JP2017183087A - Discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a short-arc type discharge lamp, which is lit in a horizontal state of one pair of electrodes inside a luminous tube, which produces no problem such as devitrification of the inner wall of the luminous tube, arc flickering, etc., due to an excessive vertical temperature difference in the radial cross-section of the electrode.SOLUTION: The discharge lamp uses one pair of electrodes, which is supported by an electrode core rod in the horizontal direction through a cylindrical recess disposed on the electrode core rod side of an electrode end face. In regard to at least one electrode, heat conduction between the electrode and the electrode core rod in the electrode upper part of the electrode cross-section is larger than in the electrode lower part.SELECTED DRAWING: Figure 2

Description

The present invention relates to a short arc discharge lamp used as a light source for exposure, such as a semiconductor element, a liquid crystal element, a printed circuit board element, etc., or as a light source for a projection apparatus for projection. Short arc type discharge lamp supported by a rod (short arc type discharge lamp that lights with the lamp axis direction horizontal).
About.

The electrode of such a short arc type discharge lamp (hereinafter referred to as a lamp) has a cylindrical recess on the electrode core rod side, and is held by the electrode core rod by inserting (press-fitting) the electrode core rod into the cylindrical recess. . The main component of the electrode is a refractory metal such as tungsten. In particular, a refractory metal containing an electron-emitting substance (hereinafter referred to as an emitter) such as thorium, lanthanum, or barium is used for the cathode.

With regard to such a cathode, in a lamp that is lit with the lamp axis direction in a vertical state, a tantalum carbide layer having a large radiation capacity is provided on the electrode surface (Patent Document 1), or a heat dissipation groove is provided on the surface of the cathode (Patent Document 2). It is known that this prevents overheating of the cathode.

However, when such a cathode is used for a horizontally lit lamp, an excessive temperature is generated between the upper portion and the lower portion of the cathode in the cathode radial cross section along the vertical direction due to the convection of the discharge gas in the arc tube. There is a difference. Thereby, the emitter of the upper part of the cathode is preferentially supplied near the tip surface of the cathode, and the emitter of the upper part is reduced before the lower part due to long-time lighting,
It will run out. As a result, the balance of the emitter supply to the vicinity of the tip surface of the cathode is lost, the arc becomes unstable, and arc flickering occurs. Furthermore, when the arc that has become unstable moves to the upper part of the cathode whose emitter has been depleted, the upper part becomes overheated, and vaporized refractory metal adheres to the inner wall of the arc tube, resulting in devitrification of the arc tube. .

In addition, the anode has a high temperature due to collision of electrons sent from the cathode by the discharge, and like the cathode, the temperature of the upper part in the anode radial section along the vertical direction is higher than the lower part. As a result, the upper portion becomes overheated. As a result, the refractory metal evaporated from the upper portion adheres to the inner wall of the arc tube, thereby causing devitrification of the arc tube.

JP-A-9-115478 JP 2000-306546 A

In view of the above problems, the problem to be solved by the present invention is to prevent overheating of the electrode upper portion in the radial cross section of the electrode in a horizontally lit lamp, and further, between the electrode upper portion and the electrode lower portion. An object of the present invention is to provide a lamp that suppresses the temperature difference and does not cause devitrification of the inner wall of the arc tube or flickering of the arc even if it is lit for a long time.

In a lamp having an arc tube, a pair of electrodes disposed opposite to each other in the arc tube, and an electrode core rod that supports the electrodes in a horizontal state, at least one of the electrodes is an electrode in a radial cross section along the vertical direction of the electrode The heat conduction between the electrode and the electrode core is greater in the electrode upper part than in the lower part. That is, heat is more easily transmitted to the electrode core in the electrode upper part than in the electrode lower part. Thereby, overheating of the electrode upper portion can be prevented, and an excessive temperature difference between the electrode lower portion and the electrode upper portion can be suppressed.

Further, at least a portion between the electrode and the electrode core rod has a heat conduction suppressor having lower heat conductivity than the electrode, so that the lower portion and the electrode can be changed without changing the shape or material of the electrode. It is possible to suppress an excessive temperature difference between the upper portion and the upper portion.

The electrode radial direction thickness D1 of the heat conduction suppressing body (heat conduction suppressing body upper part) between the electrode upper portion and the electrode core rod in the electrode radial cross section is the heat between the electrode lower portion and the electrode core rod. It is smaller than the thickness D2 in the electrode radial direction of the conduction inhibitor (lower part of the heat conduction inhibitor). As a result, even if the material of the upper part of the heat conduction suppressor and the lower part of the heat conduction suppressor are the same, heat is more easily transferred to the electrode core than the lower part of the electrode, and the lower part of the electrode And an excessive temperature difference between the electrode upper portion and the electrode upper portion can be suppressed.

The thickness D1 in the electrode radial direction of the upper part of the heat conduction suppressing body is set to 10% or more of the thickness D2 in the electrode radial direction of the lower part of the heat conduction suppressing body. As a result, it is possible to prevent an excessive temperature difference from occurring between the upper portion and the lower portion of the electrode core rod in the radial cross section so that the bonding strength between the electrode and the electrode core rod becomes insufficient.

The thickness of the heat conduction suppressor in the electrode radial direction continuously decreases along the electrode circumferential direction from the lower part of the heat conduction suppressor toward the upper part of the heat conduction suppressor. As a result, heat conduction from the electrode to the electrode through the heat conduction suppressor continuously increases along the electrode circumferential direction from the lower electrode portion toward the upper electrode portion, and from the lower electrode portion to the upper electrode portion. It is possible to suppress the occurrence of an excessive temperature difference along the circumferential direction of the electrode.

The electrode upper portion and the electrode core rod are fitted in a concavo-convex shape along the electrode axis direction via the heat conduction suppressor. Thereby, even if a thermal expansion difference arises between each of an electrode, a heat conduction suppression body, and an electrode core rod by lamp lighting, it can prevent that these joining remove | deviate.

In a lamp that is horizontally lit, it is possible to provide a lamp that prevents overheating of the upper part of the electrode and suppresses the occurrence of problems due to an excessive temperature difference between the upper part of the electrode and the lower part of the electrode. .

It is a schematic sectional drawing of the lamp | ramp which is 1st Embodiment. It is an axial section schematic diagram along the perpendicular direction of the cathode in the lamp which is a 1st embodiment. FIG. 3 is a radial cross-sectional schematic view along the vertical direction of the cathode in AA in FIG. 2. It is an axial section schematic diagram along the perpendicular direction of the cathode in the lamp which is other embodiments.

A lamp according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic sectional view of a lamp of the present invention.

As shown in FIG. 1, the lamp 1 includes an arc tube 3 and a pair of sealing tubes 4 respectively connected to both ends of the arc tube 3. The arc tube 3 and the sealing tube 4 are each made of quartz glass, and the arc tube 3 is filled with xenon gas as a discharge gas at atmospheric pressure or higher. Inside the arc tube 3, a pair of electrodes (anode 5 and cathode 6) are arranged to face each other, and one end of each of the pair of electrodes 5 and 6 protrudes from the end of the sealing tube 4 to the outside. The bars 7 are connected in the horizontal direction. The sealing tube 4 and the electrode core bar 7 are integrally hermetically sealed by the step glass 8. A base 9 that is electrically connected to the electrode core bar 7 is provided at the end of the sealing tube 4, but the base 9 may be omitted.

The electrodes used in the lamp of the first embodiment will be described with reference to FIGS.
Hereinafter, the cathode will be described as an example, but the same applies to the anode.

2 is a schematic cross-sectional view in the axial direction along the vertical direction of the cathode, and FIG. 3 is a schematic cross-sectional view in the radial direction along the vertical direction in AA of FIG. The cathode 6 has a front end surface 6 that becomes a bright spot of arc discharge.
2, a conical reduced diameter portion 63 that decreases in diameter toward the distal end surface 62, and a cylindrical body portion 64 on the rear end side of the reduced diameter portion 63. The upper part of the cathode in the extending direction is the upper part of the cathode (
Electrode upper portion) 66, and the lower portion of the cathode is the cathode lower portion (electrode lower portion) 67.
It is. The end face 65 of the cathode 6 on the side of the electrode core rod has a cylindrical recess 61 whose bottom is the tip side of the cathode 6. Inside the cylindrical recess 61, there is an end portion (core bar insertion portion) 71 of the electrode core rod 7 that supports the cathode 6, and between the cylindrical recess 61 and the core rod insertion portion 71 in the cathode radial direction. At least a part of the heat conduction suppressor 10 is interposed. The cathode 6 may be supported on the electrode core bar 7 via the heat conduction suppressor 10. As a numerical example of the cathode 6, the diameter of the body 64 of the cathode is 5 to 15 mm.
The total length of the cathode 6 is selected from the range of 12 to 30 mm, the diameter of the tip surface 62 of the cathode is selected from the range of 0.4 to 1.5 mm, and the outside of the electrode core rod 7 is selected. The diameter is 4-6m
selected by m.

The main component of the cathode 6 is a refractory metal such as tungsten, and contains an emitter such as thorium in order to enhance electron emission (eg, tritium tungsten). The main component of the electrode core 7 is a refractory metal such as tungsten. The main component of the heat conduction suppressor 10 is a metal that does not adversely affect the lamp such as not causing a chemical reaction with the sealed gas or the arc tube, and a metal having a lower thermal conductivity than tungsten, which is the main component of the cathode. Titanium and molybdenum. In this way, by using a metal having lower thermal conductivity than the cathode 6 for the heat conduction suppressor 10, it is possible to suppress the heat of the cathode 6 from being transmitted to the portion where the electrode core rod 7 and the step glass 8 are sealed, It is possible to prevent the sealing portion from being damaged. Here, the cathode upper portion 66 in the radial cross section of the cathode 6 has a higher heat conduction between the cathode 6 and the electrode core 7 than the cathode lower portion 67, so that the cathode upper portion 66 is overheated. Can be prevented. Furthermore, the heat conduction suppressing body 10 having a lower thermal conductivity than the cathode 6 is provided at least at a part between the cathode 6 and the electrode core 7 (core bar insertion portion 71), the cathode upper portion than the cathode lower portion 67. 66 has such that the heat conduction between the cathode 6 and the electrode core bar 7 is increased, thereby suppressing an excessive temperature difference between the cathode upper portion 66 and the cathode lower portion 67. be able to. For example, the heat conduction between the cathode lower portion 67 and the electrode core rod 7 is reduced by having the heat conduction suppressing body 10 between the cathode lower portion 67 and the electrode core rod 7 (core rod insertion portion 71). Thus, it is preferable to suppress an excessive temperature difference between the cathode upper portion 66 and the cathode lower portion 67.

The thickness of the thermal conduction suppressor 10 in the cathode radial direction is not uniform in the circumferential direction of the cathode, and in the cathode radial cross section along the vertical direction, the portion between the cathode upper portion 66 and the electrode core rod 7 (thermal conduction suppression). The electrode radial direction thickness D1 of the body upper part) 101 is smaller than the electrode radial direction thickness D2 of the part (heat conduction suppressing body lower part) 102 between the cathode lower part 67 and the electrode core 7. Thereby, the heat of the cathode upper portion 66 is more easily transferred to the electrode core 7 than the cathode lower portion 67, that is, the heat conduction of the cathode upper portion 66 to the electrode core is greater than that of the cathode lower portion 67. As a result, overheating of the cathode upper portion 66 can be prevented, and an excessive temperature difference between the cathode upper portion 66 and the cathode lower portion 67 can be suppressed.

Furthermore, the electrode radial direction thickness of the heat conduction suppressing body 10 continuously decreases along the circumferential direction of the cathode from the heat conduction suppressing body lower portion 102 toward the heat conduction suppressing body upper portion 101. As a result, heat conduction from the cathode 6 to the electrode core rod 7 increases from the cathode lower portion 67 toward the cathode upper portion 66 along the circumferential direction of the cathode. As a result, the cathode lower portion 67 to the cathode upper portion 6
An excessive temperature difference along the cathode circumferential direction toward 6 can be suppressed, and the temperature in the cathode circumferential direction can be made more uniform.

However, the heat conduction from the cathode 6 to the electrode pole 7 is caused by the cathode lower portion 67 to the cathode upper portion 66.
By becoming extremely large along the circumferential direction of the cathode, an excessive temperature difference occurs between the upper portion and the lower portion in the radial cross section of the core rod insertion portion 71. The bonding strength between the cathode 6 and the electrode core rod 7 may be insufficient due to the difference in thermal expansion and thermal strain accompanying this excessive temperature difference. there,
As a result of performing an experiment using lamps in which the electrode radial thickness D1 and the electrode radial thickness D2 are varied, the electrode radial thickness D1 of the heat conduction suppressor 10 is the electrode diameter. It has been found that the bonding strength between the cathode 6 and the electrode core rod 7 may be insufficient when the thickness is less than 10% of the directional thickness D2. Therefore, the electrode radial direction thickness D1 of the heat conduction suppressor 10 is desirably 10% or more of the electrode radial direction thickness D2.

Furthermore, in the first embodiment, a space (a space in the cylindrical recess) 69 is provided between the bottom surface of the cylindrical recess 61 and the heat conduction suppressor 10 in the cathode axis direction. Thereby, the heat conduction path from the cathode 6 to the electrode core rod 7 can be limited to the cylindrical portion of the heat conduction suppressor 10, and it is possible to more reliably suppress the occurrence of an excessive temperature difference along the circumferential direction of the cathode. it can. It should be noted that there is no heat conduction suppressing body 10 between the bottom surface of the cylindrical recess 61 and the electrode core 7 in the cathode axis direction, and there is a space (in the cylindrical recess) between the bottom surface of the cylindrical recess 61 and the electrode core 7. Space 69).

By using such a cathode 6, it is possible to suppress an excessive temperature difference between the cathode upper portion 66 and the cathode lower portion 67 in the cathode radial cross section, and to lose the arc tube even for a long time. It is possible to suppress the occurrence of see-through and arc flickering.

Similarly, in the anode to which the first embodiment is applied, an excessive temperature difference along the anode circumferential direction of the anode is suppressed. Thereby, the devitrification of the arc tube caused by the overheating of the anode upper portion in the anode radial cross section can be prevented. The same can be applied to a discharge lamp in which mercury is sealed in an arc tube.

An example of a method for producing the thermal conduction inhibitor 10 of the first embodiment will be described. The cathode 6 is provided with a cylindrical recess 61 on the electrode core rod side end face 65 by machining. Next, the core rod insertion portion 71 is inserted into the cylindrical recess 61 so that the axis of the cylindrical recess 61 and the axis of the electrode core rod 7 are parallel to the cathode axis direction at a predetermined interval. An appropriate amount of a powdery heat conduction inhibitor is put between 71 and the cylindrical recess 61. By heating these to a temperature equal to or higher than the melting point of the heat conduction suppressor by high frequency induction heating, the powdery heat conduction suppressor is integrated, and the cathode 6 provided with the predetermined heat conduction suppressor 10 can be produced. .

The electrode used for the lamp | ramp of other embodiment is demonstrated using FIG. In other embodiments, the cathode will be described as an example, but the same applies to the anode.

FIG. 4 is a schematic axial sectional view along the vertical direction of the cathode used in the lamp of another embodiment. On the inner peripheral surface of the cylindrical concave portion 61 of the cathode 6, there is a screw-shaped concave portion 68 disposed along the circumferential direction of the inner peripheral surface of the cylindrical concave portion 61 with the depth direction as the cathode radial direction. Core rod insertion part 71
On at least the upper side, a projection 73 whose height direction is the electrode radial direction is provided. Thereby, the recessed part 68 and the convex part 73 become uneven | corrugated shape along a cathode axial direction (electrode axial direction), and it fits in the cathode direction through the heat conduction suppression body 10. FIG.

Thereby, the electrode radial direction thickness of the heat conduction suppression body upper part 101 of the heat conduction suppression body 10 and the electrode radial direction thickness of the heat conduction suppression body lower part 102 can be easily made conspicuous. Even in a small lamp in which the outer diameter difference between the cathode 6 and the electrode core 7 is small such that the outer diameter of the portion 64 is not more than twice the outer diameter of the electrode core 7, the cathode upper portion 66 and the cathode lower portion 67. The excessive temperature difference can be suppressed. Further, the cathode upper portion 66 having the highest temperature in the cathode radial cross section and the electrode core rod 7 are fitted in a concavo-convex shape along the cathode axis direction via the heat conduction suppressor 10, thereby causing a thermal expansion difference. However, it is possible to prevent these bonds from being disconnected. In addition, by disposing the screw-shaped recess 68 on the entire circumference along the circumferential direction of the inner peripheral surface of the cylindrical recess 61, the shape of the cathode 6 becomes approximately symmetrical in the axial direction, and the temperature distribution of the cathode 6 is affected. There is no giving.

Further, the surface layer of the electrode core rod 7 (core rod insertion portion 71) in contact with the heat conduction suppressing body 10 may have a buffer layer in which the material of the electrode core rod 7 and the material of the heat conduction suppressing body 10 are mixed. The buffer layer is inclined so that the density of the material of the heat conduction suppressing body 10 continuously decreases from the heat conduction suppressing body 10 side toward the electrode core 7 side. Thereby, the thermal expansion difference between the electrode core bar 7 and the heat conduction suppressing body 10 is buffered, and a stronger connection can be made.

DESCRIPTION OF SYMBOLS 1 Lamp 3 Light-emitting tube 4 Sealing tube 5 Anode 6 Cathode 61 Cylindrical recessed part 62 Tip surface 63 Reduced diameter part 64 Body part 65 Electrode core side end surface 66 Cathode upper part (electrode upper part)
67 Cathode lower part (electrode lower part)
68 Screw-shaped recess 69 Space 7 in cylindrical recess 7 Electrode core rod 71 Core rod insertion portion 73 Projection 8 Step glass 9 Base 10 Thermal conduction suppressor 101 Thermal conduction suppressor upper part 102 Thermal conduction inhibitor lower part

Claims (6)

Arc tube,
A pair of electrodes disposed opposite to each other in the arc tube;
In a discharge lamp having an electrode core rod that supports the electrodes in a horizontal state,
At least one of the electrodes is
The electrode upper part in the radial cross section of the electrode is more than the electrode lower part,
A discharge lamp characterized in that heat conduction between the electrode and the electrode core is large. At least a portion between the electrode and the electrode core rod includes:
The discharge lamp according to claim 1, further comprising a heat conduction suppressor having lower heat conductivity than the electrode. An electrode radial direction thickness D1 of the heat conduction suppressor between the electrode upper portion and the electrode core rod is:
3. The discharge lamp according to claim 2, wherein the thickness of the heat conduction suppressor between the electrode lower portion and the electrode core is smaller than a thickness D <b> 2 in the electrode radial direction. The electrode is supported by the electrode core rod through the thermal conduction inhibitor,
4. The discharge lamp according to claim 3, wherein the electrode radial thickness D <b> 1 of the heat conduction suppressor is 10% or more of the electrode radial thickness D <b> 2. The thickness in the radial direction of the heat conduction suppressor is
From the part between the electrode lower part and the electrode core,
Towards the part between the electrode upper part and the electrode core,
5. The discharge lamp according to claim 3, wherein the discharge lamp decreases continuously along the circumferential direction of the electrode. The electrode upper part and the electrode core rod are:
6. The discharge lamp according to claim 2, wherein the discharge lamp is fitted in a concavo-convex shape along the electrode axis direction through the heat conduction suppressing body.

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