Headlamp for Motor Vehicles

The invention relates to a projection-type headlamp for motor vehicles, the headlamp having an increased luminous intensity of passing light beam above the light and darkness boundary as well as an improved penetration of light into fog.

With well-known elliptic-dioptric headlamps comprising an elliptic reflector, a screen and a lens, the lens is designed for throwing the light beam from the reflector in such a way that it is almost fully directed to below the horizontal plane so that the luminous intensity above said plane is of a minimum value. This admittedly leads to a reduction of dazzling the drivers of passing cars but, onthe other hand, due to to a poor illumination, the perception of vertical traffic signs or signals is limited, since the brightness of communicative surfaces of such signs, if illuminated by such headlamps, becomes relatively low. Apart from this, such reduced luminous intensity above the light and darkness boundary does not enable the driver to sufficiently control his activity in the upper part of his operative space. This may negatively influence any travel on untreated and unlit roads, and particularly in the absence of the so-called silhouette vision created by the lights of passing cars.

It is an object of the present invention to eliminate the drawbacks of prior art as hereinabove referred to and to provide an improved headlamp comprising a concave reflector which is designed to integrate light generated by a light source. In front of the reflector there is provided a screen to define and form the upper part of the beam of passing light, or of the fog light, and an objective to image a contract of brilliance of the screen surface on the light reflector background onto the roadway. At the lower side of the objective there is provided, according to the invention, a reflecting segment whose reflecting surface faces the objective.

In a vertical section, the reflecting surface has an inclination of focal aperture radius of the objective and constitutes a rotationally symmetric, planar, or arbitrarily formed surface. Light from the reflector edge impinges onto the reflecting surface of the reflecting segment, and the objective images the surface into the upper half-space. In the event the headlamp is provided with a refractor situated behind the objective, the light beam coming from the reflecting segment is propagated into sides by means of a zone of band lenses which is provided on the refractor and which overlaps the lower objective portion. In this way it is made possible to ensure an optimum level of luminous intensity above the light and darkness boundary, both from the viewpoint of illumination and dazzling, and to improve the visibility of vertical traffic signs and roadway markings, as well as of any possible obstacles and pedestrians, and further to improve the driver's orientation when travelling on unlit roadways as well as the position and front motion control of his own vehicle.

A preferred embodiment of the headlamp according to the present invention will hereinafter be described in the accompanying schematic drawings in which

FIG. 1 is a vertical section A--A of the headlamp;

FIG. 2 is a view P of the headlamp in the direction of the light beam;

FIG. 3 is a horizontal section B--B of the headlamp refractor; and

FIG. 4 is a projection of headlamp light beams into the roadway perspective .

As can be seen in the drawings, and particularly FIG. 1 thereof, a light source 2 of the headlamp is situated in the axis 12 and close to the apex 11 of a concave (parabolic) reflector 1. The light source 2 is constituted by a transversely or axially oriented body of approximately cylindrical shape such as a helical bulb filament, or arc of a discharge tube. The reflector 1 is followed by a screen 3 whose section edge 31 is horizontal with fog lamp whereas broken with a passing light headlamp. Downstream of the screen 3, at the distance X.sub.F therefrom, there is provided an objective 4 of diameter D (FIG. 2) which is designed for collimating rays 13, 14 coming from the reflector 1. Upstream of the objective 4 there is provided at its lower side a reflecting segment 5 having a reflecting surface 51 close to the objective 4, the inclination angle i.sub.5 thereof corresponding to the equation ##EQU1## wherein D is diameter of the objective 4 and

x.sub.F is the distance between the screen 3 and the objective 4.

The angle i.sub.5 is either longitudinally constant, or variable in a predetermined range within its length whereby the vertical dimension of light beam to be shaped by it, can be adjusted. The reflecting surface 51 of the reflecting segment 5 is either rotationally symmetric according to the axis 52 of the segment 5, or is planar. Downstream of the objective 4 is a refractor 6 provided with band lenses 62.

FIG. 2 shows the objective 4, the reflecting segment 5 and the refractor 6 provided with a zone 61 of band lenses 62, the zone 61 overlapping, either fully or partially, the reflecting surface 51 of the reflecting segment 5. The band lenses 62 of the refractor 6 are arranged in an about vertical position.

As can be seen in FIG. 3, the section B--B of the refractor 6 in the zone 61 shows the refracting profile of lenses 62 of which width H corresponds to the equation

wherein R is diameter of the band lenses 62.

In a roadway perspective comprising a central line 81, a lefthand verge 82 and a righthand verge 83, FIG. 4 shows a light beam 7 having a horizontal lefthand part 71 of the light and darkness boundary, and a righthand part 72 broken at said boundary with the passing light as well as a horizontal part 73 with the fog light. Rays 15, 16 coming from the edge of reflector 1 are directed by the reflecting segment 5 and by the objective 4 into the upper half-space where they form a light beam 91. The band lenses 62 of the refractor 6 expand the beam 91 into a light beam 92. By varying the side dimension of the beam 92 it is possible to adjust the luminous intensity to an optimum value from the viewpoint of both illumination and dazzling.

The headlamp according to the invention is designed for use for any vehicles operable on land.