Patent Publication Number: US-7901122-B2

Title: Vehicular lamp unit

Description:
BACKGROUND OF INVENTION 
     1. Field of the Invention The present invention relates to a vehicular lamp unit that uses a semiconductor light-emitting element such as an LED as a light source. 
     2. Background Art 
     There are an increasing number of cases in recent years where a vehicular lamp that includes a headlamp is mounted with an LED (semiconductor light-emitting element) that is compact, lightweight, and has excellent light-emitting efficiency. An LED chip used as the light source normally has a light-emitting surface with a generally oblong shape, and the LED chip is disposed such that a side end of the light-emitting surface coincides with a focal line of a reflective surface formed from a parabolic cylindrical curved surface or the like (see Patent Document 1 for an example). 
     Depending on driving conditions, two light distribution patterns are required of a vehicular lamp: a light distribution pattern in which diffused light is distributed in front of the vehicle and localized condensed light is weakened; and a light distribution pattern in which less diffused light is distributed in front of the vehicle and condensed light to localized portions is strengthened so that a boundary between an illuminated portion and a non-illuminated portion is clearly apparent. A particularly effective light distribution pattern during rainy weather or the like is one that reduces luminance toward the front side of the vehicle (on top of the road surface). The difference between the above two light distribution patterns is the vertical-direction spread and the intensity of condensed light in the light distribution patterns. 
     [Patent Document 1] 
     Japanese Patent Application Publication No. JP-A-2003-31011, pages 3 to 6, FIG. 1. 
     SUMMARY OF INVENTION 
     With a conventional vehicular lamp, although it may be possible to realize the above two light distribution patterns using a unit that combines a plurality of headlamps, it is impossible to modify the light distribution pattern using one headlamp. Hence, one or more embodiments of the present invention modify a vertical-direction spread and an intensity of condensed light in a light distribution pattern using one lamp. 
     A lamp unit according to one or more embodiments of the present invention is a lamp unit used in a vehicular lamp, and includes a reflector provided with a parabolic cylindrical reflective surface with a focal line in the horizontal direction; a planar light source having a light-emitting surface with a generally oblong shaped region, which includes a long side in a direction parallel to the focal line and a short side of a predetermined width; and light source driving means for rotatably supporting the planar light source, which is disposed such that the light-emitting surface faces the parabolic cylindrical reflective surface of the reflector and such that the long side on the lamp front side generally coincides with the focal line, with the long side acting as a rotational axis. According to such a configuration, rotating the oblong shaped light-emitting surface changes the region of the light-emitting surface facing the reflector in the vertical direction of the light distribution pattern. Therefore, it is possible to modify the vertical-direction spread of the light distribution pattern of light reflected from the reflector. In addition, the intensity of condensed light can be strengthened or weakened by shrinking or expanding the light distribution pattern in the vertical direction. 
     According to one or more embodiments of the present invention, the light source driving means is rotatable from a position where the light-emitting surface of the planar light source is disposed such that a normal line of the light-emitting surface is vertical to a position where the normal line of the light-emitting surface is inclined only a predetermined angle toward the front of the lamp. Furthermore, the light source driving means can rotate the light-emitting surface within a range of arbitrarily set rotational angles. According to such a configuration, it is possible to arbitrarily modify the vertical-direction spread and the intensity of condensed light in the light distribution pattern, as well as fix a predetermined light distribution pattern. In addition, the planar light source in the present invention is preferably structured from a semiconductor light-emitting element having an arrayed configuration. 
     Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a drawing showing the structure of a vehicular lamp unit according to one or more embodiments of the present invention. 
         FIG. 2  is a drawing showing the detailed structure of a semiconductor light-emitting element portion of the vehicular lamp unit according to one or more embodiments of the present invention. 
         FIG. 3  shows explanatory drawings of how the semiconductor light-emitting element portion is rotated by a drive portion (to a first position) in the vehicular lamp unit according to one or more embodiments of the present invention. 
         FIG. 4  shows explanatory drawings of how the semiconductor light-emitting element portion is rotated by the drive portion (to a second position) in the vehicular lamp unit according to one or more embodiments of the present invention. 
         FIG. 5  shows explanatory drawings of a change in the light path due to rotation of the semiconductor light-emitting element portion. 
         FIG. 6  is a drawing showing a light distribution pattern at the first position in the vehicular lamp unit according to one or more embodiments of the present invention. 
         FIG. 7  is a drawing showing a light distribution pattern at the second position in the vehicular lamp unit according to one or more embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a drawing showing the structure of a vehicular lamp unit according to one or more embodiments of the present invention. A vehicular lamp unit  100  is mainly provided with a semiconductor light-emitting element portion  10 , a drive portion  20 , a support bracket  30  that fixes the drive portion  20  and also functions as a light control member, and a reflector  40  that has a parabolic cylindrical shape and is disposed downward of the support bracket  30 . 
     The reflector  40  has a reflective surface  40   a  that is formed from a parabolic cylindrical curved surface with a focal line FL extending in the horizontal direction. Both sides of the reflective surface  40   a  are formed with a pair of side surface walls  40   b . In such a case, the focal line FL is set so as to extend in a direction perpendicular to a unit central axis Ax 1  of the lamp unit  100 . The unit central axis Ax 1  is a parabolic axis that forms a vertical cross section of the parabolic cylindrical surface. The pair of side surface walls  40   b  has a symmetrical shape in relation to the unit central axis Ax 1  and each is formed as a vertical wall that expands forward. 
     As  FIG. 1  shows, the semiconductor light-emitting element portion  10  is a light source that has a light-emitting surface  10   c  with a generally oblong shaped region, which includes a long side W in a direction parallel to the focal line FL of the parabolic cylindrical reflector  40  and a short side D of a predetermined width (see  FIG. 2 ). The drive portion  20  rotatably supports the light source (the semiconductor light-emitting element portion  10 ), which is disposed such that the light-emitting surface  10   c  faces the parabolic cylindrical reflective surface  40   a  of the reflector  40  and such that a long side W 1  on the lamp front side generally coincides with the focal line FL, with the long side W 1  acting as a rotational axis. 
       FIG. 2  is a drawing showing the structure of the semiconductor light-emitting element portion of the vehicular lamp according to one or more embodiments of the present invention. The semiconductor light-emitting element portion  10  is formed so as to structure a light-emitting surface, wherein a plurality of white light-emitting diodes  10   b  with light-emitting chips such as LEDs are disposed on a substrate  10   a . An end of a rotational axis  11 , which is provided on both ends of the long side W 1 , is held by the rotational axis of the drive portion  20  such that the long side W 1  of the oblong shaped light-emitting surface  10   c  coincides with the focal line FL, as described above. The semiconductor light-emitting element portion  10  is designed to be rotatable from a position where the light-emitting surface  10   c  is disposed facing vertically downward (i.e., facing a direction where the normal line of the light-emitting surface is vertical) to a position where the normal line of the light-emitting surface is inclined only a predetermined angle toward the front of the lamp. Details regarding the rotational range of the light-emitting surface  10   c  will be set forth later. The drive portion  20  is structured from drive parts including a motor, and is fixed on the support bracket  30 . The rotational force of the drive portion  20  is transmitted so as to rotate and set the position of the light-emitting surface  10   c  of the semiconductor light-emitting element portion  10  at a predetermined angle. 
       FIGS. 3 and 4  are explanatory drawings of how the semiconductor light-emitting element portion is rotated by the drive portion in the vehicular lamp unit according to one or more embodiments of the present invention. It should be noted that the drive portion  20  is omitted from the figures for convenience. Normally, as shown by a top view in  FIG. 3(   a ) and a vertical cross-sectional view in  FIG. 3(   b ), the semiconductor light-emitting element portion  10  is disposed at a position where the long side W 1  thereof coincides with the focal line FL, and the light-emitting surface extends for the width D from the proximity of an intersection between the unit central axis Ax 1  and the focal line FL to the rear of the lamp. The arrangement of the semiconductor light-emitting element portion  10  as described above will be referred to as a “first position” below. 
     Meanwhile, as shown in the vertical cross-sectional view of  FIG. 4(   b ), by rotating the semiconductor light-emitting element portion  10  approximately 30° clockwise through rotation of the drive portion  20 , the long side W 1  of the semiconductor light-emitting element portion  10  coincides with the focal line FL, while the light-emitting surface moves toward a position at which a normal line N of the light-emitting surface  10   c  inclines toward the front of the lamp. In other words, because the light-emitting surface inclines toward the front of the lamp, more light directly reaches the front of the lamp. The arrangement of the semiconductor light-emitting element portion  10  as described above will be referred to as a “second position” below. Using the first position as a reference, the second position is a 30° position when represented as a rotational angle measured from the reference position. 
       FIG. 5  shows schematic diagrams for explaining a change in the light path due to rotation of the semiconductor light-emitting element portion. As  FIG. 5  shows, when lit at the first position, light moves straight toward the front of the lamp, parallel to the unit central axis Ax 1 , and there is also a light path advancing downward and forward near the lamp (toward the top of the road surface). Therefore, a relatively wide range can be illuminated. On the other hand, when lit at the second position, a configuration can be achieved in which less light advances toward the top of the road surface, and condensed light is distributed in a relatively narrow range toward the front of the lamp. 
       FIG. 6  is a schematic diagram showing a light distribution pattern at the first position (at a 0° rotational angle) in the vehicular lamp unit according to one or more embodiments of the present invention. As  FIG. 6  shows, diffused light is radiated toward the front of the vehicle and the intensity of condensed light is relatively weak. 
       FIG. 7  is a schematic diagram showing a light distribution pattern at the second position (at a 30° rotational angle) in the vehicular lamp unit according to one or more embodiments of the present invention. As  FIG. 7  shows, when lit at the second position, more light moves straight toward the front of the lamp, parallel to the unit central axis Ax 1 , and it is possible to irradiate a relatively narrow range in a condensed manner. Therefore, it is possible to effectively reduce the reflective glare from the road surface for an oncoming vehicle during rainy weather, because the source of such light is diffused light radiated toward the top of the road surface. 
     The rotational angle set by the drive portion  20  is not particularly limited to an angle of 0° or 30°, and an arbitrary angle from 0° to 30° (or an angle over 30°) may be set. In such case (for example, during rotation from 0° to 30°), the light distribution pattern is assumed to gradually change. 
     During rotation, there is no sudden change in illumination condition that cannot be followed by the eyes of the driver of the vehicle, so there is no risk of creating an unsafe condition by rotating the semiconductor light-emitting element portion while driving. Thus, the driver may operate the drive portion  20  while driving to select a light distribution pattern at an arbitrary rotational angle depending on external weather, driving, or other conditions. In addition, the rotational angle may be automatically set after judging various conditions such as external brightness. 
     The drive portion  20  was described as being structured from drive parts including a motor in the above embodiments. However, embodiments of the present invention are not particularly limited to such a drive portion structured from such drive parts. Any type of mechanism may be employed, provided that an actuator, or the like, enables rotation of the semiconductor light-emitting element portion  10 . 
     According to the vehicular lamp unit of one or more embodiments of the present invention, it is possible to arbitrarily modify the light distribution pattern using one lamp, without disposing a plurality of lamps with different light distribution patterns in the vehicular lamp unit. By modifying the vertical-direction spread and the intensity of condensed light in the light distribution pattern, the reflective glare from the road surface for an oncoming vehicle, particularly during rainy weather, can be effectively reduced. 
     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. 
     DESCRIPTION OF THE REFERENCE NUMERALS 
       10  Semiconductor Light-Emitting Element Portion 
       10   a  Substrate 
       10   b  White Light-Emitting Diode 
       10   c  Light-Emitting Surface 
       20  Drive Portion 
       20   a  Rotational Axis 
       30  Support Bracket 
       40  Reflector 
       40   a  Reflective Surface 
       40   b  Side Surface Wall 
       100  Lamp Unit 
     Ax 1  Unit Central Axis 
     Fl Focal Line 
     W Long Side Of Generally Oblong Shaped Reflective Surface Of Semiconductor Light-Emitting Element Portion 
     W 1  Long Side Of Generally Oblong Shaped Reflective Surface Of Semiconductor Light-Emitting Element Portion (Lamp Front Side) 
     D Short Side Of Generally Oblong Shaped Reflective Surface Of Semiconductor Light-Emitting Element Portion 
     N Normal Line Of Generally Oblong Shaped Reflective Surface Of Semiconductor Light-Emitting Element Portion