JP3017581B2 - Electrodeless lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method in which a high-frequency electromagnetic field is applied to a discharge gas sealed in a bulb from outside the bulb without an electrode inside the bulb to generate an annular discharge in the bulb. The present invention relates to an electrodeless discharge lamp in which a discharge gas is excited to emit light.

[0002]

2. Description of the Related Art Conventionally, an electrodeless discharge lamp has been known in which a high-frequency electromagnetic field is applied to a discharge gas sealed in a bulb to generate an annular discharge in the bulb to excite the discharge gas to emit light. ing. Since this type of electrodeless discharge lamp has features such as small size, high output, and long life, it has been researched and developed in various places, and various uses as a high output point light source are considered.

As shown in FIG. 4, an electrodeless discharge lamp is provided with a bulb-shaped bulb 1 surrounding an induction coil 2, and a high-frequency current is applied to the induction coil 2 to be enclosed in the bulb 1. There is one in which a high-frequency electromagnetic field is applied to the discharged discharge gas to excite the discharge gas to emit light (Japanese Patent Application Laid-Open No. 57-78766). As the discharge gas, a gas containing mercury vapor is used, and emits light by excitation of the mercury vapor.

The magnetic field formed around the air-core coil used as the induction coil 2 is
However, the above configuration has a problem that the efficiency is low because the high frequency magnetic field inside the induction coil 2 does not act on the discharge gas. On the other hand, as shown in FIG. 5, a spherical bulb 1 made of quartz glass or the like, and an induction coil 2 having a winding wound around the bulb 1 are provided. Electrodeless discharge lamps in which a magnetic field acts on a discharge gas have been considered. In this configuration, since a high-frequency magnetic field is applied to the discharge gas inside the induction coil 2, the efficiency is higher than that in the configuration of FIG.

As a discharge gas of these electrodeless discharge lamps, a mixed gas of a luminescent substance such as mercury vapor and a rare gas is generally used. When a discharge gas containing mercury is used, the initial start is relatively easy, but there is a problem that restart is difficult. In addition, since the vapor pressure of mercury changes exponentially with an increase in temperature, it is difficult to match with a high-frequency power supply for supplying a high-frequency current to the induction coil 2.
If the matching is not achieved, there is a problem that the light cannot be turned on stably due to the disappearance or the like. On the other hand, if mercury is not contained in the discharge gas, the alignment becomes easier, but the initial startup becomes difficult. If a high voltage is applied to the induction coil, it is possible to forcibly start the induction coil. However, a high-frequency power supply capable of outputting a high voltage is required, which causes a problem that the high-frequency power supply as a lighting circuit becomes large. That is, an electrodeless discharge lamp including an electrodeless discharge lamp and a high-frequency power supply is increased in size.

In order to solve the above-mentioned problem, as shown in FIG. 6, a winding of an induction coil 2 is wound around the outer periphery of a bulb 1 to make a high-frequency magnetic field act on a discharge gas efficiently. An electrodeless discharge lamp has been proposed in which a pair of auxiliary electrodes 3a and 3b facing each other are arranged on both sides of the bulb 1 in the axial direction of the induction coil 2 so that starting is relatively easy (US). Patent 4,
No. 894,589, U.S. Pat. No. 4,902,937.
issue). In this electrodeless discharge lamp, prior to the application of the high-frequency current to the induction coil 2, a high-frequency voltage is applied between the auxiliary electrodes 3a and 3b so that the preliminary discharge is performed. Then, a high-frequency current is supplied to the induction coil 2 to facilitate starting.

[0007]

When a high frequency current is applied to the induction coil 2 to light it, a ring-shaped induction electric field is generated in the bulb 1 by the high frequency magnetic field, and the discharge gas is ionized by the induction electric field. Thus, an annular discharge occurs. Since the induction electric field links with the high-frequency magnetic field, a discharge path is formed along the winding direction of the winding of the induction coil 2 at the time of lighting. On the other hand, since the preliminary discharge occurs between the auxiliary electrodes 3a and 3b in a direction perpendicular to the induced electric field and both ends are restrained by the auxiliary electrodes 3a and 3b, the preliminary discharge is shifted to the annular discharge. Has the problem of requiring relatively large amounts of energy. That is, even if the pair of auxiliary electrodes 3a and 3b are provided, there is a problem that starting is not so easy.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrodeless discharge lamp which is easy to start, does not require a large high-frequency power source, and can be formed in a relatively small size. It is.

[0009]

According to the first aspect of the present invention, a high-frequency current is supplied from a high-frequency power supply to an induction coil having a winding wound around an outer periphery of a valve made of a light-transmitting material, and the current is applied in a radial direction of the induction coil. In an electrodeless discharge lamp that excites and emits a discharge gas by applying a high-frequency electromagnetic field formed inside a winding to a discharge gas sealed in the bulb, the bulb has a width of the induction coil in the axial direction of the induction coil. A ridge that protrudes so as to form a concave groove on the inner peripheral surface of the valve over the entire circumference in the winding direction of the induction coil, and is formed around the induction coil in the radial direction of the induction coil. The concave groove is located at a position where the electric field intensity of the ring-shaped induction electric field generated by the high-frequency magnetic field is substantially maximized.

According to the second aspect of the present invention, at least one auxiliary electrode capable of causing a preliminary discharge in which only one end is restricted by application of a high-frequency voltage in the bulb is provided in the interior space of the bulb by electrostatic. Is disposed outside the valve so as to be coupled to the valve.

[0011]

According to the structure of the first aspect, the valve forms a concave groove on the inner peripheral surface of the valve over the entire circumference in the winding direction of the induction coil within the width of the induction coil in the axial direction of the induction coil. Since the protruding ridge is provided in the radial direction of the induction coil, the concave groove is located at a position where the electric field intensity of the induction electric field generated by the high frequency magnetic field formed around the induction coil is almost maximum, Since an induced electric field having a large electric field strength can be applied to the discharge gas, the input / output efficiency is increased, and consequently, the starting can be started with lower power as compared with a case where no ridge is provided. . That is, the high-frequency power supply can be reduced in size, which leads to the overall reduction in size.

According to the second aspect of the present invention, at least one auxiliary electrode for generating a preliminary discharge in which only one end is restrained is disposed so as to be electrostatically coupled to the internal space of the bulb. By shifting to the annular discharge after the preliminary discharge, the starting can be more easily performed as compared with the configuration of the first aspect. Further, in the preliminary discharge, only one end is restrained by the auxiliary electrode, and compared to a case where a pair of auxiliary electrodes are arranged to face each other and both ends of the preliminary discharge are restrained,
The energy required for starting is reduced.

[0013]

【Example】

(Embodiment 1) As shown in FIG. 1, a bulb 1 is formed in a hermetically sealed cylindrical shape with a light-transmitting material, and is filled with, for example, 100 Torr xenon gas as a discharge gas. The winding of the induction coil 2 is wound around the outer peripheral surface of the valve 1. Here, the induction coil 2 is wound four turns, but the number of turns is not particularly limited as long as it is wound one or more turns. A single-pole auxiliary electrode 3 is arranged on the outer peripheral surface of the bulb 1 in close contact or close proximity, so that the auxiliary electrode 3 can be electrostatically coupled to the internal space of the bulb 1. The auxiliary electrode 3 is formed, for example, as a square having a side of 5 mm by a metal foil. Fig. 2
As shown in FIG. 1, a ridge 1b is provided on the inner peripheral surface of the bulb 1 so as to protrude outwardly around the entire peripheral wall in the vicinity of the central portion in the axial direction to form a concave groove 1a. The positional relationship between the ridge 1b and the induction coil 2 is set such that the bottom surface of the concave groove 1a is located near the inner peripheral surface of the induction coil 2. That is, the induction coil 2 is wound apart from the valve 1.

The induction coil 2 is supplied with a high-frequency current from the first high-frequency power supply 4a to generate a high-frequency magnetic field. The high-frequency magnetic field acts on a discharge gas inside the bulb 1 to generate an annular discharge. The gas is excited to emit light. That is, a ring-shaped induction electric field is generated in the bulb 1 by the high-frequency magnetic field, and the discharge gas in the bulb 1 is ionized by the induction electric field to generate an annular discharge.

A high-frequency voltage is applied to the auxiliary electrode 3 from a second high-frequency power supply 4b via a connection line, and a preliminary discharge is generated in the bulb 1 by a high-frequency electric field generated around the auxiliary electrode 3. It has become. In other words, the electrons accelerated by the high-frequency electric field generated around the auxiliary electrode 3 collide with the atoms of the discharge gas and are ionized, whereby the streamer advances from the auxiliary electrode 3 and a preliminary discharge occurs near the auxiliary electrode 3. It is. In such a preliminary discharge, since the auxiliary electrode 3 is monopolar, one end is restricted by the auxiliary electrode 3 but the other end is a free end, and can move relatively freely.

The first high-frequency power supply 4a and the second high-frequency power supply 4b are provided with a high-frequency generator comprising a high-frequency oscillator, an amplifier for power-amplifying the high-frequency output, and a matching section for matching the impedance. The second high-frequency power supply 4b applies a high-frequency voltage between the auxiliary electrode 3 and the ground. A parallel resonance circuit including an inductance L and a capacitor C is connected to the output of the second high-frequency power supply 4b. The resonance frequency f of the parallel resonance circuit is f = 1 / 2π (L
C) A ^1/2, the larger the smaller is the inductance L of the capacitance of the capacitor C, it is possible to increase the voltage across the inductance L. In a resonance state, the voltage across the inductance L is ideally infinite, but there is actually a loss due to the resistance component, so the output voltage of the second high frequency power supply 4b is determined by the magnitude of the inductance L.

To turn on the electrodeless discharge lamp configured as described above, first, the second high-frequency power source 4 is connected to the auxiliary electrode 3.
A pre-discharge is generated by applying a high-frequency voltage from b. The preliminary discharge gradually extends from the auxiliary electrode 3 and reaches almost the opposite side of the bulb 1. The preliminary discharge generated at this time can move freely since one end is restricted by the auxiliary electrode 3 but the other end is relatively free. When the induction coil 2 is energized from the first high-frequency power supply 4a in the state where the preliminary discharge has occurred, a high-frequency magnetic field interlinking the induction coil 2 is generated, and an induction electric field interlinking the high-frequency magnetic field is generated. Since this induction electric field is formed along the winding of the induction coil 2, the free end of the preliminary discharge generated by the auxiliary electrode 3 is induced along the induction electric field generated by the induction coil 2, and an annular discharge is generated. Will happen. Here, the preliminary discharge is guided to a portion where the electric field strength is highest in the induced electric field.

The electric field strength of the induced electric field is shown in FIG.
As shown in (the center of the induction coil 2 is the origin O), the intensity is strongest in the vicinity of the winding (the position shown by the broken line in FIG. 3), and becomes weaker as the distance from the winding in the radial direction of the induction coil 2 increases. Here, a concave groove 1 a is formed on the inner peripheral surface of the valve 1, and the bottom surface of the concave groove 1 a is closest to the induction coil 2 in the inner space of the valve 1 in the radial direction of the induction coil 2. In the internal space of the bulb 1, the electric field intensity of the induced electric field becomes maximum near the bottom surface of the concave groove 1a. Conversely, by protruding the ridge 1b so as to form the concave groove 1a in the internal space of the valve 1, a part of the internal space of the valve 1 can be brought close to the induction coil 2, The induction electric field can efficiently act on the discharge gas. As a result, the input / output efficiency increases.

When the transition from the preliminary discharge to the annular discharge is performed as described above, strong light emission is generated by the excitation of the discharge gas, and the light is turned on. After the transition to the lighting state, the light emitting state is maintained without applying a high frequency voltage to the preliminary discharge coil 3 and the auxiliary electrode 3. Here, the auxiliary electrode 3
, The power supplied to the induction coil 2 for starting the annular discharge can be reduced. That is, the power supplied from the first high-frequency power supply 4a may be set to an extent necessary for maintaining lighting, and the power supply can be reduced in size. For example, when an annular discharge is formed only by the induction coil 2 without providing the auxiliary electrode 3, if the applied voltage (0-P) between both ends of the induction coil 2 is about 1500 V or more, the auxiliary electrode By providing 3, 6
The annular discharge can be started at about 00V. This makes it easier to start and the power supply can be reduced in size.

If the induction coil 2 is wound closely to the outer peripheral surface of the bulb 1, the induced electric field can be efficiently applied to the discharge gas. When the discharge occurs, the heat of the discharge gas heats the induction coil 2 to a high temperature. When the induction coil 2 is heated in this way, the induction coil 2 is deformed or has an adverse effect such as oxidization of the surface, so that the life of the induction coil 2 is shortened. On the other hand, if the protrusion 1b is formed on the bulb 1 as described above, it is possible to secure the electric field intensity necessary for starting the annular discharge even when the induction coil 2 is not in close contact with the bulb 1. It is. As a result, the start-up is as easy as when the induction coil 2 is wound closely to the bulb 1, but the induction coil 2 is not adversely affected by heat during lighting.

Here, as the discharge gas, other single gas or mixed gas may be used instead of xenon gas. Further, the position, size, and shape of the auxiliary electrode are not particularly limited. Further, the valve 1 is not limited to a cylindrical shape, but may be any other than a spherical shape. (Embodiment 2) In this embodiment, a mixture of a rare gas and a metal or a metal halide is used as a discharge gas. The metal and the metal halide may be used alone or as a mixture. For example, NaI-TlI-InI or the like is mixed with a rare gas.

When a discharge gas containing such a substance is used, immediately after the ring discharge has occurred, excitation light emission of the rare gas is generated. If the rare gas is xenon, white light is generated. . Thereafter, the vapor pressure of the mixed substance increases, and the mixed substance emits light. As described above, high emission luminance can be obtained from the initial state, and a high-intensity electrodeless discharge lamp with good startup can be provided. Except for the components of the discharge gas, the configuration is the same as that of the first embodiment.

(Embodiment 3) In this embodiment, a means for generating a high voltage in the vicinity of the valve 1 is added to the structure of any of the first and second embodiments. For example, a means for generating a high voltage by applying an external impact force to the piezoelectric element is used. When a high voltage is generated in the vicinity of the bulb 1 when a high-frequency voltage is applied to the auxiliary electrode 3, ionization of the discharge gas becomes easy, and preliminary discharge easily occurs. Thereafter, in the same manner as in the first embodiment, it is possible to shift from the preliminary discharge to the annular discharge. This configuration is particularly effective when starting is difficult. Other configurations and operations are the same as those of the first embodiment.

[0024]

According to the first aspect of the present invention, the valve forms a concave groove on the inner peripheral surface of the valve over the entire circumference in the winding direction of the induction coil within the width of the induction coil in the axial direction of the induction coil. Since the protruding ridge is provided in the radial direction of the induction coil, the concave groove is located at a position where the electric field intensity of the induction electric field generated by the high frequency magnetic field formed around the induction coil is almost maximum, Since an induced electric field having a large electric field strength can be applied to the discharge gas, the input / output efficiency is increased, and consequently, the starting can be started with lower power as compared with a case where no ridge is provided. . That is, it is possible to reduce the size of the high-frequency power supply, which leads to an effect of reducing the overall size.

According to the second aspect of the present invention, at least one auxiliary electrode for generating a preliminary discharge in which only one end is restricted is disposed so as to be electrostatically coupled to the internal space of the bulb. By shifting to the annular discharge after the discharge, the start can be more easily performed as compared with the configuration of the first aspect. In addition, only one end of the preliminary discharge is restrained by the auxiliary electrode, and the energy required for starting is smaller than that in a case where a pair of auxiliary electrodes are arranged to face each other and both ends of the preliminary discharge are restricted. There is an advantage that it becomes smaller.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment.

FIG. 2 is a sectional view showing the first embodiment.

FIG. 3 is an explanatory diagram of an operation of the induction coil according to the first embodiment.

FIG. 4 is a sectional view showing a conventional electrodeless discharge lamp.

FIG. 5 is a side view showing another conventional electrodeless discharge lamp.

FIG. 6 is a side view showing still another conventional electrodeless discharge lamp.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 valve 1a groove 1b ridge 2 induction coil 3 auxiliary electrode 4a first high frequency power supply 4b second high frequency power supply

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shingo Higashizaka 1048 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. (72) Inventor Miki Kotani 1048 Kazuma Kazuma, Kadoma City, Osaka Matsushita Electric Works Co., Ltd. (56) References JP-A-4-229550 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 65/04

Claims (2)

(57) [Claims] 1. A high-frequency current is supplied from a high-frequency power supply to an induction coil having a winding wound around the bulb made of a light-transmitting material, and a high-frequency electromagnetic wave is formed inside the winding in the radial direction of the induction coil. In an electrodeless discharge lamp that excites and emits a discharge gas by causing a field to act on a discharge gas sealed in the bulb, the bulb is formed around the entire circumference of the induction coil in the winding direction within the width of the induction coil in the axial direction of the induction coil. A ridge that bulges to form a concave groove on the inner peripheral surface of the valve over the entire length of the valve, and a ring-shaped induction electric field generated by a high-frequency magnetic field formed around the induction coil in the radial direction of the induction coil. An electrodeless discharge lamp characterized in that a groove is located at a position where the electric field intensity is almost maximum. 2. An at least one auxiliary electrode capable of causing a preliminary discharge in which only a first end portion is restricted by application of a high-frequency voltage in a bulb is electrostatically coupled to an internal space of the bulb. 2. The electrodeless discharge lamp according to claim 1, wherein the discharge lamp is disposed outside the bulb.