Adaptive Seatbelt Load Limiting With Piezoelectric Spool Control
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Solution Overview
Problem
Existing seatbelt assemblies struggle to maintain a high interference fit during normal operating conditions while allowing the spool drum to rotate freely, which is essential for occupants to easily take in or pay out seatbelt webbing.
Innovation Solution
The adaptive load-limiting seatbelt assembly employs a Tailored Control Joint (TCJ) with a piezoelectric device that controls the interference fit between its inner and outer members. During normal conditions, the TCJ maintains a high interference fit without restricting spool drum rotation, and during dynamic events, the interference fit is dynamically controlled to regulate seatbelt webbing pay-out.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a high interference fit is maintained in the TCJ during normal operating conditions, then the spool drum rotation is restricted, but if the interference fit is reduced, then the TCJ cannot effectively control seatbelt webbing pay-out during dynamic events
Solution Approach 1:
The interference fit in the TCJ is made dynamically adjustable through piezoelectric actuators that change the interference fit level based on operating conditions. During normal operation, the interference fit is reduced to allow free spool rotation, while during dynamic events, the interference fit is increased to enable effective seatbelt webbing pay-out control.
Solution Approach 2:
The physical parameter of interference fit is changed between two states: a reduced state during normal operation that allows free rotation, and an increased state during dynamic events that provides control. This parameter change is achieved through piezoelectric actuators that expand or contract to modify the interference fit between TCJ components.
2Reliability
If the TCJ is always operatively connected to control seatbelt forces, then peak seatbelt forces are limited, but the occupant cannot freely take in and pay out seatbelt webbing during normal operation
Solution Approach 1:
The TCJ operatively connection is made dynamic rather than static. The TCJ is selectively engaged or disengaged from the spool drum based on operating conditions. During normal operation, the TCJ is disengaged to allow free webbing movement, while during dynamic events, the TCJ is engaged to provide force limitation and control.
Solution Approach 2:
The TCJ system is segmented into separate functional components that can be independently engaged or disengaged. The piezoelectric actuators, interference fit mechanisms, and locking components are arranged to allow selective activation of the force-limiting function only when needed, separating the normal operation mode from the dynamic event mode.
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 solution enables the seatbelt assembly to effectively restrain occupants during dynamic events while allowing free movement of the seatbelt webbing during normal conditions, enhancing both safety and user convenience.
Implementation Method 1
The TCJ includes a piezoelectric device that transforms electrical energy to mechanical energy to control an interference fit between members that control resistance to spool drum pay-out of the seatbelt during the dynamic event.
Data Source
AI summary
An adaptive load-limiting seatbelt assembly for a passenger vehicle includes a rotatable spool drum storing a length of seatbelt webbing and a piezoelectric device defining an interference fit between a pair of members of the piezoelectric device. The spool drum is operatively disconnected from the piezoelectric device during normal operation of the seatbelt assembly to permit free rotation of the spool drum and is operatively connected to the piezoelectric device during a dynamic event such as a vehicle crash so that the interference fit resists rotation of the spool drum in the pay-out direction to dynamically or statically control pay-out of the seatbelt webbing during the dynamic event.