuyen dpng tuong doi vai theo phuang phap boi tron Hon hpp CO xang thi k = 1,1 ^ 1,35, ta chpn k = 1,2 - Mo men xoan banh xe chu dpng dugc tinh theo cong thiic: ^b.=^dn,-Kl.-n, Til - hieu suat ciia he thong truyen lyc, so bg chpn T|t = 0,88 (Nguyen Hiiu CSn, 2007); ich - ty so tmyen chung ciia he thong tmyen lyc Thay gia tri ciia Mdm = 7,03 (Nm) vao cong thuc (5) ta tinh dugc Mbx nhu sau: M^^ =7,03.j;;,.0,88 = 6,18.i;,,, Ty so truyen hgp ly ciia he thong truyen lyc bi gioi han bai dieu kien keo va bam de cho xe c6 the chuyen dpng dupe tren duong Mo men dinh miic (Mj^) cua dgng co dupe xac dinh (Nguyin Hiru Can, 2007) nhu sau: M 8,44 ^i., = —^ = -— = 7,03 (Nm) (4) "" k 1,2 ^ -^ ^ ' Trong do: (Nm) Khi ta tinh dugc lyc leo tiep tuyen banh xe chii dgng theo cong thirc sau (Nguyen Him cdn, 2007): ^ = ^ =^ = 19,04 r^^ 0,325 (N) Voi ban kinh cua banh xe la: rbx = 0,325 (m) duong phai tuan theo bat dang thirc sau: P^>FK> SPC (7) Trong do: Pip - luc bam a banh xe chii dgng; SPc tong luc can tac dung len xe chuyen dgng - Xdc dinh tong luc cdn tdc dtiug ten xe chuyen dong So lyc tac dyng len xe chuyen dpng tren duong nam ngang the hien hinh Cac lyc can chuyen dpng bao gom: lyc can lan; luc can quan tinh; luc can khong - k - he so thich img cua dpng co, voi dgng Hinh Luc va mo men tac dung len xe chuyen dong tang tdc 116 (6) Dieu kien de xe chuyen dpng dupe hen 3.2.3 Xdc dinh ty so truyen hop ly td tr^c khuyu dgng cff den true bdnh xe chu dgng (5) Trong do: TAP CHI KHOA H O C VA CONG NGHE LAM NGHIEP SO - 2019 Cdng nghiep rirng Sir dung ly thuyet to may keo (NguySn Him Can, 2007) da tinh toan dugc gia tri cac lyc can chuyen dpng cho xe, kgt qua thu dugc nhu sau: thiet ke chi tiet may ta chgn he thong truygn luc bao gom he thong hniyen dgng xich hai cap voi cac dia xich co so rang hrong ung la Z|, Z:, Z3 va Z4, tir tinh duoc ty so truyen chung + Luc cdn lan: Pf = P^, + P^, -Z,.f+Z^.f^ = f.G = 0,03.900-27 (8) thoa man dieu kien keo va bam nhu sau: Z, Z, 36 48 _ (14) I, =i,.i-.=^.—^ = — — = 8,82 Z, Z^ 14 14 Vi xe chuyen dpng voi t6c dp kha cham, tigt Zi, Z3 - so rang dia xich chii dgng so va 3; (N) + Luc cdn khong khi: dien chan gio nho nen lyc can khong la khong dang ke co the bo qua P.,=C,,F,Vl^a (N) Z2, Z4 - so rang dia xich bi dpng so va - Kiem tra toe cua xe theo quy dinh (9) + Ltfc cdn qudn tinh: cugc thi: Voi ich ^ 8,82 thi van toe chuyen dpng tinh Mgt each gan diing, bo qua quan tinh ciia cac chi tiet chuyen dong quay ta co: C ^ ^ 900 ^ ^ ^ g 9,81 30 \ > \ ! ' Nhu da trinh bay trgn, biSn thign van cua xe kha Ion (van toe Ion nhdt ciia xe: tign cua xe duoc tinh toan nhu sau: 60.1000./,;, 60.1000.8,82 (m/s) (15) Nhu vay, voi (ich = 8,82) duoc tinh chpn o tren da thoa man digu kien keo bam cho xe Vniax = 13,89 m/s), thai gian tang ga tinh tir chuygn dpng trgn du6ng, dong thai dap ling luc bat dau khoi hanh (van toe ban dau bang toe dp toi thieu (V^e > 25 km/h) theo quy dinh kh6ng) de dat dugc van toe Ion nhat la 30 3.3 Nghign ciru hinh dang dong hoc cua xe (giay) - Luc bam duac xdc dinh nhu sau: Pb= (p.Gb (N) (11) Trong do: