JP2009238671A - Short arc type discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable discharge lamp having a sealing structure for preventing bursting of a sealing tube in lighting. <P>SOLUTION: This discharge lamp can be lighted by large electric power. An inside metallic ring 26 facing an electrode side glass tube is arranged in the sealing tube 20, and a plurality of metallic foils 36 are welded to the inside metallic ring 26. When lighting in a light emitting tube, assuming pressure as P(MPa), the thickness T mm of the sealing tube 20 and a diameter D mm of the inside metallic ring 26 are determined so as to satisfy (P-2.2)/200<(T/D<SP>2</SP>). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a short arc type discharge lamp, and more particularly to a discharge lamp sealing structure.

  In a short arc type discharge lamp, a glass sealing tube is integrally formed at both ends of an arc tube sealed with an electrode, and an electrode support rod for supporting the electrode is held by a cylindrical glass tube in the sealing tube. Is done. In the sealing structure with metal foil, the diameter of the sealing tube is reduced by heat, and the sealing tube is welded to the glass tube. Thereby, metal foil is sealed and the inside of an arc_tube | light_emitting_tube becomes an airtight state.

  In the semiconductor and liquid crystal manufacturing fields, in order to improve production efficiency, the power of short arc type discharge lamps is increasing. Therefore, in a discharge lamp having a large rated power, a metal ring is fixed to the electrode support rod, and a plurality of metal foils are welded to the metal ring. Thereby, electric power is supplied to an electrode via metal foil, a metal ring, and an electrode support rod (for example, refer patent document 1).

In order to increase the strength of the sealing tube, for example, a method is known in which the ratio of the diameter (d) of the electrode support rod and the outer diameter (D) of the sealing tube is set to be larger than a predetermined value (see Patent Document 2). ). There, the ratio (D / d) between the diameter of the electrode support bar and the outer diameter of the sealing tube is adjusted for the lamp sealing structure in which a single metal foil is connected to the electrode support bar, and the lamp is turned on. Prevent damage to the sealing tube.
JP 2007-115414 A Japanese Utility Model Publication No. 1-106063

  In the sealing structure of a lamp provided with a metal ring, a minute gap is generated near the contact surface between the metal ring and the glass tube during the sealing process. The minute gap communicates with the discharge space through the gap between the electrode support rod and the glass tube. For this reason, when the lamp is turned on, a stress is generated that causes the metal ring and the glass tube to be separated due to a pressure difference between the high pressure in the discharge space and the atmosphere. Due to this stress, the crack progresses radially outward along the contact surface and reaches the outer surface of the sealed tube.

  Further, the metal ring is heated by the heat from the electrode when the lamp is turned on, and is thermally expanded. Due to the effect of this thermal expansion, the stress applied to the sealing tube around the metal ring increases. As the number of metal foils increases and the size of the metal ring increases along with the increase in power of the lamp, the stress received by the sealing tube further increases and the sealing tube may burst.

  However, the strength of the sealing structure using the metal ring cannot be made appropriate only by relatively increasing the diameter of the sealing tube as in Patent Document 1. If the thickness of the sealing tube around the metal ring is increased more than necessary, the direction of crack propagation spreads, and the crack generated near the contact surface travels inside the glass tube or the wall of the sealing tube to the arc tube. End up. As a result, the arc tube itself ruptures, causing not only the lamp but also the entire light source device to be damaged, increasing the damage.

  As described above, when the size of the metal ring increases with the increase in power of the lamp, it is necessary to cope with the stress in the sealed tube that is different from that of the conventional lamp. It is necessary to provide the sealing structure with a reliable strength that does not incur.

  The discharge lamp of the present invention is a discharge lamp having a sealing structure using a conductive annular member such as a metal ring, holds an electrode support rod for supporting an electrode in the arc tube, and is a glass tube welded to the seal tube; And a conductive annular member facing the glass tube and electrically connecting the metal foil and the electrode support rod disposed along the axial direction.

In the present invention, the outer diameter D (mm) of the annular member and the thickness T (mm) of the sealing tube in the vicinity of the contact surface between the annular member and the glass tube are determined so as to satisfy the following expression. However, the lighting pressure in the arc tube is P (MPa).

(P-2.2) / 200 <(T / D ² )

  In the sealing structure using the annular member, the stress applied to the contact surface between the annular member and the glass tube is the surface area facing the axial direction of the annular member, that is, the size of the contact surface with the inner glass tube 24. It can be regarded as proportional. Therefore, the stress generated in the sealing tube is considered to be proportional to the square of the diameter D of the annular member. In other words, when the diameter D of the annular member is reduced, the stress is reduced by the square effect. On the other hand, it is considered that the pressure resistance of the sealed tube against stress increases in proportion to the wall thickness T.

Therefore, the ratio T / D ² between the thickness T of the sealing tube and the area D2 of the annular member is related to the sealing structure using a metal ring, particularly the sealing structure of a high-power discharge lamp. It can be an effective index representing the pressure resistance performance against the stress generated in Actually, when the relationship between the pressure in the discharge space when a crack occurred in the sealed tube (at the time of breakage) and T / D ² was found, it was found that there was a proportional relationship.

Since the discharge space pressure during lighting needs to be set smaller than the breakdown pressure, an inequality indicating the allowable pressure range in the discharge space is derived from the proportional expression. Therefore, when the pressure in the arc tube at the time of lighting is set to P, the above formula that defines the range of T / D ² values is derived.

  As described above, when the diameter of the annular member is reduced, the stress in the sealed tube is also reduced in proportion to the square thereof. Therefore, the strength of the sealing structure can be maintained without significantly changing the wall thickness T by slightly suppressing the diameter of the annular member. That is, it is not necessary to increase the thickness of the sealing tube more than necessary as the size of the annular member increases.

  In particular, in the case of a high-power discharge lamp, the diameter D of the annular member is 20 mm or more. On the other hand, the thickness T of the sealing tube has an upper limit, and the arc tube may be damaged by increasing the thickness T more than necessary. In the present invention, the balance between the thickness T of the sealing tube and the diameter D of the annular member can be adjusted based on the above formula, and a sealing structure having appropriate strength can be realized. .

  The thickness T of the sealing tube is limited by various circumstances. If the thickness of the sealing tube is too thin, it is difficult to uniformly contract the sealing tube, and the sealing process becomes complicated. Therefore, the lower limit of the thickness is preferably 1.5 mm. On the other hand, if the sealing tube is too thick, cracks may progress to the arc tube. For example, the upper limit of the wall thickness is desirably 11 mm.

  On the other hand, the range of the diameter D of the annular member is preferably determined in consideration of a high-power discharge lamp. For example, the lower limit of the diameter D of the annular member is set to 20 mm in order to realize a high power discharge lamp. On the other hand, in order to make the thickness T of the sealing tube 11 mm or less, the upper limit of the diameter D of the annular member is set to 41 mm from the above formula. However, the pressure resistance (breaking pressure) P in the arc tube is 3.5 MPa.

In the short arc type discharge lamp which is another feature of the present invention, the power during stable lighting is set to 8 kW or more in order to increase the power. And when the outer diameter of the annular member is D (mm) and the thickness of the sealing tube in the vicinity of the contact surface between the annular member and the glass tube is T (mm), the following equation is satisfied. . However, considering that the discharge space pressure at the time of lighting is 2.5 MPa, in order to ensure high safety, the pressure resistance (breakdown pressure) P in the discharge space, that is, the arc tube is set to 3.5 MPa and is substituted into the above formula. Can be obtained.

0.0065 ≦ T / D ²

A short arc type discharge lamp, which is another feature of the present invention, includes an electrode support rod that supports an electrode in an arc tube, a glass tube that is welded to a sealing tube, a glass tube, and an axial direction. A conductive annular member that electrically connects the disposed metal foil and the electrode support rod, the lighting pressure in the arc tube is P (MPa), the outer diameter of the annular member is D (mm), and the annular member The outer diameter D of the annular member and the thickness T of the sealing tube are determined so that the following formula is satisfied, where T (mm) is the thickness of the sealing tube in the vicinity of the contact surface between the tube and the glass tube. It is characterized by that.

k × (P−Pc) <T / D ²

Here, k denotes a coefficient determined from the proportional relationship between the fracture pressure of the sealing tube and T / D ^2. Pc represents a limit pressure in the arc tube based on electric power when the discharge lamp is stably lit.

  According to the present invention, it is possible to obtain a discharge lamp having a highly reliable sealing structure that prevents the sealing tube from bursting during lighting.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of a short arc type discharge lamp according to this embodiment. FIG. 2 is a schematic cross-sectional view of the anode side sealing tube.

  The short arc type discharge lamp 10 includes an anode 14 and a cathode 16 in an arc tube 12 made of quartz glass. Quartz glass sealing tubes 20 and 60 are connected to both sides of the arc tube 12 so as to face each other. Both ends of the sealing tubes 20 and 60 are closed with caps 80A and 80B.

  Inside the sealing tubes 20 and 60, parts (hereinafter referred to as mounting parts) 18A and 18B for supporting the anode 14 and the cathode 16 and sealing the discharge space 11 in the arc tube 12 are encapsulated, respectively. . Further, mercury and a rare gas are sealed in the discharge space 11.

  As shown in FIG. 2, an electrode support rod 22 that supports the anode 14 is provided inside the sealing tube 20 and is disposed along the axial direction. The electrode support rod 22 passes through a shaft hole 24A provided in a cylindrical thick glass tube (hereinafter referred to as an electrode side glass tube) 24 and is held by the electrode side glass tube 24. A cylindrical recess 24 </ b> B is formed at the arc tube side end of the electrode side glass tube 24 to ensure welding with the sealing tube 20.

  The electrode support bar 22 does not extend to the end of the sealing tube 20, and a metal lead bar 28 is coaxially disposed opposite to the electrode support bar 22 at a predetermined interval. The electrode support rod 22 and the lead rod 28 are inserted into insertion holes provided at both ends of the cylindrical glass member 34, and the glass member 34 holds the electrode support rod 22 and the lead rod 28. The lead bar 28 is connected to an external lead wire (not shown) connected to a power supply unit (not shown).

  Metal rings 26 and 32 are disposed in close contact with both ends of the glass member 34, and the electrode support bar 22 and the lead bar 28 are welded to the shaft holes 26A and 32A. A metal ring (hereinafter referred to as an inner metal ring) 26 close to the arc tube 12 abuts on the electrode side glass tube 24, and the other metal ring (hereinafter referred to as an outer metal ring) 32 allows a lead rod 28 to pass through. It contacts the annular fixed glass tube 29 to be held.

  Between the inner metal ring 26 and the outer metal ring 32, a plurality of strip-shaped metal foils 36 extend in the axial direction along the outer surface of the glass member 34 along the axial direction. It is welded to the circumferential surface of the metal ring 32. The outer metal ring 32 electrically connects the lead bar 28 and the metal foil 36, and the inner metal ring 26 connects the metal foil 36 and the electrode support bar 22, thereby connecting to the power supply unit. Electric power is supplied from the lead rod 28 to the anode 14.

  The sealing tube 20 is reduced in diameter by being heated by a gas burner or the like during the sealing process, and is welded to the electrode side glass tube 24, the glass member 34, and the fixed glass tube 29. Thereby, the inside of the sealing tube 20 is sealed, and the mounting component 18A including the electrode side glass tube 24, the inner metal ring 26, the outer metal ring 32, the glass member 34, and the fixed glass tube 29 does not move in the axial direction. To be fixed.

  3 is a cross-sectional view of the contact surface 24N between the inner metal ring 26 and the electrode side glass tube 24 in FIG.

  The discharge lamp 10 can be lit with large electric power (for example, 8 kW), and the inner metal ring 26 and the outer metal ring 32 are set to have a diameter of 20 mm or more as the electric power increases.

When the outer diameter of the inner metal ring 26 is D and the outer diameter of the sealing tube 20 is expressed as D0, the thickness (thickness) T of the sealing tube 20 is calculated based on the difference between D and D0. (= (D0−D) / 2). Then, the outer diameter D (mm) of the inner metal ring 26 and the sealing so that the ratio (T / D ² ) between the outer diameter D of the metal ring 26 and the wall thickness T of the sealing tube 20 satisfies the following expression: The wall thickness T (mm) of the tube 20 is determined.

(P-2.2) / 200 <T / D ² (1)

However, P shows the pressure in the arc_tube | light_emitting_tube 12 at the time of stable lighting. Further, the thickness of the metal foil 36 is thinner than that of the metal ring 26 and the sealing tube 20, and is ignored here.

When the power is 8 kW, the pressure in the arc tube 12 is about 2.5 MPa. However, in order to give more sufficient pressure resistance, the pressure resistance in the arc tube 12 is set to 3.5 MPa. In this case, the outer diameter D of the inner metal ring 26 and the wall thickness T of the sealing tube 20 are determined so as to satisfy the following expression.

0.0065 ≦ T / D ² (2)

  Hereinafter, the reason why the outer diameter D of the inner metal ring 26 and the thickness T of the sealing tube 20 are determined based on the above equation (1) will be described with reference to FIGS. 4 and 5.

  First, sealing tubes having different thicknesses are prepared, and a discharge lamp having the above-described sealing structure is manufactured by the above-described sealing method. Here, a discharge lamp of a type using five metal foils having a rated lamp power of 12 kW, a lamp current of 103 A, inner metal ring diameters of 20 mm and 25 mm, and a width of 10 mm, a rated lamp power of 7.5 kW, a lamp current of 183 A, a metal ring Each type of discharge lamp is prepared using six metal foils having a diameter of 27 mm and a width of 12 mm.

Next, a hydrostatic pressure experiment is performed on each discharge lamp. In the hydrostatic pressure experiment, the arc tube 12 is filled with water, and the destruction of the sealed tube is observed while applying water pressure with a pressure pump. The pressure increase rate of the water pressure is 6 MPa / 5 min. Gradually increasing the pressure, the pressure at which cracking occurs the contact surface between the inner metal ring and the glass tube as a base point, the burst pressure P _0.

Figure 4 is a graph showing the relationship between the fracture pressure _{P 0} and T / ^{D 2.} Eight discharge lamps having a metal ring outer diameter D of 20 mm and different sealing tube thicknesses T, and metal ring outer diameter D of 25 mm and sealing tube thicknesses T being different 16 Hydrostatic pressure experiments were performed on three discharge lamps and three discharge lamps having an outer diameter D of the metal ring of 27 mm and different sealing tube thicknesses T, and the measured breakdown pressure P ₀ is shown in FIG. 4 is plotted.

As is clear from FIG. 4, a proportional relationship is established between the burst pressure P ₀ and T / D ² within a certain range. That is, as shown in FIG. 4, may be indicated by a straight line relationship between the fracture pressure P ₀ and T / D ^2.

When the straight line in FIG. 4 is expressed by an equation, the proportionality coefficient is 200, and the intercept value when the straight line is extended is 2.2, and the following equation is obtained.

P ₀ = 200 × (T / D ² ) +2.2 (3)

However, the expression (3) is established when the value of T / D ² is within a predetermined range (here, 0.004 to 0.016) and is more than the limit pressure (2.2 MPa here) within the arc tube.

Expression (3) represents that the burst pressure P ₀ increases as the value of T / D ² increases. That is, by reducing the area of the metal ring 26 with a thick T, increases breaking pressure P _0. Incidentally, burst pressure P ₀ is a light emitting pipe pressure when the cracks around the inner metal ring sealing tube, this pressure corresponds to the critical stress to withstand the sealing structure. Therefore, T / D ² can be regarded as a variable representing the resistance against breakdown of the sealed tube of the discharge lamp, that is, the resistance against stress generated in the vicinity of the contact surface. Hereinafter, the T / ^{D 2} and breakdown resistance variable A.

The pressure P at the time of the discharge lamp lit, to prevent destruction of the sealing tube, must be less than the breakdown pressure P _0. Therefore, it is necessary to satisfy the following formula.

P <200 × (T / D ² ) +2.2 (4)

Therefore, Formula (1) can be obtained based on Formula (4).

For example, the pressure in the arc tube is about 2.5 MPa during operation of the discharge lamp with power of 8 kW. However, in order to provide sufficient durability, the breaking pressure P ₀ is set to 3.5 MPa (= P ₁ ). Therefore, from the equation (4), the fracture resistance variable A (= T / D ² ) needs to satisfy the following equation.

0.0065 ≦ A (5)

That is, the fracture resistance variable A must be greater than 0.0065 (= A1).

FIG. 5 is a graph showing the relationship between the outer diameter D of the inner metal ring and the thickness T of the sealing tube with respect to the breaking pressure. The relationship between D and T when the burst pressure P0 is 2.5, _3.0 , 3.5, 4.0 (MPa) is shown. From FIG. 5, the most effective ranges of D and T are obtained.

  If the thickness of the sealing tube is too thin, it is difficult to uniformly contract the sealing tube, and the sealing process becomes complicated. Here, the lower limit of the thickness is 1.5 mm. On the other hand, if the sealing tube is too thick, when the sealing tube breaks, the crack proceeds to the arc tube, and the lamp itself may be damaged. Therefore, the upper limit of the wall thickness is 11 mm here.

  When the wall thickness T is in the range of 1.5 ≦ T ≦ 11, the diameter D of the annular member may be determined so as to satisfy the above formula. However, in order to realize a high-power discharge lamp, The small diameter is set to 20 mm. On the other hand, since the upper limit of the thickness T of the sealing tube is 11 mm, the upper limit of D that satisfies Equation (4) is set to 41 mm.

  Thus, according to the present embodiment, in the discharge lamp 10 that can be lit with high power, the inner metal ring 26 facing the electrode side glass tube 24 is disposed in the sealing tube 20, and a plurality of metal foils 36 are formed. It is welded to the inner metal ring 26. Then, the thickness T (mm) of the sealing tube 20 and the diameter D (mm) of the inner metal ring 26 are determined so as to satisfy the expression (1).

  By adjusting the ratio of the thickness T to the square of the diameter D, that is, the area, rather than the ratio of the thickness T of the sealing tube and the diameter D of the inner metal ring, a sufficiently pressure-resistant sealing structure is realized. can do. By finding that the pressure resistance of the sealing structure changes not only according to the wall thickness of the sealing tube but also according to the area of the inner metal ring, the appropriate sealing tube thickness can be obtained even in a high-power discharge lamp. The inner metal ring can be defined.

  In particular, when the inner metal ring size is increased while the thickness of the sealing tube is limited, the pressure resistance is improved by slightly suppressing the diameter D of the inner metal ring, and the thickness T of the sealing tube is increased. Does not have to be larger than necessary.

  As for the expression (3), when the proportionality coefficient or the like changes depending on the size of the discharge lamp (sealing tube size) or the like, the proportionality coefficient or the like k may be determined according to the lamp structure. Also in the formulas (1) and (4), the limit pressure in the arc tube may be set to other than 2.2 MPa.

It is a schematic sectional drawing of the short arc type discharge lamp which is this embodiment. It is a schematic sectional drawing of an anode side sealing tube. It is sectional drawing of the contact surface of the inner side metal ring and electrode side glass tube in FIG. Is a graph showing the relationship between the fracture pressure and the T / D ^2. It is the graph which showed the relationship between the outer diameter D of the inner side metal ring with respect to a burst pressure, and the thickness T of a sealing tube.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Discharge lamp 11 Discharge space 12 Light emission tube 20 Sealing tube 22 Electrode support rod 24 Electrode side glass tube (glass tube)
24N Contact surface 26 Inner metal ring (annular member)
28 Lead rod 32 Outer metal ring 34 Glass member 36 Metal foil T Thickness of sealing tube D Diameter of inner metal ring P ₀ Breakdown pressure

Claims (4)

Holding an electrode support rod for supporting the electrode in the arc tube, and a glass tube welded to the sealing tube;
A conductive annular member facing the glass tube and electrically connecting the metal foil disposed along the axial direction and the electrode support rod;
The lighting pressure in the arc tube is P (MPa), the outer diameter of the annular member is D (mm), and the thickness of the sealing tube in the vicinity of the contact surface between the annular member and the glass tube is T (mm). The short arc type discharge lamp is characterized in that an outer diameter D of the annular member and a thickness T of the sealing tube are determined so that the following expression is satisfied.

(P-2.2) / 200 <T / D ²
2. The short arc type discharge lamp according to claim 1, wherein a diameter D of the annular member and a thickness T of the sealing tube are in the following ranges, respectively.

1.5 ≦ T ≦ 11, 20 ≦ D ≦ 41
A glass tube that holds an electrode support rod that supports the electrode in the arc tube and is welded to the sealing tube;
A conductive annular member facing the glass tube and electrically connecting the metal foil disposed along the axial direction and the electrode support rod;
The power at the time of stable lighting is 8 kW or more,
When the outer diameter of the annular member is D (mm) and the thickness of the sealing tube in the vicinity of the contact surface between the annular member and the glass tube is T (mm), the following formula is satisfied: A short arc type discharge lamp characterized in that an outer diameter D of the annular member and a thickness T of the sealing tube are determined.

0.0065 ≦ T / D ²
Holding an electrode support rod for supporting the electrode in the arc tube, and a glass tube welded to the sealing tube;
A conductive annular member facing the glass tube and electrically connecting the metal foil disposed along the axial direction and the electrode support rod;
The lighting pressure in the arc tube is P (MPa), the outer diameter of the annular member is D (mm), and the thickness of the sealing tube in the vicinity of the contact surface between the annular member and the glass tube is T (mm). The short arc type discharge lamp is characterized in that an outer diameter D of the annular member and a thickness T of the sealing tube are determined so that the following expression is satisfied.

k × (P−Pc) <T / D ²

Here, k represents a coefficient obtained from the proportional relation between the fracture pressure and the T / D ² of the sealing tube. Pc represents a limit pressure in the arc tube.

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