GB2149077A

GB2149077A - Headlamp for dipped light in motor vehicles

Info

Publication number: GB2149077A
Application number: GB08425108A
Authority: GB
Inventors: Christian Leitar; Gerhard Lindae; Jean-Francios Longchamp; Peter Perthus
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1983-11-04
Filing date: 1984-10-04
Publication date: 1985-06-05
Also published as: SE8405490D0; DE3339879A1; SE8405490L; GB8425108D0; GB2149077B; SE448652B; DE3339879C2; FR2554546A1; FR2554546B1

Abstract

The inner focal point (23) of the vertical ellipse (22) of the reflector (10) lies in the incandescent coil (12), and the outer focal point (24) in immediate proximity to the plane of the light exit aperture. The focal length of the horizontal ellipse (32) is shorter than that of the vertical ellipse (22), and the focal point interval of the horizontal ellipse (32) greater than that of the vertical ellipse (22), by a factor of 2:1. An upper shutter (58) is displaced in the direction of the x-axis (11) relative to the shutter (53) and is not curved. A filter (60) is arranged in front of the objective (15), and both consist of pressed glass with a surface constitution producing the blurring of the light-dark limit. With the headlamp, the range and the lateral scattering of the dipped light beam are increased and the overall length of the headlamp is reduced. <IMAGE>

Description

SPECIFICATION Headlamp for dipped light in motor vehicles The invention relates to a further development of the headlamp for dipped light in motor vehicles according to Patent Application P 33 34 459.0, and it adopts the aim to improve the range and lateral scattering of the dipped light and also to reduce the overall depth of the headlamp relative to the direction of travel.

This aim is achieved substantially by the combination of features of Claim 1. The underlying idea of the invention is to reflect the rays from the region of the horizontal meridian section intensified to the x-axis, so that the efficiency of the headlamp is increased without enlarging the objective. Furthermore, the meridian sections arranged between the vertical and horizontal meridian section are curves which exhibit the optical behaviour of ellipses in the optically utilised region, that is to say that the light rays generated in the region of the x-axis of the incandescent coil, after their reflection by the reflector, are reflected back in a longer section to the x-axis outside the reflector.

Advantageous further developments and improvements of the invention are described in the subordinate Claims. By Claim 2, the spherical aberration is reduced and the imageforming sharpness of the headlamp system increased; this reduction and increase is further improved by Claim 3. In this case the size of the circle of summit of curvature is a function of the focal length of the objective, and its construction is a factor in determining the curvature of the optically effective edge.

Motor vehicles having a soft suspension and/or a short wheel base cause pitching movements of the headlamp, inter alia, and also a jumping of the dipped light beam backwards and forwards on the road; this jumping, which is characterised as a dynamic variation of contrast, disturbs the vehicles driver in the threshold region of his subjective perception. This disturbance is eliminated, or greatlyalleviated by Claim 4,and in an improved form by Claim 5.

By Claim 6, and by Claim 7 and 8 as a further development, a horizontal light slit is formed, the height of which produces the required light distribution. The position of the upper shutter is chosen in this case so that a strong blurring is produced in the associated region of the light beam, which forms a continuous light transition. If, according to claim 9, the surface of the objective is for example not polished, then the transmission of the light rays is no longer unidirectional, so that the scattering indicatrix is broadened in a desirable manner.

An exemplary embodiment of the invention is illustrated in the drawing and explained more fully in the description of the Figure.

The sole Figure shows a headlamp for dipped light in motor vehicles in a single perspective view relative to the x-axis.

Description of the Exemplary Embodiment A headlamp for dipped light in motor vehicles has a reflector 10 with a reflector axis 11, with an incandescent coil 1 2 arranged thereon, with a shutter 53 having an optically effective edge 54, which shapes the light-dark limit of the crude light beam which is formed by the light rays generated by the incandescent coil 1 2 and reflected by the reflector 10.

An objective 1 5 constructed as a biconvex lens is arranged in front of the shutter 53 and approximately parallel to the latter.

The vertical meridian section 21 is a part of a vertical ellipse 22 having its inner focal point 23 in the incandescent coil 1 2 and having its outer focal point 24 in immediate proximity of the plane of the light exit aperture 36. The horizontal meridian section 31 is a part of a horizontal ellipse 32 having its inner focal point 33 in the region of the incandescent coil 12, preferably between the incandescent coil 1 2 and the summit 25/35.

The focal length of the horizontal ellipse 32 is also shorter than the focal length of the vertical ellipse 22.

The focal point interval, that is to say the interval of the two associated focal points, of the horizontal ellipse 32, is greater than the focal point interval of the vertical ellipse 22, namely approximately in the ratio 2:1.

The shutter 53 and its optically effective edge 54 is curved relative to the yz-plane so that the summit of the curvature lies in the region of the x-axis 11 and points towards the reflector 1 0. The curvature of the edge 54 has the shape of a parabola with a circle of summit of curvature, the radius of which is equal to 0.4 to 0.7 times the focal length of the objective 1 5.

The shutter 53, and particularly its optically effective edge 54, has a median region 55-preferably three degrees on each side of this plane-with a high image-forming sharpness; this is adjoined by a right-hand and lefthand lateral region 56, 57 with a low imageforming sharpness. Both lateral regions exhibit either an increase in the focal length of the parabola, only one half of which is illustrated at 56 in the drawing, or else they are tangents adjoining the median section 55, only half of which is likewise shown at 57. The optical effect of the edge 54 of the shutter 53 is created either by modifying the optimum image-forming interval of the shutter 53 to the objective 15, or by roughening the edge 54.

An upper shutter 58, which is arranged above the edge 54 of the shutter 53, is displaced in the direction of the x-axis 11 relative to the edge 54 and is not curved relative to the yz-plane. The optically effective edge 59 of the upper shutter 58 is curved relative to the xy-plane. The shutter 58 reduces the dipped light beam in the foreground of motor vehicle.

The objective 1 5 is an unpolished pressed glass with such a surface constitution that the image-forming quality of the objective 1 5 produces the required blurring of the light-dark limit of the dipped light beam. A weakly lightdispersing filter 60, which is arranged in front of the objective 1 5 in the ray direction 61, likewise consists of pressed glass, and its surface constitution produces a blurring of the light-dark limit in the same manner.

Claims

1. Headlamp for dipped light in motor vehicles having: a) a reflector reflects the light rays generated by an incandescent coil and forming the crude light beam, b) the vertical and horizontal meridian section of the reflector are conic section curves, c) a shutter is arranged in front of the reflector in the ray path of the crude light beam, the optically effective edge of which shapes the light-dark limit of the light beam, d) an objective forming an image of the light beam is arranged in front of the shutter, wherein:: e) the vertical meridian section is a part of a vertical ellipse having its inner focal point in the region of the incandescent coil and having its outer focal point in the region of the shutter, f) the horizontal meridian section is a part of a horizontal ellipse having its inner focal point in the region of the incandescent coil and having its outer focal point in the region of the objective, characterised by: g) of the vertical ellipse (22), the inner focal point (23) lies in the incandescent coil (12) and the outer focal point (24) in the immediate proximity of the plane of the light exit aperture 36 of the reflector (10).

h) the focal length of the horizontal ellipse (32) is shorter than that of the vertical ellipse 22, i) the mutual interval of the two focal points (focal point interval) of the horizontal ellipse (32) is greater than that of the vertical ellipse (22), j) the focal point interval of the vertical ellipse (22) is in the ratio of 1:2 to the focal point interval of the horizontal ellipse (32).

2. Headlamp according to Claim 1, characterised by: k) at least the optically effective edge (54) of the shutter (53+preferably also the shut ter (53)--is is curved relative to the yz-plane, I) the summit of the curvature lies in the region of the x-axis (11) and points towards the reflector (10).

3. Headlamp according to Claim 2, characterised by: m) the curvature of the optically effective edge (54) of the shutter (53) has the shape of a parabola, n) the radius of the circle of summit of curvature of the parabola is 0.4 to 0.7 times the focal length of the objective (15).

4. Headlamp according to claim 3, characterised by: o) the optically effective edge (54) of the shutter (53) - preferably also the shutter (53)-has a median region (55) symmetrical to the xz-plane--preferably three degrees on each side of this plane--having a greater image forming sharpness and an adjoining right-hand and left-hand lateral region (56, 57) of lesser image-forming sharpness, p) both lateral regions (56, 57) exhibit either an increase in the focal length of the parabola or else they are tangents adjacent to the median section (55).

5. Headlamp according to any of the abovementioned Claims, characterised by: q) the optical effect of the edge (54) of the shutter (53) is created either by modification of the optical image-forming interval of the shutter (53) to the objective (15) or by roughening the optically effective edge (54).

6. Headlamp according to any of the abovementioned. Claims, characterised by: r) a shutter (58) reducing the dipped light beam in the foreground of the motor vehicle is arranged above the optically effective edge (54) of the shutter (53).

7. Headlamp according to Claim 6, characterised by: s) the optically effective edge (59) of the upper shutter (58) is curved relative to the xyplane.

8. Headlamp according to Claim 6 or 7, characterised by: t) the upper shutter (58) is displaced in the direction of the x-axis (11) relative to the edge (54) of the shutter (53), u) the upper shutter (58) is not curved relative to the yz-plane.

9. Headlamp according to any of the abovementioned Claims, characterised by: v) the surface constitution of the objective (15) is such that the image-forming quality produces the required blurring of the lightdark limit.

10. Headlamp according to any of the above-mentioned Claims, characterised by: w) a filter (60), preferably a weakly lightdispersing filter, is arranged in front of the objective (15) in the ray direction (61), x) the filter (60) consists of pressed glass and exhibits a surface constitution which produces the required blurring of the light-dark limit.

11. A headlamp substantially as herein described with reference to the accompanying drawing.