EP0068631A1

EP0068631A1 - Vehicle headlamp reflector

Info

Publication number: EP0068631A1
Application number: EP82302636A
Authority: EP
Inventors: Kenneth James Jones
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1981-06-18
Filing date: 1982-05-24
Publication date: 1983-01-05
Also published as: JPS5816401A; AU8486882A

Abstract

To enable filament images to be obtained which are small and therefore easily controlled by lensing, the vehicle headlamp reflector is provided with a first paraboloidal reflective portion (13) at or near whose focus a lamp filament is disposed in use, a planar reflective portion (16) and a second paraboloidal reflective portion (14). The second paraboloidal reflective portion (14) has a larger focal length than that of the first paraboloidal reflective portion and is disposed so that an image (22) of the filament in the planar reflective portion (16) lies at or near its focus.

Description

This invention relates to a vehicle headlamp reflector and has for its object to provide such a reflector wherein, under dipped or passing beam conditions, a particularly advantageous filament image distribution can be obtained so that accurate beam control is possible.
According to the present invention, there is provided a vehicle headlamp reflector comprising a first paraboloidal reflective portion having a focus at or near to which a lamp filament is located in use, a planar reflective portion spaced from said focus and arranged to receive light from the filament in-use, and a second paraboloidal reflective portion having a longer focal length than the first paraboloidal reflective portion, the second paraboloidal reflective portion being so disposed relative to the planar reflective portion that, in use, an image of the filament in the planar reflective portion lies on or near to the focus of the second paraboloidal reflective portion.
With this form of construction, it is possible for the second paraboloidal reflective portion to have a much greater focal length than the first paraboloidal reflective portion so that much smaller filament images are projected by the second paraboloidal reflective portion than are reflected by any part of the first paraboloidal reflective portion. It is to be appreciated that smaller filament images are much easier to control by lensing than larger filament images and so are preferred in the critical parts of the beam projected by the reflector. By "critical parts" is meant those parts of the light beam projected by the headlamp where vehicle lighting regulations require a close control of the lighting intensity. Typically, close control is required in the upper central region of the beam projected by a vehicle headlamp and so, in a headlamp reflector according to the invention, the second paraboloidal reflective portion can be arranged to provide an easily controllable and relatively concentrated area of light in the required position at the top of the beam.
The vehicle headlamp reflector according to the present invention can be made more compact, for given light output than a conventional vehicle headlamp reflector.
It is particularly preferred for the vehicle headlamp reflector to comprise a dished body in which the first paraboloidal reflective portion is defined by a portion of an inner surface of the body. With such a construction, the planar reflective portion and the second paraboloidal reflective portion may be provided in a lower part of the dished body, whilst the first paraboloidal reflective portion is provided in an upper part of the dished body. It will be appreciated that, with a simple paraboloidal headlamp reflector, the lower part of the reflector is not employed under dipped (passing) beam conditions and so the planar reflective portion and the second paraboloidal reflective portion do not occupy any areas which are normally used under dipped beam conditions in such a headlamp reflector. Commonly, a filament shield is provided below the filament for preventing_light from passing downwardly into the lower part of the reflector. It is therefore within the scope of the present invention to provide a prism in an upper part of the reflector for directing light towards the planar reflective portion which may therefore be disposed in a position in which it cannot receive light directly from the filament because of the provision of the above-mentioned filament shield.
If desired or if the design of the vehicle to which the headlamp reflector is to be fitted permits, the second paraboloidal reflective portion may be disposed externally of the dished body in which the first paraboloidal reflective portion is defined. Similarly, the planar reflective portion may also be disposed externally of the dished body.
Whilst the present invention can be employed with headlamp reflectors in which the dished body has a circular front opening, it is mainly concerned with reflectors wherein the dished body has a non-circular opening, for example a modified rectangular front opening. With such non-circular reflectors, upper and lower planar portions are provided which do not take part in the reflection of useful light from the reflector. It is within the scope of the present invention to provide a window in one or other of such planar portions to enable light from the filament to emerge from the dished body and be collected by the planar reflective portion and the second paraboloidal reflective portion which are disposed externally of the dished body.
It is also within the scope of the present invention for the vehicle headlamp reflector to be provided with a third paraboloidal reflective portion having a focal length which is between those of the first and second paraboloidal reflective portions, the third paraboloidal reflective portion being defined within the dished body below the first paraboloidal reflective portion so that its focus is disposed forwardly of the lamp filament, there being a step provided between the first and third paraboloidal reflective portions internally of the dished body, said step being shaped so as to define a cut off to the upper portion of the beam projected by the first and third paraboleidal reflective portions. With such a construction, the usual filament shield is omitted or modified so as to permit light from the filament, in use, to be reflected off the third paraboloidal reflective portion under dipped (passing) beam conditions.
A vehicle headlamp reflector according to the present invention may be used in conjunction with a twin filament bulb so that it can be employed under full (main) beam conditions as well as under dipped (passing) beam conditions. With such a construction, the first paraboloidal reflective portion may extend to the lower part of the dished body.
Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:-

Figs. 1 to 3 are schematic front views of three embodiments of vehicle headlamp reflector according to the present invention, and
Fig. 4 is an illustration of the beam pattern projected by the vehicle headlamp reflector shown in Fig. 1.

Referring now to Fig. 1, the vehicle headlamp reflector illustrated therein comprises a dished body 10 having a modified rectangular front opening 11 through which light from the reflector passes in use and over which a lens element (not shown) is provided in the finished vehicle headlamp. The body 10 has a central rear opening 12 in which a single filament bulb (not shown) is mounted in use. In this embodiment, the dished body 10 is formed by injection moulding a low profile, unsaturated polyester dough moulding composition. The dished body 10 has an inner surface which defines first, second and third paraboloidal reflective portions 13, 14 and 15, respectively. Also disposed within the dished body is a planar reflective portion 16 which is mounted therein by support posts (not shown). However, it is within the scope of the present invention to mould the planar reflective portion 16 integrally with the body 10.
The portions 13 to 16 are rendered reflective by any suitable means, preferably by application of an aluminium layer thereto by a vacuum metallisation technique. The dished body 10 also includes upper and lower planar portions 17 and 18 which do not need to be rendered reflective since they are not designed to provide any useful reflections from the lamp filament. The first paraboloidal reflective portion 13 is disposed forwardly of the third paraboloidal reflective portion 15 so that a horizontal step 19 is disposed therebetween. A step 20 is defined between the first and second paraboloidal reflective portions.13 and 14. The step 20 is inclined downwardly away from the central aperture 12 and on the opposite side thereof to the step 19, the angle of inclination of the step 20 being at 15 degrees to the horizontal. The first reflective portion 13 has its focus lying on the longitudinal axis 21 of the aperture 12 in a position such that the inner end of the lamp filament lies on the focus. It is to be appreciated that the single filament bulb construction is such that the longitudinal axis of the filament lies on the axis _.21. The third paraboloidal reflective portion 15 has a longer focal length than the portion 13 and is arranged so that its focus lies on the axis 21 in a position such that the forward end of the lamp filament lies thereon. Thus, the lamp filament is disposed between the foci of the first and third paraboloidal relfective portions 13 and 15. As can be seen from Fig. 1, the planar reflective portion 16 is disposed below the central aperture 12 and is inclined at an angle of about 45 degrees with respect to the horizontal so that it faces the axis 21. The planar reflective portion 16 is arranged so that it produced an image at 22 of the inner end of the filament, ie that portion of the filament lying on the focus of the first paraboloidalreflective portion 13. The second reflective paraboloidal portion 14 has a focal length which is longer than either of the first and third paraboloidal reflective portions 13 and 15. The focus of the second paraboloidal reflective portion 14 lies at 22, ie. the image of the inner end of the bulb filament lies on the focus of the reflective portion 14.
The reflector construction of Fig. 1 produces a basic beam pattern as illustrated in Fig. 4. Referring now to Fig. 4, the first paraboloidal reflective portion 13 produces a part-annular beam portion 23 having mutually inclined upper cut-off portions 24 and 25 which are defined by the steps 19 and 20, respectively. The third paraboloidal reflective portion 15 produces a part-annular beam portion 26 which is displaced below the upper cut-off portions 24 and 25 as a result of the positioning of the filament relative to the focus of the portion 15. The second paraboloidal reflective portion 14 produces a sector-shaped beam portion 27 which is disposed in the critical part of the beam just below the upper cut-off portion 25. Because the portion 14 has a very much greater focal length than the portion 13, the images reflected thereby are small and therefore can be easily controlled to provide the necessary high intensity in exactly the required place, even where the design of the lens element is not optimised because vehicle design requirements do not permit the use of an optimised design of lens element. A typical case in this respect is the case where the vehicle lamp manufacturer requires a lens element to have a face which is not perpendicularly disposed relative to the axis 21.
Referring now to the embodiment of Fig. 2, parts which are similar to the embodiment of Fig. 1 are accorded the same reference numeral but prefixed by the numeral 1. In this embodiment, first paraboloidal reflective portion 113 occupies the whole of the useful area of the inner surface of dished body 110 so that a third paraboloidal reflective portion corresponding to portion 15 of the embodiment of
Fig. 1 is not provided. Planar portion 117 is transparent or has a transparent window (140) therein and planar reflective portion 116 is disposed externally of the body 110 as is second paraboloidal reflective portion 114. The focus of portion 114 lies at the location 122 on which the image of the inner end of the passing beam filament in the planar reflective portion 116 lies. This lamp reflector is intended to be used in conjunction with a twin filament bulb wherein the passing beam filament is disposed in the - position of the filament described with reference to Fig. 1 whilst the main or full beam filament is disposed behind the passing beam filament, ie closer to the aperture 12. As is usual with this type of twin filament bulb, the passing beam filament is provided with a filament shield 130 which serves to prevent light from this latter filament being reflected off the part of the first paraboloidal reflective portion 113 which is disposed in the lower part of the body 110. The shield 130 provides the cut-off to the top of the passing beam pattern as will be apparent to a person skilled in the art. When the main beam filament of the bulb is illuminated, light is reflected from the whole of the area of the first paraboloidal reflective portion 113. The second paraboloidal reflective portion 114 is arranged to provide the required compact beam in the same position as that indicated at 27 in Fig. 4. In fact, under passing beam conditions, the beam pattern projected by the reflector of Fig. 2 will be similar to that of Fig. 4 but with the portion 26 omitted.The embodiment of Fig. 2 is slightly less compact than that of Fig. 1 but has the advantage that it can be used under full beam conditions and that the disposition of the portion 114 externally of the body 110 means that it does not obscure any useful areas of the portion 113.
Referring now to Fig. 3, the vehicle headlamp reflector illustrated therein is similar to that of Fig. 2 and similar parts are accorded the same reference numeral in the 200 series rather than in the 100 series. In this embodiment, planar reflective portion and second paraboloidal reflective portion 214 are disposed internally of dished body 210 in the lower portion thereof. Because of the provision of lamp filament 230, light from the passing beam filament of the bulb cannot pass directly to planar reflective portion 216. Thus, a prism 231 is located in the body 210 above the bulb location so as to redirect light from the passing beam filament to the planar reflective portion 216. This embodiment is rather more compact than that of Fig. 2 but has a rather smaller effective collecting area.

Claims

1. A vehicle headlamp reflector comprising a first paraboloidal reflective portion (13, 113, 213) having a focus at or near to which a lamp filament is located in use, and a second paraboloidal reflective portion (14, 114, 214) having a longer focal length than said first paraboloidal reflective portion, (13, 113, 213) characterised in that a planar reflective portion (16, 116, 216) is spaced from the focus of the first paraboloidal reflective portion (13, 113, 213) and is arranged to receive light from the filament in use, and in that the second paraboloidal reflective portion (14,114,214) is so disposed relative to the planar reflective portion (16, 116, 216) that, in use, an image (22, 122, 222) of the filament in the planar reflective portion (16, 116, 216) lies on or near to the focus of the second paraboloidal reflective portion (14, 114, 214).

2. A reflector as claimed in claim 1, comprising a dished body (10, 110, 210) in which the first paraboloidal reflective portion (13, 113, 213) is defined by a portion of an inner surface of the body characterized in that the planar reflective portion (16, 116, 216) and the second paraboloidal reflective portion (14, 114, 214) are provided in a lower part of the dished body (10, 110, 210) and the first paraboloidal reflective portion (13, 113, 213) is provided in an upper part of the dished body (10, 110, 210).

3. A reflector as claimed in claim 2, which is for use in conjunction with a filament in"wh.ich a filament shield (230) is provided below the filament for preventing light from passing downwardly into the lower part of the reflector, characterized in that a prism (231) is provided in the upper part of the reflector for directing light towards the planar reflective portion (216).

4. A reflector as claimed in claim 1, comprising a dished body (110) in which the first paraboloidal reflective portion (113) is defined, characterized in that the second paraboloidal reflective portion (114) is disposed externally of the dished body (110).

5. A reflector as claimed in claim 4, characterized in that the planar reflective portion (116) is disposed externally of the dished body (110).

6. A reflector as claimed in claim 5, wherein the dished body (110) has a non-circular front opening (111). provided with at least one planar portion (117, 118) which does not take part in the reflection of useful light from the reflector, characterized in that a window is provided in said planar portion (117, 118) to enable light from the filament to emerge from the dished body (110) and be collected by the planar reflective portion (116) and the second paraboloidal reflective portion (114).

7. A reflector as claimed in claim 1, characterized in that a third paraboloidal reflective portion (15) having a focal length which is between those of the first and second paraboloidal reflective portions (13 and 1d) is provided, the third paraboloidal reflective portion (15) being defined below the first paraboloidal reflective portion (13) so that its focus is disposed forwardly of the lamp filament in use, there'being a step (19) provided between the first and third paraboloidal reflective portions (13 and 15), said step (19) being shaped so as to define a cut off to the upper portion of the beam projected by the first and third paraboloidal reflective portions (13 and 15) in use.

8. A reflector as claimed in claim 1, having a dished body (110, 210) in whose upper part the first paraboloidal reflective portion (113, 213) is provided, and being for use in conjunction with a double filament bulb, characterized in that the first paraboloidal reflective portion (113, 213) extends to a lower part of the dished body (110, 210).