JPH0877968A - Low-pressure discharge lamp and lighting device - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a long-life low-pressure discharge lamp capable of effectively reusing thermionic emissive material attached to a shield ring or the like arranged near an electrode. A translucent airtight container 1 in which a discharge medium is enclosed, a pair of electrodes 4 and 4 arranged in the airtight container 1 and at least one of which holds a thermionic emissive substance 6, and a thermionic emissive substance 6. A low-pressure discharge lamp L including a heating element 5 arranged so as to surround the electrodes 4 and 4 holding the low-voltage discharge lamp and a low-pressure discharge lamp L attached to the main body of the device. [Effect] Since the thermionic emissive material is lost only through the opening through which the discharge is formed in the heating element, the consumption rate of the thermionic emissive material is remarkably reduced, blackening of the lamp is reduced, and a long-life lamp is provided. can get.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low pressure discharge lamp such as a fluorescent lamp having an improved electrode section.

[0002]

2. Description of the Related Art A discharge lamp, for example, a fluorescent lamp is constructed by a filament coil in which a tungsten wire is wound in a double or triple manner at both ends of a translucent airtight container including a glass bulb having a phosphor film formed on its inner surface. In addition to the above-mentioned hot cathode, an inert gas such as argon gas and an appropriate amount of mercury are enclosed in this airtight container as a discharge medium for facilitating discharge. The coil is coated with a thermionic emissive material (emitter).

In order to light this fluorescent lamp, when a current is passed through the hot cathode to preheat the filament coil, thermionic emissive material coated on the coil releases abundant thermoelectrons into the airtight container. Is moved by being pulled by the high voltage of the electrode on the opposite side, and arc discharge easily starts. The electrons flowing by this discharge collide with mercury atoms in the airtight container to generate ultraviolet rays, and the ultraviolet rays excite the phosphor film coated on the inner surface of the airtight container to emit visible light. This emission is white, daylight, blue,
Various light colors, such as pink, are emitted from the lamp.

In this fluorescent lamp, the filament coil during lighting has a discharge bright spot (cathode spot) of around 1000 ° C., and the thermionic emissive material applied to the coil is subjected to electron and ion bombardment to evaporate or sputter. Then it is gradually consumed and diffuses into the airtight container. Then, the diffused thermionic emissive material eventually adheres to the phosphor film and the inner surface of the airtight container, and combines with mercury to form an amalgam, resulting in blackening and impairing the appearance and the luminous flux of the lamp. It is also the main cause of the decline.

Therefore, as a means for reducing the adhesion of the thermionic emissive substance to the airtight container, a cup-shaped envelope or a shield ring is provided surrounding the filament coil holding the thermionic emissive substance. With such a configuration, most of the thermoelectron emissive material evaporated or sputtered from the filament coil is deposited and deposited on the cup-shaped envelope or shield ring, and the amount deposited on the phosphor film or the inner surface of the airtight container is reduced. There is an effect that the blackening of the airtight container surface can be reduced.

However, as described above, the discharge bright spot (cathode spot) of the filament coil during lighting is about 1000 ° C., but the cup-shaped envelope and the shield ring are set to the temperature of the gas enclosed in the hermetic container. However, the temperature gradient of the thermionic emissive substance is eventually generated from the discharge bright point (cathode spot) toward the cup-shaped envelope or the shield ring, and the thermionic emissive substance evaporated from the discharge bright point (cathode spot). When the filament coil loses the thermionic emissive material when it is lost by adhering to the cup-shaped envelope or shield ring, it becomes difficult to radiate thermionic electrons at a normal voltage, making it impossible to maintain arc discharge. Then the lamp goes out and the life ends.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a long life which prevents the thermionic emissive substance held on an electrode from prematurely scattering and enables effective utilization of the thermionic emissive substance. An object of the present invention is to provide a low-pressure discharge lamp.

[0008]

A low-pressure discharge lamp according to claim 1 of the present invention is a translucent airtight container in which a discharge medium is enclosed, and at least one of which is a thermoelectron emissive member disposed in the airtight container. It is characterized in that it is provided with a pair of electrodes holding a substance and a heating element arranged so as to surround the periphery of the electrode holding a thermionic emissive substance.

A low-pressure discharge lamp according to a second aspect of the present invention is characterized in that electrodes holding a thermoelectron emissive material are provided on a pair of lead wires.

The low-pressure discharge lamp according to claim 3 of the present invention is characterized in that the electrode holding the thermionic emissive material has a filament coil.

The low-pressure discharge lamp according to claim 4 of the present invention is characterized in that the electrode holding the thermoelectron emissive material is supported by one lead wire.

A low-pressure discharge lamp according to a fifth aspect of the present invention is characterized in that the heating element surrounding the electrodes has a higher temperature than the electrodes when the lamp is lit.

The low-pressure discharge lamp according to claim 6 of the present invention is characterized in that the heating element surrounding the electrode is a resistance heating element.

The low-pressure discharge lamp according to claim 7 of the present invention is characterized in that the heating element surrounding the periphery of the electrode has an opening through which the discharge passes.

An illuminating device according to claim 8 of the present invention is a device main body, the low-pressure discharge lamp according to any one of claims 1 to 7 mounted on the device main body, and the device main body. And a lighting circuit for lighting the lamp.

[0016]

[Function] The thermionic emissive substance held on the electrode is evaporated due to the high electrode temperature at the time of lighting, or is sputtered by the ions accelerated in the cathode descending portion, and most of these scattered substances are generated by the electrode. Attempts to attach to a heating element provided near the electrode so as to surround the. However, since the heating element is higher than the temperature of the electrode, the scattered thermionic emissive material is not deposited on the heating element. Because the temperature of the heating element is high, a density gradient is formed from the heating element to the electrode. In this state, the thermoelectron emissive material is lost only through the opening provided in the heating element for allowing the discharge to pass therethrough, so the consumption rate of the thermoelectron emissive material is significantly reduced.

[0017]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. In the figure, L indicates a fluorescent lamp which is a typical low pressure discharge lamp. In the figure, 1 is a translucent airtight container made of a straight tube type glass bulb, 2 is a stem 3a, 3b, 3c, 3d sealed at both ends of the airtight container 1.
Is an internal lead wire implanted in the stem 2, 4 is an electrode, and a filament coil 4A and a pair of internal lead wires 3c constituting a hot cathode in which leg portions 4b and 4b are installed between the pair of internal lead wires 3a and 3b. , 3d, and a cylindrical heating element 5 connected between them. Since the stem 2 and the electrodes 4 sealed at both ends of the airtight container 1 are the same, only one of them is shown.

Further, a phosphor film 7 is formed on the inner surface of the airtight container 1, and an inert gas such as argon and mercury are sealed as a discharge medium inside. In addition, as shown in the left side of FIG.
The external lead wires 8a, 8b, 8c, 8d connected to the internal lead wires 3a, 3b, 3c, 3d are derived from the above, and finally as shown in the right side of FIG. A base 9 is joined to the sealing portion at the end of the airtight container 1, and the external lead wires 8a, 8b, 8c and 8d are connected to the terminal pins 9a, 9b, 9c and 9d of the base 9, respectively.

The filament coil 4A constituting the electrode 4 has a coil shape formed by winding a tungsten wire in a double or triple manner, and has (Ba, C in the coil turn).
a, Sr) O (barium oxide, calcium oxide, strontium oxide) as a main component is applied and filled.

The heating element 5 is a filament coil 4A.
It consists of a thin plate of tungsten, tantalum, etc. formed into a cylindrical shape so as to surround the circumference of the
From 5m, the leg portion 4b of the filament coil 4A,
4b extends and is arranged so as to be electrically insulated without making contact with the filament coil 4A. Further, the heating element 5 is supplied with power via the internal lead wires 3c and 3d connected to both ends.

The fluorescent lamp L having such a structure is composed of a ballast or the like in which the terminal pins 9a and 9b connected to the filament coil 4A and the terminal pins 9c and 9d connected to the heating element 5 are attached to the main body of the apparatus. It is installed in the socket (not shown) that is connected to the power supply for the lighting circuit and the power supply for heating the heating element. Then, by turning on the power source for the lighting circuit and the power source for heating the heating element, the filament coils 4A, 4A provided at both ends of the fluorescent lamp L are heated through the lighting circuit and are discharged between the coils 4A, 4A. Emits light and performs predetermined illumination, and a voltage is also applied to the heating element 5 via the internal lead wires 3c and 3d, so that the heating element 5 is heated. The temperature of the heating element 5 is set to be equal to or higher than the temperature of the discharge bright spot (cathode spot) of the filament coil 4A.

If AC lighting is performed, current alternately flows from one filament coil 4A to the other filament coil 4A and from the other filament coil 4A to one filament coil 4A, and a discharge bright spot ( The cathode spot) is at the end of the thermionic emissive material 6 applied to the coil 4A. The discharge is generated from the openings 5m, 5m at both ends of the cylindrical heating element 5 surrounding the one filament coil 4A to the other filament coil 4A facing the other.

As the lamp L continues to be lit or is repeatedly started, the thermoelectron emissive material 6 coated and filled in the filament coil 4A gradually evaporates or sputters from the discharge bright spot (cathode spot) and becomes an inert gas. It spreads inside. And most of them are filament coil 4
Attempts to adhere to the heating element 5 provided so as to surround A, but the temperature of the heating element 5 is the same as that of the filament coil 4A.
Since the temperature is set to be higher than the temperature of the discharge bright spot (cathode spot) of, the density gradient is formed from the heating element 5 toward the filament coil 4A, the vapor pressure is high on the surface of the heating element 5, and the heat is generated on the surface. The electron emissive material 6 does not adhere and accumulate.

The lamp L is also a discharge path,
Further, the openings 5m and 5m at both ends of the heating element 5, which are also the paths through which the thermionic emissive material 6 scatters, have a small opening area, and hence the loss rate is slow, and therefore, the thermionic emissive material 6 is worn out. Since the number is small, the service life of the electrode 4 can be extended.

The thermoelectron emissive material 6 evaporated or sputtered from the filament coil 4A diffuses into the airtight container 1 through the openings 5m and 5m at both ends of the cylindrical heating element 5 provided surrounding the filament coil 4A. Eventually, it adheres to the inner surface of the airtight container 1 and the phosphor film 7 surface. When the thermoelectron emissive material 6 is completely removed from the filament coil 4A, the discharge voltage between the filament coils 4A and 4A rises, and at the normal discharge sustaining voltage, no discharge occurs between the filament coils 4A and 4A and the lamp L goes out. It will not light up and it will reach the end of its life.

3 (a), 3 (b) and 3 (c) show a heating element 5 according to another embodiment of the present invention, which is shown in FIGS. 1 and 2 with openings at the left and right ends of a cylindrical body. 5m and 5m are formed, in contrast to the one shown in FIG. 3 (a), a cylindrical body is cut along the axis of the filament coil 4A to form an opening 5n. In addition, in FIG. 3B, a rectangular body is cut and raised along the axis of the filament coil 4A (cut and raised piece 5s,
5s) The opening 5p is formed. Also, FIG.
In (c), openings 5q and 5q are formed on the upper and lower sides of a normal shield ring.

Further, the heating element 5 of the present invention is not limited to one formed of the above metal plate and directly energized to generate heat, and a resistance heating wire wound in the vicinity of a cylinder (illustrated). No.) or a metal mesh (not shown) or as shown in FIG. 4 (a), a resistance heating material such as tungsten, tantalum or nichrome is applied to the outer or inner surface of the heat resistant and electrically insulating plate 5A such as ceramics. A resistance heating film 5B is formed by winding the resistance heating wire 5C around the heat resistant electric insulating plate 5A as shown in FIG. 4B.
As shown in (c), it may be a heat-resistant and electrically insulating plate on which a resistance heating element 5D made of a metal plate or a resistance heating film is arranged in a substantially spiral shape.

The heating element 5 is not limited to an endless one such as a tubular shape or a ring shape, and internal lead wires 3c and 3d are connected to the ends as shown in FIGS. 4 (b) and 4 (c). The terminal portions 5t and 5t may be formed.

Further, the electrode 4 is not limited to the lamp L using the filament coil 4A, but a thermoelectron emissive substance 6 such as BaO (barium oxide) is obtained by sintering tungsten powder as shown in FIG. Main body 4B
And a tungsten rod or a molybdenum rod 4k embedded in both ends of the main body portion 4B.
It may be the electrode 4 fixed by being erected between 3b.

The electrode 4 shown in FIG. 5 is also connected to both internal lead wires 3a,
When electricity is applied to 3b, the main body portion 4B generates heat, and discharge is maintained between the opposing electrodes 4 by the electron emission from the impregnated thermionic emissive material 6. And this main body 4B
A heating element 5 (not shown) is also provided around the main body 4B to surround the main body 4B, and the thermoelectron emissive substance 6 evaporated or sputtered from the main body 4B is the same as that described above.
(Not shown) reduces the scattering and extends the life of the lamp.

The present invention is not limited to the above embodiment. For example, at least one of the pair of electrodes arranged in the airtight container may hold the thermionic emissive substance, and the heating element may be arranged only around this electrode to surround the electrode. Further, in the above-mentioned embodiment, the electrode is provided between the pair of internal lead wires, but as shown in FIG. 3 (c), one lead wire is provided with the electrode portion 4C made of a sintered body, a metal block or the like. It is also applicable to an electrode composed of a hot cathode in which a cathode spot is formed at the time of cold start type discharge formed by applying the thermoelectron emissive substance 6 on the surface or inside. Further, the hot cathode may be a double or triple coil or a stick coil having a core wire.

The thermionic emissive material is not limited to the above-mentioned ones, but Ba-MO (however, M; Ta, Al, V, W, T
i, Zr), Ba-Ca-MO (however, M; Ta, A
1, V, W, Ti, Zr), Ba-Ca-Sr-MO
(However, M; Ta, Al, V, W, Ti, Zr), etc., or a combination thereof, or Al ₂ O ₃ , ZrO ₂ ,
A small amount of Sc ₂ O ₃ or the like may be added.

Further, the means for holding the thermionic emissive substance on the electrode is not limited to coating filling and impregnation, and other means may be used.

Further, the lamp is not limited to a straight tube type fluorescent lamp, but other low-pressure discharge lamps such as an ultraviolet lamp using an electrode provided with a thermoelectron emissive material and a rare gas light emitting lamp in which only rare gas is filled as a discharge medium. May be Further, the shape of the translucent airtight container is not limited to the straight tube shape, but a tubular glass bulb having a bent annular shape, a U shape, a W shape, or an eggplant shape (A shape, PS shape, P shape, etc.) The shape may be a ball shape (G shape), an R shape, or a flat plate formed by joining a front plate and a back plate. Further, the lamp is not limited to the one with a base, but may be of a type in which an external lead wire is directly connected to a printed circuit board or the like.

Furthermore, although the lamp using the stem is described in the above embodiment, the lamp may be a lamp in which the lead wire is directly sealed to the sealing portion without using the stem.

[0036]

As described in detail above, the thermionic emissive substance held on the electrode is vaporized from the high temperature electrode or sputtered by the ions accelerated in the cathode descending portion. Since the heating element arranged so as to surround the electrode is higher than the temperature of the electrode and has a density gradient from the heating element to the electrode, the thermoelectron emissive material is lost only through the opening in the heating element through which the discharge passes. Therefore, the consumption rate of the thermionic emissive material is remarkably reduced, blackening of the lamp is reduced, and a long-life lamp can be provided.

[Brief description of drawings]

FIG. 1 is a partially sectional front view showing an embodiment of a fluorescent lamp of the present invention.

FIG. 2 is a partially sectional front view showing an enlarged electrode of the lamp of FIG.

3 (a), (b) and (c) are perspective views showing another embodiment of the heating element of the present invention.

FIG. 4 is a partial sectional front view showing an embodiment of a heat generating portion of another heat generating element of the present invention.

FIG. 5 is a partial sectional front view showing an embodiment of another electrode of the present invention.

[Explanation of symbols]

 L: low-pressure discharge lamp (fluorescent lamp) 1: translucent airtight container (bulb) 3a, 3b, 3c, 3d: internal lead wire 4: electrode (hot cathode) 4A: filament coil 4B: main part (porous crystal body) ) 4C: Electrode part 5: Heating element 6: Thermionic emissive material

Claims (8)

[Claims] 1. A translucent airtight container enclosing a discharge medium;
A pair of electrodes, at least one of which is arranged in the airtight container and holds the thermionic emissive substance; and a heating element which is arranged so as to surround the electrodes which hold the thermionic emissive substance. Characteristic low-pressure discharge lamp. 2. The low-pressure discharge lamp according to claim 1, wherein the electrode holding the thermionic emissive material is provided on a pair of lead wires. 3. The low-pressure discharge lamp according to claim 2, wherein the electrode holding the thermionic emissive material has a filament coil. 4. The low-pressure discharge lamp according to claim 1, wherein the electrode holding the thermionic emissive material is supported by one lead wire. 5. The low-pressure discharge lamp according to claim 1, wherein the heating element surrounding the electrode has a higher temperature than the electrode when the lamp is lit. 6. The low-pressure discharge lamp according to claim 1, wherein the heating element surrounding the electrode is a resistance heating element. 7. The low-pressure discharge lamp according to claim 1, wherein the heating element surrounding the electrode has an opening through which a discharge passes. 8. A device main body, a low-pressure discharge lamp according to any one of claims 1 to 7 mounted on the device main body, and a lighting circuit mounted on the device main body for lighting the lamp. A lighting device characterized by the above.