JP2005032711A - Lighting method of high-pressure discharge lamp and lighting device, high-pressure discharge lamp device, and projection type image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting method capable of shortening a rising period of a high-pressure discharge lamp. <P>SOLUTION: Insulation of the high-pressure discharge lamp is broken by impressing high voltage pulse on it, and afterwards, whether the lamp voltage exceeds 25 V or not is judged at a step S1. If the lamp voltage does not exceed 25V (step S1: NO), a constant current control of setting a current limit level at 6A is applied (step S2), and if the lamp voltage exceeds 25V (step S1: YES), it is switched to the constant current control of setting the current limit level at 4A (step S3). When the lamp voltage rises up to 50V (step S4: YES), the constant power control is applied so that the lamp power becomes 200W (step 5). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a lighting method and a lighting device for a high pressure discharge lamp, a high pressure discharge lamp device, and a projection type image display device.

  In general, a high-pressure discharge lamp such as a high-pressure mercury lamp or a metal halide lamp has an excellent advantage that a high-luminance luminous flux can be obtained. On the other hand, the time from the start of discharge until a constant luminous flux can be obtained. (Hereinafter, referred to as “light rise time”) is long, and it has heretofore been a problem in high pressure discharge lamps to shorten the light rise time.

In particular, recent projection-type image display devices (hereinafter referred to as “projectors”) are desired to have high screen illuminance, and therefore, it is necessary to use a high-power high-pressure discharge lamp.
However, the structure of a high-pressure discharge lamp becomes larger as the output becomes higher. Therefore, the heat capacity of the lamp components including the glass bulb increases, and the lamp does not easily warm from the start of lamp operation, and the light emitting metal in the discharge space The actual situation is that the evaporation rate of the light becomes slower and the light rise time becomes longer.

In order to eliminate such problems, in the lighting method for high-pressure discharge lamps for automobiles, immediately after the start of lighting, an excessive electric power is supplied to the lamp more than at the time of steady lighting to promote light rise, and then constant power control Have been proposed (see, for example, Patent Document 1 and Patent Document 2).
JP-A-4-349396 JP-A-8-78175

However, when the lighting method for a high-pressure discharge lamp for an automobile as described above is applied to a high-pressure discharge lamp for a projector, there is a problem that the tip of the lamp electrode is melted to cause a great damage.
In other words, high-pressure discharge lamps for automobiles are standardized by the Japan Light Bulb Industry Association standards, etc., and are designed with a margin in electrode size relative to the lamp power, so that the power consumption is higher than that during steady lighting. Is designed so that the lamp electrode is not easily damaged even if the lamp is supplied, and the xenon gas is sealed at a high pressure of 500 kPa or more, so that the resistance component in the discharge space is large and the lamp current does not become excessively large. To be suppressed. Thus, in the high-pressure discharge lamp for automobiles, the electrodes are not damaged even by the lighting method disclosed in Patent Documents 1 and 2 above.

However, in a high-pressure discharge lamp for a projector, it is necessary to increase the brightness in order to ensure screen brightness.
In order to increase the brightness, it is necessary to increase the arc temperature by keeping the tip of the electrode at a high temperature during lighting. Therefore, the electrode size must be reduced as much as possible to reduce the heat capacity. In addition, it is necessary to use a point light source in order to increase the light collection efficiency of the concave reflecting mirror. However, if the distance between the electrodes is shortened, the lamp current tends to flow. If excessive power is supplied, the lamp current increases excessively. There is a fear.

Therefore, if excessive power exceeding the steady lighting condition is supplied to such a projector high-pressure discharge lamp under the same conditions as an automotive high-pressure discharge lamp, the temperature at the tip of the electrode will rise abnormally and melt, resulting in a point light source. Is difficult, and in the worst case, lighting is poor.
Here, it is conceivable that a high-pressure discharge lamp for projectors is filled with a rare gas such as xenon gas at a high pressure to increase the resistance in the discharge space. However, as described above, the high-pressure discharge lamp for projectors is relatively large. Therefore, it is difficult in terms of manufacturing technology to enclose a rare gas at a certain high pressure.

In view of the above circumstances, in the conventional method of lighting a high pressure discharge lamp for a projector, in order to prevent damage to the electrodes, the initial lighting interval from the start of lighting until constant power control is reached is the maximum during constant power control. Constant current control is performed so as to supply a current value that does not exceed the current value, and shortening of the light rise time is extremely difficult.
The present invention has been made in view of the above-described problems, and even in a high-pressure discharge lamp that has been widely used, the high-pressure discharge that can shorten the light rise time without damaging the electrodes and the like. An object of the present invention is to provide a lamp lighting method and lighting device, a high-pressure discharge lamp device, and a projection-type image display device.

  In order to achieve the above object, the lighting method of the high pressure discharge lamp according to the present invention starts the lighting in the initial lighting section after the lighting of the high pressure discharge lamp starts until the lamp voltage reaches a predetermined voltage and switches to constant power control. To a lamp current larger than a predetermined current value in all or a part of the first lighting section until reaching a lamp voltage at which an arc spot starts to be continuously formed on at least one electrode of the high-pressure discharge lamp. A first step and a second step of supplying a lamp current equal to or lower than the predetermined current value in all or a part of the second lighting section after the first lighting section has elapsed and before switching to the constant power control; It is characterized by having.

Further, according to another high-pressure discharge lamp lighting method according to the present invention, the high-pressure discharge lamp to be lit has a distance between electrodes of 0.5 mm or more and 2.0 mm or less, and an amount of mercury enclosed per arc tube volume. 150 mg / cm ³ or more and 350 mg / cm ³ or less, and argon, krypton, or xenon as a rare gas is enclosed at an enclosure pressure of 10 kPa or more and 40 kPa or less. In the initial lighting period until reaching a predetermined voltage and switching to constant power control, the lamp current is larger than a predetermined current value in the first lighting period from the start of lighting until the lamp voltage reaches a predetermined voltage of 27 V or less. In the first lighting step and the second lighting period after the first lighting period has elapsed until switching to the constant power control. And a second step of supplying a lamp current equal to or less than a predetermined current value.

With such a lighting method, a large current flows in the first lighting section that does not affect the electrode damage, so that the temperature rise of the light emitting part of the high-pressure discharge lamp is promoted and the light rise time is shortened. In addition, since the current supplied to the second lighting section is kept small, the electrode is not damaged.
Here, it is desirable that the predetermined current value is equal to a maximum value of a current supplied when the constant power control is executed.

In this way, it is possible to supply as much current as possible within a range that does not affect the electrode damage even in the second lighting period, which can contribute to shortening the light rise time.
Here, it is desirable to supply a lamp current that is approximately 1.25 times or more the predetermined current value in the first lighting section.
By doing so, the light rise time can be shortened to a satisfactory level.

  The lighting device for a high-pressure discharge lamp according to the present invention is a high-pressure discharge lamp that performs constant power control when the lamp voltage reaches a predetermined voltage after the high-voltage discharge lamp is dielectrically broken to start lighting. A current supply means for supplying current to the high-pressure discharge lamp, and from the start of lighting until reaching a lamp voltage at which an arc spot starts to be continuously formed on at least one electrode of the high-pressure discharge lamp. In the whole or part of the first lighting section, a lamp current larger than a predetermined current value is supplied, and after the passage of the first lighting section, in all or part of the second lighting section until switching to the constant power control And a current control means for controlling the current supply means so as to supply a lamp current equal to or lower than the predetermined current value.

Further, in another high pressure discharge lamp lighting device according to the present invention, the high pressure discharge lamp to be lit has an interelectrode distance of 0.5 mm or more and 2.0 mm or less, and an amount of mercury enclosed per volume in the arc tube. Is 150 mg / cm ³ or more and 350 mg / cm ³ or less, and argon, krypton, or xenon as a rare gas is enclosed at an enclosure pressure of 10 kPa or more and 40 kPa or less, and the high pressure discharge lamp is dielectrically broken to start lighting. After that, when the lamp voltage reaches a predetermined voltage, it is a high pressure discharge lamp lighting device that performs constant power control, current supply means for supplying current to the high pressure discharge lamp, from the start of lighting, A lamp current larger than a predetermined current value is supplied in all or part of the first lighting period until the lamp voltage reaches a predetermined voltage of 27 V or less. And a current for controlling the current supply means so as to supply a lamp current equal to or lower than the predetermined current value in all or a part of the second lighting period after the first lighting period has elapsed until switching to the constant power control. And a control means.

With such a lighting device, the above-described excellent lighting method can be implemented, and the light rise time can be shortened without damaging the electrodes of the high-pressure discharge lamp.
Here, it is desirable that the predetermined current value is equal to a maximum value of a current supplied when the constant power control is executed.
In this way, it is possible to supply as much current as possible within a range that does not affect the electrode damage even in the second lighting period, which can contribute to shortening the light rise time.

A high-pressure discharge lamp device according to the present invention includes a high-pressure discharge lamp and any one of the above-described lighting devices for lighting the high-pressure discharge lamp.
Furthermore, the projection-type image display device according to the present invention is characterized in that the high-pressure discharge lamp device described above is used.
Thereby, as described above, a high-pressure discharge lamp device and a projection-type image display device having a short light rise time can be obtained.

Hereinafter, a lighting device for a high pressure discharge lamp according to an embodiment of the present invention will be described by taking as an example a case where the high pressure discharge lamp is a high pressure mercury lamp.
(1) Configuration of the high-pressure mercury lamp 100 First, a characteristic configuration of the high-pressure mercury lamp 100 for a projector to be turned on in the present embodiment will be briefly described with reference to FIG.

  As shown in FIG. 1, the high-pressure mercury lamp 100 includes a light emitting portion 1 having a substantially spherical shape or a substantially spheroid shape in which a discharge space 12 is formed, and first light emitting portions 1 provided at both ends of the light emitting portion 1. A quartz glass bulb 14 having one sealing portion 2 and a second sealing portion 3, an electrode structure in which electrodes 4 and 5, molybdenum foils 6 and 7, and external leads 8 and 9 are sequentially connected to each other. Body 10 and 11 are provided.

The electrodes 4 and 5 are made of tungsten, and electrode coils 42 and 52 are fixed to the tip portions of the electrode shafts 41 and 51, respectively. The electrodes 4 and 5 are disposed so as to be substantially opposed to each other in the light emitting unit 1. The external lead wires 8 and 9 are made of molybdenum, and are led out from the end surfaces of the sealing portions 2 and 3 to the outside.
The interelectrode distance De is set in the range of 0.5 mm to 2.0 mm in order to approach the point light source.

A predetermined amount of mercury 13 which is a luminescent metal, rare gas such as argon, krypton and xenon, and halogen substances such as iodine and bromine are sealed in the light emitting unit 1 as a starting assisting gas.
Specifically, amount of the enclosed mercury 13 is in the range of arc tube volume per ^{150mg / cm 3 ~350mg / cm 3} , sealed pressure during lamp cooling of the rare gas in the range of 10KPa～40kPa, also, the halogen material The amount of encapsulation is set in the range of 1 × 10 ⁻¹⁰ mol / cm ³ to 1 × 10 ⁻⁴ mol / cm ³ .

The range of other lamp dimensions is as follows.
Lamp total length Da: 40 mm to 100 mm
Light emitting part diameter Db: 8 mm to 15 mm
Sealing part diameter Dc: 4 mm to 10 mm
In the present specification, when the numerical range is expressed as “ab”, the range including the lower limit a and the upper limit value is also indicated.

(2) Lighting Method of High Pressure Mercury Lamp 100 Next, a suitable lighting method of the high pressure mercury lamp 100 will be described.
FIG. 2 shows a lamp voltage (V) supplied after applying a high-pressure pulse to cause a dielectric breakdown in a 200 W rated high-pressure mercury lamp 100 by a lighting device described later in this embodiment (see FIG. 7). It is a graph which shows the control characteristic of a lamp current (A).

  In the high-pressure mercury lamp 100, the mercury vapor pressure increases as the temperature in the discharge space rises after dielectric breakdown, and the lamp voltage V gradually increases. However, as shown in FIG. In the first lighting section until the lamp reaches the constant voltage control, the lamp current is controlled to be 6 A, and the voltage Vb when the lamp voltage exceeds Va and switches to constant power control (50 V in this embodiment). In the second lighting period until reaching, the constant current control is performed so that the lamp current becomes 4A.

For example, the constant current of 4A is supplied by setting the current limit level to 4A in a known constant current circuit.
Then, when the lamp voltage V reaches 50 V, switching to constant power control is performed so as to maintain the rated power of 200 W of the lamp (constant power control section).
Here, the portion of the broken line in the figure shows the value of the lamp current in the conventional lighting method, and the electrode 4 is supplied by supplying a lamp current 6A higher than this in the first lighting section immediately after the start of lighting. , 5 is increased, and the temperature rise in the discharge space is promoted.

Note that the value of the voltage Va that defines the range of the first lighting period is set to 25 V, and during such a first lighting period, the maximum current value in the constant power control period (predetermined current value: 4A) The inventors of the present invention have experimentally determined that the electrodes are not damaged even when a higher lamp current (6A in this example) is supplied. Details will be described later along with experimental data.
FIG. 3 is a graph showing the relationship between the lamp voltage and the lamp power when the lamp current control is executed according to the control characteristics of the graph of FIG. 2, and FIG. 4 is the lighting when the lamp current control of FIG. It is a graph which shows the relationship between the lighting time after the start (s) and the rise of the lamp luminous flux when the luminous flux during steady lighting is 100%.

In both cases, the solid line indicates the change in the lighting method according to the present embodiment, and the broken line portion indicates the change in the conventional lighting method.
As shown in FIG. 3, in the first lighting section, a larger amount of electric power is supplied than in the conventional case by an area substantially shaded, and as a result, the time required to reach 50% luminous flux as shown in FIG. The lighting method in the present embodiment is shortened by Δt (about 12 seconds). As shown in the figure, in the prior art, it took about 45 seconds for 50% of the light to rise, so that it was shortened by about 27%.

(3) The optimum range of the lamp voltage Va and the lamp current in the first lighting section Next, based on the experiment, the optimum range of the lamp voltage Va for switching the first lighting section and the second lighting section, and also in the first lighting section Consider the optimal range of lamp current.
(Experiment 1)
First, an experiment was conducted on the optimum range of the lamp voltage Va in the 200 W high-pressure mercury lamp 100.

The lamp used in this experiment is a high-pressure mercury lamp having the same configuration as that shown in FIG. 1, and the specific specifications are as follows.
Mercury content 200 mg / cm ³ per volume
Filling pressure at the time of lamp cooling of rare gas 30kPa
Distance between electrodes De 1.5mm
Lamp total length Da: 90mm
Light emitting part diameter Db: 13 mm
Sealing part diameter Dc: 8.0 mm
In addition, each electrode uses a double-wound 8-stage coil attached to the tip of the electrode shaft, the electrode shaft diameter d1 (see FIG. 5A) is 0.4 mm, and the electrode coil 42 is used. , 52 has a diameter d2 of 0.25 mm.

  The following Table 1 shows that for the prototype lamp, the constant current value (first current limit level) supplied in the first lighting section is sequentially changed from the conventional 4A to twice that value, and each first current limit is changed. In the level value, the lamp voltage Va for defining the first lighting section (note that the lamp voltage of this Va is a constant current value (second current supplied to the first current limiting level in the second lighting section). In the following, it is sometimes referred to as “current switching voltage” in the meaning of the lamp voltage when switching to the limit level.) The degree of damage to the electrodes of the high-pressure mercury lamp when the voltage is changed is investigated.

ここで、表中の２から１４の数字は、各電流条件で１時間点灯した後の一対の電極の電極先端部の溶融した電極コイルの段数の和を示す。
図５（ａ）は、点灯実験前の電極４の拡大図であり、電極棒４１の先端に２重巻き８段の電極コイル４２が形成されている（電極５も全く同じ）。

Here, the numbers 2 to 14 in the table indicate the sum of the number of stages of the melted electrode coils at the electrode tip portions of the pair of electrodes after lighting for 1 hour under each current condition.
FIG. 5A is an enlarged view of the electrode 4 before the lighting experiment, in which an electrode rod 41 is formed with a double-winding 8-stage electrode coil 42 (the electrode 5 is exactly the same).

In the conventional lighting method (supplying a lamp current of 4 A without distinguishing between the first and second lighting sections), after lighting for one hour, as shown in FIG. The lamp is designed so that only 421 is melted.
Therefore, in this experiment, when two or more coils are melted in each electrode and the sum of the number of coils of the pair of electrodes is four or more, it is evaluated that “the electrode is damaged”. ing.

Then, as can be seen from Table 1, when the current switching voltage Va is set to 30 V or higher, except for the first current limit level of 4 A, that is, a current of 4.5 A or higher even if the lamp voltage is 30 V or higher. When energized, the number of melting stages of the coil became two or more, and it was determined that “the electrode was damaged”.
However, when the current switching voltage Va is set to 25 V, control is performed so that a current of 4.5 A or more is energized until then, and the current limit level is lowered to 4 A, the current limit voltage is reduced for all current limit levels. No damage occurred.

In Table 1, the current switching voltage Va was changed in increments of 5V. In order to obtain more detailed data, an experiment was conducted in which the current switching voltage Va was changed in increments of 1V from 20V to 30V. Experimental results as shown in Table 2 were obtained.
However, in this experiment, the first current limit level is fixed at 6A, and the second current limit value level is 4A as in the experiment of Table 1.

この実験結果から言えば、電流切替電圧が２５Ｖ以下であればコイルの溶融段数の和が２段以下であり、電極の損傷はなく、２８Ｖ以上であれば、コイルの溶融段数の和が４段以上となり電極の損傷領域と判断される。２６Ｖから２７Ｖについてはコイルの溶融段数の和が３段であり良否の判断がつかないため、溶融段数の和が３段となる点灯条件が実用上使用可能か否かを判断するべく寿命試験での評価を試みた。

According to the experimental results, if the current switching voltage is 25 V or less, the sum of the number of melting stages of the coil is 2 or less, and there is no damage to the electrodes. If the voltage is 28 V or more, the sum of the melting stages of the coil is 4 stages. Thus, it is determined that the region is a damaged region of the electrode. For 26V to 27V, the sum of the number of melting stages of the coil is 3 stages, and it cannot be judged whether it is good or bad. Therefore, in the life test, it is determined whether the lighting conditions where the sum of the number of melting stages is 3 are practically usable. I tried to evaluate.

  Here, the life test of the lamp uses a full-bridge electronic ballast of rectangular wave lighting whose rated output power is 200 W, the current limit level in the first lighting section is 6 A, and the current limit level in the second lighting period is 4 A. And three conditions of 25V, 27V, and 28V were prepared as current switching voltages. The high-pressure discharge lamp 100 was put into a state of a lamp unit 200 described later (see FIG. 9), and kept at a horizontal position in a cycle of lighting for 3.5 hours / turning off for 0.5 hours. Each sample was tested for 5 samples, and the life characteristics were judged by the illuminance maintenance rate after 1000 hours of cumulative lighting time.

  When the average value of the illuminance maintenance ratio is obtained, the average when the current switching voltage is 25V is 86.3%, whereas when the current switching voltage is 27V, it is 83.8%. When V was 28V, it was 75.5%. Since the life target performance of this 200 W type lamp is 80% or more when reaching 1000 hours, when the number of melting stages of the coil is 3, that is, when the current switching voltage is 26V to 27V, the current switching voltage is 25V. Although there was some characteristic deterioration with respect to the case, it has been clarified that it is a practically usable level because the target life performance has been cleared. Incidentally, when the current switching voltage was 28V, the expected life performance was not satisfied as expected.

From these results, it can be said that the optimum lamp voltage Va as the current switching voltage is in the range of 25 V or less as a condition that does not affect the life performance of the lamp, and 27 V or less as a practically usable condition.
(analysis)
In the experiment of Table 1, the first current limit level is set to 8 A at the maximum, but as long as it is in the first lighting section, a current higher than that is energized to supply power larger than the power during steady lighting. However, no damage to the electrode was observed.

  As described above, in conventional high-pressure discharge lamps for projectors, there is no allowance for the electrode size for high brightness, and it is necessary to apply excessive power more than that during steady lighting before shifting to constant power control. It is not desirable from the viewpoint of preventing damage, and after starting lighting, until constant power control is reached, it is common to execute constant current control uniformly at the maximum current level in the constant power control. Was common technical knowledge.

However, as has been clarified in the experiment in the present embodiment, even in the initial lighting period before the constant power control, the lamp current is set to the maximum during the constant power control until reaching a certain lamp voltage Va. It was found that the electrode was not damaged even when the value was increased.
Therefore, in order to elucidate how the discharge phenomenon between the electrodes changes before and after the lamp voltage Va, the lighting lamp was observed. Then, it was observed that a high-intensity arc occurred almost at the timing when the lamp voltage Va was reached.

  That is, arc discharge starts immediately after the start of lighting, but at the stage where the lamp voltage is smaller than Va, the vapor pressure of mercury is still low, and the discharge is performed on almost the entire surfaces of the opposing electrodes 4 and 5. However, as the lamp temperature rises, the amount of mercury evaporation increases and the vapor pressure rises. Under the vapor pressure when the lamp voltage reaches Va, thermionic emission at one location at the tip of the negative phase side electrode Points (arc spots) begin to be formed continuously, and the arc discharge shape is compressed.

When an arc spot is formed in this way, the electrode temperature at that location rises rapidly, so if a large current flows, the melting point of the electrode material will be exceeded, which will cause the electrode coil to melt. It is done.
In other words, until the arc spot is formed on at least one of the electrodes, the entire surface of the electrode is discharged, so even if a large current is applied, the temperature does not increase rapidly and the electrode is not damaged. It is.

In Table 1, an experiment was conducted on a 200 W rated high-pressure mercury lamp 100. In order to verify whether the value of the optimum current switching voltage Va varies depending on the rated power of the lamp, A similar experiment was conducted using a 120W high-pressure mercury lamp. The specific 120W lamp specifications at this time are as follows.
Mercury content 200 mg / cm ³ per volume
Nozzle gas cooling pressure during lamp cooling 20 kPa
Distance between electrodes De 1.0mm
Lamp total length Da 55mm
Light emitting part diameter Db 9.5 mm
Sealing part diameter Dc 5.0mm
In addition, an electrode is used in which a double-wound 8-stage coil is attached to the tip of the electrode shaft, the electrode shaft diameter d1 is 0.3 mm, and the electrode coil 42 has a wire diameter d2 of 0.3 mm. It is set to 15 mm.

  Table 3 below shows the experimental results.

この表３に示すように１２０Ｗ型の高圧放電ランプにおいては、ランプ電力が小さくなった分、供給される第２の電流制限レベルが小さくなっており（２．５Ａ）、第１の電流制限レベルが、当該第２の電流制限レベルと同じ２．５Ａである場合を除き、それ以上の他の全ての第１の電流制限レベルについてランプ電圧が３０Ｖ以上となるまで供給すると、電極の損傷が発生しているのが分かる。

As shown in Table 3, in the 120 W type high-pressure discharge lamp, the second current limit level to be supplied is reduced by the amount corresponding to the decrease in lamp power (2.5 A). However, unless the current is 2.5 A, which is the same as the second current limit level, supplying the lamp voltage to 30 V or higher for all other first current limit levels will cause electrode damage. You can see that

Further, when the same experiment was performed by changing the current switching voltage Va in increments of 1V, the optimum current switching voltage Va in the 120 W type high-pressure mercury lamp was also completely improved in the lamp life performance as in the experiment in Table 2 for the 200 W type. It was proved that it was 25 V or less as a condition that does not affect, and 27 V or less as a practically usable condition.
The reason why the optimum current switching voltage Va becomes the same for the two types of high-pressure mercury lamps having different rated powers of the lamps as described above is assumed to be due to the following reason.

These two types of high-pressure mercury lamps are designed based on a common design standard even if the rated power is different. That distance between the electrodes is in the range of from 0.5mm to 2.0 mm, the arc tube is enclosed in a range of mercury which is a light-emitting metal from the arc tube volume per 150 mg / cm ³ of 350 mg / cm ^3, further rare gas Argon, krypton, xenon, or the like is sealed in a gas pressure range of 10 kPa to 40 kPa.

  The lamp voltage during lamp operation is determined predominantly by the product of the vapor pressure of mercury that evaporates with the temperature rise inside the arc tube and the distance between the electrodes, but arc spots are continuously formed after the start of lighting. The lamp voltage at the start is estimated to be exactly the same value of 25V when the design criteria are followed. In other words, even if the distance between the electrodes is slightly different, an arc spot starts to be continuously formed at a mercury vapor pressure that satisfies the condition that the lamp voltage is 25V.

  When the arc spot is formed, the electrode temperature at the relevant portion is likely to increase as the lamp current increases and as the electrode size decreases. When the lamps are designed according to a common design standard, the lamp current varies depending on the rated power. However, as described above, the electrode temperature during rated power operation is the same in order to obtain high brightness. Therefore, the electrode size is also changed according to the lamp current. Therefore, when the arc spot starts to form continuously, that is, when the lamp voltage becomes 25 V or more, the number of melting stages of the electrode coil when the lamp current exceeding the rating is applied is substantially the same even in the lamp having a different rated power. It is considered to be.

Incidentally, when an additional experiment was performed on a high pressure discharge lamp of a 90 W to 350 W type other than the 120 W type and the 200 W type, for example, a 150 W type, the optimum current switching voltage Va was also the same value as described above.
As described above, if the current switching voltage Va is set to 27 V or less, it can be said that in the first lighting section defined by the current switching voltage Va, even if a larger current is applied than in the conventional case, the damage of the electrodes is within a level that does not cause a problem in practice. .
(Experiment 2)
Next, an experiment was conducted on how much current can be applied in the first lighting period to effectively shorten the light rise time.

The lamp used in the experiment has the same 200 W type specification as that used in the experiment of Table 1, the first current limit level in the first lighting section is 4 types, 4A, 5A, 6A, and 7A. The current limit level of 4A was set to 4A, and the relationship between the lighting time of each lamp and the light rise was examined. The result shown in FIG. 6 was obtained.
As shown in the figure, the light rise time is greatly shortened as the first current limiting level is increased. Further, in the first lighting section, by supplying a lamp current larger than the maximum current value (hereinafter referred to as “constant power control maximum current value”) (4A) supplied at the time of executing the constant power control, the light rises. It is understood that the time can be shortened.

  The following Table 4 shows the time (50% arrival time) required for the luminous flux to reach 50% at the time of steady lighting at each current limit level and the reduction rate of the arrival time from the experimental results of FIG. It is shown.

ここで短縮率は、第１電流制限値が従来の４Ａの場合の５０％到達時間を１００％とした場合における他の５０％到達時間を％で示したものである。また、４Ａを除く第１の電流制限レベルの値の括弧内の数字は、第１の電流制限レベルに対する倍率が記されている。

Here, the shortening rate indicates the other 50% arrival time in% when the 50% arrival time in the case where the first current limit value is the conventional 4A is 100%. Further, the numbers in parentheses of the values of the first current limit level excluding 4A indicate the magnification with respect to the first current limit level.

As shown in Table 4, when the first current limit level was 7 A, the arrival time was 56%, which was shortened by 44%. Normally, when the luminous flux reaches 50% during steady lighting, the viewer of the projector can clearly recognize the characters and figures on the screen, and thus a 44% reduction in time in this 50% arrival time is a significant effect.
Moreover, as a general human sensation, even when the 50% arrival time reduction rate is 87% (when 5A), it can be felt that the light rise time is faster than before, so in the first lighting section, it is constant. It is desirable to supply a lamp current that is approximately 1.25 times or more the power control maximum current value.

In theory, there is no particular upper limit on the first current limit level. However, the larger the current limit level, the larger the electronic components in the lighting device that must be used. I can't. From this viewpoint, the upper limit of the current value is desirably about 10A.
(4) Lighting Device FIG. 7 is a block diagram showing a configuration of a lighting device for lighting the high-pressure mercury lamp 100.

As shown in the figure, the lighting device includes a DC power supply circuit 250 and an electronic ballast 300. The electronic ballast 300 includes a DC / DC converter 301, a DC / AC inverter 302, a high voltage pulse generation circuit 303, and a control circuit. 304, a tube current detection circuit 305, and a tube voltage detection circuit 306.
The DC power supply circuit 250 generates a DC voltage with a household AC of 100 V and supplies the electronic ballast 300 with power. The DC / DC converter 301 of the electronic ballast 300 converts the DC voltage supplied from the DC power supply circuit 250 into a DC voltage having a predetermined magnitude and supplies the DC voltage to the DC / AC inverter 302.

The DC / AC inverter 302 generates an AC rectangular current having a predetermined frequency and applies it to the high-pressure mercury lamp 100. The high-pressure pulse generation circuit 303 necessary for starting the discharge of the high-pressure mercury lamp 100 includes, for example, a transformer. By applying the high-pressure pulse generated here to the high-pressure mercury lamp 100, the discharge is started. Yes.
On the other hand, a tube current detection circuit 305 and a tube voltage detection circuit 306 are connected to the input side of the DC / AC inverter 302, respectively, and indirectly detect the lamp current and lamp voltage of the high-pressure mercury lamp 100, and the detection signal Is sent to the control circuit 304. Since the lamp current and the lamp voltage detected here are different from the actual measured values of the lamp current and the lamp voltage, the control circuit 304 uses the preset current correction coefficient and voltage correction coefficient as the tube current. The current value and the voltage value detected by the detection circuit 305 and the tube voltage detection circuit 306 are multiplied to obtain a lamp current and a lamp voltage substantially equal to the actually measured values.

The control circuit 304 controls the DC / DC converter 301 and the DC / AC inverter 302 based on these detection signals and the program stored in the internal memory, and lights the high-pressure mercury lamp 100 by the lighting method described above.
FIG. 8 is a flowchart showing the contents of lighting control after dielectric breakdown of the rated high-pressure mercury lamp 100 executed by the control circuit 304. Here, a flowchart in the case of performing control according to the control characteristics shown in FIG. 2 is shown.

  First, in step S1, it is determined whether or not the lamp voltage V exceeds 25V, which is a current switching voltage. If not exceeded (step S1: NO), constant current control is performed with a current limit level of 6A (step S2). If the lamp voltage exceeds 25V (step S1: YES), 4A is set to be current limited. Switch to constant current control to be level (step S3).

This constant current control is executed by controlling the DC / DC converter 301 based on the detection signal of the tube current detection circuit 305 so that the lamp current is maintained at the set current limit level.
If the lamp voltage increases to 50 V in this state (step S4: YES), constant power control is executed so that the lamp power becomes 200 W (step S5). This constant power control is continued until the lighting is finished by turning off a power switch (not shown) in step S6.

In the constant power control, the control circuit 304 monitors the lamp current and the lamp voltage based on the detection signals of the tube current detection circuit 305 and the tube voltage detection circuit 306, so that the product of the lamp power is always 200 W, for example. This is executed by feedback control of the current value output from the DC / DC converter 301.
The voltage applied to the high-pressure mercury lamp 100 during the constant current control and constant power control is an AC voltage having a frequency in the range of about 50 Hz to 1000 Hz.

(5) Liquid Crystal Projector The high-pressure mercury lamp 100 has a small size and high brightness, and is therefore often used as a light source for liquid crystal projectors. In this case, a reflection mirror is attached and incorporated in the liquid crystal projector as a lamp unit. It is.
FIG. 9 is a partially cutaway perspective view showing the configuration of the lamp unit 200. As shown in the figure, the lamp unit 200 has a cap 20 attached to the end of the sealing portion 3 of the high-pressure mercury lamp 100, and cement 21 in the hole at the root of the reflection mirror 22 whose inner surface is a concave mirror. It is formed by adhering. At this time, in order to improve the light collection efficiency by the reflection mirror 22, the discharge arc between the electrodes 4 and 5 is attached in a state adjusted so as to substantially coincide with the optical axis of the reflection mirror 22. .

The external lead wires 8 and 9 (see FIG. 1) of the high-pressure mercury lamp 100 are respectively supplied with electric power via a lead wire 24 and a terminal 23 which pass through a through hole 25 formed in the reflection mirror 22 and are drawn to the outside. Is supplied.
FIG. 10 is a schematic diagram showing a configuration of a liquid crystal projector 400 using the lamp unit 200 and the lighting device shown in FIG.

As shown in the figure, the liquid crystal projector 400 includes a power unit 401 including the electronic ballast 300, a control unit 402, a condenser lens 403, a transmissive color liquid crystal display panel 404, and a drive motor. Lens unit 405 and cooling fan device 406.
The power supply unit 401 converts a household AC100V power supply into a predetermined DC voltage and supplies it to the electronic ballast 300, the control unit 402, and the like. The control unit 402 displays the color image by driving the color liquid crystal display panel 404 based on the image signal input from the outside. In addition, a driving motor in the lens unit 405 is controlled to execute a focusing operation or a zoom operation.

The light beam emitted from the lamp unit 200 is collected by the condenser lens 403, passes through the color liquid crystal display plate 404 disposed in the optical path, and the image formed on the liquid crystal display plate 404 is passed through the lens unit 405. Through the screen.
Such a liquid crystal projector has been remarkably spread in business use recently, and it has been a technical goal to achieve higher brightness and shorter light rise time. From the lighting device according to the present invention as a high-pressure mercury lamp for a projector, By using the light source device (hereinafter referred to as “high pressure discharge lamp device”), it is possible to sufficiently contribute to the achievement of the technical target.

It goes without saying that the high-pressure discharge lamp device according to the present invention can be applied to other projection type image display devices other than the liquid crystal projector.
(6) Modifications It should be noted that the content of the present invention is not limited to the above embodiment, and the following modifications can be considered.

  (6-1) For example, in the above-described embodiment, constant current control is performed according to the first and second current limit levels in the first lighting section and the second lighting section, respectively. It does not have to be. In the first lighting section, if a current larger than the constant power control maximum current value is supplied, the light rise time can be shortened, and in the second lighting section, a current lower than the constant power control maximum current value can be supplied. This is because the electrode is not damaged.

  That is, as shown in FIG. 11, in the first lighting section, the current may be gradually changed (increased / decreased) within the range exceeding the constant power control maximum current value (4A), or the second lighting section. Also, the current may be gradually changed at a constant power control maximum current value or less. Further, as shown in FIG. 12, in the first lighting section, the current may be changed (increase / decrease) stepwise in a range exceeding the constant power control maximum current value (4A), or the second lighting may be performed. Also in the section, the current may be changed stepwise within the constant power control maximum current value.

However, in the second lighting period, in order to shorten the light rise time as much as possible without damaging the electrode, as shown in FIG. 2, the constant power control maximum current value (so that the electrode is not damaged at this current value). It is desirable to perform constant current control with a current value approximately equal to the lamp design.
In the case of FIG. 11 and FIG. 12, there is a portion that is not energized at the constant power control maximum current value in the second lighting section, and there is a concern that the light rise time becomes long. In the total of the first lighting section and the second lighting section, a larger amount of power is supplied than in the conventional lamp, so that the light rise time can be shortened.

(6-2) It is not always necessary to supply a large current in the entire first lighting section. Even if only a part of the first lighting section is supplied, a current larger than the constant power control maximum current value is supplied. The effect of shortening the light rise time is seen by the amount. In that case, the larger the current value of the “part”, the higher the effect.
(6-3) In the above embodiment, the case where the high-pressure discharge lamp is a high-pressure mercury lamp for projectors has been described. However, a high-pressure discharge lamp such as a metal halide lamp may be used. The principle of light emission is the same as that of a high-pressure mercury lamp, and the lamp voltage rises as the internal metal vapor pressure rises, and a phenomenon in which an arc spot starts to form continuously when a specific lamp voltage is reached similarly occurs. Because. Until the arc spot is formed, the electrode is not damaged even if a large current is supplied, and the light rise time is shortened.

Needless to say, the light rise time is shortened even in a high-pressure discharge lamp other than for a projector.
(6-4) In the above embodiment, the electrode of the high-pressure discharge lamp has a shape in which an electrode coil is simply attached to the tip of the electrode rod. The part may be melted by a laser together with a part of the electrode coil, and the tip of the electrode may be processed into a hemispherical shape.

  As a result, the tip of the electrode is less likely to melt than the shape shown in FIG. 5A, and the lamp life is extended. However, even in the case of such an electrode shape, if a large current is supplied beyond the first lighting section, there is no change in that the electrode is damaged at the place where the arc spot is formed. The supply of a large current is limited to the first lighting section.

  According to the lighting method and the lighting device of the high-pressure discharge lamp according to the present invention, a large current is allowed to flow in the first lighting section from the start of lighting until the lamp voltage reaches a predetermined voltage, so that the light is not damaged. The rise time can be shortened. Moreover, since the warm-up of the electrode is accelerated by increasing the current value immediately after the start of lighting, it is possible to provide a lighting method and lighting device for a high-pressure discharge lamp that improves startability.

  In addition, by using a high-pressure discharge lamp device that combines the lighting device and the high-pressure discharge lamp as a light source device for a projection-type image display device, it is possible to realize a projection-type image display device that is reliably started and has a short light rise time. it can.

It is a figure which shows the structure of the high pressure mercury lamp for projectors used as the lighting object of the lighting method which concerns on embodiment of this invention. It is a graph which shows the control characteristic of the lamp voltage and lamp current which are supplied to the said high pressure mercury lamp in embodiment of this invention. 3 is a graph showing a relationship between lamp voltage and lamp power when a lamp voltage and a lamp current are supplied according to the control characteristics of FIG. 2. FIG. 3 is a graph showing a light rising characteristic of a high-pressure mercury lamp when a lamp voltage and a lamp current are supplied according to the control characteristics of FIG. 2. (A) is a figure which shows the tip shape of the electrode before a lighting experiment, (b) is a figure which shows the fusion | melting state of the electrode tip part in the conventional lighting method, (c) is 4 steps | paragraphs of the front end side of an electrode coil. It is a figure which shows the state which melt | dissolved and the electrode was damaged severely. It is a figure which shows the light rise characteristic of the high pressure mercury lamp in each case where the 1st current limiting level is 4A, 5A, 6A, 7A. It is a block diagram which shows the structure of the lighting device of the high pressure mercury lamp concerning embodiment of this invention. It is a flowchart for demonstrating the content of the lighting control implemented in the control circuit of the lighting device of FIG. It is a partially cutaway view showing the configuration of the lamp unit. It is a block diagram which shows the structure of the liquid crystal projector carrying the lighting device of FIG. It is a graph which shows the modification of the control characteristic of the lamp voltage and lamp current supplied to a high pressure mercury lamp in embodiment of this invention. It is a graph which shows the modification of the control characteristic of the lamp voltage and lamp current supplied to a high pressure mercury lamp in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 High pressure mercury lamp 200 Lamp unit 250 DC power supply circuit 300 Electronic ballast 301 DC / DC converter 302 DC / AC inverter 303 High voltage pulse generation circuit 304 Control circuit 305 Tube current detection circuit 306 Tube voltage detection circuit 400 Liquid crystal projector

Claims (9)

After the start of lighting of the high pressure discharge lamp, in the initial lighting section until the lamp voltage reaches a predetermined voltage and switches to constant power control,
A lamp current larger than a predetermined current value in all or part of the first lighting section from the start of lighting until reaching a lamp voltage at which an arc spot starts to be continuously formed on at least one electrode of the high-pressure discharge lamp. A first step of supplying;
A second step of supplying a lamp current equal to or lower than the predetermined current value in all or part of the second lighting period after the first lighting period has elapsed and before switching to the constant power control. How to turn on the high pressure discharge lamp. The high-pressure discharge lamp to be lit has a distance between the electrodes of 0.5 mm or more and 2.0 mm or less, and the amount of mercury enclosed per arc tube volume is 150 mg / cm ³ or more and 350 mg / cm ³ or less. Argon, krypton, or xenon is sealed as a gas at a sealing pressure of 10 kPa to 40 kPa,
After the start of lighting of the high-pressure discharge lamp, in the initial lighting section until the lamp voltage reaches a predetermined voltage and switches to constant power control,
A first step of supplying a lamp current greater than a predetermined current value in a first lighting interval from the start of lighting until the lamp voltage reaches a predetermined voltage of 27 V or less;
A second step of supplying a lamp current equal to or lower than the predetermined current value in a second lighting period after the first lighting period has elapsed until switching to the constant power control. Lighting method.   The high-pressure discharge lamp lighting method according to claim 1, wherein the predetermined current value is substantially equal to a maximum value of a current supplied when the constant power control is executed.   4. The lighting method of a high pressure discharge lamp according to claim 1, wherein a lamp current that is approximately 1.25 times or more of the predetermined current value is supplied in the first lighting section. 5. A high pressure discharge lamp lighting device that performs constant power control when the lamp voltage reaches a predetermined voltage after the high voltage discharge lamp is dielectrically broken and started to light,
Current supply means for supplying current to the high-pressure discharge lamp;
A lamp current larger than a predetermined current value is supplied in all or part of the first lighting section from the start of lighting until reaching a lamp voltage at which an arc spot starts to be continuously formed on at least one electrode of the high-pressure discharge lamp. In addition, the current supply means is controlled so as to supply a lamp current equal to or less than the predetermined current value in all or part of the second lighting section after the first lighting section elapses and before switching to the constant power control. A high-pressure discharge lamp lighting device. The high-pressure discharge lamp to be lit has a distance between the electrodes of 0.5 mm or more and 2.0 mm or less, and the amount of mercury enclosed per arc tube volume is 150 mg / cm ³ or more and 350 mg / cm ³ or less. Argon, krypton, or xenon is sealed as a gas at a sealing pressure of 10 kPa to 40 kPa,
A high pressure discharge lamp lighting device that performs constant power control when the lamp voltage reaches a predetermined voltage after the high pressure discharge lamp is dielectrically broken to start lighting,
Current supply means for supplying current to the high-pressure discharge lamp;
A lamp current larger than a predetermined current value is supplied in all or part of the first lighting section from the start of lighting until the lamp voltage reaches a predetermined voltage of 27 V or less, and after the first lighting section has elapsed, And a current control means for controlling the current supply means so as to supply a lamp current equal to or less than the predetermined current value in all or part of the second lighting section until switching to constant power control. Discharge lamp lighting device.   The high-pressure discharge lamp lighting device according to claim 5 or 6, wherein the predetermined current value is substantially equal to a maximum value of a current supplied when the constant power control is executed.   A high-pressure discharge lamp device comprising: a high-pressure discharge lamp; and the lighting device according to any one of claims 5 to 7 for lighting the high-pressure discharge lamp.   A projection-type image display device, wherein the high-pressure discharge lamp device according to claim 8 is used.

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