JP2781094B2 - 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 the discharge gas does not contain mercury, 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. On both sides of the bulb 1 in the axial direction of the induction coil 2, a pair of starting auxiliary electrodes 3a, 3b facing each other are provided.
An electrodeless discharge lamp has been proposed in which start-up is relatively easy by disposing (see U.S. Pat. No. 4,489,589). 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 starting auxiliary electrodes 3 a and 3 b so that a preliminary discharge is generated. Is intended to make the starting easier.

[0007]

Since the distance between the starting auxiliary electrodes 3a and 3b is regulated by the distance between both ends of the bulb 1 in the axial direction of the induction coil 2, the distance between the starting auxiliary electrodes 3a and 3b is limited. If the distance cannot be reduced and the electric field strength required for the occurrence of the preliminary discharge is to be obtained, it is necessary to set a relatively high frequency voltage to be applied to the starting auxiliary electrodes 3a and 3b. As a result, there arises a problem that a high-frequency power supply for applying a high-frequency voltage to the starting auxiliary electrodes 3a and 3b is enlarged. In addition, it is necessary to apply a high-frequency voltage to the starting auxiliary electrodes 3a and 3b prior to applying a high-frequency current to the induction coil 2, and it is necessary to control the timing, resulting in a complicated power supply. .

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrodeless discharge lamp which can be easily started only by applying a high-frequency current to an induction coil.

[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. In 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 the bulb, the bulb is a toroidal tube. The winding of the induction coil is wound along the tube axis direction of the valve, and a starting auxiliary member made of a conductor is disposed all around the peripheral surface surrounding the center hole of the valve. It is.

[0010]

According to the above construction, the valve is a toroidal tube, and the winding of the induction coil extends in the direction of the tube axis of the valve.
When a high-frequency current is applied to the induction coil, an induction electric field can be formed in the bulb, which is a toroidal tube. Here, since the starting auxiliary member made of a conductor is disposed on the peripheral surface surrounding the center hole of the valve, the electric field strength of the induction electric field generated by the induction coil is closer to the inner peripheral side of the valve closer to the starting auxiliary member. Since it becomes larger than the outer peripheral side, the streamer-like discharge generated when a high-frequency current is supplied to the induction coil develops along the inner peripheral surface of the bulb. As a result, compared to the case where the streamer-like discharge develops on the outer peripheral side of the bulb, the streamer-like discharge becomes a loop in a short path, and shifts to an annular discharge in a short time. In other words, the streamer-like discharge generated by the induced electric field can form a loop in a short path even when the induction coil is only energized but not the other members. As a result, starting becomes easier.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a bulb 1 is formed as a toroidal hermetic tube made of a transparent material such as quartz glass. Xenon gas of, for example, 100 Torr is sealed in the bulb 1 as a discharge gas. As the discharge gas, in addition to a rare gas such as a xenon gas, a luminescent substance such as a metal or a metal halide or a mixture of a rare gas and a luminescent substance can be sealed. The winding of the induction coil 2 is wound around the outside of the valve 1 along the tube axis direction . Here, the induction coil 2 is wound three turns, but the number of turns is not particularly limited and is one.
It only needs to be wound for at least one turn. A starting auxiliary member 3 made of a conductive material is provided on the entire peripheral surface of the center hole inside the valve 1. Various materials such as a metal foil, a conductive paint, and a transparent conductive film can be used as the start-up assisting member 3. If a transparent conductive film is used, the light output near the center of the bulb 1 will not be blocked, so that the area of the light emitting surface can be increased.

An induction coil 2 is a high frequency power supply (not shown)
To generate a high-frequency magnetic field around it, and the high-frequency magnetic field acts on the discharge gas inside the bulb 1 to generate an annular discharge, thereby exciting the discharge gas to emit light. In other words, cause induction electric field in the high-frequency magnetic field of the valve 1, this induced electric field is the discharge plasma generated in the bulb 1 is maintained. The high-frequency power supply includes a high-frequency generator that outputs a high frequency, an amplifying unit that power-amplifies the output of the high-frequency generator, and a matching unit that matches impedance.

In order to turn on the electrodeless discharge lamp configured as described above, a high-frequency current must be supplied to the induction coil 2 from a high-frequency power supply. occurs, so that the induction field interlinked to the high frequency magnetic field occurs in the valve 1. This induced electric field is formed along the conduit of the bulb 1. When the induced electric field is generated, a part of the discharge gas is ionized, and FIG.
As shown in FIG. 1, a streamer-like discharge S occurs. story
The mast-like discharge S develops along a portion where the electric field intensity is large. Here, since the inside of the valve 1 start-up aid member 3 of the conductor is disposed, the inner peripheral side of the valve 1 is larger field strength than the outer circumferential side, stream as shown in FIG. 2 (b)
The arc discharge S develops along the inner peripheral side of the bulb 1. Streamer-like discharge as in this manner FIG. 2 (c)
When the electricity S has a loop shape, an induced current starts to flow, and shifts to an annular discharge as shown in FIG.

By the way, in the case provided with no start-up auxiliary member 3, because field strength than the inner circumferential side towards the outer peripheral side closer to the induction coil 2 in the internal space of the valve 1 is large, streamer-like discharge S in FIG. 3 As shown in the figure, the gas flows along the outer peripheral side in the bulb 1. Therefore, focusing on the streamer-like discharge S, the starting auxiliary member 3
The path length of the loop is longer when the loop is provided than when the loop is not provided. That is, the supply amount of energy required to reach the annular discharge is significantly smaller when the starting assisting member 3 is provided, and the starting is facilitated by providing the starting assisting member 3.

In the above embodiment, the sectional shape parallel to the axial direction of the bulb 1 is circular, but may be other shapes such as semicircular and rectangular.

[0016]

As described above, according to the present invention, the valve is a toroidal tube and the induction coil is in the axial direction of the valve.
Since the coil is wound along the direction, when a high-frequency current is applied to the induction coil, an induction electric field is formed in the bulb, which is a toroidal tube. In addition, since the starting auxiliary member made of a conductive material is disposed on the peripheral surface surrounding the center hole of the valve, the electric field strength of the induction electric field generated by the induction coil is larger on the inner peripheral side of the valve near the starting auxiliary member. The streamer-like discharge that occurs when a high-frequency current flows through the induction coil develops along the inner circumferential surface of the bulb. As a result, compared to the case where the streamer-like discharge develops on the outer peripheral side of the bulb, the streamer-like discharge becomes a loop in a short path and shifts to the annular discharge in a short time. The streamer-like discharge generated by the induced electric field can form a loop in a short path despite the fact that the other members are not energized, which facilitates the transition to annular discharge and facilitates starting. To play.

[Brief description of the drawings]

1A and 1B show an embodiment, wherein FIG. 1A is a plan view, FIG. 1B is a side view, and FIG. 1C is a sectional view.

FIG. 2 is an operation explanatory diagram showing a starting process in the embodiment.

FIG. 3 is an operation explanatory view showing a starting process of a comparative example in which no starting assist member is provided.

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

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Valve 2 Induction coil 3 Starting auxiliary member

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shingo Higashizaka 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. References JP-A-5-190154 (JP, A) JP-A-64-65746 (JP, A) JP-A-1-159356 (JP, U) Patent 2731651 (JP, B2) (58) Fields investigated (Int) .Cl. ⁶ , 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 applying a field to a discharge gas sealed in a bulb, the bulb is a toroidal tube, and the winding of an induction coil extends along the tube axis of the bulb. wound Te, electrodeless discharge lamp in the circumferential surface surrounding a central hole of the valve, characterized in that starting aid member made of a conductive material over the entire circumference is disposed.