Hypocycloid Gear Reduction for Compact Angle Detection
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Solution Overview
Problem
Conventional rotation angle detection apparatuses, such as potentiometers, require small diameter gears for a large reduction ratio, increasing costs due to the need for high dimensional and assembly accuracy, and result in a larger size and thicker design.
Innovation Solution
A rotation angle detection apparatus featuring a hypocycloid mechanism with a fixed-side internal gear and a movable-side internal gear, both concentric with the rotating shaft, and an external gear that meshes with them, allowing for a large reduction ratio without the need for small diameter gears, thereby reducing costs and thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If small diameter gears are used to obtain a large reduction ratio, then the reduction ratio is improved, but the manufacturing cost increases due to the need for high dimensional and assembly accuracy
Solution Approach 1:
The patent transitions from using small diameter gears to using large diameter internal gears, changing the dimensional approach to achieve the same reduction ratio. The internal gear structure allows for a different spatial arrangement that avoids the manufacturing difficulties of small gears while maintaining the required reduction ratio.
Solution Approach 2:
Instead of using external gears as in conventional designs, the patent employs internal gears where the gear teeth are cut inward toward the center. This inversion of the gear structure allows for easier manufacturing with standard equipment and reduces the need for extremely high dimensional accuracy.
2Power
If gears are disposed in multiple stages to obtain a large reduction ratio, then the reduction ratio is improved, but the apparatus thickness increases
Solution Approach 1:
The patent combines multiple gear functions into a single integrated internal gear structure. The internal gear achieves a reduction ratio equivalent to multiple external gear stages by utilizing its unique tooth geometry and meshing characteristics, thereby eliminating the need for multiple stacked gear stages and reducing overall apparatus thickness.
Solution Approach 2:
The internal gear configuration allows the reduction mechanism to be arranged in a different spatial dimension, utilizing the radial space more efficiently. This enables achieving high reduction ratios without increasing the axial thickness that would result from stacking multiple external gear stages.
3Power
If the number of teeth of the movable-side internal gear is made different from the fixed-side internal gear, then the reduction ratio is improved, but the gear design complexity increases
Solution Approach 1:
The patent utilizes changes in the number of teeth parameter between the fixed-side and movable-side internal gears to achieve the desired reduction ratio. By carefully selecting different tooth counts (e.g., 36 teeth for fixed-side and 35 teeth for movable-side), the system achieves precise reduction ratios while maintaining relatively simple gear geometries that can be manufactured with standard techniques.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The apparatus achieves a large reduction ratio with a smaller number of gears, reducing component count and cost, while maintaining a compact thickness and preventing gear non-rotatability through a carefully designed gap and lubricant system.
Implementation Method 1
an external gear rotatably disposed at a position separated from the rotating shaft in the rotating body, the external gear meshing with the first internal gear and the second internal gear
Data Source
AI summary
A rotation angle detection apparatus capable of reducing the cost and having a small thickness is provided. The rotation angle detection apparatus includes: a housing; a rotating shaft rotatably disposed in the housing; a first internal gear disposed concentrically with the rotating shaft and fixed to the housing; a second internal gear disposed concentrically with the rotating shaft, and rotatably disposed in the housing, the second internal gear having a number of teeth different from a number of teeth of the first internal gear; an external gear rotatably disposed at a position separated from the rotating shaft in rotating body, the external gear meshing with the first internal gear and the second internal gear; and a detection section that detects a rotation angle of the second internal gear.