Comprehensive analysis of the three major reducer technologies for robots (I)

The precision reducer industry is a multidisciplinary industry, and its development involves many technologies such as metal materials, heat treatment, small modulus gear hardening, integration, etc. The technical characteristics of precision reducers require manufacturers to have long-term technical accumulation, master core technologies, and have strong design and research and development capabilities.

With the popularization of 4.0 and automatic industrialization, the application is more popular. Reducers are widely used in robot drive components. Reducers play a key role in robot drive. Robot reducers are precision reducers. Harmonic reducers are widely used in robotic arms. RV reducers are used in robot joint drives; small service robots and educational robots use planetary reducers, gear reducers and other micro reducers. The characteristics of robot reducers used in different industries and fields are also different. Characteristics of reducers for industrial robots and robotic arms:

(1) Product features of harmonic reducer: high reduction ratio, small tooth gap, high precision, few parts, easy installation, small size, light weight, high torque capacity, good torque, low noise; high load-bearing capacity In harmonic drive, the meshing of teeth is surface contact, and the number of teeth meshing at the same time (overlap coefficient) is relatively large, so the load per unit area is small and the load-bearing capacity is higher than other drive forms.

(2) Product features of RV reducer: RV reducer is also called RV reducer. Its main structure is composed of a cycloidal pinwheel and a planetary bracket. It has the characteristics of small size, strong impact resistance, large torque, high positioning accuracy, small vibration, and large reduction ratio. It has large torsional stiffness. The output mechanism is a planetary bracket supported at both ends. The output is output by a rigid large disc at the left end of the planetary bracket. The large disc is connected to the working mechanism with bolts. Its torsional stiffness is much greater than the output mechanism of a general cycloidal pinwheel planetary reducer. At rated torque, the elastic backlash is small; Features of reducers for small service robots and educational robots:

(1) Product features of planetary reducer: Planetary reducer is a precision reducer with a drive gap accuracy of 1 arc minute. It is also small in size, light in weight, high in load-bearing capacity, long in service life, stable in operation, low in noise, high in output torque, high in speed ratio, good in performance and safe in performance. It has the unique features of power splitting and multi-tooth meshing. It is widely used in robot drive and automatic industrial equipment.

(2) Product features of gear reducer: Gear reducer is also called gear reducer. The driving gears in the gearbox are all ground with high precision, good contact, high drive rate, single stage greater than 96.5%, double stage greater than 93%, three stage greater than 90%, stable operation, low noise, small size, light weight, long service life, high load-bearing capacity, etc. It is widely used in robots, Industry 4.0, and equipment.

Robots in different fields and industries use different technical parameters and performance characteristics of reducers and speed reducers for locks.

1. Introduction to reducer

(1) Overview of reducer

Mechanical equipment is generally composed of three major systems: power, transmission and execution. Most mechanical equipment uses gear transmission, which is precise, efficient, safe, reliable and cost-effective. Since most mechanical equipment is not suitable for direct drive by a prime mover, a reducer is needed to reduce the speed and increase the torque.

The reducer, also known as a speed reducer, plays the role of reducing the speed and increasing the torque between the prime mover and the working machine or the actuator, and is mainly used in the field of mechanical transmission. Usually, the reducer reduces the speed of the high-speed power of the motor, internal combustion engine, etc. by meshing the small gear on the input shaft with the large gear on the output shaft, and transmits a larger torque to achieve the transmission between the prime mover and the actuator.

(2) Classification of reducers

There are many types of reducers. According to the usage scenario, reducers are divided into general transmission reducers and servo (precision control) reducers; according to the accuracy, they are divided into general transmission reducers and precision reducers; according to the transmission type, they can be divided into gear reducers, worm reducers and planetary reducers; according to the number of transmission stages, they can be divided into single-stage and multi-stage reducers; according to the shape of the gear, they can be divided into cylindrical gear reducers, bevel gear reducers and conical and cylindrical gear reducers; according to the layout of the transmission, they can be divided into expansion type, split type and coaxial reducers. The structures and main features of various common reducers are as follows:

(3) Introduction to precision reducers

① Classification of precision reducers

According to the usage scenarios, reducers are divided into reducers for servo (precision control) and general transmission reducers. Precision reducers have the characteristics of small size, light weight, high precision, strong stability, etc., and can achieve precise control of mechanical transmission. They are mainly used in high-end manufacturing fields such as robots, equipment, high-end machine tools, equipment, printing machinery, etc. General transmission reducers can be divided into general reducers and special reducers: general reducers are usually small and medium-sized, and can be widely used in various industries, including worm gear reducers, cylindrical gear reducers, etc.; special reducers are usually large and extra-large, mostly non-standard, industry-specific products, including marine gearboxes, metallurgical gearboxes, wind power gearboxes, engineering machinery gearboxes, etc.

②Main features of precision reducers

According to different principles, precision reducers are mainly divided into precision planetary reducers, harmonic reducers, and RV reducers. The structural characteristics, advantages and disadvantages, and application areas of various types of precision reducers are as follows:

Development status of planetary reducer industry

In the 1880s, Germany had the first patent for a planetary gear transmission device. In the 1920s, the planetary gear transmission device was mass-produced for the first time. With the development of the machinery industry, planetary reducers are more and more widely used. In the 1950s, Germany successfully developed high-speed and high-power planetary gear reducers for the first time. In the 1960s, Italy, Britain, the Soviet Union and other countries also successively developed low-speed and heavy-load planetary reducers. With the progress of industrial automation, Germany, Italy and other countries have developed precision planetary reducers. my country began to develop and apply planetary reducers in the 1960s. In the 1970s, the NGW-type involute planetary gear reducer standard was formulated for the first time, and a variety of high-speed and high-power planetary reducers were produced. In the 1980s, the production of low-speed and high-torque planetary reducers began.

Figure 1 NGW single-stage planetary reducer

(Sun gear floating, = 2.8 ~ 4.5, zA > zC)

Figure 2 NGW single-stage planetary reducer

(Sun gear floating, >4.5, zA

Figure 3 NGW single-stage planetary reducer

(Floating zA＜zC without redundant constraints)

Figure 4 NGW type planetary gear reducer

(Both elastic oil film floating and sun gear floating load)

Figure 5 NGW single-stage planetary reducer

(Planet carrier floating)

Figure 6 Double-row spur-tooth NGW-type large-size planetary reducer

(Elastic rods are used to balance the load between the two rows of internal gears, and the end cover at the high-speed end is axially split)

Figure 7 NGW high speed planetary speed increaser (reducer)

(Sun gear and inner ring gear float at the same time)

Figure 8 NGW type two-stage planetary reducer

(The high-speed sun gear and the planet carrier float at the same time, and the low-speed sun gear floats)

Figure 9 Planetary reducer with fixed-axis gear transmission and NGW type combination

(Low speed sun gear floating)

Figure 10NGW type two-stage planetary reducer

(High-speed planetary carrier floats, low-speed sun gear floats)

Figure 11 Flange-type NGW-type two-stage planetary reducer

(High-speed planetary carrier is floating, low-speed sun gear is floating; low-speed shaft is connected by flat key or shrink sleeve keyless connection)

Figure 12 Two-stage NGW large-size planetary reducer

(The high-speed sun gear and the planet carrier float, and the low-speed sun gear floats)

Figure 13 Walking type planetary reducer for excavator

(Combination of two-stage NGW transmission and one-stage parallel shaft transmission; low-speed stage sun gear floating, intermediate stage planet carrier floating; high-speed stage with brake)

Figure 14 Rotary planetary reducer for excavator

(High-speed planetary carrier floats, low-speed sun gear floats)

Figure 15 NGW type three-stage planetary reducer

(Level 1: Planet carrier floats; Level 2: Sun gear and planet carrier float simultaneously; Level 3: Sun gear floats)

Figure 16 NGW type three-stage large-size planetary reducer

(The high-speed planet carrier floats, the intermediate sun gear and the planet carrier float at the same time, the low-speed sun gear floats and uses double-row gears, and the two rows of internal gears are evenly loaded with elastic rods)