Appointment, designs and materials of axes and shafts. Shafts and axes General information and basics of design

Axis serve to maintain different parts of machines and mechanisms rotating with them or on them. The rotation of the axis together with the parts installed on it is carried out relative to its supports, called bearings. An example of the unwilling axis can be the axis of the load-lifting machine block (Fig. 1, a), and the rotating axis is the car axis (Fig. 1, b). The axes perceive the load from the parts located on them and work on the bend.

Fig. one

Construction of axes and shafts.

Unlike axes are designed to transmit torque and in most cases to maintain rotating with them relative to bearings of various parts of the machines. The shafts carrying the parts through which the torque is transmitted is perceived from these parts of the load and, therefore, work simultaneously to bend and twist. Under action on the parts mounted on the shafts (conical gears, worm wheels, etc.) of axial loads. There are additionally operated on stretching or compression. Some shafts do not support rotating parts (car shafts, connective rolls of rolling mills, etc.), so these shafts work only on tapping. In terms of purpose, the transmissions are distinguished on which gear wheels, asterisks, coupling and other gear parts are installed, and the indigenous shafts on which not only the gear parts are installed, but also other parts, for example, flywheels, crank and so on.

Axis are straight rods (Figure 1, a, b), and the shafts distinguish straight (Fig. 1, B, d), crankshaft (Fig. 1, e) and flexible (Fig. 1, e). Straight shafts are widespread. The crankshafts in crank-connecting transmissions serve to convert the reciprocating movement into the rotational or vice versa and are used in piston machines (engines, pumps). Flexible shafts, which are multi-turn twisted from the wire of the twist springs, are used to transfer the moment between the nodes of the machines that change their relative position in operation (mechanized tool, remote control devices and control, dental bramshins, etc.). Crankshaft and flexible shafts relate to special details, they are studied in the respective special courses. The axes and shafts in most cases are round solid, and sometimes the ring cross section. Separate sections of the shafts have a round solid or ring cross section with a key groove (Fig. 1, B, d) or with slots, and sometimes a profile section. The cost of the axes and shafts of the ring section is usually greater than a solid section; They are used in cases where it is necessary to reduce the mass of the structure, for example, in airplanes (see also the axis of the satellites of the planetary gearbox in Fig. 4), or placed inside another part. Hollow welded axes and shafts made of ribbon, located along the screw line, reduce the mass to 60%.

The axis of small lengths produce the same diameter over the entire length (Fig. 1, a), and long and highly loaded - shaped (Fig. 1, b). Direct shafts depending on the purpose of either a permanent diameter along the entire length (transmission shafts, Fig. 1, B), or stepped (Fig. 1, d), i.e. Various diameters in some sections. Step shafts are most common, as their form is convenient for installation of parts on them, each of which should pass free to its place (for the shafts of the gearboxes, see the article "Toggle gearboxes" Fig. 2; 3; and "worm transmission" Fig. 2 ; 3). Sometimes the shafts are manufactured at the same time with gears (see Fig. 2) or worms (see Fig. 2; 3).

Fig. 2.

Plots of the axes and shafts, which they rely on the bearings, are called with the perception of radial loads with pinches, with the perception of axial loads - heels. End pinows operating in sliding bearings are called spikes (Fig. 2, a), and the axes located at some distance from the ends of the axes and the shafts - shaiki (Fig. 2, b). Pins of axes and shafts operating in sliding bearings are cylindrical (Fig. 2, a), conical (Fig. 2, c) and spherical (Fig. 2, d). The most common - cylindrical shschs, as they are most simple, comfortable and cheap in manufacturing, installation and work. The conical and spherical axes are applied relatively rarely, for example, for adjusting the gap in the bearings of the exact machines by moving the shaft or the bearing liner, and sometimes for axial fixation of the axis or shaft. Spherical trumps are used when the shaft besides the rotational movement must perform an angular movement in the axial plane. Cylindrical tracks operating in sliding bearings typically make several smaller diameters compared with the adjacent area of \u200b\u200bthe axis or shaft, so that the axis and shafts and the shafts can be fixed due to the casters and the shafts (Fig. 2, b) axis and shafts. Pins of axes and rolling bearings almost always perform cylindrical (Fig. 3, a, b). Connectors are relatively rarely used with a slight angle of taper to regulate gaps in rolling bearings with elastic deforming rings. On some axes and shafts for fixing rolling bearings next to the ranges, it is planned to thread for nuts (Fig. 3, b;) or ring shades for fixing spring rings.

Fig. 3.

The heights operating in the sliding bearings, called the spyers, are usually ringing (Fig. 4, a), and in some cases - comb (Fig. 4, b). Great heels are used under the action on the shafts of large axial loads; In modern engineering, they are rare.

Fig. four

The planting surfaces of the axes and shafts on which the rotating parts of the machines and the mechanisms are installed, perform cylindrical and much less often conical. The latter use, for example, to facilitate the formulation of the shaft and remove heavy parts from it with increased accuracy of the centering of parts.

The surface of the smooth transition from one stage of the axis or the shaft to the other is called quilge (see Fig. 2, a, b). The transition from the steps of a smaller diameter to the larger diameter stage is performed with the rounded groove to exit the grinding circle (see Fig. 3). To reduce the concentration of stresses, the radii of roundings of cartoons and the grooves are taken possible by large, and the depth of the grooves is smaller (GOST 10948-64 and 8820-69).

The difference between the diameters of the adjacent steps of the axes and the shafts to reduce the concentration of stresses should be minimal. The ends of the axes and shafts to facilitate the installation of rotating parts of the machines and prejudice to injury on them are made with chamfer, i.e., slightly roll up onto the cone (see Fig. 1 ... 3). The radii of numbers of cartoons and the sizes of the champers are normalized GOST 10948-64.

The length of the axes usually does not exceed 2 ... 3 m, the shafts can be longer. Under the terms of manufacture, transportation and installation, the length of the solid shafts should not exceed 6 ... 7 m. Larger shafts make composite and separate parts are connected by couplings or with the help of flanges. The diameters of the landing sections of the axes and shafts, on which rotating parts of the machines and mechanisms are installed, must be consistent with GOST 6636-69 (ST SEV 514-77).

Materials axes and shafts.

The axes and shafts are made of carbon and alloyed structural steels, as they have high strength, the ability to surface and volume strengthening, ease of receiving rolling of cylindrical blanks and good workability on machines. For axes and shafts without heat treatment, carbon steel sts3, ST4, ST5, 25, 30, 35, 40, and 45 are used. The axes and shafts, to which there are increased requirements for the carrying capacity and durability of the slots and the RACF, are carried out from the medium carbon or alloyed steels with Improving 35, 40, 40x, 40nx, etc. To increase the wear resistance of the Tsamp of the shafts rotating in the sliding bearings, the shafts are made from steels 20, 20x, 12HNZ and others with subsequent cementation and hardening of the RACF. Responsible heavily loaded shafts are manufactured from alloyed steels 40HN, 40HNMA, 30HGT, etc. The heavy-loaded shaft shafts, for example, the crankshafts of the engines are also made from modified or high-strength cast iron.

Before you understand what the shaft and the axis are different, it is necessary to have a clear idea that, in fact, these details are, for which they are used and what functions are performed. So, as you know, shafts and axes are designed to hold rotating parts on them.

Definition

Shaft - This is a detail of the mechanism having a rod shape and serving for transmission to other parts of this mechanism of torque, thereby creating a common rotational movement of all parts located on it (on the shaft) of parts: pulleys, eccentrics, wheels, etc.

Axis- This is a detail of the mechanism intended for the connection and bonding between the details of this mechanism. The axis perceives only transverse loads (bending voltage). The axes are fixed and rotating.

Axis

Comparison

The main difference between the axis from the shaft is that the axis does not transmit torque to other details. Only transverse loads have an impact on it, and it does not experience the forces of twist.

The shaft, unlike the axis, transmits the useful torque to the details that are fixed on it. In addition, the axes are both rotating and fixed. Always rotates the shaft. Most of the shafts can be divided by the geometric shape of the axis on direct, crank (eccentric) and flexible. There are also shafts of crankshaft or indirect, which serve to transform reciprocating movements into rotational. The axis is only directly in their geometrical form.

Conclusions Site

The axis carries the rotating parts of the mechanism without transferring them to any torque. The shaft transmits the useful torque to other parts, the so-called rotating force.
The axis can be both rotating and fixed. The shaft is only rotating.
The axis has only a straight form. The shaft in shape can be direct, indirect (crankshaft), eccentric and flexible.

Shafts and axles serve to maintain rotating parts (gears, couplings, pulleys, sprockets, rotors, etc.) and transmission of loads from these parts through supports on the housing. The axis are both rotating and fixed, they perceive the actions of bending moments and longitudinal forces. Shafts, unlike axes, can only be rotating. They are exposed to the longitudinal strength, bending and torque.

The structural shape of the shafts and axes depends on many factors - the appointment of the mechanism, the appointment and form of parts conjugate with the shaft or axis, the nature of loads, manufacturing and assembly technologies.

Shafts are straight, crankshaft and flexible. This tutorial addresses only the most common straight shafts. The axis is only with a direct geometric axis.

Trees and axles can be solid and hollow. When using hollow shafts and axes, you can significantly reduce the mass of the structure. For example, a hollow shaft with an opening diameter ratio to the outer diameter of the shaft 0.75 with almost equal strength with a solid shaft has a mass of 50% less. In this regard, in the lamp mechanisms, the shafts and axes of large diameter (more than 10 ... 12 mm) are carried out, as a rule, hollows. Inlet and output shafts are designed with non-separated holes for sealing the inner cavity of the mechanism or with holes closed by plugs.

Shafts and axes differ in shape: smooth and speed. Choosing a more complex step-shaped form, it is possible to ensure a uniform distribution of stresses along the shaft length and the necessary strength and rigidity under the action of internal power factors. In addition, with a stepped form, the best conditions for the assembly of parts with the shaft are created and for their fixation relative to the shaft in the axial and radial directions. The axes, due to their greater simplicity, are often performed smooth, and the shafts are usually steps, and each part corresponds to its stage on the shaft, treated with the required accuracy and roughness.

Shafts are performed in the form of a separate part (Fig. 13.1, a) or for one integer with cylindrical gears (Fig. 13.1, b, d) u conical gear wheel (Fig. 13.1, c).

In La mechanisms, the shafts are often manufactured in one integer with the details of the gear, which due to the lack of connecting elements reduces the total mass of the design and increases its reliability. However, the monolithic shaft design is not always appropriate, since the shaft and item from one material is not always required. In addition, with this embodiment, the possibility of replacing the shaft or part during operation is eliminated. In the manufacture of a monolithic structure from a large diameter billet, it should be considered that the strength properties of the material decrease with an increase in the diameter of the workpiece. The monolithic design is economically beneficial if the diameter of the part of the slightly exceeds the diameter of its own shaft, as well as in the conditions of a single production or the preparation of a forging (for example, the formation of parts elements located at the end of the shaft, disembarking).

Shafts can be made with teeth (Fig. 13.1.6), with keypads (Fig. 13.1, a), with ring grooves under support rings (Fig. 13.1, a), with threaded areas (Fig. 13.1, 6, in) and grooves for locking threaded parts (Fig. 13.1, in). Shafts may have axis (Fig. 13.1, b) and radial (Fig. 13.1, in) holes, as well as grooves for exit

grinding wheel (Fig. 13.1, a, c), cutters of cutters when cutting teeth (Fig. 13.1, b.), as well as the groove to exit the tool when cutting the thread (Fig. 13.1, B).

The axes are fixed (Fig. 13.2, a) and rotating (Fig. 13.2, boo smooth (Fig. 13.2, but) and stepped (Fig. 13.2, b).Axes, like shafts, can have teeth (slots), grooves, grooves, grooves, threads and holes. Smooth axes are standardized. Fixing these axes in the axial direction most often

it is carried out with a pin (Fig. 13.3, a). For axes (mainly fixed), a cylindrical or conical pin is applied (Fig. 13.3, b.), installation screw (Fig. 13.3, in) or a bolt resinstituer (Fig. 13.3, d). Still axles are installed on a transitional landing (for example, K7 / I6) or landing with a tension (for example, R7 / H6).

Movable axes and shafts both in radial and in axial directions are fixed in bearings, which in turn are installed in the housing. Accurate fixation of the shafts and axes in the radial direction is carried out by landing them into bearings and planting bearings into the housing. In the axial direction, the shafts and axes with the parts planned on them are connected to the bearings in one of the methods shown in Fig. 13.4. The greatest application finds a simple and cheap fixation with spring rings (Fig. 13.4, but): Eccentric 1 or concentric 2 . The presence of a gap 5 between the ring and the bearing leads to the inaccuracy of the installation of parts and to slip the surfaces of parts and shaft, i.e. to their wear. Using an intermediate ring 3 (Fig. 13.4, b) With a fitting of it in the thickness of the end of the end or the adjustment pad 4 from foil (Fig. 13.4, in) Allows you to reduce the amount of clearance 5 to a minimum. Adjusting gaskets next to the spring ring are not put in order to avoid getting gaskets into the groove for the ring. When fixing at the end of the shaft, it is convenient to use the standard end washer 5 (Fig. 13.4, d)\u003e pinned with screw 6 and fixed from turning with pin 7. The screw will stop from unscrewing the puck 8. With a significant axial load, a washer fixed with two screws (Fig. 13.4, e).

Shafts and axes

Plan 1. Purpose. 2. Classification. 3. Constructive elements of shafts and axes. 4. Materials and heat treatment. 5. Calculations of shafts and axes.

Purpose

Trees - Details intended for transmitting torque along its axis and to maintain rotating machine parts. The shaft perceives the forces acting on the details, and transmits them to supports. When working the shaft is experiencing bending and tapping.

Axis Designed to maintain rotating parts, the useful torque does not transmit. The axes are not tested. The axes can be fixed and rotating.

Classification of shafts

For appointment:

a) Trees of transmission, carrying parts gear - clutches, gears, pulleys, sprockets;

b) indigenous machines of cars;

c) other special shafts carrying workers of cars or guns - wheels or turbine wheels, crank, tools, etc.

By design and form:

a) straight;

b) crankshafts;

c) flexible.

Straight shafts are divided into:

a) smooth cylindrical;

b) stepped;

c) shafts - gears, trees - worms;

d) flange;

d) cardanny.

In the form of cross-section:

a) smooth solid cross section;

b) hollow (to accommodate a coaxial shaft, control parts, oil, cooling);

c) Slotsey.

The axes are divided into rotating, providing better bearing operations, and fixed, requiring latching of bearings into rotating parts,

Constructive elements of shafts and axes

The support of the shaft or axis is called tsazfoy . The terminal pin is called spike and intermediate - shaika .

Ring shaft thickening, which makes it one of the whole, called burtuik . Transitional surface from one cross section to another, serving to rest on the shaft of parts, is called plug.

To reduce concentration and increase strength, the transitions in the locations of the diameter of the shaft or axis are made smooth. The curvilinear surface of a smooth transition from a smaller cross section is more called gallery. Rooms are permanent and variable curvature. The variability of the radius of curvature cartlers increases the carrying capacity of the shaft by 10%. Poverty cartlers increase the length of the nave bazing.

Increasing the strength of the shafts in transitions is also achieved by removing a low-stressed material: performing unloading grooves and drill holes in the levels of large diameter. These events provide a more uniform distribution of stresses and reduce the concentration of stresses.

The shape of the shaft in length is determined by the distribution of loads, i.e. Eps of bending and torque, assembly conditions and manufacturing technology. Transitional sections of the shafts between the steps of different diameters are often performed with a semicircular groove to exit grinding circle.

The landing ends of the shafts intended for the installation of parts transmitting the torque in the machines, the mechanisms of devices are standardized. GOST sets the nominal sizes of cylindrical shafts of two versions (long and short) diameters from 0.8 to 630 mm, as well as the recommended dimensions of the ends of the thread shafts. GOST sets the main dimensions of the conical ends of the shafts with a taper 1:10 also two versions (long and short) and two types (with outer and internal thread) diameters from 3 to 630 mm.

"Highlanders of the shafts to facilitate the nozzles of parts, in order to avoid overtakes and damage to the hands of workers are performed with chamfer.

Materials and heat treatment

Selection of material and thermal processing of shafts and axes is determined by the criteria of their performance.

Main materials for shafts and axes serve carbon and doped steel due to high mechanical characteristics, the ability to strengthen and ease of obtaining cylindrical billets with rolling.

For most shafts, medium carbon and alloyed steel 45, 40x are used. For high-folded shafts of responsible machines, alloyed steel 40KHN, 40KHNGM, 30HGT, 30HGS, and other shafts from these steels are usually subjected to improvement, quenching with high leave or surface hardening with a heating of TWH and low vacation.

For the manufacture of shaped shafts - crankshafts, with large flanges and holes - and heavy shafts, along with steel, high-strength cast iron (with spherical graphite) and modified cast iron are used.

Calculation of shafts and axes

Shafts are experiencing bending and twist voltages, axis - only bend.

In the process of operation, trees are experiencing significant loads, therefore, to determine the optimal geometric dimensions it is necessary to perform a set of calculations, which includes a definition:

Static strength;

Fatigue strength;

Stiffness when bending and twisted.

At high speed speeds, it is necessary to determine the frequencies of the shaft's own oscillations in order to prevent falling into the resonant zones. Long trees are checked for stability.

The calculation of the shafts is made in several stages.

To perform the calculation of the shaft, it is necessary to know its design (the location of the load application, the location of the supports, etc.) at the same time, the development of the shaft design is impossible without at least an approximate estimate of its diameter. In practice, the following shaft calculation is usually used:

1. Pre-evaluate the average diameter at the rate only torsion With reduced allowable stresses (the bending moment is not yet known, because the location of the supports and location of the load application) is unknown).

Tolerase voltage

Where WP is the moment of resistance to the section, mm.

Pre-evaluate the diameter of the shaft can also be focused on the diameter of the shaft, with which it connects, (shafts transmit the same moment T). For example, if the shaft is connected to the motor shaft (or other machine), the diameter of its input end can be taken equal to either close to the diameter of the output end of the motor shaft.

2Dashable shaft calculation.

After evaluating the diameter of the shaft, it is developing its design. The length of the shaft plots, and, consequently, the shoulder of the force application take out of the layout. Suppose that we need to calculate the diameter of the shaft on which the sits of the gear is sitting. Draw the shaft loading scheme. For this shaft, taking into account the slope of the gear teeth and the direction of the moment T, the left support is replaced by a hinged-fixed, and the right - hinged-under-vih. The calculated loads are usually considered as concentrated, although the actual loads are not concentrated, they are distributed along the length of the hub, the width of the bearing. In our example, the shaft is loaded by the FT, FA. FR, acting in the hook and torque T. The axial force Fa gives the moment in the vertical plane

The main calculation of the shafts and axes is to construct the fusion of bending moments in the horizontal and vertical planes, constructing the result of the resulting moments, the torque-torque plumes, the equivalent points, the determination of hazardous sections.

3 stage of calculation - The verification calculation is to determine the storage factor in hazardous sections

- Reserve stock factors for normal and tangent