Patent Abstract:
A vehicle lamp includes a light guide including: a first end surface; a second end surface opposite to the first end surface; a front side surface; and a back side surface opposite to the front side surface; a light source disposed to face the first end surface of the light guide so as to emit light toward the first end surface; and a reflector disposed to face the back side surface of the light guide. The light is incident on the first end surface and travels toward the second end surface along an longitudinal direction of the light guide. A first beam of the light is output from the front side surface of the light guide. A second beam of the light is output from the back side surface, and reflected by the reflector to travel toward a forward area of the vehicle lamp.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from Japanese Patent Application No. 2008-321599, filed on Dec. 17, 2008, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND OF INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present disclosure relates to a vehicle lamp and, more particularly, a vehicle lamp using a light guide. 
         [0004]    2. Related Art 
         [0005]    In the related art, as a vehicle lamp used as the tail lamp or the stop lamp, there exists a vehicle lamp in which plural LEDs are arranged on one end portion of a rod-like light guide to obtain a linear light emission (see e.g., WO03/026031). 
         [0006]    Meanwhile, in the tail lamp or the stop lamp, a luminous area in excess of a certain value needs to be ensured under the laws and the regulations. Also, in view of the appearance during the lighting, in some cases, the luminous area should be increased. In the above vehicle lamp using the light guide, when the luminous area should be increased as a whole, it may be considered that the size of the light guide is increased. However, in this case, a luminance is lowered due to the light diffusion. In order to compensate the reduction in the luminance, it may be considered that the number of LEDs is increased or an output light of LEDs is increased. On the other hand, in such cases, cost and power consumption are increased. 
       SUMMARY OF INVENTION 
       [0007]    It is an illustrative aspect of the present invention to provide a vehicle lamp using a light guide whose luminous area is increased as compared with the related art vehicle lamp. 
         [0008]    According to one or more aspects of the present invention, there is provided a vehicle lamp comprising: a light guide comprising: a first end surface; a second end surface opposite to the first end surface; a front side surface; and a back side surface opposite to the front side surface; a light source disposed to face the first end surface of the light guide so as to emit light toward the first end surface; and a reflector disposed to face the back side surface of the light guide, wherein the light is incident on the first end surface and travels toward the second end surface along an longitudinal direction of the light guide, wherein a first beam of the light is output from the front side surface of the light guide, and wherein a second beam of the light is output from the back side surface, and reflected by the reflector to travel toward a forward area of the vehicle lamp. 
         [0009]    Other aspects and advantages of the present invention will be apparent from the following description, the drawings, and the claims. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]      FIG. 1  is a sectional view showing a vehicle lamp according to an exemplary embodiment of the present invention; 
           [0011]      FIG. 2  is a perspective view of a lighting unit; 
           [0012]      FIG. 3  is a front view of the lighting unit; and 
           [0013]      FIGS. 4A to 4D  are views showing variations of the light guide respectively. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Exemplary embodiments of the present invention will be now described in detail with reference to the drawings.  FIG. 1  is a sectional view of a vehicle lamp  10  according to an exemplary embodiment of the present invention. The vehicle lamp  10  according to the present embodiment is used as a tail lamp or a stop lamp provided to the rear side of the vehicle. 
         [0015]    The vehicle lamp  10  is provided with a lamp body  14  and a transparent cover  12  for covering a front opening of the lamp body  14 . The lamp body  14  and the cover  12  forms a lamp chamber  16 . A light guide  22  and a reflector  24  are provided in the lamp chamber  16 . 
         [0016]      FIG. 2  is a perspective view of the lighting unit  20  shown in  FIG. 1 . Also,  FIG. 3  is a front view of the lighting unit  20  shown in  FIGS. 1 and 2 . As shown in  FIGS. 2 and 3 , the lighting unit  20  includes the light guide  22 , the reflector  24 , and a light emitting unit  30 . 
         [0017]    The light guide  22  is a rod-like light guiding member that is formed by extrusion-molding a transparent resin, such as an acrylic resin. A cross sectional shape of the light guide  22  is an almost elliptical shape when viewed from a direction orthogonal to the longitudinal direction. One end surface of the light guide  22  is used as an incident surface  22   a  on which the light emitted from the light emitting unit  30  is incident. Also, a front surface  22   b  of one side surface of the light guide  22  is an almost flat surface, and steps  22   c  for diffusing the light are formed on the front surface  22   b . In the present embodiment, the steps  22   c  are formed like an oblique line. Also, in the present embodiment, the light guide  22  is formed such that its sectional area that is orthogonal to the longitudinal direction is tapered from the incident surface  22   a  to the other side surface. The light guide  22  is supported by supporting portions  22   d  that are provided to both end portions. Thus, the light, which is incident onto the incident surface  22   a , is guided inside the light guide  22  along the longitudinal direction thereof. 
         [0018]    The light emitting unit  30  is a light source that emits the light to the light guide  22 . The light emitting unit  30  includes an LED  32  that emits the light to the incident surface  22   a  of the light guide  22 , a substrate  34  that supplies electric current to the LED  32 , and a heat sink  36  for radiating heat generated from the LED  32 . 
         [0019]    The reflector  24  is a rod-like reflector. The reflector  24  is arranged along the longitudinal direction of the light guide  22 . The reflector  24  reflects a part of the light, which is emitted from the side surface of the light guide  22 , to the area ahead of the lighting equipment. A reflecting surface  24   a  of the reflector  24  is formed like an almost circular arc in a direction orthogonal to its longitudinal direction, and is formed to cover the light guide  22  at the back surface side of the light guide  22 . In the present embodiment, the reflector  24  is formed such that the size of the reflecting surface  24   a  is substantially constant along the longitudinal direction of the light guide  22 . That is, the outer periphery surface of the reflecting surface  24   a  is substantially constant along the longitudinal direction in the cross section. 
         [0020]    Next, an operation of the vehicle lamp  10  will be described. In  FIG. 1 , the light emitted from the vehicle lamp  10  is indicated with an arrow. In the vehicle lamp  10 , when electric current is supplied to the LED  32 , the light emitted from the LED  32  is incident on the incident surface  22   a  of the light guide  22 . The light incident on the light guide  22  is output from the side surface of the light guide  22 , while traveling through the light guide  22 . Here, the light output from the front surface  22   b  of the light guide  22  is diffused by the steps  22   c , and then is output to the forward area of the vehicle lamp via the cover  12  (light beams indicated with a reference symbol L 1 ). Meanwhile, the light output from the back surface of the light guide  22  is reflected by the reflecting surface  24   a  of the reflector  24 , and then is output to the forward area of the vehicle lamp via the cover  12  (light beams indicated with a reference symbol L 2 ). 
         [0021]    In this manner, in the vehicle lamp  10  according to the present embodiment, both the light beam L 1  directly output from the front surface  22   b  of the light guide  22 , and the light beam L 2  reflected by the reflecting surface  24   a  of the reflector  24  are output to the forward area of the vehicle lamp. Also, an area of the reflecting surface  24   a  acts as a luminous area as a whole, and, thus, the vehicle lamp using the reflector  24  can have a luminous area larger than that in a light guide  22  not using the reflector  24 . Further, according to the present embodiment, in order to increase the luminous area, there is no need that a size of the light guide  22  should be increased, the number of the LED  32  should be increased, or an output light of the LED  32  should be increased. Therefore, the luminous area can be increased while cost and/or power consumption can be suppressed. 
         [0022]    Also, in the vehicle lamp  10  according to the present embodiment, the light guide  22  is formed such that its sectional area that is orthogonal to the longitudinal direction is tapered from the incident surface  22   a  to the other side surface. In this case, the amount of light that propagates through the light guide  22  is reduced from the incident surface  22   a  to the other end surface. In this case, because the light is concentrated by reducing the sectional area of the light guide  22 , the light output from the light guide  22  is substantially uniform along the longitudinal direction of the light guide  22 . Those skilled in the art will appreciate that the optimum way for reducing the sectional area to make the light output from light guide  22  substantially uniform depends on the shape or material of the light guide  22 , but it can be determined adequately through the experiment or simulation. 
         [0023]    Also, in the vehicle lamp  10  according to the present embodiment, the reflector  24  is formed such that the size of the reflecting surface  24   a  is substantially constant along the longitudinal direction of the light guide  22 . In this case, because the sectional area of the light guide  22  is tapered from the incident surface  22   a  to the other end surface, the luminous area of the vehicle lamp can be substantially constant as a whole, and a given luminous area required for the vehicle lamp can be ensured. 
         [0024]      FIGS. 4A to 4D  are views showing variations of the light guide  22  according to the above embodiment. In the light guide  22  shown in  FIG. 4A , the shape of the steps  22   c  is similar to that in the above embodiment, but the area of the front surface  22   b  is formed larger than that in the above embodiment. In this case, the luminous area having high luminance can be increased in accordance with the increase in the area of the front surface  22   b.    
         [0025]    As shown in  FIG. 4B , the cross section of the light guide  22  that is orthogonal to the longitudinal direction is formed like a rectangular shape. The shape of the steps  22   c  formed on the front surface  22   b  is similar to that shown in  FIG. 4A . In this case, the reflecting surface  24   a  of the reflector  24  may be formed to correspond to the shape of the light guide  22 . 
         [0026]    In the light guide  22  shown in  FIG. 4C , the cross sectional shape of the light guide  22  has the rectangular shape as shown in  FIG. 4B , but the shape of the steps  22   c  formed on the front surface  22   b  is different from that in  FIG. 4B . Meanwhile, in the light guide  22  shown in  FIG. 4D , the cross sectional shape of the light guide  22  is similar to those in  FIGS. 2 and 3 , but the shape of the steps  22   c  formed on the front surface  22   b  is different from those in  FIGS. 2 and 3 . In  FIGS. 4C and 4D , the steps  22   c  are formed as the finer patterns. In this manner, because the steps  22   c  are formed into different shapes, the light distributing patterns that are novel in an aspect of design can be obtained. 
         [0027]    While the present invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It is aimed, therefore, to cover in the appended claim all such changes and modifications as fall within the true spirit and scope of the present invention. 
         [0028]    For example, the light guide may be formed such that its sectional area that is orthogonal to its longitudinal direction is gradually increased from the incident surface to the other end surface. Because the sectional area is gradually increased in this manner, it is possible to make a gradation light emission whose luminous intensity is gradually decreased, and the vehicle lamp that is novel in an aspect of design can be realized. For example, when the vehicle lamp is used as the tail lamp, a luminous intensity is gradually decreased from the center of the vehicle toward the left and right sides. Thus, the novel light distribution patterns can be created as compared with light distribution patterns whose luminous is uniform. The way to increase the sectional area can be determined depending on a desired light emission pattern through the experiment or simulation results. 
         [0029]    Also, the reflector may be formed such that the size of the reflecting surface is changed along the longitudinal direction of the light guide. Namely, the outer periphery surface of the reflecting surface in the cross section that is orthogonal to the longitudinal direction is changed along the longitudinal direction. For example, the size of the reflecting surface may be increased or decreased along the longitudinal direction of the light guide. In this case, because a luminous area can be changed along the longitudinal direction, it is possible to provide the vehicle lamp that is novel in an aspect of design. For example, when the vehicle lamp is used as the tail lamp, a luminous area is gradually decreased from the center of the vehicle toward the right and left sides. Thus, the novel light distributing patterns can be created such that the light gradually disappears toward the right and left sides. 
         [0030]    In the above embodiment, an LED is used as the light source. However, another light source, such as a bulb, may be used. 
         [0031]    In  FIGS. 2 and 3 , the vehicle lamp formed into a linear shape is illustrated. However, the shape of the vehicle lamp is not limited to a linear shape, and, for instance, a curved shape may be employed. For example, when the vehicle lamp is used as the tail lamp, the shape of the vehicle lamp may be formed into a curved shape to correspond to the shape of the rear body of the vehicle.

Technology Classification (CPC): 5