FIELD OF THE INVENTION 
   The present invention relates to a vehicular rearview mirror, and more particular to a vehicular rearview mirror having a composite housing structure. 
   BACKGROUND OF THE INVENTION 
   Please refer to  FIGS. 1A and 1B  which are a perspective and a resolving diagrams schematically showing a conventional structure of a conventional vehicular interior rearview mirror. The rearview mirror includes a front housing  11 , a rear housing  12 , and a mirror  13  disposed between the front and the rear housings  11  and  12 . The front and the rear housings  11  and  12  are conventionally made of a rigid plastic material such as polycarbonate (PC) or acrylonitrile-butadiene-styrene (ABS) resin for securing therebetween the mirror  13 . As is known, due to both of the front housing  11  and the mirror  13  are inflexible, it is almost impossible for them to be in very close conjunction with each other. In other words, there is a certain level of gap existing between the housing  11  and the mirror  13 . Therefore, the impact tolerance of the mirror  13  is adversely affected. Further, when a driver is seated in a vehicle, the interior rearview mirror has to be adjusted in order to have a proper view range from the mirror  13  while driving. The frequent manipulation of the rigid mirror housing  11 ,  12  would distort the mirror to some extent. The above-mentioned problems are even more serious when the housing material is aged due to long term exposure in the sunlight. 
   Compared to the interior rearview mirror that is generally planar, an exterior rearview mirror even more significantly suffers from the gap existing between the housing  11  and the mirror  13  due to its convex or aspheric (i.e. multi-radius) feature. As is known to those skilled in the art, it is relatively difficult to combine the housing with the non-planar mirror tightly. 
   SUMMARY OF THE INVENTION 
   Therefore, an object of the present invention is to provide a housing structure of a vehicular rearview mirror, which is rigid enough for securing the mirror therein and subject to close conjunction with the mirror. 
   According to a first aspect of the present invention, a vehicular rearview mirror comprises a mirror for showing thereon an image; a first housing structure made of a first material, and accommodating therein the mirror with a portion of the mirror exposed to show the image; and a second housing structure made of a second material, and disposed between and keeping in contact with the first housing structure and the exposed portion of the mirror. The second material has a flexibility higher than that of the first material. 
   Preferably, the first housing structure includes a front piece and a rear piece combined with each other to hold the mirror therein. 
   Preferably, the front piece is of a ring shape for exposing the portion of the mirror, and the second housing structure is of a ring shape in conjunction with the front piece of the ring shape. 
   Preferably, the rear piece is disposed therein a plurality of buffering posts for sustaining against the mirror to secure the mirror in the first housing structure. 
   In an embodiment, the second housing structure has a slot on an outer circumference thereof for partially receiving the front piece, and a curved portion on an inner circumference thereof for close contact with the portion of the mirror. 
   In another embodiment, the second housing structure is formed by injection molding to the front piece. 
   Preferably, the second material is selected from a group consisting of rubber and resin, e.g. natural rubber, silicone rubber and epoxy resin. 
   Preferably, the first material is selected from a group consisting of engineering plastic, metallic material, carbon fiber and wood. The engineering plastic is, for example, nylon preferably incorporated therein a proper content of glass fiber, polybutylene terephthalate (PBT), polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), high-impact polystyrene (Hi-PS), polypropylene (PP), liquid crystal polymer (LCP), polyethylene (PE) and polystyrene (PS). The metallic material, for example, is a metal or an alloy such as magnesium alloy. 
   The mirror, for example, can be a partially reflective mirror, an electrochromic mirror or a liquid crystal display. On the other hand, the mirror can have a planar, convex or aspheric shape. Preferably, the mirror is combined therewith a thin film display such as a thin-film electro-luminescence (EL) digit display, a light-emitting diode (LED), an organic light-emitting diode (OLED), a liquid crystal display (LCD) or a vacuum fluorescent display (VFD). 
   According to a second aspect of the present invention, a vehicular rearview mirror comprises a mirror for showing thereon an image; a rear housing structure having an opening for receiving therefrom the mirror; and a front housing structure combined with the rear housing structure to confine the mirror therebetween, and including an outer hollow portion in conjunction with the rear housing made of a first material and an inner hollow portion in contact with the mirror made of a second material, the second material having a flexibility higher than that of the first material. 
   Preferably, the rear housing is also made of the first material, which for example, can be plastic metallic material, carbon fiber or wood. 
   Preferably, the rear housing structure includes a plurality of buffering posts urging the mirror to sustain against the front housing to securely confine the mirror when the front housing structure is combined with the rear housing structure. 
   The second material can be selected from a group consisting of rubber, resin and any other suitable elastomeric material. For example, the second material is selected from a group consisting of natural rubber, silicone rubber and epoxy resin. 
   Preferably, the inner hollow portion has a slot on an outer circumference thereof for engaging with an inner circumferential edge of the outer hollow portion. More preferably, the inner hollow portion has a curved portion on an inner circumference thereof bent toward the mirror for close contact with the mirror. 
   Alternatively, the inner hollow portion is formed by injection molding to the outer hollow portion. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention may best be understood through the following description with reference to the accompanying drawings, in which: 
       FIG. 1A  is a perspective diagram schematically showing a conventional structure of a conventional vehicular interior rearview mirror; 
       FIG. 1B  is a resolving diagram of the rearview mirror structure of  FIG. 1A ; 
       FIG. 2A  is a perspective diagram schematically showing a structure of a vehicular rearview mirror according to a preferred embodiment of the present invention; 
       FIG. 2B  is a resolving diagram of the rearview mirror structure of  FIG. 2A ; 
       FIG. 3A  is a perspective diagram schematically showing an embodiment of the composite front housing structure of the vehicular rearview mirror of  FIG. 2 ; 
       FIG. 3B  is a resolving diagram of the composite front housing structure of  FIG. 3A ; 
       FIG. 4  is a schematic cross-sectional view of the front housing taken along the line A—A of  FIG. 3A ; and 
       FIG. 5  is a perspective diagram schematically showing an embodiment of the composite rear housing structure of the vehicular rearview mirror of FIG.  2 . 
   


   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only; it is not intended to be exhaustive or to be limited to the precise form disclosed. 
   Please refer to  FIGS. 2A and 2B . An embodiment of a vehicular rearview mirror according to the present invention includes a front housing  21 , a rear housing  22  and a mirror  23 . When assembling, the mirror  23  is put into the rear housing  22  from an opening  220 , and the front housing  21  is put on the top of the mirror  23  and combined with the rear housing  22 . The combination of the front housing  21  with the rear housing can be implemented by adhesion, engagement, welding or any other suitable technique, depending on the material of the housings. The material of the rear housing, for example, can be plastic, rubber, resin, metallic material, carbon fiber or wool, depending on practical and decoration considerations. Preferably, the rear housing is made of an engineering plastic such as nylon, PBT, PC, ABS, HI-PS, PP, LCP, PE or PS, magnesium (Mg) alloy, carbon fiber, etc. More preferably, glass fiber can be added into nylon to adjust rigidity of the rear housing when nylon is used as the material. 
   The front housing  21  is hollow for exposing a portion of the mirror  23  in order to show other cars or objects behind the vehicle on the mirror. As shown in  FIG. 3A , the front housing further includes an outer hollow portion  211  and an inner hollow portion  212 . The materials for forming the outer hollow portion  211  and the inner hollow portion  212  are different for achieving a special purpose that will be described hereinafter. The material for forming the outer hollow portion  211  is required to be rigid in order to secure the mirror  23  therein. On the other hand, the material for forming the inner hollow portion  212  has a flexibility higher than the material for forming the outer hollow portion  211 . The relatively flexible material interfaces the relatively rigid outer portion and the mirror after assembling so that a buffer is provided for the mirror to avoid the above-mentioned problems. 
   As is known, the relatively flexible material can be made in close contact with the mirror by providing a suitable pressing force without damaging the mirror. By disposing the relatively flexible material between the relatively rigid material, hardly gap is rendered after assembling. Consequently, the impact tolerance is improved. In addition, the elastomeric material itself also facilitates the reduction in impact effect. 
   For example a rubber or resin is preferred to serve as the relatively flexible material to form the inner hollow portion  212  of the front housing  21 . More specifically, the material can be natural rubber, silicone rubber or epoxy resin. Other flexible material can also be applied here as long as it can be formed to be engageable with the outer hollow portion  211  and in close contact with the mirror  23 . 
   The material for forming the outer hollow portion  211 , although not necessarily, is preferably the same as that for forming the rear housing  22 , e.g. plastic, metallic material, carbon fiber, wood, etc., to facilitate assembling. 
   The inner hollow portion  212  can be separately manufactured and then mounted to the outer hollow portion  211  to form the front housing  21 , as shown in FIG.  3 B. In this embodiment, the inner hollow portion  212  has a slot  31  on an outer circumference thereof for engaging with an inner circumferential edge  32  of the outer hollow portion  211 , as shown in  FIG. 4  which schematically show the cross-sectional view of the front housing taken along the line A—A of FIG.  3 A. The inner hollow portion  212  further has a curved portion  33  on an inner circumference thereof bent toward the mirror  23  for close contact with the mirror. When exerting a pressing force to assemble the rearview mirror, the flexible curved portion  33  will safely sustain against the mirror to result in almost no gap therebetween. When exerting a force to move the housing to adjust the view range, the interfacing flexible material serving as a buffer to avoid the distortion of the mirror. 
   Alternatively, the inner hollow portion  212  can be made in conjunction with the outer hollow portion  211  by injection molding to the outer hollow portion  211 , on the condition that proper materials are used. 
   The rear housing  22  preferably further provides therein a sustaining force to facilitate the close contact between the mirror  23  and the front housing  21 . In order to achieve this purpose, a plurality of buffering posts  221  are disposed in the rear housing  22 , as shown in  FIG. 5 , which flexibly sustains against the back of the mirror  23  when the rearview mirror is assembled. Each of the buffering posts  221  includes a rigid portion  222  and an elastomeric portion  223 . The rigid portion  222  provides sufficient support to sustain against the mirror  23 , and the elastomeric portion  223  provides sufficient buffer between the mirror  23  and the rigid portion  222 . Due to the presence of the buffering posts  221 , the mirror  23  is urged to press on the front housing  21  to reduce the gap, while the mirror  23  is also properly buffered to avoid damage. The material for forming the rigid portion  222  is preferably but not necessarily the same as that for forming the rear housing  21 , while the material for forming the elastomeric portion  223  is preferably but not necessarily the same as that for forming the inner hollow portion  212 . The rigid portion  222  can be integrally formed with the rear housing  21  or mounted to the rear housing  21 . 
   By using different kinds of mirrors, the rearview mirrors according to the present invention may have various functions. For example, in addition to general partially reflective mirror, the mirror can also be an electrochromic mirror, which change color thereof in response to light intensity received thereby in order to eliminate glare effect. The common partially reflective mirror or electrochromic mirror can be combined therewith a thin film display (see  FIG. 2B , reference numeral  24 ) to exhibit enhanced functions. For example, the driving information such as speed, revolving rate, outside image picked up by a vehicular CCD or CMOS camera can be shown on the display for the driver&#39;s reference. The thin film display, for example, can be, a light-emitting diode (LED)-, an organic light-emitting diode (OLED), a liquid crystal display (LCD) or a vacuum fluorescent display (VFD). A new trend is to directly use an LCD as the rearview mirror. Anti-glare effect may also be exhibited by the LCD rearview mirror. 
   The housing structure according to the present invention is suitable to be applied to both of the interior and exterior rearview mirrors. Especially for an exterior mirror having a convex or aspheric (i.e. multi-radius) shape, the presence of the elastomeric inner hollow portion assures of the close conjunction between the housing and the mirror of the assembled rearview mirror. 
   To sum up, by additionally providing the flexible portion to interface the rigid housing and the fragile mirror, the impact tolerance and distortion tolerance can be improved. 
   While the invention has been described in terms of what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention need not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.
A vehicular rearview mirror includes a mirror for showing thereon an image; a first housing structure made of a first material, and accommodating therein the mirror with a portion of the mirror exposed to show the image; and a second housing structure made of a second material, and disposed between and keeping in contact with the first housing structure and the exposed portion of the mirror. The second material has a flexibility higher than that of the first material.