TW202249063A - Discharge lamp and manufacturing method of electrode used in discharge lamp characterized in that a groove along the circumferential direction of the electrode is formed and the emissivity of the coating layer on the groove is greater than that of the groove, thereby, the electrode obtains the desired heat dissipation effect - Google Patents

Abstract

To construct an electrode capable of obtaining the desired heat dissipation effect. In the electrode 30 of the discharge lamp 10, the heat dissipation structure 40 constructed by the groove 42 and the two structures of being provided in the coating layer 44 and including heat dissipation function (hereinafter, the side part referred to as the heat dissipation function part J) are formed on the side 34S of the body part 34.

Description

Discharge lamp and method for producing electrode for discharge lamp

The present invention relates to a discharge lamp such as a short-circuit arc type discharge lamp, and particularly relates to heat dissipation of an electrode.

In a discharge lamp, during lighting, the tip of the electrode becomes high temperature, the electrode material such as tungsten is melted and evaporated, and the discharge tube is blackened, resulting in a decrease in the illuminance of the lamp. In order to prevent overheating of the electrode including the tip of the electrode, the surface area of the side surface of the electrode body is increased by screw-shaped or concave-convex grooves, and tungsten powder or metal oxide is sintered on the groove to form Heat dissipation layer (refer to Patent Document 1). [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2000-306546

[Problem to be solved by the invention]

For the grooves formed on the surface of the electrode, the shape of the groove (its shallowness, pitch, etc.) is determined for the purpose of enlarging the surface area of the electrode, but the heat dissipation performance, that is, the emissivity also changes due to the shape of the groove. In addition, the emissivity of the heat dissipation layer is also different due to the sintered metal oxide and other materials. Even if the heat dissipation layer is formed on the groove without considering the relationship with the groove, the heat dissipation performance cannot be further improved, and sometimes it has a heat dissipation effect. risk of decline.

Therefore, it is required to form an electrode that can obtain a desired heat dissipation effect. [means used to solve a problem]

A discharge lamp as an aspect of the present invention includes a discharge tube, and a pair of electrodes disposed opposite to each other in the discharge tube, and at least one of the electrodes, which is at least on the side of the body of the electrode, includes an electrode with an emissivity greater than that of the electrode. The heat dissipation structure of the substrate surface. Furthermore, on the heat dissipation structure, a coating layer is formed to further increase the emissivity of the side portion of the electrode trunk portion provided with the heat dissipation structure.

Moreover, the heat dissipation effect caused by the heat dissipation function of the heat dissipation structure and the heat dissipation effect of the side part of the electrode body due to the heat dissipation function of the coating can be determined according to the electrode material, the characteristics of the heat dissipation structure, and the reflectivity of the coating. work most efficiently. It is concerned with maximizing the emissivity of the side parts of the body of the electrode according to the two heat dissipation functions.

In the side part of the electrode body where the heat dissipation structure and the coating are layered, the heat dissipation effect of the grooves formed by enlarging the coating area for simply improving the heat dissipation performance of the coating can be obtained. , the heat dissipation effect that cannot be obtained.

As a heat dissipation structure, it can be applied to various structures such as grooves or concave-convex shapes, coatings, etc. For example, it is composed of grooves along the circumferential direction of the electrode body or the electrode axial direction, and the emissivity of the coating is greater than that of the grooves. .

As a coating, it can be made of materials with high emissivity, which can be selected according to electrode materials, service temperature, etc. Coating, which is composed of materials including at least metal and/or ceramics. It may also consist of a coating containing at least the same type of metal as the electrode material. In consideration of improving heat dissipation performance, for example, it may be composed of at least zirconium and/or tantalum, and may also contain tungsten, molybdenum, etc. as electrode materials.

When the heat dissipation structure is formed with grooves along the circumference of the electrode body, the emissivity of the heat dissipation structure and the coating can be 0.8 or more when expressed by the following formula. ε=1/(l+(L/S)╳(l/εo-1)) However, L represents the length in the axial direction of the region where the grooves are formed, and S represents the total cross-sectional length. εo represents the emissivity of the coating. Also, the L/S system is set to be 0.9 or less.

The thickness of the coating, the shape of the groove, etc., can be applied to various structures. For example, the distance from the center axis of the electrode to the layer surface of the coating may be shorter than the distance from the center axis of the electrode on the side of the body of the electrode not provided with a heat dissipation structure.

On the tapered surface of the tapered portion on the tip side of the electrode, it may also be provided with a non-coated heat dissipation structure that is not covered by the coating. Alternatively, a non-coated heat dissipation structure that is not covered with a coating may be provided on the side of the trunk portion of the electrode on the side closer to the electrode support rod than the heat dissipation structure. Non-coated heat dissipation structure, which can be applied to places far away from heat dissipation structure.

As a method of manufacturing a discharge lamp according to another aspect of the present invention, it is characterized in that an electrode having a columnar body and a tapered portion on the tip side is formed, and grooves along the circumferential direction of the electrode are formed on the side of the body, and are formed by coating. On the grooves, a coating having an emissivity greater than that of the grooves is formed. [Efficacy of the invention]

When according to the present invention, it is possible to constitute an electrode that can obtain a desired heat dissipation effect.

[Mode for Carrying Out the Invention]

Short-circuit arc type discharge lamp 10, which is a large-scale discharge lamp capable of outputting high-brightness light, includes a roughly spherical discharge tube (light-emitting tube) 12 made of transparent quartz glass, and is disposed opposite (coaxially) in the discharge tube 12 There is a pair of electrodes 20,30 made of tungsten. On both sides of the discharge tube 12, the sealing tubes 13A and 13B made of quartz glass are connected to the discharge tube 12 and formed integrally. In the discharge space DS in the discharge tube 12, rare gases such as mercury and halogen or argon are sealed.

The electrode 20 serving as the cathode is supported by the electrode support rod 17A. A glass tube (not shown) penetrating the electrode support rod 17A, a conductive rod 15A connected to an external power source, and a metal foil 16A connecting the electrode support rod 17A and the conductive rod 15A are sealed in the sealing tube 13A. Similarly to the electrode 30 serving as the anode, a glass tube (not shown) through which the electrode support rod 17B is penetrated, metal foil 16B, conductive rod 15B, and other components are sealed. In addition, mouthpieces 19A, 19B are attached to the ends of the sealing pipes 13A, 13B, respectively.

When a voltage is applied to the pair of electrodes 20 and 30 , an arc discharge is generated between the electrodes 20 and 30 , and light is emitted to the outside of the discharge tube 12 . Here, electric power of 1 kW or more is input. The light emitted from the discharge tube 12 is guided to a predetermined direction by a reflector (not shown).

FIG. 2 is a schematic top view of an electrode (anode) 30 . Furthermore, the electrode (cathode) 20 may also have the same structure.

The electrode 30 has an electrode tip surface 32T, and is composed of a tapered portion (hereinafter referred to as the tip-side tapered portion) 32 connected to a columnar portion (hereinafter referred to as the trunk portion) 34 of the electrode support rod 17B. Here, the electrode 30 is integrally formed, but the electrode 30 may be formed by bonding the tip-side tapered portion 32 and the trunk portion 34 by diffusion bonding such as SPS. In addition, it can also be joined through an intermediate member. The electrode 30 is made of, for example, tungsten.

A heat dissipation structure 40 is provided on the side surface 34S of the trunk portion 34 (see hatched portion in FIG. 2 ). The heat dissipation structure 40 has a higher emissivity than the surface 34T of the base material of the trunk portion 34, that is, the surface that does not dare to adopt a special heat dissipation structure, and has the function of improving heat dissipation. As shown in the enlarged part of FIG. 2 , the heat dissipation structure 40 is a structure in which grooves 42 along the circumferential direction (around the electrode axis) are formed at predetermined pitches. The groove 42 can be formed by, for example, laser or cutting.

Also, for the side surface 34S of the trunk portion 34 provided with this heat dissipation structure 40 (groove 42 ), the coating layer 44 is formed thereon. The coating 44 , here, uses a composition with a higher emissivity than the groove 42 . For example, the coating 44 is composed of zirconium nitride or zirconium carbide, zirconium compounds. Alternatively, tantalum-based materials such as tantalum nitride or ceramic-based materials such as alumina are included. Also, the coating 44 may also contain the same metal as the electrode 30, ie, tungsten, molybdenum, or the like. In addition, metals such as titanium or their oxides, alloys added with nickel, chromium, etc. can be selected according to the use temperature.

The heat dissipation structure 40 composed of the groove 42 and the two heat dissipation function parts of the coating 44 (hereinafter, this side part is referred to as the heat dissipation function part J) are formed on one side of the side surface 34S of the trunk part 34. part. As before, in order to increase the amount of heat dissipated, the grooves are formed for the purpose of increasing the surface area of the electrode, instead of making the grooves as an auxiliary heat dissipation structure, and combining the effects caused by the grooves 42. The heat dissipation function and the heat dissipation function caused by the coating 44 are formed by combining the heat dissipation function to the maximum extent in the heat dissipation function part J.

Thereby, heat dissipation (emissivity) is maximized, and an increase in electrode temperature can be suppressed. Since the coating 44 is formed on the groove 42, compared with the coating on the surface 34T of the electrode substrate, the contact area becomes larger, and the close contact of the coating can be improved.

Moreover, since the side surface 34S of the body part 34 is provided with the heat dissipation function part J, exposure to an electric arc, a torch, etc. can be suppressed. Therefore, peeling and thinning of the coating layer can be suppressed against a rise in temperature of the electrode 30 due to lamp lighting. Moreover, the groove 42 includes a heat dissipation function, so even if the coating peels off and becomes thinner, a certain degree of heat dissipation can be maintained.

In particular, as shown in FIG. 2, the height of the top 42P of the groove 42 covered with the coating 44, that is, the distance from the electrode axis C to the top 42P (layer surface), is located at a lower side than the side 34S of the trunk portion 34. It should also be close to the center side of the electrode. The top 42P of the groove 42 is located at a position retracted from the side 34S of the trunk portion 34, thereby effectively suppressing peeling and thinning of the coating caused by arc or torch.

In this embodiment, by applying the formula for calculating the emissivity of the combination groove 42 and the coating 44, the shape of the combination groove 42 and the heat dissipation (emissivity) of the coating 44 can be effectively improved. The heat dissipation (emissivity). In the following, this will be described in detail.

FIG. 3 is a graph showing the correlation between the shape of the groove 42 and the emissivity of the coating 44 . Fig. 4 is a diagram showing the shape of grooves.

The emissivity ε of the surface on which grooves are formed can be approximated by the following formula (1). ε=l/(1+(L/S)╳(l/εo－1)) ... (1) However, L represents the length in the axial direction (along the side surface 34S) of the region where the groove is formed, and S represents the entire length along the groove (total cross-sectional length) in the cross-sectional view of the groove (see FIG. 4 ).

The value of L/S is related to the groove pitch and the number of grooves, that is, the groove depth (slope length) in the groove forming range. The smaller the value of L/S, the larger the depth of the groove and the larger the number of pitches. The closer the value of L/S is to 1, the shallower the groove and the smaller the number of pitches. In addition, εo represents the intrinsic emissivity of a material.

The intrinsic emissivity εo of the replacement material is the emissivity ε of the coating 44 (herein, expressed as εcoat), thereby deriving the emissivity ε of the heat dissipation function part J (herein, expressed as εgroove+coat). However, the coating layer 44 is very thin compared with the size (depth) of the groove 42, so its thickness can be neglected.

FIG. 3 shows the emissivity εgroove+coat of the heat dissipation function part J derived from the combination of the emissivity εcoat of the coating 44 and the L/S of the groove 42 . For example, when the emissivity εcoat of the coating 44 is 0.8 and the groove 42 is formed with an L/S value of 0.35, the emissivity εgroove+coat of the heat dissipation function part J becomes 0.92. Also, when forming the groove 42 in which the emissivity εcoat of the coating layer 44 is 0.5 and the value of L/S becomes 0.2, the emissivity εgroove+coat of the heat dissipation function part becomes 0.83.

Here, L/S and the emissivity εcoat of the coating layer 44 are determined so that the emissivity εgroove+coat of the heat dissipation function part J becomes 0.8 or more. However, the L/S of the groove 42 along the circumferential direction is determined to be 0.9 or less so that the groove 42 does not have the same concave-convex shape as the rough surface. 0.8 is determined based on the emissivity of 0.4 of tungsten used as an electrode material, for example.

The emissivity εgroove+coat of the two heat dissipation functions including the groove 42 and the coating 44 is derived using the above formula (1), whereby the composition of the coating 44 and the shape of the groove 42 can be freely selected , making it the desired emissivity. For example, the emissivity of the trunk portion 34 can be effectively (synergically) increased by adopting a composition and a shape with higher heat dissipation. In particular, the emissivity of the coating 44 is determined to be greater than the emissivity of the groove 42, whereby the heat dissipation function of the coating 44 can be used as the main function, and the heat dissipation function of the groove 42 can be used as a secondary heat dissipation function part J.

For example, when the coating 44 with higher emissivity is used, the value of L/S satisfying 0.8 or more is wider, and the shapes of the grooves 42 that can be selected are more. Since the combination can be optimized, even if L/S is made large, that is, even if the groove 42 is made shallow, high emissivity can be maintained. Also, when the groove 42 is shallow, it is easier to apply (adhere) the coating 44 to the depth of the groove 42 .

With the value of L/S of the groove 42, when the coating 44 is wrongly selected, only the emissivity that is not much different from that of the coating 44 can be obtained, and a sufficient heat dissipation effect cannot be obtained. However, referring to the table of Fig. 3, even for various groove shapes (values of L/S), a high emissivity εgroove+coat can be maintained.

For the trunk portion 34 provided with such heat dissipation function portion J, on the tapered side (surface) 32S of the tip side tapered portion 32, there is provided a heat dissipation structure (not a coating) on which only grooves are formed and no coating is formed thereon. Coated thermal structure) 50.

During lamp lighting, the tapered side 32S is exposed to an electric arc or a torch. Therefore, when a coating is temporarily provided, peeling of the coating may occur. However, since such a coating is not provided, it is possible to Staining of the inside of the discharge tube 12 by the composition of the coating is suppressed. Also, by determining L/S so that the emissivity of the groove 42 becomes higher, the heat dissipation of the entire electrode 30 can be further improved.

In addition, between the heat dissipation structure 40 and the heat dissipation structure 50, the side surface part 33 which consists of an electrode base material surface is provided, and it does not adjoin and is far away from each other. By providing such a side portion 33, during lamp lighting, the arc or torch can be suppressed and moved to the heat dissipation function portion having the coating. Furthermore, the boundary portion 33P between the tip-side tapered portion 32 and the trunk portion 34 is relatively rounded, so that the coating layer 44 can be protected from abnormal discharges and overheating caused by abnormal discharges.

The electrode 30 of such a discharge lamp can be produced as follows. First, an electrode having a columnar body and a tapered portion on the tip side is molded, and the side of the body is processed by laser or cutting to form grooves along the circumferential direction. Also, coating is formed on the groove by coating. At this time, it is determined that the emissivity of the coating is greater than that of the groove, thereby forming a heat dissipation function part with a higher emissivity. In addition to spray coating, known methods such as vapor deposition, sputtering, and CVD may be used as long as uniform coating is possible. The coating after coating can also be sintered by furnace (heating device) or laser.

Next, a discharge lamp according to a second embodiment will be described using FIG. 5 . In the second embodiment, on the heat dissipation structure composed of grooves, the heat dissipation function part of the coating layer is formed on the tapered part on the tip side and the trunk part, and the heat dissipation structure formed only with grooves , which is set on the side of the electrode support rod.

Fig. 5 is a schematic plan view of electrodes of a discharge lamp according to a second embodiment. The anode 30 ′ includes a tip-side tapered portion 32 and a trunk portion 34 . On the heat dissipation structure 40 ′ formed by the groove, the heat dissipation function portion J of the coating 44 ′ is formed continuously from the midway of the trunk portion 34 to the tip side tapered portion 32 . In addition, on the side surface 34S of the trunk portion 34, on the side closer to the electrode support bar 17B than the heat dissipation function portion J, there is provided a heat dissipation structure 50' (non-coated heat dissipation structure) consisting only of grooves along the circumferential direction. .

For example, the coating 44' formed on the tapered portion 32 on the tip side can suppress peeling or disappearance due to arcs or torches, etc., for reasons such as low output of the lamp and small size of the electrodes. Therefore, in addition to the trunk portion 34, the tip-side tapered portion 32 is also formed with the coating layer 44', whereby heat dissipation can be improved. Furthermore, similarly to the first embodiment, between the heat dissipation structure 40' and the heat dissipation structure 50' formed with the coating layer 44', a region of the electrode base surface may be provided.

In the first and second embodiments, although the heat dissipation structure is formed by grooves along the circumferential direction, it may also be formed by grooves along the axial direction of the electrodes. Also, heat dissipation structures other than grooves may be used. For example, a pear skin rough surface, blackening suppressor, etc. made by sandblasting or the like may be used to form a heat dissipation structure. If blackening suppression is the main purpose, a blackening suppressor may be used, and if improvement in heat dissipation is required, grooves may be formed. If low cost is required, pear skin rough surface can be used. It is only necessary to determine the heat dissipation structure according to the shape of the electrode, the electrode material, and the ease of processing such as cutting.

In addition, in order to prevent peeling of the coating layer formed on the heat dissipation structure, it is also possible to form a coating layer of a different material as the heat dissipation structure. That is, it is possible to overlay the coating on the coating (radiation structure).

10: discharge lamp 30: electrode 40: Heat dissipation structure 42: Groove 44: coating 50: Heat dissipation structure (non-coated heat dissipation structure)

Fig. 1 is a plan view of a discharge lamp according to a first embodiment. Fig. 2 is a schematic plan view of the electrodes of the first embodiment. Fig. 3 is a diagram showing a table showing the correlation between the shape of the groove and the emissivity of the coating. Fig. 4 is a diagram showing the shape of grooves. Fig. 5 is a schematic plan view of electrodes of a discharge lamp according to a second embodiment.

17B: electrode support rod

30: electrode

32: Tip side taper

32S: tapered sides

32T: electrode tip face

33: side part

33P: Boundary

34: Torso

34S: side

34T: substrate surface

40: Heat dissipation structure

42: Groove

42P: top

44: coating

50: Heat dissipation structure (non-coated heat dissipation structure)

Claims (11)

A discharge lamp comprising: discharge tube; and A pair of electrodes are arranged facing each other in the discharge tube, At least one of the electrodes includes a heat dissipation structure with emissivity greater than that of the surface of the electrode base material in at least the side surface of the electrode body, and a side part of the electrode body with the heat dissipation structure is formed on the heat dissipation structure. emissivity of the coating. The discharge lamp according to claim 1, wherein the heat dissipation structure is formed by grooves along the circumferential direction of the electrode body or the electrode axial direction, The emissivity of the coating is greater than the emissivity of the groove. The discharge lamp according to claim 1 or 2, wherein the heat dissipation structure is formed by grooves along the circumference of the electrode body, Combined with the emissivity of the heat dissipation structure and the coating, when expressed by the following formula, it is 0.8 or more, ε=1/(1+(L/S)╳(1/εo-1)) However, L represents the axial length of the groove formation region, S represents the total cross-sectional length, εo represents the emissivity of the coating layer, and L/S is set to be 0.9 or less. The discharge lamp according to claim 1 or 2, wherein the distance from the electrode center axis to the layer surface of the coating is greater than the distance from the electrode center axis on the side of the electrode trunk without the heat dissipation structure short. The discharge lamp according to claim 1 or 2, wherein in the tapered surface of the tip-side tapered portion of the electrode, it includes a non-coated heat dissipation structure not covered by the coating. The discharge lamp according to claim 1 or 2, wherein the body side of the electrode includes a non-coated heat dissipation structure not covered by the coating on the side closer to the electrode support rod than the heat dissipation structure. The discharge lamp according to claim 5, wherein the non-coated heat dissipation structure is far away from the heat dissipation structure. The discharge lamp according to claim 1 or 2, wherein the coating contains at least metal and/or ceramics. The discharge lamp according to claim 1 or 2, wherein the coating is composed of at least the same type of metal as the electrode material. The discharge lamp according to claim 1 or 2, wherein the coating contains at least zirconium and/or tantalum. A method for manufacturing an electrode for a discharge lamp, forming an electrode having a columnar body and a tapered portion on the tip side, For the side of the torso, grooves are formed along the circumferential direction of the electrode, By coating, a coating having an emissivity greater than that of the groove is formed on the groove.

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