GB2115542A

GB2115542A - Headlamp for motor vehicle

Info

Publication number: GB2115542A
Application number: GB08230834A
Authority: GB
Inventors: Milan Cejnek
Original assignee: Autopal sro
Current assignee: Hanon Systems Autopal Services sro
Priority date: 1981-10-28
Filing date: 1982-10-28
Publication date: 1983-09-07
Also published as: CS229071B1; DD232601A3; FR2515311B1; GB2115542B; IT1153603B; FR2515311A1; DE3239861A1; IT8223964A0; SU1390087A1; YU239282A

Abstract

A motor vehicle headlamp comprises a source of light, a reflector for directing light from the source into a beam and a refractor for refracting the beam of light, the refractor including a portion on one side thereof which comprises an array of prismatic elements for refracting the light beam into a particular shape.

Description

SPECIFICATION Headlamp for a motor vehicle The invention relates to a headlamp for a motor vehicle, and in particular to a headlamp comprising a paraboloidal reflector, a refractor and a source of light having a substantially cylindrical shape which is positioned axially in the reflector displaced from the focus thereof in direction away from the origin of the paraboloidal reflector and screened by means of a shade from below.

With known headlamps for vehicles and arrangements thereof, the beam of light produced can be directed too much towards the centre of the road thereby to dazzle the eyes of drivers travelling in the opposite direction. In addition, the range of the beam to illuminate sufficiently the onside edge of the road is limited, typically of the order of 40 m.

A further drawback of known headlamps and arrangements thereof is also the necessity of a relatively accurate side adjustment of the headlamp, as the possibility of dazzling an oncoming driver increases with increasing sharpness of "inside bends" on a road.

The present invention provides a headlamp for a motor vehicle comprising a reflector, a refractor and a source of light having a substantially cylindrical shape and positioned in front of the focus of the reflector and screened from below by means of a shade, the refractor being provided on one side with a concentrating zone delimited by a sector of a circle, the circle being concentric with the centre of the refractor and limited by angles #1, 3 with respect to a vertical line of the headlamp, wherein , lies between 950 and 1200 and #3 lies between 300 and 850 and the concentrating zone of the refractor comprising vertically orientated band prisms, the meniscus profile of each of which in the vertical section is such that its refracting angle (#v) depends upon the polar angle (&num;) and upon the radius (R) in the sections in accordance with the following relationships:- #v1 is between -16 # (#f+q) # f2 # R # # cos#1-# (4 # f2+R2)2 and -48 # (#f+q) # f2 # R # # cos#1-3 # # (4 # f2+R2)2 #=#2=#/2 v2 is between 2 # f # d # -# 4.f2+R2 and 6 # f # d # -3 # # 4.f2+R2 #v3 is between 16#f f2Rcos #3-2fd(4f2+R2) sin #3 +0 (4f2+R2)2 and 48#f f2Rcos #3-#fd(4f2+R2) sin #3 +3.0 (4f2+R2)2 where focus distance of the reflector #f-distance of the source of light from the focus of the reflector length of the substantially cylindrical source of light diameter of the source of light #-angle between the highest edge of the light beam produced by the headlamp and the lowest edge of the light beam, each edge defining the furthest range of the headlamp beam at a respective side of the headlamp, at the lower portion of the concentrating zone this vertical refracting angle is #=#1 on the side of the lower part of the headlamp, and for sections #=#2 and #1=#3 on the side of the upper part of the headlamp for v2=1 and V3=+ 1, and on the side of the lower part of the headlamp for çkV2=+ 1 and V3=1.

and in the horizontal section the prismatic profile with the base on the side (-Z) of the headlamp nearer the edge of the road the refracting angle #h which is in section varies as: is is between 0 and (-tg#1)(#v1+2#) where E is between arctg (0.005) and arctg (0.025), #=#2=#/2 #h2 is between 4f/8#f fR-d(4f2-R2)/ #-2# (42+R2)2 and 32#f f2R (4f2+R2)2 #=#3 #h3 is between 4f /8Af fR-d(4f2-R2)/ sin 320 (4f2-R2)2 and 32Mf2R sin #3 (42+R2)2 The present invention further provides a headlamp for a motor vehicle comprising a source of light, a reflector for directing light from the source into a beam and a reflector for refracting the beam of light, the refractor including a portion on one side thereof which comprises an array of prismatic elements for refracting the light beam into a particular shape.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 a shows a vertical section through a headlamp according to the present invention; Fig. 1 b shows a front view of the headlamp of Fig. 1a; Fig. 2a shows an enlarged view of a portion of the front of the headlamp as shown in Fig. 1 b; Fig. 2b shows a vertical section through a headlamp refractor shown in Figure 2a; Fig. 3 shows schematically on a plane of projection, which is normal to the optical axis of the headlamp of Fig. 1 a when mounted in a vehicle, a perspective projection of a straight road showing schematically the effect of the use of a headlamp according to the present invention;; Fig. 4 shows schematically a plan view of a road and the approximate distributions of light when produced by headlamps according to the present invention and by known headlamps; Fig. 5 shows schematically a similar situation to that shown in Fig. 3 in which the road is curved and the vehicle in which a headlamp according to the present invention is mounted is travelling on the inside of the curve such that the optical axis of the headlamp is orientated towards the off-side edge of the road.

In the following description, it is assumed that the headlamps are mounted in a vehicle intended to be driven on the right hand side of a road. However, the headlamps of the present invention may be readily adapted for use in vehicles intended to be driven on the left hand side of a road.

Fig. 1 a shows a headlamp in accordance with the present invention comprising a substantially paraboloidal reflector 1, having a focal length f, a focus F, a refractor 2, a light source 3 having approximately a cylindrical shape with a length q and a diameter d. The light source 3 is situated in the reflector 1 along the axis thereof spaced away from the focus F of the reflector by a distance Af and screened from below by means of an opaque shade 4.

In the drawings, the headlamp is shown situated in a rectangular coordinate system having mutually orthogonal axes X, Y and Z with the origin of the paraboloid of the reflector 1 coincident with the origin of the coordinate system and the optical axis of the headlamp lying along the axis x. As shown in Fig. 1 b the refractor 2 is provided with a concentrating zone 5 approximately in a shape of an angular sector of a circle being concentric with the centre of the refractor 2 and limited by radial edges thereof which are, respectively at angles #1 and 3 to the upper (positive) vertical axis y of the headlamp, the relationship being:: #3 is between 30O and 850 &num;, is between 950 and 1200 The concentrating zone 5 of the refractor 2, shown enlarged in Figs. 2a and 2b, consists of vertically orientated band prisms, the meniscus profile of which in the vertical section B-B is as shown in Fig. 2b with the refracting angle v being dependent upon the angle #=-arctg (Z/y) and upon the polar radius R=(y2+z2)1/2, determined in the section according to the following relationships:: #v1 is between -16 # (#f+q) # f2 # R # # cos #1-# (4 # f2 + R2)2 and -48 # (#f+q) # f2 # R # # cos #1,-3# #; (4 # f2+R2)2 #=#2=#/2 #v2 is between 2 # f # d -O 4 # f2+R2 and 6 # f # d -3.0 4 # f2+R2 #=#3 #v3 is between 1 6Af f2R cos #3-2fd(4f2+R2) sin 3 #+# (42+R2)2 and 48#f f2R cos #2-#fd(4f2+R2) sin #3 +3.6 (4 # f2+R2) where #=the angle between the highest edge of the light beam produced by the headlamp and the lowest edge of the light beam, each edge defining the furthest range of the headlamp beams at a respective side of the headlamp.

with 0=between 0 and arctg (0.025).

At the lower portion of the concentrating zone the vertical refracting angle v is for the section #=#1 on the negative side (-y) of the lower part of the headlamp, and for the section #1=#2=#/2 and #=#3 on the positive side (+y) of the upper part of the headlamp for #v2=-1 and #v3=+1, and on the negative side by of the lower part of the headlamp for #v2=+1 and #v3=-1.

In the horizontal section C-C the prismatic profile on the side -z of the headlamp, the refracting angle (#h) is dependent upon polar coordinates #, R in the relation; #h1 is between 0 and (-tg#1)(#v1+2#) where E is between arctf (0.005) and arctg (0.025), #=#2=#/2 #h2 is between 4f/8#f fR-d(4f2-R2)/ # -2# (4f2+R2)2 and 32af fZR (4f2+R2)2 #=#3 #h3 is between 4 # f/8#f fR-d(4f2-R2)/ sin -26 (4f2-R2)2 and 32Aff2R sin 3 (4f2+R2)2 where E=setting-up vertical angle Dioptric elements of the concentrating zone 5 of the refractor 2, when shaped in this way, adjust the beam of light originating from light source 13 which has been reflected by reflector 1 so as to achieve the required shaping of the beam of light into a zig-zag shape or the shape of a "Z".

In Fig. 3 a perspective projection of the left L, central C and right R lines of a road is shown with the plane of the drawing being normal to the optical axis x of a headlamp of a vehicle on the road. The direction of the eyes of an oncoming driver is represented by a line Y and the horizontal line of the headlamp z, is inclined with respect to the road plane by an angle E; the transition between light and dark on the side of the nearer edge of the road is further than that nearer the centre of the road and is raised, with respect to this horizontal line z, through an angle 6. The dazzling zone 111 is delimited also by a zig-zag shape or a "Z" shape from below in the way as is shown by the hatching. The two horizontal lines delimiting the lower edge of the dazzling zone are joined by a line at approximately 450 thereto.The zone of increased visibility DV is evident from the course of a dashed line S representing the transition between light and dark of a known headlamp arrangement and from the couse of the solid zig-zag line representing the transition between light and dark of a headlamp according to the invention. The increase of the distance of the transition between light and dark with a headlamp of the present invention is more evident with a decrease in the angle t of the connection of the horizontal lines of the transition between light and dark. For a typical driving situation the zone DV has a length of greater than 40 m at the nearer edge of the road, the distance being defined by the difference between transition between light and dark along the road at each edge of the road.

The increase of the throw of light along the road from a headlamp according to the invention is also shown in Fig. 4, where there is shown a plan of a road having a width W and a length L, onto which, for various values of vertical adjustment E=0,59/o, 1%, 2,5% (representing the inclination of the vertical axis of the headlamp to the vertical) the transition between light and dark for a vehicle containing two headlamps according to the present invention, is shown.

The light beams produced by known headlamp arrangements and the transition between light and dark for them are shown by dashed lines in each case. It may be seen that the light beam produced by the headlamps and having a zig-zag shape provides a considerable increase in the throw of light along the road than is achievable by a known headlamp system, and thus an increase in the distance of visibility of a driver is made possible.

In Fig. 5 there is shown the reduction of the dazzling of the eyes of a driver of an oncoming vehicle when the vehicle having the headlamps is being driven around the inside of a corner. In the plane which is perpendicular to the optical axis x of the headlamps in the vehicle, a perspective projection of the road is shown wherein the vertical line y of the light beam is shifted relatively towards the remoter edge of the road due to the effect of the vehicle travelling around the corner. Known headlamp systems result in dazzle, in the area G between the crossing point of the line S representing the transition between light and dark and the line Y representing line of vision of the oncoming driver and including the centre line of the road due to the asymmetric nature of the light distribution along the road.In the zone Go dazzle may occur with known headlamp systems, the zone Go being delimited by a crossing point of the line S with a plane which is parallel to the plane of the road and includes the focus F of the headlamp. With headlamps according to the invention this dazzle is substantially eliminated completely if the angle of inclination E of the headlamp is greater than the angle 6 which represents the difference in the angles of the inclination of the transition between light and dark which define the zigzag shape of the overall light distribution pattern. When E is less than the angle 6 the dazzle is substantially reduced to a minimum, due to the zig-zag distribution of light.

In a preferred embodiment of the invention the transition between light and dark is in a zig-zag shape or the shape "Z" so that on the side of the nearer edge of the road the light is projected further from the vehicle than at the centre of the road. The required effect is produced by means of the directional effect on the beam of light from the bulb in the headlamp by dioptical elements of the refractor.

In preferred embodiments of the present invention in the headlamp the beam of light from the reflector is shaped by means of dioptrical elements in a concentrating zone of the reflector, the zone being shaped as a sector of a circle, and covering at least a central horizontal line of the reflector on the side of the remoter edge of the road i.e. towards the centre of the road, the side being dependent upon whether the vehicle is intended for use on the left hand or right hand side of the road. The transition between light and dark i.e. the edge of the light beam is in the shape of a zig-zag or in the shape of "Z" so that it is approximately horizontal even on the side of the nearer edge of the road, and at this side it is shifted upwardly with respect to the transition on the opposite side of the road.In this way the possibility of dazzling the eyes of drivers of oncoming vehicles is substantially eliminated. The distance of throw or the geometric reach of the light beam is increased as well, so that for example at the centre of the zig-zag where the central line is inclined to the two substantially horizontal lines at an angle of 45 degrees, the increase achieved, independently of the vertical inclination of the headlamp with respect to a known headlamp, is at the nearer edge of the road, a factor of two and at the horizontal line cutting the plane normal to the road and passing the nearer edge a factor of 3,75.

In a preferred embodiment of the present invention the luminous intensity of the light beam from the headlamp is increased in the area of the nearer edge of the road, especially when the distance of the geometric reach is greater than approximately 40 m from the vehicle; resulting in an increase in the distance of safe and sufficient visibility due to an increase in the illumination of the edge of the road.

This results in increased visibility of the driver and thus an increase in the maximum speed for safety when driving at night and in conditions of poor visibility. Another advantage of the headlamp according to the invention resides in the possibility of increasing the range of tolerance of side adjustment of the headlamp. In addition for headlamps with a dipped and main beam facility, there is the possibility of having a long distance light beam having a higher homogenity of luminous intensity which arises due to the meniscus vertical profile of the dioptric elements in the concentrating zone of the refractor.

Claims

1. A headlamp for a motor vehicle comprising a reflector, a refractor and a source of light having a substantially cylindrical shape and positioned in front of the focus of the reflector and screened from below by means of a shade, the refractor being provided on one side with a concentrating zone delimited by a sector of a circle, the circle being concentric with the centre of the refractor and limited by angles &num;" #1,#3 with respect to a vertical line of the headlamp, wherein &num;,, lies between 950 and 1200 and #3 lies between 300 and 850, the concentrating zone of the refractor comprising vertically orientated band prisms, the meniscus profile of each of which in the vertical section is such that its refracting angle (r) depends upon the polar angle (&num;;) and upon the radius (R) in the sections in accordance with the following relationships: #v1 is between -16 # (#f+q) # f2 # R cos i6 (4 f2+R2)

2 and -48 (Af+q) f2 @2 R # # cos #1-3 # #; (4 # f2+R2)2 #2=#/2 is is between 2 # f # d -O

4.f2+R2 and 6 # f # d -3 0;; 4 # f2+R22 #=#3 #v3 is between 1 6Af f2Rcos 3-2fd(4f2+R2) sin 3 +6 (4f2+R2)2 and 48#ff2Rcos #3-#fd(4f2+R2) sin #3 +3-fl (4f2+R2)2 where focus distance of the reflector Af-distance of the source of the light from the focus of the reflector q-length of the substantially cylindrical source of light ddiameter of the source of light wangle between the highest edge of the light beam produced by the headlamp and the lowest edge of the light beam, each defining the furthest range of the headlamp beam at a respective side of the headlamp at the lower portion of the concentrating zone this vertical refracting angle is +=+, on the side of the lower port of the headlamp, and for sections #=#2 and #=#3 on the side of the upper part of the headlamp for #v2=-1 and #v3+1, and on the side of the lower port of the headlamp for v2=+ 1 and #v3=-1.

and in the horizontal section the prismatic profile with the base on the side (-Z) of the headlamp nearer the edge of the road, the refracting angle #h of which is fn sections varies as: is between O and (-tg#1)(#v1+2#) where E is between arctg (0.005) and arctg (0.025), # 2 is is between 4f/8Af fR -d(4f2-R2)/ -2# (4f2+R2)2 and 32Af f2R (4f2+R2)2 #=#3 #h3 is between 4f/8#fR-d(4f2-R2)/ # sin #3-2# (4f2-R2)2 and 32#f f2R sin #3 (4f2+R2)2 2.A headlamp as in claim 1, wherein refracting angles of a vertical (+v) profile and horizontal (&num;h) one of band prisms of the concentrating zone of the refractor vary between reference sections #=#1, #2, #3, in a continuous way or in a discrete way.

3. A headiamp as in claims 1 and 2, wherein the angle (#) of the vertical set-out of the horizonal lines of the border of light and dark of the light beam is as follows 6 is between 0 and arctg (0.025)

4. A headlamp for a motor vehicle comprising a source of light, a reflector for directing light from the source into a beam and a refractor for refracting the beam of light, the refractor including a portion on one side thereof which comprises an array of prismatic elements for refracting the light beam into a particular shape.

5. A headlamp according to claim 4, wherein the portion is an angular segment of a circle having its centre being disposed along the optical axis of the headlamp.

6. A headlamp according to claim 4 or 5, wherein the prismatic elements are parallel and disposed substantially vertical in the headlamp.

7. A headlamp according to claim 6, wherein at the inner face of each prismatic element is inclined about a vertical axis towards the optical axis of the headlamp and each prismatic element is shaped as a substantially meniscus lens.

8. A headlamp according to claim 7 where a radial line defining an upper edge of the portion is inclined at an angle of between 30 and 85 degrees to the vertical and a radial line defining a lower edge of the portion is inclined at an angle of between 95 and 120 degrees to the vertical, the portion being disposed so as to include the horizonal line through the optical axis of the headlamp.

9. A headlamp according to claim 8 wherein the source of light is a cylindrical electric bulb with its longitudinal axis lying along the optical axis of the headlamp.

1 0. A headlamp according to claim 9 wherein the bulb is located forwardly of the focal point of the reflector.

1 A headlamp according to claim 10, further comprising an opaque shade which substantially covers the lower portion of the bulb.

12. A headlamp according to claim 1 wherein the reflector is substantially paraboloidal, the axis of revolution being disposed along the optical axis of the headlamp.

13. A headlamp substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.