Gearbox Limiting Member Prevents Ring Gear Skipping
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Solution Overview
Problem
Current power tools with gearbox assemblies, such as electric drills, experience gear skipping due to deformation of the gearbox box during long-term use, which affects gear shifting stability.
Innovation Solution
A gearbox assembly design featuring a first case and a second case coupled to form an accommodating cavity, with a ring gear, planet gear, and sun gear, where a limiting member made from a harder material than the first case material is undetachably connected to prevent axial movement of the ring gear, thereby locking its rotation and preventing gear skipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the box is formed from aluminum and uses a step structure to limit ring gear position, then the device complexity is reduced and ease of manufacture is improved, but the reliability deteriorates due to deformation during long-term use causing gear skipping
Solution Approach 1:
The limiting member is divided into multiple functional portions: a locking portion for circumferential locking, a limiting portion for axial positioning, and connection features for integration with the box. This segmentation allows each portion to perform its specific function effectively while maintaining overall reliability.
Solution Approach 2:
The limiting member is formed from a second material different from the aluminum first material, creating a composite structure where the harder limiting member is embedded in or connected to the softer aluminum box. This composite approach provides both the deformation resistance needed for reliability and the ease of manufacture from aluminum.
2Reliability
If a limiting member with locking portion is added to prevent gear skipping, then the reliability is improved, but the ease of manufacture deteriorates due to additional manufacturing steps
Solution Approach 1:
The limiting member is undetachably connected to the first case, merging two components into a single integrated assembly. This eliminates the need for separate installation and maintenance of the limiting member, improving ease of manufacture despite the added complexity of the limiting member itself.
Solution Approach 2:
The limiting member serves multiple functions simultaneously: it provides circumferential locking through the locking portion, axial positioning through the limiting portion, and structural support through its integration with the box. This multi-functionality reduces the need for additional separate components.
3Reliability
If the ring gear is allowed to move axially, then the adaptability is improved for different operating conditions, but the reliability deteriorates due to potential gear skipping
Solution Approach 1:
The ring gear is configured to be axially movably disposed in the accommodating cavity, allowing controlled movement within limits set by the limiting portion. This dynamic configuration provides adaptability for different operating conditions while the locking portion prevents circumferential skipping, resolving the contradiction between movement freedom and gear stability.
Data Source
AI summary
A power tool includes a motor, an output shaft and a gearbox assembly. The output shaft outputs torque when driven by the motor to rotate around a first axis. The gearbox assembly transmits power between the motor and the output shaft. The gearbox assembly includes a first case and a second case. The first case and the second case are configured to be coupled to each other to form an accommodating cavity. The gearbox assembly further includes a ring gear, a planet gear, a sun gear, and a front ring gear. The ring gear is rotatably disposed in the accommodating cavity. The planet gear is engaged with the ring gear. The sun gear is engaged with the planet gear.