High Pressure Discharge Lamp

Abstract

A high pressure discharge lamp can be used in a vehicle lighting device as a light source in place of a halogen lamp, and can be driven with a reduced starting voltage while being miniaturized. A gas is filled in a space between an arc tube and an outer tube of the high pressure discharge lamp, the gas being capable of dielectric barrier discharge, to reduce the starting voltage. A metal conductor is arranged in the space between the arc tube and the outer tube to stabilize the starting voltage and perform other functions. The metal conductor can also serve as a lead line. Accordingly, high voltage portions of the lamp are not exposed outside of the outer tube. This can reduce the entire size of the high pressure discharge lamp such that a housing for a headlight using a halogen lamp can be used for this type of high pressure discharge lamp.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics, features, and advantages of the presently disclosed subject matter will become clear from the following description with reference to the accompanying drawings, wherein:

FIG. 1 is a cross sectional view showing a conventional discharge lamp;

FIG. 2 is a cross sectional view showing an exemplary embodiment of a high pressure discharge lamp made in accordance with principles of the presently disclosed subject matter;

FIG. 3 is a cross sectional view showing another exemplary embodiment of a high pressure discharge lamp made in accordance with principles of the presently disclosed subject matter;

FIG. 4 is a cross sectional view showing still another exemplary embodiment of a high pressure discharge lamp made in accordance with principles of the presently disclosed subject matter; and

FIG. 5 is a cross sectional view showing yet another exemplary embodiment of a high pressure discharge lamp made in accordance with principles of the presently disclosed subject matter.

Claims

1. A high pressure discharge lamp comprising: an arc tube having a discharge space in which at least one rare gas is located, the arc tube including a pair of discharge electrodes projecting into the discharge space of the arc tube and located opposite to each other, and sealing portions located at respective ends of the arc tube, the sealing portions including at least one current feeding conductor configured to feed an electrical current to at least one of the discharge electrodes;an outer tube located adjacent the arc tube, the outer tube being hermetically sealed at opposite ends thereof to form a space between the arc tube and the outer tube, wherein the space between the arc tube and the outer tube includes a gas capable of dielectric barrier discharge; anda metal conductor located along the arc tube and in the space, the metal conductor extending from one of the sealing portions and across an area adjacent the discharge space.

2. The high pressure discharge lamp according to claim 1, further comprising: a socket terminal, wherein one portion of the metal conductor is connected to the current feeding conductor at a tip end side of the arc tube, another portion of the metal conductor is connected to the socket terminal, and the metal conductor is contained within the outer tube and serves as a feeding line to the arc tube.

3. The high pressure discharge lamp according to claim 1, wherein the metal conductor is composed of at least one of a linear and a plate-shaped metal material, and is fixed at a welded portion at which the arc tube joins with the outer tube.

4. The high pressure discharge lamp according to claim 1, wherein at least one of the sealing portions and the outer tube are welded together to form a welded portion, and the metal conductor is located at the welded portion.

5. The high pressure discharge lamp according to claim 4, wherein the metal conductor is made of at least one of a linear and a plate-shaped metal material.

6. The high pressure discharge lamp according to claim 1, wherein the metal conductor is wound around a portion of the arc tube adjacent at least one of the discharge electrodes, and at least one end of the metal conductor is fixed to the arc tube.

7. The high pressure discharge lamp according to claim 1, wherein the metal conductor is configured as a light shielding cover located on an inner surface of the outer tube and configured to form a light distribution pattern during operation of the lamp.

8. The high pressure discharge lamp according to claim 2, wherein the metal conductor is configured as a light shielding cover located on an inner surface of the outer tube and configured to form a light distribution pattern during operation of the lamp.

9. The high pressure discharge lamp according to claim 3, wherein the metal conductor is configured as a light shielding cover located on an inner surface of the outer tube and configured to form a light distribution pattern during operation of the lamp.

10. The high pressure discharge lamp according to claim 4, wherein the metal conductor is configured as a light shielding cover located on an inner surface of the outer tube and configured to form a light distribution pattern during operation of the lamp.

11. The high pressure discharge lamp according to claim 1, wherein the outer tube surrounds the arc tube.

12. The high pressure discharge lamp according to claim 1, wherein the outer tube is sealed at the sealing portions of the arc tube.

13. The high pressure discharge lamp according to claim 1, further comprising: a socket terminal, wherein one end of the metal conductor is connected to the current feeding conductor at a tip end side of the arc tube, and an opposite end of the metal conductor is connected to the socket terminal.

14. The high pressure discharge lamp according to claim 1, wherein the sealing portions and the outer tube are welded together to form welded portions, and the metal conductor is located at at least one of the welded portions.

15. A high pressure discharge lamp comprising: an arc tube having a longitudinal axis and a discharge space in which at least one rare gas is located, the arc tube including a pair of discharge electrodes projecting into the discharge space, and sealing portions located at respective ends of the arc tube, at least one of the sealing portions including at least one current feeding conductor configured to feed an electrical current to at least one of the discharge electrodes;an outer tube located adjacent the arc tube, the outer tube being sealed at opposite ends thereof to form a space between the arc tube and the outer tube, wherein the space between the arc tube and the outer tube includes a gas capable of dielectric barrier discharge; anda metal conductor located in the space adjacent the arc tube, the metal conductor extending from a first location that intersects an imaginary line perpendicularly extending from the longitudinal axis of the arc tube located at one of the sealing portions, to a second location that intersects a second imaginary line perpendicularly extending from the longitudinal axis of the arc tube located at another of the sealing portions.

16. The high pressure discharge lamp according to claim 15, further comprising: a socket terminal connected to one end of the metal conductor, wherein another end of the metal conductor is connected to the current feeding conductor at a tip end side of the arc tube, and the metal conductor is sealed within the outer tube and serves as a feeding line to the arc tube.

17. The high pressure discharge lamp according to claim 15, wherein the metal conductor is composed of at least one of a linear and a plate-shaped metal material, and is fixed at a welded portion at which the arc tube joins with the outer tube.

18. The high pressure discharge lamp according to claim 15, wherein at least one of the sealing portions and the outer tube are welded together to form a welded portion, and the metal conductor is located at the welded portion.

19. The high pressure discharge lamp according to claim 18, wherein the metal conductor is made of at least one of a linear and a plate-shaped metal material.

20. The high pressure discharge lamp according to claim 15, wherein the metal conductor is wound around a portion of the arc tube adjacent at least one of the discharge electrodes, and at least one end of the metal conductor is fixed to the arc tube.

21. The high pressure discharge lamp according to claim 15, wherein the metal conductor is configured as a light shielding cover located on an inner surface of the outer tube and forms a light distribution pattern during operation of the lamp.

22. The high pressure discharge lamp according to claim 16, wherein the metal conductor is configured as a light shielding cover located on an inner surface of the outer tube and forms a light distribution pattern during operation of the lamp.