Drive of the hulling drum

Contents

1. Engine selection and kinematic calculation

1. 1 Determination of rated electric motor power

1. 2 Determination of gear ratio of the drive and its step

2. Calculation of drives

2. 1 Calculation of worm reduction gear

2. 1. 1 Material selection and definition of allowable stresses

2. 1. 2 Determination of geometric dimensions of worm gear

2. 1. 3 Kinematic and power calculation of worm gear

2. 1. 4 Check calculation of worm gear

2. 2 Calculation of open gear front

2. 2. 1 Material selection and definition of allowable stresses

2. 2. 2 Calculation of geometric dimensions of open gearing

2. 2. 3 Kinematic and power calculation of open gearing

2. 2. 4 Check calculation of open gear front

2. 3 Calculation of open chain front

3. Preliminary calculation of gearbox shafts

4. Structural dimensions of gearbox housing

5. Gearbox sketch layout. Selection of bearings

6. Durability check of bearings

6. 1 High speed gear shaft (cher-yak)

6. 2 Low-speed gear shaft

7. Calculation of key connections

8. Check calculation of gearbox shafts

8. 1 Check calculation of speed shaft of reduction gear box (worm-k)

8. 2 Check calculation of low-speed gear shaft

9. Choice of mas-la grade

10. Thermal calculation of reduction gear

11. Gearbox assembly

12. Designing a Rahm

13. Conclusion

List of used literature

1. Motor selection and kinematic calculation of the drive.

The calculation of the drive begins with the selection of the electric motor according to the required power and operating conditions. The engine is one of the main elements of the machine unit. The design and operational characteristics of the working machine and its drive depend on the type of engine, its power, speed.

For the designed machine unit, three-phase asynchronous short-circuited electric motors of the 4A series are recommended, used for mechanism drives that have a constant or slightly changing load with a long operating mode and a large starting load. These motors operate in any direction of rotation, ensuring, if necessary, the reversibility of the machine unit. The closed and blown version allows you to use these engines for operation in contaminated conditions, in open rooms.

Individual types of 4A series engines differ in rated power Pnom and rated speed nom. The rated engine power is selected depending on its design power so that its value is large in magnitude, but closest to the design power (Pnom ≥ Rdv).

For different types of motors at the same developed power, the values ​ ​ of nominal rotation frequencies differ. Engines with a nominal speed of nn = 750 rpm are slow-moving, have large overall dimensions and, therefore, a large mass, create significant vibration loads on the supports of the structure, therefore their use is undesirable and is limited to those cases when it is not possible to carry out large reduction ratios to drive slow-moving shafts.

As rotation speed increases, overall dimensions of engines, their masses and vibration loads created by them decrease, but working life decreases. High speed motors (nnom = 2900 rpm) should not be used in cases where high gear ratios (u ≥ 60) are required to convert the rotation of the high speed motor shaft to the rotation of the driven drive shaft, since in this case the overall dimensions of the gears are unacceptably large.

In general, when selecting the engine by speed, it is necessary to focus on the selected (predetermined) drive circuit.

2. Calculation of drive gears.

The calculation of drive gears - open chain gear, worm gear and open gear is carried out in two stages.

At the first stage, design calculation is carried out in order to determine the geometric parameters of the transmission. Design calculation is carried out according to permissible contact and bending stresses arising on working surfaces of drive transmission elements. The values of permissible contact and bending stresses depend on the mechanical characteristics of the materials from which the transmission elements are made, their surfaces. The selection of materials for the manufacture of transmission elements is made in such a way that the calculated values ​ ​ of contact and bending stresses do not exceed the permissible values, but are not significantly lower than them, since an excessive safety margin (more than 15%) is not economically feasible.

Various methods of heat treatment are used to improve the mechanical properties of materials.

Volumetric hardening is the simplest and cheapest type of heat treatment, as a result of which the tooth acquires hardness throughout the volume. Disadvantages include warping and the need for subsequent finishing operations, reducing flexural strength at contact loads.

Surface quenching with high frequency currents (HF) or acetylene burner flame is used for teeth with m ≥ 5 mm. With small modules, the tooth is calcined through, becomes brittle and easily warps.

Cementation - saturation of the surface layer with carbon with subsequent hardening - a long and expensive process that provides high contact and bending strength of the teeth. It is used in cases where mass and dimensions are of crucial importance.

Nitrocementation - carbon saturation in a gas medium with the addition of nitrogen, allows to reduce the duration and cost of the cementation process.

After the final determination of the transmission parameters, a check calculation is carried out, the purpose of which is to confirm the correctness of the selection of table values, coefficients and results obtained in the design calculation, to determine the relations between the calculated and permissible stresses of bending and contact endurance.

2. 1 Calculation of worm gear box.

Worm gears are used to transfer rotation between crossing axes (usually at an angle of 90 °). The main advantage of worm gears is the possibility of high gear ratios, in special cases the gear ratio of worm gears can reach eighty. The main drawback of worm gears is the low value of p.

The number of worm turns can vary from one to four. With a decrease in the number of turns, the dimensions of the worm reduction gear are reduced, but also its size decreases to p. D., which for single-start reduction gears is 0.75. K. p. d. Four-start worm gearboxes are 0.90... 0.95, that is, it does not differ significantly from k. p. d. Gear gears (0.93... 0.96), but at the same time more compact overall gear measures are provided at the same gear ratios.

Considerable mutual sliding of the working surfaces of the worm and the worm wheel, in addition to power loss, causes heating of the worm gear elements. Heat generation during long-term operation of the reduction gear requires special measures of its additional cooling - finning of the housing, blowing.

The mutual sliding of the working surfaces of the worm and worm co-forest is due to the tendency to jam them, which causes the need to use expensive antifriction alloys for the manufacture of toothed crowns of worm wheels.

The application of power worm gears is limited to the following parameters:

- transmitted power: up to 200 kW;

- circumferential speed: up to 15 m/s;

- gear ratios: from 10 to 80.

The driving link of the worm reduction gear is a worm, which can be located under the wheel, above the wheel or on the side, the axis of the worm in this case is vertical. Each of the listed layout schemes has its advantages and disadvantages. With the lower arrangement of the worm, the lubrication conditions are better, with the upper - worse, but less likely to get into the engagement of metal particles - wear products. At circumferential speeds of the worm up to 4... 6 m/s, the lower location of the worm is preferable. At high speeds, oil mixing losses increase, in which case the worm should be placed above the wheel.

2. 2 Calculation of open gear train.

Open gears are calculated for endurance by bending stresses taking into account wear of teeth during operation. It is not necessary to check the endurance of the tooth surfaces against contact stresses, since abrasive wear of the tooth surfaces prevents them from being painted out from variable contact stresses.

11. Gearbox assembly.

Prior to assembly, inner cavity of housing is thoroughly cleaned and covered with oil-resistant paint. The reduction gear is assembled in accordance with the assembly drawing. Assembly begins with the fact that conical radial-thrust roller bearings are put on the worm shaft, previously heating them in oil to 80... 100 ° C. The assembled worm shaft is inserted into the housing.

First, worm wheel shaft assembly is fitted with key and wheel is pressed to rest against shaft collar, then spacer bushing is put on and roller conical bearings heated in oil are installed. The assembled shaft is laid in the base of the housing and the cover of the housing is put on, previously covering the surfaces of the flange joint with alcohol varnish. For alignment the cover is installed on the housing with the help of two conical pins and bolts are tightened.

Rubber cuffs are put into bearing through covers and covers with gaskets are installed. Adjustment of bearings position is performed by means of paronite gaskets of different thickness.

In worm gears, the middle plane of the gear rim of the worm wheel must be precisely aligned with the axis of the worm. The accuracy rate for this parameter is regulated by GOST 3675-81. The actual displacement of the middle plane of the gear rim of the worm wheel relative to the axis of the worm wheel is significantly higher than allowed. Therefore, the accuracy of the relative position of the worm wheel is achieved by adjustment. Axial position of worm wheels is adjusted by selection of gaskets.

The assembled gearbox is rolled and tested on the bench in accordance with the specifications.

To connect the shafts to the inner rings of the bearings, a transition fit H7/k6 is assigned [1, Table 8.11, p. 169]. To connect the worm wheel with the driven shaft of the reduction gear, a transition fit H7/m6 is assigned [1, Table 8.11, p. 169]. Transition fit H7/n6 is assigned to connect the worm to the half-coupling [1, Table 8.11, p. 169]. To connect the driven shaft of the reduction gear with the chain drive sprocket, a landing with a gap H7/h6 is assigned [1, Table 8.11, p. 169].

13. Conclusion.

During the design process, the design of the drive of the tow drum was developed, consisting of an electric motor, an open chain gear, a worm gear and an open gear. The design of the drive complies with the requirements of the design specification, since it provides the required shaft speed and power. Technical documentation has been developed - a drawing of a general type of drive, an assembly drawing of a worm gear box, drawings of parts and assemblies included in the assembly units.

In the calculation and explanatory note, the kinematic calculation of the drive was made, the gear and drive mechanisms were calculated based on the reliability of the designed elements, the sketch layout of the worm reduction gear was made, the shafts were calculated for strength and bending, general recommendations for assembling the reduction gear were given.