JPH03280353A - Cold cathode discharge lamp - Google Patents

Abstract

PURPOSE:To install an electrode shaft even in a thin bulb by joining a hollow electrode head with the electrode shaft while they are butted together at their end faces, and thereby arranging the two on the axis of the bulb. CONSTITUTION:A cold cathode 4 shall be a hollow type electrode, and it its outside dia. and inside dia. are represented by D1, D2, the outside dia. (d) of an electrode shaft 42 to be connected with the cold cathode 4 shall range as D1>d>D2, and the cold cathode 4 is butt jointed with the electrode 42 at their end faces coaxially. Thereby the joint assembly of the cold cathode 4 and electrode shaft 42 can be installed in a thin bulb. Because the cold cathode 4 is hollow, it can bear a great quantity of electron radiating substance 43 for its length.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a cold cathode discharge lamp using a cold cathode as an electrode;
In particular, the present invention relates to a cold cathode discharge lamp suitable for use as a meter pointer, and to the structure of its cold cathode.

(Prior Art) Recently, a meter using a cold cathode type low-pressure gas discharge cauterization has been proposed as a display pointer on a display panel of an automatic heavy-duty meter or electrical equipment.

This display pointer uses a pressure discharge lamp, such as a xenon glow discharge tube, whose bulb is shaped like an extremely thin hollow needle, and one end of the discharge lamp is attached to the rotating pointer shaft of the meter, and this rotating pointer shaft rotates. When moving, the discharge light also integrally surrounds the chest, so the thin discharge light functions as a pointer.
However, when this discharge lamp is turned on, it emits light by itself,
It has the advantage that special lighting is not required because the discharge lamp in the box illuminates the display scale.

A discharge lamp used as a pointer for such a meter has an internal electrode made of a cold cathode inside an elongated hollow rod-shaped bulb, and a strip-shaped external electrode along the axial direction on the outer surface of the bulb. is provided, and high frequency power is applied between these internal electrodes and external electrodes to generate glow discharge within the bulb.

A light-shielding coating made of synthetic resin is formed on the outer surface of the bulb, and this light-shielding coating is formed except for a thin strip-shaped light-transmitting slit extending in the axial direction of the bulb. Light is emitted from the slit. Therefore, this type of discharge lamp is an aperture-shaped lamp, and in addition to the bulb being thin, the light emitting area is even thinner, so that the pointer is shaped like an extremely thin needle.

By the way, a discharge lamp having such a configuration uses a cold cathode as an internal electrode. Compared to hot cathodes, cold cathodes generate less heat and suffer less thermal damage, so they not only have a longer lifespan, but also have a longer lifespan.
Since a cold cathode generates less heat than a hot cathode, it heats up less of the surrounding bulb, making it possible to reduce the bulb diameter.Conversely, cold cathodes are used for lamps with small bulb diameters. is advantageous.

Conventionally, a cold cathode is composed of an electrode head made of nickel or the like and an electrode shaft joined to the electrode head. was doing.

(Problem to be Solved by the Invention) However, recently, thin discharge lamps with inner diameters of bulbs of 3 am or less have been developed, and when trying to accommodate a cold cathode in the narrow space of such a thin bulb, the size of the electrode head becomes too large. Limited.

Moreover, since the cold cathode of this type of lamp generates a discharge between it and the external electrode, it is necessary to apply a voltage of about IKV at startup to cause the discharge, and in order to facilitate this startup discharge, it is necessary to The amount of electrons emitted must be increased. For this purpose, it is desirable that the electrode head have a large surface area.

In order to satisfy these conditions, it is desirable for the electrode head to have a hollow shape such as a cylinder, an elliptical cylinder, or a rectangular cylinder. With such a hollow structure, the outer diameter can be made small, and the can increase the surface area, increase the current value and increase the amount of electron emission,
We can expect the so-called Polo effect.

Another advantage is that the hollow portion may be filled with an electron emitting material (emitter) or getter to enhance the electrode function.

If such a small hollow electrode head is to be accommodated in a bulb, the size of the bulb is limited, so the electrode head must be placed on the central axis of the bulb.

In the conventional case, the electrode shaft was attached to and joined to the side surface of the hollow electrode head, so if an attempt was made to arrange the electrode head on the central axis of the bulb, the electrode shaft would be eccentric from the central axis of the bulb.

However, if the diameter of the bulb is small, the electrode shaft must also be placed on the central axis of the bulb, and the conventional structure in which the electrode shaft is attached to and joined to the side surface of the electrode head is not preferable.

The present invention aims to provide a cold cathode discharge lamp in which both a hollow electrode head and an electrode shaft can be arranged on the central axis of the bulb.

[Structure of the Invention] (Means for Solving the Problems) In the present invention, in a cold cathode discharge lamp configured by joining an electrode shaft to a hollow electrode head, the tip surface of the electrode shaft is connected to the hollow electrode. The electrode shaft is characterized in that a portion of the end face of the head having a diameter larger than the minimum inner diameter of the opening is joined by 6° so that the tip end face of the electrode shaft butts against the end face of the electrode head.

(Function) According to the present invention, since the electrode head and the electrode shaft can be joined by butt joining, it is possible to center them, and also to arrange them on the central axis of the bulb with a small diameter. can do.

(Embodiment) The present invention will now be described based on a first embodiment shown in FIGS. 1 to 6.

In the figure, reference numeral 1 indicates a cold cathode xenon glow discharge lamp used as an indicator needle of a meter, and this discharge lamp I is equipped with a bulb 2 having an elongated HT electric space 3 formed therein. The bulb 2 is made of a glass tube, and has, for example, an outer diameter of 2.5 mm, an inner diameter of 1.5 mm, and a total length of approximately 6 (1+i+i), and is shaped like a needle.

One end of the valve 2 has a vinci seal structure 210 as shown in FIG. 3, and the other end has a tip-off structure 250.

An internal electrode 4 is sealed in a pinch seal portion 210 formed at one end of the bulb 2. The internal electrode 4 is formed of a cold cathode and includes an electrode head 41, an electrode shaft 42 which also serves as a lead wire, and an electron emitting material (emitter) 43 filled inside the electrode head 41.

The electrode shaft 42, which also serves as a lead wire, is connected to the pinch seal portion 21.
0 is hermetically penetrated. This electrode shaft 42 has a wire diameter d
It is made of Dumet wire with a diameter of about 0.51, and the electrode head 41 is fixed to the end extending into the discharge space 3.

The electrode head 41 is formed of a low melting point metal tube, such as nickel (Ni) or zirconium (Zr)-aluminum (An) alloy, which is open at both ends.
It is formed into a wire having an outer diameter DI of 1 as, an inner diameter D2 of 0.3 mm, and a length of about 21 mm by cold wire drawing using a drawing die, a stretching roll machine, a swaging machine, or the like.

One end of this electrode head 41 is butt-welded to the tip of the electrode shaft 42, which also serves as the lead wire.

In this case, the outer diameter D1 of the opening at one end of the electrode head 41 is 1.
111% The inner diameter D2 is 0.3-1, and the outer diameter d of the tip of the electrode shaft 42 is 0.5 mm, so D! >d>D2, therefore, the tip end surface of the electrode shaft 42 can be brought into contact with one end surface of the electrode head 41. By such butt joining, the electrode head 41 and the electrode shaft 42 are joined with their centers aligned, and by sealing the electrode shaft 42 approximately on the central axis of the bulb 2, the electrode shaft 42 and the electrode shaft 42 are joined. Electrode head 4
1 is arranged approximately on the central axis of the valve 2.

The other end of the electrode head 41, that is, the discharge space 3 side, is open, and the electrode head 41 is filled with powder of an electron emitting substance 43 made of a lanthanide rare earth such as lanthanum boride (LaB). be done.

The electron emitting material 43 is designed to emit electrons toward the discharge space 3 from the front opening of the electrode rad 41 .

A phosphor coating 6 is formed on the inner surface of the bulb 2 facing the discharge space 3, and xenon gas is present in the bulb 2 at a pressure of 5 to 40 Torr, preferably 20 to 40 Torr.
It is filled to 40 Torr, specifically about 30 Torr.

An external electrode 7 is provided on the outer surface of the bulb 2 in the form of a band along the axial direction. This external electrode 7 is constructed by applying a paste such as carbon phenol or silver epoxy in a band shape along the axial direction of the bulb 2, and firing the paste.

One end of the external electrode 7 is located at a portion facing the internal electrode 4, and the other end extends to the tip end surface of the tip-off portion 250 of the bulb 2.

Further, the width of the external electrode 7 is formed in a range of 1/3 or more of the circumferential length of the bulb 2, that is, an area forming an angle of 120'' or more.

A first power receiving terminal 10 is formed on the outer surface of the end of the bulb 2 that seals the internal cold cathode 4. This first power receiving terminal IO is formed into a film shape and is connected to the lead wire 5. Therefore, this first power receiving terminal 1o is connected to the cold cathode 4.

Further, on the outer surface of the bulb 2, the first power receiving terminal 10 is provided.
A second power receiving terminal 11 is formed at a position spaced apart from each other in the axial direction. The second power receiving terminal 11 is also made by applying and firing a conductive paste such as silver epoxy, and has a predetermined width and extends in the circumferential direction. This second power receiving terminal 11 is connected to the external electrode 7. Note that the second power receiving terminal 11 is formed so as to avoid a slit portion 9 of the light shielding film 8, which will be described later.

Furthermore, a light-shielding coating 8 is formed on the outer surface of the bulb 2.

The light-shielding film 8 is made of white carbon, epoxy resin, and adhesive, and is coated on the surface of the bulb 2 on which the external electrode 7 is provided, covering the external electrode 7, and applying this coating film. It is formed by firing.

The light-shielding film 8 has a light-transmitting slit portion 9 located on a surface opposite to the surface on which the external electrode 7 is provided and extending in the axial direction. In other words, the light-transmitting slit portion 9 is formed by the light-shielding coating 8
It is formed of a transparent part that does not form a

To explain further, as shown in cross section in FIG. 5, an external electrode 7 is provided on one side of the outer surface of the bulb 2, and this external electrode 7 is covered with a light-shielding liquid i%g. A light shielding liquid f is provided on the other surface 180 degrees opposite to the external electrode 7.
A light transmitting slit portion 9 is formed in which no lall is formed.

The width of the light transmission slit portion 9 is smaller than the width of the external electrode 7.

The light within the bulb 2 is emitted to the outside only through the light transmission slit portion 9, so that the discharge lamp 1 has an aperture shape.

Note that the second power receiving terminal II is not covered with the light-shielding film 8 as shown in FIG. 6, and is a lamp! exposed on the outer surface of the

The xenon discharge lamp 1 configured in this manner is attached to a lamp holder 20.

The lamp holder 20 is made of an electrically insulating material such as synthetic resin and has a U-shaped cross section, and holds first and second power supply terminal tongues 21 and 22 spaced apart from each other in the longitudinal direction.

These power supply terminal tongue pieces 21 and 22 are formed by bending conductive plate springs such as phosphor bronze into a substantially U shape, and as shown in FIG. It is something to hold.

The lamp holder 20 is fixed to a display rotation shaft 25 of a 51° angle, and is rotated integrally with the display rotation shaft 25 when the date rotation shaft 25 rotates.

The rotating shaft 25 of this embodiment is constituted by a hollow shaft (not shown), and two coated cords (not shown) are inserted into the hollow display shaft 25, and one end of each of these coated cords is connected to the first and the second power supply terminal tongue pieces 21 and 22, and the other end is connected to a high frequency power source (not shown).

In the discharge lamp 1, the end of the internal electrode 4 on the pinch seal side is attached to the lamp holder 20. That is, the first power receiving terminal IO and the second power receiving terminal 11 formed on the outer surface of the bulb 2 are opposed to the first power feeding terminal tongue piece 21 and the second power feeding terminal tongue piece 22 on the lamp holder 20 side. When the lamp 1 is pushed into the lamp holder 20 from the opening side, the first and second power supply terminal tongues 21 and 22 are held by the clamping pieces 222 and 222, respectively.
supports the bulb 2 by sandwiching the first power receiving terminal lO and the second power receiving terminal 11. Therefore, the discharge lamp 1 is fixed to the lamp holder 20.

In this case, the first and second power supply terminal tongue pieces 21,22 are the first power receiving terminal IO and the second power receiving terminal IO and the second power receiving terminal 11, respectively.
Since the internal electrode 4 and the external electrode 7 are in electrical contact with
is connected to a high frequency power source.

The operation of an embodiment of such a configuration will be explained.

When high-frequency power is supplied between the cold cathode 4 provided inside one end of the discharge lamp 1 and the external electrode 7, glow discharge occurs between the internal cold cathode 4 and the external electrode 7 within the discharge space 3.

This glow discharge excites the xenon gas filled in the discharge space 3 and causes it to emit ultraviolet rays with a spectrum specific to xenon gas. This short wavelength light excites the phosphor coating 6, which generates visible light.

The light emitted from the phosphor coating 6 is emitted to the outside through the slit portion 9. Therefore, in addition to the fact that the bulb 2 is originally thin, the narrow slit portion 9 further restricts the light band, so that the discharge lamp 1 emits a needle-like narrow band of light.

Therefore, since the display scale is indicated by the discharge lamp 1 and is illuminated, no other special light source is required.

The lamp holder 20 is fixed to a rotating shaft 25, and when the rotating shaft 25 rotates, the lamp holder 20 also rotates integrally. Therefore, the discharge lamp l attached to the lamp holder 20 is also rotated together, and the display scale can be shown.

In the cold cathode 4 of the above embodiment, since the electrode head 41 has a hollow cylindrical shape, the hollow part of the electrode head 41 can be filled with the electron emitting material 43, so that the emission of -layer electrons is promoted. It is also possible to enhance electrode function. Therefore, even if the outer diameter of the electrode head 41 is made smaller, the amount of electrons emitted increases.

Therefore, even a thin discharge lamp with a bulb diameter of 31I11 or less can be accommodated in a narrow bulb space.

Further, as in the above embodiment, the electrode head 4! Since the hollow portion of the electrode can be filled with the electron emitting material 43, the emission of -layer molecules can be promoted and the electrode function can be enhanced.

In the case of this embodiment, the outer diameter D] of the opening at one end of the electrode head 41 is IIms, and the inner diameter D2 is 0. 3am.

The outer diameter d of the tip of the electrode shaft 42 is set to 0. '5m and D
Since the relationship I>d>02 is established, the tip end surface of the electrode shaft 42 can be brought into contact with one end surface of the electrode head 41. By such butt joining, the electrode head 41
The electrode shaft 42 and the electrode head 41 can be joined with their centers aligned with each other, and by sealing the electrode shaft 42 approximately on the central axis of the bulb 2, the electrode shaft 42 and the electrode head 41 can be connected approximately to the central axis of the bulb 2. It can be placed on the central axis.

As a result, the inner diameter of the valve 2 is 3Il or less, for example 1.5
Even a thin lamp like 1 can be attached.

Note that the present invention is not limited to the structure of the above embodiment.

That is, in the above embodiment, the hollow portion of the electrode head 41 is filled with the electron emitting material 43, but instead of the electron emitting material 43, a getter may be filled, or a mixture of the electron emitting material and the getter may be filled. Good too.

Further, the drawings from FIG. 7 onwards show different embodiments of the present invention.

In the case of FIG. 7, the hollow part of the cylindrical electrode head 41 is left as it is, and in this case, the outer diameter can be made smaller and the surface area can be increased in proportion to that, so the current value can be increased. By increasing the size, the amount of electron emission can be increased, and a hollow effect can be expected, which improves the electrode function.

In the case of Fig. 8, a hole 45 is formed on the side wall of the hollow electrode head 4.
In this case, the surface area of the electrode head 41 can be further increased, the current value can be increased, and the amount of electrons emitted can be increased.

In the case of FIG. 9, the tip of the electrode shaft 42 is sharpened into a conical shape, and the tip 46 is fitted into an opening at one end of a hollow electrode head 41 and then butted and joined. In this case, it is easy to center the electrode head 41 and the electrode shaft 42.

In the case of FIG. 10, the tip of the electrode shaft 42 is processed to be wide. As a means of processing, burrs generated by cutting can be used. As shown in FIG. 11, the cutting burr 47 produces a protrusion larger than the wire diameter of the electrode shaft 42, and the size of this protrusion increases the area of the tip surface, so the contact area between the electrode head 41 and the electrode shaft 42 increases. , the bonding strength is improved.

Further, in the present invention, the shape of the electrode head 41 is not necessarily limited to a perfectly circular cylindrical shape, but may be an elliptical shape or a rectangular cylindrical shape (not shown) as shown in FIG. 12.

In the case of such a shape, the opening on one end surface only needs to be of a size and shape that does not allow the electrode shaft 42 to pass through (the 12th
As shown in the figure, it is sufficient that the size of the minimum diameter portion D3 of the opening is smaller than the size M of the tip end surface of the electrode shaft 42.

Further, the discharge lamp of the present invention is not limited to use as a display needle of a meter, and any discharge lamp equipped with a cold cathode may be used.

Further, the discharge gas sealed in the bulb is not limited to xenon alone, and a mixed gas containing at least one of neon, argon, and krypton in addition to xenon may also be sealed.

Then, mercury may be sealed inside the bulb.

Furthermore, the valve is not limited to a straight shape, but may have a bent shape.

[Effects of the Invention] As explained above, according to the present invention, since the electrode head is made hollow, the surface area can be increased even though the outer diameter can be reduced, and the amount of electron radiation can be increased. Since such a thin electrode head is joined to the electrode shaft by butt joint, it is possible to center both of them, and they can also be placed on the central axis of the narrow bulb. Even valves can be installed.

[Brief explanation of drawings]

1 to 6 show a first embodiment of the present invention, and T
Figure 41 is an exploded perspective view of a xenon glow discharge lamp used as a meter pointer, Figure 2 is a plan view of the xenon glow discharge lamp, and Figure 3 is a cross section taken along the line ■-■ in Figure 2. Figure 4 is a sectional view taken along line IV-IV in Figure 3, Figure 5 is a sectional view taken along line IV-IV in Figure 3;
The figure is a sectional view taken along the line ■-■ in FIG. 2, FIG. 6 is a sectional view taken along the line Vl-Vl in FIG. 2, and FIGS. 7 to 12 each show other embodiments of the present invention. FIG. l...xenon glow discharge lamp, 2...bulb, 4...
... cold cathode, 6 ... phosphor wave film, 7 ... internal electrode, 8 ... light-shielding coating, 9 ... slit part, 20 ...
Lamp holder, 41...electrode head, 42...electrode shaft.

Claims (1)

[Scope of Claims] A cold cathode discharge lamp in which a cold cathode is sealed at the end of the bulb, and the cold cathode is constructed by joining an electrode shaft to a hollow electrode head with both ends open. A cold cathode discharge lamp characterized in that the tip face has a diameter larger than the minimum inner diameter of the opening on the end face of the hollow electrode head, and the electrode shaft tip face is butted against and joined to the end face of the electrode head.