Electric Power Tool Planetary Gear Shift Mechanism
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Solution Overview
Problem
Conventional electric power tools with planetary gear trains face difficulties in reliably changing the reduction ratio due to locking issues when the movable member's teeth contact those of the target gear, preventing smooth gear shifting at multiple stages.
Innovation Solution
The electric power tool incorporates a cylindrical reducer case with a slide hole and a rotary plate having an obliquely extended operation slot, a supporting member, and a biasing unit, such as elastic bodies or magnets, to ensure the movable member can engage with a target gear by applying a pressing force, allowing for reliable reduction ratio changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the movable member slides to engage with the target gear, then the reduction ratio can be changed, but the facing surfaces of the teeth may contact and lock the movable member at an incorrect position
Solution Approach 1:
The patent introduces a guiding member as an intermediary component between the movable member and the target gear. The guiding member has a guiding surface that guides the movable member during sliding engagement, ensuring that the teeth of the movable member align with the teeth of the target gear before engagement. This mediator prevents direct contact between the facing surfaces of the teeth, eliminating the locking problem while maintaining reliable engagement and reduction ratio changeability.
2Reliability
If the teeth of the movable member and target gear are positioned between adjacent teeth for engagement, then reliable engagement is achieved, but the structure becomes more complex
Solution Approach 1:
The guiding member performs the preliminary action of aligning the teeth of the movable member with the teeth of the target gear before the actual engagement occurs. By providing a guiding surface that pre-positions the components correctly during the sliding motion, the system achieves reliable engagement without requiring complex interlocking tooth structures or multiple engagement points, thus maintaining simplicity while ensuring reliability.
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 reliable engagement of the movable member with the target gear, facilitating smooth changes in reduction ratio without unnecessary force, reducing component complexity, and minimizing friction-related wear.
Implementation Method 1
a biasing unit for applying a pressing force to the supporting member in a moving direction of the supporting member when the rotary plate is rotated to a position by the driving unit
Data Source
Figure 1A~1B
Figure 1C
Figure 2A~2C
AI summary
An electric power tool includes a cylindrical reducer case a (4) ccommodating the speed reduction mechanism (2). The speed reduction mechanism includes a planetary gear train (21) and a movable member (31) which is axially slidable to be engaged with or disengaged from the planetary gear train. The electric power tool includes the reducer case (4) including a slide hole (42) formed through a sidewall of the reducer case and axially extended and a rotary plate (5) which is rotatable around a periphery of the reducer case about the axis, the rotary plate including an operation slot (51) formed axially obliquely and overlapped with the slide hole; a supporting member (34) radially outwardly protruded from the movable member and extended through the slide hole (42) and the operation slot (51); and a biasing unit (6) for applying a pressing force to the supporting member in a moving direction of the supporting member when the rotary plate (5) is rotated to a position.