The harmonic reduction gear consists of a wave generator, a flex spline, and a circular spline. Its working principle is to use the wave generator to make the flex spline undergo elastic deformation, achieving tooth engagement movement, thereby attaining low speed and high torque output. When the wave generator is installed inside the inner circle of the flex spline, the flex spline will undergo elastic deformation due to the shape of the wave generator, turning into an elliptical shape.
At this point, the teeth at both ends of the long axis of the flex spline fully mesh with the circular spline, while the teeth at both ends of the short axis completely disengage from the circular spline teeth. When the wave generator rotates continuously, the continuous change in the phase of the long and short axes of the flex spline renders the deformation of the flex spline as a continuous simple harmonic wave around the circumference, thus achieving low-speed rotation of the flex spline in the direction opposite to the wave generator's rotation relative to the stationary circular spline.
The harmonic reduction gear is characterized by its small size and light weight. Compared with ordinary gear reducers, for the same output torque, its volume can be reduced by 2/3 and its weight can be halved. For instance, in humanoid robots, a compact and lightweight harmonic reduction gear can make the robot more flexible and adaptable to various complex working environments.
Another notable advantage of the harmonic reduction gear is its high transmission ratio. The range of single-stage harmonic transmission ratios is 70 - 320, and in some devices, it can reach 1000. Multi-stage transmission ratios can exceed 30000, making the harmonic reduction gear perform exceptionally well in applications requiring large reduction ratios, such as industrial robots and CNC machines.
In addition, harmonic reduction gears have high transmission accuracy, simple and compact structure, easy installation, high load capacity, the ability to transmit motion to enclosed spaces, high transmission efficiency, and smooth motion. With the same gear precision grade, the transmission error is only about 1/4 of that of ordinary cylindrical gear transmission. Meanwhile, with only three basic components and the input and output lines being coaxial, the structure is simple and compact, and installation is convenient.
Furthermore, the harmonic transmission involves many simultaneously engaged teeth, resulting in high load capacity. In double-wave transmission, the number of simultaneously engaged teeth can exceed 30% of the total number of teeth. The flex spline uses high-strength materials, and the teeth are in surface contact with each other, further enhancing load capacity.
These advantages make harmonic reduction gears widely used in various fields, including robotics, CNC machines, photovoltaic equipment, medical instruments, semiconductor equipment, and aerospace.
The trend towards mass production of humanoid robots is becoming increasingly evident, which will bring enormous market demand for harmonic reduction gears. According to relevant data, global investment in R&D for humanoid robots continued to increase in 2022, with many tech companies entering this field. It is expected that in the coming years, the production of humanoid robots will see explosive growth.
With the mass production of humanoid robots, the demand for harmonic reduction gears will increase significantly. Taking Tesla's Optimus as an example, out of the 28 actuators in the entire body, 14 are rotary actuators, each containing a harmonic reduction gear. Based on this configuration, the number of harmonic reduction gears required for a single humanoid robot is considerable.
According to market predictions, when humanoid robots achieve large-scale mass production, the market size for harmonic reduction gears will see explosive growth. It is estimated that by 2030, the production of humanoid robots is expected to reach 660,000 units, correlating to an increase in the harmonic reduction gear market from 90 million yuan in 2024 to 11.5 billion yuan. In the long term, as humanoid robot production further increases to the tens of millions of units level, the market size for harmonic reduction gears will reach the hundred-billion-yuan level.
Additionally, as application fields expand, applying harmonic reduction gears in more high-end manufacturing areas, such as aerospace, medical instruments, semiconductor equipment, and others, will bring new opportunities and challenges for the development of harmonic reduction gears, driving continuous innovation and development in the industry.
