JP2010129375A - Short-arc electrode for discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a short-arc electrode having high heat dissipation characetristics and being lightweight. <P>SOLUTION: Since emission of heat becomes active in a high-temperature portion among anodes, it is effective for heat emission to enlarge the surface area at the place which is near the front face. Since an anode 1 is exposed via the rear end face 9 of its first body and the side wall 10 of the periphery thereof, it functions as a heat-dissipating face. Such a site is relatively near to the front face 16. When it is compared with conventional electrodes, since a heat-dissipating region in a high-temperature region can be enlarged as a whole, the amount of heat dissipated can be enlarged. Furthermore, the electrode can also be made lightweight by a portion corresponding to the weight of a hole 7. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an electrode structure of a short arc type discharge lamp, and more particularly to improvement of heat dissipation.

  Conventionally, it has been known to increase the capacity of the anode as a heat dissipation measure in the anode. However, when the capacity of the anode is increased, the amount of tungsten, which is a high melting point material, increases, and the anode becomes heavy. As a result, there is a problem that the quartz glass portion supporting the lead rod is broken or the lead rod supporting the anode is broken during transportation.

  Patent Document 1 discloses an anode in which a metal porous layer made of a mixture of tungsten and tantalum is formed on the surface of the anode. By providing such a metal porous material, the heat dissipation effect can be enhanced.

  Patent Document 2 discloses an anode in which fine fins are provided on the outer peripheral surface to increase the anode surface area and increase the radiation efficiency from the anode.

JP-A-2-256150

Japanese Patent Laid-Open No. 2002-117806

  In both Patent Documents 1 and 2, the heat dissipation effect can be enhanced by increasing the surface area of the anode, but sufficient heat dissipation cannot be performed. Furthermore, there is a limit to reducing the weight of the anode.

  An object of the present invention is to provide a short arc type electrode that is lightweight and has high heat dissipation.

  1) The short arc type discharge lamp electrode according to the present invention has a core rod bottomed hole for holding the core rod in the central portion of the rear end surface, and the central portion of the rear end surface is in the direction of the distal end. A large-diameter bottomed hole having a diameter larger than that of the core rod bottomed hole is formed, and the bottom of the large-diameter bottomed hole is provided with the core rod bottomed hole. The bottom surface of the large-diameter bottomed hole functions as a heat radiating surface. Therefore, the heat radiation area in the high temperature region can be increased, and the heat radiation amount as a whole can be increased.

  This claim corresponds to the following first to fifth embodiments.

  2) An electrode for a short arc type discharge lamp according to the present invention includes 1) a first main body near the tip, and 2) a holding hole for holding a core rod formed in the first main body. A second main body portion is formed at the rear end portion of the first main body portion so that the rear end surface of the first main body portion is exposed as a heat dissipation surface. Therefore, the heat radiation area in the high temperature region can be increased, and the heat radiation amount as a whole can be increased.

  This claim corresponds to the following first to eighth embodiments.

  3) In the short arc type discharge lamp electrode according to the present invention, a through hole larger than the diameter of the core rod is provided in the second main body portion, and the first main body portion is formed by the through hole. The rear end surface is exposed as a heat dissipation surface. Therefore, the heat radiation area in the high temperature region can be increased, and the heat radiation amount as a whole can be increased.

  4) In the electrode for a short arc type discharge lamp according to the present invention, the second main body portion is entirely or partially made of ceramics. Therefore, the second main body can be made of a material with higher heat dissipation.

  5) An electrode for a short arc type discharge lamp according to the present invention includes 1) a first body portion in the vicinity of the tip portion, and 2) a holding hole for holding a core rod formed in the first body portion, A second body portion is provided on the rear end surface of the first body portion so that an exposed portion cavity that is spatially connected to the outside is formed at a position facing the tip surface of the first body portion. Yes. Therefore, the heat radiation area in the high temperature region can be increased, and the heat radiation amount as a whole can be increased.

  This claim corresponds to the following first to eighth embodiments.

1. (First embodiment)
FIG. 1 shows a cross-sectional view of an anode 1 that is an electrode for a short arc type discharge lamp according to the present invention. As shown in FIG. 1, the anode 1 has a first main body 2 near the tip and a cylindrical second main body 3. In the present embodiment, by forming a hole 7 having a diameter α from the rear end surface of a normal electrode, the first main body portion rear end surface 9 is exposed as a heat dissipation surface, and the cylindrical second main body portion 3 is It is formed in contact with the rear end surface of the first main body 2. A holding hole 11 for holding the core rod is formed in the first main body portion rear end surface 9.

  The 1st main-body part 2 is comprised with the alloy which has a refractory metal or a refractory metal as a main component. In the present embodiment, pure tungsten having a purity of 99.9% or more is employed. Note that when tungsten is used, doped tungsten containing a small amount of thorium or the like may be used. Further, other refractory metals having a melting point of 3000 (K) or more can be employed. In the present embodiment, since the temperature of the electrode tip can be lowered, molybdenum or the like can be used when the power is not so high.

  FIG. 2 shows a state where the core rod 5 is press-fitted into the holding hole 11 of the anode 1. The anode 1 of the short arc type discharge lamp is supplied with an electron flow almost carrying current from a cathode (not shown) and an arc jet flow generated during discharge enters. This electron stream enters a narrow region of the anode front face 16 and releases energy, and the arc jet stream forms a stagnation point on the front face of the anode 1 to release a part of the energy and then moves along the side surface of the anode 1. Flowing. In any case, large energy is injected into the anode 1.

  The front surface of the anode 1 has a high temperature of nearly 3000 K or more depending on the energy injected. As a result, the metal on the front surface is evaporated and melted and worn out. The energy injected into the anode 1 is diffused by heat conduction and released from the surface of the anode 1 by heat radiation. The temperature of the anode 1 is determined in a balanced state between incident energy and thermal radiation energy.

The thermal radiation Q is given by the following equation of Stefan Boltzmann.

Q = 5.67 * (T / 100) ⁴ * εS [W / m2]... Formula (1)
Here, S is the surface area, and ε is the emissivity.

  The emissivity ε increases as the temperature increases in a general metal, and the εW of tansten is about T / 10000. When this is substituted, in the case of tungsten, the thermal radiation Q is proportional to the fifth power of the temperature. That is, since heat radiation becomes active at high temperatures, it is effective for heat radiation to increase the surface area near the anode front surface, which is a high temperature region.

  In the present invention, the rear end surface 9 of the first main body portion and the side wall 10 therearound are exposed and function as a heat radiating surface. Such a portion is relatively close to the front surface 16. Therefore, compared with the conventional electrode, the heat radiation area in the high temperature region can be increased, so that the heat radiation amount as a whole can be increased. Further, the electrode can be reduced in weight by the amount of the hole 7. Therefore, the electrode can be supported by the core rod 5 even if the depth of the holding hole 11 formed in the first main body portion rear end surface 9 is shallower than the conventional depth. Further, the heat of the first main body 2 can be efficiently transmitted to the second main body 3 and radiated by the second main body 3.

2. 2nd Embodiment In 1st Embodiment, although the 1st main-body part 2 and the 2nd main-body part 3 were comprised by the integrated object, as shown in FIG. 3, the 1st member 22 and the 2nd member 23 are separate. It may be configured to be joined. Manufacturing is easy with the same material. In addition, the second main body portion 23 can be made of cheaper molybdenum or the like. This is because the temperature of the second main body 23 is lower than that of the first main body 22.

  As shown in FIG. 3, the second main body 23 has a tapered hollow cylindrical shape with an outer diameter decreasing toward the rear end (d1> d2). In the present embodiment, the taper angle is 5 °, but may be about 0 ° to 15 °. Thus, the core 35 is on the central axis of the anode 21, and the center of the current flowing through the core 35 approximately flows on the central axis of the electrode 21, so that the generated magnetic field and magnetic field lines are shown in FIG. Is axisymmetric. The inventor speculates that if the magnetic and magnetic field lines are always axisymmetric, it is advantageous for the arcjet plasma flow to flow stably along the anode.

  In FIG. 3, you may comprise the 2nd main-body part 23 with ceramics. For example, aluminum nitride (AlN) may be employed. Since such a material has higher thermal conductivity and thermal emissivity when the lamp is lit than tungsten, the heat dissipation effect in the second main body portion 23 can be enhanced. In addition, since the thermal expansion coefficient is close to that of tungsten, it can be prevented from cracking when bonded.

Other nitride-based ceramics may be used, or a carbide-based ceramic such as silicon carbide (SiC) may be used. Other materials include aluminum nitride (AlN) having a thermal conductivity of 170 W / mK or higher, a thermal emissivity of 0.50 or higher, and a thermal expansion coefficient of 4.0 * 10 ^{−5 to} 5.0 * 10 ⁻⁶ , or silicon carbide having the same characteristics ( SiC) is preferred. In particular, aluminum nitride having a thermal conductivity of 170 to 200 W / mK, a thermal emissivity of 0.80 to 0.95, a thermal expansion coefficient of 4.5 × 10 ⁻⁶ / degrees Celsius, and a density of 3.320 kg / m ³ is suitable.

  Further, the second main body portion 23 may be divided into two or more members in the axial direction, and a portion close to the first main body portion 22 may be formed of a metal cylinder, and the other portions may be formed of a ceramic cylinder.

3. Third Embodiment FIG. 4 shows another embodiment. The anode 40 shown in FIG. 4A is provided with a groove 41 on the side surface of the first main body 42 in the circumferential direction. Thus, by providing a groove as if it is thinned, the surface area can be increased in the region where the tip temperature is high, and the amount of heat radiation can be increased.

  FIG. 4B shows the anode 50 in which holes 51 to 58 are provided in the radial direction instead of the groove 41. Thus, by providing a recess such as a groove or a hole in a region near the tip of the anode, the recess formed by the deletion can function as a heat dissipation surface.

4). Fourth Embodiment FIG. 5 shows another embodiment. The anode 60 shown in FIG. 5A has a plurality of bottomed holes 61 formed in the rear end surface 9 of the first main body portion. Thereby, a wider heat radiating surface can be arranged in a region close to a region where the tip temperature is high. In addition, it is good also as a groove shape by providing the hole with a bottom in FIG. 5A continuously.

5). Fifth Embodiment FIG. 5B shows an anode 70 in which a plurality of heat radiating windows 73 are provided in the second main body 3. The heat radiating window 73 can further increase the heat radiating area, and more easily release the heat in the space 7. In addition, about the shape of the thermal radiation window 73, it is arbitrary.

  FIG. 5C shows a modified embodiment of the anode 70 of FIG. 5B. In this embodiment, a support member 80 is provided at the rear end of the second main body 3 to support the core rod 5. Since the core rod 5 can be supported by the support member 80, the hole formed in the first main body portion rear end surface 9 can be shallowed. The core rod 5 may have a structure in which the core rod 5 is brought into contact with the first main body portion 2 without providing a hole, as long as conduction with the first main body portion 2 can be reliably ensured.

  The heat dissipation in this embodiment will be described. A plurality of heat radiating windows 85 are formed in the support member 80. In this embodiment, heat is radiated in the hole 7 from the heat radiating window 73 provided on the side wall of the second main body 3 and the heat radiating window 85 provided on the support member 80.

  The shape of the support member 80 is not limited to FIG. 5C. Since the core rod 5 only needs to be supported, as shown in FIG. 5D, a support may be configured by providing a support so that a fan-shaped hole 88 is formed.

6). Sixth Embodiment FIG. 6 shows another embodiment. The anode 90 has a spacer interposed between the first body portion 2 and the second body portion 3 so that heat can be radiated from the first body portion rear end surface 93 of the first body portion 2 to the side surface. It is. The second main body 3 has a bottomed cylindrical shape and includes a bottom surface 95, an inner surface 96, and an outer surface 97.

  The heat of the first main body portion rear end surface 93 is transmitted to the second main body portion 3 via the pin 91 and is also radiated from the bottom surface 95, the inner side surface 96 and the outer side surface 97 of the second main body portion 3.

  In the present embodiment, the pin 91 is used as a spacer. However, as a ring shape, a hole may be formed in the side surface and exposed to the outside in the same manner. Further, the number of pins is not limited.

  The material of the spacer may be any material such as metal or ceramic as long as heat can be transferred to the second main body 3.

7). Seventh Embodiment FIG. 7 shows an anode 100 according to another embodiment. In this embodiment, the shapes of the anode 90 and the second main body 103 shown in FIG. 6 are different. Specifically, the second main body portion 103 has a coil shape rather than a bottomed cylindrical shape. Since the rear end surface 93 of the first main body portion is exposed, heat can be radiated from the portion where the pins 94 do not exist in the side surface direction. Furthermore, since the 2nd main-body part 103 is coil shape, the heat of the 1st main-body part 102 is transmitted via the pin 94, and is thermally radiated from the surface of a coil.

  The structure of the spacer is the same as in FIG.

8). Eighth Embodiment FIG. 8 shows an anode 110 according to another embodiment. In this embodiment, the shapes of the anode 90 and the second main body 3 shown in FIG. 6 are different. Specifically, a plurality of disk-shaped members 115 to 117 are not fixed to the bottomed cylindrical shape, but are fixed to the core bar 5 with a predetermined interval. About the heat radiation from the 1st main-body part rear end surface 93, and the heat radiation in the 2nd main-body part 3, it is substantially the same. The structure of the spacer is the same as in FIG.

9. Other Embodiments In the present embodiment, when a ceramic heat dissipation member is added, a titanium foil is employed as an intermediate layer of the joined body, but an active metal such as zirconium and a refractory metal are desirable.

  In addition, this invention is not limited to the said structure, It can change suitably. For example, the refractory metal constituting the electrode body is not limited to the materials described above. Further, the heat dissipating member is not limited to the above-described substances and can be appropriately changed, and any of them may be one kind or a mixture of two or more kinds selected from nitride ceramics or carbonized ceramics, or two or more layers. However, the present invention is not limited to the above embodiment.

  The electrode structure of the present invention preferably employs an anode in a DC lighting type discharge lamp, but may be employed in a cathode. Moreover, it can also employ | adopt as both an anode and a cathode.

  It can also be used in an AC lighting discharge lamp.

  In a so-called vertical lighting type discharge lamp that is lit with the tube axis of the discharge lamp arranged in the vertical direction, the electrode arranged on the upper side is likely to be heated. Therefore, the electrode structure according to the present invention is preferably an electrode disposed on the upper side. However, in a vertically lit discharge lamp, it is not denied that it is adopted as an electrode arranged on the lower side, and can be adopted also for an electrode adopted on the lower side.

  Furthermore, the electrode structure according to the present invention can be employed in a horizontal lighting type discharge lamp in which the tube axis is horizontally arranged and a discharge lamp in which the tube axis is arranged obliquely.

  In addition, this invention can also be grasped | ascertained as the following technical thoughts.

  1) An electrode for a short arc type discharge lamp in which a hole with a core rod bottom for holding the core rod is formed in the central portion of the rear end surface, and the core rod is formed in the central direction of the rear end surface in the distal direction. A short arc type discharge lamp in which a large-diameter bottomed hole having a diameter larger than that of the bottomed hole is formed, and the bottom hole of the large-diameter bottomed hole is provided with the core rod bottomed hole. Electrode.

  2) A short arc type discharge lamp electrode comprising a first main body near the tip, and a holding hole for holding a core rod formed in the first main body. An electrode for a short arc type discharge lamp, wherein a second body portion is formed at a rear end portion so that a rear end surface of the first body portion is exposed as a heat radiating surface.

  In this case, the second body portion is provided with a through hole larger than the diameter of the core rod, and the rear end surface of the first body portion is exposed as a heat radiating surface by the through hole. Good.

  3) A short arc type discharge lamp electrode comprising a first main body near the tip and a holding hole for holding a core rod formed in the first main body. A second main body portion is provided on a rear end surface of the first main body portion so that an exposed portion cavity spatially connected to the outside is formed at a position facing the front end surface. Electrode for short arc discharge lamp.

  Moreover, in each said embodiment, although the case where it grasped | ascertained that a 2nd main-body part comprised an electrode was demonstrated, if it grasps | ascertains that a 2nd main-body part has a thermal radiation function, a 2nd main-body part is an electrode. It can also be interpreted as a heat dissipation part.

It is an axial center sectional view of anode 1 concerning the present invention. FIG. 2 is a cross-sectional view of an axial center where a core rod 5 is press-fitted into the anode 1 of FIG. 1. It is an axial center sectional view of the anode which constituted the 1st main part and the 2nd main part from another member. 3 is a modified embodiment of the anode 1 of FIG. 3 is a modified embodiment of the anode 1 of FIG. It is an axial center sectional view of anode 90 which connected the 1st body part and the 2nd body part with the spacer. It is an axial center sectional view of anode 100 which connected the 1st body part and the 2nd body part with the spacer. It is an axial center sectional view of anode 110 which connected the 1st body part and the 2nd body part with the spacer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anode 2 1st main-body part 3 2nd main-body part 5 Core rod 9 1st main-body part rear end surface

Claims (6)

A short arc type discharge lamp electrode in which a hole with a core rod bottom for holding the core rod is formed in the center of the rear end surface,
A large-diameter bottomed hole having a diameter larger than that of the core rod bottomed hole is formed in the center of the rear end surface in the tip direction, and the bottom of the large diameter bottomed hole is attached to the bottom of the core rod. That there is a hole,
An electrode for a short arc type discharge lamp. A first main body near the tip,
A holding hole for holding a core rod formed in the first body portion;
An electrode for a short arc type discharge lamp comprising:
A second body portion is formed at the rear end portion of the first body portion so that the rear end surface of the first body portion is exposed as a heat dissipation surface;
An electrode for a short arc type discharge lamp. In the short arc type discharge lamp electrode according to claim 2,
The second body portion is provided with a through hole larger than the diameter of the core rod,
The rear end surface of the first main body portion is exposed as a heat radiating surface by the through hole;
An electrode for a short arc type discharge lamp. In the short arc type discharge lamp electrode according to claim 2 or 3,
The second main body portion is entirely or partially made of ceramics;
An electrode for a short arc type discharge lamp. A first main body near the tip,
A holding hole for holding a core rod formed in the first body portion;
An electrode for a short arc type discharge lamp comprising:
A second body portion is provided on a rear end surface of the first body portion so that an exposed portion cavity that is spatially connected to the outside is formed at a position facing the tip surface of the first body portion. thing,
An electrode for a short arc type discharge lamp.   The short arc type discharge lamp provided with the electrode for short arc type discharge lamps in any one of Claims 1-5.

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