JP2012199229A - Electric discharge lamp for vehicle, and horizontal lighting type electric discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of brightness of an arc on an anode side, and make the brightness of the arc uniform.SOLUTION: The electric discharge lamp is provided with: a light-emitting tube 21 emitting light by a DC lighting system and comprising an outer tube 20, a light-emitting part 22, an anode side thin tube part 24 and a cathode side thin tube part 23; an anode side electrode 28 whose one end face in an axial direction is formed as an anode side opposed face 28a; and a cathode side electrode 27 whose one end face in the axial direction is formed as a cathode side opposed face 27a. Gas composed of only inactive gas, or mixture gas composed of nitrogen having a mixture ratio of 50% or less and inactive gas having a mixture ratio of 50% or more is filled outside the light-emitting tube 21 in the outer tube 20. A distance from an upper end on the anode side opposed face to a point positioned immediately above an upper end of an inner periphery of the light-emitting part is 0.65 mm or more, and a distance from a center on the cathode side opposed face to a point positioned immediately below a center of the inner periphery of the light-emitting part is 1.00 mm or less.

Description

  The present invention relates to a vehicle discharge lamp that emits light by direct current lighting and a horizontal lighting type discharge lamp. Specifically, the distance from the cathode side electrode and the anode side electrode to the inner surface of the light emitting unit is set to a predetermined distance to prevent a decrease in the brightness of the arc on the anode side and to make the brightness of the arc uniform. About.

  In particular, unlike a general illumination lamp, a vehicular headlamp requires precise light distribution control, and therefore, a light emission shape that is uniform and has a bar shape and a high contrast ratio is required. The filaments of incandescent lamps and halogen lamps have such characteristics and are therefore widely used as a light source for vehicle headlamps.

  On the other hand, in a vehicle headlamp in which a discharge lamp is used as a light source, the discharge lamp can improve brightness compared to an incandescent lamp and a halogen lamp, and also compared to an incandescent lamp and a halogen lamp. And has the advantage of a long life.

  As described above, since the discharge lamp has a higher luminance and a longer life as compared with the incandescent lamp and the halogen lamp, in recent years, a lamp equipped with a discharge lamp has become widespread as a vehicle headlamp.

  Generally, a discharge lamp used for a vehicle headlamp often emits light by alternating current lighting. This is because, when a metal halide lamp enclosing mercury and a metal halide is lit with a direct current, unevenness in color and brightness occurs in the arc due to differences in vapor pressure and mobility between mercury and other inclusions. Because.

  Therefore, as shown in Patent Document 1, an arc tube that holds a cathode side electrode and an anode side electrode and is filled with a gas such as an inert gas is not intended to protect the arc tube or stabilize temperature. A direct current lighting type discharge lamp arranged in a tube has been proposed.

  The arc tube is composed of a light emitting part in which electric discharge is performed and a pair of thin tube parts provided on the opposite side across the light emitting part. The light emitting portion is a portion where an arc is generated when discharge is performed, and is larger than the diameter of the narrow tube portion.

  In the discharge lamp, lighting is started when a high voltage pulse is applied to the electrode and discharge is performed in the light emitting portion of the arc tube.

  In a vehicle headlamp using such a discharge lamp, the diameter of the light emitting part is reduced by reducing the diameter of the cathode side electrode of the discharge lamp in order to suppress the decrease in emitted light flux and the occurrence of color unevenness. Is made smaller on the cathode side than on the anode side.

JP 2007-250225 A

  However, in the vehicle headlamp described in Patent Document 1, mercury is removed from the enclosure, and the electrodes and arc tube are made asymmetrical, thereby suppressing the decrease in luminous flux and causing color unevenness. However, depending on the shape of the light emitting part and the gas component enclosed outside the arc tube inside the outer tube, the arc brightness on the anode side may decrease or the arc brightness may be uniform. As a result, the desired light emitting state may not be ensured.

  Accordingly, it is an object of the vehicle headlamp and the horizontal lighting type discharge lamp of the present invention to prevent a decrease in the arc brightness on the anode side and to make the arc brightness uniform.

  In order to solve the above-described problems, the vehicle discharge lamp emits light by a direct current lighting method, and is continuously connected to the light emitting portion on the opposite side of the light emitting portion and the light emitting portion between the outer tube attached to the base and the light emitting portion. An arc tube provided with an anode-side thin tube portion provided on the base side and a cathode-side thin tube portion located on the opposite side of the base, and disposed in the outer tube and formed of ceramic, and at least a part of the arc tube An anode side electrode which is disposed inside the arc tube in a state of protruding from the anode side narrow tube portion to the light emitting portion and has one end surface in the axial direction located in the light emitting portion formed as an anode side facing surface; At least a part of the light emitting portion is disposed inside the light emitting tube in a state of protruding from the cathode side thin tube portion and the one end surface in the axial direction located in the light emitting portion is a cathode side facing surface. A cathode side electrode formed on the outside of the arc tube inside the outer tube, a gas composed of only an inert gas, or nitrogen with a mixing ratio of 50% or less and a mixing ratio of 50% or more A mixed gas composed of the inert gas formed is sealed, and a distance dA from the upper end of the anode-side facing surface to a point located directly above the upper end of the inner peripheral surface of the light-emitting portion is 0. The distance dLC from the center of the cathode-side facing surface to a point located directly below the center of the inner peripheral surface of the light emitting unit is set to 1.00 mm or less.

  Therefore, in a vehicle discharge lamp, the distance from the upper end of the anode-side facing surface to a point located directly above the upper end of the inner peripheral surface of the light-emitting portion is increased, and light is emitted from the center of the cathode-side facing surface. The distance to the point located directly below the center of the inner peripheral surface of the part is reduced.

  In order to solve the above-described problems, the horizontal lighting type discharge lamp is a horizontal lighting type that emits light by a direct current lighting method. The outer tube attached to the base, the light emitting part, and the opposite side across the light emitting part A light emission formed by a ceramic disposed in the outer tube, comprising an anode-side thin tube portion that is provided continuously with the light-emitting portion and located on the base side, and a cathode-side thin tube portion that is located on the opposite side of the base. A tube and one end surface in the axial direction located in the light emitting portion as an anode side facing surface are disposed inside the light emitting tube with at least a portion protruding from the anode side thin tube portion to the light emitting portion. The anode-side electrode formed and at least a part of the anode-side electrode projecting from the cathode-side thin tube portion to the light-emitting portion are arranged inside the arc tube and in the axial direction located in the light-emitting portion. A distance dA from the upper end of the anode-side facing surface to a point located directly above the upper end of the inner peripheral surface of the light emitting unit. The distance dC from the upper end of the cathode-side facing surface to a point located directly above the upper end of the inner peripheral surface of the light emitting unit is 0.7 mm or more and 1.0 mm or less. It has been made.

  Therefore, in the horizontal lighting type discharge lamp, the distance from the upper end of the anode-side facing surface to the point located directly above the upper end of the inner peripheral surface of the light emitting unit is increased, and the upper end of the cathode-side facing surface is increased. The distance from the inner peripheral surface of the light emitting unit to the point located directly above the upper end of the light emitting unit is reduced.

  The vehicle discharge lamp of the present invention is a vehicle discharge lamp that emits light by a direct current lighting system, and is continuous with the light emitting portion on the opposite side of the outer tube attached to the base and the light emitting portion and the light emitting portion. A light emitting tube formed of ceramic and disposed inside the outer tube, and at least a part of the light emitting tube formed of an anode side thin tube portion located on the base side and a cathode side thin tube portion located on the opposite side of the base. An anode-side electrode which is disposed inside the arc tube in a state of protruding from the anode-side narrow tube portion to the light-emitting portion, and has one end surface in the axial direction located in the light-emitting portion formed as an anode-side facing surface; , At least a part of the light emitting portion is disposed inside the light emitting tube in a state of protruding from the cathode side thin tube portion to the light emitting portion, and one end surface in the axial direction located in the light emitting portion is a cathode side facing surface A cathode side electrode formed on the outside of the arc tube inside the outer tube, a gas composed of only an inert gas, or nitrogen with a mixing ratio of 50% or less and a mixing ratio of 50% or more A mixed gas composed of the inert gas formed is sealed, and a distance dA from the upper end of the anode-side facing surface to a point located directly above the upper end of the inner peripheral surface of the light-emitting portion is 0. The distance dLC from the center of the cathode-side facing surface to a point located directly below the center of the inner peripheral surface of the light emitting unit is set to 1.00 mm or less.

  Therefore, it is possible to prevent the brightness of the arc on the anode side from being lowered and increase the overall brightness of the arc to make the arc brightness uniform.

  In the invention described in claim 2, the size of the portion of the inner diameter of the light emitting portion where the surface including the anode facing surface intersects is the surface of the inner diameter of the light emitting portion including the cathode facing surface. It is made larger than the size of the intersection.

  Accordingly, it is possible to easily increase the distance dA and decrease the distance dLC, and to prevent the decrease in the brightness of the arc on the anode side without increasing the manufacturing cost of the discharge lamp, and the arc. The brightness uniformity can be achieved.

  In the invention described in claim 3, the center of the anode side electrode is located below the center of the cathode side electrode.

  Accordingly, it is possible to easily increase the distance dA and decrease the distance dLC, and to prevent the decrease in the brightness of the arc on the anode side without increasing the manufacturing cost of the discharge lamp, and the arc. The brightness uniformity can be achieved.

  The horizontal lighting type discharge lamp according to the present invention is a horizontal lighting type discharge lamp that emits light by a direct current lighting method, and the light emission is performed on an outer tube attached to a base, and a light emitting part and an opposite side of the light emitting part. An arc tube formed by a ceramic disposed in the outer tube, comprising an anode side thin tube portion continuously provided in a portion and located on the base side and a cathode side thin tube portion located on the opposite side of the base; At least part of the light emitting portion is disposed inside the light emitting tube in a state of projecting from the anode side thin tube portion to the light emitting portion, and one end surface in the axial direction located in the light emitting portion is formed as an anode side facing surface. An anode side electrode and an end face in the axial direction located at the light emitting part are arranged in the negative direction while being disposed inside the arc tube with at least a part protruding from the cathode side thin tube part to the light emitting part. A distance dA from the upper end of the anode-side facing surface to a point located directly above the upper end of the inner peripheral surface of the light-emitting portion is 0.9 mm or more and 1 The distance dC from the upper end of the cathode-side facing surface to the point located directly above the upper end of the inner peripheral surface of the light emitting unit is 0.7 mm or more and 1.0 mm or less. Features.

  Therefore, it is possible to prevent the brightness of the arc on the anode side from being lowered and increase the overall brightness of the arc to make the arc brightness uniform.

  The best mode for carrying out the vehicle headlamp and the horizontal lighting type discharge lamp of the present invention will be described below with reference to the accompanying drawings.

  The vehicle headlamp 1 is mounted and arranged at both left and right ends of the front end of the vehicle body.

  As shown in FIG. 1, the vehicle headlamp 1 includes a lamp housing 2 having a recessed portion opened forward and a cover 3 that closes the opening surface of the lamp housing 2. An outer casing 4 is configured. An internal space of the lamp outer casing 4 is formed as a lamp chamber 5.

  An insertion hole 2 a penetrating back and forth is formed at the rear end of the lamp housing 2, and the insertion hole 2 a is closed by a back cover 6. A lead-out hole 6 a is formed in the back cover 6.

  A reflector 7 is supported in the lamp chamber 5 so as to be tiltable by an optical axis adjusting mechanism (not shown). A mounting hole 7 a penetrating in the front-rear direction is formed at the rear end of the reflector 7. The inner surface of the reflector 7 is formed as a reflecting surface 7b.

  A lens holder 8 is attached to the front end of the reflector 7, and a projection lens 9 is attached to the front end of the lens holder 8.

  A discharge lamp lighting device 11 integrated with a discharge lamp (vehicle discharge lamp) 10 formed in a shape extending in the front-rear direction is attached to the attachment hole 7 a of the reflector 7. The discharge lamp lighting device 11 includes a case body 12 and a lighting circuit (not shown) in which a starting circuit is integrated. A connecting portion 13 is provided at the lower end of the discharge lamp lighting device 11.

  In the discharge lamp lighting device 11, the connection portion 13 is connected to the input side connector 15 via the power supply cord 14, and the input side connector 15 is attached to the outer surface of the back cover 6. The input-side connector 15 is connected to a power supply circuit (not shown) by a connection cord (not shown), and one end of the power supply cord 14 is inserted through a lead-out hole 6a formed in the back cover 6 to be released through the power supply cord 14. It is connected to the lamp lighting device 11.

  In the above example, the discharge lamp 10 is integrated with the discharge lamp lighting device 11, but the discharge lamp 10 is connected to the discharge lamp lighting device 11 via a socket connector. May be.

  Lighting (start-up) of the discharge lamp 10 is performed by boosting the power supply voltage of the power supply circuit by the lighting circuit of the discharge lamp lighting device 11, applying a high voltage pulse to the discharge lamp 10, and starting discharge. A direct current lighting method is used as a lighting method for the discharge lamp 10, and the discharge lamp 10 is a horizontal lighting type discharge lamp.

  An extension 17 is provided at the front end of the lamp chamber 5 to shield a part of each section disposed in the lamp chamber 5. The lamp chamber 5 is provided with a shade 16 that shields a part of the light emitted from the discharge lamp 10.

  The main body 18 of the discharge lamp 10 is configured integrally with the discharge lamp lighting device 11 via a base 19 (see FIG. 2).

  The main body 18 includes, for example, an outer tube 20 made of quartz glass and an arc tube 21 made of ceramic disposed inside the outer tube 20.

  The outer tube 20 is formed by integrally forming a closing portion 20a covering the arc tube 21 and the like and a holding portion 20b protruding forward from the front end portion of the closing portion 20a.

  The arc tube 21 is composed of a light emitting portion 22 and a cathode side thin tube portion 23 and an anode side thin tube portion 24 that are continuous at both front and rear ends of the light emitting portion 22, respectively.

  The light emitting unit 22 is a second end formed integrally with a rear end portion 25a of the first member 25 formed integrally with the cathode side thin tube portion 23 located on the front side and an anode side thin tube portion 24 located on the rear side. It is comprised by the front half part 26a of the member 26, and is formed in the state by which the rear-end part 25a was fitted inside the front-end part of the front half part 26a.

  A metal iodide or metal bromide and an inert gas such as xenon or argon are sealed inside the light emitting unit 22.

  The cathode side thin tube portion 23 is located on the front side of the light emitting portion 22, the anode side thin tube portion 24 is located on the rear side of the light emitting portion 22, and the cathode side thin tube portion 23 and the anode side thin tube portion 24 extend in the front-rear direction. The outer diameter is made smaller than the outer diameter of the light emitting portion 22.

  Inside the arc tube 21, for example, a cathode side electrode 27 and an anode side electrode 28, which are formed long in the front and rear directions by a metal material such as tungsten, are disposed apart from each other in the front and rear direction. Therefore, the front end side of the discharge lamp 10 is the cathode side, and the rear end side is the anode side.

  The diameter of the cathode side electrode 27 is smaller than the diameter of the anode side electrode 28, and is, for example, half or less than the diameter of the anode side electrode 28. The diameter of the cathode side electrode 27 is, for example, 0.2 mm, and the diameter of the anode side electrode 28 is, for example, 0.45 mm. The rear surface of the cathode side electrode 27 and the front surface of the anode side electrode 28 are positioned to face each other, the rear surface of the cathode side electrode 27 is formed as a cathode side facing surface 27a, and the front surface of the anode side electrode 28 is formed as an anode side facing surface 28a. ing.

  For example, the cathode side electrode 27 protrudes rearward from the cathode side thin tube portion 23 and is located inside the light emitting portion 22, and the anode side electrode 28 is located entirely inside the light emitting portion 22, for example. ing.

  A first connecting rod 29 is connected to the front surface of the cathode side electrode 27 by welding, for example. The first connecting rod 29 is made of, for example, a metal material such as molybdenum or niobium, protrudes forward from the cathode side thin tube portion 23 of the arc tube 21, penetrates the holding portion 20 b, and protrudes outside the outer tube 20. It has the part which was made. A first conductive wire 30 is connected to a portion of the first connecting rod 29 protruding outside the outer tube 20. A portion of the first conductive wire 30 is bent by 90 ° and is positioned below the outer tube 20, and a rear end portion is connected to a first connection terminal (not shown) provided on the base 19.

  An insulating sleeve 31 is attached to a portion of the first conductive wire 30 located below the outer tube 20.

  The second connecting rod 32 is connected to the rear surface of the anode side electrode 28 by welding, for example. The second connecting rod 32 is made of a metal material such as molybdenum or niobium, for example. The second connecting rod 32 protrudes rearward from the anode side narrow tube portion 24 of the arc tube 21. A second conductive wire (not shown) is connected to the rear end portion of the second connecting rod 32, and the second conductive wire is connected to a second connection terminal (not shown) provided on the base 19 at the rear end portion. Yes.

  In the discharge lamp 10, shroud gas is sealed in a space outside the arc tube 21 inside the outer tube 20. The shroud gas is composed of, for example, an inert gas such as krypton or argon, or a mixed gas of these inert gas and nitrogen. In the case of a mixed gas, the mixing ratio of the inert gas is set to 50% or more, and the mixing ratio of nitrogen is set to 50% or less.

  Below, the dimension (distance) of each part in the light emission part 22 of the discharge lamp 10 is demonstrated (refer FIG. 3).

  In the discharge lamp 10, the distance dLC from the center (center) M1 of the cathode-side facing surface 27a of the cathode-side electrode 27 to the point P1 located directly below the center M1 in the inner peripheral surface of the light emitting unit 22 is 1. 00 mm or less. Specifically, the distance dLC in the discharge lamp 10 is set to 1.00 mm.

  In addition, the distance dA from the upper end Q of the anode-side facing surface 28a of the anode-side electrode 28 to the point P2 located just above the upper end Q in the inner peripheral surface of the light emitting unit 22 is set to 0.65 mm or more. Specifically, the distance dA in the discharge lamp 10 is set to 0.70 mm.

  Further, the distance dLA from the center (center) M2 of the anode-side facing surface 28a of the anode-side electrode 28 to the point P3 located directly below the center M2 in the inner peripheral surface of the light emitting unit 22 is set to 1.25 mm or less. . Specifically, the distance dLA in the discharge lamp 10 is 0.95 mm.

  Furthermore, in the discharge lamp 10, the inner diameter of the cathode side, that is, the diameter of the inner diameter of the light-emitting portion 22 where the surface SC including the cathode-side facing surface 27a intersects is 2.0 mm, and the inner diameter of the anode side, The diameter of the inner diameter of the light emitting portion 22 where the surface SA including the anode-side facing surface 28a intersects is 1.9 mm.

  Next, measurement data relating to the distance dA and the distance dLC described above will be described (see FIGS. 4 to 7).

  First, measurement data relating to the distance dA will be described (see FIGS. 4 and 5).

  FIG. 4 is a chart showing data obtained by measuring the “brightness on the anode side” with respect to the “distance dA” when the “inner diameter on the anode side” and the “distance dA” in the light emitting unit 22 are changed.

  In the measurement, the shroud gas enclosed in the space outside the arc tube 21 inside the outer tube 20 is gas A having a nitrogen content of 100%, and the mixing ratio of krypton gas, which is an inert gas, and nitrogen is 50. It was carried out in the case of using three kinds of gases, gas B with% gas B and gas C with 100% krypton gas content.

  “TA” in the figure is the surface temperature on the outer surface corresponding to the “inner diameter on the anode side” of the light emitting unit 22, and “brightness on the anode side” is the luminance on the anode side when the light emitting unit 22 is viewed from above. . “TA” was measured with an infrared radiation thermometer. The diameter of the anode side electrode 28 used for the measurement is 0.5 mm.

  One object of the present invention is to prevent a decrease in luminance of the arc on the anode side, and in order to achieve this object, the “luminance on the anode side” needs to be a certain value or more. .

Therefore, in the measurement data described above, when “brightness on the anode side” was 100 Mcd / m ² as a reference, a case where luminance higher than this was obtained was determined as good data. 100 Mcd / m ^{2 of} “brightness on the anode side” is a luminance necessary for securing a luminance equivalent to that of a discharge lamp driven at 35 W in a discharge lamp driven at 25 W (watts). .

  FIG. 5 is a graph when “distance dA” and “brightness on the anode side” in the data shown in FIG. 4 are plotted on the XY plane.

  As shown in FIGS. 4 and 5, data in which the content ratio of the inert gas was 50% or more and the distance dA was 0.65 mm or more was determined as good data.

  Next, measurement data related to the distance dLC will be described (see FIGS. 6 and 7).

  FIG. 6 is a chart showing data obtained by measuring the “cathode side luminance” with respect to the “distance dLC” when the “cathode side inner diameter” and the “distance dLC” in the light emitting unit 22 are changed.

  In the measurement, the shroud gas enclosed in the space outside the arc tube 21 inside the outer tube 20 is gas A having a nitrogen content of 100%, and the mixing ratio of krypton gas, which is an inert gas, and nitrogen is 50. It was carried out in the case of using three kinds of gases, gas B with% gas B and gas C with 100% krypton gas content.

  “TCC” in the figure is the surface temperature on the outer surface corresponding to “cathode side inner diameter” of the light emitting section 22, and “cathode side brightness” is the cathode side brightness when the light emitting section 22 is viewed from above. . “TCC” was measured with an infrared radiation thermometer. The diameter of the cathode side electrode 27 used for the measurement is 0.15 mm.

  One object of the present invention is to make the arc luminance uniform, and in order to achieve this purpose, in addition to the “anode side luminance”, the “cathode side luminance” has a certain value or more. Is needed.

Therefore, in the measurement data described above, when “brightness on the cathode side” was 100 Mcd / m ² as a reference, a case where luminance higher than this was obtained was determined as good data. The “cathode side brightness” of 100 Mcd / m ² is the same as the “anode side brightness” described above, and is equivalent to a discharge lamp driven at 35 W in a discharge lamp driven at 25 W (watts). This is the luminance that is required to ensure the luminance.

  FIG. 7 is a graph when the “distance dLC” and “cathode side luminance” in the data shown in FIG. 6 are plotted on the XY plane.

  As shown in FIGS. 6 and 7, data in which the content ratio of the inert gas was 50% or more and the distance dLC was 1.00 mm or less was determined as good data.

  Note that the uniformity of arc brightness is strongly related to the coldest spot temperature in the light-emitting portion 22, and in order to ensure the uniformity of arc brightness, the coldest spot temperature is set to a temperature above a certain value, for example, 950 °. C or more is desirable. When the DC lighting system is used as in the discharge lamp 10, the coldest spot temperature is normally “TCC” as described above. However, any of those judged as good data has “TCC” of 950 °. The discharge lamp which is set to C or higher and conforms to these data can ensure the uniformity of the arc brightness in terms of the coldest spot temperature.

  In order to prevent the decrease in the luminance of the arc on the anode side, which is the object of the present invention, and to achieve the uniformity of the luminance of the arc based on the measurement data shown in FIGS. It has been found that it is necessary to satisfy the three conditions (1) to (3).

  (1) The shroud gas enclosed in the space outside the arc tube 21 inside the outer tube 20 has an inert gas content ratio of 50% or more.

  (2) The distance dA from the upper end Q of the anode-side facing surface 28a of the anode-side electrode 28 to the point P2 located directly above the upper end Q in the inner peripheral surface of the light emitting unit 22 is 0.65 mm or more.

  (3) The distance dLC from the center (center) M1 of the cathode-side facing surface 27a of the cathode-side electrode 27 to the point P1 located directly below the center M1 on the inner peripheral surface of the light emitting unit 22 is 1.00 mm or less. .

  In addition, if the size (diameter) of the light emitting portion 22 on the anode side becomes too large, a location that becomes the coldest spot temperature may be generated on the anode side. In order to set the temperature to 950 ° C. or more, it is desirable to set the distance dLA to a certain value or less. In order to secure the coldest spot temperature of 950 ° C. or more, it is desirable to set the distance dLA to 1.25 mm or less. In the discharge lamp 10, the distance dLA is set to 1.00 mm, and the maximum temperature of 950 ° C. or more is set. By ensuring the cold spot temperature, the uniformity of arc brightness is ensured.

  Below, the modification of the arc tube in a discharge lamp is demonstrated (refer FIG. 8 thru | or FIG. 10).

  First, the discharge lamp according to the first modification and the second modification will be described.

  Note that the discharge lamps according to the first modification and the second modification described below are different from the above-described discharge lamp 10 in that the positions of the cathode side electrode and the anode side electrode in the vertical direction are different and the light emitting unit. The only difference is the difference in shape. Therefore, in the description of the discharge lamp according to the first modification and the second modification, only a different part compared to the discharge lamp 10 will be described in detail, and the other parts are the same as those in the discharge lamp 10. The same reference numerals are assigned to the portions, and description thereof is omitted.

  As shown in FIG. 8, the discharge lamp according to the first modification includes a light emitting tube 21A and a light emitting portion 22A and a cathode side thin tube portion 23 and an anode side thin tube portion 24, which are respectively connected to both front and rear ends of the light emitting portion 22A. Has been.

  The light emitting portion 22A is constituted by the rear end portion 25a of the first member 25 and the front half portion 26b of the second member 26A, and the rear end portion 25a is fitted inside the front end portion of the front half portion 26b. Is formed. The outer shape of the second member 26A in the vertical cross section is formed in a substantially circular shape.

  The axial center of the anode side electrode 28 is located, for example, 0.25 mm below the axial center of the cathode side electrode 27.

  In the discharge lamp according to the first modification, for example, the distance dLC is 1.00 mm, the distance dA is 0.95 mm, the distance dLA is 0.70 mm, the cathode-side inner diameter is 2.0 mm, and the anode-side inner diameter is 1. .9 mm.

  As shown in FIG. 9, the discharge lamp according to the second modification includes a light emitting tube 21B and a light emitting portion 22B and a cathode side thin tube portion 23 and an anode side thin tube portion 24 that are continuous at both front and rear ends of the light emitting portion 22B, respectively. Has been.

  The light emitting portion 22B is configured by the rear end portion 25a of the first member 25 and the front half portion 26c of the second member 26B, and the rear end portion 25a is fitted inside the front end portion of the front half portion 26c. Is formed. The outer shape of the second member 26B in the vertical cross section is formed in a vertically long oval shape.

  The axial center of the anode side electrode 28 is located, for example, 0.25 mm below the axial center of the cathode side electrode 27.

  In the discharge lamp according to the second modification, for example, the distance dLC is 1.00 mm, the distance dA is 0.95 mm, the distance dLA is 0.70 mm, the cathode-side inner diameter is 2.0 mm, and the anode-side inner diameter is 1. .9 mm.

  As described above, in the discharge lamp according to the first modification and the second modification, the axial center of the anode side electrode 28 is positioned below the axial center of the cathode side electrode 27. Accordingly, it is possible to easily increase the distance dA and decrease the distance dLC, and to prevent the decrease in the brightness of the arc on the anode side without increasing the manufacturing cost of the discharge lamp, and the arc. The brightness uniformity can be achieved.

  Next, a discharge lamp according to a third modification will be described (see FIG. 10).

  In addition, the discharge lamp which concerns on the 3rd modification shown below differs only in the formation state of an arc_tube | light_emitting_tube compared with the above-mentioned discharge lamp 10. FIG. Therefore, in the description of the discharge lamp according to the third modified example, only the portions that are different from the discharge lamp 10 will be described in detail, and the other portions will be denoted by the reference numerals assigned to similar portions in the discharge lamp 10. The same reference numerals are given and description thereof is omitted.

  The discharge lamp according to the third modification includes a light emitting tube 21C and a light emitting portion 22C and a cathode side thin tube portion 23 and an anode side thin tube portion 24 that are respectively connected to both front and rear ends of the light emitting portion 22C.

  The light emitting part 22C is a second member formed integrally with the rear half part 25b of the first member 25C formed integrally with the cathode side thin tube part 23 located on the front side and the anode side thin tube part 24 located on the rear side. 26C, and the front end portion 26d is fitted inside the rear end portion of the rear half portion 25b.

  The axis center of the cathode side electrode 27 and the axis center of the anode side electrode 28 are located on the same straight line, for example.

  In the discharge lamp according to the third modification, for example, the distance dLC is 0.75 mm, the distance dA is 0.75 mm, the distance dLA is 1.00 mm, the cathode-side inner diameter is 1.5 mm, and the anode-side inner diameter is 2 0.0 mm.

  As described above, in the discharge lamp according to the third modification, the inner diameter on the anode side is larger than the inner diameter on the cathode side. Accordingly, it is possible to easily increase the distance dA and decrease the distance dLC, and to prevent the decrease in the brightness of the arc on the anode side without increasing the manufacturing cost of the discharge lamp, and the arc. The brightness uniformity can be achieved.

  In the discharge lamp according to the third modified example, the axial center of the anode side electrode 28 is the center of the cathode side electrode 27 as in the discharge lamp according to the first modified example and the discharge lamp according to the second modified example. It is also possible to position it below the axis center.

  Next, the distance dA and the distance dC will be described with respect to the dimension (distance) of each part in the light emitting unit 22 of the discharge lamp 10 (see FIG. 11).

  As described above, the distance dA is the distance from the upper end Q of the anode-side facing surface 28a of the anode-side electrode 28 to the point P2 located directly above the upper end Q of the inner peripheral surface of the light emitting unit 22, and the distance dC Is the distance from the upper end R of the cathode-side facing surface 27a of the cathode-side electrode 27 to the point P3 located just above the upper end R of the inner peripheral surface of the light emitting section 22.

  Next, measurement data related to the distance dA and the distance dC will be described (see FIG. 12).

  FIG. 12 is a chart showing data obtained by measuring “light emission efficiency”, “arc luminance unevenness”, and “discharge lamp life” when “distance dA” and “distance dC” are changed.

  In the measurement, “arc brightness unevenness” is a value calculated by “anode side arc brightness / cathode side arc brightness”.

  One object of the present invention is to prevent a decrease in the brightness of the arc on the anode side, and in order to achieve this object, it is necessary that the “luminous efficiency” be a certain value or more. If the “efficiency” is low, the optical performance deteriorates.

  Therefore, in the above measurement data, the case where a value higher than this was obtained on the basis of 100 lm / W as the “luminescence efficiency” was determined as good data.

  Another object of the present invention is to make the arc brightness uniform, and in order to achieve this purpose, the “arc brightness unevenness” needs to be within a certain range. .

  Therefore, in the measurement data described above, the case where a value in this range was obtained with 0.7 to 1.3 as the “arc luminance unevenness” was determined as good data.

  Furthermore, in order to maintain the good performance of the discharge lamp, it is necessary to have durability that can withstand long-term use without causing leaks or cracks, and the “life of the discharge lamp” (time during which leaks do not occur) is constant. It is necessary to have the above value (time).

  Therefore, in the above measurement data, a case where a value higher than 2000 hours was determined as good data on the basis of 2000 hours as the “life of the discharge lamp”.

  As shown in FIG. 12, when the distance dA is 0.9 mm or more and 1.2 mm or less and the distance dC is 0.7 mm or more and 1.0 mm or less, “light emission efficiency”, “arc luminance unevenness”, and “discharge lamp” The “lifetime” was determined as good data.

  As described above, the diameter of the cathode-side electrode 27 is smaller than the diameter of the anode-side electrode 28 and is, for example, half or less than the diameter of the anode-side electrode 28. The light emitting portion 22 located on the outer peripheral side from the cathode-side facing surface 27a of the cathode-side electrode 27 to the anode-side facing surface 28a of the anode-side electrode 28 has substantially the same inner diameter.

  Therefore, since the distance dA is 0.9 mm or more and 1.2 mm or less and the distance dC is 0.7 mm or more and 1.0 mm or less, the distance from the anode-side facing surface 28a to the inner surface of the light emitting portion 22 directly above it, That is, the distance dA is relatively larger than the distance from the cathode-side facing surface 27a to the inner surface of the light emitting portion 22 directly above, that is, the distance dC.

  Thus, since the distance dA is relatively larger than the distance dC, it becomes difficult for the anode-side arc that becomes high temperature and the inner surface (inner wall) of the light-emitting portion 22 to come into contact with each other. The amount of heat released to 22 is suppressed, and it becomes possible to improve the light emission efficiency and the life performance.

  In addition, since the distance dA is relatively larger than the distance dC, the high-temperature anode-side arc and the inner surface (inner wall) of the light-emitting portion 22 are less likely to come into contact with each other. As a result, a good luminance balance between the anode and the cathode is secured, the uniformity of the arc luminance is improved, and the optical performance can be improved.

  In general, AC lighting type discharge lamps perform AC lighting (switching of polarity) using a ballast lighting circuit, and in order to reduce the size, weight, and cost of the ballast lighting circuit in a DC lighting type discharge lamp. However, it is necessary to perform DC lighting without providing a bridge circuit that controls polarity switching. However, when a DC lighting type discharge lamp is configured in this way, the luminous efficiency decreases and the arc luminance becomes uneven. As a result, the optical performance is likely to deteriorate due to a decrease in the life due to generation of cracks and leaks.

  However, as described above, by using the DC lighting type discharge lamp 10 in which the distance dA is 0.9 mm to 1.2 mm and the distance dC is 0.7 mm to 1.0 mm, the AC lighting system is used. It is possible to ensure “luminous efficiency”, “arc luminance unevenness”, and “discharge lamp life” that are comparable to those of other discharge lamps.

  Therefore, by using the discharge lamp 10, it is possible to use a simplified ballast lighting circuit that does not have a bridge circuit, and it is possible to reduce the size, weight, and cost.

  The shapes and structures of the respective parts shown in the best mode for carrying out the invention described above are merely examples of the embodiments performed in practicing the present invention. The range should not be interpreted in a limited way.

2 to 12 show the best mode of the vehicle discharge lamp and the horizontal lighting type discharge lamp according to the present invention, and this figure is a schematic sectional view of a vehicle headlamp equipped with the discharge lamp. . It is an expanded sectional view of a discharge lamp. It is an expanded sectional view for showing a luminous tube etc. and explaining distance dA, distance dLC, etc. FIG. 5 shows measurement data related to the distance dA together with FIG. 5, and is a chart showing data obtained by measuring the luminance on the anode side with respect to the distance dA when the inner diameter on the anode side and the distance dA are changed. It is a graph when the distance dA and the luminance on the anode side are plotted. FIG. 6 shows measurement data regarding the distance dLC together with FIG. 6, and is a chart showing data obtained by measuring the luminance on the cathode side with respect to the distance dLC when the inner diameter on the cathode side and the distance dLC are changed. It is a graph when the distance dLC and the luminance on the cathode side are plotted. FIG. 9 and FIG. 10 show a modified example of the discharge lamp, and FIG. 9 is an enlarged sectional view and an enlarged rear view showing the arc tube and the like of the discharge lamp according to the first modified example. It is the expanded sectional view and enlarged back view which show the arc tube etc. of the discharge lamp concerning a 2nd modification. It is an expanded sectional view which shows the arc tube etc. of the discharge lamp which concerns on a 3rd modification. It is an expanded sectional view for showing a luminous tube etc. and explaining distance dA, distance dC, etc. The measurement data regarding the distance dA and the distance dC is shown, and this figure is a chart showing the data obtained by measuring the luminous efficiency and the like when the distance dA and the distance dC are changed.

  DESCRIPTION OF SYMBOLS 7 ... Reflector, 10 ... Discharge lamp, 19 ... Base, 20 ... Outer tube, 21 ... Light emission tube, 22 ... Light emission part, 23 ... Cathode side thin tube part, 24 ... Anode side thin tube part, 27 ... Cathode side electrode, 27a ... Cathode side facing surface, 28 ... anode side electrode, 28a ... anode side facing surface, 21A ... arc tube, 22A ... light emitting part, 21B ... light emitting tube, 22B ... light emitting part, 21C ... light emitting tube, 22C ... light emitting part

Claims (4)

A vehicle discharge lamp that emits light by a direct current lighting method,
An outer tube attached to the base;
The outer tube comprising a light emitting portion and an anode side thin tube portion that is provided on the opposite side of the light emitting portion and is continuous with the light emitting portion and located on the base side, and a cathode side thin tube portion located on the opposite side of the base An arc tube formed of ceramic and disposed inside,
At least part of the light emitting portion is disposed inside the light emitting tube in a state of projecting from the anode side thin tube portion to the light emitting portion, and one end surface in the axial direction located in the light emitting portion is formed as an anode side facing surface. An anode side electrode;
At least a part of the light emitting portion is disposed inside the light emitting tube in a state of protruding from the cathode thin tube portion to the light emitting portion, and one end surface in the axial direction located in the light emitting portion is formed as a cathode side facing surface. A cathode side electrode,
Outside the arc tube inside the outer tube, a gas composed of only an inert gas, or nitrogen having a mixing ratio of 50% or less and an inert gas having a mixing ratio of 50% or more. Gas mixture is enclosed,
A distance dA from the upper end of the anode-side facing surface to a point located directly above the upper end of the inner peripheral surface of the light emitting unit is 0.65 mm or more,
A vehicular discharge lamp characterized in that a distance dLC from the center of the cathode-side facing surface to a point located directly below the center of the inner peripheral surface of the light emitting section is 1.00 mm or less. The size of the portion of the inner diameter of the light emitting portion where the surface including the anode-side facing surface intersects is larger than the size of the portion of the inner diameter of the light-emitting portion where the surface including the cathode-side facing surface intersects. The vehicle discharge lamp according to claim 1. The vehicle discharge lamp according to claim 1 or 2, wherein a center of the anode side electrode is positioned below a center of the cathode side electrode. A horizontal lighting type discharge lamp that emits light by a direct current lighting method,
An outer tube attached to the base;
The outer tube comprising a light emitting portion and an anode side thin tube portion that is provided on the opposite side of the light emitting portion and is continuous with the light emitting portion and located on the base side, and a cathode side thin tube portion located on the opposite side of the base An arc tube formed of ceramic and disposed inside,
At least part of the light emitting portion is disposed inside the light emitting tube in a state of projecting from the anode side thin tube portion to the light emitting portion, and one end surface in the axial direction located in the light emitting portion is formed as an anode side facing surface. An anode side electrode;
At least a part of the light emitting portion is disposed inside the light emitting tube in a state of protruding from the cathode thin tube portion to the light emitting portion, and one end surface in the axial direction located in the light emitting portion is formed as a cathode side facing surface. A cathode side electrode,
A distance dA from the upper end of the anode-side facing surface to a point located directly above the upper end of the inner peripheral surface of the light emitting unit is set to 0.9 mm or more and 1.2 mm or less,
A horizontal lighting system characterized in that a distance dC from an upper end of the cathode-side facing surface to a point located directly above the upper end of the inner peripheral surface of the light emitting unit is set to 0.7 mm or more and 1.0 mm or less. Discharge lamp.

Images