JP3017583B2 - 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. 5, 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 magnetic field is applied to the discharged discharge gas to excite the discharge gas to emit light (Japanese Patent 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. 6, a spherical bulb 1 made of quartz glass or the like and an induction coil 2 having a winding wound around the outer periphery of 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 as compared with 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. 7, a winding of an induction coil 2 is wound around the outer circumference 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, a pre-discharge is performed by applying a high-frequency voltage between the auxiliary electrodes 3a and 3b prior to the application of the high-frequency current to the induction coil 2, so that the pre-discharge occurs. Then, a high-frequency current is supplied to the induction coil 2 to facilitate starting.

[0007]

In the above arrangement, a pair of auxiliary electrodes 3a and 3b are provided outside the bulb 1. Therefore, it is impossible to make the distance between the auxiliary electrodes 3a and 3b smaller than the thickness of the bulb 1. Can not. Therefore, in order to generate the preliminary discharge, a relatively high voltage must be applied between the auxiliary electrodes 3a and 3b, and there is a problem that the power source cannot be sufficiently reduced in size. On the other hand, when a high-frequency current is applied to the induction coil 2, a high-frequency magnetic field is generated, and a ring-shaped induction electric field is generated so as to interlink with the high-frequency magnetic field, thereby generating an annular discharge and exciting and discharging the discharge gas. Here, the induction electric field is formed along the winding direction of the induction coil 2, and since both ends of the preliminary discharge are restricted by the auxiliary electrodes 3a and 3b, the induction electric field is formed in a direction orthogonal to the induction electric field. And both ends are auxiliary electrodes 3a,
To induce the preliminary discharge confined by 3b in the direction along the induced electric field to shift to the annular discharge, considerably large energy is required. That is, there is a problem that a high-frequency power supply that supplies a high-frequency current to the induction coil 2 cannot be sufficiently reduced in size.

An object of the present invention is to provide an electrodeless discharge lamp which is easy to start and can be started using a relatively small high-frequency power supply. It is.

[0009]

According to the present invention, in order to achieve the above-mentioned object, a high-frequency current is supplied from a high-frequency power supply to an induction coil in which a winding is wound around the outer periphery of a valve made of a light-transmitting material. A high-frequency voltage is applied to one end of an electrodeless discharge lamp that excites and emits a discharge gas by applying a high-frequency electromagnetic field formed inside a winding in a radial direction of a coil to a discharge gas sealed in a bulb. A single-pole auxiliary electrode capable of generating a preliminary discharge in which only a portion is restricted in the bulb is disposed on the outer surface of the bulb so as to be electrostatically coupled to the internal space of the bulb, and the position of the auxiliary electrode is adjusted. The axial direction of the induction coil is set within the width of the induction coil, and the radial direction of the induction coil is set at a position farthest from the power supply end to the induction coil.

[0010]

According to the above construction, a single-pole auxiliary electrode capable of generating a preliminary discharge in the bulb when a high-frequency voltage is applied is provided on the outer surface of the bulb so as to be electrostatically coupled to the interior space of the bulb. Since the auxiliary electrode is provided, a preliminary discharge can be generated by the auxiliary electrode before the high-frequency current is supplied to the induction coil to excite and discharge the discharge gas, so that the starting can be easily started. In addition, since the auxiliary electrode is monopolar and generates a preliminary discharge in which only one end is restrained, the other end of the preliminary discharge becomes a free end, and is generated by a high-frequency magnetic field formed around the induction coil. The energy required to induce the preliminary discharge along the generated ring-shaped induction electric field can be made relatively small. Furthermore, since the position of the auxiliary electrode is within the width of the induction coil in the axial direction of the induction coil, the position where the annular discharge is generated by the induction coil and the position where the preliminary discharge is generated are close to each other. The energy required for transition to the annular discharge is reduced. Moreover, the position of the auxiliary electrode is set at a position farthest from the feeding end to the induction coil in the radial direction of the induction coil. Since the free end of the pre-discharge is located near the feeding end at which the maximum value is obtained, the transition from the pre-discharge to the annular discharge is further facilitated. As described above, by disposing the monopolar auxiliary electrode at the above position,
The transition from the preliminary discharge to the annular discharge becomes very easy,
Startability is improved.

[0011]

【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 three 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 has a diameter of 6
mm. The position of the auxiliary electrode 3 is set within the width of the induction coil 2 in the axial direction of the induction coil 2 and farthest from the power supply end to the induction coil 2 in the radial direction of the induction coil 2.

The induction coil 2 is supplied with a high-frequency current from the first high-frequency power supply 4 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 5 via a connection line.
A preliminary discharge is generated in the bulb 1 by a high-frequency electric field generated around the bulb 1. That is, the electrons accelerated by the high-frequency electric field generated around the auxiliary electrode 3 collide with the atoms of the discharge gas and ionize them.
When sufficient phenomena are supplied to maintain the discharge by repeating such a phenomenon, the streamer advances from the auxiliary electrode 3 and a preliminary discharge occurs near the auxiliary electrode 3. 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.

A first high-frequency power supply 4 and a second high-frequency power supply 5
Includes a high-frequency generator 4a composed of a high-frequency oscillator, an amplifier 4b that amplifies power of a high-frequency output, and a matching unit 4c that matches impedance. The second high-frequency power supply 5 applies a high-frequency voltage between the auxiliary electrode 3 and the ground. To turn on the electrodeless discharge lamp configured as described above, first, the second high-frequency power source 5 is connected to the auxiliary electrode 3.
To apply a high-frequency voltage to generate a preliminary discharge. The preliminary discharge can move freely since one end is restricted by the auxiliary electrode 3 but the other end is relatively free. Then, when the induction coil 2 is energized from the first high-frequency power supply 4 in a 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 preliminary discharge generated by the auxiliary electrode 3 is induced at the free end along the induction electric field generated by the induction coil 2, as shown in FIG. As shown, an annular discharge 6 will occur. Here, the preliminary discharge is guided to a portion where the electric field strength is highest in the induced electric field.

That is, for the case where the auxiliary electrodes 3 are provided at the positions indicated by A to F in FIG. 3, the results of experiments on the supply power required to shift from the preliminary discharge to the annular discharge are shown. Obtained. According to this experimental result, the position of the induction coil 2 in the axial direction is within the width of the induction coil 2, and in the radial direction of the induction coil 2, the position is set to the position farthest from the feeding end of the induction coil 2 (ie, position C) It has been found that when the electrode 3 is provided, the supply power required to shift to the annular discharge is minimized. This is due to the property that the free end of the preliminary discharge is guided to a region where the electric field intensity is large. When the auxiliary electrode 3 is provided at the position C, the free end of the preliminary discharge is shortest in the annular discharge region. And the energy supplied from the induction coil 2 is most easily absorbed. In short, the energy required for the transition from the preliminary discharge to the annular discharge is the smallest.

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 shifting to the lighting state, the auxiliary electrode 3
The light emitting state is maintained without applying a high frequency voltage to the light emitting element. Here, by shifting from the preliminary discharge by the auxiliary electrode 3 to the annular discharge by the induction coil 2, the electric power supplied to the induction coil 2 to start the annular discharge can be reduced. That is, the power supplied from the first high-frequency power supply 4 may be set to a level necessary for maintaining lighting, and the power supply can be reduced in size. For example, the auxiliary electrode 3
When the annular discharge is formed only by the induction coil 2 without providing the voltage, the voltage applied between both ends of the induction coil 2 (0-
If it is necessary to make P) about 1500 V or more, the provision of the auxiliary electrode 3 makes it possible to start the annular discharge at about 600 V. As a result, the power supply can be reduced in size and can be easily started.

Here, as the discharge gas, other single gas or mixed gas may be used instead of xenon gas, and the gas pressure is not limited to 100 Torr. 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 in which such a substance is mixed is used, excitation light emission of the rare gas occurs immediately after the annular discharge occurs. 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. The substance to be mixed with the rare gas as a component of the discharge gas is appropriately set according to the efficiency and light color.

[0019]

According to the present invention, as described above, a single-pole auxiliary electrode capable of generating a preliminary discharge in a bulb when a high-frequency voltage is applied is electrostatically coupled to the interior space of the bulb. Since it is arranged on the outer surface of the device, a preliminary discharge can be generated by the auxiliary electrode before the high-frequency current is applied to the induction coil to excite and emit the discharge gas, and it can be easily started. There are advantages. In addition, since the auxiliary electrode is monopolar and generates a preliminary discharge in which only one end is restrained, the other end of the preliminary discharge becomes a free end, and is generated by a high-frequency magnetic field formed around the induction coil. The energy required to induce the preliminary discharge along the induced electric field can be made relatively small. Furthermore, since the position of the auxiliary electrode is within the width of the induction coil in the axial direction of the induction coil, the position where the annular discharge is generated by the induction coil and the position where the preliminary discharge is generated are close to each other. There is an advantage that the energy required for transition to the annular discharge is reduced. In addition, since the position of the auxiliary electrode is set at a position farthest from the power supply end to the induction coil in the radial direction of the induction coil, according to the result confirmed experimentally, By locating the free end of the preliminary discharge near the power supply end where the intensity becomes maximum, the transition from the preliminary discharge to the annular discharge is further facilitated. In short, as a result of disposing the monopolar auxiliary electrode at the above position, the transition from the preliminary discharge to the annular discharge becomes very easy, and there is an advantage that the startability is improved. This has the effect of reducing the size of the power supply, which leads to the overall reduction in size.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment.

FIG. 2 is a perspective view showing a lighting state of the embodiment.

FIG. 3 is a diagram showing the arrangement positions of auxiliary electrodes that were tested when determining the optimal arrangement positions of the auxiliary electrodes.

FIG. 4 is a diagram showing power supply required for shifting to an annular discharge at each position of an auxiliary electrode shown in FIG. 3;

FIG. 5 is a sectional view showing a conventional electrodeless discharge lamp.

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

FIG. 7 is a side view showing still another conventional electrodeless discharge lamp.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Valve 2 Induction coil 3 Auxiliary electrode 4 1st high frequency power supply 5 2nd high frequency power supply

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shin Shinagawa, Kazuma, Kazuma, Osaka 1048, Matsushita Electric Works, Ltd. References JP-A-4-229549 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 65/04

Claims (1)

(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, a high-frequency voltage is applied to generate a preliminary discharge in which only one end is restricted in the bulb. A possible unipolar auxiliary electrode is disposed on the outer surface of the bulb so as to be electrostatically coupled to the internal space of the bulb, and the position of the auxiliary electrode is within the width of the induction coil in the axial direction of the induction coil. An electrodeless discharge lamp characterized in that the radial direction of the induction coil is set at a position farthest from a power supply end to the induction coil.