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Consisting of only a concentric ring gear (K) that engages with a planet,
a carrier (H) and an equal velocity mechanism (V), the KHV gearing
is compact in structure, small in size and capable of providing a large
torque transmission with both a big ratio & a high efficiency.
Its speed ratio can reach 400, and its size is only about 1/4
that of a conventional multi-stage gear box.
Some other configurations were invented and patented a long time ago.
However, the development was hindered by low efficiency and interference.Usually,
for a planetary gearing, the higher the ratio, the lower the efficiency.
Since the teeth difference between the ring gear and the planet gear is
very small, it is very difficult to avoid the interference which makes
the efficiency even worse. Studying these problems for decades, the Japanese
Sumitomo Co. has developed the Cyclo reducer. Improved by hardened rollers
meshing with modified epicycloid gears, the Cyclo can reach an efficiency
of 90%, and may become a successful gearing in the world market. However,
it's difficult for other companies to design and make the special gear
cutting and grinding machines for the special gears. Moreover, it is difficult
to know how to modify the epicycloidal tooth form, which is crucial to
the efficiency. The heat treatment and grinding the hardened gears and
rollers, and the required high accuracy result in an expensive cost of
materials and fabrication.
Through years of research, I have developed and tested a series of
meshing profiles and optimizing programs to search for the best parameters
of the KHV, which can offer both large ratios and high efficiency.
The efficiency of the KHV can reach 90% with a ratio up to
400. This is much higher than the Cyclo's maximum ratio of 119.
The optimizing design enables the ring gear to have only one more tooth
than the planet gear with no interference. The ring gear can envelop the
planet gear so closely, that multi-pair teeth will be in contact to share
the torque and to reduce the stress on the teeth. Therefore, the weak part
is not the gears. It is not necessary to use special materials and high
accuracy as required by the Cyclo. Although its meshing parameters are
special and profile is unique, the KHV can be made by an ordinary
standard involute cutter, resulting in a low cost.
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