Heading as per DM - Worm-cylindrical reduction gear box

Contents

Design Task

Introduction

1. Selection of electric motor and determination of total transmission

drive numbers

2. Calculation of belt gear

3.1 Calculation of fast stage... 9 3.2 Calculation of slow stage

4. Gear gearbox arrangement

5. Calculation of shafts.. 19 5.1 Calculation of shafts for complex resistance... 19 5.2 Calculation of shafts for endurance

6. Calculation of key connections

7. Calculation of rolling bearings

8. Greasing

9. Shell Part Design

List of used literature

Introduction

In the system of training of an engineer in mechanical specialties, mastering the skills of designing machines, machine units and individual parts, familiarization with their working conditions, as well as structural features are of paramount importance. Mastering the basics of design, design and calculation is important not only for the engineer, but for the engineer, since without understanding the design of the machine and the work of its parts, the loads acting on them, it is impossible to properly manufacture the machine and its operation.

The object of the course design is a drive with a worm cylinder gear, using most general-purpose parts and assemblies. The gearbox is a combination of cylindrical and worm gears. Worm gears are used when the geometric axes of the shafts cross. The advantages of worm gears are: large gear ratios with small drive dimensions, high smoothness and quiet operation. The disadvantages of worm gears are: increased wear and a tendency to jam; the need for use in the manufacture of wheel rims from expensive antifriction materials; large axial loads on worm supports; the need to adjust the axial position of the worm wheel.

Breakdown of the total gear ratio of the drive by stages.

The distribution of the total gear ratio of the gear reduction gear between its stages largely determines the dimensions of the gear reduction gear, the degree of use of the load capacity of each of the stages, the rationality of the arrangement of the gear reduction gear units and the method of lubrication of the engagement.

There are several approaches to the distribution of the gear ratio: from the condition of obtaining gear pairs that are equal in contact stresses; according to the condition of obtaining the minimum height and length of the reduction gear box; according to the condition of minimum wheel weight; by the condition of a certain relation between the axial distances of the slow-moving and fast stages, etc.

In gear gears at the circumferential speed of the wheels V < 15 m/s, the engagements are usually lubricated by dipping the wheels into an oil bath. Dipping into the oil of the larger of the wheels of the pair is enough. Such gearboxes include almost all gearboxes found during course design in the course "Machine Parts." In them, the breakdown of the gear ratio is most often made based on the condition of equal strength of the wheels when the latter are rationally immersed in oil. The high-speed stage wheel must be immersed in oil to a depth of 0.75 to 2 heights of the tooth, but not less than 10 mm. At low circumferential speed (up to 1.5 m/s), the diving depth can reach 1/6 d, but not more than 100 mm.. In worm-cylinder gearboxes, the main factors are mass, sp. and bronze consumption for worm wheels. For all three factors, the performance improves if the gear ratio of the high-speed stage decreases. The following breakdown of gear ratio is recommended:

if utl, then ub = 8 and ut = utl/8

Calculation of shafts.

The main conditions that the shaft structures must meet are: sufficient strength; rigidity ensuring normal operation of the hooks and bearings; constructability and metal saving. Carbon and alloyed steels are used as material for shafts.

The calculation of the shaft is carried out in three stages: an approximate calculation of the shaft for torsion; calculation for complex resistance (bending and torsion); check of safety factor by endurance in the most dangerous sections.

To calculate the complex resistance, it is necessary to draw up a design diagram of the shaft: mark the points at which the conditional supports are located, determine the value and direction of the forces acting on the shaft, as well as the points of their application.

Support receiving radial and axial loads is considered hinged-stationary. With a single radial thrust bearing, the radial reaction is considered applied to the shaft at the intersection point of its geometric axis and a straight line drawn through the center of the roller at an angle (90 ° - α) to the bearing axis, where a is the contact angle .

The calculated forces and moments acting on the shaft are considered concentrated and located in the middle of the length of the elements perceiving them.

When determining the direction of action of forces in toothed worm gears, it should be borne in mind that on the driven wheel (or worm wheel) the circumferential force is driving and directed towards rotation. On the driving gear (or worm), the circumferential force is a reaction from the driven wheel side and is directed to the opposite side to the rotation. Radial force on cylindrical wheels is directed towards wheel center (to worm axis). The direction of the axial force depends on the direction of the spiral and the direction of rotation. It is directed inside the tooth.

If a belt pulley is installed on the cantilever end of the shaft protruding from the reduction gear, the load acting on the cantilever is directed along the line connecting the axes of the pulleys. If a clutch is seated on the cantilever end of the shaft protruding from the reduction gear, then they create an unbalanced radial force and a bending moment, due to the uneven distribution of load around the circumference of the clutch.

For elastic bushing-flange coupling (UVM) unbalanced radial force

FM = 0.25 Ft = 5956.430 Ft = 2 T/ dM = 2· 2382.572/0.2 = 23825.72 - where the circumferential force by the diameter of the centers of the coupling fingers.

The direction of force and torque is the most unfavorable for the shaft. The given data allow you to compose a calculation scheme of the shaft and calculate it for complex resistance.

Lubrication.

Lubricants in machines are used to reduce the intensity of wear, reduce friction forces, remove heat from friction surfaces and wear products, as well as to protect parts from corrosion.

The economy and durability of machines depends more on the right choice of oil. Typically, the friction coefficient in the friction vapors decreases as the viscosity of the oil increases, but the hydromechanical mixing loss of the lubricant increases.

Industrial oil GOST 2079975 grade is most suitable for this gearbox

And - 50A with viscosity from 47· 106 to 55· 106 m/s2. The volume of oil poured into the reducer is 4 liters.

Lubrication in this gearbox is crankcase, worm gear is lubricated by immersion of worm by 7 mm into bath with oil in lower part of housing, and other units are lubricated by spraying oil with submerged wheels and freely rotating on axis of sprinkler shaft.

Design of body parts.

The body parts are the main parts of the reduction gear box and are intended to ensure correct mutual arrangement of the coupled parts of the reduction gear box, perception of loads acting in the reduction gear box, protection of working surfaces of gears and bearings from suspended foreign particles of the environment, heat removal and also for arrangement of the oil bath.

Operability of kinematic pairs (gears, bearings, etc.) depends on rigidity of housing parts. The required stiffness is achieved by optimizing the shape and dimensions of the body parts, as well as by rational use of the stiffening ribs.

For most gearboxes, the housing is detachable. Gearboxes with the location of shaft axes in the horizontal plane usually have one connector in the plane of gearbox axes, gearboxes with shaft axes in the vertical plane (shafts are located horizontally) have several connectors. Due to the connector in the axis plane of the shafts, the most convenient assembly of the gear box is provided. The housing may not have connectors in the shaft plane. In this case, the assembly is carried out along the axes through the provided holes on the side walls of the housing.

For the manufacture of cast body parts, cast iron, steel are widely used, and light alloys are used when limiting the mass of an article.