JPH11250862A - Discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve light emission efficiency by increasing the temperature in a hollow chamber in a large diameter part. SOLUTION: A discharge lamp 10 is provided with an arc tube 11 comprising a large diameter part 12 and small diameter parts 13, and electrode members 15, 15, so the electrode members 15, 15 are energized to make arc discharge for lighting. The large diameter 12 is formed into the form of a rugby ball in which the temperature of a roughly whole wall surface facing the hollow chamber at the time of discharge lamp lighting actuation is roughly similar to a heat resistant temperature of transmissive material. Use of light emitting substance in a liquefied condition without contributing to light emission is thus eliminated, and light emitting efficiency is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp in which an electrode member is sealed at an opening in an arc tube containing a luminous substance, and more particularly, to a shape of the arc tube.

[0002]

2. Description of the Related Art Conventionally, as a discharge lamp of this type, an electrode member having a pair of electrodes is hermetically fixed to an opening of an arc tube made of a translucent ceramic, and mercury, an inert gas, metal It is known that a light emitting substance such as a halide is hermetically sealed. In this discharge lamp, the opening of the arc tube is hermetically sealed by melting a sealing glass material such as a glass frit in the gap between the electrode member and the opening of the arc tube and then cooling and solidifying the glass material.

[0003]

In the above-mentioned discharge lamp, the illumination is performed by supplying an electric current to the electrode member and performing an arc discharge. However, the inside of the arc tube becomes high temperature due to the arc discharge, and the temperature of the inner wall surface of the arc tube becomes high. Exceeds the melting temperature of the translucent ceramic, the arc tube cannot maintain its shape. If the temperature due to the arc discharge is lowered so as not to cause such a problem, there is a problem that the luminous efficiency is reduced.

Further, when the temperature inside the arc tube becomes high, the internal pressure increases, and it is necessary to increase its mechanical strength. However, increasing the wall thickness of the arc tube causes attenuation of the light quantity.

Further, the heat generated by the arc discharge is also transmitted to the vicinity of the sealing glass material. However, if the temperature of the sealing glass material exceeds the glass transition point, the sealing glass material is softened and the sealing property is impaired. For this reason, it is necessary to consider the influence of the heat of the arc discharge so that the temperature of the sealing glass material does not exceed the temperature of the glass transition point.

An object of the present invention is to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide a discharge tube having a light-emitting tube having a high mechanical strength while increasing the luminous efficiency during a lighting operation.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a large-diameter portion having a hollow chamber containing a light-emitting substance; A small-diameter portion having a small-diameter chamber communicated with the hollow chamber, a light-emitting tube formed of a light-transmitting material, and disposed from the opening of the small-diameter portion to the hollow chamber, and an electrode portion on the hollow chamber side at the tip thereof. A discharge lamp that is turned on by conducting an arc discharge by energizing the electrode member, wherein the temperature of almost the entire wall surface facing the hollow chamber when the discharge lamp is turned on has the translucency. The large diameter portion is formed so as to be substantially equal to the heat resistant temperature of the material.

An arc tube constituting a discharge lamp according to the present invention comprises a large diameter portion and a small diameter portion. The large diameter part is
It has a hollow chamber containing a luminescent substance, and a small-diameter capillary chamber is connected to this hollow chamber. Further, an electrode member having an electrode portion is arranged from the opening of the small diameter portion to the hollow chamber. The light-emitting substance is volatilized by arc discharge due to energization of the electrode member, and discharge light emission is performed. During the lighting operation of the discharge lamp, when the temperature inside the hollow chamber rises due to discharge light emission, the temperature distribution inside the hollow chamber becomes substantially elliptical. Since the shape of the large-diameter portion according to the present invention follows the temperature distribution in the lighting operation, the temperature of the inner wall surface of the large-diameter portion does not become higher than the heat-resistant temperature of the translucent material. Therefore, the light-transmitting material constituting the large-diameter portion does not thermally degrade, the life of the discharge lamp can be extended, and the low-temperature portion does not locally occur in the peripheral portion of the hollow chamber. The luminous efficiency of the electric lamp can be improved.

The light-transmitting material may be any material having heat resistance as an arc tube. For example, alumina can be formed using alumina as a main material. In this case, the heat-resistant temperature of alumina is about 1150 ° C. From the following, the inner wall surface of the large-diameter portion is formed in a shape along the temperature distribution of 1150 ° C.

[0010] In addition, the large-diameter portion has a preferable mode.
It is possible to adopt a configuration in which the temperature between the hollow chamber and the capillary chamber is the temperature at which the luminescent substance evaporates and emits light, and the lowest temperature in the hollow chamber. In this aspect, since the capillary chamber is a path for transferring heat to the sealing glass material sealing the end of the electrode member, the temperature of the portion between the hollow chamber and the capillary chamber is set to the lowest in the hollow chamber. By lowering the temperature, the heat transfer to the sealing glass material can be reduced, and the exposure of the sealing glass material to a temperature exceeding the glass transition point can be suppressed. Not bring.

Further, as another preferred embodiment of the large diameter portion,
It is possible to adopt a configuration in which a part of the inner wall surface of the large diameter portion is formed into a hemispherical surface, and the electrode portion is located at the center of the hemispherical surface. Thereby, the temperature of the inner wall surface of the large-diameter portion can be suppressed to be equal to or lower than the heat-resistant temperature, stress concentration due to the internal pressure in the large-diameter portion can be prevented, and the life of the discharge lamp can be further extended. be able to. In this case, the shape of the large diameter portion may be configured to have a cylindrical portion continuous with the hemispherical portion. Accordingly, the hemispherical portion and the cylindrical portion can be smoothly and continuously formed, the manufacture of the arc tube can be facilitated, and the load applied to the large diameter portion when the discharge lamp is turned on can be made substantially uniform.

As another preferred embodiment of the shape of the large-diameter portion, it is possible to adopt a configuration in which the maximum diameter is substantially at the central portion and a rugby ball shape is substantially equal to the temperature distribution in the hollow chamber. That is, when the discharge lamp is arranged in the horizontal direction and lit, the arc has a shape curved upward, so that the large-diameter portion is preferably a rugby ball shape adapted to the temperature distribution accompanying the arc discharge. It is.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further clarify the configuration and operation of the present invention described above, a preferred embodiment of the present invention will be described below.

FIG. 1 is a sectional view showing a discharge lamp 10 according to one embodiment of the present invention. In FIG. 1, a discharge lamp 10
Includes an arc tube 11, a light emitting substance (not shown) filled in the arc tube 11, and an electrode member 15. The arc tube 11 has a large-diameter portion 12 having a hollow chamber 12a filled with a luminescent substance, and small-diameter portions 13 extending from both sides of the large-diameter portion 12, respectively.

The large diameter portion 12 is substantially elliptical spherical.
The thickness of the tube wall is formed to be constant. Small diameter part 13
Are formed continuously at both ends of the large diameter portion 12 as thin tubes, respectively, and the inner space thereof is a thin tube chamber 13a. Further, at both ends of the small-diameter portion 13, the capillary chamber 13 is provided.
An opening 13b that opens a to the outside is formed.

As a material of the arc tube 11, a light-transmitting material such as alumina, alumina-yttria garnet, and quartz glass can be used. When DyI ₃ , CsI, TlI, NaI, or the like is used as the light-emitting substance, it is preferable to use alumina as a main raw material in consideration of its high reactivity. The arc tube 1
The thermal conductivity of the light-transmitting material of No. 1 is 0.11 cal / cm ·
s · ゜ K, and the thermal conductivity of ordinary Al ₂ O ₃ is 0.1.
08 cal / cm · s · ΔK. Such a material for the light-transmitting material can be obtained, for example, by a thermal decomposition method of an aluminum salt. The method for producing Al ₂ O ₃ by a thermal decomposition method of an aluminum salt is described in detail in JP-A-3-174454, and will not be described here.

As a method of manufacturing such an arc tube 11, for example, a slurry containing alumina as a main material is formed,
The large diameter portion 12 and the small diameter portion 13 can be integrally formed by casting. It is easy to form the small-diameter portion 13 continuous with the large-diameter portion 12 by such casting.

FIG. 2 is an enlarged sectional view showing a main part of the discharge lamp 10 of FIG. As shown in FIG. 2, the opening 13 b of the arc tube 11 is sealed with an electrode member 15. The electrode member 15 includes a sealing base 15a inserted into the opening 13b.
And a lead portion 15b provided from the end of the sealing base portion 15a to the hollow chamber 12a through the narrow tube chamber 13a, and an electrode portion 15c provided at the tip of the lead portion 15b. The sealing base 15a also serves as a terminal connected to an external lead (not shown), and is supplied with power by being connected to the external lead. The lead portion 15b extends axially through the center of the capillary chamber 13a with a predetermined gap between the lead portion 15b and the inner wall surface of the small diameter portion 13. The electrode portion 15c is connected to the tip of the lead portion 15b, is wound in a coil shape, and discharges with a discharge distance between the electrode portion 15c and the opposing electrode portion 15c.

The following materials can be used as the materials of the electrode member 15. That is, as the sealing base 15a,
Metals such as Nb and Re, alloys such as Nb-Zr, and metal-B
A material having a similar thermal expansion coefficient to that of the material of the arc tube 11, such as a cermet or a cermet such as a metal-C (N) -based metal or a metal-Si-based material can be used. The lead 15b and the electrode 15
As c, high melting point W, Mo or the like can be used.

The sealing base 15a of the electrode member 15 is
By sealing the sealing glass material 16a between the inner wall surface of the opening 13b and the inside, the inside of the arc tube 11 and the outside are sealed in an airtight state. The material of the sealing glass material 16a is S
iO ₂ -Al ₂ O ₃ -MgO _{based, Al 2 O 3 -CaO-Y} 2 O
Various types, such as a ₃ type and an Al ₂ O ₃ —SiO ₂ —Dy ₂ O ₃ type, can be used in accordance with physical properties such as a coefficient of thermal expansion with the material of the arc tube 11.

The following steps can be taken as a method of sealing with the sealing glass material 16a. First, after a luminescent substance or the like is put into the arc tube 11, the electrode member 15 is inserted into the opening 13b of the arc tube 11, and
A glass ring (not shown) forming the sealing glass material 16a is placed on the end of 3b, and these are exposed to an atmosphere of Ar gas. Then, the glass ring is irradiated with infrared rays to be heated and melted. The molten glass ring enters between the wall surface of the opening 13b and the sealing base 15a and solidifies. Thereby, the space between the inner wall surface of the opening 13b of the arc tube 11 and the outer peripheral surface of the sealing base 15a is sealed with the sealing glass material 16a.

Next, the lighting operation of the discharge lamp 10 will be described. When the discharge lamp 10 is arranged in a horizontal position and a current flows between the electrode members 15 of the discharge lamp 10, the electrode portions 15c, 1
Arc discharge occurs during 5c. Thereby, discharge energy is given to the luminescent material filled in the arc tube 11. That is, Hg evaporates from an early stage of the arc discharge to increase the vapor pressure in the arc tube 11, and the increase in the vapor pressure adjusts the luminous conditions of another luminous substance such as Dy. Then, the discharge lamp 10 is turned on when Dy or the like enters an ion state and is subjected to arc discharge. At this time, the heat due to the arc discharge in the arc tube 11
To the small diameter portion 13.

Here, the reason why the thermal conductivity of the translucent material constituting the arc tube 11 is increased is as follows.
When arc discharge occurs at the electrode portion 15c of the discharge lamp 10, the temperature inside the arc tube 11 increases. This heat is transmitted from the large-diameter portion 12 of the arc tube 11 to the small-diameter portion 13, further transmitted from the small-diameter portion 13 to the electrode member 15, and radiated by the electrode member 15.
At this time, if the thermal conductivity of the arc tube 11 is large, the large-diameter portion 1
The heat of No. 2 is quickly transferred to the small-diameter portion 13, and the temperature of the gap between the small-diameter portions 13 where the coldest portion is easily formed can be increased.
Therefore, a light-emitting substance that easily accumulates in the coolest part can contribute to light emission, and light emission efficiency can be increased.

FIG. 3 shows the results of a light emission test on a discharge lamp 10 having a high thermal conductivity. Here, the conditions under which the discharge lamp 10 was tested are as follows. The total length of the arc tube 11 is 50
mm, the distance between the electrode portions 15c was set to 14 mm, and Hg was 6 mg, and DyI ₃ -CsI was 8
5: 15% by weight of 4 mg, TlI of 2 mg and NaI of 2.5 mg were used as sealing glass material 16a at 800 ° C.
Dy ₂ O ₃ —Si having a glass transition temperature Tg that softens under pressure
O ₂ was used crystallized glass -Al ₂ O _3. Then, the electrode member 15 of the discharge lamp 10 is connected to an AC 1 through an external lead wire.
It was connected to a 00V input ballast. In addition, as a comparative example,
The thermal conductivity used was 0.08 cal / cm · s · ΔK.

The luminous efficiency in FIG. 3 is the total luminous flux (lm).
/ Electricity (W). As can be seen from FIG.
By increasing the thermal conductivity of the arc tube 11, the luminous efficiency was improved from 88.2 to 94.8. In addition, the color temperature was also close to the target value of 4000 K, and the average color rendering property, which was a relative evaluation value with respect to sunlight, was also close to the target value of 100.

As described above, in order to increase the luminous efficiency of the discharge lamp 10, the thermal conductivity of the arc tube 11 is increased to increase the temperature inside the arc tube 11. In this case, the internal pressure of the large diameter portion 12 is increased. And the pressure resistance must be increased, and the heat transfer to the small diameter portion 13 of the arc tube 11 and the sealing glass material 16a is promoted, so that the sealing glass material 16a is likely to be thermally degraded. In order to cope with such a problem, the following configuration is adopted.

The shape of the arc when the discharge lamp 10 is turned on is substantially elliptical. With such an arc shape, the temperature distribution in the arc tube 11 is shown in FIG. As shown in FIG. 4, the temperature distribution is approximately 5000 ° C. at the center of the arc, and has a substantially elliptical shape in which the temperature becomes lower toward the outer periphery. The shape of the discharge lamp 10 has the shape shown in FIG. 5 in order to reduce the thermal influence due to such temperature distribution.

FIG. 5 is a diagram showing the dimensions of each part of the discharge lamp 10. In the arc tube 11 shown in FIG. 5, the length of the large diameter portion 12 is L1, the length of the small diameter portion 13 is L2, and the large diameter portion 1 is L1.
The inside diameter of D2 is D1 and the inside diameter of the small diameter portion 13 is D2. Further, in the electrode member 15, the position of the electrode portion 15c in the hollow chamber 12a, that is, the length from the connection portion between the small diameter portion 13 and the large diameter portion 12 to the electrode portion 15c is K1, and further, the distance from the connection portion to the sealing base portion 15a is K1. The length to the inner end is K2, and the length sealed by the sealing glass material 16a is K3.

(1) The length K2 of the electrode member 15 is
When the discharge lamp 10 is turned on, the glass tip 16b of the sealing glass material 16a is set to a length that does not reach a temperature equal to or higher than the glass transition temperature Tg. As described above, the discharge lamp 1
The temperature distribution at the time of operation 0 is elliptical.
Further, as shown in FIG. 6, assuming that the temperature of the connection portion is the coldest portion temperature Tcs, the temperature T decreases from the narrow tube chamber 13a of the small diameter portion 13 toward the opening 13b. Then, at the position of the distance K0, the temperature T becomes the sealing glass material 16a.
Becomes lower than the glass transition temperature Tg at the position of the glass tip portion 16b.
Only lower. That is, the length K2 of the electrode member 15 is set so that the temperature T of the glass tip portion 16b of the sealing glass material 16a is equal to or lower than the glass transition temperature Tg.

Therefore, when the discharge lamp 10 is turned on,
The glass tip portion 16b of the sealing glass material 16a does not reach a temperature higher than the glass transition temperature Tg and is maintained at a temperature at least ΔT lower than the glass transition temperature Tg. Therefore,
The discharge lamp 10 is such that the sealing glass material 16a is not exposed to the glass transition temperature Tg or higher, and the constituent elements of the sealing glass material 16a escape and the spectral components of the discharge lamp include the spectral components of the element. It does not adversely affect the discharge characteristics. When the electrode member 15 is lengthened,
Since the small-diameter portion also becomes long, it is preferable to increase the thickness of the small-diameter portion 13 when it is necessary to increase the mechanical strength.

(2) As shown in FIG. 5, both ends of the large diameter portion 12 have a hemispherical curved surface portion 12c centered on the tip of the electrode portion 15c, and a cylindrical portion 12d continuous with the curved surface portion 12c. Is formed, and the diameter of the cylindrical portion 12d is set to D1 (= 2K
1). Such a shape is adopted for the following reason.

The temperature inside the arc tube 11 rises due to the heat of the electrode portion 15c due to the arc discharge.
Within 2c, it becomes substantially hemispherical centering on the tip of the electrode portion 15c. Here, the temperature of the wall surface of the curved surface portion 12c is 1150 ° C.
Is exceeded, the alumina itself constituting the curved surface portion 12c softens, and the durability decreases. Conversely, if there is a low-temperature portion in the curved surface portion 12c, the luminescent material in this low portion remains liquefied and does not emit light, and the luminous efficiency decreases.

In consideration of such a phenomenon, the shapes of the curved surface portion 12c and the cylindrical portion 12d of the large-diameter portion 12 are adjusted to the temperature distribution of the arc, and approximately 1150 ° C. which is the limit of the heat resistance of the alumina of the arc tube 11. It is a matched shape,
As a result, thermal deterioration of the arc tube 11 is prevented, the life of the arc tube 11 is increased, and the luminous efficiency is increased by eliminating a portion having a low temperature. Further, when the discharge lamp 10 is turned on, the pressure in the hollow chamber 12a increases, and the large-diameter portion 12
Large stress is applied to the Large diameter portion 1 of arc tube 11 described above
Since the shape 2 is the curved surface portion 12c, the stress is dispersed and applied, and there is no portion where the stress is locally concentrated, so that the durability of the discharge lamp 10 can be improved.

(3) FIG. 7 is a sectional view showing a discharge lamp 10B according to another embodiment. The discharge lamp 10B includes a large-diameter portion 12B having a rugby ball shape. Large diameter part 1
The reason why 2B is formed in such a shape is as follows.
As shown in FIG. 8, when the discharge lamp 10 </ b> B is arranged and lit in a horizontal direction, the arc may have an upwardly curved shape, and may have a temperature distribution indicated by a broken line corresponding thereto. In such a case, if the inner wall surface of the large diameter portion 12B does not conform to the shape of the arc, a partial temperature unevenness occurs on the inner wall surface of the large diameter portion 12B. Therefore, the large-diameter portion 12B is formed into a rugby ball shape adapted to the temperature distribution accompanying the arc discharge.

FIG. 9 shows a discharge lamp 10 according to another embodiment.
It is explanatory drawing explaining the structure of F and its temperature distribution. The discharge lamp 10F includes a large diameter portion 12F and a small diameter portion 13F,
A low heat transfer portion 13Fa made of a material having lower thermal conductivity than the large diameter portion 12F is formed in a part of the small diameter portion 13F. The sealing base 15a of the electrode member 15 is supported by the low heat transfer portion 13Fa via a sealing glass material 16a. This low heat transfer part 13Fa can be formed by bonding to the large diameter part 12F or by pouring a different material at the time of casting.

The reason why the low heat transfer portion 13Fa is formed in the small diameter portion 13F is as follows. If the light-transmitting material of the large-diameter portion 12F has a large thermal conductivity, the temperature of the coldest portion temperature Tcs in the large-diameter portion 12F can be increased as described above, and the emission efficiency of the discharge lamp 10F is improved. Can be done. However, the temperature rise of the coldest part temperature Tcs is caused by the
Although the temperature of the glass tip portion 16b of 6a is increased, this problem is solved by the low heat transfer portion 13Fa.

That is, as shown in the temperature distribution of FIG.
The temperature change of the large diameter portion 12F and a part of the small diameter portion 13F extended therefrom is represented by a curve Ta, and the temperature change of the low heat transfer portion 13Fa of the small diameter portion 13F is represented by a curve Tb. It is larger than the temperature gradient of the curve Ta. For this reason, the discharge lamp 10F
Even when the coldest part temperature Tcs increases during the lighting operation of, due to the large temperature gradient of the curve Tb, the temperature at the glass tip part 16b of the sealing glass material 16a becomes the glass transition temperature Tg.
Is easily reduced. Thus, the low heat transfer section 1
3Fa can reduce the temperature of the sealing glass material 16a even if the emission temperature in the discharge lamp 10F is increased. The heat of the large-diameter portion 12F is transferred to the thin-tube chamber 13a of the small-diameter portion 13F.
A ring-shaped heat insulating member 13Fb made of Al ₂ O ₃ or the like may be interposed in order to lower the temperature of the glass tip portion 16b of the sealing glass material 16a due to the heat.

The present invention is not limited to the above-described embodiment, but can be implemented in various modes without departing from the gist of the invention.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a discharge lamp 10 according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a main part of the discharge lamp 10 of FIG.

FIG. 3 is an explanatory diagram illustrating the results of a light emission test on a discharge lamp 10 having a high thermal conductivity.

FIG. 4 is an explanatory diagram illustrating a temperature distribution when the discharge lamp 10 is turned on.

FIG. 5 is a diagram showing dimensions of each part in the discharge lamp 10.

FIG. 6 is an explanatory diagram illustrating a temperature distribution of a small diameter portion 13 of the discharge lamp 10.

FIG. 7 is a sectional view showing a discharge lamp 10B according to another embodiment.

FIG. 8 is an explanatory diagram illustrating a temperature distribution of a discharge lamp 10B according to another embodiment.

FIG. 9 is an explanatory diagram illustrating a configuration and a temperature distribution of a discharge lamp 10F according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Discharge lamp 10B ... Discharge lamp 10F ... Discharge lamp 11 ... Arc tube 12a ... Hollow chamber 12 ... Large diameter part 12c ... Curved surface part 12d ... Cylindrical part 12B ... Large diameter part 12F ... Large diameter part 13 ... Small diameter part 13a ... Thin tube Chamber 13b ... opening 13F ... small diameter part 13Fa ... low heat transfer part 13Fb ... heat insulating member 15 ... electrode member 15a ... sealing base 15b ... lead part 15c ... electrode part 15, 15 ... electrode member 15c, 15c ... electrode part 16a ... Sealing glass material 16b: Glass tip

Claims (6)

[Claims] 1. A large-diameter portion having a hollow chamber containing a light-emitting substance, and a small-diameter portion having a small-diameter chamber extending from the large-diameter portion and communicating with the hollow chamber, and formed of a light-transmitting material. And an electrode member disposed from the opening of the small-diameter portion to the hollow chamber and having an electrode portion on the hollow chamber side at the tip thereof, and turned on by conducting electricity to the electrode member to perform arc discharge. In the discharge lamp to be operated, the large-diameter portion is formed such that the temperature of almost the entire wall surface facing the hollow chamber when the discharge lamp is turned on is substantially equal to the heat-resistant temperature of the translucent material. Discharge lamp. 2. The large-diameter portion according to claim 1, wherein a temperature of a portion between the hollow chamber and the capillary chamber is a temperature at which a luminescent substance evaporates and emits light, and a lowest temperature in the hollow chamber. A discharge lamp that is configured to be. 3. The electrode member according to claim 1, wherein a part of the inner wall surface of the large-diameter portion is formed as a hemisphere, and the electrode member is located at the center of the hemisphere. Discharge lamp in which is formed. 4. The discharge lamp according to claim 3, wherein the large diameter portion has a continuous cylindrical portion at the hemispherical portion. 5. The discharge lamp according to claim 1, wherein the large diameter portion is formed in a rugby ball shape having a maximum diameter substantially at a central portion. 6. The light-transmitting material according to claim 1, wherein the light-transmitting material is formed using alumina as a main raw material,
A discharge lamp configured such that the temperature of the inner wall surface of the large-diameter portion is about 1150 ° C. when the discharge lamp is turned on.