Lighting unit for vehicles and mounting method

The present invention relates to a lighting unit for vehicles, comprising a light source arranged on a circuit board and further comprising an optical attachment mounted in the direction of light emission in front of the light source, said optical attachment comprising at least one holding turret on one of the sides facing the circuit board such that, at its mounting position, the holding turret slots into a hole drilled into the circuit board, wherein the optical attachment is positive-locking to a holding body arranged on one of the sides facing away from the light source, wherein the holding body is molded to a carrier frame, and wherein the holding body or the carrier frame snaps on to the optical attachment.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to and incorporates herein by reference European Patent Application Serial No. 09 177 001.6 filed on Nov. 25, 2009.

BACKGROUND

The present invention relates to a lighting unit for vehicles, comprising a light source mounted on a circuit board and further comprising an optical attachment mounted in the direction of light emission in front of the light source, said optical attachment comprising at least one holding turret on one of the sides facing the circuit board such that, at its mounting position, the holding turret slots into a hole drilled into the circuit board, wherein the optical attachment is positive-locking to a holding body arranged on one of the sides facing away from the light source.

The present invention further relates to a method of mounting a lighting unit such that an optical attachment is joined to a circuit board populated with multiple light sources and also joined to a holding body.

Publication DE 10 2007 034 123 A1 discloses a lighting unit for vehicles comprising a circuit board populated with a light source and further comprising an optical attachment mounted in the direction of light emission in front of the light source. Said optical attachment comprises two holding turrets, each slotting into a recess in a holding body located on the back of the circuit board such that, at a mounting position, the optical attachment can be riveted to the holding body in a positive locking manner. This arrangement ensures an accurate alignment of the joined components such as the optical attachment, light source and circuit board. A disadvantage of the prior art lighting unit is that the unit is not mounted until an extra step of the process is taken after slotting the holding turrets into the recesses.

SUMMARY OF THE INVENTION

The present invention presents a lighting unit for vehicle and a method of installing said lighting unit such that the components can accurately positioned and mounted in a simple and cost-efficient manner.

In order to accomplish this task, the invention according to the characterizing clause of patent claim1is characterized in that the holding body is molded to a carrier frame and in that the holding body or the carrier frame snaps to the optical attachment.

According to the invention, a holding body is molded to a carrier frame intended to hold the light sources, the optical attachments and, preferably, the front lens. Furthermore, the optical attachment snaps to the carrier frame and/or the holding body such that the ensuing subassembly can be uninstalled in a non-destructive way, the advantage being that repairs can be made to remedy a defect.

According to one embodiment of the invention, the carrier frame may comprise a plurality of spring elements pointing in the direction of light emission, said spring elements latching to matching hooks of the optical attachment installed. An advantage is that the optical attachment need not be attached to the holding body beforehand. It is enough to preliminarily place the optical attachment on the circuit board or the holding body.

According to another embodiment of the invention, cuboid heat sink may be located between the holding body and the circuit board such that said heat sink snaps to the holding body. The heat sink and the holding body make up an assembly unit that a catch mechanism attaches to the further assembly unit made up of the optical attachment and the circuit board. This essentially reduces the number of steps required to assemble the lighting unit.

According to an embodiment of the invention, the heat sink may mount to and dismount from the holding body by a recess-to-catch connection, wherein a spring clip of the holding body presses against the bottom plate inside the heat sink. Said bottom plate is located on the side of the heat sink facing the circuit board. This may provide a floating joint between the heat sink and the holding body. The spring clip is designed such that it is able to compensate for geometric, thermal and mechanical tolerances of the subassembly and to provide a long-term and reliable thermal transition from the circuit board to the light source and the heat sink.

According to another embodiment of the invention, the holding turrets of the optical attachment in conjunction with the matching may recess in the circuit board just preliminarily position and attach the elements such that all subsequent snapping processes required to assemble the lighting unit are prevented from putting any mechanical stress on the circuit board. The advantage is that the circuit board need not be separately tested following assembly.

According to another embodiment of the invention, the circuit board may have a flexible covering layer which, at its mounting position, reaches into a gap between an edge of the hole and the holding turret in order to preliminarily clamp the optical attachment to the circuit board. This would preliminarily attach the circuit board without putting any mechanical stress on said circuit board.

The method according to the invention may comprise the following steps: Putting the optical attachment in place on the circuit board such that a first subassembly is made up by a holding turret of the optical attachment slotting into a hole drilled into said circuit board; providing a form-fit link of a heat sink to the holding body molded to a carrier frame such that a second subassembly is created; and providing a form-fit link of the first and second subassemblies.

A particular advantage of the method according to the invention is that it provides quick assembly while treating the components with care. Making two subassemblies and afterwards linking them up preferably by snap-fitting them such that they can be disassembled again reduces the number of steps of the assembly process. Moreover, a test of the circuit board is not required because it is not put under any mechanical stress during assembly.

DETAILED DESCRIPTION

A lighting unit1for vehicles may, for example, generate a low beam, daytime running light, indicator light, position light function and/or a combination of these lighting functions and is installed at the front of a motor vehicle. The lighting unit1can be elongated and integrated in a headlamp of the vehicle.

In the depicted embodiment, the lighting unit1comprises an elongated carrier frame2with a U-shaped cross-section such that said carrier frame2is mounted on a housing (not shown) of the headlamp. A plurality of rows of holding bodies4in a two-dimensional and three-dimensional arrangement are molded to a front side of the carrier frame2such that said front side is facing in the direction of light emission. Each holding body4is pot-shaped and comprises wall5protruding in the direction of light emission, wherein a top and/or a bottom wall5has a slanting face6narrowing in the direction of light emission3and serving as a locating element. The purpose of this slanting face6is to provide a detachable locking connection between the holding body4and a cuboid heat sink7, wherein the heat sink7comprises opposing side walls8each of which has a recess9that the slanting face6slots into in its assembled position.FIG. 4illustrates that a recess9is in the side wall8on either side of a mid plane M of the heat sink7. The side walls8are slightly resilient and connect to a bottom plate10that is at the front if looking in the direction of light emission3. The side walls8of the heat sink7are slightly resilient in relation to the mid plane M such that the heat sinks7easily snap on to and come off of the appropriate holding bodies4.

The holding body4further comprises a spring clip11that protrudes in the direction of light emission3and, when the heat sink7is mounted on the holding body4, presses against an inside face of the bottom plate10, thus mounting the heat sink7on the holding body4and securing it at its position.

The lighting unit1further comprises a plurality of optical attachments12which are preferably tulip-shaped and intended to reflect the light emitted by the LED light sources13. The optical attachments12interconnect in a row and follow the outline of the carrier frame2. They may form an integral whole with a lens14at the front end of the lighting unit1. Alternatively, the strip of optical attachments12can be simply placed in a recess of the lens14.

Each of the optical attachments12comprises holding turrets15′,15″ at an end facing towards the carrier frame2. A first holding turret15′ is longer than a second holding turret15″. The long holding turret15′ has a chamfered insertion end16to facilitate inserting said holding turret15′ in a hole17in a circuit board18or a hole19in the heat sink7. The cross-section of both the first holding turret15′ and the second holding turret15″ is shaped like a horseshoe such that it is easier to insert the holding turrets15′,15″ in the holes17,19. Particularly, the shorter holding turret15″ can slot into the current hole17,19on its own.

The circuit board18is designed as a flexible circuit board whose outline matches the outline of the carrier frame2and the strip of optical attachments12and the lens14. The circuit board18is populated with a plurality of the LED light sources13arranged in rows. The LED light sources13are mounted on side of the circuit board18facing the lens14.

In order to obtain a first subassembly made up of the optical attachment12and the circuit board18, the optical attachments12are preliminarily positioned and attached by the holding turrets15′,15″ slotting into the holes17of the circuit board18. At this preliminary position, the optical attachments12can be loosely attached to the circuit board18. Under preliminary attachment, the optical attachments12are clamped to the circuit board18such that lugs21of a flexible covering layer on the circuit board18protruding from the edge20of hole17in said circuit board18are bent in said hole17by the holding turrets15′,15″ to fill a gap between said edge R and20of said hole17and said holding turrets15′ and15″. This preliminarily clamps the optical attachments12to the circuit board18.

A second subassembly is obtained by linking the carrier frame2to the heat sinks7separately allocated to the holding bodies4. As described earlier, each heat sink7is locked or clamped to the matching holding body4.

The last step after making the first subassembly and the second subassembly is to provide a form-fit link between the first subassembly and the second subassembly. The first subassembly preferably snaps on to the second subassembly such that the holding turrets15′,15″ slot into the holes19of the heat sink7. In order to link up the two subassemblies, the carrier frame2comprises U-shaped spring elements22on one top and underside that protrude in the direction of light emission3. These spring elements22interact with the latching hooks23molded to the corresponding top and undersides of the optical attachments12. When the lighting unit1is fully assembled, the spring elements22interlock with the latching hooks23. The ensuing clip joint can be opened manually should disassembly be required. The number of spring elements22and latching hooks23and the distance between the two types of elements is chosen to ensure that the first subassembly reliably links to the second subassembly.

The carrier frame may be made of a POM plastic material.

In view of the foregoing, it will be seen that several advantages of the invention are achieved and attained.

The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated.

REFERENCE ITEMS