chuong 4 botruyenxich
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Chi tiet may Chng IV
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CHNG 4 B TRUYN XCH
4.1. KHI NIM CHUNG 4.1.1. Nguyn l
F1
F2
T2
n2
z2
T1
n1
z1
F2
F1
B truyn xch thc hin truyn ng t bnh xch ch ng sang bnh xch b ng nh vo s n khp gia rng trn a xch v cc mc xch.
4.1.2. Phn loi Theo cng dng chung, xch c chia lm ba loi:
- Xch ko. - Xch ti. - Xch truyn ng.
Trong chng trnh chng ta ch tm hiu v xch truyn ng m thi. Xch truyn ng c chia lm 3 loi chnh: xch ng, xch con ln v xch rng.
4.1.3. u nhc im v phm vi s dng u im:
- Khng c hin tng trt nh b truyn ai, c th lm vic khi c qu ti t ngt, hiu sut cao.
- Khng i hi phi cng xch, nn lc tc dng ln trc v nh hn - Kch thc b truyn nh hn b truyn ai nu cng cng sut - Gc m khng c ngha nh b truyn ai nn c th truyn cho nhiu
bnh xch b dn Nhc im:
- Bn l xch b mn nn gy ti trng ng, n. - C t s truyn tc thi thay i, vn tc tc thi ca xch v bnh b dn
thay i. - Phi bi trn thng xuyn v phi c bnh iu chnh xch. - Mau b mn trong mi trng c nhiu bi hoc bi trn khng tt.
Phm vi s dng
- Truyn cng sut v chuyn ng gia trc c khong cch xa, cho nhiu trc ng thi trong trng hp n < 500v/p
- Cng sut truyn thng thng < 100 kW - T s truyn < 6, hiu sut 0,95..0,97
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4.1.4. Kt cu xch truyn ng a. Xch con ln
pc
b0
1 2 3 4 5 6
Thng thng s mt xch l s chn. Cc kch thc c bn c th tra trong
bng (4.1)[1]
b Xch ng Cu to ging xch con ln nhng khng c con ln 6, nn mn nhanh. Nhng
khi lng v gi thnh thp.
c. Xch rng pc
Gm nhiu m xch xp xen k nhau, cc m xch ni vi nhau bng khp bn l. Cc m xch n khp vi bnh xch bi hai mt phng u m xch. Xch rng lm vic m, t n, kh nng ti cao xch khi lm vic khng b trt khi a xch theo phng dc trc ta dng cc m dn hng khng c rng t gia xch. Trn a xch c phay rnh.
* a xch Kt cu bnh xch nh hnh
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- Kch thc bnh xch nh, c th dng phi dp. Khi kch thc bnh xch ln, c th ghp ri may v a xch bng mi ghp hn hay bu lng. - Bin dng v kch thc rng xch ph thuc v loi v kch thc xch
4.2. THNG S HNH HC B TRUYN XCH 4.2.1. Bc xch pc
- L thng s c bn b truyn xch. - Bc xch cng ln th kh nng ti cng cao. ng thi ti trng ng, va p v ting n cng tng theo, nht l khi lm vic vi vn tc cao - tng kh nng ti c th tng s dy xch (xch ng con ln) hoc tng chiu rng xch (xch rng) - Bc xch c chn theo tiu chun
4.2.2. S rng a xch - Thng thng Z1 < Z2, nu s rng nh th xch mau b mn (v gc xoay bn l ln) v ti trng ng cng nh va p. - Do , ta hn ch s rng nh nht. Thng thng, khi v>= 2m/s. th zmin >= 19, khi v
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)50...30(2/)dd(a 2a1amin (4.2) + Khi u > 3:
10
)u9(
2
)dd(a 2a1amin
- S b, trong thc t c th chn a = (30..50)pc (4.3)
- Chiu di xch xc nh theo cng thc:
a4
)dd(
2
dda2L
22121
- S mt xch X :
cp
LX
a
p)/2z(z
2
)z(z
p
2a c2
1221
c
(4.4)
Nn chn X chn - Sau khi tnh s mt xch. Cn xc nh li chnh xc khong cch trc a:
2
21
2
2121c
2
zz8
2
)zz(X
2
)zz(Xp25,0a
(4.5)
Thng gim a mt khong a = (0,0020,004)a to chng cho b truyn xch.
4.3. NG HC TRUYN NG XCH 4.3.1. Vn tc v t s truyn trung bnh
- Vn tc trung bnh b truyn xch:
60000
p.z.nv c
(4.6)
n s vng quay ca a xch z s rng ca a xch pc bc xch
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- T s truyn trung bnh u = n1 / n2 = z2 / z1 (4.7)
Thng thng u
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4.4. NG LC HC B TRUYN XCH 4.4.1. Lc tc dng trong b truyn xch
- Lc vng Ft lin h vi lc trn nhnh cng F1 v chng F2:
t21 FFF (4.11)
- Lc cng do ly tm:
2mv vqF (4.12)
qm Khi lng mt mt xch, kg/m v vn tc vng , m/s - Lc cng ban u do trong lng nhnh xxh t do:
gaqKF mf0 (4.13)
a chiu di on xch t do bng khong cch trc g gia tc trng trng Kf h s ph thuc vng xch Kf = 6 khi xch nm ngang Kf = 3 khi xch nm nghing < 40
0 so vi phng ngang
Kf = 1 khi xch thng ng
- v02 FFF . C th ly gn ng: F1 = Ft (4.14) - Lc tc dng ln trc
tmr FKF (4.15)
Km h s trng lng xch +Km = 1,15 Khi xch nm ngang hoc nghing < 40
0
+Km = 1 Khi xch thng ng hoc nghing >= 400
4.4.2. Ti trng ng - S thay i c chu k ca vn tc nh trn l nguyn nhn thay i t s truyn tc thi, l nguyn nhn gy ti trng ng ph trong b truyn. - Vn tc v1 gy va p gia bn l xch v rng bnh xch.
4.4.3. ng nng va p - Ti thi im bn l B vo n khp, v1 v v1
gp nhau gy nn va p. Tn
tht ng nng :
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2vmv5,0E
m = 103qmpc khi lng xch tham gia va p.
vv vn tc va p.
)z/360(sinpnq5,0E 10232
m c1 (4.16)
- trnh va dp, ngi ta chn bc xch theo bng (4.2)[1] 4.5. TNH TON B TRUYN XCH
4.5.1. Cc dng hng v ch tiu tnh
FF
pc
d0
1 2
Cc dng hng ch yu trong b truyn xch bao gm: + Mn bn l + Mn rng a xch + V con ln
4.5.2. Tnh ton xch con ln theo bn mn - Tui th xch theo bn mn ph thuc vo khong cch trc,s rng z1, p sut trong bn l p, iu kin bi trn Trong , p sut sinh ra trong bn l l nh hng quan trng nht i vi tui th - Tnh ton bn mn theo p:
K
K]p[]p[
A
Fp x0
t (4.17)
Ft lc vng, N; 1
1t
d
2TF ;
1
1
6
1n
P10.55,9T ;
c11
pzd
1000
1
60000
npz
K
K.A]p[
1000
v.FP
K
KA]p[F
1c1x0
t1
x0t
Nhn c t v mu cho z01, n01
K
K
n
n
z
z
1000.60000
p.z.n.A]p[P x
01
1
01
1c01010t
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t
- 1000.60000
p.z.n.A]p[]P[ c01010
-1
01n
n
nK
-1
01z
z
zK
Ta c:
K
K
K
1
K
1]P[P x
nz
1
]P[K
KKKPP
x
nz1t
A = d0b0 din tch bn l xch 1 dy. C th ly gn ng: A=0,28pc2, mm
2
[p0] p sut cho php, tra bng (4.3)[1] Kx h s xt n s dy xch. Nu x = 1;2;3;4 th tng ng Kx = 1;1,7;2,5;3 K h s iu kin s dng xch
K = Kr Ka K0 Kdc Kb Klv (4.18)
( Cc h s ny tham kho trong tai liu [1]) [P] cng sut cho php b truyn mt dy c bc xch pc Kz = 25/z1; Kn = n01 / n1.
Tra bng 4.4[1], tm c pc 4.5.3. Kim nghim xch theo s ln va p trong mt giy
]i[X15
nz
Xp60
pnz4
L
v4i 11
c
c11 (4.24)
X s mt xch tnh theo (4.4) Z1,n1 s rng v s vng quay a xch b dn [i] s ln va p cho php. Tra bng (4.5)[1] - Kim tra theo h s an ton:
6...5]S[FFF
QS
021
(4.25)
Q ti trng ph hu cho php ca xch, bng 4.1[1] [S] h s an ton cho php. Tra bng (4.6)[1]
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4.6. TRNH T THIT K B TRUYN XCH 1. Chn loi xch 2. Chn s rng xch theo cng thc z1 = 29 2u v z2 = uz1 3. Tnh cng sut tnh ton Pt, chn bc xch pc 4. nh khong cch trc a, tnh cc ng knh a xch.. Tnh s mt
xch X theo (4.4) nn chn X l s chn v kim tra s ln va p xch trong mt giy
5. Tnh lc tc dng ln b truyn (4.15)
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