Motor-vehicle component and method for producing a motor-vehicle component

Abstract

The invention relates to a motor-vehicle component, which has a metal component body (1) with an assembly opening (2) and a friction structure (3) surrounding the assembly opening (2). The friction structure (3) is embossed and hardened and additionally has laser dimpling (9). The laser dimpling (9) is created during the laser-hardening.

Description

[0001] Motor vehicle component and method for producing a motor vehicle component

[0002] The invention relates to a motor vehicle component with a metallic component body having a mounting opening and a friction structure surrounding the mounting opening.

[0003] Automotive components, such as body components or structural components, are often connected to other components and / or add-on components or are assembled from multiple components or component parts. The components are connected using screw connections, among other methods. Screws are guided into or through assembly openings and are clamped and supported. Depending on the application, this is achieved by incorporating washers. A washer, placed between the screw head and the component body to be fastened with the screw, serves to distribute and transfer the force emanating from the underside of the screw head over a larger area of ​​the component body. In the case of through-bolts, a washer is also provided under the locking nut, depending on the application.

[0004] There is also a proposal to dispense with washers and profile the surface of at least one component in the area of ​​the clamping surface of a press fit. DE 10 2012 022 504 A1 discloses producing a surface structure for a press fit between two components using an embossing or cold pressing process and then hardening it. Hardening can be done inductively or by laser or electron beam processes.

[0005] The invention is based on the object of functionally improving a motor vehicle component with a metallic body and an embossed and hardened friction structure and of demonstrating a method for producing such a motor vehicle component.

[0006] The invention is achieved by a motor vehicle component having the features of patent claim 1.

[0007] A method for producing such a motor vehicle component is the subject of patent claim 9.

[0008] The motor vehicle component according to the invention comprises a metallic component body with a mounting opening and a friction structure surrounding the mounting opening. The mounting opening and the friction structure form a connection point on the motor vehicle component, via which a screw connection with another motor vehicle component or a component part can be made. The screw connection is realized using screw elements. Screw elements are, in particular, screws, screw bolts, or screw nuts. During an assembly process, a connecting screw is guided into or through the mounting opening and a coupling with another motor vehicle component or a component part is established. The components are clamped in this process. The mounting opening can be a through hole or a bore with an internal thread. The friction structure is embossed directly into the component body.The friction structure is embossed by material displacement, so that the friction structure has elevations and / or depressions. To ensure that the embossed friction structure interlocks better with the adjacent components, the friction structure is hardened at least in certain areas. In the motor vehicle component according to the invention, the embossed and hardened friction structure is additionally provided with laser dimplings. Laser dimplings can also be referred to as pits that are created by the influence of a laser beam on the surface structure. This process creates unevenness in the surface that is caused by the partial melting of the material by a laser beam. Laser hardening does not produce laser dimplings because hardening takes place at temperatures below the melting point of the material. Laser dimplings only form when the melting temperature is exceeded. This is the case with the invention.For this purpose, hardening is carried out at slightly higher temperatures, so that the material is partially melted and heated in the heat-affected zone around the melting area with the aim of hardening the material. Hardening and the production of the laser dimplings are carried out in a single step. The micrograph shows the laser dimplings and the structural changes caused by hardening in the area of ​​the laser dimplings.

[0009] These additional laser dimplings on the friction structure improve the functional properties of the friction structure with regard to its topology and with regard to its engagement with the adjacent component that is clamped with the motor vehicle component according to the invention. The friction structure can be manufactured extremely cost-effectively because no additional material needs to be added. It is not necessary to weld or form-fit separately manufactured washer rings to the motor vehicle component. Furthermore, hardening and the production of the laser dimplings can be carried out in a single operation. As a result, the embossed, hardened, and laser-dimpled friction structure can increase friction at or in the area around the mounting opening, and the force exerted by a screw element can be efficiently transferred to the surface in the area of ​​the friction structure.Screw elements are held more securely, and the connection can transmit higher transverse forces with the same contact force. This makes it possible to use smaller screw elements, such as assembly screws. The integrated friction structure, meaning the elimination of loose or fixed washers, reduces material and weight in the automotive component.

[0010] The friction structure is optimally adapted to the connection point of the motor vehicle component in terms of its spatial shape and arrangement. The friction structure can have ribs produced by stamping that have an annular shape. The annular shape is, in particular, a closed ring. Several rings are arranged concentrically, in particular with respect to a center of the mounting opening, i.e., they surround the mounting opening. The radius of the several ribs with an annular shape increases with respect to the mounting opening.

[0011] Particularly advantageous is the friction structure having ribs produced by stamping that extend radially outward from the mounting opening. In particular, the ribs run radially, i.e., they have a radial pattern with respect to a center point of the mounting opening. The ribs are raised above the areas adjacent to the ribs. The ribs provide the necessary friction and are subject to high loads when screwed tight. Therefore, the ribs of the friction structure should be hardened. The laser dimplings are arranged on the ribs for this purpose. As a result, the ribs do not have an exactly straight, linear pattern, particularly in the area of ​​their rib crests, but rather have surface unevenness depending on the number and arrangement of the laser dimplings.

[0012] It is also considered advantageous if the height of the rib increases slightly radially outward, with a rib crest having an average gradient of 0.025 to 3°, in particular of 0.5 to 1.5°. The gradient is preferably 1° from the radially inner end of the rib crest to the radially outer end of the rib crest. The average gradient is the arithmetically averaged gradient over a plurality of measuring points between the inner end of the rib crest and the outer end of the rib crest.

[0013] Regardless of the pitch, the ribs should have an average height measured over their length of 0.05 to 0.9 mm, in particular 0.1 to 0.4 mm. The average height is the arithmetic mean height over a large number of measuring points along the length of the rib in the area of ​​the rib crest. A rib with an average height of 0.1 mm and a pitch of 0.5 to 1.5° has a height of less than 0.1 mm on the radial inside and a height of slightly more than 0.1 mm on the radial outside. Accordingly, for a rib with an average height of 0.4 mm, the radially outer end of the rib will be slightly higher on the radial outside for a corresponding pitch of the rib. The exact values ​​depend on the length of the rib and the manufacturing tolerances.

[0014] The rib crest in particular is structured by the formation of laser dimplings because the melting point is exceeded first at the rib crest due to reduced heat dissipation into adjacent areas. The laser dimplings are arranged at a distance from one another in the longitudinal direction of the rib. There can be an area without laser dimplings, i.e. a gap, between two consecutive laser dimplings. The laser dimplings of adjacent ribs can be offset from one another in the radial direction, e.g. by half a gap. In this way, laser dimplings are preferably located in every radial area of ​​the ribs, viewed in the circumferential direction of the mounting opening, which further improves the interlocking of the friction structure with the mating component. The laser dimplings are not intended to create an additional annular structure in the form of several concentric rings on the radially arranged ribs.Rather, the dimplings should be arranged at different radial distances from rib to rib and, if possible, offset by at least half the width of a laser dimpling. The radial offset of the laser dimplings from rib to rib can also be significantly smaller, for example, 1 / n, where n is the number of ribs. In this case, all laser dimplings are offset from one another in the radial direction.

[0015] Within the scope of the invention, laser dimplings can be specifically created which differ from one another in their size and shape. In particular, ribs can be provided with laser dimplings which create a stepped structure of the ribs sloping towards the assembly opening. The shape and size of the laser dimplings can be controlled by the energy input (power, pulse duration) and the focus position of the laser, so that the ribs can be structured to a greater or lesser extent. The ribs preferably have a triangular cross-section. The ribs which taper to the rib crest have a rounded rib crest after embossing. The ribs have flanks which are preferably at an angle of 60 to 90° to one another. The heat input into the slender rib crest is particularly high during laser treatment, so that melting is more likely to occur in the area of ​​the rib crest than in the area of ​​the flanks. Through the clever design of the laser dimplings, i.e.By guiding the laser beam (irradiation angle, focus position) and using suitable performance parameters (exposure time, power), a 3D-profiled surface can be created which, thanks to heat-affected zones that can be adjusted to varying sizes, exhibits a hardness in the range of 250 to 420 HV, particularly in the range of 270 to 340 HV, at least in some areas. These hardness values ​​are only achieved in the hardened areas of the friction structure, namely where the laser treatment took place. The ribs, in particular, are among the hardened areas of the friction structure. The friction structure may have unhardened areas, particularly between the ribs.

[0016] Within the scope of the invention, the mounting opening can be completely or partially surrounded by the friction structure. The friction structure preferably borders directly on the mounting opening, optionally delimited by a chamfer at the mounting opening to facilitate installation. The friction structure is preferably circular. Its outer diameter preferably corresponds to approximately 1.5 to 2 times the diameter of the mounting opening.

[0017] The motor vehicle components according to the invention are, in particular, axles, axle components, or axle bodies, for example, subframes, as well as assemblies and supports, for example, wheel carriers. A motor vehicle component according to the invention can be manufactured from steel, preferably from interconnected shell-shaped component bodies, which have connection points designed according to the invention with mounting openings and friction structures surrounding them.

[0018] The inventive method for producing a motor vehicle component initially provides for the provision of a metallic component body made of hardenable steel with a mounting opening. The mounting opening is partially or completely surrounded by a friction structure produced by an embossing process. The embossing process can be a cold-pressing process. The friction structure produced in this way is hardened by a laser beam process. In addition, laser dimplings are formed on the friction element. During hardening by a laser beam process, the material itself is not melted, but merely heated. During the formation of laser dimplings, the material is partially melted, so that the geometric surface changes in the form of laser dimplings arise. The inventive method combines laser hardening and the production of laser dimplings.From a process engineering perspective, the advantage is that the heat input of the laser beam hardening process simultaneously forms the laser dimplings on the friction element. The energy consumption and thus the manufacturing effort are lower than with separate processes.

[0019] The laser dimplings are formed in particular on raised ribs of the friction structure, whereby the ribs are hardened simultaneously during the production of the laser dimplings.

[0020] The difference between hardening and the production of laser dimplings is that during hardening, the laser power is significantly reduced, but the exposure time is increased. If, however, the material is to be cut using a laser process, it must be melted. In this case, the intensity, i.e. the power of the laser, is increased. In terms of manufacturing technology, the production of laser dimplings lies between hardening and cutting. It takes place with a relatively long exposure time of the laser at a comparatively low intensity, so that the surface areas of the friction structure are melted but not vaporized. The material is hardened in the heat-affected zone.

[0021] When selecting suitable parameters, care must therefore be taken not to simply heat the material, as is the case with hardening, but also to adjust the intensity and irradiation duration so that surface areas are melted so that the laser dimplings are formed.

[0022] The invention is explained in more detail below with reference to exemplary embodiments schematically illustrated in the drawings. They show:

[0023] Figure 1 is a plan view of a friction structure on a motor vehicle component;

[0024] Figure 2 shows a cross section through a rib of the friction structure;

[0025] Figure 3 shows a rib of the friction structure in longitudinal section through the motor vehicle component;

[0026] Figure 4 is a diagram showing the relationship between the intensity of the laser beam and the irradiation time;

[0027] Figure 5: Micrographs of different laser dimplings;

[0028] Figure 6 is a plan view of another embodiment of a friction structure on a motor vehicle component.

[0029] Figure 1 shows a motor vehicle component 1 with a mounting opening 2 and a friction structure 3. The friction structure 3 has a plurality of radially arranged, straight ribs 4 which run from radially inward to radially outward with respect to the mounting opening 2. There are a total of 18 ribs 4 evenly distributed around the circumference. One rib 4 is shown in cross-section in Figure 2. It has a height of 0.3 mm. The ribs 4 are triangular in cross-section and widen towards their base. Their straight flanks 5, 6 are at an angle W1 of 60° to one another and terminate in a rib crest 7. The rib crest 7 is rounded. All ribs 4 are identical. They are produced using a stamping process.

[0030] In the longitudinal section of Figure 3 it can be seen that the height of the rib 4 increases linearly towards the radially outwards. The pitch angle W2 in this embodiment is 1° + / - 0.5°. A chamfer 8 is located on the radially inner mounting opening 2. Figure 1 shows, at reference numeral 9, not to scale and purely as an example, the position of a laser dimpling 9 produced by the action of a laser beam. The laser dimpling 9 was formed on the rib 4. A plurality of such laser dimplings 9 are arranged around the circumference of the friction structure 3. They are each located in the region of the ribs 4. On each rib 4 there are several laser dimplings 9 distributed in the radial direction. The laser dimplings 9 of adjacent ribs 4 can be offset from one another in the radial direction. The laser dimplings 9 are manufactured using the same laser treatment that is used to harden parts of the friction structure.

[0031] Figure 4 shows the relationship between the laser intensity (watts per square centimeter) and the irradiation time in seconds. Hardening occurs at a comparatively low intensity and a longer irradiation time. The material is not melted. When the material is melted, areas for cutting, drilling, or, after evaporation, plasma formation are reached. The production of laser dimplings lies in the area between cutting and hardening, and therefore occurs with a comparatively long irradiation time and, at the same time, low intensity, which only needs to be high enough to melt the surface. The laser dimplings can have different structures depending on the focus, pulse duration, and laser power, as can be seen from the example micrographs in Figure 5.

[0032] The microsections are not necessarily located in the plane of the highest or lowest elevation of the laser dimplings 9. Therefore, different grinding depths can occur in different grinding planes. However, the microsections make it clear that the laser dimplings 9 merge into one another to a certain extent depending on the size of the heat-affected zone, as can be seen in examples #1 and #3. The difference between the first and second embodiments lies solely in a different focus position of the laser. In examples #3 and #4, the differences arise from different pulse durations of the laser at the same power. In the embodiment in Figure 5, the surface was only slightly melted. The heat-affected zone is comparatively small and penetrates the surface only slightly. The example in Figures #6 and #7 shows a variant with a different focus position, which also changes the shape of the laser dimplings 9.The changed focus position results in a deeper heat-affected zone, while the geometric changes on the surface are comparatively small. The individual laser dimplings 9 are therefore somewhat smaller than, for example, in variants #4 and #5. Example #8 shows laser dimplings 9 arranged completely separately from one another, i.e., spaced apart to form a gap, which also extend relatively deep into the material. Compared to the variant shown in Figure 7, the laser power has been increased.

[0033] In this example, all laser dimplings 9 were produced under a protective gas atmosphere. Production without a protective gas atmosphere is possible. Different power levels were used to create different heat-affected zones of varying sizes. The examples show that not the entire surface area is necessarily hardened; hardening can also be performed only partially. HDT580F (according to DIN 10338) was used for the micrographs. Another preferred material for this process is S420MC (according to DIN EN 10149). The required hardness of the ribs is 270 to 340 HV.

[0034] The processing direction of the laser and the shielding gas are each directed from radially outside to radially inside in order to form a staircase in the rib 4.

[0035] The height of the ribs is achieved with an embossing tool, and the ribs are solidified (laser hardening) or remelted and hardened with the laser to produce laser dimplings 9. The processing direction of the laser and the shielding gas are each directed from radially outside to radially inside to form a staircase in the rib 4.

[0036] Figure 6 shows a motor vehicle component 1 with a mounting opening 2 and a friction structure 3 in a further embodiment. The friction structure 3 has a plurality of rings arranged concentrically to the mounting opening 2, which rings are formed by annular ribs 4. In this example, there are 4 rings or ribs 4 arranged at the same radial distance from one another. The ribs 4 are triangular in cross-section and widen towards their base. They each have flanks and a rounded rib crest 7. All ribs 4 are identical. They are produced using a stamping process. Laser dimplings 9 are located on the rib crest 7. Only a few of the laser dimplings 9 are shown here as examples. They are also located on the other ribs 4. The stamped ribs 4 were hardened and remelted in certain areas during the production of the laser dimplings 9.

[0037] The motor vehicle parts according to the invention are used in particular for screwing the front axle support to the longitudinal member and are generally suitable for any screw connection subject to radial and / or axial stress.

[0038] Reference symbol:

[0039] 1 - Component

[0040] 2 - Mounting opening

[0041] 3 - Friction structure

[0042] 4 - Rib

[0043] 5 - Flank

[0044] 6 - Flank

[0045] 7 - Costal crest

[0046] 8 - Chamfer

[0047] 9 - Laser Dimplings

[0048] H - Height

[0049] W1 - Angle

[0050] W2 - Angle

Claims

Patent claims 1. Motor vehicle component which has a metallic component body (1) with a mounting opening (2) and a friction structure (3) surrounding the mounting opening (2) with elevations and / or depressions, wherein the friction structure (3) is embossed and hardened, characterized in that the embossed and hardened friction structure (3) has laser dimplings (9).

2. Motor vehicle component according to claim 1, characterized in that the friction structure (3) has ribs (4) produced by embossing, which have an annular course.

3. Motor vehicle component according to claim 1, characterized in that the friction structure (3) has ribs (4) produced by embossing, which extend radially outwards from the mounting opening (2).

4. Motor vehicle component according to claim 2 or 3, characterized in that the laser dimplings (9) are arranged on the ribs (4).

5. Motor vehicle component according to one of claims 2 to 4, characterized in that the ribs (4) have an average height (H) measured over their length of 0.05 to 0.9 mm, in particular 0.1 to 0.4 mm.

6. Motor vehicle component according to one of claims 2 to 5, characterized in that the ribs (4) have a stair structure sloping towards the assembly opening (2) due to the laser dimplings (9).

7. Motor vehicle component according to claim 2 to 6, characterized in that a hardened region of the friction structure has a hardness of 250 HV to 420 HV.

8. Motor vehicle component according to claims 3 to 7, characterized in that the height (H) of the ribs (4) increases radially outwards, wherein a rib crest (7) has an average gradient of 0.025 to 3°, in particular of 0.5 to 1.5°.

9. A method for producing a motor vehicle component, wherein a mounting opening (2) is produced in a metallic component body (1), and wherein a friction structure (3) is produced circumferentially of the mounting opening (2) by a stamping process, wherein the friction structure (2) is hardened by a laser beam process, characterized in that laser dimplings (9) are formed on the friction structure (2).

10. The method according to claim 9, characterized in that the laser dimplings (9) are formed on raised ribs (4) of the friction structure (3), wherein the ribs (4) are simultaneously hardened at least in regions during the production of the laser dimplings (9).

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