JPH0817091B2 - Low pressure discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a low-pressure discharge lamp such as a cold cathode discharge lamp or a xenon glow discharge tube formed by a thin hollow bulb. .

(Prior Art) Recently, attempts have been made to directly use a low-pressure discharge lamp as a display guide on a display panel of an automobile instrument or electric device. That is, this kind of display pointer is a low-pressure discharge lamp such as a xenon glow discharge tube, the bulb inner diameter is 2mm ~ 3
In addition to forming a very thin hollow needle shape of about mm, attach one end of this discharge lamp to the rotating pointer shaft of the meter,
The discharge lamp is constructed so as to be integrally swiveled by the rotation of the rotary pointer shaft. By doing so, the discharge lamp thus functions as a pointer and the discharge lamp is lit. By doing so, the pointer itself emits light, and since it illuminates the display scale portion, there is an advantage that no special illumination is required.

The discharge lamp used as a guideline for such a meter is
By providing an internal electrode inside the elongated hollow rod-shaped valve, by providing a strip-shaped external electrode along the axial direction on the outer surface of the valve, and by applying high-frequency power between the internal electrode and the external electrode, It is configured to generate glow discharge in the bulb.

A light-shielding coating made of synthetic resin is formed on the outer surface of the bulb.This light-shielding coating is formed by removing the thin strip-shaped light-transmitting slit extending in the axial direction of the bulb. Therefore, the discharge lamp of this type is an aperture type lamp, and the light emitting portion is in the shape of an extremely thin strip.

By the way, in the discharge lamp having such a structure, the internal electrode is sealed at one end, and therefore, in order to exhaust the inside of the bulb and fill the inside with xenon gas, it is necessary to perform from the other end of the bulb. Therefore, the other end is a final sealing cut portion.

(Problems to be solved by the invention) However, in general, when sealing and cutting a thin glass tube, the sealed portion is heated and softened by a heating means such as a burner, and the softened portion is pulled by pulling the glass tube in the axial direction. A method is adopted in which the glass wall is gradually thinned to have a smaller diameter, and the glass walls are attached to each other.

When the end of the valve is cut off by such a method, the tip-off shape remains at this cut end,
The shape projects outward. In this shape, not only the outer surface projects outward, but the inner surface also projects outward (it is recessed when viewed from the inside).

For this reason, both the inside and outside surfaces of the valve end portion are shaped to face outward, the wall thickness between these inside and outside surfaces becomes thin, and the strength of this sealing cut end portion decreases. Therefore, there is a concern that the tip may be damaged if it touches any other object.

The present invention has been made based on such circumstances.
It is an object of the present invention to provide a low pressure discharge lamp in which the thickness of the sealed cut end of the bulb is increased and the mechanical strength of the sealed cut end is improved.

[Structure of the Invention] (Means for Solving the Problems) According to the invention of claim 1, a sealing cut end is formed at one end, and the sealing cut end has an inner surface protruding inward. And a thin hollow valve in which a wall thickness between the inner surface and the outer surface is thicker than other portions; and a thin hollow valve; provided on the outer surface of the valve along the axial direction and having the wall thickness. A low-pressure discharge lamp comprising: at least one external electrode formed to a position reaching a thick portion;

The invention according to claim 2 is the low-pressure discharge lamp according to claim 1, wherein the thick portion has an outer surface protruding outward.

(Operation) According to the invention of claim 1, in the sealing cut end of the valve,
A thick part is formed that has an inner surface that protrudes inward and the thickness between this inner surface and the outer surface is thicker than other parts, so that mechanical strength is improved and damage is prevented. You can

According to the second aspect of the present invention, the sealed cut end portion of the valve is a thick portion having a shape in which both the inner surface and the outer surface project, so that the mechanical strength is further improved and damage can be prevented.

(Embodiment) The present invention will be described below based on an embodiment shown in FIG. 1 to FIG.

In the figure, reference numeral 1 denotes a low-pressure discharge lamp used as a pointer for an automobile speedometer or the like. The discharge lamp of this embodiment is a cold cathode discharge lamp, and this discharge lamp 1 is provided with an elongated hollow rod-shaped glass bulb 2. ing. The glass bulb 2 has, for example, an outer diameter of 2.5 mm and a total length of about 60 mm, and is formed in a substantially needle shape.

A cold cathode 3 is sealed as an internal electrode at one end of the bulb 2, and the cold cathode 3 is connected to a lead wire 4 that hermetically penetrates the sealed end of the bulb 2.

A fluorescent film 5 is formed on the inner surface of the bulb 2, and a discharge gas containing at least one of xenon and krypton is contained in the bulb 2 in an amount of 5 to 90 torr.
It is preferably sealed at about 20 torr.

On the outer surface of the bulb 2, a strip-shaped external electrode 6 is provided along the axial direction. The external electrode 6 is formed by applying a paste such as carbon phenol or silver epoxy in the above-mentioned strip shape to a predetermined length portion of the bulb 2 and firing the paste.

In the bulb 2, the first power receiving terminal 10 is formed in a film shape on the outer surface of the end portion where the internal electrode 3 is sealed. The first power receiving terminal 10 is connected to the lead wire 4 that hermetically penetrates the sealed end of the bulb 2 and the internal cold cathode 3
It is connected.

Further, the first power receiving terminal 10 is provided on the outer surface of the valve 2.
The second power receiving terminal 11 is formed at a position spaced apart from the axis in the axial direction. The second power receiving terminal 11 is also made of a conductive paste such as silver epoxy, is separated from the first power receiving terminal 10 in the axial direction, and is formed with a predetermined width in the circumferential direction. The second power receiving terminal 11 has a light-shielding film 7 which will be described later.
The second power receiving terminal 11 is connected to the external electrode 6.

A light shielding film 7 is formed on the outer surface of the bulb 2.
The light-shielding coating 7 has components of carbon, epoxy resin, and adhesive, and is formed on the surface of the bulb 2 on which the external electrode 6 is provided so as to cover the external electrode 6. And
On the surface opposite to the surface on which the external electrode 6 is provided, a slit portion 8 for light transmission that extends in the axial direction and does not form the light shielding film 7 is formed. That is, the outer surface of the valve 2 has a third
As shown in a cross-sectional view in the figure, the external electrode 6 is provided on one surface, and the light-transmitting slit portion on which the light-shielding coating 7 is not formed on the other side surface 180 degrees facing the external electrode 6. 8 is formed. Therefore, the light in the bulb 2 is emitted to the outside only through the light transmitting slit portion 8, and thus the cold cathode fluorescent lamp 1 has an aperture shape.

It should be noted that the light-shielding film 7 has the slit portion 8 for transmitting light.
In addition to the above, the first power receiving terminal 10 and the second power receiving terminal 11 are formed on the entire surface of the valve 2, and the first power receiving terminal 10 and the second power receiving terminal 11 are covered with a light shielding film 7. Since it is not exposed, it is exposed on the outer surface of the lamp 1.

An end portion of the bulb 2 opposite to the end portion to which the internal electrode 5 is sealed is a sealing cut end portion 15. The sealing cut end portion 15 is, as shown in FIG. Outer surface 15a and inner surface 1
5b has a shape protruding outward and inward, respectively. Therefore, between the outer surface 15a and the inner surface 15b, a thick portion 16 (L) thicker than other portions is formed.

The cold cathode discharge lamp 1 configured as described above is a lamp holder.
Mounted on 20.

The lamp holder 20 is made of an electrically insulating material and has a U-shaped cross section. The first and second power supply terminal tongue pieces 21 and 22 are fixed to each other with a space in the longitudinal direction. These power supply terminal tongues 21 and 22 are made of a conductive leaf spring such as phosphor bronze and are substantially U-shaped.
As shown by the imaginary line in FIG. 3, the valve 2 is clamped by the clamping pieces 23a, 23b facing each other.

The lamp holder 20 is fixed to the pointer shaft 25 of the meter, and when the pointer shaft 25 rotates, the lamp holder 20 also rotates integrally.

Although not shown, the pointer shaft 25 of the present embodiment is a hollow shaft, and two covered cords (not shown) are inserted into the hollow pointer shaft 25, and one end of each of these covered cords is inserted. The first and second power supply terminal tongue pieces 21, 22
, And the other end is connected to a high frequency power supply.

The cold cathode discharge lamp 1 is designed such that the end portion side where the internal electrode 3 is sealed is attached to the lamp holder 20. That is, the first power receiving terminal 10 and the second power receiving terminal film 11 formed on the outer surface of the bulb 2 face the first power feeding terminal tongue piece 21 and the second power feeding terminal tongue piece 22 on the lamp holder 20 side. When this lamp 1 is pushed in from the opening side of the lamp holder 20, the first and second power supply terminal tongue pieces 21, 22 are pushed.
The clamping pieces 23a, 23b of the first power receiving terminal 10 and the second
The power receiving terminal 11 is clamped to mechanically instruct the valve 2.
Therefore, the cold cathode discharge lamp 1 is fixed to the lamp holder 20. In this case, the first and second power supply terminal tongue pieces 21, 22
Respectively make electrical contact with the first power receiving terminal 10 and the second power receiving terminal 11, respectively, so that the inner electrode 3 and the outer electrode 6 are connected to the high frequency power source by the covering cords connected to the power feeding terminal tongues 21 and 22. To be done.

According to such a configuration, the cold cathode discharge lamp 1 is supported by the lamp holder 20 on the end side where the internal electrode 3 is sealed,
In this case, since the first power supply terminal tongue piece 21 and the second power supply terminal tongue piece 22 located at two positions separated from each other in the axial direction are clamped, the lamp is surely supported despite supporting only the end portion. become.

In addition, the internal electrode 3 and the external electrode 6 are connected to the first power supply terminal tongue piece through the first power receiving terminal 10 and the second power receiving terminal 11.
Since high-frequency power is supplied via 21 and the second power supply terminal tongue piece 22, glow discharge is generated between the inner electrode 3 and the outer electrode 6 in the bulb 2.

This glow discharge excites the phosphor coating 5 to promote light emission, and this light emission is emitted from the slit portion 8 to the outside.
For this reason, since the bulb 2 is originally thin and the slit portion 8 presents a narrower band of light, the discharge lamp 1 is suitable for indicating the display scale as a pointer. Moreover, since it shines by itself, no special light source is needed.

The lamp holder 20 is fixed to the pointer shaft 25, and when the pointer shaft 25 rotates, the lamp holder 20 also rotates integrally. Therefore, the discharge lamp 1 attached to the lamp holder 20 also rotates together. Since the vehicle is turned to a position corresponding to the vehicle speed, the speed scale can be indicated.

Further, in this embodiment, as shown in FIG. 2, the sealing cut end portion 15 of the valve 2 has a shape in which both the outer surface 15a and the inner surface 15b project outward and inward, respectively. Since the thick portion 16 having a larger thickness than the other portions is formed between the inner surfaces 15b, the mechanical strength of the sealing cut end portion 15 is improved, and even if the tip portion comes into contact with something, it is damaged. The ratio becomes low.

In addition, the valve 2 having such a sealing cut end 15
Has a uniform cross-sectional shape up to this tip, and the cross-sectional area of the discharge space hardly changes until it reaches the inner surface 15b, so the external electrode 6 extended to the sealing cut end 15 is disposed.
Also, the thickness of the positive column of glow discharge generated between the other end side internal electrode 3 does not change up to the sealing cut end portion 15, and therefore the light amount at the tip end portion does not decrease, so that the brightness along the axial direction is Be uniform. Furthermore, the phosphor coating 5 formed on the inner surface of the bulb 2 can be formed to a recessed portion closer to the tip than the inner surface 15b of the sealing cut end portion 15, and emits light sufficiently to the tip, and therefore the emission length. The length can be lengthened. From this, a large useless portion that does not emit light does not remain at the tip portion, which is advantageous for indicating a scale as a pointer.

Next, a method of forming the thick portion 16 on the cut end 15 will be described.

FIG. 4 shows a glass bulb 2 having an internal electrode 3 already sealed at one end and a phosphor coating 5 formed on the inner surface (not shown in FIG. 4). The exhaust gas is exhausted from the valve 2, and the exhaust gas is filled with a discharge gas of at least one of xenon and krypton at a predetermined pressure, for example, about 20 torr.

In this state, the scheduled sealing portion of the valve 2 is heated by the heater 30 such as a gas burner. When the scheduled sealing portion of the valve 2 is softened by the heating by the heater 30, both ends of the valve 2 are pulled in the opposite directions toward the axial direction, as shown in FIG.

As a result, the softened portion of the bulb 2 is gradually thinned, the peripheral wall of the glass sticks to close the bulb 2 at this portion, and when further extended, it is cut as shown in FIG.
At the time of this cutting, a protrusion 31 is formed as a chip mark on the end of the valve 2.
Is formed.

Conventionally, this state has been left as it is, assuming that the sealing is substantially completed. Therefore, this product has a shape in which both the inner and outer surfaces face outward, and the inner surface projects outward, so the wall thickness between the inner and outer surfaces becomes thin, and the strength of this sealing cut edge part decreases. .

The valve of the present embodiment, after the above sealing cutting is completed,
The cut end 15 of the valve 2 is heated by a heater 32 such as a gas burner as shown in FIG. Then, the cut end 15 is softened. In this case, the inside of the valve 2
Since the discharge gas of about 20 torr is enclosed, the pressure is lower than the atmospheric pressure, and therefore the softened sealing cut end 15 is deformed so as to be sucked inward, and in addition, surface tension is generated on the surface of the glass, so that the sealing is performed. Both the inner and outer surfaces of the cutoff end portion 15 are transformed into a shape close to a sphere. As a result, as shown in FIG. 8, the outer surface 15a and the inner surface 15b have a shape protruding outward and inward, respectively, and a thick portion 16 is formed between them.

Therefore, the labor for forming the thick portion 16 does not require more steps than in the conventional case, and the molding can be easily performed.

The heater 32 shown in FIG.
If the heating is continued for a long time, the softened sealing edge will
It is not preferable that the heating time exceeds a predetermined time because 15 is sucked inward too much to form a thin recess.

The present invention is not limited to the configuration of the above embodiment.

That is, in the above embodiment, the thick portion of the sealing cut end portion 15
16 has described the case where both the outer surface 15a and the inner surface 15b are formed so as to project outward and inward, respectively. However, according to the present invention, as shown as a modified example in FIG. 9, at least the inner surface 15b is inward. If it projects toward the outside surface 15a
May be recessed inward. However, in this case as well, the thick portion 16 that is thicker than other portions is formed between the inner surface and the outer surface.

Furthermore, in the above-described embodiment, the case where the discharge lamp of the present invention is described as a meter guide has been described, but the present invention is not limited to this, and may be a discharge lamp used as a backlight of a liquid crystal display device or the like. .

Further, the thickness of the sealing cut end portion 15 can be set to the same size as the other portions, and the positive column can be extended to the tip of the sealing cut end portion 15 while being thick. This is because there is an electrode, and the internal electrode 3 is not necessarily required for this effect, and for example, a pair of external electrodes having different polarities may be provided on the outer surface of the bulb so as to face each other.

Furthermore, when the internal electrode is used, it is not limited to the cold cathode type and may be a hot cathode type, and at least one of xenon, krypton, neon, argon, or mercury may be enclosed inside. Good.

The valve is not limited to the linear shape and may be curved.

[Effects of the Invention] As described above, according to the invention of claim 1, since the thick portion is formed between the outer surface and the inner surface at the sealing tip portion of the valve, the strength is improved, and the valve is sealed. Damage to the tip is prevented.

Further, according to the invention of claim 2, since the sealing tip portion of the valve is a thick portion in which both the inner surface and the outer surface are projected, the mechanical strength is further improved and damage can be prevented. it can.

[Brief description of drawings]

1 to 8 show an embodiment of the present invention, FIG. 1 is an exploded perspective view of a discharge lamp and a lamp holder used as a pointer of a meter, and FIG. 2 is a II part in FIG. FIG. 3 is an enlarged sectional view of FIG. 3, FIG. 3 is a sectional view taken along line III-III in FIG. 1, FIGS. 4 to 8 are side views showing the manufacturing method in order of steps, and FIG. 9 is another embodiment of the present invention. FIG. 3 is a sectional view of a main part showing 1 ... Cold cathode discharge lamp, 2 ... bulb, 3 ... internal electrode,
6 ... External electrode, 7 ... Shading film, 8 ... Slit part for light transmission, 15 ... Sealing cut edge part, 15a ... External surface, 15b ... Internal surface, 16 ... Thick part, 20 ... Lamp holder.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidehiko Noguchi 1 Harrison Electric Co., Ltd., 5-2 Asahi-cho, Imabari-shi, Ehime (56) Reference JP-A-64-12456 (JP, A) JP Flat 2-80918 (JP, A) Actually open Sho 50-136976 (JP, U)

Claims (2)

[Claims] 1. A sealing cut end is formed at one end, and the sealing cut end has an inner surface projecting inward, and the thickness between the inner surface and the outer surface is another portion. A thin hollow valve in which a thicker wall portion is formed; and at least 1 formed along the axial direction on the outer surface of the valve and extending to a position reaching the wall portion.
A low-pressure discharge lamp, comprising: two external electrodes; 2. The low-pressure discharge lamp according to claim 1, wherein the thick wall portion has an outer surface protruding outward.