JPH0794142A - High-pressure discharge lamp - Google Patents

Abstract

PURPOSE: To avoid premature darkening by an at least main part of an electrode rod being surrounded by a sleeve, consisting of a high-melting point materiaL in a discharge container and enclosing an end of the discharge container by a plug body. CONSTITUTION: An electrode 11 is formed of an electrode rod, consisting of tungsten and an electrode head formed by a spiral part 13 engaged at a discharge part side end. An electrode rod 12 is tightly enclosed by a ceramic sleeve 17. A second introducing conductor 9b is arranged at a second end 6b, and the end 6b is placed as a closed end. The two introducing conductor 9 consist of a niobium tube, and these are deeply inserted into a hole part of the end part plug body. For evacuation and filLing, for example, a filLing part 15 is provided in the vicinity of a pump end 6a, and this charge hole part 15 is sealed by glass soldering or a fused ceramic 15 after filling. Thereby, an electrode tip end is heated quickly, and discharge arcing is started at the tip end of the electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention comprises a ceramic discharge vessel, for example provided in an external bulb, the discharge vessel having a discharge volume and an ionizable enclosure (eg metal halide). In this case, the discharge vessel has two ends provided with an opening, and the two electrodes consisting of an electrode rod and a head are connected to a lead conductor provided outside through an introduction conductor, Each lead-in conductor relates to a high-pressure discharge lamp, which is vacuum-tightly fixed in the open end.

[0002]

BACKGROUND OF THE INVENTION The high pressure discharge lamps featured in this invention are essentially metal halide discharge lamps. The color rendering of this lamp is improved by using a ceramic discharge vessel. Typical power output is 50-250W.
It is also applicable to sodium discharge lamps.

A lamp of this kind is known from EP-A-472100. In this lamp structure, the lead-in conductor is made of niobium and is deeply inserted into the stopper. The publication shows that the glow discharge phase of the discharge arc becomes very long during the ignition of the lamp. The reason is that the discharge arc is initiated in the recess of the plug body in the niobium introducing conductor. In other words, it is started at the place where it is sealed with glass solder or molten ceramic. Due to the high loading, metallic niobium can be sputtered at this point. This causes premature blackening of the discharge vessel. As an additional drawback, such a mechanism also affects the sealing property due to damage to the glass solder (solder). The damage of the glass solder impairs the hermeticity of the discharge vessel and further adversely affects the life.

The problem of extending the glow phase duration is more or less pronounced in other types of metal halide discharge lamps having a ceramic discharge vessel. For lamps with a cermet-plug (EP-A 160445), it has been proposed to utilize a plug projection located near the inwardly directed axis. The plug surrounds the electrode rod. However, the manufacture of this type of plug is very expensive.

From Japanese Utility Model Publication No. 49-14449, a metal halide discharge lamp having the following ceramic discharge vessel is known. That is, the shield in the annular quartz glass plate structure is arranged immediately after the electrode, thereby avoiding the initiation of a discharge arc in the electrode rod,
Metal halide discharge lamps are known in which damage to the glass braze (solder) melt is avoided as a result. However, the problem here is the fixing of the glass plate.

[0006]

The object of the present invention is to provide a high-pressure discharge lamp which makes it possible to keep the glow discharge phase as short as possible.

[0007]

According to the present invention, at least the main part of the electrode rod is surrounded by a sleeve made of a high melting point material in the discharge vessel, and the end portion of the discharge vessel is a plug body. Is closed by means of an arrangement in which the lead-in conductor is inserted in the opening of the plug.

Advantageous embodiments of the invention are described in the dependent claims.

According to the present invention, the electrode rod is surrounded by a sleeve made of a high melting point material as a shield. Particularly, ceramic (Al ₂ O ₃ ) is suitable, but quartz glass, hard glass, or high melting point material (for example, tungsten) is also suitable as a material.

Advantageously, the sleeve is adapted to and fixed by a recess (eg a blind hole or a hole) on the discharge side of the plug. In some cases, this recess is also used for accommodating the lead-in conductor. With metal sleeves, particularly small turns (coils of the individual loops in contact with one another) can be formed.

The sleeve preferably terminates in the electrode head on the discharge side. This head can be, for example, a roll or a sphere. Since this electrode head is expanded more than the electrode rod, the electrode head internally forms a stopper for the sleeve. The sleeve is fixed by this stopper. Besides, the electrode rod is completely covered by the sleeve. This prevents the start of a discharge arc at the electrode rod. However, complete coverage of the electrode rod area present in such discharge vessel space is not necessary. For example, it is possible to leave a small gap near the head.

The inner diameter of the sleeve is usually chosen to approximately match the diameter of the electrode rod. However, the inner diameter of the sleeve may be selected to be significantly larger than the diameter of the electrode rod.
This is particularly advantageous in the following cases. That is, it is advantageous when the electrode rod is not directly joined to the introduction conductor but is joined using a member extending in the lateral direction. However, the inner diameter of the sleeve should preferably be chosen smaller than the lateral dimension of the electrode head in order to ensure that arcing of the electrode rod is not initiated.

The discharge arc diffused by the use of the sleeve, which first occurs when the lamp is ignited, is
It no longer occurs further back than at the rear end of the electrode head (spiral). Thereby it is achieved that the electrode tip is heated relatively quickly. As a result, the discharge arc is also started relatively early at the electrode tip. In addition, the return of the discharge arc behind the electrode head and the early blackening are avoided.
Furthermore, the problem of sealing in the area of the lead-in conductor is also avoided. According to a special embodiment of the invention, the stability of the operating voltage and the emission value is additionally improved because the welding point is at the lowest possible temperature. This is based on the consideration that at low temperatures glass solder reacts significantly less with the halide of the lamp enclosure. This is achieved by: That is, the introduction conductor (for example, a niobium tube) is separated from the discharge portion as far as possible, and is deeply sealed only in the distant portion of the plug hole portion. Under such a method, most of the annular gap in the plug hole portion is filled with the sleeve. By this method, it becomes possible to condense only a small amount of the filling component in the plug hole portion. The holes can also be completely closed with glass solder.
Thereby, the lead-in conductor is shielded well (especially if it consists of niobium, which is susceptible to corrosion).

The technique of retracting the fusion seal allows for an even better configuration in which very long plugs that project relatively far from the combustion chamber can be used. The lead-in conductor (made of niobium, for example) is sealed only at the outer end of the very long plug. In this case, the long annular gap to the discharge part is very well filled and sealed by the ceramic body covering the electrode rod. The small space left in the plug area is filled with filling material up to the following locations in the discharge space, i.e. locations where the temperature and vapor pressure are high enough to produce sufficient vapor density for good emission values. Be done. The condensed inclusions that are present in the rear of the plug do not react with the solder glass and niobium due to its low temperature. The ends of the discharge vessel are preferably closed with a separate plug. However, it may have a complete constriction instead of a separate plug.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 schematically shows a metal halide discharge lamp having an output of 150 W. The lamp consists of a cylindrical outer bulb 1 which defines the lamp axis. This outer bulb is made of quartz glass and has a pinch part 2 and a base part 3 on both sides. The axially arranged discharge vessel 4 made of Al ₂ O ₃ -ceramic has a bulge at a central portion 5 and further has a cylindrical end portion 6. However, the discharge vessel 4 may be formed of, for example, a cylindrical tubular member. The discharge vessel 4 is indicated in the outer bulb 1 by means of two lead conductors 7. The lead conductor 7 is connected to the base portion 3 via a thin piece 8. The lead conductor 7 is made of molybdenum and is welded to the introduction conductor 9. The introduction conductors 9 are each sealed by glass solder 14 in the ceramic end plug 10 of the discharge vessel. This end plug 10 is also made of Al ₂
It is made of O ₃ . In addition to the inert ignition gas, the filling material of the discharge vessel is made of, for example, an additive such as argon, mercury, or a halide. The first introduction conductor 9a is arranged at the first end 6a. This first end 6a is used as the pump end when filling the lamp. This end points to the electrode 11 inside the discharge vessel. The electrode 11 is composed of an electrode rod 12 made of tungsten and an electrode head formed by a spiral portion 13 fitted at an end portion on the discharge portion side. The electrode rod 12 is a ceramic sleeve 1.
It is tightly surrounded by 7.

The second introducing conductor 9b is arranged at the second end 6b. This second end 6b is left as a closed end. The two lead conductors 9 are solid niobium tubes. These are inserted deep into the holes in the end plugs.

For evacuation and filling, eg pump end 6a
A filling hole portion 15 is provided in the vicinity of. This filling hole 15
Is glass solder or molten ceramic 16 after filling
Sealed by It is also possible to use the opening for the introducing conductor as a filling hole and insert the introducing conductor into this opening to seal it.

FIG. 2 shows in detail the lead-in conductor area at one end of the discharge vessel. A niobium tube 9 having a diameter of 1.2 mm is inserted in a ceramic stopper 10 having a length of 5 mm. The length of this niobium tube 9 is 12 mm. An electrode rod 12 made of tungsten is butted and welded to the end of the niobium tube 9 on the discharge side. The electrode rod has a diameter of 0.5 mm and a length of 6.5 mm. A spiral part 13 having an outer diameter of 1.1 mm and composed of nine spiral parts is disposed at the tip of the electrode rod 12. Electrode rod 1 from the tip 13
The length of the protruding portion 2 is 0.5 mm. The ceramic protection sleeve 17 is fixed between the spiral portion 13 and the niobium tube 9. The outer diameter of this sleeve is 1.1 mm and the bristles are 0.6 mm. The total length is 4mm,
A 2 mm section thereof is deeply inserted into the hole of the stopper 10. On the other hand, the niobium tube 9 extends outward beyond the remaining 60% of the holes. The proper insertion depth of the niobium tube is ensured by an external stop on the plug (here a wire stop 18 of niobium).
The outer diameter of the plug is 3.3 mm and the diameter of the plug hole is 1.2 mm
Is.

In this way, a capillary action portion between the hole wall and the niobium tube or ceramic sleeve is left.
This portion is sealed by the glass solder 14 over the entire length of the hole. Niobium tube 9 and ceramic sleeve 17
Are fused together as one unit. The manufacturing of this structural unit is performed as follows (FIG. 3).
That is, the electrode rod 12 and the niobium tube 9 are first welded by butting each other. Then the electrode rod 12
The sleeve 17 is put on the top of the. Is this sleeve pushed against the niobium tube 9 (Fig. 3)?
a) or pushed a little further into the further cut protrusion (Fig. 3b). The outer diameters of the niobium tube and the sleeve are almost the same. The sleeve is fixed by shifting the spiral portion 13 in the arrow direction. During the sealing of the electrode system, the niobium tube 9 and the sleeve 17 are wetted by the glass solder 14, so that the sleeve is sealed in the already existing plug hole (FIG. 1).

In another embodiment for 250 W according to FIG. 4, the discharge vessel 4'has a tapered end 6 '(though this is also suitable for smaller power levels). The plug 10 'has a diameter of 5 mm and a length of 12 mm. The diameter of the plug hole is 1.2 mm. Stopper 10 '
The side of the discharge vessel facing the discharge part extends until it projects about 50% from the end 6'of the discharge vessel. The niobium tube 9 has a diameter of 1.2 mm and a length of 12 mm and is 3 m
It is inserted into the outer end of the plug at a depth of m. In this niobium tube, electrode rods 12 having a length of 18 mm and a diameter of 0.6 mm are butted and welded. The electrode rod 12 supports a spherical head 20 at its tip. A sleeve 17 made of ceramic covers the electrode rod 12 over its entire length. This sleeve is 1.15m
It has an outer diameter of m, an inner diameter of 0.8 mm, and a length of 15 mm. The niobium tube 9 is sealed with glass solder 14 at the outermost end of the plug. In this case, the temperature load near the niobium tube is relatively small. The temperature load in this case is the first
It is about 150 ° C to 200 ° C lower than that of the example. Therefore, it is not necessary to fill all remaining annular voids of holes 32 in the plug area with glass solder as long as the sleeve is housed therein. The remaining annular void in the bore is filled with a condensable filler (halide) from the outer end to a predetermined location during lamp operation. This location has a temperature at which a vapor pressure high enough to produce the vapor pressure necessary to obtain a good emission value is obtained.
Therefore, the size of the annular void must be taken into account under the control of the filling volume. The condensate in the annular gap remote from the discharge zone reacts little with the glass solder and the niobium-introduced conductor due to the relatively low temperature.

Further, FIG. 5 shows another embodiment. In this embodiment, the diameter is 3.5 mm, and the material is ceramic or a ceramic-based material (for example, Celmet).
A rod-shaped portion 22 having a diameter of 0.3 mm and made of molybdenum, tungsten, or niobium is directly sintered in the plug body 21 made of. Inside the discharge vessel, the rod-shaped portion 22
An electrode rod 25 having a diameter of 0.5 mm is provided on the cutting portion 26 of the electrode rod.
It is fixed laterally by. The electrode rod 25 supports a spiral portion 27 having an outer diameter of 1.6 mm as a head. The plug 21 has a diameter of 1.4 m on the surface facing the discharge part.
It has a concave portion 28 having a depth of 1 mm and a depth of 1 mm. Inside this pocket is a ceramic sleeve 29 with a total length of 3.5 mm.
Has been inserted. The sleeve 29 is the electrode rod 25.
And a part of the rod-shaped portion 22 is surrounded by a space (about 1
(00 μm spacing). The sleeve has an outer diameter of 1.4 mm and 1 m
It has an inner diameter of m. The sleeve is not mounted directly on the spiral, but is spaced less than 1/10 millimeters from the spiral. The sleeve is supported in the recess 28 by direct sintering. This is possible because it approximates the coefficient of thermal expansion of the sleeve and plug.

In yet another embodiment (FIG. 6, this is FIG.
The same reference numerals are used for the same parts) and the construction of the sleeve is further simplified. The plug body 21 of this embodiment has no recess. The sleeve 31 is clamped between the flat discharge-side plug body end surface 30 and the spiral portion 27. The length of the sleeve 30 is shortened by 2.5 mm, and other dimensions are the same as those in the case of FIG. In this embodiment, the sleeve may be made of quartz glass.

Another embodiment of FIG. 7 is also constructed similarly to FIG. The spherical electrode 20 is abutted against the introduction conductor rod 22 at the rod end and welded. Sleeve 40
Is a spiral part made of a tungsten wire. The individual turns of this spiral are in contact with each other. The lead-in conductor 22 is directly sintered to the plug body 21. The sleeve is mounted in the planar notch 41 of the plug.

[0025]

According to the invention, the diffused discharge arc that occurs when the lamp is ignited no longer occurs further behind the rear end of the electrode head (spiral). Thereby it is achieved that the electrode tip is heated relatively quickly.
As a result, the discharge arc is also started relatively early at the electrode tip. In addition, spreading of the discharge arc behind the electrode head and premature blackening are avoided.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a metal halide lamp.

FIG. 2 is a detailed view of a lead-in conductor area of the lamp.

FIG. 3 is a diagram showing a manufacturing process of the electrode system according to FIG. 2;

FIG. 4 is a diagram showing another embodiment of the lamp introducing conductor region.

FIG. 5 is a diagram showing another example of the lamp introducing conductor region.

FIG. 6 is a view showing another example of the lamp introducing conductor region.

FIG. 7 is a diagram showing another example of the lamp introducing conductor region.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 External valve 2 Pinch part 3 Base 4 Discharge container 5 Central part 6 End part 7 Lead conductor 8 Thin piece 9 Introducing conductor 10 Ceramic plug body 11 Electrode 12 Electrode rod 13 Spiral part 14 Glass solder 15 Encapsulation hole part 16 Molten ceramic 17 Protection Sleeve 19 Projection 20 Spherical head 21 Plug

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Stefan Jungst Zorneding Herzog-Ludwig-Strasse 44 Germany (72) Inventor Peter Warendorf Munich Kwiddestraße 41

Claims (3)

[Claims] 1. A ceramic discharge vessel (4) is provided,
The discharge vessel (4) has a discharge volume and an ionizable fill, in which case the discharge vessel (4) has two ends (6) with openings and an electrode rod (12). ) And the head (13; 20) are connected to the lead conductor (7) provided outside through the introduction conductor (9), and each introduction conductor is vacuum-tight. In a high pressure discharge lamp fixed in an end opening, at least a major part of the electrode rod (12) is surrounded in a discharge vessel by a sleeve (17; 29) of a high melting point material, High-pressure discharge lamp, characterized in that the end of the container is sealed by a plug (10), in which case the introduction conductor is inserted into the opening of the plug (10). 2. The discharge lamp according to claim 1, wherein the sleeve (17) is inserted into a recess (28) in the discharge-side end surface (30) of the stopper. 3. The sleeve (17; 29) is made of ceramic, fused silica or a refractory material,
The high pressure discharge lamp according to claim 2.