Patent ID: 7510495
Filing Date: 2009-03-31
Classification: F16H

Abstract:
1. An automatic speed reducing ratio-switching apparatus comprising: a planetary gear mechanism including an input shaft and an output shaft, said planetary gear mechanism further including a sun gear, planet gears, and an internal gear, each of which are helical gears, and a carrier that rotatably supports said planet gears and which is integrally rotated in accordance with revolution of said planet gears; a viscous resistance member, which is provided within an inner section of said carrier internally inserted into said internal gear, said planet gears, and said internal gear, and which generates a thrust force between said internal gear and said planet gears; and a brake mechanism that causes said internal gear to be displaced in parallel by said thrust force, in a direction toward said input shaft or a direction toward said output shaft, in accordance with increase or decrease in output load, in order to brake rotational motion of said internal gear, wherein a helix angle θ of each of said helical gears making up said sun gear, said planet gears, and said internal gear, is not less than 25 degrees and not more than 45 degrees.