JP2023121350A - discharge lamp - Google Patents

Abstract

To suppress generation of crack in a flow straightening body and the like arranged in a sealed space into which a heat transfer body is encapsulated, in an electrode of a discharge lamp.SOLUTION: In a short-arc type discharge lamp 10, a sealed space is formed in an electrode (an anode) 30, and a heat transfer body M that is molten when the lamp is turned on is encapsulated in the sealed space. A flow straightening body 40 is arranged in the sealed space 50. The flow straightening body 40 has structure with a layered cross section.SELECTED DRAWING: Figure 2

Description

The present invention relates to discharge lamps, such as short arc discharge lamps, and more particularly to the heat dissipation of electrodes.

When the discharge lamp is lit, the tip of the electrode reaches a high temperature, and the electrode material such as tungsten melts and evaporates, blackening the discharge tube, and lowering the illumination of the lamp. In order to prevent overheating of the electrode including the tip of the electrode, a structure is known in which a heat conductor such as metal is sealed inside the electrode (see Patent Document 1). There, a heat conductor made of a metal with high thermal conductivity and relatively low melting point, such as silver, is sealed within the anode. As the electrode temperature rises due to lamp lighting, the heat transfer material melts and liquefies, causing heat convection in the sealed space and suppressing overheating of the electrode tip.

On the other hand, in order to promote thermal convection, there is known a configuration in which a plate-shaped member forming a flow path around the electrode axis is arranged in a sealed space (see Patent Document 2). In addition, in order to prevent high-temperature creep deformation due to the temperature difference in the closed space due to heat convection of the heat transfer body, the plate-shaped member that restricts the flow of the molten heat transfer body along the circumferential direction is sealed. There is also known a configuration in which it is arranged in space (see Patent Document 3).

JP 2004-006246 A Japanese Patent No. 6259450 Japanese Unexamined Patent Application Publication No. 2012-28168

When the lamp is lit, if convection occurs in the heat transfer body, the plate-like member arranged in the sealed space receives force from the heat transfer body. In addition, while the solidification and melting of the heat transfer body are repeated by turning off and relighting the lamp, the time difference between the solidification and melting occurs due to the difference in the temperature decrease and rise speed due to the difference in the spatial region in the sealed space. Therefore, a load is likely to be applied to a specific portion of the plate member. Such a load may cause cracks in the plate-like member, resulting in breakage.

Therefore, in the electrode, it is required to suppress the generation of cracks and the like in the plate-shaped member arranged in the sealed space that encloses the heat transfer body.

A discharge lamp, which is one aspect of the present invention, comprises a discharge tube and a pair of electrodes arranged opposite to each other in the discharge tube. A plate-like rectifying body is arranged in the sealed space.

The "rectifier" here can be constituted by a structure, a member, or the like that exerts an action, a function, or the like in relation to the flow of the heat transfer material in the closed space. For example, the rectifiers can be shaped and arranged to form a flow path around the electrode axis. Further, the rectifying body can be shaped and arranged to regulate the flow in at least one of the circumferential direction of the heat transfer body and the axial direction of the electrodes in the sealed space.

In the present invention, at least part of the rectifier is formed in multiple layers in the thickness direction. That is, it has a layered structure. There are various configurations of such multilayer rectifiers. For example, the rectifying body can be configured to have a layered structure (aggregate structure, etc.) in its cross section, and a multi-layered rectifying body can be formed by plastic working. As a plate-like rectifying body having a layered structure, a structure in which layers are formed along boundaries substantially parallel to the plate surface can be formed by, for example, rolling.

On the other hand, by laminating a plurality of thin plate-shaped or foil-shaped metals, it is possible to form a rectifying body in a multi-layered manner. For example, the rectifying body can have a structure in which metals made of different materials are laminated.

Advantageous Effects of Invention According to the present invention, in electrodes of a discharge lamp, it is possible to suppress the generation of cracks and the like in a rectifier disposed in a closed space that encloses a heat transfer body.

It is a top view of the discharge lamp which is this embodiment. 1 is a schematic cross-sectional view of an anode; FIG. It is an example of the schematic sectional drawing of the anode in the state in which the heat-transfer body solidified. It is a schematic perspective view of a rectifier. It is the figure which showed typically the partial cross section of the rectifier. It is the figure which showed the optical microscope photograph of the partial cross section of the rectifier which is an Example.

The short-arc discharge lamp 10 is a large-sized discharge lamp capable of outputting high-intensity light, and includes a substantially spherical discharge tube (arc tube) 12 made of transparent quartz glass. A pair of electrodes 20 and 30 are arranged facing each other (coaxially). On both sides of the discharge tube 12, quartz glass sealing tubes 13A and 13B are connected to the discharge tube 12 and integrally formed. A discharge space DS in the discharge tube 12 is filled with mercury and a rare gas such as halogen or argon gas.

Electrode 20, which is a cathode, is supported by electrode support rod 17A. The sealing tube 13A includes a glass tube (not shown) through which the electrode support rod 17A is inserted, a lead rod 15A connected to an external power source, a metal foil 16A connecting the electrode support rod 17A and the lead rod 15A, and the like. Sealed. Similarly, for the electrode 30, which is the anode, mounting parts such as a glass tube (not shown) through which the electrode support rod 17B is inserted, the metal foil 16B, and the lead rod 15B are sealed. In addition, caps 19A and 19B are attached to the ends of the sealing tubes 13A and 13B, respectively.

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

FIG. 2 is a schematic cross-sectional view of electrode (anode) 30 . FIG. 3 is an example of a schematic cross-sectional view of the anode with the heat transfer body solidified. FIG. 4 is a schematic perspective view of a rectifier. The electrode (cathode) 20 can also have a similar structure.

As shown in FIG. 2, the anode 30 is composed of a cylindrical body portion 34 and a truncated conical tip portion 32 having an electrode tip surface 30S. The body portion 34 has a structure in which a sealing lid 60 to which the electrode support rod 17B is attached is joined, and a sealed space 50 is formed inside the body portion 34 . Here, the body portion 34 and the tip portion 32 are formed from the same metal material such as tungsten, but they may be formed from different materials. Also, the sealing lid 60 may be molded from a different material.

The closed space 50 is formed here as a cylindrical space and is formed coaxially with respect to the electrode axis E. As shown in FIG. A heat transfer member M is enclosed in the closed space 50 . The heat transfer body M is made of a metal (for example, silver) having a lower melting point than the body part 34 and the sealing lid 60 , melts and becomes liquid when the lamp is lit, and causes convection in the sealed space 50 . FIG. 2 shows a state in which the melted heat conductor M is convecting.

A rectifier 40 is coaxially arranged in the closed space 50 . The rectifier 40 is configured as a plate-like member that adjusts the flow of the melted heat conductor M. As shown in FIG. The rectifying body 40 can be configured by a shape and arrangement that form a flow path of the heat transfer body M along the electrode axis E. It is possible to configure by a shape and arrangement that regulates flow along a direction.

The rectifier 40 here has a shape that forms a flow path around the electrode axis E. As shown in FIG. The rectifier 40 is arranged so as to be separated from the closed space bottom surface 50B and the closed space top surface 50T by a predetermined distance along the direction of the electrode axis E, and to be separated from the closed space side surface 50S by a predetermined distance in the radial direction. . The rectifier 40 is fixed by, for example, a rod-shaped or plate-shaped fixing member (not shown), or is installed as it is in the sealed space 50 without being fixed.

A rectifying body 40 as an example shown in FIG. 4 is composed of curved plates 40A and 40B having a semicircular (C-shaped) cross section, which are arranged to face each other with a gap ST therebetween. The curved plates 40A and 40B are symmetrical with respect to the electrode axis E, and the distance between the rectifier 40 and the closed space side surface 50S is substantially equal over the entire circumferential direction. Rectifier 40 here consists of a refractory metal (eg, tungsten, molybdenum, tantalum, etc.) or an alloy with a potassium additive.

When the lamp is lit, the rectifier 40 functions as a plate-like member that forms a flow path of the heat transfer member M around the electrode axis E from the opening 41A on the bottom side of the sealed space toward the opening 41B on the top side of the sealed space. , the heat of the tip of the electrode is transported to the electrode supporting rod 17B side.

When the lamp is extinguished, the heat conductor M solidifies, for example, as shown in FIG. When the lamp is turned off, the temperature drop of the heat transfer member M in the internal space of the rectifier 40 is relatively slower than in the outer space region. Therefore, the solidification of the heat transfer body M has a time difference due to the difference in the spatial region, and the heat transfer body M inside the rectifying body 40 solidifies in a state where the liquid level is lower than that of the heat transfer body M outside the rectifying body 40. A recess with a sufficient depth is formed.

FIG. 5 is a diagram schematically showing a partial cross section of the rectifier 40. As shown in FIG.

As shown in FIG. 5, the rectifying body 40 has a cross-section that forms a multi-layer structure along the thickness direction. Such a texture is brought about by the formation of a texture accompanying plastic deformation. The cross-sectional layered structure of the rectifying body 40 shown in FIG. 5 is produced here by plastic working, and the crystal grains are elongated in the rolling direction to provide the cross-sectionally layered structure. Each layer here is substantially parallel to the rolling direction, that is, along the surface of the rectifier 40, and each layer is formed to have substantially the same width (thickness) t. It can be within the range of μm to several hundred μm.

The rectifying body 40 having such a cross-sectional layered structure can suppress progress of cracks even if cracks occur inside. That is, texture boundaries stop crack propagation at the boundaries. As a result, damage to the rectifier 40 can be suppressed, and its function (electrode temperature suppression) can be exhibited until the end of the lamp life.

Such a rectifier 40 can be manufactured by a manufacturing method involving plastic working, and the working temperature, rolling reduction, etc. are determined according to the raw material and layer thickness. Then, press working such as bending may be performed on the processed plate material to bend it. For example, hot rolling can be applied, or cold rolling can be performed. Also, the surface may be treated by annealing.

The rectifier 40 described above is made of a sheet of metal material and has a structure having a multi-layered texture in its cross section. can be formed into By adjusting the bonding conditions, it is possible to form a μ-order gap between adjacent foil plates (layers). If gaps are formed between adjacent layers, crack propagation is effectively stopped.

On the other hand, it is also possible to substantially eliminate gaps between some adjacent layers. Even in this case, cracks progress along (the layer of) the crystal grain boundaries, so even if the crystal grain boundaries are peeled off, the crystal grains themselves do not break down. can be done. A layered cross section may be formed in a part of the rectifier 40 .

The multi-layered cross section may be formed by plastic working (for example, extrusion, drawing, etc.) other than rolling. Alternatively, a multi-layer cross-section may be formed by a metal 3D printer. In either case, the thickness can be constant, or the thicknesses can be different from each other.

The rectifier 40 is not limited to the shape of a curved plate having a semicircular cross-section as shown in FIG. You may arrange|position so that two rectangular-shaped metal plates may face each other. Heat transport along the electrode axis E can be effectively performed even when the rectifying body 40 is configured by pairing the metal plates having such planar surfaces. It is also possible to arrange the rectifying body 40 not by a pair of metal plates, but by arranging three or more metal plates with a predetermined interval from each other.

The rectifier 40 can be tapered toward the electrode supporting rod side, or can be triangular. Furthermore, the rectifying body 40 can also be configured as a tubular body forming an internal space. For example, the tubular body may have a circular or polygonal (including triangular) cross-section.

As described above, the rectifying body 40 can also be configured as a plate-like member that restricts the flow of the heat transfer body M along the circumferential direction of the closed space. For example, the rectifier can be configured as a single plate, or can be configured as a plate-like member having a cross-shaped or T-shaped cross section.

In this case, at least part of the rectifying body may be formed with the layered cross section. Even in such a rectifying body that regulates the flow of the heat transfer body, it is possible to suppress cracking and breakage due to receiving force from the heat transfer body by having the above-described layered structure.

The rectifying body 40 described so far has a structure having a layered structure in its cross section, but the layered structure is not limited to this. Regardless of the presence or absence of a layered structure by plastic working, it is also possible to combine plate-like materials such as different thin plate-like metals or foil-like metals and have a layered cross-section. Even by laminating plate-like members made of a plurality of materials, cracks propagate along the boundaries between adjacent layers, so damage to the rectifier due to crack generation can be suppressed.

For example, a thin plate (foil plate) of molybdenum is sandwiched between thin plate (foil plate) tungsten layers to form a layered rectifier. Since molybdenum more easily absorbs internal stress by its own elongation than tungsten, molybdenum exerts a cushioning function and can suppress breakage of the rectifier. Alternatively, a metal plate may be laminated with a material having a higher melting point than the heat transfer body (ceramics, etc.), or a recrystallized thin plate (foil plate) may be used.

Examples are described below. The rectifying body of the embodiment is a single rectangular plate rectifying body, which is formed by pressurizing tungsten as a raw material powder, sintered, and formed into a sintered body according to a predetermined processing temperature, rolling reduction, and the like. Hot rolled. Here, a partial cross section of the rectifier was observed with an optical microscope.

As shown in FIG. 6, in the rectifying body of the example, boundaries of textures having a width (thickness) of about 30 μm are formed along the rolling direction (plate surface direction), and a layered structure is formed. confirmed. Partial cracks are generated along the grain boundaries due to the influence of cross-section preparation for cross-sectional view observation.

The cross-sectionally layered rectifier shown in FIG. 6 is merely an example, and is not limited to the layered shape shown in FIG. By determining the processing temperature and reduction rate based on the thickness of each layer, it is possible to construct a rectifying body with various cross-sectional layers.

10 discharge lamp 30 anode (electrode)
40 rectifier 50 sealed space

Claims (7)

a discharge tube;
A pair of electrodes arranged oppositely in the discharge tube,
In at least one of the electrodes, a sealed space is formed in which a heat transfer body that melts when the lamp is lit is enclosed, and a plate-shaped rectifying body is disposed in the sealed space,
A discharge lamp, wherein at least part of the rectifying body is formed in a multi-layered shape in a thickness direction. 2. The discharge lamp of claim 1, wherein the rectifier has a layered structure in its cross section. 3. The discharge lamp of claim 2, wherein the flow straightener has a layered texture along boundaries substantially parallel to the plate surfaces. 4. The discharge lamp according to any one of claims 1 to 3, wherein the rectifying body has a structure in which a plurality of thin plate-like or foil-like metals are laminated. 5. The discharge lamp according to claim 4, wherein the rectifier has a structure in which metals made of different materials are laminated. 6. The discharge lamp according to any one of claims 1 to 5, wherein the rectifier has a shape and arrangement that form a flow path around the electrode axis. The rectifying body has a shape and arrangement that regulates flow along at least one of the circumferential direction and the electrode axial direction of the heat transfer body in the sealed space. Item 6. The discharge lamp according to any one of Items 1 to 5.

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