Longitudinal Drive Shaft Crash Telescoping Mechanism
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Solution Overview
Problem
Existing longitudinal drive shafts for motor vehicles are prone to uncontrolled bending during crashes, which can lead to penetration into the passenger space and injuries, and have limitations in crash path length and stability due to their design.
Innovation Solution
A longitudinal drive shaft with a homokinetic displacement joint and center bearing that allows telescoping of shaft sections during a crash, featuring a sealed homokinetic displacement joint with a closure lid that breaks at predetermined points to facilitate unhindered telescoping and prevent bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the inside diameters of the outer joint part are configured to be smaller than the outside diameter of the inner joint part to absorb energy through friction and widening, then energy absorption is improved, but uncontrolled bending out of the longitudinal drive shaft occurs during crash
Solution Approach 1:
The longitudinal drive shaft is divided into multiple shaft sections (first shaft section, second shaft section) connected by separable joints (homokinetic displacement joint, center bearing). This segmentation allows controlled telescoping of individual sections during crash while preventing uncontrolled bending of the entire shaft assembly.
Solution Approach 2:
A closure lid is introduced as an intermediary component that guides the telescoping motion of shaft sections during crash. The closure lid with its predetermined breaking points ensures controlled energy absorption while maintaining shaft stability, preventing both uncontrolled bending and penetration into passenger space.
2Loss of energy
If the shaft journal is made longer to increase crash path length for energy absorption, then energy absorption is improved, but bending-critical speeds occur that adversely affect rotation stability
Solution Approach 1:
The shaft is segmented into multiple sections that telescope independently during crash. This allows the effective crash path length to be increased without requiring a single excessively long shaft journal, thereby avoiding bending-critical speeds and maintaining rotation stability.
Solution Approach 2:
Instead of increasing the length of a single shaft journal in one dimension, the solution uses telescoping of multiple shaft sections along the axial direction. This dimensional approach increases the effective crash path length while keeping individual shaft section lengths within stable rotational speed ranges.
3Loss of energy
If axial stopping means are provided in the outer joint part to support the inner joint part during crash, then controlled energy absorption is achieved, but the shaft journal cannot be freely selected in length and maximal crash path length is limited
Solution Approach 1:
The drive shaft is segmented into multiple telescoping sections, which eliminates the constraint on shaft journal length selection. Each section can be independently dimensioned, providing design freedom while achieving controlled energy absorption through the telescoping mechanism.
Solution Approach 2:
The shaft system transitions from a static rigid structure to a dynamic telescoping structure during crash. The homokinetic displacement joint and center bearing enable controlled relative motion between shaft sections, allowing the system to adapt its crash path length based on impact conditions while maintaining controlled energy absorption.
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 solution prevents uncontrolled bending of the drive shaft during crashes by enabling controlled telescoping of shaft sections, ensuring safety and stability by guiding components to prevent penetration into the passenger space and optimizing crash path length.
Implementation Method 1
a closure lid that breaks at predetermined points to facilitate unhindered telescoping and prevent bending
Implementation Method 2
a center bearing provided between the two shaft sections is structured and configured in such a manner that the intermediate shaft, or, if a journal is used, are the carriers of the center bearing
Implementation Method 3
The homokinetic displacement joint is sealed off from the atmosphere, on the one side, by means of a sealing cap and a sealing bellows
Implementation Method 4
configured with ball grooves on their inner and outer wall, respectively, in which balls are disposed
Data Source
AI summary
A longitudinal drive shaft for motor vehicles, for transferring a torque, consists of two or more shaft sections which are connected with one another by way of an intermediate shaft or a journal. The intermediate shaft or the journal is the carrier of a center bearing and is connected to the shaft section by a homokinetic displacement joint rigidly disposed in a pipe. The parts of the center bearing and shaft sections that are displaced in a crash are configured to be smaller than the inside diameter of the pipe. The inside diameter of the outer joint ring is greater than the outside diameters of the roller bearing of the center bearing and of the pipe. The homokinetic displacement joint is sealed off with a sealing cap and a sealing bellows in the direction of the shaft section, and has a closure lid assigned to it.