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Hitachi

Hitachi Nico Transmission Co.,Ltd.

Flexible pin-type load distribution mechanism

Image : Flexible pin structure
Flexible pin structure

The planetary gears mesh multiple gears simultaneously, so errors in machining and assembly can cause load imbalances between them. Such load imbalances reduce transmission efficiency and durability, so high-precision manufacturing and uniform load distribution mechanisms are required.
Our uniform load distribution mechanism is the “flexible-pin type”, which uses a flexible structure for planetary gear support elements, applying the principles of a cantilevered beam to flex when load is applied.

Flexible pin action when under central load

Image : Cross section when under central load
Cross section when under central load

If the load is distributed evenly among the tooth faces, it is the same as when a concentrated load is applied in the center, and the pins flex as double cantilever beams, and parallelism relative to other planetary gears is not lost.
If there is any error in relative positioning between flexible pins, due to errors in machining or assembly, the planetary gear positioned here receives more load than others do, and the flexible pin supporting that gear flexes further to absorb the error. Thus, the uniform load distribution mechanism keeps load distribution even.

Flexible pin action when under eccentric load

Image : Cross section when under eccentric load
Cross section when under eccentric load

If an eccentric load is applied to the left end of a tooth face, the flexible pin flexes as shown in the diagram, and the load on the right side of the tooth face increases, mitigating the eccentric distribution of load across the width of the tooth.
The effects of gear tooth trace errors, gear casing deformation, misalignment and other problems can be absorbed and mitigated.