Steering Wheel Airbag Module Layout for Smaller Center Pads
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Solution Overview
Problem
Conventional airbag devices in steering wheels require a large mounting space due to the size of the inflator and functional components, preventing the airbag module from being made smaller than the outer diameter of the steering wheel, especially when using steering wheels with smaller center pads.
Innovation Solution
An airbag device with a cylindrical inflator secured by a mounting member featuring a circular through-hole and annular rib, along with a damper unit and securing member, allowing the inflator and damper unit to be positioned closer together, reducing the overall size of the airbag module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an inflator with a flange part and radially extended mounting pieces is used, then the inflator can be securely mounted to the bag holder, but the mounting space becomes large and prevents miniaturization of the airbag module
Solution Approach 1:
The mounting member integrates multiple functions into a single component: it provides the mounting surface for the inflator, the securing structure through integrated mounting pieces, and the support for functional components. This merging eliminates the need for separate flange parts and mounting structures, reducing overall space requirements while maintaining secure mounting.
Solution Approach 2:
The mounting pieces are positioned within the circular through-hole structure, with functional components arranged around the inflator in a nested configuration. This allows compact arrangement where smaller components are positioned within or around the space occupied by the inflator, maximizing space utilization and enabling miniaturization.
2Ease of manufacture
If functional components are positioned outside the inflator mounting space, then they can be properly assembled, but the bag holder size increases and cannot fit on steering wheels with smaller center pads
Solution Approach 1:
The mounting structure transitions from a two-dimensional flat mounting surface to a three-dimensional configuration with the circular through-hole and radially arranged mounting pieces. This allows functional components to be positioned in multiple spatial dimensions around the inflator, enabling compact arrangement that reduces the overall footprint of the bag holder while maintaining assembly feasibility.
3Strength
If multiple metal members such as housing, locking plate, inflator flange, and retainer are used, then the structure provides necessary strength, but the device complexity increases and miniaturization is hindered
Solution Approach 1:
The mounting member consolidates multiple previously separate metal members into a single integrated component. The mounting member includes the mounting surface, mounting pieces for securing the inflator, and structural elements that provide the necessary strength and stability, thereby reducing the number of parts from multiple separate metal members to one unified structure.
Solution Approach 2:
The mounting member serves multiple functions simultaneously: it acts as the housing structure, provides the locking mechanism through integrated mounting pieces, replaces the separate flange part, and functions as the retainer for functional components. This multi-functionality eliminates the need for multiple specialized metal members while maintaining all necessary structural roles.
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 airbag module is miniaturized, enabling it to fit on steering wheels with smaller center pads without increasing the overall diameter, while maintaining the functionality and securing the inflator in place during gas discharge.
Implementation Method 1
an annular rib 19b formed on an inner circumferential edge of the circular hole 19a and pressed against the circumferential side surface 4c of the inflator 4
Implementation Method 2
the horn switch mechanism is provided with a compression coil spring as a biasing member that biases the bag holder away from the core metal
Implementation Method 3
a damper unit 10 provided between the mounting member 18 and the steering wheel 1
Data Source
AI summary
To provide an airbag device provided in a steering wheel, which enables an airbag module to be made smaller so as to be compatible with a steering wheel having a smaller center pad than conventional ones. The airbag device includes an airbag module containing an airbag cushion and a cylindrical inflator that supplies inflator gas to the airbag cushion, a damper unit that dampens vibrations transmitted between the airbag module and the steering wheel, a mounting member formed of a plate material and to which the inflator and the damper unit are assembled, and an elastic member that is provided between the mounting member and the steering wheel and elastically holds the airbag module to the steering wheel. The mounting member is formed with a circular through-hole part for press-fitting the inflator to secure the inflator, and a retaining part for holding the damper unit.