Vehicle Seat Belt Pretensioner Weight Reduction via Wire Anchoring
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Solution Overview
Problem
Conventional pretensioners for vehicle seat belts are heavy and complex, leading to increased costs and assembly time due to the use of multiple heavy components and complex structures, with the need for machining and crimping, and the wire length and weight contribute to higher holding power but also increased weight and cost.
Innovation Solution
A pretensioner design with a reduced number of components, featuring a cylinder, gas generator, piston, and a wire with a folded portion connected to the piston via a connecting hole and detachment preventing member, simplifying the structure and assembly by integrating the housing and gas generator, and using a base with a fitting portion to reduce the overall weight and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the length of the wire end is increased to securely fix the wire to the piston, then the holding power of the wire is improved, but the weight of the piston and wire increases
Solution Approach 1:
The patent integrates the wire end fixing function directly into the piston structure by forming a through-hole in the piston that receives the wire end. This merging eliminates the need for separate fixing components and reduces overall weight while maintaining secure wire attachment. The piston itself becomes both the moving component and the wire anchoring point.
Solution Approach 2:
The patent changes the structural parameters of the piston by creating a through-hole that passes completely through the piston body. This allows the wire end to be secured on one side while minimizing the wire end length needed for fixation, as the wire is anchored by the piston's structural integrity rather than requiring excessive wire length for crimping or bonding.
2Reliability
If multiple heavy components are used to ensure secure fixation and gas containment, then the reliability of the pretensioner is improved, but the overall weight and complexity of the device increases
Solution Approach 1:
The patent combines multiple functions into integrated components. The piston serves dual purposes as both the gas-actuated moving element and the wire anchoring point. The pressure container is directly coupled to the piston assembly without intermediate components. This merging reduces the number of separate parts while maintaining secure fixation and gas containment through the unified structural design.
Solution Approach 2:
The piston is designed as a multi-functional component that simultaneously: (1) moves in response to gas pressure from the gas generator, (2) provides structural anchoring for the wire end through its through-hole, and (3) transmits force to move the seat belt. This universality eliminates the need for separate wire end fixtures and reduces overall device complexity.
3Strength
If conventional machining and crimping methods are used to fix components, then the strength of connections is improved, but the assembly time and manufacturing cost increase
Solution Approach 1:
The wire end is pre-formed with a specific configuration that fits into the piston's through-hole. This preliminary preparation of the wire end allows for rapid insertion and fixation without requiring time-consuming crimping or machining operations during assembly. The wire end geometry is designed to provide secure fixation through its shape complementarity with the piston hole.
4Device complexity
If a base cartridge with multiple functions is used to reduce component number, then the device complexity is reduced, but the handling difficulty and assembly effort increase due to the large size and weight of the base cartridge
Solution Approach 1:
Instead of using a single large base cartridge, the patent segments the device into lighter, more manageable components: the pressure container, the piston assembly with integrated wire anchoring, and the gas generator. These segmented components are smaller and easier to handle individually while still providing the necessary multi-functionality when assembled together.
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 reduces the weight and complexity of the pretensioner, simplifies assembly, and lowers costs by minimizing the length and weight of the piston and wire, while ensuring reliable connection and secure fixation of the wire to the piston, thereby reducing the overall weight and manufacturing costs.
Implementation Method 1
a gas generator that generates high-temperature, high-pressure gas
Implementation Method 2
a piston that is moved in the cylinder by the gas supplied from the gas generator
Data Source
AI summary
An object of the invention is to reduce the weight of a pretensioner by reducing the length of a piston and a wire of the pretensioner. A pretensioner (1) is used in a seat belt device and pulls a seat belt. Due to gas supplied into a cylinder (10) from a gas generator (4), a piston (20) is moved in the cylinder (10). A wire (60) is connected to the piston (20) and the seat belt and pulls the seat belt when the piston (20) moves. The wire (60) has both ends that are connected to the seat belt and has a folded portion (63) that is connected to the piston (20) via connecting means (51). The connecting means (51) has a connecting hole (24) that is formed in the piston (20) and through which the folded portion (63) passes and has a detachment preventing member (52) that is positioned between the folded portion (63) and the piston (20) to prevent the folded portion (63) from being detached from the connecting hole (24).