Planetary Reducer Speed Switching in Compact Power Tools
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Solution Overview
Problem
Existing power tools with reducers face challenges in reducing size while maintaining smooth and stable switching between variable speeds, often resulting in mechanical obstructions and inefficiencies due to internal gear movement and tilting.
Innovation Solution
A power tool design featuring a reducer with rotatable internal gears, planetary gears, and an engagement member that allows selective switching between different reduction ratios, enabling compact size and stable speed transitions through an actuator-operated mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the internal gear is moved with a stroke to switch between variable speeds, then speed switching is enabled, but the size in the axial direction increases and the internal gear may tilt causing improper meshing
Solution Approach 1:
Instead of moving the internal gear axially to switch speeds, the invention inverts the approach by rotating the internal gear about its own axis. The engagement member selectively engages different teeth on the internal gear at different rotational positions, achieving variable speed switching without axial movement. This eliminates the tilting problem and reduces axial size.
Solution Approach 2:
The invention introduces a dynamic rotational mechanism where the internal gear can rotate about its axis to different angular positions. The engagement member dynamically selects different teeth on the internal gear based on the rotational position, enabling smooth transition between speed ratios without mechanical stroke or tilting.
2Adaptability or versatility
If the internal gear is moved axially to switch between variable speeds, then speed switching is enabled, but meshing stability deteriorates due to gear tilting
Solution Approach 1:
The invention inverts the speed switching mechanism from axial movement to rotational movement. By rotating the internal gear about its axis and selectively engaging different teeth at different rotational positions, the invention maintains stable meshing throughout the switching process, eliminating the tilting that causes meshing instability.
Solution Approach 2:
The engagement member acts as an intermediary that selectively connects to different teeth on the internal gear based on rotational position. This intermediary mechanism ensures smooth and stable transmission of motion and force during speed switching, maintaining meshing stability while enabling variable speed operation.
3Power
If multiple planetary gear stages are arranged axially, then reduction ratios are achieved, but the axial length increases
Solution Approach 1:
The invention nests multiple planetary gear stages within a compact radial arrangement rather than extending them axially. The planetary gears and carriers are positioned radially around the central axis, with the internal gear rotating about this axis. This nesting approach achieves multiple reduction ratios while minimizing axial length.
Solution Approach 2:
The invention transitions from axial arrangement to radial arrangement of planetary gear stages. By organizing the gear stages in the radial dimension and using rotational position to select different stages, the invention achieves the same power reduction functionality with significantly reduced axial length.
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
The solution enables a compact power tool with smooth and stable variable speed switching, reducing mechanical losses and improving usability by allowing precise control of speed transitions without obstructive gear tilting.
Implementation Method 1
at least two stages of planetary gears aligned in an axial direction, the planetary gears in the at least two stages being configured to revolve within the preceding internal gear and the succeeding internal gear
Data Source
AI summary
A power tool with a small size in an axial direction includes a reducer allowing smooth and stable switching between variable speeds. The power tool includes a motor, a reducer that reduces rotation from the motor, and an actuator actuated by the rotation reduced by the reducer. The reducer includes a preceding internal gear in a preceding stage, a succeeding internal gear in a succeeding stage, an engagement member radially outward from the internal gears and switchable between a first position to restrict rotation of the preceding internal gear and a second position to restrict rotation of the succeeding internal gear, planetary gears that revolve within the internal gears, carriers supporting the planetary gears, and an operation unit to switch the engagement member selectively to the first position or the second position.