Harmonic Drive transmission device mainly consists of three basic components: a wave generator, a flexspline, and a circular spline. The wave generator is composed of a flexible bearing and a cam. The wave generator is usually installed at the input end of the reducer, with the inner ring of the flexible bearing fixed on the cam. The flexspline is a flexible elastic part typically installed at the output end of the reducer. The circular spline is a rigid ring with internal teeth, generally having two more large teeth compared to the flexspline, and is usually mounted on the reducer. So, what is the reduction principle of the harmonic drive? What are its characteristics when it operates?
When used as a reducer, the harmonic drive typically utilizes the active wave generator, the fixed circular spline, and the output flexspline to accomplish the reduction. When the wave generator enters the flexspline, it deforms it into an elliptical shape, causing the teeth at the long axis of the flexspline to mesh into the teeth grooves of the circular spline, thus completing the meshing state. At this time, the teeth at the short axis are completely non-contact, in a suspended disengaged state. The process from meshing to disengaging is referred to as dedendum meshing or addendum meshing. If the wave generator continuously rotates, it forces the flexspline to constantly deform and recover, causing the teeth to repeatedly mesh, disengage, and re-engage, thereby producing continuous differential movement, which effectively achieves the motion of the active wave generator.
Firstly, its accuracy is relatively high. Under the working condition of multiple gears, meshing occurs at two symmetrical positions 180 degrees apart, so the error during gear engagement has a more even impact on rotation, attaining very high positional and rotational accuracy.
Secondly, the transmission ratio is very large. The transmission ratio for general single-stage harmonic gear transmission can reach between 30 to 500, and the structure is relatively simple, allowing the three components to achieve high-speed operation.
Thirdly, it has a relatively high load capacity. During the transmission process of the harmonic drive, the gear meshing occurs in a surface contact, rather than point contact. Additionally, the more teeth that mesh simultaneously, the smaller the force per unit area, thereby increasing its load capacity compared to other transmission mechanisms.
Fourthly, it is relatively compact and lightweight. Compared to ordinary gear devices, it can more easily achieve miniaturization and mass production. Its high precision also results in less impact, hence higher transmission efficiency and relatively longer operational lifespan.
The above sections explain the harmonic drive principle and harmonic drive transmission characteristics during use. Hope this information is helpful to you.
