JPH04174957A - Electrodeless discharge lamp - Google Patents

Abstract

PURPOSE:To enhance the starting characteristic and brightness of an electrodeless discharge lamp by providing a capillary portion which has a sealed space in common with and integrally with a bulb, and disposing a pair of auxiliary electrodes each made of foil of conductive material, and applying a high frequency voltage to each of the pair of auxiliary electrodes at the start of the discharge lamp. CONSTITUTION:When a high frequency current is made to flow through an induction coil 3 from a high frequency generator 6 via an amplifier 5 and a matching circuit 4, a voltage is generated between coil terminals, the induction coil 3 being wound along the outer peripheral wall of a bulb 1. At the same time a voltage is applied to each of the pair of auxiliary electrodes 7, 8 each made of foil of conductive material and wound around a capillary portion 2 with a slight distance between the electrodes 7, 8. Since this interelectrode distance is small, the field intensity is greater than between the coil 3 and each electrode 7, 8. As input increases, plasma generated by the dielectric breakdown of discharged Xe gas inside the portion 2 is extended toward the main discharge space of the bulb 1. Then electron density is increased and discharge causing emission of light is caused along the coil 3 inside the bulb 1. The initial start of an electrodeless discharge lamp is therefore easy even without sealing mercury therein and also the adjustability to a high frequency circuit is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrodeless discharge lamp that does not have electrodes inside the lamp and excites a discharge gas inside the lamp to emit light using a high-frequency electromagnetic field from the outside.

[Prior Art] Electrodeless discharge lamps have been researched and developed in various places since they have characteristics such as small size, high output, and long life. Although its uses are various, for example, it is being considered to be used as a high-output point light source.

Among such electrodeless discharge lamps, for example,
In the lamp disclosed in Japanese Patent No. 7-78766, as shown in FIG.
The mercury vapor inside the bulb 22 is discharged by the electromagnetic field generated by passing a high-frequency current through this air-core coil 21. The magnetic field produced by the cylindrical coil used here is the strongest inside. However, in this example, there is no discharge space in that part, and the bulb 22 is formed using only the magnetic field outside the coil.

In addition, the shape of high-output electrodeless discharge lamps that emit light using t-magnetic waves, which have recently been developed in various places, is spherical as shown in FIG. When mercury is selected as the luminescent material, the material is sealed and the induction coil 24 is wound around the bulb 230, initial starting is relatively easy, but restarting is difficult, and as the temperature rises, Since the mercury vapor pressure changes exponentially, the matching between the circuit system and the lamp becomes very poor, making it impossible to operate the lamp stably. If mercury is not added to improve consistency,
Initial starting becomes extremely difficult, and if a high voltage is applied to force the starting, a large lighting device is required.

Problems to be Solved by Invention F] The present invention has been made in view of the above-mentioned problems, and its purpose is to provide an electroless discharge lamp that has good startability and good compatibility with a high frequency circuit. be.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention applies a high-frequency current to an induction coil wound along the outer circumferential wall of a light-transmitting bulb, thereby reducing the discharge voltage enclosed within the bulb. In an electrodeless discharge lamp that excites gas to emit light, a thin tube part forming the same airtight space as the bulb is provided integrally with the bulb,
A pair of auxiliary electrodes made of a foil-like conductive material are arranged in the thin tube part with an interval that does not cause dielectric breakdown in the air, and a high frequency voltage is applied between the two electrodes only at the time of starting. Further, the area of the pair of auxiliary electrodes is such that the area of the electrode closer to the bulb is smaller than the area of the other electrode, and the electrode closer to the bulb is set at ground potential. It is characterized by: Incidentally, instead of the auxiliary electrode, a configuration may be adopted in which an induction auxiliary coil having a number of turns greater than the number of turns of the induction coil is wound around the thin tube portion (also, mercury is added to the thin tube portion). Good too.

[Example 1] Fig. 1 shows a first example of the present invention, in which 1 is a spherical bulb having a thin tube part 2, which is airtight and translucent, and has a discharge inside. Xenon (Xe) gas as gas
O0Torr is enclosed.

Reference numeral 3 denotes an induction coil wound along the outer circumferential wall of the bulb I, which is wound three 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 numeral 7.8 denotes a pair of auxiliary electrodes made of a foil-like conductive material, which are connected to the thin tube portion 2 with a slight spacing (to the extent that dielectric breakdown does not occur in the air, in this example, a distance of 0.5 wa). The electrodes 7.8 are connected to both ends of the induction coil 3 via connecting wires 9, respectively.

In the electrodeless discharge lamp configured in this manner, 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 electrode 7 of the thin tube section 2.
, it takes about 8 minutes. However, since this distance between the electrodes is smaller than the distance between the coil terminals, the electric field strength between the electrodes 7 and 8 is greater than the electric field strength between the coil 3. Therefore, first, the dielectric breakdown of the Xe gas occurs in the thin tube portion 2. The discharge plasma generated in the thin tube section 2 extends into the main discharge space of the bulb as the input increases. Then, when the electron density increases sufficiently within the main discharge space, a ring-shaped discharge accompanied by strong light emission occurs within the bulb l, which is the main discharge space, along the induction coil 3.

Therefore, initial startup is easy even without mercury.
Furthermore, it is possible to provide an electrodeless discharge lamp that has good compatibility with high-frequency circuits.

Note that, in place of the Xe gas, other 1lilf gas or a mixture of two types of rooftop gas may of course be used.

[Example 2] Figure 2 shows a second example of the present invention, which differs from Example 1 in that the areas of the two auxiliary electrodes 7°8 are different, that is, the main discharge space is The area of the electrode 7 on the side closer to the bulb 1 that forms the area is smaller than the area of the other electrode 8 (in this example, the width of the electrode 7 is 1 mm, and the width of the electrode 8 is 10 mm).
++m) and that the electrode 7 is set to the ground potential.The other configurations are the same as those of Example 1, so the explanation will be omitted by assigning the same reference numerals to the equivalent configurations.

With this configuration, in the first embodiment, when the discharge plasma generated in the thin tube section 2 extends into the main discharge space of the bulb 1 as the input increases, the auxiliary electrode 7 on the side closer to the bulb 1 Since is the ground voltage, also the valve 1
Since the area of the auxiliary electrode 8 on the side far from the auxiliary electrode 7.8 is large, the volume (discharge space) of the part not covered by the auxiliary electrode 7.8 is small (discharge space) in the thin tube section 2, and streamer-like discharge occurs in the thin tube section 2.
It does not extend in any direction, but extends only in one direction of the bulb, which is the main discharge space, resulting in more efficient starting.

[Example 3] In this example, in addition to the sealed gas in Example 1 or Example 2, a metal halide such as NaI Ta
1-1n+ is enclosed, and the other configurations are the same as those of the previous embodiment.

With this configuration, the initial startup and initial ring-shaped discharge are performed using Xe gas, and thereafter, the vapor pressure of the metal vapor increases, causing the metal vapor to emit light.

That is, in the initial stage of lighting, white light emission from Xe gas is used, and thereafter, discharge light emission from metal vapor is used. Therefore, a high-intensity discharge lamp with very good start-up can be provided.

[Example 4] The difference from Example 1 or Example 2 is that mercury was added to the thin tube portion 2, but the other configurations are the same as Example 1 or Example 2.

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

Note that the configuration of this embodiment can of course be applied to the third embodiment.

[Example 5] This example describes the thin tube portion 2 in Example 1 or Example 2.
The voltage applied between the two electrodes 7 and 8 for starting assistance is
This is characterized in that a high-frequency oscillator is provided separately from that for the induction coil 3, which is the main discharge coil, and the other configurations are the same as those of the first or second embodiment.

In Embodiment 1 or 2, if the power supply to the starting auxiliary electrode 7.8 is not stopped after the main discharge starts, the thin tube portion 2
Although the discharge current increases and the power loss in this part becomes large, if configured as in this embodiment, the thin tube part 2 does not consume more power than the power required for starting, and the power loss in this part is small. An electrode discharge lamp can be provided.

[Example 6] In addition to the configuration of Example 1 or Example 2, the thin tube portion 2 may further be provided with a starting aid such as a piezoelectric element.
This configuration results in three-stage starting, which is effective when starting is more difficult.

[Embodiment 7] FIG. 3 shows a seventh embodiment of the present invention, in which a nearby conductor 10 is connected along the main discharge space, that is, the bulb 1, from the auxiliary electrode 7 on the side closer to the main discharge space in the second embodiment. It is characterized by the fact that it is equipped with. It goes without saying that the proximal conductor 10 may be disposed in contact with the bulb 1 or may be disposed with a predetermined gap.

With this configuration, the streamer-like discharge can easily extend in the direction along the proximal conductor 10, that is, it is possible to provide an electrodeless discharge lamp 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. In other words, the coil 11 is provided with a number of turns greater than the number of turns of the induction coil 3 which is the main discharge coil, and the auxiliary discharge is caused to occur in the thin tube portion 2. Of course, the main discharge and the auxiliary discharge may be performed using separate power supplies.

This embodiment also provides the same effects as those of the previous embodiment.

[Effects of the Invention 1] As described above, the electrodeless discharge lamp according to the present invention is provided with a thin tube part that forms the same airtight space as the bulb, and a pair of thin tube parts made of a foil-like conductive material in the thin tube part. By arranging the auxiliary electrodes at intervals that do not cause dielectric breakdown in the air, and by applying a high frequency voltage between the two electrodes only at the time of starting, or instead of the auxiliary electrodes, the induction voltage is By providing an induction assisting coil having a larger number of turns than the coil, it is possible to provide a high-intensity electrodeless discharge lamp that has good startability and good compatibility with a high-frequency circuit. Furthermore, by making the area of the pair of auxiliary electrodes smaller, the area of the electrode closer to the bulb is smaller than the area of the other electrode, and the electrode closer to the bulb is set at ground potential. By adding mercury to the part, it is possible to provide an electrodeless discharge lamp that is easier to start.

[Brief explanation of the drawing]

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

Claims (4)

[Claims] (1) An electrodeless discharge lamp in which a discharge gas sealed 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 light-transmitting bulb. A thin tube portion forming the same airtight space is provided integrally with the valve, and a pair of auxiliary electrodes made of a foil-like conductive material are disposed on the thin tube portion at an interval that does not cause dielectric breakdown in the air, An electrodeless discharge lamp characterized in that a high frequency voltage is applied between the two electrodes only at the time of starting. (2) The electrodeless device according to claim 1, wherein the area of the pair of auxiliary electrodes is such that the area of the electrode closer to the bulb is smaller than the area of the other electrode, and the electrode closer to the bulb is set at ground potential. discharge lamp. (3) An electrodeless discharge lamp characterized in that, in place of the auxiliary electrode according to claim 1, an induction auxiliary coil having a number of turns greater than the number of turns of the induction coil is provided in the thin tube portion. (4) The electrodeless discharge lamp according to claim 1, 2 or 3, wherein mercury is added to the thin tube portion.