JPH05166494A - Electrode-less discharge lamp - Google Patents

Abstract

PURPOSE:To provide an electrode-less discharge lamp which can be started using a relatively small-sized high frequency power source. CONSTITUTION:An induction coil 2 is wound around a bulb 1 made of a light transmission material. A single-pole auxiliary electrode 3 is provided around an outer side face of the bulb so as to be electrostatically coupled to an internal space of the bulb 1. As regards the axial direction of the induction coil 2, the position of the auxiliary electrode 3 is set within the width of the induction coil 2. As regards the radial direction of the induction coil 2, the position of the auxiliary electrode 3 is set to be remotest from a current supply end to the induction coil 2. If a high frequency voltage is applied to the auxiliary electrode 3, a preliminary discharge which is restrained only at one end takes place in the bulb 1. If, thereafter, a high frequency current is passed through the induction coil 2, annular discharge occurs with the result that a discharge gas is excited to generate light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention does not have an electrode inside the bulb, and a high-frequency electromagnetic field is applied to the discharge gas sealed in the bulb from the outside of the bulb to generate an annular discharge in the bulb. The present invention relates to an electrodeless discharge lamp in which 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 discharge gas sealed in a bulb is subjected to a high-frequency electromagnetic field to cause an annular discharge in the bulb to excite and discharge the discharge gas. 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 an electrodeless discharge lamp, as shown in FIG. 5, a bulb-shaped bulb 1 surrounding an induction coil 2 is provided, and a high frequency current is supplied to the induction coil 2 and enclosed in the bulb 1. There is a method in which a high-frequency magnetic field is applied to the generated discharge gas to excite the discharge gas to cause it to emit light (Japanese Patent Laid-Open No. 57-78766). A discharge gas containing mercury vapor is used, and the discharge gas emits light when excited by the mercury vapor.

By the way, the magnetic field formed around the air-core coil used as the induction coil 2 is
However, since the high-frequency magnetic field inside the induction coil 2 does not act on the discharge gas in the above configuration, there is a problem of low efficiency. 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, and a high frequency wave inside the induction coil 2 is provided. An electrodeless discharge lamp in which a magnetic field is caused to act on the discharge gas has been considered. In this configuration, since the high-frequency magnetic field is applied to the discharge gas inside the induction coil 2, the efficiency is higher than that of the configuration of FIG.

As the discharge gas of these electrodeless discharge lamps, a mixed gas of a light emitting substance such as mercury vapor and a rare gas is generally used. When the discharge gas containing mercury is used, the initial starting becomes relatively easy, but there is a problem that the restarting is difficult. Moreover, since the vapor pressure of mercury changes exponentially as the temperature rises, it is difficult to match the induction coil 2 with a high-frequency power source for supplying a high-frequency current.
If the alignment cannot be achieved, there is a problem that the lights cannot be lit stably because of disappearing. On the other hand, if mercury is not contained in the discharge gas, matching can be easily achieved, but initial starting becomes difficult. If a high voltage is applied to the induction coil, it can be forcibly started, but a high-frequency power source that can output a high voltage is required, which causes a problem that the high-frequency power source as a lighting circuit becomes large. That is, the size of the electrodeless discharge lamp including the electrodeless discharge lamp and the high frequency power source is increased.

In order to solve the above-mentioned problems, as shown in FIG. 7, the winding of the induction coil 2 is wound around the outer periphery of the valve 1 so that the high frequency magnetic field is effectively applied to the discharge gas, and 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 the starting is relatively easy (US Patent No. 4,
894,589, U.S. Pat. No. 4,902,937
issue). In this electrodeless discharge lamp, a high-frequency voltage is applied between the auxiliary electrodes 3a and 3b before the high-frequency current is applied to the induction coil 2 so that the preliminary discharge is performed. In addition, the starting is facilitated by supplying a high frequency current to the induction coil 2.

[0007]

By the way, in the above structure, since the pair of auxiliary electrodes 3a and 3b are provided outside the valve 1, it is not possible to make the distance between the auxiliary electrodes 3a and 3b smaller than the thickness of the valve 1. Can not. Therefore, in order to generate the preliminary discharge, a relatively high voltage has to be applied between both auxiliary electrodes 3a and 3b, and there is a problem that the power supply cannot be downsized sufficiently. On the other hand, when a high-frequency current is passed through 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, so that an annular discharge is generated and the discharge gas is excited to emit light. 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 restrained by the auxiliary electrodes 3a and 3b, the induction electric field is formed in the direction orthogonal to the induction electric field. And both ends are auxiliary electrodes 3a,
A considerable amount of energy is required to induce the preliminary discharge restricted by 3b in the direction along the induction electric field and transfer it to the annular discharge. That is, there is a problem that the high frequency power supply for supplying a high frequency current to the induction coil 2 cannot be sufficiently miniaturized.

An object of the present invention is to solve the above problems, and an object thereof is to provide an electrodeless discharge lamp which is easy to start and can be started by using a relatively small high frequency power source. Is.

[0009]

According to the present invention, in order to achieve the above object, a high-frequency current is supplied from a high-frequency power source to an induction coil in which a winding is wound around an outer circumference of a valve made of a light-transmissive material. In an electrodeless discharge lamp that excites the discharge gas by causing a high-frequency electromagnetic field formed inside the winding in the radial direction of the coil to act on the discharge gas sealed in the bulb, a high-frequency voltage is applied to the electrodeless discharge lamp. A single-pole auxiliary electrode that can generate a preliminary discharge in which only the part is restrained is placed 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 can be changed. The axial direction of the induction coil is within the width of the induction coil, and the radial direction of the induction coil is set at the position farthest from the feeding end to the induction coil.

[0010]

According to the above structure, the outer surface of the valve is electrostatically coupled to the inner space of the valve by a single-pole auxiliary electrode capable of generating a pre-discharge in the valve by applying a high frequency voltage. Since the auxiliary coil is provided, a preliminary discharge can be generated by the auxiliary electrode before a high-frequency current is passed through the induction coil to excite and discharge the discharge gas, so that the discharge can be easily started. Further, since the auxiliary electrode is a single pole and causes a preliminary discharge in which only one end is constrained, the other end of the preliminary discharge is a free end, and the high frequency magnetic field formed around the induction coil causes It is possible to make the energy required for inducing the preliminary discharge along the generated ring-shaped induction electric field 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, since the position of the auxiliary electrode is set at the part farthest from the feeding end to the induction coil in the radial direction of the induction coil, the result confirmed by the experiment shows that the electric field strength in the induction electric field is Since the free end of the preliminary discharge is located near the power supply end where the maximum discharge is achieved, the transition from the preliminary discharge to the annular discharge becomes easier. As described above, by disposing the unipolar auxiliary electrode in the above position,
The transition from pre-discharge to annular discharge has become much easier,
The startability is improved.

[0011]

【Example】

(Embodiment 1) As shown in FIG. 1, a bulb 1 is formed of a translucent material in an airtight cylindrical shape, and a discharge gas, for example, a xenon gas of 100 Torr is enclosed. 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 and may be one or more turns. A unipolar auxiliary electrode 3 is arranged in close contact with or close to the outer peripheral surface of the bulb 1 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, for example, made of copper foil.
It is formed as a circle of 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 in the position farthest from the feeding 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 source 4 to generate a high-frequency magnetic field, and the high-frequency magnetic field acts on the discharge gas inside the bulb 1 to cause an annular discharge, thereby causing a 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 source 5 via a connecting wire, and the auxiliary electrode 3
Pre-discharge is generated in the bulb 1 by the high frequency electric field generated around the. 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,
When enough electrons are supplied to maintain the discharge by repeating such a phenomenon, a streamer develops from the auxiliary electrode 3 and a preliminary discharge occurs in the vicinity of the auxiliary electrode 3. Since the auxiliary electrode 3 has a single pole, such a preliminary discharge is relatively free to move because one end is restricted by the auxiliary electrode 3 and the other end is a free end.

First high frequency power source 4 and second high frequency power source 5
Includes a high-frequency generator 4a including a high-frequency oscillator, an amplifier 4b for power-amplifying a high-frequency output, a matching unit 4c for impedance matching, and the like. Further, the second high frequency power supply 5 applies a high frequency voltage between the auxiliary electrode 3 and the ground. In order to turn on the electrodeless discharge lamp configured as described above, first, the second high frequency power source 5 is applied to the auxiliary electrode 3.
A high-frequency voltage is applied to generate a preliminary discharge. The preliminary discharge can move freely because one end is restrained by the auxiliary electrode 3 and the other end is relatively free. Therefore, when the induction coil 2 is energized from the first high-frequency power source 4 in the state where the preliminary discharge has occurred, a high-frequency magnetic field interlinking with the induction coil 2 is generated, and an induction electric field interlinking with this 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 as shown in FIG. As shown, an annular discharge 6 will occur. Here, the preliminary discharge is guided to a portion of the induced electric field where the electric field strength is the largest.

That is, when the auxiliary electrodes 3 were provided at the positions indicated by A to F in FIG. 3, an experiment was conducted on the power supply required to shift from the preliminary discharge to the annular discharge, and the results shown in FIG. 4 were obtained. Obtained. According to the result of this experiment, the induction coil 2 is assisted at a position that is within the width of the induction coil 2 in the axial direction and is farthest from the feeding end of the induction coil 2 in the radial direction of the induction coil 2 (that is, position C). It has been found that when the electrode 3 is provided, the power supply 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 the region where the electric field strength is large, and when the auxiliary electrode 3 is provided at the position C, the free end of the preliminary discharge is the region of the annular discharge at the shortest distance. 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 due to 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. Here, since the preliminary discharge by the auxiliary electrode 3 is changed 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 an extent necessary for maintaining lighting, and the power supply can be downsized. For example, the auxiliary electrode 3
In the case of forming an annular discharge only by the induction coil 2 without providing a coil, the voltage applied between both ends of the induction coil 2 (0-
If P) is required to be about 1500 V or higher, it becomes possible to start the annular discharge at about 600 V by providing the auxiliary electrode 3. As a result, the power supply can be downsized and can be easily started.

Here, as the discharge gas, another single gas or a mixed gas may be used instead of the 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 the cylindrical shape, but may be any shape other than the spherical shape.

(Embodiment 2) In this embodiment, a rare gas mixed with a metal or a metal halide is used as the discharge gas. The metal and the metal halide may be a single substance or a mixture. For example, NaI-TlI-InI or the like is mixed with a rare gas. When the discharge gas mixed with such a substance is used, excited light emission of the rare gas occurs immediately after the annular discharge occurs, and if the rare gas is xenon, white light is generated. After that, the vapor pressure of the mixed substance increases, and the emission color due to the mixed substance occurs. As described above, a high emission brightness can be obtained from the initial state, and a high-luminance electrodeless discharge lamp having a good rise can be provided. The configuration is the same as in Example 1 except for the components of the discharge gas. The substance mixed with the rare gas as a component of the discharge gas is appropriately set according to efficiency and light color.

[0019]

As described above, according to the present invention, a unipolar auxiliary electrode capable of generating a preliminary discharge in a bulb when a high frequency voltage is applied is electrostatically coupled to the inner space of the bulb. Since it is arranged on the outer surface of the auxiliary coil, a preliminary discharge can be generated by the auxiliary electrode before a high-frequency current is passed through the induction coil to excite and discharge the discharge gas, which facilitates starting. There are advantages. Further, since the auxiliary electrode is a single pole and causes a preliminary discharge in which only one end is constrained, the other end of the preliminary discharge is a free end, and the auxiliary electrode is formed by the 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 the transition to the annular discharge becomes small. Moreover, since the position of the auxiliary electrode is set at the position farthest from the feeding end to the induction coil in the radial direction of the induction coil, the experimentally confirmed result shows that the electric field of the induction field is Since the free end of the preliminary discharge is located near the power supply end where the intensity is maximized, the transition from the preliminary discharge to the annular discharge becomes easier. In short, as a result of disposing the unipolar auxiliary electrode at the above-mentioned position, the transition from the preliminary discharge to the annular discharge becomes very easy and there is an advantage that the startability is improved. The effect is that the power supply can be downsized and the overall size can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment.

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

FIG. 3 is a diagram showing an arrangement position of an auxiliary electrode that was tested when determining an optimum arrangement position of an auxiliary electrode.

FIG. 4 is a diagram showing supply power required for transition to annular discharge for each position of the auxiliary electrode shown in FIG.

FIG. 5 is a cross-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]

 1 Valve 2 Induction Coil 3 Auxiliary Electrode 4 First High Frequency Power Supply 5 Second High Frequency Power Supply

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shin Ogawa, 1048, Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Works Co., Ltd. (72) Inventor, Shingo Tosaka, 1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.

Claims (1)

[Claims] 1. A high-frequency electromagnetic wave formed inside a winding in the radial direction of the induction coil by passing a high-frequency current from a high-frequency power source to an induction coil having a winding wound around an outer circumference of a valve made of a translucent material. In an electrodeless discharge lamp that excites and emits discharge gas by causing a field to act on the discharge gas sealed in the bulb, it is possible to generate a preliminary discharge in which a high frequency voltage is applied and only one end is constrained. A single-pole auxiliary electrode that can be placed on the outer surface of the valve so as to be electrostatically coupled to the internal space of the valve, and the position of the auxiliary electrode is within the width of the induction coil in the axial direction of the induction coil. The electrodeless discharge lamp is characterized in that the radial direction of the induction coil is set at a position farthest from the power supply end to the induction coil.