Tires

Abstract

A tire (1) comprising a tread (10) comprising: two or more circumferential grooves (20, 21, 22, 23); a first shoulder block (40) formed on a side of a first ground contact end (E1); and a second shoulder block (50) formed on a side of a second ground contact end (E2), wherein each of the first shoulder block (40) and the second shoulder block (50) has a lateral groove (41, 51) extending in a direction intersecting the circumferential groove (20, 21, 22, 23), on the first shoulder block (40) and the second shoulder block (50), a first notch (410A, 510A) and a second notch (410B, 510B) are formed along respective edges of each of the lateral grooves (41, 51) in a region of a depth of 2.0 mm from an opening of the lateral groove (41, 51), at portions where widths of the first sipe (410A, 510A) and the second sipe (410B, 510B) are maximum, an inclination angle (θa) of a first inclined surface (41A, 51A) forming the first sipe (410A, 510A) with respect to a tread pattern surface (α) along a ground contact surface of the tread (10) is smaller than an inclination angle (θb) of a second inclined surface (41B, 51B) forming the second sipe (410B, 510B) with respect to the tread pattern surface (α), and the first notch (410A) of the first shoulder block (40) is formed along a trailing edge of the lateral groove (41) and the first notch (510A) of the second shoulder block (50) is formed along a leading edge of the lateral groove (51).

Description

[0001] The present invention relates to a tire and, more particularly, to a tire having a tread on which a plurality of circumferential grooves are formed.

[0002] Conventionally, tires having a tread formed with a plurality of circumferential grooves are widely known. The tread includes a plurality of blocks separated by the circumferential grooves. Typically, a lateral groove extending in a direction intersecting the circumferential groove is formed on each block. Furthermore, a sipe may be formed on the block along an edge of the lateral groove.

[0003] JP 2020-69964 A discloses a tire having a plurality of lateral grooves extending laterally on a shoulder block and a sipe formed along an edge of the lateral grooves. JP 2020-69964 A describes advantages of improving braking performance on a dry road surface and wet performance.

[0004] DE 102014220981 A1 describes a pneumatic vehicle tire with a tread pattern having at least one circumferential groove and at least one row of blocks delimited at least on one side by a circumferential groove, the blocks of which are separated from one another by transverse grooves delimited on the block surfaces by block edges, an incoming block edge that first enters the ground when the tire rolls (when driving forward), and the outgoing block edge provided on the adjacent block. The incoming block edge is composed of two sections, of which the section adjoining the circumferential groove is the shorter and which extend at an obtuse angle to one another, so that each block has a wedge-like or triangular projection between one section and the block edge that delimits the block in the circumferential direction at the circumferential groove.The longer section of the incoming block edge is provided with a bevel over its length, which runs along the shorter section, wherein the outgoing block edge has an overall substantially straight or slightly curved course over its entire extent, wherein the mutual distance between the incoming block edge and the outgoing block edge is greatest at the kink between the two sections of the incoming block edge and decreases in both directions starting from the kink.

[0005] DE 102018119911 A1 describes a pneumatic tire having a center main groove formed in a center zone of a tread portion in a tire width direction and extending in a zigzag shape in a tire circumferential direction, a shoulder main groove formed in the tread portion on a ground contact end side with respect to the center main groove and extending in the tire circumferential direction, a center rib defined by the center main groove and the shoulder main groove and arranged in the center zone of the tread portion in the tire width direction, and a center notch having one end communicating with the center main groove and the other end terminating in the center rib, and including a step formed at a portion adjacent to the tread portion.

[0006] EP 3388256 A1 describes a pneumatic vehicle tire of radial design with a tread having at least one shoulder-side profile rib provided with transverse grooves extending beyond the lateral edge of the ground contact patch of the tread. Each transverse groove has a groove base and groove walls, as well as, within the ground contact patch, a main section with groove edges running parallel to one another. The main section has a width of 1.5 mm to 10.0 mm between the groove walls, and a chamfer extending to the groove edge is attached to at least one groove wall. The chamfer has a main chamfer section in the direction of extension of the transverse groove and, outside the ground contact patch, a chamfer end section that is wider than the main chamfer section, at least over the majority of its extension.Each transverse groove runs outside the ground contact area as a flat depression with a continuous reduction in its depth, each depression having a width in the circumferential direction at its widest point which is at least 40% greater than the width of the main section of the transverse groove, each chamfer end section being delimited on the outer surface of the tread rib by an edge section of one of the groove edges which has at least one kink which widens the transverse groove.

[0007] US 2021 / 0129594 A1 describes a pneumatic tire comprising lug grooves in a tread of a shoulder land, the lug grooves crossing a circumferential direction and terminating at a first side within the shoulder land and passing through a contact edge at a second side, and a notch formed at an opening edge of the lug grooves, the notch being cut out of the radially inwardly cut tread. The lug grooves have a width that decreases from the first to the second side, an end position of the lug grooves is located from a main groove 5% to 35% of a transverse dimension from the main groove to the ground contact edge, and a maximum groove width position is located from the main groove 40% or less of the transverse dimension from the main groove to the ground contact edge; and the notch has a width that increases from the first to the second side.

[0008] When braking a vehicle, there may be cases where the ground contact pressure is concentrated at the edge of the lateral groove, resulting in insufficient braking performance. Since the friction coefficient of rubber is inversely proportional to the ground contact pressure, the friction coefficient of the rubber will be reduced if the ground contact pressure is concentrated on a part of the tread. Furthermore, the concentration of ground contact pressure causes significant deformation of the rubber and consequently a reduction in the ground contact area. It can be deduced that the braking performance of the tire will be significantly reduced due to these factors if the ground contact pressure is concentrated on a part of the tread.

[0009] To improve tire braking performance, it is important to distribute and reduce ground contact pressure while ensuring a large ground contact area. The tire disclosed in JP 2020-69964 A still has room for improvement in braking performance.

[0010] The problem underlying the invention is solved by a tire having the features disclosed in claim 1. Further embodiments are defined in the dependent claims.

[0011] It provides a tire with superior braking performance. It also distributes and reduces ground contact pressure while ensuring a large ground contact area.

[0012] (An) embodiment(s) of the present invention is / are described with reference to the following figures, wherein: Fig. 1 is a perspective diagram of a tire according to an embodiment of the present invention, also showing an internal structure of the tire; Fig. 2 is a diagram showing a part of a cross section in a width direction of a tire according to an embodiment of the present invention; Fig. 3 is a plan view of a tire according to an embodiment of the present invention, illustrating a portion of a tread; Fig. 4 is a plan view showing a part of a tread for magnifying a first region R1 positioned with respect to a tire equator on an outer side of a vehicle; Fig. 5 is a plan view showing a part of a tread for magnifying a second region R2 positioned with respect to a tire equator on an inner side of a vehicle; Fig. 6 is a perspective diagram showing a part of a first shoulder rib and a first intermediate rib positioned in a first region, as viewed from a tire equator side; Fig. 7 is a perspective diagram showing a part of a second shoulder rib and a second intermediate rib positioned in a second region, as viewed from a tire equator side; Fig. 8 is an enlarged view of a lateral groove formed on a first shoulder rib; and Fig. 9 a cross-sectional diagram along a line AA from Fig. 4 is.

[0013] A tire according to an embodiment of the present invention will now be described in detail with reference to the drawings.

[0014] Fig. 1 is a perspective diagram of a tire 1 according to an embodiment of the present invention and also shows an internal structure of the tire 1. As in Fig. As shown in Figure 1, the tire 1 includes a tread 10, which is a portion that contacts a road surface. The tread 10 has a plurality of circumferential grooves and is formed in an annular shape along a tire circumferential direction. On the tread 10, four circumferential grooves 20, 21, 22, and 23 extending parallel to each other are formed along the tire circumferential direction. In the present embodiment, widths of the circumferential grooves differ from each other. Furthermore, groove depths also differ among the circumferential grooves.

[0015] The tire 1 is a tire in which a mounting direction to a vehicle is fixed. The tread 10 has a tread pattern that is asymmetrical to the left and right with respect to a tire equator CL, and the mounting directions for the tire 1 are opposite between a right side of the vehicle and a left side of the vehicle. The tire equator CL refers to a line passing through a center in a tire width direction and extending along the tire circumferential direction. As will be described in detail below, the tire 1 is mounted on the vehicle in such a manner that a first circumferential groove 20, which has the shallowest depth and the narrowest width, among the four circumferential grooves is positioned on an outer side of the vehicle with respect to the tire equator CL.

[0016] In the present disclosure, the terms "left" and "right" are used for the tire 1 and its components for explanatory purposes. The "right side" of the tire 1 refers to a right side when the tire 1 mounted on the vehicle is viewed in a traveling direction of the vehicle (forward movement direction), and the "left side" refers to a left side when the tire 1 mounted on the vehicle is viewed in the traveling direction of the vehicle. In the drawings, arrows are shown showing a tire main rotation direction, the left side, and the right side. The "tire main rotation direction" refers to a rotation direction of the tire 1 when the vehicle on which the tire 1 is mounted moves forward.

[0017] The tire 1 includes a pair of sidewalls 11 extending to the outermost side in the tire width direction, and a pair of beads 12 that would be mounted on a rim of a wheel. The sidewalls 11 and the beads 12 are formed in an annular shape along the tire circumferential direction and constitute side surfaces of the tire 1. The sidewalls 11 extend from respective ends in a width direction of the tread 10 in a tire radial direction. A side rib 13 is formed to protrude toward an outer side in a tire width direction and is formed in an annular shape along the tire circumferential direction.

[0018] The tire 1 is a pneumatic tire filled with air at a predetermined pressure. The tread 10 and the sidewall 11 are formed, for example, from different types of rubber. Portions of the tire 1 from areas near the ground contact ends E1 and E2 to the left and right side ribs 13 are generally called shoulders or support portions. The shoulders may be formed of the same rubber as the ground contact surface of the tread 10 or of a different rubber.

[0019] In the present disclosure, the ground contact ends E1 and E2 refer to respective ends in the tire width direction of a portion that contacts a flat road surface when a load that is 70% of a regular load at a regular internal pressure is applied in a state where the yet-to-be-used tire 1 is mounted on a regular rim and the air is filled to reach the regular internal pressure.

[0020] Here, the "regular rim" refers to a rim specified by a tire standard and is defined as a "standard rim" in JATMA, a "design rim" in TRA, and a "measuring rim" in ETRTO. The "regular internal pressure" is a "maximum pneumatic pressure" in JATMA, a maximum value described in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table in TRA, and an "INFLATION PRESSURE" in ETRTO. The “regular load” is a “maximum load capability” in JATMA, a maximum value described in the “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” table in TRA and a “LOAD CAPACITY” in ETRTO.

[0021] The tire 1 includes a carcass 14, a belt 15, and an inner liner 16. The carcass 14 is a rubber-covered cord layer and forms a skeleton of the tire 1, which can withstand load, impact, and air pressure. The belt 15 is a reinforcing band placed between the rubber forming the tread 10 and the carcass 14. The belt 15 fixes the carcass 14 to increase rigidity of the tire 1. The inner liner 16 is a rubber layer provided on an inner peripheral surface of the carcass 14 and maintains the air pressure of the tire 1. The bead 12 includes a bead core 17 and an apex 18.

[0022] Desirably, an indication of a mounting direction with respect to the vehicle is provided on the tire 1. On the side surface of the tire 1, a mark generally called a serial number is provided. The serial number includes, for example, information such as a size code, a manufacturing period (year and week of manufacture), the manufacturing location (manufacturing factory code), and the like. By providing the serial number only on the side surface (sidewall 11) of the tire 1 facing the outside of the vehicle, or by providing different serial numbers between the sidewall facing the outside of the vehicle and a sidewall facing an inside of the vehicle, it becomes possible to indicate the mounting direction of the tire 1 to the vehicle.As a concrete example, a configuration may be adopted in which the manufacturing factory code and the size code are provided on both side surfaces of the tire 1, and the manufacturing year and week are provided only on the side surface facing the outside of the vehicle.

[0023] The rubber constituting the tread 10 may have a multi-layer structure. For example, the tread rubber has a two-layer structure including a base rubber and a cap rubber constituting a surface layer of the tread 10. A desirable example of a hardness of the cap rubber is 65 or more and 75 or less. In this case, the rigidity of the tread 10 tends to be increased, and the structure is effective in improving limit performance. The hardness of the rubber is based on JIS K6253-3 and is measured with a Type A durometer under a temperature condition of 23°C. Limit performance generally refers to the performance under a limit condition where a stable driving state can be maintained.

[0024] For example, a 300% modulus of the cover rubber is 15 or less. In this case, the stiffness of the tread tends to increase, and the structure is effective in improving the limit performance. There are no specific restrictions on the lower limit of the 300% modulus of the cover rubber, but the lower limit is, for example, 10. The 300% modulus is based on JIS K6301 and is measured under a temperature condition of 23°C. When the tread rubber has a single-layer structure, the properties of the tread rubber as a whole should desirably meet the conditions described above.

[0025] The tread 10 has blocks separated by the four circumferential grooves. The block is a protrusion that protrudes from a reference surface of the tread 10 toward an outer side in the tire radial direction. The reference surface is a virtual surface along a bottom surface of the deepest circumferential groove and refers to an outer peripheral surface of the tread 10 when none of the blocks is present. In the tread 10, the four circumferential grooves are formed in an order of the circumferential grooves 20, 21, 22, and 23 from the outer side of the vehicle. In other words, the tire 1 must be mounted on the vehicle in such a manner that the circumferential groove 20 is positioned on the outer side of the vehicle and the circumferential groove 23 is positioned on the inner side of the vehicle.

[0026] The tread 10 includes a center rib 30, shoulder ribs 40 and 50, and intermediate ribs 60 and 70 as the blocks. On the tread 10, there is no groove extending laterally in the width direction of the block, and the blocks are formed in a rib shape continuously in the tire circumferential direction. Forming each block in the rib shape contributes to preventing block collapse (particularly deformation in the lateral direction) during high-speed cornering and improving limit performance.

[0027] The center rib 30 is placed at a center in the width direction of the tread 10. The shoulder ribs 40 and 50 are placed on respective sides in the width direction of the tread 10. The ground contact end E1 is present at the first shoulder rib 40, and the ground contact end E2 is present at the second shoulder rib 50. Parts of the shoulder ribs 40 and 50 extend beyond the ground contact ends E1 and E2 to the side ribs 13. The first intermediate rib 60 is placed between the center rib 30 and the shoulder rib 40, and the second intermediate rib 70 is placed between the center rib 30 and the shoulder rib 50.

[0028] The center rib 30 is a block sandwiched between the circumferential grooves 21 and 22 formed parallel to each other along the tire circumferential direction. The center rib 30 is separated from the intermediate rib 60 by the circumferential groove 21 and is separated from the intermediate rib 70 by the circumferential groove 22. The center rib 30 is formed across the tire equator CL. In the following description, a region on the tread 10 from the tire equator CL to the ground contact end E1 positioned on the outer side of the vehicle is referred to as a first region R1, and a region from the tire equator CL to the ground contact end E2 positioned on the inner side of the vehicle is referred to as a second region R2.

[0029] The shoulder rib 40 is formed in the first region R1, which is a region on the tread 10 side near the ground contact end E1, and is separated from the intermediate rib 60 by the circumferential groove 20. The shoulder rib 50 is formed in the second region R2, which is a region on the tread 10 side near the ground contact end E2, and is separated from the intermediate rib 70 by the circumferential groove 23. The shoulder ribs 40 and 50 have, for example, approximately the same width. Alternatively, a width of the ground contact surface of the shoulder rib 40 may be slightly wider than a width of the ground contact surface of the shoulder rib 50.

[0030] The intermediate rib 60 is located in the first region R1 of the tread 10, adjacent to the shoulder rib 40 with the circumferential groove 20 therebetween, and adjacent to the center rib 30 with the circumferential groove 21 therebetween. The intermediate rib 70 is located in the second region R2 of the tread 10, adjacent to the center rib 30 with the circumferential groove 22 therebetween, and adjacent to the shoulder rib 50 with the circumferential groove 23 therebetween. The intermediate ribs 60 and 70 have, for example, approximately the same width. Alternatively, a width of the ground contact surface of the intermediate rib 60 may be slightly wider than a width of the ground contact surface of the intermediate rib 70.

[0031] On each of the above-described ribs, a plurality of lateral grooves or sipes are formed, extending in a direction intersecting the circumferential groove. The shoulder rib 40 has a lateral groove 41, and the shoulder rib 50 has a lateral groove 51. Ends of the lateral grooves 41 and 51 on the tire equator CL side desirably terminate in the shoulder rib and are not connected to the circumferential grooves. On the center rib 30 and the intermediate ribs 60 and 70, sipes are formed, which are connected to the circumferential grooves. The sipes are placed on the ribs in a staggered manner along the tire circumferential direction.

[0032] The lateral grooves and the sipes are both grooves extending in the tire width direction, but the lateral grooves are wide grooves, while the sipes are narrow-line grooves. Generally, these elements are recognized as different elements from each other. In the present disclosure, a groove with a groove width less than or equal to 1.0 mm is referred to as a sipe, and a groove with a groove width over 1.0 mm is referred to as a lateral groove. The groove width described here does not include a width of a sipe described below. The groove width refers to the shortest distance between opposite groove walls at any position of the groove walls along a length direction of the lateral groove or the sipe.In the following, unless otherwise stated, the width of the lateral groove and the sipe refers to the maximum value (maximum width) and to an opening width of the groove along a profile area α described below.

[0033] The ratio of a groove area to the ground contact area of ​​the tread 10 is not specifically limited, but a desirable example of the ratio is 33% or more and 40% or less. Ensuring a large ground contact area is effective in improving braking performance. The groove area is an area of ​​the grooves on a tread pattern surface α along the ground contact surface of the tread 10, that is, an opening area of ​​the grooves, and includes circumferential grooves, lateral grooves, sipes, and sipes. The opening of the groove refers to a top end opening of the groove facing the outer side in the tire radial direction.

[0034] The four circumferential grooves formed on the tread 10 will now be described with reference to Fig. 2 described in detail. Fig. 2 is a diagram showing a part of a cross section in the width direction of the tire 1. In Fig. 2, an illustration of the carcass 14 and the like is omitted

[0035] As in Fig. As shown in Figure 2, the first circumferential groove 20, positioned at the outermost position of the vehicle, has the shallowest depth and the narrowest width of the four circumferential grooves. By forming the circumferential groove 20 shallow and with a narrow width, it is possible to increase the rigidity of the tread 10 in the first region R1 of the tread 10, which is positioned on the outer side of the vehicle, and to improve the limit performance of maneuvering stability on a dry road surface. A width W2 of the second circumferential groove 21 formed in the first region R1 of the tread 10 is wider than a width W1 of the circumferential groove 20, but is narrower than a width W3 and W4 of the third and fourth circumferential grooves 22 and 23 formed in the second region R2 of the tread 10.

[0036] On the tread 10, two circumferential grooves are formed in each of the first region R1 and the second region R2. A total area of ​​the circumferential grooves in a plan view of the tread 10 is smaller in the first region R1 compared to the second region R2. In addition, the ground contact area of ​​the first region R1 is larger than the ground contact area of ​​the second region R2. Furthermore, a total volume of the circumferential grooves is smaller in the first region R1 compared to the second region R2. In this case, the marginal performance of maneuvering stability on a dry road surface can be more effectively improved. The tire 1 is desirable for a tire for a high-performance automobile (UHP tire) for which high marginal performance is desired.

[0037] As the rigidity of the first region R1 increases, the tire's ability to absorb shock from the road surface becomes more difficult, and ride quality may deteriorate during driving, especially on rough road surfaces. As described in detail below, the tire 1 achieves both maneuverability and ride quality performance by developing the sipe shape of the intermediate rib 60 adjacent to the circumferential groove 20.

[0038] In the present embodiment, the three circumferential grooves 21, 22, and 23 except for the circumferential groove 20 have approximately the same depth. In the present disclosure, the groove depth refers to a length from a tread pattern surface α along the ground contact surface of the tread 10 to the groove bottom along a direction perpendicular to the pattern surface α. The groove bottoms of the circumferential grooves 21, 22, and 23 are formed approximately flat. The groove walls of the circumferential grooves 21, 22, and 23 are formed at an angle close to the perpendicular with respect to the pattern surface α, but are inclined such that the groove widths become slightly narrower toward the groove bottoms. Further, the groove walls are slightly curved near the groove bottom.

[0039] For the circumferential groove 20, the groove bottom is convexly curved toward the inner side of the tire radial direction. There is no flat portion or almost no flat portion on the groove bottom of the circumferential groove 20. A groove wall 20a of the circumferential groove 20 on the tire equator CL side has a smaller inclination angle with respect to the tread surface α than the groove walls of the other circumferential grooves. On the other hand, the groove wall of the circumferential groove 20 on the ground contact end E1 side has a larger angle with respect to the tread surface α than the groove wall 20a and the groove walls of the other circumferential grooves, and is formed approximately perpendicular to the tread surface α near the groove opening. That is, the depth of the circumferential groove 20 changes gradually on the tire equator CL side from the top end of the groove wall toward the groove bottom and changes abruptly on the ground contact end E1 side.

[0040] A depth D1 of the circumferential groove 20 is desirably 50% or more and 80% or less of a depth of the deepest groove among the circumferential grooves. When the depth D1 is within this range, under a condition that the other structures are appropriately controlled, maneuvering stability on a dry road surface can be effectively improved while ensuring superior water drainage performance and superior ride quality performance. In the present embodiment, the depths of the circumferential grooves 21, 22, and 23 except for the circumferential groove 20 are approximately the same. Alternatively, a configuration may be adopted in which depths D2 and D3 of the circumferential grooves 21 and 22 are substantially the same, and a depth D4 of the circumferential groove 23 is slightly shallower than the depths D2 and D3.

[0041] The depth D1 of the circumferential groove 20 is desirably 50% or more and 80% or less of the depths D2 and D3 of the circumferential grooves 21 and 22. The depth D1 is desirably 55% or more and 70% or less of the depths D2 and D3. The relationship between the depths of the four circumferential grooves is, for example, D1 <D4≤D2=D3.

[0042] An example of the depth D1 of the circumferential groove 20 is 4.5 mm. An example of the depth D3 of the circumferential groove 22 is 7.6 mm. Unless otherwise specified, the depth of the circumferential groove refers to the depth of the deepest portion. Further, unless otherwise specified, the width of the circumferential groove refers to the width at the opening of the groove; that is, a length along the tire width direction on the tread surface α. In the present embodiment, the widths of the circumferential grooves are approximately constant, and the widths of the ribs are also approximately constant.

[0043] The width W1 of the circumferential groove 20 is desirably less than or equal to 60% of the width W3 of the circumferential groove 22 having the widest width among the circumferential grooves. The width W1 of the circumferential groove 20 is desirably less than or equal to 50%, and is more desirably 30% or more and 50% or less of the width W3 of the circumferential groove 22. When the widths W1 and W3 are in these relationships, under a condition that the other structures are appropriately controlled, maneuvering stability on a dry road surface can be effectively improved while ensuring superior water drainage performance and superior ride quality performance. An example of the width W1 is 7.0 mm or more and 8.0 mm or less.

[0044] In the present embodiment, at upper ends of the groove wall 20a of the circumferential groove 20, the groove wall of the circumferential groove 21 on the tire equator CL side, and the groove wall of the circumferential groove 23 on the tire equator CL side, regions Rz inclined at an angle of less than or equal to 60° with respect to the tread surface α are formed. In other words, the regions Rz are formed along the tire circumferential direction at edges of the center rib 30 and the intermediate rib 60 on the ground contact end E1 side and at an edge of the intermediate rib 70 on the ground contact end E2 side. The regions Rz are formed, for example, at an inclination angle of 20° or more and 50° or less with respect to the tread surface α in depth ranges within 20% of the depths of the circumferential grooves from the upper ends of the groove walls.

[0045] The width W2 of the circumferential groove 21 is greater than the width W1 of the circumferential groove 20 and is smaller than the widths W3 and W4 of the circumferential grooves 22 and 23. The width W2 is desirably 1.3 times or more and 2.5 times or less, and more desirably 1.5 times or more and 2.2 times or less of the width W1 of the circumferential groove 20. The width W2 is desirably 55% or more and 90% or less, and more desirably 65% ​​or more and 80% or less of the width W3 of the circumferential groove 22. The width W4 of the circumferential groove 23 is greater than the widths W1 and W2 of the circumferential grooves 20 and 21 and is smaller than the width W3 of the circumferential groove 22. The width W4 of the circumferential groove 23 is, for example, 1.1 times or more and 1.5 times or less of the width W2 of the circumferential groove 21 and 75% or more and 95% or less of the width W3 of the circumferential groove 22.

[0046] Thus, the relationship between the widths of the four circumferential grooves W1 <W2<W4<W3. In diesem Fall wird es einfacher, sowohl die Manövrierstabilität als auch die Fahrqualitätsleistung zu verwirklichen, während eine überlegene Wasserableitungsleistung sichergestellt wird. An der Rillenwand der Umfangsrille 20 ist keine geneigte Fläche wie etwa der Bereich Rz ausgebildet.

[0047] As described above, in the tread 10, a total of the widths W1 and W2 of the circumferential grooves 20 and 21 formed in the first region R1 is smaller than a total of the widths W3 and W4 of the circumferential grooves 22 and 23 formed in the second region R2. Due to this, the center of the center rib 30 in the width direction is positioned at a position closer to the ground contact end E1 than the tire equator CL. In addition, a distance from the intermediate rib 60 in the first region R1 to the ground contact end E1 is slightly shorter than a distance from the intermediate rib 70 in the second region R2 to the ground contact end E2.

[0048] The widths of the center rib 30 and the intermediate ribs 60 and 70 may be the same or different from each other. In the present embodiment, the rib width refers to a length of the ground contact surface of the rib along the tire width direction. For example, the width of the intermediate rib 60 is slightly larger than the widths of the center rib 30 and the intermediate rib 70. The center rib 30 and the intermediate rib 70 have approximately the same width.

[0049] The lateral grooves and the sipes formed in the blocks will now be described with reference to Fig. 3 to 5 are described in detail. Fig. 3 is a plan view showing a part of the tread 10. Fig. 4 is a plan view showing the first area R1 in an enlarged manner and Fig. 5 is a plan view showing the second area R2 in an enlarged manner. Fig. 3 a dot hatching is applied on the top side of each block (this applies analogously to Fig. 8).

[0050] As in Fig. 3 to 5, sipes 31 and 32 are formed on the center rib 30. A first sipe 31 extends from the circumferential groove 20 positioned on the ground contact end E1 side in a direction intersecting the circumferential groove 21 and terminates in the center rib 30. A second sipe 32 extends from the circumferential groove 22 positioned on the ground contact end E2 side in a direction intersecting the circumferential groove 22 and terminates in the center rib 30. That is, in the sipes 31 and 32, a first end in a length direction (which may also be referred to as a "starting end" hereinafter) is in communication with the circumferential groove, and a second end (which may also be referred to as a "terminating end" hereinafter) is positioned in the center rib 30.In addition, the sipes 31 and 32 are inclined with respect to the tire width direction such that a right-side end is positioned on a front side in the tire main rotation direction of the left-side end when viewed in the vehicle traveling direction.

[0051] The sipe 31 is formed from the circumferential groove 21 at a length beyond the tire equator CL, and the sipe 32 is formed from the circumferential groove 22 at a length beyond the tire equator CL. The sipes 31 and 32 are alternately placed along the tire circumferential direction and extend in approximately the same direction with an approximately equal inclination angle with respect to the tire width direction. Further, the sipes 31 and 32 are alternately placed along the tire circumferential direction, and the same number of sipes 31 and 32 are formed. The sipes 31 and 32 may be formed at an equal pitch from each other, but desirably, the sipes 31 and 32 are formed with a variable pitch in which the distance between the sipes is slightly varied every predetermined number of sipes in the tire circumferential direction.In the present embodiment, the numbers of sipes formed in the center rib 30 and in each of the intermediate ribs 60 and 70 are the same.

[0052] A length of the sipe 31 is longer than a length of the sipe 32, and is, for example, 2 times or more and 4 times or less, or 2 times or more and 3 times or less of the length of the sipe 32. Unless otherwise specified, the length of the sipe refers to both a length along the sipe from the starting end to the terminal end of the sipe in the plan view of the tread 10 and a length along the tire width direction (this applies analogously to the length of the lateral groove). The sipes 31 and 32 have a shallower depth in a region near the terminal end, and have, for example, a depth of less than or equal to 2.0 mm. Desirably, portions of the sipes 31 and 32 with a depth exceeding 2.0 mm do not intersect each other in the tire circumferential direction.

[0053] The depth of the sipe 31 is desirably shallower than the depth of the circumferential groove 21. Similarly, the depth of the sipe 32 is desirably shallower than the depth of the circumferential groove 22. In the present embodiment, the depths of the sipes 31 and 32 are substantially equal and are constant over the entire lengths of the sipes. The depths of the sipes 31 and 32 are desirably 70% or more and 95% or less of the depths of the circumferential grooves 21 and 22, respectively, excluding the shallow portions near the terminal ends. An example of the depths of the sipes 31 and 32 (depths of the deepest portions) is 5.8 mm.

[0054] On the center rib 30, desirably, cuts are formed along the edges of the sipes 31 and 32 in a range of a depth of 2.0 mm from the openings of the sipes. In the present embodiment, cuts (a first cut 310A and a second cut 310B) are each formed along respective edges of the sipe 31, and a cut 320A is formed along one edge of the sipe 32. That is, the cuts are formed on both sides in the width direction for the sipe 31 and only on one side in the width direction for the sipe 32. Each cut is formed, for example, in a depth range of 0.8 mm or more and 2.0 mm or less from the opening of the sipe.The sipe has a shape in which a corner of a block is chamfered at the edge of the lateral groove and the sipe, and the edge of the lateral groove and the sipe is cut and widened, and a tread pattern having the sipes is formed using a mold on which a pattern corresponding to the sipes is formed. Furthermore, a length, a width, and the like of an inclined surface formed by chamfering the corner of the block have an analogous meaning to the length, width, and the like of the sipe, and for example, the width of the inclined surface can be interpreted as the width of the sipe.

[0055] The first sipe 310A is formed at a first edge along the length direction of the sipe 31, and the second sipe 310B is formed at a second edge along the length direction of the sipe 31. The first and second edges are positioned to oppose each other in the tire circumferential direction. The first edge of the sipe 31 extends longer than the second edge on the circumferential groove 22 side, and the first sipe 310A is longer than the second sipe 310B. Each sipe is formed from a position in contact with the circumferential groove 21, but the second sipe 310B does not reach the tire equator CL. On the other hand, the first sipe 310A extends beyond the tire equator CL to the circumferential groove 22 side.

[0056] The sipe 320A is formed at a first edge along the length direction of the sipe 32. The sipe 320A is located on the same side as a first sipe S10A of the lateral groove 51 and a sipe 720A of a sipe 72, which will be described later. A groove wall constituting the second edge of the sipe 32, which is opposite to the first edge, is formed approximately perpendicular to the tread surface α. That is, the corner of the block along the second edge is not chamfered. The sipe 320A extends from the circumferential groove 22 beyond the tire equator CL to the circumferential groove 21 side and intersects the sipe 310A of the sipe 31 in the tire circumferential direction.

[0057] The inclined surfaces forming the two sipes along the sipe 31 may have an equal inclination angle with respect to the profile surface α and may be formed in an equal width. However, in the present embodiment, the inclination angle of a first inclined surface 31A forming the first sipe 310A is slightly smaller than the inclination angle of a second inclined surface 31B forming the second sipe 310B. Further, a maximum width of the first sipe 310A and the first inclined surface 31A is slightly larger than a maximum width of the second sipe 310B and the second inclined surface 31B. The inclined surfaces have bent portions 33A and 33B at intermediate portions in the length direction, and directions toward which the inclined surfaces face slightly change with the bent portions 33A and 33B as boundaries.Similarly, the widths of the inclined surfaces change with the curved portions 33A and 33B as boundaries. Widths of the inclined surfaces are gradually reduced from the curved portions 33A and 33B toward the terminal end of the slat 31.

[0058] The maximum width of the first sipe 310A and the first inclined surface 31A is, for example, 1.05 times or more and 1.30 times or less of the maximum width of the second sipe 310B and the second inclined surface 31B. In portions of the maximum widths of the sipes, desirably, the inclination angle of the first inclined surface 31A with respect to the profile surface α is 15° or more and 60° or less, and the inclination angle of the second inclined surface 31B with respect to the profile surface α is 15° or more and 60° or less. The inclination angle of the inclined surface with respect to the profile surface α may be approximately constant over the entire length of the inclined surface.

[0059] The first sipe 310A and the first inclined surface 31A have a maximum width in a range from the starting end of the sipe 31 to the bent portion 33A. On the other hand, the second sipe 310B and the second inclined surface 31B have a maximum width at the bent portion 33B. The bent portion 33B is positioned on a side closer to the tire equator CL than the bent portion 33A. The relationships between the inclination angles, widths, and the like of the inclined surface of the sipe 31 and the inclined surface of the sipe 32 are not specifically limited. For example, the maximum width of the sipe 320A and the inclined surface 32A of the sipe 32 is approximately equal to the maximum width of the second inclined surface 31B. Furthermore, the angle of inclination of the inclined surface 32A with respect to the profile surface α may be equal to the angle of inclination of the second inclined surface 31B with respect to the profile surface α.

[0060] The sipes of the center rib 30, together with the sipes of the other blocks, contribute to the distribution of ground contact pressure. The structure in which the sipes are each formed along the edges of the sipe 31 and the sipe is formed along one edge of the sipe 32 is effective in dispersing and reducing ground contact pressure while ensuring a large ground contact area, thereby improving braking performance. Since the structure of the center rib 30 significantly affects braking performance, especially during straight-line driving, the above-described shapes, sizes, positional relationships, and the like of the sipes of the center rib 30 significantly contribute to improving braking performance. In the present embodiment, the structures of the sipes of the blocks are designed with a view to improving braking performance so that a more effective function is realized by the tread 10 as a whole.

[0061] The widths of the plurality of sipes 31 may slightly differ from each other. For example, the widths of the sipes 31 adjacent in the tire circumferential direction differ from each other, and sipes 31 with 2 to 6 types of widths are formed on the center rib 30. The 2 to 6 types of sipes 31 may be arranged in such a manner that the size gradually increases along the tire circumferential direction. Similarly, for the sipe 32, the sipes of other ribs, and the side grooves 41 and 51, the widths of grooves adjacent in the tire circumferential direction may also differ from each other.

[0062] The lamellae formed on the intermediate ribs 60 and 70 will now be described with reference to Fig. 6 and Fig. 7 in addition to Fig. 3 to 5 are described in detail. Fig. 6 is a perspective diagram showing a part of the first intermediate rib 60 and the first shoulder rib 40 positioned in the first region R1, as viewed from the tire equator CL side. Fig. 7 is a perspective diagram showing a part of the second intermediate rib 70 and the second shoulder rib 50 positioned in the second region R2, as viewed from the tire equator CL side.

[0063] As in Fig. 3 and Fig. 4, sipes 61 and 62 are formed on the intermediate rib 60 adjacent to the circumferential groove 20. The first sipe 61 extends from the circumferential groove 21 positioned on the tire equator CL side in a direction intersecting the circumferential groove 21 and terminates in the intermediate rib 60. The second sipe 62 extends from the circumferential groove 20 positioned on the ground contact end E1 side in a direction intersecting the circumferential groove 20 and terminates in the intermediate rib 60. That is, in the sipes 61 and 62, a first end in a length direction communicates with the circumferential groove and a second end is positioned in the intermediate rib 60. The sipe 61 extending from the tire equator CL side is longer than the sipe 62 extending from the ground contact end E1 side.

[0064] The sipes 61 and 62 are alternately placed along the tire circumferential direction and extend in approximately the same direction at approximately the same inclination angle with respect to the tire width direction. Furthermore, the same number of sipes 61 and 62 is placed. The sipes 61 and 62 may be formed at an equal pitch from each other, but desirably, the sipes 61 and 62 are formed at a variable pitch in which the distance between the sipes is slightly varied every predetermined number of sipes in the tire circumferential direction. As will be described in detail below, the sipes 61 and 62 are formed in such lengths that portions of the sipes 61 and 62 with a depth exceeding 2.0 mm do not overlap each other in the tire circumferential direction.By forming the sipes with such lengths from respective sides in the width direction of the intermediate rib 60, it becomes possible to ensure superior ride quality performance in the tire 1 with high rigidity in the first region R1 while suppressing deformation of the intermediate rib 60 during high-speed cornering and braking. That is, both superior maneuverability (limit performance) and superior ride quality performance can be effectively achieved.

[0065] As in Fig. 3 and Fig. 5, sipes 71 and 72 are formed on the intermediate rib 70 in the second region R2. The first sipe 71 extends from the circumferential groove 22 positioned on the tire equator CL side in a direction intersecting the circumferential groove 22 and terminates in the intermediate rib 70. The second sipe 72 extends from the circumferential groove 23 positioned on the ground contact end E2 side in a direction intersecting the circumferential groove 23 and terminates in the intermediate rib 70. That is, in the sipes 71 and 72, a first end communicates with the circumferential groove and a second end is positioned in the intermediate rib 70. The sipe 71 extending from the tire equator CL side is longer than the sipe 72 extending from the ground contact end E2 side. The slat 71 has a bent portion 71C which is significantly bent.

[0066] Analogous to the sipes 61 and 62, the sipes 71 and 72 are also alternately placed along the tire circumferential direction. Furthermore, the same number of sipes 71 and 72 is placed. The sipes 71 and 72 may be formed at an equal distance from each other, but desirably, the sipes 71 and 72 are formed at a variable pitch in which the distance between the sipes is slightly varied every predetermined number of sipes in the tire circumferential direction. In the present embodiment, the sipe 72 has an inclination angle with respect to the tire width direction that is approximately equal to the inclination angles of the sipe 61 and the sipe 31 of the center rib 30, and the sipe 72 is formed to be positioned on an extension line of the sipes 31 and 61. In other words, the sipes 31, 61, and 72 are placed on approximately the same straight line.Although the slat 71 is bent, the slat 71 is formed in such a manner that a part of the slat 71 is positioned on an extension line of the slat 62 and the slat 32 of the center rib 30.

[0067] On the intermediate ribs 60 and 70, cuts are formed along the edges of the slats, respectively, in a range of 2.0 mm deep from the openings of the slats. The cuts are formed on both sides in the width direction of the slats for slats 61 and 71, and are formed only on one side in the width direction of the slats for slats 62 and 72. The cut is formed, for example, in a depth range of 0.8 mm or more and 2.0 mm or less from the opening of the slat.

[0068] The sipes along the edges of the sipes 62 and 72 are formed on the first direction of the tire circumferential direction side of the sipe 62 in the intermediate rib 60 and on the second direction of the tire circumferential direction side of the sipe 72 in the intermediate rib 70. On the tire 1 provided on the left side of the vehicle, a sipe 620A along the edge of the sipe 62 is formed only at the edge (a first edge) on the rear side in the tire main rotation direction among the edges along the length direction of the sipe 62, and a sipe 720A along the edge of the sipe 72 is formed only at the edge (a second edge) on the front side in the tire main rotation direction among the edges along the length direction of the sipe 72.In this case, the ground contact pressure can be balanced by the tread 10 as a whole, and the benefits of improving braking performance and maneuvering stability are more obvious.

[0069] As in Fig. 4 and Fig. 6, on the intermediate rib 60, sipes (a first sipe 610A and a second sipe 610B) are formed along respective edges of the sipe 61. The first sipe 610A is formed at a first edge along the length direction of the sipe 61, and the second sipe 610B is formed at a second edge, opposite to the first edge, along the length direction of the sipe 61. The first edge of the sipe 61 extends on the circumferential groove 20 side to a longer length than the second edge, and the first sipe 610A is thus longer than the second sipe 610B. All of the sipes formed along the sipes 61 and 62 have a width that decreases from a starting end of the sipe toward the terminal end of the sipe.

[0070] Inclined surfaces forming the two sipes along the sipe 61 may have different inclination angles with respect to the profile surface α, but in the present embodiment, the inclined surfaces have an approximately equal inclination angle. Furthermore, maximum widths of the two sipes (inclined surfaces) are approximately the same. At portions where the widths of the sipes are maximum, the inclination angle of each inclined surface with respect to the profile surface α is desirably 15° or more and 60° or less. The inclination angles of the first inclined surface 61A forming the first sipe 610A and the second inclined surface 61B forming the second sipe 610B with respect to the profile surface α may be approximately constant over the entire lengths of the inclined surfaces.

[0071] The sipe 620A formed along the sipe 62 is formed at a first edge along the length direction of the sipe 62. The sipe 620A is located on the same side as the first sipe 410A formed along the lateral groove 41, which will be described later. The groove wall forming the second edge of the sipe 62 opposite the first edge is formed approximately perpendicular to the profile surface α. The relationships of the inclination angle, width, and the like of the inclined surface 62A forming the sipe 620A and the inclined surfaces formed along the sipe 61 are not specifically limited. For example, the maximum width of the sipe 620A and the inclined surface 62A is larger than the maximum width of the sipe and the inclined surface formed along the sipe 61.On the tire 1 provided on the left side of the vehicle, the first edges of the sipes 61 and 62 are positioned on the rear side in the tire main rotation direction of the sipe 61.

[0072] As described above, the sipe 61 is longer than the sipe 62. The length of the sipe 61 is desirably 1.1 times or more and 2.5 times or less, and more desirably 1.2 times or more and 2.0 times or less of the length of the sipe 62. The sipes 61 and 62 are formed in such a manner that portions of the sipes 61 and 62 with a depth exceeding 2.0 mm (hereinafter also referred to as "first portion") do not overlap each other in the tire circumferential direction. In the tire width direction, a distance S1 exists between the terminal end of the first portion of the sipe 61 and the terminal end of the first portion of the sipe 62. The distance S1 is substantially equal to a distance along the tire width direction between the groove bottom of the sipe 61 and the groove bottom of the sipe 62.The slats 61 and 62 have depths that become shallower near their terminal ends, and the depth in this region is, for example, less than or equal to 2.0 mm (this portion is hereinafter referred to as the “second portion”).

[0073] A total length of the lengths of the sipes 61 and 62 along the tire width direction is desirably 60% or more and 90% or less, and more desirably 70% or more and 80% or less of the width of the intermediate rib 60. That is, the pitch S1 is desirably 10% or more and 40% or less, and more desirably 20% or more and 30% or less of the width of the intermediate rib 60. In this case, the limit performance of maneuvering stability on the dry road surface can be more effectively improved while ensuring superior ride quality performance. For example, the length of the sipe 61 is 50% or more and 65% or less with respect to the width of the intermediate rib 60, and the length of the sipe 62 is 30% or more and 45% or less with respect to the width of the intermediate rib 60.The second portions of the sipes 61 and 62 may overlap each other in the tire circumferential direction, but in the present embodiment, the entire sipes including the second portions are formed in lengths so as not to overlap each other in the tire circumferential direction.

[0074] The depth of the sipe 61 is desirably shallower than the depth of the circumferential groove 21. The depth of the sipe 62 is desirably shallower than the depth of the circumferential groove 20. The depths of the sipes 61 and 62 may be set to equal depths, but in the present embodiment, the depth of the sipe 61 is greater than the depth of the sipe 62 (depth of the sipe 61>depth of the sipe 62) because the depth D1 of the circumferential groove 20 is smaller than the depth D2 of the circumferential groove 21 (D1 <D2). Die Tiefe der Lamelle 61 (erster Abschnitt) beträgt zum Beispiel 70% oder mehr und 95% oder weniger der Tiefe D2 der Umfangsrille 21 und die Tiefe der Lamelle 62 (erster Abschnitt) beträgt zum Beispiel 70% oder mehr und 95% oder weniger der Tiefe D1 der Umfangsrille 20.

[0075] As in Fig. 5 and Fig. As shown in Fig. 7, on the intermediate rib 70, sipes (a first sipe 710A and a second sipe 710B) are formed along respective edges of the sipe 71, and a sipe 720A is formed along one edge of the sipe 72. The first sipe 710A is formed at a first edge along the length direction of the sipe 71, and the second sipe 710B is formed at a second edge opposite to the first edge and along the length direction of the sipe 71. The sipe 71 has an intermediate portion that is significantly bent to be convex in the tire circumferential direction. The sipe 71 is longer than the sipe 72 in both the length along the tire width direction and the length along the sipe.

[0076] The sipe 71 has a bent portion 71C, and, for example, the first and second edges at the bent portion 71C are bent at angles of 90° or more and 120° or less. The bent portion 71C is formed at or near a center portion in the length direction of the sipe 71. In the sipe 71, a portion from the bent portion 71C to a terminal end is gradually curved to be convex in a direction of the starting end of the sipe 71. The sipe 71 is formed to be convex in a direction identical to a width-decreasing direction of a recess 53 of the shoulder rib 50, which will be described later.

[0077] The inclined surfaces forming the two sipes along the sipe 71 may have equal inclination angles with respect to the profile surface α and may be formed in the same width. However, in the present embodiment, the inclination angles are different from each other and the widths are different from each other. The relationship between the inclination angles and widths of the two inclined surfaces changes between a range from the starting end of the sipe 71 to the bent portion 71C and a range from the bent portion 71C to the terminal end of the sipe 71. That is, the inclination angles and widths of the inclined surfaces change significantly with the bent portion 71C as a boundary.

[0078] In the range from the initial end of the sipe 71 to the bent portion 71C, the inclination angle of a first inclined surface 71A forming the first sipe 710A with respect to the profile surface α is smaller than the inclination angle of a second inclined surface 71B forming the second sipe 710B with respect to the profile surface α, and the maximum width of the first sipe 710A and the first inclined surface 71A is larger than the maximum width of the second sipe 710B and the second inclined surface 71B. The width of each of the sipes and the inclined surfaces is gradually reduced from the initial end of the sipe 71 toward the bent portion 71C.

[0079] In the range from the bent portion 71C to the terminal end of the sipe 71, the inclination angle of the first inclined surface 71A with respect to the profile surface α is larger than the inclination angle of the second inclined surface 71B with respect to the profile surface α, and the maximum width of the first inclined surface 71A is smaller than the maximum width of the second inclined surface 71B. In a predetermined range from the terminal end of the sipe 71, the depth of the sipe 71 becomes shallower and is, for example, less than or equal to 2.0 mm.

[0080] An inclined surface 72A forming the sipe 720A along the sipe 72 is formed at a first edge along the length direction of the sipe 72. A groove wall forming a second edge of the sipe 72, opposite to the first edge, is formed approximately perpendicularly with respect to the tread surface α. The relationship between the inclination angles, widths, and the like between the inclined surface 72A and the two inclined surfaces formed along the sipe 71 is not specifically limited; however, in the present embodiment, the maximum width of the sipe 720A and the inclined surface 72A is larger than the maximum widths of the two sipes and the two inclined surfaces formed along the sipe 71. In the tire 1 provided on the left side of the vehicle, the first edges of the sipes 71 and 72 are positioned on the front side in the tire main rotation direction of the sipe 71.

[0081] Analogous to the sipe of the intermediate rib 60, portions of the sipes 71 and 72 with depths exceeding 2.0 mm (first portions) do not intersect each other in the tire circumferential direction. In the tire width direction, a distance S2 exists between the terminal end of the first portion of the sipe 71 and the terminal end of the first portion of the sipe 72. The distance S2 is a distance along the tire width direction between the terminal ends of the first portions (groove bottoms) of the sipes 71 and 72. The sipes 71 and 72 have depths that become shallower near their terminal ends and are, for example, less than or equal to 2.0 mm.

[0082] The flat portions of the sipes 71 and 72, where the depths are less than or equal to 2.0 mm (second portions), may overlap each other in the tire circumferential direction. The relationship between the pitches S1 and S2 of the intermediate ribs 60 and 70 is not specifically limited. In the present embodiment, the pitch S1 is greater than the pitch S2 (S1>S2). A total length of the lengths along the tire width direction of the groove bottoms of the sipes 71 and 72 is desirably 80% or more and 99% or less of the width of the intermediate rib 70. That is, the pitch S2 is desirably 1% or more and 20% or less of the width of the intermediate rib 70.

[0083] The depth of the sipe 71 is desirably shallower than the depth of the circumferential groove 22. Similarly, the depth of the sipe 72 is desirably shallower than the depth of the circumferential groove 23. In the present embodiment, for example, the depths of the sipes 71 and 72 are substantially equal and are constant throughout the entire lengths of the sipes. The depths of the sipes 71 and 72 (first portions) are desirably 70% or more and 95% or less of the depths D2 and D3 of the circumferential grooves 21 and 22.

[0084] The structures of the sipes formed on the intermediate ribs 60 and 70, particularly, for example, the structures of the sipes 61 and 62 of the intermediate rib 60, effectively improve ride quality performance while suppressing significant rib deformation during high-speed cornering and braking. The first region R1 of the tread 10 has a large ground contact area and high rigidity, and the tire 1 is superior in terms of limit performance of maneuvering stability. However, such a tire tends to exhibit inferior ride quality performance. With the tire 1, both maneuvering stability and ride quality performance can be realized at a high level.Furthermore, the cuts formed along the edges of the sipes ensure a large ground contact area and a balanced distribution of ground contact pressure, thus contributing significantly to improvements in braking performance and maneuvering stability.

[0085] The lateral grooves formed in the shoulder ribs 40 and 50 will now be described with reference to Fig. 8 and Fig. 9 together with Fig. 3 to 7 are described in detail. Fig. Fig. 8 is a perspective diagram showing an enlarged view of a lateral groove 41 formed on the shoulder rib 40, and Fig. 9 is a cross-sectional diagram along a line AA of Fig. 4 and a cross-sectional diagram along a width direction of the lateral groove 41 at a portion of maximum widths of the sipes of the lateral groove 41.

[0086] As in Fig. 3, Fig. 4 and Fig. As shown in Fig. 6, the lateral groove 41 extending in a direction intersecting the circumferential groove 20 is formed on the shoulder rib 40 in the first region R1. The lateral groove 41 is formed from a position spaced from an end edge of the shoulder rib 40 beyond the ground contact end E1 and toward the side rib 13. The lateral groove 41 is not connected to the circumferential groove 20, and a starting end of the lateral groove 41, which is an end on the tire equator CL side, is positioned in the shoulder rib 40. In this case, the reduction of the ground contact area due to deformation of the shoulder rib 40 can be suppressed, and superior maneuverability stability and braking performance can be achieved.

[0087] The lateral grooves 41 are formed in the same number as the number of sipes of the intermediate ribs 60. The plurality of lateral grooves 41 may be formed at an equal distance from each other in the tire circumferential direction, but preferably, the lateral grooves 41 are formed at a variable pitch in which the distance between the lateral grooves 41 is slightly varied every predetermined number of the grooves in the tire circumferential direction. The lateral groove 41 is inclined in the same direction with respect to the tire width direction as the sipe of the intermediate rib 60, but its inclination angle is smaller than the sipe of the intermediate rib 60. Further, the lateral groove 41 is slightly bent in a region near the starting end, and the depth of the lateral groove 41 is gradually reduced from a bent portion 41C toward the starting end. The depth of the lateral groove 41 is deepest at the bent portion 41C.The depth of the side groove 41 is gradually reduced from the bent portion 41C toward the ground contact end E1 and is further reduced beyond the ground contact end E1 and toward the side rib 13, which is the position of the terminal end.

[0088] On the shoulder rib 40, sipes (a first sipe 410A and a second sipe 410B) are formed along respective edges of the lateral groove 41 in a range of 2.0 mm in depth from an opening of the lateral groove 41. The first sipe 410A is formed at a first edge along the length direction of the lateral groove 41, and the second sipe 410B is formed at a second edge opposite to the first edge along the length direction of the lateral groove 41. The two sipes are formed along the entire length of the lateral groove 41 on both sides in the width direction of the lateral groove 41. Each sipe is formed, for example, in a depth range of 0.8 mm or more and 2.0 mm or less from the opening of the lateral groove 41.

[0089] As in Fig. 3, Fig. 5 and Fig. As shown in Fig. 7, the lateral groove 51 extending in a direction intersecting the circumferential groove 23 is formed on the shoulder rib 50 in the second region R2. Analogous to the lateral groove 41 of the shoulder rib 40, the lateral groove 51 is formed from a position spaced from an end edge of the shoulder rib 50 beyond the ground contact end E2 and toward the side rib 13. The lateral groove 51 is not connected to the circumferential groove 23, and a starting end of the lateral groove 51, which is an end on the tire equator CL side, is positioned in the shoulder rib 50. The lateral grooves 41 and 51 are not arranged side by side along the tire width direction, and the lateral groove 51 is placed to be positioned on an extension line in the length direction of the lateral groove 41.

[0090] The lateral grooves 51 are formed in the same number as the number of sipes of the intermediate rib 70. The plurality of lateral grooves 51 may be formed at an equal distance from each other in the tire circumferential direction, but desirably, the lateral grooves 51 are formed at a variable pitch in which the distance between the lateral grooves 51 is slightly varied every predetermined number of grooves in the tire circumferential direction. In the present embodiment, the numbers of lateral grooves 41 and 51, the number of sipes of the center rib 30, and the number of sipes of the intermediate ribs 60 and 70 are the same. Similar to the lateral groove 41, the lateral groove 51 is slightly bent in a region near a starting end and has a depth that gradually decreases from the bent portion 51C toward the starting end.The depth of the side groove 51 is gradually reduced from the bent portion 51C toward the ground contact end E2 and is further reduced beyond the ground contact end E2 and toward the side rib 13, which is the position of the terminal end.

[0091] On the shoulder rib 50, sipes (a first sipe 510A and a second sipe 510B) are formed along respective edges of the lateral groove 51 in a range of 2.0 mm in depth from an opening of the lateral groove 51. The first sipe 510A is formed at a first edge along the length direction of the lateral groove 51, and the second sipe 510B is formed at a second edge opposite to the first edge along the length direction of the lateral groove 51. The two sipes are formed along the entire length of the lateral groove 51 on both sides in the width direction of the lateral groove 51. Each sipe is formed, for example, in a depth range of 0.8 mm or more and 2.0 mm or less from the opening of the lateral groove 51.

[0092] As will be described in detail below, the first sipe 410A formed along the lateral groove 41 is wider than the second sipe 410B, and the first inclined surface 41A forming the first sipe 410A has a smaller inclination angle with respect to the profile surface α than the second inclined surface 41B forming the second sipe 410B. Similarly, the first sipe 510A formed along the lateral groove 51 is wider than the second sipe 510B, and the first inclined surface 51A forming the first sipe 510A has a smaller inclination angle with respect to the profile surface α than the second inclined surface 51B forming the second sipe 510B.In the present embodiment, the first sipe is formed on the tire circumferential direction first direction side of the lateral groove 41 in the shoulder rib 40 and on the tire circumferential direction second direction side of the lateral groove 51 in the shoulder rib 50.

[0093] In the tire 1 provided on the left side of the vehicle, analogous to the sipe 620A of the intermediate rib 60, the first sipe 410A is formed along the edge of the lateral groove 41 at a first edge on the rear side in the tire main rotation direction among the edges along the length direction of the lateral groove 41. Analogous to the sipe 720A of the intermediate rib 70, the first sipe 510A is formed along the edge of the lateral groove 51 at a second edge on the front side in the tire main rotation direction among the edges along the length direction of the lateral groove 51. In this case, the ground contact pressure can be evenly distributed by the tread 10 as a whole, and the effects of improving braking performance and maneuverability become more noticeable.Each of the shoulder ribs 40 and 50 has a first edge and a second edge formed along a length direction of respective lateral grooves 41 or 51 and placed to oppose each other in the tire circumferential direction. The first edge is the so-called "trailing-side" edge, which contacts the ground after the second edge when the tire rotates in the main rotation direction. The second edge is the so-called "leading-side" edge, which contacts the ground before the first edge when the tire rotates in the main rotation direction. That is, the first sipe 410A is formed at the trailing-side edge of the lateral groove 41, and the sipe 510A is formed at the leading-side edge of the lateral groove 51.

[0094] On the shoulder rib 50, the recess 53, which has an approximately triangular shape in plan view, is formed at an end edge along the circumferential groove 23. The second region R2 of the tread 10 has a smaller ground contact area than the first region R1, but the recess 53 contributes to increasing a static friction force with respect to the road surface and improving maneuverability. The recess 53 is formed, for example, from an upper end opening of the circumferential groove 23 to a depth exceeding the cut of the shoulder rib 50. The depth of the recess 53 is desirably shallower than the depth of the lateral groove 51. The recesses 53 are formed in a fewer number than the number of lateral grooves 51 at an approximately equal pitch in the tire circumferential direction.The number of recesses 53 is, for example, 1 / 2 the number of lateral grooves 51, and each of the recesses 53 is formed to be positioned between two lateral grooves 51 in the tire circumferential direction.

[0095] The recess 53 is placed so as to be arranged side by side with the sipe 71 of the intermediate rib 70 in the tire width direction. The recess 53 is formed by a part of the groove wall of the circumferential groove 23 constituting the sidewall of the shoulder rib 50, which is recessed toward the inner side of the rib, and has the width changing along the tire circumferential direction so as to have an approximately triangular shape in plan view. The width of the recess 53 is gradually reduced in the same direction as the direction in which the sipe 71 is convex. The depth of the recess 53 is constant over the entire length in the tire circumferential direction.

[0096] The structure of the sipe will now be described in more detail using the example of the shoulder rib 40. The structures of the first sipes 410A and 510A are identical to each other except that their directions are opposite to each other with respect to the tire circumferential direction (this applies analogously to the second sipes 410B and 510B).

[0097] As in Fig. 8 and Fig. As shown in FIG. 9, a maximum width Wa of the first sipe 410A is larger than a maximum width Wb of the second sipe 410B. The two sipes and the two inclined surfaces constituting the sipes have approximately constant widths, which are maximum between the bent portion 41C of the lateral groove 41 and the ground contact end E1. The widths of the sipes are gradually reduced from the bent portion 41C of the lateral groove 41 toward the initial ends and are slightly reduced from the ground contact end E1 toward the side rib 13. On an outer side in the tire width direction with respect to the ground contact end E1, the width of the first sipe 410A and the width of the second sipe 410B may be approximately the same, and the width of the second sipe 410B may be larger than the width of the first sipe 410A.

[0098] The maximum width Wa of the first sipe 410A is desirably 1.5 times or more and 3.0 times or less, and more desirably 1.8 times or more and 2.5 times or less of the maximum width Wb of the second sipe 410B. In this case, the ground contact pressure can be more effectively balanced while ensuring a large ground contact area of ​​the tread 10. When the maximum width Wa is less than 1.5 times the maximum width Wb, the advantage tends to be reduced. On the other hand, when the maximum width Wa exceeds 3.0 times the maximum width Wb, the advantage of reducing the ground contact pressure tends to be reduced.

[0099] The maximum width Wa of the first cut 410A is desirably 30% or more and 50% or less, and more desirably 35% or more and 45% or less of the maximum width W of the lateral groove 41. Here, as in Fig. 9, the maximum width W of the lateral groove 41 is the maximum width Wa of the first sipe 410A, and the maximum width Wb of the second sipe 410B. A total of the maximum widths of the first sipe 410A and the second sipe 410B is desirably greater than or equal to 50% of the maximum width W of the lateral groove 41. In this case, the balanced distribution of the ground contact pressure can be facilitated while ensuring the large ground contact area of ​​the tread 10, and the advantages of improving maneuverability and braking performance become more apparent. The total width of the maximum widths of the two sipes is, for example, 50% or more and 80% or less, or 55% or more and 70% or less of the maximum width W.

[0100] At the portions of the first sipe 410a and the second sipe 410B where the widths are maximum, the inclination angle θa of the first inclined surface 41A with respect to the tread surface α is smaller than the inclination angle θb of the second inclined surface 41B with respect to the tread surface α. Since the widths of the two inclined surfaces between the bent portion 41C of the lateral groove 41 and the ground contact end E1 are maximum, the angle θa is smaller than the angle θb (θa<θb) at least in this region. On an outer side in the tire width direction with respect to the ground contact end E1, the angle θa may be larger than the angle θb (θa>θb).

[0101] A difference between the inclination angle θa of the first inclined surface 41A and the inclination angle θb of the second inclined surface 41B is desirably greater than or equal to 10°. In this case, the ground contact pressure can be more effectively distributed in a balanced manner while ensuring a large ground contact area of ​​the tread 10. A desirable example of the inclination angle θa of the first inclined surface 41A with respect to the tread surface α is 20° or more and 40° or less, and the inclination angle θa is more desirably 25° or more and 35° or less. A desirable example of the inclination angle θb of the second inclined surface 41B with respect to the tread surface α is 30° or more and 60° or less, and the inclination angle θb is more desirably 40° or more and 50° or less.

[0102] When the inclination angles θa and θb of the inclined surfaces exceed the above-described ranges, the benefits of reducing ground contact pressure tend to be reduced. On the other hand, when the inclination angles θa and θb of the inclined surfaces are below the above-described ranges, it becomes difficult to ensure a large ground contact area. The inclined surfaces desirably have the inclination angles θa and θb within the above-described ranges, and the difference between the angles θa and θb (θb-θa) is desirably greater than or equal to 10°. An example of a desirable range of the difference between the angles θa and θb is 10° or more and 25° or less, or 15° or more and 20° or less.

[0103] With the tire 1 having the structure described above, the ground contact pressure can be effectively dispersed while ensuring a large ground contact area, making it possible to realize superior braking performance. Furthermore, superior maneuverability can be achieved, especially on dry road surfaces. When the ground contact pressure is concentrated on a portion of the tread, the friction coefficient of the rubber is reduced and the rubber is significantly deformed, resulting in a reduction in the ground contact area and, consequently, a significant reduction in braking performance and maneuverability.In the tire 1, for example, with the sipes formed along the edges of the lateral grooves 41 and 51 formed on the shoulder ribs 40 and 50 and utilizing a synergistic effect with the sipes formed along the edges of the sipes of the center rib 30 and the intermediate ribs 60 and 70, the concentration of the ground contact pressure can be suppressed and the ground contact pressure can be effectively reduced.

[0104] As described above, in the tire 1, the rigidity of the first region R1 of the tread 10 positioned on the outer side of the vehicle is high, and the tire 1 exhibits superior maneuverability during high-speed cornering and braking. Specifically, in the tire 1, the circumferential groove 20 of the first region R1 is formed shallow and narrow, so that the lateral groove 41 of the shoulder rib 40 is spaced apart from the circumferential groove 20. With this configuration, the rigidity of the shoulder rib 40 is increased, and significant deformation of the shoulder rib 40 during high-speed cornering and braking can be suppressed. Furthermore, with the sipes 61 and 62 formed from both sides in the width direction of the intermediate rib 60, superior ride quality performance is realized while ensuring the rigidity of the first region R1.

[0105] As described, tire 1 exhibits superior braking performance and high marginal maneuverability performance, which is desirable for a UHP tire. Tire 1 also exhibits superior ride quality performance. That is, tire 1 is an innovative high-performance tire with superior braking performance, superior maneuverability, and superior ride quality performance.

[0106] The above-described embodiment of the present invention can be appropriately modified in design within a range that does not impair the object of the present invention. For example, although the block is desirably formed in a rib shape continuous in the tire circumferential direction, a lateral groove or a sipe extending laterally on the block may be formed within a range in which the desired rigidity of the tread 10 can be ensured. Although four circumferential grooves with mutually different widths are formed on the tread 10 in the above-described embodiment, the structure of the circumferential groove is not limited to this configuration.

[0107] In the above-described embodiment, the ground contact pressure is effectively dispersed by the synergistic effect of the sipes of the shoulder ribs 40 and 50, the center rib 30, and the intermediate ribs 60 and 70. However, the structure of the sipe may be modified within a range where the desired advantage of dispersing the ground contact pressure can be ensured. For example, in the center rib or the intermediate rib, it is possible to form the sipe not along an edge of a part of the sipes.

[0108] In the embodiment described above, the maximum width Wa of the first sipe 410A of the lateral groove 41 is larger than the maximum width Wb of the second sipe 410B, and the inclination angle θa of the first inclined surface 41A is smaller than the inclination angle θb of the second inclined surface 41B. However, within a range in which the desired ground contact area and the effect of reducing the ground contact pressure can be ensured, the maximum width Wa may be set to be smaller than the maximum width Wb (Wa <wb), und der winkel θa kann festgelegt sein, um kleiner zu sein als θb (θa<θb).LIST OF REFERENCE SYMBOLS 1 tire 10 Tread 11 Side wall 12 bulge 13 side rib 14 Carcass 15 belts 16 Inner core 17 Bead core 18 core riders 20, 21, 22, 23 circumferential groove 30 midrib 31, 32, 61, 62, 71, 72 slat 31A, 41A, 51A, 61A, 71A first inclined surface 31B, 41B, 51B, 61B, 71B second inclined surface 32A, 62A, 72A inclined surface 40, 50 shoulder ribs 41, 51 lateral groove 41C, 51C, 71C curved section 53 recess 60, 70 Intercostal 310A, 410A, 510A, 610A, 710A first cut 310B, 410B, 510B, 610B, 710B second notch 320A, 620A, 720A cut CL Tire Equator E1, E2 ground contact end R1 first area R2 second area

Claims

[1] A tire (1) comprising a tread (10) comprising: two or more circumferential grooves (20, 21, 22, 23); a first shoulder block (40) formed on a side of a first ground contact end (E1); and a second shoulder block (50) formed on a side of a second ground contact end (E2), wherein each of the first shoulder block (40) and the second shoulder block (50) has a lateral groove (41, 51) extending in a direction intersecting the circumferential groove (20, 21, 22, 23), on the first shoulder block (40) and the second shoulder block (50), a first notch (410A, 510A) and a second notch (410B, 510B) are formed along respective edges of each of the lateral grooves (41, 51) in a region of a depth of 2.0 mm from an opening of the lateral groove (41, 51), at portions where widths of the first sipe (410A, 510A) and the second sipe (410B, 510B) are maximum, an inclination angle (θa) of a first inclined surface (41A, 51A) forming the first sipe (410A, 510A) with respect to a tread pattern surface (α) along a ground contact surface of the tread (10) is smaller than an inclination angle (θb) of a second inclined surface (41B, 51B) forming the second sipe (410B, 510B) with respect to the tread pattern surface (α), and the first notch (410A) of the first shoulder block (40) is formed along a trailing edge of the lateral groove (41) and the first notch (510A) of the second shoulder block (50) is formed along a leading edge of the lateral groove (51). [2] The tire (1) according to claim 1, wherein, at the portions where the widths of the first sipe (410A, 510A) and the second sipe (410B, 510B) are maximum, the inclination angle (θa) of the first inclined surface (41A, 51A) with respect to the tread pattern surface (α) is 20° or more and 40° or less, and the inclination angle (θb) of the second inclined surface (41B, 51B) with respect to the tread pattern surface (α) is 30° or more and 60° or less, and is greater than or equal to 10° than the inclination angle (θa) of the first inclined surface (41A, 51A). [3] A tire (1) according to claim 1 or 2, wherein one end of the lateral groove (41, 51) terminates on one side of a tire equator (CL) in the first and second shoulder blocks (40, 50). [4] The tire (1) according to any one of claims 1 to 3, wherein a ratio of a groove area with respect to a ground contact area of the tread (10) is 33% or more and 40% or less. [5] A tire (1) according to any one of claims 1 to 4, wherein a maximum width (Wa) of the first sipe (410A, 510A) is 30% or more 50% or less of a maximum width (W) of the lateral groove (41, 51). [6] Tire (1) according to one of claims 1 to 5, wherein the tread (10) comprises a first intermediate block (60) placed adjacent to the first shoulder block (40) with a first circumferential groove (20) therebetween, and a second intermediate block (70) placed adjacent to the second shoulder block (50) with a second circumferential groove (23) therebetween, on the first intermediate block (60) and the second intermediate block (70), first sipes (61, 71) extending from third and fourth circumferential grooves (21, 22) positioned on one side of the tire equator (CL) and terminating in the intermediate block (60, 70), and second sipes (62, 72) extending from the first and second circumferential grooves (20, 23) positioned on one side of the ground contact ends (E1, E2) and terminating in the intermediate block (60, 70) are formed, and the first slat (61, 71) is longer than the second slat (62, 72). [7] Tire (1) according to claim 6, wherein on the first intermediate block (60) and the second intermediate block (70), cuts (610A, 610B, 620A, 710A, 710B, 720A) are formed along edges of the first slat (61, 71) and the second slat (62, 72) respectively in a region of a depth of 2.0 mm from an opening of each slat, and the cuts (610A, 610B, 620A, 710A, 710B, 720A) for the first slat (61, 71) are formed on both sides in a width direction and for the second slat (62, 72) only on one side in the width direction. [8] The tire (1) according to claim 7, wherein the sipe (620A, 720A) of the second sipe (62, 72) is formed on a side of a first direction of the tire circumferential direction of the second sipe (62) on the first intermediate block (60) and on a side of a second direction of the tire circumferential direction of the second sipe (72) on the second intermediate block (70). [9] Tire (1) according to one of claims 6 to 8, wherein the tyre (1) is a tyre in which a mounting direction on a vehicle is fixed, and the first sipe (71) formed on the second intermediate block (70) positioned on an inner side of the vehicle with respect to the tire equator (CL) has an intermediate portion bent such that the sipe (71) is convex in the tire circumferential direction. [10] Tire (1) according to one of claims 1 to 9, wherein the tyre (1) is a tyre in which a mounting direction on a vehicle is specified, on the second shoulder block (50) placed on an inner side of the vehicle with respect to the tire equator (CL), a recess (53) having an approximately triangular shape in plan view is formed at an end edge along the second circumferential groove (23), and a plurality of said recesses (53) are formed in a number less than a number of said lateral grooves (51) and spaced apart in the tire circumferential direction. [11] Tire (1) according to claim 10, wherein the tread (10) has a central block (30) formed on the tire equator (CL), on the center block (30), a first sipe (31) extending from a third circumferential groove (21) positioned on one side of the first ground contact end (E1) and terminating in the center block (30), and a second sipe (32) extending from a fourth circumferential groove (22) positioned on one side of the second ground contact end (E2) and terminating in the center block (30) are formed, and the first slat (31) is longer than the second slat (32). [12] Tire (1) according to claim 11, wherein on the center block (30), cuts (310A, 310B, 320A) are formed along edges of the first slat (31) and the second slat (32) in a depth range of 2.0 mm from an opening of each slat, and the cuts (310A, 310B, 320A) for the first slat (31) are formed on both sides in a width direction and for the second slat (32) only on one side in the width direction. [13] A tire (1) according to any one of claims 1 to 12, wherein a 300% modulus of rubber constituting a surface layer of the tread (10) is 15 or less.

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