Plug-In Stub Shaft Assembly With Helical Load Cancellation
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Solution Overview
Problem
Existing stub shaft assemblies for outer planetary axles in motor vehicles face challenges in optimizing production costs, noise characteristics, and ease of maintenance, particularly in supporting axial loads and facilitating disassembly without the need for jacking up the axle.
Innovation Solution
A stub shaft assembly with coaxially disposed inner and outer shafts, featuring helically toothed connections with matching helix angles to cancel out axial loads, and a releasable axial securing mechanism using a snap ring for simplified disassembly and reduced friction losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If bearings are used to support axial loads on the stub shaft, then the axial loads can be supported, but the device complexity and friction losses increase
Solution Approach 1:
The invention extracts and eliminates the bearing support structure from the stub shaft assembly. By using helical toothing with matched helix angles between the sun gear and planetary gears, the axial loads are canceled out through geometric configuration rather than mechanical support, removing the need for bearings and their associated complexity
Solution Approach 2:
The invention changes the geometric parameters of the gear toothing, specifically matching the helix angles of the sun gear and planetary gears. This parameter matching causes the axial load components to equal and opposite, canceling each other out and eliminating the need for axial load support structures
2Device complexity
If a one-piece shaft is used, then the structure is simple, but the disassembly requires jacking up the axle which reduces ease of operation
Solution Approach 1:
The stub shaft is segmented into two separate pieces: an inner shaft and an outer shaft. These segments can be independently assembled and disassembled without requiring jacking up the axle, as the connection between segments uses the helical toothing mechanism that engages and disengages through rotational motion rather than axial force
3Loss of energy
If helical toothing with matched helix angles is used, then axial loads are canceled and friction losses are reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The invention uses parameter changes by matching the helix angles of the gear toothing. By setting the helix angles of the sun gear and planetary gears to be equal, the axial load components are made equal and opposite, canceling each other out. This also optimizes the friction characteristics by ensuring proper contact between gear teeth
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 costs, installation space, maintenance, and lubrication needs, while enhancing efficiency by allowing axial load-free operation and simplified disassembly without jacking, thereby improving the structural and functional performance of the stub shaft assembly.
Implementation Method 1
a first helical toothing (11) on the inner shaft (9) and a second helical toothing (11) on the outer shaft (10)... the first helical toothing (11) and/or the second helical toothing (11)... and a toothing of the sun gear (4)... can have such helix angles that at least approximately the same axial displacements can be effected
Data Source
AI summary
A stub shaft assembly for an outer planetary axle (1) of a motor vehicle includes an inner shaft (9) and an outer shaft (10) comprising a helically toothed sun gear (4). A pair of toothings (11) with a first helical toothing and a second helical toothing is effective between the inner shaft (9) and the outer shaft (10). Also disclosed is an outer planetary axle (1) for a motor vehicle comprising at least one such stub shaft assembly.