WO2009138913A2

WO2009138913A2 - Headlamp and lamp for use in a headlamp

Info

Publication number: WO2009138913A2
Application number: PCT/IB2009/051872
Authority: WO
Inventors: Klaus Schoeller; Adam Lind
Original assignee: Philips Intellectual Property & Standards Gmbh; Koninklijke Philips Electronics N. V.
Priority date: 2008-05-14
Filing date: 2009-05-07
Publication date: 2009-11-19
Also published as: WO2009138913A3

Abstract

The invention relates to a headlamp, andin particular a motor vehicle headlamp, comprising a reflector and a lens between which is arranged a light source that is surrounded byat least one envelope, the reflector having effective reflective regions and ineffective reflective regions, and at least one envelope being provided with masking, wherein the masking (35) is designed in such a way that those rays of light emitted by the light source (36) which are directed towards an ineffective reflective region are at least partly screened off. The invention also relates to a lamp for use between the reflector and lens of a headlamp, comprising a light source and an envelope surrounding the light source, which envelope is provided with masking, the masking (35) being so designed that, when the lamp (3) is in the installed state, those rays of lightemitted bythe light source (36) which are directed towards an ineffective reflective region are at least partly screened off.

Description

HEADLAMP AND LAMP FOR USE IN A HEADLAMP

The invention relates to a headlamp, and in particular a motor vehicle headlamp, comprising a reflector and a lens between which is arranged a light source that is surrounded by at least one envelope, the reflector having effective reflective regions and ineffective reflective regions, and at least one envelope being provided with masking. The invention also relates to a lamp for use between the reflector and lens of a headlamp, the said lamp comprising a light source and an envelope surrounding the light source which is provided with masking.

As well as the incandescent lamps which have long been used in the automotive field, increasing use is also being made of discharge lamps for motor vehicle lighting, the reason for this being their considerably improved light yield over incandescent lamps. In known discharge lamps, a gas discharge, which emits very bright light, is produced between two electrodes in a sealed-off discharge vessel.

A discharge lamp usually has a base, a burner having a discharge vessel and an outer envelope. The base serves as a mounting for the burner and to position the lamp in a headlamp and to allow electrical contact to be made with it in a headlamp. It is in the discharge vessel that the actual generation of light takes place. An outer envelope made of glass is usually arranged around the discharge vessel. This serves to filter UV radiation out of the light that is emitted.

A motor vehicle headlamp has a reflector and a lamp which projects into the interior of the reflector though an opening. The lamp is exactly positioned by its base in a mounting belonging to the reflector and the discharge vessel is thus arranged at a precisely known point. The surface of the reflector is illuminated by the light that is emitted. Basically, there are two different types of motor vehicle front headlamp, those using a reflector system and those using a projector system. In reflector systems, the light that is emitted by the light source onto the reflector is directed straight from the reflector onto the road. In contrast to this, in projector systems the light emitted by the light source is reflected by the reflector and is directed onto the road by an additional lens that is arranged in front of the reflector.

A disadvantage of known headlamps is that some of the light emitted by the lamp makes its way to areas outside the surfaces of the reflector or to ineffective regions of the reflector, neither of which make any contribution, or any adequate contribution, to the desired beam of rays of light, as a result of which there is a reduction in the light yield from the headlamp. In this case, rays of light may both be directed straight into areas outside the reflector and may also be incident on ineffective regions of the reflector. It is this problem that the invention aims to remedy. The object underlying the invention is to provide a headlamp, and in particular a motor vehicle headlamp, in which the effective light yield is increased. In accordance with the invention, this object is achieved by designing the masking in such a way that those rays of light emitted by the light source which are directed towards an ineffective reflective region are at least partly screened off. In what follows, what is to be understood by the term "effective reflective regions" is those regions of a reflector that, in the reflector, lamp and lens arrangement of a headlamp, cause incident rays of light to be reflected onto the lens. Regions that do not cause incident rays of light to be reflected onto the lens are referred to in what follows as "ineffective reflective regions". In reflector systems, what is to be understood by the term "lens" is the lens forming the front of the headlamp.

The invention provides a headlamp, and in particular a motor vehicle headlamp, in which the effective light yield is increased.

The masking preferably takes the form of a coating for reflecting visible light. It becomes possible by this means for rays of light which are screened off to be redirected towards effective reflective regions of the reflector.

In a further embodiment of the invention, the coating is so designed that IR waves are not reflected but absorbed. By this means, the thermal regulation of the burner can be modified, as a function of the geometry of the coating, in such a way that it causes the burner to be of greater luminance. The coating is advantageously so designed that UV waves are transmitted. UV radiation has adverse effects on components made of plastics materials and in this way it is prevented from becoming more intense.

In an embodiment of the invention, the light source is formed by two electrodes of a high intensity discharge lamp which project into a discharge chamber in a burner envelope. The masking is preferably applied to the burner envelope.

In an embodiment of the invention the high intensity discharge lamp has an outer envelope surrounding the burner envelope and the masking is applied to the outer envelope. In a further embodiment of the invention the headlamp is in the form of a projector-type headlamp and the lens is a projector lens. It is particularly in projector-type headlamps that a considerable increase in the light yield of the headlamp can be achieved by the redirection in accordance with the invention of ineffective rays of light. The object underlying the present invention is also to provide a lamp for use between the reflector and lens of a headlamp by which the effective light yield of the headlamp is increased. In accordance with the invention, this object is achieved by so designing the masking that, when the lamp is in the installed state, those the rays of light emitted by the light source which are directed towards an ineffective reflective region are at least partly screened off. The lamp is preferably a high intensity discharge lamp having a burner envelope and an outer envelope surrounding this latter, the masking being applied to the burner envelope or the outer envelope.

Other embodiments and refinements of the invention are specified in the other dependent claims. An embodiment of the invention is shown in the drawings and will be described in detail below. In the drawings:

Fig. 1 is a schematic view of a projector-type headlamp which comprises a discharge lamp having reflective masking on the inner envelope. Fig. 2 is a schematic view of a projector-type headlamp which comprises a discharge lamp having reflective masking on the outer envelope. Fig. 3 is a schematic view of a projector-type headlamp which comprises a discharge lamp having, on the inner envelope, a version of the reflective masking for increasing the low-beam light. Fig. 4 is a view of the projector-type headlamp shown in Fig. 1 when there is no reflective masking (prior art).

The headlamp which has been selected as an embodiment comprises in essence a reflector 1 and a lens 2, between which is arranged a high intensity discharge lamp 3.

The reflector 1 takes the form of an ellipsoidal reflector in the embodiment shown in Fig. 1. Arranged on the reflector 1 is a light shield 4 that, in a known fashion, makes possible the low-beam and high-beam functions that are needed for travel on the roads. An image of the light shield 4 is formed on the road by means of the projector lens 2, thus producing a sharp light/dark cutoff.

The high intensity discharge lamp 3 is shown in an approximately horizontal installed position. The lamp 3 has a burner envelope 31 that is sealed with a vacuum-tight seal, that transmits light and that is composed of quartz glass. The burner envelope 31 encloses a discharge chamber that contains a mixture of ionizing gases that comprises at least one inert gas, and in particular xenon, and a mixture of metal halides. Two electrodes 32, 33 are arranged opposite one another in the discharge chamber of the burner envelope 31 in the usual way. The free distance between the two electrodes 32, 33 is the discharge path for the arc 36 which forms the light source. The burner envelope 31 is arranged inside an outer envelope 34. The outer envelope 34 serves in particular to filter out UV waves.

Masking 35 is applied to the burner envelope 31 of the high intensity discharge lamp 3. In the embodiment, the masking 35 is formed by a reflective coating. The masking 35 is so arranged that those emitted rays of light 36" that are directed towards an ineffective reflective region or towards areas outside the lens 2 (as indicated by a dashed line in Fig. 2) are reflected towards an effective reflective region of the reflector 1 (see the arrowed lines shown in Fig. 1). The reflective coating forming the masking 35 is so designed in this case that IR and UV waves are not reflected but are transmitted. It is only the visible that is emitted by the arc 36 formed between the electrodes 32, 33 that is reflected towards an effective reflective region of the reflector 1.

In the embodiment shown in Fig. 2, the masking 35 is applied to the outer envelope 34 of the high intensity discharge lamp 3. In this embodiment there are simply windows for passage provided laterally which transmit rays of light 36', emitted by the light source (arc) 36, towards effective reflective regions. The masking 35 is produced in the form of a reflective coating in such a way that incident rays of light 36' are reflected towards the aforementioned window. Because of the coating on the outer envelope 34, the temperature in the inner envelope 31 is, at the same time, increased by the reflection within the outer envelope 34, i.e. the luminance of the arc is increased and because of this the efficiency of the lamp is raised. In the embodiment shown in Fig. 3, the masking 35 is applied to the burner envelope 31 in such a way that the light yield in the region producing low-beam light is increased. The reflective coating is so designed in this case that IR waves are absorbed, whereby the temperature of the halides is increased at the same time and the efficiency of the lamp is thus increased as well.

Claims

CLAIMS:

1. A headlamp, and in particular a motor vehicle headlamp, comprising a reflector, a lens and a light source that is arranged between the reflector and the lens, - the light source being surrounded by at least one envelope, the reflector having effective reflective regions, i.e. ones which cause incident rays of light to be reflected onto the lens, and ineffective reflective regions, i.e. ones which do not cause incident rays of light to be reflected onto the lens, and the at least one envelope being provided with masking, characterized in that the masking (35) is designed in such a way that those rays of light emitted by the light source (36) which are directed towards an ineffective reflective region are at least partly screened off.

2. A headlamp as claimed in claim 1, characterized in that the masking (35) takes the form of a coating for reflecting visible light.

3. A headlamp as claimed in claim 1 or 2, characterized in that the coating (35) is so designed that IR waves are transmitted.

4. A headlamp as claimed in any one of claims 1 to 3, characterized in that the coating (35) is so designed that UV waves are transmitted.

5. A headlamp as claimed in any one of the preceding claims, characterized in that the light source (36) is formed by two electrodes (32, 33) of a high intensity discharge lamp (3) which project into a discharge chamber in a burner envelope (31).

6. A headlamp as claimed in claim 5, characterized in that the masking (35) is applied to the burner envelope (31).

7. A headlamp as claimed in claim 5, characterized in that the high intensity discharge lamp comprises an outer envelope (34) surrounding the burner envelope (31), and in that the masking (35) is applied to the outer envelope (34).

8. A headlamp as claimed in any one of the preceding claims, characterized in that the headlamp is in the form of a projector-type headlamp and the lens (2) is a projector lens.

9. A lamp for use between the reflector (1) and lens of a headlamp, comprising a light source (36) and an envelope surrounding the light source (36), which envelope is provided with masking, characterized in that the masking (35) is so designed that, when the lamp (3) is in the installed state, those rays of light emitted by the light source (36) which are directed towards an ineffective reflective region, i.e. a region of the reflector (1) that does not cause incident rays of light to be reflected onto the lens (2), are at least partly screened off.

10. A lamp as claimed in claim 9, characterized in that the lamp is a high intensity discharge lamp (3) having a burner envelope (31) and an outer envelope (34) surrounding this latter, the masking (35) being applied to the burner envelope (31) or the outer envelope (34).

11. A lamp as claimed in claim 9 or 10, characterized in that the masking (35) takes the form of a coating for reflecting visible light.

12. A lamp as claimed in any one of claims 9 to 11, characterized in that the coating (35) is so designed that IR waves are substantially absorbed and UV waves are substantially transmitted.