JP6562298B2 - Discharge lamp - Google Patents

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 is enclosed, and a pair of electrodes that protrude into the discharge space and face each other at a predetermined distance.
In recent years, a discharge lamp that is lit with power of 30 W or less (for example, 25 W) at the time of stable lighting has been demanded from the demand for power saving.
However, the low power discharge lamp has a problem that the brightness becomes dark.
For this reason, there has been proposed a discharge lamp in which the brightness is increased by reducing the light emitting portion (decreasing the discharge space).
However, simply reducing the size of the light emitting part causes a new problem that the light emitting part is easily damaged.
For this reason, it has been desired to develop a technique that can suppress the brightness from being reduced even in a low-power discharge lamp and can suppress damage to the light emitting unit.

JP 2004-172056 A

  The problem to be solved by the present invention is to provide a discharge lamp that can suppress a decrease in brightness and suppress damage to a light emitting unit even in a low-power discharge lamp. Is to provide.

The discharge lamp according to the embodiment is a discharge lamp that is lit with electric power of 22 W or more and 28 W or less during stable lighting.
The discharge lamp includes a light-emitting portion having a discharge space in which a metal halide is enclosed, and a pair of electrodes protruding inside the discharge space and arranged to face each other at a predetermined distance.
In the direction in which the electrode extends, the discharge space has a first region located in a central portion of the discharge space and second regions located on both sides of the first region.
The first region has a substantially cylindrical shape.
The second region has a substantially conical shape, and the dimension in a direction orthogonal to the direction in which the electrode extends is gradually reduced toward the end of the discharge space.
An angle formed between the inner wall of the light emitting unit and the electrode in the second region is 27.8 ° or more and 35.2 ° or less.

  According to the embodiment of the present invention, there is provided a discharge lamp that can suppress the brightness from being darkened and can prevent the light emitting unit from being damaged even in a low-power discharge lamp. can do.

It is a schematic diagram for illustrating the discharge lamp 100 according to the present embodiment. 3 is a schematic cross-sectional view of a light emitting unit 11. FIG.

The invention according to the embodiment is a discharge lamp that is lit at a power of 22 W or more and 28 W or less during stable lighting, and has a light emitting part having a discharge space in which a metal halide is enclosed, and projects into the discharge space. A pair of electrodes arranged to face each other at a predetermined distance.
In the direction in which the electrode extends, the discharge space has a first region located in a central portion of the discharge space and second regions located on both sides of the first region.
The first region has a substantially cylindrical shape.
The second region has a substantially conical shape, and the dimension in a direction orthogonal to the direction in which the electrode extends is gradually reduced toward the end of the discharge space.
An angle formed between the inner wall of the light emitting unit and the electrode in the second region is 27.8 ° or more and 35.2 ° or less.
According to this discharge lamp, even if it is a low power discharge lamp, it can suppress that a brightness becomes dark and can suppress that a light emission part is damaged.

Further, in the direction in which the electrode extends, the dimension of the second region may be 1.5 mm or more and 2.1 mm or less.
In this way, it is possible to more effectively suppress damage to the light emitting part.

The distance between the surface of the electrode and the inner wall of the light emitting portion in the first region in the direction perpendicular to the direction in which the electrode extends is 1.0 mm or more and 1.2 mm or less. Can do.
In this way, it is possible to more effectively suppress damage to the light emitting part.

Hereinafter, embodiments will be illustrated with reference to the drawings. In addition, in each drawing, the same code | symbol is attached | subjected to the same component and detailed description is abbreviate | omitted suitably.
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, so-called horizontal lighting can be performed.

  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.
FIG. 2 is a schematic cross-sectional view of the light emitting unit 11.

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 that has a thermal expansion coefficient close to that of the material of the inner tube 1 and that has 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 is formed from a material having translucency and heat resistance. The inner tube 1 can be formed from, for example, quartz glass.
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 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.
The dimension of the light emitting part 11 in the direction orthogonal to the axial direction of the inner tube 1 can be set to about 5 mm, for example.

A discharge space 111 is provided inside the light emitting unit 11.
The discharge space 111 has a region 111a (corresponding to an example of a first region) and a region 111b (corresponding to an example of a second region).
In the direction in which the electrode 32 extends (the axial direction of the inner tube 1), the region 111 a is located at the center portion of the discharge space 111. The region 111a has a substantially cylindrical shape.
The region 111b is located on both sides of the region 111a. In the region 111b, the dimension in the direction orthogonal to the direction in which the electrode 32 extends gradually decreases toward the end of the discharge space 111. The region 111b has a substantially conical shape.

A discharge medium is enclosed in the discharge space 111. The discharge medium includes a metal halide 2 and an inert gas.
The metal halide 2 may include, for example, indium halide, sodium halide, scandium 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.
In discharge lamp 100 according to the present embodiment, the discharge medium does not contain mercury from the viewpoint of environmental protection.

The inert gas sealed in the discharge space 111 can be, for example, a kind of gas selected from xenon, neon, argon, and krypton, or a mixed gas thereof.
The enclosure pressure of the inert gas is preferably 10 atm or more and 15 atm or less at room temperature (25 ° C.), for example.

The sealing part 12 has a plate shape and is provided on both sides of the light emitting part 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.
In addition, the light emission part 11, the sealing part 12, the boundary part 13, and the cylindrical part 14 can be formed integrally.

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 is made of, for example, molybdenum.

The electrode 32 has a linear shape. The cross-sectional shape of the electrode 32 can be circular, for example.
The thickness dimension (diameter dimension when the cross-sectional shape is circular) of the electrode 32 can be 0.2 mm or more and 0.4 mm or less.
The distance between the tips of the pair of electrodes 32 (interelectrode distance) can be, for example, 3.4 mm or more and 4.4 mm or less.

  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.

One end of the electrode 32 protrudes into the discharge space 111. The pair of electrodes 32 are provided to face each other with a predetermined distance.
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 coil 33 can be formed from, for example, a metal wire made of doped tungsten. The coil 33 is wound around the outside of the electrode 32 provided inside the sealing portion 12. 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. The lead wire 34 and the metal foil 31 can be joined by laser welding. 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 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 6, a mounting bracket 72, a bottom terminal 81, and a side terminal 82.
The main body 6 is made of an insulating material such as resin. Inside the main body 6, 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 6. The mounting bracket 72 is provided on the front end side. The mounting bracket 72 protrudes from the main body 6. 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 6. The bottom terminal 81 is provided on the rear end side. 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 6. The side terminal 82 is provided on the rear end side. 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 a headlight of an automobile, the discharge lamp 100 is mounted such that the central axis (tube axis) is substantially horizontal and the support wire 35 is positioned on the lower end side (downward). It is done. 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 or more and 28 W or less (for example, 25 W) 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 internal dimension of the light emitting unit 11 (the dimension of the discharge space 111) is reduced, it is possible to suppress the brightness from becoming dark.
This can be explained as follows.
That is, if the internal dimensions of the light emitting unit 11 are reduced, the outer dimensions of the light emitting unit 11 are also reduced. If the external dimensions of the light emitting unit 11 are reduced, the amount of heat released from the light emitting unit 11 can be reduced.
If the amount of heat released from the light emitting unit 11 decreases, the internal temperature of the light emitting unit 11 (the temperature of the discharge space 111) increases and the vapor pressure of the metal halide 2 increases.
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 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 internal dimensions of the light emitting unit 11.

However, if the internal dimension of the light emitting unit 11 is reduced, the light emitting unit 11 is easily damaged.
According to the knowledge obtained by the present inventor, the reason why the light emitting section 11 is easily damaged can be explained as follows.
The temperature of the electrode 32 increases during lighting (when discharging) and decreases due to heat dissipation when extinguished.
However, as described above, if the internal dimensions of the light emitting unit 11 are reduced, the internal temperature of the light emitting unit 11 increases.
Therefore, heat dissipation in the electrode 32 is hindered, and the temperature of the electrode 32 is easily maintained while being high.

Here, the form of discharge between the electrodes 32 varies depending on the temperature of the electrodes 32.
For example, if the discharge is started when the temperature of the electrode 32 is low, a discharge S1 occurs between the tips of the electrodes 32 as shown in FIG.
However, if discharge is started when the temperature of the electrode 32 is high, as shown in FIG. 2, between the portion near the sealing portion 12 of one electrode 32 and the tip of the other electrode 32. Discharge S2 occurs.
The region 111b of the discharge space 111 has a substantially conical shape. Therefore, as shown in FIG. 2, in the region 111b, the distance between the inner wall of the light emitting unit 11 and the discharge S2 becomes extremely short.
That is, if the internal dimension of the light emitting unit 11 is reduced, the temperature of the electrode 32 is easily maintained at a high temperature, so that the discharge S2 in which the distance from the inner wall of the light emitting unit 11 is shortened is likely to occur. Further, the distance between the inner wall of the light emitting unit 11 and the electrode 32 is also shortened.
Therefore, damage due to the discharge S2 is likely to occur on the inner wall of the light emitting unit 11 in the region 111b.

Next, the relationship between the form of the discharge space 111 and the occurrence of damage in the light emitting unit 11 will be described. Tables 1 and 2 show the relationship between the form of the discharge space 111 and the occurrence of damage in the light emitting unit 11.
In the evaluation tests in Tables 1 and 2, lighting for 1 second and turning off for 1 second were repeated 100000 times, and then the occurrence of damage and the degree of damage in the light emitting unit 11 were determined.
If the lighting for 1 second and the turning off for 1 second are repeated, the temperature of the electrode 32 is maintained high, so that the discharge S2 is likely to occur.
Further, as shown in FIG. 2, the angle formed between the inner wall of the light emitting unit 11 in the region 111b and the electrode 32 is defined as θ.
The dimension of the region 111b in the direction in which the electrode 32 extends was A.
The distance between the surface of the electrode 32 and the inner wall of the light emitting portion 11 in the region 111a in the direction orthogonal to the direction in which the electrode 32 extends was B.
The outer dimensions of the light emitting unit 11 are the same.
In addition, “○” indicates that no damage is observed, “△” indicates that damage is generated, but if there is no practical problem, “×” indicates that damage has occurred, In addition, the degree of damage is a practical problem.

As can be seen from Table 1, if the angle θ is increased, the occurrence of damage can be suppressed.
This is considered to be because if the angle θ is increased, the distance between the discharge S2 and the inner wall of the light emitting unit 11 can be increased.
That is, if the angle θ is 27.8 ° or more, the occurrence of damage due to the discharge S2 can be suppressed.

However, as can be seen from Table 2, if the angle θ is too large, the occurrence of damage cannot be suppressed.
This is considered to be because when the angle θ is too large, a portion where the thickness of the light emitting portion 11 becomes too thin is generated, and the temperature of the portion where the thickness is thin becomes too high.
That is, if the angle θ is 35.2 ° or less, the occurrence of damage due to overheating can be suppressed.

In other words, as can be seen from Tables 1 and 2, when the angle θ is 27.8 ° or more and 35.2 ° or less, the occurrence of damage due to the discharge S2 and the occurrence of damage due to overheating can be suppressed.
In this case, the dimension A is preferably 1.5 mm or more and 2.1 mm or less.
The distance B is preferably 1.0 mm or more and 1.2 mm or less.
In addition, if the form of the discharge space 111 is as described above, it is possible to obtain almost the same brightness as a discharge lamp that is lit with about 35 W of power during stable lighting.

  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.

  DESCRIPTION OF SYMBOLS 1 Inner tube, 2 Metal halide, 3 Electrode mount, 5 Outer tube, 11 Light emission part, 12 Sealing part, 31 Metal foil, 32 Electrode, 100 Discharge lamp, 101 Burner, 102 Socket, 111 Discharge space, 111a area | region, 111b region, S1 discharge, S2 discharge

Claims (3)

A discharge lamp that is lit at a power of 22 W or more and 28 W or less during stable lighting,
A light emitting part having a discharge space in which a metal halide is enclosed;
A pair of electrodes protruding into the discharge space and arranged to face each other at a predetermined distance;
Comprising
In the direction in which the electrode extends, the discharge space has a first region located in a central portion of the discharge space, and second regions located on both sides of the first region,
The first region has a substantially cylindrical shape,
The second region has a substantially conical shape, and the dimension in a direction orthogonal to the direction in which the electrode extends is gradually reduced toward the end of the discharge space.
The discharge lamp whose angle which the inner wall of the said light emission part in the said 2nd area | region and the said electrode make is 27.8 degrees or more and 35.2 degrees or less.   2. The discharge lamp according to claim 1, wherein a dimension of the second region is 1.5 mm or more and 2.1 mm or less in a direction in which the electrode extends.   The distance between the surface of the electrode and the inner wall of the light emitting portion in the first region in a direction perpendicular to the direction in which the electrode extends is 1.0 mm or more and 1.2 mm or less. Or the discharge lamp of 2.

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