disc brake

Abstract

Disc brake comprising a brake calliper (1) with a receiving space (2) and an application device arranged therein, as well as a pad shaft for arranging a brake pad, wherein the receiving space (2) is sealed off from the lining shaft by means of a closure plate (3) which is arranged detachably on the brake calliper (1), characterized in that the closure plate (3) has a metal base body and a zinc-containing coating applied thereto, that a seal (13) rests on the coating and is materially connected to the closure plate (3), and that the surface of the coating is plasma-activated at least in the contact area between the coating and the seal (13).

Description

The present invention relates to a disc brake according to the preamble of claim 1.WO 2014 / 108315 A1 and WO 2018 / 077728 A1 disclose closure plates, also referred to in the art as base plates, for covering an assembly opening of a receiving space of a disc brake. In practice, these closure plates have hitherto mostly been manufactured from an uncoated metal sheet. The closing plate is intended to protect the receiving space optimally from corrosive influences. Particularly in the region of the closure plate, high corrosive loads prevail as a result of salt-containing aqueous deposits, with the result that the closure plate should also be ideally protected, inter alia, from surface corrosion.DE 10 2022 103 864 A1 discloses a closure plate which is designed with a full-surface coating. It was recognized that the coating simultaneously causes a reduction in the surface adhesion of the seal. The problem was solved in DE 10 2022 103 864 A1 by the introduction of a depression and thus by mechanical gripping around the seal from three sides. However, this measure requires further shaping steps in the formation of the closure plate.Proceeding from the aforementioned prior art, the object of the present invention is to provide a closure plate which can be produced easily and has increased corrosion resistance.The invention achieves this object by providing a disc brake having the features of claim 1.The disc brake according to the invention comprises a brake caliper with a receiving space and a brake application device arranged therein.Furthermore, the brake caliper comprises a brake pad shaft for arranging a brake pad, which serves as part of the disc brake in particular in cooperation with a further brake pad for braking a rotating brake disc. In a preferred embodiment variant of the invention, the disc brake is designed as a sliding-caliper disc brake.The receiving space is sealed off from the lining shaft by a closure plate arranged removably on the brake caliper. The closure plate is preferably screwed to the brake caliper and covers an opening of the receiving space, which opening can preferably be formed as a mounting opening. The removability of the closure plate is ensured by loosening the screw connection.The closure plate has a metal base body and a zinc-containing coating applied thereto. This is also referred to below as zinc coating.A seal, preferably a sealing cord and particularly preferably in the embodiment as a sealing ring, rests on the coating in a bearing region and is connected to the closure plate in a materially bonded manner. Particularly preferably, the seal can be fused to the closure plate.In addition, the surface of the coating is configured to be plasma-activated at least in the bearing region or contact region between the coating and the seal. Plasma activation is identifiable, inter alia, on the basis of the different coloration of the surface and / or on the basis of a microscopically differentiable surface condition.As the metal base body of the closure plate, steel, for example, as a formed steel sheet, can preferably be used.The metallic zinc-containing coating achieves particularly effective corrosion protection, since zinc is formed as a less noble metal than the customary metals of a metal base body, such as steel, for example, as an anode layer. As a result, in the case of electrode release of zinc, the potential of the steel and / or other metals of the metal base body is reduced.In the zinc-containing coating, hydroxide is also formed as a further corrosion product on the steel surface of the closure plate in addition to the zinc ions. These two corrosion products reduce oxygen reduction on the zinc layer. This effect is also known in metallurgical fields as a self-healing effect of a coating.The zinc coating thus represents a particularly effective corrosion protection for a metal base body, in particular for a metal base body made of steel.However, it has been found that the zinc coating degrades the surface properties for seal adhesion. Thus, a seal releases from the coated surface of a closure panel much more easily than from an uncoated closure panel.This tendency was counteracted in DE 10 2022 103 864 A1 by additional shaped regions, forming a receiving groove for a seal. However, a plasma treatment of the support region is substantially more effective than these additional forming processes. While certain sheet thicknesses of the metal base body during forming, as well as stress corrosion cracking at the bending points and ultimately also a changed closure plate geometry have to be taken into account in the structural configuration of the disc brake, the construction of an existing disc brake does not need to be subjected to any further structural adaptation when plasma activation is used.As a result, the closure plate can be realized without additional deformation steps for fixing the seal within the scope of uncomplicated production. Not only is the initial hold of the seal on the closure plate improved. It is also surprising that the cohesive connection between the seal and the coating is not covered by corrosive media by the plasma activation.Thus, plasma activation represents an optimal possibility for fixing a seal under various solutions investigated, so that optimal sealing of the receiving space is achieved by a closure plate with at the same time improved corrosion protection.Further advantageous embodiments of the present invention are the subject matter of the dependent claims.In a preferred embodiment variant, zinc-containing coating has at least 80% by weight of zinc and, in addition, a further microstructure partner, preferably magnesium and / or aluminum, particularly preferably to an extent, based on all microstructure partners, of between 1-10% by weight. Zinc coatings have been used for many years for corrosion protection in various applications. However, due to pore formation and lattice damage in the metal lattice, diffusion of corrosive media through the zinc coatings has increasingly occurred. As a solution, the zinc coatings were applied as so-called thick layers to the metal surfaces, which are usually ferrous, so that the diffusion depth does not reach the metal base body. However, in the case of closure plates which are screwed with a high tightening torque against the brake caliper, with the result that the receiving space is sealed against water penetration by high compression of the seal, a zinc thick layer may possibly be displaced. A higher mechanical stability and density of the zinc layer is achieved by adding small proportions of structural partners, in particular by adding magnesium and / or aluminum.However, by increasing the density of the microstructure, an even lower adhesion of the seal to the surface of the coating is also simultaneously effected. It has surprisingly been found that a plasma treatment in such coating systems achieves an improvement in the material bond to an extent which is comparable to the material bond of identical seals with the uncoated closure plates frequently used in the field of application described above.Due to the increased density of the microstructure, a reduced layer thickness can moreover be applied for the coating, so that less diffusion occurs and a higher supporting function of the metal base body for the coating material is provided.In the plasma-activated region, the surface may be more susceptible to soiling. Therefore, plasma activation should ideally occur only over a limited area of the closure plate. In this context, it is advantageous if the width of the plasma-activated region on the closure plate is less than 20 mm, preferably less than 10 mm, particularly preferably between 0.5-8 mm.The pull-off force for detaching the seal from the closure plate upon action in a direction perpendicular to the plate base plane is preferably more than 1 N, and particularly preferably between 2-5 N. The extent of the plasma activation can be adjusted, inter alia, by the selection of the medium used for plasma formation, for example a gas, by adjusting the intensity of the ionization of this medium and by the distance of the plasma generation up to the metal surface treated. Moreover, the perimeter of the bearing surface may be determined by the size and contour of the selected seal. The withdrawal force resulting from the plasma activation can thus be adjusted to the aforementioned target values within the framework of preliminary tests, inter alia, by varying the aforementioned parameters.A particularly high dimensional stability of the closure plate and a particularly good support of the coating by the metal base body is achieved if the average layer thickness of the zinc-containing layer is less than 10 μm.In order to achieve a high degree of sealing of the receiving space, it is advantageous if the seal is formed as an elastomer and / or as a thermoplastic elastomer and preferably from silicone, from rubber and / or from a butadiene derivative. These materials can be deformed without damaging the sealing effect, forming comparatively high prestresses.It is furthermore advantageous if the material bond between the closure plate and the seal is formed free of adhesion means. Depending on the field of application, adhesives tend to be rinsed out by water or to cure or otherwise change under changing climate conditions during a prolonged service life. This can have a negative influence on the seal at the transition between the seal and the closure plate.The seal can furthermore be arranged adjacent to an edge which projects from a plate base plane of the closure plate on the receiving space side, wherein the seal is arranged recessed with respect to a contact surface formed by the edge for contact with the brake caliper. When using sealing rings or a sealing cord, deformation torques and rotational torques can act on the seal during assembly. An edge adjacent to the seal allows additional support, so that the seal does not slip out of the region between the brake caliper and the closure cover on the edge during assembly by excessively tightening the screw connection. At the same time, the edge serves as a stop against excessive tightening and associated damage to the seal during the assembly of the closure plate.For more detailed characterization of the function of the closure plate, it is advantageous if said closure plate has one or more passage openings for the passage of a brake plunger. The aforementioned passage openings are preferably sealed by separate further sealing means, e.g. a sealing bellows.Furthermore, a method for providing the disc brake according to the invention is presented, wherein the method comprises the following steps: A providing a plate-shaped metal base body, in particular by shaping; B coating, in particular full-surface coating, of the metal base body with the zinc-containing coating, preferably with provision of a coating of the entire metal base body; C at least regionally applying plasma to the coated metal base body with provision of the closure plate; and D mounting the closure plate on the provided brake caliper with liquid-tight closure of the receiving space of the brake caliper.The individual steps of the method are explained in more detail below.Step A: Providing a plate-shaped metal base body, in particular by shaping.Preferably, the provision comprises steps of both shaping and singulating. The shaping can comprise various methods of metal forming, such as rolling processes, deep-drawing processes and / or bending processes.The shaping can furthermore also comprise a punching process, for example for forming the passage openings. Drilling methods for realizing openings for the passage of screws or other mechanical connecting means can also be part of the aforementioned shaping.The separation serves for the spatial separation of the closure plate from a metal sheet.Step B: Coating, in particular full-surface coating, of the metal base body with the zinc-containing coating, preferably with provision of a coating of the entire metal base body;A zinc coating described above can be implemented in various ways. Within the scope of the invention, a zinc coating can be applied locally, inter alia by a PVD or CVD method with masking of uncoated regions. However, this is complicated in the production process. Very dense layers can also be realized within the scope of the present invention by means of a dip coating, optionally in a melt bath or an electroplating bath.In many cases, drying should be carried out after coating.Step C: At least Regional Application of Plasma to the Coated Metal Base Body.Plasma formation is known per se. Media, in particular gases, are ionized by various techniques and are thereby converted to plasma.The type of ionization and the control of the process parameters determine the extent of ionization of the gas and thus the quality of the plasma. Thus, the plasma activation of the respective coating surface can be adjusted by adjusting the process parameters and by selecting the gas.Furthermore, the skilled person can select between different geometries of the seals. A sealing cord or a sealing ring can preferably have an ovoid or round cross section. Such a sealing ring is generally simple to produce and readily available.A larger support area, on the other hand, is occupied by a sealing cord with a rectangular cross section.In a particularly preferred embodiment variant of the invention, the sealing cord, in particular the sealing ring, can be designed as a hollow chamber seal, whereby a widening of the support by deformation after assembly and thus an additionally increased sealing effect is made possible.Step D: Mounting the closure plate on the provided brake caliper with medium- or liquid-tight closure of the receiving space of the brake caliper and optionally further steps for completing the disc brake, such as, for example, inserting the brake pads and the like.The plasma can preferably be directed on a localized basis. For this purpose, in particular, the bearing region of the seal can be determined, for example, by optical means, such as cameras, and the plasma can be directed specifically into the bearing region. It is also possible, for example, to guide the closure plate movably in one plane. The plasma jet can be continuously emitted onto the moving or guided closure plate and wherein the plasma is directed exactly when the closure plate is guided further in the support region. Of course, the instrument of the plasma lead-in can also be moved while the closure plate leads to rest.The present invention is explained in more detail below on the basis of an exemplary embodiment and with the aid of a plurality of figures. Individual components shown can also be modified, so that the invention is not limited to the exemplary embodiment shown.The following are shown: FIG. 1 is a cross-sectional perspective view of a brake caliper of a disc brake according to the invention; and FIG. 2 shows comparative examinations of closure plates of a variant according to the invention and of a variant of a disc brake not according to the invention.FIG. 1 shows a section through a brake caliper 1 of a disc brake. Inside the brake caliper 1 there is arranged a receiving space 2 for a brake application device. The application device of the disc brake is not shown for reasons of clarity. However, the function of such a clamping device and its components are sufficiently known to the person skilled in the art.The receiving space 2 and the clamping device arranged therein are to be protected from the penetration of water. Therefore, the accommodation space 2 is sealed with a closure plate 3 in a watertight manner. The opening 14 covered by the closure plate 3 is often also referred to as a mounting opening, wherein the application device does not necessarily have to be introduced through this opening into the receiving space. Rather, the receiving space 2 can also have further openings through which the application device or at least individual parts of the application device, such as a brake lever, can be introduced. Said closure plate 3 is often also referred to as a base plate or floor plate in brake construction.The closure plate 3 has a receiving space side 4 and a pad shaft side 5, on which the pad shaft of the disc brake is arranged.The closure plate 3 is formed as a metal plate, in particular as a metal plate.The application device has one or more brake plungers which serve for actuating a brake pad arranged in the pad shaft.For the passage of one brake plunger each, the closure plate 3 has a passage opening 6. In the variant embodiment of the closure plate of FIG. 1, two passage openings with an identical diameter are provided.The respective passage opening 6 has marginal flanges 7 to increase the tightness, so that so-called pots are formed marginally around the passage openings 6. The flanges 7 serve for guiding the brake piston and make it possible to seal the receiving space 2 with respect to the outer region or the region of the lining shaft. In the assembled state of the closure plate 3, the flanges 7 project in the direction of the receiving space 2 relative to a plate base plane 8 of the closure plate 3.Between the passage openings 6, the closure plate 3 has a central web 9. The closure plate 3 has a circumferential edge 10 on the edge side, which has an abutment surface 11 on the edge 12 of the brake caliper 1 circumferentially surrounding the mounting opening. The contact surface 11 of the edge 10 is preferably oriented parallel to the plate base plane 8, so that the closure plate 3 has a flat trough shape with the circumferential edge 10.The encircling edge 10 serves at the same time for positioning and delimiting a seal 13, preferably as a sealing cord, in particular a sealing ring, which is arranged on the receiving space side 4 of the closure plate 3.The seal 13 is preferably designed as an elastomer. For example, it can be a silicone or a TPE, i.e. a thermoplastic elastomer.It is connected to the closure plate 3 in a materially integral manner.The material bond is preferably effected without additional adhesion agents or adhesives. For example, silicone can subsequently cure and crosslink after application to the closure plate 3. For example, acetic acid-crosslinking or neutral-crosslinking silicones are known which can be applied to the metal surface as a sealing cord. In the case of silicones or in particular also other elastomers, such as rubber- and / or butadiene-based elastomers, postcrosslinking can be effected, for example by vulcanizing agents. A vulcanizing agent is a form of a crosslinking agent with which, for example, the sealing cord is surface-wetted. Other cross-linking agents can also be used for connecting the seal, in particular sealing cord, to the surface of the closure plate 3.The closure plate 3 has, preferably distributed along the edge 10, further openings for the passage of mechanical connecting means 15, in particular screws. As a result, the closure plate 3 can be screwed to the brake caliper and thus close the receiving space 3 in a liquid-tight manner.In a preferred embodiment variant, the seal protrudes to a certain extent relative to the bearing surface 11 in the disassembled state of the closure plate 3, so that when the closure plate 3 is in contact the seal 13 is elastically deformed at the edge 12 of the mounting opening 14.The closure plate 3 is designed in the above-described shape and construction as a coated metal plate, having a metal base body and a coating which is preferably designed as a metallic coating.The metal base body is preferably made of steel, and particularly preferably of stainless steel.The coating is preferably formed to contain zinc, with a preferred zinc content of more than 80 wt %, particularly preferably between 90-99 wt %. The coating is therefore also referred to below as a zinc layer because of the high proportion by weight, although advantageously further structural partners are provided in the coating.The coating is composed of zinc subareas, for example with an average cross section of between 5-20 μm. Between these zinc sub-regions made of elemental metal, a eutectic zinc-containing mixture of zinc with at least one further structural partner is arranged. Magnesium can be used as a preferred structural partner. However, other structural partners, in particular aluminum, are also possible. The said structural partners, preferably magnesium, can preferably be present in the coating in a range of between 1-10% by weight. The eutectic mixture can preferably be formed as a MgZn 2- phase, optionally with further proportions of zinc and aluminum within the phase.Zinc layers have been used for more than 60 years as coatings for the corrosion protection of steel sheets. However, in practice, very thick layers have tended to be deposited on the metal surface of the metal base body. Thinner and thus more dimensionally stable and material-saving layers, for example of zinc with magnesium as the structural partner, are, on the other hand, only used for a few years as corrosion protection. The advantage over the conventional zinc coating is an additional better protection against diffusion due to the provision of a much more compact and ordered overcoat.At the same time, very high requirements are placed on the corrosion protection of the closure plate 3. Especially in winter, in addition to the action of conventional rainwater and melt water, a corrosion-promoting high salt content, for example due to scattering salt, is also added. Nevertheless, owing to the structural partners and the associated very compact configuration of the outer layer, the coating constitutes effective protection against corrosion even at layer thicknesses of less than 10 μm. Particularly preferably, the average layer thickness of the coating can thus be less than 10 μm and further preferably less than 8 μm.The compaction by the structural partners of the zinc layer preferably used, however, has not only advantages for the layer thickness of the coating. Rather, the compaction also brings about a lower hold of the seal 13 arranged in a materially integral manner on the coating of the closure plate 3.A further reason can also lie in an unevenly formed layer thickness. The coating is preferably applied to the surface of the metal base body in a dipping process, preferably in a hot-dip process. In the transition region between the plate base plane 8 and the edge 10, droplets of the bath can dwell for a longer time in the form-dependent fillet sections and thus form a thicker layer thickness. In these regions, however, the seal 13 also comes to rest and bonded to the closure plate 3.Overall, it was observed that the material bond of the seal on the closure plate with the applied zinc coating, in particular with the above-described structural partners, is not or only inadequate.Inadequate adhesion to the seal 13 on the closure plate 3 has the effect that the disc brake as a whole leaks and the brake fails during operation.It has been found that surface treatment of the closure plate 3, at least in the region in which the seal 13 rests on the coating of the closure plate 3, increases the strength of the material bond to an extent, i.e. whether the seal has been applied directly to the coating-free metal base body.The surface treatment is plasma activation. In this case, an ionized process gas, for example as a plasma flame, is conducted onto a metal surface. Plasma can be generated in a very different manner. There are thermal excitation, chemical excitation, beam excitation and excitation in electrostatic and / or electromagnetic fields. The plasma guidance is correspondingly variable. The plasma guidance can be carried out in a very focused manner before the application of the seal 13 on the closure plate, so that only the contact surface with the seal 13 can be subjected to such a treatment locally limited with an application width of less than 5 mm, preferably less than 2 mm.The corresponding treated support surface near the edge 10 is therefore circumferential and has an area of less than 5 mm, preferably less than 2 mm.With a corresponding guidance of the plasma conduction, the subsequent material-bonded connection to the seal 13 takes place without pores and regularly.The surface energy of the metal layer is increased in this case, so that the surface of the closure plate with the sealing ring that is plasma-activated in this way enables an intensive material bond with the sealing ring and an uninterrupted material bond in the longitudinal extension of the seal.Testing of the seal is carried out, inter alia, by means of a so-called rolling test, by means of which it is attempted to release the seal 13 from the closure plate 3 by means of a defined exertion of force.FIG. 2 shows the results of comparative tests for releasing a seal 13 from a closure plate 3 while ascertaining a pull-off force.However, in the case of a coated closure plate 3 with a non-activated surface, the pull-off force of the seal in FIG. 2 awas less than 0.6 N in all investigations and partially already separated from the surface by its own weight.In contrast, in the case of a coated closure plate 3 with a plasma-activated surface, the pull-off force of the seal 13 in FIG. 2 bwas between 3-5 N in all investigations.As a result, in the context of the present invention, a disc brake was provided with a closure plate 3 which reliably seals off the receiving space 2 in a medium-tight manner by a seal 13 adhering firmly to the material bond and which at the same time has increased corrosion protection with comparable dimensional stability compared to an uncoated closure plate.List of reference characters1 Brake caliper 2 Receiving space 3 Closure plate 4 Receiving space side 5 Lining shaft side 6 Passage opening 7 Flange 8 Plate base plane 9 Central web 10 Edge 11 Contact surface 12 Edge 13 Seal 14 Opening 15 Mechanical connecting means / screwReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedWO 2014 / 108315 A1

[0002] WO 2018 / 077728 A1

[0002] DE 10 2022 103 864 A1 [0003, 0017]

Claims

Disc brake comprising a brake caliper (1) with a receiving space (2) and a brake application device arranged therein, and a lining shaft for arranging a brake lining, wherein the receiving space (2) is sealed with respect to the lining shaft by a closure plate (3) arranged removably on the brake caliper (1), characterized in that the closure plate (3) has a metal base body and a zinc-containing coating applied thereto, in that a seal (13) rests on the coating and is connected to the closure plate (3) in a materially bonded manner, and in that the surface of the coating is configured to be plasma-activated at least in the region of contact between the coating and the seal (13).Disc brake according to claim 1, characterised in that the zinc-containing coating has at least 80% by weight of zinc and additionally a further structural partner, preferably magnesium and / or aluminium, particularly preferably in an amount, based on all structural partners, of between 1-10% by weightDisc brake according to claim 1 or 2, characterised in that the width of the plasma-activated region on the closure plate (3) is less than 20 mm, preferably less than 10 mm, particularly preferably between 0.5-8 mm.Disc brake according to one of the preceding claims, characterised in that the pull-off force for releasing the seal (13) from the closure plate (3) in the direction perpendicular to the plate base plane is more than 1 N, preferably between 2-5 N.Disc brake according to one of the preceding claims, characterised in that the average layer thickness of the zinc-containing layer is less than 10 μm.Disc brake according to one of the preceding claims, characterised in that the seal (13) is formed as an elastomer and / or thermoplastic elastomer and preferably from silicone, from rubber and / or from a butadiene derivative.Disc brake according to one of the preceding claims, characterised in that the material bond between the closure plate (3) and the seal (13) is formed free of adhesion means.Disc brakes according to one of the preceding claims, characterized in that the seal (13) is arranged adjacent to an edge (10) of the closure plate (3) which projects from a plate base plane (8) of the closure plate (3) on the receiving space side, wherein the seal (13) is arranged in a recessed manner with respect to a contact surface (11) formed by the edge (10) of the closure plate (3) for contact with the brake caliper (1).Disc brakes according to one of the preceding claims, characterized in that the closure plate (10) has one or more passage openings (6) for passing through a brake plunger.

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