Seat Belt Pretensioner Rod with Tip Reinforcement
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Solution Overview
Problem
Existing pretensioners face challenges in balancing the strength and slidability of rod-shaped power transmission members, particularly in the initial stage of driving the pinion gear, where the rod member must withstand high loads without chipping or breaking, and ensuring efficient sliding within a curved pipe.
Innovation Solution
A pretensioner design featuring a ring gear with a rod-shaped power transmission member that is plastically deformed, a tip reinforcing member with higher strength than the power transmission member, and a gas generator to enhance the strength and slidability, where the tip reinforcing member is positioned to absorb initial impact and is either molded, pressed, or hardened for increased durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the rod member is made with high strength to prevent chipping or breaking during initial collision with the pinion gear, then strength is improved, but slidability within the curved pipe deteriorates
Solution Approach 1:
The rod member is designed with non-uniform cross-sectional area along its length. The tip portion has a smaller cross-sectional area than the base portion, creating a localized weak point that deforms plastically first during pipe traversal, reducing friction and facilitating sliding. Meanwhile, the base portion maintains sufficient strength to prevent catastrophic failure during pinion gear engagement.
Solution Approach 2:
The rod member is constructed from a composite material or composite structure that combines materials with different properties. The tip portion uses a material or structure optimized for plastic deformation and low friction, while the base portion uses a material optimized for high strength, achieving both slidability and strength requirements simultaneously.
2Reliability
If the rod member is made with high strength to withstand initial collision load, then reliability is improved, but the ability to efficiently slide within curved pipe deteriorates
Solution Approach 1:
The variable cross-sectional design creates a localized deformation zone at the tip that enables efficient navigation through curved pipes, while the stronger base portion ensures reliable power transmission to the pinion gear, achieving both reliability and productivity.
Solution Approach 2:
The cross-sectional area parameter of the rod member is varied along its length, with the tip portion having a smaller area that facilitates plastic deformation and sliding, while the base portion maintains a larger area for reliable strength, optimizing both efficiency and reliability.
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 effectively prevents the power transmission member from chipping or breaking by using a stronger tip reinforcing member that collides first with the ring gear, allowing for selection of materials based on slidability and engagement properties, thus achieving both strength and slidability of the rod-shaped power transmission member.
Implementation Method 1
a gas generator disposed at an end of the pipe
Implementation Method 2
a rod-shaped power transmission member for transmitting power to the ring gear while being plastically deformed
Data Source
AI summary
Provided are a pretensioner, a retractor, and a seat belt device in which strength and slidability of a rod-shaped power transmission member may both be achieved. A pretensioner includes a ring gear on which the spool is rotatably disposed, and power transmission units for transmitting power to the ring gear in an emergency. The power transmission units includes a rod-shaped power transmission member for transmitting power to the ring gear while being plastically deformed, a tip reinforcing member disposed on a tip side of the power transmission member, a pipe for containing the power transmission member, and a gas generator disposed at an end of the pipe. The tip reinforcing member has higher strength than the power transmission member.