Integrated Planetary Gear Shaft Reduces Volume and Strength Trade-off
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Solution Overview
Problem
Existing planetary gear mechanisms face challenges in reducing volume while maintaining sufficient strength, particularly in mechanical devices where repair and durability are critical, and they often require large rotary shaft diameters to handle high torque, leading to increased volume.
Innovation Solution
A power transmission member with an integrated planetary gear holding portion, rotary shaft portion, and sun gear holding portion that allows for the attachment of planetary gears in a freely turnable manner without the need for separate planetary pins, enabling reduced volume and enhanced strength through a cylindrical design and integrated structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a through-hole is formed at the rotary center portion of each planetary gear to insert a planetary pin, then the planetary gear can be attached to the planetary carrier in a freely turnable manner, but the rim thickness is reduced and dedendum strength cannot be secured
Solution Approach 1:
The invention extracts the planetary pin as a separate component and replaces it with an integrated shaft portion formed directly on the planetary gear body. This eliminates the need for a through-hole at the rotary center, thereby preserving the full rim thickness and dedendum strength of the planetary gear while still achieving the desired attachability to the planetary carrier.
Solution Approach 2:
The shaft portion is merged integrally with the planetary gear body, forming a unified structure. This combination eliminates the separate planetary pin and the through-hole requirement, allowing the planetary gear to be attached to the planetary carrier without compromising its structural integrity and strength.
2Strength
If large rotary shaft diameters are used to handle high torque, then sufficient strength against torsional forces is achieved, but the volume of the planetary gear mechanism increases
Solution Approach 1:
The integrated structure of the planetary gear with the shaft portion eliminates the need for a separate large-diameter rotary shaft. The shaft portion is optimally sized and positioned to handle torsional forces efficiently, reducing the overall volume of the mechanism while maintaining sufficient strength.
Solution Approach 2:
Instead of increasing the diameter of the rotary shaft in one dimension to handle torque, the invention redistributes the torque handling capability across the integrated planetary gear and shaft portion structure, utilizing the radial and axial dimensions more efficiently to achieve the required strength with reduced overall volume.
3Device complexity
If the planetary gear is sandwiched between a pair of divided planetary carriers and fastened by screwing or caulking, then the planetary gear can be attached without a planetary pin, but sufficient strength against torsional force cannot be secured
Solution Approach 1:
The planetary carrier is designed as an integrated single piece rather than divided sections, and the planetary gear with its shaft portion is directly attached to this unified structure. This integration provides superior torsional strength compared to the divided carrier approach with screwing or caulking fastening methods.
Solution Approach 2:
The shaft portion is preliminarily formed integrally with the planetary gear body during manufacturing, preparing the structure in advance for direct attachment to the planetary carrier. This preliminary formation ensures that the attachment structure is optimized for torsional strength from the outset, rather than relying on post-assembly fastening methods.
Data Source
AI summary
A power transmission member is disclosed. The power transmission member allows a planetary gear mechanism to be reduced in volume while sufficient strength is guaranteed. A planetary gear holding part, a rotating shaft part, and a sun gear holding part constituting a power transmission member are formed integrally. The rotating shaft part is substantially cylindrical, and a planetary gear can be passed through the interior of the rotating shaft part and turnably mounted on the planetary gear holding part. An open window is formed in the planetary gear holding part, and a toothed part of the planetary gear is configured to mesh with a bearing-equipped outer gear through the open window.