Abstract:
A mat incorporating a heating wire and intended for installation in a motor vehicle seat for heating the motor vehicle seat. The novel mat includes further antennas or antenna components of an antenna system, which cooperates with a resonator/transponder of a child seat. The mat thus forms a part of a system for detecting the presence of a child seat placed on the motor vehicle seat.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation of copending International Application PCT/DE98/01395, filed May 20, 1998, which designated the United States. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention lies in the automotive technology field. More specifically, the invention relates to a mat with a heating wire for a motor vehicle seat heater and to a motor vehicle seat having such a mat. 
     The automotive art has long known heated seats. For heating such motor vehicle seats, it is possible to place mats in the seat which are provided with heating wires for heating the motor vehicle seat when the mat is installed in the seat. 
     The automotive art has also long known air bags used as passenger protection and restraint systems in motor vehicles. 
     When a child is present in a child seat placed on the front passenger seat, there exists a danger posed by the possible inflation of the passenger-side air bag. This is particularly prevalent when the child seat faces rearwardly, i.e., when the backrest of the child seat faces the dashboard. Devices for detecting a child seat placed in the passenger seat provide some remedy. Such a child seat can in particular be detected in contactless fashion, as follows: A transmitting antenna provided in the vehicle outputs an electromagnetic signal. A child seat placed on the passenger seat includes a resonator/transponder, which receives the signal output by the transmitting antenna, modifies it in a characteristic way, and outputs the modified signal. A receiving antenna provided in the vehicle receives the signal transmitted by the resonator. If the received signal has a signal structure that indicates the presence of a resonator and thus of a child seat in the area of the passenger seat, then tripping of the associated air bag restraint or restraints is subsequently prevented. 
     U.S. Pat. No. 5,515,933 (published German patent application DE 44 09 971 A1) describes a detection system which has a plastic film with incorporated resistor elements for weight detection and an antenna for child seat detection. 
     A disadvantage of the prior art antenna configuration is that in every case, a complicated film carrier including a weight sensor must be produced for mounting the antennas and has to be incorporated into the motor vehicle seat. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide a novel mat for a passenger seat, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which provides for a different way of mounting the antenna for child seat detection that is advantageous with regard to production cost and effort. 
     With the foregoing and other objects in view there is provided, in accordance with the invention, a mat for installation in a motor vehicle seat, comprising: 
     a mat body adapted to be mounted in or on the motor vehicle seat; 
     a heating wire for a motor vehicle seat heater integrated in the mat body; and 
     at least one antenna for transmitting or receiving electromagnetic signals integrated in the mat body. 
     In accordance with an added feature of the invention, the antenna is adapted to cooperate with a resonator or transponder of a child seat to be placed on the motor vehicle seat. 
     In accordance with an additional feature of the invention, a contact device is formed on the mat body and electrically connected to the antenna, for connecting the antenna to an electric control unit. 
     In accordance with another feature of the invention, the mat is formed of textile fabric. 
     With the above and other objects in view there is also provided, in accordance with the invention, a motor vehicle seat, comprising a seat part, a backrest connected to the seat part, a mat mounted in or on the seat part and/or the backrest, and at least one antenna in the mat for transmitting or receiving electromagnetic signals. 
     In a preferred embodiment of the invention, the mat is disposed in the seat part. 
     In accordance with again an added feature of the invention, the seat is formed with a cushion and a cushion covering, and the mat is disposed between the cushion and the cushion covering of the seat part and/or the backrest. 
     In accordance with again an additional feature of the invention, the seat is formed with a cushion and a cushion lining, and the mat is disposed between the cushion lining and the cushion. 
     In accordance with again another feature of the invention, the seat part has a thigh support, and the mat is disposed in the thigh support. 
     In accordance with a preferred embodiment of the invention, the seat part includes a base part and a thigh support disposed forward of the base part (in the forward-facing drive direction of the motor vehicle), the mat is integrated in the base part and in the thigh support, and wherein the antenna in the base part and the antenna in the thigh support are electrically interconnected and form an effective antenna area for an electromagnetic coupling. 
     In accordance with a concomitant feature of the invention, a contact device interconnects the antenna of the mat and the antenna of the base part. 
     In summary, the above objects are satisfied with the invention, in which the antenna is integrated with the mat that carries the seat heating wire, and the antenna is embodied separately from the seat heating wire. 
     Given the increasing number of motor vehicles equipped with seat heaters, it entails no further effort or expense to include the antenna of the child seat detection system in the mat that carries a seat heating wire. No additional mat for the antennas in the motor vehicle seat is needed. The antenna can be incorporated into the mat together with the seat heating wire in a single operation. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a mat with a heating wire for a motor vehicle seat heater, and motor vehicle seat with such a mat, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
    
    
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partly broken-away, perspective view of a motor vehicle seat; 
     FIG. 2 is a plan view of a mat according to the invention; and 
     FIG. 3 is a diagrammatic sectional view through a motor vehicle seat. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is seen a motor vehicle seat with a seat part  1 , a backrest  2 , and a headrest  3 . The seat part  1  and backrest  2  structurally have approximately the same design. The seat part  1  has a seat frame  15 . Seat springs  14 , which resiliently support a seat cushion  12 , are disposed on the seat frame  15 . Between the seat cushion  12  and the seat springs  14 , a seat cushion lining  13  is provided for attaching the seat cushion  12 . The seat cushion  12  is covered with a seat cushion covering  11 . A mat  4  according to the invention is indicated by dashed lines. The mat  4  has seat heating wires and one or more antennas for child seat detection, and it is disposed between the seat cushion  12  and the seat cushion covering  11 . 
     The way in which the antennas are arranged according to the invention is independent of the rest of the seat design. When a child seat is placed on the motor vehicle seat, the mat  4  has a slight spacing distance from the child seat. The child seat is equipped with a resonator. Due to the slight spacing distance, an extremely strong signal coupling between the antenna and resonator exists—preferably between a transmitting antenna and the resonator, but also between the resonator and a receiving antenna, if both transmitting and receiving antennas are disposed in the mat  4  in the motor vehicle seat. 
     The backrest  2  has approximately the same structural design as the seat part  1 : A backrest frame  25  is provided, along with a backrest spring  24 , a backrest lining  23 , a back cushion  22 , and a back cushion covering  21 . 
     According to the invention, the mat  4  can be disposed not only in the proposed ways in a seat part of the motor vehicle seat but also and in particular in the backrest of the motor vehicle seat. 
     A transmitting antenna disposed in the motor vehicle seat preferably encompasses virtually the entire available area of the seat part or backrest. Two further receiving antennas are preferably also disposed in the motor vehicle seat; these receiving antennas include the area of the seat part or the backrest inside the face occupied by the transmitting antenna, in approximately equal parts. Particularly when the left-hand half of the seat part or backrest is surrounded by one receiving antenna and the right-hand half of the seat part or back rest is surrounded by the other receiving antenna, then a child seat provided with two resonators can not only be detected; even its alignment relative to the motor vehicle seat can thus be derived. The seat having the antenna is preferably the passenger seat. 
     FIG. 2 shows the mat  4  according to the invention in plan view. A meandering heating wire  41  for the seat heater can be seen clearly, as can a single antenna loop  40 , in this case for transmitting electromagnetic signals for a child seat placed on the motor vehicle seat. Contact devices  42  for all the terminals of the mat are provided. It is understood that a plurality of seat heating wire courses and antenna conductor courses can also be disposed in such a mat. The individual heating wires and antennas can also intersect, if they are disposed in different layers of the mat and are thus electrically insulated from one another. A diagrammatic connection of the uppermost terminal  42  to an electronic control unit ECU is indicated in dashed lines. 
     FIG. 3 shows a section through a motor vehicle seat with a seat part  1  and a backrest  2 ; the seat part  1  has two components, a thigh support  18  and a base part  19 . Particularly in bucket seats, the thigh support  18  is movably supported relative to the fixedly disposed base part  19  and can be extended to the front, to adapt the vehicle seat to the body size of the occupant. In a motor vehicle seat designed in this way, the antenna area of an antenna disposed only in the base part may not be large enough for coupling with a child seat placed on it. Care must accordingly be taken that the thigh support  18  also be penetrated by an antenna. The base part  19  therefore has an antenna conductor course for child seat detection that is integrated for instance with a sensor film that furthermore includes resistor elements for detecting the weight of an occupant seated on the motor vehicle seat. The antenna arrangement of the base part  19  of the motor vehicle seat can, however, also be embodied in any other way. The mat  4  of the invention is then disposed in the thigh support  18 ; the mat  4  is connected to the antenna  40  of the base part  19  via its contact devices  42  and a cable  5 , which in the unextended state of the thigh support  18  has sufficient play, via a contact device in the base part, so that the effective antenna area for transmitting or receiving electromagnetic radiation is increased by the antenna course  40  in the seat heating mat  4  of the thigh support  18 . 
     A child seat  43  with an identification transponder  44  is diagrammatically illustrated in dashed lines.