Method and damping element for reducing the natural vibration of a component

The subject of the invention is a method for reducing the natural vibrations of a structural part and the use of a damping element to reduce the natural vibrations of the structural part.

[0002] It is generally known in the art that in-vehicle driving noise is reduced by various acoustic materials, such as damping mats and spray acoustic masses applied to vehicle structural parts. In order to obtain damping by means of damping mats applied to the places provided on the structural part of the vehicle, large-surface mats are applied, which then attach to the ground at process temperatures. As a result, the vehicle structural part is stiffened locally.

[0003] From DE 103 36 842 A1, self-adhesive and vibration damping strips for sticking to the ground, e.g. parts of a motor vehicle or equipment, are known for suppressing sound and vibration. Also described in EP 0 542 201 A1, the self-adhesive article in the form of a tape or foil contains a heat-resistant and vibration-damping adhesive applied to parts of a motor vehicle to damp vibrations and noise.

[0004] In addition, it is generally known from the prior art that process apertures are used in parts of the body during the manufacture of the car body

- 1 required for various work operations, for attaching body parts and for carrying out anti-corrosion treatments. When performing anti-corrosive treatments, these holes are intended for the introduction of varnish during immersion painting and / or as drainage holes for excess varnish. Alternatively or additionally, the holes serve to supply wax during maintenance of the interior spaces and to drain excess wax. In order to obtain the minimum noise level and tightness of the vehicle, these holes are closed later in the production process. For example, the openings are closed and sealed by hand with plugs or adhesive elements.

[0005] Such adhesive elements are known from DE 10 2008 050 772 A1. The adhesive element is multi-layered and consists of a carrier foil and a self-adhesive damping mass. At least on the other side of the carrier foil, opposite to the damping mass, an anti-corrosive layer suitable for painting is applied. The adhesive element is made of aluminum, aluminum alloy, stainless steel or polyethylene terephthalate.

[0006] The object of the invention is to propose a method for reducing the natural vibrations of the structural parts and a damping element for reducing the natural vibrations of the structural parts.

[0007] In terms of the method, the task is solved according to the invention by the features given in claim 1. 1, and in terms of the use of the damping element by the features given in claim 1. 6. Preferred developments of the invention are the subject of the dependent claims. In the method of reducing the natural vibrations of a construction part, according to the invention, the characteristics of the construction part in terms of vibrations are determined. In places designated at this point where there are vibration amplitudes exceeding the set limit value,

- 2 a damping element is locally attached, made in the form of a multilayer adhesive element with a supporting layer and self-adhesive damping mass.

[0008] As a result of the local application of multi-layer, rigid adhesive elements, the made damping elements and their precise placement in designated places ensures, compared to large, heavy and large-surface damping mats, a significant reduction in weight while improving the acoustic efficiency. The resulting reduction of natural vibrations and an increase in the damping of material vibrations is the result of the multilayer damping element gluing to the structural part, thanks to which an extremely rigid connection with high acoustic efficiency is obtained. As a result of using this method of reducing the natural vibrations of the vehicle's structural part, apart from increasing the comfort for the vehicle's passengers, one also receives a reduction in fuel consumption as a result of introducing a smaller mass and thus a reduction in emissions of harmful substances and carbon dioxide.

[0009] Compared to serial large-scale bituminous damping films, it is possible to obtain, with a simultaneous weight reduction, up to 40% to 60% damping of material vibrations. Compared to the magnetic foils used to suppress material vibrations, a further improvement in weight saving is obtained. The effect of material vibration is visible on the courses of vibration transfer curves depending on the frequency of the middle third, which can be determined, for example, using a laser vibration scanner.

[0010] Further reduction of the material input is achieved due to the smaller size of the adhesive elements compared to large-scale damping mats and due to local or point distribution in relation to

- 3 surface deployments. This particularly results in cost savings. In addition, glued components are characterized by exceptional ease of use and fastening, especially on structural parts with complex geometries. It is also possible to use glued elements automatically, which reduces production time and reduces employment, which results in further cost savings.

[0011] Embodiments of the invention will be further explained in more detail based on the drawings.

[0012] They present:

Fig. 1 schematically a damping element for the method and application according to the present invention,

Fig. 2A schematically a construction part with a damping element according to the prior art,

Fig. 2B schematically a structural part in section with a damping element according to the prior art,

Fig. 3 schematically a construction part with several damping elements applied according to Fig. 1 and

Fig. 4 schematically several damping elements applied to the support element.

[0013] All corresponding parts in all drawings have the same reference numbers.

[0014] In Fig. 1 the braking or damping element 1 according to the invention is shown (e.g. a damping element having essentially damping properties and

- 4 only partially inhibitory properties). The damping element 1 is made in the form of an adhesive element made of a multilayer layer of a support layer 1.1 and a self-adhesive damping mass 1.2.

[0015] Such a damping element is in principle known from DE 10 2008 050 772 A1. However, it is used there for another purpose, namely to close the holes in the car body.

[0016] In a particularly preferred embodiment, the support layer 1.1 is made of 5xxx aluminum alloy, with a proportion of 0.2% to 6.2% magnesium. Aluminum alloy 5xxx has a high strength, ranging from 100 N / mm² up to 450 N / mm².

[0017] As an alternative to the 5xxx aluminum alloy, the support layer 1.1 is made of stainless steel, steel or other bending rigid metal, which also has high strength. The support layer can, for example, also be made of aluminum alloy 4xxx, 5xxx or 7xxx.

[0018] Due to the high strength, the damping element 1 is particularly suitable for damping the material vibrations of the structural parts 2. Such a structural part is shown in more detail in Fig. 2. At the same time, the damping element 1 is suitable for closing openings in the structural parts 2, especially in body parts and can be applied extremely easily to structural parts 2.

[0019] The material of which the support part 1.1 is made is furthermore characterized by high corrosion resistance, which prevents corrosion of the damping element 1.

[0020] To further improve corrosion resistance, an anti-corrosive layer 1.3 is applied on both sides of the support layer 1.1. Anticorrosion layer

1.3 is made especially of varnish or foil, with varnish usually

- 5 applied in the form of so-called KTL substitute layer (KTL - cathodic immersion painting) for the base layer 1.1. Such KTL replacement layers or KTL varnish systems are special varnishes that have been optimized for later applications. They are based on polyurethane, epoxide, melamine, polyester and / or blends thereof. Usually, a glidant is also doped to the top layer of the lacquer, to provide later elasticity or flexibility of the damping element 1. Thus, it can be advantageously adapted to a given structural part.

[0021] In this context, the anti-corrosive layer 1.3 formed of lacquer or foil is applied to the support layer 1.1, usually by the Coil Coating method, which is also known for covering tapes or continuously covering a metal strip.

[0022] The corrosion protection layer 1.1 is made especially of polyethylene. Thanks to the anti-corrosive layer 1.3, the adhesion of the damping mass 1.2 made of butyl rubber to the support layer 1.1 is also improved. In addition, the anti-corrosion layer 1.3 can be varnished, so that the damping element 1 can be easily coated with vehicle paint.

[0023] To ensure the adhesion of the corrosion protection layer 1.3 on the support layer 1.1, the support layer 1.1 is applied on both sides with the adhesion enhancing layer 1.4. The adhesion enhancing layer 1.4 is usually chromium-free and is applied on both sides to the support layer 1.1 in the form of a thin liquid coating. The adhesion enhancing layer 1.4 is usually made of Henkel's Alodine® NR 1453. Such a layer improving adhesion 1.4 is characterized by the fact that it also provides corrosion protection for the supporting layer 1.1.

[0024] In a further development of the damping element 1 it is also possible

- 6 execution of the support layer 1.1 made of plastic with similar high strength. In this case, corrosion of the support layer 1.1 does not occur, which eliminates at least the anti-corrosion layer 1.3. In a preferred way, the plastic is applied at least on one side with a layer improving adhesion 1.4, which increases the already improved adhesion of the varnish applied to the support layer 1.1. Thus, the damping element 1 can be easily varnished and optically matched to the color of the construction part.

[0025] The presented multilayer structure of the damping element 1 with the support layer 1.1 made of bending rigid material and the damping mass 1.2 made of butyl rubber is characterized by particularly good acoustic properties, so-called vibration reduction properties as well as simple and flexible application.

[0026] The damping mass 1.2 made of butyl rubber is characterized in that it can be applied to sheet metal coated with corrosion protection oil. The damping element 1 is also characterized by chemical resistance to water, alcohols, diluted acids and alkalis. Butyl rubber is produced in particular on the basis of thermoplastic elastomers, polymers, adhesive resins, fillers, thixotropic auxiliaries and other modifiers. [0027] To avoid electrical conductivity between the support layer 1.1 and the body structure through the damping mass 1.2 and thereby corrosion of the support layer 1.1 and / or body components, the corrosion layer 1.3 sandwiched between the support layer 1.1 and the damping mass 1.2 is made electrically insulating.

[0028] Alternatively or in addition to the introduction of an electrically insulating corrosion protection layer 1.3, to reduce the electrical conductivity of the mass

Suppressive butyl rubber was used in which some fillers were reduced, for example carbon black.

[0029] Fig. 2A shows a top view of the construction part 2, which according to the state of the art has been equipped with a damping element 1 in the form of a large-surface damping mat (in this case the mat has both vibration reducing and damping properties), providing the required reduction or attenuation of material vibrations. Fig. 2B shows the construction part and the damping mat 1 in cross section. The drawings clearly show that the damping mat known in the art requires a lot of material, which further increases the weight of the structural part.

In contrast, in Fig. 3 the solution according to the invention is shown in the form of a structural part 2 with several damping elements 2 applied. The structural part 2 is in the embodiment shown a structural part of the vehicle body made of sheet metal. Alternatively, the structural part is a structural part used in other fields, for example in the construction industry, shipbuilding industry, aircraft construction or home appliances. The construction part 2 can also be made of steel sheet, aluminum sheet, varnished parts KTL or plastic.

[0031] Vibrations and sounds may occur during the operation of the structural part 2. In the case of the illustrated embodiment of the vehicle structural part 2, vibrations and sounds are generated on the structural part 2 by the operation of the vehicle. To minimize vibrations and sounds, the structural part 2 is applied locally to suppress and reduce material sound, i.e. several damping elements 1 in points.

[0032] For this, by means of simulation, the vibration characteristics of the construction part 2 are determined. In a particularly preferred solution, a vibration test is carried out with a laser scanner on the construction part 2 or on the joints of several construction parts 2, for example on the vehicle body. [0033] To this end, the construction part 2 not shown in more detail is attached behind one of the upper edges and is excited by means of an electrodynamic vibrator. The frequency spectrum during excitation usually includes a bandwidth of 40 Hz to 1000 Hz.

[0034] The generated vibrations of the construction part 2 are recorded, for example, by means of a laser vibration scanner not shown. For this purpose, a measuring grid with multiple scanning points is applied to the structural part 2. The structural part 2 is first stimulated by idle vibrations, i.e. without applied damping elements 1 or other means to reduce or dampen vibrations, wherein the distribution of vibrations on the structural part 2 at different frequencies is measured by means of a laser vibration scanner. At each frequency, so-called a colored map on which different frequency amplitudes are shown in different colors.

[0035] Based on the color data on the map, the frequency amplitudes are read. Areas of the structural part 2 with high frequency amplitudes stand out colorfully from other areas.

[0036] In places where the frequency amplitudes exceed the set limit value, damping element 1 is placed in each case for local stiffening of the structural part 2.

[0037] The damping element 1 is glued with a damping mass 1.2 on the construction part 2 and is thus fixed. The damping element 1 can be placed in places made of full material or in places where

- 9 where there are 2 holes on the construction part. In this case, the damping element 1 also serves to close the holes in the construction part 2. [0038] The effectiveness of the damping elements 1 placed on the construction part 2 is checked by means of a re-measurement, e.g. by means of a laser vibration scanner, and evaluated on the basis of the created colored map. The efficiency of the damping elements 1 is optimized depending on the results, possibly by means of appropriate corrections. Corrections are carried out in particular by means of damping elements 1 of a different size, corrections of the place of application of damping elements 1 and / or by means of an arrangement of additional damping elements 1.

[0039] The acoustic operation of the damping element 1 is set by means of several parameters. They are determined first by means of elasticity (elasticity modulus E), thickness, density and surface mass of the damping mass 1.2 and secondly by means of thickness, surface mass and rigidity of the support layer 1.1.

[0040] To achieve particularly good reduction or damping of material vibrations, the support layer 1.1 usually has a thickness of 0.1 mm to 0.4 mm.

[0041] Due to the layered structure of the damping elements 1 in combination with the gluing of the damping elements 1 to the construction part 2, a very high surface moment of inertia is obtained locally. As a result, a very high stiffening of the structural part 2 is obtained, and thus an improvement in the damping of material vibrations and a reduction in vibrations. The vibration reduction effect is the greater the stiffer the material of the support layer 1.1.

[0042] Especially the damping elements 1, whose supporting layer 1.1 is

- 10 made of aluminum and whose damping layer 1.2 is made of butyl rubber, have a very good vibration reducing effect. This means that the surface vibrations of the structural part 2 are significantly suppressed, which reduces material and airborne sound emissions. Other materials, e.g. bitumen, may also be used for the damping layer 1.2. The stiffness of the damping layer 1.2 is preferably lower than that of the support layer 1.1.

[0043] To ensure optimal attenuation of the damping element 1 on the contours of the structural part despite the high rigidity of the damping element 1, damping elements 1 of various sizes and shapes are produced, which allows to stiffen the area of ​​the high-amplitude construction part 2 with a matching damping element 1 or several damping elements 1.

[0044] The application of the damping elements 1 to the construction part 2 is done manually, whereby one or several damping elements 1 are applied to a place with a high vibration amplitude, determined for example by means of a laser vibration scanner 1. Such a place can also be determined by other methods .

[0045] The use of a support layer 1.1 of rigid material for bending results in a particularly advantageous possibility of alternatively or additionally automated application of the damping elements on the structural part. [0046] The damping element 1 is, as shown in Fig. 1, e.g. automatically separated from the support element 3 by a robot and then automatically mounted on the structural part 2. The attenuation of the damping elements 1 can be carried out both for braking or damping the material vibrations of the structural part 2 and

For sealing the openings in the construction part 2. Such a supporting element 3 with several damping elements 1 arranged on it is shown in fig.

4.

[0047] The support element 3 is made in the form of a pre-assembled flat sheet on which several damping elements 1 are arranged. The support element 3 is made of paper, polyethylene film or polyethylene terephthalate.

[0048] In a special solution for a specific application, for example for a vehicle, all required variants of the damping elements 1 are placed as a set on one or several sheets. The design of the support element 3 in the form of a flat sheet makes it possible to master the variety of variants of the damping elements 1 for a specific application with minimized cutting of material and space consumption. In contrast to the use of the damping elements 1 placed on the rolls, there is still the advantage of preventing the uncontrolled separation of the damping elements 1 from the support element. Separating material shortcomings due to the production process is also possible only for sheet products. In the case of roll material or endless material, however, there may be interference in the application device for automatic application of damping elements 1.