EP0558949A2 - Dipping headlamp for vehicles - Google Patents

Abstract

The dipped-beam headlamp has a reflector (10) which is subdivided into an upper part (19) and a lower part (20) which touch one another in an axial plane (17) inclined at an angle of alpha /2 to the horizontal. The transition between the two reflector parts (19, 20) is continuous in the second order. The two reflector parts (19, 20) have reflection surfaces in the form of general paraboloids, the latter containing identical parabolas in the tangent plane (17), but containing different parabolas in all the other axial sections. The result in sections through the reflector perpendicular to the optical axis (14) is ellipse-like curves of intersection (23) which have over their circumference a variable eccentricity with respect to the optical axis (14) of the reflector (10). In this case, the eccentricity in the region of the tangent plane (17) is approximately zero, and increases up to the axial plane (22) perpendicular to the tangent plane (17). This design of the reflector (10) reflects the light while forming a light/dark boundary having a section inclined at an angle of alpha . <IMAGE>

Description

State of the art

The invention relates to a low beam headlight for motor vehicles according to the preamble of claim 1.

Such a low beam headlight is known from EP 0 250 284 A1. This low beam headlamp has a reflector, a luminous element and a light plate covering the light exit opening of the reflector. The luminous element is offset upward with respect to the optical axis of the reflector so that its lower limit lies approximately on the optical axis. The reflector is divided into several sectors below and above a horizontal axial plane with different reflection surfaces. On one side of the reflector, a first sector extends from the horizontal axial plane up to an angle α to it, and on the other side of the reflector extends from the horizontal axial plane downwards at an angle α to it second sector, both sectors each having reflection surfaces in the form of paraboloid of revolution. These two sectors are connected by two adjoining sectors above and below the horizontal axial plane, which have reflection surfaces in the form of general paraboloids. A general paraboloid contains parabolas in all axial longitudinal sections, but with different focal lengths.

This known dipped-beam headlight produces a light distribution with a light-dark boundary, which has a substantially horizontal section on the oncoming traffic side and a section that rises upwards with respect to the horizontal at the angle α to the road edge of one's own lane. The lens only needs to have weakly effective optical means for shaping the light distribution. A high luminous intensity is sought just below the light-dark boundary in order to obtain a long range and the sharpest possible formation of the light-dark limit. With the light distribution generated by the known reflector, however, this has not been achieved to the desired extent.

Advantages of the invention

The low beam headlamp according to the invention with the characterizing features of claim 1 has the advantage that a high light intensity is present just below the light-dark boundary and thus a long range of light is achieved and the light-dark limit is clearly pronounced.

Advantageous refinements and developments of the invention are characterized in the subclaims.

drawing

An embodiment of the invention is shown in the drawing and explained in more detail in the following description. 1 shows a low beam headlight in vertical longitudinal section, FIG. 2 shows the reflector of the headlight in rear view, FIG. 3 shows the upper partial surface of the reflector in a cross section perpendicular to the optical axis, FIG. 4 shows images of a luminous element reflected by the upper left partial surface of the reflector, 5 images of the luminous element reflected by the lower left partial surface of the reflector and FIG. 6 the light distribution generated by the headlight.

Description of the embodiment

A low-beam headlight for motor vehicles shown in FIG. 1 has a reflector 10, the light exit opening of which is covered by a lens 11, which can have optically effective elements. Furthermore, there is a luminous element 13, which can be the filament of an incandescent lamp or the arc of a gas discharge lamp. The luminous element extends approximately parallel to the optical axis 14 of the reflector 10, but is offset upwards with respect to this so that its lower limit lies approximately on the optical axis 14.

The reflector 10 is divided into an upper part 19 and a lower part 20 in a plane 17 shown in FIG. 2 and inclined at an angle α / 2 to the horizontal 16, both of which have reflection surfaces in the form of general paraboloids. The two parts 19 and 20 continuously merge into one another in the contact plane 17, that is, that both parts have 17 common tangents in the plane of contact.

. Dabei ist vorzugsweise die Exzentrizität e der Schnittkurve 23 im Bereich der Berührungsebene 17 nahezu Null, so daß die Normale auf die Schnittkurve 23 die optische Achse 14 schneidet und die Schnittkurve 23 in diesem Bereich näherungsweise ein Kreis ist. Zur senkrechten Axialebene 22, also mit zunehmendem Winkel β zwischen einer einen Reflektorpunkt P mit der optischen Achse 14 verbindenden Geraden OP und der Berührungsebene 17, nimmt dabei die Exzentrizität e der Schnittkurve 23 zu. Bis zu einem Winkel β von etwa 45° nimmt der Abstand zwischen der Normalen 24 auf die Schnittkurve 23 und der optischen Achse 14 ebenfalls zu. Von einem Winkel β von etwa 45° bis zur senkrechten Axialebene 22 mit dem Winkel β = 90° nimmt der Abstand zwischen Normalen 24 auf die Schnittkurve 23 und der optischen Achse 14 wieder bis auf etwa Null ab. Die Exzentrizität e der Schnittkurve 23 erreicht in der senkrechten Axialebene 22 ihren Höchstwert.FIG. 3 shows a cross section through the upper part 19 of the reflector 10. The upper part 19 has a reflective surface in the form of a general paraboloid. The general paraboloid contains parabolas in all axial longitudinal sections, that is to say longitudinal sections containing the optical axis 14. However, the parabolas have different focal lengths and a common apex, so that there are different focal positions for the different parabolas. The focal point Foh, the parabola lying in the contact plane 17, lies approximately at the level of the center of the luminous element 13 on the optical axis 14. The focal point Fov, which lies in the axial plane 22 perpendicular to the contact plane 17, lies approximately at the level of the apex of the reflector facing end region of the luminous element 13 on the optical axis 14. When transitioning from the contact plane 17 to the vertical axial plane 22, the focal point of the parabola resulting in the respective axial longitudinal section "migrates" from the center of the luminous element 13 to the end region of the luminous element 13 pointing towards the reflector apex. In the cross section through the upper part 19 of the reflector 10, an elliptical cutting curve 23 results. The numerical eccentricity of the cutting curve 23 can be varied from the contact plane 17 to the vertical axial plane 22. The numerical eccentricity e of the intersection curve 23 is defined as the ratio of the distance c of the focal point F of the intersection curve 23 from the optical axis 14 to the major semiaxis a of the intersection curve 23, $\text{e = c / a}$

. The eccentricity e of the intersection curve 23 in the region of the contact plane 17 is preferably almost zero, so that the normal intersects the intersection curve 23 and the optical axis 14 Intersection curve 23 is approximately a circle in this area. The eccentricity e of the intersection curve 23 increases in relation to the vertical axial plane 22, that is to say with increasing angle β between a straight line OP connecting a reflector point P with the optical axis 14 and the contact plane 17. The distance between the normal 24 on the intersection curve 23 and the optical axis 14 also increases up to an angle β of approximately 45 °. From an angle β of approximately 45 ° to the vertical axial plane 22 with the angle β = 90 °, the distance between normals 24 on the intersection curve 23 and the optical axis 14 decreases again to approximately zero. The eccentricity e of the intersection curve 23 reaches its maximum value in the vertical axial plane 22.

FIG. 4 shows images of the luminous element 13 which are reflected by the upper part 19 of the reflector 10. The illustrations 25 to 27 of the luminous element 13 are reflected by different areas of the reflector part 19, the normals of the intersection curve resulting in cross section, as described above, each have different distances from the optical axis 14. Due to the above-described formation of the intersection curve, the image 25 of the luminous body 13, which lies at the highest, borders with its upper edge directly on a horizontal section 28 of the light-dark boundary 30. The further illustrations 26 and 27 lie below the light-dark boundary and are relative to the position of the respective reflector region Luminous body 13 inclined with respect to the horizontal. The images 27 a to c are reflected by reflector regions, all of which lie on a common parabola, but are at different distances from the optical axis 14 and therefore reflect images of different sizes. Figures 25 to 27 only come from areas seen in the direction of light emission left half of the upper reflector part 19 in order to maintain the clarity of FIG.

The lower part 20 of the reflector 10 also has a reflection surface in the form of a general paraboloid, the focal point Fuh, the parabola lying in the contact plane 17, as in the upper part 19 being approximately at the center of the luminous element 13 on the optical axis 14. The focal point Fuv, the parabola lying in the vertical axial plane 22, lies at the level of the end region of the luminous body 13 pointing away from the reflector apex on the optical axis 14 "the focal point from the center of the luminous element 13 to its end region pointing away from the reflector apex. Also in the lower part 20, the cross section perpendicular to the optical axis 14 results in an ellipse-like section curve, the eccentricity of which, starting from the contact plane 17, where this is approximately zero, reaches its maximum value in the vertical axial plane 22.

FIG. 5 shows images of the luminous element 13 which are reflected by the lower reflector part 20. The illustrations 32 to 34 of the luminous element 13 are reflected by different areas of the reflector part 20, the normals of the intersection curve resulting in cross section, as described above, each have different distances from the optical axis 14. Due to the above-described design of the intersection curve, the image 32 of the luminous body 13 lying at the highest edge directly borders with its upper edge on a section 36 of the chiaroscuro boundary 30 that rises by an angle α with respect to the horizontal are inclined in relation to the horizontal according to the position of the respective reflector region relative to the luminous element 13. The figures 32 to 34 come only from areas of the left half of the reflector part 20, as seen in the light exit direction, in order to maintain the clarity of FIG. 5.

wobei

${\text{a² = 4 · f}}_{\text{x}}\text{· z}$

und

Dabei sind:

x, y, z

die Koordinaten eines Reflektorpunkts

f_x, f_y

die Brennweiten der in der Berührungsebene 17 bzw. der in der senkrechten Axialebene 22 liegenden Parabeln

c

ein Koeffizient, der zur Anpassung des oberen Beleuchtungsrands an die geforderte Helldunkelgrenze dient

Bei einem Ausführungsbeispiel ist die Mitte des Leuchtkörpers 13 in etwa 24 mm Abstand vom Reflektorscheitel angeordnet. Die Werte der Parameter für den oberen Reflektorteil 19 sind:

${\text{f}}_{\text{x}}{\text{= 23,8, f}}_{\text{y}}\text{= 21,2 mm und c = 1,37}$

Die Werte für den unteren Reflektorteil 20 sind:

${\text{f}}_{\text{x}}{\text{= 23,8 mm , f}}_{\text{y}}\text{= 27,6 mm und c = 0}$

Vom Reflektor 10 wird durch Überlagerung sämtlicher Abbildungen des Leuchtkörpers 13 eine in Figur 6 dargestellte Lichtverteilung erzeugt, die die gesetzlich vorgeschriebene Helldunkelgrenze 30 mit dem auf der Gegenverkehrseite liegenden horizontalen Abschnitt 28 und dem auf der eigenen Fahrbahnseite liegenden, zum Fahrbahnrand hin unter dem Winkel α ansteigenden geneigten Abschnitt 36 aufweist. Die Lichtverteilung ist mittels mehrerer Isolux-Linien 38 dargestellt, das sind Linien gleicher Beleuchtungsstärke.The reflecting surfaces of the upper and lower reflector parts 19 and 20 can be calculated using the mathematical equation given below. First of all, a coordinate system with the origin O in the reflector apex and the optical axis 14 as the z axis is specified. The x-axis of the coordinate system is perpendicular to the z-axis and lies in the contact plane 17. The y-axis of the coordinate system is perpendicular to both the z-axis and the x-axis and is therefore in the vertical axial plane 22. The mathematical equation for determining the reflective surfaces is as follows:

in which

${\text{a² = 4 · f}}_{\text{x}}\text{Z}$

and

Here are:

x, y, z

the coordinates of a reflector point

f _x , f _y

the focal lengths of the parabolas lying in the contact plane 17 or in the vertical axial plane 22

c

a coefficient that is used to adapt the upper lighting margin to the required light / dark limit

In one exemplary embodiment, the center of the luminous element 13 is arranged at a distance of approximately 24 mm from the reflector apex. The values of the parameters for the upper reflector part 19 are:

${\text{f}}_{\text{x}}{\text{= 23.8, f}}_{\text{y}}\text{= 21.2 mm and c = 1.37}$

The values for the lower reflector part 20 are:

${\text{f}}_{\text{x}}{\text{= 23.8 mm, f}}_{\text{y}}\text{= 27.6 mm and c = 0}$

The reflector 10 generates a light distribution shown in FIG. 6 by superimposing all the images of the luminous element 13, which light distribution shows the legally prescribed light / dark limit 30 with the horizontal section 28 on the oncoming traffic side and the horizontal section 28 on the other side of the carriageway and rising towards the edge of the carriageway at an angle α inclined portion 36. The light distribution is shown by means of several Isolux lines 38, which are lines of the same illuminance.

In a variant of the headlamp (not shown), the upper and lower reflector parts 19 and 20 can be constructed from a plurality of sectors, which touch each other in an axial plane and are at least continuous in the first order there, that is to say they merge continuously.

Claims (8)

Low beam headlights for motor vehicles with a reflector (10), a luminous element (13) and a lens (11) covering the light exit opening of the reflector, the reflector (10) having different reflection surfaces in its upper region (19) and in its lower region (20) which, at least in some areas, are part of an at least approximately general paraboloid and are represented by the images of the luminous element (13) to form a light distribution with an approximately horizontal section (28) and a light-dark boundary (36) inclined at an angle α to the horizontal ( 30) are reflected, characterized in that cut sections (23) result in sections through the reflector (10) perpendicular to its optical axis (14), the eccentricity of which can be varied over its circumference in such a way that the highest lying, from the upper reflector area (19) reflected image (25) of the filament (13) with its upper edge borders on the horizontal section (28) of the light-dark boundary (30) and that the image (32) of the luminous element (13) lying at the highest level, reflected by the lower reflector region (20), with its upper edge on the inclined section (36) of the light-dark boundary (30) borders. Low beam headlamp according to Claim 1, characterized in that the eccentricity of the cutting curves (23) increases from approximately zero to the axial plane (22) perpendicular to the contact plane (17), starting from the contact plane (17). Low beam headlamp according to claim 1 or 2, characterized in that the upper reflector region (19) and the lower reflector region (20) touch in an axial plane (17) which is at half the angle of inclination α of the inclined section (36) with respect to the horizontal (16) ) the chiaroscuro boundary (30) and in the same direction as it is inclined. Low beam headlamp according to claim 3, characterized in that the upper reflector region (19) and the lower reflector region (20) have the same cutting curve in their contact plane (17), the focal point of which lies approximately at the center of the luminous element (13). Low beam headlamp according to claim 4, characterized in that the focal point Fov, the intersection curve of the upper reflector region (19) lying in the vertical axial plane (22), is approximately at the level of the end region of the luminous element (13) facing the reflector apex and that the focal point Fuv, the in the vertical axial plane (22) of the intersection curve of the lower reflector region (20) lies approximately at the level of the end region of the luminous element (13) pointing away from the reflector apex. Low beam headlamp according to one of the preceding claims, characterized in that the upper reflector region (19) and / or the lower reflector region (20) consists of several different sectors which are continuously connected to one another at least in the first order. Low beam headlamp according to one of claims 1 to 5, characterized in that the entire upper reflector region (19) and / or the entire lower reflector region (20) has a reflection surface in the form of a general paraboloid. Low beam headlamp according to one of the preceding claims, characterized in that the reflection surface of the upper reflector region (19) and / or the lower reflector region (20) is defined by the following equation in a Cartesian coordinate system:

in which

${\text{a² = 4 · f}}_{\text{x}}\text{Z}$

and

in which:
the z axis is the optical axis,
the x-axis lies in the plane of contact (17),
the y axis is perpendicular to both the x and z axes
x, y, z are the coordinates of a reflector point
f _x , f _{y are} the focal lengths of the intersection curve lying in the contact plane (17) or the axial plane (22) perpendicular thereto
c is a coefficient that serves to adapt the upper edge of the lighting to the required light / dark limit.

Images