Hand-held Power Tool Rear Bearing Inversion
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Solution Overview
Problem
In electric power tools with cup-shaped housings, the movable rear bearing relative to the armature shaft absorbs bearing forces, necessitating a larger front bearing, which occupies valuable space and affects electromagnetic compatibility (EMC).
Innovation Solution
The rear bearing is replaced with a fixed bearing, allowing for a smaller front bearing and improved EMC by using a roller bearing or combined radial/axial bearing, and additional support elements like detent elements or plastic parts to prevent movement, optimizing space and transmission design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a movable rear bearing is used to support the armature shaft, then the bearing forces are absorbed by the rear bearing, but the front bearing must be larger in dimension to compensate
Solution Approach 1:
The patent inverts the conventional bearing arrangement by making the rear bearing fixed and the front bearing movable. This reversal allows the rear fixed bearing to effectively absorb bearing forces while enabling the front bearing to be smaller in dimension, thus resolving the contradiction between force absorption capability and bearing size.
2Reliability
If a larger front bearing is used to compensate for the movable rear bearing, then bearing support is improved, but space in the front region of the armature shaft is reduced
Solution Approach 1:
By inverting the bearing configuration to have a fixed rear bearing and a smaller movable front bearing, the patent achieves adequate bearing support while preserving valuable space in the front region of the armature shaft for other components.
3Volume of moving object
If the front bearing is positioned closer to the armature stack, then space is saved, but electromagnetic compatibility and electrical contacting are degraded
Solution Approach 1:
The inverted bearing arrangement allows the front bearing to be smaller and positioned optimally without compromising electromagnetic compatibility. The fixed rear bearing provides stable electrical contacting through the commutator region, resolving the contradiction between space utilization and EMC performance.
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 reduces the size of the front bearing, saves space, enhances EMC, and improves electrical contacting, allowing for more compact and efficient transmission design in electric power tools.
Implementation Method 1
the rear bearing is embodied in the form of a roller bearing in order to absorb powerful forces. Preferably, the roller bearing is a ball bearing equipped with a plurality of balls situated one after another in the circumference direction and arranged in a cage comprised of a radially inner raceway and a radially outer raceway
Data Source
AI summary
The invention relates to an electric tool, in particular a hand-held electric tool, having a housing, which has a rear housing part and at least one front housing part arranged in front of the rear housing part in the longitudinal direction of the electric tool, and an electric drive motor having an armature shaft that extends in the longitudinal direction of the electric tool. The armature shaft is rotatably mounted together with a rear bearing arranged at the rear housing part. According to the invention, the rear bearing is designed as a fixed bearing.