Metal halide lamp and a vehicle lighting apparatus using the lamp

A metal halide lamp apparatus comprising:

• a metal halide lamp comprising:
• a light-transmitting discharge vessel having a discharge space portion, a sealed portion, a pair of electrodes projecting into the discharge space, the lamp being constructed and arranged so that it has a D/L ratio in a range of about 0.25 to about 1.5 and a D/L ratio being in a range of about 0.16 to about 1.1, wherein L is an interspace of tips of the electrodes, D is a maximum inner diameter of the discharge vessel, and t is a maximum wall thickness of the discharge space portion;
• an ionizable filling in the discharge space portion, which contains xenon (Xe) gas and a metal halide including at least sodium (Na) or scandium (Sc) and does not substantially include mercury (Hg);
• and a conductive wire connected electrically to each of the electrodes, the conductive wires extending from the discharge vessel;
• and
• a ballast constructed and arranged so as to have a relation between a filling pressure X (atm) of the xenon (Xe) and a maximum electrical power AA (W) provided to a following formula:
• 3<X<15, AA≧−2.5X+102.5, wherein the maximum electrical power AA (W) is a maximum wattage supplied to the metal halide lamp in four seconds after the lamp turned on.

A vehicle lighting apparatus comprising:

• a reflector having an opening and accommodating a metal halide lamp;
• wherein the metal halide lamp comprises:
• a light-transmitting discharge vessel having a discharge space portion, a sealed portion, a pair of electrodes projecting into the discharge space, the lamp being constructed and arranged such that a D/L ratio is in a range of about 0.25 to about 1.5 and a D/L ratio being in a range of about 0.16 to about 1.1, wherein L is an interspace of tips of the electrodes, D is a maximum inner diameter of the discharge vessel, and t is a maximum wall thickness of the discharge space portion;
• an ionizable filling in the discharge space, which contains xenon (Xe) gas and a metal halide including at least sodium (Na) or scandium (Sc) and does not substantially include mercury (Hg);
• and a conductive wire connected electrically to each electrode, the conductive wires extending from the discharge vessel;
• a front cover attached to the opening of the reflector;
• and
• a ballast constructed and arranged to have a relation between a filling pressure X (atm) of the xenon (Xe) and a maximum electrical power AA (W) that is in accordance with the following formula:
• 3<X<15, AA≧−2.5X+102.5,
• wherein the maximum electrical power AA (W) is a maximum wattage supplied to the metal halide lamp in four seconds after the lamp turned on.