Abstract:
A vehicle lamp includes an outer lens and an inner lens disposed inside the outer lens. The inner lens covers an area narrower than the outer lens and is supported with the body by laser welding. The inner lens and the body respectively have joint areas. A laser absorber is contained in an interface between the joint areas. The joint areas are overlapped and laser beam is emitted to the laser absorber from behind the joint area of the inner lens.

Description:
[0001]     The present application claims foreign priority based on Japanese Patent Application No. P.2004-154493, filed on May 25, 2004, the contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a method of producing vehicle lamps. More particularly, the present invention relates to the art of ensuring that two members including an inner lens are joined together with an improved external appearance in the method of producing a vehicle lamp having the inner lens disposed inside an outer lens such that the inner lens covers an area narrower than the outer lens and that two members including the inner lens are joined together by laser welding.  
         [0004]     2. Related Art  
         [0005]     In producing a vehicle lamp having an inner lens disposed inside an outer lens such that the inner lens covers an area narrower than the outer lens, the inner lens has heretofore been fitted to the outer lens by ultrasonic welding or fixed to a body by lance mating, for example.  
         [0006]     When the inner lens is joined to the outer lens by ultrasonic welding as described above, there has existed a problem of deteriorating the external appearance of the lenses in that the weld between the outer lens and the inner lens is seen through the outer lens, that the compatibilized portion between the outer lens and the inner lens is jutted out aside or that the jutted-out portion is seen through the outer lens. In the case where an inner lens and a body are injection-molded pieces, when the inner lens is fitted to the body by lance mating, the presence of an overlapped portion in the direction in which the mold like a lance is taken out makes a hole for taking out the mold in the rear of the portion above (in the direction in which the mold is taken out). Consequently, the portion on the back side of the lighting device is seen through the hole, which also deteriorates the external appearance.  
         [0007]     In addition, there also develops a problem of taking time for assembly work and machining under the prior art method described above.  
       SUMMARY OF THE INVENTION  
       [0008]     In accordance with one or more embodiments of the present invention, in a method of producing a vehicle lamp having an inner lens disposed inside an outer lens such that two members including the inner lens are joined together by laser welding to cover an area narrower than the outer lens, the two members that are joined together have joint areas, respectively; and the method thereof comprises the steps of putting the joint areas on top of each other with a laser absorber contained in the interface therebetween and emitting laser beam to the laser absorber from behind the joint area of one of the member.  
         [0009]     Therefore, the method of producing a vehicle lamp according to one or more embodiments ensures that the two members including the inner lens are joined together in a short time with an excellent external appearance.  
         [0010]     In the method of producing a vehicle lamp according to one or more embodiments, the laser welding is employed for joining purposes, so that the joining work can be done in a short time. Moreover, as irradiation energy toward the laser absorber is made readily controllable without allowing any excessive compatible portion to be jutted out a side, an excellent external appearance is offered.  
         [0011]     As the laser absorber becomes transparent by laser beam irradiation, only the undercoat color is seen through the inner lens, so that there is no fear of deteriorating the external appearance in this respect.  
         [0012]     In accordance with one or more embodiments of the present invention, the laser absorber is kneaded into the resin material of the inner lens, whereby since the cubic volume of the inner lens is smaller than those of the outer lens and the body, only a small amount of the laser absorber is needed to cope with the requirements, which results in making the use of the laser absorber less costly.  
         [0013]     In accordance with one or more embodiments of the present invention, the step of emitting laser beam further includes passing the laser beam through the inner lens and converging the laser beam to the joint area of the inner lens, whereby the irradiation energy of the laser beam effectively acts on the laser absorber.  
         [0014]     In accordance with one or more embodiments of the present invention, the laser absorber is applied by, for example, painting to the joint area of the member facing the joint area of the inner lens and the laser beam is emitted through the inner lens, whereby only a small amount of laser absorber for use will suffice.  
         [0015]     In accordance with one or more embodiments of the present invention, the adoption of the form of inserting a sheet with the laser absorber kneaded in, between the joint areas of the two members results in making reducible the amount of laser absorber used.  
         [0016]     Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1A  is a schematic front view of a vehicle lamp to be made by way of example under a method of producing a vehicle lamp according to one or more embodiments of the present invention.  
         [0018]      FIG. 1B  is a schematic sectional view taken on line b-b of  FIG. 1A .  
         [0019]      FIG. 2  is a rear view of an inner lens as an example of what has a joint area into which a laser absorber is kneaded.  
         [0020]      FIG. 3  is a sectional view showing a principal part in a laser welding process by way of example.  
         [0021]      FIG. 4  is a sectional view showing a principal part in another laser welding process by way of example.  
         [0022]      FIG. 5  is a sectional view showing a principal part in still another laser welding process by way of example.  
         [0023]      FIG. 6  is a schematic drawing showing a laser beam emission method.  
         [0024]      FIG. 7  is a schematic drawing showing another laser beam emission method.  
         [0025]      FIG. 8  is a schematic drawing showing still another laser beam emission method. 
     
    
     REFERENCE NUMERALS AND CHARACTERS  
       [0026]      10  . . . vehicle lamp,  20  . . . body (another member),  23  . . . joint area,  30  . . . inner lens,  32  . . . joint area,  40  . . . outer lens,  60  . . . laser absorber,  71  . . . laser beam,  80  . . . sheet in which laser absorber is kneaded  
       DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]     Next, embodiments of the invention will be described with reference to the accompanying drawings.  
         [0028]      FIG. 1A  and  FIG. 1B  show an example of a vehicle lamp to be produced according to one or more embodiments of the present invention.  
         [0029]     A vehicle lamp  10  is provided with a body  20  having two concave portions  21  opening forward (only one of them is shown in  FIG. 1B ). The front faces of the concave portions  21  are respectively covered with inner lenses  30 . The outside with the inner lenses  30  provided thereon is covered with an outer lens  40 . Further, light source bulbs  50  (only one of them is shown in  FIG. 1B ) are supported by the body  20  so that the light source bulbs are positioned inside the respective concave portions  21 .  
         [0030]     The body  20 , the inner lenses  30 , and the outer lens  40  are formed of thermoplastic resin by injection molding. The inner lenses  30  are supported with the body  20  by laser welding.  
         [0031]     A stepped portion  22  is formed in the open edge part of the concave portion  21  of the body  20  and the forwardly-directed area  23  of the stepped portion is made a joint area.  
         [0032]     An outwardly-projected edge  31  is formed in the circumferential portion of the inner lens  30  and the rear face  32  of the projected edge  31  is also made a joint area.  
         [0033]     The projected edge  31  of the inner lens  30  is mated with the stepped portion  22  of the body  20 . The joint area  32  of the inner lens  30  is brought into contact with the joint area  23  of the body  20 . At this time, the interface between the joint area  32  of the inner lens  30  and the joint area  23  of the body  20  is brought to such a state that a laser absorber is contained in the interface. In one or more embodiments, it is only required for such a laser absorber to be existent in the interface between the two joint areas  32  and  23 , no matter how it is shaped up.  
         [0034]     As a form in which the laser absorber exists in the interface between the two joint areas  32  and  23 , a laser absorber such as phthalcyanine is kneaded into resin material for use in molding the inner lens  30  or the body  20  and then the inner lens  30  or the body  20  may be injection-molded by using the resin material with the laser absorber kneaded in. Thus, the interface between the two joint areas  32  and  23  is brought to such a state that the laser absorber exists therein. In one or more embodiments, when the laser absorber is kneaded into the molding resin material, the laser absorber is kneaded into a small-sized member in order to make it less costly to form the interface. In other words, kneading the laser absorber into the material for use in molding the inner lens  30  smaller than the body  20  results in reducing the total cost.  
         [0035]     As the form of making the laser absorber existent in the interface, a printing method may be used for applying the laser absorber to the joint area  32  of the inner lens  30  or the joint area  23  of the body  20 , for example.  
         [0036]     There is also created a condition in which the laser absorber is existent in the interface by sandwiching a sheet with the laser absorber kneaded in, between the two joint areas  32  and  23 .  
         [0037]     In one or more embodiments, when the inner lens  30  is laser-welded to the body  20 , it is unnecessary to do the laser welding over the whole circumference of the inner lens  30 . In other words, as the interior of the lighting device is made waterproof by the joint portion between the body and the outer lens  40 , the inner lens  30  may only be fixed to the body  20  so as to prevent the inner lens  30  from slipping off. As shown in  FIG. 2 , for example, a laser absorber  60  is applied to four places separated circumferentially at substantially equal intervals along the joint area  32  of the inner lens  30 , so that the laser welding may be carried out at these four places.  
         [0038]      FIG. 3  shows a laser welding process with the laser absorber kneaded into the inner lens  30  in order that laser beam  71  emitted from a laser head  70  is passed through the projected edge  31  of the inner lens  30  from the front before being converged to the joint area  32 . Accordingly, the laser beam  71  is absorbed by the joint area  32  of the inner lens  30 , whereby the joint area  32  generates heat and melts. Further, because of heat conduction, the joint area  23  of the body  20  also generates heat and melts, so that the two joint areas  32  and  23  become compatibilized, fused and fusion-bonded. As the joint areas  32  and  23  cool then, both of them become secured.  
         [0039]      FIG. 4  shows a laser welding process with the laser absorber  60  applied to the joint area  32  of the inner lens  30  in order that the laser beam  71  emitted from the laser head  70  is passed through the projected edge  31  of the inner lens  30  from the front before being converged to the laser absorber  60  applied to the joint area  32  of the inner lens  30 . Accordingly, the laser beam  71  is absorbed by the laser absorber  60  applied to the joint area  32  of the inner lens  30 , whereby the laser absorber  60  generates heat. Because of heat conduction, the joint area  32  of the inner lens  30  and the joint area  23  of the body also generate heat and melts, so that the two joint areas  32  and  23  are compatibilized, fuses and fusion-bonded. As the joint areas  32  and  23  cool then, both of them become secured.  
         [0040]      FIG. 5  shows a laser welding process with a sheet  80  with the laser absorber kneaded in and sandwiched between the joint area  32  of the inner lens  30  and the joint area of the body  20  in order that the laser beam  71  emitted from the laser head  70  is passed through the projected edge  31  of the inner lens  30  from the front before being converged to the sheet  80  with the laser absorber kneaded in. Accordingly, the laser beam  71  is absorbed by the sheet  80  mixed with the laser absorber, whereby the sheet  80  generates heat. Because of heat conduction, the joint area  32  of the inner lens  30  and the joint area  23  of the body also generate heat and melts, so that the two joint areas  32  and  23  are compatibilized, fused and fusion-bonded. As the joint areas  32  and  23  cool then, both of them become secured.  
         [0041]     There are various methods of emitting the laser beam  71 , including, for example: a scanning method as shown in  FIG. 6  involves making the laser head  70  perform scanning in the direction of an arrow so as to emit the laser beam  71  at fusion-bonding places x, x, . . . ; a mirror control method of  FIG. 7  involves guiding the laser beam  71  to a galvano mirror  92  via a mirror  91  with the laser head  70  fixed so as to emit the laser beam  71  to prescribed fusion-bonding places x, x, . . . by turning the galvano mirror  92  (the laser beam  71  is emitted only when the galvano mirror  92  is angled as designated); and a flash method of  FIG. 8  involves using a plurality of fixed laser heads  70 ,  70 , . . . so as to emit laser beams  71 ,  71 , . . . to several welding places x, x, . . . at a time.  
         [0042]     As described above, since the inner lens and other members are joined together by the laser welding in the method of producing vehicle lamps according to one or more embodiments of the present invention, the joining work can be done in a short time. Moreover, as irradiation energy toward the laser absorber is made readily controllable without allowing any excessive compatible portion to be jutted out aside, an excellent external appearance is offered.  
         [0043]     As the laser absorber becomes transparent by laser irradiation, only the undercoat color is seen through the inner lens, so that there is no fear of deteriorating the external appearance in this respect.  
         [0044]     By kneading the laser absorber previously into the material of one of the members that are joined as a method of providing the laser absorber, work in the process of incorporating the inner lens is simplified, whereby a reduction in costs can be brought about.  
         [0045]     Furthermore by applying the laser absorber results in increasing the number of working man-hours during the process of incorporating the inner lens, the material cost can be reduced in comparison with the case where the laser absorber is kneaded into the material of the member.  
         [0046]     The adoption of the form of inserting the sheet with the laser absorber kneaded in, between the joint areas of the two members results in making reducible the amount of laser absorber required to be used.  
         [0047]     In a vehicle lamp having inner lenses, one or more embodiments of the present invention are suitable for use in ensuring that the inner lenses and other members are joined with an improved external appearance.  
         [0048]     It will be apparent to those skilled in the art that various modifications and variations can be made to the described preferred embodiments of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover all modifications and variations of this invention consistent with the scope of the appended claims and their equivalents.