Patent Publication Number: US-6984926-B2

Title: Compact self-ballasted fluorescent lamp resistant to heat deformation

Description:
This application is based on application No. 2003-55004 filed in Japan, the contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   (1) Field of the Invention 
   The present invention relates to a compact self-ballasted fluorescent lamp having an arc tube and a holder, the arc tube being made of a glass tube whose at least one part is bent, ends of the glass tube being respectively provided with an electrode equipped with a filament coil, and the holder being provided with insertion openings through which the ends of the glass tube are inserted and held. 
   (2) Related Art 
   In the present energy-saving era, compact self-ballasted fluorescent lamps started to become pervasive as light sources alternative to incandescent lamps. One example of such compact self-ballasted fluorescent lamps is shown in  FIG. 1 . This compact self-ballasted fluorescent lamp has an arc tube  910  formed by bending a glass tube  911  in a double spiral configuration, and a holder  920  made of resin and holds this arc tube  910 . This holder  920  stores therein an electronic ballast for lighting the arc tube  910 . At one end of the holder  920 , a base  924  that is the same type as for the incandescent lamps is fixed. Each end of the glass tube  911  is provided with an electrode equipped with a filament coil. 
   The arc tube of this compact self-ballasted fluorescent lamp is formed by bending a glass tube at the substantial middle, and winding the glass tube from the substantial middle up to the both ends, around an axis of spiral (hereinafter, this axis is referred to as “spiral axis”) (in  FIG. 1 , the spiral axis being in the vertical direction and corresponding to the axis of the base). Such an arc tube is advantageous over an arc tube that has ends of the glass tube running parallel to the spiral axis, or over an arc tube formed by connecting three U-shape glass tubes (so to speak, three U-shape arc tube), in that it can be made smaller for the same amount of light emission (refer to Japanese Patent Publication H9-17378). 
   The mentioned holder  920  that holds the arc tube  910  formed by winding the glass tube up to the ends includes: a holding resin member  925  with a cylindrical shape having a closed bottom and has, at the bottom wall of the cylindrical shape, insertion openings  922  through which ends of the glass tube  911  are inserted; and a resin cover  923  to be fit to the outer surface of the circumference of the holding resin member  925 . The ends of the glass tube  911 , having been inserted into the insertion openings  922 , are attached to the holding resin member  925  of the holder  920 , by means of a silicone resin and the like. 
   Meanwhile, a life test was conducted for a compact self-ballasted fluorescent lamp that uses the arc tube  910 , whose glass tube  911  is wound around up to its ends. As a result, at the ending of the lamp life, deformation due to heat was observed at areas of the holding resin member  925  and of the resin cover  923 , the areas corresponding to where the filament coils are placed within the glass tube  911 . 
   More specifically, when a life test is conducted by lighting the compact self-ballasted fluorescent lamp with the base  924  directed downward (hereinafter, this way of lighting is referred to as “downward illumination”), Sa area of an end wall  921  of the holding resin member  925  is deformed due to heat, as shown in  FIG. 1 . This Sa area is the area that positions directly over a filament coil of the glass tube  911 . 
   If a life test is conducted by lighting the compact self-ballasted fluorescent lamp with the base  924  directed in the lateral direction (hereinafter, this way of lighting is referred to as “lateral illumination”), Sb area of the circumferential wall of the resin cover  923  is deformed, as shown in  FIG. 1 . Deformation was most pronounced when the compact self-ballasted fluorescent lamp is laid so that the filament coil provided in one of the ends of the glass tube  911  positions at the top. 
   Note that  FIG. 1  shows the compact self-ballasted fluorescent lamp after ending of the life test, and is for both of the life test in the downward illumination, and the life test in the lateral illumination, for convenience purpose. 
   SUMMARY OF THE INVENTION 
   In light of the aforementioned problems, the object of the present invention is to provide a compact self-ballasted fluorescent lamp that restrains deformation of the holder, even when one or both of the electrodes generate extraordinary heat, at the end of the life. 
   In order to achieve this object, the compact self-ballasted fluorescent lamp of the present invention includes: an arc tube made of a glass tube that has a turning part, and of electrodes sealed in ends of the glass tube, the electrodes being each equipped with a respective one of filament coils; a holder that is provided with insertion openings and holds the arc tube so that the ends of the glass tube are inserted through the respective insertion openings and that the filament coils are positioned inside the holder; and heat-dissipating members provided for two places that are respectively between an outer surface of the glass tube and an inner surface of the holder, each of the places corresponding to a different one of the filament coils. 
   Here, each of the “two places” corresponds to a different one of the filament coils, and is between an outer surface of the glass tube and an inner surface of the holder that faces the outer surface of the glass tube. 
   With this construction, heat generated from the filament coils will be prevented from being directly transmitted to the holder in the vicinity of the filament coils. Moreover, the heat from the filament coils, after being transmitted to the heat-dissipating member through the glass tube surrounding the filament coils, will be dispersed in the heat-dissipating member. This prevents heat transmission from concentrating on one spot of the inner surface of the holder. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects, advantages and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings that illustrate a specific embodiment of the invention. In the drawings: 
       FIG. 1  shows a perspective view of a conventional compact self-ballasted fluorescent lamp, for showing parts of the holder deformed due to heat after a life test has been conducted for this conventional compact self-ballasted fluorescent lamp; 
       FIG. 2  shows a front partly-cut view of a compact self-ballasted fluorescent lamp of the present embodiment; 
       FIG. 3  shows a front partly-cut view of an arc tube of the present embodiment; 
       FIG. 4  is a perspective view showing how the arc tube is held by the holding resin member of the present embodiment, seen from the rear side of the holding member (illustrating only part of the arc tube inserted within the holding resin member); 
       FIG. 5A  shows a perspective view of the holding resin member of the present embodiment, which is seen from the front side thereof; 
       FIG. 5B  shows a perspective view of the holding resin member, seen from the rear side thereof; 
       FIG. 6  illustrates the holding resin member so that the inner surface of its end wall will be shown,  FIG. 6  being for showing the range of the metal plate provided within the holding resin member; 
       FIGS. 7A ,  7 B, and  7 C are schematic diagrams for explaining how to place the metal plate in the holding resin member, and how to fix the arc tube to the holding resin member; 
       FIG. 8  is a diagram showing one example of applying the present invention to a compact self-ballasted fluorescent lamp equipped with a globe; and 
       FIG. 9  is a diagram showing one example of applying the present invention to a fluorescent lamp. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following describes an embodiment in which the present invention is applied to a compact self-ballasted fluorescent lamp, with reference to  FIGS. 2–7 . 
   1. The Structure 
   (a) Overall Structure 
   As shown in  FIG. 2 , a compact self-ballasted fluorescent lamp  100  includes: an arc tube  110  formed by bending a glass tube  100  in a double-spiral configuration; and a holder  200  that is made of resin and is for holding the arc tube  110 . Note that this compact self-ballasted fluorescent lamp  100  is not provided with a globe for covering the arc tube  110  (i.e. so-called globeless type). 
   As shown in  FIG. 2 , the holder  200  has: a holding resin member  210  with a cylindrical shape having a closed bottom, and includes a circumferential wall  220  and an end wall  230  that is formed at the edge of the circumferential wall  220 ; and a resin cover  250  shaped like a cone. An inner surface of the resin cover  250  at the side of its opening (top side in  FIG. 2 ) is fit to the outer surface of the circumferential wall  220  of the holding resin member  210 , thereby creating a space to store an electronic ballast  300 . 
   The electronic ballast  300  is made up of a plurality of electric parts that include an FET power transistor  330 , capacitors  310  and  340 , and a choke coil  320 , and adopts a series inverter method. A substrate  360 , to which these electric parts are to be mounted, is attached to the holding resin member  210 . In addition, a lower part of the resin cover  250  (opposite to where the holding resin member  210  is to be fit) is provided with a base  380  that is the same type as for the incandescent lamps. 
   (b) Arc Tube 
   As shown in  FIG. 3 , the arc tube  110  is in a double-spiral configuration and includes: a turning part  121  at which the glass tube  120  is bent in the substantial middle; and two spiral parts  122  and  123 , which are formed by winding the both sides from the turning part  121  to the both ends of the glass tube  120  around a spiral axis A and in the direction B. Note that the glass tube  120  is, for example, made of a soft glass (e.g. strontium-barium silicate glass). 
   For the most part, the spiral parts  122  and  123 , of the glass tube  120 , are wound around the spiral axis A, with an inclination angle of α with respect to the spiral axis A. However, the inclination angle changes from α to β that is smaller than α, in the vicinity of the ends of the glass tube  120  (More specifically, in a range of 90 degrees from an end of the glass tube  120  around the spiral axis A, in the direction opposite to the direction B). Hereinafter, this part of the glass tube  120  is referred to as “end-vicinity part”. 
   At each end of the glass tube  120 , an electrode  130  is sealed. The electrode  130  is made up of a filament coil  131  made of tungsten, and a pair of lead wires  133  and  134  that support the filament coil  131  by way of a so-called beads glass mounting method. Note that, the ends of the glass tube  120  to which electrodes  130  are to be sealed correspond to the ends of one discharge space formed inside the arc tube  110 . 
   Each filament coil  131  is filled with an electron emissive material whose main substance is such as BaO—CaO—SrO. 
   In addition, to one end of the glass tube  120  (in this example, the end-vicinity parts having the reference sign of  124 ), an exhaust tube  140  is fixed at the time of sealing the electrode  130 , the exhaust tube  140  being used for producing a vacuum within the glass tube  120 , and sealing such as mercury and a buffer gas that are detailed later. Note that the tip of the exhaust tube  140  is sealed such as in a cut-off method, after completing the evacuation of the glass tube  120  and the sealing of such as mercury and a buffer gas. 
   In the glass tube  120 , argon as a buffer gas is sealed at 400 Pa, besides about 5 mg of mercury. Note that a buffer gas may alternatively be a mixture gas of argon and neon. 
   In addition, a phosphor  150  is applied on the inner surface of the glass tube  120 . This phosphor  150  is produced by mixing three kinds of rare-earth phosphors respectively emitting red (Y 2 O 3 :Eu), green (LaPO 4 :Ce, Tb), and blue (BaMg 2 Al 16 O 27 :Eu, Mn). 
   (c) Holder 
   The holder  200  is made up of the holding resin member  210  and the resin cover  250  (refer to  FIG. 2 ), and for which a PET (polyethylene terephthalate; having softening point of about 260° C.) is used for example. This resin has excellent heat-resistant characteristic, as well as high ultraviolet-resistant characteristic. Note that the holding resin member  210  is the holder of the present invention. 
   The holding resin member  210  is, as shown in  FIGS. 5A and 5B , made up of an end wall  230  and a circumferential wall  220 . First, the end wall  230  is described. This end wall  230  has a pair of insertion openings  231  and  232 , through which the ends of the glass tube  120  are inserted inside the holding resin member  210  (inside the holder  200 ). As shown in  FIGS. 2 and 4 , the arc tube  110  is held by attaching the end-vicinity parts  124  and  125  having been inserted through the insertion openings  231  and  232 , to the inner surface of the holding resin member  210  via a silicone  390 . Note that, in  FIG. 4 , so as to reveal the area near the end-vicinity part  124  of the glass tube  120 , a silicone resin being attached thereto is not illustrated. In addition, the part of the arc tube  110  that appears outside the holding resin member  210  is not illustrated. 
   Here, when the glass tube  120  is inserted into the holding resin member  210 , a side into which the end of the glass tube  120  is to be inserted is referred to as “lower side” and the opposite side thereto is referred to as “upper side”. 
   As shown in  FIG. 5A , in the upper side of the insertion openings  231  and  232 , guides  233  and  234  are formed to facilitate fixing of the arc tube  110  to the holding resin member  210 . Because of this arrangement, when the arc tube  110  is rotated into the direction B, so that the rotation axis coincides with its own spiral axis A, while the end-vicinity parts  124  and  125  of the glass tube  120  are made abut against the guides  233  and  234 , then the ends of the glass tube  120  will be naturally guided in the insertion openings  231  and  232 . (Alternatively, for the purpose of fixing the arc tube  110 , the holding resin member  210  may be rotated, with the rotation axis corresponding to its axis, into the opposite direction to the direction B) 
   The guides  233  and  234  are formed to coincide with the form of a circumferential portion of the end-vicinity parts  124  and  125  of the glass tube  120 , the circumferential portion positioning at the side of the holding resin member  120 . Which is to say, suppose rotating the arc tube  110  so that the rotation axis coincides with its spiral axis A, while having the spiral axis A to substantially coincide with the axis of the holding resin member  210 , then the ends of the glass tube  120  will move along a predetermined orbit. The guides  233  and  234  have forms that coincide with this orbit that the ends of the glass tube  120  are in, and so become deeper as the insertion openings  231  and  232  are nearer. 
   On the other hand, in the lower side of the insertion openings  231  and  232 , the covers  235  and  236  are formed in the form of an arc that coincides with the form of the end-vicinity parts  124  and  125  (form of circle) of the arc tube  110 , so as to be able to cover these end-vicinity parts  124  and  125 . 
   Next, the circumferential wall  220  of the holding resin member  210  is described. The circumferential wall  220  is, as shown in  FIG. 2  and  FIG. 5B , provided with: a pair of supporting members  221  and  222  for supporting the substrate  360  to which the electronic ballast  300  is mounted, from the side of the end wall  230 ; and a pair of substrate-latching members  223  and  224  to be engaged with the surface of the substrate  360  where the base  380  is (the substrate  360  is not shown in  FIGS. 5A and 5B ). 
   Next, the resin cover  250  is described. The resin cover  250  is in a cone shape as shown in  FIG. 2 , and one end thereof that opens wider (hereinafter simply referred to as “end with larger diameter”) than the other end is fit to the outer surface of the circumferential wall  220  of the holding resin member  210 . To the other end of the resin cover  250  that opens narrower (hereinafter simply “end with smaller diameter”), the base  380  is attached. 
   Fixing of the resin cover  250  to the holding resin member  210  is performed by coupling the cover-coupling members  225  and  226 , formed at the circumferential wall  220  of the holding resin member  210 , with the protrusion (unshown in the drawings) formed on the inner surface of the resin cover  250 . 
   Even after the resin cover  250  has been fixed to the holding resin member  210 , there is a clearance between the inner surface nearer the end with larger diameter of the resin cover  250 , and the outer surface of the circumferential wall  220  of the holding resin member  210 . A heat-insulation layer of this invention is formed in this clearance. 
   Note that so as to substantially coincide the axis of the resin cover  250  with the axis of the holding resin member  210 , a plurality of protrusions  227  (three or more) for locating purpose are formed on the outer surface of the circumferential wall  220 , with interval in the circumferential direction (refer to  FIGS. 4 and 5 ). 
   Inside the holder  200 , which is comprised of the holding resin member  210  and the resin cover  250  described above, a metal plate  240  is provided at an area in which the filament coils  131  are included, as shown in  FIGS. 2 and 4 . Note that each of  FIGS. 3 , and  4  illustrates only one filament coil for explanation purpose. However, the number of “filament coils  131 ” is two in the embodiment. This metal plate  240 , as shown in  FIG. 5B , is comprised of a rear-surface parts  241  and  242  to be provided at the rear surface of the end wall  230 , and side-surface parts  243  and  244  to be provided at the inner surface of the circumferential wall  220 , so as to coincide with each location of the pair of electrodes  130 . 
   The metal plate  240  is provided to make allowance for at least variations in position of the filament coils  131 , as well as to assuredly transmit the heat generated by the filament coils  131  from the glass tube  120  to the metal plate  240 . The amount of the ends of the glass tube  120  inserted inside the holding resin member  210  is determined by the length of the arc tube  110  that should appear external to the holding resin member  210  that holds it (i.e. the distance from the ends of the turning part  121  of the arc tube  110  up to the surface of the end wall  230  of the holding resin member  210 ), and not determined by the position of the filament coils  131 . Accordingly, it is quite possible to cause variations in position of the filament coils  131  within the glass tube  120 . 
   The metal plate  240  has a structure in which parts thereof that respectively correspond to the ends of the glass tube  120  (each of the “parts” being a heat-dissipating member of the present invention) are connected together by a connecting part  245 . The connecting part  245  is provided with a locating hole  246  at the substantial center thereof, the locating hole  246  being to which a locating protrusion  237  is to be fit. The locating protrusion  237  is provided at the substantial center of the end wall  230  of the holding resin member  210 . This arrangement enables to perform fixing of the metal plate  240  to the holding resin member  210 , as well as locating thereof, easily and efficiently. 
   2. Concrete Structure 
   The compact self-ballasted florescent lamp  100 , in the present embodiment, is of 12 w type that corresponds to the incandescent lamp of 60 W type, and E17 is used for its base  380 . 
   The following explains the sizes of the arc tube  110 , with use of  FIG. 3 . The arc tube  110  has 4.5 turns, which is a total number for both of the spiral parts  122  and  123 , so as to be in accordance with the luminous flux of when the incandescent lamp emits light. 
   The outer diameter Da of the arc tube  110  (i.e. outermost diameter of the spiral parts of the glass tube) is 36 mm. The tube-inner diameter φi of the glass tube  120  is 7.4 mm, and the tube-outer diameter φo of the glass tube  120  is 9 mm. Preferably, the outer diameter Da of the arc tube  110  should be in the range of 30 mm to 40 mm, inclusive, so as to have the equal size as the incandescent lamp. 
   In addition, the tube-outer diameter φo of the glass tube  120  should preferably be smaller than 10 mm. This is because if the tube-outer diameter φo becomes 10 mm or above, the flexural rigidity of the glass tube  120  will be large. This makes it difficult to form outer diameter Da of the arc tube  110  to be small such as about 36 mm. 
   Furthermore, between the part of the glass tube  120  from the turning part  121  and before the end-vicinity parts  124  and  125 , a pitch P 2   t  is 20 mm, the pitch P 2   t  being either between two adjacent spiral parts  122  or between two adjacent spiral parts  123 , in a direction parallel to the spiral axis A (i.e. vertical direction in  FIG. 3 ). In addition, a pitch P 1   t  is 10 mm, the pitch P 1   t  being between any two adjacent spiral parts  122  and  123 , in the direction parallel to the spiral axis A. This means that a minimum clearance formed between the glass tubes  120  that are adjacent to each other in a direction parallel to the spiral axis A is about 1 mm. This clearance is preferably 3 mm or below. This is because, if this clearance becomes larger than 3 mm, the length of the arc tube  110  will become large, and in addition the adjacent portions of the glass tube  120  will be far from each other, leading to inconsistencies in luminance. 
   Note that the distance between the filament coils  131  within the arc tube  110  is 400 mm, and the length of the arc tube  110  (i.e. distance from the tip of the glass tube  120  which is at the turning part  121 , to the sealing part at the ends of the glass tube  120 , in the direction parallel to the spiral axis A) is 60.0 mm. 
   The sizes of the holding resin member  210  are as follows. The inner diameter of the circumferential wall  220  is 38 mm, the outer diameter of the circumferential wall  220  is 42.7 mm, and the height of the circumferential wall  220  is about 15 mm. On the other hand, the inner diameter of the resin cover  250  that is to be fit to the outer surface of the circumferential wall  220  of the holding resin member  210  is 44.4 mm. Accordingly, the heat-insulation layer  255  formed between the holding resin member  210  and the resin cover  250  will be 0.85 mm. 
   On the other hand, as  FIG. 6  shows, the metal plate  240  is provided so that the centers of the side-surface parts  243  and  244 , in circumferential direction, coincide with the position P 1  at which the filament coils  131  are to be placed. 
   The circumferential size for the side-surface parts  243  and  244  corresponds to the range of ±40 degrees from the position P 1  around the axis O of the holding resin member  210  (the range shown by the reference number A 2  in the drawing). The aforementioned structure applies to both sides of the insertion opening  231  and  232 . In addition, the height of the side-surface parts  243  and  244  is 9 mm (i.e. the height being in the direction parallel to the spiral axis A). 
   The position P 1  at which one filament coil  131  is to be placed is located at 50 degrees from the insertion opening  231  (or from the insertion opening  232 ) around the axis O of the holding resin member  210 , in the direction that the ends of the glass tube  120  are inserted (reference number A 3  in the drawing). 
   This position P 1  is an average taken in the actual tests for fixing the arc tube  110  to the holding resin member  210 . In the tests, filament coils  131  within the glass tube  120  positioned in the range between ±15 degrees (reference number Al in the drawing) from the position P 1  around the axis O of the holding resin member  210 . 
   On the other hand, the connecting part  245  and the rear-surface parts  241  and  242 , taken altogether, constitute a band-like structure (represented in hatch pattern in  FIG. 6 ), whose width L is about 9 mm. The shapes of the rear-surface parts  241  and  242  coincide with the shape of the inner surface of the end wall  230  (including the concave part of the covers  235  and  236 ). As a matter of course, the parts that correspond to the insertion openings  231  and  232  are cut away. 
   The compact self-ballasted fluorescent lamp  100  has the maximum lamp diameter D of 40 mm and the length L of 97 mm, which is smaller than incandescent lamps having maximum lamp diameter of 60 mm and length of 100 mm. The lamp characteristics of this compact self-ballasted fluorescent lamp  100  are that the average luminous flux of 810 lm at the lamp input of 12 W, and the average lamp efficiency of 67.51 m/W. 
   3. Fixing of Arc Tube 
   The following explains, in the compact self-ballasted fluorescent lamp  100  having the aforementioned structure, how the metal plate  240  is incorporated into the holding resin member  210 , and how the arc tube  110  is fixed to the holding resin member  210  into which the metal plate  240  has been incorporated. Note here that the production method of the arc tube  110 , such operations as fixing of the electronic ballast  300  and the base  380  after the arc tube  110  has been fixed to the holding resin member  210 , and so on, are the same as those of the conventional technology, therefore are not described here. 
   (a) Incorporation of Metal Plate to Holding Resin Member 
   First, the metal plate  240  is prepared. The metal plate  240  is produced for example by press-forming an aluminum plate. Then, as  FIG. 7  shows, thus produced metal plate  240  is, for placement, inserted from the opening of the holding resin member  210  to the inside, while the rear-surface parts  241  and  242  of the metal plate  240  are kept abut against the rear surface of the end wall  230 . 
   In this operation, it should be made sure that the locating hole  246  at the center of the metal plate  240  is engaged in the locating protrusion  237  at the end wall  230  of the holding resin member  210 , as well as that edges of the respective side-surface parts  243  and  244  are abutted against the restricting protrusions  228  of the holding resin member  210 , the edges being situated in the direction into which the arc tube  110  is inserted. The metal plate  240  is thereby placed at a predetermined position within the holding resin member  210  ( FIG. 7B ) 
   (b) Fixing of Arc Tube to Holding Resin Member 
   The following explains fixing of the arc tube  110  to the holding resin member  210  in which the aforementioned metal plate  240  has been incorporated. Note that the part of the arc tube  110  that appears outside the holding resin member  210  is not described in  FIG. 7C . 
   First, the ends of the glass tube  120  are inserted through the insertion openings  231  and  232 , while keeping the holding resin member  210  upright position with its opening on top. 
   More specifically, guides  233  and  234  are formed in the upper side of the respective insertion openings  231  and  232  of the holding resin member  210 , so as to guide the ends of the glass tube  120 . Therefore, if the end-vicinity parts  124  and  125  are made abut against the guides  233  and  234 , and the glass tube  120  is rotated so that the rotation axis coincides with the spiral axis A, the ends of the glass tube  120  can enter into the holding resin member  210  through the insertion openings  231  and  232 . Needless to say, it is alternatively possible to rotate the holding resin member  210  around itself, with the glass tube  120  in fixed state. 
   Next, the arc tube  110  is rotated around the spiral axis A to adjust the position thereof, so that the portion of the arc tube exposed outside of the holding resin member  210  has a predetermined length. After the location of the arc tube  110  has been determined, a silicone resin  390  is provided to cover an area corresponding to the end-vicinity parts  124  and  125 , including the ends of the glass tube  120 . Then, the provided silicone resin  390  is hardened. The fixing of the ends of the glass tube  120  as well as the end-vicinity parts  124  and  125 , to the holding resin member  210  are thereby complete. 
   Note here that, when the end-vicinity parts  124  and  125  of the glass tube  120  is fixed by means of the silicone resin  390 , it is made sure that the metal plate  240  be also fixed to the holding resin member  210 . By doing so, fixing for both of the metal plate  240  and the glass tube  120  is enabled by only one operation of providing the silicone resin  390  for the end-vicinity parts  124  and  125  of the glass tube  120 . 
   Note that, in the above description, the silicone resin  390  is provided to cover the end-vicinity parts  124  and  125  including the ends of the glass tube  120 , and the metal plate  240 . However, it is not always necessary to entirely cover the end-vicinity parts  124  and  125  including the ends of the glass tube  120 , and the metal plate  240 , as long as the end-vicinity parts  124  and  125  of the glass tube  120 , and the metal plate  240  are fixed inside the holding resin member  210 . 
   Meanwhile, restricting protrusions  228  are provided inside the holding resin member  210 , so as to be abutted against the respective ends of the side-surface parts  243  and  244 , the ends positioning in the insertion direction of the glass tube  120 . When inserting of the glass tube  120  from the insertion openings  231  and  232  to inside of the holding resin member  210 , these restricting protrusions  228  prevent the metal plate  240  from moving in the insertion direction of the glass tube  120 . Therefore, even if not being attached to the holding resin member  210 , the metal plate  240  will not be misaligned in the insertion direction. 
   It should be noted here that in the present embodiment, the metal plate  240  is not attached to the inside of the holding resin member  210 . Alternatively, however, before the metal plate  240  is fixed to the holding resin member  210 , it is also possible to apply adhesives to the inner surface of the end wall  230  of the holding resin member  210 , or to the rear-surface parts  241  and  242  of the metal plate  240 . The above arrangement enables the metal plate  240  and the holding resin member  210  attached to each other, after the fixing. 
   4. Life Test 
   Next, a life test has been performed for the compact self-ballasted fluorescent lamp  100  structured as above. The lighting conditions are the same as those explained in the “problem to be solved by the invention” section, and the test has been performed by lighting the compact self-ballasted fluorescent lamp  100  in downward illumination and in lateral illumination. 
   As a result of the life test for the compact self-ballasted fluorescent lamp  100 , the test life thereof was 10,000 hours. Note here that the test life is a smaller one of the total lighting hours until the lamp ceases to illuminate, and the total lighting hours until the total luminous flux lowers down to 60% of the initial luminous flux (i.e. luminous flux of when 100 hours has passed after the starting of lighting). Hereinafter, the compact self-ballasted fluorescent lamp  100  of the present invention is also referred to as “invention product”, and a conventional type of compact self-ballasted fluorescent lamps without the metal plate and so on, is called “conventional product”. 
   In the life test directed to the invention product, no local deformation was observed either in the holding resin member  210  or in the resin cover  250  after finishing of the life, regardless of the posture of the lamp in lighting (i.e. whether in downward illumination or in lateral illumination). Note that at the time of finishing of the life, the protection circuit of the electronic ballast  300  worked to stop the discharge (specifically, causing breakdown of the FET power transistor  330  for lighting the arc tube  110 ). 
   There are two possible reasons why the holder  200  of the invention product did not have any local deformation. First, the metal plate  240  provided inside the holding resin member  210  is considered to have worked to prevent the heat generated from the filament coils  131  from being directly transmitted to the holding resin member  210 . 
   Secondly, the heat generated from the filament coils  131  is transmitted to the silicone resin  390  provided for fixing the glass tube  120 , and then from this silicone resin  390  to the metal plate  240 . During this process, the heat transmitted to the metal plate  240  is considered to spread over the entire metal plate  240 , and then dissipated, as well as being dispersed inside the holding resin member  210 . Here, since the amount of heat transmitted to the holding resin member  210  is small, the amount of heat transmitted to the resin cover  250  from the holding resin member  210  is accordingly small, too. 
   As a result, in the life test where the conventional product was lit in downward illumination with the filament coils positioning on top, the filament coils generated extraordinary heat, thereby deforming not only the inner surface of the holding resin member  925 , but also the resin cover  923  (refer to  FIG. 1 ). However, in the invention product, even when it resulted in the same condition, the resin cover  250  was saved from deformation. 
   Furthermore, since the invention product has the heat-insulation layer  255  between the resin cover  250  and the holding resin member  210 , the heat hot enough to deform the resin cover  250  will never be transmitted to the resin cover  250 . 
   Still further, the area in which the metal plate  240  is provided corresponds to the range of ±40 degrees, around the axis O of the holding resin member  210 , from the position where each filament coil  131  is expected to be provided. This range of area takes into consideration the positional variation of the filament coils  131  that is incident to assembly process of the arc tube  110 , and so the heat from the filament coils  131  will be prevented from being directly transmitted to the holding resin member  210 . 
   &lt;Modification Example&gt; 
   So far, the present invention has been described by way of the embodiment. However, needless to say, the present invention should not be limited to the concrete example stated above as the embodiment, and may include the following modification examples. 
   1. Compact Self-Ballasted Fluorescent Lamp 
   In the above-described embodiment, the explanation is based on the premise that the compact self-ballasted fluorescent lamp is used with no globe (i.e. an outer bulb) for covering the arc tube. However, needless to say, the present invention is also applicable to the compact self-ballasted fluorescent lamp equipped with a globe. As follows, such a compact self-ballasted fluorescent lamp equipped with a globe is explained with use of  FIG. 8 . 
   As shown in this drawing, a compact self-ballasted fluorescent lamp  401  is provided with an arc tube  410  in a double-spiral configuration, and a holder  420  to hold the arc tube  410 . In addition, a globe  430  for covering the arc tube  410  is provided for this compact self-ballasted fluorescent lamp  401 . 
   The holder  420  stores therein an electronic ballast  440  for lighting the arc tube  410 . In addition, to one end the holder  420  which is on the opposite side to the side by which the arc tube  410  is to be held, a base  450  is attached. The holder  420  is constituted by the holding resin member  421  and a resin cover  422 , just as in the embodiment. 
   Inside the holding resin member  421 , a metal plate  425  is provided at an area that includes where the filament coils are provided within the ends of the glass tube  411  constituting the arc tube  410 , just as in the embodiment. Note that the material and the size of the metal plate  425 , or the position and the range in which the metal plate  425  is to be placed, are determined according to the position at which the filament coils are to position inside the holding resin member. 
   The globe  430  is, just as the incandescent lamp, is made of glass material having excellent decorative characteristics, and is shaped like an eggplant (so called A-type). Note here that the shape of the globe  430  is A-type, but is not limited to such. 
   The rim of the opening of the globe  430  is inserted and attached between the circumferential wall of the holding resin member  421  and the resin cover  422  that is fit to and covers the outer surface of the holding resin member  421 . The attaching of the globe  430  is performed with use of an adhesive filled between the holding resin member  421  and the resin cover  422 . Note that in the aforementioned embodiment, the heat-insulation layer  255  is formed between the holding resin member  210  and the resin cover  250 . However in this modification example, the globe  430  functions as the heat-insulation layer  255  of the embodiment. 
   In addition, it is preferable that the adhesive used for attaching the globe  430  has excellent heat-resistance. This is for transmitting heat generated around filament coils, from the holding resin member  421  to the globe  430 , in a case when the filament coils generate extraordinary heat at the end of life of the compact self-ballasted fluorescent lamp  401 . Note that the size of a gap between the outer surface of the holding resin member  421  and the inner surface of the resin cover  422 , in this compact self-ballasted fluorescent lamp  401 , is set as 2.1 mm. 
   Next, the result of the life test conducted for the above-described compact self-ballasted fluorescent lamp  401  equipped with a globe is explained. The test has been conducted both in downward illumination and in lateral illumination. As a result, no deformation due to heat was observed in the holder  420 . 
   The reason for this result is considered as follows. The heat in the glass tube  411  at the end-vicinity parts  414  and  415  is transmitted to the metal plate  425 . The metal plate  425  disperses this heat for dissipation, thereby transmitting the dispersed heat to the holding resin member  421 . Therefore, not so much heat will be transmitted to the holding resin member  421 , and so, naturally, there is reduced amount of heat transmitted to the globe  430  from the holding resin member  421 . Note that the heat transmitted to the globe  430  is dispersed in the entire globe  430  then is dissipated. 
   2. Heat-Dissipating Plate 
   (a) Provision of Metal Plate 
   In the embodiment, the metal plate and the holding resin member are produced separately, and after this, the metal plate is provided inside the holding resin member. However, it is also possible to produce the metal plate and the holding resin member together, at the same time. For such a production, so called insert molding method may be used, in which the metal plate is pre-set in a mold before the holding resin member is produced in the mold, for example. 
   (b) Structure of Heat-Dissipating Member 
   In the present embodiment, the two heat-dissipating members are connected by a connecting member (“connecting part” in the embodiment) into one piece, and this piece is made of one metal plate. Alternatively, however, the heat-dissipating members may be two different bodies, without being connected to each other. In this case, the number of heat-dissipating members in the invention is two. 
   In the embodiment, a metal plate of the embodiment has a structure in which the side-surface parts and the rear-surface parts are formed as one piece. However, the side-surface parts may be a separate body from the rear-surface parts, for example. In such a case, the number of heat-dissipating members in the present invention is three (i.e. a member formed by the connecting part  245  connecting the rear-surface parts  241  and  242  of the present embodiment, and two members that are two side-surface parts  243  and  244 ). So as to provide such three separate heat-dissipating members in the holding resin member, one method is to first provide the heat-dissipating member made up of rear-surface parts, for the end wall of the holding resin member, then to insert the ends of the glass tube. While this state being kept, each of the heat-dissipating members respectively made of one side-surface part can be placed at a corresponding inner surface of the circumferential wall of the holding resin member. After this, all the three heat-dissipating members can be attached to the glass tube by means of a silicone resin. Alternatively, furthermore, all the rear-surface parts and the side-surface parts, of the embodiment, may be four separate bodies, thereby endowing the invention with four heat-dissipating members in total. 
   Furthermore, in the embodiment, the metal plate is provided to be abutted against the inner surface of the holder. However, it is not always necessary to make the metal plate abut against the inner surface of the holder. Which is to say, if the heat-dissipating plate is provided at a position between the inner surface of the holder and outer surface of the glass tube where it corresponds to the position of the filament coils, then the heat from the filament coils will be transmitted to the heat-dissipating plate, thereby reducing the amount of heat to be transmitted to the holder. 
   With this in view, a metal plate may alternatively be shaped as a tube, so as to elongate along the outer surface of the glass tube and to cover the end-vicinity parts of the glass tube, for example. Note that the tube-shaped metal plate may be fixed, at the same time when the end-vicinity parts of the glass tube are fixed within the holder by means of a silicone resin. 
   3. Holder 
   The holder, described in the aforementioned embodiment, is constituted by: a holding resin member with a cylindrical shape having a closed bottom; and a resin cover, and has a structure in which the rein cover is fit to the circumferential wall of the holding resin member. However, the holder is not limited to such a structure, and may be structured such as in the following examples. 
   One example has a structure in which the holding resin member is shaped like a disk, and the rim of the holding resin member is fixed to the inner surface of the resin cover. In this case too, the same method can be taken as described in the embodiment. That is, the metal plate is provided for the holding resin member, and the ends of the glass tube are inserted from the respective insertion openings. Then, while the described states are kept, the holding resin member, the metal plate, and the ends of the glass tube are fixed by means of a silicone resin, and then a resin cover is assembled therewith. 
   In another example, the holder is constituted by: a holding resin member with a cylindrical shape having a closed bottom; and a resin cover, just as in the embodiment. However, the structure is such as to fit the outer surface of the resin cover to the inner surface of the circumferential wall of the holding resin member. If this structure is adopted, it is necessary to provide the side-surface parts of the heat-dissipating plate inside the resin cover. 
   4. Heat-Insulation Layer 
   In the embodiment, the heat-insulation layer is an air layer realized by using the gap created between the holding resin member and the resin cover. However, for example, it is also possible to place a metal plate between the holding resin member and the resin cover, to produce the same effect as the embodiment. Note that the heat-insulation layer using the metal plate can insulate heat from the holding resin member more efficiently, compared to the heat-insulation layer using the air, and so can prevent the resin cover from deformed due to heat, to a greater extent. 
   In addition, if a metal plate is used as the heat-insulation layer, the thickness thereof is preferably in a range of 0.4 mm to 0.9 mm, inclusive. This is because if the thickness of the metal plate is thinner than 0.4 mm, enough heat-insulation effect is not obtained. Conversely, if the thickness thereof becomes thicker than 0.9 mm, although this case will achieve high heat-insulation characteristic, the diameter of the resin cover becomes too large, or that the rigidity of the metal plate becomes high, thereby sacrificing the workability of providing the metal plate, or the cost of the metal plate. 
   5. Fluorescent Lamp 
   The aforementioned embodiment describes a case when the present invention is applied to a compact self-ballasted fluorescent lamp. However, the present invention is also applicable to a fluorescent lamp as  FIG. 9  shows, for example. 
   This fluorescent lamp  501  includes: an arc tube  510  whose glass tube  510  is spirally wound from the turning part to the both ends to have a double-spiral configuration; a holder  520  that holds this arc tube  510  (both end-vicinity parts of the glass tube  511 ); and a single base  550  (e.g. GX10q-type) that can receive electricity by being fit to a socket which is an illuminating device. This fluorescent lamp  501  is different from the aforementioned compact self-ballasted fluorescent lamp  100 , in that the holder  520  does not store therein an electronic ballast, and that the base  550  is shaped differently from a screw type used for the incandescent lamp. 
   The holder  520  has the same structure as that of the aforementioned embodiment, and is constituted by a holding resin member  521  and a resin cover  522 . Inside the holding resin member  521 , a metal plate  525  is provided at a position corresponding to where the filament coils are placed in the glass tube  511 . Note that the material and the size of the metal plate  525 , or the position and the range in which the metal plate  525  is to be placed, are determined so as to take into allowance the range of positional variation of the filament coils in the glass tube  511 , the positional variation being incident to fixing of the arc tube  510  to the holder  520 . 
   In addition, between the holding resin member  521  and the resin cover  522 , a heat-insulation layer  526  is formed, just as in the embodiment. This heat-insulation layer  526  is provided at a position corresponding to where the filament coils are, within the arc tube  510  that has been incorporated in the holder  520 . 
   As already described in the related art section, in the life test directed to the fluorescent lamp  501 , too, the electron emissive material filled in the filament coils is used up, thereby causing the filament coils to generate extraordinary heat. 
   As such, even if the filament coils generate extraordinary heat, the holder  520  will be prevented from being deformed due to heat, because of the structure of having the metal plate  525  on the inner surface of the holding resin member  521  that constitutes the holder  520 , and of having the heat-insulation layer  526  between the holding resin member  521  and the resin cover  522 . Note that the discharge lamp described here is just one example to which the present invention is applied. Needless to say, the present invention is not limited to what is described in  FIG. 9 , as far as the number of turns for the spiral parts, the outer diameter of the glass tube, the annular outer diameter and the length of the arc tube, and the form of the single base. 
   That is, the fluorescent lamp of the present example is characterized by having: an arc tube made of a glass tube whose at least one part is bent, ends of the glass tube being respectively provided with an electrode equipped with a filament coil, the filament coil being applied with an electron emissive material; and a holder that is provided with insertion openings and holds the ends of glass tube in a state that the ends are inserted through the respective insertion openings, where the ends of the glass tube are inserted until the filament coils reach inside the holder, and a metal plate is provided between the inner surface of the holder and the parts of the glass tube that correspond to where the filament coils are positioned in the glass tube. 
   6. Form of Arc Tube 
   Both of the embodiment and the modification examples use an arc tube in a double-spiral configuration. However, an arc tube having other forms may alternatively be used. For example, it is also possible to use an arc tube in single-spiral configuration having only one spiral part, where its glass tube is bent at the substantial middle to form a turning part, and is wound from the turning part to one end. In this case, the heat-dissipating plate may be provided around the end at the spiral part side. 
   Furthermore, it is also possible to constitute an arc tube by a combination of three or four glass tubes respectively in U-shape. Even if the arc tube is constituted by a combination of three or four glass tubes as above, only one discharge space will be formed in the combined glass tubes on the whole. Therefore the whole of the combined glass tubes is referred to as “one glass tube”, and electrodes will be sealed in the ends of this glass tube. Note that in a case where the filament coils of the glass tube are positioned outside the holder, the problem of the present invention cannot arise. However, the present invention is still applicable to such a glass tube, in a case where, for some reason, the filament coils of the glass tube are positioned inside the holding resin member. 
   Although the present invention has been fully described byway of examples with references to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention, they should be construed as being included therein.