WAVE TRANSMISSION WITH TWO WAVE GENERATOR
06.06.2022 18:53
[3. Технічні науки]
Автор: Kotlyar Svitlana Serhiivna, Ph.D., National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”
The principle of action of wave transmission is based on change of parameters of movement owing to wave deformation of one of links of the mechanism.
The main advantages of gear wave transmission:
1. Small weight and overall dimensions with high load capacity. This is due to the fact that at the same time in the gear is 20 ... 40% of the total number of teeth, and the load on the shafts and supports are insignificant.
The mass of the wave reducer at i = 80 ... 300 is less than the planetary and multistage gears. In some designs, the transition from planetary to wave transmission can reduce the mass by half.
2. High kinematic accuracy, which is ensured by multi-pair engagement and the presence of several contact zones of the teeth.
3. Large gear ratio of one degree (i = 80 ... 300).
4. Ability to transmit motion from an airtight space.
5. Quite high efficiency (η = 0.8 ... 0.9) during gear transmission. The efficiency of wave and planetary gears are similar at the same gear ratios.
6. Possibility of use not only as a reducer or multiplier, but also as a differential.
The disadvantages of wave transmissions include: the complexity of manufacturing a flexible wheel and wave generator, the high value of the minimum gear ratio.
The advantages of wave transmission make it expedient to use it widely in mechanisms with a large gear ratio and in devices with high requirements for tightness and kinematic accuracy.
Wave transmission consists of three main links: wave generator h, flexible wheel g and rigid wheel b. The ring gear of the flexible wheel is deformed by the wave generator and engages with the central rigid wheel having a dividing diameter db. The flexible wheel is made in the form of a glass with a flange. The ring gear on the flexible wheel is cut on the outside in the middle of the glass; its wall has a small thickness, which allows it to easily deform under the action of a wave generator inserted inside. The two-wave generator consists of a carrier with two rollers. The external size of the generator along the axis is greater than the inner diameter of the cylinder by 2w0, where w0 is the radial movement of the wall of the flexible wheel along the major axis of the generator.
Fig. 1. Wave transmission:
1 - flexible wheel, 2 - rigid wheel, 3 - wave generator
When the wave generator rotates, the deformation wave moves around the circumference of the flexible wheel. Any point of the cylindrical surface of the flexible wheel moves and performs in two-wave transmission two oscillations per revolution of the wave generator. When the generator rotates, two waves travel around the circumference of the flexible wheel, regardless of its speed. The teeth of the flexible wheel are engaged throughout the working height. For one revolution of the wave generator of the gear engagement zone, one revolution is also performed, as a result of which one wheel is rotated relative to another by the number of angular steps equal to the difference of their number of teeth.
If the three main links of the wave gear rotate, it has two degrees of freedom and is called the differential mechanism. More often wave transmissions in which one of the basic links (a flexible or rigid wheel) is stopped are used. Then the mechanism has one degree of freedom. If the master is a wave generator, the mechanism works as a reducer, and if the generator is a slave, then as a multiplier.
In three-wave transmissions, the wave generator has three rollers and forms three deformation waves on the flexible wheel. The bending stress in such a flexible wheel is higher than in a two-wave transmission, so these gears are used less often.
There are wave transmissions: gear, friction and screw-nut type; with different wave generators: mechanical, electromagnetic, hydraulic.
The efficiency of a flexible wheel is determined, first of all, by its strength, and in gears with a cam wave generator - and the strength of flexible bearings.
References:
[1] Konovaliuk D.M. Detali mashyn: pidruchnyk dlia studentiv vyshchykh navchalnykh zakladiv mashynobudivnoho profiliu / D.M. Konovaliuk, R.M. Kovalchuk // Kyiv: Kondor, 2021. – 582 p.: fig. i tabl. ISBN 966798222X.
[2] Malashchenko V.O. Praktychne proektuvannia i konstruiuvannia detalei mashyn : navchalnyi posibnyk / V.O. Malashchenko, V.M. Strilets, M.M. Koziar, O.R. Strilets; Ministerstvo osvity i nauky Ukrainy, Natsionalnyi universytet vodnoho hospodarstva ta pryrodokorystuvannia // Rivne NUVHP, 2020. – 145 p.: fig. i tabl. ISBN 9789663274614.