Flange joints, Shaft supports, Roller bearings, General information - Machine parts. Course design

Flange connections

Flange connections are mainly used for connecting shafts, as well as for securing disk and drum type parts to shafts.

The torque is transmitted by the prismatic bolts (Figure 4.17) and the special elements made for planting, working on shearing and crushing, and partly by frictional forces arising on the butt surfaces when tightening the bolts.

Torque transmitted by the flange connection:

where O is the diameter of the circle of the location of the centers of the bolts; g, and c! x - respectively, the number and diameter of the prismatic bolts; 2 2 and (1 2 - respectively, the number and diameter of the clamping bolts; t ff and a p respectively , permissible stresses of bolts,/- coefficient of friction at joint of joints,/= 0,1-0,15. Usually the force of vision is not taken into account.

If all bolts are prismatic, then

where 1 - torque, H m; 2 and a is the number and diameter of the bolts, mm.

The prismatic bolts are made of carbon steels of 45, 50 or 40K alloy steel and heat treated (30-45 PJAC).

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Fig. 4.17

The holes of the floor are made by two ways - either in the joint processing of the parts to be joined, or in each of the parts separately, by the conductor, followed by the joint deployment of the hole in the details below

landing

Usually in the location of the thickness of the bolt:

The thickness of the flanges in the transition areas is: • when switching to the power belt:

• When changing to the shaft:

the bolts are counted on the cut (circumferential silo) and tension (by the force of preliminary tightening):

where st p - tensile stress; t cp - shear stresses.

Shaft supports

The support is the part of the mechanism that provides the rotational motion of the moving parts of the mechanism.

The main part of the support is the bearing, which is an intermediate element between the stationary part of the mechanism and the rotating shaft.

Depending on the type of friction, bearings are divided into two main types: rolling bearings and plain bearings.

The most common are bearings made on the basis of rolling bearings.

Rolling bearings

General Information

The rolling bearing (Figure 4.4.1) consists of the outer (1) and inner (2) rings, which connects to the trunnion and the body. Between the rings there are rolling bodies (3). On the outer surface of the inner ring and the inner surface of the outer ring (on the end surfaces of the thrust bearing rings), troughs are made-the raceways along which the rolling bodies roll during the operation of the bearing. Because of this, frictional friction occurs between the contacting surfaces of the rolling bodies and the tracks of the bearing rings. The separators (4) are guided and held at equal distances by the rolling elements during the operation of the bearings.

Fig. 4.18

There are bearings that lack some of these parts. For example, needle and some other types of special bearings do not have separators. Such bearings have a larger number of rolling bodies and, therefore, a greater load capacity. However, the limiting speeds of the bez-separator bearings are significantly lower due to increased moments of resistance to rotation.

Individual types of bearings are supplied with masseur retaining washers, sealing devices and other special parts.

The rolling bearings are classified according to the following characteristics:

but the shape of the rolling bodies:

• ball (see Figures 4.19, 4.20, 4.23, and 4.25, 4.27),

In

Fig. 4.19

• Roller:

- cylindrical rollers (Figure 4.21, Figure 4.28),

- conical rollers (Figure 4.24, Figure 4.26, a),

- rollers barrel-shaped (Figure 4.23, b, Figure 4.26, b);

• Needles (Figure 4.22),

but the direction of the perceived end:

• radial, mainly for radial loads (loads acting perpendicular to the axis of rotation of the bearing) (Figure 4.19, Figure 4.21-4.23);

• radial-thrust bearings designed to absorb simultaneously radial and axial loads acting on the bearing (Figures 4.20, 4.24);

• thrust-radial bearing axial loads with simultaneous action of a relatively small radial load (thrust-radial bearings differ from the radial-thrust values ​​of the nominal (initial) contact angle a (Figure 4.20, a), which is equal to the angle between the normal to the contact area of ​​the ball or roller with the raceway of the outer ring and the plane perpendicular to the bearing axis, the radial thrust bearings have a <36 ° and thrust-radial bearings a> 36 °;

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• thrust, designed to absorb axial loads (Figure 4.24,4.25);

• To perceive the radial and axial force of one direction at low speeds, bearings are used whose construction is shown in Fig. 4.27, - they are less than ball thrust sensitive to mutual skewing of rings;

• The bearings shown in Fig. 4.28, are used to perceive only the axial force of one direction, mainly on vertical shafts operating at low speeds - they are characterized by high load capacity and are very sensitive to skewing of rings.

Fig. 4.20

Fig. 4.21

Fig. 4.22

Fig. 4.23

Fig. 4.24

Fig. 4.25

Fig. 4.26

Fig. 4.27

Fig. 4.28

by the number of rolling series:

• single-row;

- two-row;

- four-row.

by the method of compensation of shaft misalignments:

• Non-resilient;

• Salvaging - the axes of the inner ring allowing rotation are relative to the axis of the outer ring (Figure 4.23).

Bearings with a hole of the same diameter by the ratio of overall dimensions are divided into dimensional series - a combination of series of diameters and widths (heights) that determines the overall dimensions of the bearing.

For rolling bearings according to GOST 3478-79 the following dimensional series are installed:

• Diameters: 0, 8, 9, 1, 7, 2, 3, 4, 5 (in order of increasing the size of the outer diameter of the bearing with the same hole diameter);

• width or heights: 1, 8, 9, 0, 1, 2, 3, 4, 5, 6 (in order of increasing width or height).

GOST 520-89 establishes cotes of accuracy of bearings, given in the table. The list of accuracy classes is given in order of accuracy.

Accuracy class

Bearing type

0.6, 5.4, 2, T

Radial ball bearings

Radial roller bearings

Angular contact ball bearings

0.6, 5, 4, 2

Thrust and thrust-radial

0.6X, 6, 5.4, 2

Roller conical roller bearings

Additional accuracy classes of bearings (8 and 7 - below accuracy class 0) are set for use on the order of consumers in non-compliant nodes

The accuracy classes of bearings are characterized by the values ​​of the limiting deviations, sizes, shape and position of bearing surfaces.

In the general engineering industry I most often apply! bearings of classes 0,6 and 5.

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