JPH0869774A - Small-sized metallic vapor discharge lamp and vehicular lighting system using the same - Google Patents

Abstract

PURPOSE: To provide a small-sized metallic vapor discharge lamp and a vehicular lighting system incorporating it, with which it is practicable to preventfusion deformation of electrodes using a simple structure and can preclude leakage at the sealing part. CONSTITUTION: A pair of electrodes 3 are encapsulated in a light emitting tube 1 to from a small-sized metallic vapor discharge lamp, wherein each electrode 3 is made from a rod 4, whose tip extending into the light emitting tube is folded, and the folded tip 5 is laid as stretching in the longitudinal direction of the electrode rod. Because the tip of the rod is folded in approx. U-form, the manufacture can be made easily and at a low cost, and also the section area of the foremost part is enlarged to lead to increase in the thermal capacity, and it is possible to prevent the electrode tip from fusion deformation. Because the root of the electrode is thin, it is easy to attach sealedly to the end of the tube, and leakage can also be precluded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small metal vapor discharge lamp such as a small metal halide lamp having a modified electrode structure and a vehicle lighting device using the same.

[0002]

2. Description of the Related Art NaI, S are contained in a quartz glass arc tube.
Metal halide lamps containing metal halides such as cI ₃ and LiI ₂ are widely used because of their high efficiency and excellent color rendering properties. It is being applied to commercial light sources, store lighting, and liquid crystal projector light sources.

However, in such a light source, not only downsizing but also instantaneous lighting is strongly required. That is, in general, a metal vapor discharge lamp has a property that a waiting time of several minutes is required from when the power source voltage is turned on to when the rated luminous flux is emitted. It cannot be used as a light source.

As measures against such instantaneous lighting, the high-pressure xenon gas is improved by improving the lighting circuit or by filling xenon as a rare gas filled with a metal halide in a high pressure and flowing a large current at the time of starting. It has been proposed to excite a laser beam to cause it to emit light, thereby instantaneously obtaining a luminous flux at or near the rated value. When a high-pressure xenon gas is filled, the temperature of the tube wall rises while the gas emits light, which promotes evaporation of the metal halide and gradually shifts to the light emission of the metal halide. .

However, in such a metal halide lamp, since a large current is passed at the time of starting, when a thin electrode is used, the electrode is overheated, which causes the electrode material to evaporate and the evaporated electrode material to adhere to the tube wall. There are problems such as premature blackening and thinning of the electrode, which causes breakage.

That is, when the lamp is downsized, the distance between the electrodes becomes shorter, and in the case of a metal halide lamp having a length of 10 mm or less, specifically 35 W or less, the distance between the electrodes becomes about 4.5 mm. There is no choice but to miniaturize.

The simplest shape of the electrode is a wire diameter of 0.2.
The electrode is composed of only straight rod-shaped electrode rods formed of high-melting-point metal wires of about mm to 0.3 mm. However, in the case of an electrode formed by such a straight rod-shaped electrode rod, the cross-sectional area is small, so that the heat capacity is also small. Therefore, when a large current is passed, the electrode is instantaneously and extremely overheated.

Due to such temperature rise, the tips of the electrodes are melted and deformed, the distance between the electrodes is changed due to the melted deformation, and the electrical characteristics and the light emission characteristics are varied. Further, if the tip of the electrode is melted and deformed, the arc spot becomes unstable at the time of lighting the rated output, and there is a risk of flickering or extinction.

Further, the melting of the tip of the electrode may evaporate and consume the electrode material, and the scattered material may adhere to the tube wall, leading to early blackening. To prevent this, if a thick diameter electrode rod is used, the heat capacity will be large, but heat will easily escape to the sealing portion of the arc tube through this electrode rod,
It may be difficult for the temperature of the electrode to rise to a temperature suitable for emitting thermoelectrons, the startability may be deteriorated, and extinction may occur. Further, when the electrode is large, not only is it difficult to seal the end of the arc tube, but also distortion due to the difference in thermal expansion occurs, which causes leakage.

From the above, the most general structure of the conventional electrode is a type in which an electrode rod and an electrode coil are wound around the tip of the electrode rod. In the case of such a structure, the coil portion provided at the tip of the electrode rod can increase the heat capacity, prevent the electrode from being overheated and evaporating the electrode substance. Since it can be made extremely thin, it is possible to prevent heat from escaping due to heat conduction, and it is possible to maintain an appropriate temperature at the tip of the electrode.

However, if an electrode having such an electrode coil is attempted to be miniaturized, the electrode rod and the electrode coil are made up of thin wires, so that the manufacturing is complicated and the number of parts is two, so that the assembly is troublesome. However, there is a drawback that the yield of the electrodes is low.

From the above, it is conceivable that the tip of the electrode rod has a large diameter and the electrode has a spherical shape. With such a structure, the cross-sectional area of the tip of the electrode is increased, so that the heat capacity is increased, melting deformation of the tip of the electrode can be prevented, and evaporation of the electrode substance can be prevented. Further, since the base of the electrode rod is thin, it is easy to seal the end portion of the arc tube, and it is possible to prevent distortion due to a difference in thermal expansion and prevent leakage from occurring.

[0013]

However, in the case of the electrode in which the tip portion of the electrode rod has a large diameter and is spherical, it takes time and effort to mold the electrode, and the manufacturing cost becomes high. Further, there is a problem that the shape of the tip portion is largely varied and the arc spot becomes unstable.

The present invention has been made in view of the above circumstances. An object of the present invention is to prevent melting deformation of an electrode with a simple structure and to prevent leakage of a sealing portion. An object of the present invention is to provide a vapor discharge lamp and a vehicle lighting device using the same.

[0015]

According to a first aspect of the present invention, in a small metal vapor discharge lamp in which a pair of electrodes are sealed in an arc tube, the electrodes are electrode rods, and the tip of the electrode rod extending into the arc tube is provided. It is characterized in that it is bent, and the bent tip is along the length direction of the electrode rod.

According to the invention of claim 2, the distance between the electrodes is 1
It is characterized by being 0 mm or less. The invention of claim 3 is
The bent tip has a length of 0.3 mm or more and 0.7 mm or less.

The invention of claim 4 is characterized in that the arc tube is filled with a predetermined amount of mercury, a metal halide and a rare gas. A fifth aspect of the present invention is a small-sized metal vapor discharge lamp that is lit by direct current, wherein the anode has a bent end that extends into the arc tube of the electrode rod, and the bent front end is along the length direction of the electrode rod. And The invention of claim 6 is
An illumination device for a vehicle, wherein the small metal vapor discharge lamp according to any one of claims 1 to 5 is used as a light source.

[0018]

According to the first aspect of the present invention, since the tip of the electrode rod is bent into a substantially U-shape, not only the manufacturing is easy and the cost is low, but also the cross-sectional area of the tip is large. As a result, the heat capacity is increased, and therefore even if a large current flows, overheating of the electrodes can be prevented. For this reason, melting and deformation of the electrode tips can be prevented, changes in the distance between the electrodes can be prevented, and changes in electrical characteristics and light emission characteristics can be prevented. Further, since the tip of the electrode is less likely to be melted and deformed, the arc spot becomes stable when the rated output is turned on, and it is possible to prevent flickering and extinction. Further, evaporation of the electrode material is prevented, and there is no fear that scattered material will adhere to the tube wall and cause premature blackening. Moreover, since the base of the electrode is thin, it is difficult for the heat of the electrode to escape, so that the temperature rise of the electrode can be promoted, the instant start by a large current can be made possible, and the extinction can be prevented.
Further, since the base of the electrode is thin, it is easy to seal the end of the arc tube and the occurrence of leak can be prevented.

According to the invention of claim 2, the invention of claim 1 is effective when applied to a small discharge lamp having a distance between electrodes of 10 mm or less. According to the invention of claim 3, since the length of the bent tip portion is set to 0.3 mm or more and 0.7 mm or less, the function and effect of the above-mentioned claim 1 can be obtained, and when it is less than 0.3 mm, The heat capacity of the tip portion becomes small and the above effect cannot be obtained, and when it exceeds 0.7 mm, on the contrary, the heat capacity of the tip portion becomes too large and it becomes difficult to raise the temperature, which is not suitable for instantaneous lighting.

According to the invention of claim 4, since the inventions of claims 1 to 3 are applied to the metal halide lamp, the high efficiency and the high color rendering property of the metal halide lamp can be utilized, and the size can be reduced, so that the field of use can be improved. Can be expanded.

According to the fifth aspect of the present invention, in the case of a small metal vapor discharge lamp which is operated by direct current, a U-shaped bent portion is formed at the tip of the electrode rod serving as an anode, so that the temperature rises due to the jumping of electrons. The heat capacity of the anode is increased, melting deformation of the electrode tip is prevented, evaporation of the electrode material is prevented, and there is no possibility that scattered material will adhere to the tube wall and cause premature blackening.

According to a sixth aspect of the present invention, there is provided a vehicular lighting device using the small metal vapor discharge lamp according to any one of the first to fifth aspects as a light source. Since the lighting device requires instantaneous lighting,
The small metal vapor discharge lamp according to any one of claims 1 to 5 can meet the demand.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the first embodiment shown in FIGS. FIG. 1 shows a small metal halide lamp having a rated output of 35 W, and 1 is an arc tube. The arc tube 1 is made of transparent quartz glass and has a wall thickness of 2 mm, a maximum inner diameter of about 4 mm and a maximum length of about 6.5 mm.
It has an oval shape.

Sealing tubes 2 and 2 are joined to both ends of the arc tube 1, respectively. These sealing tubes 2 and 2 are made of translucent quartz glass or hard glass, have an inner diameter of 2 mm and a length of 18 mm, and are fused to both ends of the arc tube 1.

A pair of electrodes 3, 3 are provided in the arc tube 1.
The electrodes are provided so as to face each other with the distance between the electrodes being 10 mm or less. These electrodes 3, 3 are formed by electrode rods 4, 4 made of tungsten W.
At the tip of, the bent tip 5 is bent into a U-shape,
5 is formed. That is, in the electrodes 3 and 3, the tips of the electrode rods 4 and 4 that extend inside the arc tube 1 are bent, and the bent tip portions 5 and 5 are formed along the length direction of the electrode rods 4 and 4. Therefore, the tip of the electrode has a structure in which it is bent and formed into a substantially U shape. The electrode rod 4 is made of tungsten wire with a wire diameter of 0.2 mm and a length of 7 mm.
The length L of the bent tips 5, 5 is 0.3 mm or more, 0.7
mm or less, specifically L = 0.5 mm.

The electrodes 3 and 3 are spot-welded to the metal foil conductors 6 and 6, and the metal foil conductors 6 and 6 are sealed in the sealing tubes 2 and 2. The metal foil conductors 6 and 6 are made of molybdenum foil Mo having a thickness of 1.5 μm, a width of 1.5 mm and a length of 15 mm. The metal foil conductors 6 and 6 have a wire diameter of 0.5 mm.
It is joined to an external lead wire 7 made of molybdenum or the like. The metal foil conductors 6 and 6 are sealed to the sealing tubes 2 and 2 by heating and softening the sealing tubes 2 and 2 and crushing and sealing.

The arc tube 1 is filled with a predetermined amount of mercury, a metal halide and a rare gas such as argon. Mercury Hg is encapsulated, for example, 0.7 mg, metal halides, for example, ScI-TlI-CsI in total of 2 mg, and argon Ar are encapsulated at 700 Torr.

The short arc type metal halide lamp having such a structure is used, for example, as a light source of a vehicle headlight device, as shown in a schematic structure in FIG. That is, 10 is a metal halide lamp having the above structure, 20 is a reflecting mirror that reflects the light emitted from the lamp 10, and 30 is a reflecting mirror.
Is an irradiation area, and such a headlight reflects the light emitted from the metal halide lamp 10 by the reflecting mirror 20,
The irradiation area 30 is irradiated with this reflected light.

In the metal halide lamp having such a structure, the electrodes 3 and 3 form a bent portion at the tip portion of the electrode rod 4, and the bent tip portions 5 and 5 are arranged in the longitudinal direction of the electrode rods 4 and 4. Since they are formed along the shape, that is, substantially U-shaped, the cross-sectional area of the electrode tip portion is doubled as compared with the case of one electrode rod, and the heat capacity becomes large. For this reason, the electrodes 3 and 3 do not excessively rise in temperature even when a large current is applied.

Therefore, it is possible to prevent melting deformation of the electrode tips, prevent changes in the distance between the electrodes, and prevent changes in electrical characteristics and light emission characteristics. Further, since the tip of the electrode is less likely to be melted and deformed, the arc spot becomes stable when the rated output is turned on, and it is possible to prevent flickering and extinction.

Further, since the tip of the electrode is less likely to be melted and deformed, the evaporation of the electrode substance is prevented, and there is no possibility that the scattered substance adheres to the wall of the tube to cause premature blackening, resulting in a long life.

Moreover, since the bases of the electrodes 3 and 3 are thin, the heat of the electrodes is hard to escape, which promotes the temperature rise of the electrode tips, enables instant start by a large current, and prevents the extinction. Further, since the base of the electrode is thin, the electrodes can be easily sealed to the sealing tubes 2 and 2, and the occurrence of leakage can be prevented.

From the above, it is possible to perform instantaneous lighting or instantaneous relighting when the lamp is once turned off and then turned on again. Therefore, it is effective when used as a light source of a vehicle headlight.
In particular, the structure of the electrodes 3 and 3 is a simple structure in which the tips are bent into a substantially U-shape, so that the manufacturing is easy, the number of parts is small, and the manufacturing time is short. This is effective for cost reduction.

The length L of the bent tip portions 5, 5 is 0.3 mm or more and 0.7 mm or less, specifically L = 0.5 mm.
Therefore, the above-mentioned effect is achieved. If the length L of the bent tip portions 5, 5 is less than 0.3 mm or exceeds 0.7 mm, the effect is impaired. Since this point was confirmed based on the experiment, the experiment will be explained.

In the 35 W rated metal halide lamp of the structure shown in FIG. 1 having the above dimensions, the electrodes 3,
3, the length L of the bent tip portions 5, 5 is 0.2 mm, 0.
Ten lamps each having a size of 3 mm, 0.5 mm, 0.7 mm, 0.8 mm, and 1.0 mm were manufactured, and a blinking test of 25 minutes on and 5 minutes off was performed. In this test, a visual test was performed for melting deformation of the electrode, movement of the arc spot, disappearance, and leakage of the sealed portion, and the evaluation is shown in Table 1.

[0036]

[Table 1]

From the above evaluation results, the bent tip portions 5, 5
It has been confirmed that a good result can be obtained when the length L is 0.3 mm or more and 0.7 mm or less. That is, when the length L of the bent tip portions 5 and 5 is less than 0.3 mm, the heat capacity of the electrode tip portion is small and the electrode is melted and deformed, so that the arc spot moves or the distance between the electrodes changes. Causes changes in electrical characteristics and light emission characteristics. Further, if the length L of the bent tip portions 5, 5 exceeds 0.7 mm, the heat capacity becomes too large and the temperature rise of the electrode is slowed down, which is not suitable for instantaneous lighting, and may be extinguished or sealed. Some of the parts are leaked. Therefore, the length L of the bent tip portions 5, 5 is preferably 0.3 mm or more and 0.7 mm or less.

Further, when the manufacturing time was compared between the electrode 3 of this embodiment and a conventional electrode in which the tip portion of the electrode rod has a large diameter and a spherical shape, the electrode 3 of this embodiment shows that The electrode can be manufactured in about 1/3 of the time as compared with the conventional electrode, and the yield of the conventional electrode is about 70%, whereas the electrode of this embodiment can improve the yield to 99%. It has been confirmed that this can be done, and therefore it is easy to manufacture and can be manufactured at low cost.

Further, the present invention is effective when applied to a small discharge lamp having a distance between electrodes of 10 mm or less. That is, a metal vapor discharge lamp having a distance between electrodes of 10 mm or less can be easily attached to a lighting device such as a reflecting mirror because the lamp is small, and it is effective for downsizing the lighting device. It can be applied to a light source for a lamp, a store lighting, a light source of a liquid crystal projector device, or the like.

In particular, if a metal halide is enclosed in the arc tube to form a metal halide lamp, the advantages of high efficiency and high color rendering of the metal halide lamp can be utilized and the field of use can be expanded.

In the case of the above embodiment, the small metal halide lamp of the both ends sealed type has been described, but the present invention is not limited to this, and the one end sealed type as in the second embodiment shown in FIG. It can also be used for small metal halide lamps. In the single-end sealed metal halide lamp of the second embodiment shown in FIG. 3, a crushed sealing portion 41 is formed at one end of an arc tube 40 made of quartz glass, and the sealing portion 41 is made of a pair of molybdenum and the like. The metal foil conductors 42 and 42 are sealed. The metal foil conductors 42, 42 have electrodes 43,
43 are joined, and the tips of these electrodes 43, 43 are introduced into the arc tube 40 and face each other with a distance between the electrodes of 10 mm or less.

These electrodes 43, 43 are made of tungsten W.
The electrode rods 44, 44 are formed of the above-mentioned electrode rods 44, 44, and the tip ends of the electrode rods 44, 44 have bent tip portions 45, 45 that are bent in a substantially U-shape. That is,
The electrodes 43, 43 have a structure in which the tips of the electrode rods 44, 44 are bent and formed into a substantially U shape.

External lead wires 46, 46 are connected to the metal foil conductors 42, 42. The arc tube 40 is filled with a predetermined amount of mercury and a rare gas such as a metal halide and argon.

Even with such a structure, the same effect as that of the first embodiment can be obtained. The present invention can also be implemented in a DC lighting type metal halide lamp shown in FIG. That is, the DC lighting type metal halide lamp of FIG. 4 is an example applied to the both ends sealed type metal halide lamp shown in FIG. 1, but the electrode is composed of an anode 3a and a cathode 3b.

As the anode 3a, similar to the electrode of FIG.
It is formed by the electrode rod 4, and a bent tip portion 5 bent in a substantially U shape is formed at the tip of the electrode rod 4. That is, in the anode 3, the tip of the electrode rod 4 is almost U-shaped.
It has a bent shape. On the other hand, the cathode 3b is formed simply by the electrode rod 4,
No bent tip is formed.

In the case of such a structure, in a discharge lamp normally operated by direct current, an arc spot is formed at the tip of the anode 3a due to the collision of electrons emitted from the cathode 3b, so that the temperature of the anode 3a is higher than that of the cathode 3b. Tend to rise. Therefore, if the anode 3a has a U-shaped bent structure as shown in FIG. 4, the heat capacity of the anode 3a increases, and therefore the temperature of the anode 3a does not rise excessively even when a large current is passed.

Therefore, melting deformation of the tip of the anode can be prevented, the distance between the electrodes can be prevented from changing, and the electric characteristics and the light emitting characteristics can be prevented from changing. Further, since the tip of the anode is less likely to be melted and deformed, the arc spot becomes stable when the rated output is turned on, and flicker and extinguishing can be prevented. Further, since the tip of the anode is less likely to be melted and deformed, the evaporation of the electrode material is prevented, and there is no possibility that the scattered material adheres to the tube wall to cause premature blackening, resulting in a long life.

Moreover, since the base portion of the anode 3a is thin, it is easy to seal it to the sealing tubes 2 and 2, and it is possible to prevent the occurrence of leakage. Furthermore, although the metal halide lamp has been described in the above embodiments, the present invention may be applied to electrodes of other metal vapor discharge lamps such as a high pressure sodium lamp and a mercury lamp. Further, the electrodes are not limited to those made of tungsten, and may be tungsten (tritan) containing molybdenum or thorium.

[0049]

As described above, according to the first aspect of the present invention, since the tip of the electrode rod is bent into a substantially U-shape, not only the manufacturing is easy and the cost is low, but also the tip portion is The cross-sectional area is increased, the heat capacity is increased, and melting deformation of the electrode tip can be prevented. Therefore, changes in the distance between the electrodes are also prevented, changes in electrical characteristics and light emission characteristics are prevented, and the tip of the electrodes are less likely to melt and deform, so that the arc spot is stabilized during rated output lighting, and flicker and extinguishing can be prevented. Further, evaporation of the electrode material is prevented, and there is no fear that scattered material will adhere to the tube wall and cause premature blackening. Moreover, since the electrode base is thin, it is easy to seal the end of the arc tube and the occurrence of leak can be prevented.

According to the invention of claim 2, claim 1
The invention is effective when applied to a small discharge lamp having an electrode distance of 10 mm or less. According to the invention of claim 3, since the length of the bent tip portion is set to 0.3 mm or more and 0.7 mm or less, the function and effect of the above-described claim 1 can be obtained, which is effective for instantaneous lighting.

According to the invention of claim 4, since the inventions of claims 1 to 3 are applied to the metal halide lamp, the high efficiency and the high color rendering property of the metal halide lamp can be utilized, and the size can be reduced, so that the field of use can be improved. Can be expanded.

According to the invention of claim 5, since the U-shaped bent portion is formed at the tip of the anode of the small metal vapor discharge lamp which is operated by direct current, the heat capacity of the anode is increased and the melting and deformation of the tip of the electrode is prevented. Therefore, the evaporation of the electrode material is prevented, and there is no fear that the scattered material adheres to the tube wall and causes blackening at an early stage.

According to a sixth aspect of the present invention, there is provided a vehicle lighting device comprising the small metal vapor discharge lamp according to any one of the first to fifth aspects as a light source. Since the lighting device requires instantaneous lighting,
The small metal vapor discharge lamp according to any one of claims 1 to 5 can meet the demand.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an AC lighting type double-end sealed metal halide lamp showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a light projecting device using the lamp of the embodiment.

FIG. 3 is a sectional view of a one-end sealed metal halide lamp showing a second embodiment of the present invention.

FIG. 4 is a cross-sectional view of a DC lighting type double-end sealed metal halide lamp showing a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Arc tube 2 ... Sealing tube 3 ... Electrode 4 ... Electrode rod 5 ... Bending tip part 6 ... Metal foil conductor 7 ... External lead wire 40 ... Arc tube 41 ... Sealing part 42 ... Metal foil conductor 43 ... Electrode 44 ... Electrode rod 45 ... Bending tip part 3a ... Anode 3b ... Cathode

Claims (6)

[Claims] 1. A small metal vapor discharge lamp in which a pair of electrodes are sealed in an arc tube, wherein the electrode comprises an electrode rod, the tip of the electrode rod extending into the arc tube is bent, and the bent tip portion is the length of the electrode rod. A small metal vapor discharge lamp characterized by being arranged in the vertical direction. 2. The small metal vapor discharge lamp according to claim 1, wherein the distance between the electrodes is 10 mm or less. 3. The small metal vapor discharge lamp according to claim 1, wherein a length of the bent tip portion is 0.3 mm or more and 0.7 mm or less. 4. The small metal vapor discharge lamp according to claim 1, wherein the arc tube is filled with a predetermined amount of mercury, a metal halide and a rare gas. 5. A small-sized metal vapor discharge lamp that is operated by direct current, wherein the anode has a bent end that extends into the arc tube of the electrode rod.
The small metal vapor discharge lamp according to any one of claims 1 to 4, wherein the bent tip portion is arranged along the length direction of the electrode rod. 6. A vehicle lighting device comprising the small metal vapor discharge lamp according to any one of claims 1 to 5 as a light source.