Spindle Bearing Support in Hand-Held Power Tools
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Solution Overview
Problem
Hand-held power tools, such as cordless screwdrivers, face a trade-off between achieving low concentricity error and short overall length, as increasing bearing spacing improves concentricity but at the expense of mechanical rigidity and length, while minimizing bearing spacing compromises concentricity and rigidity.
Innovation Solution
A design where the motor-side bearing is radially supported on a rotating transmission component, allowing for a longer bearing distance and high concentricity without additional components, with the motor-side bearing connected axially to the spindle and optionally supported in both axial directions, using a planetary gear to reduce motor speed to spindle speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the bearing spacing is increased to improve concentricity, then the concentricity of the spindle is improved, but the overall length of the drive train increases and mechanical rigidity decreases
Solution Approach 1:
The patent repositions the motor-side bearing from the stationary gearbox housing to a rotating transmission component (planet carrier or pinion), utilizing the rotational dimension of the transmission component to provide bearing support. This dimensional shift allows the bearing to be located closer to the spindle end face while maintaining stability through the rotating support structure, thereby achieving long bearing spacing without proportionally increasing overall length.
Solution Approach 2:
The transmission component (planet carrier or pinion) serves dual functions: it transmits mechanical power from the motor to the spindle while simultaneously providing radial support for the motor-side bearing. This multi-functionality eliminates the need for separate stationary bearing housings, allowing compact integration of bearing support within the rotating transmission element and reducing overall drive train length.
2Manufacturing precision
If the bearing spacing is increased to improve concentricity, then the concentricity of the spindle is improved, but the mechanical rigidity of the structure decreases
Solution Approach 1:
The patent transitions from a static bearing support system (fixed to stationary gearbox housing) to a dynamic bearing support system (attached to rotating transmission component). The dynamic rotation of the planet carrier or pinion provides continuous radial support to the motor-side bearing, maintaining mechanical rigidity even with increased bearing spacing, as the rotating component naturally resists radial loads through its rotational motion and structural integrity.
3Device complexity
If the motor-side bearing is supported on the stationary gearbox housing, then the structure is simple, but power loss increases due to friction
Solution Approach 1:
The patent introduces the rotating transmission component (planet carrier or pinion) as an intermediary between the motor-side bearing and the stationary gearbox housing. This intermediary rotates with the drive train, reducing relative motion and friction between the bearing support and stationary components, thereby minimizing power loss while maintaining structural simplicity through existing transmission elements.
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 compact axial structure with high concentricity quality and reduced power loss, maintaining mechanical rigidity while minimizing costs, as no additional components are required, and allows for various bearing configurations such as floating or fixed bearings.
Implementation Method 1
The gearbox is designed as a planetary gearbox, which preferably has two or more stages for reducing the drive speed of the electric drive motor to the spindle speed
Implementation Method 2
The motor-side bearing is designed as a floating bearing with axial movement, whereas the tool-side bearing is expediently designed as a fixed bearing with axial locking relative to the housing of the hand-held power tool
Data Source
AI summary
The invention relates to a hand-held power tool comprising a gearbox (4) which is coupled to a spindle (5) for receiving a tool. Said spindle is mounted above a tool-sided bearing (6) and a motor-sided bearing (7), and the motor-sided bearing is radially supported on a component (12) of the gearbox.