Method for producing a profile segment

Abstract

The invention relates to a method for producing a profile segment of a segmented casting vulcanizing mold for vehicle tires, wherein the molding surface of the profile segment forms a segment of the tread pattern of a tire to be vulcanized.

Description

The invention relates to a method for producing a tread segment of a segmented vulcanization mould for vehicle tyres, the mould surface of which moulds a segment of the tread profile of a tyre to be vulcanized.The invention further relates to a profile segment with changes in the surface profile of a subregion of the profile segment, and to a vehicle tire.Vulcanization molds for tires include molded parts which together form the radially outer surface of the tire such as the tread, shoulder region, sidewalls and bead region. The segments which form the tread are called tread segments.The term "positive profile" comprises all the sipes of the profile and possible further sipes, such as those for the insertion of laminated sheets for passenger cars and van tyres.The unvulcanized green tire blank is vulcanized in the vulcanization mold and is converted into its final rubber-elastic state by rubber crosslinking reactions. The tire receives its profile configuration by the corresponding negative configuration of the mold surfaces of the mold segments.By forming surfaces is meant those surfaces of the forming segments which give the green tyre its corresponding configuration.For tire performance, in particular for the snow and ice performance of winter tires, it is advantageous if the shell-shaped surface of the tire tread, the surface profile of the vehicle tire, has a defined roughness. The grooves of the tread profile, which delimit the raised profile elements, on the other hand, should be as "smooth" as possible in order to give the tire a high quality appearance.It is known from EP 3 261 830 B1 that fine structures which are applied to a model segment by means of plasma coating are advantageous for the adhesion of a vehicle tire produced therewith under winter conditions.It is therefore the object of the invention to provide a cost-effective and adaptable method for producing a profile segment, and a profile segment, of a segmented vulcanizing mold for vehicle tires, with which the shell-shaped tread surface of a tire to be vulcanized is to be provided with a defined roughness or a defined surface profile. It is a further object of the invention to provide a vehicle tire having such a surface profile.This object is achieved by a method according to the features of patent claim 1 and a profile segment and a vehicle tire according to the subordinate claims. The dependent claims relate to particularly expedient developments of the invention.According to the invention, there is thus provided a method for producing a profile segment of a segmented cast vulcanization mold for vehicle tires, wherein the mold surface of the profile segment molds a segment of the tread profile of a tire to be vulcanized, comprising the following steps: a) creating a rigid model segment which has a shell-shaped tread surface, b) milling the positive profile of the tread into the shell-shaped tread surface of the model segment to produce a master model, wherein the master model has a surface profile to be changed at least in a partial region, c) creating a flexible impression of preferably silicone rubber from the master model, d) creating a rigid impression of preferably gypsum from the impression of preferably silicone rubber to form a casting core segment, e) casting all annularly juxtaposed casting core segments, Preferably with an aluminium-magnesium alloy, for obtaining a vulcanization mould, which is subsequently divided into individual profile segments, characterized in that the surface profile of the master model is changed by removal by means of laser radiation in such a way that it has an average arithmetic height (Sa) of greater than 5 μm and less than 100 μm according to ISO 25178.A partial region of the surface profile is understood to mean both a region of exactly one profile block and a region of each profile block. The partial region can also extend over the entire surface profile, wherein surface profile is understood to mean the region of a profile segment which forms the vehicle tire surface profile of the vehicle tire.It has been found that changing the surface profile of model segments by means of laser radiation to a specific roughness enables vehicle tires which solve the conflict of goals between dry adhesion and snow or ice adhesion at a higher level. This is attributed to the fact that, in the case of a large contact surface between the vehicle tire and the underlying surface, which is relevant in particular for dry adhesion, a sufficient negative fraction is also provided, which can be arranged in such a way that high adhesion is achieved in the case of snow or ice adhesion. It has been found here that such roughnesses in model segments can be produced by means of laser radiation in a particularly simple and cost-effective manner. Furthermore, it has been shown that the removal by means of laser radiation enables a particularly large number of freedoms in the design of the surface profile. Different surface profiles can be generated, for example, in different regions of the tread surface.A preferred embodiment provides that the change in the surface profile in step b) is produced by means of laser cutting or laser drilling. A removal method carried out by means of laser radiation makes it possible in a particularly simple manner to produce a multiplicity of structures and surface roughnesses in different ways, wherein preferably only partial surfaces of each model segment are machined.A further preferred embodiment provides that in step b) a structure size of less than 0.1 mm×0.1 mm, in particular a surface profile Sa of greater than 10 μm, preferably of greater than 15 μm, and or of less than 80 μm, preferably of less than 60 μm, is produced. It has been found that small structure sizes, in particular surface profiles Sa of greater than 10 μm and less than 80 μm, lead to particularly good values with regard to snow or ice adhesion with particularly good dry adhesion.A further preferred embodiment provides that in step b) an Ssk value according to ISO 25178 of greater than -10, preferably of greater than -5, further preferably of greater than -3 and / or of less than 50, preferably of less than 30, further preferably of less than 20 and preferably an Sku value according to ISO 25178 of ≥3 is generated. It has been found that the preferred Ssk values, i.e. the generation of height distributions which are above the middle planes, which are also described as depressions in a plane, lead to particularly good values with regard to snow or ice adhesion in the case of particularly good dry adhesion.A further preferred embodiment provides that in step b) the surface roughnesses Sa, Ssk and / or Sku are formed differently from the shoulder zone toward the equator and or on a profile block in each case in the circumferential direction. A different formation of the surface roughnesses of the equator, i.e. of the tread surface arranged centrally between the shoulder regions, and of the shoulder zones makes it possible to produce a surface roughness in the different lateral regions of the tread which is particularly suitable for their predominant functions. Particularly effective adhesion in the circumferential direction and in the lateral direction is made possible. The predominant functions of a profile block, which are variable over the circumferential direction, can thus also be optimized.A further preferred embodiment provides that in step b) the surface roughnesses Sa, Sskand or Skuare generated in the form of a defined pattern, preferably by means of dot matrix or vectorial hatching. It has been found that an arrangement of the surface roughnesses both in the form of a dot matrix and a vectorial hatching, in particular by means of a dot matrix or vectorial hatching, can be advantageous with regard to a solution of the mentioned conflict of goals at a higher level.A further preferred embodiment provides that a short pulse laser radiation or an ultra-short pulse laser radiation is used as laser radiation and preferably targeted holes are produced. It has been found that short-pulse laser radiation and ultra-short-pulse laser radiation are particularly suitable for producing a particularly suitable surface profile and in particular targeted bores, wherein bores are blind bores which have an at least roughly approximately circular cross section.A further preferred embodiment provides that the removal of the surface profile by means of laser radiation is carried out by multiple passes with the laser radiation, wherein the focal position of the laser radiation is preferably changed between the passes and or during each pass. This allows a suitable surface profile to be produced in a simple and efficient manner.According to the invention, a profile segment of a segmented vulcanization mold for vehicle tires is provided, wherein the mold surface of the profile segment molds a segment of the tread profile of a tire to be vulcanized, preferably produced by means of a method according to the invention, wherein the profile segment has at least one partial region, wherein the at least one partial region has a modified surface profile which results from the removal by means of laser radiation of the master model, wherein the surface profile of the master model is modified by removal by means of laser radiation in such a way that the profile segment has an average arithmetic height (Sa) of greater than 5 μm and less than 100 μm according to ISO 25178.It has been found that a surface profile of profile segments having a roughness with an average arithmetic height (Sa) of greater than 5 μm and less than 100 μm, which were produced by removal of the master model by means of laser radiation and subsequent molding, enable vehicle tires which solve the conflict of goals between dry adhesion and snow or ice adhesion at a higher level.According to the invention, a vehicle tire is provided, preferably produced by a method according to the invention and or produced by a profile segment according to the invention, wherein the vehicle tire has at least one partial region with a vehicle tire surface profile, wherein the vehicle tire surface profile has an average arithmetic height (Sa) of greater than 5 μm and less than 100 μm according to ISO 25178.It has been found that a vehicle tire having a roughness with an average arithmetic height (Sa) of greater than 5 μm and less than 100 μm can solve the conflict of goals between dry adhesion and snow or ice adhesion at a higher level.A preferred embodiment provides that the vehicle tire surface profile has a structure size of less than 0.1 mm×0.1 mm, in particular a vehicle tire surface profile Sa of greater than 10 μm, preferably of greater than 15 μm, and or of less than 80 μm, preferably of less than 60 μm. It has been found that small structural sizes, in particular vehicle tire surface profiles Sa of greater than 10 μm and less than 80 μm, lead to particularly good values with regard to snow or ice adhesion with particularly good dry adhesion.A further preferred embodiment provides that the surface roughnesses Sa, Ssk and or Sku of the vehicle tire surface profile from the shoulder zone to the equator and or on a profile block in each case are formed differently in the circumferential direction. A different formation of the surface roughnesses of the equator, i.e. of the tread surface arranged centrally between the shoulder regions, and of the shoulder zones makes it possible to produce a surface roughness in the different lateral regions of the tread which is particularly suitable for their predominant functions. Particularly effective adhesion in the circumferential direction and in the lateral direction is made possible. The predominant functions of a profile block, which are variable over the circumferential direction, can thus also be optimized.The invention permits numerous embodiments. To further clarify its basic principle, one of these is illustrated in the drawings and is described below. This shows in FIG. 1 shows a peripheral section of a vehicle tire for passenger cars according to the invention in a sectional illustration with a sectional plane which contains the tire axis, shown in perspective view, FIG. 2 shows cross sections of surface profiles.FIG. 1 shows a tubeless vehicle tire of the radial type of a car with a profiled tread 1 extending from shoulder to shoulder. The profiled tread 1 and the tire sidewalls 2 are each formed extending in the circumferential direction U of the vehicle tire over the entire circumference of the vehicle tire. The tire sidewall 2 is formed at its radially inner end with a bead portion 4 for seating on the rim, respectively. In the bead region 4, a respective best bead core 5 is formed which extends over the entire circumference of the vehicle tire and is formed concentrically with respect to the tire axis. In a known manner, starting from one bead core 5 extends outwards in the radial direction R through the tyre sidewall 2 as far as the profiled tread 1, then in axial extension through the area of extension of the profiled tread 1 as far as the other tyre shoulder and from there, inwards in the radial direction R, through the second tyre sidewall 2 as far as the bead core 5 formed in the second bead area 4, a carcass 3 of radial design extends. The carcass 3 is formed in a known manner from one or more plies of carcass cords embedded in rubber. Radially outside the carcass 3 between the carcass 3 and the profiled tread 1 there is formed in a known manner a belt 6 of a plurality of belt plies of known type which extends over the entire circumference of the vehicle tyre and extends in the axial direction A from tyre shoulder to tyre shoulder. The belt plies are formed from reinforcing elements embedded in rubber-for example steel cords or other reinforcing elements known as suitable for the belt.On the inside of the carcass 3 directed towards the tire interior, a tire inner layer 7 formed from particularly airtight rubber material extends in a known manner starting from one bead region 4 along the tire sidewall 2 radially outwards as far as the tire shoulder, then in axial extension from this first tire shoulder to the second tire shoulder and from there in radial direction inwards along the second tire sidewall as far as the second bead region 4.FIG. 2 shows cross sections of surface profiles 8 which have a height difference from the highest points 9 to the lowest points 10 of 20 μm to 30 μm. As illustrated, the surface profiles 8 can have a rectangular or triangular geometry and combinations of these basic geometries. The widths to depth ratios and the distances of the individual depressions can vary here.References 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 citedEP 3 261 830 B1

[0008]

Claims

Method for producing a profile segment of a segmented cast vulcanization mold for vehicle tyres, wherein the mold surface of the profile segment molds a segment of the tread profile of a tyre to be vulcanized, having the following steps: a) creating a rigid model segment which has a shell-shaped tread surface, b) milling the positive profile of the tread (1) into the shell-shaped tread surface of the model segment to create a master model, wherein the master model has a surface profile (8) to be changed at least in a partial region, c) creating a flexible impression of preferably silicone rubber from the master model, d) creating a rigid impression of preferably gypsum from the impression of preferably silicone rubber to form a casting core segment, e) casting all ring-shaped, juxtaposed casting core segments, Preferably with an aluminium-magnesium alloy, for obtaining a vulcanization mould, which is subsequently divided into individual profile segments, characterized in that the surface profile (8) of the master model is changed by removal by means of laser radiation in such a way that it has an average arithmetic height (Sa) of greater than 5 μm and less than 100 μm according to ISO 25178.Method according to claim 1, characterised in that the change in the surface profile (8) in step b) is produced by means of laser cutting or laser drilling.Method according to Claims 1 or 2, characterized in that in step b) a structure size of less than 0.1 mm×0.1 mm, in particular a surface profile (8) Sa of greater than 10 μm, preferably of greater than 15 μm, and / or of less than 80 μm, preferably of less than 60 μm, is produced.Method according to one of the preceding claims, characterized in that in step b) an Ssk value according to ISO 25178 of greater than -10, preferably of greater than -5, more preferably of greater than -3 and / or of less than 50, preferably of less than 30, more preferably of less than 20 and preferably an Sku value according to ISO 25178 of ≥ 3 is generated.Method according to one of the preceding claims, characterized in that in step b) the surface roughnesses Sa, Ssk and / or Sku from the shoulder zone to the equator and / or on a respective profile block are formed differently in the circumferential direction.Method according to one of the preceding claims, characterized in that in step b) the surface roughnesses Sa, Ssk and / or Sku are generated in the form of a defined pattern, preferably by means of a dot matrix or vectorial hatching.Method according to one of the preceding claims, characterized in that a short-pulse laser radiation or an ultra-short-pulse laser radiation is used as laser radiation and targeted holes are preferably produced.Method according to one of the preceding claims, characterized in that the removal of the surface profile (8) by means of laser radiation is carried out by multiple passes with the laser radiation, wherein the focal position of the laser radiation is preferably changed between the passes and / or during each pass.Profile segment of a segmented vulcanization mold for vehicle tires, wherein the mold surface of the profile segment molds a segment of the tread profile of a tire to be vulcanized, preferably produced by means of a method according to one of the preceding claims, wherein the profile segment has at least one partial region, wherein the at least one partial region has a modified surface profile (8) which results from the removal by means of laser radiation of the master model, wherein the surface profile (8) of the master model is modified by removal by means of laser radiation such that the profile segment has an average arithmetic height (Sa) of greater than 5 μm and less than 100 μm according to ISO 25178.Vehicle tyre, preferably produced by a method according to one of Claims 1 to 8 and / or produced by a profile segment according to Claim 9, wherein the vehicle tyre has at least one subregion having a vehicle tyre surface profile, wherein the vehicle tyre surface profile has an average arithmetic height (Sa) of greater than 5 μm and less than 100 μm according to ISO 25178.Vehicle tyre according to Claim 10, characterized in that the vehicle tyre surface profile has a structure size of less than 0.1 mm×0.1 mm, in particular a vehicle tyre surface profile Sa of greater than 10 μm, preferably of greater than 15 μm, and / or of less than 80 μm, preferably of less than 60 μm.Vehicle tyre according to one of Claims 10 to 11, characterized in that the surface roughnesses Sa, Ssk and / or Sku of the vehicle tyre surface profile from the shoulder zone to the equator and / or on in each case one profile block are of different design in the circumferential direction.

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