GB2281386A - Vehicular headlamp designed for two-way lower beam patterns - Google Patents

Abstract

A vehicular headlamp capable of producing either of two different asymmetrical lower beam patterns for vehicles keeping to the right and for those keeping to the left, each beam pattern having its top edge delineated by a horizontal cutoff and a slanting cutoff. Included is a reflector (4) which is so optically configured as to provide, by reflecting light from an electric bulb, a symmetrical basic beam pattern having its top edge delineated by a pair of slanting cutoffs. A cutoff shade (10) is formed in one piece with a front shade (6), which covers front part of the bulb to prevent direct projection of light emitted thereby, for shading either of two predetermined parts of the reflector surface and hence for substituting a horizontal cutoff for one of the pair of slanting cutoffs of the basic beam pattern. Either of the two lower beam patterns is therefore producible merely by rearranging the cutoff shade with respect to the bulb and the reflector. The position of the cutoff shade relative to the bulb and the reflector remains unchanged despite the leveling and aiming of the lamp in use. <IMAGE>

Description

VEHICULAR HEADLAMP DESIGNED FOR TW > WAY LOWER BEAM PA'ERNS 'This invention relates generally to electric lamps for use on motor vehicles, and particularly to the improved construction of a vehicular headlamp designed for ready modification to provide a lower beam of cither of two different asymmetrical patterns required for motor vehicles traveling on the right side of the road and for those traveling on the left side of the road.

Wheeled traffic is required by the law to keep to the right in some countries and to the left in others. While the upper beam pattern of vehicle headlamps is symmetrical, the lower beam pattern is asymmetrical. Conscquently, the lower beam pattern of headlamps for vehicles travelling on the right side of the road must be a lateral reversal of the lower beam pattern of headlamps for vehicles travelling on the left side of the road.

A long familiar construction of headlamps was such that an clcctric bulb was disposed in front of a paraboloidal reflector, with the coiled filament of the bulb positioned approximatcly at the focus of the reflec- tor and with the filament axis in alignment with the optical axis of the reflector. A cutoff shade was placed under the filament to provide the required beam pattern, and divergent steps were formed on the front lens of the lamp.

An objection to this known headlamp construction is that the cutoff shade blocks an inconveniently high percentage of the light emitted by the bulb. In order to overcome this objection, and to meet the rccent demands for lamps of less and less vertical dimensions and for called slanting lamps, it has been suggested and practiced to design the rcflector so as to perform the beam control functions that had long bcen attributed to the stepped front lens. A variety of reflector designs have been proposed for these purposes, an example being one whose reflective surface is composed of a multiplicity of small segments.

Such recent headlamp constructions are still unsatisfactory, however for manufacturers exporting their products to countries having the two different traffic rules set forth above. Some headlamps have had to be designed and manufactured exclusively for countries whcre vehicles keep to the right, and others exclusively for those where vehicles keep to the left. Different dies have also had to be made for the fabrication of the two different retlectors. The two fundamentally differcnt types of headlamps have added much to their manufacturing costs, and their parts management has also been troublesome.

The present invention seeks, therefore, to provide a novel two-way headlamp construction which requires a minimum of modification for providing lamps for use in keep-to-the-right countries, and those for use in keep-to-the-left countries.

More specifically, according to the invention, a vehicular headlamp is provided which is capable of producing either of two different lower beam patterns for vehicles keeping to the right and for vehicles keeping to the left, the two lower beam patterns being in mirror-image rclationship to each other and each having a top cdge thereof delineated by a horizontal cutoff extending horizontally and by a slanting cutoff extending at an angle to the horizontal cutoff. The headlamp comprises a light source, and a reflector for reflecting the light emitted by the light source. The reflector is so optically configured as to produce a basic beam pattern of symmetrical shape having a top edge thereof delineated by a pair of slanting cutoffs.A cutoff shade is mounted in fixed rclation to the reflector and positioned between the light source and the reflector for shading either of two predetermined parts of the reflector from the light emitted by the light source, thereby substituting a horizontal cutoff for one of the pair of slanting cutoff of the basic beam pattern.

Thus, all that is required to produce either of the two asymmetrical lower beam patterns is to shade one or the other of the two predetermined parts of the reflector by the cutoff shade. This cutoff shade may be simply rearranged with respect to the light source and the reflector for shading either of the two predetermined parts of the reflector.

Preferably, the cutoff shade is formed in one piece with a front shade which is securcd to the reflector and which covers part of the light source in order to prevent the direct projection of the light emitted thereby. The one-piece construction of the cutoff shade with the front shade is preferred because the position of the front shade, and therefore of the cutoff shade, relative to the light source and the reflector is totally independent of the aiming or leveling of the beam.

Such being the improved construction of the headlamp according to the invention, the reflector and most other constituent parts thereof can be made common use of for the manufacture of the two types of headlamps in question. The only exception is the front shade together with the cutoff shade, which, however, is far inexpensive than the reflector, so that the total manufacturing costs of both types of headlamps will be remarkably less than heretofore.

The above and other features and advantagcs of the invention and the manner of realizing them will become more apparent, and the invention itself will bcst be understood, from a study of the following description and appended claims, with reference had to the attached drawings in which: Fig. 1 is a vertical section through the vehicle headlamp constructed in accordance with the novel concepts of this invention; Fig. 2 is an enlarged perspective view of the front and cutoff shades of the Fig. 1 headlamp; Fig. 3 is a perspective view of a modification of the Fig. 2 front and cutoff shades; Fig. 4 is an enlarged front view explanatory of how the reflector of Fig. 1 headlamp is optically configured according to the invention; Fig.S is an explanatory side view of the reflector; Fig. 6 is a view similar to Fig. 4 but explanatory of the notional optical divisions, referred to as the sectors and subsectors, of the surface of the reflector; Fig. 7 is an illustration of the basic lower beam pattern produced by the reflector; Fig. 8 is an illustration of filament images due to one of the sectors of the reflector; Fig. 9 is an illustration of filament images conducive to the production of the lower beam pattern for vehicles keeping to the right; Fig. 10 is an illustration of filament images conducive to the production of the lower beam pattern for vehicles keeping to the left; Fig. 11 is an illustration of how one of the subsectors of the reflector surface is shaded for the production of the lower beam pattern for vehicles keeping to the right; ; Fig. 12 is a perspective representation of the showing of Fig. 11; and Fig. 13, consisting of (a) and (b), is an illustration of the lower beam pattern for vehicles keeping to the right and of the lower beam pattern for vehicles keeping to the left.

With reference first to Fig. 1 the illustrated vehicular headlamp 1 has a generally cup-shapcd lamp body 2 having an opcn front cnd, shown directed to the left, and a front lens 3 closing the front end of the lamp body. Within the lamp body 2 there are provided a reflector 4 oriented toward the front lens 3, an electric lighting bulb S disposed forwardly and approximately centrally of the reflector, and a shade member 6 inctuding a cup-shaped front shade 10 covering the front cnd portion of the bulb.

It is understood that the reflector 4, together with the bulb 5 and shade member 6 mounted thereto, is conventionally mounted to the lamp body 2 via aiming and leveling means, not shown, whereby the beam direction of the lamp 1 is adjustably variable. The invention particularly features the fact that the reflector 4 is per se so optically configured as to provide a lower beam pattern, herein termed the basic beam pattern, common to vehicles keeping to the right and to those keeping to the left, without use of the conventional cutoff shade under the bulb filament. The optical dctails of the reflector 4, as well as the basic beam pattern, will be set forth subsequently.

The reflector 4 has a bulb hole 7 cut centrally therein for receiving the base Sa of the bulb 5 with considerable clearance. The bulb base 5a bas a mouliting flange 8 formed thereon. The inner edge portion 8a of the mounting flange 8 is pressfitted in the annular space between bulb base Sa and reflector 4, and the outer edge portion 8b of the flange is held against the rear cnd surface 4a of the reflector. With the bulb 5 thus mounted in position with respect to the reflector 4, its lower beam filament 9 is disposed in axial alignment with the reflector.

The bulb 5 is understood to include, in addition to the lower beam filament 9, an upper beam filament which is not shown because of its impertinence to the invention.

As illustrated on an enlarged scale and in perspective in Fig. 2, the shade member 6 is formed to include the cup-shaped front shade 10 covering the front cnd portion of the bulb 5 in order to prevent the direct emission of the light through the front lens 3, and a pair of mounting legs 11 extending rearwardly from the front shade. As will be understood by referring back to Fig. 1, the mounting legs 11 are inserted in and through the bulb hole 7 in the reflector 4 and have their terminal bends lia screwed to bosses 12 on the reflector.

The shade member 6 is further formed to include a cutoff shade 13 extcnding rearwardly from the head 10 in parallel spaccd relationship to the mounting legs 11. Forming anothcr feature of the invention, the cutoff shade 13 functions to prevent the light emitted by. the bulb filament 9 from impinging on that part of the reflector 4 which forms that part of the noted basic beam pattern which is unnecessary in creating a right- or left-side lower beam.

The shade member 6 may be modified as shown in Fig. 3. The modified shade member 6A has a modified cutoff shade 13A cxtending rearwardly from the front shade 10 and terminating in a bcnd 14 which may be screwed to the reflector 4 like the bends lia of the two mounting legs 11. Thus the cutoff shade 13A serves as an additional mounting leg in the modified shade member 6A.

With reference to Fig. 1 again the front lens 3 has no steps formed thereon but is of constant, or nearly constant, thickness throughout. The front lens 3 has a major portion 3a positioned forwardly of the reflector 4, and a peripheral portion 3b of annular shape extending rcarwardly therefrom and terminating in a tongue 15. This tongue is cngaged in a groove 2a of annular shape formed in the lens body 2. A suitable adhesive may be employed to make the tongue-and-groove joint fast enough to preclude the danger of accidental detachment of the front lens 3 from the lamp body 2. The inside surfaces of the peripheral portion 3b may be painted in black in order to prevent the emission of undesired light through this lens portion.

Reference is now directed to Figs. 4-6 for the discussion of the fundamental optical design of the reflective surface 16 of the reflector 4 according to the invention. Let us first assume for such discussion a three-dimensional rectangular coordinate system comprised of the x-axis, Fig. 5, which is equivalent to the optical axis of the reflector 4 and which is directed forwardly of the lamp 1, the y-axis, Fig. 4, which extends horizontally and perpendicular to the x-axis and which is directed to the right in Fig. 4, and the z-axis which extends vertically and perpendicular to the x- and y-axes and which is directed upwardly. The origin 0 of the rectangular coordinates is located approximately centrally of the bulb hole 7 of the reflector.

As indicated in Fig. 4, the reflective surface 16 may be thought of as being composed of two rcgions or sectors 17 and 18 having different beam pattern control functions. The term "sectors" are used because both regions 17 and 18 are sectorial in shape when the reflector is seen in a front view as in Fig. 4. The first sector 17 is located above the plane and has an apex angle of 150 degrees. The second sector 18 occupies the rest of the reflective surface 16 and has an apex angle of 210 degrees.Not all the reflective surface 16 is necessarily uscd for beam production; for example, for a headlamp of rectangular front design, only the part shown enclosed in the phantom outline 19 may be used. it should be noted that the reflective surface 16 is shown divided into the sectors 17 and 18 purely for the purpose of illustration; in fact, they are contiguous to each other without any glare-causing step or the like therebetween.

The reflective surface 16 is formed as a so-called freely curved surface that cannot be expressed algebraically but which can be designed with the aid of a computer with complex parametric and vectorial computations. Such freely curved reflective surfaces have so far becn very difficult to design, particularly because lower beam patterns are asymmet rical.

However, the two sectors 17 and 18 can both be symmetrical with respect to the xz-plane, as is apparent from the fact that the reflective surface 16 is so configured according to the invention as to provide the basic beam pattern common to right- and left-side traveling vehicles.

Only one side of that plane may thcrefore be designed, and this same side replicated so as to complete the symmetrical whole. Frccly curved surfaces are designed by first forming curved lines and then curved surfaces, largely through the following procedure: 1. Creation of curved lines: (a) Parameter inputting: Paramcters such as the focal distances of basic parabolas and their rates of deformation, the magnitudcs of tangents, and the aim angle ot the beam are introduced into the computer.

(b) Computation of curved Une expressions: The coordinates of the beginning and end of each curved line are obtained from the basic parab olas and their rates of deformation. Then the di reactions of tangent vectors are computed from the aim angle of the beam, and free curves such as Ferguson's curves are computed by defining their magnitudes.

2. Creation of curved planes: (a) Parameter inputting: There are input to the computer such param eters as twist vectors, the diameters of basic el lipses, and directions as to whether restrictive condi tions such as right angular relationships are imparted to the tangent vectors. The restrictive conditions on the tangent vectors correspond to the optical alignment of the axis of the filament images, and the twisting of the tangents corresponds to moving the filament images in directions at right angles with their longitudinal direction.

(b) Computation of curved plane expressions: Curved plane patches (e.g. Coons' twin three dimensional patches) are created. The determination of the patch coefficients requires tangent vectors and twist vectors concerning the coordinates of points and curved plane coordinates (curved plane parameters u and v). All of the point coordinates and some of the tangent vectors are predetermined by the freely curved lines obtained previously, so that the remainder of the tangent vectors are ascer tained from the parameters of the basic ellipses, re strictive conditions, and twist angles, and their mag nitudes are adjusted. The twist vectors are comput ed by the methods of Adini and Forrest wberever required.

The freely curved surface is created as above by subdividing the sectors 17 and 18 of the reflective surface 16 into scveral sectors illustrated by way of example in Fig. 6. The first sector 17 is therein shown as being constituted of two subsectors 17R and 171* The subsector 17R is in the first octant (y > 0, z > 0) of the yz-plane, and the subsector 17L in the second octant 01 < 0, z > 0) thereof.

The second sector 18 is shown subdivided into six subsectors I8CRU, i8CRD, 18R, 18CLU, 18CLOD and 18L. of these, the three subsectors 18CRU, 18CRD and 18R are situated on the right hand side of the xz-planc. The subsector 18CRU is situated immediately above the xyplane and has an apex angle equal to the cutoff angle of, typically, 15 degrees. The subsector 18CRD is situated immediately below the xy-plane and has the same apex angle as the subscctor 18CRU. The subsector 18R immediately underlies the subsector 18CRD. The other threc subsectors 18CLU, 18CLD and 18L are all situated on the left hand side of the xz-plane.The subscctor 18CLU is situated immediately above the xyplane and has the same apex angle as the cutoff angle. The subsector 18CLD is situated immcdiately below the xy-plane and also has the same apex angle as the cutoff angle. The subscctor 18L immediately underlies the subsector 18CLD.

Fig. 7 is a schematic representation of the basic beam pattern 20, not yet modified for use as a right- or left-side lower beam according to the invention. Symmetrical with respect to the line of the perpendicular V-V, the basic beam pattern 20 has its top edge delineated by two slanting cutoffs 21R and 21L. Both slanting cutoffs 21R and 21L are inclined at the same cutoff angle with respect to the line of the horizon H-H.

The slanting cutoff 21R is situated on the right hand side of the vcrtical line V- V and angled upwardly as it cxtends away therefrom. The other slanting cutoff 21L is situated on the left and side of the vertical line V-V and angled upwardly as it extends away therefrom.

Fig. 7 also indicates by broken lines the two horizontal cutoffs 22R and 22L which are aligned parallel to the horizontal line H-H and which are situated on the opposite sides of the vertical line V- V. The horizontal cutoffs 22R and 22L are shown by the broken lines because they do not appear in this basic beam pattern 20; either of them does appear, however, in the completed right- or left-side lower beam pattern as either of two selected subsectors of the reflective surface 16 is shad cd according to the invention, as will bccome better understood as the description proceeds.

The creation of these cutoffs of the beam pattern requires the alignment of the longitudinal axes of the filament images projected on a screen, which is mounted forwardly of the reflector 4, by arranging the tangent vectors at the terminal points of the curved plane patches at right angles with their position vectors, and the alignment of the upper longitudinal edges of the filament images by twisting the curved planes.

Figs. 8-10 are illustrations of typical arrangements of filament images produced on the screen by the reflective surface 16. The line hh in these figures cxtcnds horizontally and at right angles with the xaxis of Fig. 5, and the line v-v extends vertically and at right angles with the x-axis. The vertical line v-v is equivalent to the vertical line V-V of Fig. 7. the horizontal line h-h is made to agree with the horizontal line H-H of Fig. 7 by the aiming of the completed lamp.

Fig. 8 shows filament images due to the first sector 17 of the reflective surface 16. All the filament images are situated mostly below the horizontal line h-h and never above the broken lines 23 cquivalent to the slanting cutoff lines.

Fig. 9 shows filament images due to the subsectors 18CLU, 18C1D, 18L, 18R and 18C R D of the second sector 18. All the filament images are arranged radially about the intersection 0 of the lines h-h and v-v.

The filament images 24 due to the subsector 18CLU are explanatory of how the slanting cutoff 21R of the Fig. 7 basic beam pattern 20 is formed, and the filament images 25 due to the subsector 18CRD how the horizontal cutoff 22L is formed.

Fig. 10 shows filament images due to the subsectors 18CRU, 18CRD, 18R, 18L and 18CLD of the second sector 18. All these filament images are also arranged radially about the intersection 0 and are in mirror im- age relationship to the filament images of Fig. 9 with respect to the vertical line v-v. The filament images 26 due to the subsector 18CRU are explanatory of how the slanting cutoff 21L of the FIG. 7 basic beam pattern 20 is formed, and the filament images 27 due to the subsector 18CUD how the horizontal cutoff 22R is formed.

The basic beam pattern 20 is a combination of the individual beam patterns due to the various sectors and subsectors of the reflective surface 16. Part of the beam pattern due to the first sector 17 contributes to the creation of the high intensity zone of the beam pattern, and the beam patterns due to the subsectors 18CRU, 18CRD, 18CLU and VISCID of the second sector 18 contributes to the creation of the cutoffs.

The basic beam pattern 20 nceds, as aforesaid, modification for use as a right- or left-side beam; that is, the part of the basic beam pattern above the left-hand horizontal cutoff 22L must be shaded for providing a right-side lower beam, and the part of the basic beam pattern above the right hand horizontal cutoff 22R shaded for providing a left-side lower beam.

It might be contemplated to cmploy a front lens so configured as to deflect the light due to the reflector subsectors 18CRU or 18CLU downwardly, thereby making either of the horizontal cutoff 22R and 22L appear. This solution is objectionable because the positional relationship between reflector and front lens is subject to change as the reflector is moved relative to the front lens by the unshown aiming and leveling mechanisms of the lamp. Additionally, two different front lenses would be required for the two different Lower beam patterns, running counter to the objective of the invention, the utmost simplification of headlamp construction for providing the two beam patterns.

Therefore, according to the invention, the cutoff shade 13 is formed in one piece with the front shade 10 thereby shading either of the reflector subsectors 18CRU and 18CIIU from the light emitted by the bulb filament 9 and thereby making either of the horizontal cutoffs 22R and 22L appear. The positional relationship between reflector 4 and front shade 10 rcmains unchanged dcspite the aiming and leveling of the lamp, so that the completed lower beam patterns are not to be deformcd.

Figs. 11 and 12 are both explanatory of how the cutoff shade 13 shades the reflector subsector 1SCRU. The shading of this reflector subsector results in the creation of the horizontal cutoff 22L as in the lower beam pattern depicted at (a) in Fig. 13, which is for vehicles keeping to the right.

For providing the left-side lower beam pattern seen at (b) in Fig.

13, on the other hand, the cutoff shade 13 may be rearranged in a posi tion of symmetry to that indicated in Figs. 1, 11 and 12 with respect to the xz-plane of Figs. 4 and 5, because the basic beam pattern is bilatcrally symmetrical with respect to that plane. The cutoff shade 13 will then shade the reflector subsector 1SCLU, Fig. 6, with the consequent appearance of the horizontal cutoff 22R as at (b) in Fig. 13.

Despite the foregoing detailed disclosuIe, it is not desired that the invention be limited by the exact showing of the drawings or the description thereof. For example, the cutoff shade could be screwed or otherwise affixed to the front shade, instead of being formed in one piece therewith. Also, the invention could be applied to headlamps having stepped front lenscs. These and other modifications, alterations and adaptations of the invention will suggest themselves to one skilled in the art without departing from the scope of the invention as expressed by the daimE which follow.

Claims (3)

1. A vehicular headlamp capable of producing either of two different lower beam patterns for vehicles keeping to the right and for vehicles keeping to the left, the two lower beam patterns being in mirror-image relationship to each other and each having a top edge thercof delineated by a horizontal cutoff cxtending horizontally and by a slanting cutoff extending at an angle to the horizontal cutoff, comprising a light source, and a reflector for reflecting the light emitted by the light source, characterized in that the reflector is so optically configured as to produce a basic beam pattern of symmetrical shape having a top cdge thereof delineated by a pair of slanting cutoffs, and that a cutoff shade is mounted in fixed relation to the reflector and positioned between the light source and the reflector for shading either of two predetermined parts of the reflector from the light emitted by the light source, thereby substituting a horizontal cutoff for one of the pair of slanting cutoffs of the basic beam pattern, whereby either of the two lower beam patterns is producible merely by rearranging the cutoff shade with respect to the light source and the reflector.

2. A vehicle headlamp as claimed in claim 1, further comprising a front shade affixed to the reflector and covering part of the light source for preventing the light of the light source from being projected directly by the headlamp, characterized in that the cutoff shade is formed substantially in one piece with the front shade.

3. A vchicle headlamp as claimed in claim 2, wherein the front shade is affixed to the reflector via a plurality of mounting legs, characterized in that the cutoff shade is formed as an additional mounting leg of the front shade.