Short-arc type high pressure discharge lamp having gaps formed among electrode axes, metal foils and a glass material surface

A short-arc type high pressure discharge lamp in which durability is improved and a lamp apparatus including the same is provided.Glass material portions 52A into which glass material enters respectively are provided on both sides of an electrode axis 5402 between the outer circumferential surface 5406 thereof and a curved portion 58 of a sealed metal foil 56, and a gap S3 being continuous with a sealed space 60 remains among the glass material portion 52A, the outer circumferential portion 5406 of the electrode axis 5402, and the curved portion 58. An angle formed by a surface 52-1 of the glass material portion 52A facing the gap S3 and the curved portion 58 is an obtuse angle φ. In other words, an angle formed by the surface 52-1 of the glass material portion 52A facing the gap S3 and a surface 5602 of the curved portion 58 of the sealed metal foil 56 is the obtuse angle φ.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese Patent Application JP 2005-103540 filed in the Japanese Patent Office on Mar. 31, 2005, the entire contents of which being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a short-arc type high pressure discharge lamp and a lamp apparatus including the same.

2. Description of the Related Art

A short-arc type high pressure discharge lamp has been used as a light source of a projection type projector.FIG. 1is a sectional view showing a short-arc type high pressure discharge lamp in related art;FIG. 2is a sectional view showing a manufacturing process of a short-arc type high pressure discharge lamp in related art;FIGS. 3A through 3Care A-A line cross-sectional views ofFIG. 2;FIG. 4is an enlarged view showing portions of an electrode axis and a sealed metal foil; andFIG. 5Ais an enlarged view showing the portions of the electrode axis and sealed metal foil andFIG. 5Bis an enlarged view showing the inside of a circle inFIG. 5A.

As shown inFIG. 1, a short-arc type high pressure discharge lamp10includes: a discharge container12made of glass material such as quartz glass, a pair of electrodes14, and two sealed metal foils16. The discharge container12is formed of a pair of axis portions1202and a swelled portion1204provided between the pair of axis portions1202and having a sealed space20inside in which mercury and the like are enclosed.

Each of electrodes14has an electrode axis1402and an electrode body1404provided at an end of the electrode axis1402. With respect to the pair of electrodes14, the electrode axes1402are buried in the pair of axis portions1202respectively and the electrode bodies1404are disposed to face each other in the sealed space20. Two sealed metal foils16extend like a strip having a narrow width and are buried in the axis portions1202such that the longitudinal direction thereof is parallel to the longitudinal direction of the axis portion1202. The electrode axis1402is joined to one end in the longitudinal direction of the sealed metal foil16by resistance welding, and a lead wire18is joined to the other end in the longitudinal direction by the resistance welding. When lighting the short-arc type high pressure discharge lamp10, on connecting an outside power source to each lead wire18and on applying a voltage to each electrode14, an electric discharge occurs between the electrode bodies1404to make the sealed space20become a high temperature exceeding 300° C., mercury in the sealed space20is vaporized to be a mercury vapor pressure of around 200 atmospheric pressure for example, and light is emitted by an arc discharge occurred between the electrode bodies1404in that state.

The above short-arc type high pressure discharge lamp10is manufactured as follows. First, as shown inFIG. 2, a glass tube22whose diameter is larger than that of the axis portion1202of the discharge container12is prepared. The glass tube22has a pair of small diameter portions2202having an inner diameter larger than the width of the sealed metal foil16, and a large diameter portion2204provided between those small diameter portions2202and having a larger inner diameter than the inner diameter of the small diameter portion2202. First, with mercury as a base Ar gas and halogen gas are injected into the large diameter portion2204. Next, each of the pair of electrodes14to which the sealed metal foil16is welded is inserted respectively from each of small diameter portion2202of the glass tube22toward the large diameter portion2204to make the electrode bodies1404face each other in the large diameter portion2204. At that time, the electrode axis portion1402welded to the sealed metal foil16is positioned in the small diameter portion2202as shown inFIGS. 2 and 3A.

Next, the end portion of each small diameter portion2202positioned on the side opposite to the large diameter portion2204is irradiated with a laser light beam and is heated to fuse the end portions of the small diameter portions2202positioned around the lead wires18and so both ends of the glass tube22are sealed. Hence, the sealed space20hermetically sealed is formed inside the large diameter portion2204. Next, while cooling down the mercury in the sealed space20to prevent evaporation thereof by exposing the large diameter portion2204to liquid nitrogen, laser light beams are applied moving from the end portion of each small diameter portion2202toward the large diameter portion2204and so the whole area of the small diameter portion2202is sequentially heated. Hence, the portion of the small diameter portion2202around the lead wire18and the portion of the small diameter portion2202around the sealed metal foil16are fused. At this time, a barometric pressure inside the discharge container12is equal to or lower than the atmospheric pressure, because the large diameter portion2204is cooled down with the liquid nitrogen. Accordingly, as shown inFIG. 3B, the fused small diameter portion2202is shrunk to have a small outer diameter due to the difference in the pressure.

Further, when the inner surface of the fused small diameter portion2202contacts with both ends in the widthwise direction of the sealed metal foil16, the inner surface of the fused small diameter portion2202shrinks to come close toward the sealed metal foil16in the direction orthogonal to the widthwise direction of the sealed metal foil16as shown inFIG. 3C, because the sealed metal foil16serves as resistance. Then, the portion of the fused small diameter portion2202wraps the electrode axis1402and sealed metal foil16to be in a state where, as shown inFIG. 4, the portion of the fused small diameter portion2202, that is, the fused glass material portion closely contacts with the whole area of the rear surface1604on the side opposite to a surface1602of the sealed metal foil16to which the electrode axis1402is welded. Further, a fused glass material portion12A closely contacts with a portion of the outer circumferential surface1402A on the side opposite to the sealed metal foil16in the outer circumferential surface1402A of the electrode axis1402. The short-arc type high pressure discharge lamp10as shown inFIG. 1is obtained in this manner.

Hereupon, as shown inFIGS. 5A and 5B, since the glass material portion12A may not fully enter on both sides of the electrode axis1402between the outer circumferential surface1402A thereof and the surface1602of the sealed metal foil16to which the electrode axis1402is welded, gaps S are formed respectively. The gap S is continuous with the sealed space20. Further, it is illustrated inFIG. 5Athat the fused glass material may closely contact with half the outer circumferential surface1402A of the electrode axis1402on the side opposite to the portion to which the sealed metal foil16is welded, however, the gaps S on both sides of the electrode axis1402are in actuality continuous with each other through the half portion of the outer circumferential surface1402A of the electrode axis1402. The gaps S on both sides of the electrode axis1402are formed to be gradually small in the direction away from the electrode axis1402and along the surface1602of the sealed metal foil16, and a surface12-1of the glass material portion12A facing the gap S forms an acute angle θ with the surface1602of the sealed metal foil16. Therefore, when the short-arc type high pressure discharge lamp10is lit, mercury vapor pressure rises in the sealed space20and so pressure in the gap S also rises, and strong force almost like a wedge acts on a portion of a gap S1that is the acute angle θ formed by the surface12-1of the glass material portion12A facing the gap S and the surface1602of the sealed metal foil16.

Then, a crack may occur from that portion of the gap S1along the boundary surface between the surface1602of the sealed metal foil16and the surface12-1of the glass material portion12A, which is a disadvantage on improving the durability of the short-arc type high pressure discharge lamp10. In order to solve such problem, it has been proposed to change the shape of the sealed metal foil16(refer to Patent Reference 1).FIG. 6Ais a plan view showing portions of the electrode axis1402and the sealed metal foil16in an example of related art in which the shape of the sealed metal foil is changed; andFIG. 6Bis a BB-line cross-sectional view ofFIG. 6A. As shown inFIGS. 6A and 6B, the sealed metal foil16is wrapped up to a portion opposite to a portion welded to the sealed metal foil16along the outer circumferential surface1402A of the electrode axis1402in the portion where the electrode axis1402is welded to the sealed metal foil16and so the gaps S formed on both sides of the electrode axis1402between the outer circumferential surface1402A thereof and the surface1602of the sealed metal foil16are eliminated.

SUMMARY OF THE INVENTION

In the above-described example of the related art in which the shape of the sealed metal foil is changed, as shown inFIG. 6B, the sealed metal foil16, is bent at the portion opposite to the portion welded to the sealed metal foil16and so this time V-shaped concave portions are formed respectively on both sides of the electrode axis1402at the bent portion on the rear surface1604of the sealed metal foil16. Further, since the glass material portion12A may not completely enter the respective concave portions and gaps S2continuous with the sealed space20are formed, and since an acute angle θ is formed by a surface12-2of the glass material portion12A facing the gap S2and the rear surface1604of the sealed metal foil16similarly to the above, there is a possibility that when the short-arc type high pressure discharge lamp10is lit, a crack may occur due to strong force that acts almost like a wedge along the boundary surface between the rear surface1604of the sealed metal foil16and the surface12-2of the glass material portion12A similarly to the above. The present invention addresses the above-identified and other problems associated with conventional methods and apparatuses, and provides a short-arc type high pressure discharge lamp enabling durability to be improved and a lamp apparatus including the short-arc type high pressure discharge lamp.

A short-arc type high pressure discharge lamp according to an embodiment of the present invention includes a discharge container made of glass material, a pair of electrodes, and two sealed metal foils electrically connected to the pair of electrodes respectively. The discharge container is formed of a pair of axis portions and a swelled portion provided between the pair of axis portions and having a sealed space inside. Each of electrodes includes an electrode axis and an electrode body provided at an end of the electrode axis, the electrode axes are buried in the pair of axis portions, and the electrode bodies are disposed to face each other in the sealed space. The sealed metal foil is in the shape of a strip having a narrow width and is formed to be buried together with the electrode axis in the axis portion, in a state where a middle portion in the widthwise direction at one end in the longitudinal direction of the sealed metal foil is made into a curved portion wrapping the outer circumferential surface of the electrode axis and the most depressed bottom portion of the curved portion is joined to a portion of the outer circumferential surface of the electrode axis contacting with the bottom portion, and the other end in the longitudinal direction of the sealed metal foil is connected to an outside power source. Glass material portions into which the glass material enters respectively are provided on both sides of the electrode axis between the outer circumferential surface thereof and the curved portion of the sealed metal foil. On both sides of the electrode axis between the outer circumferential surface thereof and the curved portion of the sealed metal foil, gaps continuous with the sealed space remain respectively among the glass material portion, the outer circumferential surface of the electrode axis, and the curved portion. The gap is formed to be gradually small in the direction away from the glass material portion and along a circumferential direction of the electrode axis. The surface of the glass material portion facing the gap forms an obtuse angle with the curved portion.

A lamp apparatus according to an embodiment of the present invention includes: a short-arc type high pressure discharge lamp, a protective tube that accommodates the short-arc type high pressure discharge lamp in a hermetically sealed state, an opening provided in the front portion of the protective tube, a transparent panel that hermetically closes the opening, a reflective surface provided on the inner surface of the protective tube to reflect light emitted from the short-arc type high pressure discharge lamp and to lead forward the light through the transparent panel, and a power-feed terminal provided on the outer surface of the protective tube and connected to an outside power source. The short-arc type high pressure discharge lamp includes: a discharge container made of glass material, a pair of electrodes, and two sealed metal foils electrically connected to the pair of electrodes, respectively. The discharge container is formed of a pair of axis portions and a swelled portion provided between the pair of axis portions and having a sealed space inside. Each of electrodes includes an electrode axis and an electrode body provided at an end of the electrode axis, the electrode axes are buried in the pair of axis portions, and the electrode bodies are disposed to face each other in the sealed space. The sealed metal foil is in the shape of a strip having a narrow width and is formed to be buried together with the electrode axis in the axis portion, in a state where a middle portion in the widthwise direction at one end in the longitudinal direction of the sealed metal foil is made into a curved portion wrapping the outer circumferential surface of the electrode axis and the most depressed bottom portion of the curved portion is joined to a portion of the outer circumferential surface of the electrode axis contacting with the bottom portion. The other end in the longitudinal direction of the sealed metal foil is connected to the power-feed terminal. Glass material portions into which the glass material enters respectively are provided on both sides of the electrode axis between the outer circumferential surface thereof and the curved portion of the sealed metal foil. On both sides of the electrode axis between the outer circumferential surface thereof and the curved portion of the sealed metal foil, gaps continuous with the sealed space remain respectively among the glass material portion, the outer circumferential surface of the electrode axis, and the curved portion. The gap is formed to be gradually small in the direction away from the glass material portion and along a circumferential direction of the electrode axis. The surface of the glass material portion facing the gap forms an obtuse angle with the curved portion.

According to the embodiments of the present invention, since the surface of the glass material portion facing the gap continuous with the sealed space forms an obtuse angle with the curved portion of the sealed metal foil, the force that acts on the portion of the gap forming the obtuse angle can almost be ignored in the case in which mercury vapor pressure in the sealed space rises to cause the rise of pressure in the gap. Accordingly, a crack can be prevented from occurring at the portion of the gap along the boundary surface between the surface of the sealed metal foil and the surface of the glass material portion, which enables durability of the short-arc type high pressure discharge lamp and lamp apparatus to be improved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, an embodiment of the present invention is explained by referring to the accompanied drawings. In the following, an explanation is made with respect to the case in which a short-arc type high pressure discharge lamp according to an embodiment of the present invention is incorporated in a lamp apparatus.FIG. 7is a front view of a lamp apparatus according to a first embodiment;FIG. 8is a view seen from the side indicated by the A-arrow ofFIG. 7; andFIG. 9is a BB-line sectional view ofFIG. 7. A lamp apparatus30includes a short-arc type high pressure discharge lamp50according to an embodiment of the present invention and a protective tube40that accommodates the short-arc type high pressure discharge lamp50in a hermetically sealed state. The protective tube40includes a funnel-shaped body portion42made of hard glass having a parabolic reflective surface4202as an inner surface and a transparent panel44made of hard glass that hermetically seals a front opening of the body portion42. One of axis portions5202of the short-arc type high pressure discharge lamp50is inserted into a neck portion4204of the body portion42from the inside of the body portion42, and heat-resistant sealant46is filled in a gap formed between the outer circumferential surface of the axis portion5202and an inner circumferential surface of the neck portion4204. Therefore, the short-arc type high pressure discharge lamp50is fixed airtightly to the neck portion4204of the body portion42. Further, one of the axis portion5202of the short-arc type high pressure discharge lamp50that protrudes outward from the neck portion4202is airtightly capped with a cap48. Furthermore, a power-feed terminal48A is provided for the cap48, and one of a pair of lead wires62of the short-arc type high pressure discharge lamp50is connected to the power-feed terminal48A. Further, a power-feed terminal49A is also provided on the outside surface of the body portion42, and the other of the pair of lead wires62is connected to the power-feed terminal49A through a lead conductor49. Note that the inside of the protective tube40is sealed with nitrogen gas so that heat of the short-arc type high pressure discharge lamp50is radiated excellently to the outside of the protective tube40.

FIG. 10is a sectional view of a short-arc type high pressure discharge lamp according to an embodiment of the present invention;FIG. 11is a perspective view of a sealed metal foil to which an electrode axis and a lead wire are welded; andFIG. 12is an AA-line cross-sectional view ofFIG. 11. As shown inFIG. 10, the short-arc type high pressure discharge lamp50includes a discharge container52made of glass material, a pair of electrodes54, and two sealed metal foils56. In this embodiment, the glass material constituting the discharge container52is quartz glass. The discharge container52is formed to have a pair of axis portions5202and a swelled portion5204provided between the pair of axis portions5202and having a sealed space60inside in which mercury and the like are filled. Each of the electrodes54has an electrode axis5402and an electrode body5404provided at an end of the electrode axis5402, in which in this embodiment the pair of electrodes54are formed of tungsten and the diameter of the electrode axis5402is 0.3 mm. With respect to the pair of electrodes54, the electrode axes5402are buried in the pair of axis portions5202respectively, and the electrode bodies5404are disposed to face each other in the sealed space60.

The two sealed metal foils56extend like a strip having a narrow width. Each of sealed metal foils56is buried in the axis portion52in a state where the longitudinal direction thereof is made parallel with the longitudinal direction of the axis portion52, a middle portion in the widthwise direction at one end in the longitudinal direction of the sealed metal foil56is made into a curved portion58wrapping the outer circumferential surface5406of the electrode axis5402, and the most depressed bottom portion5802of the curved portion58is joined to a portion of the outer circumferential surface5406of the electrode axis5402contacting with this bottom portion5802. As shown inFIGS. 15A and 15B, glass material portions52A into which glass material enters are provided respectively on both sides of the electrode axis5402between the outer circumferential surface5406thereof and the curved portion58of the sealed metal foil56, and gaps S3continuous with the sealed space60remain among the glass material portion52A, the outer circumferential surface5406of the electrode axis5402, and the curved portion58.

The gap S3is formed to be gradually small in the direction away from the glass material portion52A and along a circumferential direction of the electrode axis5402. The surface52-1of the glass material portion52A facing the gap S3forms an obtuse angle φ with the curved portion58, in other words, an angle of a gap S3-1formed at a portion where the surface52-1of the glass material portion52A facing the gap S3contacts with a surface5602of the curved portion58of the sealed metal foil56facing the gap S3is an obtuse angle φ. The lead wire62is joined to the other end in the longitudinal direction of the sealed metal foil56by resistance welding and is formed to be connected to an outside power source through the power-feed terminals48A and49A described above. In this embodiment, two sealed metal foils56are made of molybdenum and the thickness thereof is 20 μm. The lead wire62is made of molybdenum and the diameter thereof is 0.4 mm. When an outside power source is connected to each lead wire62and a voltage is applied to each electrode54at the time of lighting the short-arc type high pressure discharge lamp50, an electrical discharge occurs between the electrode bodies5404, temperature of the sealed space60becomes high exceeding 300° C., mercury in the sealed space60evaporates to be mercury vapor pressure of around 200 barometric pressure, for example, and light is emitted by the arc discharge occurred between respective electrode bodies5404in that state.

Such short-arc type high pressure discharge lamp50is manufactured as follows.FIG. 13is a sectional view showing a manufacturing process of a short-arc type high pressure discharge lamp according to a first embodiment, andFIGS. 14A through 14Dare AA-line cross-sectional views ofFIG. 13. First, as shown inFIG. 13, a glass tube64having a diameter larger than that of the axis portion5202of the discharge container52is prepared. The glass tube64includes a pair of small diameter portions6402having an inner diameter larger than the width of the sealed metal foil56and a large diameter portion6404having an inner diameter larger than the inner diameter of the small diameter portion6402and provided between the small diameter portions6402. In addition, electrodes54are fixed to one end in the longitudinal direction of the pair of sealed metal foils56, respectively.

Further in detail, as shown inFIG. 12, a middle portion (a center portion in this embodiment) in the widthwise direction at one end in the longitudinal direction of the sealed metal foil56is made into a semi-cylindrical portion5812wrapping half the outer circumferential surface5406of the electrode axis5402(in other words, the semi-cylindrical portion5812whose inner radius is equal to the outer circumferential surface5406of the electrode axis5402), and the most depressed bottom portion5802of the semi-cylindrical portion5812is joined by resistance welding to the portion of the outer circumferential surface5406of the electrode axis5402contacting with the bottom portion5802. Further, a cylindrical surface portion5814is formed extending from the upper end of the semi-cylindrical portion5812, specifically, extending from the upper end of the semi-cylindrical portion5812positioned at the height approximately the radius of the electrode axis5402from the most depressed bottom portion5802of the semi-cylindrical portion5812, gradually departing from the outer circumferential surface5406of the electrode axis5402at a cylindrical surface whose radius is equal to the radius of the electrode axis5402, and continuously connecting (in a stepless manner) the upper end of the semi-cylindrical portion5812on both sides to flat portions5612remaining on both sides in the widthwise direction of the sealed metal foil56. In this way, the semi-cylindrical portion5812and cylindrical surface portions5814on both sides constitutes the curved portion58wrapping the outer circumferential surface5406of the electrode axis5402, provided in the middle portion in the widthwise direction at one end in the longitudinal direction of the sealed metal foil56. Note that a virtual line connecting the flat portions5612on both sides passes at the upper end of the outer circumferential surface5406positioned opposite to the bottom portion5802and therefore the cylindrical surface portion5814is a convex-shaped cylindrical surface toward the upper end of the outer circumferential surface5406positioned opposite to the bottom portion5802, and the depth of the curved portion58from the flat portions5612on both sides is almost equal to the diameter of the electrode axis5402.

Next, Ar gas and halogen gas with mercury as a base are injected into the large diameter portion6404. Then, a pair of electrodes54in which the electrode axis5402is welded to the bottom portion5802of the curved portion58of the sealed metal foil56are inserted respectively toward the large diameter portion6404from the small diameter portions6402of the glass tube64to make the electrode bodies5404face each other in the large diameter portion6404. At this time, as shown inFIGS. 13 and 14A, the portion of the electrode axis5402welded to the bottom portion5802of the curved portion58of the sealed metal foil56is positioned in the small diameter portion6402.

The end portions of the small diameter portions6402positioned on the opposite side to the large diameter portion6404are irradiated with laser light beams and are heated, and so the edge portion of each small diameter portion6402positioned around the lead wire62is fused to seal both the ends of the glass tube64. Hence, the hermetically sealed space60is formed inside the large diameter portion6404. Subsequently, liquid nitrogen is applied to the large diameter portion6404to cool mercury in the sealed space60not to evaporate and the whole area of the small diameter portion6402is irradiated with the laser light beam to be heated sequentially by moving the light beam from the edge portion of each small diameter portion6402toward the large diameter portion6404. Hence, the portion of the small diameter portion6402positioned around the lead wire62and the portion of the small diameter portion6402positioned around the sealed metal foil56are fused. At this time, the barometric pressure inside the discharge container52is equal to or less than the atmospheric pressure, because the large diameter portion6404has been cooled using the liquid nitrogen. Accordingly, the fused small diameter portion6402is shrunk to have a small outer diameter by the difference of the barometric pressures described above.

Then, since the sealed metal foil56becomes resistance when an inner surface of the fused small diameter portion6402comes in contact with both ends in the widthwise direction of the sealed metal foil56, the inner surface of the fused small diameter portion6402shrinks to come close toward the sealed metal foil56in the direction orthogonal to the widthwise direction of the sealed metal foil56as shown inFIGS. 14B and 14C. Further, the portion of the fused small diameter portion6402wraps the electrode axis5402and sealed metal foil56, and, as shown inFIG. 14D, the portion of the fused small diameter portion6402, that is, the fused glass material, adheres closely to the whole area of the rear surface5604on the side opposite to the surface5602where the electrode axis5402is welded in the sealed metal foil56, specifically, adheres closely to the whole area of the rear surface5604including the rear surface5604of the curved portion58. Furthermore, the fused glass material portion also adheres closely to the portion of the outer circumferential surface5406positioned on the side opposite to the sealed metal foil56in the outer circumferential surface5402A of the electrode axis5402. In this way, the short-arc type high pressure discharge lamp50shown inFIG. 7, in which the electrode axis5402and sealed metal foil56extend in parallel with the axis portion5202, is obtained.

FIG. 15Ais an enlarged view showing the portions of the electrode axis and sealed metal foil, andFIG. 15Bis an enlarged view showing the inside of a circle inFIG. 15A. As shown inFIGS. 15A and 15B, on both sides of the electrode axis5402between the outer circumferential surface5406thereof and the curved portion58of the sealed metal foil56(specifically, cylindrical surface portion5814), the glass material portions52A into which the glass material enters respectively are provided and also the gaps S3continuous with the sealed space60remain among the glass material portion52A, the outer circumferential surface5406of the electrode axis5402, and the curved portion58(specifically, cylindrical surface portion5814). The gap S3is formed to be gradually small in the direction away from the glass material portion52A and along the circumferential direction of the electrode axis5402. Further, the surface52-1of the glass material portion52A facing the gap S3forms an obtuse angle φ with the curved portion58(specifically, cylindrical surface portion5814), in other words, the angle of the gap S3-1in the portion where the surface52-1of the glass material portion52A facing the gap S3contacts with the surface5602of the curved portion58(specifically, cylindrical surface portion5814) of the sealed metal foil56facing the gap S3is the obtuse angle φ. Here, althoughFIGS. 15A and 15Bare illustrated that the fused glass material closely adheres to half the outer circumferential surface5406of the electrode axis5402positioned on the side opposite to the portion where the sealed metal foil56is welded, the gaps S3on both sides of the electrode axis5402are continuous in actuality through the half portion of the outer circumferential surface5406of this electrode axis5402.

According to this embodiment, since the angle formed by the surface52-1of the glass material portion52A facing the gap S3continuous with the sealed space60and the curved portion58of the sealed metal foil56is an obtuse angle φ, the force to act on the portion of the gap S3-1forming the obtuse angle φ between the surface52-1of the glass material portion52A facing the gap S3and the surface5602of the curved portion58of the sealed metal foil56can almost be ignored when the short-arc type high pressure discharge lamp50is lit to make mercury vapor pressure in the sealed space60rise, which causes the pressure in the gap S3to rise. Therefore, a crack can be prevented from occurring at the portion of the gap S3-1along the boundary surface between the surface5602of the sealed metal foil56and the surface52-1of the glass material portion52A, which is advantageous on improving the durability of the short-arc type high pressure discharge lamp50and lamp apparatus30.