Cycloidal Drives
The
mechanism through which the speed of an input shaft is reduced by a fixed
ratio, is known as a Cycloidal Reducer or Cycloidal Drives. The word
Cycloidal has been derived from
Hypocycloidal, which means
the curve traced by a point on the circumference of the circle. This curve
tracing process repeats inside the circumference of a larger fixed circle.
The path traced by a tooth of a planetary pinion which rotates inside a ring
gear, is similar to the curve tracing by a point on the circumference of a
circle.
Internal Configuration: Cycloidal Drives
Up to a certain extent, the appearance of the internal configuration of
Cycloidal Drives is similar to an internal gear pump, but here the output
shaft is driven by an outer gear. A bearing which has been departed from its
usual/regular form is driven by the input shaft drives. In turn, the
Cycloidal disc is driven by this departed bearing in an eccentric. The
cycloidal disc starts to move in cycloidal motion. In compare to a
stationary
ring gear, the Cycloidal Drives have a larger perimeter. Through out the face of the cycloidal disc, there are output shaft pins or rollers present in series. When the Cycloidal disc starts to rotate, the output shaft is directly driven by these output shaft pins. The radial motion which
is generated during the motion of the Cycloidal disc, is not translated to
the output shaft.
A closely and firmly attached cycloidal input gear set and a low speed
helical output gear set are present in the Cycloidal Drives. This
combination represents a very durable, quiet and efficient gearbox. A high
speed shaft along with a bearing which has been departed from its
usual/regular form and a low speed shaft assembly are the main elements in a
Cycloidal drive. It also consists cycloidal discs but number of lobe is one
less than the number of ring gear pin. The pins and ring gear roller are
fixed in the Cycloidal drives.
Characteristics of Cycloidal Drives
The transmission system provided by the Cycloidal drives are very durable
and efficient and having five times more shock load capacity. But, along
with this advantage, there are some disadvantages also. Due to their method
of transmitting motion, they show inflected torque and speed. The ripples
are caused from the eccentric motion inside the drive, and slowed speed is
the evidence of it. Industries, where smooth motion is require, problems are
generated due to these ripples. To achieve ratio below 50:1 is very hard and
also the torsional stiffness of the Cycloidal drives is low. The other
disadvantages of Cycloidal Drives are the high initial as well their high
maintenance cost.
Applications of Cycloidal Drives
For different applications, the Cycloidal drives are useful. These drives
are suitable in boats. These drives turn their propeller blades vertically
and generate lift over them. These drive vessels comparatively having deep
drafts and therefore, these are not very suitable in swallow water. These
drives have proved their reliability and robust capacity in the boat
industry.
