Seat Belt Pretensioner Gas Generator Assembly Method
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Solution Overview
Problem
Conventional pretensioners face difficulties in smoothly and stably mounting a gas generator within a pipe due to the elongated piston shape and the urging force of the spring, making it challenging to reduce the size of the pretensioner and seat belt retractor while maintaining effective gas pressure application.
Innovation Solution
The use of temporary joining members, such as protrusions inside the pipe, to securely hold the gas generator in place during assembly, allowing for stable press-fitting and accurate positioning, even when the gas generator is inserted from the same end as the piston and spring, enabling the use of a cylindrical or barrel-shaped piston for efficient gas pressure application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the piston is formed in a cylindrical or barrel shape to effectively apply gas pressure, then gas pressure application efficiency is improved, but the piston becomes elongated in axial direction making it difficult to insert into a three-dimensionally curved pipe
Solution Approach 1:
The patent reverses the conventional assembly sequence by inserting the gas generator first into the pipe, followed by the piston and spring. This inversion of the assembly order allows the elongated cylindrical piston to be installed without obstruction, resolving the contradiction between maintaining effective gas pressure application and enabling ease of insertion into the curved pipe.
2Reliability
If the gas generator is press-fitted into the pipe after inserting piston and spring, then the gas generator is secured, but the spring's urging force pushes the gas generator out making smooth and stable press-fitting difficult
Solution Approach 1:
The patent applies preliminary action by first inserting the gas generator into the pipe and positioning it with temporary joining members before inserting the spring. This preliminary positioning ensures that the gas generator is securely held in place during subsequent assembly steps, preventing the spring's urging force from pushing it out and enabling smooth press-fitting.
Solution Approach 2:
The patent introduces temporary joining members as intermediary elements to hold the gas generator in position during assembly. These temporary members act as mediators between the gas generator and the pipe, providing stable fixation during the assembly process and allowing smooth press-fitting without the gas generator being pushed out by the spring's urging force.
3Ease of manufacture
If temporary joining members are used to hold the gas generator during assembly, then stable press-fitting is achieved, but the device complexity increases
Solution Approach 1:
The patent applies the discarding principle by using temporary joining members that are removed after the gas generator is securely press-fitted into the pipe. These temporary members serve their purpose during assembly and are then discarded, allowing stable press-fitting to be achieved without permanently increasing the device complexity.
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 allows for the stable and efficient mounting of the gas generator, facilitating the reduction of pretensioner and seat belt retractor size while ensuring effective restraint of occupants during emergencies by utilizing the generated gas pressure effectively.
Implementation Method 1
a gas generator that is activated to generate gas in the event of an emergency; a piston that is activated with the gas so as to generate a driving force
Data Source
AI summary
A plurality of driving force transmitting members, a piston, a spring and a gas generator are inserted into the pipe from the end of the pipe where the gas generator is mounted. The gas generator is press-fitted in the pipe while the flat faces thereof are deformed by a pair of protrusions of the pipe. Accordingly, the gas generator is temporarily held by the protrusions of the pipe. Then, one end of the pipe is firmly pressed and the gas generator is mounted in the pipe.