tire

Abstract

The present invention provides a tire (2) capable of suppressing the influence on durability and handling stability and achieving a reduction in rolling resistance. The cap band (20) of the tire (2) is composed of a full cap band (48) covering the entire belt (14) and a pair of end cap bands (50) configured to be separated in the axial direction and cover the end (46) of the belt (14). The cross section of the cap band (20) includes the cross sections of a plurality of cap band strips (52). In the cross section of the full cap band 48, the cross sections of the plurality of cap band strips (52) are arranged side by side with gaps. In the cross section of each end cap band (50), the cross sections of the plurality of cap band strips (52) are arranged side by side without gaps. In the axial direction, the inner end (62) of the end cap band (50) is configured to be separated from the bottom (BT) of the shoulder circumferential groove (24s).

Description

Technical Field

[0001] The present invention relates to a tire, and more particularly to a tire for a passenger car. Background Art

[0002] The cap band provided between the tread and the belt includes a cap band cord substantially extending in the circumferential direction. As the cap band, a full cap band covering the entire belt and an end cap band covering the end of the belt are known.

[0003] The cap band is formed by spirally winding a cap strip including a cap cord. The cap strip is usually tightly wound without leaving a gap, but a case of sparsely winding the cap strip with a gap is studied (for example, Patent Document 1 below).

[0004] Patent Document 1: Japanese Patent Application Publication No. 2003-182307

[0005] If the cap band is formed by winding the cap band sparsely, the restraining force brought by the cap band is reduced. The reduction in restraining force will affect the contour shape of the tire's contact surface with the road surface. If the contact length increases and the contact area increases, there is a concern that the rolling resistance will increase and the handling stability will decrease. For example, if a thin tread is used, the increase in rolling resistance can be suppressed. However, the part engraved at the bottom of the circumferential groove of the tread also becomes thinner, so if deformation is concentrated in this part, there is a concern that damage such as cracks will occur. Summary of the invention

[0006] The present invention has been made in view of such actual circumstances, and an object of the present invention is to provide a tire capable of reducing rolling resistance while suppressing influence on durability and steering stability.

[0007] A tire according to one embodiment of the present invention comprises: a tread having a plurality of circumferential grooves, a belt radially located inside the tread, and a cap band radially located between the tread and the belt and formed by winding a cap band strip including a plurality of parallel cap band cords in a spiral shape. The cap band is composed of a full cap band covering the entire belt, and a pair of end cap bands arranged to be separated in the axial direction and cover the ends of the belt. The cross section of the cap band includes the cross sections of the plurality of cap band strips. In the cross section of the full cap band, the cross sections of the plurality of cap band strips are arranged side by side with gaps therebetween. In the cross section of each of the end cap bands, the cross sections of the plurality of cap band strips are arranged side by side without gaps. The circumferential groove located axially outside of the plurality of circumferential grooves is a shoulder circumferential groove, and the inner end of the end cap band is arranged to be separated from the bottom of the shoulder circumferential groove in the axial direction.

[0008] Preferably, in the tire, a circumferential groove having the largest groove width among the plurality of circumferential grooves is a wide circumferential groove, and a size of the gap is narrower than a bottom width of the wide circumferential groove.

[0009] Preferably, in the tire, the axial distance from the equatorial plane to the end of the above-mentioned belt is a reference width, the position at an axial distance from the above-mentioned equatorial plane equivalent to 0.75 times the above-mentioned reference width is a reference position, and the above-mentioned shoulder circumferential groove is located axially at a position closer to the inside than the above-mentioned reference position.

[0010] Preferably, in the tire, the band cord is a cord made of nylon fiber, or a hybrid cord in which a strand made of nylon fiber and a strand made of aramid fiber are twisted together.

[0011] Preferably, in the tire, in the axial direction, the inner end of the end cap band is located outside the shoulder circumferential groove, and the ratio of the axial distance from the end of the belt to the inner end of the end cap band to the axial distance from the end of the belt to the bottom of the shoulder circumferential groove is greater than 0.25 and less than 0.90.

[0012] Preferably, in the tire, in the axial direction, the inner end of the end cap band is located inside the shoulder circumferential groove, and the ratio of the axial distance from the end of the belt to the inner end of the end cap band to the axial distance from the end of the belt to the bottom of the shoulder circumferential groove is greater than 1.20 and less than 1.55.

[0013] Preferably, in the tire, in a reference contact patch obtained by placing a regular load on the tire as a longitudinal load and bringing the tire into contact with a flat road surface when the tire is assembled on a regular rim, the internal pressure of the tire is adjusted to a regular internal pressure, and the camber angle of the tire is set to 0°, a shape index of the reference contact patch, represented by a ratio of an equatorial contact length measured along the equatorial plane to a reference contact length at a position corresponding to 80% of a reference contact width of the reference contact patch, is 1.10 or more and 1.50 or less.

[0014] According to the present invention, it is possible to obtain a tire capable of reducing rolling resistance while suppressing influence on durability and steering stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a cross-sectional view showing a portion of a tire according to an embodiment of the present invention.

[0016] Figure 2 It is a stereogram showing the crown band.

[0017] Figure 3 This is a simplified diagram for explaining the formation method of the crown band.

[0018] Figure 4 Yes means Figure 1 A cross-sectional view of a portion of a tire is shown.

[0019] Figure 5 This is a schematic diagram for explaining a method for calculating the shape index of the ground contact surface.

[0020] Figure 6 It is a cross-sectional view showing a part of a tire according to another embodiment of the present invention.

[0021] Description of Reference Numerals

[0022] 2, 72…tire; 4…tread; 6…sidewall; 10…bead; 12…carcass; 14…belt; 20…cap band; 22…tread surface; 24, 24s, 24c, 24w…circumferential groove; 48…full cap band; 50, 74…end cap band; 52…cap band strip; 54…cap band cord. DETAILED DESCRIPTION

[0023] Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

[0024] In the present disclosure, a state where a tire is assembled on a regular rim, the internal pressure of the tire is adjusted to the regular internal pressure, and no load is applied to the tire is referred to as a regular state. In the present invention, unless otherwise mentioned, the dimensions and angles of various parts of the tire are measured in the regular state.

[0025] A regular rim means a rim specified in the standard to which the tire conforms. The "standard rim" included in the application rim in the JATMA standard, the "design rim" in the TRA standard, and the "measuring rim" in the ETRTO standard are regular rims.

[0026] The normal internal pressure means the internal pressure specified in the tire's specifications. The "maximum pressure" in the JATMA specifications, the "maximum value" in the "TIRE LOAD LIMITS AT VARIATION COLD INFLATION PRESSURES" in the TRA specifications, and the "INFLATION PRESSURE" in the ETRTO specifications are normal internal pressures. If the tire is for a passenger car, the normal internal pressure is 180 kPa unless otherwise specified.

[0027] The normal load means the load specified in the standard to which the tire is based. The "maximum load capacity" in the JATMA standard, the "maximum value" in the "TIRE LOAD LIMITS AT VARIUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads. In the case of tires for passenger cars, unless otherwise specified, the normal load is a load equivalent to 88% of the above load.

[0028] Figure 1 FIG. 2 shows a portion of a tire 2 according to an embodiment of the present invention. The tire 2 is mounted on a passenger car. Figure 1 In the embodiment, the tire 2 is assembled to the rim R. The rim R is a regular rim. Air is filled into the tire 2 to adjust the internal pressure of the tire 2 to the regular internal pressure. The tire 2 is in a regular state. The tire 2 assembled to the rim R is also called a tire-rim complex. The tire-rim complex includes a rim R and a tire 2 assembled to the rim R.

[0029] Figure 1 FIG. 2 shows a portion of a cross section of the tire 2 cut along a plane including the rotation axis of the tire 2. Figure 1 In FIG. 1 , the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. Figure 1 The direction perpendicular to the paper surface is the circumferential direction of the tire 2. Figure 1 In FIG. 2 , a dashed line CL indicates the equatorial plane of the tire 2 .

[0030] The tire 2 includes a tread 4 , a pair of sidewalls 6 , a pair of bead portions 8 , a pair of beads 10 , a carcass 12 , a belt 14 , a pair of scoops 16 , an inner liner 18 , and a cap band 20 .

[0031] The tread 4 is made of a cross-linked rubber in consideration of wear resistance and grip performance. The tread 4 comes into contact with the road surface at its outer surface 22 (also referred to as tread surface).

[0032] exist Figure 1 In the figure, the position indicated by the reference symbol TE indicates the end of the contact patch of the tire 2 that contacts the road surface, and more specifically, indicates the position on the tread surface 22 corresponding to the axial outer end of the contact patch. In the tire 2, the position TE is also called a contact reference position.

[0033] The contact surface for specifying the ground contact reference position TE (also referred to as the reference ground contact surface) is obtained, for example, using a ground contact surface shape measuring device (not shown). In the device, the tire 2 is assembled to the rim R, the internal pressure of the tire 2 is adjusted to a normal internal pressure, the camber angle of the tire 2 is set to 0°, and a normal load is applied to the tire 2 as a longitudinal load, so that the tire 2 contacts a flat road surface to obtain the reference ground contact surface. In the tire 2, the ground contact width of the reference ground contact surface (also referred to as the reference ground contact width) is represented by the axial distance from the ground contact reference position TE on one side to the ground contact reference position TE on the other side measured along the tread surface 22.

[0034] like Figure 1 As shown, a plurality of circumferential grooves 24 extending in the circumferential direction are engraved on the tread 4 of the tire 2. Four circumferential grooves 24 are engraved on the tread 4 of the tire 2. These circumferential grooves 24 are arranged in parallel in the axial direction. Among these circumferential grooves 24, the circumferential grooves 24 located on the outer side in the axial direction are shoulder circumferential grooves 24s. The circumferential grooves 24 located on the inner side in the axial direction are central circumferential grooves 24c.

[0035] The groove width and groove depth of the circumferential groove 24 are determined in consideration of drainage and grip performance. In the tire 2, the groove width of the circumferential groove 24 is 1% or more and 15% or less of the reference ground contact width. The groove depth of the circumferential groove 24 is 5 mm or more and 10 mm or less. The groove width is represented by the distance from one edge to the other edge of the circumferential groove 24. The groove depth is represented by the distance from the edge to the bottom of the circumferential groove 24.

[0036] By engraving the circumferential grooves 24, a plurality of land portions 26 are formed on the tread 4. The land portion 26 located on the outer side in the axial direction of these land portions 26 is the shoulder land portion 26s. The land portion 26 located on the inner side in the axial direction is the center land portion 26c. The land portion 26 located between the center land portion 26c and the shoulder land portion 26s is the middle land portion 26m. The center land portion 26c of the tire 2 is located on the equatorial plane.

[0037] exist Figure 1 , the length indicated by the double-headed arrow TA is the thickness of the tread 4. The thickness TA is obtained by measuring the distance from the outer surface of the cap band 20 to the tread surface 22 along the equatorial plane. In the tire 2, the thickness TA is 4 mm or more and 15 mm or less.

[0038] Each sidewall 6 is connected to an end of the tread 4. The sidewall 6 is located radially inward of the tread 4. The sidewall 6 extends from the end of the tread 4 toward the bead 8. The sidewall 6 is made of a cross-linked rubber in consideration of cut resistance.

[0039] Each bead portion 8 is located radially inward of the side wall 6. The bead portion 8 is in contact with the rim R. The bead portion 8 is made of a cross-linked rubber in consideration of wear resistance.

[0040] Each bead 10 is located axially inside the bead portion 8. The bead 10 includes a core 28 and an apex 30. Although not shown, the core 28 includes a steel wire. The apex 30 is located radially outside the core 28. The apex 30 is made of a cross-linked rubber having high rigidity.

[0041] The carcass 12 is located inside the tread 4, the pair of sidewalls 6, and the pair of bead portions 8. The carcass 12 is spanned between one bead 10 and the other bead 10. The carcass 12 has a radial structure.

[0042] The carcass 12 includes at least one carcass ply 32. The carcass 12 of the tire 2 is composed of one carcass ply 32. The carcass ply 32 is folded around each core 28.

[0043] Although not shown, the carcass ply 32 includes a plurality of carcass cords arranged in parallel. These carcass cords are covered with rubber. Each carcass cord crosses the equatorial plane. The carcass cord is a cord made of organic fibers. Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers.

[0044] The belt 14 is located radially inside the tread 4. In the tire 2, the belt 14 is located inside the tread 4 between the carcass 12 and the cap band 20. The belt 14 is laminated on the carcass 12. The width of the belt 14 of the tire 2 is 55% or more and 90% or less of the cross-sectional width of the tire 2 (see JATMA, etc.).

[0045] The belt 14 is composed of at least two layers 34 stacked in the radial direction. The belt 14 of the tire 2 is composed of two layers 34 stacked in the radial direction. The inner layer 34 of the two layers 34 is an inner layer 36, and the outer layer 34 is an outer layer 38. Figure 1 As shown, the inner layer 36 has a width wider than that of the outer layer 38. In the axial direction, the end 40 of the inner layer 36 is located outside the end 42 of the outer layer 38. The distance from the end 42 of the outer layer 38 to the end 40 of the inner layer 36 is 3 mm or more and 10 mm or less.

[0046] Although not shown, the inner layer 36 and the outer layer 38 each include a plurality of belt cords arranged in parallel. These belt cords are covered with rubber. Each belt cord is inclined relative to the equatorial plane. The material of the belt cord is steel.

[0047] Each rubbing cloth 16 is located radially inside the bead 10. The rubbing cloth 16 is in contact with the rim R. In the tire 2, the rubbing cloth 16 is composed of cloth and rubber impregnated with the cloth.

[0048] The inner liner 18 is located inside the carcass 12. The inner liner 18 forms the inner surface of the tire 2. The inner liner 18 is made of a cross-linked rubber having a low gas permeability coefficient. The inner liner 18 maintains the internal pressure of the tire 2.

[0049] The cap band 20 is located between the tread 4 and the belt 14 in the radial direction. The cap band 20 is stacked on the belt 14. In the axial direction, the end 44 of the cap band 20 is located outside the end 46 of the belt 14. The distance from the end 46 of the belt 14 to the end 44 of the cap band 20 is 5 mm or more and 10 mm or less.

[0050] The band 20 includes a band cord. In the tire 2, the band cord actually extends in the circumferential direction. Specifically, the angle formed by the band cord with respect to the circumferential direction is 5° or less. The band 20 has a jointless structure.

[0051] In the tire 2, the cap band 20 is composed of a full cap band 48 and a pair of end cap bands 50. The full cap band 48 covers the entire belt 14. The pair of end cap bands 50 are arranged separately in the axial direction. Each end cap band 50 covers the end 46 of the belt 14. Figure 1 In the embodiment of the present invention, the end cap band 50 is located between the full cap band 48 and the tread 4. The end cap band 50 can also be located between the full cap band 48 and the belt 14.

[0052] Next, a method for manufacturing the tire 2 is described. In manufacturing the tire 2, the tread 4, the bead 10, the carcass 12, the belt 14, etc. are combined to prepare the tire 2 in an uncured state. Figure 1 The green tire is put into a mold (not shown) and pressurized and heated in the mold. Figure 1 The tire 2 shown in FIG. 1 is a tire 2. The method for manufacturing the tire 2 includes a step of preparing a green tire and a step of vulcanizing the green tire.

[0053] In manufacturing the tire 2, in the green tire preparation step, an uncured cap band 20 (hereinafter, a green cap band) is formed. In the green tire vulcanization step, the green cap band is vulcanized to obtain the cap band 20 that forms a part of the tire 2. Except for the formation of the cap band 20, the method is performed in the same manner as the conventional manufacturing method, and therefore the description thereof is omitted.

[0054] In manufacturing the tire 2, in order to form the cap band 20, a Figure 2 The cap band strip 52 shown. The cap band strip 52 includes a plurality of juxtaposed cap cords 54, and these cap cords 54 are covered by a topping 56. The cap band strip 52 is in the shape of a strip. The cap cords 54 included in the cap band strip 52 extend along the length direction of the cap band strip 52.

[0055] Figure 2The band strip 52 shown includes eight band cords 54. The number of band cords 54 included in the band strip 52 is not limited to eight. The number of band cords 54 included in the band strip 52 is appropriately determined in consideration of the specifications of the tire 2, etc. In the tire 2, the number of band cords 54 included in the band strip 52 is 2 or more and 15 or less.

[0056] As described above, the cap band 20 of the tire 2 is composed of the full cap band 48 and the pair of end cap bands 50. In the tire 2, the full cap band 48 and the end cap bands 50 are composed of cap band strips 52 of the same specification. The full cap band 48 and the end cap bands 50 may also be composed of cap band strips 52 of different specifications.

[0057] Although not shown, in the manufacture of the tire 2, the cap band 20 is formed in the drum of the forming machine. After the belt 14 is formed in the drum, the cap band strip 52 is wound in a spiral shape while applying tension to the cap band strip 52, thereby forming the cap band 20. In particular, in the manufacture of the tire 2, the cap band strip 52 is wound with a gap to form the full cap band 48, and the cap band strip 52 is wound without a gap to form the end cap band 50. In other words, the full cap band 48 is formed by winding the cap band strip 52 sparsely, and the end cap band 50 is formed by winding the cap band strip 52 tightly.

[0058] In manufacturing the tire 2 , the winding tension of the band strip 52 is set to a range of 10 N to 150 N. The winding tension is represented by a load (N) per band cord 54 included in the band strip 52 .

[0059] In manufacturing the tire 2 , in order to form the cap band 20 , for example, one cap band strip 52 for the full cap band 48 and two cap band strips 52 for the end cap band 50 are prepared.

[0060] Taking the position corresponding to the equatorial plane in the tire 2 as a reference, the position corresponding to the end 58 of the full crown band 48, the position corresponding to the outer end 60 of the end crown band 50, and the position corresponding to the inner end 62 of the end crown band 50 are set on the drum of the forming machine as the end equivalent position of the full crown band 48, the outer end equivalent position of the end crown band 50, and the inner end equivalent position of the end crown band 50, respectively.

[0061] The full cap band 48 is formed by sparsely winding the cap band strip 52 for the full cap band 48 from a position corresponding to one end of the full cap band 48 toward a position corresponding to the other end. The cap band strip 52 for the end cap band 50 is tightly wound from a position corresponding to the outer end of the end cap band 50 toward a position corresponding to the inner end, thereby forming one end cap band 50. The other cap band strip 52 for the end cap band 50 is tightly wound from a position corresponding to the inner end of the end cap band 50 toward a position corresponding to the outer end, thereby forming the other end cap band 50. Thus, the cap band 20 is obtained. In forming the cap band 20, from the viewpoint of stable formation of the full cap band 48, the end 58 portion of the full cap band 48 (about one to two turns of the cap band strip 52) can also be formed by tightly winding the cap band strip 52.

[0062] In manufacturing the tire 2, from the viewpoint of being able to reduce the number of cap bands 52 used in forming the cap band 20, for example, Figure 3 The illustrated method winds the cap band strip 52 to form the cap band 20 .

[0063] exist Figure 3 In the formation example of the cap band 20 shown in (a), the cap band 20 is formed using one cap band strip 52. In this formation example, the cap band strip 52 is tightly wound from the inner end equivalent position of one end cap band 50 toward the axial outer side to form one end cap band 50. The cap band strip 52 is sparsely wound from the end equivalent position of one end of the full cap band 48 toward the other end equivalent position thereof to form the full cap band 48. The cap band strip 52 is tightly wound from the outer end equivalent position of the other end cap band 50 toward the axial inner side to form the other end cap band 50. In this way, the cap band 20 is obtained.

[0064] exist Figure 3 In the formation example of the cap band 20 shown in (b), the cap band 20 is formed using two cap band strips 52. In this formation example, the two cap band strips are sparsely wound from the equatorial plane side toward the axial outer side to form the full cap band 48. From the outer end equivalent position of the end cap band 50 toward the axial inner side, the two cap band strips 52 are tightly wound to form the left and right end cap bands 50. In this way, the cap band 20 is obtained.

[0065] Even in Figure 3 In the formation example of the cap band 20 shown in (c), the cap band 20 is also formed using two cap band strips 52. In this formation example, the two cap band strips 52 are respectively tightly wound from the inner end equivalent position of the end cap band 50 toward the axial outer side to form the left and right end cap bands 50. From the end equivalent position of the full cap band 48 toward the equatorial plane, the two cap band strips 52 are respectively sparsely wound to form the full cap band 48. In this way, the cap band 20 is obtained.

[0066] As described above, the band cords 54 included in the band 20 of the tire 2 substantially extend in the circumferential direction. The band 20 is formed by the band strip 52 including the band cords 54. The band strip 52 constituting the band 20 also substantially extends in the circumferential direction. The angle formed by the band strip 52 with respect to the circumferential direction is 5° or less.

[0067] Figure 4 Shows Figure 1 A portion of a cross section of a tire 2 is shown. Figure 4 In FIG. 1 , the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. Figure 4 The direction perpendicular to the paper surface is the circumferential direction of the tire 2 .

[0068] As described above, the cap band 20 of the tire 2 is formed by winding the cap band strip 52 in a spiral shape. The cap band 20 is an element of the tire 2 formed by winding the cap band strip 52 in a spiral shape. Figure 4 As shown, the cross section of the cap band 20 includes the cross sections of a plurality of cap band strips 52. The full cap band 48 is formed by sparsely winding the cap band strips 52, so that in the cross section of the full cap band 48, the cross sections of the plurality of cap band strips 52 are arranged side by side with gaps therebetween. The pair of end cap bands 50 located on the left and right are each formed by tightly winding the cap band strips 52, so that in the cross section of the end cap bands 50, the cross sections of the plurality of cap band strips 52 are arranged side by side without gaps therebetween.

[0069] In the tire 2, the full cap band 48 is formed by sparsely winding the cap band strip 52, which contributes to weight reduction. On the other hand, the full cap band 48 reduces the restraining force provided by the cap band 20. The reduction in restraining force affects the contour of the ground contact surface. If the contact length increases and the contact area increases, there is a concern that heat generation in the tire 2 will be promoted. In this case, the weight reduction of the full cap band 48 does not contribute to the reduction of rolling resistance.

[0070] However, at the end portion of the tread 4 of the tire 2 (hereinafter referred to as the shoulder portion 64), there is an end cap band 50 formed by tightly winding the cap band strip 52. In the tire 2, the end cap band 50 effectively constrains the shoulder portion 64 together with the full cap band 48. The increase in the contact area due to the increase in the contact length can be suppressed, and thus the heat generated due to the increase in the contact area can be suppressed. In the tire 2, the lightweight full cap band 48 can effectively contribute to the reduction of rolling resistance. The tire 2 can achieve a reduction in rolling resistance.

[0071] Since the increase in the contact area can be suppressed, the tire 2 can maintain good responsiveness. The tire 2 can suppress the influence of the lightweight full band 48 on the steering stability. The tire 2 can suppress the influence on the steering stability and achieve a reduction in rolling resistance.

[0072] exist Figure 4 In the figure, reference symbol BT indicates the bottom of the shoulder circumferential groove 24s. The bottom BT of the circumferential groove 24 is shown at the deepest part, but when the bottom extends in the axial direction like the shoulder circumferential groove 24s, the bottom BT is shown at the center.

[0073] In the tire 2, the inner end 62 of the end cap band 50 is arranged to be separated from the bottom BT of the shoulder circumferential groove 24s in the axial direction. In the tire 2, it is possible to prevent the specific deformation from being concentrated on the bottom BT of the shoulder circumferential groove 24s and causing damage such as cracks. The tire 2 can suppress the influence on durability and steering stability and achieve a reduction in rolling resistance.

[0074] In the tire 2, whether the contour of the contact patch has a curvature is determined by the shape index F of the reference contact patch. Figure 5 , the shape index F is explained.

[0075] Figure 5 A model of the contour shape of the reference ground plane is shown. Figure 5 In the figure, the up-down direction corresponds to the circumferential direction of the tire 2, and the left-right direction corresponds to the axial direction of the tire 2. The direction perpendicular to the paper surface corresponds to the radial direction of the tire 2.

[0076] exist Figure 5 In FIG. 1 , the dashed line LP is a straight line corresponding to the equatorial plane of the tire 2 in the reference contact surface. When it is difficult to identify the equatorial plane of the reference contact surface, the axial center line of the reference contact surface is used as the straight line corresponding to the equatorial plane. The double-headed arrow P100 is the length of the intersection line between the plane including the straight line LP and the reference contact surface. In the tire 2, the length P100 of the intersection line is the equatorial contact length measured along the equatorial plane in the reference contact surface.

[0077] exist Figure 5 In the figure, the solid line LM is a straight line that passes through the axial outer end of the reference ground plane (hereinafter referred to as the ground end SE) and is parallel to the straight line LP. The solid line L80 is a straight line that is located between the straight line LM and the straight line LP and is parallel to the straight line LM and the straight line LP. The double-headed arrow A100 indicates the axial distance from the straight line LP to the straight line LM. This distance A100 is equivalent to the maximum width of the reference ground plane, that is, half of the reference ground width. The double-headed arrow A80 indicates the axial distance from the straight line LP to the straight line L80. In the figure, the solid line LM is a straight line that passes through the axial outer end of the reference ground plane (hereinafter referred to as the ground end SE) and is parallel to the straight line LP. Figure 5, the ratio of the distance A80 to the distance A100 is set to 80%. In other words, the straight line L80 indicates a position corresponding to 80% of the reference contact width of the reference contact surface. The double-headed arrow P80 is the length of the intersection line between the plane including the straight line L80 and the reference contact surface. In the tire 2, the length P80 of the intersection line is the reference contact length at the position corresponding to 80% of the reference contact width in the reference contact surface.

[0078] In the tire 2, the ratio of the equatorial contact length P100 to the reference contact length P80 (P100 / P80), which is expressed using the equatorial contact length P100 and the reference contact length P80 specified in the reference contact surface, is used as a shape index F of the contour shape of the reference contact surface. The larger the value of the shape index F, the more the reference contact surface has a curved contour.

[0079] In the tire 2, the shape index F of the reference contact surface is 1.50 or less. As described above, in the tire 2, the cap band 52 is sparsely wound to form the full cap band 48, and on the other hand, the cap band 52 is tightly wound to form the end cap band 50, thereby suppressing the increase in the contact length and the increase in the contact area, thereby suppressing the heat generated by the increase in the contact area. In other words, if the shape index F of the reference contact surface is 1.50 or less, the increase in rolling resistance caused by the rounding of the contact surface can be suppressed. In contrast, if the shape index F is less than 1.10, the wear resistance is reduced. In other words, if the shape index F is 1.10 or more, good wear resistance can be maintained. Therefore, in the tire 2, from the viewpoint of suppressing the influence on wear resistance and achieving a reduction in rolling resistance, the shape index F of the reference contact surface is preferably 1.10 or more, more preferably 1.15 or more, and further preferably 1.20 or more. The shape index F is preferably 1.50 or less, more preferably 1.45 or less, and further preferably 1.40 or less.

[0080] exist Figure 4 In the figure, the length indicated by the double-headed arrow WG is the distance between the cross section of one cap band included in the cross section of the full cap band 48 and the cross section of another cap band located next to the cross section of the one cap band. The distance WG is the size of the gap constituting the full cap band 48. In addition, the state of no gap means that the distance WG is 0.5 mm or less.

[0081] In the tire 2, from the viewpoint of promoting the weight reduction of the full cap band 48 and effectively reducing the rolling resistance, the size WG of the gap of the full cap band 48 is preferably 2 mm or more, more preferably 3 mm or more. From the viewpoint that the full cap band 48 can contribute to the restraining force of the cap band 20, the size WG of the gap is preferably 12 mm or less, more preferably 11 mm or less, and further preferably 10 mm or less.

[0082] exist Figure 4 In the figure, the double-headed arrow WS is the bottom width of the central circumferential groove 24c. The bottom width WS is represented by the distance between the left and right groove walls and the bottom boundary. Figure 4 The central circumferential groove 24c shown has the largest groove width. This central circumferential groove 24c is also called a wide circumferential groove 24w. The bottom width WS of the central circumferential groove 24c is also the bottom width of the wide circumferential groove 24w.

[0083] The gap constituting the full cap band 48 is constituted by the edge 66 of the cap band strip 52. Since the full cap band 48 is constituted by winding the cap band strip 52 in a spiral shape, the edge 66 of the cap band strip 52 is arranged at the bottom portion of the circumferential groove 24. When the size of the gap is wider than the bottom width of the circumferential groove 24, there is a case where only one edge 66 of the two cap band strips constituting the gap is arranged at the bottom portion of the circumferential groove 24. In particular, when only one edge 66 is arranged at the bottom portion of the wide circumferential groove 24w having the largest groove width, the deformation caused by the edge 66 is likely to be concentrated at the bottom portion of the wide circumferential groove 24w, and depending on the degree of the concentration, there is a concern that damage such as cracks may be generated at the bottom portion of the wide circumferential groove 24w.

[0084] However, in the tire 2, the size WG of the gap in the full cap band 48 is narrower than the bottom width WS of the wide circumferential groove 24w. Therefore, two edges 66 of the cap band that constitute the gap are arranged at the bottom portion of the wide circumferential groove 24w. Since the deformation is dispersed in each edge 66, in the tire 2, the concentration of deformation caused by the presence of the edge 66 can be suppressed. Since the damage such as cracks can be prevented from occurring at the bottom portion of the wide circumferential groove 24w, the tire 2 can maintain good durability. From this point of view, in the tire 2, it is preferable that the size WG of the gap in the full cap band 48 is narrower than the bottom width WS of the wide circumferential groove 24w.

[0085] In the tire 2, from the viewpoint of effectively preventing damage such as cracks from being generated at the bottom portion of the wide circumferential groove 24w, the ratio (WG / WS) of the width WG of the gap of the cap band 52 to the bottom width WS of the wide circumferential groove 24w is preferably 0.9 or less, more preferably 0.8 or less, and further preferably 0.7 or less. From the viewpoint of reducing the weight of the full cap band 48, the ratio (WG / WS) is preferably 0.1 or more, more preferably 0.2 or more, and further preferably 0.3 or more.

[0086] exist Figure 4 , the length indicated by the double-headed arrow DS is the axial distance from the end 46 of the belt 14 to the bottom BT of the shoulder circumferential groove 24s. The length indicated by the double-headed arrow DE is the axial distance from the end 46 of the belt 14 to the inner end 62 of the end cap band 50.

[0087] As described above, in the tire 2, the inner end 62 of the end cap band 50 is arranged to be separated from the bottom BT of the shoulder circumferential groove 24s in the axial direction. In particular, in the tire 2, the inner end 62 of the end cap band 50 is located outside the shoulder circumferential groove 24s in the axial direction. In this case, the ratio (DE / DS) of the axial distance DE from the end 46 of the belt 14 to the inner end 62 of the end cap band 50 to the axial distance DS from the end 46 of the belt 14 to the bottom BT of the shoulder circumferential groove 24s is preferably 0.25 or more and preferably 0.90 or less.

[0088] By setting the ratio (DE / DS) to 0.25 or more, the end cap band 50 effectively constrains the shoulder portion 64. Since the increase in the contact area can be suppressed due to the increase in the contact length, the heat generated due to the increase in the contact area can be suppressed. The end cap band 50 contributes to the reduction of rolling resistance. From this point of view, the ratio (DE / DS) is more preferably 0.35 or more, and further preferably 0.50 or more.

[0089] By setting the ratio (DE / DS) to 0.90 or less, the inner end 62 of the end cap band 50 is configured to be sufficiently separated from the shoulder circumferential groove 24s. In the tire 2, it is possible to prevent the specific deformation from being concentrated on the bottom BT portion of the shoulder circumferential groove 24s and causing damage. The end cap band 50 contributes to ensuring durability. From this point of view, the ratio (DE / DS) is more preferably 0.80 or less, and further preferably 0.65 or less.

[0090] exist Figure 4In the tire 2, the length indicated by the double-headed arrow DB is the axial distance from the equatorial plane to the end 46 of the belt 14. In the tire 2, this distance DB is also called the reference width. The position indicated by the reference symbol PB is a position on the tread surface 22 at an axial distance from the equatorial plane equivalent to 0.75 times the reference width DB. In the tire 2, this position PB is also called the reference position. The length indicated by the double-headed arrow DG is the axial distance from the equatorial plane to the outer edge of the shoulder circumferential groove 24s.

[0091] The closer the shoulder circumferential groove 24s is to the end of the tread 4, the more likely it is that deformation is concentrated at the bottom portion of the shoulder circumferential groove 24s. However, in the tire 2, the shoulder circumferential groove 24s is located as a whole at a position inward of the reference position PB in the axial direction, so it is possible to effectively prevent the specific deformation from being concentrated at the bottom BT portion of the shoulder circumferential groove 24s and causing damage. In the tire 2, the influence of the position of the shoulder circumferential groove 24s on durability can be suppressed. From this point of view, in the tire 2, the shoulder circumferential groove 24s is preferably located as a whole at a position inward of the reference position PB in the axial direction.

[0092] In the tire 2, from the viewpoint of ensuring good durability, the ratio (DG / DB) of the axial distance DG from the equatorial plane to the outer edge of the shoulder circumferential groove 24s to the reference width DB is preferably 0.75 or less, more preferably 0.72 or less. From the viewpoint of drainage, the ratio (DG / DB) is preferably 0.55 or more, more preferably 0.60 or more.

[0093] As described above, the cap band 20 of the tire 2 includes the cap band cord 54. In the tire 2, a cord composed of an organic fiber is used as the cap band cord 54. As the organic fiber, nylon fiber, rayon fiber, polyester fiber and aramid fiber are exemplified. From the viewpoint of exerting restraining force, the cap band cord 54 is preferably a cord composed of nylon fiber, or a hybrid cord formed by twisting a strand of nylon fiber with a strand of aramid fiber. In particular, when a hybrid cord is used as the cap band cord 54, even if the cap band strip 52 is sparsely wound to form the full cap band 48, the reduction in restraining force caused by the full cap band 48 can be effectively suppressed. The tire 2 can effectively suppress the influence on durability and handling stability, and achieve a reduction in rolling resistance. From this viewpoint, the cap band cord 54 is more preferably a hybrid cord formed by twisting a strand of nylon fiber with a strand of aramid fiber.

[0094] As described above, in the tire 2, in the axial direction, the inner end 62 of the end cap band 50 is configured to be separated from the bottom BT of the shoulder circumferential groove 24s. Preferably, the gap in the full cap band 48 is configured so that its width WG is narrower than the bottom width WS of the wide circumferential groove 24w. As a result, it is possible to suppress deformation from being concentrated in the bottom portion of the circumferential groove 24, thereby achieving improved durability. Therefore, the tire 2 can adopt a thin tread with a thickness TA of less than 11 mm as the tread 4. The thin tread 4 helps to reduce rolling resistance. From this point of view, in the tire 2, it is more preferred that in the axial direction, the inner end 62 of the end cap band 50 is configured to be separated from the bottom BT of the shoulder circumferential groove 24s, and the size WG of the gap in the full cap band 48 is configured to be narrower than the bottom width WS of the wide circumferential groove 24w.

[0095] Figure 6 A portion of a tire 72 according to another embodiment of the present invention is shown. Figure 6 FIG. 2 shows a portion of a cross section of a tire 72 taken along a plane including the rotation axis of the tire 72. Figure 6 In FIG. 7 , the left-right direction is the axial direction of the tire 72, and the up-down direction is the radial direction of the tire 72. Figure 6 The direction perpendicular to the paper plane is the circumferential direction of the tire 72 .

[0096] In the tire 72, in addition to the structure of the end cap band 74, it has the same Figure 1 The structure of the tire 2 shown is substantially the same as that of the tire 2 shown in FIG. Figure 1 The same elements as those of the tire 2 shown are denoted by the same reference numerals, and description thereof will be omitted.

[0097] Even in the tire 72, Figure 1 Similar to the tire 2 shown, the cap band 20 is formed by winding the cap band strip 52 in a spiral shape, and the cross section of the cap band 20 includes the cross sections of a plurality of cap band strips 52. The full cap band 48 is formed by winding the cap band strip 52 sparsely, so that in the cross section of the full cap band 48, the cross sections of the plurality of cap band strips 52 are arranged side by side with gaps therebetween. The left and right end cap bands 74 are formed by winding the cap band strip 52 tightly, so that in the cross section of the end cap band 74, the cross sections of the plurality of cap band strips 52 are arranged side by side without gaps therebetween.

[0098] In the tire 72, the full cap band 48 formed by sparsely winding the cap band 52 contributes to weight reduction. The end cap band 74 formed by tightly winding the cap band 52 effectively restrains the shoulder portion 64 together with the full cap band 48. Since the ground contact length is suppressed and the ground contact area is increased, heat generation caused by the increase in the ground contact area can be suppressed. In the tire 72, the weight reduction of the full cap band 48 can effectively contribute to the reduction of rolling resistance. The tire 72 can achieve a reduction in rolling resistance.

[0099] In addition, in the tire 72, since the increase in the contact area is suppressed, good responsiveness can be maintained. In the tire 72, the influence of the lightweight full band 48 on the steering stability can be suppressed. The tire 72 can suppress the influence on the steering stability and achieve a reduction in rolling resistance.

[0100] Furthermore, in the tire 72, the inner end 76 of the end cap band 74 is arranged to be separated from the bottom BT of the shoulder circumferential groove 24s in the axial direction. In the tire 72, it is prevented that the abnormal deformation is concentrated on the bottom BT portion of the shoulder circumferential groove 24s and causes damage such as cracks. The tire 72 can suppress the influence on durability and steering stability and achieve a reduction in rolling resistance.

[0101] exist Figure 6 , the length indicated by the double-headed arrow DS is the axial distance from the end 46 of the belt 14 to the bottom BT of the shoulder circumferential groove 24s. The length indicated by the double-headed arrow DE is the axial distance from the end 46 of the belt 14 to the inner end 76 of the end cap band 74.

[0102] As described above, in the tire 72, the inner end 76 of the end cap band 74 is arranged to be separated from the bottom BT of the shoulder circumferential groove 24s in the axial direction. In particular, in the tire 72, the inner end 76 of the end cap band 74 is located on the inner side of the shoulder circumferential groove 24s in the axial direction. In this case, the ratio (DE / DS) of the axial distance DE from the end 46 of the belt 14 to the inner end 76 of the end cap band 74 to the axial distance DS from the end 46 of the belt 14 to the bottom BT of the shoulder circumferential groove 24s is preferably 1.20 or more and preferably 1.55 or less.

[0103] By setting the ratio (DE / DS) to 1.20 or more, the inner end 76 of the end cap band 74 is configured to be sufficiently separated from the shoulder circumferential groove 24s. In the tire 72, it is prevented that the specific deformation is concentrated on the bottom BT portion of the shoulder circumferential groove 24s and causes damage. The end cap band 74 contributes to ensuring durability. From this point of view, the ratio (DE / DS) is more preferably 1.22 or more, and further preferably 1.25 or more.

[0104] By setting the ratio (DE / DS) to 1.55 or less, the length of the end band 74 can be appropriately maintained, thereby suppressing the influence of the mass of the end band 74 on the rolling resistance. In the tire 72, low rolling resistance is maintained. From this viewpoint, the ratio (DE / DS) is more preferably 1.50 or less, and further preferably 1.45 or less.

[0105] As described above, according to the present invention, a tire capable of reducing rolling resistance while suppressing the influence on durability and steering stability is obtained. The present invention has a significant effect, especially in tires with speed signs W or higher according to the JATMA standard.

[0106] [Example]

[0107] Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the present invention is not limited to these Examples.

[0108] [Example 1]

[0109] Get equipped Figure 1 as well as Figure 4 A pneumatic tire for a passenger car having the basic structure shown in FIG. 1 and the specifications shown in Table 1 below (tire size = 215 / 55R17 94W).

[0110] In this embodiment 1, the crown band is used Figure 2 The cap band is formed by winding the cap band strip sparsely. The full cap band (FB) is formed by winding the cap band strip sparsely, and the left and right end cap bands (EB) are formed by winding the cap band strip tightly. This is indicated by "L" in the FB column of Table 1 and by "T" in the EB column. A hybrid cord composed of a strand composed of nylon fiber (structure = 940 dtex / 1) and a strand composed of aramid fiber (structure = 1100 dtex / 1) twisted together is used as the cap band cord.

[0111] The ratio of the size of the gap WG in the full cap to the bottom width WS of the wide circumferential groove (WG / WS) is set to 0.36. The ratio of the axial distance DG from the equatorial plane to the outer edge of the shoulder circumferential groove to the reference width DB (DG / DB) is set to 0.62. The ratio of the axial distance DE from the end of the belt to the inner end of the end cap to the axial distance DS from the end of the belt to the bottom BT of the shoulder circumferential groove (DE / DS) is set to 0.60.

[0112] [Comparative Example 1]

[0113] The tire of Comparative Example 1 was obtained in the same manner as in Example 1 except that the cap band was composed of only the full cap band. In Comparative Example 1, the full cap band was composed of a central portion formed by sparsely winding the cap band strip and a pair of side portions formed by tightly winding the cap band strip. This is indicated by "T+L" in the FB column of Table 1.

[0114] In this comparative example 1, the side portion is equivalent to the end cap band in Example 1, and the axial distance from the end of the belt to the inner end of the side portion is set to 0.60 times the axial distance DS from the end of the belt to the bottom BT of the shoulder circumferential groove. The size of the gap in the central portion is set to 0.36 times the bottom width WS of the wide circumferential groove.

[0115] [Comparative Example 2]

[0116] The tire of Comparative Example 2 was obtained in the same manner as in Example 1 except that the cap strip was wound without leaving a gap to form a full cap strip. The case where the cap strip was tightly wound to form a full cap strip is indicated by "T" in the FB column of Table 1.

[0117] [Comparative Example 3]

[0118] A tire of Comparative Example 3 was obtained in the same manner as in Example 1 except that the distance DE was changed so that the ratio (DE / DS) was as shown in Table 1 below. In Comparative Example 3, the inner end of the end cap band axially coincided with the bottom BT of the shoulder circumferential groove.

[0119] [Example 2]

[0120] The tire of Example 2 was obtained in the same manner as in Example 1 except that the size WG of the gap in the full cap band was changed so that the ratio (WG / WS) was as shown in Table 1 below.

[0121] [Example 3]

[0122] Get equipped Figure 6 A pneumatic tire for a passenger car having the basic structure shown in FIG. 1 and the specifications shown in Table 2 below (tire size = 195 / 55R16 87W).

[0123] Even in this embodiment 3, the crown band is used Figure 2 The cap band is formed by winding the cap band strip sparsely. The full cap band (FB) is formed by winding the cap band strip sparsely, and the left and right end cap bands (EB) are formed by winding the cap band strip tightly. This is indicated by "L" in the FB column of Table 2 and by "T" in the EB column. A hybrid cord consisting of a strand composed of nylon fiber (structure = 940 dtex / 1) and a strand composed of aramid fiber (structure = 1100 dtex / 1) twisted together is used as the cap band cord.

[0124] In this Example 3, the ratio (WG / WS) was set to 0.63, the ratio (DG / DB) was set to 0.72, and the ratio (DE / DS) was set to 1.26.

[0125] [Comparative Example 4]

[0126] A tire of Comparative Example 4 was obtained in the same manner as in Example 3 except that the cap band was composed of only the full cap band. In Comparative Example 4, the full cap band was composed of a central portion formed by sparsely winding the cap band strip and a pair of side portions formed by densely winding the cap band strip, as in Comparative Example 1.

[0127] In this comparative example 4, the size of the gap in the center portion is set to 0.63 times the bottom width WS of the wide circumferential groove. The axial distance from the end of the belt to the inner end of the side portion is set to 1.26 times the axial distance DS from the end of the belt to the bottom BT of the shoulder circumferential groove.

[0128] [Comparative Example 5]

[0129] A tire of Comparative Example 5 was obtained in the same manner as in Example 3 except that the cap band strip was wound without leaving a gap to form a full cap band.

[0130] [Comparative Example 6]

[0131] A tire of Comparative Example 6 was obtained in the same manner as in Example 3 except that the distance DE was changed so that the ratio (DE / DS) was as shown in Table 2 below. In Comparative Example 6, the inner end of the end cap band axially coincided with the bottom BT of the shoulder circumferential groove.

[0132] [Example 4]

[0133] The tire of Example 4 was obtained in the same manner as in Example 3 except that the distance DG was changed so that the ratio (DG / DB) was as shown in Table 2 below.

[0134] [Example 5]

[0135] The tire of Example 5 was obtained in the same manner as in Example 3 except that the size WG of the gap in the full cap band was changed so that the ratio (WG / WS) was as shown in Table 2 below.

[0136] [Handling stability]

[0137] The trial tire was assembled on a regular rim, filled with air and the internal pressure of the tire was adjusted to the regular internal pressure. The tire was mounted on a test vehicle (passenger car), and the test vehicle was driven on a test route on a dry asphalt road. The driver evaluated (sensory evaluation) the handling stability. The results are expressed by indexes in the following Tables 1 and 2. The larger the value, the better the tire is in terms of handling stability.

[0138] [Rolling resistance coefficient (RRC)]

[0139] The rolling resistance coefficient (RRC) of the trial tire when running on a drum at a speed of 80 km / h under the following conditions was measured using a rolling resistance tester. The results are expressed by indexes in the following Tables 1 and 2. The larger the value, the lower the rolling resistance of the tire.

[0140] Examples 1-2 and Comparative Examples 1-3

[0141] Rim: 7.0J

[0142] Internal pressure: 250kPa

[0143] Longitudinal load: 5.88kN

[0144] Examples 3-5 and Comparative Examples 4-6

[0145] Rim: 6.0J

[0146] Internal pressure: 250kPa

[0147] Longitudinal load: 4.82kN

[0148] [Durability]

[0149] Assemble the tire on a regular rim, fill the tire with air and adjust the internal pressure to the regular internal pressure. Install the tire on a drum-type driving test machine. Apply a longitudinal load to the tire and make the tire run on a drum (radius = 1.7m). The driving speed is set to 100km / h. The driving distance until the tire is broken is measured. The results are represented by indexes in the following Tables 1 and 2. The larger the value, the more superior the tire is in terms of durability. In addition, in Examples 1-2 and Comparative Examples 1-3, the longitudinal load is set to 8.86kN. In Examples 3-5 and Comparative Examples 4-6, the longitudinal load is set to 7.33kN.

[0150] [Comprehensive performance]

[0151] The total of the indexes obtained in each evaluation was calculated. The results are shown in the "comprehensive performance" column of the following Table 1 and Table 2. The larger the numerical value, the more preferable it is.

[0152]

Table 1

[0153]

[0154]

Table 2

[0155]

[0156] As shown in Tables 1 and 2, in the examples, the effects on durability and steering stability were suppressed and the rolling resistance was reduced. The superiority of the present invention is clear from the evaluation results.

[0157] [Industrial Applicability]

[0158] The above-described technology for reducing rolling resistance while suppressing the influence on durability and steering stability can also be applied to various tires.

Claims

1. A tire, characterized in that: have: The tread is provided with a plurality of circumferential grooves. a belt located radially inside the tread, and A cap band is located between the tread and the belt in the radial direction and is formed by winding a cap band strip including a plurality of cap band cords arranged in parallel in a spiral shape, The cap band is composed of a full cap band covering the entire belt and a pair of end cap bands arranged to be separated in the axial direction and cover the ends of the belt. The cross section of the cap band includes a plurality of cross sections of the cap band strips, In the cross section of the full cap band, the cross sections of the plurality of cap band strips are arranged side by side with gaps therebetween. In the cross section of each of the end cap bands, the cross sections of the plurality of cap band strips are arranged side by side without any gap. The circumferential groove located on the outer side in the axial direction among the plurality of circumferential grooves is a shoulder circumferential groove, In the axial direction, the inner end of the end cap band is configured to be separated from the bottom of the shoulder circumferential groove. The circumferential groove having the largest groove width among the plurality of circumferential grooves is a wide circumferential groove, The width of the gap is narrower than the bottom width of the wide circumferential groove, The ratio of the width of the gap to the bottom width of the wide circumferential groove is 0.3 or more and 0.7 or less. In the axial direction, the inner end of the end cap band is located on the outer side of the shoulder circumferential groove, and the ratio of the axial distance from the end of the belt to the inner end of the end cap band to the axial distance from the end of the belt to the bottom of the shoulder circumferential groove is greater than 0.25 and less than 0.90, or, in the axial direction, the inner end of the end cap band is located on the inner side of the shoulder circumferential groove, and the ratio of the axial distance from the end of the belt to the inner end of the end cap band to the axial distance from the end of the belt to the bottom of the shoulder circumferential groove is greater than 1.20 and less than 1.

55.

2. The tire according to claim 1, characterized in that The axial distance from the equatorial plane to the end of the belt is the reference width, and the position at the axial distance from the equatorial plane corresponding to 0.75 times the reference width is the reference position. The shoulder circumferential groove is located axially inward of the reference position.

3. The tire according to claim 1 or 2, characterized in that: The band cord is a cord made of nylon fiber, or a hybrid cord obtained by twisting a strand made of nylon fiber and a strand made of aramid fiber.

4. The tire according to claim 1 or 2, characterized in that: In a reference contact surface obtained by assembling a tire on a regular rim, adjusting the internal pressure of the tire to a regular internal pressure, and setting the camber angle of the tire to 0°, applying a regular load to the tire as a longitudinal load and making the tire contact with a flat road surface, The shape index of the reference ground contact surface represented by a ratio of an equatorial ground contact length measured along the equatorial plane to a reference ground contact length at a position corresponding to 80% of a reference ground contact width of the reference ground contact surface is 1.10 or more and 1.50 or less.

Images