pneumatic tires

Abstract

To provide a pneumatic tire which is small in energy loss.SOLUTION: In a pneumatic tire, a belt layer in which a plurality of belts overlap each other is formed outside in a tire radial direction of a carcass ply 12, a tread 13 is provided outside in the tire radial direction of the belt layer, and at least a first belt 21, a second belt 22, and a third belt 23 are provided as belts in order from the bottom. A width of the first belt 21 is 35% or more and 65% or less of a grounding width of the tread 13, and a low-heat-generating rubber member 25 is arranged adjacently in a tire axial direction to the first belt 21, where modulus S100 of the low-heat-generating rubber member 25 is 1.7 MPa or more and 2.4 MPa or less, and tanδ thereof is 0.015 or more and 0.025 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire. [Background technology]

[0002] Pneumatic tires are required to have low energy loss, and particularly, in pneumatic tires having multiple belts provided under the tread, such as those described in Patent Document 1 (such pneumatic tires are generally for heavy loads), low energy loss is strongly required. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 235345 Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, an object of the present invention is to provide a pneumatic tire with small energy loss. [Means for solving the problem]

[0005] In the pneumatic tire of the embodiment, a belt layer in which a plurality of overlapping belts is provided on the tire radially outer side of the carcass ply, and a tread is provided on the tire radially outer side of the belt layer, and the belts are provided in order from bottom to top with at least a first belt, a second belt, and a third belt, in this pneumatic tire, the width of the first belt is 35% to 65% of the contact width of the tread, and a low heat generating rubber member is provided axially adjacent to the first belt, and the low heat generating rubber member is At 25°C Modulus S100 is 1.7 MPa or more and 2.4 MPa or less, and At 23°C It is characterized in that tan δ is 0.015 or more and 0.025 or less. [Effects of the Invention]

[0006] The pneumatic tire of the embodiment has small energy loss because the width of the first belt and the physical property values ​​of the low heat generation rubber member have the above characteristics. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is an axial half cross-sectional view of a pneumatic tire according to an embodiment; [Figure 2] An enlarged view of the belt area in Figure 1. [Figure 3] 1 is a diagram showing the arrangement of cords in a belt according to an embodiment; [Figure 4] Cross-sectional view of the axial end of the first belt. [Figure 5] 1 is a cross-sectional view of a belt and other components during molding of a pneumatic tire. DETAILED DESCRIPTION OF THE INVENTION

[0008] The following embodiments will be described with reference to the drawings. The following embodiments are merely examples, and the scope of the invention is not limited thereto. The following embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The following embodiments and their modifications are within the scope of the invention as set forth in the claims and their equivalents.

[0009] Figure 1 shows the axial cross-sectional structure of a pneumatic tire 10 of the embodiment. The pneumatic tire 10 of the embodiment is a heavy-duty pneumatic tire. Note that Figure 1 shows only half of the tire in the axial direction, and the actual pneumatic tire 10 is symmetrical about the tire center line C except for the tread pattern. The tire axial direction is indicated by arrow A in the figure, and the tire radial direction is indicated by arrow B in the figure.

[0010] The pneumatic tire 10 has bead portions 11 on both axial sides of the tire. The bead portions 11 are made up of a bead core made of a steel wire wound in a ring shape and a rubber bead filler provided radially outside the bead core.

[0011] A carcass ply 12 is laid across the bead portions 11 on both axial sides of the tire. The carcass ply 12 is a sheet-like member in which numerous ply cords arranged in a direction perpendicular to the tire circumferential direction are covered with rubber. The carcass ply 12 forms the skeleton shape of the pneumatic tire 10 between the bead portions 11 on both axial sides of the tire, and wraps around the bead portions 11 by being folded back from the axially inner side to the axially outer side.

[0012] Further, a belt layer consisting of four belts is provided on the radially outer side of the carcass ply 12. The four belts are, in order from the radially inner side of the tire, a first belt 21, a second belt 22, a third belt 23, and a fourth belt 24. The belts 21 to 24 are members made of a large number of steel cords covered with rubber. Details of the belts 21 to 24 will be described later. A low heat generating rubber member 25, which is a rubber sheet, is provided adjacent to the first belt 21 on the axially outer side of the first belt 21.

[0013] The belts 21 to 24 are spaced apart from the carcass ply 12 in the axially outer region of the tire. In the axially outer region of the tire, a wedge-shaped rubber layer 26 having a wedge shape in the axial cross section of the tire is provided between the carcass ply 12 and the belt layer consisting of the belts 21 to 24.

[0014] A tread 13 is provided on the radially outer side of the belts 21 to 24. The tread 13 is provided with a large number of grooves, such as main grooves 14, extending in the tire circumferential direction. In this embodiment, two main grooves 14 are provided on each side of the tire center line C. Sidewalls 15 are provided on both sides of the carcass ply 12 in the tire axial direction. The tread 13 and the sidewalls 15 overlap at buttresses.

[0015] A sheet-like inner liner made of rubber with low air permeability is attached to the inside of the carcass ply 12. Rubber chafers are provided axially outward of the bead portions 11 and radially inward of the sidewalls 15. In addition to the above components, rubber components may be provided as needed.

[0016] The axial center of each of the belts 21 to 24 coincides with the tire centerline C. As shown in Figs. 2 and 3, the belt widths (axial lengths) of the belts increase in the order of the second belt 22, the third belt 23, the first belt 21, and the fourth belt 24.

[0017] The width of the first belt 21 is 35% to 65% of the contact width of the tread 13. Strictly speaking, the tire contact width refers to the axial length of the tire's contact patch when the tire is mounted on a standard rim, pressurized to a standard internal pressure, and subjected to a standard load. The standard rim refers to the rim specified for each tire by the standard system, including the standard on which the tire is based. For example, the standard rim is the standard rim for JATMA, and the "Measuring Rim" is the standard for TRA and ETRTO. The standard internal pressure refers to the air pressure specified for each tire by the standard system, including the standard on which the tire is based. For truck / bus tires and light truck tires, the standard internal pressure is the maximum air pressure for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and the "INFLATION PRESSURE" for ETRTO. The normal load refers to the "maximum load capacity" of JATMA, the maximum value listed in the TRA table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," or the "LOAD CAPACITY" of ETRTO. In the case of a pneumatic tire 10 having the shape shown in FIG. 1, the contact width of the tread 13 is usually the length between the corners 13a (see FIG. 1) of the tread 13 that exist on both sides of the tire in the axial direction.

[0018] An axial end 21a of the first belt 21 is located between the two main grooves 14 and is provided so as to avoid being below the main grooves 14. A low heat-generating rubber member 25 is provided adjacent to the axially outer side of this first belt 21. The hatched portions in Figures 1 and 2 are the low heat-generating rubber members 25.

[0019] The low-heat-generating rubber member 25 is a sheet-like rubber member having the same thickness as the first belt 21 (however, an error of ±1 mm or less is allowed). The low-heat-generating rubber member 25 is made entirely of rubber. As shown in FIGS. 1 and 2 , the axially inner end of the low-heat-generating rubber member 25 is in contact with the axially inner end 21a of the first belt 21. The axially outer end 25a of the low-heat-generating rubber member 25 is axially inner than the axially inner end 22a of the second belt 22 (toward the tire center line C), and is further axially inner than the axially inner end 23a of the third belt 23. The axially outer end 25a of the low-heat-generating rubber member 25 is axially outer than the axially outermost main groove 14.

[0020] This low heat generating rubber member 25 is sandwiched between the carcass ply 12 and the second belt 22 on the axially inner side of the tire, and between the wedge-shaped rubber layer 26 and the second belt 22 on the axially outer side of the tire.

[0021] The width of the second belt 22 is 85% or more and 100% or less of the contact width of the tread 13. The axial end 23a of the third belt 23 is located between the axially outer end 25a of the low heat generating rubber member 25 and the axial end 22a of the second belt 22. The axial distance between the axial end 22a of the second belt 22 and the axial end 23a of the third belt 23 is 10 mm or more and 20 mm or less.

[0022] Furthermore, the axial end 24a of the fourth belt 24 is located axially between the two main grooves 14. The shortest distance (distance indicated by D in FIG. 2) between the axial end 24a of the fourth belt 24 and the groove bottom (more specifically, the flat portion of the groove bottom) of the main groove 14 closer to the axial end 24a is 10 mm or more. Furthermore, the axial distance between the axial end 24a of the fourth belt 24 and the axial end 21a of the first belt 21 is 10 mm or more.

[0023] The wedge-shaped rubber layer 26 is a member made only of rubber. The wedge-shaped rubber layer 26 is made of a different type of rubber from the low heat-generating rubber member 25. Here, different types of rubber mean that at least the physical properties (for example, physical properties including modulus S100 and tan δ) are different. The lower surface of the wedge-shaped rubber layer 26 is in contact with the carcass ply 12. The upper surface of the wedge-shaped rubber layer 26 is in contact with the low heat-generating rubber member 25 on the axially inner side of the tire, with the second belt 22 at the axial center of the tire, and with the tread 13 on the axially outer side of the tire.

[0024] The low heat generating rubber member 25 is made of rubber only and does not have any cords inside. On the other hand, as shown in Fig. 3, each of the belts 21 to 24 has a large number of cords 21c to 24c arranged in parallel.

[0025] The cords 21c to 24c of the belts 21 to 24 are inclined with respect to the tire circumferential direction. Specifically, the cord 21c of the first belt 21 is inclined upward to the left when viewed from the ground contact surface side. The inclination angle θ1 of the cord 21c of the first belt 21 with respect to the tire circumferential direction is 50° or more and 60° or less. The cord 22c of the second belt 22 is inclined upward to the right when viewed from the ground contact surface side. The inclination angle θ2 of the cord 22c of the second belt 22 with respect to the tire circumferential direction is 10° or more and 30° or less. The cord 23c of the third belt 23 is inclined upward to the left when viewed from the ground contact surface side. The inclination angle θ3 of the cord 23c of the third belt 23 with respect to the tire circumferential direction is 10° or more and 30° or less. The cord 24c of the fourth belt 24 is inclined upward to the right when viewed from the ground contact surface side. The inclination angle θ4 of the cord 24c of the fourth belt 24 with respect to the tire circumferential direction is equal to or greater than 10° and equal to or less than 30°.

[0026] As can be seen from this, the cord 21c of the first belt 21 and the cord 22c of the second belt 22 cross each other at an incline in opposite directions relative to the tire circumferential direction, the cord 22c of the second belt 22 and the cord 23c of the third belt 23 cross each other at an incline in opposite directions relative to the tire circumferential direction, and the cord 23c of the third belt 23 and the cord 24c of the fourth belt 24 cross each other at an incline in opposite directions relative to the tire circumferential direction. In this way, the inclination directions of the cords 21c to 24c alternate in the order of the first belt 21 to the fourth belt 24.

[0027] Although not shown in FIGS. 1 to 3, as shown in FIG. 4, the tire axial direction end 21a of the first belt 21 is wrapped with a belt edge rubber 27. The belt edge rubber 27 is a sheet-like member made only of rubber. The belt edge rubber 27 is folded back from the tire radially outer surface of the first belt 21 to the tire radially inner surface. The tire axial direction length L1 of the belt edge rubber 27 on the tire radially inner surface of the first belt 21 is 15 mm or more and 25 mm or less. In addition, the tire axial direction length L2 of the belt edge rubber 27 on the tire radially outer surface of the first belt 21 is 5 mm or more and 15 mm or less. The tire axial direction ends 22a to 24a of the second belt 22 to the fourth belt 24 may also be wrapped with the belt edge rubber.

[0028] The rubber of each member has desirable physical property values. First, the low heat generation rubber member 25 has a modulus S100 of 1.7 MPa or more and 2.4 MPa or less, and a tan δ of 0.015 or more and 0.025 or less. The wedge-shaped rubber layer 26 has a modulus S100 of 2.1 MPa or more and 3.5 MPa or less, and a tan δ of 0.025 or more and 0.050 or less. The belt edge rubber 27 has a modulus S100 of 3.8 MPa or more and 4.6 MPa or less, and a tan δ of 0.11 or more and 0.13 or less.

[0029] The tread 13 has a modulus S100 of 1.7 MPa or more and 3.8 MPa or less and a tan δ of 0.05 or more and 0.2 or less. The sidewall 15 has a modulus S100 of 1.8 MPa or more and 2.3 MPa or less and a tan δ of 0.05 or more and 0.2 or less. The rubber used in the belts 21 to 24 (belt topping rubber) has a modulus S100 of 5.0 MPa or more and 5.4 MPa or less and a tan δ of 0.10 or more and 0.13 or less. The rubber used in the carcass ply 12 (ply topping rubber) has a modulus S100 of 4.4 MPa or more and 4.8 MPa or less and a tan δ of 0.12 or more and 0.13 or less.

[0030] The modulus S100 is a value measured in accordance with JIS K6251:2010 3.7, specifically, the tensile force when the test piece is elongated by 100% divided by the initial cross-sectional area of ​​the test piece. The test piece is a dumbbell No. 3, and the ambient temperature during measurement is 25°C. The loss tangent tanδ is a value measured in accordance with JIS K6394:2007, specifically, at a temperature of 23°C, a frequency of 20 Hz, and an elongation strain rate of 10%±2%.

[0031] In the manufacturing process of such a pneumatic tire 10, as shown in Figure 5, a wedge-shaped rubber layer 26 is attached onto the carcass ply 12, and a low-heat-generating rubber member 25 is attached so as to cover the axially inner end 26a of the wedge-shaped rubber layer 26.

[0032] Furthermore, the first belt 21 is attached onto the carcass ply 12. At this time, a portion of the first belt 21 near the tire axial end 21a and a portion of the low heat-generating rubber member 25 near the tire axially inner end 25b are arranged to overlap in the vertical direction. As a result, the portion of the low heat-generating rubber member 25 near the tire axially inner end 25b is crushed by the first belt 21 during molding, making it less likely that an air pocket will be formed between the first belt 21 and the low heat-generating rubber member 25 after molding.

[0033] Furthermore, second belts 22 to 4 belts 24 and tread 13 are laminated on top of first belt 21, and components such as sidewalls 15 are also attached to complete a green tire. When the green tire is subjected to vulcanization molding, a pneumatic tire 10 is completed.

[0034] In the pneumatic tire 10 of this embodiment, the width of the first belt 21 is 35% or more of the contact width of the tread 13, thereby maintaining the restraining force of the first belt 21. On the other hand, the width of the first belt 21 is short, at 65% or less of the contact width of the tread 13, thereby reducing energy loss. Specifically, because the width of the first belt 21 is short, the amount of heat generated between the first belt 21 and the second belt 22 and between the first belt 21 and the carcass ply 12 is reduced. In addition, a rubber portion without the first belt 21 is formed between the carcass ply 12 and the second belt 22, and this rubber portion buffers deformation of the carcass ply 12, thereby reducing hysteresis loss. For these reasons, the short width of the first belt 21 reduces energy loss. And, because energy loss is reduced, rolling resistance is reduced.

[0035] Additionally, a low heat-generating rubber member 25 is provided axially adjacent to the shortened first belt 21. This low heat-generating rubber member 25 has a modulus S100 of 1.7 MPa or more and 2.4 MPa or less and a tan δ of 0.015 or more and 0.025 or less, thereby further reducing energy loss. In particular, the modulus S100 being 1.7 MPa or more maintains the durability of the low heat-generating rubber member 25, and the modulus S100 being 2.4 MPa or less reduces energy loss. Furthermore, the tan δ being 0.015 or more prevents the modulus S100 value from becoming too low, and the tan δ being 0.025 or less reduces the amount of heat generated, thereby reducing energy loss.

[0036] In addition, if the low heat-generating rubber member 25 in this embodiment were a belt instead of the low heat-generating rubber member 25, as described above, the belt topping rubber and the flat topping rubber have larger modulus S100 and tan δ than the low heat-generating rubber member 25, resulting in greater energy loss.

[0037] Furthermore, since the low-heat-generating rubber member 25 is made of a different rubber from the wedge-shaped rubber layer 26, the physical properties of the low-heat-generating rubber member 25 can be determined separately from the physical properties required for the wedge-shaped rubber layer 26. Therefore, the physical property values ​​of the low-heat-generating rubber member 25 can be set within the above-mentioned ranges.

[0038] In detail, the low heat-generating rubber member 25 is less susceptible to the influence of the movement of the carcass ply 12 during tire rolling than the wedge-shaped rubber layer 26, and therefore the influence on durability of the low heat-generating rubber member 25 does not need to be as important as that of the wedge-shaped rubber layer 26. Therefore, a rubber with a lower modulus S100 and tan δ can be used as the low heat-generating rubber member 25.

[0039] Furthermore, the wedge-shaped rubber layer 26 has a modulus S100 of 2.1 MPa or more and 3.5 MPa or less and a tan δ of 0.025 or more and 0.050 or less, thereby further reducing the energy loss of the pneumatic tire 10. Specifically, the modulus S100 of 2.1 MPa or more maintains the durability of the wedge-shaped rubber layer 26, and the modulus S100 of 3.5 MPa or less reduces energy loss. Furthermore, the tan δ of 0.025 or more prevents the modulus S100 value from becoming too low, and the tan δ of 0.050 or less reduces the amount of heat generated, thereby reducing energy loss. Note that these values ​​of modulus S100 and tan δ are smaller than the values ​​of modulus S100 and tan δ of the wedge-shaped rubber layer of a typical pneumatic tire.

[0040] Furthermore, cord 21c of first belt 21 and cord 22c of second belt 22 intersect at an inclination in opposite directions relative to the tire circumferential direction, cord 22c of second belt 22 and cord 23c of third belt 23 intersect at an inclination in opposite directions relative to the tire circumferential direction, and cord 23c of third belt 23 and cord 24c of fourth belt 24 intersect at an inclination in opposite directions relative to the tire circumferential direction, so that the binding force of belts 21 to 24 is increased and rolling resistance is reduced.

[0041] Furthermore, since the tire axial end 21a of the first belt 21 is wrapped with the belt edge rubber 27, separation originating from the tire axial end 21a of the first belt 21 is less likely to occur, increasing the durability of the pneumatic tire 10.

[0042] Here, the belt edge rubber 27 has a modulus S100 of 3.8 MPa or more, which can further mitigate the effects of deformation of the surrounding rubber, and a modulus S100 of 4.6 MPa or less, which can prevent strain from concentrating between the cord 21c of the first belt 21 and the topping rubber around it. As a result, durability near the tire axial end 21a of the first belt 21 can be further maintained.

[0043] Furthermore, the belt closest to the contact surface of the tread 13 is the fourth belt 24, but the axial end 24a of the fourth belt 24 is at least 10 mm away from the bottom of the main groove 14 at the shortest distance, so cracks are unlikely to occur from the axial end 24a of the fourth belt 24 toward the bottom of the main groove 14.

[0044] Furthermore, since the axial end 24a of the fourth belt 24 is spaced apart from the axial ends of the other belts in the tire axial direction, no extreme difference in rigidity occurs in the tread 13. The axial end 21a of the first belt 21 is closest to the axial end 24a of the fourth belt 24 in the tire axial direction, but since the axial end 24a of the fourth belt 24 is spaced apart from the axial end 21a of the first belt 21 in the tire axial direction by 10 mm or more, no extreme difference in rigidity occurs in the tread 13.

[0045] Various modifications can be made to the above embodiment. For example, the belt layer may be provided with only three belts, the first belt 21 to the third belt 23. In this case, the cords 21c to 23c of the first belt 21 to the third belt 23 have the same characteristics as described above. Furthermore, when the fourth belt 24 is provided as described above, the cord 24c of the fourth belt 24 may be inclined upward to the left when viewed from the ground contact surface side. [Explanation of symbols]

[0046] 10...pneumatic tire, 11...bead portion, 12...carcass ply, 13...tread, 13a...corner portion, 14...main groove, 15...sidewall, 21...first belt, 21a...tire axial end, 21c...cord, 22...second belt, 22a...tire axial end, 22c...cord, 23...third belt, 23a...tire axial end, 23c...cord, 24...fourth belt, 24a...tire axial end, 24c...cord, 25...low heat generation rubber member, 25a...tire axial outer end, 25b...tire axial inner end, 26...wedge-shaped rubber layer, 26a...tire axial inner end, 27...belt edge rubber

Claims

1. A pneumatic tire having a belt layer in which a plurality of overlapping belts are provided on the tire radially outer side of a carcass ply, a tread is provided on the tire radially outer side of the belt layer, and the belts are provided in order from bottom to top with at least a first belt, a second belt, and a third belt, The width of the first belt is 35% or more and 65% or less of the ground contact width of the tread, a low heat-generating rubber member is provided adjacent to the first belt in the tire axial direction, and the low heat-generating rubber member has a modulus S100 at 25°C of 1.7 MPa or more and 2.4 MPa or less and a tan δ at 23°C of 0.015 or more and 0.025 or less.

2. 2. The pneumatic tire according to claim 1, wherein a wedge-shaped rubber layer is provided between the carcass ply and the belt layer on both sides in the tire axial direction, and the low heat generation rubber member is a sheet-shaped member made of a rubber different from the wedge-shaped rubber layer.

3. 3. The pneumatic tire according to claim 1, wherein each of the belts includes a plurality of cords inclined with respect to the tire circumferential direction, the cords of the first belt and the cords of the second belt intersect with each other at an angle in opposite directions with respect to the tire circumferential direction, and the cords of the second belt and the cords of the third belt intersect with each other at an angle in opposite directions with respect to the tire circumferential direction.

4. The pneumatic tire according to any one of claims 1 to 3, wherein an end of the first belt in the tire axial direction is wrapped with a belt edge rubber.

5. 5. The pneumatic tire according to claim 1, wherein a fourth belt is provided on the third belt, and an axial end of the fourth belt is 10 mm or more away from a groove bottom of a main groove formed in the tread at the shortest distance, and is 10 mm or more away from an axial end of the first belt in the tire axial direction.

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