Abstract:
A temperature detector for an air-conditioned vehicle seat with seat heating and/or seat ventilation is disclosed. To ensure accurate temperature measurement for regulation purposes close to the surface of the seat cushion while eliminating purely local temperature peaks, the temperature detector is provided with a flat, extended heat absorption surface, which is preferably formed by a thin, flexible layer of good thermal conductivity in which a temperature sensor in button or disc form is firmly embedded.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     Priority is claimed with respect to German Application No. 198 51 979.6-16 filed in Germany on Nov. 11, 1998, the disclosure of which is incorporated herein by reference: 
     BACKGROUND OF THE INVENTION 
     The invention relates to a temperature detector for a vehicle seat with a seat heating system and/or seat ventilation system and to a vehicle seat with an integrated temperature detector of this kind. In a known seat heating system for a motor vehicle seat (DE 197 03 516 C1), the temperature detector, which can be obtained commercially as a spherical or disc-shaped element made from a temperature-dependent resistor material, is arranged in the lower area of the back cushion, in the pressure distribution layer of the latter, and is connected to the input of a control unit, which is connected on the output side to electric heating coils of the seat heating system. The control unit controls the on time of the seat heating system in accordance with a specified control algorithm as a function of the temperature at the surface of the back cushion, measured by the temperature detector. 
     Such commercially available temperature detectors allow only the local temperature to be detected and this is subject to severe fluctuations, especially when the seat is occupied, and can vary widely from one point to another. This leads to distortion of the actual temperature value fed to the temperature-regulating system and to correspondingly deficient temperature regulation which does not meet high requirements on the comfort of the seat. 
     SUMMARY OF THE INVENTION 
     The object on which the invention is based is to provide a temperature detector of the type stated at the outset which reliably performs more accurate temperature measurement for regulation purposes and does this close to the surface of the seat while eliminating purely local temperature peaks. 
     According to the invention, the object is achieved by means of a flat, extended heat absorption surface. 
     The temperature detector according to the invention has the advantage of detecting the temperature at the surface of the seat over a wide area, thus minimizing interfering effects such as the temperature detector being acted upon on one side, the occupant side. It is thereby possible to measure the temperature as close as possible to the user of the seat, thus coming significantly closer to the goal of temperature regulation, namely to keep the temperature of the seat constant in the same range as the skin temperature. 
     Advantageous embodiments of the temperature detector according to the invention with expedient refinements and developments of the invention will become apparent from the further claims. 
     According to an advantageous embodiment of the invention, the heat absorption surface is formed by a thin, flexible layer of very good thermal conductivity into which a temperature sensor, e.g. a PTC or NTC resistor, in button or disc form is firmly embedded. The advantage of this flat construction resides in the fact that the temperature detector does not leave a visible imprint on the surface of the seat and there is therefore no problem in arranging the temperature detector directly under the cushion cover. The layer of good thermal conductivity can advantageously be produced by means of an aluminium foil but can also be produced from aluminium powder. An outside diameter of about 40 mm is sufficient to achieve the desired advantages. 
     According to an advantageous embodiment of the invention, the heat-conducting layer is perforated or in the form of a latticework structure. The air permeability thus obtained for the large-area heat absorption surface has the advantage of minimizing condensation and evaporation of moisture on the heat absorption surface and temperature fluctuations caused thereby. 
     In the case of a vehicle seat which is fitted with a temperature detector as described above, an advantageous embodiment of the invention is obtained if the temperature detector, the heat absorption surface of which is provided on one side with a layer of good thermal conductivity, is integrated in such a way into the cushion that the thermal insulating layer faces away from the cushion cover, thereby ensuring that the temperature detector is shielded on the ventilation side. 
     If the seat heating system has an electric heating mat, which is generally arranged under the cushion cover, then, according to another embodiment of the invention, the temperature detector is an integral part of the heating mat. 
     According to an advantageous embodiment of the invention, a temperature-regulating device forming part of the seat heating system is supplied with a desired value for the seat surface temperature, is connected on the input side to the temperature detector and an external detector, which is arranged on the vehicle and detects the outside temperature, and, on the output side, to the seat heating system. The temperature-regulating device regulates the surface temperature of the seat in accordance with the specified desired value and corrects the desired value as a function of the temperature value measured by the external detector. These design measures contribute to better adjustment of the seat climate to the heat sensitivity of the occupant, thus ensuring that any manual interventions that he makes in the seat-climate setting are kept to a minimum. By adapting the desired temperature value to the outside temperature, e.g. by setting the desired value for the seat surface temperature to 35° C. in summer, when the outside temperature is above 20° C., and to 36° C. in the cold part of the year, when the outside temperature is below 20° C., allowance is made for the differences in human temperature sensitivity according to the season. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The invention is described in greater detail below with reference to embodiment examples illustrated in the drawing, in which, in each case in schematic representation: 
     FIG. 1 shows parts of a longitudinal section through a vehicle seat with seat heating and a seat ventilation device, 
     FIG. 2 shows a plan view of a temperature detector integrated into the vehicle seat shown in FIG. 1, 
     FIG. 3 shows a side view of the temperature detector in FIG. 2, 
     FIG. 4 shows a plan view of the temperature detector in accordance with another embodiment example, 
     FIG. 5 shows a plan view of part of the temperature detector in accordance with a third embodiment example, on an enlarged scale, 
     FIG. 6 shows a longitudinal section through a squab component of a vehicle seat in accordance with another embodiment example. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The vehicle seat shown in longitudinal section in FIG. 1 has, as is familiar, a squab component  11  which is held adjustably on the vehicle floor, and a backrest  12 , which is connected pivotably to the squab component  11  by a latching pivot mechanism (not shown here) for tilt adjustment. The squab component  11  and the backrest  12  each have a cushion  13  and  14  respectively. The cushion  13  of the squab component  11  is secured on a cushion carrier  15 , which is here designed as a spring core of spring wire and is mounted in a frame  16  of the squab component  11 . The seat cushion  13  comprises a cushion pad  17 , which rests on the cushion carrier  15 , a ventilation layer  18  made of coarse-knit spacing fabric which covers the cushion pad  17  over its entire area and can be flooded with air, an air-permeable distribution layer  19 , which rests on the ventilation layer  18 , and an air-permeable cushion cover  20  which covers the surface of the seat cushion  13 . A cover filling  21  made of cotton wool or non-woven material is incorporated between the cushion cover  20  and the pressure distribution layer  19 . 
     Arranged in the cushion pad  17  is a plurality of air channels  24 , each of which penetrates the cushion pad  17  from the top side, that facing the ventilation layer  18 , to its bottom side, that facing away from the ventilation layer  18 . Arranged in each air channel  24  is a miniature fan or miniature blower  23  of a seat ventilation device  22  and an electric heating coil  26  of a seat heating system  25 . 
     The back cushion  14  of the backrest  12  is embodied with a backrest face and two lateral bolsters. A cavity  29 , which is open at the bottom end of the backrest  12 , is provided between the backrest cushion  14  and an air-impermeable rear wall  28 . Arranged in the cavity  29  is a central fan  30 , the intake opening  301  of which faces downwards to the open end of the cavity  29  and the delivery opening  302  of which is connected to a flexible duct  31 . A heating coil  27  of the seat heating system  25  is arranged upstream of the delivery opening  302  of the fan  13 . As in the case of the squab component  11 , the back cushion  14  is secured on a cushion carrier (not shown here) and has a cushion pad  17 , a ventilation layer  18 , which covers the latter over its entire area, a pressure distribution layer  19 , which is arranged on the ventilation layer  18 , and an air-permeable cushion cover  20  which covers the surface of the cushion. In the area of the cushion face, at the bottom end, the ventilation layer  18  is extended beyond the cushion pad  17  and connected to the flexible duct  31 . Arranged in the lower area of the back cushion  14 , in the pressure distribution layer  19 , is a temperature detector  32  and, if appropriate, also a moisture meter  33 , being arranged in such a way that it lies approximately in the lumbar region of seat users of different sizes. 
     To set a comfortable seat climate, a control unit  34  is provided, this being connected on the input side to the temperature detector  32  and the moisture meter  33  and, on the output side, to the electric circuits of the seat ventilation device  22  and the seat heating system  25 . 
     For highly accurate measurement of the cushion surface temperature, the temperature detector is provided with a flat, extended heat absorption surface  35  (FIG.  2 ), to one side of which a layer  36  with good thermal insulation properties is applied by coating or adhesive bonding. The insulating layer  36  is composed of plastic or cardboard. The heat absorption surface  35  is formed by a thin, flexible layer  37  of good thermal conductivity into which a temperature sensor  38  in button or disc form is firmly embedded. This temperature sensor can be a commercially available PTC or NTC resistor, which is connected to the control unit  34  by two pigtail leads  39 . An aluminium foil can be used as a heat-conducting layer  37 . However, the heat-conducting layer  37  can also be produced from aluminium powder. 
     In the embodiment example of the temperature detector  32  in FIG. 2, the heat-conducting layer  37  has a continuous surface. In the embodiment example of the temperature detector  32  in FIG. 4, the heat-conducting layer  37  is perforated and, in the embodiment example of the temperature detector  32  in FIG. 5, the heat-conducting layer  37  has a latticework structure. The air permeability of the heat-conducting layer  37  in the embodiment examples in FIGS. 4 and 5 has the advantage that condensation and evaporation of moisture on the heat absorption surface  35  used for temperature measurement is largely suppressed and hence temperature fluctuations caused by this at the measuring surface are minimized. On all the temperature detectors  32 , the heat-conducting layer  37  has a diameter of about 40 mm, for instance. 
     As can be seen from FIG. 1, the temperature detector  32  is arranged directly under the cushion cover  20 , i.e. as close as possible to the point at which the seat temperature is to be measured. This arrangement of the temperature detector  32  is made possible by its flat construction since this means that the temperature detector  32  does not leave a visible mark or imprint on the surface of the seat. In this configuration, the temperature detector  32  is arranged in such a way that its thermal insulating layer  36  faces away from the cushion cover  20 , i.e. towards the ventilation layer  18 . This ensures that the temperature detector  32  is shielded on the ventilation side, thus preventing its measurements from being distorted by the air blowing through the ventilation layer  18  and the pressure distribution layer  19 . 
     The control unit  34  is also connected on the input side to an external detector  40  which detects the ambient temperature. Integrated into the control unit  34  is a temperature regulator which is supplied with a desired value and adjusts the surface temperature of the seat cushion  13  and the back cushion  14  to the specified desired value. Here, the desired value is corrected in the control unit  34  as a function of the temperature value supplied by the external detector  14 . The correction can be performed in such a way that, at an external temperature of below 20° C., the desired value is set to 36° C., for example, and, at an external temperature above 20° C., the desired value is lowered to 35° C., for example. This adjustment of the temperature to be established at the surface of the seat allows for the temperature sensitivity of the user of the seat depending on the time of year. 
     The squab component  11  illustrated in longitudinal section in FIG. 6, which forms part of a modified vehicle seat, is largely identical to the squab component  11  illustrated in FIG. 1 and, to this extent, identical components are provided with identical reference numerals. The construction of the seat cushion  13  corresponds to that in FIG. 1, and this also applies to the seat ventilation device  22 . The seat heating system  25  is modified insofar as the heating coils in the air ducts  24  are omitted and replaced by a heating mat  41 , which is arranged in the seat cushion  13  between the pressure distribution layer  19  and the cushion cover  20  and replaces the cover filling of the cushion  13  in FIG.  1 . In FIG. 6, the electric heating wires, which are generally laid in a meandering patter, are denoted by  42 . Given the integration of such a heating mat  41  into the seat cushion  13 , the temperature detector, which is shown here and denoted by  32  in FIGS. 1-6, can be arranged in the heating mat  41  and be an integral component of the heating mat  41 . 
     While the above description constitutes the preferred embodiment of the invention, it will be appreciated that the invention is susceptible to modification, variation, and change without departing from the proper scope or fair meaning of the accompanying claims.