JP2018111361A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire 2 improving durability while achieving both weight saving and rigidity improvement.SOLUTION: In a pneumatic tire 2, numerous sea parts 54 which are surrounded by protrusions 50 expanding in a mesh-like form are configured on a part or whole of the inner surface. The respective sea parts 54 have the first and second ends P1 and P2 being the intersection of a profile of the sea part 54 with a first line segment SL1 representing a maximum circumferential length CL of the sea part 54, and the outside and inside ends PS and PU being the intersection of the profile of the sea part 54 with a second line segment SL2 representing a maximum radial length RL of the sea part 54. The first line segment SL1 is longer than the second line segment SL2. The outside end PS in one sea part 54 in a radial direction is located outside the inside end PU in the other sea part 54 located outside the one sea part 54.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a pneumatic tire. More particularly, the present invention relates to a pneumatic tire mounted on a racing vehicle.

  In order to reduce the weight, the side portion of the tire may be thinned. In this case, since the rigidity of the side portion may be reduced and steering stability may be impaired, a highly-crosslinked rubber is used for a member constituting the side portion (for example, a sidewall or an inner liner), thereby reducing the rigidity of the tire. It is considered to secure. An example of such examination is disclosed in Japanese Patent Laid-Open No. 2006-020159.

JP, 2006-020159, A

  The carcass of a tire is constituted by a carcass ply including a large number of carcass cords arranged in parallel. From the viewpoint of securing the rigidity described above, the inclination angle of the carcass cord may be adjusted so that the carcass cord is inclined with respect to the radial direction at the side portion of the tire. If hard rubber is used for the inner liner together with the carcass including the inclined carcass cord, it is possible to reduce the weight while ensuring the rigidity.

  By the way, hard rubber generally has small elongation and low tear strength. For this reason, a member made of hard rubber is easily cracked.

  A force acts on the tire in the running state by acceleration or braking of the vehicle. Especially in tires used in racing, this force is quite large. For this reason, in race tires, in order to reduce the weight while ensuring rigidity, when the hard rubber is used for the inner liner together with the carcass including the inclined carcass cord, the inner liner along the carcass cord is used. The establishment of a technology that can prevent the occurrence of cracks and the like and improve the durability is demanded.

  An object of the present invention is to provide a pneumatic tire in which durability is improved while achieving both weight reduction and rigidity improvement.

  The pneumatic tire according to the present invention includes a protrusion that protrudes inward from the inner surface and expands in a mesh shape. A large number of sea portions surrounded by the protrusions are formed on a part or the whole of the inner surface. These sea portions are arranged in the circumferential direction and are arranged in a staggered manner. Each sea part has a first end and a second end that are the intersection of the sea part outline and the first line segment representing the maximum circumferential length of the sea part, and the sea part outline and the radial maximum length of the sea part. It has an outer end and an inner end that are intersections with the second line segment representing the height. The first line segment is longer than the second line segment. In the radial direction, the outer end in one sea part is located outside the inner end in the other sea part located outside the one sea part.

  Preferably, in the pneumatic tire, the outline of the sea part includes a first side including the first end, a second side including the second end, an outer side including the outer end, and the inner end. Includes inner side. In the outline of the sea part, between the first side and the outer side, between the first side and the inner side, between the second side and the outer side, and The outline between the inner sides is represented by three arcs including a center arc and two side arcs. The center arc is located between the two side arcs. The center of the center arc is located outside the contour. The center of the side arc is located inside the contour. The side arc and the center arc are in contact with each other. The outline of the sea part may be an ellipse or a polygon.

  Preferably, the pneumatic tire includes a pair of beads, a carcass, and an inner liner. The carcass is bridged between one bead and the other bead. The inner liner is located inside the carcass. The carcass includes a first carcass ply and a second carcass ply. Each of the first carcass ply and the second carcass ply includes a plurality of carcass cords arranged in parallel. Each carcass cord is inclined with respect to the equator plane. The direction of inclination of the first carcass ply with respect to the carcass cord equator plane is opposite to the direction of inclination of the carcass cord with respect to the equator plane of the second carcass ply.

  Preferably, in this pneumatic tire, the absolute value of the angle formed by the carcass cord with respect to the equator plane is 80 ° or less.

  Preferably, in the pneumatic tire, the inner surface provided with the protrusions is configured in the inner liner. The hardness of the inner liner is 65 or more.

  Preferably, in this pneumatic tire, the thickness of the inner liner in the sea portion is 0.5 mm or more.

  In the pneumatic tire according to the present invention, the ridges that expand in a mesh shape on the inner surface thereof effectively prevent the occurrence of cracks and the like due to the force acting on the tire by acceleration or braking of the vehicle. This tire includes a carcass cord that is slanted with respect to the radial direction while the side portion is thinned for weight reduction and the inner liner is made of a high-hardness crosslinked rubber, for example, to ensure rigidity. Even when the carcass ply is used for the carcass, good durability can be obtained. According to the protrusion of the present invention, durability can be improved. According to the present invention, it is possible to obtain a pneumatic tire in which improvement in durability is achieved while achieving both weight reduction and improvement in rigidity.

FIG. 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing the arrangement of carcass cords included in the carcass. FIG. 3 is a development view showing a part of the inner surface of the tire of FIG. 1. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is a development view showing another example of the sea part shown in FIG. 3. FIG. 6 is a developed view showing still another example of the sea part shown in FIG. FIG. 7 is a developed view showing still another embodiment of the sea part shown in FIG. FIG. 8 is a schematic view showing a state of manufacturing the tire shown in FIG.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 shows a pneumatic tire 2. In FIG. 1, the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In FIG. 1, an alternate long and short dash line CL represents the equator plane of the tire 2. The shape of the tire 2 is symmetrical with respect to the equator plane except for the tread pattern.

  The tire 2 includes a tread 4, a pair of sidewalls 6, a pair of beads 8, a carcass 10, a belt 12, a band 14, a pair of edge bands 16, an inner liner 18, a pair of chafers 20, and a pair of first fillers 22. And a pair of second fillers 24. The tire 2 is a tubeless type. The tire 2 is attached to a vehicle (four-wheeled vehicle) traveling on a circuit. The tire 2 is for racing.

  The tread 4 forms a tread surface 26 that touches the road surface. The tread 4 is made of a crosslinked rubber. The tread 4 has no groove. The tire 2 is a slick type. Grooves may be cut into the tread 4 to form a tread pattern.

  Each sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. The sidewall 6 is made of a crosslinked rubber.

  Each bead 8 is located on the inner side in the axial direction than the sidewall 6. The bead 8 is located in the radially inner portion of the tire 2. The bead 8 includes a core 28 and an apex 30. The core 28 has a ring shape and includes a wound non-stretchable wire. The apex 30 is made of a crosslinked rubber.

  The carcass 10 includes a carcass ply 32. The carcass 10 includes a first carcass ply 34 and a second carcass ply 36, that is, two carcass plies 32. The carcass 10 may be composed of three or more carcass plies 32.

  The first carcass ply 34 and the second carcass ply 36 are bridged between the beads 8 on both sides. The first carcass ply 34 and the second carcass ply 36 are along the inside of the tread 4 and the sidewall 6. The first carcass ply 34 is folded around the bead 8 from the inner side to the outer side in the axial direction. The second carcass ply 36 is folded around the bead 8 from the outside in the axial direction toward the inside.

  FIG. 2 is a developed view schematically showing a part of the first carcass ply 34 and the second carcass ply 36. 2 corresponds to a state in which the tread surface 26 of the tire 2 is viewed from the upper side of FIG. In FIG. 2, the vertical direction is the circumferential direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the radial direction of the tire 2.

  Each of the first carcass ply 34 and the second carcass ply 36 includes a large number of carcass cords 38 and a topping rubber 40 arranged in parallel. Each carcass cord 38 is made of an organic fiber. Examples of the organic fiber include polyester fiber, nylon fiber, rayon fiber, polyethylene naphthalate fiber, and aramid fiber. In this paper, for convenience of explanation, the carcass cord 38 is represented by a solid line, but in each carcass ply 32, the carcass cord 38 is covered with a topping rubber 40.

  In each of the first carcass ply 34 and the second carcass ply 36, the carcass cord 38 is inclined with respect to the equator plane. Although not shown, the carcass cord 38 is inclined with respect to the radial direction in the portion of the sidewall 6 of the tire 2 (hereinafter also referred to as a side portion 42).

  As shown in FIG. 2, in the tire 2, the inclination direction of the carcass cord 38 in the first carcass ply 34 is opposite to the inclination direction of the carcass cord 38 in the second carcass ply 36 with respect to the equator plane. It is. In other words, the carcass cord 38 in the first carcass ply 34 intersects the carcass cord 38 in the second carcass ply 36. This intersection contributes to the rigidity of the tire 2. In the tire 2, sufficient rigidity is ensured even if the side portion 42 is thinned for weight reduction. In the tire 2, good steering stability can be obtained. From this point of view, in the tire 2, the inclination direction of the carcass cord 38 in the first carcass ply 34 with respect to the equator plane is preferably opposite to the inclination direction of the carcass cord 38 in the second carcass ply 36 with respect to the equator plane.

  In FIG. 2, symbol α represents an angle formed by the carcass cord 38 with respect to the equator plane. In the tire 2, the absolute value of the angle α is preferably 80 ° or less. Thereby, especially in the side part 42 of the tire 2, the carcass 10 effectively contributes not only to the rigidity in the radial direction but also to the rigidity in the circumferential direction. In the tire 2, sufficient rigidity is ensured even if the side portion 42 is thinned for weight reduction. In the tire 2, good steering stability can be obtained. The absolute value of the angle α is preferably 60 ° or more. Thereby, the rigidity in the radial direction is appropriately maintained. Since the rigidity of the tire 2 is appropriately ensured, the tire 2 is excellent in steering stability.

  The belt 12 is laminated with the carcass 10 on the inner side in the radial direction of the tread 4. The belt 12 includes an inner layer 44 and an outer layer 46. Although not shown, each of the inner layer 44 and the outer layer 46 includes a number of parallel belt cords. Each belt cord is inclined with respect to the equator plane.

  The band 14 is located outside the belt 12 in the radial direction. This band 14 is also called a full band. Although not shown, the band 14 includes a full band cord wound spirally. This band 14 has a jointless structure.

  Each edge band 16 is located radially outside the belt 12 and in the vicinity of the end of the belt 12. Although not illustrated, the edge band 16 includes a spirally wound edge band cord. The edge band 16 has a jointless structure.

  The inner liner 18 is located inside the carcass 10. The inner liner 18 is joined to the inner surface of the carcass 10. In the tire 2, the inner liner 18 includes the inner surface 48 of the tire 2. In other words, the inner liner 18 forms the inner surface 48 of the tire 2.

  In the tire 2, the inner liner 18 is made of a crosslinked rubber having excellent air shielding properties. A typical base rubber of the inner liner 18 is butyl rubber or halogenated butyl rubber. The inner liner 18 maintains the internal pressure of the tire 2.

  In the tire 2, the hardness of the inner liner 18 is 65 or more. The inner liner 18 is harder than the conventional inner liner. The hard inner liner 18 contributes to the rigidity of the tire 2. In the tire 2, sufficient rigidity is ensured even if the side portion 42 is thinned for weight reduction. In the tire 2, good steering stability can be obtained. From this viewpoint, in the tire 2, the hardness of the inner liner 18 is preferably 65 or more. From the viewpoint of ride comfort, the inner liner 18 preferably has a hardness of 90 or less.

  In the present invention, the hardness is measured with a type A durometer in accordance with the provisions of “JIS K6253”. The durometer is pressed against the cross section shown in FIG. 1, and the hardness is measured. The measurement is made at a temperature of 23 ° C.

  In FIG. 3, a part of the inner surface 48 of the tire 2 is shown as a development view. In FIG. 3, the vertical direction is the radial direction of the tire 2, and the horizontal direction is the circumferential direction of the tire 2. The front side of the paper surface is the inside of the tire 2, and the back side of the paper surface is the front side of the tire 2.

  FIG. 4 shows a cross section of the tire 2 along the line IV-IV in FIG. In FIG. 4, the left-right direction is the circumferential direction of the tire 2. The upper side of the page is the inside of the tire 2, and the lower side of the page is the outside of the tire 2. The direction perpendicular to the paper surface is the radial direction of the tire 2.

  In the tire 2, a protrusion 50 is provided on the inner surface 48. As shown in FIG. 3, the protrusion 50 extends in a mesh shape. As shown in FIG. 4, the protrusion 50 protrudes inward from the inner surface 48. The tire 2 includes a protrusion 50 that protrudes inward from the inner surface 48 and expands in a mesh shape.

  As described above, in the tire 2, the inner liner 18 forms the inner surface 48 of the tire 2. In the tire 2, an inner surface 48 provided with a protrusion 50 is formed in the inner liner 18.

  In the tire 2, the ridge 50 is provided in a zone from the buttress 52 to the bead 8, which is near the boundary between the tread 4 and the sidewall 6, on the inner surface 48. In other words, the protrusion 50 is provided on a part of the inner surface 48. The protrusion 50 may be provided on the entire inner surface 48.

  In this tire 2, the ridges 50 are spread in a mesh shape, and therefore, in the zone where the ridges 50 are provided, there are a number of dent-like portions surrounded by the ridges 50. To do. In the present invention, the portion surrounded by the protrusions 50 in the portion having the depression-like form is referred to as the sea portion 54. That is, in the tire 2, a large number of sea portions 54 surrounded by the protrusions 50 are formed on a part of the inner surface 48. As described above, in the tire 2, the protrusion 50 may be provided on the entire inner surface 48. In this case, in the tire 2, many sea portions 54 surrounded by the protrusions 50 are formed on the entire inner surface 48. In the tire 2, the sea portion 54 is not provided with a thin groove such as a sipe that may become a starting point of cracking due to the action of force.

  As shown in FIG. 3, in the tire 2, a large number of sea portions 54 are arranged at equal intervals in the circumferential direction, so that a large number of rows 56 of the sea portions 54 are configured. The rows 56 of these sea portions 54 are juxtaposed in the radial direction. The sea part 54 in one row 56 is, in the circumferential direction, between one sea part 54 in another row 56 located next to this one row 56 and another sea part 54 located next to this one sea part 54. Is located. In the tire 2, a large number of sea portions 54 are arranged in a staggered manner. That is, in the tire 2, a large number of sea portions 54 are arranged in the circumferential direction at a constant pitch and are arranged in a staggered manner.

  In FIG. 3, a solid line SL <b> 1 is a line segment in the circumferential direction of the sea portion 54. The sea portion 54 has the maximum circumferential length (double arrow CL in FIG. 3) in the line segment SL1. In the present invention, the line segment SL1 representing the circumferential maximum length CL of the sea portion 54 is referred to as a first line segment. In FIG. 3, reference numeral P <b> 1 is one intersection of the outline of the sea portion 54 and the first line segment SL <b> 1. This intersection P1 is also one end of the line segment SL1. Symbol P2 is the other intersection of the outline of the sea portion 54 and the first line segment SL1. This intersection point P2 is also the other end of the line segment SL1. The sea portion 54 has a first end P1 and a second end P2 that are intersections between the contour of the sea portion 54 and a first line segment SL1 that represents the circumferential maximum length CL of the sea portion 54. The line IV-IV in FIG. 3 passes through the second end P <b> 2 of one sea part 54 and the first end P <b> 1 of another sea part 54 located next to the one sea part 54.

  In FIG. 3, the solid line SL <b> 2 is a line segment in the radial direction of the sea portion 54. The sea portion 54 has the maximum radial length (double arrow RL in FIG. 3) in the line segment SL2. In the present invention, the line segment SL2 representing the maximum radial length RL of the sea portion 54 is referred to as a second line segment. In FIG. 3, the symbol PS is one intersection of the contour of the sea portion 54 and the second line segment SL2. This intersection PS is also the outer end of the line segment SL2. The code PU is. This is the other intersection of the outline of the sea part 54 and the second line segment SL2. This intersection PU is also the inner end of the line segment SL2. The sea portion 54 has an outer end PS and an inner end PU that are intersections between the contour of the sea portion 54 and a second line segment SL2 that represents the maximum radial length RL of the sea portion 54.

  In the tire 2, the first line segment SL1 is longer than the second line segment SL2. In other words, the sea portion 54 is configured such that the first line segment SL1 has a length CL larger than the length RL of the second line segment SL2 by the protrusions 50 spreading in a mesh shape. Further, in the tire 2, the outer end PS in one sea part 54 is located outside the inner end PU in the other sea part 54 located outside the one sea part 54 in the radial direction. In other words, the outer end PS in one sea part 54 is positioned outside the inner end PU in the other sea part 54 that is located outside the one sea part 54 in the radial direction by the protrusions 50 spreading in a mesh shape. In addition, a large number of sea portions 54 are formed.

  In the tire 2, the protrusions 50 that expand in a mesh shape on the inner surface 48 contribute to the rigidity of the portion of the inner surface 48 of the tire 2 in particular. In the tire 2, the protrusion 50 effectively prevents the occurrence of cracks and the like due to the force acting on the tire 2 due to acceleration or braking of the vehicle. In the tire 2, the side portion 42 is thinned for weight reduction, and in order to ensure rigidity, for example, the inner liner 18 that forms the inner surface 48 is made of a hardened cross-linked rubber, and the radial direction is reduced. Even if the carcass ply 32 including the inclined carcass cord 38 is used for the carcass 10, good durability can be obtained. According to the protrusion 50 of the present invention, durability can be improved. According to the present invention, it is possible to obtain a pneumatic tire 2 in which improvement in durability is achieved while achieving both weight reduction and improvement in rigidity.

  In the tire 2, the outline of the sea portion 54 constituted by the protrusions 50 spreading in a mesh shape has a distorted shape in which four corners of a rectangle are recessed inward. Specifically, the contour includes a first side 58 and a second side 60, and an outer side 62 and an inner side 64. The first side 58 includes the first end P1 and extends in the radial direction. The second side 60 includes the second end P2 and extends in the radial direction. The outer side 62 includes the outer end PS and extends in the radial direction. The inner side 64 includes the inner end PU and extends in the radial direction. Further, in the outline of the sea part 54, between the first side 58 and the outer side 62, between the first side 58 and the inner side 64, between the second side 60 and the outer side 62, and The contour between the second side 60 and the inner side 64 is represented by three arcs including a center arc and two side arcs. In FIG. 3, the arrow Rc represents the radius of the center arc, and the arrow Rs represents the radius of the side arc. In the tire 2, a center arc is located between the two side arcs. The center of the center arc is located outside the contour of the sea portion 54. The center of the side arc is located inside this contour. The side arc and the center arc are in contact with each other at the intersection. The side arc and the first side 58 are in contact with each other at the intersection. The side arc and the second side 60 are in contact with each other at the intersection. The side arc and the outer side 62 are in contact at the intersection of the two. The side arc and the inner side 64 are in contact with each other at the intersection.

  In the tire 2, the first side 58 and the second side 60 are parallel. The outer side 62 and the inner side 64 are also parallel. As described above, when the first side 58 and the second side 60 are parallel and the outer side 62 and the inner side 64 are parallel, the first line segment SL1 and the second line segment SL2 are mutually connected. Identified by a line segment intersecting at the center.

  5, 6, and 7 show other exemplary embodiments that the sea portion 54 of the present invention can take. In the tire 2, as shown in FIG. 5, in the outline of the sea portion 54, between the first side 58 and the outer side 62, between the first side 58 and the inner side 64, and the second side 60. And the outer side 62 and the contour between the second side 60 and the inner side 64 may be represented by straight lines instead of three arcs. In this case, the outline of the sea portion 54 has an octagonal shape. Further, in the tire 2, as shown in FIG. 6, the contour of the sea portion 54 may be configured to have a quadrangular shape, and as shown in FIG. 7, the contour of the sea portion 54 is an ellipse. It may be configured to present.

  In the tire 2, the contour of the sea portion 54 can take various forms, as shown at least in FIGS. 3, 5, 6, and 7. The outline of the sea portion 54 may be a polygon as shown in FIG. 5 or FIG. 6, or may be an ellipse as shown in FIG. Among these, as the contour of the sea part 54, from the viewpoint that the protrusion 50 having substantially the same width is obtained, and the distortion caused by the action of the force is dispersed throughout the protrusion 50 and good durability is obtained. The distorted shape shown in FIG. 3 or the contour represented by the octagon shown in FIG. 5 is preferable. The contour of the sea portion 54 is more preferably the contour represented by the distorted shape shown in FIG. 3 without the formation of corners where distortion tends to concentrate. When the contour of the sea portion 54 is represented by the distorted shape shown in FIG. 3, in the tire 2, the radius Rc of the center arc is preferably 1.4 mm or more, and preferably 1.8 mm or less. The radius Rs of the side arc is preferably 0.8 mm or more, and preferably 1.2 mm or less. The ratio of the center arc radius Rc to the side arc radius Rs is preferably 1.1 or more, and more preferably 2.3 or less.

The tire 2 described above is manufactured as follows. In the manufacture of the tire 2, a plurality of rubber members are assembled to obtain the raw cover R (unvulcanized tire 2). This raw cover R is put into the mold 66. The raw cover R is pressurized and heated in the mold 66. The rubber composition of the raw cover R flows by pressurization and heating. The rubber causes a crosslinking reaction by heating, and the tire 2 is obtained. The manufacturing method of the tire 2 is as follows:
(1) A step of preparing the raw cover R and (2) a step of pressurizing and heating the raw cover R in the mold 66 are included.

  FIG. 8 shows a state where the raw cover R is pressurized and heated in the mold 66. As shown in FIG. 8, the outer surface of the raw cover R abuts on the cavity surface of the mold 66. In the manufacture of the tire 2, an uneven pattern is formed on the outer surface of the tire 2 by using a mold 66 having an uneven pattern on the cavity surface.

  As shown in FIG. 8, a bladder 68 is located inside the raw cover R. In FIG. 8, the bladder 68 expanded by gas filling is in contact with the inner surface of the raw cover R. In the manufacture of the tire 2, a concavo-convex pattern is formed on the inner surface 48 of the tire 2 by using a bladder 68 having an uneven pattern on the outer surface. In manufacturing the tire 2, a rigid core may be used instead of the bladder 68. In this case, an uneven pattern is formed on the inner surface 48 of the tire 2 by using a rigid core having an uneven pattern on the outer surface.

  As described above, the inner surface 48 of the tire 2 is provided with the protrusions 50 that expand in a mesh shape. Therefore, in the bladder 68 that forms the inner surface 48 of the tire 2, a groove corresponding to the protrusion 50 is provided on the outer surface. This groove contributes to discharge of air existing between the raw cover R and the bladder 68 and air existing in the raw cover R. In this bladder 68, the groove extends in a mesh shape. For this reason, according to this bladder 68, air is discharged effectively. Thereby, the tire 2 which has favorable external appearance quality is obtained.

  In the manufacture of the tire 2, the bladder 68 is made of a crosslinked rubber. The bladder 68 is obtained by pressurizing and heating the rubber composition for the bladder 68 in a mold (not shown) for the bladder 68. In the present invention, the dimension and angle representing the contour of the sea portion 54 or the shape of the ridge 50 are specified by the profile in the mold for this bladder 68. In particular, the contour of the sea portion 54 or the shape of the ridge 50 is specified by the molding surface of the mold for the bladder 68 corresponding to the bottom of the groove of the bladder 68. When a rigid core is used in place of the bladder 68, the profile and the angle representing the contour of the sea portion 54 or the shape of the ridge 50 are specified by the profile of the outer surface of the rigid core.

  As described above, in the tire 2, the first line segment SL1 is longer than the second line segment SL2. Specifically, in the tire 2, the ratio of the length RL of the second line segment SL2 to the length CL of the first line segment SL1 is preferably 0.65 or more, and preferably 0.80 or less. Accordingly, the protrusion 50 for the sea portion 54 configured such that the first line segment SL1 has a length CL larger than the length RL of the second line segment SL2 is the rigidity of the portion of the inner surface 48 of the tire 2. To contribute effectively. In the tire 2, durability is improved while achieving both weight reduction and rigidity improvement. In this respect, the ratio is more preferably equal to or greater than 0.70 and is more preferably equal to or less than 0.73.

  In the tire 2, the length CL of the first line segment SL1 is preferably 5 mm or more, and preferably 10 mm or less. Accordingly, the protrusion 50 for the sea portion 54 configured such that the first line segment SL1 has a length CL larger than the length RL of the second line segment SL2 is the rigidity of the portion of the inner surface 48 of the tire 2. To contribute effectively. In the tire 2, durability is improved while achieving both weight reduction and rigidity improvement. In this respect, the length CL is more preferably 6 mm or more, and further preferably 7 mm or more. The length CL is more preferably 9 mm or less, and further preferably 8 mm or less.

  In the tire 2, the length RL of the second line segment SL2 is preferably 3 mm or more, and preferably 8 mm or less. Accordingly, the protrusion 50 for the sea portion 54 configured such that the first line segment SL1 has a length CL larger than the length RL of the second line segment SL2 is the rigidity of the portion of the inner surface 48 of the tire 2. To contribute effectively. In the tire 2, durability is improved while achieving both weight reduction and rigidity improvement. In this respect, the length RL is more preferably 4 mm or more, and further preferably 5 mm or more. The length RL is more preferably 7 mm or less, and further preferably 6 mm or less.

  In FIG. 3, a double arrow DL is a length in the radial direction from the outer end PS in one sea part 54 to the inner end PU in the other sea part 54 located radially outside the one sea part 54. The length DL is also a length in which one sea part 54 and another sea part 54 overlap in the circumferential direction.

  In the tire 2, the length DL is preferably 0.3 mm or more, and preferably 0.9 mm or less. As a result, a large number of sea portions 54 are arranged so that the outer end PS in one sea portion 54 is located outside the inner end PU in the other sea portion 54 located outside the one sea portion 54 in the radial direction. The projecting ridge 50 effectively contributes to the rigidity of the portion of the inner surface 48 of the tire 2. In the tire 2, durability is improved while achieving both weight reduction and rigidity improvement. In this respect, the length DL is more preferably 0.4 mm or more, and further preferably 0.5 mm or more. The length DL is more preferably 0.8 mm or less, and further preferably 0.7 mm or less.

  In FIG. 4, a double-headed arrow WC is the width of the protrusion 50 located between one sea part 54 and another sea part 54 located next to this one sea part 54 in the circumferential direction. The width WC is represented by the width of the top surface 70 of the ridge 50. The double arrow H is the height of the ridge 50. This height H is represented by the height from the inner surface to the top surface 70 of the protrusion 50. A double-headed arrow T is the thickness of the inner liner 18 in the sea portion 54.

  In the tire 2, the width WC of the protrusion 50 is preferably 0.3 mm or more, and preferably 2.0 mm or less. Thereby, the protrusion 50 effectively contributes to the rigidity of the portion of the inner surface 48 of the tire 2. In the tire 2, durability is improved while achieving both weight reduction and rigidity improvement. Furthermore, in manufacturing the tire 2, the groove for the protrusion 50 effectively contributes to the discharge of air. In this respect, the width WC is more preferably equal to or greater than 0.4 mm, and still more preferably equal to or greater than 0.5 mm. The width WC is more preferably 1.9 mm or less, and even more preferably 1.8 mm or less.

  In the tire 2, the height H of the protrusion 50 is preferably 0.1 mm or more, and preferably 0.4 mm or less. Thereby, the protrusion 50 effectively contributes to the rigidity of the portion of the inner surface 48 of the tire 2. In the tire 2, durability is improved while achieving both weight reduction and rigidity improvement. Furthermore, in manufacturing the tire 2, the groove for the protrusion 50 effectively contributes to the discharge of air. In this respect, the height H is more preferably equal to or greater than 0.15 mm, and still more preferably equal to or greater than 0.20 mm. The height H is more preferably 0.35 mm or less, and further preferably 0.30 mm or less.

  In the tire 2, the thickness T of the inner liner 18 in the sea portion 54 is preferably 0.5 mm or more. Thereby, the inner liner 18 effectively contributes to maintaining the internal pressure and securing the rigidity of the tire 2. In this respect, the thickness T is more preferably equal to or greater than 0.6 mm. In the tire 2, the thickness T is preferably 1.0 mm or less, whereby the influence on the durability and riding comfort by the inner liner 18 is effectively suppressed. In this respect, the thickness T is more preferably equal to or less than 0.9 mm.

  In FIG. 1, symbol PE is a position where the equator plane intersects the inner surface 48. This position PE is also the radially outer end of the contour of the inner surface 48 of the tire 2. Reference symbol ZS denotes a radially outer end of a zone provided with a protrusion 50 extending in a mesh shape. Reference sign ZU is the radially inner end of this zone. A solid line BBL is a bead base line. The bead base line is a line that defines the rim diameter (see JATMA) of the rim. The bead baseline extends in the axial direction. A double arrow NH is a radial distance from the bead base line to the intersection position PE. A double-headed arrow HS is a radial distance from the bead base line to the outer end ZS. A double arrow HU is a radial distance from the bead base line to the inner end ZU.

  When the zone in which the protrusions 50 are provided is provided in a part of the inner surface 48 as in the tire 2, the ratio of the distance HS to the distance NH is preferably 0.65 or more in the tire 2. 95 or less is preferable. Accordingly, the protrusions 50 that expand in a mesh shape effectively contribute to the rigidity of the inner surface 48 portion of the tire 2. In the tire 2, durability is improved while achieving both weight reduction and rigidity improvement. Furthermore, in manufacturing the tire 2, the groove for the protrusion 50 effectively contributes to the discharge of air.

  In the tire 2, the ratio of the distance HU to the distance NH is preferably 0.05 or more, and more preferably 0.45 or less. Accordingly, the protrusions 50 that expand in a mesh shape effectively contribute to the rigidity of the inner surface 48 portion of the tire 2. In the tire 2, durability is improved while achieving both weight reduction and rigidity improvement. Furthermore, in manufacturing the tire 2, the groove for the protrusion 50 effectively contributes to the discharge of air.

  In the present invention, the dimension and angle of each member of the tire 2 are measured in a state where the tire 2 is incorporated in a regular rim and is filled with air so as to have a regular internal pressure unless otherwise specified. At the time of measurement, no load is applied to the tire 2. In the case of the passenger car tire 2, the dimensions and angles are measured in a state where the internal pressure is 180 kPa.

  In the present specification, the normal rim means a rim defined in a standard on which the tire 2 depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims.

  In the present specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 2 relies. "Maximum air pressure" in JATMA standard, "Maximum value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA standard, and ETRTO standard

"INFLATION PRESSURE" in is the normal internal pressure.
In the present specification, the normal load means a load defined in a standard on which the tire 2 depends. “Maximum value” published in “Maximum load capacity” in the JATMA standard, “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, and “LOAD CAPACITY” in the ETRTO standard are normal loads.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
The tire shown in FIG. 1 was manufactured. The size of this tire is 225 / 40R18. In Example 1, the hardness of the inner liner was 65. The absolute value of the inclination angle α of the carcass cord included in the carcass was 80 °.

  The inner surface of Example 1 was provided with a sea part having the configuration shown in FIG. 3 by a ridge extending like a mesh. The ratio (RL / CL) of the length RL of the second line segment SL2 to the length CL of the first line segment SL1 was 0.7. The length RL of the second line segment SL2 was 5.6 mm. About 1st line segment SL1, it adjusted suitably in the range which can maintain ratio (RL / CL) at 0.7 for every row | line | column of the sea part paralleled in radial direction.

  The radius Rc of the center arc defining the contour of the sea portion was 1.6 mm. The radius Rs of the side arc was 1.0 mm.

  The length DL in which one sea part overlaps in the circumferential direction with another sea part located radially outward from the one sea part was 0.6 mm.

  The width WC of the ridge was 0.6 mm, and the height H of this ridge was 0.2 mm. The thickness of the inner liner at the sea was 0.5 mm.

[Comparative Example 1]
A tire of Comparative Example 1 was obtained in the same manner as in Example 1 except that no protrusion was provided on the inner surface.

[Comparative Example 2]
A tire of Comparative Example 2 was obtained in the same manner as in Example 1 except that a linear protrusion was provided instead of a mesh-like protrusion using a conventional bladder. In this comparative example 2, the linear protrusions are inclined and extend with respect to the radial direction.

[Example 2]
A tire of Example 2 was obtained in the same manner as Example 1 except that the outline of the sea part was configured with the outline shown in FIG. The number of sea portions provided on the inner surface is the same as that of the first embodiment.

[Example 3]
The tire of Example 3 was adjusted in the same manner as in Example 1 except that the length RL and the overlap length DL of SL2 of the second line segment were adjusted, and the outline of the sea part was configured with the outline shown in FIG. Obtained. The number of sea portions provided on the inner surface is the same as that of the first embodiment.

[Example 4]
A tire of Example 4 was obtained in the same manner as Example 1 except that the outline of the sea portion was configured with the outline shown in FIG. The number of sea portions provided on the inner surface is the same as that of the first embodiment.

[appearance]
The appearance of the prototype tire was observed to confirm the presence or absence of the effects of air remaining. The ratio of the number of tires in which the influence of air remaining was confirmed to the total number of tires prototyped was obtained. The result is an index and is shown in Table 1 below. The larger the value, the more the air is expelled and the better appearance is obtained.

[durability]
The tire was assembled in a rim (rim size = 18 × 6.0 J), and this tire was filled with air so that the internal pressure was 210 kPa. This tire was mounted on a racing four-wheeled vehicle having a displacement of 4300 cc. I let the driver drive this car on the racing circuit. When the vehicle traveled 1000 km, the inner surface of the tire was confirmed to check for the occurrence of cracks and the like. Based on the size and number of cracks, the occurrence of cracks was quantified and the results are shown in Table 1 below as an index. The larger the value, the less cracking is generated and the better the durability.

  As shown in Table 1, the tire of the example has a higher evaluation than the tire of the comparative example. From this evaluation result, the superiority of the present invention is clear.

  The technique for providing a mesh-like protrusion on the inner surface described above can be applied to various tires.

2 ... tyre 4 ... tread 6 ... side wall 8 ... bead 10 ... carcass 18 ... inner liner 28 ... core 30 ... apex 32 ... carcass ply 34 ... First carcass ply 36 ... Second carcass ply 38 ... Carcass cord 40 ... Topping rubber 42 ... Side part 48 ... Inner surface of tire 2 50 ... Projection 54 ... -Sea part 56 ... Row of sea part 54 ... First side 60 ... Second side 62 ... Outer side 64 ... Inner side 66 ... Mold 68 ... Bladder

Claims (7)

It has ridges that project inward from the inner surface and expand in a mesh shape,
A large number of sea parts surrounded by the ridges are formed on a part or the whole of the inner surface,
These sea parts are arranged in the circumferential direction and arranged in a staggered pattern,
Each sea part has a first end and a second end, which are the intersections of the sea part outline and the first line segment representing the maximum circumferential length of the sea part, and the sea part outline and the radial maximum length of the sea part. Having an outer end and an inner end that are intersections with the second line segment representing
The first line segment is longer than the second line segment,
A pneumatic tire in which, in the radial direction, the outer end in one sea part is located outside the inner end in another sea part located outside the one sea part. The outline of the sea part includes a first side including the first end, a second side including the second end, an outer side including the outer end, and an inner side including the inner end.
In the outline of the sea part,
Between the first side and the outer side, between the first side and the inner side, between the second side and the outer side, and between the second side and the inner side. The contour is represented by three arcs consisting of a center arc and two side arcs,
The center arc is located between the two side arcs,
The center of the center arc is located outside the contour, the center of the side arc is located inside the contour, and the side arc and the center arc are in contact with each other. Pneumatic tire.   The pneumatic tire according to claim 1, wherein an outline of the sea part is an ellipse or a polygon. It has a pair of beads, a carcass, and an inner liner,
The carcass is stretched between one bead and the other bead,
The inner liner is located inside the carcass;
The carcass includes a first carcass ply and a second carcass ply,
Each of the first carcass ply and the second carcass ply includes a plurality of carcass cords arranged in parallel;
Each carcass cord is inclined with respect to the equator plane,
The pneumatic according to any one of claims 1 to 3, wherein an inclination direction of the first carcass ply with respect to the equator plane of the carcass cord is opposite to an inclination direction of the carcass cord with respect to the equator plane of the second carcass ply. tire.   The pneumatic tire according to claim 4, wherein an absolute value of an angle formed by the carcass cord with respect to an equator plane is 80 ° or less. In the inner liner, the inner surface provided with the protrusion is configured,
The pneumatic tire according to claim 4 or 5, wherein the inner liner has a hardness of 65 or more.   The pneumatic tire according to claim 6, wherein a thickness of the inner liner in the sea part is 0.5 mm or more.

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