pneumatic tires

Abstract

Pneumatic tires (1), comprising: in a tread surface (21) main grooves (22) extending in a circumferential direction of the tire; Shoulder rib sections (23S) that are located at the outermost point in a tire transverse direction; at least one rib section (23M, 23C) defined by two of the main grooves (22) adjacent in a tire transverse direction; lug grooves (24) arranged in the circumferential direction of the tire in the tread surface (21) of the rib section (23M, 23C), wherein the lug grooves (24) each cross the circumferential direction of the tire and are connected at both ends to the main grooves (22), thereby defining the rib section (23M, 23C) in the circumferential direction of the tire; and a recess section (25) formed at an opening edge of the lug grooves (24), wherein the recess section (25) is a cutout from the tread surface (21) that is cut inwards in the tire radial direction; wherein the tread grooves (24) have a maximum groove width (y0) at a position of 30% to 70% of a tire transverse dimension (W) of the rib section (23M, 23C) of one of the main grooves (22) and a groove width that decreases from the maximum groove width (y0) to the main grooves (22); the recess section (25) has a recess width (x) that increases from a position of the maximum groove width (y0) of the adit grooves (24) to the main grooves (22); and wherein the groove width (y1, y1a, y1b) from both ends (24a) of the adit groove (24) is in a range of 1.5 mm or more, and less than 4.5 mm.

Description

Technical field

[0001] The present invention relates to a pneumatic tire. State of the art

[0002] A known tire, for example the tire described in patent document 1, is designed to prevent small stones from becoming wedged and to effectively reduce air column resonance. The tire includes a rib-like web section extending in a circumferential direction adjacent to a circumferential groove extending in the same direction; and a first groove section and a second groove section adjacent to the first groove section, and a partition section adjacent to the first groove section and the second groove section, which are formed within the rib-like web section. The first groove section and the second groove section each include an air chamber section, which forms a closed space when the rib-like web section comes into contact with the road surface, and a constriction groove section that communicates with the air chamber section and the circumferential groove.One end of the constriction groove section is connected to the enclosed space formed by the air chamber section and the road surface, and the other end of the constriction groove section is connected to the circumferential groove. The volume of the space formed by the constriction groove section and the road surface is smaller than the volume of the enclosed space formed by the air chamber section and the road surface. The first groove section and the second groove section extend at an inclination with respect to the tire's circumferential direction. Brief description of the invention: Technical problem

[0003] The tire described in patent document JP 2010-280 266 A incorporates a Helmholtz-type resonator, including the air chamber section and the constriction groove section, to reduce air column resonance. Furthermore, in the tire described in patent document 1, the first and second groove sections extend in an inclined direction with respect to the tire's circumference. As the rib-like rib section leads to or abuts the road surface, the groove width of the first and second groove sections increases, allowing stones wedged in the first and second groove sections to be ejected.

[0004] However, in the tire described in patent document 1, the first and second groove sections are designed such that the other end of the constricted groove section is in contact with the circumferential groove in order to reduce air column resonance. This reduces the drainage capacity and makes it difficult to ensure wet performance (braking performance on wet road surfaces).

[0005] JP 2015 024 818 A discloses a pneumatic tire comprising: main grooves in a tread surface extending in a tire circumferential direction; a rib section defined by two of the main grooves adjacent in a tire transverse direction; lug grooves arranged in the tire circumferential direction in the tread surface of the rib section, the lug grooves each intersecting the tire circumferential direction and connecting at both ends with the main grooves, thereby defining the rib section in the tire circumferential direction; and a recess section formed at an opening edge of the lug grooves, the recess section being a cutout from the tread surface cut inwards in the tire radial direction.

[0006] DE 11 2014 006 530 T5 reveals another pneumatic tire.

[0007] In light of the foregoing, it is an object of the present invention to provide a pneumatic tire that can provide reduced pattern noise and ensure wet performance. Solution to the problem

[0008] To solve the problems described above and to fulfill the task described above, a pneumatic tire according to one aspect of the present invention comprises: Main grooves in a tread surface that extend in a circumferential direction of the tire; a rib section defined by two of the main grooves that are adjacent in a tire transverse direction; Lug grooves arranged in the circumferential direction of the tire on the tread surface of the rib section, wherein the lug grooves each cross the circumferential direction of the tire and are connected at both ends to the main grooves, thereby defining the rib section in the circumferential direction of the tire; and a recessed section formed at an opening edge of the lug grooves, wherein the recessed section is a cutout from the tread surface that is cut inwards in the tire radial direction; wherein the lug grooves have a maximum groove width at a position of 30% to 70% of a tire transverse dimension of the rib section from one of the main grooves and a groove width that decreases from the maximum groove width to the main grooves; and The recess section has a recess width that increases from the position of the maximum groove width of the cleat grooves towards the main grooves. The groove width at both ends of the cleat groove is in the range of 1.5 mm or more, and less than 4.5 mm.

[0009] In accordance with the pneumatic tire design, the lug grooves have a groove width that gradually decreases towards the main grooves. This helps to suppress noise radiating outwards from the lug grooves in the tire's transverse direction. Furthermore, the recessed section provided at the opening edge of the lug groove also has a recess width that gradually increases towards the main grooves. This enhances water drainage within the lug grooves. Consequently, pattern noise is reduced, and wet grip (braking performance on wet road surfaces) is maintained.

[0010] In a pneumatic tire according to one aspect of the present invention, the ratios 0 ≤ x0 < x and 0.2(y0 - y) + x0 ≤ x ≤ 2.0(y0 - y) + x0 are preferably satisfied, wherein y0 is a maximum groove width of the lug grooves, x0 is the recess width of the recess section at the position of the maximum groove width of the lug grooves, y is a groove width of the lug grooves at any position that is further outwards in the transverse direction of the tire than the position of the maximum groove width of the lug grooves, and x is a recess width of the recess section at any position.

[0011] According to the pneumatic tire design, the width of the recessed section is determined by the change in the groove width of the tread groove. If the recessed section width is 0.2(y0 - y) + x0 or greater, a significant improvement in water drainage can be achieved. If the recessed section width is 2.0(y0 - y) + x0 or less, a significant reduction in noise radiating outwards from the tread groove in the tire's transverse direction can be achieved. Consequently, tread noise can be reduced, and a significant improvement in wet performance (braking performance on wet road surfaces) can be achieved.

[0012] In a pneumatic tire according to one aspect of the present invention, the recess section preferably has a recess depth from the tread surface inwards in the tire radial direction of 0.5 to 3.0 mm.

[0013] According to this pneumatic tire, a recess depth of 0.5 mm or more significantly improves drainage performance. Conversely, a recess depth of 3.0 mm or less significantly reduces noise emissions.

[0014] In a pneumatic tire according to one aspect of the present invention, a direction of rotation is preferably provided; and a ratio xb < xa ≤ 3.0xb is satisfied, wherein xa is a recess width of the recess section located on a rear side of the rib section in the tire circumferential direction with respect to the lug grooves, and xb is a recess width of the recess section located on a front side.

[0015] According to the pneumatic tire design, by having a wider recess width at the rear of the rib section relative to the lug groove than at the front, deformation (twisting) is suppressed and stiffness is ensured to a greater extent at the rear than at the front relative to the lug groove. Consequently, sawtooth wear is suppressed and abrasion resistance performance is improved.

[0016] In a pneumatic tire according to one aspect of the present invention, the lug grooves preferably have a groove depth G at a position where the lug grooves are in contact with the main grooves, and a groove depth G0 at a maximum groove width position, which satisfy a range of 0.2 × G0 ≤ G ≤ 0.6 × G0.

[0017] According to this pneumatic tire, the groove depth G at the end junction with the main groove is less than the groove depth G0 at the point of maximum groove width. This effectively suppresses noise emissions. By meeting the requirements of 0.2 × G0 ≤ G ≤ 0.6 × G0, drainage performance can be maintained and wet grip ensured.

[0018] In the pneumatic tire according to one aspect of the present invention, a vehicle inside / outside orientation is preferably provided when mounted on a vehicle; and The lug grooves have a groove width at a position where the lug grooves connect with the main grooves that is smaller on the outside of the vehicle than on the inside of the vehicle.

[0019] The outer side of a vehicle, when the tire is mounted, exhibits significant problems with noise emission. Therefore, according to the pneumatic tire, by making the groove width of the tread pattern on the outer side of the tire smaller than the groove width on the inner side, noise emission can be effectively suppressed, and a significant effect can be achieved.

[0020] In a pneumatic tire according to one aspect of the present invention, a ratio of 0.80 × y0 ≤ y ≤ 0.98 × y0 is preferably fulfilled at a position 0.50 × L; at a position 0.80 × L, the ratio 0.60 × y0 ≤ y ≤ 0.90 × y0 is satisfied; and at a position 1.00 × L a ratio 0.30 × y0 ≤ y ≤ 0.50 × y0 is satisfied, where L is a tire transverse dimension from a position of maximum groove width of the lug grooves to a position where the lug grooves are connected to the main grooves, y0 is a maximum groove width of the lug grooves, and y is a groove width of the lug grooves at any position that is further outward in the tire transverse direction than the position of maximum groove width of the lug grooves.

[0021] According to the pneumatic tire, by ensuring that the groove width y of the tread groove is narrow at or near the end, a groove volume can be guaranteed, wet performance can be maintained, and a significant reduction in pattern noise can be achieved. Advantageous effects of the invention

[0022] An air-filled tire according to an embodiment of the present invention can provide reduced pattern noise and maintain wet performance. Brief description of the drawings Fig. Figure 1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. Fig. Figure 2 is an enlarged top view of a section of a pneumatic tire according to an embodiment of the present invention. Fig. Figure 3 is an enlarged perspective view of a section of a pneumatic tire according to an embodiment of the present invention. Fig. Figure 4 is an enlarged cross-sectional view of a section of a pneumatic tire according to an embodiment of the present invention. Fig. Figure 5 is an enlarged top view of a section of a pneumatic tire according to another embodiment of the present invention. Fig. Figure 6 is an enlarged top view of a section of a pneumatic tire according to another embodiment of the present invention. Fig. Figure 7 is an enlarged cross-sectional view of a section of a pneumatic tire according to another embodiment of the present invention. Fig. Figure 8 is an enlarged top view of a section of a pneumatic tire according to another embodiment of the present invention. Fig. Figure 9 is a table showing the results of performance tests of pneumatic tires according to examples of the present invention. Description of embodiments

[0023] Embodiments of the present invention are described in detail below with reference to the drawings. However, the present invention is not limited to these embodiments. Components of the embodiments include elements that are essentially identical or that can be exchanged or easily devised by a person skilled in the art. Furthermore, the modified examples described in the embodiments can be combined as required within the scope of protection obvious to a person skilled in the art.

[0024] A pneumatic tire according to the present embodiment is described. Fig. Figure 1 is a meridian cross-sectional view of a pneumatic tire according to the present embodiment.

[0025] Herein, "tire radial direction" refers to the direction perpendicular to the axis of rotation (not illustrated) of a pneumatic tire 1. "Inward in tire radial direction" refers to the direction towards the axis of rotation in the tire radial direction. "Outward in tire radial direction" refers to the direction away from the axis of rotation in the tire radial direction. "Circular direction" refers to a circumferential direction with the axis of rotation as a central axis. "Transverse direction" also refers to a direction parallel to the axis of rotation. "Inward in tire transverse direction" refers to the direction towards an equatorial plane of the tire (tire equator line) CL in the transverse direction. "Outward in tire transverse direction" refers to a direction away from the equatorial plane of the tire CL in the transverse direction.“Tire equatorial plane CL” refers to the plane perpendicular to the axis of rotation of the pneumatic tire 1, which passes through the center of the tire width of the pneumatic tire 1. “Tire width” is the width in the transverse direction of the tire between components located on the outer side of the tire, or in other words, the distance between the components furthest from the tire equatorial plane CL in the transverse direction. “Tire equator line” refers to the line in the circumferential direction of the pneumatic tire 1 that lies on the tire equatorial plane CL. In the present embodiment, the tire equator line and the tire equatorial plane are designated with the same reference numeral CL.

[0026] As in Fig. As illustrated in Figure 1, the pneumatic tire 1 of the present embodiment comprises a tread section 2, shoulder sections 3 on opposite sides of the tread section 2, and sidewall sections 4 and bead sections 5, which follow one another in this order from the shoulder sections 3. The pneumatic tire 1 also comprises a carcass layer 6, a belt layer 7, and a belt reinforcement layer 8. The pneumatic tire 1 according to the present embodiment is mainly used for passenger cars, but can also be a heavy-duty pneumatic tire for trucks and buses.

[0027] The tread section 2 is made of a rubber material (tread rubber) and is exposed on the outermost side of the pneumatic tire 1 in the radial direction, its surface forming the tread pattern of the pneumatic tire 1. A tread surface 21 is formed on an outer circumferential surface of the tread section 2, in other words, on a road contact surface that comes into contact with a road surface when driving. A plurality (four in the present embodiment) of main grooves 22, extending in the circumferential direction of the tire, are arranged side by side in the transverse direction of the tire in the tread surface 21. In addition, a plurality (five in the present embodiment) of rib-like web sections 23 are defined in the tread surface 21 by the plurality of main grooves 22, extending in the circumferential direction of the tire and parallel to the tire equator line CL.In particular, in the pneumatic tire 1 of the present embodiment, the rib sections 23 include shoulder rib sections 23S, which are located at the outermost points in the transverse direction of the tire, a central rib section 23C, which is located centrally in the transverse direction of the tire (on the equatorial plane of the tire CL), and intermediate rib sections 23M, which are located in the transverse direction of the tire between the shoulder rib sections 23S and the central rib section 23C. A plurality of lug grooves 24, which extend in the circumferential direction of the tire and intersect the circumferential direction (main grooves 22), are arranged in the circumferential direction of the tire on the tread surface 21 of the rib sections 23. It should be noted that in an embodiment with five or more main grooves 22, a plurality of intermediate rib sections 23M are defined on each side of the equatorial plane of the tire CL in the transverse direction of the tire.

[0028] The shoulder sections 3 are sections of the tread section 2 that are arranged outwards on both sides in the transverse direction of the tire. Furthermore, the sidewall sections 4 are exposed at the outermost sides of the pneumatic tire 1 in the transverse direction. The bead sections 5 each enclose a tire bead core 51 and a bead filler 52. The tire bead core 51 is formed by winding a tire bead wire, which is a steel wire, into a ring shape. The bead filler 52 is a rubber material arranged in the space formed by folding over an end section of the carcass layer 6 in the transverse direction of the tire at the position of the bead core 51.

[0029] The end sections of the carcass layer 6 in the tire transverse direction are folded over the pair of bead cores 51 from the inside out, and the carcass layer 6 is stretched in a torus shape in the tire circumferential direction to form the tire skeleton. The carcass layer 6 is made of carcass cord threads (not illustrated) coated with coating rubber, arranged side by side at an angle to the tire circumferential direction along the tire meridian. The carcass cord threads are made of organic fibers (e.g., polyester, rayon, nylon, and the like). The carcass layer 6 is provided with at least one layer.

[0030] The belt layer 7 has a multi-layered structure in which at least two belts 71, 72 are layered on top of each other. In the tread section 2, the belt layer 7 is positioned radially outside the carcass layer 6, i.e., on its outer circumference, and covers the carcass layer 6 circumferentially. The belts 71, 72 are made of cord threads (not illustrated) coated with rubber and arranged side by side at a predetermined angle to the tire's circumferential direction (for example, 20 to 30 degrees). The cord threads are made of steel or organic fibers (polyester, rayon, nylon, or the like). Furthermore, the belts 71, 72 overlap each other and are arranged such that the direction of the cord threads of the respective belts intersects.

[0031] The belt reinforcement layer 8 is arranged radially outside the belt layer 7, i.e., on its outer circumference, and covers the belt layer 7 in the circumferential direction. The belt reinforcement layer 8 is made of cord threads (not illustrated) coated with rubber, arranged side by side in the transverse direction of the tire substantially parallel (±5 degrees) to the circumferential direction. The cord threads are made of steel or organic fibers (polyester, rayon, nylon, or the like). Fig. The belt reinforcement layer 8 shown in Figure 1 is arranged to cover the end sections of the belt layer 7 in the tire's transverse direction. The configuration of the belt reinforcement layer 8 is not limited to that described above. Although not shown in the drawings, a configuration can be used in which the belt reinforcement layer 8 is arranged to cover the entire belt layer 7. Alternatively, for example, a configuration with two reinforcement layers can be used, in which the inner reinforcement layer (in the tire's radial direction) is larger than the belt layer 7 in the tire's transverse direction, so that it covers the entire belt layer 7, and the outer reinforcement layer (in the tire's radial direction) is arranged to cover only the end sections of the belt layer 7 in the tire's transverse direction.In another example, a configuration with two reinforcement layers can be used, where both reinforcement layers are arranged such that they only cover the end sections of the belt layer 7 in the tire's transverse direction. In other words, the belt reinforcement layer 8 overlaps at least the end section of the belt layer 7 in the tire's transverse direction. Furthermore, the belt reinforcement layer 8 is configured by winding a ribbon-shaped strip material (e.g., with a width of 10 mm) in the tire's circumferential direction.

[0032] Fig. Figure 2 is an enlarged top view of a section of the pneumatic tire according to the present embodiment. Fig. Figure 3 is an enlarged perspective view of a section of the pneumatic tire according to the present embodiment. Fig. Figure 4 is an enlarged cross-sectional view of a section of the pneumatic tire according to the present embodiment. Fig. Figure 5 is an enlarged top view of a section of a pneumatic tire according to another embodiment. Fig. Figure 6 is an enlarged top view of a section of a pneumatic tire according to another embodiment. Fig. Figure 7 is an enlarged cross-sectional view of a section of a pneumatic tire according to another embodiment. Fig. Figure 8 is an enlarged top view of a section of a pneumatic tire according to another embodiment.

[0033] As in Fig. 2, Fig. 3 to Fig. As illustrated in Figure 4, in the tread section 2 of the pneumatic tire 1 of the present embodiment, the lug groove 24 is formed in the tread surface 21 of the central rib section 23M, which is one of the rib sections 23 defined between the adjacent main grooves in the transverse direction of the tire. The lug groove 24 of the central rib section 23M is provided at both ends 24a in conjunction with the main grooves 22. Thus, the central rib section 23M is defined in blocks that are divided in the circumferential direction of the tire.

[0034] In the central rib section 23M, a recess section 25 is formed at the opening edge of the lug groove 24. The recess section 25 is a chamfered cutout, inclined inwards from the tread surface 21 in the tire radial direction, which is connected to a groove wall 24w of the lug groove 24. It should be noted that the recess section 25 can be a flat chamfer inclined inwards from the tread surface 21 in the tire radial direction, or it can be a curved surface. It should also be noted that in the drawings, the recess section 25 is shown on both sides in the groove width direction of the lug groove 24, but it only needs to be provided on at least one side.

[0035] The lug grooves 24 of the central rib sections 23M are designed such that a groove width y is partially located along the tire transverse direction, and the groove width y is smaller than the maximum groove width y0 on the side of the first end 24a, which is connected to one of the main grooves 22, and the groove width y is smaller than the maximum groove width y0 on the side of the second end 24a, which is connected to the other main groove 22. Furthermore, the groove width y of the lug groove 24 of the central rib section 23M refers to the opening width between the groove walls 24w, excluding the recess sections 25. As the groove width y increases / decreases, the distance between the groove walls 24w increases / decreases.The lug groove 24 of the central rib section 23M has a cross-sectional area that progressively decreases from the position of the maximum groove width y0 towards the side of the first end 24a to the side of the second end 24a. The groove width y1 (y1a, y1b) at both ends 24a of the lug groove 24 of the central rib section 23M is 1.5 mm or more to ensure drainage performance and suppress noise emission, and the maximum groove width y0 is 4.5 mm or less to suppress noise emission. Furthermore, the groove depth (tire radial dimension from the groove bottom to the position of the groove width) of the lug groove 24 of the central rib section 23M ranges from 2.5 mm to 6.0 mm.

[0036] The position of the maximum groove width y0 of the lug groove 24 of the middle rib section 23M is located in a region Wa from the position where the end 24a (with one of the main grooves 22) is connected by 30% to 70% of the tire lateral dimension W of the middle rib section 23M.

[0037] The recess section 25, provided at the opening edge of the lug groove 24 of the central rib section 23M, has a recess width x that progressively increases towards the main groove 22, with which the ends 24a of the lug groove 24 are connected. In other words, the recess width x of the recess section 25 has a minimum recess width x0 at the position of the maximum groove width y0 of the lug groove 24, and the recess width x has a maximum recess width x1 at the ends 24a of the lug groove 24. "Recess width x of the recess section 25" refers to a chamfer width that slopes inward from the tread surface 21 in the tire radial direction. The recess section 25 has a cross-sectional area that progressively increases towards the ends 24a of the tunnel groove 24 of the middle web section 23M.

[0038] According to the pneumatic tire 1 configured in this manner, the lug groove 24 of the central rib section 23M has a groove width y that gradually decreases towards the ends 24a, which communicate with the main grooves 22. This suppresses the noise emitted outwards from the lug groove 24 in the transverse direction of the tire. Furthermore, the recess section 25, provided at the opening edge of the lug groove 24 of the central rib section 23M, has a recess width x that gradually increases towards the main grooves 22. This increases the drainage capacity in the lug groove 24. Consequently, according to the pneumatic tire 1 of the present embodiment, the pattern noise can be reduced and wet performance (braking performance on wet road surfaces) can be maintained.

[0039] Furthermore, in the pneumatic tire 1 of the present embodiment, the ratios 0 ≤ x0 < x and 0.2(y0 - y) + x0 ≤ x ≤ 2.0(y0 - y) + x0 are preferably satisfied, where y0 is the maximum groove width of the lug groove 24 of the central rib section 23S, x0 is the recess width of the recess section 25 at the position of the maximum groove width y0 of the lug groove 24, y is the groove width of the lug groove 24 at any position that is further outwards in the transverse direction of the tire than the position of the maximum groove width y0 of the lug groove 24, and x is the recess width of the recess section 25 at any position.

[0040] In the Fig. In the 5 illustrated configuration, 0 = x0 applies, where the recess width x0 of the recess section 25 at the position of the maximum groove width y0 of the lug grooves 24 is 0, and the recess section 25 extends outwards in the tire transverse direction from the position of the maximum groove width y0 of the lug groove 24.

[0041] According to the pneumatic tire 1, the recess width x of the recess section 25 is determined by the change in the groove width y of the lug groove 24 of the central rib section 23M. If the recess width x of the recess section 25 is 0.2(y0 - y) + x0 or more, a significant improvement in drainage performance can be achieved. If the recess width x of the recess section 25 is 2.0(y0 - y) + x0 or less, a significant reduction in noise radiating outwards in the tire's transverse direction from the lug groove 24 can be achieved. Consequently, the tread noise can be reduced, and a significant improvement in wet performance (braking performance on wet road surfaces) can be achieved.It should be noted that if the recess width x of the recess section 25 exceeds 2.0(y0 - y) + x0, the ground contact area of ​​the tread surface 21 of the shoulder rib section 23S decreases and the ground contact pressure increases. As a result, the abrasion resistance performance tends to decrease. According to the pneumatic tire 1, this can be improved.

[0042] It should be noted that, as in Fig. Figure 6 illustrates that the recessed section 25 can have a tire circumferential dimension (y + x + x) including the groove width y of the lug groove 24, which is constant in the tire transverse direction of the central rib section 23M ((y0 + x0 + x0) = (y1 + x1 + x1)). With such a configuration, the ground contact area of ​​the tread surface 21 of the central rib section 23M is constant in the tire transverse direction, and uneven wear can be suppressed.

[0043] As in Fig. As illustrated in Figure 4, in the pneumatic tire 1 of the present embodiment, the recess depth z of the recess section 25 from the tread surface 21 in the tire radial direction to the inside is preferably 0.5 mm to 3.0 mm.

[0044] According to this pneumatic tire 1, if the recess depth z of the recess section 25 is 0.5 mm or more, the effect of ensuring drainage capacity can be significantly achieved. Furthermore, if the recess depth z of the recess section 25 is 3.0 mm or less, the effect of suppressing noise emission can be significantly achieved. It should be noted that, in order to better achieve a significant effect of suppressing noise emission and ensuring drainage capacity, the recess depth z of the recess section 25 is preferably from 0.5 mm to 1.5 mm.

[0045] As in Fig. As illustrated in Figure 7, the direction of rotation is provided in the pneumatic tire 1 of the present embodiment, and the ratio xb < xa ≤ 3.0xb is preferably fulfilled, where xa is the recess width of the recess section 25, which is located on the rear side of the middle rib section 23M in the tire circumferential direction with respect to the lug groove 24, and xb is the recess width of the recess section 25, which is located on the front side.

[0046] Although not illustrated in the drawings, the direction of rotation is indicated by an indicator (for example, an arrow pointing in the direction of rotation when the vehicle is moving forward) provided on the sidewall section 4 on the side surface of the tire, which is located outwards in the transverse direction of the tire from the tread section 2.

[0047] According to pneumatic tire 1, by making the recess width xa of the recess section 25 on the rear of the central rib section 23M larger in the tire's circumferential direction with respect to the lug groove 24 than the recess width xb of the recess section 25 on the front, deformation (twisting) on ​​the rear is suppressed to a greater extent and stiffness is ensured to a greater degree than on the front with respect to the lug groove 24. As a result, sawtooth wear can be suppressed and abrasion resistance performance can be improved. In this case, the recess depth z of the recess section 25 is the same on the front and rear. It should be noted that, although not illustrated in the drawings, fulfilling the ratio xb < xa ≤ 3.0xb implies that the recess section 25 is not provided on the front.

[0048] In the pneumatic tire 1 of the present embodiment, the lug groove 24 of the middle rib section 23M preferably has a groove depth G at the position of the end 24a, which is in contact with the main groove 22, in relation to a groove depth G0 at the position of the maximum groove width y0, which covers the range 0.2 × G0 ≤ G ≤ 0.6 × G0.

[0049] According to this pneumatic tire 1, in the lug groove 24 of the central rib section 23M, the groove depth G at the position of the end 24a, which communicates with the main groove 22, is smaller than the groove depth G0 at the position of the maximum groove width y0. This allows noise emission to be effectively suppressed. By fulfilling the requirements of 0.2 × G0 ≤ G ≤ 0.6 × G0, the drainage performance can be maintained and wet performance ensured.

[0050] Furthermore, in the case of the pneumatic tire 1 of the present invention, as in Fig. Figure 8 illustrates the vehicle inside / outside orientation when the tire is mounted on a vehicle, and the lug groove 24 of the central rib section 23M preferably has the groove width y at a position where the lug groove 24 is in contact with the main groove 22, such that the groove width y1a on the outside of the vehicle is smaller than the groove width y1b on the inside of the vehicle.

[0051] The intended vehicle inward / outward orientation when the tire is mounted on a vehicle determines the orientation of the rim relative to the vehicle's interior and exterior in the tire's transverse direction when the tire is mounted on a rim, for example. Thus, when mounted on a rim, the pneumatic tire 1 has an intended vehicle inward / outward orientation in the tire's transverse direction when mounted on a vehicle. The pneumatic tire 1 includes a mounting direction indicator section (not illustrated) that indicates the mounting direction relative to a vehicle. The mounting direction indicator section consists, for example, of a marking or ridges / grooves on the sidewall section 4.For example, Regulation 30 of the Economic Commission for Europe (ECE R30) requires that an indication section of the mounting direction be provided on the sidewall section 4 on the outside of the vehicle when the tire is fitted to a vehicle.

[0052] The vehicle exterior, when the tire is mounted on a vehicle, exhibits significant problems with noise emission. Therefore, according to pneumatic tire 1, the noise emission can be effectively suppressed and a significant effect can be achieved, where the groove width y1a of the lug groove 24 of the central rib section 23M on the vehicle exterior is smaller than the groove width y1b on the vehicle interior.

[0053] Furthermore, in the pneumatic tire 1 of the present embodiment, a ratio of 0.80 × y0 ≤ y ≤ 0.98 × y0 is preferably fulfilled at position 0.50 × L; at position 0.80 × L, a ratio of 0.60 × y0 ≤ y ≤ 0.90 × y0 is fulfilled; and at position 1.00 × L a ratio 0.30 × y0 ≤ y ≤ 0.50 × y0 is satisfied, where L is the tire transverse dimension from the position of the maximum groove width y0 of the lug groove 24 to the position where the lug groove 24 is connected with the main groove 22 (the end 24a), and y is the groove width of the lug groove at any position that is further outwards in the tire transverse direction than the position of the maximum groove width y0 of the lug groove 24.

[0054] According to the pneumatic tire 1, by ensuring that the groove width y of the lug groove 24 of the middle rib section 23M is narrow at or near the end 24a, a groove volume can be ensured, wet performance can be maintained, and a significant reduction in pattern noise can be achieved.

[0055] It should be noted that in the embodiment described above, the groove 24 and the recess section 25 are located in the center of the web section 23M. However, similar effects can be achieved by placing the groove 24 and the recess section 25 in the central web section 23C. Examples

[0056] In the examples, performance tests regarding low noise performance (sample noise) and wet performance (braking performance on wet road surfaces) were carried out on a majority of pneumatic tire types under different conditions (see Fig. 9).

[0057] During the performance tests, pneumatic tires (test tires) with a tire size of 185 / 65R15 were mounted on a standard rim and inflated to the normal internal pressure. The pneumatic tire was then fitted to a test vehicle (a front-wheel-drive vehicle with a 1200 cc engine). 3 ) mounted.

[0058] Here, "normal rim" refers to a "standard rim" as defined by the Japan Automobile Tyre Manufacturers Association Inc. (JATMA), a "design rim" as defined by the Tire and Rim Association, Inc. (TRA), or a "measuring rim" as defined by the European Tyre and Rim Technical Organisation (ETRTO). "Normal inflation pressure" refers to a "maximum air pressure" as defined by JATMA, the maximum value in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" as defined by the TRA, or "INFLATION PRESSURES" as defined by the ETRTO.

[0059] In the noise reduction performance evaluation procedure, the passenger compartment noise (dB) was measured while the test vehicle traveled at a speed of 50 km / h on an ISO-specified road surface of a test track. The measured values ​​were expressed as index values ​​and evaluated using the state-of-the-art as a reference value (100). In this evaluation, higher values ​​indicate lower passenger compartment noise (reference noise) and excellent noise reduction performance.

[0060] In the wet performance evaluation procedure, the distance required by the test vehicle to come to a complete stop on a wet road surface with a water depth of 1 mm was measured after the brakes were applied from an initial speed of 100 km / h. The reciprocals of the measured values ​​were taken and expressed as index values, and the prior art was used as a benchmark (100) for evaluation. In this evaluation, higher values ​​indicate excellent wet performance.

[0061] In Fig. 9. In the pneumatic tires of the prior art example, the comparative example, and Examples 1 to 8, four main grooves are provided in the tread section, lug grooves with both ends connected to one of the main grooves are provided in each of the central rib sections defined by the four main grooves, and recess sections are provided at the opening edges of the lug grooves. In the pneumatic tire of the prior art example, the groove width of the lug groove and the recess width of the recess section do not change. In the pneumatic tire of the comparative example, the groove width of the lug groove does not change, and the recess width of the recess section increases towards the ends of the lug groove. In the pneumatic tires of Examples 1 to 8, the groove width of the lug groove decreases towards the ends, and the recess width of the recess section increases towards the ends of the lug groove.

[0062] As the test results in Fig. As can be seen in Figure 9, the pneumatic tires of examples 1 to 8 exhibit improved pattern noise and wet performance can be maintained. List of reference symbols 1 pneumatic tire 2. Tread section 21 Tread surface 22 Main groove 23M Middle Bridge Section 23C Center web section 24 stud groove 24a End, which is connected to the main groove 24w grooved wall 25 Recess section 3 Shoulder section 4 Side wall section W Tire transverse dimension of the rib section x recess width x0 Minimum recess width x1 Recess width at the end of the lug groove xa Recess width on back xb Recess width on front y Groove width of the lug groove y0 Maximum groove width of the lug groove y1 (y1a, y1b) Groove width at the end of the cleat groove

Claims

[1] Pneumatic tires (1), comprising: in a tread surface (21) main grooves (22) extending in a circumferential direction of the tire; Shoulder rib sections (23S) that are located at the outermost point in a tire transverse direction; at least one rib section (23M, 23C) defined by two of the main grooves (22) adjacent in a tire transverse direction; lug grooves (24) arranged in the circumferential direction of the tire in the tread surface (21) of the rib section (23M, 23C), wherein the lug grooves (24) each cross the circumferential direction of the tire and are connected at both ends to the main grooves (22), thereby defining the rib section (23M, 23C) in the circumferential direction of the tire; and a recess section (25) formed at an opening edge of the lug grooves (24), wherein the recess section (25) is a cutout from the tread surface (21) that is cut inwards in the tire radial direction; wherein the tread grooves (24) have a maximum groove width (y0) at a position of 30% to 70% of a tire transverse dimension (W) of the rib section (23M, 23C) of one of the main grooves (22) and a groove width that decreases from the maximum groove width (y0) to the main grooves (22); the recess section (25) has a recess width (x) that increases from a position of the maximum groove width (y0) of the adit grooves (24) to the main grooves (22); and wherein the groove width (y1, y1a, y1b) from both ends (24a) of the adit groove (24) is in a range of 1.5 mm or more, and less than 4.5 mm. [2] Pneumatic tire (1) according to claim 1, wherein the ratios 0 ≤ x0 < x and 0.2(y0 - y) + x0 ≤ x ≤ 2.0(y0 - y) + x0 are satisfied, wherein y0 is a maximum groove width of the lug grooves (24), x0 is the recess width (x) of the recess section (25) at the position of the maximum groove width y0 of the lug grooves (24), y is a groove width of the lug grooves (24) at any position which is further outwards in the transverse direction of the tire than the position of the maximum groove width y0 of the lug grooves (24), and x is a recess width of the recess section (25) at any position. [3] Pneumatic tire (1) according to claim 1 or 2, wherein the recess section (25) has a recess depth from the tread surface (21) inwards in the tire radial direction of 0.5 to 3.0 mm. [4] Pneumatic tire (1) according to any one of claims 1 to 3, wherein a direction of rotation is provided; and a ratio xb < xa ≤ 3.0xb is satisfied, where xa is a recess width (x) of the recess section (25) located on a rear side of the rib section (23M, 23C) in the tire circumferential direction with respect to the lug grooves (24), and xb is a recess width (x) of the recess section (25) located on a front side. [5] Pneumatic tire (1) according to any one of claims 1 to 4, wherein the lug grooves (24) have a groove depth G at a position where the lug grooves (24) are in contact with the main grooves (22) and a groove depth G0 at a maximum groove width position which satisfies a range of 0.2 × G0 ≤ G ≤ 0.6 × G0. [6] Pneumatic tire (1) according to any one of claims 1 to 5, wherein an inside / outside vehicle orientation is provided when mounted on a vehicle; and the lug grooves (24) have a groove width at a position where the lug grooves (24) are in contact with the main grooves (22) which is smaller on the outside of the vehicle than on the inside of the vehicle. [7] Pneumatic tire (1) according to any one of claims 1 to 6, wherein at position 0.50 × L a ratio 0.80 × y0 ≤ y ≤ 0.98 × y0 is satisfied; at a position 0.80 × L, the ratio 0.60 × y0 ≤ y ≤ 0.90 × y0 is satisfied; and at a position 1.00 × L a ratio 0.30 × y0 ≤ y ≤ 0.50 × y0 is satisfied, where L is a tire transverse dimension (W) from a position of a maximum groove width (y0) of the lug grooves (24) to a position where the lug grooves (24) are connected to the main grooves (22), y0 is a maximum groove width of the lug grooves (24), and y is a groove width of the lug grooves (24) at any position that is further outward in the tire transverse direction than the position of the maximum groove width (y0) of the lug grooves (24).

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