The principle of the reducer, the core part of the robot, is open. Why can’t we compete with Japan’s?

2019-11-05 4585
Industrial robots are widely used in car production, electrical equipment production, food machinery processing and other industrial production. With the increase of labor costs in China, the trend of robot replacing labor is more and more obvious, and the products produced by robots have good consistency, high equipment accuracy and other benefits are also paid more attention by manufacturers.
Now, the cost of global robots is mainly composed of: about 35% of the reducer, about 20% of the servo machine, about 15% of the control system, and only about 15% of the robot body machining. The world's high-end robots are mainly controlled by a few international robot companies, such as abb, FANUC and KUKA, and 75% of the precise deceleration they use is made by Japanese companies.
There are three kinds of precision reducers used in robot operation: RV Reducer, harmonic reducer and planetary reducer. The share of these three reducers in the market is about 40%, 40% and 20%.
In the articulated robot, the RV Reducer is usually placed in the position of heavy load such as base, big arm and shoulder, while the harmonic reducer is usually placed in the small arm, wrist or hand.
RV Reducer is the abbreviation of rotary vector reducer, which was first created in Japan. It is a new hybrid of traditional cycloidal pin wheel and planetary gear transmission equipment. RV Reducer has a large transmission ratio (30-260).
The principle of RV Reducer has been exposed for a long time, and there is no patent maintenance, which is different from what we have always heard. However, 80% of the RV Reducer stores in the whole operation are still occupied by Japan, and the main brands are nabotesk and Sumitomo.

 
RV Reducer structure
The transmission equipment of RV Reducer is composed of two parts: the first stage involute cylindrical gear planetary reduction organization and the second stage cycloidal pin wheel planetary reduction organization, which is a closed differential gear train.
The active sun wheel 1 is connected with the input shaft. Assuming that the involute central wheel 1 rotates clockwise, it will drive three 120 ° planetary wheels 2 to rotate around the central wheel axis and rotate counter clockwise. Three crank shafts 3 are connected with the planetary wheel 2 and roll at the same speed. Two cycloid wheels 4 with 180 ° phase difference are hinged on three crank shafts and mesh with the fixed needle wheel When its axis revolves around the axis of the needle wheel, it will also rotate in the opposite direction, that is, roll clockwise. The output structure (i.e. planetary frame) 6 is pushed by three pairs of crank shaft support bearings installed on it, which transmits the rotation vector on the cycloid wheel with a speed ratio of 1:1. (chart below)

RV Reducer operation principle
The difficulty of RV Reducer manufacturing center lies in the close coordination of various processes, including: heat treatment of tooth surface, machining accuracy, symmetry of parts, group technology, equipment accuracy, etc., and the result of the total distribution of these process assembly tolerances is product wear and life.
Domestic RV Reducer manufacturers mainly include Nantong zhenkang and Hengfengtai. In 2017, the annual output of Nantong zhenkang reached more than 200, and its products have been tried by many robot manufacturers, including foreign abb, KUKA, fanako, domestic Everett, eston and other enterprises.
The end deceleration of the reducer is achieved by the simple principle that the speed of the reducer is inversely proportional to the number of teeth through the transmission between the big and small gears. But to end the large transmission ratio, assuming that we always see the cylindrical gear, the volume of the whole gear reducer will be very large, assuming that we want to achieve as small a volume as possible, what should we do?
Harmonic reducer is the gear embedded in!
Harmonic reducer is mainly composed of wave generator, flexible gear, flexible bearing and rigid gear.

 Structure of harmonic reducer
The harmonic drive reducer is a kind of gear drive which relies on the flexible bearing on the wave generator to make the flexible gear have controllable elastic deformation and mesh with the rigid gear to transmit the motion and power. (chart below)

 Operation principle of harmonic reducer
The technical difficulties of harmonic reducer are mainly reflected in the number of flexible wheel life and machining accuracy.
In general, China's precision reducer is subject to two major categories: material and precision machining.

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