Patent Publication Number: US-8523395-B2

Title: Light emitting diode lamp and method for manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2010-164755, filed on Jul. 22, 2010, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     Embodiments relate to a light emitting diode (LED) lamp and a method for manufacturing the LED lamp. 
     BACKGROUND 
     As a substitute for an incandescent lamp, recently a light emitting diode (LED) lamp having an LED chip mounted thereon has been broadly used. Compared with an incandescent lamp, an LED lamp may have advantages in reduced power consumption and a long-lasting lifespan. 
       FIG. 14  illustrates an example of a conventional LED lamp (see, e.g., Japanese Laid-Open Patent Publication No. 2010-56059). As shown in  FIG. 14 , an LED lamp X includes LED modules  91 , a cover  92 , a heat dissipation member  93 , and a screw-in base (hereinafter, referred to as a base)  95 . Each of the LED modules  91  serves as a light emitting member that have an LED chip (not shown) mounted thereon. The cover  92  is configured to transmit light from the LED modules  91 . The cover  92  has a substantially spherical shape. The heat dissipation member  93  is configured to dissipate heat generated from the LED modules  91 . The heat dissipation member  93  is made of, e.g., aluminum. A plurality of fins  94  is formed on the heat dissipation member  93  so as to increase heat dissipation efficiency. The base  95  serves as a member for connecting the LED lamp X to a lighting apparatus having a socket for an incandescent lamp. 
     With the plurality of fins  94  provided, the heat dissipation member  93  may have a complicated structure. Also, a space should be provided inside the heat dissipation member  93  to accommodate electric wires and electronic components for supplying power to the LED modules  91 . For integrally forming the heat dissipation member  93  having such configuration, it is required to die-cast a material, e.g., aluminum. Such a die-cast process may cause a cost increase in manufacturing the LED lamp X. 
     SUMMARY 
     The present disclosure provides some embodiments of a light emitting diode (LED) lamp and a method for manufacturing the LED lamp, which are capable of increasing heat dissipation efficiency and reducing manufacturing costs. 
     In accordance with one aspect of the embodiments of the present disclosure, an LED lamp includes a plurality of LED chips and a heat dissipation member configured to dissipate heat generated from the LED chips. The heat dissipation member includes a tubular unit having a constant cross-section perpendicular to an axial direction, and a plurality of fins, each of which protrudes outwards from the tubular unit and extends in the axial direction, having a constant thickness in the axial direction. 
     With such configuration, the heat dissipation member can be manufactured from an elongated member through an extrusion casting. The extrusion casting may be lower in cost than a die casting. Therefore, the manufacturing cost of the LED lamp can be reduced while securing sufficient heat dissipation efficiency. 
     According to another embodiment of the present disclosure, the LED lamp further includes a circuit board configured to mount thereon the LED chips, wherein the circuit board is attached to one end of the heat dissipation member in the axial direction. 
     According to another embodiment of the present disclosure, the tubular unit has a cylindrical shape. 
     According to another embodiment of the present disclosure, the plurality of fins are radially disposed centering on a central axis of the tubular unit, and dimensions of the plurality of fins in a radial direction perpendicular to the axial direction are gradually increased as they approach toward the LED chips. 
     According to another embodiment of the present disclosure, the LED lamp further includes a power supply unit configured to supply power to the LED chips, wherein the power supply unit is disposed in the tubular unit. 
     According to another embodiment of the present disclosure, the heat dissipation member is made of aluminum. 
     According to another embodiment of the present disclosure, the LED lamp further includes a base attached to the other end of the heat dissipation member opposite to the LED chips. 
     According to another embodiment of the present disclosure, the LED lamp further includes a cover configured to enclose the LED chips and to transmit light generated from the LED chips. 
     According to another embodiment of the present disclosure, a surface roughening is performed on an inner surface of the cover. The surface roughening may be performed on an outer surface of the cover. 
     In accordance with another aspect of the embodiments of the present disclosure, a method for manufacturing an LED lamp includes: forming an elongated member through an extrusion casting, wherein the elongated member includes a tubular unit having a constant cross-section perpendicular to an axial direction, and a plurality of fins, each of which protrudes outwards from the tubular unit and extends in the axial direction, having a constant thickness in the axial direction; cutting the elongated extended member at cross-section planes perpendicular to the axial direction, to thereby form the heat dissipation member; and fixing LED chips to the heat dissipation member. 
     According to another embodiment of the present disclosure, the tubular unit has a cylindrical shape. 
     According to another embodiment of the present disclosure, the plurality of fins is radially disposed centering on a central axis of the tubular unit. 
     According to another embodiment of the present disclosure, the fixing LED chips further includes: attaching the LED chips on a circuit board; and fixing the circuit board to one end of the heat dissipation member in the axial direction. 
     According to another embodiment of the present disclosure, the method may further include cutting the heat dissipation member to have a dimension at one end of the fin greater than a dimension at the other end of the fin in the axial direction. 
     According to another embodiment of the present disclosure, the method further includes accommodating a power supply unit configured to supply power to the LED chips in the tubular unit. 
     According to another embodiment of the present disclosure, aluminum is used in the extrusion casting. 
     According to another embodiment of the present disclosure, the method further includes attaching a base to the other end of the heat dissipation member opposite to the LED chips. 
     Other features and advantages according to preferable embodiments of the present disclosure will be apparent from the following descriptions described in detail with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view showing one example of a light emitting diode (LED) lamp in accordance with the present disclosure. 
         FIG. 2  is a cross-sectional view taken along a II-II line in  FIG. 1 . 
         FIG. 3  is a cross-sectional view taken along a line in  FIG. 1 . 
         FIG. 4  is a cross-sectional view showing an example of an LED module in one embodiment of the LED lamp in accordance with the present disclosure. 
         FIG. 5  is a plan view showing an example of a heat dissipation member in one embodiment of the LED lamp in accordance with the present disclosure. 
         FIG. 6  is a front view showing an example of the heat dissipation member in one embodiment of the LED lamp in accordance with the present disclosure. 
         FIG. 7  is a bottom plan view showing an example of the heat dissipation member in one embodiment of the LED lamp in accordance with the present disclosure. 
         FIG. 8  is a cross-sectional view taken along a VIII-VIII line in  FIG. 6 . 
         FIG. 9  is a front view showing a circuit board of a power supply unit and electronic components mounted thereon in one embodiment of the LED lamp in accordance with the present disclosure. 
         FIG. 10  is a rear view showing the circuit board of a power supply and electronic components mounted thereon in one embodiment of the LED lamp in accordance with the present disclosure. 
         FIG. 11  is a perspective view showing an elongated member under a cutting process according to one embodiment of the LED lamp manufacturing method in accordance with the present disclosure. 
         FIG. 12  is a front view showing a shortened member under a cutting process according to one embodiment of the LED lamp manufacturing method in accordance with the present disclosure. 
         FIG. 13  is a front view showing an assembly process according to one embodiment of the LED lamp manufacturing method in accordance with the present disclosure. 
         FIG. 14  is a front view showing an example of a conventional LED lamp. 
     
    
    
     DETAILED DESCRIPTION 
     Preferable embodiments in accordance with the present disclosure will now be described in detail with reference to the accompanying drawings. 
       FIGS. 1 ,  2 , and  3  show an example of a light emitting diode (LED) lamp in accordance with one embodiment of the present disclosure. As shown in  FIGS. 1 ,  2 , and  3 , an LED lamp A according to one embodiment of the present disclosure includes a circuit board  1 , a plurality of LED modules  2 , a cover  3 , a bracket  4 , a heat dissipation member  5 , a power supply unit  6 , and a screw-in base (hereinafter, referred to as a base)  7 . As a substitute for an incandescent lamp, the LED lamp A is used in a lighting apparatus having a socket for the incandescent lamp. 
     The circuit board  1  is configured to support the LED modules  2 . The circuit board  1  includes a body made of, e.g., a glass epoxy resin, and a wiring pattern formed on the body. Alternatively, in some embodiments, the circuit board  1  may include a body, which is made of, e.g., aluminum, an insulation layer formed on the body, and a wiring pattern formed on the insulation layer. As shown in  FIG. 3 , in the present embodiment, the circuit board  1  has an approximately square shape. Referring to  FIGS. 2 and 3 , a plurality of attachment holes  11  are formed in the circuit board  1 . The attachment holes  11  serve to attach the power supply unit  6  to the circuit board  1 . 
     The LED modules  2  serve as light emitting components for emitting, e.g., white light. As shown in  FIG. 3 , in the present embodiment, four LED modules  2  are mounted on four corners of the circuit board  1 , for example. As shown in  FIG. 4 , each of the LED modules  2  includes an LED chip  21 , a substrate  22 , a wire  23 , and an encapsulation resin  24 . Alternatively, each of the LED modules  2  may include light emitting elements for emitting red light, green light, or blue light. 
     The LED chip  21  serves as a light source of the LED module  2 . The LED chip  21  may include an n-type semiconductor layer made of, e.g., a GaN-based semiconductor, a p-type semiconductor layer, and an active layer interposed between the n-type semiconductor layer and the p-type semiconductor layer. The LED chip  21  is configured to emit blue light, for example. The substrate  22  is configured to support the LED chip  21 . The substrate  22  may include a body made of, e.g., a glass epoxy resin, and a wiring pattern formed on the body. The wiring pattern includes a region for mounting the LED chip  21  and a region serving as a mounting electrode for surface-mounting the LED module  2 . 
     The wire  23  is made of, e.g., gold. The wire  23  is configured to electrically connect an upper surface of the LED chip  21  and the wiring pattern to each other. The encapsulation resin  24  covers the LED chip  21  and the wire  23 . For example, the encapsulation resin  24  is made of a material such as, e.g., a transparent epoxy resin or silicone resin mixed with a fluorescent substance. The fluorescent substance is excited by blue light emitted from the LED chip  21 , thereby emitting yellow light, for example. The yellow light emitted from the fluorescent substance and the blue light emitted from the LED chip  21  are mixed with each other to produce white light. Alternatively, in some embodiments, the encapsulation resin  24  may be made of a transparent epoxy resin or silicone resin mixed with fluorescent substances that are excited by blue light to produce red light or green light. 
     The cover  3  may protect the LED modules  2 . The cover  3  is made of, e.g., a transparent or semitransparent resin. In the present embodiment of the present disclosure, the cover  3  is configured as a semi-ellipsoid having an axial direction Na as a long axial direction. As shown in  FIG. 3 , an outer surface  32  of the cover  3  may have a smooth surface. On the other hand, an inner surface  31  of the cover  3  may have a rough surface formed through a surface roughening. For example, this surface roughening may be conducted by performing a shot-blasting treatment on a part of a die that is prepared to form the cover  3 . The part on which the shot-blasting treatment is performed corresponds to the inner surface  31  of the cover  3 . Alternatively, in some embodiments, the surface roughening may be further performed on the outer surface  32  in addition to the inner surface  31 . 
     The bracket  4  serves to realize an easy connection between the cover  3  and the heat dissipation member  5 . In the present embodiment of the present disclosure, the bracket  4  is made of, e.g., resin and has a ring-shape. 
     The heat dissipation member  5  is configured to dissipate heat generated from the LED modules  2 . The heat dissipation member  5  includes a tubular unit  51 , a plurality of fins  52 , and platforms  53 . The heat dissipation member  5  according to the present embodiment is made of, e.g., aluminum, and is formed through an extrusion casting as described later. 
     The tubular unit  51  is configured in a tubular shape having a central axis extended in the axial direction Na. In the present embodiment of the present disclosure, the tubular unit  51  is formed in a cylindrical tubular shape. The tubular unit  51  is formed to have a length covering the entire length of the heat dissipation member  5  in the axial direction Na. Cross-section of the tubular unit  51 , which is perpendicular to the axial direction Na, may have a constant shape in the axial direction Na. 
     The fins  52  are radially formed along a radial direction Nd from the tubular unit  51 , centering on the central axis of the tubular unit  51 . As shown in  FIG. 5 ,  FIG. 7 , and  FIG. 8 , when viewed from the axial direction Na, thickness of the respective fins  52  in the axial direction Na is constant. Also, gaps are formed between every two neighboring fins  52  along the axial direction Na. As shown in  FIG. 2  and  FIG. 6 , dimensions of the fins  52  in the radial direction Nd are gradually increased as approaching toward the LED modules  2  (LED chips  21 ) in the axial direction Na. 
     The platform  53  is disposed on an end portion of the heat dissipation member  5  in the axial direction Na. The platform  53  is slightly protruded from the fins  52  in the axial direction Na. As shown in  FIGS. 5 ,  6 , and  7 , the platform  53  is formed by extending the tubular unit  51  and portions of the fins  52 , which are close to the central axis of the tubular unit  51  in the radial direction Nd, in the axial direction Na. The platform  53  is configured to support the circuit board  1 . 
     The power supply unit  6  is configured to supply power to the LED modules  2  (LED chips  21 ). The power supply unit  6  includes a circuit board  61 , a plurality of electronic components  62 , and a case  63 . The circuit board  61  is made of, e.g., a glass epoxy resin. In the present embodiment of the present disclosure, the circuit board  61  is configured to have a long rectangular shape that is extended in the axial direction Na as a longitudinal direction. The electronic components  62  serve to supply power to the LED modules  2  (LED chips  21 ). As shown in  FIGS. 9 and 10 , the electronic components  62  are mounted on front and rear surfaces of the circuit board  61 . The electronic components  62  include, for example, a control IC (Integrated Circuit), a capacitor, a coil, a chip resistor, a diode, and the like. 
     The case  63  is made of, e.g., a semi-transparent resin. The case  63  includes a tubular part  63   a , a screw part  63   b , and a plurality of protrusions  63   c . The tubular part  63   a  is configured to have a cylindrical shape with a bottom whose axial direction is parallel to the axial direction Na. The tubular part  63   a  is configured to contain the circuit board  61  and the electronic components  62 . The screw part  63   b  is formed downward in the axial direction Na with respect to the tubular part  63   a . The screw part  63   b  is configured to have a male screw shape that is screw-coupled with the base  7 . 
     An outer diameter of the tubular part  63   a  of the case  63  is slightly smaller than an inner diameter of the tubular unit  51  of the heat dissipation member  5 . Therefore, in the power supply unit  6 , the tubular part  63   a  of the case  63 , and the circuit board  61  and the electronic components  62  disposed inside the tubular part  63   a  may be accommodated in the tubular unit  51  of the heat dissipation member  5 . 
     The protrusions  63   c  are configured to fix the circuit board  1 . The protrusions  63   c  are inserted into the attachment holes  11  of the circuit board  1 . Parts of the protrusion  63   c  exposing from the attachment hole  11  are thermally seared so as to securely fix the circuit board  1  to the case  63 . 
     The base  7  serves as a member to be connected to a lighting apparatus having a socket for a general-purpose lamp in compliance with, e.g., JIS (Japanese Industrial Standard). The base  7  is configured to satisfy specifications such as, e.g., E17, E26, and the like which are defined in JIS. The base  7  is connected with the screw part  63   b  of the case  63  of the power supply unit  6  through a screw coupling. 
     Next, an embodiment of a method for manufacturing the LED lamp A will be described. 
     Initially, an elongated member  5 A shown in  FIG. 11  is formed. The elongated member  5 A includes a tubular portion  51 A and a plurality of fins  52 A. Cross-section of the elongated member  5 A perpendicular to the axial direction Na has a constant shape in the axial direction Na. The tubular portion  51 A is configured to have a cylindrical shape with a central axis following in the axial direction Na. The fins  52 A are radially arranged centering on the central axis of the tubular portion  51 A. The elongated member  5 A is formed through an extrusion casting. For example, a billet made of aluminum is extruded from a die having a cross-section plane corresponding to the cross-section plane of the elongated member  5 A, thereby continuously forming the elongated member  5 A. 
     Thereafter, the elongated member  5 A is cut at cutting planes Cp. The cutting planes Cp are perpendicular to the axial direction Na and disposed at regular intervals. In this way, the elongated member  5 A is divided into a plurality of shortened members  5 B as shown in  FIG. 12 . 
     Subsequently, a tubular portion  51  B and fins  52 B of the shortened member  5 B are cut along cutting lines CI (i.e., dashed dot lines) shown in  FIG. 12 . Such a cutting process is performed by using, e.g., a wire. The cutting process along the cutting lines CI is performed on the shortened member  5 B in all radial directions thereof. In this way, the heat dissipation member  5  shown in  FIGS. 5 through 8  can be obtained. 
     Afterward, as shown in  FIG. 13 , the power supply unit  6  is inserted into the heat dissipation member  5 . The protrusions  63   c  of the power supply unit  6  and the circuit board  1  are fixed to each other such that the circuit board  1  is attached to the platforms  53  of the heat dissipation member  5 . Also, the cover  3  is attached to the heat dissipation member  5  through the bracket  4 . The base  7  is attached to the screw part  63   b  of the power supply unit  6 . Through the above described assembly process, the LED lamp A shown in  FIGS. 1 through 3  can be obtained. 
     Hereinafter, an operation of the LED lamp A will be described in detail. 
     In accordance with the present embodiment, the heat dissipation member  5  includes a tubular unit having a constant cross-section perpendicular to an axial direction, and a plurality of fins, each of which protrudes outwards from the tubular unit and extends in the axial direction, having a constant thickness in the axial direction. As such, the heat dissipation member  5  can be manufactured from the elongated member  5 A that is formed through the extrusion casting. The extrusion casting may be lower in cost than the die casting. Therefore, the manufacturing cost of the LED lamp A can be reduced. 
     In the case of using the die casting, it is difficult to widely spread a casting material to all corners of a die and thus the number of fins  52  would be limited. On the contrary, according to the present disclosure using the extrusion casting, there is no such problem. As a result, the large number of fins  52  may be formed, and heat dissipation efficiency of the heat dissipation member  5  can be improved. Moreover, in the case of using the extrusion casting, it is possible to increase a density of the heat dissipation member  5  in comparison with the die casting. The increased density may contribute to an increase of the thermal conductivity of the heat dissipation member  5  such that it improves the heat dissipation efficiency of the heat dissipation member  5 . 
     Since dimensions of the fins  52  in the radial direction Nd become larger as they approach toward the LED module  2  in the axial direction Na, it is possible to increase the surface area of the portion of the heat dissipation member  5  near the LED module  2 , which becomes hotter than the other portions thereof due to heat generated from the LED module  2 . In this way, the heat dissipation efficiency of the heat dissipation member  5  may be effectively increased. 
     As described above, the circuit board  1  is attached to the platforms  53  such that heat transfer from the LED modules  2  to the heat dissipation member  5  may be efficiently conducted. 
     By accommodating the power supply unit  6  in the tubular unit  51 , there is no need to prepare, e.g., a dedicated space for additionally disposing the power supply unit  6  in the axial direction Na. With such a configuration, miniaturization of the LED lamp A may be realized, especially, in a dimension in the axial direction Na. 
     As described above, by performing the surface roughening on the inner surface  31  of the cover  3 , light from the LED modules  2  is diffused when emitted from the outer surface  32  of the cover  3 . In this way, each of the LED modules  2  (LED chips  21 ) may not be recognized as an individual point light source when viewed from the outside of the LED lamp A. Therefore, similar to the conventional incandescent lamp, the LED lamp A may be recognized as a single light source whose light is emitted from the whole surface of the cover  3 . Alternatively, in some embodiments, a more improved diffusion effect may be obtained when the surface roughening is performed on the outer surface  32  of the cover  3  in addition to the inner surface  31  thereof. 
     As described above, the shortened member  5 B and the heat dissipation member  5  are formed from the elongated member  5 A that is made through the extrusion casting of aluminum. Therefore, by changing the cutting planes Cp or the cutting lines CI, it may be possible to easily manufacture the heat dissipation member  5  having different dimensions in the axial direction Na, or having different shapes of the fins  52  when viewed from the radial direction Nd. 
     The LED lamp A in accordance with the present disclosure is not limited to the above-described embodiments. For example, a detailed configuration of the respective components or units of the LED lamp A may be modified in various ways. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the novel embodiments described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures.