Telescoping Longitudinal Shaft Assembly Crash Energy Absorption
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Solution Overview
Problem
Longitudinal shaft assemblies in motor vehicles face challenges in crash behavior, where components may detach and penetrate the passenger compartment or fuel tank, risking injury and fire, and existing designs struggle to absorb deformation energy effectively during crashes.
Innovation Solution
A longitudinal shaft assembly design featuring a hollow first shaft with a spigot and a ball-type constant velocity joint, supported by a central rolling bearing, which telescopes during crashes to absorb deformation energy through controlled axial forces and diameter reductions, preventing deflection and maximizing energy absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the longitudinal shaft assembly is designed with rigid components to maintain structural stability, then the strength and reliability are improved, but the ability to absorb deformation energy during crashes deteriorates
Solution Approach 1:
The longitudinal shaft assembly is designed with telescoping capability, allowing the shafts to move relative to each other axially during crashes. This dynamic behavior enables the structure to adapt to crash forces by extending or compressing, thereby absorbing deformation energy while maintaining structural integrity during normal operation.
Solution Approach 2:
The shafts are designed with variable cross-sectional properties, including hollow sections with optimized wall thicknesses. This allows the structural parameters to be adjusted along the length of the shafts, providing both strength where needed and controlled deformation zones for energy absorption during crashes.
2Reliability
If the longitudinal shaft assembly is designed to prevent component detachment, then the reliability is improved, but the deformation energy absorption capability deteriorates
Solution Approach 1:
The longitudinal shaft assembly is divided into multiple shafts (first shaft, second shaft, third shaft) connected by constant velocity joints. This segmentation allows each shaft to be optimized independently - some sections for strength and connection security, others for controlled deformation and energy absorption during crashes.
Solution Approach 2:
Constant velocity joints serve as intermediary elements between the shafts, providing secure connections that prevent component detachment while allowing controlled relative movement. These joints enable the telescoping action necessary for energy absorption while maintaining reliable power transmission during normal operation.
3Strength
If the shafts are designed as solid shafts to maximize bending strength, then the strength is improved, but the weight increases
Solution Approach 1:
The shafts are designed as hollow shafts with optimized wall thicknesses rather than solid shafts. This composite-like structure provides high bending strength-to-weight ratio, maintaining the necessary structural strength while significantly reducing the overall weight of the longitudinal shaft assembly.
Solution Approach 2:
The shafts feature variable wall thicknesses along their length, with thicker sections at critical locations requiring higher strength and thinner sections where less strength is needed. This local optimization of material distribution maximizes bending strength while minimizing overall weight.
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
The design effectively absorbs crash energy by controlled deformation, reducing the risk of component deflection and penetration into the vehicle interior, while maintaining coaxiality and preventing excessive deformation that could lead to component failure.
Implementation Method 1
the outer ring is designed to deform in the event of a crash, so that axial forces are reduced as a result of the deformation of the outer ring
Implementation Method 2
the shafts are connected to one another by means of a ball-type constant velocity joint which preferably has a limited range of axial displacement. Through the axial displacement range of the ball-type constant velocity joint, movements of individual components of the longitudinal shaft assembly or of the motor vehicle in the longitudinal direction of the vehicle are compensated. In addition, deflections of the shafts with respect to one another arising from the ball-type constant velocity joint are compensated by articulation of the constant velocity joint.
Data Source
AI summary
A longitudinal shaft assembly for a motor vehicle, comprising at least a first shaft and a second shaft, a ball-type constant velocity joint for connecting the first shaft to the second shaft and at least one central bearing for supporting the longitudinal shaft assembly with respect to a body of the motor vehicle.