JP2630642B2 - Small metal halide lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD OF THE INVENTION

The present invention relates to a small metal halide lamp having a single sealed airtight container.

[Prior art]

2. Description of the Related Art High-intensity discharge lamps (HID), which have conventionally been used for lighting equipment outdoors and in factories, have recently been increasingly used for indoor lighting equipment having a low ceiling such as stores. On the other hand, lighting fixtures such as stores are required to be downsized.
Accordingly, there is a demand for downsizing the lamp. However, adopting a double-sealed hermetic container structure, which is generally adopted in the past, not only requires time and effort for molding, but also the pinch seal portion becomes large, so that the shape becomes large and heat loss from the lamp is large. Therefore, miniaturization cannot be performed as expected. In order to meet the demand for miniaturization, there are JP-A-60-232658 (conventional 1), JP-A-60-9048 (conventional 2), and JP-A-62-186455 (conventional 3). Conventionally, a one-sided sealed airtight container having a pinch seal portion at one end, a discharge medium containing a metal halide sealed in the airtight container, and one end embedded in the pinch seal portion, There is a description of a metal halide lamp including a pair of electrode shafts which are introduced into an airtight container and are bent so that their tips face each other, and a pair of electrode assemblies having coils disposed on these electrode shafts. According to Conventional Example 1, since there is one pinch seal portion,
The heat loss is smaller than that of a discharge lamp having a hermetically sealed airtight container, the luminous efficiency can be improved, and no trouble is required for molding. Further, the pinch seal portion tends to be relatively large in size as compared with the size of the discharge space. However, since there is only one pinch seal portion, there is an advantage that the hermetic container structure can be downsized. Further, in the prior art 2, a single sealed airtight container having a pinch seal portion at one end, a discharge medium containing a metal halide sealed in the airtight container, and one end embedded in the pinch seal portion, A pair of electrode shafts having a pair of electrode shafts which are introduced into the airtight container from the part and are bent so that the front ends face each other, and a substantially spherical ball disposed at the front ends of these electrode shafts. There are descriptions of metal halide lamps. Conventional lamp 2 also has one pinch seal as in conventional lamp 1.
Since it is an individual unit, there is an advantage that the airtight container structure can be downsized. Further, in the technique 3, a one-sided sealed airtight container having a pinch seal portion at one end, a discharge medium containing a metal halide sealed in the airtight container, and one end embedded in the pinch seal portion, There is a description of a metal halide lamp including a pair of electrode assemblies that are introduced into the hermetic container through the portion, are bent so that the tips face each other, and are spirally wound at the tips. In the conventional lamp 3, the tips of a pair of electrode structures are spirally wound, and are arranged in a mirror image relationship with each other so that an arc spot is always formed above the electrodes.
The magnitude of the current in the first half cycle of the mains voltage is made the same as the magnitude of the current in the next half cycle to eliminate the flicker phenomenon. Conventional lamp 3 also has one pinch seal portion as in conventional lamp 1.
Since it is an individual unit, there is an advantage that the airtight container structure can be downsized. Japanese Patent Application Laid-Open No. 52-100774 (conventional 4) discloses a double-sealed metal halide lamp having a structure in which both ends of an arc tube are narrowed in a tapered shape. There is a description of a lamp which prevents the arc near the tip of the electrode from contacting the tapered portion even if it is curved to prevent devitrification and breakage of the arc tube inner wall. Conventionally, the lamp structure of the prior art 4 is such that both ends of the arc tube of the sealed metal halide lamp are tapered so that the ratio of the arc tube main tube diameter d1 to the electrode sealing tube diameter d2 is 1.8 <d1 / d2.
<4.2 and the pipe diameter ratio between d1 and shoulder diameter d3 is 1.2 <d1 / d3
<1.6.

[Problems to be solved by the invention]

In the first conventional lamp, the arc gap is formed between the tips of the electrode shafts. Therefore, the arc spot is formed at the tip of the electrode shaft during lighting, so that the arc spot hardly moves. However, with such an electrode structure, the electrode material at the tip of the electrode is liable to be scattered by the collision of electrons during lighting, the arc gap becomes longer with the lighting time, and the lamp voltage fluctuates. Light emission becomes difficult to obtain. Further, in the second conventional lamp, a discharge is formed between a pair of balls. Therefore, immediately after the lamp is turned on, an arc spot is generated at an arbitrary position on the ball. However, since the ball is substantially spherical, the arc spot is easy to move, so that the arc spot gradually moves to the tip of the ball closest to the opposing ball after the lamp is turned on. Therefore,
As in Conventional 1, the electrode material at the tip of the ball is easily scattered,
The arc gap becomes longer with the lighting time,
There is a problem that luminous efficiency is reduced. Further, the conventional lamp has the same problem as the conventional lamp because the tip of the electrode structure is spiral, but always tries to fix the arc. In order to solve the problem that the arc gap becomes long, the electrode coil may be disposed at the tip of the electrode shaft so that an arc spot is generated at an arbitrary position on the electrode coil during lighting.
In this case, since the arc spot is not fixed on the periphery of the tip of the electrode coil each time the lamp is turned on, the arc gap is hardly changed even if the electrode material is scattered. However, in the metal halide lamp, when the discharge space is reduced due to a demand for miniaturization, the diameter of the electrode coil becomes relatively large, so that the electrode coil and the inner surface of the airtight container are relatively close to each other. The use of a single sealed airtight container makes it easy to downsize the lamp.However, since the sealed portion of the inner surface of the airtight container faces the arc, the sealed portion of the inner surface of the airtight container is more susceptible to heat from the arc. On the other hand, the temperature on the sealing portion side of the inner surface of the airtight container tends to change depending on the distance from the arc. On the other hand, since the sealing portion acts as a radiation fin, the coldest portion is likely to be formed on the sealing portion side of the inner surface of the airtight container depending on the lighting direction of the lamp. As a result of the research by the present inventors, the movement of the arc spot position changes the distance between the arc and the sealing portion side of the inner surface of the hermetic container, and therefore, the coldest cooling formed on the inner surface of the hermetic container in the discharge space. Since the vapor temperature of the metal halide changes due to a change in the internal temperature, it has been found that a metal halide lamp having a single sealed airtight container has problems such as a change in light emission characteristics. Note that the conventional lamp 4 is a metal halide lamp having a hermetically sealed airtight container in the first place, and does not have the above-described disadvantages that occur in a single sealed airtight container. That is, the root of the electrode axis, which is likely to be the coldest part, does not face the arc, so that the temperature of the coldest part is not affected when the arc spot moves. The present invention relates to a metal halide lamp that forms an arc spot on an electrode coil, a single-sealed hermetic container capable of suppressing a change in emission characteristics even when the arc spot moves by miniaturizing the hermetic container. It is an object of the present invention to provide a small metal halide lamp having the same.

[Means for Solving the Problems]

A small metal halide lamp according to the present invention includes a single-sealed hermetic container having a pinch seal portion at one end; a discharge medium containing a metal or a metal halide sealed in the hermetic container; and one end embedded in the pinch seal portion. A pair of electrode shafts which are introduced into the airtight container and bent so that the front ends face each other, and are disposed at the front end portions of the electrode shafts so that an arc spot is formed during lighting, and the outer diameter is reduced. d, a pair of electrode assemblies having an electrode coil satisfying d / D ≦ 0.2, where D is the maximum inner diameter of the hermetic container in a direction perpendicular to the virtual straight line connecting the tip ends of the electrode shafts. It is characterized by: As the electrode, an electrode in which an electrode shaft and an electrode coil are integrally formed can be used. As a discharge medium, a starting rare gas, a predetermined amount of mercury and SnI2, NaI, TI, InI,
What consists of metal halides, such as NaBr and LiBr, can be used. The present invention can use a metal halide lamp having a tube wall load of 20 to 70 W / cm 2, and is particularly effective when the tube wall load is 20 to 50 W / cm 2. In the present invention, the tube wall load refers to a value obtained by dividing the lamp input power W by the inner surface area S of the hermetic container. According to the present invention, an arc spot is formed on the electrode coil, and the position of the arc spot changes, for example, every time the lamp is turned on.
Therefore, even if the electrode material is scattered by the collision of electrons and / or ions, the arc gap is prevented from becoming longer, and the lamp voltage is less likely to increase. Furthermore, since the relationship between the outer diameter d of the electrode coil and the maximum inner diameter D in the direction perpendicular to the arc at the light emission center position in the discharge space of the hermetic container is d / D ≦ 0.2, the outer diameter of the electrode coil is In comparison, the maximum inner diameter of the airtight container is relatively large. The reason why the outer diameter d of the electrode coil is a factor of the maximum inner diameter D is that the moving area of the arc spot is within the range of the outer diameter d of the electrode coil. Therefore, even when the arc spot formed on the electrode coil moves during lighting, the distance between the arc, the hermetic container, and the inner surface is sufficiently large, so that the temperature of the coldest portion formed in the hermetic container does not easily change. Become. If d / D> 0.2, the maximum distance between the electrode coil and the inner surface of the hermetic container is too short, and the movement of the arc spot significantly changes the temperature of the coldest part of the hermetic container. The luminous efficiency changes.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a metal halide lamp having a 150 W single-sealed hermetic container as an embodiment of the present invention will be described with reference to FIG. 1 and FIG. FIG. 1 is a longitudinal sectional view, and FIG. 2 is a sectional view along II-II in FIG. Reference numeral 1 denotes an airtight container, which is made of, for example, quartz glass and has a substantially elliptical spherical discharge space having a volume of 0.5 cc formed therein. The long axis direction of the airtight container 1 is a tube axis, and a pinch seal portion 2 is formed at one end in a short axis direction orthogonal to the tube axis. The pinch seal portion 2 is pinched and sealed to form a flat shape. A rare gas for starting, a predetermined amount of mercury, and a metal halide such as SnI2, NaI, TI, InI, NaBr, and LiBr are sealed in the hermetic container 1. Reference numerals 3 and 3 denote electrode assemblies each including an electrode shaft 4, 4 and electrode coils 5, 5 disposed at the tip of the electrode shaft 4, 4. The electrode shaft is made of, for example, a pure rhenium wire having a wire diameter of 0.5 mm, one end of which is embedded in the pinch seal portion 2, is introduced into the hermetic container 1 through the pinch seal portion 2, and the tips are opposed to each other. It is bent. The electrode coils 5 and 5 are made of, for example, a thoriated tungsten wire having a wire diameter of 0.5 mm, and are attached to the bent tip portions of the electrode shafts 4 and 4 so that an arc spot is formed during lighting.
It is arranged to be wound up to four times. The outer diameter of the electrode coil is set to 1.5 mm. The electrode shafts 4, 4 are connected to metal foils 6, 6, such as molybdenum (Mo), which are sealed to the pinch seal portion 2, respectively. The metal foils 6 are connected to external conductors 7 composed of lead wires, respectively. The hermetic container 1 has a maximum inner diameter D in a direction perpendicular to a virtual straight line connecting the electrode shafts 4 and 4 with respect to the outer diameter d of the electrode coil 5 such that d / D = 0.115. The maximum inner diameter D of the airtight container 1 is set to 13 mm. In this embodiment, the lamp current I at the time of stable lighting is 1.8 A,
At this time, the lamp input power W is set to be 150 W. The inner surface area S of the hermetic container is about 3.5 cm2, and the tube wall load per unit surface area of the hermetic container is about 43 W / cm2. FIG. 3 is a characteristic diagram showing variations in lamp voltage,
This shows how the lamp voltage varies for each lighting when d / D is changed. Each variation is a variation based on ten measurements. From FIG. 3, it can be seen that the variation width becomes larger as the value of d / D becomes larger than 0.2. The table below shows the d / D and the state of occurrence of partial bulging of the airtight container 1. From the above table, the deformation of the thermal bulge occurs during the life of the lamp is in the range of d / D ≧ 0.25 and therefore d / D ≦ 0.
It can be seen that bulging during the life can be prevented if it is 2.

【The invention's effect】

The present invention is configured so that an arc spot is formed on the electrode coil, and is perpendicular to an outer diameter d of the electrode coil where the arc spot is formed and a virtual straight line connecting between the tip ends of the electrode shafts in the airtight container. The relationship of the maximum inner diameter D in the direction
Since d / D ≤ 0.2, the temperature fluctuation in the coldest part is reduced, so that the lamp voltage and the metal halide vapor pressure change are small and the emission characteristics are small, despite being a single sealed airtight container, In addition, a long-life small metal halide lamp can be provided.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS The drawings show an embodiment of the present invention, and FIG.
FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1, and FIG. 3 is a characteristic diagram showing variations in lamp voltage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Hermetic container 2 ... Pinch seal part 3 ... Electrode assembly 4 ... Electrode shaft 5 ... Electrode coil

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisanori Sano 1-1201 Funakoshi-cho, Yokosuka-shi, Kanagawa 1 Inside Yokosuka Plant, Toshiba Corporation (56) References JP-A-52-100774 (JP, A) JP-A Sho 62-186455 (JP, A) JP-A-62-170145 (JP, A) JP-A-53-31387 (JP, A)

Claims (1)

(57) [Claims] 1. A sealed airtight container having a pinch seal portion at one end; a discharge medium sealed in the airtight container and containing a metal halide; one end embedded in the pinch seal portion; A pair of electrode shafts that are introduced into the airtight container and bent so that the front ends face each other, and are disposed at the front ends of the electrode shafts so that an arc spot is formed at an arbitrary position during lighting. A pair of electrode assemblies having an electrode coil satisfying d / D ≦ 0.2, where d is the maximum inner diameter of the hermetic container in a direction perpendicular to a virtual straight line connecting the tip ends of the electrode shafts. A small metal halide lamp characterized by: