DIN 3961-1978圆柱齿轮啮合公差基础(2)

= 1.6 from gear tooth quality 9 e) Pitch error f,= 5+ 0,4 ( m,+ 0,25@) Q= 1.4 up to gear tooth quality 9= 1.6 from gear tooth quality 9 Qf) Total pitch deviation

FI'

FpQ(P

= 7,25

*

frFI

d '13 z 117

fi

= 1.4 up t o gear tooth quality 9= 1.6 from gear tooth quality 9

Q) Pitch-spandeviation

3.4 Gear tooth qualities The DIN gear tooth tolerance system contains 12 gear tooth qualities. The finer qualitites are intended for master gears and special requirements. They are so grad. uated that the tolerances of each quality amount to p times the tolerances of the preceding quality. The increments p are s

tated in Section 3.5. The limiting values of the reference diameter and module ranges are taken from the preferred number series R 20.3.5 Calculation of tolerances The tolerances are calculated according to formulae exhibiting different kinds of dependence on the gear tooth data (reference circle diameter, module, number of teeth and facewidth). The numerical factors of the formulae reproduced below apply to the 5th gear tooth quality. For calculating the tolerances from the formulae, the geometrical mean values of the ranges stated i n the Tables are used for m, and d.

p= 1.4 up to gear tooth quality 9 p= 1.6 from gear tooth quality 9h) Concentricity deviation F,= 1,68+ 2,18 * Q= 1,4

6

f

(2,3+ 1,2 log m,)

*

d1/4

i) Tooth thickness fluctuation R,= 1+ 1,28+ (1.33+ 0,7 log mn) d1/4 p= 1,4

6

k) Tooth trace total deviation Fp= 0,8 * i/b+ 4 p= 1.25 up t o gear tooth quality 6 p= 1.4 gear tooth quality 6 to 8= 1.6 gear tooth quality 8 to 12 Q

I) Tooth trace angle deviation

fq=4,16 *= 1.32 up to gear tooth quality 6 Q bp= 1.4 gear tooth quality 6 to 8 p= 1.55 gear tooth quality 8 to 12

DIN 3961-1978圆柱齿轮啮合公差;基础

Page 4 DIN 3961 m) Tooth trace form deviation tional requirements made on a gear, the better must be the gear tooth quality produced, but on the other hand the more differentiated must be the tolerancing in order t o avoid unnecessary production cost. Hence it i s possible for fundamentally different gear tooth qualities t o be prescribed for the individual parameters. Such a linking is termed a tolerance family. However it i s not desirable to form tolerance families in which a different gear tooth quality is fixed for each critical parameter. The service properties required of a gear can be classified in the following function groups: - G: uniformity of transmission of motion - L: quiet running and dynamic load-carryingcapacity- T: static load-carryingcapacity - N: no information on function

fßf=3.5.2Working deviationsa) Two-flank working deviation Fi'= 2+ 2,57 *+ (3,12+ 0,432 log m,) cp= 1,4

G,

d'h

b) Two-flank working error

fi'rp

1,8= 1,4=

*En,+1 1,6 * d '/ a+ Ff)

c) Single-flank working deviation

FI= 0,8 * ( F,

cp cp= 1.6 from gear tooth quality 9 d) Single-flank working error

= 1.4 up to gear tooth quality 9

ficp cp

= 0,7= 1.6

*

(fp+ Ff)

= 1.4 up to gear tooth quality 9

from gear tooth quality 9

3 6 Tolerances for the diameter of the tip circle .(tip cylinder) Because of the module-dependentbottom clearance and the effect of the tip circle diameter on the transverse contact ratio of the gear teeth, the tolerance f 0.05 . m i s prescribed for the diameter of the tip cylinder in the case of non-overcut tooth tips, except where agreed to the contrary. I n the case of overcut tooth tips, which are mainly used on gears for light precision engineering, the diameter of the tip cylinder is employed for indirect checking of the tooth thickness. It is smaller than the nominal dimension by 2.747 times th

e tooth thickness allowance when a= 20' and by 3.732 times t h e tooth thickness allowance when 01= 15'. For further details see DIN 58 405 Part 2, May 1972 edition, Section 2.1.

These depend largely - if not exclusively - on specific geometrical requirements, see Table 1. When tolerance families with gear tooth qualities are formed it i s therefore desirable t o choose the same gear tooth qualities each time for the tolerances of a function group. In this way tolerance families with not more than three different gear tooth qualities can arise. I f a parameter occurs in several function groups, it is the group with the finer gear tooth quality which prevails for this parameter.

4 Tolerancing4.1 Tolerance families

The tolerances chosen must be correct from the functionalI and production viewpoint. The more exacting the funcTable 1. Function groups of deviations

4.2 Application of tolerance families It will often happen that for a particular gear it i s desirable or practicable to demand only a general service property without taking special functional requirements into account (function group NI. I n these cases only a single gear tooth quality i s prescribed, e. g. quality 8. (The points to be observed and checked in these and the following cases are described in Section 5). I n other cases fulfilment of the requirements of a specific function group will be stipulated. I n such cases the letter symbol of the function group must be quoted along with the required gear tooth quality. Examples are given i n Table 2. Basically, tolerances shall be agreed only for such function groups whose deviations really matter for the application concerned. As a rule, not more than two function groups should be agreed.~~~~~

_

_

_

_

_

_

~~~

~

~

~

Function group

Important deviations *)

GL T

Uniformity of transmission of motion Quiet running and dynamic load-carryingcapacity Static load-Carringcapacity

fififpefp

F p F' i(fJ

Fr

fi'Fp

fi' Ff fHp

(F,)

fHßfHp

TRAFt

N

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