Short-arc discharge lamp

Abstract

To facilitate manufacture, and to properly control a flow of gas generated in a bulb at lighting.SOLUTION: The anode 4 has a tapered portion 41 and a skirt portion 48 whose outer periphery expands linearly in the radial direction toward the rear. The skirt part 48 has a first guide surface 48 and a second guide surface 48b for guiding the gas flowing along the tapered part 41 toward the valve 2. Angles α, β between tangents from the first guide surface 48 and the second guide surface 48b and a tangent at an intersection in the bulb 2 are both 100 ° or less. The outer diameter P2 of the skirt portion 48 = the maximum outer diameter P1. Therefore, it is possible to reduce the narrowing of the sealing tube portion of the bulb 2 at the time of manufacturing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a short arc discharge lamp, and more particularly to preventing arc oscillation. [Background technology]

[0002] Patent Document 1 discloses an anode that has a blade-shaped protrusion at the base end, which controls the flow of gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-12672 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in reality, it is practically impossible to manufacture a lamp with an anode having such blade-shaped protrusions. Generally, when manufacturing a discharge lamp, a bulb is manufactured with a sealed tube portion larger than the maximum outer diameter of the anode, and the anode is positioned in the bulb via the sealed tube portion. The bulb is then heated with a burner to reduce the diameter. This is because if the diameter of the sealed tube portion is large, a process of reducing the diameter is required.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a short arc discharge lamp that is easy to manufacture and that can appropriately control the flow of gas generated inside the bulb when lit. [Means for solving the problem]

[0006] (1) The short arc discharge lamp of the present invention comprises a bulb having an arc tube portion and sealed tube portions extending outward from both ends of the arc tube portion, a cathode disposed inside the arc tube portion, a body portion, and an anode having a tip portion connected to the body portion and tapering toward the tip, the anode being disposed opposite the cathode, the body portion comprising a tapered anode having a diameter smaller at the rear end side than at the tip side of the anode, and an anode core rod supporting the anode, the short arc discharge lamp being vertically installed and lit with the anode installed on the upper side, the body portion having a protrusion at the rear end portion whose outer periphery expands radially toward the rear of the anode, the virtual maximum diameter formed by the protrusion being approximately the same as or smaller than the maximum diameter of the body portion.

[0007] Therefore, in a vertically installed short arc discharge lamp, the gas flow can be controlled by the protrusion without providing an extra protrusion on the anode.

[0008] (2) In the short arc type discharge lamp according to the present invention, the tapered shape is a linear tapered shape or a streamlined shape, which makes it possible to control the gas flow.

[0009] (3) In the short arc type discharge lamp according to the present invention, the protrusion has a first guide surface that controls the flow of gas moving along the side surface of the anode in the bulb direction, and a second guide surface that faces the first guide surface and controls the convection of the base surface of the anode on the core rod side in the bulb direction. When a tangent to the first surface is defined as a first tangent and as an inner tangent to the bulb at the intersection of the first tangent and the inner tangent to the bulb, the angle between the first tangent and the inner tangent to the bulb on the anode tip side is 100 degrees or less. When a tangent to the second surface is defined as a second tangent and as an inner tangent to the bulb at the intersection of the second tangent and the inner tangent to the bulb, the angle between the second tangent and the inner tangent to the bulb on the anode tip side is 100 degrees or less.

[0010] Therefore, the gas flow can be controlled more efficiently.

[0011] (4) In the short arc type discharge lamp according to the present invention, the tapered shape has a taper angle defined by a line connecting the maximum diameter part of the body part and the minimum diameter part of the body part of 10 degrees or less, thereby making it possible to guide a larger amount of gas flow along the anode to the protrusion.

[0012] (5) In the short arc type discharge lamp according to the present invention, the angle at the anode tip side of the intersection angle between the first tangent and the inner tangent line of the lamp bulb and the angle at the anode tip side of the intersection angle between the second tangent and the inner tangent line of the lamp bulb are either substantially parallel or the former is smaller, thereby making it possible to further reduce turbulence around the protrusion.

[0013] (6) In the short arc type discharge lamp according to the present invention, the body is composed of a body main body and a hollow cylindrical portion located outside the body main body, and the hollow cylindrical portion has the protrusion. By configuring it from multiple members in this way, the body main body and the hollow cylindrical portion can be formed separately. This makes it possible to, for example, change the materials of the body main body and the hollow cylindrical portion, thereby reducing the overall weight.

[0014] The following explains the terms used in the claims. In the embodiment, the "protrusion" corresponds to the skirt portion 48. In the embodiment, the "first tangent" corresponds to the first imaginary extension line. Note that when the first guide surface 48a is configured as a straight line, the "first tangent" refers to the straight line itself, and when the first guide surface 48a is configured as a curved line, the tangent at the end portion corresponds to the first tangent. When the tip of the skirt portion 48 is rounded or chamfered, the tangent at the end portion may be the end portion where the rounded or chamfered processing begins.

[0015] The "linear tapered shape" or "streamlined shape" includes not only a shape in which the width of the body portion 40 gradually decreases toward the rear end surface of the electrode, as in the first embodiment, but also a streamlined shape (concave or convex) or a stepped shape. It also includes a case in which a bulge 61 having a diameter smaller than the maximum diameter portion is provided midway, as shown in FIG. 8A. Furthermore, the "second guiding surface" in the embodiment shown in FIG. 1 is a concept that includes an arc-shaped recess in the bottom surface of the anode 4, but also includes a case in which there is no recess in the bottom surface of the anode 4, as shown in FIG. 9E. Furthermore, the concept also includes a case in which there is no arc-shaped recess in the bottom surface of the anode 4, as shown in FIG. 9D. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view of a main part of a short arc discharge lamp 1 according to the present invention. [Figure 2] FIG. 4 is an enlarged cross-sectional view of a skirt portion 48. [Figure 3] 10 is a diagram for explaining gas flow control by a skirt portion 48. FIG. [Figure 4] FIG. [Figure 5] FIG. 10 is a diagram showing voltage fluctuations. [Figure 6] FIG. 10 is a diagram showing a case where a condition is satisfied and a case where a condition is not satisfied. [Figure 7] FIG. 10 shows another embodiment. [Figure 8] FIG. [Figure 9] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] (1. First embodiment) A short arc discharge lamp according to the present invention will be described with reference to the drawings. As shown in Fig. 1, the short arc discharge lamp 1 is a 13.5 kW mercury lamp, and an anode 4, a cathode 3 facing it, and a core rod 7 are arranged in a bulb 2. A bead 9 is provided between the bulb 2 and the core rod 7. In each drawing, hatching of the core rod 7 is omitted.

[0018] The anode 4 has a body portion 40 and a tip portion 46. The body portion 40 has, from the tip end to the rear end, a straight portion 42, a tapered portion 41, and a skirt portion 48. The straight portion 42 has a diameter P1, and the tip portion 46 is machined to taper from the straight portion 42. In this embodiment, the diameter P1 is set to 40 mm, but is not limited to this. The straight portion 42 tapers toward the skirt portion 48 at a taper angle θ. In this embodiment, θ is set to 5 degrees. The skirt portion 48, located at the rear end of the anode 4, has an outer periphery that linearly expands in the radial direction toward the rear of the anode 4. A rounded portion is provided between the end of the tapered portion 41 and the end of the tapered portion 41 to allow for smooth gas flow.

[0019] The first guide surface 48a of the skirt portion 48 guides gas flowing along the tapered portion 41 toward the bulb 2. The relationship between the first guide surface 48a and the bulb 2 will be described with reference to FIG. 2A. In this embodiment, the first gas guide surface 48a is formed by a straight line La. The angle of intersection between an imaginary extension line L1 of this straight line and a tangent to the inner surface of the bulb 2 at point Q1, where the angle of intersection is the angle toward the center of the bulb, is defined as α. This is because, if angle α is less than 90°, gas that strikes the bulb 2 should be guided toward the beads 9 (upward). Here, the gas has a buoyancy effect, which causes the gas to rise. Therefore, if angle α is approximately +10°, the gas is guided toward the beads 9 (upward).

[0020] As shown in FIG. 1B, the skirt portion 48 has a second guide surface 48b on the electrode bottom surface 48k. FIG. 1C is an arrow view of the anode 4 as seen from the bottom side. The donut-shaped second guide surface 48b is formed to surround the central core rod 7. As shown in FIG. 1B, the cross-sectional shape of the second guide surface 48b is arc-shaped. The intersection angle between an imaginary extension line L2 (a tangent extending from the end) of the arc and a tangent to the inner surface of the bulb 2 at point Q2 where the line intersects with the bulb 2, where the intersection angle on the bulb center side is β, is set to 100° or less. This is because, if angle β is less than 90°, the gas that hits the bulb 2 should be guided toward the beads 9 (upward). Here, the gas has a buoyancy effect, causing the gas to rise. Therefore, if angle β is approximately +10°, the gas is guided toward the beads 9 (upward).

[0021] In this embodiment, a tungsten pillar with a diameter of 40 mm is cut to increase the outer diameter of the skirt portion 48, and in order to effectively control the gas flow, P1=P2 is set. However, this is not limited to this, and P1>P2 may also be set.

[0022] The control of the gas flow by the skirt portion 48 will be described with reference to FIG.

[0023] When an arc discharge occurs, the Lorentz force acting on the arc causes it to contract, resulting in a pressure gradient from the vicinity of the cathode to the center of the arc, which acts as a driving force to cause the gas to flow along the tapered portion 41 of the anode 4.

[0024] In the anode 4, the tapered portion 41 is formed in a direction narrowing in a direction away from the cathode (toward the base of the anode 4). In this embodiment, the taper angle θ is set to 5 degrees. Therefore, the gas flowing from the cathode 3 toward the anode 4 is likely to flow toward the bead side of the anode 4 without the gas flow separating from the surface of the anode 4. This is because the gas attempts to flow along the anode 4, but the drag at that time is reduced.

[0025] If the objective is simply to control the gas flow inward, the taper angle may be greater than 10 degrees. However, increasing the taper angle reduces the cross-sectional area perpendicular to the axial direction at the rear end of the anode. As a result, it becomes difficult to efficiently transport heat from the front end of the anode to the rear end of the anode. In this embodiment, in order to ensure a cross-sectional area perpendicular to the axial direction in the smallest diameter region connected to the skirt portion 48, the taper angle θ exists and is set to 10 degrees or less. This satisfies both the heat transport and the gas flow control.

[0026] The gas that reaches the skirt portion 48 is decelerated by the first guide surface 48a and changes direction toward the valve 2, proceeding toward the valve 2 as gas flow F11 (see FIG. 3A) and colliding with the inner wall of the valve 2. Here, the angle α of the collision portion is set to 100° or less, so that a larger amount of gas is guided toward the beads 9. In this way, the speed and direction of the gas flow that collides with the valve 2 are controlled by the skirt portion 48.

[0027] Without the first guide surface 48a of the skirt portion 48, the gas flow would be constricted and would flow along the core rod 7 toward the vicinity of the beads 9 (see FIG. 1), increasing the thermal energy density of the beads 9 and increasing the thermal load near the beads 9. As a result, the glass near the beads 9 would be distorted, and in the worst case scenario, it could burst.

[0028] In contrast, when the first guide surface 48a is provided, the gas flow is dispersed radially, which reduces the thermal energy density of the gas flow and the thermal load on the bulb. As a result, the bulb is less likely to be distorted by heat, and it will not burst even if it is lit for a long time.

[0029] The gas flow toward the beads 9 in this manner descends along the core rod 7 as a downward air current and reaches the second guide surface 48b (F1-F2). Since this gas flow flows along the second guide surface 48b, it is guided in the direction of the imaginary extension line L2 shown in Fig. 1 (F3-F4). This return gas flow and the gas flow that is guided by the first guide surface 48a and collides with and flows inside the bulb 2 travel in substantially the same direction, making it difficult for turbulence to occur.

[0030] In contrast, if the second guide surface 48b were not present as shown in Figure 3B, the return gas flow could be decelerated at the bottom of the anode, but would continue to flow in a direction perpendicular to the core rod 7 and collide with the gas flow guided by the first guide surface 48a, resulting in turbulence. Such turbulence would prevent the gas flow guided by the first guide surface 48a from flowing toward the bead 9. As a result, the gas flow guided by the first guide surface 48a would continue to descend along the bulb 2 and proceed toward the tip of the cathode without slowing down, which could cause the arc to wobble.

[0031] By controlling the speed and direction of the gas flow using the two guide surfaces of the skirt portion 48, the gas flow is dispersed radially, reducing the thermal energy density of the gas flow and the thermal load on the bulb. As a result, the bulb is less likely to be distorted by heat, and it will not burst even when lit for a long time.

[0032] In order to more effectively prevent the turbulent flow, it is preferable that the imaginary extension lines L1 and L2 are substantially parallel to each other or that β>α.

[0033] The gas guided from the first guide surface 48a, colliding with the bulb 2 and flowing downward is sufficiently decelerated, and is further decelerated by the resistance of buoyancy as it flows below the bulb 2. The gas that flows below the bulb 2 rises again toward the arc region, but because it is sufficiently decelerated, it is prevented from disturbing the arc or the surrounding gas. As a result, the arc fluctuation at the cathode tip is suppressed. This results in a more uniform temperature distribution on the cathode tip surface, which flattens the wear on the cathode tip. As a result, a stable arc can be maintained for a long period of time.

[0034] The inventors manufactured four discharge lamps with different angles of α and β, as shown in Figure 4A, and four with a conventionally shaped anode (without skirt portion 48 or tapered portion 41), and compared the wear state of the cathode after operation. When α and β were less than 100°, the tip of the cathode was not significantly damaged even after long-term operation. Figure 4B is a photograph of electrode No. 1 after 2,500 hours of operation, and Figure 4C is a photograph of electrode No. 4 after 1,250 hours of operation. As can be seen, the former shows less wear to the tip than the latter, despite being operated for approximately twice the time.

[0035] Figure 5 shows the voltage waveforms during operation after 1,250 hours of operation. In this figure, the upper waveform is for electrode No. 4, and the lower waveform is for electrode No. 1. As can be seen, when there is no skirt portion 48, the voltage fluctuations are smaller than when there is one. These measurement results also show that the arc is stable in this embodiment of the present invention.

[0036] FIG. 6A shows a mercury lamp in which α is within the range of the present invention, while FIG. 6B shows a lamp in which α is outside the range. In both cases, the anode 4 has the same shape. As described above, α falls outside the range depending on the shape of the bulb 2. As described above, even if the anode 4 is the same, depending on the shape of the bulb 2, it may not be possible to control the gas flow as in the present invention. As described above, depending on the shape of the bulb 2, not only will the values ​​of angles α and β change, but the gap (described below) will also change, even for anodes of the same shape.

[0037] If the distance between the tip of the skirt portion 48 and the bulb 2 is short, the space between the electrode and the bulb becomes small, which poses a problem that it becomes difficult for the gas to flow to the top of the bulb.

[0038] A straight line is defined that runs perpendicularly from the smallest diameter part of the anode 4 to the center line of the core rod 7, and the area of ​​the hollow disk created when the line segment of this line, connecting the anode 4 to the inner wall of the bulb 2 at a distance d1, is rotated around the lamp axis is defined as S1.

[0039] Furthermore, when the line segment of the first imaginary extension line L1, which is a distance d2 from the tip of the skirt portion 48 to the first intersection point Q1, is rotated about the center line of the core rod 7, an oblique hollow disk is defined. The area of ​​this hollow disk is defined as S2.

[0040] In this embodiment, the distances d1 and d2 are set so that 0.1≦(S2 / S1)≦1. If 1<(S2 / S1), the gas flow at the bottom of the valve becomes turbulent, which in turn causes turbulence in the entire gas flow inside the valve. If (S2 / S1)<0.1, the shape change near the top and bottom of the skirt becomes too large, which can cause vortices and other turbulence in the gas flow, resulting in turbulence in the entire gas flow inside the valve.

[0041] In addition, taking into consideration the thermal load on the bulb, it is preferable to set 5≦d2 [mm].

[0042] When the shape of the first guide surface 48a of the skirt portion 48 is formed by a straight line, the straight line extending from this is taken as the virtual extension line, but this is not limited to this. As shown in Figure 2B, when the first guide surface 48a is formed by a curve, the tangent to the curve Ra at the end Q41 can be taken as the first virtual extension line L1.

[0043] In this embodiment, a straight portion 42 is provided to facilitate machining and serve as a chucking area when cutting is possible, but this is not essential. The tapered portion 41 may also be configured with a streamlined shape. As for combinations, only the tapered portion 41 may be streamlined, the tapered portion 41 and straight portion 42 may be streamlined together, or the tapered portion 41, straight portion 42, and tip portion 46 may be combined to form a single streamlined shape.

[0044] In the case of a streamlined shape, the taper angle θ may be defined as an imaginary line connecting the maximum diameter portion and the minimum diameter portion, and may be defined as the angle between this imaginary line and a straight line parallel to the center line.

[0045] In the embodiment, the taper angle θ is set to 5 degrees, but 3 to 7 degrees is most preferable, and the upper limit may be 8 to 10 degrees. As already explained, if the taper angle θ is greater than 10 degrees, the cross-sectional area perpendicular to the axial direction at the rear end of the anode becomes small, causing a problem of reduced heat dissipation. Furthermore, the lower limit may be set to less than 3 degrees, for example, about 1 or 2 degrees.

[0046] In this embodiment, the outer shape P2 of the skirt portion 48 is the same as the diameter P1 of the maximum outer diameter portion of the anode 4. Therefore, manufacturing is possible without increasing the amount of narrowing of the sealing tube portion during manufacturing. Note that the outer shape P2 of the skirt portion 48 may be approximately the same as the maximum diameter of the body portion 40, or may even be smaller than that.

[0047] In this embodiment, a 13.5 kW short arc discharge lamp has been described as an example, but the invention is particularly effective in lamps of 2 kW or more, but the scope of the invention is not limited to this.

[0048] (2. Other Embodiments) In this embodiment, the cross-sectional shape of the second guide surface 48b is an arc shape as shown in FIG. 1B, but it may also be configured to have a shape in which a straight line and an R-shape are connected.

[0049] Furthermore, a doughnut-shaped recess is formed on the entire bottom surface 48k of the second guide surface 48b. In this case, when the bottom surface of the electrode 4 is observed from the bead 9, the recess is recognized as the ends of two circles. However, instead of this shape, multiple recesses with arc-shaped cross sections may be arranged as shown in FIG. 1C. In this case, when the bottom surface of the electrode 4 is observed from the bead 9, multiple circles are recognized as being positioned on the bottom surface.

[0050] 8A , as a modification of the streamlined shape, an enlarged diameter portion 61 may be provided midway along the tapered portion 41. In this case, the enlarged diameter portion 61 has a convex streamlined shape, but is not limited to this and may also be configured as a straight line. In this case, too, the diameter of the enlarged diameter portion 61 may be set to be the same as or smaller than the maximum diameter of the body portion 40.

[0051] Furthermore, as shown in FIG. 1B, the tapered portion 41 may have a concave streamlined shape 64.

[0052] 1C shows an example of a two-stage tapered shape of tapered portion 41. In this embodiment, the taper angles are different between regions 67 and 68. In this way, tapered portion 41 may have a shape consisting of multiple straight lines or curves, or a combination of both.

[0053] Also, instead of smoothly connecting the maximum diameter portion and the tapered portion, a step 77 may be provided to gradually reduce the diameter of the electrode, as shown in Fig. 1D. Fig. 1E shows an example in which the tip 79 of the step is chamfered.

[0054] Furthermore, tapered portion 41 may be configured in a shape that combines curved portion 81 and curved portion 82, as shown in FIG. 9A.

[0055] In the anode 4 of FIG. 1A, the tip of the skirt portion 48 has an acute angled shape, but as shown in FIG. 9B, the tip 85 may be rounded so that part of the gas flows in the direction of the arrow 86. In this way, the tip of the skirt portion 48, which is a protruding portion, may be rounded or chamfered. Note that the tip of the second guide surface 48b of the skirt portion 48 may also be rounded or chamfered.

[0056] The skirt portion 48 may be made up of a plurality of straight or curved portions. An example in which the skirt portion 48 is made up of a plurality of straight portions 87, 88 is shown in FIG.

[0057] In the anode 4 of FIG. 1A, the electrode bottom surface 48k is provided with a recessed second lead surface 48b. However, as shown in FIG. 9D, the electrode bottom surface 48k may be configured with a linear portion 92a that serves as the second lead surface 48b without providing a recess. In this case, the skirt portion 48 has the first lead surface 48a that has a linear shape 92b. Although a notch 92c is provided at the tip of the skirt portion 48, this is not essential. Furthermore, as shown in FIG. 9E, the recess in the electrode bottom surface 48k may be configured with a linear recess 93 rather than an arc-shaped cross section.

[0058] Furthermore, in this embodiment, the skirt portion 48 is machined as a single unit, but it may also have a separate structure. Specifically, as shown in FIG. 9F , the anode 4 may be formed of a barrel main body 96 and a ring-shaped portion 97 including the skirt portion 48. To improve adhesion between the ring portion 97 and the barrel main body 96, threads may be cut on both of the joining surfaces of the ring portion 97 and the main body 96, and the ring portion 97 may be screwed onto the main body 96. In this way, the anode may be formed of the barrel main body 96 and a hollow cylindrical portion located outside the barrel main body 96, and a protrusion may be provided on this hollow cylindrical portion. [Explanation of symbols]

[0059] 2. Valve 3...Cathode 4...Anode 40 Torso 41 Tapered section 42 Straight section 46...Tip 48·····Skirt part 48a...1st guidance surface 48b...Second guidance surface 48k...Bottom Q1...1st intersection Q2...Second intersection L1: First virtual extension line L11...First tangent L2: Second virtual extension line L21...Second tangent

Claims

1. a bulb having an arc tube portion and sealing tube portions extending outward from both ends of the arc tube portion; a cathode disposed inside the arc tube portion; an anode having a body portion and a front end portion connected to the body portion and tapering toward a front end thereof, the anode being disposed opposite the cathode, the body portion having a tapered shape in which the diameter of the rear end side of the anode is smaller than that of the front end side of the anode; an anode core rod supporting the anode; A vertically installed short arc discharge lamp that is lit with the anode installed on the upper side, the trunk portion has a protrusion at a rear end portion, the outer periphery of which expands in the radial direction toward the rear of the anode, the virtual maximum diameter formed by the protrusion is approximately the same as or smaller than the maximum diameter of the body portion; A short arc discharge lamp characterized by:

2. 2. The short arc type discharge lamp according to claim 1, The tapered shape is a linear tapered shape or a streamlined shape; A short arc discharge lamp characterized by:

3. 2. The short arc type discharge lamp according to claim 1, the protrusion has a first guide surface that controls the flow of gas moving along the side surface of the anode in a bulb direction, and a second guide surface that faces the first guide surface and controls the convection flow at a base surface of the anode on a core rod side in the bulb direction, a tangent to the first surface is defined as a first tangent, and an inner tangent line of the enclosure at an intersection point of the first tangent line and the inner lateral surface of the enclosure is defined as a first tangent line, the angle on the anode tip side of the intersection angle between the first tangent line and the inner tangent line of the enclosure is 100 degrees or less, a tangent to the second surface is defined as a second tangent, and an inner tangent line of the enclosure at an intersection point of the second tangent line and the inner lateral surface of the enclosure is defined as the second tangent line, the angle on the anode tip side of the intersection angle between the second tangent line and the inner tangent line of the enclosure is 100 degrees or less; A short arc discharge lamp characterized by:

4. 2. The short arc type discharge lamp according to claim 1, the tapered shape has a taper angle defined by a line connecting the maximum diameter portion of the body portion and the minimum diameter portion of the body portion of 10 degrees or less; A short arc discharge lamp characterized by:

5. 5. The short arc type discharge lamp according to claim 3, the angle at the anode tip side of the intersection angle between the first tangent and the inner tangent line of the envelope on the anode tip side and the angle at the anode tip side of the intersection angle between the second tangent and the inner tangent line of the envelope on the anode tip side are substantially parallel, or the former is smaller; A short arc discharge lamp characterized by:

6. The short arc type discharge lamp according to any one of claims 1 to 4, the barrel portion is composed of a barrel main body and a hollow cylindrical portion located outside the barrel main body, and the hollow cylindrical portion has the protrusion; A short arc discharge lamp characterized by:

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