JPH09204906A - Electrodeless low-pressure discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-pressure discharge lamp in which the initial starting and restarting are facilitated, and the power loss is minimized. SOLUTION: In this discharge lamp, a high frequency electromagnetic field is worked to a discharge gas sealed within a valve 1 formed of a light transmitting material through an induction coil 2 arranged on the outside of the valve 1 to generate a high frequency discharge within the valve, whereby the discharge gas is excited to emit a light. In this case, a starting auxiliary body 7 having an electron emitting material adhered thereto is arranged within the valve 1, whereby both the ends of the starting auxiliary body 7 are short-circuited through a conductor and looped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention does not have a main electrode in a bulb, but a high-frequency electromagnetic field is applied to the discharge gas sealed in the bulb from outside the bulb to generate high-frequency discharge in the bulb. The present invention relates to an electrodeless low pressure discharge lamp that excites and emits discharge gas.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, there is known an electrodeless discharge lamp having a structure in which an induction coil 2 is arranged outside a spherical bulb 1 in which a discharge gas is filled (for example, Japanese Patent Laid-Open No. Hei 10-19990). 6-13190 gazette).

As the discharge gas sealed in the bulb 1, a mixed gas of an inert gas and mercury vapor is generally used. Further, in this electrodeless discharge lamp, the donut-shaped discharge plasma P is provided in the bulb 1 in the lighting state.
Are formed along the solenoid type induction coil 2.

[0004]

In such an electrodeless discharge lamp, an induction coil 2 arranged outside the bulb 1 is used.
When high-frequency power is applied to the discharge plasma P, the discharge plasma P is formed by the high-frequency electromagnetic field and the lamp is turned on. On the other hand, if the lighting circuit outputs the light without the lighting, the lighting circuit may continue abnormal oscillation and the lighting circuit may be damaged. Moreover, at the time of starting, since the initial electrons existing in the valve 1 are extremely small, the power required at the time of starting is inevitably large.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an electrodeless low pressure discharge lamp that is easy to start and restart and has a small power loss. .

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention applies a high-frequency electromagnetic field to a discharge gas sealed in a bulb to cause a high-frequency discharge in the bulb to excite the discharge gas to emit light. In the electrodeless low-pressure discharge lamp, a starting auxiliary member coated with an electron emissive material is arranged in the bulb, and both ends of the starting auxiliary member are short-circuited via a conductor to form a loop. It is a feature. The starting aid is preferably a refractory metal, for example, a tungsten coil is convenient.

Further, the starting auxiliary body may be arranged near the inner wall of the valve, and an insulating shield for covering at least the valve center side of the starting auxiliary body may be provided. In that case, it is preferable to use a high melting point insulating material for the shield.

[0008]

By arranging the starting auxiliary member on which the electron emissive material forming a part of the loop is attached inside the valve, at the time of starting, the high frequency electromagnetic field generated from the induction coil causes a weak high frequency to the starting auxiliary member. An electric current flows, the starting auxiliary body is heated, and thermoelectrons are generated from the electron emissive material to facilitate starting. When transitioning to the lighting state, most of the high-frequency electromagnetic field is absorbed by the discharge plasma, so that the power lost in the short-circuited loop is small.

When discharge plasma is formed at the time of starting, a transiently large current flows in the discharge space. Therefore, when the starting aid coated with electron emissive material is spatially close to the transient discharge plasma current, this transient large current causes an unnecessarily large current to flow into the short-circuited loop. However, the starting aid may be overheated and the electron emissive material may be scattered (sputtered). However, as in the present invention, by providing a shield that covers at least the valve center side of the starting aid,
Such a problem can be solved. That is, since the shield is not made of metal, the high-frequency electromagnetic field from the induction coil flows in the short-circuited loop, the effect of assisting the starting is maintained, and damage to the starting assisting body can be prevented.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment according to the present invention. In the figure, reference numeral 1 is a bulb made of a translucent material, and a phosphor 3 is applied to the inner wall surface of the bulb. Has been done,
A discharge gas consisting of a metal vapor such as mercury vapor and an inert gas such as argon gas is enclosed in the bulb 1. Reference numeral 2 denotes an induction coil, which is wound a plurality of turns along the outer peripheral wall of the bulb 1, and both ends thereof are connected to a lighting circuit 4 including a matching circuit, a high frequency generating circuit, and the like.

In this embodiment, a bulb 1 made of soda glass in the shape of a light bulb is used as the bulb 1, a stem 5 is used as the sealing portion, and two lead wires 6 are provided for the stem 5.
6 are provided. Then, a tungsten coil 7, which is a starting auxiliary member coated with an electron emissive material, is fixed to each end of the two lead wires 6 and 6 located inside the bulb. The other ends of the lead wires 6 and 6 located outside the valve are short-circuited via a conductor. A loop is formed by this short circuit, the lead wires 6 and 6, and the tungsten coil 7.

Even if the short-circuited loop is located inside the valve, which is the discharge space, or part of it is located outside the valve as in this embodiment, the effect of assisting the start-up does not change. Therefore, the short-circuited portion of the two lead wires 6 and 6 may be inside or outside the valve. A barium-containing emitter used in general fluorescent lamps was used as the electron emitting substance, and a copper wire was plated with silver and coated with Teflon as the induction coil 2.

FIGS. 2 and 3 show a different embodiment of the present invention. The difference from the above-mentioned embodiment is that the starting assisting body 7 is located near the inner wall of the valve 1 (in this embodiment, the stem 5).
And a shield 8 made of a high melting point insulating material (for example, glass or ceramics) that covers at least the valve center side of the starting auxiliary body 7, that is, the side where the discharge plasma P is formed. Since other configurations are the same as those of the above-described embodiment, the description will be omitted by giving the same reference numerals to the same configurations.

[0014]

As described above, according to the present invention, the starting assisting body coated with the electron emissive material is disposed in the valve, and both ends of the starting assisting body are short-circuited via the conductor to form a loop. As a result, at the time of starting, a weak high-frequency current flows through the starting auxiliary body by the high-frequency electromagnetic field generated from the induction coil, and the starting auxiliary body is heated to generate thermoelectrons from the electron emissive material, which facilitates starting. Become. In addition, since the discharge plasma absorbs most of the high-frequency electromagnetic field when shifting to the lighting state, less power is lost in the short-circuited loop.

Further, by disposing the starting auxiliary body near the inner wall of the valve and by providing the shield for covering at least the valve center side of the starting auxiliary body, the starting auxiliary body can be maintained while maintaining the effect of the starting auxiliary body. Can prevent damage.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional configuration diagram showing an embodiment of the present invention.

FIG. 2 is a partial cross-sectional configuration diagram showing a different embodiment of the present invention.

FIG. 3 is an enlarged side view of a part of FIG.

FIG. 4 is a partial cross-sectional perspective view showing a conventional example.

[Explanation of symbols]

 1 bulb 2 induction coil 3 phosphor 4 lighting circuit 5 stem 6 lead wire 7 starting aid 8 shield

Claims (4)

[Claims] 1. A discharge gas is produced by causing a high-frequency electromagnetic field to act on a discharge gas sealed in a bulb made of a translucent material via an induction coil arranged outside the bulb to generate a high-frequency discharge in the bulb. In an electrodeless low-pressure discharge lamp that excites and emits light, a starting auxiliary member coated with an electron emissive material is provided in the bulb, and both ends of the starting auxiliary member are short-circuited via a conductor to form a loop. An electrodeless low-pressure discharge lamp characterized in that 2. The electrodeless low-pressure discharge lamp according to claim 1, wherein the starting aid is made of a refractory metal. 3. The electrodeless low-pressure discharge lamp according to claim 2, wherein the starting aid is a tungsten coil. 4. The shield body made of a high melting point insulating material is disposed near the inner wall of the valve, and the shield body is provided with a refractory insulating material covering at least the valve center side of the start body. The electrodeless low-pressure discharge lamp according to claim 2 or 3.