Seat Belt Pretensioner Multi-Stage Torque Control
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Solution Overview
Problem
Existing seat belt pretensioner mechanisms in vehicles do not effectively manage torque during the rotation of the spool in a belt retractor to efficiently retract the seat belt in the event of a crash, leading to suboptimal occupant restraint.
Innovation Solution
A seat belt pretensioner mechanism that includes a flexible drive member and a clutch mechanism, which applies a first torque during the initial stage of rotation and a greater second torque during a subsequent stage, allowing the spool to rotate more than 360°, ensuring effective belt retraction by engaging a gas generator to activate the pretensioner upon sensing a vehicle crash condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a conventional pretensioner with a flexible drive member is used, then the seat belt can be retracted, but the torque applied during spool rotation is insufficient to efficiently retract the belt in crash conditions
Solution Approach 1:
The patent applies a multi-stage torque strategy where the drive device dynamically adjusts torque levels based on the rotation stage of the spool. During initial rotation, a first torque is applied, and during subsequent rotation stages, a second torque greater than the first torque is applied. This dynamic torque adjustment optimizes belt retraction efficiency throughout the entire rotation cycle, directly resolving the contradiction between force magnitude and retraction productivity.
2Ease of operation
If the spool rotates only 360° or less, then the mechanism is simpler, but the belt retraction is insufficient to ensure effective occupant restraint
Solution Approach 1:
The patent segments the spool rotation into multiple stages: an initial rotation stage and subsequent rotation stages. This segmentation allows the drive device to apply different torque levels at different rotation phases, enabling the spool to rotate more than 360° while maintaining manageable mechanical complexity. The segmented approach ensures sufficient belt retraction for effective occupant restraint without overwhelming structural complexity.
3Device complexity
If a single torque level is applied throughout spool rotation, then the drive mechanism is simpler, but the belt retraction performance is suboptimal
Solution Approach 1:
The drive device incorporates dynamic torque control that transitions from a first torque during initial spool rotation to a second torque during subsequent rotation stages. This dynamic adjustment optimizes belt retraction performance across the entire rotation range. The system achieves enhanced productivity through controlled complexity, where the additional control mechanisms are justified by the significant improvement in belt retraction effectiveness during crash conditions.
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 mechanism ensures efficient and effective retraction of the seat belt by applying increasing torque, enhancing occupant safety by ensuring the seat belt is securely tightened during a crash, thereby improving the restraint system's performance.
Implementation Method 1
engaging a gas generator to activate the pretensioner upon sensing a vehicle crash condition
Data Source
AI summary
A seat belt pretensioner for a belt retractor includes a member that rotates relative to a frame of the belt retractor in response to a vehicle condition to rotate a spool of the belt retractor relative to the frame. A drive device rotates the member in response to the vehicle condition. The drive device applies a first torque to the member during a first stage of rotation of the member and the spool and applies a second torque greater than the first torque during a second stage of rotation of the member and the spool. A flexible drive member rotates the member relative to the frame. The flexible drive member extends around an axis of the member more than 360° after activation of the pretensioner.