PNEUMATIC VEHICLE TIRE HAVING A REINFORCING LAYER WITH STEEL MONOFILAMENTS

Abstract

A pneumatic vehicle tire having a strength member ply comprising steel monofilaments having a cross-sectional area of 98 mm.sup.2 to 125 mm.sup.2 per meter of strength member ply, the steel has a carbon content of at least 0.86% by weight. To improve rolling resistance the monofilaments have a brass coating having a copper content of 61% by weight to 70% by weight and a zinc content of 30% by weight to 39% by weight, in that the monofilaments have a linear density of 92 g/100 m to 105 g/100 m, and the monofilaments each have a tensile density Td of 34 MPa/(g/100 m) to 39 MPa/(g/100 m). The strength member ply has an areal strength AS of 109 Nmm.sup.2 to 166 Nmm.sup.2, and the rubber material has a breaking elongation of 300% to 450%.

Claims

1. A pneumatic vehicle tire comprising a strength member ply comprising strength members made of steel which are arranged within the strength member ply substantially parallel and spaced apart from one another and are embedded in a rubber material, wherein each of the strength members is configured as a monofilament, wherein the monofilaments occupy a cross-sectional area of 98 mm.sup.2 to 125 mm.sup.2 per meter of strength member ply and wherein the steel has a carbon content of at least 0.86% by weight, wherein: the monofilaments have a brass coating having a copper content of 61% by weight to 70% by weight and a zinc content of 30% by weight to 39% by weight, the monofilaments each have a linear density of 92 g/100 m to 105 g/100 m, the monofilaments have a tensile density Td of 34 MPa/(g/100 m) to 39 MPa/(g/100 m), wherein the tensile density Td is defined as the quotient of a tensile strength and the linear density of the respective strength member, the strength member ply has an areal strength AS of 109 Nmm.sup.2 to 166 Nmm.sup.2, wherein the areal strength AS is defined as the product of a breaking strength and a diameter d of a monofilament of the strength member ply and a spacing x between the monofilament and an adjacent monofilament of the strength member ply, the rubber material has a breaking elongation of 300% to 450%.

2. The pneumatic vehicle tire as claimed in claim 1, wherein the monofilaments have a compression modulus of 138 GPa to 155 GPa and/or a compression displacement of 0.95% to 1.05% and/or a compression stress of 1400 MPa to 1500 MPa.

3. The pneumatic vehicle tire as claimed in claim 1, wherein the monofilaments each have an out-of-plane bending stiffness of 270 Nmm.sup.2 to 340 Nmm.sup.2.

4. The pneumatic vehicle tire as claimed in claim 1, wherein the monofilaments each have a tensile strength of 3500 MPa to 3700 MPa, preferably in that a force of 285 N to 325 N must be applied for an elongation of 1%.

5. The pneumatic vehicle tire as claimed in claim 1, wherein the strength member ply has a weight fraction of steel of 47% by weight to 63.5% by weight, preferably of 48.9% by weight to 62.3% by weight, particularly preferably of 52% by weight to 58% by weight and wherein the strength member ply has a spacing factor S of 2.00 to 2.67, preferably of 2.05 to 2.57, particularly preferably of 2.10 to 2.50, wherein S=1+((y+y+x)/(2d)), wherein y is a thickness of the strength member ply on a first side of a monofilament of the strength member ply, y is a thickness of the strength member ply on an opposite second side of the monofilament, x is a spacing between the monofilament and an adjacent monofilament of the strength member ply and d is a diameter of the monofilament.

6. The pneumatic vehicle tire as claimed in claim 1, wherein the monofilaments are free from a twist about their axis.

7. The pneumatic vehicle tire as claimed in claim 1, wherein the monofilaments have a twist angle of not more than 10, preferably of not more than 1.

8. The pneumatic vehicle tire as claimed in claim 1, wherein the rubber material has a tensile strength of 15 N/mm.sup.2 to 22 N/mm.sup.2.

9. The pneumatic vehicle tire as claimed in claim 1, wherein the rubber material has a Shore hardness of 77 to 81 (Shore A).

10. The pneumatic vehicle tire as claimed in claim 1, wherein the rubber material has a rebound elasticity of 38 to 45.

11. The pneumatic vehicle tire as claimed in claim 1, wherein the pneumatic vehicle tire, especially of radial construction, comprises a belt and the strength member ply is a strength member ply of the belt, preferably the belt comprises two such strength member plies, whose strength members cross at an angle of 18 to 45.

12. The pneumatic vehicle tire as claimed in claim 1, wherein the pneumatic vehicle tire, especially of radial construction, comprises a carcass and in that the strength member ply is a strength member ply of the carcass.

Description

[0050] All of the embodiments of the pneumatic vehicle tire according to the invention reproduced in this description are examples of the configuration of the invention and should be seen as non-limiting. Accordingly, further embodiments of the invention, which are the subject matter of the invention, unless explicitly explained otherwise in the description, are also provided by individual features or a plurality of features of one embodiment alone or by the combination of the features of different embodiments. Furthermore, combinations of preferred and particularly preferred embodiments can also be combined with one another.

[0051] The following provides an exemplary embodiment of a pneumatic vehicle tire according to the invention. What is concerned is a pneumatic vehicle tire of radial construction having a strength member ply comprising strength members made of steel which are arranged within the strength member ply substantially parallel and spaced apart from one another and are embedded in a rubber material, wherein each of the strength members is configured as a monofilament, wherein the monofilaments occupy a cross-sectional area of 98 mm.sup.2 to 125 mm.sup.2 per meter of strength member ply and wherein the steel has a carbon content of at least 0.86% by weight.

[0052] The tire is characterized in that the monofilaments have a brass coating having a copper content of 61% by weight to 70% by weight and a zinc content of 30% by weight to 39% by weight, in that the monofilaments each have a linear density of 92 g/100 m to 105 g/100 m, in that the monofilaments each have a tensile density Td of 34 MPa/(g/100 m) to 39 MPa/(g/100 m), wherein the tensile density Td is defined as the quotient of the tensile strength and the linear density of the strength member, in that the strength member ply has an areal strength AS of 109 Nmm.sup.2 to 166 Nmm.sup.2, wherein the areal strength AS is defined as the product of a breaking strength and a diameter of a monofilament of the strength member ply and a spacing between the monofilament and an adjacent monofilament of the strength member ply and in that the rubber material has a breaking elongation of 300% to 450%.

[0053] The monofilaments may have a compression modulus of 138 GPa to 155 GPa, a compression displacement of 0.95% to 1.05% and/or a compression stress of 1400 MPa to 1500 MPa. The monofilaments may have an out-of-plane bending stiffness of in each case 270 Nmm.sup.2 to 340 Nmm.sup.2. The monofilaments may each have a tensile strength of 3500 MPa to 3700 MPa and it is preferable when a force of 285 N to 325 N must be applied for an elongation of 1%.

[0054] The strength member ply may have a weight fraction of steel of 47% by weight to 63.5% by weight, preferably of 48.9% by weight to 62.3% by weight, particularly preferably of 52% by weight to 58% by weight, wherein the strength member ply has a spacing factor S of 2.00 to 2.67, preferably of 2.05 to 2.57, particularly preferably of 2.10 to 2.50.

[0055] The monofilaments may have a twist angle of not more than 10, preferably of not more than 1. The monofilaments may be free from a twist about their own axis.

[0056] The rubber material of the strength member ply may have a tensile strength of 15 N/mm.sup.2 to 22 N/mm.sup.2. The rubber material of the strength member ply may have a Shore hardness of 77 to 81 (Shore A). The rubber material of the strength member ply may have a rebound elasticity of 38 to 45.

[0057] Such a pneumatic vehicle tire is particularly advantageous if the strength member ply is a belt ply. It is yet more advantageous when both belt plies which cross at an angle of 18 to 45 are configured in such a way. However, an above-described strength member ply may also be a carcass ply of a pneumatic vehicle tire.

[0058] Tire tests were performed to determine the tire durability of tires. The tires concerned are pneumatic vehicle tires of radial construction of 175/65 R15 in size in each case having two belt plies. The belt plies are configured as strength member plies comprising strength members made of steel which are arranged within the respective strength member ply substantially parallel and spaced apart from one another and are embedded in a rubber material. The strength members of the two belt plies of the respective tire cross at an angle of 18 to 45.

[0059] Noninventive comparative tires (reference tire 1, reference tire 2) and inventive tires (example tires) were tested. The reference tires 1, the reference tires 2 and the example tires differ from one another only in the configuration of their belt plies.

[0060] Table 1 lists the parameters of a belt ply/of a strength member (SM) of the belt ply of a reference tire 1, reference tire 2 and of an inventive example tire.

[0061] Table 2 provides a comparative assessment of the characteristics of the tested tires.

[0062] The belt ply of an inventive example tire listed in table 1 comprises as strength members monofilaments, wherein the steel has a carbon content of at least 0.86% by weight. The monofilaments have a twist angle of not more than 1. They are especially free from a twist about their axis. The strength member ply especially has a weight fraction of steel of 57.8% and a spacing factor S of 2.19.

[0063] The belt ply of a reference tire 1 listed in table 1 comprises as strength members customary steel cords of 2 construction having a lay length of 14 mm. The steel has a carbon content of less than 0.86% by weight.

[0064] The belt ply of a reference tire 2 listed in table 1 comprises as strength members steel monofilaments having a lower linear density than the monofilaments of the example ply, wherein the steel likewise has a carbon content of at least 0.86% by weight. The monofilaments have a twist angle of not more than 1. They are especially free from a twist about their axis.

[0065] The strength members of the belt plies of the test tires each have a brass coating having a copper content of 61% by weight to 70% by weight and a zinc content of 30% by weight to 39% by weight. The rubber material of the belt plies in each case has a breaking elongation of 300% to 450%.

[0066] The tensile strength and force at 1% elongation as well as the breaking strength of the respective strength member are measured according to ASTM D 2969.

[0067] The breaking elongation of the rubber material is measured at room temperature according to DIN 53504. The tensile strength of the rubber material is measured at room temperature according to DIN 53504. The Shore hardness of the rubber material is measured at room temperature according to DIN 53505. The rebound elasticity of the rubber material is measured at room temperature according to DIN 53512.

[0068] To determine the compression modulus, the compression displacement and the compression stress a sample of a rubber cylinder, in particular a rubber cylinder composed of the same rubber material as the rubber material of the strength member ply, comprising the steel strength member arranged along the rotational axis of the cylinder was tested in comparison with a sample composed of a corresponding rubber cylinder free from such a strength member. The respective cylinder has a diameter of 15 mm and a length of 25 mm and the test was performed at room temperature with a pre-load of 2 N and a test speed of 5 mm/min. To determine the compression characteristics of the strength member the difference between the two samples with and without strength members is considered.

[0069] The out-of-plane bending stiffness of the respective strength member is measured by the customary 3-point bending test. The bending stiffness of the steel strength member in this case is determined as a result of a force acting on the strength member perpendicular to the extension direction of the strength member. A linear piece of steel strength member is tested in this case, wherein the test length and the distance between two contact points on which the strength member is supported depends on the linear density of the strength member. The measurement of the bending strength of the monofilament of the example was performed with a test length of 50.02 mm, a distance between the two contact points of 20.02 mm, a speed of 2.503 mm/s and a preload of 0.03 N.

[0070] The twist angle is calculated as atan(d/P)180/, wherein d is the diameter of the monofilament and P is the twist spacing (pitch) of the twist. To this end the monofilament is analyzed using an optical microscope. The diameter d (in millimeters) and a value that corresponds to half of the twist spacing P (in millimeters) is determined in this case. The value is determined using a draw marking on the surface of the monofilament. The value is multiplied by 2 to obtain the twist spacing P.

TABLE-US-00001 TABLE 1 Reference Reference Example tire 1 tire 2 tire Number of monofilaments per 2 1 1 strength member (SM) Lay length [mm] (SM) 14 Strength member cross-sectional 134.3 115.5 119.4 area per meter of SMP [mm.sup.2] Linear density [g/100 m] (SM) 112 75 99 Tensile density Td 28.6 49.3 36.4 [MPa/(g/100 m)] (SM) Areal strength AS [Nmm.sup.2] 120 60 116 Breaking strength [N] (SM) 445 355 445 Compression modulus [GPa] 128 145 151 (SM) Compression displacement [%] 0.80 0.90 0.97 (SM) Compression stress [N/mm.sup.2] 922 1384 1468 (SM) Out-of-plane bending stiffnesses 200 195 330 of SMs [Nmm.sup.2] Force [N] at 1% elongation 320 232 300 Tensile strength [MPa] (SM) 3200 3700 3600
Table 2 provides a comparative assessment of the characteristics of the tested tires.

TABLE-US-00002 TABLE 2 Reference tire 1 Reference tire 2 Example tire Tire durability 100% 90% 100% Handling 100% 90% 105%

[0071] The determined tire durability of the reference tires 1 is rated as 100%. It is apparent that reference tires 2 have a lower tire durability than reference tires 1. By contrast, the inventive example tires have a tire durability comparable to reference tires 1. The essential point is that tire durability is improved compared to reference tires 2 which, similarly to the inventive example tires, comprise steel monofilaments. This is made possible by the reduced tensile density Td compared to reference tires 2 and the higher areal strength AS together with the increased linear density and still high breaking elongation of the rubber material of the inventive example tires.

[0072] At the same time the linear density of the monofilaments and the strength member cross-sectional area per meter of strength member ply of the example tires and the reference tires 2 is markedly reduced compared to the reference tires 1, thus making it possible to achieve a rolling resistance which is still advantageously reduced compared to reference tires 1 in each case.

[0073] As indicated in table 2, the determination of the handling characteristics of the test tires has shown an advantage of the inventive example tires especially compared to reference tires 2. Here too, the increased linear density has proven advantageous.

[0074] The elevated values for compression modulus, compression displacement and compression stress and the markedly elevated out-of-plane bending stiffness have proven advantageous for continued advantageous rolling resistance, higher robustness and improved handling characteristics of the inventive example tires compared to reference tires 2. The elevated force at 1% elongation coupled with only a slight reduction in tensile strength have likewise proven advantageous.