JPH0427667B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a small metal halide lamp of 100 W or less and suitable for indoor lighting.

[Technical background of the invention and its problems]

In recent years, from the standpoint of energy conservation, there has been a demand for the development of compact metal halide lamps with high efficiency and high positive color rendering to replace incandescent light bulbs, which have traditionally been widely used for indoor lighting in general homes.

Conventionally, large metal halide lamps of 200W or more are already known, but among these,
Large metal halide lamps have a much higher luminous flux value than incandescent bulbs, and even when used indoors where color rendering is required, they are installed in relatively high places so that they can utilize a large amount of light. However, as light bulbs become smaller and weigh less than 100W, they are used in a manner similar to incandescent light bulbs, in which the irradiated object is directly irradiated from a relatively low place to make the irradiated object stand out. For this reason, light distribution, particularly direct illuminance, which has not been considered very important in large metal halide lamps in the past, must be considered as a very important issue.

Generally, high-pressure metal vapor discharge lamps have an arc tube structure with opposite electrodes sealed at both ends, and are often used for indoor lighting in vertical lighting, with the sealed ends facing up and down. , the brightness is obtained from visible light emitted by high-pressure discharge between both electrodes. Therefore, the brightness of the visible light emitted from the discharge space is reduced in the direction of the sealed area, and the unevenness of light distribution due to this sealed area has long been considered a problem. By installing it at a much higher position than the irradiator and using multiple lamps together, we were able to make the illuminance distribution on the irradiated surface fairly uniform.

However, for metal halide lamps of 100W or less, which are the subject of this invention, which directly irradiate the irradiated object and are installed and lit at a relatively low position such as in ordinary homes, the conventional structure may remain the same. This causes a problem of uneven brightness on the irradiated object.

[Purpose of the invention]

The present invention was developed in view of the above circumstances, and its purpose is to increase the brightness in the direction of the sealed portion, making it possible to make the light distribution characteristics uniform, and to avoid compromising high efficiency from the viewpoint of energy saving. never happens
The aim is to provide a small metal halide lamp of 100W or less.

[Summary of the invention]

In the present invention, by forming the wall thickness of the arc tube to be larger in the vicinity of the sealing part than in the main part, light is refracted in the direction of the thicker wall, and the amount of light in the direction of the sealing part is increased. By increasing the amount of light and regulating the thickness of the sealed portion, it is possible to reduce the loss of light due to the sealed portion, thereby making it possible to improve the light distribution characteristics.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

Figure 1 shows a small metal halide lamp. In the figure, 1 is an arc tube made of a light-transmitting positive heat-resistant insulator such as quartz glass, and electrodes 2 and 3 made of a high-melting point metal such as tungsten are sealed at both ends. . The electrodes 2 and 3 are metal foil conductors 4 made of molybdenum, etc.
4, and these metal foil conductors 4, 4 are sealed in sealing parts 5, 5 formed at both ends of the arc tube 1. The metal foil conductors 4, 4 are wells 6,
6, and a voltage is applied to the electrodes 2 and 3 via these widths 6 and 6. The arc tube 1 is bulged, for example, so that its discharge space is spherical or ellipsoidal, so that gas convection can occur smoothly within the discharge space. In addition, the arc tube 1 contains mercury, a starting rare gas, a metal halide as a luminescent metal,
For example, sodium iodide and scandium iodide are included.

The arc tube 1 is housed in an outer bulb 7, which has a shape and size similar to an incandescent light bulb, and has a screw cap 8 attached to one end. Lead wires 10a and 10b are sealed to the stem 9 of the outer tube 7, one electrode 2 is connected to one lead wire 10a via a support wire 11, and the other lead wire 10b is connected to one electrode 2 via a support wire 11. is connected to the other electrode 3 via a conductive wire 12 which is bent into an arcuate shape so as to move away from the arc tube 1. The inside of the outer tube 7 is maintained in a vacuum or an atmosphere of nitrogen or inert gas, and the base 8 is provided with a terminal 8a.

As shown in FIG. 2, the arc tube 1 is
The wall thickness distribution around the light emitting space is configured to be different. That is, the wall thickness t 1 of the main portion 13 of the arc tube ₁
is set to 0.3 mm to 1.5 mm, whereas at least a portion 14a of the vicinity portion 14 of the arc tube sealing portions 5, 5
In other words, the wall thickness at the boundary with the sealing parts 5, 5 is made larger than the wall thickness ₁₁ of the main part 13, and its maximum value is set to t.
mm, t/t ₁ = 1.4 to 3.3, and for the thickness t ₂ of the sealing parts 5, 5, t/t ₂ = 0.5 to 1.3. has been done.

The arc tube main portion 13 refers to the tube wall portion corresponding to the distance between the tips of the electrodes 2 and 3, that is, the arc length, and the sealing portion vicinity portion 14 refers to the tube wall portion other than the main portion 13, that is, the tube wall portion corresponding to the arc length. This refers to the tube wall portion from the tip portions 2 and 3 to the sealing portions 5 and 5.

By having such a structure with wall thickness distribution,
The light distribution characteristics are improved based on the optical effect of this thickness change. That is, according to the thickness distribution structure as described above, the amount of light on the sealed portion side increases due to the lens action of refracting light in the direction of greater thickness. FIG. 3 is shown to explain the principle in more detail, and its operation will be explained with reference to this figure. 3A shows a case where the arc tube has a spherical shape but there is no change in wall thickness, and FIG. The case where the wall thickness of the portion 14 near the portion 14 is large is shown in each case. To simplify the explanation, let us consider the case where light rays OA are emitted in the same direction from the center point O. Furthermore, in FIGS. 3A and 3B, the radius of curvature of the arc tube is the same near the sealed portion.

In the case of Fig. 3 A, since point O is the center of curvature, the angle of incidence is zero, and the light incident on point A of the glass wall reaches point B without being refracted, and Since the center of curvature of the outer surface is also at point O, B
The incident light in the OA direction is not refracted at the point and is therefore emitted in the B′C′ direction.

In the case of Fig. 3B, the incident light in the OA direction travels straight to B''.The center of curvature at point B'' is at a different position from the center of curvature at point A, and the upper part of the figure has a large wall thickness. When light is transmitted from a place with a high refractive index to a place with a low refractive index, it is transmitted at an angle larger than the angle of incidence, resulting in refracted light in the B″C″ direction.
The refracted light in the B″C″ direction is at an angle of θ ₂ with respect to the incident direction OA.
is refracted upward as shown. This is the reason why it is called a lens effect.Therefore, in the arc tube 1 shown in FIG.
Based on the lens effect, the amount of light in the direction of the sealing parts 5, 5 is increased.

In the above explanation, we considered a single ray emitted from the center point O and a case where the arc tube shape was spherical. Even if we consider the case of , the refraction effect becomes complicated, but it is easy to understand that basically the light is diffused in the direction of the sealing part 5 due to the lens effect.

Furthermore, even if the arc tube is cylindrical, the above-mentioned principle can be applied as is if the vicinity of the sealing portion is formed into a curved shape. Furthermore, in Fig. 3B, as a method of increasing the wall thickness near the sealing part, the inner wall surface is made spherical, and the curvature of the outer wall surface is increased so that the wall thickness increases near the sealing part, but the curvature of the inner wall surface is It can be understood from the above principle that even if the wall thickness is increased by making the lens smaller, there is a lens effect in almost the same way. Furthermore, in the above embodiment, the wall thickness distribution is taken up at the boundary with the sealing part as a part of increasing the wall thickness of the sealing part vicinity part 14, but it is not limited to this part, but at least If a thick part, which is a raised part of the wall, is formed somewhere, the above lens effect will be achieved. In particular, if the entire portion 14 near the sealing portion is made thick, the effect will be even more remarkable, and the thickness may be changed continuously from the main portion 13 of the arc tube to the sealing portion 5. .

Regarding the formation of a thick wall part, the wall thickness near the area to be sealed may be increased in advance during molding of the arc tube, or the thickness may be formed with a uniform thickness distribution before sealing. The wall thickness in the vicinity may be shaped so that the wall thickness gathers near the sealing portion as shown in FIG.

FIG. 4 shows the results of improving the light distribution characteristics based on the above principle. The broken line in FIG. 4 shows an example of an arc tube with a conventional structure, and the solid line shows an example of an arc tube with a wall thickness distribution and a spherical structure according to this embodiment. All 1000lm
It has a light distribution of illuminance (cd) of 1.5 cm, and is in a vertical lighting position with the cap facing upward.

Regarding the arc tube structure, both the conventional one and the example example have a spherical shape with an inner diameter of 8 mm.
Regarding the wall thickness, in the conventional case, t ₁ =
On the other hand, in the case of the embodiment, the maximum wall thickness t=0.5 mm is set from 0.7 mm in the vicinity of the sealing portion, and the wall thickness _t1 of the other portions is set to 0.7 mm. Also,
The wall thickness t ₂ of the sealing portions 5, 5 is both 2.5 mm and the same.

Therefore, for the conventional one, t/t ₁ = 0.7 mm/0.7 mm = 1 t/t ₂ = 0.7 mm/2.5 mm = 0.28 For the example, t/t ₁ = 1.5 mm/0.7 mm = 2.14 t /t ₂ =1.5mm/2.5mm=0.6.

As can be seen from Fig. 4, there is a cap in the upper part of the figure, so the dashed line is not much different from the solid line, but the solid line with the wall thickness distribution of this example has a slight illuminance in the horizontal direction. Although it decreases, the illuminance directly below is approximately three times higher than that of the dashed line.
Light distribution is uniform.

Note that not only a part of the sealing part vicinity part 14 but also
If the entire wall thickness of the vicinity portion 14 is made thicker, the above-mentioned lens effect becomes even larger and a more remarkable effect can be obtained.

From the above results, it can be seen that if t/t ₁ and t/t ₂ are selected within an appropriate range, the light distribution can be greatly improved even in a small lamp.

Next, the results of tests to find appropriate ranges for t/t ₁ and t/t ₂ will be described.

Figure 5 is a diagram showing the relationship between t/t ₁ and direct illuminance (vertical lighting on the base side).The conditions at this time are that the wall thickness of the arc tube is constant at t ₁ = 0.7 mm, and the seal is sealed. The maximum wall thickness t near the attachment part is set to 0.7 mm to 2.5 mm, and therefore t/t ₁ is varied within the range of 1 to 3.6. In addition, the wall thickness t ₂ of the sealing parts 5, 5 is 2.5
mm was constant.

As is clear from FIG. 5, the larger t/t ₁ is, the larger the above-mentioned lens effect becomes, so the amount of light directed toward the sealed portion increases and the illuminance directly below becomes higher. In particular, when t/t ₁ increases from 1.0 to 1.4, the illuminance directly below increases rapidly, and as t/t ₁ increases, the illuminance directly below also increases, but as t/t ₁ increases beyond 3.3, t Since the difference in wall thickness from t ₁ becomes too large, the difference in thermal strain of the wall of the arc tube becomes large, which is undesirable because there is a risk that the arc tube will be damaged during lighting. Therefore, it can be seen that t/t ₁ should be regulated within the range of 1.4 to 3.3.

FIG. 6 is a diagram showing the relationship between the ratio t/t ₂ of the maximum wall thickness t near the sealed portion and the wall thickness t ₂ of the sealed portion and the illuminance directly below _. is set at a constant value of 2.2 within the above regulatory range, and t/t ₂ is varied in various ways. From Figure 6, when t/t ₂ is smaller than 0.5, the wall thickness t ₂ of the sealing part becomes too large, so even though the above lens effect is achieved, the rate at which the sealing part itself blocks the optical path increases, and the direct illuminance increases. will be priced accordingly.
On the other hand, as t/t ₂ increases, the wall thickness of the sealed portion becomes relatively smaller, so the direct illuminance increases;
When t/t ₂ exceeds 1.3, the wall thickness t ₂ of the sealed part becomes too thin compared to the size of the arc tube, resulting in problems such as a decrease in yield in the sealing process and a decrease in the strength of the sealed part. Therefore, it can be seen that t/t ₂ should be regulated within the range of 0.5 to 1.3.

From the above, it can be said that t/t ₁ =1.4 to 3.3 and t/t ₂ =0.5 to 1.3 are appropriate ranges.

This means that in order to make the wall thickness of the sealed parts 5, 5 of the arc tube as thin as possible within a range that does not interfere with the manufacturing process, and to increase the amount of light toward the sealed part, t/t ₁ is required. This means that by increasing the ratio, the lens effect can be increased.

In addition, the present invention is intended to solve the non-uniformity of light distribution due to the side of the sealing part located in the downward direction during vertical lighting, for example, when the sealing parts 5, 5 at both ends of the arc tube 1 are arranged in the vertical direction. Therefore, the thickness t ₁ and the thickness t ₂ of the vicinity portion 14 may be restricted only on one sealing portion side facing downward.

Further, the reason why only the thickness of the sealing part 5 was taken up and the width was not taken up is that the metal foil conductor 4 sealed to the sealing part 5 is used in the form of an extremely thin foil, as is well known. Therefore, the sealing portion 5 also naturally has a flattened shape. With such a shape of the sealed portion 5, it is clear from calculation that when the sealed portion 5 is reduced by the same amount, the thickness has a greater influence on the volume of the entire sealed portion than the width. Therefore, when regulating the volume of the sealed portion 5 that blocks the optical path, it is more effective to focus on the thickness rather than the width.

The above results are for a 40W example, but similar results can be obtained with a small metal halide lamp of 100W or less, but the wall thickness t ₁ of the main part of the arc tube is
A value of 0.3 mm to 1.5 mm is desirable; if it is less than 0.3 mm, the pressure resistance will decrease, while if it exceeds 1.5 mm, it will be difficult to form a thick wall near the sealing part, and the lamp efficiency will also be affected. I don't like it because it comes out.

Furthermore, an outer tube 7 that generally houses the arc tube 1
The inner surface is coated with a phosphor or a diffusing substance such as silica to make it a diffused type, or it is a transparent type without a diffusing substance coated on it. It is known that in the case of a diffused type, the light distribution characteristics are much more uniform than in a transparent type. However, the light distribution of the arc tube according to the present invention is not canceled out in any way even if a diffused type outer tube is used, and it still has superiority compared to the conventional one. There are no restrictions whatsoever.

〔Effect of the invention〕

As detailed above, in the present invention, in a small metal halide lamp of 100W or less, the wall thickness near the arc tube sealing part is made thicker than the main part of the arc tube, so that the lens effect based on the above-mentioned wall thickness distribution that occurs inside the arc tube is achieved. The light is refracted toward the sealing part, increasing the amount of light in the direction of the sealing part, and by regulating the thickness of the sealing part, the blocking rate of the optical path in the direction of the sealing part is reduced. be able to. Therefore, the illuminance in the direction of the sealed portion is improved, so the light distribution is made uniform, and the illuminance directly below the lamp is particularly improved during vertical lighting. Therefore, when used in place of an incandescent light bulb for indoor lighting, the illuminance distribution of the irradiated object is improved, and the efficiency is much better than that of an incandescent light bulb, making it extremely effective as an energy-saving light source.

[Brief explanation of drawings]

Fig. 1 is a front view of a small metal halide lamp which is an embodiment of the present invention, Fig. 2 is a longitudinal sectional view of its arc tube, and Figs. 3 A and B are lens effects of the conventional lamp and the lamp of the present invention. Fig. 4 is a light distribution characteristic diagram, Fig. 5 is a characteristic diagram showing the relationship between t/t ₁ and direct illuminance, and Fig. 6 is a characteristic diagram showing the relationship between t/t ₂ and direct illuminance. FIG. DESCRIPTION OF SYMBOLS 1... Arc tube, 2, 3... Electrode, 5... Sealing part, 7... Outer tube, 8... Cap, 13... Main part of arc tube, 14... Near the arc tube sealing part Department.

Claims (1)

[Scope of Claims] 1. A small metal halide lamp of 100W or less, which is made by sealing mercury, a rare gas, and a metal halide in an arc tube made of a light-transmitting heat-resistant insulator with a pair of opposite electrodes sealed at both ends. in which the wall thickness t ₁ of the main portion of the arc tube is 0.3 mm to 1.5 mm, and the wall thickness of at least a portion of the vicinity of at least one sealing portion of the arc tube is larger than the wall thickness t ₁ of the main portion; When the maximum wall thickness is 5 mm, t/t ₁ = 1.4 to 3.3, and the thickness of at least one of the above sealed parts
A small metal halide lamp characterized in that the relationship between t ₂ mm and the above tmm is t/t ₂ =0.5 to 1.3.