FIELD OF THE INVENTION

The invention relates to a headlight for vehicles, to a reflector for a headlight and to a method of forming an illumination beam for a vehicle.

BACKGROUND OF THE INVENTION

Headlights for motor vehicles create an illumination beam projected forward of the vehicle to illuminate the road. In order to avoid glare for oncoming traffic, the intensity distribution of the illumination beam for low beam light comprises a bright/dark boundary. Regulations pertain to the specific required shape of the bright/dark boundary, which generally includes a horizontal portion and an inclined portion.

Different lamps of the incandescent type exist for motor vehicle headlights. While some lamps only comprise a single filament as light-emitting element, other lamps, such as e. g. H4, comprise two filaments and a baffle arranged proximate to a first filament to partially shield light emitted therefrom. With such two-filament types of lamps, both high beam and low beam function may be achieved by the same lamp and reflector.

Examples of known two-filament lamps are H4, HS1, and the newly proposed H19.

SUMMARY OF THE INVENTION

It may be considered an object to propose a headlight and a reflector as well as a method of forming an illumination beam in a way to avoid or minimize glare for oncoming traffic.

According to an aspect of the invention, a headlight according to claim 1 is proposed. According to a further aspect, a reflector according to claim 12 is proposed. The method of claim 13 relates to a still further aspect of the invention. Dependent claims refer to preferred embodiments.

The present inventors have considered use of lamps with symmetrical arrangement of the baffle relative to a first filament, wherein the first filament is arranged above a plane including side edges of the baffle. While a lamp of this design provides more light than lamp types with a first filament closer to the baffle, the inventor has determined that a symmetrical, horizontal arrangement of the lamp in a reflector may lead to glare by stray light. Stray light may occur due to scattering at the inner wall of the baffle and reflection at the side edges. Surprisingly, the inventors have found that glare can be reduced by arranging the lamp rotated within the reflector by a certain rotation angle.

According to an aspect of the invention, a headlight for a vehicle comprises a concave reflector and a lamp arranged within the reflector. Light emitted from the lamp is reflected at the reflector surface to create an illumination beam of desired properties.

The lamp is an incandescent, preferably halogen lamp including a sealed transparent vessel with a longitudinal axis and at least a first and second filament arranged within the vessel. Preferably, at least the portion of the vessel surrounding the filaments is cylindrical, such that the longitudinal axis may be the central longitudinal axis of the cylindrical portion.

Proximate to the first filament, a baffle is arranged to partially shield light emitted from the first filament. The baffle is preferably of concave shape and extends along the longitudinal axis for at least the length of the first filament. At least a front portion of the baffle may be arranged in between the first and second filaments.

The baffle may serve to partially shield light emitted from the first filament, such that the light emitted from the first filament which is not shielded may be reflected to form an illumination beam including a bright/dark boundary, in particular a low beam. The second filament is preferably unshielded and may serve to create a high beam, which does not comprise a bright/dark boundary.

The baffle comprises first and second upper side edges extending longitudinally, at least in a side view. Preferably, the upper side edges have at least a straight portion (in side view) extending in parallel to the longitudinal axis over the length of the first filament. The first filament is arranged above the upper side edges of the baffle, i. e. above a plane including the upper side edges (or at least the above defined straight portions thereof). In particular, the lower side of the first filament may be arranged at a distance to the plane of the edges, such as e. g. a distance of 0.1 mm or more, preferably 0.3 mm or more. In the lamp according to this aspect of the invention, the first filament is thus arranged relatively high above the baffle as compared to lamps such as the H4 and HS 1 , thus providing more light which is emitted unshielded.

According to an aspect of the invention, the arrangement of the upper side edges of the baffle is symmetrical. In a central transversal plane, i.e. a plane arranged perpendicular to the longitudinal axis running through the center of the first filament, a baffle symmetry axis may be defined from the center of the first filament centrally between the upper side edges.

According to an aspect of the invention, the lamp is arranged within the reflector rotated around its longitudinal axis by a rotation angle of 2 - 20° with respect to a horizontally symmetrical arrangement. Further preferably, the rotation angle may be at least 4°. Particularly preferable is a rotation angle of 6 - 18°. Preferably, the lamp may be arranged within the reflector such that the baffle symmetry axis is arranged rotated relative to a vertical axis by the rotation angle.

Arrangement of the lamp in the thus specified rotation position has surprisingly proven to allow concepts with greatly reduced glare, in particular in the most significant portions of the illumination beam. As will become apparent in connection with preferred embodiments, rotation of the lamp leads to different optical effects for the beam portions emitted horizontally: Viewed from the side of the lamp in the hori- zontal direction towards which the lamp is rotated, the closer upper side edge of the baffle appears lower relative to the filament, whereas viewed from the opposite horizontal side the other upper side edge appears higher, such that it may shield the filament partially or even fully. These different effects allow to use a corresponding reflector avoiding stray light being emitted into critical portions of the illumination beam. According to an aspect of the invention, the lamp may comprise a base with radially extending positioning protrusions. The positioning protrusions may be arranged symmetrically relative to a protrusion symmetry axis, which is arranged parallel to the baffle symmetry axis. Thus, the lamp may be fully symmetrical both with regard to the positioning protrusions and to the relative arrangement of the baffle and first filament. Particularly preferred are lamps with three radially extending positioning protrusions, one in parallel to the protrusion symmetry axis.

The reflector provided according to a separate aspect on the invention comprises a concave reflector surface forming an inner reflector space. An opening is provided for arrangement of a lamp including positioning protrusions, for example as explained above. The reflector comprises receiving portions for the positioning protrusions which are located at the reflector such that the lamp, if the positioning protrusions are received in the respective receiving portions, is positioned in the above described rotating position under the desired rotation angle.

According to a preferred aspect, the reflector may be a complex shape reflector comprising a plurality of reflecting segments, each arranged to project images of at least one of the filaments. A complex shape reflector may use the separate reflecting segments of the reflector surface to form a desired illumination beam from a superposition of individual filament images.

According to a preferred aspect, the lamp may be arranged within the reflector such that viewed in horizontal direction from a first side the first filament is at least partially shielded by the first upper side edge of the baffle, and viewed in opposite horizontal direction from a second, opposite side the second upper side edge of the baffle is arranged not to shield the first filament. Thus, while a horizontally symmetrical orientation of the first filament and the baffle (0° rotation) would lead to the same filament image and same amount of light at both horizontal directions, the rotated and thus asymmetrical arrangement allows the opposite horizontal portions of the reflector surface to receive light from the first filament differently.

As already mentioned, regulations for the illumination beam of vehicle headlights in different countries provide a shape of a bright/dark boundary for low beam light including a horizontal portion and an inclined portion. Particularly, the inclined portion may be arranged under an angle of e.g.15° relative to the horizontal. According to a preferred aspect, the reflector may comprise one or more first reflecting segments on a first side arranged at least substantially in horizontal direction from the first filament. The first reflecting segment may be arranged to reflect light from the first filament to a horizontal portion of a bright/dark boundary of the illumination beam. One or more second reflecting segments of the reflector may be arranged on a second side, opposite to the first side, in at least substantially horizontal direction from the first filament. The second reflecting segment may be arranged to reflect from the first filament to an inclined portion of the bright/dark boundary of the illumination beam. Thus, reflecting segments of the reflector arranged at opposite sides may be provided to direct light into different portions of the illumination beam.

Generally, the inclined portion of the bright/dark boundary will be more critical with respect to glare as compared to the horizontal portion. For this reason, it is preferred to arrange the lamp in such a rotated position that one or more second reflecting segments are illuminated by an at least partially shielded first filament rather than by the first filament fully visible and arranged at a distance to the corresponding upper side edge of the baffle, because this may lead to scattered light being reflected by the first reflecting segments.

According to a further preferred aspect, the second reflecting segment, arranged to reflect light from the first filament to an inclined portion of the bright/dark boundary, may be shaped to have a focus located on the upper edge, rather than on the first filament. This may serve to obtain a sharp projection of the upper edge of the baffle located closest to it, onto the inclined portion of the bright/dark boundary.

According to another preferred aspect of the invention, the first reflecting segment, arranged to reflect light from the first filament to a horizontal portion of the bright/dark boundary, may be shaped to have a focus located on the first filament, rather than on the corresponding upper side edge of the baffle.

The preferred type of lamp to be used in the headlight and method according to the invention may have an electrical power of more than 60 W for both the first and second filament (measured at a supply voltage of 13.2 V). Preferably, the first filament is disposed to operate at an electrical power of 62 - 68 W and the second filament at 64 - 72 W at the specified supply voltage. In operation of the first filament, the lamp may preferably emit light with a luminous flux of 1080 - 1320 lm, most preferably 1150 - 1250 lm. In operation of the second filament, the lamp may emit light with a luminous flux of 1630 - 1870 lm, preferably 1700 - 1800 lm.

These and other aspects of the invention will become apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

Fig. 1, 2 show a side view and a back view of a two-filament lamp;

Fig. 3 shows a sectional view of the lamp of fig. 1, 2 with the section along the line C...C in fig. 1;

Fig. 4 shows an enlarged side view of a portion of a burner of the filament lamp of fig. 1 - 3;

Fig. 5 shows a schematical sectional view of an embodiment of a headlight;

Fig. 6, 7a, 7b show schematical representations of arrangements of a lamp within a reflector;

Fig. 8a - 8c show horizontal views of a portion of the burner of a lamp for different rotational positions;

Fig. 9a, 9b show intensity distributions of illumination beams for different rotational positions of a lamp within a reflector. DETAILED DESCRIPTION OF EMBODIMENTS

Figs. 1, 2, 3 show a two-filament halogen incandescent lamp 10, for example of the HI 9 type. The lamp 10 comprises a base 12 and a burner 14. The base 12 comprises electrical contacts 16 and mechanical reference elements for mounting of the lamp including a positioning ring 18 and protruding therefrom in radial directions three positioning protrusions 20a, 20b, 20c. The burner 14 is fixed to the base 12 and comprises a transparent vessel 22. A first filament 24 and a second filament 26 are arranged within a cylindrical portion 28 of the transparent vessel 22. A longitudinal axis L is defined as the center of the cylindrical portion of the vessel 22.

The filaments 24, 26 are arranged within the vessel 22 mounted on mounting rods. A baffle 30 is mounted on one of the mounting rods in a position proximate to the first filament 24.

The relative arrangement of the first and second filaments 24, 26 and the baffle 30 within the cylindrical portion 28 of the vessel 22 are shown in fig. 4. Both fila- ments 24, 26 are provided as single winding structures of filament wire wound around respective straight filament axes Al, A2 extending parallel to the longitudinal axis L.

In the example, the first filament 24 has an axial length LI of about 5 mm and the second filament 26 has an axial length L2 of about 4 mm. The outer diameter of the winding structure of the first filament 24 in the example may be 1.4 mm and the outer diameter of the winding structure of the second filament 26 in the example may be 1.6 mm.

The baffle 30 arranged proximate to the first filament 24 comprises a front portion 32 arranged between the first and second filament 24, 26 which are thus optically shielded from one another.

The baffle 30 is of concave shape and comprises left and right upper side edges 34a, 34b. In the side view shown in fig. 1, fig. 4, the upper side edges 34a, 34b extend straight and in parallel to the longitudinal axis L. A straight portion of the upper side edges 34a, 34b is arranged parallel along the length LI of the first filament 24. As the skilled person will appreciate, the upper side edges 34a, 34b may have a curvature in a horizontal plane (not shown).

The baffle 30 serves to partially shield light emitted from the first filament 24, in particular light emitted into radial directions below the upper side edges 34a, 34b. If the lamp 10 is mounted in a reflector 40 of a vehicle headlight 50 as shown in fig. 5, the second filament emits light to be reflected both at upper and lower portions of the reflector 40 (dashed lines) for forming a high beam, whereas the first filament 24 emits light only to be reflected at upper portions of the reflector 40 (dotted lines) for forming a low beam 42.

In the lamp shown, the first filament 24 is arranged relatively high above the baffle 30. A plane E (fig. 3) may be defined by the upper side edges 34a, 34b. The first filament 24 is arranged above the plane E, such that in a side view (fig. 4) the full filament 24 can be seen above the respective side edge 34a, 34b of the baffle 30, with a distance of e. g. some 0.3 mm between the lower side of the first filament 24 and the upper side edges 34a, 34b.

The lamp 10 is fully symmetrical, both with respect to the base 12 and to the burner 14. As shown in the back view of fig. 2, the positioning protrusions 20a, 20b, 20c are arranged symmetrically to a protrusion symmetry axis P shown vertically. Likewise, the arrangement of the first filament 24 and the baffle 30 as shown in the section view of fig. 3 is symmetrical to a baffle symmetry axis B also shown vertically. The baffle symmetry axis B and the protrusion symmetry axis P are arranged in parallel.

The lamp 10 may be inserted into a reflector 40 of a vehicle headlight 50 as schematically shown in the sectional view of fig. 5. The lamp 10 is inserted in a back opening 36 of the refiector 40 such that the burner 14 is arranged in the inner reflector space. The lamp 10 is positioned within the reflector 40 by the mechanical reference elements 18, 20a, 20b, 20c being received in corresponding stopping positions around the mounting opening 36. In particular, the rotational position of the lamp 10 with respect to the longitudinal axis L is determined by the positioning protrusions 20a 20b, 20c being received in corresponding receiving portions 38 at the reflector 40.

Light from the first filament 24 is reflected by the inner reflective surface of the reflector 40 to form an illumination beam 42 including a bright/dark boundary suitable for low beam lighting.

The reflector 40 is a complex shape reflector comprising individually shaped reflector segments, some of which are shown in fig. 5 as 46. The illumination beam 42 is created as a superposition of images of the first filament 24. Fig. 6, 7a, 7b schematically show arrangements of the lamp 10 within the reflector 40. The lower half of the representations in Fig. 6, 7a, 7b should be understood as viewing along the longitudinal axis L from the back of the headlight (i.e. from the right in Fig. 5). In the upper half of the representations in Fig. 6, 7a, 7b, the resulting il- lumination beam 42 with bright/dark boundary 44 is depicted. As the skilled person will understand, the schematical drawings Fig. 6, 7a, 7b serve to illustrate which portions of the lamp 10 and reflector 40 are responsible for creating different parts of the illumination beam 42.

In Fig. 6, the lamp 10 is arranged within the reflector 40 in upright posi- tion, i. e. with the baffle and protrusion symmetry axes B, P oriented vertically, corresponding to a rotation angle of 0°.

As schematically shown in fig. 6, light from the first filament 24 is reflected at the reflector surface to form the illumination beam 42. An intensity distribution of the illumination beam 42 for the upright oriented lamp 10 as shown in fig. 6 is depicted in fig. 9a. As schematically indicated in fig. 6, the illumination beam 42 is a low beam including a bright/dark cut-off 44 including a horizontal portion 44a and a 15° inclined portion 44b.

As schematically indicated in fig. 6, portions 46a to the right of the reflector 40 arranged at least substantially horizontal relative to the first filament 24 re- fleet light from this filament into regions at and below the horizontal portion 44a of the bright/dark cut-off 44 of the illumination beam 42, whereas portions 46b of the reflector 40 located on the opposite left side at least substantially horizontally reflect light from the first filament 24 to or below the inclined portion 44b of the bright/dark cutoff 44.

As schematically shown in figure 6, a first reflector surface segment 46a located at the right side of a reflector 40 reflects light from the filament 24 to project a horizontal image 48a of the first filament 24. A second reflecting segment 46b located to the left of the reflector 40 projects an image 48b of the first filament 24 which is inclined by the inclination angle a of 15°. The respective rays are schematically shown as dashed lines. Fig. 8a shows, for a horizontally symmetrical arrangement of the lamp 10, the appearance of the first filament 24 and the baffle 30 with upper side edges 34a, 34b as viewed from both horizontal reflector portions 46a, 46b. From both directions, the first filament 24 is fully visible and the respective upper side

edge 34a, 34b is arranged below the lower side of the first filament 24 with a certain distance, such that a gap 33 is visible between the upper side edges 34a, 34b and the first filament 24.

As the inventors have observed, stray light, shown symbolically as dotted lines in fig. 6, is also emitted from the burner 14 of the lamp 10. Such stray portions of light may be due e. g. to reflection of light at the baffle 30. The stray light leads to slightly dislocated images 49a, 49b along the bright/dark cut-of line 44. In particular, the stray portions of light forming images 49b above the inclined portion 44b of the bright/dark cut-of line 44 can lead to glare for oncoming traffic.

Fig. 7a shows a different, slightly rotated arrangement of the lamp 10. The lamp 10 is rotated relatively to the reflector 40 in clockwise direction, i.e. to the right in fig. 7a by a rotation angle a of about 15°. Consequently, the symmetry axes B, P are arranged under the rotation angle a relative to the vertical axis.

Due to the rotated and thus non-symmetrical arrangement of the lamp 10 within the reflector 40, the appearance of a first filament 24 differs as viewed from the horizontal left and right reflector segments 46b, 46a. Fig. 8b shows the appearance of the first filament 24 viewed from the left reflector side in Fig. 7a. Due to the rotation of the lamp 10, the upper side edge 34b of the baffle 30 has been raised relative to the first filament 24, such that the gap 33 below the filament 24 is no longer visible and the filament 24 is partially shielded. Viewed from the opposite right side as shown in fig. 8c, the upper side edge 34a on the other side is lowered due to the rotation, such that the distance between the lower side of the first filament 24 and the upper side edge 34b of the baffle 30 is increased. From the right horizontal reflector portion 46a, the first filament 24 is fully visible and not shielded by the baffle 30.

As illustrated in fig. 7a, this eliminates a substantial portion of stray light emitted into the horizontal direction of the second reflector surface segment 46b, shown to the left in fig. 7a. Consequently, a stray light image 49b, which would appear at or even above the inclined portion 44b of the bright/dark cut-of line 44 (see fig. 6), is eliminated.

Next to the horizontal portion 44a of the bright/dark cut-off 44, stray light (shown as dotted lines) may still create a stray image 49a. However, this portion of the bright/dark cut-off 44 of the illumination beam 42 is less critical with regard to glare for oncoming traffic.

While in the schematic representation in fig. 7a the shape of the bright/dark cut-off 44 is shown for countries with right-hand traffic, fig. 7b shows the bright/dark cut-off 44 for left-hand traffic. The horizontal portion 44a and inclined portion 44b are arranged on opposite sides as compared to fig. 7a. Consequently, the lamp 10 is arranged rotated in counter-clockwise direction for a rotation angle a of about 15°, i.e. to the left in fig.7b. In the resulting illumination beam 42, the projected image 48b of the filament 24 positioned at the inclined portion 44b is clear without stray light, whereas a stray light image 49a may still be present at the horizontal portion 44a of the illumination beam 42.

Fig. 9b shows an intensity distribution for the illumination beam 42 generated by a lamp 10 rotated within the reflector 40 by a clockwise rotation angle a of 15° (as shown in fig. 7a).

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

For example, the specific shape of the baffle 30 and the relative arrangement to the first filament 24 may differ in different embodiments. The lamp 10 may be arranged within the reflector 40 under different rotation angles a.

These and other variations of the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims.

In the claims, any reference signs place between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in the claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.