Patent Application
20090201216
The invention relates to a motor-vehicle antenna assembly that is arranged and fastened on a mounting surface and that has a base plate facing the mounting surface and in or on which is mounted at least one antenna element and where furthermore a housing for the protection of the at least one antenna element from external influences is mounted in a sealing manner on the base plate, in accordance with the features of the introductory clauses of claim 1.
Such antenna assemblies of vehicles, especially roof antennas of automobiles, are known. One or more antenna elements designed, e.g. for services such as telephone, navigation, radio, television and the like are mounted on top of or on a base plate consisting for example, of zinc die-cast metal. In order to protect these sensitive antenna assemblies from external influences such as moisture as well as mechanical influences, the antenna assembly comprises a housing sealed against the mounting surface and/or against the base plate, especially at its edge. The housing consists as a rule of plastic and can be shaped in accordance with the design requirements at the mounting site. The antenna assembly is arranged and fastened with the base plate on the mounting surface, for example, a vehicle roof. The fastening can take place, for example, in a known manner by adhesion, for which embodiments are also known in which the base plate comprises a shaped threaded stem that is inserted in an opening in the mounting surface and provided on the opposite side with an attachment formation. These fastening possibilities are only by way of example, so that it is also worth mentioning that there are also other fastening possibilities. In the case of a formed threaded stem a seal is provided around it between the base plate and the mounting surface in order to prevent moisture from penetrating from the outside (from outside the vehicle) into the interior (vehicle passenger compartment). In such a case an open antenna system (antenna assembly) is present, so that the same pressure prevails inside the antenna assembly (inside the housing) and in the vehicle passenger compartment. This means that moisture can also readily penetrate from the vehicle passenger compartment into the interior of the antenna assembly. However, this has the disadvantageous effect that water can condense or precipitate inside the antenna assembly, during which a very large amount of such water can form in a disadvantageous manner as a consequence of strong temperature differences between the passenger space of the vehicle and the outside. However, this moisture inside the antenna assembly has an adverse effect on the functioning of the antenna elements and in the worst case in their failure, which is not desirable. On the whole, there is the disadvantage that in this antenna system that is completely open to pressure its structural parts such as antenna elements, seals and the like are heavily stressed by the penetrating moisture or by moisture forming as a consequence of pressure differences (condensed water), which results in a diminution of the service life of the entire antenna assembly.
In order to avoid these disadvantageous effects of the open pressure system, the provision of a completely pressure-closed antenna system has already been thought of. This takes place, for example, in that the entire interior of the housing is cast with an appropriate material after the mounting of the antenna elements. However, this represents on the one hand an elevated cost and leads to an increase in weight and means on the other hand that no more possibilities for repair are given. Furthermore, it is necessary in casting of the interior of the housing of the antenna assembly that the antenna elements be coordinated with this cast mass since the latter acts in a high-frequency manner as a dielectric. If other measures are taken for achieving a pressure-tight system, the expense is extremely high for coordinating the participating seals with the other elements (on the one hand, e.g. a metallic vehicle roof and on the other hand the plastic housing) in order to achieve a complete seal against pressure. Such an antenna system sealed by seals against the outside can therefore be manufacture only at very high expense for structural parts and consequently with an undesirably high cost.
The object of the invention is therefore to provide a motor-vehicle antenna assembly that, in addition to simple construction, has an elevated service life and avoids the initially described disadvantages.
This problem is solved by the features of claim 1.
The invention provides that the antenna assembly comprises means for equalizing pressure between the inside of the housing and the environment outside the antenna assembly. This achieves the goal of designing a sealed antenna system (=antenna assembly) in such a manner that the pressure differentials that result from different environmental influences (such as, e.g. by pressure differences inside and outside the system) can be compensated. As a result, all of the system's structural parts, that is, all relevant structural parts of the antenna assembly, primarily the sealing parts, experience reduced stress. Moreover, the condensation of water is avoided inside the housing, in particular on the surface of the at least one antenna element, so that on the whole an increase in the service life as well as the safety of the sealed antenna system is achieved and functional disturbances are avoided. This means that with a solution in accordance with the invention no system that is completely open to pressure but also no completely sealed system has to be made available anymore, but rather known antenna assemblies can be provided, if necessary even retrofitted, with the means for equalizing pressure in order to achieve the desired advantages.
A first embodiment of the invention provides that the means for equalizing pressure between the interior of the housing and the environment outside the antenna assembly is provided in the housing. That means that pressure is equalized between the interior of the housing of the antenna assembly and the environment outside the vehicle. Here, the antenna system can be but does not have to be sealed against the vehicle passenger compartment. In particular in the instance in which the inside of the housing is not sealed against the vehicle passenger compartment, pressure is effectively equalized with the outside in order, as already described, to avoid the undesirable formation of condensation water. In this instance, for example,, the housing can have an opening from its manufacture in which the means for equalizing pressure, e.g. a membrane, is detachably or permanently mounted. For example, this means can be clipped, snapped, adhered, wedged, or the like into the opening in the housing.
Furthermore, this variant provides in accordance with the invention that the means for equalizing pressure between the interior of the housing and the environment outside the antenna assembly is formed by the housing. This means in this instance that, for example, the membrane is not a separate structural part but rather is formed by the housing. It can be considered here, for example, that the housing and the membrane are manufactured in a plastic injection-molding process in which the housing consists of a different plastic that the membrane to be formed (two-component injection molding process).
Another variant of the invention provides in accordance with the invention that the means for equalizing pressure between the interior of the housing and environment outside the antenna assembly is provided in the base plate. The same also applies here as in the arrangement of the means for equalizing pressure in the housing, namely that the means for equalizing pressure such as, e.g. once again a membrane, is inserted as a separate structural part in the base plate or is formed by the base plate. In this instance a base plate can especially advantageously consist of plastic and is also produced in a two-component injection molding process for the realization of the membrane. If the means for equalizing pressure are provided in the base plate, it can be considered that pressure is equalized either between the interior of the housing of the antenna assembly and the environment outside the vehicle or, however, between the interior of the housing of the antenna assembly and the vehicle passenger compartment. In the last-cited instance the invention provides that the means for equalizing pressure between the interior of the housing and the environment outside the antenna assembly is provided in the base plate near a threaded stem formed on the base plate. The base plate is inserted through an opening in its structural surface with the threaded stem, that is also designed for running cables through it, and fixed on the opposite side, for example, with a fastening nut in order to arrange and fasten the antenna assembly on the vehicle roof. This means again that as a consequence of the opening in the threaded stem and the opening in the mounting surface a passage is formed between the interior of the housing and the vehicle passenger compartment, which means is provided for equalizing pressure in this passage.
A further variant of the invention provides that the means for equalizing pressure between the interior of the housing and the environment outside the antenna assembly is integrated in a seal of the antenna assembly. Thus, a further possibility of housing the means in accordance with the invention, for example, the membrane, is available, because in known systems the circumferential edge of the housing of the antenna assembly is frequently sealed with seals against the mounting surface so that there is the opportunity of housing the means for equalizing pressure in this sealing area in order to realize an equalization of pressure between the interior of the housing and the environment outside the antenna assembly.
The antenna assembly is constructed in an especially preferred manner as a motor-vehicle roof antenna so that the antenna assembly, which can be assembled in advance, can be mounted on a vehicle roof as a mounting surface. Furthermore, there is the advantage that roof antenna assemblies that are already known can be retrofitted if desired with the means in accordance with the invention for equalizing pressure.
The means for equalizing pressure is constructed in an especially preferred manner between the interior of the housing and the environment outside the antenna assembly as a membrane.
The embodiments according to
Furthermore, the roof antenna has an inner seal 4, a seal support 5, a cable seal 6 as well as a mounting hole seal 7.
In accordance with the invention, according to
The seals 4 to 7 form a seal but not a pressure-tight one for the respective structural elements from the outside and with respect the vehicle passenger compartment in order to prevent the penetration of rainwater, wash water, particles of dirt and the like into the interior of the housing 1 and into the passenger compartment. These seals have a simple design and consequently are not pressure-tight so that the system is still open and pressure equalization is not realized without the means in accordance with the invention, in particular the membrane 8.
Whereas in
The base plate 2 with the threaded stem 12 shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 102008008404.2 | Feb 2008 | DE | national |
