JPH0697607B2 - Electrodeless discharge lamp - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrodeless discharge lamp that has no electrodes inside the lamp and that excites and emits discharge gas inside the lamp by a high frequency electromagnetic field from the outside.

[Prior Art] Conventionally, electrodeless discharge lamps have been researched and developed in various places because they have characteristics of small size, high output, and long life. There are various uses, but it is considered to be used as a high-power point light source, for example.

Among such electrodeless discharge lamps, for example, Japanese Patent Laid-Open No.
In the lamp disclosed in Japanese Patent Publication No. -78766, as shown in FIG. 5, a bulb 22 is formed so as to cover the air-core coil 21,
This air-core coil 21 discharges mercury vapor in the bulb 22 by an electromagnetic field generated by flowing a high-frequency current. The magnetic field generated by the cylindrical coil used here is the strongest inside. In the example, there is no discharge space in that part, and the valve is used exclusively by using the magnetic field outside the coil.
22 are formed.

Further, the shape of the high-power electrodeless discharge lamp that has recently been developed in various places to emit light by electromagnetic waves is spherical as shown in FIG. 6, and rare gas and luminescent substance are contained in the bulb 23 formed of transparent quartz or the like. Is enclosed and an induction coil 24 is wound around the valve 23. When mercury is selected as the luminescent material, initial startup is relatively easy but restarting is difficult, and the mercury vapor pressure changes exponentially with increasing temperature. The alignment condition of is so bad that the lamp cannot be operated stably. If mercury is not added to improve the matching state, initial starting becomes very difficult, and if a high voltage is applied to forcefully start, a large lighting device is required.

[Problems to be Solved by the Invention] The present invention has been made in view of the above problems, and an object thereof is to provide an electrodeless discharge lamp having good startability and good compatibility with a high frequency circuit. is there.

[Means for Solving the Problems] In order to solve the above problems, the present invention applies a high-frequency current to an induction coil wound along the outer peripheral wall of a translucent bulb to discharge the electric charge enclosed in the bulb. In an electrodeless discharge lamp that excites and emits gas, a thin tube portion that forms the same airtight space as the bulb is provided integrally with the bulb,
A pair of auxiliary electrodes made of a foil-shaped conductive material were arranged in the thin tube portion with an interval such that dielectric breakdown did not occur in the air, and a high-frequency voltage was applied between both electrodes only at the time of starting. The area of the pair of auxiliary electrodes is smaller than the area of the other electrode on the side closer to the bulb, and the electrode on the side closer to the bulb is at ground potential. It is characterized by. Instead of the auxiliary electrode, an induction assisting coil having more turns than the induction coil may be wound around the thin tube portion, or mercury may be added to the thin tube portion. Good.

[Embodiment 1] FIG. 1 shows a first embodiment of the present invention, in which reference numeral 1 denotes a spherical bulb having a thin tube portion 2, which is airtight and transparent and has an internal discharge. Xenon (Xe) gas 100T as gas
The orr is enclosed. Reference numeral 3 denotes an induction coil wound along the outer peripheral wall of the valve 1, which is wound 3 turns in this embodiment, and both ends thereof are connected to a high frequency generator 6 via a matching circuit 4 and an amplifier 5. Reference numerals 7 and 8 denote a pair of auxiliary electrodes made of a foil-shaped conductive material, which are arranged at a small interval in the thin tube portion 2 (to the extent that dielectric breakdown does not occur in the air, in this embodiment, 0.5 m
m, separated) and the electrode
Reference numerals 7 and 8 are connected to both ends of the induction coil 3 via connection wires 9.

In the electrodeless discharge lamp configured as described above, when a high frequency current is passed through the induction coil 3, a voltage is generated between the coil terminals. This generated voltage is applied to the electrodes 7 of the thin tube portion 2,
It takes between 8 hours. However, since the distance between the electrodes is smaller than the distance between the coil terminals, the electric field strength between the electrodes 7 and 8 is larger than the electric field strength between the coils 3. Therefore, first, dielectric breakdown of Xe gas occurs in the thin tube portion 2. The discharge plasma generated in the thin tube portion 2 extends to the main discharge space of the bulb 1 as the input increases. Then, when the electron density is sufficiently increased in the main discharge space, a discharge accompanied by strong ring-shaped light emission is generated along the induction coil 3 in the bulb 1, which is the main discharge space.

Therefore, initial starting is easy without enclosing mercury,
Moreover, it is possible to provide an electrodeless discharge lamp that has good compatibility with a high frequency circuit.

Instead of Xe gas, another type of gas or 2
Of course, a mixed gas of more than one kind may be used.

[Embodiment 2] FIG. 2 shows a second embodiment of the present invention. The difference from Embodiment 1 is that the areas of the two auxiliary electrodes 7 and 8 are different, that is, the main discharge space. The area of the electrode 7 on the side closer to the bulb 1 forming the is smaller than the area of the other electrode 8 (in this embodiment, the width of the electrode 7 is 1 mm and the width of the electrode 8 is 10 mm).
And that the electrode 7 is set to the ground potential.
Since other configurations are the same as those in the first embodiment, the description will be omitted by giving the same reference numerals to the same configurations.

With this configuration, in Example 1, when the discharge plasma generated in the thin tube portion 2 extends to the main discharge space of the bulb 1 as the input increases, the auxiliary electrode 7 on the side close to the bulb 1 is formed. Is also the ground voltage, so valve 1
Since the area of the auxiliary electrode 8 on the side far from the
The volume of the part not covered by 7,8 (discharge space) becomes smaller in the thin tube part 2, and the streamer-like discharge does not extend in the direction of the thin tube part 2 but only in the direction of the valve 1 which is the main discharge space. Efficient starting is obtained.

Example 3 In this example, a metal halide such as NaI—TaI—InI in addition to the filling gas in Example 1 or 2 is used.
Is enclosed, and the other structure is the same as that of the above-mentioned embodiment.

With this configuration, the initial startup and the initial ring-shaped discharge are performed with the Xe gas, and thereafter, the vapor pressure of the metal vapor increases, so that the metal vapor emits light. In other words, the white emission of Xe gas is used at the initial stage of lighting, and then the discharge emission of metal vapor is used. Therefore, it is possible to provide a high-intensity discharge lamp with a very good rise.

[Example 4] A difference from Example 1 or Example 2 is that mercury is added to the thin tube portion 2, and other configurations are the same as those of Example 1 or Example 2.

With this configuration, the initial start-up in the thin tube portion 2 can be performed with mercury vapor that is easier to start than Xe gas, and electrons can be sufficiently supplied to the main discharge space. After that, since there is not enough mercury vapor in the main discharge space to maintain the ring-shaped discharge, the ring-shaped discharge of Xe occurs. Therefore, it is possible to provide an electrodeless discharge lamp that is easier to start.

The configuration of the present embodiment can of course be applied to the third embodiment.

[Fifth Embodiment] This embodiment is the thin tube portion 2 of the first or second embodiment.
The voltage to be applied between the two electrodes 7 and 8 for starting assistance of 1 is performed by a high-frequency oscillator provided separately from the induction coil 3 which is the main discharge coil.
Other configurations are similar to those of the first or second embodiment.

In Example 1 or Example 2, after starting the main discharge, if the power supply to the electrodes 7 and 8 for starting assistance is not stopped, the discharge current in the thin tube portion 2 increases and the power loss in this portion increases. However, if configured as in the present embodiment, the thin tube portion 2 does not consume more power than the power required for starting, and an electrodeless discharge lamp with less power loss can be provided.

[Sixth Embodiment] In addition to the configuration of the first or second embodiment, the thin tube portion 2 may be further provided with a starting assisting body such as a piezoelectric element.
With such a configuration, starting is performed in three stages, which is effective when starting is more difficult.

[Embodiment 7] FIG. 3 shows a seventh embodiment of the present invention. The auxiliary electrode 7 on the side closer to the main discharge space in the second embodiment extends from the auxiliary discharge electrode 7, that is, the proximity conductor 10 along the bulb 1. Is provided. The proximity conductor 10 may be disposed in contact with the valve 1 or may be disposed with a predetermined gap.

With such a configuration, it is possible to provide an electrodeless discharge lamp in which streamer-shaped discharge is easily extended in the direction along the adjacent conductor 10, that is, easier to start.

[Embodiment 8] FIG. 4 shows an eighth embodiment of the present invention, in which an induction assisting coil 11 is provided in the thin tube portion 2 instead of the auxiliary electrodes 7 and 8 in the first embodiment. That is, the coil 11 having the number of turns larger than the number of turns of the induction coil 3 which is the main discharge coil is provided so that the auxiliary discharge is performed in the thin tube portion 2. Of course, the main discharge and the auxiliary discharge may be performed by different power sources.

Also in this embodiment, the same effect as that of the above embodiment is obtained.

[Advantages of the Invention] As described above, in the electrodeless discharge lamp according to the present invention, a thin tube portion that forms the same airtight space as the bulb is integrally provided with the bulb, and the thin tube portion has a pair of foil-shaped conductive materials. The auxiliary electrodes are arranged with a space such that insulation breakdown does not occur in the air, and a high-frequency voltage is applied only between the two electrodes at the time of starting, or instead of the auxiliary electrodes, induction is performed in the thin tube portion. By providing the induction assisting coil having the number of turns greater than the number of turns of the coil, it is possible to provide a high-brightness electrodeless discharge lamp which has good startability and good matching with a high frequency circuit. Further, by making the area of the pair of auxiliary electrodes smaller than the area of the electrode on the side closer to the bulb than the area of the other electrode, and setting the electrode on the side close to the bulb to the ground potential, the thin tube By adding mercury to the portion, it is possible to provide an electrodeless discharge lamp with easier startability.

[Brief description of drawings]

FIG. 1 is a simplified diagram showing an embodiment of the present invention, FIGS. 2 to 4 are simplified diagrams showing different embodiments of the present invention, and FIG. 5 is a partial sectional front view showing a conventional example, FIG. 6 is a simplified diagram showing a different conventional example. 1 ... Valve, 2 ... Capillary tube part, 3 ... Induction coil, 4 ... Matching circuit, 5 ... Amplifier, 6 ... High frequency generator, 7,8 ... Auxiliary electrode, 9 ... Connection wire, 10 ... Proximity conductor, 11 ... Induction assist Coil.

Claims (4)

[Claims] 1. An electrodeless discharge lamp in which a discharge gas enclosed in the bulb is excited to emit light by passing a high-frequency current through an induction coil wound along the outer peripheral wall of the transparent bulb. A thin tube portion that forms the same airtight space as the valve is provided integrally with the valve, and a pair of auxiliary electrodes made of a foil-shaped conductive material are arranged in the thin tube portion at intervals such that dielectric breakdown does not occur in the air. At the same time, an electrodeless discharge lamp is characterized in that a high frequency voltage is applied between both electrodes only at the time of starting. 2. The area of the pair of auxiliary electrodes is smaller than the area of the other electrode on the side closer to the valve, and the electrode on the side closer to the valve is at ground potential. Electrodeless discharge lamp. 3. An electrodeless discharge lamp, characterized in that, in place of the auxiliary electrode according to claim 1, an induction assisting coil having a number of turns larger than that of the induction coil is provided in the thin tube portion. 4. The electrodeless discharge lamp according to claim 1, wherein mercury is added to the thin tube portion.