Patent Publication Number: US-8985823-B2

Title: Vehicle lamp having an LED and a drip-preventive cover

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority from Japanese Patent Application No. 2011-124923 filed on Jun. 3, 2011, the entire content of which is incorporated herein by reference. 
     BACKGROUND OF INVENTION 
     1. Field of the Invention 
     The present invention relates to a vehicle lamp having a lamp chamber inside which one or more light emitting diodes (LEDs) are mounted on a printed wiring board and a lighting control circuit is provided to control the lighting of the LEDs. 
     2. Related Art 
     A related art vehicle lamp is, for example, a combination headlamp in which two optical units are provided (see, e.g., JP 2009-241921 A). 
     A first optical unit may be an indicating lamp unit, e.g., a clearance lamp unit, a turn signal lamp unit or a daytime running lamp, disposed near a second optical unit. The second optical unit may be a headlamp unit. 
     The indicating lamp unit includes, for example, a bracket fixed to a lamp body, a first printed wiring board mounted on a first board mounting portion of the bracket, LEDs mounted on the first printed wiring board, and a plurality of reflectors mounted on the board mounting portion as to face the light emitting axes of the respective LEDs. 
     To control the lighting of LEDs, a lighting control circuit is mounted on a second printed wiring board mounted on a second board mounting portion of the bracket. The second printed wiring board is spaced rearward from the indicating lamp unit. The first and second printed wiring boards are electrically connected together by wiring. 
     SUMMARY OF INVENTION 
     According to the configuration described above, the first printed wiring board on which the LEDs are mounted and the second printed wiring board on which the lighting control circuit is mounted are provided separately. Therefore, wiring for electrically connecting the two printed wiring boards may be indispensable, the number of parts of the indicating lamp unit may be large, and the structure of the indicating lamp unit may be complicated. 
     Thus, in a conventional vehicle lamp, the occupation ratio of the indicating lamp unit to the lamp chamber may become large, thereby restricting the arrangement the indicating lamp unit inside the lamp chamber. 
     Furthermore, with a conventional vehicle lamp, because the structure of the indicating lamp unit is complicated, the lamp assembling work may become onerous. 
     Additionally, with a conventional vehicle lamp, due to the temperature difference between day and night or between the inside and outside of the lamp chamber when the lamp is turned on and off, condensation inside the lamp chamber (e.g., on the inner surface of the front cover or the inner surface of the upper wall of the lamp body) may form water drops dripping down on the light control circuit, whereby the insulation of the lighting control circuit becomes insufficient to prevent the proper control of the lighting of the LEDs. 
     One or more embodiments of the present invention provide a vehicle lamp configured in view of one or more of the above situations. Those skilled in the art, with the benefit of the present disclosure, will appreciate that other embodiments may be configured in view of other situations. 
     According to one or more embodiments of the present invention, a vehicle lamp includes a lamp body having an opening, a front cover attached to the lamp body to close the opening, and a first optical unit disposed inside a lamp chamber defined by the lamp body and the cover. The first optical unit includes a printed wiring board having a first section formed with a first conductor pattern and a second section formed with a second conductor pattern electrically coupled to the first conductor pattern, an LED mounted on the first section of the printed wiring board, and a lighting control circuit provided on the second section of the printed wiring board to control a lighting of the LED. 
     Other aspects and advantages of the invention will be apparent from the following description, the drawings and the claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic front view of a vehicle headlamp according to one or more embodiments of the present invention; 
         FIG. 2  is a horizontal sectional view of the vehicle headlamp, taken along the line II-II in  FIG. 1 ; 
         FIG. 3  is a horizontal sectional view of the vehicle headlamp, taken along the line III-III in  FIG. 1 ; 
         FIG. 4  is a vertical sectional view of a portion of the vehicle headlamp, illustrating an indicating lamp unit of the vehicle headlamp; 
         FIG. 5  is a perspective view of a bracket for supporting a printed wiring board; 
         FIG. 6  is a vertical sectional view of a portion of the vehicle headlamp, illustrating a drip-preventive cover arranged to cover a lighting control circuit; 
         FIG. 7  is a plan view of the printed wiring board; and 
         FIG. 8  is an explanatory view illustrating how two printed wiring boards are produced from a single board. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid obscuring the invention. 
     A vehicle lamp according to one or more embodiments of the present invention is a vehicle headlamp  10 . The vehicle headlamp  10  is mounted on right and left sides of the front end portion of a vehicle, on respective side in the vehicle width direction. 
     The vehicle headlamp  10  includes a lamp body  12  having a front opening, and a front cover  14  attached to a peripheral edge portion of the front opening of the lamp body  12 . A lamp chamber S is defined by the lamp body  12  and front cover  14 . 
     Inside the lamp chamber S, as shown in  FIGS. 1 and 2 , an indicating lamp unit  20  (a first optical unit), a headlamp unit  40  (a second optical unit), and another indicating lamp unit  60  (a third optical unit) are provided. The indicating lamp unit  20  is disposed in a lower region inside the lamp chamber and extends from the vehicle front side (inner side in the vehicle width direction) to the vehicle lateral side. The headlamp unit  40  is disposed in an upper region inside the lamp chamber on the inner side in the vehicle width direction, and the indicating lamp unit  60  is disposed in an upper region inside the lamp chamber on the vehicle lateral side. In the illustrated example, the indicating lamp unit  20  is a daytime running lamp, and the other indicating lamp unit  60  is a turn signal lamp. 
     The headlamp unit  40  is assembled such that a low beam lamp  41  and a high beam lamp  42  are mounted side by side in a lateral direction on a lamp bracket  15 . The headlamp unit  40  can be inclined and adjusted in the vertical and horizontal directions (the optical axes of the lamps  41 ,  42  can be inclined and adjusted in the vertical and horizontal directions) by an aiming mechanism (not shown) interposed between the back wall of the lamp body  12  and lamp bracket  15 . 
     The low beam lamp  41  has a parabolic reflector  41   a  and a light source bulb  41   b . The high beam lamp  42  has an elliptic reflecting mirror  42   a , a light source bulb  42   b  and a projection convex lens  42   c . A removable back cover  13  is mounted on an opening portion  12   a  formed in the back wall of the lamp body  12 . 
     The indicating lamp unit  60  (turn signal lamp) is disposed on the lateral surface side of the vehicle in order to provide excellent visibility. The indicating lamp unit  60  includes a parabolic reflector  61   a  fixed to the lamp body  12  and a light source bulb  61   b  inserted into a bulb insertion hole  12   b  formed in the back wall of the lamp body  12  and having a light emitting portion extended forwardly of the reflector  61   a.    
     The indicating lamp unit  20  is formed to have an oblong shape for enhanced visibility and is disposed in the lower region inside the lamp chamber S from the vehicle front side to the lateral side. 
     As shown in  FIGS. 3 and 7 , the daytime running lamp  20  includes a printed wiring board  21  having a conductor pattern  23 , LEDs  26  (light sources) mounted on the printed wiring board  21 , a lighting control circuit  28  mounted on the printed wiring board  21  to control the lighting of the LEDs  26 , and a reflector unit  27  mounted on the printed wiring board  21  to forwardly reflect light emitted by the LEDs  26 . 
     The printed wiring board  21  is configured such that the conductor pattern  23  is formed on a resin substrate having a thickness of, for example, about 1.6 mm and an insulation protection film is placed on the conductor pattern  23  to cover it except for the LED  26  mounting land portion (terminal) and lighting control circuit  28  mounting land portion (terminal) of the conductor pattern  23 . 
     As shown in  FIG. 7 , the conductor pattern  23  includes a first conductor pattern  23 A forming electrically conducting paths for the LEDs  26  and a second conductor pattern  23 B forming electrically conducting paths of the lighting control circuit  28 . The second conductor pattern  23 B is electrically coupled to the first conductor pattern  23 A. 
     More specifically, as shown in  FIG. 7 , the printed wiring board  21  has a first conductor pattern section  21 A in which the first conductor pattern  23 A is formed and a second conductor pattern section  21 B in which the second conductor pattern  23 B is formed. The first conductor pattern section  21 A has a substantially rectangular shape when viewed from above. The second conductor pattern section  21 B rearwardly extends like a tongue from a rear side of the first conductor pattern section  21 A. The LEDs  26  are mounted on the first conductor pattern section  21 A. The lighting control circuit  28  is provided on the second conductor pattern section  21 B. 
     That is, unlike the related art, wiring for electrically connecting the two printed wiring board, which may cause disconnection at a connecting point between the wiring and the printed wiring board due to vibration or the like, becomes unnecessary. 
     As shown in  FIG. 3 , a reflector unit  27  is mounted on the upper surface of the printed wiring board  21  behind the LEDs  26 . The reflector unit  27  has a plurality of reflectors  27   a  corresponding to the respective LEDs  26 . The reflectors  27   a  are arranged side by side in the lateral direction, and are formed as a one-piece structure. As shown in  FIG. 4 , the reflector unit  27  may be secured to the printed wiring board  21  by a fastening screw  17   a.    
     The reflectors  27   a  of the reflector unit  27 , as shown in  FIG. 4 , are disposed to face the light emitting axes of their corresponding LEDs  26 , whereby the emission lights of the LEDs  26  can be reflected and distributed forwardly of the lamp chamber S by the reflector unit  27  (reflectors  27   a ). Light diffusing steps are formed on an inner side of each of the reflectors  27   a , whereby lights reflected by the reflectors  27   a  are distributed forwardly as diffused lights. 
     The lighting control circuit  28  is mounted behind the reflector unit  27 . Therefore, the lighting control circuit  28  does not interfere with the light distribution from the reflector unit  27 . Further, because the lighting control circuit  28  is concealed behind the reflector unit  27 , appearance of the headlamp  10  is not deteriorated. 
     As described above, the LEDs  26 , the lighting control circuit  28  and the reflector unit  27  are mounted on the printed wiring board  21 . As shown in  FIGS. 3 ,  4  and  6 , the printed wiring board  21  is supported by a bracket  17  in a horizontal manner. The bracket  17  may be made of synthetic resin. The bracket  17  is fixed to the lamp body  12 , and extends inside the lamp chamber S. As shown in  FIG. 3 , the printed wiring board  21  may be secured to the bracket  17  by fastening screws  17   b . As shown in  FIG. 6 , the bracket  17  may be secured to the lamp body  12  by a fastening screw  17   c.    
     As shown in  FIGS. 5 and 6 , a drip-preventive cover  18  is provided to cover the lighting control circuit mounting area  21   a  (the second conductor pattern section  2113 ) of the printed wiring board  21 , on which lighting control circuit  28  is mounted, so that the lighting control circuit  28  is prevented from being affected by dew drops. The drip-preventive cover  18  has a front opening and a rear opening. The bracket  17  and the drip-preventive cover  18  may be formed as a one-piece structure, e.g., as a molded piece made of synthetic resin. This is advantageous in that no fastening means is necessary for providing the drip-preventive cover  18  on the bracket  17 . 
     That is, there is a fear that condensation can be produced inside the lamp chamber S (for example, the back surface of the front cover  14  or the upper wall of the lamp body  12 ) due to the temperature difference between day and night or between the inside and outside of the lamp chamber S when the lamp is turned on or off and such condensation can form water drops to drip downward. However, the drip-preventive cover  18  covering the lighting control circuit  28  can prevent the water drops from invading (dropping down into) the lighting control circuit  28 . This can prevent the malfunction of the lighting control circuit  28  due to the water drops, thereby enabling to secure the accurate lighting control of the LEDs  26 . 
     When the printed wiring board  21  is slid in the arrow A direction of  FIG. 6  relative to the bracket  17  so that the lighting control circuit mounting area  21   a  of the printed wiring board  21  is inserted into the front side opening  18   a  of the drip-preventive cover  18 , the printed wiring board  21  can be assembled to the bracket  17  in a state where the lighting control circuit  28  is covered with the drip-preventive cover  18 . 
     There is also a fear that, as the headlamp unit  40  having a large light emission amount turns on, the inside of the lamp chamber S becomes high in temperature to thereby lower the light emission amounts of the LEDs  26  serving as the light sources of the indicating lamp unit  20  inside the lamp chamber S or degrade the properties of electronic parts of the lighting control circuit  28 . 
     However, according to one or more embodiments of the present invention, the indicating lamp unit (daytime running lamp)  20  is disposed below the headlamp unit  40  the temperature of which becomes high when lighted, whereby heat generated by the headlamp unit  40 , due to the convection of air inside the lamp chamber  5 , is mainly transmitted upwardly inside the lamp chamber S and is hard to be transmitted downwardly inside the lamp chamber S. Therefore, the LEDs  26  serving as the light sources of the indicating lamp unit (daytime running lamp)  20  and lighting control circuit  28  are accordingly harder to be influenced by the heat of the headlamp unit  40  when lighted. 
     Further, because the LEDs  26  are mounted with their light emitting axes facing upwardly and the reflector unit  27  (reflectors  27   a ) is disposed on the upper surface side of the printed wiring board  21  with the lighting control circuit  28  mounted thereon, the LEDs  26  and lighting control circuit  28  easy to be influenced by heat are spaced from the high-temperature headlamp unit  40  at least a distance corresponding to the height of the reflector unit  27  (reflectors  27   a ). Therefore, the LEDs  26  and lighting control circuit  28  are accordingly harder to be influenced by the heat. 
     To manufacture the printed wiring board  21 , a conductive film made of copper or the like is formed on the entire surface the resin substrate B and, using a given etching mask, the conductive film is etched to thereby form the given wiring conductor pattern  23  ( 23 A,  23 B). Then, the insulation protection film is placed on the conductor pattern  23  ( 23 A,  23 B) to cover the conductor pattern  23  except for the LEDs mounting land portion (terminal) of the first conductor pattern  23 A and the lighting control circuit mounting land portion (terminal) of the second conductor pattern  23 B. Next, after the LEDs  26  and lighting control circuit  28  are mounted on the respective land portions (terminals), the resin substrate B formed with the conductor pattern  23  and insulation protection film is cut so that it has a given outer shape, thereby producing the printed wiring board  21  on which the LEDs  26  and lighting control circuit  28  are mounted. 
     As described above, the printed wiring board  21  has such a shape that the second conductor pattern section  21 B extends like a tongue from one side of the first conductor pattern section  21 A having a substantially rectangular shape. Accordingly, as shown in  FIG. 8 , two printed wiring boards  21  can be produced from a single sheet of resin substrate B in a rotationally symmetric manner. This can reduce the wasteful use of the material. 
     Specifically, a conductive film made of copper or the like is formed on the entire surface of the resin substrate B and then, using a given etching mask, the conductive film is etched, whereby the wiring conductor patterns  23 ,  23  are formed in rotational symmetry such that their respective second conductor patterns  23 B,  2313  adjoin each other in the longitudinal direction. Next, an insulation protection film is so placed on the conductor patterns  23 ,  23  as to cover their surfaces except for the LEDs mounting land portion (terminal) of the first conductor pattern  23 A and the lighting control circuit mounting land portion (terminal) of the second conductor pattern  23 B. Then, after the LEDs  26  and the lighting control circuits  28 , are mounted on their corresponding given land portions (terminals), the resin substrate B is cut so as to provide a given shape, thereby producing printed wiring boards  21 ,  21  each mounted with the LEDs  26  and the lighting control circuit  28 . Finally, when the reflectors  27 ,  27  are mounted onto the printed wiring boards  21 ,  21  respectively, the indicating lamp units  20 ,  20  to be incorporated into the lamp chamber S are completed. 
     One or more embodiments of the present invention may provide one or more of the following advantages. 
     Firstly, because the indicating lamp unit  20  is compact as a whole, the freedom of the arranging position of the indicating lamp unit  20  inside the lamp chamber S can be enhanced, thereby enabling to provide a novel vehicle headlamp with the indicating lamp unit  20  disposed at a given position inside the lamp chamber S. 
     Secondly, because the assembling of the indicating lamp unit  20  into the lamp chamber S is simplified, the lamp  10  assembling process can be simplified. 
     Thirdly, because the electrically conducting paths in the indicating lamp unit  20  are hardly disconnected, the durability of the indicating lamp unit  20  can be ensured. 
     Fourthly, because the lighting control circuit  28  is prevented against the influence of condensation, the long stable lighting control of the LEDs  26  can be ensured. 
     According to one or more embodiments of the present invention, the time required for the process for assembling the optical unit  20  into the lamp chamber S can be shortened greatly when compared with the prior art and the lamp manufacturing cost can also be reduced. 
     That is, in the case of the LEDs  26 , since, even when they are standardized LEDs of the same output, their light emission amounts (brightness levels) differ according to classes. Thus, it is advantageous that the lighting control circuit  28  mounted on the printed wiring board  21  matches (corresponds) to the classes of the LEDs  26  (lighting control circuit  28  which, for the LED  26  of a small light emission amount, can increase the light emission amount to thereby be able to provide a constant light emission amount). 
     However, conventionally, a printed wiring board for mounting the LEDs thereon and a printed wiring board for mounting a lighting control circuit thereon are formed separately. Thus, a printed wiring board with LEDs mounted thereon and a printed wiring board with a lighting control circuit mounted thereon are assembled according to separate processes. Therefore, before the printed wiring board with LEDs mounted thereon and the printed wiring board with a lighting control circuit mounted thereon are assembled into a lamp chamber as optical units, it is necessary to confirm whether the LEDs and lighting control circuit match (correspond) to each other or not. 
     Specifically, in the case of the LEDs  26 , even when they are the same standardized LEDs, they are divided into 1 to 5 ranks differing in the light emission amount (brightness). Thus, in the LEDs mounting process, there are manufactured five kinds of LEDs mounted printed wiring boards ranging from a printed wiring board  21  with LEDs  26  of a rank  1  mounted thereon to a printed wiring board  21  with LEDs  26  of a rank  5  mounted thereon. Also, in the lighting control circuit mounting process, there are manufactured five kinds of lighting control circuit mounted printed wiring boards of 
     Therefore, conventionally, before the printed wiring board with LEDs mounted thereon and the printed wiring board with a lighting control circuit mounted thereon are assembled into a lamp chamber as optical units, it is necessary to confirm whether the rank of the LEDs mounted printed wiring board (the rank of the LEDs) and the class of the lighting control circuit mounted printed wiring board match (correspond) to each other (for example, the ranks 1 to 5 and the classes of 1 to 5 match respectively) or not. 
     Thus, conventionally, since there is necessary the process to confirm whether the rank of LEDs mounted on a printed wiring board matches to the class of a lighting control circuit mounted on a printed wiring board or not, it takes time accordingly to assemble the optical unit and the facility necessary for such confirming process increases the manufacturing cost. 
     However, according to one or more embodiments of the present invention, because an LEDs mounting printed wiring board and a lighting control circuit mounting printed wiring board are structured as common printed wiring boards  21 , in a process for mounting the LEDs  26  onto the printed wiring board  21  and then mounting the lighting control circuit  28 , the LEDs  26  and lighting control circuit  28  can be mounted onto their printed wiring boards  21  with the rank of the LEDs  26  and the class of the lighting control circuit  28  confirmed. 
     Therefore, in the printed wiring boards  21  respectively with the LEDs  26  and lighting control circuit  28  manufactured in the LED/lighting control circuit mounting process, the rank of the LEDs  26  and the class of the lighting control circuit  28  always match (correspond) to each other. This can eliminate the conventionally necessary process to confirm whether the rank of LEDs mounted on a printed wiring board and the class of a lighting control circuit mounted on a printed wiring board match to each other or not. This can shorten greatly the time necessary for the process for assembling the optical unit  20  into the lamp chamber S and also can eliminate the need for provision of the above facility for confirming the rank of the LEDs and the class of the lighting control circuit, thereby enabling to reduce the manufacturing cost of the lamp  10 . 
     According to one or more embodiments, the bracket  17  and the drip-preventive cover  18  may be provided as separate pieces, and may be attached together using a screw or by other fixing means. 
     According to one or more embodiments, the LEDs  26  and lighting control circuit  28  are mounted on the upper surface side of the horizontally disposed printed wiring boards  21  and the reflectors  27  are further mounted thereon. However, the LEDs  26  and lighting control circuit  28  may be mounted on the lower surface side of the horizontally disposed printed wiring boards  21  and the reflectors  27  are further mounted thereon. 
     According to one or more embodiments, the printed wiring boards  21  with the LEDs  26 , lighting control circuit  28  and reflectors  27  mounted thereon are disposed horizontally. However, the printed wiring boards  21  with the LEDs  26  and lighting control circuit  28  may also be disposed horizontally with their board width direction being substantially vertical. The light distribution of the optical unit  20  may also be formed by the direct lights of the LEDs  26  so mounted on the printed wiring board  21  as to have light emitting axes facing forwardly of the lamp chamber, or by the direct lights of the LEDs  26  and the reflected lights of the reflector unit  27  (reflectors  27   a ) mounted on the printed wiring board  21 . 
     According to one or more embodiments, two printed wiring boards  21  are produced from a sheet of resin substrate B. However, when the printed wiring boards  21  are small in size (length), four or six boards may be produced. 
     While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.