Handheld Power Tool Housing Frictional Clamping for Bearing Preload
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Solution Overview
Problem
Hand-held power tools with motor-driven pneumatic percussion mechanisms face challenges in managing high radial forces, which can reduce the service life of roller bearings due to inadequate preload, leading to inefficient operation and reduced durability.
Innovation Solution
The solution involves a non-positive connection between housing shells that allows for axial preload of roller bearings, ensuring a compact and reliable structure by adjusting the axial distances between bearing shells and housing components, thereby distributing tension effectively across the bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the outer bearing shells are tightly fixed into the housing shells, then the structural stability is improved, but the axial preload on the rolling bearings cannot be achieved
Solution Approach 1:
The housing is divided into two separate housing shells (first housing shell and second housing shell) that are connected via a frictional connection through contact surfaces. This segmentation allows independent adjustment of axial distances and enables the application of axial preload to the bearings while maintaining structural stability through the controlled frictional connection between the two housing shells.
2Volume of moving object
If the axial distance between inner bearing shells is reduced, then the compactness is improved, but the rolling bearings cannot be properly preloaded under high radial forces
Solution Approach 1:
The solution introduces a second axial dimension for adjustment by varying the axial distance between the outer bearing shells (third and fourth axial distances) independently from the axial distance between inner bearing shells. This dimensional separation allows the housing shells to be deformed axially to apply preload to the bearings while maintaining compact overall dimensions, effectively decoupling the two distance parameters.
3Reliability
If the housing shells are made deformable, then the axial preload can be applied to bearings, but the structural rigidity is reduced
Solution Approach 1:
The housing shells are designed with controlled deformability in the axial direction, allowing them to be elastically deformed to apply axial preload to the bearings. The frictional connection between the two housing shells through contact surfaces maintains structural rigidity in other directions while permitting the necessary axial deformation for bearing preload application.
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 enhances the service life of roller bearings by providing a consistent axial preload, improving the tool's operational efficiency and durability under high radial forces, especially in eccentric applications.
Implementation Method 1
the first and second housing shells are clamped parallel to the shaft by the frictional connection. This clamping force is partially transferred to the rolling bearings, preferably ball bearings.
Data Source
Figure 1
Figure 2~3
AI summary
A hand-held power tool has a shaft (22) that couples a motor (5) to a tool-driving unit (6). The shaft (22) is supported in two rolling bearings (34, 35). The inner bearing shells (37, 46) of the rolling bearings are mounted on the shaft (22) at a first axial distance (48) from each other. A housing (28) has a second housing shell (30) connected to a first housing shell (29) by a frictional connection. The outer bearing shell (36) of the first rolling bearing is inserted into the first housing shell, and the outer bearing shell (45) of the second rolling bearing is inserted into the second housing shell. The outer bearing shells are at a second axial distance (51, 52). The first axial distance is selected relative to the second axial distance such that the first housing shell and the second housing shell are clamped parallel to the shaft by the frictional connection.