Abstract:
A heatable rear view mirror assembly providing a visible indication to a driver of heating function is disclosed. The assembly includes a mirror housing, at least one mirror pane disposed within the mirror housing, at least one heating element disposed within the mirror housing for heating the mirror pane, a thermostat disposed within the mirror housing for automatically activating the heating element, and a display element secured to the mirror housing and visible to the driver, the display element being activated by the thermostat upon activation of the heating element. A related mirror assembly is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
     The present invention concerns a heatable rear view mirror. It is in common knowledge to construct rear view mirrors for motor vehicles and especially in the present case, outside rear view mirrors, in such a manner that they may be heated. In this way, condensate, frost, snow ice or the like are removed from the mirror surface by means of a heating element in order that the mirror may provide an unobstructed field of view to the rear. The heating elements are designed, in this case, in the form of surface heating elements, which cover, essentially, the total, full surface of the mirror pane and extend themselves to the back side. Further, it is known, in the case of heatable rear view mirrors, to activate the heating element by means of a thermostat, that is, quasi-automatically, wherein, at a specified outside temperature, the thermo-switch closes the energized circuit to the heating element, so that it becomes activated. 
     Since the on and off switching of the mirror heating or of the heating element by means of the thermostat is done automatically, the driver of one of these vehicles equipped with one or more such mirrors has difficulties in recognizing whether the heating of the mirror is already automatically switched on or not. Often the mirror pane, for instance, is “blind” because of fogging or the like, yet the thermostat has still not switched itself on, since the temperature is not yet low enough, or the thermostat has directly switched to the on position before the driver checks the mirror viewing conditions. However, in the latter situation during the short time since the moment of switching on, no result is noticeable, since the mirror pane is not yet sufficiently warm. In such cases, the mirror heating is often turned on by the driver manually, but this additional manipulation by the driver is often unnecessary. If the thermostat has energized only immediately before the driver check of the mirror viewing conditions, and yet no evidence was seen thereof, then the mirror pane may not yet be sufficiently warmed. In other words, it would be desirable for the driver of a motor vehicle, which is equipped with one or more heatable rear view mirrors, to always know whether in the case of a fogged or “blind” mirror, that the automatic heating for the mirror for the elimination of this fogging is already turned on or not. If not, then in case of need, it would be possible to turn on the heater element by a separate switch which parallels the thermostat. 
     OBJECTIVES AND SUMMARY OF THE INVENTION 
     From these considerations, the present invention assumes the purpose to create a possible method for notifying the driver that the automatic mirror heating has been put into operation by the thermostat, whereby, this notification is carried out, so that the driver is not diverted from attention to street traffic. 
     For the achievement of this purpose, the present invention proposes a heatable rear view mirror, especially for motor vehicles, with at least one mirror pane contained in a mirror housing and at least one heating element dedicated to that mirror pane. The heating element is in the form of a surface heating element, which is actuated by means of a thermostat. This commonly known, heatable rear view mirror is, in accord with the invention, improved in such a manner that, in the case of an activated heating element, at least one display element is also activated, which is visible in a direct front view of the mirror. 
     With one glance at the rear view mirror, which practically every driver of the motor vehicle makes before, or immediately after starting a trip, in order to check the condition and adjustment of the mirror, the driver can thus verify whether or not the automatic mirror heating or heater equipment is switched on or off. If the visible display element seen in the direct front view of the mirror is activated, the display means that the thermostat has switched on the heating element and the mirror is already heated. In the case of a mirror which is still fogged or “blind”, the display indicates to the driver that he need not, on his own, activate the mirror heating from the instrument board, but that the mirror heating is already active, and within a short time, an unobstructed field of vision will appear through the then clear mirror. On the other hand, if the driver recognizes that the mirror is fogged, or is otherwise “blind”, and the mirror heating is still not activated, (since the display element is likewise not activated), he can directly activate the mirror heating by means of a corresponding manual switch operation. 
     Since the display element is visible in direct front view of the mirror the driver is not required to monitor any pilot light or the like on the instrument board. With a short side glance, without even moving his head, he can verify not only the condition of the mirror (adjustment and image quality) but also the on or off situation of the mirror heating. Distraction from attention to traffic is thus minimized. 
     Preferably, the display element emits light in the visible range, whereby the display element is designed as a light emitting diode (LED). LEDs are available in various colors, withstand on/off procedures in the area of several hundred thousand switching cycles, are insensitive to vibration, require no high connection costs and are easy to install. 
     In this case, the display element can be placed, for instance, behind the mirror pane and emit through the mirror pane. The display element or the LED lies thus behind the mirror pane and emits through the reflective coating directly in an outward direction. Because of the light penetration through the reflective coating from behind, there arises a certain weakening of the light emanating from the mirror surface. On this account, it is preferred, at the point where the display element will be placed, to remove, at least partially, the reflective layer in dashed lines or punctuations in order to achieve a greater emission of light. Also at this location of the display element, if the heating element is designed as a surface heater, an area must be cut out in the form of a round or rectangular shape. An advantage of the placement of the display element behind the mirror pane is that the display element is encapsulated on all sides by the mirror housing and mirror pane, and thereby protected. Furthermore, the display element lies directly in the sighting field of the driver. 
     As an alternative to the placement behind the mirror pane the display element can also be located beside the mirror pane in a designed rim area located between the mirror pane and the mirror housing. This placement has the special advantage that, in the case of a massively encrusted mirror pane (thick frost), the display element is more visible, than when it is behind the mirror pane and covered by the massive encrustation. 
     In a preferred arrangement, the display element and the thermostat are combined into one component and can thus be mounted quickly as one unit, wherein especially wiring costs are reduced. 
     Just as well, the display element and the thermostat can serve as separate items and then be brought together in a subassembly. This combination process is particularly advantageous in that it is made by a plug-in arrangement. 
     The brightness of the display element can be advantageously adjustable, in order to make sure that the display is sufficiently bright in a bright surrounding, such as during the day. In a darker situation, that is at night, it must not be so bright that it negatively affects the driver&#39;s vision. 
     In this matter, the brightness can be automatically controlled dependent upon the intensity of the ambient light and, for instance, the monitor could be a photocell. 
     The display element, in accord with the basic idea or embodiment of the present invention, can be the display, per se, for the mirror heating. Just as well, however, the display element can illuminate from behind a corresponding symbol which then makes explicitly clear, unmistakably to the driver, that the mirror heating is activated. This symbol can be, for instance, adhesively fastened to the outside mirror surface or it can be engraved in the outside mirror surface or etched therein. 
     Further details, aspects, and advantages of the present invention arise from the following to be understood as a purely illustrative and non-limiting description of an embodiment in the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     There is shown in: 
     FIG. 1 a partial sectional view through a heatable rear view mirror in accord with the invention; 
     FIG. 2 a schematic circuit diagram of the electrical components of the heatable rear view mirror of FIG. 1; 
     FIG. 3 a  is a schematic diagram of a first location of a display element; and 
     FIG. 3 b  is a schematic diagram of a second location of a display element. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference will now be made in detail to the presently preferred embodiments of the present invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, and not meant as a limitation of the invention. 
     A rear view mirror as shown in FIG. 1, under the general designation of  2 , exhibits a multilayered construction from a mirror outer, or forward, side  4  to a mirror inside, or rear, side  6 . The layers are namely, a mirror pane  8 , a reflective surface  10 , a doubled sided adherent film  12 , a semi-conductor paste  14 , a silver conducting paste  16 , a polyester film  18 , an adhesive  20  and a pane support  22 . Mirror  2  is mounted in a housing  1 . 
     The construction of the rear view mirror with the layers  8  through  22  forms in a conventional manner a heatable rear view mirror with a surface type heating element, which is essentially constructed by the semiconductor paste  14  and the silver conducting paste  16 . 
     The electrical connection necessary for the achievement of electrical current flow and thus also of heat generation is accomplished by cable  24 , connected to subassembly  26 , which group will be described below. From the subassembly  26 , a solid connection  28  is run to the heat element, which element is essentially comprised of the semiconductor paste  14  and the silver conductive paste  16 . The contacting of the connection  28  with the heating element is accomplished, for example, by one or more rivets  30 , wherein the connection zone is embedded in an insulating material  32 . A second such connection is provided to create a closed circuit in connection with the heating element, but is not shown in FIG.  1 . 
     The subassembly  26  exhibits on one end or on a side a contacting plug  34  which is insertable into a receptacle  36  on the cable  24 . From the contact plug  34  (a connection  38 ) runs to a display element  40 , which, in the depicted embodiment, is a light emitting diode (LED)  42  with an integral series resistor  44 . The LED  42  is secured in a holder  46 , which is fastened to the underside of the support plate  22 . The fastening is effected by adhesion or in that the holder is made in one piece with the support plate  22 . Further, this holder  46  also carries a thermostat  48 . A connection  50  leading away from the thermostat  48  connects to the connector  28 , which then leads to the heating element. 
     The thermostat  48  possesses a solid contact  52  and a movable contact  54 , which is, for example, comprised of bimetallic strips and is dependent upon the ambient temperature as to whether movable contact  54  makes with the solid contact  52 , thus closing the circuit, or whether contact  54  breaks from the solid contact  52 , thereby opening the circuit as shown in FIG.  1 . In the case of a closed circuit, the heating element is activated, and conversely, upon a broken circuit, the same is deactivated. 
     At that point where the display element  40 , i.e. the LED  42 , is situated, the individual layers  10  to  22  are, for example, circularly excised and form thereby an open cutout  56 . Furthermore, the reflective layer  10  is similarly circularly excised, again forming therein an open cutout, which now represents an aperture  58 . In accord with FIG. 1, aperture  58  lies coaxially to the circular cutout  56 , (and can be) of a smaller diameter or of the same size as the cutout  56 . Thus, emitted or radiated light from the LED  42  can emerge through the cutout  56  and the aperture  58  and through the mirror pane  8  to the outside. 
     Instead of the aperture  58 , in its place can be a symbol or pictogram, which is then illuminated by the LED from behind, and is visible on the outside  4  of the rear view mirror  2 . A symbol of this kind or a pictogram can also be glued to the outer surface of the mirror, or inscribed or etched therein, so that, in similar manner, it is illuminated by the LED  42  from behind. 
     The electrical circuit diagram of the assembly as shown in FIG. 1, is once again repeated in FIG.  2 . The current circuit runs from a line connection A, through the cable  24 , through the series resistor  44 , the LED  42 , the solid and the movable contacts  52 ,  54  of the thermostat  48 , as well as through the connections  50  and  28  to the heating element. The heating element is comprised of the semiconductor paste  14  and the silver conducting paste  16 . From the heating element, the current circuit runs to a line connection B, not further described in FIG.  1 . The line connections A and B are connected to the on-board electrical system of the motor vehicle. In addition to the thermostat  48 , yet another switch  60  is provided, with which the thermostat  48  can be bypassed. In other words, even with an opened thermostat  48  switch, by means of the switch  60 , the circuit between the connections A and B, through the LED  42  and the heating element can be closed. The additional switch  60  is to be located on the instrument panel of the motor vehicle and at that position can be manually operated by the driver. 
     Further, an apparatus can even be provided which can adjust the intensity of the light emitted by the LED  42  or from another display element. The operation thereof would preferably be carried out automatically. This process would be done by an appropriate sensor, for instance, a photocell or the like, which would regulate the intensity of the light from the LED  42 , that is, the display element  40 , in accord with the intensity of the ambient light. The brighter the ambient light is, just so much brighter the display element would be regulated. Conversely, the darker the surrounding light is, just so weaker would be the light emission of the display element  40 . Sufficient visibility on the one hand, yet an avoidance of a detrimental visual stimulus on the other is hereby assured. 
     For instance, the subassembly  26  can be designed as a factory assembled unit and mounted on a circuit board, which, by means of the support  46 , can be fastened onto the rear side of the support plate  22 . As an alternative to this, the single components of the subassembly  26 , including the series resistor, the display device  42  and the thermostat  48  can all be individual components. They can be put together to make up the subassembly in a plug-in connection with one another. 
     The movable contact  54  of the thermostat  48  closes the current circuit at a specified ambient temperature, so that the mirror heating is turned on by itself. The mirror pane  8  is essentially completely heated over the entire surface from behind, so that a fogging, frost, or the like is removed from the mirror pane surface by the heating of the mirror pane  8 . At the same time this is going on, the activated display element or LED  42  is visible through the cutout  56  and the aperture  58 . In one glance in the rear view mirror the driver of a motor vehicle recognizes, whether or not this heating has been switched on automatically. If, for any reason, the mirror pane  8  is fogged, covered with frost, or is otherwise “blind”, and the LED  42  does not light up, that is, the thermostat has not closed the current circuit automatically, then the driver can bypass the thermostat manually by closing the switch  60  and thus energize the mirror heating, in order to have an unobstructed view. 
     If, in the aperture  58  or, the cutout  56 , a symbol or a pictogram is arranged on the outside of the mirror, for instance, a plurality of interposed wave lines, then the driver can unmistakably be advised by the display that the mirror heating is in operation. 
     Instead of locating the subassembly  26  containing the LED  42  or another light emitting optical display element in the preferred mirror viewing area as in FIG. 3 a,  at least the display element  40 , for instance, in the form of an LED, can be located beside the mirror pane as in FIG.  3   b.  This location would be in a designed rim area, located between the mirror pane  8  and the mirror housing  1   a.  In this way, the display element  40  or the LED  42  is still in the direct viewing area of the driver, but no longer situated behind the mirror pane  8 . Under some circumstances this has the advantage, that in the case of a particularly heavily fogged mirror or a mirror surface covered with a thick layer of frost, the LED  42  situated outside of the surface of the mirror pane  8  would be more visible. 
     By means of a preferred embodiment of the present invention, it is possible to make the automatic on and off switching of a heating element for a heatable rear view mirror visible to the driver, without the necessity of the driver to look outside of his normal field of vision or to monitor a display element for the thermostat on his instrument panel. In case of need a non-activated mirror heating element can be turned on by an additional manual switch, in order to continually have a clear mirror surface and an unobstructed field of vision. 
     It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the scope and spirit of the invention, as embodied in the appended claims and their equivalents.