Course project on mechanics "electromechanical drive of the process machine"

Contents

CONTENTS

Introduction

1. Selection of electric motor and calculation of main parameters of drive

1.1.Selection of electric motor

1.2. Transmission ratio of the drive. Gear ratio of stages

1.3.Spin speed of shafts

1.4.Shapes transmitted by shafts

1.5. Moments transmitted by shafts

2. Calculation of gear train

2.1.Selection of materials and definition of allowable stresses

2.1.1.Validable contact voltages

2.1.2.Compute allowable bending stresses

2.2.Transmission Design Calculation

2.2.1.Module, number of wheel teeth and displacement factor

2.2.2.Width of gear rims and wheel diameters

2.2.3. Circular speed in engagement and degree of transmission accuracy

2.3.Value gearing calculation

2.3.1.Verifying the contact strength of teeth

2.4. Forces in engagement

3. Calculation and design of shafts

3.1. Preliminary calculation of low-speed shaft diameters

3.2 Design calculation of high-speed shaft

3.3.Production of bending and torque moments

3.4. Refined calculation of shafts

4. Selection and check of keys

5. Bearing fitting

6. Basic design dimensions of the reduction gear box

6.1.Bolt diameters

6.3. Calculation of housing elements

7. Reduction gear box lubricant

8. Gearbox assembly

9.Electric connection diagram

10. Conclusion

Bibliographic list

Introduction

The choice of the type of transmission: the connection of the shaft of the working machine with the shaft of the electric motor is possible only in relatively rare cases when the speeds of these shafts are the same, for example, in the drives of centrifugal pumps, fans and others. If this condition is not met, an upshift or downshift is required to drive the machine.

In this case, it is necessary to develop a downshift from the electric motor to the driving shaft of the machine rotating at a lower angular speed.

It is recommended to use three-phase asynchronous motors, the most common in various sectors of the national economy; their advantages compared to other types of engines: simplicity of design, lower cost, higher operational reliability. When performing course projects, it is these engines that should be selected for drives.

The required power of the motor is determined by the customer with correction for efficiency of the drive units of the working machine. Since motors with different speeds of rotation are suitable for the calculated drive, several options should be considered and the optimal suitable operating conditions should be considered. At the same time, it should be borne in mind that as the speed increases, the mass of the engine and its dimensions decrease. The cost is reduced, but the working resource is also reduced. Therefore, for general purpose drives, if not specified, engines with speeds of 1500 or 1000 rpm are preferred (respectively, the speed at the nominal mode taking into account 3% sliding nH0M= 1450 or 970 rpm).

In mechanical drive devices, belt gears are mainly used to reduce the speed of the drive shaft and accordingly increase the torque.

In the kinematic scheme of the belt drive, as a rule, the first stage is retracted directly from the electric motor to the reduction gear box.

Also, the belt gear allows the motor to be installed, if necessary, at a distance from the reduction gear and machine and, optionally, coaxially with the high-speed shaft of the reduction gear. In this project, due to its application, it became possible to design a single-stage gearbox.

Reduction gear is a mechanism for reducing rotation speed and increasing torque. Gearbox - complete mechanism connected to the engine and working machine by couplings or other detachable

devices. This fundamentally distinguishes it from the gear transmission embedded in the actuator (gear motor).

Gear or worm gears fixed on shafts are arranged in reduction gear case. Shafts rest on bearings located in housing sockets; rolling bearings are mainly used. Sliding bearings are used in special cases when the reduction gear is subject to increased requirements for vibration and noise levels, at very high speeds of rotation or in the absence of a rolling bearing of the desired size.

The most common gearboxes with shafts located in the horizontal plane.

In this design, it is recommended to use cylindrical reduction gears, which are equipped only with cylindrical gears and differ in the number of stages and the position of the shafts. The type of engagement, the gear width factor, the type of bearings, etc., do not define the type of gearbox and are only structural features.

Single-stage gearboxes. The layout capabilities of single-stage gears are very limited and are reduced mainly to the location of shaft axes in space. The engagement is in most cases oblique, rarely spur.

If the height, width and mass of the gearbox are not significant, then a smaller number of steps are taken, the gearbox will be simpler and cheaper with a shorter length.

Gearshift calculation applies to steel spur gears, helical gears and chevron gears of reduction gears, spur gears and spur gears under the following conditions for reduction gears:

shafts are supported by rolling bearings;

the housing is protected from ingress of dirt and water and has sufficient rigidity;

teeth are lubricated with oil;

a chemically non-aggressive medium;

oil temperature in the housing is not more than 95 0 С;

degree of accuracy according to standards of smoothness and contact 6-9 as per GOST 164381;

circumferential speed of gears - up to 16 m/s;

roughness parameter of working surfaces of teeth Ra < 2.5 mcm;

initial loop as per GOST 1375581.

To Create Curves and Torques

Shaft design involves 3 stages:

preliminary calculation of shafts;

shaft design study

refined (verification) calculation of the proposed design.

The refined calculation of shafts consists in determining the safety factor for dangerous sections and comparing it with the permissible [S] = 2.5.

Normal stresses from bending vary by symmetric loading cycle, and tangents by zero.

Reduction shafts experience two types of deformation: torsion and bending. Torsion deformation on shafts occurs under the action of torque applied from the side of the engine and the working machine. Deformation of shafts bending occurs due to forces in toothed engagement of closed gear and forces applied cantilevered, at output ends of shafts, from side of couplings and open gears.

Reduction gear box lubrication

Gear lubrication, lubricant grade, quantity, check

The operation of the gears, as well as other mechanisms, occurs with the relative movement of the parts, usually with the presence of lubricant.

Purpose of lubrication: (a) reduction of friction losses; b) reduction or prevention of wear and tear; c) heat removal; d) corrosion protection. Operation and long-term storage of machines without lubrication is impossible. Improving lubrication is the fastest and cheapest means of increasing the durability of machines. Lubricants shall ensure complete separation of friction surfaces as far as possible.

The operational properties of lubricants are mainly divided into: antifriction, anti-wear and anti-galling.

Lubricants are divided as follows: a) liquid (oils); b) plastic (ointment-like); c) solid (powders); d) gaseous (aerosols).

Lubrication of the gear is carried out by dipping the gear wheel into oil poured inside the housing to a level that ensures immersion of the wheel by about 10 mm.

Volume of oil bath V is determined based on 0.25 l of oil per 1kW

transmitted power: V = 0.25 * 5.5 = 1.375 l

We accept industrial oil I-G-A-32 (as per GOST 17479.487).

For inspection of oil engagement and filling there is a window in the upper part of the gear box housing. The window is closed by a cover. To communicate with the external atmosphere in the upper cover of the reduction gear box, a boot is provided to prevent the appearance of excessive pressure in the internal cavity of the reduction gear box, which is fraught with turning out of the rubber cuffs. Oil discharge hole located below reduction gear is used to drain oil. Oil discharge hole is closed with plug and sealed with gasket made of oil-resistant rubber. To remove micro chips from oil volume, magnet is used in plug of oil discharge hole. Oil level is checked by rod oil indicator .

Both liquid and plastic lubricants are used for lubrication of rolling bearings in cylindrical reducers. Liquid oils are used in crankcase lubrication of gear train in case of circumferential speed in engagement V ≥ 1 m/s. At the same time, oil is sprayed and oil mist is formed inside the crankcase, which provides lubrication of rolling bearings.

Since I have V = 1.266 m/s, we conduct lubrication with oil mist.

Gearbox assembly

Prior to assembly, inner cavity of reducer is thoroughly cleaned and covered with oil-resistant paint. Assembly is performed in accordance with assembly drawing of reduction gear box, starting from assembly of shafts:

Oil reflecting rings are put on the drive shaft and ball bearings preheated in oil to temperature (80... 100) ˚S;

Key is put into driven shaft and gear wheel is pressed until stop against shaft collar, then spacer bushing is put on and bearings heated in oil are pressed.

The assembled shafts are laid in the base of the reduction gear case and the cover of the case is put on, previously covering the surface of the joint of the cover and the case with alcohol varnish. Two conical pins are used to fix the cover of the housing relative to the housing, then bolts are tightened that attach the cover to the housing.

Then covers of bearing units with set of metal gaskets for adjustment are installed on shafts. Cuff seals are inserted into through holes prior to installation of covers.

Check a provorachivaniye of shafts lack of jamming of bearings (shafts have to be turned by hand). Covers are bolted. Plug of oil discharge hole with gasket is screwed in. Oil indicator is installed. Oil is poured into the housing and the inspection hatch is closed with a cover with a gasket made of technical cardboard, the cover is bolted.

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

Conclusion

Testing machines, therefore, their assemblies and parts is a powerful means of technological progress in mechanical engineering. Knowledge in the field of solid state physics does not allow theoretically calculating strength without using the experimental characteristics of materials. Modern machine parts are usually complex in shape and do not always fit the definition of a bar, plate or shell, the calculations for which can be performed quite accurately using materials resistance methods. Parts are subjected to complex and variable, and as a rule, not stationary stress states, work in a corrosive environment, etc.

In this work, a single-stage horizontal cylindrical reduction gear with a helical gear is designed. Technical characteristic of the reduction gear (with 4A132M8 motor): power on the driven shaft 5 .5kW, rotation speed of the driven shaft 100 rpm, non-reversible transmission. I-G-A-32 oil is used to lubricate the gear train.

The project has been completed according to the task.