The Working Principle of Harmonic drive

update:2023-05-18

abstract:Ⅰ.Basic Structure 1.Rigid gear with internal gear ring; 2.Flexible gear with outer gear ring; 3.Wave...

Ⅰ.Basic Structure

1.Rigid gear with internal gear ring;

2.Flexible gear with outer gear ring;

3.Wave generator H.

Ⅱ.Transmission Principle

The work of the harmonic drive is driven by the wave generator, the rigid gear is fixed, and the flexible gear is output.

The generator H is a rod-shaped component with rolling bearings on both ends to form rollers, which are pressed against the inner wall of the flexible gear. The flexible gear is a thin-walled gear that can produce large elastic deformations, and its inner hole diameter is slightly smaller than the total length of the wave generator.

The wave generator is a component that makes the flexible gear produce controllable elastic deformation. When the wave generator is installed in the flexible gear, it forces its cross-section from the original circular shape to an oval shape. At this time, both ends of the long shaft are completely meshed with the rigid gear, and both ends of the short shaft are completely disengaged from the rigid gear. When the wave generator rotates continuously, the deformation of the flexible gear changes continuously, so that the meshing state of the flexible gear and the rigid gear also changes continuously, from engaging in, engaging out, disengaging, and re-engaging. The cycle repeats, so as to realize the slow rotation of the flexible gear relative to the rigid gear in the opposite direction of the wave generator H.

Ⅲ.Working Formula

When working, the rigid gear is fixed, the motor drives the wave generator to rotate, and the flexible gear acts as a driven wheel to output rotation and drive the load to move. During the transmission process, the wave generator makes one revolution, and the number of cycles of deformation at a certain point on the flexible gear is called the wave number, which is represented by n. Usually, the difference between the number of teeth of a rigid gear and a flexible gear is equal to the wave number, that is, z2-z1=n.

In the formula, z2 and z1 are the number of teeth of rigid gear and flexible gear, respectively.

When the rigid gear is fixed, the generator is active, and the flexible gear is driven, the transmission ratio of the harmonic gear transmission is i=-z1/(z2-z1).

The negative sign in the above formula means that the steering of the flex gear is opposite to that of the wave generator. It can be seen that the harmonic drive can obtain a large transmission ratio.

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