JP2005100832A - Electrode for discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for discharge lamp with uniform precision and capable of being easily and precisely arranged in a discharge lamp. <P>SOLUTION: A negative electrode 2 used in a discharge lamp such as a xenon short arc lamp is a porous body in which an electrode body 20 comprising a discharge part 21 substantially discharging and a barrel part 22 supporting it and a terminal part 23 for external connection are integrally formed by sintering a raw material made of a high melting metal (for example, tungsten) after integral injection-molding by a metal injection molding method. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrode for a discharge lamp, for example, an electrode for a discharge lamp used as an electrode for a short arc lamp.

As an electrode of a high-pressure discharge lamp, an electrode obtained by adding an electron-emitting material to a refractory metal is known. Patent Document 1 is an example of such an electrode, in which a refractory metal powder is sintered to form a porous electrode body, and the hole is filled with an electron-emitting material. And the electrode which joined the electrode part manufactured in this way with the terminal part manufactured separately is attached to a discharge lamp. Further, Patent Document 2 describes that an electrode having a complicated shape can be formed by a metal injection molding method, in which an accommodating portion of a discharge portion containing an electron-emitting material is injection-molded, and then a discharge portion A manufacturing method is disclosed in which an electrode main body in which is inserted into a housing portion is sintered. And the electrode which joined the electrode part manufactured in this way with the terminal part manufactured separately is attached to the discharge lamp.
JP 2000-505939 A (pages 5-8, FIG. 1) JP-A-11-219683 (paragraphs 0020 to 0027, 0031, FIG. 3)

  However, in the discharge lamp electrode manufactured in this way, the electrode components must be joined to each other in the manufacturing process. Therefore, the electrode main body and the terminal portion, and the electrode main body may be composed of a plurality of members. For example, in the case of a discharge part that substantially discharges and a body part that supports the discharge part, there may be variations in the joining accuracy between the discharge part and the body part, and further between the body part and the terminal part. It was difficult to manufacture an electrode with uniform accuracy. As a result, due to variations in the accuracy of the individual electrodes, it is difficult to accurately arrange the electrodes in the optimal position in the discharge lamp, which causes variations in the quality of the discharge lamp. In other words, in order to ensure a stable quality of the discharge lamp, adjustments according to individual electrodes are required, and there is a problem that the assembly process is complicated. Moreover, since each member was manufactured separately, there existed a problem that a manufacturing process increased.

  Therefore, an object of the present invention is to provide an electrode for a discharge lamp that has a uniform accuracy and can easily arrange the electrode in the discharge lamp with high accuracy.

  In order to solve the above-mentioned problems, an electrode for a discharge lamp according to the present invention includes an electrode main body that substantially discharges and a terminal portion for electrical continuity with the outside, and at least the electrode main body emits easy electrons. A discharge lamp electrode containing a substance, wherein an electrode body and a terminal portion are integrally molded and sintered by a metal injection molding method. That is, the electrode body and the terminal portion are integrated in advance.

  It is preferable that the discharge end portion of the electrode body has a pointed shape, and the electron-emitting material is concentrated and contained at the tip portion.

  Since the electrode main body and the terminal portion are integrally formed by a metal injection molding method, it is not necessary to join the electrode constituent members, and an electrode with uniform accuracy can be manufactured with fewer steps. In addition, as a result of obtaining an electrode having uniform accuracy, it is possible to easily and highly accurately position the discharge portion in the discharge lamp, and it is possible to easily produce a discharge lamp having a stable quality.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same reference numerals are given to the same components in the drawings as much as possible, and duplicate descriptions are omitted.

  FIG. 1 is a longitudinal sectional view showing a configuration of a xenon short arc lamp using an electrode according to the present invention as a cathode, and FIG. 2 is a side view showing the configuration of the cathode. A hollow gas sealing portion 11 is formed in the middle portion of the rod-shaped quartz glass bulb 1, and xenon is sealed as a discharge gas at a pressure of about 10 atm (about 1 MPa). The cathode 2 and the anode 3 are opposed to each other inside the gas sealing portion 11, and external terminals 4 and 5 that are electrically connected to the cathode 2 and the anode 3, respectively, at both ends of the rod-like longitudinal direction of the glass bulb 1. It is attached.

  The cathode 2 has a base (a part extending from a part of a body part 22 described later to a terminal part 23 side end) fixed to a quartz glass bulb 1 and is composed of an electrode body 20 and a terminal part 23. Among these, the electrode main body 20 includes a discharge portion 21 that substantially discharges and a body portion 22 that is a support body thereof. The tip discharge portion 21 has a pointed shape on the side facing the anode 3 (discharge end portion), the middle barrel portion 22 has a substantially cylindrical shape, and the terminal portion 23 at the end is substantially narrower than the barrel portion 22. The connecting portion between the body portion 22 and the terminal portion 23 has a tapered shape. By making the connection part of the trunk | drum 22 and the terminal part 23 into a taper shape, the change of the diameter between the trunk | drum 22 and the terminal part 23 is made loose, and the intensity | strength with respect to breakage etc. is raised. The cathode 2 is a porous body integrally formed of a high melting point metal such as tungsten or molybdenum (in the following description, an example mainly composed of tungsten) from the discharge part 21 through the body part 22 to the terminal part 23. It is a mass and contains an electron-emitting substance as a whole. As the easy-electron emitting substance contained, for example, barium aluminate or a mixture of scandium oxide and a carbonate of an alkaline earth metal such as barium oxide, strontium oxide, or calcium oxide is used.

  The cathode 2 is manufactured by the following metal injection molding (Metal Injection Molding = MIM) method. The MIM method can not only form a complicated shape with high accuracy, but also can create an electrode with a high packing density, and can produce an electrode that is not easily consumed and has a long life. FIG. 3 is a flowchart for explaining the manufacturing process of the cathode 2. First, a mold having a predetermined space is prepared (step S1). This space has a shape in which the cathode 2 to be manufactured is enlarged at a predetermined ratio. On the other hand, a predetermined amount of a thermoplastic polymer material in which a resin such as polypropylene is added to paraffin wax as a binder is added to a tungsten powder having an electron-emissive material and an average particle diameter of 2 μm to 8 μm, and the mixture is kneaded. To form a raw material (step S2 = raw material generation step).

  Next, this raw material is heated to about 100 ° C. to 200 ° C. to be in a fluid state, and injected into the mold prepared in step S1 (step S3 = injection molding process).

  When the injection-molded raw material is solidified in the mold, the solidified molded product is taken out from the mold (step S4). Then, the molded product is heated in an inert gas with a predetermined temperature profile and then cooled to perform degreasing to evaporate and remove the binder component (step S5 = degreasing step). The degreased molded product is further heated in vacuum to perform sintering for bonding tungsten powder (step S6 = sintering step). Thereby, the cathode 2 which is an integrated porous electrode with a high filling density of tungsten is obtained.

  In the cathode 2 formed in this way, the electrode body 20 and the terminal portion 23 are integrally manufactured. That is, the cathode 2 does not need to manufacture the electrode constituent members (the discharge part 21, the body part 22, and the terminal part 23) separately, and does not need to be joined to each other. There is no individual difference of electrodes due to the difference in joining accuracy. Therefore, the cathode 2 can be manufactured uniformly and accurately.

  On the other hand, the anode 3 is made of a tungsten rod having a diameter of 3.0 mm, and the distance between the tip of the cathode 2 and the anode 3 is adjusted to 2.0 mm. In the cathode 2 and the anode 3, the respective terminal portions and the external terminals 4 and 5 are connected by wiring such as molybdenum foil. Even during this lamp assembly process, the cathode 2 has a uniform accuracy, so that the cathode 2 is aligned for each lamp, the distance between the cathode 2 and the anode 3, the assembly to the glass bulb 1, etc. Without fine adjustment for each electrode, it can be performed with high accuracy, the manufacture of the lamp is facilitated, and variation in performance among products can be suppressed.

  Then, by applying a predetermined voltage between the anode 3 and the cathode 2 from an external power source connected to the external terminals 4 and 5, an arc discharge is generated between the anode 3 and the cathode 2, thereby being enclosed. Xenon gas is excited to emit light. This light is guided to the outside through the gas sealing part 11.

  In the present embodiment, as described above, since the alignment accuracy of the cathode 2 and the anode 3 is improved, stable discharge can be performed.

  The electrode for a discharge lamp according to the present invention is not limited to the embodiment shown in FIG. As shown in FIG. 4, the tapered shape of the connecting portion between the body portion 22 and the terminal portion 23 may be connected by a curved surface instead of a truncated cone shape. Furthermore, the electron-emitting material may be concentrated and contained only in the tip 21a on the pointed side of the discharge part 21. For that purpose, in the manufacturing process described above, a raw material containing an electron-emitting substance and a raw material not containing the material are generated, and the tip 21a of the discharge part 21 is injection-molded with the raw material containing the electron-emitting substance. The portion may be formed by injection molding a raw material that does not contain an electron-emitting substance. For example, by using a mold structure disclosed in Japanese Patent Laid-Open No. 2000-280277, injection molding using two kinds of raw materials is possible.

  Further, the discharge part 21 and the body part 22 and the terminal part 23 are not limited to the configuration in which the discharge part 21 and the terminal part 23 are arranged on the same axis, and the central axes of the discharge part 21 and the terminal part 23 are shifted in parallel. A configuration in which the axial direction of the terminal portion 23 intersects at a predetermined angle may be employed. 3 and 4 show the case where the cathode 2 has a rotationally symmetric shape. However, even if the cathode 2 has a complicated shape instead of the rotationally symmetric shape, the cathode 2 is accurately manufactured by the MIM method. can do.

  In the above description, the example in which tungsten is used as the refractory metal that is the main material of the cathode 2 has been described in detail.

  The electron-emitting material is preferably a simple substance or a mixture of oxides such as calcium, barium and strontium which are alkaline earth metals. Alternatively, it may be an oxide of Group IIIa of the Periodic Table of Elements such as scandium, yttrium, lanthanum, cerium, and thorium.

  Also, here, the cathode of a xenon short arc lamp has been described as an example, but the same effect can be obtained when used as a cathode for various other discharge tubes (for example, metal halide lamps and flash lamps). It is done.

It is a longitudinal cross-sectional view which shows the structure of the xenon short arc lamp which used the electrode which concerns on this invention for the cathode. It is a side view which shows the structure of the cathode of FIG. It is a flowchart which shows the manufacturing method of the cathode of FIG. It is a side view which shows another structure of the electrode which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Glass bulb, 2 ... Cathode, 3 ... Anode, 4, 5 ... External terminal, 11 ... Gas enclosure part, 21 ... Discharge part, 22 ... Trunk part, 23 ... Terminal part.

Claims (2)

A discharge lamp electrode comprising an electrode body that substantially discharges and a terminal portion for electrical continuity with the outside, wherein at least the electrode body contains an electron-emitting material,
The electrode for a discharge lamp, wherein the electrode body and the terminal portion are integrally molded and sintered by a metal injection molding method.   The discharge lamp electrode according to claim 1, wherein the discharge end portion of the electrode body has a pointed shape, and an electron-emitting material is concentrated and contained at the tip portion.

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