The present invention concerns a heat-insulating underbody structure according to the preamble of claim 1, as well as a heat shield according to claim 9, suitable for use with said underbody.
Heat-shields, as are described for example in WO 00/22285, are well known in the field of modern vehicle technology and serve to insulate the vehicle underbody against heat generated by the individual vehicle components, in particular by exhaust pipes, catalyzers or mufflers. As these heat-shields are directly attached to the heat emitting components and therefore must be disassembled for repair work to these components and subsequently refitted, heat shields are also known which are attached to the vehicle underbody.
Thus, WO99/46147 describes a heat shield which does not need to be disassembled when replacing the above mentioned vehicle components. This heat shield abuts the underbody of a vehicle and is arranged in such a manner that it does not come into contact with the heat emitting vehicle components.
DE-U-9202228.6 describes a multi-part heat shield which is attached to the vehicle underbody by means of spacing brackets so as to create a heat insulating underbody construction. This heat insulating underbody construction comprises an air gap which is open in the front and rear and is situated between the heat shield and the underbody, so that the airstream can flow through freely between the heat shield and the vehicle underbody and thereby dissipate heat.
Unfortunately it has been shown in modern vehicles that the air heated by the engine and accompanying assemblies accumulates in the engine compartment and heats up further, due to the ever increasing improvements to engine compartment insulation means. It is not uncommon that this “self-heated” air reaches temperatures of up to 120° C. or higher. This self-heated air escapes from the open flooring and essentially streams through the space between heat shield and vehicle body when driving. It is understood that this fact leads to an undesirable increase in temperature in the underbody section and can even cause rapid aging or destruction of inner cladding materials or other sensitive components.
It is therefore the aim of the present invention to provide a heat insulating underbody structure with a heat shield which is spaced away from the vehicle underbody, the arrangement of said underbody structure ensuring that the temperatures in the gap between the heat shield and the vehicle underbody do not significantly exceed 80° C.
This aim is solved according to the invention by a heat insulating underbody structure having the features of claim 1, and in particular by an underbody structure in which the vehicle underbody is provided with a heat shield in the regions experiencing increased heat radiation, i.e. in the region of the exhaust pipe, the catalyzer or the muffler. The heat shield is spaced away from the underbody so as to form an open interspace, whereby the underbody structure comprises flow-impeding means which prevent self-heated external air, in particular hot air from the engine compartment, from circulating through the interspace. In particular, “self-heated external air” is the air which has been heated by the vehicle's own engine and its accompanying assemblies. At this point it should be explicitly mentioned that this interspace, in the following called an “open interspace”, is not a closed cavity but can allow air to flow through it, in particular so as to allow the hot air generated by the respective heat sources in the interspace to escape or to disperse.
In a first embodiment, the flow-impeding means partially comprise air-impervious interspace limiters which seal the interspace at least in the direction from which the air flows, i.e. upstream (windward). In particular a blade is suitable as a forward interspace limiter. It is understood that the interspace directly behind such a vane can have an opening from which the hot air generated in the interspace can escape. It is within the scope of the expert to design this vane in such a way that this (heated) air can be swept away by the outside airstream.
In a further embodiment, the airstream inhibiting means create an interspace limiter which is pervious to air, and this interspace limiter comprises, at least partially, a thermally stable fibrous material. Such fibrous material is well known to the expert and can comprise inorganic or organic fibers, in particular ceramic fibers.
In a preferred embodiment, the interspace is provided at least partially with a heat insulating material which is pervious to air.
In a further development of the present invention, means can be provided to link the interspace to cool surrounding air. In the following, “cool surrounding air” means the outside air which has not been heated by the vehicle itself.
In the following the invention shall be more closely described by means of an exemplary embodiment and with the aid of the Figures. These show:
In the embodiment of the inventive underbody structure shown in
In a particular embodiment of the inventive underbody structure, the space between the heat shield 2 and the underbody 1 is provided with an air pervious heat insulation material 7. This heat insulation material 7 completely fills the interspace 3. It is understood that also in the above described embodiments, the interspace 3 can at least partially comprise air pervious heat insulation material 7.
The advantages of the inventive underbody structure are immediately apparent to the expert. In particular, the upstream self-heated external air 8 flowing from the engine compartment M is prevented from flowing into the interspace 3 between the heat shield 2 and the vehicle underbody 1.
Further embodiments and particular configurations of the inventive underbody structure are within the usual technical scope of the expert. Thus, depending upon the specific requirements and/or geometries, he will vary the distance between the heat shield 2 and the underbody by 5 to 20 mm, or will use a single- or multilayer heat shield 2. He can also design the blade 4 in a suitable way, in particular so that the air present in the interspace 3 is sucked out of that space. The expert will also adapt the choice of materials to the existing requirements.
Number | Date | Country | Kind |
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20 2004 015698.9 | Oct 2004 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CH05/00627 | 10/11/2005 | WO | 00 | 12/27/2007 |