Spiral Planetary Speed Reducer With Arc Tooth Profiles for High Ratio
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Solution Overview
Problem
Existing speed reduction mechanisms using planetary gears face a trade-off between increasing the reduction ratio and maintaining a small size, as reducing the number of planetary gears compromises strength, while increasing their size to ensure strength makes the mechanism larger.
Innovation Solution
The design incorporates a rotating shaft with a single spiral tooth pinion gear and multiple spiral tooth planetary gears that mesh with an internal spiral tooth gear, allowing for a higher reduction ratio while maintaining a compact size by ensuring the strength of the mechanism through optimized gear arrangement and tooth profile contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of planetary gears is reduced to increase the reduction ratio, then the reduction ratio increases, but the strength of the speed reduction mechanism decreases
Solution Approach 1:
The patent changes the tooth profile parameter from a standard straight tooth to an arc-shaped tooth profile. This parameter change allows the planetary gears to have both a smaller diameter (enabling higher reduction ratio with fewer gears) and sufficient strength (through the arc-shaped profile that distributes contact stress more effectively).
Solution Approach 2:
The patent applies curvature by designing the tooth profile cross-section as an arc shape rather than a straight line. This curved geometry allows for optimized contact between meshing teeth, distributing the load more evenly across the tooth surface. This enables the use of smaller planetary gears (higher reduction ratio) while maintaining the necessary strength through improved stress distribution.
2Strength
If the diameter of planetary gears is increased to ensure strength, then the strength increases, but the size of the speed reduction mechanism becomes large
Solution Approach 1:
The patent modifies the tooth profile parameter to an arc shape, which allows smaller diameter planetary gears to achieve the same or greater strength compared to larger gears with straight teeth. The arc-shaped profile optimizes the contact area and stress distribution, enabling strength enhancement without increasing gear diameter.
Solution Approach 2:
By introducing curvature in the tooth profile (arc-shaped cross-section), the patent enables smaller planetary gears to maintain sufficient strength. The curved geometry increases the effective contact area between meshing teeth, distributing loads more effectively and allowing downsizing of the planetary gears while preserving strength.
3Volume of moving object
If the reduction ratio is increased to achieve downsizing, then the size decreases, but the number of planetary gears must be reduced which compromises strength
Solution Approach 1:
The patent changes the tooth profile parameter to an arc shape, which compensates for the strength loss that would normally occur when reducing the number of planetary gears. This parameter change allows the mechanism to achieve downsizing through higher reduction ratio while the arc-shaped teeth maintain the necessary strength with fewer gears.
Solution Approach 2:
The curved arc-shaped tooth profile enables the speed reduction mechanism to use fewer planetary gears (achieving higher reduction ratio and downsizing) while maintaining strength. The curvature optimizes contact stress distribution, allowing the mechanism to be both smaller and sufficiently strong with reduced gear count.
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
This configuration enables an increased reduction ratio while downsizing the speed reduction mechanism, ensuring strength without enlarging the planetary gears, thus achieving efficient torque output in a compact form.
Implementation Method 1
a first gear provided on an outer peripheral portion of the rotating shaft and including a first tooth portion that extends spirally along a longitudinal direction of the rotating shaft; a plurality of second gears each including a spiral second tooth portion that meshes with the first tooth portion
Implementation Method 2
a speed reduction mechanism using planetary gears
Data Source
AI summary
A speed reduction mechanism has an increased reduction ratio while achieving downsizing. A speed reduction mechanism 30 includes a rotating shaft 10, a pinion gear 11 including a first tooth portion 11a extending spirally along a longitudinal direction Q1 of the rotating shaft 10, three planetary gears 12 including spiral second tooth portions 12e and arranged side by side in a circumferential direction Q2 of the rotating shaft 10, a housing portion 14 housing the three planetary gears 12, and an internal gear 13 including a spiral third tooth portion 13a meshing with the second tooth portions 12e. The first tooth portion 11a has at least a part of a tooth profile cross section formed in an arc shape. The second tooth portion 12e meshes with the first tooth portion 11a in a state of being in contact with a portion where the tooth profile cross section is arc-shaped.