JPH0522333B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a discharge lamp that emits light by low pressure discharge or medium pressure discharge.

[Background Art] In general, discharge lamps used as light sources for illumination are desirably high-efficiency, high-luminance, and compact.Moreover, they are capable of low-voltage starting and re-ignition, and the lighting device (ballast, etc.) is small and lightweight. It is desired that it be possible to Incidentally, conventionally commonly used straight tube type or round fluorescent lamps are highly efficient lamps, but they are not compact. Therefore, in order to make the lamp more compact, an incandescent lamp-like compact fluorescent lamp has been considered in which the discharge portion is bent multiple times to form a spherical lamp.
However, even with such compact fluorescent lamps, the discharge length is the same as that of conventional lamps, so a high starting voltage is required, making the lighting device large, heavy, and expensive. The problem was that I had to use .
In addition, the translucent bulb (glass tube) that forms the discharge part has many bent parts, which makes bending difficult, and the bent parts are prone to cracks and uneven coating and peeling of the phosphor. However, as a result, the cost of the fluorescent lamp itself increases.

[Object of the Invention] The present invention has been made in view of the above points, and its purpose is to make the lighting device more efficient, brighter, more compact, smaller and lighter, and to reduce the cost. Our goal is to provide cheap discharge lamps.

[Disclosure of the Invention] (Embodiment) Fig. 1 shows an embodiment of the present invention, in which a discharge gas at an appropriate pressure is supplied to an airtight space 2 formed by a closed light-transmitting bulb 1 made of a glass tube. Enclosed,
In a discharge lamp that emits light by performing low to medium pressure discharge between a pair of electrodes 3 provided in a translucent bulb 1, a glass wool formed of quartz that transmits ultraviolet rays is provided in an airtight space 2. 4
Except for the approximately circular space provided in a part of the tube cross section of the light-transmitting bulb 1, the other light-transmitting bulbs 1
The glass wool 4 is arranged inside the tube with an appropriate density distribution.The density distribution of the glass wool 4 in the embodiment shown in FIG. In the past, the density gradually increased in distribution, but other density distributions of glass wool 4 are shown in Figure 2 a~
A distribution as shown in c is considered, and in the figure a, glass wool 4 is placed inside a light-transmitting bulb 1 with an inner radius r of _r0 .
The central part of the pipe (r = 0 to r ₁ ) has a steep density change.
Figure b shows the density of the glass wool 4 increased in two stages from _the center of _the tube toward the wall. Figure c shows the glass wool 4 having an eccentric distribution in which the density gradually increases from one tube wall to the other. Further, in the embodiment, the discharge gas is mercury vapor, and the inner surface of the light-transmitting bulb 1 is coated with the phosphor 5 to obtain white illumination light, but the discharge gas is neon, argon, etc. It goes without saying that the phosphor 5 may not be coated when obtaining ultraviolet rays or light of a specific wavelength. Furthermore, the relationship between the distance between the electrodes 3 and the inner radius r of the translucent bulb 1 is set to =2r so that the cross section of the plane parallel to the axial direction is approximately square in order to achieve compactness. may be longer, in this case,
Considering the rise curve of starting voltage with respect to /r, it is desirable to set it to ≦4r.

FIG. 3 is a diagram showing the manufacturing procedure of a discharge lamp, in which a phosphor 5 sprayed from a nozzle 10 is coated on the inner surface of a glass tube 1a with both ends open, then fired in a firing furnace 11, and then molded separately. The transparent bulb 1 having an airtight space 2 is formed by inserting the glass wool 4 into the glass tube 1a and welding the stem 1b with the electrodes 3 mounted to the openings at both ends of the glass tube 1a using the burner 12. Ru. Next, the air in the airtight space 2 is exhausted through the exhaust port 13 provided on one stem 1b, and the airtight space 2 is
A discharge lamp containing glass wool can be obtained by filling a predetermined amount of discharge gas in the lamp. In the embodiment, the cylindrical light-transmitting bulb 1 is formed using the glass tube 1a, but it goes without saying that the light-transmitting bulb 1 may be formed in a spherical or other shape.

The operation of the embodiment shown in FIG. 1 will be described below with reference to FIGS. 4 to 7. Now, when the power supply voltage is applied between the electrodes 3, the origin of dielectric breakdown is as follows.
Although it is affected by the tube inner radius r, the distance between the electrodes 3, the type and pressure of the discharge gas, first of all, the approximately circular shape provided in a part of the tube cross section where the glass wool 4, which is an obstruction, does not exist. (in the example, the center of the tube). In this way, when dielectric breakdown occurs and seeds of discharge are generated, when the discharge current is small and the current density is small, the influence of the obstruction caused by the glass wool 4 is small and the discharge attempts to occur over the entire cross section of the tube, but the current is large. When the current density becomes large, the part where the glass wool 4 is arranged becomes
Since the recombination loss of charges increases, the discharge is narrowed from the area where the obstruction is small and the glass wool density is low to the center of the tube in the space with a generally circular cross section, which is the area where the glass wool 4 is not arranged. I'm going to go. Therefore, when the current is small, the voltage characteristics will be the same as if the tube diameter were large, and when the current is large, the voltage characteristics would be the same as if the tube diameter was small. It will be shown. The solid line C shown in FIG. 4a shows the VI characteristic of the discharge lamp according to the present invention, and exhibits the expected characteristic that as the discharge current I increases, the voltage V between the electrodes 3 also increases. As shown by dotted lines A and B, the V-I characteristic of the conventional discharge lamp exhibits a negative characteristic, which is completely opposite to that of the conventional discharge lamp. In the figure, the dotted line A shows the V-I characteristic of a large-diameter discharge lamp with an inner radius of rb, as shown in Figure 4b, and the dotted line B shows the V-I characteristic of a small-diameter discharge lamp with an inner radius of ra. , V _AC is the power supply voltage applied between the electrodes 3. As is clear from the figure, as the current increases, the V-I characteristic of the discharge lamp according to the present invention changes.
The characteristic changes to the V-I characteristic of a small-diameter discharge lamp, and exhibits a V-I characteristic similar to that of a positive characteristic discharge lamp. Therefore, it is possible to eliminate the need for a ballast to make a discharge lamp with negative characteristics positive characteristics when viewed from the power supply side, and even when inserted as a stabilizing element, it can be achieved with a small impedance element. This makes it possible to reduce the size, weight, and cost of the lighting device. Also,
Since the distance between the electrodes 3 can be significantly shortened compared to the conventional example, starting and restriking can be performed with a low voltage, and the lighting device can be made more compact and cost-effective. On the other hand, even when the distance between the electrodes 3 is shortened, the discharge impedance increases in the steady discharge state where the discharge area expands to the sub-discharge path where the density of the glass wool 4 is high, and the lamp voltage is increased appropriately (in-tube electric field is increased). high)
This makes it possible to input sufficient power and emit sufficient positive column light, resulting in a compact discharge lamp with high light output (high brightness).

By the way, when the current density is high, the discharge current density in the tube radial direction is large in the main discharge path at the center of the tube and small in the sub-discharge path near the tube wall, as shown in Figure 5. When the light emitted from the luminescent gas itself is used as illumination light, the light emitted from the center of the tube becomes stronger, resulting in high brightness. As shown in Figure 6, the temperature distribution inside the tube in the radial direction shows that the main discharge path formed at the center of the tube has the highest temperature, and the temperature decreases toward the tube wall. is considerably lower than that at the center of the tube, so when metal vapor such as mercury vapor is used as the discharge gas, the coldest point temperature, that is, the tube wall temperature, does not become very high despite the high light output; for example, at the optimum temperature, It can be designed to maintain a certain temperature of 40 degrees Celsius, allowing it to emit light with high efficiency. Furthermore, even when the phosphor 5 is applied to the inner surface of the light-transmitting bulb 1, disadvantages such as a decrease in light conversion efficiency and accelerated deterioration of the phosphor 5 due to an increase in the temperature of the phosphor 5 can be avoided.

In addition, in the embodiment, since the glass wool 4 is made of quartz that transmits ultraviolet rays, the discharge gas sealed in the airtight space 2 is mercury vapor, and the ultraviolet rays generated by the discharge are absorbed by the light-transmitting bulb. Even if the phosphor 5 coated on the inner surface of the phosphor 1 is used to convert visible light into visible light, a decrease in luminous efficiency due to the introduction of the glass wool 4 is prevented.

On the other hand, in order to make the discharge lamp more compact and brighter, it is better to reduce /r as much as possible, and the rising curve of starting voltage with respect to /r is shown in Figure 7. teeth/
Since it starts to rise rapidly from around r=2, in order to achieve compactness and high brightness, and also to prevent the starting voltage from becoming too high, it is necessary to adjust the distance between the electrodes 3 and the inner radius r of the transparent bulb 1. It is desirable to set the relationship to <4r with the limit around 4r where the rate of change is maximum.
In the embodiment, /r is set to 2. In addition, in order to obtain a high light output by applying a sufficient electric field (lamp voltage) to the discharge lamp, the /r
Although it is better to increase /r, in the embodiment, by providing the glass wool 4, the substantial /r
The design has been made larger to make it compact, high brightness, and provide high light output.

[Effects of the Invention] As described above, the present invention has the advantage that, except for the approximately circular space provided in a part of the cross section of the tube inside the light-transmitting glass bulb, glass wool is appropriately placed inside the other glass bulbs. Since the discharge current inside the bulb is low and the current density is small, the interference caused by glass wool is small.In the initial state of discharge, the discharge attempts to occur over the entire cross section of the tube, but when the current is large When the current density becomes large, charge recombination loss etc. increases in the area where glass wool is placed, so the cross section is changed from the area where the obstruction is small and the glass wool density is low to the area where glass wool is not placed. The discharge is gradually narrowed toward the center of the tube in the approximately circular space, making it possible to light a lamp with high efficiency and high brightness despite being small and compact. It has the features of being lightweight and inexpensive to manufacture.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the present invention, and the figure a
2 is a cross-sectional view of a plane parallel to the axial direction, b is a cross-sectional view of a plane perpendicular to the axial direction, c is a density distribution diagram of glass wool in the tube diameter direction, and FIGS. 2 a to c are glass wool tube diameters. FIG. 3 is a diagram showing an example of the density distribution in the direction, FIG. 3 is a diagram showing the manufacturing procedure of the same as above, and FIGS. 4 to 7 are diagrams for explaining the operation of the same. 1 is a translucent bulb, 2 is an airtight space, 3 is an electrode,
4 is glass wool.

Claims (1)

[Claims] 1. A discharge gas at an appropriate pressure is sealed in an airtight space formed by a closed translucent glass bulb,
In a discharge lamp that emits light by performing low-pressure discharge or medium-pressure discharge between a pair of electrodes provided in the glass bulb, a pair of electrodes are provided oppositely to each other at both ends of the tube axis in the glass bulb. A discharge lamp characterized in that, except for a substantially circular space provided in a part of the cross section of the tube inside the glass bulb, glass wool is arranged inside the glass bulb with an appropriate density distribution. . 2. The discharge lamp according to claim 1, wherein the discharge gas is mercury vapor, a rare gas, or a mixed gas of mercury vapor and rare gas. 3. The discharge lamp according to claim 1, characterized in that the inner surface of the light-transmitting glass bulb is coated with a phosphor. 4 Claim 1, characterized in that the relationship between the distance between the pair of electrodes and the inner radius r of the light-transmitting glass bulb is set to be ≦4r.
Discharge lamp as described in section.