Headlight for vehicle

• US 4,799,135 A
• Filed: 10/17/1986
• Issued: 01/17/1989
• Est. Priority Date: 10/18/1985
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kuno, Nobuyoshi, Sasaki, Hiroki, Takanishi, Hiroyoshi, Inukai, Shinji
• Primary Examiner(s): Yeung, James C.
• Application Number:
  US06/920,063
• Time in Patent Office: 823 Days
• Field of Search: 362/310, 362/296, 362/61, 313/113, 313/620
• US Class Current: 362/516
• CPC Class Codes: F21S 41/172 High-intensity discharge light sources
• CPC Class Codes: F21S 41/19 Attachment of light sources or lamp holders achieving variable light distribution by movable light sources F21S41/657

Abstract

A headlight for a vehicle includes a metal halide lamp and a reflector having a focus and reflecting a light beam, emitted from the lamp, in a forward direction from the front of the vehicle. The lamp has a luminescent tube in which at least sodium is sealed, and positive and negative electrodes. The respective distal ends of the electrodes are located in the luminescent tube and spaced at a predetermined distance from each other. The lamp is positioned so that a straight line connecting the respective distal ends of the electrodes is horizontal and passes through the focus, and so as to meet the following requirement:

0≦L0/L1≦0.4,

where L0 is the distance between the focus and the distal end of the negative electrode, and L1 is the distance between the distal ends of the electrodes.

Claims

1. A headlight for a vehicle adapted to be operated by a direct-current power source, comprising:

a high-pressure metal-vapor discharge lamp including a luminescent tube having at least sodium sealed therein as a luminescent metal, and including positive and negative electrodes having their respective distal ends spaced at a predetermined distance from each other and located in the luminescent tube; and

a reflector having a focus and reflecting a light beam, emitted from the discharge lamp, in a forward direction from the front of the vehicle,

said discharge lamp being positioned along a straight line connecting the respective distal ends of the positive and negative electrodes, said straight line being horizontal and passing through the focus, and said discharge lamp being arranged to fulfill the following requirement so that the luminescent region of reddish light radiated from said at least sodium is located at the same position as the focus;

space="preserve" listing-type="equation">0≦

L0/L1≦

0.4,

where L0 is the distance between the focus and the distal end of the negative electrode, and L1 is the predetermined distance between the respective distal ends of the positive and negative electrodes;

said discharge lamp in cooperation with said reflector producing a light beam having a luminous distribution pattern with reddish light, radiation from said at least sodium, being located at a center thereof and light of other colors being located around the reddish light.

2. The headlight according to claim 1, wherein said reflector has a reflecting surface, including a parabolic surface of revolution, and an optical axis, passing through the focus and coaxial with the straight line connecting the respective distal ends of the positive and negative electrodes.

3. The headlight according to claim 1, wherein said high-pressure metal-vapor discharge lamp is a metal halide lamp.

4. The headlight according to claim 1, wherein said high-pressure metal-vapor discharge lamp is a high-pressure sodium lamp.

5. The headlight according to claim 1, wherein said reflector has a reflecting surface, including a parabolic surface of revolution, and a front opening facing the paraboloid, and said positive and negative electrodes are located on the sides of the opening and the summit of the paraboloid, respectively.

6. The headlight according to claim 1, wherein said reflector has a reflecting surface, including a parabolic surface of revolution, and a front opening facing the paraboloid, and said positive and negative electrodes are located on the sides of the summit of the paraboloid and the opening, respectively.