## Chosen the principle of the backlash of the bearing

29th April 2013 Bearing Technology 0 Comments

Chosen the principle bearing is chosen, the bearing uses of the backlash of the bearing

First, choice principle of the backlash:

1,Relatively adopt the close fit, the temperature difference of the Internal and external cycle is more greatly, needs to reduce friction moment and major groove ball bearing and bearing greater axial load or needing to improve the occasion of the cente adjusting characteristic, should adopt the large backlash group.

2,When rotating the great of accuracy requirement or needing to limit the axial displacement strictly, should adopt the small backlash group.

Second, factor related to backlash:

1,The inner circle of bearing cooperates with the axle one.

2,The bearing outer lane cooperates with exterior shell hole.

3,Influence of the temperature.

Note: Radial the intersection of backlash and reduction magnitude, exterior wall thickness of shell hole relevant with cooperate with real effective the intersection of interference and magnitude, axle diameter of matching of part.

1,Real effective interference inner circle Should be: dy =2/3 d-G* D is

Name interference, G *, for flattening the size of interference fit.

2,Real effective interference outer lane Should be: Dy =2/3 D-G* D is

Name interference, G *, for flattening the size of interference fit.

3,The heat that produces will cause the bearing internal temperature to rise, then cause the inflation of the axle, pedestal and bearing part. The backlash can increase or reduce, this depends on material of axle and pedestal, and the temperature tonsure between bearing and bearing support unit.

Third, formula of the backlash:

1: Influence of cooperating

1,Inner circle of bearing and steel solid shaft: j = dy * d/h

2,Inner circle of bearing and steel hollow shaft: j = dy * Fd

Fd =d/h * [d/d1 2 -1]/[d/d1 2 - d/h 2]

3,Bearing outer lane and outer cover of steel entity: A = Dy * H/D

4,Bearing outer lane and thin-walled outer cover of steel: A = Dy * FD

FD =H/D * [F/D 2-1]/[F/D 2 - H/D 2]

5,Bearing outer lane and gray iron outer cover: A = Dy * [FD -0.15 ]

6,Bearing outer lane and light metal case: A = Dy * [FD -0.25 ]

Note:

j –The ball track of inner circle blocks diametral expansion amount um .

Effective interference um of dy- journal .

d –Nominal dimension of internal diameter of the bearing mm .

h –The ball track of inner circle blocks the diameter mm .

B –Bearing width mm .

d1 –Hollow shaft internal diameter mm .

A –The ball track of outer lane blocks diametral shrinkage mm .

Dy –Real effective interference um of the exterior casing diameter .

H –The ball track of outer lane blocks the diameter mm .

D –Nominal diameter mm of exterior shell hole of cycle sum outside the bearing .

F –Pedestal outer cover external diameter mm .

2: Influence of the temperature

T =Г b * [De * T0- Ta -di * Ti-Ta ]

Among them Г b is a linear expansion coefficient, the bearing steel is 11.7 *10-6 mm/mm/ 0C

De is the diameter of ball track of outer lane of the bearing, di is the diameter of ball track of inner circle of the bearing.

Ta is the ambient temperature.

T0 is the temperature of outer lane of the bearing, the temperature of inner circle of Ti bearing.

Fourth, relation of axial backlash and radial backlash:

Ua = [4fe fi- 1 *Dw * Ur-Ur2 ] 1/2

Because the radial backlash is Ur very small, so Ur2 is very small, neglects and does not write.

So Ua =2 * [fe fi- 1 *Dw * Ur ] 1/2

Among them fe is a ditch camber coefficient of the outer lane, fi is a ditch camber coefficient of inner circle, Dw is the diameter of the steel ball.