As a precision reducer, which is the core component of industrial robots, compared with general-purpose reducers, robot reducers are required to have the characteristics of short transmission chain, small size, high power, light weight and easy control.

There are two main types of reducers widely used in articulated robots: RV reducers and harmonic reducers.

Cycloidal Geabox Principle

It is used for the three joints of the waist and elbow of the leg of the robot with large torque, and the industrial robot with large load uses RV for one, two and three axes. Compared with the harmonic reducer, the key to the RV reducer lies in the processing technology and assembly process. RV reducer has higher fatigue strength, stiffness and life. Unlike harmonic drive, as the use time increases, the movement accuracy will be significantly reduced. Its disadvantage is that it is heavy in weight and large in size.

Harmonic reducer:

For industrial robots with small loads or several axes at the end of large robots, the harmonic reducer is a kind of harmonic transmission device. The harmonic transmission device includes a harmonic accelerator and a harmonic reducer. Harmonic reducer mainly includes: rigid wheel, flexible wheel, bearing and wave generator, all of which are indispensable. Among them, the number of teeth of the rigid wheel is slightly larger than the number of teeth of the flexible wheel. The harmonic reducer used in small robots is characterized by small size, light weight, large carrying capacity, high motion accuracy, and large single-stage transmission ratio.

Both are meshes with small tooth difference. The difference is that one of the key gears in the harmonics is flexible, and it needs repeated high-speed deformation, so it is relatively fragile and has limited bearing capacity and life. RV usually uses a cycloidal pin wheel. Harmonics used to use an involute tooth profile. Now some manufacturers use a double arc tooth profile, which is much more advanced than the involute profile.

The two giants of the reducer are Nabtesco and Hamonica Drive, they almost monopolize the global robot reducer. Both of these reducers have micron-level machining accuracy. It is difficult for this one to have high reliability in the mass production stage, let alone high-speed operation of several thousand revolutions, and long life.

In China, the largest and most professional RV reducer manufacturer is Genius Zhenkang.

The harmonic reducer is composed of four basic components: "flexible wheel, wave generator, rigid wheel, and bearing".

The outer diameter of the flexible wheel is slightly smaller than the inner diameter of the rigid wheel. Generally, the flexible wheel has 2 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 distributed on two opposite surfaces between the center of the ellipse. During the rotation of the wave generator, the contact parts of the flexible gear and the rigid gear start to mesh. Every time the wave generator rotates 180° clockwise, the flexspline is equivalent to a counterclockwise rotation of the rigid wheel by 1 tooth number difference. In two places symmetrical at 180°, more than 30% of the total number of teeth are meshed at the same time, which also contributes to its high torque transmission.

Compared with the harmonic reducer, the RV drive is a new type of transmission. It is developed on the basis of the traditional pin pendulum planetary drive. It not only overcomes the shortcomings of the general pin pendulum drive, but also has the advantages of small size, light weight, and A series of advantages such as large transmission ratio range, long life, stable accuracy, high efficiency and smooth transmission.

The RV reducer is composed of a cycloidal pin wheel and a planetary bracket. It is widely used in industrial robots, machine tools, and medical applications due to its small size, strong impact resistance, large torque, high positioning accuracy, low vibration, and large reduction ratio. Detection equipment, satellite receiving system and other fields.

The housing and cycloidal pin wheel of the RV reducer are driven by solid steel, so the bearing capacity is strong. The flexible wheel of the harmonic reducer can continuously deform to transmit torque. This determines that the harmonic reducer has a limited ability to withstand large torques and impact loads, so it is generally used in the front end.

2. Cycloidal Geabox and Harmonic Driver Advantages and disadvantages

The harmonic reducer has a simple and compact structure and is suitable for miniaturized, low and medium load applications.

The RV reducer has good rigidity, strong impact resistance, stable transmission, and high accuracy. It is suitable for medium and heavy load applications. However, the RV reducer needs to transmit a large torque, bear a large overload impact, and ensure the expected working life. In the design, a relatively complicated over-positioning structure is used, and the manufacturing process and cost control are difficult. The RV reducer has no elastically deformed force components inside, so it can withstand a certain torque. The bearing of the RV reducer is its weak link, and it is easy to break through the bearing force limit when subjected to force and cause abnormal wear or rupture of the bearing. This problem is more prominent during high-speed operation, so the rated torque of the RV reducer decreases significantly with the input speed.

3. Can Cycloidal Gearbox replace Harmonic Driver

Compared with the harmonic drive commonly used in robots, the RV reducer has much higher fatigue strength, stiffness and life, and the accuracy of the return difference is stable. Unlike the harmonic drive, the motion accuracy will be significantly reduced as the use time increases. Therefore, high-precision robot transmissions in many countries mostly use RV reducers. Therefore, RV reducers have a trend of gradually replacing harmonic reducers in advanced robot transmissions.

These products do have a substitution relationship on some models, but these types of reducers can only achieve partial substitution. In most cases, it is difficult to replace various types of reducers. For example, in terms of speed ratio, the speed ratio of harmonics and RV is much larger than that of planets, so the field of low speed ratios is the world of planets. Of course the planetary speed ratio can be made larger, but it is difficult to replace harmonics and RV. In terms of rigidity, the rigidity of planets and RVs is better than that of harmonics. Under the working conditions that reflect rigidity, harmonics are difficult to perform well.

The characteristics of the harmonic reducer are light and small. In this regard, planetary and RV are difficult to achieve. Therefore, various types of reducers can only be replaced in some cases, but it is unrealistic if one product replaces another product in an all-round way.

Various types of reducers cannot replace each other, but a complementary relationship.

RV and harmonic drive are complementary, but it is not ruled out that after structural design optimization and manufacturing process breakthroughs, local competition will be formed in the field of medium and low load applications.

If you need to buy a precision cycloidal pinwheel RV gear reducer, please feel free to consult and contact our company sales@geniusrobotics.cn

Whatsapp: +86 15800366487