FIELD OF INVENTION
This invention relates to a wave type roof cross member for booming noise
reduction in automobile. The invention is particularly applicable to a passenger
car without restricting scope of the invention to the same.
BACKGROUND/ PRIOR ART
In the passenger cars, low frequency (30Hz-100Hz) booming noise is a common
problem. The reason for booming noise is the resonance of structural panels
due to the excitation forces entering the vehicle in operating conditions. If
frequency of the' forces from powertrain or road excitation matches with natural
frequency of any vehicle body panel, it leads to resonance of panel. This
resonated body panel excites the acoustic cavity therealong leading to booming
noise. Roof panel is one of the major panels responsible for booming noise in
vehicle.
The resonance of the roof panel leads to roof mode (deflection) (1) as shown in
fig. 1, wherein the roof mode is atleast one in number. Thus, the booming noise
is owing to the roof mode.
The roof panel is generally stiffened by means of a plurality of straight cross
members to sustain the load (if any) coming onto the roof panel.
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There are certain provisions to reduce resonance or eliminate roof mode for
- reduction in booming noise in passenger vehicle. , According to one prior art, the resonance of the roof panel is avoided by mass
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dampers (2) having weight of lkg, 2kg etc, which is placed on the straight cross
i member (3) as illustrated in fig 2. Said addition of mass on roof cross member
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leads to frequency shift, thus reducing booming noise. I
Further, in accordance with another known art, beads (4) on the top surface of
roof panel (5) are removed as in fig 3. The removal of beads leads to shift in
frequency, thereby reducing booming noise. However, bead removal (6) results
in loss in stiffness of roof panel, therefore the same is required to be
compensated by increasing roof thickness. - This eventually adds to weight of
-1-2 kg.
The increase in weight results in rise in cost and decrease in fuel efficiency of
vehicle.
In view of the above, there is a need to devise the roof panel in such away that,
it can address the aforementioned drawbacks and at the same time it can serve
the purpose efficiently.
According to another available technology where roof portion is having an
opening and limited to movable roof tray, a reinforcing support frame
structure, for use in a roof portion of a vehicle body, includes a panel enclosure
with an opening for supporting a roof panel therein. The panel enclosure
includes an intermediate portion, which may have two parts located at different
levels, with a curved border therebetween. The reinforcing frame also includes
a brace operatively attached to the panel enclosure. The reinforcing frame
structure may also include a plurality of interconnected cross-members, which
are operatively connected to the panel enclosure.
OBJECTS OF THE INVENTION
The principal object of the present invention is to provide a wave type roof cross
member for booming noise reduction in automobilewhich obviates
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