Lamp unit

In various embodiments, a lamp unit including a lamp which is inserted into a reflector and which has a base with a reference ring including at least one referencing surface which cooperatively interacts with a corresponding referencing element of a holder of the reflector, configured such that the lamp is separably connected to the holder through a bayonet coupling.

RELATED APPLICATIONS

The present application is a national stage entry according to 35 U.S.C. §371 of PCT application No. PCT/EP2010/062640 filed on Aug. 30, 2010, which claims priority from German Application No. 10 2009 040 572.0, filed on Sep. 8, 2009.

TECHNICAL FIELD

Various embodiments relate to a lamp unit.

BACKGROUND

A lamp unit of said type can in principle be used in a multiplicity of single-ended lamps. However, the main field of application is most likely to be in lamp units for vehicle headlights. A lamp unit for such motor vehicle headlights is described for example in EP 1 605 490 A2 and DE 10 2005 009 902 A1.

In these known solutions the lamp unit has a discharge lamp, such as is marketed for example under the product name “Xenarc™”. Said high-pressure discharge lamp has a single-part or multipart lamp base by way of which it can be inserted into a holder of a reflector of a motor vehicle headlight. In order to align the lamp in the reflector and prevent incorrect installation of different lamp types, one or more referencing and coding recesses are embodied on a referencing ring of the base, which recesses cooperatively interact with corresponding projections on the holder of the reflector in order to ensure that the lamp can only be inserted at a predetermined relative position with respect to the holder. Said referencing means furthermore prevents lamps of an unapproved type from being used in a motor vehicle headlight.

In the conventional solutions a plurality of radially projecting supplementary elements which form part of the headlight are additionally arranged on the base of the high-pressure discharge lamp, with which mechanical components, for example clips, brackets, coupling cages or the like come into engaging contact in order to fix the base at a defined position in the holder of the reflector.

A disadvantage with said solutions is that firstly lamp units of this type are relatively complex in terms of their structure, since the additional components must be provided for ensuring correct positional fixing. Secondly, the assembly overhead is increased due to the attachment of the additional components.

SUMMARY

Various embodiments create a lamp unit which has a simple structure and can be assembled with little effort.

According to various embodiments, the lamp unit is implemented by means of a lamp which is inserted into a reflector and has a base with a reference ring on which at least one referencing surface is embodied. This cooperatively interacts with a corresponding referencing element of a holder of the reflector. The lamp is connected to the reflector by means of a separable bayonet coupling.

Using a bayonet coupling enables the lamp to be connected directly to the reflector, so the time-consuming and labor-intensive assembly of the supplementary components, for example the clips, brackets or coupling cages described in the introduction, can be dispensed with and consequently both the equipment-related overhead and the assembly effort are reduced.

In various embodiments, the bayonet coupling embodied on the reference ring has circumferentially open-ended cutouts with which bayonet cams projecting radially from the inner circumferential surface of the holder are associated. When the lamp is inserted into the reflector, said bayonet cams are in overlapping alignment with the cutouts and engages behind the reference ring in the locked state.

Locating pegs for positioning the reference ring which are offset relative to the bayonet cams can be embodied on the inner circumferential surface of the holder.

It is preferred in this case if reference studs are embodied on an annular surface of the reference ring on the locating peg side and said reference studs can be brought into defined engaging contact with the said locating pegs.

In various embodiments, stop dogs onto which the bayonet cams run during the connecting action are embodied on the outer circumference of the base in order to define the locking position in an unmistakable manner.

In various embodiments, a stop dog is embodied on the inner circumferential surface at roughly the same axial level as the locating pegs and has a stop section extending roughly in a longitudinal direction of the reflector toward the bayonet cams and spaced apart from the inner circumferential surface.

When the lamp is inserted, the stop section drops into a latching groove of the reference ring, with an edge section of the latching groove running onto the stop dog.

The latching groove can be embodied as a recess in the sidewalls of a cutout with little outlay in terms of additional equipment.

In order to arrest the lamp base in the circumferential direction, the stop section can be engaged from behind in a locking position of the lamp by a locking projection embodied on a base surface of the cutout.

In order to enable a substantially play-free locking of the lamp base in the reflector, the latching groove can be embodied such that in the locking position the reference ring can be clamped by way of the stop dog against pretensioning elevations embodied roughly opposite the stop dog on the inner circumferential surface.

In various embodiments, a radial recess is incorporated into the inner circumferential surface roughly between the bayonet cams and the locating pegs. Arranged in said recess is an elongate spring hook extending roughly along an inner diameter of the inner circumferential surface. A hook section of the spring hook projects radially inward in the region of a bayonet cam, with a section of the cutout of the reference ring running onto said hook section during the locking action.

A shaft of the spring hook is advantageously embodied such that the spring hook clamps the reference ring in the locking position against the pretensioning elevations embodied roughly opposite the spring hook on the inner circumferential surface.

In the lamp unit according to various embodiments, as already mentioned, the supplementary components for fixing the lamp in the correct position in the reflector are superfluous, although if a lamp according to the invention is to be inserted into a conventional reflector, this can be accomplished in the conventional manner using additional radial pegs to support the supplementary components. This variant can then be used optionally in conventional holders as well as in holders according to various embodiments.

In a simply implemented exemplary embodiment with optimal fixing of the lamp in the reflector, three bayonet cams are formed on the holder of the reflector and three cutouts on the reference ring of the lamp. In principle, in a kinematic reversal or in accordance with the reversal principle, the cutouts could also be formed on the holder of the reflector and the bayonet cams on the base.

In a simply implemented exemplary embodiment, the cutouts extend roughly as far as the outer circumference of a base sleeve from which the reference ring projects radially.

According to various embodiments, the cutouts are formed roughly in a rectangular shape.

Three reference studs and three locating pegs are preferably provided in order to ensure the correct positioning of the lamp in the reflector on the face side.

The lamp unit is preferably implemented by means of a high-pressure discharge lamp for a motor vehicle headlight.

DETAILED DESCRIPTION

FIG. 1shows a three-dimensional view of a lamp unit1according to various embodiments, including a high-pressure discharge lamp4inserted into a reflector2of a motor vehicle headlight. Said lamp can be for example a metal halide high-pressure discharge lamp having an electrical power draw of approx. 25 W or a D1 to D4 lamp. High-pressure discharge lamps of this type are sufficiently well-known from the prior art, for example from EP 1 605 490 A2 or EP 0 786 791 B1, so only the components essential to an understanding of various embodimenys will be explained here and otherwise reference will be made to the cited prior art.

The special feature of the lamp unit1shown inFIG. 1consists in the fact that the reflector2and the high-pressure discharge lamp4are connected to each other by means of a bayonet coupling6, the difference compared to conventional solutions being that additional components such as clips, brackets or coupling cages are dispensed with.

FIG. 2shows an individual view of a mercury-free high-pressure discharge lamp4. This has a discharge vessel (not visible here) with an interior space into which project two diametrically opposed electrodes which are connected via metal foil fused into the discharge vessel to a current lead10in each case or to a further current lead (not shown). The discharge vessel (not visible inFIGS. 1 and 2) indicated by the reference numeral8is housed in an outer bulb9which consists likewise of fused quartz glass and optionally is provided with an ultraviolet-radiation-absorbing coating.

The outer current lead10visible inFIGS. 1 and 2is connected to a contact ring14arranged circumferentially around a base12. The axial current lead that is not shown makes electrical contact with a central contact pin16of the base12(seeFIG. 2). The interior space of the discharge vessel8is filled with an ionizable filling consisting, for example, of ultrapure xenon gas and a plurality of metal halides.

Embedded in the base12, which conventionally is implemented using multiple parts, is a metal ring embodied with spring tabs18projecting outward toward the outer bulb9. The spring tabs18embodied as welding lugs are curved with respect to a support collar20mounted onto the outer bulb9and joined to said collar by welding, for example. The high-pressure discharge lamp4is reliably centered correctly in position in the axial direction by means of the four spring tabs/welding lugs18and the correspondingly configured support collar20. With regard to further details of the structure of the base12, reference is made to the above-cited prior art.

FIG. 3shows a front view andFIG. 4a rear view of the high-pressure discharge lamp4according toFIG. 2. According thereto, the base12has a base sleeve22from which a reference ring24projects circumferentially in the radial direction. The end section of the base sleeve22furthest from the reference ring24transitions via a radial step into a contact band26on the outer circumference of which the circumferential contact ring14is formed and which encircles the central contact pin16with a clearance.

Provided on the outer circumference of the base sleeve22in the region of the radial step to the contact band26and arranged diametrically opposite each other are two (seeFIG. 4) radial pegs28which serve for securing an electrical connector by means of a bayonet union. In the exemplary embodiment shown, these two radial pegs28have no function.

The reference ring24embodied on the base sleeve22has at least one coding groove30which, in the exemplary embodiment shown, is implemented as a semicircular recess. It is ensured by means of said coding groove or coding grooves that only a specific type of high-pressure discharge lamp4can be inserted into the motor vehicle headlight at a predetermined relative position. Also implemented on the reference ring24in addition to the coding groove30are three cutouts32a,32b,32cwhich are evenly distributed around the circumference and which, in the view according toFIGS. 3 and 4, have an approximately rectangular cross-section and extend from the outer circumference of the reference ring24as far as the base sleeve22.

According toFIG. 3, three reference studs36a,36b,36coffset relative to the cutouts32and the coding groove30and likewise evenly distributed around the circumference are provided on an end face34of the reference ring24on the outer bulb side, said studs projecting somewhat from the end face34in the axial direction and being brought into engaging contact with subsequently explained elements of the reflector in order to define the axial position of the high-pressure discharge lamp in the reflector.

According to the schematic shown inFIG. 3, the outer current lead10is connected to a contact plate38which can also be seen in the bottom view according toFIG. 4and for its part is in electrical contact with the contact ring14. As can be seen fromFIG. 4, embodied on a rear end face40of the reference ring24are three stop dogs42a,42b,42cwhich are in each case arranged adjacent to one of the cutouts32and which, in the view according toFIG. 4, extend out from the rear-side end face40toward the viewer. As explained in more detail hereinbelow, said stop dogs42a,42b,42climit the relative rotation between discharge lamp4and reflector2.

Two of said stop dogs42a,42bare also visible in the view shown inFIG. 2. According thereto, the stop dogs42extend away from the outer circumference of the base sleeve22up to the outer circumference of the reference ring24and extend in the axial direction as far as the rear-side end face40(seeFIG. 2).

FIG. 5shows a three-dimensional view of the reflector2of the lamp unit1according toFIG. 1. Said reflector has a reflecting surface44(visible inFIG. 1), configured with the aim of achieving an optimal beam alignment, and a holder46which is implemented roughly as a section of a cylinder. Embodied on an inner circumferential surface48of the holder46are three bayonet cams50a,50b,50cwhich, lying on the same pitch circle as the cutouts32, are evenly distributed around the circumference, which project inward into the opening encircled by the holder46, and the geometry of which roughly corresponds to that of the cutouts32. Provided on the inner circumferential surface48, offset in relation to said bayonet cams50, are three locating pegs52a,52b,52cwhich lie on the same pitch circle as the reference studs36. The diameter of the inner circumferential surface48roughly corresponds to the outer circumference of the reference ring24.

In order to insert the high-pressure discharge lamp4into the reflector2, the cutouts32a,32b,32care first brought into overlapping alignment with one of the bayonet cams50a,50b,50cin each case and the lamp is then inserted from behind (view according toFIG. 5) into the holder46. As this is done, the bayonet cams50a,50b,50cdrop through the cutouts32a,32b,32cand the front end face34(FIG. 3) comes up onto the corresponding contact surfaces of the locating pegs52.

In a following assembly step, the high-pressure discharge lamp4is rotated to the right in the clockwise direction (view according toFIG. 6) with respect to the reflector2such that the bayonet cams50a,50b,50cengage behind the reference ring24and, after a predetermined angle of rotation, run up onto the adjacent stop dogs42a,42band42c, respectively. In this rotation angle position, the three reference studs on the front end face34of the reference ring24bear against the adjacent end faces of the three locating pegs52a,52b,52cprovided for adjusting the axial position. In this assembly position, the discharge lamp4is clamped between the locating pegs52and the bayonet cams50in the axial direction and fixed in position in the circumferential direction by means of the holder46encompassing the reference ring24, with the result that a reliable relative positioning between reflector2and high-pressure discharge lamp4is ensured with an extremely simple layout.

In the exemplary embodiment shown, the single-part or multipart base12is produced from a suitable plastic, the contact elements described being extrusion-coated in sections. The reflector is provided with a suitable coating and is likewise made of plastic.

FIG. 6shows a three-dimensional view of the reflector2of the lamp unit1fromFIG. 1according to a second exemplary embodiment. A ring54is embodied on the inner circumferential surface48of the reflector2at roughly the same axial level as the locating pegs52. The inner diameter of the ring54lies roughly between the diameter of the inner circumferential surface48and the inner diameter of the locating pegs52. Embodied on the ring54roughly between the two locating pegs52aand52baround the area of the bayonet cam50ais an elongate stop dog56which extends roughly in the longitudinal direction of the reflector2. A stop section58of the stop dog56projects outward here in the longitudinal direction toward the bayonet cam50a.

The stop dog56serves to limit the relative rotation between the discharge lamp4and the reflector2fromFIG. 1. For this purpose the reference ring24(shown inFIG. 8) of the base12fromFIG. 12according to the second exemplary embodiment has a cutout60with a latching groove62into which the stop dog56with the stop section58fromFIG. 7descends when the reference ring24is inserted into the reflector2. A recess68or70, respectively, is incorporated into a respective sidewall64or66of the cutout60in order to form the latching groove62. Embodied centrally between the recesses on a base surface of the cutout60is a locking projection72which, in a locking position of the reference ring24, engages behind the stop section58of the stop dog56fromFIG. 7, as will be explained in more detail below.

FIG. 9shows the reflector2together with the reference ring24inserted therein according to the second exemplary embodiment. For the sake of simplicity only the reference ring24is shown, as inFIG. 8, without the base12fromFIG. 2. In the position of the reference ring24shown inFIG. 9, the ring has been inserted into the holder46in the axial direction, with the cutouts32b,32cand60having been brought into overlapping alignment with the bayonet cams50a,50b,50cand the coding groove30having been brought into overlapping alignment with the corresponding referencing element of the reflector2. The stop section58of the stop dog56fromFIG. 7has in this case been inserted into the recess70of the latching groove62shown on the right inFIG. 8. If the base12fromFIG. 2is now rotated with the reference ring24relative to the reflector2in the clockwise direction in order to achieve the locking position, the stop section58slides over the locking projection72into the recess68of the latching groove62shown on the left inFIG. 8. This position of the reference ring24relative to the reflector2is shown inFIG. 10. It can be seen that the locking projection72engages behind the stop section58of the stop dog56fromFIG. 7, as a result of which the reference ring24is locked in place in the circumferential direction by means of the stop dog56.

The recess68of the latching groove62shown on the left inFIG. 8is offset somewhat toward the outside in the radial direction compared to the right-hand recess17. The offset serves to clamp the reference ring, as is explained in the following.

In the insertion position of the reference ring24shown inFIG. 9, the ring is arranged roughly free of force in the holder46. If the reference ring24is rotated as described above into the locking position shown inFIG. 10, the inward-facing side surface74on the stop dog56fromFIG. 7clamps the reference ring24against the inner circumferential surface48of the reflector2inFIG. 10by way of a base surface76of the recess68shown on the left inFIG. 8. In order to define certain areas in which the reference ring24inFIG. 10is subjected to a clamping force, two pretensioning elevations78,80arranged roughly opposite the stop dog56are embodied on the inner circumferential surface48. These pretensioning elevations78,80are formed in the axial direction roughly between the ring54and the bayonet cams50. As can be seen fromFIG. 10, the reference ring24is clamped in a defined manner between the two pretensioning elevations78,80and the stop section58of the stop dog56.

FIG. 11shows a perspective view of the reflector2according to a third exemplary embodiment. In this case the holder46is stepped back with a recess84from a rear end face82in the axial direction in the manner of a circular segment between the two locating pegs52a,52barranged at the top inFIG. 11. Said recess84extends in the axial direction roughly as far as the ring54adjacent to the referencing element86or to the locating peg52ashown at top left inFIG. 11.

A spring hook90projects from a left-hand side surface88of the recess84roughly in the circumferential direction. Said spring hook90has an elongate spring shaft92and a hook section94bent down radially inward roughly in the center of the recess84. The spring hook90, like the stop dog56fromFIG. 7, serves for positioning the lamp base12in the circumferential direction and for clamping the reference ring24in place.

In contrast to the preceding exemplary embodiment, the bayonet cams50a,50b,50care embodied on a separate retaining ring96. The latter is fixed on the reflector2, as can be seen inFIG. 12, in such a way that the bayonet cams50are positioned in accordance with the preceding exemplary embodiments.

FIG. 13shows the reflector2together with the reference ring24of the first exemplary embodiment fromFIG. 4in an insertion position. The hook section94of the spring hook90fromFIG. 11is therein inserted in the top cutout32aof the reference ring24. When the reference ring24is rotated in the clockwise direction, the hook section94comes into engaging contact with a left side surface98of the top cutout32a, thereby positioning the reference ring24in the circumferential direction. In order to clamp the reference ring24against the pretensioning elevation78,80fromFIG. 11by way of the spring hook90, the latter has a radially inward-facing concavity100on the spring shaft92adjacent to the hook section94. In the insertion position shown inFIG. 13, said concavity is arranged next to the spring hook90in the top cutout32a. When the reference ring24is rotated, the concavity slides onto an outer circumferential wall102of the reference ring24and clamps the latter against the pretensioning elevations78,80fromFIG. 11. In this case the pretensioning force is dependent on the elasticity of the spring hook90. The latter is manufactured for example from a metallic material or produced as a single piece with the injection molding method used for the holder46.

In order to clamp the reference ring24also with a high pretensioning force in the axial direction, the bayonet cams50a,50b,50cfromFIG. 12are bent inward somewhat into the drawing plane. In order to achieve a high contact pressure per unit area between the bayonet cams50a,50band50cinFIG. 14and the reference ring24, V-shaped elevations104are formed on the bayonet cams50toward the reference ring24.

A lamp unit is disclosed including a high-pressure discharge lamp which is inserted in a reflector, preferably of a motor vehicle headlight. The lamp has a base with a reference ring which is connected to the holder of the reflector by way of a bayonet interface.