JP4510844B2 - Metal halide lamp - Google Patents

Description

  The present invention relates to a metal halide lamp, and more particularly to a starting lead wire disposed in a metal halide lamp.

  As shown in FIGS. 4 (a) and 4 (b), the conventional metal halide lamp has an outer tube 102 having one end closed and a base attached to the other end, and the outer tube 102 will be described later. The arc tube 105 supported by the stem wire and having an envelope made of ceramic, a glass sleeve 110 surrounding the arc tube 105 and disposed for explosion protection, and a sleeve 110 for holding the sleeve 110 Metal plates 108 and 109 provided at both ends of the plate.

The outer tube 102 is filled with nitrogen gas so as to be 100 kPa at the time of lighting.
A glass stem 101 that supports two stem wires 103a and 103b for supplying a current to the electrodes is fused to the other end of the outer tube 102.
The arc tube 105 has a main tube portion and narrow tube portions provided at both ends of the main tube portion. Inside the arc tube 105 is a metal halide as a luminescent material, mercury as a buffer gas, and as a starting gas. A predetermined amount of each rare gas is enclosed.

In the main pipe portion, a pair of electrodes arranged to face each other are provided.
The end portions of the electrodes are electrically connected to one end portions of the power feeding bodies 104a and 104b sealed with glass frit in the narrow tube portions, respectively.
The other end portions of the power feeding bodies 104a and 104b are led out from the outside of the thin tube portion and are electrically connected to each stem wire.

In order to turn on the metal halide lamp, a drive circuit including an igniter (not shown), a ballast (not shown), a power supply circuit (not shown), and the like is usually prepared.
At the time of starting, the igniter superimposes a high voltage pulse on the sine wave voltage applied in the steady state to generate a small discharge in the vicinity of the starting lead wire 107 and the electrode 114, and the initial electron due to this small discharge is generated. As a result, as shown in FIG. 5A, arc discharge is generated between the paired electrodes in the arc tube 105 at a low starting voltage.

Thus, some conventional metal halide lamps are provided with a starting lead wire and have improved startability. (For example, see Patent Document 1)
JP-A-10-294085

However, the conventional metal halide lamp can be started at a low voltage, but has the following problems.
That is, the inner wall of the arc tube 105 becomes high temperature and high pressure during discharge, and when used for a long time, the container of the arc tube 105 may be damaged due to thermal fatigue or the like, as shown in FIG. is there.

When the container of the arc tube 105 is broken, the internal rare gas, mercury, and metal halide are released, so that the arc discharge is stopped and the current value becomes zero.
At this time, the igniter detects that the lamp voltage has become high, determines that it is a start time, and superimposes a high voltage pulse on the sine wave voltage.
As a result, at _a distance (r _b ) shorter than the distance (r _a ) between the electrodes, a dielectric breakdown occurs between the starting lead wires 107 facing one electrode, and further, an arc discharge, that is, a transition to an abnormal discharge occurs. To do.

This abnormal discharge is sometimes referred to as outer tube discharge.
Since the starting conducting wire 107 is composed of a molybdenum wire or the like having a thin wire diameter, as shown in FIG. 5 (b), the portion C that is the starting point of discharge is melted by the abnormal discharge described above. However, since the conductor portion above the melted portion C is connected to the electrode 113, the abnormal discharge continues.

For this reason, the fusing progresses, and as shown in FIG. 5C, the discharge distance (r _c ) extends to the D portion while the conductor portion above the C portion is melted.
When the discharge distance reaches the distance (r _c ), the voltage necessary for continuing the abnormal discharge cannot be supplied, and the abnormal discharge stops.
In the process up to this point, the ballast and the like are often damaged due to a large current accompanying the abnormal discharge, and the outer tube 102 becomes high temperature due to the abnormal discharge, which may cause cracks and breakage.

  The present invention has been made in view of the above problems, and provides a metal halide lamp that is less likely to cause secondary damage due to abnormal discharge even when the arc tube container is damaged. Objective.

  In order to achieve the above object, a metal halide lamp according to the present invention includes a ceramic arc tube composed of a main body portion and thin tube portions provided at both ends of the main body portion, and a pair of disposed in the main body portion. The electrode is connected to one end of the electrode and the other end is extended from the capillary tube, and is connected to one of the feeders, in proximity to or in contact with the arc tube. A metal halide lamp having a starting conducting wire, wherein a current limiting element is inserted into the starting conducting wire.

With the above-described configuration, abnormal discharge is suppressed, and occurrence of secondary damage due to abnormal discharge is suppressed.
The current limiting element may be formed of a resistor that limits current so that the abnormal discharge does not occur.
Thereby, since the amount of current flowing through the current limiting element is limited, the abnormal discharge is suppressed.

The resistance value of the current limiting element may be 1 kΩ or more and 1 MΩ or less.
As a result, the amount of current flowing through the current limiting element is limited within a range that does not increase the starting voltage, and thus the abnormal discharge is suppressed while maintaining startability.
The current limiting element may be a capacitor.
As a result, in the case of AC driving, the amount of current flowing through the current limiting element is limited, so that the abnormal discharge is suppressed.

The rated power of the metal halide lamp may be 50 W or more and 400 W or less, and the distance between the terminals at two locations of the current limiting element may be 4.5 mm or more.
This suppresses abnormal discharge from occurring between both terminals of the current limiting element.
The arc tube is housed in an outer tube, and is disposed at both ends of the sleeve for holding the sleeve, and a sleeve that surrounds at least the main body between the outer tube and the arc tube. The current limiting element may be located in a space other than the space sandwiched between the first support member and the second support member.

As a result, since heat conduction due to radiant heat and convection generated with discharge in the arc tube is blocked by the first support member or the second support member, the thermal load on the current limiting element is reduced.
That is, deterioration of the current limiting element due to heat is reduced.
Moreover, even if the arc tube is damaged, one end of the starting conducting wire may be wound around the arc tube portion that is difficult to change in shape.

Thereby, the change of the space | interval of the conducting wire for starting and the 2nd electrode is suppressed at the time of the failure | damage of an arc tube.
In other words, since the discharge distance affects the discharge state of the abnormal discharge, the deviation between the design parameter considered in suppressing the abnormal discharge and the actual parameter can be reduced, and the abnormal discharge is more reliably performed. Is suppressed.

<Configuration>
FIG. 1A and FIG. 1B are schematic views of a metal halide lamp 20 in the embodiment of the present invention.
As shown in FIG. 1A, the metal halide lamp 20 is a high-intensity discharge lamp with a rated power of 150 W, and includes a stem 1, an outer tube 2, stem wires 3a and 3b, power feeders 4a and 4b, The arc tube 5, the current limiting element 6, the starting conductor 7, the plate 8, the plate 9, the sleeve 10, the insulator 11, and the base 12.

The stem 1 is a glass member that supports the stem wires 3a and 3b.
The outer tube 2 is made of hard glass or the like, and an inert gas such as nitrogen is sealed therein so that, for example, the pressure is 100 Pa during lighting (about 300 ° C.).
The base 12 is a two-pole terminal for connecting to a socket for a lighting fixture.
One end of the stem wire 3 a is connected to one electrode terminal (not shown) inside the base 12, and the other end is welded to the power supply body 4 a through the stem 1.

One end of the stem wire 3b is connected to the other electrode terminal (not shown) inside the base 12, and the other end of the stem wire 3b is welded to the power feeder 4b.
The arc tube 5 is made of a translucent ceramic material such as alumina (thermal expansion coefficient 8.1 × 10 ⁻⁶ ), and is provided at a cylindrical main tube portion 5a and at both ends of the main tube portion 5a. The cylindrical thin tube portions 5b and 5c have a small diameter.

A predetermined metal halide, a rare gas such as mercury, neon, and argon is sealed in the discharge space inside the main tube portion 5a at a pressure of 13 kPa at room temperature, and a pair of electrodes (electrode 13 and electrode 14) face each other. Is arranged (see FIG. 3).
The electrode 13 and the electrode 14 are inserted into the above-described thin tube portions and sealed with a seal member in a state of being connected to the power feeding bodies 4a and 4b, respectively.

The sleeve 10 is made of cylindrical quartz, and prevents the outer tube 2 from being damaged when the arc tube 5 is broken and the fragments are scattered around.
The plates 8 and 9 are made of a thin plate made of stainless steel, and support the sleeve 10 at a predetermined interval from the arc tube 5.
Further, the plates 8 and 9 have a plurality of claw portions 8a and 9a through which the power feeders 4a and 4b pass, respectively, and close to the inner wall of the outer tube 2 on the outer periphery.

Here, since the rod-shaped power feeders 4 a and 4 b are inserted on the central axis in the longitudinal direction of the arc tube 5, the plates 8 and 9 are respectively connected to the power feeders 4 a and 4 b on the substantially central axis of the outer tube 2. Thus, the central axis of the arc tube 5 is guided almost on the central axis of the outer tube 2.
Further, the inside of the outer tube 2 is partitioned into three regions by the plates 8 and 9.

If attention is paid to two regions not including the arc tube 5, the plates 8 and 9 block light emitted from the arc tube 5, that is, radiant heat.
Thereby, at the time of lighting, the temperature in the two regions is lower than that in the region including the arc tube 5.
Further, the plate 8a is provided with a hole 8b through which the starting conducting wire 7 passes, as shown in FIG. 1 (b).

The insulator 11 is an insulating member inserted between the power supply body 4b in order to float the potential of the plate 9.
The starting lead wire 7 is a molybdenum wire having a wire diameter of 0.2 mm, one end is welded to the current limiting element 6, wound around the thin tube portion 5b, and arranged at the center so as to be in contact with the outer periphery of the main tube portion 5a. Furthermore, the other end is wound around the narrow tube portion 5 c near the electrode 14.

In addition, since the feeders 4a and 4b are inserted in the thin tube portions 5b and 5c, respectively, it is difficult to change the shape even if the main tube portion 5a is broken. Therefore, the thin tube portions 5b and 5c are wound around the thin tube portions 5b and 5c. The starting lead wire 7 is also less likely to change its position even if the breakage occurs.
The current limiting element 6 is a carbon film resistor having a resistance value (R _G ) of 20 kΩ, and one end is welded to the power feeder 4 a and the other end is welded to the starting conductor 7.

As shown in FIG. 3A, cap terminals 6a and 6b are respectively provided at both ends of the current limiting element 6, and the distance (L) between these cap terminals is 4.5 mm for the following reason. Is secured.
That is, when dielectric breakdown occurs between the starting lead wire 7 and the electrode 14, a large potential difference also occurs between the cap terminals 6a and 6b of the current limiting element 6, but the current limiting element 6 functions normally as a resistor. In this case, it is assumed that dielectric breakdown does not occur between the cap terminals 6a and 6b due to this potential difference.

It has been found that in order to prevent dielectric breakdown between the cap terminals 6a and 6b, a certain insulation distance (rd) should be secured between 6a and 6b.
The inventors have also confirmed that the above-mentioned insulation distance (rd) is 4.5 mm in metal halide lamps having a rated power of 50 W or more and 400 W or less, including the metal halide lamp 20 (rated power of 150 W).

As shown in FIG. 1B, the plate 8 is provided with a hole 8b through which the starting conducting wire 7 passes. The diameter of this hole is the same as that described above. The insulation distance (rd) is more than, that is, 4.5 mm or more.
As a drive circuit for driving the metal halide lamp 20, a power supply circuit (not shown) for supplying electric power, a ballast (not shown) for adjusting the lamp voltage and the lamp current, and a high voltage pulse are applied at the time of starting. An igniter (not shown) is provided.

When switched on, the power supply circuit generates a sine wave voltage having a frequency of 60 Hz and a peak voltage of 325 V (+ V ₁ , −V ₁ ) as shown in FIG.
The igniter is a circuit that operates by detecting that the lamp voltage is high. As shown in FIG. 2B, a peak voltage of 4500 V is superimposed by superimposing a high voltage pulse in the vicinity of the peak point of the sine wave. Increase to (+ V ₀ , −V ₀ ).

At the time of starting, no arc discharge is initially generated between the electrode 13 and the electrode 14 in the arc tube 5, but a slight discharge is generated in the vicinity of the starting conducting wire 7 and the electrode 14 by the superimposed high voltage pulse. Initial electrons are generated that trigger arc discharge between the electrodes.
<Operation>
FIG. 3A is a diagram illustrating an operation state of the metal halide lamp 20 at a normal time.

At the start-up time before the arc discharge occurs between the electrode 13 and the electrode 14, a high voltage pulse (+ V ₀ , −V ₀ ) of 4500 V is applied between the electrode 13 and the electrode 14, but contributes to the discharge. Since there are very few electrons in the main pipe part 5a, no arc discharge occurs between the electrodes 13 and 14.
On the other hand, when a high-voltage pulse (+ V ₀ , −V ₀ ) is applied between the starting lead wire 7 and the electrode 14, although it is spatially isolated by the ceramic thin tube portion 5 c, Since the potential gradient between the end of the conducting wire 7 and the electrode 14 becomes extremely large, a slight discharge is generated in the vicinity of the electrode 14.

The current at the time of the slight discharge becomes an extremely small value from the above mechanism.
Strictly speaking, the current limiting element 6 has a resistance value of 20 kΩ, so that a voltage drop occurs. However, since the current value is extremely small, the voltage drop value is extremely small.
Therefore, the voltage (+ V _a0 , −V _a0 ) applied to the end of the starting lead wire 7 is almost the same as the high voltage pulse (+ V ₀ , −V ₀ ).

In other words, the current limiting element 6 hardly affects the value of the high voltage pulse.
As a result, regardless of the presence or absence of the current limiting element 6, a fine discharge is generated between the electrode 14 and the starting conductor 7 by the high voltage pulse (+ V ₀ , −V ₀ ) of 4500 V superimposed by the igniter at the time of starting. This fine discharge becomes initial electrons that trigger arc discharge, and arc discharge occurs between the electrode 13 and the electrode 14.

Of course, when the resistance value of the current limiting element 6 takes a very large value, the resistance value of the current limiting element 6 cannot be ignored. Since the voltage applied between the end of the starting lead wire 7 near the electrode 14 and the electrode 14 decreases, the above-mentioned fine discharge does not occur, the initial electrons of arc discharge cannot be generated, and the starting voltage is reduced. Will rise.
The resistance value of the current limiting element 6 described above is a value obtained experimentally in a range in which the starting voltage does not increase. Strictly speaking, the resistance value is not limited to the above-described value of 20 kΩ. It has been confirmed that it should be within the range of the largest resistance value (R2) that can clear the reference, that is, within the range of 1 MΩ or less.
<When main section 5a is damaged>
Then, the case where the main pipe part 5a is damaged will be described.

FIG. 3B is a diagram showing an operation state of the metal halide lamp 20 when the main pipe portion 5a is broken.
The main part 5a becomes a small pressure vessel having a high temperature and high pressure at the time of lighting, and may be damaged due to a crack in the main part 5a due to thermal fatigue.
Along with this damage, rare gas such as metal halide, mercury, neon and argon flows out from the arc tube 5 into the outer tube 2.

Then, the main pipe portion 5a that insulates the adjacent starting lead wire 7 and the electrode 14 is damaged and dropped, whereby the starting lead wire 7 and the electrode 14 having a potential difference are exposed.
At this time, the arc discharge between the electrode 13 and the electrode 14 disappears due to breakage of the main pipe portion 5a, and the lamp voltage rises. However, the igniter that detects the rise in the lamp voltage generates a high voltage pulse (+ V _0). , −V ₀ ).

At this time, the superimposed high voltage pulse of 4500 V is applied between the electrode 13 and the electrode 14.
As a result, a breakdown occurs between the electrode 14 and the C portion of the starting conductor 7 that is closest to the electrode 14 in distance.
At this time, the discharge (hereinafter referred to as “pulse discharge”) occurs only at the moment when the high voltage pulse is applied.

In the pulse discharge, the current value is small, and the effect of the current limiting element 6 cannot be obtained.
On the other hand, even in the pulse discharge state, since the application of the high voltage pulse is not stopped, it tends to shift to arc discharge in which a larger current flows.
However, since the current flowing through the starting conducting wire 7 is limited to a current value or less required for arc discharge by the current limiting element 6, arc discharge does not occur.

The inventors have confirmed that the resistance value R1 is required to be 1 kΩ or more in the metal halide lamp 20 (rated power 150 W) in order to limit the current value to be equal to or less than the current value necessary for the transition to arc discharge.
Therefore, when the main pipe portion 5a is damaged, the resistance value range of the current limiting element 6 necessary for preventing abnormal discharge and maintaining the startability at the current level is in the range from 1 kΩ to 1 MΩ. .

As described above, according to the present embodiment, in the metal halide lamp, even when the container of the arc tube 5, that is, the main tube portion 5 a is damaged, an arc is generated between the electrode 14 and the starting lead wire 7. Since the value of the current is limited to such an extent that discharge, that is, abnormal discharge does not occur, overcurrent does not flow, and secondary damage to the ballast and the outer tube 2 is prevented.
In the present embodiment, the rated power of the metal halide lamp 20 is 150 W. However, the present invention is not limited to this, and any value in the range of 50 W to 400 W may be used as the rated power.

Also in this case, when the main pipe portion 5a is damaged, the resistance value range of the current limiting element 6 necessary for preventing abnormal discharge and maintaining the startability at the current level is from 1 kΩ to 1 MΩ. It becomes a range.
The current limiting element 6 is a carbon film resistor, but is not limited to this, and may be another type of resistor such as a chip resistor.

Moreover, although the alternating current voltage is applied to the metal halide lamp 20 of the present invention, a direct current voltage may be applied.
Further, when an AC voltage is applied to the metal halide lamp 20, a capacitor may be used instead of the carbon film resistor of the current limiting element 6.
That is, in the AC drive, since the capacitor has an impedance similar to the resistor, the value of the current flowing through the starting conductor 7 can be limited when the main pipe portion 5a is damaged, as in the case of the resistor. .

In the present embodiment, the starting lead wire 7 is disposed so as to be in contact with the outer periphery of the arc tube 5, but may be close to the arc tube 5 without being in contact with the outer periphery.
Moreover, the structure of an electrode and a power feeding body may differ from the said embodiment, for example, a single member may be sufficient as an electrode and a power feeding body.

  The present invention is applicable to a high-pressure discharge lamp that assists lighting using a starting lead wire.

(A) is the schematic (side view) of the metal halide lamp in embodiment of this invention. (B) is the schematic (top view) of the metal halide lamp in embodiment of this invention. (A) is a figure which shows the voltage waveform applied between two electrodes in an arc_tube | light_emitting_tube in a steady state. (B) is a figure which shows the voltage waveform applied between two electrodes in an arc_tube | light_emitting_tube at the time of starting. (A) is a figure which shows the operation condition in the normal time of the metal halide lamp in this Embodiment. (B) is a figure which shows the operation | movement condition at the time of the main-tube part failure | damage of the metal halide lamp in this Embodiment. (A) is the schematic (side view) of the conventional metal halide lamp. (B) is the schematic (top view) of the conventional metal halide lamp. (A) is a figure which shows the condition in the normal time of the conventional metal halide lamp. (B) is a figure which shows the condition at the time of the main part failure of the conventional metal halide lamp. (C) is a figure which shows the condition in the end stage at the time of the main part damage of the conventional metal halide lamp.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stem 2 Outer tube 3a, 3b Stem wire 4a, 4b Feeder 5 Light emission tube 5a Main tube part 5b, 5c Narrow tube part 6 Current limiting element 7 Starting lead wire 8, 9 Plate 8b Hole 8a, 9a Claw part 10 Sleeve 11 Insulation Body 12 Base 13, 14 Electrode 20 Metal halide lamp

Claims (5)

A metal halide lamp started by a drive circuit including a starting igniter provided outside,
An outer tube,
A ceramic arc tube that is included in the outer tube and includes a main body portion and thin tube portions provided at both ends of the main body portion, and
A pair of electrodes disposed in the body portion;
A power feeding body in which the electrode is connected to one end and the other end extends from the narrow tube;
Connected to one of the power feeders, and has a starting conductor in proximity to or in contact with the arc tube,
Without a drive circuit including a starting igniter inside the outer tube,
A metal halide lamp, wherein a resistor having a resistance value of 1 kΩ or more and 1 MΩ or less is inserted into the starting lead wire. Rated power is 50W or more and 400W or less,
The metal halide lamp according to claim 1, wherein an interval between terminals at two locations of the resistor is 4.5 mm or more. A sleeve surrounding at least the main body between the outer tube and the arc tube;
A first support member and a second support member disposed at both ends of the sleeve to hold the sleeve;
3. The metal halide lamp according to claim 1, wherein the resistor is located in a space other than a space sandwiched between the first support member and the second support member.   The one end of the starting conducting wire is wound around the arc tube portion that is difficult to change in shape even when the arc tube is damaged. Metal halide lamp. A lighting device having a metal halide lamp and a drive circuit for driving the metal halide lamp,
The drive circuit includes a starting igniter and is provided outside the metal halide lamp.
The metal halide lamp is
An outer tube,
A ceramic arc tube that is included in the outer tube and includes a main body portion and thin tube portions provided at both ends of the main body portion, and
A pair of electrodes disposed in the body portion;
A power feeding body in which the electrode is connected to one end and the other end extends from the narrow tube;
Connected to one of the power feeders, and with a starting conductor in proximity to or in contact with the arc tube,
Without a drive circuit including a starting igniter inside the outer tube,
A lighting device in which a resistor having a resistance value of 1 kΩ or more and 1 MΩ or less is inserted into the starting lead wire.

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