JP3994658B2 - How to turn on the metal halide lamp - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for lighting a metal halide lamp for lighting a metal halide lamp.
[0002]
[Prior art]
Metal halide lamps are used in a wide range of fields because of their high brightness, high efficiency, and high color rendering. A typical metal halide lamp contains a rare gas for starting the lamp, mercury that serves as a buffer gas, and a metal halide that emits desired light. For example, a metal halide lamp in which sodium iodide, thallium iodide, and indium iodide are enclosed in an arc tube as a metal halide, or a metal halide lamp in which sodium iodide and scandium iodide are enclosed in an arc tube as a metal halide. Is widely used.
[0003]
In the metal halide lamp, the light emission amount of each metal depends on the evaporation amount of the metal halide, but the evaporation amount is greatly influenced by the temperature change at the coldest spot of the arc tube. Moreover, the vapor pressure characteristics with respect to temperature differ for each of the enclosed mercury or metal halide. Therefore, if the power supplied to the metal halide lamp is changed from the rated value, the light emission amount and color balance of the metal will fluctuate individually due to the temperature change at the coldest spot of the arc tube, so the overall light color will be greatly It will change. For these reasons, until recently, it has been difficult to realize lighting (so-called dimming lighting) in which the light output can be freely changed by changing the power supplied to the metal halide lamp while keeping the light color characteristic substantially constant. The way of looking was powerful.
[0004]
However, in recent years, metal halide lamps have been devised in which such light color change is reduced and dimming lighting is possible (for example, Japanese Patent Laid-Open Nos. 6-84496 and 6). No. -111772 or JP-A-8-203471).
[0005]
[Problems to be solved by the invention]
However, in the conventional metal halide lamp lighting device, there is a concern that the lamp life may be impaired if the dimming lighting is performed by supplying power equal to or lower than the rated power to the lamp. In fact, in the United States, ballasts for metal halide lamps already equipped with dimming lighting means are commercially available, and considering the effect on lamp life, the lamp power during dimming lighting is set to 50% or more of the rated power, and Although there is a view that lighting is performed at the rated power for at least 15 minutes at the time of starting, the basis of this view is not necessarily clear, and the problem concerning the lamp life remains.
[0006]
The present invention has been made in view of the above circumstances, and an object thereof is to provide a lighting method of a metal halide lamp that can increase the lamp life without adversely affecting the luminous flux maintenance factor. .
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a metal halide lamp for lighting a metal halide lamp in which a metal halide, mercury, and a rare gas are sealed in a translucent container in which a pair of electrodes are hermetically sealed is provided. In the lighting method, the rated power and the power that is equal to or lower than the rated power and that is equal to or higher than the luminous flux maintenance factor at the time of lighting with the rated power are supplied from the lighting means to the metal halide lamp, and the power supplied by the lighting means is changed. When the metal halide lamp is started, the power supplied to the lamp is set to be more than the power at the inflection point at which the rate of change of the electrode temperature with respect to the stable electric power changes suddenly. Not only does the luminous flux maintenance factor not decrease, but the luminous flux maintenance factor can be further increased and the lamp life can be increased as compared with lighting with only the rated power.
[0008]
Also, as in the invention of claim 2, from pre-Symbol lit means, it is desirable to supply the rated power or less power within a predetermined time after starting the metal halide lamp.
[0009]
Further, as in the invention of claim 3 , it is desirable that the lighting means supplies power equal to or lower than the rated power to the metal halide lamp from the start.
[0010]
According to a fourth aspect of the present invention, it is desirable that the lighting means has a time for supplying power equal to or lower than the rated power to the metal halide lamp during lighting.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0012]
(Embodiment 1)
As described above, there is a concern that the lamp life may be reduced when the dimming lighting of the metal halide lamp is performed. The reason is considered to be the electrode as described below. Usually, the electrode temperature of the metal halide lamp is designed to be within a temperature range in which thermionic electrons can be sufficiently emitted when the cathode is lit at the rated power. However, if the electrode temperature is too low due to dimming lighting, electron emission from the cathode becomes insufficient as described below.
[0013]
The relationship between the thermionic emission current density J at the cathode and the absolute temperature T of the electrode is the Richardson-Dashman equation when an external electric field E is applied,
J = AT ² exp {−φ / kT + (e / 2kT) · (eE / πε ₀ ) ^1/2 } (1)
Can be used.
[0014]
In the above formula (1), A is a constant depending on the material and surface state of the electrode, φ is the work function of the electrode, k is the Boltzmann constant, e is the elementary charge, and ε ₀ is the dielectric constant of vacuum. In the formula (1), it is assumed that the external electric field E is small and the second term of the exponent part of the formula (1) can be ignored as compared with the first term. At this time, in order to obtain the necessary current density J, the electrode temperature has a threshold T _{0 at} which thermionic electrons can be emitted, and when T> T ₀ , the current necessary for lighting the metal halide lamp can be easily emitted. However, it can be seen that the current density J = 0 substantially at T <T ₀ . Therefore, if the power supplied to the metal halide lamp is reduced too much, the electrode temperature falls below the lower limit T ₀ of the appropriate temperature range, and thermionic emission at the cathode becomes insufficient.
[0015]
Actually, even when the electrode temperature drops below T ₀ , the electric field E (cathode drop voltage) near the cathode is strengthened, and the second term in the exponent part of the equation (1) becomes large (of the Schottky effect). Increase), the current density J does not immediately become zero. Further, when the electric field E is strengthened, there is a possibility that electrons are supplied from the cathode by the field electron emission mechanism in addition to the thermionic emission mechanism. Therefore, even if the electrode temperature falls below T ₀ , the discharge is caused to some extent. It is thought that it will be maintained. On the other hand, it is considered that the probability of scattering (sputtering) of the electrode material due to ion impact increases as the cathode fall voltage increases. Therefore, when the metal halide lamp is turned on in a state where the electrode temperature is lower than T ₀ , the arc tube is blackened early, and there is a possibility that the luminous flux maintenance factor may be reduced as compared with lighting with only the rated power. . Further, the blackening of the arc tube causes an increase in the arc tube temperature during lighting. Accordingly, the lamp voltage rises and the impurity gas concentration inside the arc tube rises early compared to lighting with only the rated power, and as a result, the metal halide lamp is not turned on early, thereby reducing the lamp life. The possibility is feared.
[0016]
In the United States, in order not to adversely affect the lamp life, it is considered that the electric power at the time of dimming lighting is considered to be 50% or more of the rated power for the above reason. However, it is difficult to assume that the temperature range of electrodes that can emit thermoelectrons is 50% or more of the rated power, regardless of the lamp of any manufacturer, and the basis for the value of 50% is unclear. Therefore, in order to be able to specify the power condition that will not affect the lamp life, which will be different for each lamp, the following experiment was conducted.
[0017]
If the lower limit T _{0 of the} electrode temperature at which thermionic emission is possible is known, it is considered that power conditions that do not adversely affect the luminous flux maintenance factor can be obtained. From the above, the current density J and the electrode temperature at T <T ₀ The relationship of T is considered to be different from the relationship between the current density J and the electrode temperature T when T> T ₀ . Therefore, it was considered that if the relationship between the current density J and the electrode temperature T is examined with respect to the power range in which lighting can be maintained, knowledge about the lower limit T ₀ can be obtained. However, during the lighting of the metal halide lamp, the current is limited by the ballast impedance, and it is difficult to directly measure the current density J. Therefore, instead of the current density J, the lamp current was substituted, and the relationship between the lamp current and the electrode temperature T was examined. As a result, the relationship between the power range that does not adversely affect the luminous flux maintenance factor and the electrode temperature T has been clarified. Hereinafter, the process of this experiment and the obtained results will be described as Embodiment 1 of the present invention.
[0018]
FIG. 1 is a schematic configuration diagram of a lighting device for realizing the first embodiment. As the lamp 1, a 400W metal halide lamp (part number: M400 · L / BU-SC-P) manufactured by Matsushita Electric Industrial Co., Ltd. was used. As the ballast 2 as the lighting means, various types of ballasts of various impedances are manufactured so that the lamp 1 can be supplied with electric power that is rated power or less than the rated power and ensures the luminous flux maintenance rate at the rated power or more when the lamp is turned on. Used. However, the combination of the lamp 1 and the ballast 2 used in the present embodiment is merely an example, and is not particularly limited to the present embodiment.
[0019]
The lamp 1 was started and lit by supplying various electric powers of different sizes to the lamp 1 using the lighting device of the present embodiment. Then, the electrode surface temperature near the arc end at the tip of the lower electrode after the lighting state of the lamp 1 was stabilized was measured using a thermography device. FIG. 2 shows the results of plotting the relative electrode temperatures measured by the thermography apparatus in this way against the lamp current and power, and examining the change tendency of the electrode temperature with respect to the lamp current and power. As apparent from FIG. 2, the electrode temperature tends to decrease as the power decreases as a whole. However, when viewed in detail, there is a region where the gradient of change is gentle from 300 W to 250 W. It can be seen that at power lower than this region, the rate of change with respect to the supplied power suddenly increases, and an inflection point exists in the vicinity of about 250 W.
[0020]
As seen in FIG. 2, the electrode temperature did not change much from 300 W to 250 W. When the discharge state in the vicinity of the electrode in this power range was observed, the size of the cathode bright spot decreased as the power decreased. From this, it has been found that in this power range, the electrode is at a temperature at which thermionic electrons can be sufficiently emitted, and the electrons necessary for maintaining the discharge are supplied by changing the area of the electron emission portion. On the other hand, when the discharge state in the vicinity of the electrode at the power of the inflection point (250 W) or less was observed, the cathode bright spot was unstable and the lamp 1 flickered. Since the cathode bright spot was not stable, it was found that the electrode temperature sufficient for thermionic emission was not obtained on the lower power side than the inflection point. Therefore, there is a concern that the lamp life may be adversely affected on the lower power side than the inflection point found in FIG.
[0021]
Therefore, in order to see the correlation between what is expected from the above experimental results, that is, whether the power supplied to the lamp 1 is higher or lower than the inflection point and the lamp life, the power supplied to the lamp 1 is 400 W (rated power), 270 W, and 210 W were used, and a life test was performed on the same type of lamp 1 as a sample. In this life test, one lighting time was set to 5 hours and 30 minutes, and a lighting / extinguishing cycle in which lighting was performed again for 5 hours and 30 minutes after turning off for 30 minutes was repeatedly performed. The test was interrupted at regular intervals, the lamp characteristics were measured, and the change with time was examined. A part of the result is shown in FIG.
[0022]
FIG. 3 is a plot of the luminous flux maintenance factor of each lamp 1 with respect to the lighting time, and shows a higher value of the luminous flux maintenance factor in the order of 270 W> 210 W> 400 W. Therefore, it has been found that supplying power less than the rated power to the lamp 1 has the effect of increasing the luminous flux maintenance factor in some cases, rather than impairing the luminous flux maintenance factor of the lamp 1. On the other hand, from the result that the lamp 1 that is lit at 210 W rather than 270 W has a lower luminous flux maintenance factor, as expected, the luminous flux maintenance factor is lower in the power region lower than the inflection point (250 W). It turned out to turn down. Further, as described above, at the power lower than the inflection point, the cathode bright spot was unstable and the lamp 1 flickered, and the lighting state was unstable. For these reasons, it is permissible to supply the lamp 1 with power below the inflection point found in FIG. 2 even when the luminous flux maintenance factor is improved as compared with lighting with only the rated power. It became clear that it should not be included in the lighting conditions.
[0023]
Therefore, in the present embodiment provided with the ballast 2 as the lighting means that can supply the metal halide lamp with the rated power and the power that is equal to or lower than the rated power and secures the luminous flux maintenance factor at the time of lighting with the rated power. When starting with a different power supply, specify the power that should be supplied from the ballast 2 to the lamp 1 to be more than the power at the inflection point at which the rate of change of the electrode temperature with respect to the power changes abruptly. Thus, not only the luminous flux maintenance factor does not decrease even when the dimming lighting is performed, but also the luminous flux maintenance factor can be further increased and the lamp life can be increased as compared with lighting with only the rated power.
[0024]
(Embodiment 2)
By the way, as already explained, in the United States, considering the influence on the lamp life, at the time of start-up, there is an opinion that the lamp will be lit at the rated power for a minimum of 15 minutes. Can be considered. That is, when the lamp is started with power less than or equal to the rated power, it takes time for the electrode temperature to stabilize compared to when the lamp is started with rated power. Therefore, it is thought that the reason is that the luminous flux maintenance factor decreases due to the increase in arc tube blackening due to the sputtering of the electrode material within this time. However, no reason can be found in the 15 minute period. Moreover, the question remains whether the rated power must be supplied to the lamp at the time of starting regardless of the power at the time of dimming lighting. Therefore, regardless of the power at the time of dimming lighting, it is necessary to always avoid the dimming start, and if necessary, in order to investigate how many minutes the rated lighting time is required, The experiment described was conducted.
[0025]
FIG. 4 is a schematic configuration diagram of a lighting device that realizes the lighting method of the present embodiment. The AC 200V commercial power supply and the ballast 3 are connected to each other via a path via the switch 4 and a path not via the switch 4, and the lamp 1 is connected to the output side of the ballast 3. Thus, the power supplied from the ballast 3 to the lamp 1 is switched between the rated power and the power less than or equal to the rated power according to the on / off state of the switch 4. Here, as the ballast 3, a 400W mercury lamp dimming ballast (product number: YZ40121433) manufactured by Matsushita Electric Works, Ltd. was used. As the lamp 1, a 400W metal halide lamp (part number: M400 · L / BU-SC-P) manufactured by Matsushita Electric Industrial Co., Ltd. was used. However, the combination of the ballast 3 and the lamp 1 used in the present embodiment is merely an example, and is not particularly limited to the present embodiment.
[0026]
In the present embodiment, a life test was performed in which a lighting time of one time was 5 hours and 30 minutes, and a lighting / lighting cycle in which lighting was performed again for 5 hours and 30 minutes after lighting for 30 minutes was repeated. In the present embodiment, the rated power or lower power is supplied to the lamp 1 under the following time conditions within one lighting time.
(A) The engine was started at the rated power (400 W), and 400 W of power was input to the lamp 1 even during lighting.
(B) The engine was started at the rated power (400 W), turned on at the rated power for 30 minutes, and then 270 W power was input to the lamp 1.
(C) The engine was started at the rated power (400 W), turned on at the rated power for 15 minutes, and then 270 W of power was input to the lamp 1.
(D) The engine was started at the rated power (400 W), turned on at the rated power for 4 minutes, and then 270 W of power was input to the lamp 1.
(E) Power was started at 270 W, and 270 W power was input to the lamp 1 even during lighting.
[0027]
FIG. 5 shows a part of the result of measuring the lamp characteristics by interrupting the test at regular intervals and measuring the change over time. FIG. 5 is a diagram showing a change in the luminous flux maintenance factor of the lamp 1 used in the present embodiment. In FIG. 5, curves a to e correspond to the above conditions (a) to (e). FIG. 5 shows that the luminous flux maintenance factor is good in the order of e≈d≈c>b> a. Further, although all the lamps 1 decreased by about 5% in the tens of hours from the start of the test, the lamps 1 that are turned on under the lighting conditions (e), (d), and (c) are turned on. It can be seen that a recovery phenomenon of the light intensity was observed after the time.
[0028]
In the present embodiment, 270 W is used as the power less than or equal to the rated power supplied to the lamp 1, but the power less than or equal to the rated power supplied to the lamp 1 is not particularly limited to the present embodiment. It was confirmed that the same results could be obtained with any power, so long as it was within the described power range.
[0029]
Even if dimming lighting is performed by lighting the lamp 1 with the rated power as described above and supplying the power below the rated power within a predetermined time or starting the lamp 1 with the power below the rated power. Not only does the luminous flux maintenance factor not decrease, but the luminous flux maintenance factor can be further increased and the lamp life can be increased compared to lighting with only the rated power.
[0030]
(Embodiment 3)
Since the configuration of the lighting device that realizes the lighting method of the present embodiment is the same as that of the second embodiment, illustration and description thereof are omitted.
[0031]
In the present embodiment, a life test was performed in which a lighting time of one time was 5 hours and 30 minutes, and a lighting / lighting cycle in which lighting was performed again for 5 hours and 30 minutes after lighting for 30 minutes was repeated. In addition, the lighting time at a power lower than the rated power within one lighting time was set to 0 or 2 hours, and the power at the rated power or lower was supplied to the lamp 1 under the following time conditions.
(A) The engine was started at the rated power (400 W), and 400 W was input to the lamp 1 even during lighting.
(B) Although the engine was started and lit at the rated power (400 W), 270 W of power was input to the lamp 1 for 2 hours from 1 hour to 3 hours after the start.
(C) Although the engine was started and lit at the rated power (400 W), 270 W of power was input to the lamp 1 for 2 hours from 3 hours 30 minutes after the start until the end of lighting.
(D) The lamp was started and lit with power of 270 W, but the rated power (400 W) was input to the lamp 1 for 3 hours and 30 minutes from 2 hours after the start until the end of lighting.
[0032]
The test was interrupted at regular intervals, the lamp characteristics were measured, and the change with time was examined. A part of the result is shown in FIG. FIG. 6 is a diagram showing a change in the luminous flux maintenance factor of the lamp 1 used in the present embodiment. In FIG. 6, curves A to D correspond to the above conditions (A) to (D). From FIG. 6, it can be seen that the luminous flux maintenance factors of the above (B), (C), and (D) are comparable, and both are superior to the condition (A). Therefore, conditions (B), (C), and (D) in which lighting with power below the rating is performed for 2 hours between lighting with rated power, compared to conditions (A) with lighting only with rated power. It can be seen that the luminous flux maintenance factor is increased.
[0033]
In the present embodiment, the lighting time with the power below the rating is 2 hours, but is not particularly limited to 2 hours. Although there is a difference in degree, the effect of increasing the luminous flux maintenance factor compared to lighting with only the rated power by lighting at less than the rated power between lighting at the rated power at any time Was confirmed.
[0034]
Further, in this embodiment, 270 W is used as the power less than the rated power supplied to the lamp 1, but the power less than the rated power supplied to the lamp 1 is not particularly limited to this embodiment. It was confirmed that the same results could be obtained with any power, so long as it was within the described power range.
[0035]
As described above, by providing the lamp 1 with a time equal to or lower than the rated power supplied from the ballast 3 during lighting, the luminous flux maintenance factor does not decrease even when the dimming lighting is performed. Compared with only lighting, the luminous flux maintenance factor can be further increased and the lamp life can be increased.
[0036]
【The invention's effect】
As described above, the present invention provides a method for lighting a metal halide lamp in which a metal halide lamp is formed by sealing a metal halide, mercury, or a rare gas in a translucent container in which a pair of electrodes are hermetically sealed. When the power is supplied from the lighting means to the metal halide lamp that is equal to or lower than the rated power and ensures the luminous flux maintenance rate at the rated power or higher, and the metal halide lamp is started by changing the power supplied by the lighting means. Since the power supplied to the lamp is set to be equal to or higher than the power at the inflection point at which the rate of change of the electrode temperature with respect to the stable power changes suddenly, not only the luminous flux maintenance rate does not decrease even if dimming is performed. As compared with lighting only with rated power, there is an effect that the luminous flux maintenance factor can be further increased and the lamp life can be increased.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating a lighting device for realizing a lighting method according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram of the above.
FIG. 3 is a view showing a life test result as described above.
FIG. 4 is a schematic configuration diagram illustrating a lighting device for realizing a lighting method according to a second embodiment of the present invention.
FIG. 5 is a view showing a life test result as described above.
FIG. 6 is a diagram showing a life test result of Embodiment 3 of the present invention.
[Explanation of symbols]
1 Metal halide lamp 2 Ballast

Claims (4)

In a lighting method of a metal halide lamp in which a metal halide lamp is formed by sealing a metal halide, mercury, or a rare gas in a light-transmitting container in which a pair of electrodes are hermetically sealed, the rated power is equal to or lower than the rated power. Supplying the power to the metal halide lamp from the lighting means to ensure the luminous flux maintenance rate at the time of lighting with the rated power, and when the metal halide lamp is started by changing the power supplied by the lighting means, the power supplied to the lamp A method for lighting a metal halide lamp, characterized in that the power is higher than the power at the inflection point at which the rate of change of the electrode temperature with respect to the stable electrode temperature changes rapidly . 2. The method for lighting a metal halide lamp according to claim 1 , wherein the lighting means supplies power equal to or lower than the rated power to the metal halide lamp within a predetermined time from starting . Lighting method of claim 1 wherein the metal halide lamp and supplying from said lighting means, the power follows the rated power from the start to a metal halide lamp. Lighting method of claim 1 wherein the metal halide lamp which comprises said more lighting means, the time for supplying the rated power or less power to the metal halide lamp during operation.

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