FR2484604A1 - Automotive headlamps diffuser - uses elliptical section vertical flutes on backward tilting headlamp glass so that horizontal light rays traverse circular section - Google Patents

Abstract

The diffuser uses vertical fluting in a band running the width of the headlamp front glass. The headlamp glass is tilted back from the vertical and has flutes of elliptical cross-section. The length of the flutes increases towards the outer edge of the headlamp. The headlamp unit has a bulb on its horizontal axis. The headlamp glass is tilted backwards at an angle to the vertical. A horizontal band across the middle of the front glass carries fluting which in cross-section is elliptical. The ellipse is designed so that a section taken through the horizontal plane of the headlamp is circular. Light rays therefore pass through the same optical path giving more even diffusion of the light rays. (7po).

Description

DIFFUSER FOR MOTOR VEHICLE PROJECTOR
the present invention relates to a diffuser for a projector, especially for a motor vehicle, a diffuser of the type comprising zones of cylindrical ridges el; disposed in a plane located between the horizontal plane comprising the optical axis of the projector and between a plane perpendicular to this optical axis.

 With known headlights fitted with such diffusers, it is particularly difficult to obtain a clean cut for the passing beam, because the cylindrical streaks thus inclined give a curved beam of lighting, and the suitable diffuser is of very complex streak design.

 The object of the present invention is to remedy such a drawback and to this end relates to a diffuser as defined above and characterized in that it comprises, at the level of the cut-off of the passing beam, at least one streak zone c straight sections in the shape of an ellipse portion, of constant parameter all along the streak, and with working section, along the horizontal planes parallel to the optical axis; shaped like a portion of a circle.

 The description which follows with reference to the appended diagrams will make it easier to understand how the invention can be implemented.

 Figure 1 is a front view of a diffuser according to the invention.

 FIG. 2 represents the positioning of the diffuser along section II II of FIG. 1.

 FIG. 3 represents a streak according to the invention according to section III III of FIG. 2.

 FIG. 4 represents a stripe according to the invention following section IV IV of FIG. 2.

 FIG. 5 represents the cuts of the crossing beams obtained with different diffusers.

 Figure 6 shows in perspective an embodiment of a tool capable of producing a groove according to the invention.

 In a known manner a projector is composed (see FIG. 2) of a diffuser or lens 1, of a reflector 2, of a lamp 3 with two filaments, the filament 3a of which provides the crossing beam, and possibly, as in the 'example shown, a spacer 4 disposed between the reflector 2 and the glass 1.

 The diffusing face 1b, inclined with respect to the optical axis 5 of the projector, forms, with a vertical perpendicular to this axis 5, an angleo (different from 0 and 900, and comprises a zone la (see FIG. 1) which in association with the filament 3a makes it possible to cut the so-called crossing beam.

 In accordance with the invention, the ridges of zone 1a have straight sections 5 in the form of an ellipse portion (see FIG. 3) such that the working sections S ′ parallel to the optical axis 5 are in the form of a circle portion (see figure 4).

 As represented in figure 3 the equation of the geometrical place of the generatrix of the streak, inclined according to the angle i defined above, is an ellipse defined by the following parameters: a = R and b = R cos <, R being the radius of the same streak in working section 5 (see Figure 4); and whose focal axis major axis F1 F2 is parallel to the face lb of incidence of the light rays.

 FIG. 5 represents the differences between the cuts Dt or D2, depending on whether the glass is tilted up or down J obtained using cylindrical ridges, which are deformed in curve, while the cut D obtained at Using the streaks according to the invention is sharp and without deformation.

 The production of such striations can then be carried out in the following manner using a tool as shown in FIG. 6. This tool is a volume, full in our example but which can be hollow, whose cross sections S are constant over the entire length of the tool, and are defined by the equation of the geometrical place of its generatrix, place which is an ellipse and whose parameters are for the major axis: 2a = 2R ie twice the value of the radius of an equivalent cylindrical streak, and for the minor axis: 2b = 2 R cos A i.e. the value of its major axis multiplied by the cosine of the angle of inclination of the ice 1 with respect to the vertical.

 The tool represented in FIG. 6 makes it possible to obtain hollow grooves inside the glass while keeping a constant thickness of the glass over the entire height of the part 1a.

 It is then easy to realize that the incident rays arrive obliquely on this elliptical volume and cut it along the working surface S 'which is circular, and that thus no deformation of the cut D appears.

 It is obvious that modifications can be made to such an embodiment without departing from the scope of the invention; for example if part 1a vertically forms a curve, the plane described by the major axis of the ellipse being parallel to the ice will form the same curve as the ice, moreover the streaks may be convergent by being made in relief on the face lb.

Claims (2)

 1 - High beam and passing beam projector diffuser, in particular for a motor vehicle, arranged in a plane situated between the horizontal plane comprising the optical axis (5) of the projector and between a plane perpendicular to this optical axis, characterized in that that it comprises, at the level of the intersection of the passing beam, at least one zone of streaks with a straight section (S) with a large portion of ellipse, of constant parameter all along the streak, and with a cross section work (S '), along the horizontal planes parallel to the optical axis, in the form of a portion of a circle.  2 - Diffuser according to claim 1 characterized in that the streaks match the outer shape of the ice so as to keep it a constant thickness throughout these streaks.