JP4914970B2 - Discharge lamp electrode and manufacturing method thereof - Google Patents

Description

  The present invention relates to an electrode structure of a discharge lamp, and more particularly to improvement of heat dissipation.

  Conventionally, as a heat dissipation measure in the anode, it has been known to increase the capacity of the anode. However, when the capacity of the anode is increased, there is a problem that the anode becomes heavy and the lead rod supporting the anode is broken during transportation.

  Patent Document 1 discloses an anode in which a metal porous layer made of a mixture of tungsten and tantalum is formed on the surface of the anode. By providing such a metal porous layer, the heat dissipation effect can be enhanced.

  Patent Document 2 discloses an anode in which fins are provided on the outer peripheral surface, the anode surface area is enlarged, and the radiation efficiency from the anode is increased.

JP-A-2-256150

JP 2002-117806 JP

  In both Patent Documents 1 and 2, the heat dissipation effect can be enhanced by increasing the surface area of the anode, but sufficient heat dissipation cannot be performed. Furthermore, there is a limit to reducing the weight of the anode.

  It is an object of the present invention to provide an electrode structure that can reduce the load on an electrode lead rod that supports an electrode and can suppress an increase in temperature.

  1) A discharge lamp electrode according to the present invention is 1) an electrode main body made of a high melting point material, and 2) a discharge lamp electrode provided with a hollow cylindrical heat dissipating member provided on the side of the electrode main body. 3) The heat dissipating member is made of an insulating ceramic material having higher thermal conductivity and heat radiation than the high melting point material, and substantially the same thermal expansion coefficient as the high melting point material. Since the specific gravity of the material is lighter than that of the electrode body, it is possible to provide an electrode structure that can reduce the load on the electrode lead rod that supports the electrode and can suppress an increase in temperature.

  2) The discharge lamp electrode according to the present invention has a metal buffer layer solid-phase bonded to the heat dissipation member between the electrode body and the heat dissipation member. Therefore, the adhesion between the heat dissipation member and the electrode body can be enhanced.

3) In the discharge lamp electrode according to the present invention, the heat dissipation member has a thermal conductivity of 170 W / mK or more, a thermal emissivity of 0.50 or more, and a thermal expansion coefficient of 4.0 * 10 ^{−6 to} 5.0 * 10 ⁻⁶ . Therefore, it is possible to provide an electrode structure that can reduce the load on the electrode lead rod that supports the electrode and can suppress an increase in temperature.

  4) In the discharge lamp electrode according to the present invention, the heat dissipating member is composed of one kind or a mixture of two or more kinds selected from nitride ceramics or carbide ceramics. Therefore, it is possible to provide an electrode structure that can reduce the load on the electrode lead rod that supports the electrode and can suppress an increase in temperature.

  5) In the electrode for a discharge lamp according to the present invention, the outer diameter of the electrode main body in contact with the heat radiating member is tapered as it goes from the front end to the rear end, and the heat radiating member in contact with the electrode main body The inner diameter of the inner peripheral surface is tapered as it goes from the front end to the rear end, and the inner peripheral surface of the heat radiating member and the side surface of the electrode body are fitted. Therefore, the adhesion between the heat dissipation member and the electrode body can be enhanced.

  6) In the discharge lamp electrode according to the present invention, a transmission layer in which fine powder of a ceramic material constituting the heat dissipation member is sintered is provided between the heat dissipation member and the electrode body. Therefore, the adhesion between the heat dissipation member and the electrode body can be enhanced.

  7) A method for producing an electrode for a discharge lamp according to the present invention includes: 1) preparing an electrode body composed of a high melting point material; 2) having higher thermal conductivity and heat radiation than the high melting point material; A hollow cylindrical member made of a ceramic material having substantially the same thermal expansion coefficient as that of the high melting point material and covering the side surface of the electrode body is prepared. 3) The hollow cylindrical member is mounted on the side surface of the electrode body. Therefore, it is possible to provide an electrode that can reduce the load on the electrode lead rod that supports the electrode and can suppress an increase in temperature.

  8) In the method for manufacturing an electrode for a discharge lamp according to the present invention, before mounting the hollow cylindrical member on the electrode body, the fine particle powder of the ceramic material constituting the heat dissipation member is attached to the electrode body, After sintering, the hollow cylindrical member is mounted. Therefore, the adhesion between the heat dissipation member and the electrode body can be enhanced. Thereby, an electrode with good heat conduction efficiency can be provided.

  FIG. 1 shows a cross-sectional view of an anode 1 that is an electrode for a discharge lamp according to the present invention. As shown in FIG. 1, the anode 1 includes a main body 3 and a ceramic sleeve 5 that is a heat dissipation member. The ceramic sleeve 5 is mounted on the outer peripheral surface of the body part excluding the tip of the main body part 3.

  The main body 3 is made of a refractory metal or an alloy containing a refractory metal as a main component. In the present embodiment, pure tungsten having a purity of 99.9% or more is employed. Note that when tungsten is used, doped tungsten containing a small amount of thorium or the like may be used. Further, other refractory metals having a melting point of 3000 (K) or more can be employed. In the present embodiment, since the temperature of the electrode tip can be lowered, molybdenum or the like can be used when the power is not so high.

  As shown in FIG. 1, the main body 3 has an outer diameter that decreases from the front end of the electrode toward the rear end (r1> r2), and has a tapered cylindrical shape.

  The ceramic sleeve 5 has a tapered hollow cylindrical shape in which the inner diameter of the inner peripheral surface that is in contact with the outer peripheral surface of the electrode body portion is decreased from the front end portion toward the rear end portion. In the present embodiment, the taper angle is 3 °, but it may be about 1 ° to 5 °.

  The material used was aluminum nitride (ALN), which has a higher thermal conductivity and thermal emissivity when the lamp is lit, and an approximate thermal expansion coefficient compared to tungsten constituting the main body 3.

Other nitride-based ceramics may be used, or a carbide-based ceramic such as silicon carbide (SiC) may be used. Other materials include aluminum nitride (ALN) having a thermal conductivity of 170 W / mK or more, a thermal emissivity of 0.50 or more, and a thermal expansion coefficient of 4.0 * 10 ^{−6 to} 5.0 * 10 ⁻⁶ , or silicon carbide having the same characteristics ( SiC) is preferred. In particular, aluminum nitride having a thermal conductivity of 200 W / mK, a thermal emissivity of 0.80, a thermal expansion coefficient of 4.5 × 10 ⁻⁶ / degrees (Celsius), and a density of 3,320 kg / m ³ is suitable.

  Thus, even when non-conductive nitride-based ceramics and carbide-based ceramics are used for the heat radiating portion, there is no problem in energization between the anode and the cathode because the main body portion 3 exhibits conductivity.

  If the surface of the electrode body portion outer peripheral surface and the heat radiating member inner peripheral surface is smooth, the adhesion can be enhanced, thereby improving the heat transfer performance.

  A method for manufacturing the anode 1 will be briefly described. The main body 3 is cut to a predetermined length from a tungsten rod as a raw material, and then performs a cutting process to form an outer shape. At this time, the outer diameter of the outer surface of the electrode body in contact with the ceramic sleeve 5 is cut into a taper shape having a diameter that decreases from the front end to the rear end.

  On the other hand, the ceramic sleeve 5 is formed in a tapered shape in the same manner as the outer peripheral surface of the electrode body portion when forming a molded body by metal powder injection molding.

  In this state, aluminum nitride fine powder of nitride ceramics is sintered on the outer peripheral surface of the electrode body portion in contact with the ceramic sleeve 5 to form a heat transfer layer, and a heat radiating member is press-inserted and fitted thereon. Thereby, both adhesiveness can be improved. In addition, you may make it insert and fit as it is, without sintering powder.

A discharge lamp 20 incorporating the anode 1 shown in FIG. 1 is shown in FIG. The configuration of the discharge lamp 20 is as follows. The inner volume of the arc tube: 620 cm ³ , the emission length (distance between electrodes, during lamp operation) d = 12 mm, the cathode is composed of triated tungsten (Tria: 2 wt.%), And the electrode support rods 7 and 17 have an outer diameter of 6 mm Tungsten was adopted.

The axial length L1 = 45 mm, the tip diameter r0 = 25 mm, the outer diameter of the trunk is r1 = 15 mm, and the internal volume is 10000 mm ³ . The electrode support bar 5 is made of tungsten and has an outer diameter of 6 mm.

  The heat radiation action in the anode 1 will be described. The thermal conductivity of tungsten is about 100 W / mK at a high temperature range of about 2000K. In contrast, aluminum nitride has a higher thermal conductivity than tungsten and is 200 W / mK. In general, ceramics tend to have higher thermal conductivity as the temperature rises.

  The heat accumulated in the vicinity of the electrode tip is efficiently transmitted from the tip to the ceramic sleeve 5, and further, heat is efficiently released to the light emitting atmosphere by heat radiation. As a result, since heat is transferred to the heat radiating member with high efficiency at the electrode tip, overheating of the electrode tip can be prevented.

  As described above, overheating of the electrode tip can be prevented by combining the electrode main body and the ceramic sleeve 5 having a higher thermal conductivity and thermal emissivity than the electrode main body. As a result, problems such as anode deterioration can be solved even if the current flow rate of the discharge lamp is increased.

  In the present embodiment, since the heat dissipation member having higher thermal conductivity and thermal emissivity than the electrode body is provided on the outer periphery of the electrode body with good adhesion, the heat of the electrode tip can be efficiently transferred to the side surface of the electrode. The discharge lamp according to the present invention having the electrode can dissipate heat toward the rear and the electrode tip can be prevented from being overheated, and high brightness and high output can be realized.

In the present embodiment, the ceramic sleeve 5 has a density of 3,320 kg / m ³ and tungsten has a density of 19,250 kg / m ³ . Therefore, the ceramic sleeve 5 can be configured with a mass of about 1/6 as compared with the conventional case. Thereby, the weight of the anode can be reduced as a whole. In addition, such weight reduction makes it possible to provide a high-quality discharge lamp with high workability and high productivity even when manufacturing a large output large discharge lamp. Moreover, such weight reduction can prevent not only the merit at the time of manufacture but also damage due to impact or vibration during transportation.

  Moreover, by making the shape of the said heat radiating member and an electrode side part into a taper shape, the high adhesiveness of a heat radiating member and an electrode is implement | achieved and it can be set as a structure with high heat transfer property.

  Moreover, you may make it provide the transmission layer which sintered the fine particle powder of the same raw material as the said heat radiating member between the said heat radiating member and the electrode body part outer peripheral surface. As a result, high adhesion between the heat dissipation member and the electrode can be realized, and a structure with high heat transfer can be achieved. For example, when the heat radiating member is made of nitride ceramics, a transmission layer obtained by sintering fine particles of nitride ceramics may be used. The same applies to carbide ceramics. The same applies to the case where nitride ceramics and carbide ceramics are mixed. Further, when a heat radiating member is formed by mixing tantalum carbide, tungsten carbide, tungsten, or the like into nitride ceramics and / or carbide ceramics, the same material may be mixed in the transmission layer as well.

  Furthermore, even when tantalum carbide, tungsten carbide, tungsten, or the like is not mixed as a material for the heat dissipation member, the transmission layer may be one type or a mixture of two or more types selected from tantalum carbide, tungsten carbide, and tungsten.

  In the present embodiment, the ceramic sleeve 5 can reliably release the heat at the tip of the electrode from the outer peripheral surface of the side surface of the electrode, and the temperature rise of the electrode can be suppressed. Thereby, evaporation of the electrode constituent material is suppressed, and blackening of the inner wall of the arc tube portion can be prevented. Therefore, it is possible to provide a discharge lamp with little attenuation of light radiation output.

  In the present embodiment, more heat at the electrode tip can be transported to the rear end. As a result, the gradient in which the temperature decreases after the light is extinguished can be made slower than the conventional lamp.

  Thus, according to the discharge lamp according to the present invention, it is possible to reduce the temperature of the electrode tip, suppress evaporation of the electrode constituent material, the electrode does not melt, and the arc tube inner wall is blackened Therefore, it is possible to provide a discharge lamp with little attenuation of the light radiation output.

  In the above embodiment, by providing a transmission layer obtained by sintering fine particle powder made of nitride-based ceramics or carbide-based ceramics between the heat-dissipating member and the outer peripheral surface of the electrode body part, the heat-dissipating member and the electrode are high. Although the adhesion is realized, an intermediate layer metal may be provided between the ceramic and the metal so as to be inherently bonded.

  Specifically, a molybdenum ring formed of a cylindrical thin plate is inserted into the outer periphery of the electrode body. Stress due to the difference in thermal expansion between tungsten and ceramics is applied to the molybdenum ring. The molybdenum ring itself also thermally expands in the thickness direction. Molybdenum rings relieve strain caused by thermal expansion by elastic and plastic deformation of molybdenum.

  In the present embodiment, the thickness of the molybdenum ring is 0.2 mm, but is not limited to this, and may be about 0.05 mm to 3 mm.

  In addition, when the electrode is energized, electric discharge occurs, the boundary surface between the molybdenum and the ceramic sleeve becomes close to 1000 ° C., and stress due to thermal expansion is applied. Therefore, in particular, solid phase bonding occurs between the two without providing such a manufacturing process.

  Note that a slit may be provided in the molybdenum ring so as to absorb circumferential elongation due to thermal expansion of the molybdenum ring. Specifically, as shown in FIG. 3A, a slit 61 extending in parallel with the axial direction may be provided.

  As shown in FIGS. 3B and 3C, a plurality of such slits may be provided such as slits 62a and 62b and slits 63a, 63b and 63c. 3B and 3C are cross-sectional views of the molybdenum ring perpendicular to the axial direction. When a plurality of slits are provided, it becomes a plurality of plate-like members instead of a single object, but it does not fall apart by sandwiching them with a heat radiating member while holding them.

  Thus, by providing the thin molybdenum ring between the electrode body and the ceramic sleeve, it is possible to prevent the ceramic sleeve from cracking while improving the adhesion between the electrode body and the ceramic sleeve.

  In the present embodiment, the molybdenum ring is used as the buffer metal layer. However, any type of refractory metal having high ductility may be used. For example, niobium (Nb) may be used.

  In addition, this invention is not limited to the said structure, It can change suitably. For example, the refractory metal constituting the electrode body is not limited to the above-described substances. Further, the heat dissipating member is not limited to the above-mentioned substances and can be appropriately changed, and any of them may be one kind or a mixture of two or more kinds selected from nitride ceramics or carbide ceramics, or two or more layers. However, the present invention is not limited to the above embodiment.

  The electrode structure of the present invention is preferably employed for the anode in a DC lighting type discharge lamp, but may be employed for a cathode. Moreover, it can also employ | adopt as both an anode and a cathode.

  It can also be used in an AC lighting type discharge lamp.

  In a so-called vertical lighting type discharge lamp that is lit with the tube axis of the discharge lamp arranged in the vertical direction, the electrode arranged on the upper side is likely to be heated. Therefore, the electrode structure according to the present invention is preferably used for the electrode disposed on the upper side. However, in a vertical lighting type discharge lamp, it is not denied that it is adopted for the electrode arranged on the lower side, and it can also be adopted for the electrode arranged on the lower side.

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

  The electrode structure according to the present invention is not limited to the short arc type high-pressure mercury lamp, and can be applied to various discharge lamps.

  Further, the heat radiating member of the present invention is not limited to the shape shown in the embodiment. For example, it is possible to appropriately change the shape such as providing heat radiating fins and unevenness on the outer peripheral side surface of the heat radiating member.

  The discharge lamp according to the present invention uses an anode provided with a heat radiating member made of ceramic having high thermal conductivity and high thermal radiation. Therefore, the heat radiation (radiation) efficiency of the anode side surface (aluminum nitride) is increased, the temperature of the anode side surface is lowered, the temperature gradient inside the anode is increased, the heat flow rate is increased, and the heat energy concentrated on the anode tip portion Heat dissipation can be effectively increased.

In the discharge lamp, a high heat conduction and high heat radiation ceramic used as a heat radiating member, for example, aluminum nitride, has a maximum operating temperature of 1700 degrees Celsius when it is not oxidized and has a thermal conductivity of 200 W / mK and tungsten. Higher thermal conductivity. The coefficient of thermal expansion is 4.5 × 10 ⁻⁶ / degrees (Celsius), which is almost the same as that of tungsten. Furthermore, the density is 3,320 kg / m ³ , which is about one-sixth of the mass of tungsten (19,250 kg / m ³ ), and the weight of the anode can be reduced. By reducing the weight, the burden on the weight of the anode support rod can be reduced even when manufacturing a large output large discharge lamp. Moreover, the high adhesiveness of a heat radiating member and an electrode is realizable by making the shape of the said heat radiating member and an electrode side part into a taper shape. Thereby, it can be set as a structure with high heat transfer property.

1 is a cross-sectional view of an anode 1. It is a figure for demonstrating the thermal radiation in the discharge lamp which employ | adopted the anode 1. FIG. It is a figure which shows the molybdenum ring which provided the slit.

Explanation of symbols

1 Anode 3 Electrode Body 5 Ceramic Sleeve 7 Electrode Support Bar 20 Discharge Lamp

Claims (8)

An electrode body composed of a high melting point material,
A hollow cylindrical heat radiating member provided on the side surface of the electrode body,
A discharge lamp electrode comprising:
The heat dissipating member is made of an insulating ceramic material having higher thermal conductivity and heat radiation than the high melting point material and having a thermal expansion coefficient substantially similar to the high melting point material;
An electrode for a discharge lamp. The electrode for a discharge lamp according to claim 1,
Between the electrode body and the heat dissipation member, having a metal buffer layer solid-phase bonded to the heat dissipation member,
It is characterized by. The electrode for a discharge lamp according to claim 1,
The heat dissipation member has a thermal conductivity of 170 W / mK or more, a thermal emissivity of 0.50 or more, and a thermal expansion coefficient of 4.0 * 10 ^{−6 to} 5.0 * 10 ⁻⁶ ;
It is characterized by. The electrode for a discharge lamp according to claim 3,
The heat dissipating member is composed of one kind or a mixture of two or more kinds selected from nitride ceramics or carbide ceramics;
It is characterized by. In the discharge lamp electrode according to claim 3 or 4,
The outer diameter of the electrode body in contact with the heat radiating member is tapered as it goes from the front end to the rear end, and the inner diameter of the inner peripheral surface of the heat radiating member in contact with the electrode main body is changed from the front end to the rear end. As it goes, the taper shape is reduced, and the inner peripheral surface of the heat dissipation member and the side surface of the electrode body are fitted.
It is characterized by. In the discharge lamp electrode according to any one of claims 2 to 5,
Between the heat radiating member and the electrode body, a transmission layer obtained by sintering fine powder of a ceramic material constituting the heat radiating member,
It is characterized by. Prepare an electrode body composed of high melting point material,
A ceramic material having higher thermal conductivity and thermal radiation than the high melting point material, and having a thermal expansion coefficient substantially similar to that of the high melting point material, and preparing a hollow cylindrical member covering the side surface of the electrode body,
Mounting the hollow cylindrical member on the side surface of the electrode body;
A method for producing an electrode for a discharge lamp characterized by the above. In the manufacturing method of the electrode for discharge lamps of Claim 7,
Before attaching the hollow cylindrical member to the electrode body, the fine powder of the ceramic material constituting the heat dissipation member is attached to the electrode body and sintered, and then the hollow cylindrical member is attached.
It is characterized by.

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