Pneumatic tire

Abstract

To provide a pneumatic tire that can enhance uneven wear resistance and dry grip performance.SOLUTION: A pneumatic tire 1 comprises a first profile P1 that extends from a tire equator C toward a first tread end T1. The first profile P1 comprises a first circular arc 11, a second circular arc 12, and a third circular arc 13. A curvature radius TR2 of the second circular arc 12 is 30%-40% of a curvature radius TR1 of the first circular arc 11. A curvature radius TR3 of the third circular arc 13 is 25%-40% of the curvature radius TR2 of the second circular arc 12. A second connection point 15 where the second circular arc 12 and the third circular arc 13 are connected, is located on the inside of the first tread end T1 in a tire axial direction. A separation distance La in the tire axial direction between the second connection point 15 and the tire equator C is 30%-34% of a sectional width of the tire. The third circular arc 13 extends to the outside in the tire axial direction beyond the first tread end T1.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Patent Document 1 below describes a pneumatic tire in which the outer surface of the tread portion in the tire meridian cross section is specified. This tire includes a crown arc straddling the tire equator, a middle arc connected to the crown arc, and a shoulder arc connected to the middle arc. And, the first curvature radius TR1 of the crown arc, the second curvature radius TR2 of the middle arc, and the third curvature radius TR3 of the shoulder arc are such that TR1 > TR2 > TR3. Such a tire is said to be able to effectively suppress uneven wear of the tread portion.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, during limit running on a circuit, a load exceeding 100% of the load index may act on the tire. In such a running situation, depending on the profile of the tread portion, the contact pressure may locally increase in the region near the tread edge, and there is a risk of uneven wear in the region and a decrease in the cornering force.

[0005] The present invention has been devised in view of the above problems, and an object thereof is to provide a pneumatic tire capable of improving uneven wear resistance performance and dry grip performance.

Means for Solving the Problems

[0006] The present invention relates to a pneumatic tire having a tread portion. In the tire meridian cross-section in the normal state, the tread portion includes a first profile extending from the tire equator toward the first tread end side. The first profile includes a first arc extending from the tire equator toward the outside in the tire axial direction, a second arc connected to the first arc and extending toward the outside in the tire axial direction, a third arc connected to the second arc and extending toward the outside in the tire axial direction, and a second connection point where the second arc and the third arc are connected. The first arc, the second arc, and the third arc each have a single radius of curvature. The radius of curvature TR2 of the second arc is 30% to 40% of the radius of curvature TR1 of the first arc. The radius of curvature TR3 of the third arc is 25% to 40% of the radius of curvature TR2 of the second arc. The second connection point is located on the inner side in the tire axial direction than the first tread end. The separation distance in the tire axial direction between the second connection point and the tire equator is 30% to 34% of the cross-sectional width of the tire. The third arc extends to the outside in the tire axial direction than the first tread end. It is a pneumatic tire.

Advantages of the Invention

[0007] By adopting the above configuration, the pneumatic tire of the present invention can enhance the resistance to uneven wear performance and dry grip performance.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings include exaggerated expressions and expressions different from the dimensional ratios of actual structures in order to assist in understanding the present invention. Further, when there are a plurality of embodiments, the same or common elements are denoted by the same reference numerals throughout the specification, and redundant descriptions are omitted.

[0010] FIG. 1 is a tire meridian cross-sectional view including a tire rotation axis (not shown) in the normal state of the pneumatic tire (hereinafter sometimes simply referred to as "tire") 1 of the present embodiment. The present invention is suitably used for, for example, tires for passenger cars capable of racing on a circuit. Since such a tire 1 travels at a relatively high speed, a load exceeding 100% of the load index may act during traveling. The "load index" is, in this specification, an index representing, in terms of an exponent, the maximum mass that can be allowed to load on the tire under specified conditions, that is, the maximum load capacity, as defined in the JATMA standard. However, the tire 1 of the present invention is not limited to those capable of such racing.

[0011] The "normal state" is a state in which the tire 1 is rim-mounted on a normal rim (not shown), adjusted to a normal internal pressure, and moreover, in an unloaded state. In this specification, unless otherwise specified, the dimensions of each part of the tire 1 are values measured in the normal state.

[0012] Further, the "normal rim" is a rim defined for each tire in a standard system including the standard on which the tire 1 is based. For example, it is the "standard rim" in JATMA, the "Design Rim" in TRA, and the "Measuring Rim" in ETRTO.

[0013] In addition, the "normal internal pressure" is the air pressure defined for each tire in the standard system including the standards on which Tire 1 is based. In the case of JATMA, it is the "maximum air pressure"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it is the "INFLATION PRESSURE".

[0014] As shown in FIG. 1, Tire 1 has a tread portion 2. Tire 1 further has a pair of sidewall portions 3 connected to both sides in the tire axial direction of the tread portion 2.

[0015] FIG. 2 is a view showing the profile of the tread portion 2 of the present embodiment. In this specification, the profile is a contour 1a obtained by filling the recesses provided on the surface of Tire 1 in the tire meridian cross section in the normal state. The recesses include circumferential grooves and lateral grooves described later. As shown in FIG. 2, the tread portion 2 includes a first profile P1 extending from the tire equator C toward the first tread end T1 side. The first profile P1 includes a first arc 11, a second arc 12, a third arc 13, and a second connection point 15. The first arc 11 extends outward in the tire axial direction from the tire equator C. The second arc 12 is connected to the first arc 11 and extends outward in the tire axial direction. The third arc 13 is connected to the second arc 12 and extends outward in the tire axial direction. The second connection point 15 is the point where the second arc 12 and the third arc 13 are connected. The second connection point 15 is located closer to the tire axial direction inner side than the first tread end T1.

[0016] The first arc 11, the second arc 12, and the third arc 13 each have a single radius of curvature TR1, TR2, and TR3, respectively. Also, the radius of curvature TR2 of the second arc 12 is 30% to 40% of the radius of curvature TR1 of the first arc 11. Furthermore, the radius of curvature TR3 of the third arc 13 is 25% to 40% of the radius of curvature TR2 of the second arc 12.

[0017] Also, the separation distance La in the tire axial direction between the second connection point 15 and the tire equator C is 30% to 34% of the sectional width Wt (shown in FIG. 1) of the tire 1. Further, the third arc 13 extends outward in the tire axial direction from the first tread end T1. Such a first profile P1 can smoothly ground the third arc 13 outside the first tread end T1 and expand the grounding area in a driving situation where the load index exceeds 100%. Such an expansion of the grounding area can suppress an increase in the local grounding pressure near the first tread end T1, and can suppress uneven wear near the first tread end T1 and a decrease in the cornering force. Therefore, the tire 1 of the present invention has excellent uneven wear resistance and dry grip performance. The sectional width Wt is the maximum width in the tire axial direction of the tire 1 excluding a rim guard (not shown), a pattern or characters on the tire side surface, etc.

[0018] In order to effectively exhibit the above-described action, the radius of curvature TR2 of the second arc 12 is desirably 32% or more and desirably 38% or less of the radius of curvature TR1 of the first arc 11. Also, the radius of curvature TR3 of the third arc 13 is desirably 27% or more and desirably 38% or less of the radius of curvature TR2 of the second arc 12. Further, the separation distance La in the tire axial direction between the second connection point 15 and the tire equator C is desirably 31% or more and desirably 33% or less of the sectional width Wt.

[0019] The first tread end T1 and a second tread end T2 described later are defined as the grounding positions at both ends in the tire axial direction in a state where a normal load is applied to the tire 1 in the normal state and the tire is grounded on a plane with a camber angle of 0 degrees (hereinafter referred to as the "normal load applied state"). The length in the tire axial direction between the first tread end T1 and the second tread end T2 is defined as the tread width TW (shown in FIG. 3).

[0020] In the case of a pneumatic tire with various standards defined, the "normal load" is the load defined for each tire in a standard system including the standards on which the tire is based. For JATMA, it is the "maximum load capacity"; for TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and for ETRTO, it is the "LOAD CAPACITY". In other words, the first tread end T1 and the second tread end T2 can be said to be both ends in the tire axial direction where the tread portion 2 contacts the plane during running at 100% of the load index.

[0021] The first profile P1 further includes a first connection point 14, an outer arc 16, and a third connection point 17. The first connection point 14 is the point where the first arc 11 and the second arc 12 are connected. The outer arc 16 is connected to the third arc 13 and extends outward in the tire axial direction. In this embodiment, the outer arc 16 is assumed to be a region that does not contact the ground even in situations such as circuit racing where the load index exceeds 100%. The third connection point 17 is the point where the outer arc 16 and the third arc 13 are connected. Also, each of the first connection point 14, the second connection point 15, and the third connection point 17 is a point where the radius of curvature changes on both sides in the tire axial direction.

[0022] The separation distance Lb in the tire axial direction between the outer end 13e (the same as the third connection point 17) of the third arc 13 in the tire axial direction and the tire equator C is desirably 44% or more of the section width Wt, more desirably 45% or more, desirably 48% or less, and more desirably 47% or less. Since the separation distance Lb is 44% or more and 48% or less of the section width Wt, in a running situation where the load index exceeds 100%, the third arc 13 contacts the ground and the outer arc 16 does not contact the ground, so a local increase in the contact pressure can be suppressed.

[0023] The tread portion 2 includes a second tread end T2 located on the side opposite to the first tread end T1. In the tire meridian cross-section in the normal state, the tread portion 2 includes a second profile P2 extending from the tire equator C toward the second tread end T2 side. And the second profile P2 is in line symmetry with the first profile P1 with the tire equator C as the axis of symmetry. Also in such a second profile P2, in a driving situation where the load index exceeds 100%, the third arc 13 can be smoothly grounded outside the second tread end T2 to expand the grounding area. Therefore, the tire 1 of the present embodiment has further excellent resistance to uneven wear performance and dry grip performance. Note that the second profile P2 is not limited to being in line symmetry with the first profile P1.

[0024] The radius of curvature TR1 of the first arc 11 is desirably 600 mm or more, more desirably 700 mm or more, desirably 1200 mm or less, and more desirably 1100 mm or less. Since the radius of curvature TR1 is 600 mm or more and 1200 mm or less, the contact pressure can be made uniform from the first arc 11 to the third arc 13. Note that the radius of curvature TR4 of the outer arc 16 is not particularly limited, but is desirably 15 mm or more, more desirably 20 mm or more, desirably 45 mm or less, and more desirably 40 mm or less.

[0025] The mounting direction of the tread portion 2 of the present embodiment on the vehicle is specified. The first tread end T1 is, in the present embodiment, the inner tread end located on the inner side of the vehicle when mounted on the vehicle. Also, the second tread end T2 is, in the present embodiment, the outer tread end located on the outer side of the vehicle when mounted on the vehicle. In this specification, the tread portion 2 has an inner tread portion 2A on the side of the first tread end T1 from the tire equator C, and an outer tread portion 2B on the side of the second tread end T2 from the tire equator C. Generally, during cornering, a larger lateral force acts on the outer tread portion 2B than on the inner tread portion 2A.

[0026] FIG. 3 is a plan view showing the tread portion 2 developed. As shown in FIG. 3, a plurality of circumferential grooves 20 extending in the tire circumferential direction are provided in the tread portion 2. The plurality of circumferential grooves 20 includes a first circumferential groove 21 located on the side of the first tread end T1.

[0027] The first circumferential groove 21 is arranged at a position overlapping the second arc 12 (shown in FIG. 2). And as shown in FIG. 2, it is desirable that the separation distance Lc in the tire axial direction between the outer edge 21e in the tire axial direction of the first circumferential groove 21 and the second connection point 15 is 10 mm or more. In this way, since the second connection point 15 where the ground pressure may increase is separated from the first circumferential groove 21, the occurrence of uneven wear in the vicinity of the first circumferential groove 21 is suppressed. If the separation distance Lc is excessively large, there is a possibility that the formation region of the third arc 13 in the tire axial direction becomes small. For this reason, the separation distance Lc is more preferably 15 mm or more, preferably 30 mm or less, and even more preferably 25 mm or less.

[0028] As shown in FIG. 3, all of the plurality of circumferential grooves 20 are located on the side of the first tread end T1 (inner tread end side) with respect to the tire equator C. In other words, all of the plurality of circumferential grooves 20 are arranged in the inner tread portion 2A. Thereby, since the rigidity in the tire axial direction of the outer tread portion 2B is maintained higher than the rigidity in the tire axial direction of the inner tread portion 2A, the ground pressures of the inner tread portion 2A and the outer tread portion 2B are equalized, and the dry grip performance during turning running is improved.

[0029] In the present embodiment, the plurality of circumferential grooves 20 includes a second circumferential groove 22 located on the side of the tire equator C with respect to the first circumferential groove 21. The plurality of circumferential grooves 20 in the present embodiment is composed of the first circumferential groove 21 and the second circumferential groove 22. Note that the plurality of circumferential grooves 20 may include, for example, other circumferential grooves (not shown).

[0030] Each of the first circumferential groove 21 and the second circumferential groove 22 extends linearly, for example, parallel to the tire circumferential direction. The angle θ1 of the groove width center line 21s of the first circumferential groove 21 with respect to the tire circumferential direction and the angle θ2 of the groove width center line 22s of the second circumferential groove 22 with respect to the tire circumferential direction are each desirably 5 degrees or less, and in the present embodiment, they extend at 0 degrees.

[0031] The groove width W1 of the first circumferential groove 21 and the groove width W2 of the second circumferential groove 22 are each desirably 4% or more of the tread width TW, more desirably 6% or more, desirably 14% or less, and more desirably 12% or less. The groove depth D1 (shown in FIG. 1) of the first circumferential groove 21 and the groove depth D2 of the second circumferential groove 22 are each desirably 3 mm or more, more desirably 4 mm or more, desirably 8 mm or less, and more desirably 7 mm or less. Such circumferential grooves 20 enhance the drainage performance while suppressing an excessive decrease in the rigidity of the tread portion 2.

[0032] In the present embodiment, the tread portion 2 includes a first land portion 24 defined by the first circumferential groove 21 and the first tread end T1, and a second land portion 25 defined by the second circumferential groove 22 and the second tread end T2. Further, the tread portion 2 includes, for example, a third land portion 26 defined by the first circumferential groove 21 and the second circumferential groove 22.

[0033] The tire axial width Wb of the second land portion 25 is formed to be larger than the tire axial width Wc of the third land portion 26. The tire axial width Wc of the third land portion 26 is formed to be larger than the tire axial width Wa of the first land portion 24.

[0034] Although not particularly limited, the tire axial width Wa of the first land portion 24 is desirably 5% or more of the tread width TW, more desirably 10% or more, desirably less than 25%, and more desirably 20% or less. The tire axial width Wb of the second land portion 25 is desirably 40% or more of the tread width TW, more desirably 45% or more, desirably 60% or less, and more desirably 55% or less. The tire axial width Wc of the third land portion 26 is desirably more than 5% of the tread width TW, more desirably 10% or more, desirably 25% or less, and more desirably 20% or less.

[0035] In the first land portion 24, in the present embodiment, a plurality of first lateral grooves 31 arranged at a first pitch length P11 in the tire circumferential direction are provided. Also, in the second land portion 25, for example, a plurality of second lateral grooves 32 arranged at a second pitch length P12 in the tire circumferential direction are provided. And it is desirable that the second pitch length P12 is larger than the first pitch length P11. Thereby, the rigidity in the tire circumferential direction of the second land portion 25 arranged in the outer tread portion 2B is maintained higher than the rigidity in the tire circumferential direction of the first land portion 24 arranged in the inner tread portion 2A, so that the contact pressures of the first land portion 24 and the second land portion 25 are equalized. Therefore, the uneven wear resistance performance and the dry grip performance are improved.

[0036] Each of the first lateral groove 31 and the second lateral groove 32 extends parallel to the tire axial direction. The angle θ3 of the groove width center line 31s of the first lateral groove 31 with respect to the tire axial direction and the angle θ4 of the groove width center line 32s of the second lateral groove 32 with respect to the tire axial direction are each desirably 5 degrees or less, and in the present embodiment, they extend at 0 degrees.

[0037] Each of the plurality of first lateral grooves 31 includes a tire axial inner end 31i that is closed within the first land portion 24 without connecting to the first circumferential groove 21, and is connected to the first tread end T1. Such a first lateral groove 31 improves the drainage performance while suppressing an excessive decrease in the rigidity of the first land portion 24.

[0038] The groove width W3 of the first transverse groove 31 is desirably 45% or more, more desirably 50% or more, desirably 65% or less, and more desirably 60% or less of the groove width W1 of the first circumferential groove 21. The groove depth D3 (shown in FIG. 1) of the first transverse groove 31 is desirably 80% or more, more desirably 90% or more, desirably 120% or less, and more desirably 110% or less of the groove depth D1 of the first circumferential groove 21. The first transverse groove 31 improves the drainage performance and the dry grip performance in a well-balanced manner.

[0039] The separation distance Ld in the tire axial direction between the inner end 31i of the first transverse groove 31 and the outer edge 21e of the first circumferential groove 21 is desirably 35% or more, more desirably 40% or more, desirably 55% or less, and more desirably 50% or less of the tire axial width Wa of the first land portion 24. Thereby, the above-described action is effectively exhibited.

[0040] Each of the plurality of second transverse grooves 32 includes a tire axial direction inner end 32i that closes within the second land portion 25 without connecting to the second circumferential groove 22. Such a second transverse groove 32 suppresses a decrease in the lateral rigidity of the second land portion 25. Each of the plurality of second transverse grooves 32 includes a tire axial direction outer end 32e that closes within the second land portion 25 without connecting to the second tread end T2.

[0041] Figure 4 is a schematic enlarged view of the second transverse groove 32 in Figure 3. As shown in Figure 4, in the tread plan view, each groove edge 35 of the plurality of second transverse grooves 32 includes an inner arc portion 35a that extends in an arc shape toward the inner end 32i side and an outer arc portion 35b that extends in an arc shape toward the outer end 32e side. Each groove edge 35 has the inner arc portion 35a and the outer arc portion 35b separated from each other in the tire circumferential direction. Further, the groove edge 35 includes a pair of axial portions 35c that connect the inner arc portion 35a and the outer arc portion 35b, a first circumferential portion 35d that connects the respective inner arc portions 35a and extends in the tire circumferential direction, and a second circumferential portion 35e that connects the respective outer arc portions 35b and extends in the tire circumferential direction. The axial portion 35c and each circumferential portion 35d, 35e extend linearly, respectively. That the groove edge 35 extends linearly means, in this specification, in the tread plan view, it includes not only those with an infinite (∞) radius of curvature, but also arcs with a radius of curvature of 400 mm or more.

[0042] The outer arc portion 35b is arranged in a region (the second tread end T2 side) where a large lateral force acts during turning running. For this reason, it is desirable that the radius of curvature TR7 of the outer arc portion 35b is larger than the radius of curvature TR6 of the inner arc portion 35a. Thereby, since the rigidity of the second tread end T2 side of the outer tread portion 2B (shown in Figure 3) is maintained high, the uneven wear resistance performance is improved. Although not particularly limited, it is desirable that the radius of curvature TR7 of the outer arc portion 35b is 110% or more of the radius of curvature TR6 of the inner arc portion 35a, more desirably 120% or more, desirably 300% or less, and more desirably 200% or less.

[0043] It is desirable that the groove width W4 of the second transverse groove 32 is 55% or more of the groove width W2 (shown in Figure 3) of the second circumferential groove 22, more desirably 60% or more, desirably 75% or less, and more desirably 70% or less. Further, it is desirable that the groove depth D4 (shown in Figure 1) of the second transverse groove 32 is 80% or more of the groove depth D2 of the second circumferential groove 22, more desirably 90% or more, desirably 120% or less, and more desirably 110% or less.

[0044] As shown in FIG. 3, the separation distance Le in the tire axial direction between the inner end 32i of the second lateral groove 32 and the second circumferential groove 22 is larger than the separation distance Lf in the tire axial direction between the outer end 32e of the second lateral groove 32 and the second tread end T2. Thereby, the rigidity of the second land portion 25 near the inner end 32i side is maintained larger than the rigidity of the second land portion 25 near the outer end 32e side, and the water in the second lateral groove 32 is easily discharged from the outer end 32e to the outside of the second tread end T2. Although not particularly limited, the separation distance Le is desirably 10% or more, more desirably 12% or more, desirably 20% or less, and more desirably 18% or less of the tire axial direction width Wb of the second land portion 25. The separation distance Lf is desirably 4% or more, more desirably 6% or more, desirably 12% or less, and more desirably 10% or less of the tire axial direction width Wb of the second land portion 25.

[0045] In the third land portion 26, a plurality of third lateral grooves 33 arranged at a third pitch length P13 in the tire circumferential direction are provided. The third pitch length P13 is desirably smaller than the second pitch length P12. Thereby, the circumferential rigidity of the second land portion 25 arranged in the outer tread portion 2B is maintained higher than the circumferential rigidity of the third land portion 26 arranged in the inner tread portion 2A, so that the contact pressures of the second land portion 25 and the third land portion 26 are equalized. Therefore, the uneven wear resistance performance and the dry grip performance are improved. The third pitch length P13 is, for example, the same as the first pitch length P11.

[0046] Each of the plurality of third lateral grooves 33 includes a tire axial direction inner end 33i that closes within the third land portion 26 without connecting to the second circumferential groove 22, and is connected to the first circumferential groove 21. Further, in the third lateral groove 33, for example, the groove width W5 continuously increases toward the first circumferential groove 21 side. Such a third lateral groove 33 facilitates the discharge of the water in the third lateral groove 33 to the first circumferential groove 21 and suppresses an excessive decrease in the rigidity of the third land portion 26.

[0047] The separation distance Lg in the tire axial direction between the inner end 33i of the third circumferential groove 33 and the second circumferential groove 22 is desirably 50% or more, more desirably 55% or more, desirably 70% or less, and more desirably 65% or less of the tire axial width Wc of the third land portion 26. Since the separation distance Lg is 50% or more and 70% or less of the tire axial width Wc of the third land portion 26, the drainage performance and the dry grip performance can be enhanced in a well-balanced manner. The ratio (Lg / Wc) of the separation distance Lg to the tire axial width Wc of the third land portion 26 is made larger than the ratio (Ld / Wa) of the separation distance Ld to the tire axial width Wa of the first land portion 24.

[0048] As shown in FIG. 1, the groove depth D5 of the third circumferential groove 33 is desirably 80% or more, more desirably 90% or more, desirably 120% or less, and more desirably 110% or less of the groove depth D1 of the first circumferential groove 21. Thereby, high drainage performance is exhibited.

[0049] As described above, the particularly preferred embodiments of the present invention have been described in detail. However, the present invention is not limited to the illustrated embodiments and can be implemented in various forms.

Example

[0050] A pneumatic tire having the basic structure of FIG. 1 and the basic pattern of FIG. 3 was prototyped based on the specifications in Table 1, and tests were conducted on the dry grip performance, the resistance to uneven wear performance, and the drainage performance. The main common matters are as follows. Tire size: 215 / 45R17 Air pressure: 220 kPa Rim: 17×7.5J

[0051] <Dry grip performance, resistance to uneven wear performance, and drainage performance> Each test tire was mounted on all the wheels of the following vehicle and driven on a circuit course on a dry asphalt road surface and a circuit course on a wet asphalt road surface. During this driving, a load exceeding 100% of the load index was applied to the tire. Regarding the dry grip performance, the ease of driving on the circuit course on the dry asphalt road surface was evaluated by the sensory perception of the test driver. Regarding the resistance to uneven wear performance, the occurrence state of uneven wear after driving on the circuit course on the dry asphalt road surface was evaluated by the sensory perception of the test driver. Regarding the drainage performance, the ease of driving on the circuit course on the wet asphalt road surface was evaluated by the sensory perception of the test driver. The results are shown in scores with Comparative Example 1 set as 100 in all tests. The larger the numerical value, the better. Vehicle: Rear-wheel drive passenger car with a displacement of 2400 cc Comparative Examples 1 and 2 and Examples 1 and 11 are slick tires, Examples 2 to 4 are tires having circumferential grooves and no lateral grooves, and Examples 5 to 10 are tires having circumferential grooves and lateral grooves. Regarding the table "A" means a mode in which two circumferential grooves are arranged in the inner tread portion. "B" means a mode in which the first circumferential groove is arranged in the inner tread portion and the second circumferential groove is arranged in the outer tread portion. "C" means the mode of the third lateral groove in FIG. 3. "D" means a mode in which the third lateral groove is connected to the second circumferential groove and not connected to the first circumferential groove. The test results are shown in Tables 1 and 2.

[0052]

Table 1

[0053]

Table 2

[0054] As a result of the tests, it is understood that the tires of the examples have improved dry grip performance and uneven wear resistance compared to the tires of the comparative examples. Further, in the state of 110% of the load index, the contact pressure of the contact surface 2s1 of the slick tire having the profile of Example 1 is shown in FIG. 5(A), and the contact pressure of the contact surface 2s2 of the slick tire having the profile of Comparative Example 1 is shown in FIG. 5(B). In FIG. 5, the higher the contact pressure, the darker the color. As shown in FIG. 5, the profile of Example 1 has a relatively uniform contact pressure compared to the profile of Comparative Example 1.

[0055] [Appendix] The present invention includes the following aspects.

[0056] [Invention 1] A pneumatic tire having a tread portion, In the tire meridian cross-section in the normal state, the tread portion includes a first profile extending from the tire equator to the first tread end side, The first profile includes a first arc extending from the tire equator to the outside in the tire axial direction, a second arc connected to the first arc and extending to the outside in the tire axial direction, a third arc connected to the second arc and extending to the outside in the tire axial direction, and a second connection point where the second arc and the third arc are connected, The first arc, the second arc, and the third arc each have a single radius of curvature, The radius of curvature TR2 of the second arc is 30% to 40% of the radius of curvature TR1 of the first arc, The radius of curvature TR3 of the third arc is 25% to 40% of the radius of curvature TR2 of the second arc, The second connection point is located inside the tire axial direction from the first tread end, The separation distance in the tire axial direction between the second connection point and the tire equator is 30% to 34% of the cross-sectional width of the tire, The third arc extends to the outside in the tire axial direction from the first tread end, Pneumatic tire. [Invention 2] The distance in the tire axial direction between the outer end of the third arc in the tire axial direction and the tire equator is 44% to 48% of the section width, the pneumatic tire according to Invention 1 of the present invention. [Invention 3] The radius of curvature TR1 of the first arc is 600 to 1200 mm, the pneumatic tire according to Invention 1 or 2 of the present invention. [Invention 4] The tread portion includes a second tread end located on the side opposite to the first tread end. In the tire meridian cross section in the normal state, the tread portion includes a second profile extending from the tire equator toward the second tread end side. The second profile is in line symmetry with the first profile with the tire equator as the axis of symmetry, the pneumatic tire according to any one of Inventions 1 to 3 of the present invention. [Invention 5] The mounting direction of the tread portion on the vehicle is specified. The first tread end is an inner tread end located on the inner side of the vehicle when mounted on the vehicle, the pneumatic tire according to any one of Inventions 1 to 4 of the present invention. [Invention 6] A plurality of circumferential grooves extending in the tire circumferential direction are provided in the tread portion. The plurality of circumferential grooves includes a first circumferential groove located on the side closest to the first tread end. The first circumferential groove is arranged at a position overlapping with the second arc. The distance in the tire axial direction between the outer edge of the first circumferential groove in the tire axial direction and the second connection point is 10 mm or more, the pneumatic tire according to any one of Inventions 1 to 5 of the present invention. [Invention 7] All of the plurality of circumferential grooves are located on the side of the first tread end with respect to the tire equator, the pneumatic tire according to Invention 6 of the present invention. [Invention 8] The plurality of circumferential grooves includes a second circumferential groove located closer to the tire equator than the first circumferential groove. The tread portion includes a second tread end located on the side opposite to the first tread end, a first land portion defined by the first circumferential groove and the first tread end, and a second land portion defined by the second circumferential groove and the second tread end. A plurality of first transverse grooves arranged at a first pitch length in the tire circumferential direction are provided in the first land portion. A plurality of second transverse grooves arranged at a second pitch length in the tire circumferential direction are provided in the second land portion. The pneumatic tire according to Invention 6 or 7, wherein the second pitch length is greater than the first pitch length. [Invention 9] The pneumatic tire according to Invention 8, wherein each of the plurality of first transverse grooves includes an inner end in the tire axial direction that is closed within the first land portion without connecting to the first circumferential groove, and is connected to the first tread end. [Invention 10] The pneumatic tire according to Invention 8 or 9, wherein each of the plurality of second transverse grooves includes an inner end in the tire axial direction that is closed within the second land portion without connecting to the second circumferential groove. [Invention 11] The pneumatic tire according to Invention 10, wherein each of the plurality of second transverse grooves includes an outer end in the tire axial direction that is closed within the second land portion without connecting to the second tread end. [Invention 12] In a plan view of the tread, each groove edge of the plurality of second transverse grooves includes an inner arc portion that extends in an arc shape on the inner end side and an outer arc portion that extends in an arc shape on the outer end side. The pneumatic tire according to Invention 11. [Invention 13] The pneumatic tire according to Invention 12, wherein the radius of curvature of the outer arc portion is greater than the radius of curvature of the inner arc portion. [Invention 14] The tread portion includes a third land portion defined by the first circumferential groove and the second circumferential groove. A plurality of third transverse grooves arranged at a third pitch length in the tire circumferential direction are provided in the third land portion. The pneumatic tire according to any one of 8 to 13 of the present invention, wherein the third pitch length is smaller than the second pitch length. [Invention 15] The pneumatic tire according to invention 14, wherein each of the plurality of third lateral grooves includes an inner end in the tire axial direction that closes within the third land portion without connecting to the second circumferential groove, and is connected to the first circumferential groove.

Explanation of reference numerals

[0057] 1 Pneumatic tire P1 First profile 11 First arc 12 Second arc 13 Third arc 15 Second connection point C Tire equator La Separation distance T1 First tread end Wt Tire cross-sectional width

Claims

1. A pneumatic tire having a tread portion, In the tire meridian cross-section in the normal state, the tread portion includes a first profile extending from the tire equator toward the first tread end side, The first profile includes a first arc extending from the tire equator outward in the tire axial direction, a second arc connected to the first arc and extending outward in the tire axial direction, a third arc connected to the second arc and extending outward in the tire axial direction, and a second connection point where the second arc and the third arc are connected, The first arc, the second arc, and the third arc each have a single radius of curvature, The radius of curvature TR2 of the second arc is 30% to 40% of the radius of curvature TR1 of the first arc, The radius of curvature TR3 of the third arc is 25% to 40% of the radius of curvature TR2 of the second arc, The second connection point is located inward in the tire axial direction from the first tread end, The separation distance in the tire axial direction between the second connection point and the tire equator is 30% to 34% of the cross-sectional width of the tire, The third arc extends outward in the tire axial direction from the first tread end, Pneumatic tire.

2. The separation distance in the tire axial direction between the outer end in the tire axial direction of the third arc and the tire equator is 44% to 48% of the cross-sectional width, the pneumatic tire according to claim 1.

3. The radius of curvature TR1 of the first arc is 600 to 1200 mm, the pneumatic tire according to claim 1.

4. The tread portion includes a second tread end located on the side opposite to the first tread end, In the tire meridian cross-section in the normal state, the tread portion includes a second profile extending from the tire equator toward the second tread end side, The pneumatic tire according to claim 1, wherein the second profile is in line symmetry with the first profile with the tire equator as the axis of symmetry.

5. The tread portion has a specified mounting direction on the vehicle, The pneumatic tire according to claim 1, wherein the first tread end is an inner tread end located on the inner side of the vehicle when the tire is mounted on the vehicle.

6. A plurality of circumferential grooves extending in the tire circumferential direction are provided in the tread portion, The plurality of circumferential grooves includes a first circumferential groove located closest to the first tread end side, The first circumferential groove is arranged at a position overlapping with the second arc, The pneumatic tire according to any one of claims 1 to 5, wherein the axial separation distance between the outer edge of the first circumferential groove in the tire axial direction and the second connection point is 10 mm or more.

7. The pneumatic tire according to claim 6, wherein all of the plurality of circumferential grooves are located on the first tread end side with respect to the tire equator.

8. The plurality of circumferential grooves includes a second circumferential groove located closer to the tire equator side than the first circumferential groove, The tread portion includes a second tread end located on the side opposite to the first tread end, a first land portion defined by the first circumferential groove and the first tread end, and a second land portion defined by the second circumferential groove and the second tread end, A plurality of first transverse grooves arranged at a first pitch length in the tire circumferential direction are provided in the first land portion, A plurality of second transverse grooves arranged at a second pitch length in the tire circumferential direction are provided in the second land portion, The pneumatic tire according to claim 6, wherein the second pitch length is larger than the first pitch length.

9. Each of the plurality of first lateral grooves includes a tire axial direction inner end that closes within the first land portion without connecting to the first circumferential groove, and is connected to the first tread end. The pneumatic tire according to claim 8.

10. Each of the plurality of second lateral grooves includes a tire axial direction inner end that closes within the second land portion without connecting to the second circumferential groove. The pneumatic tire according to claim 8.

11. Each of the plurality of second lateral grooves includes a tire axial direction outer end that closes within the second land portion without connecting to the second tread end. The pneumatic tire according to claim 10.

12. In a tread plan view, each groove edge of the plurality of second lateral grooves includes an inner arc portion that extends in an arc shape on the inner end side and an outer arc portion that extends in an arc shape on the outer end side. The pneumatic tire according to claim 11.

13. The radius of curvature of the outer arc portion is larger than the radius of curvature of the inner arc portion. The pneumatic tire according to claim 12.

14. The tread portion includes a third land portion defined by the first circumferential groove and the second circumferential groove. A plurality of third lateral grooves arranged at a third pitch length in the tire circumferential direction are provided in the third land portion. The third pitch length is smaller than the second pitch length. The pneumatic tire according to claim 8.

15. Each of the plurality of third lateral grooves includes a tire axial direction inner end that closes within the third land portion without connecting to the second circumferential groove, and is connected to the first circumferential groove. The pneumatic tire according to claim 14.

Images