Patent Publication Number: US-9429304-B2

Title: Light emitting module and vehicle lamp

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority from Japanese Patent Application No. 2012-013523 filed on Jan. 25, 2012, the entire content of which is incorporated herein by reference. 
     BACKGROUND OF INVENTION 
     1. Field of the Invention 
     The present invention relates to a light emitting module and a vehicle lamp having the light emitting module. 
     2. Related Art 
     For safety reasons, vehicle lamps are required to produce prescribed light distribution patterns. For example, vehicle headlamps are required to produce an oblong light distribution pattern irradiating a region extending in a vehicle width direction such that the center part of the region is irradiated brighter than a peripheral part of the region. 
     In related art vehicle lamps, semiconductor light emitting devices such as light emitting diodes (LED) are used as a light source. When using an LED as a light source of a vehicle headlamp, it is difficult to produce a light distribution pattern having a required light quantity and shape with a single LED. In view of this, a related art light source module has a plurality of series-connected LEDs arranged in a row (see, e.g., JP 2008-524045 A). 
     To produce various light distribution patterns using a single unit, a light emitting module may be configured to have an array of LED chips arranged in a matrix manner. 
     However, as the number of LED chips arranged in an array form increases, the number of interconnections, the board size, and the number of connectors are likely to increase accordingly. 
     SUMMARY OF INVENTION 
     One or more embodiments of the present invention provide a simple and compact light emitting module having an array of light emitting devices. 
     According to one or more embodiments of the present invention, a light emitting module is provided. The light emitting module includes a board having a mounting portion, the mounting portion being configured such that a plurality of light emitting devices, each of the light emitting devices having an anode side and a cathode side, are mounted on the mounting portion in an array form, a first interconnecting section having a plurality of first interconnections, the first interconnections being configured such that one end of each of the first interconnections is connected to one of the anode side and the cathode side of an associated one of the light emitting devices, a second interconnecting section having a plurality of second interconnections, the second interconnections being configured such that one end of each of the second interconnections is connected to the other of the anode side and the cathode side of an associated one of the light emitting devices, and a power supply portion provided along one side of the board and configured to receive an external power. The second interconnecting section has at least one, but less than the number of the second interconnections, collectively interconnecting portion to which another end of each of the second interconnections is connected. The first interconnecting section and the second interconnecting section are configured such that another end of each of the first interconnections and an end portion of the collectively interconnecting portion are connected to the power supply portion, and such that the light emitting devices are divided into a plurality of groups that are independently controllable to be turned on and off. 
     According to one or more embodiments of the present invention, a vehicle lamp is provided. The vehicle lamp includes the light emitting module described above, a control unit configured to control each of the groups to turn the light emitting devices on and off on a group-by-group basis, an optical member configured to forwardly project light emitted from the light emitting module, and a lamp body accommodating the light emitting module and the optical member. 
     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 vertical sectional view of a vehicle lamp according to one or more embodiments of the present invention; 
         FIG. 2  is a front view of an example of a light emitting module of the vehicle lamp; 
         FIG. 3  is a front view of another example of the light emitting module of the vehicle lamp; 
         FIG. 4  is a front view of yet another example of the light emitting module of the vehicle lamp; and 
         FIG. 5  is a front view of yet another example of the light emitting module of the vehicle lamp. 
     
    
    
     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. 
       FIG. 1  is a schematic vertical sectional view of a vehicle lamp  10  according to one or more embodiments of the present invention.  FIG. 2  is a front view of an example of a light emitting module  34  of the vehicle lamp  10 . The vehicle lamp  10  is a headlamp of a vehicle. 
     The vehicle lamp  10  is disposed at each lateral side of a front end portion of a vehicle. As shown in  FIG. 1 , the vehicle lamp  10  includes a lamp body  12  having a front opening and a cover  14  attached to a front portion of the lamp body  12  to close the opening. The lamp body  12  and the cover  14  form a lamp housing  16 , whereby a lamp chamber  18  is provided inside the lamp housing  16 . 
     A lamp unit  20  is disposed inside the lamp chamber  18 . The lamp unit  20  is configured to produce a high-beam light distribution pattern. A holding member  22  is disposed inside the lamp chamber  18 . An optical axis adjusting mechanism  24  is configured to allow the holding member  22  to turn in the left-right direction and in the front-rear direction. The holding member  22  has a base portion  26  which is made of a metal material having high thermal conductivity. The base portion  26  is arranged to face the front-rear direction. 
     The base portion  26  is provided with three pivot portions  28  at its top and bottom end portions (only two pivot portions  28  are shown in  FIG. 1 ). Heat dissipating fins  30  are provided to protrude rearward from the rear surface of the base portion  26 . A cooling fan  32  is attached to the rear faces of the heat dissipating fins  30 . 
     The light emitting module  34  is attached to a portion of the front surface of the base portion  26  including a central portion and an upper portion of the front surface of the base portion  26 . As shown in  FIG. 2 , the light emitting module  34  has a plurality of semiconductor light emitting devices  38 , a circuit board  36  having a mounting portion  36   a  on which the semiconductor light emitting devices  38  are mounted and arranged in an array form, a power supply connector  40 , a first interconnecting section  42 , and a second interconnecting section  44 . 
     Each of the semiconductor light emitting devices  38  functions as a surface emitting light source. The semiconductor light emitting devices  38  are arranged side by side in one direction such that their light emitting surfaces are faced forward. The light emitting devices  38  are, for example, LEDs, laser diodes (LDs), or electroluminescence (EL) devices. According to the illustrated example, the total of 32 LEDs are arranged in an array form, namely two rows of LEDs arranged one above the other, with 16 LEDs arranged side by side in the lateral direction in each of the rows. 
     The power supply connector  40  (an example of a power supply portion) is provided to extend along one side  36   b  of the circuit board  36 , and is configured to receive external power. The power supply connector  40  is disposed in an upper area on the circuit board  36 , and the light emitting devices  38  are disposed in a lower area on the circuit board  36 . 
     A connector portion of a wiring cord  48 , which is connected to a control circuit  46  (an example of a control unit) disposed inside the lamp chamber  18 , is connected to the power supply connector  40 . Therefore, the power is supplied from the control circuit  46  to each of the light emitting devices  38  via the wiring cord  48 , the power supply connector  40 , the first interconnecting section  42 , and the second interconnecting section  44 . The control circuit  46  controls the light emitting devices  38  to turn the light emitting devices  38  on and off on a group-by-group basis. In a case in which only one light emitting device  38  is connected to each interconnection  42   a  of the first interconnecting section  42  in the vertical direction, the control circuit  46  controls the light emitting devices  38  one by one. In addition to the turning on and off of the light emitting devices  38 , the control circuit  46  may be configured also control the light emitting amount of the respective light emitting devices  38 . 
     The first interconnecting section  42  includes a plurality of interconnections  42   a , and one end portion of each of the interconnections  42   a  is connected to the anode side  38   a  of the associated light emitting device  38 . The second interconnecting section  44  includes a plurality of interconnections  44   a , and one end portion of each of the interconnections  44   a  is connected to the cathode side  38   b  of the associated light emitting device  38 . According to the illustrated example, the second interconnecting sections  44  are arranged in a bilaterally symmetric manner such that the first interconnecting section  42  is disposed between the second interconnecting sections  44 . The light emitting devices  38  may be arranged such that their anode sides are connected to the second interconnecting section  44  and their cathode sides are connected to the first interconnecting section  42 . 
     The second interconnecting section  44  has at least one (two in the example of  FIG. 2 ) collectively interconnecting portion  44   b  to which the other end portion of each of the interconnections number  44   a  is connected. The number of the collectively interconnecting portions  44   b  is smaller than the number of the interconnections  44   a  ( 16  in the example of  FIG. 2 ) connected to the cathode sides  38   b  of the light emitting devices  38 . An end portion  44   a   1  of each of the collectively interconnecting portions  44   b  of the second interconnecting section  44  is connected to the power supply connector  40 . That is, the collectively interconnecting portion  44   b  collectively interconnects each of the interconnections  44   a  and the power supply connector  40 . The collectively interconnecting portion  44   b  has a bent portion  44   b   1  at its bottom-left or bottom-right portion. The other end portion  42   a   1  of each of the interconnections  42   a  of the first interconnecting section  42  is connected to the power supply connector  40 . 
     The wiring pattern of the first interconnecting section  42  and the second interconnecting section  44  is configured such the light emitting devices  38  divided into a plurality of groups corresponding to the respective interconnections  42   a  are independently controllable to be turned on and off on a group-by-group basis. More specifically, according to the illustrated example, the first interconnecting section  42  has a plurality of series-connecting interconnections  42   a , each of the interconnections  42   a  connecting an associated terminal of the power supply connector  40  to two associated light emitting devices  38  in series, and the interconnections  42   a  are arranged in parallel with each other. This makes it possible to control the turning on and off of the light emitting devices  38  on a group-by-group basis, each of the groups corresponding to the associated one of the series-connecting interconnections  42   a.    
     The series-connecting interconnections may be connected such that interconnection heat generation amounts are adjusted in an equalizing manner in accordance with a distribution of currents flowing through the respective series-connecting interconnections. When using the light emitting module  34  in a vehicle headlamp, to produce an intended light distribution pattern, it is designed such that a relatively large current flow through the central interconnection, thereby providing high luminance at the central region in the longitudinal direction of the light emitting area. For example, in a case in which a current of 1200 mA flows through one of the series-connecting interconnections located at the center of the light emitting area and currents of 200 mA, 300 mA and 400 mA flow, in this order from the laterally outer side, through three of the series-connecting interconnections located in a lateral end portion of the light emitting area, the three series-connecting interconnections located in the lateral end portion may be connected together, but not the series-connecting interconnection at the center. As a result, the current of 1200 mA flowing through the series-connecting interconnection at the center is input to one terminal of the power supply connector  40 , and the currents flowing through the three series-connecting interconnections located in the lateral end portion are collected and input to another terminal of the power supply connector  40  as a current of 900 mA so as to be closer to the current flowing through the one central series-connecting interconnection. In this manner, suitable power supply can be performed in view of allowable ampacity of the connector terminals. 
     According to the light emitting module  34  described above, the number of interconnections can be reduced because the second interconnecting section  44  has the collectively interconnecting portions  44   b  which is smaller in number than the interconnections  44   a  that are connected to the cathode sides  38   b  of the light emitting devices  38 . By virtue of the reduction in the number of interconnections, the wiring pattern is simplified and the area of the wiring pattern is reduced, which makes it possible to miniaturize the circuit board  36 . Further, because the number of terminals of the power supply connector  40  connected to the collectively interconnecting portion  44   b  is reduced accordingly, the power supply connector  40  can also be miniaturized. As a result, a simple and compact light emitting module can be provided. 
     As described above, the interconnections  44   a  connected to the cathode sides  38   b  of the light emitting devices  38  are connected to the collectively interconnecting portions  44   b  and then connected to the power supply connector  40  via the bent portions  41   b   1 . That is, the interconnections  42   a  connected to the anode sides  38   a  of the light emitting devices  38  and the interconnections  44   a  connected to the cathode sides  38   b  of the light emitting devices  38  are connected to the power supply connector  40  disposed on one side (upper side) of the light emitting devices  38 . 
     Therefore, it is not necessary to separately provide a connector connected to the anode sides of the light emitting devices  38  and a connector which is connected to the cathode sides of the light emitting devices  38 , and hence the number of connectors can be reduced. Further, the power supply connector  40  is provided to extend along one side  36   b  of the circuit board  36  and no connector is provided on the opposite side  36   c  of the circuit board  36  (see  FIG. 2 ). Therefore, a space for arranging the connector can be reduced and hence the circuit board  36  can be downsized. The light emitting devices  38  are arranged on a peripheral area on the circuit board  36  along the other side  36   c  of the circuit board  36 . Therefore, when arranging the light emitting devices  38  at their optimum positions, there is less need to consider the circuit board  36  interfering with other members. This increases the degree of freedom in arranging the light emitting module  34  in optical design. 
     Still further, the second interconnecting sections  44  are arranged in a bilaterally symmetric manner. Therefore, the temperature distribution on the circuit board  36  and the interconnections during the light emission from the light emitting devices  38  can be made uniform. This is effective in suppressing the differences in brightness among the light emitting devices  38 . 
     Next, other members of the vehicle lamp  10  will be described. As shown in  FIG. 1 , a lower reflector  50  is disposed below the light emitting devices  38  mounted on the light emitting module  34  and an upper reflector  52  is disposed above the light emitting devices  38 . The lower reflector  50  has, on the side of the light emitting devices  38 , an upwardly facing reflecting surface  50   a . The reflecting surface  50   a  is formed as, for example, a paraboloid surface. The upper reflector  52  has, on the side of the light emitting devices  38 , a downwardly facing reflecting surface  52   a . The reflecting surface  52   a  is formed as, for example, a hyperboloid surface. The reflecting surface  50   a  and the reflecting surface  52   a  forwardly reflect light emitted from each of the light emitting devices  38 . 
     A shade drive mechanism  56  configured to drive a movable shade  54  is disposed below the circuit board  36 . The shade drive mechanism  56  has a drive motor  58 , a transmission mechanism such as gears, and a flat cable  60 . When power is supplied from the control circuit  46  to the drive motor  58  via the flat cable  60  so that the output shaft of the drive motor  58  is rotated, the movable shade  54  is moved via the transmission mechanism connected to the output shaft. 
     More specifically, the movable shade  54  is rotatable between a shielding position C and a retracted position O. When the movable shade  54  is rotated rearward to the shielding position C, the movable shade  54  shields the light that would otherwise reflected by the lower reflector  50 . When the movable shade  54  is rotated forward to the retracted position O, the shielded condition of the lower reflector  50  is removed. Depending on the position of the movable shade  54 , the light emitted from the light emitting devices  38  towards the lower reflector  50  is controlled. In this manner, the lamp unit  20  can produce a high-beam light distribution pattern and a partial high-beam light distribution pattern in which a part of the high-beam light distribution pattern is cut. 
     A lens holder  62  is attached to the front surface of the base portion  26  (see  FIG. 1 ). The lens holder  62  is a hollow cylindrical member which is open on both front and rear sides, and is attached to the base portion  26  so as to surround the light emitting module  34  on which the light emitting devices  38  are arranged. 
     A projection lens  64  (an example of an optical member) is attached to a front end portion of the lens holder  62 . The projection lens  64  has a semispherical shape, and is disposed such that its convex surface is located on the front side. The projection lens  64  is configured to project the light emitted from the light emitting module  34  toward the front of the vehicle such that an image on a focal plane including a rear focal point is inverted. The projection lens  64  is accommodated inside the lamp body  12  together with the light emitting module  34 . 
     The optical axis adjusting mechanism  24  has two aiming screws  66 ,  68 . The aiming screw  66  is disposed at an upper rear location in the lamp chamber  18 , and has a rotation manipulation portion  66   a  and a shaft  66   b  extending forward from the rotation manipulation portion  66   a . A front end portion of the shaft  66   b  is formed with a thread  66   c.    
     The rotation manipulation portion  66   a  of the aiming screw  66  is supported rotatably by the rear wall of the lamp body  12 , and the thread  66   c  is screwed into the associated upper pivot portion  28  of the holding member  22 . When the rotation manipulation portion  66   a  is rotated to rotate the aiming screw  66  connected to the pivot portion  28 , the holding member  22  is turned toward a direction corresponding to the rotating direction with the other pivot portions  28  serving as supporting points, whereby the optical axis of the lamp unit  20  is adjusted (aiming adjustment). The aiming screw  68  has a similar function as the aiming screw  66 . 
     Next, the light distribution control of the vehicle lamp  10  will be described. The vehicle body is equipped with a camera (not shown) having an imaging device such as a charge-coupled device (CCD) or the like, and an image of an area that can be irradiated by the vehicle lamp  10  is periodically captured by the camera. Image data of the area is subjected to image processing, whereby an oncoming vehicle, a pedestrian, etc., if any, existing in the area are detected. 
     Based on this information, the control circuit  46  controls the light emitting devices  38  of the light emitting module  34  to turn the light emitting devices  38  on and off on a group-by-group basis and/or controls the movement of the movable shade  54 . In this manner, the vehicle lamp  10  can produce a suitable light distribution pattern adapted to the condition in front of the vehicle. 
       FIG. 3  is a front view of another example of the light emitting module  70 . In the following description, configurations and advantages that are similar to those of the light emitting module  34  illustrated in  FIG. 2  will be omitted. 
     According to the light emitting module  70 , each of the collectively interconnecting portions  44   b  is branched to form a branch portion  44   c  at the end portion  44   a   2  connected to the power supply connector  40 . That is, the collectively interconnecting portions  44   b  of the second interconnecting section  44  is connected to the power supply connector  40  at two locations. 
     Therefore, the amount of current flowing through each branched part of the branch portion  44   c  to the end  44   a   2  of the second interconnecting section  44  is reduced so as to make it closer to the amount of current flowing though each of the interconnections  42   a  of the first interconnecting section  42 . That is, suitable power supply can be performed in view of allowable ampacity of the terminals of the power supply connector  40 . 
       FIG. 4  is a front view of another example of a light emitting module  80 . In the following description, configurations and advantages that are similar to those of the light emitting module  34  illustrated in  FIG. 2  will be omitted. 
     According to the light emitting module  80 , the power supply portion has two first connectors  82  connected to the respective collectively interconnecting portions  44   b  of the second interconnecting section  44  and a second connector  84  connected to the first interconnecting section  42 . Therefore, the configuration of the power supply portion can be optimized in accordance to the interconnecting section to be connected. More specifically, a connector suitable for the ampacity of each of the interconnections and the number of interconnections can be selected with respect to each of the interconnecting sections. 
       FIG. 5  is a front view of another example of a light emitting module  90 . The light emitting module  90  is based on the light emitting module  34  illustrated in  FIG. 2 , and each of the second interconnecting section  44  has the branch portion  44   c  of the example illustrated in  FIG. 3  and is connected to the corresponding first connector  82  of the example illustrated in  FIG. 4 . Therefore, the light emitting module  90  provides similar advantages as the light emitting modules  34 ,  70 , and  80  described above. 
     Because a large current flows through a portion there the interconnections are connected together, like in the collectively interconnecting portions  44   b , the board may be configured so as to locally improve the heat dissipation performance at the collectively interconnecting portions. For example, through-holes may be formed through the board at a location where the collectively interconnecting portions are formed to transmit heat to the opposite surface (non-mounting surface) of the board. As another example, the circuit board  36  may be provided as a composite board of ceramic and metal, and the metal portion may be arranged directly beneath the collectively interconnecting portions. 
     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.