Frictional planetary roller mechanism and brake

A method of fabricating a frictional transmission apparatus comprising:

• a simple planetary roller mechanism having friction rollers including a sun roller, a planetary roller, and a ring roller, said planetary roller being retained by a carrier and making rolling contact with the outer periphery of said sun roller and with the inner periphery of said ring roller, said ring roller applying a squeezing force to said planetary roller and said sun roller;
• and a brake mechanism coupled to said sun roller to brake rotation of said sun roller, said method comprising the step of
• setting said squeezing force from said ring roller so that critical test torque falls within the range of 1.4-10.0 times static friction torque obtainable from said brake mechanism,
• where said critical test torque is a measurement of test torque at which any of said friction rollers starts to make sliding rotation when said test torque is input in gradually increasing values to said sun roller with said carrier and said ring roller fixed stationary.

A frictional transmission type rotational driving apparatus comprising a simple planetary roller mechanism and a motor, said simple planetary roller mechanism having friction rollers including a sun roller, a planetary roller, and a ring roller, said planetary roller being retained by a carrier and making rolling contact with the outer periphery of said sun roller and with the inner periphery of said ring roller, said motor being coupled to said sun roller to drive said sun roller, wherein:

• a brake mechanism is added to said motor;
• Y<Xd holds,
• where Y is static friction torque obtainable from said brake mechanism and Xd is a value of test torque at which any of said friction rollers starts to make sliding rotation when said test torque is input in gradually increasing values to said sun roller with said carrier and said ring roller fixed stationary;
• and
• 0.65Ys<Xs<3.4Ys holds,
• where Ys is dynamic friction torque obtainable from said brake mechanism at a rated revolution speed of said motor, and Xs is limit transmission torque transmittable by said simple planetary roller mechanism through said sun roller when said sun roller is rotated at said rated revolution speed.