JP4400125B2 - Short arc type discharge lamp lighting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a short arc type discharge lamp lighting device. In particular, a liquid crystal display device or DMD (digital mirror device) using an ultra-high pressure mercury lamp in which mercury of 0.16 mg / mm ³ or more is sealed in the arc tube and the mercury vapor pressure at the time of lighting is 110 atmospheres or more is used. The present invention relates to a lighting device for a light source discharge lamp used in a projector device such as a DLP (digital light processor).
[0002]
[Prior art]
Projection type projector devices are required to illuminate an image with a uniform and sufficient color rendering property on a rectangular screen. For this reason, a metal halide lamp enclosing mercury or a metal halide is used as a light source. It is used. In addition, these metal halide lamps have recently been further miniaturized and made point light sources, and those having an extremely small distance between electrodes have been put into practical use.
[0003]
Under such circumstances, recently, a lamp having a high mercury vapor pressure, for example, 150 atm, has been proposed in place of a metal halide lamp. This is to increase the mercury vapor pressure to suppress (narrow) the spread of the arc and to further improve the light output.
Such ultra-high pressure discharge lamps are disclosed in, for example, JP-A-2-148561, JP-A-6-52830, and Japanese Patent No. 2980882.
[0004]
In the lamp, for example, a pair of electrodes are arranged opposite to each other at an interval of 2 mm or less on an arc tube made of quartz glass, and 0.16 mg / mm ³ or more of mercury and 1 × 10 ⁻⁶ to 1 × 10 ^{− are} disposed on the arc tube. An ultra-high pressure mercury lamp filled with halogen in the range of ² mol / mm ³ is used. The main purpose of enclosing the halogen is to prevent devitrification of the arc tube, but this also causes a so-called halogen cycle.
[0005]
By the way, the ultra-high pressure mercury lamp (hereinafter, also simply referred to as a discharge lamp) has a so-called tube wall blackening, in which tungsten, which is a constituent material of the cathode, is transported to and adhered to the inner surface of the discharge vessel as the lighting time elapses. May occur. This blackening of the tube wall causes a short life of the lamp, such as a decrease in light output and, if the tube wall blackening is severe, a damage to the discharge vessel due to an increased thermal load on the tube wall.
[0006]
In the case of a discharge lamp in which a halogen gas is sealed, the life is extended by a so-called halogen cycle phenomenon. However, if the temperature of the discharge lamp changes for some reason, it may deviate from the optimum temperature range for the halogen cycle, and as a result, the above-mentioned tube wall blackening and short life problems may be caused remarkably. For example, in the case of a projector device, attention is paid to the dimming function in order to bring about a change in the use environment. As a means for that, the power input to the lamp may be changed. In this case, the temperature of the discharge lamp changes.
[0007]
Further, there are cases where the blinking operation of the discharge lamp is intense in a projector apparatus or the like. If the blinking operation of the discharge lamp is repeated at a high frequency, the rate of exposure to a temperature range unsuitable for the halogen cycle increases. In particular, since the use of projector devices for home use increases, the use of flashing discharge lamps at a high frequency becomes a serious problem.
[0008]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to provide a short arc type ultra-high pressure mercury lamp that has a long life by suppressing the blackening of the tube wall caused by transport of tungsten, which is a constituent material of the cathode, to the inner surface of the discharge vessel. is there.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a short arc type discharge lamp lighting device according to claim 1 is arranged such that an anode and a cathode are opposed to each other with an interval of 2 mm or less in an arc tube made of quartz glass. mm ³ or more mercury, noble gas, short arc discharge lamp encapsulating halogen in the range of 1 × 10 ⁻⁶ to 1 × 10 ⁻² μmol / mm ³ , and power supply for supplying direct current to this discharge lamp It consists of a device.
The discharge lamp has a coil having at least one turn on the cathode, and the power feeding device performs constant current control on the discharge lamp at the start of lighting, and then performs constant power control. In this constant current control, a first current supply period for supplying a current value of 0.3 to 0.9 times the rated current, and a current value of 1.0 to 2.0 times the rated current thereafter. A second current supply period for supplying the rated current after the lighting power of the discharge lamp is at least 1.05 to 1.5 times the rated lighting power. Switching to constant power control based on the power value is characterized.
Further, the shortest distance between the coil and the inner surface between the light emission is within 2.0 mm.
[0010]
As a result of intensive studies on the above problems, the present inventors have found that the problem of tube wall blackening due to the transport of tungsten, which is an electrode constituent material, to the inner surface of the discharge vessel is at least the cathode at the start of the lamp. When a discharge arc was formed starting from the rear end of the coil provided on the electrode, it was determined that this discharge arc was in contact with the inner surface of the discharge vessel.
As a result of this phenomenon, it has been found that evaporation of quartz glass, which is a constituent material of the discharge vessel, greatly affects the transport of tungsten because the discharge arc from the rear end of the coil contacts the inner surface of the discharge vessel. .
[0011]
The present inventors have found that, in order to solve the above-mentioned new problem relating to the short arc type discharge lamp, it is effective to adjust the current supply from the power feeding device to the discharge lamp at the initial stage of starting the lamp. is there.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the overall configuration of a short arc type high-pressure discharge lamp (hereinafter also simply referred to as “discharge lamp”) of the present invention.
The discharge lamp 1 has a substantially spherical light emitting portion 10 formed by a discharge vessel made of quartz glass, and the anode 2 and the cathode 3 are arranged in the light emitting portion 10 so as to face each other. Moreover, the sealing part 11 is formed so that it may extend from the both ends of the light emission part 10, and the conductive metal foil 4 which usually consists of molybdenum is embed | buried airtight by these shrink parts, for example with a shrink seal | sticker. . One end of the metal foil 4 is joined to the anode 2 or the cathode 3, and the other end of the metal foil 4 is joined to the external lead 5.
A coil 31 is wound around the tip of the cathode 3. The coil 31 is made of tungsten, and is configured by being tightly wound or welded. When the coil 31 is turned on, it functions as a starting seed (starting start position) due to the surface irregularity effect, and after the lighting, the heat radiation function is performed by the surface irregularity effect and the heat capacity.
[0013]
The light emitting unit 10 is filled with mercury, a rare gas, and a halogen gas.
Mercury is used to obtain a necessary visible light wavelength, for example, radiated light having a wavelength of 360 to 780 nm, and 0.16 mg / mm ³ or more is enclosed. Although the amount of sealing varies depending on the temperature condition, the vapor pressure becomes extremely high at 150 atm or higher when the lamp is turned on. In addition, by enclosing more mercury, it is possible to create a discharge lamp with a high mercury vapor pressure of 200 atm or higher and 300 atm or higher when the lamp is turned on. The higher the mercury vapor pressure, the more suitable the light source suitable for the projector device. Can be realized.
As the rare gas, for example, argon gas is sealed at about 13 kPa, and the lighting startability is improved.
As for halogen, iodine, bromine, chlorine and the like are enclosed in the form of a compound with mercury or other metals. The amount of enclosed halogen can be selected from the range of, for example, 10 ⁻⁶ to 10 ⁻² μmol / mm ³ , and its function is to extend the life using the halogen cycle. As described above, it is considered that such a halogen having a high internal pressure has an effect of preventing breakage and devitrification of the discharge vessel.
[0014]
As an example of the numerical value of such a discharge lamp, for example, the outer diameter of the light emitting part is selected from the range of φ6.0 to 15.0 mm, and the distance between the electrodes is 0.5 to 2.0 mm, for example, 9.5 mm. is selected from a range with for example 1.5 mm, the arc tube volume is 75 mm ^3, for example, selected from a range of 40~300mm ^3. The illumination condition, for example, are those that are selected from the bulb wall loading 0.8~2.0W / mm ² range, for example, 1.5 W / mm ^2, the rated voltage 80V, the rated power 200 W.
In addition, this discharge lamp is built in a projector device or the like that is miniaturized, and the entire structure is extremely miniaturized, but a high amount of light is required. Therefore, the thermal conditions in the light emitting part are extremely severe.
The discharge lamp is mounted on a presentation device such as a projector device or an overhead projector, and provides emitted light having good color rendering properties.
In addition, this type of discharge lamp is built in a projector device that is miniaturized,
[0015]
FIG. 2 shows an enlarged structure near the base of the cathode. Although (a) and (b) show the same structure, (a) is numbered for the purpose of explaining the constituent members, whereas (b) explains the physical phenomenon in the light emitting section. The code | symbol is attached | subjected with the meaning.
Here, the lamp mounted in the apparatus as the light source of the projector apparatus, such as the discharge lamp of the present invention, is strongly required to be downsized due to a strong demand for downsizing of the projector apparatus. On the other hand, since the discharge lamp is lit at a high temperature, it is necessary to take heat dissipation measures with a heat capacity for the electrode, and the electrode must have a certain size (volume). is there.
In other words, a situation occurs in which the volume of the electrode increases as the discharge lamp becomes smaller.
Therefore, as shown in the figure, the distance L between the coil 31 of the cathode 3 and the wall (inner surface) of the discharge vessel (light emitting unit 11) becomes extremely short. As numerical examples, there are lamps of 2.0 mm or less, specifically 1.5 mm or less or 1.0 mm or less. In addition, the distance defined here means the shortest distance between the coil 31 and the wall of the discharge vessel.
Thus, when the distance between the electrode and the inner surface of the discharge vessel becomes shorter, when the discharge arc is formed starting from the rear end of the coil in the initial stage of the start, the discharge arc comes into contact with the inner surface of the discharge vessel. It can be said.
Such values are theoretically different depending on the design specifications of the discharge lamp and are not preferably defined as absolute values.However, the size of the projector device and the performance required for the light source are determined to some extent by the industry. Therefore, taking this background into account, the figures are generally the above.
[0016]
The physical phenomenon in FIG. 2 is considered as follows.
That is, when the arc e is generated from the rear end portion of the coil 31, it will contact or collide with the inner surface of the discharge vessel as shown in the figure. Quartz glass (SiO ₂ ), which is a constituent material of the container, evaporates. The evaporated SiO ₂ is separated into Si and O by the discharge plasma, leading to evaporation of tungsten oxide WO from the electrode tip. When this tungsten oxide moves to the vicinity of the inner surface of the discharge vessel, which is a relatively low temperature portion, by convection, some of the oxide remains in the gas as a halogen compound such as WO ₂ Br ₂ , but part of the tungsten oxide such as tungsten or WO ₂ It is considered that tungsten oxide is deposited on the inner surface of the discharge vessel as a result of blackening of the tube wall.
[0017]
The above phenomenon occurs in a discharge lamp in which the coil and the inner surface of the discharge vessel are very close. However, if the current supplied to the discharge lamp is reduced in the initial stage of the start, the inventors have developed a discharge arc generated from the rear end of the coil. It has been found that even if it contacts the inner surface of the discharge vessel, its influence is small, and this problem does not develop.
[0018]
Specifically, at the start of lighting, the direct current supplied to the discharge lamp by the power supply device has a first current supply period and a second current supply period before reaching the rated current, and the first current supply The period is 0.3 to 0.9 times the rated current, and the second current supply period is 1.0 to 2.0 times the rated current.
Further, the second current supply period is continued at least until the power value exceeds the rated power, and then the rated current is set and the discharge lamp is also subjected to constant power control.
[0019]
FIG. 3 shows a DC current waveform and a power waveform supplied from the power feeding device to the discharge lamp. (A) is a current waveform, (b) represents a power waveform, the vertical axis represents the current value, the power value, and the horizontal axis represents time.
[0020]
The current waveform of (a) will be described.
When the discharge lamp starts lighting at time t1, a direct current I1 flows through the discharge lamp. The current value I1 is 0.3 to 0.9 times the rated current value, and this period T1 is the first current supply period. In this first current supply period T1, so-called constant current control is performed in which the current value supplied to the discharge lamp is constant, but by setting the current value to be small, undesired discharge from the coil rear end. Even if the arc is generated so as to be in contact with the inner surface of the discharge vessel, the influence can be reduced.
The first current supply period is selected from a range of 1.0 to 15.0 seconds, for example, and is 10 seconds, for example. This period is the optimum time for the discharge arc generated from the coil rear end to move favorably to the cathode tip as the cathode warms, and is set appropriately according to the discharge lamp and other lighting environment conditions. .
The current value I1 is 0.3 to 0.9 times the rated current value. If the current value I1 is smaller than this range, the discharge cannot be maintained. If the current value I1 is larger than this range, the discharge arc contacts the inner surface of the discharge vessel. Cannot be ignored. A more preferable range of the current value I1 is 0.4 to 0.8 times the rated current value. Specifically, the rated current _{I L} is set when the 2.7A, for example, to 2.0A.
[0021]
At time t2, the current value increases from I1 to I2. The current value I2 becomes 1.0 to 2.0 times the rated current _{I L,} the period T2 becomes the second current supply period. Constant current control is also performed in the second current supply period T2. The reason why the current value is increased compared to the first current supply period T1 is that the temperature rise rate in the discharge space is slowed and the rise of the light beam is slowed if the current value remains low. Further, in order for the halogen cycle to function well, it is necessary to set the temperature in the discharge lamp to an optimum temperature, and it is necessary to increase the current value also from this point.
In particular, since a small amount of current is supplied during the first current supply period, it is important to flow a current value larger than the rated current value in the sense of compensating for the small amount. That is, in the first current supply period, the current amount is set small in order to suppress the influence of undesired arc discharge generated from the rear end of the coil, and after the arc discharge has moved to the electrode tip, The content is to increase the amount of current from the viewpoint of the rise of synchrotron radiation and the optimization of the halogen cycle.
The second current supply period is selected from a range of 2 to 40 seconds, for example, and is 20 seconds, for example. Current value I2 is 1.0 to 2.0 times the rated current value I _L, it is impossible to warm the range smaller than the electrode and the electrode space near enough, also too warm to be greater than this range Electrodes and the like may be deformed. A more preferable range of the current value I2 is 1.3 to 1.8 times the rated current value. Specifically, the rated current _{I L} is set when the 2.7A, for example, to 4.0A.
[0022]
At time t3, the lighting control of the discharge lamp is changed from constant current control to constant power control. This change, the lamp current from the current value I2, changes to a lower rated current value I _L.
Here, the “rated current” refers to the central value of the design when the discharge lamp is steadily lit, and is a numerical value indicated on the discharge lamp, its packaging container, instructions, or the like. For example, for a discharge lamp with a rated power of 200 W, it is 2.7 A.
At time t4, the lamp current is determined value I _L in the reference power value and the stable discharge lamp lighting voltage of the power control.
[0023]
Note that the change from the current value I1 to I2 is not limited to a stepwise change as shown in the figure, and may be a stepwise change in multiple steps or may be a gradual change.
The change from the current value I2 to the rated current value I _L is not limited to vary gradually as illustrated, may be one which changes stepwise or if multiple step changes stepwise. These controls can be quickly changed without rapidly changing the lamp current by setting the reference power value for constant power control in multiple stages.
[0024]
(B) shows the time change of the lamp lighting power corresponding to (a), and since the so-called constant current control is performed in which the current value is constant in the periods T1 and T2, the lighting voltage rises. As a result, the lighting power is also increasing.
A discharge lamp in which mercury or the like is sealed as a luminescent substance normally employs a form in which constant current control is performed at the beginning of such lighting, and then the control shifts to constant power control. The reason is that mercury does not evaporate at the beginning of lighting and the lighting voltage is low, so that an excessive current flows if constant power control is performed. When mercury evaporates sufficiently and the lighting voltage settles down to a constant value, switching to constant power control is performed.
[0025]
Continuing the description with reference to the drawings, conventionally, at time t3 ′, the lamp power reaches a predetermined rated power value, so that the control is switched to constant power control at this point. After that, constant current control is continued. For this reason, the power value continues to rise until time t3 exceeding time t3 ′. This control is the feature of the present invention. In order to compensate for the low current value in the first current supply period T1, the timing at which switching to the constant power control can be originally performed is extended, and the constant current control is performed. That is why.
At time t3, the constant current control is switched to the constant power control. The lighting power W2 immediately before the switching is 1.05 to 1.5 times the lighting power W _L (rated power) after the switching.
[0026]
To summarize the above operations, constant current control is performed in which the current value is reduced at the start of lighting of the discharge lamp and then the current value is increased. This constant current control is continued even after the lighting voltage of the discharge lamp has sufficiently increased, and the constant current control is continued until the rated power value is exceeded when viewed in terms of the power value. After that, switching from predetermined constant current control to constant power control and lighting with predetermined power.
Such a lighting start operation can suppress the blackening of the discharge vessel, which is the problem.
[0027]
Here, numerical examples of the discharge lamp are as follows.
Emission outside diameter is in the range from Fai8～fai13mm, for example, 10.0 mm, the light emitting portion volume is in the range from 50 to 120 mm ^3, for example, 65 mm ^3, the distance between the electrodes 0.7 The range is 2 mm, for example, 1.0 mm.
The discharge lamp is lit at a rating of 200W.
[0028]
Further, as a numerical example of the electrode structure, the outer diameter of the coil 31 is φ1.0 to 2.0 mm, for example, 1.3 mm, and the length is in the range of 0.6 to 2.0 mm. For example, 1.5 mm. The outer diameter of the shaft portion 5 is in the range of Φ0.2 to 0.6 mm, for example, 0.4 mm, and the length of the shaft portion 5 is in the range of 5.0 to 10.0 mm, for example, 7. 0 mm.
The wire diameter of the coil is in the range of Φ0.1 to 0.3, for example, 0.25 mm.
[0029]
Here, the discharge lamp lighting device of the present invention has several preconditions, and the effects of the invention can be exhibited only when these preconditions are satisfied.
First, the discharge lamp of the present invention has a distance between electrodes of 2 mm or less, and 0.16 mg / mm ³ or more of mercury, a rare gas, and 1 × 10 ⁻⁶ to 1 × 10 ⁻² μmol in the light emitting part. A short arc type discharge lamp in which halogen is enclosed in a range of / mm ³ is assumed.
Because of the discharge lamp having this configuration, SiO released from the inner surface of the discharge vessel is separated into Si and O by discharge plasma, and oxygen (O) in the discharge space reacts with tungsten of the electrode to form tungsten oxide. This is because the transport of tungsten from the electrode to the inner surface of the discharge vessel becomes excessive. Here, if oxygen (O) is in an appropriate amount, it functions as a halogen cycle and functions to suppress the transport of tungsten (W) to the inner wall of the discharge vessel. However, the amount of oxygen is not as in the discharge lamp of the present invention. This is because when the amount is large, tungsten oxide (WO _x ) increases in the discharge space, and excess tungsten oxide is transported to the inner wall of the discharge vessel.
[0030]
Secondly, a discharge lamp having an electrode structure (structure shown in FIG. 2) provided with a coil in the shaft portion of the electrode is assumed. This is because this discharge lamp causes a discharge starting point at the rear end of the coil at the start of lighting, and causes an arc collision and contact with the inner surface of the discharge vessel. This problem occurs remarkably when the shortest distance (distance L in FIG. 2) between the coil and the inner surface of the discharge vessel is small. This is because the shortest distance L is small because the arc collides with and contacts the inner surface of the discharge vessel due to the discharge starting point generated at the rear end of the coil. Specifically, the shortest distance L is 2.0 mm or less, and is noticeable when the distance is 1.5 mm or less and 1.0 mm or less.
Therefore, in the discharge lamp having a large distance L, the phenomenon that the discharge arc starting from the rear end of the coil collides with and contacts the inner surface of the discharge vessel is unlikely to occur. It will not exist.
[0031]
Therefore, in a discharge lamp that does not have such a configuration and has a completely different use, a structure in which a coil is wound around an electrode may be known. However, since such a discharge lamp originally does not cause a phenomenon in which the arc collides with and contacts the inner surface of the discharge vessel, that is, there is no technical problem, such a prior art is completely different from the present invention. Can be said to be different.
[0032]
The discharge lamp of the present invention desirably has a protrusion at the tip of at least one of the electrodes. The projection at the tip of the anode or cathode can narrow the arc and quickly raise the temperature of each electrode tip from the start-up lighting, so that the arc discharge can be quickly stabilized and 0.16 mg / mm at the light emitting part. ^In the case of a short arc type discharge lamp in which ³ or more mercury, a rare gas, and halogen are enclosed in the range of 1 × 10 ⁻⁶ to 1 × 10 ⁻² μmol / mm ³ , the protrusions expand and contract in a self-controlling manner. By doing so, it becomes possible to adjust the inter-electrode distance to the optimum value.
And a projection part can regulate beforehand the direction which expands and contracts by self-control by being formed beforehand using a shaft part. However, it is also possible to form the protrusion from the so-called zero state as the lamp is lit without forming it at the time of manufacturing the discharge lamp.
[0033]
The electrode is preferably composed of tungsten having a purity of 99.9999% or more. This is because when the impurities contained in the electrode are released into the discharge space, it causes devitrification and blackening of the discharge vessel.
[0034]
As described above, in the discharge lamp lighting device of the present invention, a pair of electrodes are opposed to a light emitting tube made of quartz glass at an interval of 2 mm or less, and 0.16 mg / mm ³ or more of mercury and A short arc type discharge lamp in which halogen is enclosed in a range of 1 × 10 ⁻⁶ to 1 × 10 ⁻² μmol / mm ³ and a power supply device for supplying a direct current to the discharge lamp at the start of lighting. Is done. In this discharge lamp, at least one electrode (cathode) of the pair of electrodes includes a coil of one turn or more. The direct current supplied from the power supply device to the discharge lamp is initially 0.3 to 1.0 times the rated current, and then 1.0 to 2.0 times the rated current. Then, after that, the power becomes 1.05 to 1.5 times the rated power and then becomes a predetermined power.
[Brief description of the drawings]
FIG. 1 shows a discharge lamp according to the present invention.
FIG. 2 shows a structure of an electrode of a discharge lamp according to the present invention.
FIG. 3 shows a current waveform and a power waveform of a discharge lamp according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Discharge lamp 2 Anode 3 Cathode 4 Metal foil 5 External lead 10 Light emission part 11 Sealing part

Claims (2)

Anode and a cathode in the light emitting tube made of quartz glass is opposed at intervals of less than 2 mm, and 0.16 mg / mm ³ of mercury in the arc tube, a rare ^{gas, 1 × 10 -6 ~1 × 10} -2 In a short arc type discharge lamp lighting device comprising a short arc type discharge lamp enclosing halogen in the range of μmol / mm ³ and a power supply device for supplying a direct current to the discharge lamp,
The discharge lamp has a coil of at least one turn at the cathode,
The power feeding device is a constant current control at the start of lighting for the discharge lamp, and then a constant power control,
The constant current control supplies a current value 1.0 to 2.0 times the rated current after a first current supply period for supplying a current value 0.3 to 0.9 times the rated current. Having a second current supply period,
In the second current supply period, after the lighting power of the discharge lamp becomes at least 1.05 to 1.5 times the rated lighting power, switching to constant power control based on the rated lighting power value is performed. A short arc type discharge lamp lighting device .   2. The short arc type discharge lamp lighting device according to claim 1, wherein the shortest distance between the coil and the inner surface between the light emission is within 2.0 mm.

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