JP2005038751A - Electrodeless discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrodeless discharge lamp lighting device of a long life which prevents flow of a large current in a metal mesh and is excellent in a light distribution property. <P>SOLUTION: Of the electrodeless discharge lamp lighting device provided with a microwave oscillator 1, a waveguide 2 guiding microwave from the microwave oscillator 1, a microwave resonator 3 combined with the waveguide 2 and containing a metal mesh 3a transmitting light but not the microwave at part of it, and an electrodeless discharge lamp 4 arranged inside the microwave resonator 3 and with discharge gas containing at least mercury and rare gas sealed inside, the shape of the microwave resonator 3 is an ellipsoid of revolution 5 with a part of an elliptic curve revolved with an axis of an ellipse as an axis center, and at the same time, a direction of a maximum field generated in the microwave resonator 3 is almost vertical to the revolving axis, and a focus of the elliptic curve is made to almost match with the maximum position of the field, and the electrodeless discharge lamp 4 is arranged in the vicinity of the matched point. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrodeless discharge lamp lighting device using microwaves.

  Since the electrodeless discharge lamp does not have an electrode in the discharge space, blackening of the inner wall of the bulb due to electrode evaporation does not occur. As a result, the life of the discharge lamp can be greatly extended. Due to these characteristics, electrodeless discharge lamps have been actively studied in recent years as next-generation high-intensity discharge lamps.

  As means for lighting the electrodeless discharge lamp, there is one using microwaves. As this kind of first conventional example, for example, the one described in JP-A-59-86153 can be mentioned. As shown in FIG. 7, the microwave is converted into a high-frequency electromagnetic field through a chamber 1J4 that is a cavity resonator, and the high-frequency electromagnetic field is applied to a lamp 1J2 that is an electrodeless discharge lamp. Lights up.

  A second conventional example is disclosed in Japanese Patent Application Laid-Open No. 57-60695. As shown in FIG. 9, a spherical portion 2J41 for reflecting light is provided on a part of the inner wall of the microwave resonant cavity 2J4 as shown in FIG. 9, and the microwave resonant cavity 2J4 has a reflecting function of the spherical portion 2J41. Light is efficiently extracted outside.

  By the way, in the first conventional example, the chamber 1J4 is constituted by the metal net 1J20 having an appropriate opening rate, but the TM011 mode is used as the resonance electromagnetic field mode of the chamber 1J4 as shown in FIG. In some cases, a large current flows through the metal net 1J20. Therefore, the metal net 1J20 becomes high temperature, which may affect the life of the electrodeless discharge lamp device.

  Also in the second conventional example, the TM011 mode is used as the resonant electromagnetic field mode of the microwave resonant cavity 2J4, and a high electric field is generated near the center of the metal mesh plate 2J43 as shown in FIG. A large current flows near the center of the metal mesh plate 2J43. Therefore, the metal mesh plate 2J43 becomes high temperature, which may affect the life of the microwave discharge light source device.

Furthermore, neither the first conventional example nor the second conventional example has been particularly considered with respect to the arrangement of the electrodeless discharge lamp in the cavity resonator, and it cannot be said that the light distribution is excellent. .
JP 59-86153 A JP 57-60695 A

  The present invention has been made in view of the above problems, and its object is to prevent a large current from flowing through the metal mesh, to prolong the life, and to provide an electrodeless discharge with excellent light distribution. The object is to provide an electric lamp lighting device.

  In order to solve the above problems, in the present invention, a microwave oscillator, a waveguide for guiding the microwave from the microwave oscillator, and the waveguide are coupled, and the microwave is not transmitted and the light is not transmitted. A microwave resonator including at least a part of a transparent metal mesh, and an electrodeless discharge lamp disposed in the microwave resonator and including a discharge gas including at least mercury and a rare gas inside. The electrodeless discharge lamp lighting device is provided, and the shape of the microwave resonator is a spheroid in which a part of an elliptic curve is rotated about the axis of the ellipse, and is generated in the microwave resonator The direction of the maximum electric field is substantially perpendicular to the rotation axis, and the focal point of the elliptic curve and the maximum position of the electric field are substantially coincided with each other, and an electrodeless discharge lamp is disposed in the vicinity of the coincidence point.

  In the electrodeless discharge lamp lighting device of the present invention, the shape of the microwave resonator is a rotating ellipsoid obtained by rotating a part of an elliptic curve around the axis of the ellipse, or a rotating parabola obtained by rotating a part of a parabola. The direction of the maximum electric field generated in the microwave resonator is substantially perpendicular to the rotation axis, and the focal point of the elliptic curve and the maximum position of the electric field are substantially coincided with each other and in the vicinity of the coincidence point. Since the electrodeless discharge lamp is arranged, the electric field is not concentrated on the metal mesh arranged in the horizontal direction with respect to the electric field. Therefore, a large current does not flow in the metal mesh, and the long-life electrodeless discharge is performed. An electric lamp lighting device can be provided. In addition, since the electrodeless discharge lamp is arranged at the coincidence point in the vicinity of the focal point of the elliptic curve, the light reflected by the inner surface of the microwave resonator is condensed at the other focal point of the elliptic curve, and this condensing point Becomes a pseudo light source, and an electrodeless discharge lamp lighting device having excellent light distribution can be provided.

  Furthermore, since the coupling window at the coupling portion between the waveguide and the microwave resonator is covered with a highly reflective dielectric, part of the light from the electrodeless discharge lamp is reflected by the highly reflective dielectric. The light reflected by the dielectric returns to the microwave resonator, and the loss of light can be prevented.

(First embodiment)
A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a perspective view of the present embodiment, and FIG. 2 is a cross-sectional view of the present embodiment. 3 is a plan view of the metal mesh 3a, and FIG. 4 is a diagram showing the electric field distribution in the microwave resonator 3. As shown in FIG. FIG. 5 is a characteristic diagram showing the relationship between the focal point of the elliptic curve and the resonance center distance h.

  Next, the configuration of each unit will be described.

  The microwave oscillator 1 outputs microwaves to the waveguide 2, and is configured by, for example, a magnetron that is connected to a power source 7 and generates a microwave of 2.45 GHz with a microwave power of 750W. An antenna 11 inserted in the waveguide 2 is connected to the microwave oscillator 1.

  The waveguide 2 guides the microwave from the microwave oscillator 1 to the microwave resonator with a low loss. In the present embodiment, the waveguide 2 has a cross section orthogonal to the waveguide direction. A rectangular waveguide having a rectangular shape is used. The cross-sectional dimension of the waveguide 2 is set to 109 mm × 54.5 mm (the standard dimension of the rectangular waveguide conforming to this frequency is the model name WRJ-2, and the inner diameter nominal dimension is 109.2 mm × 54.6 mm).

  A coupling window 8 is provided on the side of the waveguide 2 where the waveguide 2 is connected to the microwave resonator 3. The coupling window 8 is for coupling the microwave energy supplied through the waveguide 2 to the microwave oscillator 1. The coupling window 8 has a rectangular shape and is set to 48 mm × 12 mm, for example. .

  The microwave resonator 3 supplies microwave energy necessary for discharging the electrodeless discharge lamp 4 by a resonant microwave electric field generated inside. The inner surface of the microwave resonator 3 is made of aluminum, which is a conductive material, and has a mirror finish.

  The shape of the microwave resonator 3 is a spheroid 5 in which a part of an elliptic curve separated by the other axis is rotated with one axis as a rotation axis, and the other axis direction is open. A metal mesh 3a is disposed in the opening. In addition, the electric field generated in the vicinity of the focal point of the elliptic curve of the microwave resonator 3 is in a direction substantially perpendicular to one of the rotation axes as shown in FIG. That is, the electric field in the vicinity of the focal point is the maximum position of the electric field generated in the microwave resonator 3.

  The metal mesh 3a is for confining the microwave, and the microwave is not transmitted but the light is transmitted. The metal mesh 3 a is disposed at the opening of the microwave resonator 3 so as to cover the opening. In the present embodiment, the metal mesh 3a has a circular shape with a diameter of about 143 mm in plan view as shown in FIG. 3, and metal bands with a width of 0.2 mm are arranged in a grid pattern at intervals of 1.8 mm. Use what you have. As the material for the metal mesh 3a, a silver-plated stainless steel that is opaque to microwaves is used. Here, the material of the metal mesh 3a may be aluminum or copper, or may be a conductor shield in which a conductive thin film such as ITO is formed.

  The electrodeless discharge lamp 4 emits light when internal electrons receive energy by a high-frequency electromagnetic field from the microwave resonator 3 and collide with discharge gas atoms. The electrodeless discharge lamp 4 is fixed in the microwave resonator 3 via a quartz glass support rod 10 fixed to the inner wall of the microwave resonator 3.

  The electrodeless discharge lamp 4 will be described in more detail. The shape is substantially spherical, and the material is a translucent material such as quartz glass, and a discharge gas contained therein is enclosed. The types of discharge gas are mercury, rare gas and metal halide. The inner wall of the electrodeless discharge lamp 4 is coated with a phosphor and a protective film. The phosphor converts ultraviolet rays radiated from mercury into visible light. The phosphor material is calcium halophosphate, red phosphor (Y, Gd) BO3: Eu, and green phosphor CaPO4. The blue phosphor BaMgAll4O23: Eu is used. Further, the protective film improves the luminous flux maintenance factor of the electrodeless discharge lamp 4 by suppressing the reaction between mercury and quartz glass forming the electrodeless discharge lamp 4. As a material for the protective film, fine particles such as alumina (Al 2 O 3), silica (SiO 2), titania (TiO 2), ceria (CeO 2), yttria (Y 2 O 3), magnesia (MgO) are used. In the normal electrodeless discharge lamp 4, it is desirable that the transmittance is high, so that the protective film is thinner than the phosphor and is formed on the inner wall of the electrodeless discharge lamp 4.

  The electrodeless discharge lamp 4 is disposed in the vicinity of the coincidence point where the focal point of the elliptic curve coincides with the maximum position of the electric field. When the electrodeless discharge lamp 4 is arranged in the vicinity of the coincidence point between the two, energy by the electric field is efficiently transmitted to the electrodeless discharge lamp 4 and the efficiency of the entire electrodeless discharge lamp lighting device can be increased. Since the electrodeless discharge lamp 4 is arranged in the vicinity of the focal point of the curve, the light reflected by the inner surface of the microwave resonator 3 is condensed on the other focal point of the elliptic curve, and this condensing point becomes a pseudo light source, which is excellent. Light distribution can be provided.

  Next, a method for determining the dimensions of the microwave resonator 3 will be described.

  As described above, the shape of the microwave resonator 3 is a spheroid 5 in which a part of an elliptic curve separated by the other axis is rotated about one axis as an axis, It is open.

Here, if one axis of the elliptic curve is a and the other axis is b (one of a and b corresponds to the long axis and one corresponds to the short axis), the microwave resonator 3 The relationship between the elliptic curve and one axis a and the other axis b is as shown in FIG. A distance from the opening surface to a position where the electric field of the resonant microwave electric field is maximized is a resonance center distance h. Furthermore, the elliptic curve is

X ^ 2 / a ^ 2 + Y ^ 2 / b ^ 2 = 1 (1)

It is represented by

Next, the resonance frequency of the resonant microwave electric field when the one axis a is fixed and the other axis b is changed is calculated by the finite element method, and the electric field distribution of the microwave electric field obtained by the finite element method is calculated. The resonance center distance h is determined from the figure. The focal point of the elliptic curve is from equation (1)

√ (b ^ 2-a ^ 2) (2)

The focal point of the elliptic curve is calculated by the equation (2). Here, the length calculated by equation (2) is the distance from the opening surface on which the metal mesh 3a is covered to the focal point.

  Next, the other axis b when the resonance center distance h substantially coincides with the focal point of the elliptic curve is determined, and the resonance frequency is calculated by the finite element method using the determined one axis a and the other axis b. .

  Finally, one axis a and the other axis b are recalculated so as to resonate at 2.45 GHz with the determined resonance frequency.

  Here, since the material of the bulb of the electrodeless discharge lamp 4 is a dielectric such as quartz glass, the resonance frequency may be lowered due to the wavelength shortening effect. The wavelength shortening effect is an effect in which, when an electromagnetic wave having a wavelength of λ0 in a vacuum propagates through a dielectric having a relative dielectric constant ε, the wavelength λ in the dielectric becomes λ = λ0 / √ε. For example, in a microwave having a frequency of 2.45 GHz, the wavelength λ0 in vacuum is about 122 mm, whereas the wavelength λ when propagating in a dielectric is, for example, polycrystalline alumina as a dielectric. Since the relative dielectric constant of alumina is about 8.5, it is calculated to be about 42 mm. In other words, when considered simply, the distance can be reduced to about one third by replacing the propagation path of the electromagnetic wave from a vacuum to a dielectric.

  Due to this wavelength shortening effect, for example, in the bulb of the electrodeless discharge lamp 4 having a diameter of 30 mm, the resonance frequency may be shifted to the lower frequency side by about 50 MHz. Since the resonance frequency shifts depending on the dielectric material as described above, it is necessary to consider an error of about ± 10% in the values of the one axis a and the other axis b obtained by the above-described calculation.

  Also, the shape of the microwave resonator 3 and the resonance frequency are in an inversely proportional relationship, and when recalculating one axis a and the other axis b so as to resonate at 2.45 GHz, recalculation is performed by proportional calculation. be able to.

  Regarding specific values, one axis a, the other axis b, etc. were determined as follows.

  One axis a (mm) which is the radius of the opening of the microwave resonator 3 is fixed to, for example, 75 mm, and the other axis b is changed from 80 mm to 110 mm to 80, 85, 90, 100, 110. I went. In addition, the focal point of the elliptic curve was calculated by equation (2), and at the same time, the resonance center distance h was determined by the finite element method. The relationship between the focal point of the elliptic curve and the resonance center distance h at this time is shown in FIG. From FIG. 5, the change of the focal point of the elliptic curve is large and the change of the resonance center distance h is small with respect to the change of the other axis b. It can also be seen that when b = 85 mm, the focal point of the elliptic curve and the resonance center distance h coincide with each other at approximately 40 mm. At about 40 mm, the resonance frequency was 2.383 GHz. Here, in calculation, in order to set the resonance frequency to 2.5 GHz, 2.5 / 2.383 = 1.49 = c, and one axis a, the other axis b, and the resonance center distance h are respectively a ′ = a / c = 75 / 1.049 = 71.5 mm, b ′ = b / c = 85 / 1.049 = 81.0 mm, and h ′ = h / c = 40 / 1.049 = Converted to approximately 38 mm.

  As shown in FIG. 2, the actually manufactured product has a microwave resonator 3 having an opening inner diameter of φ143 mm, which is approximately twice the one axis a ′, and the microwave resonator 3 has a height of the other axis b. The electrodeless discharge lamp 4 was confirmed to be turned on by setting the distance from the metal mesh 3a, which is the resonance center distance h, to approximately 75 mm, which is slightly shorter than ', and approximately 40 mm.

  As described above, according to the present embodiment, since the direction of the maximum electric field generated in the microwave resonator 3 is substantially perpendicular to the rotation axis, the electric field is concentrated on the inner surface of the microwave resonator 3. The electric field does not concentrate on the metal mesh 3a arranged in the horizontal direction with respect to the electric field. Therefore, a large current does not flow through the metal mesh 3a, the metal mesh 3a does not become high temperature, and the metal mesh 3a is not easily deteriorated, so that the life of the electrodeless discharge lamp lighting device can be extended.

  In addition, since the electrodeless discharge lamp 4 is disposed in the vicinity of the maximum position of the electric field, energy due to the electric field is efficiently transmitted to the electrodeless discharge lamp 4, and the efficiency of the entire electrodeless discharge lamp lighting device can be increased. .

  Furthermore, since the electrodeless discharge lamp 4 is disposed at the coincidence point in the vicinity of the focal point of the elliptic curve, the light is condensed at the other focal point of the elliptic curve, and this condensing point becomes a pseudo light source. It is possible to provide an electrodeless discharge lamp lighting device excellent in performance.

  In addition, a part of the light from the electrodeless discharge lamp 4 may pass through the coupling window 8 and a part of the light may be lost. In order to prevent such a case, the coupling window 8 may be covered with a dielectric having a relatively high light reflectance such as white alumina. When the coupling window 8 is closed with a dielectric having a high light reflectivity as described above, the light reflected by the dielectric returns to the inside of the microwave resonator 3, so that loss of light can be prevented.

  In the present embodiment, the output of the microwave oscillator 1 is 2.45 GHz. However, when the output is 4.9 GHz, the size of the microwave resonator 3 is approximately halved.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a cross-sectional view of the present embodiment. Here, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the present embodiment, instead of the shape of the microwave resonator 3 and the spheroid 5 as shown in FIG. 6, a part of the parabola is a rotating parabola 6 rotated about the axis of the parabola. And it calculated with the calculation method similar to 1st Embodiment, and produced the electrodeless discharge lamp lighting device. The actual dimensions are as follows. The opening inner diameter of the microwave resonator 3 is φ143 mm, the height of the microwave resonator 3 is approximately 75 mm, and further, from the metal mesh 3 a that is the resonance center distance h to the arrangement position of the electrodeless discharge lamp 4. The distance was about 41 mm. And the lighting check of the electrodeless discharge lamp 4 was performed.

  Here, in the present embodiment, in addition to the effect of the first embodiment, the electrodeless discharge lamp 4 is arranged at the focal point of the parabola, so that the light reflected by the inner surface of the microwave resonator 3 is It is possible to provide an electrodeless discharge lamp lighting device having light substantially parallel to the height direction and excellent light distribution.

  Note that the operations and effects not particularly mentioned in the present embodiment are the same as those in the first embodiment.

It is a perspective view which shows 1st Embodiment. It is sectional drawing which shows 1st Embodiment. It is a top view of the metal mesh 3a. 3 is a diagram showing an electric field distribution in the microwave resonator 3. FIG. It is a characteristic view which shows the relationship between the focus of an elliptic curve, and the resonance center distance h. It is sectional drawing which shows 2nd Embodiment. It is sectional drawing which shows a 1st prior art example. In a 1st prior art example, it is a figure which shows electric field distribution in the chamber 1J4. It is sectional drawing which shows a 2nd prior art example. In a 2nd prior art example, it is a figure which shows electric field distribution in the microwave resonant cavity 2J4.

Explanation of symbols

1 Microwave Oscillator 2 Waveguide 3 Microwave Resonator 3a Metal Mesh 4 Electrodeless Lamp 5 Spheroid 6 Rotating Paraboloid 8 Coupling Window 9 Dielectric

Claims (3)

Microwave oscillator including a microwave oscillator, a waveguide that guides microwaves from the microwave oscillator, and a metal mesh that is coupled to the waveguide and that does not transmit microwaves but transmits light at least in part An electrodeless discharge lamp lighting device comprising: a micro-resonator; and an electrodeless discharge lamp disposed in the microwave resonator and having a discharge gas containing at least mercury and a rare gas enclosed therein, The shape of the wave resonator is a spheroid in which a part of the elliptic curve is rotated around the axis of the ellipse, and the direction of the maximum electric field generated in the microwave resonator is substantially perpendicular to the rotation axis An electrodeless discharge lamp lighting device characterized in that the focal point of the elliptic curve and the maximum position of the electric field substantially coincide with each other, and an electrodeless discharge lamp is disposed in the vicinity of the coincidence point. The shape of the microwave resonator is a spheroid instead of a spheroid, and a parabolic parabola is rotated around the axis of the parabola, and the direction of the maximum electric field generated in the microwave resonator is rotated. An electrodeless electrode characterized by being substantially perpendicular to the axis, the focal point of the parabola substantially coincides with the maximum position of the electric field in the microwave resonator, and an electrodeless discharge lamp is disposed near the coincidence point Discharge lamp lighting device. 3. The electrodeless electrode according to claim 1, wherein a coupling window is provided on a waveguide side of a coupling portion between the waveguide and the microwave resonator, and the coupling window is covered with a dielectric having a high reflectance. Discharge lamp lighting device.

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