JP6733310B2 - Discharge lamp for automobile headlight - Google Patents

Description

Embodiments of the present invention relate to a discharge lamp for a vehicle headlight .

It has a light emitting portion having a discharge space inside, a sealing portion provided at an end portion of the light emitting portion, and an electrode having one end provided inside the discharge space and the other end provided inside the sealing portion. There is a discharge lamp.
In such a discharge lamp, cracks may occur in the portion of the sealing portion that seals the electrodes. When a crack is generated in the sealing portion, the metal halide or the like sealed in the discharge space may leak through the crack, leading to non-lighting.

Here, in recent years, from the demand for power saving, a discharge lamp that is lit with a power of 30 watts or less (for example, 25 watts) during stable lighting is required. However, if the discharge lamp is turned on with electric power of 30 watts or less, there is a problem that flicker is likely to occur. In this case, flicker can be suppressed by reducing the thickness of the electrode and increasing the current density. However, if the thickness of the electrode is reduced, a new problem arises in that crack leakage easily occurs in the sealing portion.
Therefore, there has been a demand for the development of a discharge lamp capable of suppressing the occurrence of crack leak in the sealing portion even if the discharge lamp is operated with a power of 30 watts or less during stable lighting.

JP, 2011-134696, A

An object of the present invention is to provide, even headlight discharge lamp of a motor vehicle to be lit with low power, headlights of a vehicle can be prevented from cracking leaks in the sealing portion It is to provide a discharge lamp.

The discharge lamp according to the embodiment is a discharge lamp for a vehicle headlight, which is lit with a power of 10 watts or more and 30 watts or less during stable lighting.
A discharge lamp for an automobile headlight includes a light emitting part having a discharge space therein ; a discharge medium sealed in the discharge space, containing a metal halide and an inert gas, and containing substantially no mercury. A sealing part provided at an end of the light emitting part ; an electrode having one end provided inside the discharge space and the other end provided inside the sealing part; inside the sealing part A metal foil provided and bonded near the other end of the electrode; and a void provided between the electrode and the metal foil.
The electrode has a thickness dimension of 0.23 mm or more and 0.32 mm or less, the metal foil is wound around the electrode, and both ends of the metal foil are separated from the electrode. The winding angle of the metal foil is 40° or more and 70° or less, and is a discharge lamp for a vehicle headlight that satisfies the following formula .
A discharge lamp for a vehicle headlight satisfies the following formula.
W (mm) /M (mm) ≤0.3
Note that W (mm) is a distance between the center of the metal foil in the direction orthogonal to the axial direction of the electrode and the end of the void on the end side of the metal foil.
M (mm) is the distance between the center of the metal foil and the end of the metal foil in the direction orthogonal to the axial direction of the electrode.

According to the embodiments of the present invention, even in a discharge lamp for a vehicle headlamp that is lit with low power, it is possible to suppress the occurrence of crack leak in the sealing portion of the vehicle headlamp discharge. A lamp can be provided.

It is a schematic diagram for illustrating the discharge lamp 100 according to the present embodiment. (A), (b) is the sectional view on the AA line in FIG. (A) is a case where the thickness dimension of the electrode 32 is large, and (b) is a case where the thickness dimension of the electrode 32 is small. It is a graph for illustrating a relation between a crack leak occurrence rate and W/M. It is the BB sectional view taken on the line in FIG. It is a graph figure for illustrating the relation between a crack leak occurrence rate and 2WxL.

Embodiments will be exemplified below with reference to the drawings. In the drawings, the same components are designated by the same reference numerals, and detailed description thereof will be appropriately omitted.
The discharge lamp according to the embodiment of the present invention may be, for example, an HID (High Intensity Discharge) lamp used as a headlight of an automobile. Further, when the discharge lamp is an HID lamp used as a headlight of an automobile, the discharge lamp can be what is called horizontal lighting.

The use of the discharge lamp according to the embodiment of the present invention is not limited to the headlight of an automobile, but here, as an example, a case where the discharge lamp is an HID lamp used for the headlight of an automobile is exemplified. To explain.

FIG. 1 is a schematic diagram for illustrating a discharge lamp 100 according to this embodiment.
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. I am trying.

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

The outer tube 5 preferably has a coefficient of thermal expansion close to that of the material of the inner tube 1 and is made of a material 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 portion 11, a sealing portion 12, a boundary portion 13, and a cylindrical portion 14. The light emitting portion 11, the sealing portion 12, the boundary portion 13, and the cylindrical portion 14 can be integrally formed.
The inner tube 1 (the light emitting section 11, the sealing section 12, the boundary section 13, and the cylindrical section 14) is formed of a material having a light-transmitting property and heat resistance. The inner tube 1 can be formed of, for example, quartz glass.

The light emitting unit 11 has a substantially elliptical 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 portion 11 in the axial direction of the inner tube 1 can be set to, for example, about 8 mm. The dimension of the light emitting unit 11 in the direction orthogonal to the axial direction of the inner tube 1 can be set to, for example, about 5 mm.

A discharge space 111 is provided inside the light emitting unit 11. The central portion of the discharge space 111 has a substantially columnar shape. Both ends of the discharge space 111 have a substantially conical shape.

A discharge medium is enclosed in the discharge space 111. The discharge medium contains the metal halide 2 and an inert gas.
Further, in 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, the phrase “substantially free of mercury” not only does not include mercury at all, but also includes the case where mercury is included as 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 can include, for example, scandium halide, indium halide, sodium halide, and zinc halide. Examples of the halogen include iodine. However, bromine, chlorine or the like can be used instead of iodine.
It should be noted that the composition of the metal halide 2 is not limited to the exemplified one, and can be changed appropriately.

The inert gas sealed in the discharge space 111 can be, for example, xenon. In addition to xenon, neon, argon, krypton, or the like can be used, or a mixed gas in which these are combined can be used. However, the inert gas is more preferably xenon. The filling pressure of the inert gas can be changed according to the purpose. For example, when increasing the total luminous flux, it is preferable that the sealing pressure is 10 atm or more and 20 atm or less at room temperature (25° C.).

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

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

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

The metal foil 31 is provided inside the sealing unit 12. The metal foil 31 is bonded near 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, or rhenium tungsten.

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 0.23 mm or more and 0.32 mm or less. By doing so, even in the discharge lamp 100 that is lit with a power of 10 watts or more and 30 watts or less during stable lighting, the occurrence of flicker can be suppressed.

The thickness dimension of the electrode 32 does not have to 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 tip end side than on the base end side. Further, the tip of the electrode 32 may be spherical. Further, as in the DC lighting type, the thickness dimension of one electrode and the thickness dimension of the other electrode may be different.

One end of the electrode 32 projects into the discharge space 111. That is, one end of the electrode 32 is provided inside the discharge space 111, and the other end is provided inside the sealing portion 12. The pair of electrodes 32 are provided so as to face each other with a predetermined distance. The distance between the tips of the pair of electrodes 32 (distance between electrodes) can be, for example, 3.4 mm or more and 4.4 mm or less. 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 electrode 32 and the metal foil 31 can be joined by, for example, laser welding.

The electrode 32 can be formed of, 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 of, for example, a metal wire made of doped tungsten. The coil 33 is provided inside the sealing unit 12. The coil 33 is wound around the outside of the electrode 32. For example, the coil 33 may 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 of, for example, molybdenum. One end portion side of the lead wire 34 is joined to the vicinity of the end portion of the metal foil 31 on the side opposite to the light emitting portion 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 pipe 1.

The support wire 35 has an L-shape and is joined to the end 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 of nickel, for example.

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

The metal band 71 is fixed near the rear end 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, the rear end side of the lead wire 34, the rear end side of the support wire 35, and the 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 metal fitting 72 projects from the main body 61. The mounting bracket 72 holds the metal band 71. The burner 101 is held in the socket 102 by holding the metal band 71 by the mounting metal fitting 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 formed 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 as a headlight of an automobile, the discharge lamp 100 has a central axis (tube axis) that is substantially horizontal and the support wire 35 that is substantially lower end side (downward). Mounted to be in position. Lighting the discharge lamp 100 mounted in such a direction is referred to as horizontal lighting.

Further, the discharge lamp 100 according to the present embodiment is a low-power specification discharge lamp.
Therefore, a lighting circuit (not shown) lights the discharge lamp 100 with electric power of 10 watts or more and 30 watts or less during stable lighting.

Next, generation of crack leak in the sealing portion 12 will be described.
2A and 2B are cross-sectional views taken along the line AA in FIG.
2A shows the case where the thickness dimension of the electrode 32 is large, and FIG. 2B shows the case where the thickness dimension of the electrode 32 is small.
As described above, the discharge lamp 100 is lit with electric power of 10 watts or more and 30 watts or less during stable lighting. The discharge lamp 100 that is lit with such low power is likely to cause flicker. In this case, flicker can be suppressed by reducing the thickness of the electrode 32 and increasing the current density. Therefore, in the discharge lamp 100, the thickness of the electrode 32 is set to 0.23 mm or more and 0.32 mm or less. By doing so, even in the discharge lamp 100 that is lit with a power of 10 watts or more and 30 watts or less during stable lighting, the occurrence of flicker can be suppressed.

However, when the thickness of the electrode 32 is reduced, the contact area between the metal foil 31 and the electrode 32 is reduced, and thus the bonding strength between the metal foil 31 and the electrode 32 may be reduced. In this case, as shown in FIG. 2B, if the metal foil 31 is wound around the electrode 32, the contact area between the metal foil 31 and the electrode 32 can be increased. It is possible to suppress a decrease in the bonding strength with.
That is, the vicinity of the center 31a of the metal foil 31 in the direction orthogonal to the axial direction of the electrode 32 is wound around the electrode 32.
In this case, when the thickness of the electrode 32 is 0.23 mm or more and 0.32 mm or less, the winding angle θ of the metal foil 31 is preferably 40° or more and 70° or less.

Here, as described above, the sealing portion 12 is formed by the pinch seal method or the shrink seal method. When the sealing portion 12 is formed by the pinch sealing method or the shrink sealing method, a portion where the molten glass cannot enter enters between the metal foil 31 and the electrode 32. Therefore, when the molten glass is cooled and hardened, a void 12a is formed in a portion where the molten glass cannot enter. That is, the void 12 a is formed between the electrode 32 and the metal foil 31.

In this case, the portion where the molten glass cannot enter occurs in the portion where the angle formed by the tangent line between the metal foil 31 and the electrode 32 is small. Therefore, as can be seen from FIGS. 2A and 2B, when the thickness dimension of the electrode 32 decreases, the void 12a increases.
Further, as described above, when the thickness dimension of the electrode 32 becomes smaller, it is necessary to increase the contact area between the metal foil 31 and the electrode 32. Therefore, the position where the void 12a is formed is in the axial direction of the electrode 32. It moves to the end side of the metal foil 31 in the orthogonal direction.

Therefore, as can be seen from FIG. 2B, the distance W between the center 31a of the metal foil 31 in the direction orthogonal to the axial direction of the electrode 32 and the end of the void 12a on the end side of the metal foil 31 is growing. As the distance W increases, the distance (distance M-distance W) in the portion where the metal foil 31 and the sealing portion 12 are in close contact with each other decreases. The distance M is the distance between the center 31 a of the metal foil 31 and the end of the metal foil 31 in the direction orthogonal to the axial direction of the electrode 32.

The crack leak occurs when a crack generated in the contact portion between the sealing portion 12 and the electrode 32 grows and reaches the end portion of the metal foil 31. Therefore, when the distance between the portions where the metal foil 31 and the sealing portion 12 are in close contact with each other becomes small, cracks easily reach the end portions of the metal foil 31, and thus crack leakage easily occurs in the sealing portion 12. If a crack leak occurs during lighting, the metal halide 2 or the like sealed in the discharge space 111 may leak through the crack, and the discharge lamp 100 may not be lit.

That is, in the discharge lamp 100 that is lit with low power, the thickness dimension of the electrode 32 is reduced in order to suppress flicker, and the electrode 32 is reduced in size in order to suppress the decrease in the bonding strength between the metal foil 31 and the electrode 32. When the amount of winding the metal foil 31 is increased, the distance between the portion where the metal foil 31 and the sealing portion 12 are in close contact with each other becomes small, and thus crack leaks easily occur.

According to the knowledge obtained by the present inventor, when the ratio (W/M) of the distance W to the distance M is set within an appropriate range, the occurrence of crack leak can be effectively suppressed.
FIG. 3 is a graph for illustrating the relationship between the crack leak occurrence rate and W/M. Note that FIG. 3 shows a case where the applied power during stable lighting is 25 watts and the discharge lamp 100 is lit for 2000 hours while blinking in the blinking cycle of the EU 120-minute mode.
The distance W is set to 0.1 mm or more and 0.3 mm or less.
The distance M is set to 0.6 mm or more and 1.0 mm or less.
The thickness dimension of the metal foil 31 is 0.015 mm or more and 0.025 mm or less.
The thickness of the electrode 32 is 0.23 mm or more and 0.32 mm or less.
The winding angle θ of the metal foil 31 is 40° or more and 70° or less.
As can be seen from FIG. 3, when W/M≦0.3, the occurrence of crack leak can be effectively suppressed.

The void 12 a also extends in the axial direction of the inner pipe 1.
FIG. 4 is a sectional view taken along line BB in FIG.
Note that the sealing portion 12 is omitted in the drawing in order to avoid complication.
The distance L in the figure is the distance between the end of the metal foil 31 on the side of the light emitting unit 11 and the end of the void 12a on the side opposite to the side of the light emitting unit 11 in the axial direction of the electrode 32. ..
In this case, as the distance L increases, the number of positions where cracks occur increases. Therefore, the crack easily reaches the end portion of the metal foil 31, and thus the crack leak easily occurs in the sealing portion 12.

According to the knowledge obtained by the present inventor, the occurrence of crack leakage can be effectively suppressed by setting the product (2W×L) of the distance 2W and the distance L within an appropriate range.
FIG. 5 is a graph for illustrating the relationship between the crack leak occurrence rate and 2W×L.
FIG. 5 shows a case where the applied power during stable lighting is 25 watts and the discharge lamp 100 is lit for 2000 hours while blinking in the blinking cycle of the EU 120-minute mode.
The distance W is set to 0.1 mm or more and 0.3 mm or less.
The distance L is 0.7 mm or more and 1.5 mm or less.
The thickness dimension of the metal foil 31 is 0.015 mm or more and 0.025 mm or less.
The thickness of the electrode 32 is 0.23 mm or more and 0.32 mm or less.
The winding angle θ of the metal foil 31 is 40° or more and 70° or less.
As can be seen from FIG. 5, if 2W×L≦0.6, the occurrence of crack leak can be effectively suppressed.

Although some embodiments of the present invention have been illustrated above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and its equivalent scope. Further, the above-described respective embodiments can be implemented in combination with each other.

1 inner tube, 2 metal halide, 5 outer tube, 11 light emitting part, 12 sealing part, 12a void, 31 metal foil, 31a center, 32 electrode, 100 discharge lamp, 101 burner, 102 socket, 111 discharge space

Claims (2)

A discharge lamp for a vehicle headlight, which is illuminated with electric power of 10 watts or more and 30 watts or less when stably lit,
A light emitting unit having a discharge space inside;
A discharge medium enclosed in the discharge space, containing a metal halide and an inert gas, and substantially free of mercury;
A sealing part provided at an end of the light emitting part;
An electrode having one end provided inside the discharge space and the other end provided inside the sealing portion;
A metal foil which is provided inside the sealing portion and which is bonded near the other end of the electrode;
A void provided between the electrode and the metal foil;
Equipped with,
The thickness dimension of the electrode is 0.23 mm or more and 0.32 mm or less,
The metal foil is wrapped around the electrode, and both ends of the metal foil are separated from the electrode,
The winding angle of the metal foil is 40° or more and 70° or less,
A discharge lamp for an automobile headlight that satisfies the following formula.
W (mm) /M (mm) ≤0.3
Note that W (mm) is a distance between the center of the metal foil in the direction orthogonal to the axial direction of the electrode and the end of the void on the end side of the metal foil.
M (mm) is the distance between the center of the metal foil and the end of the metal foil in the direction orthogonal to the axial direction of the electrode. When the distance between the end of the metal foil in the axial direction of the electrode on the side of the light emitting part and the end of the gap on the side opposite to the side of the light emitting part is L (mm) , the following formula is obtained. The discharge lamp for a vehicle headlight according to claim 1, which satisfies the above condition.
2W (mm) x L (mm) ≤ 0.6 (mm ² )

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