GB2275764A

GB2275764A - Headlight for vehicles

Info

Publication number: GB2275764A
Application number: GB9402601A
Authority: GB
Inventors: Johannes Bertling; Karl-Otto Dobler; Doris Boebel; Henning Hogrefe; Martin Lampen; Rainer Neumann
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1993-03-06
Filing date: 1994-02-10
Publication date: 1994-09-07
Anticipated expiration: 2014-02-10
Also published as: FR2702267A1; GB9402601D0; FR2702267B1; DE4307110C2; DE4307110A1; GB2275764B

Description

Headlight for vehicles

Prior art

The invention proceeds from a headlight according to the category of Claim 1.

Such a headlight in disclosed in EF 0,380,396 Al. This headlight is a combined dipped beam and main beam headlight and exhibits a light source, a reflector and an optically transmitting cover lens. Furthermore. in the case of this headlight a screening device is provided, which is designed as a movable optically opaque shield. The shield is movable between a position for dipped beam, in which position the shield screens off a selected reflector regiont serving for the generation of the main beam, against the incidence of light emitted by the light source and a position for main beam, in which position light emitted by the light source can impinge upon the selected reflector region. The selected reflector region serving for the generation of the main beam is disposed on one side of a vertical longitudinal central plane and the remaining reflector region serving for the generation of the dipped beam is disposed on the other side of the vertical longitudinal central plane. The headlight can be switched over between dipped beam and main beam by the movement of the shield. An adaptation of this headlight in the position for dipped beam to differing types of traffic, i.e. right-hand and left-hand traffic, is not provided. However. such an adaptation is required if the headlight, as is nowadays generally conventional, generates an asymmetric luminous intensity distribution with a light/dark boundary rising on the traffic's own side towards the edge of the roadway. When using such a headlight in the case of the respective other type of traffic, the rising light/dark boundary leads to a dazzling of oncoming vehicle drivers. In the case of conventional headlights, with which the light/dark. boundary is generated by a headlight mask, by regionwise peeling of the cover lens the part of the luminous intensity distribution with the rising light/dark boundary can be darkened off,, so that the luminous intensity distribution exhibits a continuous horizontal light/dark boundary. In the case of new types of headlight, in which the light/dark boundary is not generated by a headlight mask but by appropriate reflection of the light emitted by the light source by the reflector, the progression of the light/dark boundary cannot however be influenced by a regionwise peeling of' the cover lens; rather, only the luminous intensity distribution as a whole would be attenuated thereby.

Advantages of the invention The headlight according to the invention for vehicles having the features of Claim 1 has. as against the above,, the advantage that this headlight can beadapted by means of the screening device to traffic driving on the right and left. In this case, an illumination of the traffic's own side by the luminous intensity distribution generated by the selected reflector region with the rising light/dark boundary is achieved by the selected reflector region. For a conversion to the other type of traffic. by means of the screening device the selected reflector region is screened off against light emitted by the light source and thus only the horizontally extended luminous intensity distribution with the approximately horizontal light/dark boundary is generated by the headlight, with which light/dark boundary a dazzling of oncoming vehicle drivers is ruled out.

Advantageous refinements and further developments of the invention are indicated in the subclaims. If, as indicated in Claim 2, two selected reflector regions are provided. then a good illumination of the traffic's own side can be achieved for each type of trafficr since for each traffic side a luminous intensity distribution with a rising light/dark boundary is present. In the case of the embodiment of the screening devices which is indicated in Claim 6, these do not require any moving parts.

Drawing Two embodiments of the invention are shown in the drawing and explained in greater detail in the description which follows. Figure 1 shows a dipped beam headlight in a horizontal longitudinal cross section according to a first embodiment, Figure 2 shows the headlight of Figure 1 in front elevation, Figure 3 shows a measuring screen with a luminous intensity distribution generated on the latter by the dipped beam headlight and Figure 4 shows the dipped beam headlight in horizontal longitudinal cross section according to a second embodiment.

Description of the embodiments

A dipped beam headlight, shown in the Figures, for vehicles, especially motor vehicles, exhibits a reflector 10, which is provided in its crown region with an opening 12, into which a light source 14 is inserted. The light source 14 employed may be an incandescent lamp or a gas discharge lamp. In the embodiments, the reflector 10 is displaceably disposed in a housing 16, which exhibits a front light exit opening which is covered over by an optically transmitting cover lens 17 of glass or plastic, through which cover lens the light reflected by the reflector 10 passes in the light exit direction 18. The cover lens 17 is essentially designed as a smooth lens, and thus exhibits no or only weakly acting optical elements to influence the light passing through.

The reflector 10 is subdivided into a plurality of regions; in this case, an upper region 20 is disposed to extend above a horizontal longitudinal central plane HE on both sides of a vertical longitudinal central plane W. Adjoining the horizontal longitudinal central plane HE downwards there are disposed a region 22 which is on the left,, seen in the light exit direction 18. and a right hand region 24, both of which regions lie approximately symmetrically in relation to the vertical longitudinal central plane W. Adjoining the lateral regions 22 and 24 downwards there is disposed a lower region 26, which extends on both sides of the vertical longitudinal central plane W. The transition between the lateral regions 22, 24 and the lower region 26 takes place in longitudinal planes which are inclined with respect to the horizontal longitudinal central plane BE. The lateral regions 22. 24 can also be disposed somewhat differently. [sic] from as described above. By way of example, the lateral regions 22, 24 can extend beyond the horizontal central plane HE in an upward direction. in this case, it is also possible to dispose the lateral regions 22, 24 symmetrically above and below the horizontal central plane HE.

From the upper reflector region 20 and from the lower reflector region 26, light emitted by the light source 14 is reflected as a light beam which generates a horizontally extended luminous intensity distribution 32 on a measuring screen 30 disposed in front of the headlight perpendicular to its optical axis 28, without substantial influence by the cover lens 17. The shape of the upper reflector region 20 and of the lower reflector region 26 is in this case determined so that the latter reflects light emitted by the light source 14 in the manner required for the formation of the luminous intensity distribution 32. The luminous intensity distribution 32 is represented in Figure 3 with reference to a plurality of isolux lines, i.e. lines of equal luminous intensity. The luminous intensity distribution 32 exhibits an upper approximately horizontal light/dark boundary 34, which extends on both sides of the vertical longitudinal central plane W. The light/dark boundary 34 is disposed somewhat below the horizontal longitudinal central plane HE.

From the reflector region 22 lying to the left of the vertical longitudinal central plane W, light emitted by the light source 14 is reflected as a light beam which generates on the measuring screen 30 a luminous intensity distribution which is designated by 36 in Figure 3 and which is disposed to the right of the vertical longitudinal central plane VY on the measuring screen 30, since a light beam converging to the optical axis 28 is generated by the left hand reflector region 22. As against the luminous intensity distribution 32 generated by the upper reflector region 20 and by the lower reflector region 26, the luminous intensity distribution 36 exhibits a smaller extent. In an upward direction, the luminous intensity distribution 36 is limited by a light/dark boundary 38, which is inclined with respect to the horizontal longitudinal central plane HE at an angle a of approximately 15 degrees,, and specifically rising from the vertical longitudinal central plane W towards the right hand margin of the measuring screen 30. in the region of the vertical longitudinal central plane W, the light/dark boundary 38 extends approximately to the horizontal light/dark boundary 34 of the luminous intensity distribution 32.

Prom the reflector region 24 disposed to the right of the vertical longitudinal central plane W, light emitted by the light source 14 is reflected as a light beam which generates a luminous intensity distribution 40 which is disposed to the left of the vertical longitudinal central plane W and is disposed approximately in mirror image fashion in relation to the luminous intensity distribution 36 of the left hand reflector region 22. The luminous intensity distribution 40 exhibits an upper light/dark boundary 42. which in disposed to be inclined with respect to the horizontal longitudinal central plane HE and specifically rising opposite to the light/dark boundary 38 of the luminous intensity distribution 36, i.e. proceeding from the vertical longitudinal central plane W towards the left hand margin of the measuring screen 30.

Between the light source 14 and each lateral reflector region 22, 24 there is disposed a screening device which can be switched over in each instance between a first position in which light emitted by. the light source 14 can impinge upon the pertinent reflector region 22, 24 and a second position in which light emitted by the light source 14 is screened off from the pertinent reflector region 22. 24. The screening device may be designed as a shield 44 which is optically opaque and which is shown in Figure 2 and which surrounds the light source 14 over a part of its periphery. In this case. the shield 44 is pivotable about the optical axis 28 or about an axis parallel to the latter between a first position in which it is disposed in the beam path between the light source 14 and the left hand reflector region 22 and a second position in which it is disposed in the beam path between the light source 14 and the right hand reflector part 24. The shield 44 may be designed to be flat or curved and may exhibit an actuating element, projecting on the rear surface of the reflector, for the displacement of said shield. In place of the shield 44, as shown in Figure 1, it is also possible to provide two shields 46. 471 which are disposed laterally beside the light source 14, in each instance between the latter and the associated lateral reflector region 22 or 24. The shields 46, 47 are movable independently of one another and specifically between a first position in which the latter are disposed in the beam path between the light source 14 and the respective reflector region 22, 24 and a second position in which the latter do not obstruct the beam path between the light source 14 and the respective reflector region 22, 24. The movement of the shields 46, 47 can take place by displacement devices 48, which are symbolically indicated in Figure 1 and which can act electrically, pneumatically or hydraulically. However, the displacement devices 48 can also be actuated manually, by way of example by means of actuating elements 50 projecting out of the headlight.

In a position for right-hand traffic, the shield 46 associated with the right hand reflector region 24 is disposed in the beam path of the light emitted by the light source 14 so that no light is reflected by the right hand reflector region 24. The shield 44 associated with the left hand reflector region 22 in in the position in which the latter does not obstruct the beam path between the light source 14 and the left hand reflector region 22. In this position for right-hand traffic, accordingly, on the measuring screen 30 the luminous intensity distribution 32 is generated by the upper reflector region 20 and the lower reflector region 26, and the luminous intensity distribution 36 disposed to the right of the vertical longitudinal central plane W is generated by the left hand reflector region 22.

Thus, the luminous intensity distribution generated as a whole on the measuring screen 30 exhibits to the left of the vertical longitudinal central plane W, i.e. on the opposing traffic side, the upper approximately horizontal light/dark boundary 34 and to the right of the vertical longitudinal central plane W, i.e. on the traffic's own side, the light/dark boundary 38 rising from the approximately horizontal light/dark boundary 34 in the region of the vertical longitudinal central plane W towards the right hand margin of the measuring screen 30.

In the event of switching over to the position for left-hand traffic, the shield 44 associated with the left hand reflector region 22 is moved into the position in which the latter screens off the left hand reflector region 22 against light emitted by the light source 14 and the shield 46 associated with the right hand reflector region 24 is correspondingly moved into the position in which the latter does not obstruct the beam path between the light source 14 and the right hand reflector region 24. In the position for left-hand traffic, accordingly. on the measuring screen 30 the luminous intensity distribution 32 is generated by the upper and lower reflector region 20. 26 and the luminous intensity distribution 40 disposed to the left of the vertical longitudinal central plane W is generated by the right hand reflector region 24. The luminous intensity distribution generated as a whole on the measuring screen 30 thus exhibits to the right of the vertical longitudinal central plane W, i.e. on the opposing traffic side, the upper approximately horizontal light/dark boundary 34 and to the left of the vertical longitudinal central plane W, i.e. on the traffic's own side, the light/dark boundary 42 rising from the approximately horizontal light/dark boundary 34 in the region of the vertical longitudinal central plane W towards the left hand margin of the measuring screen 30.

Figure 4 shows a second embodiment of the headlight, which embodiment dif f ers from the f irst embodiment only with respect to the screening devices associated with the lateral reflector regions 22, 24. In the case of the second embodiment, the screening devices employed are stationary screens 52 and 54. which possess a variable light transmittance. The screens 52. 54 may for example exhibit two transparent. plates between which liquid crystals are disposed, which can be switched over between a condition in which these are essentially optically transmitting. and a condition in which these are essentially optically opaque, under the influence of an electrical voltage. However,, other types of embodiment of the screens 52,54 are also possible,, in which these for example exhibit a transparent plate which is provided with a coating of a material with variable optical transmittance. For a switching over of the headlight between - the position f or right-hand traf f ic and the position for left-hand traffic, an electrical voltage is applied to the screens 52, 54 or these are set to the potential zero. In this case,, each screen 52, 54 is connectable via a line including a switch 56, 58 to a voltage source. for example the onboard battery of the vehicle. The luminous intensity distributions generated in the positions for right- hand and left-hand traffic by the headlight on the measuring screen 30 are in this case the same as for the first embodiment.

If required, both screening devices 44,, 46 or respectively 52, 54 can also be situated in the position in which both lateral reflector regions 22.. 24 are screened off against the light emitted by the light source 14. In this position. only the luminous intensity distribution 32 caused by the upper and lower reflector region 22 and 26 with the approximately horizontal light/dark boundary 34 is generated by the headlight on the measuring screen 30. In association with an additional inclination of the light beam emitted by the headlight of approximately 2% in a downward direction with respect to a horizontal, the headlight can then be used as a foglight. The displacement of the inclination of the light beam of approximately 1%, as in the case of a dipped beam headlight, to 2%, as in the case of a foglight, can in this case be effected by a light range regulating device. Correspondingly. both screening devices 44, 46 or respectively, 52, 54 can also be situated in the position in which these do not obstruct the beam path between the light source 14 and both lateral reflector regions 22, 24. In this position, in addition to the luminous intensity distribution 32 generated by the upper and lower reflector region 20 and 26, the two luminous intensity distributions 36 and 40 are generated with the inclined light/dark boundaries 38 and 42.

By way of a difference from the abovedescribed headlight, the headlight could also exhibit only one selected reflector region 22 or 24 with a screening device 44 or 46 or respectively 52 or 54 associated with the latter, by which reflector region the luminous intensity distribution 36 or 40 with the inclined light/dark boundary 38 or respectively 42 is generated. In this case,, in the case of a headlight which is normally intended for right-hand traffic, only the left hand reflector region 22 is present, which generates the luminous intensity distribution 36, disposed to the right of the vertical longitudinal central plane W. with the light/dark boundary 38 rising towards the right hand margin of the measuring screen. In the case of a switching over of the headlight for left-hand trafficr the screening device 44 or respectively 52 is brought into the position in which the latter screens off.theleft hand reflector region 22 against light emitted by the light source 14. In this position, only the luminous intensity distribution 32, with the approximately horizontal upper light/dark boundary 34. caused by the upper and lower reflector region 20 and 26, is generated by the headlight on the measuring screen. Corresponding considerations apply to a headlight which is normally intended for left-hand traffic, and in which only the right hand reflector region 24 with the aasociated screening device 46 or respectively 54 is present.

j t 7

Claims

1. Headlight for vehicles having a reflector (10), having a light source (14). having an optically transmitting cover lens (17) in the beam path of the light reflected by the reflector (10) and having at least one screening device (44; 46r 47; 521 54) which is associated with at least one selected reflector region (22; 24) and which can be switched over between a position in which the latter allows light emitted by the light source (14) to pass to the selected reflector region (22; 24) and a position in which the latter screens off the selected reflector region (22; 24) against light emitted by the light source (14), characterized in that by the at least one selected reflector region (22; 24) a light beam is reflected. which generates a luminous intensity distribution (36, 40). disposed only on one side of a vertical longitudinal central plane (VV). with an upper light/dark boundary (38, 42). which boundary rises from the vertical longitudinal central plane (VV),, and in that by the remaining reflector regions (20, 26) a light beam is reflected, which generates a horizontally extended luminous intensity distribution (32), disposed on both sides of the vertical longitudinal central plane (VV) 1 with an upper, approximately horizontal light/dark boundary (34).

2. Headlight according to Claim 1, characterized in that two selected reflector regions (22, 24) are provided, which are disposed approximately symmetrically with respect to the vertical longitudinal central plane (VV). and in that the luminous intensity distributions generated by the two selected reflector regions (22, 24) are disposed on dif f erent sides of the vertical longitudinal central plane (VV).

3. Headlight according to Claim 1 or 2r characterized in that the at least one selected reflector region (22; 24) extends below a horizontal longitudinalcentral plane (HE). adjoining the latter.

4. Headlight according to one of Claims 1 to 3, characterized in that the at least one screening device (44; 46r 47) employed is an essentially optically opaque shield, which is movable between the two positions.

5. Headlight according to Claim 4, characterized in that the shield (44) is pivotable about the optical axis (28) or an axis parallel to the latter between a position in whic h it is disposed in the beam path between the light source (14) and the one selected reflector region (22). and another position in which it is disposed in the beam path between the light source (14) and the other selected reflector region (24).

6. Headlight according to one of Claims 1 to 3, characterized in that the at least one screening device (52; 54) employed is a stationary screen with variable optical transmittance, the optical transmittance of which screen is different in the two positions.

7. Headlight according to Claim 4 or 6, characterized in that both selected reflector regions (22. 24) can be screened off against the light emitted by the light source (14) at the san time by the screening device (46. 47; 52F 54), and in that the inclination of the light beam emitted by the headlight with respect to a horizontal in a downward direction is enlarged in this position of the screening device (46, 47; 52, 54) in relation to the other positions of the screening device.

8. Either of the headlights substantially as herein described with reference to the accompanying drawings.