WO2003032363A1

WO2003032363A1 - High-voltage discharge lamp, head lamp for automobile and arc tube for the high-voltage discharge lamp

Info

Publication number: WO2003032363A1
Application number: PCT/JP2001/008674
Authority: WO
Inventors: Norikazu Niimi
Original assignee: Ngk Insulators, Ltd.
Priority date: 2001-10-02
Filing date: 2001-10-02
Publication date: 2003-04-17

Abstract

A high-voltage discharge lamp (1A) includes an arc tube (2A) made of semitransparent ceramic, having a pair of openings (2a), a light emitting portion (2b) and an internal space (6) filled with an ionization light emitting substance and a starter gas; a pair of discharging electrodes (5) housed in the internal space (6); and an electrode holding member (4) to which the discharging electrodes (5) is attached and which is fixed in the opening (2a). In the light emitting portion (2b), the arc tube (2A) is provided with thick portions (2g) and a thin portion (2c). The transverse section of the thin portion (2c) has a sectional area of 35 % to 80 % of that of the thick portions (2g). The light emitting portion (2b) has a brightness center (9) located at the thin portion (2c).

Description

Description High pressure discharge lamp, automotive headlamp and arc tube for high pressure discharge lamp

TECHNICAL FIELD The present invention relates to a high-pressure discharge lamp suitable for an automobile head lamp and the like. Background art

High pressure discharge lamps using quartz discharge tubes have been widely used as automotive headlights because of their high brightness and high luminous efficiency. In a discharge lamp using such a quartz tube, since the discharge tube is transparent, a light-emitting portion formed by a luminous gas in the discharge tube can be used as a point light source of the discharge lamp.

In a head lamp for an automobile described in Japanese Patent Application Laid-Open No. 5-74404, a discharge bulb is housed in a container for shielding ultraviolet rays, and light emitted from the discharge bulb is reflected by a reflector and projected. are doing. The discharge lamp headlamp described in Japanese Patent Application Laid-Open No. 5-86684 discloses that a metal halide lamp and a high-pressure sodium lamp are used in combination as a light source for the headlamp.

In addition, the applicant of the present application has disclosed in Japanese Patent Application Laid-Open No. 2001-76667 a high-pressure discharge lamp that can be used as a pseudo-point light source of a headlamp for a vehicle. According to the description of this publication, when a quartz arc tube is used, the luminous body is housed inside the luminous tube, and when the light is emitted, the luminous body inside can be seen from the outside of the transparent quartz luminous tube. The illuminant functions as a point light source. I However, a high-pressure discharge lamp using an arc tube made of translucent polycrystalline alumina is translucent, so when viewed from the outside, the entire arc tube appears to be an integral luminous body . Therefore, the arc tube itself is made sufficiently small so that it can be used as a pseudo point light source. Specifically, the length of the arc tube is set to 6 to 15 mm, and the arc length in the discharge lamp is set to 1 to 6 mm. And, it discloses a structure that can realize a high-pressure discharge lamp using such a small arc tube. Disclosure of the invention

For example, in an automotive headlamp, an arc tube is installed at a predetermined position, and light emitted from the arc tube is reflected by a reflector (reflection plate) and projected forward. At this time, the three-dimensional positional relationship between the point light source and the reflector and the surface shape of the reflector are strictly determined in order to prevent a shift in the condensing position after the projection. Further, in the case of an automobile headlamp, there are two lighting modes, namely, a driving mode and a passing mode. As is well known, in the driving mode, the beam from the headlamp is collected and projected forward, and in the passing mode, the beam is projected diagonally downward. In the case of an automotive headlamp that uses a high-pressure discharge lamp as a pseudo point light source, the projection beam is focused by changing the positional relationship between the high-pressure discharge lamp and the reflector in accordance with different lighting modes. The position needs to be changed.

However, when the arc tube of the high pressure discharge lamp is used as a pseudo point light source, the positional relationship between the arc tube and the reflector is changed to correspond to different lighting modes, and the focusing position of the projection beam is changed. It has been found that it is practically difficult in design to change and focus the projected beam at each focusing position with high efficiency. That is, since the arc tube has a certain size, for example, when the arc tube and the reflector are almost perfectly aligned in the traveling mode and the focusing position is focused, the reflector moves in the passing mode. It is difficult by design to completely focus the projection beam on the focusing position when the light is focused. In order to solve this problem, it is effective to reduce the size of the arc tube. However, if the arc tube is further miniaturized, the production becomes difficult and the production cost may increase.

An object of the present invention is to facilitate a design that can improve the light collection efficiency of a projection beam at a focal point when a high-pressure discharge lamp is used as a pseudo point light source.

The present invention provides a light-emitting tube, which is made of translucent translucent ceramics, has a pair of openings and a light-emitting portion, and has an inner space filled with an ionized light-emitting substance and a starting gas. A pair of discharge electrodes housed in the space, and a discharge electrode are attached, and an electrode holding material fixed to the opening of the arc tube is provided, and the light emitting portion has a thick portion and a thin portion. That the cross-sectional area of the thin section is 35% or more and 80% or less of the cross-sectional area of the thick section, and that the luminance center of the light emitting section exists in the thin section. The present invention relates to a high-pressure discharge lamp.

Further, the present invention relates to a head lamp for an automobile, comprising the high pressure discharge lamp as a pseudo point light source.

Further, the present invention comprises a translucent translucent ceramic, has a pair of openings and a light emitting portion, and emits light for a high pressure discharge lamp in which an internal space is filled with an ionized light emitting substance and a starting gas. A light emitting portion having a thick portion and a thin portion, wherein a cross-sectional area of a cross section of the thin portion is 35% or more and 80% or more of a cross-sectional area of the cross section of the thick portion. The present invention relates to an arc tube characterized by the following. The inventor has provided a thick portion and a thin portion in the light emitting tube in the light emitting portion, and set the cross-sectional area of the cross section of the thin portion to 35% or more and 80% or less of the cross-sectional area of the thick portion. By doing so, the inventors have conceived of arranging the luminance center of the light emitting portion in the thin portion.

That is, when a transparent luminous tube such as a so-called quartz tube is used, the luminous body inside the luminous tube can be seen from the outside, and this luminous body functions as a point light source. In this case, the position of the focal point of the projection beam after reflection by the reflector 1 can be determined by determining the position of the luminous body inside the quartz tube and the relative position of the reflector.

The present inventor, unlike this method, presupposes an arc tube made of translucent translucent ceramics and uses the entire arc tube as a pseudo point light source. At the same time, by providing a thin portion in the light emitting portion of the arc tube, the light flux from the thin portion is increased as compared with the light flux from the thick portion, and the thin portion is set as the luminance center. The position and size of such a thin portion in the light emitting portion can be set relatively freely. Therefore, by appropriately setting the position and size of the thin portion of the arc tube, the position of the luminance center and the distribution of luminance in the arc tube can be appropriately set.

When a high-pressure discharge lamp is used as a pseudo point light source, when a projection beam is obtained using light emitted from an arc tube, the position of the luminance center set in advance as described above is regarded as a point light source. By designing the position and shape of the optical component, it becomes easy to improve the degree of focusing of the projection beam on the focal point. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a longitudinal sectional view schematically showing a high-pressure discharge lamp 1A according to one embodiment of the present invention, in which a light-emitting portion 2b is provided with a thick portion 2g and one thin portion 2c. Have been.

FIG. 2 is a longitudinal sectional view showing a main part of the arc tube 2A of the high-pressure discharge lamp of FIG. FIG. 3 is a longitudinal sectional view schematically showing a high-pressure discharge lamp 1B according to another embodiment of the present invention.

FIG. 4 is a longitudinal sectional view showing a main part of an arc tube 2B of the high-pressure discharge lamp of FIG. FIG. 5 is a schematic diagram showing an automotive headlamp 15 using a quartz tube 18.

FIG. 6 is a schematic diagram showing an automotive headlamp 20 using the high-pressure discharge lamps 2A and 2B.

FIG. 7 is a longitudinal sectional view schematically showing a high-pressure discharge lamp 11 outside the present invention. FIG. 8 is a longitudinal sectional view showing an enlarged view of a joint portion between an arc tube and an electrode holding member in a production example of the high-pressure discharge lamp of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a longitudinal sectional view of a high-pressure discharge lamp 1A according to one embodiment of the present invention, and FIG. 2 is a longitudinal sectional view showing a main part of an arc tube 2A.

The arc tube 2A includes a pair of openings 2a, and a light emitting section 2b sandwiched between the pair of openings 2a. An electrode holding member 4 is inserted into and fixed to the inner opening of each opening 2a via a bonding material 3. The inner space 6 of the arc tube 2A is filled with an ionized luminescent substance and a starting gas. In the case of a metal halide high-pressure discharge lamp, an inert gas such as argon ■ xenon and a metal halide are sealed in the inner space of the discharge tube, and mercury or zinc metal is further sealed as necessary.

The electrode holding member 4 includes a cylindrical portion 4c, a base 4b welded to an end of the cylindrical portion 4c, and an electrode holding portion 4a protruding inward from the base 4b. The electrode holding portion 4a has a cylindrical shape in this example. Electrode holding An electrode 5 protrudes from the inner end of the part 4a, and a coil 5a is wound around the tip of the electrode 5. Although the coil 5a is provided at the tip of the electrode 5 in this example, the coil 5a is not always required.

As shown in FIG. 2, neither the concave part nor the convex part is provided on the outer peripheral surface 2e of the arc tube 2A. Therefore, the outer diameter of the arc tube 2A in the light emitting section 2b is substantially constant. A concave portion 2d is provided on the inner peripheral surface 2f side of the arc tube 2A, and a thin portion 2c is provided corresponding to the concave portion 2d. In this example, one continuous thin portion 2c is provided in the light emitting portion 2b.

When electric power is supplied to the high-pressure discharge lamp 1A, a discharge arc is generated between the pair of electrodes 5, and the ionized luminescent substance emits light. By this light emission, a light flux is generated from the entire light emitting portion 2c of the arc tube. Here, since the light transmittance of the thin portion 2c is higher than the light transmittance of the thick portion 2g, light is mainly emitted from the thin portion 2c. As a result, a light portion 7 having a relatively large luminous flux is generated in the thin portion 2c of the light emitting portion 2b, and a dark portion 8 having a relatively small luminous flux is generated in the thick portion 2g. The point 9 having the smallest thickness in the thin portion 2c is the luminance center. This luminance center extends in a ring shape along the outer periphery of the arc tube 1A.

In the high-pressure discharge lamp 1B in FIG. 3, the same components as those in FIG.

The light-emitting portion 2b of the arc tube 2B of the high-pressure discharge lamp 1B is provided with two thin portions 2c, between the two thin portions 2c and outside each thin portion 2c. Each has a thick portion 2 g. Neither concave portions nor convex portions are provided on the outer peripheral surface 2e of the arc tube 2B, and the outer diameter of the arc tube 2B in the light emitting portion 2b is substantially constant. On the inner peripheral surface 2f side of the arc tube 2B, two concave portions 2d are provided, and a thin portion 2c is provided corresponding to each concave portion 2d. When electric power is supplied to the high-pressure discharge lamp 1B, a luminous flux is generated from the entire light emitting portion 2b of the arc tube. Here, the light transmittance of each thin portion 2c is Since the light transmittance is higher than g, light is mainly emitted from each thin portion 2c. In particular, the point 9 having the smallest thickness among the thin portions 2c is the luminance center. Each brightness center 2d extends in a ring shape along the outer circumference of the arc tube 1A.

FIG. 5 is a schematic diagram showing an automotive headlamp 15 using a quartz tube 18. The quartz tube 18 is housed in a container 19, and the container 19 is attached to a base 17 of a container 16 provided with a reflector. A window 14 is attached to the front side of the lamp 15. A light emitting body 22 is provided inside the quartz tube 18.

FIG. 6 is a schematic diagram showing an automotive headlamp 20 equipped with a high-pressure discharge lamp. 21 is an electrical connection means.

In FIG. 5, since the quartz light emitting tube 18 is transparent, the light emitting body 22 only needs to have an outer diameter and a length that function as a point light source. In the automotive headlamp of FIG. 6, since the entire light emitting portions of the arc tubes 2A and 2B emit light, the entire light emitting portion is turned into a pseudo point light source. Therefore, it is desirable that the outer diameter and the length of the light emitting portion 2b of the light emitting tubes 2A and 2B are substantially the same as the light emitting body 22 (FIG. 5).

From this viewpoint, specifically, it is desirable that the length L0 of the light emitting portion 2b of the arc tube be 15 mm or less and the diameter ø0 be 6 mm or less (see FIGS. 1 to 4). The discharge arc length is 1 mn! About 5 mm is required. By setting the length L 0 of the arc tube to 6 mm or more, the arc length of the inner space 6 of the arc tube can be 1 mm or more.

Here, according to the present invention, a part of the light emitting portion 2b is set as the luminance center 9, and the luminous flux is concentrated on the luminance center 9 and the vicinity thereof, so that the luminance center 9 is used as a point light source to generate a reflector and other projection beams. Position and shape of the optical components can be designed. This facilitates a design that improves the light collection efficiency at the focal position of the projection beam as compared with the conventional case. The following are examples of translucent translucent ceramics that constitute the arc tube.

Polycrystalline A1203, A1N, A10N. Or, single crystal A12O3, YAG, Y203, etc. having a surface roughness of Ra l.O im.

Also, translucent means the following light transmittance.

Total light transmittance 85% or more and linear transmittance 30% or less

Although the material of the discharge electrode and the electrode holding material is not limited, a pure metal selected from the group consisting of tungsten, molybdenum, niobium, rhenium and tantalum is preferable, or the group consisting of tungsten, molybdenum, niobium, rhenium and tantalum. An alloy of two or more selected metals is preferred. In particular, tungsten, molybdenum, or a tungsten-molybdenum alloy is preferable. Further, a composite material of these pure metals or alloys and ceramics is preferable.

The thick portion refers to a portion having a relatively large thickness in the light emitting portion, and the thin portion refers to a portion having a relatively small thickness in the light emitting portion.

In the present invention, the cross-sectional area of the cross section of the thin portion is set to 35% or more and 80% or less of the cross-sectional area of the cross section of the thick portion. If this exceeds 80%, the difference in luminance between the thick part and the thin part is reduced, and the effect of the present invention cannot be obtained. From this viewpoint, it is more preferable that the cross-sectional area of the cross section of the thin portion be 70% or less of the cross-sectional area of the cross section of the thick portion. If the cross-sectional area of the thin section is less than 35% of the cross-sectional area of the thick section, cracks are likely to occur in the thin section during light emission, so the strength of the thin section is secured. From the viewpoint that it is necessary, it is necessary to set it to 35% or more. From this viewpoint, it is more preferable that the cross-sectional area of the thin section is 50% or more of the cross-sectional area of the thick section.

Here, in the example of FIG. 1 to FIG. 4, the cross-sectional area of the thin section 2 c is It is large near the thick part 2 g and becomes minimum at the luminance center (the thinnest part) 9. In such a case where the cross-sectional area of the thin section changes stepwise or in an inclined manner, the above-mentioned “cross-sectional area of the thin section” is defined as the minimum cross-sectional area of the thin section. Take a value.

Further, the thickness of the thin portion 2c can be made substantially constant over the entire thin portion. In this case, the cross-sectional area of the cross section of the thin portion is substantially constant over the entire length of the thin portion. However, in this case, since the wall thickness changes discontinuously at the boundary between the thick part and the thin part, it is considered that the arc tube is likely to crack near this boundary during lighting. . Therefore, it is preferable that the cross-sectional area of the cross section of the thin portion continuously changes from the boundary between the thick portion and the thin portion toward the luminance center.

The luminance center means a portion having the highest luminance in the light emitting section. The luminance center does not have to be at one point, but may extend in the direction of the longitudinal section.

The luminous flux per unit area from the luminance center 9 is preferably 1.5 times or more, more preferably 2 times or more, the luminous flux per unit area from the dark part 8.

In a preferred embodiment, the outer diameter of the arc tube is substantially constant over the entire length of the light emitting section. By making the outer diameter of the arc tube substantially constant as described above, the symmetry of the projection beam is enhanced when the arc tube is used as a pseudo point light source.

In a preferred embodiment, a thin portion is formed by providing a concave portion on the inner wall surface of the arc tube. The operation and effect of this will be described.

FIG. 7 is a longitudinal sectional view schematically showing a high-pressure discharge lamp 11 outside the present invention. The arc tube 12 includes a light emitting portion 12b and a pair of openings 12a sandwiching the light emitting portion 12b. In the light emitting section 1 2b, the outer peripheral surface 1 2 of the arc tube 1 2 e, No concave or convex part is provided on the inner peripheral surface 12 f. Therefore, the outer diameter and the inner diameter of the light emitting portion 12b of the arc tube 12 are substantially constant.

When power is supplied to the high-pressure discharge lamp, a discharge arc 10 is generated between the pair of electrodes 5. When the high-pressure discharge lamp 11 is held in a horizontal direction, the discharge arc 10 tends to swell slightly upward. As a result, the temperature at the upper part of the arc tube 12 rises relatively as compared with the temperature at the lower part. In this case, when light emission stops, the upper part is cooled more rapidly than the lower part, and contracts, so that a tensile stress tends to be applied to the lower part. Such tensile stress may cause cracking of the ceramic.

In order to avoid such problems, it is necessary to set the maximum temperature in the upper part lower with a large margin so that the temperature in the upper part does not rise excessively. However, in this case, the temperature decreases at both ends of the lower part of the arc tube, so that the ionized luminescent material is liable to be liquefied, thereby lowering the luminous efficiency.

On the other hand, if a concave portion is formed on the inner peripheral surface of the arc tube, heat transfer from the discharge arc to the arc tube is reduced in the concave portion, and the temperature rise of the arc tube is suppressed. Therefore, when the discharge arc expands toward the inner peripheral surface of the arc tube as described above, it is possible to suppress a local temperature rise of the arc tube.

In a particularly preferred embodiment, for example, as shown in FIGS. 1 and 2, the arc tube is provided with one thin portion. Particularly preferably, one concave portion 2d is provided. This recess 2 d faces the internal space 6 of the arc tube. In this case, since the shape of the space formed by the internal space 6 and the concave portion 2d is similar to the shape of the discharge arc 10, the local temperature rise of the arc tube is further suppressed.

The preferred dimensions of the arc tube will be described with reference to FIGS. From the viewpoint of the operation and effect of the present invention, it is preferable that the length m of the thin portion 2c is short, and specifically, it is preferable that the total length L0 of the light emitting portion 2b is 0.7 times or less. More preferably, it is 0.5 times or less. However, if the length m of the thin portion 2c is too small, the luminous flux from the thin portion is reduced, and the meaning of providing the thin portion is rather poor. Therefore, m is preferably 0.2 times or more of L 0.

The ratio T / t between the thickness T of the thick portion and the thickness t of the thin portion can be uniquely calculated from the ratio of the cross-sectional area of the cross section as described above.

The thickness T of the thick part is preferably 0.8 mm or more, and more preferably l.lm m or more, from the viewpoint of imparting strength to the arc tube to increase the life in long-term use. Also, when the thickness T of the thick portion increases, the luminous efficiency from the arc tube decreases. Therefore, from the viewpoint of increasing the luminous efficiency of the arc tube, the thickness T of the thick part is preferably 0.85 mm or less, more preferably 0.55 mm or less.

The thickness t of the thin portion is preferably 0.6 mm or more, and more preferably 0.9 mm or more, from the viewpoint of imparting strength to the arc tube to increase the life in long-term use. Also, when the thickness t of the thin portion increases, the luminous flux at the luminance center decreases. Therefore, from the viewpoint of the operation and effect of the present invention, the thickness t of the thin portion is preferably set to 0.7 mm or less, more preferably 0.4 mm or less.

Although the material of the bonding material 3 is not particularly limited, the following materials can be exemplified. (1) Ceramics selected from the group consisting of alumina, magnesia, yttria, lanthania, and zirconia, or a plurality of ceramics selected from the group consisting of alumina, magnesia, yttria, lanthania, and zirconia Mixture of ceramics

(2) The cert. Examples of the ceramics constituting the cermet include one or more ceramics selected from the group consisting of aluminum, magnesia, yttria, lanthania, and zirconia, or a mixture thereof. it can.

The metal component of the cermet is preferably an alloy of tungsten, molybdenum, rhenium, or an alloy of two or more metals selected from the group consisting of tungsten, molybdenum, and rhenium. Thereby, high corrosion resistance to metal halide can be imparted to the plugging material. In this cermet, the ratio of the ceramic component is preferably 55% by weight or more, more preferably 60% by weight or more (the ratio of the metal component is the balance).

(3) A bonding material obtained by impregnating a ceramic composition into a porous metal (porous skeleton).

The joining material 3 will be described with reference to FIG. This joining material is described in Japanese Patent Application Laid-Open No. 2001-76667.

In order to produce the bonding material 3, glass is impregnated into a porous skeleton made of a sintered body of metal powder. This sintered body has open pores.

Examples of the material of the metal powder include pure metals such as molybdenum, tungsten, rhenium, niobium, and tantalum, and alloys thereof.

Ceramic composition to be impregnated into the metal sintered body is selected from the group consisting of _{_{A 1 2 0 3, S i}} 0 2, Y 2 0 3, D y 2 〇 _3, B ₂ 0 ₃ and Mo_〇 ₃ is preferably configured by a material which, it is particularly preferable to contain the a 1 ₂ 0 _3. Particularly preferably, it has a composition of 60% by weight of dysprosium oxide, 15% by weight of alumina, and 25% by weight of silica.

By this impregnation process, as shown in FIG. 8, an impregnated ceramic composition layer 3a and an interfacial ceramic composition layer 3b are generated. In the impregnated ceramic composition layer 3a, the open pores of the metal sintered body are impregnated with the ceramic composition. The interface ceramic composition layer 3b has the composition described above, and does not include a metal sintered body.

In the above embodiment, the high-pressure discharge lamp of the present invention is used for an automobile headlamp. The embodiment used for the pump has been described. However, the high-pressure discharge lamp of the present invention can be applied to other lighting devices to which a pseudo point light source can be applied, such as an OHP (overhead projector) and a liquid crystal projector.

Claims

The scope of the claims

1. An arc tube made of translucent translucent ceramics, having a pair of openings and a light-emitting portion, having an inner space filled with an ionized luminescent substance and a starting gas, and housed in the inner space. A pair of discharge electrodes, and an electrode holding member to which the discharge electrodes are attached, the electrode holding material being fixed to the opening, and the light emitting portion having a thick portion and a thin portion. The cross-sectional area of the thin section is not less than 35% and not more than 80% of the cross-sectional area of the cross section of the thick section, and the luminance center of the light emitting section is present in the thin section. Characterized by high-pressure discharge lamps.

2. The high-pressure discharge lamp according to claim 1, wherein the outer diameter of the arc tube is substantially constant over the entire length of the light emitting section.

3. The high-pressure discharge lamp according to claim 1, wherein a concave portion is provided on an inner wall surface of the arc tube in the thin portion.

4. The high-pressure discharge lamp according to any one of claims 1 to 3, wherein the light-emitting portion includes a plurality of the thin portions.

5. The high-pressure discharge lamp according to claim 4, wherein the arc tube has a size capable of operating as a pseudo point light source.

6. An automotive headlamp comprising the high-pressure discharge lamp according to any one of claims 1 to 5 as a pseudo point light source.

7. An arc tube for a high-pressure discharge lamp, which is made of translucent translucent ceramics, has a pair of openings and a light-emitting portion, and is to be filled with an ionized light-emitting substance and a starting gas in an internal space,

The light emitting unit includes a thick portion and a thin portion, and a cross-sectional area of a cross section of the thin portion is 35% or more and 80% or less of a cross-sectional area of a cross section of the thick portion. Characteristic, arc tube for high pressure discharge lamp.

8. The arc tube according to claim 7, wherein the outer diameter of the arc tube is substantially constant over the entire length of the light emitting section.

9. The arc tube according to claim 7, wherein a concave portion is provided in an inner wall surface of the arc tube in the thin portion.

10. The arc tube according to any one of claims 1 to 9, wherein the light emitting unit includes a plurality of the thin portions.

11. The method according to claim 11, wherein the arc tube has a size capable of operating as a pseudo point light source. An arc tube according to any one of claims 1 to 10.