pneumatic tires

Abstract

Pneumatic tires, comprising: an annular tread portion (1) extending in the tire circumferential direction (C); a pair of sidewall portions (2) arranged on both sides of the tread portion (1); a pair of bead portions (3) arranged inside said sidewall portions (2) in the tire radial direction; and a reinforcing member (10) including a plurality of reinforcing cords (11, 12, 13, 14) oriented in at least three directions and having a net-like structure, wherein at least a first, a second and a third reinforcing cord (11, 12, 13, 14) are connected at at least a part of intersection points of the reinforcing cords (11, 12, 13, 14); wherein the first reinforcing cord (11) is oriented in a first direction at an intersection point, the second reinforcing cord (12) is oriented in a second direction at the intersection point, and the third reinforcing cord (13) is oriented in a third direction at the intersection point, the first, second, and third directions differing from each other at the intersection point; the second reinforcing cord (12) runs parallel to a tire width direction (W) and is welded to the first reinforcing cord (11) and the third reinforcing cord (13) at the intersection point, so that a plurality of connected portions (15) are formed along the tire width direction (W) by the welding.

Description

Technical area

[0001] The present invention relates to a pneumatic tire provided with a reinforcing member used as a reinforcing layer represented by a belt layer, a carcass layer, or a bead reinforcing layer, and more particularly relates to a pneumatic tire enabling improvement of in-plane bending strength while maintaining excellent flexibility with respect to out-of-plane deformation of a reinforcing member, thereby enabling improvement of tire properties. State of the art

[0002] In a pneumatic tire, a carcass layer is arranged extending between a pair of bead portions, and a belt layer is arranged on one side of the outer periphery of the carcass layer in a tread portion. A reinforcing member including a plurality of reinforcing cords inclined with respect to the tire circumferential direction is used as the belt layer, and the reinforcing cords are arranged to intersect between the layers of the belt layer (see, for example, Patent Documents 1 to 3).

[0003] Here, cornering stiffness can be increased and rolling resistance can be reduced by improving the in-plane bending stiffness of the reinforcing member used as the belt layer. However, in a prior art reinforcing member, reinforcing cords are weakly bonded, making it impossible for the reinforcing member to always exhibit adequate in-plane bending stiffness. While the in-plane bending stiffness can be improved by making the reinforcing cord itself stiff, this also results in a loss of flexibility with respect to out-of-plane deformation of the reinforcing member.

[0004] In response, a reinforcing member with a net-like structure in which two reinforcing cords are connected at intersection points has been proposed (see, for example, Patent Document 4). However, the effect of improving the in-plane bending rigidity of the reinforcing member by simply connecting two intersecting reinforcing cords is rarely achieved, and thus the effects of increasing cornering rigidity and reducing rolling resistance cannot be expected.

[0005] Furthermore, while the carcass layer includes a plurality of reinforcing cords arranged in the tire radial direction, the reinforcing cords are substantially independent, resulting in only a minor contribution to the tire circumferential rigidity. As a result, when the tire circumferential rigidity is to be increased, for example, to improve steering stability, a bead reinforcing layer extending from the bead portion to a sidewall portion is generally added (see, for example, Patent Documents 5 to 7).

[0006] Nevertheless, adding a bead reinforcement layer increases tire weight. Therefore, relying on an additional bead reinforcement layer to improve tire circumferential stiffness is not always the best option.

[0007] Further, the bead reinforcing layer used is a reinforcing member including a plurality of reinforcing cords inclined with respect to the tire circumferential direction.

[0008] However, in a prior art reinforcing member, reinforcing cords are weakly bonded, making it impossible for the reinforcing member to always exhibit adequate in-plane bending stiffness. As a result, tire circumferential stiffness cannot be effectively increased. While increasing the number of bead reinforcing layers can improve tire circumferential stiffness, increasing the number of bead reinforcing layers also increases tire weight.

[0009] As a response, the use of a reinforcing member having a net-like structure in which two reinforcing cords are connected to each other at intersection points, as described above, may be considered. However, the effect of improving the in-plane bending rigidity of the reinforcing member is rarely achieved by simply connecting two intersecting reinforcing cords, and thus, the effect of increasing tire circumferential rigidity cannot be expected. List of citationsPatent literature Patent Document 1: JP 61-1505 A Patent Document 2: JP 01-501382 A Patent Document 3: JP 06-211003 A Patent Document 4: WO 2015 / 8547 Patent Document 5: JP 2012-221920 A Patent Document 6: JP 2013-35362 A Patent Document 7: JP 2014-227149 A

[0010] EP 0 157 761 A2 discloses a tire in which three reinforcing cords are meshed in a net-like structure at random intersection points such that only two of the cords are welded together at a common intersection point.

[0011] DE 30 24 367 A1 discloses a tire with a reinforcing element having a net-like structure and two reinforcing cords. Cords of one layer are welded to cords of another layer at intersection points. Another tire has three cords; however, they are not connected to each other at a common intersection point.

[0012] EP 0 131 954 A2 discloses a tire with a reinforcing element comprising a plurality of reinforcing cords. Some cords are interlaced around intersection points and thus not oriented in a determinable direction.

[0013] DE 1 272 753 B discloses a pneumatic vehicle tire with a reinforcing element having a mesh-like structure with at least a first, a second, and a third cord thread, which are interconnected at at least some of the intersecting points of the cord threads, but do not extend in the tire width direction. The threads are not mechanically woven or welded, but are bonded together at their intersection points by a separate binder. Summary of the inventionTechnical problem

[0014] An object of the present invention is to provide a pneumatic tire that enables improvement of in-plane bending rigidity while maintaining excellent flexibility with respect to out-of-plane deformation of a reinforcing member, thereby enabling improvement of tire properties. Specifically, in a pneumatic tire in which a reinforcing member is applied to a belt layer, the present invention enables cornering rigidity to be increased and rolling resistance to be reduced. Further, in a pneumatic tire in which a reinforcing member is applied to a carcass layer, the present invention enables tire circumferential rigidity to be increased without relying on an additional bead reinforcing layer. Moreover, in a pneumatic tire in which a reinforcing member is applied to a bead reinforcing layer, the present invention enables tire circumferential rigidity to be effectively increased. Solution to the problem

[0015] The pneumatic tire according to the invention for achieving the above-described object comprises an annular tread portion extending in the tire circumferential direction, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged on the inner side of these sidewall portions in the tire radial direction. This pneumatic tire is also provided with a reinforcing member including a plurality of reinforcing cords oriented in at least three directions and having a net-like structure, wherein at least first, second, and third reinforcing cords are connected at at least a portion of intersection points of the reinforcing cords.The first reinforcing cord is oriented in a first direction at an intersection point, the second reinforcing cord is oriented in a second direction at the intersection point, and the third reinforcing cord is oriented in a third direction at the intersection point, wherein the first, second, and third directions differ from each other at the intersection point. The second reinforcing cord runs parallel to a tire width direction and is welded to the first reinforcing cord and the third reinforcing cord at the intersection point, so that a plurality of connected portions along the tire width direction are formed by the welding. Advantageous effects of the invention

[0016] In the present invention, since the reinforcing member includes the plurality of reinforcing cords oriented in at least three directions and has a net-like structure in which at least three reinforcing cords oriented in different directions are connected to each other at at least a part of the intersection points of the reinforcing cords, it is possible to improve the in-plane bending rigidity while maintaining excellent flexibility with respect to out-of-plane deformation.

[0017] Thus, in a pneumatic tire further including a carcass layer arranged extending between the pair of bead portions and a belt layer arranged on an outer peripheral side of the carcass layer in the tread portion, it is possible to increase cornering rigidity and reduce rolling resistance when the reinforcing member having a net-like structure described above is used as the belt layer. The reinforcing member also exhibits excellent flexibility with respect to out-of-plane deformation, making it possible to advantageously maintain the durability of the belt layer.

[0018] The belt layer can be formed by winding the reinforcing element with a net-like structure one or more times in the tire circumferential direction, or by processing the reinforcing element with a net-like structure into a ring shape without ends. The former simplifies tire manufacturing, and the latter improves tire durability.

[0019] In a pneumatic tire further including a carcass layer arranged to extend between the pair of bead portions, when the reinforcing member having a net-like structure in a region on the bead portion side is used as the carcass layer, the tire circumferential rigidity can be increased without relying on an additional bead reinforcing layer, and the steering stability can be improved without significantly increasing the tire weight.

[0020] The carcass layer is preferably formed by processing the reinforcing element with a net-like structure into a ring shape without ends. As a result, the durability of the tire is improved.

[0021] Further, in a pneumatic tire further including a carcass layer arranged to extend between the pair of bead portions and a bead reinforcing layer embedded in the bead portion, when the reinforcing member having a net-like structure is used as the bead reinforcing layer, the tire circumferential rigidity can be effectively increased and the steering stability can be improved while suppressing an increase in the tire weight.

[0022] The density of the bonded portion of the reinforcing cords of the reinforcing element forming the bead reinforcing layer preferably increases inward in the tire radial direction. As a result, sudden changes in stiffness based on the reinforcing element are avoided, making it possible to prevent a decrease in durability.

[0023] The bead reinforcing layer is preferably formed by processing the reinforcing element with a net-like structure into a ring shape without ends. As a result, the durability of the tire is improved.

[0024] In the present invention, at least three reinforcing cords are preferably connected to each other at at least 30% of the intersection points where at least three reinforcing cords intersect. As a result, the effect of improving in-plane bending rigidity can be sufficiently achieved.

[0025] Furthermore, the intersection angle of at least three reinforcing cords connected at the intersection points is preferably 15° or greater. As a result, the effect of increasing the in-plane bending rigidity can be sufficiently achieved.

[0026] The reinforcing cord preferably includes a synthetic fiber cord with a knot strength of 1.5 (cN / dtex) or higher. With a synthetic fiber cord, the reinforcing member with a net-like structure can be easily formed. Furthermore, the synthetic fiber cord with the above-described knot strength is suitable as a tire reinforcement material.

[0027] Furthermore, the reinforcing element with a mesh-like structure is preferably coated with rubber. As a result, the integrity of the reinforcing cord is ensured, which makes it possible to improve the in-plane flexural rigidity of the reinforcing element. Brief description of the drawings Fig. 1 is a meridian cross-sectional view illustrating a pneumatic tire according to an embodiment of the present invention. Fig. 2 is a plan view illustrating an example of a reinforcing member used as a belt layer of the pneumatic tire according to the present invention. Fig.3 is an explanatory diagram illustrating a deformation mechanism of a reinforcing member having a net-like structure in which at least three reinforcing cords oriented in different directions are connected to each other at intersection points of the reinforcing cords. Fig. 4 is an explanatory diagram illustrating a deformation mechanism of the reinforcing member having a net-like structure in which two reinforcing cords oriented in different directions are connected to each other at intersection points of the reinforcing cords. Fig. 5 is a plan view illustrating a modified example of the reinforcing member used as the belt layer of the pneumatic tire according to the present invention. Fig.6 is a plan view illustrating another modified example of the reinforcing member used as the belt layer of the pneumatic tire according to the present invention. Fig. 7 is a plan view illustrating another modified example of the reinforcing member used as the belt layer of the pneumatic tire according to the present invention. Fig. 8 is a plan view illustrating another modified example of the reinforcing member used as the belt layer of the pneumatic tire according to the present invention. Fig. 9 is a plan view illustrating another modified example of the reinforcing member used as the belt layer of the pneumatic tire according to the present invention. Fig.10 is a plan view illustrating another modified example of the reinforcing member used as the belt layer of the pneumatic tire according to the present invention. Fig. 11 is a plan view illustrating another modified example of the reinforcing member used as the belt layer of the pneumatic tire according to the present invention. Fig. 12 is a plan view illustrating another modified example of the reinforcing member used as the belt layer of the pneumatic tire according to the present invention. Fig. 13 is a meridian cross-sectional view illustrating a pneumatic tire according to another embodiment of the present invention. Fig. 14 is a plan view illustrating an example of the reinforcing member used as a belt layer of the pneumatic tire according to the present invention. Fig.15 is a plan view illustrating a modified example of the reinforcing member used as the carcass layer of the pneumatic tire according to the present invention. Fig. 16 is a half cross-sectional view taken along a meridian, illustrating the pneumatic tire according to another embodiment of the present invention. Fig. Fig. 17 is a plan view showing an example of the reinforcing member used as the carcass layer of the pneumatic tire in Fig. 16 is used. Fig. 18 is a half cross-sectional view taken along a meridian, illustrating the pneumatic tire according to another embodiment of the present invention. Fig. 19 is a half cross-sectional view taken along a meridian, illustrating the pneumatic tire according to another embodiment of the present invention. Fig.20 is a half cross-sectional view taken along a meridian, illustrating the pneumatic tire according to another embodiment of the present invention. Fig. 21 is a plan view illustrating an example of the reinforcing member used as a bead reinforcing layer of the pneumatic tire according to the present invention. Fig. 22 is a plan view illustrating a modified example of the reinforcing member used as the bead reinforcing layer of the pneumatic tire according to the present invention. Fig. 23 is a plan view illustrating another modified example of the reinforcing member used as the bead reinforcing layer of the pneumatic tire according to the present invention. Fig.24 is a plan view illustrating another modified example of the reinforcing member used as the bead reinforcing layer of the pneumatic tire according to the present invention. Fig. 25 is a plan view illustrating another modified example of the reinforcing member used as the bead reinforcing layer of the pneumatic tire according to the present invention. Fig. 26 is a plan view illustrating an example of a joined portion of the reinforcing member used for the present invention. Fig. 27 is a plan view illustrating a modified example of the joined portion of the reinforcing member used in the present invention. Fig.28 is a plan view illustrating another modified example of the joined portion of the reinforcing member used in the present invention. Fig. 29 is a plan view illustrating another modified example of the joined portion of the reinforcing member used in the present invention. Fig. 30 is a plan view illustrating another modified example of the joined portion of the reinforcing member used in the present invention. Fig. 31 is a perspective view illustrating another modified example of the joined portion of the reinforcing member used in the present invention. Fig.32 is a plan view illustrating another modified example of the joined portion of the reinforcing member used in the present invention. Fig. 33 is a plan view illustrating another modified example of the joined portion of the reinforcing member used in the present invention. Fig. 34 is a perspective view illustrating another modified example of the joined portion of the reinforcing member used in the present invention. Fig. 35 is a perspective view illustrating another modified example of the joined portion of the reinforcing member used in the present invention. Fig.36 is a perspective view illustrating another modified example of the joined portion of the reinforcing member used in the present invention. Fig. 37 is a perspective view illustrating another modified example of the joined portion of the reinforcing member used in the present invention. Description of embodiments

[0028] The configuration of the present invention will be described in detail below with reference to the accompanying drawings. Fig. 1 shows a pneumatic tire according to an embodiment of the present invention. As in Fig.1, a pneumatic tire of the present embodiment includes an annular tread portion 1 extending in the tire circumferential direction, a pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3, 3 arranged inward of the sidewall portions 2 in the tire radial direction.

[0029] A carcass layer 4 is arranged extending between the pair of bead portions 3, 3. The carcass layer 4 has a plurality of reinforcing cords extending in the tire radial direction and is folded back from a tire inner side to a tire outer side around a bead core 5 installed in each of the bead portions 3. A bead filler 6 having a triangular cross-sectional shape and formed of a rubber composition is arranged on an outer periphery of the bead core 5.

[0030] On the other hand, a belt layer 7 is embedded on an outer peripheral side of the carcass layer 4 in the tread portion 1. This belt layer 7 includes a reinforcing member 10 having a specific net-like structure described below. For the purpose of improving high-speed durability, at least one layer of a belt cover layer 8 formed by arranging reinforcing cords at an angle of, for example, not more than 5° with respect to the tire circumferential direction is disposed on an outer peripheral side of the belt layer 7. Nylon, aramid, or similar synthetic fiber cords are preferably used as the reinforcing cords of the belt cover layer 8. Note that the belt cover layer 8 is not essential.

[0031] Fig.2 illustrates an example of the reinforcing member used as the belt layer of the pneumatic tire according to the present invention. As in Fig.2, the reinforcing member 10 having a net-like structure includes a plurality of reinforcing cords 11 to 14 oriented in four directions. That is, the reinforcing cord 11 extends parallel to a tire circumferential direction C, the reinforcing cord 12 extends parallel to a tire width direction W, the reinforcing cord 13 extends so as to incline to one side with respect to the tire circumferential direction C, and the reinforcing cord 14 extends so as to incline to the other side with respect to the tire circumferential direction C. The plurality of reinforcing cords 11 to 14 oriented in different directions are connected at intersection points of the reinforcing cords 11 to 14, forming a plurality of connected portions 15, 16.More specifically, at least three of the reinforcing cords 11 to 14 are integrally connected at the intersection points where at least three of the reinforcing cords 11 to 14 overlap to form a plurality of the connected portions 15, and the two reinforcing cords 13, 14 are integrally connected at the intersection points where the two reinforcing cords 13, 14 overlap to form a plurality of connected portions 16.

[0032] The material of the reinforcing cords 11 to 14 is not particularly limited, allowing the use of a synthetic fiber cord or a steel cord. Examples include a structure in which a synthetic fiber cord is used for all of the reinforcing cords 11 to 14, a structure in which a synthetic fiber cord is used for the reinforcing cords 11, 13, 14, while a steel cord is used for the reinforcing cord 12, a structure in which a steel cord is used for the reinforcing cord 11, while a synthetic fiber cord is used for the reinforcing cords 12 to 14, and a structure in which a steel cord is used for the reinforcing cords 11, 12, while a synthetic fiber cord is used for the reinforcing cords 13, 14.

[0033] The method of joining the reinforcing cords 11 to 14 is not particularly limited, allowing the use of a variety of methods. For synthetic fiber cords, the joined portions 15, 16 may be formed such that the cords form a knot, the joined portions 15, 16 may be formed such that both fiber bundles (yarns) intersect without the cords forming a knot, the joined portions 15, 16 may be formed by welding the cords together, and the joined portions 15, 16 may be formed by bonding the cords together.For steel cords, the connected portions 15, 16 may be formed such that both cords intersect without the cords forming a knot, the connected portions 15, 16 may be formed by welding the cords, and the connected portions 15, 16 may be formed by bonding the cords together. In any case, the reinforcing cords 11 to 14 must be integrally connected at intersection points such that the cords mutually regulate the cord positions.

[0034] The reinforcing member 10 configured as described above includes the plurality of reinforcing cords 11 to 14 oriented in at least three directions, and has a net-like structure in which at least three of the reinforcing cords 11 to 14 oriented in different directions are connected to each other at at least a part of the intersection points of the reinforcing cords 11 to 14, which makes it possible to improve the in-plane bending rigidity while maintaining excellent flexibility with respect to out-of-plane deformation.

[0035] Fig. 3 illustrates a deformation mechanism of a reinforcing member having a net-like structure in which at least three reinforcing cords oriented in different directions are connected to each other at intersection points of the reinforcing cords, and Fig.Figure 4 illustrates a deformation mechanism of the reinforcing member having a net-like structure in which two reinforcing cords oriented in different directions are connected to each other at intersection points of the reinforcing cords. As shown in Fig. 4, a reinforcing element 10A having a net-like structure in which the two reinforcing cords 11, 12 oriented in different directions are connected to each other at intersection points of the reinforcing cords 11, 12 is deformed like a pantograph when forces act in the plane direction thereof. In contrast, as in Fig.3, the reinforcing member 10 having a net-like structure in which at least three of the reinforcing cords 11 to 14 oriented in different directions are connected to each other at the intersection points of the reinforcing cords 11 to 14 is not easily susceptible to deformation even when forces act in the planar direction thereof, resulting in higher in-plane bending rigidity.

[0036] Thus, in a pneumatic tire further including the carcass layer 4 arranged extending between the pair of bead portions 3, 3 and the belt layer 7 arranged on the outer peripheral side of the carcass layer 4 in the tread portion 1, it is possible to increase cornering rigidity and reduce rolling resistance when the reinforcing member 10 having a net-like structure described above is used as the belt layer 7. The reinforcing member 10 also exhibits excellent flexibility with respect to out-of-plane deformation, making it possible to advantageously maintain the durability of the belt layer 7.

[0037] Fig. 5 to 8 are views illustrating modified examples of the reinforcing member used as the belt layer of the pneumatic tire according to the present invention. Fig.5, although at least three of the reinforcing cords 11 to 14 are integrally connected at the intersection points where at least three of the reinforcing cords 11 to 14 overlap to form a plurality of the connected portions 15, the connected portion 16 is not formed at the intersection points where the two reinforcing cords 13, 14 overlap.

[0038] In Fig. 6, unlike Fig. 5, the reinforcing cord 11 extending in the tire circumferential direction C is not arranged at both end positions of the reinforcing member 10 in the tire width direction W. In Fig. 7, unlike in Fig. 5, the reinforcing cord 11 extending in the tire circumferential direction C and the connected portion 15 are not arranged at both end positions of the reinforcing member 10 in the tire width direction W. In Fig. 8, unlike in Fig.5, the connected portion 16 is selectively formed at the intersection points where the two reinforcing cords 13, 14 intersect at both end portions of the reinforcing member 10 in the tire width direction W.

[0039] Fig. 9 illustrates another modified example of the reinforcing member used as the belt layer of the pneumatic tire according to the present invention. Fig. 9 shows only the left side of a tire center line CL extracted. In Fig.9, at least three of the reinforcing cords 11 to 14 are integrally connected at at least a portion of the intersection points where at least three of the reinforcing cords 11 to 14 intersect to form a plurality of connected portions 15, and the two reinforcing cords 13, 14 are integrally connected at at least a portion of the intersection points where the two reinforcing cords 13, 14 intersect to form a plurality of connected portions 16. Then, when the reinforcing member 10 is divided into four regions A1 to A4 outward in the tire width direction from the tire center line CL, the density of the connected portions 15, 16 of these regions A1 to A4 is set to increase outward in the tire width direction. According to such an arrangement, it is possible to more effectively increase the cornering rigidity and reduce the rolling resistance.

[0040] Fig.10 illustrates another modified example of the reinforcing member used as the belt layer of the pneumatic tire according to the present invention. Fig. 10, the reinforcing member 10 having a net-like structure includes the plurality of reinforcing cords 11, 13, 14 oriented in three directions. That is, the reinforcing cord 11 extends parallel to the tire circumferential direction C, the reinforcing cord 13 extends to incline to one side with respect to the tire circumferential direction C, and the reinforcing cord 14 extends to incline to the other side with respect to the tire circumferential direction C. Then, at the intersection points where the three reinforcing cords 11, 13, 14 intersect, the three reinforcing cords 11, 13, 14 are integrally connected, forming a plurality of connected portions 15.

[0041] The above-described belt layer 7 can be formed by winding the reinforcing member 10 having a net-like structure once or more in the tire circumferential direction. In this case, the reinforcing member 10 having a net-like structure can be processed in the same manner as a prior art belt member, simplifying the manufacture of the pneumatic tire. Furthermore, the reinforcing member 10 is preferably wound twice or more in the tire circumferential direction. At this time, the positions of the connected portions 15, 16 preferably differ for each winding.

[0042] Fig. 11 and Fig. 12 each illustrate another modified example of the reinforcing member used as the belt layer of the pneumatic tire according to the present invention. Fig.11, the connected portions 15 of a first layer (dashed lines) inward in the tire radial direction and the connected portions 15 of a second layer (solid lines) outward in the tire radial direction are mutually shifted in the tire circumferential direction C in a structure in which the reinforcing member 10 is wound twice with a net-like structure. In Fig. 12, the connected portions 15 of a first layer (dashed lines) inward in the tire radial direction and the connected portions 15 of a second layer (solid lines) outward in the tire radial direction are mutually shifted in the tire width direction W in a structure in which the reinforcing member 10 is wound twice with a net-like structure.

[0043] Or, the above-described belt layer 7 may be formed by processing the reinforcing member 10 having a net-like structure into a ring shape without ends. That is, the reinforcing member 10 may be woven and formed into a ring shape. In this case, the durability of the pneumatic tire is improved. Furthermore, the belt layer 7 may also be configured by manufacturing and laminating the reinforcing members 10 having a ring shape without ends and having different diameters. In such a case, the positions of the connected portions 15, 16 preferably differ between the layers.

[0044] Fig. 13 shows a pneumatic tire according to another embodiment of the present invention. As in Fig.13, the pneumatic tire of the present embodiment includes the annular tread portion 1 extending in the tire circumferential direction, the pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1, and the pair of bead portions 3, 3 arranged inward of the sidewall portions 2 in the tire radial direction.

[0045] The carcass layer 4 is arranged extending between the pair of bead portions 3, 3. The carcass layer 4 includes the reinforcing member 10 having a specific net-like structure described below and is folded from the tire inner side to the tire outer side around the bead cores 5 arranged in each of the bead portions 3. The bead filler 6 having a triangular cross-sectional shape and formed of a rubber composition is arranged on the outer periphery of the bead core 5.

[0046] On the other hand, the belt layer 7 is embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. The belt layer 7 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction and is arranged such that the reinforcing cords of different layers overlap. In the belt layer 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set in a range of, for example, 10° to 40°. Steel cords are preferably used as the reinforcing cords of the belt layer 7. For the purpose of improving high-speed durability, at least one layer of the belt cover layer 8, which is formed by arranging reinforcing cords at an angle of, for example, not more than 5° with respect to the tire circumferential direction, is arranged on the outer peripheral side of the belt layer 7.Nylon, aramid, or similar synthetic fiber cords are preferably used as the reinforcing cords of the belt cover layer 8. It should be noted that the belt cover layer 8 is not essential.

[0047] Fig. 14 illustrates an example of the reinforcing member used as the carcass layer of the pneumatic tire according to the present invention. As in Fig.14, the reinforcing member 10 having a net-like structure includes the plurality of reinforcing cords 11 to 14 oriented in four directions. That is, the reinforcing cord 11 extends parallel to the tire width direction W over the entire region in the tire width direction W, the reinforcing cord 12 extends parallel to the tire circumferential direction C in only the region adjacent to the bead core 5, the reinforcing cord 13 extends so as to incline to one side with respect to the tire width direction W only in the region on the bead portion 3 side, and the reinforcing cord 14 extends so as to incline to the other side with respect to the tire width direction W only in the region on the bead portion 3 side.Note that while the tire width direction W is the direction of the sheet-like reinforcing member 10, the tire width direction W is regarded as the tire radial direction when the reinforcing member 10 is machined on the pneumatic tire. At the intersection points of these reinforcing cords 11 to 14, at least three of the reinforcing cords 11 to 14 oriented in different directions are integrally connected to each other, forming a plurality of connected portions 15.

[0048] The material of the reinforcing cords 11 to 14 is not particularly limited, allowing the use of a synthetic fiber cord or a steel cord. Examples include a structure in which a synthetic fiber cord is used for all of the reinforcing cords 11 to 14, a structure in which a synthetic fiber cord is used for the reinforcing cords 11, 13, 14, while a steel cord is used for the reinforcing cord 12, a structure in which a steel cord is used for the reinforcing cord 11, while a synthetic fiber cord is used for the reinforcing cords 12 to 14, and a structure in which a steel cord is used for the reinforcing cords 11, 12, while a synthetic fiber cord is used for the reinforcing cords 13, 14.

[0049] The method of joining the reinforcing cords 11 to 14 is not particularly limited, allowing the use of a variety of methods. For synthetic fiber cords, the joined portion 15 may be formed such that the cords form a knot, the joined portion 15 may be formed such that both fiber bundles (yarns) intersect without the cords forming a knot, the joined portion 15 may be formed by welding the cords together, and the joined portion 15 may be formed by bonding the cords together. For steel cords, the joined portion 15 may be formed such that both threads intersect without the cords forming a knot, the joined portion 15 may be formed by welding the cords together, and the joined portion 15 may be formed by bonding the cords together.In any case, the reinforcing cords 11 to 14 must be integrally connected at intersection points in such a way that the cords mutually regulate the cord positions.

[0050] The reinforcement element 10 configured in this way, as described in the comparative explanation of Fig. 3 and Fig. 4 described above, includes the plurality of reinforcing cords 11 to 14 oriented in at least three directions in a region on the side of the bead portion 3, and has a net-like structure in which at least three of the reinforcing cords 11 to 14 oriented in different directions are connected to each other at at least a part of the intersection points of the reinforcing cords 11 to 14, which makes it possible to improve the in-plane bending rigidity while maintaining excellent flexibility with respect to the out-of-plane deformation.

[0051] In a pneumatic tire further including the carcass layer 4 arranged extending between the pair of bead portions 3, 3, when the reinforcing member 10 having a net-like structure described above is used as the carcass layer 4, the tire circumferential rigidity can be increased without relying on an additional bead reinforcing layer, and the steering stability can be improved without significantly increasing the tire weight. Note that while the reinforcing member 10 has a net-like structure in which at least three of the reinforcing cords 11 to 14 oriented in different directions are connected in a region on the bead portion 3 side, the reinforcing member 10 does not have a net-like structure on the tread portion 1 side, thereby allowing expansion in the tire molding step.From such a perspective, the reinforcing element 10 preferably has no connected points 15 in the tire radial direction outward from a maximum tire width position.

[0052] Fig. 15 illustrates a modified example of the reinforcing member used as the carcass layer of the pneumatic tire according to the present invention. Fig. 15 shows only the left side of the tire center line CL extracted. In Fig.15, at least three of the reinforcing cords 11 to 14 are integrally connected at the intersection points where at least three of the reinforcing cords 11 to 14 intersect to form a plurality of connected portions 15, and the two reinforcing cords 13, 14 are integrally connected at at least a part of the intersection points of the two reinforcing cords 13, 14 to form a plurality of connected portions 16. Then, when the area where the connected portions 15, 16 of the reinforcing member 10 are divided into four areas A1 to A4 is projected outward from the position of the bead cores 5 in the tire radial direction (from the position of the tire bead core 5 in the plan view of Fig.15 outward in the tire width direction), the density of the connected portions 15, 16 in these regions A1 to A4 is set to increase inward in the tire radial direction. However, the densities of the connected portions 15, 16 in the regions A1, A2 are equal. According to such an arrangement, it is possible to effectively improve the in-plane bending rigidity without hindering deformation of the reinforcing member 10 constituting the carcass layer 4 in the tire molding step.

[0053] Fig. 16 illustrates a pneumatic tire according to another embodiment of the present invention, and Fig. 17 represents the reinforcing element used as the carcass layer of the pneumatic tire. In Fig.16, the carcass layer 4 having a folded-over structure is folded back around the bead cores 5 arranged in each of the bead portions 3 from the inside of the tire to the outside of the tire, and the folded end portion is arranged to be inserted between the belt layer 7 and the carcass layer 4.

[0054] The reinforcing element 10 used as such a carcass layer 4, as shown in Fig.17, includes the plurality of reinforcing cords 11 to 14 oriented in at least three directions in regions on each side of the bead portion 3, and has a net-like structure in which at least three of the reinforcing cords 11 to 14 oriented in different directions are connected to each other at at least a part of the intersection points of the reinforcing cords 11 to 14. That is, while the reinforcing cord 11 extending in the tire width direction W extends over the entire region in the tire width direction W, the net-like structure including the connected portions 15 is formed only in the regions corresponding to the bead portions 3. Also in this case, it is possible to improve in-plane bending rigidity while maintaining excellent flexibility with respect to out-of-plane deformation of the reinforcing member 10.

[0055] The above-described carcass layer 4 can be formed by processing the reinforcing member 10 having a net-like structure into a ring shape without ends. That is, the reinforcing member 10 can be woven and formed into a ring shape. In this case, the durability of the pneumatic tire is improved. Of course, the carcass layer 4 can also be formed by winding the reinforcing member 10 having a net-like structure one or more times in the tire circumferential direction. In this case, the reinforcing member 10 having a net-like structure can be processed in the same manner as a prior art carcass member, simplifying the manufacturing of the pneumatic tire.

[0056] Fig. 18 to 20 each illustrate a pneumatic tire according to another embodiment of the present invention. As in Fig.18 to 20, the pneumatic tire of the present embodiment includes the annular tread portion 1 extending in the tire circumferential direction, the pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1, and the pair of bead portions 3, 3 arranged on the inner side of the sidewall portions 2 in the tire radial direction.

[0057] The carcass layer 4 is arranged extending between the pair of bead portions 3, 3. The carcass layer 4 has a plurality of reinforcing cords extending in the tire radial direction and is folded from the tire inner side to the tire outer side around the bead cores 5 arranged in each of the bead portions 3. The bead filler 6 having a triangular cross-sectional shape and formed of a rubber composition is arranged on the outer periphery of the bead core 5.

[0058] On the other hand, the belt layer 7 is embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. The belt layer 7 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction and is arranged such that the reinforcing cords of different layers overlap. In the belt layer 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set in a range of, for example, 10° to 40°. Steel cords are preferably used as the reinforcing cords of the belt layer 7. For the purpose of improving high-speed durability, at least one layer of the belt cover layer 8, which is formed by arranging reinforcing cords at an angle of, for example, not more than 5° with respect to the tire circumferential direction, is arranged on the outer peripheral side of the belt layer 7.Nylon, aramid, or similar synthetic fiber cords are preferably used as the reinforcing cords of the belt cover layer 8. It should be noted that the belt cover layer 8 is not essential.

[0059] Further, a bead reinforcing layer 9 is embedded in a region from the bead portion 3 to the sidewall portion 2. This bead reinforcing layer 9 includes the reinforcing member 10 having a specific net-like structure described below and extends along the bead filler 6 in the tire circumferential direction. The bead reinforcing layer 9 may be formed outwardly in the tire width direction from the folded-back portion of the carcass layer 4 as shown in Fig. 18 may be arranged between the folded-back portion and the bead filler 6 as in Fig. 19 or may be folded back around the bead core 5 with the carcass layer 4 to wrap the carcass layer 4, as in Fig. 20.

[0060] Fig. 21 illustrates an example of the reinforcing member used for the bead reinforcing layer of the pneumatic tire according to the present invention. As shown in Fig.21, the reinforcing member 10 having a net-like structure includes the plurality of reinforcing cords 11 to 14 oriented in four directions. That is, the reinforcing cord 11 extends parallel to a tire radial direction R, the reinforcing cord 12 extends parallel to the tire circumferential direction C, the reinforcing cord 13 extends so as to incline to one side with respect to the tire radial direction R, and the reinforcing cord 14 extends so as to incline to the other side with respect to the tire radial direction R. At the intersection points of the plurality of reinforcing cords 11 to 14, the plurality of reinforcing cords 11 to 14 oriented in different directions are connected, forming a plurality of connected portions 15, 16.More specifically, at least three of the reinforcing cords 11 to 14 are integrally connected at the intersection points of at least three of the reinforcing cords 11 to 14 to form a plurality of the connected portions 15, and the two reinforcing cords 13, 14 are integrally connected at the intersection points of the two reinforcing cords 13, 14 to form a plurality of the connected portions 16.

[0061] Fig. 22 illustrates a modified example of the reinforcing member used for the bead reinforcing layer of the pneumatic tire according to the present invention. Fig.22, although at least three of the reinforcing cords 11 to 14 are integrally connected at the intersection points where at least three of the reinforcing cords 11 to 14 overlap to form a plurality of the connected portions 15, the connected portion 16 is not formed at the intersection points where the two reinforcing cords 13, 14 overlap.

[0062] The material of the reinforcing cords 11 to 14 is not particularly limited, allowing the use of a synthetic fiber cord or a steel cord. Examples include a structure in which a synthetic fiber cord is used for all of the reinforcing cords 11 to 14, a structure in which a synthetic fiber cord is used for the reinforcing cords 11, 13, 14, while a steel cord is used for the reinforcing cord 12, a structure in which a steel cord is used for the reinforcing cord 11, while a synthetic fiber cord is used for the reinforcing cords 12 to 14, and a structure in which a steel cord is used for the reinforcing cords 11, 12, while a synthetic fiber cord is used for the reinforcing cords 13, 14.

[0063] The method of joining the reinforcing cords 11 to 14 is not particularly limited, allowing the use of a variety of methods. For synthetic fiber cords, the joined portions 15, 16 may be formed such that the cords form a knot, the joined portions 15, 16 may be formed such that both fiber bundles (yarns) intersect without the cords forming a knot, the joined portions 15, 16 may be formed by welding the cords together, and the joined portions 15, 16 may be formed by bonding the cords together.For steel cords, the connected portions 15, 16 may be formed such that both cords intersect without the cords forming a knot, the connected portions 15, 16 may be formed by welding the cords, and the connected portions 15, 16 may be formed by bonding the cords together. In any case, the reinforcing cords 11 to 14 must be integrally connected at intersection points such that the cords mutually regulate the cord positions.

[0064] The reinforcement element 10 configured in this way, as described in the comparative explanation of Fig. 3 and Fig.4 described above, includes the plurality of reinforcing cords 11 to 14 oriented in at least three directions, and has a net-like structure in which at least three reinforcing cords 11 to 14 oriented in different directions are connected to each other at at least a part of the intersection points of the reinforcing cords 11 to 14, which makes it possible to improve the in-plane bending rigidity while maintaining excellent flexibility with respect to out-of-plane deformation.

[0065] As a result, in the pneumatic tire further including the bead reinforcing layer 9 embedded in the bead portion 3, when the reinforcing member 10 having a net-like structure is used as the bead reinforcing layer 9, the tire circumferential rigidity can be effectively improved and the steering stability can be improved while suppressing an increase in tire weight. The reinforcing member 10 also exhibits excellent flexibility with respect to out-of-plane deformation, which makes it possible to advantageously maintain the durability of the bead reinforcing layer 9.

[0066] Fig. 23 to 25 each illustrate a modified example of the reinforcing member used as the bead reinforcing layer of the pneumatic tire according to the present invention. Fig.23, at least three of the reinforcing cords 11 to 14 are integrally connected at at least a part of the intersection points where at least three of the reinforcing cords 11 to 14 intersect to form a plurality of the connected portions 15, and the two reinforcing cords 13, 14 are integrally connected at at least a part of the intersection points of the two reinforcing cords 13, 14 to form a plurality of the connected portions 16. Then, when the reinforcing member 10 is divided into the four regions A1 to A4 in the tire radial direction R, the density of the connected portions 15, 16 of these regions A1 to A4 is set to increase inward in the tire radial direction.According to such an arrangement, sudden changes in rigidity based on the reinforcing member 10 are avoided, making it possible to effectively improve the in-plane bending rigidity of the bead reinforcing layer 9 while preventing a decrease in durability.

[0067] In Fig.24, when the reinforcing member 10 is divided into five regions A11 to A15 in the tire radial direction R, the number of reinforcing cords 11 to 14 in these regions A11 to A15 is set to decrease outward in the tire radial direction, and the density of the connected portions 15, 16 of the regions A11 to A15 is set to increase inward in the tire radial direction. Specifically, the connected portions 15, 16 are arranged inward in the tire radial direction only in the regions A11 to A13, the reinforcing cord 12 extending in the tire circumferential direction C is arranged inward in the tire radial direction only in the regions A11 to A13, and the reinforcing cords 13, 14 inclined with respect to the tire radial direction R are arranged inward in the tire radial direction only in the regions A11 to A14.

[0068] In Fig.25, when the reinforcing member 10 is divided into the five regions A11 to A15 in the tire radial direction R, the number of reinforcing cords 11 to 14 in these regions A11 to A15 is set to decrease outward in the tire radial direction, and the density of the connected portions 15, 16 of the regions A11 to A15 is set to increase inward in the tire radial direction. Specifically, the connected portions 15, 16 are arranged inward in the tire radial direction only in the regions A11 to A13, the reinforcing cord 12 extending in the tire circumferential direction C is arranged inward in the tire radial direction only in the regions A11 to A12, and the reinforcing cords 13, 14 inclined with respect to the tire radial direction R are arranged inward in the tire radial direction only in the regions A11 to A14.

[0069] In the examples Fig. 24 and Fig.25, while the number of reinforcing cords 11 to 14 decreases outward in the tire radial direction and the density of the connected portions 15, 16 increases inward in the tire radial direction in the reinforcing member 10, the arrangement of the reinforcing cords 11 to 14 and the connected portions 15, 16 are thus appropriately selected, which makes it possible to adjust the tire circumferential stiffness accordingly. It should be noted that in Fig. 24 and Fig. 25 the reinforcing cord 12, which extends in the tire circumferential direction C, is arranged inwardly in the tire radial direction from a peak of the bead filler 6.

[0070] The bead reinforcing layer 9 described above can be formed by processing the reinforcing member 10 having a net-like structure into a ring shape without ends. That is, the reinforcing member 10 can be woven and formed into a ring shape. In this case, the durability of the pneumatic tire is improved. Of course, the bead reinforcing layer 9 can be formed by winding the reinforcing member 10 having a net-like structure one or more times in the tire circumferential direction. In this case, the reinforcing member 10 having a net-like structure can be processed in the same manner as a prior art bead reinforcing member, simplifying the manufacturing of the pneumatic tire.

[0071] While in the pneumatic tires described above, at least three of the reinforcing cords 11 to 14 are connected at all intersection points where at least three of the reinforcing cords 11 to 14 overlap, at least three of the reinforcing cords 11 to 14 are preferably connected to each other at at least 30%, and more preferably at least 50% (most preferably at least 70%) of the intersection points where at least three of the reinforcing cords 11 to 14 overlap. As a result, the effect of improving the in-plane bending rigidity can be sufficiently achieved. If this percentage is too small, the effect of improving the in-plane bending rigidity decreases.

[0072] Furthermore, in the pneumatic tires described above, the intersection angles of at least three of the reinforcing cords 11 to 14 connected at the intersection points are preferably 15° or more, and more preferably from 20° to 75°. As a result, the effect of improving the in-plane bending rigidity can be sufficiently achieved. If this intersection angle is too small, the effect of improving the in-plane bending rigidity decreases. It should be noted that the intersection angle of the reinforcing cords 11 to 14 in the embodiments in Fig. 2, Fig. 14, Fig. 21, Fig. 22 and the like is 45°.

[0073] In the pneumatic tires described above, a synthetic fiber cord having a tensile strength of 1.5 (cN / dtex) or more, a knot strength of 1.5 (cN / dtex) or more, and a loop strength of 2.5 (cN / dtex) or more is preferably used as the reinforcing cords 11 to 14. With a synthetic fiber cord, the reinforcing member 10 having a net-like structure can be easily formed. Moreover, the synthetic fiber cord having the above-described physical properties is suitable as the tire reinforcing material.

[0074] With respect to the above-described physical properties, preferably the tensile strength is 2.0 (cN / dtex) or more, the knot strength is 2.0 (cN / dtex) or more, and the loop strength is 3.5 (cN / dtex) or more. More preferably, the tensile strength is 4.0 (cN / dtex) or more, the knot strength is 3.0 (cN / dtex) or more, and the loop strength is 5.0 (cN / dtex) or more. Most preferably, the tensile strength is 5.0 (cN / dtex) or more, the knot strength is 4.0 (cN / dtex) or more, and the loop strength is 8.0 (cN / dtex) or more. While the upper limits are not particularly restricted, values ​​of 20 (cN / dtex) or less for knot strength, 20 (cN / dtex) or less for loop strength and 15 (cN / dtex) or less for tensile strength are realistic.It should be noted that knot strength and loop strength are measured according to Japanese Industrial Standards (JIS) JIS L 1013 (Test Method for Man-Made Filament Yarns) and JIS L 1015 (Test Method for Man-Made Staple Fibers), respectively.

[0075] Suitable synthetic fiber cords include a cord containing aramid fiber, polyketone fiber, polyethylene terephthalate (PET) fiber, polyethylene naphthalate (PEN) fiber, high-molecular-weight polyethylene fiber (Toyobo Dyneema or the like), or p-phenylenebenzobisoxazole (PBO) fiber. Of course, the material may vary according to the extending direction of the cords. Further, a composite fiber cord obtained by twisting a fiber (for example, aramid fiber) made of a low-elongation material and a fiber (for example, nylon fiber) made of a high-elongation material is preferable as the material of the reinforcing member 10 having a net-like structure, since the properties of the high-elongation material increase knot strength, and the properties of the low-elongation material increase Young's modulus.Furthermore, when joining synthetic fiber cords, knots may be present or absent. However, from the perspective of reducing the thickness of the element, knots are preferably absent.

[0076] The thickness of the reinforcing cords 11 to 14 is preferably from 0.5 to 1.5 mm. If this thickness exceeds the upper limit, the rubber layer becomes thicker and the tire weight increases, worsening the rolling resistance. If this thickness is below the lower limit, the number of arranged cords must be increased to ensure the same strength, which excessively increases the density of the connected points and makes the manufacturing of the reinforcing member 10 difficult.

[0077] Furthermore, the reinforcing member 10, which forms the belt layer 7, the carcass layer 4, and the bead reinforcing layer 9, is preferably coated with rubber. As a result, the integrity of the reinforcing cords 11 to 14 is ensured, making it possible to improve the in-plane flexural rigidity of the reinforcing member 10.

[0078] Next, the joined portion of the reinforcing member used for the present invention will be specifically described with reference to Fig. 26 to 37. Fig. 26 shows an example of the three interconnected cords 21 to 23. In this example, the cords 22, 23 individually form knots that wind around the cord 21 which has no knot. Fig.27 shows an example of the three cords 21 to 23 connected together. In this example, the cord 23 individually forms a knot winding around the cords 21, 22 which have no knot. Fig. 28 shows an example of the three cords 21 to 23 connected together. In this example, the cords 22, 23 individually form knots winding around the cord 21 having no knot, and the inclination directions of the cords 22, 23 are reversed, with the knots acting as the boundary. Fig. 29 shows an example of the three cords 21 to 23 connected together. In this example, the cord 23 individually forms a knot winding around the cords 21, 22 having no knot, and the inclination directions of the cords 22, 23 are reversed, with the knot acting as the boundary. Fig.30 shows an example of the three cords 21 to 23 connected together. In this example, the cords 22, 23 individually form knots winding around the cord 21 having no knot, the knots are intertwined, and the inclination directions of the cords 22, 23 are reversed, with the knots acting as the boundary. Fig. 31 shows an example of the three cords 21 to 23 connected together. In this example, the cords 22, 23 integrally form a knot winding around the cord 21 having no knot, and the inclination directions of the cords 22, 23 are reversed, with the knot acting as the boundary.

[0079] Fig. 32 shows an example of the four cords 21 to 24 connected together. In this example, the cord 22 individually forms a knot winding around the cords 21, 23, 24 which do not have a knot. Fig.33 shows an example of the four interconnected cords 21 to 24. In this example, the cords 22, 23 individually form knots that wind around the cord 21 that has no knot, the inclination directions of the cords 22, 23 are reversed, with the knots acting as the boundary, and the cord 24 is inserted between the cords 22, 23. In Fig. 26 to 33, for example, the cord 21 having no knot is preferably oriented in the tire circumferential direction. When the cord 21 is arranged in the tire circumferential direction, a considerable amount of tension is applied to the cord 21, and since there is no curvature from a knot, the tension can be effectively withstood.

[0080] Fig.34 illustrates an example of the three cords 21 to 23 joined together by welding. When the cords 21 to 23 are chemical fibers and at least a part thereof is made of a thermoplastic resin, the cords 21 to 23 may be integrated by performing a welding process such as heat welding or ultrasonic welding while compacting the crossing portions of the cords 21 to 23 in a thickness direction. Fig. 35 shows an example of the two cord threads 21, 22 joined together by welding.

[0081] Fig.36 illustrates an example of the two cords 21, 22 joined together by another welding method. When the cords 21, 22 are chemical fibers and made of a thermosetting resin, the cords 21, 22 may be integrated by arranging an adhesive material 25 made of a thermoplastic resin so as to impregnate or wrap the fiber at the crossing portions of the cords 21, 22, and then performing a welding process such as heat welding or ultrasonic welding thereon.

[0082] Fig.37 is an example of the two cords 21, 22 connected to each other without a knot. In this example, a knot-free connecting portion is formed by intersecting yarns constituting the cords 21, 22. While the reinforcement member 10 increases in thickness when the connected portion has a knot, the thickness of the reinforcement member 10 can be reduced when a knot-free connected portion is formed.

[0083] While the above embodiments have described illustrative scenarios in which the reinforcing member having a specific mesh-like structure is applied to the belt layer, the carcass layer, or the bead reinforcing layer, a reinforcing member having a specific mesh-like structure can be applied to various reinforcing layers constituting the pneumatic tire. When applied to any reinforcing layer, the reinforcing member improves in-plane bending rigidity while maintaining excellent flexibility with respect to out-of-plane deformation, enabling improvement in various tire performance factors. Of course, such a reinforcing member having a mesh-like structure as described above can be applied simultaneously to a plurality of types of reinforcing layers. Examples

[0084] Pneumatic tires provided with an annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, a pair of bead portions disposed inward from the sidewall portions in the tire radial direction, a carcass layer disposed extending between the pair of bead portions, and a belt layer disposed on an outer peripheral side of the carcass layer in the tread portion were manufactured with a tire size of 215 / 55R17. In the tires of Examples 1 to 4, a reinforcing member ( Fig. 2, Fig. 5, Fig. 8 and Fig.10), including a plurality of reinforcing cords oriented in at least three directions, and having a net-like structure with at least three reinforcing cords oriented in different directions and connected at intersection points of the reinforcing cords, is used as the belt layer.

[0085] For comparison, a pneumatic tire according to Prior Art Example 1 was manufactured, in which two belt layers with different inclination directions with respect to the tire circumferential direction of the reinforcing cords were embedded in the tread portion. In addition, a tire according to Comparative Example 1 was manufactured, in which a reinforcing member having a net-like structure in which two reinforcing cords oriented in different directions were connected at intersection points of the plurality of reinforcing cords oriented in two different directions was used as the belt layer.

[0086] Cornering stiffness and rolling resistance of these test tires were evaluated according to the following procedures, and the results are shown in Table 1. Curve stiffness:

[0087] Each test tire was mounted on a 17 x 7J wheel mounted on a flat-belt tester, operated at an air pressure of 230 kPa, a load of 6.5 kN, and a speed of 20 km / h. The cornering stiffness was then measured at a slip angle of ±1.0°. The evaluation results were expressed as index values, with the Prior Art Example 1 assigned an index value of 100. Higher index values ​​indicate higher cornering stiffness. Rolling resistance:

[0088] Each test tire was mounted on a wheel with a rim size of 17 × 7J, which was mounted on a rolling resistance tester with a drum with a radius of 854 mm, run-in for 30 minutes at an ambient temperature of 25°C, an air pressure of 230 kPa, a load of 6.0 kN, and a speed of 80 km / h, and then the rolling resistance was measured under the same conditions. The evaluation results were expressed as index values ​​using the reciprocal of the measured values, with the prior art example 1 defined as 100. Higher index values ​​indicate lower rolling resistance. Table 1 Example of the prior art 1 Comparison example 1 Example 1 Example 2 Example 3 Example 4 Joining reinforcing cord threads of the belt layer Unavailable Available Available ( Fig. 2) Available ( Fig. 5) Available ( Fig. 8) Available ( Fig. 10) Alignment of reinforcing cord threads of the belt layer 2 directions 2 directions 4 directions 4 directions 4 directions 3 directions Curve stiffness (index value) 100 101 110 108 109 106 Rolling resistance (index value) 100 101 108 106 107 104

[0089] As can be seen from Table 1, the tires of Examples 1 to 4 showed increased cornering stiffness and reduced rolling resistance compared with those of Prior Art Example 1. On the other hand, the tire of Comparative Example 1 showed substantially no effect of improving cornering stiffness or rolling resistance.

[0090] Next, pneumatic tires having an annular tread portion extending in a tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, a pair of bead portions disposed inward from the sidewall portions in a tire radial direction, and a carcass layer disposed extending between the pair of bead portions were manufactured with a tire size of 215 / 55R17. In the tires of Examples 11 to 12, a reinforcing member ( Fig. 14 and Fig.15) including a plurality of reinforcing cords oriented in at least three directions in a region on the bead portion side and having a net-like structure having at least three reinforcing cords oriented in different directions and connected at intersection points of the reinforcing cords, is used as the carcass layer.

[0091] For comparison, a pneumatic tire of Prior Art Example 11 was manufactured in which a carcass layer including a plurality of reinforcing cords extending in the tire radial direction was arranged between the pair of bead portions. In addition, a tire of Comparative Example 11 was manufactured in which a carcass layer including a plurality of reinforcing cords extending in the tire radial direction was arranged between the pair of bead portions, and two bead reinforcing layers were embedded from the bead portion to the sidewall portion.

[0092] These test tires were evaluated for tire weight and steering stability according to the following evaluation methods and the results are shown in Table 2. Tire weight:

[0093] The weight of each test tire was measured. The evaluation results were expressed as index values ​​using the reciprocal of the measured value, with the results of Prior Art Example 11 defined as 100. Larger index values ​​indicate a lighter tire weight. Steering stability:

[0094] Each test tire was mounted on a 17 × 7J wheel, mounted on a test vehicle with a displacement of 3000 cm3, and inflated to an air pressure of 230 kPa. Sensory evaluations were performed by a test driver. The evaluation results were expressed as index values, with the prior art example 11 defined as 100. Larger index values ​​indicate better steering stability. Table 2 Example of the prior art 11 Comparison example 12 Example 11 Example 12 Joining reinforcing cord threads of the carcass layer Unavailable Unavailable Available ( Fig. 14) Available ( Fig. 15) Presence / absence of a bead reinforcement layer Unavailable Available Unavailable Unavailable Tire weight (index) 100 97 100 100 Steering stability (index value) 100 105 105 106

[0095] As can be seen from Table 2, the tires of Examples 11 and 12 allowed an increase in tire circumferential rigidity without adding a bead reinforcing layer, making it possible to improve steering stability without significantly increasing the tire weight compared to Prior Art Example 11. On the other hand, in the tire of Comparative Example 1, while the effect of improving steering stability was confirmed, the tire weight increased in proportion.

[0096] Next, pneumatic tires provided with an annular tread portion extending in a tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, a pair of bead portions disposed inward in the tire radial direction from the sidewall portions, a carcass layer disposed extending between the pair of bead portions, and a bead reinforcing layer embedded from the bead portion to the sidewall portion were manufactured with a tire size of 215 / 55R17. In the tires of Examples 21 to 24, a reinforcing member ( Fig.21 to 24) including a plurality of reinforcing cords oriented in at least three directions, and having a net-like structure having at least three reinforcing cords oriented in different directions and connected at intersection points of the reinforcing cords, is used as the bead reinforcing layer.

[0097] For comparison, a pneumatic tire of Prior Art Example 21 was manufactured without the bead reinforcing layer. In addition, a tire of Comparative Example 21 was manufactured in which two bead reinforcing layers including a plurality of reinforcing cords inclined in the tire radial direction were embedded from the bead portion to the sidewall portion.

[0098] The different test tires were evaluated in terms of tire weight and steering stability according to the following evaluation methods and the results are shown in Table 3. Tire weight:

[0099] The weight of each test tire was measured. The evaluation results were expressed as index values ​​using the reciprocal of the measured value, with the results of Prior Art Example 21 defined as 100. Larger index values ​​indicate a lighter tire weight. Steering stability:

[0100] Each test tire was mounted on a 17 × 7J wheel, mounted on a test vehicle with a displacement of 3000 cm3, and inflated to an air pressure of 230 kPa. Sensory evaluations were performed by a test driver. The evaluation results were expressed as index values, with the prior art example 21 defined as 100. Larger index values ​​indicate better steering stability. Table 3 Example of the state of the art 21 Comparative example 21 Example 21 Example 22 Example 23 Example 24 Presence / absence of a bead reinforcement layer Unavailable Available Available Available Available Available Joining reinforcing cords of the bead reinforcement layer - Unavailable Available ( Fig. 21) Available ( Fig. 22) Available ( Fig. 23) Available ( Fig. 24) Tire weight (index) 100 96 98 98 98 98 Steering stability (index value) 100 103 105 105 105 105

[0101] As can be seen from Table 3, the tires of Examples 21 to 24 exhibited high in-plane bending rigidity in the reinforcing member used as the bead reinforcing layer, which made it possible to improve steering stability while suppressing the tire weight to a minimum compared to Prior Art Example 21. On the other hand, in the tire of Comparative Example 21, while the effect of improving steering stability was confirmed, the effect was smaller than that of Examples 21 to 24, and the tire weight increased considerably. List of reference symbols 1 tread section 2 side wall section 3 bead section 4 carcass layers 5 bead core 6 bead fillers 7 belt layer 8 Belt reinforcement layer 9 Bead reinforcement layer 10 Reinforcing element 11 to 14 reinforcing cord threads 15, 16 Connected section

Claims

[1] Pneumatic tire, comprising: an annular tread portion (1) extending in the tire circumferential direction (C); a pair of sidewall portions (2) arranged on both sides of the tread portion (1); a pair of bead portions (3) arranged inside said sidewall portions (2) in the tire radial direction; and a reinforcing member (10) including a plurality of reinforcing cords (11, 12, 13, 14) oriented in at least three directions and having a net-like structure, wherein at least a first, a second and a third reinforcing cord (11, 12, 13, 14) are connected at at least a part of intersection points of the reinforcing cords (11, 12, 13, 14); wherein the first reinforcing cord (11) is oriented in a first direction at an intersection point, the second reinforcing cord (12) is oriented in a second direction at the intersection point, and the third reinforcing cord (13) is oriented in a third direction at the intersection point, the first, second, and third directions differing from each other at the intersection point; the second reinforcing cord (12) runs parallel to a tire width direction (W) and is welded to the first reinforcing cord (11) and the third reinforcing cord (13) at the intersection point, so that a plurality of connected portions (15) are formed along the tire width direction (W) by the welding. [2] A pneumatic tire according to claim 1, wherein: the pneumatic tire further comprises a carcass layer (4) arranged extending between the pair of bead portions (3), and a belt layer (7) arranged on an outer peripheral side of the carcass layer (4) in the tread portion (1); and the reinforcing element (10) having a net-like structure is used as the belt layer (7). [3] A pneumatic tire according to claim 1 or 2, wherein at least three reinforcing cords (11, 12, 13, 14) are connected to each other at at least 30% of the intersection points at which at least three reinforcing cords (11, 12, 13, 14) intersect. [4] A pneumatic tire according to any one of claims 1 to 3, wherein an intersection angle of the at least three reinforcing cords (11, 12, 13, 14) connected at intersection points is 15° or greater. [5] A pneumatic tire according to any one of claims 1 to 4, wherein the belt layer (7) is formed by winding the reinforcing member (10) having a net-like structure in the tire circumferential direction (C). [6] A pneumatic tire according to any one of claims 1 to 4, wherein the belt layer (7) is formed by processing the reinforcing member (10) having a net-like structure into a ring shape without ends. [7] A pneumatic tire according to any one of claims 1 to 6, wherein the reinforcing cord (11, 12, 13, 14) includes a synthetic fiber cord having a knot strength of 1.5 (cN / dtex) or greater. [8] A pneumatic tire according to any one of claims 1 to 7, wherein the reinforcing element (10) is coated with rubber having a net-like structure. [9] A pneumatic tire according to claim 1, wherein: the pneumatic tire further comprises a carcass layer (4) arranged to extend between the pair of bead portions (3); and the reinforcing member (10) having a net-like structure in a region on the bead portion side is used as the carcass layer (4). [10] A pneumatic tire according to claim 9, wherein at least three reinforcing cords (11, 12, 13, 14) are connected to each other at at least 30% of the intersection points at which at least three reinforcing cords (11, 12, 13, 14) intersect. [11] A pneumatic tire according to claim 9 or 10, wherein an intersection angle of the at least three reinforcing cords (11, 12, 13, 14) connected at the intersection points is 15° or greater. [12] A pneumatic tire according to any one of claims 9 to 11, wherein the carcass layer (4) is formed by processing the reinforcing member (10) having a net-like structure into a ring shape without ends. [13] A pneumatic tire according to any one of claims 9 to 12, wherein the reinforcing cord (11, 12, 13, 14) includes a synthetic fiber cord having a knot strength of 1.5 (cN / dtex) or greater. [14] A pneumatic tire according to any one of claims 9 to 13, wherein the reinforcing element (10) is coated with rubber having a net-like structure. [15] A pneumatic tire according to claim 1, wherein: the pneumatic tire further comprises a carcass layer (4) arranged to extend between the pair of bead portions (3) and a bead reinforcing layer embedded in the bead portions (3); and the reinforcing element (10) having a net-like structure is used as the bead reinforcing layer. [16] A pneumatic tire according to claim 15, wherein at least three reinforcing cords (11, 12, 13, 14) are connected to each other at at least 30% of the intersection points at which at least three reinforcing cords (11, 12, 13, 14) intersect. [17] A pneumatic tire according to claim 15 or 16, wherein an intersection angle of the at least three reinforcing cords (11, 12, 13, 14) connected at intersection points is 15° or greater. [18] A pneumatic tire according to any one of claims 15 to 17, wherein a density of the connected portions (15, 16) of the reinforcing cords (11, 12, 13, 14) of the reinforcing member (10) increases inward in the tire radial direction. [19] A pneumatic tire according to any one of claims 15 to 18, wherein the bead reinforcing layer is formed by processing the reinforcing member (10) having a net-like structure into a ring shape without ends. [20] A pneumatic tire according to any one of claims 15 to 19, wherein the reinforcing cord (11, 12, 13, 14) includes a synthetic fiber cord having a knot strength of 1.5 (cN / dtex) or greater. [21] A pneumatic tire according to any one of claims 15 to 20, wherein the reinforcing element (10) is coated with rubber having a net-like structure.

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