JP2007042334A - Anode for discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent melting and evaporation of an anode by a simple structure. <P>SOLUTION: A cavity 10 is formed in the anode, and a gas flow-in part 12 for making the gas generated at arc-discharge flow into the cavity is formed at a top end part of the anode, and a gas exhaustion part 8 for exhausting the gas flowing into the cavity outside is formed on a side face of the anode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for a positive electrode used in a discharge lamp, and particularly to a technique for preventing performance deterioration of a short arc type DC discharge lamp.

  First, the basic structure of a short arc discharge lamp (DC type), which is a type of discharge lamp conventionally used, will be described with reference to FIG.

  As shown in FIG. 8, the short arc discharge lamp 100 has a structure in which a negative electrode 102 and a positive electrode 104 are attached to both ends of the arc tube 106. At the time of arc discharge, an arc column is formed in the light emitting portion 108 (a gap between the negative electrode 102 and the positive electrode 104), and the lighting light is used for many purposes.

  However, during arc discharge, an extremely high temperature gas (gas generated by the arc column) always collides with the tip of the positive electrode 104, and the tip is heated to the vicinity of the melting point of the metal material (such as tungsten) of the positive electrode 104. . At that time, tungsten fine particles evaporated from the positive electrode adhere to the inner wall of the arc tube or recrystallize on the surface of the positive electrode. This causes deterioration of lamp performance and shortens the lamp life. In the case of a short arc discharge lamp, this problem is particularly prominent.

  For this reason, there is a social demand for a method for effectively releasing the thermal energy concentrated on the tip of the positive electrode 104. On the other hand, there is one in which the surface area of the positive electrode is increased by roughening the surface of the positive electrode and the radiation efficiency from the positive electrode is increased (see Patent Document 1). In addition, there is a tungsten positive electrode containing an appropriate amount of a high-melting-point oxide in order to prevent recrystallization of the positive electrode at a high temperature (see Patent Document 2).

JP 2003-223865 A

JP 2002-56807 A

  However, the technique of Patent Document 1 can only release heat by the amount of surface area increased by the groove provided in the positive electrode, and has not been able to sufficiently extend the life of the positive electrode. Even with the technique of Patent Document 2, the concentration of thermal energy at the tip of the positive electrode did not change at all, and the life of the positive electrode could not be extended sufficiently.

  In order to solve this problem, the applicant has disclosed a Japanese Patent Application No. 2005-33439 regarding an invention in which a cavity is provided inside a positive electrode, a gas inflow hole is provided at the front end of the positive electrode, and a pressure adjusting hole is provided at the rear end. Although the positive electrode 104 of the short arc discharge lamp of the low output type (several hundred watts) has a small outer shape (diameter is about several millimeters), a pressure adjusting hole is formed at the rear end of the positive electrode. There was a problem that it was difficult to perform highly accurate processing.

(1) The positive electrode for a discharge lamp of the present invention is
A gas inflow part that is provided at the tip and allows gas generated during arc discharge to flow in,
A cavity continuously provided in the gas inflow portion and having a cylindrical shape in the axial direction;
A gas discharge part that is continuously provided in the cavity and discharges the gas flowing into the cavity from the inflow part;
A positive electrode for a discharge lamp comprising:
The gas discharge part is formed by a cut groove extending from the side surface of the positive electrode toward the cylindrical cavity.
The cut groove includes a first surface parallel to the cylindrical axial cross section, a second surface parallel to the first surface and located on the side opposite to the tip, and the first surface. And a third surface adjacent to the second surface and the second surface, and an opening circle is formed on the first surface,
It is characterized by that.

  As a result, since the gas discharge part is formed by the cut groove directed from the side surface of the positive electrode toward the cylindrical cavity, the gas flowing into the cavity can be discharged from the gas discharge part. Can be prevented, and the life of the discharge lamp can be further increased.

(2) The positive electrode for a discharge lamp of the present invention is
A cavity provided inside the positive electrode for the discharge lamp,
A gas inflow portion for introducing gas generated during arc discharge into the cavity, provided at the tip of the positive electrode;
A gas discharge part provided on a side surface of the positive electrode for discharging the gas flowing into the cavity to the outside;
It is provided with.

  As a result, the gas flowing into the cavity can be discharged from the gas discharge section, and the positive electrode can be prevented from being damaged due to high temperature and the life of the discharge lamp can be increased.

(3) The positive electrode for a discharge lamp of the present invention is
The gas discharge part is provided by forming a groove having a predetermined width in a direction reaching the cavity from the side surface of the positive electrode and in a direction orthogonal to the axial direction of the positive electrode.
It is characterized by that.

  As a result, the gas flowing into the cavity is discharged from the gas discharge portion provided by forming a groove with a depth reaching the cavity from the side surface of the positive electrode and perpendicular to the axial direction of the positive electrode. This makes it possible to prevent the positive electrode from being damaged by high temperatures and to increase the life of the discharge lamp.

(4) The positive electrode for a discharge lamp of the present invention is
The positive electrode for a discharge lamp according to claim 2,
The gas discharge part is provided by forming a groove having a predetermined width extending in the axial direction of the positive electrode at a depth reaching the cavity from a side surface of the positive electrode.
It is characterized by that.

  As a result, the gas flowing into the cavity is discharged from a gas discharge portion provided by forming a groove having a depth reaching the cavity from the side surface of the positive electrode and extending in the axial direction of the positive electrode. This makes it possible to prevent the positive electrode from being damaged by high temperatures and to increase the life of the discharge lamp.

(5) The positive electrode for a discharge lamp of the present invention is
The positive electrode is composed of a positive electrode main body portion having a concave portion provided with a cavity therein, and a positive electrode lid portion having a predetermined length convex portion that can be fitted into the concave portion,
Forming a groove having a predetermined width extending in the axial direction from the rear end to the front end of the positive electrode body portion;
By fitting the convex part of the positive electrode lid part into the positive electrode body part, a gas discharge part for discharging the gas flowing into the cavity to the outside is provided on the side surface of the positive electrode.
It is characterized by that.

  Thereby, by fitting the convex part of the positive electrode lid part into the positive electrode main body part, it is possible to discharge the gas flowing into the cavity from the gas discharge part provided on the side surface of the positive electrode, It is possible to prevent the positive electrode from being damaged and to further increase the life of the discharge lamp.

(6) A method for producing a positive electrode for a discharge lamp according to the present invention comprises:
A gas inflow part for allowing gas generated at the time of arc discharge to flow into the cavity at the tip of the positive electrode, and providing a cavity inside the positive electrode,
A gas discharge portion for discharging the gas flowing into the cavity to the outside is a groove having a predetermined width in a direction reaching the cavity from a side surface of the positive electrode and in a direction perpendicular to the axial direction of the positive electrode Formed,
It is characterized by that.

  Thus, the gas flowing into the cavity from the gas discharge part provided by forming a groove with a depth reaching the cavity from the side surface of the positive electrode and perpendicular to the axial direction of the positive electrode Thus, it is possible to produce a positive electrode capable of preventing the positive electrode from being damaged by high temperature and increasing the life of the discharge lamp at a low cost.

(7) A method for producing a positive electrode for a discharge lamp according to the present invention comprises:
The positive electrode is composed of a positive electrode main body having a cavity therein, and a positive electrode lid that can be joined to the positive electrode main body.
Forming a gas inflow portion for allowing gas generated during arc discharge to flow into the cavity at the tip of the positive electrode;
Forming a groove with a predetermined width at a depth reaching the cavity and extending in the axial direction from the rear end to the front end of the positive electrode body part;
By joining the positive electrode lid part to the positive electrode main body part, a gas discharge part for discharging the gas flowing into the cavity to the outside is provided on the side surface of the positive electrode.
It is characterized by that.

  As a result, it is possible to discharge the gas flowing into the cavity from the gas discharge part provided on the side surface of the positive electrode by joining the positive electrode cover part to the positive electrode main body part, and the positive electrode is damaged by high temperature. Therefore, it is possible to manufacture a positive electrode that can increase the life of the discharge lamp at low cost.

1. Structure of Discharge Lamp Positive Electrode 2a FIG. 1 shows the structure of the discharge lamp positive electrode 2a of the present invention. FIG. 1A is a perspective view showing a structure of a positive electrode 2a for a discharge lamp. FIG. 1B is an α-arrow view of the discharge lamp positive electrode 2a shown in FIG. 1A.

  The discharge lamp positive electrode 2a shown in FIG. 1A is made of tungsten, which is a high melting point metal, and a conductive positive electrode support portion 4 that supports the positive electrode 2a is joined to the rear end P3 of the positive electrode 2a. . Note that the purity of tungsten used for the positive electrode 2a is 99.9% or more.

  As shown in FIG. 1A, the positive electrode 2a is formed in a cylindrical shape, and a cavity 10 is provided therein. Assuming a discharge lamp with an output of 130 W, for example, the dimensions of each part are such that the outer diameter of the positive electrode 2a is φ1.8 [mm], the inner diameter (the size of the cavity 10) is φ1.0 [mm], 3.0 [mm].

  As shown in FIG. 1A, a gas inflow hole 12 for allowing a gas generated during arc discharge to flow into the cavity is provided at the tip P1 of the positive electrode 2. In this embodiment, the diameter of the gas inflow hole 12 is the same as the size (diameter) of the cavity 10, but may be a size (diameter) different from the cavity.

  Further, as shown in FIG. 1A, a gas discharge portion 8 is provided on the side surface P <b> 2 of the positive electrode 2. As shown in FIG. 1B, the gas discharge part 8 has a groove having a predetermined width from the side face P2 of the positive electrode 2a to the same depth as the deepest part of the cavity 10 and in a direction perpendicular to the axial direction x of the positive electrode. It is formed and provided. Here, the deepest portion indicates the γ position in FIG. 1B. In this embodiment, the width of the gas discharge part is 0.5 [mm], and the depth from the side surface is 1.4 [mm]. In addition, although the gas discharge part 8 was formed from the side surface P2 of the positive electrode 2a to the same depth as the deepest part of the cavity 10, if it can connect with the cavity 10 and can discharge gas, it will reach to the deepest part of the cavity 10. May not be reached. For example, as shown in FIG. 2, the gas discharge portion 8 may be formed at a depth at the center position of the cavity 10. 2A and 2B are diagrams showing another structure of the positive electrode 2a for the discharge lamp corresponding to FIGS. 1A and 1B, respectively.

  Moreover, the gas discharge part 8 is formed by the notch groove which goes to the cylindrical-shaped cavity 10 direction from the side surface P2 of the positive electrode 2a shown to FIG. 1A. As shown in FIG. 1A, the cut groove has a first surface D1 parallel to a cross section in a cylindrical axial direction (x direction in FIG. 1A), parallel to the first surface, and the tip. The second surface D2 located on the opposite side and the first surface D1 and the third surface D3 adjacent to the second surface D2 are configured in a U shape, and the first surface includes An opening circle C is formed.

  The positive electrode 2 and the positive electrode support portion 4 shown in FIG. 1 are formed by processing a tungsten steel rod to a predetermined diameter, and the cavity 10 and the gas inflow portion 12 of the positive electrode 2 are formed by drilling the cut steel piece. It is provided by cutting. Note that the positive electrode 2 and the positive electrode support 4 shown in FIG. 1A may be integrally formed by lathe processing or the like.

  Moreover, the gas discharge part 8 is shape | molded by the U shape by performing wire electrical discharge machining from (beta) position in FIG. 1A. In addition, although the 3rd surface D3 shown to FIG. 1A is a plane, it may not become a plane depending on the processing method. For example, when a wire having the same diameter as the width of the gas discharge part moves back and forth in one direction to perform electric discharge machining, the third surface D3 shown in FIG. 1A is a curved surface.

  In this embodiment, as shown in FIG. 1A, the positive electrode 2 is formed by the wire electric discharge machining so that the gas discharge portion 8 is formed with a thickness sufficient to maintain the required strength. The electrodes can be integrally formed without being separated as described later.

  As described above, the depth of the groove constituting the gas discharge portion 8 shown in FIG. 1 may be determined so as not to prevent the outflow of gas and to obtain a desired strength of the positive electrode.

2. Gas Flow in the Discharge Lamp Positive Electrode 2a The gas flow generated during arc discharge in the discharge lamp positive electrode 2a shown in FIG. 1 will be described below with reference to FIG.

  When the arc discharge starts, first, as shown in FIG. 3, a high-temperature, high-speed gas flow is generated along with the arc column from the negative electrode 1 toward the positive electrode 2a (flow 1 in FIG. 3). This high-temperature, high-speed gas flow flow 1 flows into the cavity 10 of the positive electrode 2 from the gas inflow hole 12 (flow 2 in FIG. 3). Further, the hot gas flow 2 in the cavity moves along the cavity inner wall and is discharged from the gas discharge unit 8 (flow 3 in FIG. 3).

  Thus, by discharging the gas flowing into the cavity 10 of the positive electrode 2 from the gas discharge part 8, it is possible to prevent the positive electrode 2a from being damaged due to high temperature.

3. Structure of Positive Electrode for Discharge Lamp (Separation Type) 2b The positive electrode for discharge lamp 2b (separation type) in the second embodiment is composed of a positive electrode body 20 and a positive electrode lid 30 as shown in FIG. Is done. FIG. 4A is a diagram showing the structure of the discharge lamp positive electrode 2b after assembly. FIG. 4B is a diagram showing the structure of the discharge lamp positive electrode 2b before assembly.

  As shown in FIG. 4B, the cavity 10 is provided inside the positive electrode main body 20, and the positive electrode main body 20 has a concave portion 22 fitted into a convex portion 32 included in the positive electrode lid portion 30. Further, a gas inflow portion 12 for allowing a gas generated during arc discharge to flow into the cavity 10 is formed at the tip of the positive electrode main body portion 20.

  The positive electrode main body 20 shown in FIG. 4B has a groove 24 having a predetermined width extending from the side surface of the positive electrode to the cavity and extending in the axial direction of the positive electrode (x direction in FIG. 4). Is formed. Moreover, the gas discharge part 8 is provided by inserting the convex part 32 of the said positive electrode cover part 30 shown in FIG. 4B in the convex part 22 of the said positive electrode main-body part.

  Here, if the total cross-sectional area of the gas discharge part 8 shown in FIG. 4 is designed so as not to be smaller than the cross-sectional area of the gas inflow part 12, an experiment that can effectively prevent the positive electrode 2b from becoming hot is performed. Results were obtained. As shown in FIG. 4, the cross-sectional area of the gas inflow portion 12 is the width of the groove w, the length of the groove D, the number of grooves N, and the length of the convex portion of the positive electrode lid 30. If d, it can be calculated by S = W × (D−d) × N (when the R portion of the groove is ignored).

Specifically, the following experiment was performed on the relationship between the cross-sectional area S ₁ of the gas inlet 12 and the cross-sectional area S ₂ of the gas outlet 8. Three types of prototypes A (S ₁ > S ₂ ), B (S ₁ = S ₂ ), and C (S ₁ <S ₂ ) are prepared, and a normal electrode that is not drilled at the tip of the positive electrode The discharge lamp used was evaluated. The temperature of the electrode was measured with a thermoviewer and the temperature of the arc tube was measured with a thermocouple. As a result, the three types of prototypes A, B, and C described above had lower temperatures than ordinary discharge lamps. Further, among the three types of prototypes, the prototype A had a higher temperature, and the prototypes B and C had temperatures lower than the prototype A, which were substantially the same value. In prototype A, vortices were observed near the gas inlet 12 at the tip of the positive electrode by the thermoviewer, whereas no vortices were found in prototypes B and C. This is considered to be because if the gas discharge part 8 is small, the gas air flow that has entered from the gas inflow part 12 cannot be discharged at the same flow rate, but accumulates inside the positive electrode and a vortex is generated.

4). Gas Flow at Discharge Lamp Positive Electrode 2b A gas flow generated during arc discharge in the discharge lamp positive electrode 2b shown in FIG. 4 will be described below with reference to FIG.

  When the arc discharge starts, first, as shown in FIG. 5, a high-temperature, high-speed gas flow is generated together with the arc column from the negative electrode 1 toward the tip P1 of the positive electrode 2a (flow 1 in FIG. 5). The high-temperature, high-speed gas flow flow1 flows into the cavity of the positive electrode 2 from the gas inflow hole 12 (flow2 in FIG. 5).

  Further, the hot gas flow 2 in the cavity moves along the inner wall of the cavity and is discharged from the gas discharge unit 8 (flow 3 in FIG. 5). Here, in the discharge lamp positive electrode 2b, as shown in FIG. 5, the gas discharge part 8 is extended in the axial direction (x direction in FIG. 4) from the rear end to the front end of the positive electrode main body part 20. A groove having a width is formed and provided. For this reason, as shown in FIG. 5, the gas flow 2 in the cavity 10 hits the convex portion 24 of the positive electrode lid portion 22 and is discharged in an obliquely downward direction in the drawing (flow 3 in FIG. 5).

  In this way, by dividing the positive electrode 2b into the positive electrode main body 20 and the positive electrode lid 30 and processing them separately, the cross-sectional area of the gas discharge part and the discharge direction of the hot gas flow can be easily adjusted. Thus, the positive electrode 2b having desired performance can be produced at a low cost.

  An experiment was conducted by creating a conventional positive electrode having the same shape and size as the positive electrode 2b shown in FIG. 4 and having no cavity, gas inflow portion, and gas discharge portion. When the temperature change of the discharge electrode using the positive electrode 2b of this invention and the conventional positive electrode was compared, as shown in FIG. 6, the discharge lamp using the positive electrode 2b shown in FIG. However, it was found that the temperature rise was slow and the temperature during stabilization was about 20% lower.

  In the above embodiment, the positive electrode lid 30 having the convex portion 32 is fitted into the positive electrode main body 20. However, the positive electrode lid 30 has a structure having no convex portion, and the positive electrode main body portion. You may make it join the end surfaces of 20 and the positive electrode cover part 30 together.

5. Other Embodiments As a method for joining the members, a method such as brazing, shrink fitting, and hammering may be used as long as the method can withstand use at high temperatures.

  In the above embodiment, tungsten is used as the material of the positive electrode 2 and the positive electrode support portion 4, but other materials such as molybdenum, tantalum, niobium, rhenium, osmium, iridium, ruthenium, hafnium, and alloys thereof are used. A refractory metal may be used.

  In the above embodiment, the tip P1 of the positive electrode 2 is formed in a plane as shown in FIG. 1A. However, for example, it is formed in a pointed shape, a semicircular shape, a trapezoidal shape, or the like. You may form in a shape.

  In the above embodiment, as shown in FIG. 1, the contour of the positive electrode 2 and the cavity provided therein are both cylindrical, but the shape is not limited thereto.

  In the first embodiment, one groove having a predetermined width constituting the gas discharge portion is provided. In the second embodiment, two grooves having a predetermined width constituting the gas discharge portion are provided. You may make it provide above. Thus, by providing one or more grooves that can be connected to the cavity 10 and can discharge gas from the side surface of the positive electrode, a small-diameter electrode that can discharge gas can be easily manufactured.

  Moreover, in the said embodiment, although the gas exhaust part 8 was shape | molded in the U-shape, it is not limited to this, You may shape | mold in another shape. For example, as shown in FIG. 7A, the second surface D2 constituting the cut groove shown in FIG. 1A is formed obliquely with respect to the axial cross section of the positive electrode, and the gas discharge part 8 is provided so as to spread outward. May be. Thereby, the gas discharge direction can be changed to a direction along the second surface D2 formed obliquely with respect to the axial section of the positive electrode. 7A and 7B are diagrams showing another structure of the positive electrode 2a for the discharge lamp corresponding to FIGS. 1A and 1B, respectively.

It is a figure which shows the structure of the positive electrode 2a for discharge lamps. It is a figure which shows the other structure of the positive electrode 2a for discharge lamps. It is a figure which shows the movement of the gas inside and outside the cavity of the positive electrode 2a. It is a figure which shows the structure of the positive electrode 2b for discharge lamps. It is a figure which shows the movement of the gas inside and outside the cavity of the positive electrode 2b. It is a figure which shows the experimental result which compared the temperature change of the discharge lamp using the positive electrode 2b and the conventional positive electrode. It is a figure which shows the structure of the positive electrode for discharge lamps of other embodiment. It is a figure which shows the basic structure of the conventional short arc discharge lamp (DC type).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Negative electrode 2 ... Positive electrode 4 ... Positive electrode support part 8 ... Gas discharge part 10 ... Hollow 12 ... Gas inflow part

Claims (8)

A gas inflow part that is provided at the tip and allows gas generated during arc discharge to flow in,
A cavity continuously provided in the gas inflow portion and having a cylindrical shape in the axial direction;
A gas discharge part that is continuously provided in the cavity and discharges the gas flowing into the cavity from the inflow part;
A positive electrode for a discharge lamp comprising:
The gas discharge part is formed by a cut groove extending from the side surface of the positive electrode toward the cylindrical cavity.
The cut groove includes a first surface parallel to the cylindrical axial cross section, a second surface parallel to the first surface and located on the side opposite to the tip, and the first surface. And a third surface adjacent to the second surface and the second surface, and an opening circle is formed on the first surface,
A positive electrode for a discharge lamp. A cavity provided inside the positive electrode for the discharge lamp,
A gas inflow portion for introducing gas generated during arc discharge into the cavity, provided at the tip of the positive electrode;
A gas discharge part provided on a side surface of the positive electrode for discharging the gas flowing into the cavity to the outside;
A positive electrode for a discharge lamp, comprising: The positive electrode for a discharge lamp according to claim 2,
The gas discharge part is provided with a groove having a predetermined width in a direction reaching the cavity from a side surface of the positive electrode and in a direction orthogonal to the axial direction of the positive electrode.
It is characterized by that. The positive electrode for a discharge lamp according to claim 2,
The gas discharge part is provided by forming a groove having a predetermined width extending in the axial direction of the positive electrode at a depth reaching the cavity from a side surface of the positive electrode.
It is characterized by that. The positive electrode for a discharge lamp according to claim 4,
The positive electrode is composed of a positive electrode main body having a concave portion provided with a cavity therein, and a positive electrode lid having a predetermined length of convex portion that can be fitted into the concave portion,
Forming a groove having a predetermined width extending in the axial direction from the rear end to the front end of the positive electrode body portion;
By fitting the convex part of the positive electrode lid part into the positive electrode body part, a gas discharge part for discharging the gas flowing into the cavity to the outside is provided on the side surface of the positive electrode.
It is characterized by that.   A discharge lamp comprising the positive electrode for a discharge lamp according to any one of claims 1 to 5. A gas inflow part for allowing gas generated during arc discharge to flow into the cavity at the tip of the positive electrode and a cavity in the positive electrode are provided,
A gas discharge portion for discharging the gas flowing into the cavity to the outside is a groove having a predetermined width in a direction reaching the cavity from a side surface of the positive electrode and in a direction perpendicular to the axial direction of the positive electrode Formed,
A method for producing a positive electrode for a discharge lamp. The positive electrode is composed of a positive electrode main body having a cavity therein, and a positive electrode lid that can be joined to the positive electrode main body.
Forming a gas inflow portion for allowing gas generated during arc discharge to flow into the cavity at the tip of the positive electrode;
Forming a groove with a predetermined width at a depth reaching the cavity and extending in the axial direction from the rear end to the front end of the positive electrode body part;
By joining the positive electrode lid part to the positive electrode main body part, a gas discharge part for discharging the gas flowing into the cavity to the outside is provided on the side surface of the positive electrode.
A method for producing a positive electrode for a discharge lamp.

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