Single-Tooth Evoloid Planetary Gearbox for High-Ratio Load Capacity
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Solution Overview
Problem
Existing planetary gearboxes with high gear ratios suffer from lower load capacity due to planetary gear collisions, especially at ratios like i=12:1, and fail to achieve high torque transmission efficiently.
Innovation Solution
A planetary gear design with three rotating planetary gears equipped with evoloid gearing, featuring a sun gear with one tooth, planet gears with increased teeth count due to profile shift and shortening, and a ring gear with negative profile shift, allowing for high gear ratios like i=24:1 while preventing collisions and enhancing load capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a planetary gear with high gear ratio is designed using conventional methods, then the gear ratio is achieved, but the load capacity decreases due to planetary gear collisions
Solution Approach 1:
The patent applies parameter changes by modifying the profile shift coefficients and head height factors of the sun gear, planet gears, and ring gear. Specifically, the sun gear receives a large positive profile shift (x = +1.4 to +1.6) and head shortening (h aP = 0.1 to 0.2), while planet gears receive negative profile shift (x = -0.2 to -0.4) and the ring gear receives negative profile shift (x = -0.8 to -1.0). These parameter changes enable high gear ratios up to i=24:1 while preventing planetary gear collisions and maintaining high load capacity.
2Reliability
If the number of planetary gears is increased to three for better load distribution, then load capacity improves, but gear ratio is limited to approximately i=12:1 due to planetary gear collisions
Solution Approach 1:
The patent enables three planetary gears to operate at high gear ratios by implementing specific parameter changes: the sun gear is given a large positive profile shift factor of +1.4 to +1.6 and reduced head height factor of 0.1 to 0.2, while each planet gear receives a negative profile shift factor of -0.2 to -0.4. These modifications adjust the tooth engagement geometry to prevent collisions between planet gears, allowing the system to achieve high gear ratios of i=24:1 while maintaining three planet gears for optimal load distribution.
3Volume of moving object
If planet gear diameter is reduced for compact design, then space efficiency improves, but the number of teeth on planet gears decreases
Solution Approach 1:
The patent resolves this contradiction by applying negative profile shift to the planet gears (x = -0.2 to -0.4) and reducing the head height factor (h aP = 0.5 to 0.7). The negative profile shift modifies the tooth geometry to maintain adequate tooth count even with reduced planet gear diameter, enabling compact design while preserving sufficient teeth for reliable engagement.
4Quantity of substance
If sun gear head is shortened to increase planet gear teeth count, then planet gear engagement improves, but sun gear diameter decreases
Solution Approach 1:
The patent applies a large positive profile shift to the sun gear (x = +1.4 to +1.6) which compensates for the head shortening effect. Although the head height factor is reduced to h aP = 0.1 to 0.2 to allow more teeth on planet gears, the positive profile shift on the sun gear maintains its effective diameter and ensures proper engagement geometry.
Data Source
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AI summary
The invention relates to a planetary gearbox, comprising a sun gear having one tooth, a ring gear, planet gears and a planet carrier, on which the planet gears are rotatably arranged, wherein the sun gear, the planet gears and the ring gear have evoloid toothing. The invention further relates to a multi-stage planetary gearbox assembly. The aim of the invention is to create a planetary gearbox of the type in question which enables high load capacity even at high transmission ratios. This aim is achieved, according to the invention, in that three circulating planet gears are provided in a frame-fixed ring gear, the planet gears not hitting each other even at high transmission ratios of i=24:1 because of defined addendum modification coefficients and addendum coefficients of the individual gears of the gearbox.