JP2012038675A - Short-arc discharge lamp or electrode for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode for a short-arc discharge lamp, which has high heat dissipation properties and is lightweight.SOLUTION: An anode 1 comprises a body part 2 in the vicinity of a front end, and a heat dissipating part 3. The heat dissipating part 3 is composed of twelve cylindrical fins 3a1 to 3a12 constituted of small-diameter tungsten rods. A diameter of the cylindrical fins 3a1 to 3a12 is smaller than the body part 2, and their axes are parallel to that of a core rod 5. Therefore, the electrode for a short-arc discharge lamp, which has higher heat dissipation properties and a lighter weight in comparison with a conventional electrode in which a body part 2 is extended with its diameter fixed, can be obtained.

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 weight increases. 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 a high heat dissipation effect.

  (1) A short arc type discharge lamp electrode according to the present invention is a short arc type discharge lamp electrode comprising 1) a main body, 2) a heat radiating portion at the rear end of the main body, and 3) The heat dissipating part is arranged parallel to the electrode core bar, and is arranged on the rear end surface of the main end part in a non-contact state concentrically with a cylindrical radiator having a diameter smaller than that of the main body part, and 4) The diameter, number, and length of the columnar heat radiator are determined so that when the heat radiating portion is extended to a predetermined length while maintaining the diameter of the main body portion, the heat radiating amount is larger than the heat radiation amount in the extended portion. Therefore, it is possible to provide an electrode that is lightweight and has a high heat dissipation effect.

  (2) The short arc type discharge lamp electrode according to the present invention is a short arc type discharge lamp electrode comprising 1) a main body, 2) a heat radiating portion at the rear end of the main body, and 3) The heat radiating portion is composed of a plurality of rod-shaped heat radiators provided in parallel with the core rod of the electrode. Therefore, it is possible to provide an electrode that is lightweight and has a heat dissipation effect.

  (3) In the short arc type discharge lamp electrode according to the present invention, the rod-shaped radiator is a cylinder. Therefore, a heat radiation part can be formed using a round bar as a material.

  (4) In the electrode for a short arc type discharge lamp according to the present invention, when the heat dissipating part is extended to a predetermined length while maintaining the diameter of the main body part, the heat radiation amount in the extended part is larger than the cylinder. The diameter, number, and length of the radiator are determined. Therefore, an electrode having a high heat dissipation effect can be provided.

  (5) In the electrode for a short arc type discharge lamp according to the present invention, the diameter of the rod-shaped radiator is smaller than that of the main body. Therefore, the said heat radiator can be comprised by a small diameter round bar.

  (6) In the short arc type discharge lamp electrode according to the present invention, the rod-shaped radiators are arranged concentrically on the rear end face of the main end portion in a non-contact state. Therefore, the rod-shaped heat radiator can be disposed so as to surround the core rod.

  As such a concentric arrangement, not only a single arrangement but also a multiple arrangement may be used.

  (7) In the electrode for a short arc type discharge lamp according to the present invention, the side surface in the longitudinal direction of the rod-shaped radiator is located inside the side surface of the main body. Therefore, it is possible to provide an electrode for a short arc type discharge lamp in which the rod-shaped heat radiator does not protrude in the radial direction of the electrode main body.

  (8) In the electrode for a short arc type discharge lamp according to the present invention, a part or all of the rod-shaped radiator is made of ceramic. Therefore, a higher heat dissipation effect can be obtained.

  In the present specification, the “rod-shaped radiator” corresponds to the cylindrical fins 3a1 to 3a12 in the embodiment. Moreover, about the shape of a rod-shaped heat radiator, it is not restricted to a cylinder. The “diameter” is a concept including not only a perfect circle but also a major axis of an ellipse and a circumscribed circle in a polygon.

It is an axial center sectional view of anode 1 concerning the present invention. It is AA sectional drawing in FIG. It is a conceptual diagram for _{demonstrating} electrode efficiency (eta) _el of the electrode latter half part in the conventional electrode. It is a conceptual diagram for _{demonstrating} fin efficiency (eta) _fin of the cylindrical fin part 32 of the electrode latter half part in this case. This is an example showing the areas S _eff and _fin when various conditions are changed. This is an example showing areas S _eff , _el when various conditions are changed. This is an example showing the areas S _eff and _fin when various conditions are changed. This is an example showing areas S _eff , _el when various conditions are changed. This is an example showing the areas S _eff and _fin when various conditions are changed. This is an example showing areas S _eff , _el when various conditions are changed. It is a figure which shows deformation | transformation embodiment. It is a figure which shows deformation | transformation embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

(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. The anode 1 has a main body 2 near the tip and a heat radiating part 3. The heat radiating part 3 is composed of a plurality of cylindrical fins 3a1 to 3a12 made of small-diameter tungsten rods. The axes of the cylindrical fins 3a1 to 3a12 are parallel to the axis of the core bar 5. The diameters of the columnar fins 3a1 to 3a12 are smaller than those of the main body 2 and are fitted into bottomed holes provided radially on the rear end surface 9 of the main body 2.

  In the present embodiment, as shown in FIG. 2, since the main body 2 has a diameter of 35 mm, twelve cylindrical fins 3a1 to 3a12 having a diameter of 6 mm and a length of 30 mm are arranged concentrically.

  In the present embodiment, a plurality of cylindrical fins 3a1 to 3a12 are provided at the rear end of the main body 2. Thereby, compared with the electrode which extended the main-body part 2 with the diameter of the main-body part like the past, a heat dissipation effect is high and a lightweight electrode is obtained. Hereinafter, a description will be given with reference to FIGS. The heat dissipation capability as an electrode is determined by the distance from the tip and the surface area. What is necessary is just to determine the number and length of a cylindrical fin according to required heat dissipation capability. This will be described below.

As shown in FIG. 3, a cylindrical electrode having a radius R is divided into two, and a region from the electrode tip to the distance L1 is an electrode tip 21 and the remaining length L2 is an electrode rear half 22. Assume that the electrode tip is at a temperature T0, and the temperature of the boundary surface 31 (area S1) between the electrode tip 21 and the electrode rear half 22 is T1. Actually, the temperature of the cylindrical fin is not uniform, and the temperature of the cylindrical fin decreases along the axial direction due to heat radiation from the surface of the cylindrical fin. In general, fin efficiency is employed in order to investigate the heat dissipation effect of the fin, and the fin efficiency η _el defined as follows is employed in this case as well. In the following, in order to facilitate the calculation of the heat dissipation amount, description will be made using fin efficiency.

In this case, the electrode efficiency η _el of the electrode rear half 22 is defined by the following formula (1).

η _el = actual heat radiation from the surface of the electrode rear half 22 / heat radiation when the temperature of the entire surface of the electrode rear half 22 is T1 (1)
In FIG. 4, instead of the electrode rear half 22, N cylindrical fins having a radius r are configured. It is called a cylindrical fin portion 32. In this case as well, the fin efficiency η _fin of the cylindrical fin portion 32 is defined by Expression (2), as in the case of FIG.

η _fin = actual heat dissipation from the surface of the cylindrical fin 32 / heat dissipation when the temperature of the entire surface of the cylindrical fin 32 is T1 (2)
Assuming that the total surface areas of the rear electrode portion 22 and the cylindrical fin 32 are S _el and S _fin , respectively, the substantially enlarged areas S _el , _eff , S _fin and _eff are defined as follows.

S _el , _eff = S _el × η _el ; S _el = 2πR × L2 + πR ² Equation (3)
S _fin , _eff = S _fin × η _fin ; S _fin = 2πr × L2 + πr ² (4)
The area S _el , _eff and the area S _{fin eff} can be considered as an area obtained by substantially expanding the area S1 of the boundary surface at the temperature T1. In other words, in the case of the cylindrical electrode rear half portion 22, the end face is enlarged to the area S _el , _eff, and in the case of the cylindrical fin 32, the end face is enlarged to the areas S _{fin eff} . The amount of heat radiation increases as the enlarged area increases. The condition that the electrode to which various Ni cylindrical fins are attached has more heat radiation than the conventional cylindrical electrode is given by the following equation.

The areas S _eff , _el and S _eff , _fin when various conditions are changed are shown in FIGS. FIG. 5 shows changes in fin efficiency when the length of the cylindrical fin 32 is changed. FIG. 6 shows changes in electrode efficiency when the length of the electrode rear half 22 is changed in the conventional electrode shown in FIG. 5 and 6, for example, when the length L2 is also set to 30 mm, it is understood that it is sufficient to provide seven or more cylindrical fins having a diameter of 6 mm.

  FIG. 7 shows the fin efficiency when the tip temperature is changed, and FIG. 8 shows the change in the electrode efficiency when the length of the electrode rear half 22 is changed in the conventional electrode. Also in this case, by increasing the number of fins in the cylindrical fin portion as the temperature becomes higher, it is possible to provide an electrode having a heat dissipation effect equivalent to the conventional one.

  FIG. 9 is a calculation example in the case where the diameter of the cylindrical fin in the cylindrical fin portion is changed by three patterns of the tip temperature. Compared to the case of FIG. 10, a lighter electrode can be obtained. If the same heat dissipation efficiency is desired, the diameter and number of cylindrical fins may be changed.

  5 to 10, the case where the length L2 is the same has been described for comparison, but an electrode having a higher heat dissipation effect can be obtained by increasing the length of the cylindrical fin. That is, the number, diameter, and length of the columnar fins can be changed as appropriate so that a desired heat dissipation capability can be exhibited.

  Moreover, even when the heat dissipation effect is not so required, at least weight reduction can be achieved.

2. Other Embodiments In the above embodiment, the case where a cylindrical fin is adopted for the end face of the electrode main body has been described. However, as shown in FIG. 11, the taper has a smaller outer diameter (d1> d2) toward the rear end. The shape fins (or needle fins) 61a1 to 61an may be used. In this embodiment, the taper angle is 5 °, but the taper angle is arbitrary, and may be, for example, about 0 ° to 10 °.

All or part of the cylindrical fins may be made of ceramics. As ceramics, for example, when aluminum nitride (AlN) is employed, the thermal conductivity and thermal emissivity at the time of lamp lighting are higher than that of tungsten, so that the radiant heat effect from the fin surface can be enhanced. In addition, since the thermal expansion coefficients are approximate, it can be prevented from cracking when bonded. Further, as the ceramic, other nitride ceramics may be used, or a carbide ceramic such as silicon carbide (SiC) may be used. In particular, even in a high temperature region of 1500 ° C. or higher, the thermal conductivity is 100 to 120 W / mK, the thermal emissivity is 0.93 (0.98 or more in the far infrared region), and the thermal expansion coefficient is 4.5 × 10 ⁻⁶ / degree (Celsius). Aluminum nitride with a density of 3.32 kg / m ³ is preferred.

  Further, the shape of the electrode body 2 is arbitrary. For example, as shown in FIG. 12, the latter half of the electrode body 70 may be conical. In the case of a gently-graded conical shape, the surface area is larger than a cylindrical surface of the same diameter near the bottom of the cone. Since the temperature is high near the bottom surface and the amount of radiant heat is large, the fact that the surface area can be increased in the vicinity is advantageous from the viewpoint of radiation cooling of the electrode.

  Moreover, when each fin is comprised with ceramics, all may be comprised with ceramics, and a part may be comprised with ceramics. In particular, since the temperature becomes higher as it approaches the tip of the electrode, the portion close to the main body 2 may be made of tungsten in consideration of the service temperature of the ceramic.

  The electrode of the present invention preferably employs an anode in a DC lighting type discharge lamp, but may be employed as 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 the vertical lighting discharge type lamp, it is not denied that it is adopted for the electrode arranged on the lower side, and can be adopted on the lower side.

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

  In the present embodiment, a bottomed hole is formed on the rear end surface of the electrode body 2 and is fitted to the bottom. However, the electrode body 2 is formed by a discharge plasma sintering method (SPS method: Spark Plasma Sintering). You may make it fix a rod-shaped heat radiator to the rear-end surface.

  In this embodiment, the heat radiating part is composed of a tungsten rod having a smaller diameter than the main body part. Tungsten becomes expensive as the diameter increases. Therefore, by arranging a plurality of small-diameter tungsten rods and securing the surface area as a whole, the manufacturing cost as a whole can be reduced. Further, such parts can be reused by polishing the used parts.

  In this embodiment, when a ceramic heat radiating 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 high melting point metal are desirable.

Claims (9)

Body part,
A heat radiating portion at the rear end of the main body,
An electrode for a short arc type discharge lamp comprising:
The heat dissipating part is disposed on the rear end surface of the main end part in a non-contact state concentrically with a cylindrical heat dissipating member having a diameter smaller than that of the main body part provided in parallel with the core rod of the electrode,
Determining the diameter, number, and length of the cylindrical radiator so that it becomes larger than the heat dissipation amount in the extended portion when extending to a predetermined length with the diameter of the main body as the heat dissipation portion;
An electrode for a short arc type discharge lamp. Body part,
A heat radiating portion at the rear end of the main body,
An electrode for a short arc type discharge lamp comprising:
The heat dissipating part is composed of a plurality of rod-shaped heat dissipators provided in parallel with the core rod of the electrode;
An electrode for a short arc type discharge lamp. In the short arc type discharge lamp electrode according to claim 2,
The rod-shaped radiator is a cylinder;
An electrode for a short arc type discharge lamp. In the short arc type discharge lamp electrode according to claim 3,
Determining the diameter, number, and length of the cylindrical radiator so that it becomes larger than the heat dissipation amount in the extended portion when extending to a predetermined length with the diameter of the main body as the heat dissipation portion;
An electrode for a short arc type discharge lamp. In the short arc type discharge lamp electrode according to claim 2,
The rod-shaped radiator has a diameter smaller than that of the main body;
An electrode for a short arc type discharge lamp. In the short arc type discharge lamp electrode according to claim 2,
The rod-shaped radiator is disposed on the rear end surface of the main end portion in a non-contact state concentrically with each other,
An electrode for a short arc type discharge lamp. In the short arc type discharge lamp electrode according to claim 2,
The side surface in the longitudinal direction of the rod-shaped radiator is located inside the side surface of the main body,
An electrode for a short arc type discharge lamp. In the short arc type discharge lamp electrode according to claim 2,
A part or all of the rod-shaped radiator is made of ceramic;
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 1-8.

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