BURNER HOLDER FOR A MOTOR VEHICLE LAMP

The invention concerns a burner holder for a motor vehicle lamp, comprising a gripping pot, an adjustment ring, a base and a motor vehicle lamp, in particular a halogen lamp with a burner holder of this type.

Motor vehicle lamps, in particular halogen lamps for frontal headlight, are usually constituted of a burner, consisting of a glass bulb provided with lighting means, and a burner holder that receives the said bulb. The burner holder is usually constituted of three pieces: a gripping pot for receiving the matter bonded burner, a base for connecting the lamp to a voltage source and an adjustment holder, set between the gripping pot and the base, so as to direct the burner in relation to the base. At the present time, the three mentioned function pieces are usually made of a steel alloy. In the lamp production method, the burner is primarily fixed in the gripping pot, which is then put in an adjustment holder, welded to the base. For the direction, the burner is directed in relation to the base, generating a relative movement between the gripping pot and the adjustment holder. The gripping pot is linked, after directing, to the adjustment holder by welding spots. The creation of the welding linkage is highly automated, using laser spot welding.

The mentioned burner holders disadvantage is to be heavy, because of the used steel alloy material. Because of the high weight, the lamp receiving has corresponding requirements, as the headlights are subject to strong stress caused by the presence of vibrations that are typical to the motor vehicles.

It is known, in order to reduce the weight of the steel sheet pieces in the automobile industry, how to make some construction pieces in aluminium. However, a gripping pot made in aluminium is not adapted, because of the material elasticity, to get gripping forces that are sufficient to fix the burner. The invention intends to remedy this disadvantage. The invention's

objective is to make a burner holder that may be achieved with a weight reduction, and whose creation is highly automated. This objective is achieved, according to the invention, by making the gripping pot in steel and the ring in aluminium, and linking those using a laser- welding joint. With this invention, a burner holder was achieved for a motor vehicle lamp, whose weight is reduced and whose making is highly automated. By increasing the use of steel for the gripping pot, getting sufficient volume forces is guaranteed. By making welding linkages using laser- welding joints, the method duration can be reduced. The problem is that the linkage between the gripping pot and the adjustment holder must be made as a mixed linkage, under the form of matter bond. Such linkages are a problem, as brittle inter-metallic phases are necessarily generated during the metals mixing of steel and aluminium, during the fusion process. This problem may be solved by an appropriated choice of welding parameters.

Improving the invention, the adjustment ring comprises circumferential neck, on which the gripping pot is set, so that it covers the adjustment ring neck. This way enables the welding of the steel in the aluminium, which is necessary for a linkage of this type of mix, because of the different fusion temperatures of the two linking partners, and the higher molten-pool dynamics of the aluminium.

According to an embodiment of the present invention, the adjustment ring neck comprises at least one outside crown, which is applied in an elastic way to inside of the gripping pot. So, the slit is minimized between the gripping pot and the adjustment ring, and the welding spots quality is increased for the aluminium-steel linkage. The shape of the achieved welding spot is modified by the slit width increase. As the welding is made without any additional material during the tuck-pointing by laser ray, the material quantity that is necessary to bridge the slit increases in presence of a bigger slit width. A hollow appear in the slit area, on the upper and lower side of the welding spot, which generates a decrease of the stress limit. The smaller is the slit width, the larger is the linkage surface and the higher is stress limit. Preferably, a circumferential outside crown is set. In another embodiment of the invention, the gripping pot is made in Cr-Ni steel. This material has shown it was appropriated for making gripping pots, because of

its specific properties.

In another embodiment of the invention, the base is made in aluminium and linked using laser ray welding joints with the adjustment ring. Preferably, the adjustment ring and the base are made in AlMg4,5Mn or in AlMg5Mn. These normalized alloys not only have a resistance that is sufficient for numerous applications and a transformation ability, but also a good welding ability.

Moreover, the invention objective is to achieve a method for the making of burner holder, enabling a highly automated creation of a less heavy burner holder. According to the invention, this objective is achieved in that the griping pot is set on the adjustment ring neck and in that the gripping pot and the adjustment ring are then linked together in the neck area by laser spot welding; the linkage being made using a Niro- metallurgic impulsion, for a laser impulsion duration between 5 and 15 milliseconds.

With this invention, a method for creating a burner holder was achieved, which method enables a highly automated making of a less heavy burner holder. The impulsion duration of the laser Niro-metallurgic impulsion is usually of 10 milliseconds. This way, welding spots with a higher stress limit are achieved. The invention's objective is, moreover, to make a less heavy motor vehicle lamp that can be made in a highly automated way. This objective is achieved, according to the invention, using a burner holder according to the claims 1 to 7. Other improvements and embodiments of the invention are indicated in the other sub-claims. An example of embodiment is represented on the characters and is described in details in the following. The characters show:

Figure 1 : a lamp with a holder in lateral view;

Figure 2: the representation of the figure 1 lamp according to the section

A-A; Figure 3 : a lamp with a holder in another embodiment in a exploded view and, Figure 4: the representation of the impulsion variation of a Niro- metallurgic impulsion.

The lamp chosen as example of embodiment is essentially constituted of a burner 1, which is set in the burner holder 2. The burner 1 is essentially made as a glass bulb 11, in which is set a spiral wound filament 12 which is connected by contacts 13. The contacts 13 are led toward the outside by a gripping piece set on the glass bulb 11 toward the outside, and project out of the gripping piece 11.

The burner holder is constituted of a base 3 on which is fixed an adjustment holder 4 which receives a gripping pot 5. The base 3 is made in the example of embodiment as a piece with a metallic sheet shape. As aluminium alloy, Al Mg4,5Mn is used. The base 3 comprises an essentially circular basic plate 31 , from which a circumferential circular ring 32 was created, which delimits a hollow 321 of a pot-like shape. In the basic plate 31, notches 33, at distances of 120°, were laterally and regularly shaped. The base 3 is provided, on its lower side opposite to the ring 32, at the bottom of the hollow 321, with contacts 34, that are fixed to the base by a fixation layer 35. In the example of embodiment, the fixation layer 35 is made in PPS (polyphenylsulphide). Alternatively, polyethylene (PE) or polypropylene (PP) may be used. In the contacts 34, receptions 341 are set with a circular passage shape for the reception of the burner 1 contacts 13. The adjustment holder 4 is also made as piece with an aluminium metallic sheet shape in the same aluminium alloy than base 3. The adjustment holder 4 is essentially made of a circular basic plate 41 on which is formed a circumferential neck 42. The neck 42 is rounded toward the inside on its free extremity, reducing its diameter, so as to ease the gripping pot 5 setting. On the circumference, in the neck, and at regular distances, four outside crowns 421 were made. The outside crowns 421 are used to prevent from slits generation between the neck 42 and the gripping pot 5 on fixation locations, which will be provided with laser-welding spots.

The gripping pot 5 is achieved as a piece with a metallic sheet shape and is made in CrNi steel (X5CrNil89). It comprises an upper surface 51 with a circumferential edge folded perpendicularly to this surface. The inner diameter of the circumferential edge 52 essentially corresponds to the outer diameter of the adjustment

holder 4 neck 52. In the upper surface 51 , a hollowing 511 is set, in which lateral gripping tongues 512 project. The gripping tongues 512 are used to fix the griping piece 111 of the burner.

During the making of the lamp, the burner 1 is firstly set with its gripping piece 11 in the hollow 511 of the gripping pot upper surface 51. Then, the griping pot 5 is set on the adjustment holder 4 neck 42, which has been fixed before, using laser- welding spots, to its basic plate 41 on the base 3 ring 32. The burner that is fixed in the gripping pot 5 is set in the base 3, so that the contacts 13 project in the receptions 341 of the contacts 34; the gripping pot 5 being set on the adjustment holder neck 53. After directing the burner in relation to the base, causing a relative movement between the gripping pot 5 and the adjustment holder 4, the gripping pot 5 is linked with the adjustment holder thanks to Niro-metallurgic impulsions in the neck 42 area, using laser- welding spots. It is welded this way, from the steel in the aluminium, so as to cause a controlled fusion and hardening of the materials, through the impulsion variation. The schematic variation of the Niro-metallurgic impulsion is represented on figure 4. The initial power leads to the achievement of a fusion base, and through the following impulsion peaks, the puddle movement is interrupted. The possible matters convection process is reduced and obtain an improved welding spots surface. By impulsion durations made 10 milliseconds shorter, an improved tuck-pointing result is obtained, in relation to the welding spots dimensions and surfaces. For fixing on contacts 34, the contacts 13 are welded with the receptions 341 according to the WIG methods.