What is the difference between RV Reducer and harmonic reducer?

Update:04 Jun 2020

As an important component of the core parts, precision reducer is an indispensable part of the reliable and accurate operation of industrial robots. In fact, there are many kinds of reducers, such as harmonic gear reducer, cycloid pin wheel planetary reducer, RV Reducer, precision planetary reducer and filter gear reducer.
As the core part of industrial robot, the precision reducer, compared with the general reducer, is required to have the characteristics of short transmission chain, small size, high power, light weight and easy to control. The precise reducer makes the servo motor of the robot run at a proper speed, and reduces the rotating speed to the speed required by each part of the industrial robot accurately, so as to improve the rigidity of the mechanical body and output a greater torque at the same time.

There are two kinds of reducers widely used in articulated robots: RV Reducer and harmonic reducer. Generally, the RV Reducer is placed at the heavy load position such as the base, big arm and shoulder, that is, it is mainly used for robot joints with a weight of more than 20kg; while the harmonic reducer is placed at the small arm, wrist or hand, that is, robot joints with a weight of less than 20kg. In addition, planetary reducers are generally used in Cartesian coordinate robots.

Rv-e reducer
So, what are the principles, advantages and disadvantages of the two types of reducers?

The harmonic reducer is composed of four basic parts: flexible wheel, wave generator, rigid wheel and bearing. The outside diameter of the flexible wheel is slightly smaller than the inside diameter of the rigid wheel. Generally, the flexible wheel has two teeth less than the rigid wheel. The elliptical shape of the wave generator determines that the tooth contact points of the flexible wheel and the rigid wheel are located on two opposite sides between the center of the ellipse. During the rotation of the wave generator, the contact part of the flexible wheel and the rigid gear begins to mesh. When the wave generator rotates 180 ┬░ clockwise, the number of teeth of the flexible wheel is equal to that of the rigid wheel rotates one tooth anticlockwise. At two 180 ┬░ symmetrical positions, more than 30% of all teeth are engaged at the same time, which also results in high torque transmission.

Harmonic reducer
Compared with the harmonic reducer, RV transmission is a new kind of transmission, which is developed on the basis of the traditional pin cycloid planetary transmission. It not only overcomes the shortcomings of the general pin cycloid transmission, but also has a series of advantages such as small volume, light weight, large transmission ratio range, long life, stable accuracy, high efficiency, stable transmission and so on.
The key of RV Reducer lies in the processing and assembly process. RV Reducer has higher fatigue strength, stiffness and life. Unlike harmonic drive, its motion accuracy will be significantly reduced with the increase of service time. Its disadvantages are heavy weight and large size.
It is reported that RV Reducer is composed of cycloidal pin wheel and planetary support. It is widely used in industrial robots, machine tools, medical detection equipment, satellite receiving systems and other fields with its advantages of small size, strong impact resistance, large torque, high positioning accuracy, small vibration, large reduction ratio, etc., and has attracted more and more attention at home and abroad.

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