JP2017208216A - Discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp which enables the increase in brightness and the suppression of "white turbidity" even if it is a discharge lamp which is lit with a low power.SOLUTION: A discharge lamp according to an embodiment is a discharge lamp which lights with a power of 22-28 W(watt) in lighting with stability. The discharge lamp comprises: a light-emitting unit having therein a discharge space with a metal halide and an inert gas sealed therein; and a pair of electrodes protruding into the discharge space, and opposed to each other with a predetermined distance arranged therebetween. The thickness of a portion where the thickness of the light-emitting unit becomes maximum is 1.0-1.5 mm. The discharge lamp satisfies the following expression: 401(mm atm)≤8.8×L×P(mm atm)≤500(mm atm), where P(atm) is a pressure of the inert gas sealed in the discharge space at an atmospheric temperature (25°C), and L(mm) is a distance between tips of the pair of electrodes.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a discharge lamp.

There is a discharge lamp provided with a light emitting part having a discharge space in which a metal halide and an inert gas are sealed, and a pair of electrodes protruding inside the discharge space and arranged to face each other at a predetermined distance .
Such a discharge lamp is lit with a power of about 35 W (watts) during stable lighting. However, in recent years, a discharge lamp that is lit with a power of 28 W (watts) or less (for example, 25 W (watts)) at the time of stable lighting has been demanded due to a demand for power saving.
Such a discharge lamp that is lit at low power has a problem that the brightness is darker than a discharge lamp that is lit at a power of about 35 W (watts). In this case, the brightness can be increased by increasing the temperature of the light emitting unit.
However, when the temperature of the light emitting portion is increased, the electrode is easily sputtered. When the electrode is sputtered, a film composed of the electrode components is formed on the inner wall of the light emitting portion, resulting in “white turbidity”. When “white turbidity” occurs, the light generated inside the discharge space is shielded, resulting in a new problem that the brightness becomes dark.
Therefore, it has been desired to develop a discharge lamp capable of improving brightness and suppressing “white turbidity” even when the discharge lamp is lit with low power.

Japanese Patent No. 5428957

  The problem to be solved by the present invention is to provide a discharge lamp capable of improving brightness and suppressing “white turbidity” even when the discharge lamp is lit at low power.

The discharge lamp according to the embodiment is a discharge lamp that is lit with electric power of 22 W (watts) or more and 28 W (watts) or less during stable lighting. The discharge lamp includes: a light emitting unit having a discharge space in which a metal halide and an inert gas are enclosed; a pair of electrodes protruding inside the discharge space and arranged to face each other at a predetermined distance; It has. The thickness dimension of the portion where the thickness of the light emitting portion is maximum is 1.0 mm or more and 1.5 mm or less.
The discharge lamp is as follows when the pressure at normal temperature (25 ° C.) of the inert gas sealed in the discharge space is P (atm) and the distance between the tips of the pair of electrodes is L (mm). Satisfies the following formula.
401 (mm · atm) ≦ 8.8 × L × P (mm · atm) ≦ 500 (mm · atm)

  According to the embodiment of the present invention, it is possible to provide a discharge lamp capable of improving brightness and suppressing “white turbidity” even when the discharge lamp is lit with low power.

It is a schematic diagram for illustrating the discharge lamp 100 according to the present embodiment.

Hereinafter, embodiments will be illustrated with reference to the drawings.
The discharge lamp according to the embodiment of the present invention can be, for example, an HID (High Intensity Discharge) lamp used for an automobile headlamp. Further, when the discharge lamp is an HID lamp used for a headlight of an automobile, the discharge lamp can perform so-called horizontal lighting.

  Although the use of the discharge lamp according to the embodiment of the present invention is not limited to a vehicle headlamp, here, as an example, a case where the discharge lamp is an HID lamp used for a vehicle headlamp is an example. Will be described.

FIG. 1 is a schematic diagram for illustrating a discharge lamp 100 according to the present embodiment.
In addition, in FIG. 1, when the discharge lamp 100 is attached to an automobile, the front direction is the front end side, the rear direction is the rear end side, the upper direction is the upper end side, and the lower direction is the lower end side. It is said.

As shown in FIG. 1, the discharge lamp 100 is provided with a burner 101 and a socket 102.
The burner 101 is provided with an outer tube 5, an inner tube 1, an electrode mount 3, a support wire 35, a sleeve 4, and a metal band 71.

The outer tube 5 is provided outside the inner tube 1 and concentric with the inner tube 1. That is, the burner 101 has a double tube structure including the outer tube 5 and the inner tube 1. The outer tube 5 is joined (welded) near the cylindrical portion 14 of the inner tube 1.
Gas is enclosed in a closed space formed between the inner tube 1 and the outer tube 5. The sealed gas can be a gas capable of dielectric barrier discharge. The gas to be sealed can be, for example, a kind of gas selected from neon, argon, xenon, and nitrogen, or a mixed gas thereof. The gas sealing pressure can be, for example, 0.3 atm or less at room temperature (25 ° C.). The gas sealing pressure is more preferably 0.1 atm or less at room temperature (25 ° C.).

  The outer tube 5 is preferably formed of a material having a thermal expansion coefficient close to that of the material of the inner tube 1 and having an ultraviolet blocking property. The outer tube 5 can be formed of, for example, quartz glass to which an oxide such as titanium, cerium, or aluminum is added.

The inner tube 1 has a light emitting part 11, a sealing part 12, a boundary part 13, and a cylindrical part 14. The light emitting part 11, the sealing part 12, the boundary part 13, and the cylindrical part 14 can be integrally formed.
The inner tube 1 (the light emitting part 11, the sealing part 12, the boundary part 13, and the cylindrical part 14) is formed from a material having translucency and heat resistance. The inner tube 1 can be formed from, for example, quartz glass.

The light emitting unit 11 has a substantially ellipsoidal outer shape. The light emitting unit 11 is provided near the center of the inner tube 1. The dimension (sphere length) of the light emitting part 11 in the axial direction of the inner tube 1 can be set to about 8 mm, for example.
Details regarding the wall thickness of the light emitting unit 11 will be described later.

A discharge space 111 is provided inside the light emitting unit 11. The central portion of the discharge space 111 has a substantially cylindrical shape. Both end portions of the discharge space 111 have a substantially conical shape. Here, when the dimension of the central portion of the discharge space 111 in the direction orthogonal to the axial direction of the inner tube 1 is reduced, the distance between the discharge generated between the tips of the electrodes 32 and the inner wall 11a of the light emitting unit 11 is reduced. Since the length is shortened, damage due to discharge is likely to occur on the inner wall 11a of the light emitting unit 11. On the other hand, when the dimension of the central portion of the discharge space 111 is increased, the temperature of the light emitting unit 11 is lowered, and thus the brightness may be reduced.
Therefore, the dimension of the central portion of the discharge space 111 in the direction orthogonal to the axial direction of the inner tube 1 is preferably set to 2.0 mm or more and 2.4 mm or less.

  A discharge medium is enclosed in the discharge space 111. The discharge medium includes a metal halide 2 and an inert gas.

  In the discharge lamp 100 according to the present embodiment, the discharge medium is substantially free of mercury from the viewpoint of environmental protection. In the present specification, “substantially free of mercury” not only does not contain mercury at all, but also allows mercury to be contained to the extent of impurities. For example, the discharge medium can contain mercury as long as it is less than 2 mg / cc in the discharge space 111.

The metal halide 2 may include, for example, scandium halide, indium halide, sodium halide, zinc halide, and the like.
As the halogen, for example, iodine can be exemplified. However, bromine or chlorine can be used instead of iodine.

The inert gas sealed in the discharge space 111 can be xenon, for example. In addition to xenon, neon, argon, krypton, or the like, or a mixed gas in which these are combined can also be used.
However, the inert gas is more preferably xenon.
In addition, the detail regarding the pressure (enclosure pressure) P in normal temperature (25 degreeC) of the inert gas enclosed with the discharge space 111 is mentioned later.

  The sealing portion 12 has a plate shape and is joined to each of both end portions of the light emitting portion 11. The sealing portion 12 can be formed using, for example, a pinch seal method. Note that the sealing portion 12 may be formed by a shrink seal method and may have a cylindrical shape. A cylindrical portion 14 is joined to one sealing portion 12 via a boundary portion 13.

  The boundary portion 13 and the cylindrical portion 14 are joined to the end portion of the sealing portion 12 on the side opposite to the light emitting portion 11 side.

The electrode mount 3 is provided inside the sealing portion 12.
The electrode mount 3 includes a metal foil 31, an electrode 32, a coil 33, and a lead wire 34.

The metal foil 31 is provided inside the sealing part 12. The metal foil 31 is joined in the vicinity of the end of the electrode 32 on the side opposite to the discharge space 111 side.
The metal foil 31 has a thin plate shape and can be formed of, for example, molybdenum, rhenium molybdenum, tungsten, rhenium tungsten, or the like.

The electrode 32 has a linear shape. The cross-sectional shape of the electrode 32 can be circular, for example.
Here, when the discharge lamp 100 is turned on with a power of 22 W (watts) or more and 28 W (watts) or less during stable lighting, flickering is likely to occur. According to the knowledge obtained by the present inventor, flickering can be suppressed by reducing the thickness dimension of the electrode 32 and increasing the current density. Therefore, the thickness dimension (diameter dimension when the cross-sectional shape is circular) of the electrode 32 is preferably 0.20 mm or more and 0.33 mm or less.

The thickness dimension of the electrode 32 may not be constant in the direction in which the electrode 32 extends. For example, the thickness dimension of the electrode 32 may be larger on the distal end side than on the proximal end side. Further, the tip of the electrode 32 may be spherical. Moreover, the thickness dimension of one electrode may differ from the thickness dimension of the other electrode like a direct current lighting type.
The above-mentioned “0.20 mm or more and 0.33 mm or less” is a case where the thickness dimension of the electrode 32 is substantially constant.

The pair of electrodes 32 are provided to face each other at a predetermined distance.
In addition, the detail regarding the distance (distance between electrodes) L between the front-end | tips of a pair of electrode 32 is mentioned later.
One end of the electrode 32 protrudes into the discharge space 111. That is, one end of the electrode 32 is provided in the discharge space 111 and the other end is provided in the sealing portion 12. The other end of the electrode 32 is bonded to the vicinity of the end of the metal foil 31 on the light emitting unit 11 side. The joining of the electrode 32 and the metal foil 31 can be performed by, for example, laser welding.

  The electrode 32 can be formed from, for example, pure tungsten, doped tungsten, rhenium tungsten, or the like. The electrode 32 may contain thorium or may not contain thorium.

  The coil 33 is provided to suppress the occurrence of cracks in the sealing portion 12. The coil 33 can be formed from, for example, a metal wire made of doped tungsten. The coil 33 is provided inside the sealing portion 12. The coil 33 is wound around the outside of the electrode 32. For example, the coil 33 can have a wire diameter of about 30 μm to 100 μm and a coil pitch of 600% or less.

  The lead wire 34 has a linear shape. The cross-sectional shape of the lead wire 34 can be circular, for example. The lead wire 34 can be formed from, for example, molybdenum. One end side of the lead wire 34 is joined to the vicinity of the end of the metal foil 31 on the side opposite to the light emitting unit 11 side. Joining of the lead wire 34 and the metal foil 31 can be performed by laser welding, for example. The other end side of the lead wire 34 extends to the outside of the inner tube 1.

  The support wire 35 has an L shape and is joined to the end portion of the lead wire 34 extending from the front end side of the discharge lamp 100. The support wire 35 and the lead wire 34 can be joined by, for example, laser welding. The support wire 35 can be formed from nickel, for example.

  The sleeve 4 covers a portion of the support wire 35 that extends in parallel with the inner tube 1. The sleeve 4 has, for example, a cylindrical shape. The sleeve 4 can be formed from, for example, ceramics.

  The metal band 71 is fixed in the vicinity of the end portion on the rear end side of the outer tube 5.

The socket 102 has a main body 61, a mounting bracket 72, a bottom terminal 81, and a side terminal 82.
The main body 61 is made of an insulating material such as resin. Inside the main body 61, a rear end side of the lead wire 34, a rear end side of the support wire 35, and a rear end side of the sleeve 4 are provided.

  The mounting bracket 72 is provided at the end of the main body 61. The mounting bracket 72 is provided on the front end side of the main body 61. The mounting bracket 72 protrudes from the main body 61. The mounting bracket 72 holds the metal band 71. The burner 101 is held by the socket 102 by holding the metal band 71 by the mounting bracket 72.

  The bottom terminal 81 is provided inside the main body 61. The bottom terminal 81 is provided on the rear end side of the main body 61. The bottom terminal 81 is made of a conductive material. The bottom terminal 81 is electrically connected to the lead wire 34.

  The side terminal 82 is provided on the side wall of the main body 61. The side terminal 82 is provided on the rear end side of the main body 61. The side terminal 82 is made of a conductive material. The side terminal 82 is electrically connected to the support wire 35.

  The bottom terminal 81 and the side terminal 82 are electrically connected to a lighting circuit (not shown). In this case, the bottom terminal 81 is electrically connected to the high voltage side of the lighting circuit. The side terminal 82 is electrically connected to the low voltage side of the lighting circuit.

  When the discharge lamp 100 is used for a headlight of an automobile, the discharge lamp 100 has a central axis (tube axis) substantially horizontal and the support wire 35 substantially on the lower end side (downward). It is attached to be located. Note that lighting the discharge lamp 100 attached in such a direction is referred to as horizontal lighting.

Moreover, the discharge lamp 100 according to the present embodiment is a low-power specification discharge lamp.
Therefore, the lighting circuit lights the discharge lamp 100 with power of 22 W (watts) or more and 28 W (watts) or less during stable lighting.

  Here, when the power supplied to the discharge lamp 100 is reduced, the luminous flux is reduced and the luminous efficiency is reduced. Therefore, when the power supplied to the discharge lamp 100 is reduced, the brightness becomes darker. In this case, if the thickness dimension of the light emitting unit 11 is reduced, it is possible to suppress the brightness from becoming dark.

  This can be explained as follows. That is, if the thickness of the light emitting unit 11 is reduced, the temperature of the light emitting unit 11 and thus the temperature of the discharge space 111 are increased, and the vapor pressure of the metal halide 2 is increased.

If the vapor pressure of the metal halide 2 increases, the rate at which the electrons emitted from the electrode 32 collide with the molecules of the metal halide 2 increases. As the rate of collision between the electrons and the molecules of the metal halide 2 increases, the total luminous flux increases and the luminous efficiency increases.
Therefore, even when the power supplied to the discharge lamp 100 is small, the brightness can be suppressed from being darkened by reducing the thickness of the light emitting unit 11.

In this case, if the thickness of the light emitting unit 11 is too small, the strength of the light emitting unit 11 may be insufficient. If the thickness of the light emitting unit 11 is too large, the temperature of the light emitting unit 11 is lowered, and there is a possibility that the specified brightness cannot be obtained.
According to the knowledge obtained by the present inventor, it is preferable that the thickness T of the light emitting portion 11 where the thickness is maximum is 1.0 mm or more and 1.5 mm or less. In this way, even when the discharge lamp 100 is turned on with a power of 22 W (watts) or more and 28 W (watts) or less during stable lighting, a brightness of about 74 lm / W (lumen / watt) is obtained. It becomes possible.
In addition, the part where the thickness of the light emitting part 11 is maximum is generally the central part of the light emitting part 11 in the axial direction of the inner tube 1.

However, when the temperature of the discharge space 111 increases, the electrode 32 is easily sputtered. When the electrode 32 is sputtered, a film composed of the components of the electrode 32 is formed on the inner wall 11a of the light emitting unit 11, and "white turbidity" is generated. When “white turbidity” occurs, the light generated inside the discharge space 111 is shielded, so that the brightness becomes dark. Further, when “white turbidity” occurs, it becomes difficult to dissipate heat, so that the temperature of the discharge space 111 further increases and “white turbidity” further proceeds. For this reason, there is a possibility that the decrease in brightness proceeds rapidly.
That is, even if the specified brightness can be obtained by reducing the thickness of the light emitting unit 11, it may be difficult to maintain the obtained brightness.

Further, according to the knowledge obtained by the present inventors, in the case of the discharge lamp 100 that is lit with low power, “white turbidity” is likely to occur at the start.
This can be explained as follows.
The discharge lamp 100 that is lit with low power is difficult to be lit. Therefore, the electric power applied to the discharge lamp 100 at the time of starting becomes large. For example, in the case of the discharge lamp 100 that is lit at a power of 22 W (watts) or more and 28 W (watts) or less during stable lighting, the power applied at the start is about 55 W (watts). Therefore, in the case of the discharge lamp 100 that is lit with low power, the temperature of the discharge space 111 is likely to rise at the start.
As a result, in the case of the discharge lamp 100 that is lit with low power, “white turbidity” is likely to occur at the start.

As a result of further studies, the present inventor has an influence on the startability of the discharge lamp 100 by the pressure P of the inert gas sealed in the discharge space 111 and the distance L between the tips of the pair of electrodes 32. And gained knowledge.
Therefore, if the power applied at the time of starting can be reduced by the pressure P of the inert gas and the distance L between the tips of the pair of electrodes 32, the temperature of the discharge space 111 is prevented from rising at the time of starting. be able to. If the temperature of the discharge space 111 can be prevented from rising at the start, the “white turbidity” can be prevented from occurring at the start.

In this case, according to the knowledge obtained by the present inventors, the occurrence of “white turbidity” can be effectively suppressed if the following expression is satisfied.
401 (mm · atm) ≦ 8.8 × L × P (mm · atm) ≦ 500 (mm · atm) P is the pressure (encapsulation) of the inert gas enclosed in the discharge space 111 at room temperature (25 ° C.) Pressure), L is the distance between the tips of the pair of electrodes 32.

なお、「白濁」の評価においては、発光部１１から出射した光の発光効率が７４ ｌｍ／Ｗ（ルーメン／ワット）以上を「○」とし、７４ ｌｍ／Ｗ（ルーメン／ワット）未満を「×」としている。
また、「白濁」の評価は、ＥＵ１２０分モードの点滅サイクルで点滅させるとともに、放電ランプ１００を２０００時間点灯させた後に行った。
発光効率は、「全光束／ランプ電力（安定点灯時における印加電力）」である。
また、一対の電極３２の先端同士の間の距離Ｌが長くなりすぎると、ランプ電圧（安定点灯時における印加電圧）が高くなりすぎるおそれがある。
そのため、ランプ電圧の評価においては、点灯回路に設けられた安全装置が誤作動するほどランプ電圧が高くなった場合を「×」とし、安全装置が誤作動しなかった場合を「○」としている。
総合判定においては、「白濁」の評価およびランプ電圧の評価がともに「○」の場合を「○」とし、「白濁」の評価およびランプ電圧の評価の少なくともいずれかが「×」の場合を「×」としている。 Table 1 is a table for illustrating the relationship between the filling pressure P (atm) of the inert gas, the distance L (mm) between the tips of the pair of electrodes 32, and the occurrence of “white turbidity”. .

In the evaluation of “white turbidity”, the luminous efficiency of light emitted from the light emitting section 11 is “◯” when the luminous efficiency is 74 lm / W (lumen / watt) or more, and less than 74 lm / W (lumen / watt) is “×”. "
The evaluation of “white turbidity” was performed after blinking in the blinking cycle of the EU 120 minute mode and after the discharge lamp 100 was lit for 2000 hours.
The luminous efficiency is “total luminous flux / lamp power (applied power during stable lighting)”.
If the distance L between the tips of the pair of electrodes 32 is too long, the lamp voltage (applied voltage during stable lighting) may be too high.
Therefore, in the evaluation of the lamp voltage, the case where the lamp voltage becomes so high that the safety device provided in the lighting circuit malfunctions is indicated as “X”, and the case where the safety device does not malfunction is indicated as “◯”. .
In the comprehensive judgment, when both “white turbidity” and lamp voltage are both “◯”, “○” is indicated. When at least one of “white turbidity” and lamp voltage is “X”, × ”.

The applied power during stable lighting was about 25 W (watts), and the applied power during startup was about 55 W (watts).
The composition of the metal halide 2 was as follows.
ScI ₃ : NaI: ZnI ₂ : InBr = 1.00: 1.5: 0.3: 0.007
The amount of metal halide 2 enclosed was about 0.4 mg.
The dimension of the central portion of the discharge space 111 in the direction orthogonal to the axial direction of the inner tube 1 was set to 2.0 mm or more and 2.4 mm or less.
The thickness dimension T of the portion where the thickness of the light emitting portion 11 is maximum (for example, the central portion of the light emitting portion 11) was set to 1.0 mm or more and 1.5 mm or less.
The material of the light emitting unit 11 was quartz glass.
In addition, the dimension of the center part of the discharge space 111, the thickness dimension T of the part where the thickness of the light emitting part 11 is the maximum, and the distance L between the tips of the pair of electrodes 32 are, for example, the light emitting part 11 An x-ray can be taken and calculated from the dimensions in the taken x-ray.
The inert gas sealed in the discharge space 111 is xenon.

As can be seen from Table 1, if 401 (mm · atm) ≦ 8.8 × L × P (mm · atm) ≦ 500 (mm · atm), 22 W (Watt) or more and 28 W (Watt) at stable lighting Even in the discharge lamp 100 that is lit with the following power, the luminous efficiency can be set to 74 lm / W (lumen / watt) or more. That is, even a discharge lamp that is lit with low power can improve brightness and suppress “white turbidity”.
Furthermore, the lamp voltage can be set to an appropriate value.

In this case, as can be seen from Table 1, it is preferable to satisfy 12 atm ≦ P ≦ 15.0 atm.
Further, as can be seen from Table 1, it is preferable that 3.4 mm ≦ L ≦ 3.8 mm.

  As mentioned above, although several embodiment of this invention was illustrated, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, changes, and the like can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and equivalents thereof. Further, the above-described embodiments can be implemented in combination with each other.

  DESCRIPTION OF SYMBOLS 1 Inner tube, 2 Metal halide, 5 Outer tube, 11 Light emission part, 11a Inner wall, 12 Sealing part, 32 Electrode, 100 Discharge lamp, 101 burner, 102 Socket, 111 Discharge space

Claims (3)

A discharge lamp that is lit at a power of 22 W (watts) or more and 28 W (watts) or less during stable lighting,
A light emitting part having a discharge space in which a metal halide and an inert gas are enclosed;
A pair of electrodes protruding into the discharge space and arranged to face each other at a predetermined distance;
Comprising
The thickness dimension of the portion where the thickness of the light emitting part is maximum is 1.0 mm or more and 1.5 mm or less,
When the pressure at normal temperature (25 ° C.) of the inert gas sealed in the discharge space is P (atm) and the distance between the tips of the pair of electrodes is L (mm), the following formula is satisfied. Discharge lamp.
401 (mm · atm) ≦ 8.8 × L × P (mm · atm) ≦ 500 (mm · atm) The discharge lamp according to claim 1, wherein the pressure satisfies the following expression.
12 atm ≦ P ≦ 15.0 atm The discharge lamp according to claim 1, wherein the distance satisfies the following expression.
3.4 mm ≦ L ≦ 3.8 mm

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