Worm gearbox - heading - 3D in compass

Contents

Terms of Reference

Introduction

1. Kinematic calculation of the drive

2. Calculation of closed worm gear

3. Calculation of shafts. Gearbox Sketch Layout

4. Calculation of V-belt transmission

5. Shaft check calculations

6. Calculation of bearings

7. Calculation of key connections

8. Coupling selection

9. Gearbox design dimensions

10. Gearbox lubrication selection

Conclusion

List of used literature

Introduction

Machine parts are one of the main design courses in which they study the basics of machine and mechanism design.

The main requirements for the design of machine parts are reliability and economy. Reliability means the property of the product to maintain its operability in time. Cost effectiveness will be determined by the cost of the material, production and operation costs.

The purpose of my course design is to calculate the drive of the gearbox output shaft and determine the main parameters of the output shaft. The drive includes a worm reduction gear and a V-belt transmission.

A reduction gear is a mechanism made in the form of a separate unit and serving to transfer power from the engine to the working machine. The purpose of the reduction gear is to reduce the angular speed and increase the rotational torque of the driven shaft compared to the driving shaft. Reduction gear consists of housing accommodating transmission elements.

The main performance and calculation criteria are strength, stiffness, wear resistance, heat resistance and vibration resistance.

Worm gears. Gear gears are widespread in all branches of machine building and instrument making. It is used to transmit rotational motion between shafts crossing at an angle of 90.

Worm gears are used at low and medium power. The use of these transmissions for large capacities is limited due to the relatively low efficiency and special cooling measures are required. Distinguish: cylindrical, globoid worms; with the right, left direction of the turns; single-start, multi-start; with lower, upper or lateral arrangement of the worm.

Advantages:

- smooth and silent operation;

- compactness and quiet operation;

- possibility of large reduction;

- possibility of self-braking transmission;

Disadvantages:

- low efficiency;

- increased wear and tendency to jam;

- use of expensive antifriction materials for wheels;

-expressed requirement for assembly accuracy.

Belt gear. Transfer of mechanical energy using a flexible element - a driving belt, due to friction or engagement forces (toothed belts). It can have both constant and variable gear ratio (variator), the shafts of which can be with parallel, intersecting and crossing axes.

It consists of a driving and driven pulleys and a belt (one or more).

Advantages:

- smooth operation;

-informity;

- compensation of inaccuracy of reduction gear pulleys installation, especially by crossing angle between shafts, up to application of transmission between movable shafts;

- compensation of overloads (due to slippage);

- no need for lubrication;

- (for V-belts) possibility to obtain adjustable gear ratio (variator)

- compared to chain transmission:

- possibility of operation at high circumferential speeds;

- other drive elements are not damaged during belt break, and pulleys rotate freely (and in case of chain break it often folds, damaging the casing and locking the drive shaft)

-in comparison with gearing:

- possibility of motion transfer between shafts located at a considerable distance from each other;

Disadvantages:

- large dimensions (for the same loading conditions, the diameters of the pulleys are almost 5 times larger than the diameters of the gear wheels);

- small bearing capacity;

- short service life (within 10005000 hours);

- sliding (does not apply to toothed belts), which is why the gear ratio is unstable;

- increased load on shafts and their supports, which is due to the need for a sufficiently high pre-tension of the belt;

Conclusion

The course project was completed in full in accordance with the task. The following sections were reviewed and the following indicators were calculated:

Kinematic calculation of the drive. This section defines kinematic and power parameters of the drive;

Select worm wheel material. In the section, steels were selected for the manufacture of the worm wheel. Allowable contact stresses and allowable bending stresses are defined;

The calculation of the worm gear consisted in checking the strength of contact and bending stresses. Design contact stresses are - 5% underloading (20% underloading and 5% overloading allowed). Bending stresses are less than permissible;

Open transmission;

Calculation of gear box shafts. In this section, you selected the materials for shaft manufacturing and made an estimated calculation of the shafts. Where the diameters of the shaft sections were determined. Gear shaft bearings are also selected.

The gearbox is sketched. Where the distances between the force application sites were determined;

Check calculation of shafts for static strength. Diameters of shafts in dangerous sections are specified. An updated calculation of the output shaft for fatigue strength was carried out. Where the safety factor has been determined;

Selection and calculation of key connections. The keys under the bearing are selected here. Strength check for crushing stresses was performed;

Selection of lubrication system. Initially, the worm joint lubrication system was selected. The oil grade and the amount of oil for the oil bath are then determined. The oil level in the gearbox is determined.

An assembly drawing is made, which shows the main view of the reduction gear box and its section (top view), as well as the side. In addition to the assembly drawing, the wheel and the output shaft are detailed.

A BOM has been compiled.

The results of the calculations and the completed assembly drawing showed that the designed gearbox meets all the specified conditions and requirements. The gearbox can be used in real time.