GB1570808A

GB1570808A - Headlight for motor vehicles

Info

Publication number: GB1570808A
Application number: GB35720/77A
Authority: GB
Original assignee: Autopal sro
Current assignee: Hanon Systems Autopal Services sro
Priority date: 1976-09-01
Filing date: 1977-08-25
Publication date: 1980-07-09
Also published as: IT1087363B; DE2738622C2; DE2738622A1; FR2363758B1; DD131539A1; SU752118A1; CS188521B1; FR2363758A1

Description

(54) HEADLIGHT FOR MOTOR VEHICLES (71) We, AUTOPAL, narodni podnik of Novy Jicin, Czechoslovakia, a corporation organized and existing under the laws of the Czechoslovak Socialist Republic, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: The invention relates to a headlight for motor vehicles which may be defined as an optical system consisting of a concave reflector, of a head lens and of electric sources for a lower beam and distance one.The design of the headlight provides an increase of light efficiency because of increasing its engagement angle, a lighting of road verges or kerbs by means of a proper scattering of light from the reflector and it also reduces the intensity of glare from edges of the headlight, especially in transitions of paraboloids and section planes of a rectangular headlight, where a vector, of a tangential shift of section planes forms with a horizontal axis plane the maximum angle.

A reflector is the most complicated part of a headlight and especially if it is a rectangular headlight since this is difficult to manufacture with an accurate reflector shape with a sufficiently great engagement angle. In the sides of this reflector some shape deformation may occur which disturb regularities of projection of elemental picture of light sources and they cause an inadmissible increase of glare. This problem is solved in hitherto known headlights in that they are provided with a shallow reflector having a large focal distance and a maximum diffusion light by means of diffuser profile in dangerous zones, that causes a decreased light efficiency of such a reflector because its linear engagement angle is diminished and a more arduous mode of producing the diffuser is needed because of its deep profile of cylindrical lenses.

Other headlights shade the light coming from the source to the critical area of the reflector by means of a dispersion shade that causes a reduction in light efficiency and an increase of heat stress in such a headlight.

According to the present invention there is provided a headlight for motor vehicles, the headlight comprising a reflector, a head lens and a bulb provided with a distance beam filament, a lower beam filament and an internal mask, wherein the reflector has a first peripheral portion shaped as a first paraboloid merging with a second apical portion shaped as a second paraboloid, the focal distance of the first paraboloid being shorter than the focal distance of the second paraboloid, and the focal point of the first paraboloid lying between the distance beam filament of said bulb and the apex of said second paraboloid.

In this case the reflector is provided not only with a main reflection surface having a main focus Fh, but also with another paraboloid surface in the side having a focus F0. The value of the peripheral focus distance fo is shorter than the value of the main one fh (fo < fh). So an engagement angle 5 as well as a light efficiency are increased at keeping the same outlet radius R. There is also designed a head lens edge through which there passes the light affected by a shift a on the side paraboloid, so that the depth of the profile may be diminished, what causes a decrease of stress as well as a better production technology of the head lens.Because of this shift, the light beams from upper corners of the reflector become partially or completely convergent even at distance lighting of the headlight, and that is why it may be advantageously applied for a long range lighting of the road what cannot be done of it concerns ordinary headlights. As to the glare it is evident that in critical areas of upper corners of the headlight the vector of a tangential shift forms with a horizontal line a maximum angles, so that at a definite value of the shift a the light will be prevented from penetrating over the transition plane between light and dark and so the glare will not come in question.

In order that the invention may be clearly understood and readily carried into effect, a preferred embodiment thereof is, by way of example, hereinafter more fully described and illustrated in the accompanying drawings, in which: Figure 1 shows a horizontal section of a headlight.

Figure 2 shows a face view of a headlight.

Figure 3 shows a lower beam of the headlight from its side area.

Figure 4 shows a distance beam of the headlight from its side area.

In Fig. 1 there is a horizontal section of a headlight according to the invention which consists of a reflector 1, head lens 2 and bulb 3 with a distance beam filament 6, lower beam filament 5 and inner shade 4 of a bulb 3. A coordinate system is situated in the vertex of the main paraboloid having the axisx in its axis.

The distance of vertexes of paraboloids Ax is as follows: Ax = (yp/2) .(1/fo- 1/fh) (1) yp - a coordinate of the point P(xp,yp), where both paraboloids intersect fO - a focal distance of the side paraboloid fh - a focal distance of the main paraboloid The vertex portion of the side paraboloid as well as the marginal portion of the main paraboloid are imaginary. The profile is given by the vertex surface of the main paraboloid and by the marginal surface of the side paraboloid.

An engagement angle of an ordinary headlight is defined by:

The increase of an engagement angle increasing the light efficiency of the headlight at the same outlet radius R is defined by:

If the distance A Xf of focuses Fo and Fh iS defined as: AXF = fh-fo + Ax (4) then the increase of convergence a f of the ray going from the focus Fh to the reflexion on the side paraboloid is as follows (af is an angle formed by the ray and the reflector axis)

x,ye - coordinates of the reflexion point The angle a of a tengential shift ls::

a - a distance of the respective axis point of the filament from the focus Fh.

The equation (5) makes clear that in comparision to hitherto known headlights the side diffusion is determined by the side edge of the reflector. This fact may be advantageously applied for rectangular headlights, where - with respect to their horizontal cut-off - an undesired loss of light does not come in question by a vertical shift.

In Fig. 2, there is an side zone limited by section planes and cylindrical surfaces having an outlet radius R and a radiusyp of the contact of both paraboloids. An angle which is formed by a vector of shift sp and by the horizontal axis plane, is marked as ss and it makes possible to decompose the shift to a horizontal component ah and vertical component a: ah = a cos sp; av = a sin cp The desired beam is formed by the marginal portion of the reflector and scattered by the corresponding portion of the head lens.

The light shift through the edge of the reflector 1 is preferably taken into consideration in the design of the side zone of the head lens2 which is divided to an areas andli between the horizontal axis plane and upper section plane, to an area III between a horizontal axis plane H-H and half plane turned under it through an angle 15 round the axis x at the side of an asymmetric cut-out of the inner shade 4 of the bulb 3, to an area IV between the arealll and a lower section plane and to an area V between the horizontal axis plane and lower section plane of the headlight. In the areas I and II there are situated vertical strip lenses or prisms, which diffuse the light horizontally. The area III is not provided with a profile, the areas Iv and V are provided with strip prisms having their base at the side of the headlight edge.

Fig. 3 shows a lower beam from the side area of the reflector. A light picture without a light shift by means of an edge paraboloid is drawn with a dash line, and a light picture according to the invention is drawn with a solid line. A light beam from a clear area III makes stronger the lighting of the nearer verge of the road, so that driving around bends is safer even with poor visibility.Light beams from the area I and II are scattered by means of a head lens horizontally in the direction of arrows; the vertical component of the shift a v according to the equation (7) has a minimum value if it takes place near the horizontal axis plane, and so the reach of the headlight is not worsened, but near the transitions of the paraboloid in the upper section plane, where shape deformations of the reflector take place, the said vertical component has the maximum value, so that the difference of the convergence Aavmax of the filament face which is near to the focus Fh of the headlight according to the invention and of the headlight without a shift is a sufficient reserve for their compensation.

So the light is prevented to penetrate over the dividing line of light and dark, and the glare does not come in question.

In Fig. 4 there is shown a distance beam of a filament 6. The beam, originally a divergent one is changed by a shift a to a beam partially or fully convergent. Light beams from areas I and II are shifted by a shift on the side paraboloid from the space over the horizontal axis plane to the road and after a long range diffusion by means of the head lens 2 in a horizontal direction they ensure a perfect lighting of road verges at a distance operation of the headlight, what does not come in question if it concerns hitherto known headlights. The light beam from the area III illuminates the right side of the road over the horizontal axis plane, and a decreased luminous intensity on the side of the coming counterdriver decreases a possibility of glare of the driver if the distance beam is switched over to the lower beam too late.Light beams from areas and V are directed in the optical axis x of the headlight and under it by means of strip prisms what results in increasing the axis luminous intensity of the headlight, in improving the relation between this axial luminous intensity to the maximum one, and in increasing the lighting intensity of the road as to the distance 100 m and more.

Although the invention is illustrated and described with reference to one preferred embodiment thereof, it is to be expressly understood that it is in no way limited to the disclosure of such a preferred embodiment, but it is capable of modifications within the scope of the appended claims.

WHAT WE CLAIM IS: 1. A headlight for motor vehicles comprising a reflector, a head lens and a bulb provided with a distance beam filament, a lower beam filament and an internal mask, wherein the reflector has a first peripheral portion shaped as a first paraboloid merging with a second apical portion shaped as a second paraboloid, the focal distance of the first paraboloid being shorter than the focal distance of the second paraboloid, and the focal point of the first paraboloid lying between the distance beam filament of said bulb and the apex of said second paraboloid.

2. A headlight according to claim 1, wherein the head lens is provided with a clear area, without any profile, being situated in an area (III) limited by an arc of an outlet radius (R), by an arc of a radius (yp) in the transition of both paraboloids, by a horizontal plane (H-H) and by a semi plane on the side of an asymmetric cut out of the lower beam filament turned below the horizontal plane (H-H) through an angle 150 about the axis (x).

3. A headlight according to claim 1, wherein the diffuser is provided with strip prisms the bases of which are on the side of the headlight edge, the strip prisms are situated in an area (IV) which is limited by arc according to claim 2, by an area (III) according to claim 2, by a lower section of the horizontal plane of the reflector, and in an area (V) which is limited by arc according to claim 2, by a horizontal plane (H-H) and by a lower section of the horizontal plane of the reflector of the headlight.

4. A headlight for a motor vehicle as claimed in claim 1, substantially as hereinbefore described.

5. A headlight for a motor vehicle, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. visibility. Light beams from the area I and II are scattered by means of a head lens horizontally in the direction of arrows; the vertical component of the shift a v according to the equation (7) has a minimum value if it takes place near the horizontal axis plane, and so the reach of the headlight is not worsened, but near the transitions of the paraboloid in the upper section plane, where shape deformations of the reflector take place, the said vertical component has the maximum value, so that the difference of the convergence Aavmax of the filament face which is near to the focus Fh of the headlight according to the invention and of the headlight without a shift is a sufficient reserve for their compensation. So the light is prevented to penetrate over the dividing line of light and dark, and the glare does not come in question. In Fig. 4 there is shown a distance beam of a filament 6. The beam, originally a divergent one is changed by a shift a to a beam partially or fully convergent. Light beams from areas I and II are shifted by a shift on the side paraboloid from the space over the horizontal axis plane to the road and after a long range diffusion by means of the head lens 2 in a horizontal direction they ensure a perfect lighting of road verges at a distance operation of the headlight, what does not come in question if it concerns hitherto known headlights. The light beam from the area III illuminates the right side of the road over the horizontal axis plane, and a decreased luminous intensity on the side of the coming counterdriver decreases a possibility of glare of the driver if the distance beam is switched over to the lower beam too late.Light beams from areas and V are directed in the optical axis x of the headlight and under it by means of strip prisms what results in increasing the axis luminous intensity of the headlight, in improving the relation between this axial luminous intensity to the maximum one, and in increasing the lighting intensity of the road as to the distance 100 m and more. Although the invention is illustrated and described with reference to one preferred embodiment thereof, it is to be expressly understood that it is in no way limited to the disclosure of such a preferred embodiment, but it is capable of modifications within the scope of the appended claims. WHAT WE CLAIM IS:

1. A headlight for motor vehicles comprising a reflector, a head lens and a bulb provided with a distance beam filament, a lower beam filament and an internal mask, wherein the reflector has a first peripheral portion shaped as a first paraboloid merging with a second apical portion shaped as a second paraboloid, the focal distance of the first paraboloid being shorter than the focal distance of the second paraboloid, and the focal point of the first paraboloid lying between the distance beam filament of said bulb and the apex of said second paraboloid.