JPH10125289A - Electrodeless fluorescent lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance starting characteristics in an electrodeless fluorescent lamp provided with a shield for preventing deterioration of the lamp lifetime. SOLUTION: The bulb 1 of the lamp is provided with a grooved cavity 2 and a cylindrical projecting tube 3 projecting from the bottom face of the grooved cavity 2 toward an opening side and being closed at the tip thereof. A phosphor layer 4 is formed on the inner face of the bulb 1. Discharging gas is enclosed inside the bulb 1. An induction coil 5 is inserted into the grooved cavity 2, and is constituted of a coil portion 5a, a leading-out wire 5b on a high voltage side and a leading-out wire 5c on a ground side. The coil portion 5a is disposed in such a manner as to wind the projecting tube 3. The leading- out wire 5b on a high voltage side is disposed in such a manner as to abut against the side wall of the projecting tube 3. A shield 6 is formed into a cylindrical shape, is interposed between the induction coil 5 and the inner circumferential wall of the grooved cavity 2, and is grounded.

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 formed by applying a high-frequency current to an induction coil has no electrode in a discharge gas-filled bulb and acts on the discharge gas in the bulb. The present invention relates to an electrodeless fluorescent lamp that discharges a discharge gas to emit ultraviolet rays, and converts the ultraviolet rays into visible light by a phosphor layer formed on a bulb wall.

[0002]

2. Description of the Related Art Conventionally, an electrodeless fluorescent lamp has been known which excites a discharge gas to emit light by applying a high-frequency electromagnetic field to a discharge gas sealed in a bulb. This type of electrodeless fluorescent lamp has features such as small size, high output, and long life, and is being researched and developed in various places.

As this type of electrodeless fluorescent lamp, for example, as shown in FIG.
Is known to be formed in a shape enclosing a circle. In such an electrodeless fluorescent lamp, a discharge gas containing mercury vapor is sealed in the bulb 1, and a high-frequency electromagnetic field formed by flowing a high-frequency current through the induction coil 5 acts on the discharge gas, thereby discharging the discharge gas. When excited, ultraviolet light is emitted, and the ultraviolet light is converted into visible light by the phosphor layer 4 formed on the inner wall surface of the bulb 1 and used for illumination.

Here, in the electrodeless fluorescent lamp, a high voltage electric field is generated by the induction coil 5, so that the bulb 1 and the phosphor layer 4 in the vicinity of the induction coil 5 are blackened and the lamp life is reduced. In order to solve this problem, it is conceivable to arrange a shield 6 for shielding a high electric field generated by the induction coil 5 between the valve 1 and the induction coil 5.

[0005] By the way, for lighting of the electrodeless discharge lamp,
It is well known that there are two types of discharge: electric field discharge and magnetic field discharge. Generally, an electrodeless fluorescent lamp is a discharge caused by a magnetic field in which the discharge becomes donut-shaped by increasing the discharge current of the discharge caused by the electric field.

[0006] Each discharge has a discharge starting voltage. When the discharge start voltage by the electric field is lower than the discharge start voltage by the magnetic field, when the applied voltage is increased, the discharge by the electric field starts first, and then the discharge current gradually increases to reach the discharge start voltage by the magnetic field. When you do
Discharge by magnetic field. Conversely, if the discharge start voltage due to the magnetic field is lower than the discharge start voltage due to the electric field, there is no discharge current even if the applied voltage rises to the discharge start voltage due to the magnetic field. When the discharge start voltage is reached, the discharge current increases at a stretch, leading to discharge by a magnetic field.

That is, the firing voltage of the electrodeless fluorescent lamp is determined by the higher of the firing voltage by an electric field and the firing voltage by a magnetic field.

[0008]

Incidentally, of the above two discharge starting voltages, the discharge starting voltage due to the magnetic field is affected by the type of the charged gas, the pressure of the charged gas, the inductance of the induction coil and the like, and depends on the design of the lamp. Almost determined.

However, the discharge starting voltage due to the electric field has a great effect on the contact between the bulb 1 and the high voltage side lead 5b of the induction coil 5, and when the high voltage side lead 5b is separated from the bulb 1, the discharge starting voltage due to the electric field sharply increases. Rises. Further, if a shield 6 is provided between the bulb 1 and the induction coil 5 to prevent a decrease in lamp life, a high electric field of the induction coil 5 becomes difficult to be applied to the lamp, and a discharge starting voltage due to the electric field rises. There is a problem that the starting voltage of the electrodeless fluorescent lamp increases.

The present invention has been made to solve the above problems, and an object of the present invention is to improve the starting characteristics of an electrodeless fluorescent lamp provided with a shield for preventing a reduction in lamp life. It is to plan.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a bulb-shaped bulb having a bottomed cylindrical hollow at the center, an induction coil inserted into the hollow, and an induction coil. With a shield disposed between the inner peripheral wall of the hollow cavity and grounded, ultraviolet rays radiated by applying a high-frequency electromagnetic field formed by the induction coil to the discharge gas sealed in the bulb, In the electrodeless fluorescent lamp, which is converted into visible light by a phosphor layer formed on the bulb wall, a cylindrical protruding tube that protrudes from the bottom surface of the hollow cavity toward the induction coil and whose tip is closed is formed. By arranging the high voltage side lead wire of the induction coil in contact with the side wall of the tube, the shield makes it difficult for the high voltage electric field of the induction coil to be applied to the valve. Along with a reduction can lamp life can be secured, discharge is started at a portion of the protruding tube, you are possible to prevent the starting voltage becomes high.

The high-voltage side lead wire is electrically connected to the high-voltage side lead wire of the induction coil, and the high-voltage side lead wire itself is wound around the protruding tube by mounting the metal ring on the protruding tube. Thereby, the contact between the high-voltage side lead wire and the protruding tube becomes more reliable, and the starting voltage can be further reduced.

[0013]

FIG. 1 shows an embodiment of an electrodeless fluorescent lamp according to the present invention, wherein FIG.
FIG. 2B is a sectional view taken along line XX in FIG.

In the drawing, reference numeral 1 denotes a bulb formed of a light-transmitting material such as glass, which has a bulb-shaped hollow hollow center 2 with a bottom at the center and a bottom surface of the hollow hollow 2. And has a cylindrical projecting tube 3 projecting toward the opening side and having a closed end, and the inside thereof forms an airtight discharge space. A phosphor layer 4 is formed on the inner surface of the bulb 1. Phosphor layer 4
Is formed on the inner surface of the peripheral wall of the bulb 1 in the present embodiment, but may be formed on the outer surface of the hollow cavity 2 and the inner surface of the protruding tube 3 as necessary. Further, a discharge gas is sealed inside the bulb 1. As the discharge gas, for example, a rare gas such as argon or krypton and at least mercury are sealed.

Reference numeral 5 denotes an induction coil inserted into the hollow 2 and comprises a coil portion 5a, a high voltage side lead wire 5b, and a ground side lead wire 5c, and the coil portion 5a is provided at a position where the projecting tube 3 is wound. , And the high pressure side lead wire 5 b is disposed so as to abut the side wall of the protruding tube 3. In addition, the high-voltage side lead wire 5b and the ground-side lead wire 5c are configured to be connected to a coaxial cable (not shown) for supplying a high-frequency current from a high-frequency power supply (not shown).

Reference numeral 6 denotes a cylindrical shield disposed between the induction coil 5 and the inner peripheral wall of the hollow cavity 2. The cylindrical shield shields a high-voltage electric field generated from the induction coil 5 so that the fluorescent layer 4 The valve 1 is prevented from being deteriorated and blackened. The shield 6 is arranged to be grounded, and is provided with several cuts (slits) 7 in the axial direction so that eddy current does not flow in the circumferential direction of the shield 6 to cause power loss.

In the thus configured electrodeless fluorescent lamp, when a high-frequency current is supplied from the high-frequency power supply to the induction coil 5, the high-voltage electric field on the non-ground side of the induction coil 5 is reduced by the effect of the shield 6 grounded. The discharge is not applied to the discharge space of the spherical portion inside, but acts on the discharge gas in the portion of the protruding tube 3 to start the discharge by the electric field. Thereafter, when the discharge current increases, the discharge due to the electric field becomes a seed and shifts to the discharge due to the magnetic field.

According to this configuration, the shield 6 makes it difficult for the high-voltage electric field of the induction coil 5 to be applied to the spherical portion of the bulb 1, so that the deterioration of the bulb 1 can be reduced and the lamp life can be ensured. Since the lead wire 5b is disposed so as to contact the side wall of the protruding tube 3,
Discharge starts at the protruding tube 3 portion, which can prevent the starting voltage from increasing.

Further, when a device including the bulb 1 and the induction coil 5 is formed, in the conventional lamp, the induction coil 5 is so formed as to be in contact with the bottom surface of the hollow 2 in order to prevent the starting voltage from becoming high. It was necessary to arrange them, and it was difficult to design mechanically for fitting the valve 1 and the induction coil 5. However, according to this embodiment, it is not necessary to abut the induction coil 5 on the bottom surface of the hollow 2, and it is sufficient that the induction coil 5 abuts on the protruding tube 3, so that the mechanical design becomes easy.

Next, FIG. 2 shows a different embodiment of the present invention. A different point from the above embodiment is that a band-shaped metal ring 8 electrically connected to the high voltage side lead wire 5b of the induction coil 5 is provided. Since it is mounted on the protruding tube 3 and the other configuration is the same as that of the above-described embodiment, the description will be omitted by attaching the same reference numerals to the same configuration. Note that, instead of the metal ring 8, the high-voltage side lead wire 5 b itself may be wound around the protruding tube 3 as shown in FIG.

With this configuration, the contact between the high-voltage side lead wire 5b and the protruding tube 3 becomes more reliable, and the starting voltage can be further reduced.

[0022]

As described above, according to the present invention, in an electrodeless fluorescent lamp in which a shield is provided between an induction coil and the inner peripheral wall of a hollow cavity, the tip protrudes from the bottom surface of the hollow cavity toward the induction coil and the tip is closed. By forming a cylindrical projecting tube that has been made, and by contacting the high voltage side lead wire of the induction coil with the side wall of the projecting tube, the lamp life can be ensured by the shield and the starting voltage is prevented from increasing. Can be.

Further, by attaching a band-shaped metal ring electrically connected to the high voltage side lead wire of the induction coil to the protruding tube, or by winding the high voltage side lead wire itself around the protruding tube instead of the metal ring. Thus, the starting voltage can be further reduced.

[Brief description of the drawings]

FIGS. 1A and 1B show an embodiment of the present invention, in which FIG. 1A is a sectional view, and FIG. 1B is a sectional view taken along line XX in FIG.

FIG. 2 illustrates a different embodiment of the present invention, wherein (a)
Is a sectional view, and (b) is a sectional view taken along line XX in FIG.

FIG. 3 illustrates yet another embodiment of the present invention.
(A) is a sectional view, and (b) is a sectional view taken along line XX in (a) of FIG.

FIG. 4 is a perspective view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bulb 2 Depression cavity 3 Projection tube 4 Phosphor layer 5 Induction coil 5a Coil part 5b High voltage side lead 5c Ground side lead 6 Shield 7 Slit 8 Metal ring

Claims (3)

[Claims] 1. A bulb-shaped bulb having a cylindrical hollow with a bottom at the center, an induction coil inserted into the hollow, and an inner coil between the induction coil and the inner peripheral wall of the hollow. A shield that is grounded, and converts ultraviolet light emitted by applying a high-frequency electromagnetic field formed by the induction coil to the discharge gas sealed in the bulb to visible light by a phosphor layer formed on the bulb wall surface. In the electrodeless fluorescent lamp, a cylindrical projecting tube protruding from the bottom surface of the hollow cavity toward the induction coil and having a closed end is formed, and a high-voltage side lead wire of the induction coil is applied to a side wall of the projection tube. An electrodeless fluorescent lamp which is disposed so as to be in contact with the electrodeless fluorescent lamp. 2. The electrodeless fluorescent lamp according to claim 1, wherein a band-shaped metal ring electrically connected to a high-voltage side lead wire of said induction coil is mounted on said protruding tube. 3. The electrodeless fluorescent lamp according to claim 1, wherein a high-voltage side lead wire of said induction coil is wound around said projecting tube.