Mechanical drive with worm gear

Contents

Contents

1. MAINTAINING

2. ELECTRIC MOTOR SELECTION AND KINEMATIC CALCULATION

2.1 Kinematic diagram of the drive

2.2 Gearbox efficiency calculation

2.3 Calculation of required power and selection of electric motor

2.4 Gear ratio of reduction gear box

3. DETERMINATION OF CAPACITIES AND TRANSMITTED TORQUE MOMETINS ON SHAFTS

3.1 Capacity on shafts

3.2 Shaft speeds

3.3 Angular speeds of shafts rotation

3.4 Rotating moments of shafts

3.5 Summary Table

4. CALCULATION OF GEARS

4.1 Worm Gear

4.1.1 Selection of worm gear material

4.1.2 Definition of allowable contact and bending stresses

4.1.3 Worm gear design calculation

4.1.4 Determination of forces in the gear gear engagement

4.1.5 Check calculation of worm gear

4.1.6 Thermal calculation

4.2 V-belt transmission

4.2.1 Initial data

4.2.2 Design calculation of V-belt transmission

4.2.3 Determination of power characteristics of V-belt transmission

5. PRELIMINARY CALCULATION OF SHAFT DIAMETERS

5.1 Calculation of drive shaft

5.2 Calculation of driven shaft

6. FITTING AND CHECK CALCULATION OF COUPLINGS

7. PRE-FITTING BEARINGS

8. LAYOUT DIAGRAM

8.1 Selection of lubrication method of gears and bearings

8.1.1 Selection of transmission lubrication method

8.1.2 Selection of bearing lubrication method

8.2 Determination of dimensions of pulleys, gears, housing parts, covers

8.3 Determination of distances between points of application of forces loading shafts

8.3.1 Determination of distance between points of application of high-speed shaft forces

8.3.2 Determination of distances between low-speed shaft forces application points

9. CALCULATION OF SHAFTS BY EQUIVALENT MOMENT

9.1 Initial data

9.2 Calculation of high-speed shaft

9.3 Calculation of low-speed shaft

10. CHECK CALCULATION OF BEARINGS

10.1 Calculation of high-speed shaft bearings

10.2 Calculation of low-speed shaft bearing

11. SELECTION AND TEST CALCULATION OF KEY JOINTS

12. PURPOSE OF FITS, SURFACE ROUGHNESS, SELECTION OF DEGREE OF ACCURACY AND PURPOSE OF SURFACE SHAPE AND LOCATION TOLERANCES

12.1 Landings

12.2 Surface roughness

12.3 Surface Shape and Location Tolerances

13. CALCULATION OF SHAFTS FOR ENDURANCE

13.1 Calculation of high-speed shaft

13.2 Calculation of low-speed shaft

14. GEARBOX ASSEMBLY DESCRIPTION

15. ADJUSTMENT OF BEARINGS AND ENGAGEMENT

16. COMPUTER CALCULATION AND COMPARATIVE ANALYSIS

17. Literature

Introduction

A drive is a system of interconnected devices for driving one or more solids that are part of a machine. It is designed to convert engine parameters into parameters of a working machine (conveyor). The calculated drive consists of an electric motor, a belt gear, a reduction gear.

The electric motor is used in all types of works where it is not necessary to maintain a constant rotation speed and are the main converters of electrical energy to mechanical energy.

Reduction gear is a mechanism designed to reduce rotation speed, increase torque on slow-moving shafts and made in the form of separate units. The reduction gear consists of a housing, in which the transmission elements are placed - gears, shafts, bearings, etc. Gearboxes are classified according to the following main features: gear type (toothed, worm or gear-worm); number of stages (single-stage, two-stage, etc.); type of gear wheels (cylindrical, conical, conical-cylindrical, etc.).

A worm reduction gear is a special type of gear type (on a row with toothed and hydraulic) with a worm thread profile. The worm gear is used in the transmission of motion between crossing (usually at right angles) axes. One of the significant advantages of worm gearboxes is the ability to obtain a higher gear ratio in one stage (up to 80 in general-purpose gearboxes and up to several hundred in special gearboxes)

Belt transmissions are flexible communication transmissions consisting of a driving and driven pulleys and a belt worn on them. The main purpose is to transfer mechanical energy from the engine to transmission and actuating mechanisms, as a rule, with a decrease in speed. This drive uses V-belt transmission.

V-belt transmission has a number of advantages: simplicity of construction and operation; smoothness and noiselessness of operation, mitigation of vibration, shocks and impacts due to elasticity of belt; protection of mechanisms from overload due to possible belt slippage; possibility to transfer rotation to shafts removed over long distances; low cost.

Clutch - a device for connecting shafts, transmitting torque from one shaft to another. The choice of the type of coupling design depends on the functions that it must perform, due to the purpose of the mechanism and the mutual arrangement of the shafts to be connected, taking into account the load mode and other factors. Standard couplings shall be used when designing drive devices. The dimensions of the couplings are selected from the tables according to the design moment and landing diameter .

The toothed clutch is a universal form of compensating clutches. The toothed clutch is able to compensate for large errors in the alignment of the shafts.

Selection of bearing lubrication method

The lubrication of the bearings mounted on the shafts is carried out by the same oil to which the gear parts are lubricated, the more desirably the oil level passes through the center of the bearing lower rolling body. Oil flowing from the wheels, from the shafts and from the walls of the body also enters the bearings of the driven shaft. Oil is poured through hatch, which simultaneously serves to control assembly of engagement and its condition in operation. The hatch is closed by a cover, the handle of which performs the functions of a perfume. Oil is drained through a hole located in the lower part of the housing and closed with a plug with gaskets. Oil level is monitored using the oil indicator.

Assign fits, surface finishes, precision, and feature control frame assignments

The nominal size is the size of the product obtained by calculation or chosen for structural reasons. Manufactured products always have some deviations from the initial size.

In order for the product to meet its intended purpose, its dimensions must be kept between two permissible limit dimensions, the difference of which forms a tolerance.

The zone between the largest and smallest limit dimensions is called the tolerance field.

Different connections are subject to different requirements for accuracy conditions. Therefore, the tolerance system contains 19 quotas: 01, 0, 1, 2,..., 17 (in descending order of accuracy ).

The nature of the joint of parts is called a fit. Fit characterizes the difference in dimensions of parts before assembly. Fits can provide clearance and tension in the joint. Fits are characterized by the largest Smax gaps and Nmax interference.

A part in which the position of the tolerance field remains unchanged and does not depend on the type of fit is called the main part of the system. If the part is a hole, the connection is made in the hole system.

The main deviations are indicated in letters of the Latin alphabet:

for holes - capital A, B, C, etc.

for shafts - lower case a, v, s, etc.

For fits with a gap, it is recommended to use non-main shafts f, g, h; for transient landings - js, k, m, n; for interference landings - p, r, s.

Surface Roughness

We assign in accordance with GOST 278873.

The Ra parameter is basic for parts in mechanical engineering. Numerical value of roughness Ra (μm) is assumed: for mounting surfaces and shafts as per Table 13.13 [3, p. 324]; .for other surfaces - Table 13.14 [3, p. 324].

Mounting journals of shafts for bearings Ra 0.32

Ends of shoulders for bearings, class higher than bearing mounting surfaces Ra 0.64

Mounting surface of shafts for worm wheel Ra 1.25

Mounting surfaces of shafts for Ra 2.5 couplings

Mounting surfaces of shafts for collar Ra 0.32

Ends of shoulders for toothed wheels, class higher than surfaces of installation of these wheels Ra 2.5

Ends of shoulders for couplings, class higher than surfaces of coupling Ra 5 installation

Side surfaces of keyway Ra 0.32

Keyway base Ra 0.32

Non-operating surfaces of shaft Ra 10

In the worm wheel working drawing, we assign the roughness:

Side surface of hub Ra 5

Side surface of teeth Ra 2.5

Side base surface of crown Ra 5

Diameter of teeth vertices Ra 5

Other non-marked surfaces Ra 10

Surface Shape and Location Tolerances

Tolerances and fits of the main parts of the gearbox are accepted according to the ECU (unified system of tolerances and fits) GOST 2534682 and 2534782, we also use the recommendations for item 6.4 [2, p. 67] and 10.4.5 [2, p. 149] μm:

Radial run-out tolerance (relative to bearing mounting surface):

Mounting surfaces of hubs of various types of wheels, couplings. Tolerance values for wheel hub and coupling are 0.030 and 0.050 mm according to [2, p. 67, Table 6.4.1, para. 6.4.4];

Sealing installation surfaces 0.050 mm.

Tolerance of end run-out of shaft ledges (shoulders) for installation:

Rolling bearings are equal to 0.030 mm [2, p. 101, Tables 7.8.10, para. 7.8].;

Worm gear wheels are equal to 0.030 mm [2, p. 67, Table 6.4.2, para. 6.4.4].;

Tolerance of roundness and profile of longitudinal section:

Rolling bearings [3, p. 101, Table 7.8.9, para. 7.8]. The value of the roundness tolerance is 0.004 mm, the value of the longitudinal section profile is 0.004 mm.

Other parts installed on the shaft not more than 0.5ITn of shaft diameter at the place of installation of these parts. ITn value as per [2, p.269, Table 16.3.2];

The purpose of the tolerances of the shape and arrangement of the surfaces of the worm wheel [2, c.149, para. 10.4.5.4]:

Tolerance of radial run-out of billet surface for diameter of wheel teeth vertices is equal to 0.050 mm.

Tolerance of end run-out of base surfaces of rim and wheel hub relative to surface A: 0.035 and 0.060 mm.

Calculation of shafts for endurance

Calculations are carried out in the form of checking the safety factor S, in our case the minimum permissible value is taken in the range [S] = 1,3- 3.

Having examined the curves of bending and torques, we determine dangerous sections of the shaft.

Gearbox Assembly Description

Before assembly, clean the inner cavity of the reduction gear box housing thoroughly and cover with oil-resistant paint. The gearbox is assembled in accordance with the general view drawing. Start assembly with that on worm shaft (pos. 16) put on conic bearings (poses.39), previously their heating in oil to 80100 wasps. the assembled worm shaft is inserted into the housing (pos. 18).

At the beginning of the worm wheel shaft assembly (pos. 15) the key (pos. 50) and press the wheel to rest against the shaft collar; then the spacer bushing is put on (pos. 9) and roller conical bearings (pos. 40) heated in oil. The assembled shaft is laid in the base of the housing (pos. 18) and the cover of the housing is put on (pos.19), covering the surfaces of the flange joint with alcohol varnish. For alignment, the cover is installed on the housing using two cylindrical pins (pos. 53) and tighten the bolts (pos. 25).

Put into bearing covers (pos. 5, 6) rubber cuffs (pos. 35, 36) and blind covers are installed (pos. 3, 4).

Adjustment of bearings is performed by a set of metal gaskets (pos. 21, 22) installed under flanges of bearing covers. Check a provorachivaniye of shafts lack of jamming of bearings (shafts have to be turned by hand). Key (pos. 48) and pulley (pos. 7), (attach it by end attachment), bolt of end attachment (pos. 27) lock with pin (pos. 51). Then put key (pos. 49) and install the coupling (pos. 37).

Plug is screwed in (pos. 14) oil release hole with gasket (pos. 20) and oil indicator (pos. 2). Oil is poured into reducer and inspection hole is closed with cover with fragrance (pos. 1).

The assembled gearbox is rolled and tested on the bench according to the program set by the specifications.

Computer Calculation and Comparative Analysis

Calculation on the computer checks closed transmission. Based on the data obtained during computer-based calculation, it is possible to conclude:

The geometric transmission parameters obtained by calculation correspond to the computer result;

There are very small differences in stress calculations related to the program features of the computer.

Thermal calculation indicates that no cooling measures are required.

In general, the calculation on the computer shows that the calculation of the worm gear corresponds to the computer result.