Housing for vehicular lamp assembly
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a housing for mounting a lamp assembly such as a vehicular headlamp assembly to a vehicle body and particularly to a housing for a vehicular lamp assembly superior in impact strength, light in weight and capable of being provided at low cost. 
     2. Prior Art 
     Heretofore, as shown in FIG. 13, there has been used a housing formed by a pressed steel sheet as a housing for mounting a vehicular headlamp assembly to the body of an automobile. A vehicular lamp assembly housing 50 of this type is for mounting a body 54 of a vehicular lamp assembly which comprises a lens 51 fitted over a front opening to seal the opening, a lamp 52 as a light source supported at the rear end and a reflecting mirror 53 formed along the inner surface of the body, in such a manner that the angle in a facial direction of the lamp assembly body can be changed freely. The housing 50 is generally of a planar, annular structure provided on one side thereof with an inclination adjusting means 55 and an inclination support means 56, while on the other side there is constituted a mounting structure 57 by steel sheet for fixing the housing 50 to the body of an automobile, and at a central part of the housing there is formed at through hole 58 of a size permitting insertion therein of the rear end portion of the body 54. The inclination adjusting means 55, inclination support means 56 and mounting structure 57 are constituted as pressed members separate from the housing 50 and are rendered integral with the housing 50 by a suitable method such as welding or bolting. 
     OBJECTS OF THE INVENTION 
     Recently there has been a demand for reducing the weight of automobiles to improve fuel economy and also as to the vehicular lamp assembly housing 50 of steel sheet mentioned above, it has been desired to constitute the housing using a synthetic resin to reduce the weight thereof. However the use of resin for the vehicular lamp assembly housing 50 has not been realized yet because the housing is required to have a predetermined strength high enough to support the body 54 of the lamp assembly, and up to now there have been used steel sheet housings. 
     Further, in constituting the vehicular lamp assembly housing 50 using steel sheet, it is necessary that the inclination adjusting means 55 for adjusting the angle relative to the body of an automobile, the inclination support means 56, the mounting structure 57 for the automobile body, and other plural steel sheet members including projections, be fabricated as separate members using a die and then rendered integral by such a method as welding or bolting. Consequently, a large number of components and working steps are required and it takes much time and labor for assembly or mounting. 
     The present invention has been accomplished in view of the above-mentioned problems. It is the first object thereof to provide a vehicular lamp assembly housing obtained by constituting the conventional steel sheet housing 50 using a synthetic resin in place of steel sheet, the synthetic resin housing being superior in impact strength and permitting the reduction of weight of a vehicle. 
     It is the second object of the present invention to provide a vehicular lamp assembly housing of a low cost fabricated by integral molding using a synthetic resin material to simplify the structure of the housing itself and reduce the number of working steps. 
     SUMMARY OF THE INVENTION 
     The vehicular lamp assembly housing of the present invention, which supports the body of a vehicular lamp assembly adjustably in the mounting angle of the same body and which is fixed to the body of a vehicle in a predetermined position, is characterized in that it is constituted as an annular structure in a plane shape thereof wherein there is centrally formed a through hole which permits insertion therein of the rear end portion of the vehicular lamp assembly, and a portion thereof is retracted in the depth direction to form a three-dimensional curved surface, that the inner and outer peripheral portions are respectively formed with annular, inner and outer peripheral edges bent backwards approximately perpendicularly to the surface of the annular structure, that an annular or nearly annular, continuous reinforcing rib is erected between the inner and outer peripheral edges, and that a multitude of connecting ribs are integrally formed of a fiber-reinforced synthetic resin at suitable intervals in a crossing relation to the reinforcing rib. 
     A desired strength can be attained by using FRPP which comprises polypropylene and 40% glass fibers mixed therein. 
     Generally in the case of FRPP, as shown in FIG. 11 which is a graph of impact resistance and in FIGS. 12(a) and (b) which are graphs of rigidity (aiming holding force), impact resistance and rigidity are improved by increasing the proportion of glass fibers relative to polypropylene. However, as the proportion of glass fibers added to the resin material increases, the degree of design freedom associated with moldability becomes lower. In the present invention, therefore, a preferred range of glass fiber proportion is 30% to 50%. 
     According to the above construction, that is, a three-dimensionally twisted structure in which an annular molded frame is deformed in front and in the rear in the facial direction, a circumferential pressure is allowed to escape through a facial distortion, while a facial pressure is allowed to escape through a circumferential distortion. Thus, impact energy applied to the housing is extinguished by distortion to avoid damage. Additionally, since the inner and outer peripheral edge reinforcing rib and connecting ribs are integrally formed on the rear face of the annular frame, the rigidity of the entire annular frame can be improved without increase of weight. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view as seen from the back of a vehicular lamp assembly housing embodying the present invention; 
     FIG. 2 is a perspective view of the housing as seen in a plane direction; 
     FIG. 3 is a front view of the housing; 
     FIG. 4 is a rear view thereof; 
     FIG. 5 is a right side view thereof; 
     FIG. 6 is a sectional view taken on line VI--VI in FIG. 3; 
     FIG. 7 is an enlarged sectional view taken on line VII--VII in FIG. 4; 
     FIG. 8 is a front view of a vehicular lamp assembly as mounted to the housing; 
     FIG. 9 is a sectional view of a principal portion thereof; 
     FIG. 10 is an enlarged partial front sectional view take on line X--X in FIG. 8; 
     FIG. 11 is a graph showing impact resistance of the product of the present invention; 
     FIG. 12(a) and (b) are graphs showing rigidity in an atmosphere held at room temperature and that at 80° C., respectively; and 
     FIG. 13 is a sectional view of a vehicular lamp assembly as mounted to a conventional vehicular lamp assembly housing. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a perspective view of the whole of a vehicular lamp unit housing embodying the invention as seen from the back; FIG. 2 is a perspective view of the housing as seen in a plane direction; FIG. 3 is a front view of the housing; FIG. 4 is a rear view thereof; FIG. 5 is a right side view thereof; and FIG. 6 is a sectional view taken on line VI--VI in FIG. 3. 
     In the above figures, a housing 1 is an integrally molded housing obtained from a glass fiber-reinforced resin comprising polypropylene and 40% glass fibers mixed therein. For fixing the housing to the front grille portion of a vehicle body 30 by clamping means 31 such as bolts and nuts, mounting holes 4 are formed in flat portions 3 provided in predetermined positions of an annular frame 2 and there are also provided positioning pins 5 for the vehicle body 30. The annular frame 2, in a plane shape thereof, is centrally formed with a through hole 6 through which is inserted the rear end portion of a parabolic reflecting mirror 22 having a front opening and fixed to a lamp housing 21 of a vehicular lamp assembly 20. The frame 2 is retracted at a portion thereof (right upper poriton indicated by arrow A in this embodiment) to provide a &#34;twist shape&#34; constituted by a three-dimensional curved surface. This &#34;twist shape&#34; is for maintaining the strength of the entire housing 1, in other words, for absorbing and eliminating circumferential or facial pressure or impact applied to the frame 2 after mounting of the housing to the vehicle body, through appropriate distortion. The retreat ratio of the frame surface, that is, the size of the &#34;twist shape&#34;, can be changed in design according to the size of the vehicular lamp assembly 20 or the shape of the mounting structure on the side of the vehicle body 30. 
     The inner peripheral portion of the frame 2 which defines the through hole 6 is formed with an annular inner peripheral edge 7 bent backwards nearly perpendicularly to the surface thereof, and the outer peripheral portion of the frame 2 is formed with an annular outer peripheral edge 8 also bent backwards approximately perpendicularly to the surface thereof. Further, a generally annular continuous reinforcing rib 9 is erected between the inner peripheral edge 7 and the outer peripheral edge 8 and a large number of connecting ribs 10 are disposed at appropriate intervals in crossing relation to the reinforcing rib 9 to connect between the inner and outer peripheral edges 7 and 8. The ribs 9 and 10, as shown in FIG. 7, are each formed with a concave portion which is thicker in the crossing direction, in the position of contact with the inner surface portion of the frame 2. The concave portions 11 act to enhance the strength of the connection between the frame 2 and the ribs 9, 10 as well as the twist strength. On one side of the frame 2, more particularly on the front grille side of the vehicle body 30, there is integrally formed a grille connecting edge 12 projecting backwards of the vehicular lamp assembly 1 in the form of a crank, and retaining pins 33 projecting from a grille member 32 are press-fitted into corresponding engaging holes 13 formed in the grille connecting edge 12, thereby providing an integral connection. 
     FIG. 8 is a front view of the vehicular lamp assembly 20 as mounted to the vehicular lamp assembly housing 1; FIG. 9 is a sectional view of a principal portion thereof; and FIG. 10 is an enlarged sectional view taken on line X--X in FIG. 8. 
     In those figures, the housing 1 has a joint member 14 which pivotably connects a spherical connection end of a universal joint rod 23 projecting from the rear face of the lamp housing 21, and two bolt receiving members 15 fixed in orthogonal positions with respect to the joint member 14. The bolt receiving members 15 are each formed with internal threads for engagement with an angle adjusting bolt 26 projecting from the front to the rear side of a bolt seat 24 of the lamp housing 21, the angle adjusting bolt 26 having a head portion 25 pivotably held by the bolt seat 24. The lamp housing 21 is supported adjustably in angle through the universal joint rod 23 and two angle adjusting bolts 26. 
     Numeral 27 denotes a socket attached removably to the rear end of the parabolic reflecting mirror 22. Upon removal of the socket 27 from the rear end of the parabolic reflecting mirror 22, a light source lamp 28 mounted to the socket 27 can be taken out of the mirror 22. Numeral 29 denotes a headlight lens fitted over the opening of the parabolic reflecting mirror 22. 
     The flat portions 3 of the housing 1 with the headlamp assembly 20 attached thereto are brought into abutment with the vehicle body 30 or a bracket 34 formed on the side of the vehicle body, and the pins 5 projecting from the flat portions 3 of the frame 2 are fitted into small holes 35 formed on the side of the vehicle body 30, thereby effect positioning. At the same time, the housing is clamped and fixed by clamping means 31 such as bolts and nuts. The vehicle body portion or the bracket 34 is formed with a through hole 36 in a position opposed to the headlamp assembly 20, especially the rear end portion of the parabolic reflecting mirror 22, for removing the socket 27 from the said rear end portion. 
     The impact resistance and rigidity of the glass fiber-reinforced resin (FRPP) are improved by increasing the mixing ratio of glass fibers to polypropylene as shown in the graph of impact resistance of FIG. 11 obtained by dropping a steel ball of a predetermined weight from a predetermined height and checking the state of damage and also as shown in the graphs of rigidity (aiming holding force) obtained by the application of continuous load and measuring the resulting deformations in an atmosphere of room temperature (a) and of 80° C. (b). In the case of FRPP, however, with increase in the mixing ratio of glass fibers to the synthetic resin material, the degree of design freedom associated with moldability becomes lower. As a result of study, a polypropylene resin having a glass fiber content of 40% proved to be most preferable. 
     It goes without saying that the above construction can be suitably modified or changed in design within the scope of the objects of the present invention. For example, the method of mounting the headlamp assembly to the housing and the method of mounting the housing to the vehicle body side are not limited in their structure to the above embodiment. 
     Thus, the body of the vehicular lamp assembly housing is constituted by a polypropylene resin incorporating 30% to 50% of glass fibers therein, as described above, whereby the reduction in weight of the components can be attained without impairing impact resistance and rigidity. The housing of the invention not only has the feature that circumferential or facial pressure can be absorbed by facial or outer peripheral distortion to avoid damage of the housing itself, but also has an outstanding effect that the number of components of the housing and of working steps can be reduced to a remarkable extent to thereby improve the efficiency of the mounting operation.