JP2001076677A - High-pressure discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pseudo-point light source and to stably connect electrode members to a discharge tube by forming each current conductor with a pipe conductor inserted into the opening section of an alumina cylinder and connected by a connecting material and a bar-like conductor inserted into the through-hole of the pipe conductor and having a discharge electrode at the tip, and setting the diameter and length of the alumina cylinder to specific values. SOLUTION: An alumina cylinder of this high-pressure discharge lamp has a diameter of 1-6 mm 4 and the length of 6-15 mm. Each current conductor 4 is constituted of a metallic pipe conductor 7 and a cylindrical core 8 in it, and they are connected by welding at end sections. A discharge electrode 5 is provided at the tip of the core 8, and they are connected by welding or metallization connection. The pipe conductor 7 may be formed with a halide-resistant material, such as W or Mo. The core 8 is preferably formed with the same metal as that of the pipe conductor 7. This discharge lamp can be miniaturized, by connecting the pipe conductor 7 forming the current conductor 4 directly to a discharge tube 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-pressure discharge lamp using a discharge tube made of alumina, and more particularly to a high-pressure discharge lamp which is miniaturized and used as a pseudo point light source.

[0002]

2. Description of the Related Art High pressure discharge lamps using quartz discharge tubes have been widely used as headlights for automobiles because of their advantages such as brightness and high luminous efficiency. Such a discharge lamp using a quartz tube can be used as a point light source because the light-emitting portion of the discharge tube in the discharge tube can be used as a light source of the discharge lamp because the discharge tube is transparent. It is used as a light source for lighting that requires a point light source such as described above.

[0003]

However, when a high-pressure discharge lamp using a quartz tube as a discharge tube has been used for a long period of time, a corrosive substance such as a halide sealed inside the quartz tube causes the high pressure discharge lamp. Corrosion progresses, devitrification phenomenon appears, concealing the light source part, and it becomes as if the whole quartz tube emits light, and there is a problem that it cannot be treated as a point light source. Further, the luminous flux also decreased, and the life as a point light source was not so long at about 2000 hours.

[0004] Therefore, the use of high-pressure discharge lamps for headlamps, which use ceramic discharge tubes made of alumina, which is stable against halides and has a longer life than quartz, has been studied. Since this alumina discharge tube is translucent, when the light emission between the internal discharge electrodes is viewed from the outside of the discharge tube, it is in the same state as the entire discharge tube emits light. For this reason, the entire discharge tube must be regarded as a luminous body, and a pseudo point light source has been dealt with by reducing the size of the discharge tube.

FIG. 5 is a sectional view showing one example of such a conventional high-pressure discharge lamp. A capillary 22 made of an oxide insulator such as alumina is similarly provided at both ends of a discharge tube 21 made of an alumina cylinder. The electrode member 23 provided with the discharge electrode 24 at the tip was inserted into the through hole of the capillary and sealed. In this configuration, the entire length L can be reduced to about 10 mm, and the diameter D of the discharge tube can be reduced to about 3 mm, but the joint (sealing part) between the capillary 22 and the electrode member 23 is formed at both ends. Cracks are likely to occur due to differences in thermal expansion characteristics, which has been a major factor hindering the extension of life.

In view of the above problems, the present invention provides a high-pressure discharge lamp that uses an alumina discharge tube, can be used as a pseudo point light source, and stabilizes the connection between the electrode member and the discharge tube. As an issue.

[0007]

In order to solve the above-mentioned problems, according to the first aspect of the present invention, an electrode member is inserted and sealed at both ends of an alumina cylindrical body, and an ionized luminescent material and a starting gas are supplied. A high-pressure discharge lamp in which a filled discharge space is formed in the cylinder, wherein the electrode member is formed by a discharge electrode and a current conductor that supplies a current to the discharge electrode,
The current conductor is formed by a pipe conductor inserted into an opening of the alumina cylindrical body and joined by a joining material, and a rod-shaped conductor inserted into a through hole of the pipe conductor and having the discharge electrode at a tip thereof. The diameter of the alumina cylinder is 1 mmφ.
６6 mmφ and a length of 6 mmｍｍ15 mm.

According to a second aspect of the present invention, in the first aspect of the present invention, the bonding material between the alumina cylindrical body and the pipe conductor of the current conductor is made of a porous skeleton made of a sintered metal powder impregnable with glass. It is characterized by being formed of a glass solder.

According to a third aspect of the present invention, in the second aspect, a main component of the metal forming the porous skeleton is the same as a main component of the metal forming the pipe conductor.

According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, the inner diameter of the opening at both ends into which the pipe conductor of the alumina cylindrical body is inserted has a stepped portion and is enlarged. You.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory sectional view of a high-pressure discharge lamp according to the present invention.
The electrode member 3 is directly inserted and sealed into the opening 2a at both ends of the discharge tube 1 made of, and a luminescent substance such as a halogen compound and a starting gas are sealed inside. The cylindrical body 2 is formed of a simple cylinder made of polycrystalline alumina.
Is formed from a current conductor 4 and a discharge electrode 5 provided at the tip thereof, and the connection between the discharge tube 1 and the electrode member 3 is made via a joining material 6 described later.

The discharge electrode 5 is formed of a tungsten rod and a filament fixed to the tip thereof.
In order to reduce the size, it may be formed only of a simple tungsten rod. The current conductor 4 includes a metal pipe (pipe conductor 7) and a cylindrical core material 8 formed therein.
And both are welded at the ends. Also,
The discharge electrode 5 is provided at the tip of the core material 8 and is joined by welding or metallization. Also, the pipe conductor 7
May be formed of a halide-resistant substance such as tungsten or molybdenum. In this case, molybdenum is used. The core 8 is preferably formed of the same metal as the pipe conductor 7. Thus, the conventional capillary is eliminated and the pipe conductor constituting the current conductor is directly connected to the discharge tube 1.
, The size of the discharge lamp can be reduced.

When a high-pressure discharge lamp using an alumina discharge tube is used for an automobile headlamp, it is necessary to reduce the size as described above. Specifically, when the discharge tube is 15 mm or less in length, It is desired that the diameter be 6 mmφ or less. However, the arc length of the internal discharge part is 1 mm or more.
About 5 mm is required. In this regard, in the configuration of FIG. 1, the length L1 of the alumina cylindrical body 2 which is the discharge tube 1
If it is 6 mm or more, it is possible to form an arc length of 1 mm or more inside, and since the electrode member 3 is directly attached to the discharge tube, the diameter D1 of the discharge tube 1 can be reduced to 1 mmφ. . Therefore, a high pressure discharge lamp having a pseudo point light source suitable as a point light source such as a headlight for an automobile can be obtained by the above configuration. Note that the minimum value of the discharge tube diameter is determined by the tube wall load during lamp operation, and a tube wall load that is practical as a high-pressure discharge lamp needs to be at least 15 lumens / cm2 (0.25 mm in wall thickness) or more. Confirmed by experiment.

Next, the joining material 6 for joining the cylindrical body 2 and the pipe conductor 7 will be described. The joining material 6 is formed by impregnating a glass material 11 into a porous metal (hereinafter referred to as a porous skeleton 10). The porous skeleton 10 is a sintered body of a metal powder and has open pores. Here, in order to improve the coupling characteristics with the pipe conductor, the pipe conductor 7
It is formed from a sintered body of molybdenum powder, which is the same metal as
Pure metals, such as rhenium, and their alloys can be used.

The formation of the porous skeleton 10 and the joining of the alumina cylindrical body 2 and the pipe conductor 7 will be described with reference to the electrode part sealing process diagram of FIG. First, a metal powder is prepared, pulverized and dried, and a binder such as ethyl cellulose or an acrylic resin is added and mixed to form a paste to obtain a porous skeleton material 10a. The paste is applied to a predetermined portion, that is, a side surface of the pipe conductor 7 in a ring shape (step 2), and
Dry at -60 ° C. This calcined body has a dew point of 20 ° C.
Under a reducing atmosphere of 50 ° C., an inert gas atmosphere or a vacuum,
Firing at a temperature of 1200 ° C. to 1700 ° C. (Step 3).
By doing so, the porous skeleton 10 having open pores can be formed at the joint of the pipe conductor 7.

The open porosity of the porous skeleton 10 is preferably at least 30%, more preferably at least 40%, whereby the strength of the joint region can be further increased. Further, the open porosity is preferably 80% or less, and more preferably 70% or less, whereby the glass material is appropriately impregnated into the open pores of the porous skeleton, and the stress applied to the porous skeleton is dispersed. The durability to a heat cycle can be improved. Further, in order to appropriately generate an impregnated glass layer in which the porous skeleton 10 is impregnated with the glass braze 11, the tap density of the metal powder as a raw material of the porous skeleton 10 is set to 2.5.
It is preferable to be 3.5 g / cc.

Next, in step 4, a predetermined amount of the pipe conductor 7 is inserted into the cylindrical body 2, a glass braze 11 is attached to the sealing portion, the glass is heated and melted, and the pipe conductor 7 is joined to the cylindrical body 2 and a gap is formed. Is sealed (step 5). In addition, glass brazing 1
1 is Al ₂ O ₃ , SiO ₂ , Y ₂ O ₃ , Dy ₂ O ₃ , B ₂ O ₃
And MoO _3, and is preferably formed of a material selected from the group consisting of Al ₂ O ₃ and SiO ₂ . Then, a predetermined glass composition, for example, dysprosium oxide 60% by weight, alumina 1
A powder or frit prepared to be 5% by weight and 25% by weight of silica is crushed, a binder such as polyvinyl alcohol is added, granulated, pressed, and degreased to obtain a glass wax. Further, the attached glass brazing attached to the porous skeleton is preferably formed in a ring shape in advance.

Finally, in step 6, the core material 8 provided with the discharge electrode 5 is inserted into the pipe conductor 7, the ends are welded, and both are joined and sealed.

The pipe conductor 7 thus formed and the cylindrical body 2
As shown in FIG. 3 which is an enlarged explanatory view of the part A in FIG. 1, when the attached glass braze 11 is melted, it impregnates into the open pores of the porous skeleton 10 and becomes porous. A main phase 12 consisting of a skeleton 10 and an impregnated glass phase is formed. Further, the molten glass causes the porous skeleton 10 to slightly float from the surface of the cylindrical body 2, and an interface glass between the pipe conductor 7 and the cylindrical body 2. A layer 13 is generated. Therefore, poor wettability between the pipe conductor 7 and the glass braze 11 is improved, and the porous skeleton 10
The glass braze 11 is securely joined to the pipe conductor 7 through the via hole, and is reliably joined to the alumina cylindrical body 2 by the glass braze 11 having good wettability. That is, the current conductor 4 and the discharge tube are securely joined, and the glass braze hermetically seals the gap. In this way, the joining between the alumina cylindrical body and the pipe conductor formed of metal can be reliably performed. Furthermore, even if a crack occurs in the interface glass layer, the porous skeleton prevents the crack from developing, so that the life can be extended. Further, since the main components of the porous skeleton and the pipe conductor are the same, the porous skeleton is firmly joined to the pipe conductor.

FIG. 4 shows another shape of the cylindrical body.
5 is a step 16 at the electrode member insertion position of the opening 15a at both ends.
The diameter is increased. By providing the stepped portion 16 in this manner, when the electrode member 3 is inserted and joined, the joining material 6 or the pipe conductor 7 can be positioned in contact with the stepped portion 16 at a predetermined insertion position, so that smooth and highly accurate joining can be performed. A part can be formed.

In the above embodiment, the description has been given on the premise that the present invention is applied to a headlamp for an automobile. However, the high-pressure discharge lamp as a point light source requires a point light source for an OHP (overhead projector) or a liquid crystal projector. It can also be used as a light source.

[0022]

As described above in detail, according to the first aspect of the present invention, the conventional capillary portion is used as a pipe conductor as a component of the current conductor, and the current conductor and the cylindrical body are directly joined to each other, thereby enabling the discharge. The electric lamp can be reduced in size and used as a simulated point light source, which can be suitable as a point light source such as a headlight for an automobile.

According to the second aspect of the present invention, in addition to the effect of the first aspect of the present invention, the bonding between the alumina cylindrical body and the pipe conductor made of metal can be reliably performed, and cracks are generated in the glass. Even if it occurs, it hardly progresses and the life can be extended.

According to the third aspect of the present invention, in addition to the effect of the second aspect of the present invention, since the main components of the porous skeleton and the pipe conductor are the same, the porous skeleton is firmly joined to the pipe conductor. Can be.

According to the invention of claim 4, claims 1 to 3 are provided.
In addition to the effects of any of the inventions described above, the connection operation can be performed smoothly by providing a step portion in the insertion portion of the electrode member.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of a high-pressure discharge lamp showing an example of an embodiment of the present invention.

FIG. 2 is an explanatory view of a sealing process of an electrode section of FIG. 1;

FIG. 3 is an enlarged explanatory view of a portion A in FIG. 1;

FIG. 4 is an explanatory sectional view of a high-pressure discharge lamp showing another embodiment of the present invention.

FIG. 5 is an explanatory sectional view of a high-pressure discharge lamp using a conventional alumina discharge tube.

[Explanation of symbols]

1. discharge tube, 2. alumina cylinder, 2a opening, 3. electrode member, 4. current conductor, 5. discharge electrode, 6. joining material, 7. pipe conductor, 8. Core material, 1
0: porous skeleton, 11: glass brazing, 12: main phase of joint, 13: interfacial glass layer of joint, 15: cylindrical body, 15a: opening, 16: diameter increasing step Department.

Claims (4)

[Claims] 1. A high-pressure discharge lamp in which an electrode member is inserted into both ends of an alumina cylindrical body and sealed, and a discharge space filled with an ionized luminescent substance and a starting gas is formed in the cylinder. The electrode member is formed of a discharge electrode and a current conductor that supplies current to the discharge electrode, and the current conductor is inserted into an opening of the alumina cylindrical body and joined by a joining material, and a pipe conductor, It is inserted into a through hole of a pipe conductor, and is formed of a rod-shaped conductor having the discharge electrode at the tip, and the diameter of the alumina cylindrical body is 1 mmφ to 6 mm.
A high-pressure discharge lamp having a diameter of φ and a length of 6 mm to 15 mm. 2. A joining material for connecting a cylindrical body made of alumina and a pipe conductor of a current conductor to a porous skeleton made of a sintered body of a metal powder capable of impregnating glass and a glass solder.
The high pressure discharge lamp as described. 3. The main component of the metal forming the porous skeleton and the main component of the metal forming the pipe conductor are the same.
The high pressure discharge lamp as described. 4. The high-pressure discharge lamp according to claim 1, wherein the inner diameter of the opening at both ends into which the pipe conductor of the alumina cylindrical body is inserted has a step, and the diameter is enlarged.