Discharge lamp

Abstract

The present invention provides a discharge lamp capable of sufficiently suppressing anode consumption. The discharge lamp includes a light-emitting tube containing a light-emitting material, and an anode and a cathode disposed opposite each other inside the light-emitting tube. The anode is a generally cylindrical shape with a chamfered or rounded outer periphery at the front end opposite the cathode. The anode has a front end face that is circular when viewed from the cylindrical axis on the inner side of the chamfered or rounded outer periphery. The front end face has a recess that is formed inside a concentric circle having a diameter of at least 70% of the diameter of the front end face, but not at the center of the front end face.

Description

Technical Field

[0001] This invention relates to discharge lamps. Background Technology

[0002] Conventional short-arc discharge lamps are known to consist of a quartz glass light-emitting tube bulging out from the center, and an anode and cathode arranged opposite to each other inside the bulging part of the light-emitting tube. When the discharge lamp is energized, electrons emitted from the cathode collide with luminescent material sealed inside the light-emitting tube to generate charged particles. These charged particles collide repeatedly, causing the luminescent material sealed inside the light-emitting tube to become a plasma state, which flows towards the anode and forms an electric arc between the two electrodes.

[0003] When the discharge lamp is lit, an electric arc is formed by the collision of electrons emitted from the cathode. The anode is heated to a high temperature by the collision of electrons in this arc column, and then evaporates and is consumed. Furthermore, as the anode is consumed by the collision of electrons, the evaporated tungsten adheres to the inner wall of the light-emitting tube, causing the inner wall surface to blacken. Moreover, with prolonged use of the discharge lamp, the front end of the anode is gradually consumed, and the radiation intensity of the discharge lamp decreases sequentially. When the decrease in radiation intensity exceeds the usage limit, the discharge lamp needs to be replaced with a new one.

[0004] Therefore, various studies have been conducted on countermeasures to suppress anode consumption (such as the following patent documents 1 and 2), but it is still difficult to fully suppress anode consumption.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2011-14248

[0008] Patent Document 2: Japanese Patent Application Publication No. 2003-346709 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] In view of the above-mentioned problems, the present invention aims to provide a discharge lamp that can effectively suppress the consumption of the anode.

[0011] Technical solutions for solving the problem

[0012] The discharge lamp of the present invention comprises: Light-emitting tube, encapsulated with a light-emitting material; and The anode and cathode are arranged opposite each other inside the light-emitting tube. The anode is a generally cylindrical shape with a chamfered or rounded outer periphery at the front end opposite the cathode. The anode has a rounded front end face on the inner side of the chamfered or rounded outer periphery, which appears circular when viewed from the cylindrical axis. The front end face has a recess. The recess is formed on the inner side of a concentric circle having a diameter of at least 70% of the diameter of the front end face, and is not formed at the center of the front end face.

[0013] According to this structure, the portion with the recess is further away from the electric arc, thus its temperature decreases compared to the portion without the recess. As a result, a portion of the front end face is cooled, thereby suppressing anode evaporation and consumption. Furthermore, by forming the recess inside a concentric circle having a diameter of at least 70% of the diameter of the front end face, a portion of the front end face can be effectively cooled, thus sufficiently suppressing anode consumption.

[0014] In the discharge lamp of the present invention, the recess may also be configured such that it is formed on the inner side of a concentric circle having a diameter of at least 50% of the diameter of the front end face.

[0015] This structure allows for more effective cooling of a portion of the front end face.

[0016] In the discharge lamp of the present invention, the recess may also be formed on the outside of a concentric circle having a diameter of 20% of the diameter of the front end face.

[0017] Since the electric arc is concentrated at the center of the front end face, if a recess is formed at the center of the front end face, the initial light intensity will be reduced. However, by forming the recess on the outside of a concentric circle with a diameter of 20% of the diameter of the front end face, the initial illuminance can be adequately ensured.

[0018] In the discharge lamp of the present invention, the recess may also be configured such that it is formed in a surrounding shape around the center of the front end face. In this specification, "forming a surrounding shape around the center of the front end face" specifically refers to the configuration described later. Figure 3 , Figure 4B , Figure 4C , Figure 12 and Figure 13 It has the shape shown.

[0019] Based on this structure, from the center of the front end face in which direction ( Figure 3 , Figure 4B , Figure 4C , Figure 12 and Figure 13 The recesses are formed in both the Y and Z directions, so the tungsten that evaporates from the front end face in a specific direction will not adhere to the inner wall of the light tube and cause the inner wall surface in a specific direction to blacken only.

[0020] In the discharge lamp of the present invention, the recess may also be configured such that it is formed in an annular shape centered on the center of the front end face. In this specification, the annular shape surrounding the center of the front end face specifically refers to the shape described later. Figure 3 , Figure 4B , Figure 4C and Figure 12 The shape shown.

[0021] According to this structure, since the recesses are formed at equal distances from the center of the front end face, the directional dependence of the amount of tungsten evaporating from the front end face becomes more uniform, and the directional dependence of the blackening of the inner wall surface is improved.

[0022] In the discharge lamp of the present invention, the luminescent material may also be configured such that the amount of mercury contained is less than 20 mg / cc.

[0023] When the amount of mercury sealed in is less than 20 mg / cc, the arc diameter becomes narrower, thus concentrating energy at the center of the anode and causing it to reach a high temperature, making the anode more prone to evaporation. Therefore, this invention is particularly useful in discharge lamps with a mercury concentration of less than 20 mg / cc.

[0024] In the discharge lamp of the present invention, the maximum depth of the recess may be 0.5 mm or more.

[0025] According to this structure, the temperature drops significantly in the recessed area, thus effectively suppressing anode evaporation.

[0026] In the discharge lamp of the present invention, the area of ​​the recess is 2% or more and 25% or less of the area of ​​the front end face when viewed from the cylindrical axis.

[0027] According to this structure, while ensuring the initial illuminance, a portion of the front end face can be cooled to effectively suppress anode evaporation and consumption.

[0028] In the discharge lamp of the present invention, the front end face may also be configured such that it has an inner front end face located inside the recess and an outer front end face located outside the recess. The inner front end face is closer to the cathode than the outer front end face.

[0029] According to this structure, while ensuring the initial illuminance, a portion of the front end face can be cooled to effectively suppress anode evaporation and consumption. Attached Figure Description

[0030] Figure 1 This is an explanatory diagram showing the structure of the discharge lamp in this embodiment.

[0031] Figure 2It is a cross-sectional view of the anode including the cylindrical shaft.

[0032] Figure 3 This is a diagram showing the front end of the anode as viewed from the cathode side.

[0033] Figure 4A This is a diagram showing the front end face of the anode of Comparative Example 1 as viewed from the cathode side.

[0034] Figure 4B This is a diagram showing the front end face of the anode of Example 1 as viewed from the cathode side.

[0035] Figure 4C This is a diagram showing the front end face of the anode in Example 2 as viewed from the cathode side.

[0036] Figure 5 The results are based on a comparison of illuminance maintenance rates over lighting time.

[0037] Figure 6 It is the illuminance maintenance rate after 800 hours of illumination.

[0038] Figure 7 It is the relationship between the position of the concave part and the initial light intensity.

[0039] Figure 8 It relates the position of the concave portion to the illuminance maintenance rate after 800 hours of illumination.

[0040] Figure 9 It relates the position of the concave portion to the illuminance maintenance rate after 800 hours of illumination.

[0041] Figure 10 It relates the position of the concave portion to the illuminance maintenance rate after 800 hours of illumination.

[0042] Figure 11 It is the relationship between the diameter of the front face and the position of the concave part.

[0043] Figure 12 This is a diagram showing the front end of the anode of a discharge lamp in another embodiment, viewed from the cathode side.

[0044] Figure 13 This is a diagram showing the front end of the anode of a discharge lamp in another embodiment, viewed from the cathode side.

[0045] Figure 14 This is a diagram showing the front end of the anode of a discharge lamp in another embodiment, viewed from the cathode side.

[0046] Figure 15 This is a cross-sectional view of the anode of a discharge lamp in another embodiment, including the cylindrical shaft.

[0047] Figure 16 This is a cross-sectional view of the anode of a discharge lamp in another embodiment, including the cylindrical shaft.

[0048] Figure 17 It is a diagram showing the ratio of the area of ​​the concave part to the area of ​​the front face. Detailed Implementation

[0049] Embodiments of the discharge lamp of the present invention will be described with reference to the accompanying drawings. Furthermore, the following drawings are schematic illustrations, and the aspect ratios shown in the drawings may not necessarily correspond to the actual aspect ratios, nor may the aspect ratios be consistent between different drawings.

[0050] The following explanation will refer to the XYZ coordinate system as appropriate. Furthermore, in this specification, when representing direction, if a positive or negative orientation is distinguished, it will be indicated with a positive or negative symbol, such as "+X direction" or "-X direction". If a direction is not distinguished by positive or negative, it will only be described as "X direction". That is, in this specification, when only "X direction" is described, it includes both "+X direction" and "-X direction". This also applies to the Y and Z directions.

[0051] Figure 1 This is an explanatory diagram showing the structure of the discharge lamp according to this embodiment. The discharge lamp 1 includes a light-emitting tube 2 and an anode 3 and a cathode 4 disposed opposite each other inside the light-emitting tube 2. The anode 3 and the cathode 4 are each supported by a lead rod 5.

[0052] The light-emitting tube 2 is formed by expanding the center of a glass tube. The light-emitting tube 2 has a bulge 20 whose inner diameter increases as it moves from both ends toward the center in the X direction. The bulge 20 is shaped like a sphere or an ellipsoidal isoaxial rotational body.

[0053] The light-emitting tube 2 has a pair of sealing tube portions 21 extending continuously in opposite directions from both ends of the bulge 20 in the X direction. The sealing tube portions 21 and the bulge 20 are integrally formed from, for example, quartz glass. The central axes of the pair of sealing tube portions 21 overlap each other. Figure 1 The axis X1 is represented by [the axis].

[0054] A light-emitting space S1 is formed inside the bulge 20. Mercury is sealed in the light-emitting space S1 as a luminescent material. Furthermore, when mercury is sealed as the luminescent material, a rare gas (argon, krypton, xenon, etc.) is also sealed in the light-emitting space S1. In the light-emitting tube 2, the amount of mercury sealed as the luminescent material can be less than 20 mg / cc. When the amount of mercury sealed is less than 20 mg / cc, the arc diameter becomes narrower, thus the energy is concentrated in the center of the anode 3, resulting in high temperature, and the anode 3 is prone to evaporation. Therefore, the present invention is particularly useful in discharge lamps 1 with a mercury sealing amount of less than 20 mg / cc. Additionally, the luminescent material can also be a gaseous substance; for example, only xenon gas can be sealed in.

[0055] Inside the bulge 20, the anode 3 and the cathode 4 are arranged opposite each other in the X direction.

[0056] In this embodiment, the anode 3 is made of tungsten, and the cathode 4 is made of thorium-doped tungsten. The anode 3 is generally cylindrical, and the cylindrical axis of the anode 3 can overlap with the axis X1. The cathode 4 is generally cylindrical with a smaller diameter than the anode 3, and the cylindrical axis of the cathode 4 can also overlap with the axis X1.

[0057] Lead rod 5 is connected to anode 3 and cathode 4, and extends along the X direction within sealed tube 21. Anode 3 and cathode 4 are fixed to the front end of lead rod 5. The central axis of lead rod 5 can overlap with axis X1. Lead rod 5 is made of a material containing a high-melting-point metal, such as tungsten.

[0058] The lamp holder 6 covers the side of the sealed tube 21 away from the anode 3 and cathode 4. The lamp holder 6 is electrically connected to the lead rod 5.

[0059] Figure 2 This is a cross-sectional view of anode 3 including the cylindrical shaft X1. Additionally, Figure 3 This is a diagram showing the front end 3a of the anode 3 as viewed from the cathode 4 side.

[0060] The anode 3 is a roughly cylindrical shape with a chamfered or rounded outer periphery 31 at the front end 3a opposite the cathode 4. For example... Figure 2 As shown, in this embodiment, the outer periphery 31 of the front end 3a of the anode 3 opposite to the cathode 4 is chamfered to form a conical shape. The anode 3 has a front end face 32 that is circular when viewed from the cylindrical axis X1 direction (X direction) on the inner side of the chamfered outer periphery 31.

[0061] like Figure 2 and Figure 3 As shown, the front end face 32 has a recess 7. The recess 7 is formed in such a way that it excludes the center of the front end face 32. The recess 7 may also be formed in a surrounding shape that surrounds the center of the front end face 32. Figure 3 As shown, the recess 7 in this embodiment is formed as an annular shape centered on the center of the front end face 32.

[0062] In the front end face 32, the portion with the recess 7 is further away from the electric arc, thus its temperature decreases compared to the portion without the recess 7. As a result, a portion of the front end face 32 is kept cool, thereby suppressing the evaporation and consumption of the anode 3. Consequently, the degree of blackening on the inner surface of the light-emitting tube 2 is reduced, and the illuminance maintenance rate is improved.

[0063] like Figure 3As shown, the recess 7 is formed at least inside a concentric circle c1 (the concentric circle c1 of the front end face 32) having a diameter 70% of the diameter d of the front end face 32. If the recess 7 is formed outside the concentric circle c1 (i.e., the recess 7 is formed too far from the center of the front end face 32), the recess 7 will be formed in a thinner part of the arc discharge, making it difficult to achieve the effect of cooling a portion of the front end face 32. Therefore, by forming the recess 7 inside the concentric circle c1 of the front end face 32, a portion of the front end face 32 can be effectively cooled, thus sufficiently suppressing the consumption of the anode 3.

[0064] The recess 7 is preferably formed on the inner side of a concentric circle (not shown) having a diameter of at least 50% of the diameter d of the front end face 32. This allows for more effective cooling of a portion of the front end face 32.

[0065] However, the electric arc is concentrated at the center of the front end face 32, so if a recess 7 is formed at the center of the front end face 32, the initial light intensity is reduced. Conversely, by forming the recess 7 in a manner that excludes the center of the front end face 32, the initial illuminance can be ensured. Figure 3 As shown, the recess 7 is preferably formed on the outside of a concentric circle c2 with a diameter 20% of the diameter d of the front end face 32. This ensures adequate initial illuminance.

[0066] Additionally, the maximum depth 7a of the recess 7 (refer to...) Figure 2 The maximum depth 7a is preferably 0.5 mm or more. If the maximum depth 7a is 0.5 mm or more, the temperature drop at the part where the recess 7 is formed is large, thus significantly suppressing the evaporation of the anode 3. Furthermore, if the maximum depth 7a of the recess 7 is too deep, the electric arc will concentrate on the front end face 32 outside the recess 7, which will accelerate evaporation. Therefore, the maximum depth 7a of the recess 7 is preferably 2 mm or less.

[0067] Furthermore, when viewed from the cylindrical axis X1 (X direction), the area of ​​the recess 7 is preferably 2% to 25% of the area of ​​the front end face 32. By setting the area of ​​the recess 7 to 2% or more of the area of ​​the front end face 32, a low-temperature effect caused by the recess 7 can be obtained. In addition, if the recess 7 formed on the front end face 32 is too wide, the initial illuminance will decrease, similar to the situation where the distance between the anode 3 and the cathode 4 becomes longer. However, by making the area of ​​the recess 7 25% or less of the area of ​​the front end face 32, the initial illuminance can be ensured.

[0068] Based on the above, the discharge lamp 1 is configured as described in this embodiment to include a light-emitting tube 2 containing a light-emitting material, and an anode 3 and a cathode 4 disposed opposite each other inside the light-emitting tube 2. The anode 3 is a generally cylindrical shape with a chamfered or rounded outer periphery 31 of the front end 3a opposite to the cathode 4. The anode 3 has a front end face 32 that is circular when viewed from the cylindrical axis on the inner side of the chamfered or rounded outer periphery 31. The front end face 32 has a recess 7, which is formed on the inner side of a concentric circle c1 having a diameter of at least 70% of the diameter d of the front end face 32, and is not formed at the center of the front end face 32.

[0069] According to this structure, the portion with the recess 7 is further away from the electric arc, and therefore its temperature decreases compared to the portion without the recess 7. As a result, a portion of the front end face 32 is cooled, thus suppressing the evaporation and consumption of the anode 3. Furthermore, by forming the recess 7 at least inside a concentric circle c1 having a diameter 70% of the diameter d of the front end face 32, the temperature of a portion of the front end face 32 can be effectively reduced, thereby sufficiently suppressing the consumption of the anode 3.

[0070] Example

[0071] Hereinafter, embodiments that specifically illustrate the structure and effects of the present invention will be described.

[0072] First, the effect of the recess 7 formed on the front end face 32 of the anode 3 was verified. Specifically, a discharge lamp as described below was fabricated, and a comparative test of illuminance maintenance rate based on illumination time was conducted.

[0073] (Comparative Example 1)

[0074] A discharge lamp with a diameter of 12 mm on the front end face 32 and no recess on the front end face 32 is used as Comparative Example 1.

[0075] (Comparative Example 2)

[0076] like Figure 4A As shown, a discharge lamp with a diameter of 12 mm for the front end face 32 and an annular recess 70 with a width of 1 mm formed on a circumference with a diameter of 1 mm (i.e., an annular recess 70 with a diameter of 2 mm starting from the center of the front end face 32) is used as Comparative Example 2. In addition, the recess 70 that is finally formed is a circular plate with a diameter of 2 mm.

[0077] (Example 1)

[0078] like Figure 4B As shown, the discharge lamp 1 with a diameter of 12mm for the front end face 32 and an annular recess 7 (annular recess 7 with an inner diameter of 2mm and an outer diameter of 4mm) formed on a circumference with a diameter of 3mm is used as Example 1.

[0079] (Example 2)

[0080] like Figure 4C As shown, the discharge lamp 1 with a diameter of 12mm for the front end face 32 and an annular recess 7 (annular recess 7 with an inner diameter of 4mm and an outer diameter of 6mm) formed on a circumference with a diameter of 5mm is used as Example 2.

[0081] Mercury at 2.5 mg / cc and argon at 3.5 atm as a rare gas are sealed in the light-emitting tube 2. The distance between the front end face 32 of the anode 3 and the front end face of the cathode 4 is 9 mm, and the lamp power is 7.5 kW.

[0082] Figure 5 This represents the comparison results of illuminance maintenance rate based on lighting time. The vertical axis represents the illuminance maintenance rate when the initial illuminance is set to 100%, and the horizontal axis represents the lighting time. Figure 6 The illuminance maintenance rate after 800 hours of illumination is shown, and the illuminance maintenance rate of each discharge lamp is shown when the illuminance maintenance rate of the discharge lamp of Comparative Example 1 is set to 1. For example... Figure 5 and Figure 6 As shown, Examples 1, 2 and Comparative Example 2, which have recesses 7 and 70, are able to maintain illuminance compared to Comparative Example 1, which does not have recesses 7 and 70.

[0083] Next, the formation position of the recess relative to the front end face 32 of the anode 3 was verified. Specifically, a comparative experiment was conducted to compare the initial light output when a 1mm wide annular recess was formed at different positions on the 12mm diameter front end face 32. The light-emitting tube 2 was sealed with 2.5mg / cc of mercury and 3.5atm of argon gas as a rare gas. The distance between the front end face 32 of the anode 3 and the front end face of the cathode 4 was 9mm, and the lamp power was 7.5kW.

[0084] Figure 7 This indicates the relationship between the position of the concave portion and the initial light intensity. Here, the position of the concave portion (mm) on the horizontal axis is the diameter of the circle located at the center of the width of the annular concave portion. For example, a concave portion position of 1mm means the concave portion is located at... Figure 4A The position shown indicates that the recess is 3mm in diameter. Figure 4B The location shown.

[0085] like Figure 7 As shown, when the recess is 1 mm in size, that is, when a recess 70 also exists at the center of the front end face 32 as in Comparative Example 2 above, the initial light intensity decreases by about 3%. On the other hand, as... Figure 7 As shown, by forming the recess 7 in a manner that excludes the center of the front end face 32, the initial illuminance can be ensured.

[0086] Figure 8The diagram shows the relationship between the location of the recess and the illuminance maintenance rate after 800 hours of illumination. The vertical axis represents the illuminance maintenance rate of Comparative Example 1 (without a recess) set to 1, and the horizontal axis represents the location of the recess (mm) (i.e., the distance from the center of the front end face 32 to the center of the recess). The diameter of the front end face 32 is set to 12 mm, and the width of the recess is set to 1 mm. The lamp power is 7.5 kW.

[0087] Figure 9 and Figure 8 Similarly, the relationship between the position of the recess and the illuminance maintenance rate after 800 hours of illumination is shown. The vertical axis represents the illuminance maintenance rate of Comparative Example 1, which does not have a recess, when the illuminance maintenance rate is set to 1. The horizontal axis represents the position of the recess in proportion to the diameter of the front end face 32.

[0088] Figure 10 This is when the diameter of the front face 32 is set to 7mm and the width of the recess is set to 0.5mm. Figure 9 The corresponding chart shows the lamp power is 3.5kW.

[0089] like Figure 8 and Figure 9 As shown, when a recess is formed at a position far from the center of the front end face 32 (e.g., 10 mm), that is, when a recess is formed on the outer side of a concentric circle c1 having a diameter 70% of the diameter d of the front end face 32 (equivalent to the later description) Figure 11 In the case of a groove with a diameter of 12 mm at the front end face 32, the groove is located at a depth of 9 to 11 mm. The outer periphery of the front end face 32 is a thinner part of the arc discharge (a part with a lower temperature), so it is almost impossible to obtain an improvement effect on the concave contrast retention rate.

[0090] Similarly, as Figure 10 As shown, at a position away from the center of the front end face 32 (e.g., 5.5mm): Figure 10 In the case where the rightmost data in the diagram has a recess, that is, when a recess is formed on the outer side of the concentric circle c1 having a diameter d that is 70% of the diameter of the front end face 32 (equivalent to the case described later),... Figure 11 (The groove position is 5 to 6 mm at the 7 mm diameter of the front end face 32). The outer periphery of the front end face 32 is a thinner part of the arc discharge (a part with a lower temperature), so it is almost impossible to obtain an improvement effect on the concave contrast retention rate.

[0091] Next, for discharge lamps with a front face 32 diameter d of 7 mm, a recess width of 0.5 mm, and a lamp power of 3.5 kW; discharge lamps with a front face 32 diameter d of 9 mm, a recess width of 1 mm, and a lamp power of 5 kW; and discharge lamps with a front face 32 diameter d of 12 mm, a recess width of 1 mm, and a lamp power of 7.5 kW, the formation position of the recess relative to the front face 32 of the anode 3 was verified. Specifically, in each discharge lamp, the illuminance maintenance rate was evaluated by changing the position of the recess. The results are shown below. Figure 11 .

[0092] exist Figure 11 In the diagram, the vertical axis represents the position of the recess (mm), and the horizontal axis represents the diameter of the front end face 32 (mm). Here, the position of the recess on the vertical axis represents both the inner and outer diameters of the annular recess. For example, if the diameter d of the front end face 32 is set to 12mm, and an annular recess with a width of 1mm is formed on a circumference with a diameter of 5mm, the position of the recess is set to 4mm to 6mm.

[0093] Regarding the evaluation of illuminance maintenance rate, compared to discharge lamps without a recess on the front face 32, discharge lamps that show an improvement of 5% or more are marked as "0", discharge lamps that show an improvement of 2% or more are marked as "△", and discharge lamps that show an improvement of less than 2% are marked as "×", and are shown in the figure. Figure 11 .

[0094] like Figure 11 As shown, when a recess is formed inside a concentric circle c1 with a diameter d that is 70% of the diameter of the front end face 32, an improvement of more than 2% is obtained; when a recess is formed inside a concentric circle with a diameter d that is 50% of the diameter of the front end face 32, an improvement of more than 5% is obtained.

[0095] The embodiments of the present invention have been described above based on the accompanying drawings, but it should be understood that the specific structure is not limited to these embodiments. The scope of the present invention is not only shown by the description of the above embodiments, but also by the scope of the claims, and includes all modifications within the scope and meaning of the same claims.

[0096] The structures used in the above embodiments can be applied to any other embodiments. The specific structure of each part is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention.

[0097] [Other Implementation Methods]

[0098] (1) In the discharge lamp 1 of the above embodiment, the recess 7 is configured to be continuously formed in a surrounding shape that encloses the center of the front end face 32. However, the discharge lamp 1 is not limited to this structure. For example, such as Figure 12As shown, the recess 7 can also be discontinuously formed into a surrounding structure that encloses the center of the front end face 32. With this structure, even a simple machining device (drilling machine, etc.) can be used to machine a recess 7 on the front end face 32, rather than a machining device (milling machine, etc.) used to form a continuous groove, making it easy to form the recess 7.

[0099] (2) Furthermore, in the discharge lamp 1 of the above embodiment, the recess 7 is configured to be annular with the center of the front end face 32 as the center. However, the discharge lamp 1 is not limited to this structure. For example, such as Figure 13 As shown, the recess 7 can also be formed as a four-sided border structure centered on the center of the front end face 32. According to this structure, the recess 7 is formed at a large distance from the center of the front end face 32, thus different from the annular recess 7 (…). Figure 3 , Figure 4B , Figure 4C as well as Figure 12 Compared to other methods, it does not require precision in the position of the recess 7, which can suppress deviations in yield and lamp performance.

[0100] (3) In addition, such as Figure 14 As shown, the recess 7 may not be configured in a surrounding shape centered on the front end face 32. With this structure, it can be processed using a simple machining apparatus, and deviations in yield and lamp performance can be suppressed. Furthermore, although not shown, the recess 7 may also be configured asymmetrically, for example, in a spiral shape.

[0101] (4) Furthermore, in the discharge lamp 1 of the above embodiment, the anode 3 is configured such that the outer periphery 31 of the front end 3a opposite the cathode 4 is chamfered and is approximately cylindrical. However, the discharge lamp 1 is not limited to this structure. For example, it can also be configured as follows: Figure 15 As shown, the anode 3 is a roughly cylindrical shape with rounded corners on the outer periphery 31 of the front end 3a opposite to the cathode 4.

[0102] In addition, such as Figure 15 As shown, in the case where the outer perimeter 31 is a generally cylindrical shape with rounded corners, the diameter d of the front end face 32 does not include the portion of the outer perimeter 31 that forms rounded corners.

[0103] (5) Furthermore, in the discharge lamp 1 according to the above embodiment, the front end face 32 is configured to be disposed on a plane orthogonal to the cylindrical axis X1. That is, the front end face 32 is located on the same plane on both the inner and outer sides of the recess 7. However, the discharge lamp 1 is not limited to this structure. For example, it can also be configured as follows: Figure 16 As shown, the front end face 32 has an inner front end face 32a located inside the recess 7 and an outer front end face 32b located outside the recess 7. The inner front end face 32a is closer to the cathode 4 than the outer front end face 32b.

[0104] (6) In addition, when viewed from the cylindrical axis direction, the area of ​​the recess 7 is preferably more than 2% and less than 25% of the area of ​​the front end face 32. Figure 17 This is a diagram showing the ratio of the area of ​​the recess 7 to the area of ​​the front surface 32 for a discharge lamp with a diameter d of 12 mm, a lamp power of 7.5 kW, and varying width of the recess 7. Figure 17 Under the conditions shown, the illuminance maintenance rate was evaluated, and the results showed an improvement of more than 2% under any condition compared to a discharge lamp in which the recess 7 was not formed on the front end face 32.

[0105] (7) Furthermore, in the discharge lamp 1 of the above embodiment, the recess 7 is entirely formed on the inner side of a concentric circle c1 that excludes the center of the front end face 32 and has a diameter 70% of the diameter d of the front end face 32. However, the discharge lamp 1 is not limited to this structure. The recess 7 may also be formed on the outer side of the concentric circle c1 having a diameter 70% of the diameter d of the front end face 32.

[0106] Label Explanation

[0107] 1: Discharge lamp; 2: Light-emitting diode; 3: Anode; 3a: Front-end; 4: Cathode; 5: Lead bar; 6: Lamp holder; 7: concave part; 7a: Maximum depth; 20: Drum section; 21: Sealed tube section; 31: Outer periphery; 32: Front end face; 32a: Inner front face; 32b: External front face; 70: concave part; S1: Light-emitting space; X1: Cylindrical shaft; c1: concentric circles; c2: concentric circles.

Claims

1. A discharge lamp, comprising: Light-emitting tube, encapsulated with a light-emitting material; and The anode and cathode are arranged opposite each other inside the light-emitting tube. The anode is a generally cylindrical shape with a chamfered or rounded outer periphery at the front end opposite the cathode. The anode has a rounded front end face on the inner side of the chamfered or rounded outer periphery, which appears circular when viewed from the cylindrical axis. The front end face has a recess. The recess is formed at least inside a concentric circle having a diameter of 70% of the diameter of the front end face, and is not formed at the center of the front end face.

2. The discharge lamp according to claim 1, wherein, The recess is formed on the inner side of a concentric circle having a diameter of at least 50% of the diameter of the front end face.

3. The discharge lamp according to claim 1 or 2, wherein, The recess is formed on the outside of a concentric circle having a diameter of 20% of the diameter of the front end face.

4. The discharge lamp according to claim 1 or 2, wherein, The recess is formed in a surrounding shape that encircles the center of the front end face.

5. The discharge lamp according to claim 1 or 2, wherein, The recess is formed in a ring shape centered on the center of the front end face.

6. The discharge lamp according to claim 1 or 2, wherein, The luminescent substance is mercury, and the amount of mercury encapsulated is less than 20 mg / cc.

7. The discharge lamp according to claim 1 or 2, wherein, The maximum depth of the recess is 0.5 mm or more.

8. The discharge lamp according to claim 1 or 2, wherein, When viewed from the axial direction of the cylinder, the area of ​​the recess is more than 2% and less than 25% of the area of ​​the front end face.

9. The discharge lamp according to claim 1 or 2, wherein, The front end face includes: an inner front end face located inside the recess; and an outer front end face located outside the recess. The inner front end face is closer to the cathode than the outer front end face.

Images