Halogen filament lamp

The invention relates to a halogen lamp for motor vehicle headlights which has an electrical power consumption of between 50 watts and 100 watts and has at least one incandescent filament, the at least one incandescent filament ( 5 ) being formed according to the invention as a single coil, the dimensions and/or geometry of which are matched to an operating voltage of at least 20 volts, the length of the single coil being restricted to a range from 4.0 mm to 6.5 mm.

The halogen lamp according to the first exemplary embodiment has an essentially cylindrical lamp vessel 1 with a gastight-sealed pinch foot 2 , through which two power supply leads 3 , 4 for the incandescent filament 5 arranged in the axial direction within the lamp vessel 1 are led. The pinch foot 2 is fixed in the lamp base 6 , which is provided with two contact lugs 7 for supplying voltage to the incandescent filament 5 . FIG. 1 schematically shows the construction of this halogen lamp. This is a halogen lamp for a motor vehicle headlight with a power consumption of approximately 70 watts, which is intended for operation on a rated vehicle supply voltage of 24 volts. According to the first exemplary embodiment of the invention, the incandescent filament 5 is formed as a single coil which has a length of approximately 5.6 mm ±0.2 mm, an outside diameter of approximately 1.7 mm and 26 turns. The aforementioned specifications relate to the wound region of the incandescent filament 5 , responsible for the light emission, without taking into account the unwound ends 5 a of the incandescent filament 5 . The tungsten filament wire used for producing the single coil 5 has a diameter of 0.13 mm. The effective length of the filament wire, that is to say the length of the filament wire forming the wound region of the single coil 5 , is approximately 124.8 mm. The unwound ends 5 a of the incandescent filament 5 are respectively provided with a covering filament 8 to improve the vibration resistance and to support the incandescent filament 5 . The covering filaments 8 enclose the respective unwound ends 5 a with a clamping fit. They preferably extend over the greater part of the respective unwound end 5 a . In FIG. 2 , the construction of the incandescent filament 5 according to the first exemplary embodiment is schematically represented. According to the second exemplary embodiment of the invention, the incandescent filament 5 ′ is formed as a transversal single coil, that is to say a single coil arranged perpendicularly to the lamp axis, which has a length of approximately 5.2 mm ±0.2 mm, an outside diameter of approximately 1.9 mm and 23 turns. The aforementioned specifications relate to the wound region of the incandescent filament 5 ′, responsible for the light emission, without taking into account the unwound ends 5 a ′ of the incandescent filament 5 ′. The tungsten filament wire used for producing the single coil 5 ′ has a diameter of 0.13 mm. The effective length of the filament wire, that is to say the length of the filament wire forming the wound region of the single coil 5 ′, is approximately 124.9 mm. The unwound ends 5 a ′ of the incandescent filament 5 ′ are respectively provided with a covering filament 8 ′ to improve the vibration resistance and to support the incandescent filament 5 ′. The covering filaments 8 ′ enclose the respective unwound ends 5 a ′ with a clamping fit. They preferably extend over the greater part of the respective unwound end 5 a ′. In FIG. 3 , the construction of the incandescent filament 5 ′ according to the second exemplary embodiment is schematically represented. Both single filaments 5 , 5 ′ described in more detail above are adapted on the basis of their dimensions and geometry to an operating voltage of approximately 24 volts and a power consumption of approximately 70 watts. The single filament 5 ″ according to the third exemplary embodiment, depicted in FIG. 4 , differs from the single filaments of the two exemplary embodiments explained above only in that the unwound ends 5 a ″ are respectively surrounded with a clamping fit by a tube 8 ″ produced from molybdenum strip. The molybdenum tubes 8 ″ extend in each case over the greater part of the corresponding unwound end 5 a ″. Furthermore, the molybdenum tubes 8 ″ facilitate the welding of the filament ends to the power supply leads 3 , 4 , likewise consisting of molybdenum. The invention is not restricted to the exemplary embodiments explained in more detail above. The covering filaments 8 , 8 ′ or molybdenum tubes 8 ″ are only required if especially high requirements are demanded of the vibration resistance. Instead of covering filaments 8 , 8 ′ or molybdenum tubes 8 ″, in this case, however, other supporting means may also be used for the incandescent filament. For example, instead of covering filaments 8 , 8 ′ or molybdenum tubes 8 ″, the power supply leads 3 , 4 may be made correspondingly thick and the unwound ends 5 a , 5 a ′ of the incandescent filament 5 , 5 ′ connected to them may be made correspondingly short, so that the power supply leads 3 , 4 already ensure a great vibration resistance.