Design of gear shafts, Tolerances of cylindrical gears...

Designing Gear Shafts

Two structural combinations of gears with a shaft are used:

• Shaft-pinion-gear is manufactured in conjunction with the shaft (Figure 3.32.3.33);

• The pinion is connected to the shaft by means of keyed, splined and other joints (pinion gear).

Fig. 3.32

The quality (stiffness, accuracy, etc.) of the pinion shaft is higher, and the manufacturing cost is lower than the total cost of the shaft and the gear wheel, so they are used quite often.

In addition, pinion shafts are used for gears of small diameter (relative to the shaft diameter) when it is not possible to apply connections that transmit torque from the gear to the shaft or vice versa.

The main drawback of this design is that when the gear crown fails, you must change the shaft.

In Fig. 3.32, a shows the design of the pinion shaft, which provides the cutting of the teeth with a free tool exit.

With large gear ratios, the outer diameter of the pinion, as a rule, differs little from the diameter of the shaft and the pinion shafts are constructed according to Fig. 3.32, 6. In this case, the teeth are cut on the surface of the shaft. It is desirable to avoid recess gears, as in this case hobbing and grinding of teeth is difficult.

In Fig. 3.33 shows the design of the cantilever-pinion shaft. This design is often used for cylindrical internal gearing.

Fig. 3.33

Tolerances of cylindrical gears

Tolerances apply to involute cylindrical gears of external and internal gearing with spur, helical and chevron gears with a dividing diameter up to 4000 mm, a width of a crown or a half-chevron up to 400 mm, with a tooth module from 1 to 16 mm and with an initial contour to GOST 13755-81.

Z.2.Z.7.1. Degrees of accuracy and fork of the interfaces

1. The degrees of accuracy of gears and gears are indicated in descending order of accuracy by the numbers 5, 6, 7, 8, 9, 10.

2. For each degree of accuracy of gears and gears, the norms are set:

• kinematic accuracy;

• smooth operation;

• contact of the teeth of the wheels and gears.

3. It is allowed to combine the norms of kinematic accuracy of wheels and gears, the smoothness of operation and the norms of contact of teeth with different degrees of accuracy.

4. When combining norms of different degrees of accuracy, the norms of smoothness of operation of gears and gears can be no more than two degrees more precise or one degree coarser than the norms of kinematic accuracy.

The norms of tooth contact can be assigned to any degree more accurate than the smoothness norms of the operation of gears and gears, and for transmissions with an axial overlap factor with p & lt; 1.25 - also to one degree more coarse than the smoothness standards.

5. Regardless of the degree of accuracy of the gears and gears, the types of mating of the gears in the gear are given in Table. 3.18.

Table 3.18

Types of interfaces and sizes of guaranteed side clearances

The types of tolerance for the lateral clearance are indicated in the order of its increase by the letters d, c, b, a, z, y, x.

In the absence of special requirements for a batch or for a set of transmissions, the types of conjugations D, C, and B correspond to tolerance types d, c, b and a.

6. The norms of the side clearance and the correspondence between the type of coupling of the gears in the transmission and the type of tolerance for the lateral clearance are allowed to be changed, using also the tolerance types z, y and x.

7. The accuracy of the production of cylindrical gears and gears is determined by the degree of accuracy, and the requirements for the lateral clearance - the type of coupling according to the standards of the lateral clearance.

8. GOST 1643-81 provides:

• tolerances for dividing diameters up to 6300 mm;

• the width of the crown or half-chevron up to 1250 mm;

• tooth modules up to 56 mm;

• degrees of accuracy 1,2, 3,4, 5, 11, 12;

• the types of conjugations E and H

• additional types of norms.

Degrees of accuracy 11 and 12 are applied to gears without machining on the lateral surfaces of the tooth.

9. The industry standard of the Ministry of Machine Tool and Tool Industry OST 2 H36-1-74 provides:

• degrees of accuracy 5-9;

• One kind of conjugation - B.

Examples of designation:

1. Accuracy of transmission with a degree of accuracy in all three norms, with the type of conjugation of wheels C and the correspondence between the types of coupling and the tolerance for lateral clearance:

7-C GOST 1643-81.

Note. For transmissions in which the value of the guaranteed side clearance does not correspond to any of the indicated types of conjugations, the letter denoting the conjugation type is not indicated.

In this case, specify:

• value of the assumed guaranteed side clearance in μm;

• type of tolerance for lateral clearance.

2. The accuracy of transmission with a degree of accuracy of 7, guaranteed by a side gap of 600 μm (not corresponding to any of the indicated interfaces for a given axle distance of 450 mm) and tolerance to the side clearance of the type of:

7- 600 for GOST 1643-81

When combining the norms of different degrees of accuracy and changing the correspondence between the type of interface and the type of tolerance for the lateral play, the accuracy of the gears and gears is indicated by consecutively writing three numbers and two letters. Between themselves and from the letters written together, the numbers are separated by a dash.

The first digit denotes the degree of kinematic accuracy. The second digit indicates the degree of smooth work.

The third digit denotes the degree of tooth contact.

The first letter indicates the type of pairing.

The second letter indicates the type of tolerance for the lateral clearance.

Example of a designation:

The accuracy of transmission with a degree of 8 according to the kinematic accuracy, with a degree of 7 according to the rules of smooth operation, a degree 6 according to the norms of contact of the teeth, with the type of coupling of the wheels B and the type of tolerance for the lateral clearance a:

8- 7-6-GOST GOST 1643-81.

Z.2.Z.7.2. Precision rates

1. Tolerances and deviations according to the norms of kinematic accuracy, the norms of smooth operation and the norms of tooth contact for various degrees of accuracy of gears and gears; are established on tab. 11.204-11.209.

The values ​​in parentheses are for information only.

2. The parameters of kinematic accuracy are:

• for gears:

/y , and Y Hg - for degrees of accuracy 6, 7, 8,

T "and Vg & gt; ~ for degrees of accuracy 6, 7, 8,

/y '- for degrees of accuracy 9, 10;

r n . - at degrees of accuracy 7, 8 and diameters of cogwheels over 1600 mm, and also at degrees of accuracy 9, 10 and at any diameters of gears;

• for transmissions:

- for degrees of accuracy 6, 7, 8.

Note. It is permissible that one of the values ​​entering into the complex should exceed the limit value if the total effect of both quantities does not exceed/y. 3.1 The smoothness indicators of work:

• with an accuracy degree of 6, 7, 8 with an axial overlap factor of at least

indicated in Table. 3.19:

- for gears:

Lag and/ g - for degrees of accuracy 6, 7, 8;

// & gt; - for degrees of accuracy 7, 8;

- for broadcasts:

/ 2ког - for degrees of accuracy 6, 7, 8.

For degrees of accuracy 6, 7, 8 with coefficient of axial overlap ep, less than indicated in Table. 3.19, and degrees of accuracy 9, 10 for any parameter of smoothness of work:

• for gears:

/pbr and - for degrees of accuracy 6, 7, 8;

/ p1g - for degrees of accuracy 6, 7, 8;

/ г - for degrees of accuracy 6, 7, 8, 9, 10;

• for transmissions:

Log - for degrees of accuracy 6.7, 8.

Note. Instead of deviating the step as one of the indicators, you can use the difference of the steps Y pr .

Table 3.19

Coefficient of axial overlap, depending on the degree of accuracy

Degree of Accuracy

6

7

8

Ч

2

2.5

8.5

4. The parameters determining the contact of the teeth in the gear are:

• for gears:

- with an axial overlap factor of 8р over 1.25:

Ppxng kg px & r; r/pb,;

- with an axial overlap factor of 8p to 1.25:

or/V;

• for transmissions:

- with unregulated position of the axes:

* total contact spot/ g and /;

- with adjustable axes arrangement:

* total contact spot.

Note. It is allowed to estimate the accuracy of the gears by the total contact of their teeth with the teeth of the measuring gear wheel. In this case, the relative dimensions of the total contact patch should be accordingly increased in comparison with those indicated in Table. P.209.

5. Dependencies of the limiting deviations and tolerances on the geometrical parameters of the gears are given in Table. A.216.

6. In Table. A.217 shows the tolerances of the diameter of the tips of the teeth (1 a and the width of the gear ring b of the cylindrical wheels, and in Table A.218 the allowances for the end run-out of the sprocket of the cylindrical wheels at c = 100 mm are given module/m/1 mm.

3.2.3.7.3. Standards of the lateral clearance

1. The values ​​of the guaranteed side clearance at пт | п and the limiting deviations of the interaxal distance/ а for different types of interfaces are established, regardless of the degree of accuracy and their combination, according to Table. P.210.

2. Indicators providing a guaranteed lateral clearance are:

• for gears - А ^ Уте (Table П.211-П.213) or А се (Table A.214);

• For transmissions with unregulated axes -/ a

• For transmissions with a controlled arrangement of axes, j n t w.

thematic pictures

Also We Can Offer!

Other services that we offer

If you don’t see the necessary subject, paper type, or topic in our list of available services and examples, don’t worry! We have a number of other academic disciplines to suit the needs of anyone who visits this website looking for help.

How to ...

We made your life easier with putting together a big number of articles and guidelines on how to plan and write different types of assignments (Essay, Research Paper, Dissertation etc)