Electric lamp and discharge devices: systems – Pulsating or a.c. supply – Induction-type discharge device load
Reexamination Certificate
2001-06-15
2003-02-18
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Pulsating or a.c. supply
Induction-type discharge device load
C315S056000, C313S638000, C313S634000, C313S643000
Reexamination Certificate
active
06522084
ABSTRACT:
TECHNICAL FIELD
The present invention relates to electrodeless discharge lamp operating apparatuses.
BACKGROUND ART
Electrodelss discharge lamps (or electrodeless low-pressure discharge lamps) have excellent characteristics including a resource saving effect of long life and an energy saving effect of high efficiency, so that electrodeless discharge lamps have been widely noted in the illumination field in recent years. Hereinafter, a conventional electrodeless low-pressure discharge lamp operating apparatus will be described with reference to FIG.
2
.
FIG. 2
shows the structure of a conventional electrodeless low-pressure discharge lamp operating apparatus, and an electrodeless low-pressure discharge lamp operating apparatus having such a structure is disclosed in, for example Japanese Laid-Open Patent Publication No. 58-57254.
The electrodeless low-pressure discharge lamp operating apparatus shown in
FIG. 2
includes a discharge vessel
21
enclosing a luminescent metal and rare gas therein, a phosphor
22
applied onto an inner face of the discharge vessel
21
, and a coil
23
inserted in a recessed portion
21
a
of the discharge vessel
21
. The phosphor
22
is used to convert ultraviolet rays occurring in the discharge vessel
21
to visible light. The coil
23
is constituted by a rod-shaped core
23
a
made of a magnetic material such as ferrite and a winding
23
b.
The rod-shaped core
23
a
of the coil
23
has a rod-shaped member
26
made of a thermal conductive material in its central axis (a hatched portion in FIG.
2
). The rod-shaped member
26
serves to dissipate and suppress the heat of the coil
23
that is generated during lamp operation.
The discharge vessel
21
is supported by a metal case
25
, and the rod-shaped member
26
provided inside the recessed portion
21
a
of the discharge vessel
21
and the metal case
25
are coupled to each other. In such a structure, it is intended to minimize the heat generation of the coil by dissipating the heat generated in the coil
23
from the metal case
25
through the rod-shaped member
26
. A power source
24
for supplying high frequency alternating current to the winding
23
b
is provided in the metal case
25
. In other words, the lamp is configured so that an alternating magnetic field occurs from the coil
23
by the high frequency alternating current from the power source
24
. A lamp base
27
is attached to a part (a lower part) of the metal case
25
.
Next, the operation of the electrodeless low-pressure discharge lamp operating apparatus shown in
FIG. 2
will be described.
First, an alternating magnetic field is generated in the discharge vessel
21
from the coil
23
with the high frequency alternating current supplied from the power source
24
to the winding
23
b.
Then, an alternating electric field occurs in the discharge vessel
21
to cancel this alternating magnetic field. The luminescent metal and rare gas in the discharge vessel
21
collide with each other repeatedly so as to be excited by this alternating electric field so that a plasma is formed in the discharge vessel
21
. Ultraviolet rays are radiated from the plasma and the ultraviolet rays are converted to visible light with the phosphor
22
. Thus, the visible light is emitted outwardly from the discharge vessel
21
. In this manner, the electrodeless low-pressure discharge lamp operating apparatus shown in
FIG. 2
emits light.
In the above-described operation, the coil
23
is forced to operate at a quite high temperature caused by the heat generated by a loss due to the alternating current supplied to the winding
23
b
and the heat generated by heat conduction from the plasma. Furthermore, the recessed portion
21
a
in the discharge vessel
21
where the coil
23
is provided is constituted by a closed space, so that heat is unlikely to be dissipated, and therefore it is necessary to take some measure to dissipate the heat for the electrodeless low-pressure discharge lamp operating apparatus. Japanese Laid-Open Patent Publication No. 58-57254 describes as a measure for dissipation that the rod-shaped member
26
made of a thermal conductive material is inserted in the central axis of the rod-shaped core
23
a,
and the heat generated in the coil
23
is dissipated from the metal case
25
through the rod-shaped member
26
by coupling the rod-shaped member
26
and the metal case
25
.
In the conventional structure as above, it is necessary to use a material having good thermal conductivity for the rod-shaped member
26
, and it is generally assumed that a metal can be used. In the case of the rod-shaped member
26
made of a metal, an eddy current is generated in the rod-shaped member
26
by a magnetic field occurring in the coil
23
, and thus a loss occur. Similarly, a loss due to the eddy current also occurs in the metal case
25
. Therefore, in the above conventional structure, the generated eddy current reduces the lamp efficiency, and sufficient heat dissipation effects cannot be obtained. Furthermore, since this structure is very complicated where the rod-shaped member
26
of the central axis of the rod-shaped core
23
a
is inserted, and the rod-shaped member
26
and the metal case
25
are coupled, disadvantageously resulting in a large apparatus.
Furthermore, since a metal and rare gas are enclosed as the luminescent substance, the luminous flux is low during a period from turning on the power to evaporation of the metal, and the start of lighting takes time. In addition, the metal vapor pressure is significantly varied by the variation of the ambient temperature, so that the variation of the luminous flux disadvantageously is large. The variation of the metal vapor pressure leads to the variation of the electrical characteristics of the plasma, and therefore the power source
24
that can cope with a wide range of load variations can be of a complicated structure, disadvantageously resulting in a large apparatus. Moreover, mercury generally is used as the luminous metal to radiate ultraviolet rays. However, there is a great demand for reducing the amount of mercury used in view of environmental protection.
The present invention is carried out in view of the above problems, and it is a main object of the present invention to provide an electrodeless low-pressure discharge lamp operating apparatus that can suppress an increase of the temperature of the coil.
DISCLOSURE OF INVENTION
An electrodeless discharge lamp operating apparatus of the present invention includes a transparent discharge vessel in which a luminescent substance is enclosed; a coil for generating an alternating electromagnetic field that discharges the luminescent substance; a power source for supplying alternating current to the coil, wherein the coil comprises at least a magnetic material, and is disposed on an inner side than the outer side wall of the discharge vessel, and the luminescent substance comprises at least a rare gas, and does not comprise mercury.
In one embodiment, the coil is inserted in a recessed portion provided in the discharge vessel.
In one embodiment, a frequency of the alternating current supplied by the power source is in a range from 40 kHz or more and 500 kHz or less.
In one embodiment, the electrodeless discharge lamp operating apparatus further includes a phosphor applied onto an inner face of the discharge vessel, and ultraviolet rays occurring in the discharge vessel are converted to visible light with the phosphor.
In one embodiment, the luminescent substance is a rare gas, and the rare gas is at least one selected from the group consisting of xenon, argon, krypton, neon, and helium and a mixture of these rare gas.
It is preferable that the rare gas comprises at least xenon.
In one embodiment, a pressure in the discharge vessel before discharge start is in a range from 0.1 torr or more and 3.0 torr or less.
REFERENCES:
patent: 4119889 (1978-10-01), Hollister
patent: 4636692 (1987-01-01), Lapatovich et al.
patent: 5650695 (1997-07-01), Daniels et al.
patent: 5751110 (1998-05-01), Spaapen et al.
paten
Cho Young-Jae
Kurachi Toshiaki
Miyazaki Koji
Seki Katsushi
Takeda Mamoru
Harness Dickey & Pierce PLC
Matsushita Electric - Industrial Co., Ltd.
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