Harmonic Gear Transmission

Harmonic gear transmission is a new type of mechanism that relies on elastic deformation motion to achieve transmission.

Harmonic Gear Transmission

It breaks through the mode of mechanical transmission using rigid member mechanisms, using a flexible member to achieve mechanical transmission, thus obtaining a series of special functions that are difficult to achieve with other transmissions.

It has been widely used.

But it also brings special problems that must be solved in the design.

Introduction

In the 1950s, with the development of space science and aerospace technology, the mechanism and instrumentation of the spacecraft control system put forward new requirements for mechanical transmission, such as: large transmission ratio, small size, light weight, high transmission precision, and small variation.

For the above requirements, the emerging harmonic drive meets this requirement.

It is a transmission technology developed on the basis of elastic deformation of thin shells.

The harmonic gear drive system consists of three basic components, as shown in Figure 2-1:

  • Circular Spline
  • Flexspline
  • Wave Generator

The principle of the harmonic gear transmission is that in the flexible gear member, a moving deformation wave is generated by the action of the wave generator, and meshes with the rigid tooth to achieve the transmission purpose.

Advantage

  • The transmission ratio range is large 50~300, 3000~60000
  • 30% more engaged teeth at the same time
  • It is precisely because of the unique advantages of the simultaneous number of meshing teeth that the harmonic transmission has high precision and the bearing capacity of the teeth is large, thereby realizing a large speed ratio and a small volume.
  • Large carrying capacity
  • High precision of motion
  • Smooth movement, no impact, low noise
  • The flank clearance can be adjusted
  • The tooth surface wear is small and uniform, and the transmission efficiency is high.
  • Good coaxiality
  • Can realize the transmission of motion and power to the confined space

Disadvantages

  • Easy to fatigue damage
  • The manufacturing of flexible wheel and wave generator is more difficult
  • The lower limit of the transmission ratio is high, and the number of teeth cannot be too small.
  • The starting torque is large, and the smaller the speed ratio is, the more serious;
  • The harmonic gear drive has no intermediate shaft, so the intermediate speed cannot be obtained.
  • If the structural parameters are improperly selected or the structure timing is bad, the heat is too large, and the transmission capacity is reduced.

At present, scholars from various countries have recognized that the fatigue damage of the flexible wheel cylinder is the most important form of failure of harmonic transmission.

Application

Harmonic drives have many unique advantages that are unmatched by other drives.

In recent decades, it has been rapidly promoted to the fields of energy, communications, machine tools, instrumentation, robotics, automobiles, shipbuilding, textiles, metallurgy, conventional weapons, precision optical equipment, printing institutions, and medical devices.

The application practice at home and abroad shows that both the precision harmonic drive as a high-sensitivity servo system and the power harmonic drive that transmits large torque show good performance.

As a space transmission device and a mechanism for operating high temperature and high pressure pipelines and working under conditions of atomic radiation or other harmful media, it shows the superiority compared with some other transmissions.

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