JP3196250B2 - Metal halide lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal halide lamp effective for use as a light source of a projector device, and more particularly to a short arc having a short distance between electrodes which is used by exposing an arc tube to outside air without being covered by an outer tube. Shaped metal halide lamp.

[0002]

2. Description of the Related Art Projectors and illuminators have been known as means for enlarging images of characters, tables, figures, and the like on a display surface, and liquid crystal projectors have recently been known.

In such an image projection apparatus, light emitted from a light source is reflected by a reflecting mirror and condensed by a condenser lens, the light is transmitted through a liquid crystal plate, and an image of the light obtained by this is transmitted. This is to be projected on the screen.

In the prior art, a halogen bulb was used as the light source, but recently, a metal halide lamp having excellent luminous efficiency and good color rendering properties has been used.

A metal halide lamp is constructed by sealing a pair of electrodes in a quartz arc tube facing each other, and enclosing mercury, a metal halide, and a rare gas in the arc tube. It is known that this is a high-pressure metal vapor discharge lamp that ionizes and excites a vapor of a metal halide by discharge to emit light.

Incidentally, since the metal halide lamp used as a light source of the above-described image projection apparatus is built in an optical system such as a reflecting mirror or a condensing lens, it is desirable that the light source is close to a point light source. For this reason, the lamp is made compact.

[0007] In order to reduce the size of the lamp, it is necessary to provide a short arc lamp in which the distance between the electrodes is reduced and the arc length is shortened. Further, if the arc tube is formed in a double tube structure in which the arc tube is accommodated in the outer tube, the outer shape becomes large. Therefore, a structure is employed in which the arc tube is directly exposed to the outside air without using the outer tube.

[0008]

However, if the light-emitting tube is exposed directly to the outside air without using the outer tube and is turned on, the temperature of the light-emitting tube is easily influenced by the temperature of the outside air. In other words, in the above-mentioned liquid crystal projector device and the like, means for forcibly releasing the heat in the lamp house housing the lamp to the outside is adopted, and the light emitting tube is directly exposed to the projector device having such a heat exhaust structure. When it is installed in such a manner, the arc tube is exposed to the flow of the outside air, so that the temperature of the arc tube changes significantly.

[0009] The temperature of the arc tube affects the vapor pressure of the metal halide contained therein, and as the tube wall temperature decreases, the vapor pressure decreases. Therefore, the atomic weight of the metal halide in the arc decreases, and the luminous flux is reduced. There is a problem in that the lamp efficiency and the color rendering properties are reduced due to the decrease. Further, when the tube wall temperature becomes too high, the quartz of the arc tube reacts with the sealing metal to cause devitrification, resulting in a short life.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a lamp in which an arc tube is barely used, but the temperature of the tube wall is affected by the outside air temperature or the flow of outside air. It is an object of the present invention to provide a metal halide lamp having a small ratio and having good lamp efficiency, color rendering and life characteristics.

[0011]

According to the first aspect of the present invention,
In a metal halide lamp in which a pair of electrodes are provided in an arc tube, mercury, a metal halide compound, and a rare gas are sealed in the arc tube, and the arc tube is exposed to the outside air and used for lighting, S (cm
² ) When the rated lamp power is W (watt), the tube wall load W / S (watt / cm ² ) is set to 40 ≦ W / S ≦ 100, the distance between the electrodes is L (mm), When the inner diameter of the arc tube at the center position is D (mm) and the height of both electrodes of the pair of electrodes protruding from the sealing portion is H (mm), 0.8 ≦ D / L ≦ 2.3 It is characterized in that 9 ≦ D / H ≦ 3.0. According to a second aspect of the present invention, a pair of electrodes are provided in an arc tube, mercury, a metal halide compound, and a rare gas are sealed in the arc tube, and the arc tube is exposed to the outside air and used for lighting. In a metal halide lamp, when the inner surface area of the arc tube is S (cm ² ) and the rated lamp power is W (watt), the tube wall load W / S
(Watt / cm ² ) is set to 40 ≦ W / S ≦ 100, and when the arc tube is vertically lit, the distance between the electrodes is L.
(Mm), the inner diameter of the arc tube at the center position between the electrodes is D
(Mm), the height of the upper electrode protruding from the sealing portion is H1 (mm), the height of the lower electrode protruding from the sealing portion is H2 (mm), and 0.8 ≦ D /L≦2.3 1.9 ≦ D / H1 ≦ 3.0 1.9 ≦ D / H2 ≦ 4.5.

[0012]

According to the present invention, the tube wall load is relatively high, and the tube wall temperature of the arc tube is high. Since the temperature of the arc tube is set to be optimal, there is no adverse effect in practical use, and it is possible to prevent a decrease in lamp efficiency, color rendering and life characteristics due to changes in general exhaust air volume and ambient temperature. it can.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to one embodiment shown in the drawings.

The metal halide lamp shown in FIG. 1 is used in a bare state without covering an arc tube 10 made of quartz glass with an outer tube. The arc tube 10 has sealing tubes connected to both ends. These sealing tubes are heated and melted and crushed to form crushed sealing portions 11 and 11. A pair of electrodes 12, 12 are provided in the arc tube 10 so as to face each other, and each of the electrodes 12, 12 is formed by winding an electrode coil portion 14 made of tungsten around a tip of an electrode shaft 13 made of tungsten. It is configured.

The above-mentioned electrode shafts 13 and 13 are
1 and 11 are connected to metal foil conductors 15 and 15 made of molybdenum sealed in the sealing portions 11 and 11. External lead wires 16, 16 are connected to the metal foil conductor 15, respectively.
6 is led out from the end of the sealing portions 11 and 11. The power supply wire 1 is connected to these external leads 16, 16.
7, 17 are connected.

One end of the arc tube 10 is provided with a base 20.
Is attached. That is, a base 20 made of an insulator such as ceramics is attached to one sealing portion 11 of the arc tube 10 via an adhesive (cement) not shown. A pair of base pins 21, 2 are attached to the end of the base 20.
The power supply wires 17 are connected to the base pins 21.

The arc tube 10 is filled with mercury as a buffer metal, a metal halide as a luminescent metal, and a rare gas such as argon.

[0018] As the metal halides, such as halides of rare earth metals are used, dysprosium iodide DyI _3, iodide holmium HoI _3, iodide thulium TmI _3, it is used cesium iodide CsI _3.

In the metal halide lamp having such a configuration, in the case of a 250 W rated lamp, the distance L between the electrodes is L.
Is 9 mm, and the inner diameter D of the arc tube at the center position between the electrodes is 9.5 mm.
The electrode heights H1 and H2 are set to 4.4 mm, respectively.
The inner surface area S of the arc tube 10 is 4.5 cm ² It has become. Therefore, in this case, the tube wall load W / S is 55.6.
(Watt / cm ² ). It is said that the tube wall load W / S is preferably 40 ≦ W / S ≦ 100 (1).

The distance L (mm) between the electrodes, the inner diameter D (mm) of the arc tube at the center position between the electrodes,
Where H1 and H2 (mm) are the heights of the electrodes (H2 is the height of the lower electrode in the vertical lighting posture), 0.8 ≦ D / L ≦ 2.3 (2) 1. 9 ≦ D / H1 ≦ 3.0 (3) 1.9 ≦ D / H2 ≦ 4.5 (4)

A metal halide lamp having such a structure
Is reflected as a light source for a liquid crystal projector (not shown).
Used in combination with a mirror. And in this case run
The heat inside the lamp house housing the lamp to the outside
A heat exhaust device including a small fan for escape is installed
At the same time, the heat of the arc tube 10 is removed.
However, the arc tube 10 of the present embodiment has a tube wall load W / S of 5
5.6 (Watt / cm^Two ) And the conventional tube wall load
It is set higher than 30-35.

For this reason, even if the tube wall temperature is relatively high and the heat of the tube wall is taken away by the forcibly discharged air, the tube wall temperature is still maintained at a predetermined level or higher. Can be. In other words, since the tube wall temperature was originally raised, even if some heat was taken,
No significant impact. Therefore, the vapor pressure of the metal encapsulated in the arc tube can be kept high, the amount of light emission can be kept large, the luminous efficiency can be kept high, and the color rendering can be kept high.

In such a lamp, it is necessary to avoid formation of the coldest part having an extremely low temperature in the arc tube. In other words, when the coolest part having a remarkable temperature difference is formed on the inner surface of the arc tube, even if the temperature of the arc tube is raised, if the coolest part is cooled by the outside air, the encapsulation metal is not promoted to evaporate, and The pressure does not increase and the amount of light emission decreases. As described above, when the tube wall load is increased to increase the tube wall temperature, it is important that there is no special coldest part. For this reason, the relationship of 0.8 ≦ D / L ≦ 2.3 (2) 1.9 ≦ D / H1 ≦ 3.0 (3) 1.9 ≦ D / H2 ≦ 4.5 (4) is important. is there.

That is, D / L defines the relationship between the distance between the electrodes and the inner diameter of the arc tube at the center position between the electrodes.
This is because if the thickness of the arc tube is too large, the tube wall will be too far from the arc and the temperature of the arc tube will decrease, and the vapor pressure will decrease.On the other hand, if the arc tube is too thin, the arc will arc. , The temperature of the arc tube rises, and the quartz and the encapsulated metal react with each other to easily cause devitrification. For this reason, it is desirable that the relationship 0.8 ≦ D / L ≦ 2.3 is satisfied.

On the other hand, D / H1 and D / H2 regulate the height of the electrode. If the height of the electrode is too high, the coldest part of the electrode is placed on the sealing portion near the base of the electrode shaft at the back. If the height of the electrode is too low, the temperature of the sealing portion at the base of the electrode shaft will increase, and the quartz and the encapsulated metal will react. Therefore, it is desired that 1.9 ≦ D / H1 ≦ 3.0 (3) and 1.9 ≦ D / H2 ≦ 4.5 (4).

When the lamp is lit vertically, the temperature near the upper electrode becomes higher than the temperature near the lower electrode due to convection in the arc tube. It is better to lower it. Therefore, there is a difference between the above equations (3) and (4). In the case of horizontal lighting, both electrode heights may be 1.9 ≦ D / H1 ≦ 3.0.

In the case of the 250 W rated lamp described in the above embodiment, the tube wall load W / S is 55.6 (Watt / cm ^2). ), The tube wall load W / S may be in the range of 40 to 100.

This numerical range has been confirmed by experiments by the present inventors. To illustrate this experiment, for a 250 W rated lamp having the dimensions of the above example,
The luminous efficiency and the color rendering index were measured by changing the lamp input. The results are shown in Table 1 below.

[0029]

[Table 1]

This type of metal halide lamp has a luminous efficiency of 80 lm / W or more as a target value and an average color rendering index of 8
Therefore, from the results shown in Table 1 above, the tube wall load of the arc tube was set to 40 (watt / cm ^2). ) It turned out that we should do the above. However, when the tube wall load is 100 (watt / cm ²⁾ ), The temperature of the arc tube becomes too high, and the quartz and the encapsulated metal react to cause devitrification,
Short life. Therefore, the tube wall load W / S
It was confirmed that it was sufficient to satisfy 40 ≦ W / S ≦ 100.

The lamp power was set to 250 W and the tube wall load was set to 55.6 (watt / cm ^2). ), The relationship between the electrode distance L (mm), the inner diameter D (mm) of the arc tube at the center position between the electrodes, and the electrode height of each of the electrodes 12, 12 is represented by H1 and H2 (mm). When the luminous efficiency and the average color rendering index Ra were examined with various changes, FIG. 2 to FIG.
The characteristic results shown in FIG. From these characteristics, 0.8 ≦ D / L ≦ 2.3 (2) 1.9 ≦ D / H1 ≦ 3.0 (3) 1.9 ≦ D / H2 ≦ 4.5 (4) Is supported. The present invention is not limited to the above embodiment. That is, the metal halide sealed in the arc tube is not limited to the rare earth metal, and the halogen may be bromine other than iodine.

Further, the metal halide lamp of the present invention is not restricted to use as a light source of a liquid crystal projector device, but may be a light source such as a projector or a phantom lamp.
The present invention can be applied to a light source for general lighting and a light source for product lighting such as a store.

[0033]

As described above, according to the present invention, since the tube wall load is relatively high, the tube wall temperature of the arc tube is high, and even if the temperature falls within a normal range due to the influence of outside air. Since an optimum bulb wall temperature is obtained, there is no adverse effect in practical use, and it is possible to prevent a decrease in lamp efficiency, color rendering properties and life characteristics due to general exhaust conditions and changes in ambient temperature.

[Brief description of the drawings]

FIG. 1 is a partially sectional front view of a metal halide lamp showing one embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an inner diameter of an arc tube, a distance between electrodes, luminous efficiency, and color rendering.

FIG. 3 is a characteristic diagram showing an inner diameter of an arc tube, an electrode height H1, luminous efficiency, and color rendering.

FIG. 4 is a characteristic diagram showing the inner diameter of an arc tube, electrode height H2, luminous efficiency, and color rendering.

[Explanation of symbols]

Reference numeral 10: arc tube, 11: crushed sealing portion, 12: electrode, 13 ...
Electrode shaft, 14 ... electrode coil, 15 ... metal foil conductor, 26 ...
External lead wire, 20 ... base.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-257179 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 61/88

Claims (2)

(57) [Claims] 1. A metal halide lamp in which a pair of electrodes are provided in an arc tube, mercury, a metal halide compound, and a rare gas are sealed in the arc tube, and the arc tube is exposed to the outside air and used for lighting. When the inner surface area of the arc tube is S (cm ² ) and the rated lamp power is W (watt), the tube wall load W / S (watt / cm)
² ) is set to 40 ≦ W / S ≦ 100, the distance between the electrodes is L (mm), and the light emission at the center position between the electrodes
The inside diameter of the tube is D (mm), and a pair of electrodes protruding from the sealing part
If both height and H (mm), a metal halide lamp which is characterized in that a 0.8 ≦ D / L ≦ 2.3 1.9 ≦ D / H ≦ 3.0. 2. A metal halide lamp in which a pair of electrodes are provided inside an arc tube, mercury, a metal halide compound, and a rare gas are sealed in the arc tube, and the arc tube is exposed to the outside air and used for lighting. When the inner surface area of the arc tube is S (cm ² ) and the rated lamp power is W (watt), the tube wall load W / S (watt / cm)
² ) is set to 40 ≦ W / S ≦ 100, and when the arc tube is lit vertically, the distance between the electrodes is L (mm),
The inner diameter of the arc tube at the center position between the electrodes is D (mm), the height of the upper electrode protruding from the sealing portion is H1 (mm),
The height of the lower electrode protruding from the sealing part is H2 (m
m) and 0.8 ≦ D / L ≦ 2.3 1.9 ≦ D / H1 ≦ 3.0 1.9 ≦ D / H2 ≦ 4.5.