JP2008181737A - Microwave discharge lamp system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microwave discharge lamp system in which impedance matching of the microwave discharge lamp is performed with a simple structure and the size is made small. <P>SOLUTION: The microwave discharge lamp system combines the microwave from a microwave oscillator with a discharge lamp 3 by using an antenna 1 and a metallic chamber 5. The antenna 1 has an antenna adaptor 2 for changing the cross-section area of the antenna 1 installed in a face vertical to the length direction of the antenna 1, and impedance matching is realized. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a discharge lamp that is lit using microwaves.

In recent years, the demand for high-pressure discharge lamps is increasing not only for general lighting but also for headlights for automobiles and backlights for projectors in place of halogen lamps because of their high efficiency and high color rendering.
In particular, in a discharge lamp using microwaves, since it is possible to couple electromagnetic energy to a luminescent material in a light emitting space without having an electrode in the light emitting space, it is possible to realize an electrodeless discharge lamp.

  The electrodeless lamp does not cause blackening of the inner wall of the arc tube due to the evaporation of the electrode, so it can greatly improve the lamp life, and the substance that could not be used because it reacts with electrode materials such as sulfur Therefore, a light source with high efficiency and high color rendering can be realized.

  In the conventional microwave discharge lamp, the discharge lamp is disposed in the microwave resonant cavity, the microwave generated from the magnetron is transmitted using the waveguide, and the microwave energy is sent to the microwave resonant cavity using the coupling hole. Thus, the discharge lamp is turned on (for example, Patent Document 1).

Here, microwave discharge lamps are expected to be applied to automotive headlamps and projector backlights. However, microwave discharge lamps are expected to be used as waveguides for transmitting microwaves and microwaves for impedance matching. Since a resonant cavity is required, the device becomes very large.
For this reason, an electrodeless illumination system has been proposed in which impedance matching is enabled by providing two resonators and the lighting device is reduced in size (for example, Patent Document 2).
JP 58-16458 JP-A-2004-273412

  However, according to Patent Document 2, although it is somewhat downsized, two resonators are required for impedance matching, so that it is a large device as a headlight for an automobile or a backlight for a projector. It cannot be applied.

  The resonator here is composed of a conductor and a resonance space, and impedance matching is determined mainly by the arrangement of the two conductors and the shape of the resonance space. Therefore, once these arrangements are determined and the system is completed, the impedance cannot be readjusted.

  Therefore, when the characteristics of the discharge lamp change with time, even if the discharge lamp has not reached the end of its life, the discharge lamp may not be properly lit due to a shift in impedance matching with time. In addition, when designing a resonator for a plurality of specifications of a discharge lamp, it is necessary to change the arrangement and shape of the conductor and the entire resonance space for each of them, so that development efficiency is poor and productivity cannot be improved.

  Thus, the technical problems of the present invention are to reduce the size of the device and to perform impedance matching without using a resonator in a discharge lamp that is lit using microwaves. Another problem is to enable impedance matching to be performed appropriately and efficiently for discharge lamps before and after aging and for discharge lamps of many specifications.

A first aspect of the present invention includes a microwave oscillation source that generates a microwave, a metal chamber, an antenna that is disposed inside the metal chamber and emits a microwave, and a discharge lamp that is lit by the microwave. In the microwave discharge lamp system, the antenna is provided with at least one portion whose cross-sectional area varies along the length direction.
Here, the metal chamber is for transmitting the microwave introduced from the microwave oscillation source to the antenna to the lamp and preventing the microwave emitted from the antenna from leaking to the outside.

  In the first side face, the portion where the cross-sectional area changes may be an antenna adapter made of a conductive material attached to the antenna. Here, the antenna adapter may be composed of a first antenna adapter and a second antenna adapter, and the second antenna adapter may be attached to the outside of the first antenna adapter, or the first may be located at a different position in the antenna length direction. The antenna adapter and the second antenna adapter may be attached.

  The antenna adapter may be slidable with respect to the antenna. Furthermore, a detection unit that detects reflected power from the discharge lamp, a drive unit that slides the antenna adapter, and a control unit that controls the drive unit to feed back the position of the antenna adapter based on the detected reflected power. It is good also as a structure.

  According to the present invention, impedance matching between the microwave oscillation source and the discharge lamp is performed by providing a portion having a large cross-sectional area in a plane perpendicular to the length direction of the antenna. The necessary resonator is not necessary, and the lighting device can be downsized.

  In addition, by making the portion where the cross-sectional area of the antenna becomes large slidable, it is possible to finely adjust the impedance by moving the portion where the cross-sectional area of the antenna is large, and impedance matching becomes easy. . And a system can be completed efficiently with respect to various discharge lamp specifications.

  In addition, since the impedance can be adjusted according to the life of the discharge lamp, it is possible to obtain an appropriate lighting state even for a discharge lamp with a slightly advanced life, and it is possible to make better use of the long life characteristic that is the feature of the electrodeless discharge lamp. it can.

Hereinafter, embodiments of the microwave discharge lamp system of the present invention will be described in detail.
Note that the microwave in this specification refers to an electromagnetic wave having a frequency of 300 MHz to 300 GHz.

Example 1.
FIG. 1 is a schematic view showing the configuration of a first embodiment of a microwave discharge lamp system according to the present invention.
A microwave oscillated from a microwave oscillation source (not shown) has a frequency of 2.45 GHz, propagates through a coaxial cable, and is transmitted to the antenna 1 through the coaxial connector 7.
The antenna 1 is a copper rod having a diameter of 3 mm and a length of 25 mm, and is electrically connected to the inner conductor of the coaxial connector 7.

  The antenna adapter 2 is provided to provide a portion having a large cross-sectional area in the antenna 1 on a plane perpendicular to the length direction of the antenna 1, and has a cylindrical shape with a diameter of 10 mm and a height of 8 mm. A 3 mm hole is provided, and the antenna 1 is electrically connected to the antenna 1 through the hole. At this time, the distance from the end face of the antenna 1 to the end face (tip) of the antenna adapter 2 is 4 mm.

The microwave transmitted from the microwave oscillation source to the antenna 1 is sent to the discharge lamp 3 through the metal chamber 5.
The discharge lamp 3 is filled with a luminescent material and a rare gas, and is discharged by the microwave radiated from the antenna 1 to emit light. It is made of spherical quartz glass having a diameter of 15 mm, and is fixed by a lamp support rod 4 made of quartz glass.

The internal dimensions of the metal chamber 5 are 40 mm high, 80 mm wide and 100 mm long, and have the role of confining microwaves radiated from the antenna 1, and are extremely small compared to conventional microwave resonant cavities. It has become.
Note that the lamp side of the metal chamber 5 is formed of a metal mesh portion 6 and has a structure that substantially transmits the light emitted from the discharge lamp 3 but does not substantially transmit the microwave. .
The material of the metal chamber 5 is preferably a metal having high electrical conductivity such as copper or aluminum.

When microwaves were introduced into this microwave discharge lamp system from a microwave oscillation source and the discharge lamp 3 was turned on, the reflected power was very low at 2 W with respect to the input power of 200 W.
Thus, it was found that even without a microwave resonator, a good impedance matching can be achieved with little reflected power by changing the antenna shape.

For comparison, the antenna adapter is not provided as shown in FIG. 2, and other than that, the microwave is introduced into the same microwave discharge lamp system as in Example 1 and the discharge lamp is turned on. On the other hand, there is a reflected power of 32 W, and it can be seen that impedance matching is performed by the antenna adapter.
Note that when the luminescent material enclosed in the discharge lamp is changed, the impedance of the discharge lamp changes, so the position and dimensions of the antenna adapter must be changed in accordance with the impedance of the discharge lamp.

Example 2
FIG. 3 is a schematic diagram showing the configuration of the microwave discharge lamp system according to the second embodiment of the present invention.
The microwave discharge lamp system shown in FIG. 3 differs from the microwave discharge lamp system shown in FIG. 1 shown in FIG. 1 in the following points.

That is, in the microwave discharge lamp system shown in FIG. 3, the support rod 8 made of a dielectric for moving the antenna adapter 22 from the outside of the metal chamber 25 is connected to the antenna adapter 22. The structure is movable on the antenna 21.
Other configurations are the same as those of the microwave discharge lamp system shown in FIG.

In the microwave discharge lamp system configured as described above, the antenna adapter 22 can be moved from the outside of the metal chamber 25.
Table 1 shows the distance from the end face of the antenna 21 to the end face of the antenna adapter 22 when the antenna adapter 22 is moved, and the value of the reflected power with respect to the input power of 200 W.

  It can be seen from Table 1 that the reflected power can be adjusted by moving the antenna adapter 22. That is, the impedance of the microwave discharge lamp system can be changed by moving the antenna adapter 22. That is, the impedance can be easily readjusted even after the system is assembled.

Moreover, when the enclosure of the discharge lamp 23 is changed, the reflected power increases because the impedance of the discharge lamp changes. However, the impedance matching can be performed by changing the position of the antenna adapter to reduce the reflected power. is there.
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be modified as follows.

For example, two antenna adapters 32 may be provided as shown in FIG. According to this configuration, even in the impedance range of the discharge lamp in which the reflected power cannot be reduced with one antenna adapter 32, it is possible to reduce the reflected power as compared with the case with one antenna adapter. That is, the adjustment range of impedance can be expanded.
Further, as shown in FIG. 5, another antenna adapter 42b may be provided outside the antenna adapter 42a.
In each of the embodiments, the shape of the antenna adapter is shown as a cylindrical shape or a rectangular parallelepiped shape, but may be a spherical shape, a conical shape, a polygonal pyramid shape, a spindle shape, or a combination thereof. Moreover, although the illustrated shape is symmetric with respect to the axis of the antenna, it may be asymmetrical.

  Further, as means for automatically adjusting the position of the antenna adapter, the reflected power from the discharge lamp may be detected, and feedback may be applied based on the information on the reflected power. FIG. 6 shows a configuration for this feedback. In addition, the members 61-67 in a figure are the same as the members 21-27 of FIG. 3, respectively. The detection unit 69c detects the reflected power from the discharge lamp, and the control unit 69b arranges the antenna adapter 62 at a position where the reflected power becomes a desired value (for example, the minimum value) based on the detected reflected power. Thus, the drive part 69a of the support rod 68 is controlled.

  According to this configuration, it is possible to shorten the rise time of the discharge lamp by realizing optimum impedance matching following the change even during a period of large impedance change at the start of the discharge lamp. Even if the impedance of the discharge lamp changes due to the change over time, the reflected power can be reduced following the change over time and the efficiency is improved, so that the luminous flux maintenance factor can be improved.

The shape of the metal chamber is not limited to a rectangular parallelepiped, and a cylindrical metal chamber 55 may be used as shown in FIG. At this time, a discharge lamp may be disposed on the front end side of the antenna 51, and the shape may be appropriately changed according to the use conditions of the present microwave discharge lamp system.
In addition, although the example which used the coaxial cable for microwave transmission was described, you may set it as the structure which uses transmission lines other than coaxial cables, such as a waveguide.

It is a figure which shows an example of the microwave discharge lamp system which concerns on this invention. It is a figure which shows the comparative example of the microwave discharge lamp system which concerns on this invention. It is a figure which shows the other form of the microwave discharge lamp system which concerns on this invention. It is a figure which shows the other form of the microwave discharge lamp system which concerns on this invention. It is a figure which shows the other form of the microwave discharge lamp system which concerns on this invention. It is a figure which shows the other form of the microwave discharge lamp system which concerns on this invention. It is a figure which shows the other form of the microwave discharge lamp system which concerns on this invention.

Explanation of symbols

1, 11, 21, 31, 41, 51, 61 Antenna 2, 22, 32, 42a, 42b, 52, 62 Antenna adapter 3, 13, 23, 33, 43, 53, 63 Lamp 4, 14, 24, 34 , 44, 54, 64 Lamp support rod 5, 15, 25, 35, 45, 55, 65 Chamber 6, 16, 26, 36, 46, 56, 66 Metal mesh portion 7, 17, 27, 37, 47, 57 , 67 Connectors 8, 68 Support rod 69a Drive unit 69b Control unit 69c Detection unit

Claims (6)

In a microwave discharge lamp system including a microwave oscillation source for generating a microwave, a metal chamber, an antenna for emitting the microwave disposed inside the metal chamber, and a discharge lamp that is lit by the microwave ,
A microwave discharge lamp system, wherein the antenna is provided with at least one portion whose cross-sectional area varies along the length direction.   The microwave discharge lamp system according to claim 1, wherein the portion where the cross-sectional area changes is an antenna adapter made of a conductive material attached to the antenna.   The microwave discharge lamp system according to claim 2, wherein the antenna adapter includes a first antenna adapter and a second antenna adapter, and the second antenna adapter is attached to the outside of the first antenna adapter.   The microwave discharge according to claim 2, wherein the antenna adapter includes a first antenna adapter and a second antenna adapter, and the first antenna adapter and the second antenna adapter are attached at different positions in the length direction of the antenna. Lamp system.   The microwave discharge lamp system according to any one of claims 2 to 4, wherein the antenna adapter is slidable with respect to the antenna.   A detection unit that detects reflected power from the discharge lamp, a drive unit that slides the antenna adapter, and a control unit that controls the drive unit to feed back the position of the antenna adapter based on the detected reflected power The microwave discharge lamp system according to claim 5, further comprising:

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