Switchable Planetary Gear Set for High Torque Handheld Tools
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Solution Overview
Problem
Existing hand-held power tools with planetary gears face limitations in achieving a large gear spread, typically restricted to less than 5 times reduction, which limits torque and requires larger or more powerful motors, and lacks efficient control over slow rotational speeds.
Innovation Solution
A switchable planetary gear design with at least three axial planetary carriers and a hollow-cylindrical switching ring gear that can be adjusted to couple with either the first or second/third-stage planet carriers, allowing for a gear spread greater than 5, enabling high torque and reduced motor requirements, with a simple design using uniform or varying toothing geometries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional two-stage planetary gear is used, then the device complexity is low, but the gear spread is limited to less than 5 times reduction
Solution Approach 1:
The patent implements nested planetary stages where the second and third stage planetary gears are positioned inside the ring gear. The second stage planetary carrier is surrounded by the ring gear, and the third stage planetary gears are arranged within the space between the second stage planetary carrier and the ring gear. This nesting arrangement enables a gear spread greater than 5 times reduction while maintaining a compact structure without proportionally increasing device complexity
Solution Approach 2:
The patent divides the transmission system into three distinct planetary stages (first, second, and third stages) with separate planetary carriers and gear sets. Each stage provides independent gear reduction, and their combined effect achieves the desired gear spread greater than 5. This segmentation allows flexible configuration of reduction ratios while keeping each individual stage relatively simple
2Force
If the gear spread is increased to achieve high torque, then the torque in slow gears is improved, but the motor size and power requirements increase
Solution Approach 1:
By nesting the second and third stage planetary gears inside the ring gear, the patent achieves high gear spread (greater than 5 times reduction) in a compact arrangement. This enables high torque multiplication without requiring a larger motor, as the compact nested structure efficiently transmits and multiplies the motor's output torque through multiple planetary stages
3Ease of operation
If the rotational speed is reduced for better control, then the control over work result is improved, but the productivity decreases
Solution Approach 1:
The patent provides a switchable planetary gear mechanism that allows dynamic selection between different gear stages (first, second, and third stages) with different reduction ratios. The switching ring gear can be adjusted axially to engage with different planetary carriers, enabling the operator to select the appropriate gear stage for the current task. This dynamic switching capability allows optimization between control precision (using higher reduction stages) and productivity (using lower reduction stages) based on real-time operational requirements
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 design achieves a gear spread greater than 5, allowing for high torque in slow gears, reduced motor size, and improved control with slower rotational speeds, while maintaining a compact and component-efficient structure.
Implementation Method 1
the switching ring gear (16) is rotationally coupled to an adjacent planet carrier (8) of a first stage, in particular magnetically coupled, in such a way that the first planet carrier (8) rotates at the same speed as the switching ring gear (16)
Data Source
Figure 1
AI summary
A switchable planetary gear set in a handheld machine tool (1) has a plurality of planet carriers (8, 9, 10) with associated planet gears (12, 13, 14) and can be adjusted between at least two gear stages, wherein the gear stages can be engaged by means of an adjustable switching ring gear (16). At least three planet carriers (8, 9, 10) with associated planet gears (12, 13, 14) are provided so as to be situated axially one behind the other, wherein in a position in which it is fixed with respect to a housing, the switching ring gear (16) is rotationally coupled to the planet gears on the planet carrier of the second stage (13) and simultaneously to the planet gears on the planet carrier of the third stage (14).