Pneumatic tyre and method for producing same

Abstract

The invention relates to a pneumatic tyre having a circumferential tread (1) which is made of a rubber compound and has a tread pattern having at least one longitudinal groove (10) which extends in the circumferential direction (U) and is delimited in the axial direction (A) by longitudinal sidewalls (20), wherein a reinforcing layer made of a material having a higher rigidity than the rubber compound of the tread is provided on at least some portions of the longitudinal sidewalls, wherein the reinforcing layer is made from a rubber compound having an E-modulus from 20 to 100 MPa and a thickness in the axial direction (A) of at least 0.5 mm, and the reinforcing layer is integrally vulcanised into the tread. The invention also relates to a method for producing such a pneumatic tyre.

Description

[0001] Pneumatic tire and method for producing the same

[0002] Description:

[0003] The invention relates to a pneumatic tire, in particular for motor vehicles, with a circumferentially formed tread made of a rubber compound having a tread profile with at least one circumferentially extending longitudinal groove which is delimited in the axial direction by longitudinal sidewalls, wherein in the region of the longitudinal sidewalls at least partially a reinforcing layer made of a material with higher rigidity than the rubber compound of the tread is arranged.

[0004] The invention further relates to a method for producing a pneumatic tire, in particular for motor vehicles, with a circumferentially formed tread made of a rubber mixture which has a tread profile with at least one circumferentially extending longitudinal groove which is delimited in the axial direction by longitudinal sidewalls, wherein in the region of the longitudinal sidewalls at least partially a reinforcing layer made of a material with higher rigidity than the rubber mixture of the tread is arranged, in which in a first step a pneumatic tire blank is produced on a tire building machine, wherein on the outer circumference of the pneumatic tire blank a tread is applied to form the tread and then in a second step the pneumatic tire blank is vulcanized under the influence of pressure and temperature to form the pneumatic tire and the tread profile is molded into the tread.

[0005] Pneumatic tires of the type mentioned above are well known and are used in particular as motor vehicle tires for passenger cars, light commercial vehicles and trucks, both as summer, winter or all-season tires.

[0006] Particularly with high-performance pneumatic tires and tires optimized for rolling resistance, a conflict of objectives must be resolved between rolling resistance and the stiffness of the tread pattern incorporated into the tread. Using rubber compounds with relatively low stiffness to form the tread does achieve low rolling resistance, as these relatively soft rubber compounds exhibit low hysteresis. However, such a soft rubber compound often has a detrimental effect on the driving stability and service life of the pneumatic tire, as the longitudinal grooves in particular tend to deform under corresponding loads, which can lead, for example, to reduced steering precision and also poses the risk of premature wear or breakage of individual tread pattern blocks arranged between adjacent longitudinal grooves.

[0007] It has therefore been proposed on several occasions to equip the wear-prone longitudinal sidewalls of the longitudinal grooves and / or the corresponding transverse sidewalls of the axially extending transverse grooves with a reinforcing layer made of a material with greater rigidity than the tread rubber compound when using a rolling-resistance-optimized soft rubber compound to form the tread, in order to generate greater rigidity in this area. An example of such a pneumatic tire is the subject of WO 2017 / 093673 A1. The reinforcing layer proposed therein is made of a very hard plastic material, in particular a fiber-reinforced plastic with a small thickness of less than 0.5 mm and a correspondingly high modulus of elasticity of over 300 MPa.This is not only complex in terms of manufacturing technology, but also has the disadvantage that there is a material boundary along the reinforcement layer, where a separation from the rubber compound of the tread can occur, which brings with it a corresponding risk of failure.

[0008] The object of the invention is to propose a pneumatic tire of the type mentioned at the outset and a method for producing such a pneumatic tire, with which the disadvantages of the prior art are overcome.

[0009] To achieve the stated object, the invention proposes the design of a pneumatic tire according to the features of patent claim 1.

[0010] A method for producing a pneumatic tire with which the object of the invention is achieved is the subject of patent claim 5. Advantageous embodiments and further developments of the invention are the subject of the dependent claims.

[0011] The invention proposes a pneumatic tire in which the reinforcement layer is formed from a rubber compound with a modulus of elasticity of 20 to 100 MPa and an axial thickness of at least 0.5 mm. Due to its construction from a rubber compound, the reinforcement layer is integrally applied by vulcanization to the tread, which is also formed from a rubber compound. By forming the reinforcement layer from a rubber compound according to the invention, a material boundary that impairs grip is avoided, because the reinforcement layer is homogeneously bonded to the tread and covers the corresponding longitudinal sidewalls on the outside.

[0012] The rubber mixture of the reinforcing layer provided according to the invention with an E-modulus of 20 to 100 MPa is significantly stiffer than the rubber mixture of the tread, which usually has an E-modulus of about 4 to 15 MPa.

[0013] The values ​​of the elastic modulus of the various rubber compounds described in this invention are each determined using a corresponding vulcanizate sample of the rubber compound at 55 °C from a dynamic-mechanical measurement according to DIN 53515.

[0014] The presence of the reinforcing layer reduces the bending of the longitudinal sidewalls bordering the longitudinal groove, as well as of the tread blocks located between individual longitudinal grooves. Thus, according to the invention, an increase in the rigidity of the tread pattern and a corresponding improvement in steering precision are achieved while simultaneously optimizing rolling resistance. Rolling resistance is further reduced because only minimal movements of the tread rubber compound occur during tire rotation. The thickness of the reinforcing layer provided according to the invention in the axial direction can be varied within wide limits, being at least 0.5 mm, preferably approximately 1 to 3 mm, and more preferably 1.0-1.5 mm.

[0015] Only individual longitudinal grooves of the tread pattern, several or even all longitudinal grooves of the tread pattern can be equipped with a reinforcing layer in the manner according to the invention.

[0016] According to a further proposal of the invention, the tread has, in addition to the longitudinal grooves, also transverse grooves running transversely to the circumferential direction, which are delimited by transverse side walls, wherein the reinforcing layer is arranged at least in some areas in the region of the transverse side walls.

[0017] Furthermore, according to a further proposal of the invention, it can also be provided that the reinforcing layer is also arranged in the region of the groove base of the at least one longitudinal groove and / or the transverse grooves.

[0018] The method according to the invention for producing a pneumatic tire is characterized in that, before the vulcanization step, at least one strip for forming the reinforcing layer is applied to the tread in the region forming the longitudinal sidewalls, said strip being formed from a rubber mixture which, after vulcanization, has an E-modulus of 20 to 100 MPa and a thickness of at least 0.5 mm and covers the longitudinal sidewalls towards the outside of the pneumatic tire.

[0019] The strip may in particular have a thickness of up to 3 mm, with a thickness of 1.0-1.5 mm preferably being provided after vulcanization.

[0020] According to a further proposal of the invention, the tread also comprises transverse grooves extending transversely to the circumferential direction, which are delimited by transverse sidewalls. According to the invention, the strip for forming the reinforcing layer is then also applied to the tread in the region forming the transverse sidewalls, in order to also cover the transverse sidewalls after vulcanization. According to a further proposal of the invention, the strip for forming the reinforcing layer can also be applied to the tread in the region forming the groove base of the at least one longitudinal groove and / or the transverse grooves, in order to also cover the groove base in the finished pneumatic tire.

[0021] In particular, within the scope of the production according to the invention on a tire building machine known per se, it can be provided that a pre-profiling with grooves is introduced into the tread according to the intended course of the at least one longitudinal groove and / or the transverse grooves and then the strips are placed on the grooves to form the reinforcement layer and are vulcanized together with the tread.

[0022] Since in the method according to the invention the reinforcing layer is formed from strips of a rubber mixture which are applied to the tread, which also consists of a rubber mixture, before vulcanization, a homogeneous and inseparable bond is created between the two rubber mixtures during vulcanization, so that the reinforcing layer is incorporated integrally into the tread of the tire or its tread pattern.

[0023] Further embodiments and details of the invention are explained below with reference to the drawings illustrating an exemplary embodiment. They show:

[0024] Figure 1 shows a section through the tread profile of an embodiment of a pneumatic tire according to the invention along line VV in Figure 2;

[0025] Figure 2 shows the top view of the tread profile according to Figure 1;

[0026] Figure 3 shows a schematic representation of a tire building machine for producing a pneumatic tire;

[0027] Figure 4 shows a section through the tread profile of a further embodiment of the invention; and Figure 5 shows a section through the pneumatic tire blank of the embodiment according to Figure 4 in the region of the tread.

[0028] Figure 1 shows a schematic cross-sectional view of the tread profile of the tread 10 of a pneumatic tire 1, as used, for example, as a motor vehicle tire, in particular summer or winter tires for cars and trucks.

[0029] The central axis M as well as the axial direction A and the circumferential direction U of the pneumatic tire 1 can be seen.

[0030] When viewed in conjunction with the plan view according to Figure 2, it can also be seen that the tread profile comprises a plurality of longitudinal grooves 11 running in the circumferential direction U and transverse grooves 12 running transversely to the circumferential direction U, i.e. in the axial direction A, between which profile blocks 13 are formed. The longitudinal grooves 11 and transverse grooves 12 extend to a groove base 15, wherein the longitudinal grooves 11 are delimited in the axial direction A by longitudinal sidewalls 110 and the transverse grooves 12 are delimited in the circumferential direction U by transverse sidewalls 120.

[0031] The tread 10 shown in the figures, with the tread profile described above, is typically made of a rubber compound that is softened to optimize rolling resistance and exhibit low hysteresis. The elastic modulus of the rubber compound of the tread 10 is, for example, 4 to 15 MPa.

[0032] In order to ensure a rigidity of the longitudinal side walls 110 delimiting the longitudinal grooves 11 and of the tread blocks 13 delimited by adjacent longitudinal grooves 11 that promotes steering precision, driving stability, and wear resistance, a reinforcing layer 14 with an approximately L-shaped cross-section is introduced into the longitudinal grooves 11 as a surface-delimiting layer, as can be seen from Figure 1. This reinforcing layer 14 is made of a rubber compound with an E-modulus of 20 to 100 MPa and a thickness in the axial direction A of, for example, 1.2 mm, and which completely covers the longitudinal side walls 110 and the associated groove base 15 of the longitudinal groove 11 in a partial area towards the outside. The E-modulus of the reinforcing layer 14 is thus significantly higher than that of the rubber compound of the tread 10, and the reinforcing layer also has increased rigidity in comparison.

[0033] The measured values ​​of the elastic modulus of the rubber compound of the tread 10 and the reinforcement layer 14 were determined as dynamic storage modulus E 'mean using a corresponding vulcanizate sample of the rubber compounds at a temperature of 55 °C from a dynamic-mechanical measurement according to DIN 53513.

[0034] Alternatively, in a further embodiment according to Figure 4, it can be provided that the longitudinal groove 11 is completely covered, ie in the region of the longitudinal side walls 110 and the groove base 15, by a U-shaped reinforcement layer 14 towards the outside.

[0035] To produce and arrange this reinforcement layer 14 in the area of ​​the longitudinal groove 11, as shown in Figure 3, during the production of a pneumatic tire blank on a conventional tire building machine 2, all the individual parts (not shown) such as the core, inner layer, side walls and fabric layers for forming the carcass and the belt package with steel cord, wound bandage and finally, axially on the outside, the tread 100 made of a rubber mixture for forming the tread 10 are applied and joined together in a manner not shown in detail on the rotating bellows 20 of the tire building machine 2 in a manner known per se.

[0036] As shown in Figure 5, a tread 100 is used for this purpose, in which a pre-profiling with grooves 111 corresponding to the intended course of the at least one longitudinal groove 11 is introduced in the area forming the later longitudinal grooves 11. A strip 115 is then placed on each of these grooves 111 to form the reinforcement layer 14 and wound onto the outside of the tread 100 on the tire building machine 2.As soon as the pneumatic tire blank produced in this way is vulcanized in a subsequent manufacturing process, wherein the tread profile is introduced into the tread 10, the strips 115, which are also formed from a rubber mixture, are integrally connected as a reinforcing layer 14 with the rubber mixture of the tread 100, so that the lining of the longitudinal side walls 110 and the groove base 15 of the corresponding longitudinal groove 11 with the reinforcing layer 14 formed from the harder rubber mixture, as shown in Figure 4, is effected.

[0037] Individual or all of the longitudinal grooves 11 provided in the tread pattern can be provided with a reinforcing layer 14 in this way, just as it is also possible to cover the transverse grooves 12 present in the tread pattern equally with the reinforcing layer 14.

[0038] List of reference symbols:

[0039] 1 : Pneumatic tires

[0040] 2: Tire building machine

[0041] 10: Tread

[0042] 11 : Longitudinal groove

[0043] 12: Transverse groove

[0044] 13: Profile block

[0045] 14: Reinforcement layer

[0046] 15: Groove base

[0047] 20: Bellows

[0048] 100: Tread

[0049] 110: Longitudinal side wall

[0050] 111 : Groove

[0051] 115: Stripes

[0052] 120: Transverse side wall

[0053] A: Axial direction

[0054] M: Central axis

[0055] U: circumferential direction

[0056] V: Sectional view

Claims

Patent claims:

1. Pneumatic tire (1) with a circumferentially formed tread (10) made of a rubber compound, which has a tread profile with at least one longitudinal groove (11) running in the circumferential direction (U) and is delimited in the axial direction (A) by longitudinal side walls (110), wherein in the region of the longitudinal side walls (110) at least in some regions a reinforcing layer (14) made of a material with higher rigidity than the rubber compound of the tread (10) is arranged, characterized in that the reinforcing layer (14) is formed from a rubber compound with an E-modulus of 20 to 100 MPa and a thickness in the axial direction (A) of at least 0.5 mm and the reinforcing layer (14) is applied to the longitudinal side walls (110).

2. Pneumatic tire (1) according to claim 1, characterized in that the thickness of the reinforcing layer (14) in the axial direction (A) is 1.0 to 1.5 mm.

3. Pneumatic tire (1) according to one of claims 1 or 2, characterized in that the tread (10) has transverse grooves (12) extending transversely to the circumferential direction (U) which are delimited by transverse side walls (120), the reinforcing layer (14) being arranged at least in regions in the region of the transverse side walls (120).

4. Pneumatic tire (1) according to one of claims 1 to 3, characterized in that the reinforcing layer (14) is also arranged in the region of the groove base (15) of the at least one longitudinal groove (11) and / or the transverse grooves (12).

5. A method for producing a pneumatic tire (1) with a circumferentially formed tread (10) made of a rubber mixture, which has a tread profile with at least one longitudinal groove (11) running in the circumferential direction (U) and which is delimited in the axial direction (A) by longitudinal side walls (110), wherein in the region of the longitudinal side walls (110) at least in some regions a reinforcing layer (14) made of a material with higher stiffness than the rubber mixture of the tread (10) is arranged, in which in a first step a pneumatic tire blank is produced on a tire building machine (2), wherein on the outer circumference of the pneumatic tire- A tread strip (100) is applied to the blank to form the tread (10) and then, in a second step, the pneumatic tire blank (100) is vulcanized under the action of pressure and temperature to form the pneumatic tire (1) and the tread profile is molded into the tread (10), characterized in that before the vulcanizing step, at least one strip (115) is applied to the tread (100) in the area forming the longitudinal side walls (110) to form the reinforcing layer (14), which strip is formed from a rubber mixture which, after vulcanization, has an E-modulus of 20 to 100 MPa and a thickness of at least 0.5 mm and covers the longitudinal side walls (110).

6. The method according to claim 5, characterized in that the strip (115) for forming the reinforcing layer (14) has a thickness of 1.0 to 1.5 mm after vulcanization.

7. Method according to claim 5 or 6, characterized in that the tread (10) has transverse grooves (12) extending transversely to the circumferential direction (U) and delimited by transverse side walls (120), wherein the strip (115) for forming the reinforcing layer (14) is also applied to the tread (100) in the region forming the transverse side walls (120).

8. Method according to one of claims 5 to 7, characterized in that the strip (115) for forming the reinforcing layer (14) is also applied to the tread (100) in the region forming the groove base of the at least one longitudinal groove (11) and / or the transverse grooves (12).

9. Method according to claim 8, characterized in that a pre-profiling with grooves (111) corresponding to the intended course of the at least one longitudinal groove (11) and / or the transverse grooves (12) is introduced into the tread (100) and then the strips (115) are placed on the grooves (111) to form the reinforcing layer (14) and are vulcanized together with the tread (100).

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