METHOD FOR PRODUCEING A CONNECTION BETWEEN A FIRST PLASTIC COMPONENT AND A SECOND PLASTIC COMPONENT AND CONNECTION PRODUCE BY METHOD

Description

[0001] The invention relates to a method for producing a connection between a first plastic component and a second plastic component. State of the art

[0002] Bumpers are increasingly being manufactured with mounts for ultrasonic sensors for parking aids and parking assistants, as well as radar sensors.

[0003] From DE 10 2007 034 412 A1, a device intended for a motor vehicle is known for monitoring the distance of the vehicle from an object by means of a sensor, in particular an ultrasonic sensor, for distance measurement. The device has a holder that can be fixed in a body area of ​​the motor vehicle, in particular on a plastic part such as a bumper, by means of a mounting surface, and which receives the sensor. Furthermore, an ultrasonic welding method for fixing the device, as well as a body component made of plastic and a sensor that can be fixed to it, are disclosed.

[0004] This device, known as "Parkpilot" or "Park Distance Control," is already widely used. In this well-known system, distance sensors installed in the front or rear bumper detect objects behind the vehicle using ultrasonic pulses, similar to sonar. The sensor signals are evaluated in a control unit, which calculates the distance to the nearest detected object. As soon as the calculation indicates that an obstacle is less than, for example, 1.2 meters from the vehicle, a warning signal is emitted to the driver in the form of an intermittent tone. The pause between individual tones of the warning signal shortens as the vehicle approaches the obstacle, until the warning signal becomes a continuous tone at a distance of 30 centimeters. Simultaneously, the distance can be displayed visually on a multi-colored display located in the rear of the vehicle.

[0005] Since the brackets have to be installed as variants of the large-area component, i.e. the bumper, they are not injection-molded at the same time, but welded to the large-area base component as required.

[0006] It is also known to attach the brackets to the vehicle body using an ultrasonic welding process. For this, the corresponding surfaces of the mounting surface and the body area are smooth to maximize the contact area. However, a disadvantage of this method is that the energy input during the melting of the contact surface on the visible side of the body area can impair its visual appearance.

[0007] From EP 3 848 185 A1, a method for ultrasonic welding of two plastic components using a sonotrode is known, wherein the energy for welding is introduced into the plastic components via at least two pins of the sonotrode, wherein the two plastic components are welded together step by step, wherein each subsequent welding step takes place in an area that has already been stressed and relaxed by the preceding welding step.

[0008] The sound is coupled in through at least two protruding projections or pins. This ensures precise sound coupling, largely independent of any component tolerances or positioning inaccuracies. This prevents unwanted weld seams in the edge areas of the sonotrode and / or the component or workpiece. During the welding process, the sonotrode is positioned on the workpiece so that its central longitudinal axis runs perpendicular to the workpiece surface. The vibration is thus coupled perpendicularly into the workpiece, i.e., the components to be welded, in the direction of the sonotrode's central longitudinal axis.

[0009] US 2005 104 389 A1 shows an assembly of a trim panel made of thermoplastic material for a motor vehicle with another part having a thin section made of thermoplastic material, wherein the thin section has openings and the melting of the trim panel together with the thin section is localized exclusively at the outlines of the through-openings.

[0010] From DE 10 2012 221 605 A1, a method for joining two components or a component assembly is known, wherein the second component is a prefabricated, i.e., solid, plastic component, which is joined to the first component in the connection area by melting or liquefying the plastic material on the side facing the first component. This melting or liquefaction of the plastic material of the second component results in an intimate bond or interlocking between the plastic of the second component and the surface structure of the first component, so that a secure and firm connection between the two components is formed after the plastic has (re)solidified. One of the component surfaces is structured.

[0011] WO 2018 / 172 385 A1 discloses a method for connecting a first object to a second object, where one of the objects has a specific density profile. Ribs represent the anchor points of the two objects, which have very different densities.

[0012] JP 2016 010 883 A describes a method for joining two plastic components. These are a vehicle component, a bumper, and a sensor bracket. Ultrasonic welding is used to join the two components.

[0013] In the area where the two components are welded together, the surface is designed to form ribs. The ribs of the two components can be offset from each other before welding.

[0014] The object of the invention is to propose an optimized manufacturing process that leads to a high-strength bond.

[0015] The problem is solved by a method for producing a connection between a first plastic component and a second plastic component, wherein at least one of the two components is manufactured by injection molding, and wherein at least one fastening area is provided on the at least one component, which is injection molded with a surface structure of closely spaced grooves, and wherein the components are joined together in the fastening area using an ultrasonic welding process, and wherein the fastening area is structured with pyramids or cones.

[0016] The surface structure greatly improves the strength after welding.

[0017] The grooves are produced at least partially parallel to each other in the fastening area of ​​at least one component.

[0018] The grooves are produced in the fastening area of ​​at least one component at a distance between groove tips of 0.1 to 2 mm.

[0019] The grooves in the fastening area of ​​at least one component are produced at a depth between groove tip and groove base of 0.1 to 2 mm.

[0020] It is advantageous that the energy for welding is introduced into the plastic components via at least one pin of a sonotrode, whereby the two components are spot-welded together step by step.

[0021] In this process, each subsequent welding step takes place in an area that has already been stressed and relaxed by the previous welding step.

[0022] The components are bumpers and holders for sensors, reinforcement parts and other parts with thinner wall thickness. Description of the characters

[0023] The invention is described below by way of example with reference to the attached drawing. Fig. 1 shows a schematic representation of a front bumper, Fig. 2 shows a state-of-the-art sonotrode, Fig. 3 shows an exemplary welding path, Fig. 4 . shows a surface structure, Figs. 5a, 5b and 5c Each shows a top view of the surface of a component.

[0024] Figure 1 Figure 1 shows an embodiment with an exemplary bumper 1 as used in the front of a vehicle. The bumper 1 represents a first component 31 made of plastic. However, it could also be a sill, a tailgate, a wheel arch liner, or another plastic part on the exterior of the vehicle.

[0025] On the side 1b of the bumper 1 facing the vehicle, for example, holders 2 for various sensors are attached. Reinforcing parts, spoilers, etc., can also be connected to the first component 31 as a second component 32. The holder 2 shown as an example has an annular contact surface 3 and a cylindrical receptacle 4. A sensor is inserted into the receptacle 4 and locked in place via the tabs 5 attached to the receptacle 4 using a clip connection or a bayonet connection. The outward-facing surface 1a of the bumper 1 must not show any visible traces of the holder or holders 2 and must have a perfect paint finish.

[0026] The mounting surface 3 of the holder 2 can of course also be square or rectangular, as well as asymmetrical, to ensure precise positioning of the holder 2 on the bumper 1. A possible welding path 10 is indicated as a circular path.

[0027] On the inner side 1b of the bumper 1, a mounting area 20 for the holder 2 is indicated, which in this example is chosen to be rectangular.

[0028] A cross-section through the mounting area 20 of the bumper 1 is shown in the Figure 4 The surface of bumper 1 is designed with a grooved structure, as is also found in Figure 5a shown in the top view. The grooves 21, with their depth, are only located on the surface of the bumper 1, which has a significantly greater thickness of up to 15 mm.

[0029] The grooves are spaced less than one millimeter apart; in this example, the distance between groove tips 21a and the next is 0.7 mm. The groove depth from groove tip 21a to groove base 21b is, for example, 0.6 mm. The range for the groove tip spacing is set between 0.1 and 2 mm, and the groove depth is 0.1–2 mm. Within this range, the desired connection achieves optimal strength.

[0030] The grooves 21 are, as in Figure 5a shown, in one embodiment arranged linearly and parallel to each other. In the Figure 5b An arrangement in a checkerboard pattern is shown, in which the groove tips 21a form squares or rectangles or even a hexagonal structure. However, the small distance between the groove tips 21a and the depth to the groove base 21b are maintained.

[0031] One example design uses 1x1 mm squares with a depth of 0.2 mm and a groove tip spacing of 1.5 mm. The optimal range is a design with a spacing of 0.2 to 3 mm and a depth of 0.2 to 3 mm.

[0032] In the Figure 5c The image shows a surface structure forming small pyramids on the base of a square or rectangle. A conical structure based on circles and ellipses is also possible. The height of the pyramids or cones is between 0.1 and 2 mm, and the spacing between them is also 0.1 to 2 mm.

[0033] The cones can also be formed as truncated cones.

[0034] In the production of the connection between bumper 1 and bracket 2, i.e., a first component 31 made of plastic and a second component 32 made of plastic, the first and second components are manufactured using plastic injection molding. The first component 31 or the second component 32, or both components, have one or more mounting areas 20. These are manufactured using plastic injection molding in conjunction with the overall shape of the components.

[0035] Materials used include, for example, PP, PP with talc, PP with fiberglass, ABS, PC with ABS and ASA.

[0036] In the next step, the components 31, 32 are connected to each other in a form-fitting manner, with the fastening areas 20 serving as connection surfaces.

[0037] Ultrasonic welding processes are used as welding methods. For example, the welding process known from DE 10 2020 200 184 A1 is used.

[0038] The process uses ultrasonic welding with a sonotrode 6, as exemplified in Figure 2 The sonotrode 6 is shown. In this embodiment, the sonotrode 6 has two pins 7.

[0039] The holder 2 is spot-welded to the bumper 1 at the two pins 7 via such a sonotrode 6.

[0040] The welding process is carried out step by step by moving the sonotrode 6 along the contact surface 3 of the holder 2, which rests on the mounting area 20. In the example of the Figure 1 The sonotrode moves along a circular line in the area of ​​the ring-shaped mounting surface 3.

[0041] In the Figure 3A more linear welding path is shown. The welding points 11 are set in pairs using the sonotrode with two pins. After welding step S1, welding step S2 is performed, and so on. For welding step S1, an area for energy control 9 is marked, as is the case for welding step S4.

[0042] Following the first welding step, e.g., S1, the next step, S2, takes place in an area 9 of the plastic element that was already subjected to a specific stress during the first welding step, S1, and is now in a state of relaxation. The surface structuring with grooves 21 increases the surface area of ​​the first and / or second component 31, 32, thus improving and increasing the efficiency of the melting process.

[0043] This means that less energy, stress, and heat are required for the second welding step, S2, than for S1, since the material has not yet fully cooled and hardened. The stepwise welding process introduces less energy into the components being welded, yet the weld joint is very strong. The joint strength increases by 9 to 13% compared to a joint between components without a surface structure.

[0044] A certain time interval must be observed between the individual welding steps S1, S2... to allow the material to relax. Reference symbol list

[0045] 1 Bumper 1a Inner side of bumper 1b Outer side of bumper 2 Bracket 3 Contact surface 4 Receptacle 5 Tabs 6 Sonotrode 7 Pins 9 Area 10 Weld path 11 Weld point 20 Mounting area 21 Groove 21a Groove tip 21b Groove base 31 First component 32 Second component

Claims

1. Method for producing a connection between a first plastic component (31) and a second plastic component (32), wherein at least one of the two components is produced by plastics injection moulding, and wherein at least one fastening region (20) is provided on the at least one component (31, 32) and is moulded with a surface structure of grooves (21) having a small spacing, and wherein the components (31, 32) are connected to one another by an ultrasonic welding method in the fastening region (20), the grooves (21) being produced in the fastening region (20) of the at least one component (31, 32) with a groove apex (21a) to groove apex (21a) spacing of from 0.1 to 2 mm, characterized in that the fastening region is structured with pyramids or cones.

2. Method according to Claim 1, wherein the grooves (21) are produced in the fastening region (20) of the at least one component (31, 32) at least partially parallel to one another.

3. Method according to either of the preceding claims, wherein the grooves (21) are produced in the fastening region (20) of the at least one component (31, 32) with a depth between the groove apex (21a) and the groove base (21b) of from 0.1 to 2 mm.

4. Method according to any one of the preceding claims, wherein the energy for the welding is introduced into the plastic components via at least one pin (7) of a sonotrode (6), the two components (31, 32) being spot-welded to one another step-by-step.

5. Method according to Claim 4, characterized in that the next respective welding step is carried out in a region (9) which has already been stressed by the previous step of the welding and relaxed again.

6. Method according to any one of the preceding claims, characterized in that the components (31, 32) are bumpers (1) and holders (2) for sensors, reinforcing parts and other parts having a relatively thin wall thickness.