o an mon hoc thiet ke oto GVHD : Tran Hu Nhan
Chng 1CONG DUNG PHAN LOAI YEU CAU1.1. Cong dung :
Ly hp la mot trong nhng cum nho chu yeu cua oto may keo . Ly hp
dung e noi truc khuyu ong c vi he thong truyen lc , e truyen momen
quay ong c c em du va cat truyen ong en he thong truyen lc c nhanh
chong , dt khoat , lam nhiem vu an toan khi momen ln qua mc qui
nh
1.2. Yeu cau :
Ly hp phai am bao c cac yeu cau sau :
1. Truyen c momen quay ln nhat cua ong c ma khong b trt bat c
ieu kien s dung nao .Muon nh vay th momen ma sat cua ly hp phai ln
hn momen cc ai cua ong c mot t , ngha la he so d tr momen cua ly hp
phai ln hn 1 .
2. ong em du e tang t t momen quay len truc cua he thong truyen
lc , khong gay va ap cac banh rang . Ngoai ra khi ly hp ong em du
th oto may keo khi hanh khong giat , lam cho ngi lai met , nhat la
khi oto chay ng pho hoac khi may keo lam viec canh ong nho phai s
dung ly hp nhieu .3. M dt khoat va nhanh chong , ngha la cat hoan
toan truyen ong t ong c en he thong truyen lc thi gian rat ngan .
Neu m khong dt khoat th kho gai so em du v momen quay cua ong c va
momen quy dan en truc khuyu cua tat ca cac chi tiet chuyen ong cua
ong c se truyen mot phan en truc s cap cua hop so , cho nen khi dch
cac banh rang khoi s an khp e gai so khac se rat kho khan v tren
cac banh rang ta muon dch chuyen se co tac dung cua lc do momen noi
tren sinh ra . Ngoai ra momen ma sat cua ly hp se lam quay truc s
cap va truc trung gian cua hop so lam kho khan cho viec ong eu toc
o cac banh rang can gai . M dt khoat va nhanh chong se giam lc va
ap cac banh rang .4. Momen quan tnh cua cac chi tiet thu ong phai
nho e giam cac lc va ap len banh rang .5. Lam nhiem vu bo phan an
toan e tranh tac dung len he thong truyen lc nhng lc qua ln khi gap
qua tai .6. ieu khien de dang , lc tac dung len ban ap nho .7. am
bao ieu kien thoat nhiet tot .
8. Cac be mat ma sat thoat nhiet tot , am bao s lam viec bnh
thng .9. Ket cau n gian , trong lng nho , lam viec ben , ieu khien
va cham soc de dang .1.3. Phan loai :
Tuy theo cach truyen momen quay t truc khuyu en truc he thong
truyen lc ngi ta chia ra cac loai :
1. Ma sat Truyen momen quay bang cac be mat ma sat .2. Thuy lc
truyen momen quay bang chat long .
3. Nam cham ien truyen momen quay nh tac dung cua trng nam cham
en
4. Lien hp - truyen momen quay bang cach ket hp cac loai ke tren
.
oto may keo ly hp ma sat c dung nhieu nhat .Ly hp loai thuy lc
ngay nay cung ang c phat trien trong nganh che tao oto may keo v no
co u iem can ban la giam c tai trong va ap len he thong truyen lc
.Tuy theo hnh dang cua cac chi tiet ly hp loai ma sat ngi ta chia
ra : ly hp a (phan thu ong gom mot , hai hay a nhieu a ) , ly hp
hnh con ( a thu ong co dang hnh con ) va ly hp hnh trong (phan thu
ong lam theo kieu ma phanh va tang trong ). Loai ly hp hnh con va
tang trong ngay nay khong dung tren oto may keo na v momen quan tnh
cua chi tiet thu ong cua chung ln gay nen tai trong va ap len he
thong truyen lc khi ong ly hp .Tuy theo so a thu ong ngi ta chia ly
hp ma sat ra mot , hai hoac nhieu a .
Ly hp mot a hien nay dung nhieu tren oto may keo v no n gian gia
re , va momen quan tnh cua chi tiet thu ong be . oto tuy theo phng
phap phat sinh lc len a ep ngi ta chia ly hp loai lo xo , loai na
ly tam ay lc ep sinh ra bi cac lo xo va lc ly tam cua cac trong
khoi phu thuoc va loai ly tam .
Loai na ly tam dung oto du lch va van tai trong c nho v ay momen
cc ai cua ong c tng ng vi so vong quay tng oi cao .
Loai ly tam thng c dung e lam de dang ieu khien oto . Trong cac
ly hp loai ly tam th lc ly tam dung e ong m ly hp , con lc e ep la
do lo xo ,t khi dung lc ly tam e ep a ep . Loai ly hp nay khong c s
dung rong rai .Theo phng phap ieu khien ly hp co the chia ra loai
ieu khien bang sc ngi va loai ieu khien t ong .1.4. Chon phng an
thiet ke :
a) Ly hp ma sat kho :Ly hp ma sat kho hien nay gom loai mot a
hay nhieu a ma sat . Hien nay loai ly hp mot a ma sat co lo xo hnh
tru uc s nhieu . Lo xo ep co the dung mot lo xo trung tam (dung xe
du lch hay tai nhe ) hoac dung nhieu lo xo at xung quanh a ep (
dung tren xe tai ) .* u iem : co ket cau n gian , am bao thoat
nhiet tot , thuan tien cho cong tac bao dng va sa cha , momen quan
tnh cua chi tiet thu ong be .* Nhc iem : loai nay ong m khong em du
bang loai nhieu a .
Ly hp ly tam :
Ly hp noi ngat t ong theo che o bien thien toc o goc cua ong c
.
* u iem : khong co s trt khi ong c quay nhanh , ieu khien de
dang .
* Nhc iem : ket cau phc tap v co them ly hp phu va khp mot chieu
e truyen momen quay ngc lai khi phanh oto .
b) Ly hp ien t :
Qua trnh ong va ngat nh lc ien t cua nam cham .
* u iem : ket cau n gian , de t ong hoa qua trnh ieu khien , mat
ma sat hao mon t .
* Nhc iem : Bo phan t ong co momen quan tnh ln .c) Ly hp thuy lc
:
Co hai loai : ly hp thuy tnh va ly hp thuy ong .* u iem : giam
tai trong ong len ong c va he thong truyen lc khi thay oi ot ngot
che o lam viec . Tang s bam , khong giat khi gai so . ieu khien n
gian , de t ong hoa qua trnh ieu khien . t hao mon , cho phep khi
ong khi ang gai so .* Nhc iem : khong am bao m dt khoat , o trt ln
, ket cau phc tap .
d) Ly hp loai hon hp :
Thng dung loai ly hp ma sat ket hp thuy lc .* u iem : ket hp c u
diem cac loai ly hp tren .
* Nhc iem : ket cau phc tap , gia thanh cao .
e) Ket luan :
T bon loai ly hp tren ta thay ly hp ma sat kho mot a co c cau
dan ong ket hp thuy lc la phu hp nhat vi loai xe tai 15 tan v ket
cau n gian gia thanh thap de bao dng va sa cha . Do o ta se chon
loai ly hp mot (hoac hai ) a ma sat kho e thiet ke .1.5. Ket cau
cac chi tiet chnh va nguyen ly lam viec cua ly hp mot a ma sat kho
:
a)Cacte ly hp : lam bang gang co nhiem vu bao ve cac bo phan ben
trong cua ly hp , noi lien vi hop so bang bulong va ai oc .b)a b
ong : la mot a mong , tren a co ranh xe hng tam chia a thanh nhieu
phan bang nhau e giam o cng va tang o an hoi . Tren a coa gan cac
tam ma sat bang inh tan . a thu ng noi vi moay bang inh tan . Moay
c noi vi truc bang then hoa . Ngoai ra tren a b ong con co lo xo
giam chan tan so cao va cac tam giam chan tan so thap .c)Mam ep :
Che tao bang gang xam , co trong lng kha ln e lam thoat nhiet tot t
cac be mat ma sat . a ep phai cng e ep eu len cac vong ma sat .
Tren a ep co cho g len hoac cac ong dan hng e nh hoac hng lo xo ep
.d)on m : che tao bang thep , co ong cng cao . on m ta mot au len
ly hp , au con lai noi tiep vi a ep . Tren on m co bat vt ieu chnh
.e)Than ly hp : che tao bang thep , c bat cng vao banh a bang
bulong , tren than ly hp co khoan cac lo e at lo xo ep .f)Lo xo ep
: lo xo dang hnh tru , bo tr xung quanh , chu nen tao lc nen len a
ep .
1.6. Nguyen ly lam viec :
Ly hp ma sat hoat ong da vao lc ma sat . Momen c truyen nh ma
sat gia be mat banh a va a ma sat .a ep c noi vi banh a nh cang
phan ly va vo ly hp tao thanh phan chu ong luon quay cung van toc
vi truc khuyu ong c .Bnh thng ly hp trang thai ong va momen truyen
qua ly hp ti he thong truyen lc nh cac lo xo ep chat phan chu ong
va b ong thanh mot khoi .
Khi sang so hoac phanh , ngi lai tac dung lc vao ban ap ,qua he
thong ieu khien lam cang phan ly ay bac m ty len on m va tach a ep
khoi a b ong lam ngat momen truyen t ong c sang he thong truyen lc
.Chng IICONG TRT SINH RA TRONG QUA TRNH
ONG LY HPKhi ong ly hp se co hien tng trt cac a thi gian au cho
en khi nao a chu ong va a thu ong quay nh mot he thong ong hoc lien
.Khi cac a b trt se sinh ra cong ma sat lam nung nong cac chi tiet
cua ly hp len qua nhiet o lam viec bnh thng , lam hao mon cac tam
ma sat va nguy hiem nhat la cac lo xo ep co the b ram nhiet o nh
vay , mat kha nang ep . V the viec xac nh cong trt trong thi gian
ong ly hp la mot ieu can thiet .Trong qua trnh gai so oto theo s oi
so t thap len cao hoac t cao xuong thap ma qua trnh gai co the tien
hanh khac nhau . Khi oi so t thap len cao (th du t so I len so II ,
hoac so II len so III ) toc o goc cua truc khuyu ong c trong khi
ong ly hp cao hn toc o goc cua truc s cap hop so , v vay momen quay
cua ong c Mm khong nen ln e tranh tang cong trt . Khi oi t so cao
xuong so thap toc o goc cua truc khuyu co the thap hn toc o goc cua
truc s cap va trong trng hp nay khi ong ly hp can phai co momen Mm
nao ay cua ong c e lam ong eu cac toc o goc noi tren . Nhng trong
hai trng hp ke tren tuy theo ky thuat cua ngi lai toc o goc cua
truc khuyu va truc s cap cua hop so co the ong eu , ngha la (m = ih
.(a do o cong trt co the giam en toi thieu .Khi oto khi ong tai cho
s ong eu noi tren khong the thc hien c v (m > 0 va (a = 0 .
Trong trng hp nay cong trt se cc ai .
Nghien cu qua trnh trt cua ly hp co the da tren o th tang toc
cua oto c ghi lai t th nghiem trong thc . Qua trnh ong m ly hp se
anh hng en qua trnh trt ly hp , v vay ta se nghien cu trc tien qua
trnh ong ly hp . Qua trnh ong ly hp co the co hai trong hp sau
:1.ong ly hp ot ngot :
Luc o ong c ang quay so vong quay cao th ngi lai tha ot ngot ban
ap ly hp .Khi ong tai cho nh vay se sinh ra giat rat ln ln nhat la
khi ly hp co he so d tr ( cao . Che o ong ly hp nh the gan giong vi
s o tnh toan trnh bay di ay mac du trong thc te can tranh viec ong
ly hp ot ngot .Bieu th (a la toc o cua truc ong c trc luc ong ly hp
va (4 la toc o goc sau khi ong ly hp ( cuoi thi ky trt ) : He so ha
toc o goc tng oi cua truc ong c khi ong ly hp c bieu th la he so
nay khi ong ly hp ot ngot se co gia tr k3 = 0,35 0,52.ong ly hp em
du :
Khi ong ly hp em du se bao am cho oto khi ong tai cho c em du ,
ieu nay yeu cau quan trong khi s dung oto . Trong trng hp nay ngi
lai tha ban ap ly hp t t ke t khi cac be mat ma sat cham vao nhau ,
do o tang thi gian trt va tang cong trt . He so k3 trong trng hp
nay co gia tr k3 = 0,6 0,9 .Tuy theo che o ong ly hp ma thi gian
trt ly hp to se co gia tr sau ay ( khi khi ong tai cho ); khi ong
ly hp ot ngot to = 0,6 1,1s , khi ong em du to = 1,6 2,5 s .Neu
tiep tuc tang toc th toc o cua oto se tang ti gia tr v1 tng ng vi
toc o goc cc ai cua truc ong c (2 .
Toc o cc ai cua truc ong c c xac nh bi bo phan han che so vong
quay at trong oto van tai hoac bi s suy xet cua ngi lai . Tai thi
iem ng vi iem d ngi lai nha ly hp , ban apnhien lieu ( chan ga ) c
tha ra va toc o goc cua truc khuyu ong c ha xuong en gia tr (1 .Nhp
o ha toc o goc cua truc khuyu ong c khi tha chan ga va m ly hp c ac
trng bi he so , no bieu th s on nh lam viec cua ly hp . He so nay
co gia tr 94 105 1/s2 ( 900 1000 vg/ph/s ) .
Trong thi gian t2 gia iem d va e va thi gian chay tiep theo ngi
lai tien hanh chuyen so . Ngi lai tha ban ap ly hp ( ong ly hp ) va
ong ti an ban ap ga e tang so vong quay (m va toc o goc nay se ha
xuong do a ly hp b cuon theo . Tai iem h toc o goc cua truc ong c
la (4 va sau o bat au qua trnh tang toc o cua oto so truyen tiep
theo . Thi gian to ng vi thi gian trt ly hp khi chuyen so .
Toc o v cua oto at gia tr cc ai so truyen a cho tai iem d . toc
o nay se ha xuong trong giai oan t3 do toc o chuyen ong lam giam en
toc o ng vi iem e , luc o ly hp v cuon theo th toc o oto bat au
tang . Thi gian toan bo khi chuyen so la t4 .
e xet cac thong so c ban ac trng cho s lam viec cua ly hp chung
ta xet mo hnh cua ong c he thong truyen lc oto trnh bay tren hnh
:Jm : momen quan tnh cua banh a va cua cac chi tiet ong c quy dan
ve banh a .
Ja : momen quan tnh cua oto va rmooc quy dan en truc ly hp
=1,3884 (Nms2) ay : Go : trong lng toan bo oto ;
Go = (10000+15000).9,81 = 245250 (N) Gm : trong lng toan bo cua
rmooc ; khong co rmooc : Gm = 0
ih : ty so truyen tng ng cua hop so . ay oto ang che o khi ong
ty so truyen nay ng vi ty so truyen cua hop so tay so 1
ih = ih1 = 9.97 (xe tham khao TATRA 148S1)ip :ty so truyen cua
hop so phu.Xe khong co hop so phu do oip = 1
io : truyen lc chnh ;
io : 8.21 (xe tham khao)
rbx : ban knh lam viec cua banh xe .
rbx = 0,61 (m)
Momen can chuyen ong quy dan ve truc ly hp :
ay : ( : he so can tong cong cua ng ;
( = 0.15
K : he so can khong kh (khi oto chuyen ong vi toc o thap KFv2 =
0 );
(tl : hieu suat cua he thong truyen lc:(tl = 0.8
( Ma = 342,7 (N.m)
( : goc trt cua ly hp Cong trt cua ly hp c xac nh theo phng trnh
sau :
Tren c s phan tch tren ve hai phng phap ong ly hp chung ta co
hai phng phap e tnh cong trt cua ly hp . ay ta chon phng phap tnh
toan th hai v no n gian trong tnh toan va phu hp vi ieu kien lam
viec cua xe tai .Phng phap nay tnh en qua trnh dien bien thc te khi
ong ly hp gom hai giai oan :1.Tang momen quay cua ly hp M1 t 0 en
Ma khi bat au ong ly hp , luc o oto bat au khi ong tai cho .
2.Tang momen quay cua ly hp M1 en gia tr ma s trt cua ly hp
khong con na .
Cong cua ong c giai oan au cua thi gian t1 se tieu hao cho s trt
va nung nong ly hp .
Cong trt giai oan au L1 xac nh nh sau :
Cong cua ong c giai oan th hai cua thi gian t2 tieu ton cho viec
tang toc truc b ong cua ly hp va se thang cac sc can chuyen ong cua
oto .
Cong trt giai oan th hai se xac nh theo cong thc sau :
Cong trt toan bo cua ly hp se la :
Trong cong thc tren thi gian t1 va t2 c tnh nh sau :
= 0,857 (s)
= 1,044 (s) ay : k he so ty le , ac trng cho nhp o tang momen
cua a ly hp M1 khi ong ly hp . oi vi oto van tai k = 150 750 Nm/s .
Chon k = 400 Nm/s Gia tr cua A xac nh theo cong thc sau :
= 20,885 (Nms)1/2(m : toc o goc cua truc ong c
(m = n(/30 = 1500.(/30 = 157,1(s-1)
(a : toc o goc cua truc ly hp .Khi khi ong (a = 0Toc o goc cua
truc ong c khi ong ly hp co the tha nhan khong oi va bang toc o goc
ng vi momen cc ai cua ong c .
( L = 77,662(kJ)
T cac cong thc tren ta thay rang , cong trt tang ang ke khi tang
hieu so ((m - (a ) . e giam cong trt ngha la giam hao mon oi be mat
ma sat cua ly hp th ngi lai phai lam the nao e giam hieu so ((m -
(a ) Gia tr ln nhat cua hieu so nay xay ra khi khi ong oto tai cho
v luc o (a=0.
Khi tang khoi lng cua oto th cong trt se tang len ( khi cac
thong so khac khong thay oi ) Con khi tang ty so truyen cua he
truyen lc th cong trt se giam bt bi v luc o momen quan tnh cua oto
giam
Can phai chu y rang khi ong ly hp ot ngot se sinh ra lc xung kch
ln cac banh rang va cac chi tiet cua he thong truyen lc lam anh hng
en o ben cua cac c cau oto , do o co the ket luan s ong ly hp em du
trong khi tang nhanh momen ma sat M1 la trng hp tot nhat .Trong qua
trnh ong ly hp phan ln cong ma sat do s trt cac a thu ong se bien
thanh nhiet lam nong cac chi tiet cua ly hp , lam hao mon nhanh cac
tam ma sat . Ngoai ra con co the dan en hien tng ram lo ep lam giam
lc ep chung len a ep . e tranh hien tng nay can phai e y en kha
nang thoat nhiet khi thiet ke ly hp .Chng III
XAC NH KCH THC C BAN ,TNH TOAN CONG TRT RIENG HAO MON VA NHIET O
CUA LY HP :
Tnh toan ly hp loai ma sat nham muc ch xac nh so lng va kch thc
cac be mat ma sat can thiet e truyen momen quay cua ong c , xac nh
lc ep len be mat ma sat , xac nh ty so truyen cua c cau ieu khien
ly hp , cung nh xac nh kch thc cac chi tiet khac.Kch thc cua ly hp
c xac nh t c s co kha nang truyen momen quay ln hn momen quay cua
ong c mot t . S d phai tnh theo momen ong c la e am bao truyen c
het momen quay cua ong c en he thong truyen lc trong trng hp khi a
ma sat b dau nhn ri vao , hoac khi cac mat ma sat b hao mon , hoac
khi cac lo xo ep b mat tnh an hoi i mot t .Momen ma sat ma ly hp
can truyen la :
Ml = (.M
ay : M1: momen ma sat cua ly hp , Nm
M : momen quay cua ong c , oi vi oto lay momen cc ai cua ong c (
M = Memax ) , Nm .
( : he so d tr cua ly hp
Chon he so d tr ( can phai can than . Neu lay ( nho th khong am
bao truyen momen tot ; neu lay ( rat ln th ly hp khong the lam
nhiem vu bo phan an toan e tranh tai trong ln tac dung len he thong
truyen lc khi thay oi ot ngot che o lam viec . He so ( con lam cho
ly hp khoi mat nhieu cong do trt , nhat la oto co trong lng ln .
Khi cac tam ma sat b hao mon a ep se chuyen dch en banh a , do o
chieu dai lam viec cua lo xo ep tang len va lc ep se giam .e cho ly
hp am bao viec truyen momen ln nhat cua ong c trong ieu kien hao
mon cho phep cac tam ma sat trong s dung , th he so ( can phai lay
tng oi ln ,nhat la cac ket cau ly hp khong co ieu chnh lo xo ep .
Khi ( ln th cong trt cung giam va tang c thi gian phuc vu cua ly hp
; nhng ( ln th lc ep len a ln , phai tang so a hoac lch thc a ; do
o oi hoi lc tac dung len ban ap ieu khien ly hp phai ln va lam tang
trong lng kim loai trong ket cau .Hien nay cha co phng phap tnh
toan e xac nh tr so cua ( .Tr so ( c xac nh bang phng phap thc
nghiem co tnh en cac ieu phan tch tren e dung khi thiet ke nh sau
:oi vi oto van tai khong lam viec vi rmooc chon ( = 2 M1 = = 2
.770,085 = 1540,17 (N.m)ng knh ngoai cua vong ma sat b gii han bi
ng knh ngoai cua banh a ong c . oi vi oto co the chon ng knh ngoai
cua vong ma sat theo cong thc thc nghiem sau : = 46 (cm) ay : D2 ng
knh ngoai cua vong ma sat , cm ; Memax momen cc ai cua ong c , N.m
;
Memax = 770,085 (N.m)
C He so kinh nghiem . oi vi oto van tai trong ieu kien s dung
bnh thng chon C = 3,6 .
Do ng knh tnh toan c la qua ln , do o rat kho che tao , khoi lng
se ln , kch thc ly hp ln . V vay thay v dung ly hp mot a ma sat th
ta se chon lai kch thc cua a ma sat sau o kiem tra lai theo cac ieu
kien lam viec cua ly hp nham giam kch thc cua ly hp nhng van am bao
lam viec an toan . Ban knh ngoai vong ma sat : R2 = 18 cm (chon)Khi
thiet ke ban knh trong cua vong ma sat co the xac nh s bo nh sau
:
R1 = (0,53 0,75 )R2
Chon R1 = 0, 5556R2 = 10 (cm) Ban knh trung bnh c xac nh theo
cong thc sau: = 14.38(cm)He so ma sat ( phu thuoc vao nhieu yeu to
nguyen lieu cua be mat ma sat , tnh trang cua tam ma sat , nhiet o
va ap suat tren be mat ma sat.e n gian tnh toan co the tha nhan
rang he so ma sat ch phu thuoc bi nguyen lieu cua be mat ma sat
.
Thng oto hay dung cac be mat ma sat thep vi pherao hoac pherao
ong co he so ma sat kho ln nhat la 0,35 , nhng tnh en nhng ieu kien
nhiet o , toc o trt tng oi lam giam he so o i cho nen khi tnh ta
lay ( = 0,25 - 0,35 . Chon ( = 0,33 .Chon so be mat ma sat la p = 2
( mot a ma sat )Lc ep can thiet len cac a e truyen momen ma sat M
:
= 16227 (N)Ap suat tren vong ma sat se la :
= 230 (KN/m2 )Ap suat cho phep len be mat ma sat oi vi a ma sat
lam bang pherao la : [q] = 100 250 KN/m2 . Vay ap suat tren vong ma
sat thoa ieu kien cho phep cua vat lieu .Ap suat tren be mat ma sat
cha anh gia c kha nang chong mon cua ly hp . Khi cac ly hp co cung
mot ap suat len be mat ma sat nhng at tren oto co trong lng khac
nhau th s hao mon cua cac ly hp ay se khac nhau .Ly hp oto co trong
lng ln se hao mon nhieu v thi gian trt luc ong ly hp b keo dai hn .
Bi the can thiet phai kiem tra cong trt khi khi ong oan xe oto .oi
vi oto cong trt rieng c tnh theo cong thc :
= 551,8 (kJ/m2)Vay Lo = 551,5 < [Lo] = 400 600 kJ/m2 . Thoa
man yeu cau ve cong trt rieng cho phep .
Kiem tra nhiet o cua cac chi tiet b nung nong trong qua trnh ly
hp trt :
Trong o :
T : nhiet o tang len cua chi tiet ; oK
( : he so xac nh phan cong trt e nung nong chi tiet can tnh
( = 0,5 ( oi vi ly hp 1 a ).
L : cong trt toan bo ga :khoi lng cua chi tiet b nung nong ,
chon ga = 12 (kg)
T = 6,5 (oK) Vay ly hp thoa ieu kien nhiet o cho phep la t 8
10oK.Chng IV
PHAN TCH KET CAU CUA LY HP :
Chon loai ly hp cho oto la tuy thuoc vao ieu kien s dung
Cac loai ly hp cua oto la loai thng ong mot hoac hai a thu ong
.Ly hp mot a thu ong thng dung tat ca cac loai oto ; u iem cua no
la ket cau n gian , thoat nhiet tot va m dt khoat ; khuyet iem la
ong khong em du bang ly hp nhieu a .
Ly hp co bo giam chan at a thu ong va dung lo xo ep hnh tru at
xung quanh . Bo giam chan co tac dung dap tat cac chan ong xoan
sinh ra gia ong c va he thong truyen lc . Trc kia bo phan giam chan
dung nhieu tren oto du lch , ngay nay tren oto van tai cung dung
tng oi rong rai .
Khi can truyen momen quay ln ma kch thc bo tr can nho th co the
dung ly hp nhieu a thu ong . u iem cua ly hp nhieu a thu ong la ong
em du , khuyet iem la m khong dt khoat va ket cau phc tap .
Khi dung ly hp hai a thu ong th a chu ong trung gian c quay nh
chot gan banh a . Ngoai ra khi m ly hp , a chu ong trung gian c day
ra khoi a thu ong ang trc nh cac lo xo va nh v tr nhat nh e khoi ep
vao a thu ong ang sau nh cac chot nh v . Chot nh v nay phai ieu
chnh c .Ly hp vi on m na ly tam : ac iem cua ly hp nay la tren on m
co trong khoi phu , khi ly hp lam viec trong khoi nay se sinh ra lc
ly tam, ep manh them vao a ep , nh the cac lo xo ep co the lam vi o
cng t hn .Ly hp vi lo ep hnh con (lo xo trung tam ) co u iem la
sinh ra lc ep eu len be mat vong ma sat va co the rut ngan chieu
dai cua ly hp , v lo ep hnh con co ac iem la co the ep cho en khi
ca lo xo co the nam trong mat phang , con lo xo hnh tru khi ep con
phai e khoang cach toi thieu gia cac vong lo xo la 1 mm . Khuyet
iem khi dung lo xo ep hnh con la khoang khong gian gan truc ly hp
se chat choi , kho bo tr bac m ly hp . Ly hp nay c dung tren oto vi
momen quay can truyen ln hn 500 Nm .Khi s dung lo xo hnh con th ap
suat cua lo xo tac dung len a ep phai qua cac on , do o viec ieu
chnh ly hp tr nen phc tap .Ly hp co lo xo ep loai a : ly hp nay
dung ntren oto van tai .ac iem cua loai ly hp nay la lo xo ep lam
luon nhiem vu on m , ket cau n gian. ng ac tnh cua lo xo ep loai a
la phi tuyen .e giam tai trong ong len ong c va he thong truyen lc
mot so oto a s dung ly hp thuy lc vi hop so co cap . Sau ly hp thuy
lc bo tr ly hp ma sat e ly hp m c dt khoat , de gai so .Khi dung ly
hp thuy lc th trong lng toan bo cua ly hp se nang hn so vi ly hp ma
sat thng dung tren oto , nhng trong lng chung cua oto khong tang
len v ly hp thuy lc lam luon nhiem vu banh a ong c .
Hien nay ly hp thuy lc cha c s dung rong rai v con mot so nhc
iem can khac phuc . oto thng dung ong c cao toc , so vong quay cua
truc khuyu ln , v the khong dung ly hp khong thng ong e khoi sinh
ra va ap khi gai so .S d ly hp khong thng ong sinh ra va ap khi gai
so la v momen quan tnh phan thu ong cua ly hp nay kha ln . Ly hp
loai hnh con va loai trong (phan thu ong damg con va dang loai ma
phanh ) hien nay khong dung na la v momen quan tnh phan thu ong cua
chung kha ln .Chng V
KET CAU VA TNH TOAN CAC CHI TIET CHU YEU CUA LY HP :
1.a thu ong :
oto va may keo thng dung loai ly hp mot hai a thu ong vi tam ma
sat co he so ma sat cao la nham muc ch giam kch thc va giam kim
loai cua ly hp . Con ly hp nhieu a co the lam a thu ong co tam ma
sat hoac khong co tam ma sat . Ly hp vi a thep khong co tam ma sat
thng lam viec trong dau e tang kha nang thoat nhiet (ly hp nay at
trong hop so hoac truyen ong truc thu cong suat ).Ly hp mot a cua
oto hien nay ch dung a thu ong loai an hoi .o an hoi cua a thu ong
am bao bang cach cho no nhng hnh thu nhat nh hoac dung them nhng
chi tiet ac biet co kha nang lam giam o cng cua a .e giam o cng ,
tren a thu ong co xe cac ng hng tam . Cac ng xe nay chia a thu ong
ra nhieu phan .Cac phan nay uon ve cac pha khac nhau .So lng ng xe
t 4 en 12 tuy theo ng knh cua a .Cac ng xe nay lam cho a thu ong
venh khi b nong len luc lam viec .e giam chieu rong (tang o an hoi
) cho noi tiep cua phan ngoai vi phan trung tam cua a th ng xe co
the lam theo hnh ch T . Cac a an hoi tang them o em du khi ong ly
hp , nhng cung ong thi keo dai thi gian ong ly hp . Khuyet iem cua
a thu ong co cac phan c uon ve cac pha khac nhau la kho ma co c o
cng nh nhau tat ca cac phan .Khi at lo xo tam gn song gia a thu ong
va tam ma sat th o cng tren be mat cua a thu ong tng oi eu hn .Neu
thay oi o cng cua lo xo tam co the anh hng en o cng chung cua a thu
ong .e tang o tiep xuc ong eu va tang be mat tiep xuc cua tam ma
sat trong qua trnh ong ly hp th so lo xo tam khong c nho hn 6 . Khi
at lo xo tam gia a thu ong va tam ma sat ma muon m ly hp dt khoat
th hanh trnh dch chuyen cua a ep phai tang len mot t . ieu nay co
the thc hien c neu van gi nguyen hanh trnh cua ban ap bang cach
giam ty so truyen cua he thong dan ong ly hp va nh vay phai tang lc
tac dung len ban ap . Cung v the ma cac ly hp truyen momen quay ln
khong dung cac a thu ong an hoi co lo xo tam .e tang o em du khi
ong ly hp th a thu ong khong lam phang ma lam hnh con (goc nh
khoang 176o ) Khi ong ly hp th a hnh con se tiep xuc vi be mat ma
sat cua a ep va banh a khong tc thi , ma tien hanh t t theo qua
trnh ep a , do o lam tang o em du khi ong ly hp v momen quay c
truyen t t .a thu ong c noi vi truc ly hp nh moay , moay noi vi a
thu ong bang inh tan rat t khi dung bulong . Che tao a thu ong lien
mot khoi th khong tien ve phng dien cong nghe che tao , e hp ly hn
can che tao chung rieng re .a thu ong co the lam vi bo phan giam
chan hoac khong co giam chan . Khi at bo phan giam chan th ket cau
cua a se thay oi , trong lng va momen quan tnh se tang len . a thu
ong can co tnh chat an hoi ln e tang em du khi ong ly hp cho nen
chung c che tao bang la thep co thanh phan cacbon tiep noi vi phan
thu ong cua ly hp bang cac ranh then hoa th cac ranh then hoa c tnh
theo dap tren c s lam the nao cho a thu ong khong sinh ra tren be
mat trong nhng vet han , do o ng suat dap cho phep trung bnh va cao
( thep loai 45 en 85 ) c toi trong dau va ep e tranh venh . Lo xo
tam c che tao t la thep mong co thanh phan cacbon cao .
Neu a thu ong trc se lay la [(d] = 3- 4 MN/m2 Cac inh tan noi a
thu ong vi moay che tao bang thep vi ng knh 6- 10 mm . inh tan tnh
toan theo cat dap . ng suat cat cho phep [( ]= 30 MN/m2 , ng suat
dap cho phep [(d ] = 80 MN/m2 .2.Vong ma sat :
Vong ma sat gi vai tro quan trong khi ly hp lam viec va can phai
co cac ac tnh sau :-am bao he so ma sat can thiet va he so ma sat t
b anh hng khi co s thay oi nhiet o , toc o o trt va ap suat tren be
mat .-Co kha nang chong mon ln nhiet o cao (en 573 623 oK )-Tr lai
kha nang ma sat nh ban au c nhanh chong sau khi b nung nong hoac b
lam lanh .-Lam viec tot , nhiet o cao t b sui cac chat dnh , khong
co mui khet , khong b xop .-Co tnh chat c hoc cao (o ben , o an hoi
va o deo ).
Nguyen lieu hien nay thng dung e lam vong ma sat la pherao ,
pherao ong va trong mot so trng hp la kim loai s . Phera o hien nay
c dung rong rai nhat, chieu day tam ma sat o 3 4 mm .No che tao
bang pherao nghien nho co tham chat dnh , sau o em i ep . Cac vong
ma sat bang pherao co o ben c hoc cao , khong b xop va co the lam
viec nhiet o cao . Vong ma sat bang pherao ong hoac pherao co hat
kim loai mau va chat dnh hien nay khong c s dung na .Mac du co them
kim loai mau , he so ma sat cua cac vong ma sat nay thc te van
khong khac he so ma sat cua vong ma sat bang pherao bnh thng .Thi
gian sau nay , con dung pherao cao su e lam tam ma sat , no gom co
pherao va chat dnh bang cao su .Vong ma sat bang pherao co o dan
nhiet thap , he so ma sat cua chung phu thuoc vao nhiet o .Thi gian
gan ay tren oto bat au s dung vong ma sat bang kim loai s . Cac a
thu ong co be mat ma sat bang kim loai s c che tao bang cach em ep
bot kim loai di ap suat cao thanh cac vong ma sat
Tiep o at cac vong ma sat a ep xong len a thep roi a vao lo ien
. ay xay ra qua trnh nung chay vong ma sat co c s bot ong va gan
lien vong nay vi thep . Vong ma sat che tao bang kim loai s so vi
vong ma sat bang pherao se co o chong mon tot , he so ma sat cao hn
, hkong nhay cam vi s tang nhiet o , ap suat cho phep len be mat ma
sat cao hn va o dan nhiet tot hn. Chieu day cua tam ma sat bang kim
loai s 1,2 4 mm .ac iem cua kim loai s la b , do o can thiet phai
gan chung vi a ep bang cach nung chay .Trong ieu kien s dung bnh
thng th vong ma sat che tao bang pherao bao am kha nang lam viec
tot va che tao re . Vong ma sat bang lim loai s ch nen dung trong
trng hp can thiet v no che tao bang kim loai mau nen at tien .Cac
tam ma sat bang pherao c gan vi a thep bang cach dan hoac bang inh
tan . Phng phap dan t c dung v chat dnh ket ac biet dung e dnh tam
ma sat vao a se dnh rat chat va khi tam ma sat b mon th khong the
tach ra khoi a e thay bang tam ma sat khac c . trong trng hp nay
thng phai thay toan bo a thu ong . Phng phap gan bang inh tan c
dung nhieu . inh tan lam bang ong o , thau mem hoac bang nhom vi ng
knh t 4 6 mm theo dang hnh ong , dang inh tron co khoet rong mot au
roi khi gan b ep toe au ra , hoac dang inh tron co au na chom cau
.Tuy theo ng knh va chieu rong a ma sat ma cac inh tan co the xep
theo hai hoac 3 hang , theo loi ban c .Khi gan cac tam ma sat th au
cac inh tan phai thut xuong khoi be mat tam ma sat o 1 - 2 mm e
tranh s co sat cac inh vao a ep hoac banh a khi tam ma sat b hao
mon . S d inh tan lam bang cac kim loai mem noi tren la e khi tam
ma sat mon qua mc th inh khong lam hong mat a va banh a .Cac tam ma
sat nen gan tren a nao ma s thu nhiet cua no kho khan hn , cung v
the ma cac tam ma sat thng gan tren be mat a thu ong , v a thu ong
theo yeu cau cua ket cau phai lam mong vi trong khoi be e giam
momen quan tnh , cho nen thu nhiet kem .Con a ep va banh a co trong
khoi ln e thu nhiet , neu gan tam ma sat vao chung th se lam cho
kha nang thoat nhiet cua ly hp kem i.3.Moay a thu ong :Moay a thu
ong cua ly hp oto c at tren truc then hoa cua ly hp theo lap ghep
trt .e co the mai nhan de dang cac mat ben cua then vi ban knh
trong cua truc then hoa ngi ta lam ranh hoac ln chuyen tiep eu an
vi ban knh r . Hnh dang cua then anh hng en o vng ben cua truc ly
hp . Neu chuyen tiep ot ngot th chan then se co ng suat cuc bo rat
ln .Cac then co the lam dang than khai hoac vuong goc . Dang then
than khai am bao o ben va o chnh xac trung tam tot hn loai vuong
goc.Ta chon rang then hoa dang than khai v co nhieu u iem : Sc ben
moi cao do chan ren day hn va khong co goc ln ot ngot nen ng suat
tap trung chan then nho (tan so tap trung ng suat giam) so vi rang
hnh ch nhat . Cac phan t moi ghep c che tao bang cac phng phap hoan
thien hn do o o chnh xac cao hn . am bao o ong tam cao .
Cac then cua moay tnh theo dap va cat . Khi co nhieu a thu ong
va moi a nam tren moi moay rieng biet th coi nh momen quay truyen
en moi a eu bang nhau . Moay a thu ong che tao bang thep 40 hoac
40X
Lc tac dung len ban knh trung bnh cua cac then oi vi mot moay la
:
Trong o : Q : lc tac dung len then , (N) M : Momen cc ai cua ong
c . M = Memax = 770,085 (N.m) Z1 : so lng moay . Z1 = 1 D : ng knh
ngoai cua cac then truc ly hp .D = 55 (mm) d : ng knh trong cua cac
then tren a thu ong
d = 40 (mm)
( Q = 32425 (N) .ng suat dap cua then se la :
= 8,65 (MN/m2) < [ (d ] = 20 (MN/m2)Trong o : Z2 : so lng
then cua moayZ2 = 10
l : chieu dai lam viec cua then
l = 50 (mm)
ng suat cat cua then la :
= 7,5 (MN/m2 ) < [( ] = 10 (MN/m2)Trong o :
b : chieu rong cua chan then . b = 8,5 (mm)
Vay then thoa ng suat cho phep .4.Giam chan :Giam chan c dung
trong ly hp e tranh cho he thong truyen lc cua oto khoi nhng dao
ong xoan cong hng sinh ra khi co s trung mot trong nhng tan so cua
dao ong s hu cua he thong truyen lc vi tan so cua lc gay nen bi s
thay oi momen xoan cua ong c . Chi tiet an hoi cua giam chan dung e
giam o cng cua he thong truyen lc , do o giam dc tan so dao ong ban
than cua he thong truyen lc va triet tieu c kha nang xuat hien cong
hng tan so cao . Do o cng toi thieu cua chi tiet b an hoi cua giam
chan b gii han bi ieu kien ket cau cua ly hp cho nen he thong
truyen lc cua oto khong the tranh khoi cong hng tan so thap .Bi the
ngoai chi tiet an hoi ra can phai co chi tiet thu nang lng cua cac
dao ong cong hng tan so thap bang phng phap ma sat goi la chi tiet
ma sat .Cac giam chan cua ly hp hien nay c ket cau theo mot nguyen
tac chung , ngha la a thu ong c noi vi moay nh chi tiet an hoi . S
khac nhau va ket cau cua giam chan phu thuoc bi loai ci tiet an hoi
la lo xo hay cao su . giam chan ma chi tiet an hoi la cao su hay
vai tham cao su th khong can at chi tiet ma sat na , bi v cao su co
tnh chat ma sat ben trong chat cao su .
Mac dau giam chan co chi tiet an hoi bang cao su co ket cau n
gian nhng no khong c s dung rong rai bi v e tang hieu qua giam chan
t kch thc cua chi tiet an hoi bang cao su phai ln , do o cang lam
tang momen quan tnh cua a thu ong .Hn na khi ly hp lam viec nhiet o
se tang len lam anh hng en o ben va tnh chat ly hoc cua cao su
.Giam chan c dung nhieu la loai chi tiet co an hoi bang lo xo c at
tiep tuyen trong cac lo khoet cua a thu ong va co chi tiet ma sat
bang thep hoac bang nguyen lieu ma sat khac . So lng lo xo hnh tru
thng t 6 12 chiec . Chieu day va so lng vong ma sat c chon the nao
e momen ma sat gia phan chu ong va thu ong cua giam chan am bao thu
hut c nang lng dao ong khi cong hng . e tang hieu qua giam chan ,
co khi giam chan c thiet ke vi o cng thay oi , ban au o cng t hn va
sau o tang dan . Momen cc ai Mmax gii han o cng toi thieu cua lo xo
(khi cac vong lo xo sat vao nhau ) thng lay bang momen xac nh then
ieu kien bam ( = 0,8
= 877 (N.m) ay : G2 Trong lng tac dung len cac banh chu ong ,
(N).G2 = 15000 . 9,81 = 147150 (N)
rbx Ban knh lan cua banh xe , (m).rbx = 0,61 (m) io ty so truyen
cua truyen lc chnh .io = 8,21 ih1 ty so truyen cua hop so so 1
ih1 = 9,97
Lc tac dung len lo xo giam chan :
= 1566 (N)Trong o :R : Ban knh vong tron at lo xo giam chan .R =
70 (mm )n : so lng lo xo giam chan .
n = 8
Chon ch so cua lo xo la :
C = D/d = 4
He so tnh en s tap trung ng suat .k = 1,4 ng suat cat cho phep
cua vat lieu
[(x ] = 0,5.(b = 0,5 . 1600 = 800 (MPa)ng knh day lo xo :
= 5,3 (mm)ng knh trung bnh cua vong lo xo :D = d . C = 5,3 . 4 =
21,2 (mm)Lc ep nho nhat khi lap lo xo vao lo :
Plxmin = 300 (N)Goc xoay tng ng cua may khi lo xo chu tai :( =
5oKhoan dch chuyen cho phep cua lo xo luc lam viec : X = R. ( = 7.
5.( / 180 = 6,1 (mm)So vong lam viec cua lo xo :
= 4 (vong) Vi G : Momen quan tnh oc cc cua tiet dien day lo xo .
G = 8.104 (MPa)
So vong toan bo cua lo xo : io = i + 1,5 = 5,5 (vong)
Chieu dai cua lo xo khi cac vong st nhau :lt = (io 0,5).d = 26,5
(mm)Chieu dai cua lo xo khi cha chu tai :lo = 35 (mm)5.Truc :
Do oto ly hp va hop so c bo tr lien nhau e am bao can gat so nam
vao v tr buong lai v the tren truc ly hp con co banh rang chu ong
luon luon an khp cua hop so va thng chung c noi vi nhau qua khp1
noi hoac truyen ong khp cacang cho nen truc ly hp khong co banh
rang chu ong cua hop so .
Truc ly hp phai am bao ong tam vi truc khuyu ong c . Trong a so
trng hp o ong tam c thc hien nh hai o bi , mot at lo khoet cua banh
a hoac truc khuyu ong c , con mot c at vo hop so . e am bao o ong
tam cua hai o bi khi lap ghep ta nen lam chat nh v vo ong c va vo
ly hp . oto tren truc ly hp co banh rang chu ong cua hop so banh
rang nay co the la banh rang thang hoac banh rang nghieng . Goi cua
truc ly hp c at vao banh a . Goi nay khong nhan lc chieu truc . e
truc ly hp khong chuyen dch theo chieu truc do thanh phan lc chieu
truc banh rang gay nen , can at chi tiet nh v nam tren vo hop so
.
Goi cua truc ly hp thng c at tren o bi hng knh mot day .
Trong a so trng hp oto boi trn bi ang trc cua truc ly hp bang
cach cho dau m khi thao ly hp , m nay dung trong suot thi gian phuc
vu cho en khi thao ly hp lan khac . Trong trng hp nay o bi nen co
vong bao ve hay vong chan dau e gi m boi trn bi trc cua ly hp c thc
hien nh vu m bat tren truc ly hp qua ranh tam truc hoac bang day n
at ng tam truc khuyu .Truc ly hp cua oto thng c noi vi moay cac a
thu ong nh then hoa . Trong mot vai trng hp e n gian viec sa cha
truc , cac then c kha tren mot vanh rieng , vanh nay noi vi truc
bang inh tan .
Neu tren truc co banh rang th cua banh rang se sinh ra cac momen
uon , xoan phu them . Trong trng hp nay can phan tch tac dung cho
cu the e ve bieu o momen xoan va momen uon tac dung len truc .ng
suat tong hp do momen xoan va momen uon tac dung tai tiet dien nguy
hiem la : = MN/m2
ay : Mx : momen xoan tac dung tai tiet dien nguy hiem , MN/m
Mu : Momen uon tac dung tai tiet dien nguy hiem , MN/m
d : ng knh tai tiet dien nguy hiem , m .
Truc ly hp cua oto che tao bang cac loai thep 40X , 45, ngha la
bang cac loai thep che tao banh rang , v a so truc cua ly hp che
tao lien vi banh rang chu ong luon an khp .ng suat xoan cho phep la
[( ] = 80 120 MN/m2
Cac then cua ly hp c tnh theo chen dap va cat theo cac cong thc
tng t nh tnh moay a thu ong . ng suat chen dap cho phep khong qua
25 MN/m2 , ng suat cat cho phep khong qua MN/m2 .
6.a ep va a ep trung gian (chu ong ) :a ep ngoai va a ep trung
gian phai quay cung vi banh a , khi m hoac ong ly hp phai co kha
nang chuyen dch theo chieu truc , bi the chung c noi vi banh a bang
chot 1 , gan than ly hp bang chot 2, c van vao banh a bang chot 3 c
ep chat vao banh a hoac bang g loi cua a c ty vao cho lom 4 cua
than ly hp hoac bang nhng phng phap khac . Khi ong c lam viec cac a
nay quay cung banh a cho nen khi tnh momen quan tnh cua cac trong
khoi quay cua ong c can phai them momen quan tnh cua cac a nay .a
ep ngoai va a ep trung gian chu ong phai co trong lng kha ln e lam
thoat nhiet tot t cac be mat ma sat , bang cach hut nhiet vao ban
than chung roi truyen ra khong kh .
Cac a ep phai cng e am bao ep eu len cac vong ma sat . Muon
thoat nhiet tot oi khi tren a lam cac gan nh canh quat e gay gio
.
cac ly hp 2 a thu ong , e khong kh lanh tuan hoan tot th a ep
trung gian chu ong co cac ranh thong gio hng tam .
a ep ngoai va a ep trung gian khi lam viec chung vi cac vong ma
sat phai chong mon tot , khong c xc cac be mat lam viec , de che
tao , thoat nhiet tot va co o ben c hoc cao so vong quay ln . Bi v
cac a ep co hnh dang tng oi phc tap (co phan loi e noi vi vo ly hp
, co cho g len e nh v hoac hng lo xo ep , co cac cho loi ra e noi
vi on m hay co cac ranh thong gio ) cho nen thng c ut bang gang xam
co cau tng peclit .Cac a ep co kch thc ln se b tac dung cua lc kch
ong rat ln . Cac cho loi ra cua cac a e truyen momen quay cua ong c
se b tac dung cua lc kch ong rat ln ( do co khe h gia cho loi cua a
va than ly hp o 0,2 mm ) cho nen trong mot vai trng hp a gay nen
ran nt ay cho loi .e tang o ben , o cng vng va tuoi tho cac a ep
cua ly hp nay ngi ta che tao chung bang gang hp kim . Ngoai ra e
cng hoa cac cho uc cuc bo ngi ta co at cot bang day ong ng knh 5-7
mm c uon cong theo hnh cung vao khuon e uc . Nh cac bien phap tren
ma o ben cua cac a ep nay so vi nhng ai khac c uc bang gang thng
tang gap 1,5 lan .7. Lo xo ep :Ly hp oto s dung lo xo hnh tru , con
va lo xo a . L o xo tru c s dung rong rai va co the at xung quanh
hay trung tam . Ap lc cua a ep c truyen trc tiep hay qua cac on .
So lng va ng knh lo xo c chon nh the nao e am bao lc ep can thiet
len cac a va e bo tr hp ly tren da ep , nen thng at t 9 12 cai lo
xo . Lo xo tnh trang ep c ta mot au len a ep con au kia tren than
ly hp . Kieu bo tr nh the am bao gon gang ve ket cau va co rong cho
e at o bi ep cua bac m ly hp nam tren truc ly hp .
Bo tr lo xo xung quanh co khuyet iem la neu nh trong trng hop o
cng cua lo xo khac nhau th lc ep cua chung se khac nhau do o lam
cho lc ep cac be mat ma sat khong ong eu . Muon tranh khuyet iem
nay can phai tang yeu cau khi chon cac lo xo va phan loai thanh bo
. Muon cho ly hp lam viec tot can phai lam bo phan e hng lo xo khi
lap ghep , v du lam g noi len than ly hp hoac a ep . Cac g nay
tranh cho lo xo khoi bat ra di tac dung cua lc ly tam ln . Bo tr lo
xo trung tam dung con t .Dung lo xo trung tam co u iem la am bao
cac mat ma sat ep eu hn . Ly hp vi lo xo trung tam hnh con co u iem
so vi hnh tru la kch thc chieu dai be hn va ket cau gon gang hn .
Khi s dung cac lo xo ep trung tam hnh tru hoac hnh con th bo tr o
bi ep cua c cau ieu khien se phc tap , bi v cac lo xo phai at tren
truc ly hp .e tranh nung nong cac lo xo hnh tru bo tr xung quanh a
ep th di mat ta cua lo xo vao a ep co at tam em cach nhiet . Chieu
day cua tam em nay khoang 3 mm .Cac lo xo ly hp thng ong c at trang
thai ep ban au .Lc ep chung cua cac lo xo khi tat ca cac lo xo eu
tac dung len a ep phai bang lc P can thiet e truyen momen quay
.
= 16227 (N)
Khi m ly hp cac lo xo ep b bien dang them , do o lc ep len a se
ln hn na . Ta coi rang bien dang them cua lo xo khi m ly hp se lam
tang lc ep len 20% . Do o lc tnh toan cua lo xo c tha nhan khong
phai la P ma la P :
= 19472 (N)Khi m ly hp khe h gia cac vong lo xo lan can khong c
nho hn 1 mm . Mac du cac lo xo cua ly hp lam viec trong ieu kien
rat gan ieu kien tnh , nhng kim loai che tao no oi hoi co tnh chat
cao , ngha la phai co tnh chat an hoi on nh va co o vng ben cao .Lo
xo cua ly hp thng c che tao bang thep cacbon 85 , thep mangan 65 .
ng suat cho phep [(]=500 700 MN/m2 .Lo xo c tnh toan theo cac phng
phap sau :Tnh lc tac dung len mot lo xo Po :
= 1623 (N) ay : P : lc tac dung len tat ca cac lo xo khi a m ly
hp . n : so lng lo xo chon theo ac iem ve ket cau .Chon n = 12Chon
ch so cua lo xo :
C = D/ d = 5He so tnh en s tap trung ng suat .
k = 1,3
ng suat cat cho phep cua vat lieu
[(x ] = 0,5.(b = 0,5 . 1600 = 800 (MPa)
ng knh day lo xo :
= 5.8(mm)
Chon ng knh day lo xo la d = 6 (mm)ng knh trung bnh cua vong lo
xo :
D = d . C = 6 . 5 = 30 (mm)
Lc ep nho nhat khi lap lo xo vao lo :
Plxmin = P/n = 16227 / 12 = 1352 (N)
Khoan dch chuyen cho phep cua lo xo luc lam viec :
X = 3 (mm)
So vong lam viec cua lo xo :
= 5,3 (vong)
Vi G : Momen quan tnh oc cc cua tiet dien day lo xo .
G = 8.104 (MPa)
So vong toan bo cua lo xo :
io = i + 1,5 = 6,8 (vong)
Chieu dai cua lo xo khi cac vong st nhau :
lt = (io 0,5).d = 37,8 (mm)
o mem cua lo xo :(1 = 8C3 /(G.d) = 0,002083Chuyen v cho phep cua
lo xo :
( = (1.i.Pmax = 18 (mm)Khe h gia cac vong lo xo khi chu tai ln
nhat :( = 1 (mm)Bc lo xo : t = d + ((/ i) + ( = 10,38 (mm)Chieu dai
cua lo xo khi cha chu tai :lo = lt + (t d).i = 61 (mm) 8. on m :Cac
on m ly hp c ta mot au tren ly hp , au con lai noi tiep vi a ep .
on m dung e m ly hp , no can co o cng tot , nhat la trong mat phang
tac dung lc , con ong em dun ly hp la nh dung a thu ong an hoi
.Chon so lng cac on tuy theo kch thc ly hp va khong t hn ba chiec
.
e giam tieu hao do ma sat khi m ly hp th cac on c at tren cac
chan ta hay tren cac o thanh lan hnh tru hay cac ngong . O trt
khong c dung v no can phai boi trn , khi quay di tac dung cua lc ly
tam dau se ban tung toe hoac khi ly hp b nonh th dau se chay , do o
dau co the ri vao vong ma sat lam anh hng en kha nang lam viec cua
chung .Khi a ep chuyen ong tnh tien th cac on m ly hp phai quay t
do goi hoac cho noi cua on m vi a ep hoac ca hai cho .Khi m ly hp ,
bac m phai t cung mot luc len cac on m . Muon the cac au trong cua
chung phai nam trong mot mat phang . ieu chnh cac au trong cua on m
tien hanh bang cach dung chot va ecu nam au ngoai cua cac on , bang
cach thay oi v tr goi trung gian hoac bang cach dung cac bulong ieu
chnh van vao cac au trong cua on .oi vi cac on m che tao bang phng
phap dap , ngi ta dung thep la co thanh phan cacbon thap ,thep 80 ,
sau o em xianuya hoa . Khi tang so vong quay cua truc khuyu th ap
lc tac dung len a se tang do lc ly tam Plt cua trong khoi phu on m
ly hp sinh ra . Lc ly tam cua on m xac nh theo cong thc sau :
= ay : GP : Trong lng cua on ke ca trong khoi phu , N n : So
vong quay cua truc khuyu ong c , v/ph R : Khoang cach t trong tam
cua on en truc quay
g : Gia toc trong trng , g = 9,81 m/s2 .
Lc ep P1 len a ep do lc ly tam cua mot on sinh ra la :Trong khoi
phu cua cac on c che tao nh the nao e sinh ra lc ep P1 phoi hp vi
lc ep lo xo co the sinh ra momen quay ma sat ln hn momen cc ai cua
ong c khi ong c lam viec so vong quay ng vi momen cc ai .Lc ep
chung len a ep do tac dung cua lc ly tam va cua lo xo ep la :
ay : P : Lc ep do lo xo gay nen , N .
c : So lng on m ly hp
9. C cau ieu khien ly hp :
oi vi loai ly hp thng ong :
e ieu khien ly hp thng ong ngi ta dung dan ong loai c kh hoac c
kh co cng hoa thuy lc hay cng hoa chan khong .
oi vi dan ong c kh , ty so truyen cua dan ong id. va hanh trnh
ban ap Sb c xac nh nh sau :
Vi Va:
ay : F : Hanh trnh cua a ep khi m ly hp ( : khe h gia on m ly hp
va bac m , hay la hanh trnh chay khong cua bac m ly hp .
a,c,d,q ,g c trnh bay tren s o
Hanh trnh cua a ep khi m ly hp c xac nh nh sau :
F = (f.p ay : (f : khe h gia oi be mat ma sat khi ly hp m hoan
toan . oi vi oto(f = 0,75 1 mm p : So lng oi be mat ma sat .
Khe h ( can thiet e ly hp co the lam viec c khi cac vong ma sat
b hao mon ( v khi o khe h ( giam va a ep co the khong ep c a thu
ong vao banh a do on m ly hp b ham bi bac m ).oi vi oto tuy theo o
hao mon cho phep cua vong ma sat khe h (= 2-3 mm . Neu v tr cua cac
on m phu thuoc so vong quay ong c hoac neu o an joi cua on m ln th
khe h ( = 3,5 4 mm .oi vi dan ong c kh co cng hoa thuy lc th ty so
truyen cua dan ong id va hanh trnh cua ban ap ib xac nh nh sau :ib
=
Va
Thng ty so truyen cua dan ong ly hp oto vao khoang id = 24 45 e
giam hanh trnh cua ban ap ly hp Sd khi thiet ke can phai tang o cng
cua chi tiet dan ong . Neu cac on dan ong va cac truc b bien dang
nhieu th hanh trinh cua ban ap se tang . Dan ong thuy lc co o cng
ln hn .
Lc tac dung len ban ap Pb e m ly hp xac nh theo cong thc sau
:
ay : P : tong cac lc do lo xo ep tac dung a ep cuoi thi ly m ly
hp
(d : hieu suat cua dan ong
Thng (d = 0,7 0,8
Khi thiet ke ly hp can phai chu y en e giam lc tac dung len ban
ap va giam hanh trnh cua ban ap vi muc ch e giam cng o lao ong cho
ngi lai . oi vi oto van tai lc tac dung len ban ap ly hp khi m hoan
toan khong c qua 200 N , con oi vi oto du lch lam viec ng pho khong
c qua 150 N .Hanh trnh toan bo cua ban ap ly hp oi vi oto van tai
khong qua 180 mm , oi vi oto du lch khong qua 150 mm.Ket cau dan
ong ly hp loai c kh co cng hoa thuy lc co u iem la am bao s bt kn
cua ay vo oto nh tam quay ban ap c bo tr nam pha tren .Ban ap ly hp
che tao bang cach uc gang ren hoac dap t thep 20 hoac thep 25 .
10 . Bac m ly hp :
Bac m la bo phan trung gian e c cau ieu khien co the tac dung
len on m e m ly hp . bac m co the co o bi t hay o bi hng knh . Cung
co khi ngi ta thay o bi bac m bang vong t che tao bang than ep co
tham m . Dung vong ty che tao bang than ep se khong can boi trn khi
s dung . Boi trn cac bi va cac chi tiet trt cua bac m c tien hanh
nh vu m at ngay tren o bi hoac nh vu m at ca so cua ly hp qua ong
mem , hoac nh vong n hut dau t buong cha dau . cac ket cau hien nay
, o bi t khong co cho e bm m . Trong trng hp nay o bi c at trong
mot vong bang thep la do o o bi khong b tach ri va c bt kn buong
cha m . Buong cha m co u m e boi trn trong suot thi ky lam viec cua
oto cho en khi ai tu .11. Than ly hp :Than ly hp c gan vi banh a va
dung lam mat ta cho cac lo xo ep cung nh lam goi cho cac on m . e
lam mat ly hp ngi ta khoet cac ca so than . Than che tao bang thep
08 hay 10 , t khi che tao bang thep uc hoac gang uc .
12 . Vo ly hp :
mot vai ket cau cua oto na khung hoac khong khung vo ly hp va
hop so lam thanh mot khoi lien . cac oto khac co khung th vo ly hp
lam thanh mot khoi rieng biet .Hnh dang , kch thc cua vo va cac ca
so e thong gio phu thuoc vao ket cau cua ly hp .
Vo ly hp co loai lien mot khoi hoac loai ghep . loai lien mot
khoi vo c uc bang gang , con loai ghep th ca hai phan cua vo co the
cung c uc bang gang hoac phan di dap bang thep la .
Vo ly hp c nh v vi vo ong c theo vo banh a nh cac chot nh v va
nh v oi vi hop so theo mat bch cua nap o bi truc s cap hop so .13.
S can bang ly hp :e tranh nhng hien tng khong tot do lc ly tam sinh
ra can phai can bang cac chi tiet cua ly hp khi che tao . o chnh
xac khi can bang phu thuoc so vong quay cua ong c , bi khe h cua
cac cho noi a ep vi than ly hp va bi kch thc cua ly hp .a ep cua
oto du lch c can bang vi o chnh xac (1,5 2 )10-3 Nm, cua oto van
tai co the en (3 7 )10-3 Nm . a thu ong khi lap cung vi moay c can
bang vi o chnh xac (3 4 )10-3 Nm va thong thng ch can bang a thu
ong ly hp oto du lch . Can bang bang cach khoet cac lo nam xa tam
quay e bt lng kim loai phai khoet ..13. Tnh ben cac inh tan lap
ghep :
a)Tnh ben inh tan ghep vanh ma sat va a thu ong :inh tan ghep a
thu ong vi vanh ma sat lam bang ong thau . inh tan co dang hnh tru
, bo tr theo honh tron thanh hai day , moi day co 12 inh tan . au
inh tan thut xuong khoi be mat ma sat khoang 1 2 mm . ng knh inh d
= 5 mm .Ban knh vong inh trong : R1 = 12 cmBan knh vong inh ngoai :
R2 = 16 cm
Lc tac dung len mot inh tan vong trong :
Lc tac dung lem mot inh tan vong ngoai :
Moi ghep inh tan co the b h hong do :*inh tan b cat *inh tan b
chen dap
ng suat cat :
ng suat chen dap :
Vi s = 4 mm : chieu day tam ghep .
Vay cac inh tan eu thoa cac ieu kien ben cho phep ve ng suat cat
va ng suat chen dap .b)Tnh ben inh tan ghep moay va a thu ong :
inh tan thng che tao bang thep . Chon ng knh d = 8 mm , so lng
inh tan la n = 4 . inh tan c bo tr tren mot ng tron ban knh R = 8
mm tnh t tam a thu ong .Ket cau inh tan nh sau :Lc tac dung len mot
inh tan :
ng suat cat :
Vay inh tan a chon thoa ieu kien ben dap va ben cat .
Chng VICACH CHAN OAN H HONG- SA CHATrong qua trnh s dung , c cau
ly hp co the phat sinh nhng h hong sau :-Ly hp ong khong hoan toan
(b trt )
-Ly hp ngat khong hoan toan
-Ly hp ong ot ngot 2.Phng phap bao dng sa cha:
-Khi ly hp b trt , momen xoan t truc ong c se khong truyen hoan
toan cho cac banh chu ong (ac biet khi oto co hang leo len doc )
.Ket hp vi viec tang so vong quay cua truc khuyu ong c khi nha ban
ap ly hp , oto hau nh van khong nhch khoi cho hoac tang toc rat
cham , oi khi oto chay b giat va trong buong lai ngi thay mui khet
cua cac tam ma sat cua a b ong . Nguyen nhan ly hp trt la :+Khong
co khe h gia o truc khp noi va can nha con khi nha ban ap ly hp do
a chu ong khong ep hoan toan vao a thu ong ; e khac phuc h hong
nay, can kiem tra va ieu chnh hanh trnh t do cua ban ap ly hp .+a
ly hp b dnh dau : h hong nay la do o truc khp noi ly hp boi qua
nhieu m hoac do dau ro chay qua o truc chnh pha sau cua truc khuyu
; trong trng hp nay lc ma sat giam i ot ngot va cac a ly hp b trt .
Muon khac phuc h hong nay phai thao ri bo ly hp dung xang ra sach
cac a , con ma cac tam em dung ban chay sat hoac dua anh sach .+Ma
ma sat cac a ly hp b mon : neu ma a ly hp mon t th co the khac phuc
c bang cach ieu chnh lai hanh trnh t do cua ban ap ly hp ; neu ma a
ly hp mon nhieu th phai thay mi .+Cac lo xo ep yeu hoac gay : phai
thay mi cac lo xo .
-Bo ly hp ngat khong hoan toan :Dau hieu cua h hong nay la khi
gai cac so co kem theo tieng nghien rt cua cac banh rang hop so ,
trong o khong loai tr kha nang cac bnah rang b st me . h hong nay
co the do nhng nguyen nhan : +Khe h ln gia o chan cua khp noi va
cac au trong cua can tach ly hp ; h hong nay co the khac phuc bang
cach ieu chnh lai hanh trnh t do cua ban ap ly hp .+Cac a b ong b
lech hoac b venh , khe h khong eu nhau gia cac a do chung b venh
(con rieng tng cho th khong co khe h ) h hong nay thng phat sinh
khi bo ly hp qua nong sau khi no b trt ; Khac phuc bang cach thay
mi cac a cong venh .+Ma ma sat cac a ly hp b v : ma ma sat b v se
ket gia a b ong va a chu ong khien bo ly hp ngat khong hoan toan ;
can phai thao ly hp e thay a ma sat .+a ep b lech : khi ngat ly hp
a chu ong van tiep tuc ep tng phan vao a b ong . H hong nay phat
sinh khi cac au trong cua can tach ly hp khong nam tren mot mat
phang ; trong trng hp nay can phai ieu chnh v tr cac can tach ly hp
.- Bo ly hp ong ot ngot : Mac du nha chan ban ap cham va em nhe
,oto chuyen banh b giat . H hong nay co the xay ra trong trng hp
khp ngat b ket bac dan hng . Khi nha ban ap ly hp , khp noi se di
chuyen khong eu an theo bac dan hng con khi lc lo xo thang s ket
cua khp noi th khp noi se di chuyen nhanh , giai phong can tach ly
hp mot cach ot ngot va cac a b ep lai mot cach nhanh chong . S ong
ot ngot cua bo ly hp cung co the do nhng ngran nt nho tren cac a
chu ong gay nen sau khi chung b qua nong ; Muon khac phuc nhng h
hong tren phai thay mi nhng chi tiet b hong .TAI LIEU THAM KHAO
1.Thiet ke va tnh toan oto may keo tap I va II.Tac gia :Nguyen
Hu Can Phan nh Kien
2.Ly thuyet oto . Tac gia:Nguyen Hu Can D Quoc Thnh Pham Minh
Thai Le Th Vang
3.OTO Nha Xuat Ban MIRTac gia : V.X.Kalixki A.I.Mandon
G.E.Nagula 4.Thie ke he thong truyen ong c kh tap I,IITac gia :
Trnh Chat Le Van Uyen EMBED AutoCAD.Drawing.15
EMBED AutoCAD.Drawing.15
EMBED AutoCAD.Drawing.15
EMBED AutoCAD.Drawing.15
SVTH : Pham Phc Phong -35-
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