The present invention relates to an airbag apparatus incorporated in a steering wheel of a vehicle or the like. More particularly, the present invention pertains to an airbag apparatus that elastically support an inflator with an elastic support portion, thereby causing the inflator to function as a damper mass of a dynamic damper and causing the elastic support portion to function as a spring of the dynamic damper.
During high-speed running of a vehicle or idling of the vehicle engine, vibration transmitted to the steering wheel, which is rotated about the steering shaft, may impair driver comfort. In this regard, techniques for suppressing steering wheel vibrations have been conventionally developed and proposed. One of such techniques uses a dynamic damper that includes a weight and an elastic member, with which the weight is supported by, for example, the metal core of a steering wheel. According to the technique, when vibration the frequency of which is equal to or close to the resonance frequency of the dynamic damper is transmitted to the dynamic damper from the steering wheel, the dynamic damper resonates to absorb vibration energy of the steering wheel. This suppresses the vibration of the steering wheel.
A typical steering wheel is equipped with an incorporated airbag apparatus for protecting the driver at a collision of the vehicle. An airbag apparatus includes an airbag, a bag holder, an inflator, and a retainer, as disclosed, for example, in Japanese Laid-Open Patent Publication No. 2009-196466. The bag holder is supported by a steering wheel, and the airbag is located rearward of the bag holder. The inflator supplies gas to the airbag, thereby inflating the airbag. The retainer has an annular bag attachment portion. A peripheral portion of the opening of the airbag is held between the bag attachment portion and the bag holder. The airbag is attached to the bag holder by fastening the bag attachment portion to the bag holder. Further, the retainer includes arch portions extending rearward from multiple positions on the inner rim of the bag attachment portion. The arch portions surround the inflator from outside with respect to the radial direction of the steering shaft.
Since the airbag apparatus occupies a large part of the interior space of the steering wheel, it is difficult to incorporate the above described dynamic damper in recent steering wheels. In this regard, a structure has been proposed in which an inflator is elastically supported by a bag holder with elastic support portions, so that the inflator functions as a damper mass of a dynamic damper, and the elastic support portions function as springs of the dynamic damper. In this case, it is important that there be nothing that hinders vibrations of the inflator. In the above described airbag apparatus, the arch portions of the retainer surround the inflator while being spaced from the inflator, so that a space for vibration is ensured. This prevents the airbag from contacting the inflator.
However, since the arch portions of the retainer extend rearward from multiple positions on the inner rim of the bag attachment portion, the peripheral portion of the opening of the airbag is often exposed between the arch portions. Also, since the boundary between the inner rim of the bag attachment portion and each arch portion is often formed by bending to be curved, the peripheral portion of the airbag opening is likely to be exposed at these curved parts of the retainer. Such exposed parts of the airbag may contact high-temperature gas and may be affected by the gas heat.