Patent Publication Number: US-2013250574-A1

Title: Lighting unit and lighting device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims priority from prior Japanese Patent Application No. 2012-070006, filed on Mar. 26, 2012, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a lighting unit and a lighting device. 
     BACKGROUND 
     Currently, a lighting device which includes a light source provided with semiconductor light emitting elements such as LEDs (light emitting diodes) come in practical use. A type of this lighting device has a reflector which controls distribution of light emitted from the light source, an optical lens which diverges or converges the light received from the reflector after control of the distribution thereat, and heat radiation fins which stand on the outer wall of the reflector to dissipate heat generated from the light source to the outside, for example. According to this type of lighting equipment, however, the heat generated from the light emitting elements still has an influence on the optical lens in some cases even under dissipation of the heat from the heat radiation fins. 
     An object to be achieved by the embodiments is to provide a lighting unit and a lighting device capable of reducing the influence of heat imposed on an optical lens. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating an example of the external appearance of a lighting device according to a first embodiment. 
         FIG. 2  is a perspective view illustrating the example of the external appearance of the lighting device. 
         FIG. 3  is a perspective view illustrating a disassembled condition of a lighting unit according to the first embodiment. 
         FIG. 4  is a perspective view illustrating a disassembled condition of the lighting unit. 
         FIG. 5  is a perspective view illustrating a disassembled condition of the lighting unit. 
         FIG. 6  is a perspective view illustrating an example of a disassembled condition of the lighting device. 
         FIG. 7  is a top view of the lighting device. 
         FIG. 8  is a cross-sectional view taken along a line I-I in  FIG. 1 . 
         FIG. 9  schematically illustrates an enlarged cross section of an optical lens according to the first embodiment. 
         FIG. 10  illustrates an example of the external appearance of an enlarged cross section of the optical lens. 
         FIG. 11  schematically illustrates an enlarged cross section of heat radiation fins according to a second embodiment. 
         FIG. 12  schematically illustrates an enlarged cross section of the heat radiation fins. 
         FIG. 13  illustrates arrangement patterns of an optical lens according to the second embodiment. 
         FIG. 14  illustrates bar-shaped components according to the second embodiment. 
         FIG. 15  illustrates bar-shaped components according to the second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Each of lighting units  100 ,  200 ,  300 , and  400  according to exemplary embodiments to be discussed herein includes a board  120  which includes a mounting surface  120   a  on which light emitting elements  122  are mounted, an insulating plate (a reflector)  140  disposed on the mounting surface  120   a  of the board  120  and having holes  142  through which light emitted from the light emitting elements  122  are passed, an optical lens  160  for directing the light that is passed through the holes  142  of the insulating plate  140 , and positioning members (spacers  150   a  through  150   d ) disposed in the lighting unit to separate the insulating plate from the optical lens  160  by a predetermined distance. 
     The positioning members of each of the lighting units  100 ,  200 ,  300 , and  400  in the embodiments are disposed between the insulating plate  140  and the optical lens  160 . 
     The insulating plate  140  of each of the lighting units  100 ,  200 ,  300 , and  400  in the embodiments is formed integrally with the positioning members. 
     The insulating plate  140  of each of the lighting units  100 ,  200 ,  300 , and  400  in the embodiments has a hole on a surface facing the optical lens  160  into which the positioning member is inserted. 
     The optical lens  160  of each of the lighting units  100 ,  200 ,  300 , and  400  in the embodiments has a planar surface facing the insulating plate  140  that is substantially parallel to a surface of the insulating plate  140  facing the optical lens  160 . 
     Each of the lighting units  100 ,  200 ,  300 , and  400  in the embodiments further includes a support member (fin base  111 ) having an interior surface (a first surface)  111   a  on which the board  120  is disposed such that the interior surface  111   a  and the board are in close contact, and a plurality of heat radiation fins  112  disposed on an exterior surface (a second surface)  111   b  of the support member that is on an opposite side of the interior surface  111   a.  In this case, one end of each of the heat radiation fins  112  is embedded in the exterior surface  111   b.    
     The heat radiation fins  112  of each of the lighting units  100 ,  200 ,  300 , and  400  in the embodiments have elongated flat sides that are substantially parallel to each other and are physically separated from each other. 
     A lighting device  1  in the embodiments includes the lighting units  100 ,  200 ,  300 , and  400 , and fixing frames  10  and  20  for fixing the plural lighting units  100 ,  200 ,  300 , and  400  such that the heat radiation fins of the plural lighting units  100 ,  200 ,  300 , and  400  do not contact each other. 
     The lighting unit and the lighting device in the embodiments are hereinafter described with reference to the accompanying drawings. Similar parts in the respective embodiments are given similar reference numbers, and the same explanation is not repeated. 
     First Embodiment 
       FIGS. 1 and 2  are perspective views illustrating an example of the external appearance of the lighting device  1  according to a first embodiment.  FIG. 1  shows the lighting device  1  as diagonally viewed from above, while  FIG. 2  shows the lighting device  1  as diagonally viewed from below. 
     The lighting device  1  illustrated in  FIGS. 1 and 2  is a device attached to a high ceiling of a building such as a gymnasium to illuminate a wide space below the lighting device  1  in  FIGS. 1 and 2  through emission of light from light emitting elements such as LEDs mounted within the lighting device  1 . 
     According to the example shown in  FIGS. 1 and 2 , the lighting device  1  includes the four lighting units  100 ,  200 ,  300 , and  400 . More specifically, the lighting units  100  and  200  are fixed to the fixing frame  10 , while the lighting units  300  and  400  are fixed to the fixing frame  20 . The fixing frames  10  and  20  are joined to each other to be assembled into the lighting device  1  provided with the four lighting units  100 ,  200 ,  300 , and  400 . 
     The respective components illustrated in  FIGS. 1 and 2  are now more specifically explained. In the following description, the structure of the lighting unit  100  is chiefly discussed as a typical unit of the lighting units  100 ,  200 ,  300 , and  400  having the same structure. Similarly, the structure of the fixing frame  10  is chiefly discussed as a typical frame of the fixing frames  10  and  20  having the same structure. 
     As illustrated in  FIG. 2 , the lighting unit  100  has a housing case  190 . The housing case  190 , which is made of metal having high heat conductivity, houses a transparent bottom cover  180 , a board on which light emitting elements such as LEDs (described later) are mounted, and others. 
     As illustrated in  FIGS. 1 and 2 , the lighting unit  100  has a plurality of the heat radiation fins  112  standing above the housing case  190 . The heat radiation fins  112  dissipate heat generated from the light emitting elements housed within the housing case  190  to the outside. In some of the figures referred to in the following description, only a part of the heat radiation fins are given the reference number “ 112 ”. However, all the flat components standing above the housing case  190  correspond to the heat radiation fins  112 . 
     The fixing frame  10  fixes the lighting units  100  and  200 , and the fixing frame  20  fixes the lighting units  300  and  400 . The fixing frames  10  and  20  are made of metal, for example. The fixing frame  10  and the fixing frame  20  are secured to each other via spacers  31  through  33 . The details of the mechanism for securing the fixing frames  10  and  20  will be explained later. 
     As illustrated in  FIG. 1 , an attachment member  14 , a terminal stand  41 , and power source devices  42   a  and  42   b  are equipped on the fixing frame  10 . The attachment member  14  is made of metal, for example, and attached to a ceiling or the like. The terminal stand  41  relays power supply from a not-shown commercial alternating current power source to the power source devices  42   a  and  42   b.  The power source devices  42   a  and  42   b  supply the power relayed from the terminal stand  41  to boards mounted within the lighting units  100  and  200  via not-shown power source lines. Similarly, an attachment member  24 , a terminal stand  51 , and power source devices  52   a  and  52   b  are equipped on the fixing frame  20 . The lighting device  1  is attached to a ceiling or the like by connection between the ceiling and the attachment members  14  and  24 . 
     An example of a disassembled condition of the lighting unit  100  according to the first embodiment is now explained.  FIGS. 3 through 5  are perspective views illustrating an example of a disassembled condition of the lighting unit  100  in the first embodiment.  FIG. 3  shows an example of the lighting unit  100  as diagonally viewed from above.  FIG. 4  shows an example of the lighting unit  100  as diagonally viewed from below.  FIG. 5  illustrates an enlarged part of the lighting unit  100  shown in  FIG. 4 . 
     As illustrated in  FIGS. 3 and 4 , the lighting unit  100  in this embodiment includes a fin unit  110 , the board  120 , washers  130   a  through  130   d,  an insulating plate (a reflector)  140 , spacers  150   a  through  150   d,  an optical lens  160 , fixing screws  170   a  through  170   d,  the bottom cover  180 , and the housing case  190 . 
     The fin unit  110 , which is made of metal having high heat conductivity, has the fin base  111  and the heat radiation fins  112 . The fin base  111 , functioning as a support member on which the board  120  is disposed, has the first surface  111   a  in tight face contact with the board  120 , and the second surface  111   b  as the opposite side of the first surface  111   a  as illustrated in  FIG. 5 . The second surface  111   b  is a surface on which the heat radiation fins  112  stand. 
     The lower end of the fin base  111  has a substantially rectangular opening where the board  120 , the insulating plate  140 , the optical lens  160 , and the bottom cover  180  are housed, with the first surface  111   a  forming the bottom of the opening. As illustrated in  FIG. 5 , the opening of the fin base  111  has two steps of a first step  111   c  and a second step  111   d  such that the opening area increases step by step in the direction from the first surface  111   a  toward the lower end of the opening. 
     As illustrated in  FIGS. 3 and 4 , screw holes  113   a  and  113   b,  into which not-shown fixing screws are threaded for fixation between the housing case  190  and the like and the fin base  111 , are formed in the side surface of the outer wall of the fin base  111 . Similarly, though not shown in the figures, not-shown screw holes similar to the screw holes  113   a  and  113   b  are formed in the side surface of the fin base  111  on the side opposed to the side surface in which the screw holes  113   a  and  113   b  are formed. As illustrated in  FIG. 4 , screw holes  114   a  through  114   d,  into which the corresponding fixing screws  170   a  through  170   d  are threaded, are formed in the first surface  111   a  of the fin base  111 . 
     The heat radiation fins  112  stand on the second surface  111   b  of the fin base  111  substantially in parallel with each other with a predetermined clearance left between each other. As noted above, the heat radiation fins  112  dissipate heat generated from the light emitting elements  122  mounted on the board  120  to the outside. 
     As illustrated in  FIG. 5 , the board  120  has a mounting surface  120   a  on which the light emitting elements  122  are mounted, and a contact surface  120   b  as the opposite side of the mounting surface  120   a.  The contact surface  120   b  is a surface brought into tight face contact with the first surface  111   a  of the fin base  111 . As illustrated in  FIG. 5 , the plural light emitting elements  122  are mounted on the mounting surface  120   a.  In the respective figures referred to in the following description, a part of the light emitting elements are given the reference number “ 122 ”. However, all the semispherical components mounted on the mounting surface  120   a  of the board  120  correspond to the light emitting elements  122 . The board  120  is sized smaller than the opening area formed by the first step  111   c  so as to allow face contact between the contact surface  120   b  and the first surface  111   a  of the fin base  111 . 
     As illustrated in  FIGS. 3 through 5 , screw through holes  121   a  through  121   d,  through which the corresponding fixing screws  170   a  through  170   d  are inserted, are formed in the board  120 . It is assumed that the board  120  in the first embodiment has SMD (surface mount device) structure where the plural light emitting elements  122  are mounted on the mounting surface  120   a.  However, instead of the SMD structure, the board  120  may have COB (chip on board) structure where the plural light emitting elements  122  are arranged and mounted on a part or the entire area of the mounting surface  120   a  in a fixed regular order such as a matrix form, a staggered form, and a radial form. 
     As illustrated in  FIGS. 4 and 5 , the board  120  has connectors  123   a  and  123   b  mounted on the mounting surface  120   a,  and notches  124   a  and  124   b  are formed in the board  120 . The connectors  123   a  and  123   b  connect with one ends of the not-shown power source lines. The other ends of the power source lines pass through the notches  124   a  and  124   b  and connect with the power source devices  42   a  and  42   b.  This structure allows the board  120  to cause light emission from the light emitting elements  122  using the power supplied from the power source devices  42   a  and  42   b.    
     During light emission, the light emitting elements  122  generate heat which possibly raises the temperatures of the light emitting elements  122 . With extremely high temperatures of the light emitting elements  122 , the performance of the light emission elements  122  may deteriorate. According to the lighting unit  100  in the first embodiment, the heat radiation fins  112  stand on the second surface  111   b  as the opposite side of the first surface  111   a  brought into close face contact with the board  120 . In this case, in the lighting unit  100  according to the first embodiment, the heat generated from the light emitting elements  122  is conducted via the fin base  111  to the heat radiation fins  112  disposed on the opposite side of the light emitting elements  122 . Therefore, the heat can be dissipated with high efficiency. 
     Each of the washers  130   a  through  130   d  is a flat washer inserted between the insulating plate  140  and the board  120 , and a screw through hole, through which the corresponding one of the fixing screws  170   a  through  170   d  is inserted, is formed in the washers  130   a  through  130   d.    
     The insulating plate  140 , which is made of synthetic resin having light resistance, heat resistance, and electrical insulating characteristics, for example, controls distribution of light emitted from the light emitting elements  122  mounted on the board  120 . More specifically, as illustrated in  FIG. 5 , as for the insulating plate  140 , adjustors  142  which are through holes are formed at positions opposed to the light emitting elements  122 . The hole shapes of the adjustors  142  control the distribution of the light emitted from the light emitting elements  122 . In the respective figures to be referred to in the following description, only a part of the adjustors are given the reference number “ 142 ”. However, all the holes formed in the insulating plate  140  at positions opposed to the light emitting elements  122  correspond to the adjustors  142 . 
     As illustrated in  FIGS. 3 through 5 , screw through holes  141   a  through  141   d,  through which the fixing screws  170   a  through  170   d  are inserted, are formed in the insulating plate  140 . The insulating plate  140  is sized smaller than the opening area formed by the first step  111   c  of the fin base  111  so as to be mounted on the mounting surface  120   a  of the board  120 . 
     The spacers  150   a  through  150   d  are positioning members capable of maintaining the insulating plate  140  and the optical lens  160  in such positions as to be away from each other with a predetermined clearance left therebetween. In the spacers  150   a  through  150   d,  screw through holes, through which the fixing screws  170   a  through  170   d  are inserted, are formed. 
     The optical lens  160  diverges or converges the light having the distribution direction adjusted by the adjustors  142  of the insulating plate  140 . In the optical lens  160 , screw through holes  161   a  through  161   d,  through which the fixing screws  170   a  through  170   d  are inserted for fixation between the optical lens  160  and the fin base  111 , are formed. The optical lens  160  according to the first embodiment is sized larger than the opening area formed by the first step  111   c,  and smaller than the opening area formed by the second step  111   d,  so as to be mounted on the first step  111   c  of the fin base  111 . The optical lens  160  in the first embodiment includes Fresnel lenses and fly-eye lenses, the details of which will be described later. 
     The fixing screws  170   a  through  170   d,  which are made of metal, for example, fix the optical lens  160 , the insulating plate  140 , and the board  120  to the fin base  111 . For example, the fixing screw  170   a  is inserted through the screw through hole  161   a  of the optical lens  160 , the spacer  150   a,  the screw through hole  141   a  of the insulating plate  140 , the washer  130   a,  and the screw through hole  121   a  of the board  120  in this order to be threaded into the screw hole  114   a  formed in the first surface  111   a  of the fin base  111 . Similarly, the fixing screws  170   b,    170   c,  and  170   d  are threaded into the screw holes  114   b,    114   c,  and  114   d  of the fin base  111 , respectively. 
     The bottom cover  180  is a transparent flat plate made of polycarbonate, acrylic resin, or other materials, for example. The bottom cover  180  is sized larger than the opening area formed by the second step  111   d  and smaller than the opening area formed by the lower edge of the fin base  111  so as to be mounted on the second step  111   d  of the fin base  111 . The bottom cover  180  has the function of reducing glare of the light so intense that direct view of the light emission surface from the outside is difficult, and further the function of preventing contact between a human body and the interior of the housing case  190  from the outside. 
     The housing case  190  is made of synthetic resin such as ABS resin, or metal such as aluminum die casting, and is opened to both above and below substantially in a rectangular shape. The lower end of the opening is provided with a projection  190   a  projecting from the edge of the lower end of the opening toward the inside. The housing case  190  having this structure houses the fin base  111  to which the board  120 , the insulating plate  140 , and the optical lens  160  are fixed, and the bottom cover  180 . Screw through holes  191   a  through  191   d,  through which not-shown screws are inserted for fixation between the housing case  190  and the fixing frame  10 , are formed in the housing case  190 . 
     An example of a disassembled condition of the lighting device  1  according to this embodiment is now explained.  FIG. 6  is a perspective view illustrating an example of disassembled condition of the lighting device  1  according to the first embodiment.  FIG. 6  shows the lighting units  100  and  200  fixed to the fixing frame  10  as an example. 
     As illustrated in  FIG. 6 , the fixing frame  10  includes a pair of lower fixing portions  10   a  and  10   b,  and a pair of bridging portions  10   c  and  10   d.  The lower fixing portions  10   a  and  10   b  are flat components whose lengths in the lateral direction are substantially equivalent to the length of the housing case  190  in the height direction. The lower fixing portions  10   a  and  10   b  are positioned opposed to each other with a space left therebetween, which space is substantially equivalent to the length of the heat radiation fins  112  in an arrangement direction H 1 . The bridging portions  10   c  and  10   d  extend longer than the length of the heat radiation fins  112  in the height direction from the upper ends of the lower fixing portions  10   a  and  10   b,  and bridge the space between the lower fixing portions  10   a  and  10   b.    
     Notches  11   a  through  11   d  are formed in the lower fixing portion  10   a  of the fixing frame  10 . Similarly, notches  11   e  through  11   h  are formed in the lower fixing portion  10   b.  A not-shown fixing screw is inserted through the notch  11   a  and the screw through hole  191   a  of the housing case  190  and threaded into the screw hole  113   a  of the fin base  111 . Similarly, a not-shown fixing screw is inserted through the notch  11   b  and the screw through hole  191   b  and threaded into the screw hole  113   b.  The lower fixing portion  10   b  has a similar structure. More specifically, not-shown fixing screws are threaded via the notches  11   e  and  11   f  into the screw holes formed in the side surface of the fin base  111 . This structure allows fixation between the lighting unit  100  and the fixing frame  10 . Similarly, the lighting unit  200  is secured to the fixing frame  10  by fixing screws tightened via the notches  11   c,    11   d,    11   g,  and  11   h.    
     As illustrated in  FIG. 6 , the terminal stand  41 , and the power source devices  42   a  and  42   b  are fixed to the upper surface of the fixing frame  10 . The attachment member  14  is fixed to the fixing frame  10  by not-shown fixing screws inserted through screw through holes  14   a  and  14   b  formed in the attachment member  14  and threaded into screw holes  10   e  and  10   f  formed in the upper surface of the fixing frame  10 . 
     The mechanism for junction between the fixing frame  10  and the fixing frame  20  is now explained. As illustrated in  FIG. 6 , a pair of screw through holes  12   a  and  12   b  is formed at the position facing each other of the lower fixing portions  10   a  and  10   b  of the fixing frame  10 . Moreover, a pair of screw through holes  13   a  and  13   b  is formed at the position, which is extended portions of the bridging portion  10   c  from the lower fixing portions  10   a  and  10   b  in the upward direction, facing each other of the bridging portion  10   c.  Similarly, a pair of screw through holes  13   c  and  13   d  is formed at the position facing each other of the bridging portion  10   d.  As illustrated in  FIGS. 1 and 2 , the fixing frame  20  has screw through holes in the lower fixing portions and the bridging portions similarly to the fixing frame  10 . For example, as illustrated in  FIG. 1 , screw through holes  23   a  and  23   c,  corresponding to the screw through holes  13   a  and  13   c  of the fixing frame  10 , are formed in the fixing frame  20 . Moreover, as illustrated in  FIG. 2 , a screw through hole  22   a,  corresponding to the screw through hole  12   a  of the fixing frame  10 , is formed in the fixing frame  20 , for example. 
     According to this structure, as illustrated in  FIG. 1 , the spacer  31  is inserted between the screw through hole  13   b  of the fixing frame  10  and the screw through hole  23   a  of the fixing frame  20 . A not-shown fixing screw is inserted through the screw through hole  13   b  and threaded into the spacer  31 , and a not-shown fixing screw is inserted through the screw through hole  23   a  and threaded into the spacer  31 . Similarly, the spacer  32  is inserted between the screw through hole  13   d  of the fixing frame  10  and the screw through hole  23   c  of the fixing frame  20 . A not-shown fixing screw is inserted through the screw through hole  13   d  and threaded into the spacer  32 , and a not-shown fixing screw is inserted through the screw through hole  23   c  and threaded into the spacer  32 . Furthermore, as illustrated in  FIG. 2 , the spacer  33  is inserted between the screw through hole  12   b  of the fixing frame  10  and the screw through hole  22   a  of the fixing frame  20 . A not-shown fixing screw is inserted through the screw through hole  12   b  and threaded into the spacer  33 , and a not-shown fixing screw is inserted through the screw through hole  22   a  and threaded into the spacer  33 . 
     By junction between the fixing frame  10  and the fixing frame  20  in this manner, the large-scale lighting device  1  including the lighting units  100 ,  200 ,  300 , and  400  is produced. 
     An example of the external appearance of the lighting device  1  in the first embodiment as viewed from above is now explained.  FIG. 7  is a top view of the lighting device  1  according to the first embodiment. As illustrated in  FIG. 7 , each of the plural heat radiation fins  112  of the lighting unit  100  has the projection  112 P projecting toward the outside from the edge of the second surface  111   b  of the fin base  111  (or the housing case  190 ). More specifically, each of the plural heat radiation fins  112  stands on the second surface  111   b  such that each side of the heat radiation fins  112  longer than a predetermined side  111   e  as the edge of the second surface  111   b  extends substantially parallel with the side  111   e.  Similarly, each of heat radiation fins  212  of the lighting unit  200 , each of heat radiation fins  312  of the lighting unit  300 , and each of heat radiation fins  412  of the lighting unit  400  have similar projections as those of the heat radiation fins  112 . 
     As can be understood, each of the heat radiation fins  112 ,  212 ,  312 , and  412  according to the first embodiment has a flat shape provided with the projection producing a large area. Thus, the contact area between the respective fins and the atmospheric air increases, wherefore the heat dissipation efficiency improves. 
     Moreover, as illustrated in  FIG. 7 , the lighting units  100 ,  200 ,  300 , and  400  are fixed by the fixing frames  10  and  20  in such a condition that the heat radiation fins of each of the lighting units  100 ,  200 ,  300 , and  400  do not contact the heat radiation fins of the other lighting units. More specifically, as illustrated in  FIG. 7 , the heat radiation fins  112  do not contact the heat radiation fins  212 , and the heat radiation fins  312  do not contact the heat radiation fins  412 . In other words, the notches  11   a  through  11   h  are formed in the fixing frame  10  for fixing the lighting units  100  and  200  in such a condition as to avoid contact between the heat radiation fins  112  and the heat radiation fins  212 . Similarly, the notches are formed in the fixing frame  20  for fixing the lighting units  300  and  400  in such a condition as to avoid contact between the heat radiation fins  312  and the heat radiation fins  412 . 
     According to the lighting device  1  in the first embodiment which includes the heat radiation fins  112 ,  212 ,  312 , and  412  arranged in such a manner as to avoid contact between each other, no blockage is produced for the flow of air between the respective lighting units. Thus, the heat dissipation efficiency improves. 
     Furthermore, as illustrated in  FIG. 7 , the heat radiation fins  112  and  212  of the lighting units  100  and  200  are arranged in similar positions. In other words, the heat radiation fins  112  and  212  are located on the extension lines from each other. Similarly, the heat radiation fins  312  and  412  of the lighting units  300  and  400  are arranged in similar positions. In this case, the atmospheric air easily flows in a direction D 1  indicated in  FIG. 7  between the heat radiation fins  112  and  212 , for example. Consequently, the heat dissipation effect of the heat radiation fins  112  and  212  improves without stay of high-temperature air. 
     A cross section of the lighting unit  100  in the first embodiment is now explained.  FIG. 8  illustrates the cross section taken along a line I-I in  FIG. 1 . As can be seen from  FIG. 8 , the board  120  is brought into tight face contact with the first surface  111   a  of the fin base  111 . In the example shown in  FIG. 8 , lighting elements  122   a  through  122   f  are mounted on the board  120 . The insulating plate  140  is further laminated with the washers  130   a  and  130   c  interposed between the insulating plate  140  and the board  120 . The insulating plate  140  has adjustors  142   a  through  142   f  at positions opposed to the light emitting elements  122   a  through  122   f.  The adjustors  142   a  through  142   f  are through holes whose diameters gradually increase in the direction from the light emitting elements  122  toward the optical lens  160 . 
     The optical lens  160  is placed on the first step  111   c  of the fin base  111  with the spacers  150   a  and  150   c  inserted between the optical lens  160  and the insulating plate  140 . The fixing screw  170   a  is inserted through the optical lens  160 , the spacer  150   a,  the insulating plate  140 , the washer  130   a,  and the board  120  in this order to be threaded into the first surface  111   a  of the fin base  111 . Similarly, the fixing screw  170   c  is inserted through the optical lens  160 , the spacer  150   c,  the insulating plate  140 , the washer  130   c,  and the board  120  in this order to be threaded into the first surface  111   a  of the fin base  111 . By this fixation, the board  120 , the insulating plate  140 , and the optical lens  160  are attached to the fin base  111 . 
     According to the example shown in  FIG. 8 , a part of the spacers  150   a  and  150   c  are embedded in the screw through holes  141   a  and  141   c  of the insulating plate  140 . Thus, the screw through hole  141   a  (and other) of the insulating plate  140  is so designed as to have a larger diameter than the outside diameter of the spacer  150   a  in the range between the end of the insulating plate  140  on the insertion side of the spacer  150   a  and the middle of the insulating plate  140  such that the spacer  150   a  can be embedded in the screw through hole  141   a.    
     The bottom cover  180  is held between the second step  111   d  of the fin base  111  and the projection  190   a  of the housing case  190 . Though not shown in the figures, the bottom cover  180  is fixed to the fin base  111  by a fixing screw inserted through the projection  190   a  and the bottom cover  180  in this order and threaded into the second step  111   d.    
     According to this structure, the spacers  150   a  and  150   c  are inserted between the insulating plate  140  and the optical lens  160  so that the insulating plate  140  and the optical lens  160  can be positioned away from each other by a predetermined distance. In this case, the optical lens  160  of the lighting unit  100  in the first embodiment is not easily affected by the heat generated from the board  120 . For divergence or convergence of light in a desired condition, the optical lens  160  needs to be disposed away from the light emitting elements  122  by a predetermined distance. In the case of the lighting unit  100  in the first embodiment, the distance between the insulating plate  140  and the optical lens  160  is determined by the spacers  150   a  and  150   c,  so that the optical lens  160  can diverge or converge light in a desired condition. 
     According to the example shown in  FIG. 8  (and  FIG. 5 ), the first step  111   c  and the second step  111   d  are formed in the fin base  111 . However, these steps  111   c  and  111   d  are not mechanisms for positioning the optical lens  160  and the bottom cover  180 , but only function as portions for temporarily positioning these components  160  and  180 . The positional relationship between the insulating plate  140  and the optical lens  160  is determined only by the spacers  150   a  through  150   d.  Thus, the fin base  111  is not necessarily required to have such a stepped configuration produced by the first step  111   c  and the second step  111   d.    
     According to the first embodiment, the spacers  150   a  through  150   d  determine the positions of the insulating plate  140  and the optical lens  160  such that the two components  140  and  160  are located away from each other by a predetermined distance. However, a positioning member which has a function similar to that of the spacers  150   a  through  150   d  may be formed integrally with the insulating plate  140  or with the optical lens  160 . For example, the insulating plate  140  may have a convex corresponding to the positioning member extended from the lower surface of the insulating plate  140  toward the optical lens  160 . Similarly, the optical lens  160  may have a convex corresponding to the positioning member extended from the upper surface of the optical lens  160  toward the insulating plate  140 . 
     The optical lens  160  in the first embodiment is now explained.  FIG. 9  schematically illustrates an enlarged cross section of the optical lens  160  according to the first embodiment.  FIG. 10  illustrates an example of the external appearance of an enlarged cross section of the optical lens  160  according to the first embodiment. As illustrated in  FIGS. 9 and 10 , the optical lens  160  in the first embodiment has a Fresnel lens  160   a  at a position opposed to each of the light emitting elements  122  (adjustors  142 ), and a fly-eye lens  160   b  on the opposite side of the Fresnel lens  160   a.    
     Each of the Fresnel lens  160   a  refracts light received from the corresponding light emitting element  122  after control of light distribution by the function of the adjustor  142  to convert the light into collimated light without decreasing the total amount of the light. More specifically, the Fresnel lens  160   a  refracts the light applied thereto from the adjustor  142  in a direction substantially perpendicular to the fly-eye lens  160   b  without attenuating the light. The fly-eye lens  160   b  diffuses the light refracted by the Fresnel lens  160   a  without attenuation to supply the light toward a not-shown area on the bottom cover  180  side. 
     The Fresnel lens  160   a  and the fly-eye lens  160   b  of the optical lens  160  shown at a position opposed to the one light emitting element  122  (adjustor  142 ) in  FIG. 9  and illustrated in  FIG. 10  as the external appearance of the optical lens  160  are provided opposed to all the light emitting elements  122  (adjustors  142 ). 
     As noted above, the optical lens  160  according to the first embodiment refracts the light emitted from the light emitting elements  122  by the function of the Fresnel lens  160   a  to convert the light into collimated light, thereby illuminating a room or the like without decreasing the total amount of the light. Moreover, the optical lens  160  diffuses the light by the function of the fly-eye lens  160   b,  thereby reducing glare of the light so intense that direct view from the outside is difficult. In this case, the optical lens  160  allows illumination of the room or the like without decreasing the total amount of the light emitted from the light emitting elements  122 , and with reduction of the glare of the light. Accordingly, efficient use of the light emitted from the light emitting elements  122  for illumination of the room or the like can be realized. 
     As described above, in the lighting unit  100  according to the first embodiment, the contact surface  120   b  of the board  120  is disposed on the first surface  111   a  of the fin base  111 , and the plural heat radiation fins  112  stand on the second surface  111   b  as the opposite side of the first surface  111   a.    
     According to the lighting unit  100  in the first embodiment, therefore, the heat generated from the light emitting elements  122  mounted on the board  120  is efficiently conducted via the fin base  111  to the heat radiation fins  112  located on the opposite side of the light emitting elements  122 . Thus, heat dissipation can be efficiently achieved. 
     Particularly, when the light emitting elements  122  are high-output elements such as LEDs, the temperatures of the light emitting elements  122  easily increase. Under this condition, there is a possibility that the heat generated from the light emitting elements  122  is not efficiently conducted to the heat radiation fins when the heat radiation fins stand on the housing main body or the insulating plate made of aluminum die casting or the like. For avoiding this problem, the configuration of the respective heat radiation fins is enlarged so that a sufficient heat dissipation effect can be produced. In this case, the size and weight of the lighting unit  100  increase. On the other hand, the lighting unit  100  in the first embodiment capable of efficiently dissipating the heat does not require scale magnification of the heat radiation fins  112  even when the high-output light emitting elements  122  are employed. Accordingly, reduction of the size and weight of the lighting unit  100  (lighting device  1 ) can be realized. 
     For expansion of the configuration of the heat radiation fins, increase in the height of the heat radiation fins is needed. In this case, unnecessary areas are required so as to increase the thickness of the roots of the heat radiation fins for draft angle cutting. However, according to the lighting unit  100  in the first embodiment, the heat radiation fins  112  stand on the fin base  111  without requiring enlargement of the scale of the heat radiation fins  112 . Thus, no additional area for draft angle cutting is needed. Based on this point, reduction of the scale and weight of the lighting unit  100  (lighting device  1 ) is similarly achieved according to the first embodiment. 
     According to the lighting unit  100  in the first embodiment, each of the plural heat radiation fins  112  has the projection  112 P projecting from the edge of the second surface  111   b  of the fin base  111  toward the outside. Thus, the heat dissipation effect improves. 
     According to the lighting unit  100  in the first embodiment, the spacers  150   a  through  150   d  as positioning members determine the position of the insulating plate  140  for controlling the reflection direction of the light emitted from the light emitting elements  122 , and the position of the optical lens  160  for diverging or converging the light reflected by the insulating plate  140 , such that the two components  140  and  160  can be located away from each other by the predetermined distance. 
     Therefore, the optical lens  160  of the lighting unit  100  in the first embodiment is not easily affected by the heat generated from the board  120 , and allowed to diverge and converge the light in a desired condition. 
     According to the lighting device  1  in the first embodiment, the fixing frames  10  and  20  fix the respective lighting units  100 ,  200 ,  300 , and  400  without contact between the heat radiation fins of each of the lighting units  100 ,  200 ,  300 , and  400  and the heat radiation fins of the other lighting units. Therefore, the heat dissipation effect of the lighting device  1  in the first embodiment improves without blockage of the flow of air between the respective lighting units. 
     Second Embodiment 
     The lighting device  1 , the lighting unit  100  and others according to the first embodiment may be modified in various ways. An example of the lighting device  1 , the lighting units and others according to a second embodiment as modifications of the corresponding parts in the first embodiment is hereinafter described. In the following explanation, the lighting unit  100  is chiefly discussed similarly to the first embodiment. However, the mechanisms and the like discussed herein are applicable to the lighting units  200 ,  300 , and  400  as well. 
     According to the first embodiment, the heat radiation fins  112  stand on the second surface  111   b  of the fin base  111 . However, the standing positions of the heat radiation fins  112  on the second surface  111   b  may be determined in correspondence with the opposite positions of the light emitting elements  122  mounted on the board  120 . This structure is now explained with reference to  FIG. 11 .  FIG. 11  schematically illustrates an enlarged cross section of the heat radiation fins  112  according to the second embodiment. 
     In the example shown in  FIG. 11 , heat radiation fins  112   a  through  112   m  stand on the second surface  111   b  of the fin base  111  at the positions corresponding to the opposite side of light emitting elements  122   a  through  122   m  mounted on the board  120 . When the respective heat radiation fins  112  are disposed just above the light emitting elements  122  as in the lighting unit  100  in this example, the heat generated from the light emitting elements  122  can be efficiently conducted to the heat radiation fins  112  as indicated by arrows in  FIG. 11 . Thus, the heat dissipation effect improves. 
     The standing positions of the heat radiation fins  112  are not limited to the positions shown in  FIG. 11  but may be such positions not opposed to the light emitting elements  122 . For example, heat radiation fins  112   x  and  112   y  may stand at positions not opposed to the light emitting elements  122  as illustrated in  FIG. 11 . Also, though not shown in  FIG. 11 , a heat radiation fin may be positioned between the heat radiation fin  112   a  and the heat radiation fin  112   b  in the example shown in  FIG. 11 . 
     The standing mechanism of the heat radiation fins  112  is now explained.  FIG. 12  schematically illustrates an enlarged cross section of the heat radiation fins  112  according to the second embodiment. As illustrated in  FIG. 12 , one end of each of the heat radiation fins  112  is embedded in the second surface  111   b  of the fin base  111 . The heat radiation fins  112  in this condition are pressed by using a stick for calking or the like in the direction indicated by arrows in  FIG. 12  under contact bonding with the second surface  111   b  so as to be embedded in the fin base  111 , for example. More specifically, raised areas from the second surface  111   b  are produced by the shift of the regions of the fin base  111  pressed by the stick or the like to other regions as illustrated in  FIG. 12 , so that one ends of the respective heat radiation fins  112  can be embedded in the raised areas of the fin base  111 . 
     When the one ends of the heat radiation fins  112  are embedded in the fin base  111 , the contact area between the heat radiation fins  112  and the fin base  111  increases. In this case, the heat generated from the light emitting elements  122  of the lighting unit  100  can be efficiently conducted from the fin base  111  to the respective heat radiation fins  112 , wherefore the heat dissipation effect improves. 
     The arrangement pattern of the optical lens  160  according to the first embodiment shown in  FIGS. 9 and 10  may be determined in various ways. These pattern variations are now explained with reference to  FIG. 13 .  FIG. 13  illustrates the arrangement patterns of the optical lens  160  according to the second embodiment.  FIG. 13  shows only the light emitting elements  122  and the optical lens  160  as viewed from above (in the direction from the light emitting elements  122  to the optical lens  160 ). 
     According to an example shown in &lt;ARRANGEMENT EXAMPLE 1&gt; in  FIG. 13 , rectangular pieces of the optical lens  160  shown in  FIG. 10  are disposed at positions opposed to the respective light emitting elements  122 . Alternatively, circular pieces of the optical lens  160  may be arranged at positions opposed to the respective light emitting elements  122  as in an example shown in &lt;ARRANGEMENT EXAMPLE 2&gt; in  FIG. 13 . When the board  120  and the like are circular, such a structure is allowed where the light emitting elements  122  are mounted on the circular board  120  in a grid pattern as illustrated in an example shown in &lt;ARRANGEMENT EXAMPLE 3&gt; in  FIG. 13 . In this case, circular pieces of the optical lens  160  may be disposed at positions opposed to the respective light emitting elements  122  as in the example shown in &lt;ARRANGEMENT EXAMPLE 3&gt; in  FIG. 13 . 
     It can be understood that the heat radiation fins  112  employed in the first embodiment have flat shapes and therefore are easily bended or deformed into other shapes. For preventing this problem, the lighting unit  100  may have bar-shaped components penetrating the respective surfaces of the plural heat radiation fins. This structure is now explained with reference to  FIGS. 14 and 15 .  FIGS. 14 and 15  illustrate examples of the bar-shaped components according to the second embodiment. 
     As illustrated in  FIG. 14 , the bar-shaped components  115   a  through  115   d,  which are made of metal having high heat conductivity or the like, penetrate the surfaces of the plural heat radiation fins  112  standing on the fin base  111 . The bar-shaped components  115   a  through  115   d  provided in this manner combine the plural heat radiation fins  112  into one body. In this case, the plural heat radiation fins  112  can be reinforced for each for avoiding deformation. According to the example shown in  FIG. 14 , the bar-shaped components  115   a  through  115   d  penetrate the peripheries (four corners) of the surfaces of the plural heat radiation fins  112  so as not to block the flow of air. 
     According to an example shown in  FIG. 15 , penetrating-bar-shaped components  116   a  through  116   f  penetrate the surfaces of both the heat radiation fins  112  of the lighting unit  100  and the heat radiation fins  312  of the lighting unit  300 . According to this structure, the penetrating-bar-shaped components  116   a  through  116   f  cross and combine the plural heat radiation fins of the different lighting units into one body for reinforcement. Thus, deformation of the plural heat radiation fins can be further prevented. 
     While  FIGS. 14 and 15  show the heat radiation fins  112  and  312  not having the projections  112 P projecting from the edges of both ends of the second surface  111   b  toward the outside, the heat radiation fins  112  and  312  shown in  FIGS. 14 and 15  may have the projections  112 P. 
     The lighting device  1  installed on a high ceiling as in the above examples is applicable to a surface-mounting type lighting device attached to places other than a high ceiling. 
     The respective components fixed to the lighting device  1  via the fixing screws as in the above examples may be fixed via other fixing members such as pins instead of the fixing screws. 
     The configurations and materials of the respective parts in the foregoing embodiments are not limited to those described and depicted therein. For example, the fin unit  110 , the board  120 , the insulating plate  140 , the optical lens  160 , the bottom cover  180 , and the housing case  190  may be circular components instead of rectangular components. 
     Accordingly, improvement over the heat dissipation effect can be achieved according to the respective embodiments. 
     Although certain embodiments of the invention have been described in the foregoing description, it is intended that the scope of the invention is not limited to the embodiments disclosed as only examples but is susceptible to numerous modifications and variations. Therefore, various eliminations, replacements, and changes may be made without departing from the scope and spirit of the invention. The respective embodiments and modifications included in the scope and spirit of the invention are also included in the scope of the invention claimed in the appended claims and the equivalents thereof.