JP2017128201A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire 2 achieving excellent handling performance and small rolling resistance.SOLUTION: A tread 4 of the tire 2 comprises a base layer 26, a main part 52 and a pair of sub parts 54. A loss tangent of the main part 52 is larger than loss tangents of the sub parts 54. A loss tangent of the base layer 26 is smaller than the loss tangents of the sub parts 54. Interfaces 62 between the main part 52 and the sub parts 54 incline with respect to a radial direction, and terminals 66 of the interfaces 62 are positioned closer to inside in a shaft direction than starting ends 64 thereof. When an outermost layer of a belt 14 is designated as a reference layer 46, an interface 62a between the main part 52 and a first sub part 54a is designated as a first main interface and an interface 62b between the main part 52 and a second sub part 54b is designated as a second main interface, a starting end 64a of the first main interface 62a is positioned closer to outside than a first end 68a of the reference layer 46 and a starting end 64b of the second main interface 62b is positioned closer to inside than a second end 68b of the reference layer 46.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire.

  There are moves to reduce the impact of tires on fuel consumption and to consider the environment. In this movement, for example, a tire having a small rolling resistance is being developed from a material or structural aspect. Examination examples related to such tires are disclosed in Japanese Patent Application Laid-Open Nos. 2015-089683, 2015-128912, and 2015-131599.

Japanese Patent Application Laid-Open No. 2015-089683 JP2015-128912A JP-A-2015-131599

  The tire is configured by combining members such as a tread and a sidewall. In order to effectively reduce the rolling resistance, the ratio of each member contributing to the rolling resistance (also referred to as a contribution rate) may be examined. For example, in a tire whose size is represented by 195 / 65R15, it is estimated that the contribution rate of the tread is 40%. This trial calculation result shows that the contribution ratio of the sidewall is 13%, and the influence of the tread on the rolling resistance is considerably large.

  As a means for reducing the rolling resistance of a tire, it is common to employ rubber having a small loss tangent. According to the above-described calculation results, if the tread is made of rubber having a small loss tangent, it is expected that the rolling resistance can be greatly reduced. However, rubber with a small loss tangent affects the grip performance. For this reason, when a tread is comprised with rubber | gum with a small loss tangent, there exists a possibility that handling performance may be impaired.

  An object of the present invention is to provide a pneumatic tire in which rolling resistance is reduced without impairing handling performance.

  The pneumatic tire according to the present invention includes a tread and a belt. The belt is located on the inner side in the radial direction of the tread, and includes a plurality of layers stacked in the radial direction. The tread includes a base layer and a cap layer located on the radially outer side of the base layer. The cap layer is composed of a main part and a pair of subparts. Each sub-part is located outside the main part in the axial direction. The loss tangent of the main part is larger than the loss tangent of the subpart. The loss tangent of the base layer is smaller than the loss tangent of this subpart. The base layer includes a pair of side surfaces that form a part of the outer surface of the tread, and bridges between one first side surface and the other second side surface. The main part includes a center surface forming another part of the outer surface of the tread. The subpart includes a middle surface that forms still another part of the outer surface of the tread. The interface between the main part and the sub part is inclined with respect to the radial direction. When the boundary between the center surface and the middle surface is the start point of the interface, the end of the interface is located on the inner side in the axial direction from the start point. Out of the plurality of layers constituting the belt, the outermost layer is a reference layer, the interface between the main part and one first subpart is a first main interface, and the main part and the other second subpart. Is the second main interface, the starting end of the first main interface is located outside the first end of the reference layer in the axial direction. In the axial direction, the start end of the second main interface is located inside the second end of the reference layer.

  Preferably, in this pneumatic tire, the loss tangent of the main part is 0.18 or more and 0.22 or less.

  Preferably, in this pneumatic tire, the loss tangent of the subpart is 0.14 or more and 0.18 or less.

  Preferably, in this pneumatic tire, the loss tangent of the base layer is 0.10 or more and 0.14 or less.

  Preferably, in this pneumatic tire, the ratio of the axial distance from the equator plane to the start point of the first main interface with respect to half the axial width of the reference layer is 102% or more and 115% or less. The ratio of the axial distance from the equator plane to the starting point of the second main interface with respect to half the axial width of the reference layer is 85% or more and 98% or less.

  Preferably, in this pneumatic tire, the ratio of the length of the middle surface to the length from the boundary between the center surface and the middle surface to the end of the outer surface of the tread is 5% or more and 50% or less.

  Preferably, in this pneumatic tire, the inclination angle of the interface between the main part and the sub part is 30 ° or more and 80 ° or less.

  Preferably, in this pneumatic tire, the inclination angle of the first main interface is smaller than the inclination angle of the second main interface.

  In the pneumatic tire according to the present invention, the tread includes a main part, a pair of subparts, and a base layer. The outer surface of the tread includes a first side surface of the base layer, a first middle surface of the first subpart, a center surface of the main part, a second middle surface of the second subpart, and a second side surface of the base layer.

  In this tire, the loss tangent of the main part is larger than the loss tangent of the subpart, and the loss tangent of the base layer is smaller than the loss tangent of this subpart. In other words, the main part mainly contributes to handling performance, the base layer mainly contributes to reduction of rolling resistance, and the subpart intermediate between the main part and the base layer regarding handling performance and rolling resistance. Important contributions are considered.

  In this tire, the base layer is disposed so as to bridge the first side surface and the second side surface. In this tire, the volume of the base layer is sufficiently secured. This base layer contributes to a reduction in rolling resistance. In addition, since the side surface of the base layer is located outside the middle surface, the side surface hardly comes into contact with the road surface in the running state. In this tire, the influence of the base layer on the handling performance is suppressed.

  In this tire, the interface between the main part and the sub part is inclined with respect to the radial direction. The end of this interface is located on the inner side in the axial direction than the starting point. In the boundary portion between the main part and the sub part of the tire, the main part is widely arranged on the outer surface side of the tread, and the sub part is widely arranged on the inner surface side thereof. This tire has excellent handling performance and low rolling resistance at the beginning of use. Even if the tread wears and the volume of the main part is reduced, the thin tread contributes to the cornering power. For this reason, in this tire, even if the tread is worn by use, the handling performance is appropriately maintained. In addition, since the volume of the subpart is secured toward the inner side, a small rolling resistance can be appropriately maintained.

  Furthermore, in this tire, the outermost layer of the plurality of layers constituting the belt is used as a reference layer, and the interface between the main part and the first subpart is defined as the first main interface. Is the second main interface, the starting end of the first main interface is located outside the first end of the reference layer in the axial direction. In the axial direction, the start end of the second main interface is located inside the second end of the reference layer. In this tire, the center surface of the main part is closer to the first end side than the second end side of the reference layer. For this reason, the mounting performance can be further improved by mounting the tire on a vehicle such that the first end of the reference layer is located on the outside. In addition, since the middle part of the subpart is located between the center and side surfaces, this subpart has an effect on handling performance and rolling resistance even if the position and width of the grounding surface change. Suppress it. In this tire, it is possible to effectively reduce rolling resistance while maintaining good handling performance.

  Thus, in this tire, reduction in rolling resistance is achieved without impairing handling performance. In other words, according to the present invention, it is possible to obtain a pneumatic tire in which a reduction in rolling resistance is achieved without impairing handling performance.

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 an enlarged cross-sectional view showing a part of the tire of FIG. FIG. 3 is an enlarged cross-sectional view showing another part of the tire of FIG. 1.

  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 clinch 8, a pair of beads 10, a carcass 12, a belt 14, a band 16, an inner liner 18, and a pair of chafers 20. The tire 2 is a tubeless type. The tire 2 is mounted on a passenger car.

  The tread 4 has a shape protruding outward in the radial direction. The tread 4 forms a tread surface 22 that contacts the road surface. A groove 24 is carved in the tread 4. The groove 24 forms a tread pattern. The tread 4 has a base layer 26 and a cap layer 28. The cap layer 28 is located on the outer side in the radial direction of the base layer 26.

  In the tire 2, the tread 4 further includes a pair of wings 30. Each wing 30 is located on the axially outer side of the portion composed of the base layer 26 and the cap layer 28. In the tire 2, the wing 30 is located between the base layer 26 and the sidewall 6. The wing 30 is bonded to each of the base layer 26 and the sidewall 6 of the tread 4. The wing 30 is made of a crosslinked rubber having excellent adhesiveness.

  Each sidewall 6 extends substantially inward in the radial direction from the end 32 of the tread 4. A radially outer portion of the sidewall 6 is joined to the tread 4. The radially inner portion of the sidewall 6 is joined to the clinch 8. This sidewall 6 is made of a crosslinked rubber having excellent cut resistance and weather resistance. This sidewall 6 prevents the carcass 12 from being damaged.

  Each clinch 8 is located substantially inside the sidewall 6 in the radial direction. The clinch 8 is located outside the beads 10 and the carcass 12 in the axial direction. The clinch 8 is made of a crosslinked rubber having excellent wear resistance. The clinch 8 is in contact with a flange of a rim (not shown).

  Each bead 10 is located inside the clinch 8 in the axial direction. The bead 10 includes a core 34 and an apex 36 that extends radially outward from the core 34. The core 34 is ring-shaped and includes a wound non-stretchable wire. A typical material for the wire is steel. The apex 36 is tapered outward in the radial direction. The apex 36 is made of a highly hard crosslinked rubber.

  The carcass 12 includes a carcass ply 38. In the tire 2, the carcass 12 includes a single carcass ply 38. The carcass 12 may be composed of two or more carcass plies 38.

  In the tire 2, the carcass ply 38 is bridged between the beads 10 on both sides and is along the tread 4 and the sidewall 6. The carcass ply 38 is folded around the core 34 from the inner side to the outer side in the axial direction. Due to this folding, a main portion 40 and a folding portion 42 are formed in the carcass ply 38.

  Although not shown, the carcass ply 38 includes a large number of cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each cord with respect to the equator plane is 75 ° to 90 °. In other words, the carcass 12 has a radial structure. The cord is made of organic fiber. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The belt 14 is located on the inner side in the radial direction of the tread 4. The belt 14 is laminated with the carcass 12. The belt 14 reinforces the carcass 12.

  The belt 14 includes a plurality of layers stacked in the radial direction. In the tire 2, the belt 14 includes an inner layer 44 and an outer layer 46. The belt 14 is composed of two layers. In the tire 2, the inner layer 44 is the innermost layer of the belt 14, and the outer layer 46 is the outermost layer of the belt 14.

  As apparent from FIG. 1, the width of the inner layer 44 is slightly larger than the width of the outer layer 46 in the axial direction. In the tire 2, the axial width of the belt 14 is represented by the axial width of the inner layer 44. The axial width of the belt 14 is preferably 0.6 times or more, and preferably 0.9 times or less the cross-sectional width of the tire 2 (see JATMA). The length of the inner layer 44 protruding from the outer layer 46 (also referred to as a step length) is preferably 3 mm or more, and preferably 15 mm or less.

  Although not shown, each of the inner layer 44 and the outer layer 46 is composed of a plurality of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equator plane. The general absolute value of the tilt angle is 10 ° or more and 35 ° or less. The inclination direction of the cord of the inner layer 44 with respect to the equator plane is opposite to the inclination direction of the cord of the outer layer 46 with respect to the equator plane. A preferred material for the cord is steel. An organic fiber may be used for the cord.

  The band 16 is located on the radially outer side of the belt 14. In the axial direction, the width of the band 16 is larger than the width of the belt 14. Although not shown, the band 16 is composed of a cord and a topping rubber. The cord is wound in a spiral. The band 16 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The angle of the cord with respect to the circumferential direction is 5 ° or less, and further 2 ° or less. Since the belt 14 is restrained by this cord, lifting of the belt 14 is suppressed. The cord is made of organic fiber. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The inner liner 18 is located inside the carcass 12. The inner liner 18 is joined to the inner surface of the carcass 12. 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.

  Each chafer 20 is located in the vicinity of the bead 10. When the tire 2 is incorporated in the rim, the chafer 20 comes into contact with the rim. By this contact, the vicinity of the bead 10 is protected. In this embodiment, the chafer 20 is made of cloth and rubber impregnated in the cloth. The chafer 20 may be integrated with the clinch 8. In this case, the material of the chafer 20 is the same as that of the clinch 8.

  As described above, the tread 4 of the tire 2 has the base layer 26 and the cap layer 28. As is apparent from FIG. 1, the base layer 26 extends continuously in the axial direction from the one end 32 a side of the tread 4 toward the other end 32 b side. The base layer 26 is made of a crosslinked rubber.

  In the tire 2, the cap layer 28 is laminated with the base layer 26. As apparent from FIG. 2, the interface 48 (also referred to as a boundary line) between the cap layer 28 and the base layer 26 intersects with the outer surface 50 of the tread 4. In the tire 2, the cap layer 28 includes a main part 52 and a pair of subparts 54. In the tire 2, the end of the outer surface 50 of the tread 4 is the end 32 of the tread 4. In the tire 2, the outer surface 50 of the tread 4 is a portion from one end 32 a of the tread 4 to the other end 32 b of the outer surface of the tire 2.

  The main part 52 extends substantially continuously in the axial direction from the one end 32a side of the tread 4 toward the other end 32b side. The main part 52 is located on the equator plane portion of the tire 2. As is clear from FIG. 1, the groove 24 described above is cut into the main part 52. The groove 24 does not penetrate the main part 52. A main part 52 is located between the groove 24 and the base layer 26. The main part 52 is made of a crosslinked rubber.

  Each of the subparts 54 is located outside the main part 52 in the axial direction. The main part 52 is located at the shoulder portion of the tire 2. As is clear from FIG. 1, a part of the base layer 26 is sandwiched between the subpart 54 and the wing 30. The subpart 54 is made of a crosslinked rubber.

  In the tire 2, the outer surface 56 of the main part 52 forms a part of the outer surface 50 of the tread 4. In the present invention, the outer surface 56 of the main part 52 is referred to as a center surface. The main part 52 includes a center surface 56 that forms a part of the outer surface 50 of the tread 4.

  In the tire 2, the outer surface 58 of the subpart 54 also forms part of the outer surface 50 of the tread 4. In the present invention, the outer surface 58 of the subpart 54 is referred to as a middle surface. The subpart 54 includes a middle surface 58 that forms a part of the outer surface 50 of the tread 4. In the tire 2, subparts 54 are provided on the left and right. In particular, the middle surface 58a of the first subpart 54a located on the one end 32a side of the tread 4 is referred to as a first middle surface. The middle surface 58b of the second subpart 54b located on the other end 32b side of the tread 4 is referred to as a second middle surface.

  In the tire 2, the base layer 26 also includes a surface 60 that forms a part of the outer surface 50 of the tread 4. In the present invention, the surface 60 that forms a part of the outer surface 50 of the tread 4 of the base layer 26 is referred to as a side surface. As is apparent from FIG. 1, the base layer 26 is provided with two side surfaces 60. In other words, the base layer 26 includes a pair of side surfaces 60 that form a part of the outer surface 50 of the tread 4. Of the pair of side surfaces 60, the side surface 60a located on the one end 32a side of the tread 4 is referred to as a first side surface. The side surface 60b located 32b on the other end side of the tread 4 is referred to as a second side surface.

  In the tire 2, the outer surface 50 of the tread 4 includes a center surface 56, a pair of middle surfaces 58, and a pair of side surfaces 60. Each of the first middle surface 58 a and the second middle surface 58 b is located outside the center surface 56 in the axial direction. The first side surface 60a is located on the outer side in the axial direction of the first middle surface 58a. The second side surface 60b is located on the outer side in the axial direction of the second middle surface 58b.

  In the tire 2, the tread 4 includes a main part 52, a pair of subparts 54, and a base layer 26. The outer surface 50 of the tread 4 includes a first side surface 60a of the base layer 26, a first middle surface 58a of the first subpart 54a, a center surface 56 of the main part 52, a second middle surface 58b of the second subpart 54b, and a base layer. 26 second side surfaces 60b are provided.

  The tire 2 steps on the road surface mainly at the center surface 56. When the internal pressure of the tire 2 changes, when the load applied to the tire 2 changes, the middle surface 58 may come into contact with the road surface. The side surface 60 hardly contacts the road surface.

  In the tire 2, the loss tangent LTm of the main part 52 is larger than the loss tangent LTs of the subpart 54, and the loss tangent LTb of the base layer 26 is smaller than the loss tangent LTs of the subpart 54. That is, of the main part 52, the pair of subparts 54, and the base layer 26, the loss tangent LTm of the main part 52 is the largest, and the loss tangent LTb of the base layer 26 is the smallest. The loss tangent LTs of the subpart 54 is between the loss tangent LTm of the main part 52 and the loss tangent LTb of the base layer 26. A crosslinked rubber having a large loss tangent contributes to an improvement in grip performance, and a crosslinked rubber having a small loss tangent contributes to a reduction in rolling resistance. In the tire 2, the main part 52 mainly considers contribution to handling performance. In the base layer 26, the contribution to the reduction of rolling resistance is mainly considered. And in the subpart 54, the intermediate contribution of the main part 52 and the base layer 26 is considered regarding handling performance and rolling resistance.

In the present invention, the loss tangent (tan δ) is measured in accordance with the provisions of “JIS K 6394”. In this measurement, a plate-shaped test piece (length = 45 mm, width = 4 mm, thickness = 2 mm) is used. This test piece may be cut out from the tire 22, or a sheet may be prepared from the rubber composition and cut out from the sheet. The conditions for this measurement are as follows.
Viscoelastic spectrometer: "VESF-3" from Iwamoto Seisakusho
Initial strain: 10%
Dynamic strain: ± 1%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 30 ° C

  As is apparent from FIG. 1, in the tire 2, the base layer 26 bridges between the first side surface 60a and the second side surface 60b. In other words, the base layer 26 is disposed so as to bridge the first side surface 60a and the second side surface 60b. In the tire 2, the volume of the base layer 26 is sufficiently secured. This base layer 26 contributes to reduction of rolling resistance. Moreover, since the side surface 60 of the base layer 26 is located outside the middle surface 58, the side surface 60 hardly comes into contact with the road surface in the running state. In the tire 2, the influence on the handling performance by the base layer 26 is suppressed.

  In the tire 2, the interface 62 between the main part 52 and the sub part 54 is inclined with respect to the radial direction. When the boundary 64 between the center surface 56 and the middle surface 58 is the start end of the interface 62, the end 66 of the interface 62 is located on the inner side in the axial direction than the start end 64. As a result, at the boundary between the main part 52 and the subpart 54 of the tire 2, the main part 52 is widely arranged on the outer surface side of the tread 4 and the subpart 54 is widely arranged on the inner surface side thereof. Is done. The tire 2 is excellent in handling performance at the time of start of use and has a small rolling resistance. Even if the tire 2 is worn by use and the volume of the main part 52 is reduced, the thin tread 4 contributes to the cornering power. For this reason, in this tire 2, even if the volume of the main part 52 is reduced due to wear, the handling performance is appropriately maintained. Moreover, since the volume of the subpart 54 is secured toward the inner side, a small rolling resistance can be appropriately maintained.

  The outermost layer 46 of the belt 14 is located closest to the outer surface 50 of the tread 4 among the layers constituting the belt 14. The outermost layer 46 affects the ground contact shape of the tread 4. In view of this point, the inventors examined the position of the interface 62 between the main part 52 and the subpart 54 with respect to the end 68 of the outermost layer 46, and depending on the position of the interface 62 with respect to the end 68 of the outermost layer 46. The handling performance and rolling resistance of the tire 2 change, that is, the knowledge that the handling performance and rolling resistance can be adjusted in a well-balanced manner by adjusting the position of the interface 62 has been obtained. The following effects are based on this finding.

  As shown in FIG. 1, in the tire 2, the outermost layer 46 of the belt 14 is a reference layer, and an interface 62a between the main part 52 and the first subpart 54a is a first main interface. When the interface 62b with the second subpart 54b is the second main interface, the start end 64a of the first main interface 62a is located outside the first end 68a of the reference layer 46 in the axial direction. In the axial direction, the start end 64b of the second main interface 62b is located inside the second end 68b of the reference layer 46. In the tire 2, the center surface 56 of the main part 52 is closer to the first end 68 a side than the second end 68 b side of the reference layer 46.

  In the tire 2 mounted on a vehicle, specifically a four-wheeled vehicle, one side is located on the outer side in the width direction of the vehicle (also referred to as OUT side or S side) across the equator plane, and the other side is It is located on the inner side in the width direction of the vehicle (also called the IN side or NS side). The tire 2 having a camber angle set to a negative camber steps on the road surface mainly in the IN side portion of the tread 4 during straight traveling. In turning traveling, the ground contact surface may move to the OUT side depending on the turning direction. For this reason, it is possible to further improve the handling performance by mounting the tire 2 on the vehicle so that the first end 68a of the reference layer 46 is located outside. Further, since the middle surface 58 of the subpart 54 is disposed between the center surface 56 and the side surface 60, even if the position of the grounding surface, the width thereof, and the like change, the subpart 54 has handling performance and rolling resistance. Effectively control the impact on In the tire 2, it is possible to effectively reduce rolling resistance while maintaining good handling performance.

  Thus, in the tire 2, reduction in rolling resistance is achieved without impairing handling performance. In other words, according to the present invention, it is possible to obtain the pneumatic tire 2 in which reduction of rolling resistance is achieved without impairing handling performance.

  In the tire 2, the loss tangent LTm of the main part 52 is preferably 0.18 or more. The tire 2 having the main part 52 is excellent in handling performance. In the tire 2, the loss tangent LTm is preferably 0.22 or less. Thereby, the influence on the rolling resistance by the main part 52 is suppressed.

  In the tire 2, the loss tangent LTs of the subpart 54 is preferably 0.14 or more. The subpart 54 effectively contributes to improving the handling performance of the tire 2. In the tire 2, the loss tangent LTs is preferably 0.18 or less. Thereby, the influence on the rolling resistance by the subpart 54 is suppressed.

  In the tire 2, the loss tangent LTb of the base layer 26 is preferably 0.10 or more. Thereby, the influence on the handling performance by the base layer 26 is effectively suppressed. In the tire 2, the loss tangent LTb is preferably 0.14 or less. The base layer 26 effectively contributes to reduction of rolling resistance.

  In FIG. 1, a double arrow WB1 represents an axial distance from the equator plane to the first end 68a of the reference layer 46. A double-headed arrow WB2 represents the axial distance from the equator plane to the second end 68b of the reference layer 46. In the tire 2, the equator plane passes through the center of the reference layer 46 in the axial direction. Therefore, the distance WB1 and the distance WB2 are each equal to half the axial width of the reference layer 46. In FIG. 1, a double arrow WM1 represents an axial distance from the equator plane to the boundary between the center surface 56 and the first middle surface 58a, that is, the starting end 64a of the first main interface 62a. A double-headed arrow WM2 represents an axial distance from the equator plane to the boundary between the center surface 56 and the second middle surface 58b, that is, the start end 64b of the second main interface 62b.

  In the tire 2, the ratio of the distance WM1 to the distance WB1 is preferably 102% or more and 115% or less. By setting this ratio to 102% or more, the main part 52 effectively contributes to handling performance. In particular, when the tire 2 is mounted on a vehicle such that the first end 68a side of the reference layer 46 is located on the outside, the main part 52 contributes more effectively to handling performance. By setting this ratio to 115% or less, the influence on the rolling resistance by the main part 52 is effectively suppressed. In the tire 2, a small rolling resistance is maintained.

  In the tire 2, the ratio of the distance WM2 to the distance WB2 is preferably 85% or more and 98% or less. By setting this ratio to 85% or more, the main part 52 effectively contributes to handling performance. In the tire 2, good handling performance is maintained. By setting this ratio to 98% or less, the influence on the rolling resistance by the main part 52 is effectively suppressed. In the tire 2, a small rolling resistance is maintained.

  FIG. 2 shows a portion of the tire 2 at the first end 68 a of the reference layer 46. In FIG. 2, 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. 2, a double-headed arrow LE1 represents the length from the boundary between the center surface 56 and the first middle surface 58a, that is, the start end 64a of the first main interface 62a to the end 32a of the outer surface 50 of the tread 4. A double arrow LM1 represents the length from the start end 64a of the first main interface 62a to the boundary 70a between the first middle surface 58a and the first side surface 60a. This length LM1 is the length of the first middle surface 58a. The length LE1 and the length LM1 are measured along the outer surface 50 of the tread 4.

  In the tire 2, the ratio of the length LM1 to the length LE1 is preferably 5% or more and 50% or less. By setting this ratio to 5% or more, the first subpart 54a effectively contributes to handling performance. The influence on the handling performance by the base layer 26 is effectively suppressed. In the tire 2, good handling performance is maintained. By setting this ratio to 50% or less, the influence on the rolling resistance by the first subpart 54a is effectively suppressed. In the tire 2, a small rolling resistance is maintained.

  In FIG. 2, a solid line LB1 represents a tangent to the interface 48 between the cap layer 28 and the base layer 26 at the end 66a of the first main interface 62a. The angle α1 represents an angle formed by the first main interface 62a with respect to the tangent line LB1. This angle α1 is an inclination angle of the first main interface 62a.

  In the tire 2, the inclination angle α1 of the first main interface 62a is preferably 30 ° or more and 80 ° or less. By setting the inclination angle α1 to 30 ° or more, an increase in cornering power due to a decrease in the thickness of the tread 4 and a contribution to rolling resistance by the first subpart 54a when the tire 2 is worn out are balanced. Well arranged. In the tire 2, a small rolling resistance is maintained without impairing the handling performance. By setting the inclination angle α1 to 80 ° or less, the main part 52 is widely arranged on the outer surface side of the tread 4 at the boundary between the main part 52 and the first subpart 54a. On the inner surface side, the first subpart 54a is arranged over a wide area. In the tire 2, good handling performance and small rolling resistance can be achieved even when it is new.

  FIG. 3 shows a portion of the tire 2 at the second end 68 b of the reference layer 46. In FIG. 3, 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. 3, a double-headed arrow LE2 represents the length between the center surface 56 and the second middle surface 58b, that is, the length from the start end 64b of the second main interface 62b to the end 32b of the outer surface 50 of the tread 4. A double-headed arrow LM2 represents the length from the start end 64b of the second main interface 62b to the boundary 70b between the second middle surface 58b and the second side surface 60b. This length LM2 is the length of the second middle surface 58b. The length LE2 and the length LM2 are measured along the outer surface 50 of the tread 4.

  In the tire 2, the ratio of the length LM2 to the length LE2 is preferably 5% or more and 50% or less. By setting this ratio to 5% or more, the second subpart 54b effectively contributes to handling performance. The influence on the handling performance by the base layer 26 is effectively suppressed. In the tire 2, good handling performance is maintained. By setting this ratio to 50% or less, the influence on the rolling resistance by the second subpart 54b is effectively suppressed. In the tire 2, a small rolling resistance is maintained.

  In FIG. 3, a solid line LB2 represents a tangent to the interface 48 between the cap layer 28 and the base layer 26 at the end 66b of the second main interface 62b. The angle α2 represents an angle formed by the second main interface 62b with respect to the tangent line LB2. This angle α2 is an inclination angle of the second main interface 62b.

  In the tire 2, the inclination angle α2 of the second main interface 62b is preferably 30 ° or more and 80 ° or less. By setting the inclination angle α2 to 30 ° or more, there is a balance between an increase in cornering power due to a reduction in the thickness of the tread 4 and a contribution to rolling resistance by the second subpart 54b when the tire 2 is worn. Well arranged. In the tire 2, a small rolling resistance is maintained without impairing the handling performance. By setting the inclination angle α2 to be equal to or less than 80 °, the main part 52 is widely disposed on the outer surface side of the tread 4 at the boundary portion between the main part 52 and the second subpart 54b. The second subpart 54b is arranged over a wide range on the inner surface side. In the tire 2, good handling performance and small rolling resistance can be achieved even when it is new.

  As described above, in the tire 2, the interface 62 between the main part 52 and the sub part 54 is inclined with respect to the radial direction. Thereby, in the boundary part of the main part 52 and the subpart 54, the main part 52 which contributes to handling performance is arrange | positioned extensively in the outer surface side of the tread 4, and reduction of rolling resistance is carried out in the inner surface side of this tread 4. Subparts 54 that contribute to the above are arranged over a wide area. Then, the axial distance WM1 from the equator plane to the start end 64a of the first main interface 62a is made larger than the axial distance WM2 from the equator plane to the start end 64b of the second main interface 62b. On the end 68a side, consideration is given to the main part 52 effectively contributing to handling performance. From the standpoint that good handling performance can be achieved while maintaining a small rolling resistance, the tire 2 is mounted on the vehicle such that the first end 68a of the reference layer 46 is located outside in the width direction of the vehicle. Is preferred.

  As described above, when the camber angle of the tire 2 is set to the negative camber, the tire 2 steps on the road surface in the IN side portion of the tread 4 in the straight traveling. For this reason, the ground pressure of the IN side portion tends to be higher than the ground pressure of the OUT side portion. Therefore, when the tire 2 is mounted on a vehicle so that the first end 68a of the reference layer 46 is positioned on the OUT side, the first end 68a of the reference layer 46 is on the second end 68b side of the reference layer 46. It is expected that wear will proceed more easily than on the other side.

  In the tire 2, the inclination angle α1 of the first main interface 62a is preferably smaller than the inclination angle α2 of the second main interface 62b. The small inclination angle α1 contributes to arranging the main part 52 over a wide range on the outer surface side of the tread 4 and arranging the first sub-part 54a over a wide range on the inner surface side of the tread 4. That is, the small inclination angle α1 contributes to both good handling performance and a small rolling resistance. Although the position of the start end 64b of the second main interface 62b moves inward in the axial direction due to wear, the large inclination angle α2 suppresses the amount of displacement of the position of the start end 64b of the second main interface 62b due to this wear. Since the change in the existence ratio between the main part 52 and the second subpart 54b is small, the large inclination angle α2 suppresses changes in handling performance and rolling resistance due to wear. The tire 2 is excellent in handling performance at the time of start of use and has a small rolling resistance. Moreover, even if the tread 4 is worn by use, good handling performance and small rolling resistance are maintained. Such an effect is sufficiently exerted when the tire 2 is mounted on a vehicle such that the first end 68a of the reference layer 46 is positioned on the outer side in the vehicle width direction. From this point of view, when the inclination angle α1 of the first main interface 62a is set smaller than the inclination angle α2 of the second main interface 62b, the difference between the inclination angle α2 and the inclination angle α1 is preferably 5 ° or more, 35 degrees or less is preferable.

  In the tire 2, when the tread 4 is configured so that the inclination angle α1 of the first main interface 62a is smaller than the inclination angle α2 of the second main interface 62b, good handling performance and small rolling resistance are obtained. From the viewpoint of achievement, the inclination angle α1 is preferably 30 ° to 45 °, and the inclination angle α2 is preferably 50 ° to 65 °.

  As shown in FIG. 2, in the tire 2, a portion (linearly extending inward in the axial direction from the outer surface 50 of the tread 4) is formed on the interface 72 a between the first subpart 54 a and the base layer 26 ( Hereinafter, a first subinterface 74a) is included. The orientation of the first subinterface 74a with respect to the first main interface 62a contributes to the handling performance of the first subpart 54a. From the viewpoint of ensuring good handling performance, the angle formed by the first subinterface 74a (angle β1 in FIG. 2) with respect to the first main interface 62a is preferably 20 ° or more, and preferably 45 ° or less.

  As shown in FIG. 3, in the tire 2, a portion (linearly extending inward in the axial direction from the outer surface 50 of the tread 4) is formed on the interface 72 b between the second subpart 54 b and the base layer 26 ( Hereinafter, a second subinterface 74b) is included. The orientation of the second subinterface 74b with respect to the second main interface 62b contributes to the handling performance of the second subpart 54b. From the viewpoint of ensuring good handling performance, the angle formed by the second subinterface 74b with respect to the second main interface 62b (angle β2 in FIG. 3) is preferably 20 ° or more, and preferably 45 ° or less.

  In the present invention, the size 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 the tire 2 is filled with air so as to have a regular internal pressure. At the time of measurement, no load is applied to the tire 2. When the tire 2 is for a passenger car, 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 “INFLATION PRESSURE” in ETRTO standard are normal internal pressures.

  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. 1-3 was manufactured. The size of this tire is 195 / 65R15. The specifications of the tire of Example 1 are as shown in Table 1 below.

[Example 2-5 and Comparative Example 1-5]
Example 2-5 and Comparative Example are the same as Example 1 except that the loss tangent LTm of the main part, the loss tangent LTs of the sub part, and the loss tangent LTb of the base layer are as shown in Table 1-2 below. A tire of 1-5 was obtained.

[Comparative Example 6-7]
The ratio (WM1 / WB1) of the axial distance WM1 from the equator plane to the starting point of the first main interface to the axial distance WB1 from the equator plane to the first end of the reference layer, and the second end of the reference layer from the equator plane The ratio (WM2 / WB1) of the axial distance WM2 from the equator plane to the starting point of the second main interface with respect to the axial distance WB2 is as shown in Tables 3 and 4 below. The tire of Comparative Example 6-7 was obtained.

[Example 6-8]
A tire of Example 6-8 was obtained in the same manner as in Example 1 except that the ratio (WM1 / WB1) was as shown in Table 3 below.

[Example 9-11]
Tires of Examples 9-11 were obtained in the same manner as in Example 1, except that the ratio (WM2 / WB2) was as shown in Table 4 below.

[Example 12-13]
The ratio (LM1 / LE1) of the length LM1 of the first middle surface to the length LE1 from the start end of the first main interface to the end of the outer surface of the tread, and from the start end of the second main interface to the end of the outer surface of the tread. Tires of Examples 12-13 were obtained in the same manner as in Example 1 except that the ratio (LM2 / LE2) of the length LM2 of the second middle surface to the length LE2 was as shown in Table 5 below.

[Examples 14-15 and Comparative Example 8]
Tires of Examples 14-15 and Comparative Example 8 were obtained in the same manner as Example 1 except that the inclination angle α1 of the first main interface and the inclination angle α2 of the second main interface were as shown in Table 5 below. .

[Examples 16-19]
Tires of Examples 16-19 were obtained in the same manner as in Example 1 except that the inclination angle α1 of the first main interface was changed as shown in Table 6 below.

[Examples 20-23]
Tires of Examples 20-23 were obtained in the same manner as in Example 1 except that the inclination angle α2 of the second main interface was changed as shown in Table 7 below.

[Evaluation sample]
Evaluation was performed on a new tire (NEW) and a tire with a history of use (USED). The USED tire was produced by running a NEW tire under predetermined conditions and wearing the tread so that the wear amount was 50% of the allowable wear amount.

[Rolling resistance coefficient (RRC)]
Using a rolling resistance tester, the rolling resistance coefficient (RRC) was measured under the following measurement conditions.
Rim used: 15 x 6 JJ (aluminum alloy)
Internal pressure: 230 kPa
Load: 3.43kN
Speed: 80km / h
The results are shown in Tables 1-7 below as indices. A larger numerical value is preferable because the rolling resistance is smaller.

[Handling performance]
The tire was assembled in a rim (15 × 6JJ), and the tire was filled with air so that the internal pressure was 230 kPa. This tire was mounted on a small passenger car having a displacement of 2000 cc. The driver was driven on the racing circuit to evaluate the handling performance. The results are shown in Tables 1-7 below as indices. Larger numbers are preferable.

[Total performance]
Average values of rolling resistance and handling performance were obtained. The results are shown in Table 1-7 below as the overall performance. Larger numbers are preferable.

[Stability]
The average value of the overall performance of a new tire (NEW) and the overall performance of a tire with a history of use (USED) was obtained. The results are shown in Table 1-7 below as stability. Larger numbers are preferable.

  As shown in Table 1-7, 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 technology related to the tread described above can be applied to various types of tires.

2 ... tire 4 ... tread 6 ... sidewall 10 ... bead 12 ... carcass 14 ... belt 26 ... base layer 28 ... cap layer 44 ... inner layer ( Innermost layer)
46 ... Outer layer (outermost layer or reference layer)
48 ... Interface between cap layer 28 and base layer 50 50 ... outer surface of tread 4 52 ... main part 54, 54a, 54b ... subpart 56 ... outer surface (center surface) of main part 52
58, 58a, 58b ... outer surface (middle surface) of subpart 54
60, 60a, 60b ... surface (side surface) of the base layer 26
62, 62a, 62b ... Interface (main interface) between main part 52 and sub-part 54
64, 64a, 64b ... Start end of interface 62 66, 66a, 66b ... End of interface 62 68, 68a, 68b ... End of outermost layer 46 70, 70a, 70b ... Middle surface 58 and side Boundary with face 60

Claims (8)

With tread and belt,
The belt is located on the radially inner side of the tread and is composed of a plurality of layers stacked in the radial direction;
The tread includes a base layer and a cap layer located on the radially outer side of the base layer,
The cap layer is composed of a main part and a pair of sub-parts, and each sub-part is located outside the main part in the axial direction,
The loss tangent of the main part is larger than the loss tangent of the subpart, the loss tangent of the base layer is smaller than the loss tangent of the subpart,
The base layer includes a pair of side surfaces forming part of the outer surface of the tread, and spans between one first side surface and the other second side surface;
The main part has a center surface that forms another part of the outer surface of the tread,
The subpart has a middle surface that forms another part of the outer surface of the tread,
When the interface between the main part and the sub part is inclined with respect to the radial direction, and the boundary between the center surface and the middle surface is the start point of the interface, the end of the interface is more axial than the start point. Located inside,
Out of the plurality of layers constituting the belt, the outermost layer is a reference layer, the interface between the main part and one first subpart is a first main interface, and the main part and the other second subpart. When the interface with is the second main interface,
In the axial direction, the starting end of the first main interface is located outside the first end of the reference layer,
A pneumatic tire, wherein the starting end of the second main interface is positioned on the inner side of the second end of the reference layer in the axial direction.   The pneumatic tire according to claim 1, wherein the loss tangent of the main part is 0.18 or more and 0.22 or less.   The pneumatic tire according to claim 1 or 2, wherein the loss tangent of the subpart is 0.14 or more and 0.18 or less.   The pneumatic tire according to any one of claims 1 to 3, wherein a loss tangent of the base layer is 0.10 or more and 0.14 or less. The ratio of the axial distance from the equator plane to the start point of the first main interface with respect to half the axial width of the reference layer is 102% or more and 115% or less,
The air according to any one of claims 1 to 4, wherein a ratio of an axial distance from the equator plane to a starting point of the second main interface with respect to half of the axial width of the reference layer is 85% or more and 98% or less. Enter tire.   6. The ratio of the length of the middle surface to the length from the boundary between the center surface and the middle surface to the end of the outer surface of the tread is 5% or more and 50% or less. 6. Pneumatic tires.   The pneumatic tire according to any one of claims 1 to 6, wherein an inclination angle of an interface between the main part and the sub part is 30 ° or more and 80 ° or less.   The pneumatic tire according to any one of claims 1 to 7, wherein an inclination angle of the first main interface is smaller than an inclination angle of the second main interface.

Images