1

Nguyn c ht - lu vn bng Hiu nh PGS-TSKH Phan b

bi tp

dung sai

F

hc vin k thut qun s H ni nm 2000

2

Li ni u

Cun sch Bi tp dung sai bao gm cc dng bi tp mu v

nhng bi tp in hnh nhm vn dng nhng l thuyt hc trong

mn hc dung sai v o lng trong c kh ti HVKTQS. Trong bao gm

phn ln nhng bi tp v tnh ton chnh xc hnh hc cc chi tit v

kh, trang b k thut. Sch dng ch yu cho hc vin bc i hc ngnh c

kh ca HVKTQS. Nhng ngi lm cng tc thit k, ch to; Cn b ging

dy; cng nh sinh vin di hc v cao ng chuyn ngnh c kh cng c

th tham kho

Ni dung cun sch bao gm hai phn

Bi tp in hnh cho cc chng

Chng I. Nhng khi nim c bn v kch thc - sai lch , dung sai

v lp php

Chng II. Sai s gia cng chi tit

Chng III. Dung sai lp ghp cc b mt trn

Chng IV. Dung sai mi ghp ren h mt

Chng V. Dung sai truyn ng bnh rng

Chng VI. Gii chui kch thc

Mi chng u c phn tm tt v l thuyt (gip cho hc vin trc

khi lm bi tp n li phn hc trn lp) v phn bi tp p dng

Bi tp tng hp

So vi cun sch Hng dn bi tp c s tnh i ln trong ch to

my in nm 1984 ln bin son ny tc gi b xung mt s ni dung bi

3

tp cho ph hp vi i tng chnh l hc vin HVKTQS cng nh yu cu

chun ho ca B gio dc v o to.

Cc tiu chun Vit nam mi nht v dung sai hnh hc ca cc chi

tit my c s dng thay th cho cc tiu chun tng ng trc y.

Do khun kh cun sch c hn v vit theo chng trnh mn hc

nn c nhng phn c b qua nh thit k Calp kim tra cc chi tit ren,

then hoa v o lng.

Tuy c c gng, song khng trnh khi cn c sai st. Rt mong

c s gp ph bnh. Mi kin xin gi v a ch B mn Ch to my-

Hc vin k thut qun s.

Chng ti chn thnh cm n PGS-TSKH Phan B, PGS-TS L Vn

Chiu v cc ng nghip trong b mn Ch to my HVKTQS c

nhiu ng gp qu bu trong qu trnh bin son v chun b xut bn ti

liu ny

Cc tc gi

4

Bi tp in hnh cho cc chng

Chng I.

Nhng khi nim c bn v

kch thc - sai lch - dung sai - lp ghp

1.1. Kch thc - sai lch - dung sai.

1.1.1. Kch thc :

Kch thc l mt i lng c trng cho ln v khong cch (di,

gc) Gia cc v tr tng quan ca b mt, ng, im ca mt hay nhiu chi tit.

Kch thc bao gm (bng 1-1)

Bng 1-1. Cc loi kch thc

K hiu Th

t

Tn gi i vi l (chi tit bao)

i vi trc (chi tit b bao)

1 Kch thc danh ngha D d

2 Kch thc thc Dt dt

Dmax dmax

3 Kch thc gii hn:

- Ln nht

- Nh nht Dmin dmin

lot chi tit gia cng m bo tnh i ln chc nng th kch thc thc ca cc chi tit thuc lot phi tho mn iu kin.

* iu kin chi tit t chnh phm:

i vi l : Dmin Dt Dmax

i vi trc : dmin dt dmax

5

Hnh 1-1.Lp ghp gia trc v

1.1.2. Sai lch gii hn: (Vit tt SLGH)

SLGH l hiu i s gia kch thc gii hn v kch thc danh ngha.

Sai lch gii hn bao gm (bng 1-2)

Bng 1-2 . Cc loi sai lch ghii hn

K hiu T.T Tn gi i vi l i vi trc

Cng thc tnh

1 Sai lch gii hn trn ES ES = Dmax - D

es es = dmax - d

2 Sai lch gii hn di EI EI = Dmin - D

ei ei = dmin - d

1.1.3. Dung sai kch thc:

K hiu:

-Dung sai: T

6

-Dung sai l (chi tit bao): TD

-Dung sai trc (chi tit b bao): Td

Cng thc tnh:

-L (chi tit bao): TD = Dmax - Dmin = ES - EI (1-1)

-Trc (chi tit b bao): Td = dmax - dmin = es - ei (1-2)

1.2. Lp ghp.

Bng 1-3. Cc nhm lp ghp

Th t

Tn gi i lng c trng v k hiu

Cng thc tnh

- h ln nht Smax Smax = Dmax - dmin

- h nh nht Smin Smin = Dmin - dmax

- h trung bnh Stb Stb = S m ax S m in

2

1 Nhm lp ghp

c h

- Dung sai h TS TS = Smax - Smin

= TD + Td

- di ln nht Nmax Nmax = dmax - Dmin

- di nh nht Nmin Nmin = dmin - Dmax

- di trung bnh Ntb Ntb = 2N

minmax N

2 Nhm lp ghp

c di

- Dung sai di

TN

TN = Nmax - Nmin

= TD + Td

- di ln nht Nmax Nmax = dmax - Dmin

- h ln nht Smax Smax = Dmax - dmin

3 Nhm lp ghp

trung gian

-Dung sai ca mi lp

TNS

TNS = Nmax + Smax

= TD + Td

Tnh cht lp ghp c xc nh bi hiu s gia kch thc l v kch

thc trc.

7

Nu Dt - d t > 0 ta c lp ghp c h

- K hiu h l S: S = Dt - dt > 0

Nu dt - Dt > 0 ta c lp ghp c di

- K hiu di l N: N = dt - Dt > 0

Tu thuc tng quan gia kch thc gii hn ca l v trc, lp ghp

chia thnh ba nhm (bng 1-3).

1.3. S phn b dung sai ca lp ghp.

Khi biu din s phn b dung sai

- Thng chn trc honh (trong h to cc) lm ng 0-0, tng ng vi kch thc danh ngha. Kch thc danh ngha c chn lm gc

xc nh kch thc gii hn v sai lch gii hn.

- Biu din s phn b cc sai lch kch thc so vi kch thc danh ngha (trc tung) theo t l hp l.

V d:

V s phn b dung sai ca lp ghp c:

Kch thc danh ngha: D = d = 20 mm

Sai lch gii hn: ES = + 0,021 mm; EI = 0

es = - 0,065 mm; ei = - 0,086 mm

Bi gii:

Da vo s phn b dung sai Hnh 1-1, chng ta xc nh c tnh

cht lp ghp v cc i lng c trng ca chng.

Smax = 20,021 - 19,914 = 0,107 mm

Smin = 20,000 - 19,935 = 0,065 mm

Stb = ( 0,107 + 0,065 ) / 2 = 0,086 mm

TS = Smax - Smin = 0,107 - 0,065 = 0,042 mm

8

0D

=d=

20m

m

-0,086

Td-0,065

0,021

TD

Hnh 1-1. S phn b dung sai.

Bi tp s 1

1.1. Xc nh kch thc ng knh danh ngha ca cht (hnh 1-2a)

nu kch thc tnh ton theo iu kin lm vic nh trong bng 1-4.a

v l bc (Hnh 1-2b) nu kch thc tnh ton theo iu kin lm vic

nh trong bng 1-4.b

Hng dn: Da theo dy kch thc u tin (bng 1 I )

Bng 1-4a.

Phng n Kch thc

(mm) 1 2 3 4 5

d 9,7 13 19,5 25,5 31

9

Hnh 1-2

Bng 1-4b.

Phng n Kch thc

(mm) 1 2 3 4 5

D 7,6 9,8 16 19 33,7

1.2. Kch thc ca cc chi tit c t yu cu khng, nu kch thc danh ngha, sai lch v kch thc thc nh bng 1-5.

Bng 1-5.

Phng n 1 2 3 4 5

Kch thc danh ngha (mm) 10 16 25 32 60

Sai lch gii hn trn (mm) - 0,280 + 0,043 + 0,106 + 0,085 - 0,100

Sai lch gii hn di (mm) - 0,370 - 0 0,073 + 0,060 - 0,290

a) b)

10

Kch thc thc (mm) 9,628 16,037 25,109 32,078 60,015

1.3. Cho kch thc danh ngha v sai lch gii hn kch thc l v trc nh bng 1-6, yu cu:

- Lp s phn b khong dung sai kch thc ca lp ghp (vi t l xch: 1mm ng vi 1m).

- Xc nh cc kch thc gii hn ca chi tit.

- Xc nh cc i lng c trng ca lp ghp.

Bng 1-6.

Sai lch gii hn (mm) Phng

n Kch thc danh

ngha (mm)

ES EI es ei

1 20 + 0,021 0 - 0,006 - 0,017

2 30 + 0,006 - 0,015 0 - 0,013

3 40 + 0,039 0 + 0,008 - 0,008

4 35 + 0,064 + 0,025 + 0,099 + 0,060

5 45 + 0,062 0 + 0,027 + 0,002

1.4. Vi cc s liu cho trong bng 1-7.

- Lp s phn b khong dung sai kch thc lp ghp (vi t l xch: 1mm ng vi 1 m).

- Xc nh cc sai lch gii hn kch thc.

11

Bng 1-7.

Cc yu t cho trc (m)

Phng

n

Kch thc

danh

ngha (mm) TS , TN S , N TD Td EI , es

1 18 TS = 66 Smin = 0 TD = 33 Td = 33 EI = 0

2 30 TS = 104 Smin = 40 TD = 52 Td = 52 es = 0

3 40 TN = 87 Nmax = 85 TD = 62 Td = 25 EI = 0

4 40 TN = 126 Nmax = 253 TD = 63 Td = 63 EI = 0

5 40 TN = 187 Nmax = 77 TD = 72 Td = 115 EI = 0

6 50 Smax = 260 TD = 100 Td = 100 EI = 0

12

Chng II

Sai s gia cng cc yu t hnh hc ca chi tit

2.1. Quy Lut phn b kch thc thc khi gia cng.

Do nh hng bi rt nhiu nguyn nhn khc nhau, cc kch thc ca lot chi tit xut hin trong qu trnh gia cng trong cng mt iu kin ni

chung l khng ging nhau.

Trong iu kin sn xut hng lot vi cng mt qui trnh cng ngh, kch thc ca lot chi tit gia cng cng loi thng phn b theo lut

phn b chun (qui lut Gauss) phng trnh ng cong phn b c dng:

22

2

21

xx

ey

(2-1)

Trong :

- Sai lch bnh phng trung bnh ca cc kch thc gia cng. _

x - Sai lch ca kch thc trung bnh ca lot chi tit gia cng so vi

kch thc danh ngha. ngha l _

x = dtb - d

x - Sai lch ca cc kch thc gia cng so vi kch thc danh ngha.

ng vi kch thc di bt k th xi = di - d

e - C s lgarit t nhin.

Dng ng cong phn b chun nh Hnh 2-1. Trc i xng ca ng cong ti honh dtb - gi l trung tm phn b (TTPB). Tr s dtb

quyt nh v tr ca ng cong phn b (so vi trc tung); cn quyt nh dng ca ng cong, khi cng ln ng cong cng thp v khong phn tn kch thc cng ln cn cng nh th ngc li. Do c trng cho sai s gia cng.

13

Kch thc ca lot chi tit gia cng phn b theo lut phn b chun

nn xc sut xut hin cc chi tit c kch thc gia cng nm trong khong (x1 x2) no l P(x1 x2) s l:

P(x1 x2) =

2

1.

22

2

.

212

1

x

x

dx

xx

e

x

x

ydx

ngha hnh hc ca P(x1 x2) chnh l din tch gia ng cong mt xc sut y v trc honh trong khong (x1 + x2) (din tch phn gch-

Hnh 2-2).

x

Hnh 2-1

x

Hnh 2-2

14

Nu i bin s: z = x

th

P(x1 x2) = P(z1 z2) = 1

2

2

1

2

2

e dzz

z

z

. = (z2) - (z1) (2-2)

V ng cong i xng nn:

P(- z z) = 2

1

2

2

1

2

2

e dz

z

z

z

. = 2(z) (2-3)

Gi tr ca (z) v 2 (z) c tnh sn v lp thnh bng (xem Bng 4 [I]) (z) v (- z) l hm tch phn Laplass.

Qua tnh ton ngi ta rt ra kt lun:

1- Hu ht cc chi tit gia cng u c kch thc nm trong khong 6 ngha l khong phn tn ca kch thc gia cng phn b t x1 = - 3 n x2 = +3 so vi TTPB( kch thc dtb).

2- S chi tit c kch thc cng gn trung tm phn b cng ln.

3- iu kin cn v kch thc chi tit t tnh i ln l 6 T v trung tm phn b trng vi trung tm dung sai.

S dch chuyn trung tm phn b so vi trung tm dung sai l do nh hng ca sai s h thng. dch chuyn c xc nh bng i lng

. T2

(hnh 2-3) v c tnh theo cng thc:

. T2

= dtb -(d + ) (2-4)

15

x

Hnh 2-3

Trong : - To trung tm dung sai tnh t kch thc danh ngha.

- H s phn b tng i gia TTPB v TTDS. Tr s c gi tr dng khi trung tm phn b dch chuyn v pha sai lch dng v ngc li (so vi dtb).

V d 2-1:

Gia cng mt lot trc gm 2000 chic t yu cu kch thc l

280,0+343,0+

160

Tnh s lng chi tit trc c kch thc nm trong gii hn t - n + v xc nh gi tr bng s ca cc gii hn so vi kch thc trung bnh.

Cho bit sai s gia cng ca lot chi tit tun theo lut phn b chun.

Bi gii:

Theo iu kin cho, xc sut xut hin s chi tit c kch thc nm

trong khong - + c tnh theo cng thc (2-2)

P (- + ) = (z2) - (z1)

Vi z1 = x1

= -1; z2 = x2

= +1

16

Th: P( - + ) = 2 (1)

Theo bng 3 [I] xc nh c:

2 (1) = 0,6826

Vy xc sut xut hin s chi tit c kch thc nm trong gii hn - + l 68,26% (biu th bng din tch min gch trn hnh 2-4). S lng trc c kch thc nm trong gii hn - + l:

68 26 2000

1001365

, trc

iu kin cn lot trc c kch thc t yu cu l: 6 T. y T = 0,343 - 0,280 = 0,063 mm

Nn T

6

63

610 m

Gi tr bng s ca gii hn x1 = - v x2 = + l:

x1 = - = - 1. 63

6= - 10 m

x2 = + = 1. 10 m = + 10 m

Hnh 2-4

V d 2-2:

17

Xc nh s lng ti thiu chi tit trc (theo t l %) ca lot trc c

kch thc 40 009,0+

034,0+ khi lp chng vi lot chi tit l c kch thc

10+0,025 bo m chc chn cho mi ghp c di nu kch thc lot chi tit trc gia cng tun theo lut phn b chun v trung tm phn b trng vi trung tm dung sai.

Bi gii:

T s phn b dung sai (hnh 2-5a) chng ta thy ch c nhng chi

tit trc c kch thc nm trong khong 40,025 mm 40,034 mm khi lp

vi mi l 40 02500+ m bo chc chn c di. Xc nh s chi tit trong

khong theo cng thc (2-2).

- Xc nh sai lch x1, x2 ca cc kch thc 40,025 mm v 40,034 mm so vi kch thc trung bnh l:

dtb = d dmax min , ,

2

40 034 40 009

2 = 40,0215 mm

D=

d=20

mm

Hnh 2-5a. S phn b dung sai

18

Hnh 2-5 b. th ng cong phn b

x1 = 40,025 - 40,0215 = + 0,0035 mm

x2 = 40,034 - 40,0215 = + 0,0125 mm

Xc nh sai lch bnh phng trung bnh ca lot kch thc trc:

= T

6

25

6 = 4.17 m

i bin x z

Z1 = x1 3 5

4 170 84

,

,,

Z2 = x2 12 5

4 173 0

,

,,

Xc sut xut hin s chi tit trc c kch thc trong khong x1 x2 (min gch gch - hnh 2-5b) l:

P(x1 + x2) = (Z2) - (Z1) = (3) - (0,84)

= 0,49865 - 0,2995 = 0,19915

S lng chi tit trc tho mn iu kin trn (theo %): 19,91%

V d 2-3: Cho lot chi tit trc c kch thc 0 120.0100- phn b theo

qui lut Gauss.

19

- Xc nh gi tr ph phm khng c > 5%

- Xc nh dch chuyn cn thit ca trung tm phn b c th ch

nhn c nhng chi tit c kch thc ph phm c th sa c (kch thc ph phm sa c i vi chi tit b bao: di > dmax; i vi chi tit bao

Di < Dmin).

Bi gii:

V chi tit l trc (b bao) nn ph phm c th sa c l nhng kch thc di > dmax, do trung tm phn b phi dch chuyn v pha sai lch

dng (hnh 2-6).

Theo iu kin cho th xc sut xut hin cc chi tit t yu cu l 95%. Da vo hnh 2-6 ta c:

P(x1 + x2) = (Z2) - (Z1) = 0,95

Khong kch thc (x1 + x2) = T nn T = x1 + x2 = 120 m

x1, x2 c xc nh nh sau:

(Z1) = 0,5 tra bng tch phn Laplass (bng 3[I]) ta c Z1 = - 3 vy x1 = -3

(Z2) = 0,45 tra bng tch phn Laplass (bng 3[I]) ta c Z2 = 1,65 vy x2 = 1,65 .

Hnh 2-6

20

Thay vo: T = x1 + x2 = -3 + 1,65 = 4,65

= T

4 65

120

4 6526

, , m

Theo hnh 2-6 th dch chuyn cn thit ca trung tm phn b

bng x3 (im ng vi trung tm dung sai):

x3 = 265,1+3

=2

x+x 21 =0,877

x3 = 17,55 m

Trung tm phn b dch chuyn v pha sai lch dng mt khong:

T2

= 17,55 m

Bi tp s 2

2.1. Xc nh s lng chi tit (Theo %) c sai lch kch thc nm trong gii hn 2 v xc nh gi tr gii hn theo mm so vi trung tm phn. b nu sai s ngu nhin tun theo lut Gauss, cc kch thc nh

bng 2-1

Bng 2-1.

Phng n 1 2 3 4 5

Kch thc (mm) 000,0

030,0+80

073,0

038,0100

-

-

040,0+

083,0+140

062,0

000,050

-

003,0+

038,0+120

2-2. Vi cc kch thc l cho trong bng 2-2. Hy xc nh s lng chi tit l (theo t l %) khi lp chng vi lot trc c kch thc tng ng u cho lp ghp c h, bit sai s kch thc tun theo lut phn b

chun Gauss.

Bng 2-2.

Phng n 1 2 3 4 5

21

Kch thc l (mm)

018,0

007,0+50

-

028,0

012,040

-

-

048,0

006,0+100

-

000,0

054,0+120

030,0+

076,0+80

Kch thc trc (mm)

030,0

000,050

-

040,0

000,0140

-

054,0

000,0100

-

027,0120 002,0+

032,0+80

2.3. Vi cc kch thc cho trong bng 2-3 xc nh s lng chi tit trc khi lp vi mi l tng ng cho lp ghp c di. Bit sai s kch thc ca lot tun theo lut phn b chun; s lng chi tit trong lot l 5000

chic.

Bng 2-3.

Phng n 1 2 3 4 5

Kch thc l

(mm) 000,0030,050

021,0009,065

059,0024,0100

000,0045,0200

050,0112,040

Kch thc trc (mm)

017,0042,050

002,0032,065

087,0

000,0100

03,006,0200

060,0099,040

2.4. Xc nh dch chuyn cho php ca trung tm phn b xc sut ph phm xut hin c th sa c ca lot kch thc trc l 3%.

Vi dch chuyn cho php tnh, xc nh sai lch v dung sai ca

kch thc.

Cho bit: d = 180 mm; es = 0; = 20 m.

2.5. Xc nh dch chuyn cho php ca trung tm phn b lot kch thc l D = 50 mm ch c php ph phm sa c l 2% nu = 6 m khong dung sai cn phi phn b nh th no khi lp n vi lot trc

02,000,050

c lp ghp c h nh nht Smin = 30 m.

2.6. Cho lot kch thc bao: D = 100 mm; Sai lch phn b i xng vi kch thc danh ngha. Khong phn tn kch thc ca lot chi tit gia cng tun theo lut phn b chun Gauss v = 25 m.

- Xc nh dch chuyn ca trung tm phn b xc sut ph phm ch c 4% (trong s sa c 3%)

22

- Tnh tr s dung sai v sai lch cho php ca lot chi tit.

2.7. Xc nh kh nng xut hin khe h v di i vi cc kiu lp cho trong bng 2.4, nu kch thc trc v l tun theo lut Gauss, trung tm phn b trng vi trung tm dung sai.

Bng 2-4.

Phng n 1 2 3 4 5

Kch thc l (mm)

000,0021,030

000,0030,060

000,0035,0100

034,0005,050

050,0004,080

Kch thc trc

(mm) 002,0023,030

011,0041,060

020,0050,0100

039,0

000,050

074,0

000,080

Hng dn: D, d l hai i lng ngu nhin tun theo lut phn b

Gauss do i lng ngu nhin tng ( h S, di N) cng tun lut phn b Gauss nn:

S N T Td D, 16

2 2

dtb = d Dtb tb2 2

Tnh sai lch (S,N) theo Td v TD

- Tnh dtb v Dtb t tnh S hoc N

- Xc nh trung tm phn b ca h , di l im tng ng vi gi tr S hoc N nhn c khi kch thc l v kch thc trc c xc sut

ln nht lp vi nhau.

-Ly trc X biu th S v N: Ly gc to c S, N = 0, di (N) pha m, cn h (S) pha dng.

- Tnh P(X1 + X2) theo Z1 v Z2.

- Tnh phm vi gii hn ca S v N cng vi min phn b.

Bng 2-5.

23

Phng n 1 2 3 4 5

Khong sai s

kch thc (x1+ x2) (mm)

[- 0,005 + 0,005]

[- 0,01 +0,01]

[- 0,015 + 0,015]

[- 0,020 +0,020]

[-0,025 + 0,025]

Bng 2-6. Kt qu thng k kch thc ca cc chi tit gia cng lot trc 12h7

Khong kch thc thc (mm)

Tr s trung bnh khong

- ditb (mm)

S lng chi tit trong

khong

Sai lch kch thc

xi = ditb - dtb

Tn sut x

Ni

T 11,915 n 11,925 11,920 2 - 0,04 0,01

> 11,925 - 11,935 11,930 6 - 0,03 0,03

> 11,935 - 11,945 11,940 20 - 0,02 0,10

> 11,945 - 11,955 11,950 48 - 0,01 0,24

> 11,955 - 11,965 11,960 56 - 0,00 0,28

> 11,965 - 11,975 11,970 34 - 0,01 0,17

> 11,975 - 11,985 11,980 20 + 0,02 0,10

> 11,985 - 11,995 11,990 12 + 0,03 0,06

> 11,995 - 12,005 12,000 2 + 0,04 0,01

dtb = 11,960 N = 200 Ki = 0 nN

i 1

2.8. Hy xc nh s lng chi tit trc c kch thc vi sai s trong khong (x1 + x2) nh bng 2-5, khi chng c gia cng trn my tin Rvonve vi cc kt qu thng k nh bng 2-6.

Xc nh tr s dung sai kch thc t tnh i ln hon ton.

24

Xc nh s lng ph phm nu chi tit trc c kch thc 12h7 v trung tm phn b trng trung tm dung sai.

Hng dn : - Xc nh ' (theo trang 9[I])

- Tnh Zi qua Xi v .

- Xc nh xc sut xut hin s chi tit c kch thc c sai s trong khong (x1 + x2) theo (2-2) v bng tch phn Laplass.

- Xc nh s lng chi tit c kch thc vi sai s trong khong [x1x2].

So snh tr s T vi 6 v tnh lng ph phm (nu c)

2.2. Sai lch hnh dng v v tr b mt.

- Sai s hnh dng v v tr b mt l nhng i lng ngu nhin.

nghin cu chng ngi ta dng xc sut - thng k.

- Sai s lch tm ca hai b mt tr, cn ca hnh tr, khng song song , khng vung gc gia 2 mt phng hoc tng trc v mt

phng tun theo lut phn b Mcxoen, c hm phn b mt xc sut dng

y R eRR

.

2

2

v dng ng cong nh hnh 2-7.

- chnh xc hnh dng b mt c xt trong mt ct ngang ( van, a cnh, khng trn ...) v trong mt ct dc trc ( cn, trng,

cong trc, khng thng ng sinh ...).

- TCVN 384 - 1993 qui nh 16 cp chnh xc hnh dng,v tr, hng v do, k hiu l cp 1, cp 2.... Cp 16. Tn gi cc sai lch, k hiu v gi

tr sai lch gii hn xem cc tiu chun Vit nam: TCVN 2501-1993, TCVN

384-1993, TCVN 5906-1995, (xem cc bng 2-16, 2-16a v 2-19 1-22

25

Hnh 2- 7

- Chn chnh xc hnh dng b mt phi da vo chnh xc kch

thc ca b mt . Bng 2-7a gii thiu tng quan gia cp chnh xc hnh dng v kch thc.

Cc bng t bng 2 - 7a n 2-9 gii thiu mt s trng hp chn c

th sai s hnh dng v v tr b mt.

Ghi ch:

1- Cp chnh xc hnh dng trong khung nt m u tin s dng.

2- Ch s ghi trong cc biu th t l % gia dung sai hnh dng so vi dung sai kch thc (ly theo bn knh) ng vi ng knh danh ngha t

30 180 mm. Nu khong ng knh nh hn 30 mm th t l trn gim i, khong ng knh > 180 mm th t l trn tng ln.

3- Sai lch hnh dng thuc nhng cp chnh xc bn phi khung

m vt qa dung sai kch thc tng ng nn khng c chn.

Bng 2-7a.

Cp chnh xc hnh dng Cp chnh

xc kch thc. 1 2 3 4 5 6 7 8 9 10

26

IT5 12 20 30 50 80

IT6 12 20 30 50 80

IT7 20 30 50 80

IT8 20 30 50 80

IT9 16 25 40 65

IT10 20 30 50 80

IT11 20 30 50

IT12 16 25

Bng 2-7b. Cp chnh xc hnh dng b mt tr trong mt s trng hp c th.

Cp chnh xc

TCVN 384-1993

B mt cc loi chi tit Phng

php gia cng

(1) (2) (3)

1-2 Bi v thanh ln ca ln; b mt trc c lp ln cp chnh xc 4 b mt lp cao tc

Mi bng, mi v

doa kim cng

27

3-4 B mt lp ghp ca ln cp chnh xc 4 v b mt l c lp cc .

Ngng trc c lp ca trc chnh my cng c chnh xc tng i cao.

B mt lp ghp ca cc vng v ngng trc ca kh c con quay.

Cc ngng ca trt ca my cn.

B mt lm vic ca cp van trt v pt

tng (vi p lc cao); cht pt tng ca ng c t.

Tin mng.

mi, doa kim

cng, mi doa

5-6 B mt lp ghp ca ln cp chnh xc cp 5, 6, 0.

B mt trc v l hp c lp cc ln .

Ngng trc lp v bc lt ca ng c, hp tc , tua bin hi, my bm.

Cht pt tng ca ng c diezen, ng c

hi t, my hi nc, xi lanh ca ng c t.

Pt tng v xi lanh ca thit b thu lc

my bm, my nn kh vi p lc trung bnh v c xc mng m bo kn.

B mt lp ghp gia bc vi xi lanh v

thn trong h thng thu lc p lc cao gia bc vi u bin ca ng c.

Trc r to v a bnh rng lm vic ca

tua bin hi

Mi, tin tinh, mi

doa, doa chnh

xc cao, doa bng

dao nhiu li,

chut.

28

7-8 Ngng trc ca kh c con quay khng quan trng.

Pt tng v s mi xi lanh ca ng c t

my ko. S mi xi lanh ca diezen v ng c hi t.

L lp bc bin ca diezen, my nn kh,

my hi, ng c my ko. L lp bc trong thit b thu lc p lc trung bnh.

Mi, doa, chut,

tin trong,

khoan c chnh

xc tng i cao.

9-10 trt lm vic trong iu kin nh nhng (ti, cu trc, c cu li tu thu). Xc mng ca ng c diezen.

Pt tng v xi lanh ca my bm p lc

thp c b phn lm kn kh bng vt liu mm.

Tin

trong v tin ngoi

th, khoan.

Bng 2-8.

1-2 B mt lm vic ca trc chnh v mm cp

ca my cng c c cp chnh xc cao.Ngng trc lp v cc chi tit trc chnh my o

bnh rng.

u phn quang hc. B mt lm vic cc vng ln rt chnh xc.

Mi bng,

mi khn

3-4 B mt lm vic ca trc chnh v bn my

my cng c c cp chnh xc I; Vng ln cp chnh xc 4, 5;

Ngng trc lp bnh rng cp chnh xc 4,

5; Trc ca kh c con quay chnh xc cao. Mt cn ca kim phun.

Mi tinh,

tin tinh, mi trong

vi mt ln g t.

29

5-6 Li ct ca dao doa.

Bc lt ca my cng c cp chnh xc E, H, vng ln cp chnh xc 0, 6; b mt lp

ghp ca trc dng c o v c cu chnh xc. Trc v bc lp ca kh c con quay. B

mt trc c lp bnh rng chnh xc 6, 7; C trc khuu v trc phn phi kh ca ng c

t.

Mi - tin t

chnh xc IT7 + IT8.

Mi v tin trong

mt ln g.

7-8 Li ct ca dao khot, dao doa cn, ta r. B mt trc c lp bnh rng chnh xc cp 8,

9; c trc khuu ng c diezen.

C trc phn phi ca ng c my ko, my cng trnh; cc trc quay vi s vng

quay n = 1000 V/ph. Mt cn ca xu pp v ca l lp n trong ng c t.

Trc truyn ng c chiu di 1000 mm.

B mt ln ca bnh vt v l lp ghp tang quay my trc

Mi th, tin, tin

trong t chnh

xc IT8 + IT9

9-10 Li ct ca bn ren, ta r, mi khoan, dao phay.

B mt trc lp bnh rng chnh xc cp

10-11, b mt lp ghp ca s mi xi lanh ng c my ko.

G v rnh lp xc mng ca pt tng

t. Trc truyn dn di 1000 4000 mm.

Tin v tin trong

chnh xc IT10 IT11

30

Bng 2-9a. Cp chnh xc v hng b mt: song song

Cp chnh xc TCVN384-1993

B mt cc loi chi tit Phng php - gia

cng

1-2 B mt sng trt ca my cng c cp

chnh xc V v IV; sng trt thn my ca u phn quang hc.

B mt lm vic ca thc sin cp chnh

xc 1 v 2. Cc dng c kim cp chnh xc 0

Mi bng,

mi siu tinh xc,

co chnh xc

cao.

3-4 B mt sng trt ca my cng c chnh xc III, II.

B mt lm vic ca dng c kim cp

chnh xc 1. Sng trt c bit chnh xc ca dng c o iu chnh

Mi bng, mi v co

5-6 B mt sng trt ca my cng c cp chnh xc I; mt trt v rnh trt ca

dng c o.

Mt u vng ln chnh xc 4, 5. Mt u t ca np v vng chn cp chnh xc

4, 5.

ng tm cc l, mt u cc l, 2 mt u ca cc bnh rng trong my bm.

Mi phng,

phay t chnh

xc IT6 IT7, doa

to

31

7-8 Mt trt ca my p, my ba, mt u dao phay.

Mt t ca np v vng i vi cp

chnh xc 0; 6; cc l lp s mi - xi lanh ca ng c.

ng tm l hp lp cc trc lp bnh

rng cp chnh xc 7 - 10.

Mt bch ca van.

Phay, bo, mi, trut,

tin trong

9-10 Mt u lp trong cc my ln, nng. ng tm c bin v ng tm ca khuu,

ng c diezen.

ng tm cc trc truyn trong ti v trong truyn dn bng tay.

Mt phng ghp v cc trong thn

hp gim tc ca cc my trc.

ng tm cc l khng quan trng ca my o.

Phay th; phay v

tin trong, khoan.

Bng 2-9b. Cp chnh xc v hng b mtv o: vung gc v o mt u

Cp chnh xc

TCVN 384-1993

B mt cc loi chi tit Phng

php - gia cng

1-2 Mt u trc chnh my cng c cp chnh

xc A; trc chnh v trc tm my o rng; u phn quang hc; vng ln cp

chnh xc 4, 5

Mi bng,

mi tinh

32

3-4 Mt u trc chnh ng my cng c cp chnh xc IV, III, b mt lm vic ca ke 900

cp chnh xc 0 v I; Vai trc c lp chn cp chnh xc 4

Mi bng, mi v co

t chnh xc

IT5 IT6

5-6 Mt u trc chnh, ng my cng c chnh xc I;

B mt lm vic ca ke 900 cp chnh xc

2; mt u t ca dao xc v dao c rng; vai trc lp cp chnh xc 6, 5 v u l lp

cp chnh xc 4 v 5.

Mi, co, phay, bo

v tin trong

chnh xc IT6 + IT7

7-8 Sng trt v b mt chun ca my p,

my ba; vai trc v mt u l thn hp c lp chn cp chnh xc 0,6.

Mt u moay , bc chn, ng tm l

cht pt tng trong t, my ko.

Mi, phay,

bo, xc, tin trong

9-10 Mt u trong cc ti, vnh rng trong bnh rng my gt, my i.

Tin, phay, bo

v tin trong th

11-12 Vnh rng bnh xch trong my chnh xc

thp;

Gia cng

th

Bi tp s 3

3.1. Xc nh tr s sai lch gii hn v ghi chng ln bn v chi tit cc sai lch gii hn: thng, phng, song song gia hai mt A v B ca chi tit hnh 2-8 khi chng c kch thc danh ngha v cp chnh xc hnh

dng nh bng 2-10.

Bng 2-10.

Phng n 1 2 3 4 5

33

Kch thc L(mm) 6 50 100 2 30

Cp chnh xc 1 2 3 4 9

Hnh 2-8

3.2. Xc nh tr s dung sai v ghi chng ln bn v chi tit cc tr s dung sai: trn, tr v prphin trong mt ct dc trc ca b mt chi tit hnh 2-9 khi chng c kch thc danh ngha v cp chnh xc hnh

dng nh bng 2-11.

Bng 2-11.

Phng n 1 2 3 4 5

Kch thc d (mm) 6 6 2,5 6 7

Cp chnh xc 2 3 5 8 10

Hnh 2-9

34

3.3. Xc nh tr s sai lch gii hn v ghi chng ln bn v chi tit cc sai lch gii hn: o mt u, o hng tm ca chi tit hnh 2-10 khi chng c kch thc danh ngha v cp chnh xc v tr nh bng 2-12.

Bng 2-12.

Phng n 1 2 3 4 5

Kch thc , (mm) 25; 19 20; 30 16;25 16; 11 16; 11

Cp chnh xc 2 3 5 8 10

Hnh 2-10

2.4. Xc nh tr s dung sai gii hn v ghi chng ln bn v chi tit cc tr s dung sai; song song gia hai mt (mt A v mt B);

vung gc ca l vi mt A ca chi tit nh hnh 2 -11 khi chng c kch thc danh ngha v cp chnh xc v tr nh bng 2-13.

35

Hnh 2-11

Bng 2-13.

Phng n 1 2 3 4 5

Kch thc d(mm)

20 30 35 40 50

Cp chnh xc 4 5 6I 7 9

3.5. Xc nh chnh xc hnh dng cc b mt chi tit v ghi cc gi tr dung sai ln bn v chi tit nu kch thc ca cc chi tit cho nh bng 2-14.

Bng 2-14.

Phng n 1 2 3 4

Kch thc

(mm)

Cht pt tng

26h6 L xi lanh

150H7 Thn kim ho

22h7 L bung n

32,7H6

Hng dn :

- Xc nh cp chnh xc hnh dng b mt (da bng 2-7a).

- Xc nh gi tr dung sai cho php (da bng 2-19 theo TCVN 384 -

1993).

3.6. Xc nh chnh xc v tr b mt v ghi cc gi tr dung sai v tr vo bn v cc chi tit nu kch thc ca cc chi tit cho theo bng 2-15.

Bng 2-15.

36

Phng n 1 2 3 4

Kch thc

(mm)

Mt trc lp

bnh rng cp chnh xc 9

20 K6

C trc

khuu ng c t

60 n7

Mt u t V tr hai

tm l bin

L - 200

Hng dn:

- Da vo iu kin lm vic ca chi tit v chi tit lp vi n xc nh chnh xc v tr b mt thuc loi no.

- Quyt nh cp chnh xc (bng 2-8 2-9a)

- Xc nh gi tr sai lch cho php (bng 2-21v 2-22 theo TCVN 384-

1993).

- Ghi gi tr sai lch cho php ln bn v theo TCVN 5906- 95

Bng 2-16. K hiu dung sai hnh dng v v tr trn bn v

TCVN 5906-95

Cc c trng cn ghi dung sai K hiu

thng

phng

trn

tr

Dung sai

hnh dng

profin ca ng

profin mt

37

song song

vung gc

nghing

V tr

ng tm hay ng trc

Dung sai

v tr

khng i xng

o n Dung sai

o o ton phn

38

3.7. Gii thch cc k hiu ghi trn bn v chi tit hnh 2-12 v xc nh cp chnh xc tng ng.

Hnh 2-12

M

P

A

A1

50

2

A

Bng 2-16a. K hiu dung sai hnh dng v v tr trn bn v Cc k hiu km theo TCVN 5906-95

39

Hng dn:

- Da vo cc bng 2-16 TCVN 5906 - 95 gii thch cc k hiu.

- Da vo cc bng 2-19 n bng 2-22 theoTCVN384-1993 v bng 2-

16, 2-16a theo TCVN 5906 - 95 xc nh cp chnh xc tng ng.

3.8. Ghi k hiu nhm b mt ln bn v chi tit cho cc b mt A, B, C, D, E, F (hnh 2-10) khi cc cp nhm nh trong bng 2-17.

Bng 2- 17.

Phng n 1 2 3 4 5

Mt A 4 6c 9c 10b 12b

Mt B 4 6b 8b 8b 8b

Mt C 4 6b 6b 6b 6b

Mt E 5 5 8b 8b 10a

Mt F, D 5 6a 7a 7a 7a

Ghi ch: 1. Kch thc chiu cao ca cc k hiu hng mp m b mt l h(ring khong

cch gia cc ng k hiu == l 0,4 h v chiu rng l h) xc nh theo kh h ca con

s kch thc ghi trn bn v c kh (TCVN 6-85)

2.Cc k hiu bng ch: X, M, C, R,P theo kiu ch v k thut ngnh c kh.

R

P

C

X

M

ISO1302-1992

Bng 2-18. K hiu hng mp m Profin b mt. TCVN5707-1993

40

16

0.25

0.3

0.4

0.5

0.6

0.8

1 1.2

1.6

2 2.5

3 4 5 6 8

15

0.16

0.2

0.25

0.3

0.4

0.5

0.6

0.8

1.0

1.2

1.6 2 2.5

3.0

4.0

5.0

14

0.1

0.12

0.16

0.2

0.25

0.3

0.4

0.5

0.6

0.8

1.0

1.2

1.6 2 2.5

3.0

13

mm

0.06

0.08

0.1

0.12

0.16

0.2

0.25

0.3

0.4

0.5

0.6

0.8 1 1.2

1.6 2

12 40

50

60

80

100

120

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200

250

300

400

500

600

800

1000

1200

11

25

30

40

50

60

80

100

120

160

200

250

300

400

500

600

800

10 8 20

25

30

40

50

60

80

100

120

160

200

250

300

400

500

9

0 2 8 20

25

30

40

50

60

80

100

120

160

200

250

300

8

6 8 10

12

16

20

25

30

40

50

60

80

100

120

160

200

7

4 5 6 8 10

12

16

20

25

30

40

50

60

80

100

120

6 2.5

3 4 5 6 8 10

12

16

20

25

30

40

50

60

80

5 1.6

2.0

2.5 3 4 5 6 8 10

12

16

20

25

30

40

50

4 1

1.2

1.6

2.0

2.5 3 4 5 6 8 10

12

16

20

25

30

3 0.6

0.8 1 1.2

1.6

2.0

2.5 3 4 5 6 8 10

12

16

20

2 0.4

0.5

0.6

0.8

1.0

1.2

1.6 2 2.5 3 4 5 6 8 10

12

Cp

ch

nh

xc

1

m

0.25

0.3

0.4

0.5

0.6

0.8

1.0

1.2

1.6

2 2.5

3 4 5 6 8

B

ng

2-1

9. D

un

g sa

i

phn

g v

thn

g T

CV

N38

4-19

93

Kh

on

g k

ch t

h

c

dan

h n

gha

, mm

n 1

0

Tr

n 1

0

n

16

Tr

n 1

6

n

25

Tr

n 2

5

n

40

Tr

n 4

0

n

63

Tr

n 6

3

n

100

Tr

n 1

00

n

160

Tr

n 1

60

n

250

Tr

n 2

50

n

400

Tr

n 4

00

n

630

Tr

n 6

30

n

100

0

Tr

n 1

000

n

160

0

Tr

n 1

600

n

250

0

Tr

n 2

500

n

400

0

Tr

n 4

000

n

630

0

Tr

n 6

300

n

100

00

Ch

t

hc

h: C

hi

u d

i d

anh

ngh

a c

a

phn

ch

un

c l

y l

m k

ch

th

c

dan

h n

gha

. Nu

kh

ng

cho

tr

c p

hn

ch

un

, th

ch

iu

di

dan

h n

gha

c

a b

mt

ln

ho

c

ng

kn

h l

n d

anh

ngh

a c

a

b m

t m

t

c

ly

lm

kc

h t

h

c d

anh

ngh

a.

41

16

0.3

0.4

0.5

0.6

0.8 1 1.2

1.6 2 2.5 3 4

15

0.2

0.25

0.3

0.4

0.5

0.6

0.8

1.0

1.2

1.6 2 2.5

14

0.12

0.16

0.2

0.25

0.3

0.4

0.5

0.6

0.8

1.0

1.2

1.6

13

mm

0.08

0.1

0.12

0.16

0.2

0.25

0.3

0.4

0.5

0.6

0.8 1

12

50

60

80

100

120

160

200

250

300

400

500

600

11

30

40

50

60

80

100

120

160

200

250

300

400

10

20

25

30

40

50

60

80

100

120

160

200

250

9 12 18

20

25

30

40

50

60

80

100

120

160

8

8 10

12

16

20

25

30

40

50

60

80

100

7

5 6 8 10

12

16

20

25

30

40

50

60

6

3 4 5 6 8 10

12

16

20

25

30

40

5 2.0

2.5 3 4 5 6 8 10

12

16

20

25

4 1.2

1.6

2.0

2.5 3 4 5 6 8 10

12

16

3 0.8

1 1.2

1.6

2.0

2.5 3 4 5 6 8 10

2 0.5

0.6

0.8

1.0

1.2

1.6 2 2.5 3 4 5 6

Cp

ch

nh

xc

1

m

0..3

0.4

0.5

0.6

0.8

1.0

1.2

1.6

2 2.5

3 4

B

ng

2-2

0. D

un

g sa

i

tr

,

trn

v

pri

n m

t c

t d

c

TC

VN

384-

1993

Kh

on

g k

ch t

h

c

dan

h n

gha

, mm

n 3

Tr

n 3

n 1

0

Tr

n 1

0

n

18

Tr

n 1

8

n

30

Tr

n 3

0

n

50

Tr

n 5

0

n

120

Tr

n 1

20

n

250

Tr

n 2

50

n

400

Tr

n 4

00

n

630

Tr

n 6

30

n

100

0

Tr

n 1

000

n

160

0

Tr

n 1

600

n

250

0

Ch

t

hc

h:

n

g k

nh

dan

h n

gha

b

mt

c l

y l

m k

ch

th

c

dan

h n

gha

.

42

16

0.4

0.5

0.6

0.8 1 1.2

1.6 2 2.5 3 4 5 6 8 10

12

15

0.25

0.3

0.4

0.5

0.6

0.8 1 1.2

1.6 2 2.5 3 4 5 6 8

14

0.16

0.2

0.25

0.3

0.4

0.5

0.6

0.8

1.0

1.2

1.6 2 2.5

3.0

4.0

5.0

13

mm

0.1

0.12

0.16

0.2

0.25

0.3

0.4

0.5

0.6

0.8

1.0

1.2

1.6 2 2.5

3.0

12 60

80

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11 40

50

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8 20

25

30

40

50

60

80

100

120

160

200

250

300

400

500

8

0 2 8 20

25

30

40

50

60

80

100

120

160

200

250

300

7

6 8 10

12

16

20

25

30

40

50

60

80

100

120

160

200

6

4 5 6 8 10

12

16

20

25

30

40

50

60

80

100

120

5 2.5 3 4 5 6 8 10

12

16

20

25

30

40

50

60

80

4 1.6

2.0

2.5 3 4 5 6 8 10

12

16

20

25

30

40

50

3 1

1.2

1.6

2.0

2.5 3 4 5 6 8 10

12

16

20

25

30

2 0.6

0.8 1 1.2

1.6

2.0

2.5 3 4 5 6 8 10

12

16

20

Cp

ch

nh

xc

1

m

0.4

0.5

0.6

0.8

1.0

1.2

1.6 2 2.5 3 4 5 6 8 10

12

Bn

g 2-

21. D

un

g sa

i

son

g so

ng,

v

un

g go

c,

ngh

in

g,

o m

t m

t

v m

t m

ut

ton

ph

n

TC

VN

384-

1993

Kh

on

g k

ch t

h

c

dan

h n

gha

, mm

n 1

0

Tr

n 1

0

n

16

Tr

n 1

6

n

25

Tr

n 2

5

n

40

Tr

n 4

0

n

63

Tr

n 6

3

n

100

Tr

n 1

00

n

160

Tr

n 1

60

n

250

Tr

n 2

50

n

400

Tr

n 4

00

n

630

Tr

n 6

30

n

100

0

Tr

n 1

000

n

160

0

Tr

n 1

600

n

250

0

Tr

n 2

500

n

400

0

Tr

n 4

000

n

630

0

Tr

n 6

300

n

100

00

Ch

t

hc

h: K

hi

qui

nh

du

ng

sai

s

ong

son

g,

vu

ng

gc,

ngh

in

g ch

iu

di

dan

h n

gha

c

a ph

n c

hu

n h

oc

chi

u d

i

dan

h n

gha

c

a t

t c

b

me

t kh

o s

t (

i

vi

dun

g sa

i

son

g so

ng

l c

hi

u d

i d

anh

ngh

a c

a

chi

u l

n)

c

coi

l

kch

th

c

dan

h n

gha

,nu

kh

ng

cho

tr

c p

hn

ch

un

.

K

hi

qui

nh

o

mt

m

t,

n

g k

nh

dan

h n

ghia

ch

o tr

c

ho

c

ng

kn

h d

anh

ngh

a c

m

t m

t

c

ly

lm

kc

h

th

c d

anh

ngh

a.k

hi

qiu

n

h d

un

g sa

i

o

mt

m

t to

n p

hn

,

ng

kn

h d

anh

ngh

a c

a

b m

t m

t

kho

st

c l

y

lm

kc

h t

h

c d

anh

ngh

a

43

16

0.8 1 1.2

1.6 2 2.5 3 4 5 6 8 10

15

0.5

0.6

0.8

1.0

1.2

1.6 2 2.5 3 4 5 6

14

0.3

0.4

0.5

0.6

0.8 1 1.2

1.6 2 2.5 3 4

13

mm

0.2

0.25

0.3

0.4

0.5

0.6

0.8

1.0

1.2

1.6 2 2.5

12

120

160

200

250

300

400

500

600

800

1000

1200

1600

11 80

100

120

160

200

250

300

400

500

600

800

1000

10

50

60

80

100

120

160

200

250

300

400

500

600

9 30 40

50

60

80

100

120

160

200

250

300

400

8 20 25

30

40

50

60

80

100

120

160

200

250

7 12 18

20

25

30

40

50

60

80

100

120

160

6

8 10

12

16

20

25

30

40

50

60

80

100

5 5 6 8 10

12

16

20

25

30

40

50

60

4 3 4 5 6 8 10

12

16

20

25

30

40

3 2.0

2.5 3 4 5 6 8 10

12

16

20

25

2 1.2

1.6

2.0

2.5 3 4 5 6 8 10

12

16

Cp

ch

nh

xc

1

m

0.8 1 1.2

1.6

2.0

2.5 3 4 5 6 8 10 Bn

g 2-

20. D

un

g sa

i

o

h

ng

kn

h v

o

h

ng

kn

h t

on

ph

n

Du

ng

sai

ng

tr

c,

i x

ng,

giao

tr

c t

nh

th

eo

n

g k

nh

T

CV

N38

4-19

93

Kh

on

g k

ch t

h

c

dan

h n

gha

, mm

n 3

Tr

n 3

n 1

0

Tr

n 1

0

n

18

Tr

n 1

8

n

30

Tr

n 3

0

n

50

Tr

n 5

0

n

120

Tr

n 1

20

n

250

Tr

n 2

50

n

400

Tr

n 4

00

n

630

Tr

n 6

30

n

100

0

Tr

n 1

000

n

160

0

Tr

n 1

600

n

250

0

Ch

t

hc

h:

Kh

i qu

i

nh

du

ng

sai

o h

n

g k

nh

v

o h

n

g k

nh

to

n p

hn

,

ng

kn

h d

anh

ngh

a c

a

b m

t

kho

st

c l

y l

m k

ch

th

c

dan

h n

gha

.

Kh

i qu

i

nh

Du

ng

sai

ng

tr

c,

i x

ng,

giao

tr

c t

nh

th

eo

n

g k

nh

c

a b

mt

qu

ay k

ho

st

ho

c

ng

kn

h d

anh

ngh

a g

ia

cc

b m

t t

o p

hn

t

i

x

ng

c

l

lm

kc

h t

h

c d

anh

ngh

a.

Nu

ch

un

kh

ng

c

qu

y

nh

, th

du

ng

sai

c

ly

th

eo p

hn

t

ln

44

Chng III

dung sai lp ghp cc b mt trn

3.1. Sai lch c bn.

Tiu chun Nh nc Vit Nam (TCVN 2241-91) qui nh 28 kiu sai lch c bn cho l v cho trc (hnh 3-1), trong :

- L c bn l l c v tr min dung sai l H v sai lch c bn (sai lch

di) EI = 0.

- Trc c bn l trc c v tr min dung sai l h v sai lch c bn (sai lch trn) es = 0.

F

Hnh 3-1. Phn b min dung sai l (a) v trc (b)

45

- Cc trc c v tr min dung sai: a, b, c, cd, d, e, ef, f, fg, g v h lp vi

l c bn H; hoc cc l c v tr min dung sai: A, B, C, CD, D, E, EF, F, FG, G v H lp vi trc c bn h s cho lp ghp c h .

- Cc trc c v tr min dung sai: js, j, k, m v n lp vi l c bn H;

Hoc cc l c sai lch c bn Js, J, K, M v N lp vi trc c bn h s cho lp ghp c th c h hoc di (lp trung gian).

- Cc trc c v tr min dung sai: p, r, s, t, u, x, y, z, za, zb, zc lp vi l

c bn H; Hoc cc l c sai lch c bn: P, R, S, T, U, V, X, V, Z, ZA, ZB, ZC lp vi trc c bn h s cho lp ghp c di .

Do yu cu thc t, mi cp chnh xc ch qui nh mt s kiu lp nht

nh (xem bng 23 v 24 [I] TCVN 2245 - 91).

Mi v tr min dung sai ca trc hoc ca l bao gm 19 cp chnh xc v c cng sai lch c bn.

Khi bit sai lch c bn c th tnh sai lch cn li theo cp chnh xc

ca kch thc danh ngha:

ei = es - IT hoc es = ei + IT (3-1)

EI = ES - IT hoc ES = EI + IT (3-2)

V d 3-1: Hy xc nh sai lch gii hn (bng cch xc nh sai lch

c bn v khng c bn) cho cc chi tit ca mi ghp 20 Ha

10

11.

Bi gii:

1. L 20H10 l l c bn

- Sai lch c bn ca l 20 H10 (sai lch di) EI:

Theo bng (bng 3-2) ta c EI = 0 v v tr min dung sai l H. Min

dung sai l c bn.

- Sai lch khng c bn ca l 20 H10 (sai lch trn ES):

Theo bng (3-3) ta c IT10 = 84 m, theo cng thc (3-2)

ta c ES = EI + IT

do : ES = 0 + 84 m = 84 m

46

2. Trc 20a11.

- Sai lch c bn (sai lch trn) es:

Tra (bng 3-1) ta c es = - 300 m

- Sai lch khng c bn (sai lch di) ei:

Da vo tr s dung sai IT 11 - (bng 3-3) c : IT 11 = 130 m theo cng thc (3-1): ei = es - IT

Do ei = (-300 - 130)m = - 430 m

V d 3-2: Hy xc nh sai lch gii hn (bng cch xc nh sai lnh c bn v khng c bn) cho cc chi tit ca mi ghp 20.

67

hK

Bi gii:

1. L 20K7.

- Sai lch c bn (sai lch trn) gm: (-2 + )m (bng 3-2) vy: ES = (-2 + 8)m = 6 m.

- Sai lch khng c bn (sai lch di) EI: Da vo tr s dung sai IT7 (bng 3-3): IT7 = 21 m vy theo cng thc (3-2) c:

EI = ES - IT = (6-21) = - 15 m

2. Trc 20h6.

- Sai lch c bn (sai lch trn) es = 0 v trc c bn (bng 3-1).

- Sai lch khng c bn (sai lch di), theo cng thc (3-2).

ei = - IT = - 13 m (bng 3-3)

V d 3-3:

Cho mi ghp 30 Hd

8

8

Yu cu:

- Xc nh kch thc gii hn cc chi tit trong mi ghp (bng tra bng

tr s dung sai)

- Biu din s phn b dung sai

- Xc nh cc i lng c trng ca mi ghp.

47

- Ghi kch thc v sai lch gii hn trn bn v lp v bn v chi tit.

Bi gii

1. Xc nh kch thc gii hn cc chi tit:

-L 30H8:

Da vo bng 8 [I] ta c: ES = + 33 m; EI = 0

- Trc 30 d8:

Da vo bng 7 [I] ta c: es = - 65 m; ei = - 98 m

2. S phn b dung sai (hnh 3-2)

3. Xc nh cc i lng c trng:

- y l mi ghp c h lp ghp theo h thng l, nn khe h ln

nht:

Smax = Dmax - dmin

= 30,033 - 29,902 = 0,131 mm

Hnh 3-2. S phn b dung sai mi ghp 30 Hd

8

8

48

h nh nht: Smin = Dmin - dmax

= 30,000 - 29,935 = 0,065 mm

h trung bnh:

Stb =2

minmax SS

Stb = 2065,0131,0 = 0,098 mm

Dung sai h:

TS = Smax - Smin = TD + Td

= 0,131 - 0,65 = 0,066 m

4. Ghi kch thc, sai lch trn bn v lp v chi tit (hnh 3-3)

Hnh 3-3. Cch ghi kch thc cho bn v lp (a) v chi tit (b)

a)

b) 0

49

Bng 3-1. Sai lch c bn ca trc c kch thc t 1 n 500 mm

(TCVN 2244-91)

V tr cc min dung sai

a b c cd d e ef f fg g

Khong kch thc (mm)

Sai lch c bn es (Cho tt c cc cp chnh xc)

T 1 n 3 -270 -140 -60 -34 -20 -14 -10 -6 -4 -2

Trn 3 n 6 -270 -140 -70 -46 -30 -20 -14 -10 -6 -4

>6 n 10 -280 -150 -80 -56 -40 -25 -18 -13 -8 -5

>10 n 14

>14 n 18

-290 -150 -95 - -50 -32 - -16 - -6

>18 n 24

>24 n 30

-300 -160 -110 - -65 -40 - -20 - -7

>30 n 40 -310 -170 -120 - -80 -50 - -25 - -9

>40 n 50 -320 -180 -130

>50 n 65 -340 -190 -140 - -100 -60 - -30 - -10

>65 n 80 -360 -200 -150

>80 n 100 -380 -220 -170 - -120 -72 - -36 - -12

>100 n 120 -410 -240 -180

>120 n 140 -460 -260 -200

>140 n 160 -520 -280 -210 - -145 -85 - -43 - -14

>160 n 180 -580 -310 -230

>180 n 200 -660 -340 -240

>200 n 225 -740 -380 -260 - -170 -100 - -50 - -15

>225 n 250 -820 -420 -280

>250 n 280 -920 -480 -300 - -190 -110 - -56 - -17

>280 n 315 -1050 -540 -330

>315 n 355 -1200 -600 -360 - -210 -125 - -62 - -18

>355 n 400 -1350 -680 -400

>400 n 450 -1500 -760 -440 - -230 -135 - -68 - -20

>450 n 500 -1650 -840 -480

50

Bng 3-1. Sai lch c bn ca trc c kch thc t 1 n 500 mm (tip)

es V tr cc min dung sai ei

h js j k m n p r

Khong kch thc (mm) Tt c

cp chnh xc

5&6

7 8 T 4 7

T 37

Tt c cc cp chnh xc

T 1 n 3 0 -2 -4 -6 0 0 +2 +4 +6 +10

Trn 3 n 6 0 -2 -4 - +1 0 +4 +8 +12 +15

>6 n 10 0 -2 -5 - +1 0 +6 +10 +15 +19

>10 n 14

>14 n 18

0 -3 -6 +1 0 +7 +12 +18 +23

>18 n 24

>24 n 30

0 -4 -8 +2 0 +8 +15 +22 +28

>30 n 40

>40 n 50

0 -5 -10 +2 0 +9 +17 +26 +34

>50 n 65

>65 n 80

0 -7 -12 +2 0 +11 +20 +32 +41

+43

>80 n 100

>100 n 120

0 -9 -15 +3 0 +13 +23 +37 +51

+54

>120 n 140 +63

>140 n 160 0 2

IT -11 -18 +3 0 +15 +27 +43 +65

>160 n 180 +68

>180 n 200 +77

>200 n 225 0 -13 -21 +4 0 +17 +31 +50 +80

>225 n 250 +84

>250 n 280

>280 n 315

0 -16 -26 +4 0 +20 +34 +56 +94

+98

>315 n 355

>355 n 400

0 -18 -28 +4 0 +21 +37 +62 +108

+114

>400 n 450

>450 n 500

0 -20 -32 +5 0 +23 +40 +68 +126

+132

51

Bng 3-1. Sai lch c bn ca trc c kch thc t 1 n 500 mm (tip)

V tr cc min dung sai ei

s t u v x y z za zb zc

Kong kch thc (mm)

Sai lch c bn ei (cho tt c cc cp chnh xc)

T 1 n 3 +14 - +18 - +20 - +26 +32 +40 +60

Trn 3 n 6 +19 - +23 - +28 - +35 +42 +50 +80

>6 n 10 +23 - +28 - +34 - +42 +52 +67 +97

>10 n 14 +28 - +33 - +40 - +50 +64 +90 +130

>14 n 18 +39 45 - +60 +77 +108 +150

>18 n 24 +35 +41 +47 +54 +63 +73 +98 +136 +188

>24 n 30 +41 +48 +55 +64 +75 +88 +118 +160 +218

>30 n 40 +43 +48 +60 +68 +80 +94 +122 +148 +200 +274

>40 n 50 +54 +70 +84 +97 +114 +136 +180 +242 +325

>50 n 65 +53 +66 +87 +102 +122 +144 +172 +226 +300 +405

>65 n 80 +59 +75 +120 +120 +146 +174 +210 +274 +360 +480

>80 n 100 +71 +91 +124 +146 +178 +214 +258 +335 +445 +585

>100 n 120 +79 +104 +144 +172 +210 +254 +310 +400 +525 +690

>120 n 140 +92 +122 +170 +202 +248 +300 +365 +470 +620 +800

>140 n 160 +100 +134 +199 +228 +280 +340 +415 +535 +700 +900

>160 n 180 +108 +146 +210 +252 +310 +380 +465 +600 +780 +1000

>180 n 200 +122 +166 +230 +284 +350 +425 +520 +670 +880 +1150

>200 n 225 +130 +180 +258 +310 +385 +470 +575 +740 +960 +1250

>225 n 250 +140 +196 +284 +340 +425 +520 +640 +820 +1050 +1350

>250 n 280 +158 +218 +315 +385 +475 580 +710 +920 +1200 +1550

>280 n 315 +170 +240 +350 +425 +525 650 +790 +1000 +1300 +1700

>315 n 355 +190 +268 +390 +475 +590 +730 +900 +1150 +1500 +1900

>355 n 400 +208 +294 +435 +530 +660 +820 +1000 +1300 +1650 +2100

>400 n 450 +232 +330 +490 +595 +740 +920 +1100 +1450 +1850 +2400

52

>450 n 500 +252 +360 +540 +660 +820 +1000 +1250 +1600 +2100 +2600

Bng 3-2. Sai lch c bn ca l c kch thc t 1 n 500 mm

(TCVN2244-91)

V tr cc min dung sai

A B C CD D E EF F FG G

Khong kch thc (mm)

Sai lch c bn EI (cho tt c cc cp chnh xc)

T 1 n 3 +270 +140 +60 +34 +20 +14 +10 +6 +4 +2

Trn 3 n 6 +270 +140 +70 +46 +30 +20 +14 +10 +6 +4

>6 n 10 +280 +150 +80 +56 +40 +25 +18 +13 +8 +5

>10 n 14

>14 n 18

+290 +150 +95 - +50 +32 - +16 - +6

>18 n 24

>24 n 30

+300 +160 +110 - +65 +40 - +20 - +7

>30 n 40 +310 +170 +120 - +80 +50 - +25 - +9

>40 n 50 +320 +180 +130

>50 n 65 +340 +190 +140 - +100 +60 - +30 - +10

>65 n 80 +360 +200 +150

>80 n 100 +380 +220 +170 - +120 +72 - +36 - +12

>100 n 120 +410 +240 +180

>120 n 140 +460 +260 +200

>140 n 160 +520 +280 +210 - +145 +85 - +43 - +14

>160 n 180 +580 +310 +230

>180 n 200 +660 +340 +240

>200 n 225 +740 +380 +260 - +170 +100 - +50 - +15

>225 n 250 +820 +420 +280

>250 n 280 +920 +480 +300 - +190 +110 - +56 - +17

>280 n 315 +1050 +540 +330

>315 n 355 +1200 +600 +360 - +210 +125 - +62 - +18

>355 n 400 +1350 +680 +400

>400 n 450 +1500 +760 +440 - +230 +135 - +68 - +20

>450 n 500 +1650 +840 +480

53

Bng 3-2. Sai lch c bn ca l c kch thc t 1 n 500 mm (tip)

EI ES

H Js J K M N

Khong kch thc (mm)

6 7 8 n 8 >8 n 8 >8 n 8

T 1 n 3 0 +2 +4 +6 0 0 -2 -2 -4

Trn 3 n 6 0 +5 +6 +10 -1+ - -4+ -4 -8+

>6 n 10 0 +5 +8 +12 -1+ - -6+ -6 -10+

>10 n 14

>14 n 18

+ +6 +10 +15 -1+ - -7+ -7 -12+

>18 n 24

>24 n 30

0 +8 +12 +20 -2+ - -9+ -8 -15+

>30 n 40

>40 n 50

0

+10 +14 +24 -2+ - -9+ -9 -17+

>50 n 65

>65 n 80

0 +13 +18 +28 -2+ - -11+ -11 -20+

>80 n 100

>100 n 120

0 +16 +22 +34 -3+ - -13+ -13 -23+

>120 n 140

>140 n 160

>160 n 180

0

+18

+26

+41

-3+

-

-15+

-13

-27+

>180 n 200

>200 n 225

>225 n 250

0

+22

+30

+47

-4+

-

-17+

-31+

>250 n 280

>280 n 315

0 +25 +36 +55 -4+ - -20+ -34+

>315 n 355

>355 n 400

0 +29 +39 +60 -4+ - -21+ -37+

>400 n 450

>450 n 500

0

2IT

+33 +43 +66 -5+ - -23+ -40+

54

Bng 3-2. Sai lch c bn ca l c kch thc t 1 n 500 mm (tip)

V tr cc min dung sai ES

N P-ZC P R S T U V X Y

Khong kch

thc (mm) >IT8 n IT7

>IT7

T 1 n 3 -4 -6 -10 -14 - -18 - -20 -

Trn 3 n 6 0 -12 -15 -19 - -23 - -28 -

>6 n 10 0 -15 -19 -23 - -28 - -24 -

>10 n 14 0 -18 -23 -28 - -33 - -40 -

>14 n 18 -39 -45 -

- -41 -47 -54 -63 >18 n 24

>24 n 30

0 -22 -28 -35

-41 -48 -55 -64 -75

>30 n 40 0 -26 -34 -43 -48 -60 -68 -80 -94

>40 n 50 -54 -70 -81 -97 -114

>50 n 65 0 -32 -41 -53 -66 -87 -102 -122 -114

>65 n 80 -43 -59 -75 -102 -120 -146 -174

>80 n 100 0 -37 -51 -71 -91 -124 -146 -178 -214

>100 n 120 -54 -79 -104 -144 -172 -210 -254

>120 n 140 -63 -93 -122 -170 -202 -248 -300

>140 n 160 0 -43 -65 -100 -134 -190 -228 -280 -340

>160 n 180 -68 -108 -146 -210 -252 -310 -380

>180 n 200 -77 -122 -166 -236 -284 -350 -425

>200 n 225 0 -50 -80 -130 -180 -258 -310 -385 -470

>225 n 250 -84 -140 -196 -284 -340 -425 -520

>250 n 280 0 -56 -94 -158 -218 -315 -385 -475 -580

>280 n 315 -98 -170 -240 -350 -420 -525 -650

>315 n 355 0 -62 -108 -190 -268 -390 -475 -590 -730

>355 n 400 -114 -208 -294 -435 -530 -660 -820

>400 n 450 0 -68 -126 -232 -330 -490 -596 -740 -920

>450 n 500

ES+

-132 -252 -360 -540 -660 -820 -1000

55

Bng 3-2. Sai lch c bn ca l c kch thc t 1 n 500 mm (tip)

V tr cc min dung sai

Z ZA AB ZC

Khong kch thc (mm)

>IT7 3 4 5 6 7 8

T 1 n 3 -26 -32 -40 -60 0

Trn 3 n 6 -35 -42 -50 -80 1 1,5 3 3 4 6

>6 n 10 -42 -52 -67 -97 1 1,5 2 3 6 7

>10 n 14 -50 64 -90 -130 1 2 3 7 9

>14 n 18 -60 -77 -108 -150

>18 n 24 -73 -98 -136 -188 1,5 2 3 4 8 12

>24 n 30 -88 -118 -160 -218

>30 n 40 -112 -148 -200 -274 1,5 3 4 5 9 14

>40 n 50 -136 -180 -242 -325

>50 n 65 -172 -226 -300 -405 2 3 5 6 11 16

>65 n 80 -210 -274 -360 -480

>80 n 100 -258 -335 -445 -585 2 4 5 7 13 19

>100 n 120 -310 -400 -525 -690

>120 n 140 -365 -470 -620 -800

>140 n 160 -415 -535 -700 -900 3 4 6 7 15 23

>160 n 180 -465 -600 -780 -1000

>180 n 200 -520 -670 -880 -1150

>200 n 225 -575 -740 -960 -1250 3 4 6 9 17 26

>225 n 250 -640 -820 -1050 -1350

>250 n 280 -710 -920 -1200 -1550 4 4 7 9 20 29

>280 n 315 -790 -1000 -1300 -1700

>315 n 355 -900 -1150 -1500 -1900 4 5 7 11 21 32

>355 n 400 -1000 -1300 -1650 -2100

>400 n 450 -1100 -1450 -1850 -2400 5 7 13 23 34

>450 n 500 -1250 -1000 -2100 -2600

5

56

17

1.0

1.2

1.5

1.8

2.1

2.5

3.0

3.5

4.0

4.6

5.2

5.6

6.3

7.0

8.0

9.0

10.5

12

.5

15.0

17

.5

21.0

26

.0

32.0

40

.0

49.0

60

.0

16

0.6

0.75

0.

9 1.

1 1.

8 1.

6 1.

9 2.

2 2.

5 2.

9 3.

2 3.

6 4.

0 4.

4 5.

0 5.

5 6.

6 7.

8 9.

2 11

.0

13.5

16

.5

20.0

25

.0

31.0

38

.0

15

0.4

0.48

0.

58

0.7

0.84

1.

0 1.

2 1.

4 1.

6 1.

85

2.1

2.3

2.5

2.8

3.2

3.6

4.2

5.0

6.0

7.0

8.6

10.5

13

.0

15.5

19

.5

24.0

14

0.25

0.

3 0.

86

0.43

0.

52

0.62

0.

74

0.87

1.

0 1.

15

1.3

1.4

1.55

1.

75

2.0

2.3

2.6

3.1

3.7

4.4

5.4

6.6

8.0

9.8

12.0

15

.0

13

0.14

0.

18

0.22

0.

27

0.33

0.

39

0.46

0.

54

0.63

0.

72

0.81

0.

89

0.97

1.

1 1.

25

1.4

1.65

1.

95

2.3

2.8

3.3

4.1

5.0

6.2

7.6

9.4

12

mm

0.

1 0.

12

0.15

0.

18

0.21

0.

25

0.3

0.35

0.

4 0.

46

0.52

0.

57

0.65

0.

7 0.

8 0.

9 1.

05

1.25

1.

5 1.

75

2.1

2.6

3.2

4.0

4.9

6.0

11

60

75

90

110

130

160

190

220

250

290

320

360

400

440

500

560

660

780

920

1100

13

50

1850

20

00

2500

31

00

3800

10

48

48

58

70

84

100

120

140

160

185

210

230

250

280

320

360

420

500

600

700

860

1050

13

00

1550

19

50

2400

9 25

30

36

43

52

62

74

87

100

115

130

140

155

175

200

230

260

310

370

440

540

660

800

980

1200

15

00

8 14

18

22

27

33

39

46

54

63

72

81

89

97

110

125

140

165

195

230

280

330

410

500

620

760

940

7 10

12

15

18

21

25

30

35

40

46

52

57

63

70

80

90

105

125

150

175

210

260

320

400

490

600

6 6 8 9 11

13

16

19

22

25

29

32

36

40

44

50

56

66

78

92

115

135

165

200

250

310

380

5 4 5 6 8 9 11

13

15

18

20

23

25

27

30

35

40

46

54

65

77

93

115

140

170

215

270

4 3 4 4 5 6 7 8 10

12

14

16

18

20

22

25

29

34

40

48

57

69

84

100

125

155

195

3 2 2.5

2.8 3 4 4 5 6 8 10

12

13

15

16

18

21

24

29

35

41

50

60

74

92

115

140

2 1.2

1.5

1.5 2 2.5

2.5

3.0 4 5 7 8 9 10

11

13

15

18

21

25

30

36

45

55

67

84

105

1 0.8 1 1 1.2

1.5

1.5 2 2.5

3.5

4.5 6 7 8 9 10

11

13

15

18

22

26

33

40

49

62

76

0 0.5

0.6

0.6

0.8 1 1 1.2

1.5 2 3 4 5 6 6 7 8 9 11

13

15

18

23

28

35

43

53

Cp

ch

nh

xc

01

m

0.3

0.4

0.4

0.5

0.6

0.6

0.8

1.1

1.2 2 2.5 3 4 4.5 5 5.5

6.5 8 9 11

13

16

20

25

31

38

Kh

on

g k

ch t

h

c

mm

T

1

n 3

T

rn

3

n 6

T

rn

6

n 1

0 T

rn

10

n

18

Tr

n 1

8

n 3

0 T

rn

30

n

50

Tr

n 5

0

n 8

0 T

rn

80

n

120

T

rn

120

n

T

rn

180

n

T

rn

250

n

T

rn

315

n

T

rn

400

n

T

rn

500

n

T

rn

650

n

T

rn

800

n

T

rn

100

0

n

Tr

n 1

250

n

T

rn

160

0

n

Tr

n 2

000

n

T

rn

250

0

n

Tr

n 3

150

n

T

rn

400

0

n

Tr

n 5

000

n

T

rn

650

0

n

Tr

n 8

000

n

B

ng

3-3

. Tr

s

dun

g sa

i

57

Bi tp s 4

4.1. Hy xc nh sai lch gii hn (Theo phng php sai lch gii hn c bn v khng c bn) cho chi tit ca cc mi ghp cho trong bng 3-4.

Bng 3-4.

Phng n 1 2 3 4 5

Mi ghp 30 H

d

9

8 40

H

e

8

8 50

H

f

9

8 70

K

h

7

6 40

H

d

11

11

4.2. Cho cc mi ghp nh bng 3-5

Yu cu:

- Xc nh cc kch thc gii hn cc chi tit trong mi ghp (bng cch tra bng tr s dung sai).

- Biu din s phn b dung sai ca mi ghp.

- Xc nh cc i lng c trng ca mi ghp.

- Ghi kch thc v sai lch gii hn (kch thc ch to) cho bn v lp

v bn v chi tit trc v l.

Bng 3-5.

Phng n 1 2 3 4 5

Lp ghp 20 Hk

6

5 35 H

e

7

8 50 H

h8

8 70 HT6

100 HjS

7

6

4.3. Ni dung nh bi 3-2 nhng vi cc mi ghp cho trong bng 3-6.

Bng 3-6.

Phng n 1 2 3 4 5

Lp ghp 25 Fh8

8 30 Dh

10

10 60 H

h

11

11 85 M8

h8 100 R

h

7

6

4.4. Cho cc yu t nh Bng 3-7, yu cu:

58

- Tnh ton cc kch thc gii hn ca chi tit.

- Biu din s phn b dung sai.

- Tnh sai lch v cc c trng lp ghp.

- Ghi kch thc, sai lch ln bn v chi tit v bn v lp.

Bng 3-7.

Phng n 1 2 3 4 5

Td= 0,70 Td = 0,06 Td = 0,06 Td = 0,08 Td = 0,25

TD = 0,12 TD = 0,09 TD = 0,09 TD = 0,10 TD = 0,25

Smax = 0,26 Smin = 0,10 Nmax = 0,20 Nmax = 0,16 S min= 0

= 50 = 50 = 50 = 50 = 50

Yu t cho

trc (mm)

H l H trc H trc H l H l

4.5. Xc nh h thng lp ghp gia cc chi tit theo cc kch thc ghi trn hnh 3-4a v hnh 3-4b, yu cu ca cc mi ghp nh bng 3-8.

Thanh truyn

Cht piston

Bc thanh truynPston

Hnh 3-4 a

59

Ly c Thn kho nng

Cht ly c

p

Hnh 3-4 b

Bng 3-8.

Mi lp (hnh 3-4a) Tnh cht lp

ghp Mi lp (hnh 3-4b) Tnh cht

lp ghp

Cht pt tng vi l cht pt tng

C di Cht ly c vi thn kho nng

C h

Cht pt tng vi l bc thanh truyn

C h Kim ho 2 vi thn kim ho 1

C h

Bc thanh truyn vi l thanh truyn

C h Cht ly c vi ly c C di

60

3.2. Mt s v d chn lp ghp tiu chun:

V d 3-3b:

Chn lp ghp tiu chun ca mi ghp gia bu nng v hp kho

nng ca sng tiu lin t ng c 7,62 mm ci tin (AKM) (Hnh 3-5).

- Yu cu: di cho php ca mi ghp: Nmin 5 m v Nmax 48 m bo m bn (Cc chi tit khng b ph hu) khi p v khng b dch

chuyn tng i di tc dng ca lc dc trc P = 2500 N.

- Vt liu ca nng: Thp 50 PA

- vt liu ca hp kho nng: thp 40X

Nng

Hp kho nng

Hnh 3-5

Bi gii:

1. Chn h thng lp ghp v xc nh min dung sai ca chi tit c

bn:

- Xut pht t yu cu s dng v mc phc tp trong cng ngh ch to hai chi tit trn, chn chi tit c bn l bu nng. Do chn bu nng l

trc c bn nn y l mi ghp theo h thng trc.

- V lp ghp theo h thng trc nn ng knh ngoi ca bu nng s c v tr min dung sai h vi sai lch c bn: es = 0.

Xc nh cp chnh xc ca trc c bn theo cng thc quan h sau:

T = a . i

61

Ta c : D = d ; Trc v l c cng n v dung sai i.

Mt khc gi s trc v l c cng cp chnh xc ta c:

Td = a.i v TD = a.i

Do Nmax + Nmin = TD + Td = ai + ai nn:

a = TN

iN N

i2 2

max min (3-2b)

Trong : a- s n v dung sai

i - n v dung sai ng vi tng khong kch thc. Theo bng

14[I] ng vi kch thc 23 c i = 1,31.

TN, Nmax, Nmin: dung sai di, di ln nht v di nh nht (tnh theo m).

Thay cc gi tr cho v d trn vo cng thc 3-2b c:

a = 48 5

2 1 31

. ,

= 16

Da vo bng 15 [I] chn cp chnh xc ca trc c bn l: cp 7 (ng vi a = 16).

V vy: min dung sai ng knh ngoi ca bu nng s l: 23h7( 0 021,0 )

(-0.021) (sai lch gii hn di ca trc c bn 23 h7 xc nh theo bng 7 [I].

2. Xc nh min dung sai chi tit khng c bn (hp kho nng).

Sai lch gii hn, theo iu kin cho xc nh theo cng thc sau:

EI = es - Nmax

ES = ei - Nmin

Do vy: EI = 0 - 0,048 = - 0,048 mm

ES = - 0,021 - 0,005 = -0,026 mm

Da vo bng sai lch gii hn ca TCVN 2245 - 91 (bng 8 [I]) xc nh c min dung sai l (hp kho nng) l: 23S7 027,0 048,0

(3-2c)

62

3. V s phn b dung sai v tnh cc i lng c trng ca mi

ghp chn 23 Sh

77

.

S phn b dung sai nh hnh 3-6. Cc i lng c trng: theo (1-1), (1-2) v bng 1-3.

TD = ES - EI = - 0,027 - (-0,048) = 0,021 mm

Td = es - ei = 0 - (-0,021) = 0,021 mm

Nmax = es - EI = 0 - (-0,048) = 0,048 mm

Nmin = ei - es = - 0,021 - (- 0,027) = 0,006 mm

Vy mi ghp chn tho mn iu kin s dng cho, ngha l:

mmchonNchoN 006,0min

005,0min

Ncho

Nchon

mmmax

,

max, 0 048 0 046

4. Xc nh nhm b mt v dung sai sai lch hnh dng:

Da vo Bng 13 v Bng 18 [I] chn nhm b mt nh sau: Trc 23h7 c nhm Ra = 0,32 m , l 23 S7 c nhm Ra = 0,63 m.

Xc nh sai s hnh dng hnh hc b mt lp ghp da vo Bng 2-7. Ly sai s hnh dng bng 20% dung sai kch thc.

Hnh 3-6

63

Vy dung sai tr i vi ng knh lp ca bu nng v hp kho

nng bng:

Thd = 0,2 . TD = 0,2 . 0,021 = 0,004 mm

3. V bn v ch to (Hnh .3.7)

Hnh .3.7

V d 3-3c:

Chn lp ghp tiu chun gia piston v hp trch kh ca c cu t ng li sng AK (Hnh 3-8). Bit:

- h gia piston v hp trch kh thay i trong gii hn 0,05 n

0,10 mm.

- Kch thc lp ghp: 13,94 mm.

Hp trch Kh

Cn piston

Bi gii:

1. Chn h thng lp ghp v min dung sai cho chi tit c bn:

Hnh 3-8

64

Chi tit piston y d ch to v d thay th hn nn chn ng knh

trong ca hp trch kh trong mi ghp cho lm chi tit c bn, v vy lp ghp ca cc chi tit cho theo h thng l.

Min dung sai ng knh trong ca hp trch kh c sai lch c bn H.

Cp chnh xc l c bn c xc nh da vo s n v dung sai "a"

theo cng thc:

a = TS

i

S S

i2 2

max min (3-2d)

Trong : i - n v dung sai, chn theo bng 14 [I]

TS, Smax, Smin - dung sai h, h ln nht, h nh nht (tnh theo m)

Thay gi tr cc i lng vo (3-2d) c:

aS S

i

max min. .2

100 50

2 1 08= 25

Da vo bng 15 [I], ng vi a = 25 chn c cp chnh xc ca l c

bn l cp chnh xc 8 . Vy min dung sai ng knh trong ca hp trch

kh l: 13,94 H8 ( 13,94 027.00 ) (Sai lch gii hn l c bn 13,94 H8 tra

theo bng 8 [I]).

2. Xc nh min dung sai chi tit khng c bn (chi tit piston):

Theo iu kin cho, sai lch gii hn chi tit piston c xc nh

nh sau:

es = EI - Smin

ei = ES - Smax

Thay s vo (3-2e) ta c:

es = 0 - 0,05 = - 0,05 mm

ei = (+ 0,027) - (0,10) = - 0,073 mm

Da vo bng sai lch gii hn ca TCVN 2245-91 (bng 7 [I]) xc nh min dung sai ca trc (piston) l 13,94 d8 ( 050,0 073,0

)

(3 - 2e)

65

3. V s phn b min dung sai ca mi ghp 13,94 H

d

8

8 v xc nh

cc c trng cn li.

S phn b dung sai (hnh 3-9).

ei=-0.077

0 EI=0

es=-0.050

ES=+0.027H8

d8

0

mm

Hnh 3.9. S phn b dung sai

Cc i lng c trng:

Theo (1-1), (1-2) v bng (1-3)

TD = ES - EI = 0,027 - 0 = 0,027 mm

Td = es - ei = (- 0,05) - (-0,077) = + 0,027 mm

Smax = ES - ei = 0,027 - (-0,077) = 0,104 mm

Smin = EI - es = 0 - (- 0,05) = 0,050 mm

TS = Smax - Smin = 0,104 - 0,05 = 0,054 mm

Vy so vi iu kin cho th.

choSchonSmin05,0min

10,0max104,0max choSchonS

Lng vt qu ca Smax l 0,004 mm 0.4 % vy nn c th b qua v mi ghp tiu chun chn l bo m yu cu.

4. Xc nh nhm b mt v sai lch hnh ng ca b mt lp ghp.

66

nhm b mt: Da bng 13 v 18 [I] chn nhm b mt l v trc

nh sau:

Gia cng l 13,94 H8 bng doa tinh, t cp nhm t cp 5 7 v cp chnh xc t 8 6.

Gia cng piston 13,94 d8 bng tin tinh; cp nhm t t 5 7 v cp chnh xc t 7 9.

Chn cp nhm chung l cp 6c c:

Ra = 1,25 m

Dung sai hnh dng ly bng 20% dung sai kch thc (bng 2-7)

Thd = 0,2. 0,027 = 0,054 mm

5. V bn v ch to: (Hnh 3-10)

Hnh 3-10

Bi tp s 5

5.1. Chn lp ghp tiu chun gia cht piston v l cht piston xe A3_51, bit:

- c tnh ca lp ghp : Nmax = 0,015 mm; Smax = 0,005 mm.

- Kch thc lp ghp = 20 mm.

67

5.2. Chn lp ghp tiu chun gia cht piston v l bc thanh truyn, bit:

- c tnh lp ghp: Sm,ax = 0,095 mm; Smin = 0,045 mm

- Kch thc mi ghp: = 20mm

5.3. Chn kiu lp tiu chun gia l thn ng c v bc dn hng su pp xe 3_51.

Nmax = 0,085 mm; Nmin = 0,025 mm

- Kch thc danh ngha mi ghp: = 17 mm

5.4. Chn kiu lp tiu chun gia thn ng c v con i su pp xe A3_51, bit:

- c tnh lp ghp:

Sm,ax = 0,037 mm; Smin = 0,006 mm

- Kch thc danh ngha lp ghp: = 16 mm

5.5. Chn kiu lp tiu chun gia trc khuu v bnh rng khuu (riphng) xe A3_51.

Bit:

- c tnh lp ghp

Smax = 0,024 mm; Nmax = 0,02 mm

- Kch thc danh ngha mi ghp = 40 mm

5.6. Chn kiu lp tiu chun gia kim ho v thn kim ho (hnh 3-4) bit:

- c tnh lp ghp:

Smax = 0,420 mm; Smin = 0 mm

- Kch thc danh ngha mi ghp: = 22 mm

5.7. Chn kiu lp tiu chun gia cht ly c v ly c (Hnh 3-4) bit:

- c tnh lp ghp: Smax = 0,180 mm; Smin = 0,05 mm.

- Kch thc danh ngha lp ghp : = 70 mm

68

5.8. Chn kiu lp tiu chun gia cht ly c v thn kho nng (Hnh 3-4) bit:

- c tnh lp ghp: Smax = 0,170 mm; Smin = 0,055 mm

- Kch thc danh ngha mi ghp: = 70mm

3.3. Tnh ton chn kiu lp cho mi ghp tr trn.

Chn kiu lp cho mi ghp tr trn c th tin hnh theo hai phng php.

- Da vo kinh nghim s dng cc lp ghp chn

- Da vo c tnh yu cu ca mi ghp tin hnh tnh ton v chn

theo tiu chun (i vi cc mi ghp quan trng).

3.3.1. Tnh ton chn kiu lp c di:

Theo TCVN 2245-91, ng vi cc kch thc t 1 500 mm c 19 kiu lp c di tiu chun.

Trong mi lp c i lun xut hin di (N): Gi tr di cn tr

s dch chuyn dc trc ca bc di tc dng ca lc dc trc hoc chng xoay ca trc trong bc di tc dng ca m men xon (Mx) (Hnh.3.11).

Khi chn kiu lp di tiu chun cho mi ghp phi da vo di

cn thit m mi ghp yu cu. di cn thit phi tho mn hai iu kin:

- di phi ln chng s dch chuyn tng i gia trc v bc

di tc dng ca lc chiu trc (P) hoc m men xon (Mx)

- di khng c qu ln chi tit lp ghp khng b ph hu.

tho mn hai iu kin trn th di gii hn ca kiu lp tiu chun m ta chn phi tho mn bt ng thc sau:

Nmin t.t NN

max

min

Nmax t.t (3-3)

Trong :

69

Nmint.t: di tnh ton nh nht m bo chng c dch chuyn

dc trc o lc chiu trc P hoc xoay do m men xon Mx.

- chng dch chuyn dc trc:

Nmin t.t = ( )+++ zdZD9D

D

d

d

1

RR2110EC

EC

fP

m (3-4)

- chng s xoay tng i:

Nmin t.t = ( )+++ zdZD12D

D

d

d

2

x RR2110EC

EC

fdM2

m (3-5)

Hnh 3-11

Trong :

d* - ng knh trc trc khi lp (mm)

D*- ng knh l trc khi lp (mm)

70

D(d) ng knh l (trc ) kch thc danh ngha ca mi ghp sau khi

lp (mm)

RZD, Rzd - Nhp nh b mt l v b mt trc (m)..

l- Chiu di lp ca mi ghp - (mm)

d- Kch thc danh ngha ca lp ghp - (mm)

f1 - H s ma st theo phng chuyn ng dc trc ca chi tit

f2 - H s ma st theo phng chuyn ng quay tng i gia trc v bc.

RAD, Rzd - Chiu cao trung bnh nhp nh ca b mt bao v b bao lp ghp vi nhau (m).

Ed, ED : M un n hi ca vt liu chi tit b bao v chi tit bao - N/m2

(bng 3-9)

Bng 3-9. Tr s M dun n hi E v h s Potson ca mt s vt liu

TT Tn vt liu Tr s modun dn hi E ( N/m2)

1 Thp 2,1.1011 0.3

2 Gang 1,0.1011 0.25

3 ng 0,8.1011 0.35

4 Nhm 0,7.1011 0.35

4 cht do 0,1.1011 0.38

CD, Cd - H s xc nh theo cng thc sau:

Cd = d D

d D

212

212

- d (3-6)

CD = d D

d D

22 2

22 2

+ D (3-7)

71

D1, d(D), d2 - nh hnh 3-12

d, D - H s poatson ca vt liu chi tit b bao v chi tit bao ( theo bng 3-9)

Nmaxtt - di tnh ton ln nht, bo m chi tit khng b ph hu

- i vi chi tit b bao.

Nmaxtt =

TD

d

d

D

DZD zd

dC

E

C

Ed D

dR R

212

22

3

210 1 2, m (3-8)

- i vi chi tit bao.

Nmaxtt =

TD

d

d

D

DZD zd

DC

E

C

Ed D

dR R

22 2

22

3

210 1 2, m (3-9)

Td v TD - Gii hn chy ca vt liu chi tit b bao v chi tit bao - N/m2 (bng 3-11)

Ly tr s nh trong hai tr s tnh theo (3-8) v (3-9) lm Nmax t.t.

V d 3-4: Chn kiu lp cht tiu chun cho mi ghp c nh (hnh 3-13a) vi iu kin.

- ng knh ca trc v l ca v: d = D = 18 mm.

- ng knh ngoi ca bc d2 = 30 mm

Hnh 3-12

72

- Chiu di mi ghp l = 40 mm

- Vt liu chi tit - Thp 40, gii hn chy khng thp hn 34,107 2m

N

- M men xon trn trc Mx = 60:Nm

- H s ma st f = 0,1

- Mi ghp cp chnh xc IT6 ,lp ghp theo h thng l.

-

Hnh 3-13a

Bi gii:

+ Tnh di nh nht chng xoay tng i (truyn c m men

xon - Mx) gia trc v bc.

- Theo cng thc (3-6), (3-7) c:

Cd = 1 - = 1 - 0,3 = 0,7

CD = d D

d D22 2

22 2

2 2

2 2

30 18

30 18

+ 0,3 = 2,42

- Theo bng 3-10, ng vi cp chnh xc kch thc l IT6 v kch thc

18 th cp nhm b mt l cp 8 i vi trc v 8 i vi l, do vy:

RZd = 2,5 m ; RZD = 2,5 m (bng 3-15)

73

Bng 3-10. Quan h gia cp nhm b mt v cp chnh xc gia cng

ca l v trc

Cp chnh xc

IT5 IT6 IT7 IT8 IT6 IT7 IT8 IT9

Khong kch thc -mm

Cp nhm ca trc Cp nhm ca l

T 1 n 3 10 9

Ln hn 3 n 6 9 9 8 8

> 6 n 10 9 7 7

> 10 n 18

> 18 n 30 8 7

> 30 n 50 8 7 6

> 50 n 80 8 7 6 6

> 80 n 120

> 120 n 180 7

> 180 n 250 7 6 5 5

> 250 n 315 7 6 5

> 315 n 400 6

> 400 n 500

- M uyn n hi: Ed = ED = 2,1 . 1011 N/m2 (cng l vt liu thp 40)

- Thay cc s liu vo cng thc (3-5) c:

Nmin t.t = m145,25,22,1

1110.1,2.1,0.40.18.14,3

1210.42,27,0.60.2

74

+ Tnh di ln nht bo m bn cho chi tit.

- i vi chi tit b bao, thay cc gi tr vo cng thc (3-8) c:

5,25,22,1310.1110.1,2.218.2218.42,27,018.710.34

.max

dtt

N = 51,46 m

- i vi chi tit bao: Thay cc gi tr vo cng thc (3-9) c:

5,25,221310.2182301110.1,2.230.2

218.42,27,018.710.34

.max

,

Dtt

N = 35 m

Vy ly Nmax t.t = 35 m

Vy kiu lp m ta chn c di phi tho mn biu thc (3-3), c th

y:

mNN

m 35minmax14

Bng 3-11. Gi tr gii hn chy ( T) ca vt liu.

Mc thp

T (N/m2)

(khng nh hn)

Vt liu

T (N/m2)

(khng nh hn)

Thp 15 24 x 107 Thp 20 28 x 107

Thp 20 26 x 107 Thp 30 32 x 107

Thp 30 30 x 107 Thp 40 36 x 107

Thp 35 32 x 107 Gang c (15 38) x 107

Thp 40 34 x 107 ng thanh thic (10 11). 107

Thp 45 36 x 107 ng thau (35 65).107

Thp 15X 25 x 107 Cht do (35 65). 107

75

Chn kiu lp theo h thng l vi l c bn 18H6 (theo u bi)

Vy c di nh nht Nmin = 14 m th:

dm,in - Dmax = ei- ES = Nmin = 0,014 mm

Theo bng 3-1 chn: ei= 0,025 , ES = 0,011

Theo TCVN 2245 - 91 (bng 7,8 [I]) chn c kiu lp: 18H

s

6

6 c

di gii hn.

Nmax = 34 m

Nmin = 14 m

vi kiu lp trn tho mn yu cu nu.

Vy kiu lp c di cn chn: 18H

s

6

6.

1. Bi tp s 6A

Tnh ton chn kiu lp c di cho mi ghp vi iu kin cho nh

bng 3-12.

3.2. Tnh ton chn kiu lp lng cho trt.

Tnh ton chn kiu lp c h cho mi ghp phi da vo h cn

thit m n yu cu. h cn thit phi tho mn hai iu kin.

- Mi ghp lm vic vi hiu sut cao nht.

- To ma st t trong .

1- mi ghp lm vic c hiu sut cao nht th:

Stb Sh.s - 2(RzD + Rzd) (3-10)

Trong Stb - h trung bnh ca lp ghp c chn, v:

76

Bng 3-12.

Phng n

Thng s cho trc 1 2 3 4 5

D1(mm) 20 30 60 120 0

d=D(mm) 50 80 100 150 20

d2(mm) 70 100 150 170 30

Kch thc mi

ghp

(mm)

L(mm) 80 150 180 160 50

Mx(N.m) 3500 0 6700 2500 0 Lc tc dng

P(N) 0 7.103 5.103 15.103 20.103

Trc Thp

30

Thp

45

Thp

45

Thp

30

Thp

40

Vt liu chi tit

trong mi ghp

Bc Gang

xm

15-32

Gang

xm

28-48

Gang

xm

15-32

BPA

>ii80 260 g6L

f7L

g5L

f6L

G7L

G6L

H7L H6L Cc loi

tr bi

kim

(K1,5) >260 500 f7L f6L E8L E7L

Ti trng va n 80 h6L h5L JS7L JS6L Tt c

p v rung

ng

> 80 n 260 H7L H6L JS7L JS6L cc loi

tr

(K > 1,5) > 260 260 g6L g5L bi kim

n 120 h6L h5L H7L H6L JS7L JS6L a cn

> 120 1600 g6L g5L hai dy

82

Khng ph

thuc tnh

cht ti

trng

Tt c cc

kch thc

ng knh

k6L

hoc

js6L

k5L

hoc

js5L

K7L

hoc

Js7L

K6L

hoc

Js7L

JS7L JS6L bi kim

dp

- Vng chu ti dao ng c lp vi trc hoc l v hp sao cho c khe

h nh. Chn theo bng 3-17.

Bng 3-17. Lp ghp cc vng chu ti dao ng ca ln vi trc v l

Sai lch c bn

Ca trc Ca l v hp

Cp chnh xc ln

Kch thc lp ghp (mm)

0;6 5;4 0;6 5;4

n 80 k6L k5L K7L K6L

Ln hn 80 n 260 JS6L JS5L

Ln hn 260 h6L h5L JS7L JS6L

3.4. Chn kiu lp cho ln vi trc v l v hp.

TCVN 1479 - 74 qui nh ln c 4 cp chnh xc ch to 0; 6; 5 v 4 t

bng 3-16 n bng 3-18 gii thiu quan h cp chnh xc lp ghp ng

knh ngoi ln vi l v hp theo h trc c bn, lp ghp gia ng

knh trong vi trc theo h l c bn.

83

Chn kiu lp gia ln vi trc v l v hp ph thuc vo kt cu

ln, kch thc , iu kin lm vic ca , tr s, c tnh v trng thi

ti trng tc dng ln ng ln ca ln.

- Vng chu ti trng cc b c lp vi trc hoc l v hp sao cho c

h hoc di nh - chn theo bng 3-16.

- Vng chu ti trng chu k cn c lp c di vi trc v l v

my, khi chn da vo cng ti trng PR tc dng ln b mt lp ghp

theo cng thc (3-14) v bng 3-18.

PR = RB

K F Fd A (N/mm) (3-14)

Trong : R - phn lc hng tm tc dng ln b mt lp (N)

B - Chiu rng ln (mm)

B' = B - 2r - Chiu rng lp ghp ca ln (mm)

r - Bn knh gc ln mp ln (mm)

Kd - H s ti trng ng ca lp ghp (bng 3-19)

F - H s tnh n mc gim i ca lp ghp khi trc rng

hoc v c thnh mng (bng 3-20)

FA - H s phn b khng u ca lc hng tm R gia cc

dy con ln trong cc bi a, cn hai dy, gia cc bi kp khi c lc chiu

trc A (bng 3-21).

bo m bi sau khi lp vi trc v l v hp lm vic tt th yu

cu:

0max2,112 D (3-15)

84

Trong :

2 - h hng tm gia bi v ng ln ca sau khi lp vi cc

chi tit tng ng.

1- h hng tm gia bi v ng ln ca khi cha lp vi trc v

l v hp - gi l khe h hng tm ban u (cho trong bng 3-19).

D1max, D2max - bin dng ln nht ca vng ngoi v vng trong

tnh ti ng ln ca vng khi vng ngoi hoc vng trong lp c di vi

l v hp hoc vi trc, c tnh nh sau:

D1max = 0,75 Nmax . DD

4 (mm) (3-16)

D2max = 0,75 Nmax . d

D3(mm) (3-17)

D3 - ng knh ngoi biu kin ca vng trong v:

D3 = d + D d