Patent Publication Number: US-8985824-B2

Title: Automotive lamp having fan

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2008-191370, filed on Jul. 24, 2008, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     Recently, automotive lamps that use, as a light source, a semiconductor light emitting device such as an LED (light emitting diode) or the like, have been known. When a semiconductor light emitting device is used as a light source for an automotive lamp, the level of light intensity required of the automotive lamp must be satisfied by a maximum use of the light emission from the semiconductor light emitting device. 
     Generally, a semiconductor light emitting device produces more heat for larger current which is supplied to obtain a greater output. And this correspondingly lowers the luminance efficiency of the semiconductor light emitting device as it gets hotter due to the heating. Thus, there have been various heat radiation structures known for automotive lamps in order to radiate heat from the semiconductor light emitting device efficiently. 
     For example, in Japanese Patent Application Publication No. 2007-35335, an automotive lamp including a housing whose front end is open, a front lens closing the front end opening portion, a light source unit having a semiconductor light emitting device, a heatsink in contact with the light source unit, and a windmill fan, is disclosed. In the automotive lamp, the windmill fan is rotated by the wind occurring while an automobile is moving and an airflow occurring due to the rotation of the windmill fan flows near the heatsink to cool the heatsink. Thereby, the efficiency in radiating the heat from the semiconductor light emitting device is improved. 
     A light radiated by a semiconductor light emitting device hardly produces so-called radiation heat effect. Therefore, there is a problem that, when a light from a semiconductor light emitting device is radiated forwards through a translucent cover that covers a front end opening portion of a lamp body, the translucent cover is hardly warmed, and accordingly snow or ice adhered to the outer surface of the translucent cover hardly melts. 
     To solve the problem, it can be considered that a heat source such as a heater or the like is provided to prevent the adhesion of snow or ice to the outer surface of the translucent cover. However, this measure is not preferable because installation of a heater increases a production cost and needs power for increasing the temperature of the heater. On the other hand, it can be considered that the heat produced by the semiconductor light emitting device is used for preventing the adhesion of snow or ice to the translucent cover. This measure is preferable in terms of power saving and cost. 
     In the automotive lamp disclosed in the Japanese Patent Application Publication No. 2007-35335, the front lens is slightly warmed because the heat in the heatsink is radiated into the whole air inside the housing, and thereby the effect of melting the snow or ice on the front lens can be obtained to some extent. However, the effect is not sufficient and there is room for improvement. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the foregoing circumstances, and one of the purposes thereof is to provide a technique in which the heat produced by the semiconductor light emitting device is diffused efficiently and the heat is effectively used for preventing the adhesion of snow or ice to the translucent cover. 
     To solve the foregoing problems, an embodiment of the present invention relates to an automotive lamp. The automotive lamp comprises: a lamp chamber formed so as to include a lamp body having a front end opening portion and a translucent cover provided on the lamp body so as to cover the front end opening portion; a lamp unit that is housed inside the lamp chamber and includes a semiconductor light emitting device as a light source; a support member that includes a light source mounting portion having a mounting surface for the semiconductor light emitting device and a plurality of radiating fins, thermally in contact with the light source mounting portion and arranged such that ventilation passages extend from the lamp body side toward the translucent cover, are formed, and that supports the lamp unit; and a fan that blows air such that air flows through the ventilation passages from the lamp body side toward the translucent cover. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will now be described, by way of example only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several Figures. 
         FIG. 1  is a schematic vertical cross-sectional view of an automotive lamp according to Embodiment 1. 
         FIG. 2  is a schematic view illustrating the positional relationship between ventilation passages formed between radiating fins, and a fan. 
         FIGS. 3A and 3B  are schematic views illustrating a position where the fan is installed. 
         FIG. 4  is a schematic vertical cross-sectional view of an automotive lamp according to Embodiment 2. 
         FIG. 5  is a schematic vertical cross-sectional view of an automotive lamp comprising a direct-emitting type lamp unit. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described based on preferred embodiments with reference to the accompanying drawings. The same or equivalent constituents, members, or processes illustrated in each drawing will be denoted with the same reference numerals, and the duplicative descriptions thereof are appropriately omitted. The preferred embodiments do not intend to limit the scope of the invention but exemplify the invention. All of the features and the combinations thereof described in the embodiments are not necessarily essential to the invention. 
       FIG. 1  is a schematic vertical cross-sectional view of an automotive lamp according to Embodiment 1.  FIG. 2  is a schematic view illustrating the positional relationship between ventilation passages formed between radiating fins, and a fan. As illustrated in  FIG. 1 , the automotive lamp  10  according to Embodiment  1  comprises a lamp chamber  13  formed by a lamp body  12  having a front end opening portion, and a translucent cover  14  that is formed of a translucent material and provided on the lamp body  12  so as to cover the front end opening portion. Inside the lamp chamber  13 , a lamp unit  30  including a semiconductor light emitting device  32  as a light source is housed. The automotive lamp  10  also comprises a bracket  50  as a support member that supports the lamp unit  30 , and a fan  70  that blows air from the lamp body  12  side toward the translucent cover  14 . 
     The lamp unit  30  is a reflection-type and projector-type lamp unit, and includes the semiconductor light emitting device  32 , a reflector  34  that reflects a light from the semiconductor light emitting device  32  in the automotive front direction, a shade  36 , and a projection lens  38 . 
     The semiconductor light emitting device  32  is, for example, an LED (light emitting device), and comprises a light emitting chip  32 a covered by an approximately hemispherical cap and a thermally conductive insulating substrate  32 b formed of a ceramic or the like. The light emitting chip  32   a  is arranged on the thermally conductive insulating substrate  32   b . The semiconductor light emitting device  32  is mounted on a light source mounting portion  54  of the bracket  50 , the light source mounting portion  54  being described later, in a state where the light emission direction thereof faces the approximately vertical upside which is approximately perpendicular to the light axis (left direction in  FIG. 1 ) of the lamp unit  30 . The radiation axis of the semiconductor light emitting device  32  is adjustable in accordance with its shape or distribution of light radiated forwards. The semiconductor light emitting device  32  may have a structure in which the plurality of light emitting chips  32   a  are installed. 
     The reflector  34  is, for example, a reflecting member in which a reflecting surface composed of part of an ellipsoid of revolution is formed on the inner surface thereof, and one end thereof is fixed to the light source mounting portion  54  of the bracket  50 . The shade  36  has a planar portion  36   a  approximately horizontally arranged, and a region anterior to the planar portion  36   a  is structured as a curved portion  36   b  that is curved downwards in a concave manner, so that the light emitted by the semiconductor light emitting device  32  is not reflected. The reflector  34  is designed to be located such that the first focal point thereof is located near the semiconductor light emitting device  32 , and the second focal point thereof is located near an edge line  36   c  formed by the planar portion  36   a  and the curved portion  36   b  of the shade  36 . 
     The projection lens  38  is a plano-convex aspheric lens that projects the light reflected on the reflecting surface of the reflector  34  in the front direction of the lamp, the projection lens  38  having its front surface of a convex surface and its back surface of a planar surface. The projection lens  38  is structured such that an image on the backside focal plane is projected in the front direction of the lamp as an inverted image. The projection lens  38  is arranged on the light axis of the lamp unit  30  extending in the automotive forward-backward direction, and fixed to the tip portion on the automotive front side of the shade  36 . The back focal point of the projection lens  38  is designed, for example, to be located at the approximately same position as that of the second focal point of the reflector  34 . 
     The light emitted by the light emitting chip  32   a  of the semiconductor light emitting device  32  is reflected on the reflecting surface of the reflector  34  to enter the projection lens  38  through the second focal point of the reflector  34 . The lights entered the projection lens  38  are concentrated by the projection lens  38  so as to be radiated forwards as approximately parallel lights. Part of the lights is reflected on the planar portion  36   a  with the edge line  36   c  of the shade  36  being a border line such that the light is selectively cut, forming a diagonal cut-off line in the light distribution pattern projected in the automotive front direction. 
     The bracket  50  comprises: an approximately plate-shaped main body  52 ; a light source mounting portion  54  that protrudes from one surface of the main body  52  to extend in the light axis direction of the lamp unit  30 , and on a mounting surface thereof, which is located along the extending direction, the semiconductor light emitting device  32  is mounted; and radiating fins  56  for diffusing the heat produced by the semiconductor light emitting device  32 . 
     The main body  52  is provided with through-holes at a predetermined position in the peripheral portion thereof such that the bracket  50  is fixed to the lamp body  12 , with an aiming screw  60  that extends forwards penetrating the lamp body  12 , and a leveling shaft  62  inserted into the through-holes of the main body  52 . The leveling shaft  62  is connected to a leveling actuator  64 . The automotive lamp  10  is designed such that the light axis of the lamp unit  30  is adjustable in the horizontal direction or the vertical direction by the aiming screw  60 , the leveling shaft  62  and the leveling actuator  64 . 
     The light source mounting portion  54  has the mounting surface for the semiconductor light emitting device  32 , on which the device  32  is mounted. One end of the reflector  34  is fixed to the mounting surface side of the light source mounting portion  54 , and the shade  36  is fixed to the end portion of the light source mounting portion  54 , the end portion being on the side opposite to the main body  52 . 
     In a downward region of the light source mounting portion  54  of the main body  52 , radiating fin mounting through-holes  55  that penetrate in the automotive forward-backward direction, are provided such that the plurality of radiating fins  56  are arranged so as to penetrate the radiating fin mounting through-holes  55 . In the present embodiment, as illustrated in  FIGS. 1 and 2 , a plate-shaped base portion  57  is arranged on a surface of the light source mounting portion  54 , the surface being opposite to the mounting surface for the semiconductor light emitting device  32 . 
     The radiating fins  56  are plate fins and are thermally in contact with the surface opposite to the mounting surface of the light source mounting portion  54  through the base portion  57 . The radiating fins  56  may be provided in a protruding manner on the light source mounting portion  54  without having the base portion  57 . The radiating fins  56  are arranged such that the ventilation passages  58  formed between the plurality of radiating fins  56  extend from the lamp body  12  side toward the translucent cover  14 , that is, the air passing through the ventilation passages  58  is guided to the translucent cover  14 . The radiating fins  56  are arranged such that the ventilation passages  58  are parallel with the mounting surface of the light source mounting portion  54 . As stated above, because the radiating fins  56  are arranged so as to penetrate the radiating fin mounting through-holes  55 , the ventilation passages  58  are also provided so as to penetrate the through-holes  55 , allowing a space on the automotive backside of the main body  52  and a space on the automotive front side thereof to be connected together by the ventilation passages  58 . 
     The radiating fins  56  and the base portion  57  are formed of a metal having a high thermal conductivity such as aluminum or the like, and the heat produced by the semiconductor light emitting device  32  is conducted to the light source mounting portion  54 , and then conducted to the radiating fins  56  through the base portion  57 . The heat conducted to the radiating fins  56  is radiated from the fins  56  into the air inside the lamp chamber  13 . 
     In the present embodiment, the radiating fins  56  are arranged on a surface side opposite to the mounting surface of the light source mounting portion  54 . That is, the radiating fins  56  are provided in a protruding manner on the surface opposite to the mounting surface of the light source mounting portion  54  through the base portion  57 . Accordingly, the heat produced by the semiconductor light emitting device  32  is conducted from the light source mounting portion  54  to the radiating fins  56  arranged immediately beneath the light source mounting portion  54 . Therefore, the heat produced by the semiconductor light emitting device  32  can be conducted to the radiating fins  56  more efficiently than the case where the radiating fins  56  are provided on the surface of the main body  52  opposite to the light source mounting portion  54 . Furthermore, because the radiating fins  56  are provided under the light source mounting portion  54 , the space on the automotive backside of the main body  52  inside the lamp chamber  13  can be omitted, allowing the automotive lamp  10  to be made thinner. 
     The radiating fins  56  may be formed such that each width of the ventilation passages  58  is progressively greater as advancing from the lamp body  12  side toward the translucent cover  14  side, that is, from the upstream side toward the downstream side of the air flow. When the radiating fins  56  are formed in this way, the air passing through the ventilation passages  58  is widened in the left-right direction, and hence the warmed air can be guided to a wide area of the translucent cover  14 . 
     The fan  70  is installed on the side of the main body  52 , the side being opposite to the surface on which the light source mounting portion  54  is formed, and comprises a plurality of fan blades that are rotated by a not-illustrated fan motor, and a fan casing that is a square frame covering the outer circumference of the fan  70 . When the fan  70  starts rotating, the air inside the lamp chamber  13  is blown from the lamp body  12  side toward the translucent cover  14 . 
     Subsequently, the description will be made with respect to how the convection of the air inside the automotive lamp  10  according to the present embodiment occurs. In  FIGS. 1 and 2 , arrows indicate the flow of air. In the automotive lamp  10 , when the light emitting chip  32   a  of the semiconductor light emitting device  32  emits light, the heat resulting from the emission of light is conducted to the light source mounting portion  54  through the thermally conductive insulating substrate  32   b  with which the light emitting chip  32   a  is in contact. The heat conducted to the light source mounting portion  54  is then conducted to the base portion  57 , and thereafter conducted to the radiating fins  56  through the base portion  57 . 
     In the ventilation passages  58  formed between the plurality of radiating fins  56 , the air blown by the fan  70  flows from the lamp body  12  side to the translucent cover  14  side, and heat exchange between the radiating fins  56  and the air is performed while the air blown by the fan  70  is flowing through the ventilation passages  58 . Thereby, the heat conducted to the radiating fins  56  is radiated into the ambient air. Because air flows from the lamp body  12  side to the translucent cover  14  side in the ventilation passages  58 , and thereby the air warmed by the radiating fins  56  does not remain there, allowing the efficiency in radiating heat from the radiating fins  56  into the ambient air to be improved. 
     The air warmed due to the radiation by the radiating fins  56  while passing through the ventilation passages  58 , is directly blown to the translucent cover  14  from the radiating fins  56 . When reaching the translucent cover  14 , the air flows in the upward-downward direction along the translucent cover  14 . Because the translucent cover  14  is exposed to outside, the cover  14  has a lower temperature than the air blown from the radiating fins  56 . Accordingly, the air blown from the radiating fins  56  is cooled due to the heat exchange with the translucent cover  14  while the air flowing in the upward-downward direction along the translucent cover  14 . 
     On the other hand, the translucent cover  14  is warmed by the air directly blown from the radiating fins  56 . Thereby, the adhesion of snow or ice to the outer surface of the translucent cover  14  can be effectively suppressed, or the snow or ice adhered to the outer surface thereof can be effectively melted. The air cooled by the heat exchange with the translucent cover  14  flows backwards along the top surface or the bottom surface of the lamp body  12 , thereafter being blown again toward the translucent cover  14  by the fan  70 . 
     As stated above, the air warmed by the radiating fins  56  is cooled by the translucent cover  14 , and the cooled air is warmed again by the radiating fins  56 . Because the air inside the lamp chamber  13  is circulated in this way, the heat produced by the semiconductor light emitting device  32  can be effectively radiated. Further, the adhesion of snow or ice to the outer surface of the translucent cover  14  can be suppressed, or the snow or ice adhered to the outer surface thereof can be melted, by the heat conducted to the translucent cover  14 . 
     Subsequently, the description will be made with respect to a position where the fan  70  is installed in accordance with a shape of the translucent cover  14 .  FIGS. 3A and 3B  are schematic views illustrating a position where the fan  70  is installed. As illustrated in  FIG. 3A , when the translucent cover  14  extends in an inclined manner relative to the forward-backward direction of the light axis of the lamp unit  30 , as seen in vertical cross section, the fan  70  is installed such that the blown air flows along the translucent cover  14  from the backside to the front side thereof, as seen in vertical cross section. That is, the fan  70  is installed toward the top and toward the back of the lamp chamber  13 . 
     As illustrated in  FIG. 3B , when the translucent cover  14  extends in an inclined manner relative to the forward-backward direction of the light axis of the lamp unit  30 , as seen in horizontal cross section, the fan  70  is installed such that the blown air flows along the translucent cover  14  from the backside to the front side thereof, as seen in horizontal cross section. That is, the fan  70  is installed on the automotive outside side and on the backside of the lamp chamber  13 . 
     As stated above, by installing the fan  70  at the position in accordance with the shape of the translucent cover  14  inside the lamp chamber  13 , the air warmed by the radiating fins  56  can be blown to a wide area of the translucent cover  14  without a bias. Thereby, the heat exchange between the warmed air and the translucent cover  14  is enhanced in its efficiency, and hence the heat produced by the semiconductor light emitting device  32  can be radiated more efficiently. Further, because the air warmed by the radiating fins  56  moves along the translucent cover  14  in a longer distance, the period during the heat exchange with the translucent cover  14  is lengthened, and accordingly the air inside the lamp chamber  13  can be cooled more surely. Furthermore, an area of the translucent cover  14  capable of suppressing the adhesion of snow or ice, or an area of thereof capable of melting the adhered snow or ice, can be enlarged. 
     Operations and effects by the aforementioned structures will be collectively described below. In the present embodiment, the radiating fins  56  are provided such that the ventilation passages  58  extend from the lamp body  12  side toward the translucent cover  14 . And, the air is blown through the ventilation passages  58  from the lamp body  12  side to the translucent cover  14  side, by the fan  70 . The air warmed due to the heat produced by the semiconductor light emitting device  32  is cooled by the translucent cover  14 , and thereafter the cooled air is warmed again due to the heat produced by the semiconductor light emitting device  32 . Because the air inside the lamp chamber  13  is circulated in this way, the heat produced by the semiconductor light emitting device  32  can be radiated efficiently. 
     In this case, because the air warmed by the heat exchange with the radiating fins  56  is blown to the translucent cover  14  side without remaining near the radiating fins  56 , the heat produced by the semiconductor light emitting device  32  can be diffused efficiently. Further, because the air warmed by the radiating fins  56  is directly blown to the translucent cover  14  from the radiating fins  56 , the translucent cover  14  can be warmed efficiently, allowing the heat produced by the semiconductor light emitting device  32  to be effectively used for preventing the adhesion of snow or ice to the translucent cover  14 . Thereby, the forward visibility and running safety in winter or in cold regions, etc., can be ensured. 
     When the radiating fins  56  are installed on the surface side opposite to the mounting surface of the light source mounting portion  54 , the heat produced by the semiconductor light emitting device  32  is conducted from the light source mounting portion  54  to the radiating fins  56 , which are arranged directly beneath the portion  54 , and hence the heart produced by the device  32  can be conducted to the radiating fins  56  more efficiently. Furthermore, the space on the automotive backside of the main body  52  inside the lamp chamber  13  can be omitted, allowing the automotive lamp  10  to be made thinner. 
     When the radiating fins  56  are formed such that each width of the ventilation passages  58  is progressively greater as advancing from the body  12  side toward the translucent cover  14  side, the warmed air can be guided to a wide area of the translucent cover  14 . Thereby, the heat exchange between the warmed air and the translucent cover  14  is enhanced in its efficiency, and hence the heat produced by the semiconductor light emitting device  32  can be radiated efficiently. Furthermore, an area of the translucent cover  14  capable of suppressing the adhesion of snow or ice, or an area thereof capable of melting the adhered snow or ice, can be enlarged. 
     When the fan  70  is installed such that the blown air flows along the translucent cover  14  from the backside to the front side thereof, as seen in vertical or horizontal cross section, in the case where the translucent cover  14  is inclined relative to the forward-backward direction of the light axis of the lamp unit  30 , as seen in vertical or horizontal cross section, the warmed air can be blown to a wide area of the translucent cover  14  without a bias. Thereby, the heat produced by the semiconductor light emitting device  32  can be radiated more efficiently. In addition, because the air warmed by the radiating fins  56  moves along the translucent cover  14  in a longer distance, the air inside the lamp chamber  13  can be cooled more surely. Furthermore, an area of the translucent cover  14  capable of suppressing the adhesion of snow or ice, or an area of thereof capable of melting the adhered snow or ice, can be enlarged. 
     An automotive lamp according to Embodiment 2 is different from that of Embodiment 1 in that a first lamp unit and a second lamp unit are installed inside a lamp chamber and these lamp units use radiating fins in common. Hereinafter, the present embodiment will be described. Other structures of the automotive lamp are the same as those of Embodiment 1, and such structures are denoted with the same reference numerals and descriptions with respect thereto are omitted. 
       FIG. 4  is a schematic vertical cross-sectional view of the automotive lamp according to Embodiment 2. As illustrated in  FIG. 4 , the automotive lamp  10  according to Embodiment 2 has a structure in which a first lamp unit  130  including a semiconductor light emitting device  132  and a second lamp unit  230  including a semiconductor light emitting device  232  are housed in a lamp chamber  13  formed by a lamp body  12  and a translucent cover  14 . The automotive lamp  10  comprises a bracket  50  that supports the first lamp unit  130  and the second lamp unit  230 , and a fan  70  that blows air from the lamp body  12  side toward the translucent cover  14 . 
     The first lamp unit  130  is a reflection-type and projector-type lamp unit, and includes the semiconductor light emitting device  132 , a reflector  134 , a shade  136  and a projection lens  138 . Likewise, the second lamp unit  230  is a reflection-type and projector-type lamp unit, and includes the semiconductor light emitting device  232 , a reflector  234 , a shade  236  and a projection lens  238 . 
     The semiconductor light emitting devices  132  and  232  comprise light emitting chips  132   a  and  232   a , and thermally conductive insulating substrates  132   b  and  232   b , respectively. The semiconductor light emitting device  132  is mounted on a first light source mounting portion  154  of the bracket  50 , the light source mounting portion  154  being described later, in a state where the light emission direction thereof faces the approximately vertical upside which is approximately perpendicular to the light axis (left direction in  FIG. 4 ) of the first lamp unit  130 . The semiconductor light emitting device  232  is mounted on a second light source mounting portion  254  of the bracket  50 , the light source mounting portion  254  being described later, in a state where the light emission direction thereof faces the approximately vertical downside which is approximately perpendicular to the light axis (left direction in  FIG. 4 ) of the second lamp unit  230 . 
     One end of each of the reflectors  134  and  234  is fixed to each of the first light source mounting portion  154  and the second light source mounting portion  254 . The shades  136  and  236  include planar portions  136   a  and  236   a , curved portions  136   b  and  236   b  and edge lines  136   c  and  236   c , respectively. The reflectors  134  and  234  are designed to be located such that the first focal points thereof are located near the semiconductor light emitting devices  132  and  232 , and the second focal points thereof are located near the edge lines  136   c  and  236   c.    
     The projection lenses  138  and  238  are plano-convex aspheric lenses having their front surfaces of convex surfaces and their back surfaces of planar surfaces, respectively. Each of the lenses  138  and  238  is arranged on each of the light axes of the first lamp unit  130  and the second lamp unit  230 , and fixed to each of the tip portions on the automotive front sides of the shades  136  and  236 . The back focal points of the projection lenses  138  and  238  are designed to be located at the approximately same positions as those of the second focal points of the reflectors  134  and  234 . 
     The bracket  50  comprises: an approximately plate-shaped main body  52 ; the first light source mounting portion  154  that protrudes from one surface of the main body  52  to extend in the light axis direction of the first lamp unit  130 , on which the semiconductor light emitting device  132  is mounted; and the second light source mounting portion  254  that protrudes from one surface of the main body  52  to extend in the light axis direction of the second lamp unit  230 , on which the semiconductor light emitting device  232  is mounted. The bracket  50  also comprises radiating fins  156  for diffusing the heat produced by the semiconductor light emitting devices  132  and  232 . 
     The bracket  50  is fixed to the lamp body  12 , with an aiming screw  60  and a leveling shaft  62  that is connected to a leveling actuator  64  inserted into through-holes provided in the main body  52 . The first light source mounting portion  154  has a mounting surface for the semiconductor light emitting device  132 , on which the device  132  is mounted. The second light source mounting portion  254  has a mounting surface for the semiconductor light emitting device  232 , on which the device  232  is mounted. 
     In a region between the first light source mounting portion  154  and the second light source mounting portion  254  in the main body  52 , radiating fin mounting through-holes  55  that penetrate in the automotive forward-backward direction, are provided such that the plurality of radiating fins  156  are arranged so as to penetrate the radiating fin mounting through-holes  55 . In the present embodiment, a first base portion  157  is arranged on a surface of the first light source mounting portion  154 , the surface being opposite to the mounting surface thereof, while a second base portion  257  is arranged on a surface of the second light source mounting portion  254 , the surface being opposite to the mounting surface thereof. 
     One end of the radiating fins  156  is thermally in contact with the surface opposite to the mounting surface of the first light source mounting portion  154 , through the first base portion  157 , while the other end thereof is thermally in contact with the surface opposite to the mounting surface of the second light source mounting portion  254 , through the second base portion  257 . The radiating fins  156  may be provided in a protruding manner directly on the first light source mounting portion  154  and the second light source mounting portion  254  without having the first base portion  157  and the second base portion  257 . The radiating fins  156  may have a structure in which at least part of one end region thereof is thermally in contact with the first light source mounting portion  154 , and at least part of the other end region thereof is thermally in contact with the second light source mounting portion  254 . When the radiating fins  156  is provided in a protruding manner on the first and the second light source mounting portions  154  and  254  through the first and the second base portions  157  and  257 , at least part of the first base portion  157  and at least part of the second base portion  257  may be in contact with the first and the second light source mounting portions  154  and  254 , respectively. 
     The radiating fins  156  are arranged such that the ventilation passages formed between the plurality of radiating fins  156  extend from the lamp body  12  side toward the translucent cover  14 , in the same way as Embodiment  1 . The radiating fins  156  are arranged such that the ventilation passages are parallel with the mounting surfaces of the first and the second light source mounting portions  154  and  254 . The radiating fins  156  may be formed such that each width of the ventilation passages is progressively greater as advancing from the lamp body  12  side toward the translucent cover  14  side. 
     The fan  70  is installed on the side of the main body  52 , the side being opposite to the surfaces on which the first and the second light source mounting portions  154  and  254  are formed. 
     Subsequently, the description will be made with respect to how the convection of the air inside the automotive lamp  10  according to the present embodiment occurs. In  FIG. 4 , arrows indicate the flow of air. In the automotive lamp  10 , the heat produced by the semiconductor light emitting device  132  is conducted to the first light source mounting portion  154 . The heat conducted to the first light source mounting portion  154  is then conducted to the radiating fins  156  through the first base portion  157 . The heat produced by the semiconductor light emitting device  232  are conducted to the second light source mounting portion  254 . The heat conducted to the second light source mounting portion  254  is then conducted to the radiating fins  156  through the second base portion  257 . 
     In the ventilation passages formed between the plurality of radiating fins  156 , the air blown by the fan  70  flows from the lamp body  12  side to the translucent cover  14  side, and the heat exchange with the radiating fins  156  is performed while the air blown by the fan  70  is flowing through the ventilation passages. Thereby, the heat conducted to the radiating fins  156  is radiated into the ambient air. 
     The air warmed due to the radiation by the radiating fins  156  while passing through the ventilation passages, is directly blown to the translucent cover  14  from the radiating fins  156 . When reaching the translucent cover  14 , the air flows in the upward-downward direction along the translucent cover  14 . The air blown from the radiating fins  156  is cooled due to the heat exchange with the translucent cover  14  while the air is flowing in the upward-downward direction along the translucent cover  14 . 
     On the other hand, the translucent cover  14  is warmed by the air blown from the radiating fins  156 . Thereby, the adhesion of snow or ice to the outer surface of the translucent cover  14  can be suppressed, or the snow or ice adhered to the outer surface thereof can be melted. The air cooled by the heat exchange with the translucent cover  14  flows backwards along the top surface or the bottom surface of the lamp body  12 , thereafter being blown again toward the translucent cover  14  by the fan  70 . 
     Operations and effects by the aforementioned structures will be collectively described below. In the present embodiment, one end of the radiating fins  156  is in contact with the first light source mounting portion  154  through the first base portion  157 , while the other end thereof is in contact with the second light source mounting portion  254  through the second base portion  257 . The heat produced by the semiconductor light emitting devices  132  and  232  are radiated into the air flowing through the ventilation passages in the radiating fins  156 . That is, the first lamp unit  130  and the second lamp unit  230  use the radiating fins  156  in common. 
     Therefore, the following effects can be obtained in addition to the effects obtained by the aforementioned Embodiment 1. That is, it is not required that each of the first lamp unit  130  and the second lamp unit  230  is provided with the radiating fins  156 , and hence the space for mounting the radiating fins  156  can be reduced, allowing the automotive lamp  10  to be further miniaturized. Furthermore, because increase in the number of parts can be suppressed, the cost of the automotive lamp  10  can be reduced. 
     It is noted that the present invention should not be limited to the aforementioned embodiments, and various variations such as design modifications or the like may be made thereto based on knowledge of a person skilled in the art, and embodiments including such variations should be encompassed by the present invention. 
     For example, in the aforementioned embodiment, an LED is used as a light source; however, a semiconductor light emitting device, for example, a semiconductor laser or the like, can be used. Also, in the aforementioned embodiment, a projector-type lamp unit is used as a lamp unit; however, a parabolic-type or direct-emitting type lamp unit can be used. 
       FIG. 5  is a schematic vertical cross-sectional view of the automotive lamp  10  comprising a direct-emitting type lamp unit. As illustrated in  FIG. 5 , the automotive lamp  10  comprises a lamp unit  330  that is a direct-emitting type and projector-type lamp unit. The lamp unit  330  comprises a semiconductor light emitting device  332 , a shade  336  and a projection lens  338 . The semiconductor light emitting device  332  is mounted on the main body  52  of the bracket  50  in a state where the light emission direction thereof faces the light axis direction (left direction in  FIG. 5 ) of the lamp unit  330 . Accordingly, the light source mounting portion is composed of part of the main body  52 . 
     A base portion  357  is arranged on the surface of the main body  52  of the bracket  50 , the surface being opposite to the semiconductor light emitting device  332 . The lower end of the base portion  357  is connected to the plurality of radiating fins  56 , which are arranged so as to penetrate the radiating fin mounting through-holes  55 . Accordingly, the heat produced by the semiconductor light emitting device  332  is conducted to the radiating fins  56  through the base portion  357 . The bracket  50  may not comprise the base portion  357 , but the upper end of the radiating fins  56  may extend to the area where the base portion  357  might exist and be in contact with the light source mounting portion. 
     In the aforementioned embodiments, the lamp units  30 ,  130  and  230  are lamp units for low-beam emission in which a diagonal cut-off line is formed in the light distribution pattern; however, those lamp units may be ones for high-beam emission in which a diagonal cut-off line is not formed. 
     The automotive lamps  10  according to the aforementioned embodiments can be applied to, for example, automotive headlamps, tail lamps, or auxiliary headlamps such as fog lamps, driving lamps or the like.