Patent Publication Number: US-8118462-B2

Title: Automotive lamp

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims priority from Japanese Application No. 2008-163220, filed Jun. 23, 2008 incorporated by reference in its entirety. 
     BACKGROUND 
     The present invention relates to an automotive lamp and, in particular, to an automotive lamp whose light source is a semiconductor light emitting device. 
     DESCRIPTION OF THE RELATED ART 
     There are automotive lamps that use a semiconductor light emitting device, such as an LED (light emitting diode) or the like, as the light source. When a semiconductor light emitting device is used as the 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 proposed for automotive lamps in order to radiate heat from the semiconductor light emitting device efficiently. An example can be found in Japanese Patent Application Publication No. 2006-286395. 
     With the automotive lamp as disclosed in Japanese Patent Application Publication No. 2006-286395, however, the air inside a lamp chamber with the LED installed therein is circulated by natural convection. Accordingly, the air circulation inside the lamp chamber is not much promoted, and therefore there is room for improvement regarding the heat radiation efficiency. 
     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 an automotive lamp capable of efficiently radiating heat that is produced by the semiconductor light emitting device. 
     To resolve the foregoing problems, an automotive lamp according to one embodiment of the present invention comprises: a semiconductor light emitting device as a light source; a heatsink which radiates heat produced by the semiconductor light emitting device, the heatsink including a plurality of plate fins installed upright on a base part and a plurality of ventilation passages formed between the plate fins; a centrifugal fan which performs a forced air cooling of the plate fins by sending air through the ventilation passages of the heatsink, the centrifugal fan having air inlets open in an axial direction thereof for drawing air in and a plurality of air outlets for discharging air in a plurality of directions perpendicular to the axial direction thereof; and a lamp housing which houses the semiconductor light emitting device, heatsink, and centrifugal fan, wherein the plate fins of the heatsink are formed such that an entrance of at least one of the plurality of ventilation passages faces each of the air outlets of the centrifugal fan. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will now be described by way of examples 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 in which: 
         FIG. 1  is a schematic cross-sectional view of an automotive lamp according to a first embodiment of the present invention; 
         FIG. 2  is a perspective illustration of a heatsink and a fan of an automotive lamp according to a first embodiment of the present invention; and 
         FIG. 3  is a perspective illustration of a heatsink and a fan of an automotive lamp according to a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention will now be described by reference to the preferred embodiments. This does not intend to limit the scope of the present invention, but to exemplify the invention. 
     A detailed description is given hereinbelow of an automotive lamp according to the embodiments with reference to the accompanying drawings. 
       FIG. 1  is a schematic cross-sectional view of an automotive lamp  10  according to a first embodiment of the present invention. As illustrated in  FIG. 1 , the automotive lamp  10  is of a structure such that a lamp unit  30  is housed in a lamp housing which includes a lamp body  48  formed of a resin, which is open in the front, and an outer cover  34  formed of a translucent material, which covers the front of the lamp body  48  in an airtight manner. 
     It is to be noted that although only a single lamp unit  30  is shown in  FIG. 1 , the automotive lamp  10  houses three lamp units, namely, a first lamp unit, a second lamp unit, and a third lamp unit, within the lamp housing thereof. The first to third lamp units are of an identical structure. The first to third lamp units are installed adjacent to each other left to right in a row. That is, facing the front of the automotive lamp  10 , the first lamp unit is located on the left, the second lamp unit in the middle, and the third lamp unit on the right. The lamp unit  30  shown in  FIG. 1  is the second lamp unit located in the middle. Hereinbelow, the first to third lamp units, when they are named generically, will simply be referred to as “lamp unit  30 ”. 
     The lamp unit  30 , which is a so-called projector-type lamp unit, uses an LED as the light source. Each lamp unit  30  includes an LED  20 , a thermally conductive insulating substrate  24 , a reflector  22 , a mounting member  26 , and a projection lens  32 . The LED  20  is a white-color LED comprising a not-shown LED chip and an approximately hemispherical cap covering the LED chip. The LED  20  is disposed on the thermally conductive insulating substrate  24  which is formed of a ceramic or the like. The LED  20  is installed in a position on a light axis Ax of the lamp unit  30  such that the light emission direction thereof faces a direction perpendicular to the light axis Ax. Power is supplied to the LED  20  through a wiring pattern formed on the thermally conductive insulating substrate  24 . 
     The reflector  22 , which is shaped as a half dome made of, for instance, a polycarbonate, is disposed over the LED  20 . The reflector  22  has a reflecting surface on the inside thereof which reflects light from the LED  20  in the front direction in such a manner as to concentrate it toward the light axis Ax. 
     The projection lens  32 , which is a planoconvex aspheric lens having a convex front surface and a plane rear surface, irradiates the image of the light source formed on the rear focal plane as a reverted image. The mounting member  26  is substantially a flat plate formed of a metal having aluminum as the main component by die casting. And anchored to the upper surface thereof are the substrate  24  mounted with the LED  20  and the reflector  22 . Also, attached to the front end of the mounting member  26  is the projection lens  32 . 
     The rear end of the mounting member  26  of each lamp unit  30  is attached to a heatsink  14  which is provided in a lamp chamber  35 . The heatsink  14 , which is formed of aluminum or other metal having a high thermal conductivity, radiates heat produced by the LED  20  of each lamp unit  30  into the air inside the lamp chamber  35 . Attached to the heatsink  14  is a centrifugal fan  56 . The centrifugal fan  56  draws air in from an axial direction and sends air out in centrifugal directions. A detailed description of the structures of the heatsink  14  and the centrifugal fan  56  will be given with reference to  FIG. 2 . 
     The lamp unit  30 , the heatsink  14  and the centrifugal fan  56  are installed within the lamp chamber  35  by means of a not-shown support member in such a manner that the light emitted by each lamp unit  30  can be irradiated frontward from the automotive lamp  10 . In the first embodiment, the lamp unit  30 , the heatsink  14  and the centrifugal fan  56  are installed near the center of the lamp chamber  35 . 
       FIG. 2  is a perspective illustration of a heatsink  14  and a centrifugal fan  56  of an automotive lamp  10  according to the first embodiment of the present invention. As shown in  FIG. 2 , the heatsink  14  is comprised of a first sub-heatsink  50 , a second sub-heatsink  52 , and a third sub-heatsink  54 . In the heatsink  14 , the second sub-heatsink  52  is located in the middle, with the first sub-heatsink  50  on the left and the third sub-heatsink  54  on the right facing frontward from the automotive lamp  10 . The first lamp unit is mounted to the first sub-heatsink  50 , the second lamp unit to the second sub-heatsink  52 , and the third lamp unit to the third sub-heatsink  54  (first to third lamp units being not shown in  FIG. 2 ). 
     The first sub-heatsink  50  is comprised of a first base part  50   a  and a plurality of first plate fins  50   b  mounted upright on the first base part  50   a  in parallel with each other at predetermined intervals. Formed between the plurality of first plate fins  50   b  are a plurality of ventilation passages in parallel with each other. Also, the second sub-heatsink  52  is comprised of a second base part  52   a  and a plurality of second plate fins  52   b  disposed upright on the second base part  52   a  in parallel with each other at predetermined intervals. Formed between the plurality of second plate fins  52   b  are a plurality of ventilation passages in parallel with each other. Also, the third sub-heatsink  54  is comprised of a third base part  54   a  and a plurality of third plate fins  54   b  disposed upright on the third base part  54   a  in parallel with each other at predetermined intervals. Formed between the plurality of third plate fins  54   b  are a plurality of ventilation passages in parallel with each other. 
     The first base part  50   a , the second base part  52   a  and the third base part  54   a  are formed by a single plate member. In this manner, forming the first to third base parts  50   a  to  54   a  by a single plate member allows easy handling of the first to third sub-heatsinks  50  to  54  as a single assembly. As a result, the assembly can be installed on the lamp body  48  with great ease. Alternatively, however, the first to third base parts  50   a  to  54   a  may be formed as separate bodies, in which case the manufacture of the first to third sub-heatsinks  50  to  54  can be made easier. 
     In the first embodiment, the first plate fins  50   b  of the first sub-heatsink  50  are so formed as to extend in the left-right (horizontal) direction. The direction of extension of the plate fins meant here is the longitudinal direction of the plate fins. Also, the third plate fins  54   b  of the third sub-heatsink  54  are so formed as to extend in the left-right (horizontal) direction. On the other hand, the second plate fins  52   b  of the second sub-heatsink  52 , which is located in the middle, are so formed as to extend in the vertical direction. That is, the direction of extension of the plate fins of the second sub-heatsink  52  is perpendicular to the direction thereof of the first sub-heatsink  50  and the third sub-heatsink  54 . 
     The first plate fins  50   b  and the third plate fins  54   b  are so formed as to be approximately the same in height from the base part. On the other hand, the second plate fins  52   b  are so formed that the height from the base part thereof is about half that of the first plate fins  50   b  and the third plate fins  54   b . Accordingly, there results a space, between the first plate fins  50   b  and the third plate fins  54   b , recessed as much as the second plate fins  52   b  are lower in height than the first plate fins  50   b  and the third plate fins  54   b.    
     The centrifugal fan  56  is installed on the second plate fins  52   b  in such a manner that it fits into the above-mentioned recessed space. The centrifugal fan  56  has an air inlet  56   a  in the front in the axial direction thereof and an air inlet  56   b  in the rear in the axial direction thereof for drawing air in, an air outlet  56   c  in the left side thereof for discharging air leftward perpendicular to the axial direction thereof, and an air outlet  56   d  in the right side thereof for discharging air rightward perpendicular to the axial direction thereof. As power is supplied to a motor (not shown) of the centrifugal fan  56  and fan blades (not shown) begin rotating, air is drawn in through the axially front air inlet  56   a  and the axially rear air inlet  56   b  and then discharged leftward and rightward through the left-side air outlet  56   c  and the right-side air outlet  56   d , respectively. 
     As air is drawn in through the axially front air inlet  56   a , the pressure inside the ventilation passages of the second sub-heatsink  52  becomes negative, so that air flows into the ventilation passages between the second plate fins  52   b  from above and below. In this manner, the second sub-heatsink  52  is subjected to a forced air cooling by the intake of air caused by the centrifugal fan  56 . 
     The left-side air outlet  56   c  and the right-side air outlet  56   d  of the centrifugal fan  56  are so formed that the height thereof is about half that of the first plate fins  50   b  and the third plate fins  54   b . Hence, when the centrifugal fan  56  is installed on the second sub-heatsink  52 , the entrances of the ventilation passages of the first sub-heatsink  50  face the left-side air outlet  56   c  and the entrances of the ventilation passages of the third sub-heatsink  54  face the right-side air outlet  56   d . As a result, most of the air discharged leftward from the left-side air outlet  56   c  flows into the ventilation passages between the first plate fins  50   b , so that the first sub-heatsink  50  is subjected to a forced air cooling. Likewise, most of the air discharged rightward from the right-side air outlet  56   d  flows into the ventilation passages between the third plate fins  54   b , so that the third sub-heatsink  54  is subjected to a forced air cooling. 
     In the first embodiment, the ventilation passages of the first sub-heatsink  50  whose entrances face the left-side air outlet  56   c  of the centrifugal fan  56  extend in a direction parallel to the air discharge direction of the left-side air outlet  56   c . Also, the ventilation passages of the third sub-heatsink  54  whose entrances face the right-side air outlet  56   d  of the centrifugal fan  56  extend in a direction parallel to the air discharge direction of the right-side air outlet  56   d . Thus, extension of each ventilation passage whose entrance faces each of the air outlets of the centrifugal fan  56  in a direction parallel to the air discharge direction of each air outlet allows a smooth flow of air through each ventilation passage, and this promotes a forced air cooling of each sub-heatsink. 
     Next, the heat radiation mechanism in the automotive lamp  10  according to the first embodiment will be described. In  FIG. 2 , white arrows indicate the flows of air. In the automotive lamp  10  as shown in  FIG. 1 , as the LED  20  of each lamp unit  30  emits light, the heat resulting from the emission of light is conducted to the mounting member  26  through the thermally conductive insulating substrate  24  with which the LED  20  is in contact. The heat conducted to the mounting member  26  of each lamp unit  30  is conducted to the base part of the sub-heatsink with which the rear end of each mounting member  26  is in contact. In this manner, the thermally conductive insulating substrate  24  and the mounting member  26  function as heat conductors conducting the heat produced by the LED  20  to the sub-heatsink. The heat conducted to the base part of each sub-heatsink is conducted to the plate fins of each sub-heatsink before it is radiated into the surrounding air. 
     As the fan blades are rotated with power supplied to the motor of the centrifugal fan  56  and, air is drawn in through the axially front air inlet  56   a  and the axially rear air inlet  56   b  and then discharged leftward and rightward through the left-side air outlet  56   c  and the right-side air outlet  56   d , respectively. 
     With the intake of air through the axially front air inlet  56   a , the pressure inside the ventilation passages of the second sub-heatsink  52  becomes negative, so that, as shown in  FIG. 2 , air flows into the ventilation passages between the second plate fins  52   b  from above and below. Thus, the air whose temperature is raised by the heat radiated from the second plate fins  52   b  of the second sub-heatsink  52  is drawn in by the centrifugal fan  56 , and new air is introduced into the ventilation passages. 
     The air discharged from the left-side air outlet  56   c  of the centrifugal fan  56  flows through the entrances of the ventilation passages facing the left-side air outlet  56   c  into the ventilation passages of the first sub-heatsink  50 . As a result, the air whose temperature is raised by the heat radiated from the first plate fins  50   b  of the first sub-heatsink  50  is discharged from the exits of the ventilation passages as shown in  FIG. 2 . Similarly, the air discharged from the right-side air outlet  56   d  of the centrifugal fan  56  flows through the entrances of the ventilation passages facing the right-side air outlet  56   d  into the ventilation passages of the third sub-heatsink  54 . As a result, the air whose temperature is raised by the heat radiated from the third plate fins  54   b  of the third sub-heatsink  54  is discharged from the exits of the ventilation passages as shown in  FIG. 2 . 
     By a mechanism as described above, the sub-heatsinks of the heatsink  14  are subjected to a forced air cooling, and the heat produced by the lamp units  30  connected to the respective sub-heatsinks is radiated. In the automotive lamp  10  according to the first embodiment, the air from the centrifugal fan  56  is discharged in two directions, namely, leftward and rightward, and the plate fins are formed such that the entrances of the ventilation passages of the first sub-heatsink  50  and the third sub-heatsink  54  face the left-side air outlet  56   c  and the right-side air outlet  56   d , respectively. This configuration provides more parts of the heatsink  14  that are exposed to the drafts of air sent. As a result, the forced air cooling of the heatsink  14  is better facilitated, thus radiating the heat produced by the LED  20  more efficiently. 
     The automotive lamp  10  according to the first embodiment is so configured that the second plate fins  52   b  are provided in the axial front of the centrifugal fan  56  and thus the second sub-heatsink  52  is subjected to a forced air cooling by the intake of air caused by the centrifugal fan  56 . In this manner, the utilization of not only the discharge of air from the centrifugal fan  56  but also the intake of air thereby for forced air cooling ensures the radiation of the heat produced by the LED  20  with greater efficiency. 
     Moreover, the automotive lamp  10  is so structured that the second plate fins  52   b  of the second sub-heatsink  52 , which are subjected to forced air cooling by the intake of air caused by the centrifugal fan  56 , extend in a direction perpendicular to the direction in which the first plate fins  50   b  of the first sub-heatsink  50  and the third plate fins  54   b  of the third sub-heatsink  54 , which are subjected to forced air cooling by the discharge of air caused by the centrifugal fan  56 , extend. If the air immediately after the discharge goes back to the air inlets of the centrifugal fan, then there will be no active circulation of air inside the lamp chamber, which leads to a drop in heat radiation efficiency. Formation of the plate fins as implemented in the first embodiment can therefore prevent the air immediately after the discharge from going back to the air inlets of the centrifugal fan. And this promotes an active circulation of air inside the lamp chamber, thus improving the heat radiation efficiency. 
     Further, in the first embodiment, a recessed space is provided by the second plate fins  52   b  whose height from the base part is lower than the plate fins of the sub-heatsinks on both sides, and the centrifugal fan  56  is fitted into the recessed space. This configuration realizes a compact heat radiation structure of the heatsink  14  and the centrifugal fan  56  in combination. And this heat radiation structure can be applied for use in more automotive lamps. 
       FIG. 3  is a perspective illustration of a heatsink  114  and a fan  156  of an automotive lamp according to a second embodiment of the present invention. Though the structure of the automotive lamp according to the second embodiment is basically the same as that of the automatic lamp  10  shown in  FIG. 1 , the structure differs in the heatsink  114  and the fan  156 . Note that the structural components identical or equivalent to those in the first embodiment are denoted with the same reference numerals as those therein, and the repeated description thereof will be omitted as appropriate. 
     In the second embodiment, the heatsink  114  is comprised of a first sub-heatsink  150 , a second sub-heatsink  152 , and a third sub-heatsink  154 . In the heatsink  114 , the second sub-heatsink  152  is located in the middle, with the first sub-heatsink  150  on the left and the third sub-heatsink  154  on the right facing frontward from the automotive lamp  10 . The first lamp unit is mounted to the first sub-heatsink  150 , the second lamp unit to the second sub-heatsink  152 , and the third lamp unit to the third sub-heatsink  154  (first to third lamp units being not shown in  FIG. 3 ). 
     The first sub-heatsink  150  is comprised of a first base part  150   a  and a plurality of first plate fins  150   b  mounted upright on the first base part  150   a  in parallel with each other at predetermined intervals. Formed between the plurality of first plate fins  150   b  are a plurality of ventilation passages in parallel with each other. Also, the third sub-heatsink  154  is comprised of a third base part  154   a  and a plurality of third plate fins  154   b  mounted upright on the third base part  54   a  in parallel with each other at predetermined intervals. Formed between the plurality of third plate fins  154   b  are a plurality of ventilation passages in parallel with each other. On the other hand, the second sub-heatsink  152  is comprised of a second base part  152   a  and a plurality of pin fins  152   b  disposed upright on the second base part  152   a  in parallel with each other at predetermined intervals. 
     The first base part  150   a , the second base part  152   a  and the third base part  154   a  are formed by a single plate member. In this manner, forming the first to third base parts  150   a  to  154   a  by a single plate member allows handling of the first to third sub-heatsinks  150  to  154  as a single assembly. As a result, the handling can be easy and the assembly can be installed on the lamp body  48  with great ease. Alternatively, however, the first to third base parts  150   a  to  154   a  may be formed as separate bodies, in which case the manufacture of the first to third sub-heatsinks  150  to  154  can be made easier. 
     In the second embodiment, the first plate fins  150   b  of the first sub-heatsink  150  are so formed as to extend in the left-right (horizontal) direction. Also, the third plate fins  154   b  of the third sub-heatsink  154  are so formed as to extend in the left-right (horizontal) direction. The pin fins  152   b  of the second sub-heatsink  152  are so formed as to have a predetermined arrangement pattern. 
     The first plate fins  150   b  and the third plate fins  154   b  are so formed as to be approximately the same in height from the base part. On the other hand, the pin fins  152   b  are so formed that the height from the base part thereof is about half that of the first plate fins  150   b  and the third plate fins  154   b . Accordingly, there results a space, between the first plate fins  150   b  and the third plate fins  154   b , recessed as much as the pin fins  152   b  are lower in height than the first plate fins  150   b  and the third plate fins  154   b.    
     A fan  156  is installed on the pin fins  152   b  in such a manner that it fits into the above-mentioned recessed space. The fan  156  is a fan, which combines a centrifugal fan and an axial flow fan, structured such that the air drawn in from one axial direction can be discharged in a plurality of directions perpendicular to the axial direction and at the same time can be discharged in the other axial direction. The fan  156  has an air inlet  156   a  in the rear in the axial direction for drawing air in, a front-side air outlet  156   b  for discharging air in the front in the axial direction of the fan  156 , an air outlet  156   c  in the left side thereof for discharging air leftward perpendicular to the axial direction thereof, and an air outlet  156   d  in the right side thereof for discharging air rightward perpendicular to the axial direction thereof. As power is supplied to a motor (not shown) of the fan  156  and fan blades begin rotating (here the fan blades are not shown in  FIG. 3  for the purpose of making the pin fins  152   b  more visible), air is drawn in through the axially rear air inlet  156   a  and then discharged frontward, leftward and rightward through the front-side air outlet  156   b , the left-side air outlet  156   c  and the right-side air outlet  156   d , respectively. 
     As air is discharged frontward through the front-side air outlet  156   b , the second sub-heatsink  152  is subjected to a forced air cooling. The left-side air outlet  156   c  and the right-side air outlet  156   d  of the fan  156  are so formed that the height thereof is about half that of the first plate fins  150   b  and the third plate fins  154   b . Hence, when the fan  156  is installed on the second sub-heatsink  152 , the entrances of the ventilation passages of the first sub-heatsink  150  face the left-side air outlet  156   c  and the entrances of the ventilation passages of the third sub-heatsink  154  face the right-side air outlet  156   d . As a result, most of the air discharged leftward from the left-side air outlet  56   c  flows into the ventilation passages between the first plate fins  150   b , so that the first sub-heatsink  150  is subjected to a forced air cooling. Likewise, most of the air discharged rightward from the right-side air outlet  156   d  flows into the ventilation passages between the third plate fins  154   b , so that the third sub-heatsink  154  is subjected to a forced air cooling. 
     In this manner, in the second embodiment the air drawn in through the axially rear air inlet  156   a  is discharged in three directions, namely, frontward, leftward and rightward. Hence, the air can be sent to as many regions of the heatsink  114  as possible. As a result, the heat produced by each lamp unit can be radiated efficiently. 
     Next, a heat radiation mechanism in the automotive lamp according to the second embodiment will be described. In  FIG. 3 , white arrows indicate the flows of air. In the automotive lamp as shown in  FIG. 3 , as the LED  20  of each lamp unit  30  emits light, the heat resulting from the emission of light is conducted to the mounting member  26  through the thermally conductive insulating substrate  24  with which the LED  20  is in contact. The heat conducted to the mounting member  26  of each lamp unit  30  is conducted to the base part of each sub-heatsink with which the rear end of each mounting member  26  is in contact. The heat conducted to the first base part  150   a  and the third base part  154   a  is conducted to the first plate fins  150   b  and the third plate fins  154   b  before it is radiated into the surrounding air. Also, the heat conducted to the second base part  152   a  is conducted to the pin fins  152   b  before it is radiated into the surrounding air. 
     As the fan blades are rotated with power supplied to the motor of the fan  156  and, air is drawn in through the axially rear air inlet  156   a  and then discharged frontward, leftward and rightward through the front-side air outlet  156   b , the left-side air outlet  156   c  and the right-side air outlet  156   d , respectively. 
     With the air discharged forward from the front-side air outlet  156   b , the pin fins  152   b  are exposed to the air. The air whose temperature is raised by the heat radiated from the pin fins  152   b  is diffused in all directions through spaces between the pin fins  162 . After the second sub-heatsink  152  is subjected to a forced air cooling, the diffused air flows into the first sub-heatsink  150  and the third sub-heatsink  154 , so that the first sub-heatsink  150  and the third sub-heatsink  154  are subjected to a forced air cooling. 
     The air discharged from the left-side air outlet  156   c  of the fan  156  flows through the entrances facing the left-side air outlet  156   c  into the ventilation passages of the first sub-heatsink  150 . As a result, the air whose temperature is raised by the heat radiated from the first plate fins  150   b  is discharged from the exits of the ventilation passages as shown in  FIG. 3 . Similarly, the air discharged from the right-side air outlet  156   d  of the fan  156  flows through the entrances facing the right-side air outlet  156   d  into the ventilation passages of the third sub-heatsink  154 . As a result, the air whose temperature is raised by the heat radiated from the third plate fins  154   b  is discharged from the exits of the ventilation passages as shown in  FIG. 3 . 
     By the mechanism as described above, the sub-heatsinks of the heatsink  114  are subjected to a forced air cooling, and the heat produced by the lamp units  30  connected to the respective sub-heatsinks is radiated. In the second embodiment, the air from the fan  156  is discharged in three directions, namely, frontward, leftward and rightward. Also, the plate fins are formed such that the entrances of the ventilation passages of the first sub-heatsink  150  and the third sub-heatsink  154  face the left-side air outlet  156   c  and the right-side air outlet  156   d , respectively. Further, the pin fins  152   b  are formed in the axially front direction of the fan  156 . This configuration increases the number of parts of the heatsink  114  that are exposed to the drafts of air sent. As a result, the forced air cooling of the heatsink  114  is better facilitated, thus radiating the heat produced by the LED  20  more efficiently. 
     Also, in the second embodiment, the fins for the second sub-heatsink  152  disposed frontward of the fan  156  is pin-fin shaped. For example, if the fins for the second sub-heatsink  152  are plate fins, the air discharged forward in the axial direction will flow in the left and right directions through the ventilation passages between the plate fins and therefore the wind velocity will differ between each of the ventilation passages of the first sub-heatsink  150  and each of the ventilation passages of the third sub-heatsink  154 . By employing the pin fins as the fins for the second sub-heatsink  152  as with this second embodiment, the directional characteristics in the surface direction of air discharged forward in the axial direction can be eliminated. Thus the difference in wind velocity between each of the ventilation passages of the first sub-heatsink  150  and each of the ventilation passages of the third sub-heatsink  154  will be less likely to be caused and the forced air cooling can be done uniformly. 
     Moreover, in the second embodiment, a recessed space is provided by the pin fins  152   b  whose height from the base part is lower than the plate fins of the sub-heatsinks on both sides, and the fan  156  is fitted into the recessed space. This configuration realizes a compact heat radiation structure of the heatsink  114  and the fan  156  in combination. And this heat radiation structure can be applied for use in more automotive lamps. 
     The present invention has been described by referring to each of the above-described embodiments and such description is for illustrative purposes only. It is understood by those skilled in the art that various modifications to constituting elements and processes could be developed and that such modifications are also within the scope of the present invention. 
     In the above-described embodiments, LEDs are used as the light sources. However, this should not be considered as limiting and, for example, semiconductor light emitting devices such as semiconductor laser may be used. 
     In the above-described embodiments, a projector-type lamp unit is used but this should not be considered as limiting and, for example, a parabola-type or directi-emitting-type lamp unit may be used. 
     In the above-described embodiments, two air outlets are provided for discharging the air in the axial and vertical directions but this should not be considered as limiting. A plurality of air outlets in more different directions than two may be provided for the fan. In such a case, a plate fin is formed so that at least one entrance of the ventilation passages of the heatsink faces each air outlet. 
     In the heatsink  14  shown in  FIG. 2 , a cover or covers used to prevent the air sent from the centrifugal fan  56  from being leaked along the ventilation passages may be provided at upper ends of the first plate fins  50   b  and the third plate fins  54   b  (at the ends opposite to the first base part  50   a  side and the third base part  54   a  side). In this case, the wind velocity at regions away from the left-side air outlet  56   c  and the right-side air outlet  56   d  does not drop, so that the heat can be radiated efficiently. A similar cover or covers as described above may be applied to the heatsink  114  of  FIG. 3 .